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 1.7 2003/08/07 21:54:32 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 <netproto/key/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 static int tcp_do_rfc3390 = 1; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 135 &tcp_do_rfc3390, 0, 136 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 137 138 struct inpcbhead tcb; 139 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 140 struct inpcbinfo tcbinfo; 141 142 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 143 static void tcp_pulloutofband(struct socket *, 144 struct tcphdr *, struct mbuf *, int); 145 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 146 struct mbuf *); 147 static void tcp_xmit_timer(struct tcpcb *, int); 148 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 149 150 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 151 #ifdef INET6 152 #define ND6_HINT(tp) \ 153 do { \ 154 if ((tp) && (tp)->t_inpcb && \ 155 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ 156 (tp)->t_inpcb->in6p_route.ro_rt) \ 157 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 158 } while (0) 159 #else 160 #define ND6_HINT(tp) 161 #endif 162 163 /* 164 * Indicate whether this ack should be delayed. We can delay the ack if 165 * - delayed acks are enabled and 166 * - there is no delayed ack timer in progress and 167 * - our last ack wasn't a 0-sized window. We never want to delay 168 * the ack that opens up a 0-sized window. 169 */ 170 #define DELAY_ACK(tp) \ 171 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 172 (tp->t_flags & TF_RXWIN0SENT) == 0) 173 174 static int 175 tcp_reass(tp, th, tlenp, m) 176 struct tcpcb *tp; 177 struct tcphdr *th; 178 int *tlenp; 179 struct mbuf *m; 180 { 181 struct tseg_qent *q; 182 struct tseg_qent *p = NULL; 183 struct tseg_qent *nq; 184 struct tseg_qent *te; 185 struct socket *so = tp->t_inpcb->inp_socket; 186 int flags; 187 188 /* 189 * Call with th==0 after become established to 190 * force pre-ESTABLISHED data up to user socket. 191 */ 192 if (th == 0) 193 goto present; 194 195 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */ 196 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 197 M_NOWAIT); 198 if (te == NULL) { 199 tcpstat.tcps_rcvmemdrop++; 200 m_freem(m); 201 return (0); 202 } 203 204 /* 205 * Find a segment which begins after this one does. 206 */ 207 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 208 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 209 break; 210 p = q; 211 } 212 213 /* 214 * If there is a preceding segment, it may provide some of 215 * our data already. If so, drop the data from the incoming 216 * segment. If it provides all of our data, drop us. 217 */ 218 if (p != NULL) { 219 int i; 220 /* conversion to int (in i) handles seq wraparound */ 221 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 222 if (i > 0) { 223 if (i >= *tlenp) { 224 tcpstat.tcps_rcvduppack++; 225 tcpstat.tcps_rcvdupbyte += *tlenp; 226 m_freem(m); 227 free(te, M_TSEGQ); 228 /* 229 * Try to present any queued data 230 * at the left window edge to the user. 231 * This is needed after the 3-WHS 232 * completes. 233 */ 234 goto present; /* ??? */ 235 } 236 m_adj(m, i); 237 *tlenp -= i; 238 th->th_seq += i; 239 } 240 } 241 tcpstat.tcps_rcvoopack++; 242 tcpstat.tcps_rcvoobyte += *tlenp; 243 244 /* 245 * While we overlap succeeding segments trim them or, 246 * if they are completely covered, dequeue them. 247 */ 248 while (q) { 249 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 250 if (i <= 0) 251 break; 252 if (i < q->tqe_len) { 253 q->tqe_th->th_seq += i; 254 q->tqe_len -= i; 255 m_adj(q->tqe_m, i); 256 break; 257 } 258 259 nq = LIST_NEXT(q, tqe_q); 260 LIST_REMOVE(q, tqe_q); 261 m_freem(q->tqe_m); 262 free(q, M_TSEGQ); 263 q = nq; 264 } 265 266 /* Insert the new segment queue entry into place. */ 267 te->tqe_m = m; 268 te->tqe_th = th; 269 te->tqe_len = *tlenp; 270 271 if (p == NULL) { 272 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 273 } else { 274 LIST_INSERT_AFTER(p, te, tqe_q); 275 } 276 277 present: 278 /* 279 * Present data to user, advancing rcv_nxt through 280 * completed sequence space. 281 */ 282 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 283 return (0); 284 q = LIST_FIRST(&tp->t_segq); 285 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 286 return (0); 287 do { 288 tp->rcv_nxt += q->tqe_len; 289 flags = q->tqe_th->th_flags & TH_FIN; 290 nq = LIST_NEXT(q, tqe_q); 291 LIST_REMOVE(q, tqe_q); 292 if (so->so_state & SS_CANTRCVMORE) 293 m_freem(q->tqe_m); 294 else 295 sbappend(&so->so_rcv, q->tqe_m); 296 free(q, M_TSEGQ); 297 q = nq; 298 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 299 ND6_HINT(tp); 300 sorwakeup(so); 301 return (flags); 302 } 303 304 /* 305 * TCP input routine, follows pages 65-76 of the 306 * protocol specification dated September, 1981 very closely. 307 */ 308 #ifdef INET6 309 int 310 tcp6_input(mp, offp, proto) 311 struct mbuf **mp; 312 int *offp, proto; 313 { 314 struct mbuf *m = *mp; 315 struct in6_ifaddr *ia6; 316 317 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 318 319 /* 320 * draft-itojun-ipv6-tcp-to-anycast 321 * better place to put this in? 322 */ 323 ia6 = ip6_getdstifaddr(m); 324 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 325 struct ip6_hdr *ip6; 326 327 ip6 = mtod(m, struct ip6_hdr *); 328 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 329 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 330 return IPPROTO_DONE; 331 } 332 333 tcp_input(m, *offp, proto); 334 return IPPROTO_DONE; 335 } 336 #endif 337 338 void 339 tcp_input(m, off0, proto) 340 struct mbuf *m; 341 int off0, proto; 342 { 343 struct tcphdr *th; 344 struct ip *ip = NULL; 345 struct ipovly *ipov; 346 struct inpcb *inp = NULL; 347 u_char *optp = NULL; 348 int optlen = 0; 349 int len, tlen, off; 350 int drop_hdrlen; 351 struct tcpcb *tp = NULL; 352 int thflags; 353 struct socket *so = 0; 354 int todrop, acked, ourfinisacked, needoutput = 0; 355 u_long tiwin; 356 struct tcpopt to; /* options in this segment */ 357 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 358 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 359 struct sockaddr_in *next_hop = NULL; 360 int rstreason; /* For badport_bandlim accounting purposes */ 361 struct ip6_hdr *ip6 = NULL; 362 #ifdef INET6 363 int isipv6; 364 #else 365 const int isipv6 = 0; 366 #endif 367 #ifdef TCPDEBUG 368 short ostate = 0; 369 #endif 370 371 /* Grab info from MT_TAG mbufs prepended to the chain. */ 372 for (;m && m->m_type == MT_TAG; m = m->m_next) { 373 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 374 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 375 } 376 #ifdef INET6 377 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 378 #endif 379 bzero((char *)&to, sizeof(to)); 380 381 tcpstat.tcps_rcvtotal++; 382 383 if (isipv6) { 384 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 385 ip6 = mtod(m, struct ip6_hdr *); 386 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 387 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 388 tcpstat.tcps_rcvbadsum++; 389 goto drop; 390 } 391 th = (struct tcphdr *)((caddr_t)ip6 + off0); 392 393 /* 394 * Be proactive about unspecified IPv6 address in source. 395 * As we use all-zero to indicate unbounded/unconnected pcb, 396 * unspecified IPv6 address can be used to confuse us. 397 * 398 * Note that packets with unspecified IPv6 destination is 399 * already dropped in ip6_input. 400 */ 401 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 402 /* XXX stat */ 403 goto drop; 404 } 405 } else { 406 /* 407 * Get IP and TCP header together in first mbuf. 408 * Note: IP leaves IP header in first mbuf. 409 */ 410 if (off0 > sizeof(struct ip)) { 411 ip_stripoptions(m, (struct mbuf *)0); 412 off0 = sizeof(struct ip); 413 } 414 if (m->m_len < sizeof(struct tcpiphdr)) { 415 if ((m = m_pullup(m, sizeof(struct tcpiphdr))) == 0) { 416 tcpstat.tcps_rcvshort++; 417 return; 418 } 419 } 420 ip = mtod(m, struct ip *); 421 ipov = (struct ipovly *)ip; 422 th = (struct tcphdr *)((caddr_t)ip + off0); 423 tlen = ip->ip_len; 424 425 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 426 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 427 th->th_sum = m->m_pkthdr.csum_data; 428 else 429 th->th_sum = in_pseudo(ip->ip_src.s_addr, 430 ip->ip_dst.s_addr, 431 htonl(m->m_pkthdr.csum_data + 432 ip->ip_len + 433 IPPROTO_TCP)); 434 th->th_sum ^= 0xffff; 435 } else { 436 /* 437 * Checksum extended TCP header and data. 438 */ 439 len = sizeof(struct ip) + tlen; 440 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 441 ipov->ih_len = (u_short)tlen; 442 ipov->ih_len = htons(ipov->ih_len); 443 th->th_sum = in_cksum(m, len); 444 } 445 if (th->th_sum) { 446 tcpstat.tcps_rcvbadsum++; 447 goto drop; 448 } 449 #ifdef INET6 450 /* Re-initialization for later version check */ 451 ip->ip_v = IPVERSION; 452 #endif 453 } 454 455 /* 456 * Check that TCP offset makes sense, 457 * pull out TCP options and adjust length. XXX 458 */ 459 off = th->th_off << 2; 460 if (off < sizeof(struct tcphdr) || off > tlen) { 461 tcpstat.tcps_rcvbadoff++; 462 goto drop; 463 } 464 tlen -= off; /* tlen is used instead of ti->ti_len */ 465 if (off > sizeof(struct tcphdr)) { 466 if (isipv6) { 467 IP6_EXTHDR_CHECK(m, off0, off, ); 468 ip6 = mtod(m, struct ip6_hdr *); 469 th = (struct tcphdr *)((caddr_t)ip6 + off0); 470 } else { 471 if (m->m_len < sizeof(struct ip) + off) { 472 if ((m = m_pullup(m, sizeof(struct ip) + off)) 473 == 0) { 474 tcpstat.tcps_rcvshort++; 475 return; 476 } 477 ip = mtod(m, struct ip *); 478 ipov = (struct ipovly *)ip; 479 th = (struct tcphdr *)((caddr_t)ip + off0); 480 } 481 } 482 optlen = off - sizeof(struct tcphdr); 483 optp = (u_char *)(th + 1); 484 } 485 thflags = th->th_flags; 486 487 #ifdef TCP_DROP_SYNFIN 488 /* 489 * If the drop_synfin option is enabled, drop all packets with 490 * both the SYN and FIN bits set. This prevents e.g. nmap from 491 * identifying the TCP/IP stack. 492 * 493 * This is a violation of the TCP specification. 494 */ 495 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 496 goto drop; 497 #endif 498 499 /* 500 * Convert TCP protocol specific fields to host format. 501 */ 502 th->th_seq = ntohl(th->th_seq); 503 th->th_ack = ntohl(th->th_ack); 504 th->th_win = ntohs(th->th_win); 505 th->th_urp = ntohs(th->th_urp); 506 507 /* 508 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options, 509 * until after ip6_savecontrol() is called and before other functions 510 * which don't want those proto headers. 511 * Because ip6_savecontrol() is going to parse the mbuf to 512 * search for data to be passed up to user-land, it wants mbuf 513 * parameters to be unchanged. 514 * XXX: the call of ip6_savecontrol() has been obsoleted based on 515 * latest version of the advanced API (20020110). 516 */ 517 drop_hdrlen = off0 + off; 518 519 /* 520 * Locate pcb for segment. 521 */ 522 findpcb: 523 /* IPFIREWALL_FORWARD section */ 524 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 525 /* 526 * Transparently forwarded. Pretend to be the destination. 527 * already got one like this? 528 */ 529 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 530 ip->ip_dst, th->th_dport, 531 0, m->m_pkthdr.rcvif); 532 if (!inp) { 533 /* It's new. Try find the ambushing socket. */ 534 inp = in_pcblookup_hash(&tcbinfo, 535 ip->ip_src, th->th_sport, 536 next_hop->sin_addr, 537 next_hop->sin_port ? 538 ntohs(next_hop->sin_port) : 539 th->th_dport, 540 1, m->m_pkthdr.rcvif); 541 } 542 } else { 543 if (isipv6) 544 inp = in6_pcblookup_hash(&tcbinfo, 545 &ip6->ip6_src, th->th_sport, 546 &ip6->ip6_dst, th->th_dport, 547 1, m->m_pkthdr.rcvif); 548 else 549 inp = in_pcblookup_hash(&tcbinfo, 550 ip->ip_src, th->th_sport, 551 ip->ip_dst, th->th_dport, 552 1, m->m_pkthdr.rcvif); 553 } 554 555 #ifdef IPSEC 556 if (isipv6) { 557 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 558 ipsec6stat.in_polvio++; 559 goto drop; 560 } 561 } else { 562 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 563 ipsecstat.in_polvio++; 564 goto drop; 565 } 566 } 567 #endif 568 #ifdef FAST_IPSEC 569 if (isipv6) { 570 if (inp != NULL && ipsec6_in_reject(m, inp)) { 571 goto drop; 572 } 573 } else { 574 if (inp != NULL && ipsec4_in_reject(m, inp)) { 575 goto drop; 576 } 577 } 578 #endif 579 580 /* 581 * If the state is CLOSED (i.e., TCB does not exist) then 582 * all data in the incoming segment is discarded. 583 * If the TCB exists but is in CLOSED state, it is embryonic, 584 * but should either do a listen or a connect soon. 585 */ 586 if (inp == NULL) { 587 if (log_in_vain) { 588 #ifdef INET6 589 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 590 #else 591 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 592 #endif 593 if (isipv6) { 594 strcpy(dbuf, "["); 595 strcpy(sbuf, "["); 596 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 597 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 598 strcat(dbuf, "]"); 599 strcat(sbuf, "]"); 600 } else { 601 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 602 strcpy(sbuf, inet_ntoa(ip->ip_src)); 603 } 604 switch (log_in_vain) { 605 case 1: 606 if ((thflags & TH_SYN) == 0) 607 break; 608 case 2: 609 log(LOG_INFO, 610 "Connection attempt to TCP %s:%d " 611 "from %s:%d flags:0x%02x\n", 612 dbuf, ntohs(th->th_dport), sbuf, 613 ntohs(th->th_sport), thflags); 614 break; 615 default: 616 break; 617 } 618 } 619 if (blackhole) { 620 switch (blackhole) { 621 case 1: 622 if (thflags & TH_SYN) 623 goto drop; 624 break; 625 case 2: 626 goto drop; 627 default: 628 goto drop; 629 } 630 } 631 rstreason = BANDLIM_RST_CLOSEDPORT; 632 goto dropwithreset; 633 } 634 tp = intotcpcb(inp); 635 if (tp == NULL) { 636 rstreason = BANDLIM_RST_CLOSEDPORT; 637 goto dropwithreset; 638 } 639 if (tp->t_state == TCPS_CLOSED) 640 goto drop; 641 642 /* Unscale the window into a 32-bit value. */ 643 if ((thflags & TH_SYN) == 0) 644 tiwin = th->th_win << tp->snd_scale; 645 else 646 tiwin = th->th_win; 647 648 so = inp->inp_socket; 649 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 650 struct in_conninfo inc; 651 #ifdef TCPDEBUG 652 if (so->so_options & SO_DEBUG) { 653 ostate = tp->t_state; 654 if (isipv6) 655 bcopy((char *)ip6, (char *)tcp_saveipgen, 656 sizeof(*ip6)); 657 else 658 bcopy((char *)ip, (char *)tcp_saveipgen, 659 sizeof(*ip)); 660 tcp_savetcp = *th; 661 } 662 #endif 663 /* skip if this isn't a listen socket */ 664 if ((so->so_options & SO_ACCEPTCONN) == 0) 665 goto after_listen; 666 #ifdef INET6 667 inc.inc_isipv6 = isipv6; 668 #endif 669 if (isipv6) { 670 inc.inc6_faddr = ip6->ip6_src; 671 inc.inc6_laddr = ip6->ip6_dst; 672 inc.inc6_route.ro_rt = NULL; /* XXX */ 673 } else { 674 inc.inc_faddr = ip->ip_src; 675 inc.inc_laddr = ip->ip_dst; 676 inc.inc_route.ro_rt = NULL; /* XXX */ 677 } 678 inc.inc_fport = th->th_sport; 679 inc.inc_lport = th->th_dport; 680 681 /* 682 * If the state is LISTEN then ignore segment if it contains 683 * a RST. If the segment contains an ACK then it is bad and 684 * send a RST. If it does not contain a SYN then it is not 685 * interesting; drop it. 686 * 687 * If the state is SYN_RECEIVED (syncache) and seg contains 688 * an ACK, but not for our SYN/ACK, send a RST. If the seg 689 * contains a RST, check the sequence number to see if it 690 * is a valid reset segment. 691 */ 692 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 693 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 694 if (!syncache_expand(&inc, th, &so, m)) { 695 /* 696 * No syncache entry, or ACK was not 697 * for our SYN/ACK. Send a RST. 698 */ 699 tcpstat.tcps_badsyn++; 700 rstreason = BANDLIM_RST_OPENPORT; 701 goto dropwithreset; 702 } 703 if (so == NULL) 704 /* 705 * Could not complete 3-way handshake, 706 * connection is being closed down, and 707 * syncache will free mbuf. 708 */ 709 return; 710 /* 711 * Socket is created in state SYN_RECEIVED. 712 * Continue processing segment. 713 */ 714 inp = sotoinpcb(so); 715 tp = intotcpcb(inp); 716 /* 717 * This is what would have happened in 718 * tcp_output() when the SYN,ACK was sent. 719 */ 720 tp->snd_up = tp->snd_una; 721 tp->snd_max = tp->snd_nxt = tp->iss + 1; 722 tp->last_ack_sent = tp->rcv_nxt; 723 /* 724 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 725 * until the _second_ ACK is received: 726 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 727 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 728 * move to ESTAB, set snd_wnd to tiwin. 729 */ 730 tp->snd_wnd = tiwin; /* unscaled */ 731 goto after_listen; 732 } 733 if (thflags & TH_RST) { 734 syncache_chkrst(&inc, th); 735 goto drop; 736 } 737 if (thflags & TH_ACK) { 738 syncache_badack(&inc); 739 tcpstat.tcps_badsyn++; 740 rstreason = BANDLIM_RST_OPENPORT; 741 goto dropwithreset; 742 } 743 goto drop; 744 } 745 746 /* 747 * Segment's flags are (SYN) or (SYN|FIN). 748 */ 749 #ifdef INET6 750 /* 751 * If deprecated address is forbidden, 752 * we do not accept SYN to deprecated interface 753 * address to prevent any new inbound connection from 754 * getting established. 755 * When we do not accept SYN, we send a TCP RST, 756 * with deprecated source address (instead of dropping 757 * it). We compromise it as it is much better for peer 758 * to send a RST, and RST will be the final packet 759 * for the exchange. 760 * 761 * If we do not forbid deprecated addresses, we accept 762 * the SYN packet. RFC2462 does not suggest dropping 763 * SYN in this case. 764 * If we decipher RFC2462 5.5.4, it says like this: 765 * 1. use of deprecated addr with existing 766 * communication is okay - "SHOULD continue to be 767 * used" 768 * 2. use of it with new communication: 769 * (2a) "SHOULD NOT be used if alternate address 770 * with sufficient scope is available" 771 * (2b) nothing mentioned otherwise. 772 * Here we fall into (2b) case as we have no choice in 773 * our source address selection - we must obey the peer. 774 * 775 * The wording in RFC2462 is confusing, and there are 776 * multiple description text for deprecated address 777 * handling - worse, they are not exactly the same. 778 * I believe 5.5.4 is the best one, so we follow 5.5.4. 779 */ 780 if (isipv6 && !ip6_use_deprecated) { 781 struct in6_ifaddr *ia6; 782 783 if ((ia6 = ip6_getdstifaddr(m)) && 784 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 785 tp = NULL; 786 rstreason = BANDLIM_RST_OPENPORT; 787 goto dropwithreset; 788 } 789 } 790 #endif 791 /* 792 * If it is from this socket, drop it, it must be forged. 793 * Don't bother responding if the destination was a broadcast. 794 */ 795 if (th->th_dport == th->th_sport) { 796 if (isipv6) { 797 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 798 &ip6->ip6_src)) 799 goto drop; 800 } else { 801 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 802 goto drop; 803 } 804 } 805 /* 806 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 807 * 808 * Note that it is quite possible to receive unicast 809 * link-layer packets with a broadcast IP address. Use 810 * in_broadcast() to find them. 811 */ 812 if (m->m_flags & (M_BCAST|M_MCAST)) 813 goto drop; 814 if (isipv6) { 815 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 816 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 817 goto drop; 818 } else { 819 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 820 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 821 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 822 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 823 goto drop; 824 } 825 /* 826 * SYN appears to be valid; create compressed TCP state 827 * for syncache, or perform t/tcp connection. 828 */ 829 if (so->so_qlen <= so->so_qlimit) { 830 tcp_dooptions(&to, optp, optlen, 1); 831 if (!syncache_add(&inc, &to, th, &so, m)) 832 goto drop; 833 if (so == NULL) 834 /* 835 * Entry added to syncache, mbuf used to 836 * send SYN,ACK packet. 837 */ 838 return; 839 /* 840 * Segment passed TAO tests. 841 */ 842 inp = sotoinpcb(so); 843 tp = intotcpcb(inp); 844 tp->snd_wnd = tiwin; 845 tp->t_starttime = ticks; 846 tp->t_state = TCPS_ESTABLISHED; 847 848 /* 849 * If there is a FIN, or if there is data and the 850 * connection is local, then delay SYN,ACK(SYN) in 851 * the hope of piggy-backing it on a response 852 * segment. Otherwise must send ACK now in case 853 * the other side is slow starting. 854 */ 855 if (DELAY_ACK(tp) && 856 ((thflags & TH_FIN) || 857 (tlen != 0 && 858 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 859 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 860 callout_reset(tp->tt_delack, tcp_delacktime, 861 tcp_timer_delack, tp); 862 tp->t_flags |= TF_NEEDSYN; 863 } else 864 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 865 866 tcpstat.tcps_connects++; 867 soisconnected(so); 868 goto trimthenstep6; 869 } 870 goto drop; 871 } 872 after_listen: 873 874 /* XXX temp debugging */ 875 /* should not happen - syncache should pick up these connections */ 876 if (tp->t_state == TCPS_LISTEN) 877 panic("tcp_input: TCPS_LISTEN"); 878 879 /* 880 * Segment received on connection. 881 * Reset idle time and keep-alive timer. 882 */ 883 tp->t_rcvtime = ticks; 884 if (TCPS_HAVEESTABLISHED(tp->t_state)) 885 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 886 887 /* 888 * Process options. 889 * XXX this is tradtitional behavior, may need to be cleaned up. 890 */ 891 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 892 if (thflags & TH_SYN) { 893 if (to.to_flags & TOF_SCALE) { 894 tp->t_flags |= TF_RCVD_SCALE; 895 tp->requested_s_scale = to.to_requested_s_scale; 896 } 897 if (to.to_flags & TOF_TS) { 898 tp->t_flags |= TF_RCVD_TSTMP; 899 tp->ts_recent = to.to_tsval; 900 tp->ts_recent_age = ticks; 901 } 902 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 903 tp->t_flags |= TF_RCVD_CC; 904 if (to.to_flags & TOF_MSS) 905 tcp_mss(tp, to.to_mss); 906 } 907 908 /* 909 * Header prediction: check for the two common cases 910 * of a uni-directional data xfer. If the packet has 911 * no control flags, is in-sequence, the window didn't 912 * change and we're not retransmitting, it's a 913 * candidate. If the length is zero and the ack moved 914 * forward, we're the sender side of the xfer. Just 915 * free the data acked & wake any higher level process 916 * that was blocked waiting for space. If the length 917 * is non-zero and the ack didn't move, we're the 918 * receiver side. If we're getting packets in-order 919 * (the reassembly queue is empty), add the data to 920 * the socket buffer and note that we need a delayed ack. 921 * Make sure that the hidden state-flags are also off. 922 * Since we check for TCPS_ESTABLISHED above, it can only 923 * be TH_NEEDSYN. 924 */ 925 if (tp->t_state == TCPS_ESTABLISHED && 926 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 927 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 928 ((to.to_flags & TOF_TS) == 0 || 929 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 930 /* 931 * Using the CC option is compulsory if once started: 932 * the segment is OK if no T/TCP was negotiated or 933 * if the segment has a CC option equal to CCrecv 934 */ 935 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 936 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 937 th->th_seq == tp->rcv_nxt && 938 tiwin && tiwin == tp->snd_wnd && 939 tp->snd_nxt == tp->snd_max) { 940 941 /* 942 * If last ACK falls within this segment's sequence numbers, 943 * record the timestamp. 944 * NOTE that the test is modified according to the latest 945 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 946 */ 947 if ((to.to_flags & TOF_TS) != 0 && 948 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 949 tp->ts_recent_age = ticks; 950 tp->ts_recent = to.to_tsval; 951 } 952 953 if (tlen == 0) { 954 if (SEQ_GT(th->th_ack, tp->snd_una) && 955 SEQ_LEQ(th->th_ack, tp->snd_max) && 956 tp->snd_cwnd >= tp->snd_wnd && 957 ((!tcp_do_newreno && 958 tp->t_dupacks < tcprexmtthresh) || 959 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) { 960 /* 961 * this is a pure ack for outstanding data. 962 */ 963 ++tcpstat.tcps_predack; 964 /* 965 * "bad retransmit" recovery 966 */ 967 if (tp->t_rxtshift == 1 && 968 ticks < tp->t_badrxtwin) { 969 tp->snd_cwnd = tp->snd_cwnd_prev; 970 tp->snd_ssthresh = 971 tp->snd_ssthresh_prev; 972 tp->snd_recover = tp->snd_recover_prev; 973 if (tp->t_flags & TF_WASFRECOVERY) 974 ENTER_FASTRECOVERY(tp); 975 tp->snd_nxt = tp->snd_max; 976 tp->t_badrxtwin = 0; 977 } 978 /* 979 * Recalculate the retransmit timer / rtt. 980 * 981 * Some machines (certain windows boxes) 982 * send broken timestamp replies during the 983 * SYN+ACK phase, ignore timestamps of 0. 984 */ 985 if ((to.to_flags & TOF_TS) != 0 && 986 to.to_tsecr) { 987 tcp_xmit_timer(tp, 988 ticks - to.to_tsecr + 1); 989 } else if (tp->t_rtttime && 990 SEQ_GT(th->th_ack, tp->t_rtseq)) { 991 tcp_xmit_timer(tp, 992 ticks - tp->t_rtttime); 993 } 994 tcp_xmit_bandwidth_limit(tp, th->th_ack); 995 acked = th->th_ack - tp->snd_una; 996 tcpstat.tcps_rcvackpack++; 997 tcpstat.tcps_rcvackbyte += acked; 998 sbdrop(&so->so_snd, acked); 999 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1000 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1001 tp->snd_recover = th->th_ack - 1; 1002 tp->snd_una = th->th_ack; 1003 tp->t_dupacks = 0; 1004 m_freem(m); 1005 ND6_HINT(tp); /* some progress has been done */ 1006 1007 /* 1008 * If all outstanding data are acked, stop 1009 * retransmit timer, otherwise restart timer 1010 * using current (possibly backed-off) value. 1011 * If process is waiting for space, 1012 * wakeup/selwakeup/signal. If data 1013 * are ready to send, let tcp_output 1014 * decide between more output or persist. 1015 */ 1016 if (tp->snd_una == tp->snd_max) 1017 callout_stop(tp->tt_rexmt); 1018 else if (!callout_active(tp->tt_persist)) 1019 callout_reset(tp->tt_rexmt, 1020 tp->t_rxtcur, 1021 tcp_timer_rexmt, tp); 1022 1023 sowwakeup(so); 1024 if (so->so_snd.sb_cc) 1025 (void) tcp_output(tp); 1026 return; 1027 } 1028 } else if (th->th_ack == tp->snd_una && 1029 LIST_EMPTY(&tp->t_segq) && 1030 tlen <= sbspace(&so->so_rcv)) { 1031 /* 1032 * this is a pure, in-sequence data packet 1033 * with nothing on the reassembly queue and 1034 * we have enough buffer space to take it. 1035 */ 1036 ++tcpstat.tcps_preddat; 1037 tp->rcv_nxt += tlen; 1038 tcpstat.tcps_rcvpack++; 1039 tcpstat.tcps_rcvbyte += tlen; 1040 ND6_HINT(tp); /* some progress has been done */ 1041 /* 1042 * Add data to socket buffer. 1043 */ 1044 if (so->so_state & SS_CANTRCVMORE) { 1045 m_freem(m); 1046 } else { 1047 m_adj(m, drop_hdrlen); /* delayed header drop */ 1048 sbappend(&so->so_rcv, m); 1049 } 1050 sorwakeup(so); 1051 if (DELAY_ACK(tp)) { 1052 callout_reset(tp->tt_delack, tcp_delacktime, 1053 tcp_timer_delack, tp); 1054 } else { 1055 tp->t_flags |= TF_ACKNOW; 1056 tcp_output(tp); 1057 } 1058 return; 1059 } 1060 } 1061 1062 /* 1063 * Calculate amount of space in receive window, 1064 * and then do TCP input processing. 1065 * Receive window is amount of space in rcv queue, 1066 * but not less than advertised window. 1067 */ 1068 { int win; 1069 1070 win = sbspace(&so->so_rcv); 1071 if (win < 0) 1072 win = 0; 1073 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1074 } 1075 1076 switch (tp->t_state) { 1077 1078 /* 1079 * If the state is SYN_RECEIVED: 1080 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1081 */ 1082 case TCPS_SYN_RECEIVED: 1083 if ((thflags & TH_ACK) && 1084 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1085 SEQ_GT(th->th_ack, tp->snd_max))) { 1086 rstreason = BANDLIM_RST_OPENPORT; 1087 goto dropwithreset; 1088 } 1089 break; 1090 1091 /* 1092 * If the state is SYN_SENT: 1093 * if seg contains an ACK, but not for our SYN, drop the input. 1094 * if seg contains a RST, then drop the connection. 1095 * if seg does not contain SYN, then drop it. 1096 * Otherwise this is an acceptable SYN segment 1097 * initialize tp->rcv_nxt and tp->irs 1098 * if seg contains ack then advance tp->snd_una 1099 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1100 * arrange for segment to be acked (eventually) 1101 * continue processing rest of data/controls, beginning with URG 1102 */ 1103 case TCPS_SYN_SENT: 1104 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1105 taop = &tao_noncached; 1106 bzero(taop, sizeof(*taop)); 1107 } 1108 1109 if ((thflags & TH_ACK) && 1110 (SEQ_LEQ(th->th_ack, tp->iss) || 1111 SEQ_GT(th->th_ack, tp->snd_max))) { 1112 /* 1113 * If we have a cached CCsent for the remote host, 1114 * hence we haven't just crashed and restarted, 1115 * do not send a RST. This may be a retransmission 1116 * from the other side after our earlier ACK was lost. 1117 * Our new SYN, when it arrives, will serve as the 1118 * needed ACK. 1119 */ 1120 if (taop->tao_ccsent != 0) 1121 goto drop; 1122 else { 1123 rstreason = BANDLIM_UNLIMITED; 1124 goto dropwithreset; 1125 } 1126 } 1127 if (thflags & TH_RST) { 1128 if (thflags & TH_ACK) 1129 tp = tcp_drop(tp, ECONNREFUSED); 1130 goto drop; 1131 } 1132 if ((thflags & TH_SYN) == 0) 1133 goto drop; 1134 tp->snd_wnd = th->th_win; /* initial send window */ 1135 tp->cc_recv = to.to_cc; /* foreign CC */ 1136 1137 tp->irs = th->th_seq; 1138 tcp_rcvseqinit(tp); 1139 if (thflags & TH_ACK) { 1140 /* 1141 * Our SYN was acked. If segment contains CC.ECHO 1142 * option, check it to make sure this segment really 1143 * matches our SYN. If not, just drop it as old 1144 * duplicate, but send an RST if we're still playing 1145 * by the old rules. If no CC.ECHO option, make sure 1146 * we don't get fooled into using T/TCP. 1147 */ 1148 if (to.to_flags & TOF_CCECHO) { 1149 if (tp->cc_send != to.to_ccecho) { 1150 if (taop->tao_ccsent != 0) 1151 goto drop; 1152 else { 1153 rstreason = BANDLIM_UNLIMITED; 1154 goto dropwithreset; 1155 } 1156 } 1157 } else 1158 tp->t_flags &= ~TF_RCVD_CC; 1159 tcpstat.tcps_connects++; 1160 soisconnected(so); 1161 /* Do window scaling on this connection? */ 1162 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1163 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1164 tp->snd_scale = tp->requested_s_scale; 1165 tp->rcv_scale = tp->request_r_scale; 1166 } 1167 /* Segment is acceptable, update cache if undefined. */ 1168 if (taop->tao_ccsent == 0) 1169 taop->tao_ccsent = to.to_ccecho; 1170 1171 tp->rcv_adv += tp->rcv_wnd; 1172 tp->snd_una++; /* SYN is acked */ 1173 /* 1174 * If there's data, delay ACK; if there's also a FIN 1175 * ACKNOW will be turned on later. 1176 */ 1177 if (DELAY_ACK(tp) && tlen != 0) 1178 callout_reset(tp->tt_delack, tcp_delacktime, 1179 tcp_timer_delack, tp); 1180 else 1181 tp->t_flags |= TF_ACKNOW; 1182 /* 1183 * Received <SYN,ACK> in SYN_SENT[*] state. 1184 * Transitions: 1185 * SYN_SENT --> ESTABLISHED 1186 * SYN_SENT* --> FIN_WAIT_1 1187 */ 1188 tp->t_starttime = ticks; 1189 if (tp->t_flags & TF_NEEDFIN) { 1190 tp->t_state = TCPS_FIN_WAIT_1; 1191 tp->t_flags &= ~TF_NEEDFIN; 1192 thflags &= ~TH_SYN; 1193 } else { 1194 tp->t_state = TCPS_ESTABLISHED; 1195 callout_reset(tp->tt_keep, tcp_keepidle, 1196 tcp_timer_keep, tp); 1197 } 1198 } else { 1199 /* 1200 * Received initial SYN in SYN-SENT[*] state => 1201 * simultaneous open. If segment contains CC option 1202 * and there is a cached CC, apply TAO test. 1203 * If it succeeds, connection is * half-synchronized. 1204 * Otherwise, do 3-way handshake: 1205 * SYN-SENT -> SYN-RECEIVED 1206 * SYN-SENT* -> SYN-RECEIVED* 1207 * If there was no CC option, clear cached CC value. 1208 */ 1209 tp->t_flags |= TF_ACKNOW; 1210 callout_stop(tp->tt_rexmt); 1211 if (to.to_flags & TOF_CC) { 1212 if (taop->tao_cc != 0 && 1213 CC_GT(to.to_cc, taop->tao_cc)) { 1214 /* 1215 * update cache and make transition: 1216 * SYN-SENT -> ESTABLISHED* 1217 * SYN-SENT* -> FIN-WAIT-1* 1218 */ 1219 taop->tao_cc = to.to_cc; 1220 tp->t_starttime = ticks; 1221 if (tp->t_flags & TF_NEEDFIN) { 1222 tp->t_state = TCPS_FIN_WAIT_1; 1223 tp->t_flags &= ~TF_NEEDFIN; 1224 } else { 1225 tp->t_state = TCPS_ESTABLISHED; 1226 callout_reset(tp->tt_keep, 1227 tcp_keepidle, 1228 tcp_timer_keep, 1229 tp); 1230 } 1231 tp->t_flags |= TF_NEEDSYN; 1232 } else 1233 tp->t_state = TCPS_SYN_RECEIVED; 1234 } else { 1235 /* CC.NEW or no option => invalidate cache */ 1236 taop->tao_cc = 0; 1237 tp->t_state = TCPS_SYN_RECEIVED; 1238 } 1239 } 1240 1241 trimthenstep6: 1242 /* 1243 * Advance th->th_seq to correspond to first data byte. 1244 * If data, trim to stay within window, 1245 * dropping FIN if necessary. 1246 */ 1247 th->th_seq++; 1248 if (tlen > tp->rcv_wnd) { 1249 todrop = tlen - tp->rcv_wnd; 1250 m_adj(m, -todrop); 1251 tlen = tp->rcv_wnd; 1252 thflags &= ~TH_FIN; 1253 tcpstat.tcps_rcvpackafterwin++; 1254 tcpstat.tcps_rcvbyteafterwin += todrop; 1255 } 1256 tp->snd_wl1 = th->th_seq - 1; 1257 tp->rcv_up = th->th_seq; 1258 /* 1259 * Client side of transaction: already sent SYN and data. 1260 * If the remote host used T/TCP to validate the SYN, 1261 * our data will be ACK'd; if so, enter normal data segment 1262 * processing in the middle of step 5, ack processing. 1263 * Otherwise, goto step 6. 1264 */ 1265 if (thflags & TH_ACK) 1266 goto process_ACK; 1267 1268 goto step6; 1269 1270 /* 1271 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1272 * if segment contains a SYN and CC [not CC.NEW] option: 1273 * if state == TIME_WAIT and connection duration > MSL, 1274 * drop packet and send RST; 1275 * 1276 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1277 * ack the FIN (and data) in retransmission queue. 1278 * Complete close and delete TCPCB. Then reprocess 1279 * segment, hoping to find new TCPCB in LISTEN state; 1280 * 1281 * else must be old SYN; drop it. 1282 * else do normal processing. 1283 */ 1284 case TCPS_LAST_ACK: 1285 case TCPS_CLOSING: 1286 case TCPS_TIME_WAIT: 1287 if ((thflags & TH_SYN) && 1288 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1289 if (tp->t_state == TCPS_TIME_WAIT && 1290 (ticks - tp->t_starttime) > tcp_msl) { 1291 rstreason = BANDLIM_UNLIMITED; 1292 goto dropwithreset; 1293 } 1294 if (CC_GT(to.to_cc, tp->cc_recv)) { 1295 tp = tcp_close(tp); 1296 goto findpcb; 1297 } 1298 else 1299 goto drop; 1300 } 1301 break; /* continue normal processing */ 1302 } 1303 1304 /* 1305 * States other than LISTEN or SYN_SENT. 1306 * First check the RST flag and sequence number since reset segments 1307 * are exempt from the timestamp and connection count tests. This 1308 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1309 * below which allowed reset segments in half the sequence space 1310 * to fall though and be processed (which gives forged reset 1311 * segments with a random sequence number a 50 percent chance of 1312 * killing a connection). 1313 * Then check timestamp, if present. 1314 * Then check the connection count, if present. 1315 * Then check that at least some bytes of segment are within 1316 * receive window. If segment begins before rcv_nxt, 1317 * drop leading data (and SYN); if nothing left, just ack. 1318 * 1319 * 1320 * If the RST bit is set, check the sequence number to see 1321 * if this is a valid reset segment. 1322 * RFC 793 page 37: 1323 * In all states except SYN-SENT, all reset (RST) segments 1324 * are validated by checking their SEQ-fields. A reset is 1325 * valid if its sequence number is in the window. 1326 * Note: this does not take into account delayed ACKs, so 1327 * we should test against last_ack_sent instead of rcv_nxt. 1328 * The sequence number in the reset segment is normally an 1329 * echo of our outgoing acknowlegement numbers, but some hosts 1330 * send a reset with the sequence number at the rightmost edge 1331 * of our receive window, and we have to handle this case. 1332 * If we have multiple segments in flight, the intial reset 1333 * segment sequence numbers will be to the left of last_ack_sent, 1334 * but they will eventually catch up. 1335 * In any case, it never made sense to trim reset segments to 1336 * fit the receive window since RFC 1122 says: 1337 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1338 * 1339 * A TCP SHOULD allow a received RST segment to include data. 1340 * 1341 * DISCUSSION 1342 * It has been suggested that a RST segment could contain 1343 * ASCII text that encoded and explained the cause of the 1344 * RST. No standard has yet been established for such 1345 * data. 1346 * 1347 * If the reset segment passes the sequence number test examine 1348 * the state: 1349 * SYN_RECEIVED STATE: 1350 * If passive open, return to LISTEN state. 1351 * If active open, inform user that connection was refused. 1352 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1353 * Inform user that connection was reset, and close tcb. 1354 * CLOSING, LAST_ACK STATES: 1355 * Close the tcb. 1356 * TIME_WAIT STATE: 1357 * Drop the segment - see Stevens, vol. 2, p. 964 and 1358 * RFC 1337. 1359 */ 1360 if (thflags & TH_RST) { 1361 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1362 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1363 switch (tp->t_state) { 1364 1365 case TCPS_SYN_RECEIVED: 1366 so->so_error = ECONNREFUSED; 1367 goto close; 1368 1369 case TCPS_ESTABLISHED: 1370 case TCPS_FIN_WAIT_1: 1371 case TCPS_FIN_WAIT_2: 1372 case TCPS_CLOSE_WAIT: 1373 so->so_error = ECONNRESET; 1374 close: 1375 tp->t_state = TCPS_CLOSED; 1376 tcpstat.tcps_drops++; 1377 tp = tcp_close(tp); 1378 break; 1379 1380 case TCPS_CLOSING: 1381 case TCPS_LAST_ACK: 1382 tp = tcp_close(tp); 1383 break; 1384 1385 case TCPS_TIME_WAIT: 1386 break; 1387 } 1388 } 1389 goto drop; 1390 } 1391 1392 /* 1393 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1394 * and it's less than ts_recent, drop it. 1395 */ 1396 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1397 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1398 1399 /* Check to see if ts_recent is over 24 days old. */ 1400 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1401 /* 1402 * Invalidate ts_recent. If this segment updates 1403 * ts_recent, the age will be reset later and ts_recent 1404 * will get a valid value. If it does not, setting 1405 * ts_recent to zero will at least satisfy the 1406 * requirement that zero be placed in the timestamp 1407 * echo reply when ts_recent isn't valid. The 1408 * age isn't reset until we get a valid ts_recent 1409 * because we don't want out-of-order segments to be 1410 * dropped when ts_recent is old. 1411 */ 1412 tp->ts_recent = 0; 1413 } else { 1414 tcpstat.tcps_rcvduppack++; 1415 tcpstat.tcps_rcvdupbyte += tlen; 1416 tcpstat.tcps_pawsdrop++; 1417 if (tlen) 1418 goto dropafterack; 1419 goto drop; 1420 } 1421 } 1422 1423 /* 1424 * T/TCP mechanism 1425 * If T/TCP was negotiated and the segment doesn't have CC, 1426 * or if its CC is wrong then drop the segment. 1427 * RST segments do not have to comply with this. 1428 */ 1429 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1430 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1431 goto dropafterack; 1432 1433 /* 1434 * In the SYN-RECEIVED state, validate that the packet belongs to 1435 * this connection before trimming the data to fit the receive 1436 * window. Check the sequence number versus IRS since we know 1437 * the sequence numbers haven't wrapped. This is a partial fix 1438 * for the "LAND" DoS attack. 1439 */ 1440 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1441 rstreason = BANDLIM_RST_OPENPORT; 1442 goto dropwithreset; 1443 } 1444 1445 todrop = tp->rcv_nxt - th->th_seq; 1446 if (todrop > 0) { 1447 if (thflags & TH_SYN) { 1448 thflags &= ~TH_SYN; 1449 th->th_seq++; 1450 if (th->th_urp > 1) 1451 th->th_urp--; 1452 else 1453 thflags &= ~TH_URG; 1454 todrop--; 1455 } 1456 /* 1457 * Following if statement from Stevens, vol. 2, p. 960. 1458 */ 1459 if (todrop > tlen 1460 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1461 /* 1462 * Any valid FIN must be to the left of the window. 1463 * At this point the FIN must be a duplicate or out 1464 * of sequence; drop it. 1465 */ 1466 thflags &= ~TH_FIN; 1467 1468 /* 1469 * Send an ACK to resynchronize and drop any data. 1470 * But keep on processing for RST or ACK. 1471 */ 1472 tp->t_flags |= TF_ACKNOW; 1473 todrop = tlen; 1474 tcpstat.tcps_rcvduppack++; 1475 tcpstat.tcps_rcvdupbyte += todrop; 1476 } else { 1477 tcpstat.tcps_rcvpartduppack++; 1478 tcpstat.tcps_rcvpartdupbyte += todrop; 1479 } 1480 drop_hdrlen += todrop; /* drop from the top afterwards */ 1481 th->th_seq += todrop; 1482 tlen -= todrop; 1483 if (th->th_urp > todrop) 1484 th->th_urp -= todrop; 1485 else { 1486 thflags &= ~TH_URG; 1487 th->th_urp = 0; 1488 } 1489 } 1490 1491 /* 1492 * If new data are received on a connection after the 1493 * user processes are gone, then RST the other end. 1494 */ 1495 if ((so->so_state & SS_NOFDREF) && 1496 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1497 tp = tcp_close(tp); 1498 tcpstat.tcps_rcvafterclose++; 1499 rstreason = BANDLIM_UNLIMITED; 1500 goto dropwithreset; 1501 } 1502 1503 /* 1504 * If segment ends after window, drop trailing data 1505 * (and PUSH and FIN); if nothing left, just ACK. 1506 */ 1507 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1508 if (todrop > 0) { 1509 tcpstat.tcps_rcvpackafterwin++; 1510 if (todrop >= tlen) { 1511 tcpstat.tcps_rcvbyteafterwin += tlen; 1512 /* 1513 * If a new connection request is received 1514 * while in TIME_WAIT, drop the old connection 1515 * and start over if the sequence numbers 1516 * are above the previous ones. 1517 */ 1518 if (thflags & TH_SYN && 1519 tp->t_state == TCPS_TIME_WAIT && 1520 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1521 tp = tcp_close(tp); 1522 goto findpcb; 1523 } 1524 /* 1525 * If window is closed can only take segments at 1526 * window edge, and have to drop data and PUSH from 1527 * incoming segments. Continue processing, but 1528 * remember to ack. Otherwise, drop segment 1529 * and ack. 1530 */ 1531 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1532 tp->t_flags |= TF_ACKNOW; 1533 tcpstat.tcps_rcvwinprobe++; 1534 } else 1535 goto dropafterack; 1536 } else 1537 tcpstat.tcps_rcvbyteafterwin += todrop; 1538 m_adj(m, -todrop); 1539 tlen -= todrop; 1540 thflags &= ~(TH_PUSH|TH_FIN); 1541 } 1542 1543 /* 1544 * If last ACK falls within this segment's sequence numbers, 1545 * record its timestamp. 1546 * NOTE that the test is modified according to the latest 1547 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1548 */ 1549 if ((to.to_flags & TOF_TS) != 0 && 1550 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1551 tp->ts_recent_age = ticks; 1552 tp->ts_recent = to.to_tsval; 1553 } 1554 1555 /* 1556 * If a SYN is in the window, then this is an 1557 * error and we send an RST and drop the connection. 1558 */ 1559 if (thflags & TH_SYN) { 1560 tp = tcp_drop(tp, ECONNRESET); 1561 rstreason = BANDLIM_UNLIMITED; 1562 goto dropwithreset; 1563 } 1564 1565 /* 1566 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1567 * flag is on (half-synchronized state), then queue data for 1568 * later processing; else drop segment and return. 1569 */ 1570 if ((thflags & TH_ACK) == 0) { 1571 if (tp->t_state == TCPS_SYN_RECEIVED || 1572 (tp->t_flags & TF_NEEDSYN)) 1573 goto step6; 1574 else 1575 goto drop; 1576 } 1577 1578 /* 1579 * Ack processing. 1580 */ 1581 switch (tp->t_state) { 1582 1583 /* 1584 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1585 * ESTABLISHED state and continue processing. 1586 * The ACK was checked above. 1587 */ 1588 case TCPS_SYN_RECEIVED: 1589 1590 tcpstat.tcps_connects++; 1591 soisconnected(so); 1592 /* Do window scaling? */ 1593 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1594 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1595 tp->snd_scale = tp->requested_s_scale; 1596 tp->rcv_scale = tp->request_r_scale; 1597 } 1598 /* 1599 * Upon successful completion of 3-way handshake, 1600 * update cache.CC if it was undefined, pass any queued 1601 * data to the user, and advance state appropriately. 1602 */ 1603 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1604 taop->tao_cc == 0) 1605 taop->tao_cc = tp->cc_recv; 1606 1607 /* 1608 * Make transitions: 1609 * SYN-RECEIVED -> ESTABLISHED 1610 * SYN-RECEIVED* -> FIN-WAIT-1 1611 */ 1612 tp->t_starttime = ticks; 1613 if (tp->t_flags & TF_NEEDFIN) { 1614 tp->t_state = TCPS_FIN_WAIT_1; 1615 tp->t_flags &= ~TF_NEEDFIN; 1616 } else { 1617 tp->t_state = TCPS_ESTABLISHED; 1618 callout_reset(tp->tt_keep, tcp_keepidle, 1619 tcp_timer_keep, tp); 1620 } 1621 /* 1622 * If segment contains data or ACK, will call tcp_reass() 1623 * later; if not, do so now to pass queued data to user. 1624 */ 1625 if (tlen == 0 && (thflags & TH_FIN) == 0) 1626 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1627 (struct mbuf *)0); 1628 tp->snd_wl1 = th->th_seq - 1; 1629 /* fall into ... */ 1630 1631 /* 1632 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1633 * ACKs. If the ack is in the range 1634 * tp->snd_una < th->th_ack <= tp->snd_max 1635 * then advance tp->snd_una to th->th_ack and drop 1636 * data from the retransmission queue. If this ACK reflects 1637 * more up to date window information we update our window information. 1638 */ 1639 case TCPS_ESTABLISHED: 1640 case TCPS_FIN_WAIT_1: 1641 case TCPS_FIN_WAIT_2: 1642 case TCPS_CLOSE_WAIT: 1643 case TCPS_CLOSING: 1644 case TCPS_LAST_ACK: 1645 case TCPS_TIME_WAIT: 1646 1647 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1648 if (tlen == 0 && tiwin == tp->snd_wnd) { 1649 tcpstat.tcps_rcvdupack++; 1650 /* 1651 * If we have outstanding data (other than 1652 * a window probe), this is a completely 1653 * duplicate ack (ie, window info didn't 1654 * change), the ack is the biggest we've 1655 * seen and we've seen exactly our rexmt 1656 * threshhold of them, assume a packet 1657 * has been dropped and retransmit it. 1658 * Kludge snd_nxt & the congestion 1659 * window so we send only this one 1660 * packet. 1661 * 1662 * We know we're losing at the current 1663 * window size so do congestion avoidance 1664 * (set ssthresh to half the current window 1665 * and pull our congestion window back to 1666 * the new ssthresh). 1667 * 1668 * Dup acks mean that packets have left the 1669 * network (they're now cached at the receiver) 1670 * so bump cwnd by the amount in the receiver 1671 * to keep a constant cwnd packets in the 1672 * network. 1673 */ 1674 if (!callout_active(tp->tt_rexmt) || 1675 th->th_ack != tp->snd_una) 1676 tp->t_dupacks = 0; 1677 else if (++tp->t_dupacks > tcprexmtthresh || 1678 (tcp_do_newreno && 1679 IN_FASTRECOVERY(tp))) { 1680 tp->snd_cwnd += tp->t_maxseg; 1681 (void) tcp_output(tp); 1682 goto drop; 1683 } else if (tp->t_dupacks == tcprexmtthresh) { 1684 tcp_seq onxt = tp->snd_nxt; 1685 u_int win; 1686 if (tcp_do_newreno && 1687 SEQ_LEQ(th->th_ack, 1688 tp->snd_recover)) { 1689 tp->t_dupacks = 0; 1690 break; 1691 } 1692 win = min(tp->snd_wnd, tp->snd_cwnd) / 1693 2 / tp->t_maxseg; 1694 if (win < 2) 1695 win = 2; 1696 tp->snd_ssthresh = win * tp->t_maxseg; 1697 ENTER_FASTRECOVERY(tp); 1698 tp->snd_recover = tp->snd_max; 1699 callout_stop(tp->tt_rexmt); 1700 tp->t_rtttime = 0; 1701 tp->snd_nxt = th->th_ack; 1702 tp->snd_cwnd = tp->t_maxseg; 1703 (void) tcp_output(tp); 1704 KASSERT(tp->snd_limited <= 2, 1705 ("tp->snd_limited too big")); 1706 tp->snd_cwnd = tp->snd_ssthresh + 1707 (tp->t_maxseg * 1708 (tp->t_dupacks - tp->snd_limited)); 1709 if (SEQ_GT(onxt, tp->snd_nxt)) 1710 tp->snd_nxt = onxt; 1711 goto drop; 1712 } else if (tcp_do_limitedtransmit) { 1713 u_long oldcwnd = tp->snd_cwnd; 1714 tcp_seq oldsndmax = tp->snd_max; 1715 u_int sent; 1716 KASSERT(tp->t_dupacks == 1 || 1717 tp->t_dupacks == 2, 1718 ("dupacks not 1 or 2")); 1719 if (tp->t_dupacks == 1) { 1720 tp->snd_limited = 0; 1721 tp->snd_cwnd += tp->t_maxseg; 1722 } else { 1723 tp->snd_cwnd += 1724 tp->t_maxseg * 2; 1725 } 1726 (void) tcp_output(tp); 1727 sent = tp->snd_max - oldsndmax; 1728 if (sent > tp->t_maxseg) { 1729 KASSERT(tp->snd_limited == 0 && 1730 tp->t_dupacks == 2, 1731 ("sent too much")); 1732 tp->snd_limited = 2; 1733 } else if (sent > 0) 1734 ++tp->snd_limited; 1735 tp->snd_cwnd = oldcwnd; 1736 goto drop; 1737 } 1738 } else 1739 tp->t_dupacks = 0; 1740 break; 1741 } 1742 1743 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1744 1745 /* 1746 * If the congestion window was inflated to account 1747 * for the other side's cached packets, retract it. 1748 */ 1749 if (tcp_do_newreno) { 1750 if (IN_FASTRECOVERY(tp)) { 1751 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1752 tcp_newreno_partial_ack(tp, th); 1753 } else { 1754 /* 1755 * Window inflation should have left us 1756 * with approximately snd_ssthresh 1757 * outstanding data. 1758 * But in case we would be inclined to 1759 * send a burst, better to do it via 1760 * the slow start mechanism. 1761 */ 1762 if (SEQ_GT(th->th_ack + 1763 tp->snd_ssthresh, 1764 tp->snd_max)) 1765 tp->snd_cwnd = tp->snd_max - 1766 th->th_ack + 1767 tp->t_maxseg; 1768 else 1769 tp->snd_cwnd = tp->snd_ssthresh; 1770 } 1771 } 1772 } else { 1773 if (tp->t_dupacks >= tcprexmtthresh && 1774 tp->snd_cwnd > tp->snd_ssthresh) 1775 tp->snd_cwnd = tp->snd_ssthresh; 1776 } 1777 tp->t_dupacks = 0; 1778 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1779 tcpstat.tcps_rcvacktoomuch++; 1780 goto dropafterack; 1781 } 1782 /* 1783 * If we reach this point, ACK is not a duplicate, 1784 * i.e., it ACKs something we sent. 1785 */ 1786 if (tp->t_flags & TF_NEEDSYN) { 1787 /* 1788 * T/TCP: Connection was half-synchronized, and our 1789 * SYN has been ACK'd (so connection is now fully 1790 * synchronized). Go to non-starred state, 1791 * increment snd_una for ACK of SYN, and check if 1792 * we can do window scaling. 1793 */ 1794 tp->t_flags &= ~TF_NEEDSYN; 1795 tp->snd_una++; 1796 /* Do window scaling? */ 1797 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1798 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1799 tp->snd_scale = tp->requested_s_scale; 1800 tp->rcv_scale = tp->request_r_scale; 1801 } 1802 } 1803 1804 process_ACK: 1805 acked = th->th_ack - tp->snd_una; 1806 tcpstat.tcps_rcvackpack++; 1807 tcpstat.tcps_rcvackbyte += acked; 1808 1809 /* 1810 * If we just performed our first retransmit, and the ACK 1811 * arrives within our recovery window, then it was a mistake 1812 * to do the retransmit in the first place. Recover our 1813 * original cwnd and ssthresh, and proceed to transmit where 1814 * we left off. 1815 */ 1816 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1817 tp->snd_cwnd = tp->snd_cwnd_prev; 1818 tp->snd_ssthresh = tp->snd_ssthresh_prev; 1819 tp->snd_recover = tp->snd_recover_prev; 1820 if (tp->t_flags & TF_WASFRECOVERY) 1821 ENTER_FASTRECOVERY(tp); 1822 tp->snd_nxt = tp->snd_max; 1823 tp->t_badrxtwin = 0; /* XXX probably not required */ 1824 } 1825 1826 /* 1827 * If we have a timestamp reply, update smoothed 1828 * round trip time. If no timestamp is present but 1829 * transmit timer is running and timed sequence 1830 * number was acked, update smoothed round trip time. 1831 * Since we now have an rtt measurement, cancel the 1832 * timer backoff (cf., Phil Karn's retransmit alg.). 1833 * Recompute the initial retransmit timer. 1834 * 1835 * Some machines (certain windows boxes) send broken 1836 * timestamp replies during the SYN+ACK phase, ignore 1837 * timestamps of 0. 1838 */ 1839 if ((to.to_flags & TOF_TS) != 0 && 1840 to.to_tsecr) { 1841 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1842 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 1843 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1844 } 1845 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1846 1847 /* 1848 * If all outstanding data is acked, stop retransmit 1849 * timer and remember to restart (more output or persist). 1850 * If there is more data to be acked, restart retransmit 1851 * timer, using current (possibly backed-off) value. 1852 */ 1853 if (th->th_ack == tp->snd_max) { 1854 callout_stop(tp->tt_rexmt); 1855 needoutput = 1; 1856 } else if (!callout_active(tp->tt_persist)) 1857 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1858 tcp_timer_rexmt, tp); 1859 1860 /* 1861 * If no data (only SYN) was ACK'd, 1862 * skip rest of ACK processing. 1863 */ 1864 if (acked == 0) 1865 goto step6; 1866 1867 /* 1868 * When new data is acked, open the congestion window. 1869 * If the window gives us less than ssthresh packets 1870 * in flight, open exponentially (maxseg per packet). 1871 * Otherwise open linearly: maxseg per window 1872 * (maxseg^2 / cwnd per packet). 1873 */ 1874 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) { 1875 u_int cw = tp->snd_cwnd; 1876 u_int incr = tp->t_maxseg; 1877 if (cw > tp->snd_ssthresh) 1878 incr = incr * incr / cw; 1879 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 1880 } 1881 if (acked > so->so_snd.sb_cc) { 1882 tp->snd_wnd -= so->so_snd.sb_cc; 1883 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1884 ourfinisacked = 1; 1885 } else { 1886 sbdrop(&so->so_snd, acked); 1887 tp->snd_wnd -= acked; 1888 ourfinisacked = 0; 1889 } 1890 sowwakeup(so); 1891 /* detect una wraparound */ 1892 if (tcp_do_newreno && !IN_FASTRECOVERY(tp) && 1893 SEQ_GT(tp->snd_una, tp->snd_recover) && 1894 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1895 tp->snd_recover = th->th_ack - 1; 1896 if (tcp_do_newreno && IN_FASTRECOVERY(tp) && 1897 SEQ_GEQ(th->th_ack, tp->snd_recover)) 1898 EXIT_FASTRECOVERY(tp); 1899 tp->snd_una = th->th_ack; 1900 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1901 tp->snd_nxt = tp->snd_una; 1902 1903 switch (tp->t_state) { 1904 1905 /* 1906 * In FIN_WAIT_1 STATE in addition to the processing 1907 * for the ESTABLISHED state if our FIN is now acknowledged 1908 * then enter FIN_WAIT_2. 1909 */ 1910 case TCPS_FIN_WAIT_1: 1911 if (ourfinisacked) { 1912 /* 1913 * If we can't receive any more 1914 * data, then closing user can proceed. 1915 * Starting the timer is contrary to the 1916 * specification, but if we don't get a FIN 1917 * we'll hang forever. 1918 */ 1919 if (so->so_state & SS_CANTRCVMORE) { 1920 soisdisconnected(so); 1921 callout_reset(tp->tt_2msl, tcp_maxidle, 1922 tcp_timer_2msl, tp); 1923 } 1924 tp->t_state = TCPS_FIN_WAIT_2; 1925 } 1926 break; 1927 1928 /* 1929 * In CLOSING STATE in addition to the processing for 1930 * the ESTABLISHED state if the ACK acknowledges our FIN 1931 * then enter the TIME-WAIT state, otherwise ignore 1932 * the segment. 1933 */ 1934 case TCPS_CLOSING: 1935 if (ourfinisacked) { 1936 tp->t_state = TCPS_TIME_WAIT; 1937 tcp_canceltimers(tp); 1938 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1939 if (tp->cc_recv != 0 && 1940 (ticks - tp->t_starttime) < tcp_msl) 1941 callout_reset(tp->tt_2msl, 1942 tp->t_rxtcur * 1943 TCPTV_TWTRUNC, 1944 tcp_timer_2msl, tp); 1945 else 1946 callout_reset(tp->tt_2msl, 2 * tcp_msl, 1947 tcp_timer_2msl, tp); 1948 soisdisconnected(so); 1949 } 1950 break; 1951 1952 /* 1953 * In LAST_ACK, we may still be waiting for data to drain 1954 * and/or to be acked, as well as for the ack of our FIN. 1955 * If our FIN is now acknowledged, delete the TCB, 1956 * enter the closed state and return. 1957 */ 1958 case TCPS_LAST_ACK: 1959 if (ourfinisacked) { 1960 tp = tcp_close(tp); 1961 goto drop; 1962 } 1963 break; 1964 1965 /* 1966 * In TIME_WAIT state the only thing that should arrive 1967 * is a retransmission of the remote FIN. Acknowledge 1968 * it and restart the finack timer. 1969 */ 1970 case TCPS_TIME_WAIT: 1971 callout_reset(tp->tt_2msl, 2 * tcp_msl, 1972 tcp_timer_2msl, tp); 1973 goto dropafterack; 1974 } 1975 } 1976 1977 step6: 1978 /* 1979 * Update window information. 1980 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1981 */ 1982 if ((thflags & TH_ACK) && 1983 (SEQ_LT(tp->snd_wl1, th->th_seq) || 1984 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 1985 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 1986 /* keep track of pure window updates */ 1987 if (tlen == 0 && 1988 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 1989 tcpstat.tcps_rcvwinupd++; 1990 tp->snd_wnd = tiwin; 1991 tp->snd_wl1 = th->th_seq; 1992 tp->snd_wl2 = th->th_ack; 1993 if (tp->snd_wnd > tp->max_sndwnd) 1994 tp->max_sndwnd = tp->snd_wnd; 1995 needoutput = 1; 1996 } 1997 1998 /* 1999 * Process segments with URG. 2000 */ 2001 if ((thflags & TH_URG) && th->th_urp && 2002 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2003 /* 2004 * This is a kludge, but if we receive and accept 2005 * random urgent pointers, we'll crash in 2006 * soreceive. It's hard to imagine someone 2007 * actually wanting to send this much urgent data. 2008 */ 2009 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2010 th->th_urp = 0; /* XXX */ 2011 thflags &= ~TH_URG; /* XXX */ 2012 goto dodata; /* XXX */ 2013 } 2014 /* 2015 * If this segment advances the known urgent pointer, 2016 * then mark the data stream. This should not happen 2017 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2018 * a FIN has been received from the remote side. 2019 * In these states we ignore the URG. 2020 * 2021 * According to RFC961 (Assigned Protocols), 2022 * the urgent pointer points to the last octet 2023 * of urgent data. We continue, however, 2024 * to consider it to indicate the first octet 2025 * of data past the urgent section as the original 2026 * spec states (in one of two places). 2027 */ 2028 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2029 tp->rcv_up = th->th_seq + th->th_urp; 2030 so->so_oobmark = so->so_rcv.sb_cc + 2031 (tp->rcv_up - tp->rcv_nxt) - 1; 2032 if (so->so_oobmark == 0) 2033 so->so_state |= SS_RCVATMARK; 2034 sohasoutofband(so); 2035 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2036 } 2037 /* 2038 * Remove out of band data so doesn't get presented to user. 2039 * This can happen independent of advancing the URG pointer, 2040 * but if two URG's are pending at once, some out-of-band 2041 * data may creep in... ick. 2042 */ 2043 if (th->th_urp <= (u_long)tlen 2044 #ifdef SO_OOBINLINE 2045 && (so->so_options & SO_OOBINLINE) == 0 2046 #endif 2047 ) 2048 tcp_pulloutofband(so, th, m, 2049 drop_hdrlen); /* hdr drop is delayed */ 2050 } else { 2051 /* 2052 * If no out of band data is expected, 2053 * pull receive urgent pointer along 2054 * with the receive window. 2055 */ 2056 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2057 tp->rcv_up = tp->rcv_nxt; 2058 } 2059 dodata: /* XXX */ 2060 2061 /* 2062 * Process the segment text, merging it into the TCP sequencing queue, 2063 * and arranging for acknowledgment of receipt if necessary. 2064 * This process logically involves adjusting tp->rcv_wnd as data 2065 * is presented to the user (this happens in tcp_usrreq.c, 2066 * case PRU_RCVD). If a FIN has already been received on this 2067 * connection then we just ignore the text. 2068 */ 2069 if ((tlen || (thflags & TH_FIN)) && 2070 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2071 m_adj(m, drop_hdrlen); /* delayed header drop */ 2072 /* 2073 * Insert segment which includes th into TCP reassembly queue 2074 * with control block tp. Set thflags to whether reassembly now 2075 * includes a segment with FIN. This handles the common case 2076 * inline (segment is the next to be received on an established 2077 * connection, and the queue is empty), avoiding linkage into 2078 * and removal from the queue and repetition of various 2079 * conversions. 2080 * Set DELACK for segments received in order, but ack 2081 * immediately when segments are out of order (so 2082 * fast retransmit can work). 2083 */ 2084 if (th->th_seq == tp->rcv_nxt && 2085 LIST_EMPTY(&tp->t_segq) && 2086 TCPS_HAVEESTABLISHED(tp->t_state)) { 2087 if (DELAY_ACK(tp)) 2088 callout_reset(tp->tt_delack, tcp_delacktime, 2089 tcp_timer_delack, tp); 2090 else 2091 tp->t_flags |= TF_ACKNOW; 2092 tp->rcv_nxt += tlen; 2093 thflags = th->th_flags & TH_FIN; 2094 tcpstat.tcps_rcvpack++; 2095 tcpstat.tcps_rcvbyte += tlen; 2096 ND6_HINT(tp); 2097 if (so->so_state & SS_CANTRCVMORE) 2098 m_freem(m); 2099 else 2100 sbappend(&so->so_rcv, m); 2101 sorwakeup(so); 2102 } else { 2103 thflags = tcp_reass(tp, th, &tlen, m); 2104 tp->t_flags |= TF_ACKNOW; 2105 } 2106 2107 /* 2108 * Note the amount of data that peer has sent into 2109 * our window, in order to estimate the sender's 2110 * buffer size. 2111 */ 2112 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2113 } else { 2114 m_freem(m); 2115 thflags &= ~TH_FIN; 2116 } 2117 2118 /* 2119 * If FIN is received ACK the FIN and let the user know 2120 * that the connection is closing. 2121 */ 2122 if (thflags & TH_FIN) { 2123 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2124 socantrcvmore(so); 2125 /* 2126 * If connection is half-synchronized 2127 * (ie NEEDSYN flag on) then delay ACK, 2128 * so it may be piggybacked when SYN is sent. 2129 * Otherwise, since we received a FIN then no 2130 * more input can be expected, send ACK now. 2131 */ 2132 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2133 callout_reset(tp->tt_delack, tcp_delacktime, 2134 tcp_timer_delack, tp); 2135 else 2136 tp->t_flags |= TF_ACKNOW; 2137 tp->rcv_nxt++; 2138 } 2139 switch (tp->t_state) { 2140 2141 /* 2142 * In SYN_RECEIVED and ESTABLISHED STATES 2143 * enter the CLOSE_WAIT state. 2144 */ 2145 case TCPS_SYN_RECEIVED: 2146 tp->t_starttime = ticks; 2147 /*FALLTHROUGH*/ 2148 case TCPS_ESTABLISHED: 2149 tp->t_state = TCPS_CLOSE_WAIT; 2150 break; 2151 2152 /* 2153 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2154 * enter the CLOSING state. 2155 */ 2156 case TCPS_FIN_WAIT_1: 2157 tp->t_state = TCPS_CLOSING; 2158 break; 2159 2160 /* 2161 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2162 * starting the time-wait timer, turning off the other 2163 * standard timers. 2164 */ 2165 case TCPS_FIN_WAIT_2: 2166 tp->t_state = TCPS_TIME_WAIT; 2167 tcp_canceltimers(tp); 2168 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2169 if (tp->cc_recv != 0 && 2170 (ticks - tp->t_starttime) < tcp_msl) { 2171 callout_reset(tp->tt_2msl, 2172 tp->t_rxtcur * TCPTV_TWTRUNC, 2173 tcp_timer_2msl, tp); 2174 /* For transaction client, force ACK now. */ 2175 tp->t_flags |= TF_ACKNOW; 2176 } 2177 else 2178 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2179 tcp_timer_2msl, tp); 2180 soisdisconnected(so); 2181 break; 2182 2183 /* 2184 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2185 */ 2186 case TCPS_TIME_WAIT: 2187 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2188 tcp_timer_2msl, tp); 2189 break; 2190 } 2191 } 2192 #ifdef TCPDEBUG 2193 if (so->so_options & SO_DEBUG) 2194 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2195 &tcp_savetcp, 0); 2196 #endif 2197 2198 /* 2199 * Return any desired output. 2200 */ 2201 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2202 (void) tcp_output(tp); 2203 return; 2204 2205 dropafterack: 2206 /* 2207 * Generate an ACK dropping incoming segment if it occupies 2208 * sequence space, where the ACK reflects our state. 2209 * 2210 * We can now skip the test for the RST flag since all 2211 * paths to this code happen after packets containing 2212 * RST have been dropped. 2213 * 2214 * In the SYN-RECEIVED state, don't send an ACK unless the 2215 * segment we received passes the SYN-RECEIVED ACK test. 2216 * If it fails send a RST. This breaks the loop in the 2217 * "LAND" DoS attack, and also prevents an ACK storm 2218 * between two listening ports that have been sent forged 2219 * SYN segments, each with the source address of the other. 2220 */ 2221 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2222 (SEQ_GT(tp->snd_una, th->th_ack) || 2223 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2224 rstreason = BANDLIM_RST_OPENPORT; 2225 goto dropwithreset; 2226 } 2227 #ifdef TCPDEBUG 2228 if (so->so_options & SO_DEBUG) 2229 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2230 &tcp_savetcp, 0); 2231 #endif 2232 m_freem(m); 2233 tp->t_flags |= TF_ACKNOW; 2234 (void) tcp_output(tp); 2235 return; 2236 2237 dropwithreset: 2238 /* 2239 * Generate a RST, dropping incoming segment. 2240 * Make ACK acceptable to originator of segment. 2241 * Don't bother to respond if destination was broadcast/multicast. 2242 */ 2243 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2244 goto drop; 2245 if (isipv6) { 2246 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2247 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2248 goto drop; 2249 } else { 2250 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2251 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2252 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2253 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2254 goto drop; 2255 } 2256 /* IPv6 anycast check is done at tcp6_input() */ 2257 2258 /* 2259 * Perform bandwidth limiting. 2260 */ 2261 #ifdef ICMP_BANDLIM 2262 if (badport_bandlim(rstreason) < 0) 2263 goto drop; 2264 #endif 2265 2266 #ifdef TCPDEBUG 2267 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2268 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2269 &tcp_savetcp, 0); 2270 #endif 2271 if (thflags & TH_ACK) 2272 /* mtod() below is safe as long as hdr dropping is delayed */ 2273 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2274 TH_RST); 2275 else { 2276 if (thflags & TH_SYN) 2277 tlen++; 2278 /* mtod() below is safe as long as hdr dropping is delayed */ 2279 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2280 (tcp_seq)0, TH_RST|TH_ACK); 2281 } 2282 return; 2283 2284 drop: 2285 /* 2286 * Drop space held by incoming segment and return. 2287 */ 2288 #ifdef TCPDEBUG 2289 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2290 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2291 &tcp_savetcp, 0); 2292 #endif 2293 m_freem(m); 2294 return; 2295 } 2296 2297 /* 2298 * Parse TCP options and place in tcpopt. 2299 */ 2300 static void 2301 tcp_dooptions(to, cp, cnt, is_syn) 2302 struct tcpopt *to; 2303 u_char *cp; 2304 int cnt; 2305 { 2306 int opt, optlen; 2307 2308 to->to_flags = 0; 2309 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2310 opt = cp[0]; 2311 if (opt == TCPOPT_EOL) 2312 break; 2313 if (opt == TCPOPT_NOP) 2314 optlen = 1; 2315 else { 2316 if (cnt < 2) 2317 break; 2318 optlen = cp[1]; 2319 if (optlen < 2 || optlen > cnt) 2320 break; 2321 } 2322 switch (opt) { 2323 case TCPOPT_MAXSEG: 2324 if (optlen != TCPOLEN_MAXSEG) 2325 continue; 2326 if (!is_syn) 2327 continue; 2328 to->to_flags |= TOF_MSS; 2329 bcopy((char *)cp + 2, 2330 (char *)&to->to_mss, sizeof(to->to_mss)); 2331 to->to_mss = ntohs(to->to_mss); 2332 break; 2333 case TCPOPT_WINDOW: 2334 if (optlen != TCPOLEN_WINDOW) 2335 continue; 2336 if (! is_syn) 2337 continue; 2338 to->to_flags |= TOF_SCALE; 2339 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2340 break; 2341 case TCPOPT_TIMESTAMP: 2342 if (optlen != TCPOLEN_TIMESTAMP) 2343 continue; 2344 to->to_flags |= TOF_TS; 2345 bcopy((char *)cp + 2, 2346 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2347 to->to_tsval = ntohl(to->to_tsval); 2348 bcopy((char *)cp + 6, 2349 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2350 to->to_tsecr = ntohl(to->to_tsecr); 2351 break; 2352 case TCPOPT_CC: 2353 if (optlen != TCPOLEN_CC) 2354 continue; 2355 to->to_flags |= TOF_CC; 2356 bcopy((char *)cp + 2, 2357 (char *)&to->to_cc, sizeof(to->to_cc)); 2358 to->to_cc = ntohl(to->to_cc); 2359 break; 2360 case TCPOPT_CCNEW: 2361 if (optlen != TCPOLEN_CC) 2362 continue; 2363 if (!is_syn) 2364 continue; 2365 to->to_flags |= TOF_CCNEW; 2366 bcopy((char *)cp + 2, 2367 (char *)&to->to_cc, sizeof(to->to_cc)); 2368 to->to_cc = ntohl(to->to_cc); 2369 break; 2370 case TCPOPT_CCECHO: 2371 if (optlen != TCPOLEN_CC) 2372 continue; 2373 if (!is_syn) 2374 continue; 2375 to->to_flags |= TOF_CCECHO; 2376 bcopy((char *)cp + 2, 2377 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2378 to->to_ccecho = ntohl(to->to_ccecho); 2379 break; 2380 default: 2381 continue; 2382 } 2383 } 2384 } 2385 2386 /* 2387 * Pull out of band byte out of a segment so 2388 * it doesn't appear in the user's data queue. 2389 * It is still reflected in the segment length for 2390 * sequencing purposes. 2391 */ 2392 static void 2393 tcp_pulloutofband(so, th, m, off) 2394 struct socket *so; 2395 struct tcphdr *th; 2396 struct mbuf *m; 2397 int off; /* delayed to be droped hdrlen */ 2398 { 2399 int cnt = off + th->th_urp - 1; 2400 2401 while (cnt >= 0) { 2402 if (m->m_len > cnt) { 2403 char *cp = mtod(m, caddr_t) + cnt; 2404 struct tcpcb *tp = sototcpcb(so); 2405 2406 tp->t_iobc = *cp; 2407 tp->t_oobflags |= TCPOOB_HAVEDATA; 2408 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2409 m->m_len--; 2410 if (m->m_flags & M_PKTHDR) 2411 m->m_pkthdr.len--; 2412 return; 2413 } 2414 cnt -= m->m_len; 2415 m = m->m_next; 2416 if (m == 0) 2417 break; 2418 } 2419 panic("tcp_pulloutofband"); 2420 } 2421 2422 /* 2423 * Collect new round-trip time estimate 2424 * and update averages and current timeout. 2425 */ 2426 static void 2427 tcp_xmit_timer(tp, rtt) 2428 struct tcpcb *tp; 2429 int rtt; 2430 { 2431 int delta; 2432 2433 tcpstat.tcps_rttupdated++; 2434 tp->t_rttupdated++; 2435 if (tp->t_srtt != 0) { 2436 /* 2437 * srtt is stored as fixed point with 5 bits after the 2438 * binary point (i.e., scaled by 8). The following magic 2439 * is equivalent to the smoothing algorithm in rfc793 with 2440 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2441 * point). Adjust rtt to origin 0. 2442 */ 2443 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2444 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2445 2446 if ((tp->t_srtt += delta) <= 0) 2447 tp->t_srtt = 1; 2448 2449 /* 2450 * We accumulate a smoothed rtt variance (actually, a 2451 * smoothed mean difference), then set the retransmit 2452 * timer to smoothed rtt + 4 times the smoothed variance. 2453 * rttvar is stored as fixed point with 4 bits after the 2454 * binary point (scaled by 16). The following is 2455 * equivalent to rfc793 smoothing with an alpha of .75 2456 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2457 * rfc793's wired-in beta. 2458 */ 2459 if (delta < 0) 2460 delta = -delta; 2461 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2462 if ((tp->t_rttvar += delta) <= 0) 2463 tp->t_rttvar = 1; 2464 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2465 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2466 } else { 2467 /* 2468 * No rtt measurement yet - use the unsmoothed rtt. 2469 * Set the variance to half the rtt (so our first 2470 * retransmit happens at 3*rtt). 2471 */ 2472 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2473 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2474 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2475 } 2476 tp->t_rtttime = 0; 2477 tp->t_rxtshift = 0; 2478 2479 /* 2480 * the retransmit should happen at rtt + 4 * rttvar. 2481 * Because of the way we do the smoothing, srtt and rttvar 2482 * will each average +1/2 tick of bias. When we compute 2483 * the retransmit timer, we want 1/2 tick of rounding and 2484 * 1 extra tick because of +-1/2 tick uncertainty in the 2485 * firing of the timer. The bias will give us exactly the 2486 * 1.5 tick we need. But, because the bias is 2487 * statistical, we have to test that we don't drop below 2488 * the minimum feasible timer (which is 2 ticks). 2489 */ 2490 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2491 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2492 2493 /* 2494 * We received an ack for a packet that wasn't retransmitted; 2495 * it is probably safe to discard any error indications we've 2496 * received recently. This isn't quite right, but close enough 2497 * for now (a route might have failed after we sent a segment, 2498 * and the return path might not be symmetrical). 2499 */ 2500 tp->t_softerror = 0; 2501 } 2502 2503 /* 2504 * Determine a reasonable value for maxseg size. 2505 * If the route is known, check route for mtu. 2506 * If none, use an mss that can be handled on the outgoing 2507 * interface without forcing IP to fragment; if bigger than 2508 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2509 * to utilize large mbufs. If no route is found, route has no mtu, 2510 * or the destination isn't local, use a default, hopefully conservative 2511 * size (usually 512 or the default IP max size, but no more than the mtu 2512 * of the interface), as we can't discover anything about intervening 2513 * gateways or networks. We also initialize the congestion/slow start 2514 * window to be a single segment if the destination isn't local. 2515 * While looking at the routing entry, we also initialize other path-dependent 2516 * parameters from pre-set or cached values in the routing entry. 2517 * 2518 * Also take into account the space needed for options that we 2519 * send regularly. Make maxseg shorter by that amount to assure 2520 * that we can send maxseg amount of data even when the options 2521 * are present. Store the upper limit of the length of options plus 2522 * data in maxopd. 2523 * 2524 * NOTE that this routine is only called when we process an incoming 2525 * segment, for outgoing segments only tcp_mssopt is called. 2526 * 2527 * In case of T/TCP, we call this routine during implicit connection 2528 * setup as well (offer = -1), to initialize maxseg from the cached 2529 * MSS of our peer. 2530 */ 2531 void 2532 tcp_mss(tp, offer) 2533 struct tcpcb *tp; 2534 int offer; 2535 { 2536 struct rtentry *rt; 2537 struct ifnet *ifp; 2538 int rtt, mss; 2539 u_long bufsize; 2540 struct inpcb *inp = tp->t_inpcb; 2541 struct socket *so; 2542 struct rmxp_tao *taop; 2543 int origoffer = offer; 2544 #ifdef INET6 2545 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2546 size_t min_protoh = isipv6 ? 2547 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2548 sizeof(struct tcpiphdr); 2549 #else 2550 const int isipv6 = 0; 2551 const size_t min_protoh = sizeof(struct tcpiphdr); 2552 #endif 2553 2554 if (isipv6) 2555 rt = tcp_rtlookup6(&inp->inp_inc); 2556 else 2557 rt = tcp_rtlookup(&inp->inp_inc); 2558 if (rt == NULL) { 2559 tp->t_maxopd = tp->t_maxseg = 2560 isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2561 return; 2562 } 2563 ifp = rt->rt_ifp; 2564 so = inp->inp_socket; 2565 2566 taop = rmx_taop(rt->rt_rmx); 2567 /* 2568 * Offer == -1 means that we didn't receive SYN yet, 2569 * use cached value in that case; 2570 */ 2571 if (offer == -1) 2572 offer = taop->tao_mssopt; 2573 /* 2574 * Offer == 0 means that there was no MSS on the SYN segment, 2575 * in this case we use tcp_mssdflt. 2576 */ 2577 if (offer == 0) 2578 offer = isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2579 else 2580 /* 2581 * Sanity check: make sure that maxopd will be large 2582 * enough to allow some data on segments even is the 2583 * all the option space is used (40bytes). Otherwise 2584 * funny things may happen in tcp_output. 2585 */ 2586 offer = max(offer, 64); 2587 taop->tao_mssopt = offer; 2588 2589 /* 2590 * While we're here, check if there's an initial rtt 2591 * or rttvar. Convert from the route-table units 2592 * to scaled multiples of the slow timeout timer. 2593 */ 2594 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2595 /* 2596 * XXX the lock bit for RTT indicates that the value 2597 * is also a minimum value; this is subject to time. 2598 */ 2599 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2600 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2601 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2602 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2603 tcpstat.tcps_usedrtt++; 2604 if (rt->rt_rmx.rmx_rttvar) { 2605 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2606 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2607 tcpstat.tcps_usedrttvar++; 2608 } else { 2609 /* default variation is +- 1 rtt */ 2610 tp->t_rttvar = 2611 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2612 } 2613 TCPT_RANGESET(tp->t_rxtcur, 2614 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2615 tp->t_rttmin, TCPTV_REXMTMAX); 2616 } 2617 /* 2618 * if there's an mtu associated with the route, use it 2619 * else, use the link mtu. 2620 */ 2621 if (rt->rt_rmx.rmx_mtu) 2622 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2623 else { 2624 if (isipv6) { 2625 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2626 min_protoh; 2627 if (!in6_localaddr(&inp->in6p_faddr)) 2628 mss = min(mss, tcp_v6mssdflt); 2629 } else { 2630 mss = ifp->if_mtu - min_protoh; 2631 if (!in_localaddr(inp->inp_faddr)) 2632 mss = min(mss, tcp_mssdflt); 2633 } 2634 } 2635 mss = min(mss, offer); 2636 /* 2637 * maxopd stores the maximum length of data AND options 2638 * in a segment; maxseg is the amount of data in a normal 2639 * segment. We need to store this value (maxopd) apart 2640 * from maxseg, because now every segment carries options 2641 * and thus we normally have somewhat less data in segments. 2642 */ 2643 tp->t_maxopd = mss; 2644 2645 /* 2646 * In case of T/TCP, origoffer==-1 indicates, that no segments 2647 * were received yet. In this case we just guess, otherwise 2648 * we do the same as before T/TCP. 2649 */ 2650 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2651 (origoffer == -1 || 2652 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2653 mss -= TCPOLEN_TSTAMP_APPA; 2654 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2655 (origoffer == -1 || 2656 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2657 mss -= TCPOLEN_CC_APPA; 2658 2659 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2660 if (mss > MCLBYTES) 2661 mss &= ~(MCLBYTES-1); 2662 #else 2663 if (mss > MCLBYTES) 2664 mss = mss / MCLBYTES * MCLBYTES; 2665 #endif 2666 /* 2667 * If there's a pipesize, change the socket buffer 2668 * to that size. Make the socket buffers an integral 2669 * number of mss units; if the mss is larger than 2670 * the socket buffer, decrease the mss. 2671 */ 2672 #ifdef RTV_SPIPE 2673 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2674 #endif 2675 bufsize = so->so_snd.sb_hiwat; 2676 if (bufsize < mss) 2677 mss = bufsize; 2678 else { 2679 bufsize = roundup(bufsize, mss); 2680 if (bufsize > sb_max) 2681 bufsize = sb_max; 2682 if (bufsize > so->so_snd.sb_hiwat) 2683 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2684 } 2685 tp->t_maxseg = mss; 2686 2687 #ifdef RTV_RPIPE 2688 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2689 #endif 2690 bufsize = so->so_rcv.sb_hiwat; 2691 if (bufsize > mss) { 2692 bufsize = roundup(bufsize, mss); 2693 if (bufsize > sb_max) 2694 bufsize = sb_max; 2695 if (bufsize > so->so_rcv.sb_hiwat) 2696 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2697 } 2698 2699 /* 2700 * Set the slow-start flight size depending on whether this 2701 * is a local network or not. 2702 */ 2703 if (tcp_do_rfc3390) 2704 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 2705 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2706 (!isipv6 && in_localaddr(inp->inp_faddr))) 2707 tp->snd_cwnd = mss * ss_fltsz_local; 2708 else 2709 tp->snd_cwnd = mss * ss_fltsz; 2710 2711 if (rt->rt_rmx.rmx_ssthresh) { 2712 /* 2713 * There's some sort of gateway or interface 2714 * buffer limit on the path. Use this to set 2715 * the slow start threshhold, but set the 2716 * threshold to no less than 2*mss. 2717 */ 2718 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2719 tcpstat.tcps_usedssthresh++; 2720 } 2721 } 2722 2723 /* 2724 * Determine the MSS option to send on an outgoing SYN. 2725 */ 2726 int 2727 tcp_mssopt(tp) 2728 struct tcpcb *tp; 2729 { 2730 struct rtentry *rt; 2731 #ifdef INET6 2732 int isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2733 int min_protoh = isipv6 ? 2734 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2735 sizeof(struct tcpiphdr); 2736 #else 2737 const int isipv6 = 0; 2738 const size_t min_protoh = sizeof(struct tcpiphdr); 2739 #endif 2740 2741 if (isipv6) 2742 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 2743 else 2744 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 2745 if (rt == NULL) 2746 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2747 2748 return (rt->rt_ifp->if_mtu - min_protoh); 2749 } 2750 2751 2752 /* 2753 * When a partial ack arrives, force the retransmission of the 2754 * next unacknowledged segment. Do not clear tp->t_dupacks. 2755 * By setting snd_nxt to ti_ack, this forces retransmission timer to 2756 * be started again. 2757 */ 2758 static void 2759 tcp_newreno_partial_ack(tp, th) 2760 struct tcpcb *tp; 2761 struct tcphdr *th; 2762 { 2763 tcp_seq onxt = tp->snd_nxt; 2764 u_long ocwnd = tp->snd_cwnd; 2765 2766 callout_stop(tp->tt_rexmt); 2767 tp->t_rtttime = 0; 2768 tp->snd_nxt = th->th_ack; 2769 /* 2770 * Set snd_cwnd to one segment beyond acknowledged offset 2771 * (tp->snd_una has not yet been updated when this function is called.) 2772 */ 2773 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 2774 tp->t_flags |= TF_ACKNOW; 2775 (void) tcp_output(tp); 2776 tp->snd_cwnd = ocwnd; 2777 if (SEQ_GT(onxt, tp->snd_nxt)) 2778 tp->snd_nxt = onxt; 2779 /* 2780 * Partial window deflation. Relies on fact that tp->snd_una 2781 * not updated yet. 2782 */ 2783 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 2784 } 2785