1 /* 2 * Copyright (c) 2002-2004 Jeffrey Hsu. All rights reserved. 3 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. All advertising materials mentioning features or use of this software 15 * must display the following acknowledgement: 16 * This product includes software developed by the University of 17 * California, Berkeley and its contributors. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 35 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 36 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.20 2004/03/09 21:21:54 hsu Exp $ 37 */ 38 39 #include "opt_ipfw.h" /* for ipfw_fwd */ 40 #include "opt_inet6.h" 41 #include "opt_ipsec.h" 42 #include "opt_tcpdebug.h" 43 #include "opt_tcp_input.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/kernel.h> 48 #include <sys/sysctl.h> 49 #include <sys/malloc.h> 50 #include <sys/mbuf.h> 51 #include <sys/proc.h> /* for proc0 declaration */ 52 #include <sys/protosw.h> 53 #include <sys/socket.h> 54 #include <sys/socketvar.h> 55 #include <sys/syslog.h> 56 #include <sys/in_cksum.h> 57 58 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/ip.h> 66 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 67 #include <netinet/in_var.h> 68 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 69 #include <netinet/in_pcb.h> 70 #include <netinet/ip_var.h> 71 #include <netinet/ip6.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/nd6.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/in6_pcb.h> 76 #include <netinet/tcp.h> 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet6/tcp6_var.h> 82 #include <netinet/tcpip.h> 83 #ifdef TCPDEBUG 84 #include <netinet/tcp_debug.h> 85 86 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 87 struct tcphdr tcp_savetcp; 88 #endif /* TCPDEBUG */ 89 90 #ifdef FAST_IPSEC 91 #include <netipsec/ipsec.h> 92 #include <netipsec/ipsec6.h> 93 #endif 94 95 #ifdef IPSEC 96 #include <netinet6/ipsec.h> 97 #include <netinet6/ipsec6.h> 98 #include <netproto/key/key.h> 99 #endif /*IPSEC*/ 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_early_retransmit = 0; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 135 &tcp_do_early_retransmit, 0, "Early retransmit"); 136 137 static int tcp_do_rfc3390 = 1; 138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 139 &tcp_do_rfc3390, 0, 140 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 141 142 static int tcp_do_eifel_detect = 1; 143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 144 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 145 146 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 147 "TCP Segment Reassembly Queue"); 148 149 int tcp_reass_maxseg = 0; 150 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 151 &tcp_reass_maxseg, 0, 152 "Global maximum number of TCP Segments in Reassembly Queue"); 153 154 int tcp_reass_qsize = 0; 155 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 156 &tcp_reass_qsize, 0, 157 "Global number of TCP Segments currently in Reassembly Queue"); 158 159 static int tcp_reass_overflows = 0; 160 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 161 &tcp_reass_overflows, 0, 162 "Global number of TCP Segment Reassembly Queue Overflows"); 163 164 struct inpcbinfo tcbinfo[MAXCPU]; 165 166 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 167 static void tcp_pulloutofband(struct socket *, 168 struct tcphdr *, struct mbuf *, int); 169 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 170 struct mbuf *); 171 static void tcp_xmit_timer(struct tcpcb *, int); 172 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 173 174 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 175 #ifdef INET6 176 #define ND6_HINT(tp) \ 177 do { \ 178 if ((tp) && (tp)->t_inpcb && \ 179 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ 180 (tp)->t_inpcb->in6p_route.ro_rt) \ 181 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 182 } while (0) 183 #else 184 #define ND6_HINT(tp) 185 #endif 186 187 /* 188 * Indicate whether this ack should be delayed. We can delay the ack if 189 * - delayed acks are enabled and 190 * - there is no delayed ack timer in progress and 191 * - our last ack wasn't a 0-sized window. We never want to delay 192 * the ack that opens up a 0-sized window. 193 */ 194 #define DELAY_ACK(tp) \ 195 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 196 (tp->t_flags & TF_RXWIN0SENT) == 0) 197 198 static int 199 tcp_reass(tp, th, tlenp, m) 200 struct tcpcb *tp; 201 struct tcphdr *th; 202 int *tlenp; 203 struct mbuf *m; 204 { 205 struct tseg_qent *q; 206 struct tseg_qent *p = NULL; 207 struct tseg_qent *nq; 208 struct tseg_qent *te; 209 struct socket *so = tp->t_inpcb->inp_socket; 210 int flags; 211 212 /* 213 * Call with th==0 after become established to 214 * force pre-ESTABLISHED data up to user socket. 215 */ 216 if (th == 0) 217 goto present; 218 219 /* 220 * Limit the number of segments in the reassembly queue to prevent 221 * holding on to too many segments (and thus running out of mbufs). 222 * Make sure to let the missing segment through which caused this 223 * queue. Always keep one global queue entry spare to be able to 224 * process the missing segment. 225 */ 226 if (th->th_seq != tp->rcv_nxt && 227 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 228 tcp_reass_overflows++; 229 tcpstat.tcps_rcvmemdrop++; 230 m_freem(m); 231 return (0); 232 } 233 234 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */ 235 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 236 M_NOWAIT); 237 if (te == NULL) { 238 tcpstat.tcps_rcvmemdrop++; 239 m_freem(m); 240 return (0); 241 } 242 tcp_reass_qsize++; 243 244 /* 245 * Find a segment which begins after this one does. 246 */ 247 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 248 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 249 break; 250 p = q; 251 } 252 253 /* 254 * If there is a preceding segment, it may provide some of 255 * our data already. If so, drop the data from the incoming 256 * segment. If it provides all of our data, drop us. 257 */ 258 if (p != NULL) { 259 int i; 260 /* conversion to int (in i) handles seq wraparound */ 261 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 262 if (i > 0) { 263 if (i >= *tlenp) { 264 tcpstat.tcps_rcvduppack++; 265 tcpstat.tcps_rcvdupbyte += *tlenp; 266 m_freem(m); 267 free(te, M_TSEGQ); 268 tcp_reass_qsize--; 269 /* 270 * Try to present any queued data 271 * at the left window edge to the user. 272 * This is needed after the 3-WHS 273 * completes. 274 */ 275 goto present; /* ??? */ 276 } 277 m_adj(m, i); 278 *tlenp -= i; 279 th->th_seq += i; 280 } 281 } 282 tcpstat.tcps_rcvoopack++; 283 tcpstat.tcps_rcvoobyte += *tlenp; 284 285 /* 286 * While we overlap succeeding segments trim them or, 287 * if they are completely covered, dequeue them. 288 */ 289 while (q) { 290 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 291 if (i <= 0) 292 break; 293 if (i < q->tqe_len) { 294 q->tqe_th->th_seq += i; 295 q->tqe_len -= i; 296 m_adj(q->tqe_m, i); 297 break; 298 } 299 300 nq = LIST_NEXT(q, tqe_q); 301 LIST_REMOVE(q, tqe_q); 302 m_freem(q->tqe_m); 303 free(q, M_TSEGQ); 304 tcp_reass_qsize--; 305 q = nq; 306 } 307 308 /* Insert the new segment queue entry into place. */ 309 te->tqe_m = m; 310 te->tqe_th = th; 311 te->tqe_len = *tlenp; 312 313 if (p == NULL) { 314 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 315 } else { 316 LIST_INSERT_AFTER(p, te, tqe_q); 317 } 318 319 present: 320 /* 321 * Present data to user, advancing rcv_nxt through 322 * completed sequence space. 323 */ 324 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 325 return (0); 326 q = LIST_FIRST(&tp->t_segq); 327 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 328 return (0); 329 do { 330 tp->rcv_nxt += q->tqe_len; 331 flags = q->tqe_th->th_flags & TH_FIN; 332 nq = LIST_NEXT(q, tqe_q); 333 LIST_REMOVE(q, tqe_q); 334 if (so->so_state & SS_CANTRCVMORE) 335 m_freem(q->tqe_m); 336 else 337 sbappend(&so->so_rcv, q->tqe_m); 338 free(q, M_TSEGQ); 339 tcp_reass_qsize--; 340 q = nq; 341 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 342 ND6_HINT(tp); 343 sorwakeup(so); 344 return (flags); 345 } 346 347 /* 348 * TCP input routine, follows pages 65-76 of the 349 * protocol specification dated September, 1981 very closely. 350 */ 351 #ifdef INET6 352 int 353 tcp6_input(mp, offp, proto) 354 struct mbuf **mp; 355 int *offp, proto; 356 { 357 struct mbuf *m = *mp; 358 struct in6_ifaddr *ia6; 359 360 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 361 362 /* 363 * draft-itojun-ipv6-tcp-to-anycast 364 * better place to put this in? 365 */ 366 ia6 = ip6_getdstifaddr(m); 367 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 368 struct ip6_hdr *ip6; 369 370 ip6 = mtod(m, struct ip6_hdr *); 371 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 372 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 373 return IPPROTO_DONE; 374 } 375 376 tcp_input(m, *offp, proto); 377 return IPPROTO_DONE; 378 } 379 #endif 380 381 void 382 tcp_input(m, off0, proto) 383 struct mbuf *m; 384 int off0, proto; 385 { 386 struct tcphdr *th; 387 struct ip *ip = NULL; 388 struct ipovly *ipov; 389 struct inpcb *inp = NULL; 390 u_char *optp = NULL; 391 int optlen = 0; 392 int len, tlen, off; 393 int drop_hdrlen; 394 struct tcpcb *tp = NULL; 395 int thflags; 396 struct socket *so = 0; 397 int todrop, acked, ourfinisacked, needoutput = 0; 398 u_long tiwin; 399 struct tcpopt to; /* options in this segment */ 400 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 401 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 402 struct sockaddr_in *next_hop = NULL; 403 int rstreason; /* For badport_bandlim accounting purposes */ 404 int cpu; 405 struct ip6_hdr *ip6 = NULL; 406 #ifdef INET6 407 int isipv6; 408 #else 409 const int isipv6 = 0; 410 #endif 411 #ifdef TCPDEBUG 412 short ostate = 0; 413 #endif 414 415 /* Grab info from MT_TAG mbufs prepended to the chain. */ 416 for (;m && m->m_type == MT_TAG; m = m->m_next) { 417 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 418 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 419 } 420 #ifdef INET6 421 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 422 #endif 423 bzero((char *)&to, sizeof(to)); 424 425 tcpstat.tcps_rcvtotal++; 426 427 if (isipv6) { 428 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 429 ip6 = mtod(m, struct ip6_hdr *); 430 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 431 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 432 tcpstat.tcps_rcvbadsum++; 433 goto drop; 434 } 435 th = (struct tcphdr *)((caddr_t)ip6 + off0); 436 437 /* 438 * Be proactive about unspecified IPv6 address in source. 439 * As we use all-zero to indicate unbounded/unconnected pcb, 440 * unspecified IPv6 address can be used to confuse us. 441 * 442 * Note that packets with unspecified IPv6 destination is 443 * already dropped in ip6_input. 444 */ 445 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 446 /* XXX stat */ 447 goto drop; 448 } 449 } else { 450 /* 451 * Get IP and TCP header together in first mbuf. 452 * Note: IP leaves IP header in first mbuf. 453 */ 454 if (off0 > sizeof(struct ip)) { 455 ip_stripoptions(m); 456 off0 = sizeof(struct ip); 457 } 458 if (m->m_len < sizeof(struct tcpiphdr)) { 459 if ((m = m_pullup(m, sizeof(struct tcpiphdr))) == 0) { 460 tcpstat.tcps_rcvshort++; 461 return; 462 } 463 } 464 ip = mtod(m, struct ip *); 465 ipov = (struct ipovly *)ip; 466 th = (struct tcphdr *)((caddr_t)ip + off0); 467 tlen = ip->ip_len; 468 469 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 470 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 471 th->th_sum = m->m_pkthdr.csum_data; 472 else 473 th->th_sum = in_pseudo(ip->ip_src.s_addr, 474 ip->ip_dst.s_addr, 475 htonl(m->m_pkthdr.csum_data + 476 ip->ip_len + 477 IPPROTO_TCP)); 478 th->th_sum ^= 0xffff; 479 } else { 480 /* 481 * Checksum extended TCP header and data. 482 */ 483 len = sizeof(struct ip) + tlen; 484 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 485 ipov->ih_len = (u_short)tlen; 486 ipov->ih_len = htons(ipov->ih_len); 487 th->th_sum = in_cksum(m, len); 488 } 489 if (th->th_sum) { 490 tcpstat.tcps_rcvbadsum++; 491 goto drop; 492 } 493 #ifdef INET6 494 /* Re-initialization for later version check */ 495 ip->ip_v = IPVERSION; 496 #endif 497 } 498 499 /* 500 * Check that TCP offset makes sense, 501 * pull out TCP options and adjust length. XXX 502 */ 503 off = th->th_off << 2; 504 if (off < sizeof(struct tcphdr) || off > tlen) { 505 tcpstat.tcps_rcvbadoff++; 506 goto drop; 507 } 508 tlen -= off; /* tlen is used instead of ti->ti_len */ 509 if (off > sizeof(struct tcphdr)) { 510 if (isipv6) { 511 IP6_EXTHDR_CHECK(m, off0, off, ); 512 ip6 = mtod(m, struct ip6_hdr *); 513 th = (struct tcphdr *)((caddr_t)ip6 + off0); 514 } else { 515 if (m->m_len < sizeof(struct ip) + off) { 516 if ((m = m_pullup(m, sizeof(struct ip) + off)) 517 == 0) { 518 tcpstat.tcps_rcvshort++; 519 return; 520 } 521 ip = mtod(m, struct ip *); 522 ipov = (struct ipovly *)ip; 523 th = (struct tcphdr *)((caddr_t)ip + off0); 524 } 525 } 526 optlen = off - sizeof(struct tcphdr); 527 optp = (u_char *)(th + 1); 528 } 529 thflags = th->th_flags; 530 531 #ifdef TCP_DROP_SYNFIN 532 /* 533 * If the drop_synfin option is enabled, drop all packets with 534 * both the SYN and FIN bits set. This prevents e.g. nmap from 535 * identifying the TCP/IP stack. 536 * 537 * This is a violation of the TCP specification. 538 */ 539 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 540 goto drop; 541 #endif 542 543 /* 544 * Convert TCP protocol specific fields to host format. 545 */ 546 th->th_seq = ntohl(th->th_seq); 547 th->th_ack = ntohl(th->th_ack); 548 th->th_win = ntohs(th->th_win); 549 th->th_urp = ntohs(th->th_urp); 550 551 /* 552 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options, 553 * until after ip6_savecontrol() is called and before other functions 554 * which don't want those proto headers. 555 * Because ip6_savecontrol() is going to parse the mbuf to 556 * search for data to be passed up to user-land, it wants mbuf 557 * parameters to be unchanged. 558 * XXX: the call of ip6_savecontrol() has been obsoleted based on 559 * latest version of the advanced API (20020110). 560 */ 561 drop_hdrlen = off0 + off; 562 563 /* 564 * Locate pcb for segment. 565 */ 566 findpcb: 567 /* IPFIREWALL_FORWARD section */ 568 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 569 /* 570 * Transparently forwarded. Pretend to be the destination. 571 * already got one like this? 572 */ 573 inp = in_pcblookup_hash(&tcbinfo[mycpu->gd_cpuid], 574 ip->ip_src, th->th_sport, 575 ip->ip_dst, th->th_dport, 576 0, m->m_pkthdr.rcvif); 577 if (!inp) { 578 /* 579 * It's new. Try to find the ambushing socket. 580 */ 581 582 /* 583 * The rest of the ipfw code stores the port in 584 * host order. XXX 585 * (The IP address is still in network order.) 586 */ 587 in_port_t dport = next_hop->sin_port ? 588 htons(next_hop->sin_port) : 589 th->th_dport; 590 591 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 592 next_hop->sin_addr.s_addr, dport); 593 inp = in_pcblookup_hash(&tcbinfo[cpu], 594 ip->ip_src, th->th_sport, 595 next_hop->sin_addr, dport, 596 1, m->m_pkthdr.rcvif); 597 } 598 } else { 599 if (isipv6) 600 inp = in6_pcblookup_hash(&tcbinfo[0], 601 &ip6->ip6_src, th->th_sport, 602 &ip6->ip6_dst, th->th_dport, 603 1, m->m_pkthdr.rcvif); 604 else 605 inp = in_pcblookup_hash(&tcbinfo[mycpu->gd_cpuid], 606 ip->ip_src, th->th_sport, 607 ip->ip_dst, th->th_dport, 608 1, m->m_pkthdr.rcvif); 609 } 610 611 #ifdef IPSEC 612 if (isipv6) { 613 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 614 ipsec6stat.in_polvio++; 615 goto drop; 616 } 617 } else { 618 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 619 ipsecstat.in_polvio++; 620 goto drop; 621 } 622 } 623 #endif 624 #ifdef FAST_IPSEC 625 if (isipv6) { 626 if (inp != NULL && ipsec6_in_reject(m, inp)) { 627 goto drop; 628 } 629 } else { 630 if (inp != NULL && ipsec4_in_reject(m, inp)) { 631 goto drop; 632 } 633 } 634 #endif 635 636 /* 637 * If the state is CLOSED (i.e., TCB does not exist) then 638 * all data in the incoming segment is discarded. 639 * If the TCB exists but is in CLOSED state, it is embryonic, 640 * but should either do a listen or a connect soon. 641 */ 642 if (inp == NULL) { 643 if (log_in_vain) { 644 #ifdef INET6 645 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 646 #else 647 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 648 #endif 649 if (isipv6) { 650 strcpy(dbuf, "["); 651 strcpy(sbuf, "["); 652 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 653 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 654 strcat(dbuf, "]"); 655 strcat(sbuf, "]"); 656 } else { 657 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 658 strcpy(sbuf, inet_ntoa(ip->ip_src)); 659 } 660 switch (log_in_vain) { 661 case 1: 662 if ((thflags & TH_SYN) == 0) 663 break; 664 case 2: 665 log(LOG_INFO, 666 "Connection attempt to TCP %s:%d " 667 "from %s:%d flags:0x%02x\n", 668 dbuf, ntohs(th->th_dport), sbuf, 669 ntohs(th->th_sport), thflags); 670 break; 671 default: 672 break; 673 } 674 } 675 if (blackhole) { 676 switch (blackhole) { 677 case 1: 678 if (thflags & TH_SYN) 679 goto drop; 680 break; 681 case 2: 682 goto drop; 683 default: 684 goto drop; 685 } 686 } 687 rstreason = BANDLIM_RST_CLOSEDPORT; 688 goto dropwithreset; 689 } 690 tp = intotcpcb(inp); 691 if (tp == NULL) { 692 rstreason = BANDLIM_RST_CLOSEDPORT; 693 goto dropwithreset; 694 } 695 if (tp->t_state == TCPS_CLOSED) 696 goto drop; 697 698 /* Unscale the window into a 32-bit value. */ 699 if ((thflags & TH_SYN) == 0) 700 tiwin = th->th_win << tp->snd_scale; 701 else 702 tiwin = th->th_win; 703 704 so = inp->inp_socket; 705 706 #ifdef TCPDEBUG 707 if (so->so_options & SO_DEBUG) { 708 ostate = tp->t_state; 709 if (isipv6) 710 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 711 else 712 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 713 tcp_savetcp = *th; 714 } 715 #endif 716 717 if (so->so_options & SO_ACCEPTCONN) { 718 struct in_conninfo inc; 719 720 #ifdef INET6 721 inc.inc_isipv6 = isipv6; 722 #endif 723 if (isipv6) { 724 inc.inc6_faddr = ip6->ip6_src; 725 inc.inc6_laddr = ip6->ip6_dst; 726 inc.inc6_route.ro_rt = NULL; /* XXX */ 727 } else { 728 inc.inc_faddr = ip->ip_src; 729 inc.inc_laddr = ip->ip_dst; 730 inc.inc_route.ro_rt = NULL; /* XXX */ 731 } 732 inc.inc_fport = th->th_sport; 733 inc.inc_lport = th->th_dport; 734 735 /* 736 * If the state is LISTEN then ignore segment if it contains 737 * a RST. If the segment contains an ACK then it is bad and 738 * send a RST. If it does not contain a SYN then it is not 739 * interesting; drop it. 740 * 741 * If the state is SYN_RECEIVED (syncache) and seg contains 742 * an ACK, but not for our SYN/ACK, send a RST. If the seg 743 * contains a RST, check the sequence number to see if it 744 * is a valid reset segment. 745 */ 746 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 747 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 748 if (!syncache_expand(&inc, th, &so, m)) { 749 /* 750 * No syncache entry, or ACK was not 751 * for our SYN/ACK. Send a RST. 752 */ 753 tcpstat.tcps_badsyn++; 754 rstreason = BANDLIM_RST_OPENPORT; 755 goto dropwithreset; 756 } 757 if (so == NULL) 758 /* 759 * Could not complete 3-way handshake, 760 * connection is being closed down, and 761 * syncache will free mbuf. 762 */ 763 return; 764 /* 765 * Socket is created in state SYN_RECEIVED. 766 * Continue processing segment. 767 */ 768 inp = sotoinpcb(so); 769 tp = intotcpcb(inp); 770 /* 771 * This is what would have happened in 772 * tcp_output() when the SYN,ACK was sent. 773 */ 774 tp->snd_up = tp->snd_una; 775 tp->snd_max = tp->snd_nxt = tp->iss + 1; 776 tp->last_ack_sent = tp->rcv_nxt; 777 /* 778 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 779 * until the _second_ ACK is received: 780 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 781 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 782 * move to ESTAB, set snd_wnd to tiwin. 783 */ 784 tp->snd_wnd = tiwin; /* unscaled */ 785 goto after_listen; 786 } 787 if (thflags & TH_RST) { 788 syncache_chkrst(&inc, th); 789 goto drop; 790 } 791 if (thflags & TH_ACK) { 792 syncache_badack(&inc); 793 tcpstat.tcps_badsyn++; 794 rstreason = BANDLIM_RST_OPENPORT; 795 goto dropwithreset; 796 } 797 goto drop; 798 } 799 800 /* 801 * Segment's flags are (SYN) or (SYN|FIN). 802 */ 803 #ifdef INET6 804 /* 805 * If deprecated address is forbidden, 806 * we do not accept SYN to deprecated interface 807 * address to prevent any new inbound connection from 808 * getting established. 809 * When we do not accept SYN, we send a TCP RST, 810 * with deprecated source address (instead of dropping 811 * it). We compromise it as it is much better for peer 812 * to send a RST, and RST will be the final packet 813 * for the exchange. 814 * 815 * If we do not forbid deprecated addresses, we accept 816 * the SYN packet. RFC2462 does not suggest dropping 817 * SYN in this case. 818 * If we decipher RFC2462 5.5.4, it says like this: 819 * 1. use of deprecated addr with existing 820 * communication is okay - "SHOULD continue to be 821 * used" 822 * 2. use of it with new communication: 823 * (2a) "SHOULD NOT be used if alternate address 824 * with sufficient scope is available" 825 * (2b) nothing mentioned otherwise. 826 * Here we fall into (2b) case as we have no choice in 827 * our source address selection - we must obey the peer. 828 * 829 * The wording in RFC2462 is confusing, and there are 830 * multiple description text for deprecated address 831 * handling - worse, they are not exactly the same. 832 * I believe 5.5.4 is the best one, so we follow 5.5.4. 833 */ 834 if (isipv6 && !ip6_use_deprecated) { 835 struct in6_ifaddr *ia6; 836 837 if ((ia6 = ip6_getdstifaddr(m)) && 838 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 839 tp = NULL; 840 rstreason = BANDLIM_RST_OPENPORT; 841 goto dropwithreset; 842 } 843 } 844 #endif 845 /* 846 * If it is from this socket, drop it, it must be forged. 847 * Don't bother responding if the destination was a broadcast. 848 */ 849 if (th->th_dport == th->th_sport) { 850 if (isipv6) { 851 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 852 &ip6->ip6_src)) 853 goto drop; 854 } else { 855 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 856 goto drop; 857 } 858 } 859 /* 860 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 861 * 862 * Note that it is quite possible to receive unicast 863 * link-layer packets with a broadcast IP address. Use 864 * in_broadcast() to find them. 865 */ 866 if (m->m_flags & (M_BCAST|M_MCAST)) 867 goto drop; 868 if (isipv6) { 869 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 870 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 871 goto drop; 872 } else { 873 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 874 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 875 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 876 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 877 goto drop; 878 } 879 /* 880 * SYN appears to be valid; create compressed TCP state 881 * for syncache, or perform t/tcp connection. 882 */ 883 if (so->so_qlen <= so->so_qlimit) { 884 tcp_dooptions(&to, optp, optlen, 1); 885 if (!syncache_add(&inc, &to, th, &so, m)) 886 goto drop; 887 if (so == NULL) 888 /* 889 * Entry added to syncache, mbuf used to 890 * send SYN,ACK packet. 891 */ 892 return; 893 /* 894 * Segment passed TAO tests. 895 */ 896 inp = sotoinpcb(so); 897 tp = intotcpcb(inp); 898 tp->snd_wnd = tiwin; 899 tp->t_starttime = ticks; 900 tp->t_state = TCPS_ESTABLISHED; 901 902 /* 903 * If there is a FIN, or if there is data and the 904 * connection is local, then delay SYN,ACK(SYN) in 905 * the hope of piggy-backing it on a response 906 * segment. Otherwise must send ACK now in case 907 * the other side is slow starting. 908 */ 909 if (DELAY_ACK(tp) && 910 ((thflags & TH_FIN) || 911 (tlen != 0 && 912 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 913 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 914 callout_reset(tp->tt_delack, tcp_delacktime, 915 tcp_timer_delack, tp); 916 tp->t_flags |= TF_NEEDSYN; 917 } else 918 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 919 920 tcpstat.tcps_connects++; 921 soisconnected(so); 922 goto trimthenstep6; 923 } 924 goto drop; 925 } 926 after_listen: 927 928 /* XXX temp debugging */ 929 /* should not happen - syncache should pick up these connections */ 930 if (tp->t_state == TCPS_LISTEN) 931 panic("tcp_input: TCPS_LISTEN"); 932 933 /* 934 * Segment received on connection. 935 * Reset idle time and keep-alive timer. 936 */ 937 tp->t_rcvtime = ticks; 938 if (TCPS_HAVEESTABLISHED(tp->t_state)) 939 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 940 941 /* 942 * Process options. 943 * XXX this is tradtitional behavior, may need to be cleaned up. 944 */ 945 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 946 if (thflags & TH_SYN) { 947 if (to.to_flags & TOF_SCALE) { 948 tp->t_flags |= TF_RCVD_SCALE; 949 tp->requested_s_scale = to.to_requested_s_scale; 950 } 951 if (to.to_flags & TOF_TS) { 952 tp->t_flags |= TF_RCVD_TSTMP; 953 tp->ts_recent = to.to_tsval; 954 tp->ts_recent_age = ticks; 955 } 956 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 957 tp->t_flags |= TF_RCVD_CC; 958 if (to.to_flags & TOF_MSS) 959 tcp_mss(tp, to.to_mss); 960 } 961 962 /* 963 * Header prediction: check for the two common cases 964 * of a uni-directional data xfer. If the packet has 965 * no control flags, is in-sequence, the window didn't 966 * change and we're not retransmitting, it's a 967 * candidate. If the length is zero and the ack moved 968 * forward, we're the sender side of the xfer. Just 969 * free the data acked & wake any higher level process 970 * that was blocked waiting for space. If the length 971 * is non-zero and the ack didn't move, we're the 972 * receiver side. If we're getting packets in-order 973 * (the reassembly queue is empty), add the data to 974 * the socket buffer and note that we need a delayed ack. 975 * Make sure that the hidden state-flags are also off. 976 * Since we check for TCPS_ESTABLISHED above, it can only 977 * be TH_NEEDSYN. 978 */ 979 if (tp->t_state == TCPS_ESTABLISHED && 980 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 981 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 982 ((to.to_flags & TOF_TS) == 0 || 983 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 984 /* 985 * Using the CC option is compulsory if once started: 986 * the segment is OK if no T/TCP was negotiated or 987 * if the segment has a CC option equal to CCrecv 988 */ 989 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 990 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 991 th->th_seq == tp->rcv_nxt && 992 tiwin && tiwin == tp->snd_wnd && 993 tp->snd_nxt == tp->snd_max) { 994 995 /* 996 * If last ACK falls within this segment's sequence numbers, 997 * record the timestamp. 998 * NOTE that the test is modified according to the latest 999 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1000 */ 1001 if ((to.to_flags & TOF_TS) != 0 && 1002 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1003 tp->ts_recent_age = ticks; 1004 tp->ts_recent = to.to_tsval; 1005 } 1006 1007 if (tlen == 0) { 1008 if (SEQ_GT(th->th_ack, tp->snd_una) && 1009 SEQ_LEQ(th->th_ack, tp->snd_max) && 1010 tp->snd_cwnd >= tp->snd_wnd && 1011 ((!tcp_do_newreno && 1012 tp->t_dupacks < tcprexmtthresh) || 1013 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) { 1014 /* 1015 * this is a pure ack for outstanding data. 1016 */ 1017 ++tcpstat.tcps_predack; 1018 /* 1019 * "bad retransmit" recovery 1020 * 1021 * If Eifel detection applies, then 1022 * it is deterministic, so use it 1023 * unconditionally over the old heuristic. 1024 * Otherwise, fall back to the old heuristic. 1025 */ 1026 if (tcp_do_eifel_detect && 1027 (to.to_flags & TOF_TS) && to.to_tsecr && 1028 (tp->t_flags & TF_FIRSTACCACK)) { 1029 /* Eifel detection applicable. */ 1030 if (to.to_tsecr < tp->t_rexmtTS) { 1031 tcp_revert_congestion_state(tp); 1032 ++tcpstat.tcps_eifeldetected; 1033 } 1034 } else if (tp->t_rxtshift == 1 && 1035 ticks < tp->t_badrxtwin) { 1036 tcp_revert_congestion_state(tp); 1037 ++tcpstat.tcps_rttdetected; 1038 } 1039 tp->t_flags &= ~(TF_FIRSTACCACK | 1040 TF_FASTREXMT | TF_EARLYREXMT); 1041 /* 1042 * Recalculate the retransmit timer / rtt. 1043 * 1044 * Some machines (certain windows boxes) 1045 * send broken timestamp replies during the 1046 * SYN+ACK phase, ignore timestamps of 0. 1047 */ 1048 if ((to.to_flags & TOF_TS) != 0 && 1049 to.to_tsecr) { 1050 tcp_xmit_timer(tp, 1051 ticks - to.to_tsecr + 1); 1052 } else if (tp->t_rtttime && 1053 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1054 tcp_xmit_timer(tp, 1055 ticks - tp->t_rtttime); 1056 } 1057 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1058 acked = th->th_ack - tp->snd_una; 1059 tcpstat.tcps_rcvackpack++; 1060 tcpstat.tcps_rcvackbyte += acked; 1061 sbdrop(&so->so_snd, acked); 1062 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1063 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1064 tp->snd_recover = th->th_ack - 1; 1065 tp->snd_una = th->th_ack; 1066 tp->t_dupacks = 0; 1067 m_freem(m); 1068 ND6_HINT(tp); /* some progress has been done */ 1069 1070 /* 1071 * If all outstanding data are acked, stop 1072 * retransmit timer, otherwise restart timer 1073 * using current (possibly backed-off) value. 1074 * If process is waiting for space, 1075 * wakeup/selwakeup/signal. If data 1076 * are ready to send, let tcp_output 1077 * decide between more output or persist. 1078 */ 1079 if (tp->snd_una == tp->snd_max) 1080 callout_stop(tp->tt_rexmt); 1081 else if (!callout_active(tp->tt_persist)) 1082 callout_reset(tp->tt_rexmt, 1083 tp->t_rxtcur, 1084 tcp_timer_rexmt, tp); 1085 1086 sowwakeup(so); 1087 if (so->so_snd.sb_cc) 1088 (void) tcp_output(tp); 1089 return; 1090 } 1091 } else if (th->th_ack == tp->snd_una && 1092 LIST_EMPTY(&tp->t_segq) && 1093 tlen <= sbspace(&so->so_rcv)) { 1094 /* 1095 * this is a pure, in-sequence data packet 1096 * with nothing on the reassembly queue and 1097 * we have enough buffer space to take it. 1098 */ 1099 ++tcpstat.tcps_preddat; 1100 tp->rcv_nxt += tlen; 1101 tcpstat.tcps_rcvpack++; 1102 tcpstat.tcps_rcvbyte += tlen; 1103 ND6_HINT(tp); /* some progress has been done */ 1104 /* 1105 * Add data to socket buffer. 1106 */ 1107 if (so->so_state & SS_CANTRCVMORE) { 1108 m_freem(m); 1109 } else { 1110 m_adj(m, drop_hdrlen); /* delayed header drop */ 1111 sbappend(&so->so_rcv, m); 1112 } 1113 sorwakeup(so); 1114 if (DELAY_ACK(tp)) { 1115 callout_reset(tp->tt_delack, tcp_delacktime, 1116 tcp_timer_delack, tp); 1117 } else { 1118 tp->t_flags |= TF_ACKNOW; 1119 tcp_output(tp); 1120 } 1121 return; 1122 } 1123 } 1124 1125 /* 1126 * Calculate amount of space in receive window, 1127 * and then do TCP input processing. 1128 * Receive window is amount of space in rcv queue, 1129 * but not less than advertised window. 1130 */ 1131 { int win; 1132 1133 win = sbspace(&so->so_rcv); 1134 if (win < 0) 1135 win = 0; 1136 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1137 } 1138 1139 switch (tp->t_state) { 1140 1141 /* 1142 * If the state is SYN_RECEIVED: 1143 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1144 */ 1145 case TCPS_SYN_RECEIVED: 1146 if ((thflags & TH_ACK) && 1147 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1148 SEQ_GT(th->th_ack, tp->snd_max))) { 1149 rstreason = BANDLIM_RST_OPENPORT; 1150 goto dropwithreset; 1151 } 1152 break; 1153 1154 /* 1155 * If the state is SYN_SENT: 1156 * if seg contains an ACK, but not for our SYN, drop the input. 1157 * if seg contains a RST, then drop the connection. 1158 * if seg does not contain SYN, then drop it. 1159 * Otherwise this is an acceptable SYN segment 1160 * initialize tp->rcv_nxt and tp->irs 1161 * if seg contains ack then advance tp->snd_una 1162 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1163 * arrange for segment to be acked (eventually) 1164 * continue processing rest of data/controls, beginning with URG 1165 */ 1166 case TCPS_SYN_SENT: 1167 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1168 taop = &tao_noncached; 1169 bzero(taop, sizeof(*taop)); 1170 } 1171 1172 if ((thflags & TH_ACK) && 1173 (SEQ_LEQ(th->th_ack, tp->iss) || 1174 SEQ_GT(th->th_ack, tp->snd_max))) { 1175 /* 1176 * If we have a cached CCsent for the remote host, 1177 * hence we haven't just crashed and restarted, 1178 * do not send a RST. This may be a retransmission 1179 * from the other side after our earlier ACK was lost. 1180 * Our new SYN, when it arrives, will serve as the 1181 * needed ACK. 1182 */ 1183 if (taop->tao_ccsent != 0) 1184 goto drop; 1185 else { 1186 rstreason = BANDLIM_UNLIMITED; 1187 goto dropwithreset; 1188 } 1189 } 1190 if (thflags & TH_RST) { 1191 if (thflags & TH_ACK) 1192 tp = tcp_drop(tp, ECONNREFUSED); 1193 goto drop; 1194 } 1195 if ((thflags & TH_SYN) == 0) 1196 goto drop; 1197 tp->snd_wnd = th->th_win; /* initial send window */ 1198 tp->cc_recv = to.to_cc; /* foreign CC */ 1199 1200 tp->irs = th->th_seq; 1201 tcp_rcvseqinit(tp); 1202 if (thflags & TH_ACK) { 1203 /* 1204 * Our SYN was acked. If segment contains CC.ECHO 1205 * option, check it to make sure this segment really 1206 * matches our SYN. If not, just drop it as old 1207 * duplicate, but send an RST if we're still playing 1208 * by the old rules. If no CC.ECHO option, make sure 1209 * we don't get fooled into using T/TCP. 1210 */ 1211 if (to.to_flags & TOF_CCECHO) { 1212 if (tp->cc_send != to.to_ccecho) { 1213 if (taop->tao_ccsent != 0) 1214 goto drop; 1215 else { 1216 rstreason = BANDLIM_UNLIMITED; 1217 goto dropwithreset; 1218 } 1219 } 1220 } else 1221 tp->t_flags &= ~TF_RCVD_CC; 1222 tcpstat.tcps_connects++; 1223 soisconnected(so); 1224 /* Do window scaling on this connection? */ 1225 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1226 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1227 tp->snd_scale = tp->requested_s_scale; 1228 tp->rcv_scale = tp->request_r_scale; 1229 } 1230 /* Segment is acceptable, update cache if undefined. */ 1231 if (taop->tao_ccsent == 0) 1232 taop->tao_ccsent = to.to_ccecho; 1233 1234 tp->rcv_adv += tp->rcv_wnd; 1235 tp->snd_una++; /* SYN is acked */ 1236 /* 1237 * If there's data, delay ACK; if there's also a FIN 1238 * ACKNOW will be turned on later. 1239 */ 1240 if (DELAY_ACK(tp) && tlen != 0) 1241 callout_reset(tp->tt_delack, tcp_delacktime, 1242 tcp_timer_delack, tp); 1243 else 1244 tp->t_flags |= TF_ACKNOW; 1245 /* 1246 * Received <SYN,ACK> in SYN_SENT[*] state. 1247 * Transitions: 1248 * SYN_SENT --> ESTABLISHED 1249 * SYN_SENT* --> FIN_WAIT_1 1250 */ 1251 tp->t_starttime = ticks; 1252 if (tp->t_flags & TF_NEEDFIN) { 1253 tp->t_state = TCPS_FIN_WAIT_1; 1254 tp->t_flags &= ~TF_NEEDFIN; 1255 thflags &= ~TH_SYN; 1256 } else { 1257 tp->t_state = TCPS_ESTABLISHED; 1258 callout_reset(tp->tt_keep, tcp_keepidle, 1259 tcp_timer_keep, tp); 1260 } 1261 } else { 1262 /* 1263 * Received initial SYN in SYN-SENT[*] state => 1264 * simultaneous open. If segment contains CC option 1265 * and there is a cached CC, apply TAO test. 1266 * If it succeeds, connection is * half-synchronized. 1267 * Otherwise, do 3-way handshake: 1268 * SYN-SENT -> SYN-RECEIVED 1269 * SYN-SENT* -> SYN-RECEIVED* 1270 * If there was no CC option, clear cached CC value. 1271 */ 1272 tp->t_flags |= TF_ACKNOW; 1273 callout_stop(tp->tt_rexmt); 1274 if (to.to_flags & TOF_CC) { 1275 if (taop->tao_cc != 0 && 1276 CC_GT(to.to_cc, taop->tao_cc)) { 1277 /* 1278 * update cache and make transition: 1279 * SYN-SENT -> ESTABLISHED* 1280 * SYN-SENT* -> FIN-WAIT-1* 1281 */ 1282 taop->tao_cc = to.to_cc; 1283 tp->t_starttime = ticks; 1284 if (tp->t_flags & TF_NEEDFIN) { 1285 tp->t_state = TCPS_FIN_WAIT_1; 1286 tp->t_flags &= ~TF_NEEDFIN; 1287 } else { 1288 tp->t_state = TCPS_ESTABLISHED; 1289 callout_reset(tp->tt_keep, 1290 tcp_keepidle, 1291 tcp_timer_keep, 1292 tp); 1293 } 1294 tp->t_flags |= TF_NEEDSYN; 1295 } else 1296 tp->t_state = TCPS_SYN_RECEIVED; 1297 } else { 1298 /* CC.NEW or no option => invalidate cache */ 1299 taop->tao_cc = 0; 1300 tp->t_state = TCPS_SYN_RECEIVED; 1301 } 1302 } 1303 1304 trimthenstep6: 1305 /* 1306 * Advance th->th_seq to correspond to first data byte. 1307 * If data, trim to stay within window, 1308 * dropping FIN if necessary. 1309 */ 1310 th->th_seq++; 1311 if (tlen > tp->rcv_wnd) { 1312 todrop = tlen - tp->rcv_wnd; 1313 m_adj(m, -todrop); 1314 tlen = tp->rcv_wnd; 1315 thflags &= ~TH_FIN; 1316 tcpstat.tcps_rcvpackafterwin++; 1317 tcpstat.tcps_rcvbyteafterwin += todrop; 1318 } 1319 tp->snd_wl1 = th->th_seq - 1; 1320 tp->rcv_up = th->th_seq; 1321 /* 1322 * Client side of transaction: already sent SYN and data. 1323 * If the remote host used T/TCP to validate the SYN, 1324 * our data will be ACK'd; if so, enter normal data segment 1325 * processing in the middle of step 5, ack processing. 1326 * Otherwise, goto step 6. 1327 */ 1328 if (thflags & TH_ACK) 1329 goto process_ACK; 1330 1331 goto step6; 1332 1333 /* 1334 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1335 * if segment contains a SYN and CC [not CC.NEW] option: 1336 * if state == TIME_WAIT and connection duration > MSL, 1337 * drop packet and send RST; 1338 * 1339 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1340 * ack the FIN (and data) in retransmission queue. 1341 * Complete close and delete TCPCB. Then reprocess 1342 * segment, hoping to find new TCPCB in LISTEN state; 1343 * 1344 * else must be old SYN; drop it. 1345 * else do normal processing. 1346 */ 1347 case TCPS_LAST_ACK: 1348 case TCPS_CLOSING: 1349 case TCPS_TIME_WAIT: 1350 if ((thflags & TH_SYN) && 1351 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1352 if (tp->t_state == TCPS_TIME_WAIT && 1353 (ticks - tp->t_starttime) > tcp_msl) { 1354 rstreason = BANDLIM_UNLIMITED; 1355 goto dropwithreset; 1356 } 1357 if (CC_GT(to.to_cc, tp->cc_recv)) { 1358 tp = tcp_close(tp); 1359 goto findpcb; 1360 } 1361 else 1362 goto drop; 1363 } 1364 break; /* continue normal processing */ 1365 } 1366 1367 /* 1368 * States other than LISTEN or SYN_SENT. 1369 * First check the RST flag and sequence number since reset segments 1370 * are exempt from the timestamp and connection count tests. This 1371 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1372 * below which allowed reset segments in half the sequence space 1373 * to fall though and be processed (which gives forged reset 1374 * segments with a random sequence number a 50 percent chance of 1375 * killing a connection). 1376 * Then check timestamp, if present. 1377 * Then check the connection count, if present. 1378 * Then check that at least some bytes of segment are within 1379 * receive window. If segment begins before rcv_nxt, 1380 * drop leading data (and SYN); if nothing left, just ack. 1381 * 1382 * 1383 * If the RST bit is set, check the sequence number to see 1384 * if this is a valid reset segment. 1385 * RFC 793 page 37: 1386 * In all states except SYN-SENT, all reset (RST) segments 1387 * are validated by checking their SEQ-fields. A reset is 1388 * valid if its sequence number is in the window. 1389 * Note: this does not take into account delayed ACKs, so 1390 * we should test against last_ack_sent instead of rcv_nxt. 1391 * The sequence number in the reset segment is normally an 1392 * echo of our outgoing acknowlegement numbers, but some hosts 1393 * send a reset with the sequence number at the rightmost edge 1394 * of our receive window, and we have to handle this case. 1395 * If we have multiple segments in flight, the intial reset 1396 * segment sequence numbers will be to the left of last_ack_sent, 1397 * but they will eventually catch up. 1398 * In any case, it never made sense to trim reset segments to 1399 * fit the receive window since RFC 1122 says: 1400 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1401 * 1402 * A TCP SHOULD allow a received RST segment to include data. 1403 * 1404 * DISCUSSION 1405 * It has been suggested that a RST segment could contain 1406 * ASCII text that encoded and explained the cause of the 1407 * RST. No standard has yet been established for such 1408 * data. 1409 * 1410 * If the reset segment passes the sequence number test examine 1411 * the state: 1412 * SYN_RECEIVED STATE: 1413 * If passive open, return to LISTEN state. 1414 * If active open, inform user that connection was refused. 1415 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1416 * Inform user that connection was reset, and close tcb. 1417 * CLOSING, LAST_ACK STATES: 1418 * Close the tcb. 1419 * TIME_WAIT STATE: 1420 * Drop the segment - see Stevens, vol. 2, p. 964 and 1421 * RFC 1337. 1422 */ 1423 if (thflags & TH_RST) { 1424 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1425 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1426 switch (tp->t_state) { 1427 1428 case TCPS_SYN_RECEIVED: 1429 so->so_error = ECONNREFUSED; 1430 goto close; 1431 1432 case TCPS_ESTABLISHED: 1433 case TCPS_FIN_WAIT_1: 1434 case TCPS_FIN_WAIT_2: 1435 case TCPS_CLOSE_WAIT: 1436 so->so_error = ECONNRESET; 1437 close: 1438 tp->t_state = TCPS_CLOSED; 1439 tcpstat.tcps_drops++; 1440 tp = tcp_close(tp); 1441 break; 1442 1443 case TCPS_CLOSING: 1444 case TCPS_LAST_ACK: 1445 tp = tcp_close(tp); 1446 break; 1447 1448 case TCPS_TIME_WAIT: 1449 break; 1450 } 1451 } 1452 goto drop; 1453 } 1454 1455 /* 1456 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1457 * and it's less than ts_recent, drop it. 1458 */ 1459 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1460 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1461 1462 /* Check to see if ts_recent is over 24 days old. */ 1463 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1464 /* 1465 * Invalidate ts_recent. If this segment updates 1466 * ts_recent, the age will be reset later and ts_recent 1467 * will get a valid value. If it does not, setting 1468 * ts_recent to zero will at least satisfy the 1469 * requirement that zero be placed in the timestamp 1470 * echo reply when ts_recent isn't valid. The 1471 * age isn't reset until we get a valid ts_recent 1472 * because we don't want out-of-order segments to be 1473 * dropped when ts_recent is old. 1474 */ 1475 tp->ts_recent = 0; 1476 } else { 1477 tcpstat.tcps_rcvduppack++; 1478 tcpstat.tcps_rcvdupbyte += tlen; 1479 tcpstat.tcps_pawsdrop++; 1480 if (tlen) 1481 goto dropafterack; 1482 goto drop; 1483 } 1484 } 1485 1486 /* 1487 * T/TCP mechanism 1488 * If T/TCP was negotiated and the segment doesn't have CC, 1489 * or if its CC is wrong then drop the segment. 1490 * RST segments do not have to comply with this. 1491 */ 1492 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1493 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1494 goto dropafterack; 1495 1496 /* 1497 * In the SYN-RECEIVED state, validate that the packet belongs to 1498 * this connection before trimming the data to fit the receive 1499 * window. Check the sequence number versus IRS since we know 1500 * the sequence numbers haven't wrapped. This is a partial fix 1501 * for the "LAND" DoS attack. 1502 */ 1503 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1504 rstreason = BANDLIM_RST_OPENPORT; 1505 goto dropwithreset; 1506 } 1507 1508 todrop = tp->rcv_nxt - th->th_seq; 1509 if (todrop > 0) { 1510 if (thflags & TH_SYN) { 1511 thflags &= ~TH_SYN; 1512 th->th_seq++; 1513 if (th->th_urp > 1) 1514 th->th_urp--; 1515 else 1516 thflags &= ~TH_URG; 1517 todrop--; 1518 } 1519 /* 1520 * Following if statement from Stevens, vol. 2, p. 960. 1521 */ 1522 if (todrop > tlen 1523 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1524 /* 1525 * Any valid FIN must be to the left of the window. 1526 * At this point the FIN must be a duplicate or out 1527 * of sequence; drop it. 1528 */ 1529 thflags &= ~TH_FIN; 1530 1531 /* 1532 * Send an ACK to resynchronize and drop any data. 1533 * But keep on processing for RST or ACK. 1534 */ 1535 tp->t_flags |= TF_ACKNOW; 1536 todrop = tlen; 1537 tcpstat.tcps_rcvduppack++; 1538 tcpstat.tcps_rcvdupbyte += todrop; 1539 } else { 1540 tcpstat.tcps_rcvpartduppack++; 1541 tcpstat.tcps_rcvpartdupbyte += todrop; 1542 } 1543 drop_hdrlen += todrop; /* drop from the top afterwards */ 1544 th->th_seq += todrop; 1545 tlen -= todrop; 1546 if (th->th_urp > todrop) 1547 th->th_urp -= todrop; 1548 else { 1549 thflags &= ~TH_URG; 1550 th->th_urp = 0; 1551 } 1552 } 1553 1554 /* 1555 * If new data are received on a connection after the 1556 * user processes are gone, then RST the other end. 1557 */ 1558 if ((so->so_state & SS_NOFDREF) && 1559 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1560 tp = tcp_close(tp); 1561 tcpstat.tcps_rcvafterclose++; 1562 rstreason = BANDLIM_UNLIMITED; 1563 goto dropwithreset; 1564 } 1565 1566 /* 1567 * If segment ends after window, drop trailing data 1568 * (and PUSH and FIN); if nothing left, just ACK. 1569 */ 1570 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1571 if (todrop > 0) { 1572 tcpstat.tcps_rcvpackafterwin++; 1573 if (todrop >= tlen) { 1574 tcpstat.tcps_rcvbyteafterwin += tlen; 1575 /* 1576 * If a new connection request is received 1577 * while in TIME_WAIT, drop the old connection 1578 * and start over if the sequence numbers 1579 * are above the previous ones. 1580 */ 1581 if (thflags & TH_SYN && 1582 tp->t_state == TCPS_TIME_WAIT && 1583 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1584 tp = tcp_close(tp); 1585 goto findpcb; 1586 } 1587 /* 1588 * If window is closed can only take segments at 1589 * window edge, and have to drop data and PUSH from 1590 * incoming segments. Continue processing, but 1591 * remember to ack. Otherwise, drop segment 1592 * and ack. 1593 */ 1594 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1595 tp->t_flags |= TF_ACKNOW; 1596 tcpstat.tcps_rcvwinprobe++; 1597 } else 1598 goto dropafterack; 1599 } else 1600 tcpstat.tcps_rcvbyteafterwin += todrop; 1601 m_adj(m, -todrop); 1602 tlen -= todrop; 1603 thflags &= ~(TH_PUSH|TH_FIN); 1604 } 1605 1606 /* 1607 * If last ACK falls within this segment's sequence numbers, 1608 * record its timestamp. 1609 * NOTE that the test is modified according to the latest 1610 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1611 */ 1612 if ((to.to_flags & TOF_TS) != 0 && 1613 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1614 tp->ts_recent_age = ticks; 1615 tp->ts_recent = to.to_tsval; 1616 } 1617 1618 /* 1619 * If a SYN is in the window, then this is an 1620 * error and we send an RST and drop the connection. 1621 */ 1622 if (thflags & TH_SYN) { 1623 tp = tcp_drop(tp, ECONNRESET); 1624 rstreason = BANDLIM_UNLIMITED; 1625 goto dropwithreset; 1626 } 1627 1628 /* 1629 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1630 * flag is on (half-synchronized state), then queue data for 1631 * later processing; else drop segment and return. 1632 */ 1633 if ((thflags & TH_ACK) == 0) { 1634 if (tp->t_state == TCPS_SYN_RECEIVED || 1635 (tp->t_flags & TF_NEEDSYN)) 1636 goto step6; 1637 else 1638 goto drop; 1639 } 1640 1641 /* 1642 * Ack processing. 1643 */ 1644 switch (tp->t_state) { 1645 1646 /* 1647 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1648 * ESTABLISHED state and continue processing. 1649 * The ACK was checked above. 1650 */ 1651 case TCPS_SYN_RECEIVED: 1652 1653 tcpstat.tcps_connects++; 1654 soisconnected(so); 1655 /* Do window scaling? */ 1656 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1657 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1658 tp->snd_scale = tp->requested_s_scale; 1659 tp->rcv_scale = tp->request_r_scale; 1660 } 1661 /* 1662 * Upon successful completion of 3-way handshake, 1663 * update cache.CC if it was undefined, pass any queued 1664 * data to the user, and advance state appropriately. 1665 */ 1666 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1667 taop->tao_cc == 0) 1668 taop->tao_cc = tp->cc_recv; 1669 1670 /* 1671 * Make transitions: 1672 * SYN-RECEIVED -> ESTABLISHED 1673 * SYN-RECEIVED* -> FIN-WAIT-1 1674 */ 1675 tp->t_starttime = ticks; 1676 if (tp->t_flags & TF_NEEDFIN) { 1677 tp->t_state = TCPS_FIN_WAIT_1; 1678 tp->t_flags &= ~TF_NEEDFIN; 1679 } else { 1680 tp->t_state = TCPS_ESTABLISHED; 1681 callout_reset(tp->tt_keep, tcp_keepidle, 1682 tcp_timer_keep, tp); 1683 } 1684 /* 1685 * If segment contains data or ACK, will call tcp_reass() 1686 * later; if not, do so now to pass queued data to user. 1687 */ 1688 if (tlen == 0 && (thflags & TH_FIN) == 0) 1689 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1690 (struct mbuf *)0); 1691 tp->snd_wl1 = th->th_seq - 1; 1692 /* fall into ... */ 1693 1694 /* 1695 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1696 * ACKs. If the ack is in the range 1697 * tp->snd_una < th->th_ack <= tp->snd_max 1698 * then advance tp->snd_una to th->th_ack and drop 1699 * data from the retransmission queue. If this ACK reflects 1700 * more up to date window information we update our window information. 1701 */ 1702 case TCPS_ESTABLISHED: 1703 case TCPS_FIN_WAIT_1: 1704 case TCPS_FIN_WAIT_2: 1705 case TCPS_CLOSE_WAIT: 1706 case TCPS_CLOSING: 1707 case TCPS_LAST_ACK: 1708 case TCPS_TIME_WAIT: 1709 1710 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1711 if (tlen == 0 && tiwin == tp->snd_wnd) { 1712 tcpstat.tcps_rcvdupack++; 1713 /* 1714 * If we have outstanding data (other than 1715 * a window probe), this is a completely 1716 * duplicate ack (ie, window info didn't 1717 * change), the ack is the biggest we've 1718 * seen and we've seen exactly our rexmt 1719 * threshhold of them, assume a packet 1720 * has been dropped and retransmit it. 1721 * Kludge snd_nxt & the congestion 1722 * window so we send only this one 1723 * packet. 1724 * 1725 * We know we're losing at the current 1726 * window size so do congestion avoidance 1727 * (set ssthresh to half the current window 1728 * and pull our congestion window back to 1729 * the new ssthresh). 1730 * 1731 * Dup acks mean that packets have left the 1732 * network (they're now cached at the receiver) 1733 * so bump cwnd by the amount in the receiver 1734 * to keep a constant cwnd packets in the 1735 * network. 1736 */ 1737 if (!callout_active(tp->tt_rexmt) || 1738 th->th_ack != tp->snd_una) 1739 tp->t_dupacks = 0; 1740 else if (++tp->t_dupacks > tcprexmtthresh || 1741 (tcp_do_newreno && 1742 IN_FASTRECOVERY(tp))) { 1743 tp->snd_cwnd += tp->t_maxseg; 1744 (void) tcp_output(tp); 1745 goto drop; 1746 } else if (tp->t_dupacks == tcprexmtthresh) { 1747 tcp_seq onxt; 1748 u_int win; 1749 1750 if (tcp_do_newreno && 1751 SEQ_LEQ(th->th_ack, 1752 tp->snd_recover)) { 1753 tp->t_dupacks = 0; 1754 break; 1755 } 1756 fastretransmit: 1757 if (tcp_do_eifel_detect && 1758 (tp->t_flags & TF_RCVD_TSTMP)) { 1759 tcp_save_congestion_state(tp); 1760 tp->t_flags |= TF_FASTREXMT; 1761 } 1762 win = min(tp->snd_wnd, tp->snd_cwnd) / 1763 2 / tp->t_maxseg; 1764 if (win < 2) 1765 win = 2; 1766 tp->snd_ssthresh = win * tp->t_maxseg; 1767 ENTER_FASTRECOVERY(tp); 1768 tp->snd_recover = tp->snd_max; 1769 callout_stop(tp->tt_rexmt); 1770 tp->t_rtttime = 0; 1771 onxt = tp->snd_nxt; 1772 tp->snd_nxt = th->th_ack; 1773 tp->snd_cwnd = tp->t_maxseg; 1774 (void) tcp_output(tp); 1775 ++tcpstat.tcps_sndfastrexmit; 1776 KASSERT(tp->snd_limited <= 2, 1777 ("tp->snd_limited too big")); 1778 tp->snd_cwnd = tp->snd_ssthresh + 1779 (tp->t_maxseg * 1780 (tp->t_dupacks - tp->snd_limited)); 1781 if (SEQ_GT(onxt, tp->snd_nxt)) 1782 tp->snd_nxt = onxt; 1783 goto drop; 1784 } else if (tcp_do_limitedtransmit) { 1785 u_long oldcwnd = tp->snd_cwnd; 1786 tcp_seq oldsndmax = tp->snd_max; 1787 /* outstanding data */ 1788 uint32_t ownd = 1789 tp->snd_max - tp->snd_una; 1790 u_int sent; 1791 1792 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1793 1794 KASSERT(tp->t_dupacks == 1 || 1795 tp->t_dupacks == 2, 1796 ("dupacks not 1 or 2")); 1797 if (tp->t_dupacks == 1) 1798 tp->snd_limited = 0; 1799 tp->snd_cwnd = ownd + 1800 (tp->t_dupacks - tp->snd_limited) * 1801 tp->t_maxseg; 1802 (void) tcp_output(tp); 1803 tp->snd_cwnd = oldcwnd; 1804 sent = tp->snd_max - oldsndmax; 1805 if (sent > tp->t_maxseg) { 1806 KASSERT((tp->t_dupacks == 2 && 1807 tp->snd_limited == 0) || 1808 (sent == tp->t_maxseg + 1 && 1809 tp->t_flags & TF_SENTFIN), 1810 ("sent too much")); 1811 KASSERT(sent <= 1812 tp->t_maxseg * 2, 1813 ("sent too many segments")); 1814 tp->snd_limited = 2; 1815 tcpstat.tcps_sndlimited += 2; 1816 } else if (sent > 0) { 1817 ++tp->snd_limited; 1818 ++tcpstat.tcps_sndlimited; 1819 } else if (tcp_do_early_retransmit && 1820 (tcp_do_eifel_detect && 1821 (tp->t_flags & TF_RCVD_TSTMP)) && 1822 tcp_do_newreno && 1823 tp->t_dupacks + 1 >= 1824 iceildiv(ownd, tp->t_maxseg)) { 1825 ++tcpstat.tcps_sndearlyrexmit; 1826 tp->t_flags |= TF_EARLYREXMT; 1827 goto fastretransmit; 1828 } 1829 goto drop; 1830 } 1831 } else 1832 tp->t_dupacks = 0; 1833 break; 1834 } 1835 1836 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1837 1838 /* 1839 * If the congestion window was inflated to account 1840 * for the other side's cached packets, retract it. 1841 */ 1842 if (tcp_do_newreno) { 1843 if (IN_FASTRECOVERY(tp)) { 1844 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1845 tcp_newreno_partial_ack(tp, th); 1846 } else { 1847 /* 1848 * Window inflation should have left us 1849 * with approximately snd_ssthresh 1850 * outstanding data. 1851 * But in case we would be inclined to 1852 * send a burst, better to do it via 1853 * the slow start mechanism. 1854 */ 1855 if (SEQ_GT(th->th_ack + 1856 tp->snd_ssthresh, 1857 tp->snd_max)) 1858 tp->snd_cwnd = tp->snd_max - 1859 th->th_ack + 1860 tp->t_maxseg; 1861 else 1862 tp->snd_cwnd = tp->snd_ssthresh; 1863 } 1864 } 1865 } else { 1866 if (tp->t_dupacks >= tcprexmtthresh && 1867 tp->snd_cwnd > tp->snd_ssthresh) 1868 tp->snd_cwnd = tp->snd_ssthresh; 1869 } 1870 tp->t_dupacks = 0; 1871 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1872 tcpstat.tcps_rcvacktoomuch++; 1873 goto dropafterack; 1874 } 1875 /* 1876 * If we reach this point, ACK is not a duplicate, 1877 * i.e., it ACKs something we sent. 1878 */ 1879 if (tp->t_flags & TF_NEEDSYN) { 1880 /* 1881 * T/TCP: Connection was half-synchronized, and our 1882 * SYN has been ACK'd (so connection is now fully 1883 * synchronized). Go to non-starred state, 1884 * increment snd_una for ACK of SYN, and check if 1885 * we can do window scaling. 1886 */ 1887 tp->t_flags &= ~TF_NEEDSYN; 1888 tp->snd_una++; 1889 /* Do window scaling? */ 1890 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1891 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1892 tp->snd_scale = tp->requested_s_scale; 1893 tp->rcv_scale = tp->request_r_scale; 1894 } 1895 } 1896 1897 process_ACK: 1898 acked = th->th_ack - tp->snd_una; 1899 tcpstat.tcps_rcvackpack++; 1900 tcpstat.tcps_rcvackbyte += acked; 1901 1902 /* 1903 * If we just performed our first retransmit, and the ACK 1904 * arrives within our recovery window, then it was a mistake 1905 * to do the retransmit in the first place. Recover our 1906 * original cwnd and ssthresh, and proceed to transmit where 1907 * we left off. 1908 */ 1909 if (tcp_do_eifel_detect && acked && 1910 (to.to_flags & TOF_TS) && to.to_tsecr && 1911 (tp->t_flags & TF_FIRSTACCACK)) { 1912 /* Eifel detection applicable. */ 1913 if (to.to_tsecr < tp->t_rexmtTS) { 1914 ++tcpstat.tcps_eifeldetected; 1915 tcp_revert_congestion_state(tp); 1916 if (tp->t_rxtshift == 1 && 1917 ticks >= tp->t_badrxtwin) 1918 ++tcpstat.tcps_rttcantdetect; 1919 } 1920 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1921 tcp_revert_congestion_state(tp); 1922 ++tcpstat.tcps_rttdetected; 1923 } 1924 1925 /* 1926 * If we have a timestamp reply, update smoothed 1927 * round trip time. If no timestamp is present but 1928 * transmit timer is running and timed sequence 1929 * number was acked, update smoothed round trip time. 1930 * Since we now have an rtt measurement, cancel the 1931 * timer backoff (cf., Phil Karn's retransmit alg.). 1932 * Recompute the initial retransmit timer. 1933 * 1934 * Some machines (certain windows boxes) send broken 1935 * timestamp replies during the SYN+ACK phase, ignore 1936 * timestamps of 0. 1937 */ 1938 if ((to.to_flags & TOF_TS) != 0 && 1939 to.to_tsecr) { 1940 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1941 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 1942 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1943 } 1944 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1945 1946 /* 1947 * If all outstanding data is acked, stop retransmit 1948 * timer and remember to restart (more output or persist). 1949 * If there is more data to be acked, restart retransmit 1950 * timer, using current (possibly backed-off) value. 1951 */ 1952 if (th->th_ack == tp->snd_max) { 1953 callout_stop(tp->tt_rexmt); 1954 needoutput = 1; 1955 } else if (!callout_active(tp->tt_persist)) 1956 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1957 tcp_timer_rexmt, tp); 1958 1959 /* 1960 * If no data (only SYN) was ACK'd, 1961 * skip rest of ACK processing. 1962 */ 1963 if (acked == 0) 1964 goto step6; 1965 1966 /* Stop looking for an acceptable ACK since one was received. */ 1967 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 1968 1969 /* 1970 * When new data is acked, open the congestion window. 1971 * If the window gives us less than ssthresh packets 1972 * in flight, open exponentially (maxseg per packet). 1973 * Otherwise open linearly: maxseg per window 1974 * (maxseg^2 / cwnd per packet). 1975 */ 1976 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) { 1977 u_int cw = tp->snd_cwnd; 1978 u_int incr = tp->t_maxseg; 1979 if (cw > tp->snd_ssthresh) 1980 incr = incr * incr / cw; 1981 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 1982 } 1983 if (acked > so->so_snd.sb_cc) { 1984 tp->snd_wnd -= so->so_snd.sb_cc; 1985 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1986 ourfinisacked = 1; 1987 } else { 1988 sbdrop(&so->so_snd, acked); 1989 tp->snd_wnd -= acked; 1990 ourfinisacked = 0; 1991 } 1992 sowwakeup(so); 1993 /* detect una wraparound */ 1994 if (tcp_do_newreno && !IN_FASTRECOVERY(tp) && 1995 SEQ_GT(tp->snd_una, tp->snd_recover) && 1996 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1997 tp->snd_recover = th->th_ack - 1; 1998 if (tcp_do_newreno && IN_FASTRECOVERY(tp) && 1999 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2000 EXIT_FASTRECOVERY(tp); 2001 tp->snd_una = th->th_ack; 2002 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2003 tp->snd_nxt = tp->snd_una; 2004 2005 switch (tp->t_state) { 2006 2007 /* 2008 * In FIN_WAIT_1 STATE in addition to the processing 2009 * for the ESTABLISHED state if our FIN is now acknowledged 2010 * then enter FIN_WAIT_2. 2011 */ 2012 case TCPS_FIN_WAIT_1: 2013 if (ourfinisacked) { 2014 /* 2015 * If we can't receive any more 2016 * data, then closing user can proceed. 2017 * Starting the timer is contrary to the 2018 * specification, but if we don't get a FIN 2019 * we'll hang forever. 2020 */ 2021 if (so->so_state & SS_CANTRCVMORE) { 2022 soisdisconnected(so); 2023 callout_reset(tp->tt_2msl, tcp_maxidle, 2024 tcp_timer_2msl, tp); 2025 } 2026 tp->t_state = TCPS_FIN_WAIT_2; 2027 } 2028 break; 2029 2030 /* 2031 * In CLOSING STATE in addition to the processing for 2032 * the ESTABLISHED state if the ACK acknowledges our FIN 2033 * then enter the TIME-WAIT state, otherwise ignore 2034 * the segment. 2035 */ 2036 case TCPS_CLOSING: 2037 if (ourfinisacked) { 2038 tp->t_state = TCPS_TIME_WAIT; 2039 tcp_canceltimers(tp); 2040 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2041 if (tp->cc_recv != 0 && 2042 (ticks - tp->t_starttime) < tcp_msl) 2043 callout_reset(tp->tt_2msl, 2044 tp->t_rxtcur * 2045 TCPTV_TWTRUNC, 2046 tcp_timer_2msl, tp); 2047 else 2048 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2049 tcp_timer_2msl, tp); 2050 soisdisconnected(so); 2051 } 2052 break; 2053 2054 /* 2055 * In LAST_ACK, we may still be waiting for data to drain 2056 * and/or to be acked, as well as for the ack of our FIN. 2057 * If our FIN is now acknowledged, delete the TCB, 2058 * enter the closed state and return. 2059 */ 2060 case TCPS_LAST_ACK: 2061 if (ourfinisacked) { 2062 tp = tcp_close(tp); 2063 goto drop; 2064 } 2065 break; 2066 2067 /* 2068 * In TIME_WAIT state the only thing that should arrive 2069 * is a retransmission of the remote FIN. Acknowledge 2070 * it and restart the finack timer. 2071 */ 2072 case TCPS_TIME_WAIT: 2073 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2074 tcp_timer_2msl, tp); 2075 goto dropafterack; 2076 } 2077 } 2078 2079 step6: 2080 /* 2081 * Update window information. 2082 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2083 */ 2084 if ((thflags & TH_ACK) && 2085 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2086 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2087 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2088 /* keep track of pure window updates */ 2089 if (tlen == 0 && 2090 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2091 tcpstat.tcps_rcvwinupd++; 2092 tp->snd_wnd = tiwin; 2093 tp->snd_wl1 = th->th_seq; 2094 tp->snd_wl2 = th->th_ack; 2095 if (tp->snd_wnd > tp->max_sndwnd) 2096 tp->max_sndwnd = tp->snd_wnd; 2097 needoutput = 1; 2098 } 2099 2100 /* 2101 * Process segments with URG. 2102 */ 2103 if ((thflags & TH_URG) && th->th_urp && 2104 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2105 /* 2106 * This is a kludge, but if we receive and accept 2107 * random urgent pointers, we'll crash in 2108 * soreceive. It's hard to imagine someone 2109 * actually wanting to send this much urgent data. 2110 */ 2111 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2112 th->th_urp = 0; /* XXX */ 2113 thflags &= ~TH_URG; /* XXX */ 2114 goto dodata; /* XXX */ 2115 } 2116 /* 2117 * If this segment advances the known urgent pointer, 2118 * then mark the data stream. This should not happen 2119 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2120 * a FIN has been received from the remote side. 2121 * In these states we ignore the URG. 2122 * 2123 * According to RFC961 (Assigned Protocols), 2124 * the urgent pointer points to the last octet 2125 * of urgent data. We continue, however, 2126 * to consider it to indicate the first octet 2127 * of data past the urgent section as the original 2128 * spec states (in one of two places). 2129 */ 2130 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2131 tp->rcv_up = th->th_seq + th->th_urp; 2132 so->so_oobmark = so->so_rcv.sb_cc + 2133 (tp->rcv_up - tp->rcv_nxt) - 1; 2134 if (so->so_oobmark == 0) 2135 so->so_state |= SS_RCVATMARK; 2136 sohasoutofband(so); 2137 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2138 } 2139 /* 2140 * Remove out of band data so doesn't get presented to user. 2141 * This can happen independent of advancing the URG pointer, 2142 * but if two URG's are pending at once, some out-of-band 2143 * data may creep in... ick. 2144 */ 2145 if (th->th_urp <= (u_long)tlen 2146 #ifdef SO_OOBINLINE 2147 && (so->so_options & SO_OOBINLINE) == 0 2148 #endif 2149 ) 2150 tcp_pulloutofband(so, th, m, 2151 drop_hdrlen); /* hdr drop is delayed */ 2152 } else { 2153 /* 2154 * If no out of band data is expected, 2155 * pull receive urgent pointer along 2156 * with the receive window. 2157 */ 2158 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2159 tp->rcv_up = tp->rcv_nxt; 2160 } 2161 dodata: /* XXX */ 2162 2163 /* 2164 * Process the segment text, merging it into the TCP sequencing queue, 2165 * and arranging for acknowledgment of receipt if necessary. 2166 * This process logically involves adjusting tp->rcv_wnd as data 2167 * is presented to the user (this happens in tcp_usrreq.c, 2168 * case PRU_RCVD). If a FIN has already been received on this 2169 * connection then we just ignore the text. 2170 */ 2171 if ((tlen || (thflags & TH_FIN)) && 2172 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2173 m_adj(m, drop_hdrlen); /* delayed header drop */ 2174 /* 2175 * Insert segment which includes th into TCP reassembly queue 2176 * with control block tp. Set thflags to whether reassembly now 2177 * includes a segment with FIN. This handles the common case 2178 * inline (segment is the next to be received on an established 2179 * connection, and the queue is empty), avoiding linkage into 2180 * and removal from the queue and repetition of various 2181 * conversions. 2182 * Set DELACK for segments received in order, but ack 2183 * immediately when segments are out of order (so 2184 * fast retransmit can work). 2185 */ 2186 if (th->th_seq == tp->rcv_nxt && 2187 LIST_EMPTY(&tp->t_segq) && 2188 TCPS_HAVEESTABLISHED(tp->t_state)) { 2189 if (DELAY_ACK(tp)) 2190 callout_reset(tp->tt_delack, tcp_delacktime, 2191 tcp_timer_delack, tp); 2192 else 2193 tp->t_flags |= TF_ACKNOW; 2194 tp->rcv_nxt += tlen; 2195 thflags = th->th_flags & TH_FIN; 2196 tcpstat.tcps_rcvpack++; 2197 tcpstat.tcps_rcvbyte += tlen; 2198 ND6_HINT(tp); 2199 if (so->so_state & SS_CANTRCVMORE) 2200 m_freem(m); 2201 else 2202 sbappend(&so->so_rcv, m); 2203 sorwakeup(so); 2204 } else { 2205 thflags = tcp_reass(tp, th, &tlen, m); 2206 tp->t_flags |= TF_ACKNOW; 2207 } 2208 2209 /* 2210 * Note the amount of data that peer has sent into 2211 * our window, in order to estimate the sender's 2212 * buffer size. 2213 */ 2214 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2215 } else { 2216 m_freem(m); 2217 thflags &= ~TH_FIN; 2218 } 2219 2220 /* 2221 * If FIN is received ACK the FIN and let the user know 2222 * that the connection is closing. 2223 */ 2224 if (thflags & TH_FIN) { 2225 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2226 socantrcvmore(so); 2227 /* 2228 * If connection is half-synchronized 2229 * (ie NEEDSYN flag on) then delay ACK, 2230 * so it may be piggybacked when SYN is sent. 2231 * Otherwise, since we received a FIN then no 2232 * more input can be expected, send ACK now. 2233 */ 2234 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2235 callout_reset(tp->tt_delack, tcp_delacktime, 2236 tcp_timer_delack, tp); 2237 else 2238 tp->t_flags |= TF_ACKNOW; 2239 tp->rcv_nxt++; 2240 } 2241 switch (tp->t_state) { 2242 2243 /* 2244 * In SYN_RECEIVED and ESTABLISHED STATES 2245 * enter the CLOSE_WAIT state. 2246 */ 2247 case TCPS_SYN_RECEIVED: 2248 tp->t_starttime = ticks; 2249 /*FALLTHROUGH*/ 2250 case TCPS_ESTABLISHED: 2251 tp->t_state = TCPS_CLOSE_WAIT; 2252 break; 2253 2254 /* 2255 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2256 * enter the CLOSING state. 2257 */ 2258 case TCPS_FIN_WAIT_1: 2259 tp->t_state = TCPS_CLOSING; 2260 break; 2261 2262 /* 2263 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2264 * starting the time-wait timer, turning off the other 2265 * standard timers. 2266 */ 2267 case TCPS_FIN_WAIT_2: 2268 tp->t_state = TCPS_TIME_WAIT; 2269 tcp_canceltimers(tp); 2270 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2271 if (tp->cc_recv != 0 && 2272 (ticks - tp->t_starttime) < tcp_msl) { 2273 callout_reset(tp->tt_2msl, 2274 tp->t_rxtcur * TCPTV_TWTRUNC, 2275 tcp_timer_2msl, tp); 2276 /* For transaction client, force ACK now. */ 2277 tp->t_flags |= TF_ACKNOW; 2278 } 2279 else 2280 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2281 tcp_timer_2msl, tp); 2282 soisdisconnected(so); 2283 break; 2284 2285 /* 2286 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2287 */ 2288 case TCPS_TIME_WAIT: 2289 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2290 tcp_timer_2msl, tp); 2291 break; 2292 } 2293 } 2294 #ifdef TCPDEBUG 2295 if (so->so_options & SO_DEBUG) 2296 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2297 &tcp_savetcp, 0); 2298 #endif 2299 2300 /* 2301 * Return any desired output. 2302 */ 2303 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2304 (void) tcp_output(tp); 2305 return; 2306 2307 dropafterack: 2308 /* 2309 * Generate an ACK dropping incoming segment if it occupies 2310 * sequence space, where the ACK reflects our state. 2311 * 2312 * We can now skip the test for the RST flag since all 2313 * paths to this code happen after packets containing 2314 * RST have been dropped. 2315 * 2316 * In the SYN-RECEIVED state, don't send an ACK unless the 2317 * segment we received passes the SYN-RECEIVED ACK test. 2318 * If it fails send a RST. This breaks the loop in the 2319 * "LAND" DoS attack, and also prevents an ACK storm 2320 * between two listening ports that have been sent forged 2321 * SYN segments, each with the source address of the other. 2322 */ 2323 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2324 (SEQ_GT(tp->snd_una, th->th_ack) || 2325 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2326 rstreason = BANDLIM_RST_OPENPORT; 2327 goto dropwithreset; 2328 } 2329 #ifdef TCPDEBUG 2330 if (so->so_options & SO_DEBUG) 2331 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2332 &tcp_savetcp, 0); 2333 #endif 2334 m_freem(m); 2335 tp->t_flags |= TF_ACKNOW; 2336 (void) tcp_output(tp); 2337 return; 2338 2339 dropwithreset: 2340 /* 2341 * Generate a RST, dropping incoming segment. 2342 * Make ACK acceptable to originator of segment. 2343 * Don't bother to respond if destination was broadcast/multicast. 2344 */ 2345 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2346 goto drop; 2347 if (isipv6) { 2348 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2349 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2350 goto drop; 2351 } else { 2352 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2353 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2354 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2355 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2356 goto drop; 2357 } 2358 /* IPv6 anycast check is done at tcp6_input() */ 2359 2360 /* 2361 * Perform bandwidth limiting. 2362 */ 2363 #ifdef ICMP_BANDLIM 2364 if (badport_bandlim(rstreason) < 0) 2365 goto drop; 2366 #endif 2367 2368 #ifdef TCPDEBUG 2369 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2370 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2371 &tcp_savetcp, 0); 2372 #endif 2373 if (thflags & TH_ACK) 2374 /* mtod() below is safe as long as hdr dropping is delayed */ 2375 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2376 TH_RST); 2377 else { 2378 if (thflags & TH_SYN) 2379 tlen++; 2380 /* mtod() below is safe as long as hdr dropping is delayed */ 2381 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2382 (tcp_seq)0, TH_RST|TH_ACK); 2383 } 2384 return; 2385 2386 drop: 2387 /* 2388 * Drop space held by incoming segment and return. 2389 */ 2390 #ifdef TCPDEBUG 2391 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2392 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2393 &tcp_savetcp, 0); 2394 #endif 2395 m_freem(m); 2396 return; 2397 } 2398 2399 /* 2400 * Parse TCP options and place in tcpopt. 2401 */ 2402 static void 2403 tcp_dooptions(to, cp, cnt, is_syn) 2404 struct tcpopt *to; 2405 u_char *cp; 2406 int cnt; 2407 { 2408 int opt, optlen; 2409 2410 to->to_flags = 0; 2411 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2412 opt = cp[0]; 2413 if (opt == TCPOPT_EOL) 2414 break; 2415 if (opt == TCPOPT_NOP) 2416 optlen = 1; 2417 else { 2418 if (cnt < 2) 2419 break; 2420 optlen = cp[1]; 2421 if (optlen < 2 || optlen > cnt) 2422 break; 2423 } 2424 switch (opt) { 2425 case TCPOPT_MAXSEG: 2426 if (optlen != TCPOLEN_MAXSEG) 2427 continue; 2428 if (!is_syn) 2429 continue; 2430 to->to_flags |= TOF_MSS; 2431 bcopy((char *)cp + 2, 2432 (char *)&to->to_mss, sizeof(to->to_mss)); 2433 to->to_mss = ntohs(to->to_mss); 2434 break; 2435 case TCPOPT_WINDOW: 2436 if (optlen != TCPOLEN_WINDOW) 2437 continue; 2438 if (! is_syn) 2439 continue; 2440 to->to_flags |= TOF_SCALE; 2441 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2442 break; 2443 case TCPOPT_TIMESTAMP: 2444 if (optlen != TCPOLEN_TIMESTAMP) 2445 continue; 2446 to->to_flags |= TOF_TS; 2447 bcopy((char *)cp + 2, 2448 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2449 to->to_tsval = ntohl(to->to_tsval); 2450 bcopy((char *)cp + 6, 2451 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2452 to->to_tsecr = ntohl(to->to_tsecr); 2453 break; 2454 case TCPOPT_CC: 2455 if (optlen != TCPOLEN_CC) 2456 continue; 2457 to->to_flags |= TOF_CC; 2458 bcopy((char *)cp + 2, 2459 (char *)&to->to_cc, sizeof(to->to_cc)); 2460 to->to_cc = ntohl(to->to_cc); 2461 break; 2462 case TCPOPT_CCNEW: 2463 if (optlen != TCPOLEN_CC) 2464 continue; 2465 if (!is_syn) 2466 continue; 2467 to->to_flags |= TOF_CCNEW; 2468 bcopy((char *)cp + 2, 2469 (char *)&to->to_cc, sizeof(to->to_cc)); 2470 to->to_cc = ntohl(to->to_cc); 2471 break; 2472 case TCPOPT_CCECHO: 2473 if (optlen != TCPOLEN_CC) 2474 continue; 2475 if (!is_syn) 2476 continue; 2477 to->to_flags |= TOF_CCECHO; 2478 bcopy((char *)cp + 2, 2479 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2480 to->to_ccecho = ntohl(to->to_ccecho); 2481 break; 2482 default: 2483 continue; 2484 } 2485 } 2486 } 2487 2488 /* 2489 * Pull out of band byte out of a segment so 2490 * it doesn't appear in the user's data queue. 2491 * It is still reflected in the segment length for 2492 * sequencing purposes. 2493 */ 2494 static void 2495 tcp_pulloutofband(so, th, m, off) 2496 struct socket *so; 2497 struct tcphdr *th; 2498 struct mbuf *m; 2499 int off; /* delayed to be droped hdrlen */ 2500 { 2501 int cnt = off + th->th_urp - 1; 2502 2503 while (cnt >= 0) { 2504 if (m->m_len > cnt) { 2505 char *cp = mtod(m, caddr_t) + cnt; 2506 struct tcpcb *tp = sototcpcb(so); 2507 2508 tp->t_iobc = *cp; 2509 tp->t_oobflags |= TCPOOB_HAVEDATA; 2510 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2511 m->m_len--; 2512 if (m->m_flags & M_PKTHDR) 2513 m->m_pkthdr.len--; 2514 return; 2515 } 2516 cnt -= m->m_len; 2517 m = m->m_next; 2518 if (m == 0) 2519 break; 2520 } 2521 panic("tcp_pulloutofband"); 2522 } 2523 2524 /* 2525 * Collect new round-trip time estimate 2526 * and update averages and current timeout. 2527 */ 2528 static void 2529 tcp_xmit_timer(tp, rtt) 2530 struct tcpcb *tp; 2531 int rtt; 2532 { 2533 int delta; 2534 2535 tcpstat.tcps_rttupdated++; 2536 tp->t_rttupdated++; 2537 if (tp->t_srtt != 0) { 2538 /* 2539 * srtt is stored as fixed point with 5 bits after the 2540 * binary point (i.e., scaled by 8). The following magic 2541 * is equivalent to the smoothing algorithm in rfc793 with 2542 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2543 * point). Adjust rtt to origin 0. 2544 */ 2545 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2546 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2547 2548 if ((tp->t_srtt += delta) <= 0) 2549 tp->t_srtt = 1; 2550 2551 /* 2552 * We accumulate a smoothed rtt variance (actually, a 2553 * smoothed mean difference), then set the retransmit 2554 * timer to smoothed rtt + 4 times the smoothed variance. 2555 * rttvar is stored as fixed point with 4 bits after the 2556 * binary point (scaled by 16). The following is 2557 * equivalent to rfc793 smoothing with an alpha of .75 2558 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2559 * rfc793's wired-in beta. 2560 */ 2561 if (delta < 0) 2562 delta = -delta; 2563 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2564 if ((tp->t_rttvar += delta) <= 0) 2565 tp->t_rttvar = 1; 2566 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2567 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2568 } else { 2569 /* 2570 * No rtt measurement yet - use the unsmoothed rtt. 2571 * Set the variance to half the rtt (so our first 2572 * retransmit happens at 3*rtt). 2573 */ 2574 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2575 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2576 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2577 } 2578 tp->t_rtttime = 0; 2579 tp->t_rxtshift = 0; 2580 2581 /* 2582 * the retransmit should happen at rtt + 4 * rttvar. 2583 * Because of the way we do the smoothing, srtt and rttvar 2584 * will each average +1/2 tick of bias. When we compute 2585 * the retransmit timer, we want 1/2 tick of rounding and 2586 * 1 extra tick because of +-1/2 tick uncertainty in the 2587 * firing of the timer. The bias will give us exactly the 2588 * 1.5 tick we need. But, because the bias is 2589 * statistical, we have to test that we don't drop below 2590 * the minimum feasible timer (which is 2 ticks). 2591 */ 2592 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2593 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2594 2595 /* 2596 * We received an ack for a packet that wasn't retransmitted; 2597 * it is probably safe to discard any error indications we've 2598 * received recently. This isn't quite right, but close enough 2599 * for now (a route might have failed after we sent a segment, 2600 * and the return path might not be symmetrical). 2601 */ 2602 tp->t_softerror = 0; 2603 } 2604 2605 /* 2606 * Determine a reasonable value for maxseg size. 2607 * If the route is known, check route for mtu. 2608 * If none, use an mss that can be handled on the outgoing 2609 * interface without forcing IP to fragment; if bigger than 2610 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2611 * to utilize large mbufs. If no route is found, route has no mtu, 2612 * or the destination isn't local, use a default, hopefully conservative 2613 * size (usually 512 or the default IP max size, but no more than the mtu 2614 * of the interface), as we can't discover anything about intervening 2615 * gateways or networks. We also initialize the congestion/slow start 2616 * window to be a single segment if the destination isn't local. 2617 * While looking at the routing entry, we also initialize other path-dependent 2618 * parameters from pre-set or cached values in the routing entry. 2619 * 2620 * Also take into account the space needed for options that we 2621 * send regularly. Make maxseg shorter by that amount to assure 2622 * that we can send maxseg amount of data even when the options 2623 * are present. Store the upper limit of the length of options plus 2624 * data in maxopd. 2625 * 2626 * NOTE that this routine is only called when we process an incoming 2627 * segment, for outgoing segments only tcp_mssopt is called. 2628 * 2629 * In case of T/TCP, we call this routine during implicit connection 2630 * setup as well (offer = -1), to initialize maxseg from the cached 2631 * MSS of our peer. 2632 */ 2633 void 2634 tcp_mss(tp, offer) 2635 struct tcpcb *tp; 2636 int offer; 2637 { 2638 struct rtentry *rt; 2639 struct ifnet *ifp; 2640 int rtt, mss; 2641 u_long bufsize; 2642 struct inpcb *inp = tp->t_inpcb; 2643 struct socket *so; 2644 struct rmxp_tao *taop; 2645 int origoffer = offer; 2646 #ifdef INET6 2647 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2648 size_t min_protoh = isipv6 ? 2649 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2650 sizeof(struct tcpiphdr); 2651 #else 2652 const int isipv6 = 0; 2653 const size_t min_protoh = sizeof(struct tcpiphdr); 2654 #endif 2655 2656 if (isipv6) 2657 rt = tcp_rtlookup6(&inp->inp_inc); 2658 else 2659 rt = tcp_rtlookup(&inp->inp_inc); 2660 if (rt == NULL) { 2661 tp->t_maxopd = tp->t_maxseg = 2662 isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2663 return; 2664 } 2665 ifp = rt->rt_ifp; 2666 so = inp->inp_socket; 2667 2668 taop = rmx_taop(rt->rt_rmx); 2669 /* 2670 * Offer == -1 means that we didn't receive SYN yet, 2671 * use cached value in that case; 2672 */ 2673 if (offer == -1) 2674 offer = taop->tao_mssopt; 2675 /* 2676 * Offer == 0 means that there was no MSS on the SYN segment, 2677 * in this case we use tcp_mssdflt. 2678 */ 2679 if (offer == 0) 2680 offer = isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2681 else 2682 /* 2683 * Sanity check: make sure that maxopd will be large 2684 * enough to allow some data on segments even is the 2685 * all the option space is used (40bytes). Otherwise 2686 * funny things may happen in tcp_output. 2687 */ 2688 offer = max(offer, 64); 2689 taop->tao_mssopt = offer; 2690 2691 /* 2692 * While we're here, check if there's an initial rtt 2693 * or rttvar. Convert from the route-table units 2694 * to scaled multiples of the slow timeout timer. 2695 */ 2696 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2697 /* 2698 * XXX the lock bit for RTT indicates that the value 2699 * is also a minimum value; this is subject to time. 2700 */ 2701 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2702 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2703 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2704 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2705 tcpstat.tcps_usedrtt++; 2706 if (rt->rt_rmx.rmx_rttvar) { 2707 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2708 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2709 tcpstat.tcps_usedrttvar++; 2710 } else { 2711 /* default variation is +- 1 rtt */ 2712 tp->t_rttvar = 2713 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2714 } 2715 TCPT_RANGESET(tp->t_rxtcur, 2716 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2717 tp->t_rttmin, TCPTV_REXMTMAX); 2718 } 2719 /* 2720 * if there's an mtu associated with the route, use it 2721 * else, use the link mtu. 2722 */ 2723 if (rt->rt_rmx.rmx_mtu) 2724 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2725 else { 2726 if (isipv6) { 2727 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2728 min_protoh; 2729 if (!in6_localaddr(&inp->in6p_faddr)) 2730 mss = min(mss, tcp_v6mssdflt); 2731 } else { 2732 mss = ifp->if_mtu - min_protoh; 2733 if (!in_localaddr(inp->inp_faddr)) 2734 mss = min(mss, tcp_mssdflt); 2735 } 2736 } 2737 mss = min(mss, offer); 2738 /* 2739 * maxopd stores the maximum length of data AND options 2740 * in a segment; maxseg is the amount of data in a normal 2741 * segment. We need to store this value (maxopd) apart 2742 * from maxseg, because now every segment carries options 2743 * and thus we normally have somewhat less data in segments. 2744 */ 2745 tp->t_maxopd = mss; 2746 2747 /* 2748 * In case of T/TCP, origoffer==-1 indicates, that no segments 2749 * were received yet. In this case we just guess, otherwise 2750 * we do the same as before T/TCP. 2751 */ 2752 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2753 (origoffer == -1 || 2754 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2755 mss -= TCPOLEN_TSTAMP_APPA; 2756 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2757 (origoffer == -1 || 2758 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2759 mss -= TCPOLEN_CC_APPA; 2760 2761 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2762 if (mss > MCLBYTES) 2763 mss &= ~(MCLBYTES-1); 2764 #else 2765 if (mss > MCLBYTES) 2766 mss = mss / MCLBYTES * MCLBYTES; 2767 #endif 2768 /* 2769 * If there's a pipesize, change the socket buffer 2770 * to that size. Make the socket buffers an integral 2771 * number of mss units; if the mss is larger than 2772 * the socket buffer, decrease the mss. 2773 */ 2774 #ifdef RTV_SPIPE 2775 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2776 #endif 2777 bufsize = so->so_snd.sb_hiwat; 2778 if (bufsize < mss) 2779 mss = bufsize; 2780 else { 2781 bufsize = roundup(bufsize, mss); 2782 if (bufsize > sb_max) 2783 bufsize = sb_max; 2784 if (bufsize > so->so_snd.sb_hiwat) 2785 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2786 } 2787 tp->t_maxseg = mss; 2788 2789 #ifdef RTV_RPIPE 2790 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2791 #endif 2792 bufsize = so->so_rcv.sb_hiwat; 2793 if (bufsize > mss) { 2794 bufsize = roundup(bufsize, mss); 2795 if (bufsize > sb_max) 2796 bufsize = sb_max; 2797 if (bufsize > so->so_rcv.sb_hiwat) 2798 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2799 } 2800 2801 /* 2802 * Set the slow-start flight size depending on whether this 2803 * is a local network or not. 2804 */ 2805 if (tcp_do_rfc3390) 2806 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 2807 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2808 (!isipv6 && in_localaddr(inp->inp_faddr))) 2809 tp->snd_cwnd = mss * ss_fltsz_local; 2810 else 2811 tp->snd_cwnd = mss * ss_fltsz; 2812 2813 if (rt->rt_rmx.rmx_ssthresh) { 2814 /* 2815 * There's some sort of gateway or interface 2816 * buffer limit on the path. Use this to set 2817 * the slow start threshhold, but set the 2818 * threshold to no less than 2*mss. 2819 */ 2820 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2821 tcpstat.tcps_usedssthresh++; 2822 } 2823 } 2824 2825 /* 2826 * Determine the MSS option to send on an outgoing SYN. 2827 */ 2828 int 2829 tcp_mssopt(tp) 2830 struct tcpcb *tp; 2831 { 2832 struct rtentry *rt; 2833 #ifdef INET6 2834 int isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2835 int min_protoh = isipv6 ? 2836 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2837 sizeof(struct tcpiphdr); 2838 #else 2839 const int isipv6 = 0; 2840 const size_t min_protoh = sizeof(struct tcpiphdr); 2841 #endif 2842 2843 if (isipv6) 2844 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 2845 else 2846 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 2847 if (rt == NULL) 2848 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2849 2850 return (rt->rt_ifp->if_mtu - min_protoh); 2851 } 2852 2853 2854 /* 2855 * When a partial ack arrives, force the retransmission of the 2856 * next unacknowledged segment. Do not clear tp->t_dupacks. 2857 * By setting snd_nxt to ti_ack, this forces retransmission timer to 2858 * be started again. 2859 */ 2860 static void 2861 tcp_newreno_partial_ack(tp, th) 2862 struct tcpcb *tp; 2863 struct tcphdr *th; 2864 { 2865 tcp_seq onxt = tp->snd_nxt; 2866 u_long ocwnd = tp->snd_cwnd; 2867 2868 callout_stop(tp->tt_rexmt); 2869 tp->t_rtttime = 0; 2870 tp->snd_nxt = th->th_ack; 2871 /* 2872 * Set snd_cwnd to one segment beyond acknowledged offset 2873 * (tp->snd_una has not yet been updated when this function is called.) 2874 */ 2875 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 2876 tp->t_flags |= TF_ACKNOW; 2877 (void) tcp_output(tp); 2878 tp->snd_cwnd = ocwnd; 2879 if (SEQ_GT(onxt, tp->snd_nxt)) 2880 tp->snd_nxt = onxt; 2881 /* 2882 * Partial window deflation. Relies on fact that tp->snd_una 2883 * not updated yet. 2884 */ 2885 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 2886 } 2887