sys/netinet/tcp_reass.c

   1 /*-
   2  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
  30  */
  31
  32 #include <sys/cdefs.h>
  33 __FBSDID("$FreeBSD$");
  34
  35 #include "opt_inet.h"
  36 #include "opt_inet6.h"
  37 #include "opt_tcpdebug.h"
  38
  39 #include <sys/param.h>
  40 #include <sys/kernel.h>
  41 #include <sys/eventhandler.h>
  42 #include <sys/malloc.h>
  43 #include <sys/mbuf.h>
  44 #include <sys/socket.h>
  45 #include <sys/socketvar.h>
  46 #include <sys/sysctl.h>
  47 #include <sys/syslog.h>
  48 #include <sys/systm.h>
  49
  50 #include <vm/uma.h>
  51
  52 #include <net/if.h>
  53 #include <net/if_var.h>
  54 #include <net/route.h>
  55 #include <net/vnet.h>
  56
  57 #include <netinet/in.h>
  58 #include <netinet/in_pcb.h>
  59 #include <netinet/in_systm.h>
  60 #include <netinet/in_var.h>
  61 #include <netinet/ip.h>
  62 #include <netinet/ip_var.h>
  63 #include <netinet/ip_options.h>
  64 #include <netinet/ip6.h>
  65 #include <netinet6/in6_pcb.h>
  66 #include <netinet6/ip6_var.h>
  67 #include <netinet6/nd6.h>
  68 #include <netinet/tcp.h>
  69 #include <netinet/tcp_fsm.h>
  70 #include <netinet/tcp_seq.h>
  71 #include <netinet/tcp_timer.h>
  72 #include <netinet/tcp_var.h>
  73 #include <netinet6/tcp6_var.h>
  74 #include <netinet/tcpip.h>
  75 #ifdef TCPDEBUG
  76 #include <netinet/tcp_debug.h>
  77 #endif /* TCPDEBUG */
  78
  79 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
  80     "TCP Segment Reassembly Queue");
  81
  82 static int tcp_reass_maxseg = 0;
  83 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
  84     &tcp_reass_maxseg, 0,
  85     "Global maximum number of TCP Segments in Reassembly Queue");
  86
  87 static uma_zone_t tcp_reass_zone;
  88 SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, 0,
  89     &tcp_reass_zone,
  90     "Global number of TCP Segments currently in Reassembly Queue");
  91
  92 /* Initialize TCP reassembly queue */
  93 static void
  94 tcp_reass_zone_change(void *tag)
  95 {
  96
  97         /* Set the zone limit and read back the effective value. */
  98         tcp_reass_maxseg = nmbclusters / 16;
  99         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 100             tcp_reass_maxseg);
 101 }
 102
 103 void
 104 tcp_reass_global_init(void)
 105 {
 106
 107         tcp_reass_maxseg = nmbclusters / 16;
 108         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
 109             &tcp_reass_maxseg);
 110         tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
 111             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
 112         /* Set the zone limit and read back the effective value. */
 113         tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
 114             tcp_reass_maxseg);
 115         EVENTHANDLER_REGISTER(nmbclusters_change,
 116             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 117 }
 118
 119 void
 120 tcp_reass_flush(struct tcpcb *tp)
 121 {
 122         struct tseg_qent *qe;
 123
 124         INP_WLOCK_ASSERT(tp->t_inpcb);
 125
 126         while ((qe = LIST_FIRST(&tp->t_segq)) != NULL) {
 127                 LIST_REMOVE(qe, tqe_q);
 128                 m_freem(qe->tqe_m);
 129                 uma_zfree(tcp_reass_zone, qe);
 130                 tp->t_segqlen--;
 131         }
 132
 133         KASSERT((tp->t_segqlen == 0),
 134             ("TCP reass queue %p segment count is %d instead of 0 after flush.",
 135             tp, tp->t_segqlen));
 136 }
 137
 138 int
 139 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
 140 {
 141         struct tseg_qent *q;
 142         struct tseg_qent *p = NULL;
 143         struct tseg_qent *nq;
 144         struct tseg_qent *te = NULL;
 145         struct socket *so = tp->t_inpcb->inp_socket;
 146         char *s = NULL;
 147         int flags;
 148         struct tseg_qent tqs;
 149
 150         INP_WLOCK_ASSERT(tp->t_inpcb);
 151
 152         /*
 153          * XXX: tcp_reass() is rather inefficient with its data structures
 154          * and should be rewritten (see NetBSD for optimizations).
 155          */
 156
 157         /*
 158          * Call with th==NULL after become established to
 159          * force pre-ESTABLISHED data up to user socket.
 160          */
 161         if (th == NULL)
 162                 goto present;
 163
 164         /*
 165          * Limit the number of segments that can be queued to reduce the
 166          * potential for mbuf exhaustion. For best performance, we want to be
 167          * able to queue a full window's worth of segments. The size of the
 168          * socket receive buffer determines our advertised window and grows
 169          * automatically when socket buffer autotuning is enabled. Use it as the
 170          * basis for our queue limit.
 171          * Always let the missing segment through which caused this queue.
 172          * NB: Access to the socket buffer is left intentionally unlocked as we
 173          * can tolerate stale information here.
 174          *
 175          * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
 176          * should work but causes packets to be dropped when they shouldn't.
 177          * Investigate why and re-evaluate the below limit after the behaviour
 178          * is understood.
 179          */
 180         if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
 181             tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) {
 182                 TCPSTAT_INC(tcps_rcvreassfull);
 183                 *tlenp = 0;
 184                 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
 185                         log(LOG_DEBUG, "%s; %s: queue limit reached, "
 186                             "segment dropped\n", s, __func__);
 187                         free(s, M_TCPLOG);
 188                 }
 189                 m_freem(m);
 190                 return (0);
 191         }
 192
 193         /*
 194          * Allocate a new queue entry. If we can't, or hit the zone limit
 195          * just drop the pkt.
 196          *
 197          * Use a temporary structure on the stack for the missing segment
 198          * when the zone is exhausted. Otherwise we may get stuck.
 199          */
 200         te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
 201         if (te == NULL) {
 202                 if (th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) {
 203                         TCPSTAT_INC(tcps_rcvmemdrop);
 204                         m_freem(m);
 205                         *tlenp = 0;
 206                         if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
 207                             NULL))) {
 208                                 log(LOG_DEBUG, "%s; %s: global zone limit "
 209                                     "reached, segment dropped\n", s, __func__);
 210                                 free(s, M_TCPLOG);
 211                         }
 212                         return (0);
 213                 } else {
 214                         bzero(&tqs, sizeof(struct tseg_qent));
 215                         te = &tqs;
 216                         if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
 217                             NULL))) {
 218                                 log(LOG_DEBUG,
 219                                     "%s; %s: global zone limit reached, using "
 220                                     "stack for missing segment\n", s, __func__);
 221                                 free(s, M_TCPLOG);
 222                         }
 223                 }
 224         }
 225         tp->t_segqlen++;
 226
 227         /*
 228          * Find a segment which begins after this one does.
 229          */
 230         LIST_FOREACH(q, &tp->t_segq, tqe_q) {
 231                 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
 232                         break;
 233                 p = q;
 234         }
 235
 236         /*
 237          * If there is a preceding segment, it may provide some of
 238          * our data already.  If so, drop the data from the incoming
 239          * segment.  If it provides all of our data, drop us.
 240          */
 241         if (p != NULL) {
 242                 int i;
 243                 /* conversion to int (in i) handles seq wraparound */
 244                 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
 245                 if (i > 0) {
 246                         if (i >= *tlenp) {
 247                                 TCPSTAT_INC(tcps_rcvduppack);
 248                                 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 249                                 m_freem(m);
 250                                 if (te != &tqs)
 251                                         uma_zfree(tcp_reass_zone, te);
 252                                 tp->t_segqlen--;
 253                                 /*
 254                                  * Try to present any queued data
 255                                  * at the left window edge to the user.
 256                                  * This is needed after the 3-WHS
 257                                  * completes.
 258                                  */
 259                                 goto present;   /* ??? */
 260                         }
 261                         m_adj(m, i);
 262                         *tlenp -= i;
 263                         th->th_seq += i;
 264                 }
 265         }
 266         tp->t_rcvoopack++;
 267         TCPSTAT_INC(tcps_rcvoopack);
 268         TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
 269
 270         /*
 271          * While we overlap succeeding segments trim them or,
 272          * if they are completely covered, dequeue them.
 273          */
 274         while (q) {
 275                 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
 276                 if (i <= 0)
 277                         break;
 278                 if (i < q->tqe_len) {
 279                         q->tqe_th->th_seq += i;
 280                         q->tqe_len -= i;
 281                         m_adj(q->tqe_m, i);
 282                         break;
 283                 }
 284
 285                 nq = LIST_NEXT(q, tqe_q);
 286                 LIST_REMOVE(q, tqe_q);
 287                 m_freem(q->tqe_m);
 288                 uma_zfree(tcp_reass_zone, q);
 289                 tp->t_segqlen--;
 290                 q = nq;
 291         }
 292
 293         /* Insert the new segment queue entry into place. */
 294         te->tqe_m = m;
 295         te->tqe_th = th;
 296         te->tqe_len = *tlenp;
 297
 298         if (p == NULL) {
 299                 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
 300         } else {
 301                 KASSERT(te != &tqs, ("%s: temporary stack based entry not "
 302                     "first element in queue", __func__));
 303                 LIST_INSERT_AFTER(p, te, tqe_q);
 304         }
 305
 306 present:
 307         /*
 308          * Present data to user, advancing rcv_nxt through
 309          * completed sequence space.
 310          */
 311         if (!TCPS_HAVEESTABLISHED(tp->t_state))
 312                 return (0);
 313         q = LIST_FIRST(&tp->t_segq);
 314         if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
 315                 return (0);
 316         SOCKBUF_LOCK(&so->so_rcv);
 317         do {
 318                 tp->rcv_nxt += q->tqe_len;
 319                 flags = q->tqe_th->th_flags & TH_FIN;
 320                 nq = LIST_NEXT(q, tqe_q);
 321                 LIST_REMOVE(q, tqe_q);
 322                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
 323                         m_freem(q->tqe_m);
 324                 else
 325                         sbappendstream_locked(&so->so_rcv, q->tqe_m, 0);
 326                 if (q != &tqs)
 327                         uma_zfree(tcp_reass_zone, q);
 328                 tp->t_segqlen--;
 329                 q = nq;
 330         } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
 331         sorwakeup_locked(so);
 332         return (flags);
 333 }