err.no Git - linux-2.6/blob - net/ipv4/tcp_input.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              Implementation of the Transmission Control Protocol(TCP).
   7  *
   8  * Version:     $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
   9  *
  10  * Authors:     Ross Biro
  11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12  *              Mark Evans, <evansmp@uhura.aston.ac.uk>
  13  *              Corey Minyard <wf-rch!minyard@relay.EU.net>
  14  *              Florian La Roche, <flla@stud.uni-sb.de>
  15  *              Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
  16  *              Linus Torvalds, <torvalds@cs.helsinki.fi>
  17  *              Alan Cox, <gw4pts@gw4pts.ampr.org>
  18  *              Matthew Dillon, <dillon@apollo.west.oic.com>
  19  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  20  *              Jorge Cwik, <jorge@laser.satlink.net>
  21  */
  22
  23 /*
  24  * Changes:
  25  *              Pedro Roque     :       Fast Retransmit/Recovery.
  26  *                                      Two receive queues.
  27  *                                      Retransmit queue handled by TCP.
  28  *                                      Better retransmit timer handling.
  29  *                                      New congestion avoidance.
  30  *                                      Header prediction.
  31  *                                      Variable renaming.
  32  *
  33  *              Eric            :       Fast Retransmit.
  34  *              Randy Scott     :       MSS option defines.
  35  *              Eric Schenk     :       Fixes to slow start algorithm.
  36  *              Eric Schenk     :       Yet another double ACK bug.
  37  *              Eric Schenk     :       Delayed ACK bug fixes.
  38  *              Eric Schenk     :       Floyd style fast retrans war avoidance.
  39  *              David S. Miller :       Don't allow zero congestion window.
  40  *              Eric Schenk     :       Fix retransmitter so that it sends
  41  *                                      next packet on ack of previous packet.
  42  *              Andi Kleen      :       Moved open_request checking here
  43  *                                      and process RSTs for open_requests.
  44  *              Andi Kleen      :       Better prune_queue, and other fixes.
  45  *              Andrey Savochkin:       Fix RTT measurements in the presence of
  46  *                                      timestamps.
  47  *              Andrey Savochkin:       Check sequence numbers correctly when
  48  *                                      removing SACKs due to in sequence incoming
  49  *                                      data segments.
  50  *              Andi Kleen:             Make sure we never ack data there is not
  51  *                                      enough room for. Also make this condition
  52  *                                      a fatal error if it might still happen.
  53  *              Andi Kleen:             Add tcp_measure_rcv_mss to make
  54  *                                      connections with MSS<min(MTU,ann. MSS)
  55  *                                      work without delayed acks.
  56  *              Andi Kleen:             Process packets with PSH set in the
  57  *                                      fast path.
  58  *              J Hadi Salim:           ECN support
  59  *              Andrei Gurtov,
  60  *              Pasi Sarolahti,
  61  *              Panu Kuhlberg:          Experimental audit of TCP (re)transmission
  62  *                                      engine. Lots of bugs are found.
  63  *              Pasi Sarolahti:         F-RTO for dealing with spurious RTOs
  64  */
  65
  66 #include <linux/mm.h>
  67 #include <linux/module.h>
  68 #include <linux/sysctl.h>
  69 #include <net/tcp.h>
  70 #include <net/inet_common.h>
  71 #include <linux/ipsec.h>
  72 #include <asm/unaligned.h>
  73 #include <net/netdma.h>
  74
  75 int sysctl_tcp_timestamps __read_mostly = 1;
  76 int sysctl_tcp_window_scaling __read_mostly = 1;
  77 int sysctl_tcp_sack __read_mostly = 1;
  78 int sysctl_tcp_fack __read_mostly = 1;
  79 int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
  80 int sysctl_tcp_ecn __read_mostly;
  81 int sysctl_tcp_dsack __read_mostly = 1;
  82 int sysctl_tcp_app_win __read_mostly = 31;
  83 int sysctl_tcp_adv_win_scale __read_mostly = 2;
  84
  85 int sysctl_tcp_stdurg __read_mostly;
  86 int sysctl_tcp_rfc1337 __read_mostly;
  87 int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
  88 int sysctl_tcp_frto __read_mostly;
  89 int sysctl_tcp_nometrics_save __read_mostly;
  90
  91 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
  92 int sysctl_tcp_abc __read_mostly;
  93
  94 #define FLAG_DATA               0x01 /* Incoming frame contained data.          */
  95 #define FLAG_WIN_UPDATE         0x02 /* Incoming ACK was a window update.       */
  96 #define FLAG_DATA_ACKED         0x04 /* This ACK acknowledged new data.         */
  97 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted.  */
  98 #define FLAG_SYN_ACKED          0x10 /* This ACK acknowledged SYN.              */
  99 #define FLAG_DATA_SACKED        0x20 /* New SACK.                               */
 100 #define FLAG_ECE                0x40 /* ECE in this ACK                         */
 101 #define FLAG_DATA_LOST          0x80 /* SACK detected data lossage.             */
 102 #define FLAG_SLOWPATH           0x100 /* Do not skip RFC checks for window update.*/
 103
 104 #define FLAG_ACKED              (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
 105 #define FLAG_NOT_DUP            (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
 106 #define FLAG_CA_ALERT           (FLAG_DATA_SACKED|FLAG_ECE)
 107 #define FLAG_FORWARD_PROGRESS   (FLAG_ACKED|FLAG_DATA_SACKED)
 108
 109 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
 110 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
 111 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
 112
 113 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
 114
 115 /* Adapt the MSS value used to make delayed ack decision to the
 116  * real world.
 117  */
 118 static void tcp_measure_rcv_mss(struct sock *sk,
 119                                 const struct sk_buff *skb)
 120 {
 121         struct inet_connection_sock *icsk = inet_csk(sk);
 122         const unsigned int lss = icsk->icsk_ack.last_seg_size;
 123         unsigned int len;
 124
 125         icsk->icsk_ack.last_seg_size = 0;
 126
 127         /* skb->len may jitter because of SACKs, even if peer
 128          * sends good full-sized frames.
 129          */
 130         len = skb_shinfo(skb)->gso_size ?: skb->len;
 131         if (len >= icsk->icsk_ack.rcv_mss) {
 132                 icsk->icsk_ack.rcv_mss = len;
 133         } else {
 134                 /* Otherwise, we make more careful check taking into account,
 135                  * that SACKs block is variable.
 136                  *
 137                  * "len" is invariant segment length, including TCP header.
 138                  */
 139                 len += skb->data - skb->h.raw;
 140                 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
 141                     /* If PSH is not set, packet should be
 142                      * full sized, provided peer TCP is not badly broken.
 143                      * This observation (if it is correct 8)) allows
 144                      * to handle super-low mtu links fairly.
 145                      */
 146                     (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
 147                      !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) {
 148                         /* Subtract also invariant (if peer is RFC compliant),
 149                          * tcp header plus fixed timestamp option length.
 150                          * Resulting "len" is MSS free of SACK jitter.
 151                          */
 152                         len -= tcp_sk(sk)->tcp_header_len;
 153                         icsk->icsk_ack.last_seg_size = len;
 154                         if (len == lss) {
 155                                 icsk->icsk_ack.rcv_mss = len;
 156                                 return;
 157                         }
 158                 }
 159                 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
 160                         icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
 161                 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
 162         }
 163 }
 164
 165 static void tcp_incr_quickack(struct sock *sk)
 166 {
 167         struct inet_connection_sock *icsk = inet_csk(sk);
 168         unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
 169
 170         if (quickacks==0)
 171                 quickacks=2;
 172         if (quickacks > icsk->icsk_ack.quick)
 173                 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
 174 }
 175
 176 void tcp_enter_quickack_mode(struct sock *sk)
 177 {
 178         struct inet_connection_sock *icsk = inet_csk(sk);
 179         tcp_incr_quickack(sk);
 180         icsk->icsk_ack.pingpong = 0;
 181         icsk->icsk_ack.ato = TCP_ATO_MIN;
 182 }
 183
 184 /* Send ACKs quickly, if "quick" count is not exhausted
 185  * and the session is not interactive.
 186  */
 187
 188 static inline int tcp_in_quickack_mode(const struct sock *sk)
 189 {
 190         const struct inet_connection_sock *icsk = inet_csk(sk);
 191         return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
 192 }
 193
 194 /* Buffer size and advertised window tuning.
 195  *
 196  * 1. Tuning sk->sk_sndbuf, when connection enters established state.
 197  */
 198
 199 static void tcp_fixup_sndbuf(struct sock *sk)
 200 {
 201         int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
 202                      sizeof(struct sk_buff);
 203
 204         if (sk->sk_sndbuf < 3 * sndmem)
 205                 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
 206 }
 207
 208 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
 209  *
 210  * All tcp_full_space() is split to two parts: "network" buffer, allocated
 211  * forward and advertised in receiver window (tp->rcv_wnd) and
 212  * "application buffer", required to isolate scheduling/application
 213  * latencies from network.
 214  * window_clamp is maximal advertised window. It can be less than
 215  * tcp_full_space(), in this case tcp_full_space() - window_clamp
 216  * is reserved for "application" buffer. The less window_clamp is
 217  * the smoother our behaviour from viewpoint of network, but the lower
 218  * throughput and the higher sensitivity of the connection to losses. 8)
 219  *
 220  * rcv_ssthresh is more strict window_clamp used at "slow start"
 221  * phase to predict further behaviour of this connection.
 222  * It is used for two goals:
 223  * - to enforce header prediction at sender, even when application
 224  *   requires some significant "application buffer". It is check #1.
 225  * - to prevent pruning of receive queue because of misprediction
 226  *   of receiver window. Check #2.
 227  *
 228  * The scheme does not work when sender sends good segments opening
 229  * window and then starts to feed us spaghetti. But it should work
 230  * in common situations. Otherwise, we have to rely on queue collapsing.
 231  */
 232
 233 /* Slow part of check#2. */
 234 static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp,
 235                              const struct sk_buff *skb)
 236 {
 237         /* Optimize this! */
 238         int truesize = tcp_win_from_space(skb->truesize)/2;
 239         int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2;
 240
 241         while (tp->rcv_ssthresh <= window) {
 242                 if (truesize <= skb->len)
 243                         return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
 244
 245                 truesize >>= 1;
 246                 window >>= 1;
 247         }
 248         return 0;
 249 }
 250
 251 static void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
 252                             struct sk_buff *skb)
 253 {
 254         /* Check #1 */
 255         if (tp->rcv_ssthresh < tp->window_clamp &&
 256             (int)tp->rcv_ssthresh < tcp_space(sk) &&
 257             !tcp_memory_pressure) {
 258                 int incr;
 259
 260                 /* Check #2. Increase window, if skb with such overhead
 261                  * will fit to rcvbuf in future.
 262                  */
 263                 if (tcp_win_from_space(skb->truesize) <= skb->len)
 264                         incr = 2*tp->advmss;
 265                 else
 266                         incr = __tcp_grow_window(sk, tp, skb);
 267
 268                 if (incr) {
 269                         tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
 270                         inet_csk(sk)->icsk_ack.quick |= 1;
 271                 }
 272         }
 273 }
 274
 275 /* 3. Tuning rcvbuf, when connection enters established state. */
 276
 277 static void tcp_fixup_rcvbuf(struct sock *sk)
 278 {
 279         struct tcp_sock *tp = tcp_sk(sk);
 280         int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
 281
 282         /* Try to select rcvbuf so that 4 mss-sized segments
 283          * will fit to window and corresponding skbs will fit to our rcvbuf.
 284          * (was 3; 4 is minimum to allow fast retransmit to work.)
 285          */
 286         while (tcp_win_from_space(rcvmem) < tp->advmss)
 287                 rcvmem += 128;
 288         if (sk->sk_rcvbuf < 4 * rcvmem)
 289                 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
 290 }
 291
 292 /* 4. Try to fixup all. It is made immediately after connection enters
 293  *    established state.
 294  */
 295 static void tcp_init_buffer_space(struct sock *sk)
 296 {
 297         struct tcp_sock *tp = tcp_sk(sk);
 298         int maxwin;
 299
 300         if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
 301                 tcp_fixup_rcvbuf(sk);
 302         if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
 303                 tcp_fixup_sndbuf(sk);
 304
 305         tp->rcvq_space.space = tp->rcv_wnd;
 306
 307         maxwin = tcp_full_space(sk);
 308
 309         if (tp->window_clamp >= maxwin) {
 310                 tp->window_clamp = maxwin;
 311
 312                 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
 313                         tp->window_clamp = max(maxwin -
 314                                                (maxwin >> sysctl_tcp_app_win),
 315                                                4 * tp->advmss);
 316         }
 317
 318         /* Force reservation of one segment. */
 319         if (sysctl_tcp_app_win &&
 320             tp->window_clamp > 2 * tp->advmss &&
 321             tp->window_clamp + tp->advmss > maxwin)
 322                 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
 323
 324         tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
 325         tp->snd_cwnd_stamp = tcp_time_stamp;
 326 }
 327
 328 /* 5. Recalculate window clamp after socket hit its memory bounds. */
 329 static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
 330 {
 331         struct inet_connection_sock *icsk = inet_csk(sk);
 332
 333         icsk->icsk_ack.quick = 0;
 334
 335         if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
 336             !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
 337             !tcp_memory_pressure &&
 338             atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
 339                 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
 340                                     sysctl_tcp_rmem[2]);
 341         }
 342         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
 343                 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
 344 }
 345
 346
 347 /* Initialize RCV_MSS value.
 348  * RCV_MSS is an our guess about MSS used by the peer.
 349  * We haven't any direct information about the MSS.
 350  * It's better to underestimate the RCV_MSS rather than overestimate.
 351  * Overestimations make us ACKing less frequently than needed.
 352  * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
 353  */
 354 void tcp_initialize_rcv_mss(struct sock *sk)
 355 {
 356         struct tcp_sock *tp = tcp_sk(sk);
 357         unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
 358
 359         hint = min(hint, tp->rcv_wnd/2);
 360         hint = min(hint, TCP_MIN_RCVMSS);
 361         hint = max(hint, TCP_MIN_MSS);
 362
 363         inet_csk(sk)->icsk_ack.rcv_mss = hint;
 364 }
 365
 366 /* Receiver "autotuning" code.
 367  *
 368  * The algorithm for RTT estimation w/o timestamps is based on
 369  * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
 370  * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
 371  *
 372  * More detail on this code can be found at
 373  * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
 374  * though this reference is out of date.  A new paper
 375  * is pending.
 376  */
 377 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
 378 {
 379         u32 new_sample = tp->rcv_rtt_est.rtt;
 380         long m = sample;
 381
 382         if (m == 0)
 383                 m = 1;
 384
 385         if (new_sample != 0) {
 386                 /* If we sample in larger samples in the non-timestamp
 387                  * case, we could grossly overestimate the RTT especially
 388                  * with chatty applications or bulk transfer apps which
 389                  * are stalled on filesystem I/O.
 390                  *
 391                  * Also, since we are only going for a minimum in the
 392                  * non-timestamp case, we do not smooth things out
 393                  * else with timestamps disabled convergence takes too
 394                  * long.
 395                  */
 396                 if (!win_dep) {
 397                         m -= (new_sample >> 3);
 398                         new_sample += m;
 399                 } else if (m < new_sample)
 400                         new_sample = m << 3;
 401         } else {
 402                 /* No previous measure. */
 403                 new_sample = m << 3;
 404         }
 405
 406         if (tp->rcv_rtt_est.rtt != new_sample)
 407                 tp->rcv_rtt_est.rtt = new_sample;
 408 }
 409
 410 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
 411 {
 412         if (tp->rcv_rtt_est.time == 0)
 413                 goto new_measure;
 414         if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
 415                 return;
 416         tcp_rcv_rtt_update(tp,
 417                            jiffies - tp->rcv_rtt_est.time,
 418                            1);
 419
 420 new_measure:
 421         tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
 422         tp->rcv_rtt_est.time = tcp_time_stamp;
 423 }
 424
 425 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb)
 426 {
 427         struct tcp_sock *tp = tcp_sk(sk);
 428         if (tp->rx_opt.rcv_tsecr &&
 429             (TCP_SKB_CB(skb)->end_seq -
 430              TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
 431                 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
 432 }
 433
 434 /*
 435  * This function should be called every time data is copied to user space.
 436  * It calculates the appropriate TCP receive buffer space.
 437  */
 438 void tcp_rcv_space_adjust(struct sock *sk)
 439 {
 440         struct tcp_sock *tp = tcp_sk(sk);
 441         int time;
 442         int space;
 443
 444         if (tp->rcvq_space.time == 0)
 445                 goto new_measure;
 446
 447         time = tcp_time_stamp - tp->rcvq_space.time;
 448         if (time < (tp->rcv_rtt_est.rtt >> 3) ||
 449             tp->rcv_rtt_est.rtt == 0)
 450                 return;
 451
 452         space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
 453
 454         space = max(tp->rcvq_space.space, space);
 455
 456         if (tp->rcvq_space.space != space) {
 457                 int rcvmem;
 458
 459                 tp->rcvq_space.space = space;
 460
 461                 if (sysctl_tcp_moderate_rcvbuf &&
 462                     !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
 463                         int new_clamp = space;
 464
 465                         /* Receive space grows, normalize in order to
 466                          * take into account packet headers and sk_buff
 467                          * structure overhead.
 468                          */
 469                         space /= tp->advmss;
 470                         if (!space)
 471                                 space = 1;
 472                         rcvmem = (tp->advmss + MAX_TCP_HEADER +
 473                                   16 + sizeof(struct sk_buff));
 474                         while (tcp_win_from_space(rcvmem) < tp->advmss)
 475                                 rcvmem += 128;
 476                         space *= rcvmem;
 477                         space = min(space, sysctl_tcp_rmem[2]);
 478                         if (space > sk->sk_rcvbuf) {
 479                                 sk->sk_rcvbuf = space;
 480
 481                                 /* Make the window clamp follow along.  */
 482                                 tp->window_clamp = new_clamp;
 483                         }
 484                 }
 485         }
 486
 487 new_measure:
 488         tp->rcvq_space.seq = tp->copied_seq;
 489         tp->rcvq_space.time = tcp_time_stamp;
 490 }
 491
 492 /* There is something which you must keep in mind when you analyze the
 493  * behavior of the tp->ato delayed ack timeout interval.  When a
 494  * connection starts up, we want to ack as quickly as possible.  The
 495  * problem is that "good" TCP's do slow start at the beginning of data
 496  * transmission.  The means that until we send the first few ACK's the
 497  * sender will sit on his end and only queue most of his data, because
 498  * he can only send snd_cwnd unacked packets at any given time.  For
 499  * each ACK we send, he increments snd_cwnd and transmits more of his
 500  * queue.  -DaveM
 501  */
 502 static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
 503 {
 504         struct inet_connection_sock *icsk = inet_csk(sk);
 505         u32 now;
 506
 507         inet_csk_schedule_ack(sk);
 508
 509         tcp_measure_rcv_mss(sk, skb);
 510
 511         tcp_rcv_rtt_measure(tp);
 512
 513         now = tcp_time_stamp;
 514
 515         if (!icsk->icsk_ack.ato) {
 516                 /* The _first_ data packet received, initialize
 517                  * delayed ACK engine.
 518                  */
 519                 tcp_incr_quickack(sk);
 520                 icsk->icsk_ack.ato = TCP_ATO_MIN;
 521         } else {
 522                 int m = now - icsk->icsk_ack.lrcvtime;
 523
 524                 if (m <= TCP_ATO_MIN/2) {
 525                         /* The fastest case is the first. */
 526                         icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
 527                 } else if (m < icsk->icsk_ack.ato) {
 528                         icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
 529                         if (icsk->icsk_ack.ato > icsk->icsk_rto)
 530                                 icsk->icsk_ack.ato = icsk->icsk_rto;
 531                 } else if (m > icsk->icsk_rto) {
 532                         /* Too long gap. Apparently sender failed to
 533                          * restart window, so that we send ACKs quickly.
 534                          */
 535                         tcp_incr_quickack(sk);
 536                         sk_stream_mem_reclaim(sk);
 537                 }
 538         }
 539         icsk->icsk_ack.lrcvtime = now;
 540
 541         TCP_ECN_check_ce(tp, skb);
 542
 543         if (skb->len >= 128)
 544                 tcp_grow_window(sk, tp, skb);
 545 }
 546
 547 /* Called to compute a smoothed rtt estimate. The data fed to this
 548  * routine either comes from timestamps, or from segments that were
 549  * known _not_ to have been retransmitted [see Karn/Partridge
 550  * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
 551  * piece by Van Jacobson.
 552  * NOTE: the next three routines used to be one big routine.
 553  * To save cycles in the RFC 1323 implementation it was better to break
 554  * it up into three procedures. -- erics
 555  */
 556 static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
 557 {
 558         struct tcp_sock *tp = tcp_sk(sk);
 559         long m = mrtt; /* RTT */
 560
 561         /*      The following amusing code comes from Jacobson's
 562          *      article in SIGCOMM '88.  Note that rtt and mdev
 563          *      are scaled versions of rtt and mean deviation.
 564          *      This is designed to be as fast as possible
 565          *      m stands for "measurement".
 566          *
 567          *      On a 1990 paper the rto value is changed to:
 568          *      RTO = rtt + 4 * mdev
 569          *
 570          * Funny. This algorithm seems to be very broken.
 571          * These formulae increase RTO, when it should be decreased, increase
 572          * too slowly, when it should be increased quickly, decrease too quickly
 573          * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
 574          * does not matter how to _calculate_ it. Seems, it was trap
 575          * that VJ failed to avoid. 8)
 576          */
 577         if(m == 0)
 578                 m = 1;
 579         if (tp->srtt != 0) {
 580                 m -= (tp->srtt >> 3);   /* m is now error in rtt est */
 581                 tp->srtt += m;          /* rtt = 7/8 rtt + 1/8 new */
 582                 if (m < 0) {
 583                         m = -m;         /* m is now abs(error) */
 584                         m -= (tp->mdev >> 2);   /* similar update on mdev */
 585                         /* This is similar to one of Eifel findings.
 586                          * Eifel blocks mdev updates when rtt decreases.
 587                          * This solution is a bit different: we use finer gain
 588                          * for mdev in this case (alpha*beta).
 589                          * Like Eifel it also prevents growth of rto,
 590                          * but also it limits too fast rto decreases,
 591                          * happening in pure Eifel.
 592                          */
 593                         if (m > 0)
 594                                 m >>= 3;
 595                 } else {
 596                         m -= (tp->mdev >> 2);   /* similar update on mdev */
 597                 }
 598                 tp->mdev += m;          /* mdev = 3/4 mdev + 1/4 new */
 599                 if (tp->mdev > tp->mdev_max) {
 600                         tp->mdev_max = tp->mdev;
 601                         if (tp->mdev_max > tp->rttvar)
 602                                 tp->rttvar = tp->mdev_max;
 603                 }
 604                 if (after(tp->snd_una, tp->rtt_seq)) {
 605                         if (tp->mdev_max < tp->rttvar)
 606                                 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
 607                         tp->rtt_seq = tp->snd_nxt;
 608                         tp->mdev_max = TCP_RTO_MIN;
 609                 }
 610         } else {
 611                 /* no previous measure. */
 612                 tp->srtt = m<<3;        /* take the measured time to be rtt */
 613                 tp->mdev = m<<1;        /* make sure rto = 3*rtt */
 614                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
 615                 tp->rtt_seq = tp->snd_nxt;
 616         }
 617 }
 618
 619 /* Calculate rto without backoff.  This is the second half of Van Jacobson's
 620  * routine referred to above.
 621  */
 622 static inline void tcp_set_rto(struct sock *sk)
 623 {
 624         const struct tcp_sock *tp = tcp_sk(sk);
 625         /* Old crap is replaced with new one. 8)
 626          *
 627          * More seriously:
 628          * 1. If rtt variance happened to be less 50msec, it is hallucination.
 629          *    It cannot be less due to utterly erratic ACK generation made
 630          *    at least by solaris and freebsd. "Erratic ACKs" has _nothing_
 631          *    to do with delayed acks, because at cwnd>2 true delack timeout
 632          *    is invisible. Actually, Linux-2.4 also generates erratic
 633          *    ACKs in some circumstances.
 634          */
 635         inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
 636
 637         /* 2. Fixups made earlier cannot be right.
 638          *    If we do not estimate RTO correctly without them,
 639          *    all the algo is pure shit and should be replaced
 640          *    with correct one. It is exactly, which we pretend to do.
 641          */
 642 }
 643
 644 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
 645  * guarantees that rto is higher.
 646  */
 647 static inline void tcp_bound_rto(struct sock *sk)
 648 {
 649         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
 650                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
 651 }
 652
 653 /* Save metrics learned by this TCP session.
 654    This function is called only, when TCP finishes successfully
 655    i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
 656  */
 657 void tcp_update_metrics(struct sock *sk)
 658 {
 659         struct tcp_sock *tp = tcp_sk(sk);
 660         struct dst_entry *dst = __sk_dst_get(sk);
 661
 662         if (sysctl_tcp_nometrics_save)
 663                 return;
 664
 665         dst_confirm(dst);
 666
 667         if (dst && (dst->flags&DST_HOST)) {
 668                 const struct inet_connection_sock *icsk = inet_csk(sk);
 669                 int m;
 670
 671                 if (icsk->icsk_backoff || !tp->srtt) {
 672                         /* This session failed to estimate rtt. Why?
 673                          * Probably, no packets returned in time.
 674                          * Reset our results.
 675                          */
 676                         if (!(dst_metric_locked(dst, RTAX_RTT)))
 677                                 dst->metrics[RTAX_RTT-1] = 0;
 678                         return;
 679                 }
 680
 681                 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
 682
 683                 /* If newly calculated rtt larger than stored one,
 684                  * store new one. Otherwise, use EWMA. Remember,
 685                  * rtt overestimation is always better than underestimation.
 686                  */
 687                 if (!(dst_metric_locked(dst, RTAX_RTT))) {
 688                         if (m <= 0)
 689                                 dst->metrics[RTAX_RTT-1] = tp->srtt;
 690                         else
 691                                 dst->metrics[RTAX_RTT-1] -= (m>>3);
 692                 }
 693
 694                 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
 695                         if (m < 0)
 696                                 m = -m;
 697
 698                         /* Scale deviation to rttvar fixed point */
 699                         m >>= 1;
 700                         if (m < tp->mdev)
 701                                 m = tp->mdev;
 702
 703                         if (m >= dst_metric(dst, RTAX_RTTVAR))
 704                                 dst->metrics[RTAX_RTTVAR-1] = m;
 705                         else
 706                                 dst->metrics[RTAX_RTTVAR-1] -=
 707                                         (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
 708                 }
 709
 710                 if (tp->snd_ssthresh >= 0xFFFF) {
 711                         /* Slow start still did not finish. */
 712                         if (dst_metric(dst, RTAX_SSTHRESH) &&
 713                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
 714                             (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
 715                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
 716                         if (!dst_metric_locked(dst, RTAX_CWND) &&
 717                             tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
 718                                 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
 719                 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
 720                            icsk->icsk_ca_state == TCP_CA_Open) {
 721                         /* Cong. avoidance phase, cwnd is reliable. */
 722                         if (!dst_metric_locked(dst, RTAX_SSTHRESH))
 723                                 dst->metrics[RTAX_SSTHRESH-1] =
 724                                         max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
 725                         if (!dst_metric_locked(dst, RTAX_CWND))
 726                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
 727                 } else {
 728                         /* Else slow start did not finish, cwnd is non-sense,
 729                            ssthresh may be also invalid.
 730                          */
 731                         if (!dst_metric_locked(dst, RTAX_CWND))
 732                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
 733                         if (dst->metrics[RTAX_SSTHRESH-1] &&
 734                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
 735                             tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
 736                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
 737                 }
 738
 739                 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
 740                         if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
 741                             tp->reordering != sysctl_tcp_reordering)
 742                                 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
 743                 }
 744         }
 745 }
 746
 747 /* Numbers are taken from RFC2414.  */
 748 __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
 749 {
 750         __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
 751
 752         if (!cwnd) {
 753                 if (tp->mss_cache > 1460)
 754                         cwnd = 2;
 755                 else
 756                         cwnd = (tp->mss_cache > 1095) ? 3 : 4;
 757         }
 758         return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
 759 }
 760
 761 /* Set slow start threshold and cwnd not falling to slow start */
 762 void tcp_enter_cwr(struct sock *sk)
 763 {
 764         struct tcp_sock *tp = tcp_sk(sk);
 765
 766         tp->prior_ssthresh = 0;
 767         tp->bytes_acked = 0;
 768         if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
 769                 tp->undo_marker = 0;
 770                 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
 771                 tp->snd_cwnd = min(tp->snd_cwnd,
 772                                    tcp_packets_in_flight(tp) + 1U);
 773                 tp->snd_cwnd_cnt = 0;
 774                 tp->high_seq = tp->snd_nxt;
 775                 tp->snd_cwnd_stamp = tcp_time_stamp;
 776                 TCP_ECN_queue_cwr(tp);
 777
 778                 tcp_set_ca_state(sk, TCP_CA_CWR);
 779         }
 780 }
 781
 782 /* Initialize metrics on socket. */
 783
 784 static void tcp_init_metrics(struct sock *sk)
 785 {
 786         struct tcp_sock *tp = tcp_sk(sk);
 787         struct dst_entry *dst = __sk_dst_get(sk);
 788
 789         if (dst == NULL)
 790                 goto reset;
 791
 792         dst_confirm(dst);
 793
 794         if (dst_metric_locked(dst, RTAX_CWND))
 795                 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
 796         if (dst_metric(dst, RTAX_SSTHRESH)) {
 797                 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
 798                 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
 799                         tp->snd_ssthresh = tp->snd_cwnd_clamp;
 800         }
 801         if (dst_metric(dst, RTAX_REORDERING) &&
 802             tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
 803                 tp->rx_opt.sack_ok &= ~2;
 804                 tp->reordering = dst_metric(dst, RTAX_REORDERING);
 805         }
 806
 807         if (dst_metric(dst, RTAX_RTT) == 0)
 808                 goto reset;
 809
 810         if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
 811                 goto reset;
 812
 813         /* Initial rtt is determined from SYN,SYN-ACK.
 814          * The segment is small and rtt may appear much
 815          * less than real one. Use per-dst memory
 816          * to make it more realistic.
 817          *
 818          * A bit of theory. RTT is time passed after "normal" sized packet
 819          * is sent until it is ACKed. In normal circumstances sending small
 820          * packets force peer to delay ACKs and calculation is correct too.
 821          * The algorithm is adaptive and, provided we follow specs, it
 822          * NEVER underestimate RTT. BUT! If peer tries to make some clever
 823          * tricks sort of "quick acks" for time long enough to decrease RTT
 824          * to low value, and then abruptly stops to do it and starts to delay
 825          * ACKs, wait for troubles.
 826          */
 827         if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
 828                 tp->srtt = dst_metric(dst, RTAX_RTT);
 829                 tp->rtt_seq = tp->snd_nxt;
 830         }
 831         if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
 832                 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
 833                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
 834         }
 835         tcp_set_rto(sk);
 836         tcp_bound_rto(sk);
 837         if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
 838                 goto reset;
 839         tp->snd_cwnd = tcp_init_cwnd(tp, dst);
 840         tp->snd_cwnd_stamp = tcp_time_stamp;
 841         return;
 842
 843 reset:
 844         /* Play conservative. If timestamps are not
 845          * supported, TCP will fail to recalculate correct
 846          * rtt, if initial rto is too small. FORGET ALL AND RESET!
 847          */
 848         if (!tp->rx_opt.saw_tstamp && tp->srtt) {
 849                 tp->srtt = 0;
 850                 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
 851                 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
 852         }
 853 }
 854
 855 static void tcp_update_reordering(struct sock *sk, const int metric,
 856                                   const int ts)
 857 {
 858         struct tcp_sock *tp = tcp_sk(sk);
 859         if (metric > tp->reordering) {
 860                 tp->reordering = min(TCP_MAX_REORDERING, metric);
 861
 862                 /* This exciting event is worth to be remembered. 8) */
 863                 if (ts)
 864                         NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
 865                 else if (IsReno(tp))
 866                         NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
 867                 else if (IsFack(tp))
 868                         NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
 869                 else
 870                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
 871 #if FASTRETRANS_DEBUG > 1
 872                 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
 873                        tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
 874                        tp->reordering,
 875                        tp->fackets_out,
 876                        tp->sacked_out,
 877                        tp->undo_marker ? tp->undo_retrans : 0);
 878 #endif
 879                 /* Disable FACK yet. */
 880                 tp->rx_opt.sack_ok &= ~2;
 881         }
 882 }
 883
 884 /* This procedure tags the retransmission queue when SACKs arrive.
 885  *
 886  * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
 887  * Packets in queue with these bits set are counted in variables
 888  * sacked_out, retrans_out and lost_out, correspondingly.
 889  *
 890  * Valid combinations are:
 891  * Tag  InFlight        Description
 892  * 0    1               - orig segment is in flight.
 893  * S    0               - nothing flies, orig reached receiver.
 894  * L    0               - nothing flies, orig lost by net.
 895  * R    2               - both orig and retransmit are in flight.
 896  * L|R  1               - orig is lost, retransmit is in flight.
 897  * S|R  1               - orig reached receiver, retrans is still in flight.
 898  * (L|S|R is logically valid, it could occur when L|R is sacked,
 899  *  but it is equivalent to plain S and code short-curcuits it to S.
 900  *  L|S is logically invalid, it would mean -1 packet in flight 8))
 901  *
 902  * These 6 states form finite state machine, controlled by the following events:
 903  * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
 904  * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
 905  * 3. Loss detection event of one of three flavors:
 906  *      A. Scoreboard estimator decided the packet is lost.
 907  *         A'. Reno "three dupacks" marks head of queue lost.
 908  *         A''. Its FACK modfication, head until snd.fack is lost.
 909  *      B. SACK arrives sacking data transmitted after never retransmitted
 910  *         hole was sent out.
 911  *      C. SACK arrives sacking SND.NXT at the moment, when the
 912  *         segment was retransmitted.
 913  * 4. D-SACK added new rule: D-SACK changes any tag to S.
 914  *
 915  * It is pleasant to note, that state diagram turns out to be commutative,
 916  * so that we are allowed not to be bothered by order of our actions,
 917  * when multiple events arrive simultaneously. (see the function below).
 918  *
 919  * Reordering detection.
 920  * --------------------
 921  * Reordering metric is maximal distance, which a packet can be displaced
 922  * in packet stream. With SACKs we can estimate it:
 923  *
 924  * 1. SACK fills old hole and the corresponding segment was not
 925  *    ever retransmitted -> reordering. Alas, we cannot use it
 926  *    when segment was retransmitted.
 927  * 2. The last flaw is solved with D-SACK. D-SACK arrives
 928  *    for retransmitted and already SACKed segment -> reordering..
 929  * Both of these heuristics are not used in Loss state, when we cannot
 930  * account for retransmits accurately.
 931  */
 932 static int
 933 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
 934 {
 935         const struct inet_connection_sock *icsk = inet_csk(sk);
 936         struct tcp_sock *tp = tcp_sk(sk);
 937         unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
 938         struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
 939         struct sk_buff *cached_skb;
 940         int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
 941         int reord = tp->packets_out;
 942         int prior_fackets;
 943         u32 lost_retrans = 0;
 944         int flag = 0;
 945         int dup_sack = 0;
 946         int cached_fack_count;
 947         int i;
 948         int first_sack_index;
 949
 950         if (!tp->sacked_out)
 951                 tp->fackets_out = 0;
 952         prior_fackets = tp->fackets_out;
 953
 954         /* SACK fastpath:
 955          * if the only SACK change is the increase of the end_seq of
 956          * the first block then only apply that SACK block
 957          * and use retrans queue hinting otherwise slowpath */
 958         flag = 1;
 959         for (i = 0; i< num_sacks; i++) {
 960                 __u32 start_seq = ntohl(sp[i].start_seq);
 961                 __u32 end_seq =  ntohl(sp[i].end_seq);
 962
 963                 if (i == 0){
 964                         if (tp->recv_sack_cache[i].start_seq != start_seq)
 965                                 flag = 0;
 966                 } else {
 967                         if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
 968                             (tp->recv_sack_cache[i].end_seq != end_seq))
 969                                 flag = 0;
 970                 }
 971                 tp->recv_sack_cache[i].start_seq = start_seq;
 972                 tp->recv_sack_cache[i].end_seq = end_seq;
 973
 974                 /* Check for D-SACK. */
 975                 if (i == 0) {
 976                         u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
 977
 978                         if (before(start_seq, ack)) {
 979                                 dup_sack = 1;
 980                                 tp->rx_opt.sack_ok |= 4;
 981                                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
 982                         } else if (num_sacks > 1 &&
 983                                    !after(end_seq, ntohl(sp[1].end_seq)) &&
 984                                    !before(start_seq, ntohl(sp[1].start_seq))) {
 985                                 dup_sack = 1;
 986                                 tp->rx_opt.sack_ok |= 4;
 987                                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
 988                         }
 989
 990                         /* D-SACK for already forgotten data...
 991                          * Do dumb counting. */
 992                         if (dup_sack &&
 993                             !after(end_seq, prior_snd_una) &&
 994                             after(end_seq, tp->undo_marker))
 995                                 tp->undo_retrans--;
 996
 997                         /* Eliminate too old ACKs, but take into
 998                          * account more or less fresh ones, they can
 999                          * contain valid SACK info.
1000                          */
1001                         if (before(ack, prior_snd_una - tp->max_window))
1002                                 return 0;
1003                 }
1004         }
1005
1006         first_sack_index = 0;
1007         if (flag)
1008                 num_sacks = 1;
1009         else {
1010                 int j;
1011                 tp->fastpath_skb_hint = NULL;
1012
1013                 /* order SACK blocks to allow in order walk of the retrans queue */
1014                 for (i = num_sacks-1; i > 0; i--) {
1015                         for (j = 0; j < i; j++){
1016                                 if (after(ntohl(sp[j].start_seq),
1017                                           ntohl(sp[j+1].start_seq))){
1018                                         struct tcp_sack_block_wire tmp;
1019
1020                                         tmp = sp[j];
1021                                         sp[j] = sp[j+1];
1022                                         sp[j+1] = tmp;
1023
1024                                         /* Track where the first SACK block goes to */
1025                                         if (j == first_sack_index)
1026                                                 first_sack_index = j+1;
1027                                 }
1028
1029                         }
1030                 }
1031         }
1032
1033         /* clear flag as used for different purpose in following code */
1034         flag = 0;
1035
1036         /* Use SACK fastpath hint if valid */
1037         cached_skb = tp->fastpath_skb_hint;
1038         cached_fack_count = tp->fastpath_cnt_hint;
1039         if (!cached_skb) {
1040                 cached_skb = sk->sk_write_queue.next;
1041                 cached_fack_count = 0;
1042         }
1043
1044         for (i=0; i<num_sacks; i++, sp++) {
1045                 struct sk_buff *skb;
1046                 __u32 start_seq = ntohl(sp->start_seq);
1047                 __u32 end_seq = ntohl(sp->end_seq);
1048                 int fack_count;
1049
1050                 skb = cached_skb;
1051                 fack_count = cached_fack_count;
1052
1053                 /* Event "B" in the comment above. */
1054                 if (after(end_seq, tp->high_seq))
1055                         flag |= FLAG_DATA_LOST;
1056
1057                 sk_stream_for_retrans_queue_from(skb, sk) {
1058                         int in_sack, pcount;
1059                         u8 sacked;
1060
1061                         cached_skb = skb;
1062                         cached_fack_count = fack_count;
1063                         if (i == first_sack_index) {
1064                                 tp->fastpath_skb_hint = skb;
1065                                 tp->fastpath_cnt_hint = fack_count;
1066                         }
1067
1068                         /* The retransmission queue is always in order, so
1069                          * we can short-circuit the walk early.
1070                          */
1071                         if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1072                                 break;
1073
1074                         in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1075                                 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1076
1077                         pcount = tcp_skb_pcount(skb);
1078
1079                         if (pcount > 1 && !in_sack &&
1080                             after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1081                                 unsigned int pkt_len;
1082
1083                                 in_sack = !after(start_seq,
1084                                                  TCP_SKB_CB(skb)->seq);
1085
1086                                 if (!in_sack)
1087                                         pkt_len = (start_seq -
1088                                                    TCP_SKB_CB(skb)->seq);
1089                                 else
1090                                         pkt_len = (end_seq -
1091                                                    TCP_SKB_CB(skb)->seq);
1092                                 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size))
1093                                         break;
1094                                 pcount = tcp_skb_pcount(skb);
1095                         }
1096
1097                         fack_count += pcount;
1098
1099                         sacked = TCP_SKB_CB(skb)->sacked;
1100
1101                         /* Account D-SACK for retransmitted packet. */
1102                         if ((dup_sack && in_sack) &&
1103                             (sacked & TCPCB_RETRANS) &&
1104                             after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1105                                 tp->undo_retrans--;
1106
1107                         /* The frame is ACKed. */
1108                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1109                                 if (sacked&TCPCB_RETRANS) {
1110                                         if ((dup_sack && in_sack) &&
1111                                             (sacked&TCPCB_SACKED_ACKED))
1112                                                 reord = min(fack_count, reord);
1113                                 } else {
1114                                         /* If it was in a hole, we detected reordering. */
1115                                         if (fack_count < prior_fackets &&
1116                                             !(sacked&TCPCB_SACKED_ACKED))
1117                                                 reord = min(fack_count, reord);
1118                                 }
1119
1120                                 /* Nothing to do; acked frame is about to be dropped. */
1121                                 continue;
1122                         }
1123
1124                         if ((sacked&TCPCB_SACKED_RETRANS) &&
1125                             after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1126                             (!lost_retrans || after(end_seq, lost_retrans)))
1127                                 lost_retrans = end_seq;
1128
1129                         if (!in_sack)
1130                                 continue;
1131
1132                         if (!(sacked&TCPCB_SACKED_ACKED)) {
1133                                 if (sacked & TCPCB_SACKED_RETRANS) {
1134                                         /* If the segment is not tagged as lost,
1135                                          * we do not clear RETRANS, believing
1136                                          * that retransmission is still in flight.
1137                                          */
1138                                         if (sacked & TCPCB_LOST) {
1139                                                 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1140                                                 tp->lost_out -= tcp_skb_pcount(skb);
1141                                                 tp->retrans_out -= tcp_skb_pcount(skb);
1142
1143                                                 /* clear lost hint */
1144                                                 tp->retransmit_skb_hint = NULL;
1145                                         }
1146                                 } else {
1147                                         /* New sack for not retransmitted frame,
1148                                          * which was in hole. It is reordering.
1149                                          */
1150                                         if (!(sacked & TCPCB_RETRANS) &&
1151                                             fack_count < prior_fackets)
1152                                                 reord = min(fack_count, reord);
1153
1154                                         if (sacked & TCPCB_LOST) {
1155                                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1156                                                 tp->lost_out -= tcp_skb_pcount(skb);
1157
1158                                                 /* clear lost hint */
1159                                                 tp->retransmit_skb_hint = NULL;
1160                                         }
1161                                 }
1162
1163                                 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1164                                 flag |= FLAG_DATA_SACKED;
1165                                 tp->sacked_out += tcp_skb_pcount(skb);
1166
1167                                 if (fack_count > tp->fackets_out)
1168                                         tp->fackets_out = fack_count;
1169                         } else {
1170                                 if (dup_sack && (sacked&TCPCB_RETRANS))
1171                                         reord = min(fack_count, reord);
1172                         }
1173
1174                         /* D-SACK. We can detect redundant retransmission
1175                          * in S|R and plain R frames and clear it.
1176                          * undo_retrans is decreased above, L|R frames
1177                          * are accounted above as well.
1178                          */
1179                         if (dup_sack &&
1180                             (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1181                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1182                                 tp->retrans_out -= tcp_skb_pcount(skb);
1183                                 tp->retransmit_skb_hint = NULL;
1184                         }
1185                 }
1186         }
1187
1188         /* Check for lost retransmit. This superb idea is
1189          * borrowed from "ratehalving". Event "C".
1190          * Later note: FACK people cheated me again 8),
1191          * we have to account for reordering! Ugly,
1192          * but should help.
1193          */
1194         if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
1195                 struct sk_buff *skb;
1196
1197                 sk_stream_for_retrans_queue(skb, sk) {
1198                         if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1199                                 break;
1200                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1201                                 continue;
1202                         if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1203                             after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1204                             (IsFack(tp) ||
1205                              !before(lost_retrans,
1206                                      TCP_SKB_CB(skb)->ack_seq + tp->reordering *
1207                                      tp->mss_cache))) {
1208                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1209                                 tp->retrans_out -= tcp_skb_pcount(skb);
1210
1211                                 /* clear lost hint */
1212                                 tp->retransmit_skb_hint = NULL;
1213
1214                                 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1215                                         tp->lost_out += tcp_skb_pcount(skb);
1216                                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1217                                         flag |= FLAG_DATA_SACKED;
1218                                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1219                                 }
1220                         }
1221                 }
1222         }
1223
1224         tp->left_out = tp->sacked_out + tp->lost_out;
1225
1226         if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss)
1227                 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
1228
1229 #if FASTRETRANS_DEBUG > 0
1230         BUG_TRAP((int)tp->sacked_out >= 0);
1231         BUG_TRAP((int)tp->lost_out >= 0);
1232         BUG_TRAP((int)tp->retrans_out >= 0);
1233         BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1234 #endif
1235         return flag;
1236 }
1237
1238 /* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1239  * segments to see from the next ACKs whether any data was really missing.
1240  * If the RTO was spurious, new ACKs should arrive.
1241  */
1242 void tcp_enter_frto(struct sock *sk)
1243 {
1244         const struct inet_connection_sock *icsk = inet_csk(sk);
1245         struct tcp_sock *tp = tcp_sk(sk);
1246         struct sk_buff *skb;
1247
1248         tp->frto_counter = 1;
1249
1250         if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
1251             tp->snd_una == tp->high_seq ||
1252             (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1253                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1254                 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1255                 tcp_ca_event(sk, CA_EVENT_FRTO);
1256         }
1257
1258         /* Have to clear retransmission markers here to keep the bookkeeping
1259          * in shape, even though we are not yet in Loss state.
1260          * If something was really lost, it is eventually caught up
1261          * in tcp_enter_frto_loss.
1262          */
1263         tp->retrans_out = 0;
1264         tp->undo_marker = tp->snd_una;
1265         tp->undo_retrans = 0;
1266
1267         sk_stream_for_retrans_queue(skb, sk) {
1268                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1269         }
1270         tcp_sync_left_out(tp);
1271
1272         tcp_set_ca_state(sk, TCP_CA_Open);
1273         tp->frto_highmark = tp->snd_nxt;
1274 }
1275
1276 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1277  * which indicates that we should follow the traditional RTO recovery,
1278  * i.e. mark everything lost and do go-back-N retransmission.
1279  */
1280 static void tcp_enter_frto_loss(struct sock *sk)
1281 {
1282         struct tcp_sock *tp = tcp_sk(sk);
1283         struct sk_buff *skb;
1284         int cnt = 0;
1285
1286         tp->sacked_out = 0;
1287         tp->lost_out = 0;
1288         tp->fackets_out = 0;
1289
1290         sk_stream_for_retrans_queue(skb, sk) {
1291                 cnt += tcp_skb_pcount(skb);
1292                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1293                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1294
1295                         /* Do not mark those segments lost that were
1296                          * forward transmitted after RTO
1297                          */
1298                         if (!after(TCP_SKB_CB(skb)->end_seq,
1299                                    tp->frto_highmark)) {
1300                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1301                                 tp->lost_out += tcp_skb_pcount(skb);
1302                         }
1303                 } else {
1304                         tp->sacked_out += tcp_skb_pcount(skb);
1305                         tp->fackets_out = cnt;
1306                 }
1307         }
1308         tcp_sync_left_out(tp);
1309
1310         tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1311         tp->snd_cwnd_cnt = 0;
1312         tp->snd_cwnd_stamp = tcp_time_stamp;
1313         tp->undo_marker = 0;
1314         tp->frto_counter = 0;
1315
1316         tp->reordering = min_t(unsigned int, tp->reordering,
1317                                              sysctl_tcp_reordering);
1318         tcp_set_ca_state(sk, TCP_CA_Loss);
1319         tp->high_seq = tp->frto_highmark;
1320         TCP_ECN_queue_cwr(tp);
1321
1322         clear_all_retrans_hints(tp);
1323 }
1324
1325 void tcp_clear_retrans(struct tcp_sock *tp)
1326 {
1327         tp->left_out = 0;
1328         tp->retrans_out = 0;
1329
1330         tp->fackets_out = 0;
1331         tp->sacked_out = 0;
1332         tp->lost_out = 0;
1333
1334         tp->undo_marker = 0;
1335         tp->undo_retrans = 0;
1336 }
1337
1338 /* Enter Loss state. If "how" is not zero, forget all SACK information
1339  * and reset tags completely, otherwise preserve SACKs. If receiver
1340  * dropped its ofo queue, we will know this due to reneging detection.
1341  */
1342 void tcp_enter_loss(struct sock *sk, int how)
1343 {
1344         const struct inet_connection_sock *icsk = inet_csk(sk);
1345         struct tcp_sock *tp = tcp_sk(sk);
1346         struct sk_buff *skb;
1347         int cnt = 0;
1348
1349         /* Reduce ssthresh if it has not yet been made inside this window. */
1350         if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1351             (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1352                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1353                 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1354                 tcp_ca_event(sk, CA_EVENT_LOSS);
1355         }
1356         tp->snd_cwnd       = 1;
1357         tp->snd_cwnd_cnt   = 0;
1358         tp->snd_cwnd_stamp = tcp_time_stamp;
1359
1360         tp->bytes_acked = 0;
1361         tcp_clear_retrans(tp);
1362
1363         /* Push undo marker, if it was plain RTO and nothing
1364          * was retransmitted. */
1365         if (!how)
1366                 tp->undo_marker = tp->snd_una;
1367
1368         sk_stream_for_retrans_queue(skb, sk) {
1369                 cnt += tcp_skb_pcount(skb);
1370                 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1371                         tp->undo_marker = 0;
1372                 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1373                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1374                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1375                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1376                         tp->lost_out += tcp_skb_pcount(skb);
1377                 } else {
1378                         tp->sacked_out += tcp_skb_pcount(skb);
1379                         tp->fackets_out = cnt;
1380                 }
1381         }
1382         tcp_sync_left_out(tp);
1383
1384         tp->reordering = min_t(unsigned int, tp->reordering,
1385                                              sysctl_tcp_reordering);
1386         tcp_set_ca_state(sk, TCP_CA_Loss);
1387         tp->high_seq = tp->snd_nxt;
1388         TCP_ECN_queue_cwr(tp);
1389
1390         clear_all_retrans_hints(tp);
1391 }
1392
1393 static int tcp_check_sack_reneging(struct sock *sk)
1394 {
1395         struct sk_buff *skb;
1396
1397         /* If ACK arrived pointing to a remembered SACK,
1398          * it means that our remembered SACKs do not reflect
1399          * real state of receiver i.e.
1400          * receiver _host_ is heavily congested (or buggy).
1401          * Do processing similar to RTO timeout.
1402          */
1403         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1404             (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
1405                 struct inet_connection_sock *icsk = inet_csk(sk);
1406                 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1407
1408                 tcp_enter_loss(sk, 1);
1409                 icsk->icsk_retransmits++;
1410                 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
1411                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
1412                                           icsk->icsk_rto, TCP_RTO_MAX);
1413                 return 1;
1414         }
1415         return 0;
1416 }
1417
1418 static inline int tcp_fackets_out(struct tcp_sock *tp)
1419 {
1420         return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1421 }
1422
1423 static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
1424 {
1425         return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
1426 }
1427
1428 static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1429 {
1430         return tp->packets_out &&
1431                tcp_skb_timedout(sk, skb_peek(&sk->sk_write_queue));
1432 }
1433
1434 /* Linux NewReno/SACK/FACK/ECN state machine.
1435  * --------------------------------------
1436  *
1437  * "Open"       Normal state, no dubious events, fast path.
1438  * "Disorder"   In all the respects it is "Open",
1439  *              but requires a bit more attention. It is entered when
1440  *              we see some SACKs or dupacks. It is split of "Open"
1441  *              mainly to move some processing from fast path to slow one.
1442  * "CWR"        CWND was reduced due to some Congestion Notification event.
1443  *              It can be ECN, ICMP source quench, local device congestion.
1444  * "Recovery"   CWND was reduced, we are fast-retransmitting.
1445  * "Loss"       CWND was reduced due to RTO timeout or SACK reneging.
1446  *
1447  * tcp_fastretrans_alert() is entered:
1448  * - each incoming ACK, if state is not "Open"
1449  * - when arrived ACK is unusual, namely:
1450  *      * SACK
1451  *      * Duplicate ACK.
1452  *      * ECN ECE.
1453  *
1454  * Counting packets in flight is pretty simple.
1455  *
1456  *      in_flight = packets_out - left_out + retrans_out
1457  *
1458  *      packets_out is SND.NXT-SND.UNA counted in packets.
1459  *
1460  *      retrans_out is number of retransmitted segments.
1461  *
1462  *      left_out is number of segments left network, but not ACKed yet.
1463  *
1464  *              left_out = sacked_out + lost_out
1465  *
1466  *     sacked_out: Packets, which arrived to receiver out of order
1467  *                 and hence not ACKed. With SACKs this number is simply
1468  *                 amount of SACKed data. Even without SACKs
1469  *                 it is easy to give pretty reliable estimate of this number,
1470  *                 counting duplicate ACKs.
1471  *
1472  *       lost_out: Packets lost by network. TCP has no explicit
1473  *                 "loss notification" feedback from network (for now).
1474  *                 It means that this number can be only _guessed_.
1475  *                 Actually, it is the heuristics to predict lossage that
1476  *                 distinguishes different algorithms.
1477  *
1478  *      F.e. after RTO, when all the queue is considered as lost,
1479  *      lost_out = packets_out and in_flight = retrans_out.
1480  *
1481  *              Essentially, we have now two algorithms counting
1482  *              lost packets.
1483  *
1484  *              FACK: It is the simplest heuristics. As soon as we decided
1485  *              that something is lost, we decide that _all_ not SACKed
1486  *              packets until the most forward SACK are lost. I.e.
1487  *              lost_out = fackets_out - sacked_out and left_out = fackets_out.
1488  *              It is absolutely correct estimate, if network does not reorder
1489  *              packets. And it loses any connection to reality when reordering
1490  *              takes place. We use FACK by default until reordering
1491  *              is suspected on the path to this destination.
1492  *
1493  *              NewReno: when Recovery is entered, we assume that one segment
1494  *              is lost (classic Reno). While we are in Recovery and
1495  *              a partial ACK arrives, we assume that one more packet
1496  *              is lost (NewReno). This heuristics are the same in NewReno
1497  *              and SACK.
1498  *
1499  *  Imagine, that's all! Forget about all this shamanism about CWND inflation
1500  *  deflation etc. CWND is real congestion window, never inflated, changes
1501  *  only according to classic VJ rules.
1502  *
1503  * Really tricky (and requiring careful tuning) part of algorithm
1504  * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1505  * The first determines the moment _when_ we should reduce CWND and,
1506  * hence, slow down forward transmission. In fact, it determines the moment
1507  * when we decide that hole is caused by loss, rather than by a reorder.
1508  *
1509  * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1510  * holes, caused by lost packets.
1511  *
1512  * And the most logically complicated part of algorithm is undo
1513  * heuristics. We detect false retransmits due to both too early
1514  * fast retransmit (reordering) and underestimated RTO, analyzing
1515  * timestamps and D-SACKs. When we detect that some segments were
1516  * retransmitted by mistake and CWND reduction was wrong, we undo
1517  * window reduction and abort recovery phase. This logic is hidden
1518  * inside several functions named tcp_try_undo_<something>.
1519  */
1520
1521 /* This function decides, when we should leave Disordered state
1522  * and enter Recovery phase, reducing congestion window.
1523  *
1524  * Main question: may we further continue forward transmission
1525  * with the same cwnd?
1526  */
1527 static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1528 {
1529         __u32 packets_out;
1530
1531         /* Trick#1: The loss is proven. */
1532         if (tp->lost_out)
1533                 return 1;
1534
1535         /* Not-A-Trick#2 : Classic rule... */
1536         if (tcp_fackets_out(tp) > tp->reordering)
1537                 return 1;
1538
1539         /* Trick#3 : when we use RFC2988 timer restart, fast
1540          * retransmit can be triggered by timeout of queue head.
1541          */
1542         if (tcp_head_timedout(sk, tp))
1543                 return 1;
1544
1545         /* Trick#4: It is still not OK... But will it be useful to delay
1546          * recovery more?
1547          */
1548         packets_out = tp->packets_out;
1549         if (packets_out <= tp->reordering &&
1550             tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1551             !tcp_may_send_now(sk, tp)) {
1552                 /* We have nothing to send. This connection is limited
1553                  * either by receiver window or by application.
1554                  */
1555                 return 1;
1556         }
1557
1558         return 0;
1559 }
1560
1561 /* If we receive more dupacks than we expected counting segments
1562  * in assumption of absent reordering, interpret this as reordering.
1563  * The only another reason could be bug in receiver TCP.
1564  */
1565 static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1566 {
1567         struct tcp_sock *tp = tcp_sk(sk);
1568         u32 holes;
1569
1570         holes = max(tp->lost_out, 1U);
1571         holes = min(holes, tp->packets_out);
1572
1573         if ((tp->sacked_out + holes) > tp->packets_out) {
1574                 tp->sacked_out = tp->packets_out - holes;
1575                 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1576         }
1577 }
1578
1579 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1580
1581 static void tcp_add_reno_sack(struct sock *sk)
1582 {
1583         struct tcp_sock *tp = tcp_sk(sk);
1584         tp->sacked_out++;
1585         tcp_check_reno_reordering(sk, 0);
1586         tcp_sync_left_out(tp);
1587 }
1588
1589 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1590
1591 static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1592 {
1593         if (acked > 0) {
1594                 /* One ACK acked hole. The rest eat duplicate ACKs. */
1595                 if (acked-1 >= tp->sacked_out)
1596                         tp->sacked_out = 0;
1597                 else
1598                         tp->sacked_out -= acked-1;
1599         }
1600         tcp_check_reno_reordering(sk, acked);
1601         tcp_sync_left_out(tp);
1602 }
1603
1604 static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1605 {
1606         tp->sacked_out = 0;
1607         tp->left_out = tp->lost_out;
1608 }
1609
1610 /* Mark head of queue up as lost. */
1611 static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1612                                int packets, u32 high_seq)
1613 {
1614         struct sk_buff *skb;
1615         int cnt;
1616
1617         BUG_TRAP(packets <= tp->packets_out);
1618         if (tp->lost_skb_hint) {
1619                 skb = tp->lost_skb_hint;
1620                 cnt = tp->lost_cnt_hint;
1621         } else {
1622                 skb = sk->sk_write_queue.next;
1623                 cnt = 0;
1624         }
1625
1626         sk_stream_for_retrans_queue_from(skb, sk) {
1627                 /* TODO: do this better */
1628                 /* this is not the most efficient way to do this... */
1629                 tp->lost_skb_hint = skb;
1630                 tp->lost_cnt_hint = cnt;
1631                 cnt += tcp_skb_pcount(skb);
1632                 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq))
1633                         break;
1634                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1635                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1636                         tp->lost_out += tcp_skb_pcount(skb);
1637
1638                         /* clear xmit_retransmit_queue hints
1639                          *  if this is beyond hint */
1640                         if(tp->retransmit_skb_hint != NULL &&
1641                            before(TCP_SKB_CB(skb)->seq,
1642                                   TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) {
1643
1644                                 tp->retransmit_skb_hint = NULL;
1645                         }
1646                 }
1647         }
1648         tcp_sync_left_out(tp);
1649 }
1650
1651 /* Account newly detected lost packet(s) */
1652
1653 static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1654 {
1655         if (IsFack(tp)) {
1656                 int lost = tp->fackets_out - tp->reordering;
1657                 if (lost <= 0)
1658                         lost = 1;
1659                 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1660         } else {
1661                 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1662         }
1663
1664         /* New heuristics: it is possible only after we switched
1665          * to restart timer each time when something is ACKed.
1666          * Hence, we can detect timed out packets during fast
1667          * retransmit without falling to slow start.
1668          */
1669         if (!IsReno(tp) && tcp_head_timedout(sk, tp)) {
1670                 struct sk_buff *skb;
1671
1672                 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
1673                         : sk->sk_write_queue.next;
1674
1675                 sk_stream_for_retrans_queue_from(skb, sk) {
1676                         if (!tcp_skb_timedout(sk, skb))
1677                                 break;
1678
1679                         if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1680                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1681                                 tp->lost_out += tcp_skb_pcount(skb);
1682
1683                                 /* clear xmit_retrans hint */
1684                                 if (tp->retransmit_skb_hint &&
1685                                     before(TCP_SKB_CB(skb)->seq,
1686                                            TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
1687
1688                                         tp->retransmit_skb_hint = NULL;
1689                         }
1690                 }
1691
1692                 tp->scoreboard_skb_hint = skb;
1693
1694                 tcp_sync_left_out(tp);
1695         }
1696 }
1697
1698 /* CWND moderation, preventing bursts due to too big ACKs
1699  * in dubious situations.
1700  */
1701 static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1702 {
1703         tp->snd_cwnd = min(tp->snd_cwnd,
1704                            tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1705         tp->snd_cwnd_stamp = tcp_time_stamp;
1706 }
1707
1708 /* Lower bound on congestion window is slow start threshold
1709  * unless congestion avoidance choice decides to overide it.
1710  */
1711 static inline u32 tcp_cwnd_min(const struct sock *sk)
1712 {
1713         const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1714
1715         return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
1716 }
1717
1718 /* Decrease cwnd each second ack. */
1719 static void tcp_cwnd_down(struct sock *sk)
1720 {
1721         struct tcp_sock *tp = tcp_sk(sk);
1722         int decr = tp->snd_cwnd_cnt + 1;
1723
1724         tp->snd_cwnd_cnt = decr&1;
1725         decr >>= 1;
1726
1727         if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
1728                 tp->snd_cwnd -= decr;
1729
1730         tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1731         tp->snd_cwnd_stamp = tcp_time_stamp;
1732 }
1733
1734 /* Nothing was retransmitted or returned timestamp is less
1735  * than timestamp of the first retransmission.
1736  */
1737 static inline int tcp_packet_delayed(struct tcp_sock *tp)
1738 {
1739         return !tp->retrans_stamp ||
1740                 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1741                  (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1742 }
1743
1744 /* Undo procedures. */
1745
1746 #if FASTRETRANS_DEBUG > 1
1747 static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1748 {
1749         struct inet_sock *inet = inet_sk(sk);
1750         printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1751                msg,
1752                NIPQUAD(inet->daddr), ntohs(inet->dport),
1753                tp->snd_cwnd, tp->left_out,
1754                tp->snd_ssthresh, tp->prior_ssthresh,
1755                tp->packets_out);
1756 }
1757 #else
1758 #define DBGUNDO(x...) do { } while (0)
1759 #endif
1760
1761 static void tcp_undo_cwr(struct sock *sk, const int undo)
1762 {
1763         struct tcp_sock *tp = tcp_sk(sk);
1764
1765         if (tp->prior_ssthresh) {
1766                 const struct inet_connection_sock *icsk = inet_csk(sk);
1767
1768                 if (icsk->icsk_ca_ops->undo_cwnd)
1769                         tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
1770                 else
1771                         tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1772
1773                 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1774                         tp->snd_ssthresh = tp->prior_ssthresh;
1775                         TCP_ECN_withdraw_cwr(tp);
1776                 }
1777         } else {
1778                 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1779         }
1780         tcp_moderate_cwnd(tp);
1781         tp->snd_cwnd_stamp = tcp_time_stamp;
1782
1783         /* There is something screwy going on with the retrans hints after
1784            an undo */
1785         clear_all_retrans_hints(tp);
1786 }
1787
1788 static inline int tcp_may_undo(struct tcp_sock *tp)
1789 {
1790         return tp->undo_marker &&
1791                 (!tp->undo_retrans || tcp_packet_delayed(tp));
1792 }
1793
1794 /* People celebrate: "We love our President!" */
1795 static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1796 {
1797         if (tcp_may_undo(tp)) {
1798                 /* Happy end! We did not retransmit anything
1799                  * or our original transmission succeeded.
1800                  */
1801                 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
1802                 tcp_undo_cwr(sk, 1);
1803                 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
1804                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1805                 else
1806                         NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1807                 tp->undo_marker = 0;
1808         }
1809         if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1810                 /* Hold old state until something *above* high_seq
1811                  * is ACKed. For Reno it is MUST to prevent false
1812                  * fast retransmits (RFC2582). SACK TCP is safe. */
1813                 tcp_moderate_cwnd(tp);
1814                 return 1;
1815         }
1816         tcp_set_ca_state(sk, TCP_CA_Open);
1817         return 0;
1818 }
1819
1820 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1821 static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1822 {
1823         if (tp->undo_marker && !tp->undo_retrans) {
1824                 DBGUNDO(sk, tp, "D-SACK");
1825                 tcp_undo_cwr(sk, 1);
1826                 tp->undo_marker = 0;
1827                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1828         }
1829 }
1830
1831 /* Undo during fast recovery after partial ACK. */
1832
1833 static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1834                                 int acked)
1835 {
1836         /* Partial ACK arrived. Force Hoe's retransmit. */
1837         int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1838
1839         if (tcp_may_undo(tp)) {
1840                 /* Plain luck! Hole if filled with delayed
1841                  * packet, rather than with a retransmit.
1842                  */
1843                 if (tp->retrans_out == 0)
1844                         tp->retrans_stamp = 0;
1845
1846                 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
1847
1848                 DBGUNDO(sk, tp, "Hoe");
1849                 tcp_undo_cwr(sk, 0);
1850                 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1851
1852                 /* So... Do not make Hoe's retransmit yet.
1853                  * If the first packet was delayed, the rest
1854                  * ones are most probably delayed as well.
1855                  */
1856                 failed = 0;
1857         }
1858         return failed;
1859 }
1860
1861 /* Undo during loss recovery after partial ACK. */
1862 static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1863 {
1864         if (tcp_may_undo(tp)) {
1865                 struct sk_buff *skb;
1866                 sk_stream_for_retrans_queue(skb, sk) {
1867                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1868                 }
1869
1870                 clear_all_retrans_hints(tp);
1871
1872                 DBGUNDO(sk, tp, "partial loss");
1873                 tp->lost_out = 0;
1874                 tp->left_out = tp->sacked_out;
1875                 tcp_undo_cwr(sk, 1);
1876                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1877                 inet_csk(sk)->icsk_retransmits = 0;
1878                 tp->undo_marker = 0;
1879                 if (!IsReno(tp))
1880                         tcp_set_ca_state(sk, TCP_CA_Open);
1881                 return 1;
1882         }
1883         return 0;
1884 }
1885
1886 static inline void tcp_complete_cwr(struct sock *sk)
1887 {
1888         struct tcp_sock *tp = tcp_sk(sk);
1889         tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
1890         tp->snd_cwnd_stamp = tcp_time_stamp;
1891         tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
1892 }
1893
1894 static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1895 {
1896         tp->left_out = tp->sacked_out;
1897
1898         if (tp->retrans_out == 0)
1899                 tp->retrans_stamp = 0;
1900
1901         if (flag&FLAG_ECE)
1902                 tcp_enter_cwr(sk);
1903
1904         if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
1905                 int state = TCP_CA_Open;
1906
1907                 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1908                         state = TCP_CA_Disorder;
1909
1910                 if (inet_csk(sk)->icsk_ca_state != state) {
1911                         tcp_set_ca_state(sk, state);
1912                         tp->high_seq = tp->snd_nxt;
1913                 }
1914                 tcp_moderate_cwnd(tp);
1915         } else {
1916                 tcp_cwnd_down(sk);
1917         }
1918 }
1919
1920 static void tcp_mtup_probe_failed(struct sock *sk)
1921 {
1922         struct inet_connection_sock *icsk = inet_csk(sk);
1923
1924         icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
1925         icsk->icsk_mtup.probe_size = 0;
1926 }
1927
1928 static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
1929 {
1930         struct tcp_sock *tp = tcp_sk(sk);
1931         struct inet_connection_sock *icsk = inet_csk(sk);
1932
1933         /* FIXME: breaks with very large cwnd */
1934         tp->prior_ssthresh = tcp_current_ssthresh(sk);
1935         tp->snd_cwnd = tp->snd_cwnd *
1936                        tcp_mss_to_mtu(sk, tp->mss_cache) /
1937                        icsk->icsk_mtup.probe_size;
1938         tp->snd_cwnd_cnt = 0;
1939         tp->snd_cwnd_stamp = tcp_time_stamp;
1940         tp->rcv_ssthresh = tcp_current_ssthresh(sk);
1941
1942         icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
1943         icsk->icsk_mtup.probe_size = 0;
1944         tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
1945 }
1946
1947
1948 /* Process an event, which can update packets-in-flight not trivially.
1949  * Main goal of this function is to calculate new estimate for left_out,
1950  * taking into account both packets sitting in receiver's buffer and
1951  * packets lost by network.
1952  *
1953  * Besides that it does CWND reduction, when packet loss is detected
1954  * and changes state of machine.
1955  *
1956  * It does _not_ decide what to send, it is made in function
1957  * tcp_xmit_retransmit_queue().
1958  */
1959 static void
1960 tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1961                       int prior_packets, int flag)
1962 {
1963         struct inet_connection_sock *icsk = inet_csk(sk);
1964         struct tcp_sock *tp = tcp_sk(sk);
1965         int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1966
1967         /* Some technical things:
1968          * 1. Reno does not count dupacks (sacked_out) automatically. */
1969         if (!tp->packets_out)
1970                 tp->sacked_out = 0;
1971         /* 2. SACK counts snd_fack in packets inaccurately. */
1972         if (tp->sacked_out == 0)
1973                 tp->fackets_out = 0;
1974
1975         /* Now state machine starts.
1976          * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1977         if (flag&FLAG_ECE)
1978                 tp->prior_ssthresh = 0;
1979
1980         /* B. In all the states check for reneging SACKs. */
1981         if (tp->sacked_out && tcp_check_sack_reneging(sk))
1982                 return;
1983
1984         /* C. Process data loss notification, provided it is valid. */
1985         if ((flag&FLAG_DATA_LOST) &&
1986             before(tp->snd_una, tp->high_seq) &&
1987             icsk->icsk_ca_state != TCP_CA_Open &&
1988             tp->fackets_out > tp->reordering) {
1989                 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1990                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1991         }
1992
1993         /* D. Synchronize left_out to current state. */
1994         tcp_sync_left_out(tp);
1995
1996         /* E. Check state exit conditions. State can be terminated
1997          *    when high_seq is ACKed. */
1998         if (icsk->icsk_ca_state == TCP_CA_Open) {
1999                 if (!sysctl_tcp_frto)
2000                         BUG_TRAP(tp->retrans_out == 0);
2001                 tp->retrans_stamp = 0;
2002         } else if (!before(tp->snd_una, tp->high_seq)) {
2003                 switch (icsk->icsk_ca_state) {
2004                 case TCP_CA_Loss:
2005                         icsk->icsk_retransmits = 0;
2006                         if (tcp_try_undo_recovery(sk, tp))
2007                                 return;
2008                         break;
2009
2010                 case TCP_CA_CWR:
2011                         /* CWR is to be held something *above* high_seq
2012                          * is ACKed for CWR bit to reach receiver. */
2013                         if (tp->snd_una != tp->high_seq) {
2014                                 tcp_complete_cwr(sk);
2015                                 tcp_set_ca_state(sk, TCP_CA_Open);
2016                         }
2017                         break;
2018
2019                 case TCP_CA_Disorder:
2020                         tcp_try_undo_dsack(sk, tp);
2021                         if (!tp->undo_marker ||
2022                             /* For SACK case do not Open to allow to undo
2023                              * catching for all duplicate ACKs. */
2024                             IsReno(tp) || tp->snd_una != tp->high_seq) {
2025                                 tp->undo_marker = 0;
2026                                 tcp_set_ca_state(sk, TCP_CA_Open);
2027                         }
2028                         break;
2029
2030                 case TCP_CA_Recovery:
2031                         if (IsReno(tp))
2032                                 tcp_reset_reno_sack(tp);
2033                         if (tcp_try_undo_recovery(sk, tp))
2034                                 return;
2035                         tcp_complete_cwr(sk);
2036                         break;
2037                 }
2038         }
2039
2040         /* F. Process state. */
2041         switch (icsk->icsk_ca_state) {
2042         case TCP_CA_Recovery:
2043                 if (prior_snd_una == tp->snd_una) {
2044                         if (IsReno(tp) && is_dupack)
2045                                 tcp_add_reno_sack(sk);
2046                 } else {
2047                         int acked = prior_packets - tp->packets_out;
2048                         if (IsReno(tp))
2049                                 tcp_remove_reno_sacks(sk, tp, acked);
2050                         is_dupack = tcp_try_undo_partial(sk, tp, acked);
2051                 }
2052                 break;
2053         case TCP_CA_Loss:
2054                 if (flag&FLAG_DATA_ACKED)
2055                         icsk->icsk_retransmits = 0;
2056                 if (!tcp_try_undo_loss(sk, tp)) {
2057                         tcp_moderate_cwnd(tp);
2058                         tcp_xmit_retransmit_queue(sk);
2059                         return;
2060                 }
2061                 if (icsk->icsk_ca_state != TCP_CA_Open)
2062                         return;
2063                 /* Loss is undone; fall through to processing in Open state. */
2064         default:
2065                 if (IsReno(tp)) {
2066                         if (tp->snd_una != prior_snd_una)
2067                                 tcp_reset_reno_sack(tp);
2068                         if (is_dupack)
2069                                 tcp_add_reno_sack(sk);
2070                 }
2071
2072                 if (icsk->icsk_ca_state == TCP_CA_Disorder)
2073                         tcp_try_undo_dsack(sk, tp);
2074
2075                 if (!tcp_time_to_recover(sk, tp)) {
2076                         tcp_try_to_open(sk, tp, flag);
2077                         return;
2078                 }
2079
2080                 /* MTU probe failure: don't reduce cwnd */
2081                 if (icsk->icsk_ca_state < TCP_CA_CWR &&
2082                     icsk->icsk_mtup.probe_size &&
2083                     tp->snd_una == tp->mtu_probe.probe_seq_start) {
2084                         tcp_mtup_probe_failed(sk);
2085                         /* Restores the reduction we did in tcp_mtup_probe() */
2086                         tp->snd_cwnd++;
2087                         tcp_simple_retransmit(sk);
2088                         return;
2089                 }
2090
2091                 /* Otherwise enter Recovery state */
2092
2093                 if (IsReno(tp))
2094                         NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
2095                 else
2096                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
2097
2098                 tp->high_seq = tp->snd_nxt;
2099                 tp->prior_ssthresh = 0;
2100                 tp->undo_marker = tp->snd_una;
2101                 tp->undo_retrans = tp->retrans_out;
2102
2103                 if (icsk->icsk_ca_state < TCP_CA_CWR) {
2104                         if (!(flag&FLAG_ECE))
2105                                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2106                         tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2107                         TCP_ECN_queue_cwr(tp);
2108                 }
2109
2110                 tp->bytes_acked = 0;
2111                 tp->snd_cwnd_cnt = 0;
2112                 tcp_set_ca_state(sk, TCP_CA_Recovery);
2113         }
2114
2115         if (is_dupack || tcp_head_timedout(sk, tp))
2116                 tcp_update_scoreboard(sk, tp);
2117         tcp_cwnd_down(sk);
2118         tcp_xmit_retransmit_queue(sk);
2119 }
2120
2121 /* Read draft-ietf-tcplw-high-performance before mucking
2122  * with this code. (Supersedes RFC1323)
2123  */
2124 static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
2125 {
2126         /* RTTM Rule: A TSecr value received in a segment is used to
2127          * update the averaged RTT measurement only if the segment
2128          * acknowledges some new data, i.e., only if it advances the
2129          * left edge of the send window.
2130          *
2131          * See draft-ietf-tcplw-high-performance-00, section 3.3.
2132          * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2133          *
2134          * Changed: reset backoff as soon as we see the first valid sample.
2135          * If we do not, we get strongly overestimated rto. With timestamps
2136          * samples are accepted even from very old segments: f.e., when rtt=1
2137          * increases to 8, we retransmit 5 times and after 8 seconds delayed
2138          * answer arrives rto becomes 120 seconds! If at least one of segments
2139          * in window is lost... Voila.                          --ANK (010210)
2140          */
2141         struct tcp_sock *tp = tcp_sk(sk);
2142         const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
2143         tcp_rtt_estimator(sk, seq_rtt);
2144         tcp_set_rto(sk);
2145         inet_csk(sk)->icsk_backoff = 0;
2146         tcp_bound_rto(sk);
2147 }
2148
2149 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
2150 {
2151         /* We don't have a timestamp. Can only use
2152          * packets that are not retransmitted to determine
2153          * rtt estimates. Also, we must not reset the
2154          * backoff for rto until we get a non-retransmitted
2155          * packet. This allows us to deal with a situation
2156          * where the network delay has increased suddenly.
2157          * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2158          */
2159
2160         if (flag & FLAG_RETRANS_DATA_ACKED)
2161                 return;
2162
2163         tcp_rtt_estimator(sk, seq_rtt);
2164         tcp_set_rto(sk);
2165         inet_csk(sk)->icsk_backoff = 0;
2166         tcp_bound_rto(sk);
2167 }
2168
2169 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
2170                                       const s32 seq_rtt)
2171 {
2172         const struct tcp_sock *tp = tcp_sk(sk);
2173         /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2174         if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
2175                 tcp_ack_saw_tstamp(sk, flag);
2176         else if (seq_rtt >= 0)
2177                 tcp_ack_no_tstamp(sk, seq_rtt, flag);
2178 }
2179
2180 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
2181                            u32 in_flight, int good)
2182 {
2183         const struct inet_connection_sock *icsk = inet_csk(sk);
2184         icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good);
2185         tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
2186 }
2187
2188 /* Restart timer after forward progress on connection.
2189  * RFC2988 recommends to restart timer to now+rto.
2190  */
2191
2192 static void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
2193 {
2194         if (!tp->packets_out) {
2195                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
2196         } else {
2197                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
2198         }
2199 }
2200
2201 static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2202                          __u32 now, __s32 *seq_rtt)
2203 {
2204         struct tcp_sock *tp = tcp_sk(sk);
2205         struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2206         __u32 seq = tp->snd_una;
2207         __u32 packets_acked;
2208         int acked = 0;
2209
2210         /* If we get here, the whole TSO packet has not been
2211          * acked.
2212          */
2213         BUG_ON(!after(scb->end_seq, seq));
2214
2215         packets_acked = tcp_skb_pcount(skb);
2216         if (tcp_trim_head(sk, skb, seq - scb->seq))
2217                 return 0;
2218         packets_acked -= tcp_skb_pcount(skb);
2219
2220         if (packets_acked) {
2221                 __u8 sacked = scb->sacked;
2222
2223                 acked |= FLAG_DATA_ACKED;
2224                 if (sacked) {
2225                         if (sacked & TCPCB_RETRANS) {
2226                                 if (sacked & TCPCB_SACKED_RETRANS)
2227                                         tp->retrans_out -= packets_acked;
2228                                 acked |= FLAG_RETRANS_DATA_ACKED;
2229                                 *seq_rtt = -1;
2230                         } else if (*seq_rtt < 0)
2231                                 *seq_rtt = now - scb->when;
2232                         if (sacked & TCPCB_SACKED_ACKED)
2233                                 tp->sacked_out -= packets_acked;
2234                         if (sacked & TCPCB_LOST)
2235                                 tp->lost_out -= packets_acked;
2236                         if (sacked & TCPCB_URG) {
2237                                 if (tp->urg_mode &&
2238                                     !before(seq, tp->snd_up))
2239                                         tp->urg_mode = 0;
2240                         }
2241                 } else if (*seq_rtt < 0)
2242                         *seq_rtt = now - scb->when;
2243
2244                 if (tp->fackets_out) {
2245                         __u32 dval = min(tp->fackets_out, packets_acked);
2246                         tp->fackets_out -= dval;
2247                 }
2248                 tp->packets_out -= packets_acked;
2249
2250                 BUG_ON(tcp_skb_pcount(skb) == 0);
2251                 BUG_ON(!before(scb->seq, scb->end_seq));
2252         }
2253
2254         return acked;
2255 }
2256
2257 static u32 tcp_usrtt(struct timeval *tv)
2258 {
2259         struct timeval now;
2260
2261         do_gettimeofday(&now);
2262         return (now.tv_sec - tv->tv_sec) * 1000000 + (now.tv_usec - tv->tv_usec);
2263 }
2264
2265 /* Remove acknowledged frames from the retransmission queue. */
2266 static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
2267 {
2268         struct tcp_sock *tp = tcp_sk(sk);
2269         const struct inet_connection_sock *icsk = inet_csk(sk);
2270         struct sk_buff *skb;
2271         __u32 now = tcp_time_stamp;
2272         int acked = 0;
2273         __s32 seq_rtt = -1;
2274         u32 pkts_acked = 0;
2275         void (*rtt_sample)(struct sock *sk, u32 usrtt)
2276                 = icsk->icsk_ca_ops->rtt_sample;
2277         struct timeval tv = { .tv_sec = 0, .tv_usec = 0 };
2278
2279         while ((skb = skb_peek(&sk->sk_write_queue)) &&
2280                skb != sk->sk_send_head) {
2281                 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2282                 __u8 sacked = scb->sacked;
2283
2284                 /* If our packet is before the ack sequence we can
2285                  * discard it as it's confirmed to have arrived at
2286                  * the other end.
2287                  */
2288                 if (after(scb->end_seq, tp->snd_una)) {
2289                         if (tcp_skb_pcount(skb) > 1 &&
2290                             after(tp->snd_una, scb->seq))
2291                                 acked |= tcp_tso_acked(sk, skb,
2292                                                        now, &seq_rtt);
2293                         break;
2294                 }
2295
2296                 /* Initial outgoing SYN's get put onto the write_queue
2297                  * just like anything else we transmit.  It is not
2298                  * true data, and if we misinform our callers that
2299                  * this ACK acks real data, we will erroneously exit
2300                  * connection startup slow start one packet too
2301                  * quickly.  This is severely frowned upon behavior.
2302                  */
2303                 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2304                         acked |= FLAG_DATA_ACKED;
2305                         ++pkts_acked;
2306                 } else {
2307                         acked |= FLAG_SYN_ACKED;
2308                         tp->retrans_stamp = 0;
2309                 }
2310
2311                 /* MTU probing checks */
2312                 if (icsk->icsk_mtup.probe_size) {
2313                         if (!after(tp->mtu_probe.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) {
2314                                 tcp_mtup_probe_success(sk, skb);
2315                         }
2316                 }
2317
2318                 if (sacked) {
2319                         if (sacked & TCPCB_RETRANS) {
2320                                 if(sacked & TCPCB_SACKED_RETRANS)
2321                                         tp->retrans_out -= tcp_skb_pcount(skb);
2322                                 acked |= FLAG_RETRANS_DATA_ACKED;
2323                                 seq_rtt = -1;
2324                         } else if (seq_rtt < 0) {
2325                                 seq_rtt = now - scb->when;
2326                                 skb_get_timestamp(skb, &tv);
2327                         }
2328                         if (sacked & TCPCB_SACKED_ACKED)
2329                                 tp->sacked_out -= tcp_skb_pcount(skb);
2330                         if (sacked & TCPCB_LOST)
2331                                 tp->lost_out -= tcp_skb_pcount(skb);
2332                         if (sacked & TCPCB_URG) {
2333                                 if (tp->urg_mode &&
2334                                     !before(scb->end_seq, tp->snd_up))
2335                                         tp->urg_mode = 0;
2336                         }
2337                 } else if (seq_rtt < 0) {
2338                         seq_rtt = now - scb->when;
2339                         skb_get_timestamp(skb, &tv);
2340                 }
2341                 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2342                 tcp_packets_out_dec(tp, skb);
2343                 __skb_unlink(skb, &sk->sk_write_queue);
2344                 sk_stream_free_skb(sk, skb);
2345                 clear_all_retrans_hints(tp);
2346         }
2347
2348         if (acked&FLAG_ACKED) {
2349                 tcp_ack_update_rtt(sk, acked, seq_rtt);
2350                 tcp_ack_packets_out(sk, tp);
2351                 if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED))
2352                         (*rtt_sample)(sk, tcp_usrtt(&tv));
2353
2354                 if (icsk->icsk_ca_ops->pkts_acked)
2355                         icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);
2356         }
2357
2358 #if FASTRETRANS_DEBUG > 0
2359         BUG_TRAP((int)tp->sacked_out >= 0);
2360         BUG_TRAP((int)tp->lost_out >= 0);
2361         BUG_TRAP((int)tp->retrans_out >= 0);
2362         if (!tp->packets_out && tp->rx_opt.sack_ok) {
2363                 const struct inet_connection_sock *icsk = inet_csk(sk);
2364                 if (tp->lost_out) {
2365                         printk(KERN_DEBUG "Leak l=%u %d\n",
2366                                tp->lost_out, icsk->icsk_ca_state);
2367                         tp->lost_out = 0;
2368                 }
2369                 if (tp->sacked_out) {
2370                         printk(KERN_DEBUG "Leak s=%u %d\n",
2371                                tp->sacked_out, icsk->icsk_ca_state);
2372                         tp->sacked_out = 0;
2373                 }
2374                 if (tp->retrans_out) {
2375                         printk(KERN_DEBUG "Leak r=%u %d\n",
2376                                tp->retrans_out, icsk->icsk_ca_state);
2377                         tp->retrans_out = 0;
2378                 }
2379         }
2380 #endif
2381         *seq_rtt_p = seq_rtt;
2382         return acked;
2383 }
2384
2385 static void tcp_ack_probe(struct sock *sk)
2386 {
2387         const struct tcp_sock *tp = tcp_sk(sk);
2388         struct inet_connection_sock *icsk = inet_csk(sk);
2389
2390         /* Was it a usable window open? */
2391
2392         if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2393                    tp->snd_una + tp->snd_wnd)) {
2394                 icsk->icsk_backoff = 0;
2395                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
2396                 /* Socket must be waked up by subsequent tcp_data_snd_check().
2397                  * This function is not for random using!
2398                  */
2399         } else {
2400                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2401                                           min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2402                                           TCP_RTO_MAX);
2403         }
2404 }
2405
2406 static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
2407 {
2408         return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
2409                 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
2410 }
2411
2412 static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
2413 {
2414         const struct tcp_sock *tp = tcp_sk(sk);
2415         return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
2416                 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
2417 }
2418
2419 /* Check that window update is acceptable.
2420  * The function assumes that snd_una<=ack<=snd_next.
2421  */
2422 static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
2423                                         const u32 ack_seq, const u32 nwin)
2424 {
2425         return (after(ack, tp->snd_una) ||
2426                 after(ack_seq, tp->snd_wl1) ||
2427                 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2428 }
2429
2430 /* Update our send window.
2431  *
2432  * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2433  * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2434  */
2435 static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2436                                  struct sk_buff *skb, u32 ack, u32 ack_seq)
2437 {
2438         int flag = 0;
2439         u32 nwin = ntohs(skb->h.th->window);
2440
2441         if (likely(!skb->h.th->syn))
2442                 nwin <<= tp->rx_opt.snd_wscale;
2443
2444         if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2445                 flag |= FLAG_WIN_UPDATE;
2446                 tcp_update_wl(tp, ack, ack_seq);
2447
2448                 if (tp->snd_wnd != nwin) {
2449                         tp->snd_wnd = nwin;
2450
2451                         /* Note, it is the only place, where
2452                          * fast path is recovered for sending TCP.
2453                          */
2454                         tp->pred_flags = 0;
2455                         tcp_fast_path_check(sk, tp);
2456
2457                         if (nwin > tp->max_window) {
2458                                 tp->max_window = nwin;
2459                                 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
2460                         }
2461                 }
2462         }
2463
2464         tp->snd_una = ack;
2465
2466         return flag;
2467 }
2468
2469 static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2470 {
2471         struct tcp_sock *tp = tcp_sk(sk);
2472
2473         tcp_sync_left_out(tp);
2474
2475         if (tp->snd_una == prior_snd_una ||
2476             !before(tp->snd_una, tp->frto_highmark)) {
2477                 /* RTO was caused by loss, start retransmitting in
2478                  * go-back-N slow start
2479                  */
2480                 tcp_enter_frto_loss(sk);
2481                 return;
2482         }
2483
2484         if (tp->frto_counter == 1) {
2485                 /* First ACK after RTO advances the window: allow two new
2486                  * segments out.
2487                  */
2488                 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2489         } else {
2490                 /* Also the second ACK after RTO advances the window.
2491                  * The RTO was likely spurious. Reduce cwnd and continue
2492                  * in congestion avoidance
2493                  */
2494                 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2495                 tcp_moderate_cwnd(tp);
2496         }
2497
2498         /* F-RTO affects on two new ACKs following RTO.
2499          * At latest on third ACK the TCP behavior is back to normal.
2500          */
2501         tp->frto_counter = (tp->frto_counter + 1) % 3;
2502 }
2503
2504 /* This routine deals with incoming acks, but not outgoing ones. */
2505 static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2506 {
2507         struct inet_connection_sock *icsk = inet_csk(sk);
2508         struct tcp_sock *tp = tcp_sk(sk);
2509         u32 prior_snd_una = tp->snd_una;
2510         u32 ack_seq = TCP_SKB_CB(skb)->seq;
2511         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2512         u32 prior_in_flight;
2513         s32 seq_rtt;
2514         int prior_packets;
2515
2516         /* If the ack is newer than sent or older than previous acks
2517          * then we can probably ignore it.
2518          */
2519         if (after(ack, tp->snd_nxt))
2520                 goto uninteresting_ack;
2521
2522         if (before(ack, prior_snd_una))
2523                 goto old_ack;
2524
2525         if (sysctl_tcp_abc) {
2526                 if (icsk->icsk_ca_state < TCP_CA_CWR)
2527                         tp->bytes_acked += ack - prior_snd_una;
2528                 else if (icsk->icsk_ca_state == TCP_CA_Loss)
2529                         /* we assume just one segment left network */
2530                         tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache);
2531         }
2532
2533         if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2534                 /* Window is constant, pure forward advance.
2535                  * No more checks are required.
2536                  * Note, we use the fact that SND.UNA>=SND.WL2.
2537                  */
2538                 tcp_update_wl(tp, ack, ack_seq);
2539                 tp->snd_una = ack;
2540                 flag |= FLAG_WIN_UPDATE;
2541
2542                 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
2543
2544                 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2545         } else {
2546                 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2547                         flag |= FLAG_DATA;
2548                 else
2549                         NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2550
2551                 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2552
2553                 if (TCP_SKB_CB(skb)->sacked)
2554                         flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2555
2556                 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2557                         flag |= FLAG_ECE;
2558
2559                 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
2560         }
2561
2562         /* We passed data and got it acked, remove any soft error
2563          * log. Something worked...
2564          */
2565         sk->sk_err_soft = 0;
2566         tp->rcv_tstamp = tcp_time_stamp;
2567         prior_packets = tp->packets_out;
2568         if (!prior_packets)
2569                 goto no_queue;
2570
2571         prior_in_flight = tcp_packets_in_flight(tp);
2572
2573         /* See if we can take anything off of the retransmit queue. */
2574         flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
2575
2576         if (tp->frto_counter)
2577                 tcp_process_frto(sk, prior_snd_una);
2578
2579         if (tcp_ack_is_dubious(sk, flag)) {
2580                 /* Advance CWND, if state allows this. */
2581                 if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag))
2582                         tcp_cong_avoid(sk, ack,  seq_rtt, prior_in_flight, 0);
2583                 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2584         } else {
2585                 if ((flag & FLAG_DATA_ACKED))
2586                         tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);
2587         }
2588
2589         if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2590                 dst_confirm(sk->sk_dst_cache);
2591
2592         return 1;
2593
2594 no_queue:
2595         icsk->icsk_probes_out = 0;
2596
2597         /* If this ack opens up a zero window, clear backoff.  It was
2598          * being used to time the probes, and is probably far higher than
2599          * it needs to be for normal retransmission.
2600          */
2601         if (sk->sk_send_head)
2602                 tcp_ack_probe(sk);
2603         return 1;
2604
2605 old_ack:
2606         if (TCP_SKB_CB(skb)->sacked)
2607                 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2608
2609 uninteresting_ack:
2610         SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2611         return 0;
2612 }
2613
2614
2615 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2616  * But, this can also be called on packets in the established flow when
2617  * the fast version below fails.
2618  */
2619 void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2620 {
2621         unsigned char *ptr;
2622         struct tcphdr *th = skb->h.th;
2623         int length=(th->doff*4)-sizeof(struct tcphdr);
2624
2625         ptr = (unsigned char *)(th + 1);
2626         opt_rx->saw_tstamp = 0;
2627
2628         while(length>0) {
2629                 int opcode=*ptr++;
2630                 int opsize;
2631
2632                 switch (opcode) {
2633                         case TCPOPT_EOL:
2634                                 return;
2635                         case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
2636                                 length--;
2637                                 continue;
2638                         default:
2639                                 opsize=*ptr++;
2640                                 if (opsize < 2) /* "silly options" */
2641                                         return;
2642                                 if (opsize > length)
2643                                         return; /* don't parse partial options */
2644                                 switch(opcode) {
2645                                 case TCPOPT_MSS:
2646                                         if(opsize==TCPOLEN_MSS && th->syn && !estab) {
2647                                                 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr));
2648                                                 if (in_mss) {
2649                                                         if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
2650                                                                 in_mss = opt_rx->user_mss;
2651                                                         opt_rx->mss_clamp = in_mss;
2652                                                 }
2653                                         }
2654                                         break;
2655                                 case TCPOPT_WINDOW:
2656                                         if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
2657                                                 if (sysctl_tcp_window_scaling) {
2658                                                         __u8 snd_wscale = *(__u8 *) ptr;
2659                                                         opt_rx->wscale_ok = 1;
2660                                                         if (snd_wscale > 14) {
2661                                                                 if(net_ratelimit())
2662                                                                         printk(KERN_INFO "tcp_parse_options: Illegal window "
2663                                                                                "scaling value %d >14 received.\n",
2664                                                                                snd_wscale);
2665                                                                 snd_wscale = 14;
2666                                                         }
2667                                                         opt_rx->snd_wscale = snd_wscale;
2668                                                 }
2669                                         break;
2670                                 case TCPOPT_TIMESTAMP:
2671                                         if(opsize==TCPOLEN_TIMESTAMP) {
2672                                                 if ((estab && opt_rx->tstamp_ok) ||
2673                                                     (!estab && sysctl_tcp_timestamps)) {
2674                                                         opt_rx->saw_tstamp = 1;
2675                                                         opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr));
2676                                                         opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4)));
2677                                                 }
2678                                         }
2679                                         break;
2680                                 case TCPOPT_SACK_PERM:
2681                                         if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
2682                                                 if (sysctl_tcp_sack) {
2683                                                         opt_rx->sack_ok = 1;
2684                                                         tcp_sack_reset(opt_rx);
2685                                                 }
2686                                         }
2687                                         break;
2688
2689                                 case TCPOPT_SACK:
2690                                         if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
2691                                            !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
2692                                            opt_rx->sack_ok) {
2693                                                 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
2694                                         }
2695 #ifdef CONFIG_TCP_MD5SIG
2696                                 case TCPOPT_MD5SIG:
2697                                         /*
2698                                          * The MD5 Hash has already been
2699                                          * checked (see tcp_v{4,6}_do_rcv()).
2700                                          */
2701                                         break;
2702 #endif
2703                                 };
2704                                 ptr+=opsize-2;
2705                                 length-=opsize;
2706                 };
2707         }
2708 }
2709
2710 /* Fast parse options. This hopes to only see timestamps.
2711  * If it is wrong it falls back on tcp_parse_options().
2712  */
2713 static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
2714                                   struct tcp_sock *tp)
2715 {
2716         if (th->doff == sizeof(struct tcphdr)>>2) {
2717                 tp->rx_opt.saw_tstamp = 0;
2718                 return 0;
2719         } else if (tp->rx_opt.tstamp_ok &&
2720                    th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
2721                 __be32 *ptr = (__be32 *)(th + 1);
2722                 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
2723                                   | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
2724                         tp->rx_opt.saw_tstamp = 1;
2725                         ++ptr;
2726                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
2727                         ++ptr;
2728                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
2729                         return 1;
2730                 }
2731         }
2732         tcp_parse_options(skb, &tp->rx_opt, 1);
2733         return 1;
2734 }
2735
2736 static inline void tcp_store_ts_recent(struct tcp_sock *tp)
2737 {
2738         tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
2739         tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
2740 }
2741
2742 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
2743 {
2744         if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
2745                 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2746                  * extra check below makes sure this can only happen
2747                  * for pure ACK frames.  -DaveM
2748                  *
2749                  * Not only, also it occurs for expired timestamps.
2750                  */
2751
2752                 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
2753                    xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
2754                         tcp_store_ts_recent(tp);
2755         }
2756 }
2757
2758 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2759  *
2760  * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2761  * it can pass through stack. So, the following predicate verifies that
2762  * this segment is not used for anything but congestion avoidance or
2763  * fast retransmit. Moreover, we even are able to eliminate most of such
2764  * second order effects, if we apply some small "replay" window (~RTO)
2765  * to timestamp space.
2766  *
2767  * All these measures still do not guarantee that we reject wrapped ACKs
2768  * on networks with high bandwidth, when sequence space is recycled fastly,
2769  * but it guarantees that such events will be very rare and do not affect
2770  * connection seriously. This doesn't look nice, but alas, PAWS is really
2771  * buggy extension.
2772  *
2773  * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2774  * states that events when retransmit arrives after original data are rare.
2775  * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2776  * the biggest problem on large power networks even with minor reordering.
2777  * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2778  * up to bandwidth of 18Gigabit/sec. 8) ]
2779  */
2780
2781 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
2782 {
2783         struct tcp_sock *tp = tcp_sk(sk);
2784         struct tcphdr *th = skb->h.th;
2785         u32 seq = TCP_SKB_CB(skb)->seq;
2786         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2787
2788         return (/* 1. Pure ACK with correct sequence number. */
2789                 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
2790
2791                 /* 2. ... and duplicate ACK. */
2792                 ack == tp->snd_una &&
2793
2794                 /* 3. ... and does not update window. */
2795                 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
2796
2797                 /* 4. ... and sits in replay window. */
2798                 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
2799 }
2800
2801 static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb)
2802 {
2803         const struct tcp_sock *tp = tcp_sk(sk);
2804         return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
2805                 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
2806                 !tcp_disordered_ack(sk, skb));
2807 }
2808
2809 /* Check segment sequence number for validity.
2810  *
2811  * Segment controls are considered valid, if the segment
2812  * fits to the window after truncation to the window. Acceptability
2813  * of data (and SYN, FIN, of course) is checked separately.
2814  * See tcp_data_queue(), for example.
2815  *
2816  * Also, controls (RST is main one) are accepted using RCV.WUP instead
2817  * of RCV.NXT. Peer still did not advance his SND.UNA when we
2818  * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2819  * (borrowed from freebsd)
2820  */
2821
2822 static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
2823 {
2824         return  !before(end_seq, tp->rcv_wup) &&
2825                 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
2826 }
2827
2828 /* When we get a reset we do this. */
2829 static void tcp_reset(struct sock *sk)
2830 {
2831         /* We want the right error as BSD sees it (and indeed as we do). */
2832         switch (sk->sk_state) {
2833                 case TCP_SYN_SENT:
2834                         sk->sk_err = ECONNREFUSED;
2835                         break;
2836                 case TCP_CLOSE_WAIT:
2837                         sk->sk_err = EPIPE;
2838                         break;
2839                 case TCP_CLOSE:
2840                         return;
2841                 default:
2842                         sk->sk_err = ECONNRESET;
2843         }
2844
2845         if (!sock_flag(sk, SOCK_DEAD))
2846                 sk->sk_error_report(sk);
2847
2848         tcp_done(sk);
2849 }
2850
2851 /*
2852  *      Process the FIN bit. This now behaves as it is supposed to work
2853  *      and the FIN takes effect when it is validly part of sequence
2854  *      space. Not before when we get holes.
2855  *
2856  *      If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2857  *      (and thence onto LAST-ACK and finally, CLOSE, we never enter
2858  *      TIME-WAIT)
2859  *
2860  *      If we are in FINWAIT-1, a received FIN indicates simultaneous
2861  *      close and we go into CLOSING (and later onto TIME-WAIT)
2862  *
2863  *      If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2864  */
2865 static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
2866 {
2867         struct tcp_sock *tp = tcp_sk(sk);
2868
2869         inet_csk_schedule_ack(sk);
2870
2871         sk->sk_shutdown |= RCV_SHUTDOWN;
2872         sock_set_flag(sk, SOCK_DONE);
2873
2874         switch (sk->sk_state) {
2875                 case TCP_SYN_RECV:
2876                 case TCP_ESTABLISHED:
2877                         /* Move to CLOSE_WAIT */
2878                         tcp_set_state(sk, TCP_CLOSE_WAIT);
2879                         inet_csk(sk)->icsk_ack.pingpong = 1;
2880                         break;
2881
2882                 case TCP_CLOSE_WAIT:
2883                 case TCP_CLOSING:
2884                         /* Received a retransmission of the FIN, do
2885                          * nothing.
2886                          */
2887                         break;
2888                 case TCP_LAST_ACK:
2889                         /* RFC793: Remain in the LAST-ACK state. */
2890                         break;
2891
2892                 case TCP_FIN_WAIT1:
2893                         /* This case occurs when a simultaneous close
2894                          * happens, we must ack the received FIN and
2895                          * enter the CLOSING state.
2896                          */
2897                         tcp_send_ack(sk);
2898                         tcp_set_state(sk, TCP_CLOSING);
2899                         break;
2900                 case TCP_FIN_WAIT2:
2901                         /* Received a FIN -- send ACK and enter TIME_WAIT. */
2902                         tcp_send_ack(sk);
2903                         tcp_time_wait(sk, TCP_TIME_WAIT, 0);
2904                         break;
2905                 default:
2906                         /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2907                          * cases we should never reach this piece of code.
2908                          */
2909                         printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
2910                                __FUNCTION__, sk->sk_state);
2911                         break;
2912         };
2913
2914         /* It _is_ possible, that we have something out-of-order _after_ FIN.
2915          * Probably, we should reset in this case. For now drop them.
2916          */
2917         __skb_queue_purge(&tp->out_of_order_queue);
2918         if (tp->rx_opt.sack_ok)
2919                 tcp_sack_reset(&tp->rx_opt);
2920         sk_stream_mem_reclaim(sk);
2921
2922         if (!sock_flag(sk, SOCK_DEAD)) {
2923                 sk->sk_state_change(sk);
2924
2925                 /* Do not send POLL_HUP for half duplex close. */
2926                 if (sk->sk_shutdown == SHUTDOWN_MASK ||
2927                     sk->sk_state == TCP_CLOSE)
2928                         sk_wake_async(sk, 1, POLL_HUP);
2929                 else
2930                         sk_wake_async(sk, 1, POLL_IN);
2931         }
2932 }
2933
2934 static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
2935 {
2936         if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
2937                 if (before(seq, sp->start_seq))
2938                         sp->start_seq = seq;
2939                 if (after(end_seq, sp->end_seq))
2940                         sp->end_seq = end_seq;
2941                 return 1;
2942         }
2943         return 0;
2944 }
2945
2946 static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
2947 {
2948         if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2949                 if (before(seq, tp->rcv_nxt))
2950                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
2951                 else
2952                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
2953
2954                 tp->rx_opt.dsack = 1;
2955                 tp->duplicate_sack[0].start_seq = seq;
2956                 tp->duplicate_sack[0].end_seq = end_seq;
2957                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
2958         }
2959 }
2960
2961 static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
2962 {
2963         if (!tp->rx_opt.dsack)
2964                 tcp_dsack_set(tp, seq, end_seq);
2965         else
2966                 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
2967 }
2968
2969 static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
2970 {
2971         struct tcp_sock *tp = tcp_sk(sk);
2972
2973         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
2974             before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
2975                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
2976                 tcp_enter_quickack_mode(sk);
2977
2978                 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2979                         u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2980
2981                         if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
2982                                 end_seq = tp->rcv_nxt;
2983                         tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
2984                 }
2985         }
2986
2987         tcp_send_ack(sk);
2988 }
2989
2990 /* These routines update the SACK block as out-of-order packets arrive or
2991  * in-order packets close up the sequence space.
2992  */
2993 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
2994 {
2995         int this_sack;
2996         struct tcp_sack_block *sp = &tp->selective_acks[0];
2997         struct tcp_sack_block *swalk = sp+1;
2998
2999         /* See if the recent change to the first SACK eats into
3000          * or hits the sequence space of other SACK blocks, if so coalesce.
3001          */
3002         for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
3003                 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
3004                         int i;
3005
3006                         /* Zap SWALK, by moving every further SACK up by one slot.
3007                          * Decrease num_sacks.
3008                          */
3009                         tp->rx_opt.num_sacks--;
3010                         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3011                         for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
3012                                 sp[i] = sp[i+1];
3013                         continue;
3014                 }
3015                 this_sack++, swalk++;
3016         }
3017 }
3018
3019 static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
3020 {
3021         __u32 tmp;
3022
3023         tmp = sack1->start_seq;
3024         sack1->start_seq = sack2->start_seq;
3025         sack2->start_seq = tmp;
3026
3027         tmp = sack1->end_seq;
3028         sack1->end_seq = sack2->end_seq;
3029         sack2->end_seq = tmp;
3030 }
3031
3032 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
3033 {
3034         struct tcp_sock *tp = tcp_sk(sk);
3035         struct tcp_sack_block *sp = &tp->selective_acks[0];
3036         int cur_sacks = tp->rx_opt.num_sacks;
3037         int this_sack;
3038
3039         if (!cur_sacks)
3040                 goto new_sack;
3041
3042         for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
3043                 if (tcp_sack_extend(sp, seq, end_seq)) {
3044                         /* Rotate this_sack to the first one. */
3045                         for (; this_sack>0; this_sack--, sp--)
3046                                 tcp_sack_swap(sp, sp-1);
3047                         if (cur_sacks > 1)
3048                                 tcp_sack_maybe_coalesce(tp);
3049                         return;
3050                 }
3051         }
3052
3053         /* Could not find an adjacent existing SACK, build a new one,
3054          * put it at the front, and shift everyone else down.  We
3055          * always know there is at least one SACK present already here.
3056          *
3057          * If the sack array is full, forget about the last one.
3058          */
3059         if (this_sack >= 4) {
3060                 this_sack--;
3061                 tp->rx_opt.num_sacks--;
3062                 sp--;
3063         }
3064         for(; this_sack > 0; this_sack--, sp--)
3065                 *sp = *(sp-1);
3066
3067 new_sack:
3068         /* Build the new head SACK, and we're done. */
3069         sp->start_seq = seq;
3070         sp->end_seq = end_seq;
3071         tp->rx_opt.num_sacks++;
3072         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3073 }
3074
3075 /* RCV.NXT advances, some SACKs should be eaten. */
3076
3077 static void tcp_sack_remove(struct tcp_sock *tp)
3078 {
3079         struct tcp_sack_block *sp = &tp->selective_acks[0];
3080         int num_sacks = tp->rx_opt.num_sacks;
3081         int this_sack;
3082
3083         /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3084         if (skb_queue_empty(&tp->out_of_order_queue)) {
3085                 tp->rx_opt.num_sacks = 0;
3086                 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
3087                 return;
3088         }
3089
3090         for(this_sack = 0; this_sack < num_sacks; ) {
3091                 /* Check if the start of the sack is covered by RCV.NXT. */
3092                 if (!before(tp->rcv_nxt, sp->start_seq)) {
3093                         int i;
3094
3095                         /* RCV.NXT must cover all the block! */
3096                         BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
3097
3098                         /* Zap this SACK, by moving forward any other SACKS. */
3099                         for (i=this_sack+1; i < num_sacks; i++)
3100                                 tp->selective_acks[i-1] = tp->selective_acks[i];
3101                         num_sacks--;
3102                         continue;
3103                 }
3104                 this_sack++;
3105                 sp++;
3106         }
3107         if (num_sacks != tp->rx_opt.num_sacks) {
3108                 tp->rx_opt.num_sacks = num_sacks;
3109                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3110         }
3111 }
3112
3113 /* This one checks to see if we can put data from the
3114  * out_of_order queue into the receive_queue.
3115  */
3116 static void tcp_ofo_queue(struct sock *sk)
3117 {
3118         struct tcp_sock *tp = tcp_sk(sk);
3119         __u32 dsack_high = tp->rcv_nxt;
3120         struct sk_buff *skb;
3121
3122         while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
3123                 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
3124                         break;
3125
3126                 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3127                         __u32 dsack = dsack_high;
3128                         if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3129                                 dsack_high = TCP_SKB_CB(skb)->end_seq;
3130                         tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3131                 }
3132
3133                 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3134                         SOCK_DEBUG(sk, "ofo packet was already received \n");
3135                         __skb_unlink(skb, &tp->out_of_order_queue);
3136                         __kfree_skb(skb);
3137                         continue;
3138                 }
3139                 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3140                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3141                            TCP_SKB_CB(skb)->end_seq);
3142
3143                 __skb_unlink(skb, &tp->out_of_order_queue);
3144                 __skb_queue_tail(&sk->sk_receive_queue, skb);
3145                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3146                 if(skb->h.th->fin)
3147                         tcp_fin(skb, sk, skb->h.th);
3148         }
3149 }
3150
3151 static int tcp_prune_queue(struct sock *sk);
3152
3153 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3154 {
3155         struct tcphdr *th = skb->h.th;
3156         struct tcp_sock *tp = tcp_sk(sk);
3157         int eaten = -1;
3158
3159         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3160                 goto drop;
3161
3162         __skb_pull(skb, th->doff*4);
3163
3164         TCP_ECN_accept_cwr(tp, skb);
3165
3166         if (tp->rx_opt.dsack) {
3167                 tp->rx_opt.dsack = 0;
3168                 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3169                                                     4 - tp->rx_opt.tstamp_ok);
3170         }
3171
3172         /*  Queue data for delivery to the user.
3173          *  Packets in sequence go to the receive queue.
3174          *  Out of sequence packets to the out_of_order_queue.
3175          */
3176         if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3177                 if (tcp_receive_window(tp) == 0)
3178                         goto out_of_window;
3179
3180                 /* Ok. In sequence. In window. */
3181                 if (tp->ucopy.task == current &&
3182                     tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3183                     sock_owned_by_user(sk) && !tp->urg_data) {
3184                         int chunk = min_t(unsigned int, skb->len,
3185                                                         tp->ucopy.len);
3186
3187                         __set_current_state(TASK_RUNNING);
3188
3189                         local_bh_enable();
3190                         if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3191                                 tp->ucopy.len -= chunk;
3192                                 tp->copied_seq += chunk;
3193                                 eaten = (chunk == skb->len && !th->fin);
3194                                 tcp_rcv_space_adjust(sk);
3195                         }
3196                         local_bh_disable();
3197                 }
3198
3199                 if (eaten <= 0) {
3200 queue_and_out:
3201                         if (eaten < 0 &&
3202                             (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3203                              !sk_stream_rmem_schedule(sk, skb))) {
3204                                 if (tcp_prune_queue(sk) < 0 ||
3205                                     !sk_stream_rmem_schedule(sk, skb))
3206                                         goto drop;
3207                         }
3208                         sk_stream_set_owner_r(skb, sk);
3209                         __skb_queue_tail(&sk->sk_receive_queue, skb);
3210                 }
3211                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3212                 if(skb->len)
3213                         tcp_event_data_recv(sk, tp, skb);
3214                 if(th->fin)
3215                         tcp_fin(skb, sk, th);
3216
3217                 if (!skb_queue_empty(&tp->out_of_order_queue)) {
3218                         tcp_ofo_queue(sk);
3219
3220                         /* RFC2581. 4.2. SHOULD send immediate ACK, when
3221                          * gap in queue is filled.
3222                          */
3223                         if (skb_queue_empty(&tp->out_of_order_queue))
3224                                 inet_csk(sk)->icsk_ack.pingpong = 0;
3225                 }
3226
3227                 if (tp->rx_opt.num_sacks)
3228                         tcp_sack_remove(tp);
3229
3230                 tcp_fast_path_check(sk, tp);
3231
3232                 if (eaten > 0)
3233                         __kfree_skb(skb);
3234                 else if (!sock_flag(sk, SOCK_DEAD))
3235                         sk->sk_data_ready(sk, 0);
3236                 return;
3237         }
3238
3239         if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3240                 /* A retransmit, 2nd most common case.  Force an immediate ack. */
3241                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3242                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3243
3244 out_of_window:
3245                 tcp_enter_quickack_mode(sk);
3246                 inet_csk_schedule_ack(sk);
3247 drop:
3248                 __kfree_skb(skb);
3249                 return;
3250         }
3251
3252         /* Out of window. F.e. zero window probe. */
3253         if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3254                 goto out_of_window;
3255
3256         tcp_enter_quickack_mode(sk);
3257
3258         if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3259                 /* Partial packet, seq < rcv_next < end_seq */
3260                 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3261                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3262                            TCP_SKB_CB(skb)->end_seq);
3263
3264                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3265
3266                 /* If window is closed, drop tail of packet. But after
3267                  * remembering D-SACK for its head made in previous line.
3268                  */
3269                 if (!tcp_receive_window(tp))
3270                         goto out_of_window;
3271                 goto queue_and_out;
3272         }
3273
3274         TCP_ECN_check_ce(tp, skb);
3275
3276         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3277             !sk_stream_rmem_schedule(sk, skb)) {
3278                 if (tcp_prune_queue(sk) < 0 ||
3279                     !sk_stream_rmem_schedule(sk, skb))
3280                         goto drop;
3281         }
3282
3283         /* Disable header prediction. */
3284         tp->pred_flags = 0;
3285         inet_csk_schedule_ack(sk);
3286
3287         SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3288                    tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3289
3290         sk_stream_set_owner_r(skb, sk);
3291
3292         if (!skb_peek(&tp->out_of_order_queue)) {
3293                 /* Initial out of order segment, build 1 SACK. */
3294                 if (tp->rx_opt.sack_ok) {
3295                         tp->rx_opt.num_sacks = 1;
3296                         tp->rx_opt.dsack     = 0;
3297                         tp->rx_opt.eff_sacks = 1;
3298                         tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3299                         tp->selective_acks[0].end_seq =
3300                                                 TCP_SKB_CB(skb)->end_seq;
3301                 }
3302                 __skb_queue_head(&tp->out_of_order_queue,skb);
3303         } else {
3304                 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3305                 u32 seq = TCP_SKB_CB(skb)->seq;
3306                 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3307
3308                 if (seq == TCP_SKB_CB(skb1)->end_seq) {
3309                         __skb_append(skb1, skb, &tp->out_of_order_queue);
3310
3311                         if (!tp->rx_opt.num_sacks ||
3312                             tp->selective_acks[0].end_seq != seq)
3313                                 goto add_sack;
3314
3315                         /* Common case: data arrive in order after hole. */
3316                         tp->selective_acks[0].end_seq = end_seq;
3317                         return;
3318                 }
3319
3320                 /* Find place to insert this segment. */
3321                 do {
3322                         if (!after(TCP_SKB_CB(skb1)->seq, seq))
3323                                 break;
3324                 } while ((skb1 = skb1->prev) !=
3325                          (struct sk_buff*)&tp->out_of_order_queue);
3326
3327                 /* Do skb overlap to previous one? */
3328                 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3329                     before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3330                         if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3331                                 /* All the bits are present. Drop. */
3332                                 __kfree_skb(skb);
3333                                 tcp_dsack_set(tp, seq, end_seq);
3334                                 goto add_sack;
3335                         }
3336                         if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3337                                 /* Partial overlap. */
3338                                 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3339                         } else {
3340                                 skb1 = skb1->prev;
3341                         }
3342                 }
3343                 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3344
3345                 /* And clean segments covered by new one as whole. */
3346                 while ((skb1 = skb->next) !=
3347                        (struct sk_buff*)&tp->out_of_order_queue &&
3348                        after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3349                        if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3350                                tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3351                                break;
3352                        }
3353                        __skb_unlink(skb1, &tp->out_of_order_queue);
3354                        tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3355                        __kfree_skb(skb1);
3356                 }
3357
3358 add_sack:
3359                 if (tp->rx_opt.sack_ok)
3360                         tcp_sack_new_ofo_skb(sk, seq, end_seq);
3361         }
3362 }
3363
3364 /* Collapse contiguous sequence of skbs head..tail with
3365  * sequence numbers start..end.
3366  * Segments with FIN/SYN are not collapsed (only because this
3367  * simplifies code)
3368  */
3369 static void
3370 tcp_collapse(struct sock *sk, struct sk_buff_head *list,
3371              struct sk_buff *head, struct sk_buff *tail,
3372              u32 start, u32 end)
3373 {
3374         struct sk_buff *skb;
3375
3376         /* First, check that queue is collapsible and find
3377          * the point where collapsing can be useful. */
3378         for (skb = head; skb != tail; ) {
3379                 /* No new bits? It is possible on ofo queue. */
3380                 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3381                         struct sk_buff *next = skb->next;
3382                         __skb_unlink(skb, list);
3383                         __kfree_skb(skb);
3384                         NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3385                         skb = next;
3386                         continue;
3387                 }
3388
3389                 /* The first skb to collapse is:
3390                  * - not SYN/FIN and
3391                  * - bloated or contains data before "start" or
3392                  *   overlaps to the next one.
3393                  */
3394                 if (!skb->h.th->syn && !skb->h.th->fin &&
3395                     (tcp_win_from_space(skb->truesize) > skb->len ||
3396                      before(TCP_SKB_CB(skb)->seq, start) ||
3397                      (skb->next != tail &&
3398                       TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3399                         break;
3400
3401                 /* Decided to skip this, advance start seq. */
3402                 start = TCP_SKB_CB(skb)->end_seq;
3403                 skb = skb->next;
3404         }
3405         if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3406                 return;
3407
3408         while (before(start, end)) {
3409                 struct sk_buff *nskb;
3410                 int header = skb_headroom(skb);
3411                 int copy = SKB_MAX_ORDER(header, 0);
3412
3413                 /* Too big header? This can happen with IPv6. */
3414                 if (copy < 0)
3415                         return;
3416                 if (end-start < copy)
3417                         copy = end-start;
3418                 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3419                 if (!nskb)
3420                         return;
3421                 skb_reserve(nskb, header);
3422                 memcpy(nskb->head, skb->head, header);
3423                 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3424                 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3425                 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3426                 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3427                 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
3428                 __skb_insert(nskb, skb->prev, skb, list);
3429                 sk_stream_set_owner_r(nskb, sk);
3430
3431                 /* Copy data, releasing collapsed skbs. */
3432                 while (copy > 0) {
3433                         int offset = start - TCP_SKB_CB(skb)->seq;
3434                         int size = TCP_SKB_CB(skb)->end_seq - start;
3435
3436                         BUG_ON(offset < 0);
3437                         if (size > 0) {
3438                                 size = min(copy, size);
3439                                 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3440                                         BUG();
3441                                 TCP_SKB_CB(nskb)->end_seq += size;
3442                                 copy -= size;
3443                                 start += size;
3444                         }
3445                         if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3446                                 struct sk_buff *next = skb->next;
3447                                 __skb_unlink(skb, list);
3448                                 __kfree_skb(skb);
3449                                 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3450                                 skb = next;
3451                                 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3452                                         return;
3453                         }
3454                 }
3455         }
3456 }
3457
3458 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3459  * and tcp_collapse() them until all the queue is collapsed.
3460  */
3461 static void tcp_collapse_ofo_queue(struct sock *sk)
3462 {
3463         struct tcp_sock *tp = tcp_sk(sk);
3464         struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3465         struct sk_buff *head;
3466         u32 start, end;
3467
3468         if (skb == NULL)
3469                 return;
3470
3471         start = TCP_SKB_CB(skb)->seq;
3472         end = TCP_SKB_CB(skb)->end_seq;
3473         head = skb;
3474
3475         for (;;) {
3476                 skb = skb->next;
3477
3478                 /* Segment is terminated when we see gap or when
3479                  * we are at the end of all the queue. */
3480                 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3481                     after(TCP_SKB_CB(skb)->seq, end) ||
3482                     before(TCP_SKB_CB(skb)->end_seq, start)) {
3483                         tcp_collapse(sk, &tp->out_of_order_queue,
3484                                      head, skb, start, end);
3485                         head = skb;
3486                         if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3487                                 break;
3488                         /* Start new segment */
3489                         start = TCP_SKB_CB(skb)->seq;
3490                         end = TCP_SKB_CB(skb)->end_seq;
3491                 } else {
3492                         if (before(TCP_SKB_CB(skb)->seq, start))
3493                                 start = TCP_SKB_CB(skb)->seq;
3494                         if (after(TCP_SKB_CB(skb)->end_seq, end))
3495                                 end = TCP_SKB_CB(skb)->end_seq;
3496                 }
3497         }
3498 }
3499
3500 /* Reduce allocated memory if we can, trying to get
3501  * the socket within its memory limits again.
3502  *
3503  * Return less than zero if we should start dropping frames
3504  * until the socket owning process reads some of the data
3505  * to stabilize the situation.
3506  */
3507 static int tcp_prune_queue(struct sock *sk)
3508 {
3509         struct tcp_sock *tp = tcp_sk(sk);
3510
3511         SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3512
3513         NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3514
3515         if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3516                 tcp_clamp_window(sk, tp);
3517         else if (tcp_memory_pressure)
3518                 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3519
3520         tcp_collapse_ofo_queue(sk);
3521         tcp_collapse(sk, &sk->sk_receive_queue,
3522                      sk->sk_receive_queue.next,
3523                      (struct sk_buff*)&sk->sk_receive_queue,
3524                      tp->copied_seq, tp->rcv_nxt);
3525         sk_stream_mem_reclaim(sk);
3526
3527         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3528                 return 0;
3529
3530         /* Collapsing did not help, destructive actions follow.
3531          * This must not ever occur. */
3532
3533         /* First, purge the out_of_order queue. */
3534         if (!skb_queue_empty(&tp->out_of_order_queue)) {
3535                 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
3536                 __skb_queue_purge(&tp->out_of_order_queue);
3537
3538                 /* Reset SACK state.  A conforming SACK implementation will
3539                  * do the same at a timeout based retransmit.  When a connection
3540                  * is in a sad state like this, we care only about integrity
3541                  * of the connection not performance.
3542                  */
3543                 if (tp->rx_opt.sack_ok)
3544                         tcp_sack_reset(&tp->rx_opt);
3545                 sk_stream_mem_reclaim(sk);
3546         }
3547
3548         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3549                 return 0;
3550
3551         /* If we are really being abused, tell the caller to silently
3552          * drop receive data on the floor.  It will get retransmitted
3553          * and hopefully then we'll have sufficient space.
3554          */
3555         NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3556
3557         /* Massive buffer overcommit. */
3558         tp->pred_flags = 0;
3559         return -1;
3560 }
3561
3562
3563 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3564  * As additional protections, we do not touch cwnd in retransmission phases,
3565  * and if application hit its sndbuf limit recently.
3566  */
3567 void tcp_cwnd_application_limited(struct sock *sk)
3568 {
3569         struct tcp_sock *tp = tcp_sk(sk);
3570
3571         if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
3572             sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3573                 /* Limited by application or receiver window. */
3574                 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
3575                 u32 win_used = max(tp->snd_cwnd_used, init_win);
3576                 if (win_used < tp->snd_cwnd) {
3577                         tp->snd_ssthresh = tcp_current_ssthresh(sk);
3578                         tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3579                 }
3580                 tp->snd_cwnd_used = 0;
3581         }
3582         tp->snd_cwnd_stamp = tcp_time_stamp;
3583 }
3584
3585 static int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp)
3586 {
3587         /* If the user specified a specific send buffer setting, do
3588          * not modify it.
3589          */
3590         if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
3591                 return 0;
3592
3593         /* If we are under global TCP memory pressure, do not expand.  */
3594         if (tcp_memory_pressure)
3595                 return 0;
3596
3597         /* If we are under soft global TCP memory pressure, do not expand.  */
3598         if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
3599                 return 0;
3600
3601         /* If we filled the congestion window, do not expand.  */
3602         if (tp->packets_out >= tp->snd_cwnd)
3603                 return 0;
3604
3605         return 1;
3606 }
3607
3608 /* When incoming ACK allowed to free some skb from write_queue,
3609  * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3610  * on the exit from tcp input handler.
3611  *
3612  * PROBLEM: sndbuf expansion does not work well with largesend.
3613  */
3614 static void tcp_new_space(struct sock *sk)
3615 {
3616         struct tcp_sock *tp = tcp_sk(sk);
3617
3618         if (tcp_should_expand_sndbuf(sk, tp)) {
3619                 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
3620                         MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3621                     demanded = max_t(unsigned int, tp->snd_cwnd,
3622                                                    tp->reordering + 1);
3623                 sndmem *= 2*demanded;
3624                 if (sndmem > sk->sk_sndbuf)
3625                         sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3626                 tp->snd_cwnd_stamp = tcp_time_stamp;
3627         }
3628
3629         sk->sk_write_space(sk);
3630 }
3631
3632 static void tcp_check_space(struct sock *sk)
3633 {
3634         if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3635                 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3636                 if (sk->sk_socket &&
3637                     test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3638                         tcp_new_space(sk);
3639         }
3640 }
3641
3642 static inline void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp)
3643 {
3644         tcp_push_pending_frames(sk, tp);
3645         tcp_check_space(sk);
3646 }
3647
3648 /*
3649  * Check if sending an ack is needed.
3650  */
3651 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
3652 {
3653         struct tcp_sock *tp = tcp_sk(sk);
3654
3655             /* More than one full frame received... */
3656         if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
3657              /* ... and right edge of window advances far enough.
3658               * (tcp_recvmsg() will send ACK otherwise). Or...
3659               */
3660              && __tcp_select_window(sk) >= tp->rcv_wnd) ||
3661             /* We ACK each frame or... */
3662             tcp_in_quickack_mode(sk) ||
3663             /* We have out of order data. */
3664             (ofo_possible &&
3665              skb_peek(&tp->out_of_order_queue))) {
3666                 /* Then ack it now */
3667                 tcp_send_ack(sk);
3668         } else {
3669                 /* Else, send delayed ack. */
3670                 tcp_send_delayed_ack(sk);
3671         }
3672 }
3673
3674 static inline void tcp_ack_snd_check(struct sock *sk)
3675 {
3676         if (!inet_csk_ack_scheduled(sk)) {
3677                 /* We sent a data segment already. */
3678                 return;
3679         }
3680         __tcp_ack_snd_check(sk, 1);
3681 }
3682
3683 /*
3684  *      This routine is only called when we have urgent data
3685  *      signaled. Its the 'slow' part of tcp_urg. It could be
3686  *      moved inline now as tcp_urg is only called from one
3687  *      place. We handle URGent data wrong. We have to - as
3688  *      BSD still doesn't use the correction from RFC961.
3689  *      For 1003.1g we should support a new option TCP_STDURG to permit
3690  *      either form (or just set the sysctl tcp_stdurg).
3691  */
3692
3693 static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
3694 {
3695         struct tcp_sock *tp = tcp_sk(sk);
3696         u32 ptr = ntohs(th->urg_ptr);
3697
3698         if (ptr && !sysctl_tcp_stdurg)
3699                 ptr--;
3700         ptr += ntohl(th->seq);
3701
3702         /* Ignore urgent data that we've already seen and read. */
3703         if (after(tp->copied_seq, ptr))
3704                 return;
3705
3706         /* Do not replay urg ptr.
3707          *
3708          * NOTE: interesting situation not covered by specs.
3709          * Misbehaving sender may send urg ptr, pointing to segment,
3710          * which we already have in ofo queue. We are not able to fetch
3711          * such data and will stay in TCP_URG_NOTYET until will be eaten
3712          * by recvmsg(). Seems, we are not obliged to handle such wicked
3713          * situations. But it is worth to think about possibility of some
3714          * DoSes using some hypothetical application level deadlock.
3715          */
3716         if (before(ptr, tp->rcv_nxt))
3717                 return;
3718
3719         /* Do we already have a newer (or duplicate) urgent pointer? */
3720         if (tp->urg_data && !after(ptr, tp->urg_seq))
3721                 return;
3722
3723         /* Tell the world about our new urgent pointer. */
3724         sk_send_sigurg(sk);
3725
3726         /* We may be adding urgent data when the last byte read was
3727          * urgent. To do this requires some care. We cannot just ignore
3728          * tp->copied_seq since we would read the last urgent byte again
3729          * as data, nor can we alter copied_seq until this data arrives
3730          * or we break the semantics of SIOCATMARK (and thus sockatmark())
3731          *
3732          * NOTE. Double Dutch. Rendering to plain English: author of comment
3733          * above did something sort of  send("A", MSG_OOB); send("B", MSG_OOB);
3734          * and expect that both A and B disappear from stream. This is _wrong_.
3735          * Though this happens in BSD with high probability, this is occasional.
3736          * Any application relying on this is buggy. Note also, that fix "works"
3737          * only in this artificial test. Insert some normal data between A and B and we will
3738          * decline of BSD again. Verdict: it is better to remove to trap
3739          * buggy users.
3740          */
3741         if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
3742             !sock_flag(sk, SOCK_URGINLINE) &&
3743             tp->copied_seq != tp->rcv_nxt) {
3744                 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
3745                 tp->copied_seq++;
3746                 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
3747                         __skb_unlink(skb, &sk->sk_receive_queue);
3748                         __kfree_skb(skb);
3749                 }
3750         }
3751
3752         tp->urg_data   = TCP_URG_NOTYET;
3753         tp->urg_seq    = ptr;
3754
3755         /* Disable header prediction. */
3756         tp->pred_flags = 0;
3757 }
3758
3759 /* This is the 'fast' part of urgent handling. */
3760 static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
3761 {
3762         struct tcp_sock *tp = tcp_sk(sk);
3763
3764         /* Check if we get a new urgent pointer - normally not. */
3765         if (th->urg)
3766                 tcp_check_urg(sk,th);
3767
3768         /* Do we wait for any urgent data? - normally not... */
3769         if (tp->urg_data == TCP_URG_NOTYET) {
3770                 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
3771                           th->syn;
3772
3773                 /* Is the urgent pointer pointing into this packet? */
3774                 if (ptr < skb->len) {
3775                         u8 tmp;
3776                         if (skb_copy_bits(skb, ptr, &tmp, 1))
3777                                 BUG();
3778                         tp->urg_data = TCP_URG_VALID | tmp;
3779                         if (!sock_flag(sk, SOCK_DEAD))
3780                                 sk->sk_data_ready(sk, 0);
3781                 }
3782         }
3783 }
3784
3785 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
3786 {
3787         struct tcp_sock *tp = tcp_sk(sk);
3788         int chunk = skb->len - hlen;
3789         int err;
3790
3791         local_bh_enable();
3792         if (skb->ip_summed==CHECKSUM_UNNECESSARY)
3793                 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
3794         else
3795                 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
3796                                                        tp->ucopy.iov);
3797
3798         if (!err) {
3799                 tp->ucopy.len -= chunk;
3800                 tp->copied_seq += chunk;
3801                 tcp_rcv_space_adjust(sk);
3802         }
3803
3804         local_bh_disable();
3805         return err;
3806 }
3807
3808 static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3809 {
3810         __sum16 result;
3811
3812         if (sock_owned_by_user(sk)) {
3813                 local_bh_enable();
3814                 result = __tcp_checksum_complete(skb);
3815                 local_bh_disable();
3816         } else {
3817                 result = __tcp_checksum_complete(skb);
3818         }
3819         return result;
3820 }
3821
3822 static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3823 {
3824         return skb->ip_summed != CHECKSUM_UNNECESSARY &&
3825                 __tcp_checksum_complete_user(sk, skb);
3826 }
3827
3828 #ifdef CONFIG_NET_DMA
3829 static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen)
3830 {
3831         struct tcp_sock *tp = tcp_sk(sk);
3832         int chunk = skb->len - hlen;
3833         int dma_cookie;
3834         int copied_early = 0;
3835
3836         if (tp->ucopy.wakeup)
3837                 return 0;
3838
3839         if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
3840                 tp->ucopy.dma_chan = get_softnet_dma();
3841
3842         if (tp->ucopy.dma_chan && skb->ip_summed == CHECKSUM_UNNECESSARY) {
3843
3844                 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
3845                         skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list);
3846
3847                 if (dma_cookie < 0)
3848                         goto out;
3849
3850                 tp->ucopy.dma_cookie = dma_cookie;
3851                 copied_early = 1;
3852
3853                 tp->ucopy.len -= chunk;
3854                 tp->copied_seq += chunk;
3855                 tcp_rcv_space_adjust(sk);
3856
3857                 if ((tp->ucopy.len == 0) ||
3858                     (tcp_flag_word(skb->h.th) & TCP_FLAG_PSH) ||
3859                     (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
3860                         tp->ucopy.wakeup = 1;
3861                         sk->sk_data_ready(sk, 0);
3862                 }
3863         } else if (chunk > 0) {
3864                 tp->ucopy.wakeup = 1;
3865                 sk->sk_data_ready(sk, 0);
3866         }
3867 out:
3868         return copied_early;
3869 }
3870 #endif /* CONFIG_NET_DMA */
3871
3872 /*
3873  *      TCP receive function for the ESTABLISHED state.
3874  *
3875  *      It is split into a fast path and a slow path. The fast path is
3876  *      disabled when:
3877  *      - A zero window was announced from us - zero window probing
3878  *        is only handled properly in the slow path.
3879  *      - Out of order segments arrived.
3880  *      - Urgent data is expected.
3881  *      - There is no buffer space left
3882  *      - Unexpected TCP flags/window values/header lengths are received
3883  *        (detected by checking the TCP header against pred_flags)
3884  *      - Data is sent in both directions. Fast path only supports pure senders
3885  *        or pure receivers (this means either the sequence number or the ack
3886  *        value must stay constant)
3887  *      - Unexpected TCP option.
3888  *
3889  *      When these conditions are not satisfied it drops into a standard
3890  *      receive procedure patterned after RFC793 to handle all cases.
3891  *      The first three cases are guaranteed by proper pred_flags setting,
3892  *      the rest is checked inline. Fast processing is turned on in
3893  *      tcp_data_queue when everything is OK.
3894  */
3895 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
3896                         struct tcphdr *th, unsigned len)
3897 {
3898         struct tcp_sock *tp = tcp_sk(sk);
3899
3900         /*
3901          *      Header prediction.
3902          *      The code loosely follows the one in the famous
3903          *      "30 instruction TCP receive" Van Jacobson mail.
3904          *
3905          *      Van's trick is to deposit buffers into socket queue
3906          *      on a device interrupt, to call tcp_recv function
3907          *      on the receive process context and checksum and copy
3908          *      the buffer to user space. smart...
3909          *
3910          *      Our current scheme is not silly either but we take the
3911          *      extra cost of the net_bh soft interrupt processing...
3912          *      We do checksum and copy also but from device to kernel.
3913          */
3914
3915         tp->rx_opt.saw_tstamp = 0;
3916
3917         /*      pred_flags is 0xS?10 << 16 + snd_wnd
3918          *      if header_prediction is to be made
3919          *      'S' will always be tp->tcp_header_len >> 2
3920          *      '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3921          *  turn it off (when there are holes in the receive
3922          *       space for instance)
3923          *      PSH flag is ignored.
3924          */
3925
3926         if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
3927                 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3928                 int tcp_header_len = tp->tcp_header_len;
3929
3930                 /* Timestamp header prediction: tcp_header_len
3931                  * is automatically equal to th->doff*4 due to pred_flags
3932                  * match.
3933                  */
3934
3935                 /* Check timestamp */
3936                 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
3937                         __be32 *ptr = (__be32 *)(th + 1);
3938
3939                         /* No? Slow path! */
3940                         if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3941                                           | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
3942                                 goto slow_path;
3943
3944                         tp->rx_opt.saw_tstamp = 1;
3945                         ++ptr;
3946                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
3947                         ++ptr;
3948                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3949
3950                         /* If PAWS failed, check it more carefully in slow path */
3951                         if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
3952                                 goto slow_path;
3953
3954                         /* DO NOT update ts_recent here, if checksum fails
3955                          * and timestamp was corrupted part, it will result
3956                          * in a hung connection since we will drop all
3957                          * future packets due to the PAWS test.
3958                          */
3959                 }
3960
3961                 if (len <= tcp_header_len) {
3962                         /* Bulk data transfer: sender */
3963                         if (len == tcp_header_len) {
3964                                 /* Predicted packet is in window by definition.
3965                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3966                                  * Hence, check seq<=rcv_wup reduces to:
3967                                  */
3968                                 if (tcp_header_len ==
3969                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3970                                     tp->rcv_nxt == tp->rcv_wup)
3971                                         tcp_store_ts_recent(tp);
3972
3973                                 /* We know that such packets are checksummed
3974                                  * on entry.
3975                                  */
3976                                 tcp_ack(sk, skb, 0);
3977                                 __kfree_skb(skb);
3978                                 tcp_data_snd_check(sk, tp);
3979                                 return 0;
3980                         } else { /* Header too small */
3981                                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3982                                 goto discard;
3983                         }
3984                 } else {
3985                         int eaten = 0;
3986                         int copied_early = 0;
3987
3988                         if (tp->copied_seq == tp->rcv_nxt &&
3989                             len - tcp_header_len <= tp->ucopy.len) {
3990 #ifdef CONFIG_NET_DMA
3991                                 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
3992                                         copied_early = 1;
3993                                         eaten = 1;
3994                                 }
3995 #endif
3996                                 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) {
3997                                         __set_current_state(TASK_RUNNING);
3998
3999                                         if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
4000                                                 eaten = 1;
4001                                 }
4002                                 if (eaten) {
4003                                         /* Predicted packet is in window by definition.
4004                                          * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4005                                          * Hence, check seq<=rcv_wup reduces to:
4006                                          */
4007                                         if (tcp_header_len ==
4008                                             (sizeof(struct tcphdr) +
4009                                              TCPOLEN_TSTAMP_ALIGNED) &&
4010                                             tp->rcv_nxt == tp->rcv_wup)
4011                                                 tcp_store_ts_recent(tp);
4012
4013                                         tcp_rcv_rtt_measure_ts(sk, skb);
4014
4015                                         __skb_pull(skb, tcp_header_len);
4016                                         tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4017                                         NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
4018                                 }
4019                                 if (copied_early)
4020                                         tcp_cleanup_rbuf(sk, skb->len);
4021                         }
4022                         if (!eaten) {
4023                                 if (tcp_checksum_complete_user(sk, skb))
4024                                         goto csum_error;
4025
4026                                 /* Predicted packet is in window by definition.
4027                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4028                                  * Hence, check seq<=rcv_wup reduces to:
4029                                  */
4030                                 if (tcp_header_len ==
4031                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4032                                     tp->rcv_nxt == tp->rcv_wup)
4033                                         tcp_store_ts_recent(tp);
4034
4035                                 tcp_rcv_rtt_measure_ts(sk, skb);
4036
4037                                 if ((int)skb->truesize > sk->sk_forward_alloc)
4038                                         goto step5;
4039
4040                                 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
4041
4042                                 /* Bulk data transfer: receiver */
4043                                 __skb_pull(skb,tcp_header_len);
4044                                 __skb_queue_tail(&sk->sk_receive_queue, skb);
4045                                 sk_stream_set_owner_r(skb, sk);
4046                                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4047                         }
4048
4049                         tcp_event_data_recv(sk, tp, skb);
4050
4051                         if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
4052                                 /* Well, only one small jumplet in fast path... */
4053                                 tcp_ack(sk, skb, FLAG_DATA);
4054                                 tcp_data_snd_check(sk, tp);
4055                                 if (!inet_csk_ack_scheduled(sk))
4056                                         goto no_ack;
4057                         }
4058
4059                         __tcp_ack_snd_check(sk, 0);
4060 no_ack:
4061 #ifdef CONFIG_NET_DMA
4062                         if (copied_early)
4063                                 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
4064                         else
4065 #endif
4066                         if (eaten)
4067                                 __kfree_skb(skb);
4068                         else
4069                                 sk->sk_data_ready(sk, 0);
4070                         return 0;
4071                 }
4072         }
4073
4074 slow_path:
4075         if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
4076                 goto csum_error;
4077
4078         /*
4079          * RFC1323: H1. Apply PAWS check first.
4080          */
4081         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4082             tcp_paws_discard(sk, skb)) {
4083                 if (!th->rst) {
4084                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4085                         tcp_send_dupack(sk, skb);
4086                         goto discard;
4087                 }
4088                 /* Resets are accepted even if PAWS failed.
4089
4090                    ts_recent update must be made after we are sure
4091                    that the packet is in window.
4092                  */
4093         }
4094
4095         /*
4096          *      Standard slow path.
4097          */
4098
4099         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4100                 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4101                  * (RST) segments are validated by checking their SEQ-fields."
4102                  * And page 69: "If an incoming segment is not acceptable,
4103                  * an acknowledgment should be sent in reply (unless the RST bit
4104                  * is set, if so drop the segment and return)".
4105                  */
4106                 if (!th->rst)
4107                         tcp_send_dupack(sk, skb);
4108                 goto discard;
4109         }
4110
4111         if(th->rst) {
4112                 tcp_reset(sk);
4113                 goto discard;
4114         }
4115
4116         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4117
4118         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4119                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4120                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4121                 tcp_reset(sk);
4122                 return 1;
4123         }
4124
4125 step5:
4126         if(th->ack)
4127                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4128
4129         tcp_rcv_rtt_measure_ts(sk, skb);
4130
4131         /* Process urgent data. */
4132         tcp_urg(sk, skb, th);
4133
4134         /* step 7: process the segment text */
4135         tcp_data_queue(sk, skb);
4136
4137         tcp_data_snd_check(sk, tp);
4138         tcp_ack_snd_check(sk);
4139         return 0;
4140
4141 csum_error:
4142         TCP_INC_STATS_BH(TCP_MIB_INERRS);
4143
4144 discard:
4145         __kfree_skb(skb);
4146         return 0;
4147 }
4148
4149 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
4150                                          struct tcphdr *th, unsigned len)
4151 {
4152         struct tcp_sock *tp = tcp_sk(sk);
4153         struct inet_connection_sock *icsk = inet_csk(sk);
4154         int saved_clamp = tp->rx_opt.mss_clamp;
4155
4156         tcp_parse_options(skb, &tp->rx_opt, 0);
4157
4158         if (th->ack) {
4159                 /* rfc793:
4160                  * "If the state is SYN-SENT then
4161                  *    first check the ACK bit
4162                  *      If the ACK bit is set
4163                  *        If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4164                  *        a reset (unless the RST bit is set, if so drop
4165                  *        the segment and return)"
4166                  *
4167                  *  We do not send data with SYN, so that RFC-correct
4168                  *  test reduces to:
4169                  */
4170                 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
4171                         goto reset_and_undo;
4172
4173                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4174                     !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
4175                              tcp_time_stamp)) {
4176                         NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
4177                         goto reset_and_undo;
4178                 }
4179
4180                 /* Now ACK is acceptable.
4181                  *
4182                  * "If the RST bit is set
4183                  *    If the ACK was acceptable then signal the user "error:
4184                  *    connection reset", drop the segment, enter CLOSED state,
4185                  *    delete TCB, and return."
4186                  */
4187
4188                 if (th->rst) {
4189                         tcp_reset(sk);
4190                         goto discard;
4191                 }
4192
4193                 /* rfc793:
4194                  *   "fifth, if neither of the SYN or RST bits is set then
4195                  *    drop the segment and return."
4196                  *
4197                  *    See note below!
4198                  *                                        --ANK(990513)
4199                  */
4200                 if (!th->syn)
4201                         goto discard_and_undo;
4202
4203                 /* rfc793:
4204                  *   "If the SYN bit is on ...
4205                  *    are acceptable then ...
4206                  *    (our SYN has been ACKed), change the connection
4207                  *    state to ESTABLISHED..."
4208                  */
4209
4210                 TCP_ECN_rcv_synack(tp, th);
4211
4212                 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4213                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4214
4215                 /* Ok.. it's good. Set up sequence numbers and
4216                  * move to established.
4217                  */
4218                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4219                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4220
4221                 /* RFC1323: The window in SYN & SYN/ACK segments is
4222                  * never scaled.
4223                  */
4224                 tp->snd_wnd = ntohs(th->window);
4225                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4226
4227                 if (!tp->rx_opt.wscale_ok) {
4228                         tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4229                         tp->window_clamp = min(tp->window_clamp, 65535U);
4230                 }
4231
4232                 if (tp->rx_opt.saw_tstamp) {
4233                         tp->rx_opt.tstamp_ok       = 1;
4234                         tp->tcp_header_len =
4235                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4236                         tp->advmss          -= TCPOLEN_TSTAMP_ALIGNED;
4237                         tcp_store_ts_recent(tp);
4238                 } else {
4239                         tp->tcp_header_len = sizeof(struct tcphdr);
4240                 }
4241
4242                 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4243                         tp->rx_opt.sack_ok |= 2;
4244
4245                 tcp_mtup_init(sk);
4246                 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
4247                 tcp_initialize_rcv_mss(sk);
4248
4249                 /* Remember, tcp_poll() does not lock socket!
4250                  * Change state from SYN-SENT only after copied_seq
4251                  * is initialized. */
4252                 tp->copied_seq = tp->rcv_nxt;
4253                 smp_mb();
4254                 tcp_set_state(sk, TCP_ESTABLISHED);
4255
4256                 security_inet_conn_established(sk, skb);
4257
4258                 /* Make sure socket is routed, for correct metrics.  */
4259                 icsk->icsk_af_ops->rebuild_header(sk);
4260
4261                 tcp_init_metrics(sk);
4262
4263                 tcp_init_congestion_control(sk);
4264
4265                 /* Prevent spurious tcp_cwnd_restart() on first data
4266                  * packet.
4267                  */
4268                 tp->lsndtime = tcp_time_stamp;
4269
4270                 tcp_init_buffer_space(sk);
4271
4272                 if (sock_flag(sk, SOCK_KEEPOPEN))
4273                         inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
4274
4275                 if (!tp->rx_opt.snd_wscale)
4276                         __tcp_fast_path_on(tp, tp->snd_wnd);
4277                 else
4278                         tp->pred_flags = 0;
4279
4280                 if (!sock_flag(sk, SOCK_DEAD)) {
4281                         sk->sk_state_change(sk);
4282                         sk_wake_async(sk, 0, POLL_OUT);
4283                 }
4284
4285                 if (sk->sk_write_pending ||
4286                     icsk->icsk_accept_queue.rskq_defer_accept ||
4287                     icsk->icsk_ack.pingpong) {
4288                         /* Save one ACK. Data will be ready after
4289                          * several ticks, if write_pending is set.
4290                          *
4291                          * It may be deleted, but with this feature tcpdumps
4292                          * look so _wonderfully_ clever, that I was not able
4293                          * to stand against the temptation 8)     --ANK
4294                          */
4295                         inet_csk_schedule_ack(sk);
4296                         icsk->icsk_ack.lrcvtime = tcp_time_stamp;
4297                         icsk->icsk_ack.ato       = TCP_ATO_MIN;
4298                         tcp_incr_quickack(sk);
4299                         tcp_enter_quickack_mode(sk);
4300                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
4301                                                   TCP_DELACK_MAX, TCP_RTO_MAX);
4302
4303 discard:
4304                         __kfree_skb(skb);
4305                         return 0;
4306                 } else {
4307                         tcp_send_ack(sk);
4308                 }
4309                 return -1;
4310         }
4311
4312         /* No ACK in the segment */
4313
4314         if (th->rst) {
4315                 /* rfc793:
4316                  * "If the RST bit is set
4317                  *
4318                  *      Otherwise (no ACK) drop the segment and return."
4319                  */
4320
4321                 goto discard_and_undo;
4322         }
4323
4324         /* PAWS check. */
4325         if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4326                 goto discard_and_undo;
4327
4328         if (th->syn) {
4329                 /* We see SYN without ACK. It is attempt of
4330                  * simultaneous connect with crossed SYNs.
4331                  * Particularly, it can be connect to self.
4332                  */
4333                 tcp_set_state(sk, TCP_SYN_RECV);
4334
4335                 if (tp->rx_opt.saw_tstamp) {
4336                         tp->rx_opt.tstamp_ok = 1;
4337                         tcp_store_ts_recent(tp);
4338                         tp->tcp_header_len =
4339                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4340                 } else {
4341                         tp->tcp_header_len = sizeof(struct tcphdr);
4342                 }
4343
4344                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4345                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4346
4347                 /* RFC1323: The window in SYN & SYN/ACK segments is
4348                  * never scaled.
4349                  */
4350                 tp->snd_wnd    = ntohs(th->window);
4351                 tp->snd_wl1    = TCP_SKB_CB(skb)->seq;
4352                 tp->max_window = tp->snd_wnd;
4353
4354                 TCP_ECN_rcv_syn(tp, th);
4355
4356                 tcp_mtup_init(sk);
4357                 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
4358                 tcp_initialize_rcv_mss(sk);
4359
4360
4361                 tcp_send_synack(sk);
4362 #if 0
4363                 /* Note, we could accept data and URG from this segment.
4364                  * There are no obstacles to make this.
4365                  *
4366                  * However, if we ignore data in ACKless segments sometimes,
4367                  * we have no reasons to accept it sometimes.
4368                  * Also, seems the code doing it in step6 of tcp_rcv_state_process
4369                  * is not flawless. So, discard packet for sanity.
4370                  * Uncomment this return to process the data.
4371                  */
4372                 return -1;
4373 #else
4374                 goto discard;
4375 #endif
4376         }
4377         /* "fifth, if neither of the SYN or RST bits is set then
4378          * drop the segment and return."
4379          */
4380
4381 discard_and_undo:
4382         tcp_clear_options(&tp->rx_opt);
4383         tp->rx_opt.mss_clamp = saved_clamp;
4384         goto discard;
4385
4386 reset_and_undo:
4387         tcp_clear_options(&tp->rx_opt);
4388         tp->rx_opt.mss_clamp = saved_clamp;
4389         return 1;
4390 }
4391
4392
4393 /*
4394  *      This function implements the receiving procedure of RFC 793 for
4395  *      all states except ESTABLISHED and TIME_WAIT.
4396  *      It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4397  *      address independent.
4398  */
4399
4400 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4401                           struct tcphdr *th, unsigned len)
4402 {
4403         struct tcp_sock *tp = tcp_sk(sk);
4404         struct inet_connection_sock *icsk = inet_csk(sk);
4405         int queued = 0;
4406
4407         tp->rx_opt.saw_tstamp = 0;
4408
4409         switch (sk->sk_state) {
4410         case TCP_CLOSE:
4411                 goto discard;
4412
4413         case TCP_LISTEN:
4414                 if(th->ack)
4415                         return 1;
4416
4417                 if(th->rst)
4418                         goto discard;
4419
4420                 if(th->syn) {
4421                         if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
4422                                 return 1;
4423
4424                         /* Now we have several options: In theory there is
4425                          * nothing else in the frame. KA9Q has an option to
4426                          * send data with the syn, BSD accepts data with the
4427                          * syn up to the [to be] advertised window and
4428                          * Solaris 2.1 gives you a protocol error. For now
4429                          * we just ignore it, that fits the spec precisely
4430                          * and avoids incompatibilities. It would be nice in
4431                          * future to drop through and process the data.
4432                          *
4433                          * Now that TTCP is starting to be used we ought to
4434                          * queue this data.
4435                          * But, this leaves one open to an easy denial of
4436                          * service attack, and SYN cookies can't defend
4437                          * against this problem. So, we drop the data
4438                          * in the interest of security over speed unless
4439                          * it's still in use.
4440                          */
4441                         kfree_skb(skb);
4442                         return 0;
4443                 }
4444                 goto discard;
4445
4446         case TCP_SYN_SENT:
4447                 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4448                 if (queued >= 0)
4449                         return queued;
4450
4451                 /* Do step6 onward by hand. */
4452                 tcp_urg(sk, skb, th);
4453                 __kfree_skb(skb);
4454                 tcp_data_snd_check(sk, tp);
4455                 return 0;
4456         }
4457
4458         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4459             tcp_paws_discard(sk, skb)) {
4460                 if (!th->rst) {
4461                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4462                         tcp_send_dupack(sk, skb);
4463                         goto discard;
4464                 }
4465                 /* Reset is accepted even if it did not pass PAWS. */
4466         }
4467
4468         /* step 1: check sequence number */
4469         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4470                 if (!th->rst)
4471                         tcp_send_dupack(sk, skb);
4472                 goto discard;
4473         }
4474
4475         /* step 2: check RST bit */
4476         if(th->rst) {
4477                 tcp_reset(sk);
4478                 goto discard;
4479         }
4480
4481         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4482
4483         /* step 3: check security and precedence [ignored] */
4484
4485         /*      step 4:
4486          *
4487          *      Check for a SYN in window.
4488          */
4489         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4490                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4491                 tcp_reset(sk);
4492                 return 1;
4493         }
4494
4495         /* step 5: check the ACK field */
4496         if (th->ack) {
4497                 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4498
4499                 switch(sk->sk_state) {
4500                 case TCP_SYN_RECV:
4501                         if (acceptable) {
4502                                 tp->copied_seq = tp->rcv_nxt;
4503                                 smp_mb();
4504                                 tcp_set_state(sk, TCP_ESTABLISHED);
4505                                 sk->sk_state_change(sk);
4506
4507                                 /* Note, that this wakeup is only for marginal
4508                                  * crossed SYN case. Passively open sockets
4509                                  * are not waked up, because sk->sk_sleep ==
4510                                  * NULL and sk->sk_socket == NULL.
4511                                  */
4512                                 if (sk->sk_socket) {
4513                                         sk_wake_async(sk,0,POLL_OUT);
4514                                 }
4515
4516                                 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4517                                 tp->snd_wnd = ntohs(th->window) <<
4518                                               tp->rx_opt.snd_wscale;
4519                                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4520                                             TCP_SKB_CB(skb)->seq);
4521
4522                                 /* tcp_ack considers this ACK as duplicate
4523                                  * and does not calculate rtt.
4524                                  * Fix it at least with timestamps.
4525                                  */
4526                                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4527                                     !tp->srtt)
4528                                         tcp_ack_saw_tstamp(sk, 0);
4529
4530                                 if (tp->rx_opt.tstamp_ok)
4531                                         tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4532
4533                                 /* Make sure socket is routed, for
4534                                  * correct metrics.
4535                                  */
4536                                 icsk->icsk_af_ops->rebuild_header(sk);
4537
4538                                 tcp_init_metrics(sk);
4539
4540                                 tcp_init_congestion_control(sk);
4541
4542                                 /* Prevent spurious tcp_cwnd_restart() on
4543                                  * first data packet.
4544                                  */
4545                                 tp->lsndtime = tcp_time_stamp;
4546
4547                                 tcp_mtup_init(sk);
4548                                 tcp_initialize_rcv_mss(sk);
4549                                 tcp_init_buffer_space(sk);
4550                                 tcp_fast_path_on(tp);
4551                         } else {
4552                                 return 1;
4553                         }
4554                         break;
4555
4556                 case TCP_FIN_WAIT1:
4557                         if (tp->snd_una == tp->write_seq) {
4558                                 tcp_set_state(sk, TCP_FIN_WAIT2);
4559                                 sk->sk_shutdown |= SEND_SHUTDOWN;
4560                                 dst_confirm(sk->sk_dst_cache);
4561
4562                                 if (!sock_flag(sk, SOCK_DEAD))
4563                                         /* Wake up lingering close() */
4564                                         sk->sk_state_change(sk);
4565                                 else {
4566                                         int tmo;
4567
4568                                         if (tp->linger2 < 0 ||
4569                                             (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4570                                              after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4571                                                 tcp_done(sk);
4572                                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4573                                                 return 1;
4574                                         }
4575
4576                                         tmo = tcp_fin_time(sk);
4577                                         if (tmo > TCP_TIMEWAIT_LEN) {
4578                                                 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
4579                                         } else if (th->fin || sock_owned_by_user(sk)) {
4580                                                 /* Bad case. We could lose such FIN otherwise.
4581                                                  * It is not a big problem, but it looks confusing
4582                                                  * and not so rare event. We still can lose it now,
4583                                                  * if it spins in bh_lock_sock(), but it is really
4584                                                  * marginal case.
4585                                                  */
4586                                                 inet_csk_reset_keepalive_timer(sk, tmo);
4587                                         } else {
4588                                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4589                                                 goto discard;
4590                                         }
4591                                 }
4592                         }
4593                         break;
4594
4595                 case TCP_CLOSING:
4596                         if (tp->snd_una == tp->write_seq) {
4597                                 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4598                                 goto discard;
4599                         }
4600                         break;
4601
4602                 case TCP_LAST_ACK:
4603                         if (tp->snd_una == tp->write_seq) {
4604                                 tcp_update_metrics(sk);
4605                                 tcp_done(sk);
4606                                 goto discard;
4607                         }
4608                         break;
4609                 }
4610         } else
4611                 goto discard;
4612
4613         /* step 6: check the URG bit */
4614         tcp_urg(sk, skb, th);
4615
4616         /* step 7: process the segment text */
4617         switch (sk->sk_state) {
4618         case TCP_CLOSE_WAIT:
4619         case TCP_CLOSING:
4620         case TCP_LAST_ACK:
4621                 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4622                         break;
4623         case TCP_FIN_WAIT1:
4624         case TCP_FIN_WAIT2:
4625                 /* RFC 793 says to queue data in these states,
4626                  * RFC 1122 says we MUST send a reset.
4627                  * BSD 4.4 also does reset.
4628                  */
4629                 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4630                         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4631                             after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4632                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4633                                 tcp_reset(sk);
4634                                 return 1;
4635                         }
4636                 }
4637                 /* Fall through */
4638         case TCP_ESTABLISHED:
4639                 tcp_data_queue(sk, skb);
4640                 queued = 1;
4641                 break;
4642         }
4643
4644         /* tcp_data could move socket to TIME-WAIT */
4645         if (sk->sk_state != TCP_CLOSE) {
4646                 tcp_data_snd_check(sk, tp);
4647                 tcp_ack_snd_check(sk);
4648         }
4649
4650         if (!queued) {
4651 discard:
4652                 __kfree_skb(skb);
4653         }
4654         return 0;
4655 }
4656
4657 EXPORT_SYMBOL(sysctl_tcp_ecn);
4658 EXPORT_SYMBOL(sysctl_tcp_reordering);
4659 EXPORT_SYMBOL(tcp_parse_options);
4660 EXPORT_SYMBOL(tcp_rcv_established);
4661 EXPORT_SYMBOL(tcp_rcv_state_process);
4662 EXPORT_SYMBOL(tcp_initialize_rcv_mss);