sys/netinet/tcp_timewait.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  *      @(#)tcp_subr.c  8.2 (Berkeley) 5/24/95
  32  */
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 #include "opt_inet.h"
  38 #include "opt_inet6.h"
  39 #include "opt_tcpdebug.h"
  40
  41 #include <sys/param.h>
  42 #include <sys/systm.h>
  43 #include <sys/callout.h>
  44 #include <sys/kernel.h>
  45 #include <sys/sysctl.h>
  46 #include <sys/malloc.h>
  47 #include <sys/mbuf.h>
  48 #include <sys/priv.h>
  49 #include <sys/proc.h>
  50 #include <sys/socket.h>
  51 #include <sys/socketvar.h>
  52 #ifndef INVARIANTS
  53 #include <sys/syslog.h>
  54 #endif
  55 #include <sys/protosw.h>
  56 #include <sys/random.h>
  57
  58 #include <vm/uma.h>
  59
  60 #include <net/route.h>
  61 #include <net/if.h>
  62 #include <net/if_var.h>
  63 #include <net/vnet.h>
  64
  65 #include <netinet/in.h>
  66 #include <netinet/in_kdtrace.h>
  67 #include <netinet/in_pcb.h>
  68 #include <netinet/in_systm.h>
  69 #include <netinet/in_var.h>
  70 #include <netinet/ip.h>
  71 #include <netinet/ip_icmp.h>
  72 #include <netinet/ip_var.h>
  73 #ifdef INET6
  74 #include <netinet/ip6.h>
  75 #include <netinet6/in6_pcb.h>
  76 #include <netinet6/ip6_var.h>
  77 #include <netinet6/scope6_var.h>
  78 #include <netinet6/nd6.h>
  79 #endif
  80 #include <netinet/tcp.h>
  81 #include <netinet/tcp_fsm.h>
  82 #include <netinet/tcp_seq.h>
  83 #include <netinet/tcp_timer.h>
  84 #include <netinet/tcp_var.h>
  85 #ifdef INET6
  86 #include <netinet6/tcp6_var.h>
  87 #endif
  88 #include <netinet/tcpip.h>
  89 #ifdef TCPDEBUG
  90 #include <netinet/tcp_debug.h>
  91 #endif
  92 #ifdef INET6
  93 #include <netinet6/ip6protosw.h>
  94 #endif
  95
  96 #include <machine/in_cksum.h>
  97
  98 #include <security/mac/mac_framework.h>
  99
 100 VNET_DEFINE_STATIC(uma_zone_t, tcptw_zone);
 101 #define V_tcptw_zone            VNET(tcptw_zone)
 102 static int      maxtcptw;
 103
 104 /*
 105  * The timed wait queue contains references to each of the TCP sessions
 106  * currently in the TIME_WAIT state.  The queue pointers, including the
 107  * queue pointers in each tcptw structure, are protected using the global
 108  * timewait lock, which must be held over queue iteration and modification.
 109  *
 110  * Rules on tcptw usage:
 111  *  - a inpcb is always freed _after_ its tcptw
 112  *  - a tcptw relies on its inpcb reference counting for memory stability
 113  *  - a tcptw is dereferenceable only while its inpcb is locked
 114  */
 115 VNET_DEFINE_STATIC(TAILQ_HEAD(, tcptw), twq_2msl);
 116 #define V_twq_2msl              VNET(twq_2msl)
 117
 118 /* Global timewait lock */
 119 VNET_DEFINE_STATIC(struct rwlock, tw_lock);
 120 #define V_tw_lock               VNET(tw_lock)
 121
 122 #define TW_LOCK_INIT(tw, d)     rw_init_flags(&(tw), (d), 0)
 123 #define TW_LOCK_DESTROY(tw)     rw_destroy(&(tw))
 124 #define TW_RLOCK(tw)            rw_rlock(&(tw))
 125 #define TW_WLOCK(tw)            rw_wlock(&(tw))
 126 #define TW_RUNLOCK(tw)          rw_runlock(&(tw))
 127 #define TW_WUNLOCK(tw)          rw_wunlock(&(tw))
 128 #define TW_LOCK_ASSERT(tw)      rw_assert(&(tw), RA_LOCKED)
 129 #define TW_RLOCK_ASSERT(tw)     rw_assert(&(tw), RA_RLOCKED)
 130 #define TW_WLOCK_ASSERT(tw)     rw_assert(&(tw), RA_WLOCKED)
 131 #define TW_UNLOCK_ASSERT(tw)    rw_assert(&(tw), RA_UNLOCKED)
 132
 133 static void     tcp_tw_2msl_reset(struct tcptw *, int);
 134 static void     tcp_tw_2msl_stop(struct tcptw *, int);
 135 static int      tcp_twrespond(struct tcptw *, int);
 136
 137 static int
 138 tcptw_auto_size(void)
 139 {
 140         int halfrange;
 141
 142         /*
 143          * Max out at half the ephemeral port range so that TIME_WAIT
 144          * sockets don't tie up too many ephemeral ports.
 145          */
 146         if (V_ipport_lastauto > V_ipport_firstauto)
 147                 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2;
 148         else
 149                 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2;
 150         /* Protect against goofy port ranges smaller than 32. */
 151         return (imin(imax(halfrange, 32), maxsockets / 5));
 152 }
 153
 154 static int
 155 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
 156 {
 157         int error, new;
 158
 159         if (maxtcptw == 0)
 160                 new = tcptw_auto_size();
 161         else
 162                 new = maxtcptw;
 163         error = sysctl_handle_int(oidp, &new, 0, req);
 164         if (error == 0 && req->newptr)
 165                 if (new >= 32) {
 166                         maxtcptw = new;
 167                         uma_zone_set_max(V_tcptw_zone, maxtcptw);
 168                 }
 169         return (error);
 170 }
 171
 172 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW,
 173     &maxtcptw, 0, sysctl_maxtcptw, "IU",
 174     "Maximum number of compressed TCP TIME_WAIT entries");
 175
 176 VNET_DEFINE_STATIC(int, nolocaltimewait) = 0;
 177 #define V_nolocaltimewait       VNET(nolocaltimewait)
 178 SYSCTL_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_VNET | CTLFLAG_RW,
 179     &VNET_NAME(nolocaltimewait), 0,
 180     "Do not create compressed TCP TIME_WAIT entries for local connections");
 181
 182 void
 183 tcp_tw_zone_change(void)
 184 {
 185
 186         if (maxtcptw == 0)
 187                 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
 188 }
 189
 190 void
 191 tcp_tw_init(void)
 192 {
 193
 194         V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
 195             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 196         TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
 197         if (maxtcptw == 0)
 198                 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
 199         else
 200                 uma_zone_set_max(V_tcptw_zone, maxtcptw);
 201         TAILQ_INIT(&V_twq_2msl);
 202         TW_LOCK_INIT(V_tw_lock, "tcptw");
 203 }
 204
 205 #ifdef VIMAGE
 206 void
 207 tcp_tw_destroy(void)
 208 {
 209         struct tcptw *tw;
 210         struct epoch_tracker et;
 211
 212         INP_INFO_RLOCK_ET(&V_tcbinfo, et);
 213         while ((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL)
 214                 tcp_twclose(tw, 0);
 215         INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
 216
 217         TW_LOCK_DESTROY(V_tw_lock);
 218         uma_zdestroy(V_tcptw_zone);
 219 }
 220 #endif
 221
 222 /*
 223  * Move a TCP connection into TIME_WAIT state.
 224  *    tcbinfo is locked.
 225  *    inp is locked, and is unlocked before returning.
 226  */
 227 void
 228 tcp_twstart(struct tcpcb *tp)
 229 {
 230         struct tcptw twlocal, *tw;
 231         struct inpcb *inp = tp->t_inpcb;
 232         struct socket *so;
 233         uint32_t recwin;
 234         bool acknow, local;
 235 #ifdef INET6
 236         bool isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
 237 #endif
 238
 239         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
 240         INP_WLOCK_ASSERT(inp);
 241
 242         /* A dropped inp should never transition to TIME_WAIT state. */
 243         KASSERT((inp->inp_flags & INP_DROPPED) == 0, ("tcp_twstart: "
 244             "(inp->inp_flags & INP_DROPPED) != 0"));
 245
 246         if (V_nolocaltimewait) {
 247 #ifdef INET6
 248                 if (isipv6)
 249                         local = in6_localaddr(&inp->in6p_faddr);
 250                 else
 251 #endif
 252 #ifdef INET
 253                         local = in_localip(inp->inp_faddr);
 254 #else
 255                         local = false;
 256 #endif
 257         } else
 258                 local = false;
 259
 260         /*
 261          * For use only by DTrace.  We do not reference the state
 262          * after this point so modifying it in place is not a problem.
 263          */
 264         tcp_state_change(tp, TCPS_TIME_WAIT);
 265
 266         if (local)
 267                 tw = &twlocal;
 268         else
 269                 tw = uma_zalloc(V_tcptw_zone, M_NOWAIT);
 270         if (tw == NULL) {
 271                 /*
 272                  * Reached limit on total number of TIMEWAIT connections
 273                  * allowed. Remove a connection from TIMEWAIT queue in LRU
 274                  * fashion to make room for this connection.
 275                  *
 276                  * XXX:  Check if it possible to always have enough room
 277                  * in advance based on guarantees provided by uma_zalloc().
 278                  */
 279                 tw = tcp_tw_2msl_scan(1);
 280                 if (tw == NULL) {
 281                         tp = tcp_close(tp);
 282                         if (tp != NULL)
 283                                 INP_WUNLOCK(inp);
 284                         return;
 285                 }
 286         }
 287         /*
 288          * For !local case the tcptw will hold a reference on its inpcb
 289          * until tcp_twclose is called.
 290          */
 291         tw->tw_inpcb = inp;
 292
 293         /*
 294          * Recover last window size sent.
 295          */
 296         so = inp->inp_socket;
 297         recwin = lmin(lmax(sbspace(&so->so_rcv), 0),
 298             (long)TCP_MAXWIN << tp->rcv_scale);
 299         if (recwin < (so->so_rcv.sb_hiwat / 4) &&
 300             recwin < tp->t_maxseg)
 301                 recwin = 0;
 302         if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
 303             recwin < (tp->rcv_adv - tp->rcv_nxt))
 304                 recwin = (tp->rcv_adv - tp->rcv_nxt);
 305         tw->last_win = (u_short)(recwin >> tp->rcv_scale);
 306
 307         /*
 308          * Set t_recent if timestamps are used on the connection.
 309          */
 310         if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
 311             (TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
 312                 tw->t_recent = tp->ts_recent;
 313                 tw->ts_offset = tp->ts_offset;
 314         } else {
 315                 tw->t_recent = 0;
 316                 tw->ts_offset = 0;
 317         }
 318
 319         tw->snd_nxt = tp->snd_nxt;
 320         tw->rcv_nxt = tp->rcv_nxt;
 321         tw->iss     = tp->iss;
 322         tw->irs     = tp->irs;
 323         tw->t_starttime = tp->t_starttime;
 324         tw->tw_time = 0;
 325
 326 /* XXX
 327  * If this code will
 328  * be used for fin-wait-2 state also, then we may need
 329  * a ts_recent from the last segment.
 330  */
 331         acknow = tp->t_flags & TF_ACKNOW;
 332
 333         /*
 334          * First, discard tcpcb state, which includes stopping its timers and
 335          * freeing it.  tcp_discardcb() used to also release the inpcb, but
 336          * that work is now done in the caller.
 337          *
 338          * Note: soisdisconnected() call used to be made in tcp_discardcb(),
 339          * and might not be needed here any longer.
 340          */
 341         tcp_discardcb(tp);
 342         soisdisconnected(so);
 343         tw->tw_so_options = so->so_options;
 344         inp->inp_flags |= INP_TIMEWAIT;
 345         if (acknow)
 346                 tcp_twrespond(tw, TH_ACK);
 347         if (local)
 348                 in_pcbdrop(inp);
 349         else {
 350                 in_pcbref(inp); /* Reference from tw */
 351                 tw->tw_cred = crhold(so->so_cred);
 352                 inp->inp_ppcb = tw;
 353                 TCPSTATES_INC(TCPS_TIME_WAIT);
 354                 tcp_tw_2msl_reset(tw, 0);
 355         }
 356
 357         /*
 358          * If the inpcb owns the sole reference to the socket, then we can
 359          * detach and free the socket as it is not needed in time wait.
 360          */
 361         if (inp->inp_flags & INP_SOCKREF) {
 362                 KASSERT(so->so_state & SS_PROTOREF,
 363                     ("tcp_twstart: !SS_PROTOREF"));
 364                 inp->inp_flags &= ~INP_SOCKREF;
 365                 INP_WUNLOCK(inp);
 366                 SOCK_LOCK(so);
 367                 so->so_state &= ~SS_PROTOREF;
 368                 sofree(so);
 369         } else
 370                 INP_WUNLOCK(inp);
 371 }
 372
 373 /*
 374  * Returns 1 if the TIME_WAIT state was killed and we should start over,
 375  * looking for a pcb in the listen state.  Returns 0 otherwise.
 376  */
 377 int
 378 tcp_twcheck(struct inpcb *inp, struct tcpopt *to __unused, struct tcphdr *th,
 379     struct mbuf *m, int tlen)
 380 {
 381         struct tcptw *tw;
 382         int thflags;
 383         tcp_seq seq;
 384
 385         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
 386         INP_WLOCK_ASSERT(inp);
 387
 388         /*
 389          * XXXRW: Time wait state for inpcb has been recycled, but inpcb is
 390          * still present.  This is undesirable, but temporarily necessary
 391          * until we work out how to handle inpcb's who's timewait state has
 392          * been removed.
 393          */
 394         tw = intotw(inp);
 395         if (tw == NULL)
 396                 goto drop;
 397
 398         thflags = th->th_flags;
 399
 400         /*
 401          * NOTE: for FIN_WAIT_2 (to be added later),
 402          * must validate sequence number before accepting RST
 403          */
 404
 405         /*
 406          * If the segment contains RST:
 407          *      Drop the segment - see Stevens, vol. 2, p. 964 and
 408          *      RFC 1337.
 409          */
 410         if (thflags & TH_RST)
 411                 goto drop;
 412
 413 #if 0
 414 /* PAWS not needed at the moment */
 415         /*
 416          * RFC 1323 PAWS: If we have a timestamp reply on this segment
 417          * and it's less than ts_recent, drop it.
 418          */
 419         if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
 420             TSTMP_LT(to.to_tsval, tp->ts_recent)) {
 421                 if ((thflags & TH_ACK) == 0)
 422                         goto drop;
 423                 goto ack;
 424         }
 425         /*
 426          * ts_recent is never updated because we never accept new segments.
 427          */
 428 #endif
 429
 430         /*
 431          * If a new connection request is received
 432          * while in TIME_WAIT, drop the old connection
 433          * and start over if the sequence numbers
 434          * are above the previous ones.
 435          */
 436         if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
 437                 tcp_twclose(tw, 0);
 438                 return (1);
 439         }
 440
 441         /*
 442          * Drop the segment if it does not contain an ACK.
 443          */
 444         if ((thflags & TH_ACK) == 0)
 445                 goto drop;
 446
 447         /*
 448          * Reset the 2MSL timer if this is a duplicate FIN.
 449          */
 450         if (thflags & TH_FIN) {
 451                 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
 452                 if (seq + 1 == tw->rcv_nxt)
 453                         tcp_tw_2msl_reset(tw, 1);
 454         }
 455
 456         /*
 457          * Acknowledge the segment if it has data or is not a duplicate ACK.
 458          */
 459         if (thflags != TH_ACK || tlen != 0 ||
 460             th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) {
 461                 TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
 462                 tcp_twrespond(tw, TH_ACK);
 463                 goto dropnoprobe;
 464         }
 465 drop:
 466         TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
 467 dropnoprobe:
 468         INP_WUNLOCK(inp);
 469         m_freem(m);
 470         return (0);
 471 }
 472
 473 void
 474 tcp_twclose(struct tcptw *tw, int reuse)
 475 {
 476         struct socket *so;
 477         struct inpcb *inp;
 478
 479         /*
 480          * At this point, we are in one of two situations:
 481          *
 482          * (1) We have no socket, just an inpcb<->twtcp pair.  We can free
 483          *     all state.
 484          *
 485          * (2) We have a socket -- if we own a reference, release it and
 486          *     notify the socket layer.
 487          */
 488         inp = tw->tw_inpcb;
 489         KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait"));
 490         KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw"));
 491         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);      /* in_pcbfree() */
 492         INP_WLOCK_ASSERT(inp);
 493
 494         tcp_tw_2msl_stop(tw, reuse);
 495         inp->inp_ppcb = NULL;
 496         in_pcbdrop(inp);
 497
 498         so = inp->inp_socket;
 499         if (so != NULL) {
 500                 /*
 501                  * If there's a socket, handle two cases: first, we own a
 502                  * strong reference, which we will now release, or we don't
 503                  * in which case another reference exists (XXXRW: think
 504                  * about this more), and we don't need to take action.
 505                  */
 506                 if (inp->inp_flags & INP_SOCKREF) {
 507                         inp->inp_flags &= ~INP_SOCKREF;
 508                         INP_WUNLOCK(inp);
 509                         SOCK_LOCK(so);
 510                         KASSERT(so->so_state & SS_PROTOREF,
 511                             ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF"));
 512                         so->so_state &= ~SS_PROTOREF;
 513                         sofree(so);
 514                 } else {
 515                         /*
 516                          * If we don't own the only reference, the socket and
 517                          * inpcb need to be left around to be handled by
 518                          * tcp_usr_detach() later.
 519                          */
 520                         INP_WUNLOCK(inp);
 521                 }
 522         } else {
 523                 /*
 524                  * The socket has been already cleaned-up for us, only free the
 525                  * inpcb.
 526                  */
 527                 in_pcbfree(inp);
 528         }
 529         TCPSTAT_INC(tcps_closed);
 530 }
 531
 532 static int
 533 tcp_twrespond(struct tcptw *tw, int flags)
 534 {
 535         struct inpcb *inp = tw->tw_inpcb;
 536 #if defined(INET6) || defined(INET)
 537         struct tcphdr *th = NULL;
 538 #endif
 539         struct mbuf *m;
 540 #ifdef INET
 541         struct ip *ip = NULL;
 542 #endif
 543         u_int hdrlen, optlen;
 544         int error = 0;                  /* Keep compiler happy */
 545         struct tcpopt to;
 546 #ifdef INET6
 547         struct ip6_hdr *ip6 = NULL;
 548         int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
 549 #endif
 550         hdrlen = 0;                     /* Keep compiler happy */
 551
 552         INP_WLOCK_ASSERT(inp);
 553
 554         m = m_gethdr(M_NOWAIT, MT_DATA);
 555         if (m == NULL)
 556                 return (ENOBUFS);
 557         m->m_data += max_linkhdr;
 558
 559 #ifdef MAC
 560         mac_inpcb_create_mbuf(inp, m);
 561 #endif
 562
 563 #ifdef INET6
 564         if (isipv6) {
 565                 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 566                 ip6 = mtod(m, struct ip6_hdr *);
 567                 th = (struct tcphdr *)(ip6 + 1);
 568                 tcpip_fillheaders(inp, ip6, th);
 569         }
 570 #endif
 571 #if defined(INET6) && defined(INET)
 572         else
 573 #endif
 574 #ifdef INET
 575         {
 576                 hdrlen = sizeof(struct tcpiphdr);
 577                 ip = mtod(m, struct ip *);
 578                 th = (struct tcphdr *)(ip + 1);
 579                 tcpip_fillheaders(inp, ip, th);
 580         }
 581 #endif
 582         to.to_flags = 0;
 583
 584         /*
 585          * Send a timestamp and echo-reply if both our side and our peer
 586          * have sent timestamps in our SYN's and this is not a RST.
 587          */
 588         if (tw->t_recent && flags == TH_ACK) {
 589                 to.to_flags |= TOF_TS;
 590                 to.to_tsval = tcp_ts_getticks() + tw->ts_offset;
 591                 to.to_tsecr = tw->t_recent;
 592         }
 593         optlen = tcp_addoptions(&to, (u_char *)(th + 1));
 594
 595         m->m_len = hdrlen + optlen;
 596         m->m_pkthdr.len = m->m_len;
 597
 598         KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
 599
 600         th->th_seq = htonl(tw->snd_nxt);
 601         th->th_ack = htonl(tw->rcv_nxt);
 602         th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
 603         th->th_flags = flags;
 604         th->th_win = htons(tw->last_win);
 605
 606         m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 607 #ifdef INET6
 608         if (isipv6) {
 609                 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
 610                 th->th_sum = in6_cksum_pseudo(ip6,
 611                     sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0);
 612                 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
 613                 TCP_PROBE5(send, NULL, NULL, ip6, NULL, th);
 614                 error = ip6_output(m, inp->in6p_outputopts, NULL,
 615                     (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
 616         }
 617 #endif
 618 #if defined(INET6) && defined(INET)
 619         else
 620 #endif
 621 #ifdef INET
 622         {
 623                 m->m_pkthdr.csum_flags = CSUM_TCP;
 624                 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
 625                     htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
 626                 ip->ip_len = htons(m->m_pkthdr.len);
 627                 if (V_path_mtu_discovery)
 628                         ip->ip_off |= htons(IP_DF);
 629                 TCP_PROBE5(send, NULL, NULL, ip, NULL, th);
 630                 error = ip_output(m, inp->inp_options, NULL,
 631                     ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
 632                     NULL, inp);
 633         }
 634 #endif
 635         if (flags & TH_ACK)
 636                 TCPSTAT_INC(tcps_sndacks);
 637         else
 638                 TCPSTAT_INC(tcps_sndctrl);
 639         TCPSTAT_INC(tcps_sndtotal);
 640         return (error);
 641 }
 642
 643 static void
 644 tcp_tw_2msl_reset(struct tcptw *tw, int rearm)
 645 {
 646
 647         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
 648         INP_WLOCK_ASSERT(tw->tw_inpcb);
 649
 650         TW_WLOCK(V_tw_lock);
 651         if (rearm)
 652                 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
 653         tw->tw_time = ticks + 2 * tcp_msl;
 654         TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl);
 655         TW_WUNLOCK(V_tw_lock);
 656 }
 657
 658 static void
 659 tcp_tw_2msl_stop(struct tcptw *tw, int reuse)
 660 {
 661         struct ucred *cred;
 662         struct inpcb *inp;
 663         int released __unused;
 664
 665         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
 666
 667         TW_WLOCK(V_tw_lock);
 668         inp = tw->tw_inpcb;
 669         tw->tw_inpcb = NULL;
 670
 671         TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
 672         cred = tw->tw_cred;
 673         tw->tw_cred = NULL;
 674         TW_WUNLOCK(V_tw_lock);
 675
 676         if (cred != NULL)
 677                 crfree(cred);
 678
 679         released = in_pcbrele_wlocked(inp);
 680         KASSERT(!released, ("%s: inp should not be released here", __func__));
 681
 682         if (!reuse)
 683                 uma_zfree(V_tcptw_zone, tw);
 684         TCPSTATES_DEC(TCPS_TIME_WAIT);
 685 }
 686
 687 struct tcptw *
 688 tcp_tw_2msl_scan(int reuse)
 689 {
 690         struct tcptw *tw;
 691         struct inpcb *inp;
 692         struct epoch_tracker et;
 693
 694 #ifdef INVARIANTS
 695         if (reuse) {
 696                 /*
 697                  * Exclusive pcbinfo lock is not required in reuse case even if
 698                  * two inpcb locks can be acquired simultaneously:
 699                  *  - the inpcb transitioning to TIME_WAIT state in
 700                  *    tcp_tw_start(),
 701                  *  - the inpcb closed by tcp_twclose().
 702                  *
 703                  * It is because only inpcbs in FIN_WAIT2 or CLOSING states can
 704                  * transition in TIME_WAIT state.  Then a pcbcb cannot be in
 705                  * TIME_WAIT list and transitioning to TIME_WAIT state at same
 706                  * time.
 707                  */
 708                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
 709         }
 710 #endif
 711
 712         for (;;) {
 713                 TW_RLOCK(V_tw_lock);
 714                 tw = TAILQ_FIRST(&V_twq_2msl);
 715                 if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0)) {
 716                         TW_RUNLOCK(V_tw_lock);
 717                         break;
 718                 }
 719                 KASSERT(tw->tw_inpcb != NULL, ("%s: tw->tw_inpcb == NULL",
 720                     __func__));
 721
 722                 inp = tw->tw_inpcb;
 723                 in_pcbref(inp);
 724                 TW_RUNLOCK(V_tw_lock);
 725
 726                 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
 727                 INP_WLOCK(inp);
 728                 tw = intotw(inp);
 729                 if (in_pcbrele_wlocked(inp)) {
 730                         if (__predict_true(tw == NULL)) {
 731                                 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
 732                                 continue;
 733                         } else {
 734                                 /* This should not happen as in TIMEWAIT
 735                                  * state the inp should not be destroyed
 736                                  * before its tcptw. If INVARIANTS is
 737                                  * defined panic.
 738                                  */
 739 #ifdef INVARIANTS
 740                                 panic("%s: Panic before an infinite "
 741                                           "loop: INP_TIMEWAIT && (INP_FREED "
 742                                           "|| inp last reference) && tw != "
 743                                           "NULL", __func__);
 744 #else
 745                                 log(LOG_ERR, "%s: Avoid an infinite "
 746                                         "loop: INP_TIMEWAIT && (INP_FREED "
 747                                         "|| inp last reference) && tw != "
 748                                         "NULL", __func__);
 749 #endif
 750                                 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
 751                                 break;
 752                         }
 753                 }
 754
 755                 if (tw == NULL) {
 756                         /* tcp_twclose() has already been called */
 757                         INP_WUNLOCK(inp);
 758                         INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
 759                         continue;
 760                 }
 761
 762                 tcp_twclose(tw, reuse);
 763                 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
 764                 if (reuse)
 765                         return tw;
 766         }
 767
 768         return NULL;
 769 }