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 if (receiver->td_maxwin == 0) {
545 /* We haven't seen traffic in the other
546 * direction yet but we have to tweak window
547 * tracking to pass III and IV until that
548 * happens.
549 */
550 receiver->td_end = receiver->td_maxend = sack;
551 } else if (sack == receiver->td_end + 1) {
552 /* Likely a reply to a keepalive.
553 * Needed for III.
554 */
555 receiver->td_end++;
556 }
557
558 }
559 } else if (((state->state == TCP_CONNTRACK_SYN_SENT
560 && dir == IP_CT_DIR_ORIGINAL)
561 || (state->state == TCP_CONNTRACK_SYN_RECV
562 && dir == IP_CT_DIR_REPLY))
563 && after(end, sender->td_end)) {
564 /*
565 * RFC 793: "if a TCP is reinitialized ... then it need
566 * not wait at all; it must only be sure to use sequence
567 * numbers larger than those recently used."
568 */
569 sender->td_end =
570 sender->td_maxend = end;
571 sender->td_maxwin = (win == 0 ? 1 : win);
572
573 tcp_options(skb, dataoff, tcph, sender);
574 }
575
576 if (!(tcph->ack)) {
577 /*
578 * If there is no ACK, just pretend it was set and OK.
579 */
580 ack = sack = receiver->td_end;
581 } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
582 (TCP_FLAG_ACK|TCP_FLAG_RST))
583 && (ack == 0)) {
584 /*
585 * Broken TCP stacks, that set ACK in RST packets as well
586 * with zero ack value.
587 */
588 ack = sack = receiver->td_end;
589 }
590
591 if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)
592 /*
593 * RST sent answering SYN.
594 */
595 seq = end = sender->td_end;
596
597 pr_debug("tcp_in_window: ");
598 nf_ct_dump_tuple(tuple);
599 pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
600 seq, ack, receiver_offset, sack, receiver_offset, win, end);
601 pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
602 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
603 sender->td_end, sender->td_maxend, sender->td_maxwin,
604 sender->td_scale,
605 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
606 receiver->td_scale);
607
608 /* Is the ending sequence in the receive window (if available)? */
609 in_recv_win = !receiver->td_maxwin ||
610 after(end, sender->td_end - receiver->td_maxwin - 1);
611
612 pr_debug("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
613 before(seq, sender->td_maxend + 1),
614 (in_recv_win ? 1 : 0),
615 before(sack, receiver->td_end + 1),
616 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1));
617
618 if (before(seq, sender->td_maxend + 1) &&
619 in_recv_win &&
620 before(sack, receiver->td_end + 1) &&
621 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) {
622 /*
623 * Take into account window scaling (RFC 1323).
624 */
625 if (!tcph->syn)
626 win <<= sender->td_scale;
627
628 /*
629 * Update sender data.
630 */
631 swin = win + (sack - ack);
632 if (sender->td_maxwin < swin)
633 sender->td_maxwin = swin;
634 if (after(end, sender->td_end)) {
635 sender->td_end = end;
636 sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
637 }
638 if (tcph->ack) {
639 if (!(sender->flags & IP_CT_TCP_FLAG_MAXACK_SET)) {
640 sender->td_maxack = ack;
641 sender->flags |= IP_CT_TCP_FLAG_MAXACK_SET;
642 } else if (after(ack, sender->td_maxack))
643 sender->td_maxack = ack;
644 }
645
646 /*
647 * Update receiver data.
648 */
649 if (receiver->td_maxwin != 0 && after(end, sender->td_maxend))
650 receiver->td_maxwin += end - sender->td_maxend;
651 if (after(sack + win, receiver->td_maxend - 1)) {
652 receiver->td_maxend = sack + win;
653 if (win == 0)
654 receiver->td_maxend++;
655 }
656 if (ack == receiver->td_end)
657 receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
658
659 /*
660 * Check retransmissions.
661 */
662 if (index == TCP_ACK_SET) {
663 if (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++;
669 else {
670 state->last_dir = dir;
671 state->last_seq = seq;
672 state->last_ack = ack;
673 state->last_end = end;
674 state->last_win = win_raw;
675 state->retrans = 0;
676 }
677 }
678 res = true;
679 } else {
680 res = false;
681 if (sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL ||
682 tn->tcp_be_liberal)
683 res = true;
684 if (!res) {
685 nf_ct_l4proto_log_invalid(skb, ct,
686 "%s",
687 before(seq, sender->td_maxend + 1) ?
688 in_recv_win ?
689 before(sack, receiver->td_end + 1) ?
690 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1) ? "BUG"
691 : "ACK is under the lower bound (possible overly delayed ACK)"
692 : "ACK is over the upper bound (ACKed data not seen yet)"
693 : "SEQ is under the lower bound (already ACKed data retransmitted)"
694 : "SEQ is over the upper bound (over the window of the receiver)");
695 }
696 }
697
698 pr_debug("tcp_in_window: res=%u sender end=%u maxend=%u maxwin=%u "
699 "receiver end=%u maxend=%u maxwin=%u\n",
700 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
701 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
702
703 return res;
704 }
705
706 /* table of valid flag combinations - PUSH, ECE and CWR are always valid */
707 static const u8 tcp_valid_flags[(TCPHDR_FIN|TCPHDR_SYN|TCPHDR_RST|TCPHDR_ACK|
708 TCPHDR_URG) + 1] =
709 {
710 [TCPHDR_SYN] = 1,
711 [TCPHDR_SYN|TCPHDR_URG] = 1,
712 [TCPHDR_SYN|TCPHDR_ACK] = 1,
713 [TCPHDR_RST] = 1,
714 [TCPHDR_RST|TCPHDR_ACK] = 1,
715 [TCPHDR_FIN|TCPHDR_ACK] = 1,
716 [TCPHDR_FIN|TCPHDR_ACK|TCPHDR_URG] = 1,
717 [TCPHDR_ACK] = 1,
718 [TCPHDR_ACK|TCPHDR_URG] = 1,
719 };
720
tcp_error_log(const struct sk_buff * skb,const struct nf_hook_state * state,const char * msg)721 static void tcp_error_log(const struct sk_buff *skb,
722 const struct nf_hook_state *state,
723 const char *msg)
724 {
725 nf_l4proto_log_invalid(skb, state->net, state->pf, IPPROTO_TCP, "%s", msg);
726 }
727
728 /* 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)729 static bool tcp_error(const struct tcphdr *th,
730 struct sk_buff *skb,
731 unsigned int dataoff,
732 const struct nf_hook_state *state)
733 {
734 unsigned int tcplen = skb->len - dataoff;
735 u8 tcpflags;
736
737 /* Not whole TCP header or malformed packet */
738 if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
739 tcp_error_log(skb, state, "truncated packet");
740 return true;
741 }
742
743 /* Checksum invalid? Ignore.
744 * We skip checking packets on the outgoing path
745 * because the checksum is assumed to be correct.
746 */
747 /* FIXME: Source route IP option packets --RR */
748 if (state->net->ct.sysctl_checksum &&
749 state->hook == NF_INET_PRE_ROUTING &&
750 nf_checksum(skb, state->hook, dataoff, IPPROTO_TCP, state->pf)) {
751 tcp_error_log(skb, state, "bad checksum");
752 return true;
753 }
754
755 /* Check TCP flags. */
756 tcpflags = (tcp_flag_byte(th) & ~(TCPHDR_ECE|TCPHDR_CWR|TCPHDR_PSH));
757 if (!tcp_valid_flags[tcpflags]) {
758 tcp_error_log(skb, state, "invalid tcp flag combination");
759 return true;
760 }
761
762 return false;
763 }
764
tcp_new(struct nf_conn * ct,const struct sk_buff * skb,unsigned int dataoff,const struct tcphdr * th)765 static noinline bool tcp_new(struct nf_conn *ct, const struct sk_buff *skb,
766 unsigned int dataoff,
767 const struct tcphdr *th)
768 {
769 enum tcp_conntrack new_state;
770 struct net *net = nf_ct_net(ct);
771 const struct nf_tcp_net *tn = nf_tcp_pernet(net);
772 const struct ip_ct_tcp_state *sender = &ct->proto.tcp.seen[0];
773 const struct ip_ct_tcp_state *receiver = &ct->proto.tcp.seen[1];
774
775 /* Don't need lock here: this conntrack not in circulation yet */
776 new_state = tcp_conntracks[0][get_conntrack_index(th)][TCP_CONNTRACK_NONE];
777
778 /* Invalid: delete conntrack */
779 if (new_state >= TCP_CONNTRACK_MAX) {
780 pr_debug("nf_ct_tcp: invalid new deleting.\n");
781 return false;
782 }
783
784 if (new_state == TCP_CONNTRACK_SYN_SENT) {
785 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
786 /* SYN packet */
787 ct->proto.tcp.seen[0].td_end =
788 segment_seq_plus_len(ntohl(th->seq), skb->len,
789 dataoff, th);
790 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
791 if (ct->proto.tcp.seen[0].td_maxwin == 0)
792 ct->proto.tcp.seen[0].td_maxwin = 1;
793 ct->proto.tcp.seen[0].td_maxend =
794 ct->proto.tcp.seen[0].td_end;
795
796 tcp_options(skb, dataoff, th, &ct->proto.tcp.seen[0]);
797 } else if (tn->tcp_loose == 0) {
798 /* Don't try to pick up connections. */
799 return false;
800 } else {
801 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
802 /*
803 * We are in the middle of a connection,
804 * its history is lost for us.
805 * Let's try to use the data from the packet.
806 */
807 ct->proto.tcp.seen[0].td_end =
808 segment_seq_plus_len(ntohl(th->seq), skb->len,
809 dataoff, th);
810 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
811 if (ct->proto.tcp.seen[0].td_maxwin == 0)
812 ct->proto.tcp.seen[0].td_maxwin = 1;
813 ct->proto.tcp.seen[0].td_maxend =
814 ct->proto.tcp.seen[0].td_end +
815 ct->proto.tcp.seen[0].td_maxwin;
816
817 /* We assume SACK and liberal window checking to handle
818 * window scaling */
819 ct->proto.tcp.seen[0].flags =
820 ct->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM |
821 IP_CT_TCP_FLAG_BE_LIBERAL;
822 }
823
824 /* tcp_packet will set them */
825 ct->proto.tcp.last_index = TCP_NONE_SET;
826
827 pr_debug("%s: sender end=%u maxend=%u maxwin=%u scale=%i "
828 "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
829 __func__,
830 sender->td_end, sender->td_maxend, sender->td_maxwin,
831 sender->td_scale,
832 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
833 receiver->td_scale);
834 return true;
835 }
836
nf_conntrack_tcp_established(const struct nf_conn * ct)837 static bool nf_conntrack_tcp_established(const struct nf_conn *ct)
838 {
839 return ct->proto.tcp.state == TCP_CONNTRACK_ESTABLISHED &&
840 test_bit(IPS_ASSURED_BIT, &ct->status);
841 }
842
843 /* 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)844 int nf_conntrack_tcp_packet(struct nf_conn *ct,
845 struct sk_buff *skb,
846 unsigned int dataoff,
847 enum ip_conntrack_info ctinfo,
848 const struct nf_hook_state *state)
849 {
850 struct net *net = nf_ct_net(ct);
851 struct nf_tcp_net *tn = nf_tcp_pernet(net);
852 struct nf_conntrack_tuple *tuple;
853 enum tcp_conntrack new_state, old_state;
854 unsigned int index, *timeouts;
855 enum ip_conntrack_dir dir;
856 const struct tcphdr *th;
857 struct tcphdr _tcph;
858 unsigned long timeout;
859
860 th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
861 if (th == NULL)
862 return -NF_ACCEPT;
863
864 if (tcp_error(th, skb, dataoff, state))
865 return -NF_ACCEPT;
866
867 if (!nf_ct_is_confirmed(ct) && !tcp_new(ct, skb, dataoff, th))
868 return -NF_ACCEPT;
869
870 spin_lock_bh(&ct->lock);
871 old_state = ct->proto.tcp.state;
872 dir = CTINFO2DIR(ctinfo);
873 index = get_conntrack_index(th);
874 new_state = tcp_conntracks[dir][index][old_state];
875 tuple = &ct->tuplehash[dir].tuple;
876
877 switch (new_state) {
878 case TCP_CONNTRACK_SYN_SENT:
879 if (old_state < TCP_CONNTRACK_TIME_WAIT)
880 break;
881 /* RFC 1122: "When a connection is closed actively,
882 * it MUST linger in TIME-WAIT state for a time 2xMSL
883 * (Maximum Segment Lifetime). However, it MAY accept
884 * a new SYN from the remote TCP to reopen the connection
885 * directly from TIME-WAIT state, if..."
886 * We ignore the conditions because we are in the
887 * TIME-WAIT state anyway.
888 *
889 * Handle aborted connections: we and the server
890 * think there is an existing connection but the client
891 * aborts it and starts a new one.
892 */
893 if (((ct->proto.tcp.seen[dir].flags
894 | ct->proto.tcp.seen[!dir].flags)
895 & IP_CT_TCP_FLAG_CLOSE_INIT)
896 || (ct->proto.tcp.last_dir == dir
897 && ct->proto.tcp.last_index == TCP_RST_SET)) {
898 /* Attempt to reopen a closed/aborted connection.
899 * Delete this connection and look up again. */
900 spin_unlock_bh(&ct->lock);
901
902 /* Only repeat if we can actually remove the timer.
903 * Destruction may already be in progress in process
904 * context and we must give it a chance to terminate.
905 */
906 if (nf_ct_kill(ct))
907 return -NF_REPEAT;
908 return NF_DROP;
909 }
910 fallthrough;
911 case TCP_CONNTRACK_IGNORE:
912 /* Ignored packets:
913 *
914 * Our connection entry may be out of sync, so ignore
915 * packets which may signal the real connection between
916 * the client and the server.
917 *
918 * a) SYN in ORIGINAL
919 * b) SYN/ACK in REPLY
920 * c) ACK in reply direction after initial SYN in original.
921 *
922 * If the ignored packet is invalid, the receiver will send
923 * a RST we'll catch below.
924 */
925 if (index == TCP_SYNACK_SET
926 && ct->proto.tcp.last_index == TCP_SYN_SET
927 && ct->proto.tcp.last_dir != dir
928 && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
929 /* b) This SYN/ACK acknowledges a SYN that we earlier
930 * ignored as invalid. This means that the client and
931 * the server are both in sync, while the firewall is
932 * not. We get in sync from the previously annotated
933 * values.
934 */
935 old_state = TCP_CONNTRACK_SYN_SENT;
936 new_state = TCP_CONNTRACK_SYN_RECV;
937 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end =
938 ct->proto.tcp.last_end;
939 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend =
940 ct->proto.tcp.last_end;
941 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin =
942 ct->proto.tcp.last_win == 0 ?
943 1 : ct->proto.tcp.last_win;
944 ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale =
945 ct->proto.tcp.last_wscale;
946 ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
947 ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags =
948 ct->proto.tcp.last_flags;
949 memset(&ct->proto.tcp.seen[dir], 0,
950 sizeof(struct ip_ct_tcp_state));
951 break;
952 }
953 ct->proto.tcp.last_index = index;
954 ct->proto.tcp.last_dir = dir;
955 ct->proto.tcp.last_seq = ntohl(th->seq);
956 ct->proto.tcp.last_end =
957 segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
958 ct->proto.tcp.last_win = ntohs(th->window);
959
960 /* a) This is a SYN in ORIGINAL. The client and the server
961 * may be in sync but we are not. In that case, we annotate
962 * the TCP options and let the packet go through. If it is a
963 * valid SYN packet, the server will reply with a SYN/ACK, and
964 * then we'll get in sync. Otherwise, the server potentially
965 * responds with a challenge ACK if implementing RFC5961.
966 */
967 if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) {
968 struct ip_ct_tcp_state seen = {};
969
970 ct->proto.tcp.last_flags =
971 ct->proto.tcp.last_wscale = 0;
972 tcp_options(skb, dataoff, th, &seen);
973 if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
974 ct->proto.tcp.last_flags |=
975 IP_CT_TCP_FLAG_WINDOW_SCALE;
976 ct->proto.tcp.last_wscale = seen.td_scale;
977 }
978 if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) {
979 ct->proto.tcp.last_flags |=
980 IP_CT_TCP_FLAG_SACK_PERM;
981 }
982 /* Mark the potential for RFC5961 challenge ACK,
983 * this pose a special problem for LAST_ACK state
984 * as ACK is intrepretated as ACKing last FIN.
985 */
986 if (old_state == TCP_CONNTRACK_LAST_ACK)
987 ct->proto.tcp.last_flags |=
988 IP_CT_EXP_CHALLENGE_ACK;
989 }
990 spin_unlock_bh(&ct->lock);
991 nf_ct_l4proto_log_invalid(skb, ct, "invalid packet ignored in "
992 "state %s ", tcp_conntrack_names[old_state]);
993 return NF_ACCEPT;
994 case TCP_CONNTRACK_MAX:
995 /* Special case for SYN proxy: when the SYN to the server or
996 * the SYN/ACK from the server is lost, the client may transmit
997 * a keep-alive packet while in SYN_SENT state. This needs to
998 * be associated with the original conntrack entry in order to
999 * generate a new SYN with the correct sequence number.
1000 */
1001 if (nfct_synproxy(ct) && old_state == TCP_CONNTRACK_SYN_SENT &&
1002 index == TCP_ACK_SET && dir == IP_CT_DIR_ORIGINAL &&
1003 ct->proto.tcp.last_dir == IP_CT_DIR_ORIGINAL &&
1004 ct->proto.tcp.seen[dir].td_end - 1 == ntohl(th->seq)) {
1005 pr_debug("nf_ct_tcp: SYN proxy client keep alive\n");
1006 spin_unlock_bh(&ct->lock);
1007 return NF_ACCEPT;
1008 }
1009
1010 /* Invalid packet */
1011 pr_debug("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
1012 dir, get_conntrack_index(th), old_state);
1013 spin_unlock_bh(&ct->lock);
1014 nf_ct_l4proto_log_invalid(skb, ct, "invalid state");
1015 return -NF_ACCEPT;
1016 case TCP_CONNTRACK_TIME_WAIT:
1017 /* RFC5961 compliance cause stack to send "challenge-ACK"
1018 * e.g. in response to spurious SYNs. Conntrack MUST
1019 * not believe this ACK is acking last FIN.
1020 */
1021 if (old_state == TCP_CONNTRACK_LAST_ACK &&
1022 index == TCP_ACK_SET &&
1023 ct->proto.tcp.last_dir != dir &&
1024 ct->proto.tcp.last_index == TCP_SYN_SET &&
1025 (ct->proto.tcp.last_flags & IP_CT_EXP_CHALLENGE_ACK)) {
1026 /* Detected RFC5961 challenge ACK */
1027 ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
1028 spin_unlock_bh(&ct->lock);
1029 nf_ct_l4proto_log_invalid(skb, ct, "challenge-ack ignored");
1030 return NF_ACCEPT; /* Don't change state */
1031 }
1032 break;
1033 case TCP_CONNTRACK_SYN_SENT2:
1034 /* tcp_conntracks table is not smart enough to handle
1035 * simultaneous open.
1036 */
1037 ct->proto.tcp.last_flags |= IP_CT_TCP_SIMULTANEOUS_OPEN;
1038 break;
1039 case TCP_CONNTRACK_SYN_RECV:
1040 if (dir == IP_CT_DIR_REPLY && index == TCP_ACK_SET &&
1041 ct->proto.tcp.last_flags & IP_CT_TCP_SIMULTANEOUS_OPEN)
1042 new_state = TCP_CONNTRACK_ESTABLISHED;
1043 break;
1044 case TCP_CONNTRACK_CLOSE:
1045 if (index != TCP_RST_SET)
1046 break;
1047
1048 if (ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET) {
1049 u32 seq = ntohl(th->seq);
1050
1051 if (before(seq, ct->proto.tcp.seen[!dir].td_maxack)) {
1052 /* Invalid RST */
1053 spin_unlock_bh(&ct->lock);
1054 nf_ct_l4proto_log_invalid(skb, ct, "invalid rst");
1055 return -NF_ACCEPT;
1056 }
1057
1058 if (!nf_conntrack_tcp_established(ct) ||
1059 seq == ct->proto.tcp.seen[!dir].td_maxack)
1060 break;
1061
1062 /* Check if rst is part of train, such as
1063 * foo:80 > bar:4379: P, 235946583:235946602(19) ack 42
1064 * foo:80 > bar:4379: R, 235946602:235946602(0) ack 42
1065 */
1066 if (ct->proto.tcp.last_index == TCP_ACK_SET &&
1067 ct->proto.tcp.last_dir == dir &&
1068 seq == ct->proto.tcp.last_end)
1069 break;
1070
1071 /* ... RST sequence number doesn't match exactly, keep
1072 * established state to allow a possible challenge ACK.
1073 */
1074 new_state = old_state;
1075 }
1076 if (((test_bit(IPS_SEEN_REPLY_BIT, &ct->status)
1077 && ct->proto.tcp.last_index == TCP_SYN_SET)
1078 || (!test_bit(IPS_ASSURED_BIT, &ct->status)
1079 && ct->proto.tcp.last_index == TCP_ACK_SET))
1080 && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
1081 /* RST sent to invalid SYN or ACK we had let through
1082 * at a) and c) above:
1083 *
1084 * a) SYN was in window then
1085 * c) we hold a half-open connection.
1086 *
1087 * Delete our connection entry.
1088 * We skip window checking, because packet might ACK
1089 * segments we ignored. */
1090 goto in_window;
1091 }
1092 break;
1093 default:
1094 /* Keep compilers happy. */
1095 break;
1096 }
1097
1098 if (!tcp_in_window(ct, &ct->proto.tcp, dir, index,
1099 skb, dataoff, th)) {
1100 spin_unlock_bh(&ct->lock);
1101 return -NF_ACCEPT;
1102 }
1103 in_window:
1104 /* From now on we have got in-window packets */
1105 ct->proto.tcp.last_index = index;
1106 ct->proto.tcp.last_dir = dir;
1107
1108 pr_debug("tcp_conntracks: ");
1109 nf_ct_dump_tuple(tuple);
1110 pr_debug("syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1111 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
1112 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
1113 old_state, new_state);
1114
1115 ct->proto.tcp.state = new_state;
1116 if (old_state != new_state
1117 && new_state == TCP_CONNTRACK_FIN_WAIT)
1118 ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1119
1120 timeouts = nf_ct_timeout_lookup(ct);
1121 if (!timeouts)
1122 timeouts = tn->timeouts;
1123
1124 if (ct->proto.tcp.retrans >= tn->tcp_max_retrans &&
1125 timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1126 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1127 else if (unlikely(index == TCP_RST_SET))
1128 timeout = timeouts[TCP_CONNTRACK_CLOSE];
1129 else if ((ct->proto.tcp.seen[0].flags | ct->proto.tcp.seen[1].flags) &
1130 IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED &&
1131 timeouts[new_state] > timeouts[TCP_CONNTRACK_UNACK])
1132 timeout = timeouts[TCP_CONNTRACK_UNACK];
1133 else if (ct->proto.tcp.last_win == 0 &&
1134 timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1135 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1136 else
1137 timeout = timeouts[new_state];
1138 spin_unlock_bh(&ct->lock);
1139
1140 if (new_state != old_state)
1141 nf_conntrack_event_cache(IPCT_PROTOINFO, ct);
1142
1143 if (!test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
1144 /* If only reply is a RST, we can consider ourselves not to
1145 have an established connection: this is a fairly common
1146 problem case, so we can delete the conntrack
1147 immediately. --RR */
1148 if (th->rst) {
1149 nf_ct_kill_acct(ct, ctinfo, skb);
1150 return NF_ACCEPT;
1151 }
1152 /* ESTABLISHED without SEEN_REPLY, i.e. mid-connection
1153 * pickup with loose=1. Avoid large ESTABLISHED timeout.
1154 */
1155 if (new_state == TCP_CONNTRACK_ESTABLISHED &&
1156 timeout > timeouts[TCP_CONNTRACK_UNACK])
1157 timeout = timeouts[TCP_CONNTRACK_UNACK];
1158 } else if (!test_bit(IPS_ASSURED_BIT, &ct->status)
1159 && (old_state == TCP_CONNTRACK_SYN_RECV
1160 || old_state == TCP_CONNTRACK_ESTABLISHED)
1161 && new_state == TCP_CONNTRACK_ESTABLISHED) {
1162 /* Set ASSURED if we see valid ack in ESTABLISHED
1163 after SYN_RECV or a valid answer for a picked up
1164 connection. */
1165 set_bit(IPS_ASSURED_BIT, &ct->status);
1166 nf_conntrack_event_cache(IPCT_ASSURED, ct);
1167 }
1168 nf_ct_refresh_acct(ct, ctinfo, skb, timeout);
1169
1170 return NF_ACCEPT;
1171 }
1172
tcp_can_early_drop(const struct nf_conn * ct)1173 static bool tcp_can_early_drop(const struct nf_conn *ct)
1174 {
1175 switch (ct->proto.tcp.state) {
1176 case TCP_CONNTRACK_FIN_WAIT:
1177 case TCP_CONNTRACK_LAST_ACK:
1178 case TCP_CONNTRACK_TIME_WAIT:
1179 case TCP_CONNTRACK_CLOSE:
1180 case TCP_CONNTRACK_CLOSE_WAIT:
1181 return true;
1182 default:
1183 break;
1184 }
1185
1186 return false;
1187 }
1188
1189 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1190
1191 #include <linux/netfilter/nfnetlink.h>
1192 #include <linux/netfilter/nfnetlink_conntrack.h>
1193
tcp_to_nlattr(struct sk_buff * skb,struct nlattr * nla,struct nf_conn * ct)1194 static int tcp_to_nlattr(struct sk_buff *skb, struct nlattr *nla,
1195 struct nf_conn *ct)
1196 {
1197 struct nlattr *nest_parms;
1198 struct nf_ct_tcp_flags tmp = {};
1199
1200 spin_lock_bh(&ct->lock);
1201 nest_parms = nla_nest_start(skb, CTA_PROTOINFO_TCP);
1202 if (!nest_parms)
1203 goto nla_put_failure;
1204
1205 if (nla_put_u8(skb, CTA_PROTOINFO_TCP_STATE, ct->proto.tcp.state) ||
1206 nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL,
1207 ct->proto.tcp.seen[0].td_scale) ||
1208 nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY,
1209 ct->proto.tcp.seen[1].td_scale))
1210 goto nla_put_failure;
1211
1212 tmp.flags = ct->proto.tcp.seen[0].flags;
1213 if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_ORIGINAL,
1214 sizeof(struct nf_ct_tcp_flags), &tmp))
1215 goto nla_put_failure;
1216
1217 tmp.flags = ct->proto.tcp.seen[1].flags;
1218 if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_REPLY,
1219 sizeof(struct nf_ct_tcp_flags), &tmp))
1220 goto nla_put_failure;
1221 spin_unlock_bh(&ct->lock);
1222
1223 nla_nest_end(skb, nest_parms);
1224
1225 return 0;
1226
1227 nla_put_failure:
1228 spin_unlock_bh(&ct->lock);
1229 return -1;
1230 }
1231
1232 static const struct nla_policy tcp_nla_policy[CTA_PROTOINFO_TCP_MAX+1] = {
1233 [CTA_PROTOINFO_TCP_STATE] = { .type = NLA_U8 },
1234 [CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] = { .type = NLA_U8 },
1235 [CTA_PROTOINFO_TCP_WSCALE_REPLY] = { .type = NLA_U8 },
1236 [CTA_PROTOINFO_TCP_FLAGS_ORIGINAL] = { .len = sizeof(struct nf_ct_tcp_flags) },
1237 [CTA_PROTOINFO_TCP_FLAGS_REPLY] = { .len = sizeof(struct nf_ct_tcp_flags) },
1238 };
1239
1240 #define TCP_NLATTR_SIZE ( \
1241 NLA_ALIGN(NLA_HDRLEN + 1) + \
1242 NLA_ALIGN(NLA_HDRLEN + 1) + \
1243 NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)) + \
1244 NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)))
1245
nlattr_to_tcp(struct nlattr * cda[],struct nf_conn * ct)1246 static int nlattr_to_tcp(struct nlattr *cda[], struct nf_conn *ct)
1247 {
1248 struct nlattr *pattr = cda[CTA_PROTOINFO_TCP];
1249 struct nlattr *tb[CTA_PROTOINFO_TCP_MAX+1];
1250 int err;
1251
1252 /* updates could not contain anything about the private
1253 * protocol info, in that case skip the parsing */
1254 if (!pattr)
1255 return 0;
1256
1257 err = nla_parse_nested_deprecated(tb, CTA_PROTOINFO_TCP_MAX, pattr,
1258 tcp_nla_policy, NULL);
1259 if (err < 0)
1260 return err;
1261
1262 if (tb[CTA_PROTOINFO_TCP_STATE] &&
1263 nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]) >= TCP_CONNTRACK_MAX)
1264 return -EINVAL;
1265
1266 spin_lock_bh(&ct->lock);
1267 if (tb[CTA_PROTOINFO_TCP_STATE])
1268 ct->proto.tcp.state = nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]);
1269
1270 if (tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]) {
1271 struct nf_ct_tcp_flags *attr =
1272 nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]);
1273 ct->proto.tcp.seen[0].flags &= ~attr->mask;
1274 ct->proto.tcp.seen[0].flags |= attr->flags & attr->mask;
1275 }
1276
1277 if (tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]) {
1278 struct nf_ct_tcp_flags *attr =
1279 nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]);
1280 ct->proto.tcp.seen[1].flags &= ~attr->mask;
1281 ct->proto.tcp.seen[1].flags |= attr->flags & attr->mask;
1282 }
1283
1284 if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] &&
1285 tb[CTA_PROTOINFO_TCP_WSCALE_REPLY] &&
1286 ct->proto.tcp.seen[0].flags & IP_CT_TCP_FLAG_WINDOW_SCALE &&
1287 ct->proto.tcp.seen[1].flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
1288 ct->proto.tcp.seen[0].td_scale =
1289 nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL]);
1290 ct->proto.tcp.seen[1].td_scale =
1291 nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY]);
1292 }
1293 spin_unlock_bh(&ct->lock);
1294
1295 return 0;
1296 }
1297
tcp_nlattr_tuple_size(void)1298 static unsigned int tcp_nlattr_tuple_size(void)
1299 {
1300 static unsigned int size __read_mostly;
1301
1302 if (!size)
1303 size = nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);
1304
1305 return size;
1306 }
1307 #endif
1308
1309 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1310
1311 #include <linux/netfilter/nfnetlink.h>
1312 #include <linux/netfilter/nfnetlink_cttimeout.h>
1313
tcp_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)1314 static int tcp_timeout_nlattr_to_obj(struct nlattr *tb[],
1315 struct net *net, void *data)
1316 {
1317 struct nf_tcp_net *tn = nf_tcp_pernet(net);
1318 unsigned int *timeouts = data;
1319 int i;
1320
1321 if (!timeouts)
1322 timeouts = tn->timeouts;
1323 /* set default TCP timeouts. */
1324 for (i=0; i<TCP_CONNTRACK_TIMEOUT_MAX; i++)
1325 timeouts[i] = tn->timeouts[i];
1326
1327 if (tb[CTA_TIMEOUT_TCP_SYN_SENT]) {
1328 timeouts[TCP_CONNTRACK_SYN_SENT] =
1329 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT]))*HZ;
1330 }
1331
1332 if (tb[CTA_TIMEOUT_TCP_SYN_RECV]) {
1333 timeouts[TCP_CONNTRACK_SYN_RECV] =
1334 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_RECV]))*HZ;
1335 }
1336 if (tb[CTA_TIMEOUT_TCP_ESTABLISHED]) {
1337 timeouts[TCP_CONNTRACK_ESTABLISHED] =
1338 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_ESTABLISHED]))*HZ;
1339 }
1340 if (tb[CTA_TIMEOUT_TCP_FIN_WAIT]) {
1341 timeouts[TCP_CONNTRACK_FIN_WAIT] =
1342 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_FIN_WAIT]))*HZ;
1343 }
1344 if (tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]) {
1345 timeouts[TCP_CONNTRACK_CLOSE_WAIT] =
1346 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]))*HZ;
1347 }
1348 if (tb[CTA_TIMEOUT_TCP_LAST_ACK]) {
1349 timeouts[TCP_CONNTRACK_LAST_ACK] =
1350 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_LAST_ACK]))*HZ;
1351 }
1352 if (tb[CTA_TIMEOUT_TCP_TIME_WAIT]) {
1353 timeouts[TCP_CONNTRACK_TIME_WAIT] =
1354 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_TIME_WAIT]))*HZ;
1355 }
1356 if (tb[CTA_TIMEOUT_TCP_CLOSE]) {
1357 timeouts[TCP_CONNTRACK_CLOSE] =
1358 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE]))*HZ;
1359 }
1360 if (tb[CTA_TIMEOUT_TCP_SYN_SENT2]) {
1361 timeouts[TCP_CONNTRACK_SYN_SENT2] =
1362 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT2]))*HZ;
1363 }
1364 if (tb[CTA_TIMEOUT_TCP_RETRANS]) {
1365 timeouts[TCP_CONNTRACK_RETRANS] =
1366 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_RETRANS]))*HZ;
1367 }
1368 if (tb[CTA_TIMEOUT_TCP_UNACK]) {
1369 timeouts[TCP_CONNTRACK_UNACK] =
1370 ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_UNACK]))*HZ;
1371 }
1372
1373 timeouts[CTA_TIMEOUT_TCP_UNSPEC] = timeouts[CTA_TIMEOUT_TCP_SYN_SENT];
1374 return 0;
1375 }
1376
1377 static int
tcp_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)1378 tcp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
1379 {
1380 const unsigned int *timeouts = data;
1381
1382 if (nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT,
1383 htonl(timeouts[TCP_CONNTRACK_SYN_SENT] / HZ)) ||
1384 nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_RECV,
1385 htonl(timeouts[TCP_CONNTRACK_SYN_RECV] / HZ)) ||
1386 nla_put_be32(skb, CTA_TIMEOUT_TCP_ESTABLISHED,
1387 htonl(timeouts[TCP_CONNTRACK_ESTABLISHED] / HZ)) ||
1388 nla_put_be32(skb, CTA_TIMEOUT_TCP_FIN_WAIT,
1389 htonl(timeouts[TCP_CONNTRACK_FIN_WAIT] / HZ)) ||
1390 nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE_WAIT,
1391 htonl(timeouts[TCP_CONNTRACK_CLOSE_WAIT] / HZ)) ||
1392 nla_put_be32(skb, CTA_TIMEOUT_TCP_LAST_ACK,
1393 htonl(timeouts[TCP_CONNTRACK_LAST_ACK] / HZ)) ||
1394 nla_put_be32(skb, CTA_TIMEOUT_TCP_TIME_WAIT,
1395 htonl(timeouts[TCP_CONNTRACK_TIME_WAIT] / HZ)) ||
1396 nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE,
1397 htonl(timeouts[TCP_CONNTRACK_CLOSE] / HZ)) ||
1398 nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT2,
1399 htonl(timeouts[TCP_CONNTRACK_SYN_SENT2] / HZ)) ||
1400 nla_put_be32(skb, CTA_TIMEOUT_TCP_RETRANS,
1401 htonl(timeouts[TCP_CONNTRACK_RETRANS] / HZ)) ||
1402 nla_put_be32(skb, CTA_TIMEOUT_TCP_UNACK,
1403 htonl(timeouts[TCP_CONNTRACK_UNACK] / HZ)))
1404 goto nla_put_failure;
1405 return 0;
1406
1407 nla_put_failure:
1408 return -ENOSPC;
1409 }
1410
1411 static const struct nla_policy tcp_timeout_nla_policy[CTA_TIMEOUT_TCP_MAX+1] = {
1412 [CTA_TIMEOUT_TCP_SYN_SENT] = { .type = NLA_U32 },
1413 [CTA_TIMEOUT_TCP_SYN_RECV] = { .type = NLA_U32 },
1414 [CTA_TIMEOUT_TCP_ESTABLISHED] = { .type = NLA_U32 },
1415 [CTA_TIMEOUT_TCP_FIN_WAIT] = { .type = NLA_U32 },
1416 [CTA_TIMEOUT_TCP_CLOSE_WAIT] = { .type = NLA_U32 },
1417 [CTA_TIMEOUT_TCP_LAST_ACK] = { .type = NLA_U32 },
1418 [CTA_TIMEOUT_TCP_TIME_WAIT] = { .type = NLA_U32 },
1419 [CTA_TIMEOUT_TCP_CLOSE] = { .type = NLA_U32 },
1420 [CTA_TIMEOUT_TCP_SYN_SENT2] = { .type = NLA_U32 },
1421 [CTA_TIMEOUT_TCP_RETRANS] = { .type = NLA_U32 },
1422 [CTA_TIMEOUT_TCP_UNACK] = { .type = NLA_U32 },
1423 };
1424 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1425
nf_conntrack_tcp_init_net(struct net * net)1426 void nf_conntrack_tcp_init_net(struct net *net)
1427 {
1428 struct nf_tcp_net *tn = nf_tcp_pernet(net);
1429 int i;
1430
1431 for (i = 0; i < TCP_CONNTRACK_TIMEOUT_MAX; i++)
1432 tn->timeouts[i] = tcp_timeouts[i];
1433
1434 /* timeouts[0] is unused, make it same as SYN_SENT so
1435 * ->timeouts[0] contains 'new' timeout, like udp or icmp.
1436 */
1437 tn->timeouts[0] = tcp_timeouts[TCP_CONNTRACK_SYN_SENT];
1438 tn->tcp_loose = nf_ct_tcp_loose;
1439 tn->tcp_be_liberal = nf_ct_tcp_be_liberal;
1440 tn->tcp_max_retrans = nf_ct_tcp_max_retrans;
1441 }
1442
1443 const struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp =
1444 {
1445 .l4proto = IPPROTO_TCP,
1446 #ifdef CONFIG_NF_CONNTRACK_PROCFS
1447 .print_conntrack = tcp_print_conntrack,
1448 #endif
1449 .can_early_drop = tcp_can_early_drop,
1450 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1451 .to_nlattr = tcp_to_nlattr,
1452 .from_nlattr = nlattr_to_tcp,
1453 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
1454 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
1455 .nlattr_tuple_size = tcp_nlattr_tuple_size,
1456 .nlattr_size = TCP_NLATTR_SIZE,
1457 .nla_policy = nf_ct_port_nla_policy,
1458 #endif
1459 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1460 .ctnl_timeout = {
1461 .nlattr_to_obj = tcp_timeout_nlattr_to_obj,
1462 .obj_to_nlattr = tcp_timeout_obj_to_nlattr,
1463 .nlattr_max = CTA_TIMEOUT_TCP_MAX,
1464 .obj_size = sizeof(unsigned int) *
1465 TCP_CONNTRACK_TIMEOUT_MAX,
1466 .nla_policy = tcp_timeout_nla_policy,
1467 },
1468 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1469 };
1470
