tcp_input.c revision 131079
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 131079 2004-06-25 04:11:26Z ps $ 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/mac.h> 45#include <sys/malloc.h> 46#include <sys/mbuf.h> 47#include <sys/proc.h> /* for proc0 declaration */ 48#include <sys/protosw.h> 49#include <sys/signalvar.h> 50#include <sys/socket.h> 51#include <sys/socketvar.h> 52#include <sys/sysctl.h> 53#include <sys/syslog.h> 54#include <sys/systm.h> 55 56#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58#include <vm/uma.h> 59 60#include <net/if.h> 61#include <net/route.h> 62 63#include <netinet/in.h> 64#include <netinet/in_pcb.h> 65#include <netinet/in_systm.h> 66#include <netinet/in_var.h> 67#include <netinet/ip.h> 68#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 69#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70#include <netinet/ip_var.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 100static const int tcprexmtthresh = 3; 101tcp_cc tcp_ccgen; 102 103struct tcpstat tcpstat; 104SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 105 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 106 107static int log_in_vain = 0; 108SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 109 &log_in_vain, 0, "Log all incoming TCP connections"); 110 111static int blackhole = 0; 112SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 113 &blackhole, 0, "Do not send RST when dropping refused connections"); 114 115int tcp_delack_enabled = 1; 116SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 117 &tcp_delack_enabled, 0, 118 "Delay ACK to try and piggyback it onto a data packet"); 119 120#ifdef TCP_DROP_SYNFIN 121static int drop_synfin = 0; 122SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 123 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 124#endif 125 126static int tcp_do_rfc3042 = 1; 127SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 128 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 129 130static int tcp_do_rfc3390 = 1; 131SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 132 &tcp_do_rfc3390, 0, 133 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 134 135SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 136 "TCP Segment Reassembly Queue"); 137 138static int tcp_reass_maxseg = 0; 139SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 140 &tcp_reass_maxseg, 0, 141 "Global maximum number of TCP Segments in Reassembly Queue"); 142 143int tcp_reass_qsize = 0; 144SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 145 &tcp_reass_qsize, 0, 146 "Global number of TCP Segments currently in Reassembly Queue"); 147 148static int tcp_reass_maxqlen = 48; 149SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 150 &tcp_reass_maxqlen, 0, 151 "Maximum number of TCP Segments per individual Reassembly Queue"); 152 153static int tcp_reass_overflows = 0; 154SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 155 &tcp_reass_overflows, 0, 156 "Global number of TCP Segment Reassembly Queue Overflows"); 157 158struct inpcbhead tcb; 159#define tcb6 tcb /* for KAME src sync over BSD*'s */ 160struct inpcbinfo tcbinfo; 161struct mtx *tcbinfo_mtx; 162 163static void tcp_dooptions(struct tcpcb *, struct tcpopt *, u_char *, 164 int, int, struct tcphdr *); 165 166static void tcp_pulloutofband(struct socket *, 167 struct tcphdr *, struct mbuf *, int); 168static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 169 struct mbuf *); 170static void tcp_xmit_timer(struct tcpcb *, int); 171static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 172static int tcp_timewait(struct tcptw *, struct tcpopt *, 173 struct tcphdr *, struct mbuf *, int); 174 175/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 176#ifdef INET6 177#define ND6_HINT(tp) \ 178do { \ 179 if ((tp) && (tp)->t_inpcb && \ 180 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 181 nd6_nud_hint(NULL, NULL, 0); \ 182} while (0) 183#else 184#define ND6_HINT(tp) 185#endif 186 187/* 188 * Indicate whether this ack should be delayed. We can delay the ack if 189 * - there is no delayed ack timer in progress and 190 * - our last ack wasn't a 0-sized window. We never want to delay 191 * the ack that opens up a 0-sized window and 192 * - delayed acks are enabled or 193 * - this is a half-synchronized T/TCP connection. 194 */ 195#define DELAY_ACK(tp) \ 196 ((!callout_active(tp->tt_delack) && \ 197 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 198 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 199 200/* Initialize TCP reassembly queue */ 201uma_zone_t tcp_reass_zone; 202void 203tcp_reass_init() 204{ 205 tcp_reass_maxseg = nmbclusters / 16; 206 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 207 &tcp_reass_maxseg); 208 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 209 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 210 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 211} 212 213static int 214tcp_reass(tp, th, tlenp, m) 215 register struct tcpcb *tp; 216 register struct tcphdr *th; 217 int *tlenp; 218 struct mbuf *m; 219{ 220 struct tseg_qent *q; 221 struct tseg_qent *p = NULL; 222 struct tseg_qent *nq; 223 struct tseg_qent *te = NULL; 224 struct socket *so = tp->t_inpcb->inp_socket; 225 int flags; 226 227 /* 228 * XXX: tcp_reass() is rather inefficient with its data structures 229 * and should be rewritten (see NetBSD for optimizations). While 230 * doing that it should move to its own file tcp_reass.c. 231 */ 232 233 /* 234 * Call with th==0 after become established to 235 * force pre-ESTABLISHED data up to user socket. 236 */ 237 if (th == 0) 238 goto present; 239 240 /* 241 * Limit the number of segments in the reassembly queue to prevent 242 * holding on to too many segments (and thus running out of mbufs). 243 * Make sure to let the missing segment through which caused this 244 * queue. Always keep one global queue entry spare to be able to 245 * process the missing segment. 246 */ 247 if (th->th_seq != tp->rcv_nxt && 248 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 249 tp->t_segqlen >= tcp_reass_maxqlen)) { 250 tcp_reass_overflows++; 251 tcpstat.tcps_rcvmemdrop++; 252 m_freem(m); 253 return (0); 254 } 255 256 /* 257 * Allocate a new queue entry. If we can't, or hit the zone limit 258 * just drop the pkt. 259 */ 260 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 261 if (te == NULL) { 262 tcpstat.tcps_rcvmemdrop++; 263 m_freem(m); 264 return (0); 265 } 266 tp->t_segqlen++; 267 tcp_reass_qsize++; 268 269 /* 270 * Find a segment which begins after this one does. 271 */ 272 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 273 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 274 break; 275 p = q; 276 } 277 278 /* 279 * If there is a preceding segment, it may provide some of 280 * our data already. If so, drop the data from the incoming 281 * segment. If it provides all of our data, drop us. 282 */ 283 if (p != NULL) { 284 register int i; 285 /* conversion to int (in i) handles seq wraparound */ 286 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 287 if (i > 0) { 288 if (i >= *tlenp) { 289 tcpstat.tcps_rcvduppack++; 290 tcpstat.tcps_rcvdupbyte += *tlenp; 291 m_freem(m); 292 uma_zfree(tcp_reass_zone, te); 293 tp->t_segqlen--; 294 tcp_reass_qsize--; 295 /* 296 * Try to present any queued data 297 * at the left window edge to the user. 298 * This is needed after the 3-WHS 299 * completes. 300 */ 301 goto present; /* ??? */ 302 } 303 m_adj(m, i); 304 *tlenp -= i; 305 th->th_seq += i; 306 } 307 } 308 tcpstat.tcps_rcvoopack++; 309 tcpstat.tcps_rcvoobyte += *tlenp; 310 311 /* 312 * While we overlap succeeding segments trim them or, 313 * if they are completely covered, dequeue them. 314 */ 315 while (q) { 316 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 317 if (i <= 0) 318 break; 319 if (i < q->tqe_len) { 320 q->tqe_th->th_seq += i; 321 q->tqe_len -= i; 322 m_adj(q->tqe_m, i); 323 break; 324 } 325 326 nq = LIST_NEXT(q, tqe_q); 327 LIST_REMOVE(q, tqe_q); 328 m_freem(q->tqe_m); 329 uma_zfree(tcp_reass_zone, q); 330 tp->t_segqlen--; 331 tcp_reass_qsize--; 332 q = nq; 333 } 334 335 /* Insert the new segment queue entry into place. */ 336 te->tqe_m = m; 337 te->tqe_th = th; 338 te->tqe_len = *tlenp; 339 340 if (p == NULL) { 341 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 342 } else { 343 LIST_INSERT_AFTER(p, te, tqe_q); 344 } 345 346present: 347 /* 348 * Present data to user, advancing rcv_nxt through 349 * completed sequence space. 350 */ 351 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 352 return (0); 353 q = LIST_FIRST(&tp->t_segq); 354 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 355 return (0); 356 do { 357 tp->rcv_nxt += q->tqe_len; 358 flags = q->tqe_th->th_flags & TH_FIN; 359 nq = LIST_NEXT(q, tqe_q); 360 LIST_REMOVE(q, tqe_q); 361 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 362 m_freem(q->tqe_m); 363 else 364 sbappendstream(&so->so_rcv, q->tqe_m); 365 uma_zfree(tcp_reass_zone, q); 366 tp->t_segqlen--; 367 tcp_reass_qsize--; 368 q = nq; 369 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 370 ND6_HINT(tp); 371 sorwakeup(so); 372 return (flags); 373} 374 375/* 376 * TCP input routine, follows pages 65-76 of the 377 * protocol specification dated September, 1981 very closely. 378 */ 379#ifdef INET6 380int 381tcp6_input(mp, offp, proto) 382 struct mbuf **mp; 383 int *offp, proto; 384{ 385 register struct mbuf *m = *mp; 386 struct in6_ifaddr *ia6; 387 388 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 389 390 /* 391 * draft-itojun-ipv6-tcp-to-anycast 392 * better place to put this in? 393 */ 394 ia6 = ip6_getdstifaddr(m); 395 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 396 struct ip6_hdr *ip6; 397 398 ip6 = mtod(m, struct ip6_hdr *); 399 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 400 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 401 return IPPROTO_DONE; 402 } 403 404 tcp_input(m, *offp); 405 return IPPROTO_DONE; 406} 407#endif 408 409void 410tcp_input(m, off0) 411 register struct mbuf *m; 412 int off0; 413{ 414 register struct tcphdr *th; 415 register struct ip *ip = NULL; 416 register struct ipovly *ipov; 417 register struct inpcb *inp = NULL; 418 u_char *optp = NULL; 419 int optlen = 0; 420 int len, tlen, off; 421 int drop_hdrlen; 422 register struct tcpcb *tp = 0; 423 register int thflags; 424 struct socket *so = 0; 425 int todrop, acked, ourfinisacked, needoutput = 0; 426 u_long tiwin; 427 struct tcpopt to; /* options in this segment */ 428 struct rmxp_tao tao; /* our TAO cache entry */ 429 int headlocked = 0; 430 struct sockaddr_in *next_hop = NULL; 431 int rstreason; /* For badport_bandlim accounting purposes */ 432 433 struct ip6_hdr *ip6 = NULL; 434#ifdef INET6 435 int isipv6; 436#else 437 const int isipv6 = 0; 438#endif 439 440#ifdef TCPDEBUG 441 /* 442 * The size of tcp_saveipgen must be the size of the max ip header, 443 * now IPv6. 444 */ 445 u_char tcp_saveipgen[40]; 446 struct tcphdr tcp_savetcp; 447 short ostate = 0; 448#endif 449 450 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 451 next_hop = m_claim_next(m, PACKET_TAG_IPFORWARD); 452#ifdef INET6 453 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 454#endif 455 bzero(&tao, sizeof(tao)); 456 bzero((char *)&to, sizeof(to)); 457 458 tcpstat.tcps_rcvtotal++; 459 460 if (isipv6) { 461#ifdef INET6 462 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 463 ip6 = mtod(m, struct ip6_hdr *); 464 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 465 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 466 tcpstat.tcps_rcvbadsum++; 467 goto drop; 468 } 469 th = (struct tcphdr *)((caddr_t)ip6 + off0); 470 471 /* 472 * Be proactive about unspecified IPv6 address in source. 473 * As we use all-zero to indicate unbounded/unconnected pcb, 474 * unspecified IPv6 address can be used to confuse us. 475 * 476 * Note that packets with unspecified IPv6 destination is 477 * already dropped in ip6_input. 478 */ 479 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 480 /* XXX stat */ 481 goto drop; 482 } 483#else 484 th = NULL; /* XXX: avoid compiler warning */ 485#endif 486 } else { 487 /* 488 * Get IP and TCP header together in first mbuf. 489 * Note: IP leaves IP header in first mbuf. 490 */ 491 if (off0 > sizeof (struct ip)) { 492 ip_stripoptions(m, (struct mbuf *)0); 493 off0 = sizeof(struct ip); 494 } 495 if (m->m_len < sizeof (struct tcpiphdr)) { 496 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 497 tcpstat.tcps_rcvshort++; 498 return; 499 } 500 } 501 ip = mtod(m, struct ip *); 502 ipov = (struct ipovly *)ip; 503 th = (struct tcphdr *)((caddr_t)ip + off0); 504 tlen = ip->ip_len; 505 506 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 507 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 508 th->th_sum = m->m_pkthdr.csum_data; 509 else 510 th->th_sum = in_pseudo(ip->ip_src.s_addr, 511 ip->ip_dst.s_addr, 512 htonl(m->m_pkthdr.csum_data + 513 ip->ip_len + 514 IPPROTO_TCP)); 515 th->th_sum ^= 0xffff; 516#ifdef TCPDEBUG 517 ipov->ih_len = (u_short)tlen; 518 ipov->ih_len = htons(ipov->ih_len); 519#endif 520 } else { 521 /* 522 * Checksum extended TCP header and data. 523 */ 524 len = sizeof (struct ip) + tlen; 525 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 526 ipov->ih_len = (u_short)tlen; 527 ipov->ih_len = htons(ipov->ih_len); 528 th->th_sum = in_cksum(m, len); 529 } 530 if (th->th_sum) { 531 tcpstat.tcps_rcvbadsum++; 532 goto drop; 533 } 534#ifdef INET6 535 /* Re-initialization for later version check */ 536 ip->ip_v = IPVERSION; 537#endif 538 } 539 540 /* 541 * Check that TCP offset makes sense, 542 * pull out TCP options and adjust length. XXX 543 */ 544 off = th->th_off << 2; 545 if (off < sizeof (struct tcphdr) || off > tlen) { 546 tcpstat.tcps_rcvbadoff++; 547 goto drop; 548 } 549 tlen -= off; /* tlen is used instead of ti->ti_len */ 550 if (off > sizeof (struct tcphdr)) { 551 if (isipv6) { 552#ifdef INET6 553 IP6_EXTHDR_CHECK(m, off0, off, ); 554 ip6 = mtod(m, struct ip6_hdr *); 555 th = (struct tcphdr *)((caddr_t)ip6 + off0); 556#endif 557 } else { 558 if (m->m_len < sizeof(struct ip) + off) { 559 if ((m = m_pullup(m, sizeof (struct ip) + off)) 560 == 0) { 561 tcpstat.tcps_rcvshort++; 562 return; 563 } 564 ip = mtod(m, struct ip *); 565 ipov = (struct ipovly *)ip; 566 th = (struct tcphdr *)((caddr_t)ip + off0); 567 } 568 } 569 optlen = off - sizeof (struct tcphdr); 570 optp = (u_char *)(th + 1); 571 } 572 thflags = th->th_flags; 573 574#ifdef TCP_DROP_SYNFIN 575 /* 576 * If the drop_synfin option is enabled, drop all packets with 577 * both the SYN and FIN bits set. This prevents e.g. nmap from 578 * identifying the TCP/IP stack. 579 * 580 * This is a violation of the TCP specification. 581 */ 582 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 583 goto drop; 584#endif 585 586 /* 587 * Convert TCP protocol specific fields to host format. 588 */ 589 th->th_seq = ntohl(th->th_seq); 590 th->th_ack = ntohl(th->th_ack); 591 th->th_win = ntohs(th->th_win); 592 th->th_urp = ntohs(th->th_urp); 593 594 /* 595 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 596 * until after ip6_savecontrol() is called and before other functions 597 * which don't want those proto headers. 598 * Because ip6_savecontrol() is going to parse the mbuf to 599 * search for data to be passed up to user-land, it wants mbuf 600 * parameters to be unchanged. 601 * XXX: the call of ip6_savecontrol() has been obsoleted based on 602 * latest version of the advanced API (20020110). 603 */ 604 drop_hdrlen = off0 + off; 605 606 /* 607 * Locate pcb for segment. 608 */ 609 INP_INFO_WLOCK(&tcbinfo); 610 headlocked = 1; 611findpcb: 612 /* IPFIREWALL_FORWARD section */ 613 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 614 /* 615 * Transparently forwarded. Pretend to be the destination. 616 * already got one like this? 617 */ 618 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 619 ip->ip_dst, th->th_dport, 620 0, m->m_pkthdr.rcvif); 621 if (!inp) { 622 /* It's new. Try find the ambushing socket. */ 623 inp = in_pcblookup_hash(&tcbinfo, 624 ip->ip_src, th->th_sport, 625 next_hop->sin_addr, 626 next_hop->sin_port ? 627 ntohs(next_hop->sin_port) : 628 th->th_dport, 629 1, m->m_pkthdr.rcvif); 630 } 631 } else { 632 if (isipv6) { 633#ifdef INET6 634 inp = in6_pcblookup_hash(&tcbinfo, 635 &ip6->ip6_src, th->th_sport, 636 &ip6->ip6_dst, th->th_dport, 637 1, m->m_pkthdr.rcvif); 638#endif 639 } else 640 inp = in_pcblookup_hash(&tcbinfo, 641 ip->ip_src, th->th_sport, 642 ip->ip_dst, th->th_dport, 643 1, m->m_pkthdr.rcvif); 644 } 645 646#if defined(IPSEC) || defined(FAST_IPSEC) 647#ifdef INET6 648 if (isipv6) { 649 if (inp != NULL && ipsec6_in_reject(m, inp)) { 650#ifdef IPSEC 651 ipsec6stat.in_polvio++; 652#endif 653 goto drop; 654 } 655 } else 656#endif /* INET6 */ 657 if (inp != NULL && ipsec4_in_reject(m, inp)) { 658#ifdef IPSEC 659 ipsecstat.in_polvio++; 660#endif 661 goto drop; 662 } 663#endif /*IPSEC || FAST_IPSEC*/ 664 665 /* 666 * If the state is CLOSED (i.e., TCB does not exist) then 667 * all data in the incoming segment is discarded. 668 * If the TCB exists but is in CLOSED state, it is embryonic, 669 * but should either do a listen or a connect soon. 670 */ 671 if (inp == NULL) { 672 if (log_in_vain) { 673#ifdef INET6 674 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 675#else 676 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 677#endif 678 679 if (isipv6) { 680#ifdef INET6 681 strcpy(dbuf, "["); 682 strcpy(sbuf, "["); 683 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 684 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 685 strcat(dbuf, "]"); 686 strcat(sbuf, "]"); 687#endif 688 } else { 689 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 690 strcpy(sbuf, inet_ntoa(ip->ip_src)); 691 } 692 switch (log_in_vain) { 693 case 1: 694 if ((thflags & TH_SYN) == 0) 695 break; 696 /* FALLTHROUGH */ 697 case 2: 698 log(LOG_INFO, 699 "Connection attempt to TCP %s:%d " 700 "from %s:%d flags:0x%02x\n", 701 dbuf, ntohs(th->th_dport), sbuf, 702 ntohs(th->th_sport), thflags); 703 break; 704 default: 705 break; 706 } 707 } 708 if (blackhole) { 709 switch (blackhole) { 710 case 1: 711 if (thflags & TH_SYN) 712 goto drop; 713 break; 714 case 2: 715 goto drop; 716 default: 717 goto drop; 718 } 719 } 720 rstreason = BANDLIM_RST_CLOSEDPORT; 721 goto dropwithreset; 722 } 723 INP_LOCK(inp); 724 if (inp->inp_vflag & INP_TIMEWAIT) { 725 /* 726 * The only option of relevance is TOF_CC, and only if 727 * present in a SYN segment. See tcp_timewait(). 728 */ 729 if (thflags & TH_SYN) 730 tcp_dooptions((struct tcpcb *)NULL, &to, optp, optlen, 1, th); 731 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 732 &to, th, m, tlen)) 733 goto findpcb; 734 /* 735 * tcp_timewait unlocks inp. 736 */ 737 INP_INFO_WUNLOCK(&tcbinfo); 738 return; 739 } 740 tp = intotcpcb(inp); 741 if (tp == 0) { 742 INP_UNLOCK(inp); 743 rstreason = BANDLIM_RST_CLOSEDPORT; 744 goto dropwithreset; 745 } 746 if (tp->t_state == TCPS_CLOSED) 747 goto drop; 748 749 /* Unscale the window into a 32-bit value. */ 750 if ((thflags & TH_SYN) == 0) 751 tiwin = th->th_win << tp->snd_scale; 752 else 753 tiwin = th->th_win; 754 755#ifdef MAC 756 INP_LOCK_ASSERT(inp); 757 if (mac_check_inpcb_deliver(inp, m)) 758 goto drop; 759#endif 760 so = inp->inp_socket; 761#ifdef TCPDEBUG 762 if (so->so_options & SO_DEBUG) { 763 ostate = tp->t_state; 764 if (isipv6) 765 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 766 else 767 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 768 tcp_savetcp = *th; 769 } 770#endif 771 if (so->so_options & SO_ACCEPTCONN) { 772 struct in_conninfo inc; 773 774#ifdef INET6 775 inc.inc_isipv6 = isipv6; 776#endif 777 if (isipv6) { 778 inc.inc6_faddr = ip6->ip6_src; 779 inc.inc6_laddr = ip6->ip6_dst; 780 } else { 781 inc.inc_faddr = ip->ip_src; 782 inc.inc_laddr = ip->ip_dst; 783 } 784 inc.inc_fport = th->th_sport; 785 inc.inc_lport = th->th_dport; 786 787 /* 788 * If the state is LISTEN then ignore segment if it contains 789 * a RST. If the segment contains an ACK then it is bad and 790 * send a RST. If it does not contain a SYN then it is not 791 * interesting; drop it. 792 * 793 * If the state is SYN_RECEIVED (syncache) and seg contains 794 * an ACK, but not for our SYN/ACK, send a RST. If the seg 795 * contains a RST, check the sequence number to see if it 796 * is a valid reset segment. 797 */ 798 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 799 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 800 if (!syncache_expand(&inc, th, &so, m)) { 801 /* 802 * No syncache entry, or ACK was not 803 * for our SYN/ACK. Send a RST. 804 */ 805 tcpstat.tcps_badsyn++; 806 rstreason = BANDLIM_RST_OPENPORT; 807 goto dropwithreset; 808 } 809 if (so == NULL) { 810 /* 811 * Could not complete 3-way handshake, 812 * connection is being closed down, and 813 * syncache will free mbuf. 814 */ 815 INP_UNLOCK(inp); 816 INP_INFO_WUNLOCK(&tcbinfo); 817 return; 818 } 819 /* 820 * Socket is created in state SYN_RECEIVED. 821 * Continue processing segment. 822 */ 823 INP_UNLOCK(inp); 824 inp = sotoinpcb(so); 825 INP_LOCK(inp); 826 tp = intotcpcb(inp); 827 /* 828 * This is what would have happened in 829 * tcp_output() when the SYN,ACK was sent. 830 */ 831 tp->snd_up = tp->snd_una; 832 tp->snd_max = tp->snd_nxt = tp->iss + 1; 833 tp->last_ack_sent = tp->rcv_nxt; 834 /* 835 * RFC1323: The window in SYN & SYN/ACK 836 * segments is never scaled. 837 */ 838 tp->snd_wnd = tiwin; /* unscaled */ 839 goto after_listen; 840 } 841 if (thflags & TH_RST) { 842 syncache_chkrst(&inc, th); 843 goto drop; 844 } 845 if (thflags & TH_ACK) { 846 syncache_badack(&inc); 847 tcpstat.tcps_badsyn++; 848 rstreason = BANDLIM_RST_OPENPORT; 849 goto dropwithreset; 850 } 851 goto drop; 852 } 853 854 /* 855 * Segment's flags are (SYN) or (SYN|FIN). 856 */ 857#ifdef INET6 858 /* 859 * If deprecated address is forbidden, 860 * we do not accept SYN to deprecated interface 861 * address to prevent any new inbound connection from 862 * getting established. 863 * When we do not accept SYN, we send a TCP RST, 864 * with deprecated source address (instead of dropping 865 * it). We compromise it as it is much better for peer 866 * to send a RST, and RST will be the final packet 867 * for the exchange. 868 * 869 * If we do not forbid deprecated addresses, we accept 870 * the SYN packet. RFC2462 does not suggest dropping 871 * SYN in this case. 872 * If we decipher RFC2462 5.5.4, it says like this: 873 * 1. use of deprecated addr with existing 874 * communication is okay - "SHOULD continue to be 875 * used" 876 * 2. use of it with new communication: 877 * (2a) "SHOULD NOT be used if alternate address 878 * with sufficient scope is available" 879 * (2b) nothing mentioned otherwise. 880 * Here we fall into (2b) case as we have no choice in 881 * our source address selection - we must obey the peer. 882 * 883 * The wording in RFC2462 is confusing, and there are 884 * multiple description text for deprecated address 885 * handling - worse, they are not exactly the same. 886 * I believe 5.5.4 is the best one, so we follow 5.5.4. 887 */ 888 if (isipv6 && !ip6_use_deprecated) { 889 struct in6_ifaddr *ia6; 890 891 if ((ia6 = ip6_getdstifaddr(m)) && 892 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 893 INP_UNLOCK(inp); 894 tp = NULL; 895 rstreason = BANDLIM_RST_OPENPORT; 896 goto dropwithreset; 897 } 898 } 899#endif 900 /* 901 * If it is from this socket, drop it, it must be forged. 902 * Don't bother responding if the destination was a broadcast. 903 */ 904 if (th->th_dport == th->th_sport) { 905 if (isipv6) { 906 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 907 &ip6->ip6_src)) 908 goto drop; 909 } else { 910 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 911 goto drop; 912 } 913 } 914 /* 915 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 916 * 917 * Note that it is quite possible to receive unicast 918 * link-layer packets with a broadcast IP address. Use 919 * in_broadcast() to find them. 920 */ 921 if (m->m_flags & (M_BCAST|M_MCAST)) 922 goto drop; 923 if (isipv6) { 924 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 925 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 926 goto drop; 927 } else { 928 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 929 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 930 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 931 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 932 goto drop; 933 } 934 /* 935 * SYN appears to be valid; create compressed TCP state 936 * for syncache, or perform t/tcp connection. 937 */ 938 if (so->so_qlen <= so->so_qlimit) { 939#ifdef TCPDEBUG 940 if (so->so_options & SO_DEBUG) 941 tcp_trace(TA_INPUT, ostate, tp, 942 (void *)tcp_saveipgen, &tcp_savetcp, 0); 943#endif 944 tcp_dooptions(tp, &to, optp, optlen, 1, th); 945 if (!syncache_add(&inc, &to, th, &so, m)) 946 goto drop; 947 if (so == NULL) { 948 /* 949 * Entry added to syncache, mbuf used to 950 * send SYN,ACK packet. 951 */ 952 KASSERT(headlocked, ("headlocked")); 953 INP_UNLOCK(inp); 954 INP_INFO_WUNLOCK(&tcbinfo); 955 return; 956 } 957 /* 958 * Segment passed TAO tests. 959 */ 960 INP_UNLOCK(inp); 961 inp = sotoinpcb(so); 962 INP_LOCK(inp); 963 tp = intotcpcb(inp); 964 tp->snd_wnd = tiwin; 965 tp->t_starttime = ticks; 966 tp->t_state = TCPS_ESTABLISHED; 967 968 /* 969 * T/TCP logic: 970 * If there is a FIN or if there is data, then 971 * delay SYN,ACK(SYN) in the hope of piggy-backing 972 * it on a response segment. Otherwise must send 973 * ACK now in case the other side is slow starting. 974 */ 975 if (thflags & TH_FIN || tlen != 0) 976 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 977 else 978 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 979 tcpstat.tcps_connects++; 980 soisconnected(so); 981 goto trimthenstep6; 982 } 983 goto drop; 984 } 985after_listen: 986 987 /* XXX temp debugging */ 988 /* should not happen - syncache should pick up these connections */ 989 if (tp->t_state == TCPS_LISTEN) 990 panic("tcp_input: TCPS_LISTEN"); 991 992 /* 993 * This is the second part of the MSS DoS prevention code (after 994 * minmss on the sending side) and it deals with too many too small 995 * tcp packets in a too short timeframe (1 second). 996 * 997 * For every full second we count the number of received packets 998 * and bytes. If we get a lot of packets per second for this connection 999 * (tcp_minmssoverload) we take a closer look at it and compute the 1000 * average packet size for the past second. If that is less than 1001 * tcp_minmss we get too many packets with very small payload which 1002 * is not good and burdens our system (and every packet generates 1003 * a wakeup to the process connected to our socket). We can reasonable 1004 * expect this to be small packet DoS attack to exhaust our CPU 1005 * cycles. 1006 * 1007 * Care has to be taken for the minimum packet overload value. This 1008 * value defines the minimum number of packets per second before we 1009 * start to worry. This must not be too low to avoid killing for 1010 * example interactive connections with many small packets like 1011 * telnet or SSH. 1012 * 1013 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1014 * this check. 1015 * 1016 * Account for packet if payload packet, skip over ACK, etc. 1017 */ 1018 if (tcp_minmss && tcp_minmssoverload && 1019 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1020 if (tp->rcv_second > ticks) { 1021 tp->rcv_pps++; 1022 tp->rcv_byps += tlen + off; 1023 if (tp->rcv_pps > tcp_minmssoverload) { 1024 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1025 printf("too many small tcp packets from " 1026 "%s:%u, av. %lubyte/packet, " 1027 "dropping connection\n", 1028#ifdef INET6 1029 isipv6 ? 1030 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1031#endif 1032 inet_ntoa(inp->inp_inc.inc_faddr), 1033 inp->inp_inc.inc_fport, 1034 tp->rcv_byps / tp->rcv_pps); 1035 tp = tcp_drop(tp, ECONNRESET); 1036 tcpstat.tcps_minmssdrops++; 1037 goto drop; 1038 } 1039 } 1040 } else { 1041 tp->rcv_second = ticks + hz; 1042 tp->rcv_pps = 1; 1043 tp->rcv_byps = tlen + off; 1044 } 1045 } 1046 1047 /* 1048 * Segment received on connection. 1049 * Reset idle time and keep-alive timer. 1050 */ 1051 tp->t_rcvtime = ticks; 1052 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1053 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1054 1055 /* 1056 * Process options only when we get SYN/ACK back. The SYN case 1057 * for incoming connections is handled in tcp_syncache. 1058 * XXX this is traditional behavior, may need to be cleaned up. 1059 */ 1060 tcp_dooptions(tp, &to, optp, optlen, thflags & TH_SYN, th); 1061 if (thflags & TH_SYN) { 1062 if (to.to_flags & TOF_SCALE) { 1063 tp->t_flags |= TF_RCVD_SCALE; 1064 tp->requested_s_scale = to.to_requested_s_scale; 1065 } 1066 if (to.to_flags & TOF_TS) { 1067 tp->t_flags |= TF_RCVD_TSTMP; 1068 tp->ts_recent = to.to_tsval; 1069 tp->ts_recent_age = ticks; 1070 } 1071 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 1072 tp->t_flags |= TF_RCVD_CC; 1073 if (to.to_flags & TOF_MSS) 1074 tcp_mss(tp, to.to_mss); 1075 if (tp->sack_enable) { 1076 if (!(to.to_flags & TOF_SACK)) 1077 tp->sack_enable = 0; 1078 else 1079 tp->t_flags |= TF_SACK_PERMIT; 1080 } 1081 1082 } 1083 1084 if (tp->sack_enable) { 1085 /* Delete stale (cumulatively acked) SACK holes */ 1086 tcp_del_sackholes(tp, th); 1087 tp->rcv_laststart = th->th_seq; /* last recv'd segment*/ 1088 tp->rcv_lastend = th->th_seq + tlen; 1089 } 1090 1091 /* 1092 * Header prediction: check for the two common cases 1093 * of a uni-directional data xfer. If the packet has 1094 * no control flags, is in-sequence, the window didn't 1095 * change and we're not retransmitting, it's a 1096 * candidate. If the length is zero and the ack moved 1097 * forward, we're the sender side of the xfer. Just 1098 * free the data acked & wake any higher level process 1099 * that was blocked waiting for space. If the length 1100 * is non-zero and the ack didn't move, we're the 1101 * receiver side. If we're getting packets in-order 1102 * (the reassembly queue is empty), add the data to 1103 * the socket buffer and note that we need a delayed ack. 1104 * Make sure that the hidden state-flags are also off. 1105 * Since we check for TCPS_ESTABLISHED above, it can only 1106 * be TH_NEEDSYN. 1107 */ 1108 if (tp->t_state == TCPS_ESTABLISHED && 1109 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1110 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1111 ((to.to_flags & TOF_TS) == 0 || 1112 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1113 /* 1114 * Using the CC option is compulsory if once started: 1115 * the segment is OK if no T/TCP was negotiated or 1116 * if the segment has a CC option equal to CCrecv 1117 */ 1118 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1119 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1120 th->th_seq == tp->rcv_nxt && 1121 tiwin && tiwin == tp->snd_wnd && 1122 tp->snd_nxt == tp->snd_max) { 1123 1124 /* 1125 * If last ACK falls within this segment's sequence numbers, 1126 * record the timestamp. 1127 * NOTE that the test is modified according to the latest 1128 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1129 */ 1130 if ((to.to_flags & TOF_TS) != 0 && 1131 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1132 tp->ts_recent_age = ticks; 1133 tp->ts_recent = to.to_tsval; 1134 } 1135 1136 if (tlen == 0) { 1137 if (SEQ_GT(th->th_ack, tp->snd_una) && 1138 SEQ_LEQ(th->th_ack, tp->snd_max) && 1139 tp->snd_cwnd >= tp->snd_wnd && 1140 ((!tcp_do_newreno && !tp->sack_enable && 1141 tp->t_dupacks < tcprexmtthresh) || 1142 ((tcp_do_newreno || tp->sack_enable) && 1143 !IN_FASTRECOVERY(tp)))) { 1144 KASSERT(headlocked, ("headlocked")); 1145 INP_INFO_WUNLOCK(&tcbinfo); 1146 /* 1147 * this is a pure ack for outstanding data. 1148 */ 1149 ++tcpstat.tcps_predack; 1150 /* 1151 * "bad retransmit" recovery 1152 */ 1153 if (tp->t_rxtshift == 1 && 1154 ticks < tp->t_badrxtwin) { 1155 ++tcpstat.tcps_sndrexmitbad; 1156 tp->snd_cwnd = tp->snd_cwnd_prev; 1157 tp->snd_ssthresh = 1158 tp->snd_ssthresh_prev; 1159 tp->snd_recover = tp->snd_recover_prev; 1160 if (tp->t_flags & TF_WASFRECOVERY) 1161 ENTER_FASTRECOVERY(tp); 1162 tp->snd_nxt = tp->snd_max; 1163 tp->t_badrxtwin = 0; 1164 } 1165 1166 /* 1167 * Recalculate the transmit timer / rtt. 1168 * 1169 * Some boxes send broken timestamp replies 1170 * during the SYN+ACK phase, ignore 1171 * timestamps of 0 or we could calculate a 1172 * huge RTT and blow up the retransmit timer. 1173 */ 1174 if ((to.to_flags & TOF_TS) != 0 && 1175 to.to_tsecr) { 1176 tcp_xmit_timer(tp, 1177 ticks - to.to_tsecr + 1); 1178 } else if (tp->t_rtttime && 1179 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1180 tcp_xmit_timer(tp, 1181 ticks - tp->t_rtttime); 1182 } 1183 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1184 acked = th->th_ack - tp->snd_una; 1185 tcpstat.tcps_rcvackpack++; 1186 tcpstat.tcps_rcvackbyte += acked; 1187 sbdrop(&so->so_snd, acked); 1188 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1189 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1190 tp->snd_recover = th->th_ack - 1; 1191 tp->snd_una = th->th_ack; 1192 /* 1193 * pull snd_wl2 up to prevent seq wrap relative 1194 * to th_ack. 1195 */ 1196 tp->snd_wl2 = th->th_ack; 1197 tp->t_dupacks = 0; 1198 m_freem(m); 1199 ND6_HINT(tp); /* some progress has been done */ 1200 1201 /* 1202 * If all outstanding data are acked, stop 1203 * retransmit timer, otherwise restart timer 1204 * using current (possibly backed-off) value. 1205 * If process is waiting for space, 1206 * wakeup/selwakeup/signal. If data 1207 * are ready to send, let tcp_output 1208 * decide between more output or persist. 1209 1210#ifdef TCPDEBUG 1211 if (so->so_options & SO_DEBUG) 1212 tcp_trace(TA_INPUT, ostate, tp, 1213 (void *)tcp_saveipgen, 1214 &tcp_savetcp, 0); 1215#endif 1216 */ 1217 if (tp->snd_una == tp->snd_max) 1218 callout_stop(tp->tt_rexmt); 1219 else if (!callout_active(tp->tt_persist)) 1220 callout_reset(tp->tt_rexmt, 1221 tp->t_rxtcur, 1222 tcp_timer_rexmt, tp); 1223 1224 sowwakeup(so); 1225 if (so->so_snd.sb_cc) 1226 (void) tcp_output(tp); 1227 goto check_delack; 1228 } 1229 } else if (th->th_ack == tp->snd_una && 1230 LIST_EMPTY(&tp->t_segq) && 1231 tlen <= sbspace(&so->so_rcv)) { 1232 KASSERT(headlocked, ("headlocked")); 1233 INP_INFO_WUNLOCK(&tcbinfo); 1234 /* 1235 * this is a pure, in-sequence data packet 1236 * with nothing on the reassembly queue and 1237 * we have enough buffer space to take it. 1238 */ 1239 /* Clean receiver SACK report if present */ 1240 if (tp->sack_enable && tp->rcv_numsacks) 1241 tcp_clean_sackreport(tp); 1242 ++tcpstat.tcps_preddat; 1243 tp->rcv_nxt += tlen; 1244 /* 1245 * Pull snd_wl1 up to prevent seq wrap relative to 1246 * th_seq. 1247 */ 1248 tp->snd_wl1 = th->th_seq; 1249 /* 1250 * Pull rcv_up up to prevent seq wrap relative to 1251 * rcv_nxt. 1252 */ 1253 tp->rcv_up = tp->rcv_nxt; 1254 tcpstat.tcps_rcvpack++; 1255 tcpstat.tcps_rcvbyte += tlen; 1256 ND6_HINT(tp); /* some progress has been done */ 1257 /* 1258#ifdef TCPDEBUG 1259 if (so->so_options & SO_DEBUG) 1260 tcp_trace(TA_INPUT, ostate, tp, 1261 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1262#endif 1263 * Add data to socket buffer. 1264 */ 1265 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1266 m_freem(m); 1267 } else { 1268 m_adj(m, drop_hdrlen); /* delayed header drop */ 1269 sbappendstream(&so->so_rcv, m); 1270 } 1271 sorwakeup(so); 1272 if (DELAY_ACK(tp)) { 1273 tp->t_flags |= TF_DELACK; 1274 } else { 1275 tp->t_flags |= TF_ACKNOW; 1276 tcp_output(tp); 1277 } 1278 goto check_delack; 1279 } 1280 } 1281 1282 /* 1283 * Calculate amount of space in receive window, 1284 * and then do TCP input processing. 1285 * Receive window is amount of space in rcv queue, 1286 * but not less than advertised window. 1287 */ 1288 { int win; 1289 1290 win = sbspace(&so->so_rcv); 1291 if (win < 0) 1292 win = 0; 1293 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1294 } 1295 1296 switch (tp->t_state) { 1297 1298 /* 1299 * If the state is SYN_RECEIVED: 1300 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1301 */ 1302 case TCPS_SYN_RECEIVED: 1303 if ((thflags & TH_ACK) && 1304 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1305 SEQ_GT(th->th_ack, tp->snd_max))) { 1306 rstreason = BANDLIM_RST_OPENPORT; 1307 goto dropwithreset; 1308 } 1309 break; 1310 1311 /* 1312 * If the state is SYN_SENT: 1313 * if seg contains an ACK, but not for our SYN, drop the input. 1314 * if seg contains a RST, then drop the connection. 1315 * if seg does not contain SYN, then drop it. 1316 * Otherwise this is an acceptable SYN segment 1317 * initialize tp->rcv_nxt and tp->irs 1318 * if seg contains ack then advance tp->snd_una 1319 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1320 * arrange for segment to be acked (eventually) 1321 * continue processing rest of data/controls, beginning with URG 1322 */ 1323 case TCPS_SYN_SENT: 1324 if (tcp_do_rfc1644) 1325 tcp_hc_gettao(&inp->inp_inc, &tao); 1326 1327 if ((thflags & TH_ACK) && 1328 (SEQ_LEQ(th->th_ack, tp->iss) || 1329 SEQ_GT(th->th_ack, tp->snd_max))) { 1330 /* 1331 * If we have a cached CCsent for the remote host, 1332 * hence we haven't just crashed and restarted, 1333 * do not send a RST. This may be a retransmission 1334 * from the other side after our earlier ACK was lost. 1335 * Our new SYN, when it arrives, will serve as the 1336 * needed ACK. 1337 */ 1338 if (tao.tao_ccsent != 0) 1339 goto drop; 1340 else { 1341 rstreason = BANDLIM_UNLIMITED; 1342 goto dropwithreset; 1343 } 1344 } 1345 if (thflags & TH_RST) { 1346 if (thflags & TH_ACK) 1347 tp = tcp_drop(tp, ECONNREFUSED); 1348 goto drop; 1349 } 1350 if ((thflags & TH_SYN) == 0) 1351 goto drop; 1352 tp->snd_wnd = th->th_win; /* initial send window */ 1353 tp->cc_recv = to.to_cc; /* foreign CC */ 1354 1355 tp->irs = th->th_seq; 1356 tcp_rcvseqinit(tp); 1357 if (thflags & TH_ACK) { 1358 /* 1359 * Our SYN was acked. If segment contains CC.ECHO 1360 * option, check it to make sure this segment really 1361 * matches our SYN. If not, just drop it as old 1362 * duplicate, but send an RST if we're still playing 1363 * by the old rules. If no CC.ECHO option, make sure 1364 * we don't get fooled into using T/TCP. 1365 */ 1366 if (to.to_flags & TOF_CCECHO) { 1367 if (tp->cc_send != to.to_ccecho) { 1368 if (tao.tao_ccsent != 0) 1369 goto drop; 1370 else { 1371 rstreason = BANDLIM_UNLIMITED; 1372 goto dropwithreset; 1373 } 1374 } 1375 } else 1376 tp->t_flags &= ~TF_RCVD_CC; 1377 tcpstat.tcps_connects++; 1378 soisconnected(so); 1379#ifdef MAC 1380 SOCK_LOCK(so); 1381 mac_set_socket_peer_from_mbuf(m, so); 1382 SOCK_UNLOCK(so); 1383#endif 1384 /* Do window scaling on this connection? */ 1385 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1386 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1387 tp->snd_scale = tp->requested_s_scale; 1388 tp->rcv_scale = tp->request_r_scale; 1389 } 1390 /* Segment is acceptable, update cache if undefined. */ 1391 if (tao.tao_ccsent == 0 && tcp_do_rfc1644) 1392 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0); 1393 1394 tp->rcv_adv += tp->rcv_wnd; 1395 tp->snd_una++; /* SYN is acked */ 1396 /* 1397 * If there's data, delay ACK; if there's also a FIN 1398 * ACKNOW will be turned on later. 1399 */ 1400 if (DELAY_ACK(tp) && tlen != 0) 1401 callout_reset(tp->tt_delack, tcp_delacktime, 1402 tcp_timer_delack, tp); 1403 else 1404 tp->t_flags |= TF_ACKNOW; 1405 /* 1406 * Received <SYN,ACK> in SYN_SENT[*] state. 1407 * Transitions: 1408 * SYN_SENT --> ESTABLISHED 1409 * SYN_SENT* --> FIN_WAIT_1 1410 */ 1411 tp->t_starttime = ticks; 1412 if (tp->t_flags & TF_NEEDFIN) { 1413 tp->t_state = TCPS_FIN_WAIT_1; 1414 tp->t_flags &= ~TF_NEEDFIN; 1415 thflags &= ~TH_SYN; 1416 } else { 1417 tp->t_state = TCPS_ESTABLISHED; 1418 callout_reset(tp->tt_keep, tcp_keepidle, 1419 tcp_timer_keep, tp); 1420 } 1421 } else { 1422 /* 1423 * Received initial SYN in SYN-SENT[*] state => 1424 * simultaneous open. If segment contains CC option 1425 * and there is a cached CC, apply TAO test. 1426 * If it succeeds, connection is * half-synchronized. 1427 * Otherwise, do 3-way handshake: 1428 * SYN-SENT -> SYN-RECEIVED 1429 * SYN-SENT* -> SYN-RECEIVED* 1430 * If there was no CC option, clear cached CC value. 1431 */ 1432 tp->t_flags |= TF_ACKNOW; 1433 callout_stop(tp->tt_rexmt); 1434 if (to.to_flags & TOF_CC) { 1435 if (tao.tao_cc != 0 && 1436 CC_GT(to.to_cc, tao.tao_cc)) { 1437 /* 1438 * update cache and make transition: 1439 * SYN-SENT -> ESTABLISHED* 1440 * SYN-SENT* -> FIN-WAIT-1* 1441 */ 1442 tao.tao_cc = to.to_cc; 1443 tcp_hc_updatetao(&inp->inp_inc, 1444 TCP_HC_TAO_CC, to.to_cc, 0); 1445 tp->t_starttime = ticks; 1446 if (tp->t_flags & TF_NEEDFIN) { 1447 tp->t_state = TCPS_FIN_WAIT_1; 1448 tp->t_flags &= ~TF_NEEDFIN; 1449 } else { 1450 tp->t_state = TCPS_ESTABLISHED; 1451 callout_reset(tp->tt_keep, 1452 tcp_keepidle, 1453 tcp_timer_keep, 1454 tp); 1455 } 1456 tp->t_flags |= TF_NEEDSYN; 1457 } else 1458 tp->t_state = TCPS_SYN_RECEIVED; 1459 } else { 1460 if (tcp_do_rfc1644) { 1461 /* CC.NEW or no option => invalidate cache */ 1462 tao.tao_cc = 0; 1463 tcp_hc_updatetao(&inp->inp_inc, 1464 TCP_HC_TAO_CC, to.to_cc, 0); 1465 } 1466 tp->t_state = TCPS_SYN_RECEIVED; 1467 } 1468 } 1469 1470trimthenstep6: 1471 /* 1472 * Advance th->th_seq to correspond to first data byte. 1473 * If data, trim to stay within window, 1474 * dropping FIN if necessary. 1475 */ 1476 th->th_seq++; 1477 if (tlen > tp->rcv_wnd) { 1478 todrop = tlen - tp->rcv_wnd; 1479 m_adj(m, -todrop); 1480 tlen = tp->rcv_wnd; 1481 thflags &= ~TH_FIN; 1482 tcpstat.tcps_rcvpackafterwin++; 1483 tcpstat.tcps_rcvbyteafterwin += todrop; 1484 } 1485 tp->snd_wl1 = th->th_seq - 1; 1486 tp->rcv_up = th->th_seq; 1487 /* 1488 * Client side of transaction: already sent SYN and data. 1489 * If the remote host used T/TCP to validate the SYN, 1490 * our data will be ACK'd; if so, enter normal data segment 1491 * processing in the middle of step 5, ack processing. 1492 * Otherwise, goto step 6. 1493 */ 1494 if (thflags & TH_ACK) 1495 goto process_ACK; 1496 1497 goto step6; 1498 1499 /* 1500 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1501 * if segment contains a SYN and CC [not CC.NEW] option: 1502 * if state == TIME_WAIT and connection duration > MSL, 1503 * drop packet and send RST; 1504 * 1505 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1506 * ack the FIN (and data) in retransmission queue. 1507 * Complete close and delete TCPCB. Then reprocess 1508 * segment, hoping to find new TCPCB in LISTEN state; 1509 * 1510 * else must be old SYN; drop it. 1511 * else do normal processing. 1512 */ 1513 case TCPS_LAST_ACK: 1514 case TCPS_CLOSING: 1515 case TCPS_TIME_WAIT: 1516 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1517 if ((thflags & TH_SYN) && 1518 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1519 if (tp->t_state == TCPS_TIME_WAIT && 1520 (ticks - tp->t_starttime) > tcp_msl) { 1521 rstreason = BANDLIM_UNLIMITED; 1522 goto dropwithreset; 1523 } 1524 if (CC_GT(to.to_cc, tp->cc_recv)) { 1525 tp = tcp_close(tp); 1526 goto findpcb; 1527 } 1528 else 1529 goto drop; 1530 } 1531 break; /* continue normal processing */ 1532 } 1533 1534 /* 1535 * States other than LISTEN or SYN_SENT. 1536 * First check the RST flag and sequence number since reset segments 1537 * are exempt from the timestamp and connection count tests. This 1538 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1539 * below which allowed reset segments in half the sequence space 1540 * to fall though and be processed (which gives forged reset 1541 * segments with a random sequence number a 50 percent chance of 1542 * killing a connection). 1543 * Then check timestamp, if present. 1544 * Then check the connection count, if present. 1545 * Then check that at least some bytes of segment are within 1546 * receive window. If segment begins before rcv_nxt, 1547 * drop leading data (and SYN); if nothing left, just ack. 1548 * 1549 * 1550 * If the RST bit is set, check the sequence number to see 1551 * if this is a valid reset segment. 1552 * RFC 793 page 37: 1553 * In all states except SYN-SENT, all reset (RST) segments 1554 * are validated by checking their SEQ-fields. A reset is 1555 * valid if its sequence number is in the window. 1556 * Note: this does not take into account delayed ACKs, so 1557 * we should test against last_ack_sent instead of rcv_nxt. 1558 * The sequence number in the reset segment is normally an 1559 * echo of our outgoing acknowlegement numbers, but some hosts 1560 * send a reset with the sequence number at the rightmost edge 1561 * of our receive window, and we have to handle this case. 1562 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1563 * that brute force RST attacks are possible. To combat this, 1564 * we use a much stricter check while in the ESTABLISHED state, 1565 * only accepting RSTs where the sequence number is equal to 1566 * last_ack_sent. In all other states (the states in which a 1567 * RST is more likely), the more permissive check is used. 1568 * If we have multiple segments in flight, the intial reset 1569 * segment sequence numbers will be to the left of last_ack_sent, 1570 * but they will eventually catch up. 1571 * In any case, it never made sense to trim reset segments to 1572 * fit the receive window since RFC 1122 says: 1573 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1574 * 1575 * A TCP SHOULD allow a received RST segment to include data. 1576 * 1577 * DISCUSSION 1578 * It has been suggested that a RST segment could contain 1579 * ASCII text that encoded and explained the cause of the 1580 * RST. No standard has yet been established for such 1581 * data. 1582 * 1583 * If the reset segment passes the sequence number test examine 1584 * the state: 1585 * SYN_RECEIVED STATE: 1586 * If passive open, return to LISTEN state. 1587 * If active open, inform user that connection was refused. 1588 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1589 * Inform user that connection was reset, and close tcb. 1590 * CLOSING, LAST_ACK STATES: 1591 * Close the tcb. 1592 * TIME_WAIT STATE: 1593 * Drop the segment - see Stevens, vol. 2, p. 964 and 1594 * RFC 1337. 1595 */ 1596 if (thflags & TH_RST) { 1597 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1598 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1599 switch (tp->t_state) { 1600 1601 case TCPS_SYN_RECEIVED: 1602 so->so_error = ECONNREFUSED; 1603 goto close; 1604 1605 case TCPS_ESTABLISHED: 1606 if (tp->last_ack_sent != th->th_seq) { 1607 tcpstat.tcps_badrst++; 1608 goto drop; 1609 } 1610 case TCPS_FIN_WAIT_1: 1611 case TCPS_FIN_WAIT_2: 1612 case TCPS_CLOSE_WAIT: 1613 so->so_error = ECONNRESET; 1614 close: 1615 tp->t_state = TCPS_CLOSED; 1616 tcpstat.tcps_drops++; 1617 tp = tcp_close(tp); 1618 break; 1619 1620 case TCPS_CLOSING: 1621 case TCPS_LAST_ACK: 1622 tp = tcp_close(tp); 1623 break; 1624 1625 case TCPS_TIME_WAIT: 1626 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1627 ("timewait")); 1628 break; 1629 } 1630 } 1631 goto drop; 1632 } 1633 1634 /* 1635 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1636 * and it's less than ts_recent, drop it. 1637 */ 1638 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1639 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1640 1641 /* Check to see if ts_recent is over 24 days old. */ 1642 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1643 /* 1644 * Invalidate ts_recent. If this segment updates 1645 * ts_recent, the age will be reset later and ts_recent 1646 * will get a valid value. If it does not, setting 1647 * ts_recent to zero will at least satisfy the 1648 * requirement that zero be placed in the timestamp 1649 * echo reply when ts_recent isn't valid. The 1650 * age isn't reset until we get a valid ts_recent 1651 * because we don't want out-of-order segments to be 1652 * dropped when ts_recent is old. 1653 */ 1654 tp->ts_recent = 0; 1655 } else { 1656 tcpstat.tcps_rcvduppack++; 1657 tcpstat.tcps_rcvdupbyte += tlen; 1658 tcpstat.tcps_pawsdrop++; 1659 if (tlen) 1660 goto dropafterack; 1661 goto drop; 1662 } 1663 } 1664 1665 /* 1666 * T/TCP mechanism 1667 * If T/TCP was negotiated and the segment doesn't have CC, 1668 * or if its CC is wrong then drop the segment. 1669 * RST segments do not have to comply with this. 1670 */ 1671 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1672 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1673 goto dropafterack; 1674 1675 /* 1676 * In the SYN-RECEIVED state, validate that the packet belongs to 1677 * this connection before trimming the data to fit the receive 1678 * window. Check the sequence number versus IRS since we know 1679 * the sequence numbers haven't wrapped. This is a partial fix 1680 * for the "LAND" DoS attack. 1681 */ 1682 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1683 rstreason = BANDLIM_RST_OPENPORT; 1684 goto dropwithreset; 1685 } 1686 1687 todrop = tp->rcv_nxt - th->th_seq; 1688 if (todrop > 0) { 1689 if (thflags & TH_SYN) { 1690 thflags &= ~TH_SYN; 1691 th->th_seq++; 1692 if (th->th_urp > 1) 1693 th->th_urp--; 1694 else 1695 thflags &= ~TH_URG; 1696 todrop--; 1697 } 1698 /* 1699 * Following if statement from Stevens, vol. 2, p. 960. 1700 */ 1701 if (todrop > tlen 1702 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1703 /* 1704 * Any valid FIN must be to the left of the window. 1705 * At this point the FIN must be a duplicate or out 1706 * of sequence; drop it. 1707 */ 1708 thflags &= ~TH_FIN; 1709 1710 /* 1711 * Send an ACK to resynchronize and drop any data. 1712 * But keep on processing for RST or ACK. 1713 */ 1714 tp->t_flags |= TF_ACKNOW; 1715 todrop = tlen; 1716 tcpstat.tcps_rcvduppack++; 1717 tcpstat.tcps_rcvdupbyte += todrop; 1718 } else { 1719 tcpstat.tcps_rcvpartduppack++; 1720 tcpstat.tcps_rcvpartdupbyte += todrop; 1721 } 1722 drop_hdrlen += todrop; /* drop from the top afterwards */ 1723 th->th_seq += todrop; 1724 tlen -= todrop; 1725 if (th->th_urp > todrop) 1726 th->th_urp -= todrop; 1727 else { 1728 thflags &= ~TH_URG; 1729 th->th_urp = 0; 1730 } 1731 } 1732 1733 /* 1734 * If new data are received on a connection after the 1735 * user processes are gone, then RST the other end. 1736 */ 1737 if ((so->so_state & SS_NOFDREF) && 1738 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1739 tp = tcp_close(tp); 1740 tcpstat.tcps_rcvafterclose++; 1741 rstreason = BANDLIM_UNLIMITED; 1742 goto dropwithreset; 1743 } 1744 1745 /* 1746 * If segment ends after window, drop trailing data 1747 * (and PUSH and FIN); if nothing left, just ACK. 1748 */ 1749 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1750 if (todrop > 0) { 1751 tcpstat.tcps_rcvpackafterwin++; 1752 if (todrop >= tlen) { 1753 tcpstat.tcps_rcvbyteafterwin += tlen; 1754 /* 1755 * If a new connection request is received 1756 * while in TIME_WAIT, drop the old connection 1757 * and start over if the sequence numbers 1758 * are above the previous ones. 1759 */ 1760 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1761 if (thflags & TH_SYN && 1762 tp->t_state == TCPS_TIME_WAIT && 1763 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1764 tp = tcp_close(tp); 1765 goto findpcb; 1766 } 1767 /* 1768 * If window is closed can only take segments at 1769 * window edge, and have to drop data and PUSH from 1770 * incoming segments. Continue processing, but 1771 * remember to ack. Otherwise, drop segment 1772 * and ack. 1773 */ 1774 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1775 tp->t_flags |= TF_ACKNOW; 1776 tcpstat.tcps_rcvwinprobe++; 1777 } else 1778 goto dropafterack; 1779 } else 1780 tcpstat.tcps_rcvbyteafterwin += todrop; 1781 m_adj(m, -todrop); 1782 tlen -= todrop; 1783 thflags &= ~(TH_PUSH|TH_FIN); 1784 } 1785 1786 /* 1787 * If last ACK falls within this segment's sequence numbers, 1788 * record its timestamp. 1789 * NOTE that the test is modified according to the latest 1790 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1791 */ 1792 if ((to.to_flags & TOF_TS) != 0 && 1793 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1794 tp->ts_recent_age = ticks; 1795 tp->ts_recent = to.to_tsval; 1796 } 1797 1798 /* 1799 * If a SYN is in the window, then this is an 1800 * error and we send an RST and drop the connection. 1801 */ 1802 if (thflags & TH_SYN) { 1803 tp = tcp_drop(tp, ECONNRESET); 1804 rstreason = BANDLIM_UNLIMITED; 1805 goto drop; 1806 } 1807 1808 /* 1809 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1810 * flag is on (half-synchronized state), then queue data for 1811 * later processing; else drop segment and return. 1812 */ 1813 if ((thflags & TH_ACK) == 0) { 1814 if (tp->t_state == TCPS_SYN_RECEIVED || 1815 (tp->t_flags & TF_NEEDSYN)) 1816 goto step6; 1817 else 1818 goto drop; 1819 } 1820 1821 /* 1822 * Ack processing. 1823 */ 1824 switch (tp->t_state) { 1825 1826 /* 1827 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1828 * ESTABLISHED state and continue processing. 1829 * The ACK was checked above. 1830 */ 1831 case TCPS_SYN_RECEIVED: 1832 1833 tcpstat.tcps_connects++; 1834 soisconnected(so); 1835 /* Do window scaling? */ 1836 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1837 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1838 tp->snd_scale = tp->requested_s_scale; 1839 tp->rcv_scale = tp->request_r_scale; 1840 } 1841 /* 1842 * Upon successful completion of 3-way handshake, 1843 * update cache.CC, pass any queued data to the user, 1844 * and advance state appropriately. 1845 */ 1846 if (tcp_do_rfc1644) { 1847 tao.tao_cc = tp->cc_recv; 1848 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC, 1849 tp->cc_recv, 0); 1850 } 1851 /* 1852 * Make transitions: 1853 * SYN-RECEIVED -> ESTABLISHED 1854 * SYN-RECEIVED* -> FIN-WAIT-1 1855 */ 1856 tp->t_starttime = ticks; 1857 if (tp->t_flags & TF_NEEDFIN) { 1858 tp->t_state = TCPS_FIN_WAIT_1; 1859 tp->t_flags &= ~TF_NEEDFIN; 1860 } else { 1861 tp->t_state = TCPS_ESTABLISHED; 1862 callout_reset(tp->tt_keep, tcp_keepidle, 1863 tcp_timer_keep, tp); 1864 } 1865 /* 1866 * If segment contains data or ACK, will call tcp_reass() 1867 * later; if not, do so now to pass queued data to user. 1868 */ 1869 if (tlen == 0 && (thflags & TH_FIN) == 0) 1870 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1871 (struct mbuf *)0); 1872 tp->snd_wl1 = th->th_seq - 1; 1873 /* FALLTHROUGH */ 1874 1875 /* 1876 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1877 * ACKs. If the ack is in the range 1878 * tp->snd_una < th->th_ack <= tp->snd_max 1879 * then advance tp->snd_una to th->th_ack and drop 1880 * data from the retransmission queue. If this ACK reflects 1881 * more up to date window information we update our window information. 1882 */ 1883 case TCPS_ESTABLISHED: 1884 case TCPS_FIN_WAIT_1: 1885 case TCPS_FIN_WAIT_2: 1886 case TCPS_CLOSE_WAIT: 1887 case TCPS_CLOSING: 1888 case TCPS_LAST_ACK: 1889 case TCPS_TIME_WAIT: 1890 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1891 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1892 if (tlen == 0 && tiwin == tp->snd_wnd) { 1893 tcpstat.tcps_rcvdupack++; 1894 /* 1895 * If we have outstanding data (other than 1896 * a window probe), this is a completely 1897 * duplicate ack (ie, window info didn't 1898 * change), the ack is the biggest we've 1899 * seen and we've seen exactly our rexmt 1900 * threshhold of them, assume a packet 1901 * has been dropped and retransmit it. 1902 * Kludge snd_nxt & the congestion 1903 * window so we send only this one 1904 * packet. 1905 * 1906 * We know we're losing at the current 1907 * window size so do congestion avoidance 1908 * (set ssthresh to half the current window 1909 * and pull our congestion window back to 1910 * the new ssthresh). 1911 * 1912 * Dup acks mean that packets have left the 1913 * network (they're now cached at the receiver) 1914 * so bump cwnd by the amount in the receiver 1915 * to keep a constant cwnd packets in the 1916 * network. 1917 */ 1918 if (!callout_active(tp->tt_rexmt) || 1919 th->th_ack != tp->snd_una) 1920 tp->t_dupacks = 0; 1921 else if (++tp->t_dupacks > tcprexmtthresh || 1922 ((tcp_do_newreno || tp->sack_enable) && 1923 IN_FASTRECOVERY(tp))) { 1924 tp->snd_cwnd += tp->t_maxseg; 1925 (void) tcp_output(tp); 1926 goto drop; 1927 } else if (tp->t_dupacks == tcprexmtthresh) { 1928 tcp_seq onxt = tp->snd_nxt; 1929 u_int win; 1930 if ((tcp_do_newreno || 1931 tp->sack_enable) && 1932 SEQ_LEQ(th->th_ack, 1933 tp->snd_recover)) { 1934 tp->t_dupacks = 0; 1935 break; 1936 } 1937 win = min(tp->snd_wnd, tp->snd_cwnd) / 1938 2 / tp->t_maxseg; 1939 if (win < 2) 1940 win = 2; 1941 tp->snd_ssthresh = win * tp->t_maxseg; 1942 ENTER_FASTRECOVERY(tp); 1943 tp->snd_recover = tp->snd_max; 1944 callout_stop(tp->tt_rexmt); 1945 tp->t_rtttime = 0; 1946 if (tp->sack_enable) { 1947 tcpstat.tcps_sack_recovery_episode++; 1948 tp->snd_cwnd = 1949 tp->t_maxseg * 1950 tp->t_dupacks; 1951 (void) tcp_output(tp); 1952 tp->snd_cwnd = 1953 tp->snd_ssthresh; 1954 goto drop; 1955 } 1956 1957 tp->snd_nxt = th->th_ack; 1958 tp->snd_cwnd = tp->t_maxseg; 1959 (void) tcp_output(tp); 1960 KASSERT(tp->snd_limited <= 2, 1961 ("tp->snd_limited too big")); 1962 tp->snd_cwnd = tp->snd_ssthresh + 1963 tp->t_maxseg * 1964 (tp->t_dupacks - tp->snd_limited); 1965 if (SEQ_GT(onxt, tp->snd_nxt)) 1966 tp->snd_nxt = onxt; 1967 goto drop; 1968 } else if (tcp_do_rfc3042) { 1969 u_long oldcwnd = tp->snd_cwnd; 1970 tcp_seq oldsndmax = tp->snd_max; 1971 u_int sent; 1972 1973 KASSERT(tp->t_dupacks == 1 || 1974 tp->t_dupacks == 2, 1975 ("dupacks not 1 or 2")); 1976 if (tp->t_dupacks == 1) 1977 tp->snd_limited = 0; 1978 tp->snd_cwnd = 1979 (tp->snd_nxt - tp->snd_una) + 1980 (tp->t_dupacks - tp->snd_limited) * 1981 tp->t_maxseg; 1982 (void) tcp_output(tp); 1983 sent = tp->snd_max - oldsndmax; 1984 if (sent > tp->t_maxseg) { 1985 KASSERT((tp->t_dupacks == 2 && 1986 tp->snd_limited == 0) || 1987 (sent == tp->t_maxseg + 1 && 1988 tp->t_flags & TF_SENTFIN), 1989 ("sent too much")); 1990 tp->snd_limited = 2; 1991 } else if (sent > 0) 1992 ++tp->snd_limited; 1993 tp->snd_cwnd = oldcwnd; 1994 goto drop; 1995 } 1996 } else 1997 tp->t_dupacks = 0; 1998 break; 1999 } 2000 2001 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2002 2003 /* 2004 * If the congestion window was inflated to account 2005 * for the other side's cached packets, retract it. 2006 */ 2007 if (tcp_do_newreno || tp->sack_enable) { 2008 if (IN_FASTRECOVERY(tp)) { 2009 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2010 if (tp->sack_enable) 2011 tcp_sack_partialack(tp, th); 2012 else 2013 tcp_newreno_partial_ack(tp, th); 2014 } else { 2015 /* 2016 * Out of fast recovery. 2017 * Window inflation should have left us 2018 * with approximately snd_ssthresh 2019 * outstanding data. 2020 * But in case we would be inclined to 2021 * send a burst, better to do it via 2022 * the slow start mechanism. 2023 */ 2024 if (SEQ_GT(th->th_ack + 2025 tp->snd_ssthresh, 2026 tp->snd_max)) 2027 tp->snd_cwnd = tp->snd_max - 2028 th->th_ack + 2029 tp->t_maxseg; 2030 else 2031 tp->snd_cwnd = tp->snd_ssthresh; 2032 } 2033 } 2034 } else { 2035 if (tp->t_dupacks >= tcprexmtthresh && 2036 tp->snd_cwnd > tp->snd_ssthresh) 2037 tp->snd_cwnd = tp->snd_ssthresh; 2038 } 2039 tp->t_dupacks = 0; 2040 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2041 tcpstat.tcps_rcvacktoomuch++; 2042 goto dropafterack; 2043 } 2044 /* 2045 * If we reach this point, ACK is not a duplicate, 2046 * i.e., it ACKs something we sent. 2047 */ 2048 if (tp->t_flags & TF_NEEDSYN) { 2049 /* 2050 * T/TCP: Connection was half-synchronized, and our 2051 * SYN has been ACK'd (so connection is now fully 2052 * synchronized). Go to non-starred state, 2053 * increment snd_una for ACK of SYN, and check if 2054 * we can do window scaling. 2055 */ 2056 tp->t_flags &= ~TF_NEEDSYN; 2057 tp->snd_una++; 2058 /* Do window scaling? */ 2059 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2060 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2061 tp->snd_scale = tp->requested_s_scale; 2062 tp->rcv_scale = tp->request_r_scale; 2063 } 2064 } 2065 2066process_ACK: 2067 acked = th->th_ack - tp->snd_una; 2068 tcpstat.tcps_rcvackpack++; 2069 tcpstat.tcps_rcvackbyte += acked; 2070 2071 /* 2072 * If we just performed our first retransmit, and the ACK 2073 * arrives within our recovery window, then it was a mistake 2074 * to do the retransmit in the first place. Recover our 2075 * original cwnd and ssthresh, and proceed to transmit where 2076 * we left off. 2077 */ 2078 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2079 ++tcpstat.tcps_sndrexmitbad; 2080 tp->snd_cwnd = tp->snd_cwnd_prev; 2081 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2082 tp->snd_recover = tp->snd_recover_prev; 2083 if (tp->t_flags & TF_WASFRECOVERY) 2084 ENTER_FASTRECOVERY(tp); 2085 tp->snd_nxt = tp->snd_max; 2086 tp->t_badrxtwin = 0; /* XXX probably not required */ 2087 } 2088 2089 /* 2090 * If we have a timestamp reply, update smoothed 2091 * round trip time. If no timestamp is present but 2092 * transmit timer is running and timed sequence 2093 * number was acked, update smoothed round trip time. 2094 * Since we now have an rtt measurement, cancel the 2095 * timer backoff (cf., Phil Karn's retransmit alg.). 2096 * Recompute the initial retransmit timer. 2097 * 2098 * Some boxes send broken timestamp replies 2099 * during the SYN+ACK phase, ignore 2100 * timestamps of 0 or we could calculate a 2101 * huge RTT and blow up the retransmit timer. 2102 */ 2103 if ((to.to_flags & TOF_TS) != 0 && 2104 to.to_tsecr) { 2105 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2106 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2107 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2108 } 2109 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2110 2111 /* 2112 * If all outstanding data is acked, stop retransmit 2113 * timer and remember to restart (more output or persist). 2114 * If there is more data to be acked, restart retransmit 2115 * timer, using current (possibly backed-off) value. 2116 */ 2117 if (th->th_ack == tp->snd_max) { 2118 callout_stop(tp->tt_rexmt); 2119 needoutput = 1; 2120 } else if (!callout_active(tp->tt_persist)) 2121 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2122 tcp_timer_rexmt, tp); 2123 2124 /* 2125 * If no data (only SYN) was ACK'd, 2126 * skip rest of ACK processing. 2127 */ 2128 if (acked == 0) 2129 goto step6; 2130 2131 /* 2132 * When new data is acked, open the congestion window. 2133 * If the window gives us less than ssthresh packets 2134 * in flight, open exponentially (maxseg per packet). 2135 * Otherwise open linearly: maxseg per window 2136 * (maxseg^2 / cwnd per packet). 2137 */ 2138 if ((!tcp_do_newreno && !tp->sack_enable) || 2139 !IN_FASTRECOVERY(tp)) { 2140 register u_int cw = tp->snd_cwnd; 2141 register u_int incr = tp->t_maxseg; 2142 if (cw > tp->snd_ssthresh) 2143 incr = incr * incr / cw; 2144 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2145 } 2146 SOCKBUF_LOCK(&so->so_snd); 2147 if (acked > so->so_snd.sb_cc) { 2148 tp->snd_wnd -= so->so_snd.sb_cc; 2149 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2150 ourfinisacked = 1; 2151 } else { 2152 sbdrop_locked(&so->so_snd, acked); 2153 tp->snd_wnd -= acked; 2154 ourfinisacked = 0; 2155 } 2156 SOCKBUF_UNLOCK(&so->so_snd); 2157 sowwakeup(so); 2158 /* detect una wraparound */ 2159 if ((tcp_do_newreno || tp->sack_enable) && 2160 !IN_FASTRECOVERY(tp) && 2161 SEQ_GT(tp->snd_una, tp->snd_recover) && 2162 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2163 tp->snd_recover = th->th_ack - 1; 2164 if ((tcp_do_newreno || tp->sack_enable) && 2165 IN_FASTRECOVERY(tp) && 2166 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2167 EXIT_FASTRECOVERY(tp); 2168 tp->snd_una = th->th_ack; 2169 if (tp->sack_enable) { 2170 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2171 tp->snd_recover = tp->snd_una; 2172 } 2173 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2174 tp->snd_nxt = tp->snd_una; 2175 2176 switch (tp->t_state) { 2177 2178 /* 2179 * In FIN_WAIT_1 STATE in addition to the processing 2180 * for the ESTABLISHED state if our FIN is now acknowledged 2181 * then enter FIN_WAIT_2. 2182 */ 2183 case TCPS_FIN_WAIT_1: 2184 if (ourfinisacked) { 2185 /* 2186 * If we can't receive any more 2187 * data, then closing user can proceed. 2188 * Starting the timer is contrary to the 2189 * specification, but if we don't get a FIN 2190 * we'll hang forever. 2191 */ 2192 /* XXXjl 2193 * we should release the tp also, and use a 2194 * compressed state. 2195 */ 2196 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2197 soisdisconnected(so); 2198 callout_reset(tp->tt_2msl, tcp_maxidle, 2199 tcp_timer_2msl, tp); 2200 } 2201 tp->t_state = TCPS_FIN_WAIT_2; 2202 } 2203 break; 2204 2205 /* 2206 * In CLOSING STATE in addition to the processing for 2207 * the ESTABLISHED state if the ACK acknowledges our FIN 2208 * then enter the TIME-WAIT state, otherwise ignore 2209 * the segment. 2210 */ 2211 case TCPS_CLOSING: 2212 if (ourfinisacked) { 2213 KASSERT(headlocked, ("headlocked")); 2214 tcp_twstart(tp); 2215 INP_INFO_WUNLOCK(&tcbinfo); 2216 m_freem(m); 2217 return; 2218 } 2219 break; 2220 2221 /* 2222 * In LAST_ACK, we may still be waiting for data to drain 2223 * and/or to be acked, as well as for the ack of our FIN. 2224 * If our FIN is now acknowledged, delete the TCB, 2225 * enter the closed state and return. 2226 */ 2227 case TCPS_LAST_ACK: 2228 if (ourfinisacked) { 2229 tp = tcp_close(tp); 2230 goto drop; 2231 } 2232 break; 2233 2234 /* 2235 * In TIME_WAIT state the only thing that should arrive 2236 * is a retransmission of the remote FIN. Acknowledge 2237 * it and restart the finack timer. 2238 */ 2239 case TCPS_TIME_WAIT: 2240 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2241 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2242 tcp_timer_2msl, tp); 2243 goto dropafterack; 2244 } 2245 } 2246 2247step6: 2248 /* 2249 * Update window information. 2250 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2251 */ 2252 if ((thflags & TH_ACK) && 2253 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2254 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2255 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2256 /* keep track of pure window updates */ 2257 if (tlen == 0 && 2258 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2259 tcpstat.tcps_rcvwinupd++; 2260 tp->snd_wnd = tiwin; 2261 tp->snd_wl1 = th->th_seq; 2262 tp->snd_wl2 = th->th_ack; 2263 if (tp->snd_wnd > tp->max_sndwnd) 2264 tp->max_sndwnd = tp->snd_wnd; 2265 needoutput = 1; 2266 } 2267 2268 /* 2269 * Process segments with URG. 2270 */ 2271 if ((thflags & TH_URG) && th->th_urp && 2272 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2273 /* 2274 * This is a kludge, but if we receive and accept 2275 * random urgent pointers, we'll crash in 2276 * soreceive. It's hard to imagine someone 2277 * actually wanting to send this much urgent data. 2278 */ 2279 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2280 th->th_urp = 0; /* XXX */ 2281 thflags &= ~TH_URG; /* XXX */ 2282 goto dodata; /* XXX */ 2283 } 2284 /* 2285 * If this segment advances the known urgent pointer, 2286 * then mark the data stream. This should not happen 2287 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2288 * a FIN has been received from the remote side. 2289 * In these states we ignore the URG. 2290 * 2291 * According to RFC961 (Assigned Protocols), 2292 * the urgent pointer points to the last octet 2293 * of urgent data. We continue, however, 2294 * to consider it to indicate the first octet 2295 * of data past the urgent section as the original 2296 * spec states (in one of two places). 2297 */ 2298 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2299 tp->rcv_up = th->th_seq + th->th_urp; 2300 SOCKBUF_LOCK(&so->so_rcv); 2301 so->so_oobmark = so->so_rcv.sb_cc + 2302 (tp->rcv_up - tp->rcv_nxt) - 1; 2303 if (so->so_oobmark == 0) 2304 so->so_rcv.sb_state |= SBS_RCVATMARK; 2305 SOCKBUF_UNLOCK(&so->so_rcv); 2306 sohasoutofband(so); 2307 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2308 } 2309 /* 2310 * Remove out of band data so doesn't get presented to user. 2311 * This can happen independent of advancing the URG pointer, 2312 * but if two URG's are pending at once, some out-of-band 2313 * data may creep in... ick. 2314 */ 2315 if (th->th_urp <= (u_long)tlen && 2316 !(so->so_options & SO_OOBINLINE)) { 2317 /* hdr drop is delayed */ 2318 tcp_pulloutofband(so, th, m, drop_hdrlen); 2319 } 2320 } else { 2321 /* 2322 * If no out of band data is expected, 2323 * pull receive urgent pointer along 2324 * with the receive window. 2325 */ 2326 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2327 tp->rcv_up = tp->rcv_nxt; 2328 } 2329dodata: /* XXX */ 2330 KASSERT(headlocked, ("headlocked")); 2331 /* 2332 * Process the segment text, merging it into the TCP sequencing queue, 2333 * and arranging for acknowledgment of receipt if necessary. 2334 * This process logically involves adjusting tp->rcv_wnd as data 2335 * is presented to the user (this happens in tcp_usrreq.c, 2336 * case PRU_RCVD). If a FIN has already been received on this 2337 * connection then we just ignore the text. 2338 */ 2339 if ((tlen || (thflags & TH_FIN)) && 2340 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2341 m_adj(m, drop_hdrlen); /* delayed header drop */ 2342 /* 2343 * Insert segment which includes th into TCP reassembly queue 2344 * with control block tp. Set thflags to whether reassembly now 2345 * includes a segment with FIN. This handles the common case 2346 * inline (segment is the next to be received on an established 2347 * connection, and the queue is empty), avoiding linkage into 2348 * and removal from the queue and repetition of various 2349 * conversions. 2350 * Set DELACK for segments received in order, but ack 2351 * immediately when segments are out of order (so 2352 * fast retransmit can work). 2353 */ 2354 if (th->th_seq == tp->rcv_nxt && 2355 LIST_EMPTY(&tp->t_segq) && 2356 TCPS_HAVEESTABLISHED(tp->t_state)) { 2357 if (DELAY_ACK(tp)) 2358 tp->t_flags |= TF_DELACK; 2359 else 2360 tp->t_flags |= TF_ACKNOW; 2361 tp->rcv_nxt += tlen; 2362 thflags = th->th_flags & TH_FIN; 2363 tcpstat.tcps_rcvpack++; 2364 tcpstat.tcps_rcvbyte += tlen; 2365 ND6_HINT(tp); 2366 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2367 m_freem(m); 2368 else 2369 sbappendstream(&so->so_rcv, m); 2370 sorwakeup(so); 2371 } else { 2372 thflags = tcp_reass(tp, th, &tlen, m); 2373 tp->t_flags |= TF_ACKNOW; 2374 } 2375 if (tp->sack_enable) 2376 tcp_update_sack_list(tp); 2377 /* 2378 * Note the amount of data that peer has sent into 2379 * our window, in order to estimate the sender's 2380 * buffer size. 2381 */ 2382 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2383 } else { 2384 m_freem(m); 2385 thflags &= ~TH_FIN; 2386 } 2387 2388 /* 2389 * If FIN is received ACK the FIN and let the user know 2390 * that the connection is closing. 2391 */ 2392 if (thflags & TH_FIN) { 2393 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2394 socantrcvmore(so); 2395 /* 2396 * If connection is half-synchronized 2397 * (ie NEEDSYN flag on) then delay ACK, 2398 * so it may be piggybacked when SYN is sent. 2399 * Otherwise, since we received a FIN then no 2400 * more input can be expected, send ACK now. 2401 */ 2402 if (tp->t_flags & TF_NEEDSYN) 2403 tp->t_flags |= TF_DELACK; 2404 else 2405 tp->t_flags |= TF_ACKNOW; 2406 tp->rcv_nxt++; 2407 } 2408 switch (tp->t_state) { 2409 2410 /* 2411 * In SYN_RECEIVED and ESTABLISHED STATES 2412 * enter the CLOSE_WAIT state. 2413 */ 2414 case TCPS_SYN_RECEIVED: 2415 tp->t_starttime = ticks; 2416 /*FALLTHROUGH*/ 2417 case TCPS_ESTABLISHED: 2418 tp->t_state = TCPS_CLOSE_WAIT; 2419 break; 2420 2421 /* 2422 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2423 * enter the CLOSING state. 2424 */ 2425 case TCPS_FIN_WAIT_1: 2426 tp->t_state = TCPS_CLOSING; 2427 break; 2428 2429 /* 2430 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2431 * starting the time-wait timer, turning off the other 2432 * standard timers. 2433 */ 2434 case TCPS_FIN_WAIT_2: 2435 KASSERT(headlocked == 1, ("headlocked should be 1")); 2436 tcp_twstart(tp); 2437 INP_INFO_WUNLOCK(&tcbinfo); 2438 return; 2439 2440 /* 2441 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2442 */ 2443 case TCPS_TIME_WAIT: 2444 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2445 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2446 tcp_timer_2msl, tp); 2447 break; 2448 } 2449 } 2450 INP_INFO_WUNLOCK(&tcbinfo); 2451#ifdef TCPDEBUG 2452 if (so->so_options & SO_DEBUG) 2453 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2454 &tcp_savetcp, 0); 2455#endif 2456 2457 /* 2458 * Return any desired output. 2459 */ 2460 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2461 (void) tcp_output(tp); 2462 2463check_delack: 2464 if (tp->t_flags & TF_DELACK) { 2465 tp->t_flags &= ~TF_DELACK; 2466 callout_reset(tp->tt_delack, tcp_delacktime, 2467 tcp_timer_delack, tp); 2468 } 2469 INP_UNLOCK(inp); 2470 return; 2471 2472dropafterack: 2473 /* 2474 * Generate an ACK dropping incoming segment if it occupies 2475 * sequence space, where the ACK reflects our state. 2476 * 2477 * We can now skip the test for the RST flag since all 2478 * paths to this code happen after packets containing 2479 * RST have been dropped. 2480 * 2481 * In the SYN-RECEIVED state, don't send an ACK unless the 2482 * segment we received passes the SYN-RECEIVED ACK test. 2483 * If it fails send a RST. This breaks the loop in the 2484 * "LAND" DoS attack, and also prevents an ACK storm 2485 * between two listening ports that have been sent forged 2486 * SYN segments, each with the source address of the other. 2487 */ 2488 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2489 (SEQ_GT(tp->snd_una, th->th_ack) || 2490 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2491 rstreason = BANDLIM_RST_OPENPORT; 2492 goto dropwithreset; 2493 } 2494#ifdef TCPDEBUG 2495 if (so->so_options & SO_DEBUG) 2496 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2497 &tcp_savetcp, 0); 2498#endif 2499 KASSERT(headlocked, ("headlocked should be 1")); 2500 INP_INFO_WUNLOCK(&tcbinfo); 2501 m_freem(m); 2502 tp->t_flags |= TF_ACKNOW; 2503 (void) tcp_output(tp); 2504 INP_UNLOCK(inp); 2505 return; 2506 2507dropwithreset: 2508 /* 2509 * Generate a RST, dropping incoming segment. 2510 * Make ACK acceptable to originator of segment. 2511 * Don't bother to respond if destination was broadcast/multicast. 2512 */ 2513 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2514 goto drop; 2515 if (isipv6) { 2516 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2517 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2518 goto drop; 2519 } else { 2520 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2521 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2522 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2523 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2524 goto drop; 2525 } 2526 /* IPv6 anycast check is done at tcp6_input() */ 2527 2528 /* 2529 * Perform bandwidth limiting. 2530 */ 2531 if (badport_bandlim(rstreason) < 0) 2532 goto drop; 2533 2534#ifdef TCPDEBUG 2535 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2536 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2537 &tcp_savetcp, 0); 2538#endif 2539 2540 if (thflags & TH_ACK) 2541 /* mtod() below is safe as long as hdr dropping is delayed */ 2542 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2543 TH_RST); 2544 else { 2545 if (thflags & TH_SYN) 2546 tlen++; 2547 /* mtod() below is safe as long as hdr dropping is delayed */ 2548 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2549 (tcp_seq)0, TH_RST|TH_ACK); 2550 } 2551 2552 if (tp) 2553 INP_UNLOCK(inp); 2554 if (headlocked) 2555 INP_INFO_WUNLOCK(&tcbinfo); 2556 return; 2557 2558drop: 2559 /* 2560 * Drop space held by incoming segment and return. 2561 */ 2562#ifdef TCPDEBUG 2563 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2564 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2565 &tcp_savetcp, 0); 2566#endif 2567 if (tp) 2568 INP_UNLOCK(inp); 2569 m_freem(m); 2570 if (headlocked) 2571 INP_INFO_WUNLOCK(&tcbinfo); 2572 return; 2573} 2574 2575/* 2576 * Parse TCP options and place in tcpopt. 2577 */ 2578static void 2579tcp_dooptions(tp, to, cp, cnt, is_syn, th) 2580 struct tcpcb *tp; 2581 struct tcpopt *to; 2582 u_char *cp; 2583 int cnt; 2584 int is_syn; 2585 struct tcphdr *th; 2586{ 2587 int opt, optlen; 2588 2589 to->to_flags = 0; 2590 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2591 opt = cp[0]; 2592 if (opt == TCPOPT_EOL) 2593 break; 2594 if (opt == TCPOPT_NOP) 2595 optlen = 1; 2596 else { 2597 if (cnt < 2) 2598 break; 2599 optlen = cp[1]; 2600 if (optlen < 2 || optlen > cnt) 2601 break; 2602 } 2603 switch (opt) { 2604 case TCPOPT_MAXSEG: 2605 if (optlen != TCPOLEN_MAXSEG) 2606 continue; 2607 if (!is_syn) 2608 continue; 2609 to->to_flags |= TOF_MSS; 2610 bcopy((char *)cp + 2, 2611 (char *)&to->to_mss, sizeof(to->to_mss)); 2612 to->to_mss = ntohs(to->to_mss); 2613 break; 2614 case TCPOPT_WINDOW: 2615 if (optlen != TCPOLEN_WINDOW) 2616 continue; 2617 if (! is_syn) 2618 continue; 2619 to->to_flags |= TOF_SCALE; 2620 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2621 break; 2622 case TCPOPT_TIMESTAMP: 2623 if (optlen != TCPOLEN_TIMESTAMP) 2624 continue; 2625 to->to_flags |= TOF_TS; 2626 bcopy((char *)cp + 2, 2627 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2628 to->to_tsval = ntohl(to->to_tsval); 2629 bcopy((char *)cp + 6, 2630 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2631 to->to_tsecr = ntohl(to->to_tsecr); 2632 break; 2633 case TCPOPT_CC: 2634 if (optlen != TCPOLEN_CC) 2635 continue; 2636 to->to_flags |= TOF_CC; 2637 bcopy((char *)cp + 2, 2638 (char *)&to->to_cc, sizeof(to->to_cc)); 2639 to->to_cc = ntohl(to->to_cc); 2640 break; 2641 case TCPOPT_CCNEW: 2642 if (optlen != TCPOLEN_CC) 2643 continue; 2644 if (!is_syn) 2645 continue; 2646 to->to_flags |= TOF_CCNEW; 2647 bcopy((char *)cp + 2, 2648 (char *)&to->to_cc, sizeof(to->to_cc)); 2649 to->to_cc = ntohl(to->to_cc); 2650 break; 2651 case TCPOPT_CCECHO: 2652 if (optlen != TCPOLEN_CC) 2653 continue; 2654 if (!is_syn) 2655 continue; 2656 to->to_flags |= TOF_CCECHO; 2657 bcopy((char *)cp + 2, 2658 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2659 to->to_ccecho = ntohl(to->to_ccecho); 2660 break; 2661#ifdef TCP_SIGNATURE 2662 /* 2663 * XXX In order to reply to a host which has set the 2664 * TCP_SIGNATURE option in its initial SYN, we have to 2665 * record the fact that the option was observed here 2666 * for the syncache code to perform the correct response. 2667 */ 2668 case TCPOPT_SIGNATURE: 2669 if (optlen != TCPOLEN_SIGNATURE) 2670 continue; 2671 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2672 break; 2673#endif 2674 case TCPOPT_SACK_PERMITTED: 2675 if (!tcp_do_sack || 2676 optlen != TCPOLEN_SACK_PERMITTED) 2677 continue; 2678 if (is_syn) { 2679 /* MUST only be set on SYN */ 2680 to->to_flags |= TOF_SACK; 2681 } 2682 break; 2683 2684 case TCPOPT_SACK: 2685 if (!tp || tcp_sack_option(tp, th, cp, optlen)) 2686 continue; 2687 break; 2688 default: 2689 continue; 2690 } 2691 } 2692} 2693 2694/* 2695 * Pull out of band byte out of a segment so 2696 * it doesn't appear in the user's data queue. 2697 * It is still reflected in the segment length for 2698 * sequencing purposes. 2699 */ 2700static void 2701tcp_pulloutofband(so, th, m, off) 2702 struct socket *so; 2703 struct tcphdr *th; 2704 register struct mbuf *m; 2705 int off; /* delayed to be droped hdrlen */ 2706{ 2707 int cnt = off + th->th_urp - 1; 2708 2709 while (cnt >= 0) { 2710 if (m->m_len > cnt) { 2711 char *cp = mtod(m, caddr_t) + cnt; 2712 struct tcpcb *tp = sototcpcb(so); 2713 2714 tp->t_iobc = *cp; 2715 tp->t_oobflags |= TCPOOB_HAVEDATA; 2716 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2717 m->m_len--; 2718 if (m->m_flags & M_PKTHDR) 2719 m->m_pkthdr.len--; 2720 return; 2721 } 2722 cnt -= m->m_len; 2723 m = m->m_next; 2724 if (m == 0) 2725 break; 2726 } 2727 panic("tcp_pulloutofband"); 2728} 2729 2730/* 2731 * Collect new round-trip time estimate 2732 * and update averages and current timeout. 2733 */ 2734static void 2735tcp_xmit_timer(tp, rtt) 2736 register struct tcpcb *tp; 2737 int rtt; 2738{ 2739 register int delta; 2740 2741 tcpstat.tcps_rttupdated++; 2742 tp->t_rttupdated++; 2743 if (tp->t_srtt != 0) { 2744 /* 2745 * srtt is stored as fixed point with 5 bits after the 2746 * binary point (i.e., scaled by 8). The following magic 2747 * is equivalent to the smoothing algorithm in rfc793 with 2748 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2749 * point). Adjust rtt to origin 0. 2750 */ 2751 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2752 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2753 2754 if ((tp->t_srtt += delta) <= 0) 2755 tp->t_srtt = 1; 2756 2757 /* 2758 * We accumulate a smoothed rtt variance (actually, a 2759 * smoothed mean difference), then set the retransmit 2760 * timer to smoothed rtt + 4 times the smoothed variance. 2761 * rttvar is stored as fixed point with 4 bits after the 2762 * binary point (scaled by 16). The following is 2763 * equivalent to rfc793 smoothing with an alpha of .75 2764 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2765 * rfc793's wired-in beta. 2766 */ 2767 if (delta < 0) 2768 delta = -delta; 2769 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2770 if ((tp->t_rttvar += delta) <= 0) 2771 tp->t_rttvar = 1; 2772 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2773 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2774 } else { 2775 /* 2776 * No rtt measurement yet - use the unsmoothed rtt. 2777 * Set the variance to half the rtt (so our first 2778 * retransmit happens at 3*rtt). 2779 */ 2780 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2781 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2782 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2783 } 2784 tp->t_rtttime = 0; 2785 tp->t_rxtshift = 0; 2786 2787 /* 2788 * the retransmit should happen at rtt + 4 * rttvar. 2789 * Because of the way we do the smoothing, srtt and rttvar 2790 * will each average +1/2 tick of bias. When we compute 2791 * the retransmit timer, we want 1/2 tick of rounding and 2792 * 1 extra tick because of +-1/2 tick uncertainty in the 2793 * firing of the timer. The bias will give us exactly the 2794 * 1.5 tick we need. But, because the bias is 2795 * statistical, we have to test that we don't drop below 2796 * the minimum feasible timer (which is 2 ticks). 2797 */ 2798 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2799 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2800 2801 /* 2802 * We received an ack for a packet that wasn't retransmitted; 2803 * it is probably safe to discard any error indications we've 2804 * received recently. This isn't quite right, but close enough 2805 * for now (a route might have failed after we sent a segment, 2806 * and the return path might not be symmetrical). 2807 */ 2808 tp->t_softerror = 0; 2809} 2810 2811/* 2812 * Determine a reasonable value for maxseg size. 2813 * If the route is known, check route for mtu. 2814 * If none, use an mss that can be handled on the outgoing 2815 * interface without forcing IP to fragment; if bigger than 2816 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2817 * to utilize large mbufs. If no route is found, route has no mtu, 2818 * or the destination isn't local, use a default, hopefully conservative 2819 * size (usually 512 or the default IP max size, but no more than the mtu 2820 * of the interface), as we can't discover anything about intervening 2821 * gateways or networks. We also initialize the congestion/slow start 2822 * window to be a single segment if the destination isn't local. 2823 * While looking at the routing entry, we also initialize other path-dependent 2824 * parameters from pre-set or cached values in the routing entry. 2825 * 2826 * Also take into account the space needed for options that we 2827 * send regularly. Make maxseg shorter by that amount to assure 2828 * that we can send maxseg amount of data even when the options 2829 * are present. Store the upper limit of the length of options plus 2830 * data in maxopd. 2831 * 2832 * 2833 * In case of T/TCP, we call this routine during implicit connection 2834 * setup as well (offer = -1), to initialize maxseg from the cached 2835 * MSS of our peer. 2836 * 2837 * NOTE that this routine is only called when we process an incoming 2838 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2839 */ 2840void 2841tcp_mss(tp, offer) 2842 struct tcpcb *tp; 2843 int offer; 2844{ 2845 int rtt, mss; 2846 u_long bufsize; 2847 u_long maxmtu; 2848 struct inpcb *inp = tp->t_inpcb; 2849 struct socket *so; 2850 struct hc_metrics_lite metrics; 2851 struct rmxp_tao tao; 2852 int origoffer = offer; 2853#ifdef INET6 2854 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2855 size_t min_protoh = isipv6 ? 2856 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2857 sizeof (struct tcpiphdr); 2858#else 2859 const size_t min_protoh = sizeof(struct tcpiphdr); 2860#endif 2861 bzero(&tao, sizeof(tao)); 2862 2863 /* initialize */ 2864#ifdef INET6 2865 if (isipv6) { 2866 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2867 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2868 } else 2869#endif 2870 { 2871 maxmtu = tcp_maxmtu(&inp->inp_inc); 2872 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2873 } 2874 so = inp->inp_socket; 2875 2876 /* 2877 * no route to sender, stay with default mss and return 2878 */ 2879 if (maxmtu == 0) 2880 return; 2881 2882 /* what have we got? */ 2883 switch (offer) { 2884 case 0: 2885 /* 2886 * Offer == 0 means that there was no MSS on the SYN 2887 * segment, in this case we use tcp_mssdflt. 2888 */ 2889 offer = 2890#ifdef INET6 2891 isipv6 ? tcp_v6mssdflt : 2892#endif 2893 tcp_mssdflt; 2894 break; 2895 2896 case -1: 2897 /* 2898 * Offer == -1 means that we didn't receive SYN yet, 2899 * use cached value in that case; 2900 */ 2901 if (tcp_do_rfc1644) 2902 tcp_hc_gettao(&inp->inp_inc, &tao); 2903 if (tao.tao_mssopt != 0) 2904 offer = tao.tao_mssopt; 2905 /* FALLTHROUGH */ 2906 2907 default: 2908 /* 2909 * Prevent DoS attack with too small MSS. Round up 2910 * to at least minmss. 2911 */ 2912 offer = max(offer, tcp_minmss); 2913 /* 2914 * Sanity check: make sure that maxopd will be large 2915 * enough to allow some data on segments even if the 2916 * all the option space is used (40bytes). Otherwise 2917 * funny things may happen in tcp_output. 2918 */ 2919 offer = max(offer, 64); 2920 if (tcp_do_rfc1644) 2921 tcp_hc_updatetao(&inp->inp_inc, 2922 TCP_HC_TAO_MSSOPT, 0, offer); 2923 } 2924 2925 /* 2926 * rmx information is now retrieved from tcp_hostcache 2927 */ 2928 tcp_hc_get(&inp->inp_inc, &metrics); 2929 2930 /* 2931 * if there's a discovered mtu int tcp hostcache, use it 2932 * else, use the link mtu. 2933 */ 2934 if (metrics.rmx_mtu) 2935 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2936 else { 2937#ifdef INET6 2938 if (isipv6) { 2939 mss = maxmtu - min_protoh; 2940 if (!path_mtu_discovery && 2941 !in6_localaddr(&inp->in6p_faddr)) 2942 mss = min(mss, tcp_v6mssdflt); 2943 } else 2944#endif 2945 { 2946 mss = maxmtu - min_protoh; 2947 if (!path_mtu_discovery && 2948 !in_localaddr(inp->inp_faddr)) 2949 mss = min(mss, tcp_mssdflt); 2950 } 2951 } 2952 mss = min(mss, offer); 2953 2954 /* 2955 * maxopd stores the maximum length of data AND options 2956 * in a segment; maxseg is the amount of data in a normal 2957 * segment. We need to store this value (maxopd) apart 2958 * from maxseg, because now every segment carries options 2959 * and thus we normally have somewhat less data in segments. 2960 */ 2961 tp->t_maxopd = mss; 2962 2963 /* 2964 * In case of T/TCP, origoffer==-1 indicates, that no segments 2965 * were received yet. In this case we just guess, otherwise 2966 * we do the same as before T/TCP. 2967 */ 2968 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2969 (origoffer == -1 || 2970 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2971 mss -= TCPOLEN_TSTAMP_APPA; 2972 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2973 (origoffer == -1 || 2974 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2975 mss -= TCPOLEN_CC_APPA; 2976 tp->t_maxseg = mss; 2977 2978#if (MCLBYTES & (MCLBYTES - 1)) == 0 2979 if (mss > MCLBYTES) 2980 mss &= ~(MCLBYTES-1); 2981#else 2982 if (mss > MCLBYTES) 2983 mss = mss / MCLBYTES * MCLBYTES; 2984#endif 2985 tp->t_maxseg = mss; 2986 2987 /* 2988 * If there's a pipesize, change the socket buffer to that size, 2989 * don't change if sb_hiwat is different than default (then it 2990 * has been changed on purpose with setsockopt). 2991 * Make the socket buffers an integral number of mss units; 2992 * if the mss is larger than the socket buffer, decrease the mss. 2993 */ 2994 SOCKBUF_LOCK(&so->so_snd); 2995 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2996 bufsize = metrics.rmx_sendpipe; 2997 else 2998 bufsize = so->so_snd.sb_hiwat; 2999 if (bufsize < mss) 3000 mss = bufsize; 3001 else { 3002 bufsize = roundup(bufsize, mss); 3003 if (bufsize > sb_max) 3004 bufsize = sb_max; 3005 if (bufsize > so->so_snd.sb_hiwat) 3006 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3007 } 3008 SOCKBUF_UNLOCK(&so->so_snd); 3009 tp->t_maxseg = mss; 3010 3011 SOCKBUF_LOCK(&so->so_rcv); 3012 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3013 bufsize = metrics.rmx_recvpipe; 3014 else 3015 bufsize = so->so_rcv.sb_hiwat; 3016 if (bufsize > mss) { 3017 bufsize = roundup(bufsize, mss); 3018 if (bufsize > sb_max) 3019 bufsize = sb_max; 3020 if (bufsize > so->so_rcv.sb_hiwat) 3021 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3022 } 3023 SOCKBUF_UNLOCK(&so->so_rcv); 3024 /* 3025 * While we're here, check the others too 3026 */ 3027 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3028 tp->t_srtt = rtt; 3029 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3030 tcpstat.tcps_usedrtt++; 3031 if (metrics.rmx_rttvar) { 3032 tp->t_rttvar = metrics.rmx_rttvar; 3033 tcpstat.tcps_usedrttvar++; 3034 } else { 3035 /* default variation is +- 1 rtt */ 3036 tp->t_rttvar = 3037 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3038 } 3039 TCPT_RANGESET(tp->t_rxtcur, 3040 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3041 tp->t_rttmin, TCPTV_REXMTMAX); 3042 } 3043 if (metrics.rmx_ssthresh) { 3044 /* 3045 * There's some sort of gateway or interface 3046 * buffer limit on the path. Use this to set 3047 * the slow start threshhold, but set the 3048 * threshold to no less than 2*mss. 3049 */ 3050 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3051 tcpstat.tcps_usedssthresh++; 3052 } 3053 if (metrics.rmx_bandwidth) 3054 tp->snd_bandwidth = metrics.rmx_bandwidth; 3055 3056 /* 3057 * Set the slow-start flight size depending on whether this 3058 * is a local network or not. 3059 * 3060 * Extend this so we cache the cwnd too and retrieve it here. 3061 * Make cwnd even bigger than RFC3390 suggests but only if we 3062 * have previous experience with the remote host. Be careful 3063 * not make cwnd bigger than remote receive window or our own 3064 * send socket buffer. Maybe put some additional upper bound 3065 * on the retrieved cwnd. Should do incremental updates to 3066 * hostcache when cwnd collapses so next connection doesn't 3067 * overloads the path again. 3068 * 3069 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3070 * We currently check only in syncache_socket for that. 3071 */ 3072#define TCP_METRICS_CWND 3073#ifdef TCP_METRICS_CWND 3074 if (metrics.rmx_cwnd) 3075 tp->snd_cwnd = max(mss, 3076 min(metrics.rmx_cwnd / 2, 3077 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3078 else 3079#endif 3080 if (tcp_do_rfc3390) 3081 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3082#ifdef INET6 3083 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3084 (!isipv6 && in_localaddr(inp->inp_faddr))) 3085#else 3086 else if (in_localaddr(inp->inp_faddr)) 3087#endif 3088 tp->snd_cwnd = mss * ss_fltsz_local; 3089 else 3090 tp->snd_cwnd = mss * ss_fltsz; 3091} 3092 3093/* 3094 * Determine the MSS option to send on an outgoing SYN. 3095 */ 3096int 3097tcp_mssopt(inc) 3098 struct in_conninfo *inc; 3099{ 3100 int mss = 0; 3101 u_long maxmtu = 0; 3102 u_long thcmtu = 0; 3103 size_t min_protoh; 3104#ifdef INET6 3105 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3106#endif 3107 3108 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3109 3110#ifdef INET6 3111 if (isipv6) { 3112 mss = tcp_v6mssdflt; 3113 maxmtu = tcp_maxmtu6(inc); 3114 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3115 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3116 } else 3117#endif 3118 { 3119 mss = tcp_mssdflt; 3120 maxmtu = tcp_maxmtu(inc); 3121 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3122 min_protoh = sizeof(struct tcpiphdr); 3123 } 3124 if (maxmtu && thcmtu) 3125 mss = min(maxmtu, thcmtu) - min_protoh; 3126 else if (maxmtu || thcmtu) 3127 mss = max(maxmtu, thcmtu) - min_protoh; 3128 3129 return (mss); 3130} 3131 3132 3133/* 3134 * On a partial ack arrives, force the retransmission of the 3135 * next unacknowledged segment. Do not clear tp->t_dupacks. 3136 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3137 * be started again. 3138 */ 3139static void 3140tcp_newreno_partial_ack(tp, th) 3141 struct tcpcb *tp; 3142 struct tcphdr *th; 3143{ 3144 tcp_seq onxt = tp->snd_nxt; 3145 u_long ocwnd = tp->snd_cwnd; 3146 3147 callout_stop(tp->tt_rexmt); 3148 tp->t_rtttime = 0; 3149 tp->snd_nxt = th->th_ack; 3150 /* 3151 * Set snd_cwnd to one segment beyond acknowledged offset. 3152 * (tp->snd_una has not yet been updated when this function is called.) 3153 */ 3154 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3155 tp->t_flags |= TF_ACKNOW; 3156 (void) tcp_output(tp); 3157 tp->snd_cwnd = ocwnd; 3158 if (SEQ_GT(onxt, tp->snd_nxt)) 3159 tp->snd_nxt = onxt; 3160 /* 3161 * Partial window deflation. Relies on fact that tp->snd_una 3162 * not updated yet. 3163 */ 3164 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 3165} 3166 3167/* 3168 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3169 * looking for a pcb in the listen state. Returns 0 otherwise. 3170 */ 3171static int 3172tcp_timewait(tw, to, th, m, tlen) 3173 struct tcptw *tw; 3174 struct tcpopt *to; 3175 struct tcphdr *th; 3176 struct mbuf *m; 3177 int tlen; 3178{ 3179 int thflags; 3180 tcp_seq seq; 3181#ifdef INET6 3182 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3183#else 3184 const int isipv6 = 0; 3185#endif 3186 3187 thflags = th->th_flags; 3188 3189 /* 3190 * NOTE: for FIN_WAIT_2 (to be added later), 3191 * must validate sequence number before accepting RST 3192 */ 3193 3194 /* 3195 * If the segment contains RST: 3196 * Drop the segment - see Stevens, vol. 2, p. 964 and 3197 * RFC 1337. 3198 */ 3199 if (thflags & TH_RST) 3200 goto drop; 3201 3202 /* 3203 * If segment contains a SYN and CC [not CC.NEW] option: 3204 * if connection duration > MSL, drop packet and send RST; 3205 * 3206 * if SEG.CC > CCrecv then is new SYN. 3207 * Complete close and delete TCPCB. Then reprocess 3208 * segment, hoping to find new TCPCB in LISTEN state; 3209 * 3210 * else must be old SYN; drop it. 3211 * else do normal processing. 3212 */ 3213 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) { 3214 if ((ticks - tw->t_starttime) > tcp_msl) 3215 goto reset; 3216 if (CC_GT(to->to_cc, tw->cc_recv)) { 3217 (void) tcp_twclose(tw, 0); 3218 return (1); 3219 } 3220 goto drop; 3221 } 3222 3223#if 0 3224/* PAWS not needed at the moment */ 3225 /* 3226 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3227 * and it's less than ts_recent, drop it. 3228 */ 3229 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3230 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3231 if ((thflags & TH_ACK) == 0) 3232 goto drop; 3233 goto ack; 3234 } 3235 /* 3236 * ts_recent is never updated because we never accept new segments. 3237 */ 3238#endif 3239 3240 /* 3241 * If a new connection request is received 3242 * while in TIME_WAIT, drop the old connection 3243 * and start over if the sequence numbers 3244 * are above the previous ones. 3245 */ 3246 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3247 (void) tcp_twclose(tw, 0); 3248 return (1); 3249 } 3250 3251 /* 3252 * Drop the the segment if it does not contain an ACK. 3253 */ 3254 if ((thflags & TH_ACK) == 0) 3255 goto drop; 3256 3257 /* 3258 * Reset the 2MSL timer if this is a duplicate FIN. 3259 */ 3260 if (thflags & TH_FIN) { 3261 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3262 if (seq + 1 == tw->rcv_nxt) 3263 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3264 } 3265 3266 /* 3267 * Acknowledge the segment if it has data or is not a duplicate ACK. 3268 */ 3269 if (thflags != TH_ACK || tlen != 0 || 3270 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3271 tcp_twrespond(tw, TH_ACK); 3272 goto drop; 3273 3274reset: 3275 /* 3276 * Generate a RST, dropping incoming segment. 3277 * Make ACK acceptable to originator of segment. 3278 * Don't bother to respond if destination was broadcast/multicast. 3279 */ 3280 if (m->m_flags & (M_BCAST|M_MCAST)) 3281 goto drop; 3282 if (isipv6) { 3283 struct ip6_hdr *ip6; 3284 3285 /* IPv6 anycast check is done at tcp6_input() */ 3286 ip6 = mtod(m, struct ip6_hdr *); 3287 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3288 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3289 goto drop; 3290 } else { 3291 struct ip *ip; 3292 3293 ip = mtod(m, struct ip *); 3294 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3295 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3296 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3297 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3298 goto drop; 3299 } 3300 if (thflags & TH_ACK) { 3301 tcp_respond(NULL, 3302 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3303 } else { 3304 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3305 tcp_respond(NULL, 3306 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3307 } 3308 INP_UNLOCK(tw->tw_inpcb); 3309 return (0); 3310 3311drop: 3312 INP_UNLOCK(tw->tw_inpcb); 3313 m_freem(m); 3314 return (0); 3315} 3316