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