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: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 35 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.4 2003/07/24 01:31:07 dillon Exp $ 36 */ 37 38 #include "opt_ipfw.h" /* for ipfw_fwd */ 39 #include "opt_inet6.h" 40 #include "opt_ipsec.h" 41 #include "opt_tcpdebug.h" 42 #include "opt_tcp_input.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/kernel.h> 47 #include <sys/sysctl.h> 48 #include <sys/malloc.h> 49 #include <sys/mbuf.h> 50 #include <sys/proc.h> /* for proc0 declaration */ 51 #include <sys/protosw.h> 52 #include <sys/socket.h> 53 #include <sys/socketvar.h> 54 #include <sys/syslog.h> 55 56 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58 #include <net/if.h> 59 #include <net/route.h> 60 61 #include <netinet/in.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/ip.h> 64 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 65 #include <netinet/in_var.h> 66 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 67 #include <netinet/in_pcb.h> 68 #include <netinet/ip_var.h> 69 #include <netinet/ip6.h> 70 #include <netinet/icmp6.h> 71 #include <netinet6/nd6.h> 72 #include <netinet6/ip6_var.h> 73 #include <netinet6/in6_pcb.h> 74 #include <netinet/tcp.h> 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_seq.h> 77 #include <netinet/tcp_timer.h> 78 #include <netinet/tcp_var.h> 79 #include <netinet6/tcp6_var.h> 80 #include <netinet/tcpip.h> 81 #ifdef TCPDEBUG 82 #include <netinet/tcp_debug.h> 83 84 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 85 struct tcphdr tcp_savetcp; 86 #endif /* TCPDEBUG */ 87 88 #ifdef FAST_IPSEC 89 #include <netipsec/ipsec.h> 90 #include <netipsec/ipsec6.h> 91 #endif 92 93 #ifdef IPSEC 94 #include <netinet6/ipsec.h> 95 #include <netinet6/ipsec6.h> 96 #include <netkey/key.h> 97 #endif /*IPSEC*/ 98 99 #include <machine/in_cksum.h> 100 101 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 102 103 static const int tcprexmtthresh = 3; 104 tcp_cc tcp_ccgen; 105 106 struct tcpstat tcpstat; 107 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 108 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 109 110 static int log_in_vain = 0; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 112 &log_in_vain, 0, "Log all incoming TCP connections"); 113 114 static int blackhole = 0; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 116 &blackhole, 0, "Do not send RST when dropping refused connections"); 117 118 int tcp_delack_enabled = 1; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 120 &tcp_delack_enabled, 0, 121 "Delay ACK to try and piggyback it onto a data packet"); 122 123 #ifdef TCP_DROP_SYNFIN 124 static int drop_synfin = 0; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 126 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 127 #endif 128 129 static int tcp_do_limitedtransmit = 1; 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 131 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 132 133 struct inpcbhead tcb; 134 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 135 struct inpcbinfo tcbinfo; 136 137 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 138 static void tcp_pulloutofband(struct socket *, 139 struct tcphdr *, struct mbuf *, int); 140 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 141 struct mbuf *); 142 static void tcp_xmit_timer(struct tcpcb *, int); 143 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 144 145 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 146 #ifdef INET6 147 #define ND6_HINT(tp) \ 148 do { \ 149 if ((tp) && (tp)->t_inpcb && \ 150 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ 151 (tp)->t_inpcb->in6p_route.ro_rt) \ 152 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 153 } while (0) 154 #else 155 #define ND6_HINT(tp) 156 #endif 157 158 /* 159 * Indicate whether this ack should be delayed. We can delay the ack if 160 * - delayed acks are enabled and 161 * - there is no delayed ack timer in progress and 162 * - our last ack wasn't a 0-sized window. We never want to delay 163 * the ack that opens up a 0-sized window. 164 */ 165 #define DELAY_ACK(tp) \ 166 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 167 (tp->t_flags & TF_RXWIN0SENT) == 0) 168 169 static int 170 tcp_reass(tp, th, tlenp, m) 171 register struct tcpcb *tp; 172 register struct tcphdr *th; 173 int *tlenp; 174 struct mbuf *m; 175 { 176 struct tseg_qent *q; 177 struct tseg_qent *p = NULL; 178 struct tseg_qent *nq; 179 struct tseg_qent *te; 180 struct socket *so = tp->t_inpcb->inp_socket; 181 int flags; 182 183 /* 184 * Call with th==0 after become established to 185 * force pre-ESTABLISHED data up to user socket. 186 */ 187 if (th == 0) 188 goto present; 189 190 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */ 191 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 192 M_NOWAIT); 193 if (te == NULL) { 194 tcpstat.tcps_rcvmemdrop++; 195 m_freem(m); 196 return (0); 197 } 198 199 /* 200 * Find a segment which begins after this one does. 201 */ 202 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 203 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 204 break; 205 p = q; 206 } 207 208 /* 209 * If there is a preceding segment, it may provide some of 210 * our data already. If so, drop the data from the incoming 211 * segment. If it provides all of our data, drop us. 212 */ 213 if (p != NULL) { 214 register int i; 215 /* conversion to int (in i) handles seq wraparound */ 216 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 217 if (i > 0) { 218 if (i >= *tlenp) { 219 tcpstat.tcps_rcvduppack++; 220 tcpstat.tcps_rcvdupbyte += *tlenp; 221 m_freem(m); 222 free(te, M_TSEGQ); 223 /* 224 * Try to present any queued data 225 * at the left window edge to the user. 226 * This is needed after the 3-WHS 227 * completes. 228 */ 229 goto present; /* ??? */ 230 } 231 m_adj(m, i); 232 *tlenp -= i; 233 th->th_seq += i; 234 } 235 } 236 tcpstat.tcps_rcvoopack++; 237 tcpstat.tcps_rcvoobyte += *tlenp; 238 239 /* 240 * While we overlap succeeding segments trim them or, 241 * if they are completely covered, dequeue them. 242 */ 243 while (q) { 244 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 245 if (i <= 0) 246 break; 247 if (i < q->tqe_len) { 248 q->tqe_th->th_seq += i; 249 q->tqe_len -= i; 250 m_adj(q->tqe_m, i); 251 break; 252 } 253 254 nq = LIST_NEXT(q, tqe_q); 255 LIST_REMOVE(q, tqe_q); 256 m_freem(q->tqe_m); 257 free(q, M_TSEGQ); 258 q = nq; 259 } 260 261 /* Insert the new segment queue entry into place. */ 262 te->tqe_m = m; 263 te->tqe_th = th; 264 te->tqe_len = *tlenp; 265 266 if (p == NULL) { 267 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 268 } else { 269 LIST_INSERT_AFTER(p, te, tqe_q); 270 } 271 272 present: 273 /* 274 * Present data to user, advancing rcv_nxt through 275 * completed sequence space. 276 */ 277 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 278 return (0); 279 q = LIST_FIRST(&tp->t_segq); 280 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 281 return (0); 282 do { 283 tp->rcv_nxt += q->tqe_len; 284 flags = q->tqe_th->th_flags & TH_FIN; 285 nq = LIST_NEXT(q, tqe_q); 286 LIST_REMOVE(q, tqe_q); 287 if (so->so_state & SS_CANTRCVMORE) 288 m_freem(q->tqe_m); 289 else 290 sbappend(&so->so_rcv, q->tqe_m); 291 free(q, M_TSEGQ); 292 q = nq; 293 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 294 ND6_HINT(tp); 295 sorwakeup(so); 296 return (flags); 297 } 298 299 /* 300 * TCP input routine, follows pages 65-76 of the 301 * protocol specification dated September, 1981 very closely. 302 */ 303 #ifdef INET6 304 int 305 tcp6_input(mp, offp, proto) 306 struct mbuf **mp; 307 int *offp, proto; 308 { 309 register struct mbuf *m = *mp; 310 struct in6_ifaddr *ia6; 311 312 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 313 314 /* 315 * draft-itojun-ipv6-tcp-to-anycast 316 * better place to put this in? 317 */ 318 ia6 = ip6_getdstifaddr(m); 319 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 320 struct ip6_hdr *ip6; 321 322 ip6 = mtod(m, struct ip6_hdr *); 323 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 324 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 325 return IPPROTO_DONE; 326 } 327 328 tcp_input(m, *offp, proto); 329 return IPPROTO_DONE; 330 } 331 #endif 332 333 void 334 tcp_input(m, off0, proto) 335 register struct mbuf *m; 336 int off0, proto; 337 { 338 register struct tcphdr *th; 339 register struct ip *ip = NULL; 340 register struct ipovly *ipov; 341 register struct inpcb *inp = NULL; 342 u_char *optp = NULL; 343 int optlen = 0; 344 int len, tlen, off; 345 int drop_hdrlen; 346 register struct tcpcb *tp = NULL; 347 register int thflags; 348 struct socket *so = 0; 349 int todrop, acked, ourfinisacked, needoutput = 0; 350 u_long tiwin; 351 struct tcpopt to; /* options in this segment */ 352 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 353 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 354 struct sockaddr_in *next_hop = NULL; 355 int rstreason; /* For badport_bandlim accounting purposes */ 356 struct ip6_hdr *ip6 = NULL; 357 #ifdef INET6 358 int isipv6; 359 #else 360 const int isipv6 = 0; 361 #endif 362 #ifdef TCPDEBUG 363 short ostate = 0; 364 #endif 365 366 /* Grab info from MT_TAG mbufs prepended to the chain. */ 367 for (;m && m->m_type == MT_TAG; m = m->m_next) { 368 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 369 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 370 } 371 #ifdef INET6 372 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 373 #endif 374 bzero((char *)&to, sizeof(to)); 375 376 tcpstat.tcps_rcvtotal++; 377 378 if (isipv6) { 379 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 380 ip6 = mtod(m, struct ip6_hdr *); 381 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 382 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 383 tcpstat.tcps_rcvbadsum++; 384 goto drop; 385 } 386 th = (struct tcphdr *)((caddr_t)ip6 + off0); 387 388 /* 389 * Be proactive about unspecified IPv6 address in source. 390 * As we use all-zero to indicate unbounded/unconnected pcb, 391 * unspecified IPv6 address can be used to confuse us. 392 * 393 * Note that packets with unspecified IPv6 destination is 394 * already dropped in ip6_input. 395 */ 396 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 397 /* XXX stat */ 398 goto drop; 399 } 400 } else { 401 /* 402 * Get IP and TCP header together in first mbuf. 403 * Note: IP leaves IP header in first mbuf. 404 */ 405 if (off0 > sizeof(struct ip)) { 406 ip_stripoptions(m, (struct mbuf *)0); 407 off0 = sizeof(struct ip); 408 } 409 if (m->m_len < sizeof(struct tcpiphdr)) { 410 if ((m = m_pullup(m, sizeof(struct tcpiphdr))) == 0) { 411 tcpstat.tcps_rcvshort++; 412 return; 413 } 414 } 415 ip = mtod(m, struct ip *); 416 ipov = (struct ipovly *)ip; 417 th = (struct tcphdr *)((caddr_t)ip + off0); 418 tlen = ip->ip_len; 419 420 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 421 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 422 th->th_sum = m->m_pkthdr.csum_data; 423 else 424 th->th_sum = in_pseudo(ip->ip_src.s_addr, 425 ip->ip_dst.s_addr, 426 htonl(m->m_pkthdr.csum_data + 427 ip->ip_len + 428 IPPROTO_TCP)); 429 th->th_sum ^= 0xffff; 430 } else { 431 /* 432 * Checksum extended TCP header and data. 433 */ 434 len = sizeof(struct ip) + tlen; 435 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 436 ipov->ih_len = (u_short)tlen; 437 ipov->ih_len = htons(ipov->ih_len); 438 th->th_sum = in_cksum(m, len); 439 } 440 if (th->th_sum) { 441 tcpstat.tcps_rcvbadsum++; 442 goto drop; 443 } 444 #ifdef INET6 445 /* Re-initialization for later version check */ 446 ip->ip_v = IPVERSION; 447 #endif 448 } 449 450 /* 451 * Check that TCP offset makes sense, 452 * pull out TCP options and adjust length. XXX 453 */ 454 off = th->th_off << 2; 455 if (off < sizeof(struct tcphdr) || off > tlen) { 456 tcpstat.tcps_rcvbadoff++; 457 goto drop; 458 } 459 tlen -= off; /* tlen is used instead of ti->ti_len */ 460 if (off > sizeof(struct tcphdr)) { 461 if (isipv6) { 462 IP6_EXTHDR_CHECK(m, off0, off, ); 463 ip6 = mtod(m, struct ip6_hdr *); 464 th = (struct tcphdr *)((caddr_t)ip6 + off0); 465 } else { 466 if (m->m_len < sizeof(struct ip) + off) { 467 if ((m = m_pullup(m, sizeof(struct ip) + off)) 468 == 0) { 469 tcpstat.tcps_rcvshort++; 470 return; 471 } 472 ip = mtod(m, struct ip *); 473 ipov = (struct ipovly *)ip; 474 th = (struct tcphdr *)((caddr_t)ip + off0); 475 } 476 } 477 optlen = off - sizeof(struct tcphdr); 478 optp = (u_char *)(th + 1); 479 } 480 thflags = th->th_flags; 481 482 #ifdef TCP_DROP_SYNFIN 483 /* 484 * If the drop_synfin option is enabled, drop all packets with 485 * both the SYN and FIN bits set. This prevents e.g. nmap from 486 * identifying the TCP/IP stack. 487 * 488 * This is a violation of the TCP specification. 489 */ 490 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 491 goto drop; 492 #endif 493 494 /* 495 * Convert TCP protocol specific fields to host format. 496 */ 497 th->th_seq = ntohl(th->th_seq); 498 th->th_ack = ntohl(th->th_ack); 499 th->th_win = ntohs(th->th_win); 500 th->th_urp = ntohs(th->th_urp); 501 502 /* 503 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options, 504 * until after ip6_savecontrol() is called and before other functions 505 * which don't want those proto headers. 506 * Because ip6_savecontrol() is going to parse the mbuf to 507 * search for data to be passed up to user-land, it wants mbuf 508 * parameters to be unchanged. 509 * XXX: the call of ip6_savecontrol() has been obsoleted based on 510 * latest version of the advanced API (20020110). 511 */ 512 drop_hdrlen = off0 + off; 513 514 /* 515 * Locate pcb for segment. 516 */ 517 findpcb: 518 /* IPFIREWALL_FORWARD section */ 519 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 520 /* 521 * Transparently forwarded. Pretend to be the destination. 522 * already got one like this? 523 */ 524 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 525 ip->ip_dst, th->th_dport, 526 0, m->m_pkthdr.rcvif); 527 if (!inp) { 528 /* It's new. Try find the ambushing socket. */ 529 inp = in_pcblookup_hash(&tcbinfo, 530 ip->ip_src, th->th_sport, 531 next_hop->sin_addr, 532 next_hop->sin_port ? 533 ntohs(next_hop->sin_port) : 534 th->th_dport, 535 1, m->m_pkthdr.rcvif); 536 } 537 } else { 538 if (isipv6) 539 inp = in6_pcblookup_hash(&tcbinfo, 540 &ip6->ip6_src, th->th_sport, 541 &ip6->ip6_dst, th->th_dport, 542 1, m->m_pkthdr.rcvif); 543 else 544 inp = in_pcblookup_hash(&tcbinfo, 545 ip->ip_src, th->th_sport, 546 ip->ip_dst, th->th_dport, 547 1, m->m_pkthdr.rcvif); 548 } 549 550 #ifdef IPSEC 551 if (isipv6) { 552 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 553 ipsec6stat.in_polvio++; 554 goto drop; 555 } 556 } else { 557 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 558 ipsecstat.in_polvio++; 559 goto drop; 560 } 561 } 562 #endif 563 #ifdef FAST_IPSEC 564 if (isipv6) { 565 if (inp != NULL && ipsec6_in_reject(m, inp)) { 566 goto drop; 567 } 568 } else { 569 if (inp != NULL && ipsec4_in_reject(m, inp)) { 570 goto drop; 571 } 572 } 573 #endif 574 575 /* 576 * If the state is CLOSED (i.e., TCB does not exist) then 577 * all data in the incoming segment is discarded. 578 * If the TCB exists but is in CLOSED state, it is embryonic, 579 * but should either do a listen or a connect soon. 580 */ 581 if (inp == NULL) { 582 if (log_in_vain) { 583 #ifdef INET6 584 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 585 #else 586 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 587 #endif 588 if (isipv6) { 589 strcpy(dbuf, "["); 590 strcpy(sbuf, "["); 591 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 592 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 593 strcat(dbuf, "]"); 594 strcat(sbuf, "]"); 595 } else { 596 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 597 strcpy(sbuf, inet_ntoa(ip->ip_src)); 598 } 599 switch (log_in_vain) { 600 case 1: 601 if ((thflags & TH_SYN) == 0) 602 break; 603 case 2: 604 log(LOG_INFO, 605 "Connection attempt to TCP %s:%d " 606 "from %s:%d flags:0x%02x\n", 607 dbuf, ntohs(th->th_dport), sbuf, 608 ntohs(th->th_sport), thflags); 609 break; 610 default: 611 break; 612 } 613 } 614 if (blackhole) { 615 switch (blackhole) { 616 case 1: 617 if (thflags & TH_SYN) 618 goto drop; 619 break; 620 case 2: 621 goto drop; 622 default: 623 goto drop; 624 } 625 } 626 rstreason = BANDLIM_RST_CLOSEDPORT; 627 goto dropwithreset; 628 } 629 tp = intotcpcb(inp); 630 if (tp == NULL) { 631 rstreason = BANDLIM_RST_CLOSEDPORT; 632 goto dropwithreset; 633 } 634 if (tp->t_state == TCPS_CLOSED) 635 goto drop; 636 637 /* Unscale the window into a 32-bit value. */ 638 if ((thflags & TH_SYN) == 0) 639 tiwin = th->th_win << tp->snd_scale; 640 else 641 tiwin = th->th_win; 642 643 so = inp->inp_socket; 644 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 645 struct in_conninfo inc; 646 #ifdef TCPDEBUG 647 if (so->so_options & SO_DEBUG) { 648 ostate = tp->t_state; 649 if (isipv6) 650 bcopy((char *)ip6, (char *)tcp_saveipgen, 651 sizeof(*ip6)); 652 else 653 bcopy((char *)ip, (char *)tcp_saveipgen, 654 sizeof(*ip)); 655 tcp_savetcp = *th; 656 } 657 #endif 658 /* skip if this isn't a listen socket */ 659 if ((so->so_options & SO_ACCEPTCONN) == 0) 660 goto after_listen; 661 #ifdef INET6 662 inc.inc_isipv6 = isipv6; 663 #endif 664 if (isipv6) { 665 inc.inc6_faddr = ip6->ip6_src; 666 inc.inc6_laddr = ip6->ip6_dst; 667 inc.inc6_route.ro_rt = NULL; /* XXX */ 668 } else { 669 inc.inc_faddr = ip->ip_src; 670 inc.inc_laddr = ip->ip_dst; 671 inc.inc_route.ro_rt = NULL; /* XXX */ 672 } 673 inc.inc_fport = th->th_sport; 674 inc.inc_lport = th->th_dport; 675 676 /* 677 * If the state is LISTEN then ignore segment if it contains 678 * a RST. If the segment contains an ACK then it is bad and 679 * send a RST. If it does not contain a SYN then it is not 680 * interesting; drop it. 681 * 682 * If the state is SYN_RECEIVED (syncache) and seg contains 683 * an ACK, but not for our SYN/ACK, send a RST. If the seg 684 * contains a RST, check the sequence number to see if it 685 * is a valid reset segment. 686 */ 687 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 688 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 689 if (!syncache_expand(&inc, th, &so, m)) { 690 /* 691 * No syncache entry, or ACK was not 692 * for our SYN/ACK. Send a RST. 693 */ 694 tcpstat.tcps_badsyn++; 695 rstreason = BANDLIM_RST_OPENPORT; 696 goto dropwithreset; 697 } 698 if (so == NULL) 699 /* 700 * Could not complete 3-way handshake, 701 * connection is being closed down, and 702 * syncache will free mbuf. 703 */ 704 return; 705 /* 706 * Socket is created in state SYN_RECEIVED. 707 * Continue processing segment. 708 */ 709 inp = sotoinpcb(so); 710 tp = intotcpcb(inp); 711 /* 712 * This is what would have happened in 713 * tcp_output() when the SYN,ACK was sent. 714 */ 715 tp->snd_up = tp->snd_una; 716 tp->snd_max = tp->snd_nxt = tp->iss + 1; 717 tp->last_ack_sent = tp->rcv_nxt; 718 /* 719 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 720 * until the _second_ ACK is received: 721 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 722 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 723 * move to ESTAB, set snd_wnd to tiwin. 724 */ 725 tp->snd_wnd = tiwin; /* unscaled */ 726 goto after_listen; 727 } 728 if (thflags & TH_RST) { 729 syncache_chkrst(&inc, th); 730 goto drop; 731 } 732 if (thflags & TH_ACK) { 733 syncache_badack(&inc); 734 tcpstat.tcps_badsyn++; 735 rstreason = BANDLIM_RST_OPENPORT; 736 goto dropwithreset; 737 } 738 goto drop; 739 } 740 741 /* 742 * Segment's flags are (SYN) or (SYN|FIN). 743 */ 744 #ifdef INET6 745 /* 746 * If deprecated address is forbidden, 747 * we do not accept SYN to deprecated interface 748 * address to prevent any new inbound connection from 749 * getting established. 750 * When we do not accept SYN, we send a TCP RST, 751 * with deprecated source address (instead of dropping 752 * it). We compromise it as it is much better for peer 753 * to send a RST, and RST will be the final packet 754 * for the exchange. 755 * 756 * If we do not forbid deprecated addresses, we accept 757 * the SYN packet. RFC2462 does not suggest dropping 758 * SYN in this case. 759 * If we decipher RFC2462 5.5.4, it says like this: 760 * 1. use of deprecated addr with existing 761 * communication is okay - "SHOULD continue to be 762 * used" 763 * 2. use of it with new communication: 764 * (2a) "SHOULD NOT be used if alternate address 765 * with sufficient scope is available" 766 * (2b) nothing mentioned otherwise. 767 * Here we fall into (2b) case as we have no choice in 768 * our source address selection - we must obey the peer. 769 * 770 * The wording in RFC2462 is confusing, and there are 771 * multiple description text for deprecated address 772 * handling - worse, they are not exactly the same. 773 * I believe 5.5.4 is the best one, so we follow 5.5.4. 774 */ 775 if (isipv6 && !ip6_use_deprecated) { 776 struct in6_ifaddr *ia6; 777 778 if ((ia6 = ip6_getdstifaddr(m)) && 779 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 780 tp = NULL; 781 rstreason = BANDLIM_RST_OPENPORT; 782 goto dropwithreset; 783 } 784 } 785 #endif 786 /* 787 * If it is from this socket, drop it, it must be forged. 788 * Don't bother responding if the destination was a broadcast. 789 */ 790 if (th->th_dport == th->th_sport) { 791 if (isipv6) { 792 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 793 &ip6->ip6_src)) 794 goto drop; 795 } else { 796 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 797 goto drop; 798 } 799 } 800 /* 801 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 802 * 803 * Note that it is quite possible to receive unicast 804 * link-layer packets with a broadcast IP address. Use 805 * in_broadcast() to find them. 806 */ 807 if (m->m_flags & (M_BCAST|M_MCAST)) 808 goto drop; 809 if (isipv6) { 810 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 811 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 812 goto drop; 813 } else { 814 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 815 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 816 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 817 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 818 goto drop; 819 } 820 /* 821 * SYN appears to be valid; create compressed TCP state 822 * for syncache, or perform t/tcp connection. 823 */ 824 if (so->so_qlen <= so->so_qlimit) { 825 tcp_dooptions(&to, optp, optlen, 1); 826 if (!syncache_add(&inc, &to, th, &so, m)) 827 goto drop; 828 if (so == NULL) 829 /* 830 * Entry added to syncache, mbuf used to 831 * send SYN,ACK packet. 832 */ 833 return; 834 /* 835 * Segment passed TAO tests. 836 */ 837 inp = sotoinpcb(so); 838 tp = intotcpcb(inp); 839 tp->snd_wnd = tiwin; 840 tp->t_starttime = ticks; 841 tp->t_state = TCPS_ESTABLISHED; 842 843 /* 844 * If there is a FIN, or if there is data and the 845 * connection is local, then delay SYN,ACK(SYN) in 846 * the hope of piggy-backing it on a response 847 * segment. Otherwise must send ACK now in case 848 * the other side is slow starting. 849 */ 850 if (DELAY_ACK(tp) && 851 ((thflags & TH_FIN) || 852 (tlen != 0 && 853 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 854 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 855 callout_reset(tp->tt_delack, tcp_delacktime, 856 tcp_timer_delack, tp); 857 tp->t_flags |= TF_NEEDSYN; 858 } else 859 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 860 861 tcpstat.tcps_connects++; 862 soisconnected(so); 863 goto trimthenstep6; 864 } 865 goto drop; 866 } 867 after_listen: 868 869 /* XXX temp debugging */ 870 /* should not happen - syncache should pick up these connections */ 871 if (tp->t_state == TCPS_LISTEN) 872 panic("tcp_input: TCPS_LISTEN"); 873 874 /* 875 * Segment received on connection. 876 * Reset idle time and keep-alive timer. 877 */ 878 tp->t_rcvtime = ticks; 879 if (TCPS_HAVEESTABLISHED(tp->t_state)) 880 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 881 882 /* 883 * Process options. 884 * XXX this is tradtitional behavior, may need to be cleaned up. 885 */ 886 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 887 if (thflags & TH_SYN) { 888 if (to.to_flags & TOF_SCALE) { 889 tp->t_flags |= TF_RCVD_SCALE; 890 tp->requested_s_scale = to.to_requested_s_scale; 891 } 892 if (to.to_flags & TOF_TS) { 893 tp->t_flags |= TF_RCVD_TSTMP; 894 tp->ts_recent = to.to_tsval; 895 tp->ts_recent_age = ticks; 896 } 897 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 898 tp->t_flags |= TF_RCVD_CC; 899 if (to.to_flags & TOF_MSS) 900 tcp_mss(tp, to.to_mss); 901 } 902 903 /* 904 * Header prediction: check for the two common cases 905 * of a uni-directional data xfer. If the packet has 906 * no control flags, is in-sequence, the window didn't 907 * change and we're not retransmitting, it's a 908 * candidate. If the length is zero and the ack moved 909 * forward, we're the sender side of the xfer. Just 910 * free the data acked & wake any higher level process 911 * that was blocked waiting for space. If the length 912 * is non-zero and the ack didn't move, we're the 913 * receiver side. If we're getting packets in-order 914 * (the reassembly queue is empty), add the data to 915 * the socket buffer and note that we need a delayed ack. 916 * Make sure that the hidden state-flags are also off. 917 * Since we check for TCPS_ESTABLISHED above, it can only 918 * be TH_NEEDSYN. 919 */ 920 if (tp->t_state == TCPS_ESTABLISHED && 921 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 922 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 923 ((to.to_flags & TOF_TS) == 0 || 924 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 925 /* 926 * Using the CC option is compulsory if once started: 927 * the segment is OK if no T/TCP was negotiated or 928 * if the segment has a CC option equal to CCrecv 929 */ 930 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 931 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 932 th->th_seq == tp->rcv_nxt && 933 tiwin && tiwin == tp->snd_wnd && 934 tp->snd_nxt == tp->snd_max) { 935 936 /* 937 * If last ACK falls within this segment's sequence numbers, 938 * record the timestamp. 939 * NOTE that the test is modified according to the latest 940 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 941 */ 942 if ((to.to_flags & TOF_TS) != 0 && 943 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 944 tp->ts_recent_age = ticks; 945 tp->ts_recent = to.to_tsval; 946 } 947 948 if (tlen == 0) { 949 if (SEQ_GT(th->th_ack, tp->snd_una) && 950 SEQ_LEQ(th->th_ack, tp->snd_max) && 951 tp->snd_cwnd >= tp->snd_wnd && 952 ((!tcp_do_newreno && 953 tp->t_dupacks < tcprexmtthresh) || 954 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) { 955 /* 956 * this is a pure ack for outstanding data. 957 */ 958 ++tcpstat.tcps_predack; 959 /* 960 * "bad retransmit" recovery 961 */ 962 if (tp->t_rxtshift == 1 && 963 ticks < tp->t_badrxtwin) { 964 tp->snd_cwnd = tp->snd_cwnd_prev; 965 tp->snd_ssthresh = 966 tp->snd_ssthresh_prev; 967 tp->snd_recover = tp->snd_recover_prev; 968 if (tp->t_flags & TF_WASFRECOVERY) 969 ENTER_FASTRECOVERY(tp); 970 tp->snd_nxt = tp->snd_max; 971 tp->t_badrxtwin = 0; 972 } 973 /* 974 * Recalculate the retransmit timer / rtt. 975 * 976 * Some machines (certain windows boxes) 977 * send broken timestamp replies during the 978 * SYN+ACK phase, ignore timestamps of 0. 979 */ 980 if ((to.to_flags & TOF_TS) != 0 && 981 to.to_tsecr) { 982 tcp_xmit_timer(tp, 983 ticks - to.to_tsecr + 1); 984 } else if (tp->t_rtttime && 985 SEQ_GT(th->th_ack, tp->t_rtseq)) { 986 tcp_xmit_timer(tp, 987 ticks - tp->t_rtttime); 988 } 989 tcp_xmit_bandwidth_limit(tp, th->th_ack); 990 acked = th->th_ack - tp->snd_una; 991 tcpstat.tcps_rcvackpack++; 992 tcpstat.tcps_rcvackbyte += acked; 993 sbdrop(&so->so_snd, acked); 994 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 995 SEQ_LEQ(th->th_ack, tp->snd_recover)) 996 tp->snd_recover = th->th_ack - 1; 997 tp->snd_una = th->th_ack; 998 tp->t_dupacks = 0; 999 m_freem(m); 1000 ND6_HINT(tp); /* some progress has been done */ 1001 1002 /* 1003 * If all outstanding data are acked, stop 1004 * retransmit timer, otherwise restart timer 1005 * using current (possibly backed-off) value. 1006 * If process is waiting for space, 1007 * wakeup/selwakeup/signal. If data 1008 * are ready to send, let tcp_output 1009 * decide between more output or persist. 1010 */ 1011 if (tp->snd_una == tp->snd_max) 1012 callout_stop(tp->tt_rexmt); 1013 else if (!callout_active(tp->tt_persist)) 1014 callout_reset(tp->tt_rexmt, 1015 tp->t_rxtcur, 1016 tcp_timer_rexmt, tp); 1017 1018 sowwakeup(so); 1019 if (so->so_snd.sb_cc) 1020 (void) tcp_output(tp); 1021 return; 1022 } 1023 } else if (th->th_ack == tp->snd_una && 1024 LIST_EMPTY(&tp->t_segq) && 1025 tlen <= sbspace(&so->so_rcv)) { 1026 /* 1027 * this is a pure, in-sequence data packet 1028 * with nothing on the reassembly queue and 1029 * we have enough buffer space to take it. 1030 */ 1031 ++tcpstat.tcps_preddat; 1032 tp->rcv_nxt += tlen; 1033 tcpstat.tcps_rcvpack++; 1034 tcpstat.tcps_rcvbyte += tlen; 1035 ND6_HINT(tp); /* some progress has been done */ 1036 /* 1037 * Add data to socket buffer. 1038 */ 1039 if (so->so_state & SS_CANTRCVMORE) { 1040 m_freem(m); 1041 } else { 1042 m_adj(m, drop_hdrlen); /* delayed header drop */ 1043 sbappend(&so->so_rcv, m); 1044 } 1045 sorwakeup(so); 1046 if (DELAY_ACK(tp)) { 1047 callout_reset(tp->tt_delack, tcp_delacktime, 1048 tcp_timer_delack, tp); 1049 } else { 1050 tp->t_flags |= TF_ACKNOW; 1051 tcp_output(tp); 1052 } 1053 return; 1054 } 1055 } 1056 1057 /* 1058 * Calculate amount of space in receive window, 1059 * and then do TCP input processing. 1060 * Receive window is amount of space in rcv queue, 1061 * but not less than advertised window. 1062 */ 1063 { int win; 1064 1065 win = sbspace(&so->so_rcv); 1066 if (win < 0) 1067 win = 0; 1068 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1069 } 1070 1071 switch (tp->t_state) { 1072 1073 /* 1074 * If the state is SYN_RECEIVED: 1075 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1076 */ 1077 case TCPS_SYN_RECEIVED: 1078 if ((thflags & TH_ACK) && 1079 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1080 SEQ_GT(th->th_ack, tp->snd_max))) { 1081 rstreason = BANDLIM_RST_OPENPORT; 1082 goto dropwithreset; 1083 } 1084 break; 1085 1086 /* 1087 * If the state is SYN_SENT: 1088 * if seg contains an ACK, but not for our SYN, drop the input. 1089 * if seg contains a RST, then drop the connection. 1090 * if seg does not contain SYN, then drop it. 1091 * Otherwise this is an acceptable SYN segment 1092 * initialize tp->rcv_nxt and tp->irs 1093 * if seg contains ack then advance tp->snd_una 1094 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1095 * arrange for segment to be acked (eventually) 1096 * continue processing rest of data/controls, beginning with URG 1097 */ 1098 case TCPS_SYN_SENT: 1099 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1100 taop = &tao_noncached; 1101 bzero(taop, sizeof(*taop)); 1102 } 1103 1104 if ((thflags & TH_ACK) && 1105 (SEQ_LEQ(th->th_ack, tp->iss) || 1106 SEQ_GT(th->th_ack, tp->snd_max))) { 1107 /* 1108 * If we have a cached CCsent for the remote host, 1109 * hence we haven't just crashed and restarted, 1110 * do not send a RST. This may be a retransmission 1111 * from the other side after our earlier ACK was lost. 1112 * Our new SYN, when it arrives, will serve as the 1113 * needed ACK. 1114 */ 1115 if (taop->tao_ccsent != 0) 1116 goto drop; 1117 else { 1118 rstreason = BANDLIM_UNLIMITED; 1119 goto dropwithreset; 1120 } 1121 } 1122 if (thflags & TH_RST) { 1123 if (thflags & TH_ACK) 1124 tp = tcp_drop(tp, ECONNREFUSED); 1125 goto drop; 1126 } 1127 if ((thflags & TH_SYN) == 0) 1128 goto drop; 1129 tp->snd_wnd = th->th_win; /* initial send window */ 1130 tp->cc_recv = to.to_cc; /* foreign CC */ 1131 1132 tp->irs = th->th_seq; 1133 tcp_rcvseqinit(tp); 1134 if (thflags & TH_ACK) { 1135 /* 1136 * Our SYN was acked. If segment contains CC.ECHO 1137 * option, check it to make sure this segment really 1138 * matches our SYN. If not, just drop it as old 1139 * duplicate, but send an RST if we're still playing 1140 * by the old rules. If no CC.ECHO option, make sure 1141 * we don't get fooled into using T/TCP. 1142 */ 1143 if (to.to_flags & TOF_CCECHO) { 1144 if (tp->cc_send != to.to_ccecho) { 1145 if (taop->tao_ccsent != 0) 1146 goto drop; 1147 else { 1148 rstreason = BANDLIM_UNLIMITED; 1149 goto dropwithreset; 1150 } 1151 } 1152 } else 1153 tp->t_flags &= ~TF_RCVD_CC; 1154 tcpstat.tcps_connects++; 1155 soisconnected(so); 1156 /* Do window scaling on this connection? */ 1157 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1158 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1159 tp->snd_scale = tp->requested_s_scale; 1160 tp->rcv_scale = tp->request_r_scale; 1161 } 1162 /* Segment is acceptable, update cache if undefined. */ 1163 if (taop->tao_ccsent == 0) 1164 taop->tao_ccsent = to.to_ccecho; 1165 1166 tp->rcv_adv += tp->rcv_wnd; 1167 tp->snd_una++; /* SYN is acked */ 1168 /* 1169 * If there's data, delay ACK; if there's also a FIN 1170 * ACKNOW will be turned on later. 1171 */ 1172 if (DELAY_ACK(tp) && tlen != 0) 1173 callout_reset(tp->tt_delack, tcp_delacktime, 1174 tcp_timer_delack, tp); 1175 else 1176 tp->t_flags |= TF_ACKNOW; 1177 /* 1178 * Received <SYN,ACK> in SYN_SENT[*] state. 1179 * Transitions: 1180 * SYN_SENT --> ESTABLISHED 1181 * SYN_SENT* --> FIN_WAIT_1 1182 */ 1183 tp->t_starttime = ticks; 1184 if (tp->t_flags & TF_NEEDFIN) { 1185 tp->t_state = TCPS_FIN_WAIT_1; 1186 tp->t_flags &= ~TF_NEEDFIN; 1187 thflags &= ~TH_SYN; 1188 } else { 1189 tp->t_state = TCPS_ESTABLISHED; 1190 callout_reset(tp->tt_keep, tcp_keepidle, 1191 tcp_timer_keep, tp); 1192 } 1193 } else { 1194 /* 1195 * Received initial SYN in SYN-SENT[*] state => 1196 * simultaneous open. If segment contains CC option 1197 * and there is a cached CC, apply TAO test. 1198 * If it succeeds, connection is * half-synchronized. 1199 * Otherwise, do 3-way handshake: 1200 * SYN-SENT -> SYN-RECEIVED 1201 * SYN-SENT* -> SYN-RECEIVED* 1202 * If there was no CC option, clear cached CC value. 1203 */ 1204 tp->t_flags |= TF_ACKNOW; 1205 callout_stop(tp->tt_rexmt); 1206 if (to.to_flags & TOF_CC) { 1207 if (taop->tao_cc != 0 && 1208 CC_GT(to.to_cc, taop->tao_cc)) { 1209 /* 1210 * update cache and make transition: 1211 * SYN-SENT -> ESTABLISHED* 1212 * SYN-SENT* -> FIN-WAIT-1* 1213 */ 1214 taop->tao_cc = to.to_cc; 1215 tp->t_starttime = ticks; 1216 if (tp->t_flags & TF_NEEDFIN) { 1217 tp->t_state = TCPS_FIN_WAIT_1; 1218 tp->t_flags &= ~TF_NEEDFIN; 1219 } else { 1220 tp->t_state = TCPS_ESTABLISHED; 1221 callout_reset(tp->tt_keep, 1222 tcp_keepidle, 1223 tcp_timer_keep, 1224 tp); 1225 } 1226 tp->t_flags |= TF_NEEDSYN; 1227 } else 1228 tp->t_state = TCPS_SYN_RECEIVED; 1229 } else { 1230 /* CC.NEW or no option => invalidate cache */ 1231 taop->tao_cc = 0; 1232 tp->t_state = TCPS_SYN_RECEIVED; 1233 } 1234 } 1235 1236 trimthenstep6: 1237 /* 1238 * Advance th->th_seq to correspond to first data byte. 1239 * If data, trim to stay within window, 1240 * dropping FIN if necessary. 1241 */ 1242 th->th_seq++; 1243 if (tlen > tp->rcv_wnd) { 1244 todrop = tlen - tp->rcv_wnd; 1245 m_adj(m, -todrop); 1246 tlen = tp->rcv_wnd; 1247 thflags &= ~TH_FIN; 1248 tcpstat.tcps_rcvpackafterwin++; 1249 tcpstat.tcps_rcvbyteafterwin += todrop; 1250 } 1251 tp->snd_wl1 = th->th_seq - 1; 1252 tp->rcv_up = th->th_seq; 1253 /* 1254 * Client side of transaction: already sent SYN and data. 1255 * If the remote host used T/TCP to validate the SYN, 1256 * our data will be ACK'd; if so, enter normal data segment 1257 * processing in the middle of step 5, ack processing. 1258 * Otherwise, goto step 6. 1259 */ 1260 if (thflags & TH_ACK) 1261 goto process_ACK; 1262 1263 goto step6; 1264 1265 /* 1266 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1267 * if segment contains a SYN and CC [not CC.NEW] option: 1268 * if state == TIME_WAIT and connection duration > MSL, 1269 * drop packet and send RST; 1270 * 1271 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1272 * ack the FIN (and data) in retransmission queue. 1273 * Complete close and delete TCPCB. Then reprocess 1274 * segment, hoping to find new TCPCB in LISTEN state; 1275 * 1276 * else must be old SYN; drop it. 1277 * else do normal processing. 1278 */ 1279 case TCPS_LAST_ACK: 1280 case TCPS_CLOSING: 1281 case TCPS_TIME_WAIT: 1282 if ((thflags & TH_SYN) && 1283 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1284 if (tp->t_state == TCPS_TIME_WAIT && 1285 (ticks - tp->t_starttime) > tcp_msl) { 1286 rstreason = BANDLIM_UNLIMITED; 1287 goto dropwithreset; 1288 } 1289 if (CC_GT(to.to_cc, tp->cc_recv)) { 1290 tp = tcp_close(tp); 1291 goto findpcb; 1292 } 1293 else 1294 goto drop; 1295 } 1296 break; /* continue normal processing */ 1297 } 1298 1299 /* 1300 * States other than LISTEN or SYN_SENT. 1301 * First check the RST flag and sequence number since reset segments 1302 * are exempt from the timestamp and connection count tests. This 1303 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1304 * below which allowed reset segments in half the sequence space 1305 * to fall though and be processed (which gives forged reset 1306 * segments with a random sequence number a 50 percent chance of 1307 * killing a connection). 1308 * Then check timestamp, if present. 1309 * Then check the connection count, if present. 1310 * Then check that at least some bytes of segment are within 1311 * receive window. If segment begins before rcv_nxt, 1312 * drop leading data (and SYN); if nothing left, just ack. 1313 * 1314 * 1315 * If the RST bit is set, check the sequence number to see 1316 * if this is a valid reset segment. 1317 * RFC 793 page 37: 1318 * In all states except SYN-SENT, all reset (RST) segments 1319 * are validated by checking their SEQ-fields. A reset is 1320 * valid if its sequence number is in the window. 1321 * Note: this does not take into account delayed ACKs, so 1322 * we should test against last_ack_sent instead of rcv_nxt. 1323 * The sequence number in the reset segment is normally an 1324 * echo of our outgoing acknowlegement numbers, but some hosts 1325 * send a reset with the sequence number at the rightmost edge 1326 * of our receive window, and we have to handle this case. 1327 * If we have multiple segments in flight, the intial reset 1328 * segment sequence numbers will be to the left of last_ack_sent, 1329 * but they will eventually catch up. 1330 * In any case, it never made sense to trim reset segments to 1331 * fit the receive window since RFC 1122 says: 1332 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1333 * 1334 * A TCP SHOULD allow a received RST segment to include data. 1335 * 1336 * DISCUSSION 1337 * It has been suggested that a RST segment could contain 1338 * ASCII text that encoded and explained the cause of the 1339 * RST. No standard has yet been established for such 1340 * data. 1341 * 1342 * If the reset segment passes the sequence number test examine 1343 * the state: 1344 * SYN_RECEIVED STATE: 1345 * If passive open, return to LISTEN state. 1346 * If active open, inform user that connection was refused. 1347 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1348 * Inform user that connection was reset, and close tcb. 1349 * CLOSING, LAST_ACK STATES: 1350 * Close the tcb. 1351 * TIME_WAIT STATE: 1352 * Drop the segment - see Stevens, vol. 2, p. 964 and 1353 * RFC 1337. 1354 */ 1355 if (thflags & TH_RST) { 1356 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1357 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1358 switch (tp->t_state) { 1359 1360 case TCPS_SYN_RECEIVED: 1361 so->so_error = ECONNREFUSED; 1362 goto close; 1363 1364 case TCPS_ESTABLISHED: 1365 case TCPS_FIN_WAIT_1: 1366 case TCPS_FIN_WAIT_2: 1367 case TCPS_CLOSE_WAIT: 1368 so->so_error = ECONNRESET; 1369 close: 1370 tp->t_state = TCPS_CLOSED; 1371 tcpstat.tcps_drops++; 1372 tp = tcp_close(tp); 1373 break; 1374 1375 case TCPS_CLOSING: 1376 case TCPS_LAST_ACK: 1377 tp = tcp_close(tp); 1378 break; 1379 1380 case TCPS_TIME_WAIT: 1381 break; 1382 } 1383 } 1384 goto drop; 1385 } 1386 1387 /* 1388 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1389 * and it's less than ts_recent, drop it. 1390 */ 1391 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1392 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1393 1394 /* Check to see if ts_recent is over 24 days old. */ 1395 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1396 /* 1397 * Invalidate ts_recent. If this segment updates 1398 * ts_recent, the age will be reset later and ts_recent 1399 * will get a valid value. If it does not, setting 1400 * ts_recent to zero will at least satisfy the 1401 * requirement that zero be placed in the timestamp 1402 * echo reply when ts_recent isn't valid. The 1403 * age isn't reset until we get a valid ts_recent 1404 * because we don't want out-of-order segments to be 1405 * dropped when ts_recent is old. 1406 */ 1407 tp->ts_recent = 0; 1408 } else { 1409 tcpstat.tcps_rcvduppack++; 1410 tcpstat.tcps_rcvdupbyte += tlen; 1411 tcpstat.tcps_pawsdrop++; 1412 if (tlen) 1413 goto dropafterack; 1414 goto drop; 1415 } 1416 } 1417 1418 /* 1419 * T/TCP mechanism 1420 * If T/TCP was negotiated and the segment doesn't have CC, 1421 * or if its CC is wrong then drop the segment. 1422 * RST segments do not have to comply with this. 1423 */ 1424 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1425 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1426 goto dropafterack; 1427 1428 /* 1429 * In the SYN-RECEIVED state, validate that the packet belongs to 1430 * this connection before trimming the data to fit the receive 1431 * window. Check the sequence number versus IRS since we know 1432 * the sequence numbers haven't wrapped. This is a partial fix 1433 * for the "LAND" DoS attack. 1434 */ 1435 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1436 rstreason = BANDLIM_RST_OPENPORT; 1437 goto dropwithreset; 1438 } 1439 1440 todrop = tp->rcv_nxt - th->th_seq; 1441 if (todrop > 0) { 1442 if (thflags & TH_SYN) { 1443 thflags &= ~TH_SYN; 1444 th->th_seq++; 1445 if (th->th_urp > 1) 1446 th->th_urp--; 1447 else 1448 thflags &= ~TH_URG; 1449 todrop--; 1450 } 1451 /* 1452 * Following if statement from Stevens, vol. 2, p. 960. 1453 */ 1454 if (todrop > tlen 1455 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1456 /* 1457 * Any valid FIN must be to the left of the window. 1458 * At this point the FIN must be a duplicate or out 1459 * of sequence; drop it. 1460 */ 1461 thflags &= ~TH_FIN; 1462 1463 /* 1464 * Send an ACK to resynchronize and drop any data. 1465 * But keep on processing for RST or ACK. 1466 */ 1467 tp->t_flags |= TF_ACKNOW; 1468 todrop = tlen; 1469 tcpstat.tcps_rcvduppack++; 1470 tcpstat.tcps_rcvdupbyte += todrop; 1471 } else { 1472 tcpstat.tcps_rcvpartduppack++; 1473 tcpstat.tcps_rcvpartdupbyte += todrop; 1474 } 1475 drop_hdrlen += todrop; /* drop from the top afterwards */ 1476 th->th_seq += todrop; 1477 tlen -= todrop; 1478 if (th->th_urp > todrop) 1479 th->th_urp -= todrop; 1480 else { 1481 thflags &= ~TH_URG; 1482 th->th_urp = 0; 1483 } 1484 } 1485 1486 /* 1487 * If new data are received on a connection after the 1488 * user processes are gone, then RST the other end. 1489 */ 1490 if ((so->so_state & SS_NOFDREF) && 1491 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1492 tp = tcp_close(tp); 1493 tcpstat.tcps_rcvafterclose++; 1494 rstreason = BANDLIM_UNLIMITED; 1495 goto dropwithreset; 1496 } 1497 1498 /* 1499 * If segment ends after window, drop trailing data 1500 * (and PUSH and FIN); if nothing left, just ACK. 1501 */ 1502 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1503 if (todrop > 0) { 1504 tcpstat.tcps_rcvpackafterwin++; 1505 if (todrop >= tlen) { 1506 tcpstat.tcps_rcvbyteafterwin += tlen; 1507 /* 1508 * If a new connection request is received 1509 * while in TIME_WAIT, drop the old connection 1510 * and start over if the sequence numbers 1511 * are above the previous ones. 1512 */ 1513 if (thflags & TH_SYN && 1514 tp->t_state == TCPS_TIME_WAIT && 1515 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1516 tp = tcp_close(tp); 1517 goto findpcb; 1518 } 1519 /* 1520 * If window is closed can only take segments at 1521 * window edge, and have to drop data and PUSH from 1522 * incoming segments. Continue processing, but 1523 * remember to ack. Otherwise, drop segment 1524 * and ack. 1525 */ 1526 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1527 tp->t_flags |= TF_ACKNOW; 1528 tcpstat.tcps_rcvwinprobe++; 1529 } else 1530 goto dropafterack; 1531 } else 1532 tcpstat.tcps_rcvbyteafterwin += todrop; 1533 m_adj(m, -todrop); 1534 tlen -= todrop; 1535 thflags &= ~(TH_PUSH|TH_FIN); 1536 } 1537 1538 /* 1539 * If last ACK falls within this segment's sequence numbers, 1540 * record its timestamp. 1541 * NOTE that the test is modified according to the latest 1542 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1543 */ 1544 if ((to.to_flags & TOF_TS) != 0 && 1545 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1546 tp->ts_recent_age = ticks; 1547 tp->ts_recent = to.to_tsval; 1548 } 1549 1550 /* 1551 * If a SYN is in the window, then this is an 1552 * error and we send an RST and drop the connection. 1553 */ 1554 if (thflags & TH_SYN) { 1555 tp = tcp_drop(tp, ECONNRESET); 1556 rstreason = BANDLIM_UNLIMITED; 1557 goto dropwithreset; 1558 } 1559 1560 /* 1561 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1562 * flag is on (half-synchronized state), then queue data for 1563 * later processing; else drop segment and return. 1564 */ 1565 if ((thflags & TH_ACK) == 0) { 1566 if (tp->t_state == TCPS_SYN_RECEIVED || 1567 (tp->t_flags & TF_NEEDSYN)) 1568 goto step6; 1569 else 1570 goto drop; 1571 } 1572 1573 /* 1574 * Ack processing. 1575 */ 1576 switch (tp->t_state) { 1577 1578 /* 1579 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1580 * ESTABLISHED state and continue processing. 1581 * The ACK was checked above. 1582 */ 1583 case TCPS_SYN_RECEIVED: 1584 1585 tcpstat.tcps_connects++; 1586 soisconnected(so); 1587 /* Do window scaling? */ 1588 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1589 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1590 tp->snd_scale = tp->requested_s_scale; 1591 tp->rcv_scale = tp->request_r_scale; 1592 } 1593 /* 1594 * Upon successful completion of 3-way handshake, 1595 * update cache.CC if it was undefined, pass any queued 1596 * data to the user, and advance state appropriately. 1597 */ 1598 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1599 taop->tao_cc == 0) 1600 taop->tao_cc = tp->cc_recv; 1601 1602 /* 1603 * Make transitions: 1604 * SYN-RECEIVED -> ESTABLISHED 1605 * SYN-RECEIVED* -> FIN-WAIT-1 1606 */ 1607 tp->t_starttime = ticks; 1608 if (tp->t_flags & TF_NEEDFIN) { 1609 tp->t_state = TCPS_FIN_WAIT_1; 1610 tp->t_flags &= ~TF_NEEDFIN; 1611 } else { 1612 tp->t_state = TCPS_ESTABLISHED; 1613 callout_reset(tp->tt_keep, tcp_keepidle, 1614 tcp_timer_keep, tp); 1615 } 1616 /* 1617 * If segment contains data or ACK, will call tcp_reass() 1618 * later; if not, do so now to pass queued data to user. 1619 */ 1620 if (tlen == 0 && (thflags & TH_FIN) == 0) 1621 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1622 (struct mbuf *)0); 1623 tp->snd_wl1 = th->th_seq - 1; 1624 /* fall into ... */ 1625 1626 /* 1627 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1628 * ACKs. If the ack is in the range 1629 * tp->snd_una < th->th_ack <= tp->snd_max 1630 * then advance tp->snd_una to th->th_ack and drop 1631 * data from the retransmission queue. If this ACK reflects 1632 * more up to date window information we update our window information. 1633 */ 1634 case TCPS_ESTABLISHED: 1635 case TCPS_FIN_WAIT_1: 1636 case TCPS_FIN_WAIT_2: 1637 case TCPS_CLOSE_WAIT: 1638 case TCPS_CLOSING: 1639 case TCPS_LAST_ACK: 1640 case TCPS_TIME_WAIT: 1641 1642 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1643 if (tlen == 0 && tiwin == tp->snd_wnd) { 1644 tcpstat.tcps_rcvdupack++; 1645 /* 1646 * If we have outstanding data (other than 1647 * a window probe), this is a completely 1648 * duplicate ack (ie, window info didn't 1649 * change), the ack is the biggest we've 1650 * seen and we've seen exactly our rexmt 1651 * threshhold of them, assume a packet 1652 * has been dropped and retransmit it. 1653 * Kludge snd_nxt & the congestion 1654 * window so we send only this one 1655 * packet. 1656 * 1657 * We know we're losing at the current 1658 * window size so do congestion avoidance 1659 * (set ssthresh to half the current window 1660 * and pull our congestion window back to 1661 * the new ssthresh). 1662 * 1663 * Dup acks mean that packets have left the 1664 * network (they're now cached at the receiver) 1665 * so bump cwnd by the amount in the receiver 1666 * to keep a constant cwnd packets in the 1667 * network. 1668 */ 1669 if (!callout_active(tp->tt_rexmt) || 1670 th->th_ack != tp->snd_una) 1671 tp->t_dupacks = 0; 1672 else if (++tp->t_dupacks > tcprexmtthresh || 1673 (tcp_do_newreno && 1674 IN_FASTRECOVERY(tp))) { 1675 tp->snd_cwnd += tp->t_maxseg; 1676 (void) tcp_output(tp); 1677 goto drop; 1678 } else if (tp->t_dupacks == tcprexmtthresh) { 1679 tcp_seq onxt = tp->snd_nxt; 1680 u_int win; 1681 if (tcp_do_newreno && 1682 SEQ_LEQ(th->th_ack, 1683 tp->snd_recover)) { 1684 tp->t_dupacks = 0; 1685 break; 1686 } 1687 win = min(tp->snd_wnd, tp->snd_cwnd) / 1688 2 / tp->t_maxseg; 1689 if (win < 2) 1690 win = 2; 1691 tp->snd_ssthresh = win * tp->t_maxseg; 1692 ENTER_FASTRECOVERY(tp); 1693 tp->snd_recover = tp->snd_max; 1694 callout_stop(tp->tt_rexmt); 1695 tp->t_rtttime = 0; 1696 tp->snd_nxt = th->th_ack; 1697 tp->snd_cwnd = tp->t_maxseg; 1698 (void) tcp_output(tp); 1699 KASSERT(tp->snd_limited <= 2, 1700 ("tp->snd_limited too big")); 1701 tp->snd_cwnd = tp->snd_ssthresh + 1702 (tp->t_maxseg * 1703 (tp->t_dupacks - tp->snd_limited)); 1704 if (SEQ_GT(onxt, tp->snd_nxt)) 1705 tp->snd_nxt = onxt; 1706 goto drop; 1707 } else if (tcp_do_limitedtransmit) { 1708 u_long oldcwnd = tp->snd_cwnd; 1709 tcp_seq oldsndmax = tp->snd_max; 1710 u_int sent; 1711 KASSERT(tp->t_dupacks == 1 || 1712 tp->t_dupacks == 2, 1713 ("dupacks not 1 or 2")); 1714 if (tp->t_dupacks == 1) { 1715 tp->snd_limited = 0; 1716 tp->snd_cwnd += tp->t_maxseg; 1717 } else { 1718 tp->snd_cwnd += 1719 tp->t_maxseg * 2; 1720 } 1721 (void) tcp_output(tp); 1722 sent = tp->snd_max - oldsndmax; 1723 if (sent > tp->t_maxseg) { 1724 KASSERT(tp->snd_limited == 0 && 1725 tp->t_dupacks == 2, 1726 ("sent too much")); 1727 tp->snd_limited = 2; 1728 } else if (sent > 0) 1729 ++tp->snd_limited; 1730 tp->snd_cwnd = oldcwnd; 1731 goto drop; 1732 } 1733 } else 1734 tp->t_dupacks = 0; 1735 break; 1736 } 1737 1738 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1739 1740 /* 1741 * If the congestion window was inflated to account 1742 * for the other side's cached packets, retract it. 1743 */ 1744 if (tcp_do_newreno) { 1745 if (IN_FASTRECOVERY(tp)) { 1746 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1747 tcp_newreno_partial_ack(tp, th); 1748 } else { 1749 /* 1750 * Window inflation should have left us 1751 * with approximately snd_ssthresh 1752 * outstanding data. 1753 * But in case we would be inclined to 1754 * send a burst, better to do it via 1755 * the slow start mechanism. 1756 */ 1757 if (SEQ_GT(th->th_ack + 1758 tp->snd_ssthresh, 1759 tp->snd_max)) 1760 tp->snd_cwnd = tp->snd_max - 1761 th->th_ack + 1762 tp->t_maxseg; 1763 else 1764 tp->snd_cwnd = tp->snd_ssthresh; 1765 } 1766 } 1767 } else { 1768 if (tp->t_dupacks >= tcprexmtthresh && 1769 tp->snd_cwnd > tp->snd_ssthresh) 1770 tp->snd_cwnd = tp->snd_ssthresh; 1771 } 1772 tp->t_dupacks = 0; 1773 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1774 tcpstat.tcps_rcvacktoomuch++; 1775 goto dropafterack; 1776 } 1777 /* 1778 * If we reach this point, ACK is not a duplicate, 1779 * i.e., it ACKs something we sent. 1780 */ 1781 if (tp->t_flags & TF_NEEDSYN) { 1782 /* 1783 * T/TCP: Connection was half-synchronized, and our 1784 * SYN has been ACK'd (so connection is now fully 1785 * synchronized). Go to non-starred state, 1786 * increment snd_una for ACK of SYN, and check if 1787 * we can do window scaling. 1788 */ 1789 tp->t_flags &= ~TF_NEEDSYN; 1790 tp->snd_una++; 1791 /* Do window scaling? */ 1792 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1793 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1794 tp->snd_scale = tp->requested_s_scale; 1795 tp->rcv_scale = tp->request_r_scale; 1796 } 1797 } 1798 1799 process_ACK: 1800 acked = th->th_ack - tp->snd_una; 1801 tcpstat.tcps_rcvackpack++; 1802 tcpstat.tcps_rcvackbyte += acked; 1803 1804 /* 1805 * If we just performed our first retransmit, and the ACK 1806 * arrives within our recovery window, then it was a mistake 1807 * to do the retransmit in the first place. Recover our 1808 * original cwnd and ssthresh, and proceed to transmit where 1809 * we left off. 1810 */ 1811 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1812 tp->snd_cwnd = tp->snd_cwnd_prev; 1813 tp->snd_ssthresh = tp->snd_ssthresh_prev; 1814 tp->snd_recover = tp->snd_recover_prev; 1815 if (tp->t_flags & TF_WASFRECOVERY) 1816 ENTER_FASTRECOVERY(tp); 1817 tp->snd_nxt = tp->snd_max; 1818 tp->t_badrxtwin = 0; /* XXX probably not required */ 1819 } 1820 1821 /* 1822 * If we have a timestamp reply, update smoothed 1823 * round trip time. If no timestamp is present but 1824 * transmit timer is running and timed sequence 1825 * number was acked, update smoothed round trip time. 1826 * Since we now have an rtt measurement, cancel the 1827 * timer backoff (cf., Phil Karn's retransmit alg.). 1828 * Recompute the initial retransmit timer. 1829 * 1830 * Some machines (certain windows boxes) send broken 1831 * timestamp replies during the SYN+ACK phase, ignore 1832 * timestamps of 0. 1833 */ 1834 if ((to.to_flags & TOF_TS) != 0 && 1835 to.to_tsecr) { 1836 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1837 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 1838 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1839 } 1840 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1841 1842 /* 1843 * If all outstanding data is acked, stop retransmit 1844 * timer and remember to restart (more output or persist). 1845 * If there is more data to be acked, restart retransmit 1846 * timer, using current (possibly backed-off) value. 1847 */ 1848 if (th->th_ack == tp->snd_max) { 1849 callout_stop(tp->tt_rexmt); 1850 needoutput = 1; 1851 } else if (!callout_active(tp->tt_persist)) 1852 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1853 tcp_timer_rexmt, tp); 1854 1855 /* 1856 * If no data (only SYN) was ACK'd, 1857 * skip rest of ACK processing. 1858 */ 1859 if (acked == 0) 1860 goto step6; 1861 1862 /* 1863 * When new data is acked, open the congestion window. 1864 * If the window gives us less than ssthresh packets 1865 * in flight, open exponentially (maxseg per packet). 1866 * Otherwise open linearly: maxseg per window 1867 * (maxseg^2 / cwnd per packet). 1868 */ 1869 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) { 1870 register u_int cw = tp->snd_cwnd; 1871 register u_int incr = tp->t_maxseg; 1872 if (cw > tp->snd_ssthresh) 1873 incr = incr * incr / cw; 1874 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 1875 } 1876 if (acked > so->so_snd.sb_cc) { 1877 tp->snd_wnd -= so->so_snd.sb_cc; 1878 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1879 ourfinisacked = 1; 1880 } else { 1881 sbdrop(&so->so_snd, acked); 1882 tp->snd_wnd -= acked; 1883 ourfinisacked = 0; 1884 } 1885 sowwakeup(so); 1886 /* detect una wraparound */ 1887 if (tcp_do_newreno && !IN_FASTRECOVERY(tp) && 1888 SEQ_GT(tp->snd_una, tp->snd_recover) && 1889 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1890 tp->snd_recover = th->th_ack - 1; 1891 if (tcp_do_newreno && IN_FASTRECOVERY(tp) && 1892 SEQ_GEQ(th->th_ack, tp->snd_recover)) 1893 EXIT_FASTRECOVERY(tp); 1894 tp->snd_una = th->th_ack; 1895 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1896 tp->snd_nxt = tp->snd_una; 1897 1898 switch (tp->t_state) { 1899 1900 /* 1901 * In FIN_WAIT_1 STATE in addition to the processing 1902 * for the ESTABLISHED state if our FIN is now acknowledged 1903 * then enter FIN_WAIT_2. 1904 */ 1905 case TCPS_FIN_WAIT_1: 1906 if (ourfinisacked) { 1907 /* 1908 * If we can't receive any more 1909 * data, then closing user can proceed. 1910 * Starting the timer is contrary to the 1911 * specification, but if we don't get a FIN 1912 * we'll hang forever. 1913 */ 1914 if (so->so_state & SS_CANTRCVMORE) { 1915 soisdisconnected(so); 1916 callout_reset(tp->tt_2msl, tcp_maxidle, 1917 tcp_timer_2msl, tp); 1918 } 1919 tp->t_state = TCPS_FIN_WAIT_2; 1920 } 1921 break; 1922 1923 /* 1924 * In CLOSING STATE in addition to the processing for 1925 * the ESTABLISHED state if the ACK acknowledges our FIN 1926 * then enter the TIME-WAIT state, otherwise ignore 1927 * the segment. 1928 */ 1929 case TCPS_CLOSING: 1930 if (ourfinisacked) { 1931 tp->t_state = TCPS_TIME_WAIT; 1932 tcp_canceltimers(tp); 1933 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1934 if (tp->cc_recv != 0 && 1935 (ticks - tp->t_starttime) < tcp_msl) 1936 callout_reset(tp->tt_2msl, 1937 tp->t_rxtcur * 1938 TCPTV_TWTRUNC, 1939 tcp_timer_2msl, tp); 1940 else 1941 callout_reset(tp->tt_2msl, 2 * tcp_msl, 1942 tcp_timer_2msl, tp); 1943 soisdisconnected(so); 1944 } 1945 break; 1946 1947 /* 1948 * In LAST_ACK, we may still be waiting for data to drain 1949 * and/or to be acked, as well as for the ack of our FIN. 1950 * If our FIN is now acknowledged, delete the TCB, 1951 * enter the closed state and return. 1952 */ 1953 case TCPS_LAST_ACK: 1954 if (ourfinisacked) { 1955 tp = tcp_close(tp); 1956 goto drop; 1957 } 1958 break; 1959 1960 /* 1961 * In TIME_WAIT state the only thing that should arrive 1962 * is a retransmission of the remote FIN. Acknowledge 1963 * it and restart the finack timer. 1964 */ 1965 case TCPS_TIME_WAIT: 1966 callout_reset(tp->tt_2msl, 2 * tcp_msl, 1967 tcp_timer_2msl, tp); 1968 goto dropafterack; 1969 } 1970 } 1971 1972 step6: 1973 /* 1974 * Update window information. 1975 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1976 */ 1977 if ((thflags & TH_ACK) && 1978 (SEQ_LT(tp->snd_wl1, th->th_seq) || 1979 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 1980 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 1981 /* keep track of pure window updates */ 1982 if (tlen == 0 && 1983 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 1984 tcpstat.tcps_rcvwinupd++; 1985 tp->snd_wnd = tiwin; 1986 tp->snd_wl1 = th->th_seq; 1987 tp->snd_wl2 = th->th_ack; 1988 if (tp->snd_wnd > tp->max_sndwnd) 1989 tp->max_sndwnd = tp->snd_wnd; 1990 needoutput = 1; 1991 } 1992 1993 /* 1994 * Process segments with URG. 1995 */ 1996 if ((thflags & TH_URG) && th->th_urp && 1997 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1998 /* 1999 * This is a kludge, but if we receive and accept 2000 * random urgent pointers, we'll crash in 2001 * soreceive. It's hard to imagine someone 2002 * actually wanting to send this much urgent data. 2003 */ 2004 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2005 th->th_urp = 0; /* XXX */ 2006 thflags &= ~TH_URG; /* XXX */ 2007 goto dodata; /* XXX */ 2008 } 2009 /* 2010 * If this segment advances the known urgent pointer, 2011 * then mark the data stream. This should not happen 2012 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2013 * a FIN has been received from the remote side. 2014 * In these states we ignore the URG. 2015 * 2016 * According to RFC961 (Assigned Protocols), 2017 * the urgent pointer points to the last octet 2018 * of urgent data. We continue, however, 2019 * to consider it to indicate the first octet 2020 * of data past the urgent section as the original 2021 * spec states (in one of two places). 2022 */ 2023 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2024 tp->rcv_up = th->th_seq + th->th_urp; 2025 so->so_oobmark = so->so_rcv.sb_cc + 2026 (tp->rcv_up - tp->rcv_nxt) - 1; 2027 if (so->so_oobmark == 0) 2028 so->so_state |= SS_RCVATMARK; 2029 sohasoutofband(so); 2030 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2031 } 2032 /* 2033 * Remove out of band data so doesn't get presented to user. 2034 * This can happen independent of advancing the URG pointer, 2035 * but if two URG's are pending at once, some out-of-band 2036 * data may creep in... ick. 2037 */ 2038 if (th->th_urp <= (u_long)tlen 2039 #ifdef SO_OOBINLINE 2040 && (so->so_options & SO_OOBINLINE) == 0 2041 #endif 2042 ) 2043 tcp_pulloutofband(so, th, m, 2044 drop_hdrlen); /* hdr drop is delayed */ 2045 } else { 2046 /* 2047 * If no out of band data is expected, 2048 * pull receive urgent pointer along 2049 * with the receive window. 2050 */ 2051 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2052 tp->rcv_up = tp->rcv_nxt; 2053 } 2054 dodata: /* XXX */ 2055 2056 /* 2057 * Process the segment text, merging it into the TCP sequencing queue, 2058 * and arranging for acknowledgment of receipt if necessary. 2059 * This process logically involves adjusting tp->rcv_wnd as data 2060 * is presented to the user (this happens in tcp_usrreq.c, 2061 * case PRU_RCVD). If a FIN has already been received on this 2062 * connection then we just ignore the text. 2063 */ 2064 if ((tlen || (thflags & TH_FIN)) && 2065 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2066 m_adj(m, drop_hdrlen); /* delayed header drop */ 2067 /* 2068 * Insert segment which includes th into TCP reassembly queue 2069 * with control block tp. Set thflags to whether reassembly now 2070 * includes a segment with FIN. This handles the common case 2071 * inline (segment is the next to be received on an established 2072 * connection, and the queue is empty), avoiding linkage into 2073 * and removal from the queue and repetition of various 2074 * conversions. 2075 * Set DELACK for segments received in order, but ack 2076 * immediately when segments are out of order (so 2077 * fast retransmit can work). 2078 */ 2079 if (th->th_seq == tp->rcv_nxt && 2080 LIST_EMPTY(&tp->t_segq) && 2081 TCPS_HAVEESTABLISHED(tp->t_state)) { 2082 if (DELAY_ACK(tp)) 2083 callout_reset(tp->tt_delack, tcp_delacktime, 2084 tcp_timer_delack, tp); 2085 else 2086 tp->t_flags |= TF_ACKNOW; 2087 tp->rcv_nxt += tlen; 2088 thflags = th->th_flags & TH_FIN; 2089 tcpstat.tcps_rcvpack++; 2090 tcpstat.tcps_rcvbyte += tlen; 2091 ND6_HINT(tp); 2092 if (so->so_state & SS_CANTRCVMORE) 2093 m_freem(m); 2094 else 2095 sbappend(&so->so_rcv, m); 2096 sorwakeup(so); 2097 } else { 2098 thflags = tcp_reass(tp, th, &tlen, m); 2099 tp->t_flags |= TF_ACKNOW; 2100 } 2101 2102 /* 2103 * Note the amount of data that peer has sent into 2104 * our window, in order to estimate the sender's 2105 * buffer size. 2106 */ 2107 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2108 } else { 2109 m_freem(m); 2110 thflags &= ~TH_FIN; 2111 } 2112 2113 /* 2114 * If FIN is received ACK the FIN and let the user know 2115 * that the connection is closing. 2116 */ 2117 if (thflags & TH_FIN) { 2118 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2119 socantrcvmore(so); 2120 /* 2121 * If connection is half-synchronized 2122 * (ie NEEDSYN flag on) then delay ACK, 2123 * so it may be piggybacked when SYN is sent. 2124 * Otherwise, since we received a FIN then no 2125 * more input can be expected, send ACK now. 2126 */ 2127 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2128 callout_reset(tp->tt_delack, tcp_delacktime, 2129 tcp_timer_delack, tp); 2130 else 2131 tp->t_flags |= TF_ACKNOW; 2132 tp->rcv_nxt++; 2133 } 2134 switch (tp->t_state) { 2135 2136 /* 2137 * In SYN_RECEIVED and ESTABLISHED STATES 2138 * enter the CLOSE_WAIT state. 2139 */ 2140 case TCPS_SYN_RECEIVED: 2141 tp->t_starttime = ticks; 2142 /*FALLTHROUGH*/ 2143 case TCPS_ESTABLISHED: 2144 tp->t_state = TCPS_CLOSE_WAIT; 2145 break; 2146 2147 /* 2148 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2149 * enter the CLOSING state. 2150 */ 2151 case TCPS_FIN_WAIT_1: 2152 tp->t_state = TCPS_CLOSING; 2153 break; 2154 2155 /* 2156 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2157 * starting the time-wait timer, turning off the other 2158 * standard timers. 2159 */ 2160 case TCPS_FIN_WAIT_2: 2161 tp->t_state = TCPS_TIME_WAIT; 2162 tcp_canceltimers(tp); 2163 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2164 if (tp->cc_recv != 0 && 2165 (ticks - tp->t_starttime) < tcp_msl) { 2166 callout_reset(tp->tt_2msl, 2167 tp->t_rxtcur * TCPTV_TWTRUNC, 2168 tcp_timer_2msl, tp); 2169 /* For transaction client, force ACK now. */ 2170 tp->t_flags |= TF_ACKNOW; 2171 } 2172 else 2173 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2174 tcp_timer_2msl, tp); 2175 soisdisconnected(so); 2176 break; 2177 2178 /* 2179 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2180 */ 2181 case TCPS_TIME_WAIT: 2182 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2183 tcp_timer_2msl, tp); 2184 break; 2185 } 2186 } 2187 #ifdef TCPDEBUG 2188 if (so->so_options & SO_DEBUG) 2189 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2190 &tcp_savetcp, 0); 2191 #endif 2192 2193 /* 2194 * Return any desired output. 2195 */ 2196 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2197 (void) tcp_output(tp); 2198 return; 2199 2200 dropafterack: 2201 /* 2202 * Generate an ACK dropping incoming segment if it occupies 2203 * sequence space, where the ACK reflects our state. 2204 * 2205 * We can now skip the test for the RST flag since all 2206 * paths to this code happen after packets containing 2207 * RST have been dropped. 2208 * 2209 * In the SYN-RECEIVED state, don't send an ACK unless the 2210 * segment we received passes the SYN-RECEIVED ACK test. 2211 * If it fails send a RST. This breaks the loop in the 2212 * "LAND" DoS attack, and also prevents an ACK storm 2213 * between two listening ports that have been sent forged 2214 * SYN segments, each with the source address of the other. 2215 */ 2216 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2217 (SEQ_GT(tp->snd_una, th->th_ack) || 2218 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2219 rstreason = BANDLIM_RST_OPENPORT; 2220 goto dropwithreset; 2221 } 2222 #ifdef TCPDEBUG 2223 if (so->so_options & SO_DEBUG) 2224 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2225 &tcp_savetcp, 0); 2226 #endif 2227 m_freem(m); 2228 tp->t_flags |= TF_ACKNOW; 2229 (void) tcp_output(tp); 2230 return; 2231 2232 dropwithreset: 2233 /* 2234 * Generate a RST, dropping incoming segment. 2235 * Make ACK acceptable to originator of segment. 2236 * Don't bother to respond if destination was broadcast/multicast. 2237 */ 2238 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2239 goto drop; 2240 if (isipv6) { 2241 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2242 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2243 goto drop; 2244 } else { 2245 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2246 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2247 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2248 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2249 goto drop; 2250 } 2251 /* IPv6 anycast check is done at tcp6_input() */ 2252 2253 /* 2254 * Perform bandwidth limiting. 2255 */ 2256 #ifdef ICMP_BANDLIM 2257 if (badport_bandlim(rstreason) < 0) 2258 goto drop; 2259 #endif 2260 2261 #ifdef TCPDEBUG 2262 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2263 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2264 &tcp_savetcp, 0); 2265 #endif 2266 if (thflags & TH_ACK) 2267 /* mtod() below is safe as long as hdr dropping is delayed */ 2268 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2269 TH_RST); 2270 else { 2271 if (thflags & TH_SYN) 2272 tlen++; 2273 /* mtod() below is safe as long as hdr dropping is delayed */ 2274 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2275 (tcp_seq)0, TH_RST|TH_ACK); 2276 } 2277 return; 2278 2279 drop: 2280 /* 2281 * Drop space held by incoming segment and return. 2282 */ 2283 #ifdef TCPDEBUG 2284 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2285 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2286 &tcp_savetcp, 0); 2287 #endif 2288 m_freem(m); 2289 return; 2290 } 2291 2292 /* 2293 * Parse TCP options and place in tcpopt. 2294 */ 2295 static void 2296 tcp_dooptions(to, cp, cnt, is_syn) 2297 struct tcpopt *to; 2298 u_char *cp; 2299 int cnt; 2300 { 2301 int opt, optlen; 2302 2303 to->to_flags = 0; 2304 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2305 opt = cp[0]; 2306 if (opt == TCPOPT_EOL) 2307 break; 2308 if (opt == TCPOPT_NOP) 2309 optlen = 1; 2310 else { 2311 if (cnt < 2) 2312 break; 2313 optlen = cp[1]; 2314 if (optlen < 2 || optlen > cnt) 2315 break; 2316 } 2317 switch (opt) { 2318 case TCPOPT_MAXSEG: 2319 if (optlen != TCPOLEN_MAXSEG) 2320 continue; 2321 if (!is_syn) 2322 continue; 2323 to->to_flags |= TOF_MSS; 2324 bcopy((char *)cp + 2, 2325 (char *)&to->to_mss, sizeof(to->to_mss)); 2326 to->to_mss = ntohs(to->to_mss); 2327 break; 2328 case TCPOPT_WINDOW: 2329 if (optlen != TCPOLEN_WINDOW) 2330 continue; 2331 if (! is_syn) 2332 continue; 2333 to->to_flags |= TOF_SCALE; 2334 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2335 break; 2336 case TCPOPT_TIMESTAMP: 2337 if (optlen != TCPOLEN_TIMESTAMP) 2338 continue; 2339 to->to_flags |= TOF_TS; 2340 bcopy((char *)cp + 2, 2341 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2342 to->to_tsval = ntohl(to->to_tsval); 2343 bcopy((char *)cp + 6, 2344 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2345 to->to_tsecr = ntohl(to->to_tsecr); 2346 break; 2347 case TCPOPT_CC: 2348 if (optlen != TCPOLEN_CC) 2349 continue; 2350 to->to_flags |= TOF_CC; 2351 bcopy((char *)cp + 2, 2352 (char *)&to->to_cc, sizeof(to->to_cc)); 2353 to->to_cc = ntohl(to->to_cc); 2354 break; 2355 case TCPOPT_CCNEW: 2356 if (optlen != TCPOLEN_CC) 2357 continue; 2358 if (!is_syn) 2359 continue; 2360 to->to_flags |= TOF_CCNEW; 2361 bcopy((char *)cp + 2, 2362 (char *)&to->to_cc, sizeof(to->to_cc)); 2363 to->to_cc = ntohl(to->to_cc); 2364 break; 2365 case TCPOPT_CCECHO: 2366 if (optlen != TCPOLEN_CC) 2367 continue; 2368 if (!is_syn) 2369 continue; 2370 to->to_flags |= TOF_CCECHO; 2371 bcopy((char *)cp + 2, 2372 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2373 to->to_ccecho = ntohl(to->to_ccecho); 2374 break; 2375 default: 2376 continue; 2377 } 2378 } 2379 } 2380 2381 /* 2382 * Pull out of band byte out of a segment so 2383 * it doesn't appear in the user's data queue. 2384 * It is still reflected in the segment length for 2385 * sequencing purposes. 2386 */ 2387 static void 2388 tcp_pulloutofband(so, th, m, off) 2389 struct socket *so; 2390 struct tcphdr *th; 2391 register struct mbuf *m; 2392 int off; /* delayed to be droped hdrlen */ 2393 { 2394 int cnt = off + th->th_urp - 1; 2395 2396 while (cnt >= 0) { 2397 if (m->m_len > cnt) { 2398 char *cp = mtod(m, caddr_t) + cnt; 2399 struct tcpcb *tp = sototcpcb(so); 2400 2401 tp->t_iobc = *cp; 2402 tp->t_oobflags |= TCPOOB_HAVEDATA; 2403 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2404 m->m_len--; 2405 if (m->m_flags & M_PKTHDR) 2406 m->m_pkthdr.len--; 2407 return; 2408 } 2409 cnt -= m->m_len; 2410 m = m->m_next; 2411 if (m == 0) 2412 break; 2413 } 2414 panic("tcp_pulloutofband"); 2415 } 2416 2417 /* 2418 * Collect new round-trip time estimate 2419 * and update averages and current timeout. 2420 */ 2421 static void 2422 tcp_xmit_timer(tp, rtt) 2423 register struct tcpcb *tp; 2424 int rtt; 2425 { 2426 register int delta; 2427 2428 tcpstat.tcps_rttupdated++; 2429 tp->t_rttupdated++; 2430 if (tp->t_srtt != 0) { 2431 /* 2432 * srtt is stored as fixed point with 5 bits after the 2433 * binary point (i.e., scaled by 8). The following magic 2434 * is equivalent to the smoothing algorithm in rfc793 with 2435 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2436 * point). Adjust rtt to origin 0. 2437 */ 2438 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2439 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2440 2441 if ((tp->t_srtt += delta) <= 0) 2442 tp->t_srtt = 1; 2443 2444 /* 2445 * We accumulate a smoothed rtt variance (actually, a 2446 * smoothed mean difference), then set the retransmit 2447 * timer to smoothed rtt + 4 times the smoothed variance. 2448 * rttvar is stored as fixed point with 4 bits after the 2449 * binary point (scaled by 16). The following is 2450 * equivalent to rfc793 smoothing with an alpha of .75 2451 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2452 * rfc793's wired-in beta. 2453 */ 2454 if (delta < 0) 2455 delta = -delta; 2456 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2457 if ((tp->t_rttvar += delta) <= 0) 2458 tp->t_rttvar = 1; 2459 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2460 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2461 } else { 2462 /* 2463 * No rtt measurement yet - use the unsmoothed rtt. 2464 * Set the variance to half the rtt (so our first 2465 * retransmit happens at 3*rtt). 2466 */ 2467 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2468 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2469 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2470 } 2471 tp->t_rtttime = 0; 2472 tp->t_rxtshift = 0; 2473 2474 /* 2475 * the retransmit should happen at rtt + 4 * rttvar. 2476 * Because of the way we do the smoothing, srtt and rttvar 2477 * will each average +1/2 tick of bias. When we compute 2478 * the retransmit timer, we want 1/2 tick of rounding and 2479 * 1 extra tick because of +-1/2 tick uncertainty in the 2480 * firing of the timer. The bias will give us exactly the 2481 * 1.5 tick we need. But, because the bias is 2482 * statistical, we have to test that we don't drop below 2483 * the minimum feasible timer (which is 2 ticks). 2484 */ 2485 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2486 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2487 2488 /* 2489 * We received an ack for a packet that wasn't retransmitted; 2490 * it is probably safe to discard any error indications we've 2491 * received recently. This isn't quite right, but close enough 2492 * for now (a route might have failed after we sent a segment, 2493 * and the return path might not be symmetrical). 2494 */ 2495 tp->t_softerror = 0; 2496 } 2497 2498 /* 2499 * Determine a reasonable value for maxseg size. 2500 * If the route is known, check route for mtu. 2501 * If none, use an mss that can be handled on the outgoing 2502 * interface without forcing IP to fragment; if bigger than 2503 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2504 * to utilize large mbufs. If no route is found, route has no mtu, 2505 * or the destination isn't local, use a default, hopefully conservative 2506 * size (usually 512 or the default IP max size, but no more than the mtu 2507 * of the interface), as we can't discover anything about intervening 2508 * gateways or networks. We also initialize the congestion/slow start 2509 * window to be a single segment if the destination isn't local. 2510 * While looking at the routing entry, we also initialize other path-dependent 2511 * parameters from pre-set or cached values in the routing entry. 2512 * 2513 * Also take into account the space needed for options that we 2514 * send regularly. Make maxseg shorter by that amount to assure 2515 * that we can send maxseg amount of data even when the options 2516 * are present. Store the upper limit of the length of options plus 2517 * data in maxopd. 2518 * 2519 * NOTE that this routine is only called when we process an incoming 2520 * segment, for outgoing segments only tcp_mssopt is called. 2521 * 2522 * In case of T/TCP, we call this routine during implicit connection 2523 * setup as well (offer = -1), to initialize maxseg from the cached 2524 * MSS of our peer. 2525 */ 2526 void 2527 tcp_mss(tp, offer) 2528 struct tcpcb *tp; 2529 int offer; 2530 { 2531 register struct rtentry *rt; 2532 struct ifnet *ifp; 2533 register int rtt, mss; 2534 u_long bufsize; 2535 struct inpcb *inp = tp->t_inpcb; 2536 struct socket *so; 2537 struct rmxp_tao *taop; 2538 int origoffer = offer; 2539 #ifdef INET6 2540 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2541 size_t min_protoh = isipv6 ? 2542 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2543 sizeof(struct tcpiphdr); 2544 #else 2545 const int isipv6 = 0; 2546 const size_t min_protoh = sizeof(struct tcpiphdr); 2547 #endif 2548 2549 if (isipv6) 2550 rt = tcp_rtlookup6(&inp->inp_inc); 2551 else 2552 rt = tcp_rtlookup(&inp->inp_inc); 2553 if (rt == NULL) { 2554 tp->t_maxopd = tp->t_maxseg = 2555 isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2556 return; 2557 } 2558 ifp = rt->rt_ifp; 2559 so = inp->inp_socket; 2560 2561 taop = rmx_taop(rt->rt_rmx); 2562 /* 2563 * Offer == -1 means that we didn't receive SYN yet, 2564 * use cached value in that case; 2565 */ 2566 if (offer == -1) 2567 offer = taop->tao_mssopt; 2568 /* 2569 * Offer == 0 means that there was no MSS on the SYN segment, 2570 * in this case we use tcp_mssdflt. 2571 */ 2572 if (offer == 0) 2573 offer = isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2574 else 2575 /* 2576 * Sanity check: make sure that maxopd will be large 2577 * enough to allow some data on segments even is the 2578 * all the option space is used (40bytes). Otherwise 2579 * funny things may happen in tcp_output. 2580 */ 2581 offer = max(offer, 64); 2582 taop->tao_mssopt = offer; 2583 2584 /* 2585 * While we're here, check if there's an initial rtt 2586 * or rttvar. Convert from the route-table units 2587 * to scaled multiples of the slow timeout timer. 2588 */ 2589 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2590 /* 2591 * XXX the lock bit for RTT indicates that the value 2592 * is also a minimum value; this is subject to time. 2593 */ 2594 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2595 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2596 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2597 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2598 tcpstat.tcps_usedrtt++; 2599 if (rt->rt_rmx.rmx_rttvar) { 2600 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2601 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2602 tcpstat.tcps_usedrttvar++; 2603 } else { 2604 /* default variation is +- 1 rtt */ 2605 tp->t_rttvar = 2606 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2607 } 2608 TCPT_RANGESET(tp->t_rxtcur, 2609 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2610 tp->t_rttmin, TCPTV_REXMTMAX); 2611 } 2612 /* 2613 * if there's an mtu associated with the route, use it 2614 * else, use the link mtu. 2615 */ 2616 if (rt->rt_rmx.rmx_mtu) 2617 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2618 else { 2619 if (isipv6) { 2620 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2621 min_protoh; 2622 if (!in6_localaddr(&inp->in6p_faddr)) 2623 mss = min(mss, tcp_v6mssdflt); 2624 } else { 2625 mss = ifp->if_mtu - min_protoh; 2626 if (!in_localaddr(inp->inp_faddr)) 2627 mss = min(mss, tcp_mssdflt); 2628 } 2629 } 2630 mss = min(mss, offer); 2631 /* 2632 * maxopd stores the maximum length of data AND options 2633 * in a segment; maxseg is the amount of data in a normal 2634 * segment. We need to store this value (maxopd) apart 2635 * from maxseg, because now every segment carries options 2636 * and thus we normally have somewhat less data in segments. 2637 */ 2638 tp->t_maxopd = mss; 2639 2640 /* 2641 * In case of T/TCP, origoffer==-1 indicates, that no segments 2642 * were received yet. In this case we just guess, otherwise 2643 * we do the same as before T/TCP. 2644 */ 2645 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2646 (origoffer == -1 || 2647 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2648 mss -= TCPOLEN_TSTAMP_APPA; 2649 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2650 (origoffer == -1 || 2651 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2652 mss -= TCPOLEN_CC_APPA; 2653 2654 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2655 if (mss > MCLBYTES) 2656 mss &= ~(MCLBYTES-1); 2657 #else 2658 if (mss > MCLBYTES) 2659 mss = mss / MCLBYTES * MCLBYTES; 2660 #endif 2661 /* 2662 * If there's a pipesize, change the socket buffer 2663 * to that size. Make the socket buffers an integral 2664 * number of mss units; if the mss is larger than 2665 * the socket buffer, decrease the mss. 2666 */ 2667 #ifdef RTV_SPIPE 2668 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2669 #endif 2670 bufsize = so->so_snd.sb_hiwat; 2671 if (bufsize < mss) 2672 mss = bufsize; 2673 else { 2674 bufsize = roundup(bufsize, mss); 2675 if (bufsize > sb_max) 2676 bufsize = sb_max; 2677 if (bufsize > so->so_snd.sb_hiwat) 2678 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2679 } 2680 tp->t_maxseg = mss; 2681 2682 #ifdef RTV_RPIPE 2683 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2684 #endif 2685 bufsize = so->so_rcv.sb_hiwat; 2686 if (bufsize > mss) { 2687 bufsize = roundup(bufsize, mss); 2688 if (bufsize > sb_max) 2689 bufsize = sb_max; 2690 if (bufsize > so->so_rcv.sb_hiwat) 2691 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2692 } 2693 2694 /* 2695 * Set the slow-start flight size depending on whether this 2696 * is a local network or not. 2697 */ 2698 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2699 (!isipv6 && in_localaddr(inp->inp_faddr))) 2700 tp->snd_cwnd = mss * ss_fltsz_local; 2701 else 2702 tp->snd_cwnd = mss * ss_fltsz; 2703 2704 if (rt->rt_rmx.rmx_ssthresh) { 2705 /* 2706 * There's some sort of gateway or interface 2707 * buffer limit on the path. Use this to set 2708 * the slow start threshhold, but set the 2709 * threshold to no less than 2*mss. 2710 */ 2711 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2712 tcpstat.tcps_usedssthresh++; 2713 } 2714 } 2715 2716 /* 2717 * Determine the MSS option to send on an outgoing SYN. 2718 */ 2719 int 2720 tcp_mssopt(tp) 2721 struct tcpcb *tp; 2722 { 2723 struct rtentry *rt; 2724 #ifdef INET6 2725 int isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2726 int min_protoh = isipv6 ? 2727 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2728 sizeof(struct tcpiphdr); 2729 #else 2730 const int isipv6 = 0; 2731 const size_t min_protoh = sizeof(struct tcpiphdr); 2732 #endif 2733 2734 if (isipv6) 2735 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 2736 else 2737 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 2738 if (rt == NULL) 2739 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2740 2741 return (rt->rt_ifp->if_mtu - min_protoh); 2742 } 2743 2744 2745 /* 2746 * When a partial ack arrives, force the retransmission of the 2747 * next unacknowledged segment. Do not clear tp->t_dupacks. 2748 * By setting snd_nxt to ti_ack, this forces retransmission timer to 2749 * be started again. 2750 */ 2751 static void 2752 tcp_newreno_partial_ack(tp, th) 2753 struct tcpcb *tp; 2754 struct tcphdr *th; 2755 { 2756 tcp_seq onxt = tp->snd_nxt; 2757 u_long ocwnd = tp->snd_cwnd; 2758 2759 callout_stop(tp->tt_rexmt); 2760 tp->t_rtttime = 0; 2761 tp->snd_nxt = th->th_ack; 2762 /* 2763 * Set snd_cwnd to one segment beyond acknowledged offset 2764 * (tp->snd_una has not yet been updated when this function is called.) 2765 */ 2766 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 2767 tp->t_flags |= TF_ACKNOW; 2768 (void) tcp_output(tp); 2769 tp->snd_cwnd = ocwnd; 2770 if (SEQ_GT(onxt, tp->snd_nxt)) 2771 tp->snd_nxt = onxt; 2772 /* 2773 * Partial window deflation. Relies on fact that tp->snd_una 2774 * not updated yet. 2775 */ 2776 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 2777 } 2778