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
  49 #include <vm/uma.h>
  50
  51 #include <net/if.h>
  52 #include <net/route.h>
  53 #include <net/vnet.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 static VNET_DEFINE(int, tcp_reass_maxseg);
  78 VNET_DEFINE(int, tcp_reass_qsize);
  79 static VNET_DEFINE(int, tcp_reass_maxqlen);
  80 static VNET_DEFINE(int, tcp_reass_overflows);
  81
  82 #define V_tcp_reass_maxseg              VNET(tcp_reass_maxseg)
  83 #define V_tcp_reass_maxqlen             VNET(tcp_reass_maxqlen)
  84 #define V_tcp_reass_overflows           VNET(tcp_reass_overflows)
  85
  86 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
  87     "TCP Segment Reassembly Queue");
  88
  89 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
  90     &VNET_NAME(tcp_reass_maxseg), 0,
  91     "Global maximum number of TCP Segments in Reassembly Queue");
  92
  93 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
  94     &VNET_NAME(tcp_reass_qsize), 0,
  95     "Global number of TCP Segments currently in Reassembly Queue");
  96
  97 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW,
  98     &VNET_NAME(tcp_reass_maxqlen), 0,
  99     "Maximum number of TCP Segments per individual Reassembly Queue");
 100
 101 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
 102     &VNET_NAME(tcp_reass_overflows), 0,
 103     "Global number of TCP Segment Reassembly Queue Overflows");
 104
 105 /* Initialize TCP reassembly queue */
 106 static void
 107 tcp_reass_zone_change(void *tag)
 108 {
 109
 110         V_tcp_reass_maxseg = nmbclusters / 16;
 111         uma_zone_set_max(V_tcp_reass_zone, V_tcp_reass_maxseg);
 112 }
 113
 114 VNET_DEFINE(uma_zone_t, tcp_reass_zone);
 115
 116 void
 117 tcp_reass_init(void)
 118 {
 119
 120         V_tcp_reass_maxseg = 0;
 121         V_tcp_reass_qsize = 0;
 122         V_tcp_reass_maxqlen = 48;
 123         V_tcp_reass_overflows = 0;
 124
 125         V_tcp_reass_maxseg = nmbclusters / 16;
 126         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
 127             &V_tcp_reass_maxseg);
 128         V_tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
 129             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
 130         uma_zone_set_max(V_tcp_reass_zone, V_tcp_reass_maxseg);
 131         EVENTHANDLER_REGISTER(nmbclusters_change,
 132             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 133 }
 134
 135 int
 136 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
 137 {
 138         struct tseg_qent *q;
 139         struct tseg_qent *p = NULL;
 140         struct tseg_qent *nq;
 141         struct tseg_qent *te = NULL;
 142         struct socket *so = tp->t_inpcb->inp_socket;
 143         int flags;
 144
 145         INP_WLOCK_ASSERT(tp->t_inpcb);
 146
 147         /*
 148          * XXX: tcp_reass() is rather inefficient with its data structures
 149          * and should be rewritten (see NetBSD for optimizations).
 150          */
 151
 152         /*
 153          * Call with th==NULL after become established to
 154          * force pre-ESTABLISHED data up to user socket.
 155          */
 156         if (th == NULL)
 157                 goto present;
 158
 159         /*
 160          * Limit the number of segments in the reassembly queue to prevent
 161          * holding on to too many segments (and thus running out of mbufs).
 162          * Make sure to let the missing segment through which caused this
 163          * queue.  Always keep one global queue entry spare to be able to
 164          * process the missing segment.
 165          */
 166         if (th->th_seq != tp->rcv_nxt &&
 167             (V_tcp_reass_qsize + 1 >= V_tcp_reass_maxseg ||
 168              tp->t_segqlen >= V_tcp_reass_maxqlen)) {
 169                 V_tcp_reass_overflows++;
 170                 TCPSTAT_INC(tcps_rcvmemdrop);
 171                 m_freem(m);
 172                 *tlenp = 0;
 173                 return (0);
 174         }
 175
 176         /*
 177          * Allocate a new queue entry. If we can't, or hit the zone limit
 178          * just drop the pkt.
 179          */
 180         te = uma_zalloc(V_tcp_reass_zone, M_NOWAIT);
 181         if (te == NULL) {
 182                 TCPSTAT_INC(tcps_rcvmemdrop);
 183                 m_freem(m);
 184                 *tlenp = 0;
 185                 return (0);
 186         }
 187         tp->t_segqlen++;
 188         V_tcp_reass_qsize++;
 189
 190         /*
 191          * Find a segment which begins after this one does.
 192          */
 193         LIST_FOREACH(q, &tp->t_segq, tqe_q) {
 194                 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
 195                         break;
 196                 p = q;
 197         }
 198
 199         /*
 200          * If there is a preceding segment, it may provide some of
 201          * our data already.  If so, drop the data from the incoming
 202          * segment.  If it provides all of our data, drop us.
 203          */
 204         if (p != NULL) {
 205                 int i;
 206                 /* conversion to int (in i) handles seq wraparound */
 207                 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
 208                 if (i > 0) {
 209                         if (i >= *tlenp) {
 210                                 TCPSTAT_INC(tcps_rcvduppack);
 211                                 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 212                                 m_freem(m);
 213                                 uma_zfree(V_tcp_reass_zone, te);
 214                                 tp->t_segqlen--;
 215                                 V_tcp_reass_qsize--;
 216                                 /*
 217                                  * Try to present any queued data
 218                                  * at the left window edge to the user.
 219                                  * This is needed after the 3-WHS
 220                                  * completes.
 221                                  */
 222                                 goto present;   /* ??? */
 223                         }
 224                         m_adj(m, i);
 225                         *tlenp -= i;
 226                         th->th_seq += i;
 227                 }
 228         }
 229         TCPSTAT_INC(tcps_rcvoopack);
 230         TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
 231
 232         /*
 233          * While we overlap succeeding segments trim them or,
 234          * if they are completely covered, dequeue them.
 235          */
 236         while (q) {
 237                 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
 238                 if (i <= 0)
 239                         break;
 240                 if (i < q->tqe_len) {
 241                         q->tqe_th->th_seq += i;
 242                         q->tqe_len -= i;
 243                         m_adj(q->tqe_m, i);
 244                         break;
 245                 }
 246
 247                 nq = LIST_NEXT(q, tqe_q);
 248                 LIST_REMOVE(q, tqe_q);
 249                 m_freem(q->tqe_m);
 250                 uma_zfree(V_tcp_reass_zone, q);
 251                 tp->t_segqlen--;
 252                 V_tcp_reass_qsize--;
 253                 q = nq;
 254         }
 255
 256         /* Insert the new segment queue entry into place. */
 257         te->tqe_m = m;
 258         te->tqe_th = th;
 259         te->tqe_len = *tlenp;
 260
 261         if (p == NULL) {
 262                 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
 263         } else {
 264                 LIST_INSERT_AFTER(p, te, tqe_q);
 265         }
 266
 267 present:
 268         /*
 269          * Present data to user, advancing rcv_nxt through
 270          * completed sequence space.
 271          */
 272         if (!TCPS_HAVEESTABLISHED(tp->t_state))
 273                 return (0);
 274         q = LIST_FIRST(&tp->t_segq);
 275         if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
 276                 return (0);
 277         SOCKBUF_LOCK(&so->so_rcv);
 278         do {
 279                 tp->rcv_nxt += q->tqe_len;
 280                 flags = q->tqe_th->th_flags & TH_FIN;
 281                 nq = LIST_NEXT(q, tqe_q);
 282                 LIST_REMOVE(q, tqe_q);
 283                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
 284                         m_freem(q->tqe_m);
 285                 else
 286                         sbappendstream_locked(&so->so_rcv, q->tqe_m);
 287                 uma_zfree(V_tcp_reass_zone, q);
 288                 tp->t_segqlen--;
 289                 V_tcp_reass_qsize--;
 290                 q = nq;
 291         } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
 292         ND6_HINT(tp);
 293         sorwakeup_locked(so);
 294         return (flags);
 295 }