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 #include "opt_inet.h"
  36 #include "opt_inet6.h"
  37
  38 /* For debugging we want counters and BB logging */
  39 /* #define TCP_REASS_COUNTERS 1 */
  40 /* #define TCP_REASS_LOGGING 1 */
  41
  42 #include <sys/param.h>
  43 #include <sys/kernel.h>
  44 #include <sys/eventhandler.h>
  45 #include <sys/malloc.h>
  46 #include <sys/mbuf.h>
  47 #include <sys/socket.h>
  48 #include <sys/socketvar.h>
  49 #include <sys/sysctl.h>
  50 #include <sys/syslog.h>
  51 #include <sys/systm.h>
  52
  53 #include <vm/uma.h>
  54
  55 #include <net/if.h>
  56 #include <net/if_var.h>
  57 #include <net/route.h>
  58 #include <net/vnet.h>
  59
  60 #include <netinet/in.h>
  61 #include <netinet/in_pcb.h>
  62 #include <netinet/in_systm.h>
  63 #include <netinet/in_var.h>
  64 #include <netinet/ip.h>
  65 #include <netinet/ip_var.h>
  66 #include <netinet/ip_options.h>
  67 #include <netinet/ip6.h>
  68 #include <netinet6/in6_pcb.h>
  69 #include <netinet6/ip6_var.h>
  70 #include <netinet6/nd6.h>
  71 #include <netinet/tcp.h>
  72 #include <netinet/tcp_fsm.h>
  73 #include <netinet/tcp_seq.h>
  74 #include <netinet/tcp_timer.h>
  75 #include <netinet/tcp_var.h>
  76 #ifdef TCP_REASS_LOGGING
  77 #include <netinet/tcp_log_buf.h>
  78 #include <netinet/tcp_hpts.h>
  79 #endif
  80 #include <netinet/tcpip.h>
  81
  82 #define TCP_R_LOG_ADD           1
  83 #define TCP_R_LOG_LIMIT_REACHED 2
  84 #define TCP_R_LOG_APPEND        3
  85 #define TCP_R_LOG_PREPEND       4
  86 #define TCP_R_LOG_REPLACE       5
  87 #define TCP_R_LOG_MERGE_INTO    6
  88 #define TCP_R_LOG_NEW_ENTRY     7
  89 #define TCP_R_LOG_READ          8
  90 #define TCP_R_LOG_ZERO          9
  91 #define TCP_R_LOG_DUMP          10
  92 #define TCP_R_LOG_TRIM          11
  93
  94 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass,
  95     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
  96     "TCP Segment Reassembly Queue");
  97
  98 static SYSCTL_NODE(_net_inet_tcp_reass, OID_AUTO, stats,
  99     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
 100     "TCP Segment Reassembly stats");
 101
 102 static int tcp_reass_maxseg = 0;
 103 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
 104     &tcp_reass_maxseg, 0,
 105     "Global maximum number of TCP Segments in Reassembly Queue");
 106
 107 static uma_zone_t tcp_reass_zone;
 108 SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, 0,
 109     &tcp_reass_zone,
 110     "Global number of TCP Segments currently in Reassembly Queue");
 111
 112 static u_int tcp_reass_maxqueuelen = 100;
 113 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, maxqueuelen, CTLFLAG_RWTUN,
 114     &tcp_reass_maxqueuelen, 0,
 115     "Maximum number of TCP Segments per Reassembly Queue");
 116
 117 static int tcp_new_limits = 0;
 118 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, new_limit, CTLFLAG_RWTUN,
 119     &tcp_new_limits, 0,
 120     "Do we use the new limit method we are discussing?");
 121
 122 static u_int tcp_reass_queue_guard = 16;
 123 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, queueguard, CTLFLAG_RWTUN,
 124     &tcp_reass_queue_guard, 16,
 125     "Number of TCP Segments in Reassembly Queue where we flip over to guard mode");
 126
 127 #ifdef TCP_REASS_COUNTERS
 128
 129 counter_u64_t reass_entry;
 130 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, entry, CTLFLAG_RD,
 131     &reass_entry, "A segment entered reassembly ");
 132
 133 counter_u64_t reass_path1;
 134 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path1, CTLFLAG_RD,
 135     &reass_path1, "Took path 1");
 136
 137 counter_u64_t reass_path2;
 138 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path2, CTLFLAG_RD,
 139     &reass_path2, "Took path 2");
 140
 141 counter_u64_t reass_path3;
 142 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path3, CTLFLAG_RD,
 143     &reass_path3, "Took path 3");
 144
 145 counter_u64_t reass_path4;
 146 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path4, CTLFLAG_RD,
 147     &reass_path4, "Took path 4");
 148
 149 counter_u64_t reass_path5;
 150 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path5, CTLFLAG_RD,
 151     &reass_path5, "Took path 5");
 152
 153 counter_u64_t reass_path6;
 154 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path6, CTLFLAG_RD,
 155     &reass_path6, "Took path 6");
 156
 157 counter_u64_t reass_path7;
 158 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path7, CTLFLAG_RD,
 159     &reass_path7, "Took path 7");
 160
 161 counter_u64_t reass_fullwalk;
 162 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, fullwalk, CTLFLAG_RD,
 163     &reass_fullwalk, "Took a full walk ");
 164
 165 counter_u64_t reass_nospace;
 166 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, nospace, CTLFLAG_RD,
 167     &reass_nospace, "Had no mbuf capacity ");
 168
 169 counter_u64_t merge_fwd;
 170 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_fwd, CTLFLAG_RD,
 171     &merge_fwd, "Ran merge fwd");
 172
 173 counter_u64_t merge_into;
 174 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_into, CTLFLAG_RD,
 175     &merge_into, "Ran merge into");
 176
 177 counter_u64_t tcp_zero_input;
 178 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, zero_input, CTLFLAG_RD,
 179     &tcp_zero_input, "The reassembly buffer saw a zero len segment etc");
 180
 181 #endif
 182
 183 /* Initialize TCP reassembly queue */
 184 static void
 185 tcp_reass_zone_change(void *tag)
 186 {
 187
 188         /* Set the zone limit and read back the effective value. */
 189         tcp_reass_maxseg = nmbclusters / 16;
 190         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 191             tcp_reass_maxseg);
 192 }
 193
 194 #ifdef TCP_REASS_LOGGING
 195
 196 static void
 197 tcp_log_reassm(struct tcpcb *tp, struct tseg_qent *q, struct tseg_qent *p,
 198     tcp_seq seq, int len, uint8_t action, int instance)
 199 {
 200         struct socket *so = tptosocket(tp);
 201         uint32_t cts;
 202         struct timeval tv;
 203
 204         if (tp->t_logstate != TCP_LOG_STATE_OFF) {
 205                 union tcp_log_stackspecific log;
 206
 207                 memset(&log, 0, sizeof(log));
 208                 cts = tcp_get_usecs(&tv);
 209                 log.u_bbr.flex1 = seq;
 210                 log.u_bbr.cur_del_rate = (uint64_t)q;
 211                 log.u_bbr.delRate = (uint64_t)p;
 212                 if (q != NULL) {
 213                         log.u_bbr.flex2 = q->tqe_start;
 214                         log.u_bbr.flex3 = q->tqe_len;
 215                         log.u_bbr.flex4 = q->tqe_mbuf_cnt;
 216                         log.u_bbr.hptsi_gain = q->tqe_flags;
 217                 }
 218                 if (p != NULL)  {
 219                         log.u_bbr.flex5 = p->tqe_start;
 220                         log.u_bbr.pkts_out = p->tqe_len;
 221                         log.u_bbr.epoch = p->tqe_mbuf_cnt;
 222                         log.u_bbr.cwnd_gain = p->tqe_flags;
 223                 }
 224                 log.u_bbr.flex6 = tp->t_segqmbuflen;
 225                 log.u_bbr.flex7 = instance;
 226                 log.u_bbr.flex8 = action;
 227                 log.u_bbr.timeStamp = cts;
 228                 TCP_LOG_EVENTP(tp, NULL, &so->so_rcv, &so->so_snd,
 229                     TCP_LOG_REASS, 0,
 230                     len, &log, false, &tv);
 231         }
 232 }
 233
 234 static void
 235 tcp_reass_log_dump(struct tcpcb *tp)
 236 {
 237         struct tseg_qent *q;
 238
 239         if (tp->t_logstate != TCP_LOG_STATE_OFF) {
 240                 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
 241                         tcp_log_reassm(tp, q, NULL, q->tqe_start, q->tqe_len, TCP_R_LOG_DUMP, 0);
 242                 }
 243         };
 244 }
 245
 246 static void
 247 tcp_reass_log_new_in(struct tcpcb *tp, tcp_seq seq, int len, struct mbuf *m,
 248     int logval, struct tseg_qent *q)
 249 {
 250         int cnt;
 251         struct mbuf *t;
 252
 253         cnt = 0;
 254         t = m;
 255         while (t) {
 256                 cnt += t->m_len;
 257                 t = t->m_next;
 258         }
 259         tcp_log_reassm(tp, q, NULL, seq, len, logval, cnt);
 260 }
 261
 262 #endif
 263
 264 void
 265 tcp_reass_global_init(void)
 266 {
 267
 268         tcp_reass_maxseg = nmbclusters / 16;
 269         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
 270             &tcp_reass_maxseg);
 271         tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
 272             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 273         /* Set the zone limit and read back the effective value. */
 274         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 275             tcp_reass_maxseg);
 276 #ifdef TCP_REASS_COUNTERS
 277         reass_path1 = counter_u64_alloc(M_WAITOK);
 278         reass_path2 = counter_u64_alloc(M_WAITOK);
 279         reass_path3 = counter_u64_alloc(M_WAITOK);
 280         reass_path4 = counter_u64_alloc(M_WAITOK);
 281         reass_path5 = counter_u64_alloc(M_WAITOK);
 282         reass_path6 = counter_u64_alloc(M_WAITOK);
 283         reass_path7 = counter_u64_alloc(M_WAITOK);
 284         reass_fullwalk = counter_u64_alloc(M_WAITOK);
 285         reass_nospace = counter_u64_alloc(M_WAITOK);
 286         reass_entry = counter_u64_alloc(M_WAITOK);
 287         merge_fwd = counter_u64_alloc(M_WAITOK);
 288         merge_into = counter_u64_alloc(M_WAITOK);
 289         tcp_zero_input = counter_u64_alloc(M_WAITOK);
 290 #endif
 291         EVENTHANDLER_REGISTER(nmbclusters_change,
 292             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 293
 294 }
 295
 296 void
 297 tcp_reass_flush(struct tcpcb *tp)
 298 {
 299         struct tseg_qent *qe;
 300
 301         INP_WLOCK_ASSERT(tptoinpcb(tp));
 302
 303         while ((qe = TAILQ_FIRST(&tp->t_segq)) != NULL) {
 304                 TAILQ_REMOVE(&tp->t_segq, qe, tqe_q);
 305                 m_freem(qe->tqe_m);
 306                 uma_zfree(tcp_reass_zone, qe);
 307                 tp->t_segqlen--;
 308         }
 309         tp->t_segqmbuflen = 0;
 310         KASSERT((tp->t_segqlen == 0),
 311             ("TCP reass queue %p segment count is %d instead of 0 after flush.",
 312             tp, tp->t_segqlen));
 313 }
 314
 315 static void
 316 tcp_reass_append(struct tcpcb *tp, struct tseg_qent *last,
 317     struct mbuf *m, struct tcphdr *th, int tlen,
 318     struct mbuf *mlast, int lenofoh)
 319 {
 320
 321 #ifdef TCP_REASS_LOGGING
 322         tcp_log_reassm(tp, last, NULL, th->th_seq, tlen, TCP_R_LOG_APPEND, 0);
 323 #endif
 324         last->tqe_len += tlen;
 325         last->tqe_m->m_pkthdr.len += tlen;
 326         /* Preserve the FIN bit if its there */
 327         last->tqe_flags |= (tcp_get_flags(th) & TH_FIN);
 328         last->tqe_last->m_next = m;
 329         last->tqe_last = mlast;
 330         last->tqe_mbuf_cnt += lenofoh;
 331         tp->t_rcvoopack++;
 332         TCPSTAT_INC(tcps_rcvoopack);
 333         TCPSTAT_ADD(tcps_rcvoobyte, tlen);
 334 #ifdef TCP_REASS_LOGGING
 335         tcp_reass_log_new_in(tp, last->tqe_start, lenofoh, last->tqe_m,
 336                              TCP_R_LOG_APPEND,
 337                              last);
 338 #endif
 339 }
 340
 341 static void
 342 tcp_reass_prepend(struct tcpcb *tp, struct tseg_qent *first, struct mbuf *m, struct tcphdr *th,
 343                   int tlen, struct mbuf *mlast, int lenofoh)
 344 {
 345         int i;
 346
 347 #ifdef TCP_REASS_LOGGING
 348         tcp_log_reassm(tp, first, NULL, th->th_seq, tlen, TCP_R_LOG_PREPEND, 0);
 349 #endif
 350         if (SEQ_GT((th->th_seq + tlen), first->tqe_start)) {
 351                 /* The new data overlaps into the old */
 352                 i = (th->th_seq + tlen) - first->tqe_start;
 353 #ifdef TCP_REASS_LOGGING
 354                 tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 1);
 355 #endif
 356                 m_adj(first->tqe_m, i);
 357                 first->tqe_len -= i;
 358                 first->tqe_start += i;
 359         }
 360         /* Ok now setup our chain to point to the old first */
 361         mlast->m_next = first->tqe_m;
 362         first->tqe_m = m;
 363         first->tqe_len += tlen;
 364         first->tqe_start = th->th_seq;
 365         first->tqe_m->m_pkthdr.len = first->tqe_len;
 366         first->tqe_mbuf_cnt += lenofoh;
 367         tp->t_rcvoopack++;
 368         TCPSTAT_INC(tcps_rcvoopack);
 369         TCPSTAT_ADD(tcps_rcvoobyte, tlen);
 370 #ifdef TCP_REASS_LOGGING
 371         tcp_reass_log_new_in(tp, first->tqe_start, lenofoh, first->tqe_m,
 372                              TCP_R_LOG_PREPEND,
 373                              first);
 374 #endif
 375 }
 376
 377 static void
 378 tcp_reass_replace(struct tcpcb *tp, struct tseg_qent *q, struct mbuf *m,
 379     tcp_seq seq, int len, struct mbuf *mlast, int mbufoh, uint16_t flags)
 380 {
 381         /*
 382          * Free the data in q, and replace
 383          * it with the new segment.
 384          */
 385         int len_dif;
 386
 387 #ifdef TCP_REASS_LOGGING
 388         tcp_log_reassm(tp, q, NULL, seq, len, TCP_R_LOG_REPLACE, 0);
 389 #endif
 390         m_freem(q->tqe_m);
 391         KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
 392                 ("Tp:%p seg queue goes negative", tp));
 393         tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
 394         q->tqe_mbuf_cnt = mbufoh;
 395         q->tqe_m = m;
 396         q->tqe_last = mlast;
 397         q->tqe_start = seq;
 398         if (len > q->tqe_len)
 399                 len_dif = len - q->tqe_len;
 400         else
 401                 len_dif = 0;
 402         tp->t_rcvoopack++;
 403         TCPSTAT_INC(tcps_rcvoopack);
 404         TCPSTAT_ADD(tcps_rcvoobyte, len_dif);
 405         q->tqe_len = len;
 406         q->tqe_flags = (flags & TH_FIN);
 407         q->tqe_m->m_pkthdr.len = q->tqe_len;
 408         tp->t_segqmbuflen += mbufoh;
 409
 410 }
 411
 412 static void
 413 tcp_reass_merge_into(struct tcpcb *tp, struct tseg_qent *ent,
 414     struct tseg_qent *q)
 415 {
 416         /*
 417          * Merge q into ent and free q from the list.
 418          */
 419 #ifdef TCP_REASS_LOGGING
 420         tcp_log_reassm(tp, q, ent, 0, 0, TCP_R_LOG_MERGE_INTO, 0);
 421 #endif
 422 #ifdef TCP_REASS_COUNTERS
 423         counter_u64_add(merge_into, 1);
 424 #endif
 425         ent->tqe_last->m_next = q->tqe_m;
 426         ent->tqe_last = q->tqe_last;
 427         ent->tqe_len += q->tqe_len;
 428         ent->tqe_mbuf_cnt += q->tqe_mbuf_cnt;
 429         ent->tqe_m->m_pkthdr.len += q->tqe_len;
 430         ent->tqe_flags |= (q->tqe_flags & TH_FIN);
 431         TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
 432         uma_zfree(tcp_reass_zone, q);
 433         tp->t_segqlen--;
 434
 435 }
 436
 437 static void
 438 tcp_reass_merge_forward(struct tcpcb *tp, struct tseg_qent *ent)
 439 {
 440         struct tseg_qent *q, *qtmp;
 441         int i;
 442         tcp_seq max;
 443         /*
 444          * Given an entry merge forward anyplace
 445          * that ent overlaps forward.
 446          */
 447
 448         max = ent->tqe_start + ent->tqe_len;
 449         q = TAILQ_NEXT(ent, tqe_q);
 450         if (q == NULL) {
 451                 /* Nothing left */
 452                 return;
 453         }
 454         TAILQ_FOREACH_FROM_SAFE(q, &tp->t_segq, tqe_q, qtmp) {
 455                 if (SEQ_GT(q->tqe_start, max)) {
 456                         /* Beyond q */
 457                         break;
 458                 }
 459                 /* We have some or all that are overlapping */
 460                 if (SEQ_GEQ(max, (q->tqe_start + q->tqe_len))) {
 461                         /* It consumes it all */
 462                         tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
 463                         m_freem(q->tqe_m);
 464                         TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
 465                         uma_zfree(tcp_reass_zone, q);
 466                         tp->t_segqlen--;
 467                         continue;
 468                 }
 469                 /*
 470                  * Trim the q entry to dovetail to this one
 471                  * and then merge q into ent updating max
 472                  * in the process.
 473                  */
 474                 i = max - q->tqe_start;
 475 #ifdef TCP_REASS_LOGGING
 476                 tcp_log_reassm(tp, q, NULL, 0, i, TCP_R_LOG_TRIM, 2);
 477 #endif
 478                 m_adj(q->tqe_m, i);
 479                 q->tqe_len -= i;
 480                 q->tqe_start += i;
 481                 tcp_reass_merge_into(tp, ent, q);
 482                 max = ent->tqe_start + ent->tqe_len;
 483         }
 484 #ifdef TCP_REASS_COUNTERS
 485         counter_u64_add(merge_fwd, 1);
 486 #endif
 487 }
 488
 489 static int
 490 tcp_reass_overhead_of_chain(struct mbuf *m, struct mbuf **mlast)
 491 {
 492         int len = MSIZE;
 493
 494         if (m->m_flags & M_EXT)
 495                 len += m->m_ext.ext_size;
 496         while (m->m_next != NULL) {
 497                 m = m->m_next;
 498                 len += MSIZE;
 499                 if (m->m_flags & M_EXT)
 500                         len += m->m_ext.ext_size;
 501         }
 502         *mlast = m;
 503         return (len);
 504 }
 505
 506 /*
 507  * NOTE!!! the new tcp-reassembly code *must not* use
 508  * m_adj() with a negative index. That alters the chain
 509  * of mbufs (by possibly chopping trailing mbufs). At
 510  * the front of tcp_reass we count the mbuf overhead
 511  * and setup the tail pointer. If we use m_adj(m, -5)
 512  * we could corrupt the tail pointer. Currently the
 513  * code only uses m_adj(m, postive-num). If this
 514  * changes appropriate changes to update mlast would
 515  * be needed.
 516  */
 517 int
 518 tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
 519           int *tlenp, struct mbuf *m)
 520 {
 521         struct tseg_qent *q, *last, *first;
 522         struct tseg_qent *p = NULL;
 523         struct tseg_qent *nq = NULL;
 524         struct tseg_qent *te = NULL;
 525         struct mbuf *mlast = NULL;
 526         struct inpcb *inp = tptoinpcb(tp);
 527         struct socket *so = tptosocket(tp);
 528         struct sockbuf *sb = &so->so_rcv;
 529         char *s = NULL;
 530         int flags, i, lenofoh;
 531
 532         INP_WLOCK_ASSERT(inp);
 533         /*
 534          * XXX: tcp_reass() is rather inefficient with its data structures
 535          * and should be rewritten (see NetBSD for optimizations).
 536          */
 537
 538         KASSERT(th == NULL || (seq_start != NULL && tlenp != NULL),
 539                 ("tcp_reass called with illegal parameter combination "
 540                  "(tp=%p, th=%p, seq_start=%p, tlenp=%p, m=%p)",
 541                  tp, th, seq_start, tlenp, m));
 542         /*
 543          * Call with th==NULL after become established to
 544          * force pre-ESTABLISHED data up to user socket.
 545          */
 546         if (th == NULL)
 547                 goto present;
 548         KASSERT(SEQ_GEQ(th->th_seq, tp->rcv_nxt),
 549                 ("Attempt to add old entry to reassembly queue (th=%p, tp=%p)",
 550                  th, tp));
 551 #ifdef TCP_REASS_LOGGING
 552         tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_ADD, NULL);
 553 #endif
 554 #ifdef TCP_REASS_COUNTERS
 555         counter_u64_add(reass_entry, 1);
 556 #endif
 557         /*
 558          * Check for zero length data.
 559          */
 560         if ((*tlenp == 0) && ((tcp_get_flags(th) & TH_FIN) == 0)) {
 561                 /*
 562                  * A zero length segment does no
 563                  * one any good. We could check
 564                  * the rcv_nxt <-> rcv_wnd but thats
 565                  * already done for us by the caller.
 566                  */
 567 strip_fin:
 568 #ifdef TCP_REASS_COUNTERS
 569                 counter_u64_add(tcp_zero_input, 1);
 570 #endif
 571                 m_freem(m);
 572 #ifdef TCP_REASS_LOGGING
 573                 tcp_reass_log_dump(tp);
 574 #endif
 575                 return (0);
 576         } else if ((*tlenp == 0) &&
 577                    (tcp_get_flags(th) & TH_FIN) &&
 578                    !TCPS_HAVEESTABLISHED(tp->t_state)) {
 579                 /*
 580                  * We have not established, and we
 581                  * have a FIN and no data. Lets treat
 582                  * this as the same as if the FIN were
 583                  * not present. We don't want to save
 584                  * the FIN bit in a reassembly buffer
 585                  * we want to get established first before
 586                  * we do that (the peer will retransmit).
 587                  */
 588                 goto strip_fin;
 589         }
 590         /*
 591          * Will it fit?
 592          */
 593         lenofoh = tcp_reass_overhead_of_chain(m, &mlast);
 594         if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
 595             (sb->sb_mbcnt + tp->t_segqmbuflen + lenofoh) > sb->sb_mbmax) {
 596                 /* No room */
 597                 TCPSTAT_INC(tcps_rcvreassfull);
 598 #ifdef TCP_REASS_COUNTERS
 599                 counter_u64_add(reass_nospace, 1);
 600 #endif
 601 #ifdef TCP_REASS_LOGGING
 602                 tcp_log_reassm(tp, NULL, NULL, th->th_seq, lenofoh, TCP_R_LOG_LIMIT_REACHED, 0);
 603 #endif
 604                 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
 605                         log(LOG_DEBUG, "%s; %s: mbuf count limit reached, "
 606                             "segment dropped\n", s, __func__);
 607                         free(s, M_TCPLOG);
 608                 }
 609                 m_freem(m);
 610                 *tlenp = 0;
 611 #ifdef TCP_REASS_LOGGING
 612                 tcp_reass_log_dump(tp);
 613 #endif
 614                 return (0);
 615         }
 616         /*
 617          * First lets deal with two common cases, the
 618          * segment appends to the back of our collected
 619          * segments. Or the segment is the next in line.
 620          */
 621         last = TAILQ_LAST_FAST(&tp->t_segq, tseg_qent, tqe_q);
 622         if (last != NULL) {
 623                 if ((tcp_get_flags(th) & TH_FIN) &&
 624                     SEQ_LT((th->th_seq + *tlenp), (last->tqe_start + last->tqe_len))) {
 625                         /*
 626                          * Someone is trying to game us, dump
 627                          * the segment.
 628                          */
 629                         *tlenp = 0;
 630                         m_freem(m);
 631                         return (0);
 632                 }
 633                 if ((SEQ_GEQ(th->th_seq, last->tqe_start)) &&
 634                     (SEQ_GEQ((last->tqe_start + last->tqe_len), th->th_seq))) {
 635                         /* Common case, trailing segment is added */
 636                         /**
 637                          *                                 +--last
 638                          *                                 v
 639                          *  reassembly buffer |---|  |---| |---|
 640                          *  new segment                       |---|
 641                          */
 642 #ifdef TCP_REASS_COUNTERS
 643                         counter_u64_add(reass_path1, 1);
 644 #endif
 645                         if (SEQ_GT((last->tqe_start + last->tqe_len), th->th_seq)) {
 646                                 i = (last->tqe_start + last->tqe_len) - th->th_seq;
 647                                 if (i < *tlenp) {
 648 #ifdef TCP_REASS_LOGGING
 649                                         tcp_log_reassm(tp, last, NULL, 0, i, TCP_R_LOG_TRIM, 3);
 650                                         th->th_seq += i;
 651 #endif
 652                                         m_adj(m, i);
 653                                         *tlenp -= i;
 654                                 } else {
 655                                         /* Complete overlap */
 656                                         TCPSTAT_INC(tcps_rcvduppack);
 657                                         TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 658                                         m_freem(m);
 659                                         *tlenp = last->tqe_len;
 660                                         *seq_start = last->tqe_start;
 661                                         return (0);
 662                                 }
 663                         }
 664                         if (last->tqe_flags & TH_FIN) {
 665                                 /*
 666                                  * We have data after the FIN on the last?
 667                                  */
 668                                 *tlenp = 0;
 669                                 m_freem(m);
 670                                 return(0);
 671                         }
 672                         tcp_reass_append(tp, last, m, th, *tlenp, mlast, lenofoh);
 673                         tp->t_segqmbuflen += lenofoh;
 674                         *seq_start = last->tqe_start;
 675                         *tlenp = last->tqe_len;
 676                         return (0);
 677                 } else if (SEQ_GT(th->th_seq, (last->tqe_start + last->tqe_len))) {
 678                         /*
 679                          * Second common case, we missed
 680                          * another one and have something more
 681                          * for the end.
 682                          */
 683                         /**
 684                          *                                 +--last
 685                          *                                 v
 686                          *  reassembly buffer |---|  |---| |---|
 687                          *  new segment                           |---|
 688                          */
 689                         if (last->tqe_flags & TH_FIN) {
 690                                 /*
 691                                  * We have data after the FIN on the last?
 692                                  */
 693                                 *tlenp = 0;
 694                                 m_freem(m);
 695                                 return(0);
 696                         }
 697 #ifdef TCP_REASS_COUNTERS
 698                         counter_u64_add(reass_path2, 1);
 699 #endif
 700                         p = last;
 701                         goto new_entry;
 702                 }
 703         } else {
 704                 /* First segment (it's NULL). */
 705                 goto new_entry;
 706         }
 707         first = TAILQ_FIRST(&tp->t_segq);
 708         if (SEQ_LT(th->th_seq, first->tqe_start) &&
 709             SEQ_GEQ((th->th_seq + *tlenp),first->tqe_start) &&
 710             SEQ_LT((th->th_seq + *tlenp), (first->tqe_start + first->tqe_len))) {
 711                 /*
 712                  * The head of the queue is prepended by this and
 713                  * it may be the one I want most.
 714                  */
 715                 /**
 716                  *       first-------+
 717                  *                   v
 718                  *  rea:             |---|  |---| |---|
 719                  *  new:         |---|
 720                  * Note the case we do not deal with here is:
 721                  *   rea=     |---|   |---|   |---|
 722                  *   new=  |----|
 723                  * Due to the fact that it could be
 724                  *   new   |--------------------|
 725                  * And we might need to merge forward.
 726                  */
 727 #ifdef INVARIANTS
 728                 struct mbuf *firstmbuf;
 729 #endif
 730
 731 #ifdef TCP_REASS_COUNTERS
 732                 counter_u64_add(reass_path3, 1);
 733 #endif
 734                 if (SEQ_LT(th->th_seq, tp->rcv_nxt)) {
 735                         /*
 736                          * The resend was even before
 737                          * what we have. We need to trim it.
 738                          * Note TSNH (it should be trimmed
 739                          * before the call to tcp_reass()).
 740                          */
 741 #ifdef INVARIANTS
 742                         panic("th->th_seq:%u rcv_nxt:%u tp:%p not pre-trimmed",
 743                               th->th_seq, tp->rcv_nxt, tp);
 744 #else
 745                         i = tp->rcv_nxt - th->th_seq;
 746 #ifdef TCP_REASS_LOGGING
 747                         tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 4);
 748 #endif
 749                         m_adj(m, i);
 750                         th->th_seq += i;
 751                         *tlenp -= i;
 752 #endif
 753                 }
 754 #ifdef INVARIANTS
 755                 firstmbuf = first->tqe_m;
 756 #endif
 757                 tcp_reass_prepend(tp, first, m, th, *tlenp, mlast, lenofoh);
 758 #ifdef INVARIANTS
 759                 if (firstmbuf == first->tqe_m) {
 760                         panic("First stayed same m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
 761                               m, firstmbuf, first->tqe_m, tp, first);
 762                 } else if (first->tqe_m != m) {
 763                         panic("First did not change to m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
 764                               m, firstmbuf, first->tqe_m, tp, first);
 765                 }
 766 #endif
 767                 tp->t_segqmbuflen += lenofoh;
 768                 *seq_start = first->tqe_start;
 769                 *tlenp = first->tqe_len;
 770                 goto present;
 771         } else if (SEQ_LT((th->th_seq + *tlenp), first->tqe_start)) {
 772                 /* New segment is before our earliest segment. */
 773                 /**
 774                  *           first---->+
 775                  *                      v
 776                  *  rea=                |---| ....
 777                  *  new"         |---|
 778                  *
 779                  */
 780                 goto new_entry;
 781         }
 782         /*
 783          * Find a segment which begins after this one does.
 784          */
 785 #ifdef TCP_REASS_COUNTERS
 786         counter_u64_add(reass_fullwalk, 1);
 787 #endif
 788         TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
 789                 if (SEQ_GT(q->tqe_start, th->th_seq))
 790                         break;
 791         }
 792         p = TAILQ_PREV(q, tsegqe_head, tqe_q);
 793         /**
 794          * Now is this fit just in-between only?
 795          * i.e.:
 796          *      p---+        +----q
 797          *          v        v
 798          *     res= |--|     |--|    |--|
 799          *     nee       |-|
 800          */
 801         if (SEQ_LT((th->th_seq + *tlenp), q->tqe_start) &&
 802             ((p == NULL) || (SEQ_GT(th->th_seq, (p->tqe_start + p->tqe_len))))) {
 803                 /* Yep no overlap */
 804                 goto new_entry;
 805         }
 806         /**
 807          * If we reach here we have some (possibly all) overlap
 808          * such as:
 809          *     res=     |--|     |--|    |--|
 810          *     new=  |----|
 811          * or  new=  |-----------------|
 812          * or  new=      |--------|
 813          * or  new=            |---|
 814          * or  new=            |-----------|
 815          */
 816         if ((p != NULL) &&
 817             (SEQ_LEQ(th->th_seq, (p->tqe_start + p->tqe_len)))) {
 818                 /* conversion to int (in i) handles seq wraparound */
 819
 820 #ifdef TCP_REASS_COUNTERS
 821                 counter_u64_add(reass_path4, 1);
 822 #endif
 823                 i = p->tqe_start + p->tqe_len - th->th_seq;
 824                 if (i >= 0) {
 825                         if (i >= *tlenp) {
 826                                 /**
 827                                  *       prev seg---->+
 828                                  *                    v
 829                                  *  reassembly buffer |---|
 830                                  *  new segment        |-|
 831                                  */
 832                                 TCPSTAT_INC(tcps_rcvduppack);
 833                                 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 834                                 *tlenp = p->tqe_len;
 835                                 *seq_start = p->tqe_start;
 836                                 m_freem(m);
 837                                 /*
 838                                  * Try to present any queued data
 839                                  * at the left window edge to the user.
 840                                  * This is needed after the 3-WHS
 841                                  * completes. Note this probably
 842                                  * will not work and we will return.
 843                                  */
 844                                 return (0);
 845                         }
 846                         if (i > 0) {
 847                                 /**
 848                                  *       prev seg---->+
 849                                  *                    v
 850                                  *  reassembly buffer |---|
 851                                  *  new segment         |-----|
 852                                  */
 853 #ifdef TCP_REASS_COUNTERS
 854                                 counter_u64_add(reass_path5, 1);
 855 #endif
 856 #ifdef TCP_REASS_LOGGING
 857                                 tcp_log_reassm(tp, p, NULL, 0, i, TCP_R_LOG_TRIM, 5);
 858 #endif
 859                                 m_adj(m, i);
 860                                 *tlenp -= i;
 861                                 th->th_seq += i;
 862                         }
 863                 }
 864                 if (th->th_seq == (p->tqe_start + p->tqe_len)) {
 865                         /*
 866                          * If dovetails in with this one
 867                          * append it.
 868                          */
 869                         /**
 870                          *       prev seg---->+
 871                          *                    v
 872                          *  reassembly buffer |--|     |---|
 873                          *  new segment          |--|
 874                          * (note: it was trimmed above if it overlapped)
 875                          */
 876                         tcp_reass_append(tp, p, m, th, *tlenp, mlast, lenofoh);
 877                         tp->t_segqmbuflen += lenofoh;
 878                 } else {
 879 #ifdef INVARIANTS
 880                         panic("Impossible cut th_seq:%u p->seq:%u(%d) p:%p tp:%p",
 881                               th->th_seq, p->tqe_start, p->tqe_len,
 882                               p, tp);
 883 #endif
 884                         *tlenp = 0;
 885                         m_freem(m);
 886                         return (0);
 887                 }
 888                 q = p;
 889         } else {
 890                 /*
 891                  * The new data runs over the
 892                  * top of previously sack'd data (in q).
 893                  * It may be partially overlapping, or
 894                  * it may overlap the entire segment.
 895                  */
 896 #ifdef TCP_REASS_COUNTERS
 897                 counter_u64_add(reass_path6, 1);
 898 #endif
 899                 if (SEQ_GEQ((th->th_seq + *tlenp), (q->tqe_start + q->tqe_len))) {
 900                         /* It consumes it all */
 901                         /**
 902                          *             next seg---->+
 903                          *                          v
 904                          *  reassembly buffer |--|     |---|
 905                          *  new segment              |----------|
 906                          */
 907 #ifdef TCP_REASS_COUNTERS
 908                         counter_u64_add(reass_path7, 1);
 909 #endif
 910                         tcp_reass_replace(tp, q, m, th->th_seq, *tlenp, mlast, lenofoh, tcp_get_flags(th));
 911                 } else {
 912                         /*
 913                          * We just need to prepend the data
 914                          * to this. It does not overrun
 915                          * the end.
 916                          */
 917                         /**
 918                          *                next seg---->+
 919                          *                             v
 920                          *  reassembly buffer |--|     |---|
 921                          *  new segment                   |----------|
 922                          */
 923                         tcp_reass_prepend(tp, q, m, th, *tlenp, mlast, lenofoh);
 924                         tp->t_segqmbuflen += lenofoh;
 925                 }
 926         }
 927         /* Now does it go further than that? */
 928         tcp_reass_merge_forward(tp, q);
 929         *seq_start = q->tqe_start;
 930         *tlenp = q->tqe_len;
 931         goto present;
 932
 933         /*
 934          * When we reach here we can't combine it
 935          * with any existing segment.
 936          *
 937          * Limit the number of segments that can be queued to reduce the
 938          * potential for mbuf exhaustion. For best performance, we want to be
 939          * able to queue a full window's worth of segments. The size of the
 940          * socket receive buffer determines our advertised window and grows
 941          * automatically when socket buffer autotuning is enabled. Use it as the
 942          * basis for our queue limit.
 943          *
 944          * However, allow the user to specify a ceiling for the number of
 945          * segments in each queue.
 946          *
 947          * Always let the missing segment through which caused this queue.
 948          * NB: Access to the socket buffer is left intentionally unlocked as we
 949          * can tolerate stale information here.
 950          *
 951          * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
 952          * should work but causes packets to be dropped when they shouldn't.
 953          * Investigate why and re-evaluate the below limit after the behaviour
 954          * is understood.
 955          */
 956 new_entry:
 957         if (th->th_seq == tp->rcv_nxt && TCPS_HAVEESTABLISHED(tp->t_state)) {
 958                 tp->rcv_nxt += *tlenp;
 959                 flags = tcp_get_flags(th) & TH_FIN;
 960                 TCPSTAT_INC(tcps_rcvoopack);
 961                 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
 962                 SOCKBUF_LOCK(&so->so_rcv);
 963                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
 964                         m_freem(m);
 965                 } else {
 966                         sbappendstream_locked(&so->so_rcv, m, 0);
 967                 }
 968                 tp->t_flags |= TF_WAKESOR;
 969                 return (flags);
 970         }
 971         if (tcp_new_limits) {
 972                 if ((tp->t_segqlen > tcp_reass_queue_guard) &&
 973                     (*tlenp < MSIZE)) {
 974                         /*
 975                          * This is really a lie, we are not full but
 976                          * are getting a segment that is above
 977                          * guard threshold. If it is and its below
 978                          * a mbuf size (256) we drop it if it
 979                          * can't fill in some place.
 980                          */
 981                         TCPSTAT_INC(tcps_rcvreassfull);
 982                         *tlenp = 0;
 983                         if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
 984                                 log(LOG_DEBUG, "%s; %s: queue limit reached, "
 985                                     "segment dropped\n", s, __func__);
 986                                 free(s, M_TCPLOG);
 987                         }
 988                         m_freem(m);
 989 #ifdef TCP_REASS_LOGGING
 990                         tcp_reass_log_dump(tp);
 991 #endif
 992                         return (0);
 993                 }
 994         } else {
 995                 if (tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1,
 996                                          tcp_reass_maxqueuelen)) {
 997                         TCPSTAT_INC(tcps_rcvreassfull);
 998                         *tlenp = 0;
 999                         if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
1000                                 log(LOG_DEBUG, "%s; %s: queue limit reached, "
1001                                     "segment dropped\n", s, __func__);
1002                                 free(s, M_TCPLOG);
1003                         }
1004                         m_freem(m);
1005 #ifdef TCP_REASS_LOGGING
1006                         tcp_reass_log_dump(tp);
1007 #endif
1008                         return (0);
1009                 }
1010         }
1011         /*
1012          * Allocate a new queue entry. If we can't, or hit the zone limit
1013          * just drop the pkt.
1014          */
1015         te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
1016         if (te == NULL) {
1017                 TCPSTAT_INC(tcps_rcvmemdrop);
1018                 m_freem(m);
1019                 *tlenp = 0;
1020                 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
1021                         log(LOG_DEBUG, "%s; %s: global zone limit "
1022                             "reached, segment dropped\n", s, __func__);
1023                         free(s, M_TCPLOG);
1024                 }
1025                 return (0);
1026         }
1027         tp->t_segqlen++;
1028         tp->t_rcvoopack++;
1029         TCPSTAT_INC(tcps_rcvoopack);
1030         TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
1031         /* Insert the new segment queue entry into place. */
1032         te->tqe_m = m;
1033         te->tqe_flags = tcp_get_flags(th);
1034         te->tqe_len = *tlenp;
1035         te->tqe_start = th->th_seq;
1036         te->tqe_last = mlast;
1037         te->tqe_mbuf_cnt = lenofoh;
1038         tp->t_segqmbuflen += te->tqe_mbuf_cnt;
1039         if (p == NULL) {
1040                 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q);
1041         } else {
1042                 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q);
1043         }
1044 #ifdef TCP_REASS_LOGGING
1045         tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_NEW_ENTRY, te);
1046 #endif
1047 present:
1048         /*
1049          * Present data to user, advancing rcv_nxt through
1050          * completed sequence space.
1051          */
1052         if (!TCPS_HAVEESTABLISHED(tp->t_state))
1053                 return (0);
1054         q = TAILQ_FIRST(&tp->t_segq);
1055         KASSERT(q == NULL || SEQ_GEQ(q->tqe_start, tp->rcv_nxt),
1056                 ("Reassembly queue for %p has stale entry at head", tp));
1057         if (!q || q->tqe_start != tp->rcv_nxt) {
1058 #ifdef TCP_REASS_LOGGING
1059                 tcp_reass_log_dump(tp);
1060 #endif
1061                 return (0);
1062         }
1063         SOCKBUF_LOCK(&so->so_rcv);
1064         do {
1065                 tp->rcv_nxt += q->tqe_len;
1066                 flags = q->tqe_flags & TH_FIN;
1067                 nq = TAILQ_NEXT(q, tqe_q);
1068                 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
1069                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1070                         m_freem(q->tqe_m);
1071                 } else {
1072 #ifdef TCP_REASS_LOGGING
1073                         tcp_reass_log_new_in(tp, q->tqe_start, q->tqe_len, q->tqe_m, TCP_R_LOG_READ, q);
1074                         if (th != NULL) {
1075                                 tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 1);
1076                         } else {
1077                                 tcp_log_reassm(tp, q, NULL, 0, 0, TCP_R_LOG_READ, 1);
1078                         }
1079 #endif
1080                         sbappendstream_locked(&so->so_rcv, q->tqe_m, 0);
1081                 }
1082 #ifdef TCP_REASS_LOGGING
1083                 if (th != NULL) {
1084                         tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 2);
1085                 } else {
1086                         tcp_log_reassm(tp, q, NULL, 0, 0, TCP_R_LOG_READ, 2);
1087                 }
1088 #endif
1089                 KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
1090                         ("tp:%p seg queue goes negative", tp));
1091                 tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
1092                 uma_zfree(tcp_reass_zone, q);
1093                 tp->t_segqlen--;
1094                 q = nq;
1095         } while (q && q->tqe_start == tp->rcv_nxt);
1096         if (TAILQ_EMPTY(&tp->t_segq) &&
1097             (tp->t_segqmbuflen != 0)) {
1098 #ifdef INVARIANTS
1099                 panic("tp:%p segq:%p len:%d queue empty",
1100                       tp, &tp->t_segq, tp->t_segqmbuflen);
1101 #else
1102 #ifdef TCP_REASS_LOGGING
1103                 if (th != NULL) {
1104                         tcp_log_reassm(tp, NULL, NULL, th->th_seq, *tlenp, TCP_R_LOG_ZERO, 0);
1105                 } else {
1106                         tcp_log_reassm(tp, NULL, NULL, 0, 0, TCP_R_LOG_ZERO, 0);
1107                 }
1108 #endif
1109                 tp->t_segqmbuflen = 0;
1110 #endif
1111         }
1112 #ifdef TCP_REASS_LOGGING
1113         tcp_reass_log_dump(tp);
1114 #endif
1115         tp->t_flags |= TF_WAKESOR;
1116         return (flags);
1117 }