1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_tcpdebug.h" 40 41 #include <sys/param.h> 42 #include <sys/kernel.h> 43 #include <sys/eventhandler.h> 44 #include <sys/malloc.h> 45 #include <sys/mbuf.h> 46 #include <sys/socket.h> 47 #include <sys/socketvar.h> 48 #include <sys/sysctl.h> 49 #include <sys/syslog.h> 50 #include <sys/systm.h> 51 52 #include <vm/uma.h> 53 54 #include <net/if.h> 55 #include <net/if_var.h> 56 #include <net/route.h> 57 #include <net/vnet.h> 58 59 #include <netinet/in.h> 60 #include <netinet/in_pcb.h> 61 #include <netinet/in_systm.h> 62 #include <netinet/in_var.h> 63 #include <netinet/ip.h> 64 #include <netinet/ip_var.h> 65 #include <netinet/ip_options.h> 66 #include <netinet/ip6.h> 67 #include <netinet6/in6_pcb.h> 68 #include <netinet6/ip6_var.h> 69 #include <netinet6/nd6.h> 70 #include <netinet/tcp.h> 71 #include <netinet/tcp_fsm.h> 72 #include <netinet/tcp_seq.h> 73 #include <netinet/tcp_timer.h> 74 #include <netinet/tcp_var.h> 75 #include <netinet6/tcp6_var.h> 76 #include <netinet/tcpip.h> 77 #ifdef TCPDEBUG 78 #include <netinet/tcp_debug.h> 79 #endif /* TCPDEBUG */ 80 81 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 82 "TCP Segment Reassembly Queue"); 83 84 static int tcp_reass_maxseg = 0; 85 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 86 &tcp_reass_maxseg, 0, 87 "Global maximum number of TCP Segments in Reassembly Queue"); 88 89 static uma_zone_t tcp_reass_zone; 90 SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, 0, 91 &tcp_reass_zone, 92 "Global number of TCP Segments currently in Reassembly Queue"); 93 94 /* Initialize TCP reassembly queue */ 95 static void 96 tcp_reass_zone_change(void *tag) 97 { 98 99 /* Set the zone limit and read back the effective value. */ 100 tcp_reass_maxseg = nmbclusters / 16; 101 tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone, 102 tcp_reass_maxseg); 103 } 104 105 void 106 tcp_reass_global_init(void) 107 { 108 109 tcp_reass_maxseg = nmbclusters / 16; 110 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 111 &tcp_reass_maxseg); 112 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 113 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 114 /* Set the zone limit and read back the effective value. */ 115 tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone, 116 tcp_reass_maxseg); 117 EVENTHANDLER_REGISTER(nmbclusters_change, 118 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY); 119 } 120 121 void 122 tcp_reass_flush(struct tcpcb *tp) 123 { 124 struct tseg_qent *qe; 125 126 INP_WLOCK_ASSERT(tp->t_inpcb); 127 128 while ((qe = LIST_FIRST(&tp->t_segq)) != NULL) { 129 LIST_REMOVE(qe, tqe_q); 130 m_freem(qe->tqe_m); 131 uma_zfree(tcp_reass_zone, qe); 132 tp->t_segqlen--; 133 } 134 135 KASSERT((tp->t_segqlen == 0), 136 ("TCP reass queue %p segment count is %d instead of 0 after flush.", 137 tp, tp->t_segqlen)); 138 } 139 140 int 141 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 142 { 143 struct tseg_qent *q; 144 struct tseg_qent *p = NULL; 145 struct tseg_qent *nq; 146 struct tseg_qent *te = NULL; 147 struct socket *so = tp->t_inpcb->inp_socket; 148 char *s = NULL; 149 int flags; 150 struct tseg_qent tqs; 151 152 INP_WLOCK_ASSERT(tp->t_inpcb); 153 154 /* 155 * XXX: tcp_reass() is rather inefficient with its data structures 156 * and should be rewritten (see NetBSD for optimizations). 157 */ 158 159 /* 160 * Call with th==NULL after become established to 161 * force pre-ESTABLISHED data up to user socket. 162 */ 163 if (th == NULL) 164 goto present; 165 166 /* 167 * Limit the number of segments that can be queued to reduce the 168 * potential for mbuf exhaustion. For best performance, we want to be 169 * able to queue a full window's worth of segments. The size of the 170 * socket receive buffer determines our advertised window and grows 171 * automatically when socket buffer autotuning is enabled. Use it as the 172 * basis for our queue limit. 173 * Always let the missing segment through which caused this queue. 174 * NB: Access to the socket buffer is left intentionally unlocked as we 175 * can tolerate stale information here. 176 * 177 * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat 178 * should work but causes packets to be dropped when they shouldn't. 179 * Investigate why and re-evaluate the below limit after the behaviour 180 * is understood. 181 */ 182 if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) && 183 tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) { 184 TCPSTAT_INC(tcps_rcvreassfull); 185 *tlenp = 0; 186 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) { 187 log(LOG_DEBUG, "%s; %s: queue limit reached, " 188 "segment dropped\n", s, __func__); 189 free(s, M_TCPLOG); 190 } 191 m_freem(m); 192 return (0); 193 } 194 195 /* 196 * Allocate a new queue entry. If we can't, or hit the zone limit 197 * just drop the pkt. 198 * 199 * Use a temporary structure on the stack for the missing segment 200 * when the zone is exhausted. Otherwise we may get stuck. 201 */ 202 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 203 if (te == NULL) { 204 if (th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) { 205 TCPSTAT_INC(tcps_rcvmemdrop); 206 m_freem(m); 207 *tlenp = 0; 208 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, 209 NULL))) { 210 log(LOG_DEBUG, "%s; %s: global zone limit " 211 "reached, segment dropped\n", s, __func__); 212 free(s, M_TCPLOG); 213 } 214 return (0); 215 } else { 216 bzero(&tqs, sizeof(struct tseg_qent)); 217 te = &tqs; 218 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, 219 NULL))) { 220 log(LOG_DEBUG, 221 "%s; %s: global zone limit reached, using " 222 "stack for missing segment\n", s, __func__); 223 free(s, M_TCPLOG); 224 } 225 } 226 } 227 tp->t_segqlen++; 228 229 /* 230 * Find a segment which begins after this one does. 231 */ 232 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 233 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 234 break; 235 p = q; 236 } 237 238 /* 239 * If there is a preceding segment, it may provide some of 240 * our data already. If so, drop the data from the incoming 241 * segment. If it provides all of our data, drop us. 242 */ 243 if (p != NULL) { 244 int i; 245 /* conversion to int (in i) handles seq wraparound */ 246 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 247 if (i > 0) { 248 if (i >= *tlenp) { 249 TCPSTAT_INC(tcps_rcvduppack); 250 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp); 251 m_freem(m); 252 if (te != &tqs) 253 uma_zfree(tcp_reass_zone, te); 254 tp->t_segqlen--; 255 /* 256 * Try to present any queued data 257 * at the left window edge to the user. 258 * This is needed after the 3-WHS 259 * completes. 260 */ 261 goto present; /* ??? */ 262 } 263 m_adj(m, i); 264 *tlenp -= i; 265 th->th_seq += i; 266 } 267 } 268 tp->t_rcvoopack++; 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(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 KASSERT(te != &tqs, ("%s: temporary stack based entry not " 304 "first element in queue", __func__)); 305 LIST_INSERT_AFTER(p, te, tqe_q); 306 } 307 308 present: 309 /* 310 * Present data to user, advancing rcv_nxt through 311 * completed sequence space. 312 */ 313 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 314 return (0); 315 q = LIST_FIRST(&tp->t_segq); 316 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 317 return (0); 318 SOCKBUF_LOCK(&so->so_rcv); 319 do { 320 tp->rcv_nxt += q->tqe_len; 321 flags = q->tqe_th->th_flags & TH_FIN; 322 nq = LIST_NEXT(q, tqe_q); 323 LIST_REMOVE(q, tqe_q); 324 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 325 m_freem(q->tqe_m); 326 else 327 sbappendstream_locked(&so->so_rcv, q->tqe_m, 0); 328 if (q != &tqs) 329 uma_zfree(tcp_reass_zone, q); 330 tp->t_segqlen--; 331 q = nq; 332 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 333 sorwakeup_locked(so); 334 return (flags); 335 } 336