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/config.h>
28 #include <linux/types.h>
29 #include <linux/sched.h>
30 #include <linux/timer.h>
31 #include <linux/netfilter.h>
32 #include <linux/module.h>
34 #include <linux/tcp.h>
35 #include <linux/spinlock.h>
36 #include <linux/skbuff.h>
37 #include <linux/ipv6.h>
38 #include <net/ip6_checksum.h>
42 #include <linux/netfilter.h>
43 #include <linux/netfilter_ipv4.h>
44 #include <linux/netfilter_ipv6.h>
45 #include <net/netfilter/nf_conntrack.h>
46 #include <net/netfilter/nf_conntrack_protocol.h>
52 #define DEBUGP(format, args...)
55 /* Protects conntrack->proto.tcp */
56 static DEFINE_RWLOCK(tcp_lock
);
58 /* "Be conservative in what you do,
59 be liberal in what you accept from others."
60 If it's non-zero, we mark only out of window RST segments as INVALID. */
61 int nf_ct_tcp_be_liberal
= 0;
63 /* When connection is picked up from the middle, how many packets are required
64 to pass in each direction when we assume we are in sync - if any side uses
65 window scaling, we lost the game.
66 If it is set to zero, we disable picking up already established
68 int nf_ct_tcp_loose
= 3;
70 /* Max number of the retransmitted packets without receiving an (acceptable)
71 ACK from the destination. If this number is reached, a shorter timer
73 int nf_ct_tcp_max_retrans
= 3;
75 /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
76 closely. They're more complex. --RR */
78 static const char *tcp_conntrack_names
[] = {
92 #define MINS * 60 SECS
93 #define HOURS * 60 MINS
94 #define DAYS * 24 HOURS
96 unsigned int nf_ct_tcp_timeout_syn_sent
= 2 MINS
;
97 unsigned int nf_ct_tcp_timeout_syn_recv
= 60 SECS
;
98 unsigned int nf_ct_tcp_timeout_established
= 5 DAYS
;
99 unsigned int nf_ct_tcp_timeout_fin_wait
= 2 MINS
;
100 unsigned int nf_ct_tcp_timeout_close_wait
= 60 SECS
;
101 unsigned int nf_ct_tcp_timeout_last_ack
= 30 SECS
;
102 unsigned int nf_ct_tcp_timeout_time_wait
= 2 MINS
;
103 unsigned int nf_ct_tcp_timeout_close
= 10 SECS
;
105 /* RFC1122 says the R2 limit should be at least 100 seconds.
106 Linux uses 15 packets as limit, which corresponds
107 to ~13-30min depending on RTO. */
108 unsigned int nf_ct_tcp_timeout_max_retrans
= 5 MINS
;
110 static unsigned int * tcp_timeouts
[]
111 = { NULL
, /* TCP_CONNTRACK_NONE */
112 &nf_ct_tcp_timeout_syn_sent
, /* TCP_CONNTRACK_SYN_SENT, */
113 &nf_ct_tcp_timeout_syn_recv
, /* TCP_CONNTRACK_SYN_RECV, */
114 &nf_ct_tcp_timeout_established
, /* TCP_CONNTRACK_ESTABLISHED, */
115 &nf_ct_tcp_timeout_fin_wait
, /* TCP_CONNTRACK_FIN_WAIT, */
116 &nf_ct_tcp_timeout_close_wait
, /* TCP_CONNTRACK_CLOSE_WAIT, */
117 &nf_ct_tcp_timeout_last_ack
, /* TCP_CONNTRACK_LAST_ACK, */
118 &nf_ct_tcp_timeout_time_wait
, /* TCP_CONNTRACK_TIME_WAIT, */
119 &nf_ct_tcp_timeout_close
, /* TCP_CONNTRACK_CLOSE, */
120 NULL
, /* TCP_CONNTRACK_LISTEN */
123 #define sNO TCP_CONNTRACK_NONE
124 #define sSS TCP_CONNTRACK_SYN_SENT
125 #define sSR TCP_CONNTRACK_SYN_RECV
126 #define sES TCP_CONNTRACK_ESTABLISHED
127 #define sFW TCP_CONNTRACK_FIN_WAIT
128 #define sCW TCP_CONNTRACK_CLOSE_WAIT
129 #define sLA TCP_CONNTRACK_LAST_ACK
130 #define sTW TCP_CONNTRACK_TIME_WAIT
131 #define sCL TCP_CONNTRACK_CLOSE
132 #define sLI TCP_CONNTRACK_LISTEN
133 #define sIV TCP_CONNTRACK_MAX
134 #define sIG TCP_CONNTRACK_IGNORE
136 /* What TCP flags are set from RST/SYN/FIN/ACK. */
147 * The TCP state transition table needs a few words...
149 * We are the man in the middle. All the packets go through us
150 * but might get lost in transit to the destination.
151 * It is assumed that the destinations can't receive segments
154 * The checked segment is in window, but our windows are *not*
155 * equivalent with the ones of the sender/receiver. We always
156 * try to guess the state of the current sender.
158 * The meaning of the states are:
160 * NONE: initial state
161 * SYN_SENT: SYN-only packet seen
162 * SYN_RECV: SYN-ACK packet seen
163 * ESTABLISHED: ACK packet seen
164 * FIN_WAIT: FIN packet seen
165 * CLOSE_WAIT: ACK seen (after FIN)
166 * LAST_ACK: FIN seen (after FIN)
167 * TIME_WAIT: last ACK seen
168 * CLOSE: closed connection
170 * LISTEN state is not used.
172 * Packets marked as IGNORED (sIG):
173 * if they may be either invalid or valid
174 * and the receiver may send back a connection
175 * closing RST or a SYN/ACK.
177 * Packets marked as INVALID (sIV):
178 * if they are invalid
179 * or we do not support the request (simultaneous open)
181 static enum tcp_conntrack tcp_conntracks
[2][6][TCP_CONNTRACK_MAX
] = {
184 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
185 /*syn*/ { sSS
, sSS
, sIG
, sIG
, sIG
, sIG
, sIG
, sSS
, sSS
, sIV
},
187 * sNO -> sSS Initialize a new connection
188 * sSS -> sSS Retransmitted SYN
189 * sSR -> sIG Late retransmitted SYN?
190 * sES -> sIG Error: SYNs in window outside the SYN_SENT state
191 * are errors. Receiver will reply with RST
192 * and close the connection.
193 * Or we are not in sync and hold a dead connection.
197 * sTW -> sSS Reopened connection (RFC 1122).
200 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
201 /*synack*/ { sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
},
203 * A SYN/ACK from the client is always invalid:
204 * - either it tries to set up a simultaneous open, which is
206 * - or the firewall has just been inserted between the two hosts
207 * during the session set-up. The SYN will be retransmitted
208 * by the true client (or it'll time out).
210 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
211 /*fin*/ { sIV
, sIV
, sFW
, sFW
, sLA
, sLA
, sLA
, sTW
, sCL
, sIV
},
213 * sNO -> sIV Too late and no reason to do anything...
214 * sSS -> sIV Client migth not send FIN in this state:
215 * we enforce waiting for a SYN/ACK reply first.
216 * sSR -> sFW Close started.
218 * sFW -> sLA FIN seen in both directions, waiting for
220 * Migth be a retransmitted FIN as well...
222 * sLA -> sLA Retransmitted FIN. Remain in the same state.
226 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
227 /*ack*/ { sES
, sIV
, sES
, sES
, sCW
, sCW
, sTW
, sTW
, sCL
, sIV
},
229 * sNO -> sES Assumed.
230 * sSS -> sIV ACK is invalid: we haven't seen a SYN/ACK yet.
231 * sSR -> sES Established state is reached.
233 * sFW -> sCW Normal close request answered by ACK.
235 * sLA -> sTW Last ACK detected.
236 * sTW -> sTW Retransmitted last ACK. Remain in the same state.
239 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
240 /*rst*/ { sIV
, sCL
, sCL
, sCL
, sCL
, sCL
, sCL
, sCL
, sCL
, sIV
},
241 /*none*/ { sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
}
245 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
246 /*syn*/ { sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
},
248 * sNO -> sIV Never reached.
249 * sSS -> sIV Simultaneous open, not supported
250 * sSR -> sIV Simultaneous open, not supported.
251 * sES -> sIV Server may not initiate a connection.
255 * sTW -> sIV Reopened connection, but server may not do it.
258 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
259 /*synack*/ { sIV
, sSR
, sSR
, sIG
, sIG
, sIG
, sIG
, sIG
, sIG
, sIV
},
261 * sSS -> sSR Standard open.
262 * sSR -> sSR Retransmitted SYN/ACK.
263 * sES -> sIG Late retransmitted SYN/ACK?
264 * sFW -> sIG Might be SYN/ACK answering ignored SYN
270 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
271 /*fin*/ { sIV
, sIV
, sFW
, sFW
, sLA
, sLA
, sLA
, sTW
, sCL
, sIV
},
273 * sSS -> sIV Server might not send FIN in this state.
274 * sSR -> sFW Close started.
276 * sFW -> sLA FIN seen in both directions.
278 * sLA -> sLA Retransmitted FIN.
282 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
283 /*ack*/ { sIV
, sIG
, sSR
, sES
, sCW
, sCW
, sTW
, sTW
, sCL
, sIV
},
285 * sSS -> sIG Might be a half-open connection.
286 * sSR -> sSR Might answer late resent SYN.
288 * sFW -> sCW Normal close request answered by ACK.
290 * sLA -> sTW Last ACK detected.
291 * sTW -> sTW Retransmitted last ACK.
294 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI */
295 /*rst*/ { sIV
, sCL
, sCL
, sCL
, sCL
, sCL
, sCL
, sCL
, sCL
, sIV
},
296 /*none*/ { sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
, sIV
}
300 static int tcp_pkt_to_tuple(const struct sk_buff
*skb
,
301 unsigned int dataoff
,
302 struct nf_conntrack_tuple
*tuple
)
304 struct tcphdr _hdr
, *hp
;
306 /* Actually only need first 8 bytes. */
307 hp
= skb_header_pointer(skb
, dataoff
, 8, &_hdr
);
311 tuple
->src
.u
.tcp
.port
= hp
->source
;
312 tuple
->dst
.u
.tcp
.port
= hp
->dest
;
317 static int tcp_invert_tuple(struct nf_conntrack_tuple
*tuple
,
318 const struct nf_conntrack_tuple
*orig
)
320 tuple
->src
.u
.tcp
.port
= orig
->dst
.u
.tcp
.port
;
321 tuple
->dst
.u
.tcp
.port
= orig
->src
.u
.tcp
.port
;
325 /* Print out the per-protocol part of the tuple. */
326 static int tcp_print_tuple(struct seq_file
*s
,
327 const struct nf_conntrack_tuple
*tuple
)
329 return seq_printf(s
, "sport=%hu dport=%hu ",
330 ntohs(tuple
->src
.u
.tcp
.port
),
331 ntohs(tuple
->dst
.u
.tcp
.port
));
334 /* Print out the private part of the conntrack. */
335 static int tcp_print_conntrack(struct seq_file
*s
,
336 const struct nf_conn
*conntrack
)
338 enum tcp_conntrack state
;
340 read_lock_bh(&tcp_lock
);
341 state
= conntrack
->proto
.tcp
.state
;
342 read_unlock_bh(&tcp_lock
);
344 return seq_printf(s
, "%s ", tcp_conntrack_names
[state
]);
347 static unsigned int get_conntrack_index(const struct tcphdr
*tcph
)
349 if (tcph
->rst
) return TCP_RST_SET
;
350 else if (tcph
->syn
) return (tcph
->ack
? TCP_SYNACK_SET
: TCP_SYN_SET
);
351 else if (tcph
->fin
) return TCP_FIN_SET
;
352 else if (tcph
->ack
) return TCP_ACK_SET
;
353 else return TCP_NONE_SET
;
356 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
357 in IP Filter' by Guido van Rooij.
359 http://www.nluug.nl/events/sane2000/papers.html
360 http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
362 The boundaries and the conditions are changed according to RFC793:
363 the packet must intersect the window (i.e. segments may be
364 after the right or before the left edge) and thus receivers may ACK
365 segments after the right edge of the window.
367 td_maxend = max(sack + max(win,1)) seen in reply packets
368 td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
369 td_maxwin += seq + len - sender.td_maxend
370 if seq + len > sender.td_maxend
371 td_end = max(seq + len) seen in sent packets
373 I. Upper bound for valid data: seq <= sender.td_maxend
374 II. Lower bound for valid data: seq + len >= sender.td_end - receiver.td_maxwin
375 III. Upper bound for valid ack: sack <= receiver.td_end
376 IV. Lower bound for valid ack: ack >= receiver.td_end - MAXACKWINDOW
378 where sack is the highest right edge of sack block found in the packet.
380 The upper bound limit for a valid ack is not ignored -
381 we doesn't have to deal with fragments.
384 static inline __u32
segment_seq_plus_len(__u32 seq
,
386 unsigned int dataoff
,
389 /* XXX Should I use payload length field in IP/IPv6 header ?
391 return (seq
+ len
- dataoff
- tcph
->doff
*4
392 + (tcph
->syn
? 1 : 0) + (tcph
->fin
? 1 : 0));
395 /* Fixme: what about big packets? */
396 #define MAXACKWINCONST 66000
397 #define MAXACKWINDOW(sender) \
398 ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin \
402 * Simplified tcp_parse_options routine from tcp_input.c
404 static void tcp_options(const struct sk_buff
*skb
,
405 unsigned int dataoff
,
407 struct ip_ct_tcp_state
*state
)
409 unsigned char buff
[(15 * 4) - sizeof(struct tcphdr
)];
411 int length
= (tcph
->doff
*4) - sizeof(struct tcphdr
);
416 ptr
= skb_header_pointer(skb
, dataoff
+ sizeof(struct tcphdr
),
430 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
435 if (opsize
< 2) /* "silly options" */
438 break; /* don't parse partial options */
440 if (opcode
== TCPOPT_SACK_PERM
441 && opsize
== TCPOLEN_SACK_PERM
)
442 state
->flags
|= IP_CT_TCP_FLAG_SACK_PERM
;
443 else if (opcode
== TCPOPT_WINDOW
444 && opsize
== TCPOLEN_WINDOW
) {
445 state
->td_scale
= *(u_int8_t
*)ptr
;
447 if (state
->td_scale
> 14) {
449 state
->td_scale
= 14;
452 IP_CT_TCP_FLAG_WINDOW_SCALE
;
460 static void tcp_sack(const struct sk_buff
*skb
, unsigned int dataoff
,
461 struct tcphdr
*tcph
, __u32
*sack
)
463 unsigned char buff
[(15 * 4) - sizeof(struct tcphdr
)];
465 int length
= (tcph
->doff
*4) - sizeof(struct tcphdr
);
471 ptr
= skb_header_pointer(skb
, dataoff
+ sizeof(struct tcphdr
),
475 /* Fast path for timestamp-only option */
476 if (length
== TCPOLEN_TSTAMP_ALIGNED
*4
478 __constant_ntohl((TCPOPT_NOP
<< 24)
480 | (TCPOPT_TIMESTAMP
<< 8)
481 | TCPOLEN_TIMESTAMP
))
491 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
496 if (opsize
< 2) /* "silly options" */
499 break; /* don't parse partial options */
501 if (opcode
== TCPOPT_SACK
502 && opsize
>= (TCPOLEN_SACK_BASE
503 + TCPOLEN_SACK_PERBLOCK
)
504 && !((opsize
- TCPOLEN_SACK_BASE
)
505 % TCPOLEN_SACK_PERBLOCK
)) {
507 i
< (opsize
- TCPOLEN_SACK_BASE
);
508 i
+= TCPOLEN_SACK_PERBLOCK
) {
509 memcpy(&tmp
, (__u32
*)(ptr
+ i
) + 1,
513 if (after(tmp
, *sack
))
524 static int tcp_in_window(struct ip_ct_tcp
*state
,
525 enum ip_conntrack_dir dir
,
527 const struct sk_buff
*skb
,
528 unsigned int dataoff
,
532 struct ip_ct_tcp_state
*sender
= &state
->seen
[dir
];
533 struct ip_ct_tcp_state
*receiver
= &state
->seen
[!dir
];
534 __u32 seq
, ack
, sack
, end
, win
, swin
;
538 * Get the required data from the packet.
540 seq
= ntohl(tcph
->seq
);
541 ack
= sack
= ntohl(tcph
->ack_seq
);
542 win
= ntohs(tcph
->window
);
543 end
= segment_seq_plus_len(seq
, skb
->len
, dataoff
, tcph
);
545 if (receiver
->flags
& IP_CT_TCP_FLAG_SACK_PERM
)
546 tcp_sack(skb
, dataoff
, tcph
, &sack
);
548 DEBUGP("tcp_in_window: START\n");
549 DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
550 "seq=%u ack=%u sack=%u win=%u end=%u\n",
551 NIPQUAD(iph
->saddr
), ntohs(tcph
->source
),
552 NIPQUAD(iph
->daddr
), ntohs(tcph
->dest
),
553 seq
, ack
, sack
, win
, end
);
554 DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
555 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
556 sender
->td_end
, sender
->td_maxend
, sender
->td_maxwin
,
558 receiver
->td_end
, receiver
->td_maxend
, receiver
->td_maxwin
,
561 if (sender
->td_end
== 0) {
563 * Initialize sender data.
565 if (tcph
->syn
&& tcph
->ack
) {
567 * Outgoing SYN-ACK in reply to a SYN.
570 sender
->td_maxend
= end
;
571 sender
->td_maxwin
= (win
== 0 ? 1 : win
);
573 tcp_options(skb
, dataoff
, tcph
, sender
);
576 * Both sides must send the Window Scale option
577 * to enable window scaling in either direction.
579 if (!(sender
->flags
& IP_CT_TCP_FLAG_WINDOW_SCALE
580 && receiver
->flags
& IP_CT_TCP_FLAG_WINDOW_SCALE
))
582 receiver
->td_scale
= 0;
585 * We are in the middle of a connection,
586 * its history is lost for us.
587 * Let's try to use the data from the packet.
589 sender
->td_end
= end
;
590 sender
->td_maxwin
= (win
== 0 ? 1 : win
);
591 sender
->td_maxend
= end
+ sender
->td_maxwin
;
593 } else if (((state
->state
== TCP_CONNTRACK_SYN_SENT
594 && dir
== IP_CT_DIR_ORIGINAL
)
595 || (state
->state
== TCP_CONNTRACK_SYN_RECV
596 && dir
== IP_CT_DIR_REPLY
))
597 && after(end
, sender
->td_end
)) {
599 * RFC 793: "if a TCP is reinitialized ... then it need
600 * not wait at all; it must only be sure to use sequence
601 * numbers larger than those recently used."
604 sender
->td_maxend
= end
;
605 sender
->td_maxwin
= (win
== 0 ? 1 : win
);
607 tcp_options(skb
, dataoff
, tcph
, sender
);
612 * If there is no ACK, just pretend it was set and OK.
614 ack
= sack
= receiver
->td_end
;
615 } else if (((tcp_flag_word(tcph
) & (TCP_FLAG_ACK
|TCP_FLAG_RST
)) ==
616 (TCP_FLAG_ACK
|TCP_FLAG_RST
))
619 * Broken TCP stacks, that set ACK in RST packets as well
620 * with zero ack value.
622 ack
= sack
= receiver
->td_end
;
627 || (seq
== 0 && state
->state
== TCP_CONNTRACK_SYN_SENT
)))
629 * Packets contains no data: we assume it is valid
630 * and check the ack value only.
631 * However RST segments are always validated by their
632 * SEQ number, except when seq == 0 (reset sent answering
635 seq
= end
= sender
->td_end
;
637 DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
638 "seq=%u ack=%u sack =%u win=%u end=%u\n",
639 NIPQUAD(iph
->saddr
), ntohs(tcph
->source
),
640 NIPQUAD(iph
->daddr
), ntohs(tcph
->dest
),
641 seq
, ack
, sack
, win
, end
);
642 DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
643 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
644 sender
->td_end
, sender
->td_maxend
, sender
->td_maxwin
,
646 receiver
->td_end
, receiver
->td_maxend
, receiver
->td_maxwin
,
649 DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
650 before(seq
, sender
->td_maxend
+ 1),
651 after(end
, sender
->td_end
- receiver
->td_maxwin
- 1),
652 before(sack
, receiver
->td_end
+ 1),
653 after(ack
, receiver
->td_end
- MAXACKWINDOW(sender
)));
655 if (sender
->loose
|| receiver
->loose
||
656 (before(seq
, sender
->td_maxend
+ 1) &&
657 after(end
, sender
->td_end
- receiver
->td_maxwin
- 1) &&
658 before(sack
, receiver
->td_end
+ 1) &&
659 after(ack
, receiver
->td_end
- MAXACKWINDOW(sender
)))) {
661 * Take into account window scaling (RFC 1323).
664 win
<<= sender
->td_scale
;
667 * Update sender data.
669 swin
= win
+ (sack
- ack
);
670 if (sender
->td_maxwin
< swin
)
671 sender
->td_maxwin
= swin
;
672 if (after(end
, sender
->td_end
))
673 sender
->td_end
= end
;
675 * Update receiver data.
677 if (after(end
, sender
->td_maxend
))
678 receiver
->td_maxwin
+= end
- sender
->td_maxend
;
679 if (after(sack
+ win
, receiver
->td_maxend
- 1)) {
680 receiver
->td_maxend
= sack
+ win
;
682 receiver
->td_maxend
++;
686 * Check retransmissions.
688 if (index
== TCP_ACK_SET
) {
689 if (state
->last_dir
== dir
690 && state
->last_seq
== seq
691 && state
->last_ack
== ack
692 && state
->last_end
== end
)
695 state
->last_dir
= dir
;
696 state
->last_seq
= seq
;
697 state
->last_ack
= ack
;
698 state
->last_end
= end
;
703 * Close the window of disabled window tracking :-)
710 if (LOG_INVALID(IPPROTO_TCP
))
711 nf_log_packet(pf
, 0, skb
, NULL
, NULL
, NULL
,
713 before(seq
, sender
->td_maxend
+ 1) ?
714 after(end
, sender
->td_end
- receiver
->td_maxwin
- 1) ?
715 before(sack
, receiver
->td_end
+ 1) ?
716 after(ack
, receiver
->td_end
- MAXACKWINDOW(sender
)) ? "BUG"
717 : "ACK is under the lower bound (possible overly delayed ACK)"
718 : "ACK is over the upper bound (ACKed data not seen yet)"
719 : "SEQ is under the lower bound (already ACKed data retransmitted)"
720 : "SEQ is over the upper bound (over the window of the receiver)");
722 res
= nf_ct_tcp_be_liberal
;
725 DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
726 "receiver end=%u maxend=%u maxwin=%u\n",
727 res
, sender
->td_end
, sender
->td_maxend
, sender
->td_maxwin
,
728 receiver
->td_end
, receiver
->td_maxend
, receiver
->td_maxwin
);
733 #ifdef CONFIG_IP_NF_NAT_NEEDED
734 /* Update sender->td_end after NAT successfully mangled the packet */
735 /* Caller must linearize skb at tcp header. */
736 void nf_conntrack_tcp_update(struct sk_buff
*skb
,
737 unsigned int dataoff
,
738 struct nf_conn
*conntrack
,
741 struct tcphdr
*tcph
= (void *)skb
->data
+ dataoff
;
744 struct ip_ct_tcp_state
*sender
= &conntrack
->proto
.tcp
.seen
[dir
];
745 struct ip_ct_tcp_state
*receiver
= &conntrack
->proto
.tcp
.seen
[!dir
];
748 end
= segment_seq_plus_len(ntohl(tcph
->seq
), skb
->len
, dataoff
, tcph
);
750 write_lock_bh(&tcp_lock
);
752 * We have to worry for the ack in the reply packet only...
754 if (after(end
, conntrack
->proto
.tcp
.seen
[dir
].td_end
))
755 conntrack
->proto
.tcp
.seen
[dir
].td_end
= end
;
756 conntrack
->proto
.tcp
.last_end
= end
;
757 write_unlock_bh(&tcp_lock
);
758 DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
759 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
760 sender
->td_end
, sender
->td_maxend
, sender
->td_maxwin
,
762 receiver
->td_end
, receiver
->td_maxend
, receiver
->td_maxwin
,
777 /* table of valid flag combinations - ECE and CWR are always valid */
778 static u8 tcp_valid_flags
[(TH_FIN
|TH_SYN
|TH_RST
|TH_PUSH
|TH_ACK
|TH_URG
) + 1] =
782 [TH_SYN
|TH_PUSH
] = 1,
783 [TH_SYN
|TH_ACK
|TH_PUSH
] = 1,
786 [TH_RST
|TH_ACK
|TH_PUSH
] = 1,
789 [TH_ACK
|TH_PUSH
] = 1,
791 [TH_ACK
|TH_URG
|TH_PUSH
] = 1,
792 [TH_FIN
|TH_ACK
|TH_PUSH
] = 1,
793 [TH_FIN
|TH_ACK
|TH_URG
] = 1,
794 [TH_FIN
|TH_ACK
|TH_URG
|TH_PUSH
] = 1,
797 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c. */
798 static int tcp_error(struct sk_buff
*skb
,
799 unsigned int dataoff
,
800 enum ip_conntrack_info
*ctinfo
,
802 unsigned int hooknum
,
803 int(*csum
)(const struct sk_buff
*,unsigned int))
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 semantic of CHECKSUM_HW is different there
829 * and moreover root might send raw packets.
831 /* FIXME: Source route IP option packets --RR */
832 if (((pf
== PF_INET
&& hooknum
== NF_IP_PRE_ROUTING
) ||
833 (pf
== PF_INET6
&& hooknum
== NF_IP6_PRE_ROUTING
))
834 && skb
->ip_summed
!= CHECKSUM_UNNECESSARY
835 && csum(skb
, dataoff
)) {
836 if (LOG_INVALID(IPPROTO_TCP
))
837 nf_log_packet(pf
, 0, skb
, NULL
, NULL
, NULL
,
838 "nf_ct_tcp: bad TCP checksum ");
842 /* Check TCP flags. */
843 tcpflags
= (((u_int8_t
*)th
)[13] & ~(TH_ECE
|TH_CWR
));
844 if (!tcp_valid_flags
[tcpflags
]) {
845 if (LOG_INVALID(IPPROTO_TCP
))
846 nf_log_packet(pf
, 0, skb
, NULL
, NULL
, NULL
,
847 "nf_ct_tcp: invalid TCP flag combination ");
854 static int csum4(const struct sk_buff
*skb
, unsigned int dataoff
)
856 return csum_tcpudp_magic(skb
->nh
.iph
->saddr
, skb
->nh
.iph
->daddr
,
857 skb
->len
- dataoff
, IPPROTO_TCP
,
858 skb
->ip_summed
== CHECKSUM_HW
? skb
->csum
859 : skb_checksum(skb
, dataoff
,
860 skb
->len
- dataoff
, 0));
863 static int csum6(const struct sk_buff
*skb
, unsigned int dataoff
)
865 return csum_ipv6_magic(&skb
->nh
.ipv6h
->saddr
, &skb
->nh
.ipv6h
->daddr
,
866 skb
->len
- dataoff
, IPPROTO_TCP
,
867 skb
->ip_summed
== CHECKSUM_HW
868 ? csum_sub(skb
->csum
,
869 skb_checksum(skb
, 0, dataoff
, 0))
870 : skb_checksum(skb
, dataoff
, skb
->len
- dataoff
,
874 static int tcp_error4(struct sk_buff
*skb
,
875 unsigned int dataoff
,
876 enum ip_conntrack_info
*ctinfo
,
878 unsigned int hooknum
)
880 return tcp_error(skb
, dataoff
, ctinfo
, pf
, hooknum
, csum4
);
883 static int tcp_error6(struct sk_buff
*skb
,
884 unsigned int dataoff
,
885 enum ip_conntrack_info
*ctinfo
,
887 unsigned int hooknum
)
889 return tcp_error(skb
, dataoff
, ctinfo
, pf
, hooknum
, csum6
);
892 /* Returns verdict for packet, or -1 for invalid. */
893 static int tcp_packet(struct nf_conn
*conntrack
,
894 const struct sk_buff
*skb
,
895 unsigned int dataoff
,
896 enum ip_conntrack_info ctinfo
,
898 unsigned int hooknum
)
900 enum tcp_conntrack new_state
, old_state
;
901 enum ip_conntrack_dir dir
;
902 struct tcphdr
*th
, _tcph
;
903 unsigned long timeout
;
906 th
= skb_header_pointer(skb
, dataoff
, sizeof(_tcph
), &_tcph
);
909 write_lock_bh(&tcp_lock
);
910 old_state
= conntrack
->proto
.tcp
.state
;
911 dir
= CTINFO2DIR(ctinfo
);
912 index
= get_conntrack_index(th
);
913 new_state
= tcp_conntracks
[dir
][index
][old_state
];
916 case TCP_CONNTRACK_IGNORE
:
920 * b) SYN/ACK in REPLY
921 * c) ACK in reply direction after initial SYN in original.
923 if (index
== TCP_SYNACK_SET
924 && conntrack
->proto
.tcp
.last_index
== TCP_SYN_SET
925 && conntrack
->proto
.tcp
.last_dir
!= dir
926 && ntohl(th
->ack_seq
) ==
927 conntrack
->proto
.tcp
.last_end
) {
928 /* This SYN/ACK acknowledges a SYN that we earlier
929 * ignored as invalid. This means that the client and
930 * the server are both in sync, while the firewall is
931 * not. We kill this session and block the SYN/ACK so
932 * that the client cannot but retransmit its SYN and
933 * thus initiate a clean new session.
935 write_unlock_bh(&tcp_lock
);
936 if (LOG_INVALID(IPPROTO_TCP
))
937 nf_log_packet(pf
, 0, skb
, NULL
, NULL
, NULL
,
938 "nf_ct_tcp: killing out of sync session ");
939 if (del_timer(&conntrack
->timeout
))
940 conntrack
->timeout
.function((unsigned long)
944 conntrack
->proto
.tcp
.last_index
= index
;
945 conntrack
->proto
.tcp
.last_dir
= dir
;
946 conntrack
->proto
.tcp
.last_seq
= ntohl(th
->seq
);
947 conntrack
->proto
.tcp
.last_end
=
948 segment_seq_plus_len(ntohl(th
->seq
), skb
->len
, dataoff
, th
);
950 write_unlock_bh(&tcp_lock
);
951 if (LOG_INVALID(IPPROTO_TCP
))
952 nf_log_packet(pf
, 0, skb
, NULL
, NULL
, NULL
,
953 "nf_ct_tcp: invalid packed ignored ");
955 case TCP_CONNTRACK_MAX
:
957 DEBUGP("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
958 dir
, get_conntrack_index(th
),
960 write_unlock_bh(&tcp_lock
);
961 if (LOG_INVALID(IPPROTO_TCP
))
962 nf_log_packet(pf
, 0, skb
, NULL
, NULL
, NULL
,
963 "nf_ct_tcp: invalid state ");
965 case TCP_CONNTRACK_SYN_SENT
:
966 if (old_state
< TCP_CONNTRACK_TIME_WAIT
)
968 if ((conntrack
->proto
.tcp
.seen
[dir
].flags
&
969 IP_CT_TCP_FLAG_CLOSE_INIT
)
970 || after(ntohl(th
->seq
),
971 conntrack
->proto
.tcp
.seen
[dir
].td_end
)) {
972 /* Attempt to reopen a closed connection.
973 * Delete this connection and look up again. */
974 write_unlock_bh(&tcp_lock
);
975 if (del_timer(&conntrack
->timeout
))
976 conntrack
->timeout
.function((unsigned long)
980 write_unlock_bh(&tcp_lock
);
981 if (LOG_INVALID(IPPROTO_TCP
))
982 nf_log_packet(pf
, 0, skb
, NULL
, NULL
,
983 NULL
, "nf_ct_tcp: invalid SYN");
986 case TCP_CONNTRACK_CLOSE
:
987 if (index
== TCP_RST_SET
988 && ((test_bit(IPS_SEEN_REPLY_BIT
, &conntrack
->status
)
989 && conntrack
->proto
.tcp
.last_index
== TCP_SYN_SET
)
990 || (!test_bit(IPS_ASSURED_BIT
, &conntrack
->status
)
991 && conntrack
->proto
.tcp
.last_index
== TCP_ACK_SET
))
992 && ntohl(th
->ack_seq
) == conntrack
->proto
.tcp
.last_end
) {
993 /* RST sent to invalid SYN or ACK we had let through
994 * at a) and c) above:
996 * a) SYN was in window then
997 * c) we hold a half-open connection.
999 * Delete our connection entry.
1000 * We skip window checking, because packet might ACK
1001 * segments we ignored. */
1004 /* Just fall through */
1006 /* Keep compilers happy. */
1010 if (!tcp_in_window(&conntrack
->proto
.tcp
, dir
, index
,
1011 skb
, dataoff
, th
, pf
)) {
1012 write_unlock_bh(&tcp_lock
);
1016 /* From now on we have got in-window packets */
1017 conntrack
->proto
.tcp
.last_index
= index
;
1019 DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
1020 "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1021 NIPQUAD(iph
->saddr
), ntohs(th
->source
),
1022 NIPQUAD(iph
->daddr
), ntohs(th
->dest
),
1023 (th
->syn
? 1 : 0), (th
->ack
? 1 : 0),
1024 (th
->fin
? 1 : 0), (th
->rst
? 1 : 0),
1025 old_state
, new_state
);
1027 conntrack
->proto
.tcp
.state
= new_state
;
1028 if (old_state
!= new_state
1029 && (new_state
== TCP_CONNTRACK_FIN_WAIT
1030 || new_state
== TCP_CONNTRACK_CLOSE
))
1031 conntrack
->proto
.tcp
.seen
[dir
].flags
|= IP_CT_TCP_FLAG_CLOSE_INIT
;
1032 timeout
= conntrack
->proto
.tcp
.retrans
>= nf_ct_tcp_max_retrans
1033 && *tcp_timeouts
[new_state
] > nf_ct_tcp_timeout_max_retrans
1034 ? nf_ct_tcp_timeout_max_retrans
: *tcp_timeouts
[new_state
];
1035 write_unlock_bh(&tcp_lock
);
1037 nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE
, skb
);
1038 if (new_state
!= old_state
)
1039 nf_conntrack_event_cache(IPCT_PROTOINFO
, skb
);
1041 if (!test_bit(IPS_SEEN_REPLY_BIT
, &conntrack
->status
)) {
1042 /* If only reply is a RST, we can consider ourselves not to
1043 have an established connection: this is a fairly common
1044 problem case, so we can delete the conntrack
1045 immediately. --RR */
1047 if (del_timer(&conntrack
->timeout
))
1048 conntrack
->timeout
.function((unsigned long)
1052 } else if (!test_bit(IPS_ASSURED_BIT
, &conntrack
->status
)
1053 && (old_state
== TCP_CONNTRACK_SYN_RECV
1054 || old_state
== TCP_CONNTRACK_ESTABLISHED
)
1055 && new_state
== TCP_CONNTRACK_ESTABLISHED
) {
1056 /* Set ASSURED if we see see valid ack in ESTABLISHED
1057 after SYN_RECV or a valid answer for a picked up
1059 set_bit(IPS_ASSURED_BIT
, &conntrack
->status
);
1060 nf_conntrack_event_cache(IPCT_STATUS
, skb
);
1062 nf_ct_refresh_acct(conntrack
, ctinfo
, skb
, timeout
);
1067 /* Called when a new connection for this protocol found. */
1068 static int tcp_new(struct nf_conn
*conntrack
,
1069 const struct sk_buff
*skb
,
1070 unsigned int dataoff
)
1072 enum tcp_conntrack new_state
;
1073 struct tcphdr
*th
, _tcph
;
1075 struct ip_ct_tcp_state
*sender
= &conntrack
->proto
.tcp
.seen
[0];
1076 struct ip_ct_tcp_state
*receiver
= &conntrack
->proto
.tcp
.seen
[1];
1079 th
= skb_header_pointer(skb
, dataoff
, sizeof(_tcph
), &_tcph
);
1082 /* Don't need lock here: this conntrack not in circulation yet */
1084 = tcp_conntracks
[0][get_conntrack_index(th
)]
1085 [TCP_CONNTRACK_NONE
];
1087 /* Invalid: delete conntrack */
1088 if (new_state
>= TCP_CONNTRACK_MAX
) {
1089 DEBUGP("nf_ct_tcp: invalid new deleting.\n");
1093 if (new_state
== TCP_CONNTRACK_SYN_SENT
) {
1095 conntrack
->proto
.tcp
.seen
[0].td_end
=
1096 segment_seq_plus_len(ntohl(th
->seq
), skb
->len
,
1098 conntrack
->proto
.tcp
.seen
[0].td_maxwin
= ntohs(th
->window
);
1099 if (conntrack
->proto
.tcp
.seen
[0].td_maxwin
== 0)
1100 conntrack
->proto
.tcp
.seen
[0].td_maxwin
= 1;
1101 conntrack
->proto
.tcp
.seen
[0].td_maxend
=
1102 conntrack
->proto
.tcp
.seen
[0].td_end
;
1104 tcp_options(skb
, dataoff
, th
, &conntrack
->proto
.tcp
.seen
[0]);
1105 conntrack
->proto
.tcp
.seen
[1].flags
= 0;
1106 conntrack
->proto
.tcp
.seen
[0].loose
=
1107 conntrack
->proto
.tcp
.seen
[1].loose
= 0;
1108 } else if (nf_ct_tcp_loose
== 0) {
1109 /* Don't try to pick up connections. */
1113 * We are in the middle of a connection,
1114 * its history is lost for us.
1115 * Let's try to use the data from the packet.
1117 conntrack
->proto
.tcp
.seen
[0].td_end
=
1118 segment_seq_plus_len(ntohl(th
->seq
), skb
->len
,
1120 conntrack
->proto
.tcp
.seen
[0].td_maxwin
= ntohs(th
->window
);
1121 if (conntrack
->proto
.tcp
.seen
[0].td_maxwin
== 0)
1122 conntrack
->proto
.tcp
.seen
[0].td_maxwin
= 1;
1123 conntrack
->proto
.tcp
.seen
[0].td_maxend
=
1124 conntrack
->proto
.tcp
.seen
[0].td_end
+
1125 conntrack
->proto
.tcp
.seen
[0].td_maxwin
;
1126 conntrack
->proto
.tcp
.seen
[0].td_scale
= 0;
1128 /* We assume SACK. Should we assume window scaling too? */
1129 conntrack
->proto
.tcp
.seen
[0].flags
=
1130 conntrack
->proto
.tcp
.seen
[1].flags
= IP_CT_TCP_FLAG_SACK_PERM
;
1131 conntrack
->proto
.tcp
.seen
[0].loose
=
1132 conntrack
->proto
.tcp
.seen
[1].loose
= nf_ct_tcp_loose
;
1135 conntrack
->proto
.tcp
.seen
[1].td_end
= 0;
1136 conntrack
->proto
.tcp
.seen
[1].td_maxend
= 0;
1137 conntrack
->proto
.tcp
.seen
[1].td_maxwin
= 1;
1138 conntrack
->proto
.tcp
.seen
[1].td_scale
= 0;
1140 /* tcp_packet will set them */
1141 conntrack
->proto
.tcp
.state
= TCP_CONNTRACK_NONE
;
1142 conntrack
->proto
.tcp
.last_index
= TCP_NONE_SET
;
1144 DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1145 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1146 sender
->td_end
, sender
->td_maxend
, sender
->td_maxwin
,
1148 receiver
->td_end
, receiver
->td_maxend
, receiver
->td_maxwin
,
1149 receiver
->td_scale
);
1153 #if defined(CONFIG_NF_CT_NETLINK) || \
1154 defined(CONFIG_NF_CT_NETLINK_MODULE)
1156 #include <linux/netfilter/nfnetlink.h>
1157 #include <linux/netfilter/nfnetlink_conntrack.h>
1159 static int tcp_to_nfattr(struct sk_buff
*skb
, struct nfattr
*nfa
,
1160 const struct nf_conn
*ct
)
1162 struct nfattr
*nest_parms
;
1164 read_lock_bh(&tcp_lock
);
1165 nest_parms
= NFA_NEST(skb
, CTA_PROTOINFO_TCP
);
1166 NFA_PUT(skb
, CTA_PROTOINFO_TCP_STATE
, sizeof(u_int8_t
),
1167 &ct
->proto
.tcp
.state
);
1168 read_unlock_bh(&tcp_lock
);
1170 NFA_NEST_END(skb
, nest_parms
);
1175 read_unlock_bh(&tcp_lock
);
1179 static const size_t cta_min_tcp
[CTA_PROTOINFO_TCP_MAX
] = {
1180 [CTA_PROTOINFO_TCP_STATE
-1] = sizeof(u_int8_t
),
1183 static int nfattr_to_tcp(struct nfattr
*cda
[], struct nf_conn
*ct
)
1185 struct nfattr
*attr
= cda
[CTA_PROTOINFO_TCP
-1];
1186 struct nfattr
*tb
[CTA_PROTOINFO_TCP_MAX
];
1188 /* updates could not contain anything about the private
1189 * protocol info, in that case skip the parsing */
1193 nfattr_parse_nested(tb
, CTA_PROTOINFO_TCP_MAX
, attr
);
1195 if (nfattr_bad_size(tb
, CTA_PROTOINFO_TCP_MAX
, cta_min_tcp
))
1198 if (!tb
[CTA_PROTOINFO_TCP_STATE
-1])
1201 write_lock_bh(&tcp_lock
);
1202 ct
->proto
.tcp
.state
=
1203 *(u_int8_t
*)NFA_DATA(tb
[CTA_PROTOINFO_TCP_STATE
-1]);
1204 write_unlock_bh(&tcp_lock
);
1210 struct nf_conntrack_protocol nf_conntrack_protocol_tcp4
=
1213 .proto
= IPPROTO_TCP
,
1215 .pkt_to_tuple
= tcp_pkt_to_tuple
,
1216 .invert_tuple
= tcp_invert_tuple
,
1217 .print_tuple
= tcp_print_tuple
,
1218 .print_conntrack
= tcp_print_conntrack
,
1219 .packet
= tcp_packet
,
1221 .error
= tcp_error4
,
1222 #if defined(CONFIG_NF_CT_NETLINK) || \
1223 defined(CONFIG_NF_CT_NETLINK_MODULE)
1224 .to_nfattr
= tcp_to_nfattr
,
1225 .from_nfattr
= nfattr_to_tcp
,
1226 .tuple_to_nfattr
= nf_ct_port_tuple_to_nfattr
,
1227 .nfattr_to_tuple
= nf_ct_port_nfattr_to_tuple
,
1231 struct nf_conntrack_protocol nf_conntrack_protocol_tcp6
=
1233 .l3proto
= PF_INET6
,
1234 .proto
= IPPROTO_TCP
,
1236 .pkt_to_tuple
= tcp_pkt_to_tuple
,
1237 .invert_tuple
= tcp_invert_tuple
,
1238 .print_tuple
= tcp_print_tuple
,
1239 .print_conntrack
= tcp_print_conntrack
,
1240 .packet
= tcp_packet
,
1242 .error
= tcp_error6
,
1243 #if defined(CONFIG_NF_CT_NETLINK) || \
1244 defined(CONFIG_NF_CT_NETLINK_MODULE)
1245 .to_nfattr
= tcp_to_nfattr
,
1246 .from_nfattr
= nfattr_to_tcp
,
1247 .tuple_to_nfattr
= nf_ct_port_tuple_to_nfattr
,
1248 .nfattr_to_tuple
= nf_ct_port_nfattr_to_tuple
,
1252 EXPORT_SYMBOL(nf_conntrack_protocol_tcp4
);
1253 EXPORT_SYMBOL(nf_conntrack_protocol_tcp6
);