1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 #include "opt_tcp_sack.h" 41 42 #include <sys/param.h> 43 #include <sys/kernel.h> 44 #include <sys/malloc.h> 45 #include <sys/mbuf.h> 46 #include <sys/proc.h> /* for proc0 declaration */ 47 #include <sys/protosw.h> 48 #include <sys/signalvar.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/sysctl.h> 52 #include <sys/syslog.h> 53 #include <sys/systm.h> 54 55 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 56 57 #include <vm/uma.h> 58 59 #include <net/if.h> 60 #include <net/route.h> 61 62 #include <netinet/in.h> 63 #include <netinet/in_pcb.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/in_var.h> 66 #include <netinet/ip.h> 67 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 68 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 69 #include <netinet/ip_var.h> 70 #include <netinet/ip_options.h> 71 #include <netinet/ip6.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/in6_pcb.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/nd6.h> 76 #include <netinet/tcp.h> 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet6/tcp6_var.h> 82 #include <netinet/tcpip.h> 83 #ifdef TCPDEBUG 84 #include <netinet/tcp_debug.h> 85 #endif /* TCPDEBUG */ 86 87 #ifdef FAST_IPSEC 88 #include <netipsec/ipsec.h> 89 #include <netipsec/ipsec6.h> 90 #endif /*FAST_IPSEC*/ 91 92 #ifdef IPSEC 93 #include <netinet6/ipsec.h> 94 #include <netinet6/ipsec6.h> 95 #include <netkey/key.h> 96 #endif /*IPSEC*/ 97 98 #include <machine/in_cksum.h> 99 100 #include <security/mac/mac_framework.h> 101 102 static const int tcprexmtthresh = 3; 103 104 struct tcpstat tcpstat; 105 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 106 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 107 108 static int log_in_vain = 0; 109 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 110 &log_in_vain, 0, "Log all incoming TCP connections"); 111 112 static int blackhole = 0; 113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 114 &blackhole, 0, "Do not send RST when dropping refused connections"); 115 116 int tcp_delack_enabled = 1; 117 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 118 &tcp_delack_enabled, 0, 119 "Delay ACK to try and piggyback it onto a data packet"); 120 121 #ifdef TCP_DROP_SYNFIN 122 static int drop_synfin = 0; 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 124 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 125 #endif 126 127 static int tcp_do_rfc3042 = 1; 128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 129 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 130 131 static int tcp_do_rfc3390 = 1; 132 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 133 &tcp_do_rfc3390, 0, 134 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 135 136 static int tcp_insecure_rst = 0; 137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 138 &tcp_insecure_rst, 0, 139 "Follow the old (insecure) criteria for accepting RST packets."); 140 141 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 142 "TCP Segment Reassembly Queue"); 143 144 static int tcp_reass_maxseg = 0; 145 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 146 &tcp_reass_maxseg, 0, 147 "Global maximum number of TCP Segments in Reassembly Queue"); 148 149 int tcp_reass_qsize = 0; 150 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 151 &tcp_reass_qsize, 0, 152 "Global number of TCP Segments currently in Reassembly Queue"); 153 154 static int tcp_reass_maxqlen = 48; 155 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 156 &tcp_reass_maxqlen, 0, 157 "Maximum number of TCP Segments per individual Reassembly Queue"); 158 159 static int tcp_reass_overflows = 0; 160 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 161 &tcp_reass_overflows, 0, 162 "Global number of TCP Segment Reassembly Queue Overflows"); 163 164 struct inpcbhead tcb; 165 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 166 struct inpcbinfo tcbinfo; 167 struct mtx *tcbinfo_mtx; 168 169 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 170 171 static void tcp_pulloutofband(struct socket *, 172 struct tcphdr *, struct mbuf *, int); 173 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 174 struct mbuf *); 175 static void tcp_xmit_timer(struct tcpcb *, int); 176 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 177 static int tcp_timewait(struct inpcb *, struct tcpopt *, 178 struct tcphdr *, struct mbuf *, int); 179 180 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 181 #ifdef INET6 182 #define ND6_HINT(tp) \ 183 do { \ 184 if ((tp) && (tp)->t_inpcb && \ 185 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 186 nd6_nud_hint(NULL, NULL, 0); \ 187 } while (0) 188 #else 189 #define ND6_HINT(tp) 190 #endif 191 192 /* 193 * Indicate whether this ack should be delayed. We can delay the ack if 194 * - there is no delayed ack timer in progress and 195 * - our last ack wasn't a 0-sized window. We never want to delay 196 * the ack that opens up a 0-sized window and 197 * - delayed acks are enabled or 198 * - this is a half-synchronized T/TCP connection. 199 */ 200 #define DELAY_ACK(tp) \ 201 ((!callout_active(tp->tt_delack) && \ 202 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 203 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 204 205 /* Initialize TCP reassembly queue */ 206 static void 207 tcp_reass_zone_change(void *tag) 208 { 209 210 tcp_reass_maxseg = nmbclusters / 16; 211 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 212 } 213 214 uma_zone_t tcp_reass_zone; 215 void 216 tcp_reass_init() 217 { 218 tcp_reass_maxseg = nmbclusters / 16; 219 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 220 &tcp_reass_maxseg); 221 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 222 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 223 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 224 EVENTHANDLER_REGISTER(nmbclusters_change, 225 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY); 226 } 227 228 static int 229 tcp_reass(tp, th, tlenp, m) 230 register struct tcpcb *tp; 231 register struct tcphdr *th; 232 int *tlenp; 233 struct mbuf *m; 234 { 235 struct tseg_qent *q; 236 struct tseg_qent *p = NULL; 237 struct tseg_qent *nq; 238 struct tseg_qent *te = NULL; 239 struct socket *so = tp->t_inpcb->inp_socket; 240 int flags; 241 242 INP_LOCK_ASSERT(tp->t_inpcb); 243 244 /* 245 * XXX: tcp_reass() is rather inefficient with its data structures 246 * and should be rewritten (see NetBSD for optimizations). While 247 * doing that it should move to its own file tcp_reass.c. 248 */ 249 250 /* 251 * Call with th==NULL after become established to 252 * force pre-ESTABLISHED data up to user socket. 253 */ 254 if (th == NULL) 255 goto present; 256 257 /* 258 * Limit the number of segments in the reassembly queue to prevent 259 * holding on to too many segments (and thus running out of mbufs). 260 * Make sure to let the missing segment through which caused this 261 * queue. Always keep one global queue entry spare to be able to 262 * process the missing segment. 263 */ 264 if (th->th_seq != tp->rcv_nxt && 265 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 266 tp->t_segqlen >= tcp_reass_maxqlen)) { 267 tcp_reass_overflows++; 268 tcpstat.tcps_rcvmemdrop++; 269 m_freem(m); 270 *tlenp = 0; 271 return (0); 272 } 273 274 /* 275 * Allocate a new queue entry. If we can't, or hit the zone limit 276 * just drop the pkt. 277 */ 278 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 279 if (te == NULL) { 280 tcpstat.tcps_rcvmemdrop++; 281 m_freem(m); 282 *tlenp = 0; 283 return (0); 284 } 285 tp->t_segqlen++; 286 tcp_reass_qsize++; 287 288 /* 289 * Find a segment which begins after this one does. 290 */ 291 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 292 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 293 break; 294 p = q; 295 } 296 297 /* 298 * If there is a preceding segment, it may provide some of 299 * our data already. If so, drop the data from the incoming 300 * segment. If it provides all of our data, drop us. 301 */ 302 if (p != NULL) { 303 register int i; 304 /* conversion to int (in i) handles seq wraparound */ 305 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 306 if (i > 0) { 307 if (i >= *tlenp) { 308 tcpstat.tcps_rcvduppack++; 309 tcpstat.tcps_rcvdupbyte += *tlenp; 310 m_freem(m); 311 uma_zfree(tcp_reass_zone, te); 312 tp->t_segqlen--; 313 tcp_reass_qsize--; 314 /* 315 * Try to present any queued data 316 * at the left window edge to the user. 317 * This is needed after the 3-WHS 318 * completes. 319 */ 320 goto present; /* ??? */ 321 } 322 m_adj(m, i); 323 *tlenp -= i; 324 th->th_seq += i; 325 } 326 } 327 tcpstat.tcps_rcvoopack++; 328 tcpstat.tcps_rcvoobyte += *tlenp; 329 330 /* 331 * While we overlap succeeding segments trim them or, 332 * if they are completely covered, dequeue them. 333 */ 334 while (q) { 335 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 336 if (i <= 0) 337 break; 338 if (i < q->tqe_len) { 339 q->tqe_th->th_seq += i; 340 q->tqe_len -= i; 341 m_adj(q->tqe_m, i); 342 break; 343 } 344 345 nq = LIST_NEXT(q, tqe_q); 346 LIST_REMOVE(q, tqe_q); 347 m_freem(q->tqe_m); 348 uma_zfree(tcp_reass_zone, q); 349 tp->t_segqlen--; 350 tcp_reass_qsize--; 351 q = nq; 352 } 353 354 /* Insert the new segment queue entry into place. */ 355 te->tqe_m = m; 356 te->tqe_th = th; 357 te->tqe_len = *tlenp; 358 359 if (p == NULL) { 360 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 361 } else { 362 LIST_INSERT_AFTER(p, te, tqe_q); 363 } 364 365 present: 366 /* 367 * Present data to user, advancing rcv_nxt through 368 * completed sequence space. 369 */ 370 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 371 return (0); 372 q = LIST_FIRST(&tp->t_segq); 373 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 374 return (0); 375 SOCKBUF_LOCK(&so->so_rcv); 376 do { 377 tp->rcv_nxt += q->tqe_len; 378 flags = q->tqe_th->th_flags & TH_FIN; 379 nq = LIST_NEXT(q, tqe_q); 380 LIST_REMOVE(q, tqe_q); 381 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 382 m_freem(q->tqe_m); 383 else 384 sbappendstream_locked(&so->so_rcv, q->tqe_m); 385 uma_zfree(tcp_reass_zone, q); 386 tp->t_segqlen--; 387 tcp_reass_qsize--; 388 q = nq; 389 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 390 ND6_HINT(tp); 391 sorwakeup_locked(so); 392 return (flags); 393 } 394 395 /* 396 * TCP input routine, follows pages 65-76 of the 397 * protocol specification dated September, 1981 very closely. 398 */ 399 #ifdef INET6 400 int 401 tcp6_input(mp, offp, proto) 402 struct mbuf **mp; 403 int *offp, proto; 404 { 405 register struct mbuf *m = *mp; 406 struct in6_ifaddr *ia6; 407 408 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 409 410 /* 411 * draft-itojun-ipv6-tcp-to-anycast 412 * better place to put this in? 413 */ 414 ia6 = ip6_getdstifaddr(m); 415 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 416 struct ip6_hdr *ip6; 417 418 ip6 = mtod(m, struct ip6_hdr *); 419 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 420 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 421 return IPPROTO_DONE; 422 } 423 424 tcp_input(m, *offp); 425 return IPPROTO_DONE; 426 } 427 #endif 428 429 void 430 tcp_input(m, off0) 431 register struct mbuf *m; 432 int off0; 433 { 434 register struct tcphdr *th; 435 register struct ip *ip = NULL; 436 register struct ipovly *ipov; 437 register struct inpcb *inp = NULL; 438 u_char *optp = NULL; 439 int optlen = 0; 440 int len, tlen, off; 441 int drop_hdrlen; 442 register struct tcpcb *tp = 0; 443 register int thflags; 444 struct socket *so = 0; 445 int todrop, acked, ourfinisacked, needoutput = 0; 446 u_long tiwin; 447 struct tcpopt to; /* options in this segment */ 448 int headlocked = 0; 449 #ifdef IPFIREWALL_FORWARD 450 struct m_tag *fwd_tag; 451 #endif 452 int rstreason; /* For badport_bandlim accounting purposes */ 453 454 struct ip6_hdr *ip6 = NULL; 455 #ifdef INET6 456 int isipv6; 457 char ip6buf[INET6_ADDRSTRLEN]; 458 #else 459 const int isipv6 = 0; 460 #endif 461 462 #ifdef TCPDEBUG 463 /* 464 * The size of tcp_saveipgen must be the size of the max ip header, 465 * now IPv6. 466 */ 467 u_char tcp_saveipgen[40]; 468 struct tcphdr tcp_savetcp; 469 short ostate = 0; 470 #endif 471 472 #ifdef INET6 473 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 474 #endif 475 bzero((char *)&to, sizeof(to)); 476 477 tcpstat.tcps_rcvtotal++; 478 479 if (isipv6) { 480 #ifdef INET6 481 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 482 ip6 = mtod(m, struct ip6_hdr *); 483 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 484 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 485 tcpstat.tcps_rcvbadsum++; 486 goto drop; 487 } 488 th = (struct tcphdr *)((caddr_t)ip6 + off0); 489 490 /* 491 * Be proactive about unspecified IPv6 address in source. 492 * As we use all-zero to indicate unbounded/unconnected pcb, 493 * unspecified IPv6 address can be used to confuse us. 494 * 495 * Note that packets with unspecified IPv6 destination is 496 * already dropped in ip6_input. 497 */ 498 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 499 /* XXX stat */ 500 goto drop; 501 } 502 #else 503 th = NULL; /* XXX: avoid compiler warning */ 504 #endif 505 } else { 506 /* 507 * Get IP and TCP header together in first mbuf. 508 * Note: IP leaves IP header in first mbuf. 509 */ 510 if (off0 > sizeof (struct ip)) { 511 ip_stripoptions(m, (struct mbuf *)0); 512 off0 = sizeof(struct ip); 513 } 514 if (m->m_len < sizeof (struct tcpiphdr)) { 515 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 516 tcpstat.tcps_rcvshort++; 517 return; 518 } 519 } 520 ip = mtod(m, struct ip *); 521 ipov = (struct ipovly *)ip; 522 th = (struct tcphdr *)((caddr_t)ip + off0); 523 tlen = ip->ip_len; 524 525 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 526 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 527 th->th_sum = m->m_pkthdr.csum_data; 528 else 529 th->th_sum = in_pseudo(ip->ip_src.s_addr, 530 ip->ip_dst.s_addr, 531 htonl(m->m_pkthdr.csum_data + 532 ip->ip_len + 533 IPPROTO_TCP)); 534 th->th_sum ^= 0xffff; 535 #ifdef TCPDEBUG 536 ipov->ih_len = (u_short)tlen; 537 ipov->ih_len = htons(ipov->ih_len); 538 #endif 539 } else { 540 /* 541 * Checksum extended TCP header and data. 542 */ 543 len = sizeof (struct ip) + tlen; 544 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 545 ipov->ih_len = (u_short)tlen; 546 ipov->ih_len = htons(ipov->ih_len); 547 th->th_sum = in_cksum(m, len); 548 } 549 if (th->th_sum) { 550 tcpstat.tcps_rcvbadsum++; 551 goto drop; 552 } 553 /* Re-initialization for later version check */ 554 ip->ip_v = IPVERSION; 555 } 556 557 /* 558 * Check that TCP offset makes sense, 559 * pull out TCP options and adjust length. XXX 560 */ 561 off = th->th_off << 2; 562 if (off < sizeof (struct tcphdr) || off > tlen) { 563 tcpstat.tcps_rcvbadoff++; 564 goto drop; 565 } 566 tlen -= off; /* tlen is used instead of ti->ti_len */ 567 if (off > sizeof (struct tcphdr)) { 568 if (isipv6) { 569 #ifdef INET6 570 IP6_EXTHDR_CHECK(m, off0, off, ); 571 ip6 = mtod(m, struct ip6_hdr *); 572 th = (struct tcphdr *)((caddr_t)ip6 + off0); 573 #endif 574 } else { 575 if (m->m_len < sizeof(struct ip) + off) { 576 if ((m = m_pullup(m, sizeof (struct ip) + off)) 577 == 0) { 578 tcpstat.tcps_rcvshort++; 579 return; 580 } 581 ip = mtod(m, struct ip *); 582 ipov = (struct ipovly *)ip; 583 th = (struct tcphdr *)((caddr_t)ip + off0); 584 } 585 } 586 optlen = off - sizeof (struct tcphdr); 587 optp = (u_char *)(th + 1); 588 } 589 thflags = th->th_flags; 590 591 #ifdef TCP_DROP_SYNFIN 592 /* 593 * If the drop_synfin option is enabled, drop all packets with 594 * both the SYN and FIN bits set. This prevents e.g. nmap from 595 * identifying the TCP/IP stack. 596 * 597 * This is a violation of the TCP specification. 598 */ 599 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 600 goto drop; 601 #endif 602 603 /* 604 * Convert TCP protocol specific fields to host format. 605 */ 606 th->th_seq = ntohl(th->th_seq); 607 th->th_ack = ntohl(th->th_ack); 608 th->th_win = ntohs(th->th_win); 609 th->th_urp = ntohs(th->th_urp); 610 611 /* 612 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 613 * until after ip6_savecontrol() is called and before other functions 614 * which don't want those proto headers. 615 * Because ip6_savecontrol() is going to parse the mbuf to 616 * search for data to be passed up to user-land, it wants mbuf 617 * parameters to be unchanged. 618 * XXX: the call of ip6_savecontrol() has been obsoleted based on 619 * latest version of the advanced API (20020110). 620 */ 621 drop_hdrlen = off0 + off; 622 623 /* 624 * Locate pcb for segment. 625 */ 626 INP_INFO_WLOCK(&tcbinfo); 627 headlocked = 1; 628 findpcb: 629 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 630 #ifdef IPFIREWALL_FORWARD 631 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 632 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 633 634 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 635 struct sockaddr_in *next_hop; 636 637 next_hop = (struct sockaddr_in *)(fwd_tag+1); 638 /* 639 * Transparently forwarded. Pretend to be the destination. 640 * already got one like this? 641 */ 642 inp = in_pcblookup_hash(&tcbinfo, 643 ip->ip_src, th->th_sport, 644 ip->ip_dst, th->th_dport, 645 0, m->m_pkthdr.rcvif); 646 if (!inp) { 647 /* It's new. Try to find the ambushing socket. */ 648 inp = in_pcblookup_hash(&tcbinfo, 649 ip->ip_src, th->th_sport, 650 next_hop->sin_addr, 651 next_hop->sin_port ? 652 ntohs(next_hop->sin_port) : 653 th->th_dport, 654 INPLOOKUP_WILDCARD, 655 m->m_pkthdr.rcvif); 656 } 657 /* Remove the tag from the packet. We don't need it anymore. */ 658 m_tag_delete(m, fwd_tag); 659 } else { 660 #endif /* IPFIREWALL_FORWARD */ 661 if (isipv6) { 662 #ifdef INET6 663 inp = in6_pcblookup_hash(&tcbinfo, 664 &ip6->ip6_src, th->th_sport, 665 &ip6->ip6_dst, th->th_dport, 666 INPLOOKUP_WILDCARD, 667 m->m_pkthdr.rcvif); 668 #endif 669 } else 670 inp = in_pcblookup_hash(&tcbinfo, 671 ip->ip_src, th->th_sport, 672 ip->ip_dst, th->th_dport, 673 INPLOOKUP_WILDCARD, 674 m->m_pkthdr.rcvif); 675 #ifdef IPFIREWALL_FORWARD 676 } 677 #endif /* IPFIREWALL_FORWARD */ 678 679 #if defined(IPSEC) || defined(FAST_IPSEC) 680 #ifdef INET6 681 if (isipv6) { 682 if (inp != NULL && ipsec6_in_reject(m, inp)) { 683 #ifdef IPSEC 684 ipsec6stat.in_polvio++; 685 #endif 686 goto drop; 687 } 688 } else 689 #endif /* INET6 */ 690 if (inp != NULL && ipsec4_in_reject(m, inp)) { 691 #ifdef IPSEC 692 ipsecstat.in_polvio++; 693 #endif 694 goto drop; 695 } 696 #endif /*IPSEC || FAST_IPSEC*/ 697 698 /* 699 * If the state is CLOSED (i.e., TCB does not exist) then 700 * all data in the incoming segment is discarded. 701 * If the TCB exists but is in CLOSED state, it is embryonic, 702 * but should either do a listen or a connect soon. 703 */ 704 if (inp == NULL) { 705 if (log_in_vain) { 706 #ifdef INET6 707 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 708 #else 709 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 710 #endif 711 712 if (isipv6) { 713 #ifdef INET6 714 strcpy(dbuf, "["); 715 strcpy(sbuf, "["); 716 strcat(dbuf, 717 ip6_sprintf(ip6buf, &ip6->ip6_dst)); 718 strcat(sbuf, 719 ip6_sprintf(ip6buf, &ip6->ip6_src)); 720 strcat(dbuf, "]"); 721 strcat(sbuf, "]"); 722 #endif 723 } else { 724 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 725 strcpy(sbuf, inet_ntoa(ip->ip_src)); 726 } 727 switch (log_in_vain) { 728 case 1: 729 if ((thflags & TH_SYN) == 0) 730 break; 731 /* FALLTHROUGH */ 732 case 2: 733 log(LOG_INFO, 734 "Connection attempt to TCP %s:%d " 735 "from %s:%d flags:0x%02x\n", 736 dbuf, ntohs(th->th_dport), sbuf, 737 ntohs(th->th_sport), thflags); 738 break; 739 default: 740 break; 741 } 742 } 743 if (blackhole) { 744 switch (blackhole) { 745 case 1: 746 if (thflags & TH_SYN) 747 goto drop; 748 break; 749 case 2: 750 goto drop; 751 default: 752 goto drop; 753 } 754 } 755 rstreason = BANDLIM_RST_CLOSEDPORT; 756 goto dropwithreset; 757 } 758 INP_LOCK(inp); 759 760 /* Check the minimum TTL for socket. */ 761 if (inp->inp_ip_minttl != 0) { 762 #ifdef INET6 763 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 764 goto drop; 765 else 766 #endif 767 if (inp->inp_ip_minttl > ip->ip_ttl) 768 goto drop; 769 } 770 771 if (inp->inp_vflag & INP_TIMEWAIT) { 772 /* 773 * The only option of relevance is TOF_CC, and only if 774 * present in a SYN segment. See tcp_timewait(). 775 */ 776 if (thflags & TH_SYN) 777 tcp_dooptions(&to, optp, optlen, TO_SYN); 778 if (tcp_timewait(inp, &to, th, m, tlen)) 779 goto findpcb; 780 /* 781 * tcp_timewait unlocks inp. 782 */ 783 INP_INFO_WUNLOCK(&tcbinfo); 784 return; 785 } 786 tp = intotcpcb(inp); 787 if (tp == 0) { 788 INP_UNLOCK(inp); 789 rstreason = BANDLIM_RST_CLOSEDPORT; 790 goto dropwithreset; 791 } 792 if (tp->t_state == TCPS_CLOSED) 793 goto drop; 794 795 #ifdef MAC 796 INP_LOCK_ASSERT(inp); 797 if (mac_check_inpcb_deliver(inp, m)) 798 goto drop; 799 #endif 800 so = inp->inp_socket; 801 KASSERT(so != NULL, ("tcp_input: so == NULL")); 802 #ifdef TCPDEBUG 803 if (so->so_options & SO_DEBUG) { 804 ostate = tp->t_state; 805 if (isipv6) 806 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 807 else 808 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 809 tcp_savetcp = *th; 810 } 811 #endif 812 if (so->so_options & SO_ACCEPTCONN) { 813 struct in_conninfo inc; 814 815 bzero(&inc, sizeof(inc)); 816 #ifdef INET6 817 inc.inc_isipv6 = isipv6; 818 #endif 819 if (isipv6) { 820 inc.inc6_faddr = ip6->ip6_src; 821 inc.inc6_laddr = ip6->ip6_dst; 822 } else { 823 inc.inc_faddr = ip->ip_src; 824 inc.inc_laddr = ip->ip_dst; 825 } 826 inc.inc_fport = th->th_sport; 827 inc.inc_lport = th->th_dport; 828 829 /* 830 * If the state is LISTEN then ignore segment if it contains 831 * a RST. If the segment contains an ACK then it is bad and 832 * send a RST. If it does not contain a SYN then it is not 833 * interesting; drop it. 834 * 835 * If the state is SYN_RECEIVED (syncache) and seg contains 836 * an ACK, but not for our SYN/ACK, send a RST. If the seg 837 * contains a RST, check the sequence number to see if it 838 * is a valid reset segment. 839 */ 840 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 841 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 842 /* 843 * Parse the TCP options here because 844 * syncookies need access to the reflected 845 * timestamp. 846 */ 847 tcp_dooptions(&to, optp, optlen, 0); 848 if (!syncache_expand(&inc, &to, th, &so, m)) { 849 /* 850 * No syncache entry, or ACK was not 851 * for our SYN/ACK. Send a RST. 852 */ 853 tcpstat.tcps_badsyn++; 854 rstreason = BANDLIM_RST_OPENPORT; 855 goto dropwithreset; 856 } 857 if (so == NULL) { 858 /* 859 * Could not complete 3-way handshake, 860 * connection is being closed down, and 861 * syncache has free'd mbuf. 862 */ 863 INP_UNLOCK(inp); 864 INP_INFO_WUNLOCK(&tcbinfo); 865 return; 866 } 867 /* 868 * Socket is created in state SYN_RECEIVED. 869 * Continue processing segment. 870 */ 871 INP_UNLOCK(inp); 872 inp = sotoinpcb(so); 873 INP_LOCK(inp); 874 tp = intotcpcb(inp); 875 /* 876 * This is what would have happened in 877 * tcp_output() when the SYN,ACK was sent. 878 */ 879 tp->snd_up = tp->snd_una; 880 tp->snd_max = tp->snd_nxt = tp->iss + 1; 881 tp->last_ack_sent = tp->rcv_nxt; 882 goto after_listen; 883 } 884 if (thflags & TH_RST) { 885 syncache_chkrst(&inc, th); 886 goto drop; 887 } 888 if (thflags & TH_ACK) { 889 syncache_badack(&inc); 890 tcpstat.tcps_badsyn++; 891 rstreason = BANDLIM_RST_OPENPORT; 892 goto dropwithreset; 893 } 894 goto drop; 895 } 896 897 /* 898 * Segment's flags are (SYN) or (SYN|FIN). 899 */ 900 #ifdef INET6 901 /* 902 * If deprecated address is forbidden, 903 * we do not accept SYN to deprecated interface 904 * address to prevent any new inbound connection from 905 * getting established. 906 * When we do not accept SYN, we send a TCP RST, 907 * with deprecated source address (instead of dropping 908 * it). We compromise it as it is much better for peer 909 * to send a RST, and RST will be the final packet 910 * for the exchange. 911 * 912 * If we do not forbid deprecated addresses, we accept 913 * the SYN packet. RFC2462 does not suggest dropping 914 * SYN in this case. 915 * If we decipher RFC2462 5.5.4, it says like this: 916 * 1. use of deprecated addr with existing 917 * communication is okay - "SHOULD continue to be 918 * used" 919 * 2. use of it with new communication: 920 * (2a) "SHOULD NOT be used if alternate address 921 * with sufficient scope is available" 922 * (2b) nothing mentioned otherwise. 923 * Here we fall into (2b) case as we have no choice in 924 * our source address selection - we must obey the peer. 925 * 926 * The wording in RFC2462 is confusing, and there are 927 * multiple description text for deprecated address 928 * handling - worse, they are not exactly the same. 929 * I believe 5.5.4 is the best one, so we follow 5.5.4. 930 */ 931 if (isipv6 && !ip6_use_deprecated) { 932 struct in6_ifaddr *ia6; 933 934 if ((ia6 = ip6_getdstifaddr(m)) && 935 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 936 INP_UNLOCK(inp); 937 tp = NULL; 938 rstreason = BANDLIM_RST_OPENPORT; 939 goto dropwithreset; 940 } 941 } 942 #endif 943 /* 944 * If it is from this socket, drop it, it must be forged. 945 * Don't bother responding if the destination was a broadcast. 946 */ 947 if (th->th_dport == th->th_sport) { 948 if (isipv6) { 949 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 950 &ip6->ip6_src)) 951 goto drop; 952 } else { 953 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 954 goto drop; 955 } 956 } 957 /* 958 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 959 * 960 * Note that it is quite possible to receive unicast 961 * link-layer packets with a broadcast IP address. Use 962 * in_broadcast() to find them. 963 */ 964 if (m->m_flags & (M_BCAST|M_MCAST)) 965 goto drop; 966 if (isipv6) { 967 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 968 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 969 goto drop; 970 } else { 971 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 972 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 973 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 974 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 975 goto drop; 976 } 977 /* 978 * SYN appears to be valid; create compressed TCP state 979 * for syncache, or perform t/tcp connection. 980 */ 981 if (so->so_qlen <= so->so_qlimit) { 982 #ifdef TCPDEBUG 983 if (so->so_options & SO_DEBUG) 984 tcp_trace(TA_INPUT, ostate, tp, 985 (void *)tcp_saveipgen, &tcp_savetcp, 0); 986 #endif 987 tcp_dooptions(&to, optp, optlen, TO_SYN); 988 if (!syncache_add(&inc, &to, th, inp, &so, m)) 989 goto drop; /* XXX: does not happen */ 990 if (so == NULL) { 991 /* 992 * Entry added to syncache, mbuf used to 993 * send SYN,ACK packet. Everything unlocked 994 * already. 995 */ 996 return; 997 } 998 panic("T/TCP not supported at the moment"); 999 #if 0 /* T/TCP */ 1000 /* 1001 * Segment passed TAO tests. 1002 * XXX: Can't happen at the moment. 1003 */ 1004 INP_UNLOCK(inp); 1005 inp = sotoinpcb(so); 1006 INP_LOCK(inp); 1007 tp = intotcpcb(inp); 1008 tp->t_starttime = ticks; 1009 tp->t_state = TCPS_ESTABLISHED; 1010 1011 /* 1012 * T/TCP logic: 1013 * If there is a FIN or if there is data, then 1014 * delay SYN,ACK(SYN) in the hope of piggy-backing 1015 * it on a response segment. Otherwise must send 1016 * ACK now in case the other side is slow starting. 1017 */ 1018 if (thflags & TH_FIN || tlen != 0) 1019 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1020 else 1021 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1022 tiwin = th->th_win << tp->snd_scale; 1023 tcpstat.tcps_connects++; 1024 soisconnected(so); 1025 goto trimthenstep6; 1026 #endif /* T/TCP */ 1027 } 1028 goto drop; 1029 } 1030 after_listen: 1031 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1032 INP_LOCK_ASSERT(inp); 1033 1034 /* Syncache takes care of sockets in the listen state. */ 1035 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN")); 1036 1037 /* 1038 * This is the second part of the MSS DoS prevention code (after 1039 * minmss on the sending side) and it deals with too many too small 1040 * tcp packets in a too short timeframe (1 second). 1041 * 1042 * For every full second we count the number of received packets 1043 * and bytes. If we get a lot of packets per second for this connection 1044 * (tcp_minmssoverload) we take a closer look at it and compute the 1045 * average packet size for the past second. If that is less than 1046 * tcp_minmss we get too many packets with very small payload which 1047 * is not good and burdens our system (and every packet generates 1048 * a wakeup to the process connected to our socket). We can reasonable 1049 * expect this to be small packet DoS attack to exhaust our CPU 1050 * cycles. 1051 * 1052 * Care has to be taken for the minimum packet overload value. This 1053 * value defines the minimum number of packets per second before we 1054 * start to worry. This must not be too low to avoid killing for 1055 * example interactive connections with many small packets like 1056 * telnet or SSH. 1057 * 1058 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1059 * this check. 1060 * 1061 * Account for packet if payload packet, skip over ACK, etc. 1062 */ 1063 if (tcp_minmss && tcp_minmssoverload && 1064 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1065 if ((unsigned int)(tp->rcv_second - ticks) < hz) { 1066 tp->rcv_pps++; 1067 tp->rcv_byps += tlen + off; 1068 if (tp->rcv_pps > tcp_minmssoverload) { 1069 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1070 printf("too many small tcp packets from " 1071 "%s:%u, av. %lubyte/packet, " 1072 "dropping connection\n", 1073 #ifdef INET6 1074 isipv6 ? 1075 ip6_sprintf(ip6buf, 1076 &inp->inp_inc.inc6_faddr) : 1077 #endif 1078 inet_ntoa(inp->inp_inc.inc_faddr), 1079 inp->inp_inc.inc_fport, 1080 tp->rcv_byps / tp->rcv_pps); 1081 KASSERT(headlocked, ("tcp_input: " 1082 "after_listen: tcp_drop: head " 1083 "not locked")); 1084 tp = tcp_drop(tp, ECONNRESET); 1085 tcpstat.tcps_minmssdrops++; 1086 goto drop; 1087 } 1088 } 1089 } else { 1090 tp->rcv_second = ticks + hz; 1091 tp->rcv_pps = 1; 1092 tp->rcv_byps = tlen + off; 1093 } 1094 } 1095 1096 /* 1097 * Segment received on connection. 1098 * Reset idle time and keep-alive timer. 1099 */ 1100 tp->t_rcvtime = ticks; 1101 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1102 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1103 1104 /* 1105 * Unscale the window into a 32-bit value. 1106 * This value is bogus for the TCPS_SYN_SENT state 1107 * and is overwritten later. 1108 */ 1109 tiwin = th->th_win << tp->snd_scale; 1110 1111 /* 1112 * Parse options on any incoming segment. 1113 */ 1114 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) ? TO_SYN : 0); 1115 1116 /* 1117 * If echoed timestamp is later than the current time, 1118 * fall back to non RFC1323 RTT calculation. Normalize 1119 * timestamp if syncookies were used when this connection 1120 * was established. 1121 */ 1122 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1123 to.to_tsecr -= tp->ts_offset; 1124 if (TSTMP_GT(to.to_tsecr, ticks)) 1125 to.to_tsecr = 0; 1126 } 1127 1128 /* 1129 * Process options only when we get SYN/ACK back. The SYN case 1130 * for incoming connections is handled in tcp_syncache. 1131 * XXX this is traditional behavior, may need to be cleaned up. 1132 */ 1133 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1134 if ((to.to_flags & TOF_SCALE) && 1135 (tp->t_flags & TF_REQ_SCALE)) { 1136 tp->t_flags |= TF_RCVD_SCALE; 1137 tp->snd_scale = to.to_requested_s_scale; 1138 tp->snd_wnd = th->th_win << tp->snd_scale; 1139 tiwin = tp->snd_wnd; 1140 } 1141 if (to.to_flags & TOF_TS) { 1142 tp->t_flags |= TF_RCVD_TSTMP; 1143 tp->ts_recent = to.to_tsval; 1144 tp->ts_recent_age = ticks; 1145 } 1146 if (to.to_flags & TOF_MSS) 1147 tcp_mss(tp, to.to_mss); 1148 if (tp->sack_enable) { 1149 if (!(to.to_flags & TOF_SACK)) 1150 tp->sack_enable = 0; 1151 else 1152 tp->t_flags |= TF_SACK_PERMIT; 1153 } 1154 1155 } 1156 1157 /* 1158 * Header prediction: check for the two common cases 1159 * of a uni-directional data xfer. If the packet has 1160 * no control flags, is in-sequence, the window didn't 1161 * change and we're not retransmitting, it's a 1162 * candidate. If the length is zero and the ack moved 1163 * forward, we're the sender side of the xfer. Just 1164 * free the data acked & wake any higher level process 1165 * that was blocked waiting for space. If the length 1166 * is non-zero and the ack didn't move, we're the 1167 * receiver side. If we're getting packets in-order 1168 * (the reassembly queue is empty), add the data to 1169 * the socket buffer and note that we need a delayed ack. 1170 * Make sure that the hidden state-flags are also off. 1171 * Since we check for TCPS_ESTABLISHED above, it can only 1172 * be TH_NEEDSYN. 1173 */ 1174 if (tp->t_state == TCPS_ESTABLISHED && 1175 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1176 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1177 ((to.to_flags & TOF_TS) == 0 || 1178 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1179 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1180 tp->snd_nxt == tp->snd_max) { 1181 1182 /* 1183 * If last ACK falls within this segment's sequence numbers, 1184 * record the timestamp. 1185 * NOTE that the test is modified according to the latest 1186 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1187 */ 1188 if ((to.to_flags & TOF_TS) != 0 && 1189 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1190 tp->ts_recent_age = ticks; 1191 tp->ts_recent = to.to_tsval; 1192 } 1193 1194 if (tlen == 0) { 1195 if (SEQ_GT(th->th_ack, tp->snd_una) && 1196 SEQ_LEQ(th->th_ack, tp->snd_max) && 1197 tp->snd_cwnd >= tp->snd_wnd && 1198 ((!tcp_do_newreno && !tp->sack_enable && 1199 tp->t_dupacks < tcprexmtthresh) || 1200 ((tcp_do_newreno || tp->sack_enable) && 1201 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 && 1202 TAILQ_EMPTY(&tp->snd_holes)))) { 1203 KASSERT(headlocked, ("headlocked")); 1204 INP_INFO_WUNLOCK(&tcbinfo); 1205 headlocked = 0; 1206 /* 1207 * this is a pure ack for outstanding data. 1208 */ 1209 ++tcpstat.tcps_predack; 1210 /* 1211 * "bad retransmit" recovery 1212 */ 1213 if (tp->t_rxtshift == 1 && 1214 ticks < tp->t_badrxtwin) { 1215 ++tcpstat.tcps_sndrexmitbad; 1216 tp->snd_cwnd = tp->snd_cwnd_prev; 1217 tp->snd_ssthresh = 1218 tp->snd_ssthresh_prev; 1219 tp->snd_recover = tp->snd_recover_prev; 1220 if (tp->t_flags & TF_WASFRECOVERY) 1221 ENTER_FASTRECOVERY(tp); 1222 tp->snd_nxt = tp->snd_max; 1223 tp->t_badrxtwin = 0; 1224 } 1225 1226 /* 1227 * Recalculate the transmit timer / rtt. 1228 * 1229 * Some boxes send broken timestamp replies 1230 * during the SYN+ACK phase, ignore 1231 * timestamps of 0 or we could calculate a 1232 * huge RTT and blow up the retransmit timer. 1233 */ 1234 if ((to.to_flags & TOF_TS) != 0 && 1235 to.to_tsecr) { 1236 if (!tp->t_rttlow || 1237 tp->t_rttlow > ticks - to.to_tsecr) 1238 tp->t_rttlow = ticks - to.to_tsecr; 1239 tcp_xmit_timer(tp, 1240 ticks - to.to_tsecr + 1); 1241 } else if (tp->t_rtttime && 1242 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1243 if (!tp->t_rttlow || 1244 tp->t_rttlow > ticks - tp->t_rtttime) 1245 tp->t_rttlow = ticks - tp->t_rtttime; 1246 tcp_xmit_timer(tp, 1247 ticks - tp->t_rtttime); 1248 } 1249 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1250 acked = th->th_ack - tp->snd_una; 1251 tcpstat.tcps_rcvackpack++; 1252 tcpstat.tcps_rcvackbyte += acked; 1253 sbdrop(&so->so_snd, acked); 1254 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1255 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1256 tp->snd_recover = th->th_ack - 1; 1257 tp->snd_una = th->th_ack; 1258 /* 1259 * pull snd_wl2 up to prevent seq wrap relative 1260 * to th_ack. 1261 */ 1262 tp->snd_wl2 = th->th_ack; 1263 tp->t_dupacks = 0; 1264 m_freem(m); 1265 ND6_HINT(tp); /* some progress has been done */ 1266 1267 /* 1268 * If all outstanding data are acked, stop 1269 * retransmit timer, otherwise restart timer 1270 * using current (possibly backed-off) value. 1271 * If process is waiting for space, 1272 * wakeup/selwakeup/signal. If data 1273 * are ready to send, let tcp_output 1274 * decide between more output or persist. 1275 1276 #ifdef TCPDEBUG 1277 if (so->so_options & SO_DEBUG) 1278 tcp_trace(TA_INPUT, ostate, tp, 1279 (void *)tcp_saveipgen, 1280 &tcp_savetcp, 0); 1281 #endif 1282 */ 1283 if (tp->snd_una == tp->snd_max) 1284 callout_stop(tp->tt_rexmt); 1285 else if (!callout_active(tp->tt_persist)) 1286 callout_reset(tp->tt_rexmt, 1287 tp->t_rxtcur, 1288 tcp_timer_rexmt, tp); 1289 1290 sowwakeup(so); 1291 if (so->so_snd.sb_cc) 1292 (void) tcp_output(tp); 1293 goto check_delack; 1294 } 1295 } else if (th->th_ack == tp->snd_una && 1296 LIST_EMPTY(&tp->t_segq) && 1297 tlen <= sbspace(&so->so_rcv)) { 1298 KASSERT(headlocked, ("headlocked")); 1299 INP_INFO_WUNLOCK(&tcbinfo); 1300 headlocked = 0; 1301 /* 1302 * this is a pure, in-sequence data packet 1303 * with nothing on the reassembly queue and 1304 * we have enough buffer space to take it. 1305 */ 1306 /* Clean receiver SACK report if present */ 1307 if (tp->sack_enable && tp->rcv_numsacks) 1308 tcp_clean_sackreport(tp); 1309 ++tcpstat.tcps_preddat; 1310 tp->rcv_nxt += tlen; 1311 /* 1312 * Pull snd_wl1 up to prevent seq wrap relative to 1313 * th_seq. 1314 */ 1315 tp->snd_wl1 = th->th_seq; 1316 /* 1317 * Pull rcv_up up to prevent seq wrap relative to 1318 * rcv_nxt. 1319 */ 1320 tp->rcv_up = tp->rcv_nxt; 1321 tcpstat.tcps_rcvpack++; 1322 tcpstat.tcps_rcvbyte += tlen; 1323 ND6_HINT(tp); /* some progress has been done */ 1324 /* 1325 #ifdef TCPDEBUG 1326 if (so->so_options & SO_DEBUG) 1327 tcp_trace(TA_INPUT, ostate, tp, 1328 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1329 #endif 1330 * Add data to socket buffer. 1331 */ 1332 SOCKBUF_LOCK(&so->so_rcv); 1333 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1334 m_freem(m); 1335 } else { 1336 m_adj(m, drop_hdrlen); /* delayed header drop */ 1337 sbappendstream_locked(&so->so_rcv, m); 1338 } 1339 sorwakeup_locked(so); 1340 if (DELAY_ACK(tp)) { 1341 tp->t_flags |= TF_DELACK; 1342 } else { 1343 tp->t_flags |= TF_ACKNOW; 1344 tcp_output(tp); 1345 } 1346 goto check_delack; 1347 } 1348 } 1349 1350 /* 1351 * Calculate amount of space in receive window, 1352 * and then do TCP input processing. 1353 * Receive window is amount of space in rcv queue, 1354 * but not less than advertised window. 1355 */ 1356 { int win; 1357 1358 win = sbspace(&so->so_rcv); 1359 if (win < 0) 1360 win = 0; 1361 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1362 } 1363 1364 switch (tp->t_state) { 1365 1366 /* 1367 * If the state is SYN_RECEIVED: 1368 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1369 */ 1370 case TCPS_SYN_RECEIVED: 1371 if ((thflags & TH_ACK) && 1372 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1373 SEQ_GT(th->th_ack, tp->snd_max))) { 1374 rstreason = BANDLIM_RST_OPENPORT; 1375 goto dropwithreset; 1376 } 1377 break; 1378 1379 /* 1380 * If the state is SYN_SENT: 1381 * if seg contains an ACK, but not for our SYN, drop the input. 1382 * if seg contains a RST, then drop the connection. 1383 * if seg does not contain SYN, then drop it. 1384 * Otherwise this is an acceptable SYN segment 1385 * initialize tp->rcv_nxt and tp->irs 1386 * if seg contains ack then advance tp->snd_una 1387 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1388 * arrange for segment to be acked (eventually) 1389 * continue processing rest of data/controls, beginning with URG 1390 */ 1391 case TCPS_SYN_SENT: 1392 if ((thflags & TH_ACK) && 1393 (SEQ_LEQ(th->th_ack, tp->iss) || 1394 SEQ_GT(th->th_ack, tp->snd_max))) { 1395 rstreason = BANDLIM_UNLIMITED; 1396 goto dropwithreset; 1397 } 1398 if (thflags & TH_RST) { 1399 if (thflags & TH_ACK) { 1400 KASSERT(headlocked, ("tcp_input: after_listen" 1401 ": tcp_drop.2: head not locked")); 1402 tp = tcp_drop(tp, ECONNREFUSED); 1403 } 1404 goto drop; 1405 } 1406 if ((thflags & TH_SYN) == 0) 1407 goto drop; 1408 1409 /* Initial send window, already scaled. */ 1410 tp->snd_wnd = th->th_win; 1411 1412 tp->irs = th->th_seq; 1413 tcp_rcvseqinit(tp); 1414 if (thflags & TH_ACK) { 1415 tcpstat.tcps_connects++; 1416 soisconnected(so); 1417 #ifdef MAC 1418 SOCK_LOCK(so); 1419 mac_set_socket_peer_from_mbuf(m, so); 1420 SOCK_UNLOCK(so); 1421 #endif 1422 /* Do window scaling on this connection? */ 1423 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1424 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1425 tp->rcv_scale = tp->request_r_scale; 1426 } 1427 tp->rcv_adv += tp->rcv_wnd; 1428 tp->snd_una++; /* SYN is acked */ 1429 /* 1430 * If there's data, delay ACK; if there's also a FIN 1431 * ACKNOW will be turned on later. 1432 */ 1433 if (DELAY_ACK(tp) && tlen != 0) 1434 callout_reset(tp->tt_delack, tcp_delacktime, 1435 tcp_timer_delack, tp); 1436 else 1437 tp->t_flags |= TF_ACKNOW; 1438 /* 1439 * Received <SYN,ACK> in SYN_SENT[*] state. 1440 * Transitions: 1441 * SYN_SENT --> ESTABLISHED 1442 * SYN_SENT* --> FIN_WAIT_1 1443 */ 1444 tp->t_starttime = ticks; 1445 if (tp->t_flags & TF_NEEDFIN) { 1446 tp->t_state = TCPS_FIN_WAIT_1; 1447 tp->t_flags &= ~TF_NEEDFIN; 1448 thflags &= ~TH_SYN; 1449 } else { 1450 tp->t_state = TCPS_ESTABLISHED; 1451 callout_reset(tp->tt_keep, tcp_keepidle, 1452 tcp_timer_keep, tp); 1453 } 1454 } else { 1455 /* 1456 * Received initial SYN in SYN-SENT[*] state => 1457 * simultaneous open. If segment contains CC option 1458 * and there is a cached CC, apply TAO test. 1459 * If it succeeds, connection is * half-synchronized. 1460 * Otherwise, do 3-way handshake: 1461 * SYN-SENT -> SYN-RECEIVED 1462 * SYN-SENT* -> SYN-RECEIVED* 1463 * If there was no CC option, clear cached CC value. 1464 */ 1465 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1466 callout_stop(tp->tt_rexmt); 1467 tp->t_state = TCPS_SYN_RECEIVED; 1468 } 1469 1470 #if 0 /* T/TCP */ 1471 trimthenstep6: 1472 #endif 1473 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1474 "locked")); 1475 INP_LOCK_ASSERT(inp); 1476 1477 /* 1478 * Advance th->th_seq to correspond to first data byte. 1479 * If data, trim to stay within window, 1480 * dropping FIN if necessary. 1481 */ 1482 th->th_seq++; 1483 if (tlen > tp->rcv_wnd) { 1484 todrop = tlen - tp->rcv_wnd; 1485 m_adj(m, -todrop); 1486 tlen = tp->rcv_wnd; 1487 thflags &= ~TH_FIN; 1488 tcpstat.tcps_rcvpackafterwin++; 1489 tcpstat.tcps_rcvbyteafterwin += todrop; 1490 } 1491 tp->snd_wl1 = th->th_seq - 1; 1492 tp->rcv_up = th->th_seq; 1493 /* 1494 * Client side of transaction: already sent SYN and data. 1495 * If the remote host used T/TCP to validate the SYN, 1496 * our data will be ACK'd; if so, enter normal data segment 1497 * processing in the middle of step 5, ack processing. 1498 * Otherwise, goto step 6. 1499 */ 1500 if (thflags & TH_ACK) 1501 goto process_ACK; 1502 1503 goto step6; 1504 1505 /* 1506 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1507 * do normal processing. 1508 * 1509 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1510 */ 1511 case TCPS_LAST_ACK: 1512 case TCPS_CLOSING: 1513 case TCPS_TIME_WAIT: 1514 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1515 break; /* continue normal processing */ 1516 } 1517 1518 /* 1519 * States other than LISTEN or SYN_SENT. 1520 * First check the RST flag and sequence number since reset segments 1521 * are exempt from the timestamp and connection count tests. This 1522 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1523 * below which allowed reset segments in half the sequence space 1524 * to fall though and be processed (which gives forged reset 1525 * segments with a random sequence number a 50 percent chance of 1526 * killing a connection). 1527 * Then check timestamp, if present. 1528 * Then check the connection count, if present. 1529 * Then check that at least some bytes of segment are within 1530 * receive window. If segment begins before rcv_nxt, 1531 * drop leading data (and SYN); if nothing left, just ack. 1532 * 1533 * 1534 * If the RST bit is set, check the sequence number to see 1535 * if this is a valid reset segment. 1536 * RFC 793 page 37: 1537 * In all states except SYN-SENT, all reset (RST) segments 1538 * are validated by checking their SEQ-fields. A reset is 1539 * valid if its sequence number is in the window. 1540 * Note: this does not take into account delayed ACKs, so 1541 * we should test against last_ack_sent instead of rcv_nxt. 1542 * The sequence number in the reset segment is normally an 1543 * echo of our outgoing acknowlegement numbers, but some hosts 1544 * send a reset with the sequence number at the rightmost edge 1545 * of our receive window, and we have to handle this case. 1546 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1547 * that brute force RST attacks are possible. To combat this, 1548 * we use a much stricter check while in the ESTABLISHED state, 1549 * only accepting RSTs where the sequence number is equal to 1550 * last_ack_sent. In all other states (the states in which a 1551 * RST is more likely), the more permissive check is used. 1552 * If we have multiple segments in flight, the intial reset 1553 * segment sequence numbers will be to the left of last_ack_sent, 1554 * but they will eventually catch up. 1555 * In any case, it never made sense to trim reset segments to 1556 * fit the receive window since RFC 1122 says: 1557 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1558 * 1559 * A TCP SHOULD allow a received RST segment to include data. 1560 * 1561 * DISCUSSION 1562 * It has been suggested that a RST segment could contain 1563 * ASCII text that encoded and explained the cause of the 1564 * RST. No standard has yet been established for such 1565 * data. 1566 * 1567 * If the reset segment passes the sequence number test examine 1568 * the state: 1569 * SYN_RECEIVED STATE: 1570 * If passive open, return to LISTEN state. 1571 * If active open, inform user that connection was refused. 1572 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1573 * Inform user that connection was reset, and close tcb. 1574 * CLOSING, LAST_ACK STATES: 1575 * Close the tcb. 1576 * TIME_WAIT STATE: 1577 * Drop the segment - see Stevens, vol. 2, p. 964 and 1578 * RFC 1337. 1579 */ 1580 if (thflags & TH_RST) { 1581 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1582 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1583 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1584 switch (tp->t_state) { 1585 1586 case TCPS_SYN_RECEIVED: 1587 so->so_error = ECONNREFUSED; 1588 goto close; 1589 1590 case TCPS_ESTABLISHED: 1591 if (tp->last_ack_sent != th->th_seq && 1592 tcp_insecure_rst == 0) { 1593 tcpstat.tcps_badrst++; 1594 goto drop; 1595 } 1596 case TCPS_FIN_WAIT_1: 1597 case TCPS_FIN_WAIT_2: 1598 case TCPS_CLOSE_WAIT: 1599 so->so_error = ECONNRESET; 1600 close: 1601 tp->t_state = TCPS_CLOSED; 1602 tcpstat.tcps_drops++; 1603 KASSERT(headlocked, ("tcp_input: " 1604 "trimthenstep6: tcp_close: head not " 1605 "locked")); 1606 tp = tcp_close(tp); 1607 break; 1608 1609 case TCPS_CLOSING: 1610 case TCPS_LAST_ACK: 1611 KASSERT(headlocked, ("trimthenstep6: " 1612 "tcp_close.2: head not locked")); 1613 tp = tcp_close(tp); 1614 break; 1615 1616 case TCPS_TIME_WAIT: 1617 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1618 ("timewait")); 1619 break; 1620 } 1621 } 1622 goto drop; 1623 } 1624 1625 /* 1626 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1627 * and it's less than ts_recent, drop it. 1628 */ 1629 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1630 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1631 1632 /* Check to see if ts_recent is over 24 days old. */ 1633 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1634 /* 1635 * Invalidate ts_recent. If this segment updates 1636 * ts_recent, the age will be reset later and ts_recent 1637 * will get a valid value. If it does not, setting 1638 * ts_recent to zero will at least satisfy the 1639 * requirement that zero be placed in the timestamp 1640 * echo reply when ts_recent isn't valid. The 1641 * age isn't reset until we get a valid ts_recent 1642 * because we don't want out-of-order segments to be 1643 * dropped when ts_recent is old. 1644 */ 1645 tp->ts_recent = 0; 1646 } else { 1647 tcpstat.tcps_rcvduppack++; 1648 tcpstat.tcps_rcvdupbyte += tlen; 1649 tcpstat.tcps_pawsdrop++; 1650 if (tlen) 1651 goto dropafterack; 1652 goto drop; 1653 } 1654 } 1655 1656 /* 1657 * In the SYN-RECEIVED state, validate that the packet belongs to 1658 * this connection before trimming the data to fit the receive 1659 * window. Check the sequence number versus IRS since we know 1660 * the sequence numbers haven't wrapped. This is a partial fix 1661 * for the "LAND" DoS attack. 1662 */ 1663 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1664 rstreason = BANDLIM_RST_OPENPORT; 1665 goto dropwithreset; 1666 } 1667 1668 todrop = tp->rcv_nxt - th->th_seq; 1669 if (todrop > 0) { 1670 if (thflags & TH_SYN) { 1671 thflags &= ~TH_SYN; 1672 th->th_seq++; 1673 if (th->th_urp > 1) 1674 th->th_urp--; 1675 else 1676 thflags &= ~TH_URG; 1677 todrop--; 1678 } 1679 /* 1680 * Following if statement from Stevens, vol. 2, p. 960. 1681 */ 1682 if (todrop > tlen 1683 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1684 /* 1685 * Any valid FIN must be to the left of the window. 1686 * At this point the FIN must be a duplicate or out 1687 * of sequence; drop it. 1688 */ 1689 thflags &= ~TH_FIN; 1690 1691 /* 1692 * Send an ACK to resynchronize and drop any data. 1693 * But keep on processing for RST or ACK. 1694 */ 1695 tp->t_flags |= TF_ACKNOW; 1696 todrop = tlen; 1697 tcpstat.tcps_rcvduppack++; 1698 tcpstat.tcps_rcvdupbyte += todrop; 1699 } else { 1700 tcpstat.tcps_rcvpartduppack++; 1701 tcpstat.tcps_rcvpartdupbyte += todrop; 1702 } 1703 drop_hdrlen += todrop; /* drop from the top afterwards */ 1704 th->th_seq += todrop; 1705 tlen -= todrop; 1706 if (th->th_urp > todrop) 1707 th->th_urp -= todrop; 1708 else { 1709 thflags &= ~TH_URG; 1710 th->th_urp = 0; 1711 } 1712 } 1713 1714 /* 1715 * If new data are received on a connection after the 1716 * user processes are gone, then RST the other end. 1717 */ 1718 if ((so->so_state & SS_NOFDREF) && 1719 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1720 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1721 "locked")); 1722 tp = tcp_close(tp); 1723 tcpstat.tcps_rcvafterclose++; 1724 rstreason = BANDLIM_UNLIMITED; 1725 goto dropwithreset; 1726 } 1727 1728 /* 1729 * If segment ends after window, drop trailing data 1730 * (and PUSH and FIN); if nothing left, just ACK. 1731 */ 1732 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1733 if (todrop > 0) { 1734 tcpstat.tcps_rcvpackafterwin++; 1735 if (todrop >= tlen) { 1736 tcpstat.tcps_rcvbyteafterwin += tlen; 1737 /* 1738 * If a new connection request is received 1739 * while in TIME_WAIT, drop the old connection 1740 * and start over if the sequence numbers 1741 * are above the previous ones. 1742 */ 1743 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1744 if (thflags & TH_SYN && 1745 tp->t_state == TCPS_TIME_WAIT && 1746 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1747 KASSERT(headlocked, ("trimthenstep6: " 1748 "tcp_close.4: head not locked")); 1749 tp = tcp_close(tp); 1750 goto findpcb; 1751 } 1752 /* 1753 * If window is closed can only take segments at 1754 * window edge, and have to drop data and PUSH from 1755 * incoming segments. Continue processing, but 1756 * remember to ack. Otherwise, drop segment 1757 * and ack. 1758 */ 1759 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1760 tp->t_flags |= TF_ACKNOW; 1761 tcpstat.tcps_rcvwinprobe++; 1762 } else 1763 goto dropafterack; 1764 } else 1765 tcpstat.tcps_rcvbyteafterwin += todrop; 1766 m_adj(m, -todrop); 1767 tlen -= todrop; 1768 thflags &= ~(TH_PUSH|TH_FIN); 1769 } 1770 1771 /* 1772 * If last ACK falls within this segment's sequence numbers, 1773 * record its timestamp. 1774 * NOTE: 1775 * 1) That the test incorporates suggestions from the latest 1776 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1777 * 2) That updating only on newer timestamps interferes with 1778 * our earlier PAWS tests, so this check should be solely 1779 * predicated on the sequence space of this segment. 1780 * 3) That we modify the segment boundary check to be 1781 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1782 * instead of RFC1323's 1783 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1784 * This modified check allows us to overcome RFC1323's 1785 * limitations as described in Stevens TCP/IP Illustrated 1786 * Vol. 2 p.869. In such cases, we can still calculate the 1787 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1788 */ 1789 if ((to.to_flags & TOF_TS) != 0 && 1790 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1791 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1792 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1793 tp->ts_recent_age = ticks; 1794 tp->ts_recent = to.to_tsval; 1795 } 1796 1797 /* 1798 * If a SYN is in the window, then this is an 1799 * error and we send an RST and drop the connection. 1800 */ 1801 if (thflags & TH_SYN) { 1802 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1803 "head not locked")); 1804 tp = tcp_drop(tp, ECONNRESET); 1805 rstreason = BANDLIM_UNLIMITED; 1806 goto drop; 1807 } 1808 1809 /* 1810 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1811 * flag is on (half-synchronized state), then queue data for 1812 * later processing; else drop segment and return. 1813 */ 1814 if ((thflags & TH_ACK) == 0) { 1815 if (tp->t_state == TCPS_SYN_RECEIVED || 1816 (tp->t_flags & TF_NEEDSYN)) 1817 goto step6; 1818 else if (tp->t_flags & TF_ACKNOW) 1819 goto dropafterack; 1820 else 1821 goto drop; 1822 } 1823 1824 /* 1825 * Ack processing. 1826 */ 1827 switch (tp->t_state) { 1828 1829 /* 1830 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1831 * ESTABLISHED state and continue processing. 1832 * The ACK was checked above. 1833 */ 1834 case TCPS_SYN_RECEIVED: 1835 1836 tcpstat.tcps_connects++; 1837 soisconnected(so); 1838 /* Do window scaling? */ 1839 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1840 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1841 tp->rcv_scale = tp->request_r_scale; 1842 tp->snd_wnd = tiwin; 1843 } 1844 /* 1845 * Make transitions: 1846 * SYN-RECEIVED -> ESTABLISHED 1847 * SYN-RECEIVED* -> FIN-WAIT-1 1848 */ 1849 tp->t_starttime = ticks; 1850 if (tp->t_flags & TF_NEEDFIN) { 1851 tp->t_state = TCPS_FIN_WAIT_1; 1852 tp->t_flags &= ~TF_NEEDFIN; 1853 } else { 1854 tp->t_state = TCPS_ESTABLISHED; 1855 callout_reset(tp->tt_keep, tcp_keepidle, 1856 tcp_timer_keep, tp); 1857 } 1858 /* 1859 * If segment contains data or ACK, will call tcp_reass() 1860 * later; if not, do so now to pass queued data to user. 1861 */ 1862 if (tlen == 0 && (thflags & TH_FIN) == 0) 1863 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1864 (struct mbuf *)0); 1865 tp->snd_wl1 = th->th_seq - 1; 1866 /* FALLTHROUGH */ 1867 1868 /* 1869 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1870 * ACKs. If the ack is in the range 1871 * tp->snd_una < th->th_ack <= tp->snd_max 1872 * then advance tp->snd_una to th->th_ack and drop 1873 * data from the retransmission queue. If this ACK reflects 1874 * more up to date window information we update our window information. 1875 */ 1876 case TCPS_ESTABLISHED: 1877 case TCPS_FIN_WAIT_1: 1878 case TCPS_FIN_WAIT_2: 1879 case TCPS_CLOSE_WAIT: 1880 case TCPS_CLOSING: 1881 case TCPS_LAST_ACK: 1882 case TCPS_TIME_WAIT: 1883 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1884 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1885 tcpstat.tcps_rcvacktoomuch++; 1886 goto dropafterack; 1887 } 1888 if (tp->sack_enable && 1889 (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) 1890 tcp_sack_doack(tp, &to, th->th_ack); 1891 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1892 if (tlen == 0 && tiwin == tp->snd_wnd) { 1893 tcpstat.tcps_rcvdupack++; 1894 /* 1895 * If we have outstanding data (other than 1896 * a window probe), this is a completely 1897 * duplicate ack (ie, window info didn't 1898 * change), the ack is the biggest we've 1899 * seen and we've seen exactly our rexmt 1900 * threshhold of them, assume a packet 1901 * has been dropped and retransmit it. 1902 * Kludge snd_nxt & the congestion 1903 * window so we send only this one 1904 * packet. 1905 * 1906 * We know we're losing at the current 1907 * window size so do congestion avoidance 1908 * (set ssthresh to half the current window 1909 * and pull our congestion window back to 1910 * the new ssthresh). 1911 * 1912 * Dup acks mean that packets have left the 1913 * network (they're now cached at the receiver) 1914 * so bump cwnd by the amount in the receiver 1915 * to keep a constant cwnd packets in the 1916 * network. 1917 */ 1918 if (!callout_active(tp->tt_rexmt) || 1919 th->th_ack != tp->snd_una) 1920 tp->t_dupacks = 0; 1921 else if (++tp->t_dupacks > tcprexmtthresh || 1922 ((tcp_do_newreno || tp->sack_enable) && 1923 IN_FASTRECOVERY(tp))) { 1924 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1925 int awnd; 1926 1927 /* 1928 * Compute the amount of data in flight first. 1929 * We can inject new data into the pipe iff 1930 * we have less than 1/2 the original window's 1931 * worth of data in flight. 1932 */ 1933 awnd = (tp->snd_nxt - tp->snd_fack) + 1934 tp->sackhint.sack_bytes_rexmit; 1935 if (awnd < tp->snd_ssthresh) { 1936 tp->snd_cwnd += tp->t_maxseg; 1937 if (tp->snd_cwnd > tp->snd_ssthresh) 1938 tp->snd_cwnd = tp->snd_ssthresh; 1939 } 1940 } else 1941 tp->snd_cwnd += tp->t_maxseg; 1942 (void) tcp_output(tp); 1943 goto drop; 1944 } else if (tp->t_dupacks == tcprexmtthresh) { 1945 tcp_seq onxt = tp->snd_nxt; 1946 u_int win; 1947 1948 /* 1949 * If we're doing sack, check to 1950 * see if we're already in sack 1951 * recovery. If we're not doing sack, 1952 * check to see if we're in newreno 1953 * recovery. 1954 */ 1955 if (tp->sack_enable) { 1956 if (IN_FASTRECOVERY(tp)) { 1957 tp->t_dupacks = 0; 1958 break; 1959 } 1960 } else if (tcp_do_newreno) { 1961 if (SEQ_LEQ(th->th_ack, 1962 tp->snd_recover)) { 1963 tp->t_dupacks = 0; 1964 break; 1965 } 1966 } 1967 win = min(tp->snd_wnd, tp->snd_cwnd) / 1968 2 / tp->t_maxseg; 1969 if (win < 2) 1970 win = 2; 1971 tp->snd_ssthresh = win * tp->t_maxseg; 1972 ENTER_FASTRECOVERY(tp); 1973 tp->snd_recover = tp->snd_max; 1974 callout_stop(tp->tt_rexmt); 1975 tp->t_rtttime = 0; 1976 if (tp->sack_enable) { 1977 tcpstat.tcps_sack_recovery_episode++; 1978 tp->sack_newdata = tp->snd_nxt; 1979 tp->snd_cwnd = tp->t_maxseg; 1980 (void) tcp_output(tp); 1981 goto drop; 1982 } 1983 tp->snd_nxt = th->th_ack; 1984 tp->snd_cwnd = tp->t_maxseg; 1985 (void) tcp_output(tp); 1986 KASSERT(tp->snd_limited <= 2, 1987 ("tp->snd_limited too big")); 1988 tp->snd_cwnd = tp->snd_ssthresh + 1989 tp->t_maxseg * 1990 (tp->t_dupacks - tp->snd_limited); 1991 if (SEQ_GT(onxt, tp->snd_nxt)) 1992 tp->snd_nxt = onxt; 1993 goto drop; 1994 } else if (tcp_do_rfc3042) { 1995 u_long oldcwnd = tp->snd_cwnd; 1996 tcp_seq oldsndmax = tp->snd_max; 1997 u_int sent; 1998 1999 KASSERT(tp->t_dupacks == 1 || 2000 tp->t_dupacks == 2, 2001 ("dupacks not 1 or 2")); 2002 if (tp->t_dupacks == 1) 2003 tp->snd_limited = 0; 2004 tp->snd_cwnd = 2005 (tp->snd_nxt - tp->snd_una) + 2006 (tp->t_dupacks - tp->snd_limited) * 2007 tp->t_maxseg; 2008 (void) tcp_output(tp); 2009 sent = tp->snd_max - oldsndmax; 2010 if (sent > tp->t_maxseg) { 2011 KASSERT((tp->t_dupacks == 2 && 2012 tp->snd_limited == 0) || 2013 (sent == tp->t_maxseg + 1 && 2014 tp->t_flags & TF_SENTFIN), 2015 ("sent too much")); 2016 tp->snd_limited = 2; 2017 } else if (sent > 0) 2018 ++tp->snd_limited; 2019 tp->snd_cwnd = oldcwnd; 2020 goto drop; 2021 } 2022 } else 2023 tp->t_dupacks = 0; 2024 break; 2025 } 2026 2027 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2028 2029 /* 2030 * If the congestion window was inflated to account 2031 * for the other side's cached packets, retract it. 2032 */ 2033 if (tcp_do_newreno || tp->sack_enable) { 2034 if (IN_FASTRECOVERY(tp)) { 2035 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2036 if (tp->sack_enable) 2037 tcp_sack_partialack(tp, th); 2038 else 2039 tcp_newreno_partial_ack(tp, th); 2040 } else { 2041 /* 2042 * Out of fast recovery. 2043 * Window inflation should have left us 2044 * with approximately snd_ssthresh 2045 * outstanding data. 2046 * But in case we would be inclined to 2047 * send a burst, better to do it via 2048 * the slow start mechanism. 2049 */ 2050 if (SEQ_GT(th->th_ack + 2051 tp->snd_ssthresh, 2052 tp->snd_max)) 2053 tp->snd_cwnd = tp->snd_max - 2054 th->th_ack + 2055 tp->t_maxseg; 2056 else 2057 tp->snd_cwnd = tp->snd_ssthresh; 2058 } 2059 } 2060 } else { 2061 if (tp->t_dupacks >= tcprexmtthresh && 2062 tp->snd_cwnd > tp->snd_ssthresh) 2063 tp->snd_cwnd = tp->snd_ssthresh; 2064 } 2065 tp->t_dupacks = 0; 2066 /* 2067 * If we reach this point, ACK is not a duplicate, 2068 * i.e., it ACKs something we sent. 2069 */ 2070 if (tp->t_flags & TF_NEEDSYN) { 2071 /* 2072 * T/TCP: Connection was half-synchronized, and our 2073 * SYN has been ACK'd (so connection is now fully 2074 * synchronized). Go to non-starred state, 2075 * increment snd_una for ACK of SYN, and check if 2076 * we can do window scaling. 2077 */ 2078 tp->t_flags &= ~TF_NEEDSYN; 2079 tp->snd_una++; 2080 /* Do window scaling? */ 2081 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2082 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2083 tp->rcv_scale = tp->request_r_scale; 2084 /* Send window already scaled. */ 2085 } 2086 } 2087 2088 process_ACK: 2089 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2090 "locked")); 2091 INP_LOCK_ASSERT(inp); 2092 2093 acked = th->th_ack - tp->snd_una; 2094 tcpstat.tcps_rcvackpack++; 2095 tcpstat.tcps_rcvackbyte += acked; 2096 2097 /* 2098 * If we just performed our first retransmit, and the ACK 2099 * arrives within our recovery window, then it was a mistake 2100 * to do the retransmit in the first place. Recover our 2101 * original cwnd and ssthresh, and proceed to transmit where 2102 * we left off. 2103 */ 2104 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2105 ++tcpstat.tcps_sndrexmitbad; 2106 tp->snd_cwnd = tp->snd_cwnd_prev; 2107 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2108 tp->snd_recover = tp->snd_recover_prev; 2109 if (tp->t_flags & TF_WASFRECOVERY) 2110 ENTER_FASTRECOVERY(tp); 2111 tp->snd_nxt = tp->snd_max; 2112 tp->t_badrxtwin = 0; /* XXX probably not required */ 2113 } 2114 2115 /* 2116 * If we have a timestamp reply, update smoothed 2117 * round trip time. If no timestamp is present but 2118 * transmit timer is running and timed sequence 2119 * number was acked, update smoothed round trip time. 2120 * Since we now have an rtt measurement, cancel the 2121 * timer backoff (cf., Phil Karn's retransmit alg.). 2122 * Recompute the initial retransmit timer. 2123 * 2124 * Some boxes send broken timestamp replies 2125 * during the SYN+ACK phase, ignore 2126 * timestamps of 0 or we could calculate a 2127 * huge RTT and blow up the retransmit timer. 2128 */ 2129 if ((to.to_flags & TOF_TS) != 0 && 2130 to.to_tsecr) { 2131 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2132 tp->t_rttlow = ticks - to.to_tsecr; 2133 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2134 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2135 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2136 tp->t_rttlow = ticks - tp->t_rtttime; 2137 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2138 } 2139 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2140 2141 /* 2142 * If all outstanding data is acked, stop retransmit 2143 * timer and remember to restart (more output or persist). 2144 * If there is more data to be acked, restart retransmit 2145 * timer, using current (possibly backed-off) value. 2146 */ 2147 if (th->th_ack == tp->snd_max) { 2148 callout_stop(tp->tt_rexmt); 2149 needoutput = 1; 2150 } else if (!callout_active(tp->tt_persist)) 2151 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2152 tcp_timer_rexmt, tp); 2153 2154 /* 2155 * If no data (only SYN) was ACK'd, 2156 * skip rest of ACK processing. 2157 */ 2158 if (acked == 0) 2159 goto step6; 2160 2161 /* 2162 * When new data is acked, open the congestion window. 2163 * If the window gives us less than ssthresh packets 2164 * in flight, open exponentially (maxseg per packet). 2165 * Otherwise open linearly: maxseg per window 2166 * (maxseg^2 / cwnd per packet). 2167 */ 2168 if ((!tcp_do_newreno && !tp->sack_enable) || 2169 !IN_FASTRECOVERY(tp)) { 2170 register u_int cw = tp->snd_cwnd; 2171 register u_int incr = tp->t_maxseg; 2172 if (cw > tp->snd_ssthresh) 2173 incr = incr * incr / cw; 2174 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2175 } 2176 SOCKBUF_LOCK(&so->so_snd); 2177 if (acked > so->so_snd.sb_cc) { 2178 tp->snd_wnd -= so->so_snd.sb_cc; 2179 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2180 ourfinisacked = 1; 2181 } else { 2182 sbdrop_locked(&so->so_snd, acked); 2183 tp->snd_wnd -= acked; 2184 ourfinisacked = 0; 2185 } 2186 sowwakeup_locked(so); 2187 /* detect una wraparound */ 2188 if ((tcp_do_newreno || tp->sack_enable) && 2189 !IN_FASTRECOVERY(tp) && 2190 SEQ_GT(tp->snd_una, tp->snd_recover) && 2191 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2192 tp->snd_recover = th->th_ack - 1; 2193 if ((tcp_do_newreno || tp->sack_enable) && 2194 IN_FASTRECOVERY(tp) && 2195 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2196 EXIT_FASTRECOVERY(tp); 2197 tp->snd_una = th->th_ack; 2198 if (tp->sack_enable) { 2199 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2200 tp->snd_recover = tp->snd_una; 2201 } 2202 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2203 tp->snd_nxt = tp->snd_una; 2204 2205 switch (tp->t_state) { 2206 2207 /* 2208 * In FIN_WAIT_1 STATE in addition to the processing 2209 * for the ESTABLISHED state if our FIN is now acknowledged 2210 * then enter FIN_WAIT_2. 2211 */ 2212 case TCPS_FIN_WAIT_1: 2213 if (ourfinisacked) { 2214 /* 2215 * If we can't receive any more 2216 * data, then closing user can proceed. 2217 * Starting the timer is contrary to the 2218 * specification, but if we don't get a FIN 2219 * we'll hang forever. 2220 */ 2221 /* XXXjl 2222 * we should release the tp also, and use a 2223 * compressed state. 2224 */ 2225 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2226 soisdisconnected(so); 2227 callout_reset(tp->tt_2msl, tcp_maxidle, 2228 tcp_timer_2msl, tp); 2229 } 2230 tp->t_state = TCPS_FIN_WAIT_2; 2231 } 2232 break; 2233 2234 /* 2235 * In CLOSING STATE in addition to the processing for 2236 * the ESTABLISHED state if the ACK acknowledges our FIN 2237 * then enter the TIME-WAIT state, otherwise ignore 2238 * the segment. 2239 */ 2240 case TCPS_CLOSING: 2241 if (ourfinisacked) { 2242 KASSERT(headlocked, ("tcp_input: process_ACK: " 2243 "head not locked")); 2244 tcp_twstart(tp); 2245 INP_INFO_WUNLOCK(&tcbinfo); 2246 m_freem(m); 2247 return; 2248 } 2249 break; 2250 2251 /* 2252 * In LAST_ACK, we may still be waiting for data to drain 2253 * and/or to be acked, as well as for the ack of our FIN. 2254 * If our FIN is now acknowledged, delete the TCB, 2255 * enter the closed state and return. 2256 */ 2257 case TCPS_LAST_ACK: 2258 if (ourfinisacked) { 2259 KASSERT(headlocked, ("tcp_input: process_ACK:" 2260 " tcp_close: head not locked")); 2261 tp = tcp_close(tp); 2262 goto drop; 2263 } 2264 break; 2265 2266 /* 2267 * In TIME_WAIT state the only thing that should arrive 2268 * is a retransmission of the remote FIN. Acknowledge 2269 * it and restart the finack timer. 2270 */ 2271 case TCPS_TIME_WAIT: 2272 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2273 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2274 tcp_timer_2msl, tp); 2275 goto dropafterack; 2276 } 2277 } 2278 2279 step6: 2280 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2281 INP_LOCK_ASSERT(inp); 2282 2283 /* 2284 * Update window information. 2285 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2286 */ 2287 if ((thflags & TH_ACK) && 2288 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2289 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2290 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2291 /* keep track of pure window updates */ 2292 if (tlen == 0 && 2293 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2294 tcpstat.tcps_rcvwinupd++; 2295 tp->snd_wnd = tiwin; 2296 tp->snd_wl1 = th->th_seq; 2297 tp->snd_wl2 = th->th_ack; 2298 if (tp->snd_wnd > tp->max_sndwnd) 2299 tp->max_sndwnd = tp->snd_wnd; 2300 needoutput = 1; 2301 } 2302 2303 /* 2304 * Process segments with URG. 2305 */ 2306 if ((thflags & TH_URG) && th->th_urp && 2307 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2308 /* 2309 * This is a kludge, but if we receive and accept 2310 * random urgent pointers, we'll crash in 2311 * soreceive. It's hard to imagine someone 2312 * actually wanting to send this much urgent data. 2313 */ 2314 SOCKBUF_LOCK(&so->so_rcv); 2315 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2316 th->th_urp = 0; /* XXX */ 2317 thflags &= ~TH_URG; /* XXX */ 2318 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2319 goto dodata; /* XXX */ 2320 } 2321 /* 2322 * If this segment advances the known urgent pointer, 2323 * then mark the data stream. This should not happen 2324 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2325 * a FIN has been received from the remote side. 2326 * In these states we ignore the URG. 2327 * 2328 * According to RFC961 (Assigned Protocols), 2329 * the urgent pointer points to the last octet 2330 * of urgent data. We continue, however, 2331 * to consider it to indicate the first octet 2332 * of data past the urgent section as the original 2333 * spec states (in one of two places). 2334 */ 2335 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2336 tp->rcv_up = th->th_seq + th->th_urp; 2337 so->so_oobmark = so->so_rcv.sb_cc + 2338 (tp->rcv_up - tp->rcv_nxt) - 1; 2339 if (so->so_oobmark == 0) 2340 so->so_rcv.sb_state |= SBS_RCVATMARK; 2341 sohasoutofband(so); 2342 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2343 } 2344 SOCKBUF_UNLOCK(&so->so_rcv); 2345 /* 2346 * Remove out of band data so doesn't get presented to user. 2347 * This can happen independent of advancing the URG pointer, 2348 * but if two URG's are pending at once, some out-of-band 2349 * data may creep in... ick. 2350 */ 2351 if (th->th_urp <= (u_long)tlen && 2352 !(so->so_options & SO_OOBINLINE)) { 2353 /* hdr drop is delayed */ 2354 tcp_pulloutofband(so, th, m, drop_hdrlen); 2355 } 2356 } else { 2357 /* 2358 * If no out of band data is expected, 2359 * pull receive urgent pointer along 2360 * with the receive window. 2361 */ 2362 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2363 tp->rcv_up = tp->rcv_nxt; 2364 } 2365 dodata: /* XXX */ 2366 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2367 INP_LOCK_ASSERT(inp); 2368 2369 /* 2370 * Process the segment text, merging it into the TCP sequencing queue, 2371 * and arranging for acknowledgment of receipt if necessary. 2372 * This process logically involves adjusting tp->rcv_wnd as data 2373 * is presented to the user (this happens in tcp_usrreq.c, 2374 * case PRU_RCVD). If a FIN has already been received on this 2375 * connection then we just ignore the text. 2376 */ 2377 if ((tlen || (thflags & TH_FIN)) && 2378 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2379 tcp_seq save_start = th->th_seq; 2380 tcp_seq save_end = th->th_seq + tlen; 2381 m_adj(m, drop_hdrlen); /* delayed header drop */ 2382 /* 2383 * Insert segment which includes th into TCP reassembly queue 2384 * with control block tp. Set thflags to whether reassembly now 2385 * includes a segment with FIN. This handles the common case 2386 * inline (segment is the next to be received on an established 2387 * connection, and the queue is empty), avoiding linkage into 2388 * and removal from the queue and repetition of various 2389 * conversions. 2390 * Set DELACK for segments received in order, but ack 2391 * immediately when segments are out of order (so 2392 * fast retransmit can work). 2393 */ 2394 if (th->th_seq == tp->rcv_nxt && 2395 LIST_EMPTY(&tp->t_segq) && 2396 TCPS_HAVEESTABLISHED(tp->t_state)) { 2397 if (DELAY_ACK(tp)) 2398 tp->t_flags |= TF_DELACK; 2399 else 2400 tp->t_flags |= TF_ACKNOW; 2401 tp->rcv_nxt += tlen; 2402 thflags = th->th_flags & TH_FIN; 2403 tcpstat.tcps_rcvpack++; 2404 tcpstat.tcps_rcvbyte += tlen; 2405 ND6_HINT(tp); 2406 SOCKBUF_LOCK(&so->so_rcv); 2407 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2408 m_freem(m); 2409 else 2410 sbappendstream_locked(&so->so_rcv, m); 2411 sorwakeup_locked(so); 2412 } else { 2413 thflags = tcp_reass(tp, th, &tlen, m); 2414 tp->t_flags |= TF_ACKNOW; 2415 } 2416 if (tlen > 0 && tp->sack_enable) 2417 tcp_update_sack_list(tp, save_start, save_end); 2418 /* 2419 * Note the amount of data that peer has sent into 2420 * our window, in order to estimate the sender's 2421 * buffer size. 2422 */ 2423 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2424 } else { 2425 m_freem(m); 2426 thflags &= ~TH_FIN; 2427 } 2428 2429 /* 2430 * If FIN is received ACK the FIN and let the user know 2431 * that the connection is closing. 2432 */ 2433 if (thflags & TH_FIN) { 2434 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2435 socantrcvmore(so); 2436 /* 2437 * If connection is half-synchronized 2438 * (ie NEEDSYN flag on) then delay ACK, 2439 * so it may be piggybacked when SYN is sent. 2440 * Otherwise, since we received a FIN then no 2441 * more input can be expected, send ACK now. 2442 */ 2443 if (tp->t_flags & TF_NEEDSYN) 2444 tp->t_flags |= TF_DELACK; 2445 else 2446 tp->t_flags |= TF_ACKNOW; 2447 tp->rcv_nxt++; 2448 } 2449 switch (tp->t_state) { 2450 2451 /* 2452 * In SYN_RECEIVED and ESTABLISHED STATES 2453 * enter the CLOSE_WAIT state. 2454 */ 2455 case TCPS_SYN_RECEIVED: 2456 tp->t_starttime = ticks; 2457 /*FALLTHROUGH*/ 2458 case TCPS_ESTABLISHED: 2459 tp->t_state = TCPS_CLOSE_WAIT; 2460 break; 2461 2462 /* 2463 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2464 * enter the CLOSING state. 2465 */ 2466 case TCPS_FIN_WAIT_1: 2467 tp->t_state = TCPS_CLOSING; 2468 break; 2469 2470 /* 2471 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2472 * starting the time-wait timer, turning off the other 2473 * standard timers. 2474 */ 2475 case TCPS_FIN_WAIT_2: 2476 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2477 "TCP_FIN_WAIT_2: head not locked")); 2478 tcp_twstart(tp); 2479 INP_INFO_WUNLOCK(&tcbinfo); 2480 return; 2481 2482 /* 2483 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2484 */ 2485 case TCPS_TIME_WAIT: 2486 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2487 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2488 tcp_timer_2msl, tp); 2489 break; 2490 } 2491 } 2492 INP_INFO_WUNLOCK(&tcbinfo); 2493 headlocked = 0; 2494 #ifdef TCPDEBUG 2495 if (so->so_options & SO_DEBUG) 2496 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2497 &tcp_savetcp, 0); 2498 #endif 2499 2500 /* 2501 * Return any desired output. 2502 */ 2503 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2504 (void) tcp_output(tp); 2505 2506 check_delack: 2507 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2508 INP_LOCK_ASSERT(inp); 2509 if (tp->t_flags & TF_DELACK) { 2510 tp->t_flags &= ~TF_DELACK; 2511 callout_reset(tp->tt_delack, tcp_delacktime, 2512 tcp_timer_delack, tp); 2513 } 2514 INP_UNLOCK(inp); 2515 return; 2516 2517 dropafterack: 2518 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2519 /* 2520 * Generate an ACK dropping incoming segment if it occupies 2521 * sequence space, where the ACK reflects our state. 2522 * 2523 * We can now skip the test for the RST flag since all 2524 * paths to this code happen after packets containing 2525 * RST have been dropped. 2526 * 2527 * In the SYN-RECEIVED state, don't send an ACK unless the 2528 * segment we received passes the SYN-RECEIVED ACK test. 2529 * If it fails send a RST. This breaks the loop in the 2530 * "LAND" DoS attack, and also prevents an ACK storm 2531 * between two listening ports that have been sent forged 2532 * SYN segments, each with the source address of the other. 2533 */ 2534 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2535 (SEQ_GT(tp->snd_una, th->th_ack) || 2536 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2537 rstreason = BANDLIM_RST_OPENPORT; 2538 goto dropwithreset; 2539 } 2540 #ifdef TCPDEBUG 2541 if (so->so_options & SO_DEBUG) 2542 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2543 &tcp_savetcp, 0); 2544 #endif 2545 KASSERT(headlocked, ("headlocked should be 1")); 2546 INP_INFO_WUNLOCK(&tcbinfo); 2547 tp->t_flags |= TF_ACKNOW; 2548 (void) tcp_output(tp); 2549 INP_UNLOCK(inp); 2550 m_freem(m); 2551 return; 2552 2553 dropwithreset: 2554 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2555 /* 2556 * Generate a RST, dropping incoming segment. 2557 * Make ACK acceptable to originator of segment. 2558 * Don't bother to respond if destination was broadcast/multicast. 2559 */ 2560 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2561 goto drop; 2562 if (isipv6) { 2563 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2564 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2565 goto drop; 2566 } else { 2567 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2568 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2569 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2570 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2571 goto drop; 2572 } 2573 /* IPv6 anycast check is done at tcp6_input() */ 2574 2575 /* 2576 * Perform bandwidth limiting. 2577 */ 2578 if (badport_bandlim(rstreason) < 0) 2579 goto drop; 2580 2581 #ifdef TCPDEBUG 2582 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2583 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2584 &tcp_savetcp, 0); 2585 #endif 2586 2587 if (thflags & TH_ACK) 2588 /* mtod() below is safe as long as hdr dropping is delayed */ 2589 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2590 TH_RST); 2591 else { 2592 if (thflags & TH_SYN) 2593 tlen++; 2594 /* mtod() below is safe as long as hdr dropping is delayed */ 2595 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2596 (tcp_seq)0, TH_RST|TH_ACK); 2597 } 2598 2599 if (tp != NULL) 2600 INP_UNLOCK(inp); 2601 if (headlocked) 2602 INP_INFO_WUNLOCK(&tcbinfo); 2603 return; 2604 2605 drop: 2606 /* 2607 * Drop space held by incoming segment and return. 2608 */ 2609 #ifdef TCPDEBUG 2610 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2611 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2612 &tcp_savetcp, 0); 2613 #endif 2614 if (tp != NULL) 2615 INP_UNLOCK(inp); 2616 if (headlocked) 2617 INP_INFO_WUNLOCK(&tcbinfo); 2618 m_freem(m); 2619 return; 2620 } 2621 2622 /* 2623 * Parse TCP options and place in tcpopt. 2624 */ 2625 static void 2626 tcp_dooptions(to, cp, cnt, flags) 2627 struct tcpopt *to; 2628 u_char *cp; 2629 int cnt; 2630 int flags; 2631 { 2632 int opt, optlen; 2633 2634 to->to_flags = 0; 2635 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2636 opt = cp[0]; 2637 if (opt == TCPOPT_EOL) 2638 break; 2639 if (opt == TCPOPT_NOP) 2640 optlen = 1; 2641 else { 2642 if (cnt < 2) 2643 break; 2644 optlen = cp[1]; 2645 if (optlen < 2 || optlen > cnt) 2646 break; 2647 } 2648 switch (opt) { 2649 case TCPOPT_MAXSEG: 2650 if (optlen != TCPOLEN_MAXSEG) 2651 continue; 2652 if (!(flags & TO_SYN)) 2653 continue; 2654 to->to_flags |= TOF_MSS; 2655 bcopy((char *)cp + 2, 2656 (char *)&to->to_mss, sizeof(to->to_mss)); 2657 to->to_mss = ntohs(to->to_mss); 2658 break; 2659 case TCPOPT_WINDOW: 2660 if (optlen != TCPOLEN_WINDOW) 2661 continue; 2662 if (!(flags & TO_SYN)) 2663 continue; 2664 to->to_flags |= TOF_SCALE; 2665 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2666 break; 2667 case TCPOPT_TIMESTAMP: 2668 if (optlen != TCPOLEN_TIMESTAMP) 2669 continue; 2670 to->to_flags |= TOF_TS; 2671 bcopy((char *)cp + 2, 2672 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2673 to->to_tsval = ntohl(to->to_tsval); 2674 bcopy((char *)cp + 6, 2675 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2676 to->to_tsecr = ntohl(to->to_tsecr); 2677 break; 2678 #ifdef TCP_SIGNATURE 2679 /* 2680 * XXX In order to reply to a host which has set the 2681 * TCP_SIGNATURE option in its initial SYN, we have to 2682 * record the fact that the option was observed here 2683 * for the syncache code to perform the correct response. 2684 */ 2685 case TCPOPT_SIGNATURE: 2686 if (optlen != TCPOLEN_SIGNATURE) 2687 continue; 2688 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2689 break; 2690 #endif 2691 case TCPOPT_SACK_PERMITTED: 2692 if (optlen != TCPOLEN_SACK_PERMITTED) 2693 continue; 2694 if (!(flags & TO_SYN)) 2695 continue; 2696 if (!tcp_do_sack) 2697 continue; 2698 to->to_flags |= TOF_SACK; 2699 break; 2700 case TCPOPT_SACK: 2701 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2702 continue; 2703 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2704 to->to_sacks = cp + 2; 2705 tcpstat.tcps_sack_rcv_blocks++; 2706 break; 2707 default: 2708 continue; 2709 } 2710 } 2711 } 2712 2713 /* 2714 * Pull out of band byte out of a segment so 2715 * it doesn't appear in the user's data queue. 2716 * It is still reflected in the segment length for 2717 * sequencing purposes. 2718 */ 2719 static void 2720 tcp_pulloutofband(so, th, m, off) 2721 struct socket *so; 2722 struct tcphdr *th; 2723 register struct mbuf *m; 2724 int off; /* delayed to be droped hdrlen */ 2725 { 2726 int cnt = off + th->th_urp - 1; 2727 2728 while (cnt >= 0) { 2729 if (m->m_len > cnt) { 2730 char *cp = mtod(m, caddr_t) + cnt; 2731 struct tcpcb *tp = sototcpcb(so); 2732 2733 tp->t_iobc = *cp; 2734 tp->t_oobflags |= TCPOOB_HAVEDATA; 2735 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2736 m->m_len--; 2737 if (m->m_flags & M_PKTHDR) 2738 m->m_pkthdr.len--; 2739 return; 2740 } 2741 cnt -= m->m_len; 2742 m = m->m_next; 2743 if (m == 0) 2744 break; 2745 } 2746 panic("tcp_pulloutofband"); 2747 } 2748 2749 /* 2750 * Collect new round-trip time estimate 2751 * and update averages and current timeout. 2752 */ 2753 static void 2754 tcp_xmit_timer(tp, rtt) 2755 register struct tcpcb *tp; 2756 int rtt; 2757 { 2758 register int delta; 2759 2760 INP_LOCK_ASSERT(tp->t_inpcb); 2761 2762 tcpstat.tcps_rttupdated++; 2763 tp->t_rttupdated++; 2764 if (tp->t_srtt != 0) { 2765 /* 2766 * srtt is stored as fixed point with 5 bits after the 2767 * binary point (i.e., scaled by 8). The following magic 2768 * is equivalent to the smoothing algorithm in rfc793 with 2769 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2770 * point). Adjust rtt to origin 0. 2771 */ 2772 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2773 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2774 2775 if ((tp->t_srtt += delta) <= 0) 2776 tp->t_srtt = 1; 2777 2778 /* 2779 * We accumulate a smoothed rtt variance (actually, a 2780 * smoothed mean difference), then set the retransmit 2781 * timer to smoothed rtt + 4 times the smoothed variance. 2782 * rttvar is stored as fixed point with 4 bits after the 2783 * binary point (scaled by 16). The following is 2784 * equivalent to rfc793 smoothing with an alpha of .75 2785 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2786 * rfc793's wired-in beta. 2787 */ 2788 if (delta < 0) 2789 delta = -delta; 2790 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2791 if ((tp->t_rttvar += delta) <= 0) 2792 tp->t_rttvar = 1; 2793 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2794 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2795 } else { 2796 /* 2797 * No rtt measurement yet - use the unsmoothed rtt. 2798 * Set the variance to half the rtt (so our first 2799 * retransmit happens at 3*rtt). 2800 */ 2801 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2802 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2803 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2804 } 2805 tp->t_rtttime = 0; 2806 tp->t_rxtshift = 0; 2807 2808 /* 2809 * the retransmit should happen at rtt + 4 * rttvar. 2810 * Because of the way we do the smoothing, srtt and rttvar 2811 * will each average +1/2 tick of bias. When we compute 2812 * the retransmit timer, we want 1/2 tick of rounding and 2813 * 1 extra tick because of +-1/2 tick uncertainty in the 2814 * firing of the timer. The bias will give us exactly the 2815 * 1.5 tick we need. But, because the bias is 2816 * statistical, we have to test that we don't drop below 2817 * the minimum feasible timer (which is 2 ticks). 2818 */ 2819 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2820 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2821 2822 /* 2823 * We received an ack for a packet that wasn't retransmitted; 2824 * it is probably safe to discard any error indications we've 2825 * received recently. This isn't quite right, but close enough 2826 * for now (a route might have failed after we sent a segment, 2827 * and the return path might not be symmetrical). 2828 */ 2829 tp->t_softerror = 0; 2830 } 2831 2832 /* 2833 * Determine a reasonable value for maxseg size. 2834 * If the route is known, check route for mtu. 2835 * If none, use an mss that can be handled on the outgoing 2836 * interface without forcing IP to fragment; if bigger than 2837 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2838 * to utilize large mbufs. If no route is found, route has no mtu, 2839 * or the destination isn't local, use a default, hopefully conservative 2840 * size (usually 512 or the default IP max size, but no more than the mtu 2841 * of the interface), as we can't discover anything about intervening 2842 * gateways or networks. We also initialize the congestion/slow start 2843 * window to be a single segment if the destination isn't local. 2844 * While looking at the routing entry, we also initialize other path-dependent 2845 * parameters from pre-set or cached values in the routing entry. 2846 * 2847 * Also take into account the space needed for options that we 2848 * send regularly. Make maxseg shorter by that amount to assure 2849 * that we can send maxseg amount of data even when the options 2850 * are present. Store the upper limit of the length of options plus 2851 * data in maxopd. 2852 * 2853 * 2854 * In case of T/TCP, we call this routine during implicit connection 2855 * setup as well (offer = -1), to initialize maxseg from the cached 2856 * MSS of our peer. 2857 * 2858 * NOTE that this routine is only called when we process an incoming 2859 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2860 */ 2861 void 2862 tcp_mss(tp, offer) 2863 struct tcpcb *tp; 2864 int offer; 2865 { 2866 int rtt, mss; 2867 u_long bufsize; 2868 u_long maxmtu; 2869 struct inpcb *inp = tp->t_inpcb; 2870 struct socket *so; 2871 struct hc_metrics_lite metrics; 2872 int origoffer = offer; 2873 int mtuflags = 0; 2874 #ifdef INET6 2875 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2876 size_t min_protoh = isipv6 ? 2877 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2878 sizeof (struct tcpiphdr); 2879 #else 2880 const size_t min_protoh = sizeof(struct tcpiphdr); 2881 #endif 2882 2883 /* initialize */ 2884 #ifdef INET6 2885 if (isipv6) { 2886 maxmtu = tcp_maxmtu6(&inp->inp_inc, &mtuflags); 2887 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2888 } else 2889 #endif 2890 { 2891 maxmtu = tcp_maxmtu(&inp->inp_inc, &mtuflags); 2892 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2893 } 2894 so = inp->inp_socket; 2895 2896 /* 2897 * no route to sender, stay with default mss and return 2898 */ 2899 if (maxmtu == 0) 2900 return; 2901 2902 /* what have we got? */ 2903 switch (offer) { 2904 case 0: 2905 /* 2906 * Offer == 0 means that there was no MSS on the SYN 2907 * segment, in this case we use tcp_mssdflt. 2908 */ 2909 offer = 2910 #ifdef INET6 2911 isipv6 ? tcp_v6mssdflt : 2912 #endif 2913 tcp_mssdflt; 2914 break; 2915 2916 case -1: 2917 /* 2918 * Offer == -1 means that we didn't receive SYN yet. 2919 */ 2920 /* FALLTHROUGH */ 2921 2922 default: 2923 /* 2924 * Prevent DoS attack with too small MSS. Round up 2925 * to at least minmss. 2926 */ 2927 offer = max(offer, tcp_minmss); 2928 /* 2929 * Sanity check: make sure that maxopd will be large 2930 * enough to allow some data on segments even if the 2931 * all the option space is used (40bytes). Otherwise 2932 * funny things may happen in tcp_output. 2933 */ 2934 offer = max(offer, 64); 2935 } 2936 2937 /* 2938 * rmx information is now retrieved from tcp_hostcache 2939 */ 2940 tcp_hc_get(&inp->inp_inc, &metrics); 2941 2942 /* 2943 * if there's a discovered mtu int tcp hostcache, use it 2944 * else, use the link mtu. 2945 */ 2946 if (metrics.rmx_mtu) 2947 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2948 else { 2949 #ifdef INET6 2950 if (isipv6) { 2951 mss = maxmtu - min_protoh; 2952 if (!path_mtu_discovery && 2953 !in6_localaddr(&inp->in6p_faddr)) 2954 mss = min(mss, tcp_v6mssdflt); 2955 } else 2956 #endif 2957 { 2958 mss = maxmtu - min_protoh; 2959 if (!path_mtu_discovery && 2960 !in_localaddr(inp->inp_faddr)) 2961 mss = min(mss, tcp_mssdflt); 2962 } 2963 } 2964 mss = min(mss, offer); 2965 2966 /* 2967 * maxopd stores the maximum length of data AND options 2968 * in a segment; maxseg is the amount of data in a normal 2969 * segment. We need to store this value (maxopd) apart 2970 * from maxseg, because now every segment carries options 2971 * and thus we normally have somewhat less data in segments. 2972 */ 2973 tp->t_maxopd = mss; 2974 2975 /* 2976 * origoffer==-1 indicates, that no segments were received yet. 2977 * In this case we just guess. 2978 */ 2979 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2980 (origoffer == -1 || 2981 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2982 mss -= TCPOLEN_TSTAMP_APPA; 2983 tp->t_maxseg = mss; 2984 2985 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2986 if (mss > MCLBYTES) 2987 mss &= ~(MCLBYTES-1); 2988 #else 2989 if (mss > MCLBYTES) 2990 mss = mss / MCLBYTES * MCLBYTES; 2991 #endif 2992 tp->t_maxseg = mss; 2993 2994 /* 2995 * If there's a pipesize, change the socket buffer to that size, 2996 * don't change if sb_hiwat is different than default (then it 2997 * has been changed on purpose with setsockopt). 2998 * Make the socket buffers an integral number of mss units; 2999 * if the mss is larger than the socket buffer, decrease the mss. 3000 */ 3001 SOCKBUF_LOCK(&so->so_snd); 3002 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3003 bufsize = metrics.rmx_sendpipe; 3004 else 3005 bufsize = so->so_snd.sb_hiwat; 3006 if (bufsize < mss) 3007 mss = bufsize; 3008 else { 3009 bufsize = roundup(bufsize, mss); 3010 if (bufsize > sb_max) 3011 bufsize = sb_max; 3012 if (bufsize > so->so_snd.sb_hiwat) 3013 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3014 } 3015 SOCKBUF_UNLOCK(&so->so_snd); 3016 tp->t_maxseg = mss; 3017 3018 SOCKBUF_LOCK(&so->so_rcv); 3019 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3020 bufsize = metrics.rmx_recvpipe; 3021 else 3022 bufsize = so->so_rcv.sb_hiwat; 3023 if (bufsize > mss) { 3024 bufsize = roundup(bufsize, mss); 3025 if (bufsize > sb_max) 3026 bufsize = sb_max; 3027 if (bufsize > so->so_rcv.sb_hiwat) 3028 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3029 } 3030 SOCKBUF_UNLOCK(&so->so_rcv); 3031 /* 3032 * While we're here, check the others too 3033 */ 3034 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3035 tp->t_srtt = rtt; 3036 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3037 tcpstat.tcps_usedrtt++; 3038 if (metrics.rmx_rttvar) { 3039 tp->t_rttvar = metrics.rmx_rttvar; 3040 tcpstat.tcps_usedrttvar++; 3041 } else { 3042 /* default variation is +- 1 rtt */ 3043 tp->t_rttvar = 3044 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3045 } 3046 TCPT_RANGESET(tp->t_rxtcur, 3047 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3048 tp->t_rttmin, TCPTV_REXMTMAX); 3049 } 3050 if (metrics.rmx_ssthresh) { 3051 /* 3052 * There's some sort of gateway or interface 3053 * buffer limit on the path. Use this to set 3054 * the slow start threshhold, but set the 3055 * threshold to no less than 2*mss. 3056 */ 3057 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3058 tcpstat.tcps_usedssthresh++; 3059 } 3060 if (metrics.rmx_bandwidth) 3061 tp->snd_bandwidth = metrics.rmx_bandwidth; 3062 3063 /* 3064 * Set the slow-start flight size depending on whether this 3065 * is a local network or not. 3066 * 3067 * Extend this so we cache the cwnd too and retrieve it here. 3068 * Make cwnd even bigger than RFC3390 suggests but only if we 3069 * have previous experience with the remote host. Be careful 3070 * not make cwnd bigger than remote receive window or our own 3071 * send socket buffer. Maybe put some additional upper bound 3072 * on the retrieved cwnd. Should do incremental updates to 3073 * hostcache when cwnd collapses so next connection doesn't 3074 * overloads the path again. 3075 * 3076 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3077 * We currently check only in syncache_socket for that. 3078 */ 3079 #define TCP_METRICS_CWND 3080 #ifdef TCP_METRICS_CWND 3081 if (metrics.rmx_cwnd) 3082 tp->snd_cwnd = max(mss, 3083 min(metrics.rmx_cwnd / 2, 3084 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3085 else 3086 #endif 3087 if (tcp_do_rfc3390) 3088 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3089 #ifdef INET6 3090 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3091 (!isipv6 && in_localaddr(inp->inp_faddr))) 3092 #else 3093 else if (in_localaddr(inp->inp_faddr)) 3094 #endif 3095 tp->snd_cwnd = mss * ss_fltsz_local; 3096 else 3097 tp->snd_cwnd = mss * ss_fltsz; 3098 3099 /* Check the interface for TSO capabilities. */ 3100 if (mtuflags & CSUM_TSO) 3101 tp->t_flags |= TF_TSO; 3102 } 3103 3104 /* 3105 * Determine the MSS option to send on an outgoing SYN. 3106 */ 3107 int 3108 tcp_mssopt(inc) 3109 struct in_conninfo *inc; 3110 { 3111 int mss = 0; 3112 u_long maxmtu = 0; 3113 u_long thcmtu = 0; 3114 size_t min_protoh; 3115 #ifdef INET6 3116 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3117 #endif 3118 3119 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3120 3121 #ifdef INET6 3122 if (isipv6) { 3123 mss = tcp_v6mssdflt; 3124 maxmtu = tcp_maxmtu6(inc, NULL); 3125 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3126 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3127 } else 3128 #endif 3129 { 3130 mss = tcp_mssdflt; 3131 maxmtu = tcp_maxmtu(inc, NULL); 3132 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3133 min_protoh = sizeof(struct tcpiphdr); 3134 } 3135 if (maxmtu && thcmtu) 3136 mss = min(maxmtu, thcmtu) - min_protoh; 3137 else if (maxmtu || thcmtu) 3138 mss = max(maxmtu, thcmtu) - min_protoh; 3139 3140 return (mss); 3141 } 3142 3143 3144 /* 3145 * On a partial ack arrives, force the retransmission of the 3146 * next unacknowledged segment. Do not clear tp->t_dupacks. 3147 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3148 * be started again. 3149 */ 3150 static void 3151 tcp_newreno_partial_ack(tp, th) 3152 struct tcpcb *tp; 3153 struct tcphdr *th; 3154 { 3155 tcp_seq onxt = tp->snd_nxt; 3156 u_long ocwnd = tp->snd_cwnd; 3157 3158 callout_stop(tp->tt_rexmt); 3159 tp->t_rtttime = 0; 3160 tp->snd_nxt = th->th_ack; 3161 /* 3162 * Set snd_cwnd to one segment beyond acknowledged offset. 3163 * (tp->snd_una has not yet been updated when this function is called.) 3164 */ 3165 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3166 tp->t_flags |= TF_ACKNOW; 3167 (void) tcp_output(tp); 3168 tp->snd_cwnd = ocwnd; 3169 if (SEQ_GT(onxt, tp->snd_nxt)) 3170 tp->snd_nxt = onxt; 3171 /* 3172 * Partial window deflation. Relies on fact that tp->snd_una 3173 * not updated yet. 3174 */ 3175 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3176 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3177 else 3178 tp->snd_cwnd = 0; 3179 tp->snd_cwnd += tp->t_maxseg; 3180 } 3181 3182 /* 3183 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3184 * looking for a pcb in the listen state. Returns 0 otherwise. 3185 */ 3186 static int 3187 tcp_timewait(inp, to, th, m, tlen) 3188 struct inpcb *inp; 3189 struct tcpopt *to; 3190 struct tcphdr *th; 3191 struct mbuf *m; 3192 int tlen; 3193 { 3194 struct tcptw *tw; 3195 int thflags; 3196 tcp_seq seq; 3197 #ifdef INET6 3198 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3199 #else 3200 const int isipv6 = 0; 3201 #endif 3202 3203 /* tcbinfo lock required for tcp_twclose(), tcp_timer_2msl_reset(). */ 3204 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3205 INP_LOCK_ASSERT(inp); 3206 3207 /* 3208 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 3209 * still present. This is undesirable, but temporarily necessary 3210 * until we work out how to handle inpcb's who's timewait state has 3211 * been removed. 3212 */ 3213 tw = intotw(inp); 3214 if (tw == NULL) 3215 goto drop; 3216 3217 thflags = th->th_flags; 3218 3219 /* 3220 * NOTE: for FIN_WAIT_2 (to be added later), 3221 * must validate sequence number before accepting RST 3222 */ 3223 3224 /* 3225 * If the segment contains RST: 3226 * Drop the segment - see Stevens, vol. 2, p. 964 and 3227 * RFC 1337. 3228 */ 3229 if (thflags & TH_RST) 3230 goto drop; 3231 3232 #if 0 3233 /* PAWS not needed at the moment */ 3234 /* 3235 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3236 * and it's less than ts_recent, drop it. 3237 */ 3238 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3239 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3240 if ((thflags & TH_ACK) == 0) 3241 goto drop; 3242 goto ack; 3243 } 3244 /* 3245 * ts_recent is never updated because we never accept new segments. 3246 */ 3247 #endif 3248 3249 /* 3250 * If a new connection request is received 3251 * while in TIME_WAIT, drop the old connection 3252 * and start over if the sequence numbers 3253 * are above the previous ones. 3254 */ 3255 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3256 tcp_twclose(tw, 0); 3257 return (1); 3258 } 3259 3260 /* 3261 * Drop the the segment if it does not contain an ACK. 3262 */ 3263 if ((thflags & TH_ACK) == 0) 3264 goto drop; 3265 3266 /* 3267 * Reset the 2MSL timer if this is a duplicate FIN. 3268 */ 3269 if (thflags & TH_FIN) { 3270 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3271 if (seq + 1 == tw->rcv_nxt) 3272 tcp_timer_2msl_reset(tw, 1); 3273 } 3274 3275 /* 3276 * Acknowledge the segment if it has data or is not a duplicate ACK. 3277 */ 3278 if (thflags != TH_ACK || tlen != 0 || 3279 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3280 tcp_twrespond(tw, TH_ACK); 3281 goto drop; 3282 3283 /* 3284 * Generate a RST, dropping incoming segment. 3285 * Make ACK acceptable to originator of segment. 3286 * Don't bother to respond if destination was broadcast/multicast. 3287 */ 3288 if (m->m_flags & (M_BCAST|M_MCAST)) 3289 goto drop; 3290 if (isipv6) { 3291 struct ip6_hdr *ip6; 3292 3293 /* IPv6 anycast check is done at tcp6_input() */ 3294 ip6 = mtod(m, struct ip6_hdr *); 3295 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3296 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3297 goto drop; 3298 } else { 3299 struct ip *ip; 3300 3301 ip = mtod(m, struct ip *); 3302 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3303 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3304 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3305 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3306 goto drop; 3307 } 3308 if (thflags & TH_ACK) { 3309 tcp_respond(NULL, 3310 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3311 } else { 3312 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3313 tcp_respond(NULL, 3314 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3315 } 3316 INP_UNLOCK(inp); 3317 return (0); 3318 3319 drop: 3320 INP_UNLOCK(inp); 3321 m_freem(m); 3322 return (0); 3323 } 3324