tcp_timewait.c revision 185348
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: head/sys/netinet/tcp_timewait.c 185348 2008-11-26 22:32:07Z zec $"); 34 35#include "opt_inet.h" 36#include "opt_inet6.h" 37#include "opt_mac.h" 38#include "opt_tcpdebug.h" 39 40#include <sys/param.h> 41#include <sys/systm.h> 42#include <sys/callout.h> 43#include <sys/kernel.h> 44#include <sys/sysctl.h> 45#include <sys/malloc.h> 46#include <sys/mbuf.h> 47#include <sys/priv.h> 48#include <sys/proc.h> 49#include <sys/socket.h> 50#include <sys/socketvar.h> 51#include <sys/protosw.h> 52#include <sys/random.h> 53#include <sys/vimage.h> 54 55#include <vm/uma.h> 56 57#include <net/route.h> 58#include <net/if.h> 59 60#include <netinet/in.h> 61#include <netinet/in_systm.h> 62#include <netinet/ip.h> 63#ifdef INET6 64#include <netinet/ip6.h> 65#endif 66#include <netinet/in_pcb.h> 67#ifdef INET6 68#include <netinet6/in6_pcb.h> 69#endif 70#include <netinet/in_var.h> 71#include <netinet/ip_var.h> 72#ifdef INET6 73#include <netinet6/ip6_var.h> 74#include <netinet6/scope6_var.h> 75#include <netinet6/nd6.h> 76#endif 77#include <netinet/ip_icmp.h> 78#include <netinet/tcp.h> 79#include <netinet/tcp_fsm.h> 80#include <netinet/tcp_seq.h> 81#include <netinet/tcp_timer.h> 82#include <netinet/tcp_var.h> 83#ifdef INET6 84#include <netinet6/tcp6_var.h> 85#endif 86#include <netinet/tcpip.h> 87#ifdef TCPDEBUG 88#include <netinet/tcp_debug.h> 89#endif 90#include <netinet6/ip6protosw.h> 91 92#include <machine/in_cksum.h> 93 94#include <security/mac/mac_framework.h> 95 96static uma_zone_t tcptw_zone; 97static int maxtcptw; 98 99/* 100 * The timed wait queue contains references to each of the TCP sessions 101 * currently in the TIME_WAIT state. The queue pointers, including the 102 * queue pointers in each tcptw structure, are protected using the global 103 * tcbinfo lock, which must be held over queue iteration and modification. 104 */ 105#ifdef VIMAGE_GLOBALS 106static TAILQ_HEAD(, tcptw) twq_2msl; 107int nolocaltimewait; 108#endif 109 110static void tcp_tw_2msl_reset(struct tcptw *, int); 111static void tcp_tw_2msl_stop(struct tcptw *); 112 113static int 114tcptw_auto_size(void) 115{ 116 INIT_VNET_INET(curvnet); 117 int halfrange; 118 119 /* 120 * Max out at half the ephemeral port range so that TIME_WAIT 121 * sockets don't tie up too many ephemeral ports. 122 */ 123 if (V_ipport_lastauto > V_ipport_firstauto) 124 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2; 125 else 126 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2; 127 /* Protect against goofy port ranges smaller than 32. */ 128 return (imin(imax(halfrange, 32), maxsockets / 5)); 129} 130 131static int 132sysctl_maxtcptw(SYSCTL_HANDLER_ARGS) 133{ 134 int error, new; 135 136 if (maxtcptw == 0) 137 new = tcptw_auto_size(); 138 else 139 new = maxtcptw; 140 error = sysctl_handle_int(oidp, &new, 0, req); 141 if (error == 0 && req->newptr) 142 if (new >= 32) { 143 maxtcptw = new; 144 uma_zone_set_max(tcptw_zone, maxtcptw); 145 } 146 return (error); 147} 148 149SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW, 150 &maxtcptw, 0, sysctl_maxtcptw, "IU", 151 "Maximum number of compressed TCP TIME_WAIT entries"); 152 153SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, nolocaltimewait, 154 CTLFLAG_RW, nolocaltimewait, 0, 155 "Do not create compressed TCP TIME_WAIT entries for local connections"); 156 157void 158tcp_tw_zone_change(void) 159{ 160 161 if (maxtcptw == 0) 162 uma_zone_set_max(tcptw_zone, tcptw_auto_size()); 163} 164 165void 166tcp_tw_init(void) 167{ 168 INIT_VNET_INET(curvnet); 169 170 tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw), 171 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 172 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw); 173 if (maxtcptw == 0) 174 uma_zone_set_max(tcptw_zone, tcptw_auto_size()); 175 else 176 uma_zone_set_max(tcptw_zone, maxtcptw); 177 TAILQ_INIT(&V_twq_2msl); 178} 179 180/* 181 * Move a TCP connection into TIME_WAIT state. 182 * tcbinfo is locked. 183 * inp is locked, and is unlocked before returning. 184 */ 185void 186tcp_twstart(struct tcpcb *tp) 187{ 188#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 189 INIT_VNET_INET(tp->t_vnet); 190#endif 191 struct tcptw *tw; 192 struct inpcb *inp = tp->t_inpcb; 193 int acknow; 194 struct socket *so; 195 196 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_reset(). */ 197 INP_WLOCK_ASSERT(inp); 198 199 if (V_nolocaltimewait && in_localip(inp->inp_faddr)) { 200 tp = tcp_close(tp); 201 if (tp != NULL) 202 INP_WUNLOCK(inp); 203 return; 204 } 205 206 tw = uma_zalloc(tcptw_zone, M_NOWAIT); 207 if (tw == NULL) { 208 tw = tcp_tw_2msl_scan(1); 209 if (tw == NULL) { 210 tp = tcp_close(tp); 211 if (tp != NULL) 212 INP_WUNLOCK(inp); 213 return; 214 } 215 } 216 tw->tw_inpcb = inp; 217 218 /* 219 * Recover last window size sent. 220 */ 221 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale; 222 223 /* 224 * Set t_recent if timestamps are used on the connection. 225 */ 226 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) == 227 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) { 228 tw->t_recent = tp->ts_recent; 229 tw->ts_offset = tp->ts_offset; 230 } else { 231 tw->t_recent = 0; 232 tw->ts_offset = 0; 233 } 234 235 tw->snd_nxt = tp->snd_nxt; 236 tw->rcv_nxt = tp->rcv_nxt; 237 tw->iss = tp->iss; 238 tw->irs = tp->irs; 239 tw->t_starttime = tp->t_starttime; 240 tw->tw_time = 0; 241 242/* XXX 243 * If this code will 244 * be used for fin-wait-2 state also, then we may need 245 * a ts_recent from the last segment. 246 */ 247 acknow = tp->t_flags & TF_ACKNOW; 248 249 /* 250 * First, discard tcpcb state, which includes stopping its timers and 251 * freeing it. tcp_discardcb() used to also release the inpcb, but 252 * that work is now done in the caller. 253 * 254 * Note: soisdisconnected() call used to be made in tcp_discardcb(), 255 * and might not be needed here any longer. 256 */ 257 tcp_discardcb(tp); 258 so = inp->inp_socket; 259 soisdisconnected(so); 260 tw->tw_cred = crhold(so->so_cred); 261 SOCK_LOCK(so); 262 tw->tw_so_options = so->so_options; 263 SOCK_UNLOCK(so); 264 if (acknow) 265 tcp_twrespond(tw, TH_ACK); 266 inp->inp_ppcb = tw; 267 inp->inp_vflag |= INP_TIMEWAIT; 268 tcp_tw_2msl_reset(tw, 0); 269 270 /* 271 * If the inpcb owns the sole reference to the socket, then we can 272 * detach and free the socket as it is not needed in time wait. 273 */ 274 if (inp->inp_vflag & INP_SOCKREF) { 275 KASSERT(so->so_state & SS_PROTOREF, 276 ("tcp_twstart: !SS_PROTOREF")); 277 inp->inp_vflag &= ~INP_SOCKREF; 278 INP_WUNLOCK(inp); 279 ACCEPT_LOCK(); 280 SOCK_LOCK(so); 281 so->so_state &= ~SS_PROTOREF; 282 sofree(so); 283 } else 284 INP_WUNLOCK(inp); 285} 286 287#if 0 288/* 289 * The appromixate rate of ISN increase of Microsoft TCP stacks; 290 * the actual rate is slightly higher due to the addition of 291 * random positive increments. 292 * 293 * Most other new OSes use semi-randomized ISN values, so we 294 * do not need to worry about them. 295 */ 296#define MS_ISN_BYTES_PER_SECOND 250000 297 298/* 299 * Determine if the ISN we will generate has advanced beyond the last 300 * sequence number used by the previous connection. If so, indicate 301 * that it is safe to recycle this tw socket by returning 1. 302 */ 303int 304tcp_twrecycleable(struct tcptw *tw) 305{ 306 INIT_VNET_INET(curvnet); 307 tcp_seq new_iss = tw->iss; 308 tcp_seq new_irs = tw->irs; 309 310 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 311 new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz); 312 new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz); 313 314 if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt)) 315 return (1); 316 else 317 return (0); 318} 319#endif 320 321/* 322 * Returns 1 if the TIME_WAIT state was killed and we should start over, 323 * looking for a pcb in the listen state. Returns 0 otherwise. 324 */ 325int 326tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th, 327 struct mbuf *m, int tlen) 328{ 329#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 330 INIT_VNET_INET(curvnet); 331#endif 332 struct tcptw *tw; 333 int thflags; 334 tcp_seq seq; 335#ifdef INET6 336 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 337#else 338 const int isipv6 = 0; 339#endif 340 341 /* tcbinfo lock required for tcp_twclose(), tcp_tw_2msl_reset(). */ 342 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 343 INP_WLOCK_ASSERT(inp); 344 345 /* 346 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 347 * still present. This is undesirable, but temporarily necessary 348 * until we work out how to handle inpcb's who's timewait state has 349 * been removed. 350 */ 351 tw = intotw(inp); 352 if (tw == NULL) 353 goto drop; 354 355 thflags = th->th_flags; 356 357 /* 358 * NOTE: for FIN_WAIT_2 (to be added later), 359 * must validate sequence number before accepting RST 360 */ 361 362 /* 363 * If the segment contains RST: 364 * Drop the segment - see Stevens, vol. 2, p. 964 and 365 * RFC 1337. 366 */ 367 if (thflags & TH_RST) 368 goto drop; 369 370#if 0 371/* PAWS not needed at the moment */ 372 /* 373 * RFC 1323 PAWS: If we have a timestamp reply on this segment 374 * and it's less than ts_recent, drop it. 375 */ 376 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 377 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 378 if ((thflags & TH_ACK) == 0) 379 goto drop; 380 goto ack; 381 } 382 /* 383 * ts_recent is never updated because we never accept new segments. 384 */ 385#endif 386 387 /* 388 * If a new connection request is received 389 * while in TIME_WAIT, drop the old connection 390 * and start over if the sequence numbers 391 * are above the previous ones. 392 */ 393 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 394 tcp_twclose(tw, 0); 395 return (1); 396 } 397 398 /* 399 * Drop the the segment if it does not contain an ACK. 400 */ 401 if ((thflags & TH_ACK) == 0) 402 goto drop; 403 404 /* 405 * Reset the 2MSL timer if this is a duplicate FIN. 406 */ 407 if (thflags & TH_FIN) { 408 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 409 if (seq + 1 == tw->rcv_nxt) 410 tcp_tw_2msl_reset(tw, 1); 411 } 412 413 /* 414 * Acknowledge the segment if it has data or is not a duplicate ACK. 415 */ 416 if (thflags != TH_ACK || tlen != 0 || 417 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 418 tcp_twrespond(tw, TH_ACK); 419 goto drop; 420 421 /* 422 * Generate a RST, dropping incoming segment. 423 * Make ACK acceptable to originator of segment. 424 * Don't bother to respond if destination was broadcast/multicast. 425 */ 426 if (m->m_flags & (M_BCAST|M_MCAST)) 427 goto drop; 428 if (isipv6) { 429#ifdef INET6 430 struct ip6_hdr *ip6; 431 432 /* IPv6 anycast check is done at tcp6_input() */ 433 ip6 = mtod(m, struct ip6_hdr *); 434 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 435 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 436 goto drop; 437#endif 438 } else { 439 struct ip *ip; 440 441 ip = mtod(m, struct ip *); 442 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 443 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 444 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 445 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 446 goto drop; 447 } 448 if (thflags & TH_ACK) { 449 tcp_respond(NULL, 450 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 451 } else { 452 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 453 tcp_respond(NULL, 454 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 455 } 456 INP_WUNLOCK(inp); 457 return (0); 458 459drop: 460 INP_WUNLOCK(inp); 461 m_freem(m); 462 return (0); 463} 464 465void 466tcp_twclose(struct tcptw *tw, int reuse) 467{ 468 INIT_VNET_INET(curvnet); 469 struct socket *so; 470 struct inpcb *inp; 471 472 /* 473 * At this point, we are in one of two situations: 474 * 475 * (1) We have no socket, just an inpcb<->twtcp pair. We can free 476 * all state. 477 * 478 * (2) We have a socket -- if we own a reference, release it and 479 * notify the socket layer. 480 */ 481 inp = tw->tw_inpcb; 482 KASSERT((inp->inp_vflag & INP_TIMEWAIT), ("tcp_twclose: !timewait")); 483 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw")); 484 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_stop(). */ 485 INP_WLOCK_ASSERT(inp); 486 487 tw->tw_inpcb = NULL; 488 tcp_tw_2msl_stop(tw); 489 inp->inp_ppcb = NULL; 490 in_pcbdrop(inp); 491 492 so = inp->inp_socket; 493 if (so != NULL) { 494 /* 495 * If there's a socket, handle two cases: first, we own a 496 * strong reference, which we will now release, or we don't 497 * in which case another reference exists (XXXRW: think 498 * about this more), and we don't need to take action. 499 */ 500 if (inp->inp_vflag & INP_SOCKREF) { 501 inp->inp_vflag &= ~INP_SOCKREF; 502 INP_WUNLOCK(inp); 503 ACCEPT_LOCK(); 504 SOCK_LOCK(so); 505 KASSERT(so->so_state & SS_PROTOREF, 506 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF")); 507 so->so_state &= ~SS_PROTOREF; 508 sofree(so); 509 } else { 510 /* 511 * If we don't own the only reference, the socket and 512 * inpcb need to be left around to be handled by 513 * tcp_usr_detach() later. 514 */ 515 INP_WUNLOCK(inp); 516 } 517 } else { 518#ifdef INET6 519 if (inp->inp_vflag & INP_IPV6PROTO) 520 in6_pcbfree(inp); 521 else 522#endif 523 in_pcbfree(inp); 524 } 525 V_tcpstat.tcps_closed++; 526 crfree(tw->tw_cred); 527 tw->tw_cred = NULL; 528 if (reuse) 529 return; 530 uma_zfree(tcptw_zone, tw); 531} 532 533int 534tcp_twrespond(struct tcptw *tw, int flags) 535{ 536 INIT_VNET_INET(curvnet); 537 struct inpcb *inp = tw->tw_inpcb; 538 struct tcphdr *th; 539 struct mbuf *m; 540 struct ip *ip = NULL; 541 u_int hdrlen, optlen; 542 int error; 543 struct tcpopt to; 544#ifdef INET6 545 struct ip6_hdr *ip6 = NULL; 546 int isipv6 = inp->inp_inc.inc_isipv6; 547#endif 548 549 INP_WLOCK_ASSERT(inp); 550 551 m = m_gethdr(M_DONTWAIT, MT_DATA); 552 if (m == NULL) 553 return (ENOBUFS); 554 m->m_data += max_linkhdr; 555 556#ifdef MAC 557 mac_inpcb_create_mbuf(inp, m); 558#endif 559 560#ifdef INET6 561 if (isipv6) { 562 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 563 ip6 = mtod(m, struct ip6_hdr *); 564 th = (struct tcphdr *)(ip6 + 1); 565 tcpip_fillheaders(inp, ip6, th); 566 } else 567#endif 568 { 569 hdrlen = sizeof(struct tcpiphdr); 570 ip = mtod(m, struct ip *); 571 th = (struct tcphdr *)(ip + 1); 572 tcpip_fillheaders(inp, ip, th); 573 } 574 to.to_flags = 0; 575 576 /* 577 * Send a timestamp and echo-reply if both our side and our peer 578 * have sent timestamps in our SYN's and this is not a RST. 579 */ 580 if (tw->t_recent && flags == TH_ACK) { 581 to.to_flags |= TOF_TS; 582 to.to_tsval = ticks + tw->ts_offset; 583 to.to_tsecr = tw->t_recent; 584 } 585 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 586 587 m->m_len = hdrlen + optlen; 588 m->m_pkthdr.len = m->m_len; 589 590 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small")); 591 592 th->th_seq = htonl(tw->snd_nxt); 593 th->th_ack = htonl(tw->rcv_nxt); 594 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 595 th->th_flags = flags; 596 th->th_win = htons(tw->last_win); 597 598#ifdef INET6 599 if (isipv6) { 600 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 601 sizeof(struct tcphdr) + optlen); 602 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 603 error = ip6_output(m, inp->in6p_outputopts, NULL, 604 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp); 605 } else 606#endif 607 { 608 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 609 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP)); 610 m->m_pkthdr.csum_flags = CSUM_TCP; 611 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 612 ip->ip_len = m->m_pkthdr.len; 613 if (V_path_mtu_discovery) 614 ip->ip_off |= IP_DF; 615 error = ip_output(m, inp->inp_options, NULL, 616 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 617 NULL, inp); 618 } 619 if (flags & TH_ACK) 620 V_tcpstat.tcps_sndacks++; 621 else 622 V_tcpstat.tcps_sndctrl++; 623 V_tcpstat.tcps_sndtotal++; 624 return (error); 625} 626 627static void 628tcp_tw_2msl_reset(struct tcptw *tw, int rearm) 629{ 630 INIT_VNET_INET(curvnet); 631 632 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 633 INP_WLOCK_ASSERT(tw->tw_inpcb); 634 if (rearm) 635 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl); 636 tw->tw_time = ticks + 2 * tcp_msl; 637 TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl); 638} 639 640static void 641tcp_tw_2msl_stop(struct tcptw *tw) 642{ 643 INIT_VNET_INET(curvnet); 644 645 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 646 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl); 647} 648 649struct tcptw * 650tcp_tw_2msl_scan(int reuse) 651{ 652 INIT_VNET_INET(curvnet); 653 struct tcptw *tw; 654 655 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 656 for (;;) { 657 tw = TAILQ_FIRST(&V_twq_2msl); 658 if (tw == NULL || (!reuse && tw->tw_time > ticks)) 659 break; 660 INP_WLOCK(tw->tw_inpcb); 661 tcp_twclose(tw, reuse); 662 if (reuse) 663 return (tw); 664 } 665 return (NULL); 666} 667