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/11.2/sys/netinet/tcp_timewait.c 331722 2018-03-29 02:50:57Z eadler $");
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 #ifndef INVARIANTS
51 #include <sys/syslog.h>
52 #endif
53 #include <sys/protosw.h>
54 #include <sys/random.h>
55
56 #include <vm/uma.h>
57
58 #include <net/route.h>
59 #include <net/if.h>
60 #include <net/if_var.h>
61 #include <net/vnet.h>
62
63 #include <netinet/in.h>
64 #include <netinet/in_pcb.h>
65 #include <netinet/in_systm.h>
66 #include <netinet/in_var.h>
67 #include <netinet/ip.h>
68 #include <netinet/ip_icmp.h>
69 #include <netinet/ip_var.h>
70 #ifdef INET6
71 #include <netinet/ip6.h>
72 #include <netinet6/in6_pcb.h>
73 #include <netinet6/ip6_var.h>
74 #include <netinet6/scope6_var.h>
75 #include <netinet6/nd6.h>
76 #endif
77 #include <netinet/tcp.h>
78 #include <netinet/tcp_fsm.h>
79 #include <netinet/tcp_seq.h>
80 #include <netinet/tcp_timer.h>
81 #include <netinet/tcp_var.h>
82 #ifdef INET6
83 #include <netinet6/tcp6_var.h>
84 #endif
85 #include <netinet/tcpip.h>
86 #ifdef TCPDEBUG
87 #include <netinet/tcp_debug.h>
88 #endif
89 #ifdef INET6
90 #include <netinet6/ip6protosw.h>
91 #endif
92
93 #include <machine/in_cksum.h>
94
95 #include <security/mac/mac_framework.h>
96
97 static VNET_DEFINE(uma_zone_t, tcptw_zone);
98 #define V_tcptw_zone VNET(tcptw_zone)
99 static int maxtcptw;
100
101 /*
102 * The timed wait queue contains references to each of the TCP sessions
103 * currently in the TIME_WAIT state. The queue pointers, including the
104 * queue pointers in each tcptw structure, are protected using the global
105 * timewait lock, which must be held over queue iteration and modification.
106 *
107 * Rules on tcptw usage:
108 * - a inpcb is always freed _after_ its tcptw
109 * - a tcptw relies on its inpcb reference counting for memory stability
110 * - a tcptw is dereferenceable only while its inpcb is locked
111 */
112 static VNET_DEFINE(TAILQ_HEAD(, tcptw), twq_2msl);
113 #define V_twq_2msl VNET(twq_2msl)
114
115 /* Global timewait lock */
116 static VNET_DEFINE(struct rwlock, tw_lock);
117 #define V_tw_lock VNET(tw_lock)
118
119 #define TW_LOCK_INIT(tw, d) rw_init_flags(&(tw), (d), 0)
120 #define TW_LOCK_DESTROY(tw) rw_destroy(&(tw))
121 #define TW_RLOCK(tw) rw_rlock(&(tw))
122 #define TW_WLOCK(tw) rw_wlock(&(tw))
123 #define TW_RUNLOCK(tw) rw_runlock(&(tw))
124 #define TW_WUNLOCK(tw) rw_wunlock(&(tw))
125 #define TW_LOCK_ASSERT(tw) rw_assert(&(tw), RA_LOCKED)
126 #define TW_RLOCK_ASSERT(tw) rw_assert(&(tw), RA_RLOCKED)
127 #define TW_WLOCK_ASSERT(tw) rw_assert(&(tw), RA_WLOCKED)
128 #define TW_UNLOCK_ASSERT(tw) rw_assert(&(tw), RA_UNLOCKED)
129
130 static void tcp_tw_2msl_reset(struct tcptw *, int);
131 static void tcp_tw_2msl_stop(struct tcptw *, int);
132 static int tcp_twrespond(struct tcptw *, int);
133
134 static int
135 tcptw_auto_size(void)
136 {
137 int halfrange;
138
139 /*
140 * Max out at half the ephemeral port range so that TIME_WAIT
141 * sockets don't tie up too many ephemeral ports.
142 */
143 if (V_ipport_lastauto > V_ipport_firstauto)
144 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2;
145 else
146 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2;
147 /* Protect against goofy port ranges smaller than 32. */
148 return (imin(imax(halfrange, 32), maxsockets / 5));
149 }
150
151 static int
152 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
153 {
154 int error, new;
155
156 if (maxtcptw == 0)
157 new = tcptw_auto_size();
158 else
159 new = maxtcptw;
160 error = sysctl_handle_int(oidp, &new, 0, req);
161 if (error == 0 && req->newptr)
162 if (new >= 32) {
163 maxtcptw = new;
164 uma_zone_set_max(V_tcptw_zone, maxtcptw);
165 }
166 return (error);
167 }
168
169 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW,
170 &maxtcptw, 0, sysctl_maxtcptw, "IU",
171 "Maximum number of compressed TCP TIME_WAIT entries");
172
173 VNET_DEFINE(int, nolocaltimewait) = 0;
174 #define V_nolocaltimewait VNET(nolocaltimewait)
175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_VNET | CTLFLAG_RW,
176 &VNET_NAME(nolocaltimewait), 0,
177 "Do not create compressed TCP TIME_WAIT entries for local connections");
178
179 void
180 tcp_tw_zone_change(void)
181 {
182
183 if (maxtcptw == 0)
184 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
185 }
186
187 void
188 tcp_tw_init(void)
189 {
190
191 V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
192 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
193 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
194 if (maxtcptw == 0)
195 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
196 else
197 uma_zone_set_max(V_tcptw_zone, maxtcptw);
198 TAILQ_INIT(&V_twq_2msl);
199 TW_LOCK_INIT(V_tw_lock, "tcptw");
200 }
201
202 #ifdef VIMAGE
203 void
204 tcp_tw_destroy(void)
205 {
206 struct tcptw *tw;
207
208 INP_INFO_RLOCK(&V_tcbinfo);
209 while ((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL)
210 tcp_twclose(tw, 0);
211 INP_INFO_RUNLOCK(&V_tcbinfo);
212
213 TW_LOCK_DESTROY(V_tw_lock);
214 uma_zdestroy(V_tcptw_zone);
215 }
216 #endif
217
218 /*
219 * Move a TCP connection into TIME_WAIT state.
220 * tcbinfo is locked.
221 * inp is locked, and is unlocked before returning.
222 */
223 void
224 tcp_twstart(struct tcpcb *tp)
225 {
226 struct tcptw *tw;
227 struct inpcb *inp = tp->t_inpcb;
228 int acknow;
229 struct socket *so;
230 #ifdef INET6
231 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
232 #endif
233
234 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
235 INP_WLOCK_ASSERT(inp);
236
237 /* A dropped inp should never transition to TIME_WAIT state. */
238 KASSERT((inp->inp_flags & INP_DROPPED) == 0, ("tcp_twstart: "
239 "(inp->inp_flags & INP_DROPPED) != 0"));
240
241 if (V_nolocaltimewait) {
242 int error = 0;
243 #ifdef INET6
244 if (isipv6)
245 error = in6_localaddr(&inp->in6p_faddr);
246 #endif
247 #if defined(INET6) && defined(INET)
248 else
249 #endif
250 #ifdef INET
251 error = in_localip(inp->inp_faddr);
252 #endif
253 if (error) {
254 tp = tcp_close(tp);
255 if (tp != NULL)
256 INP_WUNLOCK(inp);
257 return;
258 }
259 }
260
261
262 /*
263 * For use only by DTrace. We do not reference the state
264 * after this point so modifying it in place is not a problem.
265 */
266 tcp_state_change(tp, TCPS_TIME_WAIT);
267
268 tw = uma_zalloc(V_tcptw_zone, M_NOWAIT);
269 if (tw == NULL) {
270 /*
271 * Reached limit on total number of TIMEWAIT connections
272 * allowed. Remove a connection from TIMEWAIT queue in LRU
273 * fashion to make room for this connection.
274 *
275 * XXX: Check if it possible to always have enough room
276 * in advance based on guarantees provided by uma_zalloc().
277 */
278 tw = tcp_tw_2msl_scan(1);
279 if (tw == NULL) {
280 tp = tcp_close(tp);
281 if (tp != NULL)
282 INP_WUNLOCK(inp);
283 return;
284 }
285 }
286 /*
287 * The tcptw will hold a reference on its inpcb until tcp_twclose
288 * is called
289 */
290 tw->tw_inpcb = inp;
291 in_pcbref(inp); /* Reference from tw */
292
293 /*
294 * Recover last window size sent.
295 */
296 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
297 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
298 else
299 tw->last_win = 0;
300
301 /*
302 * Set t_recent if timestamps are used on the connection.
303 */
304 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
305 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
306 tw->t_recent = tp->ts_recent;
307 tw->ts_offset = tp->ts_offset;
308 } else {
309 tw->t_recent = 0;
310 tw->ts_offset = 0;
311 }
312
313 tw->snd_nxt = tp->snd_nxt;
314 tw->rcv_nxt = tp->rcv_nxt;
315 tw->iss = tp->iss;
316 tw->irs = tp->irs;
317 tw->t_starttime = tp->t_starttime;
318 tw->tw_time = 0;
319
320 /* XXX
321 * If this code will
322 * be used for fin-wait-2 state also, then we may need
323 * a ts_recent from the last segment.
324 */
325 acknow = tp->t_flags & TF_ACKNOW;
326
327 /*
328 * First, discard tcpcb state, which includes stopping its timers and
329 * freeing it. tcp_discardcb() used to also release the inpcb, but
330 * that work is now done in the caller.
331 *
332 * Note: soisdisconnected() call used to be made in tcp_discardcb(),
333 * and might not be needed here any longer.
334 */
335 tcp_discardcb(tp);
336 so = inp->inp_socket;
337 soisdisconnected(so);
338 tw->tw_cred = crhold(so->so_cred);
339 SOCK_LOCK(so);
340 tw->tw_so_options = so->so_options;
341 SOCK_UNLOCK(so);
342 if (acknow)
343 tcp_twrespond(tw, TH_ACK);
344 inp->inp_ppcb = tw;
345 inp->inp_flags |= INP_TIMEWAIT;
346 TCPSTATES_INC(TCPS_TIME_WAIT);
347 tcp_tw_2msl_reset(tw, 0);
348
349 /*
350 * If the inpcb owns the sole reference to the socket, then we can
351 * detach and free the socket as it is not needed in time wait.
352 */
353 if (inp->inp_flags & INP_SOCKREF) {
354 KASSERT(so->so_state & SS_PROTOREF,
355 ("tcp_twstart: !SS_PROTOREF"));
356 inp->inp_flags &= ~INP_SOCKREF;
357 INP_WUNLOCK(inp);
358 ACCEPT_LOCK();
359 SOCK_LOCK(so);
360 so->so_state &= ~SS_PROTOREF;
361 sofree(so);
362 } else
363 INP_WUNLOCK(inp);
364 }
365
366 /*
367 * Returns 1 if the TIME_WAIT state was killed and we should start over,
368 * looking for a pcb in the listen state. Returns 0 otherwise.
369 */
370 int
371 tcp_twcheck(struct inpcb *inp, struct tcpopt *to __unused, struct tcphdr *th,
372 struct mbuf *m, int tlen)
373 {
374 struct tcptw *tw;
375 int thflags;
376 tcp_seq seq;
377
378 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
379 INP_WLOCK_ASSERT(inp);
380
381 /*
382 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is
383 * still present. This is undesirable, but temporarily necessary
384 * until we work out how to handle inpcb's who's timewait state has
385 * been removed.
386 */
387 tw = intotw(inp);
388 if (tw == NULL)
389 goto drop;
390
391 thflags = th->th_flags;
392
393 /*
394 * NOTE: for FIN_WAIT_2 (to be added later),
395 * must validate sequence number before accepting RST
396 */
397
398 /*
399 * If the segment contains RST:
400 * Drop the segment - see Stevens, vol. 2, p. 964 and
401 * RFC 1337.
402 */
403 if (thflags & TH_RST)
404 goto drop;
405
406 #if 0
407 /* PAWS not needed at the moment */
408 /*
409 * RFC 1323 PAWS: If we have a timestamp reply on this segment
410 * and it's less than ts_recent, drop it.
411 */
412 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
413 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
414 if ((thflags & TH_ACK) == 0)
415 goto drop;
416 goto ack;
417 }
418 /*
419 * ts_recent is never updated because we never accept new segments.
420 */
421 #endif
422
423 /*
424 * If a new connection request is received
425 * while in TIME_WAIT, drop the old connection
426 * and start over if the sequence numbers
427 * are above the previous ones.
428 */
429 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
430 tcp_twclose(tw, 0);
431 return (1);
432 }
433
434 /*
435 * Drop the segment if it does not contain an ACK.
436 */
437 if ((thflags & TH_ACK) == 0)
438 goto drop;
439
440 /*
441 * Reset the 2MSL timer if this is a duplicate FIN.
442 */
443 if (thflags & TH_FIN) {
444 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
445 if (seq + 1 == tw->rcv_nxt)
446 tcp_tw_2msl_reset(tw, 1);
447 }
448
449 /*
450 * Acknowledge the segment if it has data or is not a duplicate ACK.
451 */
452 if (thflags != TH_ACK || tlen != 0 ||
453 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
454 tcp_twrespond(tw, TH_ACK);
455 drop:
456 INP_WUNLOCK(inp);
457 m_freem(m);
458 return (0);
459 }
460
461 void
462 tcp_twclose(struct tcptw *tw, int reuse)
463 {
464 struct socket *so;
465 struct inpcb *inp;
466
467 /*
468 * At this point, we are in one of two situations:
469 *
470 * (1) We have no socket, just an inpcb<->twtcp pair. We can free
471 * all state.
472 *
473 * (2) We have a socket -- if we own a reference, release it and
474 * notify the socket layer.
475 */
476 inp = tw->tw_inpcb;
477 KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait"));
478 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw"));
479 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); /* in_pcbfree() */
480 INP_WLOCK_ASSERT(inp);
481
482 tcp_tw_2msl_stop(tw, reuse);
483 inp->inp_ppcb = NULL;
484 in_pcbdrop(inp);
485
486 so = inp->inp_socket;
487 if (so != NULL) {
488 /*
489 * If there's a socket, handle two cases: first, we own a
490 * strong reference, which we will now release, or we don't
491 * in which case another reference exists (XXXRW: think
492 * about this more), and we don't need to take action.
493 */
494 if (inp->inp_flags & INP_SOCKREF) {
495 inp->inp_flags &= ~INP_SOCKREF;
496 INP_WUNLOCK(inp);
497 ACCEPT_LOCK();
498 SOCK_LOCK(so);
499 KASSERT(so->so_state & SS_PROTOREF,
500 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF"));
501 so->so_state &= ~SS_PROTOREF;
502 sofree(so);
503 } else {
504 /*
505 * If we don't own the only reference, the socket and
506 * inpcb need to be left around to be handled by
507 * tcp_usr_detach() later.
508 */
509 INP_WUNLOCK(inp);
510 }
511 } else {
512 /*
513 * The socket has been already cleaned-up for us, only free the
514 * inpcb.
515 */
516 in_pcbfree(inp);
517 }
518 TCPSTAT_INC(tcps_closed);
519 }
520
521 static int
522 tcp_twrespond(struct tcptw *tw, int flags)
523 {
524 struct inpcb *inp = tw->tw_inpcb;
525 #if defined(INET6) || defined(INET)
526 struct tcphdr *th = NULL;
527 #endif
528 struct mbuf *m;
529 #ifdef INET
530 struct ip *ip = NULL;
531 #endif
532 u_int hdrlen, optlen;
533 int error = 0; /* Keep compiler happy */
534 struct tcpopt to;
535 #ifdef INET6
536 struct ip6_hdr *ip6 = NULL;
537 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
538 #endif
539 hdrlen = 0; /* Keep compiler happy */
540
541 INP_WLOCK_ASSERT(inp);
542
543 m = m_gethdr(M_NOWAIT, MT_DATA);
544 if (m == NULL)
545 return (ENOBUFS);
546 m->m_data += max_linkhdr;
547
548 #ifdef MAC
549 mac_inpcb_create_mbuf(inp, m);
550 #endif
551
552 #ifdef INET6
553 if (isipv6) {
554 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
555 ip6 = mtod(m, struct ip6_hdr *);
556 th = (struct tcphdr *)(ip6 + 1);
557 tcpip_fillheaders(inp, ip6, th);
558 }
559 #endif
560 #if defined(INET6) && defined(INET)
561 else
562 #endif
563 #ifdef INET
564 {
565 hdrlen = sizeof(struct tcpiphdr);
566 ip = mtod(m, struct ip *);
567 th = (struct tcphdr *)(ip + 1);
568 tcpip_fillheaders(inp, ip, th);
569 }
570 #endif
571 to.to_flags = 0;
572
573 /*
574 * Send a timestamp and echo-reply if both our side and our peer
575 * have sent timestamps in our SYN's and this is not a RST.
576 */
577 if (tw->t_recent && flags == TH_ACK) {
578 to.to_flags |= TOF_TS;
579 to.to_tsval = tcp_ts_getticks() + tw->ts_offset;
580 to.to_tsecr = tw->t_recent;
581 }
582 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
583
584 m->m_len = hdrlen + optlen;
585 m->m_pkthdr.len = m->m_len;
586
587 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
588
589 th->th_seq = htonl(tw->snd_nxt);
590 th->th_ack = htonl(tw->rcv_nxt);
591 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
592 th->th_flags = flags;
593 th->th_win = htons(tw->last_win);
594
595 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
596 #ifdef INET6
597 if (isipv6) {
598 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
599 th->th_sum = in6_cksum_pseudo(ip6,
600 sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0);
601 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
602 error = ip6_output(m, inp->in6p_outputopts, NULL,
603 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
604 }
605 #endif
606 #if defined(INET6) && defined(INET)
607 else
608 #endif
609 #ifdef INET
610 {
611 m->m_pkthdr.csum_flags = CSUM_TCP;
612 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
613 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
614 ip->ip_len = htons(m->m_pkthdr.len);
615 if (V_path_mtu_discovery)
616 ip->ip_off |= htons(IP_DF);
617 error = ip_output(m, inp->inp_options, NULL,
618 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
619 NULL, inp);
620 }
621 #endif
622 if (flags & TH_ACK)
623 TCPSTAT_INC(tcps_sndacks);
624 else
625 TCPSTAT_INC(tcps_sndctrl);
626 TCPSTAT_INC(tcps_sndtotal);
627 return (error);
628 }
629
630 static void
631 tcp_tw_2msl_reset(struct tcptw *tw, int rearm)
632 {
633
634 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
635 INP_WLOCK_ASSERT(tw->tw_inpcb);
636
637 TW_WLOCK(V_tw_lock);
638 if (rearm)
639 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
640 tw->tw_time = ticks + 2 * tcp_msl;
641 TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl);
642 TW_WUNLOCK(V_tw_lock);
643 }
644
645 static void
646 tcp_tw_2msl_stop(struct tcptw *tw, int reuse)
647 {
648 struct ucred *cred;
649 struct inpcb *inp;
650 int released;
651
652 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
653
654 TW_WLOCK(V_tw_lock);
655 inp = tw->tw_inpcb;
656 tw->tw_inpcb = NULL;
657
658 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
659 cred = tw->tw_cred;
660 tw->tw_cred = NULL;
661 TW_WUNLOCK(V_tw_lock);
662
663 if (cred != NULL)
664 crfree(cred);
665
666 released = in_pcbrele_wlocked(inp);
667 KASSERT(!released, ("%s: inp should not be released here", __func__));
668
669 if (!reuse)
670 uma_zfree(V_tcptw_zone, tw);
671 TCPSTATES_DEC(TCPS_TIME_WAIT);
672 }
673
674 struct tcptw *
675 tcp_tw_2msl_scan(int reuse)
676 {
677 struct tcptw *tw;
678 struct inpcb *inp;
679
680 #ifdef INVARIANTS
681 if (reuse) {
682 /*
683 * Exclusive pcbinfo lock is not required in reuse case even if
684 * two inpcb locks can be acquired simultaneously:
685 * - the inpcb transitioning to TIME_WAIT state in
686 * tcp_tw_start(),
687 * - the inpcb closed by tcp_twclose().
688 *
689 * It is because only inpcbs in FIN_WAIT2 or CLOSING states can
690 * transition in TIME_WAIT state. Then a pcbcb cannot be in
691 * TIME_WAIT list and transitioning to TIME_WAIT state at same
692 * time.
693 */
694 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
695 }
696 #endif
697
698 for (;;) {
699 TW_RLOCK(V_tw_lock);
700 tw = TAILQ_FIRST(&V_twq_2msl);
701 if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0)) {
702 TW_RUNLOCK(V_tw_lock);
703 break;
704 }
705 KASSERT(tw->tw_inpcb != NULL, ("%s: tw->tw_inpcb == NULL",
706 __func__));
707
708 inp = tw->tw_inpcb;
709 in_pcbref(inp);
710 TW_RUNLOCK(V_tw_lock);
711
712 if (INP_INFO_TRY_RLOCK(&V_tcbinfo)) {
713
714 INP_WLOCK(inp);
715 tw = intotw(inp);
716 if (in_pcbrele_wlocked(inp)) {
717 if (__predict_true(tw == NULL)) {
718 INP_INFO_RUNLOCK(&V_tcbinfo);
719 continue;
720 } else {
721 /* This should not happen as in TIMEWAIT
722 * state the inp should not be destroyed
723 * before its tcptw. If INVARIANTS is
724 * defined panic.
725 */
726 #ifdef INVARIANTS
727 panic("%s: Panic before an infinite "
728 "loop: INP_TIMEWAIT && (INP_FREED "
729 "|| inp last reference) && tw != "
730 "NULL", __func__);
731 #else
732 log(LOG_ERR, "%s: Avoid an infinite "
733 "loop: INP_TIMEWAIT && (INP_FREED "
734 "|| inp last reference) && tw != "
735 "NULL", __func__);
736 #endif
737 INP_INFO_RUNLOCK(&V_tcbinfo);
738 break;
739 }
740 }
741
742 if (tw == NULL) {
743 /* tcp_twclose() has already been called */
744 INP_WUNLOCK(inp);
745 INP_INFO_RUNLOCK(&V_tcbinfo);
746 continue;
747 }
748
749 tcp_twclose(tw, reuse);
750 INP_INFO_RUNLOCK(&V_tcbinfo);
751 if (reuse)
752 return tw;
753 } else {
754 /* INP_INFO lock is busy, continue later. */
755 INP_WLOCK(inp);
756 if (!in_pcbrele_wlocked(inp))
757 INP_WUNLOCK(inp);
758 break;
759 }
760 }
761
762 return NULL;
763 }
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