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Merge tag 'char-misc-5.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh...
[mirror_ubuntu-jammy-kernel.git] / net / netfilter / nf_conntrack_proto_tcp.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /* (C) 1999-2001 Paul `Rusty' Russell
3 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
4 * (C) 2002-2013 Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
5 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
6 */
7
8 #include <linux/types.h>
9 #include <linux/timer.h>
10 #include <linux/module.h>
11 #include <linux/in.h>
12 #include <linux/tcp.h>
13 #include <linux/spinlock.h>
14 #include <linux/skbuff.h>
15 #include <linux/ipv6.h>
16 #include <net/ip6_checksum.h>
17 #include <asm/unaligned.h>
18
19 #include <net/tcp.h>
20
21 #include <linux/netfilter.h>
22 #include <linux/netfilter_ipv4.h>
23 #include <linux/netfilter_ipv6.h>
24 #include <net/netfilter/nf_conntrack.h>
25 #include <net/netfilter/nf_conntrack_l4proto.h>
26 #include <net/netfilter/nf_conntrack_ecache.h>
27 #include <net/netfilter/nf_conntrack_seqadj.h>
28 #include <net/netfilter/nf_conntrack_synproxy.h>
29 #include <net/netfilter/nf_conntrack_timeout.h>
30 #include <net/netfilter/nf_log.h>
31 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
32 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
33
34 /* "Be conservative in what you do,
35 be liberal in what you accept from others."
36 If it's non-zero, we mark only out of window RST segments as INVALID. */
37 static int nf_ct_tcp_be_liberal __read_mostly = 0;
38
39 /* If it is set to zero, we disable picking up already established
40 connections. */
41 static int nf_ct_tcp_loose __read_mostly = 1;
42
43 /* Max number of the retransmitted packets without receiving an (acceptable)
44 ACK from the destination. If this number is reached, a shorter timer
45 will be started. */
46 static int nf_ct_tcp_max_retrans __read_mostly = 3;
47
48 /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
49 closely. They're more complex. --RR */
50
51 static const char *const tcp_conntrack_names[] = {
52 "NONE",
53 "SYN_SENT",
54 "SYN_RECV",
55 "ESTABLISHED",
56 "FIN_WAIT",
57 "CLOSE_WAIT",
58 "LAST_ACK",
59 "TIME_WAIT",
60 "CLOSE",
61 "SYN_SENT2",
62 };
63
64 #define SECS * HZ
65 #define MINS * 60 SECS
66 #define HOURS * 60 MINS
67 #define DAYS * 24 HOURS
68
69 static const unsigned int tcp_timeouts[TCP_CONNTRACK_TIMEOUT_MAX] = {
70 [TCP_CONNTRACK_SYN_SENT] = 2 MINS,
71 [TCP_CONNTRACK_SYN_RECV] = 60 SECS,
72 [TCP_CONNTRACK_ESTABLISHED] = 5 DAYS,
73 [TCP_CONNTRACK_FIN_WAIT] = 2 MINS,
74 [TCP_CONNTRACK_CLOSE_WAIT] = 60 SECS,
75 [TCP_CONNTRACK_LAST_ACK] = 30 SECS,
76 [TCP_CONNTRACK_TIME_WAIT] = 2 MINS,
77 [TCP_CONNTRACK_CLOSE] = 10 SECS,
78 [TCP_CONNTRACK_SYN_SENT2] = 2 MINS,
79 /* RFC1122 says the R2 limit should be at least 100 seconds.
80 Linux uses 15 packets as limit, which corresponds
81 to ~13-30min depending on RTO. */
82 [TCP_CONNTRACK_RETRANS] = 5 MINS,
83 [TCP_CONNTRACK_UNACK] = 5 MINS,
84 };
85
86 #define sNO TCP_CONNTRACK_NONE
87 #define sSS TCP_CONNTRACK_SYN_SENT
88 #define sSR TCP_CONNTRACK_SYN_RECV
89 #define sES TCP_CONNTRACK_ESTABLISHED
90 #define sFW TCP_CONNTRACK_FIN_WAIT
91 #define sCW TCP_CONNTRACK_CLOSE_WAIT
92 #define sLA TCP_CONNTRACK_LAST_ACK
93 #define sTW TCP_CONNTRACK_TIME_WAIT
94 #define sCL TCP_CONNTRACK_CLOSE
95 #define sS2 TCP_CONNTRACK_SYN_SENT2
96 #define sIV TCP_CONNTRACK_MAX
97 #define sIG TCP_CONNTRACK_IGNORE
98
99 /* What TCP flags are set from RST/SYN/FIN/ACK. */
100 enum tcp_bit_set {
101 TCP_SYN_SET,
102 TCP_SYNACK_SET,
103 TCP_FIN_SET,
104 TCP_ACK_SET,
105 TCP_RST_SET,
106 TCP_NONE_SET,
107 };
108
109 /*
110 * The TCP state transition table needs a few words...
111 *
112 * We are the man in the middle. All the packets go through us
113 * but might get lost in transit to the destination.
114 * It is assumed that the destinations can't receive segments
115 * we haven't seen.
116 *
117 * The checked segment is in window, but our windows are *not*
118 * equivalent with the ones of the sender/receiver. We always
119 * try to guess the state of the current sender.
120 *
121 * The meaning of the states are:
122 *
123 * NONE: initial state
124 * SYN_SENT: SYN-only packet seen
125 * SYN_SENT2: SYN-only packet seen from reply dir, simultaneous open
126 * SYN_RECV: SYN-ACK packet seen
127 * ESTABLISHED: ACK packet seen
128 * FIN_WAIT: FIN packet seen
129 * CLOSE_WAIT: ACK seen (after FIN)
130 * LAST_ACK: FIN seen (after FIN)
131 * TIME_WAIT: last ACK seen
132 * CLOSE: closed connection (RST)
133 *
134 * Packets marked as IGNORED (sIG):
135 * if they may be either invalid or valid
136 * and the receiver may send back a connection
137 * closing RST or a SYN/ACK.
138 *
139 * Packets marked as INVALID (sIV):
140 * if we regard them as truly invalid packets
141 */
142 static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
143 {
144 /* ORIGINAL */
145 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
146 /*syn*/ { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sS2 },
147 /*
148 * sNO -> sSS Initialize a new connection
149 * sSS -> sSS Retransmitted SYN
150 * sS2 -> sS2 Late retransmitted SYN
151 * sSR -> sIG
152 * sES -> sIG Error: SYNs in window outside the SYN_SENT state
153 * are errors. Receiver will reply with RST
154 * and close the connection.
155 * Or we are not in sync and hold a dead connection.
156 * sFW -> sIG
157 * sCW -> sIG
158 * sLA -> sIG
159 * sTW -> sSS Reopened connection (RFC 1122).
160 * sCL -> sSS
161 */
162 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
163 /*synack*/ { sIV, sIV, sSR, sIV, sIV, sIV, sIV, sIV, sIV, sSR },
164 /*
165 * sNO -> sIV Too late and no reason to do anything
166 * sSS -> sIV Client can't send SYN and then SYN/ACK
167 * sS2 -> sSR SYN/ACK sent to SYN2 in simultaneous open
168 * sSR -> sSR Late retransmitted SYN/ACK in simultaneous open
169 * sES -> sIV Invalid SYN/ACK packets sent by the client
170 * sFW -> sIV
171 * sCW -> sIV
172 * sLA -> sIV
173 * sTW -> sIV
174 * sCL -> sIV
175 */
176 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
177 /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
178 /*
179 * sNO -> sIV Too late and no reason to do anything...
180 * sSS -> sIV Client migth not send FIN in this state:
181 * we enforce waiting for a SYN/ACK reply first.
182 * sS2 -> sIV
183 * sSR -> sFW Close started.
184 * sES -> sFW
185 * sFW -> sLA FIN seen in both directions, waiting for
186 * the last ACK.
187 * Migth be a retransmitted FIN as well...
188 * sCW -> sLA
189 * sLA -> sLA Retransmitted FIN. Remain in the same state.
190 * sTW -> sTW
191 * sCL -> sCL
192 */
193 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
194 /*ack*/ { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
195 /*
196 * sNO -> sES Assumed.
197 * sSS -> sIV ACK is invalid: we haven't seen a SYN/ACK yet.
198 * sS2 -> sIV
199 * sSR -> sES Established state is reached.
200 * sES -> sES :-)
201 * sFW -> sCW Normal close request answered by ACK.
202 * sCW -> sCW
203 * sLA -> sTW Last ACK detected (RFC5961 challenged)
204 * sTW -> sTW Retransmitted last ACK. Remain in the same state.
205 * sCL -> sCL
206 */
207 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
208 /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL },
209 /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
210 },
211 {
212 /* REPLY */
213 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
214 /*syn*/ { sIV, sS2, sIV, sIV, sIV, sIV, sIV, sSS, sIV, sS2 },
215 /*
216 * sNO -> sIV Never reached.
217 * sSS -> sS2 Simultaneous open
218 * sS2 -> sS2 Retransmitted simultaneous SYN
219 * sSR -> sIV Invalid SYN packets sent by the server
220 * sES -> sIV
221 * sFW -> sIV
222 * sCW -> sIV
223 * sLA -> sIV
224 * sTW -> sSS Reopened connection, but server may have switched role
225 * sCL -> sIV
226 */
227 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
228 /*synack*/ { sIV, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIG, sSR },
229 /*
230 * sSS -> sSR Standard open.
231 * sS2 -> sSR Simultaneous open
232 * sSR -> sIG Retransmitted SYN/ACK, ignore it.
233 * sES -> sIG Late retransmitted SYN/ACK?
234 * sFW -> sIG Might be SYN/ACK answering ignored SYN
235 * sCW -> sIG
236 * sLA -> sIG
237 * sTW -> sIG
238 * sCL -> sIG
239 */
240 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
241 /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
242 /*
243 * sSS -> sIV Server might not send FIN in this state.
244 * sS2 -> sIV
245 * sSR -> sFW Close started.
246 * sES -> sFW
247 * sFW -> sLA FIN seen in both directions.
248 * sCW -> sLA
249 * sLA -> sLA Retransmitted FIN.
250 * sTW -> sTW
251 * sCL -> sCL
252 */
253 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
254 /*ack*/ { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIG },
255 /*
256 * sSS -> sIG Might be a half-open connection.
257 * sS2 -> sIG
258 * sSR -> sSR Might answer late resent SYN.
259 * sES -> sES :-)
260 * sFW -> sCW Normal close request answered by ACK.
261 * sCW -> sCW
262 * sLA -> sTW Last ACK detected (RFC5961 challenged)
263 * sTW -> sTW Retransmitted last ACK.
264 * sCL -> sCL
265 */
266 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
267 /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL },
268 /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
269 }
270 };
271
272 #ifdef CONFIG_NF_CONNTRACK_PROCFS
273 /* Print out the private part of the conntrack. */
274 static void tcp_print_conntrack(struct seq_file *s, struct nf_conn *ct)
275 {
276 if (test_bit(IPS_OFFLOAD_BIT, &ct->status))
277 return;
278
279 seq_printf(s, "%s ", tcp_conntrack_names[ct->proto.tcp.state]);
280 }
281 #endif
282
283 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
284 {
285 if (tcph->rst) return TCP_RST_SET;
286 else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
287 else if (tcph->fin) return TCP_FIN_SET;
288 else if (tcph->ack) return TCP_ACK_SET;
289 else return TCP_NONE_SET;
290 }
291
292 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
293 in IP Filter' by Guido van Rooij.
294
295 http://www.sane.nl/events/sane2000/papers.html
296 http://www.darkart.com/mirrors/www.obfuscation.org/ipf/
297
298 The boundaries and the conditions are changed according to RFC793:
299 the packet must intersect the window (i.e. segments may be
300 after the right or before the left edge) and thus receivers may ACK
301 segments after the right edge of the window.
302
303 td_maxend = max(sack + max(win,1)) seen in reply packets
304 td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
305 td_maxwin += seq + len - sender.td_maxend
306 if seq + len > sender.td_maxend
307 td_end = max(seq + len) seen in sent packets
308
309 I. Upper bound for valid data: seq <= sender.td_maxend
310 II. Lower bound for valid data: seq + len >= sender.td_end - receiver.td_maxwin
311 III. Upper bound for valid (s)ack: sack <= receiver.td_end
312 IV. Lower bound for valid (s)ack: sack >= receiver.td_end - MAXACKWINDOW
313
314 where sack is the highest right edge of sack block found in the packet
315 or ack in the case of packet without SACK option.
316
317 The upper bound limit for a valid (s)ack is not ignored -
318 we doesn't have to deal with fragments.
319 */
320
321 static inline __u32 segment_seq_plus_len(__u32 seq,
322 size_t len,
323 unsigned int dataoff,
324 const struct tcphdr *tcph)
325 {
326 /* XXX Should I use payload length field in IP/IPv6 header ?
327 * - YK */
328 return (seq + len - dataoff - tcph->doff*4
329 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
330 }
331
332 /* Fixme: what about big packets? */
333 #define MAXACKWINCONST 66000
334 #define MAXACKWINDOW(sender) \
335 ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin \
336 : MAXACKWINCONST)
337
338 /*
339 * Simplified tcp_parse_options routine from tcp_input.c
340 */
341 static void tcp_options(const struct sk_buff *skb,
342 unsigned int dataoff,
343 const struct tcphdr *tcph,
344 struct ip_ct_tcp_state *state)
345 {
346 unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
347 const unsigned char *ptr;
348 int length = (tcph->doff*4) - sizeof(struct tcphdr);
349
350 if (!length)
351 return;
352
353 ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
354 length, buff);
355 BUG_ON(ptr == NULL);
356
357 state->td_scale =
358 state->flags = 0;
359
360 while (length > 0) {
361 int opcode=*ptr++;
362 int opsize;
363
364 switch (opcode) {
365 case TCPOPT_EOL:
366 return;
367 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
368 length--;
369 continue;
370 default:
371 if (length < 2)
372 return;
373 opsize=*ptr++;
374 if (opsize < 2) /* "silly options" */
375 return;
376 if (opsize > length)
377 return; /* don't parse partial options */
378
379 if (opcode == TCPOPT_SACK_PERM
380 && opsize == TCPOLEN_SACK_PERM)
381 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
382 else if (opcode == TCPOPT_WINDOW
383 && opsize == TCPOLEN_WINDOW) {
384 state->td_scale = *(u_int8_t *)ptr;
385
386 if (state->td_scale > TCP_MAX_WSCALE)
387 state->td_scale = TCP_MAX_WSCALE;
388
389 state->flags |=
390 IP_CT_TCP_FLAG_WINDOW_SCALE;
391 }
392 ptr += opsize - 2;
393 length -= opsize;
394 }
395 }
396 }
397
398 static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
399 const struct tcphdr *tcph, __u32 *sack)
400 {
401 unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
402 const unsigned char *ptr;
403 int length = (tcph->doff*4) - sizeof(struct tcphdr);
404 __u32 tmp;
405
406 if (!length)
407 return;
408
409 ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
410 length, buff);
411 BUG_ON(ptr == NULL);
412
413 /* Fast path for timestamp-only option */
414 if (length == TCPOLEN_TSTAMP_ALIGNED
415 && *(__be32 *)ptr == htonl((TCPOPT_NOP << 24)
416 | (TCPOPT_NOP << 16)
417 | (TCPOPT_TIMESTAMP << 8)
418 | TCPOLEN_TIMESTAMP))
419 return;
420
421 while (length > 0) {
422 int opcode = *ptr++;
423 int opsize, i;
424
425 switch (opcode) {
426 case TCPOPT_EOL:
427 return;
428 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
429 length--;
430 continue;
431 default:
432 if (length < 2)
433 return;
434 opsize = *ptr++;
435 if (opsize < 2) /* "silly options" */
436 return;
437 if (opsize > length)
438 return; /* don't parse partial options */
439
440 if (opcode == TCPOPT_SACK
441 && opsize >= (TCPOLEN_SACK_BASE
442 + TCPOLEN_SACK_PERBLOCK)
443 && !((opsize - TCPOLEN_SACK_BASE)
444 % TCPOLEN_SACK_PERBLOCK)) {
445 for (i = 0;
446 i < (opsize - TCPOLEN_SACK_BASE);
447 i += TCPOLEN_SACK_PERBLOCK) {
448 tmp = get_unaligned_be32((__be32 *)(ptr+i)+1);
449
450 if (after(tmp, *sack))
451 *sack = tmp;
452 }
453 return;
454 }
455 ptr += opsize - 2;
456 length -= opsize;
457 }
458 }
459 }
460
461 static bool tcp_in_window(const struct nf_conn *ct,
462 struct ip_ct_tcp *state,
463 enum ip_conntrack_dir dir,
464 unsigned int index,
465 const struct sk_buff *skb,
466 unsigned int dataoff,
467 const struct tcphdr *tcph)
468 {
469 struct net *net = nf_ct_net(ct);
470 struct nf_tcp_net *tn = nf_tcp_pernet(net);
471 struct ip_ct_tcp_state *sender = &state->seen[dir];
472 struct ip_ct_tcp_state *receiver = &state->seen[!dir];
473 const struct nf_conntrack_tuple *tuple = &ct->tuplehash[dir].tuple;
474 __u32 seq, ack, sack, end, win, swin;
475 s32 receiver_offset;
476 bool res, in_recv_win;
477
478 /*
479 * Get the required data from the packet.
480 */
481 seq = ntohl(tcph->seq);
482 ack = sack = ntohl(tcph->ack_seq);
483 win = ntohs(tcph->window);
484 end = segment_seq_plus_len(seq, skb->len, dataoff, tcph);
485
486 if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
487 tcp_sack(skb, dataoff, tcph, &sack);
488
489 /* Take into account NAT sequence number mangling */
490 receiver_offset = nf_ct_seq_offset(ct, !dir, ack - 1);
491 ack -= receiver_offset;
492 sack -= receiver_offset;
493
494 pr_debug("tcp_in_window: START\n");
495 pr_debug("tcp_in_window: ");
496 nf_ct_dump_tuple(tuple);
497 pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
498 seq, ack, receiver_offset, sack, receiver_offset, win, end);
499 pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
500 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
501 sender->td_end, sender->td_maxend, sender->td_maxwin,
502 sender->td_scale,
503 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
504 receiver->td_scale);
505
506 if (sender->td_maxwin == 0) {
507 /*
508 * Initialize sender data.
509 */
510 if (tcph->syn) {
511 /*
512 * SYN-ACK in reply to a SYN
513 * or SYN from reply direction in simultaneous open.
514 */
515 sender->td_end =
516 sender->td_maxend = end;
517 sender->td_maxwin = (win == 0 ? 1 : win);
518
519 tcp_options(skb, dataoff, tcph, sender);
520 /*
521 * RFC 1323:
522 * Both sides must send the Window Scale option
523 * to enable window scaling in either direction.
524 */
525 if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
526 && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
527 sender->td_scale =
528 receiver->td_scale = 0;
529 if (!tcph->ack)
530 /* Simultaneous open */
531 return true;
532 } else {
533 /*
534 * We are in the middle of a connection,
535 * its history is lost for us.
536 * Let's try to use the data from the packet.
537 */
538 sender->td_end = end;
539 swin = win << sender->td_scale;
540 sender->td_maxwin = (swin == 0 ? 1 : swin);
541 sender->td_maxend = end + sender->td_maxwin;
542 /*
543 * We haven't seen traffic in the other direction yet
544 * but we have to tweak window tracking to pass III
545 * and IV until that happens.
546 */
547 if (receiver->td_maxwin == 0)
548 receiver->td_end = receiver->td_maxend = sack;
549 }
550 } else if (((state->state == TCP_CONNTRACK_SYN_SENT
551 && dir == IP_CT_DIR_ORIGINAL)
552 || (state->state == TCP_CONNTRACK_SYN_RECV
553 && dir == IP_CT_DIR_REPLY))
554 && after(end, sender->td_end)) {
555 /*
556 * RFC 793: "if a TCP is reinitialized ... then it need
557 * not wait at all; it must only be sure to use sequence
558 * numbers larger than those recently used."
559 */
560 sender->td_end =
561 sender->td_maxend = end;
562 sender->td_maxwin = (win == 0 ? 1 : win);
563
564 tcp_options(skb, dataoff, tcph, sender);
565 }
566
567 if (!(tcph->ack)) {
568 /*
569 * If there is no ACK, just pretend it was set and OK.
570 */
571 ack = sack = receiver->td_end;
572 } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
573 (TCP_FLAG_ACK|TCP_FLAG_RST))
574 && (ack == 0)) {
575 /*
576 * Broken TCP stacks, that set ACK in RST packets as well
577 * with zero ack value.
578 */
579 ack = sack = receiver->td_end;
580 }
581
582 if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)
583 /*
584 * RST sent answering SYN.
585 */
586 seq = end = sender->td_end;
587
588 pr_debug("tcp_in_window: ");
589 nf_ct_dump_tuple(tuple);
590 pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
591 seq, ack, receiver_offset, sack, receiver_offset, win, end);
592 pr_debug("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,
595 sender->td_scale,
596 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
597 receiver->td_scale);
598
599 /* Is the ending sequence in the receive window (if available)? */
600 in_recv_win = !receiver->td_maxwin ||
601 after(end, sender->td_end - receiver->td_maxwin - 1);
602
603 pr_debug("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
604 before(seq, sender->td_maxend + 1),
605 (in_recv_win ? 1 : 0),
606 before(sack, receiver->td_end + 1),
607 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1));
608
609 if (before(seq, sender->td_maxend + 1) &&
610 in_recv_win &&
611 before(sack, receiver->td_end + 1) &&
612 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) {
613 /*
614 * Take into account window scaling (RFC 1323).
615 */
616 if (!tcph->syn)
617 win <<= sender->td_scale;
618
619 /*
620 * Update sender data.
621 */
622 swin = win + (sack - ack);
623 if (sender->td_maxwin < swin)
624 sender->td_maxwin = swin;
625 if (after(end, sender->td_end)) {
626 sender->td_end = end;
627 sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
628 }
629 if (tcph->ack) {
630 if (!(sender->flags & IP_CT_TCP_FLAG_MAXACK_SET)) {
631 sender->td_maxack = ack;
632 sender->flags |= IP_CT_TCP_FLAG_MAXACK_SET;
633 } else if (after(ack, sender->td_maxack))
634 sender->td_maxack = ack;
635 }
636
637 /*
638 * Update receiver data.
639 */
640 if (receiver->td_maxwin != 0 && after(end, sender->td_maxend))
641 receiver->td_maxwin += end - sender->td_maxend;
642 if (after(sack + win, receiver->td_maxend - 1)) {
643 receiver->td_maxend = sack + win;
644 if (win == 0)
645 receiver->td_maxend++;
646 }
647 if (ack == receiver->td_end)
648 receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
649
650 /*
651 * Check retransmissions.
652 */
653 if (index == TCP_ACK_SET) {
654 if (state->last_dir == dir
655 && state->last_seq == seq
656 && state->last_ack == ack
657 && state->last_end == end
658 && state->last_win == win)
659 state->retrans++;
660 else {
661 state->last_dir = dir;
662 state->last_seq = seq;
663 state->last_ack = ack;
664 state->last_end = end;
665 state->last_win = win;
666 state->retrans = 0;
667 }
668 }
669 res = true;
670 } else {
671 res = false;
672 if (sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL ||
673 tn->tcp_be_liberal)
674 res = true;
675 if (!res) {
676 nf_ct_l4proto_log_invalid(skb, ct,
677 "%s",
678 before(seq, sender->td_maxend + 1) ?
679 in_recv_win ?
680 before(sack, receiver->td_end + 1) ?
681 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1) ? "BUG"
682 : "ACK is under the lower bound (possible overly delayed ACK)"
683 : "ACK is over the upper bound (ACKed data not seen yet)"
684 : "SEQ is under the lower bound (already ACKed data retransmitted)"
685 : "SEQ is over the upper bound (over the window of the receiver)");
686 }
687 }
688
689 pr_debug("tcp_in_window: res=%u sender end=%u maxend=%u maxwin=%u "
690 "receiver end=%u maxend=%u maxwin=%u\n",
691 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
692 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
693
694 return res;
695 }
696
697 /* table of valid flag combinations - PUSH, ECE and CWR are always valid */
698 static const u8 tcp_valid_flags[(TCPHDR_FIN|TCPHDR_SYN|TCPHDR_RST|TCPHDR_ACK|
699 TCPHDR_URG) + 1] =
700 {
701 [TCPHDR_SYN] = 1,
702 [TCPHDR_SYN|TCPHDR_URG] = 1,
703 [TCPHDR_SYN|TCPHDR_ACK] = 1,
704 [TCPHDR_RST] = 1,
705 [TCPHDR_RST|TCPHDR_ACK] = 1,
706 [TCPHDR_FIN|TCPHDR_ACK] = 1,
707 [TCPHDR_FIN|TCPHDR_ACK|TCPHDR_URG] = 1,
708 [TCPHDR_ACK] = 1,
709 [TCPHDR_ACK|TCPHDR_URG] = 1,
710 };
711
712 static void tcp_error_log(const struct sk_buff *skb,
713 const struct nf_hook_state *state,
714 const char *msg)
715 {
716 nf_l4proto_log_invalid(skb, state->net, state->pf, IPPROTO_TCP, "%s", msg);
717 }
718
719 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c. */
720 static bool tcp_error(const struct tcphdr *th,
721 struct sk_buff *skb,
722 unsigned int dataoff,
723 const struct nf_hook_state *state)
724 {
725 unsigned int tcplen = skb->len - dataoff;
726 u8 tcpflags;
727
728 /* Not whole TCP header or malformed packet */
729 if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
730 tcp_error_log(skb, state, "truncated packet");
731 return true;
732 }
733
734 /* Checksum invalid? Ignore.
735 * We skip checking packets on the outgoing path
736 * because the checksum is assumed to be correct.
737 */
738 /* FIXME: Source route IP option packets --RR */
739 if (state->net->ct.sysctl_checksum &&
740 state->hook == NF_INET_PRE_ROUTING &&
741 nf_checksum(skb, state->hook, dataoff, IPPROTO_TCP, state->pf)) {
742 tcp_error_log(skb, state, "bad checksum");
743 return true;
744 }
745
746 /* Check TCP flags. */
747 tcpflags = (tcp_flag_byte(th) & ~(TCPHDR_ECE|TCPHDR_CWR|TCPHDR_PSH));
748 if (!tcp_valid_flags[tcpflags]) {
749 tcp_error_log(skb, state, "invalid tcp flag combination");
750 return true;
751 }
752
753 return false;
754 }
755
756 static noinline bool tcp_new(struct nf_conn *ct, const struct sk_buff *skb,
757 unsigned int dataoff,
758 const struct tcphdr *th)
759 {
760 enum tcp_conntrack new_state;
761 struct net *net = nf_ct_net(ct);
762 const struct nf_tcp_net *tn = nf_tcp_pernet(net);
763 const struct ip_ct_tcp_state *sender = &ct->proto.tcp.seen[0];
764 const struct ip_ct_tcp_state *receiver = &ct->proto.tcp.seen[1];
765
766 /* Don't need lock here: this conntrack not in circulation yet */
767 new_state = tcp_conntracks[0][get_conntrack_index(th)][TCP_CONNTRACK_NONE];
768
769 /* Invalid: delete conntrack */
770 if (new_state >= TCP_CONNTRACK_MAX) {
771 pr_debug("nf_ct_tcp: invalid new deleting.\n");
772 return false;
773 }
774
775 if (new_state == TCP_CONNTRACK_SYN_SENT) {
776 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
777 /* SYN packet */
778 ct->proto.tcp.seen[0].td_end =
779 segment_seq_plus_len(ntohl(th->seq), skb->len,
780 dataoff, th);
781 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
782 if (ct->proto.tcp.seen[0].td_maxwin == 0)
783 ct->proto.tcp.seen[0].td_maxwin = 1;
784 ct->proto.tcp.seen[0].td_maxend =
785 ct->proto.tcp.seen[0].td_end;
786
787 tcp_options(skb, dataoff, th, &ct->proto.tcp.seen[0]);
788 } else if (tn->tcp_loose == 0) {
789 /* Don't try to pick up connections. */
790 return false;
791 } else {
792 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
793 /*
794 * We are in the middle of a connection,
795 * its history is lost for us.
796 * Let's try to use the data from the packet.
797 */
798 ct->proto.tcp.seen[0].td_end =
799 segment_seq_plus_len(ntohl(th->seq), skb->len,
800 dataoff, th);
801 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
802 if (ct->proto.tcp.seen[0].td_maxwin == 0)
803 ct->proto.tcp.seen[0].td_maxwin = 1;
804 ct->proto.tcp.seen[0].td_maxend =
805 ct->proto.tcp.seen[0].td_end +
806 ct->proto.tcp.seen[0].td_maxwin;
807
808 /* We assume SACK and liberal window checking to handle
809 * window scaling */
810 ct->proto.tcp.seen[0].flags =
811 ct->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM |
812 IP_CT_TCP_FLAG_BE_LIBERAL;
813 }
814
815 /* tcp_packet will set them */
816 ct->proto.tcp.last_index = TCP_NONE_SET;
817
818 pr_debug("%s: sender end=%u maxend=%u maxwin=%u scale=%i "
819 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
820 __func__,
821 sender->td_end, sender->td_maxend, sender->td_maxwin,
822 sender->td_scale,
823 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
824 receiver->td_scale);
825 return true;
826 }
827
828 static bool nf_conntrack_tcp_established(const struct nf_conn *ct)
829 {
830 return ct->proto.tcp.state == TCP_CONNTRACK_ESTABLISHED &&
831 test_bit(IPS_ASSURED_BIT, &ct->status);
832 }
833
834 /* Returns verdict for packet, or -1 for invalid. */
835 int nf_conntrack_tcp_packet(struct nf_conn *ct,
836 struct sk_buff *skb,
837 unsigned int dataoff,
838 enum ip_conntrack_info ctinfo,
839 const struct nf_hook_state *state)
840 {
841 struct net *net = nf_ct_net(ct);
842 struct nf_tcp_net *tn = nf_tcp_pernet(net);
843 struct nf_conntrack_tuple *tuple;
844 enum tcp_conntrack new_state, old_state;
845 unsigned int index, *timeouts;
846 enum ip_conntrack_dir dir;
847 const struct tcphdr *th;
848 struct tcphdr _tcph;
849 unsigned long timeout;
850
851 th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
852 if (th == NULL)
853 return -NF_ACCEPT;
854
855 if (tcp_error(th, skb, dataoff, state))
856 return -NF_ACCEPT;
857
858 if (!nf_ct_is_confirmed(ct) && !tcp_new(ct, skb, dataoff, th))
859 return -NF_ACCEPT;
860
861 spin_lock_bh(&ct->lock);
862 old_state = ct->proto.tcp.state;
863 dir = CTINFO2DIR(ctinfo);
864 index = get_conntrack_index(th);
865 new_state = tcp_conntracks[dir][index][old_state];
866 tuple = &ct->tuplehash[dir].tuple;
867
868 switch (new_state) {
869 case TCP_CONNTRACK_SYN_SENT:
870 if (old_state < TCP_CONNTRACK_TIME_WAIT)
871 break;
872 /* RFC 1122: "When a connection is closed actively,
873 * it MUST linger in TIME-WAIT state for a time 2xMSL
874 * (Maximum Segment Lifetime). However, it MAY accept
875 * a new SYN from the remote TCP to reopen the connection
876 * directly from TIME-WAIT state, if..."
877 * We ignore the conditions because we are in the
878 * TIME-WAIT state anyway.
879 *
880 * Handle aborted connections: we and the server
881 * think there is an existing connection but the client
882 * aborts it and starts a new one.
883 */
884 if (((ct->proto.tcp.seen[dir].flags
885 | ct->proto.tcp.seen[!dir].flags)
886 & IP_CT_TCP_FLAG_CLOSE_INIT)
887 || (ct->proto.tcp.last_dir == dir
888 && ct->proto.tcp.last_index == TCP_RST_SET)) {
889 /* Attempt to reopen a closed/aborted connection.
890 * Delete this connection and look up again. */
891 spin_unlock_bh(&ct->lock);
892
893 /* Only repeat if we can actually remove the timer.
894 * Destruction may already be in progress in process
895 * context and we must give it a chance to terminate.
896 */
897 if (nf_ct_kill(ct))
898 return -NF_REPEAT;
899 return NF_DROP;
900 }
901 /* Fall through */
902 case TCP_CONNTRACK_IGNORE:
903 /* Ignored packets:
904 *
905 * Our connection entry may be out of sync, so ignore
906 * packets which may signal the real connection between
907 * the client and the server.
908 *
909 * a) SYN in ORIGINAL
910 * b) SYN/ACK in REPLY
911 * c) ACK in reply direction after initial SYN in original.
912 *
913 * If the ignored packet is invalid, the receiver will send
914 * a RST we'll catch below.
915 */
916 if (index == TCP_SYNACK_SET
917 && ct->proto.tcp.last_index == TCP_SYN_SET
918 && ct->proto.tcp.last_dir != dir
919 && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
920 /* b) This SYN/ACK acknowledges a SYN that we earlier
921 * ignored as invalid. This means that the client and
922 * the server are both in sync, while the firewall is
923 * not. We get in sync from the previously annotated
924 * values.
925 */
926 old_state = TCP_CONNTRACK_SYN_SENT;
927 new_state = TCP_CONNTRACK_SYN_RECV;
928 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end =
929 ct->proto.tcp.last_end;
930 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend =
931 ct->proto.tcp.last_end;
932 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin =
933 ct->proto.tcp.last_win == 0 ?
934 1 : ct->proto.tcp.last_win;
935 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale =
936 ct->proto.tcp.last_wscale;
937 ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
938 ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags =
939 ct->proto.tcp.last_flags;
940 memset(&ct->proto.tcp.seen[dir], 0,
941 sizeof(struct ip_ct_tcp_state));
942 break;
943 }
944 ct->proto.tcp.last_index = index;
945 ct->proto.tcp.last_dir = dir;
946 ct->proto.tcp.last_seq = ntohl(th->seq);
947 ct->proto.tcp.last_end =
948 segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
949 ct->proto.tcp.last_win = ntohs(th->window);
950
951 /* a) This is a SYN in ORIGINAL. The client and the server
952 * may be in sync but we are not. In that case, we annotate
953 * the TCP options and let the packet go through. If it is a
954 * valid SYN packet, the server will reply with a SYN/ACK, and
955 * then we'll get in sync. Otherwise, the server potentially
956 * responds with a challenge ACK if implementing RFC5961.
957 */
958 if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) {
959 struct ip_ct_tcp_state seen = {};
960
961 ct->proto.tcp.last_flags =
962 ct->proto.tcp.last_wscale = 0;
963 tcp_options(skb, dataoff, th, &seen);
964 if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
965 ct->proto.tcp.last_flags |=
966 IP_CT_TCP_FLAG_WINDOW_SCALE;
967 ct->proto.tcp.last_wscale = seen.td_scale;
968 }
969 if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) {
970 ct->proto.tcp.last_flags |=
971 IP_CT_TCP_FLAG_SACK_PERM;
972 }
973 /* Mark the potential for RFC5961 challenge ACK,
974 * this pose a special problem for LAST_ACK state
975 * as ACK is intrepretated as ACKing last FIN.
976 */
977 if (old_state == TCP_CONNTRACK_LAST_ACK)
978 ct->proto.tcp.last_flags |=
979 IP_CT_EXP_CHALLENGE_ACK;
980 }
981 spin_unlock_bh(&ct->lock);
982 nf_ct_l4proto_log_invalid(skb, ct, "invalid packet ignored in "
983 "state %s ", tcp_conntrack_names[old_state]);
984 return NF_ACCEPT;
985 case TCP_CONNTRACK_MAX:
986 /* Special case for SYN proxy: when the SYN to the server or
987 * the SYN/ACK from the server is lost, the client may transmit
988 * a keep-alive packet while in SYN_SENT state. This needs to
989 * be associated with the original conntrack entry in order to
990 * generate a new SYN with the correct sequence number.
991 */
992 if (nfct_synproxy(ct) && old_state == TCP_CONNTRACK_SYN_SENT &&
993 index == TCP_ACK_SET && dir == IP_CT_DIR_ORIGINAL &&
994 ct->proto.tcp.last_dir == IP_CT_DIR_ORIGINAL &&
995 ct->proto.tcp.seen[dir].td_end - 1 == ntohl(th->seq)) {
996 pr_debug("nf_ct_tcp: SYN proxy client keep alive\n");
997 spin_unlock_bh(&ct->lock);
998 return NF_ACCEPT;
999 }
1000
1001 /* Invalid packet */
1002 pr_debug("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
1003 dir, get_conntrack_index(th), old_state);
1004 spin_unlock_bh(&ct->lock);
1005 nf_ct_l4proto_log_invalid(skb, ct, "invalid state");
1006 return -NF_ACCEPT;
1007 case TCP_CONNTRACK_TIME_WAIT:
1008 /* RFC5961 compliance cause stack to send "challenge-ACK"
1009 * e.g. in response to spurious SYNs. Conntrack MUST
1010 * not believe this ACK is acking last FIN.
1011 */
1012 if (old_state == TCP_CONNTRACK_LAST_ACK &&
1013 index == TCP_ACK_SET &&
1014 ct->proto.tcp.last_dir != dir &&
1015 ct->proto.tcp.last_index == TCP_SYN_SET &&
1016 (ct->proto.tcp.last_flags & IP_CT_EXP_CHALLENGE_ACK)) {
1017 /* Detected RFC5961 challenge ACK */
1018 ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
1019 spin_unlock_bh(&ct->lock);
1020 nf_ct_l4proto_log_invalid(skb, ct, "challenge-ack ignored");
1021 return NF_ACCEPT; /* Don't change state */
1022 }
1023 break;
1024 case TCP_CONNTRACK_SYN_SENT2:
1025 /* tcp_conntracks table is not smart enough to handle
1026 * simultaneous open.
1027 */
1028 ct->proto.tcp.last_flags |= IP_CT_TCP_SIMULTANEOUS_OPEN;
1029 break;
1030 case TCP_CONNTRACK_SYN_RECV:
1031 if (dir == IP_CT_DIR_REPLY && index == TCP_ACK_SET &&
1032 ct->proto.tcp.last_flags & IP_CT_TCP_SIMULTANEOUS_OPEN)
1033 new_state = TCP_CONNTRACK_ESTABLISHED;
1034 break;
1035 case TCP_CONNTRACK_CLOSE:
1036 if (index != TCP_RST_SET)
1037 break;
1038
1039 if (ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET) {
1040 u32 seq = ntohl(th->seq);
1041
1042 if (before(seq, ct->proto.tcp.seen[!dir].td_maxack)) {
1043 /* Invalid RST */
1044 spin_unlock_bh(&ct->lock);
1045 nf_ct_l4proto_log_invalid(skb, ct, "invalid rst");
1046 return -NF_ACCEPT;
1047 }
1048
1049 if (!nf_conntrack_tcp_established(ct) ||
1050 seq == ct->proto.tcp.seen[!dir].td_maxack)
1051 break;
1052
1053 /* Check if rst is part of train, such as
1054 * foo:80 > bar:4379: P, 235946583:235946602(19) ack 42
1055 * foo:80 > bar:4379: R, 235946602:235946602(0) ack 42
1056 */
1057 if (ct->proto.tcp.last_index == TCP_ACK_SET &&
1058 ct->proto.tcp.last_dir == dir &&
1059 seq == ct->proto.tcp.last_end)
1060 break;
1061
1062 /* ... RST sequence number doesn't match exactly, keep
1063 * established state to allow a possible challenge ACK.
1064 */
1065 new_state = old_state;
1066 }
1067 if (((test_bit(IPS_SEEN_REPLY_BIT, &ct->status)
1068 && ct->proto.tcp.last_index == TCP_SYN_SET)
1069 || (!test_bit(IPS_ASSURED_BIT, &ct->status)
1070 && ct->proto.tcp.last_index == TCP_ACK_SET))
1071 && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
1072 /* RST sent to invalid SYN or ACK we had let through
1073 * at a) and c) above:
1074 *
1075 * a) SYN was in window then
1076 * c) we hold a half-open connection.
1077 *
1078 * Delete our connection entry.
1079 * We skip window checking, because packet might ACK
1080 * segments we ignored. */
1081 goto in_window;
1082 }
1083 break;
1084 default:
1085 /* Keep compilers happy. */
1086 break;
1087 }
1088
1089 if (!tcp_in_window(ct, &ct->proto.tcp, dir, index,
1090 skb, dataoff, th)) {
1091 spin_unlock_bh(&ct->lock);
1092 return -NF_ACCEPT;
1093 }
1094 in_window:
1095 /* From now on we have got in-window packets */
1096 ct->proto.tcp.last_index = index;
1097 ct->proto.tcp.last_dir = dir;
1098
1099 pr_debug("tcp_conntracks: ");
1100 nf_ct_dump_tuple(tuple);
1101 pr_debug("syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1102 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
1103 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
1104 old_state, new_state);
1105
1106 ct->proto.tcp.state = new_state;
1107 if (old_state != new_state
1108 && new_state == TCP_CONNTRACK_FIN_WAIT)
1109 ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1110
1111 timeouts = nf_ct_timeout_lookup(ct);
1112 if (!timeouts)
1113 timeouts = tn->timeouts;
1114
1115 if (ct->proto.tcp.retrans >= tn->tcp_max_retrans &&
1116 timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1117 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1118 else if (unlikely(index == TCP_RST_SET))
1119 timeout = timeouts[TCP_CONNTRACK_CLOSE];
1120 else if ((ct->proto.tcp.seen[0].flags | ct->proto.tcp.seen[1].flags) &
1121 IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED &&
1122 timeouts[new_state] > timeouts[TCP_CONNTRACK_UNACK])
1123 timeout = timeouts[TCP_CONNTRACK_UNACK];
1124 else if (ct->proto.tcp.last_win == 0 &&
1125 timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1126 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1127 else
1128 timeout = timeouts[new_state];
1129 spin_unlock_bh(&ct->lock);
1130
1131 if (new_state != old_state)
1132 nf_conntrack_event_cache(IPCT_PROTOINFO, ct);
1133
1134 if (!test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
1135 /* If only reply is a RST, we can consider ourselves not to
1136 have an established connection: this is a fairly common
1137 problem case, so we can delete the conntrack
1138 immediately. --RR */
1139 if (th->rst) {
1140 nf_ct_kill_acct(ct, ctinfo, skb);
1141 return NF_ACCEPT;
1142 }
1143 /* ESTABLISHED without SEEN_REPLY, i.e. mid-connection
1144 * pickup with loose=1. Avoid large ESTABLISHED timeout.
1145 */
1146 if (new_state == TCP_CONNTRACK_ESTABLISHED &&
1147 timeout > timeouts[TCP_CONNTRACK_UNACK])
1148 timeout = timeouts[TCP_CONNTRACK_UNACK];
1149 } else if (!test_bit(IPS_ASSURED_BIT, &ct->status)
1150 && (old_state == TCP_CONNTRACK_SYN_RECV
1151 || old_state == TCP_CONNTRACK_ESTABLISHED)
1152 && new_state == TCP_CONNTRACK_ESTABLISHED) {
1153 /* Set ASSURED if we see see valid ack in ESTABLISHED
1154 after SYN_RECV or a valid answer for a picked up
1155 connection. */
1156 set_bit(IPS_ASSURED_BIT, &ct->status);
1157 nf_conntrack_event_cache(IPCT_ASSURED, ct);
1158 }
1159 nf_ct_refresh_acct(ct, ctinfo, skb, timeout);
1160
1161 return NF_ACCEPT;
1162 }
1163
1164 static bool tcp_can_early_drop(const struct nf_conn *ct)
1165 {
1166 switch (ct->proto.tcp.state) {
1167 case TCP_CONNTRACK_FIN_WAIT:
1168 case TCP_CONNTRACK_LAST_ACK:
1169 case TCP_CONNTRACK_TIME_WAIT:
1170 case TCP_CONNTRACK_CLOSE:
1171 case TCP_CONNTRACK_CLOSE_WAIT:
1172 return true;
1173 default:
1174 break;
1175 }
1176
1177 return false;
1178 }
1179
1180 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1181
1182 #include <linux/netfilter/nfnetlink.h>
1183 #include <linux/netfilter/nfnetlink_conntrack.h>
1184
1185 static int tcp_to_nlattr(struct sk_buff *skb, struct nlattr *nla,
1186 struct nf_conn *ct)
1187 {
1188 struct nlattr *nest_parms;
1189 struct nf_ct_tcp_flags tmp = {};
1190
1191 spin_lock_bh(&ct->lock);
1192 nest_parms = nla_nest_start(skb, CTA_PROTOINFO_TCP);
1193 if (!nest_parms)
1194 goto nla_put_failure;
1195
1196 if (nla_put_u8(skb, CTA_PROTOINFO_TCP_STATE, ct->proto.tcp.state) ||
1197 nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL,
1198 ct->proto.tcp.seen[0].td_scale) ||
1199 nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY,
1200 ct->proto.tcp.seen[1].td_scale))
1201 goto nla_put_failure;
1202
1203 tmp.flags = ct->proto.tcp.seen[0].flags;
1204 if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_ORIGINAL,
1205 sizeof(struct nf_ct_tcp_flags), &tmp))
1206 goto nla_put_failure;
1207
1208 tmp.flags = ct->proto.tcp.seen[1].flags;
1209 if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_REPLY,
1210 sizeof(struct nf_ct_tcp_flags), &tmp))
1211 goto nla_put_failure;
1212 spin_unlock_bh(&ct->lock);
1213
1214 nla_nest_end(skb, nest_parms);
1215
1216 return 0;
1217
1218 nla_put_failure:
1219 spin_unlock_bh(&ct->lock);
1220 return -1;
1221 }
1222
1223 static const struct nla_policy tcp_nla_policy[CTA_PROTOINFO_TCP_MAX+1] = {
1224 [CTA_PROTOINFO_TCP_STATE] = { .type = NLA_U8 },
1225 [CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] = { .type = NLA_U8 },
1226 [CTA_PROTOINFO_TCP_WSCALE_REPLY] = { .type = NLA_U8 },
1227 [CTA_PROTOINFO_TCP_FLAGS_ORIGINAL] = { .len = sizeof(struct nf_ct_tcp_flags) },
1228 [CTA_PROTOINFO_TCP_FLAGS_REPLY] = { .len = sizeof(struct nf_ct_tcp_flags) },
1229 };
1230
1231 #define TCP_NLATTR_SIZE ( \
1232 NLA_ALIGN(NLA_HDRLEN + 1) + \
1233 NLA_ALIGN(NLA_HDRLEN + 1) + \
1234 NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)) + \
1235 NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)))
1236
1237 static int nlattr_to_tcp(struct nlattr *cda[], struct nf_conn *ct)
1238 {
1239 struct nlattr *pattr = cda[CTA_PROTOINFO_TCP];
1240 struct nlattr *tb[CTA_PROTOINFO_TCP_MAX+1];
1241 int err;
1242
1243 /* updates could not contain anything about the private
1244 * protocol info, in that case skip the parsing */
1245 if (!pattr)
1246 return 0;
1247
1248 err = nla_parse_nested_deprecated(tb, CTA_PROTOINFO_TCP_MAX, pattr,
1249 tcp_nla_policy, NULL);
1250 if (err < 0)
1251 return err;
1252
1253 if (tb[CTA_PROTOINFO_TCP_STATE] &&
1254 nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]) >= TCP_CONNTRACK_MAX)
1255 return -EINVAL;
1256
1257 spin_lock_bh(&ct->lock);
1258 if (tb[CTA_PROTOINFO_TCP_STATE])
1259 ct->proto.tcp.state = nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]);
1260
1261 if (tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]) {
1262 struct nf_ct_tcp_flags *attr =
1263 nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]);
1264 ct->proto.tcp.seen[0].flags &= ~attr->mask;
1265 ct->proto.tcp.seen[0].flags |= attr->flags & attr->mask;
1266 }
1267
1268 if (tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]) {
1269 struct nf_ct_tcp_flags *attr =
1270 nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]);
1271 ct->proto.tcp.seen[1].flags &= ~attr->mask;
1272 ct->proto.tcp.seen[1].flags |= attr->flags & attr->mask;
1273 }
1274
1275 if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] &&
1276 tb[CTA_PROTOINFO_TCP_WSCALE_REPLY] &&
1277 ct->proto.tcp.seen[0].flags & IP_CT_TCP_FLAG_WINDOW_SCALE &&
1278 ct->proto.tcp.seen[1].flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
1279 ct->proto.tcp.seen[0].td_scale =
1280 nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL]);
1281 ct->proto.tcp.seen[1].td_scale =
1282 nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY]);
1283 }
1284 spin_unlock_bh(&ct->lock);
1285
1286 return 0;
1287 }
1288
1289 static unsigned int tcp_nlattr_tuple_size(void)
1290 {
1291 static unsigned int size __read_mostly;
1292
1293 if (!size)
1294 size = nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);
1295
1296 return size;
1297 }
1298 #endif
1299
1300 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1301
1302 #include <linux/netfilter/nfnetlink.h>
1303 #include <linux/netfilter/nfnetlink_cttimeout.h>
1304
1305 static int tcp_timeout_nlattr_to_obj(struct nlattr *tb[],
1306 struct net *net, void *data)
1307 {
1308 struct nf_tcp_net *tn = nf_tcp_pernet(net);
1309 unsigned int *timeouts = data;
1310 int i;
1311
1312 if (!timeouts)
1313 timeouts = tn->timeouts;
1314 /* set default TCP timeouts. */
1315 for (i=0; i<TCP_CONNTRACK_TIMEOUT_MAX; i++)
1316 timeouts[i] = tn->timeouts[i];
1317
1318 if (tb[CTA_TIMEOUT_TCP_SYN_SENT]) {
1319 timeouts[TCP_CONNTRACK_SYN_SENT] =
1320 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT]))*HZ;
1321 }
1322
1323 if (tb[CTA_TIMEOUT_TCP_SYN_RECV]) {
1324 timeouts[TCP_CONNTRACK_SYN_RECV] =
1325 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_RECV]))*HZ;
1326 }
1327 if (tb[CTA_TIMEOUT_TCP_ESTABLISHED]) {
1328 timeouts[TCP_CONNTRACK_ESTABLISHED] =
1329 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_ESTABLISHED]))*HZ;
1330 }
1331 if (tb[CTA_TIMEOUT_TCP_FIN_WAIT]) {
1332 timeouts[TCP_CONNTRACK_FIN_WAIT] =
1333 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_FIN_WAIT]))*HZ;
1334 }
1335 if (tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]) {
1336 timeouts[TCP_CONNTRACK_CLOSE_WAIT] =
1337 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]))*HZ;
1338 }
1339 if (tb[CTA_TIMEOUT_TCP_LAST_ACK]) {
1340 timeouts[TCP_CONNTRACK_LAST_ACK] =
1341 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_LAST_ACK]))*HZ;
1342 }
1343 if (tb[CTA_TIMEOUT_TCP_TIME_WAIT]) {
1344 timeouts[TCP_CONNTRACK_TIME_WAIT] =
1345 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_TIME_WAIT]))*HZ;
1346 }
1347 if (tb[CTA_TIMEOUT_TCP_CLOSE]) {
1348 timeouts[TCP_CONNTRACK_CLOSE] =
1349 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE]))*HZ;
1350 }
1351 if (tb[CTA_TIMEOUT_TCP_SYN_SENT2]) {
1352 timeouts[TCP_CONNTRACK_SYN_SENT2] =
1353 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT2]))*HZ;
1354 }
1355 if (tb[CTA_TIMEOUT_TCP_RETRANS]) {
1356 timeouts[TCP_CONNTRACK_RETRANS] =
1357 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_RETRANS]))*HZ;
1358 }
1359 if (tb[CTA_TIMEOUT_TCP_UNACK]) {
1360 timeouts[TCP_CONNTRACK_UNACK] =
1361 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_UNACK]))*HZ;
1362 }
1363
1364 timeouts[CTA_TIMEOUT_TCP_UNSPEC] = timeouts[CTA_TIMEOUT_TCP_SYN_SENT];
1365 return 0;
1366 }
1367
1368 static int
1369 tcp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
1370 {
1371 const unsigned int *timeouts = data;
1372
1373 if (nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT,
1374 htonl(timeouts[TCP_CONNTRACK_SYN_SENT] / HZ)) ||
1375 nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_RECV,
1376 htonl(timeouts[TCP_CONNTRACK_SYN_RECV] / HZ)) ||
1377 nla_put_be32(skb, CTA_TIMEOUT_TCP_ESTABLISHED,
1378 htonl(timeouts[TCP_CONNTRACK_ESTABLISHED] / HZ)) ||
1379 nla_put_be32(skb, CTA_TIMEOUT_TCP_FIN_WAIT,
1380 htonl(timeouts[TCP_CONNTRACK_FIN_WAIT] / HZ)) ||
1381 nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE_WAIT,
1382 htonl(timeouts[TCP_CONNTRACK_CLOSE_WAIT] / HZ)) ||
1383 nla_put_be32(skb, CTA_TIMEOUT_TCP_LAST_ACK,
1384 htonl(timeouts[TCP_CONNTRACK_LAST_ACK] / HZ)) ||
1385 nla_put_be32(skb, CTA_TIMEOUT_TCP_TIME_WAIT,
1386 htonl(timeouts[TCP_CONNTRACK_TIME_WAIT] / HZ)) ||
1387 nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE,
1388 htonl(timeouts[TCP_CONNTRACK_CLOSE] / HZ)) ||
1389 nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT2,
1390 htonl(timeouts[TCP_CONNTRACK_SYN_SENT2] / HZ)) ||
1391 nla_put_be32(skb, CTA_TIMEOUT_TCP_RETRANS,
1392 htonl(timeouts[TCP_CONNTRACK_RETRANS] / HZ)) ||
1393 nla_put_be32(skb, CTA_TIMEOUT_TCP_UNACK,
1394 htonl(timeouts[TCP_CONNTRACK_UNACK] / HZ)))
1395 goto nla_put_failure;
1396 return 0;
1397
1398 nla_put_failure:
1399 return -ENOSPC;
1400 }
1401
1402 static const struct nla_policy tcp_timeout_nla_policy[CTA_TIMEOUT_TCP_MAX+1] = {
1403 [CTA_TIMEOUT_TCP_SYN_SENT] = { .type = NLA_U32 },
1404 [CTA_TIMEOUT_TCP_SYN_RECV] = { .type = NLA_U32 },
1405 [CTA_TIMEOUT_TCP_ESTABLISHED] = { .type = NLA_U32 },
1406 [CTA_TIMEOUT_TCP_FIN_WAIT] = { .type = NLA_U32 },
1407 [CTA_TIMEOUT_TCP_CLOSE_WAIT] = { .type = NLA_U32 },
1408 [CTA_TIMEOUT_TCP_LAST_ACK] = { .type = NLA_U32 },
1409 [CTA_TIMEOUT_TCP_TIME_WAIT] = { .type = NLA_U32 },
1410 [CTA_TIMEOUT_TCP_CLOSE] = { .type = NLA_U32 },
1411 [CTA_TIMEOUT_TCP_SYN_SENT2] = { .type = NLA_U32 },
1412 [CTA_TIMEOUT_TCP_RETRANS] = { .type = NLA_U32 },
1413 [CTA_TIMEOUT_TCP_UNACK] = { .type = NLA_U32 },
1414 };
1415 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1416
1417 void nf_conntrack_tcp_init_net(struct net *net)
1418 {
1419 struct nf_tcp_net *tn = nf_tcp_pernet(net);
1420 int i;
1421
1422 for (i = 0; i < TCP_CONNTRACK_TIMEOUT_MAX; i++)
1423 tn->timeouts[i] = tcp_timeouts[i];
1424
1425 /* timeouts[0] is unused, make it same as SYN_SENT so
1426 * ->timeouts[0] contains 'new' timeout, like udp or icmp.
1427 */
1428 tn->timeouts[0] = tcp_timeouts[TCP_CONNTRACK_SYN_SENT];
1429 tn->tcp_loose = nf_ct_tcp_loose;
1430 tn->tcp_be_liberal = nf_ct_tcp_be_liberal;
1431 tn->tcp_max_retrans = nf_ct_tcp_max_retrans;
1432 }
1433
1434 const struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp =
1435 {
1436 .l4proto = IPPROTO_TCP,
1437 #ifdef CONFIG_NF_CONNTRACK_PROCFS
1438 .print_conntrack = tcp_print_conntrack,
1439 #endif
1440 .can_early_drop = tcp_can_early_drop,
1441 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1442 .to_nlattr = tcp_to_nlattr,
1443 .from_nlattr = nlattr_to_tcp,
1444 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
1445 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
1446 .nlattr_tuple_size = tcp_nlattr_tuple_size,
1447 .nlattr_size = TCP_NLATTR_SIZE,
1448 .nla_policy = nf_ct_port_nla_policy,
1449 #endif
1450 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1451 .ctnl_timeout = {
1452 .nlattr_to_obj = tcp_timeout_nlattr_to_obj,
1453 .obj_to_nlattr = tcp_timeout_obj_to_nlattr,
1454 .nlattr_max = CTA_TIMEOUT_TCP_MAX,
1455 .obj_size = sizeof(unsigned int) *
1456 TCP_CONNTRACK_TIMEOUT_MAX,
1457 .nla_policy = tcp_timeout_nla_policy,
1458 },
1459 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1460 };
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