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
22 #include <linux/types.h>
23 #include <linux/timer.h>
24 #include <linux/netfilter.h>
25 #include <linux/module.h>
28 #include <linux/tcp.h>
29 #include <linux/spinlock.h>
33 #include <linux/netfilter_ipv4.h>
34 #include <linux/netfilter_ipv4/ip_conntrack.h>
35 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
41 #define DEBUGP(format, args...)
44 /* Protects conntrack->proto.tcp */
45 static DEFINE_RWLOCK(tcp_lock);
47 /* "Be conservative in what you do,
48 be liberal in what you accept from others."
49 If it's non-zero, we mark only out of window RST segments as INVALID. */
50 int ip_ct_tcp_be_liberal __read_mostly = 0;
52 /* If it is set to zero, we disable picking up already established
54 int ip_ct_tcp_loose __read_mostly = 1;
56 /* Max number of the retransmitted packets without receiving an (acceptable)
57 ACK from the destination. If this number is reached, a shorter timer
59 int ip_ct_tcp_max_retrans __read_mostly = 3;
61 /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
62 closely. They're more complex. --RR */
64 static const char *tcp_conntrack_names[] = {
78 #define MINS * 60 SECS
79 #define HOURS * 60 MINS
80 #define DAYS * 24 HOURS
82 unsigned int ip_ct_tcp_timeout_syn_sent __read_mostly = 2 MINS;
83 unsigned int ip_ct_tcp_timeout_syn_recv __read_mostly = 60 SECS;
84 unsigned int ip_ct_tcp_timeout_established __read_mostly = 5 DAYS;
85 unsigned int ip_ct_tcp_timeout_fin_wait __read_mostly = 2 MINS;
86 unsigned int ip_ct_tcp_timeout_close_wait __read_mostly = 60 SECS;
87 unsigned int ip_ct_tcp_timeout_last_ack __read_mostly = 30 SECS;
88 unsigned int ip_ct_tcp_timeout_time_wait __read_mostly = 2 MINS;
89 unsigned int ip_ct_tcp_timeout_close __read_mostly = 10 SECS;
91 /* RFC1122 says the R2 limit should be at least 100 seconds.
92 Linux uses 15 packets as limit, which corresponds
93 to ~13-30min depending on RTO. */
94 unsigned int ip_ct_tcp_timeout_max_retrans __read_mostly = 5 MINS;
96 static const unsigned int * tcp_timeouts[]
97 = { NULL, /* TCP_CONNTRACK_NONE */
98 &ip_ct_tcp_timeout_syn_sent, /* TCP_CONNTRACK_SYN_SENT, */
99 &ip_ct_tcp_timeout_syn_recv, /* TCP_CONNTRACK_SYN_RECV, */
100 &ip_ct_tcp_timeout_established, /* TCP_CONNTRACK_ESTABLISHED, */
101 &ip_ct_tcp_timeout_fin_wait, /* TCP_CONNTRACK_FIN_WAIT, */
102 &ip_ct_tcp_timeout_close_wait, /* TCP_CONNTRACK_CLOSE_WAIT, */
103 &ip_ct_tcp_timeout_last_ack, /* TCP_CONNTRACK_LAST_ACK, */
104 &ip_ct_tcp_timeout_time_wait, /* TCP_CONNTRACK_TIME_WAIT, */
105 &ip_ct_tcp_timeout_close, /* TCP_CONNTRACK_CLOSE, */
106 NULL, /* TCP_CONNTRACK_LISTEN */
109 #define sNO TCP_CONNTRACK_NONE
110 #define sSS TCP_CONNTRACK_SYN_SENT
111 #define sSR TCP_CONNTRACK_SYN_RECV
112 #define sES TCP_CONNTRACK_ESTABLISHED
113 #define sFW TCP_CONNTRACK_FIN_WAIT
114 #define sCW TCP_CONNTRACK_CLOSE_WAIT
115 #define sLA TCP_CONNTRACK_LAST_ACK
116 #define sTW TCP_CONNTRACK_TIME_WAIT
117 #define sCL TCP_CONNTRACK_CLOSE
118 #define sLI TCP_CONNTRACK_LISTEN
119 #define sIV TCP_CONNTRACK_MAX
120 #define sIG TCP_CONNTRACK_IGNORE
122 /* What TCP flags are set from RST/SYN/FIN/ACK. */
133 * The TCP state transition table needs a few words...
135 * We are the man in the middle. All the packets go through us
136 * but might get lost in transit to the destination.
137 * It is assumed that the destinations can't receive segments
140 * The checked segment is in window, but our windows are *not*
141 * equivalent with the ones of the sender/receiver. We always
142 * try to guess the state of the current sender.
144 * The meaning of the states are:
146 * NONE: initial state
147 * SYN_SENT: SYN-only packet seen
148 * SYN_RECV: SYN-ACK packet seen
149 * ESTABLISHED: ACK packet seen
150 * FIN_WAIT: FIN packet seen
151 * CLOSE_WAIT: ACK seen (after FIN)
152 * LAST_ACK: FIN seen (after FIN)
153 * TIME_WAIT: last ACK seen
154 * CLOSE: closed connection
156 * LISTEN state is not used.
158 * Packets marked as IGNORED (sIG):
159 * if they may be either invalid or valid
160 * and the receiver may send back a connection
161 * closing RST or a SYN/ACK.
163 * Packets marked as INVALID (sIV):
164 * if they are invalid
165 * or we do not support the request (simultaneous open)
167 static const enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
170 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
171 /*syn*/ { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
173 * sNO -> sSS Initialize a new connection
174 * sSS -> sSS Retransmitted SYN
175 * sSR -> sIG Late retransmitted SYN?
176 * sES -> sIG Error: SYNs in window outside the SYN_SENT state
177 * are errors. Receiver will reply with RST
178 * and close the connection.
179 * Or we are not in sync and hold a dead connection.
183 * sTW -> sSS Reopened connection (RFC 1122).
186 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
187 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
189 * A SYN/ACK from the client is always invalid:
190 * - either it tries to set up a simultaneous open, which is
192 * - or the firewall has just been inserted between the two hosts
193 * during the session set-up. The SYN will be retransmitted
194 * by the true client (or it'll time out).
196 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
197 /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
199 * sNO -> sIV Too late and no reason to do anything...
200 * sSS -> sIV Client migth not send FIN in this state:
201 * we enforce waiting for a SYN/ACK reply first.
202 * sSR -> sFW Close started.
204 * sFW -> sLA FIN seen in both directions, waiting for
206 * Migth be a retransmitted FIN as well...
208 * sLA -> sLA Retransmitted FIN. Remain in the same state.
212 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
213 /*ack*/ { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
215 * sNO -> sES Assumed.
216 * sSS -> sIV ACK is invalid: we haven't seen a SYN/ACK yet.
217 * sSR -> sES Established state is reached.
219 * sFW -> sCW Normal close request answered by ACK.
221 * sLA -> sTW Last ACK detected.
222 * sTW -> sTW Retransmitted last ACK. Remain in the same state.
225 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
226 /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
227 /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
231 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
232 /*syn*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
234 * sNO -> sIV Never reached.
235 * sSS -> sIV Simultaneous open, not supported
236 * sSR -> sIV Simultaneous open, not supported.
237 * sES -> sIV Server may not initiate a connection.
241 * sTW -> sIV Reopened connection, but server may not do it.
244 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
245 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
247 * sSS -> sSR Standard open.
248 * sSR -> sSR Retransmitted SYN/ACK.
249 * sES -> sIG Late retransmitted SYN/ACK?
250 * sFW -> sIG Might be SYN/ACK answering ignored SYN
256 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
257 /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
259 * sSS -> sIV Server might not send FIN in this state.
260 * sSR -> sFW Close started.
262 * sFW -> sLA FIN seen in both directions.
264 * sLA -> sLA Retransmitted FIN.
268 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
269 /*ack*/ { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
271 * sSS -> sIG Might be a half-open connection.
272 * sSR -> sSR Might answer late resent SYN.
274 * sFW -> sCW Normal close request answered by ACK.
276 * sLA -> sTW Last ACK detected.
277 * sTW -> sTW Retransmitted last ACK.
280 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
281 /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
282 /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
286 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
287 unsigned int dataoff,
288 struct ip_conntrack_tuple *tuple)
290 struct tcphdr _hdr, *hp;
292 /* Actually only need first 8 bytes. */
293 hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
297 tuple->src.u.tcp.port = hp->source;
298 tuple->dst.u.tcp.port = hp->dest;
303 static int tcp_invert_tuple(struct ip_conntrack_tuple *tuple,
304 const struct ip_conntrack_tuple *orig)
306 tuple->src.u.tcp.port = orig->dst.u.tcp.port;
307 tuple->dst.u.tcp.port = orig->src.u.tcp.port;
311 /* Print out the per-protocol part of the tuple. */
312 static int tcp_print_tuple(struct seq_file *s,
313 const struct ip_conntrack_tuple *tuple)
315 return seq_printf(s, "sport=%hu dport=%hu ",
316 ntohs(tuple->src.u.tcp.port),
317 ntohs(tuple->dst.u.tcp.port));
320 /* Print out the private part of the conntrack. */
321 static int tcp_print_conntrack(struct seq_file *s,
322 const struct ip_conntrack *conntrack)
324 enum tcp_conntrack state;
326 read_lock_bh(&tcp_lock);
327 state = conntrack->proto.tcp.state;
328 read_unlock_bh(&tcp_lock);
330 return seq_printf(s, "%s ", tcp_conntrack_names[state]);
333 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
334 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
335 static int tcp_to_nfattr(struct sk_buff *skb, struct nfattr *nfa,
336 const struct ip_conntrack *ct)
338 struct nfattr *nest_parms;
340 read_lock_bh(&tcp_lock);
341 nest_parms = NFA_NEST(skb, CTA_PROTOINFO_TCP);
342 NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
343 &ct->proto.tcp.state);
344 read_unlock_bh(&tcp_lock);
346 NFA_NEST_END(skb, nest_parms);
351 read_unlock_bh(&tcp_lock);
355 static const size_t cta_min_tcp[CTA_PROTOINFO_TCP_MAX] = {
356 [CTA_PROTOINFO_TCP_STATE-1] = sizeof(u_int8_t),
359 static int nfattr_to_tcp(struct nfattr *cda[], struct ip_conntrack *ct)
361 struct nfattr *attr = cda[CTA_PROTOINFO_TCP-1];
362 struct nfattr *tb[CTA_PROTOINFO_TCP_MAX];
364 /* updates could not contain anything about the private
365 * protocol info, in that case skip the parsing */
369 nfattr_parse_nested(tb, CTA_PROTOINFO_TCP_MAX, attr);
371 if (nfattr_bad_size(tb, CTA_PROTOINFO_TCP_MAX, cta_min_tcp))
374 if (!tb[CTA_PROTOINFO_TCP_STATE-1])
377 write_lock_bh(&tcp_lock);
378 ct->proto.tcp.state =
379 *(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_STATE-1]);
380 write_unlock_bh(&tcp_lock);
386 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
388 if (tcph->rst) return TCP_RST_SET;
389 else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
390 else if (tcph->fin) return TCP_FIN_SET;
391 else if (tcph->ack) return TCP_ACK_SET;
392 else return TCP_NONE_SET;
395 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
396 in IP Filter' by Guido van Rooij.
398 http://www.nluug.nl/events/sane2000/papers.html
399 http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
401 The boundaries and the conditions are changed according to RFC793:
402 the packet must intersect the window (i.e. segments may be
403 after the right or before the left edge) and thus receivers may ACK
404 segments after the right edge of the window.
406 td_maxend = max(sack + max(win,1)) seen in reply packets
407 td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
408 td_maxwin += seq + len - sender.td_maxend
409 if seq + len > sender.td_maxend
410 td_end = max(seq + len) seen in sent packets
412 I. Upper bound for valid data: seq <= sender.td_maxend
413 II. Lower bound for valid data: seq + len >= sender.td_end - receiver.td_maxwin
414 III. Upper bound for valid ack: sack <= receiver.td_end
415 IV. Lower bound for valid ack: ack >= receiver.td_end - MAXACKWINDOW
417 where sack is the highest right edge of sack block found in the packet.
419 The upper bound limit for a valid ack is not ignored -
420 we doesn't have to deal with fragments.
423 static inline __u32 segment_seq_plus_len(__u32 seq,
428 return (seq + len - (iph->ihl + tcph->doff)*4
429 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
432 /* Fixme: what about big packets? */
433 #define MAXACKWINCONST 66000
434 #define MAXACKWINDOW(sender) \
435 ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin \
439 * Simplified tcp_parse_options routine from tcp_input.c
441 static void tcp_options(const struct sk_buff *skb,
444 struct ip_ct_tcp_state *state)
446 unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
448 int length = (tcph->doff*4) - sizeof(struct tcphdr);
453 ptr = skb_header_pointer(skb,
454 (iph->ihl * 4) + sizeof(struct tcphdr),
468 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
473 if (opsize < 2) /* "silly options" */
476 break; /* don't parse partial options */
478 if (opcode == TCPOPT_SACK_PERM
479 && opsize == TCPOLEN_SACK_PERM)
480 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
481 else if (opcode == TCPOPT_WINDOW
482 && opsize == TCPOLEN_WINDOW) {
483 state->td_scale = *(u_int8_t *)ptr;
485 if (state->td_scale > 14) {
487 state->td_scale = 14;
490 IP_CT_TCP_FLAG_WINDOW_SCALE;
498 static void tcp_sack(const struct sk_buff *skb,
503 unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
505 int length = (tcph->doff*4) - sizeof(struct tcphdr);
511 ptr = skb_header_pointer(skb,
512 (iph->ihl * 4) + sizeof(struct tcphdr),
516 /* Fast path for timestamp-only option */
517 if (length == TCPOLEN_TSTAMP_ALIGNED*4
519 __constant_htonl((TCPOPT_NOP << 24)
521 | (TCPOPT_TIMESTAMP << 8)
522 | TCPOLEN_TIMESTAMP))
532 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
537 if (opsize < 2) /* "silly options" */
540 break; /* don't parse partial options */
542 if (opcode == TCPOPT_SACK
543 && opsize >= (TCPOLEN_SACK_BASE
544 + TCPOLEN_SACK_PERBLOCK)
545 && !((opsize - TCPOLEN_SACK_BASE)
546 % TCPOLEN_SACK_PERBLOCK)) {
548 i < (opsize - TCPOLEN_SACK_BASE);
549 i += TCPOLEN_SACK_PERBLOCK) {
550 tmp = ntohl(*((__be32 *)(ptr+i)+1));
552 if (after(tmp, *sack))
563 static int tcp_in_window(struct ip_ct_tcp *state,
564 enum ip_conntrack_dir dir,
566 const struct sk_buff *skb,
570 struct ip_ct_tcp_state *sender = &state->seen[dir];
571 struct ip_ct_tcp_state *receiver = &state->seen[!dir];
572 __u32 seq, ack, sack, end, win, swin;
576 * Get the required data from the packet.
578 seq = ntohl(tcph->seq);
579 ack = sack = ntohl(tcph->ack_seq);
580 win = ntohs(tcph->window);
581 end = segment_seq_plus_len(seq, skb->len, iph, tcph);
583 if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
584 tcp_sack(skb, iph, tcph, &sack);
586 DEBUGP("tcp_in_window: START\n");
587 DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
588 "seq=%u ack=%u sack=%u win=%u end=%u\n",
589 NIPQUAD(iph->saddr), ntohs(tcph->source),
590 NIPQUAD(iph->daddr), ntohs(tcph->dest),
591 seq, ack, sack, win, end);
592 DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
593 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
594 sender->td_end, sender->td_maxend, sender->td_maxwin,
596 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
599 if (sender->td_end == 0) {
601 * Initialize sender data.
603 if (tcph->syn && tcph->ack) {
605 * Outgoing SYN-ACK in reply to a SYN.
608 sender->td_maxend = end;
609 sender->td_maxwin = (win == 0 ? 1 : win);
611 tcp_options(skb, iph, tcph, sender);
614 * Both sides must send the Window Scale option
615 * to enable window scaling in either direction.
617 if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
618 && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
620 receiver->td_scale = 0;
623 * We are in the middle of a connection,
624 * its history is lost for us.
625 * Let's try to use the data from the packet.
627 sender->td_end = end;
628 sender->td_maxwin = (win == 0 ? 1 : win);
629 sender->td_maxend = end + sender->td_maxwin;
631 } else if (((state->state == TCP_CONNTRACK_SYN_SENT
632 && dir == IP_CT_DIR_ORIGINAL)
633 || (state->state == TCP_CONNTRACK_SYN_RECV
634 && dir == IP_CT_DIR_REPLY))
635 && after(end, sender->td_end)) {
637 * RFC 793: "if a TCP is reinitialized ... then it need
638 * not wait at all; it must only be sure to use sequence
639 * numbers larger than those recently used."
642 sender->td_maxend = end;
643 sender->td_maxwin = (win == 0 ? 1 : win);
645 tcp_options(skb, iph, tcph, sender);
650 * If there is no ACK, just pretend it was set and OK.
652 ack = sack = receiver->td_end;
653 } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
654 (TCP_FLAG_ACK|TCP_FLAG_RST))
657 * Broken TCP stacks, that set ACK in RST packets as well
658 * with zero ack value.
660 ack = sack = receiver->td_end;
665 || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
667 * Packets contains no data: we assume it is valid
668 * and check the ack value only.
669 * However RST segments are always validated by their
670 * SEQ number, except when seq == 0 (reset sent answering
673 seq = end = sender->td_end;
675 DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
676 "seq=%u ack=%u sack =%u win=%u end=%u\n",
677 NIPQUAD(iph->saddr), ntohs(tcph->source),
678 NIPQUAD(iph->daddr), ntohs(tcph->dest),
679 seq, ack, sack, win, end);
680 DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
681 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
682 sender->td_end, sender->td_maxend, sender->td_maxwin,
684 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
687 DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
688 before(seq, sender->td_maxend + 1),
689 after(end, sender->td_end - receiver->td_maxwin - 1),
690 before(sack, receiver->td_end + 1),
691 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
693 if (before(seq, sender->td_maxend + 1) &&
694 after(end, sender->td_end - receiver->td_maxwin - 1) &&
695 before(sack, receiver->td_end + 1) &&
696 after(ack, receiver->td_end - MAXACKWINDOW(sender))) {
698 * Take into account window scaling (RFC 1323).
701 win <<= sender->td_scale;
704 * Update sender data.
706 swin = win + (sack - ack);
707 if (sender->td_maxwin < swin)
708 sender->td_maxwin = swin;
709 if (after(end, sender->td_end))
710 sender->td_end = end;
712 * Update receiver data.
714 if (after(end, sender->td_maxend))
715 receiver->td_maxwin += end - sender->td_maxend;
716 if (after(sack + win, receiver->td_maxend - 1)) {
717 receiver->td_maxend = sack + win;
719 receiver->td_maxend++;
723 * Check retransmissions.
725 if (index == TCP_ACK_SET) {
726 if (state->last_dir == dir
727 && state->last_seq == seq
728 && state->last_ack == ack
729 && state->last_end == end
730 && state->last_win == win)
733 state->last_dir = dir;
734 state->last_seq = seq;
735 state->last_ack = ack;
736 state->last_end = end;
737 state->last_win = win;
744 if (sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL ||
745 ip_ct_tcp_be_liberal)
747 if (!res && LOG_INVALID(IPPROTO_TCP))
748 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
750 before(seq, sender->td_maxend + 1) ?
751 after(end, sender->td_end - receiver->td_maxwin - 1) ?
752 before(sack, receiver->td_end + 1) ?
753 after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
754 : "ACK is under the lower bound (possible overly delayed ACK)"
755 : "ACK is over the upper bound (ACKed data not seen yet)"
756 : "SEQ is under the lower bound (already ACKed data retransmitted)"
757 : "SEQ is over the upper bound (over the window of the receiver)");
760 DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
761 "receiver end=%u maxend=%u maxwin=%u\n",
762 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
763 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
768 #ifdef CONFIG_IP_NF_NAT_NEEDED
769 /* Update sender->td_end after NAT successfully mangled the packet */
770 void ip_conntrack_tcp_update(struct sk_buff *skb,
771 struct ip_conntrack *conntrack,
772 enum ip_conntrack_dir dir)
774 struct iphdr *iph = skb->nh.iph;
775 struct tcphdr *tcph = (void *)skb->nh.iph + skb->nh.iph->ihl*4;
778 struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
779 struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
782 end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, iph, tcph);
784 write_lock_bh(&tcp_lock);
786 * We have to worry for the ack in the reply packet only...
788 if (after(end, conntrack->proto.tcp.seen[dir].td_end))
789 conntrack->proto.tcp.seen[dir].td_end = end;
790 conntrack->proto.tcp.last_end = end;
791 write_unlock_bh(&tcp_lock);
792 DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
793 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
794 sender->td_end, sender->td_maxend, sender->td_maxwin,
796 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
811 /* table of valid flag combinations - ECE and CWR are always valid */
812 static const u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
816 [TH_SYN|TH_PUSH] = 1,
817 [TH_SYN|TH_ACK|TH_PUSH] = 1,
820 [TH_RST|TH_ACK|TH_PUSH] = 1,
823 [TH_ACK|TH_PUSH] = 1,
825 [TH_ACK|TH_URG|TH_PUSH] = 1,
826 [TH_FIN|TH_ACK|TH_PUSH] = 1,
827 [TH_FIN|TH_ACK|TH_URG] = 1,
828 [TH_FIN|TH_ACK|TH_URG|TH_PUSH] = 1,
831 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c. */
832 static int tcp_error(struct sk_buff *skb,
833 enum ip_conntrack_info *ctinfo,
834 unsigned int hooknum)
836 struct iphdr *iph = skb->nh.iph;
837 struct tcphdr _tcph, *th;
838 unsigned int tcplen = skb->len - iph->ihl * 4;
841 /* Smaller that minimal TCP header? */
842 th = skb_header_pointer(skb, iph->ihl * 4,
843 sizeof(_tcph), &_tcph);
845 if (LOG_INVALID(IPPROTO_TCP))
846 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
847 "ip_ct_tcp: short packet ");
851 /* Not whole TCP header or malformed packet */
852 if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
853 if (LOG_INVALID(IPPROTO_TCP))
854 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
855 "ip_ct_tcp: truncated/malformed packet ");
859 /* Checksum invalid? Ignore.
860 * We skip checking packets on the outgoing path
861 * because it is assumed to be correct.
863 /* FIXME: Source route IP option packets --RR */
864 if (ip_conntrack_checksum && hooknum == NF_IP_PRE_ROUTING &&
865 nf_ip_checksum(skb, hooknum, iph->ihl * 4, IPPROTO_TCP)) {
866 if (LOG_INVALID(IPPROTO_TCP))
867 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
868 "ip_ct_tcp: bad TCP checksum ");
872 /* Check TCP flags. */
873 tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
874 if (!tcp_valid_flags[tcpflags]) {
875 if (LOG_INVALID(IPPROTO_TCP))
876 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
877 "ip_ct_tcp: invalid TCP flag combination ");
884 /* Returns verdict for packet, or -1 for invalid. */
885 static int tcp_packet(struct ip_conntrack *conntrack,
886 const struct sk_buff *skb,
887 enum ip_conntrack_info ctinfo)
889 enum tcp_conntrack new_state, old_state;
890 enum ip_conntrack_dir dir;
891 struct iphdr *iph = skb->nh.iph;
892 struct tcphdr *th, _tcph;
893 unsigned long timeout;
896 th = skb_header_pointer(skb, iph->ihl * 4,
897 sizeof(_tcph), &_tcph);
900 write_lock_bh(&tcp_lock);
901 old_state = conntrack->proto.tcp.state;
902 dir = CTINFO2DIR(ctinfo);
903 index = get_conntrack_index(th);
904 new_state = tcp_conntracks[dir][index][old_state];
907 case TCP_CONNTRACK_IGNORE:
911 * b) SYN/ACK in REPLY
912 * c) ACK in reply direction after initial SYN in original.
914 if (index == TCP_SYNACK_SET
915 && conntrack->proto.tcp.last_index == TCP_SYN_SET
916 && conntrack->proto.tcp.last_dir != dir
917 && ntohl(th->ack_seq) ==
918 conntrack->proto.tcp.last_end) {
919 /* This SYN/ACK acknowledges a SYN that we earlier
920 * ignored as invalid. This means that the client and
921 * the server are both in sync, while the firewall is
922 * not. We kill this session and block the SYN/ACK so
923 * that the client cannot but retransmit its SYN and
924 * thus initiate a clean new session.
926 write_unlock_bh(&tcp_lock);
927 if (LOG_INVALID(IPPROTO_TCP))
928 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
930 "killing out of sync session ");
931 if (del_timer(&conntrack->timeout))
932 conntrack->timeout.function((unsigned long)
936 conntrack->proto.tcp.last_index = index;
937 conntrack->proto.tcp.last_dir = dir;
938 conntrack->proto.tcp.last_seq = ntohl(th->seq);
939 conntrack->proto.tcp.last_end =
940 segment_seq_plus_len(ntohl(th->seq), skb->len, iph, th);
942 write_unlock_bh(&tcp_lock);
943 if (LOG_INVALID(IPPROTO_TCP))
944 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
945 "ip_ct_tcp: invalid packet ignored ");
947 case TCP_CONNTRACK_MAX:
949 DEBUGP("ip_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
950 dir, get_conntrack_index(th),
952 write_unlock_bh(&tcp_lock);
953 if (LOG_INVALID(IPPROTO_TCP))
954 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
955 "ip_ct_tcp: invalid state ");
957 case TCP_CONNTRACK_SYN_SENT:
958 if (old_state < TCP_CONNTRACK_TIME_WAIT)
960 if ((conntrack->proto.tcp.seen[dir].flags &
961 IP_CT_TCP_FLAG_CLOSE_INIT)
962 || after(ntohl(th->seq),
963 conntrack->proto.tcp.seen[dir].td_end)) {
964 /* Attempt to reopen a closed connection.
965 * Delete this connection and look up again. */
966 write_unlock_bh(&tcp_lock);
967 if (del_timer(&conntrack->timeout))
968 conntrack->timeout.function((unsigned long)
972 write_unlock_bh(&tcp_lock);
973 if (LOG_INVALID(IPPROTO_TCP))
974 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
975 NULL, "ip_ct_tcp: invalid SYN");
978 case TCP_CONNTRACK_CLOSE:
979 if (index == TCP_RST_SET
980 && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
981 && conntrack->proto.tcp.last_index == TCP_SYN_SET)
982 || (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
983 && conntrack->proto.tcp.last_index == TCP_ACK_SET))
984 && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
985 /* RST sent to invalid SYN or ACK we had let through
986 * at a) and c) above:
988 * a) SYN was in window then
989 * c) we hold a half-open connection.
991 * Delete our connection entry.
992 * We skip window checking, because packet might ACK
993 * segments we ignored. */
996 /* Just fall through */
998 /* Keep compilers happy. */
1002 if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
1004 write_unlock_bh(&tcp_lock);
1008 /* From now on we have got in-window packets */
1009 conntrack->proto.tcp.last_index = index;
1011 DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
1012 "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1013 NIPQUAD(iph->saddr), ntohs(th->source),
1014 NIPQUAD(iph->daddr), ntohs(th->dest),
1015 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
1016 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
1017 old_state, new_state);
1019 conntrack->proto.tcp.state = new_state;
1020 if (old_state != new_state
1021 && (new_state == TCP_CONNTRACK_FIN_WAIT
1022 || new_state == TCP_CONNTRACK_CLOSE))
1023 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1024 timeout = conntrack->proto.tcp.retrans >= ip_ct_tcp_max_retrans
1025 && *tcp_timeouts[new_state] > ip_ct_tcp_timeout_max_retrans
1026 ? ip_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
1027 write_unlock_bh(&tcp_lock);
1029 ip_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
1030 if (new_state != old_state)
1031 ip_conntrack_event_cache(IPCT_PROTOINFO, skb);
1033 if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
1034 /* If only reply is a RST, we can consider ourselves not to
1035 have an established connection: this is a fairly common
1036 problem case, so we can delete the conntrack
1037 immediately. --RR */
1039 if (del_timer(&conntrack->timeout))
1040 conntrack->timeout.function((unsigned long)
1044 } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
1045 && (old_state == TCP_CONNTRACK_SYN_RECV
1046 || old_state == TCP_CONNTRACK_ESTABLISHED)
1047 && new_state == TCP_CONNTRACK_ESTABLISHED) {
1048 /* Set ASSURED if we see see valid ack in ESTABLISHED
1049 after SYN_RECV or a valid answer for a picked up
1051 set_bit(IPS_ASSURED_BIT, &conntrack->status);
1052 ip_conntrack_event_cache(IPCT_STATUS, skb);
1054 ip_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
1059 /* Called when a new connection for this protocol found. */
1060 static int tcp_new(struct ip_conntrack *conntrack,
1061 const struct sk_buff *skb)
1063 enum tcp_conntrack new_state;
1064 struct iphdr *iph = skb->nh.iph;
1065 struct tcphdr *th, _tcph;
1067 struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1068 struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1071 th = skb_header_pointer(skb, iph->ihl * 4,
1072 sizeof(_tcph), &_tcph);
1075 /* Don't need lock here: this conntrack not in circulation yet */
1077 = tcp_conntracks[0][get_conntrack_index(th)]
1078 [TCP_CONNTRACK_NONE];
1080 /* Invalid: delete conntrack */
1081 if (new_state >= TCP_CONNTRACK_MAX) {
1082 DEBUGP("ip_ct_tcp: invalid new deleting.\n");
1086 if (new_state == TCP_CONNTRACK_SYN_SENT) {
1088 conntrack->proto.tcp.seen[0].td_end =
1089 segment_seq_plus_len(ntohl(th->seq), skb->len,
1091 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1092 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1093 conntrack->proto.tcp.seen[0].td_maxwin = 1;
1094 conntrack->proto.tcp.seen[0].td_maxend =
1095 conntrack->proto.tcp.seen[0].td_end;
1097 tcp_options(skb, iph, th, &conntrack->proto.tcp.seen[0]);
1098 conntrack->proto.tcp.seen[1].flags = 0;
1099 } else if (ip_ct_tcp_loose == 0) {
1100 /* Don't try to pick up connections. */
1104 * We are in the middle of a connection,
1105 * its history is lost for us.
1106 * Let's try to use the data from the packet.
1108 conntrack->proto.tcp.seen[0].td_end =
1109 segment_seq_plus_len(ntohl(th->seq), skb->len,
1111 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1112 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1113 conntrack->proto.tcp.seen[0].td_maxwin = 1;
1114 conntrack->proto.tcp.seen[0].td_maxend =
1115 conntrack->proto.tcp.seen[0].td_end +
1116 conntrack->proto.tcp.seen[0].td_maxwin;
1117 conntrack->proto.tcp.seen[0].td_scale = 0;
1119 /* We assume SACK and liberal window checking to handle
1121 conntrack->proto.tcp.seen[0].flags =
1122 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM |
1123 IP_CT_TCP_FLAG_BE_LIBERAL;
1126 conntrack->proto.tcp.seen[1].td_end = 0;
1127 conntrack->proto.tcp.seen[1].td_maxend = 0;
1128 conntrack->proto.tcp.seen[1].td_maxwin = 1;
1129 conntrack->proto.tcp.seen[1].td_scale = 0;
1131 /* tcp_packet will set them */
1132 conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1133 conntrack->proto.tcp.last_index = TCP_NONE_SET;
1135 DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1136 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1137 sender->td_end, sender->td_maxend, sender->td_maxwin,
1139 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1140 receiver->td_scale);
1144 struct ip_conntrack_protocol ip_conntrack_protocol_tcp =
1146 .proto = IPPROTO_TCP,
1148 .pkt_to_tuple = tcp_pkt_to_tuple,
1149 .invert_tuple = tcp_invert_tuple,
1150 .print_tuple = tcp_print_tuple,
1151 .print_conntrack = tcp_print_conntrack,
1152 .packet = tcp_packet,
1155 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
1156 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
1157 .to_nfattr = tcp_to_nfattr,
1158 .from_nfattr = nfattr_to_tcp,
1159 .tuple_to_nfattr = ip_ct_port_tuple_to_nfattr,
1160 .nfattr_to_tuple = ip_ct_port_nfattr_to_tuple,