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) 1982, 1986, 1988, 1990, 1993, 1994, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 68 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.68 2008/08/22 09:14:17 sephe Exp $ 69 */ 70 71 #include "opt_ipfw.h" /* for ipfw_fwd */ 72 #include "opt_inet6.h" 73 #include "opt_ipsec.h" 74 #include "opt_tcpdebug.h" 75 #include "opt_tcp_input.h" 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/sysctl.h> 81 #include <sys/malloc.h> 82 #include <sys/mbuf.h> 83 #include <sys/proc.h> /* for proc0 declaration */ 84 #include <sys/protosw.h> 85 #include <sys/socket.h> 86 #include <sys/socketvar.h> 87 #include <sys/syslog.h> 88 #include <sys/in_cksum.h> 89 90 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 91 #include <machine/stdarg.h> 92 93 #include <net/if.h> 94 #include <net/route.h> 95 96 #include <netinet/in.h> 97 #include <netinet/in_systm.h> 98 #include <netinet/ip.h> 99 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 100 #include <netinet/in_var.h> 101 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 102 #include <netinet/in_pcb.h> 103 #include <netinet/ip_var.h> 104 #include <netinet/ip6.h> 105 #include <netinet/icmp6.h> 106 #include <netinet6/nd6.h> 107 #include <netinet6/ip6_var.h> 108 #include <netinet6/in6_pcb.h> 109 #include <netinet/tcp.h> 110 #include <netinet/tcp_fsm.h> 111 #include <netinet/tcp_seq.h> 112 #include <netinet/tcp_timer.h> 113 #include <netinet/tcp_timer2.h> 114 #include <netinet/tcp_var.h> 115 #include <netinet6/tcp6_var.h> 116 #include <netinet/tcpip.h> 117 118 #ifdef TCPDEBUG 119 #include <netinet/tcp_debug.h> 120 121 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 122 struct tcphdr tcp_savetcp; 123 #endif 124 125 #ifdef FAST_IPSEC 126 #include <netproto/ipsec/ipsec.h> 127 #include <netproto/ipsec/ipsec6.h> 128 #endif 129 130 #ifdef IPSEC 131 #include <netinet6/ipsec.h> 132 #include <netinet6/ipsec6.h> 133 #include <netproto/key/key.h> 134 #endif 135 136 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 137 138 static int log_in_vain = 0; 139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 140 &log_in_vain, 0, "Log all incoming TCP connections"); 141 142 static int blackhole = 0; 143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 144 &blackhole, 0, "Do not send RST when dropping refused connections"); 145 146 int tcp_delack_enabled = 1; 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 148 &tcp_delack_enabled, 0, 149 "Delay ACK to try and piggyback it onto a data packet"); 150 151 #ifdef TCP_DROP_SYNFIN 152 static int drop_synfin = 0; 153 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 154 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 155 #endif 156 157 static int tcp_do_limitedtransmit = 1; 158 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 159 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 160 161 static int tcp_do_early_retransmit = 1; 162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 163 &tcp_do_early_retransmit, 0, "Early retransmit"); 164 165 int tcp_aggregate_acks = 1; 166 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 167 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 168 169 int tcp_do_rfc3390 = 1; 170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 171 &tcp_do_rfc3390, 0, 172 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 173 174 static int tcp_do_eifel_detect = 1; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 176 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 177 178 static int tcp_do_abc = 1; 179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 180 &tcp_do_abc, 0, 181 "TCP Appropriate Byte Counting (RFC 3465)"); 182 183 /* 184 * Define as tunable for easy testing with SACK on and off. 185 * Warning: do not change setting in the middle of an existing active TCP flow, 186 * else strange things might happen to that flow. 187 */ 188 int tcp_do_sack = 1; 189 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 190 &tcp_do_sack, 0, "Enable SACK Algorithms"); 191 192 int tcp_do_smartsack = 1; 193 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 194 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 195 196 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 197 "TCP Segment Reassembly Queue"); 198 199 int tcp_reass_maxseg = 0; 200 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 201 &tcp_reass_maxseg, 0, 202 "Global maximum number of TCP Segments in Reassembly Queue"); 203 204 int tcp_reass_qsize = 0; 205 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 206 &tcp_reass_qsize, 0, 207 "Global number of TCP Segments currently in Reassembly Queue"); 208 209 static int tcp_reass_overflows = 0; 210 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 211 &tcp_reass_overflows, 0, 212 "Global number of TCP Segment Reassembly Queue Overflows"); 213 214 int tcp_do_autorcvbuf = 1; 215 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 216 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 217 218 int tcp_autorcvbuf_inc = 16*1024; 219 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 220 &tcp_autorcvbuf_inc, 0, 221 "Incrementor step size of automatic receive buffer"); 222 223 int tcp_autorcvbuf_max = 2*1024*1024; 224 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 225 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 226 227 228 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 229 static void tcp_pulloutofband(struct socket *, 230 struct tcphdr *, struct mbuf *, int); 231 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 232 struct mbuf *); 233 static void tcp_xmit_timer(struct tcpcb *, int); 234 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 235 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 236 237 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 238 #ifdef INET6 239 #define ND6_HINT(tp) \ 240 do { \ 241 if ((tp) && (tp)->t_inpcb && \ 242 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 243 (tp)->t_inpcb->in6p_route.ro_rt) \ 244 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 245 } while (0) 246 #else 247 #define ND6_HINT(tp) 248 #endif 249 250 /* 251 * Indicate whether this ack should be delayed. We can delay the ack if 252 * - delayed acks are enabled and 253 * - there is no delayed ack timer in progress and 254 * - our last ack wasn't a 0-sized window. We never want to delay 255 * the ack that opens up a 0-sized window. 256 */ 257 #define DELAY_ACK(tp) \ 258 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 259 !(tp->t_flags & TF_RXWIN0SENT)) 260 261 #define acceptable_window_update(tp, th, tiwin) \ 262 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 263 (tp->snd_wl1 == th->th_seq && \ 264 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 265 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 266 267 static int 268 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 269 { 270 struct tseg_qent *q; 271 struct tseg_qent *p = NULL; 272 struct tseg_qent *te; 273 struct socket *so = tp->t_inpcb->inp_socket; 274 int flags; 275 276 /* 277 * Call with th == NULL after become established to 278 * force pre-ESTABLISHED data up to user socket. 279 */ 280 if (th == NULL) 281 goto present; 282 283 /* 284 * Limit the number of segments in the reassembly queue to prevent 285 * holding on to too many segments (and thus running out of mbufs). 286 * Make sure to let the missing segment through which caused this 287 * queue. Always keep one global queue entry spare to be able to 288 * process the missing segment. 289 */ 290 if (th->th_seq != tp->rcv_nxt && 291 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 292 tcp_reass_overflows++; 293 tcpstat.tcps_rcvmemdrop++; 294 m_freem(m); 295 /* no SACK block to report */ 296 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 297 return (0); 298 } 299 300 /* Allocate a new queue entry. */ 301 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 302 M_INTWAIT | M_NULLOK); 303 if (te == NULL) { 304 tcpstat.tcps_rcvmemdrop++; 305 m_freem(m); 306 /* no SACK block to report */ 307 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 308 return (0); 309 } 310 tcp_reass_qsize++; 311 312 /* 313 * Find a segment which begins after this one does. 314 */ 315 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 316 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 317 break; 318 p = q; 319 } 320 321 /* 322 * If there is a preceding segment, it may provide some of 323 * our data already. If so, drop the data from the incoming 324 * segment. If it provides all of our data, drop us. 325 */ 326 if (p != NULL) { 327 tcp_seq_diff_t i; 328 329 /* conversion to int (in i) handles seq wraparound */ 330 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 331 if (i > 0) { /* overlaps preceding segment */ 332 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 333 /* enclosing block starts w/ preceding segment */ 334 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 335 if (i >= *tlenp) { 336 /* preceding encloses incoming segment */ 337 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 338 p->tqe_len; 339 tcpstat.tcps_rcvduppack++; 340 tcpstat.tcps_rcvdupbyte += *tlenp; 341 m_freem(m); 342 kfree(te, M_TSEGQ); 343 tcp_reass_qsize--; 344 /* 345 * Try to present any queued data 346 * at the left window edge to the user. 347 * This is needed after the 3-WHS 348 * completes. 349 */ 350 goto present; /* ??? */ 351 } 352 m_adj(m, i); 353 *tlenp -= i; 354 th->th_seq += i; 355 /* incoming segment end is enclosing block end */ 356 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 357 ((th->th_flags & TH_FIN) != 0); 358 /* trim end of reported D-SACK block */ 359 tp->reportblk.rblk_end = th->th_seq; 360 } 361 } 362 tcpstat.tcps_rcvoopack++; 363 tcpstat.tcps_rcvoobyte += *tlenp; 364 365 /* 366 * While we overlap succeeding segments trim them or, 367 * if they are completely covered, dequeue them. 368 */ 369 while (q) { 370 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 371 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 372 struct tseg_qent *nq; 373 374 if (i <= 0) 375 break; 376 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 377 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 378 tp->encloseblk = tp->reportblk; 379 /* report trailing duplicate D-SACK segment */ 380 tp->reportblk.rblk_start = q->tqe_th->th_seq; 381 } 382 if ((tp->t_flags & TF_ENCLOSESEG) && 383 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 384 /* extend enclosing block if one exists */ 385 tp->encloseblk.rblk_end = qend; 386 } 387 if (i < q->tqe_len) { 388 q->tqe_th->th_seq += i; 389 q->tqe_len -= i; 390 m_adj(q->tqe_m, i); 391 break; 392 } 393 394 nq = LIST_NEXT(q, tqe_q); 395 LIST_REMOVE(q, tqe_q); 396 m_freem(q->tqe_m); 397 kfree(q, M_TSEGQ); 398 tcp_reass_qsize--; 399 q = nq; 400 } 401 402 /* Insert the new segment queue entry into place. */ 403 te->tqe_m = m; 404 te->tqe_th = th; 405 te->tqe_len = *tlenp; 406 407 /* check if can coalesce with following segment */ 408 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 409 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 410 411 te->tqe_len += q->tqe_len; 412 if (q->tqe_th->th_flags & TH_FIN) 413 te->tqe_th->th_flags |= TH_FIN; 414 m_cat(te->tqe_m, q->tqe_m); 415 tp->encloseblk.rblk_end = tend; 416 /* 417 * When not reporting a duplicate segment, use 418 * the larger enclosing block as the SACK block. 419 */ 420 if (!(tp->t_flags & TF_DUPSEG)) 421 tp->reportblk.rblk_end = tend; 422 LIST_REMOVE(q, tqe_q); 423 kfree(q, M_TSEGQ); 424 tcp_reass_qsize--; 425 } 426 427 if (p == NULL) { 428 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 429 } else { 430 /* check if can coalesce with preceding segment */ 431 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 432 p->tqe_len += te->tqe_len; 433 m_cat(p->tqe_m, te->tqe_m); 434 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 435 /* 436 * When not reporting a duplicate segment, use 437 * the larger enclosing block as the SACK block. 438 */ 439 if (!(tp->t_flags & TF_DUPSEG)) 440 tp->reportblk.rblk_start = p->tqe_th->th_seq; 441 kfree(te, M_TSEGQ); 442 tcp_reass_qsize--; 443 } else 444 LIST_INSERT_AFTER(p, te, tqe_q); 445 } 446 447 present: 448 /* 449 * Present data to user, advancing rcv_nxt through 450 * completed sequence space. 451 */ 452 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 453 return (0); 454 q = LIST_FIRST(&tp->t_segq); 455 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 456 return (0); 457 tp->rcv_nxt += q->tqe_len; 458 if (!(tp->t_flags & TF_DUPSEG)) { 459 /* no SACK block to report since ACK advanced */ 460 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 461 } 462 /* no enclosing block to report since ACK advanced */ 463 tp->t_flags &= ~TF_ENCLOSESEG; 464 flags = q->tqe_th->th_flags & TH_FIN; 465 LIST_REMOVE(q, tqe_q); 466 KASSERT(LIST_EMPTY(&tp->t_segq) || 467 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 468 ("segment not coalesced")); 469 if (so->so_state & SS_CANTRCVMORE) 470 m_freem(q->tqe_m); 471 else 472 ssb_appendstream(&so->so_rcv, q->tqe_m); 473 kfree(q, M_TSEGQ); 474 tcp_reass_qsize--; 475 ND6_HINT(tp); 476 sorwakeup(so); 477 return (flags); 478 } 479 480 /* 481 * TCP input routine, follows pages 65-76 of the 482 * protocol specification dated September, 1981 very closely. 483 */ 484 #ifdef INET6 485 int 486 tcp6_input(struct mbuf **mp, int *offp, int proto) 487 { 488 struct mbuf *m = *mp; 489 struct in6_ifaddr *ia6; 490 491 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 492 493 /* 494 * draft-itojun-ipv6-tcp-to-anycast 495 * better place to put this in? 496 */ 497 ia6 = ip6_getdstifaddr(m); 498 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 499 struct ip6_hdr *ip6; 500 501 ip6 = mtod(m, struct ip6_hdr *); 502 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 503 offsetof(struct ip6_hdr, ip6_dst)); 504 return (IPPROTO_DONE); 505 } 506 507 tcp_input(m, *offp, proto); 508 return (IPPROTO_DONE); 509 } 510 #endif 511 512 void 513 tcp_input(struct mbuf *m, ...) 514 { 515 __va_list ap; 516 int off0, proto; 517 struct tcphdr *th; 518 struct ip *ip = NULL; 519 struct ipovly *ipov; 520 struct inpcb *inp = NULL; 521 u_char *optp = NULL; 522 int optlen = 0; 523 int len, tlen, off; 524 int drop_hdrlen; 525 struct tcpcb *tp = NULL; 526 int thflags; 527 struct socket *so = 0; 528 int todrop, acked; 529 boolean_t ourfinisacked, needoutput = FALSE; 530 u_long tiwin; 531 int recvwin; 532 struct tcpopt to; /* options in this segment */ 533 struct sockaddr_in *next_hop = NULL; 534 int rstreason; /* For badport_bandlim accounting purposes */ 535 int cpu; 536 struct ip6_hdr *ip6 = NULL; 537 #ifdef INET6 538 boolean_t isipv6; 539 #else 540 const boolean_t isipv6 = FALSE; 541 #endif 542 #ifdef TCPDEBUG 543 short ostate = 0; 544 #endif 545 546 __va_start(ap, m); 547 off0 = __va_arg(ap, int); 548 proto = __va_arg(ap, int); 549 __va_end(ap); 550 551 tcpstat.tcps_rcvtotal++; 552 553 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 554 struct m_tag *mtag; 555 556 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 557 KKASSERT(mtag != NULL); 558 next_hop = m_tag_data(mtag); 559 } 560 561 #ifdef INET6 562 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 563 #endif 564 565 if (isipv6) { 566 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 567 ip6 = mtod(m, struct ip6_hdr *); 568 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 569 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 570 tcpstat.tcps_rcvbadsum++; 571 goto drop; 572 } 573 th = (struct tcphdr *)((caddr_t)ip6 + off0); 574 575 /* 576 * Be proactive about unspecified IPv6 address in source. 577 * As we use all-zero to indicate unbounded/unconnected pcb, 578 * unspecified IPv6 address can be used to confuse us. 579 * 580 * Note that packets with unspecified IPv6 destination is 581 * already dropped in ip6_input. 582 */ 583 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 584 /* XXX stat */ 585 goto drop; 586 } 587 } else { 588 /* 589 * Get IP and TCP header together in first mbuf. 590 * Note: IP leaves IP header in first mbuf. 591 */ 592 if (off0 > sizeof(struct ip)) { 593 ip_stripoptions(m); 594 off0 = sizeof(struct ip); 595 } 596 /* already checked and pulled up in ip_demux() */ 597 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 598 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 599 ip = mtod(m, struct ip *); 600 ipov = (struct ipovly *)ip; 601 th = (struct tcphdr *)((caddr_t)ip + off0); 602 tlen = ip->ip_len; 603 604 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 605 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 606 th->th_sum = m->m_pkthdr.csum_data; 607 else 608 th->th_sum = in_pseudo(ip->ip_src.s_addr, 609 ip->ip_dst.s_addr, 610 htonl(m->m_pkthdr.csum_data + 611 ip->ip_len + 612 IPPROTO_TCP)); 613 th->th_sum ^= 0xffff; 614 } else { 615 /* 616 * Checksum extended TCP header and data. 617 */ 618 len = sizeof(struct ip) + tlen; 619 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 620 ipov->ih_len = (u_short)tlen; 621 ipov->ih_len = htons(ipov->ih_len); 622 th->th_sum = in_cksum(m, len); 623 } 624 if (th->th_sum) { 625 tcpstat.tcps_rcvbadsum++; 626 goto drop; 627 } 628 #ifdef INET6 629 /* Re-initialization for later version check */ 630 ip->ip_v = IPVERSION; 631 #endif 632 } 633 634 /* 635 * Check that TCP offset makes sense, 636 * pull out TCP options and adjust length. XXX 637 */ 638 off = th->th_off << 2; 639 /* already checked and pulled up in ip_demux() */ 640 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 641 ("bad TCP data offset %d (tlen %d)", off, tlen)); 642 tlen -= off; /* tlen is used instead of ti->ti_len */ 643 if (off > sizeof(struct tcphdr)) { 644 if (isipv6) { 645 IP6_EXTHDR_CHECK(m, off0, off, ); 646 ip6 = mtod(m, struct ip6_hdr *); 647 th = (struct tcphdr *)((caddr_t)ip6 + off0); 648 } else { 649 /* already pulled up in ip_demux() */ 650 KASSERT(m->m_len >= sizeof(struct ip) + off, 651 ("TCP header and options not in one mbuf: " 652 "m_len %d, off %d", m->m_len, off)); 653 } 654 optlen = off - sizeof(struct tcphdr); 655 optp = (u_char *)(th + 1); 656 } 657 thflags = th->th_flags; 658 659 #ifdef TCP_DROP_SYNFIN 660 /* 661 * If the drop_synfin option is enabled, drop all packets with 662 * both the SYN and FIN bits set. This prevents e.g. nmap from 663 * identifying the TCP/IP stack. 664 * 665 * This is a violation of the TCP specification. 666 */ 667 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 668 goto drop; 669 #endif 670 671 /* 672 * Convert TCP protocol specific fields to host format. 673 */ 674 th->th_seq = ntohl(th->th_seq); 675 th->th_ack = ntohl(th->th_ack); 676 th->th_win = ntohs(th->th_win); 677 th->th_urp = ntohs(th->th_urp); 678 679 /* 680 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 681 * until after ip6_savecontrol() is called and before other functions 682 * which don't want those proto headers. 683 * Because ip6_savecontrol() is going to parse the mbuf to 684 * search for data to be passed up to user-land, it wants mbuf 685 * parameters to be unchanged. 686 * XXX: the call of ip6_savecontrol() has been obsoleted based on 687 * latest version of the advanced API (20020110). 688 */ 689 drop_hdrlen = off0 + off; 690 691 /* 692 * Locate pcb for segment. 693 */ 694 findpcb: 695 /* IPFIREWALL_FORWARD section */ 696 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 697 /* 698 * Transparently forwarded. Pretend to be the destination. 699 * already got one like this? 700 */ 701 cpu = mycpu->gd_cpuid; 702 inp = in_pcblookup_hash(&tcbinfo[cpu], 703 ip->ip_src, th->th_sport, 704 ip->ip_dst, th->th_dport, 705 0, m->m_pkthdr.rcvif); 706 if (!inp) { 707 /* 708 * It's new. Try to find the ambushing socket. 709 */ 710 711 /* 712 * The rest of the ipfw code stores the port in 713 * host order. XXX 714 * (The IP address is still in network order.) 715 */ 716 in_port_t dport = next_hop->sin_port ? 717 htons(next_hop->sin_port) : 718 th->th_dport; 719 720 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 721 next_hop->sin_addr.s_addr, dport); 722 inp = in_pcblookup_hash(&tcbinfo[cpu], 723 ip->ip_src, th->th_sport, 724 next_hop->sin_addr, dport, 725 1, m->m_pkthdr.rcvif); 726 } 727 } else { 728 if (isipv6) { 729 inp = in6_pcblookup_hash(&tcbinfo[0], 730 &ip6->ip6_src, th->th_sport, 731 &ip6->ip6_dst, th->th_dport, 732 1, m->m_pkthdr.rcvif); 733 } else { 734 cpu = mycpu->gd_cpuid; 735 inp = in_pcblookup_hash(&tcbinfo[cpu], 736 ip->ip_src, th->th_sport, 737 ip->ip_dst, th->th_dport, 738 1, m->m_pkthdr.rcvif); 739 } 740 } 741 742 /* 743 * If the state is CLOSED (i.e., TCB does not exist) then 744 * all data in the incoming segment is discarded. 745 * If the TCB exists but is in CLOSED state, it is embryonic, 746 * but should either do a listen or a connect soon. 747 */ 748 if (inp == NULL) { 749 if (log_in_vain) { 750 #ifdef INET6 751 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 752 #else 753 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 754 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 755 #endif 756 if (isipv6) { 757 strcpy(dbuf, "["); 758 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 759 strcat(dbuf, "]"); 760 strcpy(sbuf, "["); 761 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 762 strcat(sbuf, "]"); 763 } else { 764 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 765 strcpy(sbuf, inet_ntoa(ip->ip_src)); 766 } 767 switch (log_in_vain) { 768 case 1: 769 if (!(thflags & TH_SYN)) 770 break; 771 case 2: 772 log(LOG_INFO, 773 "Connection attempt to TCP %s:%d " 774 "from %s:%d flags:0x%02x\n", 775 dbuf, ntohs(th->th_dport), sbuf, 776 ntohs(th->th_sport), thflags); 777 break; 778 default: 779 break; 780 } 781 } 782 if (blackhole) { 783 switch (blackhole) { 784 case 1: 785 if (thflags & TH_SYN) 786 goto drop; 787 break; 788 case 2: 789 goto drop; 790 default: 791 goto drop; 792 } 793 } 794 rstreason = BANDLIM_RST_CLOSEDPORT; 795 goto dropwithreset; 796 } 797 798 #ifdef IPSEC 799 if (isipv6) { 800 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 801 ipsec6stat.in_polvio++; 802 goto drop; 803 } 804 } else { 805 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 806 ipsecstat.in_polvio++; 807 goto drop; 808 } 809 } 810 #endif 811 #ifdef FAST_IPSEC 812 if (isipv6) { 813 if (ipsec6_in_reject(m, inp)) 814 goto drop; 815 } else { 816 if (ipsec4_in_reject(m, inp)) 817 goto drop; 818 } 819 #endif 820 /* Check the minimum TTL for socket. */ 821 #ifdef INET6 822 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 823 goto drop; 824 #endif 825 826 tp = intotcpcb(inp); 827 if (tp == NULL) { 828 rstreason = BANDLIM_RST_CLOSEDPORT; 829 goto dropwithreset; 830 } 831 if (tp->t_state <= TCPS_CLOSED) 832 goto drop; 833 834 /* Unscale the window into a 32-bit value. */ 835 if (!(thflags & TH_SYN)) 836 tiwin = th->th_win << tp->snd_scale; 837 else 838 tiwin = th->th_win; 839 840 so = inp->inp_socket; 841 842 #ifdef TCPDEBUG 843 if (so->so_options & SO_DEBUG) { 844 ostate = tp->t_state; 845 if (isipv6) 846 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 847 else 848 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 849 tcp_savetcp = *th; 850 } 851 #endif 852 853 bzero(&to, sizeof to); 854 855 if (so->so_options & SO_ACCEPTCONN) { 856 struct in_conninfo inc; 857 858 #ifdef INET6 859 inc.inc_isipv6 = (isipv6 == TRUE); 860 #endif 861 if (isipv6) { 862 inc.inc6_faddr = ip6->ip6_src; 863 inc.inc6_laddr = ip6->ip6_dst; 864 inc.inc6_route.ro_rt = NULL; /* XXX */ 865 } else { 866 inc.inc_faddr = ip->ip_src; 867 inc.inc_laddr = ip->ip_dst; 868 inc.inc_route.ro_rt = NULL; /* XXX */ 869 } 870 inc.inc_fport = th->th_sport; 871 inc.inc_lport = th->th_dport; 872 873 /* 874 * If the state is LISTEN then ignore segment if it contains 875 * a RST. If the segment contains an ACK then it is bad and 876 * send a RST. If it does not contain a SYN then it is not 877 * interesting; drop it. 878 * 879 * If the state is SYN_RECEIVED (syncache) and seg contains 880 * an ACK, but not for our SYN/ACK, send a RST. If the seg 881 * contains a RST, check the sequence number to see if it 882 * is a valid reset segment. 883 */ 884 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 885 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 886 if (!syncache_expand(&inc, th, &so, m)) { 887 /* 888 * No syncache entry, or ACK was not 889 * for our SYN/ACK. Send a RST. 890 */ 891 tcpstat.tcps_badsyn++; 892 rstreason = BANDLIM_RST_OPENPORT; 893 goto dropwithreset; 894 } 895 if (so == NULL) 896 /* 897 * Could not complete 3-way handshake, 898 * connection is being closed down, and 899 * syncache will free mbuf. 900 */ 901 return; 902 /* 903 * Socket is created in state SYN_RECEIVED. 904 * Continue processing segment. 905 */ 906 inp = so->so_pcb; 907 tp = intotcpcb(inp); 908 /* 909 * This is what would have happened in 910 * tcp_output() when the SYN,ACK was sent. 911 */ 912 tp->snd_up = tp->snd_una; 913 tp->snd_max = tp->snd_nxt = tp->iss + 1; 914 tp->last_ack_sent = tp->rcv_nxt; 915 /* 916 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 917 * until the _second_ ACK is received: 918 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 919 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 920 * move to ESTAB, set snd_wnd to tiwin. 921 */ 922 tp->snd_wnd = tiwin; /* unscaled */ 923 goto after_listen; 924 } 925 if (thflags & TH_RST) { 926 syncache_chkrst(&inc, th); 927 goto drop; 928 } 929 if (thflags & TH_ACK) { 930 syncache_badack(&inc); 931 tcpstat.tcps_badsyn++; 932 rstreason = BANDLIM_RST_OPENPORT; 933 goto dropwithreset; 934 } 935 goto drop; 936 } 937 938 /* 939 * Segment's flags are (SYN) or (SYN | FIN). 940 */ 941 #ifdef INET6 942 /* 943 * If deprecated address is forbidden, 944 * we do not accept SYN to deprecated interface 945 * address to prevent any new inbound connection from 946 * getting established. 947 * When we do not accept SYN, we send a TCP RST, 948 * with deprecated source address (instead of dropping 949 * it). We compromise it as it is much better for peer 950 * to send a RST, and RST will be the final packet 951 * for the exchange. 952 * 953 * If we do not forbid deprecated addresses, we accept 954 * the SYN packet. RFC2462 does not suggest dropping 955 * SYN in this case. 956 * If we decipher RFC2462 5.5.4, it says like this: 957 * 1. use of deprecated addr with existing 958 * communication is okay - "SHOULD continue to be 959 * used" 960 * 2. use of it with new communication: 961 * (2a) "SHOULD NOT be used if alternate address 962 * with sufficient scope is available" 963 * (2b) nothing mentioned otherwise. 964 * Here we fall into (2b) case as we have no choice in 965 * our source address selection - we must obey the peer. 966 * 967 * The wording in RFC2462 is confusing, and there are 968 * multiple description text for deprecated address 969 * handling - worse, they are not exactly the same. 970 * I believe 5.5.4 is the best one, so we follow 5.5.4. 971 */ 972 if (isipv6 && !ip6_use_deprecated) { 973 struct in6_ifaddr *ia6; 974 975 if ((ia6 = ip6_getdstifaddr(m)) && 976 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 977 tp = NULL; 978 rstreason = BANDLIM_RST_OPENPORT; 979 goto dropwithreset; 980 } 981 } 982 #endif 983 /* 984 * If it is from this socket, drop it, it must be forged. 985 * Don't bother responding if the destination was a broadcast. 986 */ 987 if (th->th_dport == th->th_sport) { 988 if (isipv6) { 989 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 990 &ip6->ip6_src)) 991 goto drop; 992 } else { 993 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 994 goto drop; 995 } 996 } 997 /* 998 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 999 * 1000 * Note that it is quite possible to receive unicast 1001 * link-layer packets with a broadcast IP address. Use 1002 * in_broadcast() to find them. 1003 */ 1004 if (m->m_flags & (M_BCAST | M_MCAST)) 1005 goto drop; 1006 if (isipv6) { 1007 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1008 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1009 goto drop; 1010 } else { 1011 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1012 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1013 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1014 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1015 goto drop; 1016 } 1017 /* 1018 * SYN appears to be valid; create compressed TCP state 1019 * for syncache, or perform t/tcp connection. 1020 */ 1021 if (so->so_qlen <= so->so_qlimit) { 1022 tcp_dooptions(&to, optp, optlen, TRUE); 1023 if (!syncache_add(&inc, &to, th, &so, m)) 1024 goto drop; 1025 if (so == NULL) 1026 /* 1027 * Entry added to syncache, mbuf used to 1028 * send SYN,ACK packet. 1029 */ 1030 return; 1031 inp = so->so_pcb; 1032 tp = intotcpcb(inp); 1033 tp->snd_wnd = tiwin; 1034 tp->t_starttime = ticks; 1035 tp->t_state = TCPS_ESTABLISHED; 1036 1037 /* 1038 * If there is a FIN, or if there is data and the 1039 * connection is local, then delay SYN,ACK(SYN) in 1040 * the hope of piggy-backing it on a response 1041 * segment. Otherwise must send ACK now in case 1042 * the other side is slow starting. 1043 */ 1044 if (DELAY_ACK(tp) && 1045 ((thflags & TH_FIN) || 1046 (tlen != 0 && 1047 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1048 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1049 tcp_callout_reset(tp, tp->tt_delack, 1050 tcp_delacktime, tcp_timer_delack); 1051 tp->t_flags |= TF_NEEDSYN; 1052 } else { 1053 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1054 } 1055 1056 tcpstat.tcps_connects++; 1057 soisconnected(so); 1058 goto trimthenstep6; 1059 } 1060 goto drop; 1061 } 1062 after_listen: 1063 1064 /* should not happen - syncache should pick up these connections */ 1065 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1066 1067 /* 1068 * This is the second part of the MSS DoS prevention code (after 1069 * minmss on the sending side) and it deals with too many too small 1070 * tcp packets in a too short timeframe (1 second). 1071 * 1072 * XXX Removed. This code was crap. It does not scale to network 1073 * speed, and default values break NFS. Gone. 1074 */ 1075 /* REMOVED */ 1076 1077 /* 1078 * Segment received on connection. 1079 * 1080 * Reset idle time and keep-alive timer. Don't waste time if less 1081 * then a second has elapsed. Only update t_rcvtime for non-SYN 1082 * packets. 1083 * 1084 * Handle the case where one side thinks the connection is established 1085 * but the other side has, say, rebooted without cleaning out the 1086 * connection. The SYNs could be construed as an attack and wind 1087 * up ignored, but in case it isn't an attack we can validate the 1088 * connection by forcing a keepalive. 1089 */ 1090 if (TCPS_HAVEESTABLISHED(tp->t_state) && (ticks - tp->t_rcvtime) > hz) { 1091 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 1092 tp->t_flags |= TF_KEEPALIVE; 1093 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 1094 tcp_timer_keep); 1095 } else { 1096 tp->t_rcvtime = ticks; 1097 tp->t_flags &= ~TF_KEEPALIVE; 1098 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1099 tcp_timer_keep); 1100 } 1101 } 1102 1103 /* 1104 * Process options. 1105 * XXX this is tradtitional behavior, may need to be cleaned up. 1106 */ 1107 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1108 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1109 if (to.to_flags & TOF_SCALE) { 1110 tp->t_flags |= TF_RCVD_SCALE; 1111 tp->requested_s_scale = to.to_requested_s_scale; 1112 } 1113 if (to.to_flags & TOF_TS) { 1114 tp->t_flags |= TF_RCVD_TSTMP; 1115 tp->ts_recent = to.to_tsval; 1116 tp->ts_recent_age = ticks; 1117 } 1118 if (to.to_flags & TOF_MSS) 1119 tcp_mss(tp, to.to_mss); 1120 /* 1121 * Only set the TF_SACK_PERMITTED per-connection flag 1122 * if we got a SACK_PERMITTED option from the other side 1123 * and the global tcp_do_sack variable is true. 1124 */ 1125 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1126 tp->t_flags |= TF_SACK_PERMITTED; 1127 } 1128 1129 /* 1130 * Header prediction: check for the two common cases 1131 * of a uni-directional data xfer. If the packet has 1132 * no control flags, is in-sequence, the window didn't 1133 * change and we're not retransmitting, it's a 1134 * candidate. If the length is zero and the ack moved 1135 * forward, we're the sender side of the xfer. Just 1136 * free the data acked & wake any higher level process 1137 * that was blocked waiting for space. If the length 1138 * is non-zero and the ack didn't move, we're the 1139 * receiver side. If we're getting packets in-order 1140 * (the reassembly queue is empty), add the data to 1141 * the socket buffer and note that we need a delayed ack. 1142 * Make sure that the hidden state-flags are also off. 1143 * Since we check for TCPS_ESTABLISHED above, it can only 1144 * be TH_NEEDSYN. 1145 */ 1146 if (tp->t_state == TCPS_ESTABLISHED && 1147 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1148 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1149 (!(to.to_flags & TOF_TS) || 1150 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1151 th->th_seq == tp->rcv_nxt && 1152 tp->snd_nxt == tp->snd_max) { 1153 1154 /* 1155 * If last ACK falls within this segment's sequence numbers, 1156 * record the timestamp. 1157 * NOTE that the test is modified according to the latest 1158 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1159 */ 1160 if ((to.to_flags & TOF_TS) && 1161 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1162 tp->ts_recent_age = ticks; 1163 tp->ts_recent = to.to_tsval; 1164 } 1165 1166 if (tlen == 0) { 1167 if (SEQ_GT(th->th_ack, tp->snd_una) && 1168 SEQ_LEQ(th->th_ack, tp->snd_max) && 1169 tp->snd_cwnd >= tp->snd_wnd && 1170 !IN_FASTRECOVERY(tp)) { 1171 /* 1172 * This is a pure ack for outstanding data. 1173 */ 1174 ++tcpstat.tcps_predack; 1175 /* 1176 * "bad retransmit" recovery 1177 * 1178 * If Eifel detection applies, then 1179 * it is deterministic, so use it 1180 * unconditionally over the old heuristic. 1181 * Otherwise, fall back to the old heuristic. 1182 */ 1183 if (tcp_do_eifel_detect && 1184 (to.to_flags & TOF_TS) && to.to_tsecr && 1185 (tp->t_flags & TF_FIRSTACCACK)) { 1186 /* Eifel detection applicable. */ 1187 if (to.to_tsecr < tp->t_rexmtTS) { 1188 tcp_revert_congestion_state(tp); 1189 ++tcpstat.tcps_eifeldetected; 1190 } 1191 } else if (tp->t_rxtshift == 1 && 1192 ticks < tp->t_badrxtwin) { 1193 tcp_revert_congestion_state(tp); 1194 ++tcpstat.tcps_rttdetected; 1195 } 1196 tp->t_flags &= ~(TF_FIRSTACCACK | 1197 TF_FASTREXMT | TF_EARLYREXMT); 1198 /* 1199 * Recalculate the retransmit timer / rtt. 1200 * 1201 * Some machines (certain windows boxes) 1202 * send broken timestamp replies during the 1203 * SYN+ACK phase, ignore timestamps of 0. 1204 */ 1205 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1206 tcp_xmit_timer(tp, 1207 ticks - to.to_tsecr + 1); 1208 } else if (tp->t_rtttime && 1209 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1210 tcp_xmit_timer(tp, 1211 ticks - tp->t_rtttime); 1212 } 1213 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1214 acked = th->th_ack - tp->snd_una; 1215 tcpstat.tcps_rcvackpack++; 1216 tcpstat.tcps_rcvackbyte += acked; 1217 sbdrop(&so->so_snd.sb, acked); 1218 tp->snd_recover = th->th_ack - 1; 1219 tp->snd_una = th->th_ack; 1220 tp->t_dupacks = 0; 1221 /* 1222 * Update window information. 1223 */ 1224 if (tiwin != tp->snd_wnd && 1225 acceptable_window_update(tp, th, tiwin)) { 1226 /* keep track of pure window updates */ 1227 if (tp->snd_wl2 == th->th_ack && 1228 tiwin > tp->snd_wnd) 1229 tcpstat.tcps_rcvwinupd++; 1230 tp->snd_wnd = tiwin; 1231 tp->snd_wl1 = th->th_seq; 1232 tp->snd_wl2 = th->th_ack; 1233 if (tp->snd_wnd > tp->max_sndwnd) 1234 tp->max_sndwnd = tp->snd_wnd; 1235 } 1236 m_freem(m); 1237 ND6_HINT(tp); /* some progress has been done */ 1238 /* 1239 * If all outstanding data are acked, stop 1240 * retransmit timer, otherwise restart timer 1241 * using current (possibly backed-off) value. 1242 * If process is waiting for space, 1243 * wakeup/selwakeup/signal. If data 1244 * are ready to send, let tcp_output 1245 * decide between more output or persist. 1246 */ 1247 if (tp->snd_una == tp->snd_max) { 1248 tcp_callout_stop(tp, tp->tt_rexmt); 1249 } else if (!tcp_callout_active(tp, 1250 tp->tt_persist)) { 1251 tcp_callout_reset(tp, tp->tt_rexmt, 1252 tp->t_rxtcur, tcp_timer_rexmt); 1253 } 1254 sowwakeup(so); 1255 if (so->so_snd.ssb_cc > 0) 1256 tcp_output(tp); 1257 return; 1258 } 1259 } else if (tiwin == tp->snd_wnd && 1260 th->th_ack == tp->snd_una && 1261 LIST_EMPTY(&tp->t_segq) && 1262 tlen <= ssb_space(&so->so_rcv)) { 1263 u_long newsize = 0; /* automatic sockbuf scaling */ 1264 /* 1265 * This is a pure, in-sequence data packet 1266 * with nothing on the reassembly queue and 1267 * we have enough buffer space to take it. 1268 */ 1269 ++tcpstat.tcps_preddat; 1270 tp->rcv_nxt += tlen; 1271 tcpstat.tcps_rcvpack++; 1272 tcpstat.tcps_rcvbyte += tlen; 1273 ND6_HINT(tp); /* some progress has been done */ 1274 /* 1275 * Automatic sizing of receive socket buffer. Often the send 1276 * buffer size is not optimally adjusted to the actual network 1277 * conditions at hand (delay bandwidth product). Setting the 1278 * buffer size too small limits throughput on links with high 1279 * bandwidth and high delay (eg. trans-continental/oceanic links). 1280 * 1281 * On the receive side the socket buffer memory is only rarely 1282 * used to any significant extent. This allows us to be much 1283 * more aggressive in scaling the receive socket buffer. For 1284 * the case that the buffer space is actually used to a large 1285 * extent and we run out of kernel memory we can simply drop 1286 * the new segments; TCP on the sender will just retransmit it 1287 * later. Setting the buffer size too big may only consume too 1288 * much kernel memory if the application doesn't read() from 1289 * the socket or packet loss or reordering makes use of the 1290 * reassembly queue. 1291 * 1292 * The criteria to step up the receive buffer one notch are: 1293 * 1. the number of bytes received during the time it takes 1294 * one timestamp to be reflected back to us (the RTT); 1295 * 2. received bytes per RTT is within seven eighth of the 1296 * current socket buffer size; 1297 * 3. receive buffer size has not hit maximal automatic size; 1298 * 1299 * This algorithm does one step per RTT at most and only if 1300 * we receive a bulk stream w/o packet losses or reorderings. 1301 * Shrinking the buffer during idle times is not necessary as 1302 * it doesn't consume any memory when idle. 1303 * 1304 * TODO: Only step up if the application is actually serving 1305 * the buffer to better manage the socket buffer resources. 1306 */ 1307 if (tcp_do_autorcvbuf && 1308 to.to_tsecr && 1309 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1310 if (to.to_tsecr > tp->rfbuf_ts && 1311 to.to_tsecr - tp->rfbuf_ts < hz) { 1312 if (tp->rfbuf_cnt > 1313 (so->so_rcv.ssb_hiwat / 8 * 7) && 1314 so->so_rcv.ssb_hiwat < 1315 tcp_autorcvbuf_max) { 1316 newsize = 1317 ulmin(so->so_rcv.ssb_hiwat + 1318 tcp_autorcvbuf_inc, 1319 tcp_autorcvbuf_max); 1320 } 1321 /* Start over with next RTT. */ 1322 tp->rfbuf_ts = 0; 1323 tp->rfbuf_cnt = 0; 1324 } else 1325 tp->rfbuf_cnt += tlen; /* add up */ 1326 } 1327 /* 1328 * Add data to socket buffer. 1329 */ 1330 if (so->so_state & SS_CANTRCVMORE) { 1331 m_freem(m); 1332 } else { 1333 /* 1334 * Set new socket buffer size, give up when 1335 * limit is reached. 1336 * 1337 * Adjusting the size can mess up ACK 1338 * sequencing when pure window updates are 1339 * being avoided (which is the default), 1340 * so force an ack. 1341 */ 1342 if (newsize) { 1343 tp->t_flags |= TF_RXRESIZED; 1344 if (!ssb_reserve(&so->so_rcv, newsize, 1345 so, NULL)) { 1346 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE; 1347 } 1348 if (newsize >= 1349 (TCP_MAXWIN << tp->rcv_scale)) { 1350 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE; 1351 } 1352 } 1353 m_adj(m, drop_hdrlen); /* delayed header drop */ 1354 ssb_appendstream(&so->so_rcv, m); 1355 } 1356 sorwakeup(so); 1357 /* 1358 * This code is responsible for most of the ACKs 1359 * the TCP stack sends back after receiving a data 1360 * packet. Note that the DELAY_ACK check fails if 1361 * the delack timer is already running, which results 1362 * in an ack being sent every other packet (which is 1363 * what we want). 1364 * 1365 * We then further aggregate acks by not actually 1366 * sending one until the protocol thread has completed 1367 * processing the current backlog of packets. This 1368 * does not delay the ack any further, but allows us 1369 * to take advantage of the packet aggregation that 1370 * high speed NICs do (usually blocks of 8-10 packets) 1371 * to send a single ack rather then four or five acks, 1372 * greatly reducing the ack rate, the return channel 1373 * bandwidth, and the protocol overhead on both ends. 1374 * 1375 * Since this also has the effect of slowing down 1376 * the exponential slow-start ramp-up, systems with 1377 * very large bandwidth-delay products might want 1378 * to turn the feature off. 1379 */ 1380 if (DELAY_ACK(tp)) { 1381 tcp_callout_reset(tp, tp->tt_delack, 1382 tcp_delacktime, tcp_timer_delack); 1383 } else if (tcp_aggregate_acks) { 1384 tp->t_flags |= TF_ACKNOW; 1385 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1386 tp->t_flags |= TF_ONOUTPUTQ; 1387 tp->tt_cpu = mycpu->gd_cpuid; 1388 TAILQ_INSERT_TAIL( 1389 &tcpcbackq[tp->tt_cpu], 1390 tp, t_outputq); 1391 } 1392 } else { 1393 tp->t_flags |= TF_ACKNOW; 1394 tcp_output(tp); 1395 } 1396 return; 1397 } 1398 } 1399 1400 /* 1401 * Calculate amount of space in receive window, 1402 * and then do TCP input processing. 1403 * Receive window is amount of space in rcv queue, 1404 * but not less than advertised window. 1405 */ 1406 recvwin = ssb_space(&so->so_rcv); 1407 if (recvwin < 0) 1408 recvwin = 0; 1409 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1410 1411 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1412 tp->rfbuf_ts = 0; 1413 tp->rfbuf_cnt = 0; 1414 1415 switch (tp->t_state) { 1416 /* 1417 * If the state is SYN_RECEIVED: 1418 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1419 */ 1420 case TCPS_SYN_RECEIVED: 1421 if ((thflags & TH_ACK) && 1422 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1423 SEQ_GT(th->th_ack, tp->snd_max))) { 1424 rstreason = BANDLIM_RST_OPENPORT; 1425 goto dropwithreset; 1426 } 1427 break; 1428 1429 /* 1430 * If the state is SYN_SENT: 1431 * if seg contains an ACK, but not for our SYN, drop the input. 1432 * if seg contains a RST, then drop the connection. 1433 * if seg does not contain SYN, then drop it. 1434 * Otherwise this is an acceptable SYN segment 1435 * initialize tp->rcv_nxt and tp->irs 1436 * if seg contains ack then advance tp->snd_una 1437 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1438 * arrange for segment to be acked (eventually) 1439 * continue processing rest of data/controls, beginning with URG 1440 */ 1441 case TCPS_SYN_SENT: 1442 if ((thflags & TH_ACK) && 1443 (SEQ_LEQ(th->th_ack, tp->iss) || 1444 SEQ_GT(th->th_ack, tp->snd_max))) { 1445 rstreason = BANDLIM_UNLIMITED; 1446 goto dropwithreset; 1447 } 1448 if (thflags & TH_RST) { 1449 if (thflags & TH_ACK) 1450 tp = tcp_drop(tp, ECONNREFUSED); 1451 goto drop; 1452 } 1453 if (!(thflags & TH_SYN)) 1454 goto drop; 1455 tp->snd_wnd = th->th_win; /* initial send window */ 1456 1457 tp->irs = th->th_seq; 1458 tcp_rcvseqinit(tp); 1459 if (thflags & TH_ACK) { 1460 /* Our SYN was acked. */ 1461 tcpstat.tcps_connects++; 1462 soisconnected(so); 1463 /* Do window scaling on this connection? */ 1464 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1465 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1466 tp->snd_scale = tp->requested_s_scale; 1467 tp->rcv_scale = tp->request_r_scale; 1468 } 1469 tp->rcv_adv += tp->rcv_wnd; 1470 tp->snd_una++; /* SYN is acked */ 1471 tcp_callout_stop(tp, tp->tt_rexmt); 1472 /* 1473 * If there's data, delay ACK; if there's also a FIN 1474 * ACKNOW will be turned on later. 1475 */ 1476 if (DELAY_ACK(tp) && tlen != 0) { 1477 tcp_callout_reset(tp, tp->tt_delack, 1478 tcp_delacktime, tcp_timer_delack); 1479 } else { 1480 tp->t_flags |= TF_ACKNOW; 1481 } 1482 /* 1483 * Received <SYN,ACK> in SYN_SENT[*] state. 1484 * Transitions: 1485 * SYN_SENT --> ESTABLISHED 1486 * SYN_SENT* --> FIN_WAIT_1 1487 */ 1488 tp->t_starttime = ticks; 1489 if (tp->t_flags & TF_NEEDFIN) { 1490 tp->t_state = TCPS_FIN_WAIT_1; 1491 tp->t_flags &= ~TF_NEEDFIN; 1492 thflags &= ~TH_SYN; 1493 } else { 1494 tp->t_state = TCPS_ESTABLISHED; 1495 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1496 tcp_timer_keep); 1497 } 1498 } else { 1499 /* 1500 * Received initial SYN in SYN-SENT[*] state => 1501 * simultaneous open. 1502 * Do 3-way handshake: 1503 * SYN-SENT -> SYN-RECEIVED 1504 * SYN-SENT* -> SYN-RECEIVED* 1505 */ 1506 tp->t_flags |= TF_ACKNOW; 1507 tcp_callout_stop(tp, tp->tt_rexmt); 1508 tp->t_state = TCPS_SYN_RECEIVED; 1509 } 1510 1511 trimthenstep6: 1512 /* 1513 * Advance th->th_seq to correspond to first data byte. 1514 * If data, trim to stay within window, 1515 * dropping FIN if necessary. 1516 */ 1517 th->th_seq++; 1518 if (tlen > tp->rcv_wnd) { 1519 todrop = tlen - tp->rcv_wnd; 1520 m_adj(m, -todrop); 1521 tlen = tp->rcv_wnd; 1522 thflags &= ~TH_FIN; 1523 tcpstat.tcps_rcvpackafterwin++; 1524 tcpstat.tcps_rcvbyteafterwin += todrop; 1525 } 1526 tp->snd_wl1 = th->th_seq - 1; 1527 tp->rcv_up = th->th_seq; 1528 /* 1529 * Client side of transaction: already sent SYN and data. 1530 * If the remote host used T/TCP to validate the SYN, 1531 * our data will be ACK'd; if so, enter normal data segment 1532 * processing in the middle of step 5, ack processing. 1533 * Otherwise, goto step 6. 1534 */ 1535 if (thflags & TH_ACK) 1536 goto process_ACK; 1537 1538 goto step6; 1539 1540 /* 1541 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1542 * do normal processing (we no longer bother with T/TCP). 1543 */ 1544 case TCPS_LAST_ACK: 1545 case TCPS_CLOSING: 1546 case TCPS_TIME_WAIT: 1547 break; /* continue normal processing */ 1548 } 1549 1550 /* 1551 * States other than LISTEN or SYN_SENT. 1552 * First check the RST flag and sequence number since reset segments 1553 * are exempt from the timestamp and connection count tests. This 1554 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1555 * below which allowed reset segments in half the sequence space 1556 * to fall though and be processed (which gives forged reset 1557 * segments with a random sequence number a 50 percent chance of 1558 * killing a connection). 1559 * Then check timestamp, if present. 1560 * Then check the connection count, if present. 1561 * Then check that at least some bytes of segment are within 1562 * receive window. If segment begins before rcv_nxt, 1563 * drop leading data (and SYN); if nothing left, just ack. 1564 * 1565 * 1566 * If the RST bit is set, check the sequence number to see 1567 * if this is a valid reset segment. 1568 * RFC 793 page 37: 1569 * In all states except SYN-SENT, all reset (RST) segments 1570 * are validated by checking their SEQ-fields. A reset is 1571 * valid if its sequence number is in the window. 1572 * Note: this does not take into account delayed ACKs, so 1573 * we should test against last_ack_sent instead of rcv_nxt. 1574 * The sequence number in the reset segment is normally an 1575 * echo of our outgoing acknowledgement numbers, but some hosts 1576 * send a reset with the sequence number at the rightmost edge 1577 * of our receive window, and we have to handle this case. 1578 * If we have multiple segments in flight, the intial reset 1579 * segment sequence numbers will be to the left of last_ack_sent, 1580 * but they will eventually catch up. 1581 * In any case, it never made sense to trim reset segments to 1582 * fit the receive window since RFC 1122 says: 1583 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1584 * 1585 * A TCP SHOULD allow a received RST segment to include data. 1586 * 1587 * DISCUSSION 1588 * It has been suggested that a RST segment could contain 1589 * ASCII text that encoded and explained the cause of the 1590 * RST. No standard has yet been established for such 1591 * data. 1592 * 1593 * If the reset segment passes the sequence number test examine 1594 * the state: 1595 * SYN_RECEIVED STATE: 1596 * If passive open, return to LISTEN state. 1597 * If active open, inform user that connection was refused. 1598 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1599 * Inform user that connection was reset, and close tcb. 1600 * CLOSING, LAST_ACK STATES: 1601 * Close the tcb. 1602 * TIME_WAIT STATE: 1603 * Drop the segment - see Stevens, vol. 2, p. 964 and 1604 * RFC 1337. 1605 */ 1606 if (thflags & TH_RST) { 1607 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1608 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1609 switch (tp->t_state) { 1610 1611 case TCPS_SYN_RECEIVED: 1612 so->so_error = ECONNREFUSED; 1613 goto close; 1614 1615 case TCPS_ESTABLISHED: 1616 case TCPS_FIN_WAIT_1: 1617 case TCPS_FIN_WAIT_2: 1618 case TCPS_CLOSE_WAIT: 1619 so->so_error = ECONNRESET; 1620 close: 1621 tp->t_state = TCPS_CLOSED; 1622 tcpstat.tcps_drops++; 1623 tp = tcp_close(tp); 1624 break; 1625 1626 case TCPS_CLOSING: 1627 case TCPS_LAST_ACK: 1628 tp = tcp_close(tp); 1629 break; 1630 1631 case TCPS_TIME_WAIT: 1632 break; 1633 } 1634 } 1635 goto drop; 1636 } 1637 1638 /* 1639 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1640 * and it's less than ts_recent, drop it. 1641 */ 1642 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1643 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1644 1645 /* Check to see if ts_recent is over 24 days old. */ 1646 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1647 /* 1648 * Invalidate ts_recent. If this segment updates 1649 * ts_recent, the age will be reset later and ts_recent 1650 * will get a valid value. If it does not, setting 1651 * ts_recent to zero will at least satisfy the 1652 * requirement that zero be placed in the timestamp 1653 * echo reply when ts_recent isn't valid. The 1654 * age isn't reset until we get a valid ts_recent 1655 * because we don't want out-of-order segments to be 1656 * dropped when ts_recent is old. 1657 */ 1658 tp->ts_recent = 0; 1659 } else { 1660 tcpstat.tcps_rcvduppack++; 1661 tcpstat.tcps_rcvdupbyte += tlen; 1662 tcpstat.tcps_pawsdrop++; 1663 if (tlen) 1664 goto dropafterack; 1665 goto drop; 1666 } 1667 } 1668 1669 /* 1670 * In the SYN-RECEIVED state, validate that the packet belongs to 1671 * this connection before trimming the data to fit the receive 1672 * window. Check the sequence number versus IRS since we know 1673 * the sequence numbers haven't wrapped. This is a partial fix 1674 * for the "LAND" DoS attack. 1675 */ 1676 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1677 rstreason = BANDLIM_RST_OPENPORT; 1678 goto dropwithreset; 1679 } 1680 1681 todrop = tp->rcv_nxt - th->th_seq; 1682 if (todrop > 0) { 1683 if (TCP_DO_SACK(tp)) { 1684 /* Report duplicate segment at head of packet. */ 1685 tp->reportblk.rblk_start = th->th_seq; 1686 tp->reportblk.rblk_end = th->th_seq + tlen; 1687 if (thflags & TH_FIN) 1688 ++tp->reportblk.rblk_end; 1689 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1690 tp->reportblk.rblk_end = tp->rcv_nxt; 1691 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1692 } 1693 if (thflags & TH_SYN) { 1694 thflags &= ~TH_SYN; 1695 th->th_seq++; 1696 if (th->th_urp > 1) 1697 th->th_urp--; 1698 else 1699 thflags &= ~TH_URG; 1700 todrop--; 1701 } 1702 /* 1703 * Following if statement from Stevens, vol. 2, p. 960. 1704 */ 1705 if (todrop > tlen || 1706 (todrop == tlen && !(thflags & TH_FIN))) { 1707 /* 1708 * Any valid FIN must be to the left of the window. 1709 * At this point the FIN must be a duplicate or out 1710 * of sequence; drop it. 1711 */ 1712 thflags &= ~TH_FIN; 1713 1714 /* 1715 * Send an ACK to resynchronize and drop any data. 1716 * But keep on processing for RST or ACK. 1717 */ 1718 tp->t_flags |= TF_ACKNOW; 1719 todrop = tlen; 1720 tcpstat.tcps_rcvduppack++; 1721 tcpstat.tcps_rcvdupbyte += todrop; 1722 } else { 1723 tcpstat.tcps_rcvpartduppack++; 1724 tcpstat.tcps_rcvpartdupbyte += todrop; 1725 } 1726 drop_hdrlen += todrop; /* drop from the top afterwards */ 1727 th->th_seq += todrop; 1728 tlen -= todrop; 1729 if (th->th_urp > todrop) 1730 th->th_urp -= todrop; 1731 else { 1732 thflags &= ~TH_URG; 1733 th->th_urp = 0; 1734 } 1735 } 1736 1737 /* 1738 * If new data are received on a connection after the 1739 * user processes are gone, then RST the other end. 1740 */ 1741 if ((so->so_state & SS_NOFDREF) && 1742 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1743 tp = tcp_close(tp); 1744 tcpstat.tcps_rcvafterclose++; 1745 rstreason = BANDLIM_UNLIMITED; 1746 goto dropwithreset; 1747 } 1748 1749 /* 1750 * If segment ends after window, drop trailing data 1751 * (and PUSH and FIN); if nothing left, just ACK. 1752 */ 1753 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1754 if (todrop > 0) { 1755 tcpstat.tcps_rcvpackafterwin++; 1756 if (todrop >= tlen) { 1757 tcpstat.tcps_rcvbyteafterwin += tlen; 1758 /* 1759 * If a new connection request is received 1760 * while in TIME_WAIT, drop the old connection 1761 * and start over if the sequence numbers 1762 * are above the previous ones. 1763 */ 1764 if (thflags & TH_SYN && 1765 tp->t_state == TCPS_TIME_WAIT && 1766 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1767 tp = tcp_close(tp); 1768 goto findpcb; 1769 } 1770 /* 1771 * If window is closed can only take segments at 1772 * window edge, and have to drop data and PUSH from 1773 * incoming segments. Continue processing, but 1774 * remember to ack. Otherwise, drop segment 1775 * and ack. 1776 */ 1777 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1778 tp->t_flags |= TF_ACKNOW; 1779 tcpstat.tcps_rcvwinprobe++; 1780 } else 1781 goto dropafterack; 1782 } else 1783 tcpstat.tcps_rcvbyteafterwin += todrop; 1784 m_adj(m, -todrop); 1785 tlen -= todrop; 1786 thflags &= ~(TH_PUSH | TH_FIN); 1787 } 1788 1789 /* 1790 * If last ACK falls within this segment's sequence numbers, 1791 * record its timestamp. 1792 * NOTE: 1793 * 1) That the test incorporates suggestions from the latest 1794 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1795 * 2) That updating only on newer timestamps interferes with 1796 * our earlier PAWS tests, so this check should be solely 1797 * predicated on the sequence space of this segment. 1798 * 3) That we modify the segment boundary check to be 1799 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1800 * instead of RFC1323's 1801 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1802 * This modified check allows us to overcome RFC1323's 1803 * limitations as described in Stevens TCP/IP Illustrated 1804 * Vol. 2 p.869. In such cases, we can still calculate the 1805 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1806 */ 1807 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1808 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1809 + ((thflags & TH_SYN) != 0) 1810 + ((thflags & TH_FIN) != 0)))) { 1811 tp->ts_recent_age = ticks; 1812 tp->ts_recent = to.to_tsval; 1813 } 1814 1815 /* 1816 * If a SYN is in the window, then this is an 1817 * error and we send an RST and drop the connection. 1818 */ 1819 if (thflags & TH_SYN) { 1820 tp = tcp_drop(tp, ECONNRESET); 1821 rstreason = BANDLIM_UNLIMITED; 1822 goto dropwithreset; 1823 } 1824 1825 /* 1826 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1827 * flag is on (half-synchronized state), then queue data for 1828 * later processing; else drop segment and return. 1829 */ 1830 if (!(thflags & TH_ACK)) { 1831 if (tp->t_state == TCPS_SYN_RECEIVED || 1832 (tp->t_flags & TF_NEEDSYN)) 1833 goto step6; 1834 else 1835 goto drop; 1836 } 1837 1838 /* 1839 * Ack processing. 1840 */ 1841 switch (tp->t_state) { 1842 /* 1843 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1844 * ESTABLISHED state and continue processing. 1845 * The ACK was checked above. 1846 */ 1847 case TCPS_SYN_RECEIVED: 1848 1849 tcpstat.tcps_connects++; 1850 soisconnected(so); 1851 /* Do window scaling? */ 1852 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1853 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1854 tp->snd_scale = tp->requested_s_scale; 1855 tp->rcv_scale = tp->request_r_scale; 1856 } 1857 /* 1858 * Make transitions: 1859 * SYN-RECEIVED -> ESTABLISHED 1860 * SYN-RECEIVED* -> FIN-WAIT-1 1861 */ 1862 tp->t_starttime = ticks; 1863 if (tp->t_flags & TF_NEEDFIN) { 1864 tp->t_state = TCPS_FIN_WAIT_1; 1865 tp->t_flags &= ~TF_NEEDFIN; 1866 } else { 1867 tp->t_state = TCPS_ESTABLISHED; 1868 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1869 tcp_timer_keep); 1870 } 1871 /* 1872 * If segment contains data or ACK, will call tcp_reass() 1873 * later; if not, do so now to pass queued data to user. 1874 */ 1875 if (tlen == 0 && !(thflags & TH_FIN)) 1876 tcp_reass(tp, NULL, NULL, NULL); 1877 /* fall into ... */ 1878 1879 /* 1880 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1881 * ACKs. If the ack is in the range 1882 * tp->snd_una < th->th_ack <= tp->snd_max 1883 * then advance tp->snd_una to th->th_ack and drop 1884 * data from the retransmission queue. If this ACK reflects 1885 * more up to date window information we update our window information. 1886 */ 1887 case TCPS_ESTABLISHED: 1888 case TCPS_FIN_WAIT_1: 1889 case TCPS_FIN_WAIT_2: 1890 case TCPS_CLOSE_WAIT: 1891 case TCPS_CLOSING: 1892 case TCPS_LAST_ACK: 1893 case TCPS_TIME_WAIT: 1894 1895 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1896 if (TCP_DO_SACK(tp)) 1897 tcp_sack_update_scoreboard(tp, &to); 1898 if (tlen != 0 || tiwin != tp->snd_wnd) { 1899 tp->t_dupacks = 0; 1900 break; 1901 } 1902 tcpstat.tcps_rcvdupack++; 1903 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1904 th->th_ack != tp->snd_una) { 1905 tp->t_dupacks = 0; 1906 break; 1907 } 1908 /* 1909 * We have outstanding data (other than 1910 * a window probe), this is a completely 1911 * duplicate ack (ie, window info didn't 1912 * change), the ack is the biggest we've 1913 * seen and we've seen exactly our rexmt 1914 * threshhold of them, so assume a packet 1915 * has been dropped and retransmit it. 1916 * Kludge snd_nxt & the congestion 1917 * window so we send only this one 1918 * packet. 1919 */ 1920 if (IN_FASTRECOVERY(tp)) { 1921 if (TCP_DO_SACK(tp)) { 1922 /* No artifical cwnd inflation. */ 1923 tcp_sack_rexmt(tp, th); 1924 } else { 1925 /* 1926 * Dup acks mean that packets 1927 * have left the network 1928 * (they're now cached at the 1929 * receiver) so bump cwnd by 1930 * the amount in the receiver 1931 * to keep a constant cwnd 1932 * packets in the network. 1933 */ 1934 tp->snd_cwnd += tp->t_maxseg; 1935 tcp_output(tp); 1936 } 1937 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1938 tp->t_dupacks = 0; 1939 break; 1940 } else if (++tp->t_dupacks == tcprexmtthresh) { 1941 tcp_seq old_snd_nxt; 1942 u_int win; 1943 1944 fastretransmit: 1945 if (tcp_do_eifel_detect && 1946 (tp->t_flags & TF_RCVD_TSTMP)) { 1947 tcp_save_congestion_state(tp); 1948 tp->t_flags |= TF_FASTREXMT; 1949 } 1950 /* 1951 * We know we're losing at the current 1952 * window size, so do congestion avoidance: 1953 * set ssthresh to half the current window 1954 * and pull our congestion window back to the 1955 * new ssthresh. 1956 */ 1957 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1958 tp->t_maxseg; 1959 if (win < 2) 1960 win = 2; 1961 tp->snd_ssthresh = win * tp->t_maxseg; 1962 ENTER_FASTRECOVERY(tp); 1963 tp->snd_recover = tp->snd_max; 1964 tcp_callout_stop(tp, tp->tt_rexmt); 1965 tp->t_rtttime = 0; 1966 old_snd_nxt = tp->snd_nxt; 1967 tp->snd_nxt = th->th_ack; 1968 tp->snd_cwnd = tp->t_maxseg; 1969 tcp_output(tp); 1970 ++tcpstat.tcps_sndfastrexmit; 1971 tp->snd_cwnd = tp->snd_ssthresh; 1972 tp->rexmt_high = tp->snd_nxt; 1973 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1974 tp->snd_nxt = old_snd_nxt; 1975 KASSERT(tp->snd_limited <= 2, 1976 ("tp->snd_limited too big")); 1977 if (TCP_DO_SACK(tp)) 1978 tcp_sack_rexmt(tp, th); 1979 else 1980 tp->snd_cwnd += tp->t_maxseg * 1981 (tp->t_dupacks - tp->snd_limited); 1982 } else if (tcp_do_limitedtransmit) { 1983 u_long oldcwnd = tp->snd_cwnd; 1984 tcp_seq oldsndmax = tp->snd_max; 1985 tcp_seq oldsndnxt = tp->snd_nxt; 1986 /* outstanding data */ 1987 uint32_t ownd = tp->snd_max - tp->snd_una; 1988 u_int sent; 1989 1990 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1991 1992 KASSERT(tp->t_dupacks == 1 || 1993 tp->t_dupacks == 2, 1994 ("dupacks not 1 or 2")); 1995 if (tp->t_dupacks == 1) 1996 tp->snd_limited = 0; 1997 tp->snd_nxt = tp->snd_max; 1998 tp->snd_cwnd = ownd + 1999 (tp->t_dupacks - tp->snd_limited) * 2000 tp->t_maxseg; 2001 tcp_output(tp); 2002 2003 /* 2004 * Other acks may have been processed, 2005 * snd_nxt cannot be reset to a value less 2006 * then snd_una. 2007 */ 2008 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2009 if (SEQ_GT(oldsndnxt, tp->snd_una)) 2010 tp->snd_nxt = oldsndnxt; 2011 else 2012 tp->snd_nxt = tp->snd_una; 2013 } 2014 tp->snd_cwnd = oldcwnd; 2015 sent = tp->snd_max - oldsndmax; 2016 if (sent > tp->t_maxseg) { 2017 KASSERT((tp->t_dupacks == 2 && 2018 tp->snd_limited == 0) || 2019 (sent == tp->t_maxseg + 1 && 2020 tp->t_flags & TF_SENTFIN), 2021 ("sent too much")); 2022 KASSERT(sent <= tp->t_maxseg * 2, 2023 ("sent too many segments")); 2024 tp->snd_limited = 2; 2025 tcpstat.tcps_sndlimited += 2; 2026 } else if (sent > 0) { 2027 ++tp->snd_limited; 2028 ++tcpstat.tcps_sndlimited; 2029 } else if (tcp_do_early_retransmit && 2030 (tcp_do_eifel_detect && 2031 (tp->t_flags & TF_RCVD_TSTMP)) && 2032 ownd < 4 * tp->t_maxseg && 2033 tp->t_dupacks + 1 >= 2034 iceildiv(ownd, tp->t_maxseg) && 2035 (!TCP_DO_SACK(tp) || 2036 ownd <= tp->t_maxseg || 2037 tcp_sack_has_sacked(&tp->scb, 2038 ownd - tp->t_maxseg))) { 2039 ++tcpstat.tcps_sndearlyrexmit; 2040 tp->t_flags |= TF_EARLYREXMT; 2041 goto fastretransmit; 2042 } 2043 } 2044 goto drop; 2045 } 2046 2047 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2048 tp->t_dupacks = 0; 2049 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2050 /* 2051 * Detected optimistic ACK attack. 2052 * Force slow-start to de-synchronize attack. 2053 */ 2054 tp->snd_cwnd = tp->t_maxseg; 2055 tp->snd_wacked = 0; 2056 2057 tcpstat.tcps_rcvacktoomuch++; 2058 goto dropafterack; 2059 } 2060 /* 2061 * If we reach this point, ACK is not a duplicate, 2062 * i.e., it ACKs something we sent. 2063 */ 2064 if (tp->t_flags & TF_NEEDSYN) { 2065 /* 2066 * T/TCP: Connection was half-synchronized, and our 2067 * SYN has been ACK'd (so connection is now fully 2068 * synchronized). Go to non-starred state, 2069 * increment snd_una for ACK of SYN, and check if 2070 * we can do window scaling. 2071 */ 2072 tp->t_flags &= ~TF_NEEDSYN; 2073 tp->snd_una++; 2074 /* Do window scaling? */ 2075 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2076 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2077 tp->snd_scale = tp->requested_s_scale; 2078 tp->rcv_scale = tp->request_r_scale; 2079 } 2080 } 2081 2082 process_ACK: 2083 acked = th->th_ack - tp->snd_una; 2084 tcpstat.tcps_rcvackpack++; 2085 tcpstat.tcps_rcvackbyte += acked; 2086 2087 if (tcp_do_eifel_detect && acked > 0 && 2088 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2089 (tp->t_flags & TF_FIRSTACCACK)) { 2090 /* Eifel detection applicable. */ 2091 if (to.to_tsecr < tp->t_rexmtTS) { 2092 ++tcpstat.tcps_eifeldetected; 2093 tcp_revert_congestion_state(tp); 2094 if (tp->t_rxtshift == 1 && 2095 ticks >= tp->t_badrxtwin) 2096 ++tcpstat.tcps_rttcantdetect; 2097 } 2098 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2099 /* 2100 * If we just performed our first retransmit, 2101 * and the ACK arrives within our recovery window, 2102 * then it was a mistake to do the retransmit 2103 * in the first place. Recover our original cwnd 2104 * and ssthresh, and proceed to transmit where we 2105 * left off. 2106 */ 2107 tcp_revert_congestion_state(tp); 2108 ++tcpstat.tcps_rttdetected; 2109 } 2110 2111 /* 2112 * If we have a timestamp reply, update smoothed 2113 * round trip time. If no timestamp is present but 2114 * transmit timer is running and timed sequence 2115 * number was acked, update smoothed round trip time. 2116 * Since we now have an rtt measurement, cancel the 2117 * timer backoff (cf., Phil Karn's retransmit alg.). 2118 * Recompute the initial retransmit timer. 2119 * 2120 * Some machines (certain windows boxes) send broken 2121 * timestamp replies during the SYN+ACK phase, ignore 2122 * timestamps of 0. 2123 */ 2124 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2125 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2126 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2127 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2128 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2129 2130 /* 2131 * If no data (only SYN) was ACK'd, 2132 * skip rest of ACK processing. 2133 */ 2134 if (acked == 0) 2135 goto step6; 2136 2137 /* Stop looking for an acceptable ACK since one was received. */ 2138 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2139 2140 if (acked > so->so_snd.ssb_cc) { 2141 tp->snd_wnd -= so->so_snd.ssb_cc; 2142 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2143 ourfinisacked = TRUE; 2144 } else { 2145 sbdrop(&so->so_snd.sb, acked); 2146 tp->snd_wnd -= acked; 2147 ourfinisacked = FALSE; 2148 } 2149 sowwakeup(so); 2150 2151 /* 2152 * Update window information. 2153 * Don't look at window if no ACK: 2154 * TAC's send garbage on first SYN. 2155 */ 2156 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2157 (tp->snd_wl1 == th->th_seq && 2158 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2159 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2160 /* keep track of pure window updates */ 2161 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2162 tiwin > tp->snd_wnd) 2163 tcpstat.tcps_rcvwinupd++; 2164 tp->snd_wnd = tiwin; 2165 tp->snd_wl1 = th->th_seq; 2166 tp->snd_wl2 = th->th_ack; 2167 if (tp->snd_wnd > tp->max_sndwnd) 2168 tp->max_sndwnd = tp->snd_wnd; 2169 needoutput = TRUE; 2170 } 2171 2172 tp->snd_una = th->th_ack; 2173 if (TCP_DO_SACK(tp)) 2174 tcp_sack_update_scoreboard(tp, &to); 2175 if (IN_FASTRECOVERY(tp)) { 2176 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2177 EXIT_FASTRECOVERY(tp); 2178 needoutput = TRUE; 2179 /* 2180 * If the congestion window was inflated 2181 * to account for the other side's 2182 * cached packets, retract it. 2183 */ 2184 if (!TCP_DO_SACK(tp)) 2185 tp->snd_cwnd = tp->snd_ssthresh; 2186 2187 /* 2188 * Window inflation should have left us 2189 * with approximately snd_ssthresh outstanding 2190 * data. But, in case we would be inclined 2191 * to send a burst, better do it using 2192 * slow start. 2193 */ 2194 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2195 tp->snd_max + 2 * tp->t_maxseg)) 2196 tp->snd_cwnd = 2197 (tp->snd_max - tp->snd_una) + 2198 2 * tp->t_maxseg; 2199 2200 tp->snd_wacked = 0; 2201 } else { 2202 if (TCP_DO_SACK(tp)) { 2203 tp->snd_max_rexmt = tp->snd_max; 2204 tcp_sack_rexmt(tp, th); 2205 } else { 2206 tcp_newreno_partial_ack(tp, th, acked); 2207 } 2208 needoutput = FALSE; 2209 } 2210 } else { 2211 /* 2212 * Open the congestion window. When in slow-start, 2213 * open exponentially: maxseg per packet. Otherwise, 2214 * open linearly: maxseg per window. 2215 */ 2216 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2217 u_int abc_sslimit = 2218 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2219 tp->t_maxseg : 2 * tp->t_maxseg); 2220 2221 /* slow-start */ 2222 tp->snd_cwnd += tcp_do_abc ? 2223 min(acked, abc_sslimit) : tp->t_maxseg; 2224 } else { 2225 /* linear increase */ 2226 tp->snd_wacked += tcp_do_abc ? acked : 2227 tp->t_maxseg; 2228 if (tp->snd_wacked >= tp->snd_cwnd) { 2229 tp->snd_wacked -= tp->snd_cwnd; 2230 tp->snd_cwnd += tp->t_maxseg; 2231 } 2232 } 2233 tp->snd_cwnd = min(tp->snd_cwnd, 2234 TCP_MAXWIN << tp->snd_scale); 2235 tp->snd_recover = th->th_ack - 1; 2236 } 2237 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2238 tp->snd_nxt = tp->snd_una; 2239 2240 /* 2241 * If all outstanding data is acked, stop retransmit 2242 * timer and remember to restart (more output or persist). 2243 * If there is more data to be acked, restart retransmit 2244 * timer, using current (possibly backed-off) value. 2245 */ 2246 if (th->th_ack == tp->snd_max) { 2247 tcp_callout_stop(tp, tp->tt_rexmt); 2248 needoutput = TRUE; 2249 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2250 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2251 tcp_timer_rexmt); 2252 } 2253 2254 switch (tp->t_state) { 2255 /* 2256 * In FIN_WAIT_1 STATE in addition to the processing 2257 * for the ESTABLISHED state if our FIN is now acknowledged 2258 * then enter FIN_WAIT_2. 2259 */ 2260 case TCPS_FIN_WAIT_1: 2261 if (ourfinisacked) { 2262 /* 2263 * If we can't receive any more 2264 * data, then closing user can proceed. 2265 * Starting the timer is contrary to the 2266 * specification, but if we don't get a FIN 2267 * we'll hang forever. 2268 */ 2269 if (so->so_state & SS_CANTRCVMORE) { 2270 soisdisconnected(so); 2271 tcp_callout_reset(tp, tp->tt_2msl, 2272 tcp_maxidle, tcp_timer_2msl); 2273 } 2274 tp->t_state = TCPS_FIN_WAIT_2; 2275 } 2276 break; 2277 2278 /* 2279 * In CLOSING STATE in addition to the processing for 2280 * the ESTABLISHED state if the ACK acknowledges our FIN 2281 * then enter the TIME-WAIT state, otherwise ignore 2282 * the segment. 2283 */ 2284 case TCPS_CLOSING: 2285 if (ourfinisacked) { 2286 tp->t_state = TCPS_TIME_WAIT; 2287 tcp_canceltimers(tp); 2288 tcp_callout_reset(tp, tp->tt_2msl, 2289 2 * tcp_msl, tcp_timer_2msl); 2290 soisdisconnected(so); 2291 } 2292 break; 2293 2294 /* 2295 * In LAST_ACK, we may still be waiting for data to drain 2296 * and/or to be acked, as well as for the ack of our FIN. 2297 * If our FIN is now acknowledged, delete the TCB, 2298 * enter the closed state and return. 2299 */ 2300 case TCPS_LAST_ACK: 2301 if (ourfinisacked) { 2302 tp = tcp_close(tp); 2303 goto drop; 2304 } 2305 break; 2306 2307 /* 2308 * In TIME_WAIT state the only thing that should arrive 2309 * is a retransmission of the remote FIN. Acknowledge 2310 * it and restart the finack timer. 2311 */ 2312 case TCPS_TIME_WAIT: 2313 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2314 tcp_timer_2msl); 2315 goto dropafterack; 2316 } 2317 } 2318 2319 step6: 2320 /* 2321 * Update window information. 2322 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2323 */ 2324 if ((thflags & TH_ACK) && 2325 acceptable_window_update(tp, th, tiwin)) { 2326 /* keep track of pure window updates */ 2327 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2328 tiwin > tp->snd_wnd) 2329 tcpstat.tcps_rcvwinupd++; 2330 tp->snd_wnd = tiwin; 2331 tp->snd_wl1 = th->th_seq; 2332 tp->snd_wl2 = th->th_ack; 2333 if (tp->snd_wnd > tp->max_sndwnd) 2334 tp->max_sndwnd = tp->snd_wnd; 2335 needoutput = TRUE; 2336 } 2337 2338 /* 2339 * Process segments with URG. 2340 */ 2341 if ((thflags & TH_URG) && th->th_urp && 2342 !TCPS_HAVERCVDFIN(tp->t_state)) { 2343 /* 2344 * This is a kludge, but if we receive and accept 2345 * random urgent pointers, we'll crash in 2346 * soreceive. It's hard to imagine someone 2347 * actually wanting to send this much urgent data. 2348 */ 2349 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2350 th->th_urp = 0; /* XXX */ 2351 thflags &= ~TH_URG; /* XXX */ 2352 goto dodata; /* XXX */ 2353 } 2354 /* 2355 * If this segment advances the known urgent pointer, 2356 * then mark the data stream. This should not happen 2357 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2358 * a FIN has been received from the remote side. 2359 * In these states we ignore the URG. 2360 * 2361 * According to RFC961 (Assigned Protocols), 2362 * the urgent pointer points to the last octet 2363 * of urgent data. We continue, however, 2364 * to consider it to indicate the first octet 2365 * of data past the urgent section as the original 2366 * spec states (in one of two places). 2367 */ 2368 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2369 tp->rcv_up = th->th_seq + th->th_urp; 2370 so->so_oobmark = so->so_rcv.ssb_cc + 2371 (tp->rcv_up - tp->rcv_nxt) - 1; 2372 if (so->so_oobmark == 0) 2373 so->so_state |= SS_RCVATMARK; 2374 sohasoutofband(so); 2375 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2376 } 2377 /* 2378 * Remove out of band data so doesn't get presented to user. 2379 * This can happen independent of advancing the URG pointer, 2380 * but if two URG's are pending at once, some out-of-band 2381 * data may creep in... ick. 2382 */ 2383 if (th->th_urp <= (u_long)tlen && 2384 !(so->so_options & SO_OOBINLINE)) { 2385 /* hdr drop is delayed */ 2386 tcp_pulloutofband(so, th, m, drop_hdrlen); 2387 } 2388 } else { 2389 /* 2390 * If no out of band data is expected, 2391 * pull receive urgent pointer along 2392 * with the receive window. 2393 */ 2394 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2395 tp->rcv_up = tp->rcv_nxt; 2396 } 2397 2398 dodata: /* XXX */ 2399 /* 2400 * Process the segment text, merging it into the TCP sequencing queue, 2401 * and arranging for acknowledgment of receipt if necessary. 2402 * This process logically involves adjusting tp->rcv_wnd as data 2403 * is presented to the user (this happens in tcp_usrreq.c, 2404 * case PRU_RCVD). If a FIN has already been received on this 2405 * connection then we just ignore the text. 2406 */ 2407 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2408 m_adj(m, drop_hdrlen); /* delayed header drop */ 2409 /* 2410 * Insert segment which includes th into TCP reassembly queue 2411 * with control block tp. Set thflags to whether reassembly now 2412 * includes a segment with FIN. This handles the common case 2413 * inline (segment is the next to be received on an established 2414 * connection, and the queue is empty), avoiding linkage into 2415 * and removal from the queue and repetition of various 2416 * conversions. 2417 * Set DELACK for segments received in order, but ack 2418 * immediately when segments are out of order (so 2419 * fast retransmit can work). 2420 */ 2421 if (th->th_seq == tp->rcv_nxt && 2422 LIST_EMPTY(&tp->t_segq) && 2423 TCPS_HAVEESTABLISHED(tp->t_state)) { 2424 if (DELAY_ACK(tp)) { 2425 tcp_callout_reset(tp, tp->tt_delack, 2426 tcp_delacktime, tcp_timer_delack); 2427 } else { 2428 tp->t_flags |= TF_ACKNOW; 2429 } 2430 tp->rcv_nxt += tlen; 2431 thflags = th->th_flags & TH_FIN; 2432 tcpstat.tcps_rcvpack++; 2433 tcpstat.tcps_rcvbyte += tlen; 2434 ND6_HINT(tp); 2435 if (so->so_state & SS_CANTRCVMORE) 2436 m_freem(m); 2437 else 2438 ssb_appendstream(&so->so_rcv, m); 2439 sorwakeup(so); 2440 } else { 2441 if (!(tp->t_flags & TF_DUPSEG)) { 2442 /* Initialize SACK report block. */ 2443 tp->reportblk.rblk_start = th->th_seq; 2444 tp->reportblk.rblk_end = th->th_seq + tlen + 2445 ((thflags & TH_FIN) != 0); 2446 } 2447 thflags = tcp_reass(tp, th, &tlen, m); 2448 tp->t_flags |= TF_ACKNOW; 2449 } 2450 2451 /* 2452 * Note the amount of data that peer has sent into 2453 * our window, in order to estimate the sender's 2454 * buffer size. 2455 */ 2456 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2457 } else { 2458 m_freem(m); 2459 thflags &= ~TH_FIN; 2460 } 2461 2462 /* 2463 * If FIN is received ACK the FIN and let the user know 2464 * that the connection is closing. 2465 */ 2466 if (thflags & TH_FIN) { 2467 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2468 socantrcvmore(so); 2469 /* 2470 * If connection is half-synchronized 2471 * (ie NEEDSYN flag on) then delay ACK, 2472 * so it may be piggybacked when SYN is sent. 2473 * Otherwise, since we received a FIN then no 2474 * more input can be expected, send ACK now. 2475 */ 2476 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2477 tcp_callout_reset(tp, tp->tt_delack, 2478 tcp_delacktime, tcp_timer_delack); 2479 } else { 2480 tp->t_flags |= TF_ACKNOW; 2481 } 2482 tp->rcv_nxt++; 2483 } 2484 2485 switch (tp->t_state) { 2486 /* 2487 * In SYN_RECEIVED and ESTABLISHED STATES 2488 * enter the CLOSE_WAIT state. 2489 */ 2490 case TCPS_SYN_RECEIVED: 2491 tp->t_starttime = ticks; 2492 /*FALLTHROUGH*/ 2493 case TCPS_ESTABLISHED: 2494 tp->t_state = TCPS_CLOSE_WAIT; 2495 break; 2496 2497 /* 2498 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2499 * enter the CLOSING state. 2500 */ 2501 case TCPS_FIN_WAIT_1: 2502 tp->t_state = TCPS_CLOSING; 2503 break; 2504 2505 /* 2506 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2507 * starting the time-wait timer, turning off the other 2508 * standard timers. 2509 */ 2510 case TCPS_FIN_WAIT_2: 2511 tp->t_state = TCPS_TIME_WAIT; 2512 tcp_canceltimers(tp); 2513 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2514 tcp_timer_2msl); 2515 soisdisconnected(so); 2516 break; 2517 2518 /* 2519 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2520 */ 2521 case TCPS_TIME_WAIT: 2522 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2523 tcp_timer_2msl); 2524 break; 2525 } 2526 } 2527 2528 #ifdef TCPDEBUG 2529 if (so->so_options & SO_DEBUG) 2530 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2531 #endif 2532 2533 /* 2534 * Return any desired output. 2535 */ 2536 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2537 tcp_output(tp); 2538 return; 2539 2540 dropafterack: 2541 /* 2542 * Generate an ACK dropping incoming segment if it occupies 2543 * sequence space, where the ACK reflects our state. 2544 * 2545 * We can now skip the test for the RST flag since all 2546 * paths to this code happen after packets containing 2547 * RST have been dropped. 2548 * 2549 * In the SYN-RECEIVED state, don't send an ACK unless the 2550 * segment we received passes the SYN-RECEIVED ACK test. 2551 * If it fails send a RST. This breaks the loop in the 2552 * "LAND" DoS attack, and also prevents an ACK storm 2553 * between two listening ports that have been sent forged 2554 * SYN segments, each with the source address of the other. 2555 */ 2556 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2557 (SEQ_GT(tp->snd_una, th->th_ack) || 2558 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2559 rstreason = BANDLIM_RST_OPENPORT; 2560 goto dropwithreset; 2561 } 2562 #ifdef TCPDEBUG 2563 if (so->so_options & SO_DEBUG) 2564 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2565 #endif 2566 m_freem(m); 2567 tp->t_flags |= TF_ACKNOW; 2568 tcp_output(tp); 2569 return; 2570 2571 dropwithreset: 2572 /* 2573 * Generate a RST, dropping incoming segment. 2574 * Make ACK acceptable to originator of segment. 2575 * Don't bother to respond if destination was broadcast/multicast. 2576 */ 2577 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2578 goto drop; 2579 if (isipv6) { 2580 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2581 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2582 goto drop; 2583 } else { 2584 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2585 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2586 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2587 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2588 goto drop; 2589 } 2590 /* IPv6 anycast check is done at tcp6_input() */ 2591 2592 /* 2593 * Perform bandwidth limiting. 2594 */ 2595 #ifdef ICMP_BANDLIM 2596 if (badport_bandlim(rstreason) < 0) 2597 goto drop; 2598 #endif 2599 2600 #ifdef TCPDEBUG 2601 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2602 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2603 #endif 2604 if (thflags & TH_ACK) 2605 /* mtod() below is safe as long as hdr dropping is delayed */ 2606 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2607 TH_RST); 2608 else { 2609 if (thflags & TH_SYN) 2610 tlen++; 2611 /* mtod() below is safe as long as hdr dropping is delayed */ 2612 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2613 (tcp_seq)0, TH_RST | TH_ACK); 2614 } 2615 return; 2616 2617 drop: 2618 /* 2619 * Drop space held by incoming segment and return. 2620 */ 2621 #ifdef TCPDEBUG 2622 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2623 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2624 #endif 2625 m_freem(m); 2626 return; 2627 } 2628 2629 /* 2630 * Parse TCP options and place in tcpopt. 2631 */ 2632 static void 2633 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2634 { 2635 int opt, optlen, i; 2636 2637 to->to_flags = 0; 2638 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2639 opt = cp[0]; 2640 if (opt == TCPOPT_EOL) 2641 break; 2642 if (opt == TCPOPT_NOP) 2643 optlen = 1; 2644 else { 2645 if (cnt < 2) 2646 break; 2647 optlen = cp[1]; 2648 if (optlen < 2 || optlen > cnt) 2649 break; 2650 } 2651 switch (opt) { 2652 case TCPOPT_MAXSEG: 2653 if (optlen != TCPOLEN_MAXSEG) 2654 continue; 2655 if (!is_syn) 2656 continue; 2657 to->to_flags |= TOF_MSS; 2658 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2659 to->to_mss = ntohs(to->to_mss); 2660 break; 2661 case TCPOPT_WINDOW: 2662 if (optlen != TCPOLEN_WINDOW) 2663 continue; 2664 if (!is_syn) 2665 continue; 2666 to->to_flags |= TOF_SCALE; 2667 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2668 break; 2669 case TCPOPT_TIMESTAMP: 2670 if (optlen != TCPOLEN_TIMESTAMP) 2671 continue; 2672 to->to_flags |= TOF_TS; 2673 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2674 to->to_tsval = ntohl(to->to_tsval); 2675 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2676 to->to_tsecr = ntohl(to->to_tsecr); 2677 /* 2678 * If echoed timestamp is later than the current time, 2679 * fall back to non RFC1323 RTT calculation. 2680 */ 2681 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2682 to->to_tsecr = 0; 2683 break; 2684 case TCPOPT_SACK_PERMITTED: 2685 if (optlen != TCPOLEN_SACK_PERMITTED) 2686 continue; 2687 if (!is_syn) 2688 continue; 2689 to->to_flags |= TOF_SACK_PERMITTED; 2690 break; 2691 case TCPOPT_SACK: 2692 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2693 continue; 2694 to->to_nsackblocks = (optlen - 2) / 8; 2695 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2696 to->to_flags |= TOF_SACK; 2697 for (i = 0; i < to->to_nsackblocks; i++) { 2698 struct raw_sackblock *r = &to->to_sackblocks[i]; 2699 2700 r->rblk_start = ntohl(r->rblk_start); 2701 r->rblk_end = ntohl(r->rblk_end); 2702 } 2703 break; 2704 default: 2705 continue; 2706 } 2707 } 2708 } 2709 2710 /* 2711 * Pull out of band byte out of a segment so 2712 * it doesn't appear in the user's data queue. 2713 * It is still reflected in the segment length for 2714 * sequencing purposes. 2715 * "off" is the delayed to be dropped hdrlen. 2716 */ 2717 static void 2718 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2719 { 2720 int cnt = off + th->th_urp - 1; 2721 2722 while (cnt >= 0) { 2723 if (m->m_len > cnt) { 2724 char *cp = mtod(m, caddr_t) + cnt; 2725 struct tcpcb *tp = sototcpcb(so); 2726 2727 tp->t_iobc = *cp; 2728 tp->t_oobflags |= TCPOOB_HAVEDATA; 2729 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2730 m->m_len--; 2731 if (m->m_flags & M_PKTHDR) 2732 m->m_pkthdr.len--; 2733 return; 2734 } 2735 cnt -= m->m_len; 2736 m = m->m_next; 2737 if (m == 0) 2738 break; 2739 } 2740 panic("tcp_pulloutofband"); 2741 } 2742 2743 /* 2744 * Collect new round-trip time estimate 2745 * and update averages and current timeout. 2746 */ 2747 static void 2748 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2749 { 2750 int delta; 2751 2752 tcpstat.tcps_rttupdated++; 2753 tp->t_rttupdated++; 2754 if (tp->t_srtt != 0) { 2755 /* 2756 * srtt is stored as fixed point with 5 bits after the 2757 * binary point (i.e., scaled by 8). The following magic 2758 * is equivalent to the smoothing algorithm in rfc793 with 2759 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2760 * point). Adjust rtt to origin 0. 2761 */ 2762 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2763 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2764 2765 if ((tp->t_srtt += delta) <= 0) 2766 tp->t_srtt = 1; 2767 2768 /* 2769 * We accumulate a smoothed rtt variance (actually, a 2770 * smoothed mean difference), then set the retransmit 2771 * timer to smoothed rtt + 4 times the smoothed variance. 2772 * rttvar is stored as fixed point with 4 bits after the 2773 * binary point (scaled by 16). The following is 2774 * equivalent to rfc793 smoothing with an alpha of .75 2775 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2776 * rfc793's wired-in beta. 2777 */ 2778 if (delta < 0) 2779 delta = -delta; 2780 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2781 if ((tp->t_rttvar += delta) <= 0) 2782 tp->t_rttvar = 1; 2783 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2784 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2785 } else { 2786 /* 2787 * No rtt measurement yet - use the unsmoothed rtt. 2788 * Set the variance to half the rtt (so our first 2789 * retransmit happens at 3*rtt). 2790 */ 2791 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2792 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2793 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2794 } 2795 tp->t_rtttime = 0; 2796 tp->t_rxtshift = 0; 2797 2798 /* 2799 * the retransmit should happen at rtt + 4 * rttvar. 2800 * Because of the way we do the smoothing, srtt and rttvar 2801 * will each average +1/2 tick of bias. When we compute 2802 * the retransmit timer, we want 1/2 tick of rounding and 2803 * 1 extra tick because of +-1/2 tick uncertainty in the 2804 * firing of the timer. The bias will give us exactly the 2805 * 1.5 tick we need. But, because the bias is 2806 * statistical, we have to test that we don't drop below 2807 * the minimum feasible timer (which is 2 ticks). 2808 */ 2809 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2810 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2811 2812 /* 2813 * We received an ack for a packet that wasn't retransmitted; 2814 * it is probably safe to discard any error indications we've 2815 * received recently. This isn't quite right, but close enough 2816 * for now (a route might have failed after we sent a segment, 2817 * and the return path might not be symmetrical). 2818 */ 2819 tp->t_softerror = 0; 2820 } 2821 2822 /* 2823 * Determine a reasonable value for maxseg size. 2824 * If the route is known, check route for mtu. 2825 * If none, use an mss that can be handled on the outgoing 2826 * interface without forcing IP to fragment; if bigger than 2827 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2828 * to utilize large mbufs. If no route is found, route has no mtu, 2829 * or the destination isn't local, use a default, hopefully conservative 2830 * size (usually 512 or the default IP max size, but no more than the mtu 2831 * of the interface), as we can't discover anything about intervening 2832 * gateways or networks. We also initialize the congestion/slow start 2833 * window to be a single segment if the destination isn't local. 2834 * While looking at the routing entry, we also initialize other path-dependent 2835 * parameters from pre-set or cached values in the routing entry. 2836 * 2837 * Also take into account the space needed for options that we 2838 * send regularly. Make maxseg shorter by that amount to assure 2839 * that we can send maxseg amount of data even when the options 2840 * are present. Store the upper limit of the length of options plus 2841 * data in maxopd. 2842 * 2843 * NOTE that this routine is only called when we process an incoming 2844 * segment, for outgoing segments only tcp_mssopt is called. 2845 */ 2846 void 2847 tcp_mss(struct tcpcb *tp, int offer) 2848 { 2849 struct rtentry *rt; 2850 struct ifnet *ifp; 2851 int rtt, mss; 2852 u_long bufsize; 2853 struct inpcb *inp = tp->t_inpcb; 2854 struct socket *so; 2855 #ifdef INET6 2856 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2857 size_t min_protoh = isipv6 ? 2858 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2859 sizeof(struct tcpiphdr); 2860 #else 2861 const boolean_t isipv6 = FALSE; 2862 const size_t min_protoh = sizeof(struct tcpiphdr); 2863 #endif 2864 2865 if (isipv6) 2866 rt = tcp_rtlookup6(&inp->inp_inc); 2867 else 2868 rt = tcp_rtlookup(&inp->inp_inc); 2869 if (rt == NULL) { 2870 tp->t_maxopd = tp->t_maxseg = 2871 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2872 return; 2873 } 2874 ifp = rt->rt_ifp; 2875 so = inp->inp_socket; 2876 2877 /* 2878 * Offer == 0 means that there was no MSS on the SYN segment, 2879 * in this case we use either the interface mtu or tcp_mssdflt. 2880 * 2881 * An offer which is too large will be cut down later. 2882 */ 2883 if (offer == 0) { 2884 if (isipv6) { 2885 if (in6_localaddr(&inp->in6p_faddr)) { 2886 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 2887 min_protoh; 2888 } else { 2889 offer = tcp_v6mssdflt; 2890 } 2891 } else { 2892 if (in_localaddr(inp->inp_faddr)) 2893 offer = ifp->if_mtu - min_protoh; 2894 else 2895 offer = tcp_mssdflt; 2896 } 2897 } 2898 2899 /* 2900 * Prevent DoS attack with too small MSS. Round up 2901 * to at least minmss. 2902 * 2903 * Sanity check: make sure that maxopd will be large 2904 * enough to allow some data on segments even is the 2905 * all the option space is used (40bytes). Otherwise 2906 * funny things may happen in tcp_output. 2907 */ 2908 offer = max(offer, tcp_minmss); 2909 offer = max(offer, 64); 2910 2911 rt->rt_rmx.rmx_mssopt = offer; 2912 2913 /* 2914 * While we're here, check if there's an initial rtt 2915 * or rttvar. Convert from the route-table units 2916 * to scaled multiples of the slow timeout timer. 2917 */ 2918 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2919 /* 2920 * XXX the lock bit for RTT indicates that the value 2921 * is also a minimum value; this is subject to time. 2922 */ 2923 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2924 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2925 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2926 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2927 tcpstat.tcps_usedrtt++; 2928 if (rt->rt_rmx.rmx_rttvar) { 2929 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2930 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2931 tcpstat.tcps_usedrttvar++; 2932 } else { 2933 /* default variation is +- 1 rtt */ 2934 tp->t_rttvar = 2935 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2936 } 2937 TCPT_RANGESET(tp->t_rxtcur, 2938 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2939 tp->t_rttmin, TCPTV_REXMTMAX); 2940 } 2941 2942 /* 2943 * if there's an mtu associated with the route, use it 2944 * else, use the link mtu. Take the smaller of mss or offer 2945 * as our final mss. 2946 */ 2947 if (rt->rt_rmx.rmx_mtu) { 2948 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2949 } else { 2950 if (isipv6) 2951 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2952 else 2953 mss = ifp->if_mtu - min_protoh; 2954 } 2955 mss = min(mss, offer); 2956 2957 /* 2958 * maxopd stores the maximum length of data AND options 2959 * in a segment; maxseg is the amount of data in a normal 2960 * segment. We need to store this value (maxopd) apart 2961 * from maxseg, because now every segment carries options 2962 * and thus we normally have somewhat less data in segments. 2963 */ 2964 tp->t_maxopd = mss; 2965 2966 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 2967 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2968 mss -= TCPOLEN_TSTAMP_APPA; 2969 2970 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2971 if (mss > MCLBYTES) 2972 mss &= ~(MCLBYTES-1); 2973 #else 2974 if (mss > MCLBYTES) 2975 mss = mss / MCLBYTES * MCLBYTES; 2976 #endif 2977 /* 2978 * If there's a pipesize, change the socket buffer 2979 * to that size. Make the socket buffers an integral 2980 * number of mss units; if the mss is larger than 2981 * the socket buffer, decrease the mss. 2982 */ 2983 #ifdef RTV_SPIPE 2984 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2985 #endif 2986 bufsize = so->so_snd.ssb_hiwat; 2987 if (bufsize < mss) 2988 mss = bufsize; 2989 else { 2990 bufsize = roundup(bufsize, mss); 2991 if (bufsize > sb_max) 2992 bufsize = sb_max; 2993 if (bufsize > so->so_snd.ssb_hiwat) 2994 ssb_reserve(&so->so_snd, bufsize, so, NULL); 2995 } 2996 tp->t_maxseg = mss; 2997 2998 #ifdef RTV_RPIPE 2999 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3000 #endif 3001 bufsize = so->so_rcv.ssb_hiwat; 3002 if (bufsize > mss) { 3003 bufsize = roundup(bufsize, mss); 3004 if (bufsize > sb_max) 3005 bufsize = sb_max; 3006 if (bufsize > so->so_rcv.ssb_hiwat) 3007 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3008 } 3009 3010 /* 3011 * Set the slow-start flight size depending on whether this 3012 * is a local network or not. 3013 */ 3014 if (tcp_do_rfc3390) 3015 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3016 else 3017 tp->snd_cwnd = mss; 3018 3019 if (rt->rt_rmx.rmx_ssthresh) { 3020 /* 3021 * There's some sort of gateway or interface 3022 * buffer limit on the path. Use this to set 3023 * the slow start threshhold, but set the 3024 * threshold to no less than 2*mss. 3025 */ 3026 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3027 tcpstat.tcps_usedssthresh++; 3028 } 3029 } 3030 3031 /* 3032 * Determine the MSS option to send on an outgoing SYN. 3033 */ 3034 int 3035 tcp_mssopt(struct tcpcb *tp) 3036 { 3037 struct rtentry *rt; 3038 #ifdef INET6 3039 boolean_t isipv6 = 3040 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3041 int min_protoh = isipv6 ? 3042 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3043 sizeof(struct tcpiphdr); 3044 #else 3045 const boolean_t isipv6 = FALSE; 3046 const size_t min_protoh = sizeof(struct tcpiphdr); 3047 #endif 3048 3049 if (isipv6) 3050 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3051 else 3052 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3053 if (rt == NULL) 3054 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3055 3056 return (rt->rt_ifp->if_mtu - min_protoh); 3057 } 3058 3059 /* 3060 * When a partial ack arrives, force the retransmission of the 3061 * next unacknowledged segment. Do not exit Fast Recovery. 3062 * 3063 * Implement the Slow-but-Steady variant of NewReno by restarting the 3064 * the retransmission timer. Turn it off here so it can be restarted 3065 * later in tcp_output(). 3066 */ 3067 static void 3068 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3069 { 3070 tcp_seq old_snd_nxt = tp->snd_nxt; 3071 u_long ocwnd = tp->snd_cwnd; 3072 3073 tcp_callout_stop(tp, tp->tt_rexmt); 3074 tp->t_rtttime = 0; 3075 tp->snd_nxt = th->th_ack; 3076 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3077 tp->snd_cwnd = tp->t_maxseg; 3078 tp->t_flags |= TF_ACKNOW; 3079 tcp_output(tp); 3080 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3081 tp->snd_nxt = old_snd_nxt; 3082 /* partial window deflation */ 3083 if (ocwnd > acked) 3084 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3085 else 3086 tp->snd_cwnd = tp->t_maxseg; 3087 } 3088 3089 /* 3090 * In contrast to the Slow-but-Steady NewReno variant, 3091 * we do not reset the retransmission timer for SACK retransmissions, 3092 * except when retransmitting snd_una. 3093 */ 3094 static void 3095 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3096 { 3097 uint32_t pipe, seglen; 3098 tcp_seq nextrexmt; 3099 boolean_t lostdup; 3100 tcp_seq old_snd_nxt = tp->snd_nxt; 3101 u_long ocwnd = tp->snd_cwnd; 3102 int nseg = 0; /* consecutive new segments */ 3103 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3104 3105 tp->t_rtttime = 0; 3106 pipe = tcp_sack_compute_pipe(tp); 3107 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3108 (!tcp_do_smartsack || nseg < MAXBURST) && 3109 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3110 uint32_t sent; 3111 tcp_seq old_snd_max; 3112 int error; 3113 3114 if (nextrexmt == tp->snd_max) 3115 ++nseg; 3116 tp->snd_nxt = nextrexmt; 3117 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3118 old_snd_max = tp->snd_max; 3119 if (nextrexmt == tp->snd_una) 3120 tcp_callout_stop(tp, tp->tt_rexmt); 3121 error = tcp_output(tp); 3122 if (error != 0) 3123 break; 3124 sent = tp->snd_nxt - nextrexmt; 3125 if (sent <= 0) 3126 break; 3127 if (!lostdup) 3128 pipe += sent; 3129 tcpstat.tcps_sndsackpack++; 3130 tcpstat.tcps_sndsackbyte += sent; 3131 if (SEQ_LT(nextrexmt, old_snd_max) && 3132 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3133 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3134 } 3135 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3136 tp->snd_nxt = old_snd_nxt; 3137 tp->snd_cwnd = ocwnd; 3138 } 3139