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
  32 #include <sys/cdefs.h>
  33 #include "opt_inet.h"
  34 #include "opt_inet6.h"
  35
  36 /* For debugging we want counters and BB logging */
  37 /* #define TCP_REASS_COUNTERS 1 */
  38 /* #define TCP_REASS_LOGGING 1 */
  39
  40 #include <sys/param.h>
  41 #include <sys/kernel.h>
  42 #include <sys/eventhandler.h>
  43 #include <sys/malloc.h>
  44 #include <sys/mbuf.h>
  45 #include <sys/socket.h>
  46 #include <sys/socketvar.h>
  47 #include <sys/sysctl.h>
  48 #include <sys/syslog.h>
  49 #include <sys/systm.h>
  50
  51 #include <vm/uma.h>
  52
  53 #include <net/if.h>
  54 #include <net/if_var.h>
  55 #include <net/route.h>
  56 #include <net/vnet.h>
  57
  58 #include <netinet/in.h>
  59 #include <netinet/in_pcb.h>
  60 #include <netinet/in_systm.h>
  61 #include <netinet/in_var.h>
  62 #include <netinet/ip.h>
  63 #include <netinet/ip_var.h>
  64 #include <netinet/ip_options.h>
  65 #include <netinet/ip6.h>
  66 #include <netinet6/in6_pcb.h>
  67 #include <netinet6/ip6_var.h>
  68 #include <netinet6/nd6.h>
  69 #include <netinet/tcp.h>
  70 #include <netinet/tcp_fsm.h>
  71 #include <netinet/tcp_seq.h>
  72 #include <netinet/tcp_timer.h>
  73 #include <netinet/tcp_var.h>
  74 #ifdef TCP_REASS_LOGGING
  75 #include <netinet/tcp_log_buf.h>
  76 #include <netinet/tcp_hpts.h>
  77 #endif
  78 #include <netinet/tcpip.h>
  79
  80 #define TCP_R_LOG_ADD           1
  81 #define TCP_R_LOG_LIMIT_REACHED 2
  82 #define TCP_R_LOG_APPEND        3
  83 #define TCP_R_LOG_PREPEND       4
  84 #define TCP_R_LOG_REPLACE       5
  85 #define TCP_R_LOG_MERGE_INTO    6
  86 #define TCP_R_LOG_NEW_ENTRY     7
  87 #define TCP_R_LOG_READ          8
  88 #define TCP_R_LOG_ZERO          9
  89 #define TCP_R_LOG_DUMP          10
  90 #define TCP_R_LOG_TRIM          11
  91
  92 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass,
  93     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
  94     "TCP Segment Reassembly Queue");
  95
  96 static SYSCTL_NODE(_net_inet_tcp_reass, OID_AUTO, stats,
  97     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
  98     "TCP Segment Reassembly stats");
  99
 100 static int tcp_reass_maxseg = 0;
 101 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
 102     &tcp_reass_maxseg, 0,
 103     "Global maximum number of TCP Segments in Reassembly Queue");
 104
 105 static uma_zone_t tcp_reass_zone;
 106 SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, 0,
 107     &tcp_reass_zone,
 108     "Global number of TCP Segments currently in Reassembly Queue");
 109
 110 static u_int tcp_reass_maxqueuelen = 100;
 111 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, maxqueuelen, CTLFLAG_RWTUN,
 112     &tcp_reass_maxqueuelen, 0,
 113     "Maximum number of TCP Segments per Reassembly Queue");
 114
 115 static int tcp_new_limits = 0;
 116 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, new_limit, CTLFLAG_RWTUN,
 117     &tcp_new_limits, 0,
 118     "Do we use the new limit method we are discussing?");
 119
 120 static u_int tcp_reass_queue_guard = 16;
 121 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, queueguard, CTLFLAG_RWTUN,
 122     &tcp_reass_queue_guard, 16,
 123     "Number of TCP Segments in Reassembly Queue where we flip over to guard mode");
 124
 125 #ifdef TCP_REASS_COUNTERS
 126
 127 counter_u64_t reass_entry;
 128 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, entry, CTLFLAG_RD,
 129     &reass_entry, "A segment entered reassembly ");
 130
 131 counter_u64_t reass_path1;
 132 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path1, CTLFLAG_RD,
 133     &reass_path1, "Took path 1");
 134
 135 counter_u64_t reass_path2;
 136 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path2, CTLFLAG_RD,
 137     &reass_path2, "Took path 2");
 138
 139 counter_u64_t reass_path3;
 140 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path3, CTLFLAG_RD,
 141     &reass_path3, "Took path 3");
 142
 143 counter_u64_t reass_path4;
 144 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path4, CTLFLAG_RD,
 145     &reass_path4, "Took path 4");
 146
 147 counter_u64_t reass_path5;
 148 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path5, CTLFLAG_RD,
 149     &reass_path5, "Took path 5");
 150
 151 counter_u64_t reass_path6;
 152 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path6, CTLFLAG_RD,
 153     &reass_path6, "Took path 6");
 154
 155 counter_u64_t reass_path7;
 156 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path7, CTLFLAG_RD,
 157     &reass_path7, "Took path 7");
 158
 159 counter_u64_t reass_fullwalk;
 160 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, fullwalk, CTLFLAG_RD,
 161     &reass_fullwalk, "Took a full walk ");
 162
 163 counter_u64_t reass_nospace;
 164 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, nospace, CTLFLAG_RD,
 165     &reass_nospace, "Had no mbuf capacity ");
 166
 167 counter_u64_t merge_fwd;
 168 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_fwd, CTLFLAG_RD,
 169     &merge_fwd, "Ran merge fwd");
 170
 171 counter_u64_t merge_into;
 172 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_into, CTLFLAG_RD,
 173     &merge_into, "Ran merge into");
 174
 175 counter_u64_t tcp_zero_input;
 176 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, zero_input, CTLFLAG_RD,
 177     &tcp_zero_input, "The reassembly buffer saw a zero len segment etc");
 178
 179 #endif
 180
 181 /* Initialize TCP reassembly queue */
 182 static void
 183 tcp_reass_zone_change(void *tag)
 184 {
 185
 186         /* Set the zone limit and read back the effective value. */
 187         tcp_reass_maxseg = nmbclusters / 16;
 188         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 189             tcp_reass_maxseg);
 190 }
 191
 192 #ifdef TCP_REASS_LOGGING
 193
 194 static void
 195 tcp_log_reassm(struct tcpcb *tp, struct tseg_qent *q, struct tseg_qent *p,
 196     tcp_seq seq, int len, uint8_t action, int instance)
 197 {
 198         struct socket *so = tptosocket(tp);
 199         uint32_t cts;
 200         struct timeval tv;
 201
 202         if (tp->t_logstate != TCP_LOG_STATE_OFF) {
 203                 union tcp_log_stackspecific log;
 204
 205                 memset(&log, 0, sizeof(log));
 206                 cts = tcp_get_usecs(&tv);
 207                 log.u_bbr.flex1 = seq;
 208                 log.u_bbr.cur_del_rate = (uint64_t)q;
 209                 log.u_bbr.delRate = (uint64_t)p;
 210                 if (q != NULL) {
 211                         log.u_bbr.flex2 = q->tqe_start;
 212                         log.u_bbr.flex3 = q->tqe_len;
 213                         log.u_bbr.flex4 = q->tqe_mbuf_cnt;
 214                         log.u_bbr.hptsi_gain = q->tqe_flags;
 215                 }
 216                 if (p != NULL)  {
 217                         log.u_bbr.flex5 = p->tqe_start;
 218                         log.u_bbr.pkts_out = p->tqe_len;
 219                         log.u_bbr.epoch = p->tqe_mbuf_cnt;
 220                         log.u_bbr.cwnd_gain = p->tqe_flags;
 221                 }
 222                 log.u_bbr.flex6 = tp->t_segqmbuflen;
 223                 log.u_bbr.flex7 = instance;
 224                 log.u_bbr.flex8 = action;
 225                 log.u_bbr.timeStamp = cts;
 226                 TCP_LOG_EVENTP(tp, NULL, &so->so_rcv, &so->so_snd,
 227                     TCP_LOG_REASS, 0,
 228                     len, &log, false, &tv);
 229         }
 230 }
 231
 232 static void
 233 tcp_reass_log_dump(struct tcpcb *tp)
 234 {
 235         struct tseg_qent *q;
 236
 237         if (tp->t_logstate != TCP_LOG_STATE_OFF) {
 238                 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
 239                         tcp_log_reassm(tp, q, NULL, q->tqe_start, q->tqe_len, TCP_R_LOG_DUMP, 0);
 240                 }
 241         };
 242 }
 243
 244 static void
 245 tcp_reass_log_new_in(struct tcpcb *tp, tcp_seq seq, int len, struct mbuf *m,
 246     int logval, struct tseg_qent *q)
 247 {
 248         int cnt;
 249         struct mbuf *t;
 250
 251         cnt = 0;
 252         t = m;
 253         while (t) {
 254                 cnt += t->m_len;
 255                 t = t->m_next;
 256         }
 257         tcp_log_reassm(tp, q, NULL, seq, len, logval, cnt);
 258 }
 259
 260 #endif
 261
 262 void
 263 tcp_reass_global_init(void)
 264 {
 265
 266         tcp_reass_maxseg = nmbclusters / 16;
 267         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
 268             &tcp_reass_maxseg);
 269         tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
 270             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 271         /* Set the zone limit and read back the effective value. */
 272         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 273             tcp_reass_maxseg);
 274 #ifdef TCP_REASS_COUNTERS
 275         reass_path1 = counter_u64_alloc(M_WAITOK);
 276         reass_path2 = counter_u64_alloc(M_WAITOK);
 277         reass_path3 = counter_u64_alloc(M_WAITOK);
 278         reass_path4 = counter_u64_alloc(M_WAITOK);
 279         reass_path5 = counter_u64_alloc(M_WAITOK);
 280         reass_path6 = counter_u64_alloc(M_WAITOK);
 281         reass_path7 = counter_u64_alloc(M_WAITOK);
 282         reass_fullwalk = counter_u64_alloc(M_WAITOK);
 283         reass_nospace = counter_u64_alloc(M_WAITOK);
 284         reass_entry = counter_u64_alloc(M_WAITOK);
 285         merge_fwd = counter_u64_alloc(M_WAITOK);
 286         merge_into = counter_u64_alloc(M_WAITOK);
 287         tcp_zero_input = counter_u64_alloc(M_WAITOK);
 288 #endif
 289         EVENTHANDLER_REGISTER(nmbclusters_change,
 290             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 291
 292 }
 293
 294 void
 295 tcp_reass_flush(struct tcpcb *tp)
 296 {
 297         struct tseg_qent *qe;
 298
 299         INP_WLOCK_ASSERT(tptoinpcb(tp));
 300
 301         while ((qe = TAILQ_FIRST(&tp->t_segq)) != NULL) {
 302                 TAILQ_REMOVE(&tp->t_segq, qe, tqe_q);
 303                 m_freem(qe->tqe_m);
 304                 uma_zfree(tcp_reass_zone, qe);
 305                 tp->t_segqlen--;
 306         }
 307         tp->t_segqmbuflen = 0;
 308         KASSERT((tp->t_segqlen == 0),
 309             ("TCP reass queue %p segment count is %d instead of 0 after flush.",
 310             tp, tp->t_segqlen));
 311 }
 312
 313 static void
 314 tcp_reass_append(struct tcpcb *tp, struct tseg_qent *last,
 315     struct mbuf *m, struct tcphdr *th, int tlen,
 316     struct mbuf *mlast, int lenofoh)
 317 {
 318
 319 #ifdef TCP_REASS_LOGGING
 320         tcp_log_reassm(tp, last, NULL, th->th_seq, tlen, TCP_R_LOG_APPEND, 0);
 321 #endif
 322         last->tqe_len += tlen;
 323         last->tqe_m->m_pkthdr.len += tlen;
 324         /* Preserve the FIN bit if its there */
 325         last->tqe_flags |= (tcp_get_flags(th) & TH_FIN);
 326         last->tqe_last->m_next = m;
 327         last->tqe_last = mlast;
 328         last->tqe_mbuf_cnt += lenofoh;
 329         tp->t_rcvoopack++;
 330         TCPSTAT_INC(tcps_rcvoopack);
 331         TCPSTAT_ADD(tcps_rcvoobyte, tlen);
 332 #ifdef TCP_REASS_LOGGING
 333         tcp_reass_log_new_in(tp, last->tqe_start, lenofoh, last->tqe_m,
 334                              TCP_R_LOG_APPEND,
 335                              last);
 336 #endif
 337 }
 338
 339 static void
 340 tcp_reass_prepend(struct tcpcb *tp, struct tseg_qent *first, struct mbuf *m, struct tcphdr *th,
 341                   int tlen, struct mbuf *mlast, int lenofoh)
 342 {
 343         int i;
 344
 345 #ifdef TCP_REASS_LOGGING
 346         tcp_log_reassm(tp, first, NULL, th->th_seq, tlen, TCP_R_LOG_PREPEND, 0);
 347 #endif
 348         if (SEQ_GT((th->th_seq + tlen), first->tqe_start)) {
 349                 /* The new data overlaps into the old */
 350                 i = (th->th_seq + tlen) - first->tqe_start;
 351 #ifdef TCP_REASS_LOGGING
 352                 tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 1);
 353 #endif
 354                 m_adj(first->tqe_m, i);
 355                 first->tqe_len -= i;
 356                 first->tqe_start += i;
 357         }
 358         /* Ok now setup our chain to point to the old first */
 359         mlast->m_next = first->tqe_m;
 360         first->tqe_m = m;
 361         first->tqe_len += tlen;
 362         first->tqe_start = th->th_seq;
 363         first->tqe_m->m_pkthdr.len = first->tqe_len;
 364         first->tqe_mbuf_cnt += lenofoh;
 365         tp->t_rcvoopack++;
 366         TCPSTAT_INC(tcps_rcvoopack);
 367         TCPSTAT_ADD(tcps_rcvoobyte, tlen);
 368 #ifdef TCP_REASS_LOGGING
 369         tcp_reass_log_new_in(tp, first->tqe_start, lenofoh, first->tqe_m,
 370                              TCP_R_LOG_PREPEND,
 371                              first);
 372 #endif
 373 }
 374
 375 static void
 376 tcp_reass_replace(struct tcpcb *tp, struct tseg_qent *q, struct mbuf *m,
 377     tcp_seq seq, int len, struct mbuf *mlast, int mbufoh, uint16_t flags)
 378 {
 379         /*
 380          * Free the data in q, and replace
 381          * it with the new segment.
 382          */
 383         int len_dif;
 384
 385 #ifdef TCP_REASS_LOGGING
 386         tcp_log_reassm(tp, q, NULL, seq, len, TCP_R_LOG_REPLACE, 0);
 387 #endif
 388         m_freem(q->tqe_m);
 389         KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
 390                 ("Tp:%p seg queue goes negative", tp));
 391         tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
 392         q->tqe_mbuf_cnt = mbufoh;
 393         q->tqe_m = m;
 394         q->tqe_last = mlast;
 395         q->tqe_start = seq;
 396         if (len > q->tqe_len)
 397                 len_dif = len - q->tqe_len;
 398         else
 399                 len_dif = 0;
 400         tp->t_rcvoopack++;
 401         TCPSTAT_INC(tcps_rcvoopack);
 402         TCPSTAT_ADD(tcps_rcvoobyte, len_dif);
 403         q->tqe_len = len;
 404         q->tqe_flags = (flags & TH_FIN);
 405         q->tqe_m->m_pkthdr.len = q->tqe_len;
 406         tp->t_segqmbuflen += mbufoh;
 407
 408 }
 409
 410 static void
 411 tcp_reass_merge_into(struct tcpcb *tp, struct tseg_qent *ent,
 412     struct tseg_qent *q)
 413 {
 414         /*
 415          * Merge q into ent and free q from the list.
 416          */
 417 #ifdef TCP_REASS_LOGGING
 418         tcp_log_reassm(tp, q, ent, 0, 0, TCP_R_LOG_MERGE_INTO, 0);
 419 #endif
 420 #ifdef TCP_REASS_COUNTERS
 421         counter_u64_add(merge_into, 1);
 422 #endif
 423         ent->tqe_last->m_next = q->tqe_m;
 424         ent->tqe_last = q->tqe_last;
 425         ent->tqe_len += q->tqe_len;
 426         ent->tqe_mbuf_cnt += q->tqe_mbuf_cnt;
 427         ent->tqe_m->m_pkthdr.len += q->tqe_len;
 428         ent->tqe_flags |= (q->tqe_flags & TH_FIN);
 429         TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
 430         uma_zfree(tcp_reass_zone, q);
 431         tp->t_segqlen--;
 432
 433 }
 434
 435 static void
 436 tcp_reass_merge_forward(struct tcpcb *tp, struct tseg_qent *ent)
 437 {
 438         struct tseg_qent *q, *qtmp;
 439         int i;
 440         tcp_seq max;
 441         /*
 442          * Given an entry merge forward anyplace
 443          * that ent overlaps forward.
 444          */
 445
 446         max = ent->tqe_start + ent->tqe_len;
 447         q = TAILQ_NEXT(ent, tqe_q);
 448         if (q == NULL) {
 449                 /* Nothing left */
 450                 return;
 451         }
 452         TAILQ_FOREACH_FROM_SAFE(q, &tp->t_segq, tqe_q, qtmp) {
 453                 if (SEQ_GT(q->tqe_start, max)) {
 454                         /* Beyond q */
 455                         break;
 456                 }
 457                 /* We have some or all that are overlapping */
 458                 if (SEQ_GEQ(max, (q->tqe_start + q->tqe_len))) {
 459                         /* It consumes it all */
 460                         tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
 461                         m_freem(q->tqe_m);
 462                         TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
 463                         uma_zfree(tcp_reass_zone, q);
 464                         tp->t_segqlen--;
 465                         continue;
 466                 }
 467                 /*
 468                  * Trim the q entry to dovetail to this one
 469                  * and then merge q into ent updating max
 470                  * in the process.
 471                  */
 472                 i = max - q->tqe_start;
 473 #ifdef TCP_REASS_LOGGING
 474                 tcp_log_reassm(tp, q, NULL, 0, i, TCP_R_LOG_TRIM, 2);
 475 #endif
 476                 m_adj(q->tqe_m, i);
 477                 q->tqe_len -= i;
 478                 q->tqe_start += i;
 479                 tcp_reass_merge_into(tp, ent, q);
 480                 max = ent->tqe_start + ent->tqe_len;
 481         }
 482 #ifdef TCP_REASS_COUNTERS
 483         counter_u64_add(merge_fwd, 1);
 484 #endif
 485 }
 486
 487 static int
 488 tcp_reass_overhead_of_chain(struct mbuf *m, struct mbuf **mlast)
 489 {
 490         int len = MSIZE;
 491
 492         if (m->m_flags & M_EXT)
 493                 len += m->m_ext.ext_size;
 494         while (m->m_next != NULL) {
 495                 m = m->m_next;
 496                 len += MSIZE;
 497                 if (m->m_flags & M_EXT)
 498                         len += m->m_ext.ext_size;
 499         }
 500         *mlast = m;
 501         return (len);
 502 }
 503
 504 /*
 505  * NOTE!!! the new tcp-reassembly code *must not* use
 506  * m_adj() with a negative index. That alters the chain
 507  * of mbufs (by possibly chopping trailing mbufs). At
 508  * the front of tcp_reass we count the mbuf overhead
 509  * and setup the tail pointer. If we use m_adj(m, -5)
 510  * we could corrupt the tail pointer. Currently the
 511  * code only uses m_adj(m, postive-num). If this
 512  * changes appropriate changes to update mlast would
 513  * be needed.
 514  */
 515 int
 516 tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
 517           int *tlenp, struct mbuf *m)
 518 {
 519         struct tseg_qent *q, *last, *first;
 520         struct tseg_qent *p = NULL;
 521         struct tseg_qent *nq = NULL;
 522         struct tseg_qent *te = NULL;
 523         struct mbuf *mlast = NULL;
 524         struct inpcb *inp = tptoinpcb(tp);
 525         struct socket *so = tptosocket(tp);
 526         struct sockbuf *sb = &so->so_rcv;
 527         char *s = NULL;
 528         int flags, i, lenofoh;
 529
 530         INP_WLOCK_ASSERT(inp);
 531         /*
 532          * XXX: tcp_reass() is rather inefficient with its data structures
 533          * and should be rewritten (see NetBSD for optimizations).
 534          */
 535
 536         KASSERT(th == NULL || (seq_start != NULL && tlenp != NULL),
 537                 ("tcp_reass called with illegal parameter combination "
 538                  "(tp=%p, th=%p, seq_start=%p, tlenp=%p, m=%p)",
 539                  tp, th, seq_start, tlenp, m));
 540         /*
 541          * Call with th==NULL after become established to
 542          * force pre-ESTABLISHED data up to user socket.
 543          */
 544         if (th == NULL)
 545                 goto present;
 546         KASSERT(SEQ_GEQ(th->th_seq, tp->rcv_nxt),
 547                 ("Attempt to add old entry to reassembly queue (th=%p, tp=%p)",
 548                  th, tp));
 549 #ifdef TCP_REASS_LOGGING
 550         tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_ADD, NULL);
 551 #endif
 552 #ifdef TCP_REASS_COUNTERS
 553         counter_u64_add(reass_entry, 1);
 554 #endif
 555         /*
 556          * Check for zero length data.
 557          */
 558         if ((*tlenp == 0) && ((tcp_get_flags(th) & TH_FIN) == 0)) {
 559                 /*
 560                  * A zero length segment does no
 561                  * one any good. We could check
 562                  * the rcv_nxt <-> rcv_wnd but thats
 563                  * already done for us by the caller.
 564                  */
 565 strip_fin:
 566 #ifdef TCP_REASS_COUNTERS
 567                 counter_u64_add(tcp_zero_input, 1);
 568 #endif
 569                 m_freem(m);
 570 #ifdef TCP_REASS_LOGGING
 571                 tcp_reass_log_dump(tp);
 572 #endif
 573                 return (0);
 574         } else if ((*tlenp == 0) &&
 575                    (tcp_get_flags(th) & TH_FIN) &&
 576                    !TCPS_HAVEESTABLISHED(tp->t_state)) {
 577                 /*
 578                  * We have not established, and we
 579                  * have a FIN and no data. Lets treat
 580                  * this as the same as if the FIN were
 581                  * not present. We don't want to save
 582                  * the FIN bit in a reassembly buffer
 583                  * we want to get established first before
 584                  * we do that (the peer will retransmit).
 585                  */
 586                 goto strip_fin;
 587         }
 588         /*
 589          * Will it fit?
 590          */
 591         lenofoh = tcp_reass_overhead_of_chain(m, &mlast);
 592         if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
 593             (sb->sb_mbcnt + tp->t_segqmbuflen + lenofoh) > sb->sb_mbmax) {
 594                 /* No room */
 595                 TCPSTAT_INC(tcps_rcvreassfull);
 596 #ifdef TCP_REASS_COUNTERS
 597                 counter_u64_add(reass_nospace, 1);
 598 #endif
 599 #ifdef TCP_REASS_LOGGING
 600                 tcp_log_reassm(tp, NULL, NULL, th->th_seq, lenofoh, TCP_R_LOG_LIMIT_REACHED, 0);
 601 #endif
 602                 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
 603                         log(LOG_DEBUG, "%s; %s: mbuf count limit reached, "
 604                             "segment dropped\n", s, __func__);
 605                         free(s, M_TCPLOG);
 606                 }
 607                 m_freem(m);
 608                 *tlenp = 0;
 609 #ifdef TCP_REASS_LOGGING
 610                 tcp_reass_log_dump(tp);
 611 #endif
 612                 return (0);
 613         }
 614         /*
 615          * First lets deal with two common cases, the
 616          * segment appends to the back of our collected
 617          * segments. Or the segment is the next in line.
 618          */
 619         last = TAILQ_LAST_FAST(&tp->t_segq, tseg_qent, tqe_q);
 620         if (last != NULL) {
 621                 if ((tcp_get_flags(th) & TH_FIN) &&
 622                     SEQ_LT((th->th_seq + *tlenp), (last->tqe_start + last->tqe_len))) {
 623                         /*
 624                          * Someone is trying to game us, dump
 625                          * the segment.
 626                          */
 627                         *tlenp = 0;
 628                         m_freem(m);
 629                         return (0);
 630                 }
 631                 if ((SEQ_GEQ(th->th_seq, last->tqe_start)) &&
 632                     (SEQ_GEQ((last->tqe_start + last->tqe_len), th->th_seq))) {
 633                         /* Common case, trailing segment is added */
 634                         /**
 635                          *                                 +--last
 636                          *                                 v
 637                          *  reassembly buffer |---|  |---| |---|
 638                          *  new segment                       |---|
 639                          */
 640 #ifdef TCP_REASS_COUNTERS
 641                         counter_u64_add(reass_path1, 1);
 642 #endif
 643                         if (SEQ_GT((last->tqe_start + last->tqe_len), th->th_seq)) {
 644                                 i = (last->tqe_start + last->tqe_len) - th->th_seq;
 645                                 if (i < *tlenp) {
 646 #ifdef TCP_REASS_LOGGING
 647                                         tcp_log_reassm(tp, last, NULL, 0, i, TCP_R_LOG_TRIM, 3);
 648                                         th->th_seq += i;
 649 #endif
 650                                         m_adj(m, i);
 651                                         *tlenp -= i;
 652                                 } else {
 653                                         /* Complete overlap */
 654                                         TCPSTAT_INC(tcps_rcvduppack);
 655                                         TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 656                                         m_freem(m);
 657                                         *tlenp = last->tqe_len;
 658                                         *seq_start = last->tqe_start;
 659                                         return (0);
 660                                 }
 661                         }
 662                         if (last->tqe_flags & TH_FIN) {
 663                                 /*
 664                                  * We have data after the FIN on the last?
 665                                  */
 666                                 *tlenp = 0;
 667                                 m_freem(m);
 668                                 return(0);
 669                         }
 670                         tcp_reass_append(tp, last, m, th, *tlenp, mlast, lenofoh);
 671                         tp->t_segqmbuflen += lenofoh;
 672                         *seq_start = last->tqe_start;
 673                         *tlenp = last->tqe_len;
 674                         return (0);
 675                 } else if (SEQ_GT(th->th_seq, (last->tqe_start + last->tqe_len))) {
 676                         /*
 677                          * Second common case, we missed
 678                          * another one and have something more
 679                          * for the end.
 680                          */
 681                         /**
 682                          *                                 +--last
 683                          *                                 v
 684                          *  reassembly buffer |---|  |---| |---|
 685                          *  new segment                           |---|
 686                          */
 687                         if (last->tqe_flags & TH_FIN) {
 688                                 /*
 689                                  * We have data after the FIN on the last?
 690                                  */
 691                                 *tlenp = 0;
 692                                 m_freem(m);
 693                                 return(0);
 694                         }
 695 #ifdef TCP_REASS_COUNTERS
 696                         counter_u64_add(reass_path2, 1);
 697 #endif
 698                         p = last;
 699                         goto new_entry;
 700                 }
 701         } else {
 702                 /* First segment (it's NULL). */
 703                 goto new_entry;
 704         }
 705         first = TAILQ_FIRST(&tp->t_segq);
 706         if (SEQ_LT(th->th_seq, first->tqe_start) &&
 707             SEQ_GEQ((th->th_seq + *tlenp),first->tqe_start) &&
 708             SEQ_LT((th->th_seq + *tlenp), (first->tqe_start + first->tqe_len))) {
 709                 /*
 710                  * The head of the queue is prepended by this and
 711                  * it may be the one I want most.
 712                  */
 713                 /**
 714                  *       first-------+
 715                  *                   v
 716                  *  rea:             |---|  |---| |---|
 717                  *  new:         |---|
 718                  * Note the case we do not deal with here is:
 719                  *   rea=     |---|   |---|   |---|
 720                  *   new=  |----|
 721                  * Due to the fact that it could be
 722                  *   new   |--------------------|
 723                  * And we might need to merge forward.
 724                  */
 725 #ifdef INVARIANTS
 726                 struct mbuf *firstmbuf;
 727 #endif
 728
 729 #ifdef TCP_REASS_COUNTERS
 730                 counter_u64_add(reass_path3, 1);
 731 #endif
 732                 if (SEQ_LT(th->th_seq, tp->rcv_nxt)) {
 733                         /*
 734                          * The resend was even before
 735                          * what we have. We need to trim it.
 736                          * Note TSNH (it should be trimmed
 737                          * before the call to tcp_reass()).
 738                          */
 739 #ifdef INVARIANTS
 740                         panic("th->th_seq:%u rcv_nxt:%u tp:%p not pre-trimmed",
 741                               th->th_seq, tp->rcv_nxt, tp);
 742 #else
 743                         i = tp->rcv_nxt - th->th_seq;
 744 #ifdef TCP_REASS_LOGGING
 745                         tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 4);
 746 #endif
 747                         m_adj(m, i);
 748                         th->th_seq += i;
 749                         *tlenp -= i;
 750 #endif
 751                 }
 752 #ifdef INVARIANTS
 753                 firstmbuf = first->tqe_m;
 754 #endif
 755                 tcp_reass_prepend(tp, first, m, th, *tlenp, mlast, lenofoh);
 756 #ifdef INVARIANTS
 757                 if (firstmbuf == first->tqe_m) {
 758                         panic("First stayed same m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
 759                               m, firstmbuf, first->tqe_m, tp, first);
 760                 } else if (first->tqe_m != m) {
 761                         panic("First did not change to m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
 762                               m, firstmbuf, first->tqe_m, tp, first);
 763                 }
 764 #endif
 765                 tp->t_segqmbuflen += lenofoh;
 766                 *seq_start = first->tqe_start;
 767                 *tlenp = first->tqe_len;
 768                 goto present;
 769         } else if (SEQ_LT((th->th_seq + *tlenp), first->tqe_start)) {
 770                 /* New segment is before our earliest segment. */
 771                 /**
 772                  *           first---->+
 773                  *                      v
 774                  *  rea=                |---| ....
 775                  *  new"         |---|
 776                  *
 777                  */
 778                 goto new_entry;
 779         }
 780         /*
 781          * Find a segment which begins after this one does.
 782          */
 783 #ifdef TCP_REASS_COUNTERS
 784         counter_u64_add(reass_fullwalk, 1);
 785 #endif
 786         TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
 787                 if (SEQ_GT(q->tqe_start, th->th_seq))
 788                         break;
 789         }
 790         p = TAILQ_PREV(q, tsegqe_head, tqe_q);
 791         /**
 792          * Now is this fit just in-between only?
 793          * i.e.:
 794          *      p---+        +----q
 795          *          v        v
 796          *     res= |--|     |--|    |--|
 797          *     nee       |-|
 798          */
 799         if (SEQ_LT((th->th_seq + *tlenp), q->tqe_start) &&
 800             ((p == NULL) || (SEQ_GT(th->th_seq, (p->tqe_start + p->tqe_len))))) {
 801                 /* Yep no overlap */
 802                 goto new_entry;
 803         }
 804         /**
 805          * If we reach here we have some (possibly all) overlap
 806          * such as:
 807          *     res=     |--|     |--|    |--|
 808          *     new=  |----|
 809          * or  new=  |-----------------|
 810          * or  new=      |--------|
 811          * or  new=            |---|
 812          * or  new=            |-----------|
 813          */
 814         if ((p != NULL) &&
 815             (SEQ_LEQ(th->th_seq, (p->tqe_start + p->tqe_len)))) {
 816                 /* conversion to int (in i) handles seq wraparound */
 817
 818 #ifdef TCP_REASS_COUNTERS
 819                 counter_u64_add(reass_path4, 1);
 820 #endif
 821                 i = p->tqe_start + p->tqe_len - th->th_seq;
 822                 if (i >= 0) {
 823                         if (i >= *tlenp) {
 824                                 /**
 825                                  *       prev seg---->+
 826                                  *                    v
 827                                  *  reassembly buffer |---|
 828                                  *  new segment        |-|
 829                                  */
 830                                 TCPSTAT_INC(tcps_rcvduppack);
 831                                 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 832                                 *tlenp = p->tqe_len;
 833                                 *seq_start = p->tqe_start;
 834                                 m_freem(m);
 835                                 /*
 836                                  * Try to present any queued data
 837                                  * at the left window edge to the user.
 838                                  * This is needed after the 3-WHS
 839                                  * completes. Note this probably
 840                                  * will not work and we will return.
 841                                  */
 842                                 return (0);
 843                         }
 844                         if (i > 0) {
 845                                 /**
 846                                  *       prev seg---->+
 847                                  *                    v
 848                                  *  reassembly buffer |---|
 849                                  *  new segment         |-----|
 850                                  */
 851 #ifdef TCP_REASS_COUNTERS
 852                                 counter_u64_add(reass_path5, 1);
 853 #endif
 854 #ifdef TCP_REASS_LOGGING
 855                                 tcp_log_reassm(tp, p, NULL, 0, i, TCP_R_LOG_TRIM, 5);
 856 #endif
 857                                 m_adj(m, i);
 858                                 *tlenp -= i;
 859                                 th->th_seq += i;
 860                         }
 861                 }
 862                 if (th->th_seq == (p->tqe_start + p->tqe_len)) {
 863                         /*
 864                          * If dovetails in with this one
 865                          * append it.
 866                          */
 867                         /**
 868                          *       prev seg---->+
 869                          *                    v
 870                          *  reassembly buffer |--|     |---|
 871                          *  new segment          |--|
 872                          * (note: it was trimmed above if it overlapped)
 873                          */
 874                         tcp_reass_append(tp, p, m, th, *tlenp, mlast, lenofoh);
 875                         tp->t_segqmbuflen += lenofoh;
 876                 } else {
 877 #ifdef INVARIANTS
 878                         panic("Impossible cut th_seq:%u p->seq:%u(%d) p:%p tp:%p",
 879                               th->th_seq, p->tqe_start, p->tqe_len,
 880                               p, tp);
 881 #endif
 882                         *tlenp = 0;
 883                         m_freem(m);
 884                         return (0);
 885                 }
 886                 q = p;
 887         } else {
 888                 /*
 889                  * The new data runs over the
 890                  * top of previously sack'd data (in q).
 891                  * It may be partially overlapping, or
 892                  * it may overlap the entire segment.
 893                  */
 894 #ifdef TCP_REASS_COUNTERS
 895                 counter_u64_add(reass_path6, 1);
 896 #endif
 897                 if (SEQ_GEQ((th->th_seq + *tlenp), (q->tqe_start + q->tqe_len))) {
 898                         /* It consumes it all */
 899                         /**
 900                          *             next seg---->+
 901                          *                          v
 902                          *  reassembly buffer |--|     |---|
 903                          *  new segment              |----------|
 904                          */
 905 #ifdef TCP_REASS_COUNTERS
 906                         counter_u64_add(reass_path7, 1);
 907 #endif
 908                         tcp_reass_replace(tp, q, m, th->th_seq, *tlenp, mlast, lenofoh, tcp_get_flags(th));
 909                 } else {
 910                         /*
 911                          * We just need to prepend the data
 912                          * to this. It does not overrun
 913                          * the end.
 914                          */
 915                         /**
 916                          *                next seg---->+
 917                          *                             v
 918                          *  reassembly buffer |--|     |---|
 919                          *  new segment                   |----------|
 920                          */
 921                         tcp_reass_prepend(tp, q, m, th, *tlenp, mlast, lenofoh);
 922                         tp->t_segqmbuflen += lenofoh;
 923                 }
 924         }
 925         /* Now does it go further than that? */
 926         tcp_reass_merge_forward(tp, q);
 927         *seq_start = q->tqe_start;
 928         *tlenp = q->tqe_len;
 929         goto present;
 930
 931         /*
 932          * When we reach here we can't combine it
 933          * with any existing segment.
 934          *
 935          * Limit the number of segments that can be queued to reduce the
 936          * potential for mbuf exhaustion. For best performance, we want to be
 937          * able to queue a full window's worth of segments. The size of the
 938          * socket receive buffer determines our advertised window and grows
 939          * automatically when socket buffer autotuning is enabled. Use it as the
 940          * basis for our queue limit.
 941          *
 942          * However, allow the user to specify a ceiling for the number of
 943          * segments in each queue.
 944          *
 945          * Always let the missing segment through which caused this queue.
 946          * NB: Access to the socket buffer is left intentionally unlocked as we
 947          * can tolerate stale information here.
 948          *
 949          * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
 950          * should work but causes packets to be dropped when they shouldn't.
 951          * Investigate why and re-evaluate the below limit after the behaviour
 952          * is understood.
 953          */
 954 new_entry:
 955         if (th->th_seq == tp->rcv_nxt && TCPS_HAVEESTABLISHED(tp->t_state)) {
 956                 tp->rcv_nxt += *tlenp;
 957                 flags = tcp_get_flags(th) & TH_FIN;
 958                 TCPSTAT_INC(tcps_rcvoopack);
 959                 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
 960                 SOCKBUF_LOCK(&so->so_rcv);
 961                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
 962                         m_freem(m);
 963                 } else {
 964                         sbappendstream_locked(&so->so_rcv, m, 0);
 965                 }
 966                 tp->t_flags |= TF_WAKESOR;
 967                 return (flags);
 968         }
 969         if (tcp_new_limits) {
 970                 if ((tp->t_segqlen > tcp_reass_queue_guard) &&
 971                     (*tlenp < MSIZE)) {
 972                         /*
 973                          * This is really a lie, we are not full but
 974                          * are getting a segment that is above
 975                          * guard threshold. If it is and its below
 976                          * a mbuf size (256) we drop it if it
 977                          * can't fill in some place.
 978                          */
 979                         TCPSTAT_INC(tcps_rcvreassfull);
 980                         *tlenp = 0;
 981                         if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
 982                                 log(LOG_DEBUG, "%s; %s: queue limit reached, "
 983                                     "segment dropped\n", s, __func__);
 984                                 free(s, M_TCPLOG);
 985                         }
 986                         m_freem(m);
 987 #ifdef TCP_REASS_LOGGING
 988                         tcp_reass_log_dump(tp);
 989 #endif
 990                         return (0);
 991                 }
 992         } else {
 993                 if (tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1,
 994                                          tcp_reass_maxqueuelen)) {
 995                         TCPSTAT_INC(tcps_rcvreassfull);
 996                         *tlenp = 0;
 997                         if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
 998                                 log(LOG_DEBUG, "%s; %s: queue limit reached, "
 999                                     "segment dropped\n", s, __func__);
1000                                 free(s, M_TCPLOG);
1001                         }
1002                         m_freem(m);
1003 #ifdef TCP_REASS_LOGGING
1004                         tcp_reass_log_dump(tp);
1005 #endif
1006                         return (0);
1007                 }
1008         }
1009         /*
1010          * Allocate a new queue entry. If we can't, or hit the zone limit
1011          * just drop the pkt.
1012          */
1013         te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
1014         if (te == NULL) {
1015                 TCPSTAT_INC(tcps_rcvmemdrop);
1016                 m_freem(m);
1017                 *tlenp = 0;
1018                 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
1019                         log(LOG_DEBUG, "%s; %s: global zone limit "
1020                             "reached, segment dropped\n", s, __func__);
1021                         free(s, M_TCPLOG);
1022                 }
1023                 return (0);
1024         }
1025         tp->t_segqlen++;
1026         tp->t_rcvoopack++;
1027         TCPSTAT_INC(tcps_rcvoopack);
1028         TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
1029         /* Insert the new segment queue entry into place. */
1030         te->tqe_m = m;
1031         te->tqe_flags = tcp_get_flags(th);
1032         te->tqe_len = *tlenp;
1033         te->tqe_start = th->th_seq;
1034         te->tqe_last = mlast;
1035         te->tqe_mbuf_cnt = lenofoh;
1036         tp->t_segqmbuflen += te->tqe_mbuf_cnt;
1037         if (p == NULL) {
1038                 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q);
1039         } else {
1040                 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q);
1041         }
1042 #ifdef TCP_REASS_LOGGING
1043         tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_NEW_ENTRY, te);
1044 #endif
1045 present:
1046         /*
1047          * Present data to user, advancing rcv_nxt through
1048          * completed sequence space.
1049          */
1050         if (!TCPS_HAVEESTABLISHED(tp->t_state))
1051                 return (0);
1052         q = TAILQ_FIRST(&tp->t_segq);
1053         KASSERT(q == NULL || SEQ_GEQ(q->tqe_start, tp->rcv_nxt),
1054                 ("Reassembly queue for %p has stale entry at head", tp));
1055         if (!q || q->tqe_start != tp->rcv_nxt) {
1056 #ifdef TCP_REASS_LOGGING
1057                 tcp_reass_log_dump(tp);
1058 #endif
1059                 return (0);
1060         }
1061         SOCKBUF_LOCK(&so->so_rcv);
1062         do {
1063                 tp->rcv_nxt += q->tqe_len;
1064                 flags = q->tqe_flags & TH_FIN;
1065                 nq = TAILQ_NEXT(q, tqe_q);
1066                 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
1067                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1068                         m_freem(q->tqe_m);
1069                 } else {
1070 #ifdef TCP_REASS_LOGGING
1071                         tcp_reass_log_new_in(tp, q->tqe_start, q->tqe_len, q->tqe_m, TCP_R_LOG_READ, q);
1072                         if (th != NULL) {
1073                                 tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 1);
1074                         } else {
1075                                 tcp_log_reassm(tp, q, NULL, 0, 0, TCP_R_LOG_READ, 1);
1076                         }
1077 #endif
1078                         sbappendstream_locked(&so->so_rcv, q->tqe_m, 0);
1079                 }
1080 #ifdef TCP_REASS_LOGGING
1081                 if (th != NULL) {
1082                         tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 2);
1083                 } else {
1084                         tcp_log_reassm(tp, q, NULL, 0, 0, TCP_R_LOG_READ, 2);
1085                 }
1086 #endif
1087                 KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
1088                         ("tp:%p seg queue goes negative", tp));
1089                 tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
1090                 uma_zfree(tcp_reass_zone, q);
1091                 tp->t_segqlen--;
1092                 q = nq;
1093         } while (q && q->tqe_start == tp->rcv_nxt);
1094         if (TAILQ_EMPTY(&tp->t_segq) &&
1095             (tp->t_segqmbuflen != 0)) {
1096 #ifdef INVARIANTS
1097                 panic("tp:%p segq:%p len:%d queue empty",
1098                       tp, &tp->t_segq, tp->t_segqmbuflen);
1099 #else
1100 #ifdef TCP_REASS_LOGGING
1101                 if (th != NULL) {
1102                         tcp_log_reassm(tp, NULL, NULL, th->th_seq, *tlenp, TCP_R_LOG_ZERO, 0);
1103                 } else {
1104                         tcp_log_reassm(tp, NULL, NULL, 0, 0, TCP_R_LOG_ZERO, 0);
1105                 }
1106 #endif
1107                 tp->t_segqmbuflen = 0;
1108 #endif
1109         }
1110 #ifdef TCP_REASS_LOGGING
1111         tcp_reass_log_dump(tp);
1112 #endif
1113         tp->t_flags |= TF_WAKESOR;
1114         return (flags);
1115 }