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sys/netinet/tcp_input.c
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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: releng/5.2/sys/netinet/tcp_input.c 127031 2004-03-15 18:17:10Z fjoe $ 35 */ 36 37 #include "opt_ipfw.h" /* for ipfw_fwd */ 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_mac.h" 41 #include "opt_tcpdebug.h" 42 #include "opt_tcp_input.h" 43 44 #include <sys/param.h> 45 #include <sys/kernel.h> 46 #include <sys/mac.h> 47 #include <sys/malloc.h> 48 #include <sys/mbuf.h> 49 #include <sys/proc.h> /* for proc0 declaration */ 50 #include <sys/protosw.h> 51 #include <sys/signalvar.h> 52 #include <sys/socket.h> 53 #include <sys/socketvar.h> 54 #include <sys/sysctl.h> 55 #include <sys/syslog.h> 56 #include <sys/systm.h> 57 58 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 59 60 #include <vm/uma.h> 61 62 #include <net/if.h> 63 #include <net/route.h> 64 65 #include <netinet/in.h> 66 #include <netinet/in_pcb.h> 67 #include <netinet/in_systm.h> 68 #include <netinet/in_var.h> 69 #include <netinet/ip.h> 70 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 71 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 72 #include <netinet/ip_var.h> 73 #include <netinet/ip6.h> 74 #include <netinet/icmp6.h> 75 #include <netinet6/in6_pcb.h> 76 #include <netinet6/ip6_var.h> 77 #include <netinet6/nd6.h> 78 #include <netinet/tcp.h> 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_timer.h> 82 #include <netinet/tcp_var.h> 83 #include <netinet6/tcp6_var.h> 84 #include <netinet/tcpip.h> 85 #ifdef TCPDEBUG 86 #include <netinet/tcp_debug.h> 87 #endif /* TCPDEBUG */ 88 89 #ifdef FAST_IPSEC 90 #include <netipsec/ipsec.h> 91 #include <netipsec/ipsec6.h> 92 #endif /*FAST_IPSEC*/ 93 94 #ifdef IPSEC 95 #include <netinet6/ipsec.h> 96 #include <netinet6/ipsec6.h> 97 #include <netkey/key.h> 98 #endif /*IPSEC*/ 99 100 #include <machine/in_cksum.h> 101 102 static const int tcprexmtthresh = 3; 103 tcp_cc tcp_ccgen; 104 105 struct tcpstat tcpstat; 106 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 107 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 108 109 static int log_in_vain = 0; 110 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 111 &log_in_vain, 0, "Log all incoming TCP connections"); 112 113 static int blackhole = 0; 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 115 &blackhole, 0, "Do not send RST when dropping refused connections"); 116 117 int tcp_delack_enabled = 1; 118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 119 &tcp_delack_enabled, 0, 120 "Delay ACK to try and piggyback it onto a data packet"); 121 122 #ifdef TCP_DROP_SYNFIN 123 static int drop_synfin = 0; 124 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 125 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 126 #endif 127 128 static int tcp_do_rfc3042 = 0; 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 130 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 131 132 static int tcp_do_rfc3390 = 0; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 134 &tcp_do_rfc3390, 0, 135 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 136 137 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 138 "TCP Segment Reassembly Queue"); 139 140 static int tcp_reass_maxseg = 0; 141 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 142 &tcp_reass_maxseg, 0, 143 "Global maximum number of TCP Segments in Reassembly Queue"); 144 145 int tcp_reass_qsize = 0; 146 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 147 &tcp_reass_qsize, 0, 148 "Global number of TCP Segments currently in Reassembly Queue"); 149 150 static int tcp_reass_overflows = 0; 151 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 152 &tcp_reass_overflows, 0, 153 "Global number of TCP Segment Reassembly Queue Overflows"); 154 155 struct inpcbhead tcb; 156 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 157 struct inpcbinfo tcbinfo; 158 struct mtx *tcbinfo_mtx; 159 160 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 161 static void tcp_pulloutofband(struct socket *, 162 struct tcphdr *, struct mbuf *, int); 163 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 164 struct mbuf *); 165 static void tcp_xmit_timer(struct tcpcb *, int); 166 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 167 static int tcp_timewait(struct tcptw *, struct tcpopt *, 168 struct tcphdr *, struct mbuf *, int); 169 170 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 171 #ifdef INET6 172 #define ND6_HINT(tp) \ 173 do { \ 174 if ((tp) && (tp)->t_inpcb && \ 175 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 176 nd6_nud_hint(NULL, NULL, 0); \ 177 } while (0) 178 #else 179 #define ND6_HINT(tp) 180 #endif 181 182 /* 183 * Indicate whether this ack should be delayed. We can delay the ack if 184 * - there is no delayed ack timer in progress and 185 * - our last ack wasn't a 0-sized window. We never want to delay 186 * the ack that opens up a 0-sized window and 187 * - delayed acks are enabled or 188 * - this is a half-synchronized T/TCP connection. 189 */ 190 #define DELAY_ACK(tp) \ 191 ((!callout_active(tp->tt_delack) && \ 192 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 193 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 194 195 /* Initialize TCP reassembly queue */ 196 uma_zone_t tcp_reass_zone; 197 void 198 tcp_reass_init() 199 { 200 tcp_reass_maxseg = nmbclusters / 16; 201 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 202 &tcp_reass_maxseg); 203 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 204 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 205 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 206 } 207 208 static int 209 tcp_reass(tp, th, tlenp, m) 210 register struct tcpcb *tp; 211 register struct tcphdr *th; 212 int *tlenp; 213 struct mbuf *m; 214 { 215 struct tseg_qent *q; 216 struct tseg_qent *p = NULL; 217 struct tseg_qent *nq; 218 struct tseg_qent *te = NULL; 219 struct socket *so = tp->t_inpcb->inp_socket; 220 int flags; 221 222 /* 223 * Call with th==0 after become established to 224 * force pre-ESTABLISHED data up to user socket. 225 */ 226 if (th == 0) 227 goto present; 228 229 /* 230 * Limit the number of segments in the reassembly queue to prevent 231 * holding on to too many segments (and thus running out of mbufs). 232 * Make sure to let the missing segment through which caused this 233 * queue. Always keep one global queue entry spare to be able to 234 * process the missing segment. 235 */ 236 if (th->th_seq != tp->rcv_nxt && 237 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 238 tcp_reass_overflows++; 239 tcpstat.tcps_rcvmemdrop++; 240 m_freem(m); 241 return (0); 242 } 243 244 /* 245 * Allocate a new queue entry. If we can't, or hit the zone limit 246 * just drop the pkt. 247 */ 248 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 249 if (te == NULL) { 250 tcpstat.tcps_rcvmemdrop++; 251 m_freem(m); 252 return (0); 253 } 254 tcp_reass_qsize++; 255 256 /* 257 * Find a segment which begins after this one does. 258 */ 259 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 260 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 261 break; 262 p = q; 263 } 264 265 /* 266 * If there is a preceding segment, it may provide some of 267 * our data already. If so, drop the data from the incoming 268 * segment. If it provides all of our data, drop us. 269 */ 270 if (p != NULL) { 271 register int i; 272 /* conversion to int (in i) handles seq wraparound */ 273 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 274 if (i > 0) { 275 if (i >= *tlenp) { 276 tcpstat.tcps_rcvduppack++; 277 tcpstat.tcps_rcvdupbyte += *tlenp; 278 m_freem(m); 279 uma_zfree(tcp_reass_zone, te); 280 tcp_reass_qsize--; 281 /* 282 * Try to present any queued data 283 * at the left window edge to the user. 284 * This is needed after the 3-WHS 285 * completes. 286 */ 287 goto present; /* ??? */ 288 } 289 m_adj(m, i); 290 *tlenp -= i; 291 th->th_seq += i; 292 } 293 } 294 tcpstat.tcps_rcvoopack++; 295 tcpstat.tcps_rcvoobyte += *tlenp; 296 297 /* 298 * While we overlap succeeding segments trim them or, 299 * if they are completely covered, dequeue them. 300 */ 301 while (q) { 302 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 303 if (i <= 0) 304 break; 305 if (i < q->tqe_len) { 306 q->tqe_th->th_seq += i; 307 q->tqe_len -= i; 308 m_adj(q->tqe_m, i); 309 break; 310 } 311 312 nq = LIST_NEXT(q, tqe_q); 313 LIST_REMOVE(q, tqe_q); 314 m_freem(q->tqe_m); 315 uma_zfree(tcp_reass_zone, q); 316 tcp_reass_qsize--; 317 q = nq; 318 } 319 320 /* Insert the new segment queue entry into place. */ 321 te->tqe_m = m; 322 te->tqe_th = th; 323 te->tqe_len = *tlenp; 324 325 if (p == NULL) { 326 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 327 } else { 328 LIST_INSERT_AFTER(p, te, tqe_q); 329 } 330 331 present: 332 /* 333 * Present data to user, advancing rcv_nxt through 334 * completed sequence space. 335 */ 336 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 337 return (0); 338 q = LIST_FIRST(&tp->t_segq); 339 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 340 return (0); 341 do { 342 tp->rcv_nxt += q->tqe_len; 343 flags = q->tqe_th->th_flags & TH_FIN; 344 nq = LIST_NEXT(q, tqe_q); 345 LIST_REMOVE(q, tqe_q); 346 if (so->so_state & SS_CANTRCVMORE) 347 m_freem(q->tqe_m); 348 else 349 sbappendstream(&so->so_rcv, q->tqe_m); 350 uma_zfree(tcp_reass_zone, q); 351 tcp_reass_qsize--; 352 q = nq; 353 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 354 ND6_HINT(tp); 355 sorwakeup(so); 356 return (flags); 357 } 358 359 /* 360 * TCP input routine, follows pages 65-76 of the 361 * protocol specification dated September, 1981 very closely. 362 */ 363 #ifdef INET6 364 int 365 tcp6_input(mp, offp, proto) 366 struct mbuf **mp; 367 int *offp, proto; 368 { 369 register struct mbuf *m = *mp; 370 struct in6_ifaddr *ia6; 371 372 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 373 374 /* 375 * draft-itojun-ipv6-tcp-to-anycast 376 * better place to put this in? 377 */ 378 ia6 = ip6_getdstifaddr(m); 379 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 380 struct ip6_hdr *ip6; 381 382 ip6 = mtod(m, struct ip6_hdr *); 383 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 384 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 385 return IPPROTO_DONE; 386 } 387 388 tcp_input(m, *offp); 389 return IPPROTO_DONE; 390 } 391 #endif 392 393 void 394 tcp_input(m, off0) 395 register struct mbuf *m; 396 int off0; 397 { 398 register struct tcphdr *th; 399 register struct ip *ip = NULL; 400 register struct ipovly *ipov; 401 register struct inpcb *inp = NULL; 402 u_char *optp = NULL; 403 int optlen = 0; 404 int len, tlen, off; 405 int drop_hdrlen; 406 register struct tcpcb *tp = 0; 407 register int thflags; 408 struct socket *so = 0; 409 int todrop, acked, ourfinisacked, needoutput = 0; 410 u_long tiwin; 411 struct tcpopt to; /* options in this segment */ 412 struct rmxp_tao tao; /* our TAO cache entry */ 413 int headlocked = 0; 414 struct sockaddr_in *next_hop = NULL; 415 int rstreason; /* For badport_bandlim accounting purposes */ 416 417 struct ip6_hdr *ip6 = NULL; 418 #ifdef INET6 419 int isipv6; 420 #else 421 const int isipv6 = 0; 422 #endif 423 424 #ifdef TCPDEBUG 425 /* 426 * The size of tcp_saveipgen must be the size of the max ip header, 427 * now IPv6. 428 */ 429 u_char tcp_saveipgen[40]; 430 struct tcphdr tcp_savetcp; 431 short ostate = 0; 432 #endif 433 434 /* Grab info from MT_TAG mbufs prepended to the chain. */ 435 for (;m && m->m_type == MT_TAG; m = m->m_next) { 436 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 437 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 438 } 439 #ifdef INET6 440 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 441 #endif 442 bzero(&tao, sizeof(tao)); 443 bzero((char *)&to, sizeof(to)); 444 445 tcpstat.tcps_rcvtotal++; 446 447 if (isipv6) { 448 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 449 ip6 = mtod(m, struct ip6_hdr *); 450 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 451 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 452 tcpstat.tcps_rcvbadsum++; 453 goto drop; 454 } 455 th = (struct tcphdr *)((caddr_t)ip6 + off0); 456 457 /* 458 * Be proactive about unspecified IPv6 address in source. 459 * As we use all-zero to indicate unbounded/unconnected pcb, 460 * unspecified IPv6 address can be used to confuse us. 461 * 462 * Note that packets with unspecified IPv6 destination is 463 * already dropped in ip6_input. 464 */ 465 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 466 /* XXX stat */ 467 goto drop; 468 } 469 } else { 470 /* 471 * Get IP and TCP header together in first mbuf. 472 * Note: IP leaves IP header in first mbuf. 473 */ 474 if (off0 > sizeof (struct ip)) { 475 ip_stripoptions(m, (struct mbuf *)0); 476 off0 = sizeof(struct ip); 477 } 478 if (m->m_len < sizeof (struct tcpiphdr)) { 479 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 480 tcpstat.tcps_rcvshort++; 481 return; 482 } 483 } 484 ip = mtod(m, struct ip *); 485 ipov = (struct ipovly *)ip; 486 th = (struct tcphdr *)((caddr_t)ip + off0); 487 tlen = ip->ip_len; 488 489 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 490 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 491 th->th_sum = m->m_pkthdr.csum_data; 492 else 493 th->th_sum = in_pseudo(ip->ip_src.s_addr, 494 ip->ip_dst.s_addr, 495 htonl(m->m_pkthdr.csum_data + 496 ip->ip_len + 497 IPPROTO_TCP)); 498 th->th_sum ^= 0xffff; 499 #ifdef TCPDEBUG 500 ipov->ih_len = (u_short)tlen; 501 ipov->ih_len = htons(ipov->ih_len); 502 #endif 503 } else { 504 /* 505 * Checksum extended TCP header and data. 506 */ 507 len = sizeof (struct ip) + tlen; 508 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 509 ipov->ih_len = (u_short)tlen; 510 ipov->ih_len = htons(ipov->ih_len); 511 th->th_sum = in_cksum(m, len); 512 } 513 if (th->th_sum) { 514 tcpstat.tcps_rcvbadsum++; 515 goto drop; 516 } 517 #ifdef INET6 518 /* Re-initialization for later version check */ 519 ip->ip_v = IPVERSION; 520 #endif 521 } 522 523 /* 524 * Check that TCP offset makes sense, 525 * pull out TCP options and adjust length. XXX 526 */ 527 off = th->th_off << 2; 528 if (off < sizeof (struct tcphdr) || off > tlen) { 529 tcpstat.tcps_rcvbadoff++; 530 goto drop; 531 } 532 tlen -= off; /* tlen is used instead of ti->ti_len */ 533 if (off > sizeof (struct tcphdr)) { 534 if (isipv6) { 535 IP6_EXTHDR_CHECK(m, off0, off, ); 536 ip6 = mtod(m, struct ip6_hdr *); 537 th = (struct tcphdr *)((caddr_t)ip6 + off0); 538 } else { 539 if (m->m_len < sizeof(struct ip) + off) { 540 if ((m = m_pullup(m, sizeof (struct ip) + off)) 541 == 0) { 542 tcpstat.tcps_rcvshort++; 543 return; 544 } 545 ip = mtod(m, struct ip *); 546 ipov = (struct ipovly *)ip; 547 th = (struct tcphdr *)((caddr_t)ip + off0); 548 } 549 } 550 optlen = off - sizeof (struct tcphdr); 551 optp = (u_char *)(th + 1); 552 } 553 thflags = th->th_flags; 554 555 #ifdef TCP_DROP_SYNFIN 556 /* 557 * If the drop_synfin option is enabled, drop all packets with 558 * both the SYN and FIN bits set. This prevents e.g. nmap from 559 * identifying the TCP/IP stack. 560 * 561 * This is a violation of the TCP specification. 562 */ 563 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 564 goto drop; 565 #endif 566 567 /* 568 * Convert TCP protocol specific fields to host format. 569 */ 570 th->th_seq = ntohl(th->th_seq); 571 th->th_ack = ntohl(th->th_ack); 572 th->th_win = ntohs(th->th_win); 573 th->th_urp = ntohs(th->th_urp); 574 575 /* 576 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 577 * until after ip6_savecontrol() is called and before other functions 578 * which don't want those proto headers. 579 * Because ip6_savecontrol() is going to parse the mbuf to 580 * search for data to be passed up to user-land, it wants mbuf 581 * parameters to be unchanged. 582 * XXX: the call of ip6_savecontrol() has been obsoleted based on 583 * latest version of the advanced API (20020110). 584 */ 585 drop_hdrlen = off0 + off; 586 587 /* 588 * Locate pcb for segment. 589 */ 590 INP_INFO_WLOCK(&tcbinfo); 591 headlocked = 1; 592 findpcb: 593 /* IPFIREWALL_FORWARD section */ 594 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 595 /* 596 * Transparently forwarded. Pretend to be the destination. 597 * already got one like this? 598 */ 599 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 600 ip->ip_dst, th->th_dport, 601 0, m->m_pkthdr.rcvif); 602 if (!inp) { 603 /* It's new. Try find the ambushing socket. */ 604 inp = in_pcblookup_hash(&tcbinfo, 605 ip->ip_src, th->th_sport, 606 next_hop->sin_addr, 607 next_hop->sin_port ? 608 ntohs(next_hop->sin_port) : 609 th->th_dport, 610 1, m->m_pkthdr.rcvif); 611 } 612 } else { 613 if (isipv6) 614 inp = in6_pcblookup_hash(&tcbinfo, 615 &ip6->ip6_src, th->th_sport, 616 &ip6->ip6_dst, th->th_dport, 617 1, m->m_pkthdr.rcvif); 618 else 619 inp = in_pcblookup_hash(&tcbinfo, 620 ip->ip_src, th->th_sport, 621 ip->ip_dst, th->th_dport, 622 1, m->m_pkthdr.rcvif); 623 } 624 625 #ifdef IPSEC 626 if (isipv6) { 627 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 628 ipsec6stat.in_polvio++; 629 goto drop; 630 } 631 } else { 632 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 633 ipsecstat.in_polvio++; 634 goto drop; 635 } 636 } 637 #endif 638 #ifdef FAST_IPSEC 639 if (isipv6) { 640 if (inp != NULL && ipsec6_in_reject(m, inp)) { 641 goto drop; 642 } 643 } else 644 if (inp != NULL && ipsec4_in_reject(m, inp)) { 645 goto drop; 646 } 647 #endif /*FAST_IPSEC*/ 648 649 /* 650 * If the state is CLOSED (i.e., TCB does not exist) then 651 * all data in the incoming segment is discarded. 652 * If the TCB exists but is in CLOSED state, it is embryonic, 653 * but should either do a listen or a connect soon. 654 */ 655 if (inp == NULL) { 656 if (log_in_vain) { 657 #ifdef INET6 658 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 659 #else 660 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 661 #endif 662 663 if (isipv6) { 664 strcpy(dbuf, "["); 665 strcpy(sbuf, "["); 666 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 667 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 668 strcat(dbuf, "]"); 669 strcat(sbuf, "]"); 670 } else { 671 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 672 strcpy(sbuf, inet_ntoa(ip->ip_src)); 673 } 674 switch (log_in_vain) { 675 case 1: 676 if ((thflags & TH_SYN) == 0) 677 break; 678 /* FALLTHROUGH */ 679 case 2: 680 log(LOG_INFO, 681 "Connection attempt to TCP %s:%d " 682 "from %s:%d flags:0x%02x\n", 683 dbuf, ntohs(th->th_dport), sbuf, 684 ntohs(th->th_sport), thflags); 685 break; 686 default: 687 break; 688 } 689 } 690 if (blackhole) { 691 switch (blackhole) { 692 case 1: 693 if (thflags & TH_SYN) 694 goto drop; 695 break; 696 case 2: 697 goto drop; 698 default: 699 goto drop; 700 } 701 } 702 rstreason = BANDLIM_RST_CLOSEDPORT; 703 goto dropwithreset; 704 } 705 INP_LOCK(inp); 706 if (inp->inp_vflag & INP_TIMEWAIT) { 707 /* 708 * The only option of relevance is TOF_CC, and only if 709 * present in a SYN segment. See tcp_timewait(). 710 */ 711 if (thflags & TH_SYN) 712 tcp_dooptions(&to, optp, optlen, 1); 713 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 714 &to, th, m, tlen)) 715 goto findpcb; 716 /* 717 * tcp_timewait unlocks inp. 718 */ 719 INP_INFO_WUNLOCK(&tcbinfo); 720 return; 721 } 722 tp = intotcpcb(inp); 723 if (tp == 0) { 724 INP_UNLOCK(inp); 725 rstreason = BANDLIM_RST_CLOSEDPORT; 726 goto dropwithreset; 727 } 728 if (tp->t_state == TCPS_CLOSED) 729 goto drop; 730 731 /* Unscale the window into a 32-bit value. */ 732 if ((thflags & TH_SYN) == 0) 733 tiwin = th->th_win << tp->snd_scale; 734 else 735 tiwin = th->th_win; 736 737 #ifdef MAC 738 if (mac_check_inpcb_deliver(inp, m)) 739 goto drop; 740 #endif 741 so = inp->inp_socket; 742 #ifdef TCPDEBUG 743 if (so->so_options & SO_DEBUG) { 744 ostate = tp->t_state; 745 if (isipv6) 746 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 747 else 748 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 749 tcp_savetcp = *th; 750 } 751 #endif 752 if (so->so_options & SO_ACCEPTCONN) { 753 struct in_conninfo inc; 754 755 #ifdef INET6 756 inc.inc_isipv6 = isipv6; 757 #endif 758 if (isipv6) { 759 inc.inc6_faddr = ip6->ip6_src; 760 inc.inc6_laddr = ip6->ip6_dst; 761 } else { 762 inc.inc_faddr = ip->ip_src; 763 inc.inc_laddr = ip->ip_dst; 764 } 765 inc.inc_fport = th->th_sport; 766 inc.inc_lport = th->th_dport; 767 768 /* 769 * If the state is LISTEN then ignore segment if it contains 770 * a RST. If the segment contains an ACK then it is bad and 771 * send a RST. If it does not contain a SYN then it is not 772 * interesting; drop it. 773 * 774 * If the state is SYN_RECEIVED (syncache) and seg contains 775 * an ACK, but not for our SYN/ACK, send a RST. If the seg 776 * contains a RST, check the sequence number to see if it 777 * is a valid reset segment. 778 */ 779 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 780 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 781 if (!syncache_expand(&inc, th, &so, m)) { 782 /* 783 * No syncache entry, or ACK was not 784 * for our SYN/ACK. Send a RST. 785 */ 786 tcpstat.tcps_badsyn++; 787 rstreason = BANDLIM_RST_OPENPORT; 788 goto dropwithreset; 789 } 790 if (so == NULL) { 791 /* 792 * Could not complete 3-way handshake, 793 * connection is being closed down, and 794 * syncache will free mbuf. 795 */ 796 INP_UNLOCK(inp); 797 INP_INFO_WUNLOCK(&tcbinfo); 798 return; 799 } 800 /* 801 * Socket is created in state SYN_RECEIVED. 802 * Continue processing segment. 803 */ 804 INP_UNLOCK(inp); 805 inp = sotoinpcb(so); 806 INP_LOCK(inp); 807 tp = intotcpcb(inp); 808 /* 809 * This is what would have happened in 810 * tcp_output() when the SYN,ACK was sent. 811 */ 812 tp->snd_up = tp->snd_una; 813 tp->snd_max = tp->snd_nxt = tp->iss + 1; 814 tp->last_ack_sent = tp->rcv_nxt; 815 /* 816 * RFC1323: The window in SYN & SYN/ACK 817 * segments is never scaled. 818 */ 819 tp->snd_wnd = tiwin; /* unscaled */ 820 goto after_listen; 821 } 822 if (thflags & TH_RST) { 823 syncache_chkrst(&inc, th); 824 goto drop; 825 } 826 if (thflags & TH_ACK) { 827 syncache_badack(&inc); 828 tcpstat.tcps_badsyn++; 829 rstreason = BANDLIM_RST_OPENPORT; 830 goto dropwithreset; 831 } 832 goto drop; 833 } 834 835 /* 836 * Segment's flags are (SYN) or (SYN|FIN). 837 */ 838 #ifdef INET6 839 /* 840 * If deprecated address is forbidden, 841 * we do not accept SYN to deprecated interface 842 * address to prevent any new inbound connection from 843 * getting established. 844 * When we do not accept SYN, we send a TCP RST, 845 * with deprecated source address (instead of dropping 846 * it). We compromise it as it is much better for peer 847 * to send a RST, and RST will be the final packet 848 * for the exchange. 849 * 850 * If we do not forbid deprecated addresses, we accept 851 * the SYN packet. RFC2462 does not suggest dropping 852 * SYN in this case. 853 * If we decipher RFC2462 5.5.4, it says like this: 854 * 1. use of deprecated addr with existing 855 * communication is okay - "SHOULD continue to be 856 * used" 857 * 2. use of it with new communication: 858 * (2a) "SHOULD NOT be used if alternate address 859 * with sufficient scope is available" 860 * (2b) nothing mentioned otherwise. 861 * Here we fall into (2b) case as we have no choice in 862 * our source address selection - we must obey the peer. 863 * 864 * The wording in RFC2462 is confusing, and there are 865 * multiple description text for deprecated address 866 * handling - worse, they are not exactly the same. 867 * I believe 5.5.4 is the best one, so we follow 5.5.4. 868 */ 869 if (isipv6 && !ip6_use_deprecated) { 870 struct in6_ifaddr *ia6; 871 872 if ((ia6 = ip6_getdstifaddr(m)) && 873 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 874 INP_UNLOCK(inp); 875 tp = NULL; 876 rstreason = BANDLIM_RST_OPENPORT; 877 goto dropwithreset; 878 } 879 } 880 #endif 881 /* 882 * If it is from this socket, drop it, it must be forged. 883 * Don't bother responding if the destination was a broadcast. 884 */ 885 if (th->th_dport == th->th_sport) { 886 if (isipv6) { 887 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 888 &ip6->ip6_src)) 889 goto drop; 890 } else { 891 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 892 goto drop; 893 } 894 } 895 /* 896 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 897 * 898 * Note that it is quite possible to receive unicast 899 * link-layer packets with a broadcast IP address. Use 900 * in_broadcast() to find them. 901 */ 902 if (m->m_flags & (M_BCAST|M_MCAST)) 903 goto drop; 904 if (isipv6) { 905 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 906 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 907 goto drop; 908 } else { 909 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 910 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 911 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 912 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 913 goto drop; 914 } 915 /* 916 * SYN appears to be valid; create compressed TCP state 917 * for syncache, or perform t/tcp connection. 918 */ 919 if (so->so_qlen <= so->so_qlimit) { 920 #ifdef TCPDEBUG 921 if (so->so_options & SO_DEBUG) 922 tcp_trace(TA_INPUT, ostate, tp, 923 (void *)tcp_saveipgen, &tcp_savetcp, 0); 924 #endif 925 tcp_dooptions(&to, optp, optlen, 1); 926 if (!syncache_add(&inc, &to, th, &so, m)) 927 goto drop; 928 if (so == NULL) { 929 /* 930 * Entry added to syncache, mbuf used to 931 * send SYN,ACK packet. 932 */ 933 KASSERT(headlocked, ("headlocked")); 934 INP_UNLOCK(inp); 935 INP_INFO_WUNLOCK(&tcbinfo); 936 return; 937 } 938 /* 939 * Segment passed TAO tests. 940 */ 941 INP_UNLOCK(inp); 942 inp = sotoinpcb(so); 943 INP_LOCK(inp); 944 tp = intotcpcb(inp); 945 tp->snd_wnd = tiwin; 946 tp->t_starttime = ticks; 947 tp->t_state = TCPS_ESTABLISHED; 948 949 /* 950 * T/TCP logic: 951 * If there is a FIN or if there is data, then 952 * delay SYN,ACK(SYN) in the hope of piggy-backing 953 * it on a response segment. Otherwise must send 954 * ACK now in case the other side is slow starting. 955 */ 956 if (thflags & TH_FIN || tlen != 0) 957 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 958 else 959 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 960 tcpstat.tcps_connects++; 961 soisconnected(so); 962 goto trimthenstep6; 963 } 964 goto drop; 965 } 966 after_listen: 967 968 /* XXX temp debugging */ 969 /* should not happen - syncache should pick up these connections */ 970 if (tp->t_state == TCPS_LISTEN) 971 panic("tcp_input: TCPS_LISTEN"); 972 973 /* 974 * This is the second part of the MSS DoS prevention code (after 975 * minmss on the sending side) and it deals with too many too small 976 * tcp packets in a too short timeframe (1 second). 977 * 978 * For every full second we count the number of received packets 979 * and bytes. If we get a lot of packets per second for this connection 980 * (tcp_minmssoverload) we take a closer look at it and compute the 981 * average packet size for the past second. If that is less than 982 * tcp_minmss we get too many packets with very small payload which 983 * is not good and burdens our system (and every packet generates 984 * a wakeup to the process connected to our socket). We can reasonable 985 * expect this to be small packet DoS attack to exhaust our CPU 986 * cycles. 987 * 988 * Care has to be taken for the minimum packet overload value. This 989 * value defines the minimum number of packets per second before we 990 * start to worry. This must not be too low to avoid killing for 991 * example interactive connections with many small packets like 992 * telnet or SSH. 993 * 994 * Setting either tcp_minmssoverload or tcp_minmss to "" disables 995 * this check. 996 * 997 * Account for packet if payload packet, skip over ACK, etc. 998 */ 999 if (tcp_minmss && tcp_minmssoverload && 1000 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1001 if (tp->rcv_second > ticks) { 1002 tp->rcv_pps++; 1003 tp->rcv_byps += tlen + off; 1004 if (tp->rcv_pps > tcp_minmssoverload) { 1005 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1006 printf("too many small tcp packets from " 1007 "%s:%u, av. %lubyte/packet, " 1008 "dropping connection\n", 1009 #ifdef INET6 1010 isipv6 ? 1011 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1012 #endif 1013 inet_ntoa(inp->inp_inc.inc_faddr), 1014 inp->inp_inc.inc_fport, 1015 tp->rcv_byps / tp->rcv_pps); 1016 tp = tcp_drop(tp, ECONNRESET); 1017 tcpstat.tcps_minmssdrops++; 1018 goto drop; 1019 } 1020 } 1021 } else { 1022 tp->rcv_second = ticks + hz; 1023 tp->rcv_pps = 1; 1024 tp->rcv_byps = tlen + off; 1025 } 1026 } 1027 1028 /* 1029 * Segment received on connection. 1030 * Reset idle time and keep-alive timer. 1031 */ 1032 tp->t_rcvtime = ticks; 1033 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1034 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1035 1036 /* 1037 * Process options only when we get SYN/ACK back. The SYN case 1038 * for incoming connections is handled in tcp_syncache. 1039 * XXX this is traditional behavior, may need to be cleaned up. 1040 */ 1041 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 1042 if (thflags & TH_SYN) { 1043 if (to.to_flags & TOF_SCALE) { 1044 tp->t_flags |= TF_RCVD_SCALE; 1045 tp->requested_s_scale = to.to_requested_s_scale; 1046 } 1047 if (to.to_flags & TOF_TS) { 1048 tp->t_flags |= TF_RCVD_TSTMP; 1049 tp->ts_recent = to.to_tsval; 1050 tp->ts_recent_age = ticks; 1051 } 1052 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 1053 tp->t_flags |= TF_RCVD_CC; 1054 if (to.to_flags & TOF_MSS) 1055 tcp_mss(tp, to.to_mss); 1056 } 1057 1058 /* 1059 * Header prediction: check for the two common cases 1060 * of a uni-directional data xfer. If the packet has 1061 * no control flags, is in-sequence, the window didn't 1062 * change and we're not retransmitting, it's a 1063 * candidate. If the length is zero and the ack moved 1064 * forward, we're the sender side of the xfer. Just 1065 * free the data acked & wake any higher level process 1066 * that was blocked waiting for space. If the length 1067 * is non-zero and the ack didn't move, we're the 1068 * receiver side. If we're getting packets in-order 1069 * (the reassembly queue is empty), add the data to 1070 * the socket buffer and note that we need a delayed ack. 1071 * Make sure that the hidden state-flags are also off. 1072 * Since we check for TCPS_ESTABLISHED above, it can only 1073 * be TH_NEEDSYN. 1074 */ 1075 if (tp->t_state == TCPS_ESTABLISHED && 1076 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1077 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1078 ((to.to_flags & TOF_TS) == 0 || 1079 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1080 /* 1081 * Using the CC option is compulsory if once started: 1082 * the segment is OK if no T/TCP was negotiated or 1083 * if the segment has a CC option equal to CCrecv 1084 */ 1085 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1086 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1087 th->th_seq == tp->rcv_nxt && 1088 tiwin && tiwin == tp->snd_wnd && 1089 tp->snd_nxt == tp->snd_max) { 1090 1091 /* 1092 * If last ACK falls within this segment's sequence numbers, 1093 * record the timestamp. 1094 * NOTE that the test is modified according to the latest 1095 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1096 */ 1097 if ((to.to_flags & TOF_TS) != 0 && 1098 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1099 tp->ts_recent_age = ticks; 1100 tp->ts_recent = to.to_tsval; 1101 } 1102 1103 if (tlen == 0) { 1104 if (SEQ_GT(th->th_ack, tp->snd_una) && 1105 SEQ_LEQ(th->th_ack, tp->snd_max) && 1106 tp->snd_cwnd >= tp->snd_wnd && 1107 ((!tcp_do_newreno && 1108 tp->t_dupacks < tcprexmtthresh) || 1109 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) { 1110 KASSERT(headlocked, ("headlocked")); 1111 INP_INFO_WUNLOCK(&tcbinfo); 1112 /* 1113 * this is a pure ack for outstanding data. 1114 */ 1115 ++tcpstat.tcps_predack; 1116 /* 1117 * "bad retransmit" recovery 1118 */ 1119 if (tp->t_rxtshift == 1 && 1120 ticks < tp->t_badrxtwin) { 1121 ++tcpstat.tcps_sndrexmitbad; 1122 tp->snd_cwnd = tp->snd_cwnd_prev; 1123 tp->snd_ssthresh = 1124 tp->snd_ssthresh_prev; 1125 tp->snd_recover = tp->snd_recover_prev; 1126 if (tp->t_flags & TF_WASFRECOVERY) 1127 ENTER_FASTRECOVERY(tp); 1128 tp->snd_nxt = tp->snd_max; 1129 tp->t_badrxtwin = 0; 1130 } 1131 1132 /* 1133 * Recalculate the transmit timer / rtt. 1134 * 1135 * Some boxes send broken timestamp replies 1136 * during the SYN+ACK phase, ignore 1137 * timestamps of 0 or we could calculate a 1138 * huge RTT and blow up the retransmit timer. 1139 */ 1140 if ((to.to_flags & TOF_TS) != 0 && 1141 to.to_tsecr) { 1142 tcp_xmit_timer(tp, 1143 ticks - to.to_tsecr + 1); 1144 } else if (tp->t_rtttime && 1145 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1146 tcp_xmit_timer(tp, 1147 ticks - tp->t_rtttime); 1148 } 1149 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1150 acked = th->th_ack - tp->snd_una; 1151 tcpstat.tcps_rcvackpack++; 1152 tcpstat.tcps_rcvackbyte += acked; 1153 sbdrop(&so->so_snd, acked); 1154 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1155 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1156 tp->snd_recover = th->th_ack - 1; 1157 tp->snd_una = th->th_ack; 1158 /* 1159 * pull snd_wl2 up to prevent seq wrap relative 1160 * to th_ack. 1161 */ 1162 tp->snd_wl2 = th->th_ack; 1163 tp->t_dupacks = 0; 1164 m_freem(m); 1165 ND6_HINT(tp); /* some progress has been done */ 1166 1167 /* 1168 * If all outstanding data are acked, stop 1169 * retransmit timer, otherwise restart timer 1170 * using current (possibly backed-off) value. 1171 * If process is waiting for space, 1172 * wakeup/selwakeup/signal. If data 1173 * are ready to send, let tcp_output 1174 * decide between more output or persist. 1175 1176 #ifdef TCPDEBUG 1177 if (so->so_options & SO_DEBUG) 1178 tcp_trace(TA_INPUT, ostate, tp, 1179 (void *)tcp_saveipgen, 1180 &tcp_savetcp, 0); 1181 #endif 1182 */ 1183 if (tp->snd_una == tp->snd_max) 1184 callout_stop(tp->tt_rexmt); 1185 else if (!callout_active(tp->tt_persist)) 1186 callout_reset(tp->tt_rexmt, 1187 tp->t_rxtcur, 1188 tcp_timer_rexmt, tp); 1189 1190 sowwakeup(so); 1191 if (so->so_snd.sb_cc) 1192 (void) tcp_output(tp); 1193 goto check_delack; 1194 } 1195 } else if (th->th_ack == tp->snd_una && 1196 LIST_EMPTY(&tp->t_segq) && 1197 tlen <= sbspace(&so->so_rcv)) { 1198 KASSERT(headlocked, ("headlocked")); 1199 INP_INFO_WUNLOCK(&tcbinfo); 1200 /* 1201 * this is a pure, in-sequence data packet 1202 * with nothing on the reassembly queue and 1203 * we have enough buffer space to take it. 1204 */ 1205 ++tcpstat.tcps_preddat; 1206 tp->rcv_nxt += tlen; 1207 /* 1208 * Pull snd_wl1 up to prevent seq wrap relative to 1209 * th_seq. 1210 */ 1211 tp->snd_wl1 = th->th_seq; 1212 /* 1213 * Pull rcv_up up to prevent seq wrap relative to 1214 * rcv_nxt. 1215 */ 1216 tp->rcv_up = tp->rcv_nxt; 1217 tcpstat.tcps_rcvpack++; 1218 tcpstat.tcps_rcvbyte += tlen; 1219 ND6_HINT(tp); /* some progress has been done */ 1220 /* 1221 #ifdef TCPDEBUG 1222 if (so->so_options & SO_DEBUG) 1223 tcp_trace(TA_INPUT, ostate, tp, 1224 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1225 #endif 1226 * Add data to socket buffer. 1227 */ 1228 if (so->so_state & SS_CANTRCVMORE) { 1229 m_freem(m); 1230 } else { 1231 m_adj(m, drop_hdrlen); /* delayed header drop */ 1232 sbappendstream(&so->so_rcv, m); 1233 } 1234 sorwakeup(so); 1235 if (DELAY_ACK(tp)) { 1236 tp->t_flags |= TF_DELACK; 1237 } else { 1238 tp->t_flags |= TF_ACKNOW; 1239 tcp_output(tp); 1240 } 1241 goto check_delack; 1242 } 1243 } 1244 1245 /* 1246 * Calculate amount of space in receive window, 1247 * and then do TCP input processing. 1248 * Receive window is amount of space in rcv queue, 1249 * but not less than advertised window. 1250 */ 1251 { int win; 1252 1253 win = sbspace(&so->so_rcv); 1254 if (win < 0) 1255 win = 0; 1256 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1257 } 1258 1259 switch (tp->t_state) { 1260 1261 /* 1262 * If the state is SYN_RECEIVED: 1263 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1264 */ 1265 case TCPS_SYN_RECEIVED: 1266 if ((thflags & TH_ACK) && 1267 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1268 SEQ_GT(th->th_ack, tp->snd_max))) { 1269 rstreason = BANDLIM_RST_OPENPORT; 1270 goto dropwithreset; 1271 } 1272 break; 1273 1274 /* 1275 * If the state is SYN_SENT: 1276 * if seg contains an ACK, but not for our SYN, drop the input. 1277 * if seg contains a RST, then drop the connection. 1278 * if seg does not contain SYN, then drop it. 1279 * Otherwise this is an acceptable SYN segment 1280 * initialize tp->rcv_nxt and tp->irs 1281 * if seg contains ack then advance tp->snd_una 1282 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1283 * arrange for segment to be acked (eventually) 1284 * continue processing rest of data/controls, beginning with URG 1285 */ 1286 case TCPS_SYN_SENT: 1287 if (tcp_do_rfc1644) 1288 tcp_hc_gettao(&inp->inp_inc, &tao); 1289 1290 if ((thflags & TH_ACK) && 1291 (SEQ_LEQ(th->th_ack, tp->iss) || 1292 SEQ_GT(th->th_ack, tp->snd_max))) { 1293 /* 1294 * If we have a cached CCsent for the remote host, 1295 * hence we haven't just crashed and restarted, 1296 * do not send a RST. This may be a retransmission 1297 * from the other side after our earlier ACK was lost. 1298 * Our new SYN, when it arrives, will serve as the 1299 * needed ACK. 1300 */ 1301 if (tao.tao_ccsent != 0) 1302 goto drop; 1303 else { 1304 rstreason = BANDLIM_UNLIMITED; 1305 goto dropwithreset; 1306 } 1307 } 1308 if (thflags & TH_RST) { 1309 if (thflags & TH_ACK) 1310 tp = tcp_drop(tp, ECONNREFUSED); 1311 goto drop; 1312 } 1313 if ((thflags & TH_SYN) == 0) 1314 goto drop; 1315 tp->snd_wnd = th->th_win; /* initial send window */ 1316 tp->cc_recv = to.to_cc; /* foreign CC */ 1317 1318 tp->irs = th->th_seq; 1319 tcp_rcvseqinit(tp); 1320 if (thflags & TH_ACK) { 1321 /* 1322 * Our SYN was acked. If segment contains CC.ECHO 1323 * option, check it to make sure this segment really 1324 * matches our SYN. If not, just drop it as old 1325 * duplicate, but send an RST if we're still playing 1326 * by the old rules. If no CC.ECHO option, make sure 1327 * we don't get fooled into using T/TCP. 1328 */ 1329 if (to.to_flags & TOF_CCECHO) { 1330 if (tp->cc_send != to.to_ccecho) { 1331 if (tao.tao_ccsent != 0) 1332 goto drop; 1333 else { 1334 rstreason = BANDLIM_UNLIMITED; 1335 goto dropwithreset; 1336 } 1337 } 1338 } else 1339 tp->t_flags &= ~TF_RCVD_CC; 1340 tcpstat.tcps_connects++; 1341 soisconnected(so); 1342 #ifdef MAC 1343 mac_set_socket_peer_from_mbuf(m, so); 1344 #endif 1345 /* Do window scaling on this connection? */ 1346 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1347 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1348 tp->snd_scale = tp->requested_s_scale; 1349 tp->rcv_scale = tp->request_r_scale; 1350 } 1351 /* Segment is acceptable, update cache if undefined. */ 1352 if (tao.tao_ccsent == 0 && tcp_do_rfc1644) 1353 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0); 1354 1355 tp->rcv_adv += tp->rcv_wnd; 1356 tp->snd_una++; /* SYN is acked */ 1357 /* 1358 * If there's data, delay ACK; if there's also a FIN 1359 * ACKNOW will be turned on later. 1360 */ 1361 if (DELAY_ACK(tp) && tlen != 0) 1362 callout_reset(tp->tt_delack, tcp_delacktime, 1363 tcp_timer_delack, tp); 1364 else 1365 tp->t_flags |= TF_ACKNOW; 1366 /* 1367 * Received <SYN,ACK> in SYN_SENT[*] state. 1368 * Transitions: 1369 * SYN_SENT --> ESTABLISHED 1370 * SYN_SENT* --> FIN_WAIT_1 1371 */ 1372 tp->t_starttime = ticks; 1373 if (tp->t_flags & TF_NEEDFIN) { 1374 tp->t_state = TCPS_FIN_WAIT_1; 1375 tp->t_flags &= ~TF_NEEDFIN; 1376 thflags &= ~TH_SYN; 1377 } else { 1378 tp->t_state = TCPS_ESTABLISHED; 1379 callout_reset(tp->tt_keep, tcp_keepidle, 1380 tcp_timer_keep, tp); 1381 } 1382 } else { 1383 /* 1384 * Received initial SYN in SYN-SENT[*] state => 1385 * simultaneous open. If segment contains CC option 1386 * and there is a cached CC, apply TAO test. 1387 * If it succeeds, connection is * half-synchronized. 1388 * Otherwise, do 3-way handshake: 1389 * SYN-SENT -> SYN-RECEIVED 1390 * SYN-SENT* -> SYN-RECEIVED* 1391 * If there was no CC option, clear cached CC value. 1392 */ 1393 tp->t_flags |= TF_ACKNOW; 1394 callout_stop(tp->tt_rexmt); 1395 if (to.to_flags & TOF_CC) { 1396 if (tao.tao_cc != 0 && 1397 CC_GT(to.to_cc, tao.tao_cc)) { 1398 /* 1399 * update cache and make transition: 1400 * SYN-SENT -> ESTABLISHED* 1401 * SYN-SENT* -> FIN-WAIT-1* 1402 */ 1403 tao.tao_cc = to.to_cc; 1404 tcp_hc_updatetao(&inp->inp_inc, 1405 TCP_HC_TAO_CC, to.to_cc, 0); 1406 tp->t_starttime = ticks; 1407 if (tp->t_flags & TF_NEEDFIN) { 1408 tp->t_state = TCPS_FIN_WAIT_1; 1409 tp->t_flags &= ~TF_NEEDFIN; 1410 } else { 1411 tp->t_state = TCPS_ESTABLISHED; 1412 callout_reset(tp->tt_keep, 1413 tcp_keepidle, 1414 tcp_timer_keep, 1415 tp); 1416 } 1417 tp->t_flags |= TF_NEEDSYN; 1418 } else 1419 tp->t_state = TCPS_SYN_RECEIVED; 1420 } else { 1421 if (tcp_do_rfc1644) { 1422 /* CC.NEW or no option => invalidate cache */ 1423 tao.tao_cc = 0; 1424 tcp_hc_updatetao(&inp->inp_inc, 1425 TCP_HC_TAO_CC, to.to_cc, 0); 1426 } 1427 tp->t_state = TCPS_SYN_RECEIVED; 1428 } 1429 } 1430 1431 trimthenstep6: 1432 /* 1433 * Advance th->th_seq to correspond to first data byte. 1434 * If data, trim to stay within window, 1435 * dropping FIN if necessary. 1436 */ 1437 th->th_seq++; 1438 if (tlen > tp->rcv_wnd) { 1439 todrop = tlen - tp->rcv_wnd; 1440 m_adj(m, -todrop); 1441 tlen = tp->rcv_wnd; 1442 thflags &= ~TH_FIN; 1443 tcpstat.tcps_rcvpackafterwin++; 1444 tcpstat.tcps_rcvbyteafterwin += todrop; 1445 } 1446 tp->snd_wl1 = th->th_seq - 1; 1447 tp->rcv_up = th->th_seq; 1448 /* 1449 * Client side of transaction: already sent SYN and data. 1450 * If the remote host used T/TCP to validate the SYN, 1451 * our data will be ACK'd; if so, enter normal data segment 1452 * processing in the middle of step 5, ack processing. 1453 * Otherwise, goto step 6. 1454 */ 1455 if (thflags & TH_ACK) 1456 goto process_ACK; 1457 1458 goto step6; 1459 1460 /* 1461 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1462 * if segment contains a SYN and CC [not CC.NEW] option: 1463 * if state == TIME_WAIT and connection duration > MSL, 1464 * drop packet and send RST; 1465 * 1466 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1467 * ack the FIN (and data) in retransmission queue. 1468 * Complete close and delete TCPCB. Then reprocess 1469 * segment, hoping to find new TCPCB in LISTEN state; 1470 * 1471 * else must be old SYN; drop it. 1472 * else do normal processing. 1473 */ 1474 case TCPS_LAST_ACK: 1475 case TCPS_CLOSING: 1476 case TCPS_TIME_WAIT: 1477 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1478 if ((thflags & TH_SYN) && 1479 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1480 if (tp->t_state == TCPS_TIME_WAIT && 1481 (ticks - tp->t_starttime) > tcp_msl) { 1482 rstreason = BANDLIM_UNLIMITED; 1483 goto dropwithreset; 1484 } 1485 if (CC_GT(to.to_cc, tp->cc_recv)) { 1486 tp = tcp_close(tp); 1487 goto findpcb; 1488 } 1489 else 1490 goto drop; 1491 } 1492 break; /* continue normal processing */ 1493 } 1494 1495 /* 1496 * States other than LISTEN or SYN_SENT. 1497 * First check the RST flag and sequence number since reset segments 1498 * are exempt from the timestamp and connection count tests. This 1499 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1500 * below which allowed reset segments in half the sequence space 1501 * to fall though and be processed (which gives forged reset 1502 * segments with a random sequence number a 50 percent chance of 1503 * killing a connection). 1504 * Then check timestamp, if present. 1505 * Then check the connection count, if present. 1506 * Then check that at least some bytes of segment are within 1507 * receive window. If segment begins before rcv_nxt, 1508 * drop leading data (and SYN); if nothing left, just ack. 1509 * 1510 * 1511 * If the RST bit is set, check the sequence number to see 1512 * if this is a valid reset segment. 1513 * RFC 793 page 37: 1514 * In all states except SYN-SENT, all reset (RST) segments 1515 * are validated by checking their SEQ-fields. A reset is 1516 * valid if its sequence number is in the window. 1517 * Note: this does not take into account delayed ACKs, so 1518 * we should test against last_ack_sent instead of rcv_nxt. 1519 * The sequence number in the reset segment is normally an 1520 * echo of our outgoing acknowlegement numbers, but some hosts 1521 * send a reset with the sequence number at the rightmost edge 1522 * of our receive window, and we have to handle this case. 1523 * If we have multiple segments in flight, the intial reset 1524 * segment sequence numbers will be to the left of last_ack_sent, 1525 * but they will eventually catch up. 1526 * In any case, it never made sense to trim reset segments to 1527 * fit the receive window since RFC 1122 says: 1528 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1529 * 1530 * A TCP SHOULD allow a received RST segment to include data. 1531 * 1532 * DISCUSSION 1533 * It has been suggested that a RST segment could contain 1534 * ASCII text that encoded and explained the cause of the 1535 * RST. No standard has yet been established for such 1536 * data. 1537 * 1538 * If the reset segment passes the sequence number test examine 1539 * the state: 1540 * SYN_RECEIVED STATE: 1541 * If passive open, return to LISTEN state. 1542 * If active open, inform user that connection was refused. 1543 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1544 * Inform user that connection was reset, and close tcb. 1545 * CLOSING, LAST_ACK STATES: 1546 * Close the tcb. 1547 * TIME_WAIT STATE: 1548 * Drop the segment - see Stevens, vol. 2, p. 964 and 1549 * RFC 1337. 1550 */ 1551 if (thflags & TH_RST) { 1552 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1553 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1554 switch (tp->t_state) { 1555 1556 case TCPS_SYN_RECEIVED: 1557 so->so_error = ECONNREFUSED; 1558 goto close; 1559 1560 case TCPS_ESTABLISHED: 1561 case TCPS_FIN_WAIT_1: 1562 case TCPS_FIN_WAIT_2: 1563 case TCPS_CLOSE_WAIT: 1564 so->so_error = ECONNRESET; 1565 close: 1566 tp->t_state = TCPS_CLOSED; 1567 tcpstat.tcps_drops++; 1568 tp = tcp_close(tp); 1569 break; 1570 1571 case TCPS_CLOSING: 1572 case TCPS_LAST_ACK: 1573 tp = tcp_close(tp); 1574 break; 1575 1576 case TCPS_TIME_WAIT: 1577 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1578 ("timewait")); 1579 break; 1580 } 1581 } 1582 goto drop; 1583 } 1584 1585 /* 1586 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1587 * and it's less than ts_recent, drop it. 1588 */ 1589 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1590 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1591 1592 /* Check to see if ts_recent is over 24 days old. */ 1593 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1594 /* 1595 * Invalidate ts_recent. If this segment updates 1596 * ts_recent, the age will be reset later and ts_recent 1597 * will get a valid value. If it does not, setting 1598 * ts_recent to zero will at least satisfy the 1599 * requirement that zero be placed in the timestamp 1600 * echo reply when ts_recent isn't valid. The 1601 * age isn't reset until we get a valid ts_recent 1602 * because we don't want out-of-order segments to be 1603 * dropped when ts_recent is old. 1604 */ 1605 tp->ts_recent = 0; 1606 } else { 1607 tcpstat.tcps_rcvduppack++; 1608 tcpstat.tcps_rcvdupbyte += tlen; 1609 tcpstat.tcps_pawsdrop++; 1610 if (tlen) 1611 goto dropafterack; 1612 goto drop; 1613 } 1614 } 1615 1616 /* 1617 * T/TCP mechanism 1618 * If T/TCP was negotiated and the segment doesn't have CC, 1619 * or if its CC is wrong then drop the segment. 1620 * RST segments do not have to comply with this. 1621 */ 1622 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1623 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1624 goto dropafterack; 1625 1626 /* 1627 * In the SYN-RECEIVED state, validate that the packet belongs to 1628 * this connection before trimming the data to fit the receive 1629 * window. Check the sequence number versus IRS since we know 1630 * the sequence numbers haven't wrapped. This is a partial fix 1631 * for the "LAND" DoS attack. 1632 */ 1633 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1634 rstreason = BANDLIM_RST_OPENPORT; 1635 goto dropwithreset; 1636 } 1637 1638 todrop = tp->rcv_nxt - th->th_seq; 1639 if (todrop > 0) { 1640 if (thflags & TH_SYN) { 1641 thflags &= ~TH_SYN; 1642 th->th_seq++; 1643 if (th->th_urp > 1) 1644 th->th_urp--; 1645 else 1646 thflags &= ~TH_URG; 1647 todrop--; 1648 } 1649 /* 1650 * Following if statement from Stevens, vol. 2, p. 960. 1651 */ 1652 if (todrop > tlen 1653 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1654 /* 1655 * Any valid FIN must be to the left of the window. 1656 * At this point the FIN must be a duplicate or out 1657 * of sequence; drop it. 1658 */ 1659 thflags &= ~TH_FIN; 1660 1661 /* 1662 * Send an ACK to resynchronize and drop any data. 1663 * But keep on processing for RST or ACK. 1664 */ 1665 tp->t_flags |= TF_ACKNOW; 1666 todrop = tlen; 1667 tcpstat.tcps_rcvduppack++; 1668 tcpstat.tcps_rcvdupbyte += todrop; 1669 } else { 1670 tcpstat.tcps_rcvpartduppack++; 1671 tcpstat.tcps_rcvpartdupbyte += todrop; 1672 } 1673 drop_hdrlen += todrop; /* drop from the top afterwards */ 1674 th->th_seq += todrop; 1675 tlen -= todrop; 1676 if (th->th_urp > todrop) 1677 th->th_urp -= todrop; 1678 else { 1679 thflags &= ~TH_URG; 1680 th->th_urp = 0; 1681 } 1682 } 1683 1684 /* 1685 * If new data are received on a connection after the 1686 * user processes are gone, then RST the other end. 1687 */ 1688 if ((so->so_state & SS_NOFDREF) && 1689 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1690 tp = tcp_close(tp); 1691 tcpstat.tcps_rcvafterclose++; 1692 rstreason = BANDLIM_UNLIMITED; 1693 goto dropwithreset; 1694 } 1695 1696 /* 1697 * If segment ends after window, drop trailing data 1698 * (and PUSH and FIN); if nothing left, just ACK. 1699 */ 1700 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1701 if (todrop > 0) { 1702 tcpstat.tcps_rcvpackafterwin++; 1703 if (todrop >= tlen) { 1704 tcpstat.tcps_rcvbyteafterwin += tlen; 1705 /* 1706 * If a new connection request is received 1707 * while in TIME_WAIT, drop the old connection 1708 * and start over if the sequence numbers 1709 * are above the previous ones. 1710 */ 1711 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1712 if (thflags & TH_SYN && 1713 tp->t_state == TCPS_TIME_WAIT && 1714 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1715 tp = tcp_close(tp); 1716 goto findpcb; 1717 } 1718 /* 1719 * If window is closed can only take segments at 1720 * window edge, and have to drop data and PUSH from 1721 * incoming segments. Continue processing, but 1722 * remember to ack. Otherwise, drop segment 1723 * and ack. 1724 */ 1725 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1726 tp->t_flags |= TF_ACKNOW; 1727 tcpstat.tcps_rcvwinprobe++; 1728 } else 1729 goto dropafterack; 1730 } else 1731 tcpstat.tcps_rcvbyteafterwin += todrop; 1732 m_adj(m, -todrop); 1733 tlen -= todrop; 1734 thflags &= ~(TH_PUSH|TH_FIN); 1735 } 1736 1737 /* 1738 * If last ACK falls within this segment's sequence numbers, 1739 * record its timestamp. 1740 * NOTE that the test is modified according to the latest 1741 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1742 */ 1743 if ((to.to_flags & TOF_TS) != 0 && 1744 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1745 tp->ts_recent_age = ticks; 1746 tp->ts_recent = to.to_tsval; 1747 } 1748 1749 /* 1750 * If a SYN is in the window, then this is an 1751 * error and we send an RST and drop the connection. 1752 */ 1753 if (thflags & TH_SYN) { 1754 tp = tcp_drop(tp, ECONNRESET); 1755 rstreason = BANDLIM_UNLIMITED; 1756 goto drop; 1757 } 1758 1759 /* 1760 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1761 * flag is on (half-synchronized state), then queue data for 1762 * later processing; else drop segment and return. 1763 */ 1764 if ((thflags & TH_ACK) == 0) { 1765 if (tp->t_state == TCPS_SYN_RECEIVED || 1766 (tp->t_flags & TF_NEEDSYN)) 1767 goto step6; 1768 else 1769 goto drop; 1770 } 1771 1772 /* 1773 * Ack processing. 1774 */ 1775 switch (tp->t_state) { 1776 1777 /* 1778 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1779 * ESTABLISHED state and continue processing. 1780 * The ACK was checked above. 1781 */ 1782 case TCPS_SYN_RECEIVED: 1783 1784 tcpstat.tcps_connects++; 1785 soisconnected(so); 1786 /* Do window scaling? */ 1787 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1788 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1789 tp->snd_scale = tp->requested_s_scale; 1790 tp->rcv_scale = tp->request_r_scale; 1791 } 1792 /* 1793 * Upon successful completion of 3-way handshake, 1794 * update cache.CC, pass any queued data to the user, 1795 * and advance state appropriately. 1796 */ 1797 if (tcp_do_rfc1644) { 1798 tao.tao_cc = tp->cc_recv; 1799 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC, 1800 tp->cc_recv, 0); 1801 } 1802 /* 1803 * Make transitions: 1804 * SYN-RECEIVED -> ESTABLISHED 1805 * SYN-RECEIVED* -> FIN-WAIT-1 1806 */ 1807 tp->t_starttime = ticks; 1808 if (tp->t_flags & TF_NEEDFIN) { 1809 tp->t_state = TCPS_FIN_WAIT_1; 1810 tp->t_flags &= ~TF_NEEDFIN; 1811 } else { 1812 tp->t_state = TCPS_ESTABLISHED; 1813 callout_reset(tp->tt_keep, tcp_keepidle, 1814 tcp_timer_keep, tp); 1815 } 1816 /* 1817 * If segment contains data or ACK, will call tcp_reass() 1818 * later; if not, do so now to pass queued data to user. 1819 */ 1820 if (tlen == 0 && (thflags & TH_FIN) == 0) 1821 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1822 (struct mbuf *)0); 1823 tp->snd_wl1 = th->th_seq - 1; 1824 /* FALLTHROUGH */ 1825 1826 /* 1827 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1828 * ACKs. If the ack is in the range 1829 * tp->snd_una < th->th_ack <= tp->snd_max 1830 * then advance tp->snd_una to th->th_ack and drop 1831 * data from the retransmission queue. If this ACK reflects 1832 * more up to date window information we update our window information. 1833 */ 1834 case TCPS_ESTABLISHED: 1835 case TCPS_FIN_WAIT_1: 1836 case TCPS_FIN_WAIT_2: 1837 case TCPS_CLOSE_WAIT: 1838 case TCPS_CLOSING: 1839 case TCPS_LAST_ACK: 1840 case TCPS_TIME_WAIT: 1841 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1842 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1843 if (tlen == 0 && tiwin == tp->snd_wnd) { 1844 tcpstat.tcps_rcvdupack++; 1845 /* 1846 * If we have outstanding data (other than 1847 * a window probe), this is a completely 1848 * duplicate ack (ie, window info didn't 1849 * change), the ack is the biggest we've 1850 * seen and we've seen exactly our rexmt 1851 * threshhold of them, assume a packet 1852 * has been dropped and retransmit it. 1853 * Kludge snd_nxt & the congestion 1854 * window so we send only this one 1855 * packet. 1856 * 1857 * We know we're losing at the current 1858 * window size so do congestion avoidance 1859 * (set ssthresh to half the current window 1860 * and pull our congestion window back to 1861 * the new ssthresh). 1862 * 1863 * Dup acks mean that packets have left the 1864 * network (they're now cached at the receiver) 1865 * so bump cwnd by the amount in the receiver 1866 * to keep a constant cwnd packets in the 1867 * network. 1868 */ 1869 if (!callout_active(tp->tt_rexmt) || 1870 th->th_ack != tp->snd_una) 1871 tp->t_dupacks = 0; 1872 else if (++tp->t_dupacks > tcprexmtthresh || 1873 (tcp_do_newreno && 1874 IN_FASTRECOVERY(tp))) { 1875 tp->snd_cwnd += tp->t_maxseg; 1876 (void) tcp_output(tp); 1877 goto drop; 1878 } else if (tp->t_dupacks == tcprexmtthresh) { 1879 tcp_seq onxt = tp->snd_nxt; 1880 u_int win; 1881 if (tcp_do_newreno && 1882 SEQ_LEQ(th->th_ack, 1883 tp->snd_recover)) { 1884 tp->t_dupacks = 0; 1885 break; 1886 } 1887 win = min(tp->snd_wnd, tp->snd_cwnd) / 1888 2 / tp->t_maxseg; 1889 if (win < 2) 1890 win = 2; 1891 tp->snd_ssthresh = win * tp->t_maxseg; 1892 ENTER_FASTRECOVERY(tp); 1893 tp->snd_recover = tp->snd_max; 1894 callout_stop(tp->tt_rexmt); 1895 tp->t_rtttime = 0; 1896 tp->snd_nxt = th->th_ack; 1897 tp->snd_cwnd = tp->t_maxseg; 1898 (void) tcp_output(tp); 1899 KASSERT(tp->snd_limited <= 2, 1900 ("tp->snd_limited too big")); 1901 tp->snd_cwnd = tp->snd_ssthresh + 1902 tp->t_maxseg * 1903 (tp->t_dupacks - tp->snd_limited); 1904 if (SEQ_GT(onxt, tp->snd_nxt)) 1905 tp->snd_nxt = onxt; 1906 goto drop; 1907 } else if (tcp_do_rfc3042) { 1908 u_long oldcwnd = tp->snd_cwnd; 1909 tcp_seq oldsndmax = tp->snd_max; 1910 u_int sent; 1911 KASSERT(tp->t_dupacks == 1 || 1912 tp->t_dupacks == 2, 1913 ("dupacks not 1 or 2")); 1914 if (tp->t_dupacks == 1) { 1915 tp->snd_limited = 0; 1916 tp->snd_cwnd += tp->t_maxseg; 1917 } else { 1918 tp->snd_cwnd += 1919 tp->t_maxseg * 2; 1920 } 1921 (void) tcp_output(tp); 1922 sent = tp->snd_max - oldsndmax; 1923 if (sent > tp->t_maxseg) { 1924 KASSERT(tp->snd_limited == 0 && 1925 tp->t_dupacks == 2, 1926 ("sent too much")); 1927 tp->snd_limited = 2; 1928 } else if (sent > 0) 1929 ++tp->snd_limited; 1930 tp->snd_cwnd = oldcwnd; 1931 goto drop; 1932 } 1933 } else 1934 tp->t_dupacks = 0; 1935 break; 1936 } 1937 1938 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1939 1940 /* 1941 * If the congestion window was inflated to account 1942 * for the other side's cached packets, retract it. 1943 */ 1944 if (tcp_do_newreno) { 1945 if (IN_FASTRECOVERY(tp)) { 1946 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1947 tcp_newreno_partial_ack(tp, th); 1948 } else { 1949 /* 1950 * Window inflation should have left us 1951 * with approximately snd_ssthresh 1952 * outstanding data. 1953 * But in case we would be inclined to 1954 * send a burst, better to do it via 1955 * the slow start mechanism. 1956 */ 1957 if (SEQ_GT(th->th_ack + 1958 tp->snd_ssthresh, 1959 tp->snd_max)) 1960 tp->snd_cwnd = tp->snd_max - 1961 th->th_ack + 1962 tp->t_maxseg; 1963 else 1964 tp->snd_cwnd = tp->snd_ssthresh; 1965 } 1966 } 1967 } else { 1968 if (tp->t_dupacks >= tcprexmtthresh && 1969 tp->snd_cwnd > tp->snd_ssthresh) 1970 tp->snd_cwnd = tp->snd_ssthresh; 1971 } 1972 tp->t_dupacks = 0; 1973 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1974 tcpstat.tcps_rcvacktoomuch++; 1975 goto dropafterack; 1976 } 1977 /* 1978 * If we reach this point, ACK is not a duplicate, 1979 * i.e., it ACKs something we sent. 1980 */ 1981 if (tp->t_flags & TF_NEEDSYN) { 1982 /* 1983 * T/TCP: Connection was half-synchronized, and our 1984 * SYN has been ACK'd (so connection is now fully 1985 * synchronized). Go to non-starred state, 1986 * increment snd_una for ACK of SYN, and check if 1987 * we can do window scaling. 1988 */ 1989 tp->t_flags &= ~TF_NEEDSYN; 1990 tp->snd_una++; 1991 /* Do window scaling? */ 1992 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1993 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1994 tp->snd_scale = tp->requested_s_scale; 1995 tp->rcv_scale = tp->request_r_scale; 1996 } 1997 } 1998 1999 process_ACK: 2000 acked = th->th_ack - tp->snd_una; 2001 tcpstat.tcps_rcvackpack++; 2002 tcpstat.tcps_rcvackbyte += acked; 2003 2004 /* 2005 * If we just performed our first retransmit, and the ACK 2006 * arrives within our recovery window, then it was a mistake 2007 * to do the retransmit in the first place. Recover our 2008 * original cwnd and ssthresh, and proceed to transmit where 2009 * we left off. 2010 */ 2011 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2012 ++tcpstat.tcps_sndrexmitbad; 2013 tp->snd_cwnd = tp->snd_cwnd_prev; 2014 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2015 tp->snd_recover = tp->snd_recover_prev; 2016 if (tp->t_flags & TF_WASFRECOVERY) 2017 ENTER_FASTRECOVERY(tp); 2018 tp->snd_nxt = tp->snd_max; 2019 tp->t_badrxtwin = 0; /* XXX probably not required */ 2020 } 2021 2022 /* 2023 * If we have a timestamp reply, update smoothed 2024 * round trip time. If no timestamp is present but 2025 * transmit timer is running and timed sequence 2026 * number was acked, update smoothed round trip time. 2027 * Since we now have an rtt measurement, cancel the 2028 * timer backoff (cf., Phil Karn's retransmit alg.). 2029 * Recompute the initial retransmit timer. 2030 * 2031 * Some boxes send broken timestamp replies 2032 * during the SYN+ACK phase, ignore 2033 * timestamps of 0 or we could calculate a 2034 * huge RTT and blow up the retransmit timer. 2035 */ 2036 if ((to.to_flags & TOF_TS) != 0 && 2037 to.to_tsecr) { 2038 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2039 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2040 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2041 } 2042 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2043 2044 /* 2045 * If all outstanding data is acked, stop retransmit 2046 * timer and remember to restart (more output or persist). 2047 * If there is more data to be acked, restart retransmit 2048 * timer, using current (possibly backed-off) value. 2049 */ 2050 if (th->th_ack == tp->snd_max) { 2051 callout_stop(tp->tt_rexmt); 2052 needoutput = 1; 2053 } else if (!callout_active(tp->tt_persist)) 2054 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2055 tcp_timer_rexmt, tp); 2056 2057 /* 2058 * If no data (only SYN) was ACK'd, 2059 * skip rest of ACK processing. 2060 */ 2061 if (acked == 0) 2062 goto step6; 2063 2064 /* 2065 * When new data is acked, open the congestion window. 2066 * If the window gives us less than ssthresh packets 2067 * in flight, open exponentially (maxseg per packet). 2068 * Otherwise open linearly: maxseg per window 2069 * (maxseg^2 / cwnd per packet). 2070 */ 2071 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) { 2072 register u_int cw = tp->snd_cwnd; 2073 register u_int incr = tp->t_maxseg; 2074 if (cw > tp->snd_ssthresh) 2075 incr = incr * incr / cw; 2076 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2077 } 2078 if (acked > so->so_snd.sb_cc) { 2079 tp->snd_wnd -= so->so_snd.sb_cc; 2080 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2081 ourfinisacked = 1; 2082 } else { 2083 sbdrop(&so->so_snd, acked); 2084 tp->snd_wnd -= acked; 2085 ourfinisacked = 0; 2086 } 2087 sowwakeup(so); 2088 /* detect una wraparound */ 2089 if (tcp_do_newreno && !IN_FASTRECOVERY(tp) && 2090 SEQ_GT(tp->snd_una, tp->snd_recover) && 2091 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2092 tp->snd_recover = th->th_ack - 1; 2093 if (tcp_do_newreno && IN_FASTRECOVERY(tp) && 2094 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2095 EXIT_FASTRECOVERY(tp); 2096 tp->snd_una = th->th_ack; 2097 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2098 tp->snd_nxt = tp->snd_una; 2099 2100 switch (tp->t_state) { 2101 2102 /* 2103 * In FIN_WAIT_1 STATE in addition to the processing 2104 * for the ESTABLISHED state if our FIN is now acknowledged 2105 * then enter FIN_WAIT_2. 2106 */ 2107 case TCPS_FIN_WAIT_1: 2108 if (ourfinisacked) { 2109 /* 2110 * If we can't receive any more 2111 * data, then closing user can proceed. 2112 * Starting the timer is contrary to the 2113 * specification, but if we don't get a FIN 2114 * we'll hang forever. 2115 */ 2116 /* XXXjl 2117 * we should release the tp also, and use a 2118 * compressed state. 2119 */ 2120 if (so->so_state & SS_CANTRCVMORE) { 2121 soisdisconnected(so); 2122 callout_reset(tp->tt_2msl, tcp_maxidle, 2123 tcp_timer_2msl, tp); 2124 } 2125 tp->t_state = TCPS_FIN_WAIT_2; 2126 } 2127 break; 2128 2129 /* 2130 * In CLOSING STATE in addition to the processing for 2131 * the ESTABLISHED state if the ACK acknowledges our FIN 2132 * then enter the TIME-WAIT state, otherwise ignore 2133 * the segment. 2134 */ 2135 case TCPS_CLOSING: 2136 if (ourfinisacked) { 2137 KASSERT(headlocked, ("headlocked")); 2138 tcp_twstart(tp); 2139 INP_INFO_WUNLOCK(&tcbinfo); 2140 m_freem(m); 2141 return; 2142 } 2143 break; 2144 2145 /* 2146 * In LAST_ACK, we may still be waiting for data to drain 2147 * and/or to be acked, as well as for the ack of our FIN. 2148 * If our FIN is now acknowledged, delete the TCB, 2149 * enter the closed state and return. 2150 */ 2151 case TCPS_LAST_ACK: 2152 if (ourfinisacked) { 2153 tp = tcp_close(tp); 2154 goto drop; 2155 } 2156 break; 2157 2158 /* 2159 * In TIME_WAIT state the only thing that should arrive 2160 * is a retransmission of the remote FIN. Acknowledge 2161 * it and restart the finack timer. 2162 */ 2163 case TCPS_TIME_WAIT: 2164 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2165 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2166 tcp_timer_2msl, tp); 2167 goto dropafterack; 2168 } 2169 } 2170 2171 step6: 2172 /* 2173 * Update window information. 2174 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2175 */ 2176 if ((thflags & TH_ACK) && 2177 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2178 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2179 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2180 /* keep track of pure window updates */ 2181 if (tlen == 0 && 2182 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2183 tcpstat.tcps_rcvwinupd++; 2184 tp->snd_wnd = tiwin; 2185 tp->snd_wl1 = th->th_seq; 2186 tp->snd_wl2 = th->th_ack; 2187 if (tp->snd_wnd > tp->max_sndwnd) 2188 tp->max_sndwnd = tp->snd_wnd; 2189 needoutput = 1; 2190 } 2191 2192 /* 2193 * Process segments with URG. 2194 */ 2195 if ((thflags & TH_URG) && th->th_urp && 2196 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2197 /* 2198 * This is a kludge, but if we receive and accept 2199 * random urgent pointers, we'll crash in 2200 * soreceive. It's hard to imagine someone 2201 * actually wanting to send this much urgent data. 2202 */ 2203 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2204 th->th_urp = 0; /* XXX */ 2205 thflags &= ~TH_URG; /* XXX */ 2206 goto dodata; /* XXX */ 2207 } 2208 /* 2209 * If this segment advances the known urgent pointer, 2210 * then mark the data stream. This should not happen 2211 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2212 * a FIN has been received from the remote side. 2213 * In these states we ignore the URG. 2214 * 2215 * According to RFC961 (Assigned Protocols), 2216 * the urgent pointer points to the last octet 2217 * of urgent data. We continue, however, 2218 * to consider it to indicate the first octet 2219 * of data past the urgent section as the original 2220 * spec states (in one of two places). 2221 */ 2222 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2223 tp->rcv_up = th->th_seq + th->th_urp; 2224 so->so_oobmark = so->so_rcv.sb_cc + 2225 (tp->rcv_up - tp->rcv_nxt) - 1; 2226 if (so->so_oobmark == 0) 2227 so->so_state |= SS_RCVATMARK; 2228 sohasoutofband(so); 2229 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2230 } 2231 /* 2232 * Remove out of band data so doesn't get presented to user. 2233 * This can happen independent of advancing the URG pointer, 2234 * but if two URG's are pending at once, some out-of-band 2235 * data may creep in... ick. 2236 */ 2237 if (th->th_urp <= (u_long)tlen && 2238 !(so->so_options & SO_OOBINLINE)) { 2239 /* hdr drop is delayed */ 2240 tcp_pulloutofband(so, th, m, drop_hdrlen); 2241 } 2242 } else { 2243 /* 2244 * If no out of band data is expected, 2245 * pull receive urgent pointer along 2246 * with the receive window. 2247 */ 2248 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2249 tp->rcv_up = tp->rcv_nxt; 2250 } 2251 dodata: /* XXX */ 2252 KASSERT(headlocked, ("headlocked")); 2253 /* 2254 * Process the segment text, merging it into the TCP sequencing queue, 2255 * and arranging for acknowledgment of receipt if necessary. 2256 * This process logically involves adjusting tp->rcv_wnd as data 2257 * is presented to the user (this happens in tcp_usrreq.c, 2258 * case PRU_RCVD). If a FIN has already been received on this 2259 * connection then we just ignore the text. 2260 */ 2261 if ((tlen || (thflags & TH_FIN)) && 2262 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2263 m_adj(m, drop_hdrlen); /* delayed header drop */ 2264 /* 2265 * Insert segment which includes th into TCP reassembly queue 2266 * with control block tp. Set thflags to whether reassembly now 2267 * includes a segment with FIN. This handles the common case 2268 * inline (segment is the next to be received on an established 2269 * connection, and the queue is empty), avoiding linkage into 2270 * and removal from the queue and repetition of various 2271 * conversions. 2272 * Set DELACK for segments received in order, but ack 2273 * immediately when segments are out of order (so 2274 * fast retransmit can work). 2275 */ 2276 if (th->th_seq == tp->rcv_nxt && 2277 LIST_EMPTY(&tp->t_segq) && 2278 TCPS_HAVEESTABLISHED(tp->t_state)) { 2279 if (DELAY_ACK(tp)) 2280 tp->t_flags |= TF_DELACK; 2281 else 2282 tp->t_flags |= TF_ACKNOW; 2283 tp->rcv_nxt += tlen; 2284 thflags = th->th_flags & TH_FIN; 2285 tcpstat.tcps_rcvpack++; 2286 tcpstat.tcps_rcvbyte += tlen; 2287 ND6_HINT(tp); 2288 if (so->so_state & SS_CANTRCVMORE) 2289 m_freem(m); 2290 else 2291 sbappendstream(&so->so_rcv, m); 2292 sorwakeup(so); 2293 } else { 2294 thflags = tcp_reass(tp, th, &tlen, m); 2295 tp->t_flags |= TF_ACKNOW; 2296 } 2297 2298 /* 2299 * Note the amount of data that peer has sent into 2300 * our window, in order to estimate the sender's 2301 * buffer size. 2302 */ 2303 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2304 } else { 2305 m_freem(m); 2306 thflags &= ~TH_FIN; 2307 } 2308 2309 /* 2310 * If FIN is received ACK the FIN and let the user know 2311 * that the connection is closing. 2312 */ 2313 if (thflags & TH_FIN) { 2314 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2315 socantrcvmore(so); 2316 /* 2317 * If connection is half-synchronized 2318 * (ie NEEDSYN flag on) then delay ACK, 2319 * so it may be piggybacked when SYN is sent. 2320 * Otherwise, since we received a FIN then no 2321 * more input can be expected, send ACK now. 2322 */ 2323 if (tp->t_flags & TF_NEEDSYN) 2324 tp->t_flags |= TF_DELACK; 2325 else 2326 tp->t_flags |= TF_ACKNOW; 2327 tp->rcv_nxt++; 2328 } 2329 switch (tp->t_state) { 2330 2331 /* 2332 * In SYN_RECEIVED and ESTABLISHED STATES 2333 * enter the CLOSE_WAIT state. 2334 */ 2335 case TCPS_SYN_RECEIVED: 2336 tp->t_starttime = ticks; 2337 /*FALLTHROUGH*/ 2338 case TCPS_ESTABLISHED: 2339 tp->t_state = TCPS_CLOSE_WAIT; 2340 break; 2341 2342 /* 2343 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2344 * enter the CLOSING state. 2345 */ 2346 case TCPS_FIN_WAIT_1: 2347 tp->t_state = TCPS_CLOSING; 2348 break; 2349 2350 /* 2351 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2352 * starting the time-wait timer, turning off the other 2353 * standard timers. 2354 */ 2355 case TCPS_FIN_WAIT_2: 2356 KASSERT(headlocked == 1, ("headlocked should be 1")); 2357 tcp_twstart(tp); 2358 INP_INFO_WUNLOCK(&tcbinfo); 2359 return; 2360 2361 /* 2362 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2363 */ 2364 case TCPS_TIME_WAIT: 2365 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2366 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2367 tcp_timer_2msl, tp); 2368 break; 2369 } 2370 } 2371 INP_INFO_WUNLOCK(&tcbinfo); 2372 #ifdef TCPDEBUG 2373 if (so->so_options & SO_DEBUG) 2374 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2375 &tcp_savetcp, 0); 2376 #endif 2377 2378 /* 2379 * Return any desired output. 2380 */ 2381 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2382 (void) tcp_output(tp); 2383 2384 check_delack: 2385 if (tp->t_flags & TF_DELACK) { 2386 tp->t_flags &= ~TF_DELACK; 2387 callout_reset(tp->tt_delack, tcp_delacktime, 2388 tcp_timer_delack, tp); 2389 } 2390 INP_UNLOCK(inp); 2391 return; 2392 2393 dropafterack: 2394 /* 2395 * Generate an ACK dropping incoming segment if it occupies 2396 * sequence space, where the ACK reflects our state. 2397 * 2398 * We can now skip the test for the RST flag since all 2399 * paths to this code happen after packets containing 2400 * RST have been dropped. 2401 * 2402 * In the SYN-RECEIVED state, don't send an ACK unless the 2403 * segment we received passes the SYN-RECEIVED ACK test. 2404 * If it fails send a RST. This breaks the loop in the 2405 * "LAND" DoS attack, and also prevents an ACK storm 2406 * between two listening ports that have been sent forged 2407 * SYN segments, each with the source address of the other. 2408 */ 2409 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2410 (SEQ_GT(tp->snd_una, th->th_ack) || 2411 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2412 rstreason = BANDLIM_RST_OPENPORT; 2413 goto dropwithreset; 2414 } 2415 #ifdef TCPDEBUG 2416 if (so->so_options & SO_DEBUG) 2417 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2418 &tcp_savetcp, 0); 2419 #endif 2420 KASSERT(headlocked, ("headlocked should be 1")); 2421 INP_INFO_WUNLOCK(&tcbinfo); 2422 m_freem(m); 2423 tp->t_flags |= TF_ACKNOW; 2424 (void) tcp_output(tp); 2425 INP_UNLOCK(inp); 2426 return; 2427 2428 dropwithreset: 2429 /* 2430 * Generate a RST, dropping incoming segment. 2431 * Make ACK acceptable to originator of segment. 2432 * Don't bother to respond if destination was broadcast/multicast. 2433 */ 2434 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2435 goto drop; 2436 if (isipv6) { 2437 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2438 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2439 goto drop; 2440 } else { 2441 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2442 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2443 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2444 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2445 goto drop; 2446 } 2447 /* IPv6 anycast check is done at tcp6_input() */ 2448 2449 /* 2450 * Perform bandwidth limiting. 2451 */ 2452 if (badport_bandlim(rstreason) < 0) 2453 goto drop; 2454 2455 #ifdef TCPDEBUG 2456 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2457 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2458 &tcp_savetcp, 0); 2459 #endif 2460 2461 if (thflags & TH_ACK) 2462 /* mtod() below is safe as long as hdr dropping is delayed */ 2463 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2464 TH_RST); 2465 else { 2466 if (thflags & TH_SYN) 2467 tlen++; 2468 /* mtod() below is safe as long as hdr dropping is delayed */ 2469 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2470 (tcp_seq)0, TH_RST|TH_ACK); 2471 } 2472 2473 if (tp) 2474 INP_UNLOCK(inp); 2475 if (headlocked) 2476 INP_INFO_WUNLOCK(&tcbinfo); 2477 return; 2478 2479 drop: 2480 /* 2481 * Drop space held by incoming segment and return. 2482 */ 2483 #ifdef TCPDEBUG 2484 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2485 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2486 &tcp_savetcp, 0); 2487 #endif 2488 if (tp) 2489 INP_UNLOCK(inp); 2490 m_freem(m); 2491 if (headlocked) 2492 INP_INFO_WUNLOCK(&tcbinfo); 2493 return; 2494 } 2495 2496 /* 2497 * Parse TCP options and place in tcpopt. 2498 */ 2499 static void 2500 tcp_dooptions(to, cp, cnt, is_syn) 2501 struct tcpopt *to; 2502 u_char *cp; 2503 int cnt; 2504 int is_syn; 2505 { 2506 int opt, optlen; 2507 2508 to->to_flags = 0; 2509 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2510 opt = cp[0]; 2511 if (opt == TCPOPT_EOL) 2512 break; 2513 if (opt == TCPOPT_NOP) 2514 optlen = 1; 2515 else { 2516 if (cnt < 2) 2517 break; 2518 optlen = cp[1]; 2519 if (optlen < 2 || optlen > cnt) 2520 break; 2521 } 2522 switch (opt) { 2523 case TCPOPT_MAXSEG: 2524 if (optlen != TCPOLEN_MAXSEG) 2525 continue; 2526 if (!is_syn) 2527 continue; 2528 to->to_flags |= TOF_MSS; 2529 bcopy((char *)cp + 2, 2530 (char *)&to->to_mss, sizeof(to->to_mss)); 2531 to->to_mss = ntohs(to->to_mss); 2532 break; 2533 case TCPOPT_WINDOW: 2534 if (optlen != TCPOLEN_WINDOW) 2535 continue; 2536 if (! is_syn) 2537 continue; 2538 to->to_flags |= TOF_SCALE; 2539 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2540 break; 2541 case TCPOPT_TIMESTAMP: 2542 if (optlen != TCPOLEN_TIMESTAMP) 2543 continue; 2544 to->to_flags |= TOF_TS; 2545 bcopy((char *)cp + 2, 2546 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2547 to->to_tsval = ntohl(to->to_tsval); 2548 bcopy((char *)cp + 6, 2549 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2550 to->to_tsecr = ntohl(to->to_tsecr); 2551 break; 2552 case TCPOPT_CC: 2553 if (optlen != TCPOLEN_CC) 2554 continue; 2555 to->to_flags |= TOF_CC; 2556 bcopy((char *)cp + 2, 2557 (char *)&to->to_cc, sizeof(to->to_cc)); 2558 to->to_cc = ntohl(to->to_cc); 2559 break; 2560 case TCPOPT_CCNEW: 2561 if (optlen != TCPOLEN_CC) 2562 continue; 2563 if (!is_syn) 2564 continue; 2565 to->to_flags |= TOF_CCNEW; 2566 bcopy((char *)cp + 2, 2567 (char *)&to->to_cc, sizeof(to->to_cc)); 2568 to->to_cc = ntohl(to->to_cc); 2569 break; 2570 case TCPOPT_CCECHO: 2571 if (optlen != TCPOLEN_CC) 2572 continue; 2573 if (!is_syn) 2574 continue; 2575 to->to_flags |= TOF_CCECHO; 2576 bcopy((char *)cp + 2, 2577 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2578 to->to_ccecho = ntohl(to->to_ccecho); 2579 break; 2580 default: 2581 continue; 2582 } 2583 } 2584 } 2585 2586 /* 2587 * Pull out of band byte out of a segment so 2588 * it doesn't appear in the user's data queue. 2589 * It is still reflected in the segment length for 2590 * sequencing purposes. 2591 */ 2592 static void 2593 tcp_pulloutofband(so, th, m, off) 2594 struct socket *so; 2595 struct tcphdr *th; 2596 register struct mbuf *m; 2597 int off; /* delayed to be droped hdrlen */ 2598 { 2599 int cnt = off + th->th_urp - 1; 2600 2601 while (cnt >= 0) { 2602 if (m->m_len > cnt) { 2603 char *cp = mtod(m, caddr_t) + cnt; 2604 struct tcpcb *tp = sototcpcb(so); 2605 2606 tp->t_iobc = *cp; 2607 tp->t_oobflags |= TCPOOB_HAVEDATA; 2608 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2609 m->m_len--; 2610 if (m->m_flags & M_PKTHDR) 2611 m->m_pkthdr.len--; 2612 return; 2613 } 2614 cnt -= m->m_len; 2615 m = m->m_next; 2616 if (m == 0) 2617 break; 2618 } 2619 panic("tcp_pulloutofband"); 2620 } 2621 2622 /* 2623 * Collect new round-trip time estimate 2624 * and update averages and current timeout. 2625 */ 2626 static void 2627 tcp_xmit_timer(tp, rtt) 2628 register struct tcpcb *tp; 2629 int rtt; 2630 { 2631 register int delta; 2632 2633 tcpstat.tcps_rttupdated++; 2634 tp->t_rttupdated++; 2635 if (tp->t_srtt != 0) { 2636 /* 2637 * srtt is stored as fixed point with 5 bits after the 2638 * binary point (i.e., scaled by 8). The following magic 2639 * is equivalent to the smoothing algorithm in rfc793 with 2640 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2641 * point). Adjust rtt to origin 0. 2642 */ 2643 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2644 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2645 2646 if ((tp->t_srtt += delta) <= 0) 2647 tp->t_srtt = 1; 2648 2649 /* 2650 * We accumulate a smoothed rtt variance (actually, a 2651 * smoothed mean difference), then set the retransmit 2652 * timer to smoothed rtt + 4 times the smoothed variance. 2653 * rttvar is stored as fixed point with 4 bits after the 2654 * binary point (scaled by 16). The following is 2655 * equivalent to rfc793 smoothing with an alpha of .75 2656 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2657 * rfc793's wired-in beta. 2658 */ 2659 if (delta < 0) 2660 delta = -delta; 2661 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2662 if ((tp->t_rttvar += delta) <= 0) 2663 tp->t_rttvar = 1; 2664 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2665 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2666 } else { 2667 /* 2668 * No rtt measurement yet - use the unsmoothed rtt. 2669 * Set the variance to half the rtt (so our first 2670 * retransmit happens at 3*rtt). 2671 */ 2672 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2673 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2674 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2675 } 2676 tp->t_rtttime = 0; 2677 tp->t_rxtshift = 0; 2678 2679 /* 2680 * the retransmit should happen at rtt + 4 * rttvar. 2681 * Because of the way we do the smoothing, srtt and rttvar 2682 * will each average +1/2 tick of bias. When we compute 2683 * the retransmit timer, we want 1/2 tick of rounding and 2684 * 1 extra tick because of +-1/2 tick uncertainty in the 2685 * firing of the timer. The bias will give us exactly the 2686 * 1.5 tick we need. But, because the bias is 2687 * statistical, we have to test that we don't drop below 2688 * the minimum feasible timer (which is 2 ticks). 2689 */ 2690 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2691 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2692 2693 /* 2694 * We received an ack for a packet that wasn't retransmitted; 2695 * it is probably safe to discard any error indications we've 2696 * received recently. This isn't quite right, but close enough 2697 * for now (a route might have failed after we sent a segment, 2698 * and the return path might not be symmetrical). 2699 */ 2700 tp->t_softerror = 0; 2701 } 2702 2703 /* 2704 * Determine a reasonable value for maxseg size. 2705 * If the route is known, check route for mtu. 2706 * If none, use an mss that can be handled on the outgoing 2707 * interface without forcing IP to fragment; if bigger than 2708 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2709 * to utilize large mbufs. If no route is found, route has no mtu, 2710 * or the destination isn't local, use a default, hopefully conservative 2711 * size (usually 512 or the default IP max size, but no more than the mtu 2712 * of the interface), as we can't discover anything about intervening 2713 * gateways or networks. We also initialize the congestion/slow start 2714 * window to be a single segment if the destination isn't local. 2715 * While looking at the routing entry, we also initialize other path-dependent 2716 * parameters from pre-set or cached values in the routing entry. 2717 * 2718 * Also take into account the space needed for options that we 2719 * send regularly. Make maxseg shorter by that amount to assure 2720 * that we can send maxseg amount of data even when the options 2721 * are present. Store the upper limit of the length of options plus 2722 * data in maxopd. 2723 * 2724 * 2725 * In case of T/TCP, we call this routine during implicit connection 2726 * setup as well (offer = -1), to initialize maxseg from the cached 2727 * MSS of our peer. 2728 * 2729 * NOTE that this routine is only called when we process an incoming 2730 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2731 */ 2732 void 2733 tcp_mss(tp, offer) 2734 struct tcpcb *tp; 2735 int offer; 2736 { 2737 int rtt, mss; 2738 u_long bufsize; 2739 u_long maxmtu; 2740 struct inpcb *inp = tp->t_inpcb; 2741 struct socket *so; 2742 struct hc_metrics_lite metrics; 2743 struct rmxp_tao tao; 2744 int origoffer = offer; 2745 #ifdef INET6 2746 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2747 size_t min_protoh = isipv6 ? 2748 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2749 sizeof (struct tcpiphdr); 2750 #else 2751 const size_t min_protoh = sizeof(struct tcpiphdr); 2752 #endif 2753 bzero(&tao, sizeof(tao)); 2754 2755 /* initialize */ 2756 #ifdef INET6 2757 if (isipv6) { 2758 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2759 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2760 } else 2761 #endif 2762 { 2763 maxmtu = tcp_maxmtu(&inp->inp_inc); 2764 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2765 } 2766 so = inp->inp_socket; 2767 2768 /* 2769 * no route to sender, take default mss and return 2770 */ 2771 if (maxmtu == 0) 2772 return; 2773 2774 /* what have we got? */ 2775 switch (offer) { 2776 case 0: 2777 /* 2778 * Offer == 0 means that there was no MSS on the SYN 2779 * segment, in this case we use tcp_mssdflt. 2780 */ 2781 offer = 2782 #ifdef INET6 2783 isipv6 ? tcp_v6mssdflt : 2784 #endif 2785 tcp_mssdflt; 2786 break; 2787 2788 case -1: 2789 /* 2790 * Offer == -1 means that we didn't receive SYN yet, 2791 * use cached value in that case; 2792 */ 2793 if (tcp_do_rfc1644) 2794 tcp_hc_gettao(&inp->inp_inc, &tao); 2795 if (tao.tao_mssopt != 0) 2796 offer = tao.tao_mssopt; 2797 /* FALLTHROUGH */ 2798 2799 default: 2800 /* 2801 * Prevent DoS attack with too small MSS. Round up 2802 * to at least minmss. 2803 */ 2804 offer = max(offer, tcp_minmss); 2805 /* 2806 * Sanity check: make sure that maxopd will be large 2807 * enough to allow some data on segments even if the 2808 * all the option space is used (40bytes). Otherwise 2809 * funny things may happen in tcp_output. 2810 */ 2811 offer = max(offer, 64); 2812 if (tcp_do_rfc1644) 2813 tcp_hc_updatetao(&inp->inp_inc, 2814 TCP_HC_TAO_MSSOPT, 0, offer); 2815 } 2816 2817 /* 2818 * rmx information is now retrieved from tcp_hostcache 2819 */ 2820 tcp_hc_get(&inp->inp_inc, &metrics); 2821 2822 /* 2823 * if there's a discovered mtu int tcp hostcache, use it 2824 * else, use the link mtu. 2825 */ 2826 if (metrics.rmx_mtu) 2827 mss = metrics.rmx_mtu - min_protoh; 2828 else { 2829 #ifdef INET6 2830 if (isipv6) { 2831 mss = maxmtu - min_protoh; 2832 if (!path_mtu_discovery && 2833 !in6_localaddr(&inp->in6p_faddr)) 2834 mss = min(mss, tcp_v6mssdflt); 2835 } else 2836 #endif 2837 { 2838 mss = maxmtu - min_protoh; 2839 if (!path_mtu_discovery && 2840 !in_localaddr(inp->inp_faddr)) 2841 mss = min(mss, tcp_mssdflt); 2842 } 2843 } 2844 mss = min(mss, offer); 2845 2846 /* 2847 * maxopd stores the maximum length of data AND options 2848 * in a segment; maxseg is the amount of data in a normal 2849 * segment. We need to store this value (maxopd) apart 2850 * from maxseg, because now every segment carries options 2851 * and thus we normally have somewhat less data in segments. 2852 */ 2853 tp->t_maxopd = mss; 2854 2855 /* 2856 * In case of T/TCP, origoffer==-1 indicates, that no segments 2857 * were received yet. In this case we just guess, otherwise 2858 * we do the same as before T/TCP. 2859 */ 2860 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2861 (origoffer == -1 || 2862 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2863 mss -= TCPOLEN_TSTAMP_APPA; 2864 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2865 (origoffer == -1 || 2866 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2867 mss -= TCPOLEN_CC_APPA; 2868 tp->t_maxseg = mss; 2869 2870 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2871 if (mss > MCLBYTES) 2872 mss &= ~(MCLBYTES-1); 2873 #else 2874 if (mss > MCLBYTES) 2875 mss = mss / MCLBYTES * MCLBYTES; 2876 #endif 2877 tp->t_maxseg = mss; 2878 2879 /* 2880 * If there's a pipesize, change the socket buffer to that size, 2881 * don't change if sb_hiwat is different than default (then it 2882 * has been changed on purpose with setsockopt). 2883 * Make the socket buffers an integral number of mss units; 2884 * if the mss is larger than the socket buffer, decrease the mss. 2885 */ 2886 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2887 bufsize = metrics.rmx_sendpipe; 2888 else 2889 bufsize = so->so_snd.sb_hiwat; 2890 if (bufsize < mss) 2891 mss = bufsize; 2892 else { 2893 bufsize = roundup(bufsize, mss); 2894 if (bufsize > sb_max) 2895 bufsize = sb_max; 2896 if (bufsize > so->so_snd.sb_hiwat) 2897 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2898 } 2899 tp->t_maxseg = mss; 2900 2901 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 2902 bufsize = metrics.rmx_recvpipe; 2903 else 2904 bufsize = so->so_rcv.sb_hiwat; 2905 if (bufsize > mss) { 2906 bufsize = roundup(bufsize, mss); 2907 if (bufsize > sb_max) 2908 bufsize = sb_max; 2909 if (bufsize > so->so_rcv.sb_hiwat) 2910 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2911 } 2912 /* 2913 * While we're here, check the others too 2914 */ 2915 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 2916 tp->t_srtt = rtt; 2917 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2918 tcpstat.tcps_usedrtt++; 2919 if (metrics.rmx_rttvar) { 2920 tp->t_rttvar = metrics.rmx_rttvar; 2921 tcpstat.tcps_usedrttvar++; 2922 } else { 2923 /* default variation is +- 1 rtt */ 2924 tp->t_rttvar = 2925 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2926 } 2927 TCPT_RANGESET(tp->t_rxtcur, 2928 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2929 tp->t_rttmin, TCPTV_REXMTMAX); 2930 } 2931 if (metrics.rmx_ssthresh) { 2932 /* 2933 * There's some sort of gateway or interface 2934 * buffer limit on the path. Use this to set 2935 * the slow start threshhold, but set the 2936 * threshold to no less than 2*mss. 2937 */ 2938 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 2939 tcpstat.tcps_usedssthresh++; 2940 } 2941 if (metrics.rmx_bandwidth) 2942 tp->snd_bandwidth = metrics.rmx_bandwidth; 2943 2944 /* 2945 * Set the slow-start flight size depending on whether this 2946 * is a local network or not. 2947 * 2948 * Extend this so we cache the cwnd too and retrieve it here. 2949 * Make cwnd even bigger than RFC3390 suggests but only if we 2950 * have previous experience with the remote host. Be careful 2951 * not make cwnd bigger than remote receive window or our own 2952 * send socket buffer. Maybe put some additional upper bound 2953 * on the retrieved cwnd. Should do incremental updates to 2954 * hostcache when cwnd collapses so next connection doesn't 2955 * overloads the path again. 2956 * 2957 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 2958 * We currently check only in syncache_socket for that. 2959 */ 2960 #define TCP_METRICS_CWND 2961 #ifdef TCP_METRICS_CWND 2962 if (metrics.rmx_cwnd) 2963 tp->snd_cwnd = max(mss, 2964 min(metrics.rmx_cwnd / 2, 2965 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 2966 else 2967 #endif 2968 if (tcp_do_rfc3390) 2969 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 2970 #ifdef INET6 2971 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2972 (!isipv6 && in_localaddr(inp->inp_faddr))) 2973 #else 2974 else if (in_localaddr(inp->inp_faddr)) 2975 #endif 2976 tp->snd_cwnd = mss * ss_fltsz_local; 2977 else 2978 tp->snd_cwnd = mss * ss_fltsz; 2979 } 2980 2981 /* 2982 * Determine the MSS option to send on an outgoing SYN. 2983 */ 2984 int 2985 tcp_mssopt(inc) 2986 struct in_conninfo *inc; 2987 { 2988 int mss = 0; 2989 u_long maxmtu = 0; 2990 u_long thcmtu = 0; 2991 size_t min_protoh; 2992 #ifdef INET6 2993 int isipv6 = inc->inc_isipv6 ? 1 : 0; 2994 #endif 2995 2996 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 2997 2998 #ifdef INET6 2999 if (isipv6) { 3000 mss = tcp_v6mssdflt; 3001 maxmtu = tcp_maxmtu6(inc); 3002 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3003 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3004 } else 3005 #endif 3006 { 3007 mss = tcp_mssdflt; 3008 maxmtu = tcp_maxmtu(inc); 3009 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3010 min_protoh = sizeof(struct tcpiphdr); 3011 } 3012 if (maxmtu && thcmtu) 3013 mss = min(maxmtu, thcmtu) - min_protoh; 3014 else if (maxmtu || thcmtu) 3015 mss = max(maxmtu, thcmtu) - min_protoh; 3016 3017 return (mss); 3018 } 3019 3020 3021 /* 3022 * On a partial ack arrives, force the retransmission of the 3023 * next unacknowledged segment. Do not clear tp->t_dupacks. 3024 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3025 * be started again. 3026 */ 3027 static void 3028 tcp_newreno_partial_ack(tp, th) 3029 struct tcpcb *tp; 3030 struct tcphdr *th; 3031 { 3032 tcp_seq onxt = tp->snd_nxt; 3033 u_long ocwnd = tp->snd_cwnd; 3034 3035 callout_stop(tp->tt_rexmt); 3036 tp->t_rtttime = 0; 3037 tp->snd_nxt = th->th_ack; 3038 /* 3039 * Set snd_cwnd to one segment beyond acknowledged offset. 3040 * (tp->snd_una has not yet been updated when this function is called.) 3041 */ 3042 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3043 tp->t_flags |= TF_ACKNOW; 3044 (void) tcp_output(tp); 3045 tp->snd_cwnd = ocwnd; 3046 if (SEQ_GT(onxt, tp->snd_nxt)) 3047 tp->snd_nxt = onxt; 3048 /* 3049 * Partial window deflation. Relies on fact that tp->snd_una 3050 * not updated yet. 3051 */ 3052 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 3053 } 3054 3055 /* 3056 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3057 * looking for a pcb in the listen state. Returns 0 otherwise. 3058 */ 3059 static int 3060 tcp_timewait(tw, to, th, m, tlen) 3061 struct tcptw *tw; 3062 struct tcpopt *to; 3063 struct tcphdr *th; 3064 struct mbuf *m; 3065 int tlen; 3066 { 3067 int thflags; 3068 tcp_seq seq; 3069 #ifdef INET6 3070 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3071 #else 3072 const int isipv6 = 0; 3073 #endif 3074 3075 thflags = th->th_flags; 3076 3077 /* 3078 * NOTE: for FIN_WAIT_2 (to be added later), 3079 * must validate sequence number before accepting RST 3080 */ 3081 3082 /* 3083 * If the segment contains RST: 3084 * Drop the segment - see Stevens, vol. 2, p. 964 and 3085 * RFC 1337. 3086 */ 3087 if (thflags & TH_RST) 3088 goto drop; 3089 3090 /* 3091 * If segment contains a SYN and CC [not CC.NEW] option: 3092 * if connection duration > MSL, drop packet and send RST; 3093 * 3094 * if SEG.CC > CCrecv then is new SYN. 3095 * Complete close and delete TCPCB. Then reprocess 3096 * segment, hoping to find new TCPCB in LISTEN state; 3097 * 3098 * else must be old SYN; drop it. 3099 * else do normal processing. 3100 */ 3101 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) { 3102 if ((ticks - tw->t_starttime) > tcp_msl) 3103 goto reset; 3104 if (CC_GT(to->to_cc, tw->cc_recv)) { 3105 (void) tcp_twclose(tw, 0); 3106 return (1); 3107 } 3108 goto drop; 3109 } 3110 3111 #if 0 3112 /* PAWS not needed at the moment */ 3113 /* 3114 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3115 * and it's less than ts_recent, drop it. 3116 */ 3117 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3118 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3119 if ((thflags & TH_ACK) == 0) 3120 goto drop; 3121 goto ack; 3122 } 3123 /* 3124 * ts_recent is never updated because we never accept new segments. 3125 */ 3126 #endif 3127 3128 /* 3129 * If a new connection request is received 3130 * while in TIME_WAIT, drop the old connection 3131 * and start over if the sequence numbers 3132 * are above the previous ones. 3133 */ 3134 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3135 (void) tcp_twclose(tw, 0); 3136 return (1); 3137 } 3138 3139 /* 3140 * Drop the the segment if it does not contain an ACK. 3141 */ 3142 if ((thflags & TH_ACK) == 0) 3143 goto drop; 3144 3145 /* 3146 * Reset the 2MSL timer if this is a duplicate FIN. 3147 */ 3148 if (thflags & TH_FIN) { 3149 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3150 if (seq + 1 == tw->rcv_nxt) 3151 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3152 } 3153 3154 /* 3155 * Acknowledge the segment if it has data or is not a duplicate ACK. 3156 */ 3157 if (thflags != TH_ACK || tlen != 0 || 3158 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3159 tcp_twrespond(tw, NULL, m, TH_ACK); 3160 goto drop; 3161 3162 reset: 3163 /* 3164 * Generate a RST, dropping incoming segment. 3165 * Make ACK acceptable to originator of segment. 3166 * Don't bother to respond if destination was broadcast/multicast. 3167 */ 3168 if (m->m_flags & (M_BCAST|M_MCAST)) 3169 goto drop; 3170 if (isipv6) { 3171 struct ip6_hdr *ip6; 3172 3173 /* IPv6 anycast check is done at tcp6_input() */ 3174 ip6 = mtod(m, struct ip6_hdr *); 3175 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3176 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3177 goto drop; 3178 } else { 3179 struct ip *ip; 3180 3181 ip = mtod(m, struct ip *); 3182 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3183 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3184 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3185 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3186 goto drop; 3187 } 3188 if (thflags & TH_ACK) { 3189 tcp_respond(NULL, 3190 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3191 } else { 3192 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3193 tcp_respond(NULL, 3194 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3195 } 3196 INP_UNLOCK(tw->tw_inpcb); 3197 return (0); 3198 3199 drop: 3200 INP_UNLOCK(tw->tw_inpcb); 3201 m_freem(m); 3202 return (0); 3203 }
Cache object: 5513d11e845fa595b9be55ab5d95ba15
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