sys/netinet/tcp_reass.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 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_input.c 8.12 (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 /* For debugging we want counters and BB logging */
  42 /* #define TCP_REASS_COUNTERS 1 */
  43 /* #define TCP_REASS_LOGGING 1 */
  44
  45 #include <sys/param.h>
  46 #include <sys/kernel.h>
  47 #include <sys/eventhandler.h>
  48 #include <sys/malloc.h>
  49 #include <sys/mbuf.h>
  50 #include <sys/socket.h>
  51 #include <sys/socketvar.h>
  52 #include <sys/sysctl.h>
  53 #include <sys/syslog.h>
  54 #include <sys/systm.h>
  55
  56 #include <vm/uma.h>
  57
  58 #include <net/if.h>
  59 #include <net/if_var.h>
  60 #include <net/route.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_var.h>
  69 #include <netinet/ip_options.h>
  70 #include <netinet/ip6.h>
  71 #include <netinet6/in6_pcb.h>
  72 #include <netinet6/ip6_var.h>
  73 #include <netinet6/nd6.h>
  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 TCP_REASS_LOGGING
  80 #include <netinet/tcp_log_buf.h>
  81 #include <netinet/tcp_hpts.h>
  82 #endif
  83 #include <netinet6/tcp6_var.h>
  84 #include <netinet/tcpip.h>
  85 #ifdef TCPDEBUG
  86 #include <netinet/tcp_debug.h>
  87 #endif /* TCPDEBUG */
  88
  89 #define TCP_R_LOG_ADD           1
  90 #define TCP_R_LOG_LIMIT_REACHED 2
  91 #define TCP_R_LOG_APPEND        3
  92 #define TCP_R_LOG_PREPEND       4
  93 #define TCP_R_LOG_REPLACE       5
  94 #define TCP_R_LOG_MERGE_INTO    6
  95 #define TCP_R_LOG_NEW_ENTRY     7
  96 #define TCP_R_LOG_READ          8
  97 #define TCP_R_LOG_ZERO          9
  98 #define TCP_R_LOG_DUMP          10
  99 #define TCP_R_LOG_TRIM          11
 100
 101 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass,
 102     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
 103     "TCP Segment Reassembly Queue");
 104
 105 static SYSCTL_NODE(_net_inet_tcp_reass, OID_AUTO, stats,
 106     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
 107     "TCP Segment Reassembly stats");
 108
 109
 110 static int tcp_reass_maxseg = 0;
 111 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
 112     &tcp_reass_maxseg, 0,
 113     "Global maximum number of TCP Segments in Reassembly Queue");
 114
 115 static uma_zone_t tcp_reass_zone;
 116 SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, 0,
 117     &tcp_reass_zone,
 118     "Global number of TCP Segments currently in Reassembly Queue");
 119
 120 static u_int tcp_reass_maxqueuelen = 100;
 121 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, maxqueuelen, CTLFLAG_RWTUN,
 122     &tcp_reass_maxqueuelen, 0,
 123     "Maximum number of TCP Segments per Reassembly Queue");
 124
 125 static int tcp_new_limits = 0;
 126 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, new_limit, CTLFLAG_RWTUN,
 127     &tcp_new_limits, 0,
 128     "Do we use the new limit method we are discussing?");
 129
 130 static u_int tcp_reass_queue_guard = 16;
 131 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, queueguard, CTLFLAG_RWTUN,
 132     &tcp_reass_queue_guard, 16,
 133     "Number of TCP Segments in Reassembly Queue where we flip over to guard mode");
 134
 135 #ifdef TCP_REASS_COUNTERS
 136
 137 counter_u64_t reass_entry;
 138 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, entry, CTLFLAG_RD,
 139     &reass_entry, "A segment entered reassembly ");
 140
 141 counter_u64_t reass_path1;
 142 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path1, CTLFLAG_RD,
 143     &reass_path1, "Took path 1");
 144
 145 counter_u64_t reass_path2;
 146 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path2, CTLFLAG_RD,
 147     &reass_path2, "Took path 2");
 148
 149 counter_u64_t reass_path3;
 150 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path3, CTLFLAG_RD,
 151     &reass_path3, "Took path 3");
 152
 153 counter_u64_t reass_path4;
 154 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path4, CTLFLAG_RD,
 155     &reass_path4, "Took path 4");
 156
 157 counter_u64_t reass_path5;
 158 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path5, CTLFLAG_RD,
 159     &reass_path5, "Took path 5");
 160
 161 counter_u64_t reass_path6;
 162 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path6, CTLFLAG_RD,
 163     &reass_path6, "Took path 6");
 164
 165 counter_u64_t reass_path7;
 166 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path7, CTLFLAG_RD,
 167     &reass_path7, "Took path 7");
 168
 169 counter_u64_t reass_fullwalk;
 170 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, fullwalk, CTLFLAG_RD,
 171     &reass_fullwalk, "Took a full walk ");
 172
 173 counter_u64_t reass_nospace;
 174 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, nospace, CTLFLAG_RD,
 175     &reass_nospace, "Had no mbuf capacity ");
 176
 177 counter_u64_t merge_fwd;
 178 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_fwd, CTLFLAG_RD,
 179     &merge_fwd, "Ran merge fwd");
 180
 181 counter_u64_t merge_into;
 182 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_into, CTLFLAG_RD,
 183     &merge_into, "Ran merge into");
 184
 185 counter_u64_t tcp_zero_input;
 186 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, zero_input, CTLFLAG_RD,
 187     &tcp_zero_input, "The reassembly buffer saw a zero len segment etc");
 188
 189 #endif
 190
 191 /* Initialize TCP reassembly queue */
 192 static void
 193 tcp_reass_zone_change(void *tag)
 194 {
 195
 196         /* Set the zone limit and read back the effective value. */
 197         tcp_reass_maxseg = nmbclusters / 16;
 198         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 199             tcp_reass_maxseg);
 200 }
 201
 202 #ifdef TCP_REASS_LOGGING
 203
 204 static void
 205 tcp_log_reassm(struct tcpcb *tp, struct tseg_qent *q, struct tseg_qent *p,
 206     tcp_seq seq, int len, uint8_t action, int instance)
 207 {
 208         uint32_t cts;
 209         struct timeval tv;
 210
 211         if (tp->t_logstate != TCP_LOG_STATE_OFF) {
 212                 union tcp_log_stackspecific log;
 213
 214                 memset(&log, 0, sizeof(log));
 215                 cts = tcp_get_usecs(&tv);
 216                 log.u_bbr.flex1 = seq;
 217                 log.u_bbr.cur_del_rate = (uint64_t)q;
 218                 log.u_bbr.delRate = (uint64_t)p;
 219                 if (q != NULL) {
 220                         log.u_bbr.flex2 = q->tqe_start;
 221                         log.u_bbr.flex3 = q->tqe_len;
 222                         log.u_bbr.flex4 = q->tqe_mbuf_cnt;
 223                         log.u_bbr.hptsi_gain = q->tqe_flags;
 224                 }
 225                 if (p != NULL)  {
 226                         log.u_bbr.flex5 = p->tqe_start;
 227                         log.u_bbr.pkts_out = p->tqe_len;
 228                         log.u_bbr.epoch = p->tqe_mbuf_cnt;
 229                         log.u_bbr.cwnd_gain = p->tqe_flags;
 230                 }
 231                 log.u_bbr.flex6 = tp->t_segqmbuflen;
 232                 log.u_bbr.flex7 = instance;
 233                 log.u_bbr.flex8 = action;
 234                 log.u_bbr.timeStamp = cts;
 235                 TCP_LOG_EVENTP(tp, NULL,
 236                     &tp->t_inpcb->inp_socket->so_rcv,
 237                     &tp->t_inpcb->inp_socket->so_snd,
 238                     TCP_LOG_REASS, 0,
 239                     len, &log, false, &tv);
 240         }
 241 }
 242
 243 static void
 244 tcp_reass_log_dump(struct tcpcb *tp)
 245 {
 246         struct tseg_qent *q;
 247
 248         if (tp->t_logstate != TCP_LOG_STATE_OFF) {
 249                 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
 250                         tcp_log_reassm(tp, q, NULL, q->tqe_start, q->tqe_len, TCP_R_LOG_DUMP, 0);
 251                 }
 252         };
 253 }
 254
 255 static void
 256 tcp_reass_log_new_in(struct tcpcb *tp, tcp_seq seq, int len, struct mbuf *m,
 257     int logval, struct tseg_qent *q)
 258 {
 259         int cnt;
 260         struct mbuf *t;
 261
 262         cnt = 0;
 263         t = m;
 264         while (t) {
 265                 cnt += t->m_len;
 266                 t = t->m_next;
 267         }
 268         tcp_log_reassm(tp, q, NULL, seq, len, logval, cnt);
 269 }
 270
 271 #endif
 272
 273 void
 274 tcp_reass_global_init(void)
 275 {
 276
 277         tcp_reass_maxseg = nmbclusters / 16;
 278         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
 279             &tcp_reass_maxseg);
 280         tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
 281             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 282         /* Set the zone limit and read back the effective value. */
 283         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 284             tcp_reass_maxseg);
 285 #ifdef TCP_REASS_COUNTERS
 286         reass_path1 = counter_u64_alloc(M_WAITOK);
 287         reass_path2 = counter_u64_alloc(M_WAITOK);
 288         reass_path3 = counter_u64_alloc(M_WAITOK);
 289         reass_path4 = counter_u64_alloc(M_WAITOK);
 290         reass_path5 = counter_u64_alloc(M_WAITOK);
 291         reass_path6 = counter_u64_alloc(M_WAITOK);
 292         reass_path7 = counter_u64_alloc(M_WAITOK);
 293         reass_fullwalk = counter_u64_alloc(M_WAITOK);
 294         reass_nospace = counter_u64_alloc(M_WAITOK);
 295         reass_entry = counter_u64_alloc(M_WAITOK);
 296         merge_fwd = counter_u64_alloc(M_WAITOK);
 297         merge_into = counter_u64_alloc(M_WAITOK);
 298         tcp_zero_input = counter_u64_alloc(M_WAITOK);
 299 #endif
 300         EVENTHANDLER_REGISTER(nmbclusters_change,
 301             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 302
 303 }
 304
 305 void
 306 tcp_reass_flush(struct tcpcb *tp)
 307 {
 308         struct tseg_qent *qe;
 309
 310         INP_WLOCK_ASSERT(tp->t_inpcb);
 311
 312         while ((qe = TAILQ_FIRST(&tp->t_segq)) != NULL) {
 313                 TAILQ_REMOVE(&tp->t_segq, qe, tqe_q);
 314                 m_freem(qe->tqe_m);
 315                 uma_zfree(tcp_reass_zone, qe);
 316                 tp->t_segqlen--;
 317         }
 318         tp->t_segqmbuflen = 0;
 319         KASSERT((tp->t_segqlen == 0),
 320             ("TCP reass queue %p segment count is %d instead of 0 after flush.",
 321             tp, tp->t_segqlen));
 322 }
 323
 324 static void
 325 tcp_reass_append(struct tcpcb *tp, struct tseg_qent *last,
 326     struct mbuf *m, struct tcphdr *th, int tlen,
 327     struct mbuf *mlast, int lenofoh)
 328 {
 329
 330 #ifdef TCP_REASS_LOGGING
 331         tcp_log_reassm(tp, last, NULL, th->th_seq, tlen, TCP_R_LOG_APPEND, 0);
 332 #endif
 333         last->tqe_len += tlen;
 334         last->tqe_m->m_pkthdr.len += tlen;
 335         /* Preserve the FIN bit if its there */
 336         last->tqe_flags |= (th->th_flags & TH_FIN);
 337         last->tqe_last->m_next = m;
 338         last->tqe_last = mlast;
 339         last->tqe_mbuf_cnt += lenofoh;
 340         tp->t_rcvoopack++;
 341         TCPSTAT_INC(tcps_rcvoopack);
 342         TCPSTAT_ADD(tcps_rcvoobyte, tlen);
 343 #ifdef TCP_REASS_LOGGING
 344         tcp_reass_log_new_in(tp, last->tqe_start, lenofoh, last->tqe_m,
 345                              TCP_R_LOG_APPEND,
 346                              last);
 347 #endif
 348 }
 349
 350 static void
 351 tcp_reass_prepend(struct tcpcb *tp, struct tseg_qent *first, struct mbuf *m, struct tcphdr *th,
 352                   int tlen, struct mbuf *mlast, int lenofoh)
 353 {
 354         int i;
 355
 356 #ifdef TCP_REASS_LOGGING
 357         tcp_log_reassm(tp, first, NULL, th->th_seq, tlen, TCP_R_LOG_PREPEND, 0);
 358 #endif
 359         if (SEQ_GT((th->th_seq + tlen), first->tqe_start)) {
 360                 /* The new data overlaps into the old */
 361                 i = (th->th_seq + tlen) - first->tqe_start;
 362 #ifdef TCP_REASS_LOGGING
 363                 tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 1);
 364 #endif
 365                 m_adj(first->tqe_m, i);
 366                 first->tqe_len -= i;
 367                 first->tqe_start += i;
 368         }
 369         /* Ok now setup our chain to point to the old first */
 370         mlast->m_next = first->tqe_m;
 371         first->tqe_m = m;
 372         first->tqe_len += tlen;
 373         first->tqe_start = th->th_seq;
 374         first->tqe_m->m_pkthdr.len = first->tqe_len;
 375         first->tqe_mbuf_cnt += lenofoh;
 376         tp->t_rcvoopack++;
 377         TCPSTAT_INC(tcps_rcvoopack);
 378         TCPSTAT_ADD(tcps_rcvoobyte, tlen);
 379 #ifdef TCP_REASS_LOGGING
 380         tcp_reass_log_new_in(tp, first->tqe_start, lenofoh, first->tqe_m,
 381                              TCP_R_LOG_PREPEND,
 382                              first);
 383 #endif
 384 }
 385
 386 static void
 387 tcp_reass_replace(struct tcpcb *tp, struct tseg_qent *q, struct mbuf *m,
 388     tcp_seq seq, int len, struct mbuf *mlast, int mbufoh, uint8_t flags)
 389 {
 390         /*
 391          * Free the data in q, and replace
 392          * it with the new segment.
 393          */
 394         int len_dif;
 395
 396 #ifdef TCP_REASS_LOGGING
 397         tcp_log_reassm(tp, q, NULL, seq, len, TCP_R_LOG_REPLACE, 0);
 398 #endif
 399         m_freem(q->tqe_m);
 400         KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
 401                 ("Tp:%p seg queue goes negative", tp));
 402         tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
 403         q->tqe_mbuf_cnt = mbufoh;
 404         q->tqe_m = m;
 405         q->tqe_last = mlast;
 406         q->tqe_start = seq;
 407         if (len > q->tqe_len)
 408                 len_dif = len - q->tqe_len;
 409         else
 410                 len_dif = 0;
 411         tp->t_rcvoopack++;
 412         TCPSTAT_INC(tcps_rcvoopack);
 413         TCPSTAT_ADD(tcps_rcvoobyte, len_dif);
 414         q->tqe_len = len;
 415         q->tqe_flags = (flags & TH_FIN);
 416         q->tqe_m->m_pkthdr.len = q->tqe_len;
 417         tp->t_segqmbuflen += mbufoh;
 418
 419 }
 420
 421 static void
 422 tcp_reass_merge_into(struct tcpcb *tp, struct tseg_qent *ent,
 423     struct tseg_qent *q)
 424 {
 425         /*
 426          * Merge q into ent and free q from the list.
 427          */
 428 #ifdef TCP_REASS_LOGGING
 429         tcp_log_reassm(tp, q, ent, 0, 0, TCP_R_LOG_MERGE_INTO, 0);
 430 #endif
 431 #ifdef TCP_REASS_COUNTERS
 432         counter_u64_add(merge_into, 1);
 433 #endif
 434         ent->tqe_last->m_next = q->tqe_m;
 435         ent->tqe_last = q->tqe_last;
 436         ent->tqe_len += q->tqe_len;
 437         ent->tqe_mbuf_cnt += q->tqe_mbuf_cnt;
 438         ent->tqe_m->m_pkthdr.len += q->tqe_len;
 439         ent->tqe_flags |= (q->tqe_flags & TH_FIN);
 440         TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
 441         uma_zfree(tcp_reass_zone, q);
 442         tp->t_segqlen--;
 443
 444 }
 445
 446 static void
 447 tcp_reass_merge_forward(struct tcpcb *tp, struct tseg_qent *ent)
 448 {
 449         struct tseg_qent *q, *qtmp;
 450         int i;
 451         tcp_seq max;
 452         /*
 453          * Given an entry merge forward anyplace
 454          * that ent overlaps forward.
 455          */
 456
 457         max = ent->tqe_start + ent->tqe_len;
 458         q = TAILQ_NEXT(ent, tqe_q);
 459         if (q == NULL) {
 460                 /* Nothing left */
 461                 return;
 462         }
 463         TAILQ_FOREACH_FROM_SAFE(q, &tp->t_segq, tqe_q, qtmp) {
 464                 if (SEQ_GT(q->tqe_start, max)) {
 465                         /* Beyond q */
 466                         break;
 467                 }
 468                 /* We have some or all that are overlapping */
 469                 if (SEQ_GEQ(max, (q->tqe_start + q->tqe_len))) {
 470                         /* It consumes it all */
 471                         tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
 472                         m_freem(q->tqe_m);
 473                         TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
 474                         uma_zfree(tcp_reass_zone, q);
 475                         tp->t_segqlen--;
 476                         continue;
 477                 }
 478                 /*
 479                  * Trim the q entry to dovetail to this one
 480                  * and then merge q into ent updating max
 481                  * in the process.
 482                  */
 483                 i = max - q->tqe_start;
 484 #ifdef TCP_REASS_LOGGING
 485                 tcp_log_reassm(tp, q, NULL, 0, i, TCP_R_LOG_TRIM, 2);
 486 #endif
 487                 m_adj(q->tqe_m, i);
 488                 q->tqe_len -= i;
 489                 q->tqe_start += i;
 490                 tcp_reass_merge_into(tp, ent, q);
 491                 max = ent->tqe_start + ent->tqe_len;
 492         }
 493 #ifdef TCP_REASS_COUNTERS
 494         counter_u64_add(merge_fwd, 1);
 495 #endif
 496 }
 497
 498 static int
 499 tcp_reass_overhead_of_chain(struct mbuf *m, struct mbuf **mlast)
 500 {
 501         int len = MSIZE;
 502
 503         if (m->m_flags & M_EXT)
 504                 len += m->m_ext.ext_size;
 505         while (m->m_next != NULL) {
 506                 m = m->m_next;
 507                 len += MSIZE;
 508                 if (m->m_flags & M_EXT)
 509                         len += m->m_ext.ext_size;
 510         }
 511         *mlast = m;
 512         return (len);
 513 }
 514
 515
 516 /*
 517  * NOTE!!! the new tcp-reassembly code *must not* use
 518  * m_adj() with a negative index. That alters the chain
 519  * of mbufs (by possibly chopping trailing mbufs). At
 520  * the front of tcp_reass we count the mbuf overhead
 521  * and setup the tail pointer. If we use m_adj(m, -5)
 522  * we could corrupt the tail pointer. Currently the
 523  * code only uses m_adj(m, postive-num). If this
 524  * changes appropriate changes to update mlast would
 525  * be needed.
 526  */
 527 int
 528 tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
 529           int *tlenp, struct mbuf *m)
 530 {
 531         struct tseg_qent *q, *last, *first;
 532         struct tseg_qent *p = NULL;
 533         struct tseg_qent *nq = NULL;
 534         struct tseg_qent *te = NULL;
 535         struct mbuf *mlast = NULL;
 536         struct sockbuf *sb;
 537         struct socket *so = tp->t_inpcb->inp_socket;
 538         char *s = NULL;
 539         int flags, i, lenofoh;
 540
 541         INP_WLOCK_ASSERT(tp->t_inpcb);
 542         /*
 543          * XXX: tcp_reass() is rather inefficient with its data structures
 544          * and should be rewritten (see NetBSD for optimizations).
 545          */
 546
 547         KASSERT(th == NULL || (seq_start != NULL && tlenp != NULL),
 548                 ("tcp_reass called with illegal parameter combination "
 549                  "(tp=%p, th=%p, seq_start=%p, tlenp=%p, m=%p)",
 550                  tp, th, seq_start, tlenp, m));
 551         /*
 552          * Call with th==NULL after become established to
 553          * force pre-ESTABLISHED data up to user socket.
 554          */
 555         if (th == NULL)
 556                 goto present;
 557         KASSERT(SEQ_GEQ(th->th_seq, tp->rcv_nxt),
 558                 ("Attempt to add old entry to reassembly queue (th=%p, tp=%p)",
 559                  th, tp));
 560 #ifdef TCP_REASS_LOGGING
 561         tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_ADD, NULL);
 562 #endif
 563 #ifdef TCP_REASS_COUNTERS
 564         counter_u64_add(reass_entry, 1);
 565 #endif
 566         /*
 567          * Check for zero length data.
 568          */
 569         if ((*tlenp == 0) && ((th->th_flags & TH_FIN) == 0)) {
 570                 /*
 571                  * A zero length segment does no
 572                  * one any good. We could check
 573                  * the rcv_nxt <-> rcv_wnd but thats
 574                  * already done for us by the caller.
 575                  */
 576 #ifdef TCP_REASS_COUNTERS
 577                 counter_u64_add(tcp_zero_input, 1);
 578 #endif
 579                 m_freem(m);
 580 #ifdef TCP_REASS_LOGGING
 581                 tcp_reass_log_dump(tp);
 582 #endif
 583                 return (0);
 584         }
 585         /*
 586          * Will it fit?
 587          */
 588         lenofoh = tcp_reass_overhead_of_chain(m, &mlast);
 589         sb = &tp->t_inpcb->inp_socket->so_rcv;
 590         if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
 591             (sb->sb_mbcnt + tp->t_segqmbuflen + lenofoh) > sb->sb_mbmax) {
 592                 /* No room */
 593                 TCPSTAT_INC(tcps_rcvreassfull);
 594 #ifdef TCP_REASS_COUNTERS
 595                 counter_u64_add(reass_nospace, 1);
 596 #endif
 597 #ifdef TCP_REASS_LOGGING
 598                 tcp_log_reassm(tp, NULL, NULL, th->th_seq, lenofoh, TCP_R_LOG_LIMIT_REACHED, 0);
 599 #endif
 600                 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
 601                         log(LOG_DEBUG, "%s; %s: mbuf count limit reached, "
 602                             "segment dropped\n", s, __func__);
 603                         free(s, M_TCPLOG);
 604                 }
 605                 m_freem(m);
 606                 *tlenp = 0;
 607 #ifdef TCP_REASS_LOGGING
 608                 tcp_reass_log_dump(tp);
 609 #endif
 610                 return (0);
 611         }
 612         /*
 613          * First lets deal with two common cases, the
 614          * segment appends to the back of our collected
 615          * segments. Or the segment is the next in line.
 616          */
 617         last = TAILQ_LAST_FAST(&tp->t_segq, tseg_qent, tqe_q);
 618         if (last != NULL) {
 619                 if ((th->th_flags & TH_FIN) &&
 620                     SEQ_LT((th->th_seq + *tlenp), (last->tqe_start + last->tqe_len))) {
 621                         /*
 622                          * Someone is trying to game us, dump
 623                          * the segment.
 624                          */
 625                         *tlenp = 0;
 626                         m_freem(m);
 627                         return (0);
 628                 }
 629                 if ((SEQ_GEQ(th->th_seq, last->tqe_start)) &&
 630                     (SEQ_GEQ((last->tqe_start + last->tqe_len), th->th_seq))) {
 631                         /* Common case, trailing segment is added */
 632                         /**
 633                          *                                 +--last
 634                          *                                 v
 635                          *  reassembly buffer |---|  |---| |---|
 636                          *  new segment                       |---|
 637                          */
 638 #ifdef TCP_REASS_COUNTERS
 639                         counter_u64_add(reass_path1, 1);
 640 #endif
 641                         if (SEQ_GT((last->tqe_start + last->tqe_len), th->th_seq)) {
 642                                 i = (last->tqe_start + last->tqe_len) - th->th_seq;
 643                                 if (i < *tlenp) {
 644 #ifdef TCP_REASS_LOGGING
 645                                         tcp_log_reassm(tp, last, NULL, 0, i, TCP_R_LOG_TRIM, 3);
 646                                         th->th_seq += i;
 647 #endif
 648                                         m_adj(m, i);
 649                                         *tlenp -= i;
 650                                 } else {
 651                                         /* Complete overlap */
 652                                         TCPSTAT_INC(tcps_rcvduppack);
 653                                         TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 654                                         m_freem(m);
 655                                         *tlenp = last->tqe_len;
 656                                         *seq_start = last->tqe_start;
 657                                         return (0);
 658                                 }
 659                         }
 660                         if (last->tqe_flags & TH_FIN) {
 661                                 /*
 662                                  * We have data after the FIN on the last?
 663                                  */
 664                                 *tlenp = 0;
 665                                 m_freem(m);
 666                                 return(0);
 667                         }
 668                         tcp_reass_append(tp, last, m, th, *tlenp, mlast, lenofoh);
 669                         tp->t_segqmbuflen += lenofoh;
 670                         *seq_start = last->tqe_start;
 671                         *tlenp = last->tqe_len;
 672                         return (0);
 673                 } else if (SEQ_GT(th->th_seq, (last->tqe_start + last->tqe_len))) {
 674                         /*
 675                          * Second common case, we missed
 676                          * another one and have something more
 677                          * for the end.
 678                          */
 679                         /**
 680                          *                                 +--last
 681                          *                                 v
 682                          *  reassembly buffer |---|  |---| |---|
 683                          *  new segment                           |---|
 684                          */
 685                         if (last->tqe_flags & TH_FIN) {
 686                                 /*
 687                                  * We have data after the FIN on the last?
 688                                  */
 689                                 *tlenp = 0;
 690                                 m_freem(m);
 691                                 return(0);
 692                         }
 693 #ifdef TCP_REASS_COUNTERS
 694                         counter_u64_add(reass_path2, 1);
 695 #endif
 696                         p = last;
 697                         goto new_entry;
 698                 }
 699         } else {
 700                 /* First segment (it's NULL). */
 701                 goto new_entry;
 702         }
 703         first = TAILQ_FIRST(&tp->t_segq);
 704         if (SEQ_LT(th->th_seq, first->tqe_start) &&
 705             SEQ_GEQ((th->th_seq + *tlenp),first->tqe_start) &&
 706             SEQ_LT((th->th_seq + *tlenp), (first->tqe_start + first->tqe_len))) {
 707                 /*
 708                  * The head of the queue is prepended by this and
 709                  * it may be the one I want most.
 710                  */
 711                 /**
 712                  *       first-------+
 713                  *                   v
 714                  *  rea:             |---|  |---| |---|
 715                  *  new:         |---|
 716                  * Note the case we do not deal with here is:
 717                  *   rea=     |---|   |---|   |---|
 718                  *   new=  |----|
 719                  * Due to the fact that it could be
 720                  *   new   |--------------------|
 721                  * And we might need to merge forward.
 722                  */
 723 #ifdef INVARIANTS
 724                 struct mbuf *firstmbuf;
 725 #endif
 726
 727 #ifdef TCP_REASS_COUNTERS
 728                 counter_u64_add(reass_path3, 1);
 729 #endif
 730                 if (SEQ_LT(th->th_seq, tp->rcv_nxt)) {
 731                         /*
 732                          * The resend was even before
 733                          * what we have. We need to trim it.
 734                          * Note TSNH (it should be trimmed
 735                          * before the call to tcp_reass()).
 736                          */
 737 #ifdef INVARIANTS
 738                         panic("th->th_seq:%u rcv_nxt:%u tp:%p not pre-trimmed",
 739                               th->th_seq, tp->rcv_nxt, tp);
 740 #else
 741                         i = tp->rcv_nxt - th->th_seq;
 742 #ifdef TCP_REASS_LOGGING
 743                         tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 4);
 744 #endif
 745                         m_adj(m, i);
 746                         th->th_seq += i;
 747                         *tlenp -= i;
 748 #endif
 749                 }
 750 #ifdef INVARIANTS
 751                 firstmbuf = first->tqe_m;
 752 #endif
 753                 tcp_reass_prepend(tp, first, m, th, *tlenp, mlast, lenofoh);
 754 #ifdef INVARIANTS
 755                 if (firstmbuf == first->tqe_m) {
 756                         panic("First stayed same m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
 757                               m, firstmbuf, first->tqe_m, tp, first);
 758                 } else if (first->tqe_m != m) {
 759                         panic("First did not change to m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
 760                               m, firstmbuf, first->tqe_m, tp, first);
 761                 }
 762 #endif
 763                 tp->t_segqmbuflen += lenofoh;
 764                 *seq_start = first->tqe_start;
 765                 *tlenp = first->tqe_len;
 766                 goto present;
 767         } else if (SEQ_LT((th->th_seq + *tlenp), first->tqe_start)) {
 768                 /* New segment is before our earliest segment. */
 769                 /**
 770                  *           first---->+
 771                  *                      v
 772                  *  rea=                |---| ....
 773                  *  new"         |---|
 774                  *
 775                  */
 776                 goto new_entry;
 777         }
 778         /*
 779          * Find a segment which begins after this one does.
 780          */
 781 #ifdef TCP_REASS_COUNTERS
 782         counter_u64_add(reass_fullwalk, 1);
 783 #endif
 784         TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
 785                 if (SEQ_GT(q->tqe_start, th->th_seq))
 786                         break;
 787         }
 788         p = TAILQ_PREV(q, tsegqe_head, tqe_q);
 789         /**
 790          * Now is this fit just in-between only?
 791          * i.e.:
 792          *      p---+        +----q
 793          *          v        v
 794          *     res= |--|     |--|    |--|
 795          *     nee       |-|
 796          */
 797         if (SEQ_LT((th->th_seq + *tlenp), q->tqe_start) &&
 798             ((p == NULL) || (SEQ_GT(th->th_seq, (p->tqe_start + p->tqe_len))))) {
 799                 /* Yep no overlap */
 800                 goto new_entry;
 801         }
 802         /**
 803          * If we reach here we have some (possibly all) overlap
 804          * such as:
 805          *     res=     |--|     |--|    |--|
 806          *     new=  |----|
 807          * or  new=  |-----------------|
 808          * or  new=      |--------|
 809          * or  new=            |---|
 810          * or  new=            |-----------|
 811          */
 812         if ((p != NULL) &&
 813             (SEQ_LEQ(th->th_seq, (p->tqe_start + p->tqe_len)))) {
 814                 /* conversion to int (in i) handles seq wraparound */
 815
 816 #ifdef TCP_REASS_COUNTERS
 817                 counter_u64_add(reass_path4, 1);
 818 #endif
 819                 i = p->tqe_start + p->tqe_len - th->th_seq;
 820                 if (i >= 0) {
 821                         if (i >= *tlenp) {
 822                                 /**
 823                                  *       prev seg---->+
 824                                  *                    v
 825                                  *  reassembly buffer |---|
 826                                  *  new segment        |-|
 827                                  */
 828                                 TCPSTAT_INC(tcps_rcvduppack);
 829                                 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 830                                 *tlenp = p->tqe_len;
 831                                 *seq_start = p->tqe_start;
 832                                 m_freem(m);
 833                                 /*
 834                                  * Try to present any queued data
 835                                  * at the left window edge to the user.
 836                                  * This is needed after the 3-WHS
 837                                  * completes. Note this probably
 838                                  * will not work and we will return.
 839                                  */
 840                                 return (0);
 841                         }
 842                         if (i > 0) {
 843                                 /**
 844                                  *       prev seg---->+
 845                                  *                    v
 846                                  *  reassembly buffer |---|
 847                                  *  new segment         |-----|
 848                                  */
 849 #ifdef TCP_REASS_COUNTERS
 850                                 counter_u64_add(reass_path5, 1);
 851 #endif
 852 #ifdef TCP_REASS_LOGGING
 853                                 tcp_log_reassm(tp, p, NULL, 0, i, TCP_R_LOG_TRIM, 5);
 854 #endif
 855                                 m_adj(m, i);
 856                                 *tlenp -= i;
 857                                 th->th_seq += i;
 858                         }
 859                 }
 860                 if (th->th_seq == (p->tqe_start + p->tqe_len)) {
 861                         /*
 862                          * If dovetails in with this one
 863                          * append it.
 864                          */
 865                         /**
 866                          *       prev seg---->+
 867                          *                    v
 868                          *  reassembly buffer |--|     |---|
 869                          *  new segment          |--|
 870                          * (note: it was trimmed above if it overlapped)
 871                          */
 872                         tcp_reass_append(tp, p, m, th, *tlenp, mlast, lenofoh);
 873                         tp->t_segqmbuflen += lenofoh;
 874                 } else {
 875 #ifdef INVARIANTS
 876                         panic("Impossible cut th_seq:%u p->seq:%u(%d) p:%p tp:%p",
 877                               th->th_seq, p->tqe_start, p->tqe_len,
 878                               p, tp);
 879 #endif
 880                         *tlenp = 0;
 881                         m_freem(m);
 882                         return (0);
 883                 }
 884                 q = p;
 885         } else {
 886                 /*
 887                  * The new data runs over the
 888                  * top of previously sack'd data (in q).
 889                  * It may be partially overlapping, or
 890                  * it may overlap the entire segment.
 891                  */
 892 #ifdef TCP_REASS_COUNTERS
 893                 counter_u64_add(reass_path6, 1);
 894 #endif
 895                 if (SEQ_GEQ((th->th_seq + *tlenp), (q->tqe_start + q->tqe_len))) {
 896                         /* It consumes it all */
 897                         /**
 898                          *             next seg---->+
 899                          *                          v
 900                          *  reassembly buffer |--|     |---|
 901                          *  new segment              |----------|
 902                          */
 903 #ifdef TCP_REASS_COUNTERS
 904                         counter_u64_add(reass_path7, 1);
 905 #endif
 906                         tcp_reass_replace(tp, q, m, th->th_seq, *tlenp, mlast, lenofoh, th->th_flags);
 907                 } else {
 908                         /*
 909                          * We just need to prepend the data
 910                          * to this. It does not overrun
 911                          * the end.
 912                          */
 913                         /**
 914                          *                next seg---->+
 915                          *                             v
 916                          *  reassembly buffer |--|     |---|
 917                          *  new segment                   |----------|
 918                          */
 919                         tcp_reass_prepend(tp, q, m, th, *tlenp, mlast, lenofoh);
 920                         tp->t_segqmbuflen += lenofoh;
 921                 }
 922         }
 923         /* Now does it go further than that? */
 924         tcp_reass_merge_forward(tp, q);
 925         *seq_start = q->tqe_start;
 926         *tlenp = q->tqe_len;
 927         goto present;
 928
 929         /*
 930          * When we reach here we can't combine it
 931          * with any existing segment.
 932          *
 933          * Limit the number of segments that can be queued to reduce the
 934          * potential for mbuf exhaustion. For best performance, we want to be
 935          * able to queue a full window's worth of segments. The size of the
 936          * socket receive buffer determines our advertised window and grows
 937          * automatically when socket buffer autotuning is enabled. Use it as the
 938          * basis for our queue limit.
 939          *
 940          * However, allow the user to specify a ceiling for the number of
 941          * segments in each queue.
 942          *
 943          * Always let the missing segment through which caused this queue.
 944          * NB: Access to the socket buffer is left intentionally unlocked as we
 945          * can tolerate stale information here.
 946          *
 947          * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
 948          * should work but causes packets to be dropped when they shouldn't.
 949          * Investigate why and re-evaluate the below limit after the behaviour
 950          * is understood.
 951          */
 952 new_entry:
 953         if (th->th_seq == tp->rcv_nxt && TCPS_HAVEESTABLISHED(tp->t_state)) {
 954                 tp->rcv_nxt += *tlenp;
 955                 flags = th->th_flags & TH_FIN;
 956                 TCPSTAT_INC(tcps_rcvoopack);
 957                 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
 958                 SOCKBUF_LOCK(&so->so_rcv);
 959                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
 960                         m_freem(m);
 961                 } else {
 962                         sbappendstream_locked(&so->so_rcv, m, 0);
 963                 }
 964                 sorwakeup_locked(so);
 965                 return (flags);
 966         }
 967         if (tcp_new_limits) {
 968                 if ((tp->t_segqlen > tcp_reass_queue_guard) &&
 969                     (*tlenp < MSIZE)) {
 970                         /*
 971                          * This is really a lie, we are not full but
 972                          * are getting a segment that is above
 973                          * guard threshold. If it is and its below
 974                          * a mbuf size (256) we drop it if it
 975                          * can't fill in some place.
 976                          */
 977                         TCPSTAT_INC(tcps_rcvreassfull);
 978                         *tlenp = 0;
 979                         if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
 980                                 log(LOG_DEBUG, "%s; %s: queue limit reached, "
 981                                     "segment dropped\n", s, __func__);
 982                                 free(s, M_TCPLOG);
 983                         }
 984                         m_freem(m);
 985 #ifdef TCP_REASS_LOGGING
 986                         tcp_reass_log_dump(tp);
 987 #endif
 988                         return (0);
 989                 }
 990         } else {
 991                 if (tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1,
 992                                          tcp_reass_maxqueuelen)) {
 993                         TCPSTAT_INC(tcps_rcvreassfull);
 994                         *tlenp = 0;
 995                         if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
 996                                 log(LOG_DEBUG, "%s; %s: queue limit reached, "
 997                                     "segment dropped\n", s, __func__);
 998                                 free(s, M_TCPLOG);
 999                         }
1000                         m_freem(m);
1001 #ifdef TCP_REASS_LOGGING
1002                         tcp_reass_log_dump(tp);
1003 #endif
1004                         return (0);
1005                 }
1006         }
1007         /*
1008          * Allocate a new queue entry. If we can't, or hit the zone limit
1009          * just drop the pkt.
1010          */
1011         te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
1012         if (te == NULL) {
1013                 TCPSTAT_INC(tcps_rcvmemdrop);
1014                 m_freem(m);
1015                 *tlenp = 0;
1016                 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
1017                                        NULL))) {
1018                         log(LOG_DEBUG, "%s; %s: global zone limit "
1019                             "reached, segment dropped\n", s, __func__);
1020                         free(s, M_TCPLOG);
1021                 }
1022                 return (0);
1023         }
1024         tp->t_segqlen++;
1025         tp->t_rcvoopack++;
1026         TCPSTAT_INC(tcps_rcvoopack);
1027         TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
1028         /* Insert the new segment queue entry into place. */
1029         te->tqe_m = m;
1030         te->tqe_flags = th->th_flags;
1031         te->tqe_len = *tlenp;
1032         te->tqe_start = th->th_seq;
1033         te->tqe_last = mlast;
1034         te->tqe_mbuf_cnt = lenofoh;
1035         tp->t_segqmbuflen += te->tqe_mbuf_cnt;
1036         if (p == NULL) {
1037                 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q);
1038         } else {
1039                 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q);
1040         }
1041 #ifdef TCP_REASS_LOGGING
1042         tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_NEW_ENTRY, te);
1043 #endif
1044 present:
1045         /*
1046          * Present data to user, advancing rcv_nxt through
1047          * completed sequence space.
1048          */
1049         if (!TCPS_HAVEESTABLISHED(tp->t_state))
1050                 return (0);
1051         q = TAILQ_FIRST(&tp->t_segq);
1052         KASSERT(q == NULL || SEQ_GEQ(q->tqe_start, tp->rcv_nxt),
1053                 ("Reassembly queue for %p has stale entry at head", tp));
1054         if (!q || q->tqe_start != tp->rcv_nxt) {
1055 #ifdef TCP_REASS_LOGGING
1056                 tcp_reass_log_dump(tp);
1057 #endif
1058                 return (0);
1059         }
1060         SOCKBUF_LOCK(&so->so_rcv);
1061         do {
1062                 tp->rcv_nxt += q->tqe_len;
1063                 flags = q->tqe_flags & TH_FIN;
1064                 nq = TAILQ_NEXT(q, tqe_q);
1065                 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
1066                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1067                         m_freem(q->tqe_m);
1068                 } else {
1069 #ifdef TCP_REASS_LOGGING
1070                         tcp_reass_log_new_in(tp, q->tqe_start, q->tqe_len, q->tqe_m, TCP_R_LOG_READ, q);
1071                         if (th != NULL) {
1072                                 tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 1);
1073                         } else {
1074                                 tcp_log_reassm(tp, q, NULL, 0, 0, TCP_R_LOG_READ, 1);
1075                         }
1076 #endif
1077                         sbappendstream_locked(&so->so_rcv, q->tqe_m, 0);
1078                 }
1079 #ifdef TCP_REASS_LOGGING
1080                 if (th != NULL) {
1081                         tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 2);
1082                 } else {
1083                         tcp_log_reassm(tp, q, NULL, 0, 0, TCP_R_LOG_READ, 2);
1084                 }
1085 #endif
1086                 KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
1087                         ("tp:%p seg queue goes negative", tp));
1088                 tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
1089                 uma_zfree(tcp_reass_zone, q);
1090                 tp->t_segqlen--;
1091                 q = nq;
1092         } while (q && q->tqe_start == tp->rcv_nxt);
1093         if (TAILQ_EMPTY(&tp->t_segq) &&
1094             (tp->t_segqmbuflen != 0)) {
1095 #ifdef INVARIANTS
1096                 panic("tp:%p segq:%p len:%d queue empty",
1097                       tp, &tp->t_segq, tp->t_segqmbuflen);
1098 #else
1099 #ifdef TCP_REASS_LOGGING
1100                 if (th != NULL) {
1101                         tcp_log_reassm(tp, NULL, NULL, th->th_seq, *tlenp, TCP_R_LOG_ZERO, 0);
1102                 } else {
1103                         tcp_log_reassm(tp, NULL, NULL, 0, 0, TCP_R_LOG_ZERO, 0);
1104                 }
1105 #endif
1106                 tp->t_segqmbuflen = 0;
1107 #endif
1108         }
1109 #ifdef TCP_REASS_LOGGING
1110         tcp_reass_log_dump(tp);
1111 #endif
1112         sorwakeup_locked(so);
1113         return (flags);
1114 }