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