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/8.2/sys/netinet/tcp_reass.c 214866 2010-11-06 10:31:52Z lstewart $");
   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 int tcp_reass_sysctl_maxseg(SYSCTL_HANDLER_ARGS);
   78 static int tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS);
   79 
   80 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
   81     "TCP Segment Reassembly Queue");
   82 
   83 static VNET_DEFINE(int, tcp_reass_maxseg) = 0;
   84 #define V_tcp_reass_maxseg              VNET(tcp_reass_maxseg)
   85 SYSCTL_VNET_PROC(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
   86     &VNET_NAME(tcp_reass_maxseg), 0, &tcp_reass_sysctl_maxseg, "I",
   87     "Global maximum number of TCP Segments in Reassembly Queue");
   88 
   89 static VNET_DEFINE(int, tcp_reass_qsize) = 0;
   90 #define V_tcp_reass_qsize               VNET(tcp_reass_qsize)
   91 SYSCTL_VNET_PROC(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
   92     &VNET_NAME(tcp_reass_qsize), 0, &tcp_reass_sysctl_qsize, "I",
   93     "Global number of TCP Segments currently in Reassembly Queue");
   94 
   95 static VNET_DEFINE(int, tcp_reass_overflows) = 0;
   96 #define V_tcp_reass_overflows           VNET(tcp_reass_overflows)
   97 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
   98     &VNET_NAME(tcp_reass_overflows), 0,
   99     "Global number of TCP Segment Reassembly Queue Overflows");
  100 
  101 static VNET_DEFINE(uma_zone_t, tcp_reass_zone);
  102 #define V_tcp_reass_zone                VNET(tcp_reass_zone)
  103 
  104 /* Initialize TCP reassembly queue */
  105 static void
  106 tcp_reass_zone_change(void *tag)
  107 {
  108 
  109         V_tcp_reass_maxseg = nmbclusters / 16;
  110         uma_zone_set_max(V_tcp_reass_zone, V_tcp_reass_maxseg);
  111 }
  112 
  113 void
  114 tcp_reass_init(void)
  115 {
  116 
  117         V_tcp_reass_maxseg = nmbclusters / 16;
  118         TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
  119             &V_tcp_reass_maxseg);
  120         V_tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
  121             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  122         uma_zone_set_max(V_tcp_reass_zone, V_tcp_reass_maxseg);
  123         EVENTHANDLER_REGISTER(nmbclusters_change,
  124             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
  125 }
  126 
  127 #ifdef VIMAGE
  128 void
  129 tcp_reass_destroy(void)
  130 {
  131 
  132         uma_zdestroy(V_tcp_reass_zone);
  133 }
  134 #endif
  135 
  136 void
  137 tcp_reass_flush(struct tcpcb *tp)
  138 {
  139         struct tseg_qent *qe;
  140 
  141         INP_WLOCK_ASSERT(tp->t_inpcb);
  142 
  143         while ((qe = LIST_FIRST(&tp->t_segq)) != NULL) {
  144                 LIST_REMOVE(qe, tqe_q);
  145                 m_freem(qe->tqe_m);
  146                 uma_zfree(V_tcp_reass_zone, qe);
  147                 tp->t_segqlen--;
  148         }
  149 
  150         KASSERT((tp->t_segqlen == 0),
  151             ("TCP reass queue %p segment count is %d instead of 0 after flush.",
  152             tp, tp->t_segqlen));
  153 }
  154 
  155 static int
  156 tcp_reass_sysctl_maxseg(SYSCTL_HANDLER_ARGS)
  157 {
  158         V_tcp_reass_maxseg = uma_zone_get_max(V_tcp_reass_zone);
  159         return (sysctl_handle_int(oidp, arg1, arg2, req));
  160 }
  161 
  162 static int
  163 tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS)
  164 {
  165         V_tcp_reass_qsize = uma_zone_get_cur(V_tcp_reass_zone);
  166         return (sysctl_handle_int(oidp, arg1, arg2, req));
  167 }
  168 
  169 int
  170 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
  171 {
  172         struct tseg_qent *q;
  173         struct tseg_qent *p = NULL;
  174         struct tseg_qent *nq;
  175         struct tseg_qent *te = NULL;
  176         struct socket *so = tp->t_inpcb->inp_socket;
  177         int flags;
  178 
  179         INP_WLOCK_ASSERT(tp->t_inpcb);
  180 
  181         /*
  182          * XXX: tcp_reass() is rather inefficient with its data structures
  183          * and should be rewritten (see NetBSD for optimizations).
  184          */
  185 
  186         /*
  187          * Call with th==NULL after become established to
  188          * force pre-ESTABLISHED data up to user socket.
  189          */
  190         if (th == NULL)
  191                 goto present;
  192 
  193         /*
  194          * Limit the number of segments that can be queued to reduce the
  195          * potential for mbuf exhaustion. For best performance, we want to be
  196          * able to queue a full window's worth of segments. The size of the
  197          * socket receive buffer determines our advertised window and grows
  198          * automatically when socket buffer autotuning is enabled. Use it as the
  199          * basis for our queue limit.
  200          * Always let the missing segment through which caused this queue.
  201          * NB: Access to the socket buffer is left intentionally unlocked as we
  202          * can tolerate stale information here.
  203          *
  204          * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
  205          * should work but causes packets to be dropped when they shouldn't.
  206          * Investigate why and re-evaluate the below limit after the behaviour
  207          * is understood.
  208          */
  209         if (th->th_seq != tp->rcv_nxt &&
  210             tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) {
  211                 V_tcp_reass_overflows++;
  212                 TCPSTAT_INC(tcps_rcvmemdrop);
  213                 m_freem(m);
  214                 *tlenp = 0;
  215                 return (0);
  216         }
  217 
  218         /*
  219          * Allocate a new queue entry. If we can't, or hit the zone limit
  220          * just drop the pkt.
  221          */
  222         te = uma_zalloc(V_tcp_reass_zone, M_NOWAIT);
  223         if (te == NULL) {
  224                 TCPSTAT_INC(tcps_rcvmemdrop);
  225                 m_freem(m);
  226                 *tlenp = 0;
  227                 return (0);
  228         }
  229         tp->t_segqlen++;
  230 
  231         /*
  232          * Find a segment which begins after this one does.
  233          */
  234         LIST_FOREACH(q, &tp->t_segq, tqe_q) {
  235                 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
  236                         break;
  237                 p = q;
  238         }
  239 
  240         /*
  241          * If there is a preceding segment, it may provide some of
  242          * our data already.  If so, drop the data from the incoming
  243          * segment.  If it provides all of our data, drop us.
  244          */
  245         if (p != NULL) {
  246                 int i;
  247                 /* conversion to int (in i) handles seq wraparound */
  248                 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
  249                 if (i > 0) {
  250                         if (i >= *tlenp) {
  251                                 TCPSTAT_INC(tcps_rcvduppack);
  252                                 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
  253                                 m_freem(m);
  254                                 uma_zfree(V_tcp_reass_zone, te);
  255                                 tp->t_segqlen--;
  256                                 /*
  257                                  * Try to present any queued data
  258                                  * at the left window edge to the user.
  259                                  * This is needed after the 3-WHS
  260                                  * completes.
  261                                  */
  262                                 goto present;   /* ??? */
  263                         }
  264                         m_adj(m, i);
  265                         *tlenp -= i;
  266                         th->th_seq += i;
  267                 }
  268         }
  269         TCPSTAT_INC(tcps_rcvoopack);
  270         TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
  271 
  272         /*
  273          * While we overlap succeeding segments trim them or,
  274          * if they are completely covered, dequeue them.
  275          */
  276         while (q) {
  277                 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
  278                 if (i <= 0)
  279                         break;
  280                 if (i < q->tqe_len) {
  281                         q->tqe_th->th_seq += i;
  282                         q->tqe_len -= i;
  283                         m_adj(q->tqe_m, i);
  284                         break;
  285                 }
  286 
  287                 nq = LIST_NEXT(q, tqe_q);
  288                 LIST_REMOVE(q, tqe_q);
  289                 m_freem(q->tqe_m);
  290                 uma_zfree(V_tcp_reass_zone, q);
  291                 tp->t_segqlen--;
  292                 q = nq;
  293         }
  294 
  295         /* Insert the new segment queue entry into place. */
  296         te->tqe_m = m;
  297         te->tqe_th = th;
  298         te->tqe_len = *tlenp;
  299 
  300         if (p == NULL) {
  301                 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
  302         } else {
  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);
  326                 uma_zfree(V_tcp_reass_zone, q);
  327                 tp->t_segqlen--;
  328                 q = nq;
  329         } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
  330         ND6_HINT(tp);
  331         sorwakeup_locked(so);
  332         return (flags);
  333 }
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FreeBSD/Linux Kernel Cross Reference sys/netinet/tcp_reass.c

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