tcp_input.c revision 167721
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: head/sys/netinet/tcp_input.c 167721 2007-03-19 19:00:51Z andre $ 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 102static const int tcprexmtthresh = 3; 103 104struct tcpstat tcpstat; 105SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 106 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 107 108static int tcp_log_in_vain = 0; 109SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 110 &tcp_log_in_vain, 0, "Log all incoming TCP connections"); 111 112static int blackhole = 0; 113SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 114 &blackhole, 0, "Do not send RST when dropping refused connections"); 115 116int tcp_delack_enabled = 1; 117SYSCTL_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 122static int drop_synfin = 0; 123SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 124 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 125#endif 126 127static int tcp_do_rfc3042 = 1; 128SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 129 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 130 131static int tcp_do_rfc3390 = 1; 132SYSCTL_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 136static int tcp_insecure_rst = 0; 137SYSCTL_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 141SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 142 "TCP Segment Reassembly Queue"); 143 144static int tcp_reass_maxseg = 0; 145SYSCTL_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 149int tcp_reass_qsize = 0; 150SYSCTL_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 154static int tcp_reass_maxqlen = 48; 155SYSCTL_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 159static int tcp_reass_overflows = 0; 160SYSCTL_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 164int tcp_do_autorcvbuf = 1; 165SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 166 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 167 168int tcp_autorcvbuf_inc = 16*1024; 169SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 170 &tcp_autorcvbuf_inc, 0, 171 "Incrementor step size of automatic receive buffer"); 172 173int tcp_autorcvbuf_max = 256*1024; 174SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 175 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 176 177struct inpcbhead tcb; 178#define tcb6 tcb /* for KAME src sync over BSD*'s */ 179struct inpcbinfo tcbinfo; 180struct mtx *tcbinfo_mtx; 181 182static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 183 184static void tcp_pulloutofband(struct socket *, 185 struct tcphdr *, struct mbuf *, int); 186static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 187 struct mbuf *); 188static void tcp_xmit_timer(struct tcpcb *, int); 189static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 190static int tcp_timewait(struct inpcb *, struct tcpopt *, 191 struct tcphdr *, struct mbuf *, int); 192 193/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 194#ifdef INET6 195#define ND6_HINT(tp) \ 196do { \ 197 if ((tp) && (tp)->t_inpcb && \ 198 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 199 nd6_nud_hint(NULL, NULL, 0); \ 200} while (0) 201#else 202#define ND6_HINT(tp) 203#endif 204 205/* 206 * Indicate whether this ack should be delayed. We can delay the ack if 207 * - there is no delayed ack timer in progress and 208 * - our last ack wasn't a 0-sized window. We never want to delay 209 * the ack that opens up a 0-sized window and 210 * - delayed acks are enabled or 211 * - this is a half-synchronized T/TCP connection. 212 */ 213#define DELAY_ACK(tp) \ 214 ((!callout_active(tp->tt_delack) && \ 215 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 216 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 217 218/* Initialize TCP reassembly queue */ 219static void 220tcp_reass_zone_change(void *tag) 221{ 222 223 tcp_reass_maxseg = nmbclusters / 16; 224 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 225} 226 227uma_zone_t tcp_reass_zone; 228void 229tcp_reass_init() 230{ 231 tcp_reass_maxseg = nmbclusters / 16; 232 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 233 &tcp_reass_maxseg); 234 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 235 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 236 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 237 EVENTHANDLER_REGISTER(nmbclusters_change, 238 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY); 239} 240 241static int 242tcp_reass(tp, th, tlenp, m) 243 register struct tcpcb *tp; 244 register struct tcphdr *th; 245 int *tlenp; 246 struct mbuf *m; 247{ 248 struct tseg_qent *q; 249 struct tseg_qent *p = NULL; 250 struct tseg_qent *nq; 251 struct tseg_qent *te = NULL; 252 struct socket *so = tp->t_inpcb->inp_socket; 253 int flags; 254 255 INP_LOCK_ASSERT(tp->t_inpcb); 256 257 /* 258 * XXX: tcp_reass() is rather inefficient with its data structures 259 * and should be rewritten (see NetBSD for optimizations). While 260 * doing that it should move to its own file tcp_reass.c. 261 */ 262 263 /* 264 * Call with th==NULL after become established to 265 * force pre-ESTABLISHED data up to user socket. 266 */ 267 if (th == NULL) 268 goto present; 269 270 /* 271 * Limit the number of segments in the reassembly queue to prevent 272 * holding on to too many segments (and thus running out of mbufs). 273 * Make sure to let the missing segment through which caused this 274 * queue. Always keep one global queue entry spare to be able to 275 * process the missing segment. 276 */ 277 if (th->th_seq != tp->rcv_nxt && 278 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 279 tp->t_segqlen >= tcp_reass_maxqlen)) { 280 tcp_reass_overflows++; 281 tcpstat.tcps_rcvmemdrop++; 282 m_freem(m); 283 *tlenp = 0; 284 return (0); 285 } 286 287 /* 288 * Allocate a new queue entry. If we can't, or hit the zone limit 289 * just drop the pkt. 290 */ 291 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 292 if (te == NULL) { 293 tcpstat.tcps_rcvmemdrop++; 294 m_freem(m); 295 *tlenp = 0; 296 return (0); 297 } 298 tp->t_segqlen++; 299 tcp_reass_qsize++; 300 301 /* 302 * Find a segment which begins after this one does. 303 */ 304 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 305 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 306 break; 307 p = q; 308 } 309 310 /* 311 * If there is a preceding segment, it may provide some of 312 * our data already. If so, drop the data from the incoming 313 * segment. If it provides all of our data, drop us. 314 */ 315 if (p != NULL) { 316 register int i; 317 /* conversion to int (in i) handles seq wraparound */ 318 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 319 if (i > 0) { 320 if (i >= *tlenp) { 321 tcpstat.tcps_rcvduppack++; 322 tcpstat.tcps_rcvdupbyte += *tlenp; 323 m_freem(m); 324 uma_zfree(tcp_reass_zone, te); 325 tp->t_segqlen--; 326 tcp_reass_qsize--; 327 /* 328 * Try to present any queued data 329 * at the left window edge to the user. 330 * This is needed after the 3-WHS 331 * completes. 332 */ 333 goto present; /* ??? */ 334 } 335 m_adj(m, i); 336 *tlenp -= i; 337 th->th_seq += i; 338 } 339 } 340 tcpstat.tcps_rcvoopack++; 341 tcpstat.tcps_rcvoobyte += *tlenp; 342 343 /* 344 * While we overlap succeeding segments trim them or, 345 * if they are completely covered, dequeue them. 346 */ 347 while (q) { 348 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 349 if (i <= 0) 350 break; 351 if (i < q->tqe_len) { 352 q->tqe_th->th_seq += i; 353 q->tqe_len -= i; 354 m_adj(q->tqe_m, i); 355 break; 356 } 357 358 nq = LIST_NEXT(q, tqe_q); 359 LIST_REMOVE(q, tqe_q); 360 m_freem(q->tqe_m); 361 uma_zfree(tcp_reass_zone, q); 362 tp->t_segqlen--; 363 tcp_reass_qsize--; 364 q = nq; 365 } 366 367 /* Insert the new segment queue entry into place. */ 368 te->tqe_m = m; 369 te->tqe_th = th; 370 te->tqe_len = *tlenp; 371 372 if (p == NULL) { 373 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 374 } else { 375 LIST_INSERT_AFTER(p, te, tqe_q); 376 } 377 378present: 379 /* 380 * Present data to user, advancing rcv_nxt through 381 * completed sequence space. 382 */ 383 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 384 return (0); 385 q = LIST_FIRST(&tp->t_segq); 386 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 387 return (0); 388 SOCKBUF_LOCK(&so->so_rcv); 389 do { 390 tp->rcv_nxt += q->tqe_len; 391 flags = q->tqe_th->th_flags & TH_FIN; 392 nq = LIST_NEXT(q, tqe_q); 393 LIST_REMOVE(q, tqe_q); 394 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 395 m_freem(q->tqe_m); 396 else 397 sbappendstream_locked(&so->so_rcv, q->tqe_m); 398 uma_zfree(tcp_reass_zone, q); 399 tp->t_segqlen--; 400 tcp_reass_qsize--; 401 q = nq; 402 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 403 ND6_HINT(tp); 404 sorwakeup_locked(so); 405 return (flags); 406} 407 408/* 409 * TCP input routine, follows pages 65-76 of the 410 * protocol specification dated September, 1981 very closely. 411 */ 412#ifdef INET6 413int 414tcp6_input(mp, offp, proto) 415 struct mbuf **mp; 416 int *offp, proto; 417{ 418 register struct mbuf *m = *mp; 419 struct in6_ifaddr *ia6; 420 421 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 422 423 /* 424 * draft-itojun-ipv6-tcp-to-anycast 425 * better place to put this in? 426 */ 427 ia6 = ip6_getdstifaddr(m); 428 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 429 struct ip6_hdr *ip6; 430 431 ip6 = mtod(m, struct ip6_hdr *); 432 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 433 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 434 return IPPROTO_DONE; 435 } 436 437 tcp_input(m, *offp); 438 return IPPROTO_DONE; 439} 440#endif 441 442void 443tcp_input(m, off0) 444 register struct mbuf *m; 445 int off0; 446{ 447 register struct tcphdr *th; 448 register struct ip *ip = NULL; 449 register struct ipovly *ipov; 450 register struct inpcb *inp = NULL; 451 u_char *optp = NULL; 452 int optlen = 0; 453 int len, tlen, off; 454 int drop_hdrlen; 455 register struct tcpcb *tp = 0; 456 register int thflags; 457 struct socket *so = 0; 458 int todrop, acked, ourfinisacked, needoutput = 0; 459 u_long tiwin; 460 struct tcpopt to; /* options in this segment */ 461 int headlocked = 0; 462#ifdef IPFIREWALL_FORWARD 463 struct m_tag *fwd_tag; 464#endif 465 int rstreason; /* For badport_bandlim accounting purposes */ 466 467 struct ip6_hdr *ip6 = NULL; 468#ifdef INET6 469 int isipv6; 470 char ip6buf[INET6_ADDRSTRLEN]; 471#else 472 const int isipv6 = 0; 473#endif 474 475#ifdef TCPDEBUG 476 /* 477 * The size of tcp_saveipgen must be the size of the max ip header, 478 * now IPv6. 479 */ 480 u_char tcp_saveipgen[40]; 481 struct tcphdr tcp_savetcp; 482 short ostate = 0; 483#endif 484 485#ifdef INET6 486 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 487#endif 488 bzero((char *)&to, sizeof(to)); 489 490 tcpstat.tcps_rcvtotal++; 491 492 if (isipv6) { 493#ifdef INET6 494 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 495 ip6 = mtod(m, struct ip6_hdr *); 496 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 497 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 498 tcpstat.tcps_rcvbadsum++; 499 goto drop; 500 } 501 th = (struct tcphdr *)((caddr_t)ip6 + off0); 502 503 /* 504 * Be proactive about unspecified IPv6 address in source. 505 * As we use all-zero to indicate unbounded/unconnected pcb, 506 * unspecified IPv6 address can be used to confuse us. 507 * 508 * Note that packets with unspecified IPv6 destination is 509 * already dropped in ip6_input. 510 */ 511 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 512 /* XXX stat */ 513 goto drop; 514 } 515#else 516 th = NULL; /* XXX: avoid compiler warning */ 517#endif 518 } else { 519 /* 520 * Get IP and TCP header together in first mbuf. 521 * Note: IP leaves IP header in first mbuf. 522 */ 523 if (off0 > sizeof (struct ip)) { 524 ip_stripoptions(m, (struct mbuf *)0); 525 off0 = sizeof(struct ip); 526 } 527 if (m->m_len < sizeof (struct tcpiphdr)) { 528 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 529 tcpstat.tcps_rcvshort++; 530 return; 531 } 532 } 533 ip = mtod(m, struct ip *); 534 ipov = (struct ipovly *)ip; 535 th = (struct tcphdr *)((caddr_t)ip + off0); 536 tlen = ip->ip_len; 537 538 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 539 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 540 th->th_sum = m->m_pkthdr.csum_data; 541 else 542 th->th_sum = in_pseudo(ip->ip_src.s_addr, 543 ip->ip_dst.s_addr, 544 htonl(m->m_pkthdr.csum_data + 545 ip->ip_len + 546 IPPROTO_TCP)); 547 th->th_sum ^= 0xffff; 548#ifdef TCPDEBUG 549 ipov->ih_len = (u_short)tlen; 550 ipov->ih_len = htons(ipov->ih_len); 551#endif 552 } else { 553 /* 554 * Checksum extended TCP header and data. 555 */ 556 len = sizeof (struct ip) + tlen; 557 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 558 ipov->ih_len = (u_short)tlen; 559 ipov->ih_len = htons(ipov->ih_len); 560 th->th_sum = in_cksum(m, len); 561 } 562 if (th->th_sum) { 563 tcpstat.tcps_rcvbadsum++; 564 goto drop; 565 } 566 /* Re-initialization for later version check */ 567 ip->ip_v = IPVERSION; 568 } 569 570 /* 571 * Check that TCP offset makes sense, 572 * pull out TCP options and adjust length. XXX 573 */ 574 off = th->th_off << 2; 575 if (off < sizeof (struct tcphdr) || off > tlen) { 576 tcpstat.tcps_rcvbadoff++; 577 goto drop; 578 } 579 tlen -= off; /* tlen is used instead of ti->ti_len */ 580 if (off > sizeof (struct tcphdr)) { 581 if (isipv6) { 582#ifdef INET6 583 IP6_EXTHDR_CHECK(m, off0, off, ); 584 ip6 = mtod(m, struct ip6_hdr *); 585 th = (struct tcphdr *)((caddr_t)ip6 + off0); 586#endif 587 } else { 588 if (m->m_len < sizeof(struct ip) + off) { 589 if ((m = m_pullup(m, sizeof (struct ip) + off)) 590 == 0) { 591 tcpstat.tcps_rcvshort++; 592 return; 593 } 594 ip = mtod(m, struct ip *); 595 ipov = (struct ipovly *)ip; 596 th = (struct tcphdr *)((caddr_t)ip + off0); 597 } 598 } 599 optlen = off - sizeof (struct tcphdr); 600 optp = (u_char *)(th + 1); 601 } 602 thflags = th->th_flags; 603 604#ifdef TCP_DROP_SYNFIN 605 /* 606 * If the drop_synfin option is enabled, drop all packets with 607 * both the SYN and FIN bits set. This prevents e.g. nmap from 608 * identifying the TCP/IP stack. 609 * 610 * This is a violation of the TCP specification. 611 */ 612 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 613 goto drop; 614#endif 615 616 /* 617 * Convert TCP protocol specific fields to host format. 618 */ 619 th->th_seq = ntohl(th->th_seq); 620 th->th_ack = ntohl(th->th_ack); 621 th->th_win = ntohs(th->th_win); 622 th->th_urp = ntohs(th->th_urp); 623 624 /* 625 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 626 * until after ip6_savecontrol() is called and before other functions 627 * which don't want those proto headers. 628 * Because ip6_savecontrol() is going to parse the mbuf to 629 * search for data to be passed up to user-land, it wants mbuf 630 * parameters to be unchanged. 631 * XXX: the call of ip6_savecontrol() has been obsoleted based on 632 * latest version of the advanced API (20020110). 633 */ 634 drop_hdrlen = off0 + off; 635 636 /* 637 * Locate pcb for segment. 638 */ 639 INP_INFO_WLOCK(&tcbinfo); 640 headlocked = 1; 641findpcb: 642 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 643#ifdef IPFIREWALL_FORWARD 644 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 645 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 646 647 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 648 struct sockaddr_in *next_hop; 649 650 next_hop = (struct sockaddr_in *)(fwd_tag+1); 651 /* 652 * Transparently forwarded. Pretend to be the destination. 653 * already got one like this? 654 */ 655 inp = in_pcblookup_hash(&tcbinfo, 656 ip->ip_src, th->th_sport, 657 ip->ip_dst, th->th_dport, 658 0, m->m_pkthdr.rcvif); 659 if (!inp) { 660 /* It's new. Try to find the ambushing socket. */ 661 inp = in_pcblookup_hash(&tcbinfo, 662 ip->ip_src, th->th_sport, 663 next_hop->sin_addr, 664 next_hop->sin_port ? 665 ntohs(next_hop->sin_port) : 666 th->th_dport, 667 INPLOOKUP_WILDCARD, 668 m->m_pkthdr.rcvif); 669 } 670 /* Remove the tag from the packet. We don't need it anymore. */ 671 m_tag_delete(m, fwd_tag); 672 } else { 673#endif /* IPFIREWALL_FORWARD */ 674 if (isipv6) { 675#ifdef INET6 676 inp = in6_pcblookup_hash(&tcbinfo, 677 &ip6->ip6_src, th->th_sport, 678 &ip6->ip6_dst, th->th_dport, 679 INPLOOKUP_WILDCARD, 680 m->m_pkthdr.rcvif); 681#endif 682 } else 683 inp = in_pcblookup_hash(&tcbinfo, 684 ip->ip_src, th->th_sport, 685 ip->ip_dst, th->th_dport, 686 INPLOOKUP_WILDCARD, 687 m->m_pkthdr.rcvif); 688#ifdef IPFIREWALL_FORWARD 689 } 690#endif /* IPFIREWALL_FORWARD */ 691 692#if defined(IPSEC) || defined(FAST_IPSEC) 693#ifdef INET6 694 if (isipv6) { 695 if (inp != NULL && ipsec6_in_reject(m, inp)) { 696#ifdef IPSEC 697 ipsec6stat.in_polvio++; 698#endif 699 goto drop; 700 } 701 } else 702#endif /* INET6 */ 703 if (inp != NULL && ipsec4_in_reject(m, inp)) { 704#ifdef IPSEC 705 ipsecstat.in_polvio++; 706#endif 707 goto drop; 708 } 709#endif /*IPSEC || FAST_IPSEC*/ 710 711 /* 712 * If the state is CLOSED (i.e., TCB does not exist) then 713 * all data in the incoming segment is discarded. 714 * If the TCB exists but is in CLOSED state, it is embryonic, 715 * but should either do a listen or a connect soon. 716 */ 717 if (inp == NULL) { 718 if (tcp_log_in_vain) { 719#ifdef INET6 720 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 721#else 722 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 723#endif 724 725 if (isipv6) { 726#ifdef INET6 727 strcpy(dbuf, "["); 728 strcpy(sbuf, "["); 729 strcat(dbuf, 730 ip6_sprintf(ip6buf, &ip6->ip6_dst)); 731 strcat(sbuf, 732 ip6_sprintf(ip6buf, &ip6->ip6_src)); 733 strcat(dbuf, "]"); 734 strcat(sbuf, "]"); 735#endif 736 } else { 737 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 738 strcpy(sbuf, inet_ntoa(ip->ip_src)); 739 } 740 switch (tcp_log_in_vain) { 741 case 1: 742 if ((thflags & TH_SYN) == 0) 743 break; 744 /* FALLTHROUGH */ 745 case 2: 746 log(LOG_INFO, 747 "Connection attempt to TCP %s:%d " 748 "from %s:%d flags:0x%02x\n", 749 dbuf, ntohs(th->th_dport), sbuf, 750 ntohs(th->th_sport), thflags); 751 break; 752 default: 753 break; 754 } 755 } 756 if (blackhole) { 757 switch (blackhole) { 758 case 1: 759 if (thflags & TH_SYN) 760 goto drop; 761 break; 762 case 2: 763 goto drop; 764 default: 765 goto drop; 766 } 767 } 768 rstreason = BANDLIM_RST_CLOSEDPORT; 769 goto dropwithreset; 770 } 771 INP_LOCK(inp); 772 773 /* Check the minimum TTL for socket. */ 774 if (inp->inp_ip_minttl != 0) { 775#ifdef INET6 776 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 777 goto drop; 778 else 779#endif 780 if (inp->inp_ip_minttl > ip->ip_ttl) 781 goto drop; 782 } 783 784 if (inp->inp_vflag & INP_TIMEWAIT) { 785 /* 786 * The only option of relevance is TOF_CC, and only if 787 * present in a SYN segment. See tcp_timewait(). 788 */ 789 if (thflags & TH_SYN) 790 tcp_dooptions(&to, optp, optlen, TO_SYN); 791 if (tcp_timewait(inp, &to, th, m, tlen)) 792 goto findpcb; 793 /* 794 * tcp_timewait unlocks inp. 795 */ 796 INP_INFO_WUNLOCK(&tcbinfo); 797 return; 798 } 799 tp = intotcpcb(inp); 800 if (tp == 0) { 801 INP_UNLOCK(inp); 802 rstreason = BANDLIM_RST_CLOSEDPORT; 803 goto dropwithreset; 804 } 805 if (tp->t_state == TCPS_CLOSED) 806 goto drop; 807 808#ifdef MAC 809 INP_LOCK_ASSERT(inp); 810 if (mac_check_inpcb_deliver(inp, m)) 811 goto drop; 812#endif 813 so = inp->inp_socket; 814 KASSERT(so != NULL, ("tcp_input: so == NULL")); 815#ifdef TCPDEBUG 816 if (so->so_options & SO_DEBUG) { 817 ostate = tp->t_state; 818 if (isipv6) 819 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 820 else 821 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 822 tcp_savetcp = *th; 823 } 824#endif 825 if (so->so_options & SO_ACCEPTCONN) { 826 struct in_conninfo inc; 827 828 bzero(&inc, sizeof(inc)); 829#ifdef INET6 830 inc.inc_isipv6 = isipv6; 831#endif 832 if (isipv6) { 833 inc.inc6_faddr = ip6->ip6_src; 834 inc.inc6_laddr = ip6->ip6_dst; 835 } else { 836 inc.inc_faddr = ip->ip_src; 837 inc.inc_laddr = ip->ip_dst; 838 } 839 inc.inc_fport = th->th_sport; 840 inc.inc_lport = th->th_dport; 841 842 /* 843 * If the state is LISTEN then ignore segment if it contains 844 * a RST. If the segment contains an ACK then it is bad and 845 * send a RST. If it does not contain a SYN then it is not 846 * interesting; drop it. 847 * 848 * If the state is SYN_RECEIVED (syncache) and seg contains 849 * an ACK, but not for our SYN/ACK, send a RST. If the seg 850 * contains a RST, check the sequence number to see if it 851 * is a valid reset segment. 852 */ 853 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 854 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 855 /* 856 * Parse the TCP options here because 857 * syncookies need access to the reflected 858 * timestamp. 859 */ 860 tcp_dooptions(&to, optp, optlen, 0); 861 if (!syncache_expand(&inc, &to, th, &so, m)) { 862 /* 863 * No syncache entry, or ACK was not 864 * for our SYN/ACK. Send a RST. 865 */ 866 tcpstat.tcps_badsyn++; 867 rstreason = BANDLIM_RST_OPENPORT; 868 goto dropwithreset; 869 } 870 if (so == NULL) { 871 /* 872 * Could not complete 3-way handshake, 873 * connection is being closed down, and 874 * syncache has free'd mbuf. 875 */ 876 INP_UNLOCK(inp); 877 INP_INFO_WUNLOCK(&tcbinfo); 878 return; 879 } 880 /* 881 * Socket is created in state SYN_RECEIVED. 882 * Continue processing segment. 883 */ 884 INP_UNLOCK(inp); 885 inp = sotoinpcb(so); 886 INP_LOCK(inp); 887 tp = intotcpcb(inp); 888 /* 889 * This is what would have happened in 890 * tcp_output() when the SYN,ACK was sent. 891 */ 892 tp->snd_up = tp->snd_una; 893 tp->snd_max = tp->snd_nxt = tp->iss + 1; 894 tp->last_ack_sent = tp->rcv_nxt; 895 goto after_listen; 896 } 897 if (thflags & TH_RST) { 898 syncache_chkrst(&inc, th); 899 goto drop; 900 } 901 if (thflags & TH_ACK) { 902 syncache_badack(&inc); 903 tcpstat.tcps_badsyn++; 904 rstreason = BANDLIM_RST_OPENPORT; 905 goto dropwithreset; 906 } 907 goto drop; 908 } 909 910 /* 911 * Segment's flags are (SYN) or (SYN|FIN). 912 */ 913#ifdef INET6 914 /* 915 * If deprecated address is forbidden, 916 * we do not accept SYN to deprecated interface 917 * address to prevent any new inbound connection from 918 * getting established. 919 * When we do not accept SYN, we send a TCP RST, 920 * with deprecated source address (instead of dropping 921 * it). We compromise it as it is much better for peer 922 * to send a RST, and RST will be the final packet 923 * for the exchange. 924 * 925 * If we do not forbid deprecated addresses, we accept 926 * the SYN packet. RFC2462 does not suggest dropping 927 * SYN in this case. 928 * If we decipher RFC2462 5.5.4, it says like this: 929 * 1. use of deprecated addr with existing 930 * communication is okay - "SHOULD continue to be 931 * used" 932 * 2. use of it with new communication: 933 * (2a) "SHOULD NOT be used if alternate address 934 * with sufficient scope is available" 935 * (2b) nothing mentioned otherwise. 936 * Here we fall into (2b) case as we have no choice in 937 * our source address selection - we must obey the peer. 938 * 939 * The wording in RFC2462 is confusing, and there are 940 * multiple description text for deprecated address 941 * handling - worse, they are not exactly the same. 942 * I believe 5.5.4 is the best one, so we follow 5.5.4. 943 */ 944 if (isipv6 && !ip6_use_deprecated) { 945 struct in6_ifaddr *ia6; 946 947 if ((ia6 = ip6_getdstifaddr(m)) && 948 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 949 INP_UNLOCK(inp); 950 tp = NULL; 951 rstreason = BANDLIM_RST_OPENPORT; 952 goto dropwithreset; 953 } 954 } 955#endif 956 /* 957 * If it is from this socket, drop it, it must be forged. 958 * Don't bother responding if the destination was a broadcast. 959 */ 960 if (th->th_dport == th->th_sport) { 961 if (isipv6) { 962 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 963 &ip6->ip6_src)) 964 goto drop; 965 } else { 966 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 967 goto drop; 968 } 969 } 970 /* 971 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 972 * 973 * Note that it is quite possible to receive unicast 974 * link-layer packets with a broadcast IP address. Use 975 * in_broadcast() to find them. 976 */ 977 if (m->m_flags & (M_BCAST|M_MCAST)) 978 goto drop; 979 if (isipv6) { 980 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 981 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 982 goto drop; 983 } else { 984 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 985 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 986 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 987 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 988 goto drop; 989 } 990 /* 991 * SYN appears to be valid; create compressed TCP state 992 * for syncache, or perform t/tcp connection. 993 */ 994 if (so->so_qlen <= so->so_qlimit) { 995#ifdef TCPDEBUG 996 if (so->so_options & SO_DEBUG) 997 tcp_trace(TA_INPUT, ostate, tp, 998 (void *)tcp_saveipgen, &tcp_savetcp, 0); 999#endif 1000 tcp_dooptions(&to, optp, optlen, TO_SYN); 1001 if (!syncache_add(&inc, &to, th, inp, &so, m)) 1002 goto drop; /* XXX: does not happen */ 1003 if (so == NULL) { 1004 /* 1005 * Entry added to syncache, mbuf used to 1006 * send SYN,ACK packet. Everything unlocked 1007 * already. 1008 */ 1009 return; 1010 } 1011 panic("T/TCP not supported at the moment"); 1012#if 0 /* T/TCP */ 1013 /* 1014 * Segment passed TAO tests. 1015 * XXX: Can't happen at the moment. 1016 */ 1017 INP_UNLOCK(inp); 1018 inp = sotoinpcb(so); 1019 INP_LOCK(inp); 1020 tp = intotcpcb(inp); 1021 tp->t_starttime = ticks; 1022 tp->t_state = TCPS_ESTABLISHED; 1023 1024 /* 1025 * T/TCP logic: 1026 * If there is a FIN or if there is data, then 1027 * delay SYN,ACK(SYN) in the hope of piggy-backing 1028 * it on a response segment. Otherwise must send 1029 * ACK now in case the other side is slow starting. 1030 */ 1031 if (thflags & TH_FIN || tlen != 0) 1032 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1033 else 1034 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1035 tiwin = th->th_win << tp->snd_scale; 1036 tcpstat.tcps_connects++; 1037 soisconnected(so); 1038 goto trimthenstep6; 1039#endif /* T/TCP */ 1040 } 1041 goto drop; 1042 } 1043after_listen: 1044 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1045 INP_LOCK_ASSERT(inp); 1046 1047 /* Syncache takes care of sockets in the listen state. */ 1048 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN")); 1049 1050 /* 1051 * This is the second part of the MSS DoS prevention code (after 1052 * minmss on the sending side) and it deals with too many too small 1053 * tcp packets in a too short timeframe (1 second). 1054 * 1055 * For every full second we count the number of received packets 1056 * and bytes. If we get a lot of packets per second for this connection 1057 * (tcp_minmssoverload) we take a closer look at it and compute the 1058 * average packet size for the past second. If that is less than 1059 * tcp_minmss we get too many packets with very small payload which 1060 * is not good and burdens our system (and every packet generates 1061 * a wakeup to the process connected to our socket). We can reasonable 1062 * expect this to be small packet DoS attack to exhaust our CPU 1063 * cycles. 1064 * 1065 * Care has to be taken for the minimum packet overload value. This 1066 * value defines the minimum number of packets per second before we 1067 * start to worry. This must not be too low to avoid killing for 1068 * example interactive connections with many small packets like 1069 * telnet or SSH. 1070 * 1071 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1072 * this check. 1073 * 1074 * Account for packet if payload packet, skip over ACK, etc. 1075 */ 1076 if (tcp_minmss && tcp_minmssoverload && 1077 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1078 if ((unsigned int)(tp->rcv_second - ticks) < hz) { 1079 tp->rcv_pps++; 1080 tp->rcv_byps += tlen + off; 1081 if (tp->rcv_pps > tcp_minmssoverload) { 1082 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1083 printf("too many small tcp packets from " 1084 "%s:%u, av. %lubyte/packet, " 1085 "dropping connection\n", 1086#ifdef INET6 1087 isipv6 ? 1088 ip6_sprintf(ip6buf, 1089 &inp->inp_inc.inc6_faddr) : 1090#endif 1091 inet_ntoa(inp->inp_inc.inc_faddr), 1092 inp->inp_inc.inc_fport, 1093 tp->rcv_byps / tp->rcv_pps); 1094 KASSERT(headlocked, ("tcp_input: " 1095 "after_listen: tcp_drop: head " 1096 "not locked")); 1097 tp = tcp_drop(tp, ECONNRESET); 1098 tcpstat.tcps_minmssdrops++; 1099 goto drop; 1100 } 1101 } 1102 } else { 1103 tp->rcv_second = ticks + hz; 1104 tp->rcv_pps = 1; 1105 tp->rcv_byps = tlen + off; 1106 } 1107 } 1108 1109 /* 1110 * Segment received on connection. 1111 * Reset idle time and keep-alive timer. 1112 */ 1113 tp->t_rcvtime = ticks; 1114 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1115 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1116 1117 /* 1118 * Unscale the window into a 32-bit value. 1119 * This value is bogus for the TCPS_SYN_SENT state 1120 * and is overwritten later. 1121 */ 1122 tiwin = th->th_win << tp->snd_scale; 1123 1124 /* 1125 * Parse options on any incoming segment. 1126 */ 1127 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) ? TO_SYN : 0); 1128 1129 /* 1130 * If echoed timestamp is later than the current time, 1131 * fall back to non RFC1323 RTT calculation. Normalize 1132 * timestamp if syncookies were used when this connection 1133 * was established. 1134 */ 1135 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1136 to.to_tsecr -= tp->ts_offset; 1137 if (TSTMP_GT(to.to_tsecr, ticks)) 1138 to.to_tsecr = 0; 1139 } 1140 1141 /* 1142 * Process options only when we get SYN/ACK back. The SYN case 1143 * for incoming connections is handled in tcp_syncache. 1144 * XXX this is traditional behavior, may need to be cleaned up. 1145 */ 1146 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1147 if ((to.to_flags & TOF_SCALE) && 1148 (tp->t_flags & TF_REQ_SCALE)) { 1149 tp->t_flags |= TF_RCVD_SCALE; 1150 tp->snd_scale = to.to_wscale; 1151 tp->snd_wnd = th->th_win << tp->snd_scale; 1152 tiwin = tp->snd_wnd; 1153 } 1154 if (to.to_flags & TOF_TS) { 1155 tp->t_flags |= TF_RCVD_TSTMP; 1156 tp->ts_recent = to.to_tsval; 1157 tp->ts_recent_age = ticks; 1158 } 1159 /* Initial send window, already scaled. */ 1160 tp->snd_wnd = th->th_win; 1161 if (to.to_flags & TOF_MSS) 1162 tcp_mss(tp, to.to_mss); 1163 if (tp->sack_enable) { 1164 if (!(to.to_flags & TOF_SACK)) 1165 tp->sack_enable = 0; 1166 else 1167 tp->t_flags |= TF_SACK_PERMIT; 1168 } 1169 1170 } 1171 1172 /* 1173 * Header prediction: check for the two common cases 1174 * of a uni-directional data xfer. If the packet has 1175 * no control flags, is in-sequence, the window didn't 1176 * change and we're not retransmitting, it's a 1177 * candidate. If the length is zero and the ack moved 1178 * forward, we're the sender side of the xfer. Just 1179 * free the data acked & wake any higher level process 1180 * that was blocked waiting for space. If the length 1181 * is non-zero and the ack didn't move, we're the 1182 * receiver side. If we're getting packets in-order 1183 * (the reassembly queue is empty), add the data to 1184 * the socket buffer and note that we need a delayed ack. 1185 * Make sure that the hidden state-flags are also off. 1186 * Since we check for TCPS_ESTABLISHED above, it can only 1187 * be TH_NEEDSYN. 1188 */ 1189 if (tp->t_state == TCPS_ESTABLISHED && 1190 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1191 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1192 ((to.to_flags & TOF_TS) == 0 || 1193 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1194 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1195 tp->snd_nxt == tp->snd_max) { 1196 1197 /* 1198 * If last ACK falls within this segment's sequence numbers, 1199 * record the timestamp. 1200 * NOTE that the test is modified according to the latest 1201 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1202 */ 1203 if ((to.to_flags & TOF_TS) != 0 && 1204 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1205 tp->ts_recent_age = ticks; 1206 tp->ts_recent = to.to_tsval; 1207 } 1208 1209 if (tlen == 0) { 1210 if (SEQ_GT(th->th_ack, tp->snd_una) && 1211 SEQ_LEQ(th->th_ack, tp->snd_max) && 1212 tp->snd_cwnd >= tp->snd_wnd && 1213 ((!tcp_do_newreno && !tp->sack_enable && 1214 tp->t_dupacks < tcprexmtthresh) || 1215 ((tcp_do_newreno || tp->sack_enable) && 1216 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 && 1217 TAILQ_EMPTY(&tp->snd_holes)))) { 1218 KASSERT(headlocked, ("headlocked")); 1219 INP_INFO_WUNLOCK(&tcbinfo); 1220 headlocked = 0; 1221 /* 1222 * this is a pure ack for outstanding data. 1223 */ 1224 ++tcpstat.tcps_predack; 1225 /* 1226 * "bad retransmit" recovery 1227 */ 1228 if (tp->t_rxtshift == 1 && 1229 ticks < tp->t_badrxtwin) { 1230 ++tcpstat.tcps_sndrexmitbad; 1231 tp->snd_cwnd = tp->snd_cwnd_prev; 1232 tp->snd_ssthresh = 1233 tp->snd_ssthresh_prev; 1234 tp->snd_recover = tp->snd_recover_prev; 1235 if (tp->t_flags & TF_WASFRECOVERY) 1236 ENTER_FASTRECOVERY(tp); 1237 tp->snd_nxt = tp->snd_max; 1238 tp->t_badrxtwin = 0; 1239 } 1240 1241 /* 1242 * Recalculate the transmit timer / rtt. 1243 * 1244 * Some boxes send broken timestamp replies 1245 * during the SYN+ACK phase, ignore 1246 * timestamps of 0 or we could calculate a 1247 * huge RTT and blow up the retransmit timer. 1248 */ 1249 if ((to.to_flags & TOF_TS) != 0 && 1250 to.to_tsecr) { 1251 if (!tp->t_rttlow || 1252 tp->t_rttlow > ticks - to.to_tsecr) 1253 tp->t_rttlow = ticks - to.to_tsecr; 1254 tcp_xmit_timer(tp, 1255 ticks - to.to_tsecr + 1); 1256 } else if (tp->t_rtttime && 1257 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1258 if (!tp->t_rttlow || 1259 tp->t_rttlow > ticks - tp->t_rtttime) 1260 tp->t_rttlow = ticks - tp->t_rtttime; 1261 tcp_xmit_timer(tp, 1262 ticks - tp->t_rtttime); 1263 } 1264 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1265 acked = th->th_ack - tp->snd_una; 1266 tcpstat.tcps_rcvackpack++; 1267 tcpstat.tcps_rcvackbyte += acked; 1268 sbdrop(&so->so_snd, acked); 1269 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1270 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1271 tp->snd_recover = th->th_ack - 1; 1272 tp->snd_una = th->th_ack; 1273 /* 1274 * pull snd_wl2 up to prevent seq wrap relative 1275 * to th_ack. 1276 */ 1277 tp->snd_wl2 = th->th_ack; 1278 tp->t_dupacks = 0; 1279 m_freem(m); 1280 ND6_HINT(tp); /* some progress has been done */ 1281 1282 /* 1283 * If all outstanding data are acked, stop 1284 * retransmit timer, otherwise restart timer 1285 * using current (possibly backed-off) value. 1286 * If process is waiting for space, 1287 * wakeup/selwakeup/signal. If data 1288 * are ready to send, let tcp_output 1289 * decide between more output or persist. 1290 1291#ifdef TCPDEBUG 1292 if (so->so_options & SO_DEBUG) 1293 tcp_trace(TA_INPUT, ostate, tp, 1294 (void *)tcp_saveipgen, 1295 &tcp_savetcp, 0); 1296#endif 1297 */ 1298 if (tp->snd_una == tp->snd_max) 1299 callout_stop(tp->tt_rexmt); 1300 else if (!callout_active(tp->tt_persist)) 1301 callout_reset(tp->tt_rexmt, 1302 tp->t_rxtcur, 1303 tcp_timer_rexmt, tp); 1304 1305 sowwakeup(so); 1306 if (so->so_snd.sb_cc) 1307 (void) tcp_output(tp); 1308 goto check_delack; 1309 } 1310 } else if (th->th_ack == tp->snd_una && 1311 LIST_EMPTY(&tp->t_segq) && 1312 tlen <= sbspace(&so->so_rcv)) { 1313 int newsize = 0; /* automatic sockbuf scaling */ 1314 1315 KASSERT(headlocked, ("headlocked")); 1316 INP_INFO_WUNLOCK(&tcbinfo); 1317 headlocked = 0; 1318 /* 1319 * this is a pure, in-sequence data packet 1320 * with nothing on the reassembly queue and 1321 * we have enough buffer space to take it. 1322 */ 1323 /* Clean receiver SACK report if present */ 1324 if (tp->sack_enable && tp->rcv_numsacks) 1325 tcp_clean_sackreport(tp); 1326 ++tcpstat.tcps_preddat; 1327 tp->rcv_nxt += tlen; 1328 /* 1329 * Pull snd_wl1 up to prevent seq wrap relative to 1330 * th_seq. 1331 */ 1332 tp->snd_wl1 = th->th_seq; 1333 /* 1334 * Pull rcv_up up to prevent seq wrap relative to 1335 * rcv_nxt. 1336 */ 1337 tp->rcv_up = tp->rcv_nxt; 1338 tcpstat.tcps_rcvpack++; 1339 tcpstat.tcps_rcvbyte += tlen; 1340 ND6_HINT(tp); /* some progress has been done */ 1341#ifdef TCPDEBUG 1342 if (so->so_options & SO_DEBUG) 1343 tcp_trace(TA_INPUT, ostate, tp, 1344 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1345#endif 1346 /* 1347 * Automatic sizing of receive socket buffer. Often the send 1348 * buffer size is not optimally adjusted to the actual network 1349 * conditions at hand (delay bandwidth product). Setting the 1350 * buffer size too small limits throughput on links with high 1351 * bandwidth and high delay (eg. trans-continental/oceanic links). 1352 * 1353 * On the receive side the socket buffer memory is only rarely 1354 * used to any significant extent. This allows us to be much 1355 * more aggressive in scaling the receive socket buffer. For 1356 * the case that the buffer space is actually used to a large 1357 * extent and we run out of kernel memory we can simply drop 1358 * the new segments; TCP on the sender will just retransmit it 1359 * later. Setting the buffer size too big may only consume too 1360 * much kernel memory if the application doesn't read() from 1361 * the socket or packet loss or reordering makes use of the 1362 * reassembly queue. 1363 * 1364 * The criteria to step up the receive buffer one notch are: 1365 * 1. the number of bytes received during the time it takes 1366 * one timestamp to be reflected back to us (the RTT); 1367 * 2. received bytes per RTT is within seven eighth of the 1368 * current socket buffer size; 1369 * 3. receive buffer size has not hit maximal automatic size; 1370 * 1371 * This algorithm does one step per RTT at most and only if 1372 * we receive a bulk stream w/o packet losses or reorderings. 1373 * Shrinking the buffer during idle times is not necessary as 1374 * it doesn't consume any memory when idle. 1375 * 1376 * TODO: Only step up if the application is actually serving 1377 * the buffer to better manage the socket buffer resources. 1378 */ 1379 if (tcp_do_autorcvbuf && 1380 to.to_tsecr && 1381 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1382 if (to.to_tsecr > tp->rfbuf_ts && 1383 to.to_tsecr - tp->rfbuf_ts < hz) { 1384 if (tp->rfbuf_cnt > 1385 (so->so_rcv.sb_hiwat / 8 * 7) && 1386 so->so_rcv.sb_hiwat < 1387 tcp_autorcvbuf_max) { 1388 newsize = 1389 min(so->so_rcv.sb_hiwat + 1390 tcp_autorcvbuf_inc, 1391 tcp_autorcvbuf_max); 1392 } 1393 /* Start over with next RTT. */ 1394 tp->rfbuf_ts = 0; 1395 tp->rfbuf_cnt = 0; 1396 } else 1397 tp->rfbuf_cnt += tlen; /* add up */ 1398 } 1399 1400 /* Add data to socket buffer. */ 1401 SOCKBUF_LOCK(&so->so_rcv); 1402 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1403 m_freem(m); 1404 } else { 1405 /* 1406 * Set new socket buffer size. 1407 * Give up when limit is reached. 1408 */ 1409 if (newsize) 1410 if (!sbreserve_locked(&so->so_rcv, 1411 newsize, so, curthread)) 1412 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1413 m_adj(m, drop_hdrlen); /* delayed header drop */ 1414 sbappendstream_locked(&so->so_rcv, m); 1415 } 1416 sorwakeup_locked(so); 1417 if (DELAY_ACK(tp)) { 1418 tp->t_flags |= TF_DELACK; 1419 } else { 1420 tp->t_flags |= TF_ACKNOW; 1421 tcp_output(tp); 1422 } 1423 goto check_delack; 1424 } 1425 } 1426 1427 /* 1428 * Calculate amount of space in receive window, 1429 * and then do TCP input processing. 1430 * Receive window is amount of space in rcv queue, 1431 * but not less than advertised window. 1432 */ 1433 { int win; 1434 1435 win = sbspace(&so->so_rcv); 1436 if (win < 0) 1437 win = 0; 1438 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1439 } 1440 1441 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1442 tp->rfbuf_ts = 0; 1443 tp->rfbuf_cnt = 0; 1444 1445 switch (tp->t_state) { 1446 1447 /* 1448 * If the state is SYN_RECEIVED: 1449 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1450 */ 1451 case TCPS_SYN_RECEIVED: 1452 if ((thflags & TH_ACK) && 1453 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1454 SEQ_GT(th->th_ack, tp->snd_max))) { 1455 rstreason = BANDLIM_RST_OPENPORT; 1456 goto dropwithreset; 1457 } 1458 break; 1459 1460 /* 1461 * If the state is SYN_SENT: 1462 * if seg contains an ACK, but not for our SYN, drop the input. 1463 * if seg contains a RST, then drop the connection. 1464 * if seg does not contain SYN, then drop it. 1465 * Otherwise this is an acceptable SYN segment 1466 * initialize tp->rcv_nxt and tp->irs 1467 * if seg contains ack then advance tp->snd_una 1468 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1469 * arrange for segment to be acked (eventually) 1470 * continue processing rest of data/controls, beginning with URG 1471 */ 1472 case TCPS_SYN_SENT: 1473 if ((thflags & TH_ACK) && 1474 (SEQ_LEQ(th->th_ack, tp->iss) || 1475 SEQ_GT(th->th_ack, tp->snd_max))) { 1476 rstreason = BANDLIM_UNLIMITED; 1477 goto dropwithreset; 1478 } 1479 if (thflags & TH_RST) { 1480 if (thflags & TH_ACK) { 1481 KASSERT(headlocked, ("tcp_input: after_listen" 1482 ": tcp_drop.2: head not locked")); 1483 tp = tcp_drop(tp, ECONNREFUSED); 1484 } 1485 goto drop; 1486 } 1487 if ((thflags & TH_SYN) == 0) 1488 goto drop; 1489 1490 tp->irs = th->th_seq; 1491 tcp_rcvseqinit(tp); 1492 if (thflags & TH_ACK) { 1493 tcpstat.tcps_connects++; 1494 soisconnected(so); 1495#ifdef MAC 1496 SOCK_LOCK(so); 1497 mac_set_socket_peer_from_mbuf(m, so); 1498 SOCK_UNLOCK(so); 1499#endif 1500 /* Do window scaling on this connection? */ 1501 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1502 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1503 tp->rcv_scale = tp->request_r_scale; 1504 } 1505 tp->rcv_adv += tp->rcv_wnd; 1506 tp->snd_una++; /* SYN is acked */ 1507 /* 1508 * If there's data, delay ACK; if there's also a FIN 1509 * ACKNOW will be turned on later. 1510 */ 1511 if (DELAY_ACK(tp) && tlen != 0) 1512 callout_reset(tp->tt_delack, tcp_delacktime, 1513 tcp_timer_delack, tp); 1514 else 1515 tp->t_flags |= TF_ACKNOW; 1516 /* 1517 * Received <SYN,ACK> in SYN_SENT[*] state. 1518 * Transitions: 1519 * SYN_SENT --> ESTABLISHED 1520 * SYN_SENT* --> FIN_WAIT_1 1521 */ 1522 tp->t_starttime = ticks; 1523 if (tp->t_flags & TF_NEEDFIN) { 1524 tp->t_state = TCPS_FIN_WAIT_1; 1525 tp->t_flags &= ~TF_NEEDFIN; 1526 thflags &= ~TH_SYN; 1527 } else { 1528 tp->t_state = TCPS_ESTABLISHED; 1529 callout_reset(tp->tt_keep, tcp_keepidle, 1530 tcp_timer_keep, tp); 1531 } 1532 } else { 1533 /* 1534 * Received initial SYN in SYN-SENT[*] state => 1535 * simultaneous open. If segment contains CC option 1536 * and there is a cached CC, apply TAO test. 1537 * If it succeeds, connection is * half-synchronized. 1538 * Otherwise, do 3-way handshake: 1539 * SYN-SENT -> SYN-RECEIVED 1540 * SYN-SENT* -> SYN-RECEIVED* 1541 * If there was no CC option, clear cached CC value. 1542 */ 1543 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1544 callout_stop(tp->tt_rexmt); 1545 tp->t_state = TCPS_SYN_RECEIVED; 1546 } 1547 1548#if 0 /* T/TCP */ 1549trimthenstep6: 1550#endif 1551 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1552 "locked")); 1553 INP_LOCK_ASSERT(inp); 1554 1555 /* 1556 * Advance th->th_seq to correspond to first data byte. 1557 * If data, trim to stay within window, 1558 * dropping FIN if necessary. 1559 */ 1560 th->th_seq++; 1561 if (tlen > tp->rcv_wnd) { 1562 todrop = tlen - tp->rcv_wnd; 1563 m_adj(m, -todrop); 1564 tlen = tp->rcv_wnd; 1565 thflags &= ~TH_FIN; 1566 tcpstat.tcps_rcvpackafterwin++; 1567 tcpstat.tcps_rcvbyteafterwin += todrop; 1568 } 1569 tp->snd_wl1 = th->th_seq - 1; 1570 tp->rcv_up = th->th_seq; 1571 /* 1572 * Client side of transaction: already sent SYN and data. 1573 * If the remote host used T/TCP to validate the SYN, 1574 * our data will be ACK'd; if so, enter normal data segment 1575 * processing in the middle of step 5, ack processing. 1576 * Otherwise, goto step 6. 1577 */ 1578 if (thflags & TH_ACK) 1579 goto process_ACK; 1580 1581 goto step6; 1582 1583 /* 1584 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1585 * do normal processing. 1586 * 1587 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1588 */ 1589 case TCPS_LAST_ACK: 1590 case TCPS_CLOSING: 1591 case TCPS_TIME_WAIT: 1592 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1593 break; /* continue normal processing */ 1594 } 1595 1596 /* 1597 * States other than LISTEN or SYN_SENT. 1598 * First check the RST flag and sequence number since reset segments 1599 * are exempt from the timestamp and connection count tests. This 1600 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1601 * below which allowed reset segments in half the sequence space 1602 * to fall though and be processed (which gives forged reset 1603 * segments with a random sequence number a 50 percent chance of 1604 * killing a connection). 1605 * Then check timestamp, if present. 1606 * Then check the connection count, if present. 1607 * Then check that at least some bytes of segment are within 1608 * receive window. If segment begins before rcv_nxt, 1609 * drop leading data (and SYN); if nothing left, just ack. 1610 * 1611 * 1612 * If the RST bit is set, check the sequence number to see 1613 * if this is a valid reset segment. 1614 * RFC 793 page 37: 1615 * In all states except SYN-SENT, all reset (RST) segments 1616 * are validated by checking their SEQ-fields. A reset is 1617 * valid if its sequence number is in the window. 1618 * Note: this does not take into account delayed ACKs, so 1619 * we should test against last_ack_sent instead of rcv_nxt. 1620 * The sequence number in the reset segment is normally an 1621 * echo of our outgoing acknowlegement numbers, but some hosts 1622 * send a reset with the sequence number at the rightmost edge 1623 * of our receive window, and we have to handle this case. 1624 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1625 * that brute force RST attacks are possible. To combat this, 1626 * we use a much stricter check while in the ESTABLISHED state, 1627 * only accepting RSTs where the sequence number is equal to 1628 * last_ack_sent. In all other states (the states in which a 1629 * RST is more likely), the more permissive check is used. 1630 * If we have multiple segments in flight, the intial reset 1631 * segment sequence numbers will be to the left of last_ack_sent, 1632 * but they will eventually catch up. 1633 * In any case, it never made sense to trim reset segments to 1634 * fit the receive window since RFC 1122 says: 1635 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1636 * 1637 * A TCP SHOULD allow a received RST segment to include data. 1638 * 1639 * DISCUSSION 1640 * It has been suggested that a RST segment could contain 1641 * ASCII text that encoded and explained the cause of the 1642 * RST. No standard has yet been established for such 1643 * data. 1644 * 1645 * If the reset segment passes the sequence number test examine 1646 * the state: 1647 * SYN_RECEIVED STATE: 1648 * If passive open, return to LISTEN state. 1649 * If active open, inform user that connection was refused. 1650 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1651 * Inform user that connection was reset, and close tcb. 1652 * CLOSING, LAST_ACK STATES: 1653 * Close the tcb. 1654 * TIME_WAIT STATE: 1655 * Drop the segment - see Stevens, vol. 2, p. 964 and 1656 * RFC 1337. 1657 */ 1658 if (thflags & TH_RST) { 1659 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1660 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1661 switch (tp->t_state) { 1662 1663 case TCPS_SYN_RECEIVED: 1664 so->so_error = ECONNREFUSED; 1665 goto close; 1666 1667 case TCPS_ESTABLISHED: 1668 if (tcp_insecure_rst == 0 && 1669 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && 1670 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && 1671 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1672 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { 1673 tcpstat.tcps_badrst++; 1674 goto drop; 1675 } 1676 case TCPS_FIN_WAIT_1: 1677 case TCPS_FIN_WAIT_2: 1678 case TCPS_CLOSE_WAIT: 1679 so->so_error = ECONNRESET; 1680 close: 1681 tp->t_state = TCPS_CLOSED; 1682 tcpstat.tcps_drops++; 1683 KASSERT(headlocked, ("tcp_input: " 1684 "trimthenstep6: tcp_close: head not " 1685 "locked")); 1686 tp = tcp_close(tp); 1687 break; 1688 1689 case TCPS_CLOSING: 1690 case TCPS_LAST_ACK: 1691 KASSERT(headlocked, ("trimthenstep6: " 1692 "tcp_close.2: head not locked")); 1693 tp = tcp_close(tp); 1694 break; 1695 1696 case TCPS_TIME_WAIT: 1697 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1698 ("timewait")); 1699 break; 1700 } 1701 } 1702 goto drop; 1703 } 1704 1705 /* 1706 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1707 * and it's less than ts_recent, drop it. 1708 */ 1709 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1710 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1711 1712 /* Check to see if ts_recent is over 24 days old. */ 1713 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1714 /* 1715 * Invalidate ts_recent. If this segment updates 1716 * ts_recent, the age will be reset later and ts_recent 1717 * will get a valid value. If it does not, setting 1718 * ts_recent to zero will at least satisfy the 1719 * requirement that zero be placed in the timestamp 1720 * echo reply when ts_recent isn't valid. The 1721 * age isn't reset until we get a valid ts_recent 1722 * because we don't want out-of-order segments to be 1723 * dropped when ts_recent is old. 1724 */ 1725 tp->ts_recent = 0; 1726 } else { 1727 tcpstat.tcps_rcvduppack++; 1728 tcpstat.tcps_rcvdupbyte += tlen; 1729 tcpstat.tcps_pawsdrop++; 1730 if (tlen) 1731 goto dropafterack; 1732 goto drop; 1733 } 1734 } 1735 1736 /* 1737 * In the SYN-RECEIVED state, validate that the packet belongs to 1738 * this connection before trimming the data to fit the receive 1739 * window. Check the sequence number versus IRS since we know 1740 * the sequence numbers haven't wrapped. This is a partial fix 1741 * for the "LAND" DoS attack. 1742 */ 1743 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1744 rstreason = BANDLIM_RST_OPENPORT; 1745 goto dropwithreset; 1746 } 1747 1748 todrop = tp->rcv_nxt - th->th_seq; 1749 if (todrop > 0) { 1750 if (thflags & TH_SYN) { 1751 thflags &= ~TH_SYN; 1752 th->th_seq++; 1753 if (th->th_urp > 1) 1754 th->th_urp--; 1755 else 1756 thflags &= ~TH_URG; 1757 todrop--; 1758 } 1759 /* 1760 * Following if statement from Stevens, vol. 2, p. 960. 1761 */ 1762 if (todrop > tlen 1763 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1764 /* 1765 * Any valid FIN must be to the left of the window. 1766 * At this point the FIN must be a duplicate or out 1767 * of sequence; drop it. 1768 */ 1769 thflags &= ~TH_FIN; 1770 1771 /* 1772 * Send an ACK to resynchronize and drop any data. 1773 * But keep on processing for RST or ACK. 1774 */ 1775 tp->t_flags |= TF_ACKNOW; 1776 todrop = tlen; 1777 tcpstat.tcps_rcvduppack++; 1778 tcpstat.tcps_rcvdupbyte += todrop; 1779 } else { 1780 tcpstat.tcps_rcvpartduppack++; 1781 tcpstat.tcps_rcvpartdupbyte += todrop; 1782 } 1783 drop_hdrlen += todrop; /* drop from the top afterwards */ 1784 th->th_seq += todrop; 1785 tlen -= todrop; 1786 if (th->th_urp > todrop) 1787 th->th_urp -= todrop; 1788 else { 1789 thflags &= ~TH_URG; 1790 th->th_urp = 0; 1791 } 1792 } 1793 1794 /* 1795 * If new data are received on a connection after the 1796 * user processes are gone, then RST the other end. 1797 */ 1798 if ((so->so_state & SS_NOFDREF) && 1799 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1800 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1801 "locked")); 1802 tp = tcp_close(tp); 1803 tcpstat.tcps_rcvafterclose++; 1804 rstreason = BANDLIM_UNLIMITED; 1805 goto dropwithreset; 1806 } 1807 1808 /* 1809 * If segment ends after window, drop trailing data 1810 * (and PUSH and FIN); if nothing left, just ACK. 1811 */ 1812 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1813 if (todrop > 0) { 1814 tcpstat.tcps_rcvpackafterwin++; 1815 if (todrop >= tlen) { 1816 tcpstat.tcps_rcvbyteafterwin += tlen; 1817 /* 1818 * If a new connection request is received 1819 * while in TIME_WAIT, drop the old connection 1820 * and start over if the sequence numbers 1821 * are above the previous ones. 1822 */ 1823 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1824 if (thflags & TH_SYN && 1825 tp->t_state == TCPS_TIME_WAIT && 1826 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1827 KASSERT(headlocked, ("trimthenstep6: " 1828 "tcp_close.4: head not locked")); 1829 tp = tcp_close(tp); 1830 goto findpcb; 1831 } 1832 /* 1833 * If window is closed can only take segments at 1834 * window edge, and have to drop data and PUSH from 1835 * incoming segments. Continue processing, but 1836 * remember to ack. Otherwise, drop segment 1837 * and ack. 1838 */ 1839 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1840 tp->t_flags |= TF_ACKNOW; 1841 tcpstat.tcps_rcvwinprobe++; 1842 } else 1843 goto dropafterack; 1844 } else 1845 tcpstat.tcps_rcvbyteafterwin += todrop; 1846 m_adj(m, -todrop); 1847 tlen -= todrop; 1848 thflags &= ~(TH_PUSH|TH_FIN); 1849 } 1850 1851 /* 1852 * If last ACK falls within this segment's sequence numbers, 1853 * record its timestamp. 1854 * NOTE: 1855 * 1) That the test incorporates suggestions from the latest 1856 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1857 * 2) That updating only on newer timestamps interferes with 1858 * our earlier PAWS tests, so this check should be solely 1859 * predicated on the sequence space of this segment. 1860 * 3) That we modify the segment boundary check to be 1861 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1862 * instead of RFC1323's 1863 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1864 * This modified check allows us to overcome RFC1323's 1865 * limitations as described in Stevens TCP/IP Illustrated 1866 * Vol. 2 p.869. In such cases, we can still calculate the 1867 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1868 */ 1869 if ((to.to_flags & TOF_TS) != 0 && 1870 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1871 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1872 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1873 tp->ts_recent_age = ticks; 1874 tp->ts_recent = to.to_tsval; 1875 } 1876 1877 /* 1878 * If a SYN is in the window, then this is an 1879 * error and we send an RST and drop the connection. 1880 */ 1881 if (thflags & TH_SYN) { 1882 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1883 "head not locked")); 1884 tp = tcp_drop(tp, ECONNRESET); 1885 rstreason = BANDLIM_UNLIMITED; 1886 goto drop; 1887 } 1888 1889 /* 1890 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1891 * flag is on (half-synchronized state), then queue data for 1892 * later processing; else drop segment and return. 1893 */ 1894 if ((thflags & TH_ACK) == 0) { 1895 if (tp->t_state == TCPS_SYN_RECEIVED || 1896 (tp->t_flags & TF_NEEDSYN)) 1897 goto step6; 1898 else if (tp->t_flags & TF_ACKNOW) 1899 goto dropafterack; 1900 else 1901 goto drop; 1902 } 1903 1904 /* 1905 * Ack processing. 1906 */ 1907 switch (tp->t_state) { 1908 1909 /* 1910 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1911 * ESTABLISHED state and continue processing. 1912 * The ACK was checked above. 1913 */ 1914 case TCPS_SYN_RECEIVED: 1915 1916 tcpstat.tcps_connects++; 1917 soisconnected(so); 1918 /* Do window scaling? */ 1919 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1920 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1921 tp->rcv_scale = tp->request_r_scale; 1922 tp->snd_wnd = tiwin; 1923 } 1924 /* 1925 * Make transitions: 1926 * SYN-RECEIVED -> ESTABLISHED 1927 * SYN-RECEIVED* -> FIN-WAIT-1 1928 */ 1929 tp->t_starttime = ticks; 1930 if (tp->t_flags & TF_NEEDFIN) { 1931 tp->t_state = TCPS_FIN_WAIT_1; 1932 tp->t_flags &= ~TF_NEEDFIN; 1933 } else { 1934 tp->t_state = TCPS_ESTABLISHED; 1935 callout_reset(tp->tt_keep, tcp_keepidle, 1936 tcp_timer_keep, tp); 1937 } 1938 /* 1939 * If segment contains data or ACK, will call tcp_reass() 1940 * later; if not, do so now to pass queued data to user. 1941 */ 1942 if (tlen == 0 && (thflags & TH_FIN) == 0) 1943 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1944 (struct mbuf *)0); 1945 tp->snd_wl1 = th->th_seq - 1; 1946 /* FALLTHROUGH */ 1947 1948 /* 1949 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1950 * ACKs. If the ack is in the range 1951 * tp->snd_una < th->th_ack <= tp->snd_max 1952 * then advance tp->snd_una to th->th_ack and drop 1953 * data from the retransmission queue. If this ACK reflects 1954 * more up to date window information we update our window information. 1955 */ 1956 case TCPS_ESTABLISHED: 1957 case TCPS_FIN_WAIT_1: 1958 case TCPS_FIN_WAIT_2: 1959 case TCPS_CLOSE_WAIT: 1960 case TCPS_CLOSING: 1961 case TCPS_LAST_ACK: 1962 case TCPS_TIME_WAIT: 1963 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1964 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1965 tcpstat.tcps_rcvacktoomuch++; 1966 goto dropafterack; 1967 } 1968 if (tp->sack_enable && 1969 (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) 1970 tcp_sack_doack(tp, &to, th->th_ack); 1971 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1972 if (tlen == 0 && tiwin == tp->snd_wnd) { 1973 tcpstat.tcps_rcvdupack++; 1974 /* 1975 * If we have outstanding data (other than 1976 * a window probe), this is a completely 1977 * duplicate ack (ie, window info didn't 1978 * change), the ack is the biggest we've 1979 * seen and we've seen exactly our rexmt 1980 * threshhold of them, assume a packet 1981 * has been dropped and retransmit it. 1982 * Kludge snd_nxt & the congestion 1983 * window so we send only this one 1984 * packet. 1985 * 1986 * We know we're losing at the current 1987 * window size so do congestion avoidance 1988 * (set ssthresh to half the current window 1989 * and pull our congestion window back to 1990 * the new ssthresh). 1991 * 1992 * Dup acks mean that packets have left the 1993 * network (they're now cached at the receiver) 1994 * so bump cwnd by the amount in the receiver 1995 * to keep a constant cwnd packets in the 1996 * network. 1997 */ 1998 if (!callout_active(tp->tt_rexmt) || 1999 th->th_ack != tp->snd_una) 2000 tp->t_dupacks = 0; 2001 else if (++tp->t_dupacks > tcprexmtthresh || 2002 ((tcp_do_newreno || tp->sack_enable) && 2003 IN_FASTRECOVERY(tp))) { 2004 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 2005 int awnd; 2006 2007 /* 2008 * Compute the amount of data in flight first. 2009 * We can inject new data into the pipe iff 2010 * we have less than 1/2 the original window's 2011 * worth of data in flight. 2012 */ 2013 awnd = (tp->snd_nxt - tp->snd_fack) + 2014 tp->sackhint.sack_bytes_rexmit; 2015 if (awnd < tp->snd_ssthresh) { 2016 tp->snd_cwnd += tp->t_maxseg; 2017 if (tp->snd_cwnd > tp->snd_ssthresh) 2018 tp->snd_cwnd = tp->snd_ssthresh; 2019 } 2020 } else 2021 tp->snd_cwnd += tp->t_maxseg; 2022 (void) tcp_output(tp); 2023 goto drop; 2024 } else if (tp->t_dupacks == tcprexmtthresh) { 2025 tcp_seq onxt = tp->snd_nxt; 2026 u_int win; 2027 2028 /* 2029 * If we're doing sack, check to 2030 * see if we're already in sack 2031 * recovery. If we're not doing sack, 2032 * check to see if we're in newreno 2033 * recovery. 2034 */ 2035 if (tp->sack_enable) { 2036 if (IN_FASTRECOVERY(tp)) { 2037 tp->t_dupacks = 0; 2038 break; 2039 } 2040 } else if (tcp_do_newreno) { 2041 if (SEQ_LEQ(th->th_ack, 2042 tp->snd_recover)) { 2043 tp->t_dupacks = 0; 2044 break; 2045 } 2046 } 2047 win = min(tp->snd_wnd, tp->snd_cwnd) / 2048 2 / tp->t_maxseg; 2049 if (win < 2) 2050 win = 2; 2051 tp->snd_ssthresh = win * tp->t_maxseg; 2052 ENTER_FASTRECOVERY(tp); 2053 tp->snd_recover = tp->snd_max; 2054 callout_stop(tp->tt_rexmt); 2055 tp->t_rtttime = 0; 2056 if (tp->sack_enable) { 2057 tcpstat.tcps_sack_recovery_episode++; 2058 tp->sack_newdata = tp->snd_nxt; 2059 tp->snd_cwnd = tp->t_maxseg; 2060 (void) tcp_output(tp); 2061 goto drop; 2062 } 2063 tp->snd_nxt = th->th_ack; 2064 tp->snd_cwnd = tp->t_maxseg; 2065 (void) tcp_output(tp); 2066 KASSERT(tp->snd_limited <= 2, 2067 ("tp->snd_limited too big")); 2068 tp->snd_cwnd = tp->snd_ssthresh + 2069 tp->t_maxseg * 2070 (tp->t_dupacks - tp->snd_limited); 2071 if (SEQ_GT(onxt, tp->snd_nxt)) 2072 tp->snd_nxt = onxt; 2073 goto drop; 2074 } else if (tcp_do_rfc3042) { 2075 u_long oldcwnd = tp->snd_cwnd; 2076 tcp_seq oldsndmax = tp->snd_max; 2077 u_int sent; 2078 2079 KASSERT(tp->t_dupacks == 1 || 2080 tp->t_dupacks == 2, 2081 ("dupacks not 1 or 2")); 2082 if (tp->t_dupacks == 1) 2083 tp->snd_limited = 0; 2084 tp->snd_cwnd = 2085 (tp->snd_nxt - tp->snd_una) + 2086 (tp->t_dupacks - tp->snd_limited) * 2087 tp->t_maxseg; 2088 (void) tcp_output(tp); 2089 sent = tp->snd_max - oldsndmax; 2090 if (sent > tp->t_maxseg) { 2091 KASSERT((tp->t_dupacks == 2 && 2092 tp->snd_limited == 0) || 2093 (sent == tp->t_maxseg + 1 && 2094 tp->t_flags & TF_SENTFIN), 2095 ("sent too much")); 2096 tp->snd_limited = 2; 2097 } else if (sent > 0) 2098 ++tp->snd_limited; 2099 tp->snd_cwnd = oldcwnd; 2100 goto drop; 2101 } 2102 } else 2103 tp->t_dupacks = 0; 2104 break; 2105 } 2106 2107 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2108 2109 /* 2110 * If the congestion window was inflated to account 2111 * for the other side's cached packets, retract it. 2112 */ 2113 if (tcp_do_newreno || tp->sack_enable) { 2114 if (IN_FASTRECOVERY(tp)) { 2115 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2116 if (tp->sack_enable) 2117 tcp_sack_partialack(tp, th); 2118 else 2119 tcp_newreno_partial_ack(tp, th); 2120 } else { 2121 /* 2122 * Out of fast recovery. 2123 * Window inflation should have left us 2124 * with approximately snd_ssthresh 2125 * outstanding data. 2126 * But in case we would be inclined to 2127 * send a burst, better to do it via 2128 * the slow start mechanism. 2129 */ 2130 if (SEQ_GT(th->th_ack + 2131 tp->snd_ssthresh, 2132 tp->snd_max)) 2133 tp->snd_cwnd = tp->snd_max - 2134 th->th_ack + 2135 tp->t_maxseg; 2136 else 2137 tp->snd_cwnd = tp->snd_ssthresh; 2138 } 2139 } 2140 } else { 2141 if (tp->t_dupacks >= tcprexmtthresh && 2142 tp->snd_cwnd > tp->snd_ssthresh) 2143 tp->snd_cwnd = tp->snd_ssthresh; 2144 } 2145 tp->t_dupacks = 0; 2146 /* 2147 * If we reach this point, ACK is not a duplicate, 2148 * i.e., it ACKs something we sent. 2149 */ 2150 if (tp->t_flags & TF_NEEDSYN) { 2151 /* 2152 * T/TCP: Connection was half-synchronized, and our 2153 * SYN has been ACK'd (so connection is now fully 2154 * synchronized). Go to non-starred state, 2155 * increment snd_una for ACK of SYN, and check if 2156 * we can do window scaling. 2157 */ 2158 tp->t_flags &= ~TF_NEEDSYN; 2159 tp->snd_una++; 2160 /* Do window scaling? */ 2161 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2162 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2163 tp->rcv_scale = tp->request_r_scale; 2164 /* Send window already scaled. */ 2165 } 2166 } 2167 2168process_ACK: 2169 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2170 "locked")); 2171 INP_LOCK_ASSERT(inp); 2172 2173 acked = th->th_ack - tp->snd_una; 2174 tcpstat.tcps_rcvackpack++; 2175 tcpstat.tcps_rcvackbyte += acked; 2176 2177 /* 2178 * If we just performed our first retransmit, and the ACK 2179 * arrives within our recovery window, then it was a mistake 2180 * to do the retransmit in the first place. Recover our 2181 * original cwnd and ssthresh, and proceed to transmit where 2182 * we left off. 2183 */ 2184 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2185 ++tcpstat.tcps_sndrexmitbad; 2186 tp->snd_cwnd = tp->snd_cwnd_prev; 2187 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2188 tp->snd_recover = tp->snd_recover_prev; 2189 if (tp->t_flags & TF_WASFRECOVERY) 2190 ENTER_FASTRECOVERY(tp); 2191 tp->snd_nxt = tp->snd_max; 2192 tp->t_badrxtwin = 0; /* XXX probably not required */ 2193 } 2194 2195 /* 2196 * If we have a timestamp reply, update smoothed 2197 * round trip time. If no timestamp is present but 2198 * transmit timer is running and timed sequence 2199 * number was acked, update smoothed round trip time. 2200 * Since we now have an rtt measurement, cancel the 2201 * timer backoff (cf., Phil Karn's retransmit alg.). 2202 * Recompute the initial retransmit timer. 2203 * 2204 * Some boxes send broken timestamp replies 2205 * during the SYN+ACK phase, ignore 2206 * timestamps of 0 or we could calculate a 2207 * huge RTT and blow up the retransmit timer. 2208 */ 2209 if ((to.to_flags & TOF_TS) != 0 && 2210 to.to_tsecr) { 2211 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2212 tp->t_rttlow = ticks - to.to_tsecr; 2213 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2214 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2215 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2216 tp->t_rttlow = ticks - tp->t_rtttime; 2217 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2218 } 2219 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2220 2221 /* 2222 * If all outstanding data is acked, stop retransmit 2223 * timer and remember to restart (more output or persist). 2224 * If there is more data to be acked, restart retransmit 2225 * timer, using current (possibly backed-off) value. 2226 */ 2227 if (th->th_ack == tp->snd_max) { 2228 callout_stop(tp->tt_rexmt); 2229 needoutput = 1; 2230 } else if (!callout_active(tp->tt_persist)) 2231 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2232 tcp_timer_rexmt, tp); 2233 2234 /* 2235 * If no data (only SYN) was ACK'd, 2236 * skip rest of ACK processing. 2237 */ 2238 if (acked == 0) 2239 goto step6; 2240 2241 /* 2242 * When new data is acked, open the congestion window. 2243 * If the window gives us less than ssthresh packets 2244 * in flight, open exponentially (maxseg per packet). 2245 * Otherwise open linearly: maxseg per window 2246 * (maxseg^2 / cwnd per packet). 2247 */ 2248 if ((!tcp_do_newreno && !tp->sack_enable) || 2249 !IN_FASTRECOVERY(tp)) { 2250 register u_int cw = tp->snd_cwnd; 2251 register u_int incr = tp->t_maxseg; 2252 if (cw > tp->snd_ssthresh) 2253 incr = incr * incr / cw; 2254 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2255 } 2256 SOCKBUF_LOCK(&so->so_snd); 2257 if (acked > so->so_snd.sb_cc) { 2258 tp->snd_wnd -= so->so_snd.sb_cc; 2259 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2260 ourfinisacked = 1; 2261 } else { 2262 sbdrop_locked(&so->so_snd, acked); 2263 tp->snd_wnd -= acked; 2264 ourfinisacked = 0; 2265 } 2266 sowwakeup_locked(so); 2267 /* detect una wraparound */ 2268 if ((tcp_do_newreno || tp->sack_enable) && 2269 !IN_FASTRECOVERY(tp) && 2270 SEQ_GT(tp->snd_una, tp->snd_recover) && 2271 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2272 tp->snd_recover = th->th_ack - 1; 2273 if ((tcp_do_newreno || tp->sack_enable) && 2274 IN_FASTRECOVERY(tp) && 2275 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2276 EXIT_FASTRECOVERY(tp); 2277 tp->snd_una = th->th_ack; 2278 if (tp->sack_enable) { 2279 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2280 tp->snd_recover = tp->snd_una; 2281 } 2282 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2283 tp->snd_nxt = tp->snd_una; 2284 2285 switch (tp->t_state) { 2286 2287 /* 2288 * In FIN_WAIT_1 STATE in addition to the processing 2289 * for the ESTABLISHED state if our FIN is now acknowledged 2290 * then enter FIN_WAIT_2. 2291 */ 2292 case TCPS_FIN_WAIT_1: 2293 if (ourfinisacked) { 2294 /* 2295 * If we can't receive any more 2296 * data, then closing user can proceed. 2297 * Starting the timer is contrary to the 2298 * specification, but if we don't get a FIN 2299 * we'll hang forever. 2300 */ 2301 /* XXXjl 2302 * we should release the tp also, and use a 2303 * compressed state. 2304 */ 2305 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2306 int timeout; 2307 2308 soisdisconnected(so); 2309 timeout = (tcp_fast_finwait2_recycle) ? 2310 tcp_finwait2_timeout : tcp_maxidle; 2311 callout_reset(tp->tt_2msl, timeout, 2312 tcp_timer_2msl, tp); 2313 } 2314 tp->t_state = TCPS_FIN_WAIT_2; 2315 } 2316 break; 2317 2318 /* 2319 * In CLOSING STATE in addition to the processing for 2320 * the ESTABLISHED state if the ACK acknowledges our FIN 2321 * then enter the TIME-WAIT state, otherwise ignore 2322 * the segment. 2323 */ 2324 case TCPS_CLOSING: 2325 if (ourfinisacked) { 2326 KASSERT(headlocked, ("tcp_input: process_ACK: " 2327 "head not locked")); 2328 tcp_twstart(tp); 2329 INP_INFO_WUNLOCK(&tcbinfo); 2330 m_freem(m); 2331 return; 2332 } 2333 break; 2334 2335 /* 2336 * In LAST_ACK, we may still be waiting for data to drain 2337 * and/or to be acked, as well as for the ack of our FIN. 2338 * If our FIN is now acknowledged, delete the TCB, 2339 * enter the closed state and return. 2340 */ 2341 case TCPS_LAST_ACK: 2342 if (ourfinisacked) { 2343 KASSERT(headlocked, ("tcp_input: process_ACK:" 2344 " tcp_close: head not locked")); 2345 tp = tcp_close(tp); 2346 goto drop; 2347 } 2348 break; 2349 2350 /* 2351 * In TIME_WAIT state the only thing that should arrive 2352 * is a retransmission of the remote FIN. Acknowledge 2353 * it and restart the finack timer. 2354 */ 2355 case TCPS_TIME_WAIT: 2356 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2357 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2358 tcp_timer_2msl, tp); 2359 goto dropafterack; 2360 } 2361 } 2362 2363step6: 2364 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2365 INP_LOCK_ASSERT(inp); 2366 2367 /* 2368 * Update window information. 2369 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2370 */ 2371 if ((thflags & TH_ACK) && 2372 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2373 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2374 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2375 /* keep track of pure window updates */ 2376 if (tlen == 0 && 2377 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2378 tcpstat.tcps_rcvwinupd++; 2379 tp->snd_wnd = tiwin; 2380 tp->snd_wl1 = th->th_seq; 2381 tp->snd_wl2 = th->th_ack; 2382 if (tp->snd_wnd > tp->max_sndwnd) 2383 tp->max_sndwnd = tp->snd_wnd; 2384 needoutput = 1; 2385 } 2386 2387 /* 2388 * Process segments with URG. 2389 */ 2390 if ((thflags & TH_URG) && th->th_urp && 2391 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2392 /* 2393 * This is a kludge, but if we receive and accept 2394 * random urgent pointers, we'll crash in 2395 * soreceive. It's hard to imagine someone 2396 * actually wanting to send this much urgent data. 2397 */ 2398 SOCKBUF_LOCK(&so->so_rcv); 2399 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2400 th->th_urp = 0; /* XXX */ 2401 thflags &= ~TH_URG; /* XXX */ 2402 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2403 goto dodata; /* XXX */ 2404 } 2405 /* 2406 * If this segment advances the known urgent pointer, 2407 * then mark the data stream. This should not happen 2408 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2409 * a FIN has been received from the remote side. 2410 * In these states we ignore the URG. 2411 * 2412 * According to RFC961 (Assigned Protocols), 2413 * the urgent pointer points to the last octet 2414 * of urgent data. We continue, however, 2415 * to consider it to indicate the first octet 2416 * of data past the urgent section as the original 2417 * spec states (in one of two places). 2418 */ 2419 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2420 tp->rcv_up = th->th_seq + th->th_urp; 2421 so->so_oobmark = so->so_rcv.sb_cc + 2422 (tp->rcv_up - tp->rcv_nxt) - 1; 2423 if (so->so_oobmark == 0) 2424 so->so_rcv.sb_state |= SBS_RCVATMARK; 2425 sohasoutofband(so); 2426 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2427 } 2428 SOCKBUF_UNLOCK(&so->so_rcv); 2429 /* 2430 * Remove out of band data so doesn't get presented to user. 2431 * This can happen independent of advancing the URG pointer, 2432 * but if two URG's are pending at once, some out-of-band 2433 * data may creep in... ick. 2434 */ 2435 if (th->th_urp <= (u_long)tlen && 2436 !(so->so_options & SO_OOBINLINE)) { 2437 /* hdr drop is delayed */ 2438 tcp_pulloutofband(so, th, m, drop_hdrlen); 2439 } 2440 } else { 2441 /* 2442 * If no out of band data is expected, 2443 * pull receive urgent pointer along 2444 * with the receive window. 2445 */ 2446 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2447 tp->rcv_up = tp->rcv_nxt; 2448 } 2449dodata: /* XXX */ 2450 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2451 INP_LOCK_ASSERT(inp); 2452 2453 /* 2454 * Process the segment text, merging it into the TCP sequencing queue, 2455 * and arranging for acknowledgment of receipt if necessary. 2456 * This process logically involves adjusting tp->rcv_wnd as data 2457 * is presented to the user (this happens in tcp_usrreq.c, 2458 * case PRU_RCVD). If a FIN has already been received on this 2459 * connection then we just ignore the text. 2460 */ 2461 if ((tlen || (thflags & TH_FIN)) && 2462 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2463 tcp_seq save_start = th->th_seq; 2464 tcp_seq save_end = th->th_seq + tlen; 2465 m_adj(m, drop_hdrlen); /* delayed header drop */ 2466 /* 2467 * Insert segment which includes th into TCP reassembly queue 2468 * with control block tp. Set thflags to whether reassembly now 2469 * includes a segment with FIN. This handles the common case 2470 * inline (segment is the next to be received on an established 2471 * connection, and the queue is empty), avoiding linkage into 2472 * and removal from the queue and repetition of various 2473 * conversions. 2474 * Set DELACK for segments received in order, but ack 2475 * immediately when segments are out of order (so 2476 * fast retransmit can work). 2477 */ 2478 if (th->th_seq == tp->rcv_nxt && 2479 LIST_EMPTY(&tp->t_segq) && 2480 TCPS_HAVEESTABLISHED(tp->t_state)) { 2481 if (DELAY_ACK(tp)) 2482 tp->t_flags |= TF_DELACK; 2483 else 2484 tp->t_flags |= TF_ACKNOW; 2485 tp->rcv_nxt += tlen; 2486 thflags = th->th_flags & TH_FIN; 2487 tcpstat.tcps_rcvpack++; 2488 tcpstat.tcps_rcvbyte += tlen; 2489 ND6_HINT(tp); 2490 SOCKBUF_LOCK(&so->so_rcv); 2491 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2492 m_freem(m); 2493 else 2494 sbappendstream_locked(&so->so_rcv, m); 2495 sorwakeup_locked(so); 2496 } else { 2497 thflags = tcp_reass(tp, th, &tlen, m); 2498 tp->t_flags |= TF_ACKNOW; 2499 } 2500 if (tlen > 0 && tp->sack_enable) 2501 tcp_update_sack_list(tp, save_start, save_end); 2502 /* 2503 * Note the amount of data that peer has sent into 2504 * our window, in order to estimate the sender's 2505 * buffer size. 2506 */ 2507 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2508 } else { 2509 m_freem(m); 2510 thflags &= ~TH_FIN; 2511 } 2512 2513 /* 2514 * If FIN is received ACK the FIN and let the user know 2515 * that the connection is closing. 2516 */ 2517 if (thflags & TH_FIN) { 2518 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2519 socantrcvmore(so); 2520 /* 2521 * If connection is half-synchronized 2522 * (ie NEEDSYN flag on) then delay ACK, 2523 * so it may be piggybacked when SYN is sent. 2524 * Otherwise, since we received a FIN then no 2525 * more input can be expected, send ACK now. 2526 */ 2527 if (tp->t_flags & TF_NEEDSYN) 2528 tp->t_flags |= TF_DELACK; 2529 else 2530 tp->t_flags |= TF_ACKNOW; 2531 tp->rcv_nxt++; 2532 } 2533 switch (tp->t_state) { 2534 2535 /* 2536 * In SYN_RECEIVED and ESTABLISHED STATES 2537 * enter the CLOSE_WAIT state. 2538 */ 2539 case TCPS_SYN_RECEIVED: 2540 tp->t_starttime = ticks; 2541 /*FALLTHROUGH*/ 2542 case TCPS_ESTABLISHED: 2543 tp->t_state = TCPS_CLOSE_WAIT; 2544 break; 2545 2546 /* 2547 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2548 * enter the CLOSING state. 2549 */ 2550 case TCPS_FIN_WAIT_1: 2551 tp->t_state = TCPS_CLOSING; 2552 break; 2553 2554 /* 2555 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2556 * starting the time-wait timer, turning off the other 2557 * standard timers. 2558 */ 2559 case TCPS_FIN_WAIT_2: 2560 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2561 "TCP_FIN_WAIT_2: head not locked")); 2562 tcp_twstart(tp); 2563 INP_INFO_WUNLOCK(&tcbinfo); 2564 return; 2565 2566 /* 2567 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2568 */ 2569 case TCPS_TIME_WAIT: 2570 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2571 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2572 tcp_timer_2msl, tp); 2573 break; 2574 } 2575 } 2576 INP_INFO_WUNLOCK(&tcbinfo); 2577 headlocked = 0; 2578#ifdef TCPDEBUG 2579 if (so->so_options & SO_DEBUG) 2580 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2581 &tcp_savetcp, 0); 2582#endif 2583 2584 /* 2585 * Return any desired output. 2586 */ 2587 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2588 (void) tcp_output(tp); 2589 2590check_delack: 2591 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2592 INP_LOCK_ASSERT(inp); 2593 if (tp->t_flags & TF_DELACK) { 2594 tp->t_flags &= ~TF_DELACK; 2595 callout_reset(tp->tt_delack, tcp_delacktime, 2596 tcp_timer_delack, tp); 2597 } 2598 INP_UNLOCK(inp); 2599 return; 2600 2601dropafterack: 2602 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2603 /* 2604 * Generate an ACK dropping incoming segment if it occupies 2605 * sequence space, where the ACK reflects our state. 2606 * 2607 * We can now skip the test for the RST flag since all 2608 * paths to this code happen after packets containing 2609 * RST have been dropped. 2610 * 2611 * In the SYN-RECEIVED state, don't send an ACK unless the 2612 * segment we received passes the SYN-RECEIVED ACK test. 2613 * If it fails send a RST. This breaks the loop in the 2614 * "LAND" DoS attack, and also prevents an ACK storm 2615 * between two listening ports that have been sent forged 2616 * SYN segments, each with the source address of the other. 2617 */ 2618 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2619 (SEQ_GT(tp->snd_una, th->th_ack) || 2620 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2621 rstreason = BANDLIM_RST_OPENPORT; 2622 goto dropwithreset; 2623 } 2624#ifdef TCPDEBUG 2625 if (so->so_options & SO_DEBUG) 2626 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2627 &tcp_savetcp, 0); 2628#endif 2629 KASSERT(headlocked, ("headlocked should be 1")); 2630 INP_INFO_WUNLOCK(&tcbinfo); 2631 tp->t_flags |= TF_ACKNOW; 2632 (void) tcp_output(tp); 2633 INP_UNLOCK(inp); 2634 m_freem(m); 2635 return; 2636 2637dropwithreset: 2638 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2639 /* 2640 * Generate a RST, dropping incoming segment. 2641 * Make ACK acceptable to originator of segment. 2642 * Don't bother to respond if destination was broadcast/multicast. 2643 */ 2644 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2645 goto drop; 2646 if (isipv6) { 2647 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2648 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2649 goto drop; 2650 } else { 2651 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2652 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2653 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2654 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2655 goto drop; 2656 } 2657 /* IPv6 anycast check is done at tcp6_input() */ 2658 2659 /* 2660 * Perform bandwidth limiting. 2661 */ 2662 if (badport_bandlim(rstreason) < 0) 2663 goto drop; 2664 2665#ifdef TCPDEBUG 2666 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2667 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2668 &tcp_savetcp, 0); 2669#endif 2670 2671 if (thflags & TH_ACK) 2672 /* mtod() below is safe as long as hdr dropping is delayed */ 2673 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2674 TH_RST); 2675 else { 2676 if (thflags & TH_SYN) 2677 tlen++; 2678 /* mtod() below is safe as long as hdr dropping is delayed */ 2679 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2680 (tcp_seq)0, TH_RST|TH_ACK); 2681 } 2682 2683 if (tp != NULL) 2684 INP_UNLOCK(inp); 2685 if (headlocked) 2686 INP_INFO_WUNLOCK(&tcbinfo); 2687 return; 2688 2689drop: 2690 /* 2691 * Drop space held by incoming segment and return. 2692 */ 2693#ifdef TCPDEBUG 2694 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2695 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2696 &tcp_savetcp, 0); 2697#endif 2698 if (tp != NULL) 2699 INP_UNLOCK(inp); 2700 if (headlocked) 2701 INP_INFO_WUNLOCK(&tcbinfo); 2702 m_freem(m); 2703 return; 2704} 2705 2706/* 2707 * Parse TCP options and place in tcpopt. 2708 */ 2709static void 2710tcp_dooptions(to, cp, cnt, flags) 2711 struct tcpopt *to; 2712 u_char *cp; 2713 int cnt; 2714 int flags; 2715{ 2716 int opt, optlen; 2717 2718 to->to_flags = 0; 2719 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2720 opt = cp[0]; 2721 if (opt == TCPOPT_EOL) 2722 break; 2723 if (opt == TCPOPT_NOP) 2724 optlen = 1; 2725 else { 2726 if (cnt < 2) 2727 break; 2728 optlen = cp[1]; 2729 if (optlen < 2 || optlen > cnt) 2730 break; 2731 } 2732 switch (opt) { 2733 case TCPOPT_MAXSEG: 2734 if (optlen != TCPOLEN_MAXSEG) 2735 continue; 2736 if (!(flags & TO_SYN)) 2737 continue; 2738 to->to_flags |= TOF_MSS; 2739 bcopy((char *)cp + 2, 2740 (char *)&to->to_mss, sizeof(to->to_mss)); 2741 to->to_mss = ntohs(to->to_mss); 2742 break; 2743 case TCPOPT_WINDOW: 2744 if (optlen != TCPOLEN_WINDOW) 2745 continue; 2746 if (!(flags & TO_SYN)) 2747 continue; 2748 to->to_flags |= TOF_SCALE; 2749 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 2750 break; 2751 case TCPOPT_TIMESTAMP: 2752 if (optlen != TCPOLEN_TIMESTAMP) 2753 continue; 2754 to->to_flags |= TOF_TS; 2755 bcopy((char *)cp + 2, 2756 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2757 to->to_tsval = ntohl(to->to_tsval); 2758 bcopy((char *)cp + 6, 2759 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2760 to->to_tsecr = ntohl(to->to_tsecr); 2761 break; 2762#ifdef TCP_SIGNATURE 2763 /* 2764 * XXX In order to reply to a host which has set the 2765 * TCP_SIGNATURE option in its initial SYN, we have to 2766 * record the fact that the option was observed here 2767 * for the syncache code to perform the correct response. 2768 */ 2769 case TCPOPT_SIGNATURE: 2770 if (optlen != TCPOLEN_SIGNATURE) 2771 continue; 2772 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2773 break; 2774#endif 2775 case TCPOPT_SACK_PERMITTED: 2776 if (optlen != TCPOLEN_SACK_PERMITTED) 2777 continue; 2778 if (!(flags & TO_SYN)) 2779 continue; 2780 if (!tcp_do_sack) 2781 continue; 2782 to->to_flags |= TOF_SACK; 2783 break; 2784 case TCPOPT_SACK: 2785 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2786 continue; 2787 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2788 to->to_sacks = cp + 2; 2789 tcpstat.tcps_sack_rcv_blocks++; 2790 break; 2791 default: 2792 continue; 2793 } 2794 } 2795} 2796 2797/* 2798 * Pull out of band byte out of a segment so 2799 * it doesn't appear in the user's data queue. 2800 * It is still reflected in the segment length for 2801 * sequencing purposes. 2802 */ 2803static void 2804tcp_pulloutofband(so, th, m, off) 2805 struct socket *so; 2806 struct tcphdr *th; 2807 register struct mbuf *m; 2808 int off; /* delayed to be droped hdrlen */ 2809{ 2810 int cnt = off + th->th_urp - 1; 2811 2812 while (cnt >= 0) { 2813 if (m->m_len > cnt) { 2814 char *cp = mtod(m, caddr_t) + cnt; 2815 struct tcpcb *tp = sototcpcb(so); 2816 2817 tp->t_iobc = *cp; 2818 tp->t_oobflags |= TCPOOB_HAVEDATA; 2819 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2820 m->m_len--; 2821 if (m->m_flags & M_PKTHDR) 2822 m->m_pkthdr.len--; 2823 return; 2824 } 2825 cnt -= m->m_len; 2826 m = m->m_next; 2827 if (m == 0) 2828 break; 2829 } 2830 panic("tcp_pulloutofband"); 2831} 2832 2833/* 2834 * Collect new round-trip time estimate 2835 * and update averages and current timeout. 2836 */ 2837static void 2838tcp_xmit_timer(tp, rtt) 2839 register struct tcpcb *tp; 2840 int rtt; 2841{ 2842 register int delta; 2843 2844 INP_LOCK_ASSERT(tp->t_inpcb); 2845 2846 tcpstat.tcps_rttupdated++; 2847 tp->t_rttupdated++; 2848 if (tp->t_srtt != 0) { 2849 /* 2850 * srtt is stored as fixed point with 5 bits after the 2851 * binary point (i.e., scaled by 8). The following magic 2852 * is equivalent to the smoothing algorithm in rfc793 with 2853 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2854 * point). Adjust rtt to origin 0. 2855 */ 2856 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2857 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2858 2859 if ((tp->t_srtt += delta) <= 0) 2860 tp->t_srtt = 1; 2861 2862 /* 2863 * We accumulate a smoothed rtt variance (actually, a 2864 * smoothed mean difference), then set the retransmit 2865 * timer to smoothed rtt + 4 times the smoothed variance. 2866 * rttvar is stored as fixed point with 4 bits after the 2867 * binary point (scaled by 16). The following is 2868 * equivalent to rfc793 smoothing with an alpha of .75 2869 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2870 * rfc793's wired-in beta. 2871 */ 2872 if (delta < 0) 2873 delta = -delta; 2874 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2875 if ((tp->t_rttvar += delta) <= 0) 2876 tp->t_rttvar = 1; 2877 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2878 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2879 } else { 2880 /* 2881 * No rtt measurement yet - use the unsmoothed rtt. 2882 * Set the variance to half the rtt (so our first 2883 * retransmit happens at 3*rtt). 2884 */ 2885 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2886 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2887 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2888 } 2889 tp->t_rtttime = 0; 2890 tp->t_rxtshift = 0; 2891 2892 /* 2893 * the retransmit should happen at rtt + 4 * rttvar. 2894 * Because of the way we do the smoothing, srtt and rttvar 2895 * will each average +1/2 tick of bias. When we compute 2896 * the retransmit timer, we want 1/2 tick of rounding and 2897 * 1 extra tick because of +-1/2 tick uncertainty in the 2898 * firing of the timer. The bias will give us exactly the 2899 * 1.5 tick we need. But, because the bias is 2900 * statistical, we have to test that we don't drop below 2901 * the minimum feasible timer (which is 2 ticks). 2902 */ 2903 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2904 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2905 2906 /* 2907 * We received an ack for a packet that wasn't retransmitted; 2908 * it is probably safe to discard any error indications we've 2909 * received recently. This isn't quite right, but close enough 2910 * for now (a route might have failed after we sent a segment, 2911 * and the return path might not be symmetrical). 2912 */ 2913 tp->t_softerror = 0; 2914} 2915 2916/* 2917 * Determine a reasonable value for maxseg size. 2918 * If the route is known, check route for mtu. 2919 * If none, use an mss that can be handled on the outgoing 2920 * interface without forcing IP to fragment; if bigger than 2921 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2922 * to utilize large mbufs. If no route is found, route has no mtu, 2923 * or the destination isn't local, use a default, hopefully conservative 2924 * size (usually 512 or the default IP max size, but no more than the mtu 2925 * of the interface), as we can't discover anything about intervening 2926 * gateways or networks. We also initialize the congestion/slow start 2927 * window to be a single segment if the destination isn't local. 2928 * While looking at the routing entry, we also initialize other path-dependent 2929 * parameters from pre-set or cached values in the routing entry. 2930 * 2931 * Also take into account the space needed for options that we 2932 * send regularly. Make maxseg shorter by that amount to assure 2933 * that we can send maxseg amount of data even when the options 2934 * are present. Store the upper limit of the length of options plus 2935 * data in maxopd. 2936 * 2937 * 2938 * In case of T/TCP, we call this routine during implicit connection 2939 * setup as well (offer = -1), to initialize maxseg from the cached 2940 * MSS of our peer. 2941 * 2942 * NOTE that this routine is only called when we process an incoming 2943 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2944 */ 2945void 2946tcp_mss(tp, offer) 2947 struct tcpcb *tp; 2948 int offer; 2949{ 2950 int rtt, mss; 2951 u_long bufsize; 2952 u_long maxmtu; 2953 struct inpcb *inp = tp->t_inpcb; 2954 struct socket *so; 2955 struct hc_metrics_lite metrics; 2956 int origoffer = offer; 2957 int mtuflags = 0; 2958#ifdef INET6 2959 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2960 size_t min_protoh = isipv6 ? 2961 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2962 sizeof (struct tcpiphdr); 2963#else 2964 const size_t min_protoh = sizeof(struct tcpiphdr); 2965#endif 2966 2967 /* initialize */ 2968#ifdef INET6 2969 if (isipv6) { 2970 maxmtu = tcp_maxmtu6(&inp->inp_inc, &mtuflags); 2971 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2972 } else 2973#endif 2974 { 2975 maxmtu = tcp_maxmtu(&inp->inp_inc, &mtuflags); 2976 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2977 } 2978 so = inp->inp_socket; 2979 2980 /* 2981 * no route to sender, stay with default mss and return 2982 */ 2983 if (maxmtu == 0) 2984 return; 2985 2986 /* what have we got? */ 2987 switch (offer) { 2988 case 0: 2989 /* 2990 * Offer == 0 means that there was no MSS on the SYN 2991 * segment, in this case we use tcp_mssdflt. 2992 */ 2993 offer = 2994#ifdef INET6 2995 isipv6 ? tcp_v6mssdflt : 2996#endif 2997 tcp_mssdflt; 2998 break; 2999 3000 case -1: 3001 /* 3002 * Offer == -1 means that we didn't receive SYN yet. 3003 */ 3004 /* FALLTHROUGH */ 3005 3006 default: 3007 /* 3008 * Prevent DoS attack with too small MSS. Round up 3009 * to at least minmss. 3010 */ 3011 offer = max(offer, tcp_minmss); 3012 /* 3013 * Sanity check: make sure that maxopd will be large 3014 * enough to allow some data on segments even if the 3015 * all the option space is used (40bytes). Otherwise 3016 * funny things may happen in tcp_output. 3017 */ 3018 offer = max(offer, 64); 3019 } 3020 3021 /* 3022 * rmx information is now retrieved from tcp_hostcache 3023 */ 3024 tcp_hc_get(&inp->inp_inc, &metrics); 3025 3026 /* 3027 * if there's a discovered mtu int tcp hostcache, use it 3028 * else, use the link mtu. 3029 */ 3030 if (metrics.rmx_mtu) 3031 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3032 else { 3033#ifdef INET6 3034 if (isipv6) { 3035 mss = maxmtu - min_protoh; 3036 if (!path_mtu_discovery && 3037 !in6_localaddr(&inp->in6p_faddr)) 3038 mss = min(mss, tcp_v6mssdflt); 3039 } else 3040#endif 3041 { 3042 mss = maxmtu - min_protoh; 3043 if (!path_mtu_discovery && 3044 !in_localaddr(inp->inp_faddr)) 3045 mss = min(mss, tcp_mssdflt); 3046 } 3047 } 3048 mss = min(mss, offer); 3049 3050 /* 3051 * maxopd stores the maximum length of data AND options 3052 * in a segment; maxseg is the amount of data in a normal 3053 * segment. We need to store this value (maxopd) apart 3054 * from maxseg, because now every segment carries options 3055 * and thus we normally have somewhat less data in segments. 3056 */ 3057 tp->t_maxopd = mss; 3058 3059 /* 3060 * origoffer==-1 indicates, that no segments were received yet. 3061 * In this case we just guess. 3062 */ 3063 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3064 (origoffer == -1 || 3065 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3066 mss -= TCPOLEN_TSTAMP_APPA; 3067 tp->t_maxseg = mss; 3068 3069#if (MCLBYTES & (MCLBYTES - 1)) == 0 3070 if (mss > MCLBYTES) 3071 mss &= ~(MCLBYTES-1); 3072#else 3073 if (mss > MCLBYTES) 3074 mss = mss / MCLBYTES * MCLBYTES; 3075#endif 3076 tp->t_maxseg = mss; 3077 3078 /* 3079 * If there's a pipesize, change the socket buffer to that size, 3080 * don't change if sb_hiwat is different than default (then it 3081 * has been changed on purpose with setsockopt). 3082 * Make the socket buffers an integral number of mss units; 3083 * if the mss is larger than the socket buffer, decrease the mss. 3084 */ 3085 SOCKBUF_LOCK(&so->so_snd); 3086 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3087 bufsize = metrics.rmx_sendpipe; 3088 else 3089 bufsize = so->so_snd.sb_hiwat; 3090 if (bufsize < mss) 3091 mss = bufsize; 3092 else { 3093 bufsize = roundup(bufsize, mss); 3094 if (bufsize > sb_max) 3095 bufsize = sb_max; 3096 if (bufsize > so->so_snd.sb_hiwat) 3097 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3098 } 3099 SOCKBUF_UNLOCK(&so->so_snd); 3100 tp->t_maxseg = mss; 3101 3102 SOCKBUF_LOCK(&so->so_rcv); 3103 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3104 bufsize = metrics.rmx_recvpipe; 3105 else 3106 bufsize = so->so_rcv.sb_hiwat; 3107 if (bufsize > mss) { 3108 bufsize = roundup(bufsize, mss); 3109 if (bufsize > sb_max) 3110 bufsize = sb_max; 3111 if (bufsize > so->so_rcv.sb_hiwat) 3112 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3113 } 3114 SOCKBUF_UNLOCK(&so->so_rcv); 3115 /* 3116 * While we're here, check the others too 3117 */ 3118 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3119 tp->t_srtt = rtt; 3120 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3121 tcpstat.tcps_usedrtt++; 3122 if (metrics.rmx_rttvar) { 3123 tp->t_rttvar = metrics.rmx_rttvar; 3124 tcpstat.tcps_usedrttvar++; 3125 } else { 3126 /* default variation is +- 1 rtt */ 3127 tp->t_rttvar = 3128 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3129 } 3130 TCPT_RANGESET(tp->t_rxtcur, 3131 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3132 tp->t_rttmin, TCPTV_REXMTMAX); 3133 } 3134 if (metrics.rmx_ssthresh) { 3135 /* 3136 * There's some sort of gateway or interface 3137 * buffer limit on the path. Use this to set 3138 * the slow start threshhold, but set the 3139 * threshold to no less than 2*mss. 3140 */ 3141 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3142 tcpstat.tcps_usedssthresh++; 3143 } 3144 if (metrics.rmx_bandwidth) 3145 tp->snd_bandwidth = metrics.rmx_bandwidth; 3146 3147 /* 3148 * Set the slow-start flight size depending on whether this 3149 * is a local network or not. 3150 * 3151 * Extend this so we cache the cwnd too and retrieve it here. 3152 * Make cwnd even bigger than RFC3390 suggests but only if we 3153 * have previous experience with the remote host. Be careful 3154 * not make cwnd bigger than remote receive window or our own 3155 * send socket buffer. Maybe put some additional upper bound 3156 * on the retrieved cwnd. Should do incremental updates to 3157 * hostcache when cwnd collapses so next connection doesn't 3158 * overloads the path again. 3159 * 3160 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3161 * We currently check only in syncache_socket for that. 3162 */ 3163#define TCP_METRICS_CWND 3164#ifdef TCP_METRICS_CWND 3165 if (metrics.rmx_cwnd) 3166 tp->snd_cwnd = max(mss, 3167 min(metrics.rmx_cwnd / 2, 3168 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3169 else 3170#endif 3171 if (tcp_do_rfc3390) 3172 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3173#ifdef INET6 3174 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3175 (!isipv6 && in_localaddr(inp->inp_faddr))) 3176#else 3177 else if (in_localaddr(inp->inp_faddr)) 3178#endif 3179 tp->snd_cwnd = mss * ss_fltsz_local; 3180 else 3181 tp->snd_cwnd = mss * ss_fltsz; 3182 3183 /* Check the interface for TSO capabilities. */ 3184 if (mtuflags & CSUM_TSO) 3185 tp->t_flags |= TF_TSO; 3186} 3187 3188/* 3189 * Determine the MSS option to send on an outgoing SYN. 3190 */ 3191int 3192tcp_mssopt(inc) 3193 struct in_conninfo *inc; 3194{ 3195 int mss = 0; 3196 u_long maxmtu = 0; 3197 u_long thcmtu = 0; 3198 size_t min_protoh; 3199#ifdef INET6 3200 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3201#endif 3202 3203 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3204 3205#ifdef INET6 3206 if (isipv6) { 3207 mss = tcp_v6mssdflt; 3208 maxmtu = tcp_maxmtu6(inc, NULL); 3209 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3210 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3211 } else 3212#endif 3213 { 3214 mss = tcp_mssdflt; 3215 maxmtu = tcp_maxmtu(inc, NULL); 3216 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3217 min_protoh = sizeof(struct tcpiphdr); 3218 } 3219 if (maxmtu && thcmtu) 3220 mss = min(maxmtu, thcmtu) - min_protoh; 3221 else if (maxmtu || thcmtu) 3222 mss = max(maxmtu, thcmtu) - min_protoh; 3223 3224 return (mss); 3225} 3226 3227 3228/* 3229 * On a partial ack arrives, force the retransmission of the 3230 * next unacknowledged segment. Do not clear tp->t_dupacks. 3231 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3232 * be started again. 3233 */ 3234static void 3235tcp_newreno_partial_ack(tp, th) 3236 struct tcpcb *tp; 3237 struct tcphdr *th; 3238{ 3239 tcp_seq onxt = tp->snd_nxt; 3240 u_long ocwnd = tp->snd_cwnd; 3241 3242 callout_stop(tp->tt_rexmt); 3243 tp->t_rtttime = 0; 3244 tp->snd_nxt = th->th_ack; 3245 /* 3246 * Set snd_cwnd to one segment beyond acknowledged offset. 3247 * (tp->snd_una has not yet been updated when this function is called.) 3248 */ 3249 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3250 tp->t_flags |= TF_ACKNOW; 3251 (void) tcp_output(tp); 3252 tp->snd_cwnd = ocwnd; 3253 if (SEQ_GT(onxt, tp->snd_nxt)) 3254 tp->snd_nxt = onxt; 3255 /* 3256 * Partial window deflation. Relies on fact that tp->snd_una 3257 * not updated yet. 3258 */ 3259 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3260 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3261 else 3262 tp->snd_cwnd = 0; 3263 tp->snd_cwnd += tp->t_maxseg; 3264} 3265 3266/* 3267 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3268 * looking for a pcb in the listen state. Returns 0 otherwise. 3269 */ 3270static int 3271tcp_timewait(inp, to, th, m, tlen) 3272 struct inpcb *inp; 3273 struct tcpopt *to; 3274 struct tcphdr *th; 3275 struct mbuf *m; 3276 int tlen; 3277{ 3278 struct tcptw *tw; 3279 int thflags; 3280 tcp_seq seq; 3281#ifdef INET6 3282 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3283#else 3284 const int isipv6 = 0; 3285#endif 3286 3287 /* tcbinfo lock required for tcp_twclose(), tcp_timer_2msl_reset(). */ 3288 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3289 INP_LOCK_ASSERT(inp); 3290 3291 /* 3292 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 3293 * still present. This is undesirable, but temporarily necessary 3294 * until we work out how to handle inpcb's who's timewait state has 3295 * been removed. 3296 */ 3297 tw = intotw(inp); 3298 if (tw == NULL) 3299 goto drop; 3300 3301 thflags = th->th_flags; 3302 3303 /* 3304 * NOTE: for FIN_WAIT_2 (to be added later), 3305 * must validate sequence number before accepting RST 3306 */ 3307 3308 /* 3309 * If the segment contains RST: 3310 * Drop the segment - see Stevens, vol. 2, p. 964 and 3311 * RFC 1337. 3312 */ 3313 if (thflags & TH_RST) 3314 goto drop; 3315 3316#if 0 3317/* PAWS not needed at the moment */ 3318 /* 3319 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3320 * and it's less than ts_recent, drop it. 3321 */ 3322 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3323 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3324 if ((thflags & TH_ACK) == 0) 3325 goto drop; 3326 goto ack; 3327 } 3328 /* 3329 * ts_recent is never updated because we never accept new segments. 3330 */ 3331#endif 3332 3333 /* 3334 * If a new connection request is received 3335 * while in TIME_WAIT, drop the old connection 3336 * and start over if the sequence numbers 3337 * are above the previous ones. 3338 */ 3339 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3340 tcp_twclose(tw, 0); 3341 return (1); 3342 } 3343 3344 /* 3345 * Drop the the segment if it does not contain an ACK. 3346 */ 3347 if ((thflags & TH_ACK) == 0) 3348 goto drop; 3349 3350 /* 3351 * Reset the 2MSL timer if this is a duplicate FIN. 3352 */ 3353 if (thflags & TH_FIN) { 3354 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3355 if (seq + 1 == tw->rcv_nxt) 3356 tcp_timer_2msl_reset(tw, 1); 3357 } 3358 3359 /* 3360 * Acknowledge the segment if it has data or is not a duplicate ACK. 3361 */ 3362 if (thflags != TH_ACK || tlen != 0 || 3363 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3364 tcp_twrespond(tw, TH_ACK); 3365 goto drop; 3366 3367 /* 3368 * Generate a RST, dropping incoming segment. 3369 * Make ACK acceptable to originator of segment. 3370 * Don't bother to respond if destination was broadcast/multicast. 3371 */ 3372 if (m->m_flags & (M_BCAST|M_MCAST)) 3373 goto drop; 3374 if (isipv6) { 3375 struct ip6_hdr *ip6; 3376 3377 /* IPv6 anycast check is done at tcp6_input() */ 3378 ip6 = mtod(m, struct ip6_hdr *); 3379 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3380 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3381 goto drop; 3382 } else { 3383 struct ip *ip; 3384 3385 ip = mtod(m, struct ip *); 3386 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3387 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3388 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3389 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3390 goto drop; 3391 } 3392 if (thflags & TH_ACK) { 3393 tcp_respond(NULL, 3394 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3395 } else { 3396 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3397 tcp_respond(NULL, 3398 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3399 } 3400 INP_UNLOCK(inp); 3401 return (0); 3402 3403drop: 3404 INP_UNLOCK(inp); 3405 m_freem(m); 3406 return (0); 3407} 3408