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 static u_int tcp_reass_maxqueuelen = 100; 95 SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, maxqueuelen, CTLFLAG_RWTUN, 96 &tcp_reass_maxqueuelen, 0, 97 "Maximum number of TCP Segments per Reassembly Queue"); 98 99 /* Initialize TCP reassembly queue */ 100 static void 101 tcp_reass_zone_change(void *tag) 102 { 103 104 /* Set the zone limit and read back the effective value. */ 105 tcp_reass_maxseg = nmbclusters / 16; 106 tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone, 107 tcp_reass_maxseg); 108 } 109 110 void 111 tcp_reass_global_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, 0); 119 /* Set the zone limit and read back the effective value. */ 120 tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone, 121 tcp_reass_maxseg); 122 EVENTHANDLER_REGISTER(nmbclusters_change, 123 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY); 124 } 125 126 void 127 tcp_reass_flush(struct tcpcb *tp) 128 { 129 struct tseg_qent *qe; 130 131 INP_WLOCK_ASSERT(tp->t_inpcb); 132 133 while ((qe = LIST_FIRST(&tp->t_segq)) != NULL) { 134 LIST_REMOVE(qe, tqe_q); 135 m_freem(qe->tqe_m); 136 uma_zfree(tcp_reass_zone, qe); 137 tp->t_segqlen--; 138 } 139 140 KASSERT((tp->t_segqlen == 0), 141 ("TCP reass queue %p segment count is %d instead of 0 after flush.", 142 tp, tp->t_segqlen)); 143 } 144 145 int 146 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 147 { 148 struct tseg_qent *q; 149 struct tseg_qent *p = NULL; 150 struct tseg_qent *nq; 151 struct tseg_qent *te = NULL; 152 struct socket *so = tp->t_inpcb->inp_socket; 153 char *s = NULL; 154 int flags; 155 struct tseg_qent tqs; 156 157 INP_WLOCK_ASSERT(tp->t_inpcb); 158 159 /* 160 * XXX: tcp_reass() is rather inefficient with its data structures 161 * and should be rewritten (see NetBSD for optimizations). 162 */ 163 164 /* 165 * Call with th==NULL after become established to 166 * force pre-ESTABLISHED data up to user socket. 167 */ 168 if (th == NULL) 169 goto present; 170 171 /* 172 * Limit the number of segments that can be queued to reduce the 173 * potential for mbuf exhaustion. For best performance, we want to be 174 * able to queue a full window's worth of segments. The size of the 175 * socket receive buffer determines our advertised window and grows 176 * automatically when socket buffer autotuning is enabled. Use it as the 177 * basis for our queue limit. 178 * 179 * However, allow the user to specify a ceiling for the number of 180 * segments in each queue. 181 * 182 * Always let the missing segment through which caused this queue. 183 * NB: Access to the socket buffer is left intentionally unlocked as we 184 * can tolerate stale information here. 185 * 186 * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat 187 * should work but causes packets to be dropped when they shouldn't. 188 * Investigate why and re-evaluate the below limit after the behaviour 189 * is understood. 190 */ 191 if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) && 192 tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1, 193 tcp_reass_maxqueuelen)) { 194 TCPSTAT_INC(tcps_rcvreassfull); 195 *tlenp = 0; 196 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) { 197 log(LOG_DEBUG, "%s; %s: queue limit reached, " 198 "segment dropped\n", s, __func__); 199 free(s, M_TCPLOG); 200 } 201 m_freem(m); 202 return (0); 203 } 204 205 /* 206 * Allocate a new queue entry. If we can't, or hit the zone limit 207 * just drop the pkt. 208 * 209 * Use a temporary structure on the stack for the missing segment 210 * when the zone is exhausted. Otherwise we may get stuck. 211 */ 212 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 213 if (te == NULL) { 214 if (th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) { 215 TCPSTAT_INC(tcps_rcvmemdrop); 216 m_freem(m); 217 *tlenp = 0; 218 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, 219 NULL))) { 220 log(LOG_DEBUG, "%s; %s: global zone limit " 221 "reached, segment dropped\n", s, __func__); 222 free(s, M_TCPLOG); 223 } 224 return (0); 225 } else { 226 bzero(&tqs, sizeof(struct tseg_qent)); 227 te = &tqs; 228 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, 229 NULL))) { 230 log(LOG_DEBUG, 231 "%s; %s: global zone limit reached, using " 232 "stack for missing segment\n", s, __func__); 233 free(s, M_TCPLOG); 234 } 235 } 236 } 237 tp->t_segqlen++; 238 239 /* 240 * Find a segment which begins after this one does. 241 */ 242 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 243 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 244 break; 245 p = q; 246 } 247 248 /* 249 * If there is a preceding segment, it may provide some of 250 * our data already. If so, drop the data from the incoming 251 * segment. If it provides all of our data, drop us. 252 */ 253 if (p != NULL) { 254 int i; 255 /* conversion to int (in i) handles seq wraparound */ 256 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 257 if (i > 0) { 258 if (i >= *tlenp) { 259 TCPSTAT_INC(tcps_rcvduppack); 260 TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp); 261 m_freem(m); 262 if (te != &tqs) 263 uma_zfree(tcp_reass_zone, te); 264 tp->t_segqlen--; 265 /* 266 * Try to present any queued data 267 * at the left window edge to the user. 268 * This is needed after the 3-WHS 269 * completes. 270 */ 271 goto present; /* ??? */ 272 } 273 m_adj(m, i); 274 *tlenp -= i; 275 th->th_seq += i; 276 } 277 } 278 tp->t_rcvoopack++; 279 TCPSTAT_INC(tcps_rcvoopack); 280 TCPSTAT_ADD(tcps_rcvoobyte, *tlenp); 281 282 /* 283 * While we overlap succeeding segments trim them or, 284 * if they are completely covered, dequeue them. 285 */ 286 while (q) { 287 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 288 if (i <= 0) 289 break; 290 if (i < q->tqe_len) { 291 q->tqe_th->th_seq += i; 292 q->tqe_len -= i; 293 m_adj(q->tqe_m, i); 294 break; 295 } 296 297 nq = LIST_NEXT(q, tqe_q); 298 LIST_REMOVE(q, tqe_q); 299 m_freem(q->tqe_m); 300 uma_zfree(tcp_reass_zone, q); 301 tp->t_segqlen--; 302 q = nq; 303 } 304 305 /* Insert the new segment queue entry into place. */ 306 te->tqe_m = m; 307 te->tqe_th = th; 308 te->tqe_len = *tlenp; 309 310 if (p == NULL) { 311 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 312 } else { 313 KASSERT(te != &tqs, ("%s: temporary stack based entry not " 314 "first element in queue", __func__)); 315 LIST_INSERT_AFTER(p, te, tqe_q); 316 } 317 318 present: 319 /* 320 * Present data to user, advancing rcv_nxt through 321 * completed sequence space. 322 */ 323 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 324 return (0); 325 q = LIST_FIRST(&tp->t_segq); 326 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 327 return (0); 328 SOCKBUF_LOCK(&so->so_rcv); 329 do { 330 tp->rcv_nxt += q->tqe_len; 331 flags = q->tqe_th->th_flags & TH_FIN; 332 nq = LIST_NEXT(q, tqe_q); 333 LIST_REMOVE(q, tqe_q); 334 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 335 m_freem(q->tqe_m); 336 else 337 sbappendstream_locked(&so->so_rcv, q->tqe_m, 0); 338 if (q != &tqs) 339 uma_zfree(tcp_reass_zone, q); 340 tp->t_segqlen--; 341 q = nq; 342 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 343 sorwakeup_locked(so); 344 return (flags); 345 } 346