Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/netinet/tcp_timewait.c
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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/11.0/sys/netinet/tcp_timewait.c 302098 2016-06-23 00:32:58Z 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/if_var.h> 58 #include <net/vnet.h> 59 60 #include <netinet/in.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/in_var.h> 64 #include <netinet/ip.h> 65 #include <netinet/ip_icmp.h> 66 #include <netinet/ip_var.h> 67 #ifdef INET6 68 #include <netinet/ip6.h> 69 #include <netinet6/in6_pcb.h> 70 #include <netinet6/ip6_var.h> 71 #include <netinet6/scope6_var.h> 72 #include <netinet6/nd6.h> 73 #endif 74 #include <netinet/tcp.h> 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_seq.h> 77 #include <netinet/tcp_timer.h> 78 #include <netinet/tcp_var.h> 79 #ifdef INET6 80 #include <netinet6/tcp6_var.h> 81 #endif 82 #include <netinet/tcpip.h> 83 #ifdef TCPDEBUG 84 #include <netinet/tcp_debug.h> 85 #endif 86 #ifdef INET6 87 #include <netinet6/ip6protosw.h> 88 #endif 89 90 #include <machine/in_cksum.h> 91 92 #include <security/mac/mac_framework.h> 93 94 static VNET_DEFINE(uma_zone_t, tcptw_zone); 95 #define V_tcptw_zone VNET(tcptw_zone) 96 static int maxtcptw; 97 98 /* 99 * The timed wait queue contains references to each of the TCP sessions 100 * currently in the TIME_WAIT state. The queue pointers, including the 101 * queue pointers in each tcptw structure, are protected using the global 102 * timewait lock, which must be held over queue iteration and modification. 103 * 104 * Rules on tcptw usage: 105 * - a inpcb is always freed _after_ its tcptw 106 * - a tcptw relies on its inpcb reference counting for memory stability 107 * - a tcptw is dereferenceable only while its inpcb is locked 108 */ 109 static VNET_DEFINE(TAILQ_HEAD(, tcptw), twq_2msl); 110 #define V_twq_2msl VNET(twq_2msl) 111 112 /* Global timewait lock */ 113 static VNET_DEFINE(struct rwlock, tw_lock); 114 #define V_tw_lock VNET(tw_lock) 115 116 #define TW_LOCK_INIT(tw, d) rw_init_flags(&(tw), (d), 0) 117 #define TW_LOCK_DESTROY(tw) rw_destroy(&(tw)) 118 #define TW_RLOCK(tw) rw_rlock(&(tw)) 119 #define TW_WLOCK(tw) rw_wlock(&(tw)) 120 #define TW_RUNLOCK(tw) rw_runlock(&(tw)) 121 #define TW_WUNLOCK(tw) rw_wunlock(&(tw)) 122 #define TW_LOCK_ASSERT(tw) rw_assert(&(tw), RA_LOCKED) 123 #define TW_RLOCK_ASSERT(tw) rw_assert(&(tw), RA_RLOCKED) 124 #define TW_WLOCK_ASSERT(tw) rw_assert(&(tw), RA_WLOCKED) 125 #define TW_UNLOCK_ASSERT(tw) rw_assert(&(tw), RA_UNLOCKED) 126 127 static void tcp_tw_2msl_reset(struct tcptw *, int); 128 static void tcp_tw_2msl_stop(struct tcptw *, int); 129 static int tcp_twrespond(struct tcptw *, int); 130 131 static int 132 tcptw_auto_size(void) 133 { 134 int halfrange; 135 136 /* 137 * Max out at half the ephemeral port range so that TIME_WAIT 138 * sockets don't tie up too many ephemeral ports. 139 */ 140 if (V_ipport_lastauto > V_ipport_firstauto) 141 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2; 142 else 143 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2; 144 /* Protect against goofy port ranges smaller than 32. */ 145 return (imin(imax(halfrange, 32), maxsockets / 5)); 146 } 147 148 static int 149 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS) 150 { 151 int error, new; 152 153 if (maxtcptw == 0) 154 new = tcptw_auto_size(); 155 else 156 new = maxtcptw; 157 error = sysctl_handle_int(oidp, &new, 0, req); 158 if (error == 0 && req->newptr) 159 if (new >= 32) { 160 maxtcptw = new; 161 uma_zone_set_max(V_tcptw_zone, maxtcptw); 162 } 163 return (error); 164 } 165 166 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW, 167 &maxtcptw, 0, sysctl_maxtcptw, "IU", 168 "Maximum number of compressed TCP TIME_WAIT entries"); 169 170 VNET_DEFINE(int, nolocaltimewait) = 0; 171 #define V_nolocaltimewait VNET(nolocaltimewait) 172 SYSCTL_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_VNET | CTLFLAG_RW, 173 &VNET_NAME(nolocaltimewait), 0, 174 "Do not create compressed TCP TIME_WAIT entries for local connections"); 175 176 void 177 tcp_tw_zone_change(void) 178 { 179 180 if (maxtcptw == 0) 181 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size()); 182 } 183 184 void 185 tcp_tw_init(void) 186 { 187 188 V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw), 189 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 190 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw); 191 if (maxtcptw == 0) 192 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size()); 193 else 194 uma_zone_set_max(V_tcptw_zone, maxtcptw); 195 TAILQ_INIT(&V_twq_2msl); 196 TW_LOCK_INIT(V_tw_lock, "tcptw"); 197 } 198 199 #ifdef VIMAGE 200 void 201 tcp_tw_destroy(void) 202 { 203 struct tcptw *tw; 204 205 INP_INFO_RLOCK(&V_tcbinfo); 206 while ((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL) 207 tcp_twclose(tw, 0); 208 INP_INFO_RUNLOCK(&V_tcbinfo); 209 210 TW_LOCK_DESTROY(V_tw_lock); 211 uma_zdestroy(V_tcptw_zone); 212 } 213 #endif 214 215 /* 216 * Move a TCP connection into TIME_WAIT state. 217 * tcbinfo is locked. 218 * inp is locked, and is unlocked before returning. 219 */ 220 void 221 tcp_twstart(struct tcpcb *tp) 222 { 223 struct tcptw *tw; 224 struct inpcb *inp = tp->t_inpcb; 225 int acknow; 226 struct socket *so; 227 #ifdef INET6 228 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6; 229 #endif 230 231 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 232 INP_WLOCK_ASSERT(inp); 233 234 if (V_nolocaltimewait) { 235 int error = 0; 236 #ifdef INET6 237 if (isipv6) 238 error = in6_localaddr(&inp->in6p_faddr); 239 #endif 240 #if defined(INET6) && defined(INET) 241 else 242 #endif 243 #ifdef INET 244 error = in_localip(inp->inp_faddr); 245 #endif 246 if (error) { 247 tp = tcp_close(tp); 248 if (tp != NULL) 249 INP_WUNLOCK(inp); 250 return; 251 } 252 } 253 254 255 /* 256 * For use only by DTrace. We do not reference the state 257 * after this point so modifying it in place is not a problem. 258 */ 259 tcp_state_change(tp, TCPS_TIME_WAIT); 260 261 tw = uma_zalloc(V_tcptw_zone, M_NOWAIT); 262 if (tw == NULL) { 263 /* 264 * Reached limit on total number of TIMEWAIT connections 265 * allowed. Remove a connection from TIMEWAIT queue in LRU 266 * fashion to make room for this connection. 267 * 268 * XXX: Check if it possible to always have enough room 269 * in advance based on guarantees provided by uma_zalloc(). 270 */ 271 tw = tcp_tw_2msl_scan(1); 272 if (tw == NULL) { 273 tp = tcp_close(tp); 274 if (tp != NULL) 275 INP_WUNLOCK(inp); 276 return; 277 } 278 } 279 /* 280 * The tcptw will hold a reference on its inpcb until tcp_twclose 281 * is called 282 */ 283 tw->tw_inpcb = inp; 284 in_pcbref(inp); /* Reference from tw */ 285 286 /* 287 * Recover last window size sent. 288 */ 289 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 290 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale; 291 else 292 tw->last_win = 0; 293 294 /* 295 * Set t_recent if timestamps are used on the connection. 296 */ 297 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) == 298 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) { 299 tw->t_recent = tp->ts_recent; 300 tw->ts_offset = tp->ts_offset; 301 } else { 302 tw->t_recent = 0; 303 tw->ts_offset = 0; 304 } 305 306 tw->snd_nxt = tp->snd_nxt; 307 tw->rcv_nxt = tp->rcv_nxt; 308 tw->iss = tp->iss; 309 tw->irs = tp->irs; 310 tw->t_starttime = tp->t_starttime; 311 tw->tw_time = 0; 312 313 /* XXX 314 * If this code will 315 * be used for fin-wait-2 state also, then we may need 316 * a ts_recent from the last segment. 317 */ 318 acknow = tp->t_flags & TF_ACKNOW; 319 320 /* 321 * First, discard tcpcb state, which includes stopping its timers and 322 * freeing it. tcp_discardcb() used to also release the inpcb, but 323 * that work is now done in the caller. 324 * 325 * Note: soisdisconnected() call used to be made in tcp_discardcb(), 326 * and might not be needed here any longer. 327 */ 328 tcp_discardcb(tp); 329 so = inp->inp_socket; 330 soisdisconnected(so); 331 tw->tw_cred = crhold(so->so_cred); 332 SOCK_LOCK(so); 333 tw->tw_so_options = so->so_options; 334 SOCK_UNLOCK(so); 335 if (acknow) 336 tcp_twrespond(tw, TH_ACK); 337 inp->inp_ppcb = tw; 338 inp->inp_flags |= INP_TIMEWAIT; 339 tcp_tw_2msl_reset(tw, 0); 340 341 /* 342 * If the inpcb owns the sole reference to the socket, then we can 343 * detach and free the socket as it is not needed in time wait. 344 */ 345 if (inp->inp_flags & INP_SOCKREF) { 346 KASSERT(so->so_state & SS_PROTOREF, 347 ("tcp_twstart: !SS_PROTOREF")); 348 inp->inp_flags &= ~INP_SOCKREF; 349 INP_WUNLOCK(inp); 350 ACCEPT_LOCK(); 351 SOCK_LOCK(so); 352 so->so_state &= ~SS_PROTOREF; 353 sofree(so); 354 } else 355 INP_WUNLOCK(inp); 356 } 357 358 /* 359 * Returns 1 if the TIME_WAIT state was killed and we should start over, 360 * looking for a pcb in the listen state. Returns 0 otherwise. 361 */ 362 int 363 tcp_twcheck(struct inpcb *inp, struct tcpopt *to __unused, struct tcphdr *th, 364 struct mbuf *m, int tlen) 365 { 366 struct tcptw *tw; 367 int thflags; 368 tcp_seq seq; 369 370 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 371 INP_WLOCK_ASSERT(inp); 372 373 /* 374 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 375 * still present. This is undesirable, but temporarily necessary 376 * until we work out how to handle inpcb's who's timewait state has 377 * been removed. 378 */ 379 tw = intotw(inp); 380 if (tw == NULL) 381 goto drop; 382 383 thflags = th->th_flags; 384 385 /* 386 * NOTE: for FIN_WAIT_2 (to be added later), 387 * must validate sequence number before accepting RST 388 */ 389 390 /* 391 * If the segment contains RST: 392 * Drop the segment - see Stevens, vol. 2, p. 964 and 393 * RFC 1337. 394 */ 395 if (thflags & TH_RST) 396 goto drop; 397 398 #if 0 399 /* PAWS not needed at the moment */ 400 /* 401 * RFC 1323 PAWS: If we have a timestamp reply on this segment 402 * and it's less than ts_recent, drop it. 403 */ 404 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 405 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 406 if ((thflags & TH_ACK) == 0) 407 goto drop; 408 goto ack; 409 } 410 /* 411 * ts_recent is never updated because we never accept new segments. 412 */ 413 #endif 414 415 /* 416 * If a new connection request is received 417 * while in TIME_WAIT, drop the old connection 418 * and start over if the sequence numbers 419 * are above the previous ones. 420 */ 421 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 422 tcp_twclose(tw, 0); 423 return (1); 424 } 425 426 /* 427 * Drop the segment if it does not contain an ACK. 428 */ 429 if ((thflags & TH_ACK) == 0) 430 goto drop; 431 432 /* 433 * Reset the 2MSL timer if this is a duplicate FIN. 434 */ 435 if (thflags & TH_FIN) { 436 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 437 if (seq + 1 == tw->rcv_nxt) 438 tcp_tw_2msl_reset(tw, 1); 439 } 440 441 /* 442 * Acknowledge the segment if it has data or is not a duplicate ACK. 443 */ 444 if (thflags != TH_ACK || tlen != 0 || 445 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 446 tcp_twrespond(tw, TH_ACK); 447 drop: 448 INP_WUNLOCK(inp); 449 m_freem(m); 450 return (0); 451 } 452 453 void 454 tcp_twclose(struct tcptw *tw, int reuse) 455 { 456 struct socket *so; 457 struct inpcb *inp; 458 459 /* 460 * At this point, we are in one of two situations: 461 * 462 * (1) We have no socket, just an inpcb<->twtcp pair. We can free 463 * all state. 464 * 465 * (2) We have a socket -- if we own a reference, release it and 466 * notify the socket layer. 467 */ 468 inp = tw->tw_inpcb; 469 KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait")); 470 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw")); 471 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); /* in_pcbfree() */ 472 INP_WLOCK_ASSERT(inp); 473 474 tcp_tw_2msl_stop(tw, reuse); 475 inp->inp_ppcb = NULL; 476 in_pcbdrop(inp); 477 478 so = inp->inp_socket; 479 if (so != NULL) { 480 /* 481 * If there's a socket, handle two cases: first, we own a 482 * strong reference, which we will now release, or we don't 483 * in which case another reference exists (XXXRW: think 484 * about this more), and we don't need to take action. 485 */ 486 if (inp->inp_flags & INP_SOCKREF) { 487 inp->inp_flags &= ~INP_SOCKREF; 488 INP_WUNLOCK(inp); 489 ACCEPT_LOCK(); 490 SOCK_LOCK(so); 491 KASSERT(so->so_state & SS_PROTOREF, 492 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF")); 493 so->so_state &= ~SS_PROTOREF; 494 sofree(so); 495 } else { 496 /* 497 * If we don't own the only reference, the socket and 498 * inpcb need to be left around to be handled by 499 * tcp_usr_detach() later. 500 */ 501 INP_WUNLOCK(inp); 502 } 503 } else { 504 /* 505 * The socket has been already cleaned-up for us, only free the 506 * inpcb. 507 */ 508 in_pcbfree(inp); 509 } 510 TCPSTAT_INC(tcps_closed); 511 } 512 513 static int 514 tcp_twrespond(struct tcptw *tw, int flags) 515 { 516 struct inpcb *inp = tw->tw_inpcb; 517 #if defined(INET6) || defined(INET) 518 struct tcphdr *th = NULL; 519 #endif 520 struct mbuf *m; 521 #ifdef INET 522 struct ip *ip = NULL; 523 #endif 524 u_int hdrlen, optlen; 525 int error = 0; /* Keep compiler happy */ 526 struct tcpopt to; 527 #ifdef INET6 528 struct ip6_hdr *ip6 = NULL; 529 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6; 530 #endif 531 hdrlen = 0; /* Keep compiler happy */ 532 533 INP_WLOCK_ASSERT(inp); 534 535 m = m_gethdr(M_NOWAIT, MT_DATA); 536 if (m == NULL) 537 return (ENOBUFS); 538 m->m_data += max_linkhdr; 539 540 #ifdef MAC 541 mac_inpcb_create_mbuf(inp, m); 542 #endif 543 544 #ifdef INET6 545 if (isipv6) { 546 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 547 ip6 = mtod(m, struct ip6_hdr *); 548 th = (struct tcphdr *)(ip6 + 1); 549 tcpip_fillheaders(inp, ip6, th); 550 } 551 #endif 552 #if defined(INET6) && defined(INET) 553 else 554 #endif 555 #ifdef INET 556 { 557 hdrlen = sizeof(struct tcpiphdr); 558 ip = mtod(m, struct ip *); 559 th = (struct tcphdr *)(ip + 1); 560 tcpip_fillheaders(inp, ip, th); 561 } 562 #endif 563 to.to_flags = 0; 564 565 /* 566 * Send a timestamp and echo-reply if both our side and our peer 567 * have sent timestamps in our SYN's and this is not a RST. 568 */ 569 if (tw->t_recent && flags == TH_ACK) { 570 to.to_flags |= TOF_TS; 571 to.to_tsval = tcp_ts_getticks() + tw->ts_offset; 572 to.to_tsecr = tw->t_recent; 573 } 574 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 575 576 m->m_len = hdrlen + optlen; 577 m->m_pkthdr.len = m->m_len; 578 579 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small")); 580 581 th->th_seq = htonl(tw->snd_nxt); 582 th->th_ack = htonl(tw->rcv_nxt); 583 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 584 th->th_flags = flags; 585 th->th_win = htons(tw->last_win); 586 587 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 588 #ifdef INET6 589 if (isipv6) { 590 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 591 th->th_sum = in6_cksum_pseudo(ip6, 592 sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0); 593 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 594 error = ip6_output(m, inp->in6p_outputopts, NULL, 595 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp); 596 } 597 #endif 598 #if defined(INET6) && defined(INET) 599 else 600 #endif 601 #ifdef INET 602 { 603 m->m_pkthdr.csum_flags = CSUM_TCP; 604 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 605 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP)); 606 ip->ip_len = htons(m->m_pkthdr.len); 607 if (V_path_mtu_discovery) 608 ip->ip_off |= htons(IP_DF); 609 error = ip_output(m, inp->inp_options, NULL, 610 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 611 NULL, inp); 612 } 613 #endif 614 if (flags & TH_ACK) 615 TCPSTAT_INC(tcps_sndacks); 616 else 617 TCPSTAT_INC(tcps_sndctrl); 618 TCPSTAT_INC(tcps_sndtotal); 619 return (error); 620 } 621 622 static void 623 tcp_tw_2msl_reset(struct tcptw *tw, int rearm) 624 { 625 626 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 627 INP_WLOCK_ASSERT(tw->tw_inpcb); 628 629 TW_WLOCK(V_tw_lock); 630 if (rearm) 631 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl); 632 tw->tw_time = ticks + 2 * tcp_msl; 633 TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl); 634 TW_WUNLOCK(V_tw_lock); 635 } 636 637 static void 638 tcp_tw_2msl_stop(struct tcptw *tw, int reuse) 639 { 640 struct ucred *cred; 641 struct inpcb *inp; 642 int released; 643 644 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 645 646 TW_WLOCK(V_tw_lock); 647 inp = tw->tw_inpcb; 648 tw->tw_inpcb = NULL; 649 650 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl); 651 cred = tw->tw_cred; 652 tw->tw_cred = NULL; 653 TW_WUNLOCK(V_tw_lock); 654 655 if (cred != NULL) 656 crfree(cred); 657 658 released = in_pcbrele_wlocked(inp); 659 KASSERT(!released, ("%s: inp should not be released here", __func__)); 660 661 if (!reuse) 662 uma_zfree(V_tcptw_zone, tw); 663 TCPSTATES_DEC(TCPS_TIME_WAIT); 664 } 665 666 struct tcptw * 667 tcp_tw_2msl_scan(int reuse) 668 { 669 struct tcptw *tw; 670 struct inpcb *inp; 671 672 #ifdef INVARIANTS 673 if (reuse) { 674 /* 675 * Exclusive pcbinfo lock is not required in reuse case even if 676 * two inpcb locks can be acquired simultaneously: 677 * - the inpcb transitioning to TIME_WAIT state in 678 * tcp_tw_start(), 679 * - the inpcb closed by tcp_twclose(). 680 * 681 * It is because only inpcbs in FIN_WAIT2 or CLOSING states can 682 * transition in TIME_WAIT state. Then a pcbcb cannot be in 683 * TIME_WAIT list and transitioning to TIME_WAIT state at same 684 * time. 685 */ 686 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 687 } 688 #endif 689 690 for (;;) { 691 TW_RLOCK(V_tw_lock); 692 tw = TAILQ_FIRST(&V_twq_2msl); 693 if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0)) { 694 TW_RUNLOCK(V_tw_lock); 695 break; 696 } 697 KASSERT(tw->tw_inpcb != NULL, ("%s: tw->tw_inpcb == NULL", 698 __func__)); 699 700 inp = tw->tw_inpcb; 701 in_pcbref(inp); 702 TW_RUNLOCK(V_tw_lock); 703 704 if (INP_INFO_TRY_RLOCK(&V_tcbinfo)) { 705 706 INP_WLOCK(inp); 707 tw = intotw(inp); 708 if (in_pcbrele_wlocked(inp)) { 709 KASSERT(tw == NULL, ("%s: held last inp " 710 "reference but tw not NULL", __func__)); 711 INP_INFO_RUNLOCK(&V_tcbinfo); 712 continue; 713 } 714 715 if (tw == NULL) { 716 /* tcp_twclose() has already been called */ 717 INP_WUNLOCK(inp); 718 INP_INFO_RUNLOCK(&V_tcbinfo); 719 continue; 720 } 721 722 tcp_twclose(tw, reuse); 723 INP_INFO_RUNLOCK(&V_tcbinfo); 724 if (reuse) 725 return tw; 726 } else { 727 /* INP_INFO lock is busy, continue later. */ 728 INP_WLOCK(inp); 729 if (!in_pcbrele_wlocked(inp)) 730 INP_WUNLOCK(inp); 731 break; 732 } 733 } 734 735 return NULL; 736 }
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