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  * $FreeBSD$
  31  */
  32
  33 #include "opt_inet.h"
  34 #include "opt_inet6.h"
  35 #include "opt_tcpdebug.h"
  36
  37 #include <sys/param.h>
  38 #include <sys/kernel.h>
  39 #include <sys/malloc.h>
  40 #include <sys/mbuf.h>
  41 #include <sys/socket.h>
  42 #include <sys/socketvar.h>
  43 #include <sys/sysctl.h>
  44 #include <sys/syslog.h>
  45 #include <sys/systm.h>
  46
  47 #include <vm/uma.h>
  48
  49 #include <net/if.h>
  50 #include <net/route.h>
  51
  52 #include <netinet/in.h>
  53 #include <netinet/in_pcb.h>
  54 #include <netinet/in_systm.h>
  55 #include <netinet/in_var.h>
  56 #include <netinet/ip.h>
  57 #include <netinet/ip_var.h>
  58 #include <netinet/ip_options.h>
  59 #include <netinet/ip6.h>
  60 #include <netinet6/in6_pcb.h>
  61 #include <netinet6/ip6_var.h>
  62 #include <netinet6/nd6.h>
  63 #include <netinet/tcp.h>
  64 #include <netinet/tcp_fsm.h>
  65 #include <netinet/tcp_seq.h>
  66 #include <netinet/tcp_timer.h>
  67 #include <netinet/tcp_var.h>
  68 #include <netinet6/tcp6_var.h>
  69 #include <netinet/tcpip.h>
  70 #ifdef TCPDEBUG
  71 #include <netinet/tcp_debug.h>
  72 #endif /* TCPDEBUG */
  73
  74 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
  75     "TCP Segment Reassembly Queue");
  76
  77 static int tcp_reass_maxseg = 0;
  78 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
  79     &tcp_reass_maxseg, 0,
  80     "Global maximum number of TCP Segments in Reassembly Queue");
  81
  82 int tcp_reass_qsize = 0;
  83 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
  84     &tcp_reass_qsize, 0,
  85     "Global number of TCP Segments currently in Reassembly Queue");
  86
  87 static int tcp_reass_maxqlen = 48;
  88 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW,
  89     &tcp_reass_maxqlen, 0,
  90     "Maximum number of TCP Segments per individual Reassembly Queue");
  91
  92 static int tcp_reass_overflows = 0;
  93 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
  94     &tcp_reass_overflows, 0,
  95     "Global number of TCP Segment Reassembly Queue Overflows");
  96
  97 /* Initialize TCP reassembly queue */
  98 static void
  99 tcp_reass_zone_change(void *tag)
 100 {
 101
 102         tcp_reass_maxseg = nmbclusters / 16;
 103         uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
 104 }
 105
 106 uma_zone_t      tcp_reass_zone;
 107
 108 void
 109 tcp_reass_init(void)
 110 {
 111
 112         tcp_reass_maxseg = nmbclusters / 16;
 113         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
 114             &tcp_reass_maxseg);
 115         tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
 116             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
 117         uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
 118         EVENTHANDLER_REGISTER(nmbclusters_change,
 119             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 120 }
 121
 122 int
 123 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
 124 {
 125         struct tseg_qent *q;
 126         struct tseg_qent *p = NULL;
 127         struct tseg_qent *nq;
 128         struct tseg_qent *te = NULL;
 129         struct socket *so = tp->t_inpcb->inp_socket;
 130         int flags;
 131
 132         INP_LOCK_ASSERT(tp->t_inpcb);
 133
 134         /*
 135          * XXX: tcp_reass() is rather inefficient with its data structures
 136          * and should be rewritten (see NetBSD for optimizations).  While
 137          * doing that it should move to its own file tcp_reass.c.
 138          */
 139
 140         /*
 141          * Call with th==NULL after become established to
 142          * force pre-ESTABLISHED data up to user socket.
 143          */
 144         if (th == NULL)
 145                 goto present;
 146
 147         /*
 148          * Limit the number of segments in the reassembly queue to prevent
 149          * holding on to too many segments (and thus running out of mbufs).
 150          * Make sure to let the missing segment through which caused this
 151          * queue.  Always keep one global queue entry spare to be able to
 152          * process the missing segment.
 153          */
 154         if (th->th_seq != tp->rcv_nxt &&
 155             (tcp_reass_qsize + 1 >= tcp_reass_maxseg ||
 156              tp->t_segqlen >= tcp_reass_maxqlen)) {
 157                 tcp_reass_overflows++;
 158                 tcpstat.tcps_rcvmemdrop++;
 159                 m_freem(m);
 160                 *tlenp = 0;
 161                 return (0);
 162         }
 163
 164         /*
 165          * Allocate a new queue entry. If we can't, or hit the zone limit
 166          * just drop the pkt.
 167          */
 168         te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
 169         if (te == NULL) {
 170                 tcpstat.tcps_rcvmemdrop++;
 171                 m_freem(m);
 172                 *tlenp = 0;
 173                 return (0);
 174         }
 175         tp->t_segqlen++;
 176         tcp_reass_qsize++;
 177
 178         /*
 179          * Find a segment which begins after this one does.
 180          */
 181         LIST_FOREACH(q, &tp->t_segq, tqe_q) {
 182                 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
 183                         break;
 184                 p = q;
 185         }
 186
 187         /*
 188          * If there is a preceding segment, it may provide some of
 189          * our data already.  If so, drop the data from the incoming
 190          * segment.  If it provides all of our data, drop us.
 191          */
 192         if (p != NULL) {
 193                 int i;
 194                 /* conversion to int (in i) handles seq wraparound */
 195                 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
 196                 if (i > 0) {
 197                         if (i >= *tlenp) {
 198                                 tcpstat.tcps_rcvduppack++;
 199                                 tcpstat.tcps_rcvdupbyte += *tlenp;
 200                                 m_freem(m);
 201                                 uma_zfree(tcp_reass_zone, te);
 202                                 tp->t_segqlen--;
 203                                 tcp_reass_qsize--;
 204                                 /*
 205                                  * Try to present any queued data
 206                                  * at the left window edge to the user.
 207                                  * This is needed after the 3-WHS
 208                                  * completes.
 209                                  */
 210                                 goto present;   /* ??? */
 211                         }
 212                         m_adj(m, i);
 213                         *tlenp -= i;
 214                         th->th_seq += i;
 215                 }
 216         }
 217         tcpstat.tcps_rcvoopack++;
 218         tcpstat.tcps_rcvoobyte += *tlenp;
 219
 220         /*
 221          * While we overlap succeeding segments trim them or,
 222          * if they are completely covered, dequeue them.
 223          */
 224         while (q) {
 225                 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
 226                 if (i <= 0)
 227                         break;
 228                 if (i < q->tqe_len) {
 229                         q->tqe_th->th_seq += i;
 230                         q->tqe_len -= i;
 231                         m_adj(q->tqe_m, i);
 232                         break;
 233                 }
 234
 235                 nq = LIST_NEXT(q, tqe_q);
 236                 LIST_REMOVE(q, tqe_q);
 237                 m_freem(q->tqe_m);
 238                 uma_zfree(tcp_reass_zone, q);
 239                 tp->t_segqlen--;
 240                 tcp_reass_qsize--;
 241                 q = nq;
 242         }
 243
 244         /* Insert the new segment queue entry into place. */
 245         te->tqe_m = m;
 246         te->tqe_th = th;
 247         te->tqe_len = *tlenp;
 248
 249         if (p == NULL) {
 250                 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
 251         } else {
 252                 LIST_INSERT_AFTER(p, te, tqe_q);
 253         }
 254
 255 present:
 256         /*
 257          * Present data to user, advancing rcv_nxt through
 258          * completed sequence space.
 259          */
 260         if (!TCPS_HAVEESTABLISHED(tp->t_state))
 261                 return (0);
 262         q = LIST_FIRST(&tp->t_segq);
 263         if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
 264                 return (0);
 265         SOCKBUF_LOCK(&so->so_rcv);
 266         do {
 267                 tp->rcv_nxt += q->tqe_len;
 268                 flags = q->tqe_th->th_flags & TH_FIN;
 269                 nq = LIST_NEXT(q, tqe_q);
 270                 LIST_REMOVE(q, tqe_q);
 271                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
 272                         m_freem(q->tqe_m);
 273                 else
 274                         sbappendstream_locked(&so->so_rcv, q->tqe_m);
 275                 uma_zfree(tcp_reass_zone, q);
 276                 tp->t_segqlen--;
 277                 tcp_reass_qsize--;
 278                 q = nq;
 279         } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
 280         ND6_HINT(tp);
 281         sorwakeup_locked(so);
 282         return (flags);
 283 }