tcp_reass.c

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    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: releng/7.3/sys/netinet/tcp_reass.c 181822 2008-08-18 08:11:48Z rwatson $");
   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 
   54 #include <netinet/in.h>
   55 #include <netinet/in_pcb.h>
   56 #include <netinet/in_systm.h>
   57 #include <netinet/in_var.h>
   58 #include <netinet/ip.h>
   59 #include <netinet/ip_var.h>
   60 #include <netinet/ip_options.h>
   61 #include <netinet/ip6.h>
   62 #include <netinet6/in6_pcb.h>
   63 #include <netinet6/ip6_var.h>
   64 #include <netinet6/nd6.h>
   65 #include <netinet/tcp.h>
   66 #include <netinet/tcp_fsm.h>
   67 #include <netinet/tcp_seq.h>
   68 #include <netinet/tcp_timer.h>
   69 #include <netinet/tcp_var.h>
   70 #include <netinet6/tcp6_var.h>
   71 #include <netinet/tcpip.h>
   72 #ifdef TCPDEBUG
   73 #include <netinet/tcp_debug.h>
   74 #endif /* TCPDEBUG */
   75 
   76 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
   77     "TCP Segment Reassembly Queue");
   78 
   79 static int tcp_reass_maxseg = 0;
   80 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
   81     &tcp_reass_maxseg, 0,
   82     "Global maximum number of TCP Segments in Reassembly Queue");
   83 
   84 int tcp_reass_qsize = 0;
   85 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
   86     &tcp_reass_qsize, 0,
   87     "Global number of TCP Segments currently in Reassembly Queue");
   88 
   89 static int tcp_reass_maxqlen = 48;
   90 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW,
   91     &tcp_reass_maxqlen, 0,
   92     "Maximum number of TCP Segments per individual Reassembly Queue");
   93 
   94 static int tcp_reass_overflows = 0;
   95 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
   96     &tcp_reass_overflows, 0,
   97     "Global number of TCP Segment Reassembly Queue Overflows");
   98 
   99 /* Initialize TCP reassembly queue */
  100 static void
  101 tcp_reass_zone_change(void *tag)
  102 {
  103 
  104         tcp_reass_maxseg = nmbclusters / 16;
  105         uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
  106 }
  107 
  108 uma_zone_t      tcp_reass_zone;
  109 
  110 void
  111 tcp_reass_init(void)
  112 {
  113 
  114         tcp_reass_maxseg = nmbclusters / 16;
  115         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
  116             &tcp_reass_maxseg);
  117         tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
  118             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  119         uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
  120         EVENTHANDLER_REGISTER(nmbclusters_change,
  121             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
  122 }
  123 
  124 int
  125 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
  126 {
  127         struct tseg_qent *q;
  128         struct tseg_qent *p = NULL;
  129         struct tseg_qent *nq;
  130         struct tseg_qent *te = NULL;
  131         struct socket *so = tp->t_inpcb->inp_socket;
  132         int flags;
  133 
  134         INP_WLOCK_ASSERT(tp->t_inpcb);
  135 
  136         /*
  137          * XXX: tcp_reass() is rather inefficient with its data structures
  138          * and should be rewritten (see NetBSD for optimizations).  While
  139          * doing that it should move to its own file tcp_reass.c.
  140          */
  141 
  142         /*
  143          * Call with th==NULL after become established to
  144          * force pre-ESTABLISHED data up to user socket.
  145          */
  146         if (th == NULL)
  147                 goto present;
  148 
  149         /*
  150          * Limit the number of segments in the reassembly queue to prevent
  151          * holding on to too many segments (and thus running out of mbufs).
  152          * Make sure to let the missing segment through which caused this
  153          * queue.  Always keep one global queue entry spare to be able to
  154          * process the missing segment.
  155          */
  156         if (th->th_seq != tp->rcv_nxt &&
  157             (tcp_reass_qsize + 1 >= tcp_reass_maxseg ||
  158              tp->t_segqlen >= tcp_reass_maxqlen)) {
  159                 tcp_reass_overflows++;
  160                 tcpstat.tcps_rcvmemdrop++;
  161                 m_freem(m);
  162                 *tlenp = 0;
  163                 return (0);
  164         }
  165 
  166         /*
  167          * Allocate a new queue entry. If we can't, or hit the zone limit
  168          * just drop the pkt.
  169          */
  170         te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
  171         if (te == NULL) {
  172                 tcpstat.tcps_rcvmemdrop++;
  173                 m_freem(m);
  174                 *tlenp = 0;
  175                 return (0);
  176         }
  177         tp->t_segqlen++;
  178         tcp_reass_qsize++;
  179 
  180         /*
  181          * Find a segment which begins after this one does.
  182          */
  183         LIST_FOREACH(q, &tp->t_segq, tqe_q) {
  184                 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
  185                         break;
  186                 p = q;
  187         }
  188 
  189         /*
  190          * If there is a preceding segment, it may provide some of
  191          * our data already.  If so, drop the data from the incoming
  192          * segment.  If it provides all of our data, drop us.
  193          */
  194         if (p != NULL) {
  195                 int i;
  196                 /* conversion to int (in i) handles seq wraparound */
  197                 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
  198                 if (i > 0) {
  199                         if (i >= *tlenp) {
  200                                 tcpstat.tcps_rcvduppack++;
  201                                 tcpstat.tcps_rcvdupbyte += *tlenp;
  202                                 m_freem(m);
  203                                 uma_zfree(tcp_reass_zone, te);
  204                                 tp->t_segqlen--;
  205                                 tcp_reass_qsize--;
  206                                 /*
  207                                  * Try to present any queued data
  208                                  * at the left window edge to the user.
  209                                  * This is needed after the 3-WHS
  210                                  * completes.
  211                                  */
  212                                 goto present;   /* ??? */
  213                         }
  214                         m_adj(m, i);
  215                         *tlenp -= i;
  216                         th->th_seq += i;
  217                 }
  218         }
  219         tcpstat.tcps_rcvoopack++;
  220         tcpstat.tcps_rcvoobyte += *tlenp;
  221 
  222         /*
  223          * While we overlap succeeding segments trim them or,
  224          * if they are completely covered, dequeue them.
  225          */
  226         while (q) {
  227                 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
  228                 if (i <= 0)
  229                         break;
  230                 if (i < q->tqe_len) {
  231                         q->tqe_th->th_seq += i;
  232                         q->tqe_len -= i;
  233                         m_adj(q->tqe_m, i);
  234                         break;
  235                 }
  236 
  237                 nq = LIST_NEXT(q, tqe_q);
  238                 LIST_REMOVE(q, tqe_q);
  239                 m_freem(q->tqe_m);
  240                 uma_zfree(tcp_reass_zone, q);
  241                 tp->t_segqlen--;
  242                 tcp_reass_qsize--;
  243                 q = nq;
  244         }
  245 
  246         /* Insert the new segment queue entry into place. */
  247         te->tqe_m = m;
  248         te->tqe_th = th;
  249         te->tqe_len = *tlenp;
  250 
  251         if (p == NULL) {
  252                 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
  253         } else {
  254                 LIST_INSERT_AFTER(p, te, tqe_q);
  255         }
  256 
  257 present:
  258         /*
  259          * Present data to user, advancing rcv_nxt through
  260          * completed sequence space.
  261          */
  262         if (!TCPS_HAVEESTABLISHED(tp->t_state))
  263                 return (0);
  264         q = LIST_FIRST(&tp->t_segq);
  265         if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
  266                 return (0);
  267         SOCKBUF_LOCK(&so->so_rcv);
  268         do {
  269                 tp->rcv_nxt += q->tqe_len;
  270                 flags = q->tqe_th->th_flags & TH_FIN;
  271                 nq = LIST_NEXT(q, tqe_q);
  272                 LIST_REMOVE(q, tqe_q);
  273                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
  274                         m_freem(q->tqe_m);
  275                 else
  276                         sbappendstream_locked(&so->so_rcv, q->tqe_m);
  277                 uma_zfree(tcp_reass_zone, q);
  278                 tp->t_segqlen--;
  279                 tcp_reass_qsize--;
  280                 q = nq;
  281         } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
  282         ND6_HINT(tp);
  283         sorwakeup_locked(so);
  284         return (flags);
  285 }
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FreeBSD/Linux Kernel Cross Reference sys/netinet/tcp_reass.c

FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_reass.c
