tcp_input.c revision 106271
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 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 34 * $FreeBSD: head/sys/netinet/tcp_input.c 106271 2002-10-31 23:24:13Z jeff $ 35 */ 36 37#include "opt_ipfw.h" /* for ipfw_fwd */ 38#include "opt_inet6.h" 39#include "opt_ipsec.h" 40#include "opt_mac.h" 41#include "opt_tcpdebug.h" 42#include "opt_tcp_input.h" 43 44#include <sys/param.h> 45#include <sys/kernel.h> 46#include <sys/mac.h> 47#include <sys/malloc.h> 48#include <sys/mbuf.h> 49#include <sys/proc.h> /* for proc0 declaration */ 50#include <sys/protosw.h> 51#include <sys/signalvar.h> 52#include <sys/socket.h> 53#include <sys/socketvar.h> 54#include <sys/sysctl.h> 55#include <sys/syslog.h> 56#include <sys/systm.h> 57 58#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 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#ifdef INET6 90#include <netipsec/ipsec6.h> 91#endif 92#endif /*FAST_IPSEC*/ 93 94#ifdef IPSEC 95#include <netinet6/ipsec.h> 96#include <netinet6/ipsec6.h> 97#include <netkey/key.h> 98#endif /*IPSEC*/ 99 100#include <machine/in_cksum.h> 101 102MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 103 104static const int tcprexmtthresh = 3; 105tcp_cc tcp_ccgen; 106 107struct tcpstat tcpstat; 108SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 109 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 110 111static int log_in_vain = 0; 112SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 113 &log_in_vain, 0, "Log all incoming TCP connections"); 114 115static int blackhole = 0; 116SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 117 &blackhole, 0, "Do not send RST when dropping refused connections"); 118 119int tcp_delack_enabled = 1; 120SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 121 &tcp_delack_enabled, 0, 122 "Delay ACK to try and piggyback it onto a data packet"); 123 124#ifdef TCP_DROP_SYNFIN 125static int drop_synfin = 0; 126SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 127 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 128#endif 129 130struct inpcbhead tcb; 131#define tcb6 tcb /* for KAME src sync over BSD*'s */ 132struct inpcbinfo tcbinfo; 133struct mtx *tcbinfo_mtx; 134 135static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 136static void tcp_pulloutofband(struct socket *, 137 struct tcphdr *, struct mbuf *, int); 138static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 139 struct mbuf *); 140static void tcp_xmit_timer(struct tcpcb *, int); 141static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 142 143/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 144#ifdef INET6 145#define ND6_HINT(tp) \ 146do { \ 147 if ((tp) && (tp)->t_inpcb && \ 148 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ 149 (tp)->t_inpcb->in6p_route.ro_rt) \ 150 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 151} while (0) 152#else 153#define ND6_HINT(tp) 154#endif 155 156/* 157 * Indicate whether this ack should be delayed. We can delay the ack if 158 * - delayed acks are enabled and 159 * - there is no delayed ack timer in progress and 160 * - our last ack wasn't a 0-sized window. We never want to delay 161 * the ack that opens up a 0-sized window. 162 */ 163#define DELAY_ACK(tp) \ 164 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 165 (tp->t_flags & TF_RXWIN0SENT) == 0) 166 167static int 168tcp_reass(tp, th, tlenp, m) 169 register struct tcpcb *tp; 170 register struct tcphdr *th; 171 int *tlenp; 172 struct mbuf *m; 173{ 174 struct tseg_qent *q; 175 struct tseg_qent *p = NULL; 176 struct tseg_qent *nq; 177 struct tseg_qent *te; 178 struct socket *so = tp->t_inpcb->inp_socket; 179 int flags; 180 181 /* 182 * Call with th==0 after become established to 183 * force pre-ESTABLISHED data up to user socket. 184 */ 185 if (th == 0) 186 goto present; 187 188 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */ 189 MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ, 190 M_NOWAIT); 191 if (te == NULL) { 192 tcpstat.tcps_rcvmemdrop++; 193 m_freem(m); 194 return (0); 195 } 196 197 /* 198 * Find a segment which begins after this one does. 199 */ 200 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 201 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 202 break; 203 p = q; 204 } 205 206 /* 207 * If there is a preceding segment, it may provide some of 208 * our data already. If so, drop the data from the incoming 209 * segment. If it provides all of our data, drop us. 210 */ 211 if (p != NULL) { 212 register int i; 213 /* conversion to int (in i) handles seq wraparound */ 214 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 215 if (i > 0) { 216 if (i >= *tlenp) { 217 tcpstat.tcps_rcvduppack++; 218 tcpstat.tcps_rcvdupbyte += *tlenp; 219 m_freem(m); 220 FREE(te, M_TSEGQ); 221 /* 222 * Try to present any queued data 223 * at the left window edge to the user. 224 * This is needed after the 3-WHS 225 * completes. 226 */ 227 goto present; /* ??? */ 228 } 229 m_adj(m, i); 230 *tlenp -= i; 231 th->th_seq += i; 232 } 233 } 234 tcpstat.tcps_rcvoopack++; 235 tcpstat.tcps_rcvoobyte += *tlenp; 236 237 /* 238 * While we overlap succeeding segments trim them or, 239 * if they are completely covered, dequeue them. 240 */ 241 while (q) { 242 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 243 if (i <= 0) 244 break; 245 if (i < q->tqe_len) { 246 q->tqe_th->th_seq += i; 247 q->tqe_len -= i; 248 m_adj(q->tqe_m, i); 249 break; 250 } 251 252 nq = LIST_NEXT(q, tqe_q); 253 LIST_REMOVE(q, tqe_q); 254 m_freem(q->tqe_m); 255 FREE(q, M_TSEGQ); 256 q = nq; 257 } 258 259 /* Insert the new segment queue entry into place. */ 260 te->tqe_m = m; 261 te->tqe_th = th; 262 te->tqe_len = *tlenp; 263 264 if (p == NULL) { 265 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 266 } else { 267 LIST_INSERT_AFTER(p, te, tqe_q); 268 } 269 270present: 271 /* 272 * Present data to user, advancing rcv_nxt through 273 * completed sequence space. 274 */ 275 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 276 return (0); 277 q = LIST_FIRST(&tp->t_segq); 278 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 279 return (0); 280 do { 281 tp->rcv_nxt += q->tqe_len; 282 flags = q->tqe_th->th_flags & TH_FIN; 283 nq = LIST_NEXT(q, tqe_q); 284 LIST_REMOVE(q, tqe_q); 285 if (so->so_state & SS_CANTRCVMORE) 286 m_freem(q->tqe_m); 287 else 288 sbappend(&so->so_rcv, q->tqe_m); 289 FREE(q, M_TSEGQ); 290 q = nq; 291 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 292 ND6_HINT(tp); 293 sorwakeup(so); 294 return (flags); 295} 296 297/* 298 * TCP input routine, follows pages 65-76 of the 299 * protocol specification dated September, 1981 very closely. 300 */ 301#ifdef INET6 302int 303tcp6_input(mp, offp, proto) 304 struct mbuf **mp; 305 int *offp, proto; 306{ 307 register struct mbuf *m = *mp; 308 struct in6_ifaddr *ia6; 309 310 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 311 312 /* 313 * draft-itojun-ipv6-tcp-to-anycast 314 * better place to put this in? 315 */ 316 ia6 = ip6_getdstifaddr(m); 317 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 318 struct ip6_hdr *ip6; 319 320 ip6 = mtod(m, struct ip6_hdr *); 321 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 322 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 323 return IPPROTO_DONE; 324 } 325 326 tcp_input(m, *offp); 327 return IPPROTO_DONE; 328} 329#endif 330 331void 332tcp_input(m, off0) 333 register struct mbuf *m; 334 int off0; 335{ 336 register struct tcphdr *th; 337 register struct ip *ip = NULL; 338 register struct ipovly *ipov; 339 register struct inpcb *inp = NULL; 340 u_char *optp = NULL; 341 int optlen = 0; 342 int len, tlen, off; 343 int drop_hdrlen; 344 register struct tcpcb *tp = 0; 345 register int thflags; 346 struct socket *so = 0; 347 int todrop, acked, ourfinisacked, needoutput = 0; 348 u_long tiwin; 349 struct tcpopt to; /* options in this segment */ 350 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 351 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 352 int headlocked = 0; 353 struct sockaddr_in *next_hop = NULL; 354 int rstreason; /* For badport_bandlim accounting purposes */ 355 356 struct ip6_hdr *ip6 = NULL; 357#ifdef INET6 358 int isipv6; 359#else 360 const int isipv6 = 0; 361#endif 362 363#ifdef TCPDEBUG 364 /* 365 * The size of tcp_saveipgen must be the size of the max ip header, 366 * now IPv6. 367 */ 368 u_char tcp_saveipgen[40]; 369 struct tcphdr tcp_savetcp; 370 short ostate = 0; 371#endif 372 373#ifdef MAC 374 int error; 375#endif 376 377 /* Grab info from MT_TAG mbufs prepended to the chain. */ 378 for (;m && m->m_type == MT_TAG; m = m->m_next) { 379 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 380 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 381 } 382#ifdef INET6 383 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 384#endif 385 bzero((char *)&to, sizeof(to)); 386 387 tcpstat.tcps_rcvtotal++; 388 389 if (isipv6) { 390 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 391 ip6 = mtod(m, struct ip6_hdr *); 392 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 393 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 394 tcpstat.tcps_rcvbadsum++; 395 goto drop; 396 } 397 th = (struct tcphdr *)((caddr_t)ip6 + off0); 398 399 /* 400 * Be proactive about unspecified IPv6 address in source. 401 * As we use all-zero to indicate unbounded/unconnected pcb, 402 * unspecified IPv6 address can be used to confuse us. 403 * 404 * Note that packets with unspecified IPv6 destination is 405 * already dropped in ip6_input. 406 */ 407 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 408 /* XXX stat */ 409 goto drop; 410 } 411 } else { 412 /* 413 * Get IP and TCP header together in first mbuf. 414 * Note: IP leaves IP header in first mbuf. 415 */ 416 if (off0 > sizeof (struct ip)) { 417 ip_stripoptions(m, (struct mbuf *)0); 418 off0 = sizeof(struct ip); 419 } 420 if (m->m_len < sizeof (struct tcpiphdr)) { 421 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 422 tcpstat.tcps_rcvshort++; 423 return; 424 } 425 } 426 ip = mtod(m, struct ip *); 427 ipov = (struct ipovly *)ip; 428 th = (struct tcphdr *)((caddr_t)ip + off0); 429 tlen = ip->ip_len; 430 431 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 432 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 433 th->th_sum = m->m_pkthdr.csum_data; 434 else 435 th->th_sum = in_pseudo(ip->ip_src.s_addr, 436 ip->ip_dst.s_addr, 437 htonl(m->m_pkthdr.csum_data + 438 ip->ip_len + 439 IPPROTO_TCP)); 440 th->th_sum ^= 0xffff; 441 } else { 442 /* 443 * Checksum extended TCP header and data. 444 */ 445 len = sizeof (struct ip) + tlen; 446 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 447 ipov->ih_len = (u_short)tlen; 448 ipov->ih_len = htons(ipov->ih_len); 449 th->th_sum = in_cksum(m, len); 450 } 451 if (th->th_sum) { 452 tcpstat.tcps_rcvbadsum++; 453 goto drop; 454 } 455#ifdef INET6 456 /* Re-initialization for later version check */ 457 ip->ip_v = IPVERSION; 458#endif 459 } 460 461 /* 462 * Check that TCP offset makes sense, 463 * pull out TCP options and adjust length. XXX 464 */ 465 off = th->th_off << 2; 466 if (off < sizeof (struct tcphdr) || off > tlen) { 467 tcpstat.tcps_rcvbadoff++; 468 goto drop; 469 } 470 tlen -= off; /* tlen is used instead of ti->ti_len */ 471 if (off > sizeof (struct tcphdr)) { 472 if (isipv6) { 473 IP6_EXTHDR_CHECK(m, off0, off, ); 474 ip6 = mtod(m, struct ip6_hdr *); 475 th = (struct tcphdr *)((caddr_t)ip6 + off0); 476 } else { 477 if (m->m_len < sizeof(struct ip) + off) { 478 if ((m = m_pullup(m, sizeof (struct ip) + off)) 479 == 0) { 480 tcpstat.tcps_rcvshort++; 481 return; 482 } 483 ip = mtod(m, struct ip *); 484 ipov = (struct ipovly *)ip; 485 th = (struct tcphdr *)((caddr_t)ip + off0); 486 } 487 } 488 optlen = off - sizeof (struct tcphdr); 489 optp = (u_char *)(th + 1); 490 } 491 thflags = th->th_flags; 492 493#ifdef TCP_DROP_SYNFIN 494 /* 495 * If the drop_synfin option is enabled, drop all packets with 496 * both the SYN and FIN bits set. This prevents e.g. nmap from 497 * identifying the TCP/IP stack. 498 * 499 * This is a violation of the TCP specification. 500 */ 501 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 502 goto drop; 503#endif 504 505 /* 506 * Convert TCP protocol specific fields to host format. 507 */ 508 th->th_seq = ntohl(th->th_seq); 509 th->th_ack = ntohl(th->th_ack); 510 th->th_win = ntohs(th->th_win); 511 th->th_urp = ntohs(th->th_urp); 512 513 /* 514 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options, 515 * until after ip6_savecontrol() is called and before other functions 516 * which don't want those proto headers. 517 * Because ip6_savecontrol() is going to parse the mbuf to 518 * search for data to be passed up to user-land, it wants mbuf 519 * parameters to be unchanged. 520 * XXX: the call of ip6_savecontrol() has been obsoleted based on 521 * latest version of the advanced API (20020110). 522 */ 523 drop_hdrlen = off0 + off; 524 525 /* 526 * Locate pcb for segment. 527 */ 528 INP_INFO_WLOCK(&tcbinfo); 529 headlocked = 1; 530findpcb: 531 /* IPFIREWALL_FORWARD section */ 532 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 533 /* 534 * Transparently forwarded. Pretend to be the destination. 535 * already got one like this? 536 */ 537 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 538 ip->ip_dst, th->th_dport, 539 0, m->m_pkthdr.rcvif); 540 if (!inp) { 541 /* It's new. Try find the ambushing socket. */ 542 inp = in_pcblookup_hash(&tcbinfo, 543 ip->ip_src, th->th_sport, 544 next_hop->sin_addr, 545 next_hop->sin_port ? 546 ntohs(next_hop->sin_port) : 547 th->th_dport, 548 1, m->m_pkthdr.rcvif); 549 } 550 } else { 551 if (isipv6) 552 inp = in6_pcblookup_hash(&tcbinfo, 553 &ip6->ip6_src, th->th_sport, 554 &ip6->ip6_dst, th->th_dport, 555 1, m->m_pkthdr.rcvif); 556 else 557 inp = in_pcblookup_hash(&tcbinfo, 558 ip->ip_src, th->th_sport, 559 ip->ip_dst, th->th_dport, 560 1, m->m_pkthdr.rcvif); 561 } 562 563#ifdef IPSEC 564 if (isipv6) { 565 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 566 ipsec6stat.in_polvio++; 567 goto drop; 568 } 569 } else { 570 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 571 ipsecstat.in_polvio++; 572 goto drop; 573 } 574 } 575#endif 576#ifdef FAST_IPSEC 577 if (isipv6) { 578 if (inp != NULL && ipsec6_in_reject(m, inp)) { 579 goto drop; 580 } 581 } else if (inp != NULL && ipsec4_in_reject(m, inp)) { 582 goto drop; 583 } 584#endif /*FAST_IPSEC*/ 585 586 /* 587 * If the state is CLOSED (i.e., TCB does not exist) then 588 * all data in the incoming segment is discarded. 589 * If the TCB exists but is in CLOSED state, it is embryonic, 590 * but should either do a listen or a connect soon. 591 */ 592 if (inp == NULL) { 593 if (log_in_vain) { 594#ifdef INET6 595 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 596#else 597 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 598#endif 599 600 if (isipv6) { 601 strcpy(dbuf, "["); 602 strcpy(sbuf, "["); 603 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 604 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 605 strcat(dbuf, "]"); 606 strcat(sbuf, "]"); 607 } else { 608 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 609 strcpy(sbuf, inet_ntoa(ip->ip_src)); 610 } 611 switch (log_in_vain) { 612 case 1: 613 if (thflags & TH_SYN) 614 log(LOG_INFO, 615 "Connection attempt to TCP %s:%d " 616 "from %s:%d\n", 617 dbuf, ntohs(th->th_dport), sbuf, 618 ntohs(th->th_sport)); 619 break; 620 case 2: 621 log(LOG_INFO, 622 "Connection attempt to TCP %s:%d " 623 "from %s:%d flags:0x%x\n", 624 dbuf, ntohs(th->th_dport), sbuf, 625 ntohs(th->th_sport), thflags); 626 break; 627 default: 628 break; 629 } 630 } 631 if (blackhole) { 632 switch (blackhole) { 633 case 1: 634 if (thflags & TH_SYN) 635 goto drop; 636 break; 637 case 2: 638 goto drop; 639 default: 640 goto drop; 641 } 642 } 643 rstreason = BANDLIM_RST_CLOSEDPORT; 644 goto dropwithreset; 645 } 646 INP_LOCK(inp); 647 tp = intotcpcb(inp); 648 if (tp == 0) { 649 INP_UNLOCK(inp); 650 rstreason = BANDLIM_RST_CLOSEDPORT; 651 goto dropwithreset; 652 } 653 if (tp->t_state == TCPS_CLOSED) 654 goto drop; 655 656 /* Unscale the window into a 32-bit value. */ 657 if ((thflags & TH_SYN) == 0) 658 tiwin = th->th_win << tp->snd_scale; 659 else 660 tiwin = th->th_win; 661 662 so = inp->inp_socket; 663#ifdef MAC 664 error = mac_check_socket_deliver(so, m); 665 if (error) 666 goto drop; 667#endif 668 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 669 struct in_conninfo inc; 670#ifdef TCPDEBUG 671 if (so->so_options & SO_DEBUG) { 672 ostate = tp->t_state; 673 if (isipv6) 674 bcopy((char *)ip6, (char *)tcp_saveipgen, 675 sizeof(*ip6)); 676 else 677 bcopy((char *)ip, (char *)tcp_saveipgen, 678 sizeof(*ip)); 679 tcp_savetcp = *th; 680 } 681#endif 682 /* skip if this isn't a listen socket */ 683 if ((so->so_options & SO_ACCEPTCONN) == 0) 684 goto after_listen; 685#ifdef INET6 686 inc.inc_isipv6 = isipv6; 687#endif 688 if (isipv6) { 689 inc.inc6_faddr = ip6->ip6_src; 690 inc.inc6_laddr = ip6->ip6_dst; 691 inc.inc6_route.ro_rt = NULL; /* XXX */ 692 } else { 693 inc.inc_faddr = ip->ip_src; 694 inc.inc_laddr = ip->ip_dst; 695 inc.inc_route.ro_rt = NULL; /* XXX */ 696 } 697 inc.inc_fport = th->th_sport; 698 inc.inc_lport = th->th_dport; 699 700 /* 701 * If the state is LISTEN then ignore segment if it contains 702 * a RST. If the segment contains an ACK then it is bad and 703 * send a RST. If it does not contain a SYN then it is not 704 * interesting; drop it. 705 * 706 * If the state is SYN_RECEIVED (syncache) and seg contains 707 * an ACK, but not for our SYN/ACK, send a RST. If the seg 708 * contains a RST, check the sequence number to see if it 709 * is a valid reset segment. 710 */ 711 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 712 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 713 if (!syncache_expand(&inc, th, &so, m)) { 714 /* 715 * No syncache entry, or ACK was not 716 * for our SYN/ACK. Send a RST. 717 */ 718 tcpstat.tcps_badsyn++; 719 rstreason = BANDLIM_RST_OPENPORT; 720 goto dropwithreset; 721 } 722 if (so == NULL) { 723 /* 724 * Could not complete 3-way handshake, 725 * connection is being closed down, and 726 * syncache will free mbuf. 727 */ 728 INP_UNLOCK(inp); 729 INP_INFO_WUNLOCK(&tcbinfo); 730 return; 731 } 732 /* 733 * Socket is created in state SYN_RECEIVED. 734 * Continue processing segment. 735 */ 736 INP_UNLOCK(inp); 737 inp = sotoinpcb(so); 738 INP_LOCK(inp); 739 tp = intotcpcb(inp); 740 /* 741 * This is what would have happened in 742 * tcp_output() when the SYN,ACK was sent. 743 */ 744 tp->snd_up = tp->snd_una; 745 tp->snd_max = tp->snd_nxt = tp->iss + 1; 746 tp->last_ack_sent = tp->rcv_nxt; 747/* 748 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 749 * until the _second_ ACK is received: 750 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 751 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 752 * move to ESTAB, set snd_wnd to tiwin. 753 */ 754 tp->snd_wnd = tiwin; /* unscaled */ 755 goto after_listen; 756 } 757 if (thflags & TH_RST) { 758 syncache_chkrst(&inc, th); 759 goto drop; 760 } 761 if (thflags & TH_ACK) { 762 syncache_badack(&inc); 763 tcpstat.tcps_badsyn++; 764 rstreason = BANDLIM_RST_OPENPORT; 765 goto dropwithreset; 766 } 767 goto drop; 768 } 769 770 /* 771 * Segment's flags are (SYN) or (SYN|FIN). 772 */ 773#ifdef INET6 774 /* 775 * If deprecated address is forbidden, 776 * we do not accept SYN to deprecated interface 777 * address to prevent any new inbound connection from 778 * getting established. 779 * When we do not accept SYN, we send a TCP RST, 780 * with deprecated source address (instead of dropping 781 * it). We compromise it as it is much better for peer 782 * to send a RST, and RST will be the final packet 783 * for the exchange. 784 * 785 * If we do not forbid deprecated addresses, we accept 786 * the SYN packet. RFC2462 does not suggest dropping 787 * SYN in this case. 788 * If we decipher RFC2462 5.5.4, it says like this: 789 * 1. use of deprecated addr with existing 790 * communication is okay - "SHOULD continue to be 791 * used" 792 * 2. use of it with new communication: 793 * (2a) "SHOULD NOT be used if alternate address 794 * with sufficient scope is available" 795 * (2b) nothing mentioned otherwise. 796 * Here we fall into (2b) case as we have no choice in 797 * our source address selection - we must obey the peer. 798 * 799 * The wording in RFC2462 is confusing, and there are 800 * multiple description text for deprecated address 801 * handling - worse, they are not exactly the same. 802 * I believe 5.5.4 is the best one, so we follow 5.5.4. 803 */ 804 if (isipv6 && !ip6_use_deprecated) { 805 struct in6_ifaddr *ia6; 806 807 if ((ia6 = ip6_getdstifaddr(m)) && 808 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 809 INP_UNLOCK(inp); 810 tp = NULL; 811 rstreason = BANDLIM_RST_OPENPORT; 812 goto dropwithreset; 813 } 814 } 815#endif 816 /* 817 * If it is from this socket, drop it, it must be forged. 818 * Don't bother responding if the destination was a broadcast. 819 */ 820 if (th->th_dport == th->th_sport) { 821 if (isipv6) { 822 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 823 &ip6->ip6_src)) 824 goto drop; 825 } else { 826 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 827 goto drop; 828 } 829 } 830 /* 831 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 832 * 833 * Note that it is quite possible to receive unicast 834 * link-layer packets with a broadcast IP address. Use 835 * in_broadcast() to find them. 836 */ 837 if (m->m_flags & (M_BCAST|M_MCAST)) 838 goto drop; 839 if (isipv6) { 840 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 841 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 842 goto drop; 843 } else { 844 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 845 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 846 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 847 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 848 goto drop; 849 } 850 /* 851 * SYN appears to be valid; create compressed TCP state 852 * for syncache, or perform t/tcp connection. 853 */ 854 if (so->so_qlen <= so->so_qlimit) { 855 tcp_dooptions(&to, optp, optlen, 1); 856 if (!syncache_add(&inc, &to, th, &so, m)) 857 goto drop; 858 if (so == NULL) { 859 /* 860 * Entry added to syncache, mbuf used to 861 * send SYN,ACK packet. 862 */ 863 KASSERT(headlocked, ("headlocked")); 864 INP_UNLOCK(inp); 865 INP_INFO_WUNLOCK(&tcbinfo); 866 return; 867 } 868 /* 869 * Segment passed TAO tests. 870 */ 871 INP_UNLOCK(inp); 872 inp = sotoinpcb(so); 873 INP_LOCK(inp); 874 tp = intotcpcb(inp); 875 tp->snd_wnd = tiwin; 876 tp->t_starttime = ticks; 877 tp->t_state = TCPS_ESTABLISHED; 878 879 /* 880 * If there is a FIN, or if there is data and the 881 * connection is local, then delay SYN,ACK(SYN) in 882 * the hope of piggy-backing it on a response 883 * segment. Otherwise must send ACK now in case 884 * the other side is slow starting. 885 */ 886 if (DELAY_ACK(tp) && 887 ((thflags & TH_FIN) || 888 (tlen != 0 && 889 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 890 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 891 callout_reset(tp->tt_delack, tcp_delacktime, 892 tcp_timer_delack, tp); 893 tp->t_flags |= TF_NEEDSYN; 894 } else 895 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 896 897 tcpstat.tcps_connects++; 898 soisconnected(so); 899 goto trimthenstep6; 900 } 901 goto drop; 902 } 903after_listen: 904 905/* XXX temp debugging */ 906 /* should not happen - syncache should pick up these connections */ 907 if (tp->t_state == TCPS_LISTEN) 908 panic("tcp_input: TCPS_LISTEN"); 909 910 /* 911 * Segment received on connection. 912 * Reset idle time and keep-alive timer. 913 */ 914 tp->t_rcvtime = ticks; 915 if (TCPS_HAVEESTABLISHED(tp->t_state)) 916 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 917 918 /* 919 * Process options. 920 * XXX this is tradtitional behavior, may need to be cleaned up. 921 */ 922 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 923 if (thflags & TH_SYN) { 924 if (to.to_flags & TOF_SCALE) { 925 tp->t_flags |= TF_RCVD_SCALE; 926 tp->requested_s_scale = to.to_requested_s_scale; 927 } 928 if (to.to_flags & TOF_TS) { 929 tp->t_flags |= TF_RCVD_TSTMP; 930 tp->ts_recent = to.to_tsval; 931 tp->ts_recent_age = ticks; 932 } 933 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 934 tp->t_flags |= TF_RCVD_CC; 935 if (to.to_flags & TOF_MSS) 936 tcp_mss(tp, to.to_mss); 937 } 938 939 /* 940 * Header prediction: check for the two common cases 941 * of a uni-directional data xfer. If the packet has 942 * no control flags, is in-sequence, the window didn't 943 * change and we're not retransmitting, it's a 944 * candidate. If the length is zero and the ack moved 945 * forward, we're the sender side of the xfer. Just 946 * free the data acked & wake any higher level process 947 * that was blocked waiting for space. If the length 948 * is non-zero and the ack didn't move, we're the 949 * receiver side. If we're getting packets in-order 950 * (the reassembly queue is empty), add the data to 951 * the socket buffer and note that we need a delayed ack. 952 * Make sure that the hidden state-flags are also off. 953 * Since we check for TCPS_ESTABLISHED above, it can only 954 * be TH_NEEDSYN. 955 */ 956 if (tp->t_state == TCPS_ESTABLISHED && 957 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 958 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 959 ((to.to_flags & TOF_TS) == 0 || 960 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 961 /* 962 * Using the CC option is compulsory if once started: 963 * the segment is OK if no T/TCP was negotiated or 964 * if the segment has a CC option equal to CCrecv 965 */ 966 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 967 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 968 th->th_seq == tp->rcv_nxt && 969 tiwin && tiwin == tp->snd_wnd && 970 tp->snd_nxt == tp->snd_max) { 971 972 /* 973 * If last ACK falls within this segment's sequence numbers, 974 * record the timestamp. 975 * NOTE that the test is modified according to the latest 976 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 977 */ 978 if ((to.to_flags & TOF_TS) != 0 && 979 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 980 tp->ts_recent_age = ticks; 981 tp->ts_recent = to.to_tsval; 982 } 983 984 if (tlen == 0) { 985 if (SEQ_GT(th->th_ack, tp->snd_una) && 986 SEQ_LEQ(th->th_ack, tp->snd_max) && 987 tp->snd_cwnd >= tp->snd_wnd && 988 tp->t_dupacks < tcprexmtthresh) { 989 KASSERT(headlocked, ("headlocked")); 990 INP_INFO_WUNLOCK(&tcbinfo); 991 headlocked = 0; 992 /* 993 * this is a pure ack for outstanding data. 994 */ 995 ++tcpstat.tcps_predack; 996 /* 997 * "bad retransmit" recovery 998 */ 999 if (tp->t_rxtshift == 1 && 1000 ticks < tp->t_badrxtwin) { 1001 tp->snd_cwnd = tp->snd_cwnd_prev; 1002 tp->snd_ssthresh = 1003 tp->snd_ssthresh_prev; 1004 tp->snd_nxt = tp->snd_max; 1005 tp->t_badrxtwin = 0; 1006 } 1007 1008 /* 1009 * Recalculate the transmit timer / rtt. 1010 * 1011 * Some boxes send broken timestamp replies 1012 * during the SYN+ACK phase, ignore 1013 * timestamps of 0 or we could calculate a 1014 * huge RTT and blow up the retransmit timer. 1015 */ 1016 if ((to.to_flags & TOF_TS) != 0 && 1017 to.to_tsecr) { 1018 tcp_xmit_timer(tp, 1019 ticks - to.to_tsecr + 1); 1020 } else if (tp->t_rtttime && 1021 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1022 tcp_xmit_timer(tp, 1023 ticks - tp->t_rtttime); 1024 } 1025 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1026 acked = th->th_ack - tp->snd_una; 1027 tcpstat.tcps_rcvackpack++; 1028 tcpstat.tcps_rcvackbyte += acked; 1029 sbdrop(&so->so_snd, acked); 1030 /* 1031 * pull snd_wl2 up to prevent seq wrap relative 1032 * to th_ack. 1033 */ 1034 tp->snd_wl2 = tp->snd_una = th->th_ack; 1035 tp->t_dupacks = 0; 1036 m_freem(m); 1037 ND6_HINT(tp); /* some progress has been done */ 1038 1039 /* 1040 * If all outstanding data are acked, stop 1041 * retransmit timer, otherwise restart timer 1042 * using current (possibly backed-off) value. 1043 * If process is waiting for space, 1044 * wakeup/selwakeup/signal. If data 1045 * are ready to send, let tcp_output 1046 * decide between more output or persist. 1047 */ 1048 if (tp->snd_una == tp->snd_max) 1049 callout_stop(tp->tt_rexmt); 1050 else if (!callout_active(tp->tt_persist)) 1051 callout_reset(tp->tt_rexmt, 1052 tp->t_rxtcur, 1053 tcp_timer_rexmt, tp); 1054 1055 sowwakeup(so); 1056 if (so->so_snd.sb_cc) 1057 (void) tcp_output(tp); 1058 INP_UNLOCK(inp); 1059 return; 1060 } 1061 } else if (th->th_ack == tp->snd_una && 1062 LIST_EMPTY(&tp->t_segq) && 1063 tlen <= sbspace(&so->so_rcv)) { 1064 KASSERT(headlocked, ("headlocked")); 1065 INP_INFO_WUNLOCK(&tcbinfo); 1066 headlocked = 0; 1067 /* 1068 * this is a pure, in-sequence data packet 1069 * with nothing on the reassembly queue and 1070 * we have enough buffer space to take it. 1071 */ 1072 ++tcpstat.tcps_preddat; 1073 tp->rcv_nxt += tlen; 1074 /* 1075 * Pull snd_wl1 up to prevent seq wrap relative to 1076 * th_seq. 1077 */ 1078 tp->snd_wl1 = th->th_seq; 1079 /* 1080 * Pull rcv_up up to prevent seq wrap relative to 1081 * rcv_nxt. 1082 */ 1083 tp->rcv_up = tp->rcv_nxt; 1084 tcpstat.tcps_rcvpack++; 1085 tcpstat.tcps_rcvbyte += tlen; 1086 ND6_HINT(tp); /* some progress has been done */ 1087 /* 1088 * Add data to socket buffer. 1089 */ 1090 if (so->so_state & SS_CANTRCVMORE) { 1091 m_freem(m); 1092 } else { 1093 m_adj(m, drop_hdrlen); /* delayed header drop */ 1094 sbappend(&so->so_rcv, m); 1095 } 1096 sorwakeup(so); 1097 if (DELAY_ACK(tp)) { 1098 callout_reset(tp->tt_delack, tcp_delacktime, 1099 tcp_timer_delack, tp); 1100 } else { 1101 tp->t_flags |= TF_ACKNOW; 1102 tcp_output(tp); 1103 } 1104 INP_UNLOCK(inp); 1105 return; 1106 } 1107 } 1108 1109 /* 1110 * Calculate amount of space in receive window, 1111 * and then do TCP input processing. 1112 * Receive window is amount of space in rcv queue, 1113 * but not less than advertised window. 1114 */ 1115 { int win; 1116 1117 win = sbspace(&so->so_rcv); 1118 if (win < 0) 1119 win = 0; 1120 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1121 } 1122 1123 switch (tp->t_state) { 1124 1125 /* 1126 * If the state is SYN_RECEIVED: 1127 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1128 */ 1129 case TCPS_SYN_RECEIVED: 1130 if ((thflags & TH_ACK) && 1131 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1132 SEQ_GT(th->th_ack, tp->snd_max))) { 1133 rstreason = BANDLIM_RST_OPENPORT; 1134 goto dropwithreset; 1135 } 1136 break; 1137 1138 /* 1139 * If the state is SYN_SENT: 1140 * if seg contains an ACK, but not for our SYN, drop the input. 1141 * if seg contains a RST, then drop the connection. 1142 * if seg does not contain SYN, then drop it. 1143 * Otherwise this is an acceptable SYN segment 1144 * initialize tp->rcv_nxt and tp->irs 1145 * if seg contains ack then advance tp->snd_una 1146 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1147 * arrange for segment to be acked (eventually) 1148 * continue processing rest of data/controls, beginning with URG 1149 */ 1150 case TCPS_SYN_SENT: 1151 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1152 taop = &tao_noncached; 1153 bzero(taop, sizeof(*taop)); 1154 } 1155 1156 if ((thflags & TH_ACK) && 1157 (SEQ_LEQ(th->th_ack, tp->iss) || 1158 SEQ_GT(th->th_ack, tp->snd_max))) { 1159 /* 1160 * If we have a cached CCsent for the remote host, 1161 * hence we haven't just crashed and restarted, 1162 * do not send a RST. This may be a retransmission 1163 * from the other side after our earlier ACK was lost. 1164 * Our new SYN, when it arrives, will serve as the 1165 * needed ACK. 1166 */ 1167 if (taop->tao_ccsent != 0) 1168 goto drop; 1169 else { 1170 rstreason = BANDLIM_UNLIMITED; 1171 goto dropwithreset; 1172 } 1173 } 1174 if (thflags & TH_RST) { 1175 if (thflags & TH_ACK) 1176 tp = tcp_drop(tp, ECONNREFUSED); 1177 goto drop; 1178 } 1179 if ((thflags & TH_SYN) == 0) 1180 goto drop; 1181 tp->snd_wnd = th->th_win; /* initial send window */ 1182 tp->cc_recv = to.to_cc; /* foreign CC */ 1183 1184 tp->irs = th->th_seq; 1185 tcp_rcvseqinit(tp); 1186 if (thflags & TH_ACK) { 1187 /* 1188 * Our SYN was acked. If segment contains CC.ECHO 1189 * option, check it to make sure this segment really 1190 * matches our SYN. If not, just drop it as old 1191 * duplicate, but send an RST if we're still playing 1192 * by the old rules. If no CC.ECHO option, make sure 1193 * we don't get fooled into using T/TCP. 1194 */ 1195 if (to.to_flags & TOF_CCECHO) { 1196 if (tp->cc_send != to.to_ccecho) { 1197 if (taop->tao_ccsent != 0) 1198 goto drop; 1199 else { 1200 rstreason = BANDLIM_UNLIMITED; 1201 goto dropwithreset; 1202 } 1203 } 1204 } else 1205 tp->t_flags &= ~TF_RCVD_CC; 1206 tcpstat.tcps_connects++; 1207 soisconnected(so); 1208#ifdef MAC 1209 mac_set_socket_peer_from_mbuf(m, so); 1210#endif 1211 /* Do window scaling on this connection? */ 1212 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1213 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1214 tp->snd_scale = tp->requested_s_scale; 1215 tp->rcv_scale = tp->request_r_scale; 1216 } 1217 /* Segment is acceptable, update cache if undefined. */ 1218 if (taop->tao_ccsent == 0) 1219 taop->tao_ccsent = to.to_ccecho; 1220 1221 tp->rcv_adv += tp->rcv_wnd; 1222 tp->snd_una++; /* SYN is acked */ 1223 /* 1224 * If there's data, delay ACK; if there's also a FIN 1225 * ACKNOW will be turned on later. 1226 */ 1227 if (DELAY_ACK(tp) && tlen != 0) 1228 callout_reset(tp->tt_delack, tcp_delacktime, 1229 tcp_timer_delack, tp); 1230 else 1231 tp->t_flags |= TF_ACKNOW; 1232 /* 1233 * Received <SYN,ACK> in SYN_SENT[*] state. 1234 * Transitions: 1235 * SYN_SENT --> ESTABLISHED 1236 * SYN_SENT* --> FIN_WAIT_1 1237 */ 1238 tp->t_starttime = ticks; 1239 if (tp->t_flags & TF_NEEDFIN) { 1240 tp->t_state = TCPS_FIN_WAIT_1; 1241 tp->t_flags &= ~TF_NEEDFIN; 1242 thflags &= ~TH_SYN; 1243 } else { 1244 tp->t_state = TCPS_ESTABLISHED; 1245 callout_reset(tp->tt_keep, tcp_keepidle, 1246 tcp_timer_keep, tp); 1247 } 1248 } else { 1249 /* 1250 * Received initial SYN in SYN-SENT[*] state => 1251 * simultaneous open. If segment contains CC option 1252 * and there is a cached CC, apply TAO test. 1253 * If it succeeds, connection is * half-synchronized. 1254 * Otherwise, do 3-way handshake: 1255 * SYN-SENT -> SYN-RECEIVED 1256 * SYN-SENT* -> SYN-RECEIVED* 1257 * If there was no CC option, clear cached CC value. 1258 */ 1259 tp->t_flags |= TF_ACKNOW; 1260 callout_stop(tp->tt_rexmt); 1261 if (to.to_flags & TOF_CC) { 1262 if (taop->tao_cc != 0 && 1263 CC_GT(to.to_cc, taop->tao_cc)) { 1264 /* 1265 * update cache and make transition: 1266 * SYN-SENT -> ESTABLISHED* 1267 * SYN-SENT* -> FIN-WAIT-1* 1268 */ 1269 taop->tao_cc = to.to_cc; 1270 tp->t_starttime = ticks; 1271 if (tp->t_flags & TF_NEEDFIN) { 1272 tp->t_state = TCPS_FIN_WAIT_1; 1273 tp->t_flags &= ~TF_NEEDFIN; 1274 } else { 1275 tp->t_state = TCPS_ESTABLISHED; 1276 callout_reset(tp->tt_keep, 1277 tcp_keepidle, 1278 tcp_timer_keep, 1279 tp); 1280 } 1281 tp->t_flags |= TF_NEEDSYN; 1282 } else 1283 tp->t_state = TCPS_SYN_RECEIVED; 1284 } else { 1285 /* CC.NEW or no option => invalidate cache */ 1286 taop->tao_cc = 0; 1287 tp->t_state = TCPS_SYN_RECEIVED; 1288 } 1289 } 1290 1291trimthenstep6: 1292 /* 1293 * Advance th->th_seq to correspond to first data byte. 1294 * If data, trim to stay within window, 1295 * dropping FIN if necessary. 1296 */ 1297 th->th_seq++; 1298 if (tlen > tp->rcv_wnd) { 1299 todrop = tlen - tp->rcv_wnd; 1300 m_adj(m, -todrop); 1301 tlen = tp->rcv_wnd; 1302 thflags &= ~TH_FIN; 1303 tcpstat.tcps_rcvpackafterwin++; 1304 tcpstat.tcps_rcvbyteafterwin += todrop; 1305 } 1306 tp->snd_wl1 = th->th_seq - 1; 1307 tp->rcv_up = th->th_seq; 1308 /* 1309 * Client side of transaction: already sent SYN and data. 1310 * If the remote host used T/TCP to validate the SYN, 1311 * our data will be ACK'd; if so, enter normal data segment 1312 * processing in the middle of step 5, ack processing. 1313 * Otherwise, goto step 6. 1314 */ 1315 if (thflags & TH_ACK) 1316 goto process_ACK; 1317 1318 goto step6; 1319 1320 /* 1321 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1322 * if segment contains a SYN and CC [not CC.NEW] option: 1323 * if state == TIME_WAIT and connection duration > MSL, 1324 * drop packet and send RST; 1325 * 1326 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1327 * ack the FIN (and data) in retransmission queue. 1328 * Complete close and delete TCPCB. Then reprocess 1329 * segment, hoping to find new TCPCB in LISTEN state; 1330 * 1331 * else must be old SYN; drop it. 1332 * else do normal processing. 1333 */ 1334 case TCPS_LAST_ACK: 1335 case TCPS_CLOSING: 1336 case TCPS_TIME_WAIT: 1337 if ((thflags & TH_SYN) && 1338 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1339 if (tp->t_state == TCPS_TIME_WAIT && 1340 (ticks - tp->t_starttime) > tcp_msl) { 1341 rstreason = BANDLIM_UNLIMITED; 1342 goto dropwithreset; 1343 } 1344 if (CC_GT(to.to_cc, tp->cc_recv)) { 1345 tp = tcp_close(tp); 1346 goto findpcb; 1347 } 1348 else 1349 goto drop; 1350 } 1351 break; /* continue normal processing */ 1352 } 1353 1354 /* 1355 * States other than LISTEN or SYN_SENT. 1356 * First check the RST flag and sequence number since reset segments 1357 * are exempt from the timestamp and connection count tests. This 1358 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1359 * below which allowed reset segments in half the sequence space 1360 * to fall though and be processed (which gives forged reset 1361 * segments with a random sequence number a 50 percent chance of 1362 * killing a connection). 1363 * Then check timestamp, if present. 1364 * Then check the connection count, if present. 1365 * Then check that at least some bytes of segment are within 1366 * receive window. If segment begins before rcv_nxt, 1367 * drop leading data (and SYN); if nothing left, just ack. 1368 * 1369 * 1370 * If the RST bit is set, check the sequence number to see 1371 * if this is a valid reset segment. 1372 * RFC 793 page 37: 1373 * In all states except SYN-SENT, all reset (RST) segments 1374 * are validated by checking their SEQ-fields. A reset is 1375 * valid if its sequence number is in the window. 1376 * Note: this does not take into account delayed ACKs, so 1377 * we should test against last_ack_sent instead of rcv_nxt. 1378 * The sequence number in the reset segment is normally an 1379 * echo of our outgoing acknowlegement numbers, but some hosts 1380 * send a reset with the sequence number at the rightmost edge 1381 * of our receive window, and we have to handle this case. 1382 * If we have multiple segments in flight, the intial reset 1383 * segment sequence numbers will be to the left of last_ack_sent, 1384 * but they will eventually catch up. 1385 * In any case, it never made sense to trim reset segments to 1386 * fit the receive window since RFC 1122 says: 1387 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1388 * 1389 * A TCP SHOULD allow a received RST segment to include data. 1390 * 1391 * DISCUSSION 1392 * It has been suggested that a RST segment could contain 1393 * ASCII text that encoded and explained the cause of the 1394 * RST. No standard has yet been established for such 1395 * data. 1396 * 1397 * If the reset segment passes the sequence number test examine 1398 * the state: 1399 * SYN_RECEIVED STATE: 1400 * If passive open, return to LISTEN state. 1401 * If active open, inform user that connection was refused. 1402 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1403 * Inform user that connection was reset, and close tcb. 1404 * CLOSING, LAST_ACK STATES: 1405 * Close the tcb. 1406 * TIME_WAIT STATE: 1407 * Drop the segment - see Stevens, vol. 2, p. 964 and 1408 * RFC 1337. 1409 */ 1410 if (thflags & TH_RST) { 1411 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1412 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1413 switch (tp->t_state) { 1414 1415 case TCPS_SYN_RECEIVED: 1416 so->so_error = ECONNREFUSED; 1417 goto close; 1418 1419 case TCPS_ESTABLISHED: 1420 case TCPS_FIN_WAIT_1: 1421 case TCPS_FIN_WAIT_2: 1422 case TCPS_CLOSE_WAIT: 1423 so->so_error = ECONNRESET; 1424 close: 1425 tp->t_state = TCPS_CLOSED; 1426 tcpstat.tcps_drops++; 1427 tp = tcp_close(tp); 1428 break; 1429 1430 case TCPS_CLOSING: 1431 case TCPS_LAST_ACK: 1432 tp = tcp_close(tp); 1433 break; 1434 1435 case TCPS_TIME_WAIT: 1436 break; 1437 } 1438 } 1439 goto drop; 1440 } 1441 1442 /* 1443 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1444 * and it's less than ts_recent, drop it. 1445 */ 1446 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1447 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1448 1449 /* Check to see if ts_recent is over 24 days old. */ 1450 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1451 /* 1452 * Invalidate ts_recent. If this segment updates 1453 * ts_recent, the age will be reset later and ts_recent 1454 * will get a valid value. If it does not, setting 1455 * ts_recent to zero will at least satisfy the 1456 * requirement that zero be placed in the timestamp 1457 * echo reply when ts_recent isn't valid. The 1458 * age isn't reset until we get a valid ts_recent 1459 * because we don't want out-of-order segments to be 1460 * dropped when ts_recent is old. 1461 */ 1462 tp->ts_recent = 0; 1463 } else { 1464 tcpstat.tcps_rcvduppack++; 1465 tcpstat.tcps_rcvdupbyte += tlen; 1466 tcpstat.tcps_pawsdrop++; 1467 goto dropafterack; 1468 } 1469 } 1470 1471 /* 1472 * T/TCP mechanism 1473 * If T/TCP was negotiated and the segment doesn't have CC, 1474 * or if its CC is wrong then drop the segment. 1475 * RST segments do not have to comply with this. 1476 */ 1477 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1478 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1479 goto dropafterack; 1480 1481 /* 1482 * In the SYN-RECEIVED state, validate that the packet belongs to 1483 * this connection before trimming the data to fit the receive 1484 * window. Check the sequence number versus IRS since we know 1485 * the sequence numbers haven't wrapped. This is a partial fix 1486 * for the "LAND" DoS attack. 1487 */ 1488 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1489 rstreason = BANDLIM_RST_OPENPORT; 1490 goto dropwithreset; 1491 } 1492 1493 todrop = tp->rcv_nxt - th->th_seq; 1494 if (todrop > 0) { 1495 if (thflags & TH_SYN) { 1496 thflags &= ~TH_SYN; 1497 th->th_seq++; 1498 if (th->th_urp > 1) 1499 th->th_urp--; 1500 else 1501 thflags &= ~TH_URG; 1502 todrop--; 1503 } 1504 /* 1505 * Following if statement from Stevens, vol. 2, p. 960. 1506 */ 1507 if (todrop > tlen 1508 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1509 /* 1510 * Any valid FIN must be to the left of the window. 1511 * At this point the FIN must be a duplicate or out 1512 * of sequence; drop it. 1513 */ 1514 thflags &= ~TH_FIN; 1515 1516 /* 1517 * Send an ACK to resynchronize and drop any data. 1518 * But keep on processing for RST or ACK. 1519 */ 1520 tp->t_flags |= TF_ACKNOW; 1521 todrop = tlen; 1522 tcpstat.tcps_rcvduppack++; 1523 tcpstat.tcps_rcvdupbyte += todrop; 1524 } else { 1525 tcpstat.tcps_rcvpartduppack++; 1526 tcpstat.tcps_rcvpartdupbyte += todrop; 1527 } 1528 drop_hdrlen += todrop; /* drop from the top afterwards */ 1529 th->th_seq += todrop; 1530 tlen -= todrop; 1531 if (th->th_urp > todrop) 1532 th->th_urp -= todrop; 1533 else { 1534 thflags &= ~TH_URG; 1535 th->th_urp = 0; 1536 } 1537 } 1538 1539 /* 1540 * If new data are received on a connection after the 1541 * user processes are gone, then RST the other end. 1542 */ 1543 if ((so->so_state & SS_NOFDREF) && 1544 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1545 tp = tcp_close(tp); 1546 tcpstat.tcps_rcvafterclose++; 1547 rstreason = BANDLIM_UNLIMITED; 1548 goto dropwithreset; 1549 } 1550 1551 /* 1552 * If segment ends after window, drop trailing data 1553 * (and PUSH and FIN); if nothing left, just ACK. 1554 */ 1555 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1556 if (todrop > 0) { 1557 tcpstat.tcps_rcvpackafterwin++; 1558 if (todrop >= tlen) { 1559 tcpstat.tcps_rcvbyteafterwin += tlen; 1560 /* 1561 * If a new connection request is received 1562 * while in TIME_WAIT, drop the old connection 1563 * and start over if the sequence numbers 1564 * are above the previous ones. 1565 */ 1566 if (thflags & TH_SYN && 1567 tp->t_state == TCPS_TIME_WAIT && 1568 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1569 tp = tcp_close(tp); 1570 goto findpcb; 1571 } 1572 /* 1573 * If window is closed can only take segments at 1574 * window edge, and have to drop data and PUSH from 1575 * incoming segments. Continue processing, but 1576 * remember to ack. Otherwise, drop segment 1577 * and ack. 1578 */ 1579 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1580 tp->t_flags |= TF_ACKNOW; 1581 tcpstat.tcps_rcvwinprobe++; 1582 } else 1583 goto dropafterack; 1584 } else 1585 tcpstat.tcps_rcvbyteafterwin += todrop; 1586 m_adj(m, -todrop); 1587 tlen -= todrop; 1588 thflags &= ~(TH_PUSH|TH_FIN); 1589 } 1590 1591 /* 1592 * If last ACK falls within this segment's sequence numbers, 1593 * record its timestamp. 1594 * NOTE that the test is modified according to the latest 1595 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1596 */ 1597 if ((to.to_flags & TOF_TS) != 0 && 1598 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1599 tp->ts_recent_age = ticks; 1600 tp->ts_recent = to.to_tsval; 1601 } 1602 1603 /* 1604 * If a SYN is in the window, then this is an 1605 * error and we send an RST and drop the connection. 1606 */ 1607 if (thflags & TH_SYN) { 1608 tp = tcp_drop(tp, ECONNRESET); 1609 rstreason = BANDLIM_UNLIMITED; 1610 goto dropwithreset; 1611 } 1612 1613 /* 1614 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1615 * flag is on (half-synchronized state), then queue data for 1616 * later processing; else drop segment and return. 1617 */ 1618 if ((thflags & TH_ACK) == 0) { 1619 if (tp->t_state == TCPS_SYN_RECEIVED || 1620 (tp->t_flags & TF_NEEDSYN)) 1621 goto step6; 1622 else 1623 goto drop; 1624 } 1625 1626 /* 1627 * Ack processing. 1628 */ 1629 switch (tp->t_state) { 1630 1631 /* 1632 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1633 * ESTABLISHED state and continue processing. 1634 * The ACK was checked above. 1635 */ 1636 case TCPS_SYN_RECEIVED: 1637 1638 tcpstat.tcps_connects++; 1639 soisconnected(so); 1640 /* Do window scaling? */ 1641 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1642 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1643 tp->snd_scale = tp->requested_s_scale; 1644 tp->rcv_scale = tp->request_r_scale; 1645 } 1646 /* 1647 * Upon successful completion of 3-way handshake, 1648 * update cache.CC if it was undefined, pass any queued 1649 * data to the user, and advance state appropriately. 1650 */ 1651 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1652 taop->tao_cc == 0) 1653 taop->tao_cc = tp->cc_recv; 1654 1655 /* 1656 * Make transitions: 1657 * SYN-RECEIVED -> ESTABLISHED 1658 * SYN-RECEIVED* -> FIN-WAIT-1 1659 */ 1660 tp->t_starttime = ticks; 1661 if (tp->t_flags & TF_NEEDFIN) { 1662 tp->t_state = TCPS_FIN_WAIT_1; 1663 tp->t_flags &= ~TF_NEEDFIN; 1664 } else { 1665 tp->t_state = TCPS_ESTABLISHED; 1666 callout_reset(tp->tt_keep, tcp_keepidle, 1667 tcp_timer_keep, tp); 1668 } 1669 /* 1670 * If segment contains data or ACK, will call tcp_reass() 1671 * later; if not, do so now to pass queued data to user. 1672 */ 1673 if (tlen == 0 && (thflags & TH_FIN) == 0) 1674 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1675 (struct mbuf *)0); 1676 tp->snd_wl1 = th->th_seq - 1; 1677 /* FALLTHROUGH */ 1678 1679 /* 1680 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1681 * ACKs. If the ack is in the range 1682 * tp->snd_una < th->th_ack <= tp->snd_max 1683 * then advance tp->snd_una to th->th_ack and drop 1684 * data from the retransmission queue. If this ACK reflects 1685 * more up to date window information we update our window information. 1686 */ 1687 case TCPS_ESTABLISHED: 1688 case TCPS_FIN_WAIT_1: 1689 case TCPS_FIN_WAIT_2: 1690 case TCPS_CLOSE_WAIT: 1691 case TCPS_CLOSING: 1692 case TCPS_LAST_ACK: 1693 case TCPS_TIME_WAIT: 1694 1695 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1696 if (tlen == 0 && tiwin == tp->snd_wnd) { 1697 tcpstat.tcps_rcvdupack++; 1698 /* 1699 * If we have outstanding data (other than 1700 * a window probe), this is a completely 1701 * duplicate ack (ie, window info didn't 1702 * change), the ack is the biggest we've 1703 * seen and we've seen exactly our rexmt 1704 * threshhold of them, assume a packet 1705 * has been dropped and retransmit it. 1706 * Kludge snd_nxt & the congestion 1707 * window so we send only this one 1708 * packet. 1709 * 1710 * We know we're losing at the current 1711 * window size so do congestion avoidance 1712 * (set ssthresh to half the current window 1713 * and pull our congestion window back to 1714 * the new ssthresh). 1715 * 1716 * Dup acks mean that packets have left the 1717 * network (they're now cached at the receiver) 1718 * so bump cwnd by the amount in the receiver 1719 * to keep a constant cwnd packets in the 1720 * network. 1721 */ 1722 if (!callout_active(tp->tt_rexmt) || 1723 th->th_ack != tp->snd_una) 1724 tp->t_dupacks = 0; 1725 else if (++tp->t_dupacks == tcprexmtthresh) { 1726 tcp_seq onxt = tp->snd_nxt; 1727 u_int win = 1728 min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1729 tp->t_maxseg; 1730 if (tcp_do_newreno && 1731 SEQ_LT(th->th_ack, 1732 tp->snd_recover)) { 1733 /* False retransmit, should not 1734 * cut window 1735 */ 1736 tp->snd_cwnd += tp->t_maxseg; 1737 tp->t_dupacks = 0; 1738 (void) tcp_output(tp); 1739 goto drop; 1740 } 1741 if (win < 2) 1742 win = 2; 1743 tp->snd_ssthresh = win * tp->t_maxseg; 1744 tp->snd_recover = tp->snd_max; 1745 callout_stop(tp->tt_rexmt); 1746 tp->t_rtttime = 0; 1747 tp->snd_nxt = th->th_ack; 1748 tp->snd_cwnd = tp->t_maxseg; 1749 (void) tcp_output(tp); 1750 tp->snd_cwnd = tp->snd_ssthresh + 1751 tp->t_maxseg * tp->t_dupacks; 1752 if (SEQ_GT(onxt, tp->snd_nxt)) 1753 tp->snd_nxt = onxt; 1754 goto drop; 1755 } else if (tp->t_dupacks > tcprexmtthresh) { 1756 tp->snd_cwnd += tp->t_maxseg; 1757 (void) tcp_output(tp); 1758 goto drop; 1759 } 1760 } else 1761 tp->t_dupacks = 0; 1762 break; 1763 } 1764 /* 1765 * If the congestion window was inflated to account 1766 * for the other side's cached packets, retract it. 1767 */ 1768 if (tcp_do_newreno) { 1769 int is_partialack = SEQ_LT(th->th_ack, tp->snd_recover); 1770 if (tp->t_dupacks >= tcprexmtthresh) { 1771 if (is_partialack) { 1772 tcp_newreno_partial_ack(tp, th); 1773 } else { 1774 /* 1775 * Window inflation should have left us 1776 * with approximately snd_ssthresh 1777 * outstanding data. 1778 * But in case we would be inclined to 1779 * send a burst, better to do it via 1780 * the slow start mechanism. 1781 */ 1782 if (SEQ_GT(th->th_ack + 1783 tp->snd_ssthresh, 1784 tp->snd_max)) 1785 tp->snd_cwnd = tp->snd_max - 1786 th->th_ack + 1787 tp->t_maxseg; 1788 else 1789 tp->snd_cwnd = tp->snd_ssthresh; 1790 } 1791 } 1792 /* 1793 * Reset dupacks, except on partial acks in 1794 * fast recovery. 1795 */ 1796 if (!(tp->t_dupacks >= tcprexmtthresh && is_partialack)) 1797 tp->t_dupacks = 0; 1798 } else { 1799 if (tp->t_dupacks >= tcprexmtthresh && 1800 tp->snd_cwnd > tp->snd_ssthresh) 1801 tp->snd_cwnd = tp->snd_ssthresh; 1802 tp->t_dupacks = 0; 1803 } 1804 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1805 tcpstat.tcps_rcvacktoomuch++; 1806 goto dropafterack; 1807 } 1808 /* 1809 * If we reach this point, ACK is not a duplicate, 1810 * i.e., it ACKs something we sent. 1811 */ 1812 if (tp->t_flags & TF_NEEDSYN) { 1813 /* 1814 * T/TCP: Connection was half-synchronized, and our 1815 * SYN has been ACK'd (so connection is now fully 1816 * synchronized). Go to non-starred state, 1817 * increment snd_una for ACK of SYN, and check if 1818 * we can do window scaling. 1819 */ 1820 tp->t_flags &= ~TF_NEEDSYN; 1821 tp->snd_una++; 1822 /* Do window scaling? */ 1823 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1824 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1825 tp->snd_scale = tp->requested_s_scale; 1826 tp->rcv_scale = tp->request_r_scale; 1827 } 1828 } 1829 1830process_ACK: 1831 acked = th->th_ack - tp->snd_una; 1832 tcpstat.tcps_rcvackpack++; 1833 tcpstat.tcps_rcvackbyte += acked; 1834 1835 /* 1836 * If we just performed our first retransmit, and the ACK 1837 * arrives within our recovery window, then it was a mistake 1838 * to do the retransmit in the first place. Recover our 1839 * original cwnd and ssthresh, and proceed to transmit where 1840 * we left off. 1841 */ 1842 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1843 ++tcpstat.tcps_sndrexmitbad; 1844 tp->snd_cwnd = tp->snd_cwnd_prev; 1845 tp->snd_ssthresh = tp->snd_ssthresh_prev; 1846 tp->snd_nxt = tp->snd_max; 1847 tp->t_badrxtwin = 0; /* XXX probably not required */ 1848 } 1849 1850 /* 1851 * If we have a timestamp reply, update smoothed 1852 * round trip time. If no timestamp is present but 1853 * transmit timer is running and timed sequence 1854 * number was acked, update smoothed round trip time. 1855 * Since we now have an rtt measurement, cancel the 1856 * timer backoff (cf., Phil Karn's retransmit alg.). 1857 * Recompute the initial retransmit timer. 1858 * 1859 * Some boxes send broken timestamp replies 1860 * during the SYN+ACK phase, ignore 1861 * timestamps of 0 or we could calculate a 1862 * huge RTT and blow up the retransmit timer. 1863 */ 1864 if ((to.to_flags & TOF_TS) != 0 && 1865 to.to_tsecr) { 1866 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1867 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 1868 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1869 } 1870 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1871 1872 /* 1873 * If all outstanding data is acked, stop retransmit 1874 * timer and remember to restart (more output or persist). 1875 * If there is more data to be acked, restart retransmit 1876 * timer, using current (possibly backed-off) value. 1877 */ 1878 if (th->th_ack == tp->snd_max) { 1879 callout_stop(tp->tt_rexmt); 1880 needoutput = 1; 1881 } else if (!callout_active(tp->tt_persist)) 1882 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1883 tcp_timer_rexmt, tp); 1884 1885 /* 1886 * If no data (only SYN) was ACK'd, 1887 * skip rest of ACK processing. 1888 */ 1889 if (acked == 0) 1890 goto step6; 1891 1892 /* 1893 * When new data is acked, open the congestion window. 1894 * If the window gives us less than ssthresh packets 1895 * in flight, open exponentially (maxseg per packet). 1896 * Otherwise open linearly: maxseg per window 1897 * (maxseg^2 / cwnd per packet). 1898 */ 1899 { 1900 register u_int cw = tp->snd_cwnd; 1901 register u_int incr = tp->t_maxseg; 1902 1903 if (cw > tp->snd_ssthresh) 1904 incr = incr * incr / cw; 1905 /* 1906 * If t_dupacks != 0 here, it indicates that we are still 1907 * in NewReno fast recovery mode, so we leave the congestion 1908 * window alone. 1909 */ 1910 if (!tcp_do_newreno || tp->t_dupacks == 0) 1911 tp->snd_cwnd = min(cw + incr,TCP_MAXWIN<<tp->snd_scale); 1912 } 1913 if (acked > so->so_snd.sb_cc) { 1914 tp->snd_wnd -= so->so_snd.sb_cc; 1915 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1916 ourfinisacked = 1; 1917 } else { 1918 sbdrop(&so->so_snd, acked); 1919 tp->snd_wnd -= acked; 1920 ourfinisacked = 0; 1921 } 1922 sowwakeup(so); 1923 tp->snd_una = th->th_ack; 1924 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1925 tp->snd_nxt = tp->snd_una; 1926 1927 switch (tp->t_state) { 1928 1929 /* 1930 * In FIN_WAIT_1 STATE in addition to the processing 1931 * for the ESTABLISHED state if our FIN is now acknowledged 1932 * then enter FIN_WAIT_2. 1933 */ 1934 case TCPS_FIN_WAIT_1: 1935 if (ourfinisacked) { 1936 /* 1937 * If we can't receive any more 1938 * data, then closing user can proceed. 1939 * Starting the timer is contrary to the 1940 * specification, but if we don't get a FIN 1941 * we'll hang forever. 1942 */ 1943 if (so->so_state & SS_CANTRCVMORE) { 1944 soisdisconnected(so); 1945 callout_reset(tp->tt_2msl, tcp_maxidle, 1946 tcp_timer_2msl, tp); 1947 } 1948 tp->t_state = TCPS_FIN_WAIT_2; 1949 } 1950 break; 1951 1952 /* 1953 * In CLOSING STATE in addition to the processing for 1954 * the ESTABLISHED state if the ACK acknowledges our FIN 1955 * then enter the TIME-WAIT state, otherwise ignore 1956 * the segment. 1957 */ 1958 case TCPS_CLOSING: 1959 if (ourfinisacked) { 1960 tp->t_state = TCPS_TIME_WAIT; 1961 tcp_canceltimers(tp); 1962 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1963 if (tp->cc_recv != 0 && 1964 (ticks - tp->t_starttime) < tcp_msl) 1965 callout_reset(tp->tt_2msl, 1966 tp->t_rxtcur * 1967 TCPTV_TWTRUNC, 1968 tcp_timer_2msl, tp); 1969 else 1970 callout_reset(tp->tt_2msl, 2 * tcp_msl, 1971 tcp_timer_2msl, tp); 1972 soisdisconnected(so); 1973 } 1974 break; 1975 1976 /* 1977 * In LAST_ACK, we may still be waiting for data to drain 1978 * and/or to be acked, as well as for the ack of our FIN. 1979 * If our FIN is now acknowledged, delete the TCB, 1980 * enter the closed state and return. 1981 */ 1982 case TCPS_LAST_ACK: 1983 if (ourfinisacked) { 1984 tp = tcp_close(tp); 1985 goto drop; 1986 } 1987 break; 1988 1989 /* 1990 * In TIME_WAIT state the only thing that should arrive 1991 * is a retransmission of the remote FIN. Acknowledge 1992 * it and restart the finack timer. 1993 */ 1994 case TCPS_TIME_WAIT: 1995 callout_reset(tp->tt_2msl, 2 * tcp_msl, 1996 tcp_timer_2msl, tp); 1997 goto dropafterack; 1998 } 1999 } 2000 2001step6: 2002 /* 2003 * Update window information. 2004 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2005 */ 2006 if ((thflags & TH_ACK) && 2007 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2008 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2009 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2010 /* keep track of pure window updates */ 2011 if (tlen == 0 && 2012 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2013 tcpstat.tcps_rcvwinupd++; 2014 tp->snd_wnd = tiwin; 2015 tp->snd_wl1 = th->th_seq; 2016 tp->snd_wl2 = th->th_ack; 2017 if (tp->snd_wnd > tp->max_sndwnd) 2018 tp->max_sndwnd = tp->snd_wnd; 2019 needoutput = 1; 2020 } 2021 2022 /* 2023 * Process segments with URG. 2024 */ 2025 if ((thflags & TH_URG) && th->th_urp && 2026 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2027 /* 2028 * This is a kludge, but if we receive and accept 2029 * random urgent pointers, we'll crash in 2030 * soreceive. It's hard to imagine someone 2031 * actually wanting to send this much urgent data. 2032 */ 2033 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2034 th->th_urp = 0; /* XXX */ 2035 thflags &= ~TH_URG; /* XXX */ 2036 goto dodata; /* XXX */ 2037 } 2038 /* 2039 * If this segment advances the known urgent pointer, 2040 * then mark the data stream. This should not happen 2041 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2042 * a FIN has been received from the remote side. 2043 * In these states we ignore the URG. 2044 * 2045 * According to RFC961 (Assigned Protocols), 2046 * the urgent pointer points to the last octet 2047 * of urgent data. We continue, however, 2048 * to consider it to indicate the first octet 2049 * of data past the urgent section as the original 2050 * spec states (in one of two places). 2051 */ 2052 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2053 tp->rcv_up = th->th_seq + th->th_urp; 2054 so->so_oobmark = so->so_rcv.sb_cc + 2055 (tp->rcv_up - tp->rcv_nxt) - 1; 2056 if (so->so_oobmark == 0) 2057 so->so_state |= SS_RCVATMARK; 2058 sohasoutofband(so); 2059 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2060 } 2061 /* 2062 * Remove out of band data so doesn't get presented to user. 2063 * This can happen independent of advancing the URG pointer, 2064 * but if two URG's are pending at once, some out-of-band 2065 * data may creep in... ick. 2066 */ 2067 if (th->th_urp <= (u_long)tlen && 2068 !(so->so_options & SO_OOBINLINE)) { 2069 /* hdr drop is delayed */ 2070 tcp_pulloutofband(so, th, m, drop_hdrlen); 2071 } 2072 } else { 2073 /* 2074 * If no out of band data is expected, 2075 * pull receive urgent pointer along 2076 * with the receive window. 2077 */ 2078 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2079 tp->rcv_up = tp->rcv_nxt; 2080 } 2081dodata: /* XXX */ 2082 KASSERT(headlocked, ("headlocked")); 2083 INP_INFO_WUNLOCK(&tcbinfo); 2084 headlocked = 0; 2085 /* 2086 * Process the segment text, merging it into the TCP sequencing queue, 2087 * and arranging for acknowledgment of receipt if necessary. 2088 * This process logically involves adjusting tp->rcv_wnd as data 2089 * is presented to the user (this happens in tcp_usrreq.c, 2090 * case PRU_RCVD). If a FIN has already been received on this 2091 * connection then we just ignore the text. 2092 */ 2093 if ((tlen || (thflags & TH_FIN)) && 2094 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2095 m_adj(m, drop_hdrlen); /* delayed header drop */ 2096 /* 2097 * Insert segment which includes th into TCP reassembly queue 2098 * with control block tp. Set thflags to whether reassembly now 2099 * includes a segment with FIN. This handles the common case 2100 * inline (segment is the next to be received on an established 2101 * connection, and the queue is empty), avoiding linkage into 2102 * and removal from the queue and repetition of various 2103 * conversions. 2104 * Set DELACK for segments received in order, but ack 2105 * immediately when segments are out of order (so 2106 * fast retransmit can work). 2107 */ 2108 if (th->th_seq == tp->rcv_nxt && 2109 LIST_EMPTY(&tp->t_segq) && 2110 TCPS_HAVEESTABLISHED(tp->t_state)) { 2111 if (DELAY_ACK(tp)) 2112 callout_reset(tp->tt_delack, tcp_delacktime, 2113 tcp_timer_delack, tp); 2114 else 2115 tp->t_flags |= TF_ACKNOW; 2116 tp->rcv_nxt += tlen; 2117 thflags = th->th_flags & TH_FIN; 2118 tcpstat.tcps_rcvpack++; 2119 tcpstat.tcps_rcvbyte += tlen; 2120 ND6_HINT(tp); 2121 if (so->so_state & SS_CANTRCVMORE) 2122 m_freem(m); 2123 else 2124 sbappend(&so->so_rcv, m); 2125 sorwakeup(so); 2126 } else { 2127 thflags = tcp_reass(tp, th, &tlen, m); 2128 tp->t_flags |= TF_ACKNOW; 2129 } 2130 2131 /* 2132 * Note the amount of data that peer has sent into 2133 * our window, in order to estimate the sender's 2134 * buffer size. 2135 */ 2136 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2137 } else { 2138 m_freem(m); 2139 thflags &= ~TH_FIN; 2140 } 2141 2142 /* 2143 * If FIN is received ACK the FIN and let the user know 2144 * that the connection is closing. 2145 */ 2146 if (thflags & TH_FIN) { 2147 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2148 socantrcvmore(so); 2149 /* 2150 * If connection is half-synchronized 2151 * (ie NEEDSYN flag on) then delay ACK, 2152 * so it may be piggybacked when SYN is sent. 2153 * Otherwise, since we received a FIN then no 2154 * more input can be expected, send ACK now. 2155 */ 2156 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2157 callout_reset(tp->tt_delack, tcp_delacktime, 2158 tcp_timer_delack, tp); 2159 else 2160 tp->t_flags |= TF_ACKNOW; 2161 tp->rcv_nxt++; 2162 } 2163 switch (tp->t_state) { 2164 2165 /* 2166 * In SYN_RECEIVED and ESTABLISHED STATES 2167 * enter the CLOSE_WAIT state. 2168 */ 2169 case TCPS_SYN_RECEIVED: 2170 tp->t_starttime = ticks; 2171 /*FALLTHROUGH*/ 2172 case TCPS_ESTABLISHED: 2173 tp->t_state = TCPS_CLOSE_WAIT; 2174 break; 2175 2176 /* 2177 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2178 * enter the CLOSING state. 2179 */ 2180 case TCPS_FIN_WAIT_1: 2181 tp->t_state = TCPS_CLOSING; 2182 break; 2183 2184 /* 2185 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2186 * starting the time-wait timer, turning off the other 2187 * standard timers. 2188 */ 2189 case TCPS_FIN_WAIT_2: 2190 tp->t_state = TCPS_TIME_WAIT; 2191 tcp_canceltimers(tp); 2192 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2193 if (tp->cc_recv != 0 && 2194 (ticks - tp->t_starttime) < tcp_msl) { 2195 callout_reset(tp->tt_2msl, 2196 tp->t_rxtcur * TCPTV_TWTRUNC, 2197 tcp_timer_2msl, tp); 2198 /* For transaction client, force ACK now. */ 2199 tp->t_flags |= TF_ACKNOW; 2200 } 2201 else 2202 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2203 tcp_timer_2msl, tp); 2204 soisdisconnected(so); 2205 break; 2206 2207 /* 2208 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2209 */ 2210 case TCPS_TIME_WAIT: 2211 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2212 tcp_timer_2msl, tp); 2213 break; 2214 } 2215 } 2216#ifdef TCPDEBUG 2217 if (so->so_options & SO_DEBUG) 2218 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2219 &tcp_savetcp, 0); 2220#endif 2221 2222 /* 2223 * Return any desired output. 2224 */ 2225 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2226 (void) tcp_output(tp); 2227 INP_UNLOCK(inp); 2228 return; 2229 2230dropafterack: 2231 /* 2232 * Generate an ACK dropping incoming segment if it occupies 2233 * sequence space, where the ACK reflects our state. 2234 * 2235 * We can now skip the test for the RST flag since all 2236 * paths to this code happen after packets containing 2237 * RST have been dropped. 2238 * 2239 * In the SYN-RECEIVED state, don't send an ACK unless the 2240 * segment we received passes the SYN-RECEIVED ACK test. 2241 * If it fails send a RST. This breaks the loop in the 2242 * "LAND" DoS attack, and also prevents an ACK storm 2243 * between two listening ports that have been sent forged 2244 * SYN segments, each with the source address of the other. 2245 */ 2246 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2247 (SEQ_GT(tp->snd_una, th->th_ack) || 2248 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2249 rstreason = BANDLIM_RST_OPENPORT; 2250 goto dropwithreset; 2251 } 2252#ifdef TCPDEBUG 2253 if (so->so_options & SO_DEBUG) 2254 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2255 &tcp_savetcp, 0); 2256#endif 2257 if (headlocked) 2258 INP_INFO_WUNLOCK(&tcbinfo); 2259 m_freem(m); 2260 tp->t_flags |= TF_ACKNOW; 2261 (void) tcp_output(tp); 2262 INP_UNLOCK(inp); 2263 return; 2264 2265dropwithreset: 2266 /* 2267 * Generate a RST, dropping incoming segment. 2268 * Make ACK acceptable to originator of segment. 2269 * Don't bother to respond if destination was broadcast/multicast. 2270 */ 2271 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2272 goto drop; 2273 if (isipv6) { 2274 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2275 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2276 goto drop; 2277 } else { 2278 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2279 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2280 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2281 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2282 goto drop; 2283 } 2284 /* IPv6 anycast check is done at tcp6_input() */ 2285 2286 /* 2287 * Perform bandwidth limiting. 2288 */ 2289 if (badport_bandlim(rstreason) < 0) 2290 goto drop; 2291 2292#ifdef TCPDEBUG 2293 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2294 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2295 &tcp_savetcp, 0); 2296#endif 2297 2298 if (tp) 2299 INP_UNLOCK(inp); 2300 2301 if (thflags & TH_ACK) 2302 /* mtod() below is safe as long as hdr dropping is delayed */ 2303 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2304 TH_RST); 2305 else { 2306 if (thflags & TH_SYN) 2307 tlen++; 2308 /* mtod() below is safe as long as hdr dropping is delayed */ 2309 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2310 (tcp_seq)0, TH_RST|TH_ACK); 2311 } 2312 if (headlocked) 2313 INP_INFO_WUNLOCK(&tcbinfo); 2314 return; 2315 2316drop: 2317 /* 2318 * Drop space held by incoming segment and return. 2319 */ 2320#ifdef TCPDEBUG 2321 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2322 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2323 &tcp_savetcp, 0); 2324#endif 2325 if (tp) 2326 INP_UNLOCK(inp); 2327 m_freem(m); 2328 if (headlocked) 2329 INP_INFO_WUNLOCK(&tcbinfo); 2330 return; 2331} 2332 2333/* 2334 * Parse TCP options and place in tcpopt. 2335 */ 2336static void 2337tcp_dooptions(to, cp, cnt, is_syn) 2338 struct tcpopt *to; 2339 u_char *cp; 2340 int cnt; 2341{ 2342 int opt, optlen; 2343 2344 to->to_flags = 0; 2345 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2346 opt = cp[0]; 2347 if (opt == TCPOPT_EOL) 2348 break; 2349 if (opt == TCPOPT_NOP) 2350 optlen = 1; 2351 else { 2352 if (cnt < 2) 2353 break; 2354 optlen = cp[1]; 2355 if (optlen < 2 || optlen > cnt) 2356 break; 2357 } 2358 switch (opt) { 2359 case TCPOPT_MAXSEG: 2360 if (optlen != TCPOLEN_MAXSEG) 2361 continue; 2362 if (!is_syn) 2363 continue; 2364 to->to_flags |= TOF_MSS; 2365 bcopy((char *)cp + 2, 2366 (char *)&to->to_mss, sizeof(to->to_mss)); 2367 to->to_mss = ntohs(to->to_mss); 2368 break; 2369 case TCPOPT_WINDOW: 2370 if (optlen != TCPOLEN_WINDOW) 2371 continue; 2372 if (! is_syn) 2373 continue; 2374 to->to_flags |= TOF_SCALE; 2375 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2376 break; 2377 case TCPOPT_TIMESTAMP: 2378 if (optlen != TCPOLEN_TIMESTAMP) 2379 continue; 2380 to->to_flags |= TOF_TS; 2381 bcopy((char *)cp + 2, 2382 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2383 to->to_tsval = ntohl(to->to_tsval); 2384 bcopy((char *)cp + 6, 2385 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2386 to->to_tsecr = ntohl(to->to_tsecr); 2387 break; 2388 case TCPOPT_CC: 2389 if (optlen != TCPOLEN_CC) 2390 continue; 2391 to->to_flags |= TOF_CC; 2392 bcopy((char *)cp + 2, 2393 (char *)&to->to_cc, sizeof(to->to_cc)); 2394 to->to_cc = ntohl(to->to_cc); 2395 break; 2396 case TCPOPT_CCNEW: 2397 if (optlen != TCPOLEN_CC) 2398 continue; 2399 if (!is_syn) 2400 continue; 2401 to->to_flags |= TOF_CCNEW; 2402 bcopy((char *)cp + 2, 2403 (char *)&to->to_cc, sizeof(to->to_cc)); 2404 to->to_cc = ntohl(to->to_cc); 2405 break; 2406 case TCPOPT_CCECHO: 2407 if (optlen != TCPOLEN_CC) 2408 continue; 2409 if (!is_syn) 2410 continue; 2411 to->to_flags |= TOF_CCECHO; 2412 bcopy((char *)cp + 2, 2413 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2414 to->to_ccecho = ntohl(to->to_ccecho); 2415 break; 2416 default: 2417 continue; 2418 } 2419 } 2420} 2421 2422/* 2423 * Pull out of band byte out of a segment so 2424 * it doesn't appear in the user's data queue. 2425 * It is still reflected in the segment length for 2426 * sequencing purposes. 2427 */ 2428static void 2429tcp_pulloutofband(so, th, m, off) 2430 struct socket *so; 2431 struct tcphdr *th; 2432 register struct mbuf *m; 2433 int off; /* delayed to be droped hdrlen */ 2434{ 2435 int cnt = off + th->th_urp - 1; 2436 2437 while (cnt >= 0) { 2438 if (m->m_len > cnt) { 2439 char *cp = mtod(m, caddr_t) + cnt; 2440 struct tcpcb *tp = sototcpcb(so); 2441 2442 tp->t_iobc = *cp; 2443 tp->t_oobflags |= TCPOOB_HAVEDATA; 2444 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2445 m->m_len--; 2446 if (m->m_flags & M_PKTHDR) 2447 m->m_pkthdr.len--; 2448 return; 2449 } 2450 cnt -= m->m_len; 2451 m = m->m_next; 2452 if (m == 0) 2453 break; 2454 } 2455 panic("tcp_pulloutofband"); 2456} 2457 2458/* 2459 * Collect new round-trip time estimate 2460 * and update averages and current timeout. 2461 */ 2462static void 2463tcp_xmit_timer(tp, rtt) 2464 register struct tcpcb *tp; 2465 int rtt; 2466{ 2467 register int delta; 2468 2469 tcpstat.tcps_rttupdated++; 2470 tp->t_rttupdated++; 2471 if (tp->t_srtt != 0) { 2472 /* 2473 * srtt is stored as fixed point with 5 bits after the 2474 * binary point (i.e., scaled by 8). The following magic 2475 * is equivalent to the smoothing algorithm in rfc793 with 2476 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2477 * point). Adjust rtt to origin 0. 2478 */ 2479 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2480 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2481 2482 if ((tp->t_srtt += delta) <= 0) 2483 tp->t_srtt = 1; 2484 2485 /* 2486 * We accumulate a smoothed rtt variance (actually, a 2487 * smoothed mean difference), then set the retransmit 2488 * timer to smoothed rtt + 4 times the smoothed variance. 2489 * rttvar is stored as fixed point with 4 bits after the 2490 * binary point (scaled by 16). The following is 2491 * equivalent to rfc793 smoothing with an alpha of .75 2492 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2493 * rfc793's wired-in beta. 2494 */ 2495 if (delta < 0) 2496 delta = -delta; 2497 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2498 if ((tp->t_rttvar += delta) <= 0) 2499 tp->t_rttvar = 1; 2500 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2501 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2502 } else { 2503 /* 2504 * No rtt measurement yet - use the unsmoothed rtt. 2505 * Set the variance to half the rtt (so our first 2506 * retransmit happens at 3*rtt). 2507 */ 2508 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2509 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2510 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2511 } 2512 tp->t_rtttime = 0; 2513 tp->t_rxtshift = 0; 2514 2515 /* 2516 * the retransmit should happen at rtt + 4 * rttvar. 2517 * Because of the way we do the smoothing, srtt and rttvar 2518 * will each average +1/2 tick of bias. When we compute 2519 * the retransmit timer, we want 1/2 tick of rounding and 2520 * 1 extra tick because of +-1/2 tick uncertainty in the 2521 * firing of the timer. The bias will give us exactly the 2522 * 1.5 tick we need. But, because the bias is 2523 * statistical, we have to test that we don't drop below 2524 * the minimum feasible timer (which is 2 ticks). 2525 */ 2526 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2527 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2528 2529 /* 2530 * We received an ack for a packet that wasn't retransmitted; 2531 * it is probably safe to discard any error indications we've 2532 * received recently. This isn't quite right, but close enough 2533 * for now (a route might have failed after we sent a segment, 2534 * and the return path might not be symmetrical). 2535 */ 2536 tp->t_softerror = 0; 2537} 2538 2539/* 2540 * Determine a reasonable value for maxseg size. 2541 * If the route is known, check route for mtu. 2542 * If none, use an mss that can be handled on the outgoing 2543 * interface without forcing IP to fragment; if bigger than 2544 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2545 * to utilize large mbufs. If no route is found, route has no mtu, 2546 * or the destination isn't local, use a default, hopefully conservative 2547 * size (usually 512 or the default IP max size, but no more than the mtu 2548 * of the interface), as we can't discover anything about intervening 2549 * gateways or networks. We also initialize the congestion/slow start 2550 * window to be a single segment if the destination isn't local. 2551 * While looking at the routing entry, we also initialize other path-dependent 2552 * parameters from pre-set or cached values in the routing entry. 2553 * 2554 * Also take into account the space needed for options that we 2555 * send regularly. Make maxseg shorter by that amount to assure 2556 * that we can send maxseg amount of data even when the options 2557 * are present. Store the upper limit of the length of options plus 2558 * data in maxopd. 2559 * 2560 * NOTE that this routine is only called when we process an incoming 2561 * segment, for outgoing segments only tcp_mssopt is called. 2562 * 2563 * In case of T/TCP, we call this routine during implicit connection 2564 * setup as well (offer = -1), to initialize maxseg from the cached 2565 * MSS of our peer. 2566 */ 2567void 2568tcp_mss(tp, offer) 2569 struct tcpcb *tp; 2570 int offer; 2571{ 2572 register struct rtentry *rt; 2573 struct ifnet *ifp; 2574 register int rtt, mss; 2575 u_long bufsize; 2576 struct inpcb *inp = tp->t_inpcb; 2577 struct socket *so; 2578 struct rmxp_tao *taop; 2579 int origoffer = offer; 2580#ifdef INET6 2581 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2582 size_t min_protoh = isipv6 ? 2583 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2584 sizeof (struct tcpiphdr); 2585#else 2586 const int isipv6 = 0; 2587 const size_t min_protoh = sizeof (struct tcpiphdr); 2588#endif 2589 2590 if (isipv6) 2591 rt = tcp_rtlookup6(&inp->inp_inc); 2592 else 2593 rt = tcp_rtlookup(&inp->inp_inc); 2594 if (rt == NULL) { 2595 tp->t_maxopd = tp->t_maxseg = 2596 isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2597 return; 2598 } 2599 ifp = rt->rt_ifp; 2600 so = inp->inp_socket; 2601 2602 taop = rmx_taop(rt->rt_rmx); 2603 /* 2604 * Offer == -1 means that we didn't receive SYN yet, 2605 * use cached value in that case; 2606 */ 2607 if (offer == -1) 2608 offer = taop->tao_mssopt; 2609 /* 2610 * Offer == 0 means that there was no MSS on the SYN segment, 2611 * in this case we use tcp_mssdflt. 2612 */ 2613 if (offer == 0) 2614 offer = isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2615 else 2616 /* 2617 * Sanity check: make sure that maxopd will be large 2618 * enough to allow some data on segments even is the 2619 * all the option space is used (40bytes). Otherwise 2620 * funny things may happen in tcp_output. 2621 */ 2622 offer = max(offer, 64); 2623 taop->tao_mssopt = offer; 2624 2625 /* 2626 * While we're here, check if there's an initial rtt 2627 * or rttvar. Convert from the route-table units 2628 * to scaled multiples of the slow timeout timer. 2629 */ 2630 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2631 /* 2632 * XXX the lock bit for RTT indicates that the value 2633 * is also a minimum value; this is subject to time. 2634 */ 2635 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2636 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2637 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2638 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2639 tcpstat.tcps_usedrtt++; 2640 if (rt->rt_rmx.rmx_rttvar) { 2641 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2642 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2643 tcpstat.tcps_usedrttvar++; 2644 } else { 2645 /* default variation is +- 1 rtt */ 2646 tp->t_rttvar = 2647 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2648 } 2649 TCPT_RANGESET(tp->t_rxtcur, 2650 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2651 tp->t_rttmin, TCPTV_REXMTMAX); 2652 } 2653 /* 2654 * if there's an mtu associated with the route, use it 2655 * else, use the link mtu. 2656 */ 2657 if (rt->rt_rmx.rmx_mtu) 2658 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2659 else { 2660 if (isipv6) { 2661 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2662 min_protoh; 2663 if (!in6_localaddr(&inp->in6p_faddr)) 2664 mss = min(mss, tcp_v6mssdflt); 2665 } else { 2666 mss = ifp->if_mtu - min_protoh; 2667 if (!in_localaddr(inp->inp_faddr)) 2668 mss = min(mss, tcp_mssdflt); 2669 } 2670 } 2671 mss = min(mss, offer); 2672 /* 2673 * maxopd stores the maximum length of data AND options 2674 * in a segment; maxseg is the amount of data in a normal 2675 * segment. We need to store this value (maxopd) apart 2676 * from maxseg, because now every segment carries options 2677 * and thus we normally have somewhat less data in segments. 2678 */ 2679 tp->t_maxopd = mss; 2680 2681 /* 2682 * In case of T/TCP, origoffer==-1 indicates, that no segments 2683 * were received yet. In this case we just guess, otherwise 2684 * we do the same as before T/TCP. 2685 */ 2686 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2687 (origoffer == -1 || 2688 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2689 mss -= TCPOLEN_TSTAMP_APPA; 2690 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2691 (origoffer == -1 || 2692 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2693 mss -= TCPOLEN_CC_APPA; 2694 2695#if (MCLBYTES & (MCLBYTES - 1)) == 0 2696 if (mss > MCLBYTES) 2697 mss &= ~(MCLBYTES-1); 2698#else 2699 if (mss > MCLBYTES) 2700 mss = mss / MCLBYTES * MCLBYTES; 2701#endif 2702 /* 2703 * If there's a pipesize, change the socket buffer 2704 * to that size. Make the socket buffers an integral 2705 * number of mss units; if the mss is larger than 2706 * the socket buffer, decrease the mss. 2707 */ 2708#ifdef RTV_SPIPE 2709 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2710#endif 2711 bufsize = so->so_snd.sb_hiwat; 2712 if (bufsize < mss) 2713 mss = bufsize; 2714 else { 2715 bufsize = roundup(bufsize, mss); 2716 if (bufsize > sb_max) 2717 bufsize = sb_max; 2718 if (bufsize > so->so_snd.sb_hiwat) 2719 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2720 } 2721 tp->t_maxseg = mss; 2722 2723#ifdef RTV_RPIPE 2724 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2725#endif 2726 bufsize = so->so_rcv.sb_hiwat; 2727 if (bufsize > mss) { 2728 bufsize = roundup(bufsize, mss); 2729 if (bufsize > sb_max) 2730 bufsize = sb_max; 2731 if (bufsize > so->so_rcv.sb_hiwat) 2732 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2733 } 2734 2735 /* 2736 * Set the slow-start flight size depending on whether this 2737 * is a local network or not. 2738 */ 2739 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2740 (!isipv6 && in_localaddr(inp->inp_faddr))) 2741 tp->snd_cwnd = mss * ss_fltsz_local; 2742 else 2743 tp->snd_cwnd = mss * ss_fltsz; 2744 2745 if (rt->rt_rmx.rmx_ssthresh) { 2746 /* 2747 * There's some sort of gateway or interface 2748 * buffer limit on the path. Use this to set 2749 * the slow start threshhold, but set the 2750 * threshold to no less than 2*mss. 2751 */ 2752 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2753 tcpstat.tcps_usedssthresh++; 2754 } 2755} 2756 2757/* 2758 * Determine the MSS option to send on an outgoing SYN. 2759 */ 2760int 2761tcp_mssopt(tp) 2762 struct tcpcb *tp; 2763{ 2764 struct rtentry *rt; 2765#ifdef INET6 2766 int isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2767 size_t min_protoh = isipv6 ? 2768 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2769 sizeof (struct tcpiphdr); 2770#else 2771 const int isipv6 = 0; 2772 const size_t min_protoh = sizeof (struct tcpiphdr); 2773#endif 2774 2775 if (isipv6) 2776 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 2777 else 2778 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 2779 if (rt == NULL) 2780 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2781 2782 return (rt->rt_ifp->if_mtu - min_protoh); 2783} 2784 2785 2786/* 2787 * On a partial ack arrives, force the retransmission of the 2788 * next unacknowledged segment. Do not clear tp->t_dupacks. 2789 * By setting snd_nxt to ti_ack, this forces retransmission timer to 2790 * be started again. 2791 */ 2792static void 2793tcp_newreno_partial_ack(tp, th) 2794 struct tcpcb *tp; 2795 struct tcphdr *th; 2796{ 2797 tcp_seq onxt = tp->snd_nxt; 2798 u_long ocwnd = tp->snd_cwnd; 2799 2800 callout_stop(tp->tt_rexmt); 2801 tp->t_rtttime = 0; 2802 tp->snd_nxt = th->th_ack; 2803 /* 2804 * Set snd_cwnd to one segment beyond acknowledged offset. 2805 * (tp->snd_una has not yet been updated when this function is called.) 2806 */ 2807 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 2808 tp->t_flags |= TF_ACKNOW; 2809 (void) tcp_output(tp); 2810 tp->snd_cwnd = ocwnd; 2811 if (SEQ_GT(onxt, tp->snd_nxt)) 2812 tp->snd_nxt = onxt; 2813 /* 2814 * Partial window deflation. Relies on fact that tp->snd_una 2815 * not updated yet. 2816 */ 2817 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 2818} 2819