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@netfilter.org>
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 /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
35 closely. They're more complex. --RR */
36
37 static const char *const tcp_conntrack_names[] = {
38 "NONE",
39 "SYN_SENT",
40 "SYN_RECV",
41 "ESTABLISHED",
42 "FIN_WAIT",
43 "CLOSE_WAIT",
44 "LAST_ACK",
45 "TIME_WAIT",
46 "CLOSE",
47 "SYN_SENT2",
48 };
49
50 enum nf_ct_tcp_action {
51 NFCT_TCP_IGNORE,
52 NFCT_TCP_INVALID,
53 NFCT_TCP_ACCEPT,
54 };
55
56 #define SECS * HZ
57 #define MINS * 60 SECS
58 #define HOURS * 60 MINS
59 #define DAYS * 24 HOURS
60
61 static const unsigned int tcp_timeouts[TCP_CONNTRACK_TIMEOUT_MAX] = {
62 [TCP_CONNTRACK_SYN_SENT] = 2 MINS,
63 [TCP_CONNTRACK_SYN_RECV] = 60 SECS,
64 [TCP_CONNTRACK_ESTABLISHED] = 5 DAYS,
65 [TCP_CONNTRACK_FIN_WAIT] = 2 MINS,
66 [TCP_CONNTRACK_CLOSE_WAIT] = 60 SECS,
67 [TCP_CONNTRACK_LAST_ACK] = 30 SECS,
68 [TCP_CONNTRACK_TIME_WAIT] = 2 MINS,
69 [TCP_CONNTRACK_CLOSE] = 10 SECS,
70 [TCP_CONNTRACK_SYN_SENT2] = 2 MINS,
71 /* RFC1122 says the R2 limit should be at least 100 seconds.
72 Linux uses 15 packets as limit, which corresponds
73 to ~13-30min depending on RTO. */
74 [TCP_CONNTRACK_RETRANS] = 5 MINS,
75 [TCP_CONNTRACK_UNACK] = 5 MINS,
76 };
77
78 #define sNO TCP_CONNTRACK_NONE
79 #define sSS TCP_CONNTRACK_SYN_SENT
80 #define sSR TCP_CONNTRACK_SYN_RECV
81 #define sES TCP_CONNTRACK_ESTABLISHED
82 #define sFW TCP_CONNTRACK_FIN_WAIT
83 #define sCW TCP_CONNTRACK_CLOSE_WAIT
84 #define sLA TCP_CONNTRACK_LAST_ACK
85 #define sTW TCP_CONNTRACK_TIME_WAIT
86 #define sCL TCP_CONNTRACK_CLOSE
87 #define sS2 TCP_CONNTRACK_SYN_SENT2
88 #define sIV TCP_CONNTRACK_MAX
89 #define sIG TCP_CONNTRACK_IGNORE
90
91 /* What TCP flags are set from RST/SYN/FIN/ACK. */
92 enum tcp_bit_set {
93 TCP_SYN_SET,
94 TCP_SYNACK_SET,
95 TCP_FIN_SET,
96 TCP_ACK_SET,
97 TCP_RST_SET,
98 TCP_NONE_SET,
99 };
100
101 /*
102 * The TCP state transition table needs a few words...
103 *
104 * We are the man in the middle. All the packets go through us
105 * but might get lost in transit to the destination.
106 * It is assumed that the destinations can't receive segments
107 * we haven't seen.
108 *
109 * The checked segment is in window, but our windows are *not*
110 * equivalent with the ones of the sender/receiver. We always
111 * try to guess the state of the current sender.
112 *
113 * The meaning of the states are:
114 *
115 * NONE: initial state
116 * SYN_SENT: SYN-only packet seen
117 * SYN_SENT2: SYN-only packet seen from reply dir, simultaneous open
118 * SYN_RECV: SYN-ACK packet seen
119 * ESTABLISHED: ACK packet seen
120 * FIN_WAIT: FIN packet seen
121 * CLOSE_WAIT: ACK seen (after FIN)
122 * LAST_ACK: FIN seen (after FIN)
123 * TIME_WAIT: last ACK seen
124 * CLOSE: closed connection (RST)
125 *
126 * Packets marked as IGNORED (sIG):
127 * if they may be either invalid or valid
128 * and the receiver may send back a connection
129 * closing RST or a SYN/ACK.
130 *
131 * Packets marked as INVALID (sIV):
132 * if we regard them as truly invalid packets
133 */
134 static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
135 {
136 /* ORIGINAL */
137 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
138 /*syn*/ { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sS2 },
139 /*
140 * sNO -> sSS Initialize a new connection
141 * sSS -> sSS Retransmitted SYN
142 * sS2 -> sS2 Late retransmitted SYN
143 * sSR -> sIG
144 * sES -> sIG Error: SYNs in window outside the SYN_SENT state
145 * are errors. Receiver will reply with RST
146 * and close the connection.
147 * Or we are not in sync and hold a dead connection.
148 * sFW -> sIG
149 * sCW -> sIG
150 * sLA -> sIG
151 * sTW -> sSS Reopened connection (RFC 1122).
152 * sCL -> sSS
153 */
154 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
155 /*synack*/ { sIV, sIV, sSR, sIV, sIV, sIV, sIV, sIV, sIV, sSR },
156 /*
157 * sNO -> sIV Too late and no reason to do anything
158 * sSS -> sIV Client can't send SYN and then SYN/ACK
159 * sS2 -> sSR SYN/ACK sent to SYN2 in simultaneous open
160 * sSR -> sSR Late retransmitted SYN/ACK in simultaneous open
161 * sES -> sIV Invalid SYN/ACK packets sent by the client
162 * sFW -> sIV
163 * sCW -> sIV
164 * sLA -> sIV
165 * sTW -> sIV
166 * sCL -> sIV
167 */
168 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
169 /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
170 /*
171 * sNO -> sIV Too late and no reason to do anything...
172 * sSS -> sIV Client migth not send FIN in this state:
173 * we enforce waiting for a SYN/ACK reply first.
174 * sS2 -> sIV
175 * sSR -> sFW Close started.
176 * sES -> sFW
177 * sFW -> sLA FIN seen in both directions, waiting for
178 * the last ACK.
179 * Migth be a retransmitted FIN as well...
180 * sCW -> sLA
181 * sLA -> sLA Retransmitted FIN. Remain in the same state.
182 * sTW -> sTW
183 * sCL -> sCL
184 */
185 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
186 /*ack*/ { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
187 /*
188 * sNO -> sES Assumed.
189 * sSS -> sIV ACK is invalid: we haven't seen a SYN/ACK yet.
190 * sS2 -> sIV
191 * sSR -> sES Established state is reached.
192 * sES -> sES :-)
193 * sFW -> sCW Normal close request answered by ACK.
194 * sCW -> sCW
195 * sLA -> sTW Last ACK detected (RFC5961 challenged)
196 * sTW -> sTW Retransmitted last ACK. Remain in the same state.
197 * sCL -> sCL
198 */
199 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
200 /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL },
201 /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
202 },
203 {
204 /* REPLY */
205 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
206 /*syn*/ { sIV, sS2, sIV, sIV, sIV, sIV, sIV, sSS, sIV, sS2 },
207 /*
208 * sNO -> sIV Never reached.
209 * sSS -> sS2 Simultaneous open
210 * sS2 -> sS2 Retransmitted simultaneous SYN
211 * sSR -> sIV Invalid SYN packets sent by the server
212 * sES -> sIV
213 * sFW -> sIV
214 * sCW -> sIV
215 * sLA -> sIV
216 * sTW -> sSS Reopened connection, but server may have switched role
217 * sCL -> sIV
218 */
219 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
220 /*synack*/ { sIV, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIG, sSR },
221 /*
222 * sSS -> sSR Standard open.
223 * sS2 -> sSR Simultaneous open
224 * sSR -> sIG Retransmitted SYN/ACK, ignore it.
225 * sES -> sIG Late retransmitted SYN/ACK?
226 * sFW -> sIG Might be SYN/ACK answering ignored SYN
227 * sCW -> sIG
228 * sLA -> sIG
229 * sTW -> sIG
230 * sCL -> sIG
231 */
232 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
233 /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
234 /*
235 * sSS -> sIV Server might not send FIN in this state.
236 * sS2 -> sIV
237 * sSR -> sFW Close started.
238 * sES -> sFW
239 * sFW -> sLA FIN seen in both directions.
240 * sCW -> sLA
241 * sLA -> sLA Retransmitted FIN.
242 * sTW -> sTW
243 * sCL -> sCL
244 */
245 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
246 /*ack*/ { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIG },
247 /*
248 * sSS -> sIG Might be a half-open connection.
249 * sS2 -> sIG
250 * sSR -> sSR Might answer late resent SYN.
251 * sES -> sES :-)
252 * sFW -> sCW Normal close request answered by ACK.
253 * sCW -> sCW
254 * sLA -> sTW Last ACK detected (RFC5961 challenged)
255 * sTW -> sTW Retransmitted last ACK.
256 * sCL -> sCL
257 */
258 /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */
259 /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL },
260 /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
261 }
262 };
263
264 #ifdef CONFIG_NF_CONNTRACK_PROCFS
265 /* Print out the private part of the conntrack. */
tcp_print_conntrack(struct seq_file * s,struct nf_conn * ct)266 static void tcp_print_conntrack(struct seq_file *s, struct nf_conn *ct)
267 {
268 if (test_bit(IPS_OFFLOAD_BIT, &ct->status))
269 return;
270
271 seq_printf(s, "%s ", tcp_conntrack_names[ct->proto.tcp.state]);
272 }
273 #endif
274
get_conntrack_index(const struct tcphdr * tcph)275 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
276 {
277 if (tcph->rst) return TCP_RST_SET;
278 else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
279 else if (tcph->fin) return TCP_FIN_SET;
280 else if (tcph->ack) return TCP_ACK_SET;
281 else return TCP_NONE_SET;
282 }
283
284 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
285 in IP Filter' by Guido van Rooij.
286
287 http://www.sane.nl/events/sane2000/papers.html
288 http://www.darkart.com/mirrors/www.obfuscation.org/ipf/
289
290 The boundaries and the conditions are changed according to RFC793:
291 the packet must intersect the window (i.e. segments may be
292 after the right or before the left edge) and thus receivers may ACK
293 segments after the right edge of the window.
294
295 td_maxend = max(sack + max(win,1)) seen in reply packets
296 td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
297 td_maxwin += seq + len - sender.td_maxend
298 if seq + len > sender.td_maxend
299 td_end = max(seq + len) seen in sent packets
300
301 I. Upper bound for valid data: seq <= sender.td_maxend
302 II. Lower bound for valid data: seq + len >= sender.td_end - receiver.td_maxwin
303 III. Upper bound for valid (s)ack: sack <= receiver.td_end
304 IV. Lower bound for valid (s)ack: sack >= receiver.td_end - MAXACKWINDOW
305
306 where sack is the highest right edge of sack block found in the packet
307 or ack in the case of packet without SACK option.
308
309 The upper bound limit for a valid (s)ack is not ignored -
310 we doesn't have to deal with fragments.
311 */
312
segment_seq_plus_len(__u32 seq,size_t len,unsigned int dataoff,const struct tcphdr * tcph)313 static inline __u32 segment_seq_plus_len(__u32 seq,
314 size_t len,
315 unsigned int dataoff,
316 const struct tcphdr *tcph)
317 {
318 /* XXX Should I use payload length field in IP/IPv6 header ?
319 * - YK */
320 return (seq + len - dataoff - tcph->doff*4
321 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
322 }
323
324 /* Fixme: what about big packets? */
325 #define MAXACKWINCONST 66000
326 #define MAXACKWINDOW(sender) \
327 ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin \
328 : MAXACKWINCONST)
329
330 /*
331 * Simplified tcp_parse_options routine from tcp_input.c
332 */
tcp_options(const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * tcph,struct ip_ct_tcp_state * state)333 static void tcp_options(const struct sk_buff *skb,
334 unsigned int dataoff,
335 const struct tcphdr *tcph,
336 struct ip_ct_tcp_state *state)
337 {
338 unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
339 const unsigned char *ptr;
340 int length = (tcph->doff*4) - sizeof(struct tcphdr);
341
342 if (!length)
343 return;
344
345 ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
346 length, buff);
347 if (!ptr)
348 return;
349
350 state->td_scale = 0;
351 state->flags &= IP_CT_TCP_FLAG_BE_LIBERAL;
352
353 while (length > 0) {
354 int opcode=*ptr++;
355 int opsize;
356
357 switch (opcode) {
358 case TCPOPT_EOL:
359 return;
360 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
361 length--;
362 continue;
363 default:
364 if (length < 2)
365 return;
366 opsize=*ptr++;
367 if (opsize < 2) /* "silly options" */
368 return;
369 if (opsize > length)
370 return; /* don't parse partial options */
371
372 if (opcode == TCPOPT_SACK_PERM
373 && opsize == TCPOLEN_SACK_PERM)
374 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
375 else if (opcode == TCPOPT_WINDOW
376 && opsize == TCPOLEN_WINDOW) {
377 state->td_scale = *(u_int8_t *)ptr;
378
379 if (state->td_scale > TCP_MAX_WSCALE)
380 state->td_scale = TCP_MAX_WSCALE;
381
382 state->flags |=
383 IP_CT_TCP_FLAG_WINDOW_SCALE;
384 }
385 ptr += opsize - 2;
386 length -= opsize;
387 }
388 }
389 }
390
tcp_sack(const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * tcph,__u32 * sack)391 static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
392 const struct tcphdr *tcph, __u32 *sack)
393 {
394 unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
395 const unsigned char *ptr;
396 int length = (tcph->doff*4) - sizeof(struct tcphdr);
397 __u32 tmp;
398
399 if (!length)
400 return;
401
402 ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
403 length, buff);
404 if (!ptr)
405 return;
406
407 /* Fast path for timestamp-only option */
408 if (length == TCPOLEN_TSTAMP_ALIGNED
409 && *(__be32 *)ptr == htonl((TCPOPT_NOP << 24)
410 | (TCPOPT_NOP << 16)
411 | (TCPOPT_TIMESTAMP << 8)
412 | TCPOLEN_TIMESTAMP))
413 return;
414
415 while (length > 0) {
416 int opcode = *ptr++;
417 int opsize, i;
418
419 switch (opcode) {
420 case TCPOPT_EOL:
421 return;
422 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
423 length--;
424 continue;
425 default:
426 if (length < 2)
427 return;
428 opsize = *ptr++;
429 if (opsize < 2) /* "silly options" */
430 return;
431 if (opsize > length)
432 return; /* don't parse partial options */
433
434 if (opcode == TCPOPT_SACK
435 && opsize >= (TCPOLEN_SACK_BASE
436 + TCPOLEN_SACK_PERBLOCK)
437 && !((opsize - TCPOLEN_SACK_BASE)
438 % TCPOLEN_SACK_PERBLOCK)) {
439 for (i = 0;
440 i < (opsize - TCPOLEN_SACK_BASE);
441 i += TCPOLEN_SACK_PERBLOCK) {
442 tmp = get_unaligned_be32((__be32 *)(ptr+i)+1);
443
444 if (after(tmp, *sack))
445 *sack = tmp;
446 }
447 return;
448 }
449 ptr += opsize - 2;
450 length -= opsize;
451 }
452 }
453 }
454
tcp_init_sender(struct ip_ct_tcp_state * sender,struct ip_ct_tcp_state * receiver,const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * tcph,u32 end,u32 win,enum ip_conntrack_dir dir)455 static void tcp_init_sender(struct ip_ct_tcp_state *sender,
456 struct ip_ct_tcp_state *receiver,
457 const struct sk_buff *skb,
458 unsigned int dataoff,
459 const struct tcphdr *tcph,
460 u32 end, u32 win,
461 enum ip_conntrack_dir dir)
462 {
463 /* SYN-ACK in reply to a SYN
464 * or SYN from reply direction in simultaneous open.
465 */
466 sender->td_end =
467 sender->td_maxend = end;
468 sender->td_maxwin = (win == 0 ? 1 : win);
469
470 tcp_options(skb, dataoff, tcph, sender);
471 /* RFC 1323:
472 * Both sides must send the Window Scale option
473 * to enable window scaling in either direction.
474 */
475 if (dir == IP_CT_DIR_REPLY &&
476 !(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE &&
477 receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE)) {
478 sender->td_scale = 0;
479 receiver->td_scale = 0;
480 }
481 }
482
483 __printf(6, 7)
nf_tcp_log_invalid(const struct sk_buff * skb,const struct nf_conn * ct,const struct nf_hook_state * state,const struct ip_ct_tcp_state * sender,enum nf_ct_tcp_action ret,const char * fmt,...)484 static enum nf_ct_tcp_action nf_tcp_log_invalid(const struct sk_buff *skb,
485 const struct nf_conn *ct,
486 const struct nf_hook_state *state,
487 const struct ip_ct_tcp_state *sender,
488 enum nf_ct_tcp_action ret,
489 const char *fmt, ...)
490 {
491 const struct nf_tcp_net *tn = nf_tcp_pernet(nf_ct_net(ct));
492 struct va_format vaf;
493 va_list args;
494 bool be_liberal;
495
496 be_liberal = sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL || tn->tcp_be_liberal;
497 if (be_liberal)
498 return NFCT_TCP_ACCEPT;
499
500 va_start(args, fmt);
501 vaf.fmt = fmt;
502 vaf.va = &args;
503 nf_ct_l4proto_log_invalid(skb, ct, state, "%pV", &vaf);
504 va_end(args);
505
506 return ret;
507 }
508
509 static enum nf_ct_tcp_action
tcp_in_window(struct nf_conn * ct,enum ip_conntrack_dir dir,unsigned int index,const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * tcph,const struct nf_hook_state * hook_state)510 tcp_in_window(struct nf_conn *ct, enum ip_conntrack_dir dir,
511 unsigned int index, const struct sk_buff *skb,
512 unsigned int dataoff, const struct tcphdr *tcph,
513 const struct nf_hook_state *hook_state)
514 {
515 struct ip_ct_tcp *state = &ct->proto.tcp;
516 struct ip_ct_tcp_state *sender = &state->seen[dir];
517 struct ip_ct_tcp_state *receiver = &state->seen[!dir];
518 __u32 seq, ack, sack, end, win, swin;
519 bool in_recv_win, seq_ok;
520 s32 receiver_offset;
521 u16 win_raw;
522
523 /*
524 * Get the required data from the packet.
525 */
526 seq = ntohl(tcph->seq);
527 ack = sack = ntohl(tcph->ack_seq);
528 win_raw = ntohs(tcph->window);
529 win = win_raw;
530 end = segment_seq_plus_len(seq, skb->len, dataoff, tcph);
531
532 if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
533 tcp_sack(skb, dataoff, tcph, &sack);
534
535 /* Take into account NAT sequence number mangling */
536 receiver_offset = nf_ct_seq_offset(ct, !dir, ack - 1);
537 ack -= receiver_offset;
538 sack -= receiver_offset;
539
540 if (sender->td_maxwin == 0) {
541 /*
542 * Initialize sender data.
543 */
544 if (tcph->syn) {
545 tcp_init_sender(sender, receiver,
546 skb, dataoff, tcph,
547 end, win, dir);
548 if (!tcph->ack)
549 /* Simultaneous open */
550 return NFCT_TCP_ACCEPT;
551 } else {
552 /*
553 * We are in the middle of a connection,
554 * its history is lost for us.
555 * Let's try to use the data from the packet.
556 */
557 sender->td_end = end;
558 swin = win << sender->td_scale;
559 sender->td_maxwin = (swin == 0 ? 1 : swin);
560 sender->td_maxend = end + sender->td_maxwin;
561 if (receiver->td_maxwin == 0) {
562 /* We haven't seen traffic in the other
563 * direction yet but we have to tweak window
564 * tracking to pass III and IV until that
565 * happens.
566 */
567 receiver->td_end = receiver->td_maxend = sack;
568 } else if (sack == receiver->td_end + 1) {
569 /* Likely a reply to a keepalive.
570 * Needed for III.
571 */
572 receiver->td_end++;
573 }
574
575 }
576 } else if (tcph->syn &&
577 after(end, sender->td_end) &&
578 (state->state == TCP_CONNTRACK_SYN_SENT ||
579 state->state == TCP_CONNTRACK_SYN_RECV)) {
580 /*
581 * RFC 793: "if a TCP is reinitialized ... then it need
582 * not wait at all; it must only be sure to use sequence
583 * numbers larger than those recently used."
584 *
585 * Re-init state for this direction, just like for the first
586 * syn(-ack) reply, it might differ in seq, ack or tcp options.
587 */
588 tcp_init_sender(sender, receiver,
589 skb, dataoff, tcph,
590 end, win, dir);
591
592 if (dir == IP_CT_DIR_REPLY && !tcph->ack)
593 return NFCT_TCP_ACCEPT;
594 }
595
596 if (!(tcph->ack)) {
597 /*
598 * If there is no ACK, just pretend it was set and OK.
599 */
600 ack = sack = receiver->td_end;
601 } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
602 (TCP_FLAG_ACK|TCP_FLAG_RST))
603 && (ack == 0)) {
604 /*
605 * Broken TCP stacks, that set ACK in RST packets as well
606 * with zero ack value.
607 */
608 ack = sack = receiver->td_end;
609 }
610
611 if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)
612 /*
613 * RST sent answering SYN.
614 */
615 seq = end = sender->td_end;
616
617 seq_ok = before(seq, sender->td_maxend + 1);
618 if (!seq_ok) {
619 u32 overshot = end - sender->td_maxend + 1;
620 bool ack_ok;
621
622 ack_ok = after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1);
623 in_recv_win = receiver->td_maxwin &&
624 after(end, sender->td_end - receiver->td_maxwin - 1);
625
626 if (in_recv_win &&
627 ack_ok &&
628 overshot <= receiver->td_maxwin &&
629 before(sack, receiver->td_end + 1)) {
630 /* Work around TCPs that send more bytes than allowed by
631 * the receive window.
632 *
633 * If the (marked as invalid) packet is allowed to pass by
634 * the ruleset and the peer acks this data, then its possible
635 * all future packets will trigger 'ACK is over upper bound' check.
636 *
637 * Thus if only the sequence check fails then do update td_end so
638 * possible ACK for this data can update internal state.
639 */
640 sender->td_end = end;
641 sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
642
643 return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE,
644 "%u bytes more than expected", overshot);
645 }
646
647 return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_INVALID,
648 "SEQ is over upper bound %u (over the window of the receiver)",
649 sender->td_maxend + 1);
650 }
651
652 if (!before(sack, receiver->td_end + 1))
653 return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_INVALID,
654 "ACK is over upper bound %u (ACKed data not seen yet)",
655 receiver->td_end + 1);
656
657 /* Is the ending sequence in the receive window (if available)? */
658 in_recv_win = !receiver->td_maxwin ||
659 after(end, sender->td_end - receiver->td_maxwin - 1);
660 if (!in_recv_win)
661 return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE,
662 "SEQ is under lower bound %u (already ACKed data retransmitted)",
663 sender->td_end - receiver->td_maxwin - 1);
664 if (!after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1))
665 return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE,
666 "ignored ACK under lower bound %u (possible overly delayed)",
667 receiver->td_end - MAXACKWINDOW(sender) - 1);
668
669 /* Take into account window scaling (RFC 1323). */
670 if (!tcph->syn)
671 win <<= sender->td_scale;
672
673 /* Update sender data. */
674 swin = win + (sack - ack);
675 if (sender->td_maxwin < swin)
676 sender->td_maxwin = swin;
677 if (after(end, sender->td_end)) {
678 sender->td_end = end;
679 sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
680 }
681 if (tcph->ack) {
682 if (!(sender->flags & IP_CT_TCP_FLAG_MAXACK_SET)) {
683 sender->td_maxack = ack;
684 sender->flags |= IP_CT_TCP_FLAG_MAXACK_SET;
685 } else if (after(ack, sender->td_maxack)) {
686 sender->td_maxack = ack;
687 }
688 }
689
690 /* Update receiver data. */
691 if (receiver->td_maxwin != 0 && after(end, sender->td_maxend))
692 receiver->td_maxwin += end - sender->td_maxend;
693 if (after(sack + win, receiver->td_maxend - 1)) {
694 receiver->td_maxend = sack + win;
695 if (win == 0)
696 receiver->td_maxend++;
697 }
698 if (ack == receiver->td_end)
699 receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
700
701 /* Check retransmissions. */
702 if (index == TCP_ACK_SET) {
703 if (state->last_dir == dir &&
704 state->last_seq == seq &&
705 state->last_ack == ack &&
706 state->last_end == end &&
707 state->last_win == win_raw) {
708 state->retrans++;
709 } else {
710 state->last_dir = dir;
711 state->last_seq = seq;
712 state->last_ack = ack;
713 state->last_end = end;
714 state->last_win = win_raw;
715 state->retrans = 0;
716 }
717 }
718
719 return NFCT_TCP_ACCEPT;
720 }
721
nf_tcp_handle_invalid(struct nf_conn * ct,enum ip_conntrack_dir dir,int index,const struct sk_buff * skb,const struct nf_hook_state * hook_state)722 static void __cold nf_tcp_handle_invalid(struct nf_conn *ct,
723 enum ip_conntrack_dir dir,
724 int index,
725 const struct sk_buff *skb,
726 const struct nf_hook_state *hook_state)
727 {
728 const unsigned int *timeouts;
729 const struct nf_tcp_net *tn;
730 unsigned int timeout;
731 u32 expires;
732
733 if (!test_bit(IPS_ASSURED_BIT, &ct->status) ||
734 test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status))
735 return;
736
737 /* We don't want to have connections hanging around in ESTABLISHED
738 * state for long time 'just because' conntrack deemed a FIN/RST
739 * out-of-window.
740 *
741 * Shrink the timeout just like when there is unacked data.
742 * This speeds up eviction of 'dead' connections where the
743 * connection and conntracks internal state are out of sync.
744 */
745 switch (index) {
746 case TCP_RST_SET:
747 case TCP_FIN_SET:
748 break;
749 default:
750 return;
751 }
752
753 if (ct->proto.tcp.last_dir != dir &&
754 (ct->proto.tcp.last_index == TCP_FIN_SET ||
755 ct->proto.tcp.last_index == TCP_RST_SET)) {
756 expires = nf_ct_expires(ct);
757 if (expires < 120 * HZ)
758 return;
759
760 tn = nf_tcp_pernet(nf_ct_net(ct));
761 timeouts = nf_ct_timeout_lookup(ct);
762 if (!timeouts)
763 timeouts = tn->timeouts;
764
765 timeout = READ_ONCE(timeouts[TCP_CONNTRACK_UNACK]);
766 if (expires > timeout) {
767 nf_ct_l4proto_log_invalid(skb, ct, hook_state,
768 "packet (index %d, dir %d) response for index %d lower timeout to %u",
769 index, dir, ct->proto.tcp.last_index, timeout);
770
771 WRITE_ONCE(ct->timeout, timeout + nfct_time_stamp);
772 }
773 } else {
774 ct->proto.tcp.last_index = index;
775 ct->proto.tcp.last_dir = dir;
776 }
777 }
778
779 /* table of valid flag combinations - PUSH, ECE and CWR are always valid */
780 static const u8 tcp_valid_flags[(TCPHDR_FIN|TCPHDR_SYN|TCPHDR_RST|TCPHDR_ACK|
781 TCPHDR_URG) + 1] =
782 {
783 [TCPHDR_SYN] = 1,
784 [TCPHDR_SYN|TCPHDR_URG] = 1,
785 [TCPHDR_SYN|TCPHDR_ACK] = 1,
786 [TCPHDR_RST] = 1,
787 [TCPHDR_RST|TCPHDR_ACK] = 1,
788 [TCPHDR_FIN|TCPHDR_ACK] = 1,
789 [TCPHDR_FIN|TCPHDR_ACK|TCPHDR_URG] = 1,
790 [TCPHDR_ACK] = 1,
791 [TCPHDR_ACK|TCPHDR_URG] = 1,
792 };
793
tcp_error_log(const struct sk_buff * skb,const struct nf_hook_state * state,const char * msg)794 static void tcp_error_log(const struct sk_buff *skb,
795 const struct nf_hook_state *state,
796 const char *msg)
797 {
798 nf_l4proto_log_invalid(skb, state, IPPROTO_TCP, "%s", msg);
799 }
800
801 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c. */
tcp_error(const struct tcphdr * th,struct sk_buff * skb,unsigned int dataoff,const struct nf_hook_state * state)802 static bool tcp_error(const struct tcphdr *th,
803 struct sk_buff *skb,
804 unsigned int dataoff,
805 const struct nf_hook_state *state)
806 {
807 unsigned int tcplen = skb->len - dataoff;
808 u8 tcpflags;
809
810 /* Not whole TCP header or malformed packet */
811 if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
812 tcp_error_log(skb, state, "truncated packet");
813 return true;
814 }
815
816 /* Checksum invalid? Ignore.
817 * We skip checking packets on the outgoing path
818 * because the checksum is assumed to be correct.
819 */
820 /* FIXME: Source route IP option packets --RR */
821 if (state->net->ct.sysctl_checksum &&
822 state->hook == NF_INET_PRE_ROUTING &&
823 nf_checksum(skb, state->hook, dataoff, IPPROTO_TCP, state->pf)) {
824 tcp_error_log(skb, state, "bad checksum");
825 return true;
826 }
827
828 /* Check TCP flags. */
829 tcpflags = (tcp_flag_byte(th) & ~(TCPHDR_ECE|TCPHDR_CWR|TCPHDR_PSH));
830 if (!tcp_valid_flags[tcpflags]) {
831 tcp_error_log(skb, state, "invalid tcp flag combination");
832 return true;
833 }
834
835 return false;
836 }
837
tcp_new(struct nf_conn * ct,const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * th)838 static noinline bool tcp_new(struct nf_conn *ct, const struct sk_buff *skb,
839 unsigned int dataoff,
840 const struct tcphdr *th)
841 {
842 enum tcp_conntrack new_state;
843 struct net *net = nf_ct_net(ct);
844 const struct nf_tcp_net *tn = nf_tcp_pernet(net);
845
846 /* Don't need lock here: this conntrack not in circulation yet */
847 new_state = tcp_conntracks[0][get_conntrack_index(th)][TCP_CONNTRACK_NONE];
848
849 /* Invalid: delete conntrack */
850 if (new_state >= TCP_CONNTRACK_MAX) {
851 pr_debug("nf_ct_tcp: invalid new deleting.\n");
852 return false;
853 }
854
855 if (new_state == TCP_CONNTRACK_SYN_SENT) {
856 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
857 /* SYN packet */
858 ct->proto.tcp.seen[0].td_end =
859 segment_seq_plus_len(ntohl(th->seq), skb->len,
860 dataoff, th);
861 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
862 if (ct->proto.tcp.seen[0].td_maxwin == 0)
863 ct->proto.tcp.seen[0].td_maxwin = 1;
864 ct->proto.tcp.seen[0].td_maxend =
865 ct->proto.tcp.seen[0].td_end;
866
867 tcp_options(skb, dataoff, th, &ct->proto.tcp.seen[0]);
868 } else if (tn->tcp_loose == 0) {
869 /* Don't try to pick up connections. */
870 return false;
871 } else {
872 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
873 /*
874 * We are in the middle of a connection,
875 * its history is lost for us.
876 * Let's try to use the data from the packet.
877 */
878 ct->proto.tcp.seen[0].td_end =
879 segment_seq_plus_len(ntohl(th->seq), skb->len,
880 dataoff, th);
881 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
882 if (ct->proto.tcp.seen[0].td_maxwin == 0)
883 ct->proto.tcp.seen[0].td_maxwin = 1;
884 ct->proto.tcp.seen[0].td_maxend =
885 ct->proto.tcp.seen[0].td_end +
886 ct->proto.tcp.seen[0].td_maxwin;
887
888 /* We assume SACK and liberal window checking to handle
889 * window scaling */
890 ct->proto.tcp.seen[0].flags =
891 ct->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM |
892 IP_CT_TCP_FLAG_BE_LIBERAL;
893 }
894
895 /* tcp_packet will set them */
896 ct->proto.tcp.last_index = TCP_NONE_SET;
897 return true;
898 }
899
tcp_can_early_drop(const struct nf_conn * ct)900 static bool tcp_can_early_drop(const struct nf_conn *ct)
901 {
902 switch (ct->proto.tcp.state) {
903 case TCP_CONNTRACK_FIN_WAIT:
904 case TCP_CONNTRACK_LAST_ACK:
905 case TCP_CONNTRACK_TIME_WAIT:
906 case TCP_CONNTRACK_CLOSE:
907 case TCP_CONNTRACK_CLOSE_WAIT:
908 return true;
909 default:
910 break;
911 }
912
913 return false;
914 }
915
nf_conntrack_tcp_set_closing(struct nf_conn * ct)916 void nf_conntrack_tcp_set_closing(struct nf_conn *ct)
917 {
918 enum tcp_conntrack old_state;
919 const unsigned int *timeouts;
920 u32 timeout;
921
922 if (!nf_ct_is_confirmed(ct))
923 return;
924
925 spin_lock_bh(&ct->lock);
926 old_state = ct->proto.tcp.state;
927 ct->proto.tcp.state = TCP_CONNTRACK_CLOSE;
928
929 if (old_state == TCP_CONNTRACK_CLOSE ||
930 test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status)) {
931 spin_unlock_bh(&ct->lock);
932 return;
933 }
934
935 timeouts = nf_ct_timeout_lookup(ct);
936 if (!timeouts) {
937 const struct nf_tcp_net *tn;
938
939 tn = nf_tcp_pernet(nf_ct_net(ct));
940 timeouts = tn->timeouts;
941 }
942
943 timeout = timeouts[TCP_CONNTRACK_CLOSE];
944 WRITE_ONCE(ct->timeout, timeout + nfct_time_stamp);
945
946 spin_unlock_bh(&ct->lock);
947
948 nf_conntrack_event_cache(IPCT_PROTOINFO, ct);
949 }
950
nf_ct_tcp_state_reset(struct ip_ct_tcp_state * state)951 static void nf_ct_tcp_state_reset(struct ip_ct_tcp_state *state)
952 {
953 state->td_end = 0;
954 state->td_maxend = 0;
955 state->td_maxwin = 0;
956 state->td_maxack = 0;
957 state->td_scale = 0;
958 state->flags &= IP_CT_TCP_FLAG_BE_LIBERAL;
959 }
960
961 /* Returns verdict for packet, or -1 for invalid. */
nf_conntrack_tcp_packet(struct nf_conn * ct,struct sk_buff * skb,unsigned int dataoff,enum ip_conntrack_info ctinfo,const struct nf_hook_state * state)962 int nf_conntrack_tcp_packet(struct nf_conn *ct,
963 struct sk_buff *skb,
964 unsigned int dataoff,
965 enum ip_conntrack_info ctinfo,
966 const struct nf_hook_state *state)
967 {
968 struct net *net = nf_ct_net(ct);
969 struct nf_tcp_net *tn = nf_tcp_pernet(net);
970 enum tcp_conntrack new_state, old_state;
971 unsigned int index, *timeouts;
972 enum nf_ct_tcp_action res;
973 enum ip_conntrack_dir dir;
974 const struct tcphdr *th;
975 struct tcphdr _tcph;
976 unsigned long timeout;
977
978 th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
979 if (th == NULL)
980 return -NF_ACCEPT;
981
982 if (tcp_error(th, skb, dataoff, state))
983 return -NF_ACCEPT;
984
985 if (!nf_ct_is_confirmed(ct) && !tcp_new(ct, skb, dataoff, th))
986 return -NF_ACCEPT;
987
988 spin_lock_bh(&ct->lock);
989 old_state = ct->proto.tcp.state;
990 dir = CTINFO2DIR(ctinfo);
991 index = get_conntrack_index(th);
992 new_state = tcp_conntracks[dir][index][old_state];
993
994 switch (new_state) {
995 case TCP_CONNTRACK_SYN_SENT:
996 if (old_state < TCP_CONNTRACK_TIME_WAIT)
997 break;
998 /* RFC 1122: "When a connection is closed actively,
999 * it MUST linger in TIME-WAIT state for a time 2xMSL
1000 * (Maximum Segment Lifetime). However, it MAY accept
1001 * a new SYN from the remote TCP to reopen the connection
1002 * directly from TIME-WAIT state, if..."
1003 * We ignore the conditions because we are in the
1004 * TIME-WAIT state anyway.
1005 *
1006 * Handle aborted connections: we and the server
1007 * think there is an existing connection but the client
1008 * aborts it and starts a new one.
1009 */
1010 if (((ct->proto.tcp.seen[dir].flags
1011 | ct->proto.tcp.seen[!dir].flags)
1012 & IP_CT_TCP_FLAG_CLOSE_INIT)
1013 || (ct->proto.tcp.last_dir == dir
1014 && ct->proto.tcp.last_index == TCP_RST_SET)) {
1015 /* Attempt to reopen a closed/aborted connection.
1016 * Delete this connection and look up again. */
1017 spin_unlock_bh(&ct->lock);
1018
1019 /* Only repeat if we can actually remove the timer.
1020 * Destruction may already be in progress in process
1021 * context and we must give it a chance to terminate.
1022 */
1023 if (nf_ct_kill(ct))
1024 return -NF_REPEAT;
1025 return NF_DROP;
1026 }
1027 fallthrough;
1028 case TCP_CONNTRACK_IGNORE:
1029 /* Ignored packets:
1030 *
1031 * Our connection entry may be out of sync, so ignore
1032 * packets which may signal the real connection between
1033 * the client and the server.
1034 *
1035 * a) SYN in ORIGINAL
1036 * b) SYN/ACK in REPLY
1037 * c) ACK in reply direction after initial SYN in original.
1038 *
1039 * If the ignored packet is invalid, the receiver will send
1040 * a RST we'll catch below.
1041 */
1042 if (index == TCP_SYNACK_SET
1043 && ct->proto.tcp.last_index == TCP_SYN_SET
1044 && ct->proto.tcp.last_dir != dir
1045 && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
1046 /* b) This SYN/ACK acknowledges a SYN that we earlier
1047 * ignored as invalid. This means that the client and
1048 * the server are both in sync, while the firewall is
1049 * not. We get in sync from the previously annotated
1050 * values.
1051 */
1052 old_state = TCP_CONNTRACK_SYN_SENT;
1053 new_state = TCP_CONNTRACK_SYN_RECV;
1054 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end =
1055 ct->proto.tcp.last_end;
1056 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend =
1057 ct->proto.tcp.last_end;
1058 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin =
1059 ct->proto.tcp.last_win == 0 ?
1060 1 : ct->proto.tcp.last_win;
1061 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale =
1062 ct->proto.tcp.last_wscale;
1063 ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
1064 ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags =
1065 ct->proto.tcp.last_flags;
1066 nf_ct_tcp_state_reset(&ct->proto.tcp.seen[dir]);
1067 break;
1068 }
1069 ct->proto.tcp.last_index = index;
1070 ct->proto.tcp.last_dir = dir;
1071 ct->proto.tcp.last_seq = ntohl(th->seq);
1072 ct->proto.tcp.last_end =
1073 segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
1074 ct->proto.tcp.last_win = ntohs(th->window);
1075
1076 /* a) This is a SYN in ORIGINAL. The client and the server
1077 * may be in sync but we are not. In that case, we annotate
1078 * the TCP options and let the packet go through. If it is a
1079 * valid SYN packet, the server will reply with a SYN/ACK, and
1080 * then we'll get in sync. Otherwise, the server potentially
1081 * responds with a challenge ACK if implementing RFC5961.
1082 */
1083 if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) {
1084 struct ip_ct_tcp_state seen = {};
1085
1086 ct->proto.tcp.last_flags =
1087 ct->proto.tcp.last_wscale = 0;
1088 tcp_options(skb, dataoff, th, &seen);
1089 if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
1090 ct->proto.tcp.last_flags |=
1091 IP_CT_TCP_FLAG_WINDOW_SCALE;
1092 ct->proto.tcp.last_wscale = seen.td_scale;
1093 }
1094 if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) {
1095 ct->proto.tcp.last_flags |=
1096 IP_CT_TCP_FLAG_SACK_PERM;
1097 }
1098 /* Mark the potential for RFC5961 challenge ACK,
1099 * this pose a special problem for LAST_ACK state
1100 * as ACK is intrepretated as ACKing last FIN.
1101 */
1102 if (old_state == TCP_CONNTRACK_LAST_ACK)
1103 ct->proto.tcp.last_flags |=
1104 IP_CT_EXP_CHALLENGE_ACK;
1105 }
1106
1107 /* possible challenge ack reply to syn */
1108 if (old_state == TCP_CONNTRACK_SYN_SENT &&
1109 index == TCP_ACK_SET &&
1110 dir == IP_CT_DIR_REPLY)
1111 ct->proto.tcp.last_ack = ntohl(th->ack_seq);
1112
1113 spin_unlock_bh(&ct->lock);
1114 nf_ct_l4proto_log_invalid(skb, ct, state,
1115 "packet (index %d) in dir %d ignored, state %s",
1116 index, dir,
1117 tcp_conntrack_names[old_state]);
1118 return NF_ACCEPT;
1119 case TCP_CONNTRACK_MAX:
1120 /* Special case for SYN proxy: when the SYN to the server or
1121 * the SYN/ACK from the server is lost, the client may transmit
1122 * a keep-alive packet while in SYN_SENT state. This needs to
1123 * be associated with the original conntrack entry in order to
1124 * generate a new SYN with the correct sequence number.
1125 */
1126 if (nfct_synproxy(ct) && old_state == TCP_CONNTRACK_SYN_SENT &&
1127 index == TCP_ACK_SET && dir == IP_CT_DIR_ORIGINAL &&
1128 ct->proto.tcp.last_dir == IP_CT_DIR_ORIGINAL &&
1129 ct->proto.tcp.seen[dir].td_end - 1 == ntohl(th->seq)) {
1130 pr_debug("nf_ct_tcp: SYN proxy client keep alive\n");
1131 spin_unlock_bh(&ct->lock);
1132 return NF_ACCEPT;
1133 }
1134
1135 /* Invalid packet */
1136 spin_unlock_bh(&ct->lock);
1137 nf_ct_l4proto_log_invalid(skb, ct, state,
1138 "packet (index %d) in dir %d invalid, state %s",
1139 index, dir,
1140 tcp_conntrack_names[old_state]);
1141 return -NF_ACCEPT;
1142 case TCP_CONNTRACK_TIME_WAIT:
1143 /* RFC5961 compliance cause stack to send "challenge-ACK"
1144 * e.g. in response to spurious SYNs. Conntrack MUST
1145 * not believe this ACK is acking last FIN.
1146 */
1147 if (old_state == TCP_CONNTRACK_LAST_ACK &&
1148 index == TCP_ACK_SET &&
1149 ct->proto.tcp.last_dir != dir &&
1150 ct->proto.tcp.last_index == TCP_SYN_SET &&
1151 (ct->proto.tcp.last_flags & IP_CT_EXP_CHALLENGE_ACK)) {
1152 /* Detected RFC5961 challenge ACK */
1153 ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
1154 spin_unlock_bh(&ct->lock);
1155 nf_ct_l4proto_log_invalid(skb, ct, state, "challenge-ack ignored");
1156 return NF_ACCEPT; /* Don't change state */
1157 }
1158 break;
1159 case TCP_CONNTRACK_SYN_SENT2:
1160 /* tcp_conntracks table is not smart enough to handle
1161 * simultaneous open.
1162 */
1163 ct->proto.tcp.last_flags |= IP_CT_TCP_SIMULTANEOUS_OPEN;
1164 break;
1165 case TCP_CONNTRACK_SYN_RECV:
1166 if (dir == IP_CT_DIR_REPLY && index == TCP_ACK_SET &&
1167 ct->proto.tcp.last_flags & IP_CT_TCP_SIMULTANEOUS_OPEN)
1168 new_state = TCP_CONNTRACK_ESTABLISHED;
1169 break;
1170 case TCP_CONNTRACK_CLOSE:
1171 if (index != TCP_RST_SET)
1172 break;
1173
1174 /* If we are closing, tuple might have been re-used already.
1175 * last_index, last_ack, and all other ct fields used for
1176 * sequence/window validation are outdated in that case.
1177 *
1178 * As the conntrack can already be expired by GC under pressure,
1179 * just skip validation checks.
1180 */
1181 if (tcp_can_early_drop(ct))
1182 goto in_window;
1183
1184 /* td_maxack might be outdated if we let a SYN through earlier */
1185 if ((ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET) &&
1186 ct->proto.tcp.last_index != TCP_SYN_SET) {
1187 u32 seq = ntohl(th->seq);
1188
1189 /* If we are not in established state and SEQ=0 this is most
1190 * likely an answer to a SYN we let go through above (last_index
1191 * can be updated due to out-of-order ACKs).
1192 */
1193 if (seq == 0 && !nf_conntrack_tcp_established(ct))
1194 break;
1195
1196 if (before(seq, ct->proto.tcp.seen[!dir].td_maxack) &&
1197 !tn->tcp_ignore_invalid_rst) {
1198 /* Invalid RST */
1199 spin_unlock_bh(&ct->lock);
1200 nf_ct_l4proto_log_invalid(skb, ct, state, "invalid rst");
1201 return -NF_ACCEPT;
1202 }
1203
1204 if (!nf_conntrack_tcp_established(ct) ||
1205 seq == ct->proto.tcp.seen[!dir].td_maxack)
1206 break;
1207
1208 /* Check if rst is part of train, such as
1209 * foo:80 > bar:4379: P, 235946583:235946602(19) ack 42
1210 * foo:80 > bar:4379: R, 235946602:235946602(0) ack 42
1211 */
1212 if (ct->proto.tcp.last_index == TCP_ACK_SET &&
1213 ct->proto.tcp.last_dir == dir &&
1214 seq == ct->proto.tcp.last_end)
1215 break;
1216
1217 /* ... RST sequence number doesn't match exactly, keep
1218 * established state to allow a possible challenge ACK.
1219 */
1220 new_state = old_state;
1221 }
1222 if (((test_bit(IPS_SEEN_REPLY_BIT, &ct->status)
1223 && ct->proto.tcp.last_index == TCP_SYN_SET)
1224 || (!test_bit(IPS_ASSURED_BIT, &ct->status)
1225 && ct->proto.tcp.last_index == TCP_ACK_SET))
1226 && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
1227 /* RST sent to invalid SYN or ACK we had let through
1228 * at a) and c) above:
1229 *
1230 * a) SYN was in window then
1231 * c) we hold a half-open connection.
1232 *
1233 * Delete our connection entry.
1234 * We skip window checking, because packet might ACK
1235 * segments we ignored. */
1236 goto in_window;
1237 }
1238
1239 /* Reset in response to a challenge-ack we let through earlier */
1240 if (old_state == TCP_CONNTRACK_SYN_SENT &&
1241 ct->proto.tcp.last_index == TCP_ACK_SET &&
1242 ct->proto.tcp.last_dir == IP_CT_DIR_REPLY &&
1243 ntohl(th->seq) == ct->proto.tcp.last_ack)
1244 goto in_window;
1245
1246 break;
1247 default:
1248 /* Keep compilers happy. */
1249 break;
1250 }
1251
1252 res = tcp_in_window(ct, dir, index,
1253 skb, dataoff, th, state);
1254 switch (res) {
1255 case NFCT_TCP_IGNORE:
1256 spin_unlock_bh(&ct->lock);
1257 return NF_ACCEPT;
1258 case NFCT_TCP_INVALID:
1259 nf_tcp_handle_invalid(ct, dir, index, skb, state);
1260 spin_unlock_bh(&ct->lock);
1261 return -NF_ACCEPT;
1262 case NFCT_TCP_ACCEPT:
1263 break;
1264 }
1265 in_window:
1266 /* From now on we have got in-window packets */
1267 ct->proto.tcp.last_index = index;
1268 ct->proto.tcp.last_dir = dir;
1269
1270 ct->proto.tcp.state = new_state;
1271 if (old_state != new_state
1272 && new_state == TCP_CONNTRACK_FIN_WAIT)
1273 ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1274
1275 timeouts = nf_ct_timeout_lookup(ct);
1276 if (!timeouts)
1277 timeouts = tn->timeouts;
1278
1279 if (ct->proto.tcp.retrans >= tn->tcp_max_retrans &&
1280 timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1281 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1282 else if (unlikely(index == TCP_RST_SET))
1283 timeout = timeouts[TCP_CONNTRACK_CLOSE];
1284 else if ((ct->proto.tcp.seen[0].flags | ct->proto.tcp.seen[1].flags) &
1285 IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED &&
1286 timeouts[new_state] > timeouts[TCP_CONNTRACK_UNACK])
1287 timeout = timeouts[TCP_CONNTRACK_UNACK];
1288 else if (ct->proto.tcp.last_win == 0 &&
1289 timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1290 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1291 else
1292 timeout = timeouts[new_state];
1293 spin_unlock_bh(&ct->lock);
1294
1295 if (new_state != old_state)
1296 nf_conntrack_event_cache(IPCT_PROTOINFO, ct);
1297
1298 if (!test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
1299 /* If only reply is a RST, we can consider ourselves not to
1300 have an established connection: this is a fairly common
1301 problem case, so we can delete the conntrack
1302 immediately. --RR */
1303 if (th->rst) {
1304 nf_ct_kill_acct(ct, ctinfo, skb);
1305 return NF_ACCEPT;
1306 }
1307
1308 if (index == TCP_SYN_SET && old_state == TCP_CONNTRACK_SYN_SENT) {
1309 /* do not renew timeout on SYN retransmit.
1310 *
1311 * Else port reuse by client or NAT middlebox can keep
1312 * entry alive indefinitely (including nat info).
1313 */
1314 return NF_ACCEPT;
1315 }
1316
1317 /* ESTABLISHED without SEEN_REPLY, i.e. mid-connection
1318 * pickup with loose=1. Avoid large ESTABLISHED timeout.
1319 */
1320 if (new_state == TCP_CONNTRACK_ESTABLISHED &&
1321 timeout > timeouts[TCP_CONNTRACK_UNACK])
1322 timeout = timeouts[TCP_CONNTRACK_UNACK];
1323 } else if (!test_bit(IPS_ASSURED_BIT, &ct->status)
1324 && (old_state == TCP_CONNTRACK_SYN_RECV
1325 || old_state == TCP_CONNTRACK_ESTABLISHED)
1326 && new_state == TCP_CONNTRACK_ESTABLISHED) {
1327 /* Set ASSURED if we see valid ack in ESTABLISHED
1328 after SYN_RECV or a valid answer for a picked up
1329 connection. */
1330 set_bit(IPS_ASSURED_BIT, &ct->status);
1331 nf_conntrack_event_cache(IPCT_ASSURED, ct);
1332 }
1333 nf_ct_refresh_acct(ct, ctinfo, skb, timeout);
1334
1335 return NF_ACCEPT;
1336 }
1337
1338 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1339
1340 #include <linux/netfilter/nfnetlink.h>
1341 #include <linux/netfilter/nfnetlink_conntrack.h>
1342
tcp_to_nlattr(struct sk_buff * skb,struct nlattr * nla,struct nf_conn * ct,bool destroy)1343 static int tcp_to_nlattr(struct sk_buff *skb, struct nlattr *nla,
1344 struct nf_conn *ct, bool destroy)
1345 {
1346 struct nlattr *nest_parms;
1347 struct nf_ct_tcp_flags tmp = {};
1348
1349 spin_lock_bh(&ct->lock);
1350 nest_parms = nla_nest_start(skb, CTA_PROTOINFO_TCP);
1351 if (!nest_parms)
1352 goto nla_put_failure;
1353
1354 if (nla_put_u8(skb, CTA_PROTOINFO_TCP_STATE, ct->proto.tcp.state))
1355 goto nla_put_failure;
1356
1357 if (destroy)
1358 goto skip_state;
1359
1360 if (nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL,
1361 ct->proto.tcp.seen[0].td_scale) ||
1362 nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY,
1363 ct->proto.tcp.seen[1].td_scale))
1364 goto nla_put_failure;
1365
1366 tmp.flags = ct->proto.tcp.seen[0].flags;
1367 if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_ORIGINAL,
1368 sizeof(struct nf_ct_tcp_flags), &tmp))
1369 goto nla_put_failure;
1370
1371 tmp.flags = ct->proto.tcp.seen[1].flags;
1372 if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_REPLY,
1373 sizeof(struct nf_ct_tcp_flags), &tmp))
1374 goto nla_put_failure;
1375 skip_state:
1376 spin_unlock_bh(&ct->lock);
1377 nla_nest_end(skb, nest_parms);
1378
1379 return 0;
1380
1381 nla_put_failure:
1382 spin_unlock_bh(&ct->lock);
1383 return -1;
1384 }
1385
1386 static const struct nla_policy tcp_nla_policy[CTA_PROTOINFO_TCP_MAX+1] = {
1387 [CTA_PROTOINFO_TCP_STATE] = { .type = NLA_U8 },
1388 [CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] = { .type = NLA_U8 },
1389 [CTA_PROTOINFO_TCP_WSCALE_REPLY] = { .type = NLA_U8 },
1390 [CTA_PROTOINFO_TCP_FLAGS_ORIGINAL] = { .len = sizeof(struct nf_ct_tcp_flags) },
1391 [CTA_PROTOINFO_TCP_FLAGS_REPLY] = { .len = sizeof(struct nf_ct_tcp_flags) },
1392 };
1393
1394 #define TCP_NLATTR_SIZE ( \
1395 NLA_ALIGN(NLA_HDRLEN + 1) + \
1396 NLA_ALIGN(NLA_HDRLEN + 1) + \
1397 NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)) + \
1398 NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)))
1399
nlattr_to_tcp(struct nlattr * cda[],struct nf_conn * ct)1400 static int nlattr_to_tcp(struct nlattr *cda[], struct nf_conn *ct)
1401 {
1402 struct nlattr *pattr = cda[CTA_PROTOINFO_TCP];
1403 struct nlattr *tb[CTA_PROTOINFO_TCP_MAX+1];
1404 int err;
1405
1406 /* updates could not contain anything about the private
1407 * protocol info, in that case skip the parsing */
1408 if (!pattr)
1409 return 0;
1410
1411 err = nla_parse_nested_deprecated(tb, CTA_PROTOINFO_TCP_MAX, pattr,
1412 tcp_nla_policy, NULL);
1413 if (err < 0)
1414 return err;
1415
1416 if (tb[CTA_PROTOINFO_TCP_STATE] &&
1417 nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]) >= TCP_CONNTRACK_MAX)
1418 return -EINVAL;
1419
1420 spin_lock_bh(&ct->lock);
1421 if (tb[CTA_PROTOINFO_TCP_STATE])
1422 ct->proto.tcp.state = nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]);
1423
1424 if (tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]) {
1425 struct nf_ct_tcp_flags *attr =
1426 nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]);
1427 ct->proto.tcp.seen[0].flags &= ~attr->mask;
1428 ct->proto.tcp.seen[0].flags |= attr->flags & attr->mask;
1429 }
1430
1431 if (tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]) {
1432 struct nf_ct_tcp_flags *attr =
1433 nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]);
1434 ct->proto.tcp.seen[1].flags &= ~attr->mask;
1435 ct->proto.tcp.seen[1].flags |= attr->flags & attr->mask;
1436 }
1437
1438 if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] &&
1439 tb[CTA_PROTOINFO_TCP_WSCALE_REPLY] &&
1440 ct->proto.tcp.seen[0].flags & IP_CT_TCP_FLAG_WINDOW_SCALE &&
1441 ct->proto.tcp.seen[1].flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
1442 ct->proto.tcp.seen[0].td_scale =
1443 nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL]);
1444 ct->proto.tcp.seen[1].td_scale =
1445 nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY]);
1446 }
1447 spin_unlock_bh(&ct->lock);
1448
1449 return 0;
1450 }
1451
tcp_nlattr_tuple_size(void)1452 static unsigned int tcp_nlattr_tuple_size(void)
1453 {
1454 static unsigned int size __read_mostly;
1455
1456 if (!size)
1457 size = nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);
1458
1459 return size;
1460 }
1461 #endif
1462
1463 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1464
1465 #include <linux/netfilter/nfnetlink.h>
1466 #include <linux/netfilter/nfnetlink_cttimeout.h>
1467
tcp_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)1468 static int tcp_timeout_nlattr_to_obj(struct nlattr *tb[],
1469 struct net *net, void *data)
1470 {
1471 struct nf_tcp_net *tn = nf_tcp_pernet(net);
1472 unsigned int *timeouts = data;
1473 int i;
1474
1475 if (!timeouts)
1476 timeouts = tn->timeouts;
1477 /* set default TCP timeouts. */
1478 for (i=0; i<TCP_CONNTRACK_TIMEOUT_MAX; i++)
1479 timeouts[i] = tn->timeouts[i];
1480
1481 if (tb[CTA_TIMEOUT_TCP_SYN_SENT]) {
1482 timeouts[TCP_CONNTRACK_SYN_SENT] =
1483 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT]))*HZ;
1484 }
1485
1486 if (tb[CTA_TIMEOUT_TCP_SYN_RECV]) {
1487 timeouts[TCP_CONNTRACK_SYN_RECV] =
1488 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_RECV]))*HZ;
1489 }
1490 if (tb[CTA_TIMEOUT_TCP_ESTABLISHED]) {
1491 timeouts[TCP_CONNTRACK_ESTABLISHED] =
1492 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_ESTABLISHED]))*HZ;
1493 }
1494 if (tb[CTA_TIMEOUT_TCP_FIN_WAIT]) {
1495 timeouts[TCP_CONNTRACK_FIN_WAIT] =
1496 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_FIN_WAIT]))*HZ;
1497 }
1498 if (tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]) {
1499 timeouts[TCP_CONNTRACK_CLOSE_WAIT] =
1500 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]))*HZ;
1501 }
1502 if (tb[CTA_TIMEOUT_TCP_LAST_ACK]) {
1503 timeouts[TCP_CONNTRACK_LAST_ACK] =
1504 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_LAST_ACK]))*HZ;
1505 }
1506 if (tb[CTA_TIMEOUT_TCP_TIME_WAIT]) {
1507 timeouts[TCP_CONNTRACK_TIME_WAIT] =
1508 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_TIME_WAIT]))*HZ;
1509 }
1510 if (tb[CTA_TIMEOUT_TCP_CLOSE]) {
1511 timeouts[TCP_CONNTRACK_CLOSE] =
1512 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE]))*HZ;
1513 }
1514 if (tb[CTA_TIMEOUT_TCP_SYN_SENT2]) {
1515 timeouts[TCP_CONNTRACK_SYN_SENT2] =
1516 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT2]))*HZ;
1517 }
1518 if (tb[CTA_TIMEOUT_TCP_RETRANS]) {
1519 timeouts[TCP_CONNTRACK_RETRANS] =
1520 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_RETRANS]))*HZ;
1521 }
1522 if (tb[CTA_TIMEOUT_TCP_UNACK]) {
1523 timeouts[TCP_CONNTRACK_UNACK] =
1524 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_UNACK]))*HZ;
1525 }
1526
1527 timeouts[CTA_TIMEOUT_TCP_UNSPEC] = timeouts[CTA_TIMEOUT_TCP_SYN_SENT];
1528 return 0;
1529 }
1530
1531 static int
tcp_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)1532 tcp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
1533 {
1534 const unsigned int *timeouts = data;
1535
1536 if (nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT,
1537 htonl(timeouts[TCP_CONNTRACK_SYN_SENT] / HZ)) ||
1538 nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_RECV,
1539 htonl(timeouts[TCP_CONNTRACK_SYN_RECV] / HZ)) ||
1540 nla_put_be32(skb, CTA_TIMEOUT_TCP_ESTABLISHED,
1541 htonl(timeouts[TCP_CONNTRACK_ESTABLISHED] / HZ)) ||
1542 nla_put_be32(skb, CTA_TIMEOUT_TCP_FIN_WAIT,
1543 htonl(timeouts[TCP_CONNTRACK_FIN_WAIT] / HZ)) ||
1544 nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE_WAIT,
1545 htonl(timeouts[TCP_CONNTRACK_CLOSE_WAIT] / HZ)) ||
1546 nla_put_be32(skb, CTA_TIMEOUT_TCP_LAST_ACK,
1547 htonl(timeouts[TCP_CONNTRACK_LAST_ACK] / HZ)) ||
1548 nla_put_be32(skb, CTA_TIMEOUT_TCP_TIME_WAIT,
1549 htonl(timeouts[TCP_CONNTRACK_TIME_WAIT] / HZ)) ||
1550 nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE,
1551 htonl(timeouts[TCP_CONNTRACK_CLOSE] / HZ)) ||
1552 nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT2,
1553 htonl(timeouts[TCP_CONNTRACK_SYN_SENT2] / HZ)) ||
1554 nla_put_be32(skb, CTA_TIMEOUT_TCP_RETRANS,
1555 htonl(timeouts[TCP_CONNTRACK_RETRANS] / HZ)) ||
1556 nla_put_be32(skb, CTA_TIMEOUT_TCP_UNACK,
1557 htonl(timeouts[TCP_CONNTRACK_UNACK] / HZ)))
1558 goto nla_put_failure;
1559 return 0;
1560
1561 nla_put_failure:
1562 return -ENOSPC;
1563 }
1564
1565 static const struct nla_policy tcp_timeout_nla_policy[CTA_TIMEOUT_TCP_MAX+1] = {
1566 [CTA_TIMEOUT_TCP_SYN_SENT] = { .type = NLA_U32 },
1567 [CTA_TIMEOUT_TCP_SYN_RECV] = { .type = NLA_U32 },
1568 [CTA_TIMEOUT_TCP_ESTABLISHED] = { .type = NLA_U32 },
1569 [CTA_TIMEOUT_TCP_FIN_WAIT] = { .type = NLA_U32 },
1570 [CTA_TIMEOUT_TCP_CLOSE_WAIT] = { .type = NLA_U32 },
1571 [CTA_TIMEOUT_TCP_LAST_ACK] = { .type = NLA_U32 },
1572 [CTA_TIMEOUT_TCP_TIME_WAIT] = { .type = NLA_U32 },
1573 [CTA_TIMEOUT_TCP_CLOSE] = { .type = NLA_U32 },
1574 [CTA_TIMEOUT_TCP_SYN_SENT2] = { .type = NLA_U32 },
1575 [CTA_TIMEOUT_TCP_RETRANS] = { .type = NLA_U32 },
1576 [CTA_TIMEOUT_TCP_UNACK] = { .type = NLA_U32 },
1577 };
1578 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1579
nf_conntrack_tcp_init_net(struct net * net)1580 void nf_conntrack_tcp_init_net(struct net *net)
1581 {
1582 struct nf_tcp_net *tn = nf_tcp_pernet(net);
1583 int i;
1584
1585 for (i = 0; i < TCP_CONNTRACK_TIMEOUT_MAX; i++)
1586 tn->timeouts[i] = tcp_timeouts[i];
1587
1588 /* timeouts[0] is unused, make it same as SYN_SENT so
1589 * ->timeouts[0] contains 'new' timeout, like udp or icmp.
1590 */
1591 tn->timeouts[0] = tcp_timeouts[TCP_CONNTRACK_SYN_SENT];
1592
1593 /* If it is set to zero, we disable picking up already established
1594 * connections.
1595 */
1596 tn->tcp_loose = 1;
1597
1598 /* "Be conservative in what you do,
1599 * be liberal in what you accept from others."
1600 * If it's non-zero, we mark only out of window RST segments as INVALID.
1601 */
1602 tn->tcp_be_liberal = 0;
1603
1604 /* If it's non-zero, we turn off RST sequence number check */
1605 tn->tcp_ignore_invalid_rst = 0;
1606
1607 /* Max number of the retransmitted packets without receiving an (acceptable)
1608 * ACK from the destination. If this number is reached, a shorter timer
1609 * will be started.
1610 */
1611 tn->tcp_max_retrans = 3;
1612
1613 #if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
1614 tn->offload_timeout = 30 * HZ;
1615 #endif
1616 }
1617
1618 const struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp =
1619 {
1620 .l4proto = IPPROTO_TCP,
1621 #ifdef CONFIG_NF_CONNTRACK_PROCFS
1622 .print_conntrack = tcp_print_conntrack,
1623 #endif
1624 .can_early_drop = tcp_can_early_drop,
1625 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1626 .to_nlattr = tcp_to_nlattr,
1627 .from_nlattr = nlattr_to_tcp,
1628 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
1629 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
1630 .nlattr_tuple_size = tcp_nlattr_tuple_size,
1631 .nlattr_size = TCP_NLATTR_SIZE,
1632 .nla_policy = nf_ct_port_nla_policy,
1633 #endif
1634 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1635 .ctnl_timeout = {
1636 .nlattr_to_obj = tcp_timeout_nlattr_to_obj,
1637 .obj_to_nlattr = tcp_timeout_obj_to_nlattr,
1638 .nlattr_max = CTA_TIMEOUT_TCP_MAX,
1639 .obj_size = sizeof(unsigned int) *
1640 TCP_CONNTRACK_TIMEOUT_MAX,
1641 .nla_policy = tcp_timeout_nla_policy,
1642 },
1643 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1644 };
1645