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_inet.h" 73 #include "opt_inet6.h" 74 #include "opt_ipsec.h" 75 #include "opt_tcpdebug.h" 76 #include "opt_tcp_input.h" 77 78 #include <sys/param.h> 79 #include <sys/systm.h> 80 #include <sys/kernel.h> 81 #include <sys/sysctl.h> 82 #include <sys/malloc.h> 83 #include <sys/mbuf.h> 84 #include <sys/proc.h> /* for proc0 declaration */ 85 #include <sys/protosw.h> 86 #include <sys/socket.h> 87 #include <sys/socketvar.h> 88 #include <sys/syslog.h> 89 #include <sys/in_cksum.h> 90 91 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 92 #include <machine/stdarg.h> 93 94 #include <net/if.h> 95 #include <net/route.h> 96 97 #include <netinet/in.h> 98 #include <netinet/in_systm.h> 99 #include <netinet/ip.h> 100 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 101 #include <netinet/in_var.h> 102 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 103 #include <netinet/in_pcb.h> 104 #include <netinet/ip_var.h> 105 #include <netinet/ip6.h> 106 #include <netinet/icmp6.h> 107 #include <netinet6/nd6.h> 108 #include <netinet6/ip6_var.h> 109 #include <netinet6/in6_pcb.h> 110 #include <netinet/tcp.h> 111 #include <netinet/tcp_fsm.h> 112 #include <netinet/tcp_seq.h> 113 #include <netinet/tcp_timer.h> 114 #include <netinet/tcp_timer2.h> 115 #include <netinet/tcp_var.h> 116 #include <netinet6/tcp6_var.h> 117 #include <netinet/tcpip.h> 118 119 #ifdef TCPDEBUG 120 #include <netinet/tcp_debug.h> 121 122 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 123 struct tcphdr tcp_savetcp; 124 #endif 125 126 #ifdef FAST_IPSEC 127 #include <netproto/ipsec/ipsec.h> 128 #include <netproto/ipsec/ipsec6.h> 129 #endif 130 131 #ifdef IPSEC 132 #include <netinet6/ipsec.h> 133 #include <netinet6/ipsec6.h> 134 #include <netproto/key/key.h> 135 #endif 136 137 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 138 139 static int log_in_vain = 0; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 141 &log_in_vain, 0, "Log all incoming TCP connections"); 142 143 static int blackhole = 0; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 145 &blackhole, 0, "Do not send RST when dropping refused connections"); 146 147 int tcp_delack_enabled = 1; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 149 &tcp_delack_enabled, 0, 150 "Delay ACK to try and piggyback it onto a data packet"); 151 152 #ifdef TCP_DROP_SYNFIN 153 static int drop_synfin = 0; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 156 #endif 157 158 static int tcp_do_limitedtransmit = 1; 159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 161 162 static int tcp_do_early_retransmit = 1; 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 164 &tcp_do_early_retransmit, 0, "Early retransmit"); 165 166 int tcp_aggregate_acks = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 169 170 int tcp_do_rfc3390 = 1; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 172 &tcp_do_rfc3390, 0, 173 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 174 175 static int tcp_do_eifel_detect = 1; 176 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 177 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 178 179 static int tcp_do_abc = 1; 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 181 &tcp_do_abc, 0, 182 "TCP Appropriate Byte Counting (RFC 3465)"); 183 184 /* 185 * Define as tunable for easy testing with SACK on and off. 186 * Warning: do not change setting in the middle of an existing active TCP flow, 187 * else strange things might happen to that flow. 188 */ 189 int tcp_do_sack = 1; 190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 191 &tcp_do_sack, 0, "Enable SACK Algorithms"); 192 193 int tcp_do_smartsack = 1; 194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 195 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 196 197 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 198 "TCP Segment Reassembly Queue"); 199 200 int tcp_reass_maxseg = 0; 201 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 202 &tcp_reass_maxseg, 0, 203 "Global maximum number of TCP Segments in Reassembly Queue"); 204 205 int tcp_reass_qsize = 0; 206 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 207 &tcp_reass_qsize, 0, 208 "Global number of TCP Segments currently in Reassembly Queue"); 209 210 static int tcp_reass_overflows = 0; 211 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 212 &tcp_reass_overflows, 0, 213 "Global number of TCP Segment Reassembly Queue Overflows"); 214 215 int tcp_do_autorcvbuf = 1; 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 217 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 218 219 int tcp_autorcvbuf_inc = 16*1024; 220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 221 &tcp_autorcvbuf_inc, 0, 222 "Incrementor step size of automatic receive buffer"); 223 224 int tcp_autorcvbuf_max = 2*1024*1024; 225 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 226 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 227 228 229 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 230 static void tcp_pulloutofband(struct socket *, 231 struct tcphdr *, struct mbuf *, int); 232 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 233 struct mbuf *); 234 static void tcp_xmit_timer(struct tcpcb *, int); 235 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 236 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 237 238 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 239 #ifdef INET6 240 #define ND6_HINT(tp) \ 241 do { \ 242 if ((tp) && (tp)->t_inpcb && \ 243 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 244 (tp)->t_inpcb->in6p_route.ro_rt) \ 245 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 246 } while (0) 247 #else 248 #define ND6_HINT(tp) 249 #endif 250 251 /* 252 * Indicate whether this ack should be delayed. We can delay the ack if 253 * - delayed acks are enabled and 254 * - there is no delayed ack timer in progress and 255 * - our last ack wasn't a 0-sized window. We never want to delay 256 * the ack that opens up a 0-sized window. 257 */ 258 #define DELAY_ACK(tp) \ 259 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 260 !(tp->t_flags & TF_RXWIN0SENT)) 261 262 #define acceptable_window_update(tp, th, tiwin) \ 263 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 264 (tp->snd_wl1 == th->th_seq && \ 265 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 266 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 267 268 static int 269 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 270 { 271 struct tseg_qent *q; 272 struct tseg_qent *p = NULL; 273 struct tseg_qent *te; 274 struct socket *so = tp->t_inpcb->inp_socket; 275 int flags; 276 277 /* 278 * Call with th == NULL after become established to 279 * force pre-ESTABLISHED data up to user socket. 280 */ 281 if (th == NULL) 282 goto present; 283 284 /* 285 * Limit the number of segments in the reassembly queue to prevent 286 * holding on to too many segments (and thus running out of mbufs). 287 * Make sure to let the missing segment through which caused this 288 * queue. Always keep one global queue entry spare to be able to 289 * process the missing segment. 290 */ 291 if (th->th_seq != tp->rcv_nxt && 292 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 293 tcp_reass_overflows++; 294 tcpstat.tcps_rcvmemdrop++; 295 m_freem(m); 296 /* no SACK block to report */ 297 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 298 return (0); 299 } 300 301 /* Allocate a new queue entry. */ 302 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 303 M_INTWAIT | M_NULLOK); 304 if (te == NULL) { 305 tcpstat.tcps_rcvmemdrop++; 306 m_freem(m); 307 /* no SACK block to report */ 308 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 309 return (0); 310 } 311 tcp_reass_qsize++; 312 313 /* 314 * Find a segment which begins after this one does. 315 */ 316 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 317 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 318 break; 319 p = q; 320 } 321 322 /* 323 * If there is a preceding segment, it may provide some of 324 * our data already. If so, drop the data from the incoming 325 * segment. If it provides all of our data, drop us. 326 */ 327 if (p != NULL) { 328 tcp_seq_diff_t i; 329 330 /* conversion to int (in i) handles seq wraparound */ 331 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 332 if (i > 0) { /* overlaps preceding segment */ 333 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 334 /* enclosing block starts w/ preceding segment */ 335 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 336 if (i >= *tlenp) { 337 /* preceding encloses incoming segment */ 338 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 339 p->tqe_len; 340 tcpstat.tcps_rcvduppack++; 341 tcpstat.tcps_rcvdupbyte += *tlenp; 342 m_freem(m); 343 kfree(te, M_TSEGQ); 344 tcp_reass_qsize--; 345 /* 346 * Try to present any queued data 347 * at the left window edge to the user. 348 * This is needed after the 3-WHS 349 * completes. 350 */ 351 goto present; /* ??? */ 352 } 353 m_adj(m, i); 354 *tlenp -= i; 355 th->th_seq += i; 356 /* incoming segment end is enclosing block end */ 357 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 358 ((th->th_flags & TH_FIN) != 0); 359 /* trim end of reported D-SACK block */ 360 tp->reportblk.rblk_end = th->th_seq; 361 } 362 } 363 tcpstat.tcps_rcvoopack++; 364 tcpstat.tcps_rcvoobyte += *tlenp; 365 366 /* 367 * While we overlap succeeding segments trim them or, 368 * if they are completely covered, dequeue them. 369 */ 370 while (q) { 371 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 372 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 373 struct tseg_qent *nq; 374 375 if (i <= 0) 376 break; 377 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 378 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 379 tp->encloseblk = tp->reportblk; 380 /* report trailing duplicate D-SACK segment */ 381 tp->reportblk.rblk_start = q->tqe_th->th_seq; 382 } 383 if ((tp->t_flags & TF_ENCLOSESEG) && 384 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 385 /* extend enclosing block if one exists */ 386 tp->encloseblk.rblk_end = qend; 387 } 388 if (i < q->tqe_len) { 389 q->tqe_th->th_seq += i; 390 q->tqe_len -= i; 391 m_adj(q->tqe_m, i); 392 break; 393 } 394 395 nq = LIST_NEXT(q, tqe_q); 396 LIST_REMOVE(q, tqe_q); 397 m_freem(q->tqe_m); 398 kfree(q, M_TSEGQ); 399 tcp_reass_qsize--; 400 q = nq; 401 } 402 403 /* Insert the new segment queue entry into place. */ 404 te->tqe_m = m; 405 te->tqe_th = th; 406 te->tqe_len = *tlenp; 407 408 /* check if can coalesce with following segment */ 409 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 410 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 411 412 te->tqe_len += q->tqe_len; 413 if (q->tqe_th->th_flags & TH_FIN) 414 te->tqe_th->th_flags |= TH_FIN; 415 m_cat(te->tqe_m, q->tqe_m); 416 tp->encloseblk.rblk_end = tend; 417 /* 418 * When not reporting a duplicate segment, use 419 * the larger enclosing block as the SACK block. 420 */ 421 if (!(tp->t_flags & TF_DUPSEG)) 422 tp->reportblk.rblk_end = tend; 423 LIST_REMOVE(q, tqe_q); 424 kfree(q, M_TSEGQ); 425 tcp_reass_qsize--; 426 } 427 428 if (p == NULL) { 429 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 430 } else { 431 /* check if can coalesce with preceding segment */ 432 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 433 p->tqe_len += te->tqe_len; 434 m_cat(p->tqe_m, te->tqe_m); 435 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 436 /* 437 * When not reporting a duplicate segment, use 438 * the larger enclosing block as the SACK block. 439 */ 440 if (!(tp->t_flags & TF_DUPSEG)) 441 tp->reportblk.rblk_start = p->tqe_th->th_seq; 442 kfree(te, M_TSEGQ); 443 tcp_reass_qsize--; 444 } else 445 LIST_INSERT_AFTER(p, te, tqe_q); 446 } 447 448 present: 449 /* 450 * Present data to user, advancing rcv_nxt through 451 * completed sequence space. 452 */ 453 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 454 return (0); 455 q = LIST_FIRST(&tp->t_segq); 456 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 457 return (0); 458 tp->rcv_nxt += q->tqe_len; 459 if (!(tp->t_flags & TF_DUPSEG)) { 460 /* no SACK block to report since ACK advanced */ 461 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 462 } 463 /* no enclosing block to report since ACK advanced */ 464 tp->t_flags &= ~TF_ENCLOSESEG; 465 flags = q->tqe_th->th_flags & TH_FIN; 466 LIST_REMOVE(q, tqe_q); 467 KASSERT(LIST_EMPTY(&tp->t_segq) || 468 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 469 ("segment not coalesced")); 470 if (so->so_state & SS_CANTRCVMORE) 471 m_freem(q->tqe_m); 472 else 473 ssb_appendstream(&so->so_rcv, q->tqe_m); 474 kfree(q, M_TSEGQ); 475 tcp_reass_qsize--; 476 ND6_HINT(tp); 477 sorwakeup(so); 478 return (flags); 479 } 480 481 /* 482 * TCP input routine, follows pages 65-76 of the 483 * protocol specification dated September, 1981 very closely. 484 */ 485 #ifdef INET6 486 int 487 tcp6_input(struct mbuf **mp, int *offp, int proto) 488 { 489 struct mbuf *m = *mp; 490 struct in6_ifaddr *ia6; 491 492 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 493 494 /* 495 * draft-itojun-ipv6-tcp-to-anycast 496 * better place to put this in? 497 */ 498 ia6 = ip6_getdstifaddr(m); 499 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 500 struct ip6_hdr *ip6; 501 502 ip6 = mtod(m, struct ip6_hdr *); 503 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 504 offsetof(struct ip6_hdr, ip6_dst)); 505 return (IPPROTO_DONE); 506 } 507 508 tcp_input(m, *offp, proto); 509 return (IPPROTO_DONE); 510 } 511 #endif 512 513 void 514 tcp_input(struct mbuf *m, ...) 515 { 516 __va_list ap; 517 int off0, proto; 518 struct tcphdr *th; 519 struct ip *ip = NULL; 520 struct ipovly *ipov; 521 struct inpcb *inp = NULL; 522 u_char *optp = NULL; 523 int optlen = 0; 524 int tlen, off; 525 int len = 0; 526 int drop_hdrlen; 527 struct tcpcb *tp = NULL; 528 int thflags; 529 struct socket *so = 0; 530 int todrop, acked; 531 boolean_t ourfinisacked, needoutput = FALSE; 532 u_long tiwin; 533 int recvwin; 534 struct tcpopt to; /* options in this segment */ 535 struct sockaddr_in *next_hop = NULL; 536 int rstreason; /* For badport_bandlim accounting purposes */ 537 int cpu; 538 struct ip6_hdr *ip6 = NULL; 539 #ifdef INET6 540 boolean_t isipv6; 541 #else 542 const boolean_t isipv6 = FALSE; 543 #endif 544 #ifdef TCPDEBUG 545 short ostate = 0; 546 #endif 547 548 __va_start(ap, m); 549 off0 = __va_arg(ap, int); 550 proto = __va_arg(ap, int); 551 __va_end(ap); 552 553 tcpstat.tcps_rcvtotal++; 554 555 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 556 struct m_tag *mtag; 557 558 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 559 KKASSERT(mtag != NULL); 560 next_hop = m_tag_data(mtag); 561 } 562 563 #ifdef INET6 564 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 565 #endif 566 567 if (isipv6) { 568 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 569 ip6 = mtod(m, struct ip6_hdr *); 570 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 571 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 572 tcpstat.tcps_rcvbadsum++; 573 goto drop; 574 } 575 th = (struct tcphdr *)((caddr_t)ip6 + off0); 576 577 /* 578 * Be proactive about unspecified IPv6 address in source. 579 * As we use all-zero to indicate unbounded/unconnected pcb, 580 * unspecified IPv6 address can be used to confuse us. 581 * 582 * Note that packets with unspecified IPv6 destination is 583 * already dropped in ip6_input. 584 */ 585 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 586 /* XXX stat */ 587 goto drop; 588 } 589 } else { 590 /* 591 * Get IP and TCP header together in first mbuf. 592 * Note: IP leaves IP header in first mbuf. 593 */ 594 if (off0 > sizeof(struct ip)) { 595 ip_stripoptions(m); 596 off0 = sizeof(struct ip); 597 } 598 /* already checked and pulled up in ip_demux() */ 599 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 600 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 601 ip = mtod(m, struct ip *); 602 ipov = (struct ipovly *)ip; 603 th = (struct tcphdr *)((caddr_t)ip + off0); 604 tlen = ip->ip_len; 605 606 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 607 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 608 th->th_sum = m->m_pkthdr.csum_data; 609 else 610 th->th_sum = in_pseudo(ip->ip_src.s_addr, 611 ip->ip_dst.s_addr, 612 htonl(m->m_pkthdr.csum_data + 613 ip->ip_len + 614 IPPROTO_TCP)); 615 th->th_sum ^= 0xffff; 616 } else { 617 /* 618 * Checksum extended TCP header and data. 619 */ 620 len = sizeof(struct ip) + tlen; 621 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 622 ipov->ih_len = (u_short)tlen; 623 ipov->ih_len = htons(ipov->ih_len); 624 th->th_sum = in_cksum(m, len); 625 } 626 if (th->th_sum) { 627 tcpstat.tcps_rcvbadsum++; 628 goto drop; 629 } 630 #ifdef INET6 631 /* Re-initialization for later version check */ 632 ip->ip_v = IPVERSION; 633 #endif 634 } 635 636 /* 637 * Check that TCP offset makes sense, 638 * pull out TCP options and adjust length. XXX 639 */ 640 off = th->th_off << 2; 641 /* already checked and pulled up in ip_demux() */ 642 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 643 ("bad TCP data offset %d (tlen %d)", off, tlen)); 644 tlen -= off; /* tlen is used instead of ti->ti_len */ 645 if (off > sizeof(struct tcphdr)) { 646 if (isipv6) { 647 IP6_EXTHDR_CHECK(m, off0, off, ); 648 ip6 = mtod(m, struct ip6_hdr *); 649 th = (struct tcphdr *)((caddr_t)ip6 + off0); 650 } else { 651 /* already pulled up in ip_demux() */ 652 KASSERT(m->m_len >= sizeof(struct ip) + off, 653 ("TCP header and options not in one mbuf: " 654 "m_len %d, off %d", m->m_len, off)); 655 } 656 optlen = off - sizeof(struct tcphdr); 657 optp = (u_char *)(th + 1); 658 } 659 thflags = th->th_flags; 660 661 #ifdef TCP_DROP_SYNFIN 662 /* 663 * If the drop_synfin option is enabled, drop all packets with 664 * both the SYN and FIN bits set. This prevents e.g. nmap from 665 * identifying the TCP/IP stack. 666 * 667 * This is a violation of the TCP specification. 668 */ 669 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 670 goto drop; 671 #endif 672 673 /* 674 * Convert TCP protocol specific fields to host format. 675 */ 676 th->th_seq = ntohl(th->th_seq); 677 th->th_ack = ntohl(th->th_ack); 678 th->th_win = ntohs(th->th_win); 679 th->th_urp = ntohs(th->th_urp); 680 681 /* 682 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 683 * until after ip6_savecontrol() is called and before other functions 684 * which don't want those proto headers. 685 * Because ip6_savecontrol() is going to parse the mbuf to 686 * search for data to be passed up to user-land, it wants mbuf 687 * parameters to be unchanged. 688 * XXX: the call of ip6_savecontrol() has been obsoleted based on 689 * latest version of the advanced API (20020110). 690 */ 691 drop_hdrlen = off0 + off; 692 693 /* 694 * Locate pcb for segment. 695 */ 696 findpcb: 697 /* IPFIREWALL_FORWARD section */ 698 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 699 /* 700 * Transparently forwarded. Pretend to be the destination. 701 * already got one like this? 702 */ 703 cpu = mycpu->gd_cpuid; 704 inp = in_pcblookup_hash(&tcbinfo[cpu], 705 ip->ip_src, th->th_sport, 706 ip->ip_dst, th->th_dport, 707 0, m->m_pkthdr.rcvif); 708 if (!inp) { 709 /* 710 * It's new. Try to find the ambushing socket. 711 */ 712 713 /* 714 * The rest of the ipfw code stores the port in 715 * host order. XXX 716 * (The IP address is still in network order.) 717 */ 718 in_port_t dport = next_hop->sin_port ? 719 htons(next_hop->sin_port) : 720 th->th_dport; 721 722 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 723 next_hop->sin_addr.s_addr, dport); 724 inp = in_pcblookup_hash(&tcbinfo[cpu], 725 ip->ip_src, th->th_sport, 726 next_hop->sin_addr, dport, 727 1, m->m_pkthdr.rcvif); 728 } 729 } else { 730 if (isipv6) { 731 inp = in6_pcblookup_hash(&tcbinfo[0], 732 &ip6->ip6_src, th->th_sport, 733 &ip6->ip6_dst, th->th_dport, 734 1, m->m_pkthdr.rcvif); 735 } else { 736 cpu = mycpu->gd_cpuid; 737 inp = in_pcblookup_hash(&tcbinfo[cpu], 738 ip->ip_src, th->th_sport, 739 ip->ip_dst, th->th_dport, 740 1, m->m_pkthdr.rcvif); 741 } 742 } 743 744 /* 745 * If the state is CLOSED (i.e., TCB does not exist) then 746 * all data in the incoming segment is discarded. 747 * If the TCB exists but is in CLOSED state, it is embryonic, 748 * but should either do a listen or a connect soon. 749 */ 750 if (inp == NULL) { 751 if (log_in_vain) { 752 #ifdef INET6 753 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 754 #else 755 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 756 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 757 #endif 758 if (isipv6) { 759 strcpy(dbuf, "["); 760 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 761 strcat(dbuf, "]"); 762 strcpy(sbuf, "["); 763 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 764 strcat(sbuf, "]"); 765 } else { 766 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 767 strcpy(sbuf, inet_ntoa(ip->ip_src)); 768 } 769 switch (log_in_vain) { 770 case 1: 771 if (!(thflags & TH_SYN)) 772 break; 773 case 2: 774 log(LOG_INFO, 775 "Connection attempt to TCP %s:%d " 776 "from %s:%d flags:0x%02x\n", 777 dbuf, ntohs(th->th_dport), sbuf, 778 ntohs(th->th_sport), thflags); 779 break; 780 default: 781 break; 782 } 783 } 784 if (blackhole) { 785 switch (blackhole) { 786 case 1: 787 if (thflags & TH_SYN) 788 goto drop; 789 break; 790 case 2: 791 goto drop; 792 default: 793 goto drop; 794 } 795 } 796 rstreason = BANDLIM_RST_CLOSEDPORT; 797 goto dropwithreset; 798 } 799 800 #ifdef IPSEC 801 if (isipv6) { 802 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 803 ipsec6stat.in_polvio++; 804 goto drop; 805 } 806 } else { 807 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 808 ipsecstat.in_polvio++; 809 goto drop; 810 } 811 } 812 #endif 813 #ifdef FAST_IPSEC 814 if (isipv6) { 815 if (ipsec6_in_reject(m, inp)) 816 goto drop; 817 } else { 818 if (ipsec4_in_reject(m, inp)) 819 goto drop; 820 } 821 #endif 822 /* Check the minimum TTL for socket. */ 823 #ifdef INET6 824 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 825 goto drop; 826 #endif 827 828 tp = intotcpcb(inp); 829 if (tp == NULL) { 830 rstreason = BANDLIM_RST_CLOSEDPORT; 831 goto dropwithreset; 832 } 833 if (tp->t_state <= TCPS_CLOSED) 834 goto drop; 835 836 /* Unscale the window into a 32-bit value. */ 837 if (!(thflags & TH_SYN)) 838 tiwin = th->th_win << tp->snd_scale; 839 else 840 tiwin = th->th_win; 841 842 so = inp->inp_socket; 843 844 #ifdef TCPDEBUG 845 if (so->so_options & SO_DEBUG) { 846 ostate = tp->t_state; 847 if (isipv6) 848 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 849 else 850 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 851 tcp_savetcp = *th; 852 } 853 #endif 854 855 bzero(&to, sizeof to); 856 857 if (so->so_options & SO_ACCEPTCONN) { 858 struct in_conninfo inc; 859 860 #ifdef INET6 861 inc.inc_isipv6 = (isipv6 == TRUE); 862 #endif 863 if (isipv6) { 864 inc.inc6_faddr = ip6->ip6_src; 865 inc.inc6_laddr = ip6->ip6_dst; 866 inc.inc6_route.ro_rt = NULL; /* XXX */ 867 } else { 868 inc.inc_faddr = ip->ip_src; 869 inc.inc_laddr = ip->ip_dst; 870 inc.inc_route.ro_rt = NULL; /* XXX */ 871 } 872 inc.inc_fport = th->th_sport; 873 inc.inc_lport = th->th_dport; 874 875 /* 876 * If the state is LISTEN then ignore segment if it contains 877 * a RST. If the segment contains an ACK then it is bad and 878 * send a RST. If it does not contain a SYN then it is not 879 * interesting; drop it. 880 * 881 * If the state is SYN_RECEIVED (syncache) and seg contains 882 * an ACK, but not for our SYN/ACK, send a RST. If the seg 883 * contains a RST, check the sequence number to see if it 884 * is a valid reset segment. 885 */ 886 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 887 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 888 if (!syncache_expand(&inc, th, &so, m)) { 889 /* 890 * No syncache entry, or ACK was not 891 * for our SYN/ACK. Send a RST. 892 */ 893 tcpstat.tcps_badsyn++; 894 rstreason = BANDLIM_RST_OPENPORT; 895 goto dropwithreset; 896 } 897 if (so == NULL) 898 /* 899 * Could not complete 3-way handshake, 900 * connection is being closed down, and 901 * syncache will free mbuf. 902 */ 903 return; 904 /* 905 * Socket is created in state SYN_RECEIVED. 906 * Continue processing segment. 907 */ 908 inp = so->so_pcb; 909 tp = intotcpcb(inp); 910 /* 911 * This is what would have happened in 912 * tcp_output() when the SYN,ACK was sent. 913 */ 914 tp->snd_up = tp->snd_una; 915 tp->snd_max = tp->snd_nxt = tp->iss + 1; 916 tp->last_ack_sent = tp->rcv_nxt; 917 /* 918 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 919 * until the _second_ ACK is received: 920 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 921 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 922 * move to ESTAB, set snd_wnd to tiwin. 923 */ 924 tp->snd_wnd = tiwin; /* unscaled */ 925 goto after_listen; 926 } 927 if (thflags & TH_RST) { 928 syncache_chkrst(&inc, th); 929 goto drop; 930 } 931 if (thflags & TH_ACK) { 932 syncache_badack(&inc); 933 tcpstat.tcps_badsyn++; 934 rstreason = BANDLIM_RST_OPENPORT; 935 goto dropwithreset; 936 } 937 goto drop; 938 } 939 940 /* 941 * Segment's flags are (SYN) or (SYN | FIN). 942 */ 943 #ifdef INET6 944 /* 945 * If deprecated address is forbidden, 946 * we do not accept SYN to deprecated interface 947 * address to prevent any new inbound connection from 948 * getting established. 949 * When we do not accept SYN, we send a TCP RST, 950 * with deprecated source address (instead of dropping 951 * it). We compromise it as it is much better for peer 952 * to send a RST, and RST will be the final packet 953 * for the exchange. 954 * 955 * If we do not forbid deprecated addresses, we accept 956 * the SYN packet. RFC2462 does not suggest dropping 957 * SYN in this case. 958 * If we decipher RFC2462 5.5.4, it says like this: 959 * 1. use of deprecated addr with existing 960 * communication is okay - "SHOULD continue to be 961 * used" 962 * 2. use of it with new communication: 963 * (2a) "SHOULD NOT be used if alternate address 964 * with sufficient scope is available" 965 * (2b) nothing mentioned otherwise. 966 * Here we fall into (2b) case as we have no choice in 967 * our source address selection - we must obey the peer. 968 * 969 * The wording in RFC2462 is confusing, and there are 970 * multiple description text for deprecated address 971 * handling - worse, they are not exactly the same. 972 * I believe 5.5.4 is the best one, so we follow 5.5.4. 973 */ 974 if (isipv6 && !ip6_use_deprecated) { 975 struct in6_ifaddr *ia6; 976 977 if ((ia6 = ip6_getdstifaddr(m)) && 978 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 979 tp = NULL; 980 rstreason = BANDLIM_RST_OPENPORT; 981 goto dropwithreset; 982 } 983 } 984 #endif 985 /* 986 * If it is from this socket, drop it, it must be forged. 987 * Don't bother responding if the destination was a broadcast. 988 */ 989 if (th->th_dport == th->th_sport) { 990 if (isipv6) { 991 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 992 &ip6->ip6_src)) 993 goto drop; 994 } else { 995 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 996 goto drop; 997 } 998 } 999 /* 1000 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1001 * 1002 * Note that it is quite possible to receive unicast 1003 * link-layer packets with a broadcast IP address. Use 1004 * in_broadcast() to find them. 1005 */ 1006 if (m->m_flags & (M_BCAST | M_MCAST)) 1007 goto drop; 1008 if (isipv6) { 1009 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1010 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1011 goto drop; 1012 } else { 1013 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1014 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1015 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1016 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1017 goto drop; 1018 } 1019 /* 1020 * SYN appears to be valid; create compressed TCP state 1021 * for syncache, or perform t/tcp connection. 1022 */ 1023 if (so->so_qlen <= so->so_qlimit) { 1024 tcp_dooptions(&to, optp, optlen, TRUE); 1025 if (!syncache_add(&inc, &to, th, &so, m)) 1026 goto drop; 1027 if (so == NULL) 1028 /* 1029 * Entry added to syncache, mbuf used to 1030 * send SYN,ACK packet. 1031 */ 1032 return; 1033 inp = so->so_pcb; 1034 tp = intotcpcb(inp); 1035 tp->snd_wnd = tiwin; 1036 tp->t_starttime = ticks; 1037 tp->t_state = TCPS_ESTABLISHED; 1038 1039 /* 1040 * If there is a FIN, or if there is data and the 1041 * connection is local, then delay SYN,ACK(SYN) in 1042 * the hope of piggy-backing it on a response 1043 * segment. Otherwise must send ACK now in case 1044 * the other side is slow starting. 1045 */ 1046 if (DELAY_ACK(tp) && 1047 ((thflags & TH_FIN) || 1048 (tlen != 0 && 1049 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1050 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1051 tcp_callout_reset(tp, tp->tt_delack, 1052 tcp_delacktime, tcp_timer_delack); 1053 tp->t_flags |= TF_NEEDSYN; 1054 } else { 1055 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1056 } 1057 1058 tcpstat.tcps_connects++; 1059 soisconnected(so); 1060 goto trimthenstep6; 1061 } 1062 goto drop; 1063 } 1064 after_listen: 1065 1066 /* should not happen - syncache should pick up these connections */ 1067 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1068 1069 /* 1070 * This is the second part of the MSS DoS prevention code (after 1071 * minmss on the sending side) and it deals with too many too small 1072 * tcp packets in a too short timeframe (1 second). 1073 * 1074 * XXX Removed. This code was crap. It does not scale to network 1075 * speed, and default values break NFS. Gone. 1076 */ 1077 /* REMOVED */ 1078 1079 /* 1080 * Segment received on connection. 1081 * 1082 * Reset idle time and keep-alive timer. Don't waste time if less 1083 * then a second has elapsed. Only update t_rcvtime for non-SYN 1084 * packets. 1085 * 1086 * Handle the case where one side thinks the connection is established 1087 * but the other side has, say, rebooted without cleaning out the 1088 * connection. The SYNs could be construed as an attack and wind 1089 * up ignored, but in case it isn't an attack we can validate the 1090 * connection by forcing a keepalive. 1091 */ 1092 if (TCPS_HAVEESTABLISHED(tp->t_state) && (ticks - tp->t_rcvtime) > hz) { 1093 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 1094 tp->t_flags |= TF_KEEPALIVE; 1095 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 1096 tcp_timer_keep); 1097 } else { 1098 tp->t_rcvtime = ticks; 1099 tp->t_flags &= ~TF_KEEPALIVE; 1100 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1101 tcp_timer_keep); 1102 } 1103 } 1104 1105 /* 1106 * Process options. 1107 * XXX this is tradtitional behavior, may need to be cleaned up. 1108 */ 1109 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1110 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1111 if (to.to_flags & TOF_SCALE) { 1112 tp->t_flags |= TF_RCVD_SCALE; 1113 tp->requested_s_scale = to.to_requested_s_scale; 1114 } 1115 if (to.to_flags & TOF_TS) { 1116 tp->t_flags |= TF_RCVD_TSTMP; 1117 tp->ts_recent = to.to_tsval; 1118 tp->ts_recent_age = ticks; 1119 } 1120 if (to.to_flags & TOF_MSS) 1121 tcp_mss(tp, to.to_mss); 1122 /* 1123 * Only set the TF_SACK_PERMITTED per-connection flag 1124 * if we got a SACK_PERMITTED option from the other side 1125 * and the global tcp_do_sack variable is true. 1126 */ 1127 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1128 tp->t_flags |= TF_SACK_PERMITTED; 1129 } 1130 1131 /* 1132 * Header prediction: check for the two common cases 1133 * of a uni-directional data xfer. If the packet has 1134 * no control flags, is in-sequence, the window didn't 1135 * change and we're not retransmitting, it's a 1136 * candidate. If the length is zero and the ack moved 1137 * forward, we're the sender side of the xfer. Just 1138 * free the data acked & wake any higher level process 1139 * that was blocked waiting for space. If the length 1140 * is non-zero and the ack didn't move, we're the 1141 * receiver side. If we're getting packets in-order 1142 * (the reassembly queue is empty), add the data to 1143 * the socket buffer and note that we need a delayed ack. 1144 * Make sure that the hidden state-flags are also off. 1145 * Since we check for TCPS_ESTABLISHED above, it can only 1146 * be TH_NEEDSYN. 1147 */ 1148 if (tp->t_state == TCPS_ESTABLISHED && 1149 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1150 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1151 (!(to.to_flags & TOF_TS) || 1152 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1153 th->th_seq == tp->rcv_nxt && 1154 tp->snd_nxt == tp->snd_max) { 1155 1156 /* 1157 * If last ACK falls within this segment's sequence numbers, 1158 * record the timestamp. 1159 * NOTE that the test is modified according to the latest 1160 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1161 */ 1162 if ((to.to_flags & TOF_TS) && 1163 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1164 tp->ts_recent_age = ticks; 1165 tp->ts_recent = to.to_tsval; 1166 } 1167 1168 if (tlen == 0) { 1169 if (SEQ_GT(th->th_ack, tp->snd_una) && 1170 SEQ_LEQ(th->th_ack, tp->snd_max) && 1171 tp->snd_cwnd >= tp->snd_wnd && 1172 !IN_FASTRECOVERY(tp)) { 1173 /* 1174 * This is a pure ack for outstanding data. 1175 */ 1176 ++tcpstat.tcps_predack; 1177 /* 1178 * "bad retransmit" recovery 1179 * 1180 * If Eifel detection applies, then 1181 * it is deterministic, so use it 1182 * unconditionally over the old heuristic. 1183 * Otherwise, fall back to the old heuristic. 1184 */ 1185 if (tcp_do_eifel_detect && 1186 (to.to_flags & TOF_TS) && to.to_tsecr && 1187 (tp->t_flags & TF_FIRSTACCACK)) { 1188 /* Eifel detection applicable. */ 1189 if (to.to_tsecr < tp->t_rexmtTS) { 1190 tcp_revert_congestion_state(tp); 1191 ++tcpstat.tcps_eifeldetected; 1192 } 1193 } else if (tp->t_rxtshift == 1 && 1194 ticks < tp->t_badrxtwin) { 1195 tcp_revert_congestion_state(tp); 1196 ++tcpstat.tcps_rttdetected; 1197 } 1198 tp->t_flags &= ~(TF_FIRSTACCACK | 1199 TF_FASTREXMT | TF_EARLYREXMT); 1200 /* 1201 * Recalculate the retransmit timer / rtt. 1202 * 1203 * Some machines (certain windows boxes) 1204 * send broken timestamp replies during the 1205 * SYN+ACK phase, ignore timestamps of 0. 1206 */ 1207 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1208 tcp_xmit_timer(tp, 1209 ticks - to.to_tsecr + 1); 1210 } else if (tp->t_rtttime && 1211 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1212 tcp_xmit_timer(tp, 1213 ticks - tp->t_rtttime); 1214 } 1215 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1216 acked = th->th_ack - tp->snd_una; 1217 tcpstat.tcps_rcvackpack++; 1218 tcpstat.tcps_rcvackbyte += acked; 1219 sbdrop(&so->so_snd.sb, acked); 1220 tp->snd_recover = th->th_ack - 1; 1221 tp->snd_una = th->th_ack; 1222 tp->t_dupacks = 0; 1223 /* 1224 * Update window information. 1225 */ 1226 if (tiwin != tp->snd_wnd && 1227 acceptable_window_update(tp, th, tiwin)) { 1228 /* keep track of pure window updates */ 1229 if (tp->snd_wl2 == th->th_ack && 1230 tiwin > tp->snd_wnd) 1231 tcpstat.tcps_rcvwinupd++; 1232 tp->snd_wnd = tiwin; 1233 tp->snd_wl1 = th->th_seq; 1234 tp->snd_wl2 = th->th_ack; 1235 if (tp->snd_wnd > tp->max_sndwnd) 1236 tp->max_sndwnd = tp->snd_wnd; 1237 } 1238 m_freem(m); 1239 ND6_HINT(tp); /* some progress has been done */ 1240 /* 1241 * If all outstanding data are acked, stop 1242 * retransmit timer, otherwise restart timer 1243 * using current (possibly backed-off) value. 1244 * If process is waiting for space, 1245 * wakeup/selwakeup/signal. If data 1246 * are ready to send, let tcp_output 1247 * decide between more output or persist. 1248 */ 1249 if (tp->snd_una == tp->snd_max) { 1250 tcp_callout_stop(tp, tp->tt_rexmt); 1251 } else if (!tcp_callout_active(tp, 1252 tp->tt_persist)) { 1253 tcp_callout_reset(tp, tp->tt_rexmt, 1254 tp->t_rxtcur, tcp_timer_rexmt); 1255 } 1256 sowwakeup(so); 1257 if (so->so_snd.ssb_cc > 0) 1258 tcp_output(tp); 1259 return; 1260 } 1261 } else if (tiwin == tp->snd_wnd && 1262 th->th_ack == tp->snd_una && 1263 LIST_EMPTY(&tp->t_segq) && 1264 tlen <= ssb_space(&so->so_rcv)) { 1265 u_long newsize = 0; /* automatic sockbuf scaling */ 1266 /* 1267 * This is a pure, in-sequence data packet 1268 * with nothing on the reassembly queue and 1269 * we have enough buffer space to take it. 1270 */ 1271 ++tcpstat.tcps_preddat; 1272 tp->rcv_nxt += tlen; 1273 tcpstat.tcps_rcvpack++; 1274 tcpstat.tcps_rcvbyte += tlen; 1275 ND6_HINT(tp); /* some progress has been done */ 1276 /* 1277 * Automatic sizing of receive socket buffer. Often the send 1278 * buffer size is not optimally adjusted to the actual network 1279 * conditions at hand (delay bandwidth product). Setting the 1280 * buffer size too small limits throughput on links with high 1281 * bandwidth and high delay (eg. trans-continental/oceanic links). 1282 * 1283 * On the receive side the socket buffer memory is only rarely 1284 * used to any significant extent. This allows us to be much 1285 * more aggressive in scaling the receive socket buffer. For 1286 * the case that the buffer space is actually used to a large 1287 * extent and we run out of kernel memory we can simply drop 1288 * the new segments; TCP on the sender will just retransmit it 1289 * later. Setting the buffer size too big may only consume too 1290 * much kernel memory if the application doesn't read() from 1291 * the socket or packet loss or reordering makes use of the 1292 * reassembly queue. 1293 * 1294 * The criteria to step up the receive buffer one notch are: 1295 * 1. the number of bytes received during the time it takes 1296 * one timestamp to be reflected back to us (the RTT); 1297 * 2. received bytes per RTT is within seven eighth of the 1298 * current socket buffer size; 1299 * 3. receive buffer size has not hit maximal automatic size; 1300 * 1301 * This algorithm does one step per RTT at most and only if 1302 * we receive a bulk stream w/o packet losses or reorderings. 1303 * Shrinking the buffer during idle times is not necessary as 1304 * it doesn't consume any memory when idle. 1305 * 1306 * TODO: Only step up if the application is actually serving 1307 * the buffer to better manage the socket buffer resources. 1308 */ 1309 if (tcp_do_autorcvbuf && 1310 to.to_tsecr && 1311 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1312 if (to.to_tsecr > tp->rfbuf_ts && 1313 to.to_tsecr - tp->rfbuf_ts < hz) { 1314 if (tp->rfbuf_cnt > 1315 (so->so_rcv.ssb_hiwat / 8 * 7) && 1316 so->so_rcv.ssb_hiwat < 1317 tcp_autorcvbuf_max) { 1318 newsize = 1319 ulmin(so->so_rcv.ssb_hiwat + 1320 tcp_autorcvbuf_inc, 1321 tcp_autorcvbuf_max); 1322 } 1323 /* Start over with next RTT. */ 1324 tp->rfbuf_ts = 0; 1325 tp->rfbuf_cnt = 0; 1326 } else 1327 tp->rfbuf_cnt += tlen; /* add up */ 1328 } 1329 /* 1330 * Add data to socket buffer. 1331 */ 1332 if (so->so_state & SS_CANTRCVMORE) { 1333 m_freem(m); 1334 } else { 1335 /* 1336 * Set new socket buffer size, give up when 1337 * limit is reached. 1338 * 1339 * Adjusting the size can mess up ACK 1340 * sequencing when pure window updates are 1341 * being avoided (which is the default), 1342 * so force an ack. 1343 */ 1344 if (newsize) { 1345 tp->t_flags |= TF_RXRESIZED; 1346 if (!ssb_reserve(&so->so_rcv, newsize, 1347 so, NULL)) { 1348 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1349 } 1350 if (newsize >= 1351 (TCP_MAXWIN << tp->rcv_scale)) { 1352 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1353 } 1354 } 1355 m_adj(m, drop_hdrlen); /* delayed header drop */ 1356 ssb_appendstream(&so->so_rcv, m); 1357 } 1358 sorwakeup(so); 1359 /* 1360 * This code is responsible for most of the ACKs 1361 * the TCP stack sends back after receiving a data 1362 * packet. Note that the DELAY_ACK check fails if 1363 * the delack timer is already running, which results 1364 * in an ack being sent every other packet (which is 1365 * what we want). 1366 * 1367 * We then further aggregate acks by not actually 1368 * sending one until the protocol thread has completed 1369 * processing the current backlog of packets. This 1370 * does not delay the ack any further, but allows us 1371 * to take advantage of the packet aggregation that 1372 * high speed NICs do (usually blocks of 8-10 packets) 1373 * to send a single ack rather then four or five acks, 1374 * greatly reducing the ack rate, the return channel 1375 * bandwidth, and the protocol overhead on both ends. 1376 * 1377 * Since this also has the effect of slowing down 1378 * the exponential slow-start ramp-up, systems with 1379 * very large bandwidth-delay products might want 1380 * to turn the feature off. 1381 */ 1382 if (DELAY_ACK(tp)) { 1383 tcp_callout_reset(tp, tp->tt_delack, 1384 tcp_delacktime, tcp_timer_delack); 1385 } else if (tcp_aggregate_acks) { 1386 tp->t_flags |= TF_ACKNOW; 1387 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1388 tp->t_flags |= TF_ONOUTPUTQ; 1389 tp->tt_cpu = mycpu->gd_cpuid; 1390 TAILQ_INSERT_TAIL( 1391 &tcpcbackq[tp->tt_cpu], 1392 tp, t_outputq); 1393 } 1394 } else { 1395 tp->t_flags |= TF_ACKNOW; 1396 tcp_output(tp); 1397 } 1398 return; 1399 } 1400 } 1401 1402 /* 1403 * Calculate amount of space in receive window, 1404 * and then do TCP input processing. 1405 * Receive window is amount of space in rcv queue, 1406 * but not less than advertised window. 1407 */ 1408 recvwin = ssb_space(&so->so_rcv); 1409 if (recvwin < 0) 1410 recvwin = 0; 1411 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1412 1413 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1414 tp->rfbuf_ts = 0; 1415 tp->rfbuf_cnt = 0; 1416 1417 switch (tp->t_state) { 1418 /* 1419 * If the state is SYN_RECEIVED: 1420 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1421 */ 1422 case TCPS_SYN_RECEIVED: 1423 if ((thflags & TH_ACK) && 1424 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1425 SEQ_GT(th->th_ack, tp->snd_max))) { 1426 rstreason = BANDLIM_RST_OPENPORT; 1427 goto dropwithreset; 1428 } 1429 break; 1430 1431 /* 1432 * If the state is SYN_SENT: 1433 * if seg contains an ACK, but not for our SYN, drop the input. 1434 * if seg contains a RST, then drop the connection. 1435 * if seg does not contain SYN, then drop it. 1436 * Otherwise this is an acceptable SYN segment 1437 * initialize tp->rcv_nxt and tp->irs 1438 * if seg contains ack then advance tp->snd_una 1439 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1440 * arrange for segment to be acked (eventually) 1441 * continue processing rest of data/controls, beginning with URG 1442 */ 1443 case TCPS_SYN_SENT: 1444 if ((thflags & TH_ACK) && 1445 (SEQ_LEQ(th->th_ack, tp->iss) || 1446 SEQ_GT(th->th_ack, tp->snd_max))) { 1447 rstreason = BANDLIM_UNLIMITED; 1448 goto dropwithreset; 1449 } 1450 if (thflags & TH_RST) { 1451 if (thflags & TH_ACK) 1452 tp = tcp_drop(tp, ECONNREFUSED); 1453 goto drop; 1454 } 1455 if (!(thflags & TH_SYN)) 1456 goto drop; 1457 tp->snd_wnd = th->th_win; /* initial send window */ 1458 1459 tp->irs = th->th_seq; 1460 tcp_rcvseqinit(tp); 1461 if (thflags & TH_ACK) { 1462 /* Our SYN was acked. */ 1463 tcpstat.tcps_connects++; 1464 soisconnected(so); 1465 /* Do window scaling on this connection? */ 1466 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1467 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1468 tp->snd_scale = tp->requested_s_scale; 1469 tp->rcv_scale = tp->request_r_scale; 1470 } 1471 tp->rcv_adv += tp->rcv_wnd; 1472 tp->snd_una++; /* SYN is acked */ 1473 tcp_callout_stop(tp, tp->tt_rexmt); 1474 /* 1475 * If there's data, delay ACK; if there's also a FIN 1476 * ACKNOW will be turned on later. 1477 */ 1478 if (DELAY_ACK(tp) && tlen != 0) { 1479 tcp_callout_reset(tp, tp->tt_delack, 1480 tcp_delacktime, tcp_timer_delack); 1481 } else { 1482 tp->t_flags |= TF_ACKNOW; 1483 } 1484 /* 1485 * Received <SYN,ACK> in SYN_SENT[*] state. 1486 * Transitions: 1487 * SYN_SENT --> ESTABLISHED 1488 * SYN_SENT* --> FIN_WAIT_1 1489 */ 1490 tp->t_starttime = ticks; 1491 if (tp->t_flags & TF_NEEDFIN) { 1492 tp->t_state = TCPS_FIN_WAIT_1; 1493 tp->t_flags &= ~TF_NEEDFIN; 1494 thflags &= ~TH_SYN; 1495 } else { 1496 tp->t_state = TCPS_ESTABLISHED; 1497 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1498 tcp_timer_keep); 1499 } 1500 } else { 1501 /* 1502 * Received initial SYN in SYN-SENT[*] state => 1503 * simultaneous open. 1504 * Do 3-way handshake: 1505 * SYN-SENT -> SYN-RECEIVED 1506 * SYN-SENT* -> SYN-RECEIVED* 1507 */ 1508 tp->t_flags |= TF_ACKNOW; 1509 tcp_callout_stop(tp, tp->tt_rexmt); 1510 tp->t_state = TCPS_SYN_RECEIVED; 1511 } 1512 1513 trimthenstep6: 1514 /* 1515 * Advance th->th_seq to correspond to first data byte. 1516 * If data, trim to stay within window, 1517 * dropping FIN if necessary. 1518 */ 1519 th->th_seq++; 1520 if (tlen > tp->rcv_wnd) { 1521 todrop = tlen - tp->rcv_wnd; 1522 m_adj(m, -todrop); 1523 tlen = tp->rcv_wnd; 1524 thflags &= ~TH_FIN; 1525 tcpstat.tcps_rcvpackafterwin++; 1526 tcpstat.tcps_rcvbyteafterwin += todrop; 1527 } 1528 tp->snd_wl1 = th->th_seq - 1; 1529 tp->rcv_up = th->th_seq; 1530 /* 1531 * Client side of transaction: already sent SYN and data. 1532 * If the remote host used T/TCP to validate the SYN, 1533 * our data will be ACK'd; if so, enter normal data segment 1534 * processing in the middle of step 5, ack processing. 1535 * Otherwise, goto step 6. 1536 */ 1537 if (thflags & TH_ACK) 1538 goto process_ACK; 1539 1540 goto step6; 1541 1542 /* 1543 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1544 * do normal processing (we no longer bother with T/TCP). 1545 */ 1546 case TCPS_LAST_ACK: 1547 case TCPS_CLOSING: 1548 case TCPS_TIME_WAIT: 1549 break; /* continue normal processing */ 1550 } 1551 1552 /* 1553 * States other than LISTEN or SYN_SENT. 1554 * First check the RST flag and sequence number since reset segments 1555 * are exempt from the timestamp and connection count tests. This 1556 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1557 * below which allowed reset segments in half the sequence space 1558 * to fall though and be processed (which gives forged reset 1559 * segments with a random sequence number a 50 percent chance of 1560 * killing a connection). 1561 * Then check timestamp, if present. 1562 * Then check the connection count, if present. 1563 * Then check that at least some bytes of segment are within 1564 * receive window. If segment begins before rcv_nxt, 1565 * drop leading data (and SYN); if nothing left, just ack. 1566 * 1567 * 1568 * If the RST bit is set, check the sequence number to see 1569 * if this is a valid reset segment. 1570 * RFC 793 page 37: 1571 * In all states except SYN-SENT, all reset (RST) segments 1572 * are validated by checking their SEQ-fields. A reset is 1573 * valid if its sequence number is in the window. 1574 * Note: this does not take into account delayed ACKs, so 1575 * we should test against last_ack_sent instead of rcv_nxt. 1576 * The sequence number in the reset segment is normally an 1577 * echo of our outgoing acknowledgement numbers, but some hosts 1578 * send a reset with the sequence number at the rightmost edge 1579 * of our receive window, and we have to handle this case. 1580 * If we have multiple segments in flight, the intial reset 1581 * segment sequence numbers will be to the left of last_ack_sent, 1582 * but they will eventually catch up. 1583 * In any case, it never made sense to trim reset segments to 1584 * fit the receive window since RFC 1122 says: 1585 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1586 * 1587 * A TCP SHOULD allow a received RST segment to include data. 1588 * 1589 * DISCUSSION 1590 * It has been suggested that a RST segment could contain 1591 * ASCII text that encoded and explained the cause of the 1592 * RST. No standard has yet been established for such 1593 * data. 1594 * 1595 * If the reset segment passes the sequence number test examine 1596 * the state: 1597 * SYN_RECEIVED STATE: 1598 * If passive open, return to LISTEN state. 1599 * If active open, inform user that connection was refused. 1600 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1601 * Inform user that connection was reset, and close tcb. 1602 * CLOSING, LAST_ACK STATES: 1603 * Close the tcb. 1604 * TIME_WAIT STATE: 1605 * Drop the segment - see Stevens, vol. 2, p. 964 and 1606 * RFC 1337. 1607 */ 1608 if (thflags & TH_RST) { 1609 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1610 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1611 switch (tp->t_state) { 1612 1613 case TCPS_SYN_RECEIVED: 1614 so->so_error = ECONNREFUSED; 1615 goto close; 1616 1617 case TCPS_ESTABLISHED: 1618 case TCPS_FIN_WAIT_1: 1619 case TCPS_FIN_WAIT_2: 1620 case TCPS_CLOSE_WAIT: 1621 so->so_error = ECONNRESET; 1622 close: 1623 tp->t_state = TCPS_CLOSED; 1624 tcpstat.tcps_drops++; 1625 tp = tcp_close(tp); 1626 break; 1627 1628 case TCPS_CLOSING: 1629 case TCPS_LAST_ACK: 1630 tp = tcp_close(tp); 1631 break; 1632 1633 case TCPS_TIME_WAIT: 1634 break; 1635 } 1636 } 1637 goto drop; 1638 } 1639 1640 /* 1641 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1642 * and it's less than ts_recent, drop it. 1643 */ 1644 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1645 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1646 1647 /* Check to see if ts_recent is over 24 days old. */ 1648 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1649 /* 1650 * Invalidate ts_recent. If this segment updates 1651 * ts_recent, the age will be reset later and ts_recent 1652 * will get a valid value. If it does not, setting 1653 * ts_recent to zero will at least satisfy the 1654 * requirement that zero be placed in the timestamp 1655 * echo reply when ts_recent isn't valid. The 1656 * age isn't reset until we get a valid ts_recent 1657 * because we don't want out-of-order segments to be 1658 * dropped when ts_recent is old. 1659 */ 1660 tp->ts_recent = 0; 1661 } else { 1662 tcpstat.tcps_rcvduppack++; 1663 tcpstat.tcps_rcvdupbyte += tlen; 1664 tcpstat.tcps_pawsdrop++; 1665 if (tlen) 1666 goto dropafterack; 1667 goto drop; 1668 } 1669 } 1670 1671 /* 1672 * In the SYN-RECEIVED state, validate that the packet belongs to 1673 * this connection before trimming the data to fit the receive 1674 * window. Check the sequence number versus IRS since we know 1675 * the sequence numbers haven't wrapped. This is a partial fix 1676 * for the "LAND" DoS attack. 1677 */ 1678 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1679 rstreason = BANDLIM_RST_OPENPORT; 1680 goto dropwithreset; 1681 } 1682 1683 todrop = tp->rcv_nxt - th->th_seq; 1684 if (todrop > 0) { 1685 if (TCP_DO_SACK(tp)) { 1686 /* Report duplicate segment at head of packet. */ 1687 tp->reportblk.rblk_start = th->th_seq; 1688 tp->reportblk.rblk_end = th->th_seq + tlen; 1689 if (thflags & TH_FIN) 1690 ++tp->reportblk.rblk_end; 1691 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1692 tp->reportblk.rblk_end = tp->rcv_nxt; 1693 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1694 } 1695 if (thflags & TH_SYN) { 1696 thflags &= ~TH_SYN; 1697 th->th_seq++; 1698 if (th->th_urp > 1) 1699 th->th_urp--; 1700 else 1701 thflags &= ~TH_URG; 1702 todrop--; 1703 } 1704 /* 1705 * Following if statement from Stevens, vol. 2, p. 960. 1706 */ 1707 if (todrop > tlen || 1708 (todrop == tlen && !(thflags & TH_FIN))) { 1709 /* 1710 * Any valid FIN must be to the left of the window. 1711 * At this point the FIN must be a duplicate or out 1712 * of sequence; drop it. 1713 */ 1714 thflags &= ~TH_FIN; 1715 1716 /* 1717 * Send an ACK to resynchronize and drop any data. 1718 * But keep on processing for RST or ACK. 1719 */ 1720 tp->t_flags |= TF_ACKNOW; 1721 todrop = tlen; 1722 tcpstat.tcps_rcvduppack++; 1723 tcpstat.tcps_rcvdupbyte += todrop; 1724 } else { 1725 tcpstat.tcps_rcvpartduppack++; 1726 tcpstat.tcps_rcvpartdupbyte += todrop; 1727 } 1728 drop_hdrlen += todrop; /* drop from the top afterwards */ 1729 th->th_seq += todrop; 1730 tlen -= todrop; 1731 if (th->th_urp > todrop) 1732 th->th_urp -= todrop; 1733 else { 1734 thflags &= ~TH_URG; 1735 th->th_urp = 0; 1736 } 1737 } 1738 1739 /* 1740 * If new data are received on a connection after the 1741 * user processes are gone, then RST the other end. 1742 */ 1743 if ((so->so_state & SS_NOFDREF) && 1744 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1745 tp = tcp_close(tp); 1746 tcpstat.tcps_rcvafterclose++; 1747 rstreason = BANDLIM_UNLIMITED; 1748 goto dropwithreset; 1749 } 1750 1751 /* 1752 * If segment ends after window, drop trailing data 1753 * (and PUSH and FIN); if nothing left, just ACK. 1754 */ 1755 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1756 if (todrop > 0) { 1757 tcpstat.tcps_rcvpackafterwin++; 1758 if (todrop >= tlen) { 1759 tcpstat.tcps_rcvbyteafterwin += tlen; 1760 /* 1761 * If a new connection request is received 1762 * while in TIME_WAIT, drop the old connection 1763 * and start over if the sequence numbers 1764 * are above the previous ones. 1765 */ 1766 if (thflags & TH_SYN && 1767 tp->t_state == TCPS_TIME_WAIT && 1768 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1769 tp = tcp_close(tp); 1770 goto findpcb; 1771 } 1772 /* 1773 * If window is closed can only take segments at 1774 * window edge, and have to drop data and PUSH from 1775 * incoming segments. Continue processing, but 1776 * remember to ack. Otherwise, drop segment 1777 * and ack. 1778 */ 1779 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1780 tp->t_flags |= TF_ACKNOW; 1781 tcpstat.tcps_rcvwinprobe++; 1782 } else 1783 goto dropafterack; 1784 } else 1785 tcpstat.tcps_rcvbyteafterwin += todrop; 1786 m_adj(m, -todrop); 1787 tlen -= todrop; 1788 thflags &= ~(TH_PUSH | TH_FIN); 1789 } 1790 1791 /* 1792 * If last ACK falls within this segment's sequence numbers, 1793 * record its timestamp. 1794 * NOTE: 1795 * 1) That the test incorporates suggestions from the latest 1796 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1797 * 2) That updating only on newer timestamps interferes with 1798 * our earlier PAWS tests, so this check should be solely 1799 * predicated on the sequence space of this segment. 1800 * 3) That we modify the segment boundary check to be 1801 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1802 * instead of RFC1323's 1803 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1804 * This modified check allows us to overcome RFC1323's 1805 * limitations as described in Stevens TCP/IP Illustrated 1806 * Vol. 2 p.869. In such cases, we can still calculate the 1807 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1808 */ 1809 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1810 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1811 + ((thflags & TH_SYN) != 0) 1812 + ((thflags & TH_FIN) != 0)))) { 1813 tp->ts_recent_age = ticks; 1814 tp->ts_recent = to.to_tsval; 1815 } 1816 1817 /* 1818 * If a SYN is in the window, then this is an 1819 * error and we send an RST and drop the connection. 1820 */ 1821 if (thflags & TH_SYN) { 1822 tp = tcp_drop(tp, ECONNRESET); 1823 rstreason = BANDLIM_UNLIMITED; 1824 goto dropwithreset; 1825 } 1826 1827 /* 1828 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1829 * flag is on (half-synchronized state), then queue data for 1830 * later processing; else drop segment and return. 1831 */ 1832 if (!(thflags & TH_ACK)) { 1833 if (tp->t_state == TCPS_SYN_RECEIVED || 1834 (tp->t_flags & TF_NEEDSYN)) 1835 goto step6; 1836 else 1837 goto drop; 1838 } 1839 1840 /* 1841 * Ack processing. 1842 */ 1843 switch (tp->t_state) { 1844 /* 1845 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1846 * ESTABLISHED state and continue processing. 1847 * The ACK was checked above. 1848 */ 1849 case TCPS_SYN_RECEIVED: 1850 1851 tcpstat.tcps_connects++; 1852 soisconnected(so); 1853 /* Do window scaling? */ 1854 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1855 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1856 tp->snd_scale = tp->requested_s_scale; 1857 tp->rcv_scale = tp->request_r_scale; 1858 } 1859 /* 1860 * Make transitions: 1861 * SYN-RECEIVED -> ESTABLISHED 1862 * SYN-RECEIVED* -> FIN-WAIT-1 1863 */ 1864 tp->t_starttime = ticks; 1865 if (tp->t_flags & TF_NEEDFIN) { 1866 tp->t_state = TCPS_FIN_WAIT_1; 1867 tp->t_flags &= ~TF_NEEDFIN; 1868 } else { 1869 tp->t_state = TCPS_ESTABLISHED; 1870 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1871 tcp_timer_keep); 1872 } 1873 /* 1874 * If segment contains data or ACK, will call tcp_reass() 1875 * later; if not, do so now to pass queued data to user. 1876 */ 1877 if (tlen == 0 && !(thflags & TH_FIN)) 1878 tcp_reass(tp, NULL, NULL, NULL); 1879 /* fall into ... */ 1880 1881 /* 1882 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1883 * ACKs. If the ack is in the range 1884 * tp->snd_una < th->th_ack <= tp->snd_max 1885 * then advance tp->snd_una to th->th_ack and drop 1886 * data from the retransmission queue. If this ACK reflects 1887 * more up to date window information we update our window information. 1888 */ 1889 case TCPS_ESTABLISHED: 1890 case TCPS_FIN_WAIT_1: 1891 case TCPS_FIN_WAIT_2: 1892 case TCPS_CLOSE_WAIT: 1893 case TCPS_CLOSING: 1894 case TCPS_LAST_ACK: 1895 case TCPS_TIME_WAIT: 1896 1897 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1898 if (TCP_DO_SACK(tp)) 1899 tcp_sack_update_scoreboard(tp, &to); 1900 if (tlen != 0 || tiwin != tp->snd_wnd) { 1901 tp->t_dupacks = 0; 1902 break; 1903 } 1904 tcpstat.tcps_rcvdupack++; 1905 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1906 th->th_ack != tp->snd_una) { 1907 tp->t_dupacks = 0; 1908 break; 1909 } 1910 /* 1911 * We have outstanding data (other than 1912 * a window probe), this is a completely 1913 * duplicate ack (ie, window info didn't 1914 * change), the ack is the biggest we've 1915 * seen and we've seen exactly our rexmt 1916 * threshhold of them, so assume a packet 1917 * has been dropped and retransmit it. 1918 * Kludge snd_nxt & the congestion 1919 * window so we send only this one 1920 * packet. 1921 */ 1922 if (IN_FASTRECOVERY(tp)) { 1923 if (TCP_DO_SACK(tp)) { 1924 /* No artifical cwnd inflation. */ 1925 tcp_sack_rexmt(tp, th); 1926 } else { 1927 /* 1928 * Dup acks mean that packets 1929 * have left the network 1930 * (they're now cached at the 1931 * receiver) so bump cwnd by 1932 * the amount in the receiver 1933 * to keep a constant cwnd 1934 * packets in the network. 1935 */ 1936 tp->snd_cwnd += tp->t_maxseg; 1937 tcp_output(tp); 1938 } 1939 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1940 tp->t_dupacks = 0; 1941 break; 1942 } else if (++tp->t_dupacks == tcprexmtthresh) { 1943 tcp_seq old_snd_nxt; 1944 u_int win; 1945 1946 fastretransmit: 1947 if (tcp_do_eifel_detect && 1948 (tp->t_flags & TF_RCVD_TSTMP)) { 1949 tcp_save_congestion_state(tp); 1950 tp->t_flags |= TF_FASTREXMT; 1951 } 1952 /* 1953 * We know we're losing at the current 1954 * window size, so do congestion avoidance: 1955 * set ssthresh to half the current window 1956 * and pull our congestion window back to the 1957 * new ssthresh. 1958 */ 1959 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1960 tp->t_maxseg; 1961 if (win < 2) 1962 win = 2; 1963 tp->snd_ssthresh = win * tp->t_maxseg; 1964 ENTER_FASTRECOVERY(tp); 1965 tp->snd_recover = tp->snd_max; 1966 tcp_callout_stop(tp, tp->tt_rexmt); 1967 tp->t_rtttime = 0; 1968 old_snd_nxt = tp->snd_nxt; 1969 tp->snd_nxt = th->th_ack; 1970 tp->snd_cwnd = tp->t_maxseg; 1971 tcp_output(tp); 1972 ++tcpstat.tcps_sndfastrexmit; 1973 tp->snd_cwnd = tp->snd_ssthresh; 1974 tp->rexmt_high = tp->snd_nxt; 1975 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1976 tp->snd_nxt = old_snd_nxt; 1977 KASSERT(tp->snd_limited <= 2, 1978 ("tp->snd_limited too big")); 1979 if (TCP_DO_SACK(tp)) 1980 tcp_sack_rexmt(tp, th); 1981 else 1982 tp->snd_cwnd += tp->t_maxseg * 1983 (tp->t_dupacks - tp->snd_limited); 1984 } else if (tcp_do_limitedtransmit) { 1985 u_long oldcwnd = tp->snd_cwnd; 1986 tcp_seq oldsndmax = tp->snd_max; 1987 tcp_seq oldsndnxt = tp->snd_nxt; 1988 /* outstanding data */ 1989 uint32_t ownd = tp->snd_max - tp->snd_una; 1990 u_int sent; 1991 1992 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1993 1994 KASSERT(tp->t_dupacks == 1 || 1995 tp->t_dupacks == 2, 1996 ("dupacks not 1 or 2")); 1997 if (tp->t_dupacks == 1) 1998 tp->snd_limited = 0; 1999 tp->snd_nxt = tp->snd_max; 2000 tp->snd_cwnd = ownd + 2001 (tp->t_dupacks - tp->snd_limited) * 2002 tp->t_maxseg; 2003 tcp_output(tp); 2004 2005 /* 2006 * Other acks may have been processed, 2007 * snd_nxt cannot be reset to a value less 2008 * then snd_una. 2009 */ 2010 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2011 if (SEQ_GT(oldsndnxt, tp->snd_una)) 2012 tp->snd_nxt = oldsndnxt; 2013 else 2014 tp->snd_nxt = tp->snd_una; 2015 } 2016 tp->snd_cwnd = oldcwnd; 2017 sent = tp->snd_max - oldsndmax; 2018 if (sent > tp->t_maxseg) { 2019 KASSERT((tp->t_dupacks == 2 && 2020 tp->snd_limited == 0) || 2021 (sent == tp->t_maxseg + 1 && 2022 tp->t_flags & TF_SENTFIN), 2023 ("sent too much")); 2024 KASSERT(sent <= tp->t_maxseg * 2, 2025 ("sent too many segments")); 2026 tp->snd_limited = 2; 2027 tcpstat.tcps_sndlimited += 2; 2028 } else if (sent > 0) { 2029 ++tp->snd_limited; 2030 ++tcpstat.tcps_sndlimited; 2031 } else if (tcp_do_early_retransmit && 2032 (tcp_do_eifel_detect && 2033 (tp->t_flags & TF_RCVD_TSTMP)) && 2034 ownd < 4 * tp->t_maxseg && 2035 tp->t_dupacks + 1 >= 2036 iceildiv(ownd, tp->t_maxseg) && 2037 (!TCP_DO_SACK(tp) || 2038 ownd <= tp->t_maxseg || 2039 tcp_sack_has_sacked(&tp->scb, 2040 ownd - tp->t_maxseg))) { 2041 ++tcpstat.tcps_sndearlyrexmit; 2042 tp->t_flags |= TF_EARLYREXMT; 2043 goto fastretransmit; 2044 } 2045 } 2046 goto drop; 2047 } 2048 2049 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2050 tp->t_dupacks = 0; 2051 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2052 /* 2053 * Detected optimistic ACK attack. 2054 * Force slow-start to de-synchronize attack. 2055 */ 2056 tp->snd_cwnd = tp->t_maxseg; 2057 tp->snd_wacked = 0; 2058 2059 tcpstat.tcps_rcvacktoomuch++; 2060 goto dropafterack; 2061 } 2062 /* 2063 * If we reach this point, ACK is not a duplicate, 2064 * i.e., it ACKs something we sent. 2065 */ 2066 if (tp->t_flags & TF_NEEDSYN) { 2067 /* 2068 * T/TCP: Connection was half-synchronized, and our 2069 * SYN has been ACK'd (so connection is now fully 2070 * synchronized). Go to non-starred state, 2071 * increment snd_una for ACK of SYN, and check if 2072 * we can do window scaling. 2073 */ 2074 tp->t_flags &= ~TF_NEEDSYN; 2075 tp->snd_una++; 2076 /* Do window scaling? */ 2077 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2078 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2079 tp->snd_scale = tp->requested_s_scale; 2080 tp->rcv_scale = tp->request_r_scale; 2081 } 2082 } 2083 2084 process_ACK: 2085 acked = th->th_ack - tp->snd_una; 2086 tcpstat.tcps_rcvackpack++; 2087 tcpstat.tcps_rcvackbyte += acked; 2088 2089 if (tcp_do_eifel_detect && acked > 0 && 2090 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2091 (tp->t_flags & TF_FIRSTACCACK)) { 2092 /* Eifel detection applicable. */ 2093 if (to.to_tsecr < tp->t_rexmtTS) { 2094 ++tcpstat.tcps_eifeldetected; 2095 tcp_revert_congestion_state(tp); 2096 if (tp->t_rxtshift == 1 && 2097 ticks >= tp->t_badrxtwin) 2098 ++tcpstat.tcps_rttcantdetect; 2099 } 2100 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2101 /* 2102 * If we just performed our first retransmit, 2103 * and the ACK arrives within our recovery window, 2104 * then it was a mistake to do the retransmit 2105 * in the first place. Recover our original cwnd 2106 * and ssthresh, and proceed to transmit where we 2107 * left off. 2108 */ 2109 tcp_revert_congestion_state(tp); 2110 ++tcpstat.tcps_rttdetected; 2111 } 2112 2113 /* 2114 * If we have a timestamp reply, update smoothed 2115 * round trip time. If no timestamp is present but 2116 * transmit timer is running and timed sequence 2117 * number was acked, update smoothed round trip time. 2118 * Since we now have an rtt measurement, cancel the 2119 * timer backoff (cf., Phil Karn's retransmit alg.). 2120 * Recompute the initial retransmit timer. 2121 * 2122 * Some machines (certain windows boxes) send broken 2123 * timestamp replies during the SYN+ACK phase, ignore 2124 * timestamps of 0. 2125 */ 2126 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2127 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2128 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2129 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2130 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2131 2132 /* 2133 * If no data (only SYN) was ACK'd, 2134 * skip rest of ACK processing. 2135 */ 2136 if (acked == 0) 2137 goto step6; 2138 2139 /* Stop looking for an acceptable ACK since one was received. */ 2140 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2141 2142 if (acked > so->so_snd.ssb_cc) { 2143 tp->snd_wnd -= so->so_snd.ssb_cc; 2144 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2145 ourfinisacked = TRUE; 2146 } else { 2147 sbdrop(&so->so_snd.sb, acked); 2148 tp->snd_wnd -= acked; 2149 ourfinisacked = FALSE; 2150 } 2151 sowwakeup(so); 2152 2153 /* 2154 * Update window information. 2155 * Don't look at window if no ACK: 2156 * TAC's send garbage on first SYN. 2157 */ 2158 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2159 (tp->snd_wl1 == th->th_seq && 2160 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2161 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2162 /* keep track of pure window updates */ 2163 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2164 tiwin > tp->snd_wnd) 2165 tcpstat.tcps_rcvwinupd++; 2166 tp->snd_wnd = tiwin; 2167 tp->snd_wl1 = th->th_seq; 2168 tp->snd_wl2 = th->th_ack; 2169 if (tp->snd_wnd > tp->max_sndwnd) 2170 tp->max_sndwnd = tp->snd_wnd; 2171 needoutput = TRUE; 2172 } 2173 2174 tp->snd_una = th->th_ack; 2175 if (TCP_DO_SACK(tp)) 2176 tcp_sack_update_scoreboard(tp, &to); 2177 if (IN_FASTRECOVERY(tp)) { 2178 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2179 EXIT_FASTRECOVERY(tp); 2180 needoutput = TRUE; 2181 /* 2182 * If the congestion window was inflated 2183 * to account for the other side's 2184 * cached packets, retract it. 2185 */ 2186 if (!TCP_DO_SACK(tp)) 2187 tp->snd_cwnd = tp->snd_ssthresh; 2188 2189 /* 2190 * Window inflation should have left us 2191 * with approximately snd_ssthresh outstanding 2192 * data. But, in case we would be inclined 2193 * to send a burst, better do it using 2194 * slow start. 2195 */ 2196 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2197 tp->snd_max + 2 * tp->t_maxseg)) 2198 tp->snd_cwnd = 2199 (tp->snd_max - tp->snd_una) + 2200 2 * tp->t_maxseg; 2201 2202 tp->snd_wacked = 0; 2203 } else { 2204 if (TCP_DO_SACK(tp)) { 2205 tp->snd_max_rexmt = tp->snd_max; 2206 tcp_sack_rexmt(tp, th); 2207 } else { 2208 tcp_newreno_partial_ack(tp, th, acked); 2209 } 2210 needoutput = FALSE; 2211 } 2212 } else { 2213 /* 2214 * Open the congestion window. When in slow-start, 2215 * open exponentially: maxseg per packet. Otherwise, 2216 * open linearly: maxseg per window. 2217 */ 2218 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2219 u_int abc_sslimit = 2220 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2221 tp->t_maxseg : 2 * tp->t_maxseg); 2222 2223 /* slow-start */ 2224 tp->snd_cwnd += tcp_do_abc ? 2225 min(acked, abc_sslimit) : tp->t_maxseg; 2226 } else { 2227 /* linear increase */ 2228 tp->snd_wacked += tcp_do_abc ? acked : 2229 tp->t_maxseg; 2230 if (tp->snd_wacked >= tp->snd_cwnd) { 2231 tp->snd_wacked -= tp->snd_cwnd; 2232 tp->snd_cwnd += tp->t_maxseg; 2233 } 2234 } 2235 tp->snd_cwnd = min(tp->snd_cwnd, 2236 TCP_MAXWIN << tp->snd_scale); 2237 tp->snd_recover = th->th_ack - 1; 2238 } 2239 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2240 tp->snd_nxt = tp->snd_una; 2241 2242 /* 2243 * If all outstanding data is acked, stop retransmit 2244 * timer and remember to restart (more output or persist). 2245 * If there is more data to be acked, restart retransmit 2246 * timer, using current (possibly backed-off) value. 2247 */ 2248 if (th->th_ack == tp->snd_max) { 2249 tcp_callout_stop(tp, tp->tt_rexmt); 2250 needoutput = TRUE; 2251 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2252 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2253 tcp_timer_rexmt); 2254 } 2255 2256 switch (tp->t_state) { 2257 /* 2258 * In FIN_WAIT_1 STATE in addition to the processing 2259 * for the ESTABLISHED state if our FIN is now acknowledged 2260 * then enter FIN_WAIT_2. 2261 */ 2262 case TCPS_FIN_WAIT_1: 2263 if (ourfinisacked) { 2264 /* 2265 * If we can't receive any more 2266 * data, then closing user can proceed. 2267 * Starting the timer is contrary to the 2268 * specification, but if we don't get a FIN 2269 * we'll hang forever. 2270 */ 2271 if (so->so_state & SS_CANTRCVMORE) { 2272 soisdisconnected(so); 2273 tcp_callout_reset(tp, tp->tt_2msl, 2274 tcp_maxidle, tcp_timer_2msl); 2275 } 2276 tp->t_state = TCPS_FIN_WAIT_2; 2277 } 2278 break; 2279 2280 /* 2281 * In CLOSING STATE in addition to the processing for 2282 * the ESTABLISHED state if the ACK acknowledges our FIN 2283 * then enter the TIME-WAIT state, otherwise ignore 2284 * the segment. 2285 */ 2286 case TCPS_CLOSING: 2287 if (ourfinisacked) { 2288 tp->t_state = TCPS_TIME_WAIT; 2289 tcp_canceltimers(tp); 2290 tcp_callout_reset(tp, tp->tt_2msl, 2291 2 * tcp_msl, tcp_timer_2msl); 2292 soisdisconnected(so); 2293 } 2294 break; 2295 2296 /* 2297 * In LAST_ACK, we may still be waiting for data to drain 2298 * and/or to be acked, as well as for the ack of our FIN. 2299 * If our FIN is now acknowledged, delete the TCB, 2300 * enter the closed state and return. 2301 */ 2302 case TCPS_LAST_ACK: 2303 if (ourfinisacked) { 2304 tp = tcp_close(tp); 2305 goto drop; 2306 } 2307 break; 2308 2309 /* 2310 * In TIME_WAIT state the only thing that should arrive 2311 * is a retransmission of the remote FIN. Acknowledge 2312 * it and restart the finack timer. 2313 */ 2314 case TCPS_TIME_WAIT: 2315 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2316 tcp_timer_2msl); 2317 goto dropafterack; 2318 } 2319 } 2320 2321 step6: 2322 /* 2323 * Update window information. 2324 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2325 */ 2326 if ((thflags & TH_ACK) && 2327 acceptable_window_update(tp, th, tiwin)) { 2328 /* keep track of pure window updates */ 2329 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2330 tiwin > tp->snd_wnd) 2331 tcpstat.tcps_rcvwinupd++; 2332 tp->snd_wnd = tiwin; 2333 tp->snd_wl1 = th->th_seq; 2334 tp->snd_wl2 = th->th_ack; 2335 if (tp->snd_wnd > tp->max_sndwnd) 2336 tp->max_sndwnd = tp->snd_wnd; 2337 needoutput = TRUE; 2338 } 2339 2340 /* 2341 * Process segments with URG. 2342 */ 2343 if ((thflags & TH_URG) && th->th_urp && 2344 !TCPS_HAVERCVDFIN(tp->t_state)) { 2345 /* 2346 * This is a kludge, but if we receive and accept 2347 * random urgent pointers, we'll crash in 2348 * soreceive. It's hard to imagine someone 2349 * actually wanting to send this much urgent data. 2350 */ 2351 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2352 th->th_urp = 0; /* XXX */ 2353 thflags &= ~TH_URG; /* XXX */ 2354 goto dodata; /* XXX */ 2355 } 2356 /* 2357 * If this segment advances the known urgent pointer, 2358 * then mark the data stream. This should not happen 2359 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2360 * a FIN has been received from the remote side. 2361 * In these states we ignore the URG. 2362 * 2363 * According to RFC961 (Assigned Protocols), 2364 * the urgent pointer points to the last octet 2365 * of urgent data. We continue, however, 2366 * to consider it to indicate the first octet 2367 * of data past the urgent section as the original 2368 * spec states (in one of two places). 2369 */ 2370 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2371 tp->rcv_up = th->th_seq + th->th_urp; 2372 so->so_oobmark = so->so_rcv.ssb_cc + 2373 (tp->rcv_up - tp->rcv_nxt) - 1; 2374 if (so->so_oobmark == 0) 2375 so->so_state |= SS_RCVATMARK; 2376 sohasoutofband(so); 2377 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2378 } 2379 /* 2380 * Remove out of band data so doesn't get presented to user. 2381 * This can happen independent of advancing the URG pointer, 2382 * but if two URG's are pending at once, some out-of-band 2383 * data may creep in... ick. 2384 */ 2385 if (th->th_urp <= (u_long)tlen && 2386 !(so->so_options & SO_OOBINLINE)) { 2387 /* hdr drop is delayed */ 2388 tcp_pulloutofband(so, th, m, drop_hdrlen); 2389 } 2390 } else { 2391 /* 2392 * If no out of band data is expected, 2393 * pull receive urgent pointer along 2394 * with the receive window. 2395 */ 2396 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2397 tp->rcv_up = tp->rcv_nxt; 2398 } 2399 2400 dodata: /* XXX */ 2401 /* 2402 * Process the segment text, merging it into the TCP sequencing queue, 2403 * and arranging for acknowledgment of receipt if necessary. 2404 * This process logically involves adjusting tp->rcv_wnd as data 2405 * is presented to the user (this happens in tcp_usrreq.c, 2406 * case PRU_RCVD). If a FIN has already been received on this 2407 * connection then we just ignore the text. 2408 */ 2409 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2410 m_adj(m, drop_hdrlen); /* delayed header drop */ 2411 /* 2412 * Insert segment which includes th into TCP reassembly queue 2413 * with control block tp. Set thflags to whether reassembly now 2414 * includes a segment with FIN. This handles the common case 2415 * inline (segment is the next to be received on an established 2416 * connection, and the queue is empty), avoiding linkage into 2417 * and removal from the queue and repetition of various 2418 * conversions. 2419 * Set DELACK for segments received in order, but ack 2420 * immediately when segments are out of order (so 2421 * fast retransmit can work). 2422 */ 2423 if (th->th_seq == tp->rcv_nxt && 2424 LIST_EMPTY(&tp->t_segq) && 2425 TCPS_HAVEESTABLISHED(tp->t_state)) { 2426 if (DELAY_ACK(tp)) { 2427 tcp_callout_reset(tp, tp->tt_delack, 2428 tcp_delacktime, tcp_timer_delack); 2429 } else { 2430 tp->t_flags |= TF_ACKNOW; 2431 } 2432 tp->rcv_nxt += tlen; 2433 thflags = th->th_flags & TH_FIN; 2434 tcpstat.tcps_rcvpack++; 2435 tcpstat.tcps_rcvbyte += tlen; 2436 ND6_HINT(tp); 2437 if (so->so_state & SS_CANTRCVMORE) 2438 m_freem(m); 2439 else 2440 ssb_appendstream(&so->so_rcv, m); 2441 sorwakeup(so); 2442 } else { 2443 if (!(tp->t_flags & TF_DUPSEG)) { 2444 /* Initialize SACK report block. */ 2445 tp->reportblk.rblk_start = th->th_seq; 2446 tp->reportblk.rblk_end = th->th_seq + tlen + 2447 ((thflags & TH_FIN) != 0); 2448 } 2449 thflags = tcp_reass(tp, th, &tlen, m); 2450 tp->t_flags |= TF_ACKNOW; 2451 } 2452 2453 /* 2454 * Note the amount of data that peer has sent into 2455 * our window, in order to estimate the sender's 2456 * buffer size. 2457 */ 2458 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2459 } else { 2460 m_freem(m); 2461 thflags &= ~TH_FIN; 2462 } 2463 2464 /* 2465 * If FIN is received ACK the FIN and let the user know 2466 * that the connection is closing. 2467 */ 2468 if (thflags & TH_FIN) { 2469 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2470 socantrcvmore(so); 2471 /* 2472 * If connection is half-synchronized 2473 * (ie NEEDSYN flag on) then delay ACK, 2474 * so it may be piggybacked when SYN is sent. 2475 * Otherwise, since we received a FIN then no 2476 * more input can be expected, send ACK now. 2477 */ 2478 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2479 tcp_callout_reset(tp, tp->tt_delack, 2480 tcp_delacktime, tcp_timer_delack); 2481 } else { 2482 tp->t_flags |= TF_ACKNOW; 2483 } 2484 tp->rcv_nxt++; 2485 } 2486 2487 switch (tp->t_state) { 2488 /* 2489 * In SYN_RECEIVED and ESTABLISHED STATES 2490 * enter the CLOSE_WAIT state. 2491 */ 2492 case TCPS_SYN_RECEIVED: 2493 tp->t_starttime = ticks; 2494 /*FALLTHROUGH*/ 2495 case TCPS_ESTABLISHED: 2496 tp->t_state = TCPS_CLOSE_WAIT; 2497 break; 2498 2499 /* 2500 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2501 * enter the CLOSING state. 2502 */ 2503 case TCPS_FIN_WAIT_1: 2504 tp->t_state = TCPS_CLOSING; 2505 break; 2506 2507 /* 2508 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2509 * starting the time-wait timer, turning off the other 2510 * standard timers. 2511 */ 2512 case TCPS_FIN_WAIT_2: 2513 tp->t_state = TCPS_TIME_WAIT; 2514 tcp_canceltimers(tp); 2515 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2516 tcp_timer_2msl); 2517 soisdisconnected(so); 2518 break; 2519 2520 /* 2521 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2522 */ 2523 case TCPS_TIME_WAIT: 2524 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2525 tcp_timer_2msl); 2526 break; 2527 } 2528 } 2529 2530 #ifdef TCPDEBUG 2531 if (so->so_options & SO_DEBUG) 2532 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2533 #endif 2534 2535 /* 2536 * Return any desired output. 2537 */ 2538 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2539 tcp_output(tp); 2540 return; 2541 2542 dropafterack: 2543 /* 2544 * Generate an ACK dropping incoming segment if it occupies 2545 * sequence space, where the ACK reflects our state. 2546 * 2547 * We can now skip the test for the RST flag since all 2548 * paths to this code happen after packets containing 2549 * RST have been dropped. 2550 * 2551 * In the SYN-RECEIVED state, don't send an ACK unless the 2552 * segment we received passes the SYN-RECEIVED ACK test. 2553 * If it fails send a RST. This breaks the loop in the 2554 * "LAND" DoS attack, and also prevents an ACK storm 2555 * between two listening ports that have been sent forged 2556 * SYN segments, each with the source address of the other. 2557 */ 2558 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2559 (SEQ_GT(tp->snd_una, th->th_ack) || 2560 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2561 rstreason = BANDLIM_RST_OPENPORT; 2562 goto dropwithreset; 2563 } 2564 #ifdef TCPDEBUG 2565 if (so->so_options & SO_DEBUG) 2566 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2567 #endif 2568 m_freem(m); 2569 tp->t_flags |= TF_ACKNOW; 2570 tcp_output(tp); 2571 return; 2572 2573 dropwithreset: 2574 /* 2575 * Generate a RST, dropping incoming segment. 2576 * Make ACK acceptable to originator of segment. 2577 * Don't bother to respond if destination was broadcast/multicast. 2578 */ 2579 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2580 goto drop; 2581 if (isipv6) { 2582 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2583 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2584 goto drop; 2585 } else { 2586 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2587 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2588 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2589 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2590 goto drop; 2591 } 2592 /* IPv6 anycast check is done at tcp6_input() */ 2593 2594 /* 2595 * Perform bandwidth limiting. 2596 */ 2597 #ifdef ICMP_BANDLIM 2598 if (badport_bandlim(rstreason) < 0) 2599 goto drop; 2600 #endif 2601 2602 #ifdef TCPDEBUG 2603 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2604 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2605 #endif 2606 if (thflags & TH_ACK) 2607 /* mtod() below is safe as long as hdr dropping is delayed */ 2608 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2609 TH_RST); 2610 else { 2611 if (thflags & TH_SYN) 2612 tlen++; 2613 /* mtod() below is safe as long as hdr dropping is delayed */ 2614 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2615 (tcp_seq)0, TH_RST | TH_ACK); 2616 } 2617 return; 2618 2619 drop: 2620 /* 2621 * Drop space held by incoming segment and return. 2622 */ 2623 #ifdef TCPDEBUG 2624 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2625 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2626 #endif 2627 m_freem(m); 2628 return; 2629 } 2630 2631 /* 2632 * Parse TCP options and place in tcpopt. 2633 */ 2634 static void 2635 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2636 { 2637 int opt, optlen, i; 2638 2639 to->to_flags = 0; 2640 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2641 opt = cp[0]; 2642 if (opt == TCPOPT_EOL) 2643 break; 2644 if (opt == TCPOPT_NOP) 2645 optlen = 1; 2646 else { 2647 if (cnt < 2) 2648 break; 2649 optlen = cp[1]; 2650 if (optlen < 2 || optlen > cnt) 2651 break; 2652 } 2653 switch (opt) { 2654 case TCPOPT_MAXSEG: 2655 if (optlen != TCPOLEN_MAXSEG) 2656 continue; 2657 if (!is_syn) 2658 continue; 2659 to->to_flags |= TOF_MSS; 2660 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2661 to->to_mss = ntohs(to->to_mss); 2662 break; 2663 case TCPOPT_WINDOW: 2664 if (optlen != TCPOLEN_WINDOW) 2665 continue; 2666 if (!is_syn) 2667 continue; 2668 to->to_flags |= TOF_SCALE; 2669 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2670 break; 2671 case TCPOPT_TIMESTAMP: 2672 if (optlen != TCPOLEN_TIMESTAMP) 2673 continue; 2674 to->to_flags |= TOF_TS; 2675 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2676 to->to_tsval = ntohl(to->to_tsval); 2677 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2678 to->to_tsecr = ntohl(to->to_tsecr); 2679 /* 2680 * If echoed timestamp is later than the current time, 2681 * fall back to non RFC1323 RTT calculation. 2682 */ 2683 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2684 to->to_tsecr = 0; 2685 break; 2686 case TCPOPT_SACK_PERMITTED: 2687 if (optlen != TCPOLEN_SACK_PERMITTED) 2688 continue; 2689 if (!is_syn) 2690 continue; 2691 to->to_flags |= TOF_SACK_PERMITTED; 2692 break; 2693 case TCPOPT_SACK: 2694 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2695 continue; 2696 to->to_nsackblocks = (optlen - 2) / 8; 2697 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2698 to->to_flags |= TOF_SACK; 2699 for (i = 0; i < to->to_nsackblocks; i++) { 2700 struct raw_sackblock *r = &to->to_sackblocks[i]; 2701 2702 r->rblk_start = ntohl(r->rblk_start); 2703 r->rblk_end = ntohl(r->rblk_end); 2704 } 2705 break; 2706 #ifdef TCP_SIGNATURE 2707 /* 2708 * XXX In order to reply to a host which has set the 2709 * TCP_SIGNATURE option in its initial SYN, we have to 2710 * record the fact that the option was observed here 2711 * for the syncache code to perform the correct response. 2712 */ 2713 case TCPOPT_SIGNATURE: 2714 if (optlen != TCPOLEN_SIGNATURE) 2715 continue; 2716 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2717 break; 2718 #endif /* TCP_SIGNATURE */ 2719 default: 2720 continue; 2721 } 2722 } 2723 } 2724 2725 /* 2726 * Pull out of band byte out of a segment so 2727 * it doesn't appear in the user's data queue. 2728 * It is still reflected in the segment length for 2729 * sequencing purposes. 2730 * "off" is the delayed to be dropped hdrlen. 2731 */ 2732 static void 2733 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2734 { 2735 int cnt = off + th->th_urp - 1; 2736 2737 while (cnt >= 0) { 2738 if (m->m_len > cnt) { 2739 char *cp = mtod(m, caddr_t) + cnt; 2740 struct tcpcb *tp = sototcpcb(so); 2741 2742 tp->t_iobc = *cp; 2743 tp->t_oobflags |= TCPOOB_HAVEDATA; 2744 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2745 m->m_len--; 2746 if (m->m_flags & M_PKTHDR) 2747 m->m_pkthdr.len--; 2748 return; 2749 } 2750 cnt -= m->m_len; 2751 m = m->m_next; 2752 if (m == 0) 2753 break; 2754 } 2755 panic("tcp_pulloutofband"); 2756 } 2757 2758 /* 2759 * Collect new round-trip time estimate 2760 * and update averages and current timeout. 2761 */ 2762 static void 2763 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2764 { 2765 int delta; 2766 2767 tcpstat.tcps_rttupdated++; 2768 tp->t_rttupdated++; 2769 if (tp->t_srtt != 0) { 2770 /* 2771 * srtt is stored as fixed point with 5 bits after the 2772 * binary point (i.e., scaled by 8). The following magic 2773 * is equivalent to the smoothing algorithm in rfc793 with 2774 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2775 * point). Adjust rtt to origin 0. 2776 */ 2777 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2778 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2779 2780 if ((tp->t_srtt += delta) <= 0) 2781 tp->t_srtt = 1; 2782 2783 /* 2784 * We accumulate a smoothed rtt variance (actually, a 2785 * smoothed mean difference), then set the retransmit 2786 * timer to smoothed rtt + 4 times the smoothed variance. 2787 * rttvar is stored as fixed point with 4 bits after the 2788 * binary point (scaled by 16). The following is 2789 * equivalent to rfc793 smoothing with an alpha of .75 2790 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2791 * rfc793's wired-in beta. 2792 */ 2793 if (delta < 0) 2794 delta = -delta; 2795 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2796 if ((tp->t_rttvar += delta) <= 0) 2797 tp->t_rttvar = 1; 2798 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2799 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2800 } else { 2801 /* 2802 * No rtt measurement yet - use the unsmoothed rtt. 2803 * Set the variance to half the rtt (so our first 2804 * retransmit happens at 3*rtt). 2805 */ 2806 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2807 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2808 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2809 } 2810 tp->t_rtttime = 0; 2811 tp->t_rxtshift = 0; 2812 2813 /* 2814 * the retransmit should happen at rtt + 4 * rttvar. 2815 * Because of the way we do the smoothing, srtt and rttvar 2816 * will each average +1/2 tick of bias. When we compute 2817 * the retransmit timer, we want 1/2 tick of rounding and 2818 * 1 extra tick because of +-1/2 tick uncertainty in the 2819 * firing of the timer. The bias will give us exactly the 2820 * 1.5 tick we need. But, because the bias is 2821 * statistical, we have to test that we don't drop below 2822 * the minimum feasible timer (which is 2 ticks). 2823 */ 2824 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2825 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2826 2827 /* 2828 * We received an ack for a packet that wasn't retransmitted; 2829 * it is probably safe to discard any error indications we've 2830 * received recently. This isn't quite right, but close enough 2831 * for now (a route might have failed after we sent a segment, 2832 * and the return path might not be symmetrical). 2833 */ 2834 tp->t_softerror = 0; 2835 } 2836 2837 /* 2838 * Determine a reasonable value for maxseg size. 2839 * If the route is known, check route for mtu. 2840 * If none, use an mss that can be handled on the outgoing 2841 * interface without forcing IP to fragment; if bigger than 2842 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2843 * to utilize large mbufs. If no route is found, route has no mtu, 2844 * or the destination isn't local, use a default, hopefully conservative 2845 * size (usually 512 or the default IP max size, but no more than the mtu 2846 * of the interface), as we can't discover anything about intervening 2847 * gateways or networks. We also initialize the congestion/slow start 2848 * window to be a single segment if the destination isn't local. 2849 * While looking at the routing entry, we also initialize other path-dependent 2850 * parameters from pre-set or cached values in the routing entry. 2851 * 2852 * Also take into account the space needed for options that we 2853 * send regularly. Make maxseg shorter by that amount to assure 2854 * that we can send maxseg amount of data even when the options 2855 * are present. Store the upper limit of the length of options plus 2856 * data in maxopd. 2857 * 2858 * NOTE that this routine is only called when we process an incoming 2859 * segment, for outgoing segments only tcp_mssopt is called. 2860 */ 2861 void 2862 tcp_mss(struct tcpcb *tp, int offer) 2863 { 2864 struct rtentry *rt; 2865 struct ifnet *ifp; 2866 int rtt, mss; 2867 u_long bufsize; 2868 struct inpcb *inp = tp->t_inpcb; 2869 struct socket *so; 2870 #ifdef INET6 2871 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2872 size_t min_protoh = isipv6 ? 2873 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2874 sizeof(struct tcpiphdr); 2875 #else 2876 const boolean_t isipv6 = FALSE; 2877 const size_t min_protoh = sizeof(struct tcpiphdr); 2878 #endif 2879 2880 if (isipv6) 2881 rt = tcp_rtlookup6(&inp->inp_inc); 2882 else 2883 rt = tcp_rtlookup(&inp->inp_inc); 2884 if (rt == NULL) { 2885 tp->t_maxopd = tp->t_maxseg = 2886 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2887 return; 2888 } 2889 ifp = rt->rt_ifp; 2890 so = inp->inp_socket; 2891 2892 /* 2893 * Offer == 0 means that there was no MSS on the SYN segment, 2894 * in this case we use either the interface mtu or tcp_mssdflt. 2895 * 2896 * An offer which is too large will be cut down later. 2897 */ 2898 if (offer == 0) { 2899 if (isipv6) { 2900 if (in6_localaddr(&inp->in6p_faddr)) { 2901 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 2902 min_protoh; 2903 } else { 2904 offer = tcp_v6mssdflt; 2905 } 2906 } else { 2907 if (in_localaddr(inp->inp_faddr)) 2908 offer = ifp->if_mtu - min_protoh; 2909 else 2910 offer = tcp_mssdflt; 2911 } 2912 } 2913 2914 /* 2915 * Prevent DoS attack with too small MSS. Round up 2916 * to at least minmss. 2917 * 2918 * Sanity check: make sure that maxopd will be large 2919 * enough to allow some data on segments even is the 2920 * all the option space is used (40bytes). Otherwise 2921 * funny things may happen in tcp_output. 2922 */ 2923 offer = max(offer, tcp_minmss); 2924 offer = max(offer, 64); 2925 2926 rt->rt_rmx.rmx_mssopt = offer; 2927 2928 /* 2929 * While we're here, check if there's an initial rtt 2930 * or rttvar. Convert from the route-table units 2931 * to scaled multiples of the slow timeout timer. 2932 */ 2933 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2934 /* 2935 * XXX the lock bit for RTT indicates that the value 2936 * is also a minimum value; this is subject to time. 2937 */ 2938 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2939 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2940 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2941 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2942 tcpstat.tcps_usedrtt++; 2943 if (rt->rt_rmx.rmx_rttvar) { 2944 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2945 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2946 tcpstat.tcps_usedrttvar++; 2947 } else { 2948 /* default variation is +- 1 rtt */ 2949 tp->t_rttvar = 2950 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2951 } 2952 TCPT_RANGESET(tp->t_rxtcur, 2953 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2954 tp->t_rttmin, TCPTV_REXMTMAX); 2955 } 2956 2957 /* 2958 * if there's an mtu associated with the route, use it 2959 * else, use the link mtu. Take the smaller of mss or offer 2960 * as our final mss. 2961 */ 2962 if (rt->rt_rmx.rmx_mtu) { 2963 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2964 } else { 2965 if (isipv6) 2966 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2967 else 2968 mss = ifp->if_mtu - min_protoh; 2969 } 2970 mss = min(mss, offer); 2971 2972 /* 2973 * maxopd stores the maximum length of data AND options 2974 * in a segment; maxseg is the amount of data in a normal 2975 * segment. We need to store this value (maxopd) apart 2976 * from maxseg, because now every segment carries options 2977 * and thus we normally have somewhat less data in segments. 2978 */ 2979 tp->t_maxopd = mss; 2980 2981 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 2982 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2983 mss -= TCPOLEN_TSTAMP_APPA; 2984 2985 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2986 if (mss > MCLBYTES) 2987 mss &= ~(MCLBYTES-1); 2988 #else 2989 if (mss > MCLBYTES) 2990 mss = mss / MCLBYTES * MCLBYTES; 2991 #endif 2992 /* 2993 * If there's a pipesize, change the socket buffer 2994 * to that size. Make the socket buffers an integral 2995 * number of mss units; if the mss is larger than 2996 * the socket buffer, decrease the mss. 2997 */ 2998 #ifdef RTV_SPIPE 2999 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3000 #endif 3001 bufsize = so->so_snd.ssb_hiwat; 3002 if (bufsize < mss) 3003 mss = bufsize; 3004 else { 3005 bufsize = roundup(bufsize, mss); 3006 if (bufsize > sb_max) 3007 bufsize = sb_max; 3008 if (bufsize > so->so_snd.ssb_hiwat) 3009 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3010 } 3011 tp->t_maxseg = mss; 3012 3013 #ifdef RTV_RPIPE 3014 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3015 #endif 3016 bufsize = so->so_rcv.ssb_hiwat; 3017 if (bufsize > mss) { 3018 bufsize = roundup(bufsize, mss); 3019 if (bufsize > sb_max) 3020 bufsize = sb_max; 3021 if (bufsize > so->so_rcv.ssb_hiwat) 3022 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3023 } 3024 3025 /* 3026 * Set the slow-start flight size depending on whether this 3027 * is a local network or not. 3028 */ 3029 if (tcp_do_rfc3390) 3030 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3031 else 3032 tp->snd_cwnd = mss; 3033 3034 if (rt->rt_rmx.rmx_ssthresh) { 3035 /* 3036 * There's some sort of gateway or interface 3037 * buffer limit on the path. Use this to set 3038 * the slow start threshhold, but set the 3039 * threshold to no less than 2*mss. 3040 */ 3041 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3042 tcpstat.tcps_usedssthresh++; 3043 } 3044 } 3045 3046 /* 3047 * Determine the MSS option to send on an outgoing SYN. 3048 */ 3049 int 3050 tcp_mssopt(struct tcpcb *tp) 3051 { 3052 struct rtentry *rt; 3053 #ifdef INET6 3054 boolean_t isipv6 = 3055 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3056 int min_protoh = isipv6 ? 3057 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3058 sizeof(struct tcpiphdr); 3059 #else 3060 const boolean_t isipv6 = FALSE; 3061 const size_t min_protoh = sizeof(struct tcpiphdr); 3062 #endif 3063 3064 if (isipv6) 3065 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3066 else 3067 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3068 if (rt == NULL) 3069 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3070 3071 return (rt->rt_ifp->if_mtu - min_protoh); 3072 } 3073 3074 /* 3075 * When a partial ack arrives, force the retransmission of the 3076 * next unacknowledged segment. Do not exit Fast Recovery. 3077 * 3078 * Implement the Slow-but-Steady variant of NewReno by restarting the 3079 * the retransmission timer. Turn it off here so it can be restarted 3080 * later in tcp_output(). 3081 */ 3082 static void 3083 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3084 { 3085 tcp_seq old_snd_nxt = tp->snd_nxt; 3086 u_long ocwnd = tp->snd_cwnd; 3087 3088 tcp_callout_stop(tp, tp->tt_rexmt); 3089 tp->t_rtttime = 0; 3090 tp->snd_nxt = th->th_ack; 3091 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3092 tp->snd_cwnd = tp->t_maxseg; 3093 tp->t_flags |= TF_ACKNOW; 3094 tcp_output(tp); 3095 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3096 tp->snd_nxt = old_snd_nxt; 3097 /* partial window deflation */ 3098 if (ocwnd > acked) 3099 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3100 else 3101 tp->snd_cwnd = tp->t_maxseg; 3102 } 3103 3104 /* 3105 * In contrast to the Slow-but-Steady NewReno variant, 3106 * we do not reset the retransmission timer for SACK retransmissions, 3107 * except when retransmitting snd_una. 3108 */ 3109 static void 3110 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3111 { 3112 uint32_t pipe, seglen; 3113 tcp_seq nextrexmt; 3114 boolean_t lostdup; 3115 tcp_seq old_snd_nxt = tp->snd_nxt; 3116 u_long ocwnd = tp->snd_cwnd; 3117 int nseg = 0; /* consecutive new segments */ 3118 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3119 3120 tp->t_rtttime = 0; 3121 pipe = tcp_sack_compute_pipe(tp); 3122 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3123 (!tcp_do_smartsack || nseg < MAXBURST) && 3124 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3125 uint32_t sent; 3126 tcp_seq old_snd_max; 3127 int error; 3128 3129 if (nextrexmt == tp->snd_max) 3130 ++nseg; 3131 tp->snd_nxt = nextrexmt; 3132 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3133 old_snd_max = tp->snd_max; 3134 if (nextrexmt == tp->snd_una) 3135 tcp_callout_stop(tp, tp->tt_rexmt); 3136 error = tcp_output(tp); 3137 if (error != 0) 3138 break; 3139 sent = tp->snd_nxt - nextrexmt; 3140 if (sent <= 0) 3141 break; 3142 if (!lostdup) 3143 pipe += sent; 3144 tcpstat.tcps_sndsackpack++; 3145 tcpstat.tcps_sndsackbyte += sent; 3146 if (SEQ_LT(nextrexmt, old_snd_max) && 3147 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3148 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3149 } 3150 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3151 tp->snd_nxt = old_snd_nxt; 3152 tp->snd_cwnd = ocwnd; 3153 } 3154