tcp_input.c revision 149404
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: head/sys/netinet/tcp_input.c 149404 2005-08-24 02:48:45Z ps $ 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 100static const int tcprexmtthresh = 3; 101 102struct tcpstat tcpstat; 103SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 104 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 105 106static int log_in_vain = 0; 107SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 108 &log_in_vain, 0, "Log all incoming TCP connections"); 109 110static int blackhole = 0; 111SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 112 &blackhole, 0, "Do not send RST when dropping refused connections"); 113 114int tcp_delack_enabled = 1; 115SYSCTL_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 120static int drop_synfin = 0; 121SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 122 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 123#endif 124 125static int tcp_do_rfc3042 = 1; 126SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 127 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 128 129static int tcp_do_rfc3390 = 1; 130SYSCTL_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 134static int tcp_insecure_rst = 0; 135SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 136 &tcp_insecure_rst, 0, 137 "Follow the old (insecure) criteria for accepting RST packets."); 138 139SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 140 "TCP Segment Reassembly Queue"); 141 142static int tcp_reass_maxseg = 0; 143SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 144 &tcp_reass_maxseg, 0, 145 "Global maximum number of TCP Segments in Reassembly Queue"); 146 147int tcp_reass_qsize = 0; 148SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 149 &tcp_reass_qsize, 0, 150 "Global number of TCP Segments currently in Reassembly Queue"); 151 152static int tcp_reass_maxqlen = 48; 153SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 154 &tcp_reass_maxqlen, 0, 155 "Maximum number of TCP Segments per individual Reassembly Queue"); 156 157static int tcp_reass_overflows = 0; 158SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 159 &tcp_reass_overflows, 0, 160 "Global number of TCP Segment Reassembly Queue Overflows"); 161 162struct inpcbhead tcb; 163#define tcb6 tcb /* for KAME src sync over BSD*'s */ 164struct inpcbinfo tcbinfo; 165struct mtx *tcbinfo_mtx; 166 167static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 168 169static void tcp_pulloutofband(struct socket *, 170 struct tcphdr *, struct mbuf *, int); 171static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 172 struct mbuf *); 173static void tcp_xmit_timer(struct tcpcb *, int); 174static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 175static int tcp_timewait(struct tcptw *, struct tcpopt *, 176 struct tcphdr *, struct mbuf *, int); 177 178/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 179#ifdef INET6 180#define ND6_HINT(tp) \ 181do { \ 182 if ((tp) && (tp)->t_inpcb && \ 183 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 184 nd6_nud_hint(NULL, NULL, 0); \ 185} while (0) 186#else 187#define ND6_HINT(tp) 188#endif 189 190/* 191 * Indicate whether this ack should be delayed. We can delay the ack if 192 * - there is no delayed ack timer in progress and 193 * - our last ack wasn't a 0-sized window. We never want to delay 194 * the ack that opens up a 0-sized window and 195 * - delayed acks are enabled or 196 * - this is a half-synchronized T/TCP connection. 197 */ 198#define DELAY_ACK(tp) \ 199 ((!callout_active(tp->tt_delack) && \ 200 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 201 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 202 203/* Initialize TCP reassembly queue */ 204uma_zone_t tcp_reass_zone; 205void 206tcp_reass_init() 207{ 208 tcp_reass_maxseg = nmbclusters / 16; 209 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 210 &tcp_reass_maxseg); 211 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 212 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 213 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 214} 215 216static int 217tcp_reass(tp, th, tlenp, m) 218 register struct tcpcb *tp; 219 register struct tcphdr *th; 220 int *tlenp; 221 struct mbuf *m; 222{ 223 struct tseg_qent *q; 224 struct tseg_qent *p = NULL; 225 struct tseg_qent *nq; 226 struct tseg_qent *te = NULL; 227 struct socket *so = tp->t_inpcb->inp_socket; 228 int flags; 229 230 INP_LOCK_ASSERT(tp->t_inpcb); 231 232 /* 233 * XXX: tcp_reass() is rather inefficient with its data structures 234 * and should be rewritten (see NetBSD for optimizations). While 235 * doing that it should move to its own file tcp_reass.c. 236 */ 237 238 /* 239 * Call with th==NULL after become established to 240 * force pre-ESTABLISHED data up to user socket. 241 */ 242 if (th == NULL) 243 goto present; 244 245 /* 246 * Limit the number of segments in the reassembly queue to prevent 247 * holding on to too many segments (and thus running out of mbufs). 248 * Make sure to let the missing segment through which caused this 249 * queue. Always keep one global queue entry spare to be able to 250 * process the missing segment. 251 */ 252 if (th->th_seq != tp->rcv_nxt && 253 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 254 tp->t_segqlen >= tcp_reass_maxqlen)) { 255 tcp_reass_overflows++; 256 tcpstat.tcps_rcvmemdrop++; 257 m_freem(m); 258 *tlenp = 0; 259 return (0); 260 } 261 262 /* 263 * Allocate a new queue entry. If we can't, or hit the zone limit 264 * just drop the pkt. 265 */ 266 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 267 if (te == NULL) { 268 tcpstat.tcps_rcvmemdrop++; 269 m_freem(m); 270 *tlenp = 0; 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 353present: 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 388int 389tcp6_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 417void 418tcp_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; 617findpcb: 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); 743 744 /* Check the minimum TTL for socket. */ 745 if (inp->inp_ip_minttl && inp->inp_ip_minttl > ip->ip_ttl) 746 goto drop; 747 748 if (inp->inp_vflag & INP_TIMEWAIT) { 749 /* 750 * The only option of relevance is TOF_CC, and only if 751 * present in a SYN segment. See tcp_timewait(). 752 */ 753 if (thflags & TH_SYN) 754 tcp_dooptions(&to, optp, optlen, 1); 755 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 756 &to, th, m, tlen)) 757 goto findpcb; 758 /* 759 * tcp_timewait unlocks inp. 760 */ 761 INP_INFO_WUNLOCK(&tcbinfo); 762 return; 763 } 764 tp = intotcpcb(inp); 765 if (tp == 0) { 766 INP_UNLOCK(inp); 767 rstreason = BANDLIM_RST_CLOSEDPORT; 768 goto dropwithreset; 769 } 770 if (tp->t_state == TCPS_CLOSED) 771 goto drop; 772 773 /* Unscale the window into a 32-bit value. */ 774 if ((thflags & TH_SYN) == 0) 775 tiwin = th->th_win << tp->snd_scale; 776 else 777 tiwin = th->th_win; 778 779#ifdef MAC 780 INP_LOCK_ASSERT(inp); 781 if (mac_check_inpcb_deliver(inp, m)) 782 goto drop; 783#endif 784 so = inp->inp_socket; 785#ifdef TCPDEBUG 786 if (so->so_options & SO_DEBUG) { 787 ostate = tp->t_state; 788 if (isipv6) 789 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 790 else 791 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 792 tcp_savetcp = *th; 793 } 794#endif 795 if (so->so_options & SO_ACCEPTCONN) { 796 struct in_conninfo inc; 797 798#ifdef INET6 799 inc.inc_isipv6 = isipv6; 800#endif 801 if (isipv6) { 802 inc.inc6_faddr = ip6->ip6_src; 803 inc.inc6_laddr = ip6->ip6_dst; 804 } else { 805 inc.inc_faddr = ip->ip_src; 806 inc.inc_laddr = ip->ip_dst; 807 } 808 inc.inc_fport = th->th_sport; 809 inc.inc_lport = th->th_dport; 810 811 /* 812 * If the state is LISTEN then ignore segment if it contains 813 * a RST. If the segment contains an ACK then it is bad and 814 * send a RST. If it does not contain a SYN then it is not 815 * interesting; drop it. 816 * 817 * If the state is SYN_RECEIVED (syncache) and seg contains 818 * an ACK, but not for our SYN/ACK, send a RST. If the seg 819 * contains a RST, check the sequence number to see if it 820 * is a valid reset segment. 821 */ 822 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 823 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 824 if (!syncache_expand(&inc, th, &so, m)) { 825 /* 826 * No syncache entry, or ACK was not 827 * for our SYN/ACK. Send a RST. 828 */ 829 tcpstat.tcps_badsyn++; 830 rstreason = BANDLIM_RST_OPENPORT; 831 goto dropwithreset; 832 } 833 if (so == NULL) { 834 /* 835 * Could not complete 3-way handshake, 836 * connection is being closed down, and 837 * syncache will free mbuf. 838 */ 839 INP_UNLOCK(inp); 840 INP_INFO_WUNLOCK(&tcbinfo); 841 return; 842 } 843 /* 844 * Socket is created in state SYN_RECEIVED. 845 * Continue processing segment. 846 */ 847 INP_UNLOCK(inp); 848 inp = sotoinpcb(so); 849 INP_LOCK(inp); 850 tp = intotcpcb(inp); 851 /* 852 * This is what would have happened in 853 * tcp_output() when the SYN,ACK was sent. 854 */ 855 tp->snd_up = tp->snd_una; 856 tp->snd_max = tp->snd_nxt = tp->iss + 1; 857 tp->last_ack_sent = tp->rcv_nxt; 858 /* 859 * RFC1323: The window in SYN & SYN/ACK 860 * segments is never scaled. 861 */ 862 tp->snd_wnd = tiwin; /* unscaled */ 863 goto after_listen; 864 } 865 if (thflags & TH_RST) { 866 syncache_chkrst(&inc, th); 867 goto drop; 868 } 869 if (thflags & TH_ACK) { 870 syncache_badack(&inc); 871 tcpstat.tcps_badsyn++; 872 rstreason = BANDLIM_RST_OPENPORT; 873 goto dropwithreset; 874 } 875 goto drop; 876 } 877 878 /* 879 * Segment's flags are (SYN) or (SYN|FIN). 880 */ 881#ifdef INET6 882 /* 883 * If deprecated address is forbidden, 884 * we do not accept SYN to deprecated interface 885 * address to prevent any new inbound connection from 886 * getting established. 887 * When we do not accept SYN, we send a TCP RST, 888 * with deprecated source address (instead of dropping 889 * it). We compromise it as it is much better for peer 890 * to send a RST, and RST will be the final packet 891 * for the exchange. 892 * 893 * If we do not forbid deprecated addresses, we accept 894 * the SYN packet. RFC2462 does not suggest dropping 895 * SYN in this case. 896 * If we decipher RFC2462 5.5.4, it says like this: 897 * 1. use of deprecated addr with existing 898 * communication is okay - "SHOULD continue to be 899 * used" 900 * 2. use of it with new communication: 901 * (2a) "SHOULD NOT be used if alternate address 902 * with sufficient scope is available" 903 * (2b) nothing mentioned otherwise. 904 * Here we fall into (2b) case as we have no choice in 905 * our source address selection - we must obey the peer. 906 * 907 * The wording in RFC2462 is confusing, and there are 908 * multiple description text for deprecated address 909 * handling - worse, they are not exactly the same. 910 * I believe 5.5.4 is the best one, so we follow 5.5.4. 911 */ 912 if (isipv6 && !ip6_use_deprecated) { 913 struct in6_ifaddr *ia6; 914 915 if ((ia6 = ip6_getdstifaddr(m)) && 916 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 917 INP_UNLOCK(inp); 918 tp = NULL; 919 rstreason = BANDLIM_RST_OPENPORT; 920 goto dropwithreset; 921 } 922 } 923#endif 924 /* 925 * If it is from this socket, drop it, it must be forged. 926 * Don't bother responding if the destination was a broadcast. 927 */ 928 if (th->th_dport == th->th_sport) { 929 if (isipv6) { 930 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 931 &ip6->ip6_src)) 932 goto drop; 933 } else { 934 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 935 goto drop; 936 } 937 } 938 /* 939 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 940 * 941 * Note that it is quite possible to receive unicast 942 * link-layer packets with a broadcast IP address. Use 943 * in_broadcast() to find them. 944 */ 945 if (m->m_flags & (M_BCAST|M_MCAST)) 946 goto drop; 947 if (isipv6) { 948 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 949 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 950 goto drop; 951 } else { 952 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 953 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 954 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 955 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 956 goto drop; 957 } 958 /* 959 * SYN appears to be valid; create compressed TCP state 960 * for syncache, or perform t/tcp connection. 961 */ 962 if (so->so_qlen <= so->so_qlimit) { 963#ifdef TCPDEBUG 964 if (so->so_options & SO_DEBUG) 965 tcp_trace(TA_INPUT, ostate, tp, 966 (void *)tcp_saveipgen, &tcp_savetcp, 0); 967#endif 968 tcp_dooptions(&to, optp, optlen, 1); 969 if (!syncache_add(&inc, &to, th, &so, m)) 970 goto drop; 971 if (so == NULL) { 972 /* 973 * Entry added to syncache, mbuf used to 974 * send SYN,ACK packet. 975 */ 976 KASSERT(headlocked, ("headlocked")); 977 INP_UNLOCK(inp); 978 INP_INFO_WUNLOCK(&tcbinfo); 979 return; 980 } 981 /* 982 * Segment passed TAO tests. 983 */ 984 INP_UNLOCK(inp); 985 inp = sotoinpcb(so); 986 INP_LOCK(inp); 987 tp = intotcpcb(inp); 988 tp->snd_wnd = tiwin; 989 tp->t_starttime = ticks; 990 tp->t_state = TCPS_ESTABLISHED; 991 992 /* 993 * T/TCP logic: 994 * If there is a FIN or if there is data, then 995 * delay SYN,ACK(SYN) in the hope of piggy-backing 996 * it on a response segment. Otherwise must send 997 * ACK now in case the other side is slow starting. 998 */ 999 if (thflags & TH_FIN || tlen != 0) 1000 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1001 else 1002 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1003 tcpstat.tcps_connects++; 1004 soisconnected(so); 1005 goto trimthenstep6; 1006 } 1007 goto drop; 1008 } 1009after_listen: 1010 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1011 INP_LOCK_ASSERT(inp); 1012 1013 /* XXX temp debugging */ 1014 /* should not happen - syncache should pick up these connections */ 1015 if (tp->t_state == TCPS_LISTEN) 1016 panic("tcp_input: TCPS_LISTEN"); 1017 1018 /* 1019 * This is the second part of the MSS DoS prevention code (after 1020 * minmss on the sending side) and it deals with too many too small 1021 * tcp packets in a too short timeframe (1 second). 1022 * 1023 * For every full second we count the number of received packets 1024 * and bytes. If we get a lot of packets per second for this connection 1025 * (tcp_minmssoverload) we take a closer look at it and compute the 1026 * average packet size for the past second. If that is less than 1027 * tcp_minmss we get too many packets with very small payload which 1028 * is not good and burdens our system (and every packet generates 1029 * a wakeup to the process connected to our socket). We can reasonable 1030 * expect this to be small packet DoS attack to exhaust our CPU 1031 * cycles. 1032 * 1033 * Care has to be taken for the minimum packet overload value. This 1034 * value defines the minimum number of packets per second before we 1035 * start to worry. This must not be too low to avoid killing for 1036 * example interactive connections with many small packets like 1037 * telnet or SSH. 1038 * 1039 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1040 * this check. 1041 * 1042 * Account for packet if payload packet, skip over ACK, etc. 1043 */ 1044 if (tcp_minmss && tcp_minmssoverload && 1045 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1046 if ((unsigned int)(tp->rcv_second - ticks) < hz) { 1047 tp->rcv_pps++; 1048 tp->rcv_byps += tlen + off; 1049 if (tp->rcv_pps > tcp_minmssoverload) { 1050 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1051 printf("too many small tcp packets from " 1052 "%s:%u, av. %lubyte/packet, " 1053 "dropping connection\n", 1054#ifdef INET6 1055 isipv6 ? 1056 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1057#endif 1058 inet_ntoa(inp->inp_inc.inc_faddr), 1059 inp->inp_inc.inc_fport, 1060 tp->rcv_byps / tp->rcv_pps); 1061 KASSERT(headlocked, ("tcp_input: " 1062 "after_listen: tcp_drop: head " 1063 "not locked")); 1064 tp = tcp_drop(tp, ECONNRESET); 1065 tcpstat.tcps_minmssdrops++; 1066 goto drop; 1067 } 1068 } 1069 } else { 1070 tp->rcv_second = ticks + hz; 1071 tp->rcv_pps = 1; 1072 tp->rcv_byps = tlen + off; 1073 } 1074 } 1075 1076 /* 1077 * Segment received on connection. 1078 * Reset idle time and keep-alive timer. 1079 */ 1080 tp->t_rcvtime = ticks; 1081 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1082 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1083 1084 /* 1085 * Process options only when we get SYN/ACK back. The SYN case 1086 * for incoming connections is handled in tcp_syncache. 1087 * XXX this is traditional behavior, may need to be cleaned up. 1088 */ 1089 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 1090 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1091 if (to.to_flags & TOF_SCALE) { 1092 tp->t_flags |= TF_RCVD_SCALE; 1093 tp->requested_s_scale = to.to_requested_s_scale; 1094 } 1095 if (to.to_flags & TOF_TS) { 1096 tp->t_flags |= TF_RCVD_TSTMP; 1097 tp->ts_recent = to.to_tsval; 1098 tp->ts_recent_age = ticks; 1099 } 1100 if (to.to_flags & TOF_MSS) 1101 tcp_mss(tp, to.to_mss); 1102 if (tp->sack_enable) { 1103 if (!(to.to_flags & TOF_SACK)) 1104 tp->sack_enable = 0; 1105 else 1106 tp->t_flags |= TF_SACK_PERMIT; 1107 } 1108 1109 } 1110 1111 /* 1112 * Header prediction: check for the two common cases 1113 * of a uni-directional data xfer. If the packet has 1114 * no control flags, is in-sequence, the window didn't 1115 * change and we're not retransmitting, it's a 1116 * candidate. If the length is zero and the ack moved 1117 * forward, we're the sender side of the xfer. Just 1118 * free the data acked & wake any higher level process 1119 * that was blocked waiting for space. If the length 1120 * is non-zero and the ack didn't move, we're the 1121 * receiver side. If we're getting packets in-order 1122 * (the reassembly queue is empty), add the data to 1123 * the socket buffer and note that we need a delayed ack. 1124 * Make sure that the hidden state-flags are also off. 1125 * Since we check for TCPS_ESTABLISHED above, it can only 1126 * be TH_NEEDSYN. 1127 */ 1128 if (tp->t_state == TCPS_ESTABLISHED && 1129 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1130 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1131 ((to.to_flags & TOF_TS) == 0 || 1132 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1133 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1134 tp->snd_nxt == tp->snd_max) { 1135 1136 /* 1137 * If last ACK falls within this segment's sequence numbers, 1138 * record the timestamp. 1139 * NOTE that the test is modified according to the latest 1140 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1141 */ 1142 if ((to.to_flags & TOF_TS) != 0 && 1143 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1144 tp->ts_recent_age = ticks; 1145 tp->ts_recent = to.to_tsval; 1146 } 1147 1148 if (tlen == 0) { 1149 if (SEQ_GT(th->th_ack, tp->snd_una) && 1150 SEQ_LEQ(th->th_ack, tp->snd_max) && 1151 tp->snd_cwnd >= tp->snd_wnd && 1152 ((!tcp_do_newreno && !tp->sack_enable && 1153 tp->t_dupacks < tcprexmtthresh) || 1154 ((tcp_do_newreno || tp->sack_enable) && 1155 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 && 1156 TAILQ_EMPTY(&tp->snd_holes)))) { 1157 KASSERT(headlocked, ("headlocked")); 1158 INP_INFO_WUNLOCK(&tcbinfo); 1159 headlocked = 0; 1160 /* 1161 * this is a pure ack for outstanding data. 1162 */ 1163 ++tcpstat.tcps_predack; 1164 /* 1165 * "bad retransmit" recovery 1166 */ 1167 if (tp->t_rxtshift == 1 && 1168 ticks < tp->t_badrxtwin) { 1169 ++tcpstat.tcps_sndrexmitbad; 1170 tp->snd_cwnd = tp->snd_cwnd_prev; 1171 tp->snd_ssthresh = 1172 tp->snd_ssthresh_prev; 1173 tp->snd_recover = tp->snd_recover_prev; 1174 if (tp->t_flags & TF_WASFRECOVERY) 1175 ENTER_FASTRECOVERY(tp); 1176 tp->snd_nxt = tp->snd_max; 1177 tp->t_badrxtwin = 0; 1178 } 1179 1180 /* 1181 * Recalculate the transmit timer / rtt. 1182 * 1183 * Some boxes send broken timestamp replies 1184 * during the SYN+ACK phase, ignore 1185 * timestamps of 0 or we could calculate a 1186 * huge RTT and blow up the retransmit timer. 1187 */ 1188 if ((to.to_flags & TOF_TS) != 0 && 1189 to.to_tsecr) { 1190 tcp_xmit_timer(tp, 1191 ticks - to.to_tsecr + 1); 1192 } else if (tp->t_rtttime && 1193 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1194 tcp_xmit_timer(tp, 1195 ticks - tp->t_rtttime); 1196 } 1197 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1198 acked = th->th_ack - tp->snd_una; 1199 tcpstat.tcps_rcvackpack++; 1200 tcpstat.tcps_rcvackbyte += acked; 1201 sbdrop(&so->so_snd, acked); 1202 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1203 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1204 tp->snd_recover = th->th_ack - 1; 1205 tp->snd_una = th->th_ack; 1206 /* 1207 * pull snd_wl2 up to prevent seq wrap relative 1208 * to th_ack. 1209 */ 1210 tp->snd_wl2 = th->th_ack; 1211 tp->t_dupacks = 0; 1212 m_freem(m); 1213 ND6_HINT(tp); /* some progress has been done */ 1214 1215 /* 1216 * If all outstanding data are acked, stop 1217 * retransmit timer, otherwise restart timer 1218 * using current (possibly backed-off) value. 1219 * If process is waiting for space, 1220 * wakeup/selwakeup/signal. If data 1221 * are ready to send, let tcp_output 1222 * decide between more output or persist. 1223 1224#ifdef TCPDEBUG 1225 if (so->so_options & SO_DEBUG) 1226 tcp_trace(TA_INPUT, ostate, tp, 1227 (void *)tcp_saveipgen, 1228 &tcp_savetcp, 0); 1229#endif 1230 */ 1231 if (tp->snd_una == tp->snd_max) 1232 callout_stop(tp->tt_rexmt); 1233 else if (!callout_active(tp->tt_persist)) 1234 callout_reset(tp->tt_rexmt, 1235 tp->t_rxtcur, 1236 tcp_timer_rexmt, tp); 1237 1238 sowwakeup(so); 1239 if (so->so_snd.sb_cc) 1240 (void) tcp_output(tp); 1241 goto check_delack; 1242 } 1243 } else if (th->th_ack == tp->snd_una && 1244 LIST_EMPTY(&tp->t_segq) && 1245 tlen <= sbspace(&so->so_rcv)) { 1246 KASSERT(headlocked, ("headlocked")); 1247 INP_INFO_WUNLOCK(&tcbinfo); 1248 headlocked = 0; 1249 /* 1250 * this is a pure, in-sequence data packet 1251 * with nothing on the reassembly queue and 1252 * we have enough buffer space to take it. 1253 */ 1254 /* Clean receiver SACK report if present */ 1255 if (tp->sack_enable && tp->rcv_numsacks) 1256 tcp_clean_sackreport(tp); 1257 ++tcpstat.tcps_preddat; 1258 tp->rcv_nxt += tlen; 1259 /* 1260 * Pull snd_wl1 up to prevent seq wrap relative to 1261 * th_seq. 1262 */ 1263 tp->snd_wl1 = th->th_seq; 1264 /* 1265 * Pull rcv_up up to prevent seq wrap relative to 1266 * rcv_nxt. 1267 */ 1268 tp->rcv_up = tp->rcv_nxt; 1269 tcpstat.tcps_rcvpack++; 1270 tcpstat.tcps_rcvbyte += tlen; 1271 ND6_HINT(tp); /* some progress has been done */ 1272 /* 1273#ifdef TCPDEBUG 1274 if (so->so_options & SO_DEBUG) 1275 tcp_trace(TA_INPUT, ostate, tp, 1276 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1277#endif 1278 * Add data to socket buffer. 1279 */ 1280 SOCKBUF_LOCK(&so->so_rcv); 1281 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1282 m_freem(m); 1283 } else { 1284 m_adj(m, drop_hdrlen); /* delayed header drop */ 1285 sbappendstream_locked(&so->so_rcv, m); 1286 } 1287 sorwakeup_locked(so); 1288 if (DELAY_ACK(tp)) { 1289 tp->t_flags |= TF_DELACK; 1290 } else { 1291 tp->t_flags |= TF_ACKNOW; 1292 tcp_output(tp); 1293 } 1294 goto check_delack; 1295 } 1296 } 1297 1298 /* 1299 * Calculate amount of space in receive window, 1300 * and then do TCP input processing. 1301 * Receive window is amount of space in rcv queue, 1302 * but not less than advertised window. 1303 */ 1304 { int win; 1305 1306 win = sbspace(&so->so_rcv); 1307 if (win < 0) 1308 win = 0; 1309 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1310 } 1311 1312 switch (tp->t_state) { 1313 1314 /* 1315 * If the state is SYN_RECEIVED: 1316 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1317 */ 1318 case TCPS_SYN_RECEIVED: 1319 if ((thflags & TH_ACK) && 1320 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1321 SEQ_GT(th->th_ack, tp->snd_max))) { 1322 rstreason = BANDLIM_RST_OPENPORT; 1323 goto dropwithreset; 1324 } 1325 break; 1326 1327 /* 1328 * If the state is SYN_SENT: 1329 * if seg contains an ACK, but not for our SYN, drop the input. 1330 * if seg contains a RST, then drop the connection. 1331 * if seg does not contain SYN, then drop it. 1332 * Otherwise this is an acceptable SYN segment 1333 * initialize tp->rcv_nxt and tp->irs 1334 * if seg contains ack then advance tp->snd_una 1335 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1336 * arrange for segment to be acked (eventually) 1337 * continue processing rest of data/controls, beginning with URG 1338 */ 1339 case TCPS_SYN_SENT: 1340 if ((thflags & TH_ACK) && 1341 (SEQ_LEQ(th->th_ack, tp->iss) || 1342 SEQ_GT(th->th_ack, tp->snd_max))) { 1343 rstreason = BANDLIM_UNLIMITED; 1344 goto dropwithreset; 1345 } 1346 if (thflags & TH_RST) { 1347 if (thflags & TH_ACK) { 1348 KASSERT(headlocked, ("tcp_input: after_listen" 1349 ": tcp_drop.2: head not locked")); 1350 tp = tcp_drop(tp, ECONNREFUSED); 1351 } 1352 goto drop; 1353 } 1354 if ((thflags & TH_SYN) == 0) 1355 goto drop; 1356 tp->snd_wnd = th->th_win; /* initial send window */ 1357 1358 tp->irs = th->th_seq; 1359 tcp_rcvseqinit(tp); 1360 if (thflags & TH_ACK) { 1361 tcpstat.tcps_connects++; 1362 soisconnected(so); 1363#ifdef MAC 1364 SOCK_LOCK(so); 1365 mac_set_socket_peer_from_mbuf(m, so); 1366 SOCK_UNLOCK(so); 1367#endif 1368 /* Do window scaling on this connection? */ 1369 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1370 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1371 tp->snd_scale = tp->requested_s_scale; 1372 tp->rcv_scale = tp->request_r_scale; 1373 } 1374 tp->rcv_adv += tp->rcv_wnd; 1375 tp->snd_una++; /* SYN is acked */ 1376 /* 1377 * If there's data, delay ACK; if there's also a FIN 1378 * ACKNOW will be turned on later. 1379 */ 1380 if (DELAY_ACK(tp) && tlen != 0) 1381 callout_reset(tp->tt_delack, tcp_delacktime, 1382 tcp_timer_delack, tp); 1383 else 1384 tp->t_flags |= TF_ACKNOW; 1385 /* 1386 * Received <SYN,ACK> in SYN_SENT[*] state. 1387 * Transitions: 1388 * SYN_SENT --> ESTABLISHED 1389 * SYN_SENT* --> FIN_WAIT_1 1390 */ 1391 tp->t_starttime = ticks; 1392 if (tp->t_flags & TF_NEEDFIN) { 1393 tp->t_state = TCPS_FIN_WAIT_1; 1394 tp->t_flags &= ~TF_NEEDFIN; 1395 thflags &= ~TH_SYN; 1396 } else { 1397 tp->t_state = TCPS_ESTABLISHED; 1398 callout_reset(tp->tt_keep, tcp_keepidle, 1399 tcp_timer_keep, tp); 1400 } 1401 } else { 1402 /* 1403 * Received initial SYN in SYN-SENT[*] state => 1404 * simultaneous open. If segment contains CC option 1405 * and there is a cached CC, apply TAO test. 1406 * If it succeeds, connection is * half-synchronized. 1407 * Otherwise, do 3-way handshake: 1408 * SYN-SENT -> SYN-RECEIVED 1409 * SYN-SENT* -> SYN-RECEIVED* 1410 * If there was no CC option, clear cached CC value. 1411 */ 1412 tp->t_flags |= TF_ACKNOW; 1413 callout_stop(tp->tt_rexmt); 1414 tp->t_state = TCPS_SYN_RECEIVED; 1415 } 1416 1417trimthenstep6: 1418 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1419 "locked")); 1420 INP_LOCK_ASSERT(inp); 1421 1422 /* 1423 * Advance th->th_seq to correspond to first data byte. 1424 * If data, trim to stay within window, 1425 * dropping FIN if necessary. 1426 */ 1427 th->th_seq++; 1428 if (tlen > tp->rcv_wnd) { 1429 todrop = tlen - tp->rcv_wnd; 1430 m_adj(m, -todrop); 1431 tlen = tp->rcv_wnd; 1432 thflags &= ~TH_FIN; 1433 tcpstat.tcps_rcvpackafterwin++; 1434 tcpstat.tcps_rcvbyteafterwin += todrop; 1435 } 1436 tp->snd_wl1 = th->th_seq - 1; 1437 tp->rcv_up = th->th_seq; 1438 /* 1439 * Client side of transaction: already sent SYN and data. 1440 * If the remote host used T/TCP to validate the SYN, 1441 * our data will be ACK'd; if so, enter normal data segment 1442 * processing in the middle of step 5, ack processing. 1443 * Otherwise, goto step 6. 1444 */ 1445 if (thflags & TH_ACK) 1446 goto process_ACK; 1447 1448 goto step6; 1449 1450 /* 1451 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1452 * do normal processing. 1453 * 1454 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1455 */ 1456 case TCPS_LAST_ACK: 1457 case TCPS_CLOSING: 1458 case TCPS_TIME_WAIT: 1459 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1460 break; /* continue normal processing */ 1461 } 1462 1463 /* 1464 * States other than LISTEN or SYN_SENT. 1465 * First check the RST flag and sequence number since reset segments 1466 * are exempt from the timestamp and connection count tests. This 1467 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1468 * below which allowed reset segments in half the sequence space 1469 * to fall though and be processed (which gives forged reset 1470 * segments with a random sequence number a 50 percent chance of 1471 * killing a connection). 1472 * Then check timestamp, if present. 1473 * Then check the connection count, if present. 1474 * Then check that at least some bytes of segment are within 1475 * receive window. If segment begins before rcv_nxt, 1476 * drop leading data (and SYN); if nothing left, just ack. 1477 * 1478 * 1479 * If the RST bit is set, check the sequence number to see 1480 * if this is a valid reset segment. 1481 * RFC 793 page 37: 1482 * In all states except SYN-SENT, all reset (RST) segments 1483 * are validated by checking their SEQ-fields. A reset is 1484 * valid if its sequence number is in the window. 1485 * Note: this does not take into account delayed ACKs, so 1486 * we should test against last_ack_sent instead of rcv_nxt. 1487 * The sequence number in the reset segment is normally an 1488 * echo of our outgoing acknowlegement numbers, but some hosts 1489 * send a reset with the sequence number at the rightmost edge 1490 * of our receive window, and we have to handle this case. 1491 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1492 * that brute force RST attacks are possible. To combat this, 1493 * we use a much stricter check while in the ESTABLISHED state, 1494 * only accepting RSTs where the sequence number is equal to 1495 * last_ack_sent. In all other states (the states in which a 1496 * RST is more likely), the more permissive check is used. 1497 * If we have multiple segments in flight, the intial reset 1498 * segment sequence numbers will be to the left of last_ack_sent, 1499 * but they will eventually catch up. 1500 * In any case, it never made sense to trim reset segments to 1501 * fit the receive window since RFC 1122 says: 1502 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1503 * 1504 * A TCP SHOULD allow a received RST segment to include data. 1505 * 1506 * DISCUSSION 1507 * It has been suggested that a RST segment could contain 1508 * ASCII text that encoded and explained the cause of the 1509 * RST. No standard has yet been established for such 1510 * data. 1511 * 1512 * If the reset segment passes the sequence number test examine 1513 * the state: 1514 * SYN_RECEIVED STATE: 1515 * If passive open, return to LISTEN state. 1516 * If active open, inform user that connection was refused. 1517 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1518 * Inform user that connection was reset, and close tcb. 1519 * CLOSING, LAST_ACK STATES: 1520 * Close the tcb. 1521 * TIME_WAIT STATE: 1522 * Drop the segment - see Stevens, vol. 2, p. 964 and 1523 * RFC 1337. 1524 */ 1525 if (thflags & TH_RST) { 1526 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1527 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1528 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1529 switch (tp->t_state) { 1530 1531 case TCPS_SYN_RECEIVED: 1532 so->so_error = ECONNREFUSED; 1533 goto close; 1534 1535 case TCPS_ESTABLISHED: 1536 if (tp->last_ack_sent != th->th_seq && 1537 tcp_insecure_rst == 0) { 1538 tcpstat.tcps_badrst++; 1539 goto drop; 1540 } 1541 case TCPS_FIN_WAIT_1: 1542 case TCPS_FIN_WAIT_2: 1543 case TCPS_CLOSE_WAIT: 1544 so->so_error = ECONNRESET; 1545 close: 1546 tp->t_state = TCPS_CLOSED; 1547 tcpstat.tcps_drops++; 1548 KASSERT(headlocked, ("tcp_input: " 1549 "trimthenstep6: tcp_close: head not " 1550 "locked")); 1551 tp = tcp_close(tp); 1552 break; 1553 1554 case TCPS_CLOSING: 1555 case TCPS_LAST_ACK: 1556 KASSERT(headlocked, ("trimthenstep6: " 1557 "tcp_close.2: head not locked")); 1558 tp = tcp_close(tp); 1559 break; 1560 1561 case TCPS_TIME_WAIT: 1562 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1563 ("timewait")); 1564 break; 1565 } 1566 } 1567 goto drop; 1568 } 1569 1570 /* 1571 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1572 * and it's less than ts_recent, drop it. 1573 */ 1574 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1575 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1576 1577 /* Check to see if ts_recent is over 24 days old. */ 1578 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1579 /* 1580 * Invalidate ts_recent. If this segment updates 1581 * ts_recent, the age will be reset later and ts_recent 1582 * will get a valid value. If it does not, setting 1583 * ts_recent to zero will at least satisfy the 1584 * requirement that zero be placed in the timestamp 1585 * echo reply when ts_recent isn't valid. The 1586 * age isn't reset until we get a valid ts_recent 1587 * because we don't want out-of-order segments to be 1588 * dropped when ts_recent is old. 1589 */ 1590 tp->ts_recent = 0; 1591 } else { 1592 tcpstat.tcps_rcvduppack++; 1593 tcpstat.tcps_rcvdupbyte += tlen; 1594 tcpstat.tcps_pawsdrop++; 1595 if (tlen) 1596 goto dropafterack; 1597 goto drop; 1598 } 1599 } 1600 1601 /* 1602 * In the SYN-RECEIVED state, validate that the packet belongs to 1603 * this connection before trimming the data to fit the receive 1604 * window. Check the sequence number versus IRS since we know 1605 * the sequence numbers haven't wrapped. This is a partial fix 1606 * for the "LAND" DoS attack. 1607 */ 1608 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1609 rstreason = BANDLIM_RST_OPENPORT; 1610 goto dropwithreset; 1611 } 1612 1613 todrop = tp->rcv_nxt - th->th_seq; 1614 if (todrop > 0) { 1615 if (thflags & TH_SYN) { 1616 thflags &= ~TH_SYN; 1617 th->th_seq++; 1618 if (th->th_urp > 1) 1619 th->th_urp--; 1620 else 1621 thflags &= ~TH_URG; 1622 todrop--; 1623 } 1624 /* 1625 * Following if statement from Stevens, vol. 2, p. 960. 1626 */ 1627 if (todrop > tlen 1628 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1629 /* 1630 * Any valid FIN must be to the left of the window. 1631 * At this point the FIN must be a duplicate or out 1632 * of sequence; drop it. 1633 */ 1634 thflags &= ~TH_FIN; 1635 1636 /* 1637 * Send an ACK to resynchronize and drop any data. 1638 * But keep on processing for RST or ACK. 1639 */ 1640 tp->t_flags |= TF_ACKNOW; 1641 todrop = tlen; 1642 tcpstat.tcps_rcvduppack++; 1643 tcpstat.tcps_rcvdupbyte += todrop; 1644 } else { 1645 tcpstat.tcps_rcvpartduppack++; 1646 tcpstat.tcps_rcvpartdupbyte += todrop; 1647 } 1648 drop_hdrlen += todrop; /* drop from the top afterwards */ 1649 th->th_seq += todrop; 1650 tlen -= todrop; 1651 if (th->th_urp > todrop) 1652 th->th_urp -= todrop; 1653 else { 1654 thflags &= ~TH_URG; 1655 th->th_urp = 0; 1656 } 1657 } 1658 1659 /* 1660 * If new data are received on a connection after the 1661 * user processes are gone, then RST the other end. 1662 */ 1663 if ((so->so_state & SS_NOFDREF) && 1664 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1665 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1666 "locked")); 1667 tp = tcp_close(tp); 1668 tcpstat.tcps_rcvafterclose++; 1669 rstreason = BANDLIM_UNLIMITED; 1670 goto dropwithreset; 1671 } 1672 1673 /* 1674 * If segment ends after window, drop trailing data 1675 * (and PUSH and FIN); if nothing left, just ACK. 1676 */ 1677 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1678 if (todrop > 0) { 1679 tcpstat.tcps_rcvpackafterwin++; 1680 if (todrop >= tlen) { 1681 tcpstat.tcps_rcvbyteafterwin += tlen; 1682 /* 1683 * If a new connection request is received 1684 * while in TIME_WAIT, drop the old connection 1685 * and start over if the sequence numbers 1686 * are above the previous ones. 1687 */ 1688 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1689 if (thflags & TH_SYN && 1690 tp->t_state == TCPS_TIME_WAIT && 1691 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1692 KASSERT(headlocked, ("trimthenstep6: " 1693 "tcp_close.4: head not locked")); 1694 tp = tcp_close(tp); 1695 goto findpcb; 1696 } 1697 /* 1698 * If window is closed can only take segments at 1699 * window edge, and have to drop data and PUSH from 1700 * incoming segments. Continue processing, but 1701 * remember to ack. Otherwise, drop segment 1702 * and ack. 1703 */ 1704 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1705 tp->t_flags |= TF_ACKNOW; 1706 tcpstat.tcps_rcvwinprobe++; 1707 } else 1708 goto dropafterack; 1709 } else 1710 tcpstat.tcps_rcvbyteafterwin += todrop; 1711 m_adj(m, -todrop); 1712 tlen -= todrop; 1713 thflags &= ~(TH_PUSH|TH_FIN); 1714 } 1715 1716 /* 1717 * If last ACK falls within this segment's sequence numbers, 1718 * record its timestamp. 1719 * NOTE: 1720 * 1) That the test incorporates suggestions from the latest 1721 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1722 * 2) That updating only on newer timestamps interferes with 1723 * our earlier PAWS tests, so this check should be solely 1724 * predicated on the sequence space of this segment. 1725 * 3) That we modify the segment boundary check to be 1726 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1727 * instead of RFC1323's 1728 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1729 * This modified check allows us to overcome RFC1323's 1730 * limitations as described in Stevens TCP/IP Illustrated 1731 * Vol. 2 p.869. In such cases, we can still calculate the 1732 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1733 */ 1734 if ((to.to_flags & TOF_TS) != 0 && 1735 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1736 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1737 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1738 tp->ts_recent_age = ticks; 1739 tp->ts_recent = to.to_tsval; 1740 } 1741 1742 /* 1743 * If a SYN is in the window, then this is an 1744 * error and we send an RST and drop the connection. 1745 */ 1746 if (thflags & TH_SYN) { 1747 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1748 "head not locked")); 1749 tp = tcp_drop(tp, ECONNRESET); 1750 rstreason = BANDLIM_UNLIMITED; 1751 goto drop; 1752 } 1753 1754 /* 1755 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1756 * flag is on (half-synchronized state), then queue data for 1757 * later processing; else drop segment and return. 1758 */ 1759 if ((thflags & TH_ACK) == 0) { 1760 if (tp->t_state == TCPS_SYN_RECEIVED || 1761 (tp->t_flags & TF_NEEDSYN)) 1762 goto step6; 1763 else 1764 goto drop; 1765 } 1766 1767 /* 1768 * Ack processing. 1769 */ 1770 switch (tp->t_state) { 1771 1772 /* 1773 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1774 * ESTABLISHED state and continue processing. 1775 * The ACK was checked above. 1776 */ 1777 case TCPS_SYN_RECEIVED: 1778 1779 tcpstat.tcps_connects++; 1780 soisconnected(so); 1781 /* Do window scaling? */ 1782 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1783 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1784 tp->snd_scale = tp->requested_s_scale; 1785 tp->rcv_scale = tp->request_r_scale; 1786 } 1787 /* 1788 * Make transitions: 1789 * SYN-RECEIVED -> ESTABLISHED 1790 * SYN-RECEIVED* -> FIN-WAIT-1 1791 */ 1792 tp->t_starttime = ticks; 1793 if (tp->t_flags & TF_NEEDFIN) { 1794 tp->t_state = TCPS_FIN_WAIT_1; 1795 tp->t_flags &= ~TF_NEEDFIN; 1796 } else { 1797 tp->t_state = TCPS_ESTABLISHED; 1798 callout_reset(tp->tt_keep, tcp_keepidle, 1799 tcp_timer_keep, tp); 1800 } 1801 /* 1802 * If segment contains data or ACK, will call tcp_reass() 1803 * later; if not, do so now to pass queued data to user. 1804 */ 1805 if (tlen == 0 && (thflags & TH_FIN) == 0) 1806 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1807 (struct mbuf *)0); 1808 tp->snd_wl1 = th->th_seq - 1; 1809 /* FALLTHROUGH */ 1810 1811 /* 1812 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1813 * ACKs. If the ack is in the range 1814 * tp->snd_una < th->th_ack <= tp->snd_max 1815 * then advance tp->snd_una to th->th_ack and drop 1816 * data from the retransmission queue. If this ACK reflects 1817 * more up to date window information we update our window information. 1818 */ 1819 case TCPS_ESTABLISHED: 1820 case TCPS_FIN_WAIT_1: 1821 case TCPS_FIN_WAIT_2: 1822 case TCPS_CLOSE_WAIT: 1823 case TCPS_CLOSING: 1824 case TCPS_LAST_ACK: 1825 case TCPS_TIME_WAIT: 1826 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1827 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1828 tcpstat.tcps_rcvacktoomuch++; 1829 goto dropafterack; 1830 } 1831 if (tp->sack_enable && 1832 (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) 1833 tcp_sack_doack(tp, &to, th->th_ack); 1834 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1835 if (tlen == 0 && tiwin == tp->snd_wnd) { 1836 tcpstat.tcps_rcvdupack++; 1837 /* 1838 * If we have outstanding data (other than 1839 * a window probe), this is a completely 1840 * duplicate ack (ie, window info didn't 1841 * change), the ack is the biggest we've 1842 * seen and we've seen exactly our rexmt 1843 * threshhold of them, assume a packet 1844 * has been dropped and retransmit it. 1845 * Kludge snd_nxt & the congestion 1846 * window so we send only this one 1847 * packet. 1848 * 1849 * We know we're losing at the current 1850 * window size so do congestion avoidance 1851 * (set ssthresh to half the current window 1852 * and pull our congestion window back to 1853 * the new ssthresh). 1854 * 1855 * Dup acks mean that packets have left the 1856 * network (they're now cached at the receiver) 1857 * so bump cwnd by the amount in the receiver 1858 * to keep a constant cwnd packets in the 1859 * network. 1860 */ 1861 if (!callout_active(tp->tt_rexmt) || 1862 th->th_ack != tp->snd_una) 1863 tp->t_dupacks = 0; 1864 else if (++tp->t_dupacks > tcprexmtthresh || 1865 ((tcp_do_newreno || tp->sack_enable) && 1866 IN_FASTRECOVERY(tp))) { 1867 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1868 int awnd; 1869 1870 /* 1871 * Compute the amount of data in flight first. 1872 * We can inject new data into the pipe iff 1873 * we have less than 1/2 the original window's 1874 * worth of data in flight. 1875 */ 1876 awnd = (tp->snd_nxt - tp->snd_fack) + 1877 tp->sackhint.sack_bytes_rexmit; 1878 if (awnd < tp->snd_ssthresh) { 1879 tp->snd_cwnd += tp->t_maxseg; 1880 if (tp->snd_cwnd > tp->snd_ssthresh) 1881 tp->snd_cwnd = tp->snd_ssthresh; 1882 } 1883 } else 1884 tp->snd_cwnd += tp->t_maxseg; 1885 (void) tcp_output(tp); 1886 goto drop; 1887 } else if (tp->t_dupacks == tcprexmtthresh) { 1888 tcp_seq onxt = tp->snd_nxt; 1889 u_int win; 1890 1891 /* 1892 * If we're doing sack, check to 1893 * see if we're already in sack 1894 * recovery. If we're not doing sack, 1895 * check to see if we're in newreno 1896 * recovery. 1897 */ 1898 if (tp->sack_enable) { 1899 if (IN_FASTRECOVERY(tp)) { 1900 tp->t_dupacks = 0; 1901 break; 1902 } 1903 } else if (tcp_do_newreno) { 1904 if (SEQ_LEQ(th->th_ack, 1905 tp->snd_recover)) { 1906 tp->t_dupacks = 0; 1907 break; 1908 } 1909 } 1910 win = min(tp->snd_wnd, tp->snd_cwnd) / 1911 2 / tp->t_maxseg; 1912 if (win < 2) 1913 win = 2; 1914 tp->snd_ssthresh = win * tp->t_maxseg; 1915 ENTER_FASTRECOVERY(tp); 1916 tp->snd_recover = tp->snd_max; 1917 callout_stop(tp->tt_rexmt); 1918 tp->t_rtttime = 0; 1919 if (tp->sack_enable) { 1920 tcpstat.tcps_sack_recovery_episode++; 1921 tp->sack_newdata = tp->snd_nxt; 1922 tp->snd_cwnd = tp->t_maxseg; 1923 (void) tcp_output(tp); 1924 goto drop; 1925 } 1926 tp->snd_nxt = th->th_ack; 1927 tp->snd_cwnd = tp->t_maxseg; 1928 (void) tcp_output(tp); 1929 KASSERT(tp->snd_limited <= 2, 1930 ("tp->snd_limited too big")); 1931 tp->snd_cwnd = tp->snd_ssthresh + 1932 tp->t_maxseg * 1933 (tp->t_dupacks - tp->snd_limited); 1934 if (SEQ_GT(onxt, tp->snd_nxt)) 1935 tp->snd_nxt = onxt; 1936 goto drop; 1937 } else if (tcp_do_rfc3042) { 1938 u_long oldcwnd = tp->snd_cwnd; 1939 tcp_seq oldsndmax = tp->snd_max; 1940 u_int sent; 1941 1942 KASSERT(tp->t_dupacks == 1 || 1943 tp->t_dupacks == 2, 1944 ("dupacks not 1 or 2")); 1945 if (tp->t_dupacks == 1) 1946 tp->snd_limited = 0; 1947 tp->snd_cwnd = 1948 (tp->snd_nxt - tp->snd_una) + 1949 (tp->t_dupacks - tp->snd_limited) * 1950 tp->t_maxseg; 1951 (void) tcp_output(tp); 1952 sent = tp->snd_max - oldsndmax; 1953 if (sent > tp->t_maxseg) { 1954 KASSERT((tp->t_dupacks == 2 && 1955 tp->snd_limited == 0) || 1956 (sent == tp->t_maxseg + 1 && 1957 tp->t_flags & TF_SENTFIN), 1958 ("sent too much")); 1959 tp->snd_limited = 2; 1960 } else if (sent > 0) 1961 ++tp->snd_limited; 1962 tp->snd_cwnd = oldcwnd; 1963 goto drop; 1964 } 1965 } else 1966 tp->t_dupacks = 0; 1967 break; 1968 } 1969 1970 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1971 1972 /* 1973 * If the congestion window was inflated to account 1974 * for the other side's cached packets, retract it. 1975 */ 1976 if (tcp_do_newreno || tp->sack_enable) { 1977 if (IN_FASTRECOVERY(tp)) { 1978 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1979 if (tp->sack_enable) 1980 tcp_sack_partialack(tp, th); 1981 else 1982 tcp_newreno_partial_ack(tp, th); 1983 } else { 1984 /* 1985 * Out of fast recovery. 1986 * Window inflation should have left us 1987 * with approximately snd_ssthresh 1988 * outstanding data. 1989 * But in case we would be inclined to 1990 * send a burst, better to do it via 1991 * the slow start mechanism. 1992 */ 1993 if (SEQ_GT(th->th_ack + 1994 tp->snd_ssthresh, 1995 tp->snd_max)) 1996 tp->snd_cwnd = tp->snd_max - 1997 th->th_ack + 1998 tp->t_maxseg; 1999 else 2000 tp->snd_cwnd = tp->snd_ssthresh; 2001 } 2002 } 2003 } else { 2004 if (tp->t_dupacks >= tcprexmtthresh && 2005 tp->snd_cwnd > tp->snd_ssthresh) 2006 tp->snd_cwnd = tp->snd_ssthresh; 2007 } 2008 tp->t_dupacks = 0; 2009 /* 2010 * If we reach this point, ACK is not a duplicate, 2011 * i.e., it ACKs something we sent. 2012 */ 2013 if (tp->t_flags & TF_NEEDSYN) { 2014 /* 2015 * T/TCP: Connection was half-synchronized, and our 2016 * SYN has been ACK'd (so connection is now fully 2017 * synchronized). Go to non-starred state, 2018 * increment snd_una for ACK of SYN, and check if 2019 * we can do window scaling. 2020 */ 2021 tp->t_flags &= ~TF_NEEDSYN; 2022 tp->snd_una++; 2023 /* Do window scaling? */ 2024 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2025 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2026 tp->snd_scale = tp->requested_s_scale; 2027 tp->rcv_scale = tp->request_r_scale; 2028 } 2029 } 2030 2031process_ACK: 2032 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2033 "locked")); 2034 INP_LOCK_ASSERT(inp); 2035 2036 acked = th->th_ack - tp->snd_una; 2037 tcpstat.tcps_rcvackpack++; 2038 tcpstat.tcps_rcvackbyte += acked; 2039 2040 /* 2041 * If we just performed our first retransmit, and the ACK 2042 * arrives within our recovery window, then it was a mistake 2043 * to do the retransmit in the first place. Recover our 2044 * original cwnd and ssthresh, and proceed to transmit where 2045 * we left off. 2046 */ 2047 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2048 ++tcpstat.tcps_sndrexmitbad; 2049 tp->snd_cwnd = tp->snd_cwnd_prev; 2050 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2051 tp->snd_recover = tp->snd_recover_prev; 2052 if (tp->t_flags & TF_WASFRECOVERY) 2053 ENTER_FASTRECOVERY(tp); 2054 tp->snd_nxt = tp->snd_max; 2055 tp->t_badrxtwin = 0; /* XXX probably not required */ 2056 } 2057 2058 /* 2059 * If we have a timestamp reply, update smoothed 2060 * round trip time. If no timestamp is present but 2061 * transmit timer is running and timed sequence 2062 * number was acked, update smoothed round trip time. 2063 * Since we now have an rtt measurement, cancel the 2064 * timer backoff (cf., Phil Karn's retransmit alg.). 2065 * Recompute the initial retransmit timer. 2066 * 2067 * Some boxes send broken timestamp replies 2068 * during the SYN+ACK phase, ignore 2069 * timestamps of 0 or we could calculate a 2070 * huge RTT and blow up the retransmit timer. 2071 */ 2072 if ((to.to_flags & TOF_TS) != 0 && 2073 to.to_tsecr) { 2074 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2075 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2076 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2077 } 2078 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2079 2080 /* 2081 * If all outstanding data is acked, stop retransmit 2082 * timer and remember to restart (more output or persist). 2083 * If there is more data to be acked, restart retransmit 2084 * timer, using current (possibly backed-off) value. 2085 */ 2086 if (th->th_ack == tp->snd_max) { 2087 callout_stop(tp->tt_rexmt); 2088 needoutput = 1; 2089 } else if (!callout_active(tp->tt_persist)) 2090 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2091 tcp_timer_rexmt, tp); 2092 2093 /* 2094 * If no data (only SYN) was ACK'd, 2095 * skip rest of ACK processing. 2096 */ 2097 if (acked == 0) 2098 goto step6; 2099 2100 /* 2101 * When new data is acked, open the congestion window. 2102 * If the window gives us less than ssthresh packets 2103 * in flight, open exponentially (maxseg per packet). 2104 * Otherwise open linearly: maxseg per window 2105 * (maxseg^2 / cwnd per packet). 2106 */ 2107 if ((!tcp_do_newreno && !tp->sack_enable) || 2108 !IN_FASTRECOVERY(tp)) { 2109 register u_int cw = tp->snd_cwnd; 2110 register u_int incr = tp->t_maxseg; 2111 if (cw > tp->snd_ssthresh) 2112 incr = incr * incr / cw; 2113 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2114 } 2115 SOCKBUF_LOCK(&so->so_snd); 2116 if (acked > so->so_snd.sb_cc) { 2117 tp->snd_wnd -= so->so_snd.sb_cc; 2118 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2119 ourfinisacked = 1; 2120 } else { 2121 sbdrop_locked(&so->so_snd, acked); 2122 tp->snd_wnd -= acked; 2123 ourfinisacked = 0; 2124 } 2125 sowwakeup_locked(so); 2126 /* detect una wraparound */ 2127 if ((tcp_do_newreno || tp->sack_enable) && 2128 !IN_FASTRECOVERY(tp) && 2129 SEQ_GT(tp->snd_una, tp->snd_recover) && 2130 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2131 tp->snd_recover = th->th_ack - 1; 2132 if ((tcp_do_newreno || tp->sack_enable) && 2133 IN_FASTRECOVERY(tp) && 2134 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2135 EXIT_FASTRECOVERY(tp); 2136 tp->snd_una = th->th_ack; 2137 if (tp->sack_enable) { 2138 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2139 tp->snd_recover = tp->snd_una; 2140 } 2141 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2142 tp->snd_nxt = tp->snd_una; 2143 2144 switch (tp->t_state) { 2145 2146 /* 2147 * In FIN_WAIT_1 STATE in addition to the processing 2148 * for the ESTABLISHED state if our FIN is now acknowledged 2149 * then enter FIN_WAIT_2. 2150 */ 2151 case TCPS_FIN_WAIT_1: 2152 if (ourfinisacked) { 2153 /* 2154 * If we can't receive any more 2155 * data, then closing user can proceed. 2156 * Starting the timer is contrary to the 2157 * specification, but if we don't get a FIN 2158 * we'll hang forever. 2159 */ 2160 /* XXXjl 2161 * we should release the tp also, and use a 2162 * compressed state. 2163 */ 2164 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2165 soisdisconnected(so); 2166 callout_reset(tp->tt_2msl, tcp_maxidle, 2167 tcp_timer_2msl, tp); 2168 } 2169 tp->t_state = TCPS_FIN_WAIT_2; 2170 } 2171 break; 2172 2173 /* 2174 * In CLOSING STATE in addition to the processing for 2175 * the ESTABLISHED state if the ACK acknowledges our FIN 2176 * then enter the TIME-WAIT state, otherwise ignore 2177 * the segment. 2178 */ 2179 case TCPS_CLOSING: 2180 if (ourfinisacked) { 2181 KASSERT(headlocked, ("tcp_input: process_ACK: " 2182 "head not locked")); 2183 tcp_twstart(tp); 2184 INP_INFO_WUNLOCK(&tcbinfo); 2185 m_freem(m); 2186 return; 2187 } 2188 break; 2189 2190 /* 2191 * In LAST_ACK, we may still be waiting for data to drain 2192 * and/or to be acked, as well as for the ack of our FIN. 2193 * If our FIN is now acknowledged, delete the TCB, 2194 * enter the closed state and return. 2195 */ 2196 case TCPS_LAST_ACK: 2197 if (ourfinisacked) { 2198 KASSERT(headlocked, ("tcp_input: process_ACK:" 2199 " tcp_close: head not locked")); 2200 tp = tcp_close(tp); 2201 goto drop; 2202 } 2203 break; 2204 2205 /* 2206 * In TIME_WAIT state the only thing that should arrive 2207 * is a retransmission of the remote FIN. Acknowledge 2208 * it and restart the finack timer. 2209 */ 2210 case TCPS_TIME_WAIT: 2211 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2212 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2213 tcp_timer_2msl, tp); 2214 goto dropafterack; 2215 } 2216 } 2217 2218step6: 2219 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2220 INP_LOCK_ASSERT(inp); 2221 2222 /* 2223 * Update window information. 2224 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2225 */ 2226 if ((thflags & TH_ACK) && 2227 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2228 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2229 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2230 /* keep track of pure window updates */ 2231 if (tlen == 0 && 2232 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2233 tcpstat.tcps_rcvwinupd++; 2234 tp->snd_wnd = tiwin; 2235 tp->snd_wl1 = th->th_seq; 2236 tp->snd_wl2 = th->th_ack; 2237 if (tp->snd_wnd > tp->max_sndwnd) 2238 tp->max_sndwnd = tp->snd_wnd; 2239 needoutput = 1; 2240 } 2241 2242 /* 2243 * Process segments with URG. 2244 */ 2245 if ((thflags & TH_URG) && th->th_urp && 2246 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2247 /* 2248 * This is a kludge, but if we receive and accept 2249 * random urgent pointers, we'll crash in 2250 * soreceive. It's hard to imagine someone 2251 * actually wanting to send this much urgent data. 2252 */ 2253 SOCKBUF_LOCK(&so->so_rcv); 2254 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2255 th->th_urp = 0; /* XXX */ 2256 thflags &= ~TH_URG; /* XXX */ 2257 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2258 goto dodata; /* XXX */ 2259 } 2260 /* 2261 * If this segment advances the known urgent pointer, 2262 * then mark the data stream. This should not happen 2263 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2264 * a FIN has been received from the remote side. 2265 * In these states we ignore the URG. 2266 * 2267 * According to RFC961 (Assigned Protocols), 2268 * the urgent pointer points to the last octet 2269 * of urgent data. We continue, however, 2270 * to consider it to indicate the first octet 2271 * of data past the urgent section as the original 2272 * spec states (in one of two places). 2273 */ 2274 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2275 tp->rcv_up = th->th_seq + th->th_urp; 2276 so->so_oobmark = so->so_rcv.sb_cc + 2277 (tp->rcv_up - tp->rcv_nxt) - 1; 2278 if (so->so_oobmark == 0) 2279 so->so_rcv.sb_state |= SBS_RCVATMARK; 2280 sohasoutofband(so); 2281 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2282 } 2283 SOCKBUF_UNLOCK(&so->so_rcv); 2284 /* 2285 * Remove out of band data so doesn't get presented to user. 2286 * This can happen independent of advancing the URG pointer, 2287 * but if two URG's are pending at once, some out-of-band 2288 * data may creep in... ick. 2289 */ 2290 if (th->th_urp <= (u_long)tlen && 2291 !(so->so_options & SO_OOBINLINE)) { 2292 /* hdr drop is delayed */ 2293 tcp_pulloutofband(so, th, m, drop_hdrlen); 2294 } 2295 } else { 2296 /* 2297 * If no out of band data is expected, 2298 * pull receive urgent pointer along 2299 * with the receive window. 2300 */ 2301 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2302 tp->rcv_up = tp->rcv_nxt; 2303 } 2304dodata: /* XXX */ 2305 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2306 INP_LOCK_ASSERT(inp); 2307 2308 /* 2309 * Process the segment text, merging it into the TCP sequencing queue, 2310 * and arranging for acknowledgment of receipt if necessary. 2311 * This process logically involves adjusting tp->rcv_wnd as data 2312 * is presented to the user (this happens in tcp_usrreq.c, 2313 * case PRU_RCVD). If a FIN has already been received on this 2314 * connection then we just ignore the text. 2315 */ 2316 if ((tlen || (thflags & TH_FIN)) && 2317 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2318 tcp_seq save_start = th->th_seq; 2319 tcp_seq save_end = th->th_seq + tlen; 2320 m_adj(m, drop_hdrlen); /* delayed header drop */ 2321 /* 2322 * Insert segment which includes th into TCP reassembly queue 2323 * with control block tp. Set thflags to whether reassembly now 2324 * includes a segment with FIN. This handles the common case 2325 * inline (segment is the next to be received on an established 2326 * connection, and the queue is empty), avoiding linkage into 2327 * and removal from the queue and repetition of various 2328 * conversions. 2329 * Set DELACK for segments received in order, but ack 2330 * immediately when segments are out of order (so 2331 * fast retransmit can work). 2332 */ 2333 if (th->th_seq == tp->rcv_nxt && 2334 LIST_EMPTY(&tp->t_segq) && 2335 TCPS_HAVEESTABLISHED(tp->t_state)) { 2336 if (DELAY_ACK(tp)) 2337 tp->t_flags |= TF_DELACK; 2338 else 2339 tp->t_flags |= TF_ACKNOW; 2340 tp->rcv_nxt += tlen; 2341 thflags = th->th_flags & TH_FIN; 2342 tcpstat.tcps_rcvpack++; 2343 tcpstat.tcps_rcvbyte += tlen; 2344 ND6_HINT(tp); 2345 SOCKBUF_LOCK(&so->so_rcv); 2346 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2347 m_freem(m); 2348 else 2349 sbappendstream_locked(&so->so_rcv, m); 2350 sorwakeup_locked(so); 2351 } else { 2352 thflags = tcp_reass(tp, th, &tlen, m); 2353 tp->t_flags |= TF_ACKNOW; 2354 } 2355 if (tlen > 0 && tp->sack_enable) 2356 tcp_update_sack_list(tp, save_start, save_end); 2357 /* 2358 * Note the amount of data that peer has sent into 2359 * our window, in order to estimate the sender's 2360 * buffer size. 2361 */ 2362 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2363 } else { 2364 m_freem(m); 2365 thflags &= ~TH_FIN; 2366 } 2367 2368 /* 2369 * If FIN is received ACK the FIN and let the user know 2370 * that the connection is closing. 2371 */ 2372 if (thflags & TH_FIN) { 2373 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2374 socantrcvmore(so); 2375 /* 2376 * If connection is half-synchronized 2377 * (ie NEEDSYN flag on) then delay ACK, 2378 * so it may be piggybacked when SYN is sent. 2379 * Otherwise, since we received a FIN then no 2380 * more input can be expected, send ACK now. 2381 */ 2382 if (tp->t_flags & TF_NEEDSYN) 2383 tp->t_flags |= TF_DELACK; 2384 else 2385 tp->t_flags |= TF_ACKNOW; 2386 tp->rcv_nxt++; 2387 } 2388 switch (tp->t_state) { 2389 2390 /* 2391 * In SYN_RECEIVED and ESTABLISHED STATES 2392 * enter the CLOSE_WAIT state. 2393 */ 2394 case TCPS_SYN_RECEIVED: 2395 tp->t_starttime = ticks; 2396 /*FALLTHROUGH*/ 2397 case TCPS_ESTABLISHED: 2398 tp->t_state = TCPS_CLOSE_WAIT; 2399 break; 2400 2401 /* 2402 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2403 * enter the CLOSING state. 2404 */ 2405 case TCPS_FIN_WAIT_1: 2406 tp->t_state = TCPS_CLOSING; 2407 break; 2408 2409 /* 2410 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2411 * starting the time-wait timer, turning off the other 2412 * standard timers. 2413 */ 2414 case TCPS_FIN_WAIT_2: 2415 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2416 "TCP_FIN_WAIT_2: head not locked")); 2417 tcp_twstart(tp); 2418 INP_INFO_WUNLOCK(&tcbinfo); 2419 return; 2420 2421 /* 2422 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2423 */ 2424 case TCPS_TIME_WAIT: 2425 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2426 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2427 tcp_timer_2msl, tp); 2428 break; 2429 } 2430 } 2431 INP_INFO_WUNLOCK(&tcbinfo); 2432 headlocked = 0; 2433#ifdef TCPDEBUG 2434 if (so->so_options & SO_DEBUG) 2435 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2436 &tcp_savetcp, 0); 2437#endif 2438 2439 /* 2440 * Return any desired output. 2441 */ 2442 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2443 (void) tcp_output(tp); 2444 2445check_delack: 2446 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2447 INP_LOCK_ASSERT(inp); 2448 if (tp->t_flags & TF_DELACK) { 2449 tp->t_flags &= ~TF_DELACK; 2450 callout_reset(tp->tt_delack, tcp_delacktime, 2451 tcp_timer_delack, tp); 2452 } 2453 INP_UNLOCK(inp); 2454 return; 2455 2456dropafterack: 2457 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2458 /* 2459 * Generate an ACK dropping incoming segment if it occupies 2460 * sequence space, where the ACK reflects our state. 2461 * 2462 * We can now skip the test for the RST flag since all 2463 * paths to this code happen after packets containing 2464 * RST have been dropped. 2465 * 2466 * In the SYN-RECEIVED state, don't send an ACK unless the 2467 * segment we received passes the SYN-RECEIVED ACK test. 2468 * If it fails send a RST. This breaks the loop in the 2469 * "LAND" DoS attack, and also prevents an ACK storm 2470 * between two listening ports that have been sent forged 2471 * SYN segments, each with the source address of the other. 2472 */ 2473 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2474 (SEQ_GT(tp->snd_una, th->th_ack) || 2475 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2476 rstreason = BANDLIM_RST_OPENPORT; 2477 goto dropwithreset; 2478 } 2479#ifdef TCPDEBUG 2480 if (so->so_options & SO_DEBUG) 2481 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2482 &tcp_savetcp, 0); 2483#endif 2484 KASSERT(headlocked, ("headlocked should be 1")); 2485 INP_INFO_WUNLOCK(&tcbinfo); 2486 tp->t_flags |= TF_ACKNOW; 2487 (void) tcp_output(tp); 2488 INP_UNLOCK(inp); 2489 m_freem(m); 2490 return; 2491 2492dropwithreset: 2493 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2494 /* 2495 * Generate a RST, dropping incoming segment. 2496 * Make ACK acceptable to originator of segment. 2497 * Don't bother to respond if destination was broadcast/multicast. 2498 */ 2499 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2500 goto drop; 2501 if (isipv6) { 2502 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2503 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2504 goto drop; 2505 } else { 2506 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2507 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2508 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2509 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2510 goto drop; 2511 } 2512 /* IPv6 anycast check is done at tcp6_input() */ 2513 2514 /* 2515 * Perform bandwidth limiting. 2516 */ 2517 if (badport_bandlim(rstreason) < 0) 2518 goto drop; 2519 2520#ifdef TCPDEBUG 2521 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2522 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2523 &tcp_savetcp, 0); 2524#endif 2525 2526 if (thflags & TH_ACK) 2527 /* mtod() below is safe as long as hdr dropping is delayed */ 2528 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2529 TH_RST); 2530 else { 2531 if (thflags & TH_SYN) 2532 tlen++; 2533 /* mtod() below is safe as long as hdr dropping is delayed */ 2534 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2535 (tcp_seq)0, TH_RST|TH_ACK); 2536 } 2537 2538 if (tp) 2539 INP_UNLOCK(inp); 2540 if (headlocked) 2541 INP_INFO_WUNLOCK(&tcbinfo); 2542 return; 2543 2544drop: 2545 /* 2546 * Drop space held by incoming segment and return. 2547 */ 2548#ifdef TCPDEBUG 2549 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2550 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2551 &tcp_savetcp, 0); 2552#endif 2553 if (tp) 2554 INP_UNLOCK(inp); 2555 if (headlocked) 2556 INP_INFO_WUNLOCK(&tcbinfo); 2557 m_freem(m); 2558 return; 2559} 2560 2561/* 2562 * Parse TCP options and place in tcpopt. 2563 */ 2564static void 2565tcp_dooptions(to, cp, cnt, is_syn) 2566 struct tcpopt *to; 2567 u_char *cp; 2568 int cnt; 2569 int is_syn; 2570{ 2571 int opt, optlen; 2572 2573 to->to_flags = 0; 2574 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2575 opt = cp[0]; 2576 if (opt == TCPOPT_EOL) 2577 break; 2578 if (opt == TCPOPT_NOP) 2579 optlen = 1; 2580 else { 2581 if (cnt < 2) 2582 break; 2583 optlen = cp[1]; 2584 if (optlen < 2 || optlen > cnt) 2585 break; 2586 } 2587 switch (opt) { 2588 case TCPOPT_MAXSEG: 2589 if (optlen != TCPOLEN_MAXSEG) 2590 continue; 2591 if (!is_syn) 2592 continue; 2593 to->to_flags |= TOF_MSS; 2594 bcopy((char *)cp + 2, 2595 (char *)&to->to_mss, sizeof(to->to_mss)); 2596 to->to_mss = ntohs(to->to_mss); 2597 break; 2598 case TCPOPT_WINDOW: 2599 if (optlen != TCPOLEN_WINDOW) 2600 continue; 2601 if (! is_syn) 2602 continue; 2603 to->to_flags |= TOF_SCALE; 2604 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2605 break; 2606 case TCPOPT_TIMESTAMP: 2607 if (optlen != TCPOLEN_TIMESTAMP) 2608 continue; 2609 to->to_flags |= TOF_TS; 2610 bcopy((char *)cp + 2, 2611 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2612 to->to_tsval = ntohl(to->to_tsval); 2613 bcopy((char *)cp + 6, 2614 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2615 to->to_tsecr = ntohl(to->to_tsecr); 2616 /* 2617 * If echoed timestamp is later than the current time, 2618 * fall back to non RFC1323 RTT calculation. 2619 */ 2620 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks)) 2621 to->to_tsecr = 0; 2622 break; 2623#ifdef TCP_SIGNATURE 2624 /* 2625 * XXX In order to reply to a host which has set the 2626 * TCP_SIGNATURE option in its initial SYN, we have to 2627 * record the fact that the option was observed here 2628 * for the syncache code to perform the correct response. 2629 */ 2630 case TCPOPT_SIGNATURE: 2631 if (optlen != TCPOLEN_SIGNATURE) 2632 continue; 2633 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2634 break; 2635#endif 2636 case TCPOPT_SACK_PERMITTED: 2637 if (!tcp_do_sack || 2638 optlen != TCPOLEN_SACK_PERMITTED) 2639 continue; 2640 if (is_syn) { 2641 /* MUST only be set on SYN */ 2642 to->to_flags |= TOF_SACK; 2643 } 2644 break; 2645 case TCPOPT_SACK: 2646 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2647 continue; 2648 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2649 to->to_sacks = cp + 2; 2650 tcpstat.tcps_sack_rcv_blocks++; 2651 break; 2652 default: 2653 continue; 2654 } 2655 } 2656} 2657 2658/* 2659 * Pull out of band byte out of a segment so 2660 * it doesn't appear in the user's data queue. 2661 * It is still reflected in the segment length for 2662 * sequencing purposes. 2663 */ 2664static void 2665tcp_pulloutofband(so, th, m, off) 2666 struct socket *so; 2667 struct tcphdr *th; 2668 register struct mbuf *m; 2669 int off; /* delayed to be droped hdrlen */ 2670{ 2671 int cnt = off + th->th_urp - 1; 2672 2673 while (cnt >= 0) { 2674 if (m->m_len > cnt) { 2675 char *cp = mtod(m, caddr_t) + cnt; 2676 struct tcpcb *tp = sototcpcb(so); 2677 2678 tp->t_iobc = *cp; 2679 tp->t_oobflags |= TCPOOB_HAVEDATA; 2680 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2681 m->m_len--; 2682 if (m->m_flags & M_PKTHDR) 2683 m->m_pkthdr.len--; 2684 return; 2685 } 2686 cnt -= m->m_len; 2687 m = m->m_next; 2688 if (m == 0) 2689 break; 2690 } 2691 panic("tcp_pulloutofband"); 2692} 2693 2694/* 2695 * Collect new round-trip time estimate 2696 * and update averages and current timeout. 2697 */ 2698static void 2699tcp_xmit_timer(tp, rtt) 2700 register struct tcpcb *tp; 2701 int rtt; 2702{ 2703 register int delta; 2704 2705 INP_LOCK_ASSERT(tp->t_inpcb); 2706 2707 tcpstat.tcps_rttupdated++; 2708 tp->t_rttupdated++; 2709 if (tp->t_srtt != 0) { 2710 /* 2711 * srtt is stored as fixed point with 5 bits after the 2712 * binary point (i.e., scaled by 8). The following magic 2713 * is equivalent to the smoothing algorithm in rfc793 with 2714 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2715 * point). Adjust rtt to origin 0. 2716 */ 2717 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2718 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2719 2720 if ((tp->t_srtt += delta) <= 0) 2721 tp->t_srtt = 1; 2722 2723 /* 2724 * We accumulate a smoothed rtt variance (actually, a 2725 * smoothed mean difference), then set the retransmit 2726 * timer to smoothed rtt + 4 times the smoothed variance. 2727 * rttvar is stored as fixed point with 4 bits after the 2728 * binary point (scaled by 16). The following is 2729 * equivalent to rfc793 smoothing with an alpha of .75 2730 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2731 * rfc793's wired-in beta. 2732 */ 2733 if (delta < 0) 2734 delta = -delta; 2735 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2736 if ((tp->t_rttvar += delta) <= 0) 2737 tp->t_rttvar = 1; 2738 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2739 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2740 } else { 2741 /* 2742 * No rtt measurement yet - use the unsmoothed rtt. 2743 * Set the variance to half the rtt (so our first 2744 * retransmit happens at 3*rtt). 2745 */ 2746 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2747 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2748 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2749 } 2750 tp->t_rtttime = 0; 2751 tp->t_rxtshift = 0; 2752 2753 /* 2754 * the retransmit should happen at rtt + 4 * rttvar. 2755 * Because of the way we do the smoothing, srtt and rttvar 2756 * will each average +1/2 tick of bias. When we compute 2757 * the retransmit timer, we want 1/2 tick of rounding and 2758 * 1 extra tick because of +-1/2 tick uncertainty in the 2759 * firing of the timer. The bias will give us exactly the 2760 * 1.5 tick we need. But, because the bias is 2761 * statistical, we have to test that we don't drop below 2762 * the minimum feasible timer (which is 2 ticks). 2763 */ 2764 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2765 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2766 2767 /* 2768 * We received an ack for a packet that wasn't retransmitted; 2769 * it is probably safe to discard any error indications we've 2770 * received recently. This isn't quite right, but close enough 2771 * for now (a route might have failed after we sent a segment, 2772 * and the return path might not be symmetrical). 2773 */ 2774 tp->t_softerror = 0; 2775} 2776 2777/* 2778 * Determine a reasonable value for maxseg size. 2779 * If the route is known, check route for mtu. 2780 * If none, use an mss that can be handled on the outgoing 2781 * interface without forcing IP to fragment; if bigger than 2782 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2783 * to utilize large mbufs. If no route is found, route has no mtu, 2784 * or the destination isn't local, use a default, hopefully conservative 2785 * size (usually 512 or the default IP max size, but no more than the mtu 2786 * of the interface), as we can't discover anything about intervening 2787 * gateways or networks. We also initialize the congestion/slow start 2788 * window to be a single segment if the destination isn't local. 2789 * While looking at the routing entry, we also initialize other path-dependent 2790 * parameters from pre-set or cached values in the routing entry. 2791 * 2792 * Also take into account the space needed for options that we 2793 * send regularly. Make maxseg shorter by that amount to assure 2794 * that we can send maxseg amount of data even when the options 2795 * are present. Store the upper limit of the length of options plus 2796 * data in maxopd. 2797 * 2798 * 2799 * In case of T/TCP, we call this routine during implicit connection 2800 * setup as well (offer = -1), to initialize maxseg from the cached 2801 * MSS of our peer. 2802 * 2803 * NOTE that this routine is only called when we process an incoming 2804 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2805 */ 2806void 2807tcp_mss(tp, offer) 2808 struct tcpcb *tp; 2809 int offer; 2810{ 2811 int rtt, mss; 2812 u_long bufsize; 2813 u_long maxmtu; 2814 struct inpcb *inp = tp->t_inpcb; 2815 struct socket *so; 2816 struct hc_metrics_lite metrics; 2817 int origoffer = offer; 2818#ifdef INET6 2819 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2820 size_t min_protoh = isipv6 ? 2821 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2822 sizeof (struct tcpiphdr); 2823#else 2824 const size_t min_protoh = sizeof(struct tcpiphdr); 2825#endif 2826 2827 /* initialize */ 2828#ifdef INET6 2829 if (isipv6) { 2830 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2831 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2832 } else 2833#endif 2834 { 2835 maxmtu = tcp_maxmtu(&inp->inp_inc); 2836 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2837 } 2838 so = inp->inp_socket; 2839 2840 /* 2841 * no route to sender, stay with default mss and return 2842 */ 2843 if (maxmtu == 0) 2844 return; 2845 2846 /* what have we got? */ 2847 switch (offer) { 2848 case 0: 2849 /* 2850 * Offer == 0 means that there was no MSS on the SYN 2851 * segment, in this case we use tcp_mssdflt. 2852 */ 2853 offer = 2854#ifdef INET6 2855 isipv6 ? tcp_v6mssdflt : 2856#endif 2857 tcp_mssdflt; 2858 break; 2859 2860 case -1: 2861 /* 2862 * Offer == -1 means that we didn't receive SYN yet. 2863 */ 2864 /* FALLTHROUGH */ 2865 2866 default: 2867 /* 2868 * Prevent DoS attack with too small MSS. Round up 2869 * to at least minmss. 2870 */ 2871 offer = max(offer, tcp_minmss); 2872 /* 2873 * Sanity check: make sure that maxopd will be large 2874 * enough to allow some data on segments even if the 2875 * all the option space is used (40bytes). Otherwise 2876 * funny things may happen in tcp_output. 2877 */ 2878 offer = max(offer, 64); 2879 } 2880 2881 /* 2882 * rmx information is now retrieved from tcp_hostcache 2883 */ 2884 tcp_hc_get(&inp->inp_inc, &metrics); 2885 2886 /* 2887 * if there's a discovered mtu int tcp hostcache, use it 2888 * else, use the link mtu. 2889 */ 2890 if (metrics.rmx_mtu) 2891 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2892 else { 2893#ifdef INET6 2894 if (isipv6) { 2895 mss = maxmtu - min_protoh; 2896 if (!path_mtu_discovery && 2897 !in6_localaddr(&inp->in6p_faddr)) 2898 mss = min(mss, tcp_v6mssdflt); 2899 } else 2900#endif 2901 { 2902 mss = maxmtu - min_protoh; 2903 if (!path_mtu_discovery && 2904 !in_localaddr(inp->inp_faddr)) 2905 mss = min(mss, tcp_mssdflt); 2906 } 2907 } 2908 mss = min(mss, offer); 2909 2910 /* 2911 * maxopd stores the maximum length of data AND options 2912 * in a segment; maxseg is the amount of data in a normal 2913 * segment. We need to store this value (maxopd) apart 2914 * from maxseg, because now every segment carries options 2915 * and thus we normally have somewhat less data in segments. 2916 */ 2917 tp->t_maxopd = mss; 2918 2919 /* 2920 * origoffer==-1 indicates, that no segments were received yet. 2921 * In this case we just guess. 2922 */ 2923 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2924 (origoffer == -1 || 2925 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2926 mss -= TCPOLEN_TSTAMP_APPA; 2927 tp->t_maxseg = mss; 2928 2929#if (MCLBYTES & (MCLBYTES - 1)) == 0 2930 if (mss > MCLBYTES) 2931 mss &= ~(MCLBYTES-1); 2932#else 2933 if (mss > MCLBYTES) 2934 mss = mss / MCLBYTES * MCLBYTES; 2935#endif 2936 tp->t_maxseg = mss; 2937 2938 /* 2939 * If there's a pipesize, change the socket buffer to that size, 2940 * don't change if sb_hiwat is different than default (then it 2941 * has been changed on purpose with setsockopt). 2942 * Make the socket buffers an integral number of mss units; 2943 * if the mss is larger than the socket buffer, decrease the mss. 2944 */ 2945 SOCKBUF_LOCK(&so->so_snd); 2946 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2947 bufsize = metrics.rmx_sendpipe; 2948 else 2949 bufsize = so->so_snd.sb_hiwat; 2950 if (bufsize < mss) 2951 mss = bufsize; 2952 else { 2953 bufsize = roundup(bufsize, mss); 2954 if (bufsize > sb_max) 2955 bufsize = sb_max; 2956 if (bufsize > so->so_snd.sb_hiwat) 2957 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 2958 } 2959 SOCKBUF_UNLOCK(&so->so_snd); 2960 tp->t_maxseg = mss; 2961 2962 SOCKBUF_LOCK(&so->so_rcv); 2963 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 2964 bufsize = metrics.rmx_recvpipe; 2965 else 2966 bufsize = so->so_rcv.sb_hiwat; 2967 if (bufsize > mss) { 2968 bufsize = roundup(bufsize, mss); 2969 if (bufsize > sb_max) 2970 bufsize = sb_max; 2971 if (bufsize > so->so_rcv.sb_hiwat) 2972 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 2973 } 2974 SOCKBUF_UNLOCK(&so->so_rcv); 2975 /* 2976 * While we're here, check the others too 2977 */ 2978 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 2979 tp->t_srtt = rtt; 2980 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2981 tcpstat.tcps_usedrtt++; 2982 if (metrics.rmx_rttvar) { 2983 tp->t_rttvar = metrics.rmx_rttvar; 2984 tcpstat.tcps_usedrttvar++; 2985 } else { 2986 /* default variation is +- 1 rtt */ 2987 tp->t_rttvar = 2988 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2989 } 2990 TCPT_RANGESET(tp->t_rxtcur, 2991 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2992 tp->t_rttmin, TCPTV_REXMTMAX); 2993 } 2994 if (metrics.rmx_ssthresh) { 2995 /* 2996 * There's some sort of gateway or interface 2997 * buffer limit on the path. Use this to set 2998 * the slow start threshhold, but set the 2999 * threshold to no less than 2*mss. 3000 */ 3001 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3002 tcpstat.tcps_usedssthresh++; 3003 } 3004 if (metrics.rmx_bandwidth) 3005 tp->snd_bandwidth = metrics.rmx_bandwidth; 3006 3007 /* 3008 * Set the slow-start flight size depending on whether this 3009 * is a local network or not. 3010 * 3011 * Extend this so we cache the cwnd too and retrieve it here. 3012 * Make cwnd even bigger than RFC3390 suggests but only if we 3013 * have previous experience with the remote host. Be careful 3014 * not make cwnd bigger than remote receive window or our own 3015 * send socket buffer. Maybe put some additional upper bound 3016 * on the retrieved cwnd. Should do incremental updates to 3017 * hostcache when cwnd collapses so next connection doesn't 3018 * overloads the path again. 3019 * 3020 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3021 * We currently check only in syncache_socket for that. 3022 */ 3023#define TCP_METRICS_CWND 3024#ifdef TCP_METRICS_CWND 3025 if (metrics.rmx_cwnd) 3026 tp->snd_cwnd = max(mss, 3027 min(metrics.rmx_cwnd / 2, 3028 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3029 else 3030#endif 3031 if (tcp_do_rfc3390) 3032 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3033#ifdef INET6 3034 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3035 (!isipv6 && in_localaddr(inp->inp_faddr))) 3036#else 3037 else if (in_localaddr(inp->inp_faddr)) 3038#endif 3039 tp->snd_cwnd = mss * ss_fltsz_local; 3040 else 3041 tp->snd_cwnd = mss * ss_fltsz; 3042} 3043 3044/* 3045 * Determine the MSS option to send on an outgoing SYN. 3046 */ 3047int 3048tcp_mssopt(inc) 3049 struct in_conninfo *inc; 3050{ 3051 int mss = 0; 3052 u_long maxmtu = 0; 3053 u_long thcmtu = 0; 3054 size_t min_protoh; 3055#ifdef INET6 3056 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3057#endif 3058 3059 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3060 3061#ifdef INET6 3062 if (isipv6) { 3063 mss = tcp_v6mssdflt; 3064 maxmtu = tcp_maxmtu6(inc); 3065 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3066 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3067 } else 3068#endif 3069 { 3070 mss = tcp_mssdflt; 3071 maxmtu = tcp_maxmtu(inc); 3072 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3073 min_protoh = sizeof(struct tcpiphdr); 3074 } 3075 if (maxmtu && thcmtu) 3076 mss = min(maxmtu, thcmtu) - min_protoh; 3077 else if (maxmtu || thcmtu) 3078 mss = max(maxmtu, thcmtu) - min_protoh; 3079 3080 return (mss); 3081} 3082 3083 3084/* 3085 * On a partial ack arrives, force the retransmission of the 3086 * next unacknowledged segment. Do not clear tp->t_dupacks. 3087 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3088 * be started again. 3089 */ 3090static void 3091tcp_newreno_partial_ack(tp, th) 3092 struct tcpcb *tp; 3093 struct tcphdr *th; 3094{ 3095 tcp_seq onxt = tp->snd_nxt; 3096 u_long ocwnd = tp->snd_cwnd; 3097 3098 callout_stop(tp->tt_rexmt); 3099 tp->t_rtttime = 0; 3100 tp->snd_nxt = th->th_ack; 3101 /* 3102 * Set snd_cwnd to one segment beyond acknowledged offset. 3103 * (tp->snd_una has not yet been updated when this function is called.) 3104 */ 3105 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3106 tp->t_flags |= TF_ACKNOW; 3107 (void) tcp_output(tp); 3108 tp->snd_cwnd = ocwnd; 3109 if (SEQ_GT(onxt, tp->snd_nxt)) 3110 tp->snd_nxt = onxt; 3111 /* 3112 * Partial window deflation. Relies on fact that tp->snd_una 3113 * not updated yet. 3114 */ 3115 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3116 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3117 else 3118 tp->snd_cwnd = 0; 3119 tp->snd_cwnd += tp->t_maxseg; 3120} 3121 3122/* 3123 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3124 * looking for a pcb in the listen state. Returns 0 otherwise. 3125 */ 3126static int 3127tcp_timewait(tw, to, th, m, tlen) 3128 struct tcptw *tw; 3129 struct tcpopt *to; 3130 struct tcphdr *th; 3131 struct mbuf *m; 3132 int tlen; 3133{ 3134 int thflags; 3135 tcp_seq seq; 3136#ifdef INET6 3137 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3138#else 3139 const int isipv6 = 0; 3140#endif 3141 3142 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */ 3143 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3144 INP_LOCK_ASSERT(tw->tw_inpcb); 3145 3146 thflags = th->th_flags; 3147 3148 /* 3149 * NOTE: for FIN_WAIT_2 (to be added later), 3150 * must validate sequence number before accepting RST 3151 */ 3152 3153 /* 3154 * If the segment contains RST: 3155 * Drop the segment - see Stevens, vol. 2, p. 964 and 3156 * RFC 1337. 3157 */ 3158 if (thflags & TH_RST) 3159 goto drop; 3160 3161#if 0 3162/* PAWS not needed at the moment */ 3163 /* 3164 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3165 * and it's less than ts_recent, drop it. 3166 */ 3167 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3168 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3169 if ((thflags & TH_ACK) == 0) 3170 goto drop; 3171 goto ack; 3172 } 3173 /* 3174 * ts_recent is never updated because we never accept new segments. 3175 */ 3176#endif 3177 3178 /* 3179 * If a new connection request is received 3180 * while in TIME_WAIT, drop the old connection 3181 * and start over if the sequence numbers 3182 * are above the previous ones. 3183 */ 3184 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3185 (void) tcp_twclose(tw, 0); 3186 return (1); 3187 } 3188 3189 /* 3190 * Drop the the segment if it does not contain an ACK. 3191 */ 3192 if ((thflags & TH_ACK) == 0) 3193 goto drop; 3194 3195 /* 3196 * Reset the 2MSL timer if this is a duplicate FIN. 3197 */ 3198 if (thflags & TH_FIN) { 3199 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3200 if (seq + 1 == tw->rcv_nxt) 3201 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3202 } 3203 3204 /* 3205 * Acknowledge the segment if it has data or is not a duplicate ACK. 3206 */ 3207 if (thflags != TH_ACK || tlen != 0 || 3208 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3209 tcp_twrespond(tw, TH_ACK); 3210 goto drop; 3211 3212 /* 3213 * Generate a RST, dropping incoming segment. 3214 * Make ACK acceptable to originator of segment. 3215 * Don't bother to respond if destination was broadcast/multicast. 3216 */ 3217 if (m->m_flags & (M_BCAST|M_MCAST)) 3218 goto drop; 3219 if (isipv6) { 3220 struct ip6_hdr *ip6; 3221 3222 /* IPv6 anycast check is done at tcp6_input() */ 3223 ip6 = mtod(m, struct ip6_hdr *); 3224 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3225 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3226 goto drop; 3227 } else { 3228 struct ip *ip; 3229 3230 ip = mtod(m, struct ip *); 3231 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3232 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3233 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3234 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3235 goto drop; 3236 } 3237 if (thflags & TH_ACK) { 3238 tcp_respond(NULL, 3239 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3240 } else { 3241 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3242 tcp_respond(NULL, 3243 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3244 } 3245 INP_UNLOCK(tw->tw_inpcb); 3246 return (0); 3247 3248drop: 3249 INP_UNLOCK(tw->tw_inpcb); 3250 m_freem(m); 3251 return (0); 3252} 3253