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

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>:
   9  *      - Real stateful connection tracking
  10  *      - Modified state transitions table
  11  *      - Window scaling support added
  12  *      - SACK support added
  13  *
  14  * Willy Tarreau:
  15  *      - State table bugfixes
  16  *      - More robust state changes
  17  *      - Tuning timer parameters
  18  *
  19  * version 2.2
  20  */
  21
  22 #include <linux/config.h>
  23 #include <linux/types.h>
  24 #include <linux/sched.h>
  25 #include <linux/timer.h>
  26 #include <linux/netfilter.h>
  27 #include <linux/module.h>
  28 #include <linux/in.h>
  29 #include <linux/ip.h>
  30 #include <linux/tcp.h>
  31 #include <linux/spinlock.h>
  32
  33 #include <net/tcp.h>
  34
  35 #include <linux/netfilter.h>
  36 #include <linux/netfilter_ipv4.h>
  37 #include <linux/netfilter_ipv4/ip_conntrack.h>
  38 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
  39
  40 #if 0
  41 #define DEBUGP printk
  42 #define DEBUGP_VARS
  43 #else
  44 #define DEBUGP(format, args...)
  45 #endif
  46
  47 /* Protects conntrack->proto.tcp */
  48 static DEFINE_RWLOCK(tcp_lock);
  49
  50 /* "Be conservative in what you do,
  51     be liberal in what you accept from others."
  52     If it's non-zero, we mark only out of window RST segments as INVALID. */
  53 int ip_ct_tcp_be_liberal = 0;
  54
  55 /* When connection is picked up from the middle, how many packets are required
  56    to pass in each direction when we assume we are in sync - if any side uses
  57    window scaling, we lost the game.
  58    If it is set to zero, we disable picking up already established
  59    connections. */
  60 int ip_ct_tcp_loose = 3;
  61
  62 /* Max number of the retransmitted packets without receiving an (acceptable)
  63    ACK from the destination. If this number is reached, a shorter timer
  64    will be started. */
  65 int ip_ct_tcp_max_retrans = 3;
  66
  67   /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
  68      closely.  They're more complex. --RR */
  69
  70 static const char *tcp_conntrack_names[] = {
  71         "NONE",
  72         "SYN_SENT",
  73         "SYN_RECV",
  74         "ESTABLISHED",
  75         "FIN_WAIT",
  76         "CLOSE_WAIT",
  77         "LAST_ACK",
  78         "TIME_WAIT",
  79         "CLOSE",
  80         "LISTEN"
  81 };
  82
  83 #define SECS * HZ
  84 #define MINS * 60 SECS
  85 #define HOURS * 60 MINS
  86 #define DAYS * 24 HOURS
  87
  88 unsigned long ip_ct_tcp_timeout_syn_sent =      2 MINS;
  89 unsigned long ip_ct_tcp_timeout_syn_recv =     60 SECS;
  90 unsigned long ip_ct_tcp_timeout_established =   5 DAYS;
  91 unsigned long ip_ct_tcp_timeout_fin_wait =      2 MINS;
  92 unsigned long ip_ct_tcp_timeout_close_wait =   60 SECS;
  93 unsigned long ip_ct_tcp_timeout_last_ack =     30 SECS;
  94 unsigned long ip_ct_tcp_timeout_time_wait =     2 MINS;
  95 unsigned long ip_ct_tcp_timeout_close =        10 SECS;
  96
  97 /* RFC1122 says the R2 limit should be at least 100 seconds.
  98    Linux uses 15 packets as limit, which corresponds
  99    to ~13-30min depending on RTO. */
 100 unsigned long ip_ct_tcp_timeout_max_retrans =     5 MINS;
 101
 102 static unsigned long * tcp_timeouts[]
 103 = { NULL,                              /*      TCP_CONNTRACK_NONE */
 104     &ip_ct_tcp_timeout_syn_sent,       /*      TCP_CONNTRACK_SYN_SENT, */
 105     &ip_ct_tcp_timeout_syn_recv,       /*      TCP_CONNTRACK_SYN_RECV, */
 106     &ip_ct_tcp_timeout_established,    /*      TCP_CONNTRACK_ESTABLISHED,      */
 107     &ip_ct_tcp_timeout_fin_wait,       /*      TCP_CONNTRACK_FIN_WAIT, */
 108     &ip_ct_tcp_timeout_close_wait,     /*      TCP_CONNTRACK_CLOSE_WAIT,       */
 109     &ip_ct_tcp_timeout_last_ack,       /*      TCP_CONNTRACK_LAST_ACK, */
 110     &ip_ct_tcp_timeout_time_wait,      /*      TCP_CONNTRACK_TIME_WAIT,        */
 111     &ip_ct_tcp_timeout_close,          /*      TCP_CONNTRACK_CLOSE,    */
 112     NULL,                              /*      TCP_CONNTRACK_LISTEN */
 113  };
 114
 115 #define sNO TCP_CONNTRACK_NONE
 116 #define sSS TCP_CONNTRACK_SYN_SENT
 117 #define sSR TCP_CONNTRACK_SYN_RECV
 118 #define sES TCP_CONNTRACK_ESTABLISHED
 119 #define sFW TCP_CONNTRACK_FIN_WAIT
 120 #define sCW TCP_CONNTRACK_CLOSE_WAIT
 121 #define sLA TCP_CONNTRACK_LAST_ACK
 122 #define sTW TCP_CONNTRACK_TIME_WAIT
 123 #define sCL TCP_CONNTRACK_CLOSE
 124 #define sLI TCP_CONNTRACK_LISTEN
 125 #define sIV TCP_CONNTRACK_MAX
 126 #define sIG TCP_CONNTRACK_IGNORE
 127
 128 /* What TCP flags are set from RST/SYN/FIN/ACK. */
 129 enum tcp_bit_set {
 130         TCP_SYN_SET,
 131         TCP_SYNACK_SET,
 132         TCP_FIN_SET,
 133         TCP_ACK_SET,
 134         TCP_RST_SET,
 135         TCP_NONE_SET,
 136 };
 137
 138 /*
 139  * The TCP state transition table needs a few words...
 140  *
 141  * We are the man in the middle. All the packets go through us
 142  * but might get lost in transit to the destination.
 143  * It is assumed that the destinations can't receive segments
 144  * we haven't seen.
 145  *
 146  * The checked segment is in window, but our windows are *not*
 147  * equivalent with the ones of the sender/receiver. We always
 148  * try to guess the state of the current sender.
 149  *
 150  * The meaning of the states are:
 151  *
 152  * NONE:        initial state
 153  * SYN_SENT:    SYN-only packet seen
 154  * SYN_RECV:    SYN-ACK packet seen
 155  * ESTABLISHED: ACK packet seen
 156  * FIN_WAIT:    FIN packet seen
 157  * CLOSE_WAIT:  ACK seen (after FIN)
 158  * LAST_ACK:    FIN seen (after FIN)
 159  * TIME_WAIT:   last ACK seen
 160  * CLOSE:       closed connection
 161  *
 162  * LISTEN state is not used.
 163  *
 164  * Packets marked as IGNORED (sIG):
 165  *      if they may be either invalid or valid
 166  *      and the receiver may send back a connection
 167  *      closing RST or a SYN/ACK.
 168  *
 169  * Packets marked as INVALID (sIV):
 170  *      if they are invalid
 171  *      or we do not support the request (simultaneous open)
 172  */
 173 static enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
 174         {
 175 /* ORIGINAL */
 176 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 177 /*syn*/    { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
 178 /*
 179  *      sNO -> sSS      Initialize a new connection
 180  *      sSS -> sSS      Retransmitted SYN
 181  *      sSR -> sIG      Late retransmitted SYN?
 182  *      sES -> sIG      Error: SYNs in window outside the SYN_SENT state
 183  *                      are errors. Receiver will reply with RST
 184  *                      and close the connection.
 185  *                      Or we are not in sync and hold a dead connection.
 186  *      sFW -> sIG
 187  *      sCW -> sIG
 188  *      sLA -> sIG
 189  *      sTW -> sSS      Reopened connection (RFC 1122).
 190  *      sCL -> sSS
 191  */
 192 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 193 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 194 /*
 195  * A SYN/ACK from the client is always invalid:
 196  *      - either it tries to set up a simultaneous open, which is
 197  *        not supported;
 198  *      - or the firewall has just been inserted between the two hosts
 199  *        during the session set-up. The SYN will be retransmitted
 200  *        by the true client (or it'll time out).
 201  */
 202 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 203 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 204 /*
 205  *      sNO -> sIV      Too late and no reason to do anything...
 206  *      sSS -> sIV      Client migth not send FIN in this state:
 207  *                      we enforce waiting for a SYN/ACK reply first.
 208  *      sSR -> sFW      Close started.
 209  *      sES -> sFW
 210  *      sFW -> sLA      FIN seen in both directions, waiting for
 211  *                      the last ACK.
 212  *                      Migth be a retransmitted FIN as well...
 213  *      sCW -> sLA
 214  *      sLA -> sLA      Retransmitted FIN. Remain in the same state.
 215  *      sTW -> sTW
 216  *      sCL -> sCL
 217  */
 218 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 219 /*ack*/    { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 220 /*
 221  *      sNO -> sES      Assumed.
 222  *      sSS -> sIV      ACK is invalid: we haven't seen a SYN/ACK yet.
 223  *      sSR -> sES      Established state is reached.
 224  *      sES -> sES      :-)
 225  *      sFW -> sCW      Normal close request answered by ACK.
 226  *      sCW -> sCW
 227  *      sLA -> sTW      Last ACK detected.
 228  *      sTW -> sTW      Retransmitted last ACK. Remain in the same state.
 229  *      sCL -> sCL
 230  */
 231 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 232 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 233 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 234         },
 235         {
 236 /* REPLY */
 237 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 238 /*syn*/    { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 239 /*
 240  *      sNO -> sIV      Never reached.
 241  *      sSS -> sIV      Simultaneous open, not supported
 242  *      sSR -> sIV      Simultaneous open, not supported.
 243  *      sES -> sIV      Server may not initiate a connection.
 244  *      sFW -> sIV
 245  *      sCW -> sIV
 246  *      sLA -> sIV
 247  *      sTW -> sIV      Reopened connection, but server may not do it.
 248  *      sCL -> sIV
 249  */
 250 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 251 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
 252 /*
 253  *      sSS -> sSR      Standard open.
 254  *      sSR -> sSR      Retransmitted SYN/ACK.
 255  *      sES -> sIG      Late retransmitted SYN/ACK?
 256  *      sFW -> sIG      Might be SYN/ACK answering ignored SYN
 257  *      sCW -> sIG
 258  *      sLA -> sIG
 259  *      sTW -> sIG
 260  *      sCL -> sIG
 261  */
 262 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 263 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 264 /*
 265  *      sSS -> sIV      Server might not send FIN in this state.
 266  *      sSR -> sFW      Close started.
 267  *      sES -> sFW
 268  *      sFW -> sLA      FIN seen in both directions.
 269  *      sCW -> sLA
 270  *      sLA -> sLA      Retransmitted FIN.
 271  *      sTW -> sTW
 272  *      sCL -> sCL
 273  */
 274 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 275 /*ack*/    { sIV, sIV, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 276 /*
 277  *      sSS -> sIV      Might be a half-open connection.
 278  *      sSR -> sSR      Might answer late resent SYN.
 279  *      sES -> sES      :-)
 280  *      sFW -> sCW      Normal close request answered by ACK.
 281  *      sCW -> sCW
 282  *      sLA -> sTW      Last ACK detected.
 283  *      sTW -> sTW      Retransmitted last ACK.
 284  *      sCL -> sCL
 285  */
 286 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 287 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 288 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 289         }
 290 };
 291
 292 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
 293                             unsigned int dataoff,
 294                             struct ip_conntrack_tuple *tuple)
 295 {
 296         struct tcphdr _hdr, *hp;
 297
 298         /* Actually only need first 8 bytes. */
 299         hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
 300         if (hp == NULL)
 301                 return 0;
 302
 303         tuple->src.u.tcp.port = hp->source;
 304         tuple->dst.u.tcp.port = hp->dest;
 305
 306         return 1;
 307 }
 308
 309 static int tcp_invert_tuple(struct ip_conntrack_tuple *tuple,
 310                             const struct ip_conntrack_tuple *orig)
 311 {
 312         tuple->src.u.tcp.port = orig->dst.u.tcp.port;
 313         tuple->dst.u.tcp.port = orig->src.u.tcp.port;
 314         return 1;
 315 }
 316
 317 /* Print out the per-protocol part of the tuple. */
 318 static int tcp_print_tuple(struct seq_file *s,
 319                            const struct ip_conntrack_tuple *tuple)
 320 {
 321         return seq_printf(s, "sport=%hu dport=%hu ",
 322                           ntohs(tuple->src.u.tcp.port),
 323                           ntohs(tuple->dst.u.tcp.port));
 324 }
 325
 326 /* Print out the private part of the conntrack. */
 327 static int tcp_print_conntrack(struct seq_file *s,
 328                                const struct ip_conntrack *conntrack)
 329 {
 330         enum tcp_conntrack state;
 331
 332         read_lock_bh(&tcp_lock);
 333         state = conntrack->proto.tcp.state;
 334         read_unlock_bh(&tcp_lock);
 335
 336         return seq_printf(s, "%s ", tcp_conntrack_names[state]);
 337 }
 338
 339 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 340     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 341 static int tcp_to_nfattr(struct sk_buff *skb, struct nfattr *nfa,
 342                          const struct ip_conntrack *ct)
 343 {
 344         read_lock_bh(&tcp_lock);
 345         NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
 346                 &ct->proto.tcp.state);
 347         read_unlock_bh(&tcp_lock);
 348
 349         return 0;
 350
 351 nfattr_failure:
 352         return -1;
 353 }
 354 #endif
 355
 356 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
 357 {
 358         if (tcph->rst) return TCP_RST_SET;
 359         else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
 360         else if (tcph->fin) return TCP_FIN_SET;
 361         else if (tcph->ack) return TCP_ACK_SET;
 362         else return TCP_NONE_SET;
 363 }
 364
 365 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
 366    in IP Filter' by Guido van Rooij.
 367
 368    http://www.nluug.nl/events/sane2000/papers.html
 369    http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
 370
 371    The boundaries and the conditions are changed according to RFC793:
 372    the packet must intersect the window (i.e. segments may be
 373    after the right or before the left edge) and thus receivers may ACK
 374    segments after the right edge of the window.
 375
 376         td_maxend = max(sack + max(win,1)) seen in reply packets
 377         td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
 378         td_maxwin += seq + len - sender.td_maxend
 379                         if seq + len > sender.td_maxend
 380         td_end    = max(seq + len) seen in sent packets
 381
 382    I.   Upper bound for valid data:     seq <= sender.td_maxend
 383    II.  Lower bound for valid data:     seq + len >= sender.td_end - receiver.td_maxwin
 384    III. Upper bound for valid ack:      sack <= receiver.td_end
 385    IV.  Lower bound for valid ack:      ack >= receiver.td_end - MAXACKWINDOW
 386
 387    where sack is the highest right edge of sack block found in the packet.
 388
 389    The upper bound limit for a valid ack is not ignored -
 390    we doesn't have to deal with fragments.
 391 */
 392
 393 static inline __u32 segment_seq_plus_len(__u32 seq,
 394                                          size_t len,
 395                                          struct iphdr *iph,
 396                                          struct tcphdr *tcph)
 397 {
 398         return (seq + len - (iph->ihl + tcph->doff)*4
 399                 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
 400 }
 401
 402 /* Fixme: what about big packets? */
 403 #define MAXACKWINCONST                  66000
 404 #define MAXACKWINDOW(sender)                                            \
 405         ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin     \
 406                                               : MAXACKWINCONST)
 407
 408 /*
 409  * Simplified tcp_parse_options routine from tcp_input.c
 410  */
 411 static void tcp_options(const struct sk_buff *skb,
 412                         struct iphdr *iph,
 413                         struct tcphdr *tcph,
 414                         struct ip_ct_tcp_state *state)
 415 {
 416         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 417         unsigned char *ptr;
 418         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 419
 420         if (!length)
 421                 return;
 422
 423         ptr = skb_header_pointer(skb,
 424                                  (iph->ihl * 4) + sizeof(struct tcphdr),
 425                                  length, buff);
 426         BUG_ON(ptr == NULL);
 427
 428         state->td_scale =
 429         state->flags = 0;
 430
 431         while (length > 0) {
 432                 int opcode=*ptr++;
 433                 int opsize;
 434
 435                 switch (opcode) {
 436                 case TCPOPT_EOL:
 437                         return;
 438                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 439                         length--;
 440                         continue;
 441                 default:
 442                         opsize=*ptr++;
 443                         if (opsize < 2) /* "silly options" */
 444                                 return;
 445                         if (opsize > length)
 446                                 break;  /* don't parse partial options */
 447
 448                         if (opcode == TCPOPT_SACK_PERM
 449                             && opsize == TCPOLEN_SACK_PERM)
 450                                 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
 451                         else if (opcode == TCPOPT_WINDOW
 452                                  && opsize == TCPOLEN_WINDOW) {
 453                                 state->td_scale = *(u_int8_t *)ptr;
 454
 455                                 if (state->td_scale > 14) {
 456                                         /* See RFC1323 */
 457                                         state->td_scale = 14;
 458                                 }
 459                                 state->flags |=
 460                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
 461                         }
 462                         ptr += opsize - 2;
 463                         length -= opsize;
 464                 }
 465         }
 466 }
 467
 468 static void tcp_sack(const struct sk_buff *skb,
 469                      struct iphdr *iph,
 470                      struct tcphdr *tcph,
 471                      __u32 *sack)
 472 {
 473         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 474         unsigned char *ptr;
 475         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 476         __u32 tmp;
 477
 478         if (!length)
 479                 return;
 480
 481         ptr = skb_header_pointer(skb,
 482                                  (iph->ihl * 4) + sizeof(struct tcphdr),
 483                                  length, buff);
 484         BUG_ON(ptr == NULL);
 485
 486         /* Fast path for timestamp-only option */
 487         if (length == TCPOLEN_TSTAMP_ALIGNED*4
 488             && *(__u32 *)ptr ==
 489                 __constant_ntohl((TCPOPT_NOP << 24)
 490                                  | (TCPOPT_NOP << 16)
 491                                  | (TCPOPT_TIMESTAMP << 8)
 492                                  | TCPOLEN_TIMESTAMP))
 493                 return;
 494
 495         while (length > 0) {
 496                 int opcode=*ptr++;
 497                 int opsize, i;
 498
 499                 switch (opcode) {
 500                 case TCPOPT_EOL:
 501                         return;
 502                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 503                         length--;
 504                         continue;
 505                 default:
 506                         opsize=*ptr++;
 507                         if (opsize < 2) /* "silly options" */
 508                                 return;
 509                         if (opsize > length)
 510                                 break;  /* don't parse partial options */
 511
 512                         if (opcode == TCPOPT_SACK
 513                             && opsize >= (TCPOLEN_SACK_BASE
 514                                           + TCPOLEN_SACK_PERBLOCK)
 515                             && !((opsize - TCPOLEN_SACK_BASE)
 516                                  % TCPOLEN_SACK_PERBLOCK)) {
 517                                 for (i = 0;
 518                                      i < (opsize - TCPOLEN_SACK_BASE);
 519                                      i += TCPOLEN_SACK_PERBLOCK) {
 520                                         tmp = ntohl(*((u_int32_t *)(ptr+i)+1));
 521
 522                                         if (after(tmp, *sack))
 523                                                 *sack = tmp;
 524                                 }
 525                                 return;
 526                         }
 527                         ptr += opsize - 2;
 528                         length -= opsize;
 529                 }
 530         }
 531 }
 532
 533 static int tcp_in_window(struct ip_ct_tcp *state,
 534                          enum ip_conntrack_dir dir,
 535                          unsigned int index,
 536                          const struct sk_buff *skb,
 537                          struct iphdr *iph,
 538                          struct tcphdr *tcph)
 539 {
 540         struct ip_ct_tcp_state *sender = &state->seen[dir];
 541         struct ip_ct_tcp_state *receiver = &state->seen[!dir];
 542         __u32 seq, ack, sack, end, win, swin;
 543         int res;
 544
 545         /*
 546          * Get the required data from the packet.
 547          */
 548         seq = ntohl(tcph->seq);
 549         ack = sack = ntohl(tcph->ack_seq);
 550         win = ntohs(tcph->window);
 551         end = segment_seq_plus_len(seq, skb->len, iph, tcph);
 552
 553         if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
 554                 tcp_sack(skb, iph, tcph, &sack);
 555
 556         DEBUGP("tcp_in_window: START\n");
 557         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 558                "seq=%u ack=%u sack=%u win=%u end=%u\n",
 559                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 560                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 561                 seq, ack, sack, win, end);
 562         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 563                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 564                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 565                 sender->td_scale,
 566                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 567                 receiver->td_scale);
 568
 569         if (sender->td_end == 0) {
 570                 /*
 571                  * Initialize sender data.
 572                  */
 573                 if (tcph->syn && tcph->ack) {
 574                         /*
 575                          * Outgoing SYN-ACK in reply to a SYN.
 576                          */
 577                         sender->td_end =
 578                         sender->td_maxend = end;
 579                         sender->td_maxwin = (win == 0 ? 1 : win);
 580
 581                         tcp_options(skb, iph, tcph, sender);
 582                         /*
 583                          * RFC 1323:
 584                          * Both sides must send the Window Scale option
 585                          * to enable window scaling in either direction.
 586                          */
 587                         if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
 588                               && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
 589                                 sender->td_scale =
 590                                 receiver->td_scale = 0;
 591                 } else {
 592                         /*
 593                          * We are in the middle of a connection,
 594                          * its history is lost for us.
 595                          * Let's try to use the data from the packet.
 596                          */
 597                         sender->td_end = end;
 598                         sender->td_maxwin = (win == 0 ? 1 : win);
 599                         sender->td_maxend = end + sender->td_maxwin;
 600                 }
 601         } else if (((state->state == TCP_CONNTRACK_SYN_SENT
 602                      && dir == IP_CT_DIR_ORIGINAL)
 603                     || (state->state == TCP_CONNTRACK_SYN_RECV
 604                         && dir == IP_CT_DIR_REPLY))
 605                     && after(end, sender->td_end)) {
 606                 /*
 607                  * RFC 793: "if a TCP is reinitialized ... then it need
 608                  * not wait at all; it must only be sure to use sequence
 609                  * numbers larger than those recently used."
 610                  */
 611                 sender->td_end =
 612                 sender->td_maxend = end;
 613                 sender->td_maxwin = (win == 0 ? 1 : win);
 614
 615                 tcp_options(skb, iph, tcph, sender);
 616         }
 617
 618         if (!(tcph->ack)) {
 619                 /*
 620                  * If there is no ACK, just pretend it was set and OK.
 621                  */
 622                 ack = sack = receiver->td_end;
 623         } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
 624                     (TCP_FLAG_ACK|TCP_FLAG_RST))
 625                    && (ack == 0)) {
 626                 /*
 627                  * Broken TCP stacks, that set ACK in RST packets as well
 628                  * with zero ack value.
 629                  */
 630                 ack = sack = receiver->td_end;
 631         }
 632
 633         if (seq == end
 634             && (!tcph->rst
 635                 || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
 636                 /*
 637                  * Packets contains no data: we assume it is valid
 638                  * and check the ack value only.
 639                  * However RST segments are always validated by their
 640                  * SEQ number, except when seq == 0 (reset sent answering
 641                  * SYN.
 642                  */
 643                 seq = end = sender->td_end;
 644
 645         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 646                "seq=%u ack=%u sack =%u win=%u end=%u\n",
 647                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 648                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 649                 seq, ack, sack, win, end);
 650         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 651                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 652                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 653                 sender->td_scale,
 654                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 655                 receiver->td_scale);
 656
 657         DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
 658                 before(seq, sender->td_maxend + 1),
 659                 after(end, sender->td_end - receiver->td_maxwin - 1),
 660                 before(sack, receiver->td_end + 1),
 661                 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
 662
 663         if (sender->loose || receiver->loose ||
 664             (before(seq, sender->td_maxend + 1) &&
 665              after(end, sender->td_end - receiver->td_maxwin - 1) &&
 666              before(sack, receiver->td_end + 1) &&
 667              after(ack, receiver->td_end - MAXACKWINDOW(sender)))) {
 668                 /*
 669                  * Take into account window scaling (RFC 1323).
 670                  */
 671                 if (!tcph->syn)
 672                         win <<= sender->td_scale;
 673
 674                 /*
 675                  * Update sender data.
 676                  */
 677                 swin = win + (sack - ack);
 678                 if (sender->td_maxwin < swin)
 679                         sender->td_maxwin = swin;
 680                 if (after(end, sender->td_end))
 681                         sender->td_end = end;
 682                 /*
 683                  * Update receiver data.
 684                  */
 685                 if (after(end, sender->td_maxend))
 686                         receiver->td_maxwin += end - sender->td_maxend;
 687                 if (after(sack + win, receiver->td_maxend - 1)) {
 688                         receiver->td_maxend = sack + win;
 689                         if (win == 0)
 690                                 receiver->td_maxend++;
 691                 }
 692
 693                 /*
 694                  * Check retransmissions.
 695                  */
 696                 if (index == TCP_ACK_SET) {
 697                         if (state->last_dir == dir
 698                             && state->last_seq == seq
 699                             && state->last_ack == ack
 700                             && state->last_end == end)
 701                                 state->retrans++;
 702                         else {
 703                                 state->last_dir = dir;
 704                                 state->last_seq = seq;
 705                                 state->last_ack = ack;
 706                                 state->last_end = end;
 707                                 state->retrans = 0;
 708                         }
 709                 }
 710                 /*
 711                  * Close the window of disabled window tracking :-)
 712                  */
 713                 if (sender->loose)
 714                         sender->loose--;
 715
 716                 res = 1;
 717         } else {
 718                 if (LOG_INVALID(IPPROTO_TCP))
 719                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 720                         "ip_ct_tcp: %s ",
 721                         before(seq, sender->td_maxend + 1) ?
 722                         after(end, sender->td_end - receiver->td_maxwin - 1) ?
 723                         before(sack, receiver->td_end + 1) ?
 724                         after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
 725                         : "ACK is under the lower bound (possible overly delayed ACK)"
 726                         : "ACK is over the upper bound (ACKed data not seen yet)"
 727                         : "SEQ is under the lower bound (already ACKed data retransmitted)"
 728                         : "SEQ is over the upper bound (over the window of the receiver)");
 729
 730                 res = ip_ct_tcp_be_liberal;
 731         }
 732
 733         DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
 734                "receiver end=%u maxend=%u maxwin=%u\n",
 735                 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
 736                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
 737
 738         return res;
 739 }
 740
 741 #ifdef CONFIG_IP_NF_NAT_NEEDED
 742 /* Update sender->td_end after NAT successfully mangled the packet */
 743 void ip_conntrack_tcp_update(struct sk_buff *skb,
 744                              struct ip_conntrack *conntrack,
 745                              enum ip_conntrack_dir dir)
 746 {
 747         struct iphdr *iph = skb->nh.iph;
 748         struct tcphdr *tcph = (void *)skb->nh.iph + skb->nh.iph->ihl*4;
 749         __u32 end;
 750 #ifdef DEBUGP_VARS
 751         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
 752         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
 753 #endif
 754
 755         end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, iph, tcph);
 756
 757         write_lock_bh(&tcp_lock);
 758         /*
 759          * We have to worry for the ack in the reply packet only...
 760          */
 761         if (after(end, conntrack->proto.tcp.seen[dir].td_end))
 762                 conntrack->proto.tcp.seen[dir].td_end = end;
 763         conntrack->proto.tcp.last_end = end;
 764         write_unlock_bh(&tcp_lock);
 765         DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
 766                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 767                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 768                 sender->td_scale,
 769                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 770                 receiver->td_scale);
 771 }
 772
 773 #endif
 774
 775 #define TH_FIN  0x01
 776 #define TH_SYN  0x02
 777 #define TH_RST  0x04
 778 #define TH_PUSH 0x08
 779 #define TH_ACK  0x10
 780 #define TH_URG  0x20
 781 #define TH_ECE  0x40
 782 #define TH_CWR  0x80
 783
 784 /* table of valid flag combinations - ECE and CWR are always valid */
 785 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 786 {
 787         [TH_SYN]                        = 1,
 788         [TH_SYN|TH_ACK]                 = 1,
 789         [TH_SYN|TH_ACK|TH_PUSH]         = 1,
 790         [TH_RST]                        = 1,
 791         [TH_RST|TH_ACK]                 = 1,
 792         [TH_RST|TH_ACK|TH_PUSH]         = 1,
 793         [TH_FIN|TH_ACK]                 = 1,
 794         [TH_ACK]                        = 1,
 795         [TH_ACK|TH_PUSH]                = 1,
 796         [TH_ACK|TH_URG]                 = 1,
 797         [TH_ACK|TH_URG|TH_PUSH]         = 1,
 798         [TH_FIN|TH_ACK|TH_PUSH]         = 1,
 799         [TH_FIN|TH_ACK|TH_URG]          = 1,
 800         [TH_FIN|TH_ACK|TH_URG|TH_PUSH]  = 1,
 801 };
 802
 803 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
 804 static int tcp_error(struct sk_buff *skb,
 805                      enum ip_conntrack_info *ctinfo,
 806                      unsigned int hooknum)
 807 {
 808         struct iphdr *iph = skb->nh.iph;
 809         struct tcphdr _tcph, *th;
 810         unsigned int tcplen = skb->len - iph->ihl * 4;
 811         u_int8_t tcpflags;
 812
 813         /* Smaller that minimal TCP header? */
 814         th = skb_header_pointer(skb, iph->ihl * 4,
 815                                 sizeof(_tcph), &_tcph);
 816         if (th == NULL) {
 817                 if (LOG_INVALID(IPPROTO_TCP))
 818                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 819                                 "ip_ct_tcp: short packet ");
 820                 return -NF_ACCEPT;
 821         }
 822
 823         /* Not whole TCP header or malformed packet */
 824         if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
 825                 if (LOG_INVALID(IPPROTO_TCP))
 826                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 827                                 "ip_ct_tcp: truncated/malformed packet ");
 828                 return -NF_ACCEPT;
 829         }
 830
 831         /* Checksum invalid? Ignore.
 832          * We skip checking packets on the outgoing path
 833          * because the semantic of CHECKSUM_HW is different there
 834          * and moreover root might send raw packets.
 835          */
 836         /* FIXME: Source route IP option packets --RR */
 837         if (hooknum == NF_IP_PRE_ROUTING
 838             && skb->ip_summed != CHECKSUM_UNNECESSARY
 839             && csum_tcpudp_magic(iph->saddr, iph->daddr, tcplen, IPPROTO_TCP,
 840                                  skb->ip_summed == CHECKSUM_HW ? skb->csum
 841                                  : skb_checksum(skb, iph->ihl*4, tcplen, 0))) {
 842                 if (LOG_INVALID(IPPROTO_TCP))
 843                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 844                                   "ip_ct_tcp: bad TCP checksum ");
 845                 return -NF_ACCEPT;
 846         }
 847
 848         /* Check TCP flags. */
 849         tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
 850         if (!tcp_valid_flags[tcpflags]) {
 851                 if (LOG_INVALID(IPPROTO_TCP))
 852                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 853                                   "ip_ct_tcp: invalid TCP flag combination ");
 854                 return -NF_ACCEPT;
 855         }
 856
 857         return NF_ACCEPT;
 858 }
 859
 860 /* Returns verdict for packet, or -1 for invalid. */
 861 static int tcp_packet(struct ip_conntrack *conntrack,
 862                       const struct sk_buff *skb,
 863                       enum ip_conntrack_info ctinfo)
 864 {
 865         enum tcp_conntrack new_state, old_state;
 866         enum ip_conntrack_dir dir;
 867         struct iphdr *iph = skb->nh.iph;
 868         struct tcphdr *th, _tcph;
 869         unsigned long timeout;
 870         unsigned int index;
 871
 872         th = skb_header_pointer(skb, iph->ihl * 4,
 873                                 sizeof(_tcph), &_tcph);
 874         BUG_ON(th == NULL);
 875
 876         write_lock_bh(&tcp_lock);
 877         old_state = conntrack->proto.tcp.state;
 878         dir = CTINFO2DIR(ctinfo);
 879         index = get_conntrack_index(th);
 880         new_state = tcp_conntracks[dir][index][old_state];
 881
 882         switch (new_state) {
 883         case TCP_CONNTRACK_IGNORE:
 884                 /* Either SYN in ORIGINAL
 885                  * or SYN/ACK in REPLY. */
 886                 if (index == TCP_SYNACK_SET
 887                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 888                     && conntrack->proto.tcp.last_dir != dir
 889                     && ntohl(th->ack_seq) ==
 890                              conntrack->proto.tcp.last_end) {
 891                         /* This SYN/ACK acknowledges a SYN that we earlier
 892                          * ignored as invalid. This means that the client and
 893                          * the server are both in sync, while the firewall is
 894                          * not. We kill this session and block the SYN/ACK so
 895                          * that the client cannot but retransmit its SYN and
 896                          * thus initiate a clean new session.
 897                          */
 898                         write_unlock_bh(&tcp_lock);
 899                         if (LOG_INVALID(IPPROTO_TCP))
 900                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 901                                               NULL, "ip_ct_tcp: "
 902                                               "killing out of sync session ");
 903                         if (del_timer(&conntrack->timeout))
 904                                 conntrack->timeout.function((unsigned long)
 905                                                             conntrack);
 906                         return -NF_DROP;
 907                 }
 908                 conntrack->proto.tcp.last_index = index;
 909                 conntrack->proto.tcp.last_dir = dir;
 910                 conntrack->proto.tcp.last_seq = ntohl(th->seq);
 911                 conntrack->proto.tcp.last_end =
 912                     segment_seq_plus_len(ntohl(th->seq), skb->len, iph, th);
 913
 914                 write_unlock_bh(&tcp_lock);
 915                 if (LOG_INVALID(IPPROTO_TCP))
 916                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 917                                   "ip_ct_tcp: invalid packet ignored ");
 918                 return NF_ACCEPT;
 919         case TCP_CONNTRACK_MAX:
 920                 /* Invalid packet */
 921                 DEBUGP("ip_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
 922                        dir, get_conntrack_index(th),
 923                        old_state);
 924                 write_unlock_bh(&tcp_lock);
 925                 if (LOG_INVALID(IPPROTO_TCP))
 926                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 927                                   "ip_ct_tcp: invalid state ");
 928                 return -NF_ACCEPT;
 929         case TCP_CONNTRACK_SYN_SENT:
 930                 if (old_state < TCP_CONNTRACK_TIME_WAIT)
 931                         break;
 932                 if ((conntrack->proto.tcp.seen[dir].flags &
 933                          IP_CT_TCP_FLAG_CLOSE_INIT)
 934                     || after(ntohl(th->seq),
 935                              conntrack->proto.tcp.seen[dir].td_end)) {
 936                         /* Attempt to reopen a closed connection.
 937                         * Delete this connection and look up again. */
 938                         write_unlock_bh(&tcp_lock);
 939                         if (del_timer(&conntrack->timeout))
 940                                 conntrack->timeout.function((unsigned long)
 941                                                             conntrack);
 942                         return -NF_REPEAT;
 943                 } else {
 944                         write_unlock_bh(&tcp_lock);
 945                         if (LOG_INVALID(IPPROTO_TCP))
 946                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 947                                               NULL, "ip_ct_tcp: invalid SYN");
 948                         return -NF_ACCEPT;
 949                 }
 950         case TCP_CONNTRACK_CLOSE:
 951                 if (index == TCP_RST_SET
 952                     && test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
 953                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 954                     && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
 955                         /* RST sent to invalid SYN we had let trough
 956                          * SYN was in window then, tear down connection.
 957                          * We skip window checking, because packet might ACK
 958                          * segments we ignored in the SYN. */
 959                         goto in_window;
 960                 }
 961                 /* Just fall trough */
 962         default:
 963                 /* Keep compilers happy. */
 964                 break;
 965         }
 966
 967         if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
 968                            skb, iph, th)) {
 969                 write_unlock_bh(&tcp_lock);
 970                 return -NF_ACCEPT;
 971         }
 972     in_window:
 973         /* From now on we have got in-window packets */
 974         conntrack->proto.tcp.last_index = index;
 975
 976         DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 977                "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
 978                 NIPQUAD(iph->saddr), ntohs(th->source),
 979                 NIPQUAD(iph->daddr), ntohs(th->dest),
 980                 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
 981                 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
 982                 old_state, new_state);
 983
 984         conntrack->proto.tcp.state = new_state;
 985         if (old_state != new_state
 986             && (new_state == TCP_CONNTRACK_FIN_WAIT
 987                 || new_state == TCP_CONNTRACK_CLOSE))
 988                 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
 989         timeout = conntrack->proto.tcp.retrans >= ip_ct_tcp_max_retrans
 990                   && *tcp_timeouts[new_state] > ip_ct_tcp_timeout_max_retrans
 991                   ? ip_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
 992         write_unlock_bh(&tcp_lock);
 993
 994         ip_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 995         if (new_state != old_state)
 996                 ip_conntrack_event_cache(IPCT_PROTOINFO, skb);
 997
 998         if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
 999                 /* If only reply is a RST, we can consider ourselves not to
1000                    have an established connection: this is a fairly common
1001                    problem case, so we can delete the conntrack
1002                    immediately.  --RR */
1003                 if (th->rst) {
1004                         if (del_timer(&conntrack->timeout))
1005                                 conntrack->timeout.function((unsigned long)
1006                                                             conntrack);
1007                         return NF_ACCEPT;
1008                 }
1009         } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
1010                    && (old_state == TCP_CONNTRACK_SYN_RECV
1011                        || old_state == TCP_CONNTRACK_ESTABLISHED)
1012                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
1013                 /* Set ASSURED if we see see valid ack in ESTABLISHED
1014                    after SYN_RECV or a valid answer for a picked up
1015                    connection. */
1016                         set_bit(IPS_ASSURED_BIT, &conntrack->status);
1017         }
1018         ip_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
1019
1020         return NF_ACCEPT;
1021 }
1022
1023 /* Called when a new connection for this protocol found. */
1024 static int tcp_new(struct ip_conntrack *conntrack,
1025                    const struct sk_buff *skb)
1026 {
1027         enum tcp_conntrack new_state;
1028         struct iphdr *iph = skb->nh.iph;
1029         struct tcphdr *th, _tcph;
1030 #ifdef DEBUGP_VARS
1031         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1032         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1033 #endif
1034
1035         th = skb_header_pointer(skb, iph->ihl * 4,
1036                                 sizeof(_tcph), &_tcph);
1037         BUG_ON(th == NULL);
1038
1039         /* Don't need lock here: this conntrack not in circulation yet */
1040         new_state
1041                 = tcp_conntracks[0][get_conntrack_index(th)]
1042                 [TCP_CONNTRACK_NONE];
1043
1044         /* Invalid: delete conntrack */
1045         if (new_state >= TCP_CONNTRACK_MAX) {
1046                 DEBUGP("ip_ct_tcp: invalid new deleting.\n");
1047                 return 0;
1048         }
1049
1050         if (new_state == TCP_CONNTRACK_SYN_SENT) {
1051                 /* SYN packet */
1052                 conntrack->proto.tcp.seen[0].td_end =
1053                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1054                                              iph, th);
1055                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1056                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1057                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1058                 conntrack->proto.tcp.seen[0].td_maxend =
1059                         conntrack->proto.tcp.seen[0].td_end;
1060
1061                 tcp_options(skb, iph, th, &conntrack->proto.tcp.seen[0]);
1062                 conntrack->proto.tcp.seen[1].flags = 0;
1063                 conntrack->proto.tcp.seen[0].loose =
1064                 conntrack->proto.tcp.seen[1].loose = 0;
1065         } else if (ip_ct_tcp_loose == 0) {
1066                 /* Don't try to pick up connections. */
1067                 return 0;
1068         } else {
1069                 /*
1070                  * We are in the middle of a connection,
1071                  * its history is lost for us.
1072                  * Let's try to use the data from the packet.
1073                  */
1074                 conntrack->proto.tcp.seen[0].td_end =
1075                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1076                                              iph, th);
1077                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1078                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1079                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1080                 conntrack->proto.tcp.seen[0].td_maxend =
1081                         conntrack->proto.tcp.seen[0].td_end +
1082                         conntrack->proto.tcp.seen[0].td_maxwin;
1083                 conntrack->proto.tcp.seen[0].td_scale = 0;
1084
1085                 /* We assume SACK. Should we assume window scaling too? */
1086                 conntrack->proto.tcp.seen[0].flags =
1087                 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM;
1088                 conntrack->proto.tcp.seen[0].loose =
1089                 conntrack->proto.tcp.seen[1].loose = ip_ct_tcp_loose;
1090         }
1091
1092         conntrack->proto.tcp.seen[1].td_end = 0;
1093         conntrack->proto.tcp.seen[1].td_maxend = 0;
1094         conntrack->proto.tcp.seen[1].td_maxwin = 1;
1095         conntrack->proto.tcp.seen[1].td_scale = 0;
1096
1097         /* tcp_packet will set them */
1098         conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1099         conntrack->proto.tcp.last_index = TCP_NONE_SET;
1100
1101         DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1102                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1103                 sender->td_end, sender->td_maxend, sender->td_maxwin,
1104                 sender->td_scale,
1105                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1106                 receiver->td_scale);
1107         return 1;
1108 }
1109
1110 struct ip_conntrack_protocol ip_conntrack_protocol_tcp =
1111 {
1112         .proto                  = IPPROTO_TCP,
1113         .name                   = "tcp",
1114         .pkt_to_tuple           = tcp_pkt_to_tuple,
1115         .invert_tuple           = tcp_invert_tuple,
1116         .print_tuple            = tcp_print_tuple,
1117         .print_conntrack        = tcp_print_conntrack,
1118         .packet                 = tcp_packet,
1119         .new                    = tcp_new,
1120         .error                  = tcp_error,
1121 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
1122     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
1123         .to_nfattr              = tcp_to_nfattr,
1124         .tuple_to_nfattr        = ip_ct_port_tuple_to_nfattr,
1125         .nfattr_to_tuple        = ip_ct_port_nfattr_to_tuple,
1126 #endif
1127 };