1 /* $OpenBSD: tcp_input.c,v 1.386 2023/01/22 12:05:44 mvs Exp $ */ 2 /* $NetBSD: tcp_input.c,v 1.23 1996/02/13 23:43:44 christos Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 33 * 34 * NRL grants permission for redistribution and use in source and binary 35 * forms, with or without modification, of the software and documentation 36 * created at NRL provided that the following conditions are met: 37 * 38 * 1. Redistributions of source code must retain the above copyright 39 * notice, this list of conditions and the following disclaimer. 40 * 2. Redistributions in binary form must reproduce the above copyright 41 * notice, this list of conditions and the following disclaimer in the 42 * documentation and/or other materials provided with the distribution. 43 * 3. All advertising materials mentioning features or use of this software 44 * must display the following acknowledgements: 45 * This product includes software developed by the University of 46 * California, Berkeley and its contributors. 47 * This product includes software developed at the Information 48 * Technology Division, US Naval Research Laboratory. 49 * 4. Neither the name of the NRL nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 54 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 55 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 56 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 57 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 58 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 59 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 60 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 61 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 62 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 63 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 64 * 65 * The views and conclusions contained in the software and documentation 66 * are those of the authors and should not be interpreted as representing 67 * official policies, either expressed or implied, of the US Naval 68 * Research Laboratory (NRL). 69 */ 70 71 #include "pf.h" 72 73 #include <sys/param.h> 74 #include <sys/systm.h> 75 #include <sys/mbuf.h> 76 #include <sys/protosw.h> 77 #include <sys/socket.h> 78 #include <sys/socketvar.h> 79 #include <sys/timeout.h> 80 #include <sys/kernel.h> 81 #include <sys/pool.h> 82 83 #include <net/if.h> 84 #include <net/if_var.h> 85 #include <net/route.h> 86 87 #include <netinet/in.h> 88 #include <netinet/ip.h> 89 #include <netinet/in_pcb.h> 90 #include <netinet/ip_var.h> 91 #include <netinet/tcp.h> 92 #include <netinet/tcp_fsm.h> 93 #include <netinet/tcp_seq.h> 94 #include <netinet/tcp_timer.h> 95 #include <netinet/tcp_var.h> 96 #include <netinet/tcp_debug.h> 97 98 #if NPF > 0 99 #include <net/pfvar.h> 100 #endif 101 102 struct tcpiphdr tcp_saveti; 103 104 int tcp_mss_adv(struct mbuf *, int); 105 int tcp_flush_queue(struct tcpcb *); 106 107 #ifdef INET6 108 #include <netinet6/in6_var.h> 109 #include <netinet6/nd6.h> 110 111 struct tcpipv6hdr tcp_saveti6; 112 113 /* for the packet header length in the mbuf */ 114 #define M_PH_LEN(m) (((struct mbuf *)(m))->m_pkthdr.len) 115 #define M_V6_LEN(m) (M_PH_LEN(m) - sizeof(struct ip6_hdr)) 116 #define M_V4_LEN(m) (M_PH_LEN(m) - sizeof(struct ip)) 117 #endif /* INET6 */ 118 119 int tcprexmtthresh = 3; 120 int tcptv_keep_init = TCPTV_KEEP_INIT; 121 122 int tcp_rst_ppslim = 100; /* 100pps */ 123 int tcp_rst_ppslim_count = 0; 124 struct timeval tcp_rst_ppslim_last; 125 126 int tcp_ackdrop_ppslim = 100; /* 100pps */ 127 int tcp_ackdrop_ppslim_count = 0; 128 struct timeval tcp_ackdrop_ppslim_last; 129 130 #define TCP_PAWS_IDLE TCP_TIME(24 * 24 * 60 * 60) 131 132 /* for modulo comparisons of timestamps */ 133 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) 134 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) 135 136 /* for TCP SACK comparisons */ 137 #define SEQ_MIN(a,b) (SEQ_LT(a,b) ? (a) : (b)) 138 #define SEQ_MAX(a,b) (SEQ_GT(a,b) ? (a) : (b)) 139 140 /* 141 * Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. 142 */ 143 #ifdef INET6 144 #define ND6_HINT(tp) \ 145 do { \ 146 if (tp && tp->t_inpcb && (tp->t_inpcb->inp_flags & INP_IPV6) && \ 147 rtisvalid(tp->t_inpcb->inp_route6.ro_rt)) { \ 148 nd6_nud_hint(tp->t_inpcb->inp_route6.ro_rt); \ 149 } \ 150 } while (0) 151 #else 152 #define ND6_HINT(tp) 153 #endif 154 155 #ifdef TCP_ECN 156 /* 157 * ECN (Explicit Congestion Notification) support based on RFC3168 158 * implementation note: 159 * snd_last is used to track a recovery phase. 160 * when cwnd is reduced, snd_last is set to snd_max. 161 * while snd_last > snd_una, the sender is in a recovery phase and 162 * its cwnd should not be reduced again. 163 * snd_last follows snd_una when not in a recovery phase. 164 */ 165 #endif 166 167 /* 168 * Macro to compute ACK transmission behavior. Delay the ACK unless 169 * we have already delayed an ACK (must send an ACK every two segments). 170 * We also ACK immediately if we received a PUSH and the ACK-on-PUSH 171 * option is enabled or when the packet is coming from a loopback 172 * interface. 173 */ 174 #define TCP_SETUP_ACK(tp, tiflags, m) \ 175 do { \ 176 struct ifnet *ifp = NULL; \ 177 if (m && (m->m_flags & M_PKTHDR)) \ 178 ifp = if_get(m->m_pkthdr.ph_ifidx); \ 179 if (TCP_TIMER_ISARMED(tp, TCPT_DELACK) || \ 180 (tcp_ack_on_push && (tiflags) & TH_PUSH) || \ 181 (ifp && (ifp->if_flags & IFF_LOOPBACK))) \ 182 tp->t_flags |= TF_ACKNOW; \ 183 else \ 184 TCP_TIMER_ARM(tp, TCPT_DELACK, tcp_delack_msecs); \ 185 if_put(ifp); \ 186 } while (0) 187 188 void tcp_sack_partialack(struct tcpcb *, struct tcphdr *); 189 void tcp_newreno_partialack(struct tcpcb *, struct tcphdr *); 190 191 void syn_cache_put(struct syn_cache *); 192 void syn_cache_rm(struct syn_cache *); 193 int syn_cache_respond(struct syn_cache *, struct mbuf *, uint32_t); 194 void syn_cache_timer(void *); 195 void syn_cache_reaper(void *); 196 void syn_cache_insert(struct syn_cache *, struct tcpcb *); 197 void syn_cache_reset(struct sockaddr *, struct sockaddr *, 198 struct tcphdr *, u_int); 199 int syn_cache_add(struct sockaddr *, struct sockaddr *, struct tcphdr *, 200 unsigned int, struct socket *, struct mbuf *, u_char *, int, 201 struct tcp_opt_info *, tcp_seq *, uint32_t); 202 struct socket *syn_cache_get(struct sockaddr *, struct sockaddr *, 203 struct tcphdr *, unsigned int, unsigned int, struct socket *, 204 struct mbuf *, uint32_t); 205 struct syn_cache *syn_cache_lookup(struct sockaddr *, struct sockaddr *, 206 struct syn_cache_head **, u_int); 207 208 /* 209 * Insert segment ti into reassembly queue of tcp with 210 * control block tp. Return TH_FIN if reassembly now includes 211 * a segment with FIN. The macro form does the common case inline 212 * (segment is the next to be received on an established connection, 213 * and the queue is empty), avoiding linkage into and removal 214 * from the queue and repetition of various conversions. 215 * Set DELACK for segments received in order, but ack immediately 216 * when segments are out of order (so fast retransmit can work). 217 */ 218 219 int 220 tcp_reass(struct tcpcb *tp, struct tcphdr *th, struct mbuf *m, int *tlen) 221 { 222 struct tcpqent *p, *q, *nq, *tiqe; 223 224 /* 225 * Allocate a new queue entry, before we throw away any data. 226 * If we can't, just drop the packet. XXX 227 */ 228 tiqe = pool_get(&tcpqe_pool, PR_NOWAIT); 229 if (tiqe == NULL) { 230 tiqe = TAILQ_LAST(&tp->t_segq, tcpqehead); 231 if (tiqe != NULL && th->th_seq == tp->rcv_nxt) { 232 /* Reuse last entry since new segment fills a hole */ 233 m_freem(tiqe->tcpqe_m); 234 TAILQ_REMOVE(&tp->t_segq, tiqe, tcpqe_q); 235 } 236 if (tiqe == NULL || th->th_seq != tp->rcv_nxt) { 237 /* Flush segment queue for this connection */ 238 tcp_freeq(tp); 239 tcpstat_inc(tcps_rcvmemdrop); 240 m_freem(m); 241 return (0); 242 } 243 } 244 245 /* 246 * Find a segment which begins after this one does. 247 */ 248 for (p = NULL, q = TAILQ_FIRST(&tp->t_segq); q != NULL; 249 p = q, q = TAILQ_NEXT(q, tcpqe_q)) 250 if (SEQ_GT(q->tcpqe_tcp->th_seq, th->th_seq)) 251 break; 252 253 /* 254 * If there is a preceding segment, it may provide some of 255 * our data already. If so, drop the data from the incoming 256 * segment. If it provides all of our data, drop us. 257 */ 258 if (p != NULL) { 259 struct tcphdr *phdr = p->tcpqe_tcp; 260 int i; 261 262 /* conversion to int (in i) handles seq wraparound */ 263 i = phdr->th_seq + phdr->th_reseqlen - th->th_seq; 264 if (i > 0) { 265 if (i >= *tlen) { 266 tcpstat_pkt(tcps_rcvduppack, tcps_rcvdupbyte, 267 *tlen); 268 m_freem(m); 269 pool_put(&tcpqe_pool, tiqe); 270 return (0); 271 } 272 m_adj(m, i); 273 *tlen -= i; 274 th->th_seq += i; 275 } 276 } 277 tcpstat_pkt(tcps_rcvoopack, tcps_rcvoobyte, *tlen); 278 tp->t_rcvoopack++; 279 280 /* 281 * While we overlap succeeding segments trim them or, 282 * if they are completely covered, dequeue them. 283 */ 284 for (; q != NULL; q = nq) { 285 struct tcphdr *qhdr = q->tcpqe_tcp; 286 int i = (th->th_seq + *tlen) - qhdr->th_seq; 287 288 if (i <= 0) 289 break; 290 if (i < qhdr->th_reseqlen) { 291 qhdr->th_seq += i; 292 qhdr->th_reseqlen -= i; 293 m_adj(q->tcpqe_m, i); 294 break; 295 } 296 nq = TAILQ_NEXT(q, tcpqe_q); 297 m_freem(q->tcpqe_m); 298 TAILQ_REMOVE(&tp->t_segq, q, tcpqe_q); 299 pool_put(&tcpqe_pool, q); 300 } 301 302 /* Insert the new segment queue entry into place. */ 303 tiqe->tcpqe_m = m; 304 th->th_reseqlen = *tlen; 305 tiqe->tcpqe_tcp = th; 306 if (p == NULL) { 307 TAILQ_INSERT_HEAD(&tp->t_segq, tiqe, tcpqe_q); 308 } else { 309 TAILQ_INSERT_AFTER(&tp->t_segq, p, tiqe, tcpqe_q); 310 } 311 312 if (th->th_seq != tp->rcv_nxt) 313 return (0); 314 315 return (tcp_flush_queue(tp)); 316 } 317 318 int 319 tcp_flush_queue(struct tcpcb *tp) 320 { 321 struct socket *so = tp->t_inpcb->inp_socket; 322 struct tcpqent *q, *nq; 323 int flags; 324 325 /* 326 * Present data to user, advancing rcv_nxt through 327 * completed sequence space. 328 */ 329 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 330 return (0); 331 q = TAILQ_FIRST(&tp->t_segq); 332 if (q == NULL || q->tcpqe_tcp->th_seq != tp->rcv_nxt) 333 return (0); 334 if (tp->t_state == TCPS_SYN_RECEIVED && q->tcpqe_tcp->th_reseqlen) 335 return (0); 336 do { 337 tp->rcv_nxt += q->tcpqe_tcp->th_reseqlen; 338 flags = q->tcpqe_tcp->th_flags & TH_FIN; 339 340 nq = TAILQ_NEXT(q, tcpqe_q); 341 TAILQ_REMOVE(&tp->t_segq, q, tcpqe_q); 342 ND6_HINT(tp); 343 if (so->so_rcv.sb_state & SS_CANTRCVMORE) 344 m_freem(q->tcpqe_m); 345 else 346 sbappendstream(so, &so->so_rcv, q->tcpqe_m); 347 pool_put(&tcpqe_pool, q); 348 q = nq; 349 } while (q != NULL && q->tcpqe_tcp->th_seq == tp->rcv_nxt); 350 tp->t_flags |= TF_BLOCKOUTPUT; 351 sorwakeup(so); 352 tp->t_flags &= ~TF_BLOCKOUTPUT; 353 return (flags); 354 } 355 356 /* 357 * TCP input routine, follows pages 65-76 of the 358 * protocol specification dated September, 1981 very closely. 359 */ 360 int 361 tcp_input(struct mbuf **mp, int *offp, int proto, int af) 362 { 363 struct mbuf *m = *mp; 364 int iphlen = *offp; 365 struct ip *ip = NULL; 366 struct inpcb *inp = NULL; 367 u_int8_t *optp = NULL; 368 int optlen = 0; 369 int tlen, off; 370 struct tcpcb *otp = NULL, *tp = NULL; 371 int tiflags; 372 struct socket *so = NULL; 373 int todrop, acked, ourfinisacked; 374 int hdroptlen = 0; 375 short ostate; 376 caddr_t saveti; 377 tcp_seq iss, *reuse = NULL; 378 uint32_t now; 379 u_long tiwin; 380 struct tcp_opt_info opti; 381 struct tcphdr *th; 382 #ifdef INET6 383 struct ip6_hdr *ip6 = NULL; 384 #endif /* INET6 */ 385 #ifdef TCP_ECN 386 u_char iptos; 387 #endif 388 389 tcpstat_inc(tcps_rcvtotal); 390 391 opti.ts_present = 0; 392 opti.maxseg = 0; 393 now = tcp_now(); 394 395 /* 396 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 397 */ 398 if (m->m_flags & (M_BCAST|M_MCAST)) 399 goto drop; 400 401 /* 402 * Get IP and TCP header together in first mbuf. 403 * Note: IP leaves IP header in first mbuf. 404 */ 405 IP6_EXTHDR_GET(th, struct tcphdr *, m, iphlen, sizeof(*th)); 406 if (!th) { 407 tcpstat_inc(tcps_rcvshort); 408 return IPPROTO_DONE; 409 } 410 411 tlen = m->m_pkthdr.len - iphlen; 412 switch (af) { 413 case AF_INET: 414 ip = mtod(m, struct ip *); 415 #ifdef TCP_ECN 416 /* save ip_tos before clearing it for checksum */ 417 iptos = ip->ip_tos; 418 #endif 419 break; 420 #ifdef INET6 421 case AF_INET6: 422 ip6 = mtod(m, struct ip6_hdr *); 423 #ifdef TCP_ECN 424 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 425 #endif 426 427 /* 428 * Be proactive about unspecified IPv6 address in source. 429 * As we use all-zero to indicate unbounded/unconnected pcb, 430 * unspecified IPv6 address can be used to confuse us. 431 * 432 * Note that packets with unspecified IPv6 destination is 433 * already dropped in ip6_input. 434 */ 435 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 436 /* XXX stat */ 437 goto drop; 438 } 439 440 /* Discard packets to multicast */ 441 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) { 442 /* XXX stat */ 443 goto drop; 444 } 445 break; 446 #endif 447 default: 448 unhandled_af(af); 449 } 450 451 /* 452 * Checksum extended TCP header and data. 453 */ 454 if ((m->m_pkthdr.csum_flags & M_TCP_CSUM_IN_OK) == 0) { 455 int sum; 456 457 if (m->m_pkthdr.csum_flags & M_TCP_CSUM_IN_BAD) { 458 tcpstat_inc(tcps_rcvbadsum); 459 goto drop; 460 } 461 tcpstat_inc(tcps_inswcsum); 462 switch (af) { 463 case AF_INET: 464 sum = in4_cksum(m, IPPROTO_TCP, iphlen, tlen); 465 break; 466 #ifdef INET6 467 case AF_INET6: 468 sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 469 tlen); 470 break; 471 #endif 472 } 473 if (sum != 0) { 474 tcpstat_inc(tcps_rcvbadsum); 475 goto drop; 476 } 477 } 478 479 /* 480 * Check that TCP offset makes sense, 481 * pull out TCP options and adjust length. XXX 482 */ 483 off = th->th_off << 2; 484 if (off < sizeof(struct tcphdr) || off > tlen) { 485 tcpstat_inc(tcps_rcvbadoff); 486 goto drop; 487 } 488 tlen -= off; 489 if (off > sizeof(struct tcphdr)) { 490 IP6_EXTHDR_GET(th, struct tcphdr *, m, iphlen, off); 491 if (!th) { 492 tcpstat_inc(tcps_rcvshort); 493 return IPPROTO_DONE; 494 } 495 optlen = off - sizeof(struct tcphdr); 496 optp = (u_int8_t *)(th + 1); 497 /* 498 * Do quick retrieval of timestamp options ("options 499 * prediction?"). If timestamp is the only option and it's 500 * formatted as recommended in RFC 1323 appendix A, we 501 * quickly get the values now and not bother calling 502 * tcp_dooptions(), etc. 503 */ 504 if ((optlen == TCPOLEN_TSTAMP_APPA || 505 (optlen > TCPOLEN_TSTAMP_APPA && 506 optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && 507 *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) && 508 (th->th_flags & TH_SYN) == 0) { 509 opti.ts_present = 1; 510 opti.ts_val = ntohl(*(u_int32_t *)(optp + 4)); 511 opti.ts_ecr = ntohl(*(u_int32_t *)(optp + 8)); 512 optp = NULL; /* we've parsed the options */ 513 } 514 } 515 tiflags = th->th_flags; 516 517 /* 518 * Convert TCP protocol specific fields to host format. 519 */ 520 th->th_seq = ntohl(th->th_seq); 521 th->th_ack = ntohl(th->th_ack); 522 th->th_win = ntohs(th->th_win); 523 th->th_urp = ntohs(th->th_urp); 524 525 if (th->th_dport == 0) { 526 tcpstat_inc(tcps_noport); 527 goto dropwithreset_ratelim; 528 } 529 530 /* 531 * Locate pcb for segment. 532 */ 533 #if NPF > 0 534 inp = pf_inp_lookup(m); 535 #endif 536 findpcb: 537 if (inp == NULL) { 538 switch (af) { 539 #ifdef INET6 540 case AF_INET6: 541 inp = in6_pcblookup(&tcbtable, &ip6->ip6_src, 542 th->th_sport, &ip6->ip6_dst, th->th_dport, 543 m->m_pkthdr.ph_rtableid); 544 break; 545 #endif 546 case AF_INET: 547 inp = in_pcblookup(&tcbtable, ip->ip_src, 548 th->th_sport, ip->ip_dst, th->th_dport, 549 m->m_pkthdr.ph_rtableid); 550 break; 551 } 552 } 553 if (inp == NULL) { 554 tcpstat_inc(tcps_pcbhashmiss); 555 switch (af) { 556 #ifdef INET6 557 case AF_INET6: 558 inp = in6_pcblookup_listen(&tcbtable, &ip6->ip6_dst, 559 th->th_dport, m, m->m_pkthdr.ph_rtableid); 560 break; 561 #endif /* INET6 */ 562 case AF_INET: 563 inp = in_pcblookup_listen(&tcbtable, ip->ip_dst, 564 th->th_dport, m, m->m_pkthdr.ph_rtableid); 565 break; 566 } 567 /* 568 * If the state is CLOSED (i.e., TCB does not exist) then 569 * all data in the incoming segment is discarded. 570 * If the TCB exists but is in CLOSED state, it is embryonic, 571 * but should either do a listen or a connect soon. 572 */ 573 } 574 #ifdef IPSEC 575 if (ipsec_in_use) { 576 struct m_tag *mtag; 577 struct tdb *tdb = NULL; 578 int error; 579 580 /* Find most recent IPsec tag */ 581 mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL); 582 if (mtag != NULL) { 583 struct tdb_ident *tdbi; 584 585 tdbi = (struct tdb_ident *)(mtag + 1); 586 tdb = gettdb(tdbi->rdomain, tdbi->spi, 587 &tdbi->dst, tdbi->proto); 588 } 589 error = ipsp_spd_lookup(m, af, iphlen, IPSP_DIRECTION_IN, 590 tdb, inp, NULL, NULL); 591 tdb_unref(tdb); 592 if (error) { 593 tcpstat_inc(tcps_rcvnosec); 594 goto drop; 595 } 596 } 597 #endif /* IPSEC */ 598 599 if (inp == NULL) { 600 tcpstat_inc(tcps_noport); 601 goto dropwithreset_ratelim; 602 } 603 604 KASSERT(sotoinpcb(inp->inp_socket) == inp); 605 KASSERT(intotcpcb(inp) == NULL || intotcpcb(inp)->t_inpcb == inp); 606 soassertlocked(inp->inp_socket); 607 608 /* Check the minimum TTL for socket. */ 609 switch (af) { 610 case AF_INET: 611 if (inp->inp_ip_minttl && inp->inp_ip_minttl > ip->ip_ttl) 612 goto drop; 613 break; 614 #ifdef INET6 615 case AF_INET6: 616 if (inp->inp_ip6_minhlim && 617 inp->inp_ip6_minhlim > ip6->ip6_hlim) 618 goto drop; 619 break; 620 #endif 621 } 622 623 tp = intotcpcb(inp); 624 if (tp == NULL) 625 goto dropwithreset_ratelim; 626 if (tp->t_state == TCPS_CLOSED) 627 goto drop; 628 629 /* Unscale the window into a 32-bit value. */ 630 if ((tiflags & TH_SYN) == 0) 631 tiwin = th->th_win << tp->snd_scale; 632 else 633 tiwin = th->th_win; 634 635 so = inp->inp_socket; 636 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 637 union syn_cache_sa src; 638 union syn_cache_sa dst; 639 640 bzero(&src, sizeof(src)); 641 bzero(&dst, sizeof(dst)); 642 switch (af) { 643 case AF_INET: 644 src.sin.sin_len = sizeof(struct sockaddr_in); 645 src.sin.sin_family = AF_INET; 646 src.sin.sin_addr = ip->ip_src; 647 src.sin.sin_port = th->th_sport; 648 649 dst.sin.sin_len = sizeof(struct sockaddr_in); 650 dst.sin.sin_family = AF_INET; 651 dst.sin.sin_addr = ip->ip_dst; 652 dst.sin.sin_port = th->th_dport; 653 break; 654 #ifdef INET6 655 case AF_INET6: 656 src.sin6.sin6_len = sizeof(struct sockaddr_in6); 657 src.sin6.sin6_family = AF_INET6; 658 src.sin6.sin6_addr = ip6->ip6_src; 659 src.sin6.sin6_port = th->th_sport; 660 661 dst.sin6.sin6_len = sizeof(struct sockaddr_in6); 662 dst.sin6.sin6_family = AF_INET6; 663 dst.sin6.sin6_addr = ip6->ip6_dst; 664 dst.sin6.sin6_port = th->th_dport; 665 break; 666 #endif /* INET6 */ 667 } 668 669 if (so->so_options & SO_DEBUG) { 670 otp = tp; 671 ostate = tp->t_state; 672 switch (af) { 673 #ifdef INET6 674 case AF_INET6: 675 saveti = (caddr_t) &tcp_saveti6; 676 memcpy(&tcp_saveti6.ti6_i, ip6, sizeof(*ip6)); 677 memcpy(&tcp_saveti6.ti6_t, th, sizeof(*th)); 678 break; 679 #endif 680 case AF_INET: 681 saveti = (caddr_t) &tcp_saveti; 682 memcpy(&tcp_saveti.ti_i, ip, sizeof(*ip)); 683 memcpy(&tcp_saveti.ti_t, th, sizeof(*th)); 684 break; 685 } 686 } 687 if (so->so_options & SO_ACCEPTCONN) { 688 switch (tiflags & (TH_RST|TH_SYN|TH_ACK)) { 689 690 case TH_SYN|TH_ACK|TH_RST: 691 case TH_SYN|TH_RST: 692 case TH_ACK|TH_RST: 693 case TH_RST: 694 syn_cache_reset(&src.sa, &dst.sa, th, 695 inp->inp_rtableid); 696 goto drop; 697 698 case TH_SYN|TH_ACK: 699 /* 700 * Received a SYN,ACK. This should 701 * never happen while we are in 702 * LISTEN. Send an RST. 703 */ 704 goto badsyn; 705 706 case TH_ACK: 707 so = syn_cache_get(&src.sa, &dst.sa, 708 th, iphlen, tlen, so, m, now); 709 if (so == NULL) { 710 /* 711 * We don't have a SYN for 712 * this ACK; send an RST. 713 */ 714 goto badsyn; 715 } else if (so == (struct socket *)(-1)) { 716 /* 717 * We were unable to create 718 * the connection. If the 719 * 3-way handshake was 720 * completed, and RST has 721 * been sent to the peer. 722 * Since the mbuf might be 723 * in use for the reply, 724 * do not free it. 725 */ 726 m = *mp = NULL; 727 goto drop; 728 } else { 729 /* 730 * We have created a 731 * full-blown connection. 732 */ 733 tp = NULL; 734 in_pcbunref(inp); 735 inp = in_pcbref(sotoinpcb(so)); 736 tp = intotcpcb(inp); 737 if (tp == NULL) 738 goto badsyn; /*XXX*/ 739 740 } 741 break; 742 743 default: 744 /* 745 * None of RST, SYN or ACK was set. 746 * This is an invalid packet for a 747 * TCB in LISTEN state. Send a RST. 748 */ 749 goto badsyn; 750 751 case TH_SYN: 752 /* 753 * Received a SYN. 754 */ 755 #ifdef INET6 756 /* 757 * If deprecated address is forbidden, we do 758 * not accept SYN to deprecated interface 759 * address to prevent any new inbound 760 * connection from getting established. 761 * When we do not accept SYN, we send a TCP 762 * RST, with deprecated source address (instead 763 * of dropping it). We compromise it as it is 764 * much better for peer to send a RST, and 765 * RST will be the final packet for the 766 * exchange. 767 * 768 * If we do not forbid deprecated addresses, we 769 * accept the SYN packet. RFC2462 does not 770 * suggest dropping SYN in this case. 771 * If we decipher RFC2462 5.5.4, it says like 772 * this: 773 * 1. use of deprecated addr with existing 774 * communication is okay - "SHOULD continue 775 * to be used" 776 * 2. use of it with new communication: 777 * (2a) "SHOULD NOT be used if alternate 778 * address with sufficient scope is 779 * available" 780 * (2b) nothing mentioned otherwise. 781 * Here we fall into (2b) case as we have no 782 * choice in our source address selection - we 783 * must obey the peer. 784 * 785 * The wording in RFC2462 is confusing, and 786 * there are multiple description text for 787 * deprecated address handling - worse, they 788 * are not exactly the same. I believe 5.5.4 789 * is the best one, so we follow 5.5.4. 790 */ 791 if (ip6 && !ip6_use_deprecated) { 792 struct in6_ifaddr *ia6; 793 struct ifnet *ifp = 794 if_get(m->m_pkthdr.ph_ifidx); 795 796 if (ifp && 797 (ia6 = in6ifa_ifpwithaddr(ifp, 798 &ip6->ip6_dst)) && 799 (ia6->ia6_flags & 800 IN6_IFF_DEPRECATED)) { 801 tp = NULL; 802 if_put(ifp); 803 goto dropwithreset; 804 } 805 if_put(ifp); 806 } 807 #endif 808 809 /* 810 * LISTEN socket received a SYN 811 * from itself? This can't possibly 812 * be valid; drop the packet. 813 */ 814 if (th->th_dport == th->th_sport) { 815 switch (af) { 816 #ifdef INET6 817 case AF_INET6: 818 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, 819 &ip6->ip6_dst)) { 820 tcpstat_inc(tcps_badsyn); 821 goto drop; 822 } 823 break; 824 #endif /* INET6 */ 825 case AF_INET: 826 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) { 827 tcpstat_inc(tcps_badsyn); 828 goto drop; 829 } 830 break; 831 } 832 } 833 834 /* 835 * SYN looks ok; create compressed TCP 836 * state for it. 837 */ 838 if (so->so_qlen > so->so_qlimit || 839 syn_cache_add(&src.sa, &dst.sa, th, iphlen, 840 so, m, optp, optlen, &opti, reuse, now) 841 == -1) { 842 tcpstat_inc(tcps_dropsyn); 843 goto drop; 844 } 845 in_pcbunref(inp); 846 return IPPROTO_DONE; 847 } 848 } 849 } 850 851 #ifdef DIAGNOSTIC 852 /* 853 * Should not happen now that all embryonic connections 854 * are handled with compressed state. 855 */ 856 if (tp->t_state == TCPS_LISTEN) 857 panic("tcp_input: TCPS_LISTEN"); 858 #endif 859 860 #if NPF > 0 861 pf_inp_link(m, inp); 862 #endif 863 864 /* 865 * Segment received on connection. 866 * Reset idle time and keep-alive timer. 867 */ 868 tp->t_rcvtime = now; 869 if (TCPS_HAVEESTABLISHED(tp->t_state)) 870 TCP_TIMER_ARM(tp, TCPT_KEEP, TCP_TIME(tcp_keepidle)); 871 872 if (tp->sack_enable) 873 tcp_del_sackholes(tp, th); /* Delete stale SACK holes */ 874 875 /* 876 * Process options. 877 */ 878 #ifdef TCP_SIGNATURE 879 if (optp || (tp->t_flags & TF_SIGNATURE)) 880 #else 881 if (optp) 882 #endif 883 if (tcp_dooptions(tp, optp, optlen, th, m, iphlen, &opti, 884 m->m_pkthdr.ph_rtableid, now)) 885 goto drop; 886 887 if (opti.ts_present && opti.ts_ecr) { 888 int rtt_test; 889 890 /* subtract out the tcp timestamp modulator */ 891 opti.ts_ecr -= tp->ts_modulate; 892 893 /* make sure ts_ecr is sensible */ 894 rtt_test = now - opti.ts_ecr; 895 if (rtt_test < 0 || rtt_test > TCP_RTT_MAX) 896 opti.ts_ecr = 0; 897 } 898 899 #ifdef TCP_ECN 900 /* if congestion experienced, set ECE bit in subsequent packets. */ 901 if ((iptos & IPTOS_ECN_MASK) == IPTOS_ECN_CE) { 902 tp->t_flags |= TF_RCVD_CE; 903 tcpstat_inc(tcps_ecn_rcvce); 904 } 905 #endif 906 /* 907 * Header prediction: check for the two common cases 908 * of a uni-directional data xfer. If the packet has 909 * no control flags, is in-sequence, the window didn't 910 * change and we're not retransmitting, it's a 911 * candidate. If the length is zero and the ack moved 912 * forward, we're the sender side of the xfer. Just 913 * free the data acked & wake any higher level process 914 * that was blocked waiting for space. If the length 915 * is non-zero and the ack didn't move, we're the 916 * receiver side. If we're getting packets in-order 917 * (the reassembly queue is empty), add the data to 918 * the socket buffer and note that we need a delayed ack. 919 */ 920 if (tp->t_state == TCPS_ESTABLISHED && 921 #ifdef TCP_ECN 922 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ECE|TH_CWR|TH_ACK)) == TH_ACK && 923 #else 924 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 925 #endif 926 (!opti.ts_present || TSTMP_GEQ(opti.ts_val, tp->ts_recent)) && 927 th->th_seq == tp->rcv_nxt && 928 tiwin && tiwin == tp->snd_wnd && 929 tp->snd_nxt == tp->snd_max) { 930 931 /* 932 * If last ACK falls within this segment's sequence numbers, 933 * record the timestamp. 934 * Fix from Braden, see Stevens p. 870 935 */ 936 if (opti.ts_present && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 937 tp->ts_recent_age = now; 938 tp->ts_recent = opti.ts_val; 939 } 940 941 if (tlen == 0) { 942 if (SEQ_GT(th->th_ack, tp->snd_una) && 943 SEQ_LEQ(th->th_ack, tp->snd_max) && 944 tp->snd_cwnd >= tp->snd_wnd && 945 tp->t_dupacks == 0) { 946 /* 947 * this is a pure ack for outstanding data. 948 */ 949 tcpstat_inc(tcps_predack); 950 if (opti.ts_present && opti.ts_ecr) 951 tcp_xmit_timer(tp, now - opti.ts_ecr); 952 else if (tp->t_rtttime && 953 SEQ_GT(th->th_ack, tp->t_rtseq)) 954 tcp_xmit_timer(tp, now - tp->t_rtttime); 955 acked = th->th_ack - tp->snd_una; 956 tcpstat_pkt(tcps_rcvackpack, tcps_rcvackbyte, 957 acked); 958 tp->t_rcvacktime = now; 959 ND6_HINT(tp); 960 sbdrop(so, &so->so_snd, acked); 961 962 /* 963 * If we had a pending ICMP message that 964 * refers to data that have just been 965 * acknowledged, disregard the recorded ICMP 966 * message. 967 */ 968 if ((tp->t_flags & TF_PMTUD_PEND) && 969 SEQ_GT(th->th_ack, tp->t_pmtud_th_seq)) 970 tp->t_flags &= ~TF_PMTUD_PEND; 971 972 /* 973 * Keep track of the largest chunk of data 974 * acknowledged since last PMTU update 975 */ 976 if (tp->t_pmtud_mss_acked < acked) 977 tp->t_pmtud_mss_acked = acked; 978 979 tp->snd_una = th->th_ack; 980 /* Pull snd_wl2 up to prevent seq wrap. */ 981 tp->snd_wl2 = th->th_ack; 982 /* 983 * We want snd_last to track snd_una so 984 * as to avoid sequence wraparound problems 985 * for very large transfers. 986 */ 987 #ifdef TCP_ECN 988 if (SEQ_GT(tp->snd_una, tp->snd_last)) 989 #endif 990 tp->snd_last = tp->snd_una; 991 m_freem(m); 992 993 /* 994 * If all outstanding data are acked, stop 995 * retransmit timer, otherwise restart timer 996 * using current (possibly backed-off) value. 997 * If process is waiting for space, 998 * wakeup/selwakeup/signal. If data 999 * are ready to send, let tcp_output 1000 * decide between more output or persist. 1001 */ 1002 if (tp->snd_una == tp->snd_max) 1003 TCP_TIMER_DISARM(tp, TCPT_REXMT); 1004 else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) 1005 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 1006 1007 tcp_update_sndspace(tp); 1008 if (sb_notify(so, &so->so_snd)) { 1009 tp->t_flags |= TF_BLOCKOUTPUT; 1010 sowwakeup(so); 1011 tp->t_flags &= ~TF_BLOCKOUTPUT; 1012 } 1013 if (so->so_snd.sb_cc || 1014 tp->t_flags & TF_NEEDOUTPUT) 1015 (void) tcp_output(tp); 1016 in_pcbunref(inp); 1017 return IPPROTO_DONE; 1018 } 1019 } else if (th->th_ack == tp->snd_una && 1020 TAILQ_EMPTY(&tp->t_segq) && 1021 tlen <= sbspace(so, &so->so_rcv)) { 1022 /* 1023 * This is a pure, in-sequence data packet 1024 * with nothing on the reassembly queue and 1025 * we have enough buffer space to take it. 1026 */ 1027 /* Clean receiver SACK report if present */ 1028 if (tp->sack_enable && tp->rcv_numsacks) 1029 tcp_clean_sackreport(tp); 1030 tcpstat_inc(tcps_preddat); 1031 tp->rcv_nxt += tlen; 1032 /* Pull snd_wl1 and rcv_up up to prevent seq wrap. */ 1033 tp->snd_wl1 = th->th_seq; 1034 /* Packet has most recent segment, no urgent exists. */ 1035 tp->rcv_up = tp->rcv_nxt; 1036 tcpstat_pkt(tcps_rcvpack, tcps_rcvbyte, tlen); 1037 ND6_HINT(tp); 1038 1039 TCP_SETUP_ACK(tp, tiflags, m); 1040 /* 1041 * Drop TCP, IP headers and TCP options then add data 1042 * to socket buffer. 1043 */ 1044 if (so->so_rcv.sb_state & SS_CANTRCVMORE) 1045 m_freem(m); 1046 else { 1047 if (tp->t_srtt != 0 && tp->rfbuf_ts != 0 && 1048 now - tp->rfbuf_ts > (tp->t_srtt >> 1049 (TCP_RTT_SHIFT + TCP_RTT_BASE_SHIFT))) { 1050 tcp_update_rcvspace(tp); 1051 /* Start over with next RTT. */ 1052 tp->rfbuf_cnt = 0; 1053 tp->rfbuf_ts = 0; 1054 } else 1055 tp->rfbuf_cnt += tlen; 1056 m_adj(m, iphlen + off); 1057 sbappendstream(so, &so->so_rcv, m); 1058 } 1059 tp->t_flags |= TF_BLOCKOUTPUT; 1060 sorwakeup(so); 1061 tp->t_flags &= ~TF_BLOCKOUTPUT; 1062 if (tp->t_flags & (TF_ACKNOW|TF_NEEDOUTPUT)) 1063 (void) tcp_output(tp); 1064 in_pcbunref(inp); 1065 return IPPROTO_DONE; 1066 } 1067 } 1068 1069 /* 1070 * Compute mbuf offset to TCP data segment. 1071 */ 1072 hdroptlen = iphlen + off; 1073 1074 /* 1075 * Calculate amount of space in receive window, 1076 * and then do TCP input processing. 1077 * Receive window is amount of space in rcv queue, 1078 * but not less than advertised window. 1079 */ 1080 { int win; 1081 1082 win = sbspace(so, &so->so_rcv); 1083 if (win < 0) 1084 win = 0; 1085 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1086 } 1087 1088 switch (tp->t_state) { 1089 1090 /* 1091 * If the state is SYN_RECEIVED: 1092 * if seg contains SYN/ACK, send an RST. 1093 * if seg contains an ACK, but not for our SYN/ACK, send an RST 1094 */ 1095 1096 case TCPS_SYN_RECEIVED: 1097 if (tiflags & TH_ACK) { 1098 if (tiflags & TH_SYN) { 1099 tcpstat_inc(tcps_badsyn); 1100 goto dropwithreset; 1101 } 1102 if (SEQ_LEQ(th->th_ack, tp->snd_una) || 1103 SEQ_GT(th->th_ack, tp->snd_max)) 1104 goto dropwithreset; 1105 } 1106 break; 1107 1108 /* 1109 * If the state is SYN_SENT: 1110 * if seg contains an ACK, but not for our SYN, drop the input. 1111 * if seg contains a RST, then drop the connection. 1112 * if seg does not contain SYN, then drop it. 1113 * Otherwise this is an acceptable SYN segment 1114 * initialize tp->rcv_nxt and tp->irs 1115 * if seg contains ack then advance tp->snd_una 1116 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1117 * arrange for segment to be acked (eventually) 1118 * continue processing rest of data/controls, beginning with URG 1119 */ 1120 case TCPS_SYN_SENT: 1121 if ((tiflags & TH_ACK) && 1122 (SEQ_LEQ(th->th_ack, tp->iss) || 1123 SEQ_GT(th->th_ack, tp->snd_max))) 1124 goto dropwithreset; 1125 if (tiflags & TH_RST) { 1126 #ifdef TCP_ECN 1127 /* if ECN is enabled, fall back to non-ecn at rexmit */ 1128 if (tcp_do_ecn && !(tp->t_flags & TF_DISABLE_ECN)) 1129 goto drop; 1130 #endif 1131 if (tiflags & TH_ACK) 1132 tp = tcp_drop(tp, ECONNREFUSED); 1133 goto drop; 1134 } 1135 if ((tiflags & TH_SYN) == 0) 1136 goto drop; 1137 if (tiflags & TH_ACK) { 1138 tp->snd_una = th->th_ack; 1139 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1140 tp->snd_nxt = tp->snd_una; 1141 } 1142 TCP_TIMER_DISARM(tp, TCPT_REXMT); 1143 tp->irs = th->th_seq; 1144 tcp_mss(tp, opti.maxseg); 1145 /* Reset initial window to 1 segment for retransmit */ 1146 if (tp->t_rxtshift > 0) 1147 tp->snd_cwnd = tp->t_maxseg; 1148 tcp_rcvseqinit(tp); 1149 tp->t_flags |= TF_ACKNOW; 1150 /* 1151 * If we've sent a SACK_PERMITTED option, and the peer 1152 * also replied with one, then TF_SACK_PERMIT should have 1153 * been set in tcp_dooptions(). If it was not, disable SACKs. 1154 */ 1155 if (tp->sack_enable) 1156 tp->sack_enable = tp->t_flags & TF_SACK_PERMIT; 1157 #ifdef TCP_ECN 1158 /* 1159 * if ECE is set but CWR is not set for SYN-ACK, or 1160 * both ECE and CWR are set for simultaneous open, 1161 * peer is ECN capable. 1162 */ 1163 if (tcp_do_ecn) { 1164 switch (tiflags & (TH_ACK|TH_ECE|TH_CWR)) { 1165 case TH_ACK|TH_ECE: 1166 case TH_ECE|TH_CWR: 1167 tp->t_flags |= TF_ECN_PERMIT; 1168 tiflags &= ~(TH_ECE|TH_CWR); 1169 tcpstat_inc(tcps_ecn_accepts); 1170 } 1171 } 1172 #endif 1173 1174 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { 1175 tcpstat_inc(tcps_connects); 1176 tp->t_flags |= TF_BLOCKOUTPUT; 1177 soisconnected(so); 1178 tp->t_flags &= ~TF_BLOCKOUTPUT; 1179 tp->t_state = TCPS_ESTABLISHED; 1180 TCP_TIMER_ARM(tp, TCPT_KEEP, TCP_TIME(tcp_keepidle)); 1181 /* Do window scaling on this connection? */ 1182 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1183 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1184 tp->snd_scale = tp->requested_s_scale; 1185 tp->rcv_scale = tp->request_r_scale; 1186 } 1187 tcp_flush_queue(tp); 1188 1189 /* 1190 * if we didn't have to retransmit the SYN, 1191 * use its rtt as our initial srtt & rtt var. 1192 */ 1193 if (tp->t_rtttime) 1194 tcp_xmit_timer(tp, now - tp->t_rtttime); 1195 /* 1196 * Since new data was acked (the SYN), open the 1197 * congestion window by one MSS. We do this 1198 * here, because we won't go through the normal 1199 * ACK processing below. And since this is the 1200 * start of the connection, we know we are in 1201 * the exponential phase of slow-start. 1202 */ 1203 tp->snd_cwnd += tp->t_maxseg; 1204 } else 1205 tp->t_state = TCPS_SYN_RECEIVED; 1206 1207 #if 0 1208 trimthenstep6: 1209 #endif 1210 /* 1211 * Advance th->th_seq to correspond to first data byte. 1212 * If data, trim to stay within window, 1213 * dropping FIN if necessary. 1214 */ 1215 th->th_seq++; 1216 if (tlen > tp->rcv_wnd) { 1217 todrop = tlen - tp->rcv_wnd; 1218 m_adj(m, -todrop); 1219 tlen = tp->rcv_wnd; 1220 tiflags &= ~TH_FIN; 1221 tcpstat_pkt(tcps_rcvpackafterwin, tcps_rcvbyteafterwin, 1222 todrop); 1223 } 1224 tp->snd_wl1 = th->th_seq - 1; 1225 tp->rcv_up = th->th_seq; 1226 goto step6; 1227 /* 1228 * If a new connection request is received while in TIME_WAIT, 1229 * drop the old connection and start over if the if the 1230 * timestamp or the sequence numbers are above the previous 1231 * ones. 1232 */ 1233 case TCPS_TIME_WAIT: 1234 if (((tiflags & (TH_SYN|TH_ACK)) == TH_SYN) && 1235 ((opti.ts_present && 1236 TSTMP_LT(tp->ts_recent, opti.ts_val)) || 1237 SEQ_GT(th->th_seq, tp->rcv_nxt))) { 1238 #if NPF > 0 1239 /* 1240 * The socket will be recreated but the new state 1241 * has already been linked to the socket. Remove the 1242 * link between old socket and new state. 1243 */ 1244 pf_inp_unlink(inp); 1245 #endif 1246 /* 1247 * Advance the iss by at least 32768, but 1248 * clear the msb in order to make sure 1249 * that SEG_LT(snd_nxt, iss). 1250 */ 1251 iss = tp->snd_nxt + 1252 ((arc4random() & 0x7fffffff) | 0x8000); 1253 reuse = &iss; 1254 tp = tcp_close(tp); 1255 in_pcbunref(inp); 1256 inp = NULL; 1257 goto findpcb; 1258 } 1259 } 1260 1261 /* 1262 * States other than LISTEN or SYN_SENT. 1263 * First check timestamp, if present. 1264 * Then check that at least some bytes of segment are within 1265 * receive window. If segment begins before rcv_nxt, 1266 * drop leading data (and SYN); if nothing left, just ack. 1267 * 1268 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1269 * and it's less than opti.ts_recent, drop it. 1270 */ 1271 if (opti.ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && 1272 TSTMP_LT(opti.ts_val, tp->ts_recent)) { 1273 1274 /* Check to see if ts_recent is over 24 days old. */ 1275 if ((int)(now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1276 /* 1277 * Invalidate ts_recent. If this segment updates 1278 * ts_recent, the age will be reset later and ts_recent 1279 * will get a valid value. If it does not, setting 1280 * ts_recent to zero will at least satisfy the 1281 * requirement that zero be placed in the timestamp 1282 * echo reply when ts_recent isn't valid. The 1283 * age isn't reset until we get a valid ts_recent 1284 * because we don't want out-of-order segments to be 1285 * dropped when ts_recent is old. 1286 */ 1287 tp->ts_recent = 0; 1288 } else { 1289 tcpstat_pkt(tcps_rcvduppack, tcps_rcvdupbyte, tlen); 1290 tcpstat_inc(tcps_pawsdrop); 1291 if (tlen) 1292 goto dropafterack; 1293 goto drop; 1294 } 1295 } 1296 1297 todrop = tp->rcv_nxt - th->th_seq; 1298 if (todrop > 0) { 1299 if (tiflags & TH_SYN) { 1300 tiflags &= ~TH_SYN; 1301 th->th_seq++; 1302 if (th->th_urp > 1) 1303 th->th_urp--; 1304 else 1305 tiflags &= ~TH_URG; 1306 todrop--; 1307 } 1308 if (todrop > tlen || 1309 (todrop == tlen && (tiflags & TH_FIN) == 0)) { 1310 /* 1311 * Any valid FIN must be to the left of the 1312 * window. At this point, FIN must be a 1313 * duplicate or out-of-sequence, so drop it. 1314 */ 1315 tiflags &= ~TH_FIN; 1316 /* 1317 * Send ACK to resynchronize, and drop any data, 1318 * but keep on processing for RST or ACK. 1319 */ 1320 tp->t_flags |= TF_ACKNOW; 1321 todrop = tlen; 1322 tcpstat_pkt(tcps_rcvduppack, tcps_rcvdupbyte, todrop); 1323 } else { 1324 tcpstat_pkt(tcps_rcvpartduppack, tcps_rcvpartdupbyte, 1325 todrop); 1326 } 1327 hdroptlen += todrop; /* drop from head afterwards */ 1328 th->th_seq += todrop; 1329 tlen -= todrop; 1330 if (th->th_urp > todrop) 1331 th->th_urp -= todrop; 1332 else { 1333 tiflags &= ~TH_URG; 1334 th->th_urp = 0; 1335 } 1336 } 1337 1338 /* 1339 * If new data are received on a connection after the 1340 * user processes are gone, then RST the other end. 1341 */ 1342 if ((so->so_state & SS_NOFDREF) && 1343 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1344 tp = tcp_close(tp); 1345 tcpstat_inc(tcps_rcvafterclose); 1346 goto dropwithreset; 1347 } 1348 1349 /* 1350 * If segment ends after window, drop trailing data 1351 * (and PUSH and FIN); if nothing left, just ACK. 1352 */ 1353 todrop = (th->th_seq + tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1354 if (todrop > 0) { 1355 tcpstat_inc(tcps_rcvpackafterwin); 1356 if (todrop >= tlen) { 1357 tcpstat_add(tcps_rcvbyteafterwin, tlen); 1358 /* 1359 * If window is closed can only take segments at 1360 * window edge, and have to drop data and PUSH from 1361 * incoming segments. Continue processing, but 1362 * remember to ack. Otherwise, drop segment 1363 * and ack. 1364 */ 1365 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1366 tp->t_flags |= TF_ACKNOW; 1367 tcpstat_inc(tcps_rcvwinprobe); 1368 } else 1369 goto dropafterack; 1370 } else 1371 tcpstat_add(tcps_rcvbyteafterwin, todrop); 1372 m_adj(m, -todrop); 1373 tlen -= todrop; 1374 tiflags &= ~(TH_PUSH|TH_FIN); 1375 } 1376 1377 /* 1378 * If last ACK falls within this segment's sequence numbers, 1379 * record its timestamp if it's more recent. 1380 * NOTE that the test is modified according to the latest 1381 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1382 */ 1383 if (opti.ts_present && TSTMP_GEQ(opti.ts_val, tp->ts_recent) && 1384 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1385 tp->ts_recent_age = now; 1386 tp->ts_recent = opti.ts_val; 1387 } 1388 1389 /* 1390 * If the RST bit is set examine the state: 1391 * SYN_RECEIVED STATE: 1392 * If passive open, return to LISTEN state. 1393 * If active open, inform user that connection was refused. 1394 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 1395 * Inform user that connection was reset, and close tcb. 1396 * CLOSING, LAST_ACK, TIME_WAIT STATES 1397 * Close the tcb. 1398 */ 1399 if (tiflags & TH_RST) { 1400 if (th->th_seq != tp->last_ack_sent && 1401 th->th_seq != tp->rcv_nxt && 1402 th->th_seq != (tp->rcv_nxt + 1)) 1403 goto drop; 1404 1405 switch (tp->t_state) { 1406 case TCPS_SYN_RECEIVED: 1407 #ifdef TCP_ECN 1408 /* if ECN is enabled, fall back to non-ecn at rexmit */ 1409 if (tcp_do_ecn && !(tp->t_flags & TF_DISABLE_ECN)) 1410 goto drop; 1411 #endif 1412 so->so_error = ECONNREFUSED; 1413 goto close; 1414 1415 case TCPS_ESTABLISHED: 1416 case TCPS_FIN_WAIT_1: 1417 case TCPS_FIN_WAIT_2: 1418 case TCPS_CLOSE_WAIT: 1419 so->so_error = ECONNRESET; 1420 close: 1421 tp->t_state = TCPS_CLOSED; 1422 tcpstat_inc(tcps_drops); 1423 tp = tcp_close(tp); 1424 goto drop; 1425 case TCPS_CLOSING: 1426 case TCPS_LAST_ACK: 1427 case TCPS_TIME_WAIT: 1428 tp = tcp_close(tp); 1429 goto drop; 1430 } 1431 } 1432 1433 /* 1434 * If a SYN is in the window, then this is an 1435 * error and we ACK and drop the packet. 1436 */ 1437 if (tiflags & TH_SYN) 1438 goto dropafterack_ratelim; 1439 1440 /* 1441 * If the ACK bit is off we drop the segment and return. 1442 */ 1443 if ((tiflags & TH_ACK) == 0) { 1444 if (tp->t_flags & TF_ACKNOW) 1445 goto dropafterack; 1446 else 1447 goto drop; 1448 } 1449 1450 /* 1451 * Ack processing. 1452 */ 1453 switch (tp->t_state) { 1454 1455 /* 1456 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1457 * ESTABLISHED state and continue processing. 1458 * The ACK was checked above. 1459 */ 1460 case TCPS_SYN_RECEIVED: 1461 tcpstat_inc(tcps_connects); 1462 tp->t_flags |= TF_BLOCKOUTPUT; 1463 soisconnected(so); 1464 tp->t_flags &= ~TF_BLOCKOUTPUT; 1465 tp->t_state = TCPS_ESTABLISHED; 1466 TCP_TIMER_ARM(tp, TCPT_KEEP, TCP_TIME(tcp_keepidle)); 1467 /* Do window scaling? */ 1468 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1469 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1470 tp->snd_scale = tp->requested_s_scale; 1471 tp->rcv_scale = tp->request_r_scale; 1472 tiwin = th->th_win << tp->snd_scale; 1473 } 1474 tcp_flush_queue(tp); 1475 tp->snd_wl1 = th->th_seq - 1; 1476 /* fall into ... */ 1477 1478 /* 1479 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1480 * ACKs. If the ack is in the range 1481 * tp->snd_una < th->th_ack <= tp->snd_max 1482 * then advance tp->snd_una to th->th_ack and drop 1483 * data from the retransmission queue. If this ACK reflects 1484 * more up to date window information we update our window information. 1485 */ 1486 case TCPS_ESTABLISHED: 1487 case TCPS_FIN_WAIT_1: 1488 case TCPS_FIN_WAIT_2: 1489 case TCPS_CLOSE_WAIT: 1490 case TCPS_CLOSING: 1491 case TCPS_LAST_ACK: 1492 case TCPS_TIME_WAIT: 1493 #ifdef TCP_ECN 1494 /* 1495 * if we receive ECE and are not already in recovery phase, 1496 * reduce cwnd by half but don't slow-start. 1497 * advance snd_last to snd_max not to reduce cwnd again 1498 * until all outstanding packets are acked. 1499 */ 1500 if (tcp_do_ecn && (tiflags & TH_ECE)) { 1501 if ((tp->t_flags & TF_ECN_PERMIT) && 1502 SEQ_GEQ(tp->snd_una, tp->snd_last)) { 1503 u_int win; 1504 1505 win = min(tp->snd_wnd, tp->snd_cwnd) / tp->t_maxseg; 1506 if (win > 1) { 1507 tp->snd_ssthresh = win / 2 * tp->t_maxseg; 1508 tp->snd_cwnd = tp->snd_ssthresh; 1509 tp->snd_last = tp->snd_max; 1510 tp->t_flags |= TF_SEND_CWR; 1511 tcpstat_inc(tcps_cwr_ecn); 1512 } 1513 } 1514 tcpstat_inc(tcps_ecn_rcvece); 1515 } 1516 /* 1517 * if we receive CWR, we know that the peer has reduced 1518 * its congestion window. stop sending ecn-echo. 1519 */ 1520 if ((tiflags & TH_CWR)) { 1521 tp->t_flags &= ~TF_RCVD_CE; 1522 tcpstat_inc(tcps_ecn_rcvcwr); 1523 } 1524 #endif /* TCP_ECN */ 1525 1526 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1527 /* 1528 * Duplicate/old ACK processing. 1529 * Increments t_dupacks: 1530 * Pure duplicate (same seq/ack/window, no data) 1531 * Doesn't affect t_dupacks: 1532 * Data packets. 1533 * Normal window updates (window opens) 1534 * Resets t_dupacks: 1535 * New data ACKed. 1536 * Window shrinks 1537 * Old ACK 1538 */ 1539 if (tlen) { 1540 /* Drop very old ACKs unless th_seq matches */ 1541 if (th->th_seq != tp->rcv_nxt && 1542 SEQ_LT(th->th_ack, 1543 tp->snd_una - tp->max_sndwnd)) { 1544 tcpstat_inc(tcps_rcvacktooold); 1545 goto drop; 1546 } 1547 break; 1548 } 1549 /* 1550 * If we get an old ACK, there is probably packet 1551 * reordering going on. Be conservative and reset 1552 * t_dupacks so that we are less aggressive in 1553 * doing a fast retransmit. 1554 */ 1555 if (th->th_ack != tp->snd_una) { 1556 tp->t_dupacks = 0; 1557 break; 1558 } 1559 if (tiwin == tp->snd_wnd) { 1560 tcpstat_inc(tcps_rcvdupack); 1561 /* 1562 * If we have outstanding data (other than 1563 * a window probe), this is a completely 1564 * duplicate ack (ie, window info didn't 1565 * change), the ack is the biggest we've 1566 * seen and we've seen exactly our rexmt 1567 * threshold of them, assume a packet 1568 * has been dropped and retransmit it. 1569 * Kludge snd_nxt & the congestion 1570 * window so we send only this one 1571 * packet. 1572 * 1573 * We know we're losing at the current 1574 * window size so do congestion avoidance 1575 * (set ssthresh to half the current window 1576 * and pull our congestion window back to 1577 * the new ssthresh). 1578 * 1579 * Dup acks mean that packets have left the 1580 * network (they're now cached at the receiver) 1581 * so bump cwnd by the amount in the receiver 1582 * to keep a constant cwnd packets in the 1583 * network. 1584 */ 1585 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0) 1586 tp->t_dupacks = 0; 1587 else if (++tp->t_dupacks == tcprexmtthresh) { 1588 tcp_seq onxt = tp->snd_nxt; 1589 u_long win = 1590 ulmin(tp->snd_wnd, tp->snd_cwnd) / 1591 2 / tp->t_maxseg; 1592 1593 if (SEQ_LT(th->th_ack, tp->snd_last)){ 1594 /* 1595 * False fast retx after 1596 * timeout. Do not cut window. 1597 */ 1598 tp->t_dupacks = 0; 1599 goto drop; 1600 } 1601 if (win < 2) 1602 win = 2; 1603 tp->snd_ssthresh = win * tp->t_maxseg; 1604 tp->snd_last = tp->snd_max; 1605 if (tp->sack_enable) { 1606 TCP_TIMER_DISARM(tp, TCPT_REXMT); 1607 tp->t_rtttime = 0; 1608 #ifdef TCP_ECN 1609 tp->t_flags |= TF_SEND_CWR; 1610 #endif 1611 tcpstat_inc(tcps_cwr_frecovery); 1612 tcpstat_inc(tcps_sack_recovery_episode); 1613 /* 1614 * tcp_output() will send 1615 * oldest SACK-eligible rtx. 1616 */ 1617 (void) tcp_output(tp); 1618 tp->snd_cwnd = tp->snd_ssthresh+ 1619 tp->t_maxseg * tp->t_dupacks; 1620 goto drop; 1621 } 1622 TCP_TIMER_DISARM(tp, TCPT_REXMT); 1623 tp->t_rtttime = 0; 1624 tp->snd_nxt = th->th_ack; 1625 tp->snd_cwnd = tp->t_maxseg; 1626 #ifdef TCP_ECN 1627 tp->t_flags |= TF_SEND_CWR; 1628 #endif 1629 tcpstat_inc(tcps_cwr_frecovery); 1630 tcpstat_inc(tcps_sndrexmitfast); 1631 (void) tcp_output(tp); 1632 1633 tp->snd_cwnd = tp->snd_ssthresh + 1634 tp->t_maxseg * tp->t_dupacks; 1635 if (SEQ_GT(onxt, tp->snd_nxt)) 1636 tp->snd_nxt = onxt; 1637 goto drop; 1638 } else if (tp->t_dupacks > tcprexmtthresh) { 1639 tp->snd_cwnd += tp->t_maxseg; 1640 (void) tcp_output(tp); 1641 goto drop; 1642 } 1643 } else if (tiwin < tp->snd_wnd) { 1644 /* 1645 * The window was retracted! Previous dup 1646 * ACKs may have been due to packets arriving 1647 * after the shrunken window, not a missing 1648 * packet, so play it safe and reset t_dupacks 1649 */ 1650 tp->t_dupacks = 0; 1651 } 1652 break; 1653 } 1654 /* 1655 * If the congestion window was inflated to account 1656 * for the other side's cached packets, retract it. 1657 */ 1658 if (tp->t_dupacks >= tcprexmtthresh) { 1659 /* Check for a partial ACK */ 1660 if (SEQ_LT(th->th_ack, tp->snd_last)) { 1661 if (tp->sack_enable) 1662 tcp_sack_partialack(tp, th); 1663 else 1664 tcp_newreno_partialack(tp, th); 1665 } else { 1666 /* Out of fast recovery */ 1667 tp->snd_cwnd = tp->snd_ssthresh; 1668 if (tcp_seq_subtract(tp->snd_max, th->th_ack) < 1669 tp->snd_ssthresh) 1670 tp->snd_cwnd = 1671 tcp_seq_subtract(tp->snd_max, 1672 th->th_ack); 1673 tp->t_dupacks = 0; 1674 } 1675 } else { 1676 /* 1677 * Reset the duplicate ACK counter if we 1678 * were not in fast recovery. 1679 */ 1680 tp->t_dupacks = 0; 1681 } 1682 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1683 tcpstat_inc(tcps_rcvacktoomuch); 1684 goto dropafterack_ratelim; 1685 } 1686 acked = th->th_ack - tp->snd_una; 1687 tcpstat_pkt(tcps_rcvackpack, tcps_rcvackbyte, acked); 1688 tp->t_rcvacktime = now; 1689 1690 /* 1691 * If we have a timestamp reply, update smoothed 1692 * round trip time. If no timestamp is present but 1693 * transmit timer is running and timed sequence 1694 * number was acked, update smoothed round trip time. 1695 * Since we now have an rtt measurement, cancel the 1696 * timer backoff (cf., Phil Karn's retransmit alg.). 1697 * Recompute the initial retransmit timer. 1698 */ 1699 if (opti.ts_present && opti.ts_ecr) 1700 tcp_xmit_timer(tp, now - opti.ts_ecr); 1701 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 1702 tcp_xmit_timer(tp, now - tp->t_rtttime); 1703 1704 /* 1705 * If all outstanding data is acked, stop retransmit 1706 * timer and remember to restart (more output or persist). 1707 * If there is more data to be acked, restart retransmit 1708 * timer, using current (possibly backed-off) value. 1709 */ 1710 if (th->th_ack == tp->snd_max) { 1711 TCP_TIMER_DISARM(tp, TCPT_REXMT); 1712 tp->t_flags |= TF_NEEDOUTPUT; 1713 } else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) 1714 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 1715 /* 1716 * When new data is acked, open the congestion window. 1717 * If the window gives us less than ssthresh packets 1718 * in flight, open exponentially (maxseg per packet). 1719 * Otherwise open linearly: maxseg per window 1720 * (maxseg^2 / cwnd per packet). 1721 */ 1722 { 1723 u_int cw = tp->snd_cwnd; 1724 u_int incr = tp->t_maxseg; 1725 1726 if (cw > tp->snd_ssthresh) 1727 incr = max(incr * incr / cw, 1); 1728 if (tp->t_dupacks < tcprexmtthresh) 1729 tp->snd_cwnd = ulmin(cw + incr, 1730 TCP_MAXWIN << tp->snd_scale); 1731 } 1732 ND6_HINT(tp); 1733 if (acked > so->so_snd.sb_cc) { 1734 if (tp->snd_wnd > so->so_snd.sb_cc) 1735 tp->snd_wnd -= so->so_snd.sb_cc; 1736 else 1737 tp->snd_wnd = 0; 1738 sbdrop(so, &so->so_snd, (int)so->so_snd.sb_cc); 1739 ourfinisacked = 1; 1740 } else { 1741 sbdrop(so, &so->so_snd, acked); 1742 if (tp->snd_wnd > acked) 1743 tp->snd_wnd -= acked; 1744 else 1745 tp->snd_wnd = 0; 1746 ourfinisacked = 0; 1747 } 1748 1749 tcp_update_sndspace(tp); 1750 if (sb_notify(so, &so->so_snd)) { 1751 tp->t_flags |= TF_BLOCKOUTPUT; 1752 sowwakeup(so); 1753 tp->t_flags &= ~TF_BLOCKOUTPUT; 1754 } 1755 1756 /* 1757 * If we had a pending ICMP message that referred to data 1758 * that have just been acknowledged, disregard the recorded 1759 * ICMP message. 1760 */ 1761 if ((tp->t_flags & TF_PMTUD_PEND) && 1762 SEQ_GT(th->th_ack, tp->t_pmtud_th_seq)) 1763 tp->t_flags &= ~TF_PMTUD_PEND; 1764 1765 /* 1766 * Keep track of the largest chunk of data acknowledged 1767 * since last PMTU update 1768 */ 1769 if (tp->t_pmtud_mss_acked < acked) 1770 tp->t_pmtud_mss_acked = acked; 1771 1772 tp->snd_una = th->th_ack; 1773 #ifdef TCP_ECN 1774 /* sync snd_last with snd_una */ 1775 if (SEQ_GT(tp->snd_una, tp->snd_last)) 1776 tp->snd_last = tp->snd_una; 1777 #endif 1778 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1779 tp->snd_nxt = tp->snd_una; 1780 1781 switch (tp->t_state) { 1782 1783 /* 1784 * In FIN_WAIT_1 STATE in addition to the processing 1785 * for the ESTABLISHED state if our FIN is now acknowledged 1786 * then enter FIN_WAIT_2. 1787 */ 1788 case TCPS_FIN_WAIT_1: 1789 if (ourfinisacked) { 1790 /* 1791 * If we can't receive any more 1792 * data, then closing user can proceed. 1793 * Starting the timer is contrary to the 1794 * specification, but if we don't get a FIN 1795 * we'll hang forever. 1796 */ 1797 if (so->so_rcv.sb_state & SS_CANTRCVMORE) { 1798 tp->t_flags |= TF_BLOCKOUTPUT; 1799 soisdisconnected(so); 1800 tp->t_flags &= ~TF_BLOCKOUTPUT; 1801 TCP_TIMER_ARM(tp, TCPT_2MSL, 1802 TCP_TIME(tcp_maxidle)); 1803 } 1804 tp->t_state = TCPS_FIN_WAIT_2; 1805 } 1806 break; 1807 1808 /* 1809 * In CLOSING STATE in addition to the processing for 1810 * the ESTABLISHED state if the ACK acknowledges our FIN 1811 * then enter the TIME-WAIT state, otherwise ignore 1812 * the segment. 1813 */ 1814 case TCPS_CLOSING: 1815 if (ourfinisacked) { 1816 tp->t_state = TCPS_TIME_WAIT; 1817 tcp_canceltimers(tp); 1818 TCP_TIMER_ARM(tp, TCPT_2MSL, 1819 TCP_TIME(2 * TCPTV_MSL)); 1820 tp->t_flags |= TF_BLOCKOUTPUT; 1821 soisdisconnected(so); 1822 tp->t_flags &= ~TF_BLOCKOUTPUT; 1823 } 1824 break; 1825 1826 /* 1827 * In LAST_ACK, we may still be waiting for data to drain 1828 * and/or to be acked, as well as for the ack of our FIN. 1829 * If our FIN is now acknowledged, delete the TCB, 1830 * enter the closed state and return. 1831 */ 1832 case TCPS_LAST_ACK: 1833 if (ourfinisacked) { 1834 tp = tcp_close(tp); 1835 goto drop; 1836 } 1837 break; 1838 1839 /* 1840 * In TIME_WAIT state the only thing that should arrive 1841 * is a retransmission of the remote FIN. Acknowledge 1842 * it and restart the finack timer. 1843 */ 1844 case TCPS_TIME_WAIT: 1845 TCP_TIMER_ARM(tp, TCPT_2MSL, TCP_TIME(2 * TCPTV_MSL)); 1846 goto dropafterack; 1847 } 1848 } 1849 1850 step6: 1851 /* 1852 * Update window information. 1853 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1854 */ 1855 if ((tiflags & TH_ACK) && 1856 (SEQ_LT(tp->snd_wl1, th->th_seq) || (tp->snd_wl1 == th->th_seq && 1857 (SEQ_LT(tp->snd_wl2, th->th_ack) || 1858 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 1859 /* keep track of pure window updates */ 1860 if (tlen == 0 && 1861 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 1862 tcpstat_inc(tcps_rcvwinupd); 1863 tp->snd_wnd = tiwin; 1864 tp->snd_wl1 = th->th_seq; 1865 tp->snd_wl2 = th->th_ack; 1866 if (tp->snd_wnd > tp->max_sndwnd) 1867 tp->max_sndwnd = tp->snd_wnd; 1868 tp->t_flags |= TF_NEEDOUTPUT; 1869 } 1870 1871 /* 1872 * Process segments with URG. 1873 */ 1874 if ((tiflags & TH_URG) && th->th_urp && 1875 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1876 /* 1877 * This is a kludge, but if we receive and accept 1878 * random urgent pointers, we'll crash in 1879 * soreceive. It's hard to imagine someone 1880 * actually wanting to send this much urgent data. 1881 */ 1882 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 1883 th->th_urp = 0; /* XXX */ 1884 tiflags &= ~TH_URG; /* XXX */ 1885 goto dodata; /* XXX */ 1886 } 1887 /* 1888 * If this segment advances the known urgent pointer, 1889 * then mark the data stream. This should not happen 1890 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1891 * a FIN has been received from the remote side. 1892 * In these states we ignore the URG. 1893 * 1894 * According to RFC961 (Assigned Protocols), 1895 * the urgent pointer points to the last octet 1896 * of urgent data. We continue, however, 1897 * to consider it to indicate the first octet 1898 * of data past the urgent section as the original 1899 * spec states (in one of two places). 1900 */ 1901 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 1902 tp->rcv_up = th->th_seq + th->th_urp; 1903 so->so_oobmark = so->so_rcv.sb_cc + 1904 (tp->rcv_up - tp->rcv_nxt) - 1; 1905 if (so->so_oobmark == 0) 1906 so->so_rcv.sb_state |= SS_RCVATMARK; 1907 sohasoutofband(so); 1908 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1909 } 1910 /* 1911 * Remove out of band data so doesn't get presented to user. 1912 * This can happen independent of advancing the URG pointer, 1913 * but if two URG's are pending at once, some out-of-band 1914 * data may creep in... ick. 1915 */ 1916 if (th->th_urp <= (u_int16_t) tlen && 1917 (so->so_options & SO_OOBINLINE) == 0) 1918 tcp_pulloutofband(so, th->th_urp, m, hdroptlen); 1919 } else 1920 /* 1921 * If no out of band data is expected, 1922 * pull receive urgent pointer along 1923 * with the receive window. 1924 */ 1925 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1926 tp->rcv_up = tp->rcv_nxt; 1927 dodata: /* XXX */ 1928 1929 /* 1930 * Process the segment text, merging it into the TCP sequencing queue, 1931 * and arranging for acknowledgment of receipt if necessary. 1932 * This process logically involves adjusting tp->rcv_wnd as data 1933 * is presented to the user (this happens in tcp_usrreq.c, 1934 * case PRU_RCVD). If a FIN has already been received on this 1935 * connection then we just ignore the text. 1936 */ 1937 if ((tlen || (tiflags & TH_FIN)) && 1938 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1939 tcp_seq laststart = th->th_seq; 1940 tcp_seq lastend = th->th_seq + tlen; 1941 1942 if (th->th_seq == tp->rcv_nxt && TAILQ_EMPTY(&tp->t_segq) && 1943 tp->t_state == TCPS_ESTABLISHED) { 1944 TCP_SETUP_ACK(tp, tiflags, m); 1945 tp->rcv_nxt += tlen; 1946 tiflags = th->th_flags & TH_FIN; 1947 tcpstat_pkt(tcps_rcvpack, tcps_rcvbyte, tlen); 1948 ND6_HINT(tp); 1949 if (so->so_rcv.sb_state & SS_CANTRCVMORE) 1950 m_freem(m); 1951 else { 1952 m_adj(m, hdroptlen); 1953 sbappendstream(so, &so->so_rcv, m); 1954 } 1955 tp->t_flags |= TF_BLOCKOUTPUT; 1956 sorwakeup(so); 1957 tp->t_flags &= ~TF_BLOCKOUTPUT; 1958 } else { 1959 m_adj(m, hdroptlen); 1960 tiflags = tcp_reass(tp, th, m, &tlen); 1961 tp->t_flags |= TF_ACKNOW; 1962 } 1963 if (tp->sack_enable) 1964 tcp_update_sack_list(tp, laststart, lastend); 1965 1966 /* 1967 * variable len never referenced again in modern BSD, 1968 * so why bother computing it ?? 1969 */ 1970 #if 0 1971 /* 1972 * Note the amount of data that peer has sent into 1973 * our window, in order to estimate the sender's 1974 * buffer size. 1975 */ 1976 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1977 #endif /* 0 */ 1978 } else { 1979 m_freem(m); 1980 tiflags &= ~TH_FIN; 1981 } 1982 1983 /* 1984 * If FIN is received ACK the FIN and let the user know 1985 * that the connection is closing. Ignore a FIN received before 1986 * the connection is fully established. 1987 */ 1988 if ((tiflags & TH_FIN) && TCPS_HAVEESTABLISHED(tp->t_state)) { 1989 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1990 tp->t_flags |= TF_BLOCKOUTPUT; 1991 socantrcvmore(so); 1992 tp->t_flags &= ~TF_BLOCKOUTPUT; 1993 tp->t_flags |= TF_ACKNOW; 1994 tp->rcv_nxt++; 1995 } 1996 switch (tp->t_state) { 1997 1998 /* 1999 * In ESTABLISHED STATE enter the CLOSE_WAIT state. 2000 */ 2001 case TCPS_ESTABLISHED: 2002 tp->t_state = TCPS_CLOSE_WAIT; 2003 break; 2004 2005 /* 2006 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2007 * enter the CLOSING state. 2008 */ 2009 case TCPS_FIN_WAIT_1: 2010 tp->t_state = TCPS_CLOSING; 2011 break; 2012 2013 /* 2014 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2015 * starting the time-wait timer, turning off the other 2016 * standard timers. 2017 */ 2018 case TCPS_FIN_WAIT_2: 2019 tp->t_state = TCPS_TIME_WAIT; 2020 tcp_canceltimers(tp); 2021 TCP_TIMER_ARM(tp, TCPT_2MSL, TCP_TIME(2 * TCPTV_MSL)); 2022 tp->t_flags |= TF_BLOCKOUTPUT; 2023 soisdisconnected(so); 2024 tp->t_flags &= ~TF_BLOCKOUTPUT; 2025 break; 2026 2027 /* 2028 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2029 */ 2030 case TCPS_TIME_WAIT: 2031 TCP_TIMER_ARM(tp, TCPT_2MSL, TCP_TIME(2 * TCPTV_MSL)); 2032 break; 2033 } 2034 } 2035 if (otp) 2036 tcp_trace(TA_INPUT, ostate, tp, otp, saveti, 0, tlen); 2037 2038 /* 2039 * Return any desired output. 2040 */ 2041 if (tp->t_flags & (TF_ACKNOW|TF_NEEDOUTPUT)) 2042 (void) tcp_output(tp); 2043 in_pcbunref(inp); 2044 return IPPROTO_DONE; 2045 2046 badsyn: 2047 /* 2048 * Received a bad SYN. Increment counters and dropwithreset. 2049 */ 2050 tcpstat_inc(tcps_badsyn); 2051 tp = NULL; 2052 goto dropwithreset; 2053 2054 dropafterack_ratelim: 2055 if (ppsratecheck(&tcp_ackdrop_ppslim_last, &tcp_ackdrop_ppslim_count, 2056 tcp_ackdrop_ppslim) == 0) { 2057 /* XXX stat */ 2058 goto drop; 2059 } 2060 /* ...fall into dropafterack... */ 2061 2062 dropafterack: 2063 /* 2064 * Generate an ACK dropping incoming segment if it occupies 2065 * sequence space, where the ACK reflects our state. 2066 */ 2067 if (tiflags & TH_RST) 2068 goto drop; 2069 m_freem(m); 2070 tp->t_flags |= TF_ACKNOW; 2071 (void) tcp_output(tp); 2072 in_pcbunref(inp); 2073 return IPPROTO_DONE; 2074 2075 dropwithreset_ratelim: 2076 /* 2077 * We may want to rate-limit RSTs in certain situations, 2078 * particularly if we are sending an RST in response to 2079 * an attempt to connect to or otherwise communicate with 2080 * a port for which we have no socket. 2081 */ 2082 if (ppsratecheck(&tcp_rst_ppslim_last, &tcp_rst_ppslim_count, 2083 tcp_rst_ppslim) == 0) { 2084 /* XXX stat */ 2085 goto drop; 2086 } 2087 /* ...fall into dropwithreset... */ 2088 2089 dropwithreset: 2090 /* 2091 * Generate a RST, dropping incoming segment. 2092 * Make ACK acceptable to originator of segment. 2093 * Don't bother to respond to RST. 2094 */ 2095 if (tiflags & TH_RST) 2096 goto drop; 2097 if (tiflags & TH_ACK) { 2098 tcp_respond(tp, mtod(m, caddr_t), th, (tcp_seq)0, th->th_ack, 2099 TH_RST, m->m_pkthdr.ph_rtableid, now); 2100 } else { 2101 if (tiflags & TH_SYN) 2102 tlen++; 2103 tcp_respond(tp, mtod(m, caddr_t), th, th->th_seq + tlen, 2104 (tcp_seq)0, TH_RST|TH_ACK, m->m_pkthdr.ph_rtableid, now); 2105 } 2106 m_freem(m); 2107 in_pcbunref(inp); 2108 return IPPROTO_DONE; 2109 2110 drop: 2111 /* 2112 * Drop space held by incoming segment and return. 2113 */ 2114 if (otp) 2115 tcp_trace(TA_DROP, ostate, tp, otp, saveti, 0, tlen); 2116 2117 m_freem(m); 2118 in_pcbunref(inp); 2119 return IPPROTO_DONE; 2120 } 2121 2122 int 2123 tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcphdr *th, 2124 struct mbuf *m, int iphlen, struct tcp_opt_info *oi, 2125 u_int rtableid, uint32_t now) 2126 { 2127 u_int16_t mss = 0; 2128 int opt, optlen; 2129 #ifdef TCP_SIGNATURE 2130 caddr_t sigp = NULL; 2131 struct tdb *tdb = NULL; 2132 #endif /* TCP_SIGNATURE */ 2133 2134 for (; cp && cnt > 0; cnt -= optlen, cp += optlen) { 2135 opt = cp[0]; 2136 if (opt == TCPOPT_EOL) 2137 break; 2138 if (opt == TCPOPT_NOP) 2139 optlen = 1; 2140 else { 2141 if (cnt < 2) 2142 break; 2143 optlen = cp[1]; 2144 if (optlen < 2 || optlen > cnt) 2145 break; 2146 } 2147 switch (opt) { 2148 2149 default: 2150 continue; 2151 2152 case TCPOPT_MAXSEG: 2153 if (optlen != TCPOLEN_MAXSEG) 2154 continue; 2155 if (!(th->th_flags & TH_SYN)) 2156 continue; 2157 if (TCPS_HAVERCVDSYN(tp->t_state)) 2158 continue; 2159 memcpy(&mss, cp + 2, sizeof(mss)); 2160 mss = ntohs(mss); 2161 oi->maxseg = mss; 2162 break; 2163 2164 case TCPOPT_WINDOW: 2165 if (optlen != TCPOLEN_WINDOW) 2166 continue; 2167 if (!(th->th_flags & TH_SYN)) 2168 continue; 2169 if (TCPS_HAVERCVDSYN(tp->t_state)) 2170 continue; 2171 tp->t_flags |= TF_RCVD_SCALE; 2172 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2173 break; 2174 2175 case TCPOPT_TIMESTAMP: 2176 if (optlen != TCPOLEN_TIMESTAMP) 2177 continue; 2178 oi->ts_present = 1; 2179 memcpy(&oi->ts_val, cp + 2, sizeof(oi->ts_val)); 2180 oi->ts_val = ntohl(oi->ts_val); 2181 memcpy(&oi->ts_ecr, cp + 6, sizeof(oi->ts_ecr)); 2182 oi->ts_ecr = ntohl(oi->ts_ecr); 2183 2184 if (!(th->th_flags & TH_SYN)) 2185 continue; 2186 if (TCPS_HAVERCVDSYN(tp->t_state)) 2187 continue; 2188 /* 2189 * A timestamp received in a SYN makes 2190 * it ok to send timestamp requests and replies. 2191 */ 2192 tp->t_flags |= TF_RCVD_TSTMP; 2193 tp->ts_recent = oi->ts_val; 2194 tp->ts_recent_age = now; 2195 break; 2196 2197 case TCPOPT_SACK_PERMITTED: 2198 if (!tp->sack_enable || optlen!=TCPOLEN_SACK_PERMITTED) 2199 continue; 2200 if (!(th->th_flags & TH_SYN)) 2201 continue; 2202 if (TCPS_HAVERCVDSYN(tp->t_state)) 2203 continue; 2204 /* MUST only be set on SYN */ 2205 tp->t_flags |= TF_SACK_PERMIT; 2206 break; 2207 case TCPOPT_SACK: 2208 tcp_sack_option(tp, th, cp, optlen); 2209 break; 2210 #ifdef TCP_SIGNATURE 2211 case TCPOPT_SIGNATURE: 2212 if (optlen != TCPOLEN_SIGNATURE) 2213 continue; 2214 2215 if (sigp && timingsafe_bcmp(sigp, cp + 2, 16)) 2216 goto bad; 2217 2218 sigp = cp + 2; 2219 break; 2220 #endif /* TCP_SIGNATURE */ 2221 } 2222 } 2223 2224 #ifdef TCP_SIGNATURE 2225 if (tp->t_flags & TF_SIGNATURE) { 2226 union sockaddr_union src, dst; 2227 2228 memset(&src, 0, sizeof(union sockaddr_union)); 2229 memset(&dst, 0, sizeof(union sockaddr_union)); 2230 2231 switch (tp->pf) { 2232 case 0: 2233 case AF_INET: 2234 src.sa.sa_len = sizeof(struct sockaddr_in); 2235 src.sa.sa_family = AF_INET; 2236 src.sin.sin_addr = mtod(m, struct ip *)->ip_src; 2237 dst.sa.sa_len = sizeof(struct sockaddr_in); 2238 dst.sa.sa_family = AF_INET; 2239 dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst; 2240 break; 2241 #ifdef INET6 2242 case AF_INET6: 2243 src.sa.sa_len = sizeof(struct sockaddr_in6); 2244 src.sa.sa_family = AF_INET6; 2245 src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src; 2246 dst.sa.sa_len = sizeof(struct sockaddr_in6); 2247 dst.sa.sa_family = AF_INET6; 2248 dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst; 2249 break; 2250 #endif /* INET6 */ 2251 } 2252 2253 tdb = gettdbbysrcdst(rtable_l2(rtableid), 2254 0, &src, &dst, IPPROTO_TCP); 2255 2256 /* 2257 * We don't have an SA for this peer, so we turn off 2258 * TF_SIGNATURE on the listen socket 2259 */ 2260 if (tdb == NULL && tp->t_state == TCPS_LISTEN) 2261 tp->t_flags &= ~TF_SIGNATURE; 2262 2263 } 2264 2265 if ((sigp ? TF_SIGNATURE : 0) ^ (tp->t_flags & TF_SIGNATURE)) { 2266 tcpstat_inc(tcps_rcvbadsig); 2267 goto bad; 2268 } 2269 2270 if (sigp) { 2271 char sig[16]; 2272 2273 if (tdb == NULL) { 2274 tcpstat_inc(tcps_rcvbadsig); 2275 goto bad; 2276 } 2277 2278 if (tcp_signature(tdb, tp->pf, m, th, iphlen, 1, sig) < 0) 2279 goto bad; 2280 2281 if (timingsafe_bcmp(sig, sigp, 16)) { 2282 tcpstat_inc(tcps_rcvbadsig); 2283 goto bad; 2284 } 2285 2286 tcpstat_inc(tcps_rcvgoodsig); 2287 } 2288 2289 tdb_unref(tdb); 2290 #endif /* TCP_SIGNATURE */ 2291 2292 return (0); 2293 2294 #ifdef TCP_SIGNATURE 2295 bad: 2296 tdb_unref(tdb); 2297 #endif /* TCP_SIGNATURE */ 2298 return (-1); 2299 } 2300 2301 u_long 2302 tcp_seq_subtract(u_long a, u_long b) 2303 { 2304 return ((long)(a - b)); 2305 } 2306 2307 /* 2308 * This function is called upon receipt of new valid data (while not in header 2309 * prediction mode), and it updates the ordered list of sacks. 2310 */ 2311 void 2312 tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_laststart, 2313 tcp_seq rcv_lastend) 2314 { 2315 /* 2316 * First reported block MUST be the most recent one. Subsequent 2317 * blocks SHOULD be in the order in which they arrived at the 2318 * receiver. These two conditions make the implementation fully 2319 * compliant with RFC 2018. 2320 */ 2321 int i, j = 0, count = 0, lastpos = -1; 2322 struct sackblk sack, firstsack, temp[MAX_SACK_BLKS]; 2323 2324 /* First clean up current list of sacks */ 2325 for (i = 0; i < tp->rcv_numsacks; i++) { 2326 sack = tp->sackblks[i]; 2327 if (sack.start == 0 && sack.end == 0) { 2328 count++; /* count = number of blocks to be discarded */ 2329 continue; 2330 } 2331 if (SEQ_LEQ(sack.end, tp->rcv_nxt)) { 2332 tp->sackblks[i].start = tp->sackblks[i].end = 0; 2333 count++; 2334 } else { 2335 temp[j].start = tp->sackblks[i].start; 2336 temp[j++].end = tp->sackblks[i].end; 2337 } 2338 } 2339 tp->rcv_numsacks -= count; 2340 if (tp->rcv_numsacks == 0) { /* no sack blocks currently (fast path) */ 2341 tcp_clean_sackreport(tp); 2342 if (SEQ_LT(tp->rcv_nxt, rcv_laststart)) { 2343 /* ==> need first sack block */ 2344 tp->sackblks[0].start = rcv_laststart; 2345 tp->sackblks[0].end = rcv_lastend; 2346 tp->rcv_numsacks = 1; 2347 } 2348 return; 2349 } 2350 /* Otherwise, sack blocks are already present. */ 2351 for (i = 0; i < tp->rcv_numsacks; i++) 2352 tp->sackblks[i] = temp[i]; /* first copy back sack list */ 2353 if (SEQ_GEQ(tp->rcv_nxt, rcv_lastend)) 2354 return; /* sack list remains unchanged */ 2355 /* 2356 * From here, segment just received should be (part of) the 1st sack. 2357 * Go through list, possibly coalescing sack block entries. 2358 */ 2359 firstsack.start = rcv_laststart; 2360 firstsack.end = rcv_lastend; 2361 for (i = 0; i < tp->rcv_numsacks; i++) { 2362 sack = tp->sackblks[i]; 2363 if (SEQ_LT(sack.end, firstsack.start) || 2364 SEQ_GT(sack.start, firstsack.end)) 2365 continue; /* no overlap */ 2366 if (sack.start == firstsack.start && sack.end == firstsack.end){ 2367 /* 2368 * identical block; delete it here since we will 2369 * move it to the front of the list. 2370 */ 2371 tp->sackblks[i].start = tp->sackblks[i].end = 0; 2372 lastpos = i; /* last posn with a zero entry */ 2373 continue; 2374 } 2375 if (SEQ_LEQ(sack.start, firstsack.start)) 2376 firstsack.start = sack.start; /* merge blocks */ 2377 if (SEQ_GEQ(sack.end, firstsack.end)) 2378 firstsack.end = sack.end; /* merge blocks */ 2379 tp->sackblks[i].start = tp->sackblks[i].end = 0; 2380 lastpos = i; /* last posn with a zero entry */ 2381 } 2382 if (lastpos != -1) { /* at least one merge */ 2383 for (i = 0, j = 1; i < tp->rcv_numsacks; i++) { 2384 sack = tp->sackblks[i]; 2385 if (sack.start == 0 && sack.end == 0) 2386 continue; 2387 temp[j++] = sack; 2388 } 2389 tp->rcv_numsacks = j; /* including first blk (added later) */ 2390 for (i = 1; i < tp->rcv_numsacks; i++) /* now copy back */ 2391 tp->sackblks[i] = temp[i]; 2392 } else { /* no merges -- shift sacks by 1 */ 2393 if (tp->rcv_numsacks < MAX_SACK_BLKS) 2394 tp->rcv_numsacks++; 2395 for (i = tp->rcv_numsacks-1; i > 0; i--) 2396 tp->sackblks[i] = tp->sackblks[i-1]; 2397 } 2398 tp->sackblks[0] = firstsack; 2399 return; 2400 } 2401 2402 /* 2403 * Process the TCP SACK option. tp->snd_holes is an ordered list 2404 * of holes (oldest to newest, in terms of the sequence space). 2405 */ 2406 void 2407 tcp_sack_option(struct tcpcb *tp, struct tcphdr *th, u_char *cp, int optlen) 2408 { 2409 int tmp_olen; 2410 u_char *tmp_cp; 2411 struct sackhole *cur, *p, *temp; 2412 2413 if (!tp->sack_enable) 2414 return; 2415 /* SACK without ACK doesn't make sense. */ 2416 if ((th->th_flags & TH_ACK) == 0) 2417 return; 2418 /* Make sure the ACK on this segment is in [snd_una, snd_max]. */ 2419 if (SEQ_LT(th->th_ack, tp->snd_una) || 2420 SEQ_GT(th->th_ack, tp->snd_max)) 2421 return; 2422 /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ 2423 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2424 return; 2425 /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ 2426 tmp_cp = cp + 2; 2427 tmp_olen = optlen - 2; 2428 tcpstat_inc(tcps_sack_rcv_opts); 2429 if (tp->snd_numholes < 0) 2430 tp->snd_numholes = 0; 2431 if (tp->t_maxseg == 0) 2432 panic("tcp_sack_option"); /* Should never happen */ 2433 while (tmp_olen > 0) { 2434 struct sackblk sack; 2435 2436 memcpy(&sack.start, tmp_cp, sizeof(tcp_seq)); 2437 sack.start = ntohl(sack.start); 2438 memcpy(&sack.end, tmp_cp + sizeof(tcp_seq), sizeof(tcp_seq)); 2439 sack.end = ntohl(sack.end); 2440 tmp_olen -= TCPOLEN_SACK; 2441 tmp_cp += TCPOLEN_SACK; 2442 if (SEQ_LEQ(sack.end, sack.start)) 2443 continue; /* bad SACK fields */ 2444 if (SEQ_LEQ(sack.end, tp->snd_una)) 2445 continue; /* old block */ 2446 if (SEQ_GT(th->th_ack, tp->snd_una)) { 2447 if (SEQ_LT(sack.start, th->th_ack)) 2448 continue; 2449 } 2450 if (SEQ_GT(sack.end, tp->snd_max)) 2451 continue; 2452 if (tp->snd_holes == NULL) { /* first hole */ 2453 tp->snd_holes = (struct sackhole *) 2454 pool_get(&sackhl_pool, PR_NOWAIT); 2455 if (tp->snd_holes == NULL) { 2456 /* ENOBUFS, so ignore SACKed block for now */ 2457 goto dropped; 2458 } 2459 cur = tp->snd_holes; 2460 cur->start = th->th_ack; 2461 cur->end = sack.start; 2462 cur->rxmit = cur->start; 2463 cur->next = NULL; 2464 tp->snd_numholes = 1; 2465 tp->rcv_lastsack = sack.end; 2466 /* 2467 * dups is at least one. If more data has been 2468 * SACKed, it can be greater than one. 2469 */ 2470 cur->dups = min(tcprexmtthresh, 2471 ((sack.end - cur->end)/tp->t_maxseg)); 2472 if (cur->dups < 1) 2473 cur->dups = 1; 2474 continue; /* with next sack block */ 2475 } 2476 /* Go thru list of holes: p = previous, cur = current */ 2477 p = cur = tp->snd_holes; 2478 while (cur) { 2479 if (SEQ_LEQ(sack.end, cur->start)) 2480 /* SACKs data before the current hole */ 2481 break; /* no use going through more holes */ 2482 if (SEQ_GEQ(sack.start, cur->end)) { 2483 /* SACKs data beyond the current hole */ 2484 cur->dups++; 2485 if (((sack.end - cur->end)/tp->t_maxseg) >= 2486 tcprexmtthresh) 2487 cur->dups = tcprexmtthresh; 2488 p = cur; 2489 cur = cur->next; 2490 continue; 2491 } 2492 if (SEQ_LEQ(sack.start, cur->start)) { 2493 /* Data acks at least the beginning of hole */ 2494 if (SEQ_GEQ(sack.end, cur->end)) { 2495 /* Acks entire hole, so delete hole */ 2496 if (p != cur) { 2497 p->next = cur->next; 2498 pool_put(&sackhl_pool, cur); 2499 cur = p->next; 2500 } else { 2501 cur = cur->next; 2502 pool_put(&sackhl_pool, p); 2503 p = cur; 2504 tp->snd_holes = p; 2505 } 2506 tp->snd_numholes--; 2507 continue; 2508 } 2509 /* otherwise, move start of hole forward */ 2510 cur->start = sack.end; 2511 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 2512 p = cur; 2513 cur = cur->next; 2514 continue; 2515 } 2516 /* move end of hole backward */ 2517 if (SEQ_GEQ(sack.end, cur->end)) { 2518 cur->end = sack.start; 2519 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 2520 cur->dups++; 2521 if (((sack.end - cur->end)/tp->t_maxseg) >= 2522 tcprexmtthresh) 2523 cur->dups = tcprexmtthresh; 2524 p = cur; 2525 cur = cur->next; 2526 continue; 2527 } 2528 if (SEQ_LT(cur->start, sack.start) && 2529 SEQ_GT(cur->end, sack.end)) { 2530 /* 2531 * ACKs some data in middle of a hole; need to 2532 * split current hole 2533 */ 2534 if (tp->snd_numholes >= TCP_SACKHOLE_LIMIT) 2535 goto dropped; 2536 temp = (struct sackhole *) 2537 pool_get(&sackhl_pool, PR_NOWAIT); 2538 if (temp == NULL) 2539 goto dropped; /* ENOBUFS */ 2540 temp->next = cur->next; 2541 temp->start = sack.end; 2542 temp->end = cur->end; 2543 temp->dups = cur->dups; 2544 temp->rxmit = SEQ_MAX(cur->rxmit, temp->start); 2545 cur->end = sack.start; 2546 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 2547 cur->dups++; 2548 if (((sack.end - cur->end)/tp->t_maxseg) >= 2549 tcprexmtthresh) 2550 cur->dups = tcprexmtthresh; 2551 cur->next = temp; 2552 p = temp; 2553 cur = p->next; 2554 tp->snd_numholes++; 2555 } 2556 } 2557 /* At this point, p points to the last hole on the list */ 2558 if (SEQ_LT(tp->rcv_lastsack, sack.start)) { 2559 /* 2560 * Need to append new hole at end. 2561 * Last hole is p (and it's not NULL). 2562 */ 2563 if (tp->snd_numholes >= TCP_SACKHOLE_LIMIT) 2564 goto dropped; 2565 temp = (struct sackhole *) 2566 pool_get(&sackhl_pool, PR_NOWAIT); 2567 if (temp == NULL) 2568 goto dropped; /* ENOBUFS */ 2569 temp->start = tp->rcv_lastsack; 2570 temp->end = sack.start; 2571 temp->dups = min(tcprexmtthresh, 2572 ((sack.end - sack.start)/tp->t_maxseg)); 2573 if (temp->dups < 1) 2574 temp->dups = 1; 2575 temp->rxmit = temp->start; 2576 temp->next = 0; 2577 p->next = temp; 2578 tp->rcv_lastsack = sack.end; 2579 tp->snd_numholes++; 2580 } 2581 } 2582 return; 2583 dropped: 2584 tcpstat_inc(tcps_sack_drop_opts); 2585 } 2586 2587 /* 2588 * Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if 2589 * it is completely acked; otherwise, tcp_sack_option(), called from 2590 * tcp_dooptions(), will fix up the hole. 2591 */ 2592 void 2593 tcp_del_sackholes(struct tcpcb *tp, struct tcphdr *th) 2594 { 2595 if (tp->sack_enable && tp->t_state != TCPS_LISTEN) { 2596 /* max because this could be an older ack just arrived */ 2597 tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ? 2598 th->th_ack : tp->snd_una; 2599 struct sackhole *cur = tp->snd_holes; 2600 struct sackhole *prev; 2601 while (cur) 2602 if (SEQ_LEQ(cur->end, lastack)) { 2603 prev = cur; 2604 cur = cur->next; 2605 pool_put(&sackhl_pool, prev); 2606 tp->snd_numholes--; 2607 } else if (SEQ_LT(cur->start, lastack)) { 2608 cur->start = lastack; 2609 if (SEQ_LT(cur->rxmit, cur->start)) 2610 cur->rxmit = cur->start; 2611 break; 2612 } else 2613 break; 2614 tp->snd_holes = cur; 2615 } 2616 } 2617 2618 /* 2619 * Delete all receiver-side SACK information. 2620 */ 2621 void 2622 tcp_clean_sackreport(struct tcpcb *tp) 2623 { 2624 int i; 2625 2626 tp->rcv_numsacks = 0; 2627 for (i = 0; i < MAX_SACK_BLKS; i++) 2628 tp->sackblks[i].start = tp->sackblks[i].end=0; 2629 2630 } 2631 2632 /* 2633 * Partial ack handling within a sack recovery episode. When a partial ack 2634 * arrives, turn off retransmission timer, deflate the window, do not clear 2635 * tp->t_dupacks. 2636 */ 2637 void 2638 tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th) 2639 { 2640 /* Turn off retx. timer (will start again next segment) */ 2641 TCP_TIMER_DISARM(tp, TCPT_REXMT); 2642 tp->t_rtttime = 0; 2643 /* 2644 * Partial window deflation. This statement relies on the 2645 * fact that tp->snd_una has not been updated yet. 2646 */ 2647 if (tp->snd_cwnd > (th->th_ack - tp->snd_una)) { 2648 tp->snd_cwnd -= th->th_ack - tp->snd_una; 2649 tp->snd_cwnd += tp->t_maxseg; 2650 } else 2651 tp->snd_cwnd = tp->t_maxseg; 2652 tp->snd_cwnd += tp->t_maxseg; 2653 tp->t_flags |= TF_NEEDOUTPUT; 2654 } 2655 2656 /* 2657 * Pull out of band byte out of a segment so 2658 * it doesn't appear in the user's data queue. 2659 * It is still reflected in the segment length for 2660 * sequencing purposes. 2661 */ 2662 void 2663 tcp_pulloutofband(struct socket *so, u_int urgent, struct mbuf *m, int off) 2664 { 2665 int cnt = off + urgent - 1; 2666 2667 while (cnt >= 0) { 2668 if (m->m_len > cnt) { 2669 char *cp = mtod(m, caddr_t) + cnt; 2670 struct tcpcb *tp = sototcpcb(so); 2671 2672 tp->t_iobc = *cp; 2673 tp->t_oobflags |= TCPOOB_HAVEDATA; 2674 memmove(cp, cp + 1, m->m_len - cnt - 1); 2675 m->m_len--; 2676 return; 2677 } 2678 cnt -= m->m_len; 2679 m = m->m_next; 2680 if (m == NULL) 2681 break; 2682 } 2683 panic("tcp_pulloutofband"); 2684 } 2685 2686 /* 2687 * Collect new round-trip time estimate 2688 * and update averages and current timeout. 2689 */ 2690 void 2691 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2692 { 2693 int delta, rttmin; 2694 2695 if (rtt < 0) 2696 rtt = 0; 2697 else if (rtt > TCP_RTT_MAX) 2698 rtt = TCP_RTT_MAX; 2699 2700 tcpstat_inc(tcps_rttupdated); 2701 if (tp->t_srtt != 0) { 2702 /* 2703 * delta is fixed point with 2 (TCP_RTT_BASE_SHIFT) bits 2704 * after the binary point (scaled by 4), whereas 2705 * srtt is stored as fixed point with 5 bits after the 2706 * binary point (i.e., scaled by 32). The following magic 2707 * is equivalent to the smoothing algorithm in rfc793 with 2708 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2709 * point). 2710 */ 2711 delta = (rtt << TCP_RTT_BASE_SHIFT) - 2712 (tp->t_srtt >> TCP_RTT_SHIFT); 2713 if ((tp->t_srtt += delta) <= 0) 2714 tp->t_srtt = 1 << TCP_RTT_BASE_SHIFT; 2715 /* 2716 * We accumulate a smoothed rtt variance (actually, a 2717 * smoothed mean difference), then set the retransmit 2718 * timer to smoothed rtt + 4 times the smoothed variance. 2719 * rttvar is stored as fixed point with 4 bits after the 2720 * binary point (scaled by 16). The following is 2721 * equivalent to rfc793 smoothing with an alpha of .75 2722 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2723 * rfc793's wired-in beta. 2724 */ 2725 if (delta < 0) 2726 delta = -delta; 2727 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); 2728 if ((tp->t_rttvar += delta) <= 0) 2729 tp->t_rttvar = 1 << TCP_RTT_BASE_SHIFT; 2730 } else { 2731 /* 2732 * No rtt measurement yet - use the unsmoothed rtt. 2733 * Set the variance to half the rtt (so our first 2734 * retransmit happens at 3*rtt). 2735 */ 2736 tp->t_srtt = (rtt + 1) << (TCP_RTT_SHIFT + TCP_RTT_BASE_SHIFT); 2737 tp->t_rttvar = (rtt + 1) << 2738 (TCP_RTTVAR_SHIFT + TCP_RTT_BASE_SHIFT - 1); 2739 } 2740 tp->t_rtttime = 0; 2741 tp->t_rxtshift = 0; 2742 2743 /* 2744 * the retransmit should happen at rtt + 4 * rttvar. 2745 * Because of the way we do the smoothing, srtt and rttvar 2746 * will each average +1/2 tick of bias. When we compute 2747 * the retransmit timer, we want 1/2 tick of rounding and 2748 * 1 extra tick because of +-1/2 tick uncertainty in the 2749 * firing of the timer. The bias will give us exactly the 2750 * 1.5 tick we need. But, because the bias is 2751 * statistical, we have to test that we don't drop below 2752 * the minimum feasible timer (which is 2 ticks). 2753 */ 2754 rttmin = min(max(tp->t_rttmin, rtt + 2 * (TCP_TIME(1) / hz)), 2755 TCPTV_REXMTMAX); 2756 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), rttmin, TCPTV_REXMTMAX); 2757 2758 /* 2759 * We received an ack for a packet that wasn't retransmitted; 2760 * it is probably safe to discard any error indications we've 2761 * received recently. This isn't quite right, but close enough 2762 * for now (a route might have failed after we sent a segment, 2763 * and the return path might not be symmetrical). 2764 */ 2765 tp->t_softerror = 0; 2766 } 2767 2768 /* 2769 * Determine a reasonable value for maxseg size. 2770 * If the route is known, check route for mtu. 2771 * If none, use an mss that can be handled on the outgoing 2772 * interface without forcing IP to fragment; if bigger than 2773 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2774 * to utilize large mbufs. If no route is found, route has no mtu, 2775 * or the destination isn't local, use a default, hopefully conservative 2776 * size (usually 512 or the default IP max size, but no more than the mtu 2777 * of the interface), as we can't discover anything about intervening 2778 * gateways or networks. We also initialize the congestion/slow start 2779 * window to be a single segment if the destination isn't local. 2780 * While looking at the routing entry, we also initialize other path-dependent 2781 * parameters from pre-set or cached values in the routing entry. 2782 * 2783 * Also take into account the space needed for options that we 2784 * send regularly. Make maxseg shorter by that amount to assure 2785 * that we can send maxseg amount of data even when the options 2786 * are present. Store the upper limit of the length of options plus 2787 * data in maxopd. 2788 * 2789 * NOTE: offer == -1 indicates that the maxseg size changed due to 2790 * Path MTU discovery. 2791 */ 2792 int 2793 tcp_mss(struct tcpcb *tp, int offer) 2794 { 2795 struct rtentry *rt; 2796 struct ifnet *ifp = NULL; 2797 int mss, mssopt; 2798 int iphlen; 2799 struct inpcb *inp; 2800 2801 inp = tp->t_inpcb; 2802 2803 mssopt = mss = tcp_mssdflt; 2804 2805 rt = in_pcbrtentry(inp); 2806 2807 if (rt == NULL) 2808 goto out; 2809 2810 ifp = if_get(rt->rt_ifidx); 2811 if (ifp == NULL) 2812 goto out; 2813 2814 switch (tp->pf) { 2815 #ifdef INET6 2816 case AF_INET6: 2817 iphlen = sizeof(struct ip6_hdr); 2818 break; 2819 #endif 2820 case AF_INET: 2821 iphlen = sizeof(struct ip); 2822 break; 2823 default: 2824 /* the family does not support path MTU discovery */ 2825 goto out; 2826 } 2827 2828 /* 2829 * if there's an mtu associated with the route and we support 2830 * path MTU discovery for the underlying protocol family, use it. 2831 */ 2832 if (rt->rt_mtu) { 2833 /* 2834 * One may wish to lower MSS to take into account options, 2835 * especially security-related options. 2836 */ 2837 if (tp->pf == AF_INET6 && rt->rt_mtu < IPV6_MMTU) { 2838 /* 2839 * RFC2460 section 5, last paragraph: if path MTU is 2840 * smaller than 1280, use 1280 as packet size and 2841 * attach fragment header. 2842 */ 2843 mss = IPV6_MMTU - iphlen - sizeof(struct ip6_frag) - 2844 sizeof(struct tcphdr); 2845 } else { 2846 mss = rt->rt_mtu - iphlen - 2847 sizeof(struct tcphdr); 2848 } 2849 } else if (ifp->if_flags & IFF_LOOPBACK) { 2850 mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr); 2851 } else if (tp->pf == AF_INET) { 2852 if (ip_mtudisc) 2853 mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr); 2854 } 2855 #ifdef INET6 2856 else if (tp->pf == AF_INET6) { 2857 /* 2858 * for IPv6, path MTU discovery is always turned on, 2859 * or the node must use packet size <= 1280. 2860 */ 2861 mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr); 2862 } 2863 #endif /* INET6 */ 2864 2865 /* Calculate the value that we offer in TCPOPT_MAXSEG */ 2866 if (offer != -1) { 2867 mssopt = ifp->if_mtu - iphlen - sizeof(struct tcphdr); 2868 mssopt = max(tcp_mssdflt, mssopt); 2869 } 2870 out: 2871 if_put(ifp); 2872 /* 2873 * The current mss, t_maxseg, is initialized to the default value. 2874 * If we compute a smaller value, reduce the current mss. 2875 * If we compute a larger value, return it for use in sending 2876 * a max seg size option, but don't store it for use 2877 * unless we received an offer at least that large from peer. 2878 * 2879 * However, do not accept offers lower than the minimum of 2880 * the interface MTU and 216. 2881 */ 2882 if (offer > 0) 2883 tp->t_peermss = offer; 2884 if (tp->t_peermss) 2885 mss = min(mss, max(tp->t_peermss, 216)); 2886 2887 /* sanity - at least max opt. space */ 2888 mss = max(mss, 64); 2889 2890 /* 2891 * maxopd stores the maximum length of data AND options 2892 * in a segment; maxseg is the amount of data in a normal 2893 * segment. We need to store this value (maxopd) apart 2894 * from maxseg, because now every segment carries options 2895 * and thus we normally have somewhat less data in segments. 2896 */ 2897 tp->t_maxopd = mss; 2898 2899 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2900 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP) 2901 mss -= TCPOLEN_TSTAMP_APPA; 2902 #ifdef TCP_SIGNATURE 2903 if (tp->t_flags & TF_SIGNATURE) 2904 mss -= TCPOLEN_SIGLEN; 2905 #endif 2906 2907 if (offer == -1) { 2908 /* mss changed due to Path MTU discovery */ 2909 tp->t_flags &= ~TF_PMTUD_PEND; 2910 tp->t_pmtud_mtu_sent = 0; 2911 tp->t_pmtud_mss_acked = 0; 2912 if (mss < tp->t_maxseg) { 2913 /* 2914 * Follow suggestion in RFC 2414 to reduce the 2915 * congestion window by the ratio of the old 2916 * segment size to the new segment size. 2917 */ 2918 tp->snd_cwnd = ulmax((tp->snd_cwnd / tp->t_maxseg) * 2919 mss, mss); 2920 } 2921 } else if (tcp_do_rfc3390 == 2) { 2922 /* increase initial window */ 2923 tp->snd_cwnd = ulmin(10 * mss, ulmax(2 * mss, 14600)); 2924 } else if (tcp_do_rfc3390) { 2925 /* increase initial window */ 2926 tp->snd_cwnd = ulmin(4 * mss, ulmax(2 * mss, 4380)); 2927 } else 2928 tp->snd_cwnd = mss; 2929 2930 tp->t_maxseg = mss; 2931 2932 return (offer != -1 ? mssopt : mss); 2933 } 2934 2935 u_int 2936 tcp_hdrsz(struct tcpcb *tp) 2937 { 2938 u_int hlen; 2939 2940 switch (tp->pf) { 2941 #ifdef INET6 2942 case AF_INET6: 2943 hlen = sizeof(struct ip6_hdr); 2944 break; 2945 #endif 2946 case AF_INET: 2947 hlen = sizeof(struct ip); 2948 break; 2949 default: 2950 hlen = 0; 2951 break; 2952 } 2953 hlen += sizeof(struct tcphdr); 2954 2955 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2956 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP) 2957 hlen += TCPOLEN_TSTAMP_APPA; 2958 #ifdef TCP_SIGNATURE 2959 if (tp->t_flags & TF_SIGNATURE) 2960 hlen += TCPOLEN_SIGLEN; 2961 #endif 2962 return (hlen); 2963 } 2964 2965 /* 2966 * Set connection variables based on the effective MSS. 2967 * We are passed the TCPCB for the actual connection. If we 2968 * are the server, we are called by the compressed state engine 2969 * when the 3-way handshake is complete. If we are the client, 2970 * we are called when we receive the SYN,ACK from the server. 2971 * 2972 * NOTE: The t_maxseg value must be initialized in the TCPCB 2973 * before this routine is called! 2974 */ 2975 void 2976 tcp_mss_update(struct tcpcb *tp) 2977 { 2978 int mss; 2979 u_long bufsize; 2980 struct rtentry *rt; 2981 struct socket *so; 2982 2983 so = tp->t_inpcb->inp_socket; 2984 mss = tp->t_maxseg; 2985 2986 rt = in_pcbrtentry(tp->t_inpcb); 2987 2988 if (rt == NULL) 2989 return; 2990 2991 bufsize = so->so_snd.sb_hiwat; 2992 if (bufsize < mss) { 2993 mss = bufsize; 2994 /* Update t_maxseg and t_maxopd */ 2995 tcp_mss(tp, mss); 2996 } else { 2997 bufsize = roundup(bufsize, mss); 2998 if (bufsize > sb_max) 2999 bufsize = sb_max; 3000 (void)sbreserve(so, &so->so_snd, bufsize); 3001 } 3002 3003 bufsize = so->so_rcv.sb_hiwat; 3004 if (bufsize > mss) { 3005 bufsize = roundup(bufsize, mss); 3006 if (bufsize > sb_max) 3007 bufsize = sb_max; 3008 (void)sbreserve(so, &so->so_rcv, bufsize); 3009 } 3010 3011 } 3012 3013 /* 3014 * When a partial ack arrives, force the retransmission of the 3015 * next unacknowledged segment. Do not clear tp->t_dupacks. 3016 * By setting snd_nxt to ti_ack, this forces retransmission timer 3017 * to be started again. 3018 */ 3019 void 3020 tcp_newreno_partialack(struct tcpcb *tp, struct tcphdr *th) 3021 { 3022 /* 3023 * snd_una has not been updated and the socket send buffer 3024 * not yet drained of the acked data, so we have to leave 3025 * snd_una as it was to get the correct data offset in 3026 * tcp_output(). 3027 */ 3028 tcp_seq onxt = tp->snd_nxt; 3029 u_long ocwnd = tp->snd_cwnd; 3030 3031 TCP_TIMER_DISARM(tp, TCPT_REXMT); 3032 tp->t_rtttime = 0; 3033 tp->snd_nxt = th->th_ack; 3034 /* 3035 * Set snd_cwnd to one segment beyond acknowledged offset 3036 * (tp->snd_una not yet updated when this function is called) 3037 */ 3038 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3039 (void)tcp_output(tp); 3040 tp->snd_cwnd = ocwnd; 3041 if (SEQ_GT(onxt, tp->snd_nxt)) 3042 tp->snd_nxt = onxt; 3043 /* 3044 * Partial window deflation. Relies on fact that tp->snd_una 3045 * not updated yet. 3046 */ 3047 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3048 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3049 else 3050 tp->snd_cwnd = 0; 3051 tp->snd_cwnd += tp->t_maxseg; 3052 } 3053 3054 int 3055 tcp_mss_adv(struct mbuf *m, int af) 3056 { 3057 int mss = 0; 3058 int iphlen; 3059 struct ifnet *ifp = NULL; 3060 3061 if (m && (m->m_flags & M_PKTHDR)) 3062 ifp = if_get(m->m_pkthdr.ph_ifidx); 3063 3064 switch (af) { 3065 case AF_INET: 3066 if (ifp != NULL) 3067 mss = ifp->if_mtu; 3068 iphlen = sizeof(struct ip); 3069 break; 3070 #ifdef INET6 3071 case AF_INET6: 3072 if (ifp != NULL) 3073 mss = ifp->if_mtu; 3074 iphlen = sizeof(struct ip6_hdr); 3075 break; 3076 #endif 3077 default: 3078 unhandled_af(af); 3079 } 3080 if_put(ifp); 3081 mss = mss - iphlen - sizeof(struct tcphdr); 3082 return (max(mss, tcp_mssdflt)); 3083 } 3084 3085 /* 3086 * TCP compressed state engine. Currently used to hold compressed 3087 * state for SYN_RECEIVED. 3088 */ 3089 3090 /* syn hash parameters */ 3091 int tcp_syn_hash_size = TCP_SYN_HASH_SIZE; 3092 int tcp_syn_cache_limit = TCP_SYN_HASH_SIZE*TCP_SYN_BUCKET_SIZE; 3093 int tcp_syn_bucket_limit = 3*TCP_SYN_BUCKET_SIZE; 3094 int tcp_syn_use_limit = 100000; 3095 3096 struct syn_cache_set tcp_syn_cache[2]; 3097 int tcp_syn_cache_active; 3098 3099 #define SYN_HASH(sa, sp, dp, rand) \ 3100 (((sa)->s_addr ^ (rand)[0]) * \ 3101 (((((u_int32_t)(dp))<<16) + ((u_int32_t)(sp))) ^ (rand)[4])) 3102 #ifndef INET6 3103 #define SYN_HASHALL(hash, src, dst, rand) \ 3104 do { \ 3105 hash = SYN_HASH(&satosin(src)->sin_addr, \ 3106 satosin(src)->sin_port, \ 3107 satosin(dst)->sin_port, (rand)); \ 3108 } while (/*CONSTCOND*/ 0) 3109 #else 3110 #define SYN_HASH6(sa, sp, dp, rand) \ 3111 (((sa)->s6_addr32[0] ^ (rand)[0]) * \ 3112 ((sa)->s6_addr32[1] ^ (rand)[1]) * \ 3113 ((sa)->s6_addr32[2] ^ (rand)[2]) * \ 3114 ((sa)->s6_addr32[3] ^ (rand)[3]) * \ 3115 (((((u_int32_t)(dp))<<16) + ((u_int32_t)(sp))) ^ (rand)[4])) 3116 3117 #define SYN_HASHALL(hash, src, dst, rand) \ 3118 do { \ 3119 switch ((src)->sa_family) { \ 3120 case AF_INET: \ 3121 hash = SYN_HASH(&satosin(src)->sin_addr, \ 3122 satosin(src)->sin_port, \ 3123 satosin(dst)->sin_port, (rand)); \ 3124 break; \ 3125 case AF_INET6: \ 3126 hash = SYN_HASH6(&satosin6(src)->sin6_addr, \ 3127 satosin6(src)->sin6_port, \ 3128 satosin6(dst)->sin6_port, (rand)); \ 3129 break; \ 3130 default: \ 3131 hash = 0; \ 3132 } \ 3133 } while (/*CONSTCOND*/0) 3134 #endif /* INET6 */ 3135 3136 void 3137 syn_cache_rm(struct syn_cache *sc) 3138 { 3139 sc->sc_flags |= SCF_DEAD; 3140 TAILQ_REMOVE(&sc->sc_buckethead->sch_bucket, sc, sc_bucketq); 3141 sc->sc_tp = NULL; 3142 LIST_REMOVE(sc, sc_tpq); 3143 sc->sc_buckethead->sch_length--; 3144 timeout_del(&sc->sc_timer); 3145 sc->sc_set->scs_count--; 3146 } 3147 3148 void 3149 syn_cache_put(struct syn_cache *sc) 3150 { 3151 m_free(sc->sc_ipopts); 3152 if (sc->sc_route4.ro_rt != NULL) { 3153 rtfree(sc->sc_route4.ro_rt); 3154 sc->sc_route4.ro_rt = NULL; 3155 } 3156 timeout_set(&sc->sc_timer, syn_cache_reaper, sc); 3157 timeout_add(&sc->sc_timer, 0); 3158 } 3159 3160 struct pool syn_cache_pool; 3161 3162 /* 3163 * We don't estimate RTT with SYNs, so each packet starts with the default 3164 * RTT and each timer step has a fixed timeout value. 3165 */ 3166 #define SYN_CACHE_TIMER_ARM(sc) \ 3167 do { \ 3168 TCPT_RANGESET((sc)->sc_rxtcur, \ 3169 TCPTV_SRTTDFLT * tcp_backoff[(sc)->sc_rxtshift], TCPTV_MIN, \ 3170 TCPTV_REXMTMAX); \ 3171 if (!timeout_initialized(&(sc)->sc_timer)) \ 3172 timeout_set_proc(&(sc)->sc_timer, syn_cache_timer, (sc)); \ 3173 timeout_add_msec(&(sc)->sc_timer, (sc)->sc_rxtcur); \ 3174 } while (/*CONSTCOND*/0) 3175 3176 void 3177 syn_cache_init(void) 3178 { 3179 int i; 3180 3181 /* Initialize the hash buckets. */ 3182 tcp_syn_cache[0].scs_buckethead = mallocarray(tcp_syn_hash_size, 3183 sizeof(struct syn_cache_head), M_SYNCACHE, M_WAITOK|M_ZERO); 3184 tcp_syn_cache[1].scs_buckethead = mallocarray(tcp_syn_hash_size, 3185 sizeof(struct syn_cache_head), M_SYNCACHE, M_WAITOK|M_ZERO); 3186 tcp_syn_cache[0].scs_size = tcp_syn_hash_size; 3187 tcp_syn_cache[1].scs_size = tcp_syn_hash_size; 3188 for (i = 0; i < tcp_syn_hash_size; i++) { 3189 TAILQ_INIT(&tcp_syn_cache[0].scs_buckethead[i].sch_bucket); 3190 TAILQ_INIT(&tcp_syn_cache[1].scs_buckethead[i].sch_bucket); 3191 } 3192 3193 /* Initialize the syn cache pool. */ 3194 pool_init(&syn_cache_pool, sizeof(struct syn_cache), 0, IPL_SOFTNET, 3195 0, "syncache", NULL); 3196 } 3197 3198 void 3199 syn_cache_insert(struct syn_cache *sc, struct tcpcb *tp) 3200 { 3201 struct syn_cache_set *set = &tcp_syn_cache[tcp_syn_cache_active]; 3202 struct syn_cache_head *scp; 3203 struct syn_cache *sc2; 3204 int i; 3205 3206 NET_ASSERT_LOCKED(); 3207 3208 /* 3209 * If there are no entries in the hash table, reinitialize 3210 * the hash secrets. To avoid useless cache swaps and 3211 * reinitialization, use it until the limit is reached. 3212 * An empty cache is also the opportunity to resize the hash. 3213 */ 3214 if (set->scs_count == 0 && set->scs_use <= 0) { 3215 set->scs_use = tcp_syn_use_limit; 3216 if (set->scs_size != tcp_syn_hash_size) { 3217 scp = mallocarray(tcp_syn_hash_size, sizeof(struct 3218 syn_cache_head), M_SYNCACHE, M_NOWAIT|M_ZERO); 3219 if (scp == NULL) { 3220 /* Try again next time. */ 3221 set->scs_use = 0; 3222 } else { 3223 free(set->scs_buckethead, M_SYNCACHE, 3224 set->scs_size * 3225 sizeof(struct syn_cache_head)); 3226 set->scs_buckethead = scp; 3227 set->scs_size = tcp_syn_hash_size; 3228 for (i = 0; i < tcp_syn_hash_size; i++) 3229 TAILQ_INIT(&scp[i].sch_bucket); 3230 } 3231 } 3232 arc4random_buf(set->scs_random, sizeof(set->scs_random)); 3233 tcpstat_inc(tcps_sc_seedrandom); 3234 } 3235 3236 SYN_HASHALL(sc->sc_hash, &sc->sc_src.sa, &sc->sc_dst.sa, 3237 set->scs_random); 3238 scp = &set->scs_buckethead[sc->sc_hash % set->scs_size]; 3239 sc->sc_buckethead = scp; 3240 3241 /* 3242 * Make sure that we don't overflow the per-bucket 3243 * limit or the total cache size limit. 3244 */ 3245 if (scp->sch_length >= tcp_syn_bucket_limit) { 3246 tcpstat_inc(tcps_sc_bucketoverflow); 3247 /* 3248 * Someone might attack our bucket hash function. Reseed 3249 * with random as soon as the passive syn cache gets empty. 3250 */ 3251 set->scs_use = 0; 3252 /* 3253 * The bucket is full. Toss the oldest element in the 3254 * bucket. This will be the first entry in the bucket. 3255 */ 3256 sc2 = TAILQ_FIRST(&scp->sch_bucket); 3257 #ifdef DIAGNOSTIC 3258 /* 3259 * This should never happen; we should always find an 3260 * entry in our bucket. 3261 */ 3262 if (sc2 == NULL) 3263 panic("%s: bucketoverflow: impossible", __func__); 3264 #endif 3265 syn_cache_rm(sc2); 3266 syn_cache_put(sc2); 3267 } else if (set->scs_count >= tcp_syn_cache_limit) { 3268 struct syn_cache_head *scp2, *sce; 3269 3270 tcpstat_inc(tcps_sc_overflowed); 3271 /* 3272 * The cache is full. Toss the oldest entry in the 3273 * first non-empty bucket we can find. 3274 * 3275 * XXX We would really like to toss the oldest 3276 * entry in the cache, but we hope that this 3277 * condition doesn't happen very often. 3278 */ 3279 scp2 = scp; 3280 if (TAILQ_EMPTY(&scp2->sch_bucket)) { 3281 sce = &set->scs_buckethead[set->scs_size]; 3282 for (++scp2; scp2 != scp; scp2++) { 3283 if (scp2 >= sce) 3284 scp2 = &set->scs_buckethead[0]; 3285 if (! TAILQ_EMPTY(&scp2->sch_bucket)) 3286 break; 3287 } 3288 #ifdef DIAGNOSTIC 3289 /* 3290 * This should never happen; we should always find a 3291 * non-empty bucket. 3292 */ 3293 if (scp2 == scp) 3294 panic("%s: cacheoverflow: impossible", 3295 __func__); 3296 #endif 3297 } 3298 sc2 = TAILQ_FIRST(&scp2->sch_bucket); 3299 syn_cache_rm(sc2); 3300 syn_cache_put(sc2); 3301 } 3302 3303 /* 3304 * Initialize the entry's timer. 3305 */ 3306 sc->sc_rxttot = 0; 3307 sc->sc_rxtshift = 0; 3308 SYN_CACHE_TIMER_ARM(sc); 3309 3310 /* Link it from tcpcb entry */ 3311 LIST_INSERT_HEAD(&tp->t_sc, sc, sc_tpq); 3312 3313 /* Put it into the bucket. */ 3314 TAILQ_INSERT_TAIL(&scp->sch_bucket, sc, sc_bucketq); 3315 scp->sch_length++; 3316 sc->sc_set = set; 3317 set->scs_count++; 3318 set->scs_use--; 3319 3320 tcpstat_inc(tcps_sc_added); 3321 3322 /* 3323 * If the active cache has exceeded its use limit and 3324 * the passive syn cache is empty, exchange their roles. 3325 */ 3326 if (set->scs_use <= 0 && 3327 tcp_syn_cache[!tcp_syn_cache_active].scs_count == 0) 3328 tcp_syn_cache_active = !tcp_syn_cache_active; 3329 } 3330 3331 /* 3332 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 3333 * If we have retransmitted an entry the maximum number of times, expire 3334 * that entry. 3335 */ 3336 void 3337 syn_cache_timer(void *arg) 3338 { 3339 struct syn_cache *sc = arg; 3340 uint32_t now; 3341 3342 NET_LOCK(); 3343 if (sc->sc_flags & SCF_DEAD) 3344 goto out; 3345 3346 now = tcp_now(); 3347 3348 if (__predict_false(sc->sc_rxtshift == TCP_MAXRXTSHIFT)) { 3349 /* Drop it -- too many retransmissions. */ 3350 goto dropit; 3351 } 3352 3353 /* 3354 * Compute the total amount of time this entry has 3355 * been on a queue. If this entry has been on longer 3356 * than the keep alive timer would allow, expire it. 3357 */ 3358 sc->sc_rxttot += sc->sc_rxtcur; 3359 if (sc->sc_rxttot >= TCP_TIME(tcptv_keep_init)) 3360 goto dropit; 3361 3362 tcpstat_inc(tcps_sc_retransmitted); 3363 (void) syn_cache_respond(sc, NULL, now); 3364 3365 /* Advance the timer back-off. */ 3366 sc->sc_rxtshift++; 3367 SYN_CACHE_TIMER_ARM(sc); 3368 3369 out: 3370 NET_UNLOCK(); 3371 return; 3372 3373 dropit: 3374 tcpstat_inc(tcps_sc_timed_out); 3375 syn_cache_rm(sc); 3376 syn_cache_put(sc); 3377 NET_UNLOCK(); 3378 } 3379 3380 void 3381 syn_cache_reaper(void *arg) 3382 { 3383 struct syn_cache *sc = arg; 3384 3385 pool_put(&syn_cache_pool, (sc)); 3386 return; 3387 } 3388 3389 /* 3390 * Remove syn cache created by the specified tcb entry, 3391 * because this does not make sense to keep them 3392 * (if there's no tcb entry, syn cache entry will never be used) 3393 */ 3394 void 3395 syn_cache_cleanup(struct tcpcb *tp) 3396 { 3397 struct syn_cache *sc, *nsc; 3398 3399 NET_ASSERT_LOCKED(); 3400 3401 LIST_FOREACH_SAFE(sc, &tp->t_sc, sc_tpq, nsc) { 3402 #ifdef DIAGNOSTIC 3403 if (sc->sc_tp != tp) 3404 panic("invalid sc_tp in syn_cache_cleanup"); 3405 #endif 3406 syn_cache_rm(sc); 3407 syn_cache_put(sc); 3408 } 3409 /* just for safety */ 3410 LIST_INIT(&tp->t_sc); 3411 } 3412 3413 /* 3414 * Find an entry in the syn cache. 3415 */ 3416 struct syn_cache * 3417 syn_cache_lookup(struct sockaddr *src, struct sockaddr *dst, 3418 struct syn_cache_head **headp, u_int rtableid) 3419 { 3420 struct syn_cache_set *sets[2]; 3421 struct syn_cache *sc; 3422 struct syn_cache_head *scp; 3423 u_int32_t hash; 3424 int i; 3425 3426 NET_ASSERT_LOCKED(); 3427 3428 /* Check the active cache first, the passive cache is likely empty. */ 3429 sets[0] = &tcp_syn_cache[tcp_syn_cache_active]; 3430 sets[1] = &tcp_syn_cache[!tcp_syn_cache_active]; 3431 for (i = 0; i < 2; i++) { 3432 if (sets[i]->scs_count == 0) 3433 continue; 3434 SYN_HASHALL(hash, src, dst, sets[i]->scs_random); 3435 scp = &sets[i]->scs_buckethead[hash % sets[i]->scs_size]; 3436 *headp = scp; 3437 TAILQ_FOREACH(sc, &scp->sch_bucket, sc_bucketq) { 3438 if (sc->sc_hash != hash) 3439 continue; 3440 if (!bcmp(&sc->sc_src, src, src->sa_len) && 3441 !bcmp(&sc->sc_dst, dst, dst->sa_len) && 3442 rtable_l2(rtableid) == rtable_l2(sc->sc_rtableid)) 3443 return (sc); 3444 } 3445 } 3446 return (NULL); 3447 } 3448 3449 /* 3450 * This function gets called when we receive an ACK for a 3451 * socket in the LISTEN state. We look up the connection 3452 * in the syn cache, and if its there, we pull it out of 3453 * the cache and turn it into a full-blown connection in 3454 * the SYN-RECEIVED state. 3455 * 3456 * The return values may not be immediately obvious, and their effects 3457 * can be subtle, so here they are: 3458 * 3459 * NULL SYN was not found in cache; caller should drop the 3460 * packet and send an RST. 3461 * 3462 * -1 We were unable to create the new connection, and are 3463 * aborting it. An ACK,RST is being sent to the peer 3464 * (unless we got screwy sequence numbers; see below), 3465 * because the 3-way handshake has been completed. Caller 3466 * should not free the mbuf, since we may be using it. If 3467 * we are not, we will free it. 3468 * 3469 * Otherwise, the return value is a pointer to the new socket 3470 * associated with the connection. 3471 */ 3472 struct socket * 3473 syn_cache_get(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, 3474 u_int hlen, u_int tlen, struct socket *so, struct mbuf *m, uint32_t now) 3475 { 3476 struct syn_cache *sc; 3477 struct syn_cache_head *scp; 3478 struct inpcb *inp, *oldinp; 3479 struct tcpcb *tp = NULL; 3480 struct mbuf *am; 3481 struct socket *oso; 3482 3483 NET_ASSERT_LOCKED(); 3484 3485 sc = syn_cache_lookup(src, dst, &scp, sotoinpcb(so)->inp_rtableid); 3486 if (sc == NULL) 3487 return (NULL); 3488 3489 /* 3490 * Verify the sequence and ack numbers. Try getting the correct 3491 * response again. 3492 */ 3493 if ((th->th_ack != sc->sc_iss + 1) || 3494 SEQ_LEQ(th->th_seq, sc->sc_irs) || 3495 SEQ_GT(th->th_seq, sc->sc_irs + 1 + sc->sc_win)) { 3496 (void) syn_cache_respond(sc, m, now); 3497 return ((struct socket *)(-1)); 3498 } 3499 3500 /* Remove this cache entry */ 3501 syn_cache_rm(sc); 3502 3503 /* 3504 * Ok, create the full blown connection, and set things up 3505 * as they would have been set up if we had created the 3506 * connection when the SYN arrived. If we can't create 3507 * the connection, abort it. 3508 */ 3509 oso = so; 3510 so = sonewconn(so, SS_ISCONNECTED, M_DONTWAIT); 3511 if (so == NULL) 3512 goto resetandabort; 3513 3514 oldinp = sotoinpcb(oso); 3515 inp = sotoinpcb(so); 3516 3517 #ifdef IPSEC 3518 /* 3519 * We need to copy the required security levels 3520 * from the old pcb. Ditto for any other 3521 * IPsec-related information. 3522 */ 3523 memcpy(inp->inp_seclevel, oldinp->inp_seclevel, 3524 sizeof(oldinp->inp_seclevel)); 3525 #endif /* IPSEC */ 3526 #ifdef INET6 3527 /* 3528 * inp still has the OLD in_pcb stuff, set the 3529 * v6-related flags on the new guy, too. 3530 */ 3531 inp->inp_flags |= (oldinp->inp_flags & INP_IPV6); 3532 if (inp->inp_flags & INP_IPV6) { 3533 inp->inp_ipv6.ip6_hlim = oldinp->inp_ipv6.ip6_hlim; 3534 inp->inp_hops = oldinp->inp_hops; 3535 } else 3536 #endif /* INET6 */ 3537 { 3538 inp->inp_ip.ip_ttl = oldinp->inp_ip.ip_ttl; 3539 } 3540 3541 #if NPF > 0 3542 if (m->m_pkthdr.pf.flags & PF_TAG_DIVERTED) { 3543 struct pf_divert *divert; 3544 3545 divert = pf_find_divert(m); 3546 KASSERT(divert != NULL); 3547 inp->inp_rtableid = divert->rdomain; 3548 } else 3549 #endif 3550 /* inherit rtable from listening socket */ 3551 inp->inp_rtableid = sc->sc_rtableid; 3552 3553 inp->inp_lport = th->th_dport; 3554 switch (src->sa_family) { 3555 #ifdef INET6 3556 case AF_INET6: 3557 inp->inp_laddr6 = satosin6(dst)->sin6_addr; 3558 break; 3559 #endif /* INET6 */ 3560 case AF_INET: 3561 inp->inp_laddr = satosin(dst)->sin_addr; 3562 inp->inp_options = ip_srcroute(m); 3563 if (inp->inp_options == NULL) { 3564 inp->inp_options = sc->sc_ipopts; 3565 sc->sc_ipopts = NULL; 3566 } 3567 break; 3568 } 3569 in_pcbrehash(inp); 3570 3571 /* 3572 * Give the new socket our cached route reference. 3573 */ 3574 if (src->sa_family == AF_INET) 3575 inp->inp_route = sc->sc_route4; /* struct assignment */ 3576 #ifdef INET6 3577 else 3578 inp->inp_route6 = sc->sc_route6; 3579 #endif 3580 sc->sc_route4.ro_rt = NULL; 3581 3582 am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ 3583 if (am == NULL) 3584 goto resetandabort; 3585 am->m_len = src->sa_len; 3586 memcpy(mtod(am, caddr_t), src, src->sa_len); 3587 if (in_pcbconnect(inp, am)) { 3588 (void) m_free(am); 3589 goto resetandabort; 3590 } 3591 (void) m_free(am); 3592 3593 tp = intotcpcb(inp); 3594 tp->t_flags = sototcpcb(oso)->t_flags & (TF_NOPUSH|TF_NODELAY); 3595 if (sc->sc_request_r_scale != 15) { 3596 tp->requested_s_scale = sc->sc_requested_s_scale; 3597 tp->request_r_scale = sc->sc_request_r_scale; 3598 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 3599 } 3600 if (sc->sc_flags & SCF_TIMESTAMP) 3601 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 3602 3603 tp->t_template = tcp_template(tp); 3604 if (tp->t_template == 0) { 3605 tp = tcp_drop(tp, ENOBUFS); /* destroys socket */ 3606 so = NULL; 3607 goto abort; 3608 } 3609 tp->sack_enable = sc->sc_flags & SCF_SACK_PERMIT; 3610 tp->ts_modulate = sc->sc_modulate; 3611 tp->ts_recent = sc->sc_timestamp; 3612 tp->iss = sc->sc_iss; 3613 tp->irs = sc->sc_irs; 3614 tcp_sendseqinit(tp); 3615 tp->snd_last = tp->snd_una; 3616 #ifdef TCP_ECN 3617 if (sc->sc_flags & SCF_ECN_PERMIT) { 3618 tp->t_flags |= TF_ECN_PERMIT; 3619 tcpstat_inc(tcps_ecn_accepts); 3620 } 3621 #endif 3622 if (sc->sc_flags & SCF_SACK_PERMIT) 3623 tp->t_flags |= TF_SACK_PERMIT; 3624 #ifdef TCP_SIGNATURE 3625 if (sc->sc_flags & SCF_SIGNATURE) 3626 tp->t_flags |= TF_SIGNATURE; 3627 #endif 3628 tcp_rcvseqinit(tp); 3629 tp->t_state = TCPS_SYN_RECEIVED; 3630 tp->t_rcvtime = now; 3631 tp->t_sndtime = now; 3632 tp->t_rcvacktime = now; 3633 tp->t_sndacktime = now; 3634 TCP_TIMER_ARM(tp, TCPT_KEEP, TCP_TIME(tcptv_keep_init)); 3635 tcpstat_inc(tcps_accepts); 3636 3637 tcp_mss(tp, sc->sc_peermaxseg); /* sets t_maxseg */ 3638 if (sc->sc_peermaxseg) 3639 tcp_mss_update(tp); 3640 /* Reset initial window to 1 segment for retransmit */ 3641 if (sc->sc_rxtshift > 0) 3642 tp->snd_cwnd = tp->t_maxseg; 3643 tp->snd_wl1 = sc->sc_irs; 3644 tp->rcv_up = sc->sc_irs + 1; 3645 3646 /* 3647 * This is what would have happened in tcp_output() when 3648 * the SYN,ACK was sent. 3649 */ 3650 tp->snd_up = tp->snd_una; 3651 tp->snd_max = tp->snd_nxt = tp->iss+1; 3652 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 3653 if (sc->sc_win > 0 && SEQ_GT(tp->rcv_nxt + sc->sc_win, tp->rcv_adv)) 3654 tp->rcv_adv = tp->rcv_nxt + sc->sc_win; 3655 tp->last_ack_sent = tp->rcv_nxt; 3656 3657 tcpstat_inc(tcps_sc_completed); 3658 syn_cache_put(sc); 3659 return (so); 3660 3661 resetandabort: 3662 tcp_respond(NULL, mtod(m, caddr_t), th, (tcp_seq)0, th->th_ack, TH_RST, 3663 m->m_pkthdr.ph_rtableid, now); 3664 abort: 3665 m_freem(m); 3666 if (so != NULL) 3667 soabort(so); 3668 syn_cache_put(sc); 3669 tcpstat_inc(tcps_sc_aborted); 3670 return ((struct socket *)(-1)); 3671 } 3672 3673 /* 3674 * This function is called when we get a RST for a 3675 * non-existent connection, so that we can see if the 3676 * connection is in the syn cache. If it is, zap it. 3677 */ 3678 3679 void 3680 syn_cache_reset(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, 3681 u_int rtableid) 3682 { 3683 struct syn_cache *sc; 3684 struct syn_cache_head *scp; 3685 3686 NET_ASSERT_LOCKED(); 3687 3688 if ((sc = syn_cache_lookup(src, dst, &scp, rtableid)) == NULL) 3689 return; 3690 if (SEQ_LT(th->th_seq, sc->sc_irs) || 3691 SEQ_GT(th->th_seq, sc->sc_irs + 1)) 3692 return; 3693 syn_cache_rm(sc); 3694 tcpstat_inc(tcps_sc_reset); 3695 syn_cache_put(sc); 3696 } 3697 3698 void 3699 syn_cache_unreach(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, 3700 u_int rtableid) 3701 { 3702 struct syn_cache *sc; 3703 struct syn_cache_head *scp; 3704 3705 NET_ASSERT_LOCKED(); 3706 3707 if ((sc = syn_cache_lookup(src, dst, &scp, rtableid)) == NULL) 3708 return; 3709 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 3710 if (ntohl (th->th_seq) != sc->sc_iss) { 3711 return; 3712 } 3713 3714 /* 3715 * If we've retransmitted 3 times and this is our second error, 3716 * we remove the entry. Otherwise, we allow it to continue on. 3717 * This prevents us from incorrectly nuking an entry during a 3718 * spurious network outage. 3719 * 3720 * See tcp_notify(). 3721 */ 3722 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtshift < 3) { 3723 sc->sc_flags |= SCF_UNREACH; 3724 return; 3725 } 3726 3727 syn_cache_rm(sc); 3728 tcpstat_inc(tcps_sc_unreach); 3729 syn_cache_put(sc); 3730 } 3731 3732 /* 3733 * Given a LISTEN socket and an inbound SYN request, add 3734 * this to the syn cache, and send back a segment: 3735 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 3736 * to the source. 3737 * 3738 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 3739 * Doing so would require that we hold onto the data and deliver it 3740 * to the application. However, if we are the target of a SYN-flood 3741 * DoS attack, an attacker could send data which would eventually 3742 * consume all available buffer space if it were ACKed. By not ACKing 3743 * the data, we avoid this DoS scenario. 3744 */ 3745 3746 int 3747 syn_cache_add(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, 3748 u_int iphlen, struct socket *so, struct mbuf *m, u_char *optp, int optlen, 3749 struct tcp_opt_info *oi, tcp_seq *issp, uint32_t now) 3750 { 3751 struct tcpcb tb, *tp; 3752 long win; 3753 struct syn_cache *sc; 3754 struct syn_cache_head *scp; 3755 struct mbuf *ipopts; 3756 3757 tp = sototcpcb(so); 3758 3759 /* 3760 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 3761 * 3762 * Note this check is performed in tcp_input() very early on. 3763 */ 3764 3765 /* 3766 * Initialize some local state. 3767 */ 3768 win = sbspace(so, &so->so_rcv); 3769 if (win > TCP_MAXWIN) 3770 win = TCP_MAXWIN; 3771 3772 bzero(&tb, sizeof(tb)); 3773 #ifdef TCP_SIGNATURE 3774 if (optp || (tp->t_flags & TF_SIGNATURE)) { 3775 #else 3776 if (optp) { 3777 #endif 3778 tb.pf = tp->pf; 3779 tb.sack_enable = tp->sack_enable; 3780 tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 3781 #ifdef TCP_SIGNATURE 3782 if (tp->t_flags & TF_SIGNATURE) 3783 tb.t_flags |= TF_SIGNATURE; 3784 #endif 3785 tb.t_state = TCPS_LISTEN; 3786 if (tcp_dooptions(&tb, optp, optlen, th, m, iphlen, oi, 3787 sotoinpcb(so)->inp_rtableid, now)) 3788 return (-1); 3789 } 3790 3791 switch (src->sa_family) { 3792 case AF_INET: 3793 /* 3794 * Remember the IP options, if any. 3795 */ 3796 ipopts = ip_srcroute(m); 3797 break; 3798 default: 3799 ipopts = NULL; 3800 } 3801 3802 /* 3803 * See if we already have an entry for this connection. 3804 * If we do, resend the SYN,ACK. We do not count this 3805 * as a retransmission (XXX though maybe we should). 3806 */ 3807 sc = syn_cache_lookup(src, dst, &scp, sotoinpcb(so)->inp_rtableid); 3808 if (sc != NULL) { 3809 tcpstat_inc(tcps_sc_dupesyn); 3810 if (ipopts) { 3811 /* 3812 * If we were remembering a previous source route, 3813 * forget it and use the new one we've been given. 3814 */ 3815 m_free(sc->sc_ipopts); 3816 sc->sc_ipopts = ipopts; 3817 } 3818 sc->sc_timestamp = tb.ts_recent; 3819 if (syn_cache_respond(sc, m, now) == 0) { 3820 tcpstat_inc(tcps_sndacks); 3821 tcpstat_inc(tcps_sndtotal); 3822 } 3823 return (0); 3824 } 3825 3826 sc = pool_get(&syn_cache_pool, PR_NOWAIT|PR_ZERO); 3827 if (sc == NULL) { 3828 m_free(ipopts); 3829 return (-1); 3830 } 3831 3832 /* 3833 * Fill in the cache, and put the necessary IP and TCP 3834 * options into the reply. 3835 */ 3836 memcpy(&sc->sc_src, src, src->sa_len); 3837 memcpy(&sc->sc_dst, dst, dst->sa_len); 3838 sc->sc_rtableid = sotoinpcb(so)->inp_rtableid; 3839 sc->sc_flags = 0; 3840 sc->sc_ipopts = ipopts; 3841 sc->sc_irs = th->th_seq; 3842 3843 sc->sc_iss = issp ? *issp : arc4random(); 3844 sc->sc_peermaxseg = oi->maxseg; 3845 sc->sc_ourmaxseg = tcp_mss_adv(m, sc->sc_src.sa.sa_family); 3846 sc->sc_win = win; 3847 sc->sc_timestamp = tb.ts_recent; 3848 if ((tb.t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP)) == 3849 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) { 3850 sc->sc_flags |= SCF_TIMESTAMP; 3851 sc->sc_modulate = arc4random(); 3852 } 3853 if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 3854 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 3855 sc->sc_requested_s_scale = tb.requested_s_scale; 3856 sc->sc_request_r_scale = 0; 3857 /* 3858 * Pick the smallest possible scaling factor that 3859 * will still allow us to scale up to sb_max. 3860 * 3861 * We do this because there are broken firewalls that 3862 * will corrupt the window scale option, leading to 3863 * the other endpoint believing that our advertised 3864 * window is unscaled. At scale factors larger than 3865 * 5 the unscaled window will drop below 1500 bytes, 3866 * leading to serious problems when traversing these 3867 * broken firewalls. 3868 * 3869 * With the default sbmax of 256K, a scale factor 3870 * of 3 will be chosen by this algorithm. Those who 3871 * choose a larger sbmax should watch out 3872 * for the compatibility problems mentioned above. 3873 * 3874 * RFC1323: The Window field in a SYN (i.e., a <SYN> 3875 * or <SYN,ACK>) segment itself is never scaled. 3876 */ 3877 while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT && 3878 (TCP_MAXWIN << sc->sc_request_r_scale) < sb_max) 3879 sc->sc_request_r_scale++; 3880 } else { 3881 sc->sc_requested_s_scale = 15; 3882 sc->sc_request_r_scale = 15; 3883 } 3884 #ifdef TCP_ECN 3885 /* 3886 * if both ECE and CWR flag bits are set, peer is ECN capable. 3887 */ 3888 if (tcp_do_ecn && 3889 (th->th_flags & (TH_ECE|TH_CWR)) == (TH_ECE|TH_CWR)) 3890 sc->sc_flags |= SCF_ECN_PERMIT; 3891 #endif 3892 /* 3893 * Set SCF_SACK_PERMIT if peer did send a SACK_PERMITTED option 3894 * (i.e., if tcp_dooptions() did set TF_SACK_PERMIT). 3895 */ 3896 if (tb.sack_enable && (tb.t_flags & TF_SACK_PERMIT)) 3897 sc->sc_flags |= SCF_SACK_PERMIT; 3898 #ifdef TCP_SIGNATURE 3899 if (tb.t_flags & TF_SIGNATURE) 3900 sc->sc_flags |= SCF_SIGNATURE; 3901 #endif 3902 sc->sc_tp = tp; 3903 if (syn_cache_respond(sc, m, now) == 0) { 3904 syn_cache_insert(sc, tp); 3905 tcpstat_inc(tcps_sndacks); 3906 tcpstat_inc(tcps_sndtotal); 3907 } else { 3908 syn_cache_put(sc); 3909 tcpstat_inc(tcps_sc_dropped); 3910 } 3911 3912 return (0); 3913 } 3914 3915 int 3916 syn_cache_respond(struct syn_cache *sc, struct mbuf *m, uint32_t now) 3917 { 3918 u_int8_t *optp; 3919 int optlen, error; 3920 u_int16_t tlen; 3921 struct ip *ip = NULL; 3922 #ifdef INET6 3923 struct ip6_hdr *ip6 = NULL; 3924 #endif 3925 struct tcphdr *th; 3926 u_int hlen; 3927 struct inpcb *inp; 3928 3929 switch (sc->sc_src.sa.sa_family) { 3930 case AF_INET: 3931 hlen = sizeof(struct ip); 3932 break; 3933 #ifdef INET6 3934 case AF_INET6: 3935 hlen = sizeof(struct ip6_hdr); 3936 break; 3937 #endif 3938 default: 3939 m_freem(m); 3940 return (EAFNOSUPPORT); 3941 } 3942 3943 /* Compute the size of the TCP options. */ 3944 optlen = 4 + (sc->sc_request_r_scale != 15 ? 4 : 0) + 3945 ((sc->sc_flags & SCF_SACK_PERMIT) ? 4 : 0) + 3946 #ifdef TCP_SIGNATURE 3947 ((sc->sc_flags & SCF_SIGNATURE) ? TCPOLEN_SIGLEN : 0) + 3948 #endif 3949 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0); 3950 3951 tlen = hlen + sizeof(struct tcphdr) + optlen; 3952 3953 /* 3954 * Create the IP+TCP header from scratch. 3955 */ 3956 m_freem(m); 3957 #ifdef DIAGNOSTIC 3958 if (max_linkhdr + tlen > MCLBYTES) 3959 return (ENOBUFS); 3960 #endif 3961 MGETHDR(m, M_DONTWAIT, MT_DATA); 3962 if (m && max_linkhdr + tlen > MHLEN) { 3963 MCLGET(m, M_DONTWAIT); 3964 if ((m->m_flags & M_EXT) == 0) { 3965 m_freem(m); 3966 m = NULL; 3967 } 3968 } 3969 if (m == NULL) 3970 return (ENOBUFS); 3971 3972 /* Fixup the mbuf. */ 3973 m->m_data += max_linkhdr; 3974 m->m_len = m->m_pkthdr.len = tlen; 3975 m->m_pkthdr.ph_ifidx = 0; 3976 m->m_pkthdr.ph_rtableid = sc->sc_rtableid; 3977 memset(mtod(m, u_char *), 0, tlen); 3978 3979 switch (sc->sc_src.sa.sa_family) { 3980 case AF_INET: 3981 ip = mtod(m, struct ip *); 3982 ip->ip_dst = sc->sc_src.sin.sin_addr; 3983 ip->ip_src = sc->sc_dst.sin.sin_addr; 3984 ip->ip_p = IPPROTO_TCP; 3985 th = (struct tcphdr *)(ip + 1); 3986 th->th_dport = sc->sc_src.sin.sin_port; 3987 th->th_sport = sc->sc_dst.sin.sin_port; 3988 break; 3989 #ifdef INET6 3990 case AF_INET6: 3991 ip6 = mtod(m, struct ip6_hdr *); 3992 ip6->ip6_dst = sc->sc_src.sin6.sin6_addr; 3993 ip6->ip6_src = sc->sc_dst.sin6.sin6_addr; 3994 ip6->ip6_nxt = IPPROTO_TCP; 3995 /* ip6_plen will be updated in ip6_output() */ 3996 th = (struct tcphdr *)(ip6 + 1); 3997 th->th_dport = sc->sc_src.sin6.sin6_port; 3998 th->th_sport = sc->sc_dst.sin6.sin6_port; 3999 break; 4000 #endif 4001 default: 4002 unhandled_af(sc->sc_src.sa.sa_family); 4003 } 4004 4005 th->th_seq = htonl(sc->sc_iss); 4006 th->th_ack = htonl(sc->sc_irs + 1); 4007 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 4008 th->th_flags = TH_SYN|TH_ACK; 4009 #ifdef TCP_ECN 4010 /* Set ECE for SYN-ACK if peer supports ECN. */ 4011 if (tcp_do_ecn && (sc->sc_flags & SCF_ECN_PERMIT)) 4012 th->th_flags |= TH_ECE; 4013 #endif 4014 th->th_win = htons(sc->sc_win); 4015 /* th_sum already 0 */ 4016 /* th_urp already 0 */ 4017 4018 /* Tack on the TCP options. */ 4019 optp = (u_int8_t *)(th + 1); 4020 *optp++ = TCPOPT_MAXSEG; 4021 *optp++ = 4; 4022 *optp++ = (sc->sc_ourmaxseg >> 8) & 0xff; 4023 *optp++ = sc->sc_ourmaxseg & 0xff; 4024 4025 /* Include SACK_PERMIT_HDR option if peer has already done so. */ 4026 if (sc->sc_flags & SCF_SACK_PERMIT) { 4027 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMIT_HDR); 4028 optp += 4; 4029 } 4030 4031 if (sc->sc_request_r_scale != 15) { 4032 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 4033 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 4034 sc->sc_request_r_scale); 4035 optp += 4; 4036 } 4037 4038 if (sc->sc_flags & SCF_TIMESTAMP) { 4039 u_int32_t *lp = (u_int32_t *)(optp); 4040 /* Form timestamp option as shown in appendix A of RFC 1323. */ 4041 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 4042 *lp++ = htonl(now + sc->sc_modulate); 4043 *lp = htonl(sc->sc_timestamp); 4044 optp += TCPOLEN_TSTAMP_APPA; 4045 } 4046 4047 #ifdef TCP_SIGNATURE 4048 if (sc->sc_flags & SCF_SIGNATURE) { 4049 union sockaddr_union src, dst; 4050 struct tdb *tdb; 4051 4052 bzero(&src, sizeof(union sockaddr_union)); 4053 bzero(&dst, sizeof(union sockaddr_union)); 4054 src.sa.sa_len = sc->sc_src.sa.sa_len; 4055 src.sa.sa_family = sc->sc_src.sa.sa_family; 4056 dst.sa.sa_len = sc->sc_dst.sa.sa_len; 4057 dst.sa.sa_family = sc->sc_dst.sa.sa_family; 4058 4059 switch (sc->sc_src.sa.sa_family) { 4060 case 0: /*default to PF_INET*/ 4061 case AF_INET: 4062 src.sin.sin_addr = mtod(m, struct ip *)->ip_src; 4063 dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst; 4064 break; 4065 #ifdef INET6 4066 case AF_INET6: 4067 src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src; 4068 dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst; 4069 break; 4070 #endif /* INET6 */ 4071 } 4072 4073 tdb = gettdbbysrcdst(rtable_l2(sc->sc_rtableid), 4074 0, &src, &dst, IPPROTO_TCP); 4075 if (tdb == NULL) { 4076 m_freem(m); 4077 return (EPERM); 4078 } 4079 4080 /* Send signature option */ 4081 *(optp++) = TCPOPT_SIGNATURE; 4082 *(optp++) = TCPOLEN_SIGNATURE; 4083 4084 if (tcp_signature(tdb, sc->sc_src.sa.sa_family, m, th, 4085 hlen, 0, optp) < 0) { 4086 m_freem(m); 4087 tdb_unref(tdb); 4088 return (EINVAL); 4089 } 4090 tdb_unref(tdb); 4091 optp += 16; 4092 4093 /* Pad options list to the next 32 bit boundary and 4094 * terminate it. 4095 */ 4096 *optp++ = TCPOPT_NOP; 4097 *optp++ = TCPOPT_EOL; 4098 } 4099 #endif /* TCP_SIGNATURE */ 4100 4101 /* Compute the packet's checksum. */ 4102 switch (sc->sc_src.sa.sa_family) { 4103 case AF_INET: 4104 ip->ip_len = htons(tlen - hlen); 4105 th->th_sum = 0; 4106 th->th_sum = in_cksum(m, tlen); 4107 break; 4108 #ifdef INET6 4109 case AF_INET6: 4110 ip6->ip6_plen = htons(tlen - hlen); 4111 th->th_sum = 0; 4112 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 4113 break; 4114 #endif 4115 } 4116 4117 /* use IPsec policy and ttl from listening socket, on SYN ACK */ 4118 inp = sc->sc_tp ? sc->sc_tp->t_inpcb : NULL; 4119 4120 /* 4121 * Fill in some straggling IP bits. Note the stack expects 4122 * ip_len to be in host order, for convenience. 4123 */ 4124 switch (sc->sc_src.sa.sa_family) { 4125 case AF_INET: 4126 ip->ip_len = htons(tlen); 4127 ip->ip_ttl = inp ? inp->inp_ip.ip_ttl : ip_defttl; 4128 if (inp != NULL) 4129 ip->ip_tos = inp->inp_ip.ip_tos; 4130 break; 4131 #ifdef INET6 4132 case AF_INET6: 4133 ip6->ip6_vfc &= ~IPV6_VERSION_MASK; 4134 ip6->ip6_vfc |= IPV6_VERSION; 4135 ip6->ip6_plen = htons(tlen - hlen); 4136 /* ip6_hlim will be initialized afterwards */ 4137 /* leave flowlabel = 0, it is legal and require no state mgmt */ 4138 break; 4139 #endif 4140 } 4141 4142 switch (sc->sc_src.sa.sa_family) { 4143 case AF_INET: 4144 error = ip_output(m, sc->sc_ipopts, &sc->sc_route4, 4145 (ip_mtudisc ? IP_MTUDISC : 0), NULL, inp, 0); 4146 break; 4147 #ifdef INET6 4148 case AF_INET6: 4149 ip6->ip6_hlim = in6_selecthlim(inp); 4150 4151 error = ip6_output(m, NULL /*XXX*/, &sc->sc_route6, 0, 4152 NULL, NULL); 4153 break; 4154 #endif 4155 default: 4156 error = EAFNOSUPPORT; 4157 break; 4158 } 4159 return (error); 4160 } 4161