1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 34 * $FreeBSD$ 35 */ 36 37 #include "opt_ipfw.h" /* for ipfw_fwd */ 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_tcpdebug.h" 41 #include "opt_tcp_input.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/kernel.h> 46 #include <sys/sysctl.h> 47 #include <sys/malloc.h> 48 #include <sys/mbuf.h> 49 #include <sys/proc.h> /* for proc0 declaration */ 50 #include <sys/protosw.h> 51 #include <sys/socket.h> 52 #include <sys/socketvar.h> 53 #include <sys/syslog.h> 54 55 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 56 57 #include <net/if.h> 58 #include <net/route.h> 59 60 #include <netinet/in.h> 61 #include <netinet/in_systm.h> 62 #include <netinet/ip.h> 63 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 64 #include <netinet/in_var.h> 65 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 66 #include <netinet/in_pcb.h> 67 #include <netinet/ip_var.h> 68 #ifdef INET6 69 #include <netinet/ip6.h> 70 #include <netinet/icmp6.h> 71 #include <netinet6/nd6.h> 72 #include <netinet6/ip6_var.h> 73 #include <netinet6/in6_pcb.h> 74 #endif 75 #include <netinet/tcp.h> 76 #include <netinet/tcp_fsm.h> 77 #include <netinet/tcp_seq.h> 78 #include <netinet/tcp_timer.h> 79 #include <netinet/tcp_var.h> 80 #ifdef INET6 81 #include <netinet6/tcp6_var.h> 82 #endif 83 #include <netinet/tcpip.h> 84 #ifdef TCPDEBUG 85 #include <netinet/tcp_debug.h> 86 87 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 88 struct tcphdr tcp_savetcp; 89 #endif /* TCPDEBUG */ 90 91 #ifdef IPSEC 92 #include <netinet6/ipsec.h> 93 #ifdef INET6 94 #include <netinet6/ipsec6.h> 95 #endif 96 #include <netkey/key.h> 97 #endif /*IPSEC*/ 98 99 #include <machine/in_cksum.h> 100 101 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 102 103 static int tcprexmtthresh = 3; 104 tcp_seq tcp_iss; 105 tcp_cc tcp_ccgen; 106 107 struct tcpstat tcpstat; 108 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RD, 109 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 110 111 static int log_in_vain = 0; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 113 &log_in_vain, 0, "Log all incoming TCP connections"); 114 115 static int blackhole = 0; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 117 &blackhole, 0, "Do not send RST when dropping refused connections"); 118 119 int tcp_delack_enabled = 1; 120 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 121 &tcp_delack_enabled, 0, 122 "Delay ACK to try and piggyback it onto a data packet"); 123 124 int tcp_lq_overflow = 1; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcp_lq_overflow, CTLFLAG_RW, 126 &tcp_lq_overflow, 0, 127 "Listen Queue Overflow"); 128 129 #ifdef TCP_DROP_SYNFIN 130 static int drop_synfin = 0; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 132 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 133 #endif 134 135 #ifdef TCP_RESTRICT_RST 136 static int restrict_rst = 0; 137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, restrict_rst, CTLFLAG_RW, 138 &restrict_rst, 0, "Restrict RST emission"); 139 #endif 140 141 struct inpcbhead tcb; 142 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 143 struct inpcbinfo tcbinfo; 144 145 static void tcp_dooptions __P((struct tcpcb *, 146 u_char *, int, struct tcphdr *, struct tcpopt *)); 147 static void tcp_pulloutofband __P((struct socket *, 148 struct tcphdr *, struct mbuf *, int)); 149 static int tcp_reass __P((struct tcpcb *, struct tcphdr *, int *, 150 struct mbuf *)); 151 static void tcp_xmit_timer __P((struct tcpcb *, int)); 152 static int tcp_newreno __P((struct tcpcb *, struct tcphdr *)); 153 154 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 155 #ifdef INET6 156 #define ND6_HINT(tp) \ 157 do { \ 158 if ((tp) && (tp)->t_inpcb && \ 159 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ 160 (tp)->t_inpcb->in6p_route.ro_rt) \ 161 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 162 } while (0) 163 #else 164 #define ND6_HINT(tp) 165 #endif 166 167 /* 168 * Insert segment which inludes th into reassembly queue of tcp with 169 * control block tp. Return TH_FIN if reassembly now includes 170 * a segment with FIN. The macro form does the common case inline 171 * (segment is the next to be received on an established connection, 172 * and the queue is empty), avoiding linkage into and removal 173 * from the queue and repetition of various conversions. 174 * Set DELACK for segments received in order, but ack immediately 175 * when segments are out of order (so fast retransmit can work). 176 */ 177 #define TCP_REASS(tp, th, tlenp, m, so, flags) { \ 178 if ((th)->th_seq == (tp)->rcv_nxt && \ 179 LIST_EMPTY(&(tp)->t_segq) && \ 180 (tp)->t_state == TCPS_ESTABLISHED) { \ 181 if (tcp_delack_enabled) \ 182 callout_reset(tp->tt_delack, tcp_delacktime, \ 183 tcp_timer_delack, tp); \ 184 else \ 185 tp->t_flags |= TF_ACKNOW; \ 186 (tp)->rcv_nxt += *(tlenp); \ 187 flags = (th)->th_flags & TH_FIN; \ 188 tcpstat.tcps_rcvpack++;\ 189 tcpstat.tcps_rcvbyte += *(tlenp);\ 190 ND6_HINT(tp); \ 191 sbappend(&(so)->so_rcv, (m)); \ 192 sorwakeup(so); \ 193 } else { \ 194 (flags) = tcp_reass((tp), (th), (tlenp), (m)); \ 195 tp->t_flags |= TF_ACKNOW; \ 196 } \ 197 } 198 199 static int 200 tcp_reass(tp, th, tlenp, m) 201 register struct tcpcb *tp; 202 register struct tcphdr *th; 203 int *tlenp; 204 struct mbuf *m; 205 { 206 struct tseg_qent *q; 207 struct tseg_qent *p = NULL; 208 struct tseg_qent *nq; 209 struct tseg_qent *te; 210 struct socket *so = tp->t_inpcb->inp_socket; 211 int flags; 212 213 /* 214 * Call with th==0 after become established to 215 * force pre-ESTABLISHED data up to user socket. 216 */ 217 if (th == 0) 218 goto present; 219 220 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */ 221 MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ, 222 M_NOWAIT); 223 if (te == NULL) { 224 tcpstat.tcps_rcvmemdrop++; 225 m_freem(m); 226 return (0); 227 } 228 229 /* 230 * Find a segment which begins after this one does. 231 */ 232 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 233 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 234 break; 235 p = q; 236 } 237 238 /* 239 * If there is a preceding segment, it may provide some of 240 * our data already. If so, drop the data from the incoming 241 * segment. If it provides all of our data, drop us. 242 */ 243 if (p != NULL) { 244 register int i; 245 /* conversion to int (in i) handles seq wraparound */ 246 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 247 if (i > 0) { 248 if (i >= *tlenp) { 249 tcpstat.tcps_rcvduppack++; 250 tcpstat.tcps_rcvdupbyte += *tlenp; 251 m_freem(m); 252 FREE(te, M_TSEGQ); 253 /* 254 * Try to present any queued data 255 * at the left window edge to the user. 256 * This is needed after the 3-WHS 257 * completes. 258 */ 259 goto present; /* ??? */ 260 } 261 m_adj(m, i); 262 *tlenp -= i; 263 th->th_seq += i; 264 } 265 } 266 tcpstat.tcps_rcvoopack++; 267 tcpstat.tcps_rcvoobyte += *tlenp; 268 269 /* 270 * While we overlap succeeding segments trim them or, 271 * if they are completely covered, dequeue them. 272 */ 273 while (q) { 274 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 275 if (i <= 0) 276 break; 277 if (i < q->tqe_len) { 278 q->tqe_th->th_seq += i; 279 q->tqe_len -= i; 280 m_adj(q->tqe_m, i); 281 break; 282 } 283 284 nq = LIST_NEXT(q, tqe_q); 285 LIST_REMOVE(q, tqe_q); 286 m_freem(q->tqe_m); 287 FREE(q, M_TSEGQ); 288 q = nq; 289 } 290 291 /* Insert the new segment queue entry into place. */ 292 te->tqe_m = m; 293 te->tqe_th = th; 294 te->tqe_len = *tlenp; 295 296 if (p == NULL) { 297 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 298 } else { 299 LIST_INSERT_AFTER(p, te, tqe_q); 300 } 301 302 present: 303 /* 304 * Present data to user, advancing rcv_nxt through 305 * completed sequence space. 306 */ 307 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 308 return (0); 309 q = LIST_FIRST(&tp->t_segq); 310 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 311 return (0); 312 do { 313 tp->rcv_nxt += q->tqe_len; 314 flags = q->tqe_th->th_flags & TH_FIN; 315 nq = LIST_NEXT(q, tqe_q); 316 LIST_REMOVE(q, tqe_q); 317 if (so->so_state & SS_CANTRCVMORE) 318 m_freem(q->tqe_m); 319 else 320 sbappend(&so->so_rcv, q->tqe_m); 321 FREE(q, M_TSEGQ); 322 q = nq; 323 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 324 ND6_HINT(tp); 325 sorwakeup(so); 326 return (flags); 327 } 328 329 /* 330 * TCP input routine, follows pages 65-76 of the 331 * protocol specification dated September, 1981 very closely. 332 */ 333 #ifdef INET6 334 int 335 tcp6_input(mp, offp, proto) 336 struct mbuf **mp; 337 int *offp, proto; 338 { 339 register struct mbuf *m = *mp; 340 341 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 342 343 /* 344 * draft-itojun-ipv6-tcp-to-anycast 345 * better place to put this in? 346 */ 347 if (m->m_flags & M_ANYCAST6) { 348 struct ip6_hdr *ip6; 349 350 ip6 = mtod(m, struct ip6_hdr *); 351 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 352 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 353 return IPPROTO_DONE; 354 } 355 356 tcp_input(m, *offp, proto); 357 return IPPROTO_DONE; 358 } 359 #endif 360 361 void 362 tcp_input(m, off0, proto) 363 register struct mbuf *m; 364 int off0, proto; 365 { 366 register struct tcphdr *th; 367 register struct ip *ip = NULL; 368 register struct ipovly *ipov; 369 register struct inpcb *inp; 370 u_char *optp = NULL; 371 int optlen = 0; 372 int len, tlen, off; 373 int drop_hdrlen; 374 register struct tcpcb *tp = 0; 375 register int thflags; 376 struct socket *so = 0; 377 int todrop, acked, ourfinisacked, needoutput = 0; 378 struct in_addr laddr; 379 #ifdef INET6 380 struct in6_addr laddr6; 381 #endif 382 int dropsocket = 0; 383 int iss = 0; 384 u_long tiwin; 385 struct tcpopt to; /* options in this segment */ 386 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 387 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 388 #ifdef TCPDEBUG 389 short ostate = 0; 390 #endif 391 #ifdef INET6 392 struct ip6_hdr *ip6 = NULL; 393 int isipv6; 394 #endif /* INET6 */ 395 396 #ifdef INET6 397 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 398 #endif 399 bzero((char *)&to, sizeof(to)); 400 401 tcpstat.tcps_rcvtotal++; 402 403 #ifdef INET6 404 if (isipv6) { 405 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 406 ip6 = mtod(m, struct ip6_hdr *); 407 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 408 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 409 tcpstat.tcps_rcvbadsum++; 410 goto drop; 411 } 412 th = (struct tcphdr *)((caddr_t)ip6 + off0); 413 } else 414 #endif /* INET6 */ 415 { 416 /* 417 * Get IP and TCP header together in first mbuf. 418 * Note: IP leaves IP header in first mbuf. 419 */ 420 if (off0 > sizeof (struct ip)) { 421 ip_stripoptions(m, (struct mbuf *)0); 422 off0 = sizeof(struct ip); 423 } 424 if (m->m_len < sizeof (struct tcpiphdr)) { 425 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 426 tcpstat.tcps_rcvshort++; 427 return; 428 } 429 } 430 ip = mtod(m, struct ip *); 431 ipov = (struct ipovly *)ip; 432 th = (struct tcphdr *)((caddr_t)ip + off0); 433 tlen = ip->ip_len; 434 435 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 436 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 437 th->th_sum = m->m_pkthdr.csum_data; 438 else 439 th->th_sum = in_pseudo(ip->ip_src.s_addr, 440 ip->ip_dst.s_addr, htonl(m->m_pkthdr.csum_data + 441 ip->ip_len + IPPROTO_TCP)); 442 th->th_sum ^= 0xffff; 443 } else { 444 /* 445 * Checksum extended TCP header and data. 446 */ 447 len = sizeof (struct ip) + tlen; 448 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 449 ipov->ih_len = (u_short)tlen; 450 HTONS(ipov->ih_len); 451 th->th_sum = in_cksum(m, len); 452 } 453 if (th->th_sum) { 454 tcpstat.tcps_rcvbadsum++; 455 goto drop; 456 } 457 #ifdef INET6 458 /* Re-initialization for later version check */ 459 ip->ip_v = IPVERSION; 460 #endif 461 } 462 463 /* 464 * Check that TCP offset makes sense, 465 * pull out TCP options and adjust length. XXX 466 */ 467 off = th->th_off << 2; 468 if (off < sizeof (struct tcphdr) || off > tlen) { 469 tcpstat.tcps_rcvbadoff++; 470 goto drop; 471 } 472 tlen -= off; /* tlen is used instead of ti->ti_len */ 473 if (off > sizeof (struct tcphdr)) { 474 #ifdef INET6 475 if (isipv6) { 476 IP6_EXTHDR_CHECK(m, off0, off, ); 477 ip6 = mtod(m, struct ip6_hdr *); 478 th = (struct tcphdr *)((caddr_t)ip6 + off0); 479 } else 480 #endif /* INET6 */ 481 { 482 if (m->m_len < sizeof(struct ip) + off) { 483 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 484 tcpstat.tcps_rcvshort++; 485 return; 486 } 487 ip = mtod(m, struct ip *); 488 ipov = (struct ipovly *)ip; 489 th = (struct tcphdr *)((caddr_t)ip + off0); 490 } 491 } 492 optlen = off - sizeof (struct tcphdr); 493 optp = (u_char *)(th + 1); 494 } 495 thflags = th->th_flags; 496 497 #ifdef TCP_DROP_SYNFIN 498 /* 499 * If the drop_synfin option is enabled, drop all packets with 500 * both the SYN and FIN bits set. This prevents e.g. nmap from 501 * identifying the TCP/IP stack. 502 * 503 * This is incompatible with RFC1644 extensions (T/TCP). 504 */ 505 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 506 goto drop; 507 #endif 508 509 /* 510 * Convert TCP protocol specific fields to host format. 511 */ 512 NTOHL(th->th_seq); 513 NTOHL(th->th_ack); 514 NTOHS(th->th_win); 515 NTOHS(th->th_urp); 516 517 /* 518 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options, 519 * until after ip6_savecontrol() is called and before other functions 520 * which don't want those proto headers. 521 * Because ip6_savecontrol() is going to parse the mbuf to 522 * search for data to be passed up to user-land, it wants mbuf 523 * parameters to be unchanged. 524 */ 525 drop_hdrlen = off0 + off; 526 527 /* 528 * Locate pcb for segment. 529 */ 530 findpcb: 531 #ifdef IPFIREWALL_FORWARD 532 if (ip_fw_fwd_addr != NULL 533 #ifdef INET6 534 && isipv6 == NULL /* IPv6 support is not yet */ 535 #endif /* INET6 */ 536 ) { 537 /* 538 * Diverted. Pretend to be the destination. 539 * already got one like this? 540 */ 541 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 542 ip->ip_dst, th->th_dport, 0, m->m_pkthdr.rcvif); 543 if (!inp) { 544 /* 545 * No, then it's new. Try find the ambushing socket 546 */ 547 if (!ip_fw_fwd_addr->sin_port) { 548 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, 549 th->th_sport, ip_fw_fwd_addr->sin_addr, 550 th->th_dport, 1, m->m_pkthdr.rcvif); 551 } else { 552 inp = in_pcblookup_hash(&tcbinfo, 553 ip->ip_src, th->th_sport, 554 ip_fw_fwd_addr->sin_addr, 555 ntohs(ip_fw_fwd_addr->sin_port), 1, 556 m->m_pkthdr.rcvif); 557 } 558 } 559 ip_fw_fwd_addr = NULL; 560 } else 561 #endif /* IPFIREWALL_FORWARD */ 562 { 563 #ifdef INET6 564 if (isipv6) 565 inp = in6_pcblookup_hash(&tcbinfo, &ip6->ip6_src, th->th_sport, 566 &ip6->ip6_dst, th->th_dport, 1, 567 m->m_pkthdr.rcvif); 568 else 569 #endif /* INET6 */ 570 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 571 ip->ip_dst, th->th_dport, 1, m->m_pkthdr.rcvif); 572 } 573 574 #ifdef IPSEC 575 #ifdef INET6 576 if (isipv6) { 577 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 578 ipsec6stat.in_polvio++; 579 goto drop; 580 } 581 } else 582 #endif /* INET6 */ 583 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 584 ipsecstat.in_polvio++; 585 goto drop; 586 } 587 #endif /*IPSEC*/ 588 589 /* 590 * If the state is CLOSED (i.e., TCB does not exist) then 591 * all data in the incoming segment is discarded. 592 * If the TCB exists but is in CLOSED state, it is embryonic, 593 * but should either do a listen or a connect soon. 594 */ 595 if (inp == NULL) { 596 if (log_in_vain) { 597 #ifdef INET6 598 char dbuf[INET6_ADDRSTRLEN], sbuf[INET6_ADDRSTRLEN]; 599 #else /* INET6 */ 600 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 601 #endif /* INET6 */ 602 603 #ifdef INET6 604 if (isipv6) { 605 strcpy(dbuf, ip6_sprintf(&ip6->ip6_dst)); 606 strcpy(sbuf, ip6_sprintf(&ip6->ip6_src)); 607 } else 608 #endif 609 { 610 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 611 strcpy(sbuf, inet_ntoa(ip->ip_src)); 612 } 613 switch (log_in_vain) { 614 case 1: 615 if(thflags & TH_SYN) 616 log(LOG_INFO, 617 "Connection attempt to TCP %s:%d from %s:%d\n", 618 dbuf, ntohs(th->th_dport), 619 sbuf, 620 ntohs(th->th_sport)); 621 break; 622 case 2: 623 log(LOG_INFO, 624 "Connection attempt to TCP %s:%d from %s:%d flags:0x%x\n", 625 dbuf, ntohs(th->th_dport), sbuf, 626 ntohs(th->th_sport), thflags); 627 break; 628 default: 629 break; 630 } 631 } 632 if (blackhole) { 633 switch (blackhole) { 634 case 1: 635 if (thflags & TH_SYN) 636 goto drop; 637 break; 638 case 2: 639 goto drop; 640 default: 641 goto drop; 642 } 643 } 644 goto maybedropwithreset; 645 } 646 tp = intotcpcb(inp); 647 if (tp == 0) 648 goto maybedropwithreset; 649 if (tp->t_state == TCPS_CLOSED) 650 goto drop; 651 652 /* Unscale the window into a 32-bit value. */ 653 if ((thflags & TH_SYN) == 0) 654 tiwin = th->th_win << tp->snd_scale; 655 else 656 tiwin = th->th_win; 657 658 #ifdef INET6 659 /* save packet options if user wanted */ 660 if (isipv6 && inp->in6p_flags & INP_CONTROLOPTS) { 661 if (inp->in6p_options) { 662 m_freem(inp->in6p_options); 663 inp->in6p_options = 0; 664 } 665 ip6_savecontrol(inp, &inp->in6p_options, ip6, m); 666 } 667 /* else, should also do ip_srcroute() here? */ 668 #endif /* INET6 */ 669 670 so = inp->inp_socket; 671 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 672 #ifdef TCPDEBUG 673 if (so->so_options & SO_DEBUG) { 674 ostate = tp->t_state; 675 #ifdef INET6 676 if (isipv6) 677 bcopy((char *)ip6, (char *)tcp_saveipgen, 678 sizeof(*ip6)); 679 else 680 #endif /* INET6 */ 681 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 682 tcp_savetcp = *th; 683 } 684 #endif 685 if (so->so_options & SO_ACCEPTCONN) { 686 register struct tcpcb *tp0 = tp; 687 struct socket *so2; 688 #ifdef IPSEC 689 struct socket *oso; 690 #endif 691 #ifdef INET6 692 struct inpcb *oinp = sotoinpcb(so); 693 #endif /* INET6 */ 694 695 #ifndef IPSEC 696 /* 697 * Current IPsec implementation makes incorrect IPsec 698 * cache if this check is done here. 699 * So delay this until duplicated socket is created. 700 */ 701 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 702 /* 703 * Note: dropwithreset makes sure we don't 704 * send a RST in response to a RST. 705 */ 706 if (thflags & TH_ACK) { 707 tcpstat.tcps_badsyn++; 708 goto maybedropwithreset; 709 } 710 goto drop; 711 } 712 #endif 713 so2 = sonewconn(so, 0); 714 if (so2 == 0) { 715 tcpstat.tcps_listendrop++; 716 so2 = sodropablereq(so); 717 if (so2) { 718 if (tcp_lq_overflow) 719 sototcpcb(so2)->t_flags |= 720 TF_LQ_OVERFLOW; 721 tcp_drop(sototcpcb(so2), ETIMEDOUT); 722 so2 = sonewconn(so, 0); 723 } 724 if (!so2) 725 goto drop; 726 } 727 #ifdef IPSEC 728 oso = so; 729 #endif 730 so = so2; 731 /* 732 * This is ugly, but .... 733 * 734 * Mark socket as temporary until we're 735 * committed to keeping it. The code at 736 * ``drop'' and ``dropwithreset'' check the 737 * flag dropsocket to see if the temporary 738 * socket created here should be discarded. 739 * We mark the socket as discardable until 740 * we're committed to it below in TCPS_LISTEN. 741 */ 742 dropsocket++; 743 inp = (struct inpcb *)so->so_pcb; 744 #ifdef INET6 745 if (isipv6) 746 inp->in6p_laddr = ip6->ip6_dst; 747 else { 748 if ((inp->inp_flags & IN6P_BINDV6ONLY) == 0) { 749 inp->inp_vflag &= ~INP_IPV6; 750 inp->inp_vflag |= INP_IPV4; 751 } 752 #endif /* INET6 */ 753 inp->inp_laddr = ip->ip_dst; 754 #ifdef INET6 755 } 756 #endif /* INET6 */ 757 inp->inp_lport = th->th_dport; 758 if (in_pcbinshash(inp) != 0) { 759 /* 760 * Undo the assignments above if we failed to 761 * put the PCB on the hash lists. 762 */ 763 #ifdef INET6 764 if (isipv6) 765 inp->in6p_laddr = in6addr_any; 766 else 767 #endif /* INET6 */ 768 inp->inp_laddr.s_addr = INADDR_ANY; 769 inp->inp_lport = 0; 770 goto drop; 771 } 772 #ifdef IPSEC 773 /* 774 * To avoid creating incorrectly cached IPsec 775 * association, this is need to be done here. 776 * 777 * Subject: (KAME-snap 748) 778 * From: Wayne Knowles <w.knowles@niwa.cri.nz> 779 * ftp://ftp.kame.net/pub/mail-list/snap-users/748 780 */ 781 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 782 /* 783 * Note: dropwithreset makes sure we don't 784 * send a RST in response to a RST. 785 */ 786 if (thflags & TH_ACK) { 787 tcpstat.tcps_badsyn++; 788 goto maybedropwithreset; 789 } 790 goto drop; 791 } 792 #endif 793 #ifdef INET6 794 if (isipv6) { 795 /* 796 * inherit socket options from the listening 797 * socket. 798 */ 799 inp->inp_flags |= 800 oinp->inp_flags & INP_CONTROLOPTS; 801 if (inp->inp_flags & INP_CONTROLOPTS) { 802 if (inp->in6p_options) { 803 m_freem(inp->in6p_options); 804 inp->in6p_options = 0; 805 } 806 ip6_savecontrol(inp, 807 &inp->in6p_options, 808 ip6, m); 809 } 810 } else 811 #endif /* INET6 */ 812 inp->inp_options = ip_srcroute(); 813 #ifdef IPSEC 814 /* copy old policy into new socket's */ 815 if (ipsec_copy_policy(sotoinpcb(oso)->inp_sp, 816 inp->inp_sp)) 817 printf("tcp_input: could not copy policy\n"); 818 #endif 819 tp = intotcpcb(inp); 820 tp->t_state = TCPS_LISTEN; 821 tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT); 822 823 /* Compute proper scaling value from buffer space */ 824 while (tp->request_r_scale < TCP_MAX_WINSHIFT && 825 TCP_MAXWIN << tp->request_r_scale < 826 so->so_rcv.sb_hiwat) 827 tp->request_r_scale++; 828 } 829 } 830 831 /* 832 * Segment received on connection. 833 * Reset idle time and keep-alive timer. 834 */ 835 tp->t_rcvtime = ticks; 836 if (TCPS_HAVEESTABLISHED(tp->t_state)) 837 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 838 839 /* 840 * Process options if not in LISTEN state, 841 * else do it below (after getting remote address). 842 */ 843 if (tp->t_state != TCPS_LISTEN) 844 tcp_dooptions(tp, optp, optlen, th, &to); 845 846 /* 847 * Header prediction: check for the two common cases 848 * of a uni-directional data xfer. If the packet has 849 * no control flags, is in-sequence, the window didn't 850 * change and we're not retransmitting, it's a 851 * candidate. If the length is zero and the ack moved 852 * forward, we're the sender side of the xfer. Just 853 * free the data acked & wake any higher level process 854 * that was blocked waiting for space. If the length 855 * is non-zero and the ack didn't move, we're the 856 * receiver side. If we're getting packets in-order 857 * (the reassembly queue is empty), add the data to 858 * the socket buffer and note that we need a delayed ack. 859 * Make sure that the hidden state-flags are also off. 860 * Since we check for TCPS_ESTABLISHED above, it can only 861 * be TH_NEEDSYN. 862 */ 863 if (tp->t_state == TCPS_ESTABLISHED && 864 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 865 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 866 ((to.to_flag & TOF_TS) == 0 || 867 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 868 /* 869 * Using the CC option is compulsory if once started: 870 * the segment is OK if no T/TCP was negotiated or 871 * if the segment has a CC option equal to CCrecv 872 */ 873 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 874 ((to.to_flag & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 875 th->th_seq == tp->rcv_nxt && 876 tiwin && tiwin == tp->snd_wnd && 877 tp->snd_nxt == tp->snd_max) { 878 879 /* 880 * If last ACK falls within this segment's sequence numbers, 881 * record the timestamp. 882 * NOTE that the test is modified according to the latest 883 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 884 */ 885 if ((to.to_flag & TOF_TS) != 0 && 886 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 887 tp->ts_recent_age = ticks; 888 tp->ts_recent = to.to_tsval; 889 } 890 891 if (tlen == 0) { 892 if (SEQ_GT(th->th_ack, tp->snd_una) && 893 SEQ_LEQ(th->th_ack, tp->snd_max) && 894 tp->snd_cwnd >= tp->snd_wnd && 895 tp->t_dupacks < tcprexmtthresh) { 896 /* 897 * this is a pure ack for outstanding data. 898 */ 899 ++tcpstat.tcps_predack; 900 /* 901 * "bad retransmit" recovery 902 */ 903 if (tp->t_rxtshift == 1 && 904 ticks < tp->t_badrxtwin) { 905 tp->snd_cwnd = tp->snd_cwnd_prev; 906 tp->snd_ssthresh = 907 tp->snd_ssthresh_prev; 908 tp->snd_nxt = tp->snd_max; 909 tp->t_badrxtwin = 0; 910 } 911 if ((to.to_flag & TOF_TS) != 0) 912 tcp_xmit_timer(tp, 913 ticks - to.to_tsecr + 1); 914 else if (tp->t_rtttime && 915 SEQ_GT(th->th_ack, tp->t_rtseq)) 916 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 917 acked = th->th_ack - tp->snd_una; 918 tcpstat.tcps_rcvackpack++; 919 tcpstat.tcps_rcvackbyte += acked; 920 sbdrop(&so->so_snd, acked); 921 tp->snd_una = th->th_ack; 922 m_freem(m); 923 ND6_HINT(tp); /* some progress has been done */ 924 925 /* 926 * If all outstanding data are acked, stop 927 * retransmit timer, otherwise restart timer 928 * using current (possibly backed-off) value. 929 * If process is waiting for space, 930 * wakeup/selwakeup/signal. If data 931 * are ready to send, let tcp_output 932 * decide between more output or persist. 933 */ 934 if (tp->snd_una == tp->snd_max) 935 callout_stop(tp->tt_rexmt); 936 else if (!callout_active(tp->tt_persist)) 937 callout_reset(tp->tt_rexmt, 938 tp->t_rxtcur, 939 tcp_timer_rexmt, tp); 940 941 sowwakeup(so); 942 if (so->so_snd.sb_cc) 943 (void) tcp_output(tp); 944 return; 945 } 946 } else if (th->th_ack == tp->snd_una && 947 LIST_EMPTY(&tp->t_segq) && 948 tlen <= sbspace(&so->so_rcv)) { 949 /* 950 * this is a pure, in-sequence data packet 951 * with nothing on the reassembly queue and 952 * we have enough buffer space to take it. 953 */ 954 ++tcpstat.tcps_preddat; 955 tp->rcv_nxt += tlen; 956 tcpstat.tcps_rcvpack++; 957 tcpstat.tcps_rcvbyte += tlen; 958 ND6_HINT(tp); /* some progress has been done */ 959 /* 960 * Add data to socket buffer. 961 */ 962 m_adj(m, drop_hdrlen); /* delayed header drop */ 963 sbappend(&so->so_rcv, m); 964 sorwakeup(so); 965 if (tcp_delack_enabled) { 966 callout_reset(tp->tt_delack, tcp_delacktime, 967 tcp_timer_delack, tp); 968 } else { 969 tp->t_flags |= TF_ACKNOW; 970 tcp_output(tp); 971 } 972 return; 973 } 974 } 975 976 /* 977 * Calculate amount of space in receive window, 978 * and then do TCP input processing. 979 * Receive window is amount of space in rcv queue, 980 * but not less than advertised window. 981 */ 982 { int win; 983 984 win = sbspace(&so->so_rcv); 985 if (win < 0) 986 win = 0; 987 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 988 } 989 990 switch (tp->t_state) { 991 992 /* 993 * If the state is LISTEN then ignore segment if it contains an RST. 994 * If the segment contains an ACK then it is bad and send a RST. 995 * If it does not contain a SYN then it is not interesting; drop it. 996 * If it is from this socket, drop it, it must be forged. 997 * Don't bother responding if the destination was a broadcast. 998 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 999 * tp->iss, and send a segment: 1000 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1001 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 1002 * Fill in remote peer address fields if not previously specified. 1003 * Enter SYN_RECEIVED state, and process any other fields of this 1004 * segment in this state. 1005 */ 1006 case TCPS_LISTEN: { 1007 register struct sockaddr_in *sin; 1008 #ifdef INET6 1009 register struct sockaddr_in6 *sin6; 1010 #endif 1011 1012 if (thflags & TH_RST) 1013 goto drop; 1014 if (thflags & TH_ACK) 1015 goto maybedropwithreset; 1016 if ((thflags & TH_SYN) == 0) 1017 goto drop; 1018 if (th->th_dport == th->th_sport) { 1019 #ifdef INET6 1020 if (isipv6) { 1021 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1022 &ip6->ip6_src)) 1023 goto drop; 1024 } else 1025 #endif /* INET6 */ 1026 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1027 goto drop; 1028 } 1029 /* 1030 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1031 * in_broadcast() should never return true on a received 1032 * packet with M_BCAST not set. 1033 * 1034 * Packets with a multicast source address should also 1035 * be discarded. 1036 */ 1037 if (m->m_flags & (M_BCAST|M_MCAST)) 1038 goto drop; 1039 #ifdef INET6 1040 if (isipv6) { 1041 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1042 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1043 goto drop; 1044 } else 1045 #endif 1046 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1047 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1048 ip->ip_src.s_addr == htonl(INADDR_BROADCAST)) 1049 goto drop; 1050 #ifdef INET6 1051 if (isipv6) { 1052 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, 1053 M_SONAME, M_NOWAIT); 1054 if (sin6 == NULL) 1055 goto drop; 1056 bzero(sin6, sizeof(*sin6)); 1057 sin6->sin6_family = AF_INET6; 1058 sin6->sin6_len = sizeof(*sin6); 1059 sin6->sin6_addr = ip6->ip6_src; 1060 sin6->sin6_port = th->th_sport; 1061 laddr6 = inp->in6p_laddr; 1062 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 1063 inp->in6p_laddr = ip6->ip6_dst; 1064 if (in6_pcbconnect(inp, (struct sockaddr *)sin6, 1065 &proc0)) { 1066 inp->in6p_laddr = laddr6; 1067 FREE(sin6, M_SONAME); 1068 goto drop; 1069 } 1070 FREE(sin6, M_SONAME); 1071 } else 1072 #endif 1073 { 1074 MALLOC(sin, struct sockaddr_in *, sizeof *sin, M_SONAME, 1075 M_NOWAIT); 1076 if (sin == NULL) 1077 goto drop; 1078 sin->sin_family = AF_INET; 1079 sin->sin_len = sizeof(*sin); 1080 sin->sin_addr = ip->ip_src; 1081 sin->sin_port = th->th_sport; 1082 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 1083 laddr = inp->inp_laddr; 1084 if (inp->inp_laddr.s_addr == INADDR_ANY) 1085 inp->inp_laddr = ip->ip_dst; 1086 if (in_pcbconnect(inp, (struct sockaddr *)sin, &proc0)) { 1087 inp->inp_laddr = laddr; 1088 FREE(sin, M_SONAME); 1089 goto drop; 1090 } 1091 FREE(sin, M_SONAME); 1092 } 1093 tp->t_template = tcp_template(tp); 1094 if (tp->t_template == 0) { 1095 tp = tcp_drop(tp, ENOBUFS); 1096 dropsocket = 0; /* socket is already gone */ 1097 goto drop; 1098 } 1099 if ((taop = tcp_gettaocache(inp)) == NULL) { 1100 taop = &tao_noncached; 1101 bzero(taop, sizeof(*taop)); 1102 } 1103 tcp_dooptions(tp, optp, optlen, th, &to); 1104 if (iss) 1105 tp->iss = iss; 1106 else 1107 tp->iss = tcp_iss; 1108 tcp_iss += TCP_ISSINCR/4; 1109 tp->irs = th->th_seq; 1110 tcp_sendseqinit(tp); 1111 tcp_rcvseqinit(tp); 1112 tp->snd_recover = tp->snd_una; 1113 /* 1114 * Initialization of the tcpcb for transaction; 1115 * set SND.WND = SEG.WND, 1116 * initialize CCsend and CCrecv. 1117 */ 1118 tp->snd_wnd = tiwin; /* initial send-window */ 1119 tp->cc_send = CC_INC(tcp_ccgen); 1120 tp->cc_recv = to.to_cc; 1121 /* 1122 * Perform TAO test on incoming CC (SEG.CC) option, if any. 1123 * - compare SEG.CC against cached CC from the same host, 1124 * if any. 1125 * - if SEG.CC > chached value, SYN must be new and is accepted 1126 * immediately: save new CC in the cache, mark the socket 1127 * connected, enter ESTABLISHED state, turn on flag to 1128 * send a SYN in the next segment. 1129 * A virtual advertised window is set in rcv_adv to 1130 * initialize SWS prevention. Then enter normal segment 1131 * processing: drop SYN, process data and FIN. 1132 * - otherwise do a normal 3-way handshake. 1133 */ 1134 if ((to.to_flag & TOF_CC) != 0) { 1135 if (((tp->t_flags & TF_NOPUSH) != 0) && 1136 taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) { 1137 1138 taop->tao_cc = to.to_cc; 1139 tp->t_starttime = ticks; 1140 tp->t_state = TCPS_ESTABLISHED; 1141 1142 /* 1143 * If there is a FIN, or if there is data and the 1144 * connection is local, then delay SYN,ACK(SYN) in 1145 * the hope of piggy-backing it on a response 1146 * segment. Otherwise must send ACK now in case 1147 * the other side is slow starting. 1148 */ 1149 if (tcp_delack_enabled && ((thflags & TH_FIN) || 1150 (tlen != 0 && 1151 #ifdef INET6 1152 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) 1153 || 1154 (!isipv6 && 1155 #endif 1156 in_localaddr(inp->inp_faddr) 1157 #ifdef INET6 1158 )) 1159 #endif 1160 ))) { 1161 callout_reset(tp->tt_delack, tcp_delacktime, 1162 tcp_timer_delack, tp); 1163 tp->t_flags |= TF_NEEDSYN; 1164 } else 1165 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1166 1167 /* 1168 * Limit the `virtual advertised window' to TCP_MAXWIN 1169 * here. Even if we requested window scaling, it will 1170 * become effective only later when our SYN is acked. 1171 */ 1172 tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN); 1173 tcpstat.tcps_connects++; 1174 soisconnected(so); 1175 callout_reset(tp->tt_keep, tcp_keepinit, 1176 tcp_timer_keep, tp); 1177 dropsocket = 0; /* committed to socket */ 1178 tcpstat.tcps_accepts++; 1179 goto trimthenstep6; 1180 } 1181 /* else do standard 3-way handshake */ 1182 } else { 1183 /* 1184 * No CC option, but maybe CC.NEW: 1185 * invalidate cached value. 1186 */ 1187 taop->tao_cc = 0; 1188 } 1189 /* 1190 * TAO test failed or there was no CC option, 1191 * do a standard 3-way handshake. 1192 */ 1193 tp->t_flags |= TF_ACKNOW; 1194 tp->t_state = TCPS_SYN_RECEIVED; 1195 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 1196 dropsocket = 0; /* committed to socket */ 1197 tcpstat.tcps_accepts++; 1198 goto trimthenstep6; 1199 } 1200 1201 /* 1202 * If the state is SYN_RECEIVED: 1203 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1204 */ 1205 case TCPS_SYN_RECEIVED: 1206 if ((thflags & TH_ACK) && 1207 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1208 SEQ_GT(th->th_ack, tp->snd_max))) 1209 goto maybedropwithreset; 1210 break; 1211 1212 /* 1213 * If the state is SYN_SENT: 1214 * if seg contains an ACK, but not for our SYN, drop the input. 1215 * if seg contains a RST, then drop the connection. 1216 * if seg does not contain SYN, then drop it. 1217 * Otherwise this is an acceptable SYN segment 1218 * initialize tp->rcv_nxt and tp->irs 1219 * if seg contains ack then advance tp->snd_una 1220 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1221 * arrange for segment to be acked (eventually) 1222 * continue processing rest of data/controls, beginning with URG 1223 */ 1224 case TCPS_SYN_SENT: 1225 if ((taop = tcp_gettaocache(inp)) == NULL) { 1226 taop = &tao_noncached; 1227 bzero(taop, sizeof(*taop)); 1228 } 1229 1230 if ((thflags & TH_ACK) && 1231 (SEQ_LEQ(th->th_ack, tp->iss) || 1232 SEQ_GT(th->th_ack, tp->snd_max))) { 1233 /* 1234 * If we have a cached CCsent for the remote host, 1235 * hence we haven't just crashed and restarted, 1236 * do not send a RST. This may be a retransmission 1237 * from the other side after our earlier ACK was lost. 1238 * Our new SYN, when it arrives, will serve as the 1239 * needed ACK. 1240 */ 1241 if (taop->tao_ccsent != 0) 1242 goto drop; 1243 else 1244 goto dropwithreset; 1245 } 1246 if (thflags & TH_RST) { 1247 if (thflags & TH_ACK) 1248 tp = tcp_drop(tp, ECONNREFUSED); 1249 goto drop; 1250 } 1251 if ((thflags & TH_SYN) == 0) 1252 goto drop; 1253 tp->snd_wnd = th->th_win; /* initial send window */ 1254 tp->cc_recv = to.to_cc; /* foreign CC */ 1255 1256 tp->irs = th->th_seq; 1257 tcp_rcvseqinit(tp); 1258 if (thflags & TH_ACK) { 1259 /* 1260 * Our SYN was acked. If segment contains CC.ECHO 1261 * option, check it to make sure this segment really 1262 * matches our SYN. If not, just drop it as old 1263 * duplicate, but send an RST if we're still playing 1264 * by the old rules. If no CC.ECHO option, make sure 1265 * we don't get fooled into using T/TCP. 1266 */ 1267 if (to.to_flag & TOF_CCECHO) { 1268 if (tp->cc_send != to.to_ccecho) { 1269 if (taop->tao_ccsent != 0) 1270 goto drop; 1271 else 1272 goto dropwithreset; 1273 } 1274 } else 1275 tp->t_flags &= ~TF_RCVD_CC; 1276 tcpstat.tcps_connects++; 1277 soisconnected(so); 1278 /* Do window scaling on this connection? */ 1279 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1280 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1281 tp->snd_scale = tp->requested_s_scale; 1282 tp->rcv_scale = tp->request_r_scale; 1283 } 1284 /* Segment is acceptable, update cache if undefined. */ 1285 if (taop->tao_ccsent == 0) 1286 taop->tao_ccsent = to.to_ccecho; 1287 1288 tp->rcv_adv += tp->rcv_wnd; 1289 tp->snd_una++; /* SYN is acked */ 1290 /* 1291 * If there's data, delay ACK; if there's also a FIN 1292 * ACKNOW will be turned on later. 1293 */ 1294 if (tcp_delack_enabled && tlen != 0) 1295 callout_reset(tp->tt_delack, tcp_delacktime, 1296 tcp_timer_delack, tp); 1297 else 1298 tp->t_flags |= TF_ACKNOW; 1299 /* 1300 * Received <SYN,ACK> in SYN_SENT[*] state. 1301 * Transitions: 1302 * SYN_SENT --> ESTABLISHED 1303 * SYN_SENT* --> FIN_WAIT_1 1304 */ 1305 tp->t_starttime = ticks; 1306 if (tp->t_flags & TF_NEEDFIN) { 1307 tp->t_state = TCPS_FIN_WAIT_1; 1308 tp->t_flags &= ~TF_NEEDFIN; 1309 thflags &= ~TH_SYN; 1310 } else { 1311 tp->t_state = TCPS_ESTABLISHED; 1312 callout_reset(tp->tt_keep, tcp_keepidle, 1313 tcp_timer_keep, tp); 1314 } 1315 } else { 1316 /* 1317 * Received initial SYN in SYN-SENT[*] state => simul- 1318 * taneous open. If segment contains CC option and there is 1319 * a cached CC, apply TAO test; if it succeeds, connection is 1320 * half-synchronized. Otherwise, do 3-way handshake: 1321 * SYN-SENT -> SYN-RECEIVED 1322 * SYN-SENT* -> SYN-RECEIVED* 1323 * If there was no CC option, clear cached CC value. 1324 */ 1325 tp->t_flags |= TF_ACKNOW; 1326 callout_stop(tp->tt_rexmt); 1327 if (to.to_flag & TOF_CC) { 1328 if (taop->tao_cc != 0 && 1329 CC_GT(to.to_cc, taop->tao_cc)) { 1330 /* 1331 * update cache and make transition: 1332 * SYN-SENT -> ESTABLISHED* 1333 * SYN-SENT* -> FIN-WAIT-1* 1334 */ 1335 taop->tao_cc = to.to_cc; 1336 tp->t_starttime = ticks; 1337 if (tp->t_flags & TF_NEEDFIN) { 1338 tp->t_state = TCPS_FIN_WAIT_1; 1339 tp->t_flags &= ~TF_NEEDFIN; 1340 } else { 1341 tp->t_state = TCPS_ESTABLISHED; 1342 callout_reset(tp->tt_keep, 1343 tcp_keepidle, 1344 tcp_timer_keep, 1345 tp); 1346 } 1347 tp->t_flags |= TF_NEEDSYN; 1348 } else 1349 tp->t_state = TCPS_SYN_RECEIVED; 1350 } else { 1351 /* CC.NEW or no option => invalidate cache */ 1352 taop->tao_cc = 0; 1353 tp->t_state = TCPS_SYN_RECEIVED; 1354 } 1355 } 1356 1357 trimthenstep6: 1358 /* 1359 * Advance th->th_seq to correspond to first data byte. 1360 * If data, trim to stay within window, 1361 * dropping FIN if necessary. 1362 */ 1363 th->th_seq++; 1364 if (tlen > tp->rcv_wnd) { 1365 todrop = tlen - tp->rcv_wnd; 1366 m_adj(m, -todrop); 1367 tlen = tp->rcv_wnd; 1368 thflags &= ~TH_FIN; 1369 tcpstat.tcps_rcvpackafterwin++; 1370 tcpstat.tcps_rcvbyteafterwin += todrop; 1371 } 1372 tp->snd_wl1 = th->th_seq - 1; 1373 tp->rcv_up = th->th_seq; 1374 /* 1375 * Client side of transaction: already sent SYN and data. 1376 * If the remote host used T/TCP to validate the SYN, 1377 * our data will be ACK'd; if so, enter normal data segment 1378 * processing in the middle of step 5, ack processing. 1379 * Otherwise, goto step 6. 1380 */ 1381 if (thflags & TH_ACK) 1382 goto process_ACK; 1383 goto step6; 1384 /* 1385 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1386 * if segment contains a SYN and CC [not CC.NEW] option: 1387 * if state == TIME_WAIT and connection duration > MSL, 1388 * drop packet and send RST; 1389 * 1390 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1391 * ack the FIN (and data) in retransmission queue. 1392 * Complete close and delete TCPCB. Then reprocess 1393 * segment, hoping to find new TCPCB in LISTEN state; 1394 * 1395 * else must be old SYN; drop it. 1396 * else do normal processing. 1397 */ 1398 case TCPS_LAST_ACK: 1399 case TCPS_CLOSING: 1400 case TCPS_TIME_WAIT: 1401 if ((thflags & TH_SYN) && 1402 (to.to_flag & TOF_CC) && tp->cc_recv != 0) { 1403 if (tp->t_state == TCPS_TIME_WAIT && 1404 (ticks - tp->t_starttime) > tcp_msl) 1405 goto dropwithreset; 1406 if (CC_GT(to.to_cc, tp->cc_recv)) { 1407 tp = tcp_close(tp); 1408 goto findpcb; 1409 } 1410 else 1411 goto drop; 1412 } 1413 break; /* continue normal processing */ 1414 } 1415 1416 /* 1417 * States other than LISTEN or SYN_SENT. 1418 * First check the RST flag and sequence number since reset segments 1419 * are exempt from the timestamp and connection count tests. This 1420 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1421 * below which allowed reset segments in half the sequence space 1422 * to fall though and be processed (which gives forged reset 1423 * segments with a random sequence number a 50 percent chance of 1424 * killing a connection). 1425 * Then check timestamp, if present. 1426 * Then check the connection count, if present. 1427 * Then check that at least some bytes of segment are within 1428 * receive window. If segment begins before rcv_nxt, 1429 * drop leading data (and SYN); if nothing left, just ack. 1430 * 1431 * 1432 * If the RST bit is set, check the sequence number to see 1433 * if this is a valid reset segment. 1434 * RFC 793 page 37: 1435 * In all states except SYN-SENT, all reset (RST) segments 1436 * are validated by checking their SEQ-fields. A reset is 1437 * valid if its sequence number is in the window. 1438 * Note: this does not take into account delayed ACKs, so 1439 * we should test against last_ack_sent instead of rcv_nxt. 1440 * The sequence number in the reset segment is normally an 1441 * echo of our outgoing acknowlegement numbers, but some hosts 1442 * send a reset with the sequence number at the rightmost edge 1443 * of our receive window, and we have to handle this case. 1444 * If we have multiple segments in flight, the intial reset 1445 * segment sequence numbers will be to the left of last_ack_sent, 1446 * but they will eventually catch up. 1447 * In any case, it never made sense to trim reset segments to 1448 * fit the receive window since RFC 1122 says: 1449 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1450 * 1451 * A TCP SHOULD allow a received RST segment to include data. 1452 * 1453 * DISCUSSION 1454 * It has been suggested that a RST segment could contain 1455 * ASCII text that encoded and explained the cause of the 1456 * RST. No standard has yet been established for such 1457 * data. 1458 * 1459 * If the reset segment passes the sequence number test examine 1460 * the state: 1461 * SYN_RECEIVED STATE: 1462 * If passive open, return to LISTEN state. 1463 * If active open, inform user that connection was refused. 1464 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 1465 * Inform user that connection was reset, and close tcb. 1466 * CLOSING, LAST_ACK STATES: 1467 * Close the tcb. 1468 * TIME_WAIT STATE: 1469 * Drop the segment - see Stevens, vol. 2, p. 964 and 1470 * RFC 1337. 1471 */ 1472 if (thflags & TH_RST) { 1473 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1474 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1475 switch (tp->t_state) { 1476 1477 case TCPS_SYN_RECEIVED: 1478 so->so_error = ECONNREFUSED; 1479 goto close; 1480 1481 case TCPS_ESTABLISHED: 1482 case TCPS_FIN_WAIT_1: 1483 case TCPS_FIN_WAIT_2: 1484 case TCPS_CLOSE_WAIT: 1485 so->so_error = ECONNRESET; 1486 close: 1487 tp->t_state = TCPS_CLOSED; 1488 tcpstat.tcps_drops++; 1489 tp = tcp_close(tp); 1490 break; 1491 1492 case TCPS_CLOSING: 1493 case TCPS_LAST_ACK: 1494 tp = tcp_close(tp); 1495 break; 1496 1497 case TCPS_TIME_WAIT: 1498 break; 1499 } 1500 } 1501 goto drop; 1502 } 1503 1504 /* 1505 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1506 * and it's less than ts_recent, drop it. 1507 */ 1508 if ((to.to_flag & TOF_TS) != 0 && tp->ts_recent && 1509 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1510 1511 /* Check to see if ts_recent is over 24 days old. */ 1512 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1513 /* 1514 * Invalidate ts_recent. If this segment updates 1515 * ts_recent, the age will be reset later and ts_recent 1516 * will get a valid value. If it does not, setting 1517 * ts_recent to zero will at least satisfy the 1518 * requirement that zero be placed in the timestamp 1519 * echo reply when ts_recent isn't valid. The 1520 * age isn't reset until we get a valid ts_recent 1521 * because we don't want out-of-order segments to be 1522 * dropped when ts_recent is old. 1523 */ 1524 tp->ts_recent = 0; 1525 } else { 1526 tcpstat.tcps_rcvduppack++; 1527 tcpstat.tcps_rcvdupbyte += tlen; 1528 tcpstat.tcps_pawsdrop++; 1529 goto dropafterack; 1530 } 1531 } 1532 1533 /* 1534 * T/TCP mechanism 1535 * If T/TCP was negotiated and the segment doesn't have CC, 1536 * or if its CC is wrong then drop the segment. 1537 * RST segments do not have to comply with this. 1538 */ 1539 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1540 ((to.to_flag & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1541 goto dropafterack; 1542 1543 /* 1544 * In the SYN-RECEIVED state, validate that the packet belongs to 1545 * this connection before trimming the data to fit the receive 1546 * window. Check the sequence number versus IRS since we know 1547 * the sequence numbers haven't wrapped. This is a partial fix 1548 * for the "LAND" DoS attack. 1549 */ 1550 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) 1551 goto maybedropwithreset; 1552 1553 todrop = tp->rcv_nxt - th->th_seq; 1554 if (todrop > 0) { 1555 if (thflags & TH_SYN) { 1556 thflags &= ~TH_SYN; 1557 th->th_seq++; 1558 if (th->th_urp > 1) 1559 th->th_urp--; 1560 else 1561 thflags &= ~TH_URG; 1562 todrop--; 1563 } 1564 /* 1565 * Following if statement from Stevens, vol. 2, p. 960. 1566 */ 1567 if (todrop > tlen 1568 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1569 /* 1570 * Any valid FIN must be to the left of the window. 1571 * At this point the FIN must be a duplicate or out 1572 * of sequence; drop it. 1573 */ 1574 thflags &= ~TH_FIN; 1575 1576 /* 1577 * Send an ACK to resynchronize and drop any data. 1578 * But keep on processing for RST or ACK. 1579 */ 1580 tp->t_flags |= TF_ACKNOW; 1581 todrop = tlen; 1582 tcpstat.tcps_rcvduppack++; 1583 tcpstat.tcps_rcvdupbyte += todrop; 1584 } else { 1585 tcpstat.tcps_rcvpartduppack++; 1586 tcpstat.tcps_rcvpartdupbyte += todrop; 1587 } 1588 drop_hdrlen += todrop; /* drop from the top afterwards */ 1589 th->th_seq += todrop; 1590 tlen -= todrop; 1591 if (th->th_urp > todrop) 1592 th->th_urp -= todrop; 1593 else { 1594 thflags &= ~TH_URG; 1595 th->th_urp = 0; 1596 } 1597 } 1598 1599 /* 1600 * If new data are received on a connection after the 1601 * user processes are gone, then RST the other end. 1602 */ 1603 if ((so->so_state & SS_NOFDREF) && 1604 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1605 tp = tcp_close(tp); 1606 tcpstat.tcps_rcvafterclose++; 1607 goto dropwithreset; 1608 } 1609 1610 /* 1611 * If segment ends after window, drop trailing data 1612 * (and PUSH and FIN); if nothing left, just ACK. 1613 */ 1614 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1615 if (todrop > 0) { 1616 tcpstat.tcps_rcvpackafterwin++; 1617 if (todrop >= tlen) { 1618 tcpstat.tcps_rcvbyteafterwin += tlen; 1619 /* 1620 * If a new connection request is received 1621 * while in TIME_WAIT, drop the old connection 1622 * and start over if the sequence numbers 1623 * are above the previous ones. 1624 */ 1625 if (thflags & TH_SYN && 1626 tp->t_state == TCPS_TIME_WAIT && 1627 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1628 iss = tp->snd_nxt + TCP_ISSINCR; 1629 tp = tcp_close(tp); 1630 goto findpcb; 1631 } 1632 /* 1633 * If window is closed can only take segments at 1634 * window edge, and have to drop data and PUSH from 1635 * incoming segments. Continue processing, but 1636 * remember to ack. Otherwise, drop segment 1637 * and ack. 1638 */ 1639 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1640 tp->t_flags |= TF_ACKNOW; 1641 tcpstat.tcps_rcvwinprobe++; 1642 } else 1643 goto dropafterack; 1644 } else 1645 tcpstat.tcps_rcvbyteafterwin += todrop; 1646 m_adj(m, -todrop); 1647 tlen -= todrop; 1648 thflags &= ~(TH_PUSH|TH_FIN); 1649 } 1650 1651 /* 1652 * If last ACK falls within this segment's sequence numbers, 1653 * record its timestamp. 1654 * NOTE that the test is modified according to the latest 1655 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1656 */ 1657 if ((to.to_flag & TOF_TS) != 0 && 1658 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1659 tp->ts_recent_age = ticks; 1660 tp->ts_recent = to.to_tsval; 1661 } 1662 1663 /* 1664 * If a SYN is in the window, then this is an 1665 * error and we send an RST and drop the connection. 1666 */ 1667 if (thflags & TH_SYN) { 1668 tp = tcp_drop(tp, ECONNRESET); 1669 goto dropwithreset; 1670 } 1671 1672 /* 1673 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1674 * flag is on (half-synchronized state), then queue data for 1675 * later processing; else drop segment and return. 1676 */ 1677 if ((thflags & TH_ACK) == 0) { 1678 if (tp->t_state == TCPS_SYN_RECEIVED || 1679 (tp->t_flags & TF_NEEDSYN)) 1680 goto step6; 1681 else 1682 goto drop; 1683 } 1684 1685 /* 1686 * Ack processing. 1687 */ 1688 switch (tp->t_state) { 1689 1690 /* 1691 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1692 * ESTABLISHED state and continue processing. 1693 * The ACK was checked above. 1694 */ 1695 case TCPS_SYN_RECEIVED: 1696 1697 tcpstat.tcps_connects++; 1698 soisconnected(so); 1699 /* Do window scaling? */ 1700 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1701 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1702 tp->snd_scale = tp->requested_s_scale; 1703 tp->rcv_scale = tp->request_r_scale; 1704 } 1705 /* 1706 * Upon successful completion of 3-way handshake, 1707 * update cache.CC if it was undefined, pass any queued 1708 * data to the user, and advance state appropriately. 1709 */ 1710 if ((taop = tcp_gettaocache(inp)) != NULL && 1711 taop->tao_cc == 0) 1712 taop->tao_cc = tp->cc_recv; 1713 1714 /* 1715 * Make transitions: 1716 * SYN-RECEIVED -> ESTABLISHED 1717 * SYN-RECEIVED* -> FIN-WAIT-1 1718 */ 1719 tp->t_starttime = ticks; 1720 if (tp->t_flags & TF_NEEDFIN) { 1721 tp->t_state = TCPS_FIN_WAIT_1; 1722 tp->t_flags &= ~TF_NEEDFIN; 1723 } else { 1724 tp->t_state = TCPS_ESTABLISHED; 1725 callout_reset(tp->tt_keep, tcp_keepidle, 1726 tcp_timer_keep, tp); 1727 } 1728 /* 1729 * If segment contains data or ACK, will call tcp_reass() 1730 * later; if not, do so now to pass queued data to user. 1731 */ 1732 if (tlen == 0 && (thflags & TH_FIN) == 0) 1733 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1734 (struct mbuf *)0); 1735 tp->snd_wl1 = th->th_seq - 1; 1736 /* fall into ... */ 1737 1738 /* 1739 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1740 * ACKs. If the ack is in the range 1741 * tp->snd_una < th->th_ack <= tp->snd_max 1742 * then advance tp->snd_una to th->th_ack and drop 1743 * data from the retransmission queue. If this ACK reflects 1744 * more up to date window information we update our window information. 1745 */ 1746 case TCPS_ESTABLISHED: 1747 case TCPS_FIN_WAIT_1: 1748 case TCPS_FIN_WAIT_2: 1749 case TCPS_CLOSE_WAIT: 1750 case TCPS_CLOSING: 1751 case TCPS_LAST_ACK: 1752 case TCPS_TIME_WAIT: 1753 1754 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1755 if (tlen == 0 && tiwin == tp->snd_wnd) { 1756 tcpstat.tcps_rcvdupack++; 1757 /* 1758 * If we have outstanding data (other than 1759 * a window probe), this is a completely 1760 * duplicate ack (ie, window info didn't 1761 * change), the ack is the biggest we've 1762 * seen and we've seen exactly our rexmt 1763 * threshhold of them, assume a packet 1764 * has been dropped and retransmit it. 1765 * Kludge snd_nxt & the congestion 1766 * window so we send only this one 1767 * packet. 1768 * 1769 * We know we're losing at the current 1770 * window size so do congestion avoidance 1771 * (set ssthresh to half the current window 1772 * and pull our congestion window back to 1773 * the new ssthresh). 1774 * 1775 * Dup acks mean that packets have left the 1776 * network (they're now cached at the receiver) 1777 * so bump cwnd by the amount in the receiver 1778 * to keep a constant cwnd packets in the 1779 * network. 1780 */ 1781 if (!callout_active(tp->tt_rexmt) || 1782 th->th_ack != tp->snd_una) 1783 tp->t_dupacks = 0; 1784 else if (++tp->t_dupacks == tcprexmtthresh) { 1785 tcp_seq onxt = tp->snd_nxt; 1786 u_int win = 1787 min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1788 tp->t_maxseg; 1789 if (tcp_do_newreno && SEQ_LT(th->th_ack, 1790 tp->snd_recover)) { 1791 /* False retransmit, should not 1792 * cut window 1793 */ 1794 tp->snd_cwnd += tp->t_maxseg; 1795 tp->t_dupacks = 0; 1796 (void) tcp_output(tp); 1797 goto drop; 1798 } 1799 if (win < 2) 1800 win = 2; 1801 tp->snd_ssthresh = win * tp->t_maxseg; 1802 tp->snd_recover = tp->snd_max; 1803 callout_stop(tp->tt_rexmt); 1804 tp->t_rtttime = 0; 1805 tp->snd_nxt = th->th_ack; 1806 tp->snd_cwnd = tp->t_maxseg; 1807 (void) tcp_output(tp); 1808 tp->snd_cwnd = tp->snd_ssthresh + 1809 tp->t_maxseg * tp->t_dupacks; 1810 if (SEQ_GT(onxt, tp->snd_nxt)) 1811 tp->snd_nxt = onxt; 1812 goto drop; 1813 } else if (tp->t_dupacks > tcprexmtthresh) { 1814 tp->snd_cwnd += tp->t_maxseg; 1815 (void) tcp_output(tp); 1816 goto drop; 1817 } 1818 } else 1819 tp->t_dupacks = 0; 1820 break; 1821 } 1822 /* 1823 * If the congestion window was inflated to account 1824 * for the other side's cached packets, retract it. 1825 */ 1826 if (tcp_do_newreno == 0) { 1827 if (tp->t_dupacks >= tcprexmtthresh && 1828 tp->snd_cwnd > tp->snd_ssthresh) 1829 tp->snd_cwnd = tp->snd_ssthresh; 1830 tp->t_dupacks = 0; 1831 } else if (tp->t_dupacks >= tcprexmtthresh && 1832 !tcp_newreno(tp, th)) { 1833 /* 1834 * Window inflation should have left us with approx. 1835 * snd_ssthresh outstanding data. But in case we 1836 * would be inclined to send a burst, better to do 1837 * it via the slow start mechanism. 1838 */ 1839 if (SEQ_GT(th->th_ack + tp->snd_ssthresh, tp->snd_max)) 1840 tp->snd_cwnd = 1841 tp->snd_max - th->th_ack + tp->t_maxseg; 1842 else 1843 tp->snd_cwnd = tp->snd_ssthresh; 1844 tp->t_dupacks = 0; 1845 } 1846 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1847 tcpstat.tcps_rcvacktoomuch++; 1848 goto dropafterack; 1849 } 1850 /* 1851 * If we reach this point, ACK is not a duplicate, 1852 * i.e., it ACKs something we sent. 1853 */ 1854 if (tp->t_flags & TF_NEEDSYN) { 1855 /* 1856 * T/TCP: Connection was half-synchronized, and our 1857 * SYN has been ACK'd (so connection is now fully 1858 * synchronized). Go to non-starred state, 1859 * increment snd_una for ACK of SYN, and check if 1860 * we can do window scaling. 1861 */ 1862 tp->t_flags &= ~TF_NEEDSYN; 1863 tp->snd_una++; 1864 /* Do window scaling? */ 1865 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1866 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1867 tp->snd_scale = tp->requested_s_scale; 1868 tp->rcv_scale = tp->request_r_scale; 1869 } 1870 } 1871 1872 process_ACK: 1873 acked = th->th_ack - tp->snd_una; 1874 tcpstat.tcps_rcvackpack++; 1875 tcpstat.tcps_rcvackbyte += acked; 1876 1877 /* 1878 * If we just performed our first retransmit, and the ACK 1879 * arrives within our recovery window, then it was a mistake 1880 * to do the retransmit in the first place. Recover our 1881 * original cwnd and ssthresh, and proceed to transmit where 1882 * we left off. 1883 */ 1884 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1885 tp->snd_cwnd = tp->snd_cwnd_prev; 1886 tp->snd_ssthresh = tp->snd_ssthresh_prev; 1887 tp->snd_nxt = tp->snd_max; 1888 tp->t_badrxtwin = 0; /* XXX probably not required */ 1889 } 1890 1891 /* 1892 * If we have a timestamp reply, update smoothed 1893 * round trip time. If no timestamp is present but 1894 * transmit timer is running and timed sequence 1895 * number was acked, update smoothed round trip time. 1896 * Since we now have an rtt measurement, cancel the 1897 * timer backoff (cf., Phil Karn's retransmit alg.). 1898 * Recompute the initial retransmit timer. 1899 */ 1900 if (to.to_flag & TOF_TS) 1901 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1902 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 1903 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1904 1905 /* 1906 * If all outstanding data is acked, stop retransmit 1907 * timer and remember to restart (more output or persist). 1908 * If there is more data to be acked, restart retransmit 1909 * timer, using current (possibly backed-off) value. 1910 */ 1911 if (th->th_ack == tp->snd_max) { 1912 callout_stop(tp->tt_rexmt); 1913 needoutput = 1; 1914 } else if (!callout_active(tp->tt_persist)) 1915 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1916 tcp_timer_rexmt, tp); 1917 1918 /* 1919 * If no data (only SYN) was ACK'd, 1920 * skip rest of ACK processing. 1921 */ 1922 if (acked == 0) 1923 goto step6; 1924 1925 /* 1926 * When new data is acked, open the congestion window. 1927 * If the window gives us less than ssthresh packets 1928 * in flight, open exponentially (maxseg per packet). 1929 * Otherwise open linearly: maxseg per window 1930 * (maxseg^2 / cwnd per packet). 1931 */ 1932 { 1933 register u_int cw = tp->snd_cwnd; 1934 register u_int incr = tp->t_maxseg; 1935 1936 if (cw > tp->snd_ssthresh) 1937 incr = incr * incr / cw; 1938 /* 1939 * If t_dupacks != 0 here, it indicates that we are still 1940 * in NewReno fast recovery mode, so we leave the congestion 1941 * window alone. 1942 */ 1943 if (tcp_do_newreno == 0 || tp->t_dupacks == 0) 1944 tp->snd_cwnd = min(cw + incr,TCP_MAXWIN<<tp->snd_scale); 1945 } 1946 if (acked > so->so_snd.sb_cc) { 1947 tp->snd_wnd -= so->so_snd.sb_cc; 1948 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1949 ourfinisacked = 1; 1950 } else { 1951 sbdrop(&so->so_snd, acked); 1952 tp->snd_wnd -= acked; 1953 ourfinisacked = 0; 1954 } 1955 sowwakeup(so); 1956 tp->snd_una = th->th_ack; 1957 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1958 tp->snd_nxt = tp->snd_una; 1959 1960 switch (tp->t_state) { 1961 1962 /* 1963 * In FIN_WAIT_1 STATE in addition to the processing 1964 * for the ESTABLISHED state if our FIN is now acknowledged 1965 * then enter FIN_WAIT_2. 1966 */ 1967 case TCPS_FIN_WAIT_1: 1968 if (ourfinisacked) { 1969 /* 1970 * If we can't receive any more 1971 * data, then closing user can proceed. 1972 * Starting the timer is contrary to the 1973 * specification, but if we don't get a FIN 1974 * we'll hang forever. 1975 */ 1976 if (so->so_state & SS_CANTRCVMORE) { 1977 soisdisconnected(so); 1978 callout_reset(tp->tt_2msl, tcp_maxidle, 1979 tcp_timer_2msl, tp); 1980 } 1981 tp->t_state = TCPS_FIN_WAIT_2; 1982 } 1983 break; 1984 1985 /* 1986 * In CLOSING STATE in addition to the processing for 1987 * the ESTABLISHED state if the ACK acknowledges our FIN 1988 * then enter the TIME-WAIT state, otherwise ignore 1989 * the segment. 1990 */ 1991 case TCPS_CLOSING: 1992 if (ourfinisacked) { 1993 tp->t_state = TCPS_TIME_WAIT; 1994 tcp_canceltimers(tp); 1995 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1996 if (tp->cc_recv != 0 && 1997 (ticks - tp->t_starttime) < tcp_msl) 1998 callout_reset(tp->tt_2msl, 1999 tp->t_rxtcur * 2000 TCPTV_TWTRUNC, 2001 tcp_timer_2msl, tp); 2002 else 2003 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2004 tcp_timer_2msl, tp); 2005 soisdisconnected(so); 2006 } 2007 break; 2008 2009 /* 2010 * In LAST_ACK, we may still be waiting for data to drain 2011 * and/or to be acked, as well as for the ack of our FIN. 2012 * If our FIN is now acknowledged, delete the TCB, 2013 * enter the closed state and return. 2014 */ 2015 case TCPS_LAST_ACK: 2016 if (ourfinisacked) { 2017 tp = tcp_close(tp); 2018 goto drop; 2019 } 2020 break; 2021 2022 /* 2023 * In TIME_WAIT state the only thing that should arrive 2024 * is a retransmission of the remote FIN. Acknowledge 2025 * it and restart the finack timer. 2026 */ 2027 case TCPS_TIME_WAIT: 2028 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2029 tcp_timer_2msl, tp); 2030 goto dropafterack; 2031 } 2032 } 2033 2034 step6: 2035 /* 2036 * Update window information. 2037 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2038 */ 2039 if ((thflags & TH_ACK) && 2040 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2041 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2042 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2043 /* keep track of pure window updates */ 2044 if (tlen == 0 && 2045 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2046 tcpstat.tcps_rcvwinupd++; 2047 tp->snd_wnd = tiwin; 2048 tp->snd_wl1 = th->th_seq; 2049 tp->snd_wl2 = th->th_ack; 2050 if (tp->snd_wnd > tp->max_sndwnd) 2051 tp->max_sndwnd = tp->snd_wnd; 2052 needoutput = 1; 2053 } 2054 2055 /* 2056 * Process segments with URG. 2057 */ 2058 if ((thflags & TH_URG) && th->th_urp && 2059 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2060 /* 2061 * This is a kludge, but if we receive and accept 2062 * random urgent pointers, we'll crash in 2063 * soreceive. It's hard to imagine someone 2064 * actually wanting to send this much urgent data. 2065 */ 2066 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2067 th->th_urp = 0; /* XXX */ 2068 thflags &= ~TH_URG; /* XXX */ 2069 goto dodata; /* XXX */ 2070 } 2071 /* 2072 * If this segment advances the known urgent pointer, 2073 * then mark the data stream. This should not happen 2074 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2075 * a FIN has been received from the remote side. 2076 * In these states we ignore the URG. 2077 * 2078 * According to RFC961 (Assigned Protocols), 2079 * the urgent pointer points to the last octet 2080 * of urgent data. We continue, however, 2081 * to consider it to indicate the first octet 2082 * of data past the urgent section as the original 2083 * spec states (in one of two places). 2084 */ 2085 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2086 tp->rcv_up = th->th_seq + th->th_urp; 2087 so->so_oobmark = so->so_rcv.sb_cc + 2088 (tp->rcv_up - tp->rcv_nxt) - 1; 2089 if (so->so_oobmark == 0) 2090 so->so_state |= SS_RCVATMARK; 2091 sohasoutofband(so); 2092 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2093 } 2094 /* 2095 * Remove out of band data so doesn't get presented to user. 2096 * This can happen independent of advancing the URG pointer, 2097 * but if two URG's are pending at once, some out-of-band 2098 * data may creep in... ick. 2099 */ 2100 if (th->th_urp <= (u_long)tlen 2101 #ifdef SO_OOBINLINE 2102 && (so->so_options & SO_OOBINLINE) == 0 2103 #endif 2104 ) 2105 tcp_pulloutofband(so, th, m, 2106 drop_hdrlen); /* hdr drop is delayed */ 2107 } else 2108 /* 2109 * If no out of band data is expected, 2110 * pull receive urgent pointer along 2111 * with the receive window. 2112 */ 2113 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2114 tp->rcv_up = tp->rcv_nxt; 2115 dodata: /* XXX */ 2116 2117 /* 2118 * Process the segment text, merging it into the TCP sequencing queue, 2119 * and arranging for acknowledgment of receipt if necessary. 2120 * This process logically involves adjusting tp->rcv_wnd as data 2121 * is presented to the user (this happens in tcp_usrreq.c, 2122 * case PRU_RCVD). If a FIN has already been received on this 2123 * connection then we just ignore the text. 2124 */ 2125 if ((tlen || (thflags&TH_FIN)) && 2126 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2127 m_adj(m, drop_hdrlen); /* delayed header drop */ 2128 TCP_REASS(tp, th, &tlen, m, so, thflags); 2129 /* 2130 * Note the amount of data that peer has sent into 2131 * our window, in order to estimate the sender's 2132 * buffer size. 2133 */ 2134 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2135 } else { 2136 m_freem(m); 2137 thflags &= ~TH_FIN; 2138 } 2139 2140 /* 2141 * If FIN is received ACK the FIN and let the user know 2142 * that the connection is closing. 2143 */ 2144 if (thflags & TH_FIN) { 2145 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2146 socantrcvmore(so); 2147 /* 2148 * If connection is half-synchronized 2149 * (ie NEEDSYN flag on) then delay ACK, 2150 * so it may be piggybacked when SYN is sent. 2151 * Otherwise, since we received a FIN then no 2152 * more input can be expected, send ACK now. 2153 */ 2154 if (tcp_delack_enabled && (tp->t_flags & TF_NEEDSYN)) 2155 callout_reset(tp->tt_delack, tcp_delacktime, 2156 tcp_timer_delack, tp); 2157 else 2158 tp->t_flags |= TF_ACKNOW; 2159 tp->rcv_nxt++; 2160 } 2161 switch (tp->t_state) { 2162 2163 /* 2164 * In SYN_RECEIVED and ESTABLISHED STATES 2165 * enter the CLOSE_WAIT state. 2166 */ 2167 case TCPS_SYN_RECEIVED: 2168 tp->t_starttime = ticks; 2169 /*FALLTHROUGH*/ 2170 case TCPS_ESTABLISHED: 2171 tp->t_state = TCPS_CLOSE_WAIT; 2172 break; 2173 2174 /* 2175 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2176 * enter the CLOSING state. 2177 */ 2178 case TCPS_FIN_WAIT_1: 2179 tp->t_state = TCPS_CLOSING; 2180 break; 2181 2182 /* 2183 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2184 * starting the time-wait timer, turning off the other 2185 * standard timers. 2186 */ 2187 case TCPS_FIN_WAIT_2: 2188 tp->t_state = TCPS_TIME_WAIT; 2189 tcp_canceltimers(tp); 2190 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2191 if (tp->cc_recv != 0 && 2192 (ticks - tp->t_starttime) < tcp_msl) { 2193 callout_reset(tp->tt_2msl, 2194 tp->t_rxtcur * TCPTV_TWTRUNC, 2195 tcp_timer_2msl, tp); 2196 /* For transaction client, force ACK now. */ 2197 tp->t_flags |= TF_ACKNOW; 2198 } 2199 else 2200 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2201 tcp_timer_2msl, tp); 2202 soisdisconnected(so); 2203 break; 2204 2205 /* 2206 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2207 */ 2208 case TCPS_TIME_WAIT: 2209 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2210 tcp_timer_2msl, tp); 2211 break; 2212 } 2213 } 2214 #ifdef TCPDEBUG 2215 if (so->so_options & SO_DEBUG) 2216 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2217 &tcp_savetcp, 0); 2218 #endif 2219 2220 /* 2221 * Return any desired output. 2222 */ 2223 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2224 (void) tcp_output(tp); 2225 return; 2226 2227 dropafterack: 2228 /* 2229 * Generate an ACK dropping incoming segment if it occupies 2230 * sequence space, where the ACK reflects our state. 2231 * 2232 * We can now skip the test for the RST flag since all 2233 * paths to this code happen after packets containing 2234 * RST have been dropped. 2235 * 2236 * In the SYN-RECEIVED state, don't send an ACK unless the 2237 * segment we received passes the SYN-RECEIVED ACK test. 2238 * If it fails send a RST. This breaks the loop in the 2239 * "LAND" DoS attack, and also prevents an ACK storm 2240 * between two listening ports that have been sent forged 2241 * SYN segments, each with the source address of the other. 2242 */ 2243 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2244 (SEQ_GT(tp->snd_una, th->th_ack) || 2245 SEQ_GT(th->th_ack, tp->snd_max)) ) 2246 goto maybedropwithreset; 2247 #ifdef TCPDEBUG 2248 if (so->so_options & SO_DEBUG) 2249 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2250 &tcp_savetcp, 0); 2251 #endif 2252 m_freem(m); 2253 tp->t_flags |= TF_ACKNOW; 2254 (void) tcp_output(tp); 2255 return; 2256 2257 2258 /* 2259 * Conditionally drop with reset or just drop depending on whether 2260 * we think we are under attack or not. 2261 */ 2262 maybedropwithreset: 2263 if (badport_bandlim(1) < 0) 2264 goto drop; 2265 /* fall through */ 2266 dropwithreset: 2267 #ifdef TCP_RESTRICT_RST 2268 if (restrict_rst) 2269 goto drop; 2270 #endif 2271 /* 2272 * Generate a RST, dropping incoming segment. 2273 * Make ACK acceptable to originator of segment. 2274 * Don't bother to respond if destination was broadcast/multicast. 2275 */ 2276 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2277 goto drop; 2278 #ifdef INET6 2279 if (isipv6) { 2280 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2281 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2282 goto drop; 2283 } else 2284 #endif /* INET6 */ 2285 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2286 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2287 ip->ip_src.s_addr == htonl(INADDR_BROADCAST)) 2288 goto drop; 2289 /* IPv6 anycast check is done at tcp6_input() */ 2290 #ifdef TCPDEBUG 2291 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2292 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2293 &tcp_savetcp, 0); 2294 #endif 2295 if (thflags & TH_ACK) 2296 /* mtod() below is safe as long as hdr dropping is delayed */ 2297 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2298 TH_RST); 2299 else { 2300 if (thflags & TH_SYN) 2301 tlen++; 2302 /* mtod() below is safe as long as hdr dropping is delayed */ 2303 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2304 (tcp_seq)0, TH_RST|TH_ACK); 2305 } 2306 /* destroy temporarily created socket */ 2307 if (dropsocket) 2308 (void) soabort(so); 2309 return; 2310 2311 drop: 2312 /* 2313 * Drop space held by incoming segment and return. 2314 */ 2315 #ifdef TCPDEBUG 2316 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2317 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2318 &tcp_savetcp, 0); 2319 #endif 2320 m_freem(m); 2321 /* destroy temporarily created socket */ 2322 if (dropsocket) 2323 (void) soabort(so); 2324 return; 2325 } 2326 2327 static void 2328 tcp_dooptions(tp, cp, cnt, th, to) 2329 struct tcpcb *tp; 2330 u_char *cp; 2331 int cnt; 2332 struct tcphdr *th; 2333 struct tcpopt *to; 2334 { 2335 u_short mss = 0; 2336 int opt, optlen; 2337 2338 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2339 opt = cp[0]; 2340 if (opt == TCPOPT_EOL) 2341 break; 2342 if (opt == TCPOPT_NOP) 2343 optlen = 1; 2344 else { 2345 if (cnt < 2) 2346 break; 2347 optlen = cp[1]; 2348 if (optlen < 2 || optlen > cnt) 2349 break; 2350 } 2351 switch (opt) { 2352 2353 default: 2354 continue; 2355 2356 case TCPOPT_MAXSEG: 2357 if (optlen != TCPOLEN_MAXSEG) 2358 continue; 2359 if (!(th->th_flags & TH_SYN)) 2360 continue; 2361 bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); 2362 NTOHS(mss); 2363 break; 2364 2365 case TCPOPT_WINDOW: 2366 if (optlen != TCPOLEN_WINDOW) 2367 continue; 2368 if (!(th->th_flags & TH_SYN)) 2369 continue; 2370 tp->t_flags |= TF_RCVD_SCALE; 2371 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2372 break; 2373 2374 case TCPOPT_TIMESTAMP: 2375 if (optlen != TCPOLEN_TIMESTAMP) 2376 continue; 2377 to->to_flag |= TOF_TS; 2378 bcopy((char *)cp + 2, 2379 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2380 NTOHL(to->to_tsval); 2381 bcopy((char *)cp + 6, 2382 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2383 NTOHL(to->to_tsecr); 2384 2385 /* 2386 * A timestamp received in a SYN makes 2387 * it ok to send timestamp requests and replies. 2388 */ 2389 if (th->th_flags & TH_SYN) { 2390 tp->t_flags |= TF_RCVD_TSTMP; 2391 tp->ts_recent = to->to_tsval; 2392 tp->ts_recent_age = ticks; 2393 } 2394 break; 2395 case TCPOPT_CC: 2396 if (optlen != TCPOLEN_CC) 2397 continue; 2398 to->to_flag |= TOF_CC; 2399 bcopy((char *)cp + 2, 2400 (char *)&to->to_cc, sizeof(to->to_cc)); 2401 NTOHL(to->to_cc); 2402 /* 2403 * A CC or CC.new option received in a SYN makes 2404 * it ok to send CC in subsequent segments. 2405 */ 2406 if (th->th_flags & TH_SYN) 2407 tp->t_flags |= TF_RCVD_CC; 2408 break; 2409 case TCPOPT_CCNEW: 2410 if (optlen != TCPOLEN_CC) 2411 continue; 2412 if (!(th->th_flags & TH_SYN)) 2413 continue; 2414 to->to_flag |= TOF_CCNEW; 2415 bcopy((char *)cp + 2, 2416 (char *)&to->to_cc, sizeof(to->to_cc)); 2417 NTOHL(to->to_cc); 2418 /* 2419 * A CC or CC.new option received in a SYN makes 2420 * it ok to send CC in subsequent segments. 2421 */ 2422 tp->t_flags |= TF_RCVD_CC; 2423 break; 2424 case TCPOPT_CCECHO: 2425 if (optlen != TCPOLEN_CC) 2426 continue; 2427 if (!(th->th_flags & TH_SYN)) 2428 continue; 2429 to->to_flag |= TOF_CCECHO; 2430 bcopy((char *)cp + 2, 2431 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2432 NTOHL(to->to_ccecho); 2433 break; 2434 } 2435 } 2436 if (th->th_flags & TH_SYN) 2437 tcp_mss(tp, mss); /* sets t_maxseg */ 2438 } 2439 2440 /* 2441 * Pull out of band byte out of a segment so 2442 * it doesn't appear in the user's data queue. 2443 * It is still reflected in the segment length for 2444 * sequencing purposes. 2445 */ 2446 static void 2447 tcp_pulloutofband(so, th, m, off) 2448 struct socket *so; 2449 struct tcphdr *th; 2450 register struct mbuf *m; 2451 int off; /* delayed to be droped hdrlen */ 2452 { 2453 int cnt = off + th->th_urp - 1; 2454 2455 while (cnt >= 0) { 2456 if (m->m_len > cnt) { 2457 char *cp = mtod(m, caddr_t) + cnt; 2458 struct tcpcb *tp = sototcpcb(so); 2459 2460 tp->t_iobc = *cp; 2461 tp->t_oobflags |= TCPOOB_HAVEDATA; 2462 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2463 m->m_len--; 2464 if (m->m_flags & M_PKTHDR) 2465 m->m_pkthdr.len--; 2466 return; 2467 } 2468 cnt -= m->m_len; 2469 m = m->m_next; 2470 if (m == 0) 2471 break; 2472 } 2473 panic("tcp_pulloutofband"); 2474 } 2475 2476 /* 2477 * Collect new round-trip time estimate 2478 * and update averages and current timeout. 2479 */ 2480 static void 2481 tcp_xmit_timer(tp, rtt) 2482 register struct tcpcb *tp; 2483 int rtt; 2484 { 2485 register int delta; 2486 2487 tcpstat.tcps_rttupdated++; 2488 tp->t_rttupdated++; 2489 if (tp->t_srtt != 0) { 2490 /* 2491 * srtt is stored as fixed point with 5 bits after the 2492 * binary point (i.e., scaled by 8). The following magic 2493 * is equivalent to the smoothing algorithm in rfc793 with 2494 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2495 * point). Adjust rtt to origin 0. 2496 */ 2497 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2498 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2499 2500 if ((tp->t_srtt += delta) <= 0) 2501 tp->t_srtt = 1; 2502 2503 /* 2504 * We accumulate a smoothed rtt variance (actually, a 2505 * smoothed mean difference), then set the retransmit 2506 * timer to smoothed rtt + 4 times the smoothed variance. 2507 * rttvar is stored as fixed point with 4 bits after the 2508 * binary point (scaled by 16). The following is 2509 * equivalent to rfc793 smoothing with an alpha of .75 2510 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2511 * rfc793's wired-in beta. 2512 */ 2513 if (delta < 0) 2514 delta = -delta; 2515 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2516 if ((tp->t_rttvar += delta) <= 0) 2517 tp->t_rttvar = 1; 2518 } else { 2519 /* 2520 * No rtt measurement yet - use the unsmoothed rtt. 2521 * Set the variance to half the rtt (so our first 2522 * retransmit happens at 3*rtt). 2523 */ 2524 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2525 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2526 } 2527 tp->t_rtttime = 0; 2528 tp->t_rxtshift = 0; 2529 2530 /* 2531 * the retransmit should happen at rtt + 4 * rttvar. 2532 * Because of the way we do the smoothing, srtt and rttvar 2533 * will each average +1/2 tick of bias. When we compute 2534 * the retransmit timer, we want 1/2 tick of rounding and 2535 * 1 extra tick because of +-1/2 tick uncertainty in the 2536 * firing of the timer. The bias will give us exactly the 2537 * 1.5 tick we need. But, because the bias is 2538 * statistical, we have to test that we don't drop below 2539 * the minimum feasible timer (which is 2 ticks). 2540 */ 2541 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2542 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2543 2544 /* 2545 * We received an ack for a packet that wasn't retransmitted; 2546 * it is probably safe to discard any error indications we've 2547 * received recently. This isn't quite right, but close enough 2548 * for now (a route might have failed after we sent a segment, 2549 * and the return path might not be symmetrical). 2550 */ 2551 tp->t_softerror = 0; 2552 } 2553 2554 /* 2555 * Determine a reasonable value for maxseg size. 2556 * If the route is known, check route for mtu. 2557 * If none, use an mss that can be handled on the outgoing 2558 * interface without forcing IP to fragment; if bigger than 2559 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2560 * to utilize large mbufs. If no route is found, route has no mtu, 2561 * or the destination isn't local, use a default, hopefully conservative 2562 * size (usually 512 or the default IP max size, but no more than the mtu 2563 * of the interface), as we can't discover anything about intervening 2564 * gateways or networks. We also initialize the congestion/slow start 2565 * window to be a single segment if the destination isn't local. 2566 * While looking at the routing entry, we also initialize other path-dependent 2567 * parameters from pre-set or cached values in the routing entry. 2568 * 2569 * Also take into account the space needed for options that we 2570 * send regularly. Make maxseg shorter by that amount to assure 2571 * that we can send maxseg amount of data even when the options 2572 * are present. Store the upper limit of the length of options plus 2573 * data in maxopd. 2574 * 2575 * NOTE that this routine is only called when we process an incoming 2576 * segment, for outgoing segments only tcp_mssopt is called. 2577 * 2578 * In case of T/TCP, we call this routine during implicit connection 2579 * setup as well (offer = -1), to initialize maxseg from the cached 2580 * MSS of our peer. 2581 */ 2582 void 2583 tcp_mss(tp, offer) 2584 struct tcpcb *tp; 2585 int offer; 2586 { 2587 register struct rtentry *rt; 2588 struct ifnet *ifp; 2589 register int rtt, mss; 2590 u_long bufsize; 2591 struct inpcb *inp; 2592 struct socket *so; 2593 struct rmxp_tao *taop; 2594 int origoffer = offer; 2595 #ifdef INET6 2596 int isipv6; 2597 int min_protoh; 2598 #endif 2599 2600 inp = tp->t_inpcb; 2601 #ifdef INET6 2602 isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2603 min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr) 2604 : sizeof (struct tcpiphdr); 2605 #else 2606 #define min_protoh (sizeof (struct tcpiphdr)) 2607 #endif 2608 #ifdef INET6 2609 if (isipv6) 2610 rt = tcp_rtlookup6(inp); 2611 else 2612 #endif 2613 rt = tcp_rtlookup(inp); 2614 if (rt == NULL) { 2615 tp->t_maxopd = tp->t_maxseg = 2616 #ifdef INET6 2617 isipv6 ? tcp_v6mssdflt : 2618 #endif /* INET6 */ 2619 tcp_mssdflt; 2620 return; 2621 } 2622 ifp = rt->rt_ifp; 2623 so = inp->inp_socket; 2624 2625 taop = rmx_taop(rt->rt_rmx); 2626 /* 2627 * Offer == -1 means that we didn't receive SYN yet, 2628 * use cached value in that case; 2629 */ 2630 if (offer == -1) 2631 offer = taop->tao_mssopt; 2632 /* 2633 * Offer == 0 means that there was no MSS on the SYN segment, 2634 * in this case we use tcp_mssdflt. 2635 */ 2636 if (offer == 0) 2637 offer = 2638 #ifdef INET6 2639 isipv6 ? tcp_v6mssdflt : 2640 #endif /* INET6 */ 2641 tcp_mssdflt; 2642 else 2643 /* 2644 * Sanity check: make sure that maxopd will be large 2645 * enough to allow some data on segments even is the 2646 * all the option space is used (40bytes). Otherwise 2647 * funny things may happen in tcp_output. 2648 */ 2649 offer = max(offer, 64); 2650 taop->tao_mssopt = offer; 2651 2652 /* 2653 * While we're here, check if there's an initial rtt 2654 * or rttvar. Convert from the route-table units 2655 * to scaled multiples of the slow timeout timer. 2656 */ 2657 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2658 /* 2659 * XXX the lock bit for RTT indicates that the value 2660 * is also a minimum value; this is subject to time. 2661 */ 2662 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2663 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2664 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2665 tcpstat.tcps_usedrtt++; 2666 if (rt->rt_rmx.rmx_rttvar) { 2667 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2668 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2669 tcpstat.tcps_usedrttvar++; 2670 } else { 2671 /* default variation is +- 1 rtt */ 2672 tp->t_rttvar = 2673 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2674 } 2675 TCPT_RANGESET(tp->t_rxtcur, 2676 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2677 tp->t_rttmin, TCPTV_REXMTMAX); 2678 } 2679 /* 2680 * if there's an mtu associated with the route, use it 2681 * else, use the link mtu. 2682 */ 2683 if (rt->rt_rmx.rmx_mtu) 2684 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2685 else 2686 { 2687 mss = 2688 #ifdef INET6 2689 (isipv6 ? nd_ifinfo[rt->rt_ifp->if_index].linkmtu : 2690 #endif 2691 ifp->if_mtu 2692 #ifdef INET6 2693 ) 2694 #endif 2695 - min_protoh; 2696 #ifdef INET6 2697 if (isipv6) { 2698 if (!in6_localaddr(&inp->in6p_faddr)) 2699 mss = min(mss, tcp_v6mssdflt); 2700 } else 2701 #endif 2702 if (!in_localaddr(inp->inp_faddr)) 2703 mss = min(mss, tcp_mssdflt); 2704 } 2705 mss = min(mss, offer); 2706 /* 2707 * maxopd stores the maximum length of data AND options 2708 * in a segment; maxseg is the amount of data in a normal 2709 * segment. We need to store this value (maxopd) apart 2710 * from maxseg, because now every segment carries options 2711 * and thus we normally have somewhat less data in segments. 2712 */ 2713 tp->t_maxopd = mss; 2714 2715 /* 2716 * In case of T/TCP, origoffer==-1 indicates, that no segments 2717 * were received yet. In this case we just guess, otherwise 2718 * we do the same as before T/TCP. 2719 */ 2720 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2721 (origoffer == -1 || 2722 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2723 mss -= TCPOLEN_TSTAMP_APPA; 2724 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2725 (origoffer == -1 || 2726 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2727 mss -= TCPOLEN_CC_APPA; 2728 2729 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2730 if (mss > MCLBYTES) 2731 mss &= ~(MCLBYTES-1); 2732 #else 2733 if (mss > MCLBYTES) 2734 mss = mss / MCLBYTES * MCLBYTES; 2735 #endif 2736 /* 2737 * If there's a pipesize, change the socket buffer 2738 * to that size. Make the socket buffers an integral 2739 * number of mss units; if the mss is larger than 2740 * the socket buffer, decrease the mss. 2741 */ 2742 #ifdef RTV_SPIPE 2743 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2744 #endif 2745 bufsize = so->so_snd.sb_hiwat; 2746 if (bufsize < mss) 2747 mss = bufsize; 2748 else { 2749 bufsize = roundup(bufsize, mss); 2750 if (bufsize > sb_max) 2751 bufsize = sb_max; 2752 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2753 } 2754 tp->t_maxseg = mss; 2755 2756 #ifdef RTV_RPIPE 2757 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2758 #endif 2759 bufsize = so->so_rcv.sb_hiwat; 2760 if (bufsize > mss) { 2761 bufsize = roundup(bufsize, mss); 2762 if (bufsize > sb_max) 2763 bufsize = sb_max; 2764 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2765 } 2766 2767 /* 2768 * Set the slow-start flight size depending on whether this 2769 * is a local network or not. 2770 */ 2771 if ( 2772 #ifdef INET6 2773 (isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2774 (!isipv6 && 2775 #endif 2776 in_localaddr(inp->inp_faddr) 2777 #ifdef INET6 2778 ) 2779 #endif 2780 ) 2781 tp->snd_cwnd = mss * ss_fltsz_local; 2782 else 2783 tp->snd_cwnd = mss * ss_fltsz; 2784 2785 if (rt->rt_rmx.rmx_ssthresh) { 2786 /* 2787 * There's some sort of gateway or interface 2788 * buffer limit on the path. Use this to set 2789 * the slow start threshhold, but set the 2790 * threshold to no less than 2*mss. 2791 */ 2792 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2793 tcpstat.tcps_usedssthresh++; 2794 } 2795 } 2796 2797 /* 2798 * Determine the MSS option to send on an outgoing SYN. 2799 */ 2800 int 2801 tcp_mssopt(tp) 2802 struct tcpcb *tp; 2803 { 2804 struct rtentry *rt; 2805 #ifdef INET6 2806 int isipv6; 2807 int min_protoh; 2808 #endif 2809 2810 #ifdef INET6 2811 isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2812 min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr) 2813 : sizeof (struct tcpiphdr); 2814 #else 2815 #define min_protoh (sizeof (struct tcpiphdr)) 2816 #endif 2817 #ifdef INET6 2818 if (isipv6) 2819 rt = tcp_rtlookup6(tp->t_inpcb); 2820 else 2821 #endif /* INET6 */ 2822 rt = tcp_rtlookup(tp->t_inpcb); 2823 if (rt == NULL) 2824 return 2825 #ifdef INET6 2826 isipv6 ? tcp_v6mssdflt : 2827 #endif /* INET6 */ 2828 tcp_mssdflt; 2829 2830 return rt->rt_ifp->if_mtu - min_protoh; 2831 } 2832 2833 2834 /* 2835 * Checks for partial ack. If partial ack arrives, force the retransmission 2836 * of the next unacknowledged segment, do not clear tp->t_dupacks, and return 2837 * 1. By setting snd_nxt to ti_ack, this forces retransmission timer to 2838 * be started again. If the ack advances at least to tp->snd_recover, return 0. 2839 */ 2840 static int 2841 tcp_newreno(tp, th) 2842 struct tcpcb *tp; 2843 struct tcphdr *th; 2844 { 2845 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2846 tcp_seq onxt = tp->snd_nxt; 2847 u_long ocwnd = tp->snd_cwnd; 2848 2849 callout_stop(tp->tt_rexmt); 2850 tp->t_rtttime = 0; 2851 tp->snd_nxt = th->th_ack; 2852 /* 2853 * Set snd_cwnd to one segment beyond acknowledged offset 2854 * (tp->snd_una has not yet been updated when this function 2855 * is called) 2856 */ 2857 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 2858 (void) tcp_output(tp); 2859 tp->snd_cwnd = ocwnd; 2860 if (SEQ_GT(onxt, tp->snd_nxt)) 2861 tp->snd_nxt = onxt; 2862 /* 2863 * Partial window deflation. Relies on fact that tp->snd_una 2864 * not updated yet. 2865 */ 2866 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 2867 return (1); 2868 } 2869 return (0); 2870 } 2871