1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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.
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
15 * - State table bugfixes
16 * - More robust state changes
17 * - Tuning timer parameters
19 * 27 Oct 2004: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
20 * - genelized Layer 3 protocol part.
22 * Derived from net/ipv4/netfilter/ip_conntrack_proto_tcp.c
27 #include <linux/types.h>
28 #include <linux/sched.h>
29 #include <linux/timer.h>
30 #include <linux/netfilter.h>
31 #include <linux/module.h>
33 #include <linux/tcp.h>
34 #include <linux/spinlock.h>
35 #include <linux/skbuff.h>
36 #include <linux/ipv6.h>
37 #include <net/ip6_checksum.h>
41 #include <linux/netfilter.h>
42 #include <linux/netfilter_ipv4.h>
43 #include <linux/netfilter_ipv6.h>
44 #include <net/netfilter/nf_conntrack.h>
45 #include <net/netfilter/nf_conntrack_protocol.h>
51 #define DEBUGP(format, args...)
54 /* Protects conntrack->proto.tcp */
55 static DEFINE_RWLOCK(tcp_lock);
57 /* "Be conservative in what you do,
58 be liberal in what you accept from others."
59 If it's non-zero, we mark only out of window RST segments as INVALID. */
60 int nf_ct_tcp_be_liberal __read_mostly = 0;
62 /* When connection is picked up from the middle, how many packets are required
63 to pass in each direction when we assume we are in sync - if any side uses
64 window scaling, we lost the game.
65 If it is set to zero, we disable picking up already established
67 int nf_ct_tcp_loose __read_mostly = 3;
69 /* Max number of the retransmitted packets without receiving an (acceptable)
70 ACK from the destination. If this number is reached, a shorter timer
72 int nf_ct_tcp_max_retrans __read_mostly = 3;
74 /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
75 closely. They're more complex. --RR */
77 static const char *tcp_conntrack_names[] = {
91 #define MINS * 60 SECS
92 #define HOURS * 60 MINS
93 #define DAYS * 24 HOURS
95 unsigned int nf_ct_tcp_timeout_syn_sent __read_mostly = 2 MINS;
96 unsigned int nf_ct_tcp_timeout_syn_recv __read_mostly = 60 SECS;
97 unsigned int nf_ct_tcp_timeout_established __read_mostly = 5 DAYS;
98 unsigned int nf_ct_tcp_timeout_fin_wait __read_mostly = 2 MINS;
99 unsigned int nf_ct_tcp_timeout_close_wait __read_mostly = 60 SECS;
100 unsigned int nf_ct_tcp_timeout_last_ack __read_mostly = 30 SECS;
101 unsigned int nf_ct_tcp_timeout_time_wait __read_mostly = 2 MINS;
102 unsigned int nf_ct_tcp_timeout_close __read_mostly = 10 SECS;
104 /* RFC1122 says the R2 limit should be at least 100 seconds.
105 Linux uses 15 packets as limit, which corresponds
106 to ~13-30min depending on RTO. */
107 unsigned int nf_ct_tcp_timeout_max_retrans __read_mostly = 5 MINS;
109 static unsigned int * tcp_timeouts[]
110 = { NULL, /* TCP_CONNTRACK_NONE */
111 &nf_ct_tcp_timeout_syn_sent, /* TCP_CONNTRACK_SYN_SENT, */
112 &nf_ct_tcp_timeout_syn_recv, /* TCP_CONNTRACK_SYN_RECV, */
113 &nf_ct_tcp_timeout_established, /* TCP_CONNTRACK_ESTABLISHED, */
114 &nf_ct_tcp_timeout_fin_wait, /* TCP_CONNTRACK_FIN_WAIT, */
115 &nf_ct_tcp_timeout_close_wait, /* TCP_CONNTRACK_CLOSE_WAIT, */
116 &nf_ct_tcp_timeout_last_ack, /* TCP_CONNTRACK_LAST_ACK, */
117 &nf_ct_tcp_timeout_time_wait, /* TCP_CONNTRACK_TIME_WAIT, */
118 &nf_ct_tcp_timeout_close, /* TCP_CONNTRACK_CLOSE, */
119 NULL, /* TCP_CONNTRACK_LISTEN */
122 #define sNO TCP_CONNTRACK_NONE
123 #define sSS TCP_CONNTRACK_SYN_SENT
124 #define sSR TCP_CONNTRACK_SYN_RECV
125 #define sES TCP_CONNTRACK_ESTABLISHED
126 #define sFW TCP_CONNTRACK_FIN_WAIT
127 #define sCW TCP_CONNTRACK_CLOSE_WAIT
128 #define sLA TCP_CONNTRACK_LAST_ACK
129 #define sTW TCP_CONNTRACK_TIME_WAIT
130 #define sCL TCP_CONNTRACK_CLOSE
131 #define sLI TCP_CONNTRACK_LISTEN
132 #define sIV TCP_CONNTRACK_MAX
133 #define sIG TCP_CONNTRACK_IGNORE
135 /* What TCP flags are set from RST/SYN/FIN/ACK. */
146 * The TCP state transition table needs a few words...
148 * We are the man in the middle. All the packets go through us
149 * but might get lost in transit to the destination.
150 * It is assumed that the destinations can't receive segments
153 * The checked segment is in window, but our windows are *not*
154 * equivalent with the ones of the sender/receiver. We always
155 * try to guess the state of the current sender.
157 * The meaning of the states are:
159 * NONE: initial state
160 * SYN_SENT: SYN-only packet seen
161 * SYN_RECV: SYN-ACK packet seen
162 * ESTABLISHED: ACK packet seen
163 * FIN_WAIT: FIN packet seen
164 * CLOSE_WAIT: ACK seen (after FIN)
165 * LAST_ACK: FIN seen (after FIN)
166 * TIME_WAIT: last ACK seen
167 * CLOSE: closed connection
169 * LISTEN state is not used.
171 * Packets marked as IGNORED (sIG):
172 * if they may be either invalid or valid
173 * and the receiver may send back a connection
174 * closing RST or a SYN/ACK.
176 * Packets marked as INVALID (sIV):
177 * if they are invalid
178 * or we do not support the request (simultaneous open)
180 static enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
183 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
184 /*syn*/ { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
186 * sNO -> sSS Initialize a new connection
187 * sSS -> sSS Retransmitted SYN
188 * sSR -> sIG Late retransmitted SYN?
189 * sES -> sIG Error: SYNs in window outside the SYN_SENT state
190 * are errors. Receiver will reply with RST
191 * and close the connection.
192 * Or we are not in sync and hold a dead connection.
196 * sTW -> sSS Reopened connection (RFC 1122).
199 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
200 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
202 * A SYN/ACK from the client is always invalid:
203 * - either it tries to set up a simultaneous open, which is
205 * - or the firewall has just been inserted between the two hosts
206 * during the session set-up. The SYN will be retransmitted
207 * by the true client (or it'll time out).
209 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
210 /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
212 * sNO -> sIV Too late and no reason to do anything...
213 * sSS -> sIV Client migth not send FIN in this state:
214 * we enforce waiting for a SYN/ACK reply first.
215 * sSR -> sFW Close started.
217 * sFW -> sLA FIN seen in both directions, waiting for
219 * Migth be a retransmitted FIN as well...
221 * sLA -> sLA Retransmitted FIN. Remain in the same state.
225 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
226 /*ack*/ { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
228 * sNO -> sES Assumed.
229 * sSS -> sIV ACK is invalid: we haven't seen a SYN/ACK yet.
230 * sSR -> sES Established state is reached.
232 * sFW -> sCW Normal close request answered by ACK.
234 * sLA -> sTW Last ACK detected.
235 * sTW -> sTW Retransmitted last ACK. Remain in the same state.
238 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
239 /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
240 /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
244 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
245 /*syn*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
247 * sNO -> sIV Never reached.
248 * sSS -> sIV Simultaneous open, not supported
249 * sSR -> sIV Simultaneous open, not supported.
250 * sES -> sIV Server may not initiate a connection.
254 * sTW -> sIV Reopened connection, but server may not do it.
257 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
258 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
260 * sSS -> sSR Standard open.
261 * sSR -> sSR Retransmitted SYN/ACK.
262 * sES -> sIG Late retransmitted SYN/ACK?
263 * sFW -> sIG Might be SYN/ACK answering ignored SYN
269 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
270 /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
272 * sSS -> sIV Server might not send FIN in this state.
273 * sSR -> sFW Close started.
275 * sFW -> sLA FIN seen in both directions.
277 * sLA -> sLA Retransmitted FIN.
281 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
282 /*ack*/ { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
284 * sSS -> sIG Might be a half-open connection.
285 * sSR -> sSR Might answer late resent SYN.
287 * sFW -> sCW Normal close request answered by ACK.
289 * sLA -> sTW Last ACK detected.
290 * sTW -> sTW Retransmitted last ACK.
293 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
294 /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
295 /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
299 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
300 unsigned int dataoff,
301 struct nf_conntrack_tuple *tuple)
303 struct tcphdr _hdr, *hp;
305 /* Actually only need first 8 bytes. */
306 hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
310 tuple->src.u.tcp.port = hp->source;
311 tuple->dst.u.tcp.port = hp->dest;
316 static int tcp_invert_tuple(struct nf_conntrack_tuple *tuple,
317 const struct nf_conntrack_tuple *orig)
319 tuple->src.u.tcp.port = orig->dst.u.tcp.port;
320 tuple->dst.u.tcp.port = orig->src.u.tcp.port;
324 /* Print out the per-protocol part of the tuple. */
325 static int tcp_print_tuple(struct seq_file *s,
326 const struct nf_conntrack_tuple *tuple)
328 return seq_printf(s, "sport=%hu dport=%hu ",
329 ntohs(tuple->src.u.tcp.port),
330 ntohs(tuple->dst.u.tcp.port));
333 /* Print out the private part of the conntrack. */
334 static int tcp_print_conntrack(struct seq_file *s,
335 const struct nf_conn *conntrack)
337 enum tcp_conntrack state;
339 read_lock_bh(&tcp_lock);
340 state = conntrack->proto.tcp.state;
341 read_unlock_bh(&tcp_lock);
343 return seq_printf(s, "%s ", tcp_conntrack_names[state]);
346 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
348 if (tcph->rst) return TCP_RST_SET;
349 else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
350 else if (tcph->fin) return TCP_FIN_SET;
351 else if (tcph->ack) return TCP_ACK_SET;
352 else return TCP_NONE_SET;
355 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
356 in IP Filter' by Guido van Rooij.
358 http://www.nluug.nl/events/sane2000/papers.html
359 http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
361 The boundaries and the conditions are changed according to RFC793:
362 the packet must intersect the window (i.e. segments may be
363 after the right or before the left edge) and thus receivers may ACK
364 segments after the right edge of the window.
366 td_maxend = max(sack + max(win,1)) seen in reply packets
367 td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
368 td_maxwin += seq + len - sender.td_maxend
369 if seq + len > sender.td_maxend
370 td_end = max(seq + len) seen in sent packets
372 I. Upper bound for valid data: seq <= sender.td_maxend
373 II. Lower bound for valid data: seq + len >= sender.td_end - receiver.td_maxwin
374 III. Upper bound for valid ack: sack <= receiver.td_end
375 IV. Lower bound for valid ack: ack >= receiver.td_end - MAXACKWINDOW
377 where sack is the highest right edge of sack block found in the packet.
379 The upper bound limit for a valid ack is not ignored -
380 we doesn't have to deal with fragments.
383 static inline __u32 segment_seq_plus_len(__u32 seq,
385 unsigned int dataoff,
388 /* XXX Should I use payload length field in IP/IPv6 header ?
390 return (seq + len - dataoff - tcph->doff*4
391 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
394 /* Fixme: what about big packets? */
395 #define MAXACKWINCONST 66000
396 #define MAXACKWINDOW(sender) \
397 ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin \
401 * Simplified tcp_parse_options routine from tcp_input.c
403 static void tcp_options(const struct sk_buff *skb,
404 unsigned int dataoff,
406 struct ip_ct_tcp_state *state)
408 unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
410 int length = (tcph->doff*4) - sizeof(struct tcphdr);
415 ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
429 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
434 if (opsize < 2) /* "silly options" */
437 break; /* don't parse partial options */
439 if (opcode == TCPOPT_SACK_PERM
440 && opsize == TCPOLEN_SACK_PERM)
441 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
442 else if (opcode == TCPOPT_WINDOW
443 && opsize == TCPOLEN_WINDOW) {
444 state->td_scale = *(u_int8_t *)ptr;
446 if (state->td_scale > 14) {
448 state->td_scale = 14;
451 IP_CT_TCP_FLAG_WINDOW_SCALE;
459 static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
460 struct tcphdr *tcph, __u32 *sack)
462 unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
464 int length = (tcph->doff*4) - sizeof(struct tcphdr);
470 ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
474 /* Fast path for timestamp-only option */
475 if (length == TCPOLEN_TSTAMP_ALIGNED*4
477 __constant_ntohl((TCPOPT_NOP << 24)
479 | (TCPOPT_TIMESTAMP << 8)
480 | TCPOLEN_TIMESTAMP))
490 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
495 if (opsize < 2) /* "silly options" */
498 break; /* don't parse partial options */
500 if (opcode == TCPOPT_SACK
501 && opsize >= (TCPOLEN_SACK_BASE
502 + TCPOLEN_SACK_PERBLOCK)
503 && !((opsize - TCPOLEN_SACK_BASE)
504 % TCPOLEN_SACK_PERBLOCK)) {
506 i < (opsize - TCPOLEN_SACK_BASE);
507 i += TCPOLEN_SACK_PERBLOCK) {
508 memcpy(&tmp, (__u32 *)(ptr + i) + 1,
512 if (after(tmp, *sack))
523 static int tcp_in_window(struct ip_ct_tcp *state,
524 enum ip_conntrack_dir dir,
526 const struct sk_buff *skb,
527 unsigned int dataoff,
531 struct ip_ct_tcp_state *sender = &state->seen[dir];
532 struct ip_ct_tcp_state *receiver = &state->seen[!dir];
533 __u32 seq, ack, sack, end, win, swin;
537 * Get the required data from the packet.
539 seq = ntohl(tcph->seq);
540 ack = sack = ntohl(tcph->ack_seq);
541 win = ntohs(tcph->window);
542 end = segment_seq_plus_len(seq, skb->len, dataoff, tcph);
544 if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
545 tcp_sack(skb, dataoff, tcph, &sack);
547 DEBUGP("tcp_in_window: START\n");
548 DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
549 "seq=%u ack=%u sack=%u win=%u end=%u\n",
550 NIPQUAD(iph->saddr), ntohs(tcph->source),
551 NIPQUAD(iph->daddr), ntohs(tcph->dest),
552 seq, ack, sack, win, end);
553 DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
554 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
555 sender->td_end, sender->td_maxend, sender->td_maxwin,
557 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
560 if (sender->td_end == 0) {
562 * Initialize sender data.
564 if (tcph->syn && tcph->ack) {
566 * Outgoing SYN-ACK in reply to a SYN.
569 sender->td_maxend = end;
570 sender->td_maxwin = (win == 0 ? 1 : win);
572 tcp_options(skb, dataoff, tcph, sender);
575 * Both sides must send the Window Scale option
576 * to enable window scaling in either direction.
578 if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
579 && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
581 receiver->td_scale = 0;
584 * We are in the middle of a connection,
585 * its history is lost for us.
586 * Let's try to use the data from the packet.
588 sender->td_end = end;
589 sender->td_maxwin = (win == 0 ? 1 : win);
590 sender->td_maxend = end + sender->td_maxwin;
592 } else if (((state->state == TCP_CONNTRACK_SYN_SENT
593 && dir == IP_CT_DIR_ORIGINAL)
594 || (state->state == TCP_CONNTRACK_SYN_RECV
595 && dir == IP_CT_DIR_REPLY))
596 && after(end, sender->td_end)) {
598 * RFC 793: "if a TCP is reinitialized ... then it need
599 * not wait at all; it must only be sure to use sequence
600 * numbers larger than those recently used."
603 sender->td_maxend = end;
604 sender->td_maxwin = (win == 0 ? 1 : win);
606 tcp_options(skb, dataoff, tcph, sender);
611 * If there is no ACK, just pretend it was set and OK.
613 ack = sack = receiver->td_end;
614 } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
615 (TCP_FLAG_ACK|TCP_FLAG_RST))
618 * Broken TCP stacks, that set ACK in RST packets as well
619 * with zero ack value.
621 ack = sack = receiver->td_end;
626 || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
628 * Packets contains no data: we assume it is valid
629 * and check the ack value only.
630 * However RST segments are always validated by their
631 * SEQ number, except when seq == 0 (reset sent answering
634 seq = end = sender->td_end;
636 DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
637 "seq=%u ack=%u sack =%u win=%u end=%u\n",
638 NIPQUAD(iph->saddr), ntohs(tcph->source),
639 NIPQUAD(iph->daddr), ntohs(tcph->dest),
640 seq, ack, sack, win, end);
641 DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
642 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
643 sender->td_end, sender->td_maxend, sender->td_maxwin,
645 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
648 DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
649 before(seq, sender->td_maxend + 1),
650 after(end, sender->td_end - receiver->td_maxwin - 1),
651 before(sack, receiver->td_end + 1),
652 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
654 if (sender->loose || receiver->loose ||
655 (before(seq, sender->td_maxend + 1) &&
656 after(end, sender->td_end - receiver->td_maxwin - 1) &&
657 before(sack, receiver->td_end + 1) &&
658 after(ack, receiver->td_end - MAXACKWINDOW(sender)))) {
660 * Take into account window scaling (RFC 1323).
663 win <<= sender->td_scale;
666 * Update sender data.
668 swin = win + (sack - ack);
669 if (sender->td_maxwin < swin)
670 sender->td_maxwin = swin;
671 if (after(end, sender->td_end))
672 sender->td_end = end;
674 * Update receiver data.
676 if (after(end, sender->td_maxend))
677 receiver->td_maxwin += end - sender->td_maxend;
678 if (after(sack + win, receiver->td_maxend - 1)) {
679 receiver->td_maxend = sack + win;
681 receiver->td_maxend++;
685 * Check retransmissions.
687 if (index == TCP_ACK_SET) {
688 if (state->last_dir == dir
689 && state->last_seq == seq
690 && state->last_ack == ack
691 && state->last_end == end
692 && state->last_win == win)
695 state->last_dir = dir;
696 state->last_seq = seq;
697 state->last_ack = ack;
698 state->last_end = end;
699 state->last_win = win;
704 * Close the window of disabled window tracking :-)
711 if (LOG_INVALID(IPPROTO_TCP))
712 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
714 before(seq, sender->td_maxend + 1) ?
715 after(end, sender->td_end - receiver->td_maxwin - 1) ?
716 before(sack, receiver->td_end + 1) ?
717 after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
718 : "ACK is under the lower bound (possible overly delayed ACK)"
719 : "ACK is over the upper bound (ACKed data not seen yet)"
720 : "SEQ is under the lower bound (already ACKed data retransmitted)"
721 : "SEQ is over the upper bound (over the window of the receiver)");
723 res = nf_ct_tcp_be_liberal;
726 DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
727 "receiver end=%u maxend=%u maxwin=%u\n",
728 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
729 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
734 #ifdef CONFIG_IP_NF_NAT_NEEDED
735 /* Update sender->td_end after NAT successfully mangled the packet */
736 /* Caller must linearize skb at tcp header. */
737 void nf_conntrack_tcp_update(struct sk_buff *skb,
738 unsigned int dataoff,
739 struct nf_conn *conntrack,
742 struct tcphdr *tcph = (void *)skb->data + dataoff;
745 struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
746 struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
749 end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, dataoff, tcph);
751 write_lock_bh(&tcp_lock);
753 * We have to worry for the ack in the reply packet only...
755 if (after(end, conntrack->proto.tcp.seen[dir].td_end))
756 conntrack->proto.tcp.seen[dir].td_end = end;
757 conntrack->proto.tcp.last_end = end;
758 write_unlock_bh(&tcp_lock);
759 DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
760 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
761 sender->td_end, sender->td_maxend, sender->td_maxwin,
763 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
778 /* table of valid flag combinations - ECE and CWR are always valid */
779 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
783 [TH_SYN|TH_PUSH] = 1,
784 [TH_SYN|TH_ACK|TH_PUSH] = 1,
787 [TH_RST|TH_ACK|TH_PUSH] = 1,
790 [TH_ACK|TH_PUSH] = 1,
792 [TH_ACK|TH_URG|TH_PUSH] = 1,
793 [TH_FIN|TH_ACK|TH_PUSH] = 1,
794 [TH_FIN|TH_ACK|TH_URG] = 1,
795 [TH_FIN|TH_ACK|TH_URG|TH_PUSH] = 1,
798 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c. */
799 static int tcp_error(struct sk_buff *skb,
800 unsigned int dataoff,
801 enum ip_conntrack_info *ctinfo,
803 unsigned int hooknum)
805 struct tcphdr _tcph, *th;
806 unsigned int tcplen = skb->len - dataoff;
809 /* Smaller that minimal TCP header? */
810 th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
812 if (LOG_INVALID(IPPROTO_TCP))
813 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
814 "nf_ct_tcp: short packet ");
818 /* Not whole TCP header or malformed packet */
819 if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
820 if (LOG_INVALID(IPPROTO_TCP))
821 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
822 "nf_ct_tcp: truncated/malformed packet ");
826 /* Checksum invalid? Ignore.
827 * We skip checking packets on the outgoing path
828 * because the checksum is assumed to be correct.
830 /* FIXME: Source route IP option packets --RR */
831 if (nf_conntrack_checksum &&
832 ((pf == PF_INET && hooknum == NF_IP_PRE_ROUTING) ||
833 (pf == PF_INET6 && hooknum == NF_IP6_PRE_ROUTING)) &&
834 nf_checksum(skb, hooknum, dataoff, IPPROTO_TCP, pf)) {
835 if (LOG_INVALID(IPPROTO_TCP))
836 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
837 "nf_ct_tcp: bad TCP checksum ");
841 /* Check TCP flags. */
842 tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
843 if (!tcp_valid_flags[tcpflags]) {
844 if (LOG_INVALID(IPPROTO_TCP))
845 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
846 "nf_ct_tcp: invalid TCP flag combination ");
853 /* Returns verdict for packet, or -1 for invalid. */
854 static int tcp_packet(struct nf_conn *conntrack,
855 const struct sk_buff *skb,
856 unsigned int dataoff,
857 enum ip_conntrack_info ctinfo,
859 unsigned int hooknum)
861 enum tcp_conntrack new_state, old_state;
862 enum ip_conntrack_dir dir;
863 struct tcphdr *th, _tcph;
864 unsigned long timeout;
867 th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
870 write_lock_bh(&tcp_lock);
871 old_state = conntrack->proto.tcp.state;
872 dir = CTINFO2DIR(ctinfo);
873 index = get_conntrack_index(th);
874 new_state = tcp_conntracks[dir][index][old_state];
877 case TCP_CONNTRACK_IGNORE:
881 * b) SYN/ACK in REPLY
882 * c) ACK in reply direction after initial SYN in original.
884 if (index == TCP_SYNACK_SET
885 && conntrack->proto.tcp.last_index == TCP_SYN_SET
886 && conntrack->proto.tcp.last_dir != dir
887 && ntohl(th->ack_seq) ==
888 conntrack->proto.tcp.last_end) {
889 /* This SYN/ACK acknowledges a SYN that we earlier
890 * ignored as invalid. This means that the client and
891 * the server are both in sync, while the firewall is
892 * not. We kill this session and block the SYN/ACK so
893 * that the client cannot but retransmit its SYN and
894 * thus initiate a clean new session.
896 write_unlock_bh(&tcp_lock);
897 if (LOG_INVALID(IPPROTO_TCP))
898 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
899 "nf_ct_tcp: killing out of sync session ");
900 if (del_timer(&conntrack->timeout))
901 conntrack->timeout.function((unsigned long)
905 conntrack->proto.tcp.last_index = index;
906 conntrack->proto.tcp.last_dir = dir;
907 conntrack->proto.tcp.last_seq = ntohl(th->seq);
908 conntrack->proto.tcp.last_end =
909 segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
911 write_unlock_bh(&tcp_lock);
912 if (LOG_INVALID(IPPROTO_TCP))
913 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
914 "nf_ct_tcp: invalid packed ignored ");
916 case TCP_CONNTRACK_MAX:
918 DEBUGP("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
919 dir, get_conntrack_index(th),
921 write_unlock_bh(&tcp_lock);
922 if (LOG_INVALID(IPPROTO_TCP))
923 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
924 "nf_ct_tcp: invalid state ");
926 case TCP_CONNTRACK_SYN_SENT:
927 if (old_state < TCP_CONNTRACK_TIME_WAIT)
929 if ((conntrack->proto.tcp.seen[dir].flags &
930 IP_CT_TCP_FLAG_CLOSE_INIT)
931 || after(ntohl(th->seq),
932 conntrack->proto.tcp.seen[dir].td_end)) {
933 /* Attempt to reopen a closed connection.
934 * Delete this connection and look up again. */
935 write_unlock_bh(&tcp_lock);
936 if (del_timer(&conntrack->timeout))
937 conntrack->timeout.function((unsigned long)
941 write_unlock_bh(&tcp_lock);
942 if (LOG_INVALID(IPPROTO_TCP))
943 nf_log_packet(pf, 0, skb, NULL, NULL,
944 NULL, "nf_ct_tcp: invalid SYN");
947 case TCP_CONNTRACK_CLOSE:
948 if (index == TCP_RST_SET
949 && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
950 && conntrack->proto.tcp.last_index == TCP_SYN_SET)
951 || (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
952 && conntrack->proto.tcp.last_index == TCP_ACK_SET))
953 && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
954 /* RST sent to invalid SYN or ACK we had let through
955 * at a) and c) above:
957 * a) SYN was in window then
958 * c) we hold a half-open connection.
960 * Delete our connection entry.
961 * We skip window checking, because packet might ACK
962 * segments we ignored. */
965 /* Just fall through */
967 /* Keep compilers happy. */
971 if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
972 skb, dataoff, th, pf)) {
973 write_unlock_bh(&tcp_lock);
977 /* From now on we have got in-window packets */
978 conntrack->proto.tcp.last_index = index;
980 DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
981 "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
982 NIPQUAD(iph->saddr), ntohs(th->source),
983 NIPQUAD(iph->daddr), ntohs(th->dest),
984 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
985 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
986 old_state, new_state);
988 conntrack->proto.tcp.state = new_state;
989 if (old_state != new_state
990 && (new_state == TCP_CONNTRACK_FIN_WAIT
991 || new_state == TCP_CONNTRACK_CLOSE))
992 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
993 timeout = conntrack->proto.tcp.retrans >= nf_ct_tcp_max_retrans
994 && *tcp_timeouts[new_state] > nf_ct_tcp_timeout_max_retrans
995 ? nf_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
996 write_unlock_bh(&tcp_lock);
998 nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
999 if (new_state != old_state)
1000 nf_conntrack_event_cache(IPCT_PROTOINFO, skb);
1002 if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
1003 /* If only reply is a RST, we can consider ourselves not to
1004 have an established connection: this is a fairly common
1005 problem case, so we can delete the conntrack
1006 immediately. --RR */
1008 if (del_timer(&conntrack->timeout))
1009 conntrack->timeout.function((unsigned long)
1013 } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
1014 && (old_state == TCP_CONNTRACK_SYN_RECV
1015 || old_state == TCP_CONNTRACK_ESTABLISHED)
1016 && new_state == TCP_CONNTRACK_ESTABLISHED) {
1017 /* Set ASSURED if we see see valid ack in ESTABLISHED
1018 after SYN_RECV or a valid answer for a picked up
1020 set_bit(IPS_ASSURED_BIT, &conntrack->status);
1021 nf_conntrack_event_cache(IPCT_STATUS, skb);
1023 nf_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
1028 /* Called when a new connection for this protocol found. */
1029 static int tcp_new(struct nf_conn *conntrack,
1030 const struct sk_buff *skb,
1031 unsigned int dataoff)
1033 enum tcp_conntrack new_state;
1034 struct tcphdr *th, _tcph;
1036 struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1037 struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1040 th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
1043 /* Don't need lock here: this conntrack not in circulation yet */
1045 = tcp_conntracks[0][get_conntrack_index(th)]
1046 [TCP_CONNTRACK_NONE];
1048 /* Invalid: delete conntrack */
1049 if (new_state >= TCP_CONNTRACK_MAX) {
1050 DEBUGP("nf_ct_tcp: invalid new deleting.\n");
1054 if (new_state == TCP_CONNTRACK_SYN_SENT) {
1056 conntrack->proto.tcp.seen[0].td_end =
1057 segment_seq_plus_len(ntohl(th->seq), skb->len,
1059 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1060 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1061 conntrack->proto.tcp.seen[0].td_maxwin = 1;
1062 conntrack->proto.tcp.seen[0].td_maxend =
1063 conntrack->proto.tcp.seen[0].td_end;
1065 tcp_options(skb, dataoff, th, &conntrack->proto.tcp.seen[0]);
1066 conntrack->proto.tcp.seen[1].flags = 0;
1067 conntrack->proto.tcp.seen[0].loose =
1068 conntrack->proto.tcp.seen[1].loose = 0;
1069 } else if (nf_ct_tcp_loose == 0) {
1070 /* Don't try to pick up connections. */
1074 * We are in the middle of a connection,
1075 * its history is lost for us.
1076 * Let's try to use the data from the packet.
1078 conntrack->proto.tcp.seen[0].td_end =
1079 segment_seq_plus_len(ntohl(th->seq), skb->len,
1081 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1082 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1083 conntrack->proto.tcp.seen[0].td_maxwin = 1;
1084 conntrack->proto.tcp.seen[0].td_maxend =
1085 conntrack->proto.tcp.seen[0].td_end +
1086 conntrack->proto.tcp.seen[0].td_maxwin;
1087 conntrack->proto.tcp.seen[0].td_scale = 0;
1089 /* We assume SACK. Should we assume window scaling too? */
1090 conntrack->proto.tcp.seen[0].flags =
1091 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM;
1092 conntrack->proto.tcp.seen[0].loose =
1093 conntrack->proto.tcp.seen[1].loose = nf_ct_tcp_loose;
1096 conntrack->proto.tcp.seen[1].td_end = 0;
1097 conntrack->proto.tcp.seen[1].td_maxend = 0;
1098 conntrack->proto.tcp.seen[1].td_maxwin = 1;
1099 conntrack->proto.tcp.seen[1].td_scale = 0;
1101 /* tcp_packet will set them */
1102 conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1103 conntrack->proto.tcp.last_index = TCP_NONE_SET;
1105 DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1106 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1107 sender->td_end, sender->td_maxend, sender->td_maxwin,
1109 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1110 receiver->td_scale);
1114 #if defined(CONFIG_NF_CT_NETLINK) || \
1115 defined(CONFIG_NF_CT_NETLINK_MODULE)
1117 #include <linux/netfilter/nfnetlink.h>
1118 #include <linux/netfilter/nfnetlink_conntrack.h>
1120 static int tcp_to_nfattr(struct sk_buff *skb, struct nfattr *nfa,
1121 const struct nf_conn *ct)
1123 struct nfattr *nest_parms;
1125 read_lock_bh(&tcp_lock);
1126 nest_parms = NFA_NEST(skb, CTA_PROTOINFO_TCP);
1127 NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
1128 &ct->proto.tcp.state);
1129 read_unlock_bh(&tcp_lock);
1131 NFA_NEST_END(skb, nest_parms);
1136 read_unlock_bh(&tcp_lock);
1140 static const size_t cta_min_tcp[CTA_PROTOINFO_TCP_MAX] = {
1141 [CTA_PROTOINFO_TCP_STATE-1] = sizeof(u_int8_t),
1144 static int nfattr_to_tcp(struct nfattr *cda[], struct nf_conn *ct)
1146 struct nfattr *attr = cda[CTA_PROTOINFO_TCP-1];
1147 struct nfattr *tb[CTA_PROTOINFO_TCP_MAX];
1149 /* updates could not contain anything about the private
1150 * protocol info, in that case skip the parsing */
1154 nfattr_parse_nested(tb, CTA_PROTOINFO_TCP_MAX, attr);
1156 if (nfattr_bad_size(tb, CTA_PROTOINFO_TCP_MAX, cta_min_tcp))
1159 if (!tb[CTA_PROTOINFO_TCP_STATE-1])
1162 write_lock_bh(&tcp_lock);
1163 ct->proto.tcp.state =
1164 *(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_STATE-1]);
1165 write_unlock_bh(&tcp_lock);
1171 struct nf_conntrack_protocol nf_conntrack_protocol_tcp4 =
1174 .proto = IPPROTO_TCP,
1176 .pkt_to_tuple = tcp_pkt_to_tuple,
1177 .invert_tuple = tcp_invert_tuple,
1178 .print_tuple = tcp_print_tuple,
1179 .print_conntrack = tcp_print_conntrack,
1180 .packet = tcp_packet,
1183 #if defined(CONFIG_NF_CT_NETLINK) || \
1184 defined(CONFIG_NF_CT_NETLINK_MODULE)
1185 .to_nfattr = tcp_to_nfattr,
1186 .from_nfattr = nfattr_to_tcp,
1187 .tuple_to_nfattr = nf_ct_port_tuple_to_nfattr,
1188 .nfattr_to_tuple = nf_ct_port_nfattr_to_tuple,
1192 struct nf_conntrack_protocol nf_conntrack_protocol_tcp6 =
1194 .l3proto = PF_INET6,
1195 .proto = IPPROTO_TCP,
1197 .pkt_to_tuple = tcp_pkt_to_tuple,
1198 .invert_tuple = tcp_invert_tuple,
1199 .print_tuple = tcp_print_tuple,
1200 .print_conntrack = tcp_print_conntrack,
1201 .packet = tcp_packet,
1204 #if defined(CONFIG_NF_CT_NETLINK) || \
1205 defined(CONFIG_NF_CT_NETLINK_MODULE)
1206 .to_nfattr = tcp_to_nfattr,
1207 .from_nfattr = nfattr_to_tcp,
1208 .tuple_to_nfattr = nf_ct_port_tuple_to_nfattr,
1209 .nfattr_to_tuple = nf_ct_port_nfattr_to_tuple,
1213 EXPORT_SYMBOL(nf_conntrack_protocol_tcp4);
1214 EXPORT_SYMBOL(nf_conntrack_protocol_tcp6);