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 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 41 #include <sys/param.h> 42 #include <sys/kernel.h> 43 #include <sys/mac.h> 44 #include <sys/malloc.h> 45 #include <sys/mbuf.h> 46 #include <sys/proc.h> /* for proc0 declaration */ 47 #include <sys/protosw.h> 48 #include <sys/signalvar.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/sysctl.h> 52 #include <sys/syslog.h> 53 #include <sys/systm.h> 54 55 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 56 57 #include <vm/uma.h> 58 59 #include <net/if.h> 60 #include <net/route.h> 61 62 #include <netinet/in.h> 63 #include <netinet/in_pcb.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/in_var.h> 66 #include <netinet/ip.h> 67 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 68 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 69 #include <netinet/ip_var.h> 70 #include <netinet/ip6.h> 71 #include <netinet/icmp6.h> 72 #include <netinet6/in6_pcb.h> 73 #include <netinet6/ip6_var.h> 74 #include <netinet6/nd6.h> 75 #include <netinet/tcp.h> 76 #include <netinet/tcp_fsm.h> 77 #include <netinet/tcp_seq.h> 78 #include <netinet/tcp_timer.h> 79 #include <netinet/tcp_var.h> 80 #include <netinet6/tcp6_var.h> 81 #include <netinet/tcpip.h> 82 #ifdef TCPDEBUG 83 #include <netinet/tcp_debug.h> 84 #endif /* TCPDEBUG */ 85 86 #ifdef FAST_IPSEC 87 #include <netipsec/ipsec.h> 88 #include <netipsec/ipsec6.h> 89 #endif /*FAST_IPSEC*/ 90 91 #ifdef IPSEC 92 #include <netinet6/ipsec.h> 93 #include <netinet6/ipsec6.h> 94 #include <netkey/key.h> 95 #endif /*IPSEC*/ 96 97 #include <machine/in_cksum.h> 98 99 static const int tcprexmtthresh = 3; 100 tcp_cc tcp_ccgen; 101 102 struct tcpstat tcpstat; 103 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 104 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 105 106 static int log_in_vain = 0; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 108 &log_in_vain, 0, "Log all incoming TCP connections"); 109 110 static int blackhole = 0; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 112 &blackhole, 0, "Do not send RST when dropping refused connections"); 113 114 int tcp_delack_enabled = 1; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 116 &tcp_delack_enabled, 0, 117 "Delay ACK to try and piggyback it onto a data packet"); 118 119 #ifdef TCP_DROP_SYNFIN 120 static int drop_synfin = 0; 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 122 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 123 #endif 124 125 static int tcp_do_rfc3042 = 1; 126 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 127 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 128 129 static int tcp_do_rfc3390 = 1; 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 131 &tcp_do_rfc3390, 0, 132 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 133 134 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 135 "TCP Segment Reassembly Queue"); 136 137 static int tcp_reass_maxseg = 0; 138 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 139 &tcp_reass_maxseg, 0, 140 "Global maximum number of TCP Segments in Reassembly Queue"); 141 142 int tcp_reass_qsize = 0; 143 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 144 &tcp_reass_qsize, 0, 145 "Global number of TCP Segments currently in Reassembly Queue"); 146 147 static int tcp_reass_maxqlen = 48; 148 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 149 &tcp_reass_maxqlen, 0, 150 "Maximum number of TCP Segments per individual Reassembly Queue"); 151 152 static int tcp_reass_overflows = 0; 153 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 154 &tcp_reass_overflows, 0, 155 "Global number of TCP Segment Reassembly Queue Overflows"); 156 157 struct inpcbhead tcb; 158 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 159 struct inpcbinfo tcbinfo; 160 struct mtx *tcbinfo_mtx; 161 162 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 163 static void tcp_pulloutofband(struct socket *, 164 struct tcphdr *, struct mbuf *, int); 165 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 166 struct mbuf *); 167 static void tcp_xmit_timer(struct tcpcb *, int); 168 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 169 static int tcp_timewait(struct tcptw *, struct tcpopt *, 170 struct tcphdr *, struct mbuf *, int); 171 172 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 173 #ifdef INET6 174 #define ND6_HINT(tp) \ 175 do { \ 176 if ((tp) && (tp)->t_inpcb && \ 177 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 178 nd6_nud_hint(NULL, NULL, 0); \ 179 } while (0) 180 #else 181 #define ND6_HINT(tp) 182 #endif 183 184 /* 185 * Indicate whether this ack should be delayed. We can delay the ack if 186 * - there is no delayed ack timer in progress and 187 * - our last ack wasn't a 0-sized window. We never want to delay 188 * the ack that opens up a 0-sized window and 189 * - delayed acks are enabled or 190 * - this is a half-synchronized T/TCP connection. 191 */ 192 #define DELAY_ACK(tp) \ 193 ((!callout_active(tp->tt_delack) && \ 194 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 195 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 196 197 /* Initialize TCP reassembly queue */ 198 uma_zone_t tcp_reass_zone; 199 void 200 tcp_reass_init() 201 { 202 tcp_reass_maxseg = nmbclusters / 16; 203 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 204 &tcp_reass_maxseg); 205 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 206 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 207 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 208 } 209 210 static int 211 tcp_reass(tp, th, tlenp, m) 212 register struct tcpcb *tp; 213 register struct tcphdr *th; 214 int *tlenp; 215 struct mbuf *m; 216 { 217 struct tseg_qent *q; 218 struct tseg_qent *p = NULL; 219 struct tseg_qent *nq; 220 struct tseg_qent *te = NULL; 221 struct socket *so = tp->t_inpcb->inp_socket; 222 int flags; 223 224 /* 225 * XXX: tcp_reass() is rather inefficient with its data structures 226 * and should be rewritten (see NetBSD for optimizations). While 227 * doing that it should move to its own file tcp_reass.c. 228 */ 229 230 /* 231 * Call with th==0 after become established to 232 * force pre-ESTABLISHED data up to user socket. 233 */ 234 if (th == 0) 235 goto present; 236 237 /* 238 * Limit the number of segments in the reassembly queue to prevent 239 * holding on to too many segments (and thus running out of mbufs). 240 * Make sure to let the missing segment through which caused this 241 * queue. Always keep one global queue entry spare to be able to 242 * process the missing segment. 243 */ 244 if (th->th_seq != tp->rcv_nxt && 245 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 246 tp->t_segqlen >= tcp_reass_maxqlen)) { 247 tcp_reass_overflows++; 248 tcpstat.tcps_rcvmemdrop++; 249 m_freem(m); 250 return (0); 251 } 252 253 /* 254 * Allocate a new queue entry. If we can't, or hit the zone limit 255 * just drop the pkt. 256 */ 257 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 258 if (te == NULL) { 259 tcpstat.tcps_rcvmemdrop++; 260 m_freem(m); 261 return (0); 262 } 263 tp->t_segqlen++; 264 tcp_reass_qsize++; 265 266 /* 267 * Find a segment which begins after this one does. 268 */ 269 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 270 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 271 break; 272 p = q; 273 } 274 275 /* 276 * If there is a preceding segment, it may provide some of 277 * our data already. If so, drop the data from the incoming 278 * segment. If it provides all of our data, drop us. 279 */ 280 if (p != NULL) { 281 register int i; 282 /* conversion to int (in i) handles seq wraparound */ 283 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 284 if (i > 0) { 285 if (i >= *tlenp) { 286 tcpstat.tcps_rcvduppack++; 287 tcpstat.tcps_rcvdupbyte += *tlenp; 288 m_freem(m); 289 uma_zfree(tcp_reass_zone, te); 290 tp->t_segqlen--; 291 tcp_reass_qsize--; 292 /* 293 * Try to present any queued data 294 * at the left window edge to the user. 295 * This is needed after the 3-WHS 296 * completes. 297 */ 298 goto present; /* ??? */ 299 } 300 m_adj(m, i); 301 *tlenp -= i; 302 th->th_seq += i; 303 } 304 } 305 tcpstat.tcps_rcvoopack++; 306 tcpstat.tcps_rcvoobyte += *tlenp; 307 308 /* 309 * While we overlap succeeding segments trim them or, 310 * if they are completely covered, dequeue them. 311 */ 312 while (q) { 313 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 314 if (i <= 0) 315 break; 316 if (i < q->tqe_len) { 317 q->tqe_th->th_seq += i; 318 q->tqe_len -= i; 319 m_adj(q->tqe_m, i); 320 break; 321 } 322 323 nq = LIST_NEXT(q, tqe_q); 324 LIST_REMOVE(q, tqe_q); 325 m_freem(q->tqe_m); 326 uma_zfree(tcp_reass_zone, q); 327 tp->t_segqlen--; 328 tcp_reass_qsize--; 329 q = nq; 330 } 331 332 /* Insert the new segment queue entry into place. */ 333 te->tqe_m = m; 334 te->tqe_th = th; 335 te->tqe_len = *tlenp; 336 337 if (p == NULL) { 338 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 339 } else { 340 LIST_INSERT_AFTER(p, te, tqe_q); 341 } 342 343 present: 344 /* 345 * Present data to user, advancing rcv_nxt through 346 * completed sequence space. 347 */ 348 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 349 return (0); 350 q = LIST_FIRST(&tp->t_segq); 351 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 352 return (0); 353 do { 354 tp->rcv_nxt += q->tqe_len; 355 flags = q->tqe_th->th_flags & TH_FIN; 356 nq = LIST_NEXT(q, tqe_q); 357 LIST_REMOVE(q, tqe_q); 358 if (so->so_state & SS_CANTRCVMORE) 359 m_freem(q->tqe_m); 360 else 361 sbappendstream(&so->so_rcv, q->tqe_m); 362 uma_zfree(tcp_reass_zone, q); 363 tp->t_segqlen--; 364 tcp_reass_qsize--; 365 q = nq; 366 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 367 ND6_HINT(tp); 368 sorwakeup(so); 369 return (flags); 370 } 371 372 /* 373 * TCP input routine, follows pages 65-76 of the 374 * protocol specification dated September, 1981 very closely. 375 */ 376 #ifdef INET6 377 int 378 tcp6_input(mp, offp, proto) 379 struct mbuf **mp; 380 int *offp, proto; 381 { 382 register struct mbuf *m = *mp; 383 struct in6_ifaddr *ia6; 384 385 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 386 387 /* 388 * draft-itojun-ipv6-tcp-to-anycast 389 * better place to put this in? 390 */ 391 ia6 = ip6_getdstifaddr(m); 392 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 393 struct ip6_hdr *ip6; 394 395 ip6 = mtod(m, struct ip6_hdr *); 396 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 397 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 398 return IPPROTO_DONE; 399 } 400 401 tcp_input(m, *offp); 402 return IPPROTO_DONE; 403 } 404 #endif 405 406 void 407 tcp_input(m, off0) 408 register struct mbuf *m; 409 int off0; 410 { 411 register struct tcphdr *th; 412 register struct ip *ip = NULL; 413 register struct ipovly *ipov; 414 register struct inpcb *inp = NULL; 415 u_char *optp = NULL; 416 int optlen = 0; 417 int len, tlen, off; 418 int drop_hdrlen; 419 register struct tcpcb *tp = 0; 420 register int thflags; 421 struct socket *so = 0; 422 int todrop, acked, ourfinisacked, needoutput = 0; 423 u_long tiwin; 424 struct tcpopt to; /* options in this segment */ 425 struct rmxp_tao tao; /* our TAO cache entry */ 426 int headlocked = 0; 427 struct sockaddr_in *next_hop = NULL; 428 int rstreason; /* For badport_bandlim accounting purposes */ 429 430 struct ip6_hdr *ip6 = NULL; 431 #ifdef INET6 432 int isipv6; 433 #else 434 const int isipv6 = 0; 435 #endif 436 437 #ifdef TCPDEBUG 438 /* 439 * The size of tcp_saveipgen must be the size of the max ip header, 440 * now IPv6. 441 */ 442 u_char tcp_saveipgen[40]; 443 struct tcphdr tcp_savetcp; 444 short ostate = 0; 445 #endif 446 447 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 448 next_hop = ip_claim_next_hop(m); 449 #ifdef INET6 450 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 451 #endif 452 bzero(&tao, sizeof(tao)); 453 bzero((char *)&to, sizeof(to)); 454 455 tcpstat.tcps_rcvtotal++; 456 457 if (isipv6) { 458 #ifdef INET6 459 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 460 ip6 = mtod(m, struct ip6_hdr *); 461 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 462 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 463 tcpstat.tcps_rcvbadsum++; 464 goto drop; 465 } 466 th = (struct tcphdr *)((caddr_t)ip6 + off0); 467 468 /* 469 * Be proactive about unspecified IPv6 address in source. 470 * As we use all-zero to indicate unbounded/unconnected pcb, 471 * unspecified IPv6 address can be used to confuse us. 472 * 473 * Note that packets with unspecified IPv6 destination is 474 * already dropped in ip6_input. 475 */ 476 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 477 /* XXX stat */ 478 goto drop; 479 } 480 #else 481 th = NULL; /* XXX: avoid compiler warning */ 482 #endif 483 } else { 484 /* 485 * Get IP and TCP header together in first mbuf. 486 * Note: IP leaves IP header in first mbuf. 487 */ 488 if (off0 > sizeof (struct ip)) { 489 ip_stripoptions(m, (struct mbuf *)0); 490 off0 = sizeof(struct ip); 491 } 492 if (m->m_len < sizeof (struct tcpiphdr)) { 493 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 494 tcpstat.tcps_rcvshort++; 495 return; 496 } 497 } 498 ip = mtod(m, struct ip *); 499 ipov = (struct ipovly *)ip; 500 th = (struct tcphdr *)((caddr_t)ip + off0); 501 tlen = ip->ip_len; 502 503 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 504 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 505 th->th_sum = m->m_pkthdr.csum_data; 506 else 507 th->th_sum = in_pseudo(ip->ip_src.s_addr, 508 ip->ip_dst.s_addr, 509 htonl(m->m_pkthdr.csum_data + 510 ip->ip_len + 511 IPPROTO_TCP)); 512 th->th_sum ^= 0xffff; 513 #ifdef TCPDEBUG 514 ipov->ih_len = (u_short)tlen; 515 ipov->ih_len = htons(ipov->ih_len); 516 #endif 517 } else { 518 /* 519 * Checksum extended TCP header and data. 520 */ 521 len = sizeof (struct ip) + tlen; 522 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 523 ipov->ih_len = (u_short)tlen; 524 ipov->ih_len = htons(ipov->ih_len); 525 th->th_sum = in_cksum(m, len); 526 } 527 if (th->th_sum) { 528 tcpstat.tcps_rcvbadsum++; 529 goto drop; 530 } 531 #ifdef INET6 532 /* Re-initialization for later version check */ 533 ip->ip_v = IPVERSION; 534 #endif 535 } 536 537 /* 538 * Check that TCP offset makes sense, 539 * pull out TCP options and adjust length. XXX 540 */ 541 off = th->th_off << 2; 542 if (off < sizeof (struct tcphdr) || off > tlen) { 543 tcpstat.tcps_rcvbadoff++; 544 goto drop; 545 } 546 tlen -= off; /* tlen is used instead of ti->ti_len */ 547 if (off > sizeof (struct tcphdr)) { 548 if (isipv6) { 549 #ifdef INET6 550 IP6_EXTHDR_CHECK(m, off0, off, ); 551 ip6 = mtod(m, struct ip6_hdr *); 552 th = (struct tcphdr *)((caddr_t)ip6 + off0); 553 #endif 554 } else { 555 if (m->m_len < sizeof(struct ip) + off) { 556 if ((m = m_pullup(m, sizeof (struct ip) + off)) 557 == 0) { 558 tcpstat.tcps_rcvshort++; 559 return; 560 } 561 ip = mtod(m, struct ip *); 562 ipov = (struct ipovly *)ip; 563 th = (struct tcphdr *)((caddr_t)ip + off0); 564 } 565 } 566 optlen = off - sizeof (struct tcphdr); 567 optp = (u_char *)(th + 1); 568 } 569 thflags = th->th_flags; 570 571 #ifdef TCP_DROP_SYNFIN 572 /* 573 * If the drop_synfin option is enabled, drop all packets with 574 * both the SYN and FIN bits set. This prevents e.g. nmap from 575 * identifying the TCP/IP stack. 576 * 577 * This is a violation of the TCP specification. 578 */ 579 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 580 goto drop; 581 #endif 582 583 /* 584 * Convert TCP protocol specific fields to host format. 585 */ 586 th->th_seq = ntohl(th->th_seq); 587 th->th_ack = ntohl(th->th_ack); 588 th->th_win = ntohs(th->th_win); 589 th->th_urp = ntohs(th->th_urp); 590 591 /* 592 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 593 * until after ip6_savecontrol() is called and before other functions 594 * which don't want those proto headers. 595 * Because ip6_savecontrol() is going to parse the mbuf to 596 * search for data to be passed up to user-land, it wants mbuf 597 * parameters to be unchanged. 598 * XXX: the call of ip6_savecontrol() has been obsoleted based on 599 * latest version of the advanced API (20020110). 600 */ 601 drop_hdrlen = off0 + off; 602 603 /* 604 * Locate pcb for segment. 605 */ 606 INP_INFO_WLOCK(&tcbinfo); 607 headlocked = 1; 608 findpcb: 609 /* IPFIREWALL_FORWARD section */ 610 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 611 /* 612 * Transparently forwarded. Pretend to be the destination. 613 * already got one like this? 614 */ 615 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 616 ip->ip_dst, th->th_dport, 617 0, m->m_pkthdr.rcvif); 618 if (!inp) { 619 /* It's new. Try find the ambushing socket. */ 620 inp = in_pcblookup_hash(&tcbinfo, 621 ip->ip_src, th->th_sport, 622 next_hop->sin_addr, 623 next_hop->sin_port ? 624 ntohs(next_hop->sin_port) : 625 th->th_dport, 626 1, m->m_pkthdr.rcvif); 627 } 628 } else { 629 if (isipv6) { 630 #ifdef INET6 631 inp = in6_pcblookup_hash(&tcbinfo, 632 &ip6->ip6_src, th->th_sport, 633 &ip6->ip6_dst, th->th_dport, 634 1, m->m_pkthdr.rcvif); 635 #endif 636 } else 637 inp = in_pcblookup_hash(&tcbinfo, 638 ip->ip_src, th->th_sport, 639 ip->ip_dst, th->th_dport, 640 1, m->m_pkthdr.rcvif); 641 } 642 643 #if defined(IPSEC) || defined(FAST_IPSEC) 644 if (isipv6) { 645 if (inp != NULL && ipsec6_in_reject(m, inp)) { 646 #ifdef IPSEC 647 ipsec6stat.in_polvio++; 648 #endif /*IPSEC*/ 649 goto drop; 650 } 651 } else if (inp != NULL && ipsec4_in_reject(m, inp)) { 652 #ifdef IPSEC 653 ipsecstat.in_polvio++; 654 #endif /*IPSEC*/ 655 goto drop; 656 } 657 #endif /*IPSEC || FAST_IPSEC*/ 658 659 /* 660 * If the state is CLOSED (i.e., TCB does not exist) then 661 * all data in the incoming segment is discarded. 662 * If the TCB exists but is in CLOSED state, it is embryonic, 663 * but should either do a listen or a connect soon. 664 */ 665 if (inp == NULL) { 666 if (log_in_vain) { 667 #ifdef INET6 668 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 669 #else 670 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 671 #endif 672 673 if (isipv6) { 674 #ifdef INET6 675 strcpy(dbuf, "["); 676 strcpy(sbuf, "["); 677 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 678 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 679 strcat(dbuf, "]"); 680 strcat(sbuf, "]"); 681 #endif 682 } else { 683 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 684 strcpy(sbuf, inet_ntoa(ip->ip_src)); 685 } 686 switch (log_in_vain) { 687 case 1: 688 if ((thflags & TH_SYN) == 0) 689 break; 690 /* FALLTHROUGH */ 691 case 2: 692 log(LOG_INFO, 693 "Connection attempt to TCP %s:%d " 694 "from %s:%d flags:0x%02x\n", 695 dbuf, ntohs(th->th_dport), sbuf, 696 ntohs(th->th_sport), thflags); 697 break; 698 default: 699 break; 700 } 701 } 702 if (blackhole) { 703 switch (blackhole) { 704 case 1: 705 if (thflags & TH_SYN) 706 goto drop; 707 break; 708 case 2: 709 goto drop; 710 default: 711 goto drop; 712 } 713 } 714 rstreason = BANDLIM_RST_CLOSEDPORT; 715 goto dropwithreset; 716 } 717 INP_LOCK(inp); 718 if (inp->inp_vflag & INP_TIMEWAIT) { 719 /* 720 * The only option of relevance is TOF_CC, and only if 721 * present in a SYN segment. See tcp_timewait(). 722 */ 723 if (thflags & TH_SYN) 724 tcp_dooptions(&to, optp, optlen, 1); 725 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 726 &to, th, m, tlen)) 727 goto findpcb; 728 /* 729 * tcp_timewait unlocks inp. 730 */ 731 INP_INFO_WUNLOCK(&tcbinfo); 732 return; 733 } 734 tp = intotcpcb(inp); 735 if (tp == 0) { 736 INP_UNLOCK(inp); 737 rstreason = BANDLIM_RST_CLOSEDPORT; 738 goto dropwithreset; 739 } 740 if (tp->t_state == TCPS_CLOSED) 741 goto drop; 742 743 /* Unscale the window into a 32-bit value. */ 744 if ((thflags & TH_SYN) == 0) 745 tiwin = th->th_win << tp->snd_scale; 746 else 747 tiwin = th->th_win; 748 749 #ifdef MAC 750 if (mac_check_inpcb_deliver(inp, m)) 751 goto drop; 752 #endif 753 so = inp->inp_socket; 754 #ifdef TCPDEBUG 755 if (so->so_options & SO_DEBUG) { 756 ostate = tp->t_state; 757 if (isipv6) 758 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 759 else 760 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 761 tcp_savetcp = *th; 762 } 763 #endif 764 if (so->so_options & SO_ACCEPTCONN) { 765 struct in_conninfo inc; 766 767 #ifdef INET6 768 inc.inc_isipv6 = isipv6; 769 #endif 770 if (isipv6) { 771 inc.inc6_faddr = ip6->ip6_src; 772 inc.inc6_laddr = ip6->ip6_dst; 773 } else { 774 inc.inc_faddr = ip->ip_src; 775 inc.inc_laddr = ip->ip_dst; 776 } 777 inc.inc_fport = th->th_sport; 778 inc.inc_lport = th->th_dport; 779 780 /* 781 * If the state is LISTEN then ignore segment if it contains 782 * a RST. If the segment contains an ACK then it is bad and 783 * send a RST. If it does not contain a SYN then it is not 784 * interesting; drop it. 785 * 786 * If the state is SYN_RECEIVED (syncache) and seg contains 787 * an ACK, but not for our SYN/ACK, send a RST. If the seg 788 * contains a RST, check the sequence number to see if it 789 * is a valid reset segment. 790 */ 791 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 792 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 793 if (!syncache_expand(&inc, th, &so, m)) { 794 /* 795 * No syncache entry, or ACK was not 796 * for our SYN/ACK. Send a RST. 797 */ 798 tcpstat.tcps_badsyn++; 799 rstreason = BANDLIM_RST_OPENPORT; 800 goto dropwithreset; 801 } 802 if (so == NULL) { 803 /* 804 * Could not complete 3-way handshake, 805 * connection is being closed down, and 806 * syncache will free mbuf. 807 */ 808 INP_UNLOCK(inp); 809 INP_INFO_WUNLOCK(&tcbinfo); 810 return; 811 } 812 /* 813 * Socket is created in state SYN_RECEIVED. 814 * Continue processing segment. 815 */ 816 INP_UNLOCK(inp); 817 inp = sotoinpcb(so); 818 INP_LOCK(inp); 819 tp = intotcpcb(inp); 820 /* 821 * This is what would have happened in 822 * tcp_output() when the SYN,ACK was sent. 823 */ 824 tp->snd_up = tp->snd_una; 825 tp->snd_max = tp->snd_nxt = tp->iss + 1; 826 tp->last_ack_sent = tp->rcv_nxt; 827 /* 828 * RFC1323: The window in SYN & SYN/ACK 829 * segments is never scaled. 830 */ 831 tp->snd_wnd = tiwin; /* unscaled */ 832 goto after_listen; 833 } 834 if (thflags & TH_RST) { 835 syncache_chkrst(&inc, th); 836 goto drop; 837 } 838 if (thflags & TH_ACK) { 839 syncache_badack(&inc); 840 tcpstat.tcps_badsyn++; 841 rstreason = BANDLIM_RST_OPENPORT; 842 goto dropwithreset; 843 } 844 goto drop; 845 } 846 847 /* 848 * Segment's flags are (SYN) or (SYN|FIN). 849 */ 850 #ifdef INET6 851 /* 852 * If deprecated address is forbidden, 853 * we do not accept SYN to deprecated interface 854 * address to prevent any new inbound connection from 855 * getting established. 856 * When we do not accept SYN, we send a TCP RST, 857 * with deprecated source address (instead of dropping 858 * it). We compromise it as it is much better for peer 859 * to send a RST, and RST will be the final packet 860 * for the exchange. 861 * 862 * If we do not forbid deprecated addresses, we accept 863 * the SYN packet. RFC2462 does not suggest dropping 864 * SYN in this case. 865 * If we decipher RFC2462 5.5.4, it says like this: 866 * 1. use of deprecated addr with existing 867 * communication is okay - "SHOULD continue to be 868 * used" 869 * 2. use of it with new communication: 870 * (2a) "SHOULD NOT be used if alternate address 871 * with sufficient scope is available" 872 * (2b) nothing mentioned otherwise. 873 * Here we fall into (2b) case as we have no choice in 874 * our source address selection - we must obey the peer. 875 * 876 * The wording in RFC2462 is confusing, and there are 877 * multiple description text for deprecated address 878 * handling - worse, they are not exactly the same. 879 * I believe 5.5.4 is the best one, so we follow 5.5.4. 880 */ 881 if (isipv6 && !ip6_use_deprecated) { 882 struct in6_ifaddr *ia6; 883 884 if ((ia6 = ip6_getdstifaddr(m)) && 885 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 886 INP_UNLOCK(inp); 887 tp = NULL; 888 rstreason = BANDLIM_RST_OPENPORT; 889 goto dropwithreset; 890 } 891 } 892 #endif 893 /* 894 * If it is from this socket, drop it, it must be forged. 895 * Don't bother responding if the destination was a broadcast. 896 */ 897 if (th->th_dport == th->th_sport) { 898 if (isipv6) { 899 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 900 &ip6->ip6_src)) 901 goto drop; 902 } else { 903 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 904 goto drop; 905 } 906 } 907 /* 908 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 909 * 910 * Note that it is quite possible to receive unicast 911 * link-layer packets with a broadcast IP address. Use 912 * in_broadcast() to find them. 913 */ 914 if (m->m_flags & (M_BCAST|M_MCAST)) 915 goto drop; 916 if (isipv6) { 917 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 918 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 919 goto drop; 920 } else { 921 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 922 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 923 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 924 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 925 goto drop; 926 } 927 /* 928 * SYN appears to be valid; create compressed TCP state 929 * for syncache, or perform t/tcp connection. 930 */ 931 if (so->so_qlen <= so->so_qlimit) { 932 #ifdef TCPDEBUG 933 if (so->so_options & SO_DEBUG) 934 tcp_trace(TA_INPUT, ostate, tp, 935 (void *)tcp_saveipgen, &tcp_savetcp, 0); 936 #endif 937 tcp_dooptions(&to, optp, optlen, 1); 938 if (!syncache_add(&inc, &to, th, &so, m)) 939 goto drop; 940 if (so == NULL) { 941 /* 942 * Entry added to syncache, mbuf used to 943 * send SYN,ACK packet. 944 */ 945 KASSERT(headlocked, ("headlocked")); 946 INP_UNLOCK(inp); 947 INP_INFO_WUNLOCK(&tcbinfo); 948 return; 949 } 950 /* 951 * Segment passed TAO tests. 952 */ 953 INP_UNLOCK(inp); 954 inp = sotoinpcb(so); 955 INP_LOCK(inp); 956 tp = intotcpcb(inp); 957 tp->snd_wnd = tiwin; 958 tp->t_starttime = ticks; 959 tp->t_state = TCPS_ESTABLISHED; 960 961 /* 962 * T/TCP logic: 963 * If there is a FIN or if there is data, then 964 * delay SYN,ACK(SYN) in the hope of piggy-backing 965 * it on a response segment. Otherwise must send 966 * ACK now in case the other side is slow starting. 967 */ 968 if (thflags & TH_FIN || tlen != 0) 969 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 970 else 971 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 972 tcpstat.tcps_connects++; 973 soisconnected(so); 974 goto trimthenstep6; 975 } 976 goto drop; 977 } 978 after_listen: 979 980 /* XXX temp debugging */ 981 /* should not happen - syncache should pick up these connections */ 982 if (tp->t_state == TCPS_LISTEN) 983 panic("tcp_input: TCPS_LISTEN"); 984 985 /* 986 * This is the second part of the MSS DoS prevention code (after 987 * minmss on the sending side) and it deals with too many too small 988 * tcp packets in a too short timeframe (1 second). 989 * 990 * For every full second we count the number of received packets 991 * and bytes. If we get a lot of packets per second for this connection 992 * (tcp_minmssoverload) we take a closer look at it and compute the 993 * average packet size for the past second. If that is less than 994 * tcp_minmss we get too many packets with very small payload which 995 * is not good and burdens our system (and every packet generates 996 * a wakeup to the process connected to our socket). We can reasonable 997 * expect this to be small packet DoS attack to exhaust our CPU 998 * cycles. 999 * 1000 * Care has to be taken for the minimum packet overload value. This 1001 * value defines the minimum number of packets per second before we 1002 * start to worry. This must not be too low to avoid killing for 1003 * example interactive connections with many small packets like 1004 * telnet or SSH. 1005 * 1006 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1007 * this check. 1008 * 1009 * Account for packet if payload packet, skip over ACK, etc. 1010 */ 1011 if (tcp_minmss && tcp_minmssoverload && 1012 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1013 if (tp->rcv_second > ticks) { 1014 tp->rcv_pps++; 1015 tp->rcv_byps += tlen + off; 1016 if (tp->rcv_pps > tcp_minmssoverload) { 1017 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1018 printf("too many small tcp packets from " 1019 "%s:%u, av. %lubyte/packet, " 1020 "dropping connection\n", 1021 #ifdef INET6 1022 isipv6 ? 1023 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1024 #endif 1025 inet_ntoa(inp->inp_inc.inc_faddr), 1026 inp->inp_inc.inc_fport, 1027 tp->rcv_byps / tp->rcv_pps); 1028 tp = tcp_drop(tp, ECONNRESET); 1029 tcpstat.tcps_minmssdrops++; 1030 goto drop; 1031 } 1032 } 1033 } else { 1034 tp->rcv_second = ticks + hz; 1035 tp->rcv_pps = 1; 1036 tp->rcv_byps = tlen + off; 1037 } 1038 } 1039 1040 /* 1041 * Segment received on connection. 1042 * Reset idle time and keep-alive timer. 1043 */ 1044 tp->t_rcvtime = ticks; 1045 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1046 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1047 1048 /* 1049 * Process options only when we get SYN/ACK back. The SYN case 1050 * for incoming connections is handled in tcp_syncache. 1051 * XXX this is traditional behavior, may need to be cleaned up. 1052 */ 1053 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 1054 if (thflags & TH_SYN) { 1055 if (to.to_flags & TOF_SCALE) { 1056 tp->t_flags |= TF_RCVD_SCALE; 1057 tp->requested_s_scale = to.to_requested_s_scale; 1058 } 1059 if (to.to_flags & TOF_TS) { 1060 tp->t_flags |= TF_RCVD_TSTMP; 1061 tp->ts_recent = to.to_tsval; 1062 tp->ts_recent_age = ticks; 1063 } 1064 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 1065 tp->t_flags |= TF_RCVD_CC; 1066 if (to.to_flags & TOF_MSS) 1067 tcp_mss(tp, to.to_mss); 1068 } 1069 1070 /* 1071 * Header prediction: check for the two common cases 1072 * of a uni-directional data xfer. If the packet has 1073 * no control flags, is in-sequence, the window didn't 1074 * change and we're not retransmitting, it's a 1075 * candidate. If the length is zero and the ack moved 1076 * forward, we're the sender side of the xfer. Just 1077 * free the data acked & wake any higher level process 1078 * that was blocked waiting for space. If the length 1079 * is non-zero and the ack didn't move, we're the 1080 * receiver side. If we're getting packets in-order 1081 * (the reassembly queue is empty), add the data to 1082 * the socket buffer and note that we need a delayed ack. 1083 * Make sure that the hidden state-flags are also off. 1084 * Since we check for TCPS_ESTABLISHED above, it can only 1085 * be TH_NEEDSYN. 1086 */ 1087 if (tp->t_state == TCPS_ESTABLISHED && 1088 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1089 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1090 ((to.to_flags & TOF_TS) == 0 || 1091 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1092 /* 1093 * Using the CC option is compulsory if once started: 1094 * the segment is OK if no T/TCP was negotiated or 1095 * if the segment has a CC option equal to CCrecv 1096 */ 1097 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1098 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1099 th->th_seq == tp->rcv_nxt && 1100 tiwin && tiwin == tp->snd_wnd && 1101 tp->snd_nxt == tp->snd_max) { 1102 1103 /* 1104 * If last ACK falls within this segment's sequence numbers, 1105 * record the timestamp. 1106 * NOTE that the test is modified according to the latest 1107 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1108 */ 1109 if ((to.to_flags & TOF_TS) != 0 && 1110 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1111 tp->ts_recent_age = ticks; 1112 tp->ts_recent = to.to_tsval; 1113 } 1114 1115 if (tlen == 0) { 1116 if (SEQ_GT(th->th_ack, tp->snd_una) && 1117 SEQ_LEQ(th->th_ack, tp->snd_max) && 1118 tp->snd_cwnd >= tp->snd_wnd && 1119 ((!tcp_do_newreno && 1120 tp->t_dupacks < tcprexmtthresh) || 1121 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) { 1122 KASSERT(headlocked, ("headlocked")); 1123 INP_INFO_WUNLOCK(&tcbinfo); 1124 /* 1125 * this is a pure ack for outstanding data. 1126 */ 1127 ++tcpstat.tcps_predack; 1128 /* 1129 * "bad retransmit" recovery 1130 */ 1131 if (tp->t_rxtshift == 1 && 1132 ticks < tp->t_badrxtwin) { 1133 ++tcpstat.tcps_sndrexmitbad; 1134 tp->snd_cwnd = tp->snd_cwnd_prev; 1135 tp->snd_ssthresh = 1136 tp->snd_ssthresh_prev; 1137 tp->snd_recover = tp->snd_recover_prev; 1138 if (tp->t_flags & TF_WASFRECOVERY) 1139 ENTER_FASTRECOVERY(tp); 1140 tp->snd_nxt = tp->snd_max; 1141 tp->t_badrxtwin = 0; 1142 } 1143 1144 /* 1145 * Recalculate the transmit timer / rtt. 1146 * 1147 * Some boxes send broken timestamp replies 1148 * during the SYN+ACK phase, ignore 1149 * timestamps of 0 or we could calculate a 1150 * huge RTT and blow up the retransmit timer. 1151 */ 1152 if ((to.to_flags & TOF_TS) != 0 && 1153 to.to_tsecr) { 1154 tcp_xmit_timer(tp, 1155 ticks - to.to_tsecr + 1); 1156 } else if (tp->t_rtttime && 1157 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1158 tcp_xmit_timer(tp, 1159 ticks - tp->t_rtttime); 1160 } 1161 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1162 acked = th->th_ack - tp->snd_una; 1163 tcpstat.tcps_rcvackpack++; 1164 tcpstat.tcps_rcvackbyte += acked; 1165 sbdrop(&so->so_snd, acked); 1166 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1167 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1168 tp->snd_recover = th->th_ack - 1; 1169 tp->snd_una = th->th_ack; 1170 /* 1171 * pull snd_wl2 up to prevent seq wrap relative 1172 * to th_ack. 1173 */ 1174 tp->snd_wl2 = th->th_ack; 1175 tp->t_dupacks = 0; 1176 m_freem(m); 1177 ND6_HINT(tp); /* some progress has been done */ 1178 1179 /* 1180 * If all outstanding data are acked, stop 1181 * retransmit timer, otherwise restart timer 1182 * using current (possibly backed-off) value. 1183 * If process is waiting for space, 1184 * wakeup/selwakeup/signal. If data 1185 * are ready to send, let tcp_output 1186 * decide between more output or persist. 1187 1188 #ifdef TCPDEBUG 1189 if (so->so_options & SO_DEBUG) 1190 tcp_trace(TA_INPUT, ostate, tp, 1191 (void *)tcp_saveipgen, 1192 &tcp_savetcp, 0); 1193 #endif 1194 */ 1195 if (tp->snd_una == tp->snd_max) 1196 callout_stop(tp->tt_rexmt); 1197 else if (!callout_active(tp->tt_persist)) 1198 callout_reset(tp->tt_rexmt, 1199 tp->t_rxtcur, 1200 tcp_timer_rexmt, tp); 1201 1202 sowwakeup(so); 1203 if (so->so_snd.sb_cc) 1204 (void) tcp_output(tp); 1205 goto check_delack; 1206 } 1207 } else if (th->th_ack == tp->snd_una && 1208 LIST_EMPTY(&tp->t_segq) && 1209 tlen <= sbspace(&so->so_rcv)) { 1210 KASSERT(headlocked, ("headlocked")); 1211 INP_INFO_WUNLOCK(&tcbinfo); 1212 /* 1213 * this is a pure, in-sequence data packet 1214 * with nothing on the reassembly queue and 1215 * we have enough buffer space to take it. 1216 */ 1217 ++tcpstat.tcps_preddat; 1218 tp->rcv_nxt += tlen; 1219 /* 1220 * Pull snd_wl1 up to prevent seq wrap relative to 1221 * th_seq. 1222 */ 1223 tp->snd_wl1 = th->th_seq; 1224 /* 1225 * Pull rcv_up up to prevent seq wrap relative to 1226 * rcv_nxt. 1227 */ 1228 tp->rcv_up = tp->rcv_nxt; 1229 tcpstat.tcps_rcvpack++; 1230 tcpstat.tcps_rcvbyte += tlen; 1231 ND6_HINT(tp); /* some progress has been done */ 1232 /* 1233 #ifdef TCPDEBUG 1234 if (so->so_options & SO_DEBUG) 1235 tcp_trace(TA_INPUT, ostate, tp, 1236 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1237 #endif 1238 * Add data to socket buffer. 1239 */ 1240 if (so->so_state & SS_CANTRCVMORE) { 1241 m_freem(m); 1242 } else { 1243 m_adj(m, drop_hdrlen); /* delayed header drop */ 1244 sbappendstream(&so->so_rcv, m); 1245 } 1246 sorwakeup(so); 1247 if (DELAY_ACK(tp)) { 1248 tp->t_flags |= TF_DELACK; 1249 } else { 1250 tp->t_flags |= TF_ACKNOW; 1251 tcp_output(tp); 1252 } 1253 goto check_delack; 1254 } 1255 } 1256 1257 /* 1258 * Calculate amount of space in receive window, 1259 * and then do TCP input processing. 1260 * Receive window is amount of space in rcv queue, 1261 * but not less than advertised window. 1262 */ 1263 { int win; 1264 1265 win = sbspace(&so->so_rcv); 1266 if (win < 0) 1267 win = 0; 1268 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1269 } 1270 1271 switch (tp->t_state) { 1272 1273 /* 1274 * If the state is SYN_RECEIVED: 1275 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1276 */ 1277 case TCPS_SYN_RECEIVED: 1278 if ((thflags & TH_ACK) && 1279 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1280 SEQ_GT(th->th_ack, tp->snd_max))) { 1281 rstreason = BANDLIM_RST_OPENPORT; 1282 goto dropwithreset; 1283 } 1284 break; 1285 1286 /* 1287 * If the state is SYN_SENT: 1288 * if seg contains an ACK, but not for our SYN, drop the input. 1289 * if seg contains a RST, then drop the connection. 1290 * if seg does not contain SYN, then drop it. 1291 * Otherwise this is an acceptable SYN segment 1292 * initialize tp->rcv_nxt and tp->irs 1293 * if seg contains ack then advance tp->snd_una 1294 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1295 * arrange for segment to be acked (eventually) 1296 * continue processing rest of data/controls, beginning with URG 1297 */ 1298 case TCPS_SYN_SENT: 1299 if (tcp_do_rfc1644) 1300 tcp_hc_gettao(&inp->inp_inc, &tao); 1301 1302 if ((thflags & TH_ACK) && 1303 (SEQ_LEQ(th->th_ack, tp->iss) || 1304 SEQ_GT(th->th_ack, tp->snd_max))) { 1305 /* 1306 * If we have a cached CCsent for the remote host, 1307 * hence we haven't just crashed and restarted, 1308 * do not send a RST. This may be a retransmission 1309 * from the other side after our earlier ACK was lost. 1310 * Our new SYN, when it arrives, will serve as the 1311 * needed ACK. 1312 */ 1313 if (tao.tao_ccsent != 0) 1314 goto drop; 1315 else { 1316 rstreason = BANDLIM_UNLIMITED; 1317 goto dropwithreset; 1318 } 1319 } 1320 if (thflags & TH_RST) { 1321 if (thflags & TH_ACK) 1322 tp = tcp_drop(tp, ECONNREFUSED); 1323 goto drop; 1324 } 1325 if ((thflags & TH_SYN) == 0) 1326 goto drop; 1327 tp->snd_wnd = th->th_win; /* initial send window */ 1328 tp->cc_recv = to.to_cc; /* foreign CC */ 1329 1330 tp->irs = th->th_seq; 1331 tcp_rcvseqinit(tp); 1332 if (thflags & TH_ACK) { 1333 /* 1334 * Our SYN was acked. If segment contains CC.ECHO 1335 * option, check it to make sure this segment really 1336 * matches our SYN. If not, just drop it as old 1337 * duplicate, but send an RST if we're still playing 1338 * by the old rules. If no CC.ECHO option, make sure 1339 * we don't get fooled into using T/TCP. 1340 */ 1341 if (to.to_flags & TOF_CCECHO) { 1342 if (tp->cc_send != to.to_ccecho) { 1343 if (tao.tao_ccsent != 0) 1344 goto drop; 1345 else { 1346 rstreason = BANDLIM_UNLIMITED; 1347 goto dropwithreset; 1348 } 1349 } 1350 } else 1351 tp->t_flags &= ~TF_RCVD_CC; 1352 tcpstat.tcps_connects++; 1353 soisconnected(so); 1354 #ifdef MAC 1355 mac_set_socket_peer_from_mbuf(m, so); 1356 #endif 1357 /* Do window scaling on this connection? */ 1358 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1359 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1360 tp->snd_scale = tp->requested_s_scale; 1361 tp->rcv_scale = tp->request_r_scale; 1362 } 1363 /* Segment is acceptable, update cache if undefined. */ 1364 if (tao.tao_ccsent == 0 && tcp_do_rfc1644) 1365 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0); 1366 1367 tp->rcv_adv += tp->rcv_wnd; 1368 tp->snd_una++; /* SYN is acked */ 1369 /* 1370 * If there's data, delay ACK; if there's also a FIN 1371 * ACKNOW will be turned on later. 1372 */ 1373 if (DELAY_ACK(tp) && tlen != 0) 1374 callout_reset(tp->tt_delack, tcp_delacktime, 1375 tcp_timer_delack, tp); 1376 else 1377 tp->t_flags |= TF_ACKNOW; 1378 /* 1379 * Received <SYN,ACK> in SYN_SENT[*] state. 1380 * Transitions: 1381 * SYN_SENT --> ESTABLISHED 1382 * SYN_SENT* --> FIN_WAIT_1 1383 */ 1384 tp->t_starttime = ticks; 1385 if (tp->t_flags & TF_NEEDFIN) { 1386 tp->t_state = TCPS_FIN_WAIT_1; 1387 tp->t_flags &= ~TF_NEEDFIN; 1388 thflags &= ~TH_SYN; 1389 } else { 1390 tp->t_state = TCPS_ESTABLISHED; 1391 callout_reset(tp->tt_keep, tcp_keepidle, 1392 tcp_timer_keep, tp); 1393 } 1394 } else { 1395 /* 1396 * Received initial SYN in SYN-SENT[*] state => 1397 * simultaneous open. If segment contains CC option 1398 * and there is a cached CC, apply TAO test. 1399 * If it succeeds, connection is * half-synchronized. 1400 * Otherwise, do 3-way handshake: 1401 * SYN-SENT -> SYN-RECEIVED 1402 * SYN-SENT* -> SYN-RECEIVED* 1403 * If there was no CC option, clear cached CC value. 1404 */ 1405 tp->t_flags |= TF_ACKNOW; 1406 callout_stop(tp->tt_rexmt); 1407 if (to.to_flags & TOF_CC) { 1408 if (tao.tao_cc != 0 && 1409 CC_GT(to.to_cc, tao.tao_cc)) { 1410 /* 1411 * update cache and make transition: 1412 * SYN-SENT -> ESTABLISHED* 1413 * SYN-SENT* -> FIN-WAIT-1* 1414 */ 1415 tao.tao_cc = to.to_cc; 1416 tcp_hc_updatetao(&inp->inp_inc, 1417 TCP_HC_TAO_CC, to.to_cc, 0); 1418 tp->t_starttime = ticks; 1419 if (tp->t_flags & TF_NEEDFIN) { 1420 tp->t_state = TCPS_FIN_WAIT_1; 1421 tp->t_flags &= ~TF_NEEDFIN; 1422 } else { 1423 tp->t_state = TCPS_ESTABLISHED; 1424 callout_reset(tp->tt_keep, 1425 tcp_keepidle, 1426 tcp_timer_keep, 1427 tp); 1428 } 1429 tp->t_flags |= TF_NEEDSYN; 1430 } else 1431 tp->t_state = TCPS_SYN_RECEIVED; 1432 } else { 1433 if (tcp_do_rfc1644) { 1434 /* CC.NEW or no option => invalidate cache */ 1435 tao.tao_cc = 0; 1436 tcp_hc_updatetao(&inp->inp_inc, 1437 TCP_HC_TAO_CC, to.to_cc, 0); 1438 } 1439 tp->t_state = TCPS_SYN_RECEIVED; 1440 } 1441 } 1442 1443 trimthenstep6: 1444 /* 1445 * Advance th->th_seq to correspond to first data byte. 1446 * If data, trim to stay within window, 1447 * dropping FIN if necessary. 1448 */ 1449 th->th_seq++; 1450 if (tlen > tp->rcv_wnd) { 1451 todrop = tlen - tp->rcv_wnd; 1452 m_adj(m, -todrop); 1453 tlen = tp->rcv_wnd; 1454 thflags &= ~TH_FIN; 1455 tcpstat.tcps_rcvpackafterwin++; 1456 tcpstat.tcps_rcvbyteafterwin += todrop; 1457 } 1458 tp->snd_wl1 = th->th_seq - 1; 1459 tp->rcv_up = th->th_seq; 1460 /* 1461 * Client side of transaction: already sent SYN and data. 1462 * If the remote host used T/TCP to validate the SYN, 1463 * our data will be ACK'd; if so, enter normal data segment 1464 * processing in the middle of step 5, ack processing. 1465 * Otherwise, goto step 6. 1466 */ 1467 if (thflags & TH_ACK) 1468 goto process_ACK; 1469 1470 goto step6; 1471 1472 /* 1473 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1474 * if segment contains a SYN and CC [not CC.NEW] option: 1475 * if state == TIME_WAIT and connection duration > MSL, 1476 * drop packet and send RST; 1477 * 1478 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1479 * ack the FIN (and data) in retransmission queue. 1480 * Complete close and delete TCPCB. Then reprocess 1481 * segment, hoping to find new TCPCB in LISTEN state; 1482 * 1483 * else must be old SYN; drop it. 1484 * else do normal processing. 1485 */ 1486 case TCPS_LAST_ACK: 1487 case TCPS_CLOSING: 1488 case TCPS_TIME_WAIT: 1489 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1490 if ((thflags & TH_SYN) && 1491 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1492 if (tp->t_state == TCPS_TIME_WAIT && 1493 (ticks - tp->t_starttime) > tcp_msl) { 1494 rstreason = BANDLIM_UNLIMITED; 1495 goto dropwithreset; 1496 } 1497 if (CC_GT(to.to_cc, tp->cc_recv)) { 1498 tp = tcp_close(tp); 1499 goto findpcb; 1500 } 1501 else 1502 goto drop; 1503 } 1504 break; /* continue normal processing */ 1505 } 1506 1507 /* 1508 * States other than LISTEN or SYN_SENT. 1509 * First check the RST flag and sequence number since reset segments 1510 * are exempt from the timestamp and connection count tests. This 1511 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1512 * below which allowed reset segments in half the sequence space 1513 * to fall though and be processed (which gives forged reset 1514 * segments with a random sequence number a 50 percent chance of 1515 * killing a connection). 1516 * Then check timestamp, if present. 1517 * Then check the connection count, if present. 1518 * Then check that at least some bytes of segment are within 1519 * receive window. If segment begins before rcv_nxt, 1520 * drop leading data (and SYN); if nothing left, just ack. 1521 * 1522 * 1523 * If the RST bit is set, check the sequence number to see 1524 * if this is a valid reset segment. 1525 * RFC 793 page 37: 1526 * In all states except SYN-SENT, all reset (RST) segments 1527 * are validated by checking their SEQ-fields. A reset is 1528 * valid if its sequence number is in the window. 1529 * Note: this does not take into account delayed ACKs, so 1530 * we should test against last_ack_sent instead of rcv_nxt. 1531 * The sequence number in the reset segment is normally an 1532 * echo of our outgoing acknowlegement numbers, but some hosts 1533 * send a reset with the sequence number at the rightmost edge 1534 * of our receive window, and we have to handle this case. 1535 * If we have multiple segments in flight, the intial reset 1536 * segment sequence numbers will be to the left of last_ack_sent, 1537 * but they will eventually catch up. 1538 * In any case, it never made sense to trim reset segments to 1539 * fit the receive window since RFC 1122 says: 1540 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1541 * 1542 * A TCP SHOULD allow a received RST segment to include data. 1543 * 1544 * DISCUSSION 1545 * It has been suggested that a RST segment could contain 1546 * ASCII text that encoded and explained the cause of the 1547 * RST. No standard has yet been established for such 1548 * data. 1549 * 1550 * If the reset segment passes the sequence number test examine 1551 * the state: 1552 * SYN_RECEIVED STATE: 1553 * If passive open, return to LISTEN state. 1554 * If active open, inform user that connection was refused. 1555 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1556 * Inform user that connection was reset, and close tcb. 1557 * CLOSING, LAST_ACK STATES: 1558 * Close the tcb. 1559 * TIME_WAIT STATE: 1560 * Drop the segment - see Stevens, vol. 2, p. 964 and 1561 * RFC 1337. 1562 */ 1563 if (thflags & TH_RST) { 1564 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1565 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1566 switch (tp->t_state) { 1567 1568 case TCPS_SYN_RECEIVED: 1569 so->so_error = ECONNREFUSED; 1570 goto close; 1571 1572 case TCPS_ESTABLISHED: 1573 case TCPS_FIN_WAIT_1: 1574 case TCPS_FIN_WAIT_2: 1575 case TCPS_CLOSE_WAIT: 1576 so->so_error = ECONNRESET; 1577 close: 1578 tp->t_state = TCPS_CLOSED; 1579 tcpstat.tcps_drops++; 1580 tp = tcp_close(tp); 1581 break; 1582 1583 case TCPS_CLOSING: 1584 case TCPS_LAST_ACK: 1585 tp = tcp_close(tp); 1586 break; 1587 1588 case TCPS_TIME_WAIT: 1589 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1590 ("timewait")); 1591 break; 1592 } 1593 } 1594 goto drop; 1595 } 1596 1597 /* 1598 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1599 * and it's less than ts_recent, drop it. 1600 */ 1601 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1602 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1603 1604 /* Check to see if ts_recent is over 24 days old. */ 1605 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1606 /* 1607 * Invalidate ts_recent. If this segment updates 1608 * ts_recent, the age will be reset later and ts_recent 1609 * will get a valid value. If it does not, setting 1610 * ts_recent to zero will at least satisfy the 1611 * requirement that zero be placed in the timestamp 1612 * echo reply when ts_recent isn't valid. The 1613 * age isn't reset until we get a valid ts_recent 1614 * because we don't want out-of-order segments to be 1615 * dropped when ts_recent is old. 1616 */ 1617 tp->ts_recent = 0; 1618 } else { 1619 tcpstat.tcps_rcvduppack++; 1620 tcpstat.tcps_rcvdupbyte += tlen; 1621 tcpstat.tcps_pawsdrop++; 1622 if (tlen) 1623 goto dropafterack; 1624 goto drop; 1625 } 1626 } 1627 1628 /* 1629 * T/TCP mechanism 1630 * If T/TCP was negotiated and the segment doesn't have CC, 1631 * or if its CC is wrong then drop the segment. 1632 * RST segments do not have to comply with this. 1633 */ 1634 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1635 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1636 goto dropafterack; 1637 1638 /* 1639 * In the SYN-RECEIVED state, validate that the packet belongs to 1640 * this connection before trimming the data to fit the receive 1641 * window. Check the sequence number versus IRS since we know 1642 * the sequence numbers haven't wrapped. This is a partial fix 1643 * for the "LAND" DoS attack. 1644 */ 1645 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1646 rstreason = BANDLIM_RST_OPENPORT; 1647 goto dropwithreset; 1648 } 1649 1650 todrop = tp->rcv_nxt - th->th_seq; 1651 if (todrop > 0) { 1652 if (thflags & TH_SYN) { 1653 thflags &= ~TH_SYN; 1654 th->th_seq++; 1655 if (th->th_urp > 1) 1656 th->th_urp--; 1657 else 1658 thflags &= ~TH_URG; 1659 todrop--; 1660 } 1661 /* 1662 * Following if statement from Stevens, vol. 2, p. 960. 1663 */ 1664 if (todrop > tlen 1665 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1666 /* 1667 * Any valid FIN must be to the left of the window. 1668 * At this point the FIN must be a duplicate or out 1669 * of sequence; drop it. 1670 */ 1671 thflags &= ~TH_FIN; 1672 1673 /* 1674 * Send an ACK to resynchronize and drop any data. 1675 * But keep on processing for RST or ACK. 1676 */ 1677 tp->t_flags |= TF_ACKNOW; 1678 todrop = tlen; 1679 tcpstat.tcps_rcvduppack++; 1680 tcpstat.tcps_rcvdupbyte += todrop; 1681 } else { 1682 tcpstat.tcps_rcvpartduppack++; 1683 tcpstat.tcps_rcvpartdupbyte += todrop; 1684 } 1685 drop_hdrlen += todrop; /* drop from the top afterwards */ 1686 th->th_seq += todrop; 1687 tlen -= todrop; 1688 if (th->th_urp > todrop) 1689 th->th_urp -= todrop; 1690 else { 1691 thflags &= ~TH_URG; 1692 th->th_urp = 0; 1693 } 1694 } 1695 1696 /* 1697 * If new data are received on a connection after the 1698 * user processes are gone, then RST the other end. 1699 */ 1700 if ((so->so_state & SS_NOFDREF) && 1701 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1702 tp = tcp_close(tp); 1703 tcpstat.tcps_rcvafterclose++; 1704 rstreason = BANDLIM_UNLIMITED; 1705 goto dropwithreset; 1706 } 1707 1708 /* 1709 * If segment ends after window, drop trailing data 1710 * (and PUSH and FIN); if nothing left, just ACK. 1711 */ 1712 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1713 if (todrop > 0) { 1714 tcpstat.tcps_rcvpackafterwin++; 1715 if (todrop >= tlen) { 1716 tcpstat.tcps_rcvbyteafterwin += tlen; 1717 /* 1718 * If a new connection request is received 1719 * while in TIME_WAIT, drop the old connection 1720 * and start over if the sequence numbers 1721 * are above the previous ones. 1722 */ 1723 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1724 if (thflags & TH_SYN && 1725 tp->t_state == TCPS_TIME_WAIT && 1726 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1727 tp = tcp_close(tp); 1728 goto findpcb; 1729 } 1730 /* 1731 * If window is closed can only take segments at 1732 * window edge, and have to drop data and PUSH from 1733 * incoming segments. Continue processing, but 1734 * remember to ack. Otherwise, drop segment 1735 * and ack. 1736 */ 1737 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1738 tp->t_flags |= TF_ACKNOW; 1739 tcpstat.tcps_rcvwinprobe++; 1740 } else 1741 goto dropafterack; 1742 } else 1743 tcpstat.tcps_rcvbyteafterwin += todrop; 1744 m_adj(m, -todrop); 1745 tlen -= todrop; 1746 thflags &= ~(TH_PUSH|TH_FIN); 1747 } 1748 1749 /* 1750 * If last ACK falls within this segment's sequence numbers, 1751 * record its timestamp. 1752 * NOTE that the test is modified according to the latest 1753 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1754 */ 1755 if ((to.to_flags & TOF_TS) != 0 && 1756 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1757 tp->ts_recent_age = ticks; 1758 tp->ts_recent = to.to_tsval; 1759 } 1760 1761 /* 1762 * If a SYN is in the window, then this is an 1763 * error and we send an RST and drop the connection. 1764 */ 1765 if (thflags & TH_SYN) { 1766 tp = tcp_drop(tp, ECONNRESET); 1767 rstreason = BANDLIM_UNLIMITED; 1768 goto drop; 1769 } 1770 1771 /* 1772 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1773 * flag is on (half-synchronized state), then queue data for 1774 * later processing; else drop segment and return. 1775 */ 1776 if ((thflags & TH_ACK) == 0) { 1777 if (tp->t_state == TCPS_SYN_RECEIVED || 1778 (tp->t_flags & TF_NEEDSYN)) 1779 goto step6; 1780 else 1781 goto drop; 1782 } 1783 1784 /* 1785 * Ack processing. 1786 */ 1787 switch (tp->t_state) { 1788 1789 /* 1790 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1791 * ESTABLISHED state and continue processing. 1792 * The ACK was checked above. 1793 */ 1794 case TCPS_SYN_RECEIVED: 1795 1796 tcpstat.tcps_connects++; 1797 soisconnected(so); 1798 /* Do window scaling? */ 1799 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1800 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1801 tp->snd_scale = tp->requested_s_scale; 1802 tp->rcv_scale = tp->request_r_scale; 1803 } 1804 /* 1805 * Upon successful completion of 3-way handshake, 1806 * update cache.CC, pass any queued data to the user, 1807 * and advance state appropriately. 1808 */ 1809 if (tcp_do_rfc1644) { 1810 tao.tao_cc = tp->cc_recv; 1811 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC, 1812 tp->cc_recv, 0); 1813 } 1814 /* 1815 * Make transitions: 1816 * SYN-RECEIVED -> ESTABLISHED 1817 * SYN-RECEIVED* -> FIN-WAIT-1 1818 */ 1819 tp->t_starttime = ticks; 1820 if (tp->t_flags & TF_NEEDFIN) { 1821 tp->t_state = TCPS_FIN_WAIT_1; 1822 tp->t_flags &= ~TF_NEEDFIN; 1823 } else { 1824 tp->t_state = TCPS_ESTABLISHED; 1825 callout_reset(tp->tt_keep, tcp_keepidle, 1826 tcp_timer_keep, tp); 1827 } 1828 /* 1829 * If segment contains data or ACK, will call tcp_reass() 1830 * later; if not, do so now to pass queued data to user. 1831 */ 1832 if (tlen == 0 && (thflags & TH_FIN) == 0) 1833 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1834 (struct mbuf *)0); 1835 tp->snd_wl1 = th->th_seq - 1; 1836 /* FALLTHROUGH */ 1837 1838 /* 1839 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1840 * ACKs. If the ack is in the range 1841 * tp->snd_una < th->th_ack <= tp->snd_max 1842 * then advance tp->snd_una to th->th_ack and drop 1843 * data from the retransmission queue. If this ACK reflects 1844 * more up to date window information we update our window information. 1845 */ 1846 case TCPS_ESTABLISHED: 1847 case TCPS_FIN_WAIT_1: 1848 case TCPS_FIN_WAIT_2: 1849 case TCPS_CLOSE_WAIT: 1850 case TCPS_CLOSING: 1851 case TCPS_LAST_ACK: 1852 case TCPS_TIME_WAIT: 1853 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1854 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1855 if (tlen == 0 && tiwin == tp->snd_wnd) { 1856 tcpstat.tcps_rcvdupack++; 1857 /* 1858 * If we have outstanding data (other than 1859 * a window probe), this is a completely 1860 * duplicate ack (ie, window info didn't 1861 * change), the ack is the biggest we've 1862 * seen and we've seen exactly our rexmt 1863 * threshhold of them, assume a packet 1864 * has been dropped and retransmit it. 1865 * Kludge snd_nxt & the congestion 1866 * window so we send only this one 1867 * packet. 1868 * 1869 * We know we're losing at the current 1870 * window size so do congestion avoidance 1871 * (set ssthresh to half the current window 1872 * and pull our congestion window back to 1873 * the new ssthresh). 1874 * 1875 * Dup acks mean that packets have left the 1876 * network (they're now cached at the receiver) 1877 * so bump cwnd by the amount in the receiver 1878 * to keep a constant cwnd packets in the 1879 * network. 1880 */ 1881 if (!callout_active(tp->tt_rexmt) || 1882 th->th_ack != tp->snd_una) 1883 tp->t_dupacks = 0; 1884 else if (++tp->t_dupacks > tcprexmtthresh || 1885 (tcp_do_newreno && 1886 IN_FASTRECOVERY(tp))) { 1887 tp->snd_cwnd += tp->t_maxseg; 1888 (void) tcp_output(tp); 1889 goto drop; 1890 } else if (tp->t_dupacks == tcprexmtthresh) { 1891 tcp_seq onxt = tp->snd_nxt; 1892 u_int win; 1893 if (tcp_do_newreno && 1894 SEQ_LEQ(th->th_ack, 1895 tp->snd_recover)) { 1896 tp->t_dupacks = 0; 1897 break; 1898 } 1899 win = min(tp->snd_wnd, tp->snd_cwnd) / 1900 2 / tp->t_maxseg; 1901 if (win < 2) 1902 win = 2; 1903 tp->snd_ssthresh = win * tp->t_maxseg; 1904 ENTER_FASTRECOVERY(tp); 1905 tp->snd_recover = tp->snd_max; 1906 callout_stop(tp->tt_rexmt); 1907 tp->t_rtttime = 0; 1908 tp->snd_nxt = th->th_ack; 1909 tp->snd_cwnd = tp->t_maxseg; 1910 (void) tcp_output(tp); 1911 KASSERT(tp->snd_limited <= 2, 1912 ("tp->snd_limited too big")); 1913 tp->snd_cwnd = tp->snd_ssthresh + 1914 tp->t_maxseg * 1915 (tp->t_dupacks - tp->snd_limited); 1916 if (SEQ_GT(onxt, tp->snd_nxt)) 1917 tp->snd_nxt = onxt; 1918 goto drop; 1919 } else if (tcp_do_rfc3042) { 1920 u_long oldcwnd = tp->snd_cwnd; 1921 tcp_seq oldsndmax = tp->snd_max; 1922 u_int sent; 1923 1924 KASSERT(tp->t_dupacks == 1 || 1925 tp->t_dupacks == 2, 1926 ("dupacks not 1 or 2")); 1927 if (tp->t_dupacks == 1) 1928 tp->snd_limited = 0; 1929 tp->snd_cwnd = 1930 (tp->snd_nxt - tp->snd_una) + 1931 (tp->t_dupacks - tp->snd_limited) * 1932 tp->t_maxseg; 1933 (void) tcp_output(tp); 1934 sent = tp->snd_max - oldsndmax; 1935 if (sent > tp->t_maxseg) { 1936 KASSERT((tp->t_dupacks == 2 && 1937 tp->snd_limited == 0) || 1938 (sent == tp->t_maxseg + 1 && 1939 tp->t_flags & TF_SENTFIN), 1940 ("sent too much")); 1941 tp->snd_limited = 2; 1942 } else if (sent > 0) 1943 ++tp->snd_limited; 1944 tp->snd_cwnd = oldcwnd; 1945 goto drop; 1946 } 1947 } else 1948 tp->t_dupacks = 0; 1949 break; 1950 } 1951 1952 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1953 1954 /* 1955 * If the congestion window was inflated to account 1956 * for the other side's cached packets, retract it. 1957 */ 1958 if (tcp_do_newreno) { 1959 if (IN_FASTRECOVERY(tp)) { 1960 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1961 tcp_newreno_partial_ack(tp, th); 1962 } else { 1963 /* 1964 * Window inflation should have left us 1965 * with approximately snd_ssthresh 1966 * outstanding data. 1967 * But in case we would be inclined to 1968 * send a burst, better to do it via 1969 * the slow start mechanism. 1970 */ 1971 if (SEQ_GT(th->th_ack + 1972 tp->snd_ssthresh, 1973 tp->snd_max)) 1974 tp->snd_cwnd = tp->snd_max - 1975 th->th_ack + 1976 tp->t_maxseg; 1977 else 1978 tp->snd_cwnd = tp->snd_ssthresh; 1979 } 1980 } 1981 } else { 1982 if (tp->t_dupacks >= tcprexmtthresh && 1983 tp->snd_cwnd > tp->snd_ssthresh) 1984 tp->snd_cwnd = tp->snd_ssthresh; 1985 } 1986 tp->t_dupacks = 0; 1987 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1988 tcpstat.tcps_rcvacktoomuch++; 1989 goto dropafterack; 1990 } 1991 /* 1992 * If we reach this point, ACK is not a duplicate, 1993 * i.e., it ACKs something we sent. 1994 */ 1995 if (tp->t_flags & TF_NEEDSYN) { 1996 /* 1997 * T/TCP: Connection was half-synchronized, and our 1998 * SYN has been ACK'd (so connection is now fully 1999 * synchronized). Go to non-starred state, 2000 * increment snd_una for ACK of SYN, and check if 2001 * we can do window scaling. 2002 */ 2003 tp->t_flags &= ~TF_NEEDSYN; 2004 tp->snd_una++; 2005 /* Do window scaling? */ 2006 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2007 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2008 tp->snd_scale = tp->requested_s_scale; 2009 tp->rcv_scale = tp->request_r_scale; 2010 } 2011 } 2012 2013 process_ACK: 2014 acked = th->th_ack - tp->snd_una; 2015 tcpstat.tcps_rcvackpack++; 2016 tcpstat.tcps_rcvackbyte += acked; 2017 2018 /* 2019 * If we just performed our first retransmit, and the ACK 2020 * arrives within our recovery window, then it was a mistake 2021 * to do the retransmit in the first place. Recover our 2022 * original cwnd and ssthresh, and proceed to transmit where 2023 * we left off. 2024 */ 2025 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2026 ++tcpstat.tcps_sndrexmitbad; 2027 tp->snd_cwnd = tp->snd_cwnd_prev; 2028 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2029 tp->snd_recover = tp->snd_recover_prev; 2030 if (tp->t_flags & TF_WASFRECOVERY) 2031 ENTER_FASTRECOVERY(tp); 2032 tp->snd_nxt = tp->snd_max; 2033 tp->t_badrxtwin = 0; /* XXX probably not required */ 2034 } 2035 2036 /* 2037 * If we have a timestamp reply, update smoothed 2038 * round trip time. If no timestamp is present but 2039 * transmit timer is running and timed sequence 2040 * number was acked, update smoothed round trip time. 2041 * Since we now have an rtt measurement, cancel the 2042 * timer backoff (cf., Phil Karn's retransmit alg.). 2043 * Recompute the initial retransmit timer. 2044 * 2045 * Some boxes send broken timestamp replies 2046 * during the SYN+ACK phase, ignore 2047 * timestamps of 0 or we could calculate a 2048 * huge RTT and blow up the retransmit timer. 2049 */ 2050 if ((to.to_flags & TOF_TS) != 0 && 2051 to.to_tsecr) { 2052 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2053 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2054 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2055 } 2056 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2057 2058 /* 2059 * If all outstanding data is acked, stop retransmit 2060 * timer and remember to restart (more output or persist). 2061 * If there is more data to be acked, restart retransmit 2062 * timer, using current (possibly backed-off) value. 2063 */ 2064 if (th->th_ack == tp->snd_max) { 2065 callout_stop(tp->tt_rexmt); 2066 needoutput = 1; 2067 } else if (!callout_active(tp->tt_persist)) 2068 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2069 tcp_timer_rexmt, tp); 2070 2071 /* 2072 * If no data (only SYN) was ACK'd, 2073 * skip rest of ACK processing. 2074 */ 2075 if (acked == 0) 2076 goto step6; 2077 2078 /* 2079 * When new data is acked, open the congestion window. 2080 * If the window gives us less than ssthresh packets 2081 * in flight, open exponentially (maxseg per packet). 2082 * Otherwise open linearly: maxseg per window 2083 * (maxseg^2 / cwnd per packet). 2084 */ 2085 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) { 2086 register u_int cw = tp->snd_cwnd; 2087 register u_int incr = tp->t_maxseg; 2088 if (cw > tp->snd_ssthresh) 2089 incr = incr * incr / cw; 2090 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2091 } 2092 if (acked > so->so_snd.sb_cc) { 2093 tp->snd_wnd -= so->so_snd.sb_cc; 2094 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2095 ourfinisacked = 1; 2096 } else { 2097 sbdrop(&so->so_snd, acked); 2098 tp->snd_wnd -= acked; 2099 ourfinisacked = 0; 2100 } 2101 sowwakeup(so); 2102 /* detect una wraparound */ 2103 if (tcp_do_newreno && !IN_FASTRECOVERY(tp) && 2104 SEQ_GT(tp->snd_una, tp->snd_recover) && 2105 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2106 tp->snd_recover = th->th_ack - 1; 2107 if (tcp_do_newreno && IN_FASTRECOVERY(tp) && 2108 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2109 EXIT_FASTRECOVERY(tp); 2110 tp->snd_una = th->th_ack; 2111 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2112 tp->snd_nxt = tp->snd_una; 2113 2114 switch (tp->t_state) { 2115 2116 /* 2117 * In FIN_WAIT_1 STATE in addition to the processing 2118 * for the ESTABLISHED state if our FIN is now acknowledged 2119 * then enter FIN_WAIT_2. 2120 */ 2121 case TCPS_FIN_WAIT_1: 2122 if (ourfinisacked) { 2123 /* 2124 * If we can't receive any more 2125 * data, then closing user can proceed. 2126 * Starting the timer is contrary to the 2127 * specification, but if we don't get a FIN 2128 * we'll hang forever. 2129 */ 2130 /* XXXjl 2131 * we should release the tp also, and use a 2132 * compressed state. 2133 */ 2134 if (so->so_state & SS_CANTRCVMORE) { 2135 soisdisconnected(so); 2136 callout_reset(tp->tt_2msl, tcp_maxidle, 2137 tcp_timer_2msl, tp); 2138 } 2139 tp->t_state = TCPS_FIN_WAIT_2; 2140 } 2141 break; 2142 2143 /* 2144 * In CLOSING STATE in addition to the processing for 2145 * the ESTABLISHED state if the ACK acknowledges our FIN 2146 * then enter the TIME-WAIT state, otherwise ignore 2147 * the segment. 2148 */ 2149 case TCPS_CLOSING: 2150 if (ourfinisacked) { 2151 KASSERT(headlocked, ("headlocked")); 2152 tcp_twstart(tp); 2153 INP_INFO_WUNLOCK(&tcbinfo); 2154 m_freem(m); 2155 return; 2156 } 2157 break; 2158 2159 /* 2160 * In LAST_ACK, we may still be waiting for data to drain 2161 * and/or to be acked, as well as for the ack of our FIN. 2162 * If our FIN is now acknowledged, delete the TCB, 2163 * enter the closed state and return. 2164 */ 2165 case TCPS_LAST_ACK: 2166 if (ourfinisacked) { 2167 tp = tcp_close(tp); 2168 goto drop; 2169 } 2170 break; 2171 2172 /* 2173 * In TIME_WAIT state the only thing that should arrive 2174 * is a retransmission of the remote FIN. Acknowledge 2175 * it and restart the finack timer. 2176 */ 2177 case TCPS_TIME_WAIT: 2178 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2179 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2180 tcp_timer_2msl, tp); 2181 goto dropafterack; 2182 } 2183 } 2184 2185 step6: 2186 /* 2187 * Update window information. 2188 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2189 */ 2190 if ((thflags & TH_ACK) && 2191 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2192 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2193 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2194 /* keep track of pure window updates */ 2195 if (tlen == 0 && 2196 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2197 tcpstat.tcps_rcvwinupd++; 2198 tp->snd_wnd = tiwin; 2199 tp->snd_wl1 = th->th_seq; 2200 tp->snd_wl2 = th->th_ack; 2201 if (tp->snd_wnd > tp->max_sndwnd) 2202 tp->max_sndwnd = tp->snd_wnd; 2203 needoutput = 1; 2204 } 2205 2206 /* 2207 * Process segments with URG. 2208 */ 2209 if ((thflags & TH_URG) && th->th_urp && 2210 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2211 /* 2212 * This is a kludge, but if we receive and accept 2213 * random urgent pointers, we'll crash in 2214 * soreceive. It's hard to imagine someone 2215 * actually wanting to send this much urgent data. 2216 */ 2217 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2218 th->th_urp = 0; /* XXX */ 2219 thflags &= ~TH_URG; /* XXX */ 2220 goto dodata; /* XXX */ 2221 } 2222 /* 2223 * If this segment advances the known urgent pointer, 2224 * then mark the data stream. This should not happen 2225 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2226 * a FIN has been received from the remote side. 2227 * In these states we ignore the URG. 2228 * 2229 * According to RFC961 (Assigned Protocols), 2230 * the urgent pointer points to the last octet 2231 * of urgent data. We continue, however, 2232 * to consider it to indicate the first octet 2233 * of data past the urgent section as the original 2234 * spec states (in one of two places). 2235 */ 2236 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2237 tp->rcv_up = th->th_seq + th->th_urp; 2238 so->so_oobmark = so->so_rcv.sb_cc + 2239 (tp->rcv_up - tp->rcv_nxt) - 1; 2240 if (so->so_oobmark == 0) 2241 so->so_state |= SS_RCVATMARK; 2242 sohasoutofband(so); 2243 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2244 } 2245 /* 2246 * Remove out of band data so doesn't get presented to user. 2247 * This can happen independent of advancing the URG pointer, 2248 * but if two URG's are pending at once, some out-of-band 2249 * data may creep in... ick. 2250 */ 2251 if (th->th_urp <= (u_long)tlen && 2252 !(so->so_options & SO_OOBINLINE)) { 2253 /* hdr drop is delayed */ 2254 tcp_pulloutofband(so, th, m, drop_hdrlen); 2255 } 2256 } else { 2257 /* 2258 * If no out of band data is expected, 2259 * pull receive urgent pointer along 2260 * with the receive window. 2261 */ 2262 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2263 tp->rcv_up = tp->rcv_nxt; 2264 } 2265 dodata: /* XXX */ 2266 KASSERT(headlocked, ("headlocked")); 2267 /* 2268 * Process the segment text, merging it into the TCP sequencing queue, 2269 * and arranging for acknowledgment of receipt if necessary. 2270 * This process logically involves adjusting tp->rcv_wnd as data 2271 * is presented to the user (this happens in tcp_usrreq.c, 2272 * case PRU_RCVD). If a FIN has already been received on this 2273 * connection then we just ignore the text. 2274 */ 2275 if ((tlen || (thflags & TH_FIN)) && 2276 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2277 m_adj(m, drop_hdrlen); /* delayed header drop */ 2278 /* 2279 * Insert segment which includes th into TCP reassembly queue 2280 * with control block tp. Set thflags to whether reassembly now 2281 * includes a segment with FIN. This handles the common case 2282 * inline (segment is the next to be received on an established 2283 * connection, and the queue is empty), avoiding linkage into 2284 * and removal from the queue and repetition of various 2285 * conversions. 2286 * Set DELACK for segments received in order, but ack 2287 * immediately when segments are out of order (so 2288 * fast retransmit can work). 2289 */ 2290 if (th->th_seq == tp->rcv_nxt && 2291 LIST_EMPTY(&tp->t_segq) && 2292 TCPS_HAVEESTABLISHED(tp->t_state)) { 2293 if (DELAY_ACK(tp)) 2294 tp->t_flags |= TF_DELACK; 2295 else 2296 tp->t_flags |= TF_ACKNOW; 2297 tp->rcv_nxt += tlen; 2298 thflags = th->th_flags & TH_FIN; 2299 tcpstat.tcps_rcvpack++; 2300 tcpstat.tcps_rcvbyte += tlen; 2301 ND6_HINT(tp); 2302 if (so->so_state & SS_CANTRCVMORE) 2303 m_freem(m); 2304 else 2305 sbappendstream(&so->so_rcv, m); 2306 sorwakeup(so); 2307 } else { 2308 thflags = tcp_reass(tp, th, &tlen, m); 2309 tp->t_flags |= TF_ACKNOW; 2310 } 2311 2312 /* 2313 * Note the amount of data that peer has sent into 2314 * our window, in order to estimate the sender's 2315 * buffer size. 2316 */ 2317 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2318 } else { 2319 m_freem(m); 2320 thflags &= ~TH_FIN; 2321 } 2322 2323 /* 2324 * If FIN is received ACK the FIN and let the user know 2325 * that the connection is closing. 2326 */ 2327 if (thflags & TH_FIN) { 2328 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2329 socantrcvmore(so); 2330 /* 2331 * If connection is half-synchronized 2332 * (ie NEEDSYN flag on) then delay ACK, 2333 * so it may be piggybacked when SYN is sent. 2334 * Otherwise, since we received a FIN then no 2335 * more input can be expected, send ACK now. 2336 */ 2337 if (tp->t_flags & TF_NEEDSYN) 2338 tp->t_flags |= TF_DELACK; 2339 else 2340 tp->t_flags |= TF_ACKNOW; 2341 tp->rcv_nxt++; 2342 } 2343 switch (tp->t_state) { 2344 2345 /* 2346 * In SYN_RECEIVED and ESTABLISHED STATES 2347 * enter the CLOSE_WAIT state. 2348 */ 2349 case TCPS_SYN_RECEIVED: 2350 tp->t_starttime = ticks; 2351 /*FALLTHROUGH*/ 2352 case TCPS_ESTABLISHED: 2353 tp->t_state = TCPS_CLOSE_WAIT; 2354 break; 2355 2356 /* 2357 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2358 * enter the CLOSING state. 2359 */ 2360 case TCPS_FIN_WAIT_1: 2361 tp->t_state = TCPS_CLOSING; 2362 break; 2363 2364 /* 2365 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2366 * starting the time-wait timer, turning off the other 2367 * standard timers. 2368 */ 2369 case TCPS_FIN_WAIT_2: 2370 KASSERT(headlocked == 1, ("headlocked should be 1")); 2371 tcp_twstart(tp); 2372 INP_INFO_WUNLOCK(&tcbinfo); 2373 return; 2374 2375 /* 2376 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2377 */ 2378 case TCPS_TIME_WAIT: 2379 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2380 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2381 tcp_timer_2msl, tp); 2382 break; 2383 } 2384 } 2385 INP_INFO_WUNLOCK(&tcbinfo); 2386 #ifdef TCPDEBUG 2387 if (so->so_options & SO_DEBUG) 2388 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2389 &tcp_savetcp, 0); 2390 #endif 2391 2392 /* 2393 * Return any desired output. 2394 */ 2395 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2396 (void) tcp_output(tp); 2397 2398 check_delack: 2399 if (tp->t_flags & TF_DELACK) { 2400 tp->t_flags &= ~TF_DELACK; 2401 callout_reset(tp->tt_delack, tcp_delacktime, 2402 tcp_timer_delack, tp); 2403 } 2404 INP_UNLOCK(inp); 2405 return; 2406 2407 dropafterack: 2408 /* 2409 * Generate an ACK dropping incoming segment if it occupies 2410 * sequence space, where the ACK reflects our state. 2411 * 2412 * We can now skip the test for the RST flag since all 2413 * paths to this code happen after packets containing 2414 * RST have been dropped. 2415 * 2416 * In the SYN-RECEIVED state, don't send an ACK unless the 2417 * segment we received passes the SYN-RECEIVED ACK test. 2418 * If it fails send a RST. This breaks the loop in the 2419 * "LAND" DoS attack, and also prevents an ACK storm 2420 * between two listening ports that have been sent forged 2421 * SYN segments, each with the source address of the other. 2422 */ 2423 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2424 (SEQ_GT(tp->snd_una, th->th_ack) || 2425 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2426 rstreason = BANDLIM_RST_OPENPORT; 2427 goto dropwithreset; 2428 } 2429 #ifdef TCPDEBUG 2430 if (so->so_options & SO_DEBUG) 2431 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2432 &tcp_savetcp, 0); 2433 #endif 2434 KASSERT(headlocked, ("headlocked should be 1")); 2435 INP_INFO_WUNLOCK(&tcbinfo); 2436 m_freem(m); 2437 tp->t_flags |= TF_ACKNOW; 2438 (void) tcp_output(tp); 2439 INP_UNLOCK(inp); 2440 return; 2441 2442 dropwithreset: 2443 /* 2444 * Generate a RST, dropping incoming segment. 2445 * Make ACK acceptable to originator of segment. 2446 * Don't bother to respond if destination was broadcast/multicast. 2447 */ 2448 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2449 goto drop; 2450 if (isipv6) { 2451 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2452 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2453 goto drop; 2454 } else { 2455 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2456 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2457 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2458 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2459 goto drop; 2460 } 2461 /* IPv6 anycast check is done at tcp6_input() */ 2462 2463 /* 2464 * Perform bandwidth limiting. 2465 */ 2466 if (badport_bandlim(rstreason) < 0) 2467 goto drop; 2468 2469 #ifdef TCPDEBUG 2470 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2471 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2472 &tcp_savetcp, 0); 2473 #endif 2474 2475 if (thflags & TH_ACK) 2476 /* mtod() below is safe as long as hdr dropping is delayed */ 2477 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2478 TH_RST); 2479 else { 2480 if (thflags & TH_SYN) 2481 tlen++; 2482 /* mtod() below is safe as long as hdr dropping is delayed */ 2483 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2484 (tcp_seq)0, TH_RST|TH_ACK); 2485 } 2486 2487 if (tp) 2488 INP_UNLOCK(inp); 2489 if (headlocked) 2490 INP_INFO_WUNLOCK(&tcbinfo); 2491 return; 2492 2493 drop: 2494 /* 2495 * Drop space held by incoming segment and return. 2496 */ 2497 #ifdef TCPDEBUG 2498 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2499 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2500 &tcp_savetcp, 0); 2501 #endif 2502 if (tp) 2503 INP_UNLOCK(inp); 2504 m_freem(m); 2505 if (headlocked) 2506 INP_INFO_WUNLOCK(&tcbinfo); 2507 return; 2508 } 2509 2510 /* 2511 * Parse TCP options and place in tcpopt. 2512 */ 2513 static void 2514 tcp_dooptions(to, cp, cnt, is_syn) 2515 struct tcpopt *to; 2516 u_char *cp; 2517 int cnt; 2518 int is_syn; 2519 { 2520 int opt, optlen; 2521 2522 to->to_flags = 0; 2523 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2524 opt = cp[0]; 2525 if (opt == TCPOPT_EOL) 2526 break; 2527 if (opt == TCPOPT_NOP) 2528 optlen = 1; 2529 else { 2530 if (cnt < 2) 2531 break; 2532 optlen = cp[1]; 2533 if (optlen < 2 || optlen > cnt) 2534 break; 2535 } 2536 switch (opt) { 2537 case TCPOPT_MAXSEG: 2538 if (optlen != TCPOLEN_MAXSEG) 2539 continue; 2540 if (!is_syn) 2541 continue; 2542 to->to_flags |= TOF_MSS; 2543 bcopy((char *)cp + 2, 2544 (char *)&to->to_mss, sizeof(to->to_mss)); 2545 to->to_mss = ntohs(to->to_mss); 2546 break; 2547 case TCPOPT_WINDOW: 2548 if (optlen != TCPOLEN_WINDOW) 2549 continue; 2550 if (! is_syn) 2551 continue; 2552 to->to_flags |= TOF_SCALE; 2553 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2554 break; 2555 case TCPOPT_TIMESTAMP: 2556 if (optlen != TCPOLEN_TIMESTAMP) 2557 continue; 2558 to->to_flags |= TOF_TS; 2559 bcopy((char *)cp + 2, 2560 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2561 to->to_tsval = ntohl(to->to_tsval); 2562 bcopy((char *)cp + 6, 2563 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2564 to->to_tsecr = ntohl(to->to_tsecr); 2565 break; 2566 case TCPOPT_CC: 2567 if (optlen != TCPOLEN_CC) 2568 continue; 2569 to->to_flags |= TOF_CC; 2570 bcopy((char *)cp + 2, 2571 (char *)&to->to_cc, sizeof(to->to_cc)); 2572 to->to_cc = ntohl(to->to_cc); 2573 break; 2574 case TCPOPT_CCNEW: 2575 if (optlen != TCPOLEN_CC) 2576 continue; 2577 if (!is_syn) 2578 continue; 2579 to->to_flags |= TOF_CCNEW; 2580 bcopy((char *)cp + 2, 2581 (char *)&to->to_cc, sizeof(to->to_cc)); 2582 to->to_cc = ntohl(to->to_cc); 2583 break; 2584 case TCPOPT_CCECHO: 2585 if (optlen != TCPOLEN_CC) 2586 continue; 2587 if (!is_syn) 2588 continue; 2589 to->to_flags |= TOF_CCECHO; 2590 bcopy((char *)cp + 2, 2591 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2592 to->to_ccecho = ntohl(to->to_ccecho); 2593 break; 2594 #ifdef TCP_SIGNATURE 2595 /* 2596 * XXX In order to reply to a host which has set the 2597 * TCP_SIGNATURE option in its initial SYN, we have to 2598 * record the fact that the option was observed here 2599 * for the syncache code to perform the correct response. 2600 */ 2601 case TCPOPT_SIGNATURE: 2602 if (optlen != TCPOLEN_SIGNATURE) 2603 continue; 2604 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2605 break; 2606 #endif 2607 default: 2608 continue; 2609 } 2610 } 2611 } 2612 2613 /* 2614 * Pull out of band byte out of a segment so 2615 * it doesn't appear in the user's data queue. 2616 * It is still reflected in the segment length for 2617 * sequencing purposes. 2618 */ 2619 static void 2620 tcp_pulloutofband(so, th, m, off) 2621 struct socket *so; 2622 struct tcphdr *th; 2623 register struct mbuf *m; 2624 int off; /* delayed to be droped hdrlen */ 2625 { 2626 int cnt = off + th->th_urp - 1; 2627 2628 while (cnt >= 0) { 2629 if (m->m_len > cnt) { 2630 char *cp = mtod(m, caddr_t) + cnt; 2631 struct tcpcb *tp = sototcpcb(so); 2632 2633 tp->t_iobc = *cp; 2634 tp->t_oobflags |= TCPOOB_HAVEDATA; 2635 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2636 m->m_len--; 2637 if (m->m_flags & M_PKTHDR) 2638 m->m_pkthdr.len--; 2639 return; 2640 } 2641 cnt -= m->m_len; 2642 m = m->m_next; 2643 if (m == 0) 2644 break; 2645 } 2646 panic("tcp_pulloutofband"); 2647 } 2648 2649 /* 2650 * Collect new round-trip time estimate 2651 * and update averages and current timeout. 2652 */ 2653 static void 2654 tcp_xmit_timer(tp, rtt) 2655 register struct tcpcb *tp; 2656 int rtt; 2657 { 2658 register int delta; 2659 2660 tcpstat.tcps_rttupdated++; 2661 tp->t_rttupdated++; 2662 if (tp->t_srtt != 0) { 2663 /* 2664 * srtt is stored as fixed point with 5 bits after the 2665 * binary point (i.e., scaled by 8). The following magic 2666 * is equivalent to the smoothing algorithm in rfc793 with 2667 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2668 * point). Adjust rtt to origin 0. 2669 */ 2670 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2671 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2672 2673 if ((tp->t_srtt += delta) <= 0) 2674 tp->t_srtt = 1; 2675 2676 /* 2677 * We accumulate a smoothed rtt variance (actually, a 2678 * smoothed mean difference), then set the retransmit 2679 * timer to smoothed rtt + 4 times the smoothed variance. 2680 * rttvar is stored as fixed point with 4 bits after the 2681 * binary point (scaled by 16). The following is 2682 * equivalent to rfc793 smoothing with an alpha of .75 2683 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2684 * rfc793's wired-in beta. 2685 */ 2686 if (delta < 0) 2687 delta = -delta; 2688 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2689 if ((tp->t_rttvar += delta) <= 0) 2690 tp->t_rttvar = 1; 2691 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2692 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2693 } else { 2694 /* 2695 * No rtt measurement yet - use the unsmoothed rtt. 2696 * Set the variance to half the rtt (so our first 2697 * retransmit happens at 3*rtt). 2698 */ 2699 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2700 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2701 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2702 } 2703 tp->t_rtttime = 0; 2704 tp->t_rxtshift = 0; 2705 2706 /* 2707 * the retransmit should happen at rtt + 4 * rttvar. 2708 * Because of the way we do the smoothing, srtt and rttvar 2709 * will each average +1/2 tick of bias. When we compute 2710 * the retransmit timer, we want 1/2 tick of rounding and 2711 * 1 extra tick because of +-1/2 tick uncertainty in the 2712 * firing of the timer. The bias will give us exactly the 2713 * 1.5 tick we need. But, because the bias is 2714 * statistical, we have to test that we don't drop below 2715 * the minimum feasible timer (which is 2 ticks). 2716 */ 2717 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2718 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2719 2720 /* 2721 * We received an ack for a packet that wasn't retransmitted; 2722 * it is probably safe to discard any error indications we've 2723 * received recently. This isn't quite right, but close enough 2724 * for now (a route might have failed after we sent a segment, 2725 * and the return path might not be symmetrical). 2726 */ 2727 tp->t_softerror = 0; 2728 } 2729 2730 /* 2731 * Determine a reasonable value for maxseg size. 2732 * If the route is known, check route for mtu. 2733 * If none, use an mss that can be handled on the outgoing 2734 * interface without forcing IP to fragment; if bigger than 2735 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2736 * to utilize large mbufs. If no route is found, route has no mtu, 2737 * or the destination isn't local, use a default, hopefully conservative 2738 * size (usually 512 or the default IP max size, but no more than the mtu 2739 * of the interface), as we can't discover anything about intervening 2740 * gateways or networks. We also initialize the congestion/slow start 2741 * window to be a single segment if the destination isn't local. 2742 * While looking at the routing entry, we also initialize other path-dependent 2743 * parameters from pre-set or cached values in the routing entry. 2744 * 2745 * Also take into account the space needed for options that we 2746 * send regularly. Make maxseg shorter by that amount to assure 2747 * that we can send maxseg amount of data even when the options 2748 * are present. Store the upper limit of the length of options plus 2749 * data in maxopd. 2750 * 2751 * 2752 * In case of T/TCP, we call this routine during implicit connection 2753 * setup as well (offer = -1), to initialize maxseg from the cached 2754 * MSS of our peer. 2755 * 2756 * NOTE that this routine is only called when we process an incoming 2757 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2758 */ 2759 void 2760 tcp_mss(tp, offer) 2761 struct tcpcb *tp; 2762 int offer; 2763 { 2764 int rtt, mss; 2765 u_long bufsize; 2766 u_long maxmtu; 2767 struct inpcb *inp = tp->t_inpcb; 2768 struct socket *so; 2769 struct hc_metrics_lite metrics; 2770 struct rmxp_tao tao; 2771 int origoffer = offer; 2772 #ifdef INET6 2773 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2774 size_t min_protoh = isipv6 ? 2775 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2776 sizeof (struct tcpiphdr); 2777 #else 2778 const size_t min_protoh = sizeof(struct tcpiphdr); 2779 #endif 2780 bzero(&tao, sizeof(tao)); 2781 2782 /* initialize */ 2783 #ifdef INET6 2784 if (isipv6) { 2785 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2786 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2787 } else 2788 #endif 2789 { 2790 maxmtu = tcp_maxmtu(&inp->inp_inc); 2791 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2792 } 2793 so = inp->inp_socket; 2794 2795 /* 2796 * no route to sender, take default mss and return 2797 */ 2798 if (maxmtu == 0) 2799 return; 2800 2801 /* what have we got? */ 2802 switch (offer) { 2803 case 0: 2804 /* 2805 * Offer == 0 means that there was no MSS on the SYN 2806 * segment, in this case we use tcp_mssdflt. 2807 */ 2808 offer = 2809 #ifdef INET6 2810 isipv6 ? tcp_v6mssdflt : 2811 #endif 2812 tcp_mssdflt; 2813 break; 2814 2815 case -1: 2816 /* 2817 * Offer == -1 means that we didn't receive SYN yet, 2818 * use cached value in that case; 2819 */ 2820 if (tcp_do_rfc1644) 2821 tcp_hc_gettao(&inp->inp_inc, &tao); 2822 if (tao.tao_mssopt != 0) 2823 offer = tao.tao_mssopt; 2824 /* FALLTHROUGH */ 2825 2826 default: 2827 /* 2828 * Prevent DoS attack with too small MSS. Round up 2829 * to at least minmss. 2830 */ 2831 offer = max(offer, tcp_minmss); 2832 /* 2833 * Sanity check: make sure that maxopd will be large 2834 * enough to allow some data on segments even if the 2835 * all the option space is used (40bytes). Otherwise 2836 * funny things may happen in tcp_output. 2837 */ 2838 offer = max(offer, 64); 2839 if (tcp_do_rfc1644) 2840 tcp_hc_updatetao(&inp->inp_inc, 2841 TCP_HC_TAO_MSSOPT, 0, offer); 2842 } 2843 2844 /* 2845 * rmx information is now retrieved from tcp_hostcache 2846 */ 2847 tcp_hc_get(&inp->inp_inc, &metrics); 2848 2849 /* 2850 * if there's a discovered mtu int tcp hostcache, use it 2851 * else, use the link mtu. 2852 */ 2853 if (metrics.rmx_mtu) 2854 mss = metrics.rmx_mtu - min_protoh; 2855 else { 2856 #ifdef INET6 2857 if (isipv6) { 2858 mss = maxmtu - min_protoh; 2859 if (!path_mtu_discovery && 2860 !in6_localaddr(&inp->in6p_faddr)) 2861 mss = min(mss, tcp_v6mssdflt); 2862 } else 2863 #endif 2864 { 2865 mss = maxmtu - min_protoh; 2866 if (!path_mtu_discovery && 2867 !in_localaddr(inp->inp_faddr)) 2868 mss = min(mss, tcp_mssdflt); 2869 } 2870 } 2871 mss = min(mss, offer); 2872 2873 /* 2874 * maxopd stores the maximum length of data AND options 2875 * in a segment; maxseg is the amount of data in a normal 2876 * segment. We need to store this value (maxopd) apart 2877 * from maxseg, because now every segment carries options 2878 * and thus we normally have somewhat less data in segments. 2879 */ 2880 tp->t_maxopd = mss; 2881 2882 /* 2883 * In case of T/TCP, origoffer==-1 indicates, that no segments 2884 * were received yet. In this case we just guess, otherwise 2885 * we do the same as before T/TCP. 2886 */ 2887 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2888 (origoffer == -1 || 2889 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2890 mss -= TCPOLEN_TSTAMP_APPA; 2891 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2892 (origoffer == -1 || 2893 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2894 mss -= TCPOLEN_CC_APPA; 2895 tp->t_maxseg = mss; 2896 2897 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2898 if (mss > MCLBYTES) 2899 mss &= ~(MCLBYTES-1); 2900 #else 2901 if (mss > MCLBYTES) 2902 mss = mss / MCLBYTES * MCLBYTES; 2903 #endif 2904 tp->t_maxseg = mss; 2905 2906 /* 2907 * If there's a pipesize, change the socket buffer to that size, 2908 * don't change if sb_hiwat is different than default (then it 2909 * has been changed on purpose with setsockopt). 2910 * Make the socket buffers an integral number of mss units; 2911 * if the mss is larger than the socket buffer, decrease the mss. 2912 */ 2913 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2914 bufsize = metrics.rmx_sendpipe; 2915 else 2916 bufsize = so->so_snd.sb_hiwat; 2917 if (bufsize < mss) 2918 mss = bufsize; 2919 else { 2920 bufsize = roundup(bufsize, mss); 2921 if (bufsize > sb_max) 2922 bufsize = sb_max; 2923 if (bufsize > so->so_snd.sb_hiwat) 2924 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2925 } 2926 tp->t_maxseg = mss; 2927 2928 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 2929 bufsize = metrics.rmx_recvpipe; 2930 else 2931 bufsize = so->so_rcv.sb_hiwat; 2932 if (bufsize > mss) { 2933 bufsize = roundup(bufsize, mss); 2934 if (bufsize > sb_max) 2935 bufsize = sb_max; 2936 if (bufsize > so->so_rcv.sb_hiwat) 2937 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2938 } 2939 /* 2940 * While we're here, check the others too 2941 */ 2942 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 2943 tp->t_srtt = rtt; 2944 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2945 tcpstat.tcps_usedrtt++; 2946 if (metrics.rmx_rttvar) { 2947 tp->t_rttvar = metrics.rmx_rttvar; 2948 tcpstat.tcps_usedrttvar++; 2949 } else { 2950 /* default variation is +- 1 rtt */ 2951 tp->t_rttvar = 2952 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2953 } 2954 TCPT_RANGESET(tp->t_rxtcur, 2955 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2956 tp->t_rttmin, TCPTV_REXMTMAX); 2957 } 2958 if (metrics.rmx_ssthresh) { 2959 /* 2960 * There's some sort of gateway or interface 2961 * buffer limit on the path. Use this to set 2962 * the slow start threshhold, but set the 2963 * threshold to no less than 2*mss. 2964 */ 2965 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 2966 tcpstat.tcps_usedssthresh++; 2967 } 2968 if (metrics.rmx_bandwidth) 2969 tp->snd_bandwidth = metrics.rmx_bandwidth; 2970 2971 /* 2972 * Set the slow-start flight size depending on whether this 2973 * is a local network or not. 2974 * 2975 * Extend this so we cache the cwnd too and retrieve it here. 2976 * Make cwnd even bigger than RFC3390 suggests but only if we 2977 * have previous experience with the remote host. Be careful 2978 * not make cwnd bigger than remote receive window or our own 2979 * send socket buffer. Maybe put some additional upper bound 2980 * on the retrieved cwnd. Should do incremental updates to 2981 * hostcache when cwnd collapses so next connection doesn't 2982 * overloads the path again. 2983 * 2984 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 2985 * We currently check only in syncache_socket for that. 2986 */ 2987 #define TCP_METRICS_CWND 2988 #ifdef TCP_METRICS_CWND 2989 if (metrics.rmx_cwnd) 2990 tp->snd_cwnd = max(mss, 2991 min(metrics.rmx_cwnd / 2, 2992 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 2993 else 2994 #endif 2995 if (tcp_do_rfc3390) 2996 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 2997 #ifdef INET6 2998 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2999 (!isipv6 && in_localaddr(inp->inp_faddr))) 3000 #else 3001 else if (in_localaddr(inp->inp_faddr)) 3002 #endif 3003 tp->snd_cwnd = mss * ss_fltsz_local; 3004 else 3005 tp->snd_cwnd = mss * ss_fltsz; 3006 } 3007 3008 /* 3009 * Determine the MSS option to send on an outgoing SYN. 3010 */ 3011 int 3012 tcp_mssopt(inc) 3013 struct in_conninfo *inc; 3014 { 3015 int mss = 0; 3016 u_long maxmtu = 0; 3017 u_long thcmtu = 0; 3018 size_t min_protoh; 3019 #ifdef INET6 3020 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3021 #endif 3022 3023 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3024 3025 #ifdef INET6 3026 if (isipv6) { 3027 mss = tcp_v6mssdflt; 3028 maxmtu = tcp_maxmtu6(inc); 3029 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3030 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3031 } else 3032 #endif 3033 { 3034 mss = tcp_mssdflt; 3035 maxmtu = tcp_maxmtu(inc); 3036 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3037 min_protoh = sizeof(struct tcpiphdr); 3038 } 3039 if (maxmtu && thcmtu) 3040 mss = min(maxmtu, thcmtu) - min_protoh; 3041 else if (maxmtu || thcmtu) 3042 mss = max(maxmtu, thcmtu) - min_protoh; 3043 3044 return (mss); 3045 } 3046 3047 3048 /* 3049 * On a partial ack arrives, force the retransmission of the 3050 * next unacknowledged segment. Do not clear tp->t_dupacks. 3051 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3052 * be started again. 3053 */ 3054 static void 3055 tcp_newreno_partial_ack(tp, th) 3056 struct tcpcb *tp; 3057 struct tcphdr *th; 3058 { 3059 tcp_seq onxt = tp->snd_nxt; 3060 u_long ocwnd = tp->snd_cwnd; 3061 3062 callout_stop(tp->tt_rexmt); 3063 tp->t_rtttime = 0; 3064 tp->snd_nxt = th->th_ack; 3065 /* 3066 * Set snd_cwnd to one segment beyond acknowledged offset. 3067 * (tp->snd_una has not yet been updated when this function is called.) 3068 */ 3069 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3070 tp->t_flags |= TF_ACKNOW; 3071 (void) tcp_output(tp); 3072 tp->snd_cwnd = ocwnd; 3073 if (SEQ_GT(onxt, tp->snd_nxt)) 3074 tp->snd_nxt = onxt; 3075 /* 3076 * Partial window deflation. Relies on fact that tp->snd_una 3077 * not updated yet. 3078 */ 3079 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 3080 } 3081 3082 /* 3083 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3084 * looking for a pcb in the listen state. Returns 0 otherwise. 3085 */ 3086 static int 3087 tcp_timewait(tw, to, th, m, tlen) 3088 struct tcptw *tw; 3089 struct tcpopt *to; 3090 struct tcphdr *th; 3091 struct mbuf *m; 3092 int tlen; 3093 { 3094 int thflags; 3095 tcp_seq seq; 3096 #ifdef INET6 3097 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3098 #else 3099 const int isipv6 = 0; 3100 #endif 3101 3102 thflags = th->th_flags; 3103 3104 /* 3105 * NOTE: for FIN_WAIT_2 (to be added later), 3106 * must validate sequence number before accepting RST 3107 */ 3108 3109 /* 3110 * If the segment contains RST: 3111 * Drop the segment - see Stevens, vol. 2, p. 964 and 3112 * RFC 1337. 3113 */ 3114 if (thflags & TH_RST) 3115 goto drop; 3116 3117 /* 3118 * If segment contains a SYN and CC [not CC.NEW] option: 3119 * if connection duration > MSL, drop packet and send RST; 3120 * 3121 * if SEG.CC > CCrecv then is new SYN. 3122 * Complete close and delete TCPCB. Then reprocess 3123 * segment, hoping to find new TCPCB in LISTEN state; 3124 * 3125 * else must be old SYN; drop it. 3126 * else do normal processing. 3127 */ 3128 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) { 3129 if ((ticks - tw->t_starttime) > tcp_msl) 3130 goto reset; 3131 if (CC_GT(to->to_cc, tw->cc_recv)) { 3132 (void) tcp_twclose(tw, 0); 3133 return (1); 3134 } 3135 goto drop; 3136 } 3137 3138 #if 0 3139 /* PAWS not needed at the moment */ 3140 /* 3141 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3142 * and it's less than ts_recent, drop it. 3143 */ 3144 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3145 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3146 if ((thflags & TH_ACK) == 0) 3147 goto drop; 3148 goto ack; 3149 } 3150 /* 3151 * ts_recent is never updated because we never accept new segments. 3152 */ 3153 #endif 3154 3155 /* 3156 * If a new connection request is received 3157 * while in TIME_WAIT, drop the old connection 3158 * and start over if the sequence numbers 3159 * are above the previous ones. 3160 */ 3161 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3162 (void) tcp_twclose(tw, 0); 3163 return (1); 3164 } 3165 3166 /* 3167 * Drop the the segment if it does not contain an ACK. 3168 */ 3169 if ((thflags & TH_ACK) == 0) 3170 goto drop; 3171 3172 /* 3173 * Reset the 2MSL timer if this is a duplicate FIN. 3174 */ 3175 if (thflags & TH_FIN) { 3176 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3177 if (seq + 1 == tw->rcv_nxt) 3178 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3179 } 3180 3181 /* 3182 * Acknowledge the segment if it has data or is not a duplicate ACK. 3183 */ 3184 if (thflags != TH_ACK || tlen != 0 || 3185 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3186 tcp_twrespond(tw, TH_ACK); 3187 goto drop; 3188 3189 reset: 3190 /* 3191 * Generate a RST, dropping incoming segment. 3192 * Make ACK acceptable to originator of segment. 3193 * Don't bother to respond if destination was broadcast/multicast. 3194 */ 3195 if (m->m_flags & (M_BCAST|M_MCAST)) 3196 goto drop; 3197 if (isipv6) { 3198 struct ip6_hdr *ip6; 3199 3200 /* IPv6 anycast check is done at tcp6_input() */ 3201 ip6 = mtod(m, struct ip6_hdr *); 3202 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3203 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3204 goto drop; 3205 } else { 3206 struct ip *ip; 3207 3208 ip = mtod(m, struct ip *); 3209 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3210 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3211 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3212 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3213 goto drop; 3214 } 3215 if (thflags & TH_ACK) { 3216 tcp_respond(NULL, 3217 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3218 } else { 3219 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3220 tcp_respond(NULL, 3221 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3222 } 3223 INP_UNLOCK(tw->tw_inpcb); 3224 return (0); 3225 3226 drop: 3227 INP_UNLOCK(tw->tw_inpcb); 3228 m_freem(m); 3229 return (0); 3230 } 3231