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/malloc.h>
  42 #include <sys/mbuf.h>
  43 #include <sys/socket.h>
  44 #include <sys/socketvar.h>
  45 #include <sys/sysctl.h>
  46 #include <sys/syslog.h>
  47 #include <sys/systm.h>
  48 #include <sys/vimage.h>
  49
  50 #include <vm/uma.h>
  51
  52 #include <net/if.h>
  53 #include <net/route.h>
  54
  55 #include <netinet/in.h>
  56 #include <netinet/in_pcb.h>
  57 #include <netinet/in_systm.h>
  58 #include <netinet/in_var.h>
  59 #include <netinet/ip.h>
  60 #include <netinet/ip_var.h>
  61 #include <netinet/ip_options.h>
  62 #include <netinet/ip6.h>
  63 #include <netinet6/in6_pcb.h>
  64 #include <netinet6/ip6_var.h>
  65 #include <netinet6/nd6.h>
  66 #include <netinet/tcp.h>
  67 #include <netinet/tcp_fsm.h>
  68 #include <netinet/tcp_seq.h>
  69 #include <netinet/tcp_timer.h>
  70 #include <netinet/tcp_var.h>
  71 #include <netinet6/tcp6_var.h>
  72 #include <netinet/tcpip.h>
  73 #ifdef TCPDEBUG
  74 #include <netinet/tcp_debug.h>
  75 #endif /* TCPDEBUG */
  76
  77 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
  78     "TCP Segment Reassembly Queue");
  79
  80 static int tcp_reass_maxseg = 0;
  81 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
  82     &tcp_reass_maxseg, 0,
  83     "Global maximum number of TCP Segments in Reassembly Queue");
  84
  85 int tcp_reass_qsize = 0;
  86 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
  87     &tcp_reass_qsize, 0,
  88     "Global number of TCP Segments currently in Reassembly Queue");
  89
  90 static int tcp_reass_maxqlen = 48;
  91 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW,
  92     &tcp_reass_maxqlen, 0,
  93     "Maximum number of TCP Segments per individual Reassembly Queue");
  94
  95 static int tcp_reass_overflows = 0;
  96 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
  97     &tcp_reass_overflows, 0,
  98     "Global number of TCP Segment Reassembly Queue Overflows");
  99
 100 /* Initialize TCP reassembly queue */
 101 static void
 102 tcp_reass_zone_change(void *tag)
 103 {
 104
 105         V_tcp_reass_maxseg = nmbclusters / 16;
 106         uma_zone_set_max(tcp_reass_zone, V_tcp_reass_maxseg);
 107 }
 108
 109 uma_zone_t      tcp_reass_zone;
 110
 111 void
 112 tcp_reass_init(void)
 113 {
 114
 115         V_tcp_reass_maxseg = nmbclusters / 16;
 116         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
 117             &V_tcp_reass_maxseg);
 118         tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
 119             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
 120         uma_zone_set_max(tcp_reass_zone, V_tcp_reass_maxseg);
 121         EVENTHANDLER_REGISTER(nmbclusters_change,
 122             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 123 }
 124
 125 int
 126 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
 127 {
 128         struct tseg_qent *q;
 129         struct tseg_qent *p = NULL;
 130         struct tseg_qent *nq;
 131         struct tseg_qent *te = NULL;
 132         struct socket *so = tp->t_inpcb->inp_socket;
 133         int flags;
 134
 135         INP_WLOCK_ASSERT(tp->t_inpcb);
 136
 137         /*
 138          * XXX: tcp_reass() is rather inefficient with its data structures
 139          * and should be rewritten (see NetBSD for optimizations).  While
 140          * doing that it should move to its own file tcp_reass.c.
 141          */
 142
 143         /*
 144          * Call with th==NULL after become established to
 145          * force pre-ESTABLISHED data up to user socket.
 146          */
 147         if (th == NULL)
 148                 goto present;
 149
 150         /*
 151          * Limit the number of segments in the reassembly queue to prevent
 152          * holding on to too many segments (and thus running out of mbufs).
 153          * Make sure to let the missing segment through which caused this
 154          * queue.  Always keep one global queue entry spare to be able to
 155          * process the missing segment.
 156          */
 157         if (th->th_seq != tp->rcv_nxt &&
 158             (V_tcp_reass_qsize + 1 >= V_tcp_reass_maxseg ||
 159              tp->t_segqlen >= V_tcp_reass_maxqlen)) {
 160                 V_tcp_reass_overflows++;
 161                 V_tcpstat.tcps_rcvmemdrop++;
 162                 m_freem(m);
 163                 *tlenp = 0;
 164                 return (0);
 165         }
 166
 167         /*
 168          * Allocate a new queue entry. If we can't, or hit the zone limit
 169          * just drop the pkt.
 170          */
 171         te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
 172         if (te == NULL) {
 173                 V_tcpstat.tcps_rcvmemdrop++;
 174                 m_freem(m);
 175                 *tlenp = 0;
 176                 return (0);
 177         }
 178         tp->t_segqlen++;
 179         V_tcp_reass_qsize++;
 180
 181         /*
 182          * Find a segment which begins after this one does.
 183          */
 184         LIST_FOREACH(q, &tp->t_segq, tqe_q) {
 185                 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
 186                         break;
 187                 p = q;
 188         }
 189
 190         /*
 191          * If there is a preceding segment, it may provide some of
 192          * our data already.  If so, drop the data from the incoming
 193          * segment.  If it provides all of our data, drop us.
 194          */
 195         if (p != NULL) {
 196                 int i;
 197                 /* conversion to int (in i) handles seq wraparound */
 198                 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
 199                 if (i > 0) {
 200                         if (i >= *tlenp) {
 201                                 V_tcpstat.tcps_rcvduppack++;
 202                                 V_tcpstat.tcps_rcvdupbyte += *tlenp;
 203                                 m_freem(m);
 204                                 uma_zfree(tcp_reass_zone, te);
 205                                 tp->t_segqlen--;
 206                                 V_tcp_reass_qsize--;
 207                                 /*
 208                                  * Try to present any queued data
 209                                  * at the left window edge to the user.
 210                                  * This is needed after the 3-WHS
 211                                  * completes.
 212                                  */
 213                                 goto present;   /* ??? */
 214                         }
 215                         m_adj(m, i);
 216                         *tlenp -= i;
 217                         th->th_seq += i;
 218                 }
 219         }
 220         V_tcpstat.tcps_rcvoopack++;
 221         V_tcpstat.tcps_rcvoobyte += *tlenp;
 222
 223         /*
 224          * While we overlap succeeding segments trim them or,
 225          * if they are completely covered, dequeue them.
 226          */
 227         while (q) {
 228                 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
 229                 if (i <= 0)
 230                         break;
 231                 if (i < q->tqe_len) {
 232                         q->tqe_th->th_seq += i;
 233                         q->tqe_len -= i;
 234                         m_adj(q->tqe_m, i);
 235                         break;
 236                 }
 237
 238                 nq = LIST_NEXT(q, tqe_q);
 239                 LIST_REMOVE(q, tqe_q);
 240                 m_freem(q->tqe_m);
 241                 uma_zfree(tcp_reass_zone, q);
 242                 tp->t_segqlen--;
 243                 V_tcp_reass_qsize--;
 244                 q = nq;
 245         }
 246
 247         /* Insert the new segment queue entry into place. */
 248         te->tqe_m = m;
 249         te->tqe_th = th;
 250         te->tqe_len = *tlenp;
 251
 252         if (p == NULL) {
 253                 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
 254         } else {
 255                 LIST_INSERT_AFTER(p, te, tqe_q);
 256         }
 257
 258 present:
 259         /*
 260          * Present data to user, advancing rcv_nxt through
 261          * completed sequence space.
 262          */
 263         if (!TCPS_HAVEESTABLISHED(tp->t_state))
 264                 return (0);
 265         q = LIST_FIRST(&tp->t_segq);
 266         if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
 267                 return (0);
 268         SOCKBUF_LOCK(&so->so_rcv);
 269         do {
 270                 tp->rcv_nxt += q->tqe_len;
 271                 flags = q->tqe_th->th_flags & TH_FIN;
 272                 nq = LIST_NEXT(q, tqe_q);
 273                 LIST_REMOVE(q, tqe_q);
 274                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
 275                         m_freem(q->tqe_m);
 276                 else
 277                         sbappendstream_locked(&so->so_rcv, q->tqe_m);
 278                 uma_zfree(tcp_reass_zone, q);
 279                 tp->t_segqlen--;
 280                 V_tcp_reass_qsize--;
 281                 q = nq;
 282         } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
 283         ND6_HINT(tp);
 284         sorwakeup_locked(so);
 285         return (flags);
 286 }