1 /*-
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95
30 */
31
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD: releng/9.1/sys/netinet/tcp_timewait.c 238247 2012-07-08 14:21:36Z bz $");
34
35 #include "opt_inet.h"
36 #include "opt_inet6.h"
37 #include "opt_tcpdebug.h"
38
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/callout.h>
42 #include <sys/kernel.h>
43 #include <sys/sysctl.h>
44 #include <sys/malloc.h>
45 #include <sys/mbuf.h>
46 #include <sys/priv.h>
47 #include <sys/proc.h>
48 #include <sys/socket.h>
49 #include <sys/socketvar.h>
50 #include <sys/protosw.h>
51 #include <sys/random.h>
52
53 #include <vm/uma.h>
54
55 #include <net/route.h>
56 #include <net/if.h>
57 #include <net/vnet.h>
58
59 #include <netinet/in.h>
60 #include <netinet/in_pcb.h>
61 #include <netinet/in_systm.h>
62 #include <netinet/in_var.h>
63 #include <netinet/ip.h>
64 #include <netinet/ip_icmp.h>
65 #include <netinet/ip_var.h>
66 #ifdef INET6
67 #include <netinet/ip6.h>
68 #include <netinet6/in6_pcb.h>
69 #include <netinet6/ip6_var.h>
70 #include <netinet6/scope6_var.h>
71 #include <netinet6/nd6.h>
72 #endif
73 #include <netinet/tcp.h>
74 #include <netinet/tcp_fsm.h>
75 #include <netinet/tcp_seq.h>
76 #include <netinet/tcp_timer.h>
77 #include <netinet/tcp_var.h>
78 #ifdef INET6
79 #include <netinet6/tcp6_var.h>
80 #endif
81 #include <netinet/tcpip.h>
82 #ifdef TCPDEBUG
83 #include <netinet/tcp_debug.h>
84 #endif
85 #ifdef INET6
86 #include <netinet6/ip6protosw.h>
87 #endif
88
89 #include <machine/in_cksum.h>
90
91 #include <security/mac/mac_framework.h>
92
93 static VNET_DEFINE(uma_zone_t, tcptw_zone);
94 #define V_tcptw_zone VNET(tcptw_zone)
95 static int maxtcptw;
96
97 /*
98 * The timed wait queue contains references to each of the TCP sessions
99 * currently in the TIME_WAIT state. The queue pointers, including the
100 * queue pointers in each tcptw structure, are protected using the global
101 * tcbinfo lock, which must be held over queue iteration and modification.
102 */
103 static VNET_DEFINE(TAILQ_HEAD(, tcptw), twq_2msl);
104 #define V_twq_2msl VNET(twq_2msl)
105
106 static void tcp_tw_2msl_reset(struct tcptw *, int);
107 static void tcp_tw_2msl_stop(struct tcptw *);
108
109 static int
110 tcptw_auto_size(void)
111 {
112 int halfrange;
113
114 /*
115 * Max out at half the ephemeral port range so that TIME_WAIT
116 * sockets don't tie up too many ephemeral ports.
117 */
118 if (V_ipport_lastauto > V_ipport_firstauto)
119 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2;
120 else
121 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2;
122 /* Protect against goofy port ranges smaller than 32. */
123 return (imin(imax(halfrange, 32), maxsockets / 5));
124 }
125
126 static int
127 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
128 {
129 int error, new;
130
131 if (maxtcptw == 0)
132 new = tcptw_auto_size();
133 else
134 new = maxtcptw;
135 error = sysctl_handle_int(oidp, &new, 0, req);
136 if (error == 0 && req->newptr)
137 if (new >= 32) {
138 maxtcptw = new;
139 uma_zone_set_max(V_tcptw_zone, maxtcptw);
140 }
141 return (error);
142 }
143
144 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW,
145 &maxtcptw, 0, sysctl_maxtcptw, "IU",
146 "Maximum number of compressed TCP TIME_WAIT entries");
147
148 VNET_DEFINE(int, nolocaltimewait) = 0;
149 #define V_nolocaltimewait VNET(nolocaltimewait)
150 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_RW,
151 &VNET_NAME(nolocaltimewait), 0,
152 "Do not create compressed TCP TIME_WAIT entries for local connections");
153
154 void
155 tcp_tw_zone_change(void)
156 {
157
158 if (maxtcptw == 0)
159 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
160 }
161
162 void
163 tcp_tw_init(void)
164 {
165
166 V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
167 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
168 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
169 if (maxtcptw == 0)
170 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
171 else
172 uma_zone_set_max(V_tcptw_zone, maxtcptw);
173 TAILQ_INIT(&V_twq_2msl);
174 }
175
176 #ifdef VIMAGE
177 void
178 tcp_tw_destroy(void)
179 {
180 struct tcptw *tw;
181
182 INP_INFO_WLOCK(&V_tcbinfo);
183 while((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL)
184 tcp_twclose(tw, 0);
185 INP_INFO_WUNLOCK(&V_tcbinfo);
186
187 uma_zdestroy(V_tcptw_zone);
188 }
189 #endif
190
191 /*
192 * Move a TCP connection into TIME_WAIT state.
193 * tcbinfo is locked.
194 * inp is locked, and is unlocked before returning.
195 */
196 void
197 tcp_twstart(struct tcpcb *tp)
198 {
199 struct tcptw *tw;
200 struct inpcb *inp = tp->t_inpcb;
201 int acknow;
202 struct socket *so;
203 #ifdef INET6
204 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
205 #endif
206
207 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_reset(). */
208 INP_WLOCK_ASSERT(inp);
209
210 if (V_nolocaltimewait) {
211 int error = 0;
212 #ifdef INET6
213 if (isipv6)
214 error = in6_localaddr(&inp->in6p_faddr);
215 #endif
216 #if defined(INET6) && defined(INET)
217 else
218 #endif
219 #ifdef INET
220 error = in_localip(inp->inp_faddr);
221 #endif
222 if (error) {
223 tp = tcp_close(tp);
224 if (tp != NULL)
225 INP_WUNLOCK(inp);
226 return;
227 }
228 }
229
230 tw = uma_zalloc(V_tcptw_zone, M_NOWAIT);
231 if (tw == NULL) {
232 tw = tcp_tw_2msl_scan(1);
233 if (tw == NULL) {
234 tp = tcp_close(tp);
235 if (tp != NULL)
236 INP_WUNLOCK(inp);
237 return;
238 }
239 }
240 tw->tw_inpcb = inp;
241
242 /*
243 * Recover last window size sent.
244 */
245 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
246 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
247 else
248 tw->last_win = 0;
249
250 /*
251 * Set t_recent if timestamps are used on the connection.
252 */
253 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
254 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
255 tw->t_recent = tp->ts_recent;
256 tw->ts_offset = tp->ts_offset;
257 } else {
258 tw->t_recent = 0;
259 tw->ts_offset = 0;
260 }
261
262 tw->snd_nxt = tp->snd_nxt;
263 tw->rcv_nxt = tp->rcv_nxt;
264 tw->iss = tp->iss;
265 tw->irs = tp->irs;
266 tw->t_starttime = tp->t_starttime;
267 tw->tw_time = 0;
268
269 /* XXX
270 * If this code will
271 * be used for fin-wait-2 state also, then we may need
272 * a ts_recent from the last segment.
273 */
274 acknow = tp->t_flags & TF_ACKNOW;
275
276 /*
277 * First, discard tcpcb state, which includes stopping its timers and
278 * freeing it. tcp_discardcb() used to also release the inpcb, but
279 * that work is now done in the caller.
280 *
281 * Note: soisdisconnected() call used to be made in tcp_discardcb(),
282 * and might not be needed here any longer.
283 */
284 tcp_discardcb(tp);
285 so = inp->inp_socket;
286 soisdisconnected(so);
287 tw->tw_cred = crhold(so->so_cred);
288 SOCK_LOCK(so);
289 tw->tw_so_options = so->so_options;
290 SOCK_UNLOCK(so);
291 if (acknow)
292 tcp_twrespond(tw, TH_ACK);
293 inp->inp_ppcb = tw;
294 inp->inp_flags |= INP_TIMEWAIT;
295 tcp_tw_2msl_reset(tw, 0);
296
297 /*
298 * If the inpcb owns the sole reference to the socket, then we can
299 * detach and free the socket as it is not needed in time wait.
300 */
301 if (inp->inp_flags & INP_SOCKREF) {
302 KASSERT(so->so_state & SS_PROTOREF,
303 ("tcp_twstart: !SS_PROTOREF"));
304 inp->inp_flags &= ~INP_SOCKREF;
305 INP_WUNLOCK(inp);
306 ACCEPT_LOCK();
307 SOCK_LOCK(so);
308 so->so_state &= ~SS_PROTOREF;
309 sofree(so);
310 } else
311 INP_WUNLOCK(inp);
312 }
313
314 #if 0
315 /*
316 * The appromixate rate of ISN increase of Microsoft TCP stacks;
317 * the actual rate is slightly higher due to the addition of
318 * random positive increments.
319 *
320 * Most other new OSes use semi-randomized ISN values, so we
321 * do not need to worry about them.
322 */
323 #define MS_ISN_BYTES_PER_SECOND 250000
324
325 /*
326 * Determine if the ISN we will generate has advanced beyond the last
327 * sequence number used by the previous connection. If so, indicate
328 * that it is safe to recycle this tw socket by returning 1.
329 */
330 int
331 tcp_twrecycleable(struct tcptw *tw)
332 {
333 tcp_seq new_iss = tw->iss;
334 tcp_seq new_irs = tw->irs;
335
336 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
337 new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
338 new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
339
340 if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
341 return (1);
342 else
343 return (0);
344 }
345 #endif
346
347 /*
348 * Returns 1 if the TIME_WAIT state was killed and we should start over,
349 * looking for a pcb in the listen state. Returns 0 otherwise.
350 */
351 int
352 tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
353 struct mbuf *m, int tlen)
354 {
355 struct tcptw *tw;
356 int thflags;
357 tcp_seq seq;
358
359 /* tcbinfo lock required for tcp_twclose(), tcp_tw_2msl_reset(). */
360 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
361 INP_WLOCK_ASSERT(inp);
362
363 /*
364 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is
365 * still present. This is undesirable, but temporarily necessary
366 * until we work out how to handle inpcb's who's timewait state has
367 * been removed.
368 */
369 tw = intotw(inp);
370 if (tw == NULL)
371 goto drop;
372
373 thflags = th->th_flags;
374
375 /*
376 * NOTE: for FIN_WAIT_2 (to be added later),
377 * must validate sequence number before accepting RST
378 */
379
380 /*
381 * If the segment contains RST:
382 * Drop the segment - see Stevens, vol. 2, p. 964 and
383 * RFC 1337.
384 */
385 if (thflags & TH_RST)
386 goto drop;
387
388 #if 0
389 /* PAWS not needed at the moment */
390 /*
391 * RFC 1323 PAWS: If we have a timestamp reply on this segment
392 * and it's less than ts_recent, drop it.
393 */
394 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
395 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
396 if ((thflags & TH_ACK) == 0)
397 goto drop;
398 goto ack;
399 }
400 /*
401 * ts_recent is never updated because we never accept new segments.
402 */
403 #endif
404
405 /*
406 * If a new connection request is received
407 * while in TIME_WAIT, drop the old connection
408 * and start over if the sequence numbers
409 * are above the previous ones.
410 */
411 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
412 tcp_twclose(tw, 0);
413 return (1);
414 }
415
416 /*
417 * Drop the segment if it does not contain an ACK.
418 */
419 if ((thflags & TH_ACK) == 0)
420 goto drop;
421
422 /*
423 * Reset the 2MSL timer if this is a duplicate FIN.
424 */
425 if (thflags & TH_FIN) {
426 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
427 if (seq + 1 == tw->rcv_nxt)
428 tcp_tw_2msl_reset(tw, 1);
429 }
430
431 /*
432 * Acknowledge the segment if it has data or is not a duplicate ACK.
433 */
434 if (thflags != TH_ACK || tlen != 0 ||
435 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
436 tcp_twrespond(tw, TH_ACK);
437 drop:
438 INP_WUNLOCK(inp);
439 m_freem(m);
440 return (0);
441 }
442
443 void
444 tcp_twclose(struct tcptw *tw, int reuse)
445 {
446 struct socket *so;
447 struct inpcb *inp;
448
449 /*
450 * At this point, we are in one of two situations:
451 *
452 * (1) We have no socket, just an inpcb<->twtcp pair. We can free
453 * all state.
454 *
455 * (2) We have a socket -- if we own a reference, release it and
456 * notify the socket layer.
457 */
458 inp = tw->tw_inpcb;
459 KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait"));
460 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw"));
461 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_stop(). */
462 INP_WLOCK_ASSERT(inp);
463
464 tw->tw_inpcb = NULL;
465 tcp_tw_2msl_stop(tw);
466 inp->inp_ppcb = NULL;
467 in_pcbdrop(inp);
468
469 so = inp->inp_socket;
470 if (so != NULL) {
471 /*
472 * If there's a socket, handle two cases: first, we own a
473 * strong reference, which we will now release, or we don't
474 * in which case another reference exists (XXXRW: think
475 * about this more), and we don't need to take action.
476 */
477 if (inp->inp_flags & INP_SOCKREF) {
478 inp->inp_flags &= ~INP_SOCKREF;
479 INP_WUNLOCK(inp);
480 ACCEPT_LOCK();
481 SOCK_LOCK(so);
482 KASSERT(so->so_state & SS_PROTOREF,
483 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF"));
484 so->so_state &= ~SS_PROTOREF;
485 sofree(so);
486 } else {
487 /*
488 * If we don't own the only reference, the socket and
489 * inpcb need to be left around to be handled by
490 * tcp_usr_detach() later.
491 */
492 INP_WUNLOCK(inp);
493 }
494 } else
495 in_pcbfree(inp);
496 TCPSTAT_INC(tcps_closed);
497 crfree(tw->tw_cred);
498 tw->tw_cred = NULL;
499 if (reuse)
500 return;
501 uma_zfree(V_tcptw_zone, tw);
502 }
503
504 int
505 tcp_twrespond(struct tcptw *tw, int flags)
506 {
507 struct inpcb *inp = tw->tw_inpcb;
508 #if defined(INET6) || defined(INET)
509 struct tcphdr *th = NULL;
510 #endif
511 struct mbuf *m;
512 #ifdef INET
513 struct ip *ip = NULL;
514 #endif
515 u_int hdrlen, optlen;
516 int error = 0; /* Keep compiler happy */
517 struct tcpopt to;
518 #ifdef INET6
519 struct ip6_hdr *ip6 = NULL;
520 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
521 #endif
522
523 INP_WLOCK_ASSERT(inp);
524
525 m = m_gethdr(M_DONTWAIT, MT_DATA);
526 if (m == NULL)
527 return (ENOBUFS);
528 m->m_data += max_linkhdr;
529
530 #ifdef MAC
531 mac_inpcb_create_mbuf(inp, m);
532 #endif
533
534 #ifdef INET6
535 if (isipv6) {
536 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
537 ip6 = mtod(m, struct ip6_hdr *);
538 th = (struct tcphdr *)(ip6 + 1);
539 tcpip_fillheaders(inp, ip6, th);
540 }
541 #endif
542 #if defined(INET6) && defined(INET)
543 else
544 #endif
545 #ifdef INET
546 {
547 hdrlen = sizeof(struct tcpiphdr);
548 ip = mtod(m, struct ip *);
549 th = (struct tcphdr *)(ip + 1);
550 tcpip_fillheaders(inp, ip, th);
551 }
552 #endif
553 to.to_flags = 0;
554
555 /*
556 * Send a timestamp and echo-reply if both our side and our peer
557 * have sent timestamps in our SYN's and this is not a RST.
558 */
559 if (tw->t_recent && flags == TH_ACK) {
560 to.to_flags |= TOF_TS;
561 to.to_tsval = tcp_ts_getticks() + tw->ts_offset;
562 to.to_tsecr = tw->t_recent;
563 }
564 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
565
566 m->m_len = hdrlen + optlen;
567 m->m_pkthdr.len = m->m_len;
568
569 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
570
571 th->th_seq = htonl(tw->snd_nxt);
572 th->th_ack = htonl(tw->rcv_nxt);
573 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
574 th->th_flags = flags;
575 th->th_win = htons(tw->last_win);
576
577 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
578 #ifdef INET6
579 if (isipv6) {
580 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
581 th->th_sum = in6_cksum_pseudo(ip6,
582 sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0);
583 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
584 error = ip6_output(m, inp->in6p_outputopts, NULL,
585 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
586 }
587 #endif
588 #if defined(INET6) && defined(INET)
589 else
590 #endif
591 #ifdef INET
592 {
593 m->m_pkthdr.csum_flags = CSUM_TCP;
594 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
595 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
596 ip->ip_len = m->m_pkthdr.len;
597 if (V_path_mtu_discovery)
598 ip->ip_off |= IP_DF;
599 error = ip_output(m, inp->inp_options, NULL,
600 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
601 NULL, inp);
602 }
603 #endif
604 if (flags & TH_ACK)
605 TCPSTAT_INC(tcps_sndacks);
606 else
607 TCPSTAT_INC(tcps_sndctrl);
608 TCPSTAT_INC(tcps_sndtotal);
609 return (error);
610 }
611
612 static void
613 tcp_tw_2msl_reset(struct tcptw *tw, int rearm)
614 {
615
616 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
617 INP_WLOCK_ASSERT(tw->tw_inpcb);
618 if (rearm)
619 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
620 tw->tw_time = ticks + 2 * tcp_msl;
621 TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl);
622 }
623
624 static void
625 tcp_tw_2msl_stop(struct tcptw *tw)
626 {
627
628 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
629 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
630 }
631
632 struct tcptw *
633 tcp_tw_2msl_scan(int reuse)
634 {
635 struct tcptw *tw;
636
637 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
638 for (;;) {
639 tw = TAILQ_FIRST(&V_twq_2msl);
640 if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0))
641 break;
642 INP_WLOCK(tw->tw_inpcb);
643 tcp_twclose(tw, reuse);
644 if (reuse)
645 return (tw);
646 }
647 return (NULL);
648 }
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