1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 34 * $FreeBSD$ 35 */ 36 37 #include "opt_ipfw.h" /* for ipfw_fwd */ 38 #include "opt_inet.h" 39 #include "opt_inet6.h" 40 #include "opt_ipsec.h" 41 #include "opt_mac.h" 42 #include "opt_tcpdebug.h" 43 #include "opt_tcp_input.h" 44 45 #include <sys/param.h> 46 #include <sys/kernel.h> 47 #include <sys/mac.h> 48 #include <sys/malloc.h> 49 #include <sys/mbuf.h> 50 #include <sys/proc.h> /* for proc0 declaration */ 51 #include <sys/protosw.h> 52 #include <sys/signalvar.h> 53 #include <sys/socket.h> 54 #include <sys/socketvar.h> 55 #include <sys/sysctl.h> 56 #include <sys/syslog.h> 57 #include <sys/systm.h> 58 59 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 60 61 #include <vm/uma.h> 62 63 #include <net/if.h> 64 #include <net/route.h> 65 66 #include <netinet/in.h> 67 #include <netinet/in_pcb.h> 68 #include <netinet/in_systm.h> 69 #include <netinet/in_var.h> 70 #include <netinet/ip.h> 71 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 72 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 73 #include <netinet/ip_var.h> 74 #include <netinet/ip6.h> 75 #include <netinet/icmp6.h> 76 #include <netinet6/in6_pcb.h> 77 #include <netinet6/ip6_var.h> 78 #include <netinet6/nd6.h> 79 #include <netinet/tcp.h> 80 #include <netinet/tcp_fsm.h> 81 #include <netinet/tcp_seq.h> 82 #include <netinet/tcp_timer.h> 83 #include <netinet/tcp_var.h> 84 #include <netinet6/tcp6_var.h> 85 #include <netinet/tcpip.h> 86 #ifdef TCPDEBUG 87 #include <netinet/tcp_debug.h> 88 #endif /* TCPDEBUG */ 89 90 #ifdef FAST_IPSEC 91 #include <netipsec/ipsec.h> 92 #include <netipsec/ipsec6.h> 93 #endif /*FAST_IPSEC*/ 94 95 #ifdef IPSEC 96 #include <netinet6/ipsec.h> 97 #include <netinet6/ipsec6.h> 98 #include <netkey/key.h> 99 #endif /*IPSEC*/ 100 101 #include <machine/in_cksum.h> 102 103 static const int tcprexmtthresh = 3; 104 tcp_cc tcp_ccgen; 105 106 struct tcpstat tcpstat; 107 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 108 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 109 110 static int log_in_vain = 0; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 112 &log_in_vain, 0, "Log all incoming TCP connections"); 113 114 static int blackhole = 0; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 116 &blackhole, 0, "Do not send RST when dropping refused connections"); 117 118 int tcp_delack_enabled = 1; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 120 &tcp_delack_enabled, 0, 121 "Delay ACK to try and piggyback it onto a data packet"); 122 123 #ifdef TCP_DROP_SYNFIN 124 static int drop_synfin = 0; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 126 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 127 #endif 128 129 static int tcp_do_rfc3042 = 1; 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 131 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 132 133 static int tcp_do_rfc3390 = 1; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 135 &tcp_do_rfc3390, 0, 136 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 137 138 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 139 "TCP Segment Reassembly Queue"); 140 141 static int tcp_reass_maxseg = 0; 142 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 143 &tcp_reass_maxseg, 0, 144 "Global maximum number of TCP Segments in Reassembly Queue"); 145 146 int tcp_reass_qsize = 0; 147 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 148 &tcp_reass_qsize, 0, 149 "Global number of TCP Segments currently in Reassembly Queue"); 150 151 static int tcp_reass_maxqlen = 48; 152 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 153 &tcp_reass_maxqlen, 0, 154 "Maximum number of TCP Segments per individual Reassembly Queue"); 155 156 static int tcp_reass_overflows = 0; 157 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 158 &tcp_reass_overflows, 0, 159 "Global number of TCP Segment Reassembly Queue Overflows"); 160 161 struct inpcbhead tcb; 162 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 163 struct inpcbinfo tcbinfo; 164 struct mtx *tcbinfo_mtx; 165 166 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 167 static void tcp_pulloutofband(struct socket *, 168 struct tcphdr *, struct mbuf *, int); 169 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 170 struct mbuf *); 171 static void tcp_xmit_timer(struct tcpcb *, int); 172 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 173 static int tcp_timewait(struct tcptw *, struct tcpopt *, 174 struct tcphdr *, struct mbuf *, int); 175 176 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 177 #ifdef INET6 178 #define ND6_HINT(tp) \ 179 do { \ 180 if ((tp) && (tp)->t_inpcb && \ 181 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 182 nd6_nud_hint(NULL, NULL, 0); \ 183 } while (0) 184 #else 185 #define ND6_HINT(tp) 186 #endif 187 188 /* 189 * Indicate whether this ack should be delayed. We can delay the ack if 190 * - there is no delayed ack timer in progress and 191 * - our last ack wasn't a 0-sized window. We never want to delay 192 * the ack that opens up a 0-sized window and 193 * - delayed acks are enabled or 194 * - this is a half-synchronized T/TCP connection. 195 */ 196 #define DELAY_ACK(tp) \ 197 ((!callout_active(tp->tt_delack) && \ 198 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 199 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 200 201 /* Initialize TCP reassembly queue */ 202 uma_zone_t tcp_reass_zone; 203 void 204 tcp_reass_init() 205 { 206 tcp_reass_maxseg = nmbclusters / 16; 207 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 208 &tcp_reass_maxseg); 209 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 210 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 211 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 212 } 213 214 static int 215 tcp_reass(tp, th, tlenp, m) 216 register struct tcpcb *tp; 217 register struct tcphdr *th; 218 int *tlenp; 219 struct mbuf *m; 220 { 221 struct tseg_qent *q; 222 struct tseg_qent *p = NULL; 223 struct tseg_qent *nq; 224 struct tseg_qent *te = NULL; 225 struct socket *so = tp->t_inpcb->inp_socket; 226 int flags; 227 228 /* 229 * XXX: tcp_reass() is rather inefficient with its data structures 230 * and should be rewritten (see NetBSD for optimizations). While 231 * doing that it should move to its own file tcp_reass.c. 232 */ 233 234 /* 235 * Call with th==0 after become established to 236 * force pre-ESTABLISHED data up to user socket. 237 */ 238 if (th == 0) 239 goto present; 240 241 /* 242 * Limit the number of segments in the reassembly queue to prevent 243 * holding on to too many segments (and thus running out of mbufs). 244 * Make sure to let the missing segment through which caused this 245 * queue. Always keep one global queue entry spare to be able to 246 * process the missing segment. 247 */ 248 if (th->th_seq != tp->rcv_nxt && 249 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 250 tp->t_segqlen >= tcp_reass_maxqlen)) { 251 tcp_reass_overflows++; 252 tcpstat.tcps_rcvmemdrop++; 253 m_freem(m); 254 return (0); 255 } 256 257 /* 258 * Allocate a new queue entry. If we can't, or hit the zone limit 259 * just drop the pkt. 260 */ 261 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 262 if (te == NULL) { 263 tcpstat.tcps_rcvmemdrop++; 264 m_freem(m); 265 return (0); 266 } 267 tp->t_segqlen++; 268 tcp_reass_qsize++; 269 270 /* 271 * Find a segment which begins after this one does. 272 */ 273 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 274 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 275 break; 276 p = q; 277 } 278 279 /* 280 * If there is a preceding segment, it may provide some of 281 * our data already. If so, drop the data from the incoming 282 * segment. If it provides all of our data, drop us. 283 */ 284 if (p != NULL) { 285 register int i; 286 /* conversion to int (in i) handles seq wraparound */ 287 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 288 if (i > 0) { 289 if (i >= *tlenp) { 290 tcpstat.tcps_rcvduppack++; 291 tcpstat.tcps_rcvdupbyte += *tlenp; 292 m_freem(m); 293 uma_zfree(tcp_reass_zone, te); 294 tp->t_segqlen--; 295 tcp_reass_qsize--; 296 /* 297 * Try to present any queued data 298 * at the left window edge to the user. 299 * This is needed after the 3-WHS 300 * completes. 301 */ 302 goto present; /* ??? */ 303 } 304 m_adj(m, i); 305 *tlenp -= i; 306 th->th_seq += i; 307 } 308 } 309 tcpstat.tcps_rcvoopack++; 310 tcpstat.tcps_rcvoobyte += *tlenp; 311 312 /* 313 * While we overlap succeeding segments trim them or, 314 * if they are completely covered, dequeue them. 315 */ 316 while (q) { 317 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 318 if (i <= 0) 319 break; 320 if (i < q->tqe_len) { 321 q->tqe_th->th_seq += i; 322 q->tqe_len -= i; 323 m_adj(q->tqe_m, i); 324 break; 325 } 326 327 nq = LIST_NEXT(q, tqe_q); 328 LIST_REMOVE(q, tqe_q); 329 m_freem(q->tqe_m); 330 uma_zfree(tcp_reass_zone, q); 331 tp->t_segqlen--; 332 tcp_reass_qsize--; 333 q = nq; 334 } 335 336 /* Insert the new segment queue entry into place. */ 337 te->tqe_m = m; 338 te->tqe_th = th; 339 te->tqe_len = *tlenp; 340 341 if (p == NULL) { 342 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 343 } else { 344 LIST_INSERT_AFTER(p, te, tqe_q); 345 } 346 347 present: 348 /* 349 * Present data to user, advancing rcv_nxt through 350 * completed sequence space. 351 */ 352 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 353 return (0); 354 q = LIST_FIRST(&tp->t_segq); 355 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 356 return (0); 357 do { 358 tp->rcv_nxt += q->tqe_len; 359 flags = q->tqe_th->th_flags & TH_FIN; 360 nq = LIST_NEXT(q, tqe_q); 361 LIST_REMOVE(q, tqe_q); 362 if (so->so_state & SS_CANTRCVMORE) 363 m_freem(q->tqe_m); 364 else 365 sbappendstream(&so->so_rcv, q->tqe_m); 366 uma_zfree(tcp_reass_zone, q); 367 tp->t_segqlen--; 368 tcp_reass_qsize--; 369 q = nq; 370 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 371 ND6_HINT(tp); 372 sorwakeup(so); 373 return (flags); 374 } 375 376 /* 377 * TCP input routine, follows pages 65-76 of the 378 * protocol specification dated September, 1981 very closely. 379 */ 380 #ifdef INET6 381 int 382 tcp6_input(mp, offp, proto) 383 struct mbuf **mp; 384 int *offp, proto; 385 { 386 register struct mbuf *m = *mp; 387 struct in6_ifaddr *ia6; 388 389 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 390 391 /* 392 * draft-itojun-ipv6-tcp-to-anycast 393 * better place to put this in? 394 */ 395 ia6 = ip6_getdstifaddr(m); 396 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 397 struct ip6_hdr *ip6; 398 399 ip6 = mtod(m, struct ip6_hdr *); 400 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 401 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 402 return IPPROTO_DONE; 403 } 404 405 tcp_input(m, *offp); 406 return IPPROTO_DONE; 407 } 408 #endif 409 410 void 411 tcp_input(m, off0) 412 register struct mbuf *m; 413 int off0; 414 { 415 register struct tcphdr *th; 416 register struct ip *ip = NULL; 417 register struct ipovly *ipov; 418 register struct inpcb *inp = NULL; 419 u_char *optp = NULL; 420 int optlen = 0; 421 int len, tlen, off; 422 int drop_hdrlen; 423 register struct tcpcb *tp = 0; 424 register int thflags; 425 struct socket *so = 0; 426 int todrop, acked, ourfinisacked, needoutput = 0; 427 u_long tiwin; 428 struct tcpopt to; /* options in this segment */ 429 struct rmxp_tao tao; /* our TAO cache entry */ 430 int headlocked = 0; 431 struct sockaddr_in *next_hop = NULL; 432 int rstreason; /* For badport_bandlim accounting purposes */ 433 434 struct ip6_hdr *ip6 = NULL; 435 #ifdef INET6 436 int isipv6; 437 #else 438 const int isipv6 = 0; 439 #endif 440 441 #ifdef TCPDEBUG 442 /* 443 * The size of tcp_saveipgen must be the size of the max ip header, 444 * now IPv6. 445 */ 446 u_char tcp_saveipgen[40]; 447 struct tcphdr tcp_savetcp; 448 short ostate = 0; 449 #endif 450 451 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 452 next_hop = ip_claim_next_hop(m); 453 #ifdef INET6 454 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 455 #endif 456 bzero(&tao, sizeof(tao)); 457 bzero((char *)&to, sizeof(to)); 458 459 tcpstat.tcps_rcvtotal++; 460 461 if (isipv6) { 462 #ifdef INET6 463 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 464 ip6 = mtod(m, struct ip6_hdr *); 465 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 466 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 467 tcpstat.tcps_rcvbadsum++; 468 goto drop; 469 } 470 th = (struct tcphdr *)((caddr_t)ip6 + off0); 471 472 /* 473 * Be proactive about unspecified IPv6 address in source. 474 * As we use all-zero to indicate unbounded/unconnected pcb, 475 * unspecified IPv6 address can be used to confuse us. 476 * 477 * Note that packets with unspecified IPv6 destination is 478 * already dropped in ip6_input. 479 */ 480 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 481 /* XXX stat */ 482 goto drop; 483 } 484 #else 485 th = NULL; /* XXX: avoid compiler warning */ 486 #endif 487 } else { 488 /* 489 * Get IP and TCP header together in first mbuf. 490 * Note: IP leaves IP header in first mbuf. 491 */ 492 if (off0 > sizeof (struct ip)) { 493 ip_stripoptions(m, (struct mbuf *)0); 494 off0 = sizeof(struct ip); 495 } 496 if (m->m_len < sizeof (struct tcpiphdr)) { 497 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 498 tcpstat.tcps_rcvshort++; 499 return; 500 } 501 } 502 ip = mtod(m, struct ip *); 503 ipov = (struct ipovly *)ip; 504 th = (struct tcphdr *)((caddr_t)ip + off0); 505 tlen = ip->ip_len; 506 507 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 508 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 509 th->th_sum = m->m_pkthdr.csum_data; 510 else 511 th->th_sum = in_pseudo(ip->ip_src.s_addr, 512 ip->ip_dst.s_addr, 513 htonl(m->m_pkthdr.csum_data + 514 ip->ip_len + 515 IPPROTO_TCP)); 516 th->th_sum ^= 0xffff; 517 #ifdef TCPDEBUG 518 ipov->ih_len = (u_short)tlen; 519 ipov->ih_len = htons(ipov->ih_len); 520 #endif 521 } else { 522 /* 523 * Checksum extended TCP header and data. 524 */ 525 len = sizeof (struct ip) + tlen; 526 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 527 ipov->ih_len = (u_short)tlen; 528 ipov->ih_len = htons(ipov->ih_len); 529 th->th_sum = in_cksum(m, len); 530 } 531 if (th->th_sum) { 532 tcpstat.tcps_rcvbadsum++; 533 goto drop; 534 } 535 #ifdef INET6 536 /* Re-initialization for later version check */ 537 ip->ip_v = IPVERSION; 538 #endif 539 } 540 541 /* 542 * Check that TCP offset makes sense, 543 * pull out TCP options and adjust length. XXX 544 */ 545 off = th->th_off << 2; 546 if (off < sizeof (struct tcphdr) || off > tlen) { 547 tcpstat.tcps_rcvbadoff++; 548 goto drop; 549 } 550 tlen -= off; /* tlen is used instead of ti->ti_len */ 551 if (off > sizeof (struct tcphdr)) { 552 if (isipv6) { 553 #ifdef INET6 554 IP6_EXTHDR_CHECK(m, off0, off, ); 555 ip6 = mtod(m, struct ip6_hdr *); 556 th = (struct tcphdr *)((caddr_t)ip6 + off0); 557 #endif 558 } else { 559 if (m->m_len < sizeof(struct ip) + off) { 560 if ((m = m_pullup(m, sizeof (struct ip) + off)) 561 == 0) { 562 tcpstat.tcps_rcvshort++; 563 return; 564 } 565 ip = mtod(m, struct ip *); 566 ipov = (struct ipovly *)ip; 567 th = (struct tcphdr *)((caddr_t)ip + off0); 568 } 569 } 570 optlen = off - sizeof (struct tcphdr); 571 optp = (u_char *)(th + 1); 572 } 573 thflags = th->th_flags; 574 575 #ifdef TCP_DROP_SYNFIN 576 /* 577 * If the drop_synfin option is enabled, drop all packets with 578 * both the SYN and FIN bits set. This prevents e.g. nmap from 579 * identifying the TCP/IP stack. 580 * 581 * This is a violation of the TCP specification. 582 */ 583 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 584 goto drop; 585 #endif 586 587 /* 588 * Convert TCP protocol specific fields to host format. 589 */ 590 th->th_seq = ntohl(th->th_seq); 591 th->th_ack = ntohl(th->th_ack); 592 th->th_win = ntohs(th->th_win); 593 th->th_urp = ntohs(th->th_urp); 594 595 /* 596 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 597 * until after ip6_savecontrol() is called and before other functions 598 * which don't want those proto headers. 599 * Because ip6_savecontrol() is going to parse the mbuf to 600 * search for data to be passed up to user-land, it wants mbuf 601 * parameters to be unchanged. 602 * XXX: the call of ip6_savecontrol() has been obsoleted based on 603 * latest version of the advanced API (20020110). 604 */ 605 drop_hdrlen = off0 + off; 606 607 /* 608 * Locate pcb for segment. 609 */ 610 INP_INFO_WLOCK(&tcbinfo); 611 headlocked = 1; 612 findpcb: 613 /* IPFIREWALL_FORWARD section */ 614 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 615 /* 616 * Transparently forwarded. Pretend to be the destination. 617 * already got one like this? 618 */ 619 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 620 ip->ip_dst, th->th_dport, 621 0, m->m_pkthdr.rcvif); 622 if (!inp) { 623 /* It's new. Try find the ambushing socket. */ 624 inp = in_pcblookup_hash(&tcbinfo, 625 ip->ip_src, th->th_sport, 626 next_hop->sin_addr, 627 next_hop->sin_port ? 628 ntohs(next_hop->sin_port) : 629 th->th_dport, 630 1, m->m_pkthdr.rcvif); 631 } 632 } else { 633 if (isipv6) { 634 #ifdef INET6 635 inp = in6_pcblookup_hash(&tcbinfo, 636 &ip6->ip6_src, th->th_sport, 637 &ip6->ip6_dst, th->th_dport, 638 1, m->m_pkthdr.rcvif); 639 #endif 640 } else 641 inp = in_pcblookup_hash(&tcbinfo, 642 ip->ip_src, th->th_sport, 643 ip->ip_dst, th->th_dport, 644 1, m->m_pkthdr.rcvif); 645 } 646 647 #if defined(IPSEC) || defined(FAST_IPSEC) 648 if (isipv6) { 649 if (inp != NULL && ipsec6_in_reject(m, inp)) { 650 #ifdef IPSEC 651 ipsec6stat.in_polvio++; 652 #endif /*IPSEC*/ 653 goto drop; 654 } 655 } else if (inp != NULL && ipsec4_in_reject(m, inp)) { 656 #ifdef IPSEC 657 ipsecstat.in_polvio++; 658 #endif /*IPSEC*/ 659 goto drop; 660 } 661 #endif /*IPSEC || FAST_IPSEC*/ 662 663 /* 664 * If the state is CLOSED (i.e., TCB does not exist) then 665 * all data in the incoming segment is discarded. 666 * If the TCB exists but is in CLOSED state, it is embryonic, 667 * but should either do a listen or a connect soon. 668 */ 669 if (inp == NULL) { 670 if (log_in_vain) { 671 #ifdef INET6 672 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 673 #else 674 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 675 #endif 676 677 if (isipv6) { 678 #ifdef INET6 679 strcpy(dbuf, "["); 680 strcpy(sbuf, "["); 681 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 682 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 683 strcat(dbuf, "]"); 684 strcat(sbuf, "]"); 685 #endif 686 } else { 687 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 688 strcpy(sbuf, inet_ntoa(ip->ip_src)); 689 } 690 switch (log_in_vain) { 691 case 1: 692 if ((thflags & TH_SYN) == 0) 693 break; 694 /* FALLTHROUGH */ 695 case 2: 696 log(LOG_INFO, 697 "Connection attempt to TCP %s:%d " 698 "from %s:%d flags:0x%02x\n", 699 dbuf, ntohs(th->th_dport), sbuf, 700 ntohs(th->th_sport), thflags); 701 break; 702 default: 703 break; 704 } 705 } 706 if (blackhole) { 707 switch (blackhole) { 708 case 1: 709 if (thflags & TH_SYN) 710 goto drop; 711 break; 712 case 2: 713 goto drop; 714 default: 715 goto drop; 716 } 717 } 718 rstreason = BANDLIM_RST_CLOSEDPORT; 719 goto dropwithreset; 720 } 721 INP_LOCK(inp); 722 if (inp->inp_vflag & INP_TIMEWAIT) { 723 /* 724 * The only option of relevance is TOF_CC, and only if 725 * present in a SYN segment. See tcp_timewait(). 726 */ 727 if (thflags & TH_SYN) 728 tcp_dooptions(&to, optp, optlen, 1); 729 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 730 &to, th, m, tlen)) 731 goto findpcb; 732 /* 733 * tcp_timewait unlocks inp. 734 */ 735 INP_INFO_WUNLOCK(&tcbinfo); 736 return; 737 } 738 tp = intotcpcb(inp); 739 if (tp == 0) { 740 INP_UNLOCK(inp); 741 rstreason = BANDLIM_RST_CLOSEDPORT; 742 goto dropwithreset; 743 } 744 if (tp->t_state == TCPS_CLOSED) 745 goto drop; 746 747 /* Unscale the window into a 32-bit value. */ 748 if ((thflags & TH_SYN) == 0) 749 tiwin = th->th_win << tp->snd_scale; 750 else 751 tiwin = th->th_win; 752 753 #ifdef MAC 754 if (mac_check_inpcb_deliver(inp, m)) 755 goto drop; 756 #endif 757 so = inp->inp_socket; 758 #ifdef TCPDEBUG 759 if (so->so_options & SO_DEBUG) { 760 ostate = tp->t_state; 761 if (isipv6) 762 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 763 else 764 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 765 tcp_savetcp = *th; 766 } 767 #endif 768 if (so->so_options & SO_ACCEPTCONN) { 769 struct in_conninfo inc; 770 771 #ifdef INET6 772 inc.inc_isipv6 = isipv6; 773 #endif 774 if (isipv6) { 775 inc.inc6_faddr = ip6->ip6_src; 776 inc.inc6_laddr = ip6->ip6_dst; 777 } else { 778 inc.inc_faddr = ip->ip_src; 779 inc.inc_laddr = ip->ip_dst; 780 } 781 inc.inc_fport = th->th_sport; 782 inc.inc_lport = th->th_dport; 783 784 /* 785 * If the state is LISTEN then ignore segment if it contains 786 * a RST. If the segment contains an ACK then it is bad and 787 * send a RST. If it does not contain a SYN then it is not 788 * interesting; drop it. 789 * 790 * If the state is SYN_RECEIVED (syncache) and seg contains 791 * an ACK, but not for our SYN/ACK, send a RST. If the seg 792 * contains a RST, check the sequence number to see if it 793 * is a valid reset segment. 794 */ 795 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 796 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 797 if (!syncache_expand(&inc, th, &so, m)) { 798 /* 799 * No syncache entry, or ACK was not 800 * for our SYN/ACK. Send a RST. 801 */ 802 tcpstat.tcps_badsyn++; 803 rstreason = BANDLIM_RST_OPENPORT; 804 goto dropwithreset; 805 } 806 if (so == NULL) { 807 /* 808 * Could not complete 3-way handshake, 809 * connection is being closed down, and 810 * syncache will free mbuf. 811 */ 812 INP_UNLOCK(inp); 813 INP_INFO_WUNLOCK(&tcbinfo); 814 return; 815 } 816 /* 817 * Socket is created in state SYN_RECEIVED. 818 * Continue processing segment. 819 */ 820 INP_UNLOCK(inp); 821 inp = sotoinpcb(so); 822 INP_LOCK(inp); 823 tp = intotcpcb(inp); 824 /* 825 * This is what would have happened in 826 * tcp_output() when the SYN,ACK was sent. 827 */ 828 tp->snd_up = tp->snd_una; 829 tp->snd_max = tp->snd_nxt = tp->iss + 1; 830 tp->last_ack_sent = tp->rcv_nxt; 831 /* 832 * RFC1323: The window in SYN & SYN/ACK 833 * segments is never scaled. 834 */ 835 tp->snd_wnd = tiwin; /* unscaled */ 836 goto after_listen; 837 } 838 if (thflags & TH_RST) { 839 syncache_chkrst(&inc, th); 840 goto drop; 841 } 842 if (thflags & TH_ACK) { 843 syncache_badack(&inc); 844 tcpstat.tcps_badsyn++; 845 rstreason = BANDLIM_RST_OPENPORT; 846 goto dropwithreset; 847 } 848 goto drop; 849 } 850 851 /* 852 * Segment's flags are (SYN) or (SYN|FIN). 853 */ 854 #ifdef INET6 855 /* 856 * If deprecated address is forbidden, 857 * we do not accept SYN to deprecated interface 858 * address to prevent any new inbound connection from 859 * getting established. 860 * When we do not accept SYN, we send a TCP RST, 861 * with deprecated source address (instead of dropping 862 * it). We compromise it as it is much better for peer 863 * to send a RST, and RST will be the final packet 864 * for the exchange. 865 * 866 * If we do not forbid deprecated addresses, we accept 867 * the SYN packet. RFC2462 does not suggest dropping 868 * SYN in this case. 869 * If we decipher RFC2462 5.5.4, it says like this: 870 * 1. use of deprecated addr with existing 871 * communication is okay - "SHOULD continue to be 872 * used" 873 * 2. use of it with new communication: 874 * (2a) "SHOULD NOT be used if alternate address 875 * with sufficient scope is available" 876 * (2b) nothing mentioned otherwise. 877 * Here we fall into (2b) case as we have no choice in 878 * our source address selection - we must obey the peer. 879 * 880 * The wording in RFC2462 is confusing, and there are 881 * multiple description text for deprecated address 882 * handling - worse, they are not exactly the same. 883 * I believe 5.5.4 is the best one, so we follow 5.5.4. 884 */ 885 if (isipv6 && !ip6_use_deprecated) { 886 struct in6_ifaddr *ia6; 887 888 if ((ia6 = ip6_getdstifaddr(m)) && 889 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 890 INP_UNLOCK(inp); 891 tp = NULL; 892 rstreason = BANDLIM_RST_OPENPORT; 893 goto dropwithreset; 894 } 895 } 896 #endif 897 /* 898 * If it is from this socket, drop it, it must be forged. 899 * Don't bother responding if the destination was a broadcast. 900 */ 901 if (th->th_dport == th->th_sport) { 902 if (isipv6) { 903 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 904 &ip6->ip6_src)) 905 goto drop; 906 } else { 907 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 908 goto drop; 909 } 910 } 911 /* 912 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 913 * 914 * Note that it is quite possible to receive unicast 915 * link-layer packets with a broadcast IP address. Use 916 * in_broadcast() to find them. 917 */ 918 if (m->m_flags & (M_BCAST|M_MCAST)) 919 goto drop; 920 if (isipv6) { 921 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 922 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 923 goto drop; 924 } else { 925 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 926 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 927 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 928 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 929 goto drop; 930 } 931 /* 932 * SYN appears to be valid; create compressed TCP state 933 * for syncache, or perform t/tcp connection. 934 */ 935 if (so->so_qlen <= so->so_qlimit) { 936 #ifdef TCPDEBUG 937 if (so->so_options & SO_DEBUG) 938 tcp_trace(TA_INPUT, ostate, tp, 939 (void *)tcp_saveipgen, &tcp_savetcp, 0); 940 #endif 941 tcp_dooptions(&to, optp, optlen, 1); 942 if (!syncache_add(&inc, &to, th, &so, m)) 943 goto drop; 944 if (so == NULL) { 945 /* 946 * Entry added to syncache, mbuf used to 947 * send SYN,ACK packet. 948 */ 949 KASSERT(headlocked, ("headlocked")); 950 INP_UNLOCK(inp); 951 INP_INFO_WUNLOCK(&tcbinfo); 952 return; 953 } 954 /* 955 * Segment passed TAO tests. 956 */ 957 INP_UNLOCK(inp); 958 inp = sotoinpcb(so); 959 INP_LOCK(inp); 960 tp = intotcpcb(inp); 961 tp->snd_wnd = tiwin; 962 tp->t_starttime = ticks; 963 tp->t_state = TCPS_ESTABLISHED; 964 965 /* 966 * T/TCP logic: 967 * If there is a FIN or if there is data, then 968 * delay SYN,ACK(SYN) in the hope of piggy-backing 969 * it on a response segment. Otherwise must send 970 * ACK now in case the other side is slow starting. 971 */ 972 if (thflags & TH_FIN || tlen != 0) 973 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 974 else 975 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 976 tcpstat.tcps_connects++; 977 soisconnected(so); 978 goto trimthenstep6; 979 } 980 goto drop; 981 } 982 after_listen: 983 984 /* XXX temp debugging */ 985 /* should not happen - syncache should pick up these connections */ 986 if (tp->t_state == TCPS_LISTEN) 987 panic("tcp_input: TCPS_LISTEN"); 988 989 /* 990 * This is the second part of the MSS DoS prevention code (after 991 * minmss on the sending side) and it deals with too many too small 992 * tcp packets in a too short timeframe (1 second). 993 * 994 * For every full second we count the number of received packets 995 * and bytes. If we get a lot of packets per second for this connection 996 * (tcp_minmssoverload) we take a closer look at it and compute the 997 * average packet size for the past second. If that is less than 998 * tcp_minmss we get too many packets with very small payload which 999 * is not good and burdens our system (and every packet generates 1000 * a wakeup to the process connected to our socket). We can reasonable 1001 * expect this to be small packet DoS attack to exhaust our CPU 1002 * cycles. 1003 * 1004 * Care has to be taken for the minimum packet overload value. This 1005 * value defines the minimum number of packets per second before we 1006 * start to worry. This must not be too low to avoid killing for 1007 * example interactive connections with many small packets like 1008 * telnet or SSH. 1009 * 1010 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1011 * this check. 1012 * 1013 * Account for packet if payload packet, skip over ACK, etc. 1014 */ 1015 if (tcp_minmss && tcp_minmssoverload && 1016 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1017 if (tp->rcv_second > ticks) { 1018 tp->rcv_pps++; 1019 tp->rcv_byps += tlen + off; 1020 if (tp->rcv_pps > tcp_minmssoverload) { 1021 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1022 printf("too many small tcp packets from " 1023 "%s:%u, av. %lubyte/packet, " 1024 "dropping connection\n", 1025 #ifdef INET6 1026 isipv6 ? 1027 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1028 #endif 1029 inet_ntoa(inp->inp_inc.inc_faddr), 1030 inp->inp_inc.inc_fport, 1031 tp->rcv_byps / tp->rcv_pps); 1032 tp = tcp_drop(tp, ECONNRESET); 1033 tcpstat.tcps_minmssdrops++; 1034 goto drop; 1035 } 1036 } 1037 } else { 1038 tp->rcv_second = ticks + hz; 1039 tp->rcv_pps = 1; 1040 tp->rcv_byps = tlen + off; 1041 } 1042 } 1043 1044 /* 1045 * Segment received on connection. 1046 * Reset idle time and keep-alive timer. 1047 */ 1048 tp->t_rcvtime = ticks; 1049 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1050 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1051 1052 /* 1053 * Process options only when we get SYN/ACK back. The SYN case 1054 * for incoming connections is handled in tcp_syncache. 1055 * XXX this is traditional behavior, may need to be cleaned up. 1056 */ 1057 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 1058 if (thflags & TH_SYN) { 1059 if (to.to_flags & TOF_SCALE) { 1060 tp->t_flags |= TF_RCVD_SCALE; 1061 tp->requested_s_scale = to.to_requested_s_scale; 1062 } 1063 if (to.to_flags & TOF_TS) { 1064 tp->t_flags |= TF_RCVD_TSTMP; 1065 tp->ts_recent = to.to_tsval; 1066 tp->ts_recent_age = ticks; 1067 } 1068 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 1069 tp->t_flags |= TF_RCVD_CC; 1070 if (to.to_flags & TOF_MSS) 1071 tcp_mss(tp, to.to_mss); 1072 } 1073 1074 /* 1075 * Header prediction: check for the two common cases 1076 * of a uni-directional data xfer. If the packet has 1077 * no control flags, is in-sequence, the window didn't 1078 * change and we're not retransmitting, it's a 1079 * candidate. If the length is zero and the ack moved 1080 * forward, we're the sender side of the xfer. Just 1081 * free the data acked & wake any higher level process 1082 * that was blocked waiting for space. If the length 1083 * is non-zero and the ack didn't move, we're the 1084 * receiver side. If we're getting packets in-order 1085 * (the reassembly queue is empty), add the data to 1086 * the socket buffer and note that we need a delayed ack. 1087 * Make sure that the hidden state-flags are also off. 1088 * Since we check for TCPS_ESTABLISHED above, it can only 1089 * be TH_NEEDSYN. 1090 */ 1091 if (tp->t_state == TCPS_ESTABLISHED && 1092 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1093 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1094 ((to.to_flags & TOF_TS) == 0 || 1095 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1096 /* 1097 * Using the CC option is compulsory if once started: 1098 * the segment is OK if no T/TCP was negotiated or 1099 * if the segment has a CC option equal to CCrecv 1100 */ 1101 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1102 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1103 th->th_seq == tp->rcv_nxt && 1104 tiwin && tiwin == tp->snd_wnd && 1105 tp->snd_nxt == tp->snd_max) { 1106 1107 /* 1108 * If last ACK falls within this segment's sequence numbers, 1109 * record the timestamp. 1110 * NOTE that the test is modified according to the latest 1111 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1112 */ 1113 if ((to.to_flags & TOF_TS) != 0 && 1114 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1115 tp->ts_recent_age = ticks; 1116 tp->ts_recent = to.to_tsval; 1117 } 1118 1119 if (tlen == 0) { 1120 if (SEQ_GT(th->th_ack, tp->snd_una) && 1121 SEQ_LEQ(th->th_ack, tp->snd_max) && 1122 tp->snd_cwnd >= tp->snd_wnd && 1123 ((!tcp_do_newreno && 1124 tp->t_dupacks < tcprexmtthresh) || 1125 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) { 1126 KASSERT(headlocked, ("headlocked")); 1127 INP_INFO_WUNLOCK(&tcbinfo); 1128 /* 1129 * this is a pure ack for outstanding data. 1130 */ 1131 ++tcpstat.tcps_predack; 1132 /* 1133 * "bad retransmit" recovery 1134 */ 1135 if (tp->t_rxtshift == 1 && 1136 ticks < tp->t_badrxtwin) { 1137 ++tcpstat.tcps_sndrexmitbad; 1138 tp->snd_cwnd = tp->snd_cwnd_prev; 1139 tp->snd_ssthresh = 1140 tp->snd_ssthresh_prev; 1141 tp->snd_recover = tp->snd_recover_prev; 1142 if (tp->t_flags & TF_WASFRECOVERY) 1143 ENTER_FASTRECOVERY(tp); 1144 tp->snd_nxt = tp->snd_max; 1145 tp->t_badrxtwin = 0; 1146 } 1147 1148 /* 1149 * Recalculate the transmit timer / rtt. 1150 * 1151 * Some boxes send broken timestamp replies 1152 * during the SYN+ACK phase, ignore 1153 * timestamps of 0 or we could calculate a 1154 * huge RTT and blow up the retransmit timer. 1155 */ 1156 if ((to.to_flags & TOF_TS) != 0 && 1157 to.to_tsecr) { 1158 tcp_xmit_timer(tp, 1159 ticks - to.to_tsecr + 1); 1160 } else if (tp->t_rtttime && 1161 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1162 tcp_xmit_timer(tp, 1163 ticks - tp->t_rtttime); 1164 } 1165 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1166 acked = th->th_ack - tp->snd_una; 1167 tcpstat.tcps_rcvackpack++; 1168 tcpstat.tcps_rcvackbyte += acked; 1169 sbdrop(&so->so_snd, acked); 1170 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1171 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1172 tp->snd_recover = th->th_ack - 1; 1173 tp->snd_una = th->th_ack; 1174 /* 1175 * pull snd_wl2 up to prevent seq wrap relative 1176 * to th_ack. 1177 */ 1178 tp->snd_wl2 = th->th_ack; 1179 tp->t_dupacks = 0; 1180 m_freem(m); 1181 ND6_HINT(tp); /* some progress has been done */ 1182 1183 /* 1184 * If all outstanding data are acked, stop 1185 * retransmit timer, otherwise restart timer 1186 * using current (possibly backed-off) value. 1187 * If process is waiting for space, 1188 * wakeup/selwakeup/signal. If data 1189 * are ready to send, let tcp_output 1190 * decide between more output or persist. 1191 1192 #ifdef TCPDEBUG 1193 if (so->so_options & SO_DEBUG) 1194 tcp_trace(TA_INPUT, ostate, tp, 1195 (void *)tcp_saveipgen, 1196 &tcp_savetcp, 0); 1197 #endif 1198 */ 1199 if (tp->snd_una == tp->snd_max) 1200 callout_stop(tp->tt_rexmt); 1201 else if (!callout_active(tp->tt_persist)) 1202 callout_reset(tp->tt_rexmt, 1203 tp->t_rxtcur, 1204 tcp_timer_rexmt, tp); 1205 1206 sowwakeup(so); 1207 if (so->so_snd.sb_cc) 1208 (void) tcp_output(tp); 1209 goto check_delack; 1210 } 1211 } else if (th->th_ack == tp->snd_una && 1212 LIST_EMPTY(&tp->t_segq) && 1213 tlen <= sbspace(&so->so_rcv)) { 1214 KASSERT(headlocked, ("headlocked")); 1215 INP_INFO_WUNLOCK(&tcbinfo); 1216 /* 1217 * this is a pure, in-sequence data packet 1218 * with nothing on the reassembly queue and 1219 * we have enough buffer space to take it. 1220 */ 1221 ++tcpstat.tcps_preddat; 1222 tp->rcv_nxt += tlen; 1223 /* 1224 * Pull snd_wl1 up to prevent seq wrap relative to 1225 * th_seq. 1226 */ 1227 tp->snd_wl1 = th->th_seq; 1228 /* 1229 * Pull rcv_up up to prevent seq wrap relative to 1230 * rcv_nxt. 1231 */ 1232 tp->rcv_up = tp->rcv_nxt; 1233 tcpstat.tcps_rcvpack++; 1234 tcpstat.tcps_rcvbyte += tlen; 1235 ND6_HINT(tp); /* some progress has been done */ 1236 /* 1237 #ifdef TCPDEBUG 1238 if (so->so_options & SO_DEBUG) 1239 tcp_trace(TA_INPUT, ostate, tp, 1240 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1241 #endif 1242 * Add data to socket buffer. 1243 */ 1244 if (so->so_state & SS_CANTRCVMORE) { 1245 m_freem(m); 1246 } else { 1247 m_adj(m, drop_hdrlen); /* delayed header drop */ 1248 sbappendstream(&so->so_rcv, m); 1249 } 1250 sorwakeup(so); 1251 if (DELAY_ACK(tp)) { 1252 tp->t_flags |= TF_DELACK; 1253 } else { 1254 tp->t_flags |= TF_ACKNOW; 1255 tcp_output(tp); 1256 } 1257 goto check_delack; 1258 } 1259 } 1260 1261 /* 1262 * Calculate amount of space in receive window, 1263 * and then do TCP input processing. 1264 * Receive window is amount of space in rcv queue, 1265 * but not less than advertised window. 1266 */ 1267 { int win; 1268 1269 win = sbspace(&so->so_rcv); 1270 if (win < 0) 1271 win = 0; 1272 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1273 } 1274 1275 switch (tp->t_state) { 1276 1277 /* 1278 * If the state is SYN_RECEIVED: 1279 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1280 */ 1281 case TCPS_SYN_RECEIVED: 1282 if ((thflags & TH_ACK) && 1283 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1284 SEQ_GT(th->th_ack, tp->snd_max))) { 1285 rstreason = BANDLIM_RST_OPENPORT; 1286 goto dropwithreset; 1287 } 1288 break; 1289 1290 /* 1291 * If the state is SYN_SENT: 1292 * if seg contains an ACK, but not for our SYN, drop the input. 1293 * if seg contains a RST, then drop the connection. 1294 * if seg does not contain SYN, then drop it. 1295 * Otherwise this is an acceptable SYN segment 1296 * initialize tp->rcv_nxt and tp->irs 1297 * if seg contains ack then advance tp->snd_una 1298 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1299 * arrange for segment to be acked (eventually) 1300 * continue processing rest of data/controls, beginning with URG 1301 */ 1302 case TCPS_SYN_SENT: 1303 if (tcp_do_rfc1644) 1304 tcp_hc_gettao(&inp->inp_inc, &tao); 1305 1306 if ((thflags & TH_ACK) && 1307 (SEQ_LEQ(th->th_ack, tp->iss) || 1308 SEQ_GT(th->th_ack, tp->snd_max))) { 1309 /* 1310 * If we have a cached CCsent for the remote host, 1311 * hence we haven't just crashed and restarted, 1312 * do not send a RST. This may be a retransmission 1313 * from the other side after our earlier ACK was lost. 1314 * Our new SYN, when it arrives, will serve as the 1315 * needed ACK. 1316 */ 1317 if (tao.tao_ccsent != 0) 1318 goto drop; 1319 else { 1320 rstreason = BANDLIM_UNLIMITED; 1321 goto dropwithreset; 1322 } 1323 } 1324 if (thflags & TH_RST) { 1325 if (thflags & TH_ACK) 1326 tp = tcp_drop(tp, ECONNREFUSED); 1327 goto drop; 1328 } 1329 if ((thflags & TH_SYN) == 0) 1330 goto drop; 1331 tp->snd_wnd = th->th_win; /* initial send window */ 1332 tp->cc_recv = to.to_cc; /* foreign CC */ 1333 1334 tp->irs = th->th_seq; 1335 tcp_rcvseqinit(tp); 1336 if (thflags & TH_ACK) { 1337 /* 1338 * Our SYN was acked. If segment contains CC.ECHO 1339 * option, check it to make sure this segment really 1340 * matches our SYN. If not, just drop it as old 1341 * duplicate, but send an RST if we're still playing 1342 * by the old rules. If no CC.ECHO option, make sure 1343 * we don't get fooled into using T/TCP. 1344 */ 1345 if (to.to_flags & TOF_CCECHO) { 1346 if (tp->cc_send != to.to_ccecho) { 1347 if (tao.tao_ccsent != 0) 1348 goto drop; 1349 else { 1350 rstreason = BANDLIM_UNLIMITED; 1351 goto dropwithreset; 1352 } 1353 } 1354 } else 1355 tp->t_flags &= ~TF_RCVD_CC; 1356 tcpstat.tcps_connects++; 1357 soisconnected(so); 1358 #ifdef MAC 1359 mac_set_socket_peer_from_mbuf(m, so); 1360 #endif 1361 /* Do window scaling on this connection? */ 1362 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1363 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1364 tp->snd_scale = tp->requested_s_scale; 1365 tp->rcv_scale = tp->request_r_scale; 1366 } 1367 /* Segment is acceptable, update cache if undefined. */ 1368 if (tao.tao_ccsent == 0 && tcp_do_rfc1644) 1369 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0); 1370 1371 tp->rcv_adv += tp->rcv_wnd; 1372 tp->snd_una++; /* SYN is acked */ 1373 /* 1374 * If there's data, delay ACK; if there's also a FIN 1375 * ACKNOW will be turned on later. 1376 */ 1377 if (DELAY_ACK(tp) && tlen != 0) 1378 callout_reset(tp->tt_delack, tcp_delacktime, 1379 tcp_timer_delack, tp); 1380 else 1381 tp->t_flags |= TF_ACKNOW; 1382 /* 1383 * Received <SYN,ACK> in SYN_SENT[*] state. 1384 * Transitions: 1385 * SYN_SENT --> ESTABLISHED 1386 * SYN_SENT* --> FIN_WAIT_1 1387 */ 1388 tp->t_starttime = ticks; 1389 if (tp->t_flags & TF_NEEDFIN) { 1390 tp->t_state = TCPS_FIN_WAIT_1; 1391 tp->t_flags &= ~TF_NEEDFIN; 1392 thflags &= ~TH_SYN; 1393 } else { 1394 tp->t_state = TCPS_ESTABLISHED; 1395 callout_reset(tp->tt_keep, tcp_keepidle, 1396 tcp_timer_keep, tp); 1397 } 1398 } else { 1399 /* 1400 * Received initial SYN in SYN-SENT[*] state => 1401 * simultaneous open. If segment contains CC option 1402 * and there is a cached CC, apply TAO test. 1403 * If it succeeds, connection is * half-synchronized. 1404 * Otherwise, do 3-way handshake: 1405 * SYN-SENT -> SYN-RECEIVED 1406 * SYN-SENT* -> SYN-RECEIVED* 1407 * If there was no CC option, clear cached CC value. 1408 */ 1409 tp->t_flags |= TF_ACKNOW; 1410 callout_stop(tp->tt_rexmt); 1411 if (to.to_flags & TOF_CC) { 1412 if (tao.tao_cc != 0 && 1413 CC_GT(to.to_cc, tao.tao_cc)) { 1414 /* 1415 * update cache and make transition: 1416 * SYN-SENT -> ESTABLISHED* 1417 * SYN-SENT* -> FIN-WAIT-1* 1418 */ 1419 tao.tao_cc = to.to_cc; 1420 tcp_hc_updatetao(&inp->inp_inc, 1421 TCP_HC_TAO_CC, to.to_cc, 0); 1422 tp->t_starttime = ticks; 1423 if (tp->t_flags & TF_NEEDFIN) { 1424 tp->t_state = TCPS_FIN_WAIT_1; 1425 tp->t_flags &= ~TF_NEEDFIN; 1426 } else { 1427 tp->t_state = TCPS_ESTABLISHED; 1428 callout_reset(tp->tt_keep, 1429 tcp_keepidle, 1430 tcp_timer_keep, 1431 tp); 1432 } 1433 tp->t_flags |= TF_NEEDSYN; 1434 } else 1435 tp->t_state = TCPS_SYN_RECEIVED; 1436 } else { 1437 if (tcp_do_rfc1644) { 1438 /* CC.NEW or no option => invalidate cache */ 1439 tao.tao_cc = 0; 1440 tcp_hc_updatetao(&inp->inp_inc, 1441 TCP_HC_TAO_CC, to.to_cc, 0); 1442 } 1443 tp->t_state = TCPS_SYN_RECEIVED; 1444 } 1445 } 1446 1447 trimthenstep6: 1448 /* 1449 * Advance th->th_seq to correspond to first data byte. 1450 * If data, trim to stay within window, 1451 * dropping FIN if necessary. 1452 */ 1453 th->th_seq++; 1454 if (tlen > tp->rcv_wnd) { 1455 todrop = tlen - tp->rcv_wnd; 1456 m_adj(m, -todrop); 1457 tlen = tp->rcv_wnd; 1458 thflags &= ~TH_FIN; 1459 tcpstat.tcps_rcvpackafterwin++; 1460 tcpstat.tcps_rcvbyteafterwin += todrop; 1461 } 1462 tp->snd_wl1 = th->th_seq - 1; 1463 tp->rcv_up = th->th_seq; 1464 /* 1465 * Client side of transaction: already sent SYN and data. 1466 * If the remote host used T/TCP to validate the SYN, 1467 * our data will be ACK'd; if so, enter normal data segment 1468 * processing in the middle of step 5, ack processing. 1469 * Otherwise, goto step 6. 1470 */ 1471 if (thflags & TH_ACK) 1472 goto process_ACK; 1473 1474 goto step6; 1475 1476 /* 1477 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1478 * if segment contains a SYN and CC [not CC.NEW] option: 1479 * if state == TIME_WAIT and connection duration > MSL, 1480 * drop packet and send RST; 1481 * 1482 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1483 * ack the FIN (and data) in retransmission queue. 1484 * Complete close and delete TCPCB. Then reprocess 1485 * segment, hoping to find new TCPCB in LISTEN state; 1486 * 1487 * else must be old SYN; drop it. 1488 * else do normal processing. 1489 */ 1490 case TCPS_LAST_ACK: 1491 case TCPS_CLOSING: 1492 case TCPS_TIME_WAIT: 1493 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1494 if ((thflags & TH_SYN) && 1495 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1496 if (tp->t_state == TCPS_TIME_WAIT && 1497 (ticks - tp->t_starttime) > tcp_msl) { 1498 rstreason = BANDLIM_UNLIMITED; 1499 goto dropwithreset; 1500 } 1501 if (CC_GT(to.to_cc, tp->cc_recv)) { 1502 tp = tcp_close(tp); 1503 goto findpcb; 1504 } 1505 else 1506 goto drop; 1507 } 1508 break; /* continue normal processing */ 1509 } 1510 1511 /* 1512 * States other than LISTEN or SYN_SENT. 1513 * First check the RST flag and sequence number since reset segments 1514 * are exempt from the timestamp and connection count tests. This 1515 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1516 * below which allowed reset segments in half the sequence space 1517 * to fall though and be processed (which gives forged reset 1518 * segments with a random sequence number a 50 percent chance of 1519 * killing a connection). 1520 * Then check timestamp, if present. 1521 * Then check the connection count, if present. 1522 * Then check that at least some bytes of segment are within 1523 * receive window. If segment begins before rcv_nxt, 1524 * drop leading data (and SYN); if nothing left, just ack. 1525 * 1526 * 1527 * If the RST bit is set, check the sequence number to see 1528 * if this is a valid reset segment. 1529 * RFC 793 page 37: 1530 * In all states except SYN-SENT, all reset (RST) segments 1531 * are validated by checking their SEQ-fields. A reset is 1532 * valid if its sequence number is in the window. 1533 * Note: this does not take into account delayed ACKs, so 1534 * we should test against last_ack_sent instead of rcv_nxt. 1535 * The sequence number in the reset segment is normally an 1536 * echo of our outgoing acknowlegement numbers, but some hosts 1537 * send a reset with the sequence number at the rightmost edge 1538 * of our receive window, and we have to handle this case. 1539 * If we have multiple segments in flight, the intial reset 1540 * segment sequence numbers will be to the left of last_ack_sent, 1541 * but they will eventually catch up. 1542 * In any case, it never made sense to trim reset segments to 1543 * fit the receive window since RFC 1122 says: 1544 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1545 * 1546 * A TCP SHOULD allow a received RST segment to include data. 1547 * 1548 * DISCUSSION 1549 * It has been suggested that a RST segment could contain 1550 * ASCII text that encoded and explained the cause of the 1551 * RST. No standard has yet been established for such 1552 * data. 1553 * 1554 * If the reset segment passes the sequence number test examine 1555 * the state: 1556 * SYN_RECEIVED STATE: 1557 * If passive open, return to LISTEN state. 1558 * If active open, inform user that connection was refused. 1559 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1560 * Inform user that connection was reset, and close tcb. 1561 * CLOSING, LAST_ACK STATES: 1562 * Close the tcb. 1563 * TIME_WAIT STATE: 1564 * Drop the segment - see Stevens, vol. 2, p. 964 and 1565 * RFC 1337. 1566 */ 1567 if (thflags & TH_RST) { 1568 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1569 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1570 switch (tp->t_state) { 1571 1572 case TCPS_SYN_RECEIVED: 1573 so->so_error = ECONNREFUSED; 1574 goto close; 1575 1576 case TCPS_ESTABLISHED: 1577 case TCPS_FIN_WAIT_1: 1578 case TCPS_FIN_WAIT_2: 1579 case TCPS_CLOSE_WAIT: 1580 so->so_error = ECONNRESET; 1581 close: 1582 tp->t_state = TCPS_CLOSED; 1583 tcpstat.tcps_drops++; 1584 tp = tcp_close(tp); 1585 break; 1586 1587 case TCPS_CLOSING: 1588 case TCPS_LAST_ACK: 1589 tp = tcp_close(tp); 1590 break; 1591 1592 case TCPS_TIME_WAIT: 1593 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1594 ("timewait")); 1595 break; 1596 } 1597 } 1598 goto drop; 1599 } 1600 1601 /* 1602 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1603 * and it's less than ts_recent, drop it. 1604 */ 1605 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1606 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1607 1608 /* Check to see if ts_recent is over 24 days old. */ 1609 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1610 /* 1611 * Invalidate ts_recent. If this segment updates 1612 * ts_recent, the age will be reset later and ts_recent 1613 * will get a valid value. If it does not, setting 1614 * ts_recent to zero will at least satisfy the 1615 * requirement that zero be placed in the timestamp 1616 * echo reply when ts_recent isn't valid. The 1617 * age isn't reset until we get a valid ts_recent 1618 * because we don't want out-of-order segments to be 1619 * dropped when ts_recent is old. 1620 */ 1621 tp->ts_recent = 0; 1622 } else { 1623 tcpstat.tcps_rcvduppack++; 1624 tcpstat.tcps_rcvdupbyte += tlen; 1625 tcpstat.tcps_pawsdrop++; 1626 if (tlen) 1627 goto dropafterack; 1628 goto drop; 1629 } 1630 } 1631 1632 /* 1633 * T/TCP mechanism 1634 * If T/TCP was negotiated and the segment doesn't have CC, 1635 * or if its CC is wrong then drop the segment. 1636 * RST segments do not have to comply with this. 1637 */ 1638 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1639 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1640 goto dropafterack; 1641 1642 /* 1643 * In the SYN-RECEIVED state, validate that the packet belongs to 1644 * this connection before trimming the data to fit the receive 1645 * window. Check the sequence number versus IRS since we know 1646 * the sequence numbers haven't wrapped. This is a partial fix 1647 * for the "LAND" DoS attack. 1648 */ 1649 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1650 rstreason = BANDLIM_RST_OPENPORT; 1651 goto dropwithreset; 1652 } 1653 1654 todrop = tp->rcv_nxt - th->th_seq; 1655 if (todrop > 0) { 1656 if (thflags & TH_SYN) { 1657 thflags &= ~TH_SYN; 1658 th->th_seq++; 1659 if (th->th_urp > 1) 1660 th->th_urp--; 1661 else 1662 thflags &= ~TH_URG; 1663 todrop--; 1664 } 1665 /* 1666 * Following if statement from Stevens, vol. 2, p. 960. 1667 */ 1668 if (todrop > tlen 1669 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1670 /* 1671 * Any valid FIN must be to the left of the window. 1672 * At this point the FIN must be a duplicate or out 1673 * of sequence; drop it. 1674 */ 1675 thflags &= ~TH_FIN; 1676 1677 /* 1678 * Send an ACK to resynchronize and drop any data. 1679 * But keep on processing for RST or ACK. 1680 */ 1681 tp->t_flags |= TF_ACKNOW; 1682 todrop = tlen; 1683 tcpstat.tcps_rcvduppack++; 1684 tcpstat.tcps_rcvdupbyte += todrop; 1685 } else { 1686 tcpstat.tcps_rcvpartduppack++; 1687 tcpstat.tcps_rcvpartdupbyte += todrop; 1688 } 1689 drop_hdrlen += todrop; /* drop from the top afterwards */ 1690 th->th_seq += todrop; 1691 tlen -= todrop; 1692 if (th->th_urp > todrop) 1693 th->th_urp -= todrop; 1694 else { 1695 thflags &= ~TH_URG; 1696 th->th_urp = 0; 1697 } 1698 } 1699 1700 /* 1701 * If new data are received on a connection after the 1702 * user processes are gone, then RST the other end. 1703 */ 1704 if ((so->so_state & SS_NOFDREF) && 1705 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1706 tp = tcp_close(tp); 1707 tcpstat.tcps_rcvafterclose++; 1708 rstreason = BANDLIM_UNLIMITED; 1709 goto dropwithreset; 1710 } 1711 1712 /* 1713 * If segment ends after window, drop trailing data 1714 * (and PUSH and FIN); if nothing left, just ACK. 1715 */ 1716 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1717 if (todrop > 0) { 1718 tcpstat.tcps_rcvpackafterwin++; 1719 if (todrop >= tlen) { 1720 tcpstat.tcps_rcvbyteafterwin += tlen; 1721 /* 1722 * If a new connection request is received 1723 * while in TIME_WAIT, drop the old connection 1724 * and start over if the sequence numbers 1725 * are above the previous ones. 1726 */ 1727 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1728 if (thflags & TH_SYN && 1729 tp->t_state == TCPS_TIME_WAIT && 1730 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1731 tp = tcp_close(tp); 1732 goto findpcb; 1733 } 1734 /* 1735 * If window is closed can only take segments at 1736 * window edge, and have to drop data and PUSH from 1737 * incoming segments. Continue processing, but 1738 * remember to ack. Otherwise, drop segment 1739 * and ack. 1740 */ 1741 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1742 tp->t_flags |= TF_ACKNOW; 1743 tcpstat.tcps_rcvwinprobe++; 1744 } else 1745 goto dropafterack; 1746 } else 1747 tcpstat.tcps_rcvbyteafterwin += todrop; 1748 m_adj(m, -todrop); 1749 tlen -= todrop; 1750 thflags &= ~(TH_PUSH|TH_FIN); 1751 } 1752 1753 /* 1754 * If last ACK falls within this segment's sequence numbers, 1755 * record its timestamp. 1756 * NOTE that the test is modified according to the latest 1757 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1758 */ 1759 if ((to.to_flags & TOF_TS) != 0 && 1760 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1761 tp->ts_recent_age = ticks; 1762 tp->ts_recent = to.to_tsval; 1763 } 1764 1765 /* 1766 * If a SYN is in the window, then this is an 1767 * error and we send an RST and drop the connection. 1768 */ 1769 if (thflags & TH_SYN) { 1770 tp = tcp_drop(tp, ECONNRESET); 1771 rstreason = BANDLIM_UNLIMITED; 1772 goto drop; 1773 } 1774 1775 /* 1776 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1777 * flag is on (half-synchronized state), then queue data for 1778 * later processing; else drop segment and return. 1779 */ 1780 if ((thflags & TH_ACK) == 0) { 1781 if (tp->t_state == TCPS_SYN_RECEIVED || 1782 (tp->t_flags & TF_NEEDSYN)) 1783 goto step6; 1784 else 1785 goto drop; 1786 } 1787 1788 /* 1789 * Ack processing. 1790 */ 1791 switch (tp->t_state) { 1792 1793 /* 1794 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1795 * ESTABLISHED state and continue processing. 1796 * The ACK was checked above. 1797 */ 1798 case TCPS_SYN_RECEIVED: 1799 1800 tcpstat.tcps_connects++; 1801 soisconnected(so); 1802 /* Do window scaling? */ 1803 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1804 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1805 tp->snd_scale = tp->requested_s_scale; 1806 tp->rcv_scale = tp->request_r_scale; 1807 } 1808 /* 1809 * Upon successful completion of 3-way handshake, 1810 * update cache.CC, pass any queued data to the user, 1811 * and advance state appropriately. 1812 */ 1813 if (tcp_do_rfc1644) { 1814 tao.tao_cc = tp->cc_recv; 1815 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC, 1816 tp->cc_recv, 0); 1817 } 1818 /* 1819 * Make transitions: 1820 * SYN-RECEIVED -> ESTABLISHED 1821 * SYN-RECEIVED* -> FIN-WAIT-1 1822 */ 1823 tp->t_starttime = ticks; 1824 if (tp->t_flags & TF_NEEDFIN) { 1825 tp->t_state = TCPS_FIN_WAIT_1; 1826 tp->t_flags &= ~TF_NEEDFIN; 1827 } else { 1828 tp->t_state = TCPS_ESTABLISHED; 1829 callout_reset(tp->tt_keep, tcp_keepidle, 1830 tcp_timer_keep, tp); 1831 } 1832 /* 1833 * If segment contains data or ACK, will call tcp_reass() 1834 * later; if not, do so now to pass queued data to user. 1835 */ 1836 if (tlen == 0 && (thflags & TH_FIN) == 0) 1837 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1838 (struct mbuf *)0); 1839 tp->snd_wl1 = th->th_seq - 1; 1840 /* FALLTHROUGH */ 1841 1842 /* 1843 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1844 * ACKs. If the ack is in the range 1845 * tp->snd_una < th->th_ack <= tp->snd_max 1846 * then advance tp->snd_una to th->th_ack and drop 1847 * data from the retransmission queue. If this ACK reflects 1848 * more up to date window information we update our window information. 1849 */ 1850 case TCPS_ESTABLISHED: 1851 case TCPS_FIN_WAIT_1: 1852 case TCPS_FIN_WAIT_2: 1853 case TCPS_CLOSE_WAIT: 1854 case TCPS_CLOSING: 1855 case TCPS_LAST_ACK: 1856 case TCPS_TIME_WAIT: 1857 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1858 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1859 if (tlen == 0 && tiwin == tp->snd_wnd) { 1860 tcpstat.tcps_rcvdupack++; 1861 /* 1862 * If we have outstanding data (other than 1863 * a window probe), this is a completely 1864 * duplicate ack (ie, window info didn't 1865 * change), the ack is the biggest we've 1866 * seen and we've seen exactly our rexmt 1867 * threshhold of them, assume a packet 1868 * has been dropped and retransmit it. 1869 * Kludge snd_nxt & the congestion 1870 * window so we send only this one 1871 * packet. 1872 * 1873 * We know we're losing at the current 1874 * window size so do congestion avoidance 1875 * (set ssthresh to half the current window 1876 * and pull our congestion window back to 1877 * the new ssthresh). 1878 * 1879 * Dup acks mean that packets have left the 1880 * network (they're now cached at the receiver) 1881 * so bump cwnd by the amount in the receiver 1882 * to keep a constant cwnd packets in the 1883 * network. 1884 */ 1885 if (!callout_active(tp->tt_rexmt) || 1886 th->th_ack != tp->snd_una) 1887 tp->t_dupacks = 0; 1888 else if (++tp->t_dupacks > tcprexmtthresh || 1889 (tcp_do_newreno && 1890 IN_FASTRECOVERY(tp))) { 1891 tp->snd_cwnd += tp->t_maxseg; 1892 (void) tcp_output(tp); 1893 goto drop; 1894 } else if (tp->t_dupacks == tcprexmtthresh) { 1895 tcp_seq onxt = tp->snd_nxt; 1896 u_int win; 1897 if (tcp_do_newreno && 1898 SEQ_LEQ(th->th_ack, 1899 tp->snd_recover)) { 1900 tp->t_dupacks = 0; 1901 break; 1902 } 1903 win = min(tp->snd_wnd, tp->snd_cwnd) / 1904 2 / tp->t_maxseg; 1905 if (win < 2) 1906 win = 2; 1907 tp->snd_ssthresh = win * tp->t_maxseg; 1908 ENTER_FASTRECOVERY(tp); 1909 tp->snd_recover = tp->snd_max; 1910 callout_stop(tp->tt_rexmt); 1911 tp->t_rtttime = 0; 1912 tp->snd_nxt = th->th_ack; 1913 tp->snd_cwnd = tp->t_maxseg; 1914 (void) tcp_output(tp); 1915 KASSERT(tp->snd_limited <= 2, 1916 ("tp->snd_limited too big")); 1917 tp->snd_cwnd = tp->snd_ssthresh + 1918 tp->t_maxseg * 1919 (tp->t_dupacks - tp->snd_limited); 1920 if (SEQ_GT(onxt, tp->snd_nxt)) 1921 tp->snd_nxt = onxt; 1922 goto drop; 1923 } else if (tcp_do_rfc3042) { 1924 u_long oldcwnd = tp->snd_cwnd; 1925 tcp_seq oldsndmax = tp->snd_max; 1926 u_int sent; 1927 1928 KASSERT(tp->t_dupacks == 1 || 1929 tp->t_dupacks == 2, 1930 ("dupacks not 1 or 2")); 1931 if (tp->t_dupacks == 1) 1932 tp->snd_limited = 0; 1933 tp->snd_cwnd = 1934 (tp->snd_nxt - tp->snd_una) + 1935 (tp->t_dupacks - tp->snd_limited) * 1936 tp->t_maxseg; 1937 (void) tcp_output(tp); 1938 sent = tp->snd_max - oldsndmax; 1939 if (sent > tp->t_maxseg) { 1940 KASSERT((tp->t_dupacks == 2 && 1941 tp->snd_limited == 0) || 1942 (sent == tp->t_maxseg + 1 && 1943 tp->t_flags & TF_SENTFIN), 1944 ("sent too much")); 1945 tp->snd_limited = 2; 1946 } else if (sent > 0) 1947 ++tp->snd_limited; 1948 tp->snd_cwnd = oldcwnd; 1949 goto drop; 1950 } 1951 } else 1952 tp->t_dupacks = 0; 1953 break; 1954 } 1955 1956 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1957 1958 /* 1959 * If the congestion window was inflated to account 1960 * for the other side's cached packets, retract it. 1961 */ 1962 if (tcp_do_newreno) { 1963 if (IN_FASTRECOVERY(tp)) { 1964 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1965 tcp_newreno_partial_ack(tp, th); 1966 } else { 1967 /* 1968 * Window inflation should have left us 1969 * with approximately snd_ssthresh 1970 * outstanding data. 1971 * But in case we would be inclined to 1972 * send a burst, better to do it via 1973 * the slow start mechanism. 1974 */ 1975 if (SEQ_GT(th->th_ack + 1976 tp->snd_ssthresh, 1977 tp->snd_max)) 1978 tp->snd_cwnd = tp->snd_max - 1979 th->th_ack + 1980 tp->t_maxseg; 1981 else 1982 tp->snd_cwnd = tp->snd_ssthresh; 1983 } 1984 } 1985 } else { 1986 if (tp->t_dupacks >= tcprexmtthresh && 1987 tp->snd_cwnd > tp->snd_ssthresh) 1988 tp->snd_cwnd = tp->snd_ssthresh; 1989 } 1990 tp->t_dupacks = 0; 1991 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1992 tcpstat.tcps_rcvacktoomuch++; 1993 goto dropafterack; 1994 } 1995 /* 1996 * If we reach this point, ACK is not a duplicate, 1997 * i.e., it ACKs something we sent. 1998 */ 1999 if (tp->t_flags & TF_NEEDSYN) { 2000 /* 2001 * T/TCP: Connection was half-synchronized, and our 2002 * SYN has been ACK'd (so connection is now fully 2003 * synchronized). Go to non-starred state, 2004 * increment snd_una for ACK of SYN, and check if 2005 * we can do window scaling. 2006 */ 2007 tp->t_flags &= ~TF_NEEDSYN; 2008 tp->snd_una++; 2009 /* Do window scaling? */ 2010 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2011 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2012 tp->snd_scale = tp->requested_s_scale; 2013 tp->rcv_scale = tp->request_r_scale; 2014 } 2015 } 2016 2017 process_ACK: 2018 acked = th->th_ack - tp->snd_una; 2019 tcpstat.tcps_rcvackpack++; 2020 tcpstat.tcps_rcvackbyte += acked; 2021 2022 /* 2023 * If we just performed our first retransmit, and the ACK 2024 * arrives within our recovery window, then it was a mistake 2025 * to do the retransmit in the first place. Recover our 2026 * original cwnd and ssthresh, and proceed to transmit where 2027 * we left off. 2028 */ 2029 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2030 ++tcpstat.tcps_sndrexmitbad; 2031 tp->snd_cwnd = tp->snd_cwnd_prev; 2032 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2033 tp->snd_recover = tp->snd_recover_prev; 2034 if (tp->t_flags & TF_WASFRECOVERY) 2035 ENTER_FASTRECOVERY(tp); 2036 tp->snd_nxt = tp->snd_max; 2037 tp->t_badrxtwin = 0; /* XXX probably not required */ 2038 } 2039 2040 /* 2041 * If we have a timestamp reply, update smoothed 2042 * round trip time. If no timestamp is present but 2043 * transmit timer is running and timed sequence 2044 * number was acked, update smoothed round trip time. 2045 * Since we now have an rtt measurement, cancel the 2046 * timer backoff (cf., Phil Karn's retransmit alg.). 2047 * Recompute the initial retransmit timer. 2048 * 2049 * Some boxes send broken timestamp replies 2050 * during the SYN+ACK phase, ignore 2051 * timestamps of 0 or we could calculate a 2052 * huge RTT and blow up the retransmit timer. 2053 */ 2054 if ((to.to_flags & TOF_TS) != 0 && 2055 to.to_tsecr) { 2056 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2057 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2058 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2059 } 2060 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2061 2062 /* 2063 * If all outstanding data is acked, stop retransmit 2064 * timer and remember to restart (more output or persist). 2065 * If there is more data to be acked, restart retransmit 2066 * timer, using current (possibly backed-off) value. 2067 */ 2068 if (th->th_ack == tp->snd_max) { 2069 callout_stop(tp->tt_rexmt); 2070 needoutput = 1; 2071 } else if (!callout_active(tp->tt_persist)) 2072 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2073 tcp_timer_rexmt, tp); 2074 2075 /* 2076 * If no data (only SYN) was ACK'd, 2077 * skip rest of ACK processing. 2078 */ 2079 if (acked == 0) 2080 goto step6; 2081 2082 /* 2083 * When new data is acked, open the congestion window. 2084 * If the window gives us less than ssthresh packets 2085 * in flight, open exponentially (maxseg per packet). 2086 * Otherwise open linearly: maxseg per window 2087 * (maxseg^2 / cwnd per packet). 2088 */ 2089 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) { 2090 register u_int cw = tp->snd_cwnd; 2091 register u_int incr = tp->t_maxseg; 2092 if (cw > tp->snd_ssthresh) 2093 incr = incr * incr / cw; 2094 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2095 } 2096 if (acked > so->so_snd.sb_cc) { 2097 tp->snd_wnd -= so->so_snd.sb_cc; 2098 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2099 ourfinisacked = 1; 2100 } else { 2101 sbdrop(&so->so_snd, acked); 2102 tp->snd_wnd -= acked; 2103 ourfinisacked = 0; 2104 } 2105 sowwakeup(so); 2106 /* detect una wraparound */ 2107 if (tcp_do_newreno && !IN_FASTRECOVERY(tp) && 2108 SEQ_GT(tp->snd_una, tp->snd_recover) && 2109 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2110 tp->snd_recover = th->th_ack - 1; 2111 if (tcp_do_newreno && IN_FASTRECOVERY(tp) && 2112 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2113 EXIT_FASTRECOVERY(tp); 2114 tp->snd_una = th->th_ack; 2115 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2116 tp->snd_nxt = tp->snd_una; 2117 2118 switch (tp->t_state) { 2119 2120 /* 2121 * In FIN_WAIT_1 STATE in addition to the processing 2122 * for the ESTABLISHED state if our FIN is now acknowledged 2123 * then enter FIN_WAIT_2. 2124 */ 2125 case TCPS_FIN_WAIT_1: 2126 if (ourfinisacked) { 2127 /* 2128 * If we can't receive any more 2129 * data, then closing user can proceed. 2130 * Starting the timer is contrary to the 2131 * specification, but if we don't get a FIN 2132 * we'll hang forever. 2133 */ 2134 /* XXXjl 2135 * we should release the tp also, and use a 2136 * compressed state. 2137 */ 2138 if (so->so_state & SS_CANTRCVMORE) { 2139 soisdisconnected(so); 2140 callout_reset(tp->tt_2msl, tcp_maxidle, 2141 tcp_timer_2msl, tp); 2142 } 2143 tp->t_state = TCPS_FIN_WAIT_2; 2144 } 2145 break; 2146 2147 /* 2148 * In CLOSING STATE in addition to the processing for 2149 * the ESTABLISHED state if the ACK acknowledges our FIN 2150 * then enter the TIME-WAIT state, otherwise ignore 2151 * the segment. 2152 */ 2153 case TCPS_CLOSING: 2154 if (ourfinisacked) { 2155 KASSERT(headlocked, ("headlocked")); 2156 tcp_twstart(tp); 2157 INP_INFO_WUNLOCK(&tcbinfo); 2158 m_freem(m); 2159 return; 2160 } 2161 break; 2162 2163 /* 2164 * In LAST_ACK, we may still be waiting for data to drain 2165 * and/or to be acked, as well as for the ack of our FIN. 2166 * If our FIN is now acknowledged, delete the TCB, 2167 * enter the closed state and return. 2168 */ 2169 case TCPS_LAST_ACK: 2170 if (ourfinisacked) { 2171 tp = tcp_close(tp); 2172 goto drop; 2173 } 2174 break; 2175 2176 /* 2177 * In TIME_WAIT state the only thing that should arrive 2178 * is a retransmission of the remote FIN. Acknowledge 2179 * it and restart the finack timer. 2180 */ 2181 case TCPS_TIME_WAIT: 2182 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2183 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2184 tcp_timer_2msl, tp); 2185 goto dropafterack; 2186 } 2187 } 2188 2189 step6: 2190 /* 2191 * Update window information. 2192 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2193 */ 2194 if ((thflags & TH_ACK) && 2195 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2196 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2197 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2198 /* keep track of pure window updates */ 2199 if (tlen == 0 && 2200 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2201 tcpstat.tcps_rcvwinupd++; 2202 tp->snd_wnd = tiwin; 2203 tp->snd_wl1 = th->th_seq; 2204 tp->snd_wl2 = th->th_ack; 2205 if (tp->snd_wnd > tp->max_sndwnd) 2206 tp->max_sndwnd = tp->snd_wnd; 2207 needoutput = 1; 2208 } 2209 2210 /* 2211 * Process segments with URG. 2212 */ 2213 if ((thflags & TH_URG) && th->th_urp && 2214 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2215 /* 2216 * This is a kludge, but if we receive and accept 2217 * random urgent pointers, we'll crash in 2218 * soreceive. It's hard to imagine someone 2219 * actually wanting to send this much urgent data. 2220 */ 2221 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2222 th->th_urp = 0; /* XXX */ 2223 thflags &= ~TH_URG; /* XXX */ 2224 goto dodata; /* XXX */ 2225 } 2226 /* 2227 * If this segment advances the known urgent pointer, 2228 * then mark the data stream. This should not happen 2229 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2230 * a FIN has been received from the remote side. 2231 * In these states we ignore the URG. 2232 * 2233 * According to RFC961 (Assigned Protocols), 2234 * the urgent pointer points to the last octet 2235 * of urgent data. We continue, however, 2236 * to consider it to indicate the first octet 2237 * of data past the urgent section as the original 2238 * spec states (in one of two places). 2239 */ 2240 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2241 tp->rcv_up = th->th_seq + th->th_urp; 2242 so->so_oobmark = so->so_rcv.sb_cc + 2243 (tp->rcv_up - tp->rcv_nxt) - 1; 2244 if (so->so_oobmark == 0) 2245 so->so_state |= SS_RCVATMARK; 2246 sohasoutofband(so); 2247 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2248 } 2249 /* 2250 * Remove out of band data so doesn't get presented to user. 2251 * This can happen independent of advancing the URG pointer, 2252 * but if two URG's are pending at once, some out-of-band 2253 * data may creep in... ick. 2254 */ 2255 if (th->th_urp <= (u_long)tlen && 2256 !(so->so_options & SO_OOBINLINE)) { 2257 /* hdr drop is delayed */ 2258 tcp_pulloutofband(so, th, m, drop_hdrlen); 2259 } 2260 } else { 2261 /* 2262 * If no out of band data is expected, 2263 * pull receive urgent pointer along 2264 * with the receive window. 2265 */ 2266 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2267 tp->rcv_up = tp->rcv_nxt; 2268 } 2269 dodata: /* XXX */ 2270 KASSERT(headlocked, ("headlocked")); 2271 /* 2272 * Process the segment text, merging it into the TCP sequencing queue, 2273 * and arranging for acknowledgment of receipt if necessary. 2274 * This process logically involves adjusting tp->rcv_wnd as data 2275 * is presented to the user (this happens in tcp_usrreq.c, 2276 * case PRU_RCVD). If a FIN has already been received on this 2277 * connection then we just ignore the text. 2278 */ 2279 if ((tlen || (thflags & TH_FIN)) && 2280 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2281 m_adj(m, drop_hdrlen); /* delayed header drop */ 2282 /* 2283 * Insert segment which includes th into TCP reassembly queue 2284 * with control block tp. Set thflags to whether reassembly now 2285 * includes a segment with FIN. This handles the common case 2286 * inline (segment is the next to be received on an established 2287 * connection, and the queue is empty), avoiding linkage into 2288 * and removal from the queue and repetition of various 2289 * conversions. 2290 * Set DELACK for segments received in order, but ack 2291 * immediately when segments are out of order (so 2292 * fast retransmit can work). 2293 */ 2294 if (th->th_seq == tp->rcv_nxt && 2295 LIST_EMPTY(&tp->t_segq) && 2296 TCPS_HAVEESTABLISHED(tp->t_state)) { 2297 if (DELAY_ACK(tp)) 2298 tp->t_flags |= TF_DELACK; 2299 else 2300 tp->t_flags |= TF_ACKNOW; 2301 tp->rcv_nxt += tlen; 2302 thflags = th->th_flags & TH_FIN; 2303 tcpstat.tcps_rcvpack++; 2304 tcpstat.tcps_rcvbyte += tlen; 2305 ND6_HINT(tp); 2306 if (so->so_state & SS_CANTRCVMORE) 2307 m_freem(m); 2308 else 2309 sbappendstream(&so->so_rcv, m); 2310 sorwakeup(so); 2311 } else { 2312 thflags = tcp_reass(tp, th, &tlen, m); 2313 tp->t_flags |= TF_ACKNOW; 2314 } 2315 2316 /* 2317 * Note the amount of data that peer has sent into 2318 * our window, in order to estimate the sender's 2319 * buffer size. 2320 */ 2321 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2322 } else { 2323 m_freem(m); 2324 thflags &= ~TH_FIN; 2325 } 2326 2327 /* 2328 * If FIN is received ACK the FIN and let the user know 2329 * that the connection is closing. 2330 */ 2331 if (thflags & TH_FIN) { 2332 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2333 socantrcvmore(so); 2334 /* 2335 * If connection is half-synchronized 2336 * (ie NEEDSYN flag on) then delay ACK, 2337 * so it may be piggybacked when SYN is sent. 2338 * Otherwise, since we received a FIN then no 2339 * more input can be expected, send ACK now. 2340 */ 2341 if (tp->t_flags & TF_NEEDSYN) 2342 tp->t_flags |= TF_DELACK; 2343 else 2344 tp->t_flags |= TF_ACKNOW; 2345 tp->rcv_nxt++; 2346 } 2347 switch (tp->t_state) { 2348 2349 /* 2350 * In SYN_RECEIVED and ESTABLISHED STATES 2351 * enter the CLOSE_WAIT state. 2352 */ 2353 case TCPS_SYN_RECEIVED: 2354 tp->t_starttime = ticks; 2355 /*FALLTHROUGH*/ 2356 case TCPS_ESTABLISHED: 2357 tp->t_state = TCPS_CLOSE_WAIT; 2358 break; 2359 2360 /* 2361 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2362 * enter the CLOSING state. 2363 */ 2364 case TCPS_FIN_WAIT_1: 2365 tp->t_state = TCPS_CLOSING; 2366 break; 2367 2368 /* 2369 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2370 * starting the time-wait timer, turning off the other 2371 * standard timers. 2372 */ 2373 case TCPS_FIN_WAIT_2: 2374 KASSERT(headlocked == 1, ("headlocked should be 1")); 2375 tcp_twstart(tp); 2376 INP_INFO_WUNLOCK(&tcbinfo); 2377 return; 2378 2379 /* 2380 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2381 */ 2382 case TCPS_TIME_WAIT: 2383 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2384 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2385 tcp_timer_2msl, tp); 2386 break; 2387 } 2388 } 2389 INP_INFO_WUNLOCK(&tcbinfo); 2390 #ifdef TCPDEBUG 2391 if (so->so_options & SO_DEBUG) 2392 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2393 &tcp_savetcp, 0); 2394 #endif 2395 2396 /* 2397 * Return any desired output. 2398 */ 2399 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2400 (void) tcp_output(tp); 2401 2402 check_delack: 2403 if (tp->t_flags & TF_DELACK) { 2404 tp->t_flags &= ~TF_DELACK; 2405 callout_reset(tp->tt_delack, tcp_delacktime, 2406 tcp_timer_delack, tp); 2407 } 2408 INP_UNLOCK(inp); 2409 return; 2410 2411 dropafterack: 2412 /* 2413 * Generate an ACK dropping incoming segment if it occupies 2414 * sequence space, where the ACK reflects our state. 2415 * 2416 * We can now skip the test for the RST flag since all 2417 * paths to this code happen after packets containing 2418 * RST have been dropped. 2419 * 2420 * In the SYN-RECEIVED state, don't send an ACK unless the 2421 * segment we received passes the SYN-RECEIVED ACK test. 2422 * If it fails send a RST. This breaks the loop in the 2423 * "LAND" DoS attack, and also prevents an ACK storm 2424 * between two listening ports that have been sent forged 2425 * SYN segments, each with the source address of the other. 2426 */ 2427 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2428 (SEQ_GT(tp->snd_una, th->th_ack) || 2429 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2430 rstreason = BANDLIM_RST_OPENPORT; 2431 goto dropwithreset; 2432 } 2433 #ifdef TCPDEBUG 2434 if (so->so_options & SO_DEBUG) 2435 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2436 &tcp_savetcp, 0); 2437 #endif 2438 KASSERT(headlocked, ("headlocked should be 1")); 2439 INP_INFO_WUNLOCK(&tcbinfo); 2440 m_freem(m); 2441 tp->t_flags |= TF_ACKNOW; 2442 (void) tcp_output(tp); 2443 INP_UNLOCK(inp); 2444 return; 2445 2446 dropwithreset: 2447 /* 2448 * Generate a RST, dropping incoming segment. 2449 * Make ACK acceptable to originator of segment. 2450 * Don't bother to respond if destination was broadcast/multicast. 2451 */ 2452 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2453 goto drop; 2454 if (isipv6) { 2455 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2456 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2457 goto drop; 2458 } else { 2459 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2460 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2461 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2462 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2463 goto drop; 2464 } 2465 /* IPv6 anycast check is done at tcp6_input() */ 2466 2467 /* 2468 * Perform bandwidth limiting. 2469 */ 2470 if (badport_bandlim(rstreason) < 0) 2471 goto drop; 2472 2473 #ifdef TCPDEBUG 2474 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2475 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2476 &tcp_savetcp, 0); 2477 #endif 2478 2479 if (thflags & TH_ACK) 2480 /* mtod() below is safe as long as hdr dropping is delayed */ 2481 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2482 TH_RST); 2483 else { 2484 if (thflags & TH_SYN) 2485 tlen++; 2486 /* mtod() below is safe as long as hdr dropping is delayed */ 2487 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2488 (tcp_seq)0, TH_RST|TH_ACK); 2489 } 2490 2491 if (tp) 2492 INP_UNLOCK(inp); 2493 if (headlocked) 2494 INP_INFO_WUNLOCK(&tcbinfo); 2495 return; 2496 2497 drop: 2498 /* 2499 * Drop space held by incoming segment and return. 2500 */ 2501 #ifdef TCPDEBUG 2502 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2503 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2504 &tcp_savetcp, 0); 2505 #endif 2506 if (tp) 2507 INP_UNLOCK(inp); 2508 m_freem(m); 2509 if (headlocked) 2510 INP_INFO_WUNLOCK(&tcbinfo); 2511 return; 2512 } 2513 2514 /* 2515 * Parse TCP options and place in tcpopt. 2516 */ 2517 static void 2518 tcp_dooptions(to, cp, cnt, is_syn) 2519 struct tcpopt *to; 2520 u_char *cp; 2521 int cnt; 2522 int is_syn; 2523 { 2524 int opt, optlen; 2525 2526 to->to_flags = 0; 2527 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2528 opt = cp[0]; 2529 if (opt == TCPOPT_EOL) 2530 break; 2531 if (opt == TCPOPT_NOP) 2532 optlen = 1; 2533 else { 2534 if (cnt < 2) 2535 break; 2536 optlen = cp[1]; 2537 if (optlen < 2 || optlen > cnt) 2538 break; 2539 } 2540 switch (opt) { 2541 case TCPOPT_MAXSEG: 2542 if (optlen != TCPOLEN_MAXSEG) 2543 continue; 2544 if (!is_syn) 2545 continue; 2546 to->to_flags |= TOF_MSS; 2547 bcopy((char *)cp + 2, 2548 (char *)&to->to_mss, sizeof(to->to_mss)); 2549 to->to_mss = ntohs(to->to_mss); 2550 break; 2551 case TCPOPT_WINDOW: 2552 if (optlen != TCPOLEN_WINDOW) 2553 continue; 2554 if (! is_syn) 2555 continue; 2556 to->to_flags |= TOF_SCALE; 2557 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2558 break; 2559 case TCPOPT_TIMESTAMP: 2560 if (optlen != TCPOLEN_TIMESTAMP) 2561 continue; 2562 to->to_flags |= TOF_TS; 2563 bcopy((char *)cp + 2, 2564 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2565 to->to_tsval = ntohl(to->to_tsval); 2566 bcopy((char *)cp + 6, 2567 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2568 to->to_tsecr = ntohl(to->to_tsecr); 2569 break; 2570 case TCPOPT_CC: 2571 if (optlen != TCPOLEN_CC) 2572 continue; 2573 to->to_flags |= TOF_CC; 2574 bcopy((char *)cp + 2, 2575 (char *)&to->to_cc, sizeof(to->to_cc)); 2576 to->to_cc = ntohl(to->to_cc); 2577 break; 2578 case TCPOPT_CCNEW: 2579 if (optlen != TCPOLEN_CC) 2580 continue; 2581 if (!is_syn) 2582 continue; 2583 to->to_flags |= TOF_CCNEW; 2584 bcopy((char *)cp + 2, 2585 (char *)&to->to_cc, sizeof(to->to_cc)); 2586 to->to_cc = ntohl(to->to_cc); 2587 break; 2588 case TCPOPT_CCECHO: 2589 if (optlen != TCPOLEN_CC) 2590 continue; 2591 if (!is_syn) 2592 continue; 2593 to->to_flags |= TOF_CCECHO; 2594 bcopy((char *)cp + 2, 2595 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2596 to->to_ccecho = ntohl(to->to_ccecho); 2597 break; 2598 #ifdef TCP_SIGNATURE 2599 /* 2600 * XXX In order to reply to a host which has set the 2601 * TCP_SIGNATURE option in its initial SYN, we have to 2602 * record the fact that the option was observed here 2603 * for the syncache code to perform the correct response. 2604 */ 2605 case TCPOPT_SIGNATURE: 2606 if (optlen != TCPOLEN_SIGNATURE) 2607 continue; 2608 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2609 break; 2610 #endif 2611 default: 2612 continue; 2613 } 2614 } 2615 } 2616 2617 /* 2618 * Pull out of band byte out of a segment so 2619 * it doesn't appear in the user's data queue. 2620 * It is still reflected in the segment length for 2621 * sequencing purposes. 2622 */ 2623 static void 2624 tcp_pulloutofband(so, th, m, off) 2625 struct socket *so; 2626 struct tcphdr *th; 2627 register struct mbuf *m; 2628 int off; /* delayed to be droped hdrlen */ 2629 { 2630 int cnt = off + th->th_urp - 1; 2631 2632 while (cnt >= 0) { 2633 if (m->m_len > cnt) { 2634 char *cp = mtod(m, caddr_t) + cnt; 2635 struct tcpcb *tp = sototcpcb(so); 2636 2637 tp->t_iobc = *cp; 2638 tp->t_oobflags |= TCPOOB_HAVEDATA; 2639 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2640 m->m_len--; 2641 if (m->m_flags & M_PKTHDR) 2642 m->m_pkthdr.len--; 2643 return; 2644 } 2645 cnt -= m->m_len; 2646 m = m->m_next; 2647 if (m == 0) 2648 break; 2649 } 2650 panic("tcp_pulloutofband"); 2651 } 2652 2653 /* 2654 * Collect new round-trip time estimate 2655 * and update averages and current timeout. 2656 */ 2657 static void 2658 tcp_xmit_timer(tp, rtt) 2659 register struct tcpcb *tp; 2660 int rtt; 2661 { 2662 register int delta; 2663 2664 tcpstat.tcps_rttupdated++; 2665 tp->t_rttupdated++; 2666 if (tp->t_srtt != 0) { 2667 /* 2668 * srtt is stored as fixed point with 5 bits after the 2669 * binary point (i.e., scaled by 8). The following magic 2670 * is equivalent to the smoothing algorithm in rfc793 with 2671 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2672 * point). Adjust rtt to origin 0. 2673 */ 2674 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2675 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2676 2677 if ((tp->t_srtt += delta) <= 0) 2678 tp->t_srtt = 1; 2679 2680 /* 2681 * We accumulate a smoothed rtt variance (actually, a 2682 * smoothed mean difference), then set the retransmit 2683 * timer to smoothed rtt + 4 times the smoothed variance. 2684 * rttvar is stored as fixed point with 4 bits after the 2685 * binary point (scaled by 16). The following is 2686 * equivalent to rfc793 smoothing with an alpha of .75 2687 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2688 * rfc793's wired-in beta. 2689 */ 2690 if (delta < 0) 2691 delta = -delta; 2692 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2693 if ((tp->t_rttvar += delta) <= 0) 2694 tp->t_rttvar = 1; 2695 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2696 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2697 } else { 2698 /* 2699 * No rtt measurement yet - use the unsmoothed rtt. 2700 * Set the variance to half the rtt (so our first 2701 * retransmit happens at 3*rtt). 2702 */ 2703 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2704 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2705 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2706 } 2707 tp->t_rtttime = 0; 2708 tp->t_rxtshift = 0; 2709 2710 /* 2711 * the retransmit should happen at rtt + 4 * rttvar. 2712 * Because of the way we do the smoothing, srtt and rttvar 2713 * will each average +1/2 tick of bias. When we compute 2714 * the retransmit timer, we want 1/2 tick of rounding and 2715 * 1 extra tick because of +-1/2 tick uncertainty in the 2716 * firing of the timer. The bias will give us exactly the 2717 * 1.5 tick we need. But, because the bias is 2718 * statistical, we have to test that we don't drop below 2719 * the minimum feasible timer (which is 2 ticks). 2720 */ 2721 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2722 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2723 2724 /* 2725 * We received an ack for a packet that wasn't retransmitted; 2726 * it is probably safe to discard any error indications we've 2727 * received recently. This isn't quite right, but close enough 2728 * for now (a route might have failed after we sent a segment, 2729 * and the return path might not be symmetrical). 2730 */ 2731 tp->t_softerror = 0; 2732 } 2733 2734 /* 2735 * Determine a reasonable value for maxseg size. 2736 * If the route is known, check route for mtu. 2737 * If none, use an mss that can be handled on the outgoing 2738 * interface without forcing IP to fragment; if bigger than 2739 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2740 * to utilize large mbufs. If no route is found, route has no mtu, 2741 * or the destination isn't local, use a default, hopefully conservative 2742 * size (usually 512 or the default IP max size, but no more than the mtu 2743 * of the interface), as we can't discover anything about intervening 2744 * gateways or networks. We also initialize the congestion/slow start 2745 * window to be a single segment if the destination isn't local. 2746 * While looking at the routing entry, we also initialize other path-dependent 2747 * parameters from pre-set or cached values in the routing entry. 2748 * 2749 * Also take into account the space needed for options that we 2750 * send regularly. Make maxseg shorter by that amount to assure 2751 * that we can send maxseg amount of data even when the options 2752 * are present. Store the upper limit of the length of options plus 2753 * data in maxopd. 2754 * 2755 * 2756 * In case of T/TCP, we call this routine during implicit connection 2757 * setup as well (offer = -1), to initialize maxseg from the cached 2758 * MSS of our peer. 2759 * 2760 * NOTE that this routine is only called when we process an incoming 2761 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2762 */ 2763 void 2764 tcp_mss(tp, offer) 2765 struct tcpcb *tp; 2766 int offer; 2767 { 2768 int rtt, mss; 2769 u_long bufsize; 2770 u_long maxmtu; 2771 struct inpcb *inp = tp->t_inpcb; 2772 struct socket *so; 2773 struct hc_metrics_lite metrics; 2774 struct rmxp_tao tao; 2775 int origoffer = offer; 2776 #ifdef INET6 2777 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2778 size_t min_protoh = isipv6 ? 2779 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2780 sizeof (struct tcpiphdr); 2781 #else 2782 const size_t min_protoh = sizeof(struct tcpiphdr); 2783 #endif 2784 bzero(&tao, sizeof(tao)); 2785 2786 /* initialize */ 2787 #ifdef INET6 2788 if (isipv6) { 2789 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2790 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2791 } else 2792 #endif 2793 { 2794 maxmtu = tcp_maxmtu(&inp->inp_inc); 2795 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2796 } 2797 so = inp->inp_socket; 2798 2799 /* 2800 * no route to sender, take default mss and return 2801 */ 2802 if (maxmtu == 0) 2803 return; 2804 2805 /* what have we got? */ 2806 switch (offer) { 2807 case 0: 2808 /* 2809 * Offer == 0 means that there was no MSS on the SYN 2810 * segment, in this case we use tcp_mssdflt. 2811 */ 2812 offer = 2813 #ifdef INET6 2814 isipv6 ? tcp_v6mssdflt : 2815 #endif 2816 tcp_mssdflt; 2817 break; 2818 2819 case -1: 2820 /* 2821 * Offer == -1 means that we didn't receive SYN yet, 2822 * use cached value in that case; 2823 */ 2824 if (tcp_do_rfc1644) 2825 tcp_hc_gettao(&inp->inp_inc, &tao); 2826 if (tao.tao_mssopt != 0) 2827 offer = tao.tao_mssopt; 2828 /* FALLTHROUGH */ 2829 2830 default: 2831 /* 2832 * Prevent DoS attack with too small MSS. Round up 2833 * to at least minmss. 2834 */ 2835 offer = max(offer, tcp_minmss); 2836 /* 2837 * Sanity check: make sure that maxopd will be large 2838 * enough to allow some data on segments even if the 2839 * all the option space is used (40bytes). Otherwise 2840 * funny things may happen in tcp_output. 2841 */ 2842 offer = max(offer, 64); 2843 if (tcp_do_rfc1644) 2844 tcp_hc_updatetao(&inp->inp_inc, 2845 TCP_HC_TAO_MSSOPT, 0, offer); 2846 } 2847 2848 /* 2849 * rmx information is now retrieved from tcp_hostcache 2850 */ 2851 tcp_hc_get(&inp->inp_inc, &metrics); 2852 2853 /* 2854 * if there's a discovered mtu int tcp hostcache, use it 2855 * else, use the link mtu. 2856 */ 2857 if (metrics.rmx_mtu) 2858 mss = metrics.rmx_mtu - min_protoh; 2859 else { 2860 #ifdef INET6 2861 if (isipv6) { 2862 mss = maxmtu - min_protoh; 2863 if (!path_mtu_discovery && 2864 !in6_localaddr(&inp->in6p_faddr)) 2865 mss = min(mss, tcp_v6mssdflt); 2866 } else 2867 #endif 2868 { 2869 mss = maxmtu - min_protoh; 2870 if (!path_mtu_discovery && 2871 !in_localaddr(inp->inp_faddr)) 2872 mss = min(mss, tcp_mssdflt); 2873 } 2874 } 2875 mss = min(mss, offer); 2876 2877 /* 2878 * maxopd stores the maximum length of data AND options 2879 * in a segment; maxseg is the amount of data in a normal 2880 * segment. We need to store this value (maxopd) apart 2881 * from maxseg, because now every segment carries options 2882 * and thus we normally have somewhat less data in segments. 2883 */ 2884 tp->t_maxopd = mss; 2885 2886 /* 2887 * In case of T/TCP, origoffer==-1 indicates, that no segments 2888 * were received yet. In this case we just guess, otherwise 2889 * we do the same as before T/TCP. 2890 */ 2891 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2892 (origoffer == -1 || 2893 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2894 mss -= TCPOLEN_TSTAMP_APPA; 2895 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2896 (origoffer == -1 || 2897 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2898 mss -= TCPOLEN_CC_APPA; 2899 tp->t_maxseg = mss; 2900 2901 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2902 if (mss > MCLBYTES) 2903 mss &= ~(MCLBYTES-1); 2904 #else 2905 if (mss > MCLBYTES) 2906 mss = mss / MCLBYTES * MCLBYTES; 2907 #endif 2908 tp->t_maxseg = mss; 2909 2910 /* 2911 * If there's a pipesize, change the socket buffer to that size, 2912 * don't change if sb_hiwat is different than default (then it 2913 * has been changed on purpose with setsockopt). 2914 * Make the socket buffers an integral number of mss units; 2915 * if the mss is larger than the socket buffer, decrease the mss. 2916 */ 2917 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2918 bufsize = metrics.rmx_sendpipe; 2919 else 2920 bufsize = so->so_snd.sb_hiwat; 2921 if (bufsize < mss) 2922 mss = bufsize; 2923 else { 2924 bufsize = roundup(bufsize, mss); 2925 if (bufsize > sb_max) 2926 bufsize = sb_max; 2927 if (bufsize > so->so_snd.sb_hiwat) 2928 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2929 } 2930 tp->t_maxseg = mss; 2931 2932 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 2933 bufsize = metrics.rmx_recvpipe; 2934 else 2935 bufsize = so->so_rcv.sb_hiwat; 2936 if (bufsize > mss) { 2937 bufsize = roundup(bufsize, mss); 2938 if (bufsize > sb_max) 2939 bufsize = sb_max; 2940 if (bufsize > so->so_rcv.sb_hiwat) 2941 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2942 } 2943 /* 2944 * While we're here, check the others too 2945 */ 2946 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 2947 tp->t_srtt = rtt; 2948 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2949 tcpstat.tcps_usedrtt++; 2950 if (metrics.rmx_rttvar) { 2951 tp->t_rttvar = metrics.rmx_rttvar; 2952 tcpstat.tcps_usedrttvar++; 2953 } else { 2954 /* default variation is +- 1 rtt */ 2955 tp->t_rttvar = 2956 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2957 } 2958 TCPT_RANGESET(tp->t_rxtcur, 2959 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2960 tp->t_rttmin, TCPTV_REXMTMAX); 2961 } 2962 if (metrics.rmx_ssthresh) { 2963 /* 2964 * There's some sort of gateway or interface 2965 * buffer limit on the path. Use this to set 2966 * the slow start threshhold, but set the 2967 * threshold to no less than 2*mss. 2968 */ 2969 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 2970 tcpstat.tcps_usedssthresh++; 2971 } 2972 if (metrics.rmx_bandwidth) 2973 tp->snd_bandwidth = metrics.rmx_bandwidth; 2974 2975 /* 2976 * Set the slow-start flight size depending on whether this 2977 * is a local network or not. 2978 * 2979 * Extend this so we cache the cwnd too and retrieve it here. 2980 * Make cwnd even bigger than RFC3390 suggests but only if we 2981 * have previous experience with the remote host. Be careful 2982 * not make cwnd bigger than remote receive window or our own 2983 * send socket buffer. Maybe put some additional upper bound 2984 * on the retrieved cwnd. Should do incremental updates to 2985 * hostcache when cwnd collapses so next connection doesn't 2986 * overloads the path again. 2987 * 2988 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 2989 * We currently check only in syncache_socket for that. 2990 */ 2991 #define TCP_METRICS_CWND 2992 #ifdef TCP_METRICS_CWND 2993 if (metrics.rmx_cwnd) 2994 tp->snd_cwnd = max(mss, 2995 min(metrics.rmx_cwnd / 2, 2996 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 2997 else 2998 #endif 2999 if (tcp_do_rfc3390) 3000 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3001 #ifdef INET6 3002 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3003 (!isipv6 && in_localaddr(inp->inp_faddr))) 3004 #else 3005 else if (in_localaddr(inp->inp_faddr)) 3006 #endif 3007 tp->snd_cwnd = mss * ss_fltsz_local; 3008 else 3009 tp->snd_cwnd = mss * ss_fltsz; 3010 } 3011 3012 /* 3013 * Determine the MSS option to send on an outgoing SYN. 3014 */ 3015 int 3016 tcp_mssopt(inc) 3017 struct in_conninfo *inc; 3018 { 3019 int mss = 0; 3020 u_long maxmtu = 0; 3021 u_long thcmtu = 0; 3022 size_t min_protoh; 3023 #ifdef INET6 3024 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3025 #endif 3026 3027 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3028 3029 #ifdef INET6 3030 if (isipv6) { 3031 mss = tcp_v6mssdflt; 3032 maxmtu = tcp_maxmtu6(inc); 3033 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3034 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3035 } else 3036 #endif 3037 { 3038 mss = tcp_mssdflt; 3039 maxmtu = tcp_maxmtu(inc); 3040 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3041 min_protoh = sizeof(struct tcpiphdr); 3042 } 3043 if (maxmtu && thcmtu) 3044 mss = min(maxmtu, thcmtu) - min_protoh; 3045 else if (maxmtu || thcmtu) 3046 mss = max(maxmtu, thcmtu) - min_protoh; 3047 3048 return (mss); 3049 } 3050 3051 3052 /* 3053 * On a partial ack arrives, force the retransmission of the 3054 * next unacknowledged segment. Do not clear tp->t_dupacks. 3055 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3056 * be started again. 3057 */ 3058 static void 3059 tcp_newreno_partial_ack(tp, th) 3060 struct tcpcb *tp; 3061 struct tcphdr *th; 3062 { 3063 tcp_seq onxt = tp->snd_nxt; 3064 u_long ocwnd = tp->snd_cwnd; 3065 3066 callout_stop(tp->tt_rexmt); 3067 tp->t_rtttime = 0; 3068 tp->snd_nxt = th->th_ack; 3069 /* 3070 * Set snd_cwnd to one segment beyond acknowledged offset. 3071 * (tp->snd_una has not yet been updated when this function is called.) 3072 */ 3073 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3074 tp->t_flags |= TF_ACKNOW; 3075 (void) tcp_output(tp); 3076 tp->snd_cwnd = ocwnd; 3077 if (SEQ_GT(onxt, tp->snd_nxt)) 3078 tp->snd_nxt = onxt; 3079 /* 3080 * Partial window deflation. Relies on fact that tp->snd_una 3081 * not updated yet. 3082 */ 3083 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 3084 } 3085 3086 /* 3087 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3088 * looking for a pcb in the listen state. Returns 0 otherwise. 3089 */ 3090 static int 3091 tcp_timewait(tw, to, th, m, tlen) 3092 struct tcptw *tw; 3093 struct tcpopt *to; 3094 struct tcphdr *th; 3095 struct mbuf *m; 3096 int tlen; 3097 { 3098 int thflags; 3099 tcp_seq seq; 3100 #ifdef INET6 3101 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3102 #else 3103 const int isipv6 = 0; 3104 #endif 3105 3106 thflags = th->th_flags; 3107 3108 /* 3109 * NOTE: for FIN_WAIT_2 (to be added later), 3110 * must validate sequence number before accepting RST 3111 */ 3112 3113 /* 3114 * If the segment contains RST: 3115 * Drop the segment - see Stevens, vol. 2, p. 964 and 3116 * RFC 1337. 3117 */ 3118 if (thflags & TH_RST) 3119 goto drop; 3120 3121 /* 3122 * If segment contains a SYN and CC [not CC.NEW] option: 3123 * if connection duration > MSL, drop packet and send RST; 3124 * 3125 * if SEG.CC > CCrecv then is new SYN. 3126 * Complete close and delete TCPCB. Then reprocess 3127 * segment, hoping to find new TCPCB in LISTEN state; 3128 * 3129 * else must be old SYN; drop it. 3130 * else do normal processing. 3131 */ 3132 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) { 3133 if ((ticks - tw->t_starttime) > tcp_msl) 3134 goto reset; 3135 if (CC_GT(to->to_cc, tw->cc_recv)) { 3136 (void) tcp_twclose(tw, 0); 3137 return (1); 3138 } 3139 goto drop; 3140 } 3141 3142 #if 0 3143 /* PAWS not needed at the moment */ 3144 /* 3145 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3146 * and it's less than ts_recent, drop it. 3147 */ 3148 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3149 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3150 if ((thflags & TH_ACK) == 0) 3151 goto drop; 3152 goto ack; 3153 } 3154 /* 3155 * ts_recent is never updated because we never accept new segments. 3156 */ 3157 #endif 3158 3159 /* 3160 * If a new connection request is received 3161 * while in TIME_WAIT, drop the old connection 3162 * and start over if the sequence numbers 3163 * are above the previous ones. 3164 */ 3165 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3166 (void) tcp_twclose(tw, 0); 3167 return (1); 3168 } 3169 3170 /* 3171 * Drop the the segment if it does not contain an ACK. 3172 */ 3173 if ((thflags & TH_ACK) == 0) 3174 goto drop; 3175 3176 /* 3177 * Reset the 2MSL timer if this is a duplicate FIN. 3178 */ 3179 if (thflags & TH_FIN) { 3180 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3181 if (seq + 1 == tw->rcv_nxt) 3182 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3183 } 3184 3185 /* 3186 * Acknowledge the segment if it has data or is not a duplicate ACK. 3187 */ 3188 if (thflags != TH_ACK || tlen != 0 || 3189 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3190 tcp_twrespond(tw, TH_ACK); 3191 goto drop; 3192 3193 reset: 3194 /* 3195 * Generate a RST, dropping incoming segment. 3196 * Make ACK acceptable to originator of segment. 3197 * Don't bother to respond if destination was broadcast/multicast. 3198 */ 3199 if (m->m_flags & (M_BCAST|M_MCAST)) 3200 goto drop; 3201 if (isipv6) { 3202 struct ip6_hdr *ip6; 3203 3204 /* IPv6 anycast check is done at tcp6_input() */ 3205 ip6 = mtod(m, struct ip6_hdr *); 3206 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3207 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3208 goto drop; 3209 } else { 3210 struct ip *ip; 3211 3212 ip = mtod(m, struct ip *); 3213 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3214 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3215 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3216 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3217 goto drop; 3218 } 3219 if (thflags & TH_ACK) { 3220 tcp_respond(NULL, 3221 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3222 } else { 3223 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3224 tcp_respond(NULL, 3225 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3226 } 3227 INP_UNLOCK(tw->tw_inpcb); 3228 return (0); 3229 3230 drop: 3231 INP_UNLOCK(tw->tw_inpcb); 3232 m_freem(m); 3233 return (0); 3234 } 3235