1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 #include "opt_tcp_sack.h" 41 42 #include <sys/param.h> 43 #include <sys/kernel.h> 44 #include <sys/mac.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/proc.h> /* for proc0 declaration */ 48 #include <sys/protosw.h> 49 #include <sys/signalvar.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 #include <sys/syslog.h> 54 #include <sys/systm.h> 55 56 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/in_var.h> 67 #include <netinet/ip.h> 68 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 69 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70 #include <netinet/ip_var.h> 71 #include <netinet/ip_options.h> 72 #include <netinet/ip6.h> 73 #include <netinet/icmp6.h> 74 #include <netinet6/in6_pcb.h> 75 #include <netinet6/ip6_var.h> 76 #include <netinet6/nd6.h> 77 #include <netinet/tcp.h> 78 #include <netinet/tcp_fsm.h> 79 #include <netinet/tcp_seq.h> 80 #include <netinet/tcp_timer.h> 81 #include <netinet/tcp_var.h> 82 #include <netinet6/tcp6_var.h> 83 #include <netinet/tcpip.h> 84 #ifdef TCPDEBUG 85 #include <netinet/tcp_debug.h> 86 #endif /* TCPDEBUG */ 87 88 #ifdef FAST_IPSEC 89 #include <netipsec/ipsec.h> 90 #include <netipsec/ipsec6.h> 91 #endif /*FAST_IPSEC*/ 92 93 #ifdef IPSEC 94 #include <netinet6/ipsec.h> 95 #include <netinet6/ipsec6.h> 96 #include <netkey/key.h> 97 #endif /*IPSEC*/ 98 99 #include <machine/in_cksum.h> 100 101 static const int tcprexmtthresh = 3; 102 103 struct tcpstat tcpstat; 104 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 105 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 106 107 static int log_in_vain = 0; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 109 &log_in_vain, 0, "Log all incoming TCP connections"); 110 111 static int blackhole = 0; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 113 &blackhole, 0, "Do not send RST when dropping refused connections"); 114 115 int tcp_delack_enabled = 1; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 117 &tcp_delack_enabled, 0, 118 "Delay ACK to try and piggyback it onto a data packet"); 119 120 #ifdef TCP_DROP_SYNFIN 121 static int drop_synfin = 0; 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 123 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 124 #endif 125 126 static int tcp_do_rfc3042 = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 128 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 129 130 static int tcp_do_rfc3390 = 1; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 132 &tcp_do_rfc3390, 0, 133 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 134 135 static int tcp_insecure_rst = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 137 &tcp_insecure_rst, 0, 138 "Follow the old (insecure) criteria for accepting RST packets."); 139 140 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 141 "TCP Segment Reassembly Queue"); 142 143 static int tcp_reass_maxseg = 0; 144 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 145 &tcp_reass_maxseg, 0, 146 "Global maximum number of TCP Segments in Reassembly Queue"); 147 148 int tcp_reass_qsize = 0; 149 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 150 &tcp_reass_qsize, 0, 151 "Global number of TCP Segments currently in Reassembly Queue"); 152 153 static int tcp_reass_maxqlen = 48; 154 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 155 &tcp_reass_maxqlen, 0, 156 "Maximum number of TCP Segments per individual Reassembly Queue"); 157 158 static int tcp_reass_overflows = 0; 159 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 160 &tcp_reass_overflows, 0, 161 "Global number of TCP Segment Reassembly Queue Overflows"); 162 163 struct inpcbhead tcb; 164 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 165 struct inpcbinfo tcbinfo; 166 struct mtx *tcbinfo_mtx; 167 168 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 169 170 static void tcp_pulloutofband(struct socket *, 171 struct tcphdr *, struct mbuf *, int); 172 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 173 struct mbuf *); 174 static void tcp_xmit_timer(struct tcpcb *, int); 175 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 176 static int tcp_timewait(struct inpcb *, struct tcpopt *, 177 struct tcphdr *, struct mbuf *, int); 178 179 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 180 #ifdef INET6 181 #define ND6_HINT(tp) \ 182 do { \ 183 if ((tp) && (tp)->t_inpcb && \ 184 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 185 nd6_nud_hint(NULL, NULL, 0); \ 186 } while (0) 187 #else 188 #define ND6_HINT(tp) 189 #endif 190 191 /* 192 * Indicate whether this ack should be delayed. We can delay the ack if 193 * - there is no delayed ack timer in progress and 194 * - our last ack wasn't a 0-sized window. We never want to delay 195 * the ack that opens up a 0-sized window and 196 * - delayed acks are enabled or 197 * - this is a half-synchronized T/TCP connection. 198 */ 199 #define DELAY_ACK(tp) \ 200 ((!callout_active(tp->tt_delack) && \ 201 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 202 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 203 204 /* Initialize TCP reassembly queue */ 205 static void 206 tcp_reass_zone_change(void *tag) 207 { 208 209 tcp_reass_maxseg = nmbclusters / 16; 210 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 211 } 212 213 uma_zone_t tcp_reass_zone; 214 void 215 tcp_reass_init() 216 { 217 tcp_reass_maxseg = nmbclusters / 16; 218 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 219 &tcp_reass_maxseg); 220 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 221 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 222 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 223 EVENTHANDLER_REGISTER(nmbclusters_change, 224 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY); 225 } 226 227 static int 228 tcp_reass(tp, th, tlenp, m) 229 register struct tcpcb *tp; 230 register struct tcphdr *th; 231 int *tlenp; 232 struct mbuf *m; 233 { 234 struct tseg_qent *q; 235 struct tseg_qent *p = NULL; 236 struct tseg_qent *nq; 237 struct tseg_qent *te = NULL; 238 struct socket *so = tp->t_inpcb->inp_socket; 239 int flags; 240 241 INP_LOCK_ASSERT(tp->t_inpcb); 242 243 /* 244 * XXX: tcp_reass() is rather inefficient with its data structures 245 * and should be rewritten (see NetBSD for optimizations). While 246 * doing that it should move to its own file tcp_reass.c. 247 */ 248 249 /* 250 * Call with th==NULL after become established to 251 * force pre-ESTABLISHED data up to user socket. 252 */ 253 if (th == NULL) 254 goto present; 255 256 /* 257 * Limit the number of segments in the reassembly queue to prevent 258 * holding on to too many segments (and thus running out of mbufs). 259 * Make sure to let the missing segment through which caused this 260 * queue. Always keep one global queue entry spare to be able to 261 * process the missing segment. 262 */ 263 if (th->th_seq != tp->rcv_nxt && 264 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 265 tp->t_segqlen >= tcp_reass_maxqlen)) { 266 tcp_reass_overflows++; 267 tcpstat.tcps_rcvmemdrop++; 268 m_freem(m); 269 *tlenp = 0; 270 return (0); 271 } 272 273 /* 274 * Allocate a new queue entry. If we can't, or hit the zone limit 275 * just drop the pkt. 276 */ 277 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 278 if (te == NULL) { 279 tcpstat.tcps_rcvmemdrop++; 280 m_freem(m); 281 *tlenp = 0; 282 return (0); 283 } 284 tp->t_segqlen++; 285 tcp_reass_qsize++; 286 287 /* 288 * Find a segment which begins after this one does. 289 */ 290 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 291 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 292 break; 293 p = q; 294 } 295 296 /* 297 * If there is a preceding segment, it may provide some of 298 * our data already. If so, drop the data from the incoming 299 * segment. If it provides all of our data, drop us. 300 */ 301 if (p != NULL) { 302 register int i; 303 /* conversion to int (in i) handles seq wraparound */ 304 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 305 if (i > 0) { 306 if (i >= *tlenp) { 307 tcpstat.tcps_rcvduppack++; 308 tcpstat.tcps_rcvdupbyte += *tlenp; 309 m_freem(m); 310 uma_zfree(tcp_reass_zone, te); 311 tp->t_segqlen--; 312 tcp_reass_qsize--; 313 /* 314 * Try to present any queued data 315 * at the left window edge to the user. 316 * This is needed after the 3-WHS 317 * completes. 318 */ 319 goto present; /* ??? */ 320 } 321 m_adj(m, i); 322 *tlenp -= i; 323 th->th_seq += i; 324 } 325 } 326 tcpstat.tcps_rcvoopack++; 327 tcpstat.tcps_rcvoobyte += *tlenp; 328 329 /* 330 * While we overlap succeeding segments trim them or, 331 * if they are completely covered, dequeue them. 332 */ 333 while (q) { 334 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 335 if (i <= 0) 336 break; 337 if (i < q->tqe_len) { 338 q->tqe_th->th_seq += i; 339 q->tqe_len -= i; 340 m_adj(q->tqe_m, i); 341 break; 342 } 343 344 nq = LIST_NEXT(q, tqe_q); 345 LIST_REMOVE(q, tqe_q); 346 m_freem(q->tqe_m); 347 uma_zfree(tcp_reass_zone, q); 348 tp->t_segqlen--; 349 tcp_reass_qsize--; 350 q = nq; 351 } 352 353 /* Insert the new segment queue entry into place. */ 354 te->tqe_m = m; 355 te->tqe_th = th; 356 te->tqe_len = *tlenp; 357 358 if (p == NULL) { 359 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 360 } else { 361 LIST_INSERT_AFTER(p, te, tqe_q); 362 } 363 364 present: 365 /* 366 * Present data to user, advancing rcv_nxt through 367 * completed sequence space. 368 */ 369 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 370 return (0); 371 q = LIST_FIRST(&tp->t_segq); 372 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 373 return (0); 374 SOCKBUF_LOCK(&so->so_rcv); 375 do { 376 tp->rcv_nxt += q->tqe_len; 377 flags = q->tqe_th->th_flags & TH_FIN; 378 nq = LIST_NEXT(q, tqe_q); 379 LIST_REMOVE(q, tqe_q); 380 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 381 m_freem(q->tqe_m); 382 else 383 sbappendstream_locked(&so->so_rcv, q->tqe_m); 384 uma_zfree(tcp_reass_zone, q); 385 tp->t_segqlen--; 386 tcp_reass_qsize--; 387 q = nq; 388 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 389 ND6_HINT(tp); 390 sorwakeup_locked(so); 391 return (flags); 392 } 393 394 /* 395 * TCP input routine, follows pages 65-76 of the 396 * protocol specification dated September, 1981 very closely. 397 */ 398 #ifdef INET6 399 int 400 tcp6_input(mp, offp, proto) 401 struct mbuf **mp; 402 int *offp, proto; 403 { 404 register struct mbuf *m = *mp; 405 struct in6_ifaddr *ia6; 406 407 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 408 409 /* 410 * draft-itojun-ipv6-tcp-to-anycast 411 * better place to put this in? 412 */ 413 ia6 = ip6_getdstifaddr(m); 414 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 415 struct ip6_hdr *ip6; 416 417 ip6 = mtod(m, struct ip6_hdr *); 418 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 419 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 420 return IPPROTO_DONE; 421 } 422 423 tcp_input(m, *offp); 424 return IPPROTO_DONE; 425 } 426 #endif 427 428 void 429 tcp_input(m, off0) 430 register struct mbuf *m; 431 int off0; 432 { 433 register struct tcphdr *th; 434 register struct ip *ip = NULL; 435 register struct ipovly *ipov; 436 register struct inpcb *inp = NULL; 437 u_char *optp = NULL; 438 int optlen = 0; 439 int len, tlen, off; 440 int drop_hdrlen; 441 register struct tcpcb *tp = 0; 442 register int thflags; 443 struct socket *so = 0; 444 int todrop, acked, ourfinisacked, needoutput = 0; 445 u_long tiwin; 446 struct tcpopt to; /* options in this segment */ 447 int headlocked = 0; 448 #ifdef IPFIREWALL_FORWARD 449 struct m_tag *fwd_tag; 450 #endif 451 int rstreason; /* For badport_bandlim accounting purposes */ 452 453 struct ip6_hdr *ip6 = NULL; 454 #ifdef INET6 455 int isipv6; 456 #else 457 const int isipv6 = 0; 458 #endif 459 460 #ifdef TCPDEBUG 461 /* 462 * The size of tcp_saveipgen must be the size of the max ip header, 463 * now IPv6. 464 */ 465 u_char tcp_saveipgen[40]; 466 struct tcphdr tcp_savetcp; 467 short ostate = 0; 468 #endif 469 470 #ifdef INET6 471 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 472 #endif 473 bzero((char *)&to, sizeof(to)); 474 475 tcpstat.tcps_rcvtotal++; 476 477 if (isipv6) { 478 #ifdef INET6 479 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 480 ip6 = mtod(m, struct ip6_hdr *); 481 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 482 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 483 tcpstat.tcps_rcvbadsum++; 484 goto drop; 485 } 486 th = (struct tcphdr *)((caddr_t)ip6 + off0); 487 488 /* 489 * Be proactive about unspecified IPv6 address in source. 490 * As we use all-zero to indicate unbounded/unconnected pcb, 491 * unspecified IPv6 address can be used to confuse us. 492 * 493 * Note that packets with unspecified IPv6 destination is 494 * already dropped in ip6_input. 495 */ 496 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 497 /* XXX stat */ 498 goto drop; 499 } 500 #else 501 th = NULL; /* XXX: avoid compiler warning */ 502 #endif 503 } else { 504 /* 505 * Get IP and TCP header together in first mbuf. 506 * Note: IP leaves IP header in first mbuf. 507 */ 508 if (off0 > sizeof (struct ip)) { 509 ip_stripoptions(m, (struct mbuf *)0); 510 off0 = sizeof(struct ip); 511 } 512 if (m->m_len < sizeof (struct tcpiphdr)) { 513 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 514 tcpstat.tcps_rcvshort++; 515 return; 516 } 517 } 518 ip = mtod(m, struct ip *); 519 ipov = (struct ipovly *)ip; 520 th = (struct tcphdr *)((caddr_t)ip + off0); 521 tlen = ip->ip_len; 522 523 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 524 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 525 th->th_sum = m->m_pkthdr.csum_data; 526 else 527 th->th_sum = in_pseudo(ip->ip_src.s_addr, 528 ip->ip_dst.s_addr, 529 htonl(m->m_pkthdr.csum_data + 530 ip->ip_len + 531 IPPROTO_TCP)); 532 th->th_sum ^= 0xffff; 533 #ifdef TCPDEBUG 534 ipov->ih_len = (u_short)tlen; 535 ipov->ih_len = htons(ipov->ih_len); 536 #endif 537 } else { 538 /* 539 * Checksum extended TCP header and data. 540 */ 541 len = sizeof (struct ip) + tlen; 542 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 543 ipov->ih_len = (u_short)tlen; 544 ipov->ih_len = htons(ipov->ih_len); 545 th->th_sum = in_cksum(m, len); 546 } 547 if (th->th_sum) { 548 tcpstat.tcps_rcvbadsum++; 549 goto drop; 550 } 551 #ifdef INET6 552 /* Re-initialization for later version check */ 553 ip->ip_v = IPVERSION; 554 #endif 555 } 556 557 /* 558 * Check that TCP offset makes sense, 559 * pull out TCP options and adjust length. XXX 560 */ 561 off = th->th_off << 2; 562 if (off < sizeof (struct tcphdr) || off > tlen) { 563 tcpstat.tcps_rcvbadoff++; 564 goto drop; 565 } 566 tlen -= off; /* tlen is used instead of ti->ti_len */ 567 if (off > sizeof (struct tcphdr)) { 568 if (isipv6) { 569 #ifdef INET6 570 IP6_EXTHDR_CHECK(m, off0, off, ); 571 ip6 = mtod(m, struct ip6_hdr *); 572 th = (struct tcphdr *)((caddr_t)ip6 + off0); 573 #endif 574 } else { 575 if (m->m_len < sizeof(struct ip) + off) { 576 if ((m = m_pullup(m, sizeof (struct ip) + off)) 577 == 0) { 578 tcpstat.tcps_rcvshort++; 579 return; 580 } 581 ip = mtod(m, struct ip *); 582 ipov = (struct ipovly *)ip; 583 th = (struct tcphdr *)((caddr_t)ip + off0); 584 } 585 } 586 optlen = off - sizeof (struct tcphdr); 587 optp = (u_char *)(th + 1); 588 } 589 thflags = th->th_flags; 590 591 #ifdef TCP_DROP_SYNFIN 592 /* 593 * If the drop_synfin option is enabled, drop all packets with 594 * both the SYN and FIN bits set. This prevents e.g. nmap from 595 * identifying the TCP/IP stack. 596 * 597 * This is a violation of the TCP specification. 598 */ 599 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 600 goto drop; 601 #endif 602 603 /* 604 * Convert TCP protocol specific fields to host format. 605 */ 606 th->th_seq = ntohl(th->th_seq); 607 th->th_ack = ntohl(th->th_ack); 608 th->th_win = ntohs(th->th_win); 609 th->th_urp = ntohs(th->th_urp); 610 611 /* 612 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 613 * until after ip6_savecontrol() is called and before other functions 614 * which don't want those proto headers. 615 * Because ip6_savecontrol() is going to parse the mbuf to 616 * search for data to be passed up to user-land, it wants mbuf 617 * parameters to be unchanged. 618 * XXX: the call of ip6_savecontrol() has been obsoleted based on 619 * latest version of the advanced API (20020110). 620 */ 621 drop_hdrlen = off0 + off; 622 623 /* 624 * Locate pcb for segment. 625 */ 626 INP_INFO_WLOCK(&tcbinfo); 627 headlocked = 1; 628 findpcb: 629 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 630 #ifdef IPFIREWALL_FORWARD 631 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 632 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 633 634 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 635 struct sockaddr_in *next_hop; 636 637 next_hop = (struct sockaddr_in *)(fwd_tag+1); 638 /* 639 * Transparently forwarded. Pretend to be the destination. 640 * already got one like this? 641 */ 642 inp = in_pcblookup_hash(&tcbinfo, 643 ip->ip_src, th->th_sport, 644 ip->ip_dst, th->th_dport, 645 0, m->m_pkthdr.rcvif); 646 if (!inp) { 647 /* It's new. Try to find the ambushing socket. */ 648 inp = in_pcblookup_hash(&tcbinfo, 649 ip->ip_src, th->th_sport, 650 next_hop->sin_addr, 651 next_hop->sin_port ? 652 ntohs(next_hop->sin_port) : 653 th->th_dport, 654 1, m->m_pkthdr.rcvif); 655 } 656 /* Remove the tag from the packet. We don't need it anymore. */ 657 m_tag_delete(m, fwd_tag); 658 } else { 659 #endif /* IPFIREWALL_FORWARD */ 660 if (isipv6) { 661 #ifdef INET6 662 inp = in6_pcblookup_hash(&tcbinfo, 663 &ip6->ip6_src, th->th_sport, 664 &ip6->ip6_dst, th->th_dport, 665 1, m->m_pkthdr.rcvif); 666 #endif 667 } else 668 inp = in_pcblookup_hash(&tcbinfo, 669 ip->ip_src, th->th_sport, 670 ip->ip_dst, th->th_dport, 671 1, m->m_pkthdr.rcvif); 672 #ifdef IPFIREWALL_FORWARD 673 } 674 #endif /* IPFIREWALL_FORWARD */ 675 676 #if defined(IPSEC) || defined(FAST_IPSEC) 677 #ifdef INET6 678 if (isipv6) { 679 if (inp != NULL && ipsec6_in_reject(m, inp)) { 680 #ifdef IPSEC 681 ipsec6stat.in_polvio++; 682 #endif 683 goto drop; 684 } 685 } else 686 #endif /* INET6 */ 687 if (inp != NULL && ipsec4_in_reject(m, inp)) { 688 #ifdef IPSEC 689 ipsecstat.in_polvio++; 690 #endif 691 goto drop; 692 } 693 #endif /*IPSEC || FAST_IPSEC*/ 694 695 /* 696 * If the state is CLOSED (i.e., TCB does not exist) then 697 * all data in the incoming segment is discarded. 698 * If the TCB exists but is in CLOSED state, it is embryonic, 699 * but should either do a listen or a connect soon. 700 */ 701 if (inp == NULL) { 702 if (log_in_vain) { 703 #ifdef INET6 704 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 705 #else 706 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 707 #endif 708 709 if (isipv6) { 710 #ifdef INET6 711 strcpy(dbuf, "["); 712 strcpy(sbuf, "["); 713 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 714 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 715 strcat(dbuf, "]"); 716 strcat(sbuf, "]"); 717 #endif 718 } else { 719 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 720 strcpy(sbuf, inet_ntoa(ip->ip_src)); 721 } 722 switch (log_in_vain) { 723 case 1: 724 if ((thflags & TH_SYN) == 0) 725 break; 726 /* FALLTHROUGH */ 727 case 2: 728 log(LOG_INFO, 729 "Connection attempt to TCP %s:%d " 730 "from %s:%d flags:0x%02x\n", 731 dbuf, ntohs(th->th_dport), sbuf, 732 ntohs(th->th_sport), thflags); 733 break; 734 default: 735 break; 736 } 737 } 738 if (blackhole) { 739 switch (blackhole) { 740 case 1: 741 if (thflags & TH_SYN) 742 goto drop; 743 break; 744 case 2: 745 goto drop; 746 default: 747 goto drop; 748 } 749 } 750 rstreason = BANDLIM_RST_CLOSEDPORT; 751 goto dropwithreset; 752 } 753 INP_LOCK(inp); 754 755 /* Check the minimum TTL for socket. */ 756 if (inp->inp_ip_minttl != 0) { 757 #ifdef INET6 758 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 759 goto drop; 760 else 761 #endif 762 if (inp->inp_ip_minttl > ip->ip_ttl) 763 goto drop; 764 } 765 766 if (inp->inp_vflag & INP_TIMEWAIT) { 767 /* 768 * The only option of relevance is TOF_CC, and only if 769 * present in a SYN segment. See tcp_timewait(). 770 */ 771 if (thflags & TH_SYN) 772 tcp_dooptions(&to, optp, optlen, 1); 773 if (tcp_timewait(inp, &to, th, m, tlen)) 774 goto findpcb; 775 /* 776 * tcp_timewait unlocks inp. 777 */ 778 INP_INFO_WUNLOCK(&tcbinfo); 779 return; 780 } 781 tp = intotcpcb(inp); 782 if (tp == 0) { 783 INP_UNLOCK(inp); 784 rstreason = BANDLIM_RST_CLOSEDPORT; 785 goto dropwithreset; 786 } 787 if (tp->t_state == TCPS_CLOSED) 788 goto drop; 789 790 #ifdef MAC 791 INP_LOCK_ASSERT(inp); 792 if (mac_check_inpcb_deliver(inp, m)) 793 goto drop; 794 #endif 795 so = inp->inp_socket; 796 KASSERT(so != NULL, ("tcp_input: so == NULL")); 797 #ifdef TCPDEBUG 798 if (so->so_options & SO_DEBUG) { 799 ostate = tp->t_state; 800 if (isipv6) 801 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 802 else 803 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 804 tcp_savetcp = *th; 805 } 806 #endif 807 if (so->so_options & SO_ACCEPTCONN) { 808 struct in_conninfo inc; 809 810 #ifdef INET6 811 inc.inc_isipv6 = isipv6; 812 #endif 813 if (isipv6) { 814 inc.inc6_faddr = ip6->ip6_src; 815 inc.inc6_laddr = ip6->ip6_dst; 816 } else { 817 inc.inc_faddr = ip->ip_src; 818 inc.inc_laddr = ip->ip_dst; 819 } 820 inc.inc_fport = th->th_sport; 821 inc.inc_lport = th->th_dport; 822 823 /* 824 * If the state is LISTEN then ignore segment if it contains 825 * a RST. If the segment contains an ACK then it is bad and 826 * send a RST. If it does not contain a SYN then it is not 827 * interesting; drop it. 828 * 829 * If the state is SYN_RECEIVED (syncache) and seg contains 830 * an ACK, but not for our SYN/ACK, send a RST. If the seg 831 * contains a RST, check the sequence number to see if it 832 * is a valid reset segment. 833 */ 834 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 835 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 836 if (!syncache_expand(&inc, th, &so, m)) { 837 /* 838 * No syncache entry, or ACK was not 839 * for our SYN/ACK. Send a RST. 840 */ 841 tcpstat.tcps_badsyn++; 842 rstreason = BANDLIM_RST_OPENPORT; 843 goto dropwithreset; 844 } 845 if (so == NULL) { 846 /* 847 * Could not complete 3-way handshake, 848 * connection is being closed down, and 849 * syncache has free'd mbuf. 850 */ 851 INP_UNLOCK(inp); 852 INP_INFO_WUNLOCK(&tcbinfo); 853 return; 854 } 855 /* 856 * Socket is created in state SYN_RECEIVED. 857 * Continue processing segment. 858 */ 859 INP_UNLOCK(inp); 860 inp = sotoinpcb(so); 861 INP_LOCK(inp); 862 tp = intotcpcb(inp); 863 /* 864 * This is what would have happened in 865 * tcp_output() when the SYN,ACK was sent. 866 */ 867 tp->snd_up = tp->snd_una; 868 tp->snd_max = tp->snd_nxt = tp->iss + 1; 869 tp->last_ack_sent = tp->rcv_nxt; 870 goto after_listen; 871 } 872 if (thflags & TH_RST) { 873 syncache_chkrst(&inc, th); 874 goto drop; 875 } 876 if (thflags & TH_ACK) { 877 syncache_badack(&inc); 878 tcpstat.tcps_badsyn++; 879 rstreason = BANDLIM_RST_OPENPORT; 880 goto dropwithreset; 881 } 882 goto drop; 883 } 884 885 /* 886 * Segment's flags are (SYN) or (SYN|FIN). 887 */ 888 #ifdef INET6 889 /* 890 * If deprecated address is forbidden, 891 * we do not accept SYN to deprecated interface 892 * address to prevent any new inbound connection from 893 * getting established. 894 * When we do not accept SYN, we send a TCP RST, 895 * with deprecated source address (instead of dropping 896 * it). We compromise it as it is much better for peer 897 * to send a RST, and RST will be the final packet 898 * for the exchange. 899 * 900 * If we do not forbid deprecated addresses, we accept 901 * the SYN packet. RFC2462 does not suggest dropping 902 * SYN in this case. 903 * If we decipher RFC2462 5.5.4, it says like this: 904 * 1. use of deprecated addr with existing 905 * communication is okay - "SHOULD continue to be 906 * used" 907 * 2. use of it with new communication: 908 * (2a) "SHOULD NOT be used if alternate address 909 * with sufficient scope is available" 910 * (2b) nothing mentioned otherwise. 911 * Here we fall into (2b) case as we have no choice in 912 * our source address selection - we must obey the peer. 913 * 914 * The wording in RFC2462 is confusing, and there are 915 * multiple description text for deprecated address 916 * handling - worse, they are not exactly the same. 917 * I believe 5.5.4 is the best one, so we follow 5.5.4. 918 */ 919 if (isipv6 && !ip6_use_deprecated) { 920 struct in6_ifaddr *ia6; 921 922 if ((ia6 = ip6_getdstifaddr(m)) && 923 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 924 INP_UNLOCK(inp); 925 tp = NULL; 926 rstreason = BANDLIM_RST_OPENPORT; 927 goto dropwithreset; 928 } 929 } 930 #endif 931 /* 932 * If it is from this socket, drop it, it must be forged. 933 * Don't bother responding if the destination was a broadcast. 934 */ 935 if (th->th_dport == th->th_sport) { 936 if (isipv6) { 937 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 938 &ip6->ip6_src)) 939 goto drop; 940 } else { 941 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 942 goto drop; 943 } 944 } 945 /* 946 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 947 * 948 * Note that it is quite possible to receive unicast 949 * link-layer packets with a broadcast IP address. Use 950 * in_broadcast() to find them. 951 */ 952 if (m->m_flags & (M_BCAST|M_MCAST)) 953 goto drop; 954 if (isipv6) { 955 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 956 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 957 goto drop; 958 } else { 959 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 960 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 961 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 962 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 963 goto drop; 964 } 965 /* 966 * SYN appears to be valid; create compressed TCP state 967 * for syncache, or perform t/tcp connection. 968 */ 969 if (so->so_qlen <= so->so_qlimit) { 970 #ifdef TCPDEBUG 971 if (so->so_options & SO_DEBUG) 972 tcp_trace(TA_INPUT, ostate, tp, 973 (void *)tcp_saveipgen, &tcp_savetcp, 0); 974 #endif 975 tcp_dooptions(&to, optp, optlen, 1); 976 if (!syncache_add(&inc, &to, th, &so, m)) 977 goto drop; 978 if (so == NULL) { 979 /* 980 * Entry added to syncache, mbuf used to 981 * send SYN,ACK packet. 982 */ 983 KASSERT(headlocked, ("headlocked")); 984 INP_UNLOCK(inp); 985 INP_INFO_WUNLOCK(&tcbinfo); 986 return; 987 } 988 /* 989 * Segment passed TAO tests. 990 * XXX: Can't happen at the moment. 991 */ 992 INP_UNLOCK(inp); 993 inp = sotoinpcb(so); 994 INP_LOCK(inp); 995 tp = intotcpcb(inp); 996 tp->t_starttime = ticks; 997 tp->t_state = TCPS_ESTABLISHED; 998 999 /* 1000 * T/TCP logic: 1001 * If there is a FIN or if there is data, then 1002 * delay SYN,ACK(SYN) in the hope of piggy-backing 1003 * it on a response segment. Otherwise must send 1004 * ACK now in case the other side is slow starting. 1005 */ 1006 if (thflags & TH_FIN || tlen != 0) 1007 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1008 else 1009 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1010 tiwin = th->th_win << tp->snd_scale; 1011 tcpstat.tcps_connects++; 1012 soisconnected(so); 1013 goto trimthenstep6; 1014 } 1015 goto drop; 1016 } 1017 after_listen: 1018 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1019 INP_LOCK_ASSERT(inp); 1020 1021 /* Syncache takes care of sockets in the listen state. */ 1022 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN")); 1023 1024 /* 1025 * This is the second part of the MSS DoS prevention code (after 1026 * minmss on the sending side) and it deals with too many too small 1027 * tcp packets in a too short timeframe (1 second). 1028 * 1029 * For every full second we count the number of received packets 1030 * and bytes. If we get a lot of packets per second for this connection 1031 * (tcp_minmssoverload) we take a closer look at it and compute the 1032 * average packet size for the past second. If that is less than 1033 * tcp_minmss we get too many packets with very small payload which 1034 * is not good and burdens our system (and every packet generates 1035 * a wakeup to the process connected to our socket). We can reasonable 1036 * expect this to be small packet DoS attack to exhaust our CPU 1037 * cycles. 1038 * 1039 * Care has to be taken for the minimum packet overload value. This 1040 * value defines the minimum number of packets per second before we 1041 * start to worry. This must not be too low to avoid killing for 1042 * example interactive connections with many small packets like 1043 * telnet or SSH. 1044 * 1045 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1046 * this check. 1047 * 1048 * Account for packet if payload packet, skip over ACK, etc. 1049 */ 1050 if (tcp_minmss && tcp_minmssoverload && 1051 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1052 if ((unsigned int)(tp->rcv_second - ticks) < hz) { 1053 tp->rcv_pps++; 1054 tp->rcv_byps += tlen + off; 1055 if (tp->rcv_pps > tcp_minmssoverload) { 1056 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1057 printf("too many small tcp packets from " 1058 "%s:%u, av. %lubyte/packet, " 1059 "dropping connection\n", 1060 #ifdef INET6 1061 isipv6 ? 1062 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1063 #endif 1064 inet_ntoa(inp->inp_inc.inc_faddr), 1065 inp->inp_inc.inc_fport, 1066 tp->rcv_byps / tp->rcv_pps); 1067 KASSERT(headlocked, ("tcp_input: " 1068 "after_listen: tcp_drop: head " 1069 "not locked")); 1070 tp = tcp_drop(tp, ECONNRESET); 1071 tcpstat.tcps_minmssdrops++; 1072 goto drop; 1073 } 1074 } 1075 } else { 1076 tp->rcv_second = ticks + hz; 1077 tp->rcv_pps = 1; 1078 tp->rcv_byps = tlen + off; 1079 } 1080 } 1081 1082 /* 1083 * Segment received on connection. 1084 * Reset idle time and keep-alive timer. 1085 */ 1086 tp->t_rcvtime = ticks; 1087 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1088 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1089 1090 /* 1091 * Unscale the window into a 32-bit value. 1092 * This value is bogus for the TCPS_SYN_SENT state 1093 * and is overwritten later. 1094 */ 1095 tiwin = th->th_win << tp->snd_scale; 1096 1097 /* 1098 * Process options only when we get SYN/ACK back. The SYN case 1099 * for incoming connections is handled in tcp_syncache. 1100 * XXX this is traditional behavior, may need to be cleaned up. 1101 */ 1102 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 1103 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1104 if ((to.to_flags & TOF_SCALE) && 1105 (tp->t_flags & TF_REQ_SCALE)) { 1106 tp->t_flags |= TF_RCVD_SCALE; 1107 tp->snd_scale = to.to_requested_s_scale; 1108 tp->snd_wnd = th->th_win << tp->snd_scale; 1109 tiwin = tp->snd_wnd; 1110 } 1111 if (to.to_flags & TOF_TS) { 1112 tp->t_flags |= TF_RCVD_TSTMP; 1113 tp->ts_recent = to.to_tsval; 1114 tp->ts_recent_age = ticks; 1115 } 1116 if (to.to_flags & TOF_MSS) 1117 tcp_mss(tp, to.to_mss); 1118 if (tp->sack_enable) { 1119 if (!(to.to_flags & TOF_SACK)) 1120 tp->sack_enable = 0; 1121 else 1122 tp->t_flags |= TF_SACK_PERMIT; 1123 } 1124 1125 } 1126 1127 /* 1128 * Header prediction: check for the two common cases 1129 * of a uni-directional data xfer. If the packet has 1130 * no control flags, is in-sequence, the window didn't 1131 * change and we're not retransmitting, it's a 1132 * candidate. If the length is zero and the ack moved 1133 * forward, we're the sender side of the xfer. Just 1134 * free the data acked & wake any higher level process 1135 * that was blocked waiting for space. If the length 1136 * is non-zero and the ack didn't move, we're the 1137 * receiver side. If we're getting packets in-order 1138 * (the reassembly queue is empty), add the data to 1139 * the socket buffer and note that we need a delayed ack. 1140 * Make sure that the hidden state-flags are also off. 1141 * Since we check for TCPS_ESTABLISHED above, it can only 1142 * be TH_NEEDSYN. 1143 */ 1144 if (tp->t_state == TCPS_ESTABLISHED && 1145 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1146 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1147 ((to.to_flags & TOF_TS) == 0 || 1148 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1149 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1150 tp->snd_nxt == tp->snd_max) { 1151 1152 /* 1153 * If last ACK falls within this segment's sequence numbers, 1154 * record the timestamp. 1155 * NOTE that the test is modified according to the latest 1156 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1157 */ 1158 if ((to.to_flags & TOF_TS) != 0 && 1159 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1160 tp->ts_recent_age = ticks; 1161 tp->ts_recent = to.to_tsval; 1162 } 1163 1164 if (tlen == 0) { 1165 if (SEQ_GT(th->th_ack, tp->snd_una) && 1166 SEQ_LEQ(th->th_ack, tp->snd_max) && 1167 tp->snd_cwnd >= tp->snd_wnd && 1168 ((!tcp_do_newreno && !tp->sack_enable && 1169 tp->t_dupacks < tcprexmtthresh) || 1170 ((tcp_do_newreno || tp->sack_enable) && 1171 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 && 1172 TAILQ_EMPTY(&tp->snd_holes)))) { 1173 KASSERT(headlocked, ("headlocked")); 1174 INP_INFO_WUNLOCK(&tcbinfo); 1175 headlocked = 0; 1176 /* 1177 * this is a pure ack for outstanding data. 1178 */ 1179 ++tcpstat.tcps_predack; 1180 /* 1181 * "bad retransmit" recovery 1182 */ 1183 if (tp->t_rxtshift == 1 && 1184 ticks < tp->t_badrxtwin) { 1185 ++tcpstat.tcps_sndrexmitbad; 1186 tp->snd_cwnd = tp->snd_cwnd_prev; 1187 tp->snd_ssthresh = 1188 tp->snd_ssthresh_prev; 1189 tp->snd_recover = tp->snd_recover_prev; 1190 if (tp->t_flags & TF_WASFRECOVERY) 1191 ENTER_FASTRECOVERY(tp); 1192 tp->snd_nxt = tp->snd_max; 1193 tp->t_badrxtwin = 0; 1194 } 1195 1196 /* 1197 * Recalculate the transmit timer / rtt. 1198 * 1199 * Some boxes send broken timestamp replies 1200 * during the SYN+ACK phase, ignore 1201 * timestamps of 0 or we could calculate a 1202 * huge RTT and blow up the retransmit timer. 1203 */ 1204 if ((to.to_flags & TOF_TS) != 0 && 1205 to.to_tsecr) { 1206 if (!tp->t_rttlow || 1207 tp->t_rttlow > ticks - to.to_tsecr) 1208 tp->t_rttlow = ticks - to.to_tsecr; 1209 tcp_xmit_timer(tp, 1210 ticks - to.to_tsecr + 1); 1211 } else if (tp->t_rtttime && 1212 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1213 if (!tp->t_rttlow || 1214 tp->t_rttlow > ticks - tp->t_rtttime) 1215 tp->t_rttlow = ticks - tp->t_rtttime; 1216 tcp_xmit_timer(tp, 1217 ticks - tp->t_rtttime); 1218 } 1219 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1220 acked = th->th_ack - tp->snd_una; 1221 tcpstat.tcps_rcvackpack++; 1222 tcpstat.tcps_rcvackbyte += acked; 1223 sbdrop(&so->so_snd, acked); 1224 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1225 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1226 tp->snd_recover = th->th_ack - 1; 1227 tp->snd_una = th->th_ack; 1228 /* 1229 * pull snd_wl2 up to prevent seq wrap relative 1230 * to th_ack. 1231 */ 1232 tp->snd_wl2 = th->th_ack; 1233 tp->t_dupacks = 0; 1234 m_freem(m); 1235 ND6_HINT(tp); /* some progress has been done */ 1236 1237 /* 1238 * If all outstanding data are acked, stop 1239 * retransmit timer, otherwise restart timer 1240 * using current (possibly backed-off) value. 1241 * If process is waiting for space, 1242 * wakeup/selwakeup/signal. If data 1243 * are ready to send, let tcp_output 1244 * decide between more output or persist. 1245 1246 #ifdef TCPDEBUG 1247 if (so->so_options & SO_DEBUG) 1248 tcp_trace(TA_INPUT, ostate, tp, 1249 (void *)tcp_saveipgen, 1250 &tcp_savetcp, 0); 1251 #endif 1252 */ 1253 if (tp->snd_una == tp->snd_max) 1254 callout_stop(tp->tt_rexmt); 1255 else if (!callout_active(tp->tt_persist)) 1256 callout_reset(tp->tt_rexmt, 1257 tp->t_rxtcur, 1258 tcp_timer_rexmt, tp); 1259 1260 sowwakeup(so); 1261 if (so->so_snd.sb_cc) 1262 (void) tcp_output(tp); 1263 goto check_delack; 1264 } 1265 } else if (th->th_ack == tp->snd_una && 1266 LIST_EMPTY(&tp->t_segq) && 1267 tlen <= sbspace(&so->so_rcv)) { 1268 KASSERT(headlocked, ("headlocked")); 1269 INP_INFO_WUNLOCK(&tcbinfo); 1270 headlocked = 0; 1271 /* 1272 * this is a pure, in-sequence data packet 1273 * with nothing on the reassembly queue and 1274 * we have enough buffer space to take it. 1275 */ 1276 /* Clean receiver SACK report if present */ 1277 if (tp->sack_enable && tp->rcv_numsacks) 1278 tcp_clean_sackreport(tp); 1279 ++tcpstat.tcps_preddat; 1280 tp->rcv_nxt += tlen; 1281 /* 1282 * Pull snd_wl1 up to prevent seq wrap relative to 1283 * th_seq. 1284 */ 1285 tp->snd_wl1 = th->th_seq; 1286 /* 1287 * Pull rcv_up up to prevent seq wrap relative to 1288 * rcv_nxt. 1289 */ 1290 tp->rcv_up = tp->rcv_nxt; 1291 tcpstat.tcps_rcvpack++; 1292 tcpstat.tcps_rcvbyte += tlen; 1293 ND6_HINT(tp); /* some progress has been done */ 1294 /* 1295 #ifdef TCPDEBUG 1296 if (so->so_options & SO_DEBUG) 1297 tcp_trace(TA_INPUT, ostate, tp, 1298 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1299 #endif 1300 * Add data to socket buffer. 1301 */ 1302 SOCKBUF_LOCK(&so->so_rcv); 1303 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1304 m_freem(m); 1305 } else { 1306 m_adj(m, drop_hdrlen); /* delayed header drop */ 1307 sbappendstream_locked(&so->so_rcv, m); 1308 } 1309 sorwakeup_locked(so); 1310 if (DELAY_ACK(tp)) { 1311 tp->t_flags |= TF_DELACK; 1312 } else { 1313 tp->t_flags |= TF_ACKNOW; 1314 tcp_output(tp); 1315 } 1316 goto check_delack; 1317 } 1318 } 1319 1320 /* 1321 * Calculate amount of space in receive window, 1322 * and then do TCP input processing. 1323 * Receive window is amount of space in rcv queue, 1324 * but not less than advertised window. 1325 */ 1326 { int win; 1327 1328 win = sbspace(&so->so_rcv); 1329 if (win < 0) 1330 win = 0; 1331 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1332 } 1333 1334 switch (tp->t_state) { 1335 1336 /* 1337 * If the state is SYN_RECEIVED: 1338 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1339 */ 1340 case TCPS_SYN_RECEIVED: 1341 if ((thflags & TH_ACK) && 1342 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1343 SEQ_GT(th->th_ack, tp->snd_max))) { 1344 rstreason = BANDLIM_RST_OPENPORT; 1345 goto dropwithreset; 1346 } 1347 break; 1348 1349 /* 1350 * If the state is SYN_SENT: 1351 * if seg contains an ACK, but not for our SYN, drop the input. 1352 * if seg contains a RST, then drop the connection. 1353 * if seg does not contain SYN, then drop it. 1354 * Otherwise this is an acceptable SYN segment 1355 * initialize tp->rcv_nxt and tp->irs 1356 * if seg contains ack then advance tp->snd_una 1357 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1358 * arrange for segment to be acked (eventually) 1359 * continue processing rest of data/controls, beginning with URG 1360 */ 1361 case TCPS_SYN_SENT: 1362 if ((thflags & TH_ACK) && 1363 (SEQ_LEQ(th->th_ack, tp->iss) || 1364 SEQ_GT(th->th_ack, tp->snd_max))) { 1365 rstreason = BANDLIM_UNLIMITED; 1366 goto dropwithreset; 1367 } 1368 if (thflags & TH_RST) { 1369 if (thflags & TH_ACK) { 1370 KASSERT(headlocked, ("tcp_input: after_listen" 1371 ": tcp_drop.2: head not locked")); 1372 tp = tcp_drop(tp, ECONNREFUSED); 1373 } 1374 goto drop; 1375 } 1376 if ((thflags & TH_SYN) == 0) 1377 goto drop; 1378 1379 /* Initial send window, already scaled. */ 1380 tp->snd_wnd = th->th_win; 1381 1382 tp->irs = th->th_seq; 1383 tcp_rcvseqinit(tp); 1384 if (thflags & TH_ACK) { 1385 tcpstat.tcps_connects++; 1386 soisconnected(so); 1387 #ifdef MAC 1388 SOCK_LOCK(so); 1389 mac_set_socket_peer_from_mbuf(m, so); 1390 SOCK_UNLOCK(so); 1391 #endif 1392 /* Do window scaling on this connection? */ 1393 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1394 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1395 tp->rcv_scale = tp->request_r_scale; 1396 } 1397 tp->rcv_adv += tp->rcv_wnd; 1398 tp->snd_una++; /* SYN is acked */ 1399 /* 1400 * If there's data, delay ACK; if there's also a FIN 1401 * ACKNOW will be turned on later. 1402 */ 1403 if (DELAY_ACK(tp) && tlen != 0) 1404 callout_reset(tp->tt_delack, tcp_delacktime, 1405 tcp_timer_delack, tp); 1406 else 1407 tp->t_flags |= TF_ACKNOW; 1408 /* 1409 * Received <SYN,ACK> in SYN_SENT[*] state. 1410 * Transitions: 1411 * SYN_SENT --> ESTABLISHED 1412 * SYN_SENT* --> FIN_WAIT_1 1413 */ 1414 tp->t_starttime = ticks; 1415 if (tp->t_flags & TF_NEEDFIN) { 1416 tp->t_state = TCPS_FIN_WAIT_1; 1417 tp->t_flags &= ~TF_NEEDFIN; 1418 thflags &= ~TH_SYN; 1419 } else { 1420 tp->t_state = TCPS_ESTABLISHED; 1421 callout_reset(tp->tt_keep, tcp_keepidle, 1422 tcp_timer_keep, tp); 1423 } 1424 } else { 1425 /* 1426 * Received initial SYN in SYN-SENT[*] state => 1427 * simultaneous open. If segment contains CC option 1428 * and there is a cached CC, apply TAO test. 1429 * If it succeeds, connection is * half-synchronized. 1430 * Otherwise, do 3-way handshake: 1431 * SYN-SENT -> SYN-RECEIVED 1432 * SYN-SENT* -> SYN-RECEIVED* 1433 * If there was no CC option, clear cached CC value. 1434 */ 1435 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1436 callout_stop(tp->tt_rexmt); 1437 tp->t_state = TCPS_SYN_RECEIVED; 1438 } 1439 1440 trimthenstep6: 1441 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1442 "locked")); 1443 INP_LOCK_ASSERT(inp); 1444 1445 /* 1446 * Advance th->th_seq to correspond to first data byte. 1447 * If data, trim to stay within window, 1448 * dropping FIN if necessary. 1449 */ 1450 th->th_seq++; 1451 if (tlen > tp->rcv_wnd) { 1452 todrop = tlen - tp->rcv_wnd; 1453 m_adj(m, -todrop); 1454 tlen = tp->rcv_wnd; 1455 thflags &= ~TH_FIN; 1456 tcpstat.tcps_rcvpackafterwin++; 1457 tcpstat.tcps_rcvbyteafterwin += todrop; 1458 } 1459 tp->snd_wl1 = th->th_seq - 1; 1460 tp->rcv_up = th->th_seq; 1461 /* 1462 * Client side of transaction: already sent SYN and data. 1463 * If the remote host used T/TCP to validate the SYN, 1464 * our data will be ACK'd; if so, enter normal data segment 1465 * processing in the middle of step 5, ack processing. 1466 * Otherwise, goto step 6. 1467 */ 1468 if (thflags & TH_ACK) 1469 goto process_ACK; 1470 1471 goto step6; 1472 1473 /* 1474 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1475 * do normal processing. 1476 * 1477 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1478 */ 1479 case TCPS_LAST_ACK: 1480 case TCPS_CLOSING: 1481 case TCPS_TIME_WAIT: 1482 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1483 break; /* continue normal processing */ 1484 } 1485 1486 /* 1487 * States other than LISTEN or SYN_SENT. 1488 * First check the RST flag and sequence number since reset segments 1489 * are exempt from the timestamp and connection count tests. This 1490 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1491 * below which allowed reset segments in half the sequence space 1492 * to fall though and be processed (which gives forged reset 1493 * segments with a random sequence number a 50 percent chance of 1494 * killing a connection). 1495 * Then check timestamp, if present. 1496 * Then check the connection count, if present. 1497 * Then check that at least some bytes of segment are within 1498 * receive window. If segment begins before rcv_nxt, 1499 * drop leading data (and SYN); if nothing left, just ack. 1500 * 1501 * 1502 * If the RST bit is set, check the sequence number to see 1503 * if this is a valid reset segment. 1504 * RFC 793 page 37: 1505 * In all states except SYN-SENT, all reset (RST) segments 1506 * are validated by checking their SEQ-fields. A reset is 1507 * valid if its sequence number is in the window. 1508 * Note: this does not take into account delayed ACKs, so 1509 * we should test against last_ack_sent instead of rcv_nxt. 1510 * The sequence number in the reset segment is normally an 1511 * echo of our outgoing acknowlegement numbers, but some hosts 1512 * send a reset with the sequence number at the rightmost edge 1513 * of our receive window, and we have to handle this case. 1514 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1515 * that brute force RST attacks are possible. To combat this, 1516 * we use a much stricter check while in the ESTABLISHED state, 1517 * only accepting RSTs where the sequence number is equal to 1518 * last_ack_sent. In all other states (the states in which a 1519 * RST is more likely), the more permissive check is used. 1520 * If we have multiple segments in flight, the intial reset 1521 * segment sequence numbers will be to the left of last_ack_sent, 1522 * but they will eventually catch up. 1523 * In any case, it never made sense to trim reset segments to 1524 * fit the receive window since RFC 1122 says: 1525 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1526 * 1527 * A TCP SHOULD allow a received RST segment to include data. 1528 * 1529 * DISCUSSION 1530 * It has been suggested that a RST segment could contain 1531 * ASCII text that encoded and explained the cause of the 1532 * RST. No standard has yet been established for such 1533 * data. 1534 * 1535 * If the reset segment passes the sequence number test examine 1536 * the state: 1537 * SYN_RECEIVED STATE: 1538 * If passive open, return to LISTEN state. 1539 * If active open, inform user that connection was refused. 1540 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1541 * Inform user that connection was reset, and close tcb. 1542 * CLOSING, LAST_ACK STATES: 1543 * Close the tcb. 1544 * TIME_WAIT STATE: 1545 * Drop the segment - see Stevens, vol. 2, p. 964 and 1546 * RFC 1337. 1547 */ 1548 if (thflags & TH_RST) { 1549 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1550 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1551 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1552 switch (tp->t_state) { 1553 1554 case TCPS_SYN_RECEIVED: 1555 so->so_error = ECONNREFUSED; 1556 goto close; 1557 1558 case TCPS_ESTABLISHED: 1559 if (tp->last_ack_sent != th->th_seq && 1560 tcp_insecure_rst == 0) { 1561 tcpstat.tcps_badrst++; 1562 goto drop; 1563 } 1564 case TCPS_FIN_WAIT_1: 1565 case TCPS_FIN_WAIT_2: 1566 case TCPS_CLOSE_WAIT: 1567 so->so_error = ECONNRESET; 1568 close: 1569 tp->t_state = TCPS_CLOSED; 1570 tcpstat.tcps_drops++; 1571 KASSERT(headlocked, ("tcp_input: " 1572 "trimthenstep6: tcp_close: head not " 1573 "locked")); 1574 tp = tcp_close(tp); 1575 break; 1576 1577 case TCPS_CLOSING: 1578 case TCPS_LAST_ACK: 1579 KASSERT(headlocked, ("trimthenstep6: " 1580 "tcp_close.2: head not locked")); 1581 tp = tcp_close(tp); 1582 break; 1583 1584 case TCPS_TIME_WAIT: 1585 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1586 ("timewait")); 1587 break; 1588 } 1589 } 1590 goto drop; 1591 } 1592 1593 /* 1594 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1595 * and it's less than ts_recent, drop it. 1596 */ 1597 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1598 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1599 1600 /* Check to see if ts_recent is over 24 days old. */ 1601 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1602 /* 1603 * Invalidate ts_recent. If this segment updates 1604 * ts_recent, the age will be reset later and ts_recent 1605 * will get a valid value. If it does not, setting 1606 * ts_recent to zero will at least satisfy the 1607 * requirement that zero be placed in the timestamp 1608 * echo reply when ts_recent isn't valid. The 1609 * age isn't reset until we get a valid ts_recent 1610 * because we don't want out-of-order segments to be 1611 * dropped when ts_recent is old. 1612 */ 1613 tp->ts_recent = 0; 1614 } else { 1615 tcpstat.tcps_rcvduppack++; 1616 tcpstat.tcps_rcvdupbyte += tlen; 1617 tcpstat.tcps_pawsdrop++; 1618 if (tlen) 1619 goto dropafterack; 1620 goto drop; 1621 } 1622 } 1623 1624 /* 1625 * In the SYN-RECEIVED state, validate that the packet belongs to 1626 * this connection before trimming the data to fit the receive 1627 * window. Check the sequence number versus IRS since we know 1628 * the sequence numbers haven't wrapped. This is a partial fix 1629 * for the "LAND" DoS attack. 1630 */ 1631 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1632 rstreason = BANDLIM_RST_OPENPORT; 1633 goto dropwithreset; 1634 } 1635 1636 todrop = tp->rcv_nxt - th->th_seq; 1637 if (todrop > 0) { 1638 if (thflags & TH_SYN) { 1639 thflags &= ~TH_SYN; 1640 th->th_seq++; 1641 if (th->th_urp > 1) 1642 th->th_urp--; 1643 else 1644 thflags &= ~TH_URG; 1645 todrop--; 1646 } 1647 /* 1648 * Following if statement from Stevens, vol. 2, p. 960. 1649 */ 1650 if (todrop > tlen 1651 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1652 /* 1653 * Any valid FIN must be to the left of the window. 1654 * At this point the FIN must be a duplicate or out 1655 * of sequence; drop it. 1656 */ 1657 thflags &= ~TH_FIN; 1658 1659 /* 1660 * Send an ACK to resynchronize and drop any data. 1661 * But keep on processing for RST or ACK. 1662 */ 1663 tp->t_flags |= TF_ACKNOW; 1664 todrop = tlen; 1665 tcpstat.tcps_rcvduppack++; 1666 tcpstat.tcps_rcvdupbyte += todrop; 1667 } else { 1668 tcpstat.tcps_rcvpartduppack++; 1669 tcpstat.tcps_rcvpartdupbyte += todrop; 1670 } 1671 drop_hdrlen += todrop; /* drop from the top afterwards */ 1672 th->th_seq += todrop; 1673 tlen -= todrop; 1674 if (th->th_urp > todrop) 1675 th->th_urp -= todrop; 1676 else { 1677 thflags &= ~TH_URG; 1678 th->th_urp = 0; 1679 } 1680 } 1681 1682 /* 1683 * If new data are received on a connection after the 1684 * user processes are gone, then RST the other end. 1685 */ 1686 if ((so->so_state & SS_NOFDREF) && 1687 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1688 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1689 "locked")); 1690 tp = tcp_close(tp); 1691 tcpstat.tcps_rcvafterclose++; 1692 rstreason = BANDLIM_UNLIMITED; 1693 goto dropwithreset; 1694 } 1695 1696 /* 1697 * If segment ends after window, drop trailing data 1698 * (and PUSH and FIN); if nothing left, just ACK. 1699 */ 1700 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1701 if (todrop > 0) { 1702 tcpstat.tcps_rcvpackafterwin++; 1703 if (todrop >= tlen) { 1704 tcpstat.tcps_rcvbyteafterwin += tlen; 1705 /* 1706 * If a new connection request is received 1707 * while in TIME_WAIT, drop the old connection 1708 * and start over if the sequence numbers 1709 * are above the previous ones. 1710 */ 1711 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1712 if (thflags & TH_SYN && 1713 tp->t_state == TCPS_TIME_WAIT && 1714 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1715 KASSERT(headlocked, ("trimthenstep6: " 1716 "tcp_close.4: head not locked")); 1717 tp = tcp_close(tp); 1718 goto findpcb; 1719 } 1720 /* 1721 * If window is closed can only take segments at 1722 * window edge, and have to drop data and PUSH from 1723 * incoming segments. Continue processing, but 1724 * remember to ack. Otherwise, drop segment 1725 * and ack. 1726 */ 1727 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1728 tp->t_flags |= TF_ACKNOW; 1729 tcpstat.tcps_rcvwinprobe++; 1730 } else 1731 goto dropafterack; 1732 } else 1733 tcpstat.tcps_rcvbyteafterwin += todrop; 1734 m_adj(m, -todrop); 1735 tlen -= todrop; 1736 thflags &= ~(TH_PUSH|TH_FIN); 1737 } 1738 1739 /* 1740 * If last ACK falls within this segment's sequence numbers, 1741 * record its timestamp. 1742 * NOTE: 1743 * 1) That the test incorporates suggestions from the latest 1744 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1745 * 2) That updating only on newer timestamps interferes with 1746 * our earlier PAWS tests, so this check should be solely 1747 * predicated on the sequence space of this segment. 1748 * 3) That we modify the segment boundary check to be 1749 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1750 * instead of RFC1323's 1751 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1752 * This modified check allows us to overcome RFC1323's 1753 * limitations as described in Stevens TCP/IP Illustrated 1754 * Vol. 2 p.869. In such cases, we can still calculate the 1755 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1756 */ 1757 if ((to.to_flags & TOF_TS) != 0 && 1758 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1759 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1760 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1761 tp->ts_recent_age = ticks; 1762 tp->ts_recent = to.to_tsval; 1763 } 1764 1765 /* 1766 * If a SYN is in the window, then this is an 1767 * error and we send an RST and drop the connection. 1768 */ 1769 if (thflags & TH_SYN) { 1770 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1771 "head not locked")); 1772 tp = tcp_drop(tp, ECONNRESET); 1773 rstreason = BANDLIM_UNLIMITED; 1774 goto drop; 1775 } 1776 1777 /* 1778 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1779 * flag is on (half-synchronized state), then queue data for 1780 * later processing; else drop segment and return. 1781 */ 1782 if ((thflags & TH_ACK) == 0) { 1783 if (tp->t_state == TCPS_SYN_RECEIVED || 1784 (tp->t_flags & TF_NEEDSYN)) 1785 goto step6; 1786 else 1787 goto drop; 1788 } 1789 1790 /* 1791 * Ack processing. 1792 */ 1793 switch (tp->t_state) { 1794 1795 /* 1796 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1797 * ESTABLISHED state and continue processing. 1798 * The ACK was checked above. 1799 */ 1800 case TCPS_SYN_RECEIVED: 1801 1802 tcpstat.tcps_connects++; 1803 soisconnected(so); 1804 /* Do window scaling? */ 1805 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1806 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1807 tp->rcv_scale = tp->request_r_scale; 1808 tp->snd_wnd = tiwin; 1809 } 1810 /* 1811 * Make transitions: 1812 * SYN-RECEIVED -> ESTABLISHED 1813 * SYN-RECEIVED* -> FIN-WAIT-1 1814 */ 1815 tp->t_starttime = ticks; 1816 if (tp->t_flags & TF_NEEDFIN) { 1817 tp->t_state = TCPS_FIN_WAIT_1; 1818 tp->t_flags &= ~TF_NEEDFIN; 1819 } else { 1820 tp->t_state = TCPS_ESTABLISHED; 1821 callout_reset(tp->tt_keep, tcp_keepidle, 1822 tcp_timer_keep, tp); 1823 } 1824 /* 1825 * If segment contains data or ACK, will call tcp_reass() 1826 * later; if not, do so now to pass queued data to user. 1827 */ 1828 if (tlen == 0 && (thflags & TH_FIN) == 0) 1829 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1830 (struct mbuf *)0); 1831 tp->snd_wl1 = th->th_seq - 1; 1832 /* FALLTHROUGH */ 1833 1834 /* 1835 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1836 * ACKs. If the ack is in the range 1837 * tp->snd_una < th->th_ack <= tp->snd_max 1838 * then advance tp->snd_una to th->th_ack and drop 1839 * data from the retransmission queue. If this ACK reflects 1840 * more up to date window information we update our window information. 1841 */ 1842 case TCPS_ESTABLISHED: 1843 case TCPS_FIN_WAIT_1: 1844 case TCPS_FIN_WAIT_2: 1845 case TCPS_CLOSE_WAIT: 1846 case TCPS_CLOSING: 1847 case TCPS_LAST_ACK: 1848 case TCPS_TIME_WAIT: 1849 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1850 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1851 tcpstat.tcps_rcvacktoomuch++; 1852 goto dropafterack; 1853 } 1854 if (tp->sack_enable && 1855 (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) 1856 tcp_sack_doack(tp, &to, th->th_ack); 1857 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1858 if (tlen == 0 && tiwin == tp->snd_wnd) { 1859 tcpstat.tcps_rcvdupack++; 1860 /* 1861 * If we have outstanding data (other than 1862 * a window probe), this is a completely 1863 * duplicate ack (ie, window info didn't 1864 * change), the ack is the biggest we've 1865 * seen and we've seen exactly our rexmt 1866 * threshhold of them, assume a packet 1867 * has been dropped and retransmit it. 1868 * Kludge snd_nxt & the congestion 1869 * window so we send only this one 1870 * packet. 1871 * 1872 * We know we're losing at the current 1873 * window size so do congestion avoidance 1874 * (set ssthresh to half the current window 1875 * and pull our congestion window back to 1876 * the new ssthresh). 1877 * 1878 * Dup acks mean that packets have left the 1879 * network (they're now cached at the receiver) 1880 * so bump cwnd by the amount in the receiver 1881 * to keep a constant cwnd packets in the 1882 * network. 1883 */ 1884 if (!callout_active(tp->tt_rexmt) || 1885 th->th_ack != tp->snd_una) 1886 tp->t_dupacks = 0; 1887 else if (++tp->t_dupacks > tcprexmtthresh || 1888 ((tcp_do_newreno || tp->sack_enable) && 1889 IN_FASTRECOVERY(tp))) { 1890 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1891 int awnd; 1892 1893 /* 1894 * Compute the amount of data in flight first. 1895 * We can inject new data into the pipe iff 1896 * we have less than 1/2 the original window's 1897 * worth of data in flight. 1898 */ 1899 awnd = (tp->snd_nxt - tp->snd_fack) + 1900 tp->sackhint.sack_bytes_rexmit; 1901 if (awnd < tp->snd_ssthresh) { 1902 tp->snd_cwnd += tp->t_maxseg; 1903 if (tp->snd_cwnd > tp->snd_ssthresh) 1904 tp->snd_cwnd = tp->snd_ssthresh; 1905 } 1906 } else 1907 tp->snd_cwnd += tp->t_maxseg; 1908 (void) tcp_output(tp); 1909 goto drop; 1910 } else if (tp->t_dupacks == tcprexmtthresh) { 1911 tcp_seq onxt = tp->snd_nxt; 1912 u_int win; 1913 1914 /* 1915 * If we're doing sack, check to 1916 * see if we're already in sack 1917 * recovery. If we're not doing sack, 1918 * check to see if we're in newreno 1919 * recovery. 1920 */ 1921 if (tp->sack_enable) { 1922 if (IN_FASTRECOVERY(tp)) { 1923 tp->t_dupacks = 0; 1924 break; 1925 } 1926 } else if (tcp_do_newreno) { 1927 if (SEQ_LEQ(th->th_ack, 1928 tp->snd_recover)) { 1929 tp->t_dupacks = 0; 1930 break; 1931 } 1932 } 1933 win = min(tp->snd_wnd, tp->snd_cwnd) / 1934 2 / tp->t_maxseg; 1935 if (win < 2) 1936 win = 2; 1937 tp->snd_ssthresh = win * tp->t_maxseg; 1938 ENTER_FASTRECOVERY(tp); 1939 tp->snd_recover = tp->snd_max; 1940 callout_stop(tp->tt_rexmt); 1941 tp->t_rtttime = 0; 1942 if (tp->sack_enable) { 1943 tcpstat.tcps_sack_recovery_episode++; 1944 tp->sack_newdata = tp->snd_nxt; 1945 tp->snd_cwnd = tp->t_maxseg; 1946 (void) tcp_output(tp); 1947 goto drop; 1948 } 1949 tp->snd_nxt = th->th_ack; 1950 tp->snd_cwnd = tp->t_maxseg; 1951 (void) tcp_output(tp); 1952 KASSERT(tp->snd_limited <= 2, 1953 ("tp->snd_limited too big")); 1954 tp->snd_cwnd = tp->snd_ssthresh + 1955 tp->t_maxseg * 1956 (tp->t_dupacks - tp->snd_limited); 1957 if (SEQ_GT(onxt, tp->snd_nxt)) 1958 tp->snd_nxt = onxt; 1959 goto drop; 1960 } else if (tcp_do_rfc3042) { 1961 u_long oldcwnd = tp->snd_cwnd; 1962 tcp_seq oldsndmax = tp->snd_max; 1963 u_int sent; 1964 1965 KASSERT(tp->t_dupacks == 1 || 1966 tp->t_dupacks == 2, 1967 ("dupacks not 1 or 2")); 1968 if (tp->t_dupacks == 1) 1969 tp->snd_limited = 0; 1970 tp->snd_cwnd = 1971 (tp->snd_nxt - tp->snd_una) + 1972 (tp->t_dupacks - tp->snd_limited) * 1973 tp->t_maxseg; 1974 (void) tcp_output(tp); 1975 sent = tp->snd_max - oldsndmax; 1976 if (sent > tp->t_maxseg) { 1977 KASSERT((tp->t_dupacks == 2 && 1978 tp->snd_limited == 0) || 1979 (sent == tp->t_maxseg + 1 && 1980 tp->t_flags & TF_SENTFIN), 1981 ("sent too much")); 1982 tp->snd_limited = 2; 1983 } else if (sent > 0) 1984 ++tp->snd_limited; 1985 tp->snd_cwnd = oldcwnd; 1986 goto drop; 1987 } 1988 } else 1989 tp->t_dupacks = 0; 1990 break; 1991 } 1992 1993 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1994 1995 /* 1996 * If the congestion window was inflated to account 1997 * for the other side's cached packets, retract it. 1998 */ 1999 if (tcp_do_newreno || tp->sack_enable) { 2000 if (IN_FASTRECOVERY(tp)) { 2001 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2002 if (tp->sack_enable) 2003 tcp_sack_partialack(tp, th); 2004 else 2005 tcp_newreno_partial_ack(tp, th); 2006 } else { 2007 /* 2008 * Out of fast recovery. 2009 * Window inflation should have left us 2010 * with approximately snd_ssthresh 2011 * outstanding data. 2012 * But in case we would be inclined to 2013 * send a burst, better to do it via 2014 * the slow start mechanism. 2015 */ 2016 if (SEQ_GT(th->th_ack + 2017 tp->snd_ssthresh, 2018 tp->snd_max)) 2019 tp->snd_cwnd = tp->snd_max - 2020 th->th_ack + 2021 tp->t_maxseg; 2022 else 2023 tp->snd_cwnd = tp->snd_ssthresh; 2024 } 2025 } 2026 } else { 2027 if (tp->t_dupacks >= tcprexmtthresh && 2028 tp->snd_cwnd > tp->snd_ssthresh) 2029 tp->snd_cwnd = tp->snd_ssthresh; 2030 } 2031 tp->t_dupacks = 0; 2032 /* 2033 * If we reach this point, ACK is not a duplicate, 2034 * i.e., it ACKs something we sent. 2035 */ 2036 if (tp->t_flags & TF_NEEDSYN) { 2037 /* 2038 * T/TCP: Connection was half-synchronized, and our 2039 * SYN has been ACK'd (so connection is now fully 2040 * synchronized). Go to non-starred state, 2041 * increment snd_una for ACK of SYN, and check if 2042 * we can do window scaling. 2043 */ 2044 tp->t_flags &= ~TF_NEEDSYN; 2045 tp->snd_una++; 2046 /* Do window scaling? */ 2047 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2048 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2049 tp->rcv_scale = tp->request_r_scale; 2050 /* Send window already scaled. */ 2051 } 2052 } 2053 2054 process_ACK: 2055 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2056 "locked")); 2057 INP_LOCK_ASSERT(inp); 2058 2059 acked = th->th_ack - tp->snd_una; 2060 tcpstat.tcps_rcvackpack++; 2061 tcpstat.tcps_rcvackbyte += acked; 2062 2063 /* 2064 * If we just performed our first retransmit, and the ACK 2065 * arrives within our recovery window, then it was a mistake 2066 * to do the retransmit in the first place. Recover our 2067 * original cwnd and ssthresh, and proceed to transmit where 2068 * we left off. 2069 */ 2070 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2071 ++tcpstat.tcps_sndrexmitbad; 2072 tp->snd_cwnd = tp->snd_cwnd_prev; 2073 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2074 tp->snd_recover = tp->snd_recover_prev; 2075 if (tp->t_flags & TF_WASFRECOVERY) 2076 ENTER_FASTRECOVERY(tp); 2077 tp->snd_nxt = tp->snd_max; 2078 tp->t_badrxtwin = 0; /* XXX probably not required */ 2079 } 2080 2081 /* 2082 * If we have a timestamp reply, update smoothed 2083 * round trip time. If no timestamp is present but 2084 * transmit timer is running and timed sequence 2085 * number was acked, update smoothed round trip time. 2086 * Since we now have an rtt measurement, cancel the 2087 * timer backoff (cf., Phil Karn's retransmit alg.). 2088 * Recompute the initial retransmit timer. 2089 * 2090 * Some boxes send broken timestamp replies 2091 * during the SYN+ACK phase, ignore 2092 * timestamps of 0 or we could calculate a 2093 * huge RTT and blow up the retransmit timer. 2094 */ 2095 if ((to.to_flags & TOF_TS) != 0 && 2096 to.to_tsecr) { 2097 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2098 tp->t_rttlow = ticks - to.to_tsecr; 2099 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2100 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2101 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2102 tp->t_rttlow = ticks - tp->t_rtttime; 2103 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2104 } 2105 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2106 2107 /* 2108 * If all outstanding data is acked, stop retransmit 2109 * timer and remember to restart (more output or persist). 2110 * If there is more data to be acked, restart retransmit 2111 * timer, using current (possibly backed-off) value. 2112 */ 2113 if (th->th_ack == tp->snd_max) { 2114 callout_stop(tp->tt_rexmt); 2115 needoutput = 1; 2116 } else if (!callout_active(tp->tt_persist)) 2117 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2118 tcp_timer_rexmt, tp); 2119 2120 /* 2121 * If no data (only SYN) was ACK'd, 2122 * skip rest of ACK processing. 2123 */ 2124 if (acked == 0) 2125 goto step6; 2126 2127 /* 2128 * When new data is acked, open the congestion window. 2129 * If the window gives us less than ssthresh packets 2130 * in flight, open exponentially (maxseg per packet). 2131 * Otherwise open linearly: maxseg per window 2132 * (maxseg^2 / cwnd per packet). 2133 */ 2134 if ((!tcp_do_newreno && !tp->sack_enable) || 2135 !IN_FASTRECOVERY(tp)) { 2136 register u_int cw = tp->snd_cwnd; 2137 register u_int incr = tp->t_maxseg; 2138 if (cw > tp->snd_ssthresh) 2139 incr = incr * incr / cw; 2140 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2141 } 2142 SOCKBUF_LOCK(&so->so_snd); 2143 if (acked > so->so_snd.sb_cc) { 2144 tp->snd_wnd -= so->so_snd.sb_cc; 2145 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2146 ourfinisacked = 1; 2147 } else { 2148 sbdrop_locked(&so->so_snd, acked); 2149 tp->snd_wnd -= acked; 2150 ourfinisacked = 0; 2151 } 2152 sowwakeup_locked(so); 2153 /* detect una wraparound */ 2154 if ((tcp_do_newreno || tp->sack_enable) && 2155 !IN_FASTRECOVERY(tp) && 2156 SEQ_GT(tp->snd_una, tp->snd_recover) && 2157 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2158 tp->snd_recover = th->th_ack - 1; 2159 if ((tcp_do_newreno || tp->sack_enable) && 2160 IN_FASTRECOVERY(tp) && 2161 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2162 EXIT_FASTRECOVERY(tp); 2163 tp->snd_una = th->th_ack; 2164 if (tp->sack_enable) { 2165 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2166 tp->snd_recover = tp->snd_una; 2167 } 2168 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2169 tp->snd_nxt = tp->snd_una; 2170 2171 switch (tp->t_state) { 2172 2173 /* 2174 * In FIN_WAIT_1 STATE in addition to the processing 2175 * for the ESTABLISHED state if our FIN is now acknowledged 2176 * then enter FIN_WAIT_2. 2177 */ 2178 case TCPS_FIN_WAIT_1: 2179 if (ourfinisacked) { 2180 /* 2181 * If we can't receive any more 2182 * data, then closing user can proceed. 2183 * Starting the timer is contrary to the 2184 * specification, but if we don't get a FIN 2185 * we'll hang forever. 2186 */ 2187 /* XXXjl 2188 * we should release the tp also, and use a 2189 * compressed state. 2190 */ 2191 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2192 soisdisconnected(so); 2193 callout_reset(tp->tt_2msl, tcp_maxidle, 2194 tcp_timer_2msl, tp); 2195 } 2196 tp->t_state = TCPS_FIN_WAIT_2; 2197 } 2198 break; 2199 2200 /* 2201 * In CLOSING STATE in addition to the processing for 2202 * the ESTABLISHED state if the ACK acknowledges our FIN 2203 * then enter the TIME-WAIT state, otherwise ignore 2204 * the segment. 2205 */ 2206 case TCPS_CLOSING: 2207 if (ourfinisacked) { 2208 KASSERT(headlocked, ("tcp_input: process_ACK: " 2209 "head not locked")); 2210 tcp_twstart(tp); 2211 INP_INFO_WUNLOCK(&tcbinfo); 2212 m_freem(m); 2213 return; 2214 } 2215 break; 2216 2217 /* 2218 * In LAST_ACK, we may still be waiting for data to drain 2219 * and/or to be acked, as well as for the ack of our FIN. 2220 * If our FIN is now acknowledged, delete the TCB, 2221 * enter the closed state and return. 2222 */ 2223 case TCPS_LAST_ACK: 2224 if (ourfinisacked) { 2225 KASSERT(headlocked, ("tcp_input: process_ACK:" 2226 " tcp_close: head not locked")); 2227 tp = tcp_close(tp); 2228 goto drop; 2229 } 2230 break; 2231 2232 /* 2233 * In TIME_WAIT state the only thing that should arrive 2234 * is a retransmission of the remote FIN. Acknowledge 2235 * it and restart the finack timer. 2236 */ 2237 case TCPS_TIME_WAIT: 2238 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2239 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2240 tcp_timer_2msl, tp); 2241 goto dropafterack; 2242 } 2243 } 2244 2245 step6: 2246 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2247 INP_LOCK_ASSERT(inp); 2248 2249 /* 2250 * Update window information. 2251 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2252 */ 2253 if ((thflags & TH_ACK) && 2254 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2255 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2256 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2257 /* keep track of pure window updates */ 2258 if (tlen == 0 && 2259 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2260 tcpstat.tcps_rcvwinupd++; 2261 tp->snd_wnd = tiwin; 2262 tp->snd_wl1 = th->th_seq; 2263 tp->snd_wl2 = th->th_ack; 2264 if (tp->snd_wnd > tp->max_sndwnd) 2265 tp->max_sndwnd = tp->snd_wnd; 2266 needoutput = 1; 2267 } 2268 2269 /* 2270 * Process segments with URG. 2271 */ 2272 if ((thflags & TH_URG) && th->th_urp && 2273 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2274 /* 2275 * This is a kludge, but if we receive and accept 2276 * random urgent pointers, we'll crash in 2277 * soreceive. It's hard to imagine someone 2278 * actually wanting to send this much urgent data. 2279 */ 2280 SOCKBUF_LOCK(&so->so_rcv); 2281 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2282 th->th_urp = 0; /* XXX */ 2283 thflags &= ~TH_URG; /* XXX */ 2284 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2285 goto dodata; /* XXX */ 2286 } 2287 /* 2288 * If this segment advances the known urgent pointer, 2289 * then mark the data stream. This should not happen 2290 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2291 * a FIN has been received from the remote side. 2292 * In these states we ignore the URG. 2293 * 2294 * According to RFC961 (Assigned Protocols), 2295 * the urgent pointer points to the last octet 2296 * of urgent data. We continue, however, 2297 * to consider it to indicate the first octet 2298 * of data past the urgent section as the original 2299 * spec states (in one of two places). 2300 */ 2301 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2302 tp->rcv_up = th->th_seq + th->th_urp; 2303 so->so_oobmark = so->so_rcv.sb_cc + 2304 (tp->rcv_up - tp->rcv_nxt) - 1; 2305 if (so->so_oobmark == 0) 2306 so->so_rcv.sb_state |= SBS_RCVATMARK; 2307 sohasoutofband(so); 2308 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2309 } 2310 SOCKBUF_UNLOCK(&so->so_rcv); 2311 /* 2312 * Remove out of band data so doesn't get presented to user. 2313 * This can happen independent of advancing the URG pointer, 2314 * but if two URG's are pending at once, some out-of-band 2315 * data may creep in... ick. 2316 */ 2317 if (th->th_urp <= (u_long)tlen && 2318 !(so->so_options & SO_OOBINLINE)) { 2319 /* hdr drop is delayed */ 2320 tcp_pulloutofband(so, th, m, drop_hdrlen); 2321 } 2322 } else { 2323 /* 2324 * If no out of band data is expected, 2325 * pull receive urgent pointer along 2326 * with the receive window. 2327 */ 2328 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2329 tp->rcv_up = tp->rcv_nxt; 2330 } 2331 dodata: /* XXX */ 2332 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2333 INP_LOCK_ASSERT(inp); 2334 2335 /* 2336 * Process the segment text, merging it into the TCP sequencing queue, 2337 * and arranging for acknowledgment of receipt if necessary. 2338 * This process logically involves adjusting tp->rcv_wnd as data 2339 * is presented to the user (this happens in tcp_usrreq.c, 2340 * case PRU_RCVD). If a FIN has already been received on this 2341 * connection then we just ignore the text. 2342 */ 2343 if ((tlen || (thflags & TH_FIN)) && 2344 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2345 tcp_seq save_start = th->th_seq; 2346 tcp_seq save_end = th->th_seq + tlen; 2347 m_adj(m, drop_hdrlen); /* delayed header drop */ 2348 /* 2349 * Insert segment which includes th into TCP reassembly queue 2350 * with control block tp. Set thflags to whether reassembly now 2351 * includes a segment with FIN. This handles the common case 2352 * inline (segment is the next to be received on an established 2353 * connection, and the queue is empty), avoiding linkage into 2354 * and removal from the queue and repetition of various 2355 * conversions. 2356 * Set DELACK for segments received in order, but ack 2357 * immediately when segments are out of order (so 2358 * fast retransmit can work). 2359 */ 2360 if (th->th_seq == tp->rcv_nxt && 2361 LIST_EMPTY(&tp->t_segq) && 2362 TCPS_HAVEESTABLISHED(tp->t_state)) { 2363 if (DELAY_ACK(tp)) 2364 tp->t_flags |= TF_DELACK; 2365 else 2366 tp->t_flags |= TF_ACKNOW; 2367 tp->rcv_nxt += tlen; 2368 thflags = th->th_flags & TH_FIN; 2369 tcpstat.tcps_rcvpack++; 2370 tcpstat.tcps_rcvbyte += tlen; 2371 ND6_HINT(tp); 2372 SOCKBUF_LOCK(&so->so_rcv); 2373 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2374 m_freem(m); 2375 else 2376 sbappendstream_locked(&so->so_rcv, m); 2377 sorwakeup_locked(so); 2378 } else { 2379 thflags = tcp_reass(tp, th, &tlen, m); 2380 tp->t_flags |= TF_ACKNOW; 2381 } 2382 if (tlen > 0 && tp->sack_enable) 2383 tcp_update_sack_list(tp, save_start, save_end); 2384 /* 2385 * Note the amount of data that peer has sent into 2386 * our window, in order to estimate the sender's 2387 * buffer size. 2388 */ 2389 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2390 } else { 2391 m_freem(m); 2392 thflags &= ~TH_FIN; 2393 } 2394 2395 /* 2396 * If FIN is received ACK the FIN and let the user know 2397 * that the connection is closing. 2398 */ 2399 if (thflags & TH_FIN) { 2400 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2401 socantrcvmore(so); 2402 /* 2403 * If connection is half-synchronized 2404 * (ie NEEDSYN flag on) then delay ACK, 2405 * so it may be piggybacked when SYN is sent. 2406 * Otherwise, since we received a FIN then no 2407 * more input can be expected, send ACK now. 2408 */ 2409 if (tp->t_flags & TF_NEEDSYN) 2410 tp->t_flags |= TF_DELACK; 2411 else 2412 tp->t_flags |= TF_ACKNOW; 2413 tp->rcv_nxt++; 2414 } 2415 switch (tp->t_state) { 2416 2417 /* 2418 * In SYN_RECEIVED and ESTABLISHED STATES 2419 * enter the CLOSE_WAIT state. 2420 */ 2421 case TCPS_SYN_RECEIVED: 2422 tp->t_starttime = ticks; 2423 /*FALLTHROUGH*/ 2424 case TCPS_ESTABLISHED: 2425 tp->t_state = TCPS_CLOSE_WAIT; 2426 break; 2427 2428 /* 2429 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2430 * enter the CLOSING state. 2431 */ 2432 case TCPS_FIN_WAIT_1: 2433 tp->t_state = TCPS_CLOSING; 2434 break; 2435 2436 /* 2437 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2438 * starting the time-wait timer, turning off the other 2439 * standard timers. 2440 */ 2441 case TCPS_FIN_WAIT_2: 2442 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2443 "TCP_FIN_WAIT_2: head not locked")); 2444 tcp_twstart(tp); 2445 INP_INFO_WUNLOCK(&tcbinfo); 2446 return; 2447 2448 /* 2449 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2450 */ 2451 case TCPS_TIME_WAIT: 2452 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2453 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2454 tcp_timer_2msl, tp); 2455 break; 2456 } 2457 } 2458 INP_INFO_WUNLOCK(&tcbinfo); 2459 headlocked = 0; 2460 #ifdef TCPDEBUG 2461 if (so->so_options & SO_DEBUG) 2462 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2463 &tcp_savetcp, 0); 2464 #endif 2465 2466 /* 2467 * Return any desired output. 2468 */ 2469 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2470 (void) tcp_output(tp); 2471 2472 check_delack: 2473 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2474 INP_LOCK_ASSERT(inp); 2475 if (tp->t_flags & TF_DELACK) { 2476 tp->t_flags &= ~TF_DELACK; 2477 callout_reset(tp->tt_delack, tcp_delacktime, 2478 tcp_timer_delack, tp); 2479 } 2480 INP_UNLOCK(inp); 2481 return; 2482 2483 dropafterack: 2484 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2485 /* 2486 * Generate an ACK dropping incoming segment if it occupies 2487 * sequence space, where the ACK reflects our state. 2488 * 2489 * We can now skip the test for the RST flag since all 2490 * paths to this code happen after packets containing 2491 * RST have been dropped. 2492 * 2493 * In the SYN-RECEIVED state, don't send an ACK unless the 2494 * segment we received passes the SYN-RECEIVED ACK test. 2495 * If it fails send a RST. This breaks the loop in the 2496 * "LAND" DoS attack, and also prevents an ACK storm 2497 * between two listening ports that have been sent forged 2498 * SYN segments, each with the source address of the other. 2499 */ 2500 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2501 (SEQ_GT(tp->snd_una, th->th_ack) || 2502 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2503 rstreason = BANDLIM_RST_OPENPORT; 2504 goto dropwithreset; 2505 } 2506 #ifdef TCPDEBUG 2507 if (so->so_options & SO_DEBUG) 2508 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2509 &tcp_savetcp, 0); 2510 #endif 2511 KASSERT(headlocked, ("headlocked should be 1")); 2512 INP_INFO_WUNLOCK(&tcbinfo); 2513 tp->t_flags |= TF_ACKNOW; 2514 (void) tcp_output(tp); 2515 INP_UNLOCK(inp); 2516 m_freem(m); 2517 return; 2518 2519 dropwithreset: 2520 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2521 /* 2522 * Generate a RST, dropping incoming segment. 2523 * Make ACK acceptable to originator of segment. 2524 * Don't bother to respond if destination was broadcast/multicast. 2525 */ 2526 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2527 goto drop; 2528 if (isipv6) { 2529 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2530 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2531 goto drop; 2532 } else { 2533 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2534 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2535 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2536 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2537 goto drop; 2538 } 2539 /* IPv6 anycast check is done at tcp6_input() */ 2540 2541 /* 2542 * Perform bandwidth limiting. 2543 */ 2544 if (badport_bandlim(rstreason) < 0) 2545 goto drop; 2546 2547 #ifdef TCPDEBUG 2548 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2549 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2550 &tcp_savetcp, 0); 2551 #endif 2552 2553 if (thflags & TH_ACK) 2554 /* mtod() below is safe as long as hdr dropping is delayed */ 2555 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2556 TH_RST); 2557 else { 2558 if (thflags & TH_SYN) 2559 tlen++; 2560 /* mtod() below is safe as long as hdr dropping is delayed */ 2561 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2562 (tcp_seq)0, TH_RST|TH_ACK); 2563 } 2564 2565 if (tp != NULL) 2566 INP_UNLOCK(inp); 2567 if (headlocked) 2568 INP_INFO_WUNLOCK(&tcbinfo); 2569 return; 2570 2571 drop: 2572 /* 2573 * Drop space held by incoming segment and return. 2574 */ 2575 #ifdef TCPDEBUG 2576 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2577 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2578 &tcp_savetcp, 0); 2579 #endif 2580 if (tp != NULL) 2581 INP_UNLOCK(inp); 2582 if (headlocked) 2583 INP_INFO_WUNLOCK(&tcbinfo); 2584 m_freem(m); 2585 return; 2586 } 2587 2588 /* 2589 * Parse TCP options and place in tcpopt. 2590 */ 2591 static void 2592 tcp_dooptions(to, cp, cnt, is_syn) 2593 struct tcpopt *to; 2594 u_char *cp; 2595 int cnt; 2596 int is_syn; 2597 { 2598 int opt, optlen; 2599 2600 to->to_flags = 0; 2601 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2602 opt = cp[0]; 2603 if (opt == TCPOPT_EOL) 2604 break; 2605 if (opt == TCPOPT_NOP) 2606 optlen = 1; 2607 else { 2608 if (cnt < 2) 2609 break; 2610 optlen = cp[1]; 2611 if (optlen < 2 || optlen > cnt) 2612 break; 2613 } 2614 switch (opt) { 2615 case TCPOPT_MAXSEG: 2616 if (optlen != TCPOLEN_MAXSEG) 2617 continue; 2618 if (!is_syn) 2619 continue; 2620 to->to_flags |= TOF_MSS; 2621 bcopy((char *)cp + 2, 2622 (char *)&to->to_mss, sizeof(to->to_mss)); 2623 to->to_mss = ntohs(to->to_mss); 2624 break; 2625 case TCPOPT_WINDOW: 2626 if (optlen != TCPOLEN_WINDOW) 2627 continue; 2628 if (! is_syn) 2629 continue; 2630 to->to_flags |= TOF_SCALE; 2631 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2632 break; 2633 case TCPOPT_TIMESTAMP: 2634 if (optlen != TCPOLEN_TIMESTAMP) 2635 continue; 2636 to->to_flags |= TOF_TS; 2637 bcopy((char *)cp + 2, 2638 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2639 to->to_tsval = ntohl(to->to_tsval); 2640 bcopy((char *)cp + 6, 2641 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2642 to->to_tsecr = ntohl(to->to_tsecr); 2643 /* 2644 * If echoed timestamp is later than the current time, 2645 * fall back to non RFC1323 RTT calculation. 2646 */ 2647 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks)) 2648 to->to_tsecr = 0; 2649 break; 2650 #ifdef TCP_SIGNATURE 2651 /* 2652 * XXX In order to reply to a host which has set the 2653 * TCP_SIGNATURE option in its initial SYN, we have to 2654 * record the fact that the option was observed here 2655 * for the syncache code to perform the correct response. 2656 */ 2657 case TCPOPT_SIGNATURE: 2658 if (optlen != TCPOLEN_SIGNATURE) 2659 continue; 2660 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2661 break; 2662 #endif 2663 case TCPOPT_SACK_PERMITTED: 2664 if (!tcp_do_sack || 2665 optlen != TCPOLEN_SACK_PERMITTED) 2666 continue; 2667 if (is_syn) { 2668 /* MUST only be set on SYN */ 2669 to->to_flags |= TOF_SACK; 2670 } 2671 break; 2672 case TCPOPT_SACK: 2673 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2674 continue; 2675 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2676 to->to_sacks = cp + 2; 2677 tcpstat.tcps_sack_rcv_blocks++; 2678 break; 2679 default: 2680 continue; 2681 } 2682 } 2683 } 2684 2685 /* 2686 * Pull out of band byte out of a segment so 2687 * it doesn't appear in the user's data queue. 2688 * It is still reflected in the segment length for 2689 * sequencing purposes. 2690 */ 2691 static void 2692 tcp_pulloutofband(so, th, m, off) 2693 struct socket *so; 2694 struct tcphdr *th; 2695 register struct mbuf *m; 2696 int off; /* delayed to be droped hdrlen */ 2697 { 2698 int cnt = off + th->th_urp - 1; 2699 2700 while (cnt >= 0) { 2701 if (m->m_len > cnt) { 2702 char *cp = mtod(m, caddr_t) + cnt; 2703 struct tcpcb *tp = sototcpcb(so); 2704 2705 tp->t_iobc = *cp; 2706 tp->t_oobflags |= TCPOOB_HAVEDATA; 2707 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2708 m->m_len--; 2709 if (m->m_flags & M_PKTHDR) 2710 m->m_pkthdr.len--; 2711 return; 2712 } 2713 cnt -= m->m_len; 2714 m = m->m_next; 2715 if (m == 0) 2716 break; 2717 } 2718 panic("tcp_pulloutofband"); 2719 } 2720 2721 /* 2722 * Collect new round-trip time estimate 2723 * and update averages and current timeout. 2724 */ 2725 static void 2726 tcp_xmit_timer(tp, rtt) 2727 register struct tcpcb *tp; 2728 int rtt; 2729 { 2730 register int delta; 2731 2732 INP_LOCK_ASSERT(tp->t_inpcb); 2733 2734 tcpstat.tcps_rttupdated++; 2735 tp->t_rttupdated++; 2736 if (tp->t_srtt != 0) { 2737 /* 2738 * srtt is stored as fixed point with 5 bits after the 2739 * binary point (i.e., scaled by 8). The following magic 2740 * is equivalent to the smoothing algorithm in rfc793 with 2741 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2742 * point). Adjust rtt to origin 0. 2743 */ 2744 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2745 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2746 2747 if ((tp->t_srtt += delta) <= 0) 2748 tp->t_srtt = 1; 2749 2750 /* 2751 * We accumulate a smoothed rtt variance (actually, a 2752 * smoothed mean difference), then set the retransmit 2753 * timer to smoothed rtt + 4 times the smoothed variance. 2754 * rttvar is stored as fixed point with 4 bits after the 2755 * binary point (scaled by 16). The following is 2756 * equivalent to rfc793 smoothing with an alpha of .75 2757 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2758 * rfc793's wired-in beta. 2759 */ 2760 if (delta < 0) 2761 delta = -delta; 2762 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2763 if ((tp->t_rttvar += delta) <= 0) 2764 tp->t_rttvar = 1; 2765 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2766 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2767 } else { 2768 /* 2769 * No rtt measurement yet - use the unsmoothed rtt. 2770 * Set the variance to half the rtt (so our first 2771 * retransmit happens at 3*rtt). 2772 */ 2773 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2774 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2775 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2776 } 2777 tp->t_rtttime = 0; 2778 tp->t_rxtshift = 0; 2779 2780 /* 2781 * the retransmit should happen at rtt + 4 * rttvar. 2782 * Because of the way we do the smoothing, srtt and rttvar 2783 * will each average +1/2 tick of bias. When we compute 2784 * the retransmit timer, we want 1/2 tick of rounding and 2785 * 1 extra tick because of +-1/2 tick uncertainty in the 2786 * firing of the timer. The bias will give us exactly the 2787 * 1.5 tick we need. But, because the bias is 2788 * statistical, we have to test that we don't drop below 2789 * the minimum feasible timer (which is 2 ticks). 2790 */ 2791 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2792 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2793 2794 /* 2795 * We received an ack for a packet that wasn't retransmitted; 2796 * it is probably safe to discard any error indications we've 2797 * received recently. This isn't quite right, but close enough 2798 * for now (a route might have failed after we sent a segment, 2799 * and the return path might not be symmetrical). 2800 */ 2801 tp->t_softerror = 0; 2802 } 2803 2804 /* 2805 * Determine a reasonable value for maxseg size. 2806 * If the route is known, check route for mtu. 2807 * If none, use an mss that can be handled on the outgoing 2808 * interface without forcing IP to fragment; if bigger than 2809 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2810 * to utilize large mbufs. If no route is found, route has no mtu, 2811 * or the destination isn't local, use a default, hopefully conservative 2812 * size (usually 512 or the default IP max size, but no more than the mtu 2813 * of the interface), as we can't discover anything about intervening 2814 * gateways or networks. We also initialize the congestion/slow start 2815 * window to be a single segment if the destination isn't local. 2816 * While looking at the routing entry, we also initialize other path-dependent 2817 * parameters from pre-set or cached values in the routing entry. 2818 * 2819 * Also take into account the space needed for options that we 2820 * send regularly. Make maxseg shorter by that amount to assure 2821 * that we can send maxseg amount of data even when the options 2822 * are present. Store the upper limit of the length of options plus 2823 * data in maxopd. 2824 * 2825 * 2826 * In case of T/TCP, we call this routine during implicit connection 2827 * setup as well (offer = -1), to initialize maxseg from the cached 2828 * MSS of our peer. 2829 * 2830 * NOTE that this routine is only called when we process an incoming 2831 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2832 */ 2833 void 2834 tcp_mss(tp, offer) 2835 struct tcpcb *tp; 2836 int offer; 2837 { 2838 int rtt, mss; 2839 u_long bufsize; 2840 u_long maxmtu; 2841 struct inpcb *inp = tp->t_inpcb; 2842 struct socket *so; 2843 struct hc_metrics_lite metrics; 2844 int origoffer = offer; 2845 #ifdef INET6 2846 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2847 size_t min_protoh = isipv6 ? 2848 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2849 sizeof (struct tcpiphdr); 2850 #else 2851 const size_t min_protoh = sizeof(struct tcpiphdr); 2852 #endif 2853 2854 /* initialize */ 2855 #ifdef INET6 2856 if (isipv6) { 2857 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2858 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2859 } else 2860 #endif 2861 { 2862 maxmtu = tcp_maxmtu(&inp->inp_inc); 2863 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2864 } 2865 so = inp->inp_socket; 2866 2867 /* 2868 * no route to sender, stay with default mss and return 2869 */ 2870 if (maxmtu == 0) 2871 return; 2872 2873 /* what have we got? */ 2874 switch (offer) { 2875 case 0: 2876 /* 2877 * Offer == 0 means that there was no MSS on the SYN 2878 * segment, in this case we use tcp_mssdflt. 2879 */ 2880 offer = 2881 #ifdef INET6 2882 isipv6 ? tcp_v6mssdflt : 2883 #endif 2884 tcp_mssdflt; 2885 break; 2886 2887 case -1: 2888 /* 2889 * Offer == -1 means that we didn't receive SYN yet. 2890 */ 2891 /* FALLTHROUGH */ 2892 2893 default: 2894 /* 2895 * Prevent DoS attack with too small MSS. Round up 2896 * to at least minmss. 2897 */ 2898 offer = max(offer, tcp_minmss); 2899 /* 2900 * Sanity check: make sure that maxopd will be large 2901 * enough to allow some data on segments even if the 2902 * all the option space is used (40bytes). Otherwise 2903 * funny things may happen in tcp_output. 2904 */ 2905 offer = max(offer, 64); 2906 } 2907 2908 /* 2909 * rmx information is now retrieved from tcp_hostcache 2910 */ 2911 tcp_hc_get(&inp->inp_inc, &metrics); 2912 2913 /* 2914 * if there's a discovered mtu int tcp hostcache, use it 2915 * else, use the link mtu. 2916 */ 2917 if (metrics.rmx_mtu) 2918 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2919 else { 2920 #ifdef INET6 2921 if (isipv6) { 2922 mss = maxmtu - min_protoh; 2923 if (!path_mtu_discovery && 2924 !in6_localaddr(&inp->in6p_faddr)) 2925 mss = min(mss, tcp_v6mssdflt); 2926 } else 2927 #endif 2928 { 2929 mss = maxmtu - min_protoh; 2930 if (!path_mtu_discovery && 2931 !in_localaddr(inp->inp_faddr)) 2932 mss = min(mss, tcp_mssdflt); 2933 } 2934 } 2935 mss = min(mss, offer); 2936 2937 /* 2938 * maxopd stores the maximum length of data AND options 2939 * in a segment; maxseg is the amount of data in a normal 2940 * segment. We need to store this value (maxopd) apart 2941 * from maxseg, because now every segment carries options 2942 * and thus we normally have somewhat less data in segments. 2943 */ 2944 tp->t_maxopd = mss; 2945 2946 /* 2947 * origoffer==-1 indicates, that no segments were received yet. 2948 * In this case we just guess. 2949 */ 2950 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2951 (origoffer == -1 || 2952 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2953 mss -= TCPOLEN_TSTAMP_APPA; 2954 tp->t_maxseg = mss; 2955 2956 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2957 if (mss > MCLBYTES) 2958 mss &= ~(MCLBYTES-1); 2959 #else 2960 if (mss > MCLBYTES) 2961 mss = mss / MCLBYTES * MCLBYTES; 2962 #endif 2963 tp->t_maxseg = mss; 2964 2965 /* 2966 * If there's a pipesize, change the socket buffer to that size, 2967 * don't change if sb_hiwat is different than default (then it 2968 * has been changed on purpose with setsockopt). 2969 * Make the socket buffers an integral number of mss units; 2970 * if the mss is larger than the socket buffer, decrease the mss. 2971 */ 2972 SOCKBUF_LOCK(&so->so_snd); 2973 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2974 bufsize = metrics.rmx_sendpipe; 2975 else 2976 bufsize = so->so_snd.sb_hiwat; 2977 if (bufsize < mss) 2978 mss = bufsize; 2979 else { 2980 bufsize = roundup(bufsize, mss); 2981 if (bufsize > sb_max) 2982 bufsize = sb_max; 2983 if (bufsize > so->so_snd.sb_hiwat) 2984 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 2985 } 2986 SOCKBUF_UNLOCK(&so->so_snd); 2987 tp->t_maxseg = mss; 2988 2989 SOCKBUF_LOCK(&so->so_rcv); 2990 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 2991 bufsize = metrics.rmx_recvpipe; 2992 else 2993 bufsize = so->so_rcv.sb_hiwat; 2994 if (bufsize > mss) { 2995 bufsize = roundup(bufsize, mss); 2996 if (bufsize > sb_max) 2997 bufsize = sb_max; 2998 if (bufsize > so->so_rcv.sb_hiwat) 2999 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3000 } 3001 SOCKBUF_UNLOCK(&so->so_rcv); 3002 /* 3003 * While we're here, check the others too 3004 */ 3005 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3006 tp->t_srtt = rtt; 3007 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3008 tcpstat.tcps_usedrtt++; 3009 if (metrics.rmx_rttvar) { 3010 tp->t_rttvar = metrics.rmx_rttvar; 3011 tcpstat.tcps_usedrttvar++; 3012 } else { 3013 /* default variation is +- 1 rtt */ 3014 tp->t_rttvar = 3015 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3016 } 3017 TCPT_RANGESET(tp->t_rxtcur, 3018 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3019 tp->t_rttmin, TCPTV_REXMTMAX); 3020 } 3021 if (metrics.rmx_ssthresh) { 3022 /* 3023 * There's some sort of gateway or interface 3024 * buffer limit on the path. Use this to set 3025 * the slow start threshhold, but set the 3026 * threshold to no less than 2*mss. 3027 */ 3028 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3029 tcpstat.tcps_usedssthresh++; 3030 } 3031 if (metrics.rmx_bandwidth) 3032 tp->snd_bandwidth = metrics.rmx_bandwidth; 3033 3034 /* 3035 * Set the slow-start flight size depending on whether this 3036 * is a local network or not. 3037 * 3038 * Extend this so we cache the cwnd too and retrieve it here. 3039 * Make cwnd even bigger than RFC3390 suggests but only if we 3040 * have previous experience with the remote host. Be careful 3041 * not make cwnd bigger than remote receive window or our own 3042 * send socket buffer. Maybe put some additional upper bound 3043 * on the retrieved cwnd. Should do incremental updates to 3044 * hostcache when cwnd collapses so next connection doesn't 3045 * overloads the path again. 3046 * 3047 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3048 * We currently check only in syncache_socket for that. 3049 */ 3050 #define TCP_METRICS_CWND 3051 #ifdef TCP_METRICS_CWND 3052 if (metrics.rmx_cwnd) 3053 tp->snd_cwnd = max(mss, 3054 min(metrics.rmx_cwnd / 2, 3055 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3056 else 3057 #endif 3058 if (tcp_do_rfc3390) 3059 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3060 #ifdef INET6 3061 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3062 (!isipv6 && in_localaddr(inp->inp_faddr))) 3063 #else 3064 else if (in_localaddr(inp->inp_faddr)) 3065 #endif 3066 tp->snd_cwnd = mss * ss_fltsz_local; 3067 else 3068 tp->snd_cwnd = mss * ss_fltsz; 3069 } 3070 3071 /* 3072 * Determine the MSS option to send on an outgoing SYN. 3073 */ 3074 int 3075 tcp_mssopt(inc) 3076 struct in_conninfo *inc; 3077 { 3078 int mss = 0; 3079 u_long maxmtu = 0; 3080 u_long thcmtu = 0; 3081 size_t min_protoh; 3082 #ifdef INET6 3083 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3084 #endif 3085 3086 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3087 3088 #ifdef INET6 3089 if (isipv6) { 3090 mss = tcp_v6mssdflt; 3091 maxmtu = tcp_maxmtu6(inc); 3092 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3093 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3094 } else 3095 #endif 3096 { 3097 mss = tcp_mssdflt; 3098 maxmtu = tcp_maxmtu(inc); 3099 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3100 min_protoh = sizeof(struct tcpiphdr); 3101 } 3102 if (maxmtu && thcmtu) 3103 mss = min(maxmtu, thcmtu) - min_protoh; 3104 else if (maxmtu || thcmtu) 3105 mss = max(maxmtu, thcmtu) - min_protoh; 3106 3107 return (mss); 3108 } 3109 3110 3111 /* 3112 * On a partial ack arrives, force the retransmission of the 3113 * next unacknowledged segment. Do not clear tp->t_dupacks. 3114 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3115 * be started again. 3116 */ 3117 static void 3118 tcp_newreno_partial_ack(tp, th) 3119 struct tcpcb *tp; 3120 struct tcphdr *th; 3121 { 3122 tcp_seq onxt = tp->snd_nxt; 3123 u_long ocwnd = tp->snd_cwnd; 3124 3125 callout_stop(tp->tt_rexmt); 3126 tp->t_rtttime = 0; 3127 tp->snd_nxt = th->th_ack; 3128 /* 3129 * Set snd_cwnd to one segment beyond acknowledged offset. 3130 * (tp->snd_una has not yet been updated when this function is called.) 3131 */ 3132 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3133 tp->t_flags |= TF_ACKNOW; 3134 (void) tcp_output(tp); 3135 tp->snd_cwnd = ocwnd; 3136 if (SEQ_GT(onxt, tp->snd_nxt)) 3137 tp->snd_nxt = onxt; 3138 /* 3139 * Partial window deflation. Relies on fact that tp->snd_una 3140 * not updated yet. 3141 */ 3142 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3143 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3144 else 3145 tp->snd_cwnd = 0; 3146 tp->snd_cwnd += tp->t_maxseg; 3147 } 3148 3149 /* 3150 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3151 * looking for a pcb in the listen state. Returns 0 otherwise. 3152 */ 3153 static int 3154 tcp_timewait(inp, to, th, m, tlen) 3155 struct inpcb *inp; 3156 struct tcpopt *to; 3157 struct tcphdr *th; 3158 struct mbuf *m; 3159 int tlen; 3160 { 3161 struct tcptw *tw; 3162 int thflags; 3163 tcp_seq seq; 3164 #ifdef INET6 3165 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3166 #else 3167 const int isipv6 = 0; 3168 #endif 3169 3170 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */ 3171 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3172 INP_LOCK_ASSERT(inp); 3173 3174 /* 3175 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 3176 * still present. This is undesirable, but temporarily necessary 3177 * until we work out how to handle inpcb's who's timewait state has 3178 * been removed. 3179 */ 3180 tw = intotw(inp); 3181 if (tw == NULL) 3182 goto drop; 3183 3184 thflags = th->th_flags; 3185 3186 /* 3187 * NOTE: for FIN_WAIT_2 (to be added later), 3188 * must validate sequence number before accepting RST 3189 */ 3190 3191 /* 3192 * If the segment contains RST: 3193 * Drop the segment - see Stevens, vol. 2, p. 964 and 3194 * RFC 1337. 3195 */ 3196 if (thflags & TH_RST) 3197 goto drop; 3198 3199 #if 0 3200 /* PAWS not needed at the moment */ 3201 /* 3202 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3203 * and it's less than ts_recent, drop it. 3204 */ 3205 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3206 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3207 if ((thflags & TH_ACK) == 0) 3208 goto drop; 3209 goto ack; 3210 } 3211 /* 3212 * ts_recent is never updated because we never accept new segments. 3213 */ 3214 #endif 3215 3216 /* 3217 * If a new connection request is received 3218 * while in TIME_WAIT, drop the old connection 3219 * and start over if the sequence numbers 3220 * are above the previous ones. 3221 */ 3222 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3223 tcp_twclose(tw, 0); 3224 return (1); 3225 } 3226 3227 /* 3228 * Drop the the segment if it does not contain an ACK. 3229 */ 3230 if ((thflags & TH_ACK) == 0) 3231 goto drop; 3232 3233 /* 3234 * Reset the 2MSL timer if this is a duplicate FIN. 3235 */ 3236 if (thflags & TH_FIN) { 3237 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3238 if (seq + 1 == tw->rcv_nxt) 3239 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3240 } 3241 3242 /* 3243 * Acknowledge the segment if it has data or is not a duplicate ACK. 3244 */ 3245 if (thflags != TH_ACK || tlen != 0 || 3246 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3247 tcp_twrespond(tw, TH_ACK); 3248 goto drop; 3249 3250 /* 3251 * Generate a RST, dropping incoming segment. 3252 * Make ACK acceptable to originator of segment. 3253 * Don't bother to respond if destination was broadcast/multicast. 3254 */ 3255 if (m->m_flags & (M_BCAST|M_MCAST)) 3256 goto drop; 3257 if (isipv6) { 3258 struct ip6_hdr *ip6; 3259 3260 /* IPv6 anycast check is done at tcp6_input() */ 3261 ip6 = mtod(m, struct ip6_hdr *); 3262 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3263 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3264 goto drop; 3265 } else { 3266 struct ip *ip; 3267 3268 ip = mtod(m, struct ip *); 3269 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3270 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3271 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3272 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3273 goto drop; 3274 } 3275 if (thflags & TH_ACK) { 3276 tcp_respond(NULL, 3277 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3278 } else { 3279 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3280 tcp_respond(NULL, 3281 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3282 } 3283 INP_UNLOCK(inp); 3284 return (0); 3285 3286 drop: 3287 INP_UNLOCK(inp); 3288 m_freem(m); 3289 return (0); 3290 } 3291