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 1.46 2004/12/21 02:54:15 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 #define acceptable_window_update(tp, th, tiwin) \ 256 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 257 (tp->snd_wl1 == th->th_seq && \ 258 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 259 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 260 261 static int 262 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 263 { 264 struct tseg_qent *q; 265 struct tseg_qent *p = NULL; 266 struct tseg_qent *te; 267 struct socket *so = tp->t_inpcb->inp_socket; 268 int flags; 269 270 /* 271 * Call with th == NULL after become established to 272 * force pre-ESTABLISHED data up to user socket. 273 */ 274 if (th == NULL) 275 goto present; 276 277 /* 278 * Limit the number of segments in the reassembly queue to prevent 279 * holding on to too many segments (and thus running out of mbufs). 280 * Make sure to let the missing segment through which caused this 281 * queue. Always keep one global queue entry spare to be able to 282 * process the missing segment. 283 */ 284 if (th->th_seq != tp->rcv_nxt && 285 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 286 tcp_reass_overflows++; 287 tcpstat.tcps_rcvmemdrop++; 288 m_freem(m); 289 /* no SACK block to report */ 290 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 291 return (0); 292 } 293 294 /* Allocate a new queue entry. */ 295 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 296 M_INTWAIT | M_NULLOK); 297 if (te == NULL) { 298 tcpstat.tcps_rcvmemdrop++; 299 m_freem(m); 300 /* no SACK block to report */ 301 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 302 return (0); 303 } 304 tcp_reass_qsize++; 305 306 /* 307 * Find a segment which begins after this one does. 308 */ 309 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 310 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 311 break; 312 p = q; 313 } 314 315 /* 316 * If there is a preceding segment, it may provide some of 317 * our data already. If so, drop the data from the incoming 318 * segment. If it provides all of our data, drop us. 319 */ 320 if (p != NULL) { 321 int i; 322 323 /* conversion to int (in i) handles seq wraparound */ 324 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 325 if (i > 0) { /* overlaps preceding segment */ 326 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 327 /* enclosing block starts w/ preceding segment */ 328 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 329 if (i >= *tlenp) { 330 /* preceding encloses incoming segment */ 331 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 332 p->tqe_len; 333 tcpstat.tcps_rcvduppack++; 334 tcpstat.tcps_rcvdupbyte += *tlenp; 335 m_freem(m); 336 free(te, M_TSEGQ); 337 tcp_reass_qsize--; 338 /* 339 * Try to present any queued data 340 * at the left window edge to the user. 341 * This is needed after the 3-WHS 342 * completes. 343 */ 344 goto present; /* ??? */ 345 } 346 m_adj(m, i); 347 *tlenp -= i; 348 th->th_seq += i; 349 /* incoming segment end is enclosing block end */ 350 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 351 ((th->th_flags & TH_FIN) != 0); 352 /* trim end of reported D-SACK block */ 353 tp->reportblk.rblk_end = th->th_seq; 354 } 355 } 356 tcpstat.tcps_rcvoopack++; 357 tcpstat.tcps_rcvoobyte += *tlenp; 358 359 /* 360 * While we overlap succeeding segments trim them or, 361 * if they are completely covered, dequeue them. 362 */ 363 while (q) { 364 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 365 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 366 struct tseg_qent *nq; 367 368 if (i <= 0) 369 break; 370 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 371 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 372 tp->encloseblk = tp->reportblk; 373 /* report trailing duplicate D-SACK segment */ 374 tp->reportblk.rblk_start = q->tqe_th->th_seq; 375 } 376 if ((tp->t_flags & TF_ENCLOSESEG) && 377 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 378 /* extend enclosing block if one exists */ 379 tp->encloseblk.rblk_end = qend; 380 } 381 if (i < q->tqe_len) { 382 q->tqe_th->th_seq += i; 383 q->tqe_len -= i; 384 m_adj(q->tqe_m, i); 385 break; 386 } 387 388 nq = LIST_NEXT(q, tqe_q); 389 LIST_REMOVE(q, tqe_q); 390 m_freem(q->tqe_m); 391 free(q, M_TSEGQ); 392 tcp_reass_qsize--; 393 q = nq; 394 } 395 396 /* Insert the new segment queue entry into place. */ 397 te->tqe_m = m; 398 te->tqe_th = th; 399 te->tqe_len = *tlenp; 400 401 /* check if can coalesce with following segment */ 402 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 403 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 404 405 te->tqe_len += q->tqe_len; 406 if (q->tqe_th->th_flags & TH_FIN) 407 te->tqe_th->th_flags |= TH_FIN; 408 m_cat(te->tqe_m, q->tqe_m); 409 tp->encloseblk.rblk_end = tend; 410 /* 411 * When not reporting a duplicate segment, use 412 * the larger enclosing block as the SACK block. 413 */ 414 if (!(tp->t_flags & TF_DUPSEG)) 415 tp->reportblk.rblk_end = tend; 416 LIST_REMOVE(q, tqe_q); 417 free(q, M_TSEGQ); 418 tcp_reass_qsize--; 419 } 420 421 if (p == NULL) { 422 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 423 } else { 424 /* check if can coalesce with preceding segment */ 425 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 426 p->tqe_len += te->tqe_len; 427 m_cat(p->tqe_m, te->tqe_m); 428 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 429 /* 430 * When not reporting a duplicate segment, use 431 * the larger enclosing block as the SACK block. 432 */ 433 if (!(tp->t_flags & TF_DUPSEG)) 434 tp->reportblk.rblk_start = p->tqe_th->th_seq; 435 free(te, M_TSEGQ); 436 tcp_reass_qsize--; 437 } else 438 LIST_INSERT_AFTER(p, te, tqe_q); 439 } 440 441 present: 442 /* 443 * Present data to user, advancing rcv_nxt through 444 * completed sequence space. 445 */ 446 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 447 return (0); 448 q = LIST_FIRST(&tp->t_segq); 449 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 450 return (0); 451 tp->rcv_nxt += q->tqe_len; 452 if (!(tp->t_flags & TF_DUPSEG)) { 453 /* no SACK block to report since ACK advanced */ 454 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 455 } 456 /* no enclosing block to report since ACK advanced */ 457 tp->t_flags &= ~TF_ENCLOSESEG; 458 flags = q->tqe_th->th_flags & TH_FIN; 459 LIST_REMOVE(q, tqe_q); 460 KASSERT(LIST_EMPTY(&tp->t_segq) || 461 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 462 ("segment not coalesced")); 463 if (so->so_state & SS_CANTRCVMORE) 464 m_freem(q->tqe_m); 465 else 466 sbappendstream(&so->so_rcv, q->tqe_m); 467 free(q, M_TSEGQ); 468 tcp_reass_qsize--; 469 ND6_HINT(tp); 470 sorwakeup(so); 471 return (flags); 472 } 473 474 /* 475 * TCP input routine, follows pages 65-76 of the 476 * protocol specification dated September, 1981 very closely. 477 */ 478 #ifdef INET6 479 int 480 tcp6_input(struct mbuf **mp, int *offp, int proto) 481 { 482 struct mbuf *m = *mp; 483 struct in6_ifaddr *ia6; 484 485 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 486 487 /* 488 * draft-itojun-ipv6-tcp-to-anycast 489 * better place to put this in? 490 */ 491 ia6 = ip6_getdstifaddr(m); 492 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 493 struct ip6_hdr *ip6; 494 495 ip6 = mtod(m, struct ip6_hdr *); 496 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 497 offsetof(struct ip6_hdr, ip6_dst)); 498 return (IPPROTO_DONE); 499 } 500 501 tcp_input(m, *offp, proto); 502 return (IPPROTO_DONE); 503 } 504 #endif 505 506 void 507 tcp_input(struct mbuf *m, ...) 508 { 509 __va_list ap; 510 int off0, proto; 511 struct tcphdr *th; 512 struct ip *ip = NULL; 513 struct ipovly *ipov; 514 struct inpcb *inp = NULL; 515 u_char *optp = NULL; 516 int optlen = 0; 517 int len, tlen, off; 518 int drop_hdrlen; 519 struct tcpcb *tp = NULL; 520 int thflags; 521 struct socket *so = 0; 522 int todrop, acked; 523 boolean_t ourfinisacked, needoutput = FALSE; 524 u_long tiwin; 525 int recvwin; 526 struct tcpopt to; /* options in this segment */ 527 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 528 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 529 struct sockaddr_in *next_hop = NULL; 530 int rstreason; /* For badport_bandlim accounting purposes */ 531 int cpu; 532 struct ip6_hdr *ip6 = NULL; 533 #ifdef INET6 534 boolean_t isipv6; 535 #else 536 const boolean_t isipv6 = FALSE; 537 #endif 538 #ifdef TCPDEBUG 539 short ostate = 0; 540 #endif 541 542 __va_start(ap, m); 543 off0 = __va_arg(ap, int); 544 proto = __va_arg(ap, int); 545 __va_end(ap); 546 547 tcpstat.tcps_rcvtotal++; 548 549 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */ 550 while (m->m_type == MT_TAG) { 551 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 552 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 553 m = m->m_next; 554 } 555 556 #ifdef INET6 557 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 558 #endif 559 560 if (isipv6) { 561 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 562 ip6 = mtod(m, struct ip6_hdr *); 563 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 564 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 565 tcpstat.tcps_rcvbadsum++; 566 goto drop; 567 } 568 th = (struct tcphdr *)((caddr_t)ip6 + off0); 569 570 /* 571 * Be proactive about unspecified IPv6 address in source. 572 * As we use all-zero to indicate unbounded/unconnected pcb, 573 * unspecified IPv6 address can be used to confuse us. 574 * 575 * Note that packets with unspecified IPv6 destination is 576 * already dropped in ip6_input. 577 */ 578 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 579 /* XXX stat */ 580 goto drop; 581 } 582 } else { 583 /* 584 * Get IP and TCP header together in first mbuf. 585 * Note: IP leaves IP header in first mbuf. 586 */ 587 if (off0 > sizeof(struct ip)) { 588 ip_stripoptions(m); 589 off0 = sizeof(struct ip); 590 } 591 /* already checked and pulled up in ip_demux() */ 592 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 593 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 594 ip = mtod(m, struct ip *); 595 ipov = (struct ipovly *)ip; 596 th = (struct tcphdr *)((caddr_t)ip + off0); 597 tlen = ip->ip_len; 598 599 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 600 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 601 th->th_sum = m->m_pkthdr.csum_data; 602 else 603 th->th_sum = in_pseudo(ip->ip_src.s_addr, 604 ip->ip_dst.s_addr, 605 htonl(m->m_pkthdr.csum_data + 606 ip->ip_len + 607 IPPROTO_TCP)); 608 th->th_sum ^= 0xffff; 609 } else { 610 /* 611 * Checksum extended TCP header and data. 612 */ 613 len = sizeof(struct ip) + tlen; 614 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 615 ipov->ih_len = (u_short)tlen; 616 ipov->ih_len = htons(ipov->ih_len); 617 th->th_sum = in_cksum(m, len); 618 } 619 if (th->th_sum) { 620 tcpstat.tcps_rcvbadsum++; 621 goto drop; 622 } 623 #ifdef INET6 624 /* Re-initialization for later version check */ 625 ip->ip_v = IPVERSION; 626 #endif 627 } 628 629 /* 630 * Check that TCP offset makes sense, 631 * pull out TCP options and adjust length. XXX 632 */ 633 off = th->th_off << 2; 634 /* already checked and pulled up in ip_demux() */ 635 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 636 ("bad TCP data offset %d (tlen %d)", off, tlen)); 637 tlen -= off; /* tlen is used instead of ti->ti_len */ 638 if (off > sizeof(struct tcphdr)) { 639 if (isipv6) { 640 IP6_EXTHDR_CHECK(m, off0, off, ); 641 ip6 = mtod(m, struct ip6_hdr *); 642 th = (struct tcphdr *)((caddr_t)ip6 + off0); 643 } else { 644 /* already pulled up in ip_demux() */ 645 KASSERT(m->m_len >= sizeof(struct ip) + off, 646 ("TCP header and options not in one mbuf: " 647 "m_len %d, off %d", m->m_len, off)); 648 } 649 optlen = off - sizeof(struct tcphdr); 650 optp = (u_char *)(th + 1); 651 } 652 thflags = th->th_flags; 653 654 #ifdef TCP_DROP_SYNFIN 655 /* 656 * If the drop_synfin option is enabled, drop all packets with 657 * both the SYN and FIN bits set. This prevents e.g. nmap from 658 * identifying the TCP/IP stack. 659 * 660 * This is a violation of the TCP specification. 661 */ 662 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 663 goto drop; 664 #endif 665 666 /* 667 * Convert TCP protocol specific fields to host format. 668 */ 669 th->th_seq = ntohl(th->th_seq); 670 th->th_ack = ntohl(th->th_ack); 671 th->th_win = ntohs(th->th_win); 672 th->th_urp = ntohs(th->th_urp); 673 674 /* 675 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 676 * until after ip6_savecontrol() is called and before other functions 677 * which don't want those proto headers. 678 * Because ip6_savecontrol() is going to parse the mbuf to 679 * search for data to be passed up to user-land, it wants mbuf 680 * parameters to be unchanged. 681 * XXX: the call of ip6_savecontrol() has been obsoleted based on 682 * latest version of the advanced API (20020110). 683 */ 684 drop_hdrlen = off0 + off; 685 686 /* 687 * Locate pcb for segment. 688 */ 689 findpcb: 690 /* IPFIREWALL_FORWARD section */ 691 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 692 /* 693 * Transparently forwarded. Pretend to be the destination. 694 * already got one like this? 695 */ 696 cpu = mycpu->gd_cpuid; 697 inp = in_pcblookup_hash(&tcbinfo[cpu], 698 ip->ip_src, th->th_sport, 699 ip->ip_dst, th->th_dport, 700 0, m->m_pkthdr.rcvif); 701 if (!inp) { 702 /* 703 * It's new. Try to find the ambushing socket. 704 */ 705 706 /* 707 * The rest of the ipfw code stores the port in 708 * host order. XXX 709 * (The IP address is still in network order.) 710 */ 711 in_port_t dport = next_hop->sin_port ? 712 htons(next_hop->sin_port) : 713 th->th_dport; 714 715 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 716 next_hop->sin_addr.s_addr, dport); 717 inp = in_pcblookup_hash(&tcbinfo[cpu], 718 ip->ip_src, th->th_sport, 719 next_hop->sin_addr, dport, 720 1, m->m_pkthdr.rcvif); 721 } 722 } else { 723 if (isipv6) { 724 inp = in6_pcblookup_hash(&tcbinfo[0], 725 &ip6->ip6_src, th->th_sport, 726 &ip6->ip6_dst, th->th_dport, 727 1, m->m_pkthdr.rcvif); 728 } else { 729 cpu = mycpu->gd_cpuid; 730 inp = in_pcblookup_hash(&tcbinfo[cpu], 731 ip->ip_src, th->th_sport, 732 ip->ip_dst, th->th_dport, 733 1, m->m_pkthdr.rcvif); 734 } 735 } 736 737 /* 738 * If the state is CLOSED (i.e., TCB does not exist) then 739 * all data in the incoming segment is discarded. 740 * If the TCB exists but is in CLOSED state, it is embryonic, 741 * but should either do a listen or a connect soon. 742 */ 743 if (inp == NULL) { 744 if (log_in_vain) { 745 #ifdef INET6 746 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 747 #else 748 char dbuf[4 * sizeof "123"], sbuf[4 * sizeof "123"]; 749 #endif 750 if (isipv6) { 751 strcpy(dbuf, "["); 752 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 753 strcat(dbuf, "]"); 754 strcpy(sbuf, "["); 755 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 756 strcat(sbuf, "]"); 757 } else { 758 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 759 strcpy(sbuf, inet_ntoa(ip->ip_src)); 760 } 761 switch (log_in_vain) { 762 case 1: 763 if (!(thflags & TH_SYN)) 764 break; 765 case 2: 766 log(LOG_INFO, 767 "Connection attempt to TCP %s:%d " 768 "from %s:%d flags:0x%02x\n", 769 dbuf, ntohs(th->th_dport), sbuf, 770 ntohs(th->th_sport), thflags); 771 break; 772 default: 773 break; 774 } 775 } 776 if (blackhole) { 777 switch (blackhole) { 778 case 1: 779 if (thflags & TH_SYN) 780 goto drop; 781 break; 782 case 2: 783 goto drop; 784 default: 785 goto drop; 786 } 787 } 788 rstreason = BANDLIM_RST_CLOSEDPORT; 789 goto dropwithreset; 790 } 791 792 #ifdef IPSEC 793 if (isipv6) { 794 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 795 ipsec6stat.in_polvio++; 796 goto drop; 797 } 798 } else { 799 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 800 ipsecstat.in_polvio++; 801 goto drop; 802 } 803 } 804 #endif 805 #ifdef FAST_IPSEC 806 if (isipv6) { 807 if (ipsec6_in_reject(m, inp)) 808 goto drop; 809 } else { 810 if (ipsec4_in_reject(m, inp)) 811 goto drop; 812 } 813 #endif 814 815 tp = intotcpcb(inp); 816 if (tp == NULL) { 817 rstreason = BANDLIM_RST_CLOSEDPORT; 818 goto dropwithreset; 819 } 820 if (tp->t_state <= TCPS_CLOSED) 821 goto drop; 822 823 /* Unscale the window into a 32-bit value. */ 824 if (!(thflags & TH_SYN)) 825 tiwin = th->th_win << tp->snd_scale; 826 else 827 tiwin = th->th_win; 828 829 so = inp->inp_socket; 830 831 #ifdef TCPDEBUG 832 if (so->so_options & SO_DEBUG) { 833 ostate = tp->t_state; 834 if (isipv6) 835 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 836 else 837 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 838 tcp_savetcp = *th; 839 } 840 #endif 841 842 bzero(&to, sizeof(to)); 843 844 if (so->so_options & SO_ACCEPTCONN) { 845 struct in_conninfo inc; 846 847 #ifdef INET6 848 inc.inc_isipv6 = (isipv6 == TRUE); 849 #endif 850 if (isipv6) { 851 inc.inc6_faddr = ip6->ip6_src; 852 inc.inc6_laddr = ip6->ip6_dst; 853 inc.inc6_route.ro_rt = NULL; /* XXX */ 854 } else { 855 inc.inc_faddr = ip->ip_src; 856 inc.inc_laddr = ip->ip_dst; 857 inc.inc_route.ro_rt = NULL; /* XXX */ 858 } 859 inc.inc_fport = th->th_sport; 860 inc.inc_lport = th->th_dport; 861 862 /* 863 * If the state is LISTEN then ignore segment if it contains 864 * a RST. If the segment contains an ACK then it is bad and 865 * send a RST. If it does not contain a SYN then it is not 866 * interesting; drop it. 867 * 868 * If the state is SYN_RECEIVED (syncache) and seg contains 869 * an ACK, but not for our SYN/ACK, send a RST. If the seg 870 * contains a RST, check the sequence number to see if it 871 * is a valid reset segment. 872 */ 873 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 874 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 875 if (!syncache_expand(&inc, th, &so, m)) { 876 /* 877 * No syncache entry, or ACK was not 878 * for our SYN/ACK. Send a RST. 879 */ 880 tcpstat.tcps_badsyn++; 881 rstreason = BANDLIM_RST_OPENPORT; 882 goto dropwithreset; 883 } 884 if (so == NULL) 885 /* 886 * Could not complete 3-way handshake, 887 * connection is being closed down, and 888 * syncache will free mbuf. 889 */ 890 return; 891 /* 892 * Socket is created in state SYN_RECEIVED. 893 * Continue processing segment. 894 */ 895 inp = sotoinpcb(so); 896 tp = intotcpcb(inp); 897 /* 898 * This is what would have happened in 899 * tcp_output() when the SYN,ACK was sent. 900 */ 901 tp->snd_up = tp->snd_una; 902 tp->snd_max = tp->snd_nxt = tp->iss + 1; 903 tp->last_ack_sent = tp->rcv_nxt; 904 /* 905 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 906 * until the _second_ ACK is received: 907 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 908 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 909 * move to ESTAB, set snd_wnd to tiwin. 910 */ 911 tp->snd_wnd = tiwin; /* unscaled */ 912 goto after_listen; 913 } 914 if (thflags & TH_RST) { 915 syncache_chkrst(&inc, th); 916 goto drop; 917 } 918 if (thflags & TH_ACK) { 919 syncache_badack(&inc); 920 tcpstat.tcps_badsyn++; 921 rstreason = BANDLIM_RST_OPENPORT; 922 goto dropwithreset; 923 } 924 goto drop; 925 } 926 927 /* 928 * Segment's flags are (SYN) or (SYN | FIN). 929 */ 930 #ifdef INET6 931 /* 932 * If deprecated address is forbidden, 933 * we do not accept SYN to deprecated interface 934 * address to prevent any new inbound connection from 935 * getting established. 936 * When we do not accept SYN, we send a TCP RST, 937 * with deprecated source address (instead of dropping 938 * it). We compromise it as it is much better for peer 939 * to send a RST, and RST will be the final packet 940 * for the exchange. 941 * 942 * If we do not forbid deprecated addresses, we accept 943 * the SYN packet. RFC2462 does not suggest dropping 944 * SYN in this case. 945 * If we decipher RFC2462 5.5.4, it says like this: 946 * 1. use of deprecated addr with existing 947 * communication is okay - "SHOULD continue to be 948 * used" 949 * 2. use of it with new communication: 950 * (2a) "SHOULD NOT be used if alternate address 951 * with sufficient scope is available" 952 * (2b) nothing mentioned otherwise. 953 * Here we fall into (2b) case as we have no choice in 954 * our source address selection - we must obey the peer. 955 * 956 * The wording in RFC2462 is confusing, and there are 957 * multiple description text for deprecated address 958 * handling - worse, they are not exactly the same. 959 * I believe 5.5.4 is the best one, so we follow 5.5.4. 960 */ 961 if (isipv6 && !ip6_use_deprecated) { 962 struct in6_ifaddr *ia6; 963 964 if ((ia6 = ip6_getdstifaddr(m)) && 965 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 966 tp = NULL; 967 rstreason = BANDLIM_RST_OPENPORT; 968 goto dropwithreset; 969 } 970 } 971 #endif 972 /* 973 * If it is from this socket, drop it, it must be forged. 974 * Don't bother responding if the destination was a broadcast. 975 */ 976 if (th->th_dport == th->th_sport) { 977 if (isipv6) { 978 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 979 &ip6->ip6_src)) 980 goto drop; 981 } else { 982 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 983 goto drop; 984 } 985 } 986 /* 987 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 988 * 989 * Note that it is quite possible to receive unicast 990 * link-layer packets with a broadcast IP address. Use 991 * in_broadcast() to find them. 992 */ 993 if (m->m_flags & (M_BCAST | M_MCAST)) 994 goto drop; 995 if (isipv6) { 996 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 997 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 998 goto drop; 999 } else { 1000 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1001 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1002 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1003 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1004 goto drop; 1005 } 1006 /* 1007 * SYN appears to be valid; create compressed TCP state 1008 * for syncache, or perform t/tcp connection. 1009 */ 1010 if (so->so_qlen <= so->so_qlimit) { 1011 tcp_dooptions(&to, optp, optlen, TRUE); 1012 if (!syncache_add(&inc, &to, th, &so, m)) 1013 goto drop; 1014 if (so == NULL) 1015 /* 1016 * Entry added to syncache, mbuf used to 1017 * send SYN,ACK packet. 1018 */ 1019 return; 1020 /* 1021 * Segment passed TAO tests. 1022 */ 1023 inp = sotoinpcb(so); 1024 tp = intotcpcb(inp); 1025 tp->snd_wnd = tiwin; 1026 tp->t_starttime = ticks; 1027 tp->t_state = TCPS_ESTABLISHED; 1028 1029 /* 1030 * If there is a FIN, or if there is data and the 1031 * connection is local, then delay SYN,ACK(SYN) in 1032 * the hope of piggy-backing it on a response 1033 * segment. Otherwise must send ACK now in case 1034 * the other side is slow starting. 1035 */ 1036 if (DELAY_ACK(tp) && 1037 ((thflags & TH_FIN) || 1038 (tlen != 0 && 1039 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1040 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1041 callout_reset(tp->tt_delack, tcp_delacktime, 1042 tcp_timer_delack, tp); 1043 tp->t_flags |= TF_NEEDSYN; 1044 } else 1045 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1046 1047 tcpstat.tcps_connects++; 1048 soisconnected(so); 1049 goto trimthenstep6; 1050 } 1051 goto drop; 1052 } 1053 after_listen: 1054 1055 /* should not happen - syncache should pick up these connections */ 1056 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1057 1058 /* 1059 * Segment received on connection. 1060 * Reset idle time and keep-alive timer. 1061 */ 1062 tp->t_rcvtime = ticks; 1063 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1064 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1065 1066 /* 1067 * Process options. 1068 * XXX this is tradtitional behavior, may need to be cleaned up. 1069 */ 1070 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1071 if (thflags & TH_SYN) { 1072 if (to.to_flags & TOF_SCALE) { 1073 tp->t_flags |= TF_RCVD_SCALE; 1074 tp->requested_s_scale = to.to_requested_s_scale; 1075 } 1076 if (to.to_flags & TOF_TS) { 1077 tp->t_flags |= TF_RCVD_TSTMP; 1078 tp->ts_recent = to.to_tsval; 1079 tp->ts_recent_age = ticks; 1080 } 1081 if (to.to_flags & (TOF_CC | TOF_CCNEW)) 1082 tp->t_flags |= TF_RCVD_CC; 1083 if (to.to_flags & TOF_MSS) 1084 tcp_mss(tp, to.to_mss); 1085 /* 1086 * Only set the TF_SACK_PERMITTED per-connection flag 1087 * if we got a SACK_PERMITTED option from the other side 1088 * and the global tcp_do_sack variable is true. 1089 */ 1090 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1091 tp->t_flags |= TF_SACK_PERMITTED; 1092 } 1093 1094 /* 1095 * Header prediction: check for the two common cases 1096 * of a uni-directional data xfer. If the packet has 1097 * no control flags, is in-sequence, the window didn't 1098 * change and we're not retransmitting, it's a 1099 * candidate. If the length is zero and the ack moved 1100 * forward, we're the sender side of the xfer. Just 1101 * free the data acked & wake any higher level process 1102 * that was blocked waiting for space. If the length 1103 * is non-zero and the ack didn't move, we're the 1104 * receiver side. If we're getting packets in-order 1105 * (the reassembly queue is empty), add the data to 1106 * the socket buffer and note that we need a delayed ack. 1107 * Make sure that the hidden state-flags are also off. 1108 * Since we check for TCPS_ESTABLISHED above, it can only 1109 * be TH_NEEDSYN. 1110 */ 1111 if (tp->t_state == TCPS_ESTABLISHED && 1112 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1113 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1114 (!(to.to_flags & TOF_TS) || 1115 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1116 /* 1117 * Using the CC option is compulsory if once started: 1118 * the segment is OK if no T/TCP was negotiated or 1119 * if the segment has a CC option equal to CCrecv 1120 */ 1121 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1122 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) && 1123 th->th_seq == tp->rcv_nxt && 1124 tp->snd_nxt == tp->snd_max) { 1125 1126 /* 1127 * If last ACK falls within this segment's sequence numbers, 1128 * record the timestamp. 1129 * NOTE that the test is modified according to the latest 1130 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1131 */ 1132 if ((to.to_flags & TOF_TS) && 1133 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1134 tp->ts_recent_age = ticks; 1135 tp->ts_recent = to.to_tsval; 1136 } 1137 1138 if (tlen == 0) { 1139 if (SEQ_GT(th->th_ack, tp->snd_una) && 1140 SEQ_LEQ(th->th_ack, tp->snd_max) && 1141 tp->snd_cwnd >= tp->snd_wnd && 1142 !IN_FASTRECOVERY(tp)) { 1143 /* 1144 * this is a pure ack for outstanding data. 1145 */ 1146 ++tcpstat.tcps_predack; 1147 /* 1148 * "bad retransmit" recovery 1149 * 1150 * If Eifel detection applies, then 1151 * it is deterministic, so use it 1152 * unconditionally over the old heuristic. 1153 * Otherwise, fall back to the old heuristic. 1154 */ 1155 if (tcp_do_eifel_detect && 1156 (to.to_flags & TOF_TS) && to.to_tsecr && 1157 (tp->t_flags & TF_FIRSTACCACK)) { 1158 /* Eifel detection applicable. */ 1159 if (to.to_tsecr < tp->t_rexmtTS) { 1160 tcp_revert_congestion_state(tp); 1161 ++tcpstat.tcps_eifeldetected; 1162 } 1163 } else if (tp->t_rxtshift == 1 && 1164 ticks < tp->t_badrxtwin) { 1165 tcp_revert_congestion_state(tp); 1166 ++tcpstat.tcps_rttdetected; 1167 } 1168 tp->t_flags &= ~(TF_FIRSTACCACK | 1169 TF_FASTREXMT | TF_EARLYREXMT); 1170 /* 1171 * Recalculate the retransmit timer / rtt. 1172 * 1173 * Some machines (certain windows boxes) 1174 * send broken timestamp replies during the 1175 * SYN+ACK phase, ignore timestamps of 0. 1176 */ 1177 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1178 tcp_xmit_timer(tp, 1179 ticks - to.to_tsecr + 1); 1180 } else if (tp->t_rtttime && 1181 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1182 tcp_xmit_timer(tp, 1183 ticks - tp->t_rtttime); 1184 } 1185 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1186 acked = th->th_ack - tp->snd_una; 1187 tcpstat.tcps_rcvackpack++; 1188 tcpstat.tcps_rcvackbyte += acked; 1189 sbdrop(&so->so_snd, acked); 1190 tp->snd_recover = th->th_ack - 1; 1191 tp->snd_una = th->th_ack; 1192 tp->t_dupacks = 0; 1193 /* 1194 * Update window information. 1195 */ 1196 if (tiwin != tp->snd_wnd && 1197 acceptable_window_update(tp, th, tiwin)) { 1198 /* keep track of pure window updates */ 1199 if (tp->snd_wl2 == th->th_ack && 1200 tiwin > tp->snd_wnd) 1201 tcpstat.tcps_rcvwinupd++; 1202 tp->snd_wnd = tiwin; 1203 tp->snd_wl1 = th->th_seq; 1204 tp->snd_wl2 = th->th_ack; 1205 if (tp->snd_wnd > tp->max_sndwnd) 1206 tp->max_sndwnd = tp->snd_wnd; 1207 } 1208 m_freem(m); 1209 ND6_HINT(tp); /* some progress has been done */ 1210 /* 1211 * If all outstanding data are acked, stop 1212 * retransmit timer, otherwise restart timer 1213 * using current (possibly backed-off) value. 1214 * If process is waiting for space, 1215 * wakeup/selwakeup/signal. If data 1216 * are ready to send, let tcp_output 1217 * decide between more output or persist. 1218 */ 1219 if (tp->snd_una == tp->snd_max) 1220 callout_stop(tp->tt_rexmt); 1221 else if (!callout_active(tp->tt_persist)) 1222 callout_reset(tp->tt_rexmt, 1223 tp->t_rxtcur, 1224 tcp_timer_rexmt, tp); 1225 1226 sowwakeup(so); 1227 if (so->so_snd.sb_cc) 1228 tcp_output(tp); 1229 return; 1230 } 1231 } else if (tiwin == tp->snd_wnd && 1232 th->th_ack == tp->snd_una && 1233 LIST_EMPTY(&tp->t_segq) && 1234 tlen <= sbspace(&so->so_rcv)) { 1235 /* 1236 * this is a pure, in-sequence data packet 1237 * with nothing on the reassembly queue and 1238 * we have enough buffer space to take it. 1239 */ 1240 ++tcpstat.tcps_preddat; 1241 tp->rcv_nxt += tlen; 1242 tcpstat.tcps_rcvpack++; 1243 tcpstat.tcps_rcvbyte += tlen; 1244 ND6_HINT(tp); /* some progress has been done */ 1245 /* 1246 * Add data to socket buffer. 1247 */ 1248 if (so->so_state & SS_CANTRCVMORE) { 1249 m_freem(m); 1250 } else { 1251 m_adj(m, drop_hdrlen); /* delayed header drop */ 1252 sbappendstream(&so->so_rcv, m); 1253 } 1254 sorwakeup(so); 1255 1256 /* 1257 * This code is responsible for most of the ACKs 1258 * the TCP stack sends back after receiving a data 1259 * packet. Note that the DELAY_ACK check fails if 1260 * the delack timer is already running, which results 1261 * in an ack being sent every other packet (which is 1262 * what we want). 1263 */ 1264 if (DELAY_ACK(tp)) { 1265 callout_reset(tp->tt_delack, tcp_delacktime, 1266 tcp_timer_delack, tp); 1267 } else { 1268 tp->t_flags |= TF_ACKNOW; 1269 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1270 tp->t_flags |= TF_ONOUTPUTQ; 1271 tp->tt_cpu = mycpu->gd_cpuid; 1272 TAILQ_INSERT_TAIL( 1273 &tcpcbackq[tp->tt_cpu], 1274 tp, t_outputq); 1275 } 1276 } 1277 return; 1278 } 1279 } 1280 1281 /* 1282 * Calculate amount of space in receive window, 1283 * and then do TCP input processing. 1284 * Receive window is amount of space in rcv queue, 1285 * but not less than advertised window. 1286 */ 1287 recvwin = sbspace(&so->so_rcv); 1288 if (recvwin < 0) 1289 recvwin = 0; 1290 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1291 1292 switch (tp->t_state) { 1293 /* 1294 * If the state is SYN_RECEIVED: 1295 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1296 */ 1297 case TCPS_SYN_RECEIVED: 1298 if ((thflags & TH_ACK) && 1299 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1300 SEQ_GT(th->th_ack, tp->snd_max))) { 1301 rstreason = BANDLIM_RST_OPENPORT; 1302 goto dropwithreset; 1303 } 1304 break; 1305 1306 /* 1307 * If the state is SYN_SENT: 1308 * if seg contains an ACK, but not for our SYN, drop the input. 1309 * if seg contains a RST, then drop the connection. 1310 * if seg does not contain SYN, then drop it. 1311 * Otherwise this is an acceptable SYN segment 1312 * initialize tp->rcv_nxt and tp->irs 1313 * if seg contains ack then advance tp->snd_una 1314 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1315 * arrange for segment to be acked (eventually) 1316 * continue processing rest of data/controls, beginning with URG 1317 */ 1318 case TCPS_SYN_SENT: 1319 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1320 taop = &tao_noncached; 1321 bzero(taop, sizeof(*taop)); 1322 } 1323 1324 if ((thflags & TH_ACK) && 1325 (SEQ_LEQ(th->th_ack, tp->iss) || 1326 SEQ_GT(th->th_ack, tp->snd_max))) { 1327 /* 1328 * If we have a cached CCsent for the remote host, 1329 * hence we haven't just crashed and restarted, 1330 * do not send a RST. This may be a retransmission 1331 * from the other side after our earlier ACK was lost. 1332 * Our new SYN, when it arrives, will serve as the 1333 * needed ACK. 1334 */ 1335 if (taop->tao_ccsent != 0) 1336 goto drop; 1337 else { 1338 rstreason = BANDLIM_UNLIMITED; 1339 goto dropwithreset; 1340 } 1341 } 1342 if (thflags & TH_RST) { 1343 if (thflags & TH_ACK) 1344 tp = tcp_drop(tp, ECONNREFUSED); 1345 goto drop; 1346 } 1347 if (!(thflags & TH_SYN)) 1348 goto drop; 1349 tp->snd_wnd = th->th_win; /* initial send window */ 1350 tp->cc_recv = to.to_cc; /* foreign CC */ 1351 1352 tp->irs = th->th_seq; 1353 tcp_rcvseqinit(tp); 1354 if (thflags & TH_ACK) { 1355 /* 1356 * Our SYN was acked. If segment contains CC.ECHO 1357 * option, check it to make sure this segment really 1358 * matches our SYN. If not, just drop it as old 1359 * duplicate, but send an RST if we're still playing 1360 * by the old rules. If no CC.ECHO option, make sure 1361 * we don't get fooled into using T/TCP. 1362 */ 1363 if (to.to_flags & TOF_CCECHO) { 1364 if (tp->cc_send != to.to_ccecho) { 1365 if (taop->tao_ccsent != 0) 1366 goto drop; 1367 else { 1368 rstreason = BANDLIM_UNLIMITED; 1369 goto dropwithreset; 1370 } 1371 } 1372 } else 1373 tp->t_flags &= ~TF_RCVD_CC; 1374 tcpstat.tcps_connects++; 1375 soisconnected(so); 1376 /* Do window scaling on this connection? */ 1377 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1378 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1379 tp->snd_scale = tp->requested_s_scale; 1380 tp->rcv_scale = tp->request_r_scale; 1381 } 1382 /* Segment is acceptable, update cache if undefined. */ 1383 if (taop->tao_ccsent == 0) 1384 taop->tao_ccsent = to.to_ccecho; 1385 1386 tp->rcv_adv += tp->rcv_wnd; 1387 tp->snd_una++; /* SYN is acked */ 1388 callout_stop(tp->tt_rexmt); 1389 /* 1390 * If there's data, delay ACK; if there's also a FIN 1391 * ACKNOW will be turned on later. 1392 */ 1393 if (DELAY_ACK(tp) && tlen != 0) 1394 callout_reset(tp->tt_delack, tcp_delacktime, 1395 tcp_timer_delack, tp); 1396 else 1397 tp->t_flags |= TF_ACKNOW; 1398 /* 1399 * Received <SYN,ACK> in SYN_SENT[*] state. 1400 * Transitions: 1401 * SYN_SENT --> ESTABLISHED 1402 * SYN_SENT* --> FIN_WAIT_1 1403 */ 1404 tp->t_starttime = ticks; 1405 if (tp->t_flags & TF_NEEDFIN) { 1406 tp->t_state = TCPS_FIN_WAIT_1; 1407 tp->t_flags &= ~TF_NEEDFIN; 1408 thflags &= ~TH_SYN; 1409 } else { 1410 tp->t_state = TCPS_ESTABLISHED; 1411 callout_reset(tp->tt_keep, tcp_keepidle, 1412 tcp_timer_keep, tp); 1413 } 1414 } else { 1415 /* 1416 * Received initial SYN in SYN-SENT[*] state => 1417 * simultaneous open. If segment contains CC option 1418 * and there is a cached CC, apply TAO test. 1419 * If it succeeds, connection is * half-synchronized. 1420 * Otherwise, do 3-way handshake: 1421 * SYN-SENT -> SYN-RECEIVED 1422 * SYN-SENT* -> SYN-RECEIVED* 1423 * If there was no CC option, clear cached CC value. 1424 */ 1425 tp->t_flags |= TF_ACKNOW; 1426 callout_stop(tp->tt_rexmt); 1427 if (to.to_flags & TOF_CC) { 1428 if (taop->tao_cc != 0 && 1429 CC_GT(to.to_cc, taop->tao_cc)) { 1430 /* 1431 * update cache and make transition: 1432 * SYN-SENT -> ESTABLISHED* 1433 * SYN-SENT* -> FIN-WAIT-1* 1434 */ 1435 taop->tao_cc = to.to_cc; 1436 tp->t_starttime = ticks; 1437 if (tp->t_flags & TF_NEEDFIN) { 1438 tp->t_state = TCPS_FIN_WAIT_1; 1439 tp->t_flags &= ~TF_NEEDFIN; 1440 } else { 1441 tp->t_state = TCPS_ESTABLISHED; 1442 callout_reset(tp->tt_keep, 1443 tcp_keepidle, 1444 tcp_timer_keep, 1445 tp); 1446 } 1447 tp->t_flags |= TF_NEEDSYN; 1448 } else 1449 tp->t_state = TCPS_SYN_RECEIVED; 1450 } else { 1451 /* CC.NEW or no option => invalidate cache */ 1452 taop->tao_cc = 0; 1453 tp->t_state = TCPS_SYN_RECEIVED; 1454 } 1455 } 1456 1457 trimthenstep6: 1458 /* 1459 * Advance th->th_seq to correspond to first data byte. 1460 * If data, trim to stay within window, 1461 * dropping FIN if necessary. 1462 */ 1463 th->th_seq++; 1464 if (tlen > tp->rcv_wnd) { 1465 todrop = tlen - tp->rcv_wnd; 1466 m_adj(m, -todrop); 1467 tlen = tp->rcv_wnd; 1468 thflags &= ~TH_FIN; 1469 tcpstat.tcps_rcvpackafterwin++; 1470 tcpstat.tcps_rcvbyteafterwin += todrop; 1471 } 1472 tp->snd_wl1 = th->th_seq - 1; 1473 tp->rcv_up = th->th_seq; 1474 /* 1475 * Client side of transaction: already sent SYN and data. 1476 * If the remote host used T/TCP to validate the SYN, 1477 * our data will be ACK'd; if so, enter normal data segment 1478 * processing in the middle of step 5, ack processing. 1479 * Otherwise, goto step 6. 1480 */ 1481 if (thflags & TH_ACK) 1482 goto process_ACK; 1483 1484 goto step6; 1485 1486 /* 1487 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1488 * if segment contains a SYN and CC [not CC.NEW] option: 1489 * if state == TIME_WAIT and connection duration > MSL, 1490 * drop packet and send RST; 1491 * 1492 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1493 * ack the FIN (and data) in retransmission queue. 1494 * Complete close and delete TCPCB. Then reprocess 1495 * segment, hoping to find new TCPCB in LISTEN state; 1496 * 1497 * else must be old SYN; drop it. 1498 * else do normal processing. 1499 */ 1500 case TCPS_LAST_ACK: 1501 case TCPS_CLOSING: 1502 case TCPS_TIME_WAIT: 1503 if ((thflags & TH_SYN) && 1504 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1505 if (tp->t_state == TCPS_TIME_WAIT && 1506 (ticks - tp->t_starttime) > tcp_msl) { 1507 rstreason = BANDLIM_UNLIMITED; 1508 goto dropwithreset; 1509 } 1510 if (CC_GT(to.to_cc, tp->cc_recv)) { 1511 tp = tcp_close(tp); 1512 goto findpcb; 1513 } 1514 else 1515 goto drop; 1516 } 1517 break; /* continue normal processing */ 1518 } 1519 1520 /* 1521 * States other than LISTEN or SYN_SENT. 1522 * First check the RST flag and sequence number since reset segments 1523 * are exempt from the timestamp and connection count tests. This 1524 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1525 * below which allowed reset segments in half the sequence space 1526 * to fall though and be processed (which gives forged reset 1527 * segments with a random sequence number a 50 percent chance of 1528 * killing a connection). 1529 * Then check timestamp, if present. 1530 * Then check the connection count, if present. 1531 * Then check that at least some bytes of segment are within 1532 * receive window. If segment begins before rcv_nxt, 1533 * drop leading data (and SYN); if nothing left, just ack. 1534 * 1535 * 1536 * If the RST bit is set, check the sequence number to see 1537 * if this is a valid reset segment. 1538 * RFC 793 page 37: 1539 * In all states except SYN-SENT, all reset (RST) segments 1540 * are validated by checking their SEQ-fields. A reset is 1541 * valid if its sequence number is in the window. 1542 * Note: this does not take into account delayed ACKs, so 1543 * we should test against last_ack_sent instead of rcv_nxt. 1544 * The sequence number in the reset segment is normally an 1545 * echo of our outgoing acknowledgement numbers, but some hosts 1546 * send a reset with the sequence number at the rightmost edge 1547 * of our receive window, and we have to handle this case. 1548 * If we have multiple segments in flight, the intial reset 1549 * segment sequence numbers will be to the left of last_ack_sent, 1550 * but they will eventually catch up. 1551 * In any case, it never made sense to trim reset segments to 1552 * fit the receive window since RFC 1122 says: 1553 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1554 * 1555 * A TCP SHOULD allow a received RST segment to include data. 1556 * 1557 * DISCUSSION 1558 * It has been suggested that a RST segment could contain 1559 * ASCII text that encoded and explained the cause of the 1560 * RST. No standard has yet been established for such 1561 * data. 1562 * 1563 * If the reset segment passes the sequence number test examine 1564 * the state: 1565 * SYN_RECEIVED STATE: 1566 * If passive open, return to LISTEN state. 1567 * If active open, inform user that connection was refused. 1568 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1569 * Inform user that connection was reset, and close tcb. 1570 * CLOSING, LAST_ACK STATES: 1571 * Close the tcb. 1572 * TIME_WAIT STATE: 1573 * Drop the segment - see Stevens, vol. 2, p. 964 and 1574 * RFC 1337. 1575 */ 1576 if (thflags & TH_RST) { 1577 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1578 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1579 switch (tp->t_state) { 1580 1581 case TCPS_SYN_RECEIVED: 1582 so->so_error = ECONNREFUSED; 1583 goto close; 1584 1585 case TCPS_ESTABLISHED: 1586 case TCPS_FIN_WAIT_1: 1587 case TCPS_FIN_WAIT_2: 1588 case TCPS_CLOSE_WAIT: 1589 so->so_error = ECONNRESET; 1590 close: 1591 tp->t_state = TCPS_CLOSED; 1592 tcpstat.tcps_drops++; 1593 tp = tcp_close(tp); 1594 break; 1595 1596 case TCPS_CLOSING: 1597 case TCPS_LAST_ACK: 1598 tp = tcp_close(tp); 1599 break; 1600 1601 case TCPS_TIME_WAIT: 1602 break; 1603 } 1604 } 1605 goto drop; 1606 } 1607 1608 /* 1609 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1610 * and it's less than ts_recent, drop it. 1611 */ 1612 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1613 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1614 1615 /* Check to see if ts_recent is over 24 days old. */ 1616 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1617 /* 1618 * Invalidate ts_recent. If this segment updates 1619 * ts_recent, the age will be reset later and ts_recent 1620 * will get a valid value. If it does not, setting 1621 * ts_recent to zero will at least satisfy the 1622 * requirement that zero be placed in the timestamp 1623 * echo reply when ts_recent isn't valid. The 1624 * age isn't reset until we get a valid ts_recent 1625 * because we don't want out-of-order segments to be 1626 * dropped when ts_recent is old. 1627 */ 1628 tp->ts_recent = 0; 1629 } else { 1630 tcpstat.tcps_rcvduppack++; 1631 tcpstat.tcps_rcvdupbyte += tlen; 1632 tcpstat.tcps_pawsdrop++; 1633 if (tlen) 1634 goto dropafterack; 1635 goto drop; 1636 } 1637 } 1638 1639 /* 1640 * T/TCP mechanism 1641 * If T/TCP was negotiated and the segment doesn't have CC, 1642 * or if its CC is wrong then drop the segment. 1643 * RST segments do not have to comply with this. 1644 */ 1645 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1646 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc)) 1647 goto dropafterack; 1648 1649 /* 1650 * In the SYN-RECEIVED state, validate that the packet belongs to 1651 * this connection before trimming the data to fit the receive 1652 * window. Check the sequence number versus IRS since we know 1653 * the sequence numbers haven't wrapped. This is a partial fix 1654 * for the "LAND" DoS attack. 1655 */ 1656 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1657 rstreason = BANDLIM_RST_OPENPORT; 1658 goto dropwithreset; 1659 } 1660 1661 todrop = tp->rcv_nxt - th->th_seq; 1662 if (todrop > 0) { 1663 if (TCP_DO_SACK(tp)) { 1664 /* Report duplicate segment at head of packet. */ 1665 tp->reportblk.rblk_start = th->th_seq; 1666 tp->reportblk.rblk_end = th->th_seq + tlen; 1667 if (thflags & TH_FIN) 1668 ++tp->reportblk.rblk_end; 1669 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1670 tp->reportblk.rblk_end = tp->rcv_nxt; 1671 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1672 } 1673 if (thflags & TH_SYN) { 1674 thflags &= ~TH_SYN; 1675 th->th_seq++; 1676 if (th->th_urp > 1) 1677 th->th_urp--; 1678 else 1679 thflags &= ~TH_URG; 1680 todrop--; 1681 } 1682 /* 1683 * Following if statement from Stevens, vol. 2, p. 960. 1684 */ 1685 if (todrop > tlen || 1686 (todrop == tlen && !(thflags & TH_FIN))) { 1687 /* 1688 * Any valid FIN must be to the left of the window. 1689 * At this point the FIN must be a duplicate or out 1690 * of sequence; drop it. 1691 */ 1692 thflags &= ~TH_FIN; 1693 1694 /* 1695 * Send an ACK to resynchronize and drop any data. 1696 * But keep on processing for RST or ACK. 1697 */ 1698 tp->t_flags |= TF_ACKNOW; 1699 todrop = tlen; 1700 tcpstat.tcps_rcvduppack++; 1701 tcpstat.tcps_rcvdupbyte += todrop; 1702 } else { 1703 tcpstat.tcps_rcvpartduppack++; 1704 tcpstat.tcps_rcvpartdupbyte += todrop; 1705 } 1706 drop_hdrlen += todrop; /* drop from the top afterwards */ 1707 th->th_seq += todrop; 1708 tlen -= todrop; 1709 if (th->th_urp > todrop) 1710 th->th_urp -= todrop; 1711 else { 1712 thflags &= ~TH_URG; 1713 th->th_urp = 0; 1714 } 1715 } 1716 1717 /* 1718 * If new data are received on a connection after the 1719 * user processes are gone, then RST the other end. 1720 */ 1721 if ((so->so_state & SS_NOFDREF) && 1722 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1723 tp = tcp_close(tp); 1724 tcpstat.tcps_rcvafterclose++; 1725 rstreason = BANDLIM_UNLIMITED; 1726 goto dropwithreset; 1727 } 1728 1729 /* 1730 * If segment ends after window, drop trailing data 1731 * (and PUSH and FIN); if nothing left, just ACK. 1732 */ 1733 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1734 if (todrop > 0) { 1735 tcpstat.tcps_rcvpackafterwin++; 1736 if (todrop >= tlen) { 1737 tcpstat.tcps_rcvbyteafterwin += tlen; 1738 /* 1739 * If a new connection request is received 1740 * while in TIME_WAIT, drop the old connection 1741 * and start over if the sequence numbers 1742 * are above the previous ones. 1743 */ 1744 if (thflags & TH_SYN && 1745 tp->t_state == TCPS_TIME_WAIT && 1746 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1747 tp = tcp_close(tp); 1748 goto findpcb; 1749 } 1750 /* 1751 * If window is closed can only take segments at 1752 * window edge, and have to drop data and PUSH from 1753 * incoming segments. Continue processing, but 1754 * remember to ack. Otherwise, drop segment 1755 * and ack. 1756 */ 1757 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1758 tp->t_flags |= TF_ACKNOW; 1759 tcpstat.tcps_rcvwinprobe++; 1760 } else 1761 goto dropafterack; 1762 } else 1763 tcpstat.tcps_rcvbyteafterwin += todrop; 1764 m_adj(m, -todrop); 1765 tlen -= todrop; 1766 thflags &= ~(TH_PUSH | TH_FIN); 1767 } 1768 1769 /* 1770 * If last ACK falls within this segment's sequence numbers, 1771 * record its timestamp. 1772 * NOTE that the test is modified according to the latest 1773 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1774 */ 1775 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1776 tp->ts_recent_age = ticks; 1777 tp->ts_recent = to.to_tsval; 1778 } 1779 1780 /* 1781 * If a SYN is in the window, then this is an 1782 * error and we send an RST and drop the connection. 1783 */ 1784 if (thflags & TH_SYN) { 1785 tp = tcp_drop(tp, ECONNRESET); 1786 rstreason = BANDLIM_UNLIMITED; 1787 goto dropwithreset; 1788 } 1789 1790 /* 1791 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1792 * flag is on (half-synchronized state), then queue data for 1793 * later processing; else drop segment and return. 1794 */ 1795 if (!(thflags & TH_ACK)) { 1796 if (tp->t_state == TCPS_SYN_RECEIVED || 1797 (tp->t_flags & TF_NEEDSYN)) 1798 goto step6; 1799 else 1800 goto drop; 1801 } 1802 1803 /* 1804 * Ack processing. 1805 */ 1806 switch (tp->t_state) { 1807 /* 1808 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1809 * ESTABLISHED state and continue processing. 1810 * The ACK was checked above. 1811 */ 1812 case TCPS_SYN_RECEIVED: 1813 1814 tcpstat.tcps_connects++; 1815 soisconnected(so); 1816 /* Do window scaling? */ 1817 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1818 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1819 tp->snd_scale = tp->requested_s_scale; 1820 tp->rcv_scale = tp->request_r_scale; 1821 } 1822 /* 1823 * Upon successful completion of 3-way handshake, 1824 * update cache.CC if it was undefined, pass any queued 1825 * data to the user, and advance state appropriately. 1826 */ 1827 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1828 taop->tao_cc == 0) 1829 taop->tao_cc = tp->cc_recv; 1830 1831 /* 1832 * Make transitions: 1833 * SYN-RECEIVED -> ESTABLISHED 1834 * SYN-RECEIVED* -> FIN-WAIT-1 1835 */ 1836 tp->t_starttime = ticks; 1837 if (tp->t_flags & TF_NEEDFIN) { 1838 tp->t_state = TCPS_FIN_WAIT_1; 1839 tp->t_flags &= ~TF_NEEDFIN; 1840 } else { 1841 tp->t_state = TCPS_ESTABLISHED; 1842 callout_reset(tp->tt_keep, tcp_keepidle, 1843 tcp_timer_keep, tp); 1844 } 1845 /* 1846 * If segment contains data or ACK, will call tcp_reass() 1847 * later; if not, do so now to pass queued data to user. 1848 */ 1849 if (tlen == 0 && !(thflags & TH_FIN)) 1850 tcp_reass(tp, NULL, NULL, NULL); 1851 /* fall into ... */ 1852 1853 /* 1854 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1855 * ACKs. If the ack is in the range 1856 * tp->snd_una < th->th_ack <= tp->snd_max 1857 * then advance tp->snd_una to th->th_ack and drop 1858 * data from the retransmission queue. If this ACK reflects 1859 * more up to date window information we update our window information. 1860 */ 1861 case TCPS_ESTABLISHED: 1862 case TCPS_FIN_WAIT_1: 1863 case TCPS_FIN_WAIT_2: 1864 case TCPS_CLOSE_WAIT: 1865 case TCPS_CLOSING: 1866 case TCPS_LAST_ACK: 1867 case TCPS_TIME_WAIT: 1868 1869 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1870 if (TCP_DO_SACK(tp)) 1871 tcp_sack_update_scoreboard(tp, &to); 1872 if (tlen != 0 || tiwin != tp->snd_wnd) { 1873 tp->t_dupacks = 0; 1874 break; 1875 } 1876 tcpstat.tcps_rcvdupack++; 1877 if (!callout_active(tp->tt_rexmt) || 1878 th->th_ack != tp->snd_una) { 1879 tp->t_dupacks = 0; 1880 break; 1881 } 1882 /* 1883 * We have outstanding data (other than 1884 * a window probe), this is a completely 1885 * duplicate ack (ie, window info didn't 1886 * change), the ack is the biggest we've 1887 * seen and we've seen exactly our rexmt 1888 * threshhold of them, so assume a packet 1889 * has been dropped and retransmit it. 1890 * Kludge snd_nxt & the congestion 1891 * window so we send only this one 1892 * packet. 1893 */ 1894 if (IN_FASTRECOVERY(tp)) { 1895 if (TCP_DO_SACK(tp)) { 1896 /* No artifical cwnd inflation. */ 1897 tcp_sack_rexmt(tp, th); 1898 } else { 1899 /* 1900 * Dup acks mean that packets 1901 * have left the network 1902 * (they're now cached at the 1903 * receiver) so bump cwnd by 1904 * the amount in the receiver 1905 * to keep a constant cwnd 1906 * packets in the network. 1907 */ 1908 tp->snd_cwnd += tp->t_maxseg; 1909 tcp_output(tp); 1910 } 1911 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1912 tp->t_dupacks = 0; 1913 break; 1914 } else if (++tp->t_dupacks == tcprexmtthresh) { 1915 tcp_seq old_snd_nxt; 1916 u_int win; 1917 1918 fastretransmit: 1919 if (tcp_do_eifel_detect && 1920 (tp->t_flags & TF_RCVD_TSTMP)) { 1921 tcp_save_congestion_state(tp); 1922 tp->t_flags |= TF_FASTREXMT; 1923 } 1924 /* 1925 * We know we're losing at the current 1926 * window size, so do congestion avoidance: 1927 * set ssthresh to half the current window 1928 * and pull our congestion window back to the 1929 * new ssthresh. 1930 */ 1931 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1932 tp->t_maxseg; 1933 if (win < 2) 1934 win = 2; 1935 tp->snd_ssthresh = win * tp->t_maxseg; 1936 ENTER_FASTRECOVERY(tp); 1937 tp->snd_recover = tp->snd_max; 1938 callout_stop(tp->tt_rexmt); 1939 tp->t_rtttime = 0; 1940 old_snd_nxt = tp->snd_nxt; 1941 tp->snd_nxt = th->th_ack; 1942 tp->snd_cwnd = tp->t_maxseg; 1943 tcp_output(tp); 1944 ++tcpstat.tcps_sndfastrexmit; 1945 tp->snd_cwnd = tp->snd_ssthresh; 1946 tp->rexmt_high = tp->snd_nxt; 1947 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1948 tp->snd_nxt = old_snd_nxt; 1949 KASSERT(tp->snd_limited <= 2, 1950 ("tp->snd_limited too big")); 1951 if (TCP_DO_SACK(tp)) 1952 tcp_sack_rexmt(tp, th); 1953 else 1954 tp->snd_cwnd += tp->t_maxseg * 1955 (tp->t_dupacks - tp->snd_limited); 1956 } else if (tcp_do_limitedtransmit) { 1957 u_long oldcwnd = tp->snd_cwnd; 1958 tcp_seq oldsndmax = tp->snd_max; 1959 /* outstanding data */ 1960 uint32_t ownd = tp->snd_max - tp->snd_una; 1961 u_int sent; 1962 1963 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1964 1965 KASSERT(tp->t_dupacks == 1 || 1966 tp->t_dupacks == 2, 1967 ("dupacks not 1 or 2")); 1968 if (tp->t_dupacks == 1) 1969 tp->snd_limited = 0; 1970 tp->snd_cwnd = ownd + 1971 (tp->t_dupacks - tp->snd_limited) * 1972 tp->t_maxseg; 1973 tcp_output(tp); 1974 tp->snd_cwnd = oldcwnd; 1975 sent = tp->snd_max - oldsndmax; 1976 if (sent > tp->t_maxseg) { 1977 KASSERT((tp->t_dupacks == 2 && 1978 tp->snd_limited == 0) || 1979 (sent == tp->t_maxseg + 1 && 1980 tp->t_flags & TF_SENTFIN), 1981 ("sent too much")); 1982 KASSERT(sent <= tp->t_maxseg * 2, 1983 ("sent too many segments")); 1984 tp->snd_limited = 2; 1985 tcpstat.tcps_sndlimited += 2; 1986 } else if (sent > 0) { 1987 ++tp->snd_limited; 1988 ++tcpstat.tcps_sndlimited; 1989 } else if (tcp_do_early_retransmit && 1990 (tcp_do_eifel_detect && 1991 (tp->t_flags & TF_RCVD_TSTMP)) && 1992 ownd < 4 * tp->t_maxseg && 1993 tp->t_dupacks + 1 >= 1994 iceildiv(ownd, tp->t_maxseg) && 1995 (!TCP_DO_SACK(tp) || 1996 ownd <= tp->t_maxseg || 1997 tcp_sack_has_sacked(&tp->scb, 1998 ownd - tp->t_maxseg))) { 1999 ++tcpstat.tcps_sndearlyrexmit; 2000 tp->t_flags |= TF_EARLYREXMT; 2001 goto fastretransmit; 2002 } 2003 } 2004 goto drop; 2005 } 2006 2007 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2008 tp->t_dupacks = 0; 2009 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2010 /* 2011 * Detected optimistic ACK attack. 2012 * Force slow-start to de-synchronize attack. 2013 */ 2014 tp->snd_cwnd = tp->t_maxseg; 2015 2016 tcpstat.tcps_rcvacktoomuch++; 2017 goto dropafterack; 2018 } 2019 /* 2020 * If we reach this point, ACK is not a duplicate, 2021 * i.e., it ACKs something we sent. 2022 */ 2023 if (tp->t_flags & TF_NEEDSYN) { 2024 /* 2025 * T/TCP: Connection was half-synchronized, and our 2026 * SYN has been ACK'd (so connection is now fully 2027 * synchronized). Go to non-starred state, 2028 * increment snd_una for ACK of SYN, and check if 2029 * we can do window scaling. 2030 */ 2031 tp->t_flags &= ~TF_NEEDSYN; 2032 tp->snd_una++; 2033 /* Do window scaling? */ 2034 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2035 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2036 tp->snd_scale = tp->requested_s_scale; 2037 tp->rcv_scale = tp->request_r_scale; 2038 } 2039 } 2040 2041 process_ACK: 2042 acked = th->th_ack - tp->snd_una; 2043 tcpstat.tcps_rcvackpack++; 2044 tcpstat.tcps_rcvackbyte += acked; 2045 2046 if (tcp_do_eifel_detect && acked > 0 && 2047 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2048 (tp->t_flags & TF_FIRSTACCACK)) { 2049 /* Eifel detection applicable. */ 2050 if (to.to_tsecr < tp->t_rexmtTS) { 2051 ++tcpstat.tcps_eifeldetected; 2052 tcp_revert_congestion_state(tp); 2053 if (tp->t_rxtshift == 1 && 2054 ticks >= tp->t_badrxtwin) 2055 ++tcpstat.tcps_rttcantdetect; 2056 } 2057 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2058 /* 2059 * If we just performed our first retransmit, 2060 * and the ACK arrives within our recovery window, 2061 * then it was a mistake to do the retransmit 2062 * in the first place. Recover our original cwnd 2063 * and ssthresh, and proceed to transmit where we 2064 * left off. 2065 */ 2066 tcp_revert_congestion_state(tp); 2067 ++tcpstat.tcps_rttdetected; 2068 } 2069 2070 /* 2071 * If we have a timestamp reply, update smoothed 2072 * round trip time. If no timestamp is present but 2073 * transmit timer is running and timed sequence 2074 * number was acked, update smoothed round trip time. 2075 * Since we now have an rtt measurement, cancel the 2076 * timer backoff (cf., Phil Karn's retransmit alg.). 2077 * Recompute the initial retransmit timer. 2078 * 2079 * Some machines (certain windows boxes) send broken 2080 * timestamp replies during the SYN+ACK phase, ignore 2081 * timestamps of 0. 2082 */ 2083 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2084 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2085 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2086 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2087 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2088 2089 /* 2090 * If no data (only SYN) was ACK'd, 2091 * skip rest of ACK processing. 2092 */ 2093 if (acked == 0) 2094 goto step6; 2095 2096 /* Stop looking for an acceptable ACK since one was received. */ 2097 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2098 2099 if (acked > so->so_snd.sb_cc) { 2100 tp->snd_wnd -= so->so_snd.sb_cc; 2101 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2102 ourfinisacked = TRUE; 2103 } else { 2104 sbdrop(&so->so_snd, acked); 2105 tp->snd_wnd -= acked; 2106 ourfinisacked = FALSE; 2107 } 2108 sowwakeup(so); 2109 2110 /* 2111 * Update window information. 2112 * Don't look at window if no ACK: 2113 * TAC's send garbage on first SYN. 2114 */ 2115 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2116 (tp->snd_wl1 == th->th_seq && 2117 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2118 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2119 /* keep track of pure window updates */ 2120 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2121 tiwin > tp->snd_wnd) 2122 tcpstat.tcps_rcvwinupd++; 2123 tp->snd_wnd = tiwin; 2124 tp->snd_wl1 = th->th_seq; 2125 tp->snd_wl2 = th->th_ack; 2126 if (tp->snd_wnd > tp->max_sndwnd) 2127 tp->max_sndwnd = tp->snd_wnd; 2128 needoutput = TRUE; 2129 } 2130 2131 tp->snd_una = th->th_ack; 2132 if (TCP_DO_SACK(tp)) 2133 tcp_sack_update_scoreboard(tp, &to); 2134 if (IN_FASTRECOVERY(tp)) { 2135 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2136 EXIT_FASTRECOVERY(tp); 2137 needoutput = TRUE; 2138 /* 2139 * If the congestion window was inflated 2140 * to account for the other side's 2141 * cached packets, retract it. 2142 * 2143 * Window inflation should have left us 2144 * with approximately snd_ssthresh outstanding 2145 * data. But, in case we would be inclined 2146 * to send a burst, better do it using 2147 * slow start. 2148 */ 2149 if (!TCP_DO_SACK(tp)) 2150 tp->snd_cwnd = tp->snd_ssthresh; 2151 2152 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2153 tp->snd_max + 2 * tp->t_maxseg)) 2154 tp->snd_cwnd = 2155 (tp->snd_max - tp->snd_una) + 2156 2 * tp->t_maxseg; 2157 } else { 2158 if (TCP_DO_SACK(tp)) { 2159 tp->snd_max_rexmt = tp->snd_max; 2160 tcp_sack_rexmt(tp, th); 2161 } else { 2162 tcp_newreno_partial_ack(tp, th, acked); 2163 } 2164 needoutput = FALSE; 2165 } 2166 } else { 2167 /* 2168 * When new data is acked, open the congestion window. 2169 * If the window gives us less than ssthresh packets 2170 * in flight, open exponentially (maxseg per packet). 2171 * Otherwise open linearly: maxseg per window 2172 * (maxseg^2 / cwnd per packet). 2173 */ 2174 u_int cw = tp->snd_cwnd; 2175 u_int incr; 2176 2177 if (cw > tp->snd_ssthresh) 2178 incr = tp->t_maxseg * tp->t_maxseg / cw; 2179 else 2180 incr = tp->t_maxseg; 2181 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2182 tp->snd_recover = th->th_ack - 1; 2183 } 2184 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2185 tp->snd_nxt = tp->snd_una; 2186 2187 /* 2188 * If all outstanding data is acked, stop retransmit 2189 * timer and remember to restart (more output or persist). 2190 * If there is more data to be acked, restart retransmit 2191 * timer, using current (possibly backed-off) value. 2192 */ 2193 if (th->th_ack == tp->snd_max) { 2194 callout_stop(tp->tt_rexmt); 2195 needoutput = TRUE; 2196 } else if (!callout_active(tp->tt_persist)) 2197 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2198 tcp_timer_rexmt, tp); 2199 2200 switch (tp->t_state) { 2201 /* 2202 * In FIN_WAIT_1 STATE in addition to the processing 2203 * for the ESTABLISHED state if our FIN is now acknowledged 2204 * then enter FIN_WAIT_2. 2205 */ 2206 case TCPS_FIN_WAIT_1: 2207 if (ourfinisacked) { 2208 /* 2209 * If we can't receive any more 2210 * data, then closing user can proceed. 2211 * Starting the timer is contrary to the 2212 * specification, but if we don't get a FIN 2213 * we'll hang forever. 2214 */ 2215 if (so->so_state & SS_CANTRCVMORE) { 2216 soisdisconnected(so); 2217 callout_reset(tp->tt_2msl, tcp_maxidle, 2218 tcp_timer_2msl, tp); 2219 } 2220 tp->t_state = TCPS_FIN_WAIT_2; 2221 } 2222 break; 2223 2224 /* 2225 * In CLOSING STATE in addition to the processing for 2226 * the ESTABLISHED state if the ACK acknowledges our FIN 2227 * then enter the TIME-WAIT state, otherwise ignore 2228 * the segment. 2229 */ 2230 case TCPS_CLOSING: 2231 if (ourfinisacked) { 2232 tp->t_state = TCPS_TIME_WAIT; 2233 tcp_canceltimers(tp); 2234 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2235 if (tp->cc_recv != 0 && 2236 (ticks - tp->t_starttime) < tcp_msl) 2237 callout_reset(tp->tt_2msl, 2238 tp->t_rxtcur * TCPTV_TWTRUNC, 2239 tcp_timer_2msl, tp); 2240 else 2241 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2242 tcp_timer_2msl, tp); 2243 soisdisconnected(so); 2244 } 2245 break; 2246 2247 /* 2248 * In LAST_ACK, we may still be waiting for data to drain 2249 * and/or to be acked, as well as for the ack of our FIN. 2250 * If our FIN is now acknowledged, delete the TCB, 2251 * enter the closed state and return. 2252 */ 2253 case TCPS_LAST_ACK: 2254 if (ourfinisacked) { 2255 tp = tcp_close(tp); 2256 goto drop; 2257 } 2258 break; 2259 2260 /* 2261 * In TIME_WAIT state the only thing that should arrive 2262 * is a retransmission of the remote FIN. Acknowledge 2263 * it and restart the finack timer. 2264 */ 2265 case TCPS_TIME_WAIT: 2266 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2267 tcp_timer_2msl, tp); 2268 goto dropafterack; 2269 } 2270 } 2271 2272 step6: 2273 /* 2274 * Update window information. 2275 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2276 */ 2277 if ((thflags & TH_ACK) && 2278 acceptable_window_update(tp, th, tiwin)) { 2279 /* keep track of pure window updates */ 2280 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2281 tiwin > tp->snd_wnd) 2282 tcpstat.tcps_rcvwinupd++; 2283 tp->snd_wnd = tiwin; 2284 tp->snd_wl1 = th->th_seq; 2285 tp->snd_wl2 = th->th_ack; 2286 if (tp->snd_wnd > tp->max_sndwnd) 2287 tp->max_sndwnd = tp->snd_wnd; 2288 needoutput = TRUE; 2289 } 2290 2291 /* 2292 * Process segments with URG. 2293 */ 2294 if ((thflags & TH_URG) && th->th_urp && 2295 !TCPS_HAVERCVDFIN(tp->t_state)) { 2296 /* 2297 * This is a kludge, but if we receive and accept 2298 * random urgent pointers, we'll crash in 2299 * soreceive. It's hard to imagine someone 2300 * actually wanting to send this much urgent data. 2301 */ 2302 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2303 th->th_urp = 0; /* XXX */ 2304 thflags &= ~TH_URG; /* XXX */ 2305 goto dodata; /* XXX */ 2306 } 2307 /* 2308 * If this segment advances the known urgent pointer, 2309 * then mark the data stream. This should not happen 2310 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2311 * a FIN has been received from the remote side. 2312 * In these states we ignore the URG. 2313 * 2314 * According to RFC961 (Assigned Protocols), 2315 * the urgent pointer points to the last octet 2316 * of urgent data. We continue, however, 2317 * to consider it to indicate the first octet 2318 * of data past the urgent section as the original 2319 * spec states (in one of two places). 2320 */ 2321 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2322 tp->rcv_up = th->th_seq + th->th_urp; 2323 so->so_oobmark = so->so_rcv.sb_cc + 2324 (tp->rcv_up - tp->rcv_nxt) - 1; 2325 if (so->so_oobmark == 0) 2326 so->so_state |= SS_RCVATMARK; 2327 sohasoutofband(so); 2328 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2329 } 2330 /* 2331 * Remove out of band data so doesn't get presented to user. 2332 * This can happen independent of advancing the URG pointer, 2333 * but if two URG's are pending at once, some out-of-band 2334 * data may creep in... ick. 2335 */ 2336 if (th->th_urp <= (u_long)tlen && 2337 !(so->so_options & SO_OOBINLINE)) { 2338 /* hdr drop is delayed */ 2339 tcp_pulloutofband(so, th, m, drop_hdrlen); 2340 } 2341 } else { 2342 /* 2343 * If no out of band data is expected, 2344 * pull receive urgent pointer along 2345 * with the receive window. 2346 */ 2347 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2348 tp->rcv_up = tp->rcv_nxt; 2349 } 2350 2351 dodata: /* XXX */ 2352 /* 2353 * Process the segment text, merging it into the TCP sequencing queue, 2354 * and arranging for acknowledgment of receipt if necessary. 2355 * This process logically involves adjusting tp->rcv_wnd as data 2356 * is presented to the user (this happens in tcp_usrreq.c, 2357 * case PRU_RCVD). If a FIN has already been received on this 2358 * connection then we just ignore the text. 2359 */ 2360 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2361 m_adj(m, drop_hdrlen); /* delayed header drop */ 2362 /* 2363 * Insert segment which includes th into TCP reassembly queue 2364 * with control block tp. Set thflags to whether reassembly now 2365 * includes a segment with FIN. This handles the common case 2366 * inline (segment is the next to be received on an established 2367 * connection, and the queue is empty), avoiding linkage into 2368 * and removal from the queue and repetition of various 2369 * conversions. 2370 * Set DELACK for segments received in order, but ack 2371 * immediately when segments are out of order (so 2372 * fast retransmit can work). 2373 */ 2374 if (th->th_seq == tp->rcv_nxt && 2375 LIST_EMPTY(&tp->t_segq) && 2376 TCPS_HAVEESTABLISHED(tp->t_state)) { 2377 if (DELAY_ACK(tp)) 2378 callout_reset(tp->tt_delack, tcp_delacktime, 2379 tcp_timer_delack, tp); 2380 else 2381 tp->t_flags |= TF_ACKNOW; 2382 tp->rcv_nxt += tlen; 2383 thflags = th->th_flags & TH_FIN; 2384 tcpstat.tcps_rcvpack++; 2385 tcpstat.tcps_rcvbyte += tlen; 2386 ND6_HINT(tp); 2387 if (so->so_state & SS_CANTRCVMORE) 2388 m_freem(m); 2389 else 2390 sbappendstream(&so->so_rcv, m); 2391 sorwakeup(so); 2392 } else { 2393 if (!(tp->t_flags & TF_DUPSEG)) { 2394 /* Initialize SACK report block. */ 2395 tp->reportblk.rblk_start = th->th_seq; 2396 tp->reportblk.rblk_end = th->th_seq + tlen + 2397 ((thflags & TH_FIN) != 0); 2398 } 2399 thflags = tcp_reass(tp, th, &tlen, m); 2400 tp->t_flags |= TF_ACKNOW; 2401 } 2402 2403 /* 2404 * Note the amount of data that peer has sent into 2405 * our window, in order to estimate the sender's 2406 * buffer size. 2407 */ 2408 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2409 } else { 2410 m_freem(m); 2411 thflags &= ~TH_FIN; 2412 } 2413 2414 /* 2415 * If FIN is received ACK the FIN and let the user know 2416 * that the connection is closing. 2417 */ 2418 if (thflags & TH_FIN) { 2419 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2420 socantrcvmore(so); 2421 /* 2422 * If connection is half-synchronized 2423 * (ie NEEDSYN flag on) then delay ACK, 2424 * so it may be piggybacked when SYN is sent. 2425 * Otherwise, since we received a FIN then no 2426 * more input can be expected, send ACK now. 2427 */ 2428 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2429 callout_reset(tp->tt_delack, tcp_delacktime, 2430 tcp_timer_delack, tp); 2431 else 2432 tp->t_flags |= TF_ACKNOW; 2433 tp->rcv_nxt++; 2434 } 2435 2436 switch (tp->t_state) { 2437 /* 2438 * In SYN_RECEIVED and ESTABLISHED STATES 2439 * enter the CLOSE_WAIT state. 2440 */ 2441 case TCPS_SYN_RECEIVED: 2442 tp->t_starttime = ticks; 2443 /*FALLTHROUGH*/ 2444 case TCPS_ESTABLISHED: 2445 tp->t_state = TCPS_CLOSE_WAIT; 2446 break; 2447 2448 /* 2449 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2450 * enter the CLOSING state. 2451 */ 2452 case TCPS_FIN_WAIT_1: 2453 tp->t_state = TCPS_CLOSING; 2454 break; 2455 2456 /* 2457 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2458 * starting the time-wait timer, turning off the other 2459 * standard timers. 2460 */ 2461 case TCPS_FIN_WAIT_2: 2462 tp->t_state = TCPS_TIME_WAIT; 2463 tcp_canceltimers(tp); 2464 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2465 if (tp->cc_recv != 0 && 2466 (ticks - tp->t_starttime) < tcp_msl) { 2467 callout_reset(tp->tt_2msl, 2468 tp->t_rxtcur * TCPTV_TWTRUNC, 2469 tcp_timer_2msl, tp); 2470 /* For transaction client, force ACK now. */ 2471 tp->t_flags |= TF_ACKNOW; 2472 } 2473 else 2474 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2475 tcp_timer_2msl, tp); 2476 soisdisconnected(so); 2477 break; 2478 2479 /* 2480 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2481 */ 2482 case TCPS_TIME_WAIT: 2483 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2484 tcp_timer_2msl, tp); 2485 break; 2486 } 2487 } 2488 2489 #ifdef TCPDEBUG 2490 if (so->so_options & SO_DEBUG) 2491 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2492 #endif 2493 2494 /* 2495 * Return any desired output. 2496 */ 2497 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2498 tcp_output(tp); 2499 return; 2500 2501 dropafterack: 2502 /* 2503 * Generate an ACK dropping incoming segment if it occupies 2504 * sequence space, where the ACK reflects our state. 2505 * 2506 * We can now skip the test for the RST flag since all 2507 * paths to this code happen after packets containing 2508 * RST have been dropped. 2509 * 2510 * In the SYN-RECEIVED state, don't send an ACK unless the 2511 * segment we received passes the SYN-RECEIVED ACK test. 2512 * If it fails send a RST. This breaks the loop in the 2513 * "LAND" DoS attack, and also prevents an ACK storm 2514 * between two listening ports that have been sent forged 2515 * SYN segments, each with the source address of the other. 2516 */ 2517 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2518 (SEQ_GT(tp->snd_una, th->th_ack) || 2519 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2520 rstreason = BANDLIM_RST_OPENPORT; 2521 goto dropwithreset; 2522 } 2523 #ifdef TCPDEBUG 2524 if (so->so_options & SO_DEBUG) 2525 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2526 #endif 2527 m_freem(m); 2528 tp->t_flags |= TF_ACKNOW; 2529 tcp_output(tp); 2530 return; 2531 2532 dropwithreset: 2533 /* 2534 * Generate a RST, dropping incoming segment. 2535 * Make ACK acceptable to originator of segment. 2536 * Don't bother to respond if destination was broadcast/multicast. 2537 */ 2538 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2539 goto drop; 2540 if (isipv6) { 2541 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2542 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2543 goto drop; 2544 } else { 2545 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2546 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2547 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2548 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2549 goto drop; 2550 } 2551 /* IPv6 anycast check is done at tcp6_input() */ 2552 2553 /* 2554 * Perform bandwidth limiting. 2555 */ 2556 #ifdef ICMP_BANDLIM 2557 if (badport_bandlim(rstreason) < 0) 2558 goto drop; 2559 #endif 2560 2561 #ifdef TCPDEBUG 2562 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2563 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2564 #endif 2565 if (thflags & TH_ACK) 2566 /* mtod() below is safe as long as hdr dropping is delayed */ 2567 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2568 TH_RST); 2569 else { 2570 if (thflags & TH_SYN) 2571 tlen++; 2572 /* mtod() below is safe as long as hdr dropping is delayed */ 2573 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2574 (tcp_seq)0, TH_RST | TH_ACK); 2575 } 2576 return; 2577 2578 drop: 2579 /* 2580 * Drop space held by incoming segment and return. 2581 */ 2582 #ifdef TCPDEBUG 2583 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2584 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2585 #endif 2586 m_freem(m); 2587 return; 2588 } 2589 2590 /* 2591 * Parse TCP options and place in tcpopt. 2592 */ 2593 static void 2594 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2595 { 2596 int opt, optlen, i; 2597 2598 to->to_flags = 0; 2599 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2600 opt = cp[0]; 2601 if (opt == TCPOPT_EOL) 2602 break; 2603 if (opt == TCPOPT_NOP) 2604 optlen = 1; 2605 else { 2606 if (cnt < 2) 2607 break; 2608 optlen = cp[1]; 2609 if (optlen < 2 || optlen > cnt) 2610 break; 2611 } 2612 switch (opt) { 2613 case TCPOPT_MAXSEG: 2614 if (optlen != TCPOLEN_MAXSEG) 2615 continue; 2616 if (!is_syn) 2617 continue; 2618 to->to_flags |= TOF_MSS; 2619 bcopy(cp + 2, &to->to_mss, sizeof(to->to_mss)); 2620 to->to_mss = ntohs(to->to_mss); 2621 break; 2622 case TCPOPT_WINDOW: 2623 if (optlen != TCPOLEN_WINDOW) 2624 continue; 2625 if (!is_syn) 2626 continue; 2627 to->to_flags |= TOF_SCALE; 2628 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2629 break; 2630 case TCPOPT_TIMESTAMP: 2631 if (optlen != TCPOLEN_TIMESTAMP) 2632 continue; 2633 to->to_flags |= TOF_TS; 2634 bcopy(cp + 2, &to->to_tsval, sizeof(to->to_tsval)); 2635 to->to_tsval = ntohl(to->to_tsval); 2636 bcopy(cp + 6, &to->to_tsecr, sizeof(to->to_tsecr)); 2637 to->to_tsecr = ntohl(to->to_tsecr); 2638 break; 2639 case TCPOPT_CC: 2640 if (optlen != TCPOLEN_CC) 2641 continue; 2642 to->to_flags |= TOF_CC; 2643 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc)); 2644 to->to_cc = ntohl(to->to_cc); 2645 break; 2646 case TCPOPT_CCNEW: 2647 if (optlen != TCPOLEN_CC) 2648 continue; 2649 if (!is_syn) 2650 continue; 2651 to->to_flags |= TOF_CCNEW; 2652 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc)); 2653 to->to_cc = ntohl(to->to_cc); 2654 break; 2655 case TCPOPT_CCECHO: 2656 if (optlen != TCPOLEN_CC) 2657 continue; 2658 if (!is_syn) 2659 continue; 2660 to->to_flags |= TOF_CCECHO; 2661 bcopy(cp + 2, &to->to_ccecho, sizeof(to->to_ccecho)); 2662 to->to_ccecho = ntohl(to->to_ccecho); 2663 break; 2664 case TCPOPT_SACK_PERMITTED: 2665 if (optlen != TCPOLEN_SACK_PERMITTED) 2666 continue; 2667 if (!is_syn) 2668 continue; 2669 to->to_flags |= TOF_SACK_PERMITTED; 2670 break; 2671 case TCPOPT_SACK: 2672 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2673 continue; 2674 to->to_nsackblocks = (optlen - 2) / 8; 2675 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2676 to->to_flags |= TOF_SACK; 2677 for (i = 0; i < to->to_nsackblocks; i++) { 2678 struct raw_sackblock *r = &to->to_sackblocks[i]; 2679 2680 r->rblk_start = ntohl(r->rblk_start); 2681 r->rblk_end = ntohl(r->rblk_end); 2682 } 2683 break; 2684 default: 2685 continue; 2686 } 2687 } 2688 } 2689 2690 /* 2691 * Pull out of band byte out of a segment so 2692 * it doesn't appear in the user's data queue. 2693 * It is still reflected in the segment length for 2694 * sequencing purposes. 2695 * "off" is the delayed to be dropped hdrlen. 2696 */ 2697 static void 2698 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2699 { 2700 int cnt = off + th->th_urp - 1; 2701 2702 while (cnt >= 0) { 2703 if (m->m_len > cnt) { 2704 char *cp = mtod(m, caddr_t) + cnt; 2705 struct tcpcb *tp = sototcpcb(so); 2706 2707 tp->t_iobc = *cp; 2708 tp->t_oobflags |= TCPOOB_HAVEDATA; 2709 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2710 m->m_len--; 2711 if (m->m_flags & M_PKTHDR) 2712 m->m_pkthdr.len--; 2713 return; 2714 } 2715 cnt -= m->m_len; 2716 m = m->m_next; 2717 if (m == 0) 2718 break; 2719 } 2720 panic("tcp_pulloutofband"); 2721 } 2722 2723 /* 2724 * Collect new round-trip time estimate 2725 * and update averages and current timeout. 2726 */ 2727 static void 2728 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2729 { 2730 int delta; 2731 2732 tcpstat.tcps_rttupdated++; 2733 tp->t_rttupdated++; 2734 if (tp->t_srtt != 0) { 2735 /* 2736 * srtt is stored as fixed point with 5 bits after the 2737 * binary point (i.e., scaled by 8). The following magic 2738 * is equivalent to the smoothing algorithm in rfc793 with 2739 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2740 * point). Adjust rtt to origin 0. 2741 */ 2742 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2743 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2744 2745 if ((tp->t_srtt += delta) <= 0) 2746 tp->t_srtt = 1; 2747 2748 /* 2749 * We accumulate a smoothed rtt variance (actually, a 2750 * smoothed mean difference), then set the retransmit 2751 * timer to smoothed rtt + 4 times the smoothed variance. 2752 * rttvar is stored as fixed point with 4 bits after the 2753 * binary point (scaled by 16). The following is 2754 * equivalent to rfc793 smoothing with an alpha of .75 2755 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2756 * rfc793's wired-in beta. 2757 */ 2758 if (delta < 0) 2759 delta = -delta; 2760 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2761 if ((tp->t_rttvar += delta) <= 0) 2762 tp->t_rttvar = 1; 2763 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2764 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2765 } else { 2766 /* 2767 * No rtt measurement yet - use the unsmoothed rtt. 2768 * Set the variance to half the rtt (so our first 2769 * retransmit happens at 3*rtt). 2770 */ 2771 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2772 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2773 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2774 } 2775 tp->t_rtttime = 0; 2776 tp->t_rxtshift = 0; 2777 2778 /* 2779 * the retransmit should happen at rtt + 4 * rttvar. 2780 * Because of the way we do the smoothing, srtt and rttvar 2781 * will each average +1/2 tick of bias. When we compute 2782 * the retransmit timer, we want 1/2 tick of rounding and 2783 * 1 extra tick because of +-1/2 tick uncertainty in the 2784 * firing of the timer. The bias will give us exactly the 2785 * 1.5 tick we need. But, because the bias is 2786 * statistical, we have to test that we don't drop below 2787 * the minimum feasible timer (which is 2 ticks). 2788 */ 2789 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2790 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2791 2792 /* 2793 * We received an ack for a packet that wasn't retransmitted; 2794 * it is probably safe to discard any error indications we've 2795 * received recently. This isn't quite right, but close enough 2796 * for now (a route might have failed after we sent a segment, 2797 * and the return path might not be symmetrical). 2798 */ 2799 tp->t_softerror = 0; 2800 } 2801 2802 /* 2803 * Determine a reasonable value for maxseg size. 2804 * If the route is known, check route for mtu. 2805 * If none, use an mss that can be handled on the outgoing 2806 * interface without forcing IP to fragment; if bigger than 2807 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2808 * to utilize large mbufs. If no route is found, route has no mtu, 2809 * or the destination isn't local, use a default, hopefully conservative 2810 * size (usually 512 or the default IP max size, but no more than the mtu 2811 * of the interface), as we can't discover anything about intervening 2812 * gateways or networks. We also initialize the congestion/slow start 2813 * window to be a single segment if the destination isn't local. 2814 * While looking at the routing entry, we also initialize other path-dependent 2815 * parameters from pre-set or cached values in the routing entry. 2816 * 2817 * Also take into account the space needed for options that we 2818 * send regularly. Make maxseg shorter by that amount to assure 2819 * that we can send maxseg amount of data even when the options 2820 * are present. Store the upper limit of the length of options plus 2821 * data in maxopd. 2822 * 2823 * NOTE that this routine is only called when we process an incoming 2824 * segment, for outgoing segments only tcp_mssopt is called. 2825 * 2826 * In case of T/TCP, we call this routine during implicit connection 2827 * setup as well (offer = -1), to initialize maxseg from the cached 2828 * MSS of our peer. 2829 */ 2830 void 2831 tcp_mss(struct tcpcb *tp, int offer) 2832 { 2833 struct rtentry *rt; 2834 struct ifnet *ifp; 2835 int rtt, mss; 2836 u_long bufsize; 2837 struct inpcb *inp = tp->t_inpcb; 2838 struct socket *so; 2839 struct rmxp_tao *taop; 2840 int origoffer = offer; 2841 #ifdef INET6 2842 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2843 size_t min_protoh = isipv6 ? 2844 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2845 sizeof(struct tcpiphdr); 2846 #else 2847 const boolean_t isipv6 = FALSE; 2848 const size_t min_protoh = sizeof(struct tcpiphdr); 2849 #endif 2850 2851 if (isipv6) 2852 rt = tcp_rtlookup6(&inp->inp_inc); 2853 else 2854 rt = tcp_rtlookup(&inp->inp_inc); 2855 if (rt == NULL) { 2856 tp->t_maxopd = tp->t_maxseg = 2857 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2858 return; 2859 } 2860 ifp = rt->rt_ifp; 2861 so = inp->inp_socket; 2862 2863 taop = rmx_taop(rt->rt_rmx); 2864 /* 2865 * Offer == -1 means that we didn't receive SYN yet, 2866 * use cached value in that case; 2867 */ 2868 if (offer == -1) 2869 offer = taop->tao_mssopt; 2870 /* 2871 * Offer == 0 means that there was no MSS on the SYN segment, 2872 * in this case we use tcp_mssdflt. 2873 */ 2874 if (offer == 0) 2875 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2876 else 2877 /* 2878 * Sanity check: make sure that maxopd will be large 2879 * enough to allow some data on segments even is the 2880 * all the option space is used (40bytes). Otherwise 2881 * funny things may happen in tcp_output. 2882 */ 2883 offer = max(offer, 64); 2884 taop->tao_mssopt = offer; 2885 2886 /* 2887 * While we're here, check if there's an initial rtt 2888 * or rttvar. Convert from the route-table units 2889 * to scaled multiples of the slow timeout timer. 2890 */ 2891 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2892 /* 2893 * XXX the lock bit for RTT indicates that the value 2894 * is also a minimum value; this is subject to time. 2895 */ 2896 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2897 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2898 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2899 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2900 tcpstat.tcps_usedrtt++; 2901 if (rt->rt_rmx.rmx_rttvar) { 2902 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2903 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2904 tcpstat.tcps_usedrttvar++; 2905 } else { 2906 /* default variation is +- 1 rtt */ 2907 tp->t_rttvar = 2908 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2909 } 2910 TCPT_RANGESET(tp->t_rxtcur, 2911 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2912 tp->t_rttmin, TCPTV_REXMTMAX); 2913 } 2914 /* 2915 * if there's an mtu associated with the route, use it 2916 * else, use the link mtu. 2917 */ 2918 if (rt->rt_rmx.rmx_mtu) 2919 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2920 else { 2921 if (isipv6) { 2922 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2923 min_protoh; 2924 if (!in6_localaddr(&inp->in6p_faddr)) 2925 mss = min(mss, tcp_v6mssdflt); 2926 } else { 2927 mss = ifp->if_mtu - min_protoh; 2928 if (!in_localaddr(inp->inp_faddr)) 2929 mss = min(mss, tcp_mssdflt); 2930 } 2931 } 2932 mss = min(mss, offer); 2933 /* 2934 * maxopd stores the maximum length of data AND options 2935 * in a segment; maxseg is the amount of data in a normal 2936 * segment. We need to store this value (maxopd) apart 2937 * from maxseg, because now every segment carries options 2938 * and thus we normally have somewhat less data in segments. 2939 */ 2940 tp->t_maxopd = mss; 2941 2942 /* 2943 * In case of T/TCP, origoffer==-1 indicates, that no segments 2944 * were received yet. In this case we just guess, otherwise 2945 * we do the same as before T/TCP. 2946 */ 2947 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 2948 (origoffer == -1 || 2949 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2950 mss -= TCPOLEN_TSTAMP_APPA; 2951 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 2952 (origoffer == -1 || 2953 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2954 mss -= TCPOLEN_CC_APPA; 2955 2956 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2957 if (mss > MCLBYTES) 2958 mss &= ~(MCLBYTES-1); 2959 #else 2960 if (mss > MCLBYTES) 2961 mss = mss / MCLBYTES * MCLBYTES; 2962 #endif 2963 /* 2964 * If there's a pipesize, change the socket buffer 2965 * to that size. Make the socket buffers an integral 2966 * number of mss units; if the mss is larger than 2967 * the socket buffer, decrease the mss. 2968 */ 2969 #ifdef RTV_SPIPE 2970 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2971 #endif 2972 bufsize = so->so_snd.sb_hiwat; 2973 if (bufsize < mss) 2974 mss = bufsize; 2975 else { 2976 bufsize = roundup(bufsize, mss); 2977 if (bufsize > sb_max) 2978 bufsize = sb_max; 2979 if (bufsize > so->so_snd.sb_hiwat) 2980 sbreserve(&so->so_snd, bufsize, so, NULL); 2981 } 2982 tp->t_maxseg = mss; 2983 2984 #ifdef RTV_RPIPE 2985 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2986 #endif 2987 bufsize = so->so_rcv.sb_hiwat; 2988 if (bufsize > mss) { 2989 bufsize = roundup(bufsize, mss); 2990 if (bufsize > sb_max) 2991 bufsize = sb_max; 2992 if (bufsize > so->so_rcv.sb_hiwat) 2993 sbreserve(&so->so_rcv, bufsize, so, NULL); 2994 } 2995 2996 /* 2997 * Set the slow-start flight size depending on whether this 2998 * is a local network or not. 2999 */ 3000 if (tcp_do_rfc3390) 3001 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3002 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3003 (!isipv6 && in_localaddr(inp->inp_faddr))) 3004 tp->snd_cwnd = mss * ss_fltsz_local; 3005 else 3006 tp->snd_cwnd = mss * ss_fltsz; 3007 3008 if (rt->rt_rmx.rmx_ssthresh) { 3009 /* 3010 * There's some sort of gateway or interface 3011 * buffer limit on the path. Use this to set 3012 * the slow start threshhold, but set the 3013 * threshold to no less than 2*mss. 3014 */ 3015 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3016 tcpstat.tcps_usedssthresh++; 3017 } 3018 } 3019 3020 /* 3021 * Determine the MSS option to send on an outgoing SYN. 3022 */ 3023 int 3024 tcp_mssopt(struct tcpcb *tp) 3025 { 3026 struct rtentry *rt; 3027 #ifdef INET6 3028 boolean_t isipv6 = 3029 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3030 int min_protoh = isipv6 ? 3031 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3032 sizeof(struct tcpiphdr); 3033 #else 3034 const boolean_t isipv6 = FALSE; 3035 const size_t min_protoh = sizeof(struct tcpiphdr); 3036 #endif 3037 3038 if (isipv6) 3039 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3040 else 3041 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3042 if (rt == NULL) 3043 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3044 3045 return (rt->rt_ifp->if_mtu - min_protoh); 3046 } 3047 3048 /* 3049 * When a partial ack arrives, force the retransmission of the 3050 * next unacknowledged segment. Do not exit Fast Recovery. 3051 * 3052 * Implement the Slow-but-Steady variant of NewReno by restarting the 3053 * the retransmission timer. Turn it off here so it can be restarted 3054 * later in tcp_output(). 3055 */ 3056 static void 3057 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3058 { 3059 tcp_seq old_snd_nxt = tp->snd_nxt; 3060 u_long ocwnd = tp->snd_cwnd; 3061 3062 callout_stop(tp->tt_rexmt); 3063 tp->t_rtttime = 0; 3064 tp->snd_nxt = th->th_ack; 3065 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3066 tp->snd_cwnd = tp->t_maxseg; 3067 tp->t_flags |= TF_ACKNOW; 3068 tcp_output(tp); 3069 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3070 tp->snd_nxt = old_snd_nxt; 3071 /* partial window deflation */ 3072 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3073 } 3074 3075 /* 3076 * In contrast to the Slow-but-Steady NewReno variant, 3077 * we do not reset the retransmission timer for SACK retransmissions, 3078 * except when retransmitting snd_una. 3079 */ 3080 static void 3081 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3082 { 3083 uint32_t pipe, seglen; 3084 tcp_seq nextrexmt; 3085 boolean_t lostdup; 3086 tcp_seq old_snd_nxt = tp->snd_nxt; 3087 u_long ocwnd = tp->snd_cwnd; 3088 int nseg = 0; /* consecutive new segments */ 3089 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3090 3091 tp->t_rtttime = 0; 3092 pipe = tcp_sack_compute_pipe(tp); 3093 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3094 (!tcp_do_smartsack || nseg < MAXBURST) && 3095 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3096 uint32_t sent; 3097 tcp_seq old_snd_max; 3098 int error; 3099 3100 if (nextrexmt == tp->snd_max) ++nseg; 3101 tp->snd_nxt = nextrexmt; 3102 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3103 old_snd_max = tp->snd_max; 3104 if (nextrexmt == tp->snd_una) 3105 callout_stop(tp->tt_rexmt); 3106 error = tcp_output(tp); 3107 if (error != 0) 3108 break; 3109 sent = tp->snd_nxt - nextrexmt; 3110 if (sent <= 0) 3111 break; 3112 if (!lostdup) 3113 pipe += sent; 3114 tcpstat.tcps_sndsackpack++; 3115 tcpstat.tcps_sndsackbyte += sent; 3116 if (SEQ_LT(nextrexmt, old_snd_max) && 3117 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3118 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3119 } 3120 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3121 tp->snd_nxt = old_snd_nxt; 3122 tp->snd_cwnd = ocwnd; 3123 } 3124