1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/kernel.h> 42 #include <sys/malloc.h> 43 #include <sys/mbuf.h> 44 #include <sys/proc.h> /* for proc0 declaration */ 45 #include <sys/protosw.h> 46 #include <sys/signalvar.h> 47 #include <sys/socket.h> 48 #include <sys/socketvar.h> 49 #include <sys/sysctl.h> 50 #include <sys/syslog.h> 51 #include <sys/systm.h> 52 53 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 54 55 #include <vm/uma.h> 56 57 #include <net/if.h> 58 #include <net/route.h> 59 60 #include <netinet/in.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/in_var.h> 64 #include <netinet/ip.h> 65 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 66 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 67 #include <netinet/ip_var.h> 68 #include <netinet/ip_options.h> 69 #include <netinet/ip6.h> 70 #include <netinet/icmp6.h> 71 #include <netinet6/in6_pcb.h> 72 #include <netinet6/ip6_var.h> 73 #include <netinet6/nd6.h> 74 #include <netinet/tcp.h> 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_seq.h> 77 #include <netinet/tcp_timer.h> 78 #include <netinet/tcp_var.h> 79 #include <netinet6/tcp6_var.h> 80 #include <netinet/tcpip.h> 81 #ifdef TCPDEBUG 82 #include <netinet/tcp_debug.h> 83 #endif /* TCPDEBUG */ 84 85 #ifdef FAST_IPSEC 86 #include <netipsec/ipsec.h> 87 #include <netipsec/ipsec6.h> 88 #endif /*FAST_IPSEC*/ 89 90 #ifdef IPSEC 91 #include <netinet6/ipsec.h> 92 #include <netinet6/ipsec6.h> 93 #include <netkey/key.h> 94 #endif /*IPSEC*/ 95 96 #include <machine/in_cksum.h> 97 98 #include <security/mac/mac_framework.h> 99 100 static const int tcprexmtthresh = 3; 101 102 struct tcpstat tcpstat; 103 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 104 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 105 106 static int tcp_log_in_vain = 0; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 108 &tcp_log_in_vain, 0, "Log all incoming TCP segments to closed ports"); 109 110 static int blackhole = 0; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 112 &blackhole, 0, "Do not send RST on segments to closed ports"); 113 114 int tcp_delack_enabled = 1; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 116 &tcp_delack_enabled, 0, 117 "Delay ACK to try and piggyback it onto a data packet"); 118 119 static int drop_synfin = 0; 120 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 121 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 122 123 static int tcp_do_rfc3042 = 1; 124 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 125 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 126 127 static int tcp_do_rfc3390 = 1; 128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 129 &tcp_do_rfc3390, 0, 130 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 131 132 static int tcp_insecure_rst = 0; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 134 &tcp_insecure_rst, 0, 135 "Follow the old (insecure) criteria for accepting RST packets"); 136 137 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 138 "TCP Segment Reassembly Queue"); 139 140 static int tcp_reass_maxseg = 0; 141 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 142 &tcp_reass_maxseg, 0, 143 "Global maximum number of TCP Segments in Reassembly Queue"); 144 145 int tcp_reass_qsize = 0; 146 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 147 &tcp_reass_qsize, 0, 148 "Global number of TCP Segments currently in Reassembly Queue"); 149 150 static int tcp_reass_maxqlen = 48; 151 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 152 &tcp_reass_maxqlen, 0, 153 "Maximum number of TCP Segments per individual Reassembly Queue"); 154 155 static int tcp_reass_overflows = 0; 156 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 157 &tcp_reass_overflows, 0, 158 "Global number of TCP Segment Reassembly Queue Overflows"); 159 160 int tcp_do_autorcvbuf = 1; 161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 162 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 163 164 int tcp_autorcvbuf_inc = 16*1024; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 166 &tcp_autorcvbuf_inc, 0, 167 "Incrementor step size of automatic receive buffer"); 168 169 int tcp_autorcvbuf_max = 256*1024; 170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 171 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 172 173 struct inpcbhead tcb; 174 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 175 struct inpcbinfo tcbinfo; 176 struct mtx *tcbinfo_mtx; 177 178 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 179 static int tcp_do_segment(struct mbuf *, struct tcphdr *, 180 struct socket *, struct tcpcb *, int, int); 181 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, 182 struct tcpcb *, int, int); 183 static void tcp_pulloutofband(struct socket *, 184 struct tcphdr *, struct mbuf *, int); 185 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 186 struct mbuf *); 187 static void tcp_xmit_timer(struct tcpcb *, int); 188 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 189 static int tcp_timewait(struct inpcb *, struct tcpopt *, 190 struct tcphdr *, struct mbuf *, int); 191 192 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 193 #ifdef INET6 194 #define ND6_HINT(tp) \ 195 do { \ 196 if ((tp) && (tp)->t_inpcb && \ 197 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 198 nd6_nud_hint(NULL, NULL, 0); \ 199 } while (0) 200 #else 201 #define ND6_HINT(tp) 202 #endif 203 204 /* 205 * Indicate whether this ack should be delayed. We can delay the ack if 206 * - there is no delayed ack timer in progress and 207 * - our last ack wasn't a 0-sized window. We never want to delay 208 * the ack that opens up a 0-sized window and 209 * - delayed acks are enabled or 210 * - this is a half-synchronized T/TCP connection. 211 */ 212 #define DELAY_ACK(tp) \ 213 ((!callout_active(tp->tt_delack) && \ 214 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 215 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 216 217 /* Initialize TCP reassembly queue */ 218 static void 219 tcp_reass_zone_change(void *tag) 220 { 221 222 tcp_reass_maxseg = nmbclusters / 16; 223 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 224 } 225 226 uma_zone_t tcp_reass_zone; 227 void 228 tcp_reass_init() 229 { 230 tcp_reass_maxseg = nmbclusters / 16; 231 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 232 &tcp_reass_maxseg); 233 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 234 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 235 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 236 EVENTHANDLER_REGISTER(nmbclusters_change, 237 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY); 238 } 239 240 static int 241 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 242 { 243 struct tseg_qent *q; 244 struct tseg_qent *p = NULL; 245 struct tseg_qent *nq; 246 struct tseg_qent *te = NULL; 247 struct socket *so = tp->t_inpcb->inp_socket; 248 int flags; 249 250 INP_LOCK_ASSERT(tp->t_inpcb); 251 252 /* 253 * XXX: tcp_reass() is rather inefficient with its data structures 254 * and should be rewritten (see NetBSD for optimizations). While 255 * doing that it should move to its own file tcp_reass.c. 256 */ 257 258 /* 259 * Call with th==NULL after become established to 260 * force pre-ESTABLISHED data up to user socket. 261 */ 262 if (th == NULL) 263 goto present; 264 265 /* 266 * Limit the number of segments in the reassembly queue to prevent 267 * holding on to too many segments (and thus running out of mbufs). 268 * Make sure to let the missing segment through which caused this 269 * queue. Always keep one global queue entry spare to be able to 270 * process the missing segment. 271 */ 272 if (th->th_seq != tp->rcv_nxt && 273 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 274 tp->t_segqlen >= tcp_reass_maxqlen)) { 275 tcp_reass_overflows++; 276 tcpstat.tcps_rcvmemdrop++; 277 m_freem(m); 278 *tlenp = 0; 279 return (0); 280 } 281 282 /* 283 * Allocate a new queue entry. If we can't, or hit the zone limit 284 * just drop the pkt. 285 */ 286 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 287 if (te == NULL) { 288 tcpstat.tcps_rcvmemdrop++; 289 m_freem(m); 290 *tlenp = 0; 291 return (0); 292 } 293 tp->t_segqlen++; 294 tcp_reass_qsize++; 295 296 /* 297 * Find a segment which begins after this one does. 298 */ 299 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 300 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 301 break; 302 p = q; 303 } 304 305 /* 306 * If there is a preceding segment, it may provide some of 307 * our data already. If so, drop the data from the incoming 308 * segment. If it provides all of our data, drop us. 309 */ 310 if (p != NULL) { 311 int i; 312 /* conversion to int (in i) handles seq wraparound */ 313 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 314 if (i > 0) { 315 if (i >= *tlenp) { 316 tcpstat.tcps_rcvduppack++; 317 tcpstat.tcps_rcvdupbyte += *tlenp; 318 m_freem(m); 319 uma_zfree(tcp_reass_zone, te); 320 tp->t_segqlen--; 321 tcp_reass_qsize--; 322 /* 323 * Try to present any queued data 324 * at the left window edge to the user. 325 * This is needed after the 3-WHS 326 * completes. 327 */ 328 goto present; /* ??? */ 329 } 330 m_adj(m, i); 331 *tlenp -= i; 332 th->th_seq += i; 333 } 334 } 335 tcpstat.tcps_rcvoopack++; 336 tcpstat.tcps_rcvoobyte += *tlenp; 337 338 /* 339 * While we overlap succeeding segments trim them or, 340 * if they are completely covered, dequeue them. 341 */ 342 while (q) { 343 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 344 if (i <= 0) 345 break; 346 if (i < q->tqe_len) { 347 q->tqe_th->th_seq += i; 348 q->tqe_len -= i; 349 m_adj(q->tqe_m, i); 350 break; 351 } 352 353 nq = LIST_NEXT(q, tqe_q); 354 LIST_REMOVE(q, tqe_q); 355 m_freem(q->tqe_m); 356 uma_zfree(tcp_reass_zone, q); 357 tp->t_segqlen--; 358 tcp_reass_qsize--; 359 q = nq; 360 } 361 362 /* Insert the new segment queue entry into place. */ 363 te->tqe_m = m; 364 te->tqe_th = th; 365 te->tqe_len = *tlenp; 366 367 if (p == NULL) { 368 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 369 } else { 370 LIST_INSERT_AFTER(p, te, tqe_q); 371 } 372 373 present: 374 /* 375 * Present data to user, advancing rcv_nxt through 376 * completed sequence space. 377 */ 378 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 379 return (0); 380 q = LIST_FIRST(&tp->t_segq); 381 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 382 return (0); 383 SOCKBUF_LOCK(&so->so_rcv); 384 do { 385 tp->rcv_nxt += q->tqe_len; 386 flags = q->tqe_th->th_flags & TH_FIN; 387 nq = LIST_NEXT(q, tqe_q); 388 LIST_REMOVE(q, tqe_q); 389 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 390 m_freem(q->tqe_m); 391 else 392 sbappendstream_locked(&so->so_rcv, q->tqe_m); 393 uma_zfree(tcp_reass_zone, q); 394 tp->t_segqlen--; 395 tcp_reass_qsize--; 396 q = nq; 397 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 398 ND6_HINT(tp); 399 sorwakeup_locked(so); 400 return (flags); 401 } 402 403 /* 404 * TCP input routine, follows pages 65-76 of the 405 * protocol specification dated September, 1981 very closely. 406 */ 407 #ifdef INET6 408 int 409 tcp6_input(struct mbuf **mp, int *offp, int proto) 410 { 411 struct mbuf *m = *mp; 412 struct in6_ifaddr *ia6; 413 414 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 415 416 /* 417 * draft-itojun-ipv6-tcp-to-anycast 418 * better place to put this in? 419 */ 420 ia6 = ip6_getdstifaddr(m); 421 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 422 struct ip6_hdr *ip6; 423 424 ip6 = mtod(m, struct ip6_hdr *); 425 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 426 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 427 return IPPROTO_DONE; 428 } 429 430 tcp_input(m, *offp); 431 return IPPROTO_DONE; 432 } 433 #endif 434 435 void 436 tcp_input(struct mbuf *m, int off0) 437 { 438 struct tcphdr *th; 439 struct ip *ip = NULL; 440 struct ipovly *ipov; 441 struct inpcb *inp = NULL; 442 struct tcpcb *tp = NULL; 443 struct socket *so = NULL; 444 u_char *optp = NULL; 445 int optlen = 0; 446 int len, tlen, off; 447 int drop_hdrlen; 448 int thflags; 449 int rstreason = 0; /* For badport_bandlim accounting purposes */ 450 #ifdef IPFIREWALL_FORWARD 451 struct m_tag *fwd_tag; 452 #endif 453 #ifdef INET6 454 struct ip6_hdr *ip6 = NULL; 455 int isipv6; 456 char ip6buf[INET6_ADDRSTRLEN]; 457 #else 458 const int isipv6 = 0; 459 #endif 460 struct tcpopt to; /* options in this segment */ 461 462 #ifdef TCPDEBUG 463 /* 464 * The size of tcp_saveipgen must be the size of the max ip header, 465 * now IPv6. 466 */ 467 u_char tcp_saveipgen[IP6_HDR_LEN]; 468 struct tcphdr tcp_savetcp; 469 short ostate = 0; 470 #endif 471 472 #ifdef INET6 473 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 474 #endif 475 476 to.to_flags = 0; 477 tcpstat.tcps_rcvtotal++; 478 479 if (isipv6) { 480 #ifdef INET6 481 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 482 ip6 = mtod(m, struct ip6_hdr *); 483 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 484 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 485 tcpstat.tcps_rcvbadsum++; 486 goto drop; 487 } 488 th = (struct tcphdr *)((caddr_t)ip6 + off0); 489 490 /* 491 * Be proactive about unspecified IPv6 address in source. 492 * As we use all-zero to indicate unbounded/unconnected pcb, 493 * unspecified IPv6 address can be used to confuse us. 494 * 495 * Note that packets with unspecified IPv6 destination is 496 * already dropped in ip6_input. 497 */ 498 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 499 /* XXX stat */ 500 goto drop; 501 } 502 #else 503 th = NULL; /* XXX: avoid compiler warning */ 504 #endif 505 } else { 506 /* 507 * Get IP and TCP header together in first mbuf. 508 * Note: IP leaves IP header in first mbuf. 509 */ 510 if (off0 > sizeof (struct ip)) { 511 ip_stripoptions(m, (struct mbuf *)0); 512 off0 = sizeof(struct ip); 513 } 514 if (m->m_len < sizeof (struct tcpiphdr)) { 515 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 516 == NULL) { 517 tcpstat.tcps_rcvshort++; 518 return; 519 } 520 } 521 ip = mtod(m, struct ip *); 522 ipov = (struct ipovly *)ip; 523 th = (struct tcphdr *)((caddr_t)ip + off0); 524 tlen = ip->ip_len; 525 526 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 527 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 528 th->th_sum = m->m_pkthdr.csum_data; 529 else 530 th->th_sum = in_pseudo(ip->ip_src.s_addr, 531 ip->ip_dst.s_addr, 532 htonl(m->m_pkthdr.csum_data + 533 ip->ip_len + 534 IPPROTO_TCP)); 535 th->th_sum ^= 0xffff; 536 #ifdef TCPDEBUG 537 ipov->ih_len = (u_short)tlen; 538 ipov->ih_len = htons(ipov->ih_len); 539 #endif 540 } else { 541 /* 542 * Checksum extended TCP header and data. 543 */ 544 len = sizeof (struct ip) + tlen; 545 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 546 ipov->ih_len = (u_short)tlen; 547 ipov->ih_len = htons(ipov->ih_len); 548 th->th_sum = in_cksum(m, len); 549 } 550 if (th->th_sum) { 551 tcpstat.tcps_rcvbadsum++; 552 goto drop; 553 } 554 /* Re-initialization for later version check */ 555 ip->ip_v = IPVERSION; 556 } 557 558 /* 559 * Check that TCP offset makes sense, 560 * pull out TCP options and adjust length. XXX 561 */ 562 off = th->th_off << 2; 563 if (off < sizeof (struct tcphdr) || off > tlen) { 564 tcpstat.tcps_rcvbadoff++; 565 goto drop; 566 } 567 tlen -= off; /* tlen is used instead of ti->ti_len */ 568 if (off > sizeof (struct tcphdr)) { 569 if (isipv6) { 570 #ifdef INET6 571 IP6_EXTHDR_CHECK(m, off0, off, ); 572 ip6 = mtod(m, struct ip6_hdr *); 573 th = (struct tcphdr *)((caddr_t)ip6 + off0); 574 #endif 575 } else { 576 if (m->m_len < sizeof(struct ip) + off) { 577 if ((m = m_pullup(m, sizeof (struct ip) + off)) 578 == NULL) { 579 tcpstat.tcps_rcvshort++; 580 return; 581 } 582 ip = mtod(m, struct ip *); 583 ipov = (struct ipovly *)ip; 584 th = (struct tcphdr *)((caddr_t)ip + off0); 585 } 586 } 587 optlen = off - sizeof (struct tcphdr); 588 optp = (u_char *)(th + 1); 589 } 590 thflags = th->th_flags; 591 592 /* 593 * If the drop_synfin option is enabled, drop all packets with 594 * both the SYN and FIN bits set. This prevents e.g. nmap from 595 * identifying the TCP/IP stack. 596 * 597 * This is a violation of the TCP specification. 598 */ 599 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 600 goto drop; 601 602 /* 603 * Convert TCP protocol specific fields to host format. 604 */ 605 th->th_seq = ntohl(th->th_seq); 606 th->th_ack = ntohl(th->th_ack); 607 th->th_win = ntohs(th->th_win); 608 th->th_urp = ntohs(th->th_urp); 609 610 /* 611 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 612 */ 613 drop_hdrlen = off0 + off; 614 615 /* 616 * Locate pcb for segment. 617 */ 618 INP_INFO_WLOCK(&tcbinfo); 619 findpcb: 620 INP_INFO_WLOCK_ASSERT(&tcbinfo); 621 #ifdef IPFIREWALL_FORWARD 622 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 623 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 624 625 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 626 struct sockaddr_in *next_hop; 627 628 next_hop = (struct sockaddr_in *)(fwd_tag+1); 629 /* 630 * Transparently forwarded. Pretend to be the destination. 631 * already got one like this? 632 */ 633 inp = in_pcblookup_hash(&tcbinfo, 634 ip->ip_src, th->th_sport, 635 ip->ip_dst, th->th_dport, 636 0, m->m_pkthdr.rcvif); 637 if (!inp) { 638 /* It's new. Try to find the ambushing socket. */ 639 inp = in_pcblookup_hash(&tcbinfo, 640 ip->ip_src, th->th_sport, 641 next_hop->sin_addr, 642 next_hop->sin_port ? 643 ntohs(next_hop->sin_port) : 644 th->th_dport, 645 INPLOOKUP_WILDCARD, 646 m->m_pkthdr.rcvif); 647 } 648 /* Remove the tag from the packet. We don't need it anymore. */ 649 m_tag_delete(m, fwd_tag); 650 } else 651 #endif /* IPFIREWALL_FORWARD */ 652 { 653 if (isipv6) { 654 #ifdef INET6 655 inp = in6_pcblookup_hash(&tcbinfo, 656 &ip6->ip6_src, th->th_sport, 657 &ip6->ip6_dst, th->th_dport, 658 INPLOOKUP_WILDCARD, 659 m->m_pkthdr.rcvif); 660 #endif 661 } else 662 inp = in_pcblookup_hash(&tcbinfo, 663 ip->ip_src, th->th_sport, 664 ip->ip_dst, th->th_dport, 665 INPLOOKUP_WILDCARD, 666 m->m_pkthdr.rcvif); 667 } 668 669 #if defined(IPSEC) || defined(FAST_IPSEC) 670 #ifdef INET6 671 if (isipv6 && inp != NULL && ipsec6_in_reject(m, inp)) { 672 #ifdef IPSEC 673 ipsec6stat.in_polvio++; 674 #endif 675 goto dropunlock; 676 } else 677 #endif /* INET6 */ 678 if (inp != NULL && ipsec4_in_reject(m, inp)) { 679 #ifdef IPSEC 680 ipsecstat.in_polvio++; 681 #endif 682 goto dropunlock; 683 } 684 #endif /*IPSEC || FAST_IPSEC*/ 685 686 /* 687 * If the INPCB does not exist then all data in the incoming 688 * segment is discarded and an appropriate RST is sent back. 689 */ 690 if (inp == NULL) { 691 /* 692 * Log communication attempts to ports that are not 693 * in use. 694 */ 695 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 696 tcp_log_in_vain == 2) { 697 #ifndef INET6 698 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 699 #else 700 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 701 if (isipv6) { 702 strcpy(dbuf, "["); 703 strcat(dbuf, 704 ip6_sprintf(ip6buf, &ip6->ip6_dst)); 705 strcat(dbuf, "]"); 706 strcpy(sbuf, "["); 707 strcat(sbuf, 708 ip6_sprintf(ip6buf, &ip6->ip6_src)); 709 strcat(sbuf, "]"); 710 } else 711 #endif /* INET6 */ 712 { 713 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 714 strcpy(sbuf, inet_ntoa(ip->ip_src)); 715 } 716 log(LOG_INFO, 717 "Connection attempt to TCP %s:%d " 718 "from %s:%d flags:0x%02x\n", 719 dbuf, ntohs(th->th_dport), sbuf, 720 ntohs(th->th_sport), thflags); 721 } 722 /* 723 * When blackholing do not respond with a RST but 724 * completely ignore the segment and drop it. 725 */ 726 if ((blackhole == 1 && (thflags & TH_SYN)) || 727 blackhole == 2) 728 goto dropunlock; 729 730 rstreason = BANDLIM_RST_CLOSEDPORT; 731 goto dropwithreset; 732 } 733 INP_LOCK(inp); 734 735 /* Check the minimum TTL for socket. */ 736 if (inp->inp_ip_minttl != 0) { 737 #ifdef INET6 738 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 739 goto dropunlock; 740 else 741 #endif 742 if (inp->inp_ip_minttl > ip->ip_ttl) 743 goto dropunlock; 744 } 745 746 /* 747 * A previous connection in TIMEWAIT state is supposed to catch 748 * stray or duplicate segments arriving late. If this segment 749 * was a legitimate new connection attempt the old INPCB gets 750 * removed and we can try again to find a listening socket. 751 */ 752 if (inp->inp_vflag & INP_TIMEWAIT) { 753 if (thflags & TH_SYN) 754 tcp_dooptions(&to, optp, optlen, TO_SYN); 755 if (tcp_timewait(inp, &to, th, m, tlen)) 756 goto findpcb; 757 /* tcp_timewait unlocks inp. */ 758 INP_INFO_WUNLOCK(&tcbinfo); 759 return; 760 } 761 /* 762 * The TCPCB may no longer exist if the connection is winding 763 * down or it is in the CLOSED state. Either way we drop the 764 * segment and send an appropriate response. 765 */ 766 tp = intotcpcb(inp); 767 if (tp == NULL) { 768 INP_UNLOCK(inp); 769 rstreason = BANDLIM_RST_CLOSEDPORT; 770 goto dropwithreset; 771 } 772 if (tp->t_state == TCPS_CLOSED) 773 goto dropunlock; /* XXX: dropwithreset??? */ 774 775 #ifdef MAC 776 INP_LOCK_ASSERT(inp); 777 if (mac_check_inpcb_deliver(inp, m)) 778 goto dropunlock; 779 #endif 780 so = inp->inp_socket; 781 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 782 #ifdef TCPDEBUG 783 if (so->so_options & SO_DEBUG) { 784 ostate = tp->t_state; 785 if (isipv6) 786 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 787 else 788 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 789 tcp_savetcp = *th; 790 } 791 #endif 792 /* 793 * When the socket is accepting connections (the INPCB is in LISTEN 794 * state) we look into the SYN cache if this is a new connection 795 * attempt or the completion of a previous one. 796 */ 797 if (so->so_options & SO_ACCEPTCONN) { 798 struct in_conninfo inc; 799 800 bzero(&inc, sizeof(inc)); 801 inc.inc_isipv6 = isipv6; 802 #ifdef INET6 803 if (isipv6) { 804 inc.inc6_faddr = ip6->ip6_src; 805 inc.inc6_laddr = ip6->ip6_dst; 806 } else 807 #endif 808 { 809 inc.inc_faddr = ip->ip_src; 810 inc.inc_laddr = ip->ip_dst; 811 } 812 inc.inc_fport = th->th_sport; 813 inc.inc_lport = th->th_dport; 814 815 /* 816 * If the state is LISTEN then ignore segment if it contains 817 * a RST. If the segment contains an ACK then it is bad and 818 * send a RST. If it does not contain a SYN then it is not 819 * interesting; drop it. 820 * 821 * If the state is SYN_RECEIVED (syncache) and seg contains 822 * an ACK, but not for our SYN/ACK, send a RST. If the seg 823 * contains a RST, check the sequence number to see if it 824 * is a valid reset segment. 825 */ 826 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 827 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 828 /* 829 * Parse the TCP options here because 830 * syncookies need access to the reflected 831 * timestamp. 832 */ 833 tcp_dooptions(&to, optp, optlen, 0); 834 if (!syncache_expand(&inc, &to, th, &so, m)) { 835 /* 836 * No syncache entry, or ACK was not 837 * for our SYN/ACK. Send a RST. 838 */ 839 tcpstat.tcps_badsyn++; 840 rstreason = BANDLIM_RST_OPENPORT; 841 goto dropwithreset; 842 } 843 if (so == NULL) { 844 /* 845 * Could not complete 3-way handshake, 846 * connection is being closed down, and 847 * syncache has free'd mbuf. 848 */ 849 INP_UNLOCK(inp); 850 INP_INFO_WUNLOCK(&tcbinfo); 851 return; 852 } 853 /* 854 * Socket is created in state SYN_RECEIVED. 855 * Continue processing segment. 856 */ 857 INP_UNLOCK(inp); /* listen socket */ 858 inp = sotoinpcb(so); 859 INP_LOCK(inp); /* new connection */ 860 tp = intotcpcb(inp); 861 /* 862 * Process the segment and the data it 863 * contains. tcp_do_segment() consumes 864 * the mbuf chain and unlocks the inpcb. 865 * XXX: The potential return value of 866 * TIME_WAIT nuked is supposed to be 867 * handled above. 868 */ 869 if (tcp_do_segment(m, th, so, tp, 870 drop_hdrlen, tlen)) 871 goto findpcb; /* TIME_WAIT nuked */ 872 return; 873 } 874 if (thflags & TH_RST) { 875 syncache_chkrst(&inc, th); 876 goto dropunlock; 877 } 878 if (thflags & TH_ACK) { 879 syncache_badack(&inc); 880 tcpstat.tcps_badsyn++; 881 rstreason = BANDLIM_RST_OPENPORT; 882 goto dropwithreset; 883 } 884 goto dropunlock; 885 } 886 887 /* 888 * Segment's flags are (SYN) or (SYN|FIN). 889 */ 890 #ifdef INET6 891 /* 892 * If deprecated address is forbidden, 893 * we do not accept SYN to deprecated interface 894 * address to prevent any new inbound connection from 895 * getting established. 896 * When we do not accept SYN, we send a TCP RST, 897 * with deprecated source address (instead of dropping 898 * it). We compromise it as it is much better for peer 899 * to send a RST, and RST will be the final packet 900 * for the exchange. 901 * 902 * If we do not forbid deprecated addresses, we accept 903 * the SYN packet. RFC2462 does not suggest dropping 904 * SYN in this case. 905 * If we decipher RFC2462 5.5.4, it says like this: 906 * 1. use of deprecated addr with existing 907 * communication is okay - "SHOULD continue to be 908 * used" 909 * 2. use of it with new communication: 910 * (2a) "SHOULD NOT be used if alternate address 911 * with sufficient scope is available" 912 * (2b) nothing mentioned otherwise. 913 * Here we fall into (2b) case as we have no choice in 914 * our source address selection - we must obey the peer. 915 * 916 * The wording in RFC2462 is confusing, and there are 917 * multiple description text for deprecated address 918 * handling - worse, they are not exactly the same. 919 * I believe 5.5.4 is the best one, so we follow 5.5.4. 920 */ 921 if (isipv6 && !ip6_use_deprecated) { 922 struct in6_ifaddr *ia6; 923 924 if ((ia6 = ip6_getdstifaddr(m)) && 925 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 926 INP_UNLOCK(inp); 927 tp = NULL; 928 rstreason = BANDLIM_RST_OPENPORT; 929 goto dropwithreset; 930 } 931 } 932 #endif 933 /* 934 * Basic sanity checks on incoming SYN requests: 935 * 936 * Don't bother responding if the destination was a 937 * broadcast according to RFC1122 4.2.3.10, p. 104. 938 * 939 * If it is from this socket, drop it, it must be forged. 940 * 941 * Note that it is quite possible to receive unicast 942 * link-layer packets with a broadcast IP address. Use 943 * in_broadcast() to find them. 944 */ 945 if (m->m_flags & (M_BCAST|M_MCAST)) 946 goto dropunlock; 947 if (isipv6) { 948 #ifdef INET6 949 if (th->th_dport == th->th_sport && 950 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) 951 goto dropunlock; 952 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 953 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 954 goto dropunlock; 955 #endif 956 } else { 957 if (th->th_dport == th->th_sport && 958 ip->ip_dst.s_addr == ip->ip_src.s_addr) 959 goto dropunlock; 960 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 961 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 962 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 963 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 964 goto dropunlock; 965 } 966 /* 967 * SYN appears to be valid. Create compressed TCP state 968 * for syncache. 969 */ 970 if (so->so_qlen <= so->so_qlimit) { 971 #ifdef TCPDEBUG 972 if (so->so_options & SO_DEBUG) 973 tcp_trace(TA_INPUT, ostate, tp, 974 (void *)tcp_saveipgen, &tcp_savetcp, 0); 975 #endif 976 tcp_dooptions(&to, optp, optlen, TO_SYN); 977 if (!syncache_add(&inc, &to, th, inp, &so, m)) 978 goto dropunlock; 979 /* 980 * Entry added to syncache, mbuf used to 981 * send SYN-ACK packet. Everything unlocked 982 * already. 983 */ 984 return; 985 } 986 /* Catch all. Everthing that makes it down here is junk. */ 987 goto dropunlock; 988 } 989 990 /* 991 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or 992 * later state. tcp_do_segment() always consumes the mbuf chain 993 * and unlocks the inpcb. 994 */ 995 if (tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen)) 996 goto findpcb; /* XXX: TIME_WAIT was nuked. */ 997 return; 998 999 dropwithreset: 1000 INP_INFO_WLOCK_ASSERT(&tcbinfo); 1001 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1002 m = NULL; /* mbuf chain got consumed. */ 1003 dropunlock: 1004 INP_INFO_WLOCK_ASSERT(&tcbinfo); 1005 if (tp != NULL) 1006 INP_UNLOCK(inp); 1007 INP_INFO_WUNLOCK(&tcbinfo); 1008 drop: 1009 INP_INFO_UNLOCK_ASSERT(&tcbinfo); 1010 if (m != NULL) 1011 m_freem(m); 1012 return; 1013 } 1014 1015 static int 1016 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1017 struct tcpcb *tp, int drop_hdrlen, int tlen) 1018 { 1019 int thflags, acked, ourfinisacked, needoutput = 0; 1020 int headlocked = 1; 1021 int rstreason, todrop, win; 1022 u_long tiwin; 1023 struct tcpopt to; 1024 1025 #ifdef TCPDEBUG 1026 /* 1027 * The size of tcp_saveipgen must be the size of the max ip header, 1028 * now IPv6. 1029 */ 1030 u_char tcp_saveipgen[IP6_HDR_LEN]; 1031 struct tcphdr tcp_savetcp; 1032 short ostate = 0; 1033 #endif 1034 thflags = th->th_flags; 1035 1036 INP_INFO_WLOCK_ASSERT(&tcbinfo); 1037 INP_LOCK_ASSERT(tp->t_inpcb); 1038 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", __func__)); 1039 1040 /* 1041 * Segment received on connection. 1042 * Reset idle time and keep-alive timer. 1043 */ 1044 tp->t_rcvtime = ticks; 1045 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1046 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1047 1048 /* 1049 * Unscale the window into a 32-bit value. 1050 * This value is bogus for the TCPS_SYN_SENT state 1051 * and is overwritten later. 1052 */ 1053 tiwin = th->th_win << tp->snd_scale; 1054 1055 /* 1056 * Parse options on any incoming segment. 1057 */ 1058 tcp_dooptions(&to, (u_char *)(th + 1), 1059 (th->th_off << 2) - sizeof(struct tcphdr), 1060 (thflags & TH_SYN) ? TO_SYN : 0); 1061 1062 /* 1063 * If echoed timestamp is later than the current time, 1064 * fall back to non RFC1323 RTT calculation. Normalize 1065 * timestamp if syncookies were used when this connection 1066 * was established. 1067 */ 1068 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1069 to.to_tsecr -= tp->ts_offset; 1070 if (TSTMP_GT(to.to_tsecr, ticks)) 1071 to.to_tsecr = 0; 1072 } 1073 1074 /* 1075 * Process options only when we get SYN/ACK back. The SYN case 1076 * for incoming connections is handled in tcp_syncache. 1077 * XXX this is traditional behavior, may need to be cleaned up. 1078 */ 1079 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1080 if ((to.to_flags & TOF_SCALE) && 1081 (tp->t_flags & TF_REQ_SCALE)) { 1082 tp->t_flags |= TF_RCVD_SCALE; 1083 tp->snd_scale = to.to_wscale; 1084 tp->snd_wnd = th->th_win << tp->snd_scale; 1085 tiwin = tp->snd_wnd; 1086 } 1087 if (to.to_flags & TOF_TS) { 1088 tp->t_flags |= TF_RCVD_TSTMP; 1089 tp->ts_recent = to.to_tsval; 1090 tp->ts_recent_age = ticks; 1091 } 1092 /* Initial send window, already scaled. */ 1093 tp->snd_wnd = th->th_win; 1094 if (to.to_flags & TOF_MSS) 1095 tcp_mss(tp, to.to_mss); 1096 if (tp->sack_enable) { 1097 if (!(to.to_flags & TOF_SACKPERM)) 1098 tp->sack_enable = 0; 1099 else 1100 tp->t_flags |= TF_SACK_PERMIT; 1101 } 1102 1103 } 1104 1105 /* 1106 * Header prediction: check for the two common cases 1107 * of a uni-directional data xfer. If the packet has 1108 * no control flags, is in-sequence, the window didn't 1109 * change and we're not retransmitting, it's a 1110 * candidate. If the length is zero and the ack moved 1111 * forward, we're the sender side of the xfer. Just 1112 * free the data acked & wake any higher level process 1113 * that was blocked waiting for space. If the length 1114 * is non-zero and the ack didn't move, we're the 1115 * receiver side. If we're getting packets in-order 1116 * (the reassembly queue is empty), add the data to 1117 * the socket buffer and note that we need a delayed ack. 1118 * Make sure that the hidden state-flags are also off. 1119 * Since we check for TCPS_ESTABLISHED above, it can only 1120 * be TH_NEEDSYN. 1121 */ 1122 if (tp->t_state == TCPS_ESTABLISHED && 1123 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1124 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1125 ((to.to_flags & TOF_TS) == 0 || 1126 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1127 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1128 tp->snd_nxt == tp->snd_max) { 1129 1130 /* 1131 * If last ACK falls within this segment's sequence numbers, 1132 * record the timestamp. 1133 * NOTE that the test is modified according to the latest 1134 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1135 */ 1136 if ((to.to_flags & TOF_TS) != 0 && 1137 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1138 tp->ts_recent_age = ticks; 1139 tp->ts_recent = to.to_tsval; 1140 } 1141 1142 if (tlen == 0) { 1143 if (SEQ_GT(th->th_ack, tp->snd_una) && 1144 SEQ_LEQ(th->th_ack, tp->snd_max) && 1145 tp->snd_cwnd >= tp->snd_wnd && 1146 ((!tcp_do_newreno && !tp->sack_enable && 1147 tp->t_dupacks < tcprexmtthresh) || 1148 ((tcp_do_newreno || tp->sack_enable) && 1149 !IN_FASTRECOVERY(tp) && 1150 (to.to_flags & TOF_SACK) == 0 && 1151 TAILQ_EMPTY(&tp->snd_holes)))) { 1152 KASSERT(headlocked, 1153 ("%s: headlocked", __func__)); 1154 INP_INFO_WUNLOCK(&tcbinfo); 1155 headlocked = 0; 1156 /* 1157 * this is a pure ack for outstanding data. 1158 */ 1159 ++tcpstat.tcps_predack; 1160 /* 1161 * "bad retransmit" recovery 1162 */ 1163 if (tp->t_rxtshift == 1 && 1164 ticks < tp->t_badrxtwin) { 1165 ++tcpstat.tcps_sndrexmitbad; 1166 tp->snd_cwnd = tp->snd_cwnd_prev; 1167 tp->snd_ssthresh = 1168 tp->snd_ssthresh_prev; 1169 tp->snd_recover = tp->snd_recover_prev; 1170 if (tp->t_flags & TF_WASFRECOVERY) 1171 ENTER_FASTRECOVERY(tp); 1172 tp->snd_nxt = tp->snd_max; 1173 tp->t_badrxtwin = 0; 1174 } 1175 1176 /* 1177 * Recalculate the transmit timer / rtt. 1178 * 1179 * Some boxes send broken timestamp replies 1180 * during the SYN+ACK phase, ignore 1181 * timestamps of 0 or we could calculate a 1182 * huge RTT and blow up the retransmit timer. 1183 */ 1184 if ((to.to_flags & TOF_TS) != 0 && 1185 to.to_tsecr) { 1186 if (!tp->t_rttlow || 1187 tp->t_rttlow > ticks - to.to_tsecr) 1188 tp->t_rttlow = ticks - to.to_tsecr; 1189 tcp_xmit_timer(tp, 1190 ticks - to.to_tsecr + 1); 1191 } else if (tp->t_rtttime && 1192 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1193 if (!tp->t_rttlow || 1194 tp->t_rttlow > ticks - tp->t_rtttime) 1195 tp->t_rttlow = ticks - tp->t_rtttime; 1196 tcp_xmit_timer(tp, 1197 ticks - tp->t_rtttime); 1198 } 1199 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1200 acked = th->th_ack - tp->snd_una; 1201 tcpstat.tcps_rcvackpack++; 1202 tcpstat.tcps_rcvackbyte += acked; 1203 sbdrop(&so->so_snd, acked); 1204 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1205 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1206 tp->snd_recover = th->th_ack - 1; 1207 tp->snd_una = th->th_ack; 1208 /* 1209 * pull snd_wl2 up to prevent seq wrap relative 1210 * to th_ack. 1211 */ 1212 tp->snd_wl2 = th->th_ack; 1213 tp->t_dupacks = 0; 1214 m_freem(m); 1215 ND6_HINT(tp); /* some progress has been done */ 1216 1217 /* 1218 * If all outstanding data are acked, stop 1219 * retransmit timer, otherwise restart timer 1220 * using current (possibly backed-off) value. 1221 * If process is waiting for space, 1222 * wakeup/selwakeup/signal. If data 1223 * are ready to send, let tcp_output 1224 * decide between more output or persist. 1225 1226 #ifdef TCPDEBUG 1227 if (so->so_options & SO_DEBUG) 1228 tcp_trace(TA_INPUT, ostate, tp, 1229 (void *)tcp_saveipgen, 1230 &tcp_savetcp, 0); 1231 #endif 1232 */ 1233 if (tp->snd_una == tp->snd_max) 1234 callout_stop(tp->tt_rexmt); 1235 else if (!callout_active(tp->tt_persist)) 1236 callout_reset(tp->tt_rexmt, 1237 tp->t_rxtcur, 1238 tcp_timer_rexmt, tp); 1239 1240 sowwakeup(so); 1241 if (so->so_snd.sb_cc) 1242 (void) tcp_output(tp); 1243 goto check_delack; 1244 } 1245 } else if (th->th_ack == tp->snd_una && 1246 LIST_EMPTY(&tp->t_segq) && 1247 tlen <= sbspace(&so->so_rcv)) { 1248 int newsize = 0; /* automatic sockbuf scaling */ 1249 1250 KASSERT(headlocked, ("%s: headlocked", __func__)); 1251 INP_INFO_WUNLOCK(&tcbinfo); 1252 headlocked = 0; 1253 /* 1254 * this is a pure, in-sequence data packet 1255 * with nothing on the reassembly queue and 1256 * we have enough buffer space to take it. 1257 */ 1258 /* Clean receiver SACK report if present */ 1259 if (tp->sack_enable && tp->rcv_numsacks) 1260 tcp_clean_sackreport(tp); 1261 ++tcpstat.tcps_preddat; 1262 tp->rcv_nxt += tlen; 1263 /* 1264 * Pull snd_wl1 up to prevent seq wrap relative to 1265 * th_seq. 1266 */ 1267 tp->snd_wl1 = th->th_seq; 1268 /* 1269 * Pull rcv_up up to prevent seq wrap relative to 1270 * rcv_nxt. 1271 */ 1272 tp->rcv_up = tp->rcv_nxt; 1273 tcpstat.tcps_rcvpack++; 1274 tcpstat.tcps_rcvbyte += tlen; 1275 ND6_HINT(tp); /* some progress has been done */ 1276 #ifdef TCPDEBUG 1277 if (so->so_options & SO_DEBUG) 1278 tcp_trace(TA_INPUT, ostate, tp, 1279 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1280 #endif 1281 /* 1282 * Automatic sizing of receive socket buffer. Often the send 1283 * buffer size is not optimally adjusted to the actual network 1284 * conditions at hand (delay bandwidth product). Setting the 1285 * buffer size too small limits throughput on links with high 1286 * bandwidth and high delay (eg. trans-continental/oceanic links). 1287 * 1288 * On the receive side the socket buffer memory is only rarely 1289 * used to any significant extent. This allows us to be much 1290 * more aggressive in scaling the receive socket buffer. For 1291 * the case that the buffer space is actually used to a large 1292 * extent and we run out of kernel memory we can simply drop 1293 * the new segments; TCP on the sender will just retransmit it 1294 * later. Setting the buffer size too big may only consume too 1295 * much kernel memory if the application doesn't read() from 1296 * the socket or packet loss or reordering makes use of the 1297 * reassembly queue. 1298 * 1299 * The criteria to step up the receive buffer one notch are: 1300 * 1. the number of bytes received during the time it takes 1301 * one timestamp to be reflected back to us (the RTT); 1302 * 2. received bytes per RTT is within seven eighth of the 1303 * current socket buffer size; 1304 * 3. receive buffer size has not hit maximal automatic size; 1305 * 1306 * This algorithm does one step per RTT at most and only if 1307 * we receive a bulk stream w/o packet losses or reorderings. 1308 * Shrinking the buffer during idle times is not necessary as 1309 * it doesn't consume any memory when idle. 1310 * 1311 * TODO: Only step up if the application is actually serving 1312 * the buffer to better manage the socket buffer resources. 1313 */ 1314 if (tcp_do_autorcvbuf && 1315 to.to_tsecr && 1316 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1317 if (to.to_tsecr > tp->rfbuf_ts && 1318 to.to_tsecr - tp->rfbuf_ts < hz) { 1319 if (tp->rfbuf_cnt > 1320 (so->so_rcv.sb_hiwat / 8 * 7) && 1321 so->so_rcv.sb_hiwat < 1322 tcp_autorcvbuf_max) { 1323 newsize = 1324 min(so->so_rcv.sb_hiwat + 1325 tcp_autorcvbuf_inc, 1326 tcp_autorcvbuf_max); 1327 } 1328 /* Start over with next RTT. */ 1329 tp->rfbuf_ts = 0; 1330 tp->rfbuf_cnt = 0; 1331 } else 1332 tp->rfbuf_cnt += tlen; /* add up */ 1333 } 1334 1335 /* Add data to socket buffer. */ 1336 SOCKBUF_LOCK(&so->so_rcv); 1337 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1338 m_freem(m); 1339 } else { 1340 /* 1341 * Set new socket buffer size. 1342 * Give up when limit is reached. 1343 */ 1344 if (newsize) 1345 if (!sbreserve_locked(&so->so_rcv, 1346 newsize, so, curthread)) 1347 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1348 m_adj(m, drop_hdrlen); /* delayed header drop */ 1349 sbappendstream_locked(&so->so_rcv, m); 1350 } 1351 sorwakeup_locked(so); 1352 if (DELAY_ACK(tp)) { 1353 tp->t_flags |= TF_DELACK; 1354 } else { 1355 tp->t_flags |= TF_ACKNOW; 1356 tcp_output(tp); 1357 } 1358 goto check_delack; 1359 } 1360 } 1361 1362 /* 1363 * Calculate amount of space in receive window, 1364 * and then do TCP input processing. 1365 * Receive window is amount of space in rcv queue, 1366 * but not less than advertised window. 1367 */ 1368 win = sbspace(&so->so_rcv); 1369 if (win < 0) 1370 win = 0; 1371 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1372 1373 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1374 tp->rfbuf_ts = 0; 1375 tp->rfbuf_cnt = 0; 1376 1377 switch (tp->t_state) { 1378 1379 /* 1380 * If the state is SYN_RECEIVED: 1381 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1382 */ 1383 case TCPS_SYN_RECEIVED: 1384 if ((thflags & TH_ACK) && 1385 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1386 SEQ_GT(th->th_ack, tp->snd_max))) { 1387 rstreason = BANDLIM_RST_OPENPORT; 1388 goto dropwithreset; 1389 } 1390 break; 1391 1392 /* 1393 * If the state is SYN_SENT: 1394 * if seg contains an ACK, but not for our SYN, drop the input. 1395 * if seg contains a RST, then drop the connection. 1396 * if seg does not contain SYN, then drop it. 1397 * Otherwise this is an acceptable SYN segment 1398 * initialize tp->rcv_nxt and tp->irs 1399 * if seg contains ack then advance tp->snd_una 1400 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1401 * arrange for segment to be acked (eventually) 1402 * continue processing rest of data/controls, beginning with URG 1403 */ 1404 case TCPS_SYN_SENT: 1405 if ((thflags & TH_ACK) && 1406 (SEQ_LEQ(th->th_ack, tp->iss) || 1407 SEQ_GT(th->th_ack, tp->snd_max))) { 1408 rstreason = BANDLIM_UNLIMITED; 1409 goto dropwithreset; 1410 } 1411 if (thflags & TH_RST) { 1412 if (thflags & TH_ACK) { 1413 KASSERT(headlocked, ("%s: after_listen: " 1414 "tcp_drop.2: head not locked", __func__)); 1415 tp = tcp_drop(tp, ECONNREFUSED); 1416 } 1417 goto drop; 1418 } 1419 if ((thflags & TH_SYN) == 0) 1420 goto drop; 1421 1422 tp->irs = th->th_seq; 1423 tcp_rcvseqinit(tp); 1424 if (thflags & TH_ACK) { 1425 tcpstat.tcps_connects++; 1426 soisconnected(so); 1427 #ifdef MAC 1428 SOCK_LOCK(so); 1429 mac_set_socket_peer_from_mbuf(m, so); 1430 SOCK_UNLOCK(so); 1431 #endif 1432 /* Do window scaling on this connection? */ 1433 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1434 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1435 tp->rcv_scale = tp->request_r_scale; 1436 } 1437 tp->rcv_adv += tp->rcv_wnd; 1438 tp->snd_una++; /* SYN is acked */ 1439 /* 1440 * If there's data, delay ACK; if there's also a FIN 1441 * ACKNOW will be turned on later. 1442 */ 1443 if (DELAY_ACK(tp) && tlen != 0) 1444 callout_reset(tp->tt_delack, tcp_delacktime, 1445 tcp_timer_delack, tp); 1446 else 1447 tp->t_flags |= TF_ACKNOW; 1448 /* 1449 * Received <SYN,ACK> in SYN_SENT[*] state. 1450 * Transitions: 1451 * SYN_SENT --> ESTABLISHED 1452 * SYN_SENT* --> FIN_WAIT_1 1453 */ 1454 tp->t_starttime = ticks; 1455 if (tp->t_flags & TF_NEEDFIN) { 1456 tp->t_state = TCPS_FIN_WAIT_1; 1457 tp->t_flags &= ~TF_NEEDFIN; 1458 thflags &= ~TH_SYN; 1459 } else { 1460 tp->t_state = TCPS_ESTABLISHED; 1461 callout_reset(tp->tt_keep, tcp_keepidle, 1462 tcp_timer_keep, tp); 1463 } 1464 } else { 1465 /* 1466 * Received initial SYN in SYN-SENT[*] state => 1467 * simultaneous open. If segment contains CC option 1468 * and there is a cached CC, apply TAO test. 1469 * If it succeeds, connection is * half-synchronized. 1470 * Otherwise, do 3-way handshake: 1471 * SYN-SENT -> SYN-RECEIVED 1472 * SYN-SENT* -> SYN-RECEIVED* 1473 * If there was no CC option, clear cached CC value. 1474 */ 1475 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1476 callout_stop(tp->tt_rexmt); 1477 tp->t_state = TCPS_SYN_RECEIVED; 1478 } 1479 1480 KASSERT(headlocked, ("%s: trimthenstep6: head not locked", 1481 __func__)); 1482 INP_LOCK_ASSERT(tp->t_inpcb); 1483 1484 /* 1485 * Advance th->th_seq to correspond to first data byte. 1486 * If data, trim to stay within window, 1487 * dropping FIN if necessary. 1488 */ 1489 th->th_seq++; 1490 if (tlen > tp->rcv_wnd) { 1491 todrop = tlen - tp->rcv_wnd; 1492 m_adj(m, -todrop); 1493 tlen = tp->rcv_wnd; 1494 thflags &= ~TH_FIN; 1495 tcpstat.tcps_rcvpackafterwin++; 1496 tcpstat.tcps_rcvbyteafterwin += todrop; 1497 } 1498 tp->snd_wl1 = th->th_seq - 1; 1499 tp->rcv_up = th->th_seq; 1500 /* 1501 * Client side of transaction: already sent SYN and data. 1502 * If the remote host used T/TCP to validate the SYN, 1503 * our data will be ACK'd; if so, enter normal data segment 1504 * processing in the middle of step 5, ack processing. 1505 * Otherwise, goto step 6. 1506 */ 1507 if (thflags & TH_ACK) 1508 goto process_ACK; 1509 1510 goto step6; 1511 1512 /* 1513 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1514 * do normal processing. 1515 * 1516 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1517 */ 1518 case TCPS_LAST_ACK: 1519 case TCPS_CLOSING: 1520 case TCPS_TIME_WAIT: 1521 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: timewait", 1522 __func__)); 1523 break; /* continue normal processing */ 1524 } 1525 1526 /* 1527 * States other than LISTEN or SYN_SENT. 1528 * First check the RST flag and sequence number since reset segments 1529 * are exempt from the timestamp and connection count tests. This 1530 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1531 * below which allowed reset segments in half the sequence space 1532 * to fall though and be processed (which gives forged reset 1533 * segments with a random sequence number a 50 percent chance of 1534 * killing a connection). 1535 * Then check timestamp, if present. 1536 * Then check the connection count, if present. 1537 * Then check that at least some bytes of segment are within 1538 * receive window. If segment begins before rcv_nxt, 1539 * drop leading data (and SYN); if nothing left, just ack. 1540 * 1541 * 1542 * If the RST bit is set, check the sequence number to see 1543 * if this is a valid reset segment. 1544 * RFC 793 page 37: 1545 * In all states except SYN-SENT, all reset (RST) segments 1546 * are validated by checking their SEQ-fields. A reset is 1547 * valid if its sequence number is in the window. 1548 * Note: this does not take into account delayed ACKs, so 1549 * we should test against last_ack_sent instead of rcv_nxt. 1550 * The sequence number in the reset segment is normally an 1551 * echo of our outgoing acknowlegement numbers, but some hosts 1552 * send a reset with the sequence number at the rightmost edge 1553 * of our receive window, and we have to handle this case. 1554 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1555 * that brute force RST attacks are possible. To combat this, 1556 * we use a much stricter check while in the ESTABLISHED state, 1557 * only accepting RSTs where the sequence number is equal to 1558 * last_ack_sent. In all other states (the states in which a 1559 * RST is more likely), the more permissive check is used. 1560 * If we have multiple segments in flight, the intial reset 1561 * segment sequence numbers will be to the left of last_ack_sent, 1562 * but they will eventually catch up. 1563 * In any case, it never made sense to trim reset segments to 1564 * fit the receive window since RFC 1122 says: 1565 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1566 * 1567 * A TCP SHOULD allow a received RST segment to include data. 1568 * 1569 * DISCUSSION 1570 * It has been suggested that a RST segment could contain 1571 * ASCII text that encoded and explained the cause of the 1572 * RST. No standard has yet been established for such 1573 * data. 1574 * 1575 * If the reset segment passes the sequence number test examine 1576 * the state: 1577 * SYN_RECEIVED STATE: 1578 * If passive open, return to LISTEN state. 1579 * If active open, inform user that connection was refused. 1580 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1581 * Inform user that connection was reset, and close tcb. 1582 * CLOSING, LAST_ACK STATES: 1583 * Close the tcb. 1584 * TIME_WAIT STATE: 1585 * Drop the segment - see Stevens, vol. 2, p. 964 and 1586 * RFC 1337. 1587 */ 1588 if (thflags & TH_RST) { 1589 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1590 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1591 switch (tp->t_state) { 1592 1593 case TCPS_SYN_RECEIVED: 1594 so->so_error = ECONNREFUSED; 1595 goto close; 1596 1597 case TCPS_ESTABLISHED: 1598 if (tcp_insecure_rst == 0 && 1599 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && 1600 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && 1601 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1602 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { 1603 tcpstat.tcps_badrst++; 1604 goto drop; 1605 } 1606 case TCPS_FIN_WAIT_1: 1607 case TCPS_FIN_WAIT_2: 1608 case TCPS_CLOSE_WAIT: 1609 so->so_error = ECONNRESET; 1610 close: 1611 tp->t_state = TCPS_CLOSED; 1612 tcpstat.tcps_drops++; 1613 KASSERT(headlocked, ("%s: trimthenstep6: " 1614 "tcp_close: head not locked", __func__)); 1615 tp = tcp_close(tp); 1616 break; 1617 1618 case TCPS_CLOSING: 1619 case TCPS_LAST_ACK: 1620 KASSERT(headlocked, ("%s: trimthenstep6: " 1621 "tcp_close.2: head not locked", __func__)); 1622 tp = tcp_close(tp); 1623 break; 1624 1625 case TCPS_TIME_WAIT: 1626 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1627 ("%s: timewait", __func__)); 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 * In the SYN-RECEIVED state, validate that the packet belongs to 1667 * this connection before trimming the data to fit the receive 1668 * window. Check the sequence number versus IRS since we know 1669 * the sequence numbers haven't wrapped. This is a partial fix 1670 * for the "LAND" DoS attack. 1671 */ 1672 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1673 rstreason = BANDLIM_RST_OPENPORT; 1674 goto dropwithreset; 1675 } 1676 1677 todrop = tp->rcv_nxt - th->th_seq; 1678 if (todrop > 0) { 1679 if (thflags & TH_SYN) { 1680 thflags &= ~TH_SYN; 1681 th->th_seq++; 1682 if (th->th_urp > 1) 1683 th->th_urp--; 1684 else 1685 thflags &= ~TH_URG; 1686 todrop--; 1687 } 1688 /* 1689 * Following if statement from Stevens, vol. 2, p. 960. 1690 */ 1691 if (todrop > tlen 1692 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1693 /* 1694 * Any valid FIN must be to the left of the window. 1695 * At this point the FIN must be a duplicate or out 1696 * of sequence; drop it. 1697 */ 1698 thflags &= ~TH_FIN; 1699 1700 /* 1701 * Send an ACK to resynchronize and drop any data. 1702 * But keep on processing for RST or ACK. 1703 */ 1704 tp->t_flags |= TF_ACKNOW; 1705 todrop = tlen; 1706 tcpstat.tcps_rcvduppack++; 1707 tcpstat.tcps_rcvdupbyte += todrop; 1708 } else { 1709 tcpstat.tcps_rcvpartduppack++; 1710 tcpstat.tcps_rcvpartdupbyte += todrop; 1711 } 1712 drop_hdrlen += todrop; /* drop from the top afterwards */ 1713 th->th_seq += todrop; 1714 tlen -= todrop; 1715 if (th->th_urp > todrop) 1716 th->th_urp -= todrop; 1717 else { 1718 thflags &= ~TH_URG; 1719 th->th_urp = 0; 1720 } 1721 } 1722 1723 /* 1724 * If new data are received on a connection after the 1725 * user processes are gone, then RST the other end. 1726 */ 1727 if ((so->so_state & SS_NOFDREF) && 1728 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1729 KASSERT(headlocked, ("%s: trimthenstep6: tcp_close.3: head " 1730 "not locked", __func__)); 1731 tp = tcp_close(tp); 1732 tcpstat.tcps_rcvafterclose++; 1733 rstreason = BANDLIM_UNLIMITED; 1734 goto dropwithreset; 1735 } 1736 1737 /* 1738 * If segment ends after window, drop trailing data 1739 * (and PUSH and FIN); if nothing left, just ACK. 1740 */ 1741 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1742 if (todrop > 0) { 1743 tcpstat.tcps_rcvpackafterwin++; 1744 if (todrop >= tlen) { 1745 tcpstat.tcps_rcvbyteafterwin += tlen; 1746 /* 1747 * If a new connection request is received 1748 * while in TIME_WAIT, drop the old connection 1749 * and start over if the sequence numbers 1750 * are above the previous ones. 1751 */ 1752 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: timewait", 1753 __func__)); 1754 if (thflags & TH_SYN && 1755 tp->t_state == TCPS_TIME_WAIT && 1756 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1757 KASSERT(headlocked, ("%s: trimthenstep6: " 1758 "tcp_close.4: head not locked", __func__)); 1759 tp = tcp_close(tp); 1760 /* XXX: Shouldn't be possible. */ 1761 return (1); 1762 } 1763 /* 1764 * If window is closed can only take segments at 1765 * window edge, and have to drop data and PUSH from 1766 * incoming segments. Continue processing, but 1767 * remember to ack. Otherwise, drop segment 1768 * and ack. 1769 */ 1770 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1771 tp->t_flags |= TF_ACKNOW; 1772 tcpstat.tcps_rcvwinprobe++; 1773 } else 1774 goto dropafterack; 1775 } else 1776 tcpstat.tcps_rcvbyteafterwin += todrop; 1777 m_adj(m, -todrop); 1778 tlen -= todrop; 1779 thflags &= ~(TH_PUSH|TH_FIN); 1780 } 1781 1782 /* 1783 * If last ACK falls within this segment's sequence numbers, 1784 * record its timestamp. 1785 * NOTE: 1786 * 1) That the test incorporates suggestions from the latest 1787 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1788 * 2) That updating only on newer timestamps interferes with 1789 * our earlier PAWS tests, so this check should be solely 1790 * predicated on the sequence space of this segment. 1791 * 3) That we modify the segment boundary check to be 1792 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1793 * instead of RFC1323's 1794 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1795 * This modified check allows us to overcome RFC1323's 1796 * limitations as described in Stevens TCP/IP Illustrated 1797 * Vol. 2 p.869. In such cases, we can still calculate the 1798 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1799 */ 1800 if ((to.to_flags & TOF_TS) != 0 && 1801 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1802 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1803 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1804 tp->ts_recent_age = ticks; 1805 tp->ts_recent = to.to_tsval; 1806 } 1807 1808 /* 1809 * If a SYN is in the window, then this is an 1810 * error and we send an RST and drop the connection. 1811 */ 1812 if (thflags & TH_SYN) { 1813 KASSERT(headlocked, ("%s: tcp_drop: trimthenstep6: " 1814 "head not locked", __func__)); 1815 tp = tcp_drop(tp, ECONNRESET); 1816 rstreason = BANDLIM_UNLIMITED; 1817 goto drop; 1818 } 1819 1820 /* 1821 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1822 * flag is on (half-synchronized state), then queue data for 1823 * later processing; else drop segment and return. 1824 */ 1825 if ((thflags & TH_ACK) == 0) { 1826 if (tp->t_state == TCPS_SYN_RECEIVED || 1827 (tp->t_flags & TF_NEEDSYN)) 1828 goto step6; 1829 else if (tp->t_flags & TF_ACKNOW) 1830 goto dropafterack; 1831 else 1832 goto drop; 1833 } 1834 1835 /* 1836 * Ack processing. 1837 */ 1838 switch (tp->t_state) { 1839 1840 /* 1841 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1842 * ESTABLISHED state and continue processing. 1843 * The ACK was checked above. 1844 */ 1845 case TCPS_SYN_RECEIVED: 1846 1847 tcpstat.tcps_connects++; 1848 soisconnected(so); 1849 /* Do window scaling? */ 1850 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1851 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1852 tp->rcv_scale = tp->request_r_scale; 1853 tp->snd_wnd = tiwin; 1854 } 1855 /* 1856 * Make transitions: 1857 * SYN-RECEIVED -> ESTABLISHED 1858 * SYN-RECEIVED* -> FIN-WAIT-1 1859 */ 1860 tp->t_starttime = ticks; 1861 if (tp->t_flags & TF_NEEDFIN) { 1862 tp->t_state = TCPS_FIN_WAIT_1; 1863 tp->t_flags &= ~TF_NEEDFIN; 1864 } else { 1865 tp->t_state = TCPS_ESTABLISHED; 1866 callout_reset(tp->tt_keep, tcp_keepidle, 1867 tcp_timer_keep, tp); 1868 } 1869 /* 1870 * If segment contains data or ACK, will call tcp_reass() 1871 * later; if not, do so now to pass queued data to user. 1872 */ 1873 if (tlen == 0 && (thflags & TH_FIN) == 0) 1874 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1875 (struct mbuf *)0); 1876 tp->snd_wl1 = th->th_seq - 1; 1877 /* FALLTHROUGH */ 1878 1879 /* 1880 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1881 * ACKs. If the ack is in the range 1882 * tp->snd_una < th->th_ack <= tp->snd_max 1883 * then advance tp->snd_una to th->th_ack and drop 1884 * data from the retransmission queue. If this ACK reflects 1885 * more up to date window information we update our window information. 1886 */ 1887 case TCPS_ESTABLISHED: 1888 case TCPS_FIN_WAIT_1: 1889 case TCPS_FIN_WAIT_2: 1890 case TCPS_CLOSE_WAIT: 1891 case TCPS_CLOSING: 1892 case TCPS_LAST_ACK: 1893 case TCPS_TIME_WAIT: 1894 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: timewait", 1895 __func__)); 1896 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1897 tcpstat.tcps_rcvacktoomuch++; 1898 goto dropafterack; 1899 } 1900 if (tp->sack_enable && 1901 ((to.to_flags & TOF_SACK) || 1902 !TAILQ_EMPTY(&tp->snd_holes))) 1903 tcp_sack_doack(tp, &to, th->th_ack); 1904 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1905 if (tlen == 0 && tiwin == tp->snd_wnd) { 1906 tcpstat.tcps_rcvdupack++; 1907 /* 1908 * If we have outstanding data (other than 1909 * a window probe), this is a completely 1910 * duplicate ack (ie, window info didn't 1911 * change), the ack is the biggest we've 1912 * seen and we've seen exactly our rexmt 1913 * threshhold of them, assume a packet 1914 * has been dropped and retransmit it. 1915 * Kludge snd_nxt & the congestion 1916 * window so we send only this one 1917 * packet. 1918 * 1919 * We know we're losing at the current 1920 * window size so do congestion avoidance 1921 * (set ssthresh to half the current window 1922 * and pull our congestion window back to 1923 * the new ssthresh). 1924 * 1925 * Dup acks mean that packets have left the 1926 * network (they're now cached at the receiver) 1927 * so bump cwnd by the amount in the receiver 1928 * to keep a constant cwnd packets in the 1929 * network. 1930 */ 1931 if (!callout_active(tp->tt_rexmt) || 1932 th->th_ack != tp->snd_una) 1933 tp->t_dupacks = 0; 1934 else if (++tp->t_dupacks > tcprexmtthresh || 1935 ((tcp_do_newreno || tp->sack_enable) && 1936 IN_FASTRECOVERY(tp))) { 1937 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1938 int awnd; 1939 1940 /* 1941 * Compute the amount of data in flight first. 1942 * We can inject new data into the pipe iff 1943 * we have less than 1/2 the original window's 1944 * worth of data in flight. 1945 */ 1946 awnd = (tp->snd_nxt - tp->snd_fack) + 1947 tp->sackhint.sack_bytes_rexmit; 1948 if (awnd < tp->snd_ssthresh) { 1949 tp->snd_cwnd += tp->t_maxseg; 1950 if (tp->snd_cwnd > tp->snd_ssthresh) 1951 tp->snd_cwnd = tp->snd_ssthresh; 1952 } 1953 } else 1954 tp->snd_cwnd += tp->t_maxseg; 1955 (void) tcp_output(tp); 1956 goto drop; 1957 } else if (tp->t_dupacks == tcprexmtthresh) { 1958 tcp_seq onxt = tp->snd_nxt; 1959 u_int win; 1960 1961 /* 1962 * If we're doing sack, check to 1963 * see if we're already in sack 1964 * recovery. If we're not doing sack, 1965 * check to see if we're in newreno 1966 * recovery. 1967 */ 1968 if (tp->sack_enable) { 1969 if (IN_FASTRECOVERY(tp)) { 1970 tp->t_dupacks = 0; 1971 break; 1972 } 1973 } else if (tcp_do_newreno) { 1974 if (SEQ_LEQ(th->th_ack, 1975 tp->snd_recover)) { 1976 tp->t_dupacks = 0; 1977 break; 1978 } 1979 } 1980 win = min(tp->snd_wnd, tp->snd_cwnd) / 1981 2 / tp->t_maxseg; 1982 if (win < 2) 1983 win = 2; 1984 tp->snd_ssthresh = win * tp->t_maxseg; 1985 ENTER_FASTRECOVERY(tp); 1986 tp->snd_recover = tp->snd_max; 1987 callout_stop(tp->tt_rexmt); 1988 tp->t_rtttime = 0; 1989 if (tp->sack_enable) { 1990 tcpstat.tcps_sack_recovery_episode++; 1991 tp->sack_newdata = tp->snd_nxt; 1992 tp->snd_cwnd = tp->t_maxseg; 1993 (void) tcp_output(tp); 1994 goto drop; 1995 } 1996 tp->snd_nxt = th->th_ack; 1997 tp->snd_cwnd = tp->t_maxseg; 1998 (void) tcp_output(tp); 1999 KASSERT(tp->snd_limited <= 2, 2000 ("%s: tp->snd_limited too big", 2001 __func__)); 2002 tp->snd_cwnd = tp->snd_ssthresh + 2003 tp->t_maxseg * 2004 (tp->t_dupacks - tp->snd_limited); 2005 if (SEQ_GT(onxt, tp->snd_nxt)) 2006 tp->snd_nxt = onxt; 2007 goto drop; 2008 } else if (tcp_do_rfc3042) { 2009 u_long oldcwnd = tp->snd_cwnd; 2010 tcp_seq oldsndmax = tp->snd_max; 2011 u_int sent; 2012 2013 KASSERT(tp->t_dupacks == 1 || 2014 tp->t_dupacks == 2, 2015 ("%s: dupacks not 1 or 2", 2016 __func__)); 2017 if (tp->t_dupacks == 1) 2018 tp->snd_limited = 0; 2019 tp->snd_cwnd = 2020 (tp->snd_nxt - tp->snd_una) + 2021 (tp->t_dupacks - tp->snd_limited) * 2022 tp->t_maxseg; 2023 (void) tcp_output(tp); 2024 sent = tp->snd_max - oldsndmax; 2025 if (sent > tp->t_maxseg) { 2026 KASSERT((tp->t_dupacks == 2 && 2027 tp->snd_limited == 0) || 2028 (sent == tp->t_maxseg + 1 && 2029 tp->t_flags & TF_SENTFIN), 2030 ("%s: sent too much", 2031 __func__)); 2032 tp->snd_limited = 2; 2033 } else if (sent > 0) 2034 ++tp->snd_limited; 2035 tp->snd_cwnd = oldcwnd; 2036 goto drop; 2037 } 2038 } else 2039 tp->t_dupacks = 0; 2040 break; 2041 } 2042 2043 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2044 ("%s: th_ack <= snd_una", __func__)); 2045 2046 /* 2047 * If the congestion window was inflated to account 2048 * for the other side's cached packets, retract it. 2049 */ 2050 if (tcp_do_newreno || tp->sack_enable) { 2051 if (IN_FASTRECOVERY(tp)) { 2052 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2053 if (tp->sack_enable) 2054 tcp_sack_partialack(tp, th); 2055 else 2056 tcp_newreno_partial_ack(tp, th); 2057 } else { 2058 /* 2059 * Out of fast recovery. 2060 * Window inflation should have left us 2061 * with approximately snd_ssthresh 2062 * outstanding data. 2063 * But in case we would be inclined to 2064 * send a burst, better to do it via 2065 * the slow start mechanism. 2066 */ 2067 if (SEQ_GT(th->th_ack + 2068 tp->snd_ssthresh, 2069 tp->snd_max)) 2070 tp->snd_cwnd = tp->snd_max - 2071 th->th_ack + 2072 tp->t_maxseg; 2073 else 2074 tp->snd_cwnd = tp->snd_ssthresh; 2075 } 2076 } 2077 } else { 2078 if (tp->t_dupacks >= tcprexmtthresh && 2079 tp->snd_cwnd > tp->snd_ssthresh) 2080 tp->snd_cwnd = tp->snd_ssthresh; 2081 } 2082 tp->t_dupacks = 0; 2083 /* 2084 * If we reach this point, ACK is not a duplicate, 2085 * i.e., it ACKs something we sent. 2086 */ 2087 if (tp->t_flags & TF_NEEDSYN) { 2088 /* 2089 * T/TCP: Connection was half-synchronized, and our 2090 * SYN has been ACK'd (so connection is now fully 2091 * synchronized). Go to non-starred state, 2092 * increment snd_una for ACK of SYN, and check if 2093 * we can do window scaling. 2094 */ 2095 tp->t_flags &= ~TF_NEEDSYN; 2096 tp->snd_una++; 2097 /* Do window scaling? */ 2098 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2099 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2100 tp->rcv_scale = tp->request_r_scale; 2101 /* Send window already scaled. */ 2102 } 2103 } 2104 2105 process_ACK: 2106 KASSERT(headlocked, ("%s: process_ACK: head not locked", 2107 __func__)); 2108 INP_LOCK_ASSERT(tp->t_inpcb); 2109 2110 acked = th->th_ack - tp->snd_una; 2111 tcpstat.tcps_rcvackpack++; 2112 tcpstat.tcps_rcvackbyte += acked; 2113 2114 /* 2115 * If we just performed our first retransmit, and the ACK 2116 * arrives within our recovery window, then it was a mistake 2117 * to do the retransmit in the first place. Recover our 2118 * original cwnd and ssthresh, and proceed to transmit where 2119 * we left off. 2120 */ 2121 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2122 ++tcpstat.tcps_sndrexmitbad; 2123 tp->snd_cwnd = tp->snd_cwnd_prev; 2124 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2125 tp->snd_recover = tp->snd_recover_prev; 2126 if (tp->t_flags & TF_WASFRECOVERY) 2127 ENTER_FASTRECOVERY(tp); 2128 tp->snd_nxt = tp->snd_max; 2129 tp->t_badrxtwin = 0; /* XXX probably not required */ 2130 } 2131 2132 /* 2133 * If we have a timestamp reply, update smoothed 2134 * round trip time. If no timestamp is present but 2135 * transmit timer is running and timed sequence 2136 * number was acked, update smoothed round trip time. 2137 * Since we now have an rtt measurement, cancel the 2138 * timer backoff (cf., Phil Karn's retransmit alg.). 2139 * Recompute the initial retransmit timer. 2140 * 2141 * Some boxes send broken timestamp replies 2142 * during the SYN+ACK phase, ignore 2143 * timestamps of 0 or we could calculate a 2144 * huge RTT and blow up the retransmit timer. 2145 */ 2146 if ((to.to_flags & TOF_TS) != 0 && 2147 to.to_tsecr) { 2148 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2149 tp->t_rttlow = ticks - to.to_tsecr; 2150 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2151 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2152 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2153 tp->t_rttlow = ticks - tp->t_rtttime; 2154 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2155 } 2156 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2157 2158 /* 2159 * If all outstanding data is acked, stop retransmit 2160 * timer and remember to restart (more output or persist). 2161 * If there is more data to be acked, restart retransmit 2162 * timer, using current (possibly backed-off) value. 2163 */ 2164 if (th->th_ack == tp->snd_max) { 2165 callout_stop(tp->tt_rexmt); 2166 needoutput = 1; 2167 } else if (!callout_active(tp->tt_persist)) 2168 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2169 tcp_timer_rexmt, tp); 2170 2171 /* 2172 * If no data (only SYN) was ACK'd, 2173 * skip rest of ACK processing. 2174 */ 2175 if (acked == 0) 2176 goto step6; 2177 2178 /* 2179 * When new data is acked, open the congestion window. 2180 * If the window gives us less than ssthresh packets 2181 * in flight, open exponentially (maxseg per packet). 2182 * Otherwise open linearly: maxseg per window 2183 * (maxseg^2 / cwnd per packet). 2184 */ 2185 if ((!tcp_do_newreno && !tp->sack_enable) || 2186 !IN_FASTRECOVERY(tp)) { 2187 u_int cw = tp->snd_cwnd; 2188 u_int incr = tp->t_maxseg; 2189 if (cw > tp->snd_ssthresh) 2190 incr = incr * incr / cw; 2191 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2192 } 2193 SOCKBUF_LOCK(&so->so_snd); 2194 if (acked > so->so_snd.sb_cc) { 2195 tp->snd_wnd -= so->so_snd.sb_cc; 2196 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2197 ourfinisacked = 1; 2198 } else { 2199 sbdrop_locked(&so->so_snd, acked); 2200 tp->snd_wnd -= acked; 2201 ourfinisacked = 0; 2202 } 2203 sowwakeup_locked(so); 2204 /* detect una wraparound */ 2205 if ((tcp_do_newreno || tp->sack_enable) && 2206 !IN_FASTRECOVERY(tp) && 2207 SEQ_GT(tp->snd_una, tp->snd_recover) && 2208 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2209 tp->snd_recover = th->th_ack - 1; 2210 if ((tcp_do_newreno || tp->sack_enable) && 2211 IN_FASTRECOVERY(tp) && 2212 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2213 EXIT_FASTRECOVERY(tp); 2214 tp->snd_una = th->th_ack; 2215 if (tp->sack_enable) { 2216 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2217 tp->snd_recover = tp->snd_una; 2218 } 2219 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2220 tp->snd_nxt = tp->snd_una; 2221 2222 switch (tp->t_state) { 2223 2224 /* 2225 * In FIN_WAIT_1 STATE in addition to the processing 2226 * for the ESTABLISHED state if our FIN is now acknowledged 2227 * then enter FIN_WAIT_2. 2228 */ 2229 case TCPS_FIN_WAIT_1: 2230 if (ourfinisacked) { 2231 /* 2232 * If we can't receive any more 2233 * data, then closing user can proceed. 2234 * Starting the timer is contrary to the 2235 * specification, but if we don't get a FIN 2236 * we'll hang forever. 2237 */ 2238 /* XXXjl 2239 * we should release the tp also, and use a 2240 * compressed state. 2241 */ 2242 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2243 int timeout; 2244 2245 soisdisconnected(so); 2246 timeout = (tcp_fast_finwait2_recycle) ? 2247 tcp_finwait2_timeout : tcp_maxidle; 2248 callout_reset(tp->tt_2msl, timeout, 2249 tcp_timer_2msl, tp); 2250 } 2251 tp->t_state = TCPS_FIN_WAIT_2; 2252 } 2253 break; 2254 2255 /* 2256 * In CLOSING STATE in addition to the processing for 2257 * the ESTABLISHED state if the ACK acknowledges our FIN 2258 * then enter the TIME-WAIT state, otherwise ignore 2259 * the segment. 2260 */ 2261 case TCPS_CLOSING: 2262 if (ourfinisacked) { 2263 KASSERT(headlocked, ("%s: process_ACK: " 2264 "head not locked", __func__)); 2265 tcp_twstart(tp); 2266 INP_INFO_WUNLOCK(&tcbinfo); 2267 headlocked = 0; 2268 m_freem(m); 2269 return (0); 2270 } 2271 break; 2272 2273 /* 2274 * In LAST_ACK, we may still be waiting for data to drain 2275 * and/or to be acked, as well as for the ack of our FIN. 2276 * If our FIN is now acknowledged, delete the TCB, 2277 * enter the closed state and return. 2278 */ 2279 case TCPS_LAST_ACK: 2280 if (ourfinisacked) { 2281 KASSERT(headlocked, ("%s: process_ACK: " 2282 "tcp_close: head not locked", __func__)); 2283 tp = tcp_close(tp); 2284 goto drop; 2285 } 2286 break; 2287 2288 /* 2289 * In TIME_WAIT state the only thing that should arrive 2290 * is a retransmission of the remote FIN. Acknowledge 2291 * it and restart the finack timer. 2292 */ 2293 case TCPS_TIME_WAIT: 2294 KASSERT(tp->t_state != TCPS_TIME_WAIT, 2295 ("%s: timewait", __func__)); 2296 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2297 tcp_timer_2msl, tp); 2298 goto dropafterack; 2299 } 2300 } 2301 2302 step6: 2303 KASSERT(headlocked, ("%s: step6: head not locked", __func__)); 2304 INP_LOCK_ASSERT(tp->t_inpcb); 2305 2306 /* 2307 * Update window information. 2308 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2309 */ 2310 if ((thflags & TH_ACK) && 2311 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2312 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2313 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2314 /* keep track of pure window updates */ 2315 if (tlen == 0 && 2316 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2317 tcpstat.tcps_rcvwinupd++; 2318 tp->snd_wnd = tiwin; 2319 tp->snd_wl1 = th->th_seq; 2320 tp->snd_wl2 = th->th_ack; 2321 if (tp->snd_wnd > tp->max_sndwnd) 2322 tp->max_sndwnd = tp->snd_wnd; 2323 needoutput = 1; 2324 } 2325 2326 /* 2327 * Process segments with URG. 2328 */ 2329 if ((thflags & TH_URG) && th->th_urp && 2330 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2331 /* 2332 * This is a kludge, but if we receive and accept 2333 * random urgent pointers, we'll crash in 2334 * soreceive. It's hard to imagine someone 2335 * actually wanting to send this much urgent data. 2336 */ 2337 SOCKBUF_LOCK(&so->so_rcv); 2338 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2339 th->th_urp = 0; /* XXX */ 2340 thflags &= ~TH_URG; /* XXX */ 2341 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2342 goto dodata; /* XXX */ 2343 } 2344 /* 2345 * If this segment advances the known urgent pointer, 2346 * then mark the data stream. This should not happen 2347 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2348 * a FIN has been received from the remote side. 2349 * In these states we ignore the URG. 2350 * 2351 * According to RFC961 (Assigned Protocols), 2352 * the urgent pointer points to the last octet 2353 * of urgent data. We continue, however, 2354 * to consider it to indicate the first octet 2355 * of data past the urgent section as the original 2356 * spec states (in one of two places). 2357 */ 2358 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2359 tp->rcv_up = th->th_seq + th->th_urp; 2360 so->so_oobmark = so->so_rcv.sb_cc + 2361 (tp->rcv_up - tp->rcv_nxt) - 1; 2362 if (so->so_oobmark == 0) 2363 so->so_rcv.sb_state |= SBS_RCVATMARK; 2364 sohasoutofband(so); 2365 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2366 } 2367 SOCKBUF_UNLOCK(&so->so_rcv); 2368 /* 2369 * Remove out of band data so doesn't get presented to user. 2370 * This can happen independent of advancing the URG pointer, 2371 * but if two URG's are pending at once, some out-of-band 2372 * data may creep in... ick. 2373 */ 2374 if (th->th_urp <= (u_long)tlen && 2375 !(so->so_options & SO_OOBINLINE)) { 2376 /* hdr drop is delayed */ 2377 tcp_pulloutofband(so, th, m, drop_hdrlen); 2378 } 2379 } else { 2380 /* 2381 * If no out of band data is expected, 2382 * pull receive urgent pointer along 2383 * with the receive window. 2384 */ 2385 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2386 tp->rcv_up = tp->rcv_nxt; 2387 } 2388 dodata: /* XXX */ 2389 KASSERT(headlocked, ("%s: dodata: head not locked", __func__)); 2390 INP_LOCK_ASSERT(tp->t_inpcb); 2391 2392 /* 2393 * Process the segment text, merging it into the TCP sequencing queue, 2394 * and arranging for acknowledgment of receipt if necessary. 2395 * This process logically involves adjusting tp->rcv_wnd as data 2396 * is presented to the user (this happens in tcp_usrreq.c, 2397 * case PRU_RCVD). If a FIN has already been received on this 2398 * connection then we just ignore the text. 2399 */ 2400 if ((tlen || (thflags & TH_FIN)) && 2401 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2402 tcp_seq save_start = th->th_seq; 2403 tcp_seq save_end = th->th_seq + tlen; 2404 m_adj(m, drop_hdrlen); /* delayed header drop */ 2405 /* 2406 * Insert segment which includes th into TCP reassembly queue 2407 * with control block tp. Set thflags to whether reassembly now 2408 * includes a segment with FIN. This handles the common case 2409 * inline (segment is the next to be received on an established 2410 * connection, and the queue is empty), avoiding linkage into 2411 * and removal from the queue and repetition of various 2412 * conversions. 2413 * Set DELACK for segments received in order, but ack 2414 * immediately when segments are out of order (so 2415 * fast retransmit can work). 2416 */ 2417 if (th->th_seq == tp->rcv_nxt && 2418 LIST_EMPTY(&tp->t_segq) && 2419 TCPS_HAVEESTABLISHED(tp->t_state)) { 2420 if (DELAY_ACK(tp)) 2421 tp->t_flags |= TF_DELACK; 2422 else 2423 tp->t_flags |= TF_ACKNOW; 2424 tp->rcv_nxt += tlen; 2425 thflags = th->th_flags & TH_FIN; 2426 tcpstat.tcps_rcvpack++; 2427 tcpstat.tcps_rcvbyte += tlen; 2428 ND6_HINT(tp); 2429 SOCKBUF_LOCK(&so->so_rcv); 2430 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2431 m_freem(m); 2432 else 2433 sbappendstream_locked(&so->so_rcv, m); 2434 sorwakeup_locked(so); 2435 } else { 2436 thflags = tcp_reass(tp, th, &tlen, m); 2437 tp->t_flags |= TF_ACKNOW; 2438 } 2439 if (tlen > 0 && tp->sack_enable) 2440 tcp_update_sack_list(tp, save_start, save_end); 2441 #if 0 2442 /* 2443 * Note the amount of data that peer has sent into 2444 * our window, in order to estimate the sender's 2445 * buffer size. 2446 * XXX: Unused. 2447 */ 2448 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2449 #endif 2450 } else { 2451 m_freem(m); 2452 thflags &= ~TH_FIN; 2453 } 2454 2455 /* 2456 * If FIN is received ACK the FIN and let the user know 2457 * that the connection is closing. 2458 */ 2459 if (thflags & TH_FIN) { 2460 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2461 socantrcvmore(so); 2462 /* 2463 * If connection is half-synchronized 2464 * (ie NEEDSYN flag on) then delay ACK, 2465 * so it may be piggybacked when SYN is sent. 2466 * Otherwise, since we received a FIN then no 2467 * more input can be expected, send ACK now. 2468 */ 2469 if (tp->t_flags & TF_NEEDSYN) 2470 tp->t_flags |= TF_DELACK; 2471 else 2472 tp->t_flags |= TF_ACKNOW; 2473 tp->rcv_nxt++; 2474 } 2475 switch (tp->t_state) { 2476 2477 /* 2478 * In SYN_RECEIVED and ESTABLISHED STATES 2479 * enter the CLOSE_WAIT state. 2480 */ 2481 case TCPS_SYN_RECEIVED: 2482 tp->t_starttime = ticks; 2483 /*FALLTHROUGH*/ 2484 case TCPS_ESTABLISHED: 2485 tp->t_state = TCPS_CLOSE_WAIT; 2486 break; 2487 2488 /* 2489 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2490 * enter the CLOSING state. 2491 */ 2492 case TCPS_FIN_WAIT_1: 2493 tp->t_state = TCPS_CLOSING; 2494 break; 2495 2496 /* 2497 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2498 * starting the time-wait timer, turning off the other 2499 * standard timers. 2500 */ 2501 case TCPS_FIN_WAIT_2: 2502 KASSERT(headlocked == 1, ("%s: dodata: " 2503 "TCP_FIN_WAIT_2: head not locked", __func__)); 2504 tcp_twstart(tp); 2505 INP_INFO_WUNLOCK(&tcbinfo); 2506 return (0); 2507 2508 /* 2509 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2510 */ 2511 case TCPS_TIME_WAIT: 2512 KASSERT(tp->t_state != TCPS_TIME_WAIT, 2513 ("%s: timewait", __func__)); 2514 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2515 tcp_timer_2msl, tp); 2516 break; 2517 } 2518 } 2519 INP_INFO_WUNLOCK(&tcbinfo); 2520 headlocked = 0; 2521 #ifdef TCPDEBUG 2522 if (so->so_options & SO_DEBUG) 2523 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2524 &tcp_savetcp, 0); 2525 #endif 2526 2527 /* 2528 * Return any desired output. 2529 */ 2530 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2531 (void) tcp_output(tp); 2532 2533 check_delack: 2534 KASSERT(headlocked == 0, ("%s: check_delack: head locked", 2535 __func__)); 2536 INP_LOCK_ASSERT(tp->t_inpcb); 2537 if (tp->t_flags & TF_DELACK) { 2538 tp->t_flags &= ~TF_DELACK; 2539 callout_reset(tp->tt_delack, tcp_delacktime, 2540 tcp_timer_delack, tp); 2541 } 2542 INP_UNLOCK(tp->t_inpcb); 2543 return (0); 2544 2545 dropafterack: 2546 KASSERT(headlocked, ("%s: dropafterack: head not locked", __func__)); 2547 /* 2548 * Generate an ACK dropping incoming segment if it occupies 2549 * sequence space, where the ACK reflects our state. 2550 * 2551 * We can now skip the test for the RST flag since all 2552 * paths to this code happen after packets containing 2553 * RST have been dropped. 2554 * 2555 * In the SYN-RECEIVED state, don't send an ACK unless the 2556 * segment we received passes the SYN-RECEIVED ACK test. 2557 * If it fails send a RST. This breaks the loop in the 2558 * "LAND" DoS attack, and also prevents an ACK storm 2559 * between two listening ports that have been sent forged 2560 * SYN segments, each with the source address of the other. 2561 */ 2562 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2563 (SEQ_GT(tp->snd_una, th->th_ack) || 2564 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2565 rstreason = BANDLIM_RST_OPENPORT; 2566 goto dropwithreset; 2567 } 2568 #ifdef TCPDEBUG 2569 if (so->so_options & SO_DEBUG) 2570 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2571 &tcp_savetcp, 0); 2572 #endif 2573 KASSERT(headlocked, ("%s: headlocked should be 1", __func__)); 2574 INP_INFO_WUNLOCK(&tcbinfo); 2575 tp->t_flags |= TF_ACKNOW; 2576 (void) tcp_output(tp); 2577 INP_UNLOCK(tp->t_inpcb); 2578 m_freem(m); 2579 return (0); 2580 2581 dropwithreset: 2582 KASSERT(headlocked, ("%s: dropwithreset: head not locked", __func__)); 2583 2584 tcp_dropwithreset(m, th, tp, tlen, rstreason); 2585 2586 if (tp != NULL) 2587 INP_UNLOCK(tp->t_inpcb); 2588 if (headlocked) 2589 INP_INFO_WUNLOCK(&tcbinfo); 2590 return (0); 2591 2592 drop: 2593 /* 2594 * Drop space held by incoming segment and return. 2595 */ 2596 #ifdef TCPDEBUG 2597 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2598 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2599 &tcp_savetcp, 0); 2600 #endif 2601 if (tp != NULL) 2602 INP_UNLOCK(tp->t_inpcb); 2603 if (headlocked) 2604 INP_INFO_WUNLOCK(&tcbinfo); 2605 m_freem(m); 2606 return (0); 2607 } 2608 2609 2610 /* 2611 * Issue RST on TCP segment. The mbuf must still include the original 2612 * packet header. 2613 */ 2614 static void 2615 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 2616 int tlen, int rstreason) 2617 { 2618 struct ip *ip; 2619 #ifdef INET6 2620 struct ip6_hdr *ip6; 2621 #endif 2622 2623 /* 2624 * Generate a RST, dropping incoming segment. 2625 * Make ACK acceptable to originator of segment. 2626 * Don't bother to respond if destination was broadcast/multicast. 2627 */ 2628 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2629 goto drop; 2630 #ifdef INET6 2631 if (mtod(m, struct ip *)->ip_v == 6) { 2632 ip6 = mtod(m, struct ip6_hdr *); 2633 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2634 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2635 goto drop; 2636 /* IPv6 anycast check is done at tcp6_input() */ 2637 } else 2638 #endif 2639 { 2640 ip = mtod(m, struct ip *); 2641 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2642 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2643 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2644 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2645 goto drop; 2646 } 2647 2648 /* Perform bandwidth limiting. */ 2649 if (badport_bandlim(rstreason) < 0) 2650 goto drop; 2651 2652 /* tcp_respond consumes the mbuf chain. */ 2653 if (th->th_flags & TH_ACK) { 2654 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 2655 th->th_ack, TH_RST); 2656 } else { 2657 if (th->th_flags & TH_SYN) 2658 tlen++; 2659 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2660 (tcp_seq)0, TH_RST|TH_ACK); 2661 } 2662 return; 2663 drop: 2664 m_freem(m); 2665 return; 2666 } 2667 2668 /* 2669 * Parse TCP options and place in tcpopt. 2670 */ 2671 static void 2672 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 2673 { 2674 int opt, optlen; 2675 2676 to->to_flags = 0; 2677 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2678 opt = cp[0]; 2679 if (opt == TCPOPT_EOL) 2680 break; 2681 if (opt == TCPOPT_NOP) 2682 optlen = 1; 2683 else { 2684 if (cnt < 2) 2685 break; 2686 optlen = cp[1]; 2687 if (optlen < 2 || optlen > cnt) 2688 break; 2689 } 2690 switch (opt) { 2691 case TCPOPT_MAXSEG: 2692 if (optlen != TCPOLEN_MAXSEG) 2693 continue; 2694 if (!(flags & TO_SYN)) 2695 continue; 2696 to->to_flags |= TOF_MSS; 2697 bcopy((char *)cp + 2, 2698 (char *)&to->to_mss, sizeof(to->to_mss)); 2699 to->to_mss = ntohs(to->to_mss); 2700 break; 2701 case TCPOPT_WINDOW: 2702 if (optlen != TCPOLEN_WINDOW) 2703 continue; 2704 if (!(flags & TO_SYN)) 2705 continue; 2706 to->to_flags |= TOF_SCALE; 2707 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 2708 break; 2709 case TCPOPT_TIMESTAMP: 2710 if (optlen != TCPOLEN_TIMESTAMP) 2711 continue; 2712 to->to_flags |= TOF_TS; 2713 bcopy((char *)cp + 2, 2714 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2715 to->to_tsval = ntohl(to->to_tsval); 2716 bcopy((char *)cp + 6, 2717 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2718 to->to_tsecr = ntohl(to->to_tsecr); 2719 break; 2720 #ifdef TCP_SIGNATURE 2721 /* 2722 * XXX In order to reply to a host which has set the 2723 * TCP_SIGNATURE option in its initial SYN, we have to 2724 * record the fact that the option was observed here 2725 * for the syncache code to perform the correct response. 2726 */ 2727 case TCPOPT_SIGNATURE: 2728 if (optlen != TCPOLEN_SIGNATURE) 2729 continue; 2730 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2731 break; 2732 #endif 2733 case TCPOPT_SACK_PERMITTED: 2734 if (optlen != TCPOLEN_SACK_PERMITTED) 2735 continue; 2736 if (!(flags & TO_SYN)) 2737 continue; 2738 if (!tcp_do_sack) 2739 continue; 2740 to->to_flags |= TOF_SACKPERM; 2741 break; 2742 case TCPOPT_SACK: 2743 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2744 continue; 2745 if (flags & TO_SYN) 2746 continue; 2747 to->to_flags |= TOF_SACK; 2748 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2749 to->to_sacks = cp + 2; 2750 tcpstat.tcps_sack_rcv_blocks++; 2751 break; 2752 default: 2753 continue; 2754 } 2755 } 2756 } 2757 2758 /* 2759 * Pull out of band byte out of a segment so 2760 * it doesn't appear in the user's data queue. 2761 * It is still reflected in the segment length for 2762 * sequencing purposes. 2763 */ 2764 static void 2765 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 2766 int off) 2767 { 2768 int cnt = off + th->th_urp - 1; 2769 2770 while (cnt >= 0) { 2771 if (m->m_len > cnt) { 2772 char *cp = mtod(m, caddr_t) + cnt; 2773 struct tcpcb *tp = sototcpcb(so); 2774 2775 tp->t_iobc = *cp; 2776 tp->t_oobflags |= TCPOOB_HAVEDATA; 2777 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2778 m->m_len--; 2779 if (m->m_flags & M_PKTHDR) 2780 m->m_pkthdr.len--; 2781 return; 2782 } 2783 cnt -= m->m_len; 2784 m = m->m_next; 2785 if (m == NULL) 2786 break; 2787 } 2788 panic("tcp_pulloutofband"); 2789 } 2790 2791 /* 2792 * Collect new round-trip time estimate 2793 * and update averages and current timeout. 2794 */ 2795 static void 2796 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2797 { 2798 int delta; 2799 2800 INP_LOCK_ASSERT(tp->t_inpcb); 2801 2802 tcpstat.tcps_rttupdated++; 2803 tp->t_rttupdated++; 2804 if (tp->t_srtt != 0) { 2805 /* 2806 * srtt is stored as fixed point with 5 bits after the 2807 * binary point (i.e., scaled by 8). The following magic 2808 * is equivalent to the smoothing algorithm in rfc793 with 2809 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2810 * point). Adjust rtt to origin 0. 2811 */ 2812 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2813 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2814 2815 if ((tp->t_srtt += delta) <= 0) 2816 tp->t_srtt = 1; 2817 2818 /* 2819 * We accumulate a smoothed rtt variance (actually, a 2820 * smoothed mean difference), then set the retransmit 2821 * timer to smoothed rtt + 4 times the smoothed variance. 2822 * rttvar is stored as fixed point with 4 bits after the 2823 * binary point (scaled by 16). The following is 2824 * equivalent to rfc793 smoothing with an alpha of .75 2825 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2826 * rfc793's wired-in beta. 2827 */ 2828 if (delta < 0) 2829 delta = -delta; 2830 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2831 if ((tp->t_rttvar += delta) <= 0) 2832 tp->t_rttvar = 1; 2833 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2834 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2835 } else { 2836 /* 2837 * No rtt measurement yet - use the unsmoothed rtt. 2838 * Set the variance to half the rtt (so our first 2839 * retransmit happens at 3*rtt). 2840 */ 2841 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2842 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2843 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2844 } 2845 tp->t_rtttime = 0; 2846 tp->t_rxtshift = 0; 2847 2848 /* 2849 * the retransmit should happen at rtt + 4 * rttvar. 2850 * Because of the way we do the smoothing, srtt and rttvar 2851 * will each average +1/2 tick of bias. When we compute 2852 * the retransmit timer, we want 1/2 tick of rounding and 2853 * 1 extra tick because of +-1/2 tick uncertainty in the 2854 * firing of the timer. The bias will give us exactly the 2855 * 1.5 tick we need. But, because the bias is 2856 * statistical, we have to test that we don't drop below 2857 * the minimum feasible timer (which is 2 ticks). 2858 */ 2859 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2860 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2861 2862 /* 2863 * We received an ack for a packet that wasn't retransmitted; 2864 * it is probably safe to discard any error indications we've 2865 * received recently. This isn't quite right, but close enough 2866 * for now (a route might have failed after we sent a segment, 2867 * and the return path might not be symmetrical). 2868 */ 2869 tp->t_softerror = 0; 2870 } 2871 2872 /* 2873 * Determine a reasonable value for maxseg size. 2874 * If the route is known, check route for mtu. 2875 * If none, use an mss that can be handled on the outgoing 2876 * interface without forcing IP to fragment; if bigger than 2877 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2878 * to utilize large mbufs. If no route is found, route has no mtu, 2879 * or the destination isn't local, use a default, hopefully conservative 2880 * size (usually 512 or the default IP max size, but no more than the mtu 2881 * of the interface), as we can't discover anything about intervening 2882 * gateways or networks. We also initialize the congestion/slow start 2883 * window to be a single segment if the destination isn't local. 2884 * While looking at the routing entry, we also initialize other path-dependent 2885 * parameters from pre-set or cached values in the routing entry. 2886 * 2887 * Also take into account the space needed for options that we 2888 * send regularly. Make maxseg shorter by that amount to assure 2889 * that we can send maxseg amount of data even when the options 2890 * are present. Store the upper limit of the length of options plus 2891 * data in maxopd. 2892 * 2893 * 2894 * In case of T/TCP, we call this routine during implicit connection 2895 * setup as well (offer = -1), to initialize maxseg from the cached 2896 * MSS of our peer. 2897 * 2898 * NOTE that this routine is only called when we process an incoming 2899 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2900 */ 2901 void 2902 tcp_mss(struct tcpcb *tp, int offer) 2903 { 2904 int rtt, mss; 2905 u_long bufsize; 2906 u_long maxmtu; 2907 struct inpcb *inp = tp->t_inpcb; 2908 struct socket *so; 2909 struct hc_metrics_lite metrics; 2910 int origoffer = offer; 2911 int mtuflags = 0; 2912 #ifdef INET6 2913 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2914 size_t min_protoh = isipv6 ? 2915 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2916 sizeof (struct tcpiphdr); 2917 #else 2918 const size_t min_protoh = sizeof(struct tcpiphdr); 2919 #endif 2920 2921 /* initialize */ 2922 #ifdef INET6 2923 if (isipv6) { 2924 maxmtu = tcp_maxmtu6(&inp->inp_inc, &mtuflags); 2925 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2926 } else 2927 #endif 2928 { 2929 maxmtu = tcp_maxmtu(&inp->inp_inc, &mtuflags); 2930 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2931 } 2932 so = inp->inp_socket; 2933 2934 /* 2935 * no route to sender, stay with default mss and return 2936 */ 2937 if (maxmtu == 0) 2938 return; 2939 2940 /* what have we got? */ 2941 switch (offer) { 2942 case 0: 2943 /* 2944 * Offer == 0 means that there was no MSS on the SYN 2945 * segment, in this case we use tcp_mssdflt. 2946 */ 2947 offer = 2948 #ifdef INET6 2949 isipv6 ? tcp_v6mssdflt : 2950 #endif 2951 tcp_mssdflt; 2952 break; 2953 2954 case -1: 2955 /* 2956 * Offer == -1 means that we didn't receive SYN yet. 2957 */ 2958 /* FALLTHROUGH */ 2959 2960 default: 2961 /* 2962 * Prevent DoS attack with too small MSS. Round up 2963 * to at least minmss. 2964 */ 2965 offer = max(offer, tcp_minmss); 2966 /* 2967 * Sanity check: make sure that maxopd will be large 2968 * enough to allow some data on segments even if the 2969 * all the option space is used (40bytes). Otherwise 2970 * funny things may happen in tcp_output. 2971 */ 2972 offer = max(offer, 64); 2973 } 2974 2975 /* 2976 * rmx information is now retrieved from tcp_hostcache 2977 */ 2978 tcp_hc_get(&inp->inp_inc, &metrics); 2979 2980 /* 2981 * if there's a discovered mtu int tcp hostcache, use it 2982 * else, use the link mtu. 2983 */ 2984 if (metrics.rmx_mtu) 2985 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2986 else { 2987 #ifdef INET6 2988 if (isipv6) { 2989 mss = maxmtu - min_protoh; 2990 if (!path_mtu_discovery && 2991 !in6_localaddr(&inp->in6p_faddr)) 2992 mss = min(mss, tcp_v6mssdflt); 2993 } else 2994 #endif 2995 { 2996 mss = maxmtu - min_protoh; 2997 if (!path_mtu_discovery && 2998 !in_localaddr(inp->inp_faddr)) 2999 mss = min(mss, tcp_mssdflt); 3000 } 3001 } 3002 mss = min(mss, offer); 3003 3004 /* 3005 * maxopd stores the maximum length of data AND options 3006 * in a segment; maxseg is the amount of data in a normal 3007 * segment. We need to store this value (maxopd) apart 3008 * from maxseg, because now every segment carries options 3009 * and thus we normally have somewhat less data in segments. 3010 */ 3011 tp->t_maxopd = mss; 3012 3013 /* 3014 * origoffer==-1 indicates, that no segments were received yet. 3015 * In this case we just guess. 3016 */ 3017 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3018 (origoffer == -1 || 3019 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3020 mss -= TCPOLEN_TSTAMP_APPA; 3021 tp->t_maxseg = mss; 3022 3023 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3024 if (mss > MCLBYTES) 3025 mss &= ~(MCLBYTES-1); 3026 #else 3027 if (mss > MCLBYTES) 3028 mss = mss / MCLBYTES * MCLBYTES; 3029 #endif 3030 tp->t_maxseg = mss; 3031 3032 /* 3033 * If there's a pipesize, change the socket buffer to that size, 3034 * don't change if sb_hiwat is different than default (then it 3035 * has been changed on purpose with setsockopt). 3036 * Make the socket buffers an integral number of mss units; 3037 * if the mss is larger than the socket buffer, decrease the mss. 3038 */ 3039 SOCKBUF_LOCK(&so->so_snd); 3040 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3041 bufsize = metrics.rmx_sendpipe; 3042 else 3043 bufsize = so->so_snd.sb_hiwat; 3044 if (bufsize < mss) 3045 mss = bufsize; 3046 else { 3047 bufsize = roundup(bufsize, mss); 3048 if (bufsize > sb_max) 3049 bufsize = sb_max; 3050 if (bufsize > so->so_snd.sb_hiwat) 3051 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3052 } 3053 SOCKBUF_UNLOCK(&so->so_snd); 3054 tp->t_maxseg = mss; 3055 3056 SOCKBUF_LOCK(&so->so_rcv); 3057 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3058 bufsize = metrics.rmx_recvpipe; 3059 else 3060 bufsize = so->so_rcv.sb_hiwat; 3061 if (bufsize > mss) { 3062 bufsize = roundup(bufsize, mss); 3063 if (bufsize > sb_max) 3064 bufsize = sb_max; 3065 if (bufsize > so->so_rcv.sb_hiwat) 3066 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3067 } 3068 SOCKBUF_UNLOCK(&so->so_rcv); 3069 /* 3070 * While we're here, check the others too 3071 */ 3072 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3073 tp->t_srtt = rtt; 3074 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3075 tcpstat.tcps_usedrtt++; 3076 if (metrics.rmx_rttvar) { 3077 tp->t_rttvar = metrics.rmx_rttvar; 3078 tcpstat.tcps_usedrttvar++; 3079 } else { 3080 /* default variation is +- 1 rtt */ 3081 tp->t_rttvar = 3082 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3083 } 3084 TCPT_RANGESET(tp->t_rxtcur, 3085 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3086 tp->t_rttmin, TCPTV_REXMTMAX); 3087 } 3088 if (metrics.rmx_ssthresh) { 3089 /* 3090 * There's some sort of gateway or interface 3091 * buffer limit on the path. Use this to set 3092 * the slow start threshhold, but set the 3093 * threshold to no less than 2*mss. 3094 */ 3095 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3096 tcpstat.tcps_usedssthresh++; 3097 } 3098 if (metrics.rmx_bandwidth) 3099 tp->snd_bandwidth = metrics.rmx_bandwidth; 3100 3101 /* 3102 * Set the slow-start flight size depending on whether this 3103 * is a local network or not. 3104 * 3105 * Extend this so we cache the cwnd too and retrieve it here. 3106 * Make cwnd even bigger than RFC3390 suggests but only if we 3107 * have previous experience with the remote host. Be careful 3108 * not make cwnd bigger than remote receive window or our own 3109 * send socket buffer. Maybe put some additional upper bound 3110 * on the retrieved cwnd. Should do incremental updates to 3111 * hostcache when cwnd collapses so next connection doesn't 3112 * overloads the path again. 3113 * 3114 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3115 * We currently check only in syncache_socket for that. 3116 */ 3117 #define TCP_METRICS_CWND 3118 #ifdef TCP_METRICS_CWND 3119 if (metrics.rmx_cwnd) 3120 tp->snd_cwnd = max(mss, 3121 min(metrics.rmx_cwnd / 2, 3122 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3123 else 3124 #endif 3125 if (tcp_do_rfc3390) 3126 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3127 #ifdef INET6 3128 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3129 (!isipv6 && in_localaddr(inp->inp_faddr))) 3130 #else 3131 else if (in_localaddr(inp->inp_faddr)) 3132 #endif 3133 tp->snd_cwnd = mss * ss_fltsz_local; 3134 else 3135 tp->snd_cwnd = mss * ss_fltsz; 3136 3137 /* Check the interface for TSO capabilities. */ 3138 if (mtuflags & CSUM_TSO) 3139 tp->t_flags |= TF_TSO; 3140 } 3141 3142 /* 3143 * Determine the MSS option to send on an outgoing SYN. 3144 */ 3145 int 3146 tcp_mssopt(struct in_conninfo *inc) 3147 { 3148 int mss = 0; 3149 u_long maxmtu = 0; 3150 u_long thcmtu = 0; 3151 size_t min_protoh; 3152 #ifdef INET6 3153 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3154 #endif 3155 3156 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3157 3158 #ifdef INET6 3159 if (isipv6) { 3160 mss = tcp_v6mssdflt; 3161 maxmtu = tcp_maxmtu6(inc, NULL); 3162 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3163 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3164 } else 3165 #endif 3166 { 3167 mss = tcp_mssdflt; 3168 maxmtu = tcp_maxmtu(inc, NULL); 3169 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3170 min_protoh = sizeof(struct tcpiphdr); 3171 } 3172 if (maxmtu && thcmtu) 3173 mss = min(maxmtu, thcmtu) - min_protoh; 3174 else if (maxmtu || thcmtu) 3175 mss = max(maxmtu, thcmtu) - min_protoh; 3176 3177 return (mss); 3178 } 3179 3180 3181 /* 3182 * On a partial ack arrives, force the retransmission of the 3183 * next unacknowledged segment. Do not clear tp->t_dupacks. 3184 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3185 * be started again. 3186 */ 3187 static void 3188 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3189 { 3190 tcp_seq onxt = tp->snd_nxt; 3191 u_long ocwnd = tp->snd_cwnd; 3192 3193 callout_stop(tp->tt_rexmt); 3194 tp->t_rtttime = 0; 3195 tp->snd_nxt = th->th_ack; 3196 /* 3197 * Set snd_cwnd to one segment beyond acknowledged offset. 3198 * (tp->snd_una has not yet been updated when this function is called.) 3199 */ 3200 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3201 tp->t_flags |= TF_ACKNOW; 3202 (void) tcp_output(tp); 3203 tp->snd_cwnd = ocwnd; 3204 if (SEQ_GT(onxt, tp->snd_nxt)) 3205 tp->snd_nxt = onxt; 3206 /* 3207 * Partial window deflation. Relies on fact that tp->snd_una 3208 * not updated yet. 3209 */ 3210 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3211 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3212 else 3213 tp->snd_cwnd = 0; 3214 tp->snd_cwnd += tp->t_maxseg; 3215 } 3216 3217 /* 3218 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3219 * looking for a pcb in the listen state. Returns 0 otherwise. 3220 */ 3221 static int 3222 tcp_timewait(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th, 3223 struct mbuf *m, int tlen) 3224 { 3225 struct tcptw *tw; 3226 int thflags; 3227 tcp_seq seq; 3228 #ifdef INET6 3229 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3230 #else 3231 const int isipv6 = 0; 3232 #endif 3233 3234 /* tcbinfo lock required for tcp_twclose(), tcp_timer_2msl_reset(). */ 3235 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3236 INP_LOCK_ASSERT(inp); 3237 3238 /* 3239 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 3240 * still present. This is undesirable, but temporarily necessary 3241 * until we work out how to handle inpcb's who's timewait state has 3242 * been removed. 3243 */ 3244 tw = intotw(inp); 3245 if (tw == NULL) 3246 goto drop; 3247 3248 thflags = th->th_flags; 3249 3250 /* 3251 * NOTE: for FIN_WAIT_2 (to be added later), 3252 * must validate sequence number before accepting RST 3253 */ 3254 3255 /* 3256 * If the segment contains RST: 3257 * Drop the segment - see Stevens, vol. 2, p. 964 and 3258 * RFC 1337. 3259 */ 3260 if (thflags & TH_RST) 3261 goto drop; 3262 3263 #if 0 3264 /* PAWS not needed at the moment */ 3265 /* 3266 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3267 * and it's less than ts_recent, drop it. 3268 */ 3269 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3270 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3271 if ((thflags & TH_ACK) == 0) 3272 goto drop; 3273 goto ack; 3274 } 3275 /* 3276 * ts_recent is never updated because we never accept new segments. 3277 */ 3278 #endif 3279 3280 /* 3281 * If a new connection request is received 3282 * while in TIME_WAIT, drop the old connection 3283 * and start over if the sequence numbers 3284 * are above the previous ones. 3285 */ 3286 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3287 tcp_twclose(tw, 0); 3288 return (1); 3289 } 3290 3291 /* 3292 * Drop the the segment if it does not contain an ACK. 3293 */ 3294 if ((thflags & TH_ACK) == 0) 3295 goto drop; 3296 3297 /* 3298 * Reset the 2MSL timer if this is a duplicate FIN. 3299 */ 3300 if (thflags & TH_FIN) { 3301 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3302 if (seq + 1 == tw->rcv_nxt) 3303 tcp_timer_2msl_reset(tw, 1); 3304 } 3305 3306 /* 3307 * Acknowledge the segment if it has data or is not a duplicate ACK. 3308 */ 3309 if (thflags != TH_ACK || tlen != 0 || 3310 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3311 tcp_twrespond(tw, TH_ACK); 3312 goto drop; 3313 3314 /* 3315 * Generate a RST, dropping incoming segment. 3316 * Make ACK acceptable to originator of segment. 3317 * Don't bother to respond if destination was broadcast/multicast. 3318 */ 3319 if (m->m_flags & (M_BCAST|M_MCAST)) 3320 goto drop; 3321 if (isipv6) { 3322 struct ip6_hdr *ip6; 3323 3324 /* IPv6 anycast check is done at tcp6_input() */ 3325 ip6 = mtod(m, struct ip6_hdr *); 3326 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3327 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3328 goto drop; 3329 } else { 3330 struct ip *ip; 3331 3332 ip = mtod(m, struct ip *); 3333 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3334 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3335 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3336 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3337 goto drop; 3338 } 3339 if (thflags & TH_ACK) { 3340 tcp_respond(NULL, 3341 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3342 } else { 3343 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3344 tcp_respond(NULL, 3345 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3346 } 3347 INP_UNLOCK(inp); 3348 return (0); 3349 3350 drop: 3351 INP_UNLOCK(inp); 3352 m_freem(m); 3353 return (0); 3354 } 3355