1 /* 2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 53 * The Regents of the University of California. All rights reserved. 54 * 55 * Redistribution and use in source and binary forms, with or without 56 * modification, are permitted provided that the following conditions 57 * are met: 58 * 1. Redistributions of source code must retain the above copyright 59 * notice, this list of conditions and the following disclaimer. 60 * 2. Redistributions in binary form must reproduce the above copyright 61 * notice, this list of conditions and the following disclaimer in the 62 * documentation and/or other materials provided with the distribution. 63 * 3. All advertising materials mentioning features or use of this software 64 * must display the following acknowledgement: 65 * This product includes software developed by the University of 66 * California, Berkeley and its contributors. 67 * 4. Neither the name of the University nor the names of its contributors 68 * may be used to endorse or promote products derived from this software 69 * without specific prior written permission. 70 * 71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 81 * SUCH DAMAGE. 82 * 83 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 84 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 85 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.38 2004/11/14 00:49:08 hsu Exp $ 86 */ 87 88 #include "opt_ipfw.h" /* for ipfw_fwd */ 89 #include "opt_inet6.h" 90 #include "opt_ipsec.h" 91 #include "opt_tcpdebug.h" 92 #include "opt_tcp_input.h" 93 94 #include <sys/param.h> 95 #include <sys/systm.h> 96 #include <sys/kernel.h> 97 #include <sys/sysctl.h> 98 #include <sys/malloc.h> 99 #include <sys/mbuf.h> 100 #include <sys/proc.h> /* for proc0 declaration */ 101 #include <sys/protosw.h> 102 #include <sys/socket.h> 103 #include <sys/socketvar.h> 104 #include <sys/syslog.h> 105 #include <sys/in_cksum.h> 106 107 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 108 #include <machine/stdarg.h> 109 110 #include <net/if.h> 111 #include <net/route.h> 112 113 #include <netinet/in.h> 114 #include <netinet/in_systm.h> 115 #include <netinet/ip.h> 116 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 117 #include <netinet/in_var.h> 118 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 119 #include <netinet/in_pcb.h> 120 #include <netinet/ip_var.h> 121 #include <netinet/ip6.h> 122 #include <netinet/icmp6.h> 123 #include <netinet6/nd6.h> 124 #include <netinet6/ip6_var.h> 125 #include <netinet6/in6_pcb.h> 126 #include <netinet/tcp.h> 127 #include <netinet/tcp_fsm.h> 128 #include <netinet/tcp_seq.h> 129 #include <netinet/tcp_timer.h> 130 #include <netinet/tcp_var.h> 131 #include <netinet6/tcp6_var.h> 132 #include <netinet/tcpip.h> 133 134 #ifdef TCPDEBUG 135 #include <netinet/tcp_debug.h> 136 137 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 138 struct tcphdr tcp_savetcp; 139 #endif 140 141 #ifdef FAST_IPSEC 142 #include <netproto/ipsec/ipsec.h> 143 #include <netproto/ipsec/ipsec6.h> 144 #endif 145 146 #ifdef IPSEC 147 #include <netinet6/ipsec.h> 148 #include <netinet6/ipsec6.h> 149 #include <netproto/key/key.h> 150 #endif 151 152 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 153 154 tcp_cc tcp_ccgen; 155 static int log_in_vain = 0; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 157 &log_in_vain, 0, "Log all incoming TCP connections"); 158 159 static int blackhole = 0; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 161 &blackhole, 0, "Do not send RST when dropping refused connections"); 162 163 int tcp_delack_enabled = 1; 164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 165 &tcp_delack_enabled, 0, 166 "Delay ACK to try and piggyback it onto a data packet"); 167 168 #ifdef TCP_DROP_SYNFIN 169 static int drop_synfin = 0; 170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 171 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 172 #endif 173 174 static int tcp_do_limitedtransmit = 1; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 176 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 177 178 static int tcp_do_early_retransmit = 1; 179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 180 &tcp_do_early_retransmit, 0, "Early retransmit"); 181 182 static int tcp_do_rfc3390 = 1; 183 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 184 &tcp_do_rfc3390, 0, 185 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 186 187 static int tcp_do_eifel_detect = 1; 188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 189 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 190 191 /* 192 * Define as tunable for easy testing with SACK on and off. 193 * Warning: do not change setting in the middle of an existing active TCP flow, 194 * else strange things might happen to that flow. 195 */ 196 int tcp_do_sack = 1; 197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 198 &tcp_do_sack, 0, "Enable SACK Algorithms"); 199 200 int tcp_do_smartsack = 1; 201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 202 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 203 204 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 205 "TCP Segment Reassembly Queue"); 206 207 int tcp_reass_maxseg = 0; 208 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 209 &tcp_reass_maxseg, 0, 210 "Global maximum number of TCP Segments in Reassembly Queue"); 211 212 int tcp_reass_qsize = 0; 213 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 214 &tcp_reass_qsize, 0, 215 "Global number of TCP Segments currently in Reassembly Queue"); 216 217 static int tcp_reass_overflows = 0; 218 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 219 &tcp_reass_overflows, 0, 220 "Global number of TCP Segment Reassembly Queue Overflows"); 221 222 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 223 static void tcp_pulloutofband(struct socket *, 224 struct tcphdr *, struct mbuf *, int); 225 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 226 struct mbuf *); 227 static void tcp_xmit_timer(struct tcpcb *, int); 228 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 229 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 230 231 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 232 #ifdef INET6 233 #define ND6_HINT(tp) \ 234 do { \ 235 if ((tp) && (tp)->t_inpcb && \ 236 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 237 (tp)->t_inpcb->in6p_route.ro_rt) \ 238 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 239 } while (0) 240 #else 241 #define ND6_HINT(tp) 242 #endif 243 244 /* 245 * Indicate whether this ack should be delayed. We can delay the ack if 246 * - delayed acks are enabled and 247 * - there is no delayed ack timer in progress and 248 * - our last ack wasn't a 0-sized window. We never want to delay 249 * the ack that opens up a 0-sized window. 250 */ 251 #define DELAY_ACK(tp) \ 252 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 253 !(tp->t_flags & TF_RXWIN0SENT)) 254 255 static int 256 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 257 { 258 struct tseg_qent *q; 259 struct tseg_qent *p = NULL; 260 struct tseg_qent *te; 261 struct socket *so = tp->t_inpcb->inp_socket; 262 int flags; 263 264 /* 265 * Call with th == NULL after become established to 266 * force pre-ESTABLISHED data up to user socket. 267 */ 268 if (th == NULL) 269 goto present; 270 271 /* 272 * Limit the number of segments in the reassembly queue to prevent 273 * holding on to too many segments (and thus running out of mbufs). 274 * Make sure to let the missing segment through which caused this 275 * queue. Always keep one global queue entry spare to be able to 276 * process the missing segment. 277 */ 278 if (th->th_seq != tp->rcv_nxt && 279 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 280 tcp_reass_overflows++; 281 tcpstat.tcps_rcvmemdrop++; 282 m_freem(m); 283 /* no SACK block to report */ 284 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 285 return (0); 286 } 287 288 /* Allocate a new queue entry. */ 289 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 290 M_INTWAIT | M_NULLOK); 291 if (te == NULL) { 292 tcpstat.tcps_rcvmemdrop++; 293 m_freem(m); 294 /* no SACK block to report */ 295 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 296 return (0); 297 } 298 tcp_reass_qsize++; 299 300 /* 301 * Find a segment which begins after this one does. 302 */ 303 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 304 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 305 break; 306 p = q; 307 } 308 309 /* 310 * If there is a preceding segment, it may provide some of 311 * our data already. If so, drop the data from the incoming 312 * segment. If it provides all of our data, drop us. 313 */ 314 if (p != NULL) { 315 int i; 316 317 /* conversion to int (in i) handles seq wraparound */ 318 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 319 if (i > 0) { /* overlaps preceding segment */ 320 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 321 /* enclosing block starts w/ preceding segment */ 322 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 323 if (i >= *tlenp) { 324 /* preceding encloses incoming segment */ 325 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 326 p->tqe_len; 327 tcpstat.tcps_rcvduppack++; 328 tcpstat.tcps_rcvdupbyte += *tlenp; 329 m_freem(m); 330 free(te, M_TSEGQ); 331 tcp_reass_qsize--; 332 /* 333 * Try to present any queued data 334 * at the left window edge to the user. 335 * This is needed after the 3-WHS 336 * completes. 337 */ 338 goto present; /* ??? */ 339 } 340 m_adj(m, i); 341 *tlenp -= i; 342 th->th_seq += i; 343 /* incoming segment end is enclosing block end */ 344 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 345 ((th->th_flags & TH_FIN) != 0); 346 /* trim end of reported D-SACK block */ 347 tp->reportblk.rblk_end = th->th_seq; 348 } 349 } 350 tcpstat.tcps_rcvoopack++; 351 tcpstat.tcps_rcvoobyte += *tlenp; 352 353 /* 354 * While we overlap succeeding segments trim them or, 355 * if they are completely covered, dequeue them. 356 */ 357 while (q) { 358 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 359 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 360 struct tseg_qent *nq; 361 362 if (i <= 0) 363 break; 364 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 365 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 366 tp->encloseblk = tp->reportblk; 367 /* report trailing duplicate D-SACK segment */ 368 tp->reportblk.rblk_start = q->tqe_th->th_seq; 369 } 370 if ((tp->t_flags & TF_ENCLOSESEG) && 371 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 372 /* extend enclosing block if one exists */ 373 tp->encloseblk.rblk_end = qend; 374 } 375 if (i < q->tqe_len) { 376 q->tqe_th->th_seq += i; 377 q->tqe_len -= i; 378 m_adj(q->tqe_m, i); 379 break; 380 } 381 382 nq = LIST_NEXT(q, tqe_q); 383 LIST_REMOVE(q, tqe_q); 384 m_freem(q->tqe_m); 385 free(q, M_TSEGQ); 386 tcp_reass_qsize--; 387 q = nq; 388 } 389 390 /* Insert the new segment queue entry into place. */ 391 te->tqe_m = m; 392 te->tqe_th = th; 393 te->tqe_len = *tlenp; 394 395 /* check if can coalesce with following segment */ 396 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 397 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 398 399 te->tqe_len += q->tqe_len; 400 m_cat(te->tqe_m, q->tqe_m); 401 tp->encloseblk.rblk_end = tend; 402 /* 403 * When not reporting a duplicate segment, use 404 * the larger enclosing block as the SACK block. 405 */ 406 if (!(tp->t_flags & TF_DUPSEG)) 407 tp->reportblk.rblk_end = tend; 408 LIST_REMOVE(q, tqe_q); 409 free(q, M_TSEGQ); 410 tcp_reass_qsize--; 411 } 412 413 if (p == NULL) { 414 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 415 } else { 416 /* check if can coalesce with preceding segment */ 417 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 418 p->tqe_len += *tlenp; 419 m_cat(p->tqe_m, m); 420 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 421 /* 422 * When not reporting a duplicate segment, use 423 * the larger enclosing block as the SACK block. 424 */ 425 if (!(tp->t_flags & TF_DUPSEG)) 426 tp->reportblk.rblk_start = p->tqe_th->th_seq; 427 free(te, M_TSEGQ); tcp_reass_qsize--; 428 } else 429 LIST_INSERT_AFTER(p, te, tqe_q); 430 } 431 432 present: 433 /* 434 * Present data to user, advancing rcv_nxt through 435 * completed sequence space. 436 */ 437 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 438 return (0); 439 q = LIST_FIRST(&tp->t_segq); 440 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 441 return (0); 442 tp->rcv_nxt += q->tqe_len; 443 if (!(tp->t_flags & TF_DUPSEG)) { 444 /* no SACK block to report since ACK advanced */ 445 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 446 } 447 /* no enclosing block to report since ACK advanced */ 448 tp->t_flags &= ~TF_ENCLOSESEG; 449 flags = q->tqe_th->th_flags & TH_FIN; 450 LIST_REMOVE(q, tqe_q); 451 KASSERT(LIST_EMPTY(&tp->t_segq) || 452 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 453 ("segment not coalesced")); 454 if (so->so_state & SS_CANTRCVMORE) 455 m_freem(q->tqe_m); 456 else 457 sbappend(&so->so_rcv, q->tqe_m); 458 free(q, M_TSEGQ); 459 tcp_reass_qsize--; 460 ND6_HINT(tp); 461 sorwakeup(so); 462 return (flags); 463 } 464 465 /* 466 * TCP input routine, follows pages 65-76 of the 467 * protocol specification dated September, 1981 very closely. 468 */ 469 #ifdef INET6 470 int 471 tcp6_input(struct mbuf **mp, int *offp, int proto) 472 { 473 struct mbuf *m = *mp; 474 struct in6_ifaddr *ia6; 475 476 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 477 478 /* 479 * draft-itojun-ipv6-tcp-to-anycast 480 * better place to put this in? 481 */ 482 ia6 = ip6_getdstifaddr(m); 483 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 484 struct ip6_hdr *ip6; 485 486 ip6 = mtod(m, struct ip6_hdr *); 487 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 488 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 489 return (IPPROTO_DONE); 490 } 491 492 tcp_input(m, *offp, proto); 493 return (IPPROTO_DONE); 494 } 495 #endif 496 497 void 498 tcp_input(struct mbuf *m, ...) 499 { 500 __va_list ap; 501 int off0, proto; 502 struct tcphdr *th; 503 struct ip *ip = NULL; 504 struct ipovly *ipov; 505 struct inpcb *inp = NULL; 506 u_char *optp = NULL; 507 int optlen = 0; 508 int len, tlen, off; 509 int drop_hdrlen; 510 struct tcpcb *tp = NULL; 511 int thflags; 512 struct socket *so = 0; 513 int todrop, acked; 514 boolean_t ourfinisacked, needoutput = FALSE; 515 u_long tiwin; 516 int recvwin; 517 struct tcpopt to; /* options in this segment */ 518 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 519 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 520 struct sockaddr_in *next_hop = NULL; 521 int rstreason; /* For badport_bandlim accounting purposes */ 522 int cpu; 523 struct ip6_hdr *ip6 = NULL; 524 #ifdef INET6 525 boolean_t isipv6; 526 #else 527 const boolean_t isipv6 = FALSE; 528 #endif 529 #ifdef TCPDEBUG 530 short ostate = 0; 531 #endif 532 533 __va_start(ap, m); 534 off0 = __va_arg(ap, int); 535 proto = __va_arg(ap, int); 536 __va_end(ap); 537 538 tcpstat.tcps_rcvtotal++; 539 540 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */ 541 while (m->m_type == MT_TAG) { 542 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 543 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 544 m = m->m_next; 545 } 546 547 #ifdef INET6 548 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 549 #endif 550 551 if (isipv6) { 552 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 553 ip6 = mtod(m, struct ip6_hdr *); 554 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 555 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 556 tcpstat.tcps_rcvbadsum++; 557 goto drop; 558 } 559 th = (struct tcphdr *)((caddr_t)ip6 + off0); 560 561 /* 562 * Be proactive about unspecified IPv6 address in source. 563 * As we use all-zero to indicate unbounded/unconnected pcb, 564 * unspecified IPv6 address can be used to confuse us. 565 * 566 * Note that packets with unspecified IPv6 destination is 567 * already dropped in ip6_input. 568 */ 569 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 570 /* XXX stat */ 571 goto drop; 572 } 573 } else { 574 /* 575 * Get IP and TCP header together in first mbuf. 576 * Note: IP leaves IP header in first mbuf. 577 */ 578 if (off0 > sizeof(struct ip)) { 579 ip_stripoptions(m); 580 off0 = sizeof(struct ip); 581 } 582 /* already checked and pulled up in ip_demux() */ 583 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 584 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 585 ip = mtod(m, struct ip *); 586 ipov = (struct ipovly *)ip; 587 th = (struct tcphdr *)((caddr_t)ip + off0); 588 tlen = ip->ip_len; 589 590 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 591 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 592 th->th_sum = m->m_pkthdr.csum_data; 593 else 594 th->th_sum = in_pseudo(ip->ip_src.s_addr, 595 ip->ip_dst.s_addr, 596 htonl(m->m_pkthdr.csum_data + 597 ip->ip_len + 598 IPPROTO_TCP)); 599 th->th_sum ^= 0xffff; 600 } else { 601 /* 602 * Checksum extended TCP header and data. 603 */ 604 len = sizeof(struct ip) + tlen; 605 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 606 ipov->ih_len = (u_short)tlen; 607 ipov->ih_len = htons(ipov->ih_len); 608 th->th_sum = in_cksum(m, len); 609 } 610 if (th->th_sum) { 611 tcpstat.tcps_rcvbadsum++; 612 goto drop; 613 } 614 #ifdef INET6 615 /* Re-initialization for later version check */ 616 ip->ip_v = IPVERSION; 617 #endif 618 } 619 620 /* 621 * Check that TCP offset makes sense, 622 * pull out TCP options and adjust length. XXX 623 */ 624 off = th->th_off << 2; 625 /* already checked and pulled up in ip_demux() */ 626 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 627 ("bad TCP data offset %d (tlen %d)", off, tlen)); 628 tlen -= off; /* tlen is used instead of ti->ti_len */ 629 if (off > sizeof(struct tcphdr)) { 630 if (isipv6) { 631 IP6_EXTHDR_CHECK(m, off0, off, ); 632 ip6 = mtod(m, struct ip6_hdr *); 633 th = (struct tcphdr *)((caddr_t)ip6 + off0); 634 } else { 635 /* already pulled up in ip_demux() */ 636 KASSERT(m->m_len >= sizeof(struct ip) + off, 637 ("TCP header and options not in one mbuf: " 638 "m_len %d, off %d", m->m_len, off)); 639 } 640 optlen = off - sizeof(struct tcphdr); 641 optp = (u_char *)(th + 1); 642 } 643 thflags = th->th_flags; 644 645 #ifdef TCP_DROP_SYNFIN 646 /* 647 * If the drop_synfin option is enabled, drop all packets with 648 * both the SYN and FIN bits set. This prevents e.g. nmap from 649 * identifying the TCP/IP stack. 650 * 651 * This is a violation of the TCP specification. 652 */ 653 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 654 goto drop; 655 #endif 656 657 /* 658 * Convert TCP protocol specific fields to host format. 659 */ 660 th->th_seq = ntohl(th->th_seq); 661 th->th_ack = ntohl(th->th_ack); 662 th->th_win = ntohs(th->th_win); 663 th->th_urp = ntohs(th->th_urp); 664 665 /* 666 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 667 * until after ip6_savecontrol() is called and before other functions 668 * which don't want those proto headers. 669 * Because ip6_savecontrol() is going to parse the mbuf to 670 * search for data to be passed up to user-land, it wants mbuf 671 * parameters to be unchanged. 672 * XXX: the call of ip6_savecontrol() has been obsoleted based on 673 * latest version of the advanced API (20020110). 674 */ 675 drop_hdrlen = off0 + off; 676 677 /* 678 * Locate pcb for segment. 679 */ 680 findpcb: 681 /* IPFIREWALL_FORWARD section */ 682 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 683 /* 684 * Transparently forwarded. Pretend to be the destination. 685 * already got one like this? 686 */ 687 cpu = mycpu->gd_cpuid; 688 inp = in_pcblookup_hash(&tcbinfo[cpu], 689 ip->ip_src, th->th_sport, 690 ip->ip_dst, th->th_dport, 691 0, m->m_pkthdr.rcvif); 692 if (!inp) { 693 /* 694 * It's new. Try to find the ambushing socket. 695 */ 696 697 /* 698 * The rest of the ipfw code stores the port in 699 * host order. XXX 700 * (The IP address is still in network order.) 701 */ 702 in_port_t dport = next_hop->sin_port ? 703 htons(next_hop->sin_port) : 704 th->th_dport; 705 706 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 707 next_hop->sin_addr.s_addr, dport); 708 inp = in_pcblookup_hash(&tcbinfo[cpu], 709 ip->ip_src, th->th_sport, 710 next_hop->sin_addr, dport, 711 1, m->m_pkthdr.rcvif); 712 } 713 } else { 714 if (isipv6) { 715 inp = in6_pcblookup_hash(&tcbinfo[0], 716 &ip6->ip6_src, th->th_sport, 717 &ip6->ip6_dst, th->th_dport, 718 1, m->m_pkthdr.rcvif); 719 } else { 720 cpu = mycpu->gd_cpuid; 721 inp = in_pcblookup_hash(&tcbinfo[cpu], 722 ip->ip_src, th->th_sport, 723 ip->ip_dst, th->th_dport, 724 1, m->m_pkthdr.rcvif); 725 } 726 } 727 728 /* 729 * If the state is CLOSED (i.e., TCB does not exist) then 730 * all data in the incoming segment is discarded. 731 * If the TCB exists but is in CLOSED state, it is embryonic, 732 * but should either do a listen or a connect soon. 733 */ 734 if (inp == NULL) { 735 if (log_in_vain) { 736 #ifdef INET6 737 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 738 #else 739 char dbuf[4 * sizeof "123"], sbuf[4 * sizeof "123"]; 740 #endif 741 if (isipv6) { 742 strcpy(dbuf, "["); 743 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 744 strcat(dbuf, "]"); 745 strcpy(sbuf, "["); 746 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 747 strcat(sbuf, "]"); 748 } else { 749 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 750 strcpy(sbuf, inet_ntoa(ip->ip_src)); 751 } 752 switch (log_in_vain) { 753 case 1: 754 if (!(thflags & TH_SYN)) 755 break; 756 case 2: 757 log(LOG_INFO, 758 "Connection attempt to TCP %s:%d " 759 "from %s:%d flags:0x%02x\n", 760 dbuf, ntohs(th->th_dport), sbuf, 761 ntohs(th->th_sport), thflags); 762 break; 763 default: 764 break; 765 } 766 } 767 if (blackhole) { 768 switch (blackhole) { 769 case 1: 770 if (thflags & TH_SYN) 771 goto drop; 772 break; 773 case 2: 774 goto drop; 775 default: 776 goto drop; 777 } 778 } 779 rstreason = BANDLIM_RST_CLOSEDPORT; 780 goto dropwithreset; 781 } 782 783 #ifdef IPSEC 784 if (isipv6) { 785 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 786 ipsec6stat.in_polvio++; 787 goto drop; 788 } 789 } else { 790 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 791 ipsecstat.in_polvio++; 792 goto drop; 793 } 794 } 795 #endif 796 #ifdef FAST_IPSEC 797 if (isipv6) { 798 if (ipsec6_in_reject(m, inp)) 799 goto drop; 800 } else { 801 if (ipsec4_in_reject(m, inp)) 802 goto drop; 803 } 804 #endif 805 806 tp = intotcpcb(inp); 807 if (tp == NULL) { 808 rstreason = BANDLIM_RST_CLOSEDPORT; 809 goto dropwithreset; 810 } 811 if (tp->t_state <= TCPS_CLOSED) 812 goto drop; 813 814 /* Unscale the window into a 32-bit value. */ 815 if (!(thflags & TH_SYN)) 816 tiwin = th->th_win << tp->snd_scale; 817 else 818 tiwin = th->th_win; 819 820 so = inp->inp_socket; 821 822 #ifdef TCPDEBUG 823 if (so->so_options & SO_DEBUG) { 824 ostate = tp->t_state; 825 if (isipv6) 826 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 827 else 828 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 829 tcp_savetcp = *th; 830 } 831 #endif 832 833 bzero(&to, sizeof(to)); 834 835 if (so->so_options & SO_ACCEPTCONN) { 836 struct in_conninfo inc; 837 838 #ifdef INET6 839 inc.inc_isipv6 = (isipv6 == TRUE); 840 #endif 841 if (isipv6) { 842 inc.inc6_faddr = ip6->ip6_src; 843 inc.inc6_laddr = ip6->ip6_dst; 844 inc.inc6_route.ro_rt = NULL; /* XXX */ 845 } else { 846 inc.inc_faddr = ip->ip_src; 847 inc.inc_laddr = ip->ip_dst; 848 inc.inc_route.ro_rt = NULL; /* XXX */ 849 } 850 inc.inc_fport = th->th_sport; 851 inc.inc_lport = th->th_dport; 852 853 /* 854 * If the state is LISTEN then ignore segment if it contains 855 * a RST. If the segment contains an ACK then it is bad and 856 * send a RST. If it does not contain a SYN then it is not 857 * interesting; drop it. 858 * 859 * If the state is SYN_RECEIVED (syncache) and seg contains 860 * an ACK, but not for our SYN/ACK, send a RST. If the seg 861 * contains a RST, check the sequence number to see if it 862 * is a valid reset segment. 863 */ 864 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 865 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 866 if (!syncache_expand(&inc, th, &so, m)) { 867 /* 868 * No syncache entry, or ACK was not 869 * for our SYN/ACK. Send a RST. 870 */ 871 tcpstat.tcps_badsyn++; 872 rstreason = BANDLIM_RST_OPENPORT; 873 goto dropwithreset; 874 } 875 if (so == NULL) 876 /* 877 * Could not complete 3-way handshake, 878 * connection is being closed down, and 879 * syncache will free mbuf. 880 */ 881 return; 882 /* 883 * Socket is created in state SYN_RECEIVED. 884 * Continue processing segment. 885 */ 886 inp = sotoinpcb(so); 887 tp = intotcpcb(inp); 888 /* 889 * This is what would have happened in 890 * tcp_output() when the SYN,ACK was sent. 891 */ 892 tp->snd_up = tp->snd_una; 893 tp->snd_max = tp->snd_nxt = tp->iss + 1; 894 tp->last_ack_sent = tp->rcv_nxt; 895 /* 896 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 897 * until the _second_ ACK is received: 898 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 899 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 900 * move to ESTAB, set snd_wnd to tiwin. 901 */ 902 tp->snd_wnd = tiwin; /* unscaled */ 903 goto after_listen; 904 } 905 if (thflags & TH_RST) { 906 syncache_chkrst(&inc, th); 907 goto drop; 908 } 909 if (thflags & TH_ACK) { 910 syncache_badack(&inc); 911 tcpstat.tcps_badsyn++; 912 rstreason = BANDLIM_RST_OPENPORT; 913 goto dropwithreset; 914 } 915 goto drop; 916 } 917 918 /* 919 * Segment's flags are (SYN) or (SYN | FIN). 920 */ 921 #ifdef INET6 922 /* 923 * If deprecated address is forbidden, 924 * we do not accept SYN to deprecated interface 925 * address to prevent any new inbound connection from 926 * getting established. 927 * When we do not accept SYN, we send a TCP RST, 928 * with deprecated source address (instead of dropping 929 * it). We compromise it as it is much better for peer 930 * to send a RST, and RST will be the final packet 931 * for the exchange. 932 * 933 * If we do not forbid deprecated addresses, we accept 934 * the SYN packet. RFC2462 does not suggest dropping 935 * SYN in this case. 936 * If we decipher RFC2462 5.5.4, it says like this: 937 * 1. use of deprecated addr with existing 938 * communication is okay - "SHOULD continue to be 939 * used" 940 * 2. use of it with new communication: 941 * (2a) "SHOULD NOT be used if alternate address 942 * with sufficient scope is available" 943 * (2b) nothing mentioned otherwise. 944 * Here we fall into (2b) case as we have no choice in 945 * our source address selection - we must obey the peer. 946 * 947 * The wording in RFC2462 is confusing, and there are 948 * multiple description text for deprecated address 949 * handling - worse, they are not exactly the same. 950 * I believe 5.5.4 is the best one, so we follow 5.5.4. 951 */ 952 if (isipv6 && !ip6_use_deprecated) { 953 struct in6_ifaddr *ia6; 954 955 if ((ia6 = ip6_getdstifaddr(m)) && 956 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 957 tp = NULL; 958 rstreason = BANDLIM_RST_OPENPORT; 959 goto dropwithreset; 960 } 961 } 962 #endif 963 /* 964 * If it is from this socket, drop it, it must be forged. 965 * Don't bother responding if the destination was a broadcast. 966 */ 967 if (th->th_dport == th->th_sport) { 968 if (isipv6) { 969 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 970 &ip6->ip6_src)) 971 goto drop; 972 } else { 973 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 974 goto drop; 975 } 976 } 977 /* 978 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 979 * 980 * Note that it is quite possible to receive unicast 981 * link-layer packets with a broadcast IP address. Use 982 * in_broadcast() to find them. 983 */ 984 if (m->m_flags & (M_BCAST | M_MCAST)) 985 goto drop; 986 if (isipv6) { 987 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 988 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 989 goto drop; 990 } else { 991 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 992 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 993 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 994 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 995 goto drop; 996 } 997 /* 998 * SYN appears to be valid; create compressed TCP state 999 * for syncache, or perform t/tcp connection. 1000 */ 1001 if (so->so_qlen <= so->so_qlimit) { 1002 tcp_dooptions(&to, optp, optlen, TRUE); 1003 if (!syncache_add(&inc, &to, th, &so, m)) 1004 goto drop; 1005 if (so == NULL) 1006 /* 1007 * Entry added to syncache, mbuf used to 1008 * send SYN,ACK packet. 1009 */ 1010 return; 1011 /* 1012 * Segment passed TAO tests. 1013 */ 1014 inp = sotoinpcb(so); 1015 tp = intotcpcb(inp); 1016 tp->snd_wnd = tiwin; 1017 tp->t_starttime = ticks; 1018 tp->t_state = TCPS_ESTABLISHED; 1019 1020 /* 1021 * If there is a FIN, or if there is data and the 1022 * connection is local, then delay SYN,ACK(SYN) in 1023 * the hope of piggy-backing it on a response 1024 * segment. Otherwise must send ACK now in case 1025 * the other side is slow starting. 1026 */ 1027 if (DELAY_ACK(tp) && 1028 ((thflags & TH_FIN) || 1029 (tlen != 0 && 1030 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1031 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1032 callout_reset(tp->tt_delack, tcp_delacktime, 1033 tcp_timer_delack, tp); 1034 tp->t_flags |= TF_NEEDSYN; 1035 } else 1036 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1037 1038 tcpstat.tcps_connects++; 1039 soisconnected(so); 1040 goto trimthenstep6; 1041 } 1042 goto drop; 1043 } 1044 after_listen: 1045 1046 /* should not happen - syncache should pick up these connections */ 1047 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1048 1049 /* 1050 * Segment received on connection. 1051 * Reset idle time and keep-alive timer. 1052 */ 1053 tp->t_rcvtime = ticks; 1054 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1055 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1056 1057 /* 1058 * Process options. 1059 * XXX this is tradtitional behavior, may need to be cleaned up. 1060 */ 1061 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1062 if (thflags & TH_SYN) { 1063 if (to.to_flags & TOF_SCALE) { 1064 tp->t_flags |= TF_RCVD_SCALE; 1065 tp->requested_s_scale = to.to_requested_s_scale; 1066 } 1067 if (to.to_flags & TOF_TS) { 1068 tp->t_flags |= TF_RCVD_TSTMP; 1069 tp->ts_recent = to.to_tsval; 1070 tp->ts_recent_age = ticks; 1071 } 1072 if (to.to_flags & (TOF_CC | TOF_CCNEW)) 1073 tp->t_flags |= TF_RCVD_CC; 1074 if (to.to_flags & TOF_MSS) 1075 tcp_mss(tp, to.to_mss); 1076 /* 1077 * Only set the TF_SACK_PERMITTED per-connection flag 1078 * if we got a SACK_PERMITTED option from the other side 1079 * and the global tcp_do_sack variable is true. 1080 */ 1081 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1082 tp->t_flags |= TF_SACK_PERMITTED; 1083 } 1084 1085 /* 1086 * Header prediction: check for the two common cases 1087 * of a uni-directional data xfer. If the packet has 1088 * no control flags, is in-sequence, the window didn't 1089 * change and we're not retransmitting, it's a 1090 * candidate. If the length is zero and the ack moved 1091 * forward, we're the sender side of the xfer. Just 1092 * free the data acked & wake any higher level process 1093 * that was blocked waiting for space. If the length 1094 * is non-zero and the ack didn't move, we're the 1095 * receiver side. If we're getting packets in-order 1096 * (the reassembly queue is empty), add the data to 1097 * the socket buffer and note that we need a delayed ack. 1098 * Make sure that the hidden state-flags are also off. 1099 * Since we check for TCPS_ESTABLISHED above, it can only 1100 * be TH_NEEDSYN. 1101 */ 1102 if (tp->t_state == TCPS_ESTABLISHED && 1103 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1104 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1105 (!(to.to_flags & TOF_TS) || 1106 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1107 /* 1108 * Using the CC option is compulsory if once started: 1109 * the segment is OK if no T/TCP was negotiated or 1110 * if the segment has a CC option equal to CCrecv 1111 */ 1112 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1113 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) && 1114 th->th_seq == tp->rcv_nxt && 1115 tiwin && tiwin == tp->snd_wnd && 1116 tp->snd_nxt == tp->snd_max) { 1117 1118 /* 1119 * If last ACK falls within this segment's sequence numbers, 1120 * record the timestamp. 1121 * NOTE that the test is modified according to the latest 1122 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1123 */ 1124 if ((to.to_flags & TOF_TS) && 1125 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1126 tp->ts_recent_age = ticks; 1127 tp->ts_recent = to.to_tsval; 1128 } 1129 1130 if (tlen == 0) { 1131 if (SEQ_GT(th->th_ack, tp->snd_una) && 1132 SEQ_LEQ(th->th_ack, tp->snd_max) && 1133 tp->snd_cwnd >= tp->snd_wnd && 1134 !IN_FASTRECOVERY(tp)) { 1135 /* 1136 * this is a pure ack for outstanding data. 1137 */ 1138 ++tcpstat.tcps_predack; 1139 /* 1140 * "bad retransmit" recovery 1141 * 1142 * If Eifel detection applies, then 1143 * it is deterministic, so use it 1144 * unconditionally over the old heuristic. 1145 * Otherwise, fall back to the old heuristic. 1146 */ 1147 if (tcp_do_eifel_detect && 1148 (to.to_flags & TOF_TS) && to.to_tsecr && 1149 (tp->t_flags & TF_FIRSTACCACK)) { 1150 /* Eifel detection applicable. */ 1151 if (to.to_tsecr < tp->t_rexmtTS) { 1152 tcp_revert_congestion_state(tp); 1153 ++tcpstat.tcps_eifeldetected; 1154 } 1155 } else if (tp->t_rxtshift == 1 && 1156 ticks < tp->t_badrxtwin) { 1157 tcp_revert_congestion_state(tp); 1158 ++tcpstat.tcps_rttdetected; 1159 } 1160 tp->t_flags &= ~(TF_FIRSTACCACK | 1161 TF_FASTREXMT | TF_EARLYREXMT); 1162 /* 1163 * Recalculate the retransmit timer / rtt. 1164 * 1165 * Some machines (certain windows boxes) 1166 * send broken timestamp replies during the 1167 * SYN+ACK phase, ignore timestamps of 0. 1168 */ 1169 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1170 tcp_xmit_timer(tp, 1171 ticks - to.to_tsecr + 1); 1172 } else if (tp->t_rtttime && 1173 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1174 tcp_xmit_timer(tp, 1175 ticks - tp->t_rtttime); 1176 } 1177 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1178 acked = th->th_ack - tp->snd_una; 1179 tcpstat.tcps_rcvackpack++; 1180 tcpstat.tcps_rcvackbyte += acked; 1181 sbdrop(&so->so_snd, acked); 1182 tp->snd_recover = th->th_ack - 1; 1183 tp->snd_una = th->th_ack; 1184 tp->t_dupacks = 0; 1185 m_freem(m); 1186 ND6_HINT(tp); /* some progress has been done */ 1187 1188 /* 1189 * If all outstanding data are acked, stop 1190 * retransmit timer, otherwise restart timer 1191 * using current (possibly backed-off) value. 1192 * If process is waiting for space, 1193 * wakeup/selwakeup/signal. If data 1194 * are ready to send, let tcp_output 1195 * decide between more output or persist. 1196 */ 1197 if (tp->snd_una == tp->snd_max) 1198 callout_stop(tp->tt_rexmt); 1199 else if (!callout_active(tp->tt_persist)) 1200 callout_reset(tp->tt_rexmt, 1201 tp->t_rxtcur, 1202 tcp_timer_rexmt, tp); 1203 1204 sowwakeup(so); 1205 if (so->so_snd.sb_cc) 1206 (void) tcp_output(tp); 1207 return; 1208 } 1209 } else if (th->th_ack == tp->snd_una && 1210 LIST_EMPTY(&tp->t_segq) && 1211 tlen <= sbspace(&so->so_rcv)) { 1212 /* 1213 * this is a pure, in-sequence data packet 1214 * with nothing on the reassembly queue and 1215 * we have enough buffer space to take it. 1216 */ 1217 ++tcpstat.tcps_preddat; 1218 tp->rcv_nxt += tlen; 1219 tcpstat.tcps_rcvpack++; 1220 tcpstat.tcps_rcvbyte += tlen; 1221 ND6_HINT(tp); /* some progress has been done */ 1222 /* 1223 * Add data to socket buffer. 1224 */ 1225 if (so->so_state & SS_CANTRCVMORE) { 1226 m_freem(m); 1227 } else { 1228 m_adj(m, drop_hdrlen); /* delayed header drop */ 1229 sbappend(&so->so_rcv, m); 1230 } 1231 sorwakeup(so); 1232 1233 /* 1234 * This code is responsible for most of the ACKs 1235 * the TCP stack sends back after receiving a data 1236 * packet. Note that the DELAY_ACK check fails if 1237 * the delack timer is already running, which results 1238 * in an ack being sent every other packet (which is 1239 * what we want). 1240 */ 1241 if (DELAY_ACK(tp)) { 1242 callout_reset(tp->tt_delack, tcp_delacktime, 1243 tcp_timer_delack, tp); 1244 } else { 1245 tp->t_flags |= TF_ACKNOW; 1246 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1247 tp->t_flags |= TF_ONOUTPUTQ; 1248 tp->tt_cpu = mycpu->gd_cpuid; 1249 TAILQ_INSERT_TAIL( 1250 &tcpcbackq[tp->tt_cpu], 1251 tp, t_outputq); 1252 } 1253 } 1254 return; 1255 } 1256 } 1257 1258 /* 1259 * Calculate amount of space in receive window, 1260 * and then do TCP input processing. 1261 * Receive window is amount of space in rcv queue, 1262 * but not less than advertised window. 1263 */ 1264 recvwin = sbspace(&so->so_rcv); 1265 if (recvwin < 0) 1266 recvwin = 0; 1267 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1268 1269 switch (tp->t_state) { 1270 /* 1271 * If the state is SYN_RECEIVED: 1272 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1273 */ 1274 case TCPS_SYN_RECEIVED: 1275 if ((thflags & TH_ACK) && 1276 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1277 SEQ_GT(th->th_ack, tp->snd_max))) { 1278 rstreason = BANDLIM_RST_OPENPORT; 1279 goto dropwithreset; 1280 } 1281 break; 1282 1283 /* 1284 * If the state is SYN_SENT: 1285 * if seg contains an ACK, but not for our SYN, drop the input. 1286 * if seg contains a RST, then drop the connection. 1287 * if seg does not contain SYN, then drop it. 1288 * Otherwise this is an acceptable SYN segment 1289 * initialize tp->rcv_nxt and tp->irs 1290 * if seg contains ack then advance tp->snd_una 1291 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1292 * arrange for segment to be acked (eventually) 1293 * continue processing rest of data/controls, beginning with URG 1294 */ 1295 case TCPS_SYN_SENT: 1296 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1297 taop = &tao_noncached; 1298 bzero(taop, sizeof(*taop)); 1299 } 1300 1301 if ((thflags & TH_ACK) && 1302 (SEQ_LEQ(th->th_ack, tp->iss) || 1303 SEQ_GT(th->th_ack, tp->snd_max))) { 1304 /* 1305 * If we have a cached CCsent for the remote host, 1306 * hence we haven't just crashed and restarted, 1307 * do not send a RST. This may be a retransmission 1308 * from the other side after our earlier ACK was lost. 1309 * Our new SYN, when it arrives, will serve as the 1310 * needed ACK. 1311 */ 1312 if (taop->tao_ccsent != 0) 1313 goto drop; 1314 else { 1315 rstreason = BANDLIM_UNLIMITED; 1316 goto dropwithreset; 1317 } 1318 } 1319 if (thflags & TH_RST) { 1320 if (thflags & TH_ACK) 1321 tp = tcp_drop(tp, ECONNREFUSED); 1322 goto drop; 1323 } 1324 if (!(thflags & TH_SYN)) 1325 goto drop; 1326 tp->snd_wnd = th->th_win; /* initial send window */ 1327 tp->cc_recv = to.to_cc; /* foreign CC */ 1328 1329 tp->irs = th->th_seq; 1330 tcp_rcvseqinit(tp); 1331 if (thflags & TH_ACK) { 1332 /* 1333 * Our SYN was acked. If segment contains CC.ECHO 1334 * option, check it to make sure this segment really 1335 * matches our SYN. If not, just drop it as old 1336 * duplicate, but send an RST if we're still playing 1337 * by the old rules. If no CC.ECHO option, make sure 1338 * we don't get fooled into using T/TCP. 1339 */ 1340 if (to.to_flags & TOF_CCECHO) { 1341 if (tp->cc_send != to.to_ccecho) { 1342 if (taop->tao_ccsent != 0) 1343 goto drop; 1344 else { 1345 rstreason = BANDLIM_UNLIMITED; 1346 goto dropwithreset; 1347 } 1348 } 1349 } else 1350 tp->t_flags &= ~TF_RCVD_CC; 1351 tcpstat.tcps_connects++; 1352 soisconnected(so); 1353 /* Do window scaling on this connection? */ 1354 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1355 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1356 tp->snd_scale = tp->requested_s_scale; 1357 tp->rcv_scale = tp->request_r_scale; 1358 } 1359 /* Segment is acceptable, update cache if undefined. */ 1360 if (taop->tao_ccsent == 0) 1361 taop->tao_ccsent = to.to_ccecho; 1362 1363 tp->rcv_adv += tp->rcv_wnd; 1364 tp->snd_una++; /* SYN is acked */ 1365 callout_stop(tp->tt_rexmt); 1366 /* 1367 * If there's data, delay ACK; if there's also a FIN 1368 * ACKNOW will be turned on later. 1369 */ 1370 if (DELAY_ACK(tp) && tlen != 0) 1371 callout_reset(tp->tt_delack, tcp_delacktime, 1372 tcp_timer_delack, tp); 1373 else 1374 tp->t_flags |= TF_ACKNOW; 1375 /* 1376 * Received <SYN,ACK> in SYN_SENT[*] state. 1377 * Transitions: 1378 * SYN_SENT --> ESTABLISHED 1379 * SYN_SENT* --> FIN_WAIT_1 1380 */ 1381 tp->t_starttime = ticks; 1382 if (tp->t_flags & TF_NEEDFIN) { 1383 tp->t_state = TCPS_FIN_WAIT_1; 1384 tp->t_flags &= ~TF_NEEDFIN; 1385 thflags &= ~TH_SYN; 1386 } else { 1387 tp->t_state = TCPS_ESTABLISHED; 1388 callout_reset(tp->tt_keep, tcp_keepidle, 1389 tcp_timer_keep, tp); 1390 } 1391 } else { 1392 /* 1393 * Received initial SYN in SYN-SENT[*] state => 1394 * simultaneous open. If segment contains CC option 1395 * and there is a cached CC, apply TAO test. 1396 * If it succeeds, connection is * half-synchronized. 1397 * Otherwise, do 3-way handshake: 1398 * SYN-SENT -> SYN-RECEIVED 1399 * SYN-SENT* -> SYN-RECEIVED* 1400 * If there was no CC option, clear cached CC value. 1401 */ 1402 tp->t_flags |= TF_ACKNOW; 1403 callout_stop(tp->tt_rexmt); 1404 if (to.to_flags & TOF_CC) { 1405 if (taop->tao_cc != 0 && 1406 CC_GT(to.to_cc, taop->tao_cc)) { 1407 /* 1408 * update cache and make transition: 1409 * SYN-SENT -> ESTABLISHED* 1410 * SYN-SENT* -> FIN-WAIT-1* 1411 */ 1412 taop->tao_cc = to.to_cc; 1413 tp->t_starttime = ticks; 1414 if (tp->t_flags & TF_NEEDFIN) { 1415 tp->t_state = TCPS_FIN_WAIT_1; 1416 tp->t_flags &= ~TF_NEEDFIN; 1417 } else { 1418 tp->t_state = TCPS_ESTABLISHED; 1419 callout_reset(tp->tt_keep, 1420 tcp_keepidle, 1421 tcp_timer_keep, 1422 tp); 1423 } 1424 tp->t_flags |= TF_NEEDSYN; 1425 } else 1426 tp->t_state = TCPS_SYN_RECEIVED; 1427 } else { 1428 /* CC.NEW or no option => invalidate cache */ 1429 taop->tao_cc = 0; 1430 tp->t_state = TCPS_SYN_RECEIVED; 1431 } 1432 } 1433 1434 trimthenstep6: 1435 /* 1436 * Advance th->th_seq to correspond to first data byte. 1437 * If data, trim to stay within window, 1438 * dropping FIN if necessary. 1439 */ 1440 th->th_seq++; 1441 if (tlen > tp->rcv_wnd) { 1442 todrop = tlen - tp->rcv_wnd; 1443 m_adj(m, -todrop); 1444 tlen = tp->rcv_wnd; 1445 thflags &= ~TH_FIN; 1446 tcpstat.tcps_rcvpackafterwin++; 1447 tcpstat.tcps_rcvbyteafterwin += todrop; 1448 } 1449 tp->snd_wl1 = th->th_seq - 1; 1450 tp->rcv_up = th->th_seq; 1451 /* 1452 * Client side of transaction: already sent SYN and data. 1453 * If the remote host used T/TCP to validate the SYN, 1454 * our data will be ACK'd; if so, enter normal data segment 1455 * processing in the middle of step 5, ack processing. 1456 * Otherwise, goto step 6. 1457 */ 1458 if (thflags & TH_ACK) 1459 goto process_ACK; 1460 1461 goto step6; 1462 1463 /* 1464 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1465 * if segment contains a SYN and CC [not CC.NEW] option: 1466 * if state == TIME_WAIT and connection duration > MSL, 1467 * drop packet and send RST; 1468 * 1469 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1470 * ack the FIN (and data) in retransmission queue. 1471 * Complete close and delete TCPCB. Then reprocess 1472 * segment, hoping to find new TCPCB in LISTEN state; 1473 * 1474 * else must be old SYN; drop it. 1475 * else do normal processing. 1476 */ 1477 case TCPS_LAST_ACK: 1478 case TCPS_CLOSING: 1479 case TCPS_TIME_WAIT: 1480 if ((thflags & TH_SYN) && 1481 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1482 if (tp->t_state == TCPS_TIME_WAIT && 1483 (ticks - tp->t_starttime) > tcp_msl) { 1484 rstreason = BANDLIM_UNLIMITED; 1485 goto dropwithreset; 1486 } 1487 if (CC_GT(to.to_cc, tp->cc_recv)) { 1488 tp = tcp_close(tp); 1489 goto findpcb; 1490 } 1491 else 1492 goto drop; 1493 } 1494 break; /* continue normal processing */ 1495 } 1496 1497 /* 1498 * States other than LISTEN or SYN_SENT. 1499 * First check the RST flag and sequence number since reset segments 1500 * are exempt from the timestamp and connection count tests. This 1501 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1502 * below which allowed reset segments in half the sequence space 1503 * to fall though and be processed (which gives forged reset 1504 * segments with a random sequence number a 50 percent chance of 1505 * killing a connection). 1506 * Then check timestamp, if present. 1507 * Then check the connection count, if present. 1508 * Then check that at least some bytes of segment are within 1509 * receive window. If segment begins before rcv_nxt, 1510 * drop leading data (and SYN); if nothing left, just ack. 1511 * 1512 * 1513 * If the RST bit is set, check the sequence number to see 1514 * if this is a valid reset segment. 1515 * RFC 793 page 37: 1516 * In all states except SYN-SENT, all reset (RST) segments 1517 * are validated by checking their SEQ-fields. A reset is 1518 * valid if its sequence number is in the window. 1519 * Note: this does not take into account delayed ACKs, so 1520 * we should test against last_ack_sent instead of rcv_nxt. 1521 * The sequence number in the reset segment is normally an 1522 * echo of our outgoing acknowledgement numbers, but some hosts 1523 * send a reset with the sequence number at the rightmost edge 1524 * of our receive window, and we have to handle this case. 1525 * If we have multiple segments in flight, the intial reset 1526 * segment sequence numbers will be to the left of last_ack_sent, 1527 * but they will eventually catch up. 1528 * In any case, it never made sense to trim reset segments to 1529 * fit the receive window since RFC 1122 says: 1530 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1531 * 1532 * A TCP SHOULD allow a received RST segment to include data. 1533 * 1534 * DISCUSSION 1535 * It has been suggested that a RST segment could contain 1536 * ASCII text that encoded and explained the cause of the 1537 * RST. No standard has yet been established for such 1538 * data. 1539 * 1540 * If the reset segment passes the sequence number test examine 1541 * the state: 1542 * SYN_RECEIVED STATE: 1543 * If passive open, return to LISTEN state. 1544 * If active open, inform user that connection was refused. 1545 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1546 * Inform user that connection was reset, and close tcb. 1547 * CLOSING, LAST_ACK STATES: 1548 * Close the tcb. 1549 * TIME_WAIT STATE: 1550 * Drop the segment - see Stevens, vol. 2, p. 964 and 1551 * RFC 1337. 1552 */ 1553 if (thflags & TH_RST) { 1554 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1555 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1556 switch (tp->t_state) { 1557 1558 case TCPS_SYN_RECEIVED: 1559 so->so_error = ECONNREFUSED; 1560 goto close; 1561 1562 case TCPS_ESTABLISHED: 1563 case TCPS_FIN_WAIT_1: 1564 case TCPS_FIN_WAIT_2: 1565 case TCPS_CLOSE_WAIT: 1566 so->so_error = ECONNRESET; 1567 close: 1568 tp->t_state = TCPS_CLOSED; 1569 tcpstat.tcps_drops++; 1570 tp = tcp_close(tp); 1571 break; 1572 1573 case TCPS_CLOSING: 1574 case TCPS_LAST_ACK: 1575 tp = tcp_close(tp); 1576 break; 1577 1578 case TCPS_TIME_WAIT: 1579 break; 1580 } 1581 } 1582 goto drop; 1583 } 1584 1585 /* 1586 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1587 * and it's less than ts_recent, drop it. 1588 */ 1589 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1590 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1591 1592 /* Check to see if ts_recent is over 24 days old. */ 1593 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1594 /* 1595 * Invalidate ts_recent. If this segment updates 1596 * ts_recent, the age will be reset later and ts_recent 1597 * will get a valid value. If it does not, setting 1598 * ts_recent to zero will at least satisfy the 1599 * requirement that zero be placed in the timestamp 1600 * echo reply when ts_recent isn't valid. The 1601 * age isn't reset until we get a valid ts_recent 1602 * because we don't want out-of-order segments to be 1603 * dropped when ts_recent is old. 1604 */ 1605 tp->ts_recent = 0; 1606 } else { 1607 tcpstat.tcps_rcvduppack++; 1608 tcpstat.tcps_rcvdupbyte += tlen; 1609 tcpstat.tcps_pawsdrop++; 1610 if (tlen) 1611 goto dropafterack; 1612 goto drop; 1613 } 1614 } 1615 1616 /* 1617 * T/TCP mechanism 1618 * If T/TCP was negotiated and the segment doesn't have CC, 1619 * or if its CC is wrong then drop the segment. 1620 * RST segments do not have to comply with this. 1621 */ 1622 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1623 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc)) 1624 goto dropafterack; 1625 1626 /* 1627 * In the SYN-RECEIVED state, validate that the packet belongs to 1628 * this connection before trimming the data to fit the receive 1629 * window. Check the sequence number versus IRS since we know 1630 * the sequence numbers haven't wrapped. This is a partial fix 1631 * for the "LAND" DoS attack. 1632 */ 1633 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1634 rstreason = BANDLIM_RST_OPENPORT; 1635 goto dropwithreset; 1636 } 1637 1638 todrop = tp->rcv_nxt - th->th_seq; 1639 if (todrop > 0) { 1640 if (TCP_DO_SACK(tp)) { 1641 /* Report duplicate segment at head of packet. */ 1642 tp->reportblk.rblk_start = th->th_seq; 1643 tp->reportblk.rblk_end = th->th_seq + tlen; 1644 if (thflags & TH_FIN) 1645 ++tp->reportblk.rblk_end; 1646 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1647 tp->reportblk.rblk_end = tp->rcv_nxt; 1648 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1649 } 1650 if (thflags & TH_SYN) { 1651 thflags &= ~TH_SYN; 1652 th->th_seq++; 1653 if (th->th_urp > 1) 1654 th->th_urp--; 1655 else 1656 thflags &= ~TH_URG; 1657 todrop--; 1658 } 1659 /* 1660 * Following if statement from Stevens, vol. 2, p. 960. 1661 */ 1662 if (todrop > tlen || 1663 (todrop == tlen && !(thflags & TH_FIN))) { 1664 /* 1665 * Any valid FIN must be to the left of the window. 1666 * At this point the FIN must be a duplicate or out 1667 * of sequence; drop it. 1668 */ 1669 thflags &= ~TH_FIN; 1670 1671 /* 1672 * Send an ACK to resynchronize and drop any data. 1673 * But keep on processing for RST or ACK. 1674 */ 1675 tp->t_flags |= TF_ACKNOW; 1676 todrop = tlen; 1677 tcpstat.tcps_rcvduppack++; 1678 tcpstat.tcps_rcvdupbyte += todrop; 1679 } else { 1680 tcpstat.tcps_rcvpartduppack++; 1681 tcpstat.tcps_rcvpartdupbyte += todrop; 1682 } 1683 drop_hdrlen += todrop; /* drop from the top afterwards */ 1684 th->th_seq += todrop; 1685 tlen -= todrop; 1686 if (th->th_urp > todrop) 1687 th->th_urp -= todrop; 1688 else { 1689 thflags &= ~TH_URG; 1690 th->th_urp = 0; 1691 } 1692 } 1693 1694 /* 1695 * If new data are received on a connection after the 1696 * user processes are gone, then RST the other end. 1697 */ 1698 if ((so->so_state & SS_NOFDREF) && 1699 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1700 tp = tcp_close(tp); 1701 tcpstat.tcps_rcvafterclose++; 1702 rstreason = BANDLIM_UNLIMITED; 1703 goto dropwithreset; 1704 } 1705 1706 /* 1707 * If segment ends after window, drop trailing data 1708 * (and PUSH and FIN); if nothing left, just ACK. 1709 */ 1710 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1711 if (todrop > 0) { 1712 tcpstat.tcps_rcvpackafterwin++; 1713 if (todrop >= tlen) { 1714 tcpstat.tcps_rcvbyteafterwin += tlen; 1715 /* 1716 * If a new connection request is received 1717 * while in TIME_WAIT, drop the old connection 1718 * and start over if the sequence numbers 1719 * are above the previous ones. 1720 */ 1721 if (thflags & TH_SYN && 1722 tp->t_state == TCPS_TIME_WAIT && 1723 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1724 tp = tcp_close(tp); 1725 goto findpcb; 1726 } 1727 /* 1728 * If window is closed can only take segments at 1729 * window edge, and have to drop data and PUSH from 1730 * incoming segments. Continue processing, but 1731 * remember to ack. Otherwise, drop segment 1732 * and ack. 1733 */ 1734 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1735 tp->t_flags |= TF_ACKNOW; 1736 tcpstat.tcps_rcvwinprobe++; 1737 } else 1738 goto dropafterack; 1739 } else 1740 tcpstat.tcps_rcvbyteafterwin += todrop; 1741 m_adj(m, -todrop); 1742 tlen -= todrop; 1743 thflags &= ~(TH_PUSH | TH_FIN); 1744 } 1745 1746 /* 1747 * If last ACK falls within this segment's sequence numbers, 1748 * record its timestamp. 1749 * NOTE that the test is modified according to the latest 1750 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1751 */ 1752 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1753 tp->ts_recent_age = ticks; 1754 tp->ts_recent = to.to_tsval; 1755 } 1756 1757 /* 1758 * If a SYN is in the window, then this is an 1759 * error and we send an RST and drop the connection. 1760 */ 1761 if (thflags & TH_SYN) { 1762 tp = tcp_drop(tp, ECONNRESET); 1763 rstreason = BANDLIM_UNLIMITED; 1764 goto dropwithreset; 1765 } 1766 1767 /* 1768 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1769 * flag is on (half-synchronized state), then queue data for 1770 * later processing; else drop segment and return. 1771 */ 1772 if (!(thflags & TH_ACK)) { 1773 if (tp->t_state == TCPS_SYN_RECEIVED || 1774 (tp->t_flags & TF_NEEDSYN)) 1775 goto step6; 1776 else 1777 goto drop; 1778 } 1779 1780 /* 1781 * Ack processing. 1782 */ 1783 switch (tp->t_state) { 1784 /* 1785 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1786 * ESTABLISHED state and continue processing. 1787 * The ACK was checked above. 1788 */ 1789 case TCPS_SYN_RECEIVED: 1790 1791 tcpstat.tcps_connects++; 1792 soisconnected(so); 1793 /* Do window scaling? */ 1794 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1795 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1796 tp->snd_scale = tp->requested_s_scale; 1797 tp->rcv_scale = tp->request_r_scale; 1798 } 1799 /* 1800 * Upon successful completion of 3-way handshake, 1801 * update cache.CC if it was undefined, pass any queued 1802 * data to the user, and advance state appropriately. 1803 */ 1804 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1805 taop->tao_cc == 0) 1806 taop->tao_cc = tp->cc_recv; 1807 1808 /* 1809 * Make transitions: 1810 * SYN-RECEIVED -> ESTABLISHED 1811 * SYN-RECEIVED* -> FIN-WAIT-1 1812 */ 1813 tp->t_starttime = ticks; 1814 if (tp->t_flags & TF_NEEDFIN) { 1815 tp->t_state = TCPS_FIN_WAIT_1; 1816 tp->t_flags &= ~TF_NEEDFIN; 1817 } else { 1818 tp->t_state = TCPS_ESTABLISHED; 1819 callout_reset(tp->tt_keep, tcp_keepidle, 1820 tcp_timer_keep, tp); 1821 } 1822 /* 1823 * If segment contains data or ACK, will call tcp_reass() 1824 * later; if not, do so now to pass queued data to user. 1825 */ 1826 if (tlen == 0 && !(thflags & TH_FIN)) 1827 (void) tcp_reass(tp, NULL, NULL, NULL); 1828 /* fall into ... */ 1829 1830 /* 1831 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1832 * ACKs. If the ack is in the range 1833 * tp->snd_una < th->th_ack <= tp->snd_max 1834 * then advance tp->snd_una to th->th_ack and drop 1835 * data from the retransmission queue. If this ACK reflects 1836 * more up to date window information we update our window information. 1837 */ 1838 case TCPS_ESTABLISHED: 1839 case TCPS_FIN_WAIT_1: 1840 case TCPS_FIN_WAIT_2: 1841 case TCPS_CLOSE_WAIT: 1842 case TCPS_CLOSING: 1843 case TCPS_LAST_ACK: 1844 case TCPS_TIME_WAIT: 1845 1846 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1847 if (TCP_DO_SACK(tp)) 1848 tcp_sack_update_scoreboard(tp, &to); 1849 if (tlen != 0 || tiwin != tp->snd_wnd) { 1850 tp->t_dupacks = 0; 1851 break; 1852 } 1853 tcpstat.tcps_rcvdupack++; 1854 if (!callout_active(tp->tt_rexmt) || 1855 th->th_ack != tp->snd_una) { 1856 tp->t_dupacks = 0; 1857 break; 1858 } 1859 /* 1860 * We have outstanding data (other than 1861 * a window probe), this is a completely 1862 * duplicate ack (ie, window info didn't 1863 * change), the ack is the biggest we've 1864 * seen and we've seen exactly our rexmt 1865 * threshhold of them, so assume a packet 1866 * has been dropped and retransmit it. 1867 * Kludge snd_nxt & the congestion 1868 * window so we send only this one 1869 * packet. 1870 */ 1871 if (IN_FASTRECOVERY(tp)) { 1872 if (TCP_DO_SACK(tp)) { 1873 /* No artifical cwnd inflation. */ 1874 tcp_sack_rexmt(tp, th); 1875 } else { 1876 /* 1877 * Dup acks mean that packets 1878 * have left the network 1879 * (they're now cached at the 1880 * receiver) so bump cwnd by 1881 * the amount in the receiver 1882 * to keep a constant cwnd 1883 * packets in the network. 1884 */ 1885 tp->snd_cwnd += tp->t_maxseg; 1886 (void) tcp_output(tp); 1887 } 1888 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1889 tp->t_dupacks = 0; 1890 break; 1891 } else if (++tp->t_dupacks == tcprexmtthresh) { 1892 tcp_seq old_snd_nxt; 1893 u_int win; 1894 1895 fastretransmit: 1896 if (tcp_do_eifel_detect && 1897 (tp->t_flags & TF_RCVD_TSTMP)) { 1898 tcp_save_congestion_state(tp); 1899 tp->t_flags |= TF_FASTREXMT; 1900 } 1901 /* 1902 * We know we're losing at the current 1903 * window size, so do congestion avoidance: 1904 * set ssthresh to half the current window 1905 * and pull our congestion window back to the 1906 * new ssthresh. 1907 */ 1908 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1909 tp->t_maxseg; 1910 if (win < 2) 1911 win = 2; 1912 tp->snd_ssthresh = win * tp->t_maxseg; 1913 ENTER_FASTRECOVERY(tp); 1914 tp->snd_recover = tp->snd_max; 1915 callout_stop(tp->tt_rexmt); 1916 tp->t_rtttime = 0; 1917 old_snd_nxt = tp->snd_nxt; 1918 tp->snd_nxt = th->th_ack; 1919 tp->snd_cwnd = tp->t_maxseg; 1920 (void) tcp_output(tp); 1921 ++tcpstat.tcps_sndfastrexmit; 1922 tp->snd_cwnd = tp->snd_ssthresh; 1923 tp->rexmt_high = tp->snd_nxt; 1924 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1925 tp->snd_nxt = old_snd_nxt; 1926 KASSERT(tp->snd_limited <= 2, 1927 ("tp->snd_limited too big")); 1928 if (TCP_DO_SACK(tp)) 1929 tcp_sack_rexmt(tp, th); 1930 else 1931 tp->snd_cwnd += tp->t_maxseg * 1932 (tp->t_dupacks - tp->snd_limited); 1933 } else if (tcp_do_limitedtransmit) { 1934 u_long oldcwnd = tp->snd_cwnd; 1935 tcp_seq oldsndmax = tp->snd_max; 1936 /* outstanding data */ 1937 uint32_t ownd = tp->snd_max - tp->snd_una; 1938 u_int sent; 1939 1940 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1941 1942 KASSERT(tp->t_dupacks == 1 || 1943 tp->t_dupacks == 2, 1944 ("dupacks not 1 or 2")); 1945 if (tp->t_dupacks == 1) 1946 tp->snd_limited = 0; 1947 tp->snd_cwnd = ownd + 1948 (tp->t_dupacks - tp->snd_limited) * 1949 tp->t_maxseg; 1950 (void) tcp_output(tp); 1951 tp->snd_cwnd = oldcwnd; 1952 sent = tp->snd_max - oldsndmax; 1953 if (sent > tp->t_maxseg) { 1954 KASSERT((tp->t_dupacks == 2 && 1955 tp->snd_limited == 0) || 1956 (sent == tp->t_maxseg + 1 && 1957 tp->t_flags & TF_SENTFIN), 1958 ("sent too much")); 1959 KASSERT(sent <= tp->t_maxseg * 2, 1960 ("sent too many segments")); 1961 tp->snd_limited = 2; 1962 tcpstat.tcps_sndlimited += 2; 1963 } else if (sent > 0) { 1964 ++tp->snd_limited; 1965 ++tcpstat.tcps_sndlimited; 1966 } else if (tcp_do_early_retransmit && 1967 (tcp_do_eifel_detect && 1968 (tp->t_flags & TF_RCVD_TSTMP)) && 1969 ownd < 4 * tp->t_maxseg && 1970 tp->t_dupacks + 1 >= 1971 iceildiv(ownd, tp->t_maxseg) && 1972 (!TCP_DO_SACK(tp) || 1973 ownd <= tp->t_maxseg || 1974 tcp_sack_has_sacked(&tp->scb, 1975 ownd - tp->t_maxseg))) { 1976 ++tcpstat.tcps_sndearlyrexmit; 1977 tp->t_flags |= TF_EARLYREXMT; 1978 goto fastretransmit; 1979 } 1980 } 1981 goto drop; 1982 } 1983 1984 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1985 tp->t_dupacks = 0; 1986 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1987 /* 1988 * Detected optimistic ACK attack. 1989 * Force slow-start to de-synchronize attack. 1990 */ 1991 tp->snd_cwnd = tp->t_maxseg; 1992 1993 tcpstat.tcps_rcvacktoomuch++; 1994 goto dropafterack; 1995 } 1996 /* 1997 * If we reach this point, ACK is not a duplicate, 1998 * i.e., it ACKs something we sent. 1999 */ 2000 if (tp->t_flags & TF_NEEDSYN) { 2001 /* 2002 * T/TCP: Connection was half-synchronized, and our 2003 * SYN has been ACK'd (so connection is now fully 2004 * synchronized). Go to non-starred state, 2005 * increment snd_una for ACK of SYN, and check if 2006 * we can do window scaling. 2007 */ 2008 tp->t_flags &= ~TF_NEEDSYN; 2009 tp->snd_una++; 2010 /* Do window scaling? */ 2011 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2012 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2013 tp->snd_scale = tp->requested_s_scale; 2014 tp->rcv_scale = tp->request_r_scale; 2015 } 2016 } 2017 2018 process_ACK: 2019 acked = th->th_ack - tp->snd_una; 2020 tcpstat.tcps_rcvackpack++; 2021 tcpstat.tcps_rcvackbyte += acked; 2022 2023 if (tcp_do_eifel_detect && acked > 0 && 2024 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2025 (tp->t_flags & TF_FIRSTACCACK)) { 2026 /* Eifel detection applicable. */ 2027 if (to.to_tsecr < tp->t_rexmtTS) { 2028 ++tcpstat.tcps_eifeldetected; 2029 tcp_revert_congestion_state(tp); 2030 if (tp->t_rxtshift == 1 && 2031 ticks >= tp->t_badrxtwin) 2032 ++tcpstat.tcps_rttcantdetect; 2033 } 2034 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2035 /* 2036 * If we just performed our first retransmit, 2037 * and the ACK arrives within our recovery window, 2038 * then it was a mistake to do the retransmit 2039 * in the first place. Recover our original cwnd 2040 * and ssthresh, and proceed to transmit where we 2041 * left off. 2042 */ 2043 tcp_revert_congestion_state(tp); 2044 ++tcpstat.tcps_rttdetected; 2045 } 2046 2047 /* 2048 * If we have a timestamp reply, update smoothed 2049 * round trip time. If no timestamp is present but 2050 * transmit timer is running and timed sequence 2051 * number was acked, update smoothed round trip time. 2052 * Since we now have an rtt measurement, cancel the 2053 * timer backoff (cf., Phil Karn's retransmit alg.). 2054 * Recompute the initial retransmit timer. 2055 * 2056 * Some machines (certain windows boxes) send broken 2057 * timestamp replies during the SYN+ACK phase, ignore 2058 * timestamps of 0. 2059 */ 2060 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2061 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2062 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2063 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2064 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2065 2066 /* 2067 * If no data (only SYN) was ACK'd, 2068 * skip rest of ACK processing. 2069 */ 2070 if (acked == 0) 2071 goto step6; 2072 2073 /* Stop looking for an acceptable ACK since one was received. */ 2074 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2075 2076 if (acked > so->so_snd.sb_cc) { 2077 tp->snd_wnd -= so->so_snd.sb_cc; 2078 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2079 ourfinisacked = TRUE; 2080 } else { 2081 sbdrop(&so->so_snd, acked); 2082 tp->snd_wnd -= acked; 2083 ourfinisacked = FALSE; 2084 } 2085 sowwakeup(so); 2086 2087 /* 2088 * Update window information. 2089 * Don't look at window if no ACK: 2090 * TAC's send garbage on first SYN. 2091 */ 2092 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2093 (tp->snd_wl1 == th->th_seq && 2094 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2095 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2096 /* keep track of pure window updates */ 2097 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2098 tiwin > tp->snd_wnd) 2099 tcpstat.tcps_rcvwinupd++; 2100 tp->snd_wnd = tiwin; 2101 tp->snd_wl1 = th->th_seq; 2102 tp->snd_wl2 = th->th_ack; 2103 if (tp->snd_wnd > tp->max_sndwnd) 2104 tp->max_sndwnd = tp->snd_wnd; 2105 needoutput = TRUE; 2106 } 2107 2108 tp->snd_una = th->th_ack; 2109 if (TCP_DO_SACK(tp)) 2110 tcp_sack_update_scoreboard(tp, &to); 2111 if (IN_FASTRECOVERY(tp)) { 2112 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2113 EXIT_FASTRECOVERY(tp); 2114 needoutput = TRUE; 2115 /* 2116 * If the congestion window was inflated 2117 * to account for the other side's 2118 * cached packets, retract it. 2119 * 2120 * Window inflation should have left us 2121 * with approximately snd_ssthresh outstanding 2122 * data. But, in case we would be inclined 2123 * to send a burst, better do it using 2124 * slow start. 2125 */ 2126 if (!TCP_DO_SACK(tp)) 2127 tp->snd_cwnd = tp->snd_ssthresh; 2128 2129 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2130 tp->snd_max + 2 * tp->t_maxseg)) 2131 tp->snd_cwnd = 2132 (tp->snd_max - tp->snd_una) + 2133 2 * tp->t_maxseg; 2134 } else { 2135 if (TCP_DO_SACK(tp)) { 2136 tp->snd_max_rexmt = tp->snd_max; 2137 tcp_sack_rexmt(tp, th); 2138 } else { 2139 tcp_newreno_partial_ack(tp, th, acked); 2140 } 2141 needoutput = FALSE; 2142 } 2143 } else { 2144 /* 2145 * When new data is acked, open the congestion window. 2146 * If the window gives us less than ssthresh packets 2147 * in flight, open exponentially (maxseg per packet). 2148 * Otherwise open linearly: maxseg per window 2149 * (maxseg^2 / cwnd per packet). 2150 */ 2151 u_int cw = tp->snd_cwnd; 2152 u_int incr; 2153 2154 if (cw > tp->snd_ssthresh) 2155 incr = tp->t_maxseg * tp->t_maxseg / cw; 2156 else 2157 incr = tp->t_maxseg; 2158 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2159 tp->snd_recover = th->th_ack - 1; 2160 } 2161 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2162 tp->snd_nxt = tp->snd_una; 2163 2164 /* 2165 * If all outstanding data is acked, stop retransmit 2166 * timer and remember to restart (more output or persist). 2167 * If there is more data to be acked, restart retransmit 2168 * timer, using current (possibly backed-off) value. 2169 */ 2170 if (th->th_ack == tp->snd_max) { 2171 callout_stop(tp->tt_rexmt); 2172 needoutput = TRUE; 2173 } else if (!callout_active(tp->tt_persist)) 2174 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2175 tcp_timer_rexmt, tp); 2176 2177 switch (tp->t_state) { 2178 /* 2179 * In FIN_WAIT_1 STATE in addition to the processing 2180 * for the ESTABLISHED state if our FIN is now acknowledged 2181 * then enter FIN_WAIT_2. 2182 */ 2183 case TCPS_FIN_WAIT_1: 2184 if (ourfinisacked) { 2185 /* 2186 * If we can't receive any more 2187 * data, then closing user can proceed. 2188 * Starting the timer is contrary to the 2189 * specification, but if we don't get a FIN 2190 * we'll hang forever. 2191 */ 2192 if (so->so_state & SS_CANTRCVMORE) { 2193 soisdisconnected(so); 2194 callout_reset(tp->tt_2msl, tcp_maxidle, 2195 tcp_timer_2msl, tp); 2196 } 2197 tp->t_state = TCPS_FIN_WAIT_2; 2198 } 2199 break; 2200 2201 /* 2202 * In CLOSING STATE in addition to the processing for 2203 * the ESTABLISHED state if the ACK acknowledges our FIN 2204 * then enter the TIME-WAIT state, otherwise ignore 2205 * the segment. 2206 */ 2207 case TCPS_CLOSING: 2208 if (ourfinisacked) { 2209 tp->t_state = TCPS_TIME_WAIT; 2210 tcp_canceltimers(tp); 2211 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2212 if (tp->cc_recv != 0 && 2213 (ticks - tp->t_starttime) < tcp_msl) 2214 callout_reset(tp->tt_2msl, 2215 tp->t_rxtcur * TCPTV_TWTRUNC, 2216 tcp_timer_2msl, tp); 2217 else 2218 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2219 tcp_timer_2msl, tp); 2220 soisdisconnected(so); 2221 } 2222 break; 2223 2224 /* 2225 * In LAST_ACK, we may still be waiting for data to drain 2226 * and/or to be acked, as well as for the ack of our FIN. 2227 * If our FIN is now acknowledged, delete the TCB, 2228 * enter the closed state and return. 2229 */ 2230 case TCPS_LAST_ACK: 2231 if (ourfinisacked) { 2232 tp = tcp_close(tp); 2233 goto drop; 2234 } 2235 break; 2236 2237 /* 2238 * In TIME_WAIT state the only thing that should arrive 2239 * is a retransmission of the remote FIN. Acknowledge 2240 * it and restart the finack timer. 2241 */ 2242 case TCPS_TIME_WAIT: 2243 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2244 tcp_timer_2msl, tp); 2245 goto dropafterack; 2246 } 2247 } 2248 2249 step6: 2250 /* 2251 * Update window information. 2252 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2253 */ 2254 if ((thflags & TH_ACK) && 2255 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2256 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2257 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2258 /* keep track of pure window updates */ 2259 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2260 tiwin > tp->snd_wnd) 2261 tcpstat.tcps_rcvwinupd++; 2262 tp->snd_wnd = tiwin; 2263 tp->snd_wl1 = th->th_seq; 2264 tp->snd_wl2 = th->th_ack; 2265 if (tp->snd_wnd > tp->max_sndwnd) 2266 tp->max_sndwnd = tp->snd_wnd; 2267 needoutput = TRUE; 2268 } 2269 2270 /* 2271 * Process segments with URG. 2272 */ 2273 if ((thflags & TH_URG) && th->th_urp && 2274 !TCPS_HAVERCVDFIN(tp->t_state)) { 2275 /* 2276 * This is a kludge, but if we receive and accept 2277 * random urgent pointers, we'll crash in 2278 * soreceive. It's hard to imagine someone 2279 * actually wanting to send this much urgent data. 2280 */ 2281 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2282 th->th_urp = 0; /* XXX */ 2283 thflags &= ~TH_URG; /* XXX */ 2284 goto dodata; /* XXX */ 2285 } 2286 /* 2287 * If this segment advances the known urgent pointer, 2288 * then mark the data stream. This should not happen 2289 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2290 * a FIN has been received from the remote side. 2291 * In these states we ignore the URG. 2292 * 2293 * According to RFC961 (Assigned Protocols), 2294 * the urgent pointer points to the last octet 2295 * of urgent data. We continue, however, 2296 * to consider it to indicate the first octet 2297 * of data past the urgent section as the original 2298 * spec states (in one of two places). 2299 */ 2300 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2301 tp->rcv_up = th->th_seq + th->th_urp; 2302 so->so_oobmark = so->so_rcv.sb_cc + 2303 (tp->rcv_up - tp->rcv_nxt) - 1; 2304 if (so->so_oobmark == 0) 2305 so->so_state |= SS_RCVATMARK; 2306 sohasoutofband(so); 2307 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2308 } 2309 /* 2310 * Remove out of band data so doesn't get presented to user. 2311 * This can happen independent of advancing the URG pointer, 2312 * but if two URG's are pending at once, some out-of-band 2313 * data may creep in... ick. 2314 */ 2315 if (th->th_urp <= (u_long)tlen && 2316 !(so->so_options & SO_OOBINLINE)) { 2317 /* hdr drop is delayed */ 2318 tcp_pulloutofband(so, th, m, drop_hdrlen); 2319 } 2320 } else { 2321 /* 2322 * If no out of band data is expected, 2323 * pull receive urgent pointer along 2324 * with the receive window. 2325 */ 2326 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2327 tp->rcv_up = tp->rcv_nxt; 2328 } 2329 2330 dodata: /* XXX */ 2331 /* 2332 * Process the segment text, merging it into the TCP sequencing queue, 2333 * and arranging for acknowledgment of receipt if necessary. 2334 * This process logically involves adjusting tp->rcv_wnd as data 2335 * is presented to the user (this happens in tcp_usrreq.c, 2336 * case PRU_RCVD). If a FIN has already been received on this 2337 * connection then we just ignore the text. 2338 */ 2339 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2340 m_adj(m, drop_hdrlen); /* delayed header drop */ 2341 /* 2342 * Insert segment which includes th into TCP reassembly queue 2343 * with control block tp. Set thflags to whether reassembly now 2344 * includes a segment with FIN. This handles the common case 2345 * inline (segment is the next to be received on an established 2346 * connection, and the queue is empty), avoiding linkage into 2347 * and removal from the queue and repetition of various 2348 * conversions. 2349 * Set DELACK for segments received in order, but ack 2350 * immediately when segments are out of order (so 2351 * fast retransmit can work). 2352 */ 2353 if (th->th_seq == tp->rcv_nxt && 2354 LIST_EMPTY(&tp->t_segq) && 2355 TCPS_HAVEESTABLISHED(tp->t_state)) { 2356 if (DELAY_ACK(tp)) 2357 callout_reset(tp->tt_delack, tcp_delacktime, 2358 tcp_timer_delack, tp); 2359 else 2360 tp->t_flags |= TF_ACKNOW; 2361 tp->rcv_nxt += tlen; 2362 thflags = th->th_flags & TH_FIN; 2363 tcpstat.tcps_rcvpack++; 2364 tcpstat.tcps_rcvbyte += tlen; 2365 ND6_HINT(tp); 2366 if (so->so_state & SS_CANTRCVMORE) 2367 m_freem(m); 2368 else 2369 sbappend(&so->so_rcv, m); 2370 sorwakeup(so); 2371 } else { 2372 if (!(tp->t_flags & TF_DUPSEG)) { 2373 /* Initialize SACK report block. */ 2374 tp->reportblk.rblk_start = th->th_seq; 2375 tp->reportblk.rblk_end = th->th_seq + tlen + 2376 ((thflags & TH_FIN) != 0); 2377 } 2378 thflags = tcp_reass(tp, th, &tlen, m); 2379 tp->t_flags |= TF_ACKNOW; 2380 } 2381 2382 /* 2383 * Note the amount of data that peer has sent into 2384 * our window, in order to estimate the sender's 2385 * buffer size. 2386 */ 2387 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2388 } else { 2389 m_freem(m); 2390 thflags &= ~TH_FIN; 2391 } 2392 2393 /* 2394 * If FIN is received ACK the FIN and let the user know 2395 * that the connection is closing. 2396 */ 2397 if (thflags & TH_FIN) { 2398 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2399 socantrcvmore(so); 2400 /* 2401 * If connection is half-synchronized 2402 * (ie NEEDSYN flag on) then delay ACK, 2403 * so it may be piggybacked when SYN is sent. 2404 * Otherwise, since we received a FIN then no 2405 * more input can be expected, send ACK now. 2406 */ 2407 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2408 callout_reset(tp->tt_delack, tcp_delacktime, 2409 tcp_timer_delack, tp); 2410 else 2411 tp->t_flags |= TF_ACKNOW; 2412 tp->rcv_nxt++; 2413 } 2414 2415 switch (tp->t_state) { 2416 /* 2417 * In SYN_RECEIVED and ESTABLISHED STATES 2418 * enter the CLOSE_WAIT state. 2419 */ 2420 case TCPS_SYN_RECEIVED: 2421 tp->t_starttime = ticks; 2422 /*FALLTHROUGH*/ 2423 case TCPS_ESTABLISHED: 2424 tp->t_state = TCPS_CLOSE_WAIT; 2425 break; 2426 2427 /* 2428 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2429 * enter the CLOSING state. 2430 */ 2431 case TCPS_FIN_WAIT_1: 2432 tp->t_state = TCPS_CLOSING; 2433 break; 2434 2435 /* 2436 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2437 * starting the time-wait timer, turning off the other 2438 * standard timers. 2439 */ 2440 case TCPS_FIN_WAIT_2: 2441 tp->t_state = TCPS_TIME_WAIT; 2442 tcp_canceltimers(tp); 2443 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2444 if (tp->cc_recv != 0 && 2445 (ticks - tp->t_starttime) < tcp_msl) { 2446 callout_reset(tp->tt_2msl, 2447 tp->t_rxtcur * TCPTV_TWTRUNC, 2448 tcp_timer_2msl, tp); 2449 /* For transaction client, force ACK now. */ 2450 tp->t_flags |= TF_ACKNOW; 2451 } 2452 else 2453 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2454 tcp_timer_2msl, tp); 2455 soisdisconnected(so); 2456 break; 2457 2458 /* 2459 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2460 */ 2461 case TCPS_TIME_WAIT: 2462 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2463 tcp_timer_2msl, tp); 2464 break; 2465 } 2466 } 2467 2468 #ifdef TCPDEBUG 2469 if (so->so_options & SO_DEBUG) 2470 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2471 &tcp_savetcp, 0); 2472 #endif 2473 2474 /* 2475 * Return any desired output. 2476 */ 2477 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2478 (void) tcp_output(tp); 2479 return; 2480 2481 dropafterack: 2482 /* 2483 * Generate an ACK dropping incoming segment if it occupies 2484 * sequence space, where the ACK reflects our state. 2485 * 2486 * We can now skip the test for the RST flag since all 2487 * paths to this code happen after packets containing 2488 * RST have been dropped. 2489 * 2490 * In the SYN-RECEIVED state, don't send an ACK unless the 2491 * segment we received passes the SYN-RECEIVED ACK test. 2492 * If it fails send a RST. This breaks the loop in the 2493 * "LAND" DoS attack, and also prevents an ACK storm 2494 * between two listening ports that have been sent forged 2495 * SYN segments, each with the source address of the other. 2496 */ 2497 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2498 (SEQ_GT(tp->snd_una, th->th_ack) || 2499 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2500 rstreason = BANDLIM_RST_OPENPORT; 2501 goto dropwithreset; 2502 } 2503 #ifdef TCPDEBUG 2504 if (so->so_options & SO_DEBUG) 2505 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2506 &tcp_savetcp, 0); 2507 #endif 2508 m_freem(m); 2509 tp->t_flags |= TF_ACKNOW; 2510 (void) tcp_output(tp); 2511 return; 2512 2513 dropwithreset: 2514 /* 2515 * Generate a RST, dropping incoming segment. 2516 * Make ACK acceptable to originator of segment. 2517 * Don't bother to respond if destination was broadcast/multicast. 2518 */ 2519 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2520 goto drop; 2521 if (isipv6) { 2522 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2523 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2524 goto drop; 2525 } else { 2526 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2527 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2528 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2529 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2530 goto drop; 2531 } 2532 /* IPv6 anycast check is done at tcp6_input() */ 2533 2534 /* 2535 * Perform bandwidth limiting. 2536 */ 2537 #ifdef ICMP_BANDLIM 2538 if (badport_bandlim(rstreason) < 0) 2539 goto drop; 2540 #endif 2541 2542 #ifdef TCPDEBUG 2543 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2544 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2545 &tcp_savetcp, 0); 2546 #endif 2547 if (thflags & TH_ACK) 2548 /* mtod() below is safe as long as hdr dropping is delayed */ 2549 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2550 TH_RST); 2551 else { 2552 if (thflags & TH_SYN) 2553 tlen++; 2554 /* mtod() below is safe as long as hdr dropping is delayed */ 2555 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2556 (tcp_seq)0, TH_RST | TH_ACK); 2557 } 2558 return; 2559 2560 drop: 2561 /* 2562 * Drop space held by incoming segment and return. 2563 */ 2564 #ifdef TCPDEBUG 2565 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2566 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2567 &tcp_savetcp, 0); 2568 #endif 2569 m_freem(m); 2570 return; 2571 } 2572 2573 /* 2574 * Parse TCP options and place in tcpopt. 2575 */ 2576 static void 2577 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2578 { 2579 int opt, optlen, i; 2580 2581 to->to_flags = 0; 2582 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2583 opt = cp[0]; 2584 if (opt == TCPOPT_EOL) 2585 break; 2586 if (opt == TCPOPT_NOP) 2587 optlen = 1; 2588 else { 2589 if (cnt < 2) 2590 break; 2591 optlen = cp[1]; 2592 if (optlen < 2 || optlen > cnt) 2593 break; 2594 } 2595 switch (opt) { 2596 case TCPOPT_MAXSEG: 2597 if (optlen != TCPOLEN_MAXSEG) 2598 continue; 2599 if (!is_syn) 2600 continue; 2601 to->to_flags |= TOF_MSS; 2602 bcopy(cp + 2, &to->to_mss, sizeof(to->to_mss)); 2603 to->to_mss = ntohs(to->to_mss); 2604 break; 2605 case TCPOPT_WINDOW: 2606 if (optlen != TCPOLEN_WINDOW) 2607 continue; 2608 if (!is_syn) 2609 continue; 2610 to->to_flags |= TOF_SCALE; 2611 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2612 break; 2613 case TCPOPT_TIMESTAMP: 2614 if (optlen != TCPOLEN_TIMESTAMP) 2615 continue; 2616 to->to_flags |= TOF_TS; 2617 bcopy(cp + 2, &to->to_tsval, sizeof(to->to_tsval)); 2618 to->to_tsval = ntohl(to->to_tsval); 2619 bcopy(cp + 6, &to->to_tsecr, sizeof(to->to_tsecr)); 2620 to->to_tsecr = ntohl(to->to_tsecr); 2621 break; 2622 case TCPOPT_CC: 2623 if (optlen != TCPOLEN_CC) 2624 continue; 2625 to->to_flags |= TOF_CC; 2626 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc)); 2627 to->to_cc = ntohl(to->to_cc); 2628 break; 2629 case TCPOPT_CCNEW: 2630 if (optlen != TCPOLEN_CC) 2631 continue; 2632 if (!is_syn) 2633 continue; 2634 to->to_flags |= TOF_CCNEW; 2635 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc)); 2636 to->to_cc = ntohl(to->to_cc); 2637 break; 2638 case TCPOPT_CCECHO: 2639 if (optlen != TCPOLEN_CC) 2640 continue; 2641 if (!is_syn) 2642 continue; 2643 to->to_flags |= TOF_CCECHO; 2644 bcopy(cp + 2, &to->to_ccecho, sizeof(to->to_ccecho)); 2645 to->to_ccecho = ntohl(to->to_ccecho); 2646 break; 2647 case TCPOPT_SACK_PERMITTED: 2648 if (optlen != TCPOLEN_SACK_PERMITTED) 2649 continue; 2650 if (!is_syn) 2651 continue; 2652 to->to_flags |= TOF_SACK_PERMITTED; 2653 break; 2654 case TCPOPT_SACK: 2655 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2656 continue; 2657 to->to_nsackblocks = (optlen - 2) / 8; 2658 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2659 to->to_flags |= TOF_SACK; 2660 for (i = 0; i < to->to_nsackblocks; i++) { 2661 struct raw_sackblock *r = &to->to_sackblocks[i]; 2662 2663 r->rblk_start = ntohl(r->rblk_start); 2664 r->rblk_end = ntohl(r->rblk_end); 2665 } 2666 break; 2667 default: 2668 continue; 2669 } 2670 } 2671 } 2672 2673 /* 2674 * Pull out of band byte out of a segment so 2675 * it doesn't appear in the user's data queue. 2676 * It is still reflected in the segment length for 2677 * sequencing purposes. 2678 * "off" is the delayed to be dropped hdrlen. 2679 */ 2680 static void 2681 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2682 { 2683 int cnt = off + th->th_urp - 1; 2684 2685 while (cnt >= 0) { 2686 if (m->m_len > cnt) { 2687 char *cp = mtod(m, caddr_t) + cnt; 2688 struct tcpcb *tp = sototcpcb(so); 2689 2690 tp->t_iobc = *cp; 2691 tp->t_oobflags |= TCPOOB_HAVEDATA; 2692 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2693 m->m_len--; 2694 if (m->m_flags & M_PKTHDR) 2695 m->m_pkthdr.len--; 2696 return; 2697 } 2698 cnt -= m->m_len; 2699 m = m->m_next; 2700 if (m == 0) 2701 break; 2702 } 2703 panic("tcp_pulloutofband"); 2704 } 2705 2706 /* 2707 * Collect new round-trip time estimate 2708 * and update averages and current timeout. 2709 */ 2710 static void 2711 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2712 { 2713 int delta; 2714 2715 tcpstat.tcps_rttupdated++; 2716 tp->t_rttupdated++; 2717 if (tp->t_srtt != 0) { 2718 /* 2719 * srtt is stored as fixed point with 5 bits after the 2720 * binary point (i.e., scaled by 8). The following magic 2721 * is equivalent to the smoothing algorithm in rfc793 with 2722 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2723 * point). Adjust rtt to origin 0. 2724 */ 2725 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2726 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2727 2728 if ((tp->t_srtt += delta) <= 0) 2729 tp->t_srtt = 1; 2730 2731 /* 2732 * We accumulate a smoothed rtt variance (actually, a 2733 * smoothed mean difference), then set the retransmit 2734 * timer to smoothed rtt + 4 times the smoothed variance. 2735 * rttvar is stored as fixed point with 4 bits after the 2736 * binary point (scaled by 16). The following is 2737 * equivalent to rfc793 smoothing with an alpha of .75 2738 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2739 * rfc793's wired-in beta. 2740 */ 2741 if (delta < 0) 2742 delta = -delta; 2743 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2744 if ((tp->t_rttvar += delta) <= 0) 2745 tp->t_rttvar = 1; 2746 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2747 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2748 } else { 2749 /* 2750 * No rtt measurement yet - use the unsmoothed rtt. 2751 * Set the variance to half the rtt (so our first 2752 * retransmit happens at 3*rtt). 2753 */ 2754 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2755 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2756 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2757 } 2758 tp->t_rtttime = 0; 2759 tp->t_rxtshift = 0; 2760 2761 /* 2762 * the retransmit should happen at rtt + 4 * rttvar. 2763 * Because of the way we do the smoothing, srtt and rttvar 2764 * will each average +1/2 tick of bias. When we compute 2765 * the retransmit timer, we want 1/2 tick of rounding and 2766 * 1 extra tick because of +-1/2 tick uncertainty in the 2767 * firing of the timer. The bias will give us exactly the 2768 * 1.5 tick we need. But, because the bias is 2769 * statistical, we have to test that we don't drop below 2770 * the minimum feasible timer (which is 2 ticks). 2771 */ 2772 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2773 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2774 2775 /* 2776 * We received an ack for a packet that wasn't retransmitted; 2777 * it is probably safe to discard any error indications we've 2778 * received recently. This isn't quite right, but close enough 2779 * for now (a route might have failed after we sent a segment, 2780 * and the return path might not be symmetrical). 2781 */ 2782 tp->t_softerror = 0; 2783 } 2784 2785 /* 2786 * Determine a reasonable value for maxseg size. 2787 * If the route is known, check route for mtu. 2788 * If none, use an mss that can be handled on the outgoing 2789 * interface without forcing IP to fragment; if bigger than 2790 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2791 * to utilize large mbufs. If no route is found, route has no mtu, 2792 * or the destination isn't local, use a default, hopefully conservative 2793 * size (usually 512 or the default IP max size, but no more than the mtu 2794 * of the interface), as we can't discover anything about intervening 2795 * gateways or networks. We also initialize the congestion/slow start 2796 * window to be a single segment if the destination isn't local. 2797 * While looking at the routing entry, we also initialize other path-dependent 2798 * parameters from pre-set or cached values in the routing entry. 2799 * 2800 * Also take into account the space needed for options that we 2801 * send regularly. Make maxseg shorter by that amount to assure 2802 * that we can send maxseg amount of data even when the options 2803 * are present. Store the upper limit of the length of options plus 2804 * data in maxopd. 2805 * 2806 * NOTE that this routine is only called when we process an incoming 2807 * segment, for outgoing segments only tcp_mssopt is called. 2808 * 2809 * In case of T/TCP, we call this routine during implicit connection 2810 * setup as well (offer = -1), to initialize maxseg from the cached 2811 * MSS of our peer. 2812 */ 2813 void 2814 tcp_mss(struct tcpcb *tp, int offer) 2815 { 2816 struct rtentry *rt; 2817 struct ifnet *ifp; 2818 int rtt, mss; 2819 u_long bufsize; 2820 struct inpcb *inp = tp->t_inpcb; 2821 struct socket *so; 2822 struct rmxp_tao *taop; 2823 int origoffer = offer; 2824 #ifdef INET6 2825 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2826 size_t min_protoh = isipv6 ? 2827 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2828 sizeof(struct tcpiphdr); 2829 #else 2830 const boolean_t isipv6 = FALSE; 2831 const size_t min_protoh = sizeof(struct tcpiphdr); 2832 #endif 2833 2834 if (isipv6) 2835 rt = tcp_rtlookup6(&inp->inp_inc); 2836 else 2837 rt = tcp_rtlookup(&inp->inp_inc); 2838 if (rt == NULL) { 2839 tp->t_maxopd = tp->t_maxseg = 2840 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2841 return; 2842 } 2843 ifp = rt->rt_ifp; 2844 so = inp->inp_socket; 2845 2846 taop = rmx_taop(rt->rt_rmx); 2847 /* 2848 * Offer == -1 means that we didn't receive SYN yet, 2849 * use cached value in that case; 2850 */ 2851 if (offer == -1) 2852 offer = taop->tao_mssopt; 2853 /* 2854 * Offer == 0 means that there was no MSS on the SYN segment, 2855 * in this case we use tcp_mssdflt. 2856 */ 2857 if (offer == 0) 2858 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2859 else 2860 /* 2861 * Sanity check: make sure that maxopd will be large 2862 * enough to allow some data on segments even is the 2863 * all the option space is used (40bytes). Otherwise 2864 * funny things may happen in tcp_output. 2865 */ 2866 offer = max(offer, 64); 2867 taop->tao_mssopt = offer; 2868 2869 /* 2870 * While we're here, check if there's an initial rtt 2871 * or rttvar. Convert from the route-table units 2872 * to scaled multiples of the slow timeout timer. 2873 */ 2874 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2875 /* 2876 * XXX the lock bit for RTT indicates that the value 2877 * is also a minimum value; this is subject to time. 2878 */ 2879 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2880 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2881 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2882 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2883 tcpstat.tcps_usedrtt++; 2884 if (rt->rt_rmx.rmx_rttvar) { 2885 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2886 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2887 tcpstat.tcps_usedrttvar++; 2888 } else { 2889 /* default variation is +- 1 rtt */ 2890 tp->t_rttvar = 2891 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2892 } 2893 TCPT_RANGESET(tp->t_rxtcur, 2894 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2895 tp->t_rttmin, TCPTV_REXMTMAX); 2896 } 2897 /* 2898 * if there's an mtu associated with the route, use it 2899 * else, use the link mtu. 2900 */ 2901 if (rt->rt_rmx.rmx_mtu) 2902 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2903 else { 2904 if (isipv6) { 2905 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2906 min_protoh; 2907 if (!in6_localaddr(&inp->in6p_faddr)) 2908 mss = min(mss, tcp_v6mssdflt); 2909 } else { 2910 mss = ifp->if_mtu - min_protoh; 2911 if (!in_localaddr(inp->inp_faddr)) 2912 mss = min(mss, tcp_mssdflt); 2913 } 2914 } 2915 mss = min(mss, offer); 2916 /* 2917 * maxopd stores the maximum length of data AND options 2918 * in a segment; maxseg is the amount of data in a normal 2919 * segment. We need to store this value (maxopd) apart 2920 * from maxseg, because now every segment carries options 2921 * and thus we normally have somewhat less data in segments. 2922 */ 2923 tp->t_maxopd = mss; 2924 2925 /* 2926 * In case of T/TCP, origoffer==-1 indicates, that no segments 2927 * were received yet. In this case we just guess, otherwise 2928 * we do the same as before T/TCP. 2929 */ 2930 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 2931 (origoffer == -1 || 2932 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2933 mss -= TCPOLEN_TSTAMP_APPA; 2934 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 2935 (origoffer == -1 || 2936 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2937 mss -= TCPOLEN_CC_APPA; 2938 2939 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2940 if (mss > MCLBYTES) 2941 mss &= ~(MCLBYTES-1); 2942 #else 2943 if (mss > MCLBYTES) 2944 mss = mss / MCLBYTES * MCLBYTES; 2945 #endif 2946 /* 2947 * If there's a pipesize, change the socket buffer 2948 * to that size. Make the socket buffers an integral 2949 * number of mss units; if the mss is larger than 2950 * the socket buffer, decrease the mss. 2951 */ 2952 #ifdef RTV_SPIPE 2953 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2954 #endif 2955 bufsize = so->so_snd.sb_hiwat; 2956 if (bufsize < mss) 2957 mss = bufsize; 2958 else { 2959 bufsize = roundup(bufsize, mss); 2960 if (bufsize > sb_max) 2961 bufsize = sb_max; 2962 if (bufsize > so->so_snd.sb_hiwat) 2963 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2964 } 2965 tp->t_maxseg = mss; 2966 2967 #ifdef RTV_RPIPE 2968 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2969 #endif 2970 bufsize = so->so_rcv.sb_hiwat; 2971 if (bufsize > mss) { 2972 bufsize = roundup(bufsize, mss); 2973 if (bufsize > sb_max) 2974 bufsize = sb_max; 2975 if (bufsize > so->so_rcv.sb_hiwat) 2976 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2977 } 2978 2979 /* 2980 * Set the slow-start flight size depending on whether this 2981 * is a local network or not. 2982 */ 2983 if (tcp_do_rfc3390) 2984 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 2985 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2986 (!isipv6 && in_localaddr(inp->inp_faddr))) 2987 tp->snd_cwnd = mss * ss_fltsz_local; 2988 else 2989 tp->snd_cwnd = mss * ss_fltsz; 2990 2991 if (rt->rt_rmx.rmx_ssthresh) { 2992 /* 2993 * There's some sort of gateway or interface 2994 * buffer limit on the path. Use this to set 2995 * the slow start threshhold, but set the 2996 * threshold to no less than 2*mss. 2997 */ 2998 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2999 tcpstat.tcps_usedssthresh++; 3000 } 3001 } 3002 3003 /* 3004 * Determine the MSS option to send on an outgoing SYN. 3005 */ 3006 int 3007 tcp_mssopt(struct tcpcb *tp) 3008 { 3009 struct rtentry *rt; 3010 #ifdef INET6 3011 boolean_t isipv6 = 3012 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3013 int min_protoh = isipv6 ? 3014 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3015 sizeof(struct tcpiphdr); 3016 #else 3017 const boolean_t isipv6 = FALSE; 3018 const size_t min_protoh = sizeof(struct tcpiphdr); 3019 #endif 3020 3021 if (isipv6) 3022 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3023 else 3024 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3025 if (rt == NULL) 3026 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3027 3028 return (rt->rt_ifp->if_mtu - min_protoh); 3029 } 3030 3031 /* 3032 * When a partial ack arrives, force the retransmission of the 3033 * next unacknowledged segment. Do not exit Fast Recovery. 3034 * 3035 * Implement the Slow-but-Steady variant of NewReno by restarting the 3036 * the retransmission timer. Turn it off here so it can be restarted 3037 * later in tcp_output(). 3038 */ 3039 static void 3040 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3041 { 3042 tcp_seq old_snd_nxt = tp->snd_nxt; 3043 u_long ocwnd = tp->snd_cwnd; 3044 3045 callout_stop(tp->tt_rexmt); 3046 tp->t_rtttime = 0; 3047 tp->snd_nxt = th->th_ack; 3048 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3049 tp->snd_cwnd = tp->t_maxseg; 3050 tp->t_flags |= TF_ACKNOW; 3051 (void) tcp_output(tp); 3052 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3053 tp->snd_nxt = old_snd_nxt; 3054 /* partial window deflation */ 3055 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3056 } 3057 3058 /* 3059 * In contrast to the Slow-but-Steady NewReno variant, 3060 * we do not reset the retransmission timer for SACK retransmissions, 3061 * except when retransmitting snd_una. 3062 */ 3063 static void 3064 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3065 { 3066 uint32_t pipe, seglen; 3067 tcp_seq nextrexmt; 3068 boolean_t lostdup; 3069 tcp_seq old_snd_nxt = tp->snd_nxt; 3070 u_long ocwnd = tp->snd_cwnd; 3071 int nseg = 0; /* consecutive new segments */ 3072 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3073 3074 tp->t_rtttime = 0; 3075 pipe = tcp_sack_compute_pipe(tp); 3076 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3077 (!tcp_do_smartsack || nseg < MAXBURST) && 3078 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3079 uint32_t sent; 3080 tcp_seq old_snd_max; 3081 int error; 3082 3083 if (nextrexmt == tp->snd_max) ++nseg; 3084 tp->snd_nxt = nextrexmt; 3085 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3086 old_snd_max = tp->snd_max; 3087 if (nextrexmt == tp->snd_una) 3088 callout_stop(tp->tt_rexmt); 3089 error = tcp_output(tp); 3090 if (error != 0) 3091 break; 3092 sent = tp->snd_nxt - nextrexmt; 3093 if (sent <= 0) 3094 break; 3095 if (!lostdup) 3096 pipe += sent; 3097 tcpstat.tcps_sndsackpack++; 3098 tcpstat.tcps_sndsackbyte += sent; 3099 if (SEQ_LT(nextrexmt, old_snd_max) && 3100 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3101 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3102 } 3103 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3104 tp->snd_nxt = old_snd_nxt; 3105 tp->snd_cwnd = ocwnd; 3106 } 3107