sys/netinet/tcp_reass.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  *      @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
  32  */
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 #include "opt_inet.h"
  38 #include "opt_inet6.h"
  39
  40 /* For debugging we want counters and BB logging */
  41 /* #define TCP_REASS_COUNTERS 1 */
  42 /* #define TCP_REASS_LOGGING 1 */
  43
  44 #include <sys/param.h>
  45 #include <sys/kernel.h>
  46 #include <sys/eventhandler.h>
  47 #include <sys/malloc.h>
  48 #include <sys/mbuf.h>
  49 #include <sys/socket.h>
  50 #include <sys/socketvar.h>
  51 #include <sys/sysctl.h>
  52 #include <sys/syslog.h>
  53 #include <sys/systm.h>
  54
  55 #include <vm/uma.h>
  56
  57 #include <net/if.h>
  58 #include <net/if_var.h>
  59 #include <net/route.h>
  60 #include <net/vnet.h>
  61
  62 #include <netinet/in.h>
  63 #include <netinet/in_pcb.h>
  64 #include <netinet/in_systm.h>
  65 #include <netinet/in_var.h>
  66 #include <netinet/ip.h>
  67 #include <netinet/ip_var.h>
  68 #include <netinet/ip_options.h>
  69 #include <netinet/ip6.h>
  70 #include <netinet6/in6_pcb.h>
  71 #include <netinet6/ip6_var.h>
  72 #include <netinet6/nd6.h>
  73 #include <netinet/tcp.h>
  74 #include <netinet/tcp_fsm.h>
  75 #include <netinet/tcp_seq.h>
  76 #include <netinet/tcp_timer.h>
  77 #include <netinet/tcp_var.h>
  78 #ifdef TCP_REASS_LOGGING
  79 #include <netinet/tcp_log_buf.h>
  80 #include <netinet/tcp_hpts.h>
  81 #endif
  82 #include <netinet/tcpip.h>
  83
  84 #define TCP_R_LOG_ADD           1
  85 #define TCP_R_LOG_LIMIT_REACHED 2
  86 #define TCP_R_LOG_APPEND        3
  87 #define TCP_R_LOG_PREPEND       4
  88 #define TCP_R_LOG_REPLACE       5
  89 #define TCP_R_LOG_MERGE_INTO    6
  90 #define TCP_R_LOG_NEW_ENTRY     7
  91 #define TCP_R_LOG_READ          8
  92 #define TCP_R_LOG_ZERO          9
  93 #define TCP_R_LOG_DUMP          10
  94 #define TCP_R_LOG_TRIM          11
  95
  96 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass,
  97     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
  98     "TCP Segment Reassembly Queue");
  99
 100 static SYSCTL_NODE(_net_inet_tcp_reass, OID_AUTO, stats,
 101     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
 102     "TCP Segment Reassembly stats");
 103
 104 static int tcp_reass_maxseg = 0;
 105 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
 106     &tcp_reass_maxseg, 0,
 107     "Global maximum number of TCP Segments in Reassembly Queue");
 108
 109 static uma_zone_t tcp_reass_zone;
 110 SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, 0,
 111     &tcp_reass_zone,
 112     "Global number of TCP Segments currently in Reassembly Queue");
 113
 114 static u_int tcp_reass_maxqueuelen = 100;
 115 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, maxqueuelen, CTLFLAG_RWTUN,
 116     &tcp_reass_maxqueuelen, 0,
 117     "Maximum number of TCP Segments per Reassembly Queue");
 118
 119 static int tcp_new_limits = 0;
 120 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, new_limit, CTLFLAG_RWTUN,
 121     &tcp_new_limits, 0,
 122     "Do we use the new limit method we are discussing?");
 123
 124 static u_int tcp_reass_queue_guard = 16;
 125 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, queueguard, CTLFLAG_RWTUN,
 126     &tcp_reass_queue_guard, 16,
 127     "Number of TCP Segments in Reassembly Queue where we flip over to guard mode");
 128
 129 #ifdef TCP_REASS_COUNTERS
 130
 131 counter_u64_t reass_entry;
 132 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, entry, CTLFLAG_RD,
 133     &reass_entry, "A segment entered reassembly ");
 134
 135 counter_u64_t reass_path1;
 136 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path1, CTLFLAG_RD,
 137     &reass_path1, "Took path 1");
 138
 139 counter_u64_t reass_path2;
 140 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path2, CTLFLAG_RD,
 141     &reass_path2, "Took path 2");
 142
 143 counter_u64_t reass_path3;
 144 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path3, CTLFLAG_RD,
 145     &reass_path3, "Took path 3");
 146
 147 counter_u64_t reass_path4;
 148 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path4, CTLFLAG_RD,
 149     &reass_path4, "Took path 4");
 150
 151 counter_u64_t reass_path5;
 152 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path5, CTLFLAG_RD,
 153     &reass_path5, "Took path 5");
 154
 155 counter_u64_t reass_path6;
 156 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path6, CTLFLAG_RD,
 157     &reass_path6, "Took path 6");
 158
 159 counter_u64_t reass_path7;
 160 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path7, CTLFLAG_RD,
 161     &reass_path7, "Took path 7");
 162
 163 counter_u64_t reass_fullwalk;
 164 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, fullwalk, CTLFLAG_RD,
 165     &reass_fullwalk, "Took a full walk ");
 166
 167 counter_u64_t reass_nospace;
 168 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, nospace, CTLFLAG_RD,
 169     &reass_nospace, "Had no mbuf capacity ");
 170
 171 counter_u64_t merge_fwd;
 172 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_fwd, CTLFLAG_RD,
 173     &merge_fwd, "Ran merge fwd");
 174
 175 counter_u64_t merge_into;
 176 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_into, CTLFLAG_RD,
 177     &merge_into, "Ran merge into");
 178
 179 counter_u64_t tcp_zero_input;
 180 SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, zero_input, CTLFLAG_RD,
 181     &tcp_zero_input, "The reassembly buffer saw a zero len segment etc");
 182
 183 #endif
 184
 185 /* Initialize TCP reassembly queue */
 186 static void
 187 tcp_reass_zone_change(void *tag)
 188 {
 189
 190         /* Set the zone limit and read back the effective value. */
 191         tcp_reass_maxseg = nmbclusters / 16;
 192         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 193             tcp_reass_maxseg);
 194 }
 195
 196 #ifdef TCP_REASS_LOGGING
 197
 198 static void
 199 tcp_log_reassm(struct tcpcb *tp, struct tseg_qent *q, struct tseg_qent *p,
 200     tcp_seq seq, int len, uint8_t action, int instance)
 201 {
 202         struct socket *so = tptosocket(tp);
 203         uint32_t cts;
 204         struct timeval tv;
 205
 206         if (tp->t_logstate != TCP_LOG_STATE_OFF) {
 207                 union tcp_log_stackspecific log;
 208
 209                 memset(&log, 0, sizeof(log));
 210                 cts = tcp_get_usecs(&tv);
 211                 log.u_bbr.flex1 = seq;
 212                 log.u_bbr.cur_del_rate = (uint64_t)q;
 213                 log.u_bbr.delRate = (uint64_t)p;
 214                 if (q != NULL) {
 215                         log.u_bbr.flex2 = q->tqe_start;
 216                         log.u_bbr.flex3 = q->tqe_len;
 217                         log.u_bbr.flex4 = q->tqe_mbuf_cnt;
 218                         log.u_bbr.hptsi_gain = q->tqe_flags;
 219                 }
 220                 if (p != NULL)  {
 221                         log.u_bbr.flex5 = p->tqe_start;
 222                         log.u_bbr.pkts_out = p->tqe_len;
 223                         log.u_bbr.epoch = p->tqe_mbuf_cnt;
 224                         log.u_bbr.cwnd_gain = p->tqe_flags;
 225                 }
 226                 log.u_bbr.flex6 = tp->t_segqmbuflen;
 227                 log.u_bbr.flex7 = instance;
 228                 log.u_bbr.flex8 = action;
 229                 log.u_bbr.timeStamp = cts;
 230                 TCP_LOG_EVENTP(tp, NULL, &so->so_rcv, &so->so_snd,
 231                     TCP_LOG_REASS, 0,
 232                     len, &log, false, &tv);
 233         }
 234 }
 235
 236 static void
 237 tcp_reass_log_dump(struct tcpcb *tp)
 238 {
 239         struct tseg_qent *q;
 240
 241         if (tp->t_logstate != TCP_LOG_STATE_OFF) {
 242                 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
 243                         tcp_log_reassm(tp, q, NULL, q->tqe_start, q->tqe_len, TCP_R_LOG_DUMP, 0);
 244                 }
 245         };
 246 }
 247
 248 static void
 249 tcp_reass_log_new_in(struct tcpcb *tp, tcp_seq seq, int len, struct mbuf *m,
 250     int logval, struct tseg_qent *q)
 251 {
 252         int cnt;
 253         struct mbuf *t;
 254
 255         cnt = 0;
 256         t = m;
 257         while (t) {
 258                 cnt += t->m_len;
 259                 t = t->m_next;
 260         }
 261         tcp_log_reassm(tp, q, NULL, seq, len, logval, cnt);
 262 }
 263
 264 #endif
 265
 266 void
 267 tcp_reass_global_init(void)
 268 {
 269
 270         tcp_reass_maxseg = nmbclusters / 16;
 271         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
 272             &tcp_reass_maxseg);
 273         tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
 274             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 275         /* Set the zone limit and read back the effective value. */
 276         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 277             tcp_reass_maxseg);
 278 #ifdef TCP_REASS_COUNTERS
 279         reass_path1 = counter_u64_alloc(M_WAITOK);
 280         reass_path2 = counter_u64_alloc(M_WAITOK);
 281         reass_path3 = counter_u64_alloc(M_WAITOK);
 282         reass_path4 = counter_u64_alloc(M_WAITOK);
 283         reass_path5 = counter_u64_alloc(M_WAITOK);
 284         reass_path6 = counter_u64_alloc(M_WAITOK);
 285         reass_path7 = counter_u64_alloc(M_WAITOK);
 286         reass_fullwalk = counter_u64_alloc(M_WAITOK);
 287         reass_nospace = counter_u64_alloc(M_WAITOK);
 288         reass_entry = counter_u64_alloc(M_WAITOK);
 289         merge_fwd = counter_u64_alloc(M_WAITOK);
 290         merge_into = counter_u64_alloc(M_WAITOK);
 291         tcp_zero_input = counter_u64_alloc(M_WAITOK);
 292 #endif
 293         EVENTHANDLER_REGISTER(nmbclusters_change,
 294             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 295
 296 }
 297
 298 void
 299 tcp_reass_flush(struct tcpcb *tp)
 300 {
 301         struct tseg_qent *qe;
 302
 303         INP_WLOCK_ASSERT(tptoinpcb(tp));
 304
 305         while ((qe = TAILQ_FIRST(&tp->t_segq)) != NULL) {
 306                 TAILQ_REMOVE(&tp->t_segq, qe, tqe_q);
 307                 m_freem(qe->tqe_m);
 308                 uma_zfree(tcp_reass_zone, qe);
 309                 tp->t_segqlen--;
 310         }
 311         tp->t_segqmbuflen = 0;
 312         KASSERT((tp->t_segqlen == 0),
 313             ("TCP reass queue %p segment count is %d instead of 0 after flush.",
 314             tp, tp->t_segqlen));
 315 }
 316
 317 static void
 318 tcp_reass_append(struct tcpcb *tp, struct tseg_qent *last,
 319     struct mbuf *m, struct tcphdr *th, int tlen,
 320     struct mbuf *mlast, int lenofoh)
 321 {
 322
 323 #ifdef TCP_REASS_LOGGING
 324         tcp_log_reassm(tp, last, NULL, th->th_seq, tlen, TCP_R_LOG_APPEND, 0);
 325 #endif
 326         last->tqe_len += tlen;
 327         last->tqe_m->m_pkthdr.len += tlen;
 328         /* Preserve the FIN bit if its there */
 329         last->tqe_flags |= (tcp_get_flags(th) & TH_FIN);
 330         last->tqe_last->m_next = m;
 331         last->tqe_last = mlast;
 332         last->tqe_mbuf_cnt += lenofoh;
 333         tp->t_rcvoopack++;
 334         TCPSTAT_INC(tcps_rcvoopack);
 335         TCPSTAT_ADD(tcps_rcvoobyte, tlen);
 336 #ifdef TCP_REASS_LOGGING
 337         tcp_reass_log_new_in(tp, last->tqe_start, lenofoh, last->tqe_m,
 338                              TCP_R_LOG_APPEND,
 339                              last);
 340 #endif
 341 }
 342
 343 static void
 344 tcp_reass_prepend(struct tcpcb *tp, struct tseg_qent *first, struct mbuf *m, struct tcphdr *th,
 345                   int tlen, struct mbuf *mlast, int lenofoh)
 346 {
 347         int i;
 348
 349 #ifdef TCP_REASS_LOGGING
 350         tcp_log_reassm(tp, first, NULL, th->th_seq, tlen, TCP_R_LOG_PREPEND, 0);
 351 #endif
 352         if (SEQ_GT((th->th_seq + tlen), first->tqe_start)) {
 353                 /* The new data overlaps into the old */
 354                 i = (th->th_seq + tlen) - first->tqe_start;
 355 #ifdef TCP_REASS_LOGGING
 356                 tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 1);
 357 #endif
 358                 m_adj(first->tqe_m, i);
 359                 first->tqe_len -= i;
 360                 first->tqe_start += i;
 361         }
 362         /* Ok now setup our chain to point to the old first */
 363         mlast->m_next = first->tqe_m;
 364         first->tqe_m = m;
 365         first->tqe_len += tlen;
 366         first->tqe_start = th->th_seq;
 367         first->tqe_m->m_pkthdr.len = first->tqe_len;
 368         first->tqe_mbuf_cnt += lenofoh;
 369         tp->t_rcvoopack++;
 370         TCPSTAT_INC(tcps_rcvoopack);
 371         TCPSTAT_ADD(tcps_rcvoobyte, tlen);
 372 #ifdef TCP_REASS_LOGGING
 373         tcp_reass_log_new_in(tp, first->tqe_start, lenofoh, first->tqe_m,
 374                              TCP_R_LOG_PREPEND,
 375                              first);
 376 #endif
 377 }
 378
 379 static void
 380 tcp_reass_replace(struct tcpcb *tp, struct tseg_qent *q, struct mbuf *m,
 381     tcp_seq seq, int len, struct mbuf *mlast, int mbufoh, uint16_t flags)
 382 {
 383         /*
 384          * Free the data in q, and replace
 385          * it with the new segment.
 386          */
 387         int len_dif;
 388
 389 #ifdef TCP_REASS_LOGGING
 390         tcp_log_reassm(tp, q, NULL, seq, len, TCP_R_LOG_REPLACE, 0);
 391 #endif
 392         m_freem(q->tqe_m);
 393         KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
 394                 ("Tp:%p seg queue goes negative", tp));
 395         tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
 396         q->tqe_mbuf_cnt = mbufoh;
 397         q->tqe_m = m;
 398         q->tqe_last = mlast;
 399         q->tqe_start = seq;
 400         if (len > q->tqe_len)
 401                 len_dif = len - q->tqe_len;
 402         else
 403                 len_dif = 0;
 404         tp->t_rcvoopack++;
 405         TCPSTAT_INC(tcps_rcvoopack);
 406         TCPSTAT_ADD(tcps_rcvoobyte, len_dif);
 407         q->tqe_len = len;
 408         q->tqe_flags = (flags & TH_FIN);
 409         q->tqe_m->m_pkthdr.len = q->tqe_len;
 410         tp->t_segqmbuflen += mbufoh;
 411
 412 }
 413
 414 static void
 415 tcp_reass_merge_into(struct tcpcb *tp, struct tseg_qent *ent,
 416     struct tseg_qent *q)
 417 {
 418         /*
 419          * Merge q into ent and free q from the list.
 420          */
 421 #ifdef TCP_REASS_LOGGING
 422         tcp_log_reassm(tp, q, ent, 0, 0, TCP_R_LOG_MERGE_INTO, 0);
 423 #endif
 424 #ifdef TCP_REASS_COUNTERS
 425         counter_u64_add(merge_into, 1);
 426 #endif
 427         ent->tqe_last->m_next = q->tqe_m;
 428         ent->tqe_last = q->tqe_last;
 429         ent->tqe_len += q->tqe_len;
 430         ent->tqe_mbuf_cnt += q->tqe_mbuf_cnt;
 431         ent->tqe_m->m_pkthdr.len += q->tqe_len;
 432         ent->tqe_flags |= (q->tqe_flags & TH_FIN);
 433         TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
 434         uma_zfree(tcp_reass_zone, q);
 435         tp->t_segqlen--;
 436
 437 }
 438
 439 static void
 440 tcp_reass_merge_forward(struct tcpcb *tp, struct tseg_qent *ent)
 441 {
 442         struct tseg_qent *q, *qtmp;
 443         int i;
 444         tcp_seq max;
 445         /*
 446          * Given an entry merge forward anyplace
 447          * that ent overlaps forward.
 448          */
 449
 450         max = ent->tqe_start + ent->tqe_len;
 451         q = TAILQ_NEXT(ent, tqe_q);
 452         if (q == NULL) {
 453                 /* Nothing left */
 454                 return;
 455         }
 456         TAILQ_FOREACH_FROM_SAFE(q, &tp->t_segq, tqe_q, qtmp) {
 457                 if (SEQ_GT(q->tqe_start, max)) {
 458                         /* Beyond q */
 459                         break;
 460                 }
 461                 /* We have some or all that are overlapping */
 462                 if (SEQ_GEQ(max, (q->tqe_start + q->tqe_len))) {
 463                         /* It consumes it all */
 464                         tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
 465                         m_freem(q->tqe_m);
 466                         TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
 467                         uma_zfree(tcp_reass_zone, q);
 468                         tp->t_segqlen--;
 469                         continue;
 470                 }
 471                 /*
 472                  * Trim the q entry to dovetail to this one
 473                  * and then merge q into ent updating max
 474                  * in the process.
 475                  */
 476                 i = max - q->tqe_start;
 477 #ifdef TCP_REASS_LOGGING
 478                 tcp_log_reassm(tp, q, NULL, 0, i, TCP_R_LOG_TRIM, 2);
 479 #endif
 480                 m_adj(q->tqe_m, i);
 481                 q->tqe_len -= i;
 482                 q->tqe_start += i;
 483                 tcp_reass_merge_into(tp, ent, q);
 484                 max = ent->tqe_start + ent->tqe_len;
 485         }
 486 #ifdef TCP_REASS_COUNTERS
 487         counter_u64_add(merge_fwd, 1);
 488 #endif
 489 }
 490
 491 static int
 492 tcp_reass_overhead_of_chain(struct mbuf *m, struct mbuf **mlast)
 493 {
 494         int len = MSIZE;
 495
 496         if (m->m_flags & M_EXT)
 497                 len += m->m_ext.ext_size;
 498         while (m->m_next != NULL) {
 499                 m = m->m_next;
 500                 len += MSIZE;
 501                 if (m->m_flags & M_EXT)
 502                         len += m->m_ext.ext_size;
 503         }
 504         *mlast = m;
 505         return (len);
 506 }
 507
 508 /*
 509  * NOTE!!! the new tcp-reassembly code *must not* use
 510  * m_adj() with a negative index. That alters the chain
 511  * of mbufs (by possibly chopping trailing mbufs). At
 512  * the front of tcp_reass we count the mbuf overhead
 513  * and setup the tail pointer. If we use m_adj(m, -5)
 514  * we could corrupt the tail pointer. Currently the
 515  * code only uses m_adj(m, postive-num). If this
 516  * changes appropriate changes to update mlast would
 517  * be needed.
 518  */
 519 int
 520 tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
 521           int *tlenp, struct mbuf *m)
 522 {
 523         struct tseg_qent *q, *last, *first;
 524         struct tseg_qent *p = NULL;
 525         struct tseg_qent *nq = NULL;
 526         struct tseg_qent *te = NULL;
 527         struct mbuf *mlast = NULL;
 528         struct inpcb *inp = tptoinpcb(tp);
 529         struct socket *so = tptosocket(tp);
 530         struct sockbuf *sb = &so->so_rcv;
 531         char *s = NULL;
 532         int flags, i, lenofoh;
 533
 534         INP_WLOCK_ASSERT(inp);
 535         /*
 536          * XXX: tcp_reass() is rather inefficient with its data structures
 537          * and should be rewritten (see NetBSD for optimizations).
 538          */
 539
 540         KASSERT(th == NULL || (seq_start != NULL && tlenp != NULL),
 541                 ("tcp_reass called with illegal parameter combination "
 542                  "(tp=%p, th=%p, seq_start=%p, tlenp=%p, m=%p)",
 543                  tp, th, seq_start, tlenp, m));
 544         /*
 545          * Call with th==NULL after become established to
 546          * force pre-ESTABLISHED data up to user socket.
 547          */
 548         if (th == NULL)
 549                 goto present;
 550         KASSERT(SEQ_GEQ(th->th_seq, tp->rcv_nxt),
 551                 ("Attempt to add old entry to reassembly queue (th=%p, tp=%p)",
 552                  th, tp));
 553 #ifdef TCP_REASS_LOGGING
 554         tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_ADD, NULL);
 555 #endif
 556 #ifdef TCP_REASS_COUNTERS
 557         counter_u64_add(reass_entry, 1);
 558 #endif
 559         /*
 560          * Check for zero length data.
 561          */
 562         if ((*tlenp == 0) && ((tcp_get_flags(th) & TH_FIN) == 0)) {
 563                 /*
 564                  * A zero length segment does no
 565                  * one any good. We could check
 566                  * the rcv_nxt <-> rcv_wnd but thats
 567                  * already done for us by the caller.
 568                  */
 569 strip_fin:
 570 #ifdef TCP_REASS_COUNTERS
 571                 counter_u64_add(tcp_zero_input, 1);
 572 #endif
 573                 m_freem(m);
 574 #ifdef TCP_REASS_LOGGING
 575                 tcp_reass_log_dump(tp);
 576 #endif
 577                 return (0);
 578         } else if ((*tlenp == 0) &&
 579                    (tcp_get_flags(th) & TH_FIN) &&
 580                    !TCPS_HAVEESTABLISHED(tp->t_state)) {
 581                 /*
 582                  * We have not established, and we
 583                  * have a FIN and no data. Lets treat
 584                  * this as the same as if the FIN were
 585                  * not present. We don't want to save
 586                  * the FIN bit in a reassembly buffer
 587                  * we want to get established first before
 588                  * we do that (the peer will retransmit).
 589                  */
 590                 goto strip_fin;
 591         }
 592         /*
 593          * Will it fit?
 594          */
 595         lenofoh = tcp_reass_overhead_of_chain(m, &mlast);
 596         if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
 597             (sb->sb_mbcnt + tp->t_segqmbuflen + lenofoh) > sb->sb_mbmax) {
 598                 /* No room */
 599                 TCPSTAT_INC(tcps_rcvreassfull);
 600 #ifdef TCP_REASS_COUNTERS
 601                 counter_u64_add(reass_nospace, 1);
 602 #endif
 603 #ifdef TCP_REASS_LOGGING
 604                 tcp_log_reassm(tp, NULL, NULL, th->th_seq, lenofoh, TCP_R_LOG_LIMIT_REACHED, 0);
 605 #endif
 606                 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
 607                         log(LOG_DEBUG, "%s; %s: mbuf count limit reached, "
 608                             "segment dropped\n", s, __func__);
 609                         free(s, M_TCPLOG);
 610                 }
 611                 m_freem(m);
 612                 *tlenp = 0;
 613 #ifdef TCP_REASS_LOGGING
 614                 tcp_reass_log_dump(tp);
 615 #endif
 616                 return (0);
 617         }
 618         /*
 619          * First lets deal with two common cases, the
 620          * segment appends to the back of our collected
 621          * segments. Or the segment is the next in line.
 622          */
 623         last = TAILQ_LAST_FAST(&tp->t_segq, tseg_qent, tqe_q);
 624         if (last != NULL) {
 625                 if ((tcp_get_flags(th) & TH_FIN) &&
 626                     SEQ_LT((th->th_seq + *tlenp), (last->tqe_start + last->tqe_len))) {
 627                         /*
 628                          * Someone is trying to game us, dump
 629                          * the segment.
 630                          */
 631                         *tlenp = 0;
 632                         m_freem(m);
 633                         return (0);
 634                 }
 635                 if ((SEQ_GEQ(th->th_seq, last->tqe_start)) &&
 636                     (SEQ_GEQ((last->tqe_start + last->tqe_len), th->th_seq))) {
 637                         /* Common case, trailing segment is added */
 638                         /**
 639                          *                                 +--last
 640                          *                                 v
 641                          *  reassembly buffer |---|  |---| |---|
 642                          *  new segment                       |---|
 643                          */
 644 #ifdef TCP_REASS_COUNTERS
 645                         counter_u64_add(reass_path1, 1);
 646 #endif
 647                         if (SEQ_GT((last->tqe_start + last->tqe_len), th->th_seq)) {
 648                                 i = (last->tqe_start + last->tqe_len) - th->th_seq;
 649                                 if (i < *tlenp) {
 650 #ifdef TCP_REASS_LOGGING
 651                                         tcp_log_reassm(tp, last, NULL, 0, i, TCP_R_LOG_TRIM, 3);
 652                                         th->th_seq += i;
 653 #endif
 654                                         m_adj(m, i);
 655                                         *tlenp -= i;
 656                                 } else {
 657                                         /* Complete overlap */
 658                                         TCPSTAT_INC(tcps_rcvduppack);
 659                                         TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 660                                         m_freem(m);
 661                                         *tlenp = last->tqe_len;
 662                                         *seq_start = last->tqe_start;
 663                                         return (0);
 664                                 }
 665                         }
 666                         if (last->tqe_flags & TH_FIN) {
 667                                 /*
 668                                  * We have data after the FIN on the last?
 669                                  */
 670                                 *tlenp = 0;
 671                                 m_freem(m);
 672                                 return(0);
 673                         }
 674                         tcp_reass_append(tp, last, m, th, *tlenp, mlast, lenofoh);
 675                         tp->t_segqmbuflen += lenofoh;
 676                         *seq_start = last->tqe_start;
 677                         *tlenp = last->tqe_len;
 678                         return (0);
 679                 } else if (SEQ_GT(th->th_seq, (last->tqe_start + last->tqe_len))) {
 680                         /*
 681                          * Second common case, we missed
 682                          * another one and have something more
 683                          * for the end.
 684                          */
 685                         /**
 686                          *                                 +--last
 687                          *                                 v
 688                          *  reassembly buffer |---|  |---| |---|
 689                          *  new segment                           |---|
 690                          */
 691                         if (last->tqe_flags & TH_FIN) {
 692                                 /*
 693                                  * We have data after the FIN on the last?
 694                                  */
 695                                 *tlenp = 0;
 696                                 m_freem(m);
 697                                 return(0);
 698                         }
 699 #ifdef TCP_REASS_COUNTERS
 700                         counter_u64_add(reass_path2, 1);
 701 #endif
 702                         p = last;
 703                         goto new_entry;
 704                 }
 705         } else {
 706                 /* First segment (it's NULL). */
 707                 goto new_entry;
 708         }
 709         first = TAILQ_FIRST(&tp->t_segq);
 710         if (SEQ_LT(th->th_seq, first->tqe_start) &&
 711             SEQ_GEQ((th->th_seq + *tlenp),first->tqe_start) &&
 712             SEQ_LT((th->th_seq + *tlenp), (first->tqe_start + first->tqe_len))) {
 713                 /*
 714                  * The head of the queue is prepended by this and
 715                  * it may be the one I want most.
 716                  */
 717                 /**
 718                  *       first-------+
 719                  *                   v
 720                  *  rea:             |---|  |---| |---|
 721                  *  new:         |---|
 722                  * Note the case we do not deal with here is:
 723                  *   rea=     |---|   |---|   |---|
 724                  *   new=  |----|
 725                  * Due to the fact that it could be
 726                  *   new   |--------------------|
 727                  * And we might need to merge forward.
 728                  */
 729 #ifdef INVARIANTS
 730                 struct mbuf *firstmbuf;
 731 #endif
 732
 733 #ifdef TCP_REASS_COUNTERS
 734                 counter_u64_add(reass_path3, 1);
 735 #endif
 736                 if (SEQ_LT(th->th_seq, tp->rcv_nxt)) {
 737                         /*
 738                          * The resend was even before
 739                          * what we have. We need to trim it.
 740                          * Note TSNH (it should be trimmed
 741                          * before the call to tcp_reass()).
 742                          */
 743 #ifdef INVARIANTS
 744                         panic("th->th_seq:%u rcv_nxt:%u tp:%p not pre-trimmed",
 745                               th->th_seq, tp->rcv_nxt, tp);
 746 #else
 747                         i = tp->rcv_nxt - th->th_seq;
 748 #ifdef TCP_REASS_LOGGING
 749                         tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 4);
 750 #endif
 751                         m_adj(m, i);
 752                         th->th_seq += i;
 753                         *tlenp -= i;
 754 #endif
 755                 }
 756 #ifdef INVARIANTS
 757                 firstmbuf = first->tqe_m;
 758 #endif
 759                 tcp_reass_prepend(tp, first, m, th, *tlenp, mlast, lenofoh);
 760 #ifdef INVARIANTS
 761                 if (firstmbuf == first->tqe_m) {
 762                         panic("First stayed same m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
 763                               m, firstmbuf, first->tqe_m, tp, first);
 764                 } else if (first->tqe_m != m) {
 765                         panic("First did not change to m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
 766                               m, firstmbuf, first->tqe_m, tp, first);
 767                 }
 768 #endif
 769                 tp->t_segqmbuflen += lenofoh;
 770                 *seq_start = first->tqe_start;
 771                 *tlenp = first->tqe_len;
 772                 goto present;
 773         } else if (SEQ_LT((th->th_seq + *tlenp), first->tqe_start)) {
 774                 /* New segment is before our earliest segment. */
 775                 /**
 776                  *           first---->+
 777                  *                      v
 778                  *  rea=                |---| ....
 779                  *  new"         |---|
 780                  *
 781                  */
 782                 goto new_entry;
 783         }
 784         /*
 785          * Find a segment which begins after this one does.
 786          */
 787 #ifdef TCP_REASS_COUNTERS
 788         counter_u64_add(reass_fullwalk, 1);
 789 #endif
 790         TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
 791                 if (SEQ_GT(q->tqe_start, th->th_seq))
 792                         break;
 793         }
 794         p = TAILQ_PREV(q, tsegqe_head, tqe_q);
 795         /**
 796          * Now is this fit just in-between only?
 797          * i.e.:
 798          *      p---+        +----q
 799          *          v        v
 800          *     res= |--|     |--|    |--|
 801          *     nee       |-|
 802          */
 803         if (SEQ_LT((th->th_seq + *tlenp), q->tqe_start) &&
 804             ((p == NULL) || (SEQ_GT(th->th_seq, (p->tqe_start + p->tqe_len))))) {
 805                 /* Yep no overlap */
 806                 goto new_entry;
 807         }
 808         /**
 809          * If we reach here we have some (possibly all) overlap
 810          * such as:
 811          *     res=     |--|     |--|    |--|
 812          *     new=  |----|
 813          * or  new=  |-----------------|
 814          * or  new=      |--------|
 815          * or  new=            |---|
 816          * or  new=            |-----------|
 817          */
 818         if ((p != NULL) &&
 819             (SEQ_LEQ(th->th_seq, (p->tqe_start + p->tqe_len)))) {
 820                 /* conversion to int (in i) handles seq wraparound */
 821
 822 #ifdef TCP_REASS_COUNTERS
 823                 counter_u64_add(reass_path4, 1);
 824 #endif
 825                 i = p->tqe_start + p->tqe_len - th->th_seq;
 826                 if (i >= 0) {
 827                         if (i >= *tlenp) {
 828                                 /**
 829                                  *       prev seg---->+
 830                                  *                    v
 831                                  *  reassembly buffer |---|
 832                                  *  new segment        |-|
 833                                  */
 834                                 TCPSTAT_INC(tcps_rcvduppack);
 835                                 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 836                                 *tlenp = p->tqe_len;
 837                                 *seq_start = p->tqe_start;
 838                                 m_freem(m);
 839                                 /*
 840                                  * Try to present any queued data
 841                                  * at the left window edge to the user.
 842                                  * This is needed after the 3-WHS
 843                                  * completes. Note this probably
 844                                  * will not work and we will return.
 845                                  */
 846                                 return (0);
 847                         }
 848                         if (i > 0) {
 849                                 /**
 850                                  *       prev seg---->+
 851                                  *                    v
 852                                  *  reassembly buffer |---|
 853                                  *  new segment         |-----|
 854                                  */
 855 #ifdef TCP_REASS_COUNTERS
 856                                 counter_u64_add(reass_path5, 1);
 857 #endif
 858 #ifdef TCP_REASS_LOGGING
 859                                 tcp_log_reassm(tp, p, NULL, 0, i, TCP_R_LOG_TRIM, 5);
 860 #endif
 861                                 m_adj(m, i);
 862                                 *tlenp -= i;
 863                                 th->th_seq += i;
 864                         }
 865                 }
 866                 if (th->th_seq == (p->tqe_start + p->tqe_len)) {
 867                         /*
 868                          * If dovetails in with this one
 869                          * append it.
 870                          */
 871                         /**
 872                          *       prev seg---->+
 873                          *                    v
 874                          *  reassembly buffer |--|     |---|
 875                          *  new segment          |--|
 876                          * (note: it was trimmed above if it overlapped)
 877                          */
 878                         tcp_reass_append(tp, p, m, th, *tlenp, mlast, lenofoh);
 879                         tp->t_segqmbuflen += lenofoh;
 880                 } else {
 881 #ifdef INVARIANTS
 882                         panic("Impossible cut th_seq:%u p->seq:%u(%d) p:%p tp:%p",
 883                               th->th_seq, p->tqe_start, p->tqe_len,
 884                               p, tp);
 885 #endif
 886                         *tlenp = 0;
 887                         m_freem(m);
 888                         return (0);
 889                 }
 890                 q = p;
 891         } else {
 892                 /*
 893                  * The new data runs over the
 894                  * top of previously sack'd data (in q).
 895                  * It may be partially overlapping, or
 896                  * it may overlap the entire segment.
 897                  */
 898 #ifdef TCP_REASS_COUNTERS
 899                 counter_u64_add(reass_path6, 1);
 900 #endif
 901                 if (SEQ_GEQ((th->th_seq + *tlenp), (q->tqe_start + q->tqe_len))) {
 902                         /* It consumes it all */
 903                         /**
 904                          *             next seg---->+
 905                          *                          v
 906                          *  reassembly buffer |--|     |---|
 907                          *  new segment              |----------|
 908                          */
 909 #ifdef TCP_REASS_COUNTERS
 910                         counter_u64_add(reass_path7, 1);
 911 #endif
 912                         tcp_reass_replace(tp, q, m, th->th_seq, *tlenp, mlast, lenofoh, tcp_get_flags(th));
 913                 } else {
 914                         /*
 915                          * We just need to prepend the data
 916                          * to this. It does not overrun
 917                          * the end.
 918                          */
 919                         /**
 920                          *                next seg---->+
 921                          *                             v
 922                          *  reassembly buffer |--|     |---|
 923                          *  new segment                   |----------|
 924                          */
 925                         tcp_reass_prepend(tp, q, m, th, *tlenp, mlast, lenofoh);
 926                         tp->t_segqmbuflen += lenofoh;
 927                 }
 928         }
 929         /* Now does it go further than that? */
 930         tcp_reass_merge_forward(tp, q);
 931         *seq_start = q->tqe_start;
 932         *tlenp = q->tqe_len;
 933         goto present;
 934
 935         /*
 936          * When we reach here we can't combine it
 937          * with any existing segment.
 938          *
 939          * Limit the number of segments that can be queued to reduce the
 940          * potential for mbuf exhaustion. For best performance, we want to be
 941          * able to queue a full window's worth of segments. The size of the
 942          * socket receive buffer determines our advertised window and grows
 943          * automatically when socket buffer autotuning is enabled. Use it as the
 944          * basis for our queue limit.
 945          *
 946          * However, allow the user to specify a ceiling for the number of
 947          * segments in each queue.
 948          *
 949          * Always let the missing segment through which caused this queue.
 950          * NB: Access to the socket buffer is left intentionally unlocked as we
 951          * can tolerate stale information here.
 952          *
 953          * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
 954          * should work but causes packets to be dropped when they shouldn't.
 955          * Investigate why and re-evaluate the below limit after the behaviour
 956          * is understood.
 957          */
 958 new_entry:
 959         if (th->th_seq == tp->rcv_nxt && TCPS_HAVEESTABLISHED(tp->t_state)) {
 960                 tp->rcv_nxt += *tlenp;
 961                 flags = tcp_get_flags(th) & TH_FIN;
 962                 TCPSTAT_INC(tcps_rcvoopack);
 963                 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
 964                 SOCKBUF_LOCK(&so->so_rcv);
 965                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
 966                         m_freem(m);
 967                 } else {
 968                         sbappendstream_locked(&so->so_rcv, m, 0);
 969                 }
 970                 tp->t_flags |= TF_WAKESOR;
 971                 return (flags);
 972         }
 973         if (tcp_new_limits) {
 974                 if ((tp->t_segqlen > tcp_reass_queue_guard) &&
 975                     (*tlenp < MSIZE)) {
 976                         /*
 977                          * This is really a lie, we are not full but
 978                          * are getting a segment that is above
 979                          * guard threshold. If it is and its below
 980                          * a mbuf size (256) we drop it if it
 981                          * can't fill in some place.
 982                          */
 983                         TCPSTAT_INC(tcps_rcvreassfull);
 984                         *tlenp = 0;
 985                         if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
 986                                 log(LOG_DEBUG, "%s; %s: queue limit reached, "
 987                                     "segment dropped\n", s, __func__);
 988                                 free(s, M_TCPLOG);
 989                         }
 990                         m_freem(m);
 991 #ifdef TCP_REASS_LOGGING
 992                         tcp_reass_log_dump(tp);
 993 #endif
 994                         return (0);
 995                 }
 996         } else {
 997                 if (tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1,
 998                                          tcp_reass_maxqueuelen)) {
 999                         TCPSTAT_INC(tcps_rcvreassfull);
1000                         *tlenp = 0;
1001                         if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
1002                                 log(LOG_DEBUG, "%s; %s: queue limit reached, "
1003                                     "segment dropped\n", s, __func__);
1004                                 free(s, M_TCPLOG);
1005                         }
1006                         m_freem(m);
1007 #ifdef TCP_REASS_LOGGING
1008                         tcp_reass_log_dump(tp);
1009 #endif
1010                         return (0);
1011                 }
1012         }
1013         /*
1014          * Allocate a new queue entry. If we can't, or hit the zone limit
1015          * just drop the pkt.
1016          */
1017         te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
1018         if (te == NULL) {
1019                 TCPSTAT_INC(tcps_rcvmemdrop);
1020                 m_freem(m);
1021                 *tlenp = 0;
1022                 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
1023                         log(LOG_DEBUG, "%s; %s: global zone limit "
1024                             "reached, segment dropped\n", s, __func__);
1025                         free(s, M_TCPLOG);
1026                 }
1027                 return (0);
1028         }
1029         tp->t_segqlen++;
1030         tp->t_rcvoopack++;
1031         TCPSTAT_INC(tcps_rcvoopack);
1032         TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
1033         /* Insert the new segment queue entry into place. */
1034         te->tqe_m = m;
1035         te->tqe_flags = tcp_get_flags(th);
1036         te->tqe_len = *tlenp;
1037         te->tqe_start = th->th_seq;
1038         te->tqe_last = mlast;
1039         te->tqe_mbuf_cnt = lenofoh;
1040         tp->t_segqmbuflen += te->tqe_mbuf_cnt;
1041         if (p == NULL) {
1042                 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q);
1043         } else {
1044                 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q);
1045         }
1046 #ifdef TCP_REASS_LOGGING
1047         tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_NEW_ENTRY, te);
1048 #endif
1049 present:
1050         /*
1051          * Present data to user, advancing rcv_nxt through
1052          * completed sequence space.
1053          */
1054         if (!TCPS_HAVEESTABLISHED(tp->t_state))
1055                 return (0);
1056         q = TAILQ_FIRST(&tp->t_segq);
1057         KASSERT(q == NULL || SEQ_GEQ(q->tqe_start, tp->rcv_nxt),
1058                 ("Reassembly queue for %p has stale entry at head", tp));
1059         if (!q || q->tqe_start != tp->rcv_nxt) {
1060 #ifdef TCP_REASS_LOGGING
1061                 tcp_reass_log_dump(tp);
1062 #endif
1063                 return (0);
1064         }
1065         SOCKBUF_LOCK(&so->so_rcv);
1066         do {
1067                 tp->rcv_nxt += q->tqe_len;
1068                 flags = q->tqe_flags & TH_FIN;
1069                 nq = TAILQ_NEXT(q, tqe_q);
1070                 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
1071                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1072                         m_freem(q->tqe_m);
1073                 } else {
1074 #ifdef TCP_REASS_LOGGING
1075                         tcp_reass_log_new_in(tp, q->tqe_start, q->tqe_len, q->tqe_m, TCP_R_LOG_READ, q);
1076                         if (th != NULL) {
1077                                 tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 1);
1078                         } else {
1079                                 tcp_log_reassm(tp, q, NULL, 0, 0, TCP_R_LOG_READ, 1);
1080                         }
1081 #endif
1082                         sbappendstream_locked(&so->so_rcv, q->tqe_m, 0);
1083                 }
1084 #ifdef TCP_REASS_LOGGING
1085                 if (th != NULL) {
1086                         tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 2);
1087                 } else {
1088                         tcp_log_reassm(tp, q, NULL, 0, 0, TCP_R_LOG_READ, 2);
1089                 }
1090 #endif
1091                 KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
1092                         ("tp:%p seg queue goes negative", tp));
1093                 tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
1094                 uma_zfree(tcp_reass_zone, q);
1095                 tp->t_segqlen--;
1096                 q = nq;
1097         } while (q && q->tqe_start == tp->rcv_nxt);
1098         if (TAILQ_EMPTY(&tp->t_segq) &&
1099             (tp->t_segqmbuflen != 0)) {
1100 #ifdef INVARIANTS
1101                 panic("tp:%p segq:%p len:%d queue empty",
1102                       tp, &tp->t_segq, tp->t_segqmbuflen);
1103 #else
1104 #ifdef TCP_REASS_LOGGING
1105                 if (th != NULL) {
1106                         tcp_log_reassm(tp, NULL, NULL, th->th_seq, *tlenp, TCP_R_LOG_ZERO, 0);
1107                 } else {
1108                         tcp_log_reassm(tp, NULL, NULL, 0, 0, TCP_R_LOG_ZERO, 0);
1109                 }
1110 #endif
1111                 tp->t_segqmbuflen = 0;
1112 #endif
1113         }
1114 #ifdef TCP_REASS_LOGGING
1115         tcp_reass_log_dump(tp);
1116 #endif
1117         tp->t_flags |= TF_WAKESOR;
1118         return (flags);
1119 }