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 int tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS);
  78
  79 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
  80     "TCP Segment Reassembly Queue");
  81
  82 static VNET_DEFINE(int, tcp_reass_maxseg) = 0;
  83 #define V_tcp_reass_maxseg              VNET(tcp_reass_maxseg)
  84 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
  85     &VNET_NAME(tcp_reass_maxseg), 0,
  86     "Global maximum number of TCP Segments in Reassembly Queue");
  87
  88 SYSCTL_VNET_PROC(_net_inet_tcp_reass, OID_AUTO, cursegments,
  89     (CTLTYPE_INT | CTLFLAG_RD), NULL, 0, &tcp_reass_sysctl_qsize, "I",
  90     "Global number of TCP Segments currently in Reassembly Queue");
  91
  92 static VNET_DEFINE(int, tcp_reass_overflows) = 0;
  93 #define V_tcp_reass_overflows           VNET(tcp_reass_overflows)
  94 SYSCTL_VNET_INT(_net_inet_tcp_reass, OID_AUTO, overflows,
  95     CTLTYPE_INT | CTLFLAG_RD,
  96     &VNET_NAME(tcp_reass_overflows), 0,
  97     "Global number of TCP Segment Reassembly Queue Overflows");
  98
  99 static VNET_DEFINE(uma_zone_t, tcp_reass_zone);
 100 #define V_tcp_reass_zone                VNET(tcp_reass_zone)
 101
 102 /* Initialize TCP reassembly queue */
 103 static void
 104 tcp_reass_zone_change(void *tag)
 105 {
 106
 107         /* Set the zone limit and read back the effective value. */
 108         V_tcp_reass_maxseg = nmbclusters / 16;
 109         V_tcp_reass_maxseg = uma_zone_set_max(V_tcp_reass_zone,
 110             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         /* Set the zone limit and read back the effective value. */
 123         V_tcp_reass_maxseg = uma_zone_set_max(V_tcp_reass_zone,
 124             V_tcp_reass_maxseg);
 125         EVENTHANDLER_REGISTER(nmbclusters_change,
 126             tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
 127 }
 128
 129 #ifdef VIMAGE
 130 void
 131 tcp_reass_destroy(void)
 132 {
 133
 134         uma_zdestroy(V_tcp_reass_zone);
 135 }
 136 #endif
 137
 138 void
 139 tcp_reass_flush(struct tcpcb *tp)
 140 {
 141         struct tseg_qent *qe;
 142
 143         INP_WLOCK_ASSERT(tp->t_inpcb);
 144
 145         while ((qe = LIST_FIRST(&tp->t_segq)) != NULL) {
 146                 LIST_REMOVE(qe, tqe_q);
 147                 m_freem(qe->tqe_m);
 148                 uma_zfree(V_tcp_reass_zone, qe);
 149                 tp->t_segqlen--;
 150         }
 151
 152         KASSERT((tp->t_segqlen == 0),
 153             ("TCP reass queue %p segment count is %d instead of 0 after flush.",
 154             tp, tp->t_segqlen));
 155 }
 156
 157 static int
 158 tcp_reass_sysctl_qsize(SYSCTL_HANDLER_ARGS)
 159 {
 160         int qsize;
 161
 162         qsize = uma_zone_get_cur(V_tcp_reass_zone);
 163         return (sysctl_handle_int(oidp, &qsize, 0, req));
 164 }
 165
 166 int
 167 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
 168 {
 169         struct tseg_qent *q;
 170         struct tseg_qent *p = NULL;
 171         struct tseg_qent *nq;
 172         struct tseg_qent *te = NULL;
 173         struct socket *so = tp->t_inpcb->inp_socket;
 174         char *s = NULL;
 175         int flags;
 176         struct tseg_qent tqs;
 177
 178         INP_WLOCK_ASSERT(tp->t_inpcb);
 179
 180         /*
 181          * XXX: tcp_reass() is rather inefficient with its data structures
 182          * and should be rewritten (see NetBSD for optimizations).
 183          */
 184
 185         /*
 186          * Call with th==NULL after become established to
 187          * force pre-ESTABLISHED data up to user socket.
 188          */
 189         if (th == NULL)
 190                 goto present;
 191
 192         /*
 193          * Limit the number of segments that can be queued to reduce the
 194          * potential for mbuf exhaustion. For best performance, we want to be
 195          * able to queue a full window's worth of segments. The size of the
 196          * socket receive buffer determines our advertised window and grows
 197          * automatically when socket buffer autotuning is enabled. Use it as the
 198          * basis for our queue limit.
 199          * Always let the missing segment through which caused this queue.
 200          * NB: Access to the socket buffer is left intentionally unlocked as we
 201          * can tolerate stale information here.
 202          *
 203          * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
 204          * should work but causes packets to be dropped when they shouldn't.
 205          * Investigate why and re-evaluate the below limit after the behaviour
 206          * is understood.
 207          */
 208         if (th->th_seq != tp->rcv_nxt &&
 209             tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) {
 210                 V_tcp_reass_overflows++;
 211                 TCPSTAT_INC(tcps_rcvmemdrop);
 212                 m_freem(m);
 213                 *tlenp = 0;
 214                 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
 215                         log(LOG_DEBUG, "%s; %s: queue limit reached, "
 216                             "segment dropped\n", s, __func__);
 217                         free(s, M_TCPLOG);
 218                 }
 219                 return (0);
 220         }
 221
 222         /*
 223          * Allocate a new queue entry. If we can't, or hit the zone limit
 224          * just drop the pkt.
 225          *
 226          * Use a temporary structure on the stack for the missing segment
 227          * when the zone is exhausted. Otherwise we may get stuck.
 228          */
 229         te = uma_zalloc(V_tcp_reass_zone, M_NOWAIT);
 230         if (te == NULL) {
 231                 if (th->th_seq != tp->rcv_nxt) {
 232                         TCPSTAT_INC(tcps_rcvmemdrop);
 233                         m_freem(m);
 234                         *tlenp = 0;
 235                         if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
 236                             NULL))) {
 237                                 log(LOG_DEBUG, "%s; %s: global zone limit "
 238                                     "reached, segment dropped\n", s, __func__);
 239                                 free(s, M_TCPLOG);
 240                         }
 241                         return (0);
 242                 } else {
 243                         bzero(&tqs, sizeof(struct tseg_qent));
 244                         te = &tqs;
 245                         if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
 246                             NULL))) {
 247                                 log(LOG_DEBUG,
 248                                     "%s; %s: global zone limit reached, using "
 249                                     "stack for missing segment\n", s, __func__);
 250                                 free(s, M_TCPLOG);
 251                         }
 252                 }
 253         }
 254         tp->t_segqlen++;
 255
 256         /*
 257          * Find a segment which begins after this one does.
 258          */
 259         LIST_FOREACH(q, &tp->t_segq, tqe_q) {
 260                 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
 261                         break;
 262                 p = q;
 263         }
 264
 265         /*
 266          * If there is a preceding segment, it may provide some of
 267          * our data already.  If so, drop the data from the incoming
 268          * segment.  If it provides all of our data, drop us.
 269          */
 270         if (p != NULL) {
 271                 int i;
 272                 /* conversion to int (in i) handles seq wraparound */
 273                 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
 274                 if (i > 0) {
 275                         if (i >= *tlenp) {
 276                                 TCPSTAT_INC(tcps_rcvduppack);
 277                                 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 278                                 m_freem(m);
 279                                 uma_zfree(V_tcp_reass_zone, te);
 280                                 tp->t_segqlen--;
 281                                 /*
 282                                  * Try to present any queued data
 283                                  * at the left window edge to the user.
 284                                  * This is needed after the 3-WHS
 285                                  * completes.
 286                                  */
 287                                 goto present;   /* ??? */
 288                         }
 289                         m_adj(m, i);
 290                         *tlenp -= i;
 291                         th->th_seq += i;
 292                 }
 293         }
 294         tp->t_rcvoopack++;
 295         TCPSTAT_INC(tcps_rcvoopack);
 296         TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
 297
 298         /*
 299          * While we overlap succeeding segments trim them or,
 300          * if they are completely covered, dequeue them.
 301          */
 302         while (q) {
 303                 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
 304                 if (i <= 0)
 305                         break;
 306                 if (i < q->tqe_len) {
 307                         q->tqe_th->th_seq += i;
 308                         q->tqe_len -= i;
 309                         m_adj(q->tqe_m, i);
 310                         break;
 311                 }
 312
 313                 nq = LIST_NEXT(q, tqe_q);
 314                 LIST_REMOVE(q, tqe_q);
 315                 m_freem(q->tqe_m);
 316                 uma_zfree(V_tcp_reass_zone, q);
 317                 tp->t_segqlen--;
 318                 q = nq;
 319         }
 320
 321         /* Insert the new segment queue entry into place. */
 322         te->tqe_m = m;
 323         te->tqe_th = th;
 324         te->tqe_len = *tlenp;
 325
 326         if (p == NULL) {
 327                 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
 328         } else {
 329                 KASSERT(te != &tqs, ("%s: temporary stack based entry not "
 330                     "first element in queue", __func__));
 331                 LIST_INSERT_AFTER(p, te, tqe_q);
 332         }
 333
 334 present:
 335         /*
 336          * Present data to user, advancing rcv_nxt through
 337          * completed sequence space.
 338          */
 339         if (!TCPS_HAVEESTABLISHED(tp->t_state))
 340                 return (0);
 341         q = LIST_FIRST(&tp->t_segq);
 342         if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
 343                 return (0);
 344         SOCKBUF_LOCK(&so->so_rcv);
 345         do {
 346                 tp->rcv_nxt += q->tqe_len;
 347                 flags = q->tqe_th->th_flags & TH_FIN;
 348                 nq = LIST_NEXT(q, tqe_q);
 349                 LIST_REMOVE(q, tqe_q);
 350                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
 351                         m_freem(q->tqe_m);
 352                 else
 353                         sbappendstream_locked(&so->so_rcv, q->tqe_m);
 354                 if (q != &tqs)
 355                         uma_zfree(V_tcp_reass_zone, q);
 356                 tp->t_segqlen--;
 357                 q = nq;
 358         } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
 359         ND6_HINT(tp);
 360         sorwakeup_locked(so);
 361         return (flags);
 362 }