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 /* "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. */
tcp_print_conntrack(struct seq_file * s,struct nf_conn * ct)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
get_conntrack_index(const struct tcphdr * tcph)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
segment_seq_plus_len(__u32 seq,size_t len,unsigned int dataoff,const struct tcphdr * tcph)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 */
tcp_options(const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * tcph,struct ip_ct_tcp_state * state)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
tcp_sack(const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * tcph,__u32 * sack)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
tcp_in_window(const struct nf_conn * ct,struct ip_ct_tcp * state,enum ip_conntrack_dir dir,unsigned int index,const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * tcph)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 u16 win_raw;
476 s32 receiver_offset;
477 bool res, in_recv_win;
478
479 /*
480 * Get the required data from the packet.
481 */
482 seq = ntohl(tcph->seq);
483 ack = sack = ntohl(tcph->ack_seq);
484 win_raw = ntohs(tcph->window);
485 win = win_raw;
486 end = segment_seq_plus_len(seq, skb->len, dataoff, tcph);
487
488 if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
489 tcp_sack(skb, dataoff, tcph, &sack);
490
491 /* Take into account NAT sequence number mangling */
492 receiver_offset = nf_ct_seq_offset(ct, !dir, ack - 1);
493 ack -= receiver_offset;
494 sack -= receiver_offset;
495
496 pr_debug("tcp_in_window: START\n");
497 pr_debug("tcp_in_window: ");
498 nf_ct_dump_tuple(tuple);
499 pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
500 seq, ack, receiver_offset, sack, receiver_offset, win, end);
501 pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
502 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
503 sender->td_end, sender->td_maxend, sender->td_maxwin,
504 sender->td_scale,
505 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
506 receiver->td_scale);
507
508 if (sender->td_maxwin == 0) {
509 /*
510 * Initialize sender data.
511 */
512 if (tcph->syn) {
513 /*
514 * SYN-ACK in reply to a SYN
515 * or SYN from reply direction in simultaneous open.
516 */
517 sender->td_end =
518 sender->td_maxend = end;
519 sender->td_maxwin = (win == 0 ? 1 : win);
520
521 tcp_options(skb, dataoff, tcph, sender);
522 /*
523 * RFC 1323:
524 * Both sides must send the Window Scale option
525 * to enable window scaling in either direction.
526 */
527 if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
528 && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
529 sender->td_scale =
530 receiver->td_scale = 0;
531 if (!tcph->ack)
532 /* Simultaneous open */
533 return true;
534 } else {
535 /*
536 * We are in the middle of a connection,
537 * its history is lost for us.
538 * Let's try to use the data from the packet.
539 */
540 sender->td_end = end;
541 swin = win << sender->td_scale;
542 sender->td_maxwin = (swin == 0 ? 1 : swin);
543 sender->td_maxend = end + sender->td_maxwin;
544 /*
545 * We haven't seen traffic in the other direction yet
546 * but we have to tweak window tracking to pass III
547 * and IV until that happens.
548 */
549 if (receiver->td_maxwin == 0)
550 receiver->td_end = receiver->td_maxend = sack;
551 }
552 } else if (((state->state == TCP_CONNTRACK_SYN_SENT
553 && dir == IP_CT_DIR_ORIGINAL)
554 || (state->state == TCP_CONNTRACK_SYN_RECV
555 && dir == IP_CT_DIR_REPLY))
556 && after(end, sender->td_end)) {
557 /*
558 * RFC 793: "if a TCP is reinitialized ... then it need
559 * not wait at all; it must only be sure to use sequence
560 * numbers larger than those recently used."
561 */
562 sender->td_end =
563 sender->td_maxend = end;
564 sender->td_maxwin = (win == 0 ? 1 : win);
565
566 tcp_options(skb, dataoff, tcph, sender);
567 }
568
569 if (!(tcph->ack)) {
570 /*
571 * If there is no ACK, just pretend it was set and OK.
572 */
573 ack = sack = receiver->td_end;
574 } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
575 (TCP_FLAG_ACK|TCP_FLAG_RST))
576 && (ack == 0)) {
577 /*
578 * Broken TCP stacks, that set ACK in RST packets as well
579 * with zero ack value.
580 */
581 ack = sack = receiver->td_end;
582 }
583
584 if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)
585 /*
586 * RST sent answering SYN.
587 */
588 seq = end = sender->td_end;
589
590 pr_debug("tcp_in_window: ");
591 nf_ct_dump_tuple(tuple);
592 pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
593 seq, ack, receiver_offset, sack, receiver_offset, win, end);
594 pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
595 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
596 sender->td_end, sender->td_maxend, sender->td_maxwin,
597 sender->td_scale,
598 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
599 receiver->td_scale);
600
601 /* Is the ending sequence in the receive window (if available)? */
602 in_recv_win = !receiver->td_maxwin ||
603 after(end, sender->td_end - receiver->td_maxwin - 1);
604
605 pr_debug("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
606 before(seq, sender->td_maxend + 1),
607 (in_recv_win ? 1 : 0),
608 before(sack, receiver->td_end + 1),
609 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1));
610
611 if (before(seq, sender->td_maxend + 1) &&
612 in_recv_win &&
613 before(sack, receiver->td_end + 1) &&
614 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) {
615 /*
616 * Take into account window scaling (RFC 1323).
617 */
618 if (!tcph->syn)
619 win <<= sender->td_scale;
620
621 /*
622 * Update sender data.
623 */
624 swin = win + (sack - ack);
625 if (sender->td_maxwin < swin)
626 sender->td_maxwin = swin;
627 if (after(end, sender->td_end)) {
628 sender->td_end = end;
629 sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
630 }
631 if (tcph->ack) {
632 if (!(sender->flags & IP_CT_TCP_FLAG_MAXACK_SET)) {
633 sender->td_maxack = ack;
634 sender->flags |= IP_CT_TCP_FLAG_MAXACK_SET;
635 } else if (after(ack, sender->td_maxack))
636 sender->td_maxack = ack;
637 }
638
639 /*
640 * Update receiver data.
641 */
642 if (receiver->td_maxwin != 0 && after(end, sender->td_maxend))
643 receiver->td_maxwin += end - sender->td_maxend;
644 if (after(sack + win, receiver->td_maxend - 1)) {
645 receiver->td_maxend = sack + win;
646 if (win == 0)
647 receiver->td_maxend++;
648 }
649 if (ack == receiver->td_end)
650 receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
651
652 /*
653 * Check retransmissions.
654 */
655 if (index == TCP_ACK_SET) {
656 if (state->last_dir == dir
657 && state->last_seq == seq
658 && state->last_ack == ack
659 && state->last_end == end
660 && state->last_win == win_raw)
661 state->retrans++;
662 else {
663 state->last_dir = dir;
664 state->last_seq = seq;
665 state->last_ack = ack;
666 state->last_end = end;
667 state->last_win = win_raw;
668 state->retrans = 0;
669 }
670 }
671 res = true;
672 } else {
673 res = false;
674 if (sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL ||
675 tn->tcp_be_liberal)
676 res = true;
677 if (!res) {
678 nf_ct_l4proto_log_invalid(skb, ct,
679 "%s",
680 before(seq, sender->td_maxend + 1) ?
681 in_recv_win ?
682 before(sack, receiver->td_end + 1) ?
683 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1) ? "BUG"
684 : "ACK is under the lower bound (possible overly delayed ACK)"
685 : "ACK is over the upper bound (ACKed data not seen yet)"
686 : "SEQ is under the lower bound (already ACKed data retransmitted)"
687 : "SEQ is over the upper bound (over the window of the receiver)");
688 }
689 }
690
691 pr_debug("tcp_in_window: res=%u sender end=%u maxend=%u maxwin=%u "
692 "receiver end=%u maxend=%u maxwin=%u\n",
693 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
694 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
695
696 return res;
697 }
698
699 /* table of valid flag combinations - PUSH, ECE and CWR are always valid */
700 static const u8 tcp_valid_flags[(TCPHDR_FIN|TCPHDR_SYN|TCPHDR_RST|TCPHDR_ACK|
701 TCPHDR_URG) + 1] =
702 {
703 [TCPHDR_SYN] = 1,
704 [TCPHDR_SYN|TCPHDR_URG] = 1,
705 [TCPHDR_SYN|TCPHDR_ACK] = 1,
706 [TCPHDR_RST] = 1,
707 [TCPHDR_RST|TCPHDR_ACK] = 1,
708 [TCPHDR_FIN|TCPHDR_ACK] = 1,
709 [TCPHDR_FIN|TCPHDR_ACK|TCPHDR_URG] = 1,
710 [TCPHDR_ACK] = 1,
711 [TCPHDR_ACK|TCPHDR_URG] = 1,
712 };
713
tcp_error_log(const struct sk_buff * skb,const struct nf_hook_state * state,const char * msg)714 static void tcp_error_log(const struct sk_buff *skb,
715 const struct nf_hook_state *state,
716 const char *msg)
717 {
718 nf_l4proto_log_invalid(skb, state->net, state->pf, IPPROTO_TCP, "%s", msg);
719 }
720
721 /* 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)722 static bool tcp_error(const struct tcphdr *th,
723 struct sk_buff *skb,
724 unsigned int dataoff,
725 const struct nf_hook_state *state)
726 {
727 unsigned int tcplen = skb->len - dataoff;
728 u8 tcpflags;
729
730 /* Not whole TCP header or malformed packet */
731 if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
732 tcp_error_log(skb, state, "truncated packet");
733 return true;
734 }
735
736 /* Checksum invalid? Ignore.
737 * We skip checking packets on the outgoing path
738 * because the checksum is assumed to be correct.
739 */
740 /* FIXME: Source route IP option packets --RR */
741 if (state->net->ct.sysctl_checksum &&
742 state->hook == NF_INET_PRE_ROUTING &&
743 nf_checksum(skb, state->hook, dataoff, IPPROTO_TCP, state->pf)) {
744 tcp_error_log(skb, state, "bad checksum");
745 return true;
746 }
747
748 /* Check TCP flags. */
749 tcpflags = (tcp_flag_byte(th) & ~(TCPHDR_ECE|TCPHDR_CWR|TCPHDR_PSH));
750 if (!tcp_valid_flags[tcpflags]) {
751 tcp_error_log(skb, state, "invalid tcp flag combination");
752 return true;
753 }
754
755 return false;
756 }
757
tcp_new(struct nf_conn * ct,const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * th)758 static noinline bool tcp_new(struct nf_conn *ct, const struct sk_buff *skb,
759 unsigned int dataoff,
760 const struct tcphdr *th)
761 {
762 enum tcp_conntrack new_state;
763 struct net *net = nf_ct_net(ct);
764 const struct nf_tcp_net *tn = nf_tcp_pernet(net);
765 const struct ip_ct_tcp_state *sender = &ct->proto.tcp.seen[0];
766 const struct ip_ct_tcp_state *receiver = &ct->proto.tcp.seen[1];
767
768 /* Don't need lock here: this conntrack not in circulation yet */
769 new_state = tcp_conntracks[0][get_conntrack_index(th)][TCP_CONNTRACK_NONE];
770
771 /* Invalid: delete conntrack */
772 if (new_state >= TCP_CONNTRACK_MAX) {
773 pr_debug("nf_ct_tcp: invalid new deleting.\n");
774 return false;
775 }
776
777 if (new_state == TCP_CONNTRACK_SYN_SENT) {
778 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
779 /* SYN packet */
780 ct->proto.tcp.seen[0].td_end =
781 segment_seq_plus_len(ntohl(th->seq), skb->len,
782 dataoff, th);
783 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
784 if (ct->proto.tcp.seen[0].td_maxwin == 0)
785 ct->proto.tcp.seen[0].td_maxwin = 1;
786 ct->proto.tcp.seen[0].td_maxend =
787 ct->proto.tcp.seen[0].td_end;
788
789 tcp_options(skb, dataoff, th, &ct->proto.tcp.seen[0]);
790 } else if (tn->tcp_loose == 0) {
791 /* Don't try to pick up connections. */
792 return false;
793 } else {
794 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
795 /*
796 * We are in the middle of a connection,
797 * its history is lost for us.
798 * Let's try to use the data from the packet.
799 */
800 ct->proto.tcp.seen[0].td_end =
801 segment_seq_plus_len(ntohl(th->seq), skb->len,
802 dataoff, th);
803 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
804 if (ct->proto.tcp.seen[0].td_maxwin == 0)
805 ct->proto.tcp.seen[0].td_maxwin = 1;
806 ct->proto.tcp.seen[0].td_maxend =
807 ct->proto.tcp.seen[0].td_end +
808 ct->proto.tcp.seen[0].td_maxwin;
809
810 /* We assume SACK and liberal window checking to handle
811 * window scaling */
812 ct->proto.tcp.seen[0].flags =
813 ct->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM |
814 IP_CT_TCP_FLAG_BE_LIBERAL;
815 }
816
817 /* tcp_packet will set them */
818 ct->proto.tcp.last_index = TCP_NONE_SET;
819
820 pr_debug("%s: sender end=%u maxend=%u maxwin=%u scale=%i "
821 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
822 __func__,
823 sender->td_end, sender->td_maxend, sender->td_maxwin,
824 sender->td_scale,
825 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
826 receiver->td_scale);
827 return true;
828 }
829
nf_conntrack_tcp_established(const struct nf_conn * ct)830 static bool nf_conntrack_tcp_established(const struct nf_conn *ct)
831 {
832 return ct->proto.tcp.state == TCP_CONNTRACK_ESTABLISHED &&
833 test_bit(IPS_ASSURED_BIT, &ct->status);
834 }
835
836 /* 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)837 int nf_conntrack_tcp_packet(struct nf_conn *ct,
838 struct sk_buff *skb,
839 unsigned int dataoff,
840 enum ip_conntrack_info ctinfo,
841 const struct nf_hook_state *state)
842 {
843 struct net *net = nf_ct_net(ct);
844 struct nf_tcp_net *tn = nf_tcp_pernet(net);
845 struct nf_conntrack_tuple *tuple;
846 enum tcp_conntrack new_state, old_state;
847 unsigned int index, *timeouts;
848 enum ip_conntrack_dir dir;
849 const struct tcphdr *th;
850 struct tcphdr _tcph;
851 unsigned long timeout;
852
853 th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
854 if (th == NULL)
855 return -NF_ACCEPT;
856
857 if (tcp_error(th, skb, dataoff, state))
858 return -NF_ACCEPT;
859
860 if (!nf_ct_is_confirmed(ct) && !tcp_new(ct, skb, dataoff, th))
861 return -NF_ACCEPT;
862
863 spin_lock_bh(&ct->lock);
864 old_state = ct->proto.tcp.state;
865 dir = CTINFO2DIR(ctinfo);
866 index = get_conntrack_index(th);
867 new_state = tcp_conntracks[dir][index][old_state];
868 tuple = &ct->tuplehash[dir].tuple;
869
870 switch (new_state) {
871 case TCP_CONNTRACK_SYN_SENT:
872 if (old_state < TCP_CONNTRACK_TIME_WAIT)
873 break;
874 /* RFC 1122: "When a connection is closed actively,
875 * it MUST linger in TIME-WAIT state for a time 2xMSL
876 * (Maximum Segment Lifetime). However, it MAY accept
877 * a new SYN from the remote TCP to reopen the connection
878 * directly from TIME-WAIT state, if..."
879 * We ignore the conditions because we are in the
880 * TIME-WAIT state anyway.
881 *
882 * Handle aborted connections: we and the server
883 * think there is an existing connection but the client
884 * aborts it and starts a new one.
885 */
886 if (((ct->proto.tcp.seen[dir].flags
887 | ct->proto.tcp.seen[!dir].flags)
888 & IP_CT_TCP_FLAG_CLOSE_INIT)
889 || (ct->proto.tcp.last_dir == dir
890 && ct->proto.tcp.last_index == TCP_RST_SET)) {
891 /* Attempt to reopen a closed/aborted connection.
892 * Delete this connection and look up again. */
893 spin_unlock_bh(&ct->lock);
894
895 /* Only repeat if we can actually remove the timer.
896 * Destruction may already be in progress in process
897 * context and we must give it a chance to terminate.
898 */
899 if (nf_ct_kill(ct))
900 return -NF_REPEAT;
901 return NF_DROP;
902 }
903 /* Fall through */
904 case TCP_CONNTRACK_IGNORE:
905 /* Ignored packets:
906 *
907 * Our connection entry may be out of sync, so ignore
908 * packets which may signal the real connection between
909 * the client and the server.
910 *
911 * a) SYN in ORIGINAL
912 * b) SYN/ACK in REPLY
913 * c) ACK in reply direction after initial SYN in original.
914 *
915 * If the ignored packet is invalid, the receiver will send
916 * a RST we'll catch below.
917 */
918 if (index == TCP_SYNACK_SET
919 && ct->proto.tcp.last_index == TCP_SYN_SET
920 && ct->proto.tcp.last_dir != dir
921 && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
922 /* b) This SYN/ACK acknowledges a SYN that we earlier
923 * ignored as invalid. This means that the client and
924 * the server are both in sync, while the firewall is
925 * not. We get in sync from the previously annotated
926 * values.
927 */
928 old_state = TCP_CONNTRACK_SYN_SENT;
929 new_state = TCP_CONNTRACK_SYN_RECV;
930 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end =
931 ct->proto.tcp.last_end;
932 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend =
933 ct->proto.tcp.last_end;
934 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin =
935 ct->proto.tcp.last_win == 0 ?
936 1 : ct->proto.tcp.last_win;
937 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale =
938 ct->proto.tcp.last_wscale;
939 ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
940 ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags =
941 ct->proto.tcp.last_flags;
942 memset(&ct->proto.tcp.seen[dir], 0,
943 sizeof(struct ip_ct_tcp_state));
944 break;
945 }
946 ct->proto.tcp.last_index = index;
947 ct->proto.tcp.last_dir = dir;
948 ct->proto.tcp.last_seq = ntohl(th->seq);
949 ct->proto.tcp.last_end =
950 segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
951 ct->proto.tcp.last_win = ntohs(th->window);
952
953 /* a) This is a SYN in ORIGINAL. The client and the server
954 * may be in sync but we are not. In that case, we annotate
955 * the TCP options and let the packet go through. If it is a
956 * valid SYN packet, the server will reply with a SYN/ACK, and
957 * then we'll get in sync. Otherwise, the server potentially
958 * responds with a challenge ACK if implementing RFC5961.
959 */
960 if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) {
961 struct ip_ct_tcp_state seen = {};
962
963 ct->proto.tcp.last_flags =
964 ct->proto.tcp.last_wscale = 0;
965 tcp_options(skb, dataoff, th, &seen);
966 if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
967 ct->proto.tcp.last_flags |=
968 IP_CT_TCP_FLAG_WINDOW_SCALE;
969 ct->proto.tcp.last_wscale = seen.td_scale;
970 }
971 if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) {
972 ct->proto.tcp.last_flags |=
973 IP_CT_TCP_FLAG_SACK_PERM;
974 }
975 /* Mark the potential for RFC5961 challenge ACK,
976 * this pose a special problem for LAST_ACK state
977 * as ACK is intrepretated as ACKing last FIN.
978 */
979 if (old_state == TCP_CONNTRACK_LAST_ACK)
980 ct->proto.tcp.last_flags |=
981 IP_CT_EXP_CHALLENGE_ACK;
982 }
983 spin_unlock_bh(&ct->lock);
984 nf_ct_l4proto_log_invalid(skb, ct, "invalid packet ignored in "
985 "state %s ", tcp_conntrack_names[old_state]);
986 return NF_ACCEPT;
987 case TCP_CONNTRACK_MAX:
988 /* Special case for SYN proxy: when the SYN to the server or
989 * the SYN/ACK from the server is lost, the client may transmit
990 * a keep-alive packet while in SYN_SENT state. This needs to
991 * be associated with the original conntrack entry in order to
992 * generate a new SYN with the correct sequence number.
993 */
994 if (nfct_synproxy(ct) && old_state == TCP_CONNTRACK_SYN_SENT &&
995 index == TCP_ACK_SET && dir == IP_CT_DIR_ORIGINAL &&
996 ct->proto.tcp.last_dir == IP_CT_DIR_ORIGINAL &&
997 ct->proto.tcp.seen[dir].td_end - 1 == ntohl(th->seq)) {
998 pr_debug("nf_ct_tcp: SYN proxy client keep alive\n");
999 spin_unlock_bh(&ct->lock);
1000 return NF_ACCEPT;
1001 }
1002
1003 /* Invalid packet */
1004 pr_debug("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
1005 dir, get_conntrack_index(th), old_state);
1006 spin_unlock_bh(&ct->lock);
1007 nf_ct_l4proto_log_invalid(skb, ct, "invalid state");
1008 return -NF_ACCEPT;
1009 case TCP_CONNTRACK_TIME_WAIT:
1010 /* RFC5961 compliance cause stack to send "challenge-ACK"
1011 * e.g. in response to spurious SYNs. Conntrack MUST
1012 * not believe this ACK is acking last FIN.
1013 */
1014 if (old_state == TCP_CONNTRACK_LAST_ACK &&
1015 index == TCP_ACK_SET &&
1016 ct->proto.tcp.last_dir != dir &&
1017 ct->proto.tcp.last_index == TCP_SYN_SET &&
1018 (ct->proto.tcp.last_flags & IP_CT_EXP_CHALLENGE_ACK)) {
1019 /* Detected RFC5961 challenge ACK */
1020 ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
1021 spin_unlock_bh(&ct->lock);
1022 nf_ct_l4proto_log_invalid(skb, ct, "challenge-ack ignored");
1023 return NF_ACCEPT; /* Don't change state */
1024 }
1025 break;
1026 case TCP_CONNTRACK_SYN_SENT2:
1027 /* tcp_conntracks table is not smart enough to handle
1028 * simultaneous open.
1029 */
1030 ct->proto.tcp.last_flags |= IP_CT_TCP_SIMULTANEOUS_OPEN;
1031 break;
1032 case TCP_CONNTRACK_SYN_RECV:
1033 if (dir == IP_CT_DIR_REPLY && index == TCP_ACK_SET &&
1034 ct->proto.tcp.last_flags & IP_CT_TCP_SIMULTANEOUS_OPEN)
1035 new_state = TCP_CONNTRACK_ESTABLISHED;
1036 break;
1037 case TCP_CONNTRACK_CLOSE:
1038 if (index != TCP_RST_SET)
1039 break;
1040
1041 if (ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET) {
1042 u32 seq = ntohl(th->seq);
1043
1044 if (before(seq, ct->proto.tcp.seen[!dir].td_maxack)) {
1045 /* Invalid RST */
1046 spin_unlock_bh(&ct->lock);
1047 nf_ct_l4proto_log_invalid(skb, ct, "invalid rst");
1048 return -NF_ACCEPT;
1049 }
1050
1051 if (!nf_conntrack_tcp_established(ct) ||
1052 seq == ct->proto.tcp.seen[!dir].td_maxack)
1053 break;
1054
1055 /* Check if rst is part of train, such as
1056 * foo:80 > bar:4379: P, 235946583:235946602(19) ack 42
1057 * foo:80 > bar:4379: R, 235946602:235946602(0) ack 42
1058 */
1059 if (ct->proto.tcp.last_index == TCP_ACK_SET &&
1060 ct->proto.tcp.last_dir == dir &&
1061 seq == ct->proto.tcp.last_end)
1062 break;
1063
1064 /* ... RST sequence number doesn't match exactly, keep
1065 * established state to allow a possible challenge ACK.
1066 */
1067 new_state = old_state;
1068 }
1069 if (((test_bit(IPS_SEEN_REPLY_BIT, &ct->status)
1070 && ct->proto.tcp.last_index == TCP_SYN_SET)
1071 || (!test_bit(IPS_ASSURED_BIT, &ct->status)
1072 && ct->proto.tcp.last_index == TCP_ACK_SET))
1073 && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
1074 /* RST sent to invalid SYN or ACK we had let through
1075 * at a) and c) above:
1076 *
1077 * a) SYN was in window then
1078 * c) we hold a half-open connection.
1079 *
1080 * Delete our connection entry.
1081 * We skip window checking, because packet might ACK
1082 * segments we ignored. */
1083 goto in_window;
1084 }
1085 break;
1086 default:
1087 /* Keep compilers happy. */
1088 break;
1089 }
1090
1091 if (!tcp_in_window(ct, &ct->proto.tcp, dir, index,
1092 skb, dataoff, th)) {
1093 spin_unlock_bh(&ct->lock);
1094 return -NF_ACCEPT;
1095 }
1096 in_window:
1097 /* From now on we have got in-window packets */
1098 ct->proto.tcp.last_index = index;
1099 ct->proto.tcp.last_dir = dir;
1100
1101 pr_debug("tcp_conntracks: ");
1102 nf_ct_dump_tuple(tuple);
1103 pr_debug("syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1104 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
1105 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
1106 old_state, new_state);
1107
1108 ct->proto.tcp.state = new_state;
1109 if (old_state != new_state
1110 && new_state == TCP_CONNTRACK_FIN_WAIT)
1111 ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1112
1113 timeouts = nf_ct_timeout_lookup(ct);
1114 if (!timeouts)
1115 timeouts = tn->timeouts;
1116
1117 if (ct->proto.tcp.retrans >= tn->tcp_max_retrans &&
1118 timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1119 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1120 else if (unlikely(index == TCP_RST_SET))
1121 timeout = timeouts[TCP_CONNTRACK_CLOSE];
1122 else if ((ct->proto.tcp.seen[0].flags | ct->proto.tcp.seen[1].flags) &
1123 IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED &&
1124 timeouts[new_state] > timeouts[TCP_CONNTRACK_UNACK])
1125 timeout = timeouts[TCP_CONNTRACK_UNACK];
1126 else if (ct->proto.tcp.last_win == 0 &&
1127 timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1128 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1129 else
1130 timeout = timeouts[new_state];
1131 spin_unlock_bh(&ct->lock);
1132
1133 if (new_state != old_state)
1134 nf_conntrack_event_cache(IPCT_PROTOINFO, ct);
1135
1136 if (!test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
1137 /* If only reply is a RST, we can consider ourselves not to
1138 have an established connection: this is a fairly common
1139 problem case, so we can delete the conntrack
1140 immediately. --RR */
1141 if (th->rst) {
1142 nf_ct_kill_acct(ct, ctinfo, skb);
1143 return NF_ACCEPT;
1144 }
1145 /* ESTABLISHED without SEEN_REPLY, i.e. mid-connection
1146 * pickup with loose=1. Avoid large ESTABLISHED timeout.
1147 */
1148 if (new_state == TCP_CONNTRACK_ESTABLISHED &&
1149 timeout > timeouts[TCP_CONNTRACK_UNACK])
1150 timeout = timeouts[TCP_CONNTRACK_UNACK];
1151 } else if (!test_bit(IPS_ASSURED_BIT, &ct->status)
1152 && (old_state == TCP_CONNTRACK_SYN_RECV
1153 || old_state == TCP_CONNTRACK_ESTABLISHED)
1154 && new_state == TCP_CONNTRACK_ESTABLISHED) {
1155 /* Set ASSURED if we see see valid ack in ESTABLISHED
1156 after SYN_RECV or a valid answer for a picked up
1157 connection. */
1158 set_bit(IPS_ASSURED_BIT, &ct->status);
1159 nf_conntrack_event_cache(IPCT_ASSURED, ct);
1160 }
1161 nf_ct_refresh_acct(ct, ctinfo, skb, timeout);
1162
1163 return NF_ACCEPT;
1164 }
1165
tcp_can_early_drop(const struct nf_conn * ct)1166 static bool tcp_can_early_drop(const struct nf_conn *ct)
1167 {
1168 switch (ct->proto.tcp.state) {
1169 case TCP_CONNTRACK_FIN_WAIT:
1170 case TCP_CONNTRACK_LAST_ACK:
1171 case TCP_CONNTRACK_TIME_WAIT:
1172 case TCP_CONNTRACK_CLOSE:
1173 case TCP_CONNTRACK_CLOSE_WAIT:
1174 return true;
1175 default:
1176 break;
1177 }
1178
1179 return false;
1180 }
1181
1182 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1183
1184 #include <linux/netfilter/nfnetlink.h>
1185 #include <linux/netfilter/nfnetlink_conntrack.h>
1186
tcp_to_nlattr(struct sk_buff * skb,struct nlattr * nla,struct nf_conn * ct)1187 static int tcp_to_nlattr(struct sk_buff *skb, struct nlattr *nla,
1188 struct nf_conn *ct)
1189 {
1190 struct nlattr *nest_parms;
1191 struct nf_ct_tcp_flags tmp = {};
1192
1193 spin_lock_bh(&ct->lock);
1194 nest_parms = nla_nest_start(skb, CTA_PROTOINFO_TCP);
1195 if (!nest_parms)
1196 goto nla_put_failure;
1197
1198 if (nla_put_u8(skb, CTA_PROTOINFO_TCP_STATE, ct->proto.tcp.state) ||
1199 nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL,
1200 ct->proto.tcp.seen[0].td_scale) ||
1201 nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY,
1202 ct->proto.tcp.seen[1].td_scale))
1203 goto nla_put_failure;
1204
1205 tmp.flags = ct->proto.tcp.seen[0].flags;
1206 if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_ORIGINAL,
1207 sizeof(struct nf_ct_tcp_flags), &tmp))
1208 goto nla_put_failure;
1209
1210 tmp.flags = ct->proto.tcp.seen[1].flags;
1211 if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_REPLY,
1212 sizeof(struct nf_ct_tcp_flags), &tmp))
1213 goto nla_put_failure;
1214 spin_unlock_bh(&ct->lock);
1215
1216 nla_nest_end(skb, nest_parms);
1217
1218 return 0;
1219
1220 nla_put_failure:
1221 spin_unlock_bh(&ct->lock);
1222 return -1;
1223 }
1224
1225 static const struct nla_policy tcp_nla_policy[CTA_PROTOINFO_TCP_MAX+1] = {
1226 [CTA_PROTOINFO_TCP_STATE] = { .type = NLA_U8 },
1227 [CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] = { .type = NLA_U8 },
1228 [CTA_PROTOINFO_TCP_WSCALE_REPLY] = { .type = NLA_U8 },
1229 [CTA_PROTOINFO_TCP_FLAGS_ORIGINAL] = { .len = sizeof(struct nf_ct_tcp_flags) },
1230 [CTA_PROTOINFO_TCP_FLAGS_REPLY] = { .len = sizeof(struct nf_ct_tcp_flags) },
1231 };
1232
1233 #define TCP_NLATTR_SIZE ( \
1234 NLA_ALIGN(NLA_HDRLEN + 1) + \
1235 NLA_ALIGN(NLA_HDRLEN + 1) + \
1236 NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)) + \
1237 NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)))
1238
nlattr_to_tcp(struct nlattr * cda[],struct nf_conn * ct)1239 static int nlattr_to_tcp(struct nlattr *cda[], struct nf_conn *ct)
1240 {
1241 struct nlattr *pattr = cda[CTA_PROTOINFO_TCP];
1242 struct nlattr *tb[CTA_PROTOINFO_TCP_MAX+1];
1243 int err;
1244
1245 /* updates could not contain anything about the private
1246 * protocol info, in that case skip the parsing */
1247 if (!pattr)
1248 return 0;
1249
1250 err = nla_parse_nested_deprecated(tb, CTA_PROTOINFO_TCP_MAX, pattr,
1251 tcp_nla_policy, NULL);
1252 if (err < 0)
1253 return err;
1254
1255 if (tb[CTA_PROTOINFO_TCP_STATE] &&
1256 nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]) >= TCP_CONNTRACK_MAX)
1257 return -EINVAL;
1258
1259 spin_lock_bh(&ct->lock);
1260 if (tb[CTA_PROTOINFO_TCP_STATE])
1261 ct->proto.tcp.state = nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]);
1262
1263 if (tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]) {
1264 struct nf_ct_tcp_flags *attr =
1265 nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]);
1266 ct->proto.tcp.seen[0].flags &= ~attr->mask;
1267 ct->proto.tcp.seen[0].flags |= attr->flags & attr->mask;
1268 }
1269
1270 if (tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]) {
1271 struct nf_ct_tcp_flags *attr =
1272 nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]);
1273 ct->proto.tcp.seen[1].flags &= ~attr->mask;
1274 ct->proto.tcp.seen[1].flags |= attr->flags & attr->mask;
1275 }
1276
1277 if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] &&
1278 tb[CTA_PROTOINFO_TCP_WSCALE_REPLY] &&
1279 ct->proto.tcp.seen[0].flags & IP_CT_TCP_FLAG_WINDOW_SCALE &&
1280 ct->proto.tcp.seen[1].flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
1281 ct->proto.tcp.seen[0].td_scale =
1282 nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL]);
1283 ct->proto.tcp.seen[1].td_scale =
1284 nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY]);
1285 }
1286 spin_unlock_bh(&ct->lock);
1287
1288 return 0;
1289 }
1290
tcp_nlattr_tuple_size(void)1291 static unsigned int tcp_nlattr_tuple_size(void)
1292 {
1293 static unsigned int size __read_mostly;
1294
1295 if (!size)
1296 size = nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);
1297
1298 return size;
1299 }
1300 #endif
1301
1302 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1303
1304 #include <linux/netfilter/nfnetlink.h>
1305 #include <linux/netfilter/nfnetlink_cttimeout.h>
1306
tcp_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)1307 static int tcp_timeout_nlattr_to_obj(struct nlattr *tb[],
1308 struct net *net, void *data)
1309 {
1310 struct nf_tcp_net *tn = nf_tcp_pernet(net);
1311 unsigned int *timeouts = data;
1312 int i;
1313
1314 if (!timeouts)
1315 timeouts = tn->timeouts;
1316 /* set default TCP timeouts. */
1317 for (i=0; i<TCP_CONNTRACK_TIMEOUT_MAX; i++)
1318 timeouts[i] = tn->timeouts[i];
1319
1320 if (tb[CTA_TIMEOUT_TCP_SYN_SENT]) {
1321 timeouts[TCP_CONNTRACK_SYN_SENT] =
1322 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT]))*HZ;
1323 }
1324
1325 if (tb[CTA_TIMEOUT_TCP_SYN_RECV]) {
1326 timeouts[TCP_CONNTRACK_SYN_RECV] =
1327 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_RECV]))*HZ;
1328 }
1329 if (tb[CTA_TIMEOUT_TCP_ESTABLISHED]) {
1330 timeouts[TCP_CONNTRACK_ESTABLISHED] =
1331 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_ESTABLISHED]))*HZ;
1332 }
1333 if (tb[CTA_TIMEOUT_TCP_FIN_WAIT]) {
1334 timeouts[TCP_CONNTRACK_FIN_WAIT] =
1335 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_FIN_WAIT]))*HZ;
1336 }
1337 if (tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]) {
1338 timeouts[TCP_CONNTRACK_CLOSE_WAIT] =
1339 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]))*HZ;
1340 }
1341 if (tb[CTA_TIMEOUT_TCP_LAST_ACK]) {
1342 timeouts[TCP_CONNTRACK_LAST_ACK] =
1343 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_LAST_ACK]))*HZ;
1344 }
1345 if (tb[CTA_TIMEOUT_TCP_TIME_WAIT]) {
1346 timeouts[TCP_CONNTRACK_TIME_WAIT] =
1347 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_TIME_WAIT]))*HZ;
1348 }
1349 if (tb[CTA_TIMEOUT_TCP_CLOSE]) {
1350 timeouts[TCP_CONNTRACK_CLOSE] =
1351 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE]))*HZ;
1352 }
1353 if (tb[CTA_TIMEOUT_TCP_SYN_SENT2]) {
1354 timeouts[TCP_CONNTRACK_SYN_SENT2] =
1355 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT2]))*HZ;
1356 }
1357 if (tb[CTA_TIMEOUT_TCP_RETRANS]) {
1358 timeouts[TCP_CONNTRACK_RETRANS] =
1359 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_RETRANS]))*HZ;
1360 }
1361 if (tb[CTA_TIMEOUT_TCP_UNACK]) {
1362 timeouts[TCP_CONNTRACK_UNACK] =
1363 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_UNACK]))*HZ;
1364 }
1365
1366 timeouts[CTA_TIMEOUT_TCP_UNSPEC] = timeouts[CTA_TIMEOUT_TCP_SYN_SENT];
1367 return 0;
1368 }
1369
1370 static int
tcp_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)1371 tcp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
1372 {
1373 const unsigned int *timeouts = data;
1374
1375 if (nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT,
1376 htonl(timeouts[TCP_CONNTRACK_SYN_SENT] / HZ)) ||
1377 nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_RECV,
1378 htonl(timeouts[TCP_CONNTRACK_SYN_RECV] / HZ)) ||
1379 nla_put_be32(skb, CTA_TIMEOUT_TCP_ESTABLISHED,
1380 htonl(timeouts[TCP_CONNTRACK_ESTABLISHED] / HZ)) ||
1381 nla_put_be32(skb, CTA_TIMEOUT_TCP_FIN_WAIT,
1382 htonl(timeouts[TCP_CONNTRACK_FIN_WAIT] / HZ)) ||
1383 nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE_WAIT,
1384 htonl(timeouts[TCP_CONNTRACK_CLOSE_WAIT] / HZ)) ||
1385 nla_put_be32(skb, CTA_TIMEOUT_TCP_LAST_ACK,
1386 htonl(timeouts[TCP_CONNTRACK_LAST_ACK] / HZ)) ||
1387 nla_put_be32(skb, CTA_TIMEOUT_TCP_TIME_WAIT,
1388 htonl(timeouts[TCP_CONNTRACK_TIME_WAIT] / HZ)) ||
1389 nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE,
1390 htonl(timeouts[TCP_CONNTRACK_CLOSE] / HZ)) ||
1391 nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT2,
1392 htonl(timeouts[TCP_CONNTRACK_SYN_SENT2] / HZ)) ||
1393 nla_put_be32(skb, CTA_TIMEOUT_TCP_RETRANS,
1394 htonl(timeouts[TCP_CONNTRACK_RETRANS] / HZ)) ||
1395 nla_put_be32(skb, CTA_TIMEOUT_TCP_UNACK,
1396 htonl(timeouts[TCP_CONNTRACK_UNACK] / HZ)))
1397 goto nla_put_failure;
1398 return 0;
1399
1400 nla_put_failure:
1401 return -ENOSPC;
1402 }
1403
1404 static const struct nla_policy tcp_timeout_nla_policy[CTA_TIMEOUT_TCP_MAX+1] = {
1405 [CTA_TIMEOUT_TCP_SYN_SENT] = { .type = NLA_U32 },
1406 [CTA_TIMEOUT_TCP_SYN_RECV] = { .type = NLA_U32 },
1407 [CTA_TIMEOUT_TCP_ESTABLISHED] = { .type = NLA_U32 },
1408 [CTA_TIMEOUT_TCP_FIN_WAIT] = { .type = NLA_U32 },
1409 [CTA_TIMEOUT_TCP_CLOSE_WAIT] = { .type = NLA_U32 },
1410 [CTA_TIMEOUT_TCP_LAST_ACK] = { .type = NLA_U32 },
1411 [CTA_TIMEOUT_TCP_TIME_WAIT] = { .type = NLA_U32 },
1412 [CTA_TIMEOUT_TCP_CLOSE] = { .type = NLA_U32 },
1413 [CTA_TIMEOUT_TCP_SYN_SENT2] = { .type = NLA_U32 },
1414 [CTA_TIMEOUT_TCP_RETRANS] = { .type = NLA_U32 },
1415 [CTA_TIMEOUT_TCP_UNACK] = { .type = NLA_U32 },
1416 };
1417 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1418
nf_conntrack_tcp_init_net(struct net * net)1419 void nf_conntrack_tcp_init_net(struct net *net)
1420 {
1421 struct nf_tcp_net *tn = nf_tcp_pernet(net);
1422 int i;
1423
1424 for (i = 0; i < TCP_CONNTRACK_TIMEOUT_MAX; i++)
1425 tn->timeouts[i] = tcp_timeouts[i];
1426
1427 /* timeouts[0] is unused, make it same as SYN_SENT so
1428 * ->timeouts[0] contains 'new' timeout, like udp or icmp.
1429 */
1430 tn->timeouts[0] = tcp_timeouts[TCP_CONNTRACK_SYN_SENT];
1431 tn->tcp_loose = nf_ct_tcp_loose;
1432 tn->tcp_be_liberal = nf_ct_tcp_be_liberal;
1433 tn->tcp_max_retrans = nf_ct_tcp_max_retrans;
1434 }
1435
1436 const struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp =
1437 {
1438 .l4proto = IPPROTO_TCP,
1439 #ifdef CONFIG_NF_CONNTRACK_PROCFS
1440 .print_conntrack = tcp_print_conntrack,
1441 #endif
1442 .can_early_drop = tcp_can_early_drop,
1443 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1444 .to_nlattr = tcp_to_nlattr,
1445 .from_nlattr = nlattr_to_tcp,
1446 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
1447 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
1448 .nlattr_tuple_size = tcp_nlattr_tuple_size,
1449 .nlattr_size = TCP_NLATTR_SIZE,
1450 .nla_policy = nf_ct_port_nla_policy,
1451 #endif
1452 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1453 .ctnl_timeout = {
1454 .nlattr_to_obj = tcp_timeout_nlattr_to_obj,
1455 .obj_to_nlattr = tcp_timeout_obj_to_nlattr,
1456 .nlattr_max = CTA_TIMEOUT_TCP_MAX,
1457 .obj_size = sizeof(unsigned int) *
1458 TCP_CONNTRACK_TIMEOUT_MAX,
1459 .nla_policy = tcp_timeout_nla_policy,
1460 },
1461 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1462 };
1463
