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 */ 69 70 #include "opt_inet.h" 71 #include "opt_inet6.h" 72 #include "opt_ipsec.h" 73 #include "opt_tcpdebug.h" 74 #include "opt_tcp_input.h" 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/sysctl.h> 80 #include <sys/malloc.h> 81 #include <sys/mbuf.h> 82 #include <sys/proc.h> /* for proc0 declaration */ 83 #include <sys/protosw.h> 84 #include <sys/socket.h> 85 #include <sys/socketvar.h> 86 #include <sys/syslog.h> 87 #include <sys/in_cksum.h> 88 89 #include <sys/socketvar2.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 int tcp_sosnd_agglim = 2; 229 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_agglim, CTLFLAG_RW, 230 &tcp_sosnd_agglim, 0, "TCP sosend mbuf aggregation limit"); 231 232 int tcp_sosnd_async = 1; 233 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_async, CTLFLAG_RW, 234 &tcp_sosnd_async, 0, "TCP asynchronized pru_send"); 235 236 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 237 static void tcp_pulloutofband(struct socket *, 238 struct tcphdr *, struct mbuf *, int); 239 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 240 struct mbuf *); 241 static void tcp_xmit_timer(struct tcpcb *, int); 242 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 243 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 244 static int tcp_rmx_msl(const struct tcpcb *); 245 static void tcp_established(struct tcpcb *); 246 247 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 248 #ifdef INET6 249 #define ND6_HINT(tp) \ 250 do { \ 251 if ((tp) && (tp)->t_inpcb && \ 252 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 253 (tp)->t_inpcb->in6p_route.ro_rt) \ 254 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 255 } while (0) 256 #else 257 #define ND6_HINT(tp) 258 #endif 259 260 /* 261 * Indicate whether this ack should be delayed. We can delay the ack if 262 * - delayed acks are enabled and 263 * - there is no delayed ack timer in progress and 264 * - our last ack wasn't a 0-sized window. We never want to delay 265 * the ack that opens up a 0-sized window. 266 */ 267 #define DELAY_ACK(tp) \ 268 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 269 !(tp->t_flags & TF_RXWIN0SENT)) 270 271 #define acceptable_window_update(tp, th, tiwin) \ 272 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 273 (tp->snd_wl1 == th->th_seq && \ 274 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 275 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 276 277 static int 278 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 279 { 280 struct tseg_qent *q; 281 struct tseg_qent *p = NULL; 282 struct tseg_qent *te; 283 struct socket *so = tp->t_inpcb->inp_socket; 284 int flags; 285 286 /* 287 * Call with th == NULL after become established to 288 * force pre-ESTABLISHED data up to user socket. 289 */ 290 if (th == NULL) 291 goto present; 292 293 /* 294 * Limit the number of segments in the reassembly queue to prevent 295 * holding on to too many segments (and thus running out of mbufs). 296 * Make sure to let the missing segment through which caused this 297 * queue. Always keep one global queue entry spare to be able to 298 * process the missing segment. 299 */ 300 if (th->th_seq != tp->rcv_nxt && 301 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 302 tcp_reass_overflows++; 303 tcpstat.tcps_rcvmemdrop++; 304 m_freem(m); 305 /* no SACK block to report */ 306 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 307 return (0); 308 } 309 310 /* Allocate a new queue entry. */ 311 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 312 if (te == NULL) { 313 tcpstat.tcps_rcvmemdrop++; 314 m_freem(m); 315 /* no SACK block to report */ 316 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 317 return (0); 318 } 319 atomic_add_int(&tcp_reass_qsize, 1); 320 321 /* 322 * Find a segment which begins after this one does. 323 */ 324 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 325 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 326 break; 327 p = q; 328 } 329 330 /* 331 * If there is a preceding segment, it may provide some of 332 * our data already. If so, drop the data from the incoming 333 * segment. If it provides all of our data, drop us. 334 */ 335 if (p != NULL) { 336 tcp_seq_diff_t i; 337 338 /* conversion to int (in i) handles seq wraparound */ 339 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 340 if (i > 0) { /* overlaps preceding segment */ 341 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 342 /* enclosing block starts w/ preceding segment */ 343 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 344 if (i >= *tlenp) { 345 /* preceding encloses incoming segment */ 346 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 347 p->tqe_len; 348 tcpstat.tcps_rcvduppack++; 349 tcpstat.tcps_rcvdupbyte += *tlenp; 350 m_freem(m); 351 kfree(te, M_TSEGQ); 352 atomic_add_int(&tcp_reass_qsize, -1); 353 /* 354 * Try to present any queued data 355 * at the left window edge to the user. 356 * This is needed after the 3-WHS 357 * completes. 358 */ 359 goto present; /* ??? */ 360 } 361 m_adj(m, i); 362 *tlenp -= i; 363 th->th_seq += i; 364 /* incoming segment end is enclosing block end */ 365 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 366 ((th->th_flags & TH_FIN) != 0); 367 /* trim end of reported D-SACK block */ 368 tp->reportblk.rblk_end = th->th_seq; 369 } 370 } 371 tcpstat.tcps_rcvoopack++; 372 tcpstat.tcps_rcvoobyte += *tlenp; 373 374 /* 375 * While we overlap succeeding segments trim them or, 376 * if they are completely covered, dequeue them. 377 */ 378 while (q) { 379 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 380 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 381 struct tseg_qent *nq; 382 383 if (i <= 0) 384 break; 385 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 386 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 387 tp->encloseblk = tp->reportblk; 388 /* report trailing duplicate D-SACK segment */ 389 tp->reportblk.rblk_start = q->tqe_th->th_seq; 390 } 391 if ((tp->t_flags & TF_ENCLOSESEG) && 392 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 393 /* extend enclosing block if one exists */ 394 tp->encloseblk.rblk_end = qend; 395 } 396 if (i < q->tqe_len) { 397 q->tqe_th->th_seq += i; 398 q->tqe_len -= i; 399 m_adj(q->tqe_m, i); 400 break; 401 } 402 403 nq = LIST_NEXT(q, tqe_q); 404 LIST_REMOVE(q, tqe_q); 405 m_freem(q->tqe_m); 406 kfree(q, M_TSEGQ); 407 atomic_add_int(&tcp_reass_qsize, -1); 408 q = nq; 409 } 410 411 /* Insert the new segment queue entry into place. */ 412 te->tqe_m = m; 413 te->tqe_th = th; 414 te->tqe_len = *tlenp; 415 416 /* check if can coalesce with following segment */ 417 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 418 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 419 420 te->tqe_len += q->tqe_len; 421 if (q->tqe_th->th_flags & TH_FIN) 422 te->tqe_th->th_flags |= TH_FIN; 423 m_cat(te->tqe_m, q->tqe_m); 424 tp->encloseblk.rblk_end = tend; 425 /* 426 * When not reporting a duplicate segment, use 427 * the larger enclosing block as the SACK block. 428 */ 429 if (!(tp->t_flags & TF_DUPSEG)) 430 tp->reportblk.rblk_end = tend; 431 LIST_REMOVE(q, tqe_q); 432 kfree(q, M_TSEGQ); 433 atomic_add_int(&tcp_reass_qsize, -1); 434 } 435 436 if (p == NULL) { 437 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 438 } else { 439 /* check if can coalesce with preceding segment */ 440 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 441 p->tqe_len += te->tqe_len; 442 m_cat(p->tqe_m, te->tqe_m); 443 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 444 /* 445 * When not reporting a duplicate segment, use 446 * the larger enclosing block as the SACK block. 447 */ 448 if (!(tp->t_flags & TF_DUPSEG)) 449 tp->reportblk.rblk_start = p->tqe_th->th_seq; 450 kfree(te, M_TSEGQ); 451 atomic_add_int(&tcp_reass_qsize, -1); 452 } else { 453 LIST_INSERT_AFTER(p, te, tqe_q); 454 } 455 } 456 457 present: 458 /* 459 * Present data to user, advancing rcv_nxt through 460 * completed sequence space. 461 */ 462 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 463 return (0); 464 q = LIST_FIRST(&tp->t_segq); 465 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 466 return (0); 467 tp->rcv_nxt += q->tqe_len; 468 if (!(tp->t_flags & TF_DUPSEG)) { 469 /* no SACK block to report since ACK advanced */ 470 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 471 } 472 /* no enclosing block to report since ACK advanced */ 473 tp->t_flags &= ~TF_ENCLOSESEG; 474 flags = q->tqe_th->th_flags & TH_FIN; 475 LIST_REMOVE(q, tqe_q); 476 KASSERT(LIST_EMPTY(&tp->t_segq) || 477 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 478 ("segment not coalesced")); 479 if (so->so_state & SS_CANTRCVMORE) { 480 m_freem(q->tqe_m); 481 } else { 482 lwkt_gettoken(&so->so_rcv.ssb_token); 483 ssb_appendstream(&so->so_rcv, q->tqe_m); 484 lwkt_reltoken(&so->so_rcv.ssb_token); 485 } 486 kfree(q, M_TSEGQ); 487 atomic_add_int(&tcp_reass_qsize, -1); 488 ND6_HINT(tp); 489 sorwakeup(so); 490 return (flags); 491 } 492 493 /* 494 * TCP input routine, follows pages 65-76 of the 495 * protocol specification dated September, 1981 very closely. 496 */ 497 #ifdef INET6 498 int 499 tcp6_input(struct mbuf **mp, int *offp, int proto) 500 { 501 struct mbuf *m = *mp; 502 struct in6_ifaddr *ia6; 503 504 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 505 506 /* 507 * draft-itojun-ipv6-tcp-to-anycast 508 * better place to put this in? 509 */ 510 ia6 = ip6_getdstifaddr(m); 511 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 512 struct ip6_hdr *ip6; 513 514 ip6 = mtod(m, struct ip6_hdr *); 515 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 516 offsetof(struct ip6_hdr, ip6_dst)); 517 return (IPPROTO_DONE); 518 } 519 520 tcp_input(mp, offp, proto); 521 return (IPPROTO_DONE); 522 } 523 #endif 524 525 int 526 tcp_input(struct mbuf **mp, int *offp, int proto) 527 { 528 int off0; 529 struct tcphdr *th; 530 struct ip *ip = NULL; 531 struct ipovly *ipov; 532 struct inpcb *inp = NULL; 533 u_char *optp = NULL; 534 int optlen = 0; 535 int tlen, off; 536 int len = 0; 537 int drop_hdrlen; 538 struct tcpcb *tp = NULL; 539 int thflags; 540 struct socket *so = NULL; 541 int todrop, acked; 542 boolean_t ourfinisacked, needoutput = FALSE; 543 u_long tiwin; 544 int recvwin; 545 struct tcpopt to; /* options in this segment */ 546 struct sockaddr_in *next_hop = NULL; 547 int rstreason; /* For badport_bandlim accounting purposes */ 548 int cpu; 549 struct ip6_hdr *ip6 = NULL; 550 struct mbuf *m; 551 #ifdef INET6 552 boolean_t isipv6; 553 #else 554 const boolean_t isipv6 = FALSE; 555 #endif 556 #ifdef TCPDEBUG 557 short ostate = 0; 558 #endif 559 560 off0 = *offp; 561 m = *mp; 562 *mp = NULL; 563 564 tcpstat.tcps_rcvtotal++; 565 566 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 567 struct m_tag *mtag; 568 569 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 570 KKASSERT(mtag != NULL); 571 next_hop = m_tag_data(mtag); 572 } 573 574 #ifdef INET6 575 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 576 #endif 577 578 if (isipv6) { 579 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 580 ip6 = mtod(m, struct ip6_hdr *); 581 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 582 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 583 tcpstat.tcps_rcvbadsum++; 584 goto drop; 585 } 586 th = (struct tcphdr *)((caddr_t)ip6 + off0); 587 588 /* 589 * Be proactive about unspecified IPv6 address in source. 590 * As we use all-zero to indicate unbounded/unconnected pcb, 591 * unspecified IPv6 address can be used to confuse us. 592 * 593 * Note that packets with unspecified IPv6 destination is 594 * already dropped in ip6_input. 595 */ 596 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 597 /* XXX stat */ 598 goto drop; 599 } 600 } else { 601 /* 602 * Get IP and TCP header together in first mbuf. 603 * Note: IP leaves IP header in first mbuf. 604 */ 605 if (off0 > sizeof(struct ip)) { 606 ip_stripoptions(m); 607 off0 = sizeof(struct ip); 608 } 609 /* already checked and pulled up in ip_demux() */ 610 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 611 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 612 ip = mtod(m, struct ip *); 613 ipov = (struct ipovly *)ip; 614 th = (struct tcphdr *)((caddr_t)ip + off0); 615 tlen = ip->ip_len; 616 617 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 618 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 619 th->th_sum = m->m_pkthdr.csum_data; 620 else 621 th->th_sum = in_pseudo(ip->ip_src.s_addr, 622 ip->ip_dst.s_addr, 623 htonl(m->m_pkthdr.csum_data + 624 ip->ip_len + 625 IPPROTO_TCP)); 626 th->th_sum ^= 0xffff; 627 } else { 628 /* 629 * Checksum extended TCP header and data. 630 */ 631 len = sizeof(struct ip) + tlen; 632 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 633 ipov->ih_len = (u_short)tlen; 634 ipov->ih_len = htons(ipov->ih_len); 635 th->th_sum = in_cksum(m, len); 636 } 637 if (th->th_sum) { 638 tcpstat.tcps_rcvbadsum++; 639 goto drop; 640 } 641 #ifdef INET6 642 /* Re-initialization for later version check */ 643 ip->ip_v = IPVERSION; 644 #endif 645 } 646 647 /* 648 * Check that TCP offset makes sense, 649 * pull out TCP options and adjust length. XXX 650 */ 651 off = th->th_off << 2; 652 /* already checked and pulled up in ip_demux() */ 653 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 654 ("bad TCP data offset %d (tlen %d)", off, tlen)); 655 tlen -= off; /* tlen is used instead of ti->ti_len */ 656 if (off > sizeof(struct tcphdr)) { 657 if (isipv6) { 658 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 659 ip6 = mtod(m, struct ip6_hdr *); 660 th = (struct tcphdr *)((caddr_t)ip6 + off0); 661 } else { 662 /* already pulled up in ip_demux() */ 663 KASSERT(m->m_len >= sizeof(struct ip) + off, 664 ("TCP header and options not in one mbuf: " 665 "m_len %d, off %d", m->m_len, off)); 666 } 667 optlen = off - sizeof(struct tcphdr); 668 optp = (u_char *)(th + 1); 669 } 670 thflags = th->th_flags; 671 672 #ifdef TCP_DROP_SYNFIN 673 /* 674 * If the drop_synfin option is enabled, drop all packets with 675 * both the SYN and FIN bits set. This prevents e.g. nmap from 676 * identifying the TCP/IP stack. 677 * 678 * This is a violation of the TCP specification. 679 */ 680 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 681 goto drop; 682 #endif 683 684 /* 685 * Convert TCP protocol specific fields to host format. 686 */ 687 th->th_seq = ntohl(th->th_seq); 688 th->th_ack = ntohl(th->th_ack); 689 th->th_win = ntohs(th->th_win); 690 th->th_urp = ntohs(th->th_urp); 691 692 /* 693 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 694 * until after ip6_savecontrol() is called and before other functions 695 * which don't want those proto headers. 696 * Because ip6_savecontrol() is going to parse the mbuf to 697 * search for data to be passed up to user-land, it wants mbuf 698 * parameters to be unchanged. 699 * XXX: the call of ip6_savecontrol() has been obsoleted based on 700 * latest version of the advanced API (20020110). 701 */ 702 drop_hdrlen = off0 + off; 703 704 /* 705 * Locate pcb for segment. 706 */ 707 findpcb: 708 /* IPFIREWALL_FORWARD section */ 709 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 710 /* 711 * Transparently forwarded. Pretend to be the destination. 712 * already got one like this? 713 */ 714 cpu = mycpu->gd_cpuid; 715 inp = in_pcblookup_hash(&tcbinfo[cpu], 716 ip->ip_src, th->th_sport, 717 ip->ip_dst, th->th_dport, 718 0, m->m_pkthdr.rcvif); 719 if (!inp) { 720 /* 721 * It's new. Try to find the ambushing socket. 722 */ 723 724 /* 725 * The rest of the ipfw code stores the port in 726 * host order. XXX 727 * (The IP address is still in network order.) 728 */ 729 in_port_t dport = next_hop->sin_port ? 730 htons(next_hop->sin_port) : 731 th->th_dport; 732 733 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 734 next_hop->sin_addr.s_addr, dport); 735 inp = in_pcblookup_hash(&tcbinfo[cpu], 736 ip->ip_src, th->th_sport, 737 next_hop->sin_addr, dport, 738 1, m->m_pkthdr.rcvif); 739 } 740 } else { 741 if (isipv6) { 742 inp = in6_pcblookup_hash(&tcbinfo[0], 743 &ip6->ip6_src, th->th_sport, 744 &ip6->ip6_dst, th->th_dport, 745 1, m->m_pkthdr.rcvif); 746 } else { 747 cpu = mycpu->gd_cpuid; 748 inp = in_pcblookup_hash(&tcbinfo[cpu], 749 ip->ip_src, th->th_sport, 750 ip->ip_dst, th->th_dport, 751 1, m->m_pkthdr.rcvif); 752 } 753 } 754 755 /* 756 * If the state is CLOSED (i.e., TCB does not exist) then 757 * all data in the incoming segment is discarded. 758 * If the TCB exists but is in CLOSED state, it is embryonic, 759 * but should either do a listen or a connect soon. 760 */ 761 if (inp == NULL) { 762 if (log_in_vain) { 763 #ifdef INET6 764 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 765 #else 766 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 767 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 768 #endif 769 if (isipv6) { 770 strcpy(dbuf, "["); 771 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 772 strcat(dbuf, "]"); 773 strcpy(sbuf, "["); 774 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 775 strcat(sbuf, "]"); 776 } else { 777 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 778 strcpy(sbuf, inet_ntoa(ip->ip_src)); 779 } 780 switch (log_in_vain) { 781 case 1: 782 if (!(thflags & TH_SYN)) 783 break; 784 case 2: 785 log(LOG_INFO, 786 "Connection attempt to TCP %s:%d " 787 "from %s:%d flags:0x%02x\n", 788 dbuf, ntohs(th->th_dport), sbuf, 789 ntohs(th->th_sport), thflags); 790 break; 791 default: 792 break; 793 } 794 } 795 if (blackhole) { 796 switch (blackhole) { 797 case 1: 798 if (thflags & TH_SYN) 799 goto drop; 800 break; 801 case 2: 802 goto drop; 803 default: 804 goto drop; 805 } 806 } 807 rstreason = BANDLIM_RST_CLOSEDPORT; 808 goto dropwithreset; 809 } 810 811 #ifdef IPSEC 812 if (isipv6) { 813 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 814 ipsec6stat.in_polvio++; 815 goto drop; 816 } 817 } else { 818 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 819 ipsecstat.in_polvio++; 820 goto drop; 821 } 822 } 823 #endif 824 #ifdef FAST_IPSEC 825 if (isipv6) { 826 if (ipsec6_in_reject(m, inp)) 827 goto drop; 828 } else { 829 if (ipsec4_in_reject(m, inp)) 830 goto drop; 831 } 832 #endif 833 /* Check the minimum TTL for socket. */ 834 #ifdef INET6 835 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 836 goto drop; 837 #endif 838 839 tp = intotcpcb(inp); 840 if (tp == NULL) { 841 rstreason = BANDLIM_RST_CLOSEDPORT; 842 goto dropwithreset; 843 } 844 if (tp->t_state <= TCPS_CLOSED) 845 goto drop; 846 847 /* Unscale the window into a 32-bit value. */ 848 if (!(thflags & TH_SYN)) 849 tiwin = th->th_win << tp->snd_scale; 850 else 851 tiwin = th->th_win; 852 853 so = inp->inp_socket; 854 855 #ifdef TCPDEBUG 856 if (so->so_options & SO_DEBUG) { 857 ostate = tp->t_state; 858 if (isipv6) 859 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 860 else 861 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 862 tcp_savetcp = *th; 863 } 864 #endif 865 866 bzero(&to, sizeof to); 867 868 if (so->so_options & SO_ACCEPTCONN) { 869 struct in_conninfo inc; 870 871 #ifdef INET6 872 inc.inc_isipv6 = (isipv6 == TRUE); 873 #endif 874 if (isipv6) { 875 inc.inc6_faddr = ip6->ip6_src; 876 inc.inc6_laddr = ip6->ip6_dst; 877 inc.inc6_route.ro_rt = NULL; /* XXX */ 878 } else { 879 inc.inc_faddr = ip->ip_src; 880 inc.inc_laddr = ip->ip_dst; 881 inc.inc_route.ro_rt = NULL; /* XXX */ 882 } 883 inc.inc_fport = th->th_sport; 884 inc.inc_lport = th->th_dport; 885 886 /* 887 * If the state is LISTEN then ignore segment if it contains 888 * a RST. If the segment contains an ACK then it is bad and 889 * send a RST. If it does not contain a SYN then it is not 890 * interesting; drop it. 891 * 892 * If the state is SYN_RECEIVED (syncache) and seg contains 893 * an ACK, but not for our SYN/ACK, send a RST. If the seg 894 * contains a RST, check the sequence number to see if it 895 * is a valid reset segment. 896 */ 897 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 898 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 899 if (!syncache_expand(&inc, th, &so, m)) { 900 /* 901 * No syncache entry, or ACK was not 902 * for our SYN/ACK. Send a RST. 903 */ 904 tcpstat.tcps_badsyn++; 905 rstreason = BANDLIM_RST_OPENPORT; 906 goto dropwithreset; 907 } 908 909 /* 910 * Could not complete 3-way handshake, 911 * connection is being closed down, and 912 * syncache will free mbuf. 913 */ 914 if (so == NULL) 915 return(IPPROTO_DONE); 916 917 /* 918 * We must be in the correct protocol thread 919 * for this connection. 920 */ 921 KKASSERT(so->so_port == &curthread->td_msgport); 922 923 /* 924 * Socket is created in state SYN_RECEIVED. 925 * Continue processing segment. 926 */ 927 inp = so->so_pcb; 928 tp = intotcpcb(inp); 929 /* 930 * This is what would have happened in 931 * tcp_output() when the SYN,ACK was sent. 932 */ 933 tp->snd_up = tp->snd_una; 934 tp->snd_max = tp->snd_nxt = tp->iss + 1; 935 tp->last_ack_sent = tp->rcv_nxt; 936 /* 937 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 938 * until the _second_ ACK is received: 939 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 940 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 941 * move to ESTAB, set snd_wnd to tiwin. 942 */ 943 tp->snd_wnd = tiwin; /* unscaled */ 944 goto after_listen; 945 } 946 if (thflags & TH_RST) { 947 syncache_chkrst(&inc, th); 948 goto drop; 949 } 950 if (thflags & TH_ACK) { 951 syncache_badack(&inc); 952 tcpstat.tcps_badsyn++; 953 rstreason = BANDLIM_RST_OPENPORT; 954 goto dropwithreset; 955 } 956 goto drop; 957 } 958 959 /* 960 * Segment's flags are (SYN) or (SYN | FIN). 961 */ 962 #ifdef INET6 963 /* 964 * If deprecated address is forbidden, 965 * we do not accept SYN to deprecated interface 966 * address to prevent any new inbound connection from 967 * getting established. 968 * When we do not accept SYN, we send a TCP RST, 969 * with deprecated source address (instead of dropping 970 * it). We compromise it as it is much better for peer 971 * to send a RST, and RST will be the final packet 972 * for the exchange. 973 * 974 * If we do not forbid deprecated addresses, we accept 975 * the SYN packet. RFC2462 does not suggest dropping 976 * SYN in this case. 977 * If we decipher RFC2462 5.5.4, it says like this: 978 * 1. use of deprecated addr with existing 979 * communication is okay - "SHOULD continue to be 980 * used" 981 * 2. use of it with new communication: 982 * (2a) "SHOULD NOT be used if alternate address 983 * with sufficient scope is available" 984 * (2b) nothing mentioned otherwise. 985 * Here we fall into (2b) case as we have no choice in 986 * our source address selection - we must obey the peer. 987 * 988 * The wording in RFC2462 is confusing, and there are 989 * multiple description text for deprecated address 990 * handling - worse, they are not exactly the same. 991 * I believe 5.5.4 is the best one, so we follow 5.5.4. 992 */ 993 if (isipv6 && !ip6_use_deprecated) { 994 struct in6_ifaddr *ia6; 995 996 if ((ia6 = ip6_getdstifaddr(m)) && 997 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 998 tp = NULL; 999 rstreason = BANDLIM_RST_OPENPORT; 1000 goto dropwithreset; 1001 } 1002 } 1003 #endif 1004 /* 1005 * If it is from this socket, drop it, it must be forged. 1006 * Don't bother responding if the destination was a broadcast. 1007 */ 1008 if (th->th_dport == th->th_sport) { 1009 if (isipv6) { 1010 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1011 &ip6->ip6_src)) 1012 goto drop; 1013 } else { 1014 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1015 goto drop; 1016 } 1017 } 1018 /* 1019 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1020 * 1021 * Note that it is quite possible to receive unicast 1022 * link-layer packets with a broadcast IP address. Use 1023 * in_broadcast() to find them. 1024 */ 1025 if (m->m_flags & (M_BCAST | M_MCAST)) 1026 goto drop; 1027 if (isipv6) { 1028 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1029 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1030 goto drop; 1031 } else { 1032 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1033 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1034 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1035 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1036 goto drop; 1037 } 1038 /* 1039 * SYN appears to be valid; create compressed TCP state 1040 * for syncache, or perform t/tcp connection. 1041 */ 1042 if (so->so_qlen <= so->so_qlimit) { 1043 tcp_dooptions(&to, optp, optlen, TRUE); 1044 if (!syncache_add(&inc, &to, th, so, m)) 1045 goto drop; 1046 1047 /* 1048 * Entry added to syncache, mbuf used to 1049 * send SYN,ACK packet. 1050 */ 1051 return(IPPROTO_DONE); 1052 } 1053 goto drop; 1054 } 1055 1056 after_listen: 1057 /* 1058 * Should not happen - syncache should pick up these connections. 1059 * 1060 * Once we are past handling listen sockets we must be in the 1061 * correct protocol processing thread. 1062 */ 1063 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1064 KKASSERT(so->so_port == &curthread->td_msgport); 1065 1066 /* 1067 * This is the second part of the MSS DoS prevention code (after 1068 * minmss on the sending side) and it deals with too many too small 1069 * tcp packets in a too short timeframe (1 second). 1070 * 1071 * XXX Removed. This code was crap. It does not scale to network 1072 * speed, and default values break NFS. Gone. 1073 */ 1074 /* REMOVED */ 1075 1076 /* 1077 * Segment received on connection. 1078 * 1079 * Reset idle time and keep-alive timer. Don't waste time if less 1080 * then a second has elapsed. 1081 */ 1082 if ((int)(ticks - tp->t_rcvtime) > hz) 1083 tcp_timer_keep_activity(tp, thflags); 1084 1085 /* 1086 * Process options. 1087 * XXX this is tradtitional behavior, may need to be cleaned up. 1088 */ 1089 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1090 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1091 if (to.to_flags & TOF_SCALE) { 1092 tp->t_flags |= TF_RCVD_SCALE; 1093 tp->requested_s_scale = to.to_requested_s_scale; 1094 } 1095 if (to.to_flags & TOF_TS) { 1096 tp->t_flags |= TF_RCVD_TSTMP; 1097 tp->ts_recent = to.to_tsval; 1098 tp->ts_recent_age = ticks; 1099 } 1100 if (!(to.to_flags & TOF_MSS)) 1101 to.to_mss = 0; 1102 tcp_mss(tp, to.to_mss); 1103 /* 1104 * Only set the TF_SACK_PERMITTED per-connection flag 1105 * if we got a SACK_PERMITTED option from the other side 1106 * and the global tcp_do_sack variable is true. 1107 */ 1108 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1109 tp->t_flags |= TF_SACK_PERMITTED; 1110 } 1111 1112 /* 1113 * Header prediction: check for the two common cases 1114 * of a uni-directional data xfer. If the packet has 1115 * no control flags, is in-sequence, the window didn't 1116 * change and we're not retransmitting, it's a 1117 * candidate. If the length is zero and the ack moved 1118 * forward, we're the sender side of the xfer. Just 1119 * free the data acked & wake any higher level process 1120 * that was blocked waiting for space. If the length 1121 * is non-zero and the ack didn't move, we're the 1122 * receiver side. If we're getting packets in-order 1123 * (the reassembly queue is empty), add the data to 1124 * the socket buffer and note that we need a delayed ack. 1125 * Make sure that the hidden state-flags are also off. 1126 * Since we check for TCPS_ESTABLISHED above, it can only 1127 * be TH_NEEDSYN. 1128 */ 1129 if (tp->t_state == TCPS_ESTABLISHED && 1130 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1131 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1132 (!(to.to_flags & TOF_TS) || 1133 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1134 th->th_seq == tp->rcv_nxt && 1135 tp->snd_nxt == tp->snd_max) { 1136 1137 /* 1138 * If last ACK falls within this segment's sequence numbers, 1139 * record the timestamp. 1140 * NOTE that the test is modified according to the latest 1141 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1142 */ 1143 if ((to.to_flags & TOF_TS) && 1144 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1145 tp->ts_recent_age = ticks; 1146 tp->ts_recent = to.to_tsval; 1147 } 1148 1149 if (tlen == 0) { 1150 if (SEQ_GT(th->th_ack, tp->snd_una) && 1151 SEQ_LEQ(th->th_ack, tp->snd_max) && 1152 tp->snd_cwnd >= tp->snd_wnd && 1153 !IN_FASTRECOVERY(tp)) { 1154 /* 1155 * This is a pure ack for outstanding data. 1156 */ 1157 ++tcpstat.tcps_predack; 1158 /* 1159 * "bad retransmit" recovery 1160 * 1161 * If Eifel detection applies, then 1162 * it is deterministic, so use it 1163 * unconditionally over the old heuristic. 1164 * Otherwise, fall back to the old heuristic. 1165 */ 1166 if (tcp_do_eifel_detect && 1167 (to.to_flags & TOF_TS) && to.to_tsecr && 1168 (tp->t_flags & TF_FIRSTACCACK)) { 1169 /* Eifel detection applicable. */ 1170 if (to.to_tsecr < tp->t_rexmtTS) { 1171 tcp_revert_congestion_state(tp); 1172 ++tcpstat.tcps_eifeldetected; 1173 if (tp->t_rxtshift != 1 || 1174 ticks >= tp->t_badrxtwin) 1175 ++tcpstat.tcps_rttcantdetect; 1176 } 1177 } else if (tp->t_rxtshift == 1 && 1178 ticks < tp->t_badrxtwin) { 1179 tcp_revert_congestion_state(tp); 1180 ++tcpstat.tcps_rttdetected; 1181 } 1182 tp->t_flags &= ~(TF_FIRSTACCACK | 1183 TF_FASTREXMT | TF_EARLYREXMT); 1184 /* 1185 * Recalculate the retransmit timer / rtt. 1186 * 1187 * Some machines (certain windows boxes) 1188 * send broken timestamp replies during the 1189 * SYN+ACK phase, ignore timestamps of 0. 1190 */ 1191 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1192 tcp_xmit_timer(tp, 1193 ticks - to.to_tsecr + 1); 1194 } else if (tp->t_rtttime && 1195 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1196 tcp_xmit_timer(tp, 1197 ticks - tp->t_rtttime); 1198 } 1199 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1200 acked = th->th_ack - tp->snd_una; 1201 tcpstat.tcps_rcvackpack++; 1202 tcpstat.tcps_rcvackbyte += acked; 1203 sbdrop(&so->so_snd.sb, acked); 1204 tp->snd_recover = th->th_ack - 1; 1205 tp->snd_una = th->th_ack; 1206 tp->t_dupacks = 0; 1207 /* 1208 * Update window information. 1209 */ 1210 if (tiwin != tp->snd_wnd && 1211 acceptable_window_update(tp, th, tiwin)) { 1212 /* keep track of pure window updates */ 1213 if (tp->snd_wl2 == th->th_ack && 1214 tiwin > tp->snd_wnd) 1215 tcpstat.tcps_rcvwinupd++; 1216 tp->snd_wnd = tiwin; 1217 tp->snd_wl1 = th->th_seq; 1218 tp->snd_wl2 = th->th_ack; 1219 if (tp->snd_wnd > tp->max_sndwnd) 1220 tp->max_sndwnd = tp->snd_wnd; 1221 } 1222 m_freem(m); 1223 ND6_HINT(tp); /* some progress has been done */ 1224 /* 1225 * If all outstanding data are acked, stop 1226 * retransmit timer, otherwise restart timer 1227 * using current (possibly backed-off) value. 1228 * If process is waiting for space, 1229 * wakeup/selwakeup/signal. If data 1230 * are ready to send, let tcp_output 1231 * decide between more output or persist. 1232 */ 1233 if (tp->snd_una == tp->snd_max) { 1234 tcp_callout_stop(tp, tp->tt_rexmt); 1235 } else if (!tcp_callout_active(tp, 1236 tp->tt_persist)) { 1237 tcp_callout_reset(tp, tp->tt_rexmt, 1238 tp->t_rxtcur, tcp_timer_rexmt); 1239 } 1240 sowwakeup(so); 1241 if (so->so_snd.ssb_cc > 0) 1242 tcp_output(tp); 1243 return(IPPROTO_DONE); 1244 } 1245 } else if (tiwin == tp->snd_wnd && 1246 th->th_ack == tp->snd_una && 1247 LIST_EMPTY(&tp->t_segq) && 1248 tlen <= ssb_space(&so->so_rcv)) { 1249 u_long newsize = 0; /* automatic sockbuf scaling */ 1250 /* 1251 * This is a pure, in-sequence data packet 1252 * with nothing on the reassembly queue and 1253 * we have enough buffer space to take it. 1254 */ 1255 ++tcpstat.tcps_preddat; 1256 tp->rcv_nxt += tlen; 1257 tcpstat.tcps_rcvpack++; 1258 tcpstat.tcps_rcvbyte += tlen; 1259 ND6_HINT(tp); /* some progress has been done */ 1260 /* 1261 * Automatic sizing of receive socket buffer. Often the send 1262 * buffer size is not optimally adjusted to the actual network 1263 * conditions at hand (delay bandwidth product). Setting the 1264 * buffer size too small limits throughput on links with high 1265 * bandwidth and high delay (eg. trans-continental/oceanic links). 1266 * 1267 * On the receive side the socket buffer memory is only rarely 1268 * used to any significant extent. This allows us to be much 1269 * more aggressive in scaling the receive socket buffer. For 1270 * the case that the buffer space is actually used to a large 1271 * extent and we run out of kernel memory we can simply drop 1272 * the new segments; TCP on the sender will just retransmit it 1273 * later. Setting the buffer size too big may only consume too 1274 * much kernel memory if the application doesn't read() from 1275 * the socket or packet loss or reordering makes use of the 1276 * reassembly queue. 1277 * 1278 * The criteria to step up the receive buffer one notch are: 1279 * 1. the number of bytes received during the time it takes 1280 * one timestamp to be reflected back to us (the RTT); 1281 * 2. received bytes per RTT is within seven eighth of the 1282 * current socket buffer size; 1283 * 3. receive buffer size has not hit maximal automatic size; 1284 * 1285 * This algorithm does one step per RTT at most and only if 1286 * we receive a bulk stream w/o packet losses or reorderings. 1287 * Shrinking the buffer during idle times is not necessary as 1288 * it doesn't consume any memory when idle. 1289 * 1290 * TODO: Only step up if the application is actually serving 1291 * the buffer to better manage the socket buffer resources. 1292 */ 1293 if (tcp_do_autorcvbuf && 1294 to.to_tsecr && 1295 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1296 if (to.to_tsecr > tp->rfbuf_ts && 1297 to.to_tsecr - tp->rfbuf_ts < hz) { 1298 if (tp->rfbuf_cnt > 1299 (so->so_rcv.ssb_hiwat / 8 * 7) && 1300 so->so_rcv.ssb_hiwat < 1301 tcp_autorcvbuf_max) { 1302 newsize = 1303 ulmin(so->so_rcv.ssb_hiwat + 1304 tcp_autorcvbuf_inc, 1305 tcp_autorcvbuf_max); 1306 } 1307 /* Start over with next RTT. */ 1308 tp->rfbuf_ts = 0; 1309 tp->rfbuf_cnt = 0; 1310 } else 1311 tp->rfbuf_cnt += tlen; /* add up */ 1312 } 1313 /* 1314 * Add data to socket buffer. 1315 */ 1316 if (so->so_state & SS_CANTRCVMORE) { 1317 m_freem(m); 1318 } else { 1319 /* 1320 * Set new socket buffer size, give up when 1321 * limit is reached. 1322 * 1323 * Adjusting the size can mess up ACK 1324 * sequencing when pure window updates are 1325 * being avoided (which is the default), 1326 * so force an ack. 1327 */ 1328 lwkt_gettoken(&so->so_rcv.ssb_token); 1329 if (newsize) { 1330 tp->t_flags |= TF_RXRESIZED; 1331 if (!ssb_reserve(&so->so_rcv, newsize, 1332 so, NULL)) { 1333 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1334 } 1335 if (newsize >= 1336 (TCP_MAXWIN << tp->rcv_scale)) { 1337 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1338 } 1339 } 1340 m_adj(m, drop_hdrlen); /* delayed header drop */ 1341 ssb_appendstream(&so->so_rcv, m); 1342 lwkt_reltoken(&so->so_rcv.ssb_token); 1343 } 1344 sorwakeup(so); 1345 /* 1346 * This code is responsible for most of the ACKs 1347 * the TCP stack sends back after receiving a data 1348 * packet. Note that the DELAY_ACK check fails if 1349 * the delack timer is already running, which results 1350 * in an ack being sent every other packet (which is 1351 * what we want). 1352 * 1353 * We then further aggregate acks by not actually 1354 * sending one until the protocol thread has completed 1355 * processing the current backlog of packets. This 1356 * does not delay the ack any further, but allows us 1357 * to take advantage of the packet aggregation that 1358 * high speed NICs do (usually blocks of 8-10 packets) 1359 * to send a single ack rather then four or five acks, 1360 * greatly reducing the ack rate, the return channel 1361 * bandwidth, and the protocol overhead on both ends. 1362 * 1363 * Since this also has the effect of slowing down 1364 * the exponential slow-start ramp-up, systems with 1365 * very large bandwidth-delay products might want 1366 * to turn the feature off. 1367 */ 1368 if (DELAY_ACK(tp)) { 1369 tcp_callout_reset(tp, tp->tt_delack, 1370 tcp_delacktime, tcp_timer_delack); 1371 } else if (tcp_aggregate_acks) { 1372 tp->t_flags |= TF_ACKNOW; 1373 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1374 tp->t_flags |= TF_ONOUTPUTQ; 1375 tp->tt_cpu = mycpu->gd_cpuid; 1376 TAILQ_INSERT_TAIL( 1377 &tcpcbackq[tp->tt_cpu], 1378 tp, t_outputq); 1379 } 1380 } else { 1381 tp->t_flags |= TF_ACKNOW; 1382 tcp_output(tp); 1383 } 1384 return(IPPROTO_DONE); 1385 } 1386 } 1387 1388 /* 1389 * Calculate amount of space in receive window, 1390 * and then do TCP input processing. 1391 * Receive window is amount of space in rcv queue, 1392 * but not less than advertised window. 1393 */ 1394 recvwin = ssb_space(&so->so_rcv); 1395 if (recvwin < 0) 1396 recvwin = 0; 1397 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1398 1399 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1400 tp->rfbuf_ts = 0; 1401 tp->rfbuf_cnt = 0; 1402 1403 switch (tp->t_state) { 1404 /* 1405 * If the state is SYN_RECEIVED: 1406 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1407 */ 1408 case TCPS_SYN_RECEIVED: 1409 if ((thflags & TH_ACK) && 1410 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1411 SEQ_GT(th->th_ack, tp->snd_max))) { 1412 rstreason = BANDLIM_RST_OPENPORT; 1413 goto dropwithreset; 1414 } 1415 break; 1416 1417 /* 1418 * If the state is SYN_SENT: 1419 * if seg contains an ACK, but not for our SYN, drop the input. 1420 * if seg contains a RST, then drop the connection. 1421 * if seg does not contain SYN, then drop it. 1422 * Otherwise this is an acceptable SYN segment 1423 * initialize tp->rcv_nxt and tp->irs 1424 * if seg contains ack then advance tp->snd_una 1425 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1426 * arrange for segment to be acked (eventually) 1427 * continue processing rest of data/controls, beginning with URG 1428 */ 1429 case TCPS_SYN_SENT: 1430 if ((thflags & TH_ACK) && 1431 (SEQ_LEQ(th->th_ack, tp->iss) || 1432 SEQ_GT(th->th_ack, tp->snd_max))) { 1433 rstreason = BANDLIM_UNLIMITED; 1434 goto dropwithreset; 1435 } 1436 if (thflags & TH_RST) { 1437 if (thflags & TH_ACK) 1438 tp = tcp_drop(tp, ECONNREFUSED); 1439 goto drop; 1440 } 1441 if (!(thflags & TH_SYN)) 1442 goto drop; 1443 tp->snd_wnd = th->th_win; /* initial send window */ 1444 1445 tp->irs = th->th_seq; 1446 tcp_rcvseqinit(tp); 1447 if (thflags & TH_ACK) { 1448 /* Our SYN was acked. */ 1449 tcpstat.tcps_connects++; 1450 soisconnected(so); 1451 /* Do window scaling on this connection? */ 1452 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1453 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1454 tp->snd_scale = tp->requested_s_scale; 1455 tp->rcv_scale = tp->request_r_scale; 1456 } 1457 tp->rcv_adv += tp->rcv_wnd; 1458 tp->snd_una++; /* SYN is acked */ 1459 tcp_callout_stop(tp, tp->tt_rexmt); 1460 /* 1461 * If there's data, delay ACK; if there's also a FIN 1462 * ACKNOW will be turned on later. 1463 */ 1464 if (DELAY_ACK(tp) && tlen != 0) { 1465 tcp_callout_reset(tp, tp->tt_delack, 1466 tcp_delacktime, tcp_timer_delack); 1467 } else { 1468 tp->t_flags |= TF_ACKNOW; 1469 } 1470 /* 1471 * Received <SYN,ACK> in SYN_SENT[*] state. 1472 * Transitions: 1473 * SYN_SENT --> ESTABLISHED 1474 * SYN_SENT* --> FIN_WAIT_1 1475 */ 1476 tp->t_starttime = ticks; 1477 if (tp->t_flags & TF_NEEDFIN) { 1478 tp->t_state = TCPS_FIN_WAIT_1; 1479 tp->t_flags &= ~TF_NEEDFIN; 1480 thflags &= ~TH_SYN; 1481 } else { 1482 tcp_established(tp); 1483 } 1484 } else { 1485 /* 1486 * Received initial SYN in SYN-SENT[*] state => 1487 * simultaneous open. 1488 * Do 3-way handshake: 1489 * SYN-SENT -> SYN-RECEIVED 1490 * SYN-SENT* -> SYN-RECEIVED* 1491 */ 1492 tp->t_flags |= TF_ACKNOW; 1493 tcp_callout_stop(tp, tp->tt_rexmt); 1494 tp->t_state = TCPS_SYN_RECEIVED; 1495 } 1496 1497 /* 1498 * Advance th->th_seq to correspond to first data byte. 1499 * If data, trim to stay within window, 1500 * dropping FIN if necessary. 1501 */ 1502 th->th_seq++; 1503 if (tlen > tp->rcv_wnd) { 1504 todrop = tlen - tp->rcv_wnd; 1505 m_adj(m, -todrop); 1506 tlen = tp->rcv_wnd; 1507 thflags &= ~TH_FIN; 1508 tcpstat.tcps_rcvpackafterwin++; 1509 tcpstat.tcps_rcvbyteafterwin += todrop; 1510 } 1511 tp->snd_wl1 = th->th_seq - 1; 1512 tp->rcv_up = th->th_seq; 1513 /* 1514 * Client side of transaction: already sent SYN and data. 1515 * If the remote host used T/TCP to validate the SYN, 1516 * our data will be ACK'd; if so, enter normal data segment 1517 * processing in the middle of step 5, ack processing. 1518 * Otherwise, goto step 6. 1519 */ 1520 if (thflags & TH_ACK) 1521 goto process_ACK; 1522 1523 goto step6; 1524 1525 /* 1526 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1527 * do normal processing (we no longer bother with T/TCP). 1528 */ 1529 case TCPS_LAST_ACK: 1530 case TCPS_CLOSING: 1531 case TCPS_TIME_WAIT: 1532 break; /* continue normal processing */ 1533 } 1534 1535 /* 1536 * States other than LISTEN or SYN_SENT. 1537 * First check the RST flag and sequence number since reset segments 1538 * are exempt from the timestamp and connection count tests. This 1539 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1540 * below which allowed reset segments in half the sequence space 1541 * to fall though and be processed (which gives forged reset 1542 * segments with a random sequence number a 50 percent chance of 1543 * killing a connection). 1544 * Then check timestamp, if present. 1545 * Then check the connection count, if present. 1546 * Then check that at least some bytes of segment are within 1547 * receive window. If segment begins before rcv_nxt, 1548 * drop leading data (and SYN); if nothing left, just ack. 1549 * 1550 * 1551 * If the RST bit is set, check the sequence number to see 1552 * if this is a valid reset segment. 1553 * RFC 793 page 37: 1554 * In all states except SYN-SENT, all reset (RST) segments 1555 * are validated by checking their SEQ-fields. A reset is 1556 * valid if its sequence number is in the window. 1557 * Note: this does not take into account delayed ACKs, so 1558 * we should test against last_ack_sent instead of rcv_nxt. 1559 * The sequence number in the reset segment is normally an 1560 * echo of our outgoing acknowledgement numbers, but some hosts 1561 * send a reset with the sequence number at the rightmost edge 1562 * of our receive window, and we have to handle this case. 1563 * If we have multiple segments in flight, the intial reset 1564 * segment sequence numbers will be to the left of last_ack_sent, 1565 * but they will eventually catch up. 1566 * In any case, it never made sense to trim reset segments to 1567 * fit the receive window since RFC 1122 says: 1568 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1569 * 1570 * A TCP SHOULD allow a received RST segment to include data. 1571 * 1572 * DISCUSSION 1573 * It has been suggested that a RST segment could contain 1574 * ASCII text that encoded and explained the cause of the 1575 * RST. No standard has yet been established for such 1576 * data. 1577 * 1578 * If the reset segment passes the sequence number test examine 1579 * the state: 1580 * SYN_RECEIVED STATE: 1581 * If passive open, return to LISTEN state. 1582 * If active open, inform user that connection was refused. 1583 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1584 * Inform user that connection was reset, and close tcb. 1585 * CLOSING, LAST_ACK STATES: 1586 * Close the tcb. 1587 * TIME_WAIT STATE: 1588 * Drop the segment - see Stevens, vol. 2, p. 964 and 1589 * RFC 1337. 1590 */ 1591 if (thflags & TH_RST) { 1592 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1593 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1594 switch (tp->t_state) { 1595 1596 case TCPS_SYN_RECEIVED: 1597 so->so_error = ECONNREFUSED; 1598 goto close; 1599 1600 case TCPS_ESTABLISHED: 1601 case TCPS_FIN_WAIT_1: 1602 case TCPS_FIN_WAIT_2: 1603 case TCPS_CLOSE_WAIT: 1604 so->so_error = ECONNRESET; 1605 close: 1606 tp->t_state = TCPS_CLOSED; 1607 tcpstat.tcps_drops++; 1608 tp = tcp_close(tp); 1609 break; 1610 1611 case TCPS_CLOSING: 1612 case TCPS_LAST_ACK: 1613 tp = tcp_close(tp); 1614 break; 1615 1616 case TCPS_TIME_WAIT: 1617 break; 1618 } 1619 } 1620 goto drop; 1621 } 1622 1623 /* 1624 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1625 * and it's less than ts_recent, drop it. 1626 */ 1627 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1628 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1629 1630 /* Check to see if ts_recent is over 24 days old. */ 1631 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1632 /* 1633 * Invalidate ts_recent. If this segment updates 1634 * ts_recent, the age will be reset later and ts_recent 1635 * will get a valid value. If it does not, setting 1636 * ts_recent to zero will at least satisfy the 1637 * requirement that zero be placed in the timestamp 1638 * echo reply when ts_recent isn't valid. The 1639 * age isn't reset until we get a valid ts_recent 1640 * because we don't want out-of-order segments to be 1641 * dropped when ts_recent is old. 1642 */ 1643 tp->ts_recent = 0; 1644 } else { 1645 tcpstat.tcps_rcvduppack++; 1646 tcpstat.tcps_rcvdupbyte += tlen; 1647 tcpstat.tcps_pawsdrop++; 1648 if (tlen) 1649 goto dropafterack; 1650 goto drop; 1651 } 1652 } 1653 1654 /* 1655 * In the SYN-RECEIVED state, validate that the packet belongs to 1656 * this connection before trimming the data to fit the receive 1657 * window. Check the sequence number versus IRS since we know 1658 * the sequence numbers haven't wrapped. This is a partial fix 1659 * for the "LAND" DoS attack. 1660 */ 1661 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1662 rstreason = BANDLIM_RST_OPENPORT; 1663 goto dropwithreset; 1664 } 1665 1666 todrop = tp->rcv_nxt - th->th_seq; 1667 if (todrop > 0) { 1668 if (TCP_DO_SACK(tp)) { 1669 /* Report duplicate segment at head of packet. */ 1670 tp->reportblk.rblk_start = th->th_seq; 1671 tp->reportblk.rblk_end = th->th_seq + tlen; 1672 if (thflags & TH_FIN) 1673 ++tp->reportblk.rblk_end; 1674 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1675 tp->reportblk.rblk_end = tp->rcv_nxt; 1676 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1677 } 1678 if (thflags & TH_SYN) { 1679 thflags &= ~TH_SYN; 1680 th->th_seq++; 1681 if (th->th_urp > 1) 1682 th->th_urp--; 1683 else 1684 thflags &= ~TH_URG; 1685 todrop--; 1686 } 1687 /* 1688 * Following if statement from Stevens, vol. 2, p. 960. 1689 */ 1690 if (todrop > tlen || 1691 (todrop == tlen && !(thflags & TH_FIN))) { 1692 /* 1693 * Any valid FIN must be to the left of the window. 1694 * At this point the FIN must be a duplicate or out 1695 * of sequence; drop it. 1696 */ 1697 thflags &= ~TH_FIN; 1698 1699 /* 1700 * Send an ACK to resynchronize and drop any data. 1701 * But keep on processing for RST or ACK. 1702 */ 1703 tp->t_flags |= TF_ACKNOW; 1704 todrop = tlen; 1705 tcpstat.tcps_rcvduppack++; 1706 tcpstat.tcps_rcvdupbyte += todrop; 1707 } else { 1708 tcpstat.tcps_rcvpartduppack++; 1709 tcpstat.tcps_rcvpartdupbyte += todrop; 1710 } 1711 drop_hdrlen += todrop; /* drop from the top afterwards */ 1712 th->th_seq += todrop; 1713 tlen -= todrop; 1714 if (th->th_urp > todrop) 1715 th->th_urp -= todrop; 1716 else { 1717 thflags &= ~TH_URG; 1718 th->th_urp = 0; 1719 } 1720 } 1721 1722 /* 1723 * If new data are received on a connection after the 1724 * user processes are gone, then RST the other end. 1725 */ 1726 if ((so->so_state & SS_NOFDREF) && 1727 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1728 tp = tcp_close(tp); 1729 tcpstat.tcps_rcvafterclose++; 1730 rstreason = BANDLIM_UNLIMITED; 1731 goto dropwithreset; 1732 } 1733 1734 /* 1735 * If segment ends after window, drop trailing data 1736 * (and PUSH and FIN); if nothing left, just ACK. 1737 */ 1738 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1739 if (todrop > 0) { 1740 tcpstat.tcps_rcvpackafterwin++; 1741 if (todrop >= tlen) { 1742 tcpstat.tcps_rcvbyteafterwin += tlen; 1743 /* 1744 * If a new connection request is received 1745 * while in TIME_WAIT, drop the old connection 1746 * and start over if the sequence numbers 1747 * are above the previous ones. 1748 */ 1749 if (thflags & TH_SYN && 1750 tp->t_state == TCPS_TIME_WAIT && 1751 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1752 tp = tcp_close(tp); 1753 goto findpcb; 1754 } 1755 /* 1756 * If window is closed can only take segments at 1757 * window edge, and have to drop data and PUSH from 1758 * incoming segments. Continue processing, but 1759 * remember to ack. Otherwise, drop segment 1760 * and ack. 1761 */ 1762 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1763 tp->t_flags |= TF_ACKNOW; 1764 tcpstat.tcps_rcvwinprobe++; 1765 } else 1766 goto dropafterack; 1767 } else 1768 tcpstat.tcps_rcvbyteafterwin += todrop; 1769 m_adj(m, -todrop); 1770 tlen -= todrop; 1771 thflags &= ~(TH_PUSH | TH_FIN); 1772 } 1773 1774 /* 1775 * If last ACK falls within this segment's sequence numbers, 1776 * record its timestamp. 1777 * NOTE: 1778 * 1) That the test incorporates suggestions from the latest 1779 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1780 * 2) That updating only on newer timestamps interferes with 1781 * our earlier PAWS tests, so this check should be solely 1782 * predicated on the sequence space of this segment. 1783 * 3) That we modify the segment boundary check to be 1784 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1785 * instead of RFC1323's 1786 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1787 * This modified check allows us to overcome RFC1323's 1788 * limitations as described in Stevens TCP/IP Illustrated 1789 * Vol. 2 p.869. In such cases, we can still calculate the 1790 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1791 */ 1792 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1793 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1794 + ((thflags & TH_SYN) != 0) 1795 + ((thflags & TH_FIN) != 0)))) { 1796 tp->ts_recent_age = ticks; 1797 tp->ts_recent = to.to_tsval; 1798 } 1799 1800 /* 1801 * If a SYN is in the window, then this is an 1802 * error and we send an RST and drop the connection. 1803 */ 1804 if (thflags & TH_SYN) { 1805 tp = tcp_drop(tp, ECONNRESET); 1806 rstreason = BANDLIM_UNLIMITED; 1807 goto dropwithreset; 1808 } 1809 1810 /* 1811 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1812 * flag is on (half-synchronized state), then queue data for 1813 * later processing; else drop segment and return. 1814 */ 1815 if (!(thflags & TH_ACK)) { 1816 if (tp->t_state == TCPS_SYN_RECEIVED || 1817 (tp->t_flags & TF_NEEDSYN)) 1818 goto step6; 1819 else 1820 goto drop; 1821 } 1822 1823 /* 1824 * Ack processing. 1825 */ 1826 switch (tp->t_state) { 1827 /* 1828 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1829 * ESTABLISHED state and continue processing. 1830 * The ACK was checked above. 1831 */ 1832 case TCPS_SYN_RECEIVED: 1833 1834 tcpstat.tcps_connects++; 1835 soisconnected(so); 1836 /* Do window scaling? */ 1837 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1838 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1839 tp->snd_scale = tp->requested_s_scale; 1840 tp->rcv_scale = tp->request_r_scale; 1841 } 1842 /* 1843 * Make transitions: 1844 * SYN-RECEIVED -> ESTABLISHED 1845 * SYN-RECEIVED* -> FIN-WAIT-1 1846 */ 1847 tp->t_starttime = ticks; 1848 if (tp->t_flags & TF_NEEDFIN) { 1849 tp->t_state = TCPS_FIN_WAIT_1; 1850 tp->t_flags &= ~TF_NEEDFIN; 1851 } else { 1852 tcp_established(tp); 1853 } 1854 /* 1855 * If segment contains data or ACK, will call tcp_reass() 1856 * later; if not, do so now to pass queued data to user. 1857 */ 1858 if (tlen == 0 && !(thflags & TH_FIN)) 1859 tcp_reass(tp, NULL, NULL, NULL); 1860 /* fall into ... */ 1861 1862 /* 1863 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1864 * ACKs. If the ack is in the range 1865 * tp->snd_una < th->th_ack <= tp->snd_max 1866 * then advance tp->snd_una to th->th_ack and drop 1867 * data from the retransmission queue. If this ACK reflects 1868 * more up to date window information we update our window information. 1869 */ 1870 case TCPS_ESTABLISHED: 1871 case TCPS_FIN_WAIT_1: 1872 case TCPS_FIN_WAIT_2: 1873 case TCPS_CLOSE_WAIT: 1874 case TCPS_CLOSING: 1875 case TCPS_LAST_ACK: 1876 case TCPS_TIME_WAIT: 1877 1878 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1879 if (TCP_DO_SACK(tp)) 1880 tcp_sack_update_scoreboard(tp, &to); 1881 if (tlen != 0 || tiwin != tp->snd_wnd) { 1882 tp->t_dupacks = 0; 1883 break; 1884 } 1885 tcpstat.tcps_rcvdupack++; 1886 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1887 th->th_ack != tp->snd_una) { 1888 tp->t_dupacks = 0; 1889 break; 1890 } 1891 /* 1892 * We have outstanding data (other than 1893 * a window probe), this is a completely 1894 * duplicate ack (ie, window info didn't 1895 * change), the ack is the biggest we've 1896 * seen and we've seen exactly our rexmt 1897 * threshhold of them, so assume a packet 1898 * has been dropped and retransmit it. 1899 * Kludge snd_nxt & the congestion 1900 * window so we send only this one 1901 * packet. 1902 */ 1903 if (IN_FASTRECOVERY(tp)) { 1904 if (TCP_DO_SACK(tp)) { 1905 /* No artifical cwnd inflation. */ 1906 tcp_sack_rexmt(tp, th); 1907 } else { 1908 /* 1909 * Dup acks mean that packets 1910 * have left the network 1911 * (they're now cached at the 1912 * receiver) so bump cwnd by 1913 * the amount in the receiver 1914 * to keep a constant cwnd 1915 * packets in the network. 1916 */ 1917 tp->snd_cwnd += tp->t_maxseg; 1918 tcp_output(tp); 1919 } 1920 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1921 tp->t_dupacks = 0; 1922 break; 1923 } else if (++tp->t_dupacks == tcprexmtthresh) { 1924 tcp_seq old_snd_nxt; 1925 u_int win; 1926 1927 fastretransmit: 1928 if (tcp_do_eifel_detect && 1929 (tp->t_flags & TF_RCVD_TSTMP)) { 1930 tcp_save_congestion_state(tp); 1931 tp->t_flags |= TF_FASTREXMT; 1932 } 1933 /* 1934 * We know we're losing at the current 1935 * window size, so do congestion avoidance: 1936 * set ssthresh to half the current window 1937 * and pull our congestion window back to the 1938 * new ssthresh. 1939 */ 1940 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1941 tp->t_maxseg; 1942 if (win < 2) 1943 win = 2; 1944 tp->snd_ssthresh = win * tp->t_maxseg; 1945 ENTER_FASTRECOVERY(tp); 1946 tp->snd_recover = tp->snd_max; 1947 tcp_callout_stop(tp, tp->tt_rexmt); 1948 tp->t_rtttime = 0; 1949 old_snd_nxt = tp->snd_nxt; 1950 tp->snd_nxt = th->th_ack; 1951 tp->snd_cwnd = tp->t_maxseg; 1952 tcp_output(tp); 1953 ++tcpstat.tcps_sndfastrexmit; 1954 tp->snd_cwnd = tp->snd_ssthresh; 1955 tp->rexmt_high = tp->snd_nxt; 1956 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1957 tp->snd_nxt = old_snd_nxt; 1958 KASSERT(tp->snd_limited <= 2, 1959 ("tp->snd_limited too big")); 1960 if (TCP_DO_SACK(tp)) 1961 tcp_sack_rexmt(tp, th); 1962 else 1963 tp->snd_cwnd += tp->t_maxseg * 1964 (tp->t_dupacks - tp->snd_limited); 1965 } else if (tcp_do_limitedtransmit) { 1966 u_long oldcwnd = tp->snd_cwnd; 1967 tcp_seq oldsndmax = tp->snd_max; 1968 tcp_seq oldsndnxt = tp->snd_nxt; 1969 /* outstanding data */ 1970 uint32_t ownd = tp->snd_max - tp->snd_una; 1971 u_int sent; 1972 1973 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1974 1975 KASSERT(tp->t_dupacks == 1 || 1976 tp->t_dupacks == 2, 1977 ("dupacks not 1 or 2")); 1978 if (tp->t_dupacks == 1) 1979 tp->snd_limited = 0; 1980 tp->snd_nxt = tp->snd_max; 1981 tp->snd_cwnd = ownd + 1982 (tp->t_dupacks - tp->snd_limited) * 1983 tp->t_maxseg; 1984 tcp_output(tp); 1985 1986 /* 1987 * Other acks may have been processed, 1988 * snd_nxt cannot be reset to a value less 1989 * then snd_una. 1990 */ 1991 if (SEQ_LT(oldsndnxt, oldsndmax)) { 1992 if (SEQ_GT(oldsndnxt, tp->snd_una)) 1993 tp->snd_nxt = oldsndnxt; 1994 else 1995 tp->snd_nxt = tp->snd_una; 1996 } 1997 tp->snd_cwnd = oldcwnd; 1998 sent = tp->snd_max - oldsndmax; 1999 if (sent > tp->t_maxseg) { 2000 KASSERT((tp->t_dupacks == 2 && 2001 tp->snd_limited == 0) || 2002 (sent == tp->t_maxseg + 1 && 2003 tp->t_flags & TF_SENTFIN), 2004 ("sent too much")); 2005 KASSERT(sent <= tp->t_maxseg * 2, 2006 ("sent too many segments")); 2007 tp->snd_limited = 2; 2008 tcpstat.tcps_sndlimited += 2; 2009 } else if (sent > 0) { 2010 ++tp->snd_limited; 2011 ++tcpstat.tcps_sndlimited; 2012 } else if (tcp_do_early_retransmit && 2013 (tcp_do_eifel_detect && 2014 (tp->t_flags & TF_RCVD_TSTMP)) && 2015 ownd < 4 * tp->t_maxseg && 2016 tp->t_dupacks + 1 >= 2017 iceildiv(ownd, tp->t_maxseg) && 2018 (!TCP_DO_SACK(tp) || 2019 ownd <= tp->t_maxseg || 2020 tcp_sack_has_sacked(&tp->scb, 2021 ownd - tp->t_maxseg))) { 2022 ++tcpstat.tcps_sndearlyrexmit; 2023 tp->t_flags |= TF_EARLYREXMT; 2024 goto fastretransmit; 2025 } 2026 } 2027 goto drop; 2028 } 2029 2030 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2031 tp->t_dupacks = 0; 2032 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2033 /* 2034 * Detected optimistic ACK attack. 2035 * Force slow-start to de-synchronize attack. 2036 */ 2037 tp->snd_cwnd = tp->t_maxseg; 2038 tp->snd_wacked = 0; 2039 2040 tcpstat.tcps_rcvacktoomuch++; 2041 goto dropafterack; 2042 } 2043 /* 2044 * If we reach this point, ACK is not a duplicate, 2045 * i.e., it ACKs something we sent. 2046 */ 2047 if (tp->t_flags & TF_NEEDSYN) { 2048 /* 2049 * T/TCP: Connection was half-synchronized, and our 2050 * SYN has been ACK'd (so connection is now fully 2051 * synchronized). Go to non-starred state, 2052 * increment snd_una for ACK of SYN, and check if 2053 * we can do window scaling. 2054 */ 2055 tp->t_flags &= ~TF_NEEDSYN; 2056 tp->snd_una++; 2057 /* Do window scaling? */ 2058 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2059 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2060 tp->snd_scale = tp->requested_s_scale; 2061 tp->rcv_scale = tp->request_r_scale; 2062 } 2063 } 2064 2065 process_ACK: 2066 acked = th->th_ack - tp->snd_una; 2067 tcpstat.tcps_rcvackpack++; 2068 tcpstat.tcps_rcvackbyte += acked; 2069 2070 if (tcp_do_eifel_detect && acked > 0 && 2071 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2072 (tp->t_flags & TF_FIRSTACCACK)) { 2073 /* Eifel detection applicable. */ 2074 if (to.to_tsecr < tp->t_rexmtTS) { 2075 ++tcpstat.tcps_eifeldetected; 2076 tcp_revert_congestion_state(tp); 2077 if (tp->t_rxtshift != 1 || 2078 ticks >= tp->t_badrxtwin) 2079 ++tcpstat.tcps_rttcantdetect; 2080 } 2081 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2082 /* 2083 * If we just performed our first retransmit, 2084 * and the ACK arrives within our recovery window, 2085 * then it was a mistake to do the retransmit 2086 * in the first place. Recover our original cwnd 2087 * and ssthresh, and proceed to transmit where we 2088 * left off. 2089 */ 2090 tcp_revert_congestion_state(tp); 2091 ++tcpstat.tcps_rttdetected; 2092 } 2093 2094 /* 2095 * If we have a timestamp reply, update smoothed 2096 * round trip time. If no timestamp is present but 2097 * transmit timer is running and timed sequence 2098 * number was acked, update smoothed round trip time. 2099 * Since we now have an rtt measurement, cancel the 2100 * timer backoff (cf., Phil Karn's retransmit alg.). 2101 * Recompute the initial retransmit timer. 2102 * 2103 * Some machines (certain windows boxes) send broken 2104 * timestamp replies during the SYN+ACK phase, ignore 2105 * timestamps of 0. 2106 */ 2107 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2108 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2109 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2110 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2111 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2112 2113 /* 2114 * If no data (only SYN) was ACK'd, 2115 * skip rest of ACK processing. 2116 */ 2117 if (acked == 0) 2118 goto step6; 2119 2120 /* Stop looking for an acceptable ACK since one was received. */ 2121 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2122 2123 if (acked > so->so_snd.ssb_cc) { 2124 tp->snd_wnd -= so->so_snd.ssb_cc; 2125 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2126 ourfinisacked = TRUE; 2127 } else { 2128 sbdrop(&so->so_snd.sb, acked); 2129 tp->snd_wnd -= acked; 2130 ourfinisacked = FALSE; 2131 } 2132 sowwakeup(so); 2133 2134 /* 2135 * Update window information. 2136 * Don't look at window if no ACK: 2137 * TAC's send garbage on first SYN. 2138 */ 2139 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2140 (tp->snd_wl1 == th->th_seq && 2141 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2142 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2143 /* keep track of pure window updates */ 2144 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2145 tiwin > tp->snd_wnd) 2146 tcpstat.tcps_rcvwinupd++; 2147 tp->snd_wnd = tiwin; 2148 tp->snd_wl1 = th->th_seq; 2149 tp->snd_wl2 = th->th_ack; 2150 if (tp->snd_wnd > tp->max_sndwnd) 2151 tp->max_sndwnd = tp->snd_wnd; 2152 needoutput = TRUE; 2153 } 2154 2155 tp->snd_una = th->th_ack; 2156 if (TCP_DO_SACK(tp)) 2157 tcp_sack_update_scoreboard(tp, &to); 2158 if (IN_FASTRECOVERY(tp)) { 2159 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2160 EXIT_FASTRECOVERY(tp); 2161 needoutput = TRUE; 2162 /* 2163 * If the congestion window was inflated 2164 * to account for the other side's 2165 * cached packets, retract it. 2166 */ 2167 if (!TCP_DO_SACK(tp)) 2168 tp->snd_cwnd = tp->snd_ssthresh; 2169 2170 /* 2171 * Window inflation should have left us 2172 * with approximately snd_ssthresh outstanding 2173 * data. But, in case we would be inclined 2174 * to send a burst, better do it using 2175 * slow start. 2176 */ 2177 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2178 tp->snd_max + 2 * tp->t_maxseg)) 2179 tp->snd_cwnd = 2180 (tp->snd_max - tp->snd_una) + 2181 2 * tp->t_maxseg; 2182 2183 tp->snd_wacked = 0; 2184 } else { 2185 if (TCP_DO_SACK(tp)) { 2186 tp->snd_max_rexmt = tp->snd_max; 2187 tcp_sack_rexmt(tp, th); 2188 } else { 2189 tcp_newreno_partial_ack(tp, th, acked); 2190 } 2191 needoutput = FALSE; 2192 } 2193 } else { 2194 /* 2195 * Open the congestion window. When in slow-start, 2196 * open exponentially: maxseg per packet. Otherwise, 2197 * open linearly: maxseg per window. 2198 */ 2199 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2200 u_int abc_sslimit = 2201 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2202 tp->t_maxseg : 2 * tp->t_maxseg); 2203 2204 /* slow-start */ 2205 tp->snd_cwnd += tcp_do_abc ? 2206 min(acked, abc_sslimit) : tp->t_maxseg; 2207 } else { 2208 /* linear increase */ 2209 tp->snd_wacked += tcp_do_abc ? acked : 2210 tp->t_maxseg; 2211 if (tp->snd_wacked >= tp->snd_cwnd) { 2212 tp->snd_wacked -= tp->snd_cwnd; 2213 tp->snd_cwnd += tp->t_maxseg; 2214 } 2215 } 2216 tp->snd_cwnd = min(tp->snd_cwnd, 2217 TCP_MAXWIN << tp->snd_scale); 2218 tp->snd_recover = th->th_ack - 1; 2219 } 2220 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2221 tp->snd_nxt = tp->snd_una; 2222 2223 /* 2224 * If all outstanding data is acked, stop retransmit 2225 * timer and remember to restart (more output or persist). 2226 * If there is more data to be acked, restart retransmit 2227 * timer, using current (possibly backed-off) value. 2228 */ 2229 if (th->th_ack == tp->snd_max) { 2230 tcp_callout_stop(tp, tp->tt_rexmt); 2231 needoutput = TRUE; 2232 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2233 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2234 tcp_timer_rexmt); 2235 } 2236 2237 switch (tp->t_state) { 2238 /* 2239 * In FIN_WAIT_1 STATE in addition to the processing 2240 * for the ESTABLISHED state if our FIN is now acknowledged 2241 * then enter FIN_WAIT_2. 2242 */ 2243 case TCPS_FIN_WAIT_1: 2244 if (ourfinisacked) { 2245 /* 2246 * If we can't receive any more 2247 * data, then closing user can proceed. 2248 * Starting the timer is contrary to the 2249 * specification, but if we don't get a FIN 2250 * we'll hang forever. 2251 */ 2252 if (so->so_state & SS_CANTRCVMORE) { 2253 soisdisconnected(so); 2254 tcp_callout_reset(tp, tp->tt_2msl, 2255 tp->t_maxidle, tcp_timer_2msl); 2256 } 2257 tp->t_state = TCPS_FIN_WAIT_2; 2258 } 2259 break; 2260 2261 /* 2262 * In CLOSING STATE in addition to the processing for 2263 * the ESTABLISHED state if the ACK acknowledges our FIN 2264 * then enter the TIME-WAIT state, otherwise ignore 2265 * the segment. 2266 */ 2267 case TCPS_CLOSING: 2268 if (ourfinisacked) { 2269 tp->t_state = TCPS_TIME_WAIT; 2270 tcp_canceltimers(tp); 2271 tcp_callout_reset(tp, tp->tt_2msl, 2272 2 * tcp_rmx_msl(tp), 2273 tcp_timer_2msl); 2274 soisdisconnected(so); 2275 } 2276 break; 2277 2278 /* 2279 * In LAST_ACK, we may still be waiting for data to drain 2280 * and/or to be acked, as well as for the ack of our FIN. 2281 * If our FIN is now acknowledged, delete the TCB, 2282 * enter the closed state and return. 2283 */ 2284 case TCPS_LAST_ACK: 2285 if (ourfinisacked) { 2286 tp = tcp_close(tp); 2287 goto drop; 2288 } 2289 break; 2290 2291 /* 2292 * In TIME_WAIT state the only thing that should arrive 2293 * is a retransmission of the remote FIN. Acknowledge 2294 * it and restart the finack timer. 2295 */ 2296 case TCPS_TIME_WAIT: 2297 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2298 tcp_timer_2msl); 2299 goto dropafterack; 2300 } 2301 } 2302 2303 step6: 2304 /* 2305 * Update window information. 2306 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2307 */ 2308 if ((thflags & TH_ACK) && 2309 acceptable_window_update(tp, th, tiwin)) { 2310 /* keep track of pure window updates */ 2311 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2312 tiwin > tp->snd_wnd) 2313 tcpstat.tcps_rcvwinupd++; 2314 tp->snd_wnd = tiwin; 2315 tp->snd_wl1 = th->th_seq; 2316 tp->snd_wl2 = th->th_ack; 2317 if (tp->snd_wnd > tp->max_sndwnd) 2318 tp->max_sndwnd = tp->snd_wnd; 2319 needoutput = TRUE; 2320 } 2321 2322 /* 2323 * Process segments with URG. 2324 */ 2325 if ((thflags & TH_URG) && th->th_urp && 2326 !TCPS_HAVERCVDFIN(tp->t_state)) { 2327 /* 2328 * This is a kludge, but if we receive and accept 2329 * random urgent pointers, we'll crash in 2330 * soreceive. It's hard to imagine someone 2331 * actually wanting to send this much urgent data. 2332 */ 2333 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2334 th->th_urp = 0; /* XXX */ 2335 thflags &= ~TH_URG; /* XXX */ 2336 goto dodata; /* XXX */ 2337 } 2338 /* 2339 * If this segment advances the known urgent pointer, 2340 * then mark the data stream. This should not happen 2341 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2342 * a FIN has been received from the remote side. 2343 * In these states we ignore the URG. 2344 * 2345 * According to RFC961 (Assigned Protocols), 2346 * the urgent pointer points to the last octet 2347 * of urgent data. We continue, however, 2348 * to consider it to indicate the first octet 2349 * of data past the urgent section as the original 2350 * spec states (in one of two places). 2351 */ 2352 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2353 tp->rcv_up = th->th_seq + th->th_urp; 2354 so->so_oobmark = so->so_rcv.ssb_cc + 2355 (tp->rcv_up - tp->rcv_nxt) - 1; 2356 if (so->so_oobmark == 0) 2357 sosetstate(so, SS_RCVATMARK); 2358 sohasoutofband(so); 2359 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2360 } 2361 /* 2362 * Remove out of band data so doesn't get presented to user. 2363 * This can happen independent of advancing the URG pointer, 2364 * but if two URG's are pending at once, some out-of-band 2365 * data may creep in... ick. 2366 */ 2367 if (th->th_urp <= (u_long)tlen && 2368 !(so->so_options & SO_OOBINLINE)) { 2369 /* hdr drop is delayed */ 2370 tcp_pulloutofband(so, th, m, drop_hdrlen); 2371 } 2372 } else { 2373 /* 2374 * If no out of band data is expected, 2375 * pull receive urgent pointer along 2376 * with the receive window. 2377 */ 2378 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2379 tp->rcv_up = tp->rcv_nxt; 2380 } 2381 2382 dodata: /* XXX */ 2383 /* 2384 * Process the segment text, merging it into the TCP sequencing queue, 2385 * and arranging for acknowledgment of receipt if necessary. 2386 * This process logically involves adjusting tp->rcv_wnd as data 2387 * is presented to the user (this happens in tcp_usrreq.c, 2388 * case PRU_RCVD). If a FIN has already been received on this 2389 * connection then we just ignore the text. 2390 */ 2391 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2392 m_adj(m, drop_hdrlen); /* delayed header drop */ 2393 /* 2394 * Insert segment which includes th into TCP reassembly queue 2395 * with control block tp. Set thflags to whether reassembly now 2396 * includes a segment with FIN. This handles the common case 2397 * inline (segment is the next to be received on an established 2398 * connection, and the queue is empty), avoiding linkage into 2399 * and removal from the queue and repetition of various 2400 * conversions. 2401 * Set DELACK for segments received in order, but ack 2402 * immediately when segments are out of order (so 2403 * fast retransmit can work). 2404 */ 2405 if (th->th_seq == tp->rcv_nxt && 2406 LIST_EMPTY(&tp->t_segq) && 2407 TCPS_HAVEESTABLISHED(tp->t_state)) { 2408 if (DELAY_ACK(tp)) { 2409 tcp_callout_reset(tp, tp->tt_delack, 2410 tcp_delacktime, tcp_timer_delack); 2411 } else { 2412 tp->t_flags |= TF_ACKNOW; 2413 } 2414 tp->rcv_nxt += tlen; 2415 thflags = th->th_flags & TH_FIN; 2416 tcpstat.tcps_rcvpack++; 2417 tcpstat.tcps_rcvbyte += tlen; 2418 ND6_HINT(tp); 2419 if (so->so_state & SS_CANTRCVMORE) { 2420 m_freem(m); 2421 } else { 2422 lwkt_gettoken(&so->so_rcv.ssb_token); 2423 ssb_appendstream(&so->so_rcv, m); 2424 lwkt_reltoken(&so->so_rcv.ssb_token); 2425 } 2426 sorwakeup(so); 2427 } else { 2428 if (!(tp->t_flags & TF_DUPSEG)) { 2429 /* Initialize SACK report block. */ 2430 tp->reportblk.rblk_start = th->th_seq; 2431 tp->reportblk.rblk_end = th->th_seq + tlen + 2432 ((thflags & TH_FIN) != 0); 2433 } 2434 thflags = tcp_reass(tp, th, &tlen, m); 2435 tp->t_flags |= TF_ACKNOW; 2436 } 2437 2438 /* 2439 * Note the amount of data that peer has sent into 2440 * our window, in order to estimate the sender's 2441 * buffer size. 2442 */ 2443 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2444 } else { 2445 m_freem(m); 2446 thflags &= ~TH_FIN; 2447 } 2448 2449 /* 2450 * If FIN is received ACK the FIN and let the user know 2451 * that the connection is closing. 2452 */ 2453 if (thflags & TH_FIN) { 2454 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2455 socantrcvmore(so); 2456 /* 2457 * If connection is half-synchronized 2458 * (ie NEEDSYN flag on) then delay ACK, 2459 * so it may be piggybacked when SYN is sent. 2460 * Otherwise, since we received a FIN then no 2461 * more input can be expected, send ACK now. 2462 */ 2463 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2464 tcp_callout_reset(tp, tp->tt_delack, 2465 tcp_delacktime, tcp_timer_delack); 2466 } else { 2467 tp->t_flags |= TF_ACKNOW; 2468 } 2469 tp->rcv_nxt++; 2470 } 2471 2472 switch (tp->t_state) { 2473 /* 2474 * In SYN_RECEIVED and ESTABLISHED STATES 2475 * enter the CLOSE_WAIT state. 2476 */ 2477 case TCPS_SYN_RECEIVED: 2478 tp->t_starttime = ticks; 2479 /*FALLTHROUGH*/ 2480 case TCPS_ESTABLISHED: 2481 tp->t_state = TCPS_CLOSE_WAIT; 2482 break; 2483 2484 /* 2485 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2486 * enter the CLOSING state. 2487 */ 2488 case TCPS_FIN_WAIT_1: 2489 tp->t_state = TCPS_CLOSING; 2490 break; 2491 2492 /* 2493 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2494 * starting the time-wait timer, turning off the other 2495 * standard timers. 2496 */ 2497 case TCPS_FIN_WAIT_2: 2498 tp->t_state = TCPS_TIME_WAIT; 2499 tcp_canceltimers(tp); 2500 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2501 tcp_timer_2msl); 2502 soisdisconnected(so); 2503 break; 2504 2505 /* 2506 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2507 */ 2508 case TCPS_TIME_WAIT: 2509 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2510 tcp_timer_2msl); 2511 break; 2512 } 2513 } 2514 2515 #ifdef TCPDEBUG 2516 if (so->so_options & SO_DEBUG) 2517 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2518 #endif 2519 2520 /* 2521 * Return any desired output. 2522 */ 2523 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2524 tcp_output(tp); 2525 return(IPPROTO_DONE); 2526 2527 dropafterack: 2528 /* 2529 * Generate an ACK dropping incoming segment if it occupies 2530 * sequence space, where the ACK reflects our state. 2531 * 2532 * We can now skip the test for the RST flag since all 2533 * paths to this code happen after packets containing 2534 * RST have been dropped. 2535 * 2536 * In the SYN-RECEIVED state, don't send an ACK unless the 2537 * segment we received passes the SYN-RECEIVED ACK test. 2538 * If it fails send a RST. This breaks the loop in the 2539 * "LAND" DoS attack, and also prevents an ACK storm 2540 * between two listening ports that have been sent forged 2541 * SYN segments, each with the source address of the other. 2542 */ 2543 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2544 (SEQ_GT(tp->snd_una, th->th_ack) || 2545 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2546 rstreason = BANDLIM_RST_OPENPORT; 2547 goto dropwithreset; 2548 } 2549 #ifdef TCPDEBUG 2550 if (so->so_options & SO_DEBUG) 2551 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2552 #endif 2553 m_freem(m); 2554 tp->t_flags |= TF_ACKNOW; 2555 tcp_output(tp); 2556 return(IPPROTO_DONE); 2557 2558 dropwithreset: 2559 /* 2560 * Generate a RST, dropping incoming segment. 2561 * Make ACK acceptable to originator of segment. 2562 * Don't bother to respond if destination was broadcast/multicast. 2563 */ 2564 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2565 goto drop; 2566 if (isipv6) { 2567 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2568 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2569 goto drop; 2570 } else { 2571 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2572 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2573 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2574 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2575 goto drop; 2576 } 2577 /* IPv6 anycast check is done at tcp6_input() */ 2578 2579 /* 2580 * Perform bandwidth limiting. 2581 */ 2582 #ifdef ICMP_BANDLIM 2583 if (badport_bandlim(rstreason) < 0) 2584 goto drop; 2585 #endif 2586 2587 #ifdef TCPDEBUG 2588 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2589 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2590 #endif 2591 if (thflags & TH_ACK) 2592 /* mtod() below is safe as long as hdr dropping is delayed */ 2593 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2594 TH_RST); 2595 else { 2596 if (thflags & TH_SYN) 2597 tlen++; 2598 /* mtod() below is safe as long as hdr dropping is delayed */ 2599 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2600 (tcp_seq)0, TH_RST | TH_ACK); 2601 } 2602 return(IPPROTO_DONE); 2603 2604 drop: 2605 /* 2606 * Drop space held by incoming segment and return. 2607 */ 2608 #ifdef TCPDEBUG 2609 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2610 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2611 #endif 2612 m_freem(m); 2613 return(IPPROTO_DONE); 2614 } 2615 2616 /* 2617 * Parse TCP options and place in tcpopt. 2618 */ 2619 static void 2620 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2621 { 2622 int opt, optlen, i; 2623 2624 to->to_flags = 0; 2625 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2626 opt = cp[0]; 2627 if (opt == TCPOPT_EOL) 2628 break; 2629 if (opt == TCPOPT_NOP) 2630 optlen = 1; 2631 else { 2632 if (cnt < 2) 2633 break; 2634 optlen = cp[1]; 2635 if (optlen < 2 || optlen > cnt) 2636 break; 2637 } 2638 switch (opt) { 2639 case TCPOPT_MAXSEG: 2640 if (optlen != TCPOLEN_MAXSEG) 2641 continue; 2642 if (!is_syn) 2643 continue; 2644 to->to_flags |= TOF_MSS; 2645 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2646 to->to_mss = ntohs(to->to_mss); 2647 break; 2648 case TCPOPT_WINDOW: 2649 if (optlen != TCPOLEN_WINDOW) 2650 continue; 2651 if (!is_syn) 2652 continue; 2653 to->to_flags |= TOF_SCALE; 2654 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2655 break; 2656 case TCPOPT_TIMESTAMP: 2657 if (optlen != TCPOLEN_TIMESTAMP) 2658 continue; 2659 to->to_flags |= TOF_TS; 2660 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2661 to->to_tsval = ntohl(to->to_tsval); 2662 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2663 to->to_tsecr = ntohl(to->to_tsecr); 2664 /* 2665 * If echoed timestamp is later than the current time, 2666 * fall back to non RFC1323 RTT calculation. 2667 */ 2668 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2669 to->to_tsecr = 0; 2670 break; 2671 case TCPOPT_SACK_PERMITTED: 2672 if (optlen != TCPOLEN_SACK_PERMITTED) 2673 continue; 2674 if (!is_syn) 2675 continue; 2676 to->to_flags |= TOF_SACK_PERMITTED; 2677 break; 2678 case TCPOPT_SACK: 2679 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2680 continue; 2681 to->to_nsackblocks = (optlen - 2) / 8; 2682 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2683 to->to_flags |= TOF_SACK; 2684 for (i = 0; i < to->to_nsackblocks; i++) { 2685 struct raw_sackblock *r = &to->to_sackblocks[i]; 2686 2687 r->rblk_start = ntohl(r->rblk_start); 2688 r->rblk_end = ntohl(r->rblk_end); 2689 2690 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { 2691 /* 2692 * Invalid SACK block; discard all 2693 * SACK blocks 2694 */ 2695 tcpstat.tcps_rcvbadsackopt++; 2696 to->to_nsackblocks = 0; 2697 to->to_sackblocks = NULL; 2698 to->to_flags &= ~TOF_SACK; 2699 break; 2700 } 2701 } 2702 break; 2703 #ifdef TCP_SIGNATURE 2704 /* 2705 * XXX In order to reply to a host which has set the 2706 * TCP_SIGNATURE option in its initial SYN, we have to 2707 * record the fact that the option was observed here 2708 * for the syncache code to perform the correct response. 2709 */ 2710 case TCPOPT_SIGNATURE: 2711 if (optlen != TCPOLEN_SIGNATURE) 2712 continue; 2713 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2714 break; 2715 #endif /* TCP_SIGNATURE */ 2716 default: 2717 continue; 2718 } 2719 } 2720 } 2721 2722 /* 2723 * Pull out of band byte out of a segment so 2724 * it doesn't appear in the user's data queue. 2725 * It is still reflected in the segment length for 2726 * sequencing purposes. 2727 * "off" is the delayed to be dropped hdrlen. 2728 */ 2729 static void 2730 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2731 { 2732 int cnt = off + th->th_urp - 1; 2733 2734 while (cnt >= 0) { 2735 if (m->m_len > cnt) { 2736 char *cp = mtod(m, caddr_t) + cnt; 2737 struct tcpcb *tp = sototcpcb(so); 2738 2739 tp->t_iobc = *cp; 2740 tp->t_oobflags |= TCPOOB_HAVEDATA; 2741 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2742 m->m_len--; 2743 if (m->m_flags & M_PKTHDR) 2744 m->m_pkthdr.len--; 2745 return; 2746 } 2747 cnt -= m->m_len; 2748 m = m->m_next; 2749 if (m == NULL) 2750 break; 2751 } 2752 panic("tcp_pulloutofband"); 2753 } 2754 2755 /* 2756 * Collect new round-trip time estimate 2757 * and update averages and current timeout. 2758 */ 2759 static void 2760 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2761 { 2762 int delta; 2763 2764 tcpstat.tcps_rttupdated++; 2765 tp->t_rttupdated++; 2766 if (tp->t_srtt != 0) { 2767 /* 2768 * srtt is stored as fixed point with 5 bits after the 2769 * binary point (i.e., scaled by 8). The following magic 2770 * is equivalent to the smoothing algorithm in rfc793 with 2771 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2772 * point). Adjust rtt to origin 0. 2773 */ 2774 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2775 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2776 2777 if ((tp->t_srtt += delta) <= 0) 2778 tp->t_srtt = 1; 2779 2780 /* 2781 * We accumulate a smoothed rtt variance (actually, a 2782 * smoothed mean difference), then set the retransmit 2783 * timer to smoothed rtt + 4 times the smoothed variance. 2784 * rttvar is stored as fixed point with 4 bits after the 2785 * binary point (scaled by 16). The following is 2786 * equivalent to rfc793 smoothing with an alpha of .75 2787 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2788 * rfc793's wired-in beta. 2789 */ 2790 if (delta < 0) 2791 delta = -delta; 2792 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2793 if ((tp->t_rttvar += delta) <= 0) 2794 tp->t_rttvar = 1; 2795 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2796 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2797 } else { 2798 /* 2799 * No rtt measurement yet - use the unsmoothed rtt. 2800 * Set the variance to half the rtt (so our first 2801 * retransmit happens at 3*rtt). 2802 */ 2803 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2804 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2805 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2806 } 2807 tp->t_rtttime = 0; 2808 tp->t_rxtshift = 0; 2809 2810 /* 2811 * the retransmit should happen at rtt + 4 * rttvar. 2812 * Because of the way we do the smoothing, srtt and rttvar 2813 * will each average +1/2 tick of bias. When we compute 2814 * the retransmit timer, we want 1/2 tick of rounding and 2815 * 1 extra tick because of +-1/2 tick uncertainty in the 2816 * firing of the timer. The bias will give us exactly the 2817 * 1.5 tick we need. But, because the bias is 2818 * statistical, we have to test that we don't drop below 2819 * the minimum feasible timer (which is 2 ticks). 2820 */ 2821 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2822 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2823 2824 /* 2825 * We received an ack for a packet that wasn't retransmitted; 2826 * it is probably safe to discard any error indications we've 2827 * received recently. This isn't quite right, but close enough 2828 * for now (a route might have failed after we sent a segment, 2829 * and the return path might not be symmetrical). 2830 */ 2831 tp->t_softerror = 0; 2832 } 2833 2834 /* 2835 * Determine a reasonable value for maxseg size. 2836 * If the route is known, check route for mtu. 2837 * If none, use an mss that can be handled on the outgoing 2838 * interface without forcing IP to fragment; if bigger than 2839 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2840 * to utilize large mbufs. If no route is found, route has no mtu, 2841 * or the destination isn't local, use a default, hopefully conservative 2842 * size (usually 512 or the default IP max size, but no more than the mtu 2843 * of the interface), as we can't discover anything about intervening 2844 * gateways or networks. We also initialize the congestion/slow start 2845 * window to be a single segment if the destination isn't local. 2846 * While looking at the routing entry, we also initialize other path-dependent 2847 * parameters from pre-set or cached values in the routing entry. 2848 * 2849 * Also take into account the space needed for options that we 2850 * send regularly. Make maxseg shorter by that amount to assure 2851 * that we can send maxseg amount of data even when the options 2852 * are present. Store the upper limit of the length of options plus 2853 * data in maxopd. 2854 * 2855 * NOTE that this routine is only called when we process an incoming 2856 * segment, for outgoing segments only tcp_mssopt is called. 2857 */ 2858 void 2859 tcp_mss(struct tcpcb *tp, int offer) 2860 { 2861 struct rtentry *rt; 2862 struct ifnet *ifp; 2863 int rtt, mss; 2864 u_long bufsize; 2865 struct inpcb *inp = tp->t_inpcb; 2866 struct socket *so; 2867 #ifdef INET6 2868 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2869 size_t min_protoh = isipv6 ? 2870 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2871 sizeof(struct tcpiphdr); 2872 #else 2873 const boolean_t isipv6 = FALSE; 2874 const size_t min_protoh = sizeof(struct tcpiphdr); 2875 #endif 2876 2877 if (isipv6) 2878 rt = tcp_rtlookup6(&inp->inp_inc); 2879 else 2880 rt = tcp_rtlookup(&inp->inp_inc); 2881 if (rt == NULL) { 2882 tp->t_maxopd = tp->t_maxseg = 2883 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2884 return; 2885 } 2886 ifp = rt->rt_ifp; 2887 so = inp->inp_socket; 2888 2889 /* 2890 * Offer == 0 means that there was no MSS on the SYN segment, 2891 * in this case we use either the interface mtu or tcp_mssdflt. 2892 * 2893 * An offer which is too large will be cut down later. 2894 */ 2895 if (offer == 0) { 2896 if (isipv6) { 2897 if (in6_localaddr(&inp->in6p_faddr)) { 2898 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 2899 min_protoh; 2900 } else { 2901 offer = tcp_v6mssdflt; 2902 } 2903 } else { 2904 if (in_localaddr(inp->inp_faddr)) 2905 offer = ifp->if_mtu - min_protoh; 2906 else 2907 offer = tcp_mssdflt; 2908 } 2909 } 2910 2911 /* 2912 * Prevent DoS attack with too small MSS. Round up 2913 * to at least minmss. 2914 * 2915 * Sanity check: make sure that maxopd will be large 2916 * enough to allow some data on segments even is the 2917 * all the option space is used (40bytes). Otherwise 2918 * funny things may happen in tcp_output. 2919 */ 2920 offer = max(offer, tcp_minmss); 2921 offer = max(offer, 64); 2922 2923 rt->rt_rmx.rmx_mssopt = offer; 2924 2925 /* 2926 * While we're here, check if there's an initial rtt 2927 * or rttvar. Convert from the route-table units 2928 * to scaled multiples of the slow timeout timer. 2929 */ 2930 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2931 /* 2932 * XXX the lock bit for RTT indicates that the value 2933 * is also a minimum value; this is subject to time. 2934 */ 2935 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2936 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2937 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2938 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2939 tcpstat.tcps_usedrtt++; 2940 if (rt->rt_rmx.rmx_rttvar) { 2941 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2942 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2943 tcpstat.tcps_usedrttvar++; 2944 } else { 2945 /* default variation is +- 1 rtt */ 2946 tp->t_rttvar = 2947 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2948 } 2949 TCPT_RANGESET(tp->t_rxtcur, 2950 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2951 tp->t_rttmin, TCPTV_REXMTMAX); 2952 } 2953 2954 /* 2955 * if there's an mtu associated with the route, use it 2956 * else, use the link mtu. Take the smaller of mss or offer 2957 * as our final mss. 2958 */ 2959 if (rt->rt_rmx.rmx_mtu) { 2960 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2961 } else { 2962 if (isipv6) 2963 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2964 else 2965 mss = ifp->if_mtu - min_protoh; 2966 } 2967 mss = min(mss, offer); 2968 2969 /* 2970 * maxopd stores the maximum length of data AND options 2971 * in a segment; maxseg is the amount of data in a normal 2972 * segment. We need to store this value (maxopd) apart 2973 * from maxseg, because now every segment carries options 2974 * and thus we normally have somewhat less data in segments. 2975 */ 2976 tp->t_maxopd = mss; 2977 2978 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 2979 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2980 mss -= TCPOLEN_TSTAMP_APPA; 2981 2982 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2983 if (mss > MCLBYTES) 2984 mss &= ~(MCLBYTES-1); 2985 #else 2986 if (mss > MCLBYTES) 2987 mss = mss / MCLBYTES * MCLBYTES; 2988 #endif 2989 /* 2990 * If there's a pipesize, change the socket buffer 2991 * to that size. Make the socket buffers an integral 2992 * number of mss units; if the mss is larger than 2993 * the socket buffer, decrease the mss. 2994 */ 2995 #ifdef RTV_SPIPE 2996 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2997 #endif 2998 bufsize = so->so_snd.ssb_hiwat; 2999 if (bufsize < mss) 3000 mss = bufsize; 3001 else { 3002 bufsize = roundup(bufsize, mss); 3003 if (bufsize > sb_max) 3004 bufsize = sb_max; 3005 if (bufsize > so->so_snd.ssb_hiwat) 3006 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3007 } 3008 tp->t_maxseg = mss; 3009 3010 #ifdef RTV_RPIPE 3011 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3012 #endif 3013 bufsize = so->so_rcv.ssb_hiwat; 3014 if (bufsize > mss) { 3015 bufsize = roundup(bufsize, mss); 3016 if (bufsize > sb_max) 3017 bufsize = sb_max; 3018 if (bufsize > so->so_rcv.ssb_hiwat) { 3019 lwkt_gettoken(&so->so_rcv.ssb_token); 3020 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3021 lwkt_reltoken(&so->so_rcv.ssb_token); 3022 } 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 3155 /* 3156 * Reset idle time and keep-alive timer, typically called when a valid 3157 * tcp packet is received but may also be called when FASTKEEP is set 3158 * to prevent the previous long-timeout from calculating to a drop. 3159 * 3160 * Only update t_rcvtime for non-SYN packets. 3161 * 3162 * Handle the case where one side thinks the connection is established 3163 * but the other side has, say, rebooted without cleaning out the 3164 * connection. The SYNs could be construed as an attack and wind 3165 * up ignored, but in case it isn't an attack we can validate the 3166 * connection by forcing a keepalive. 3167 */ 3168 void 3169 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3170 { 3171 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3172 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3173 tp->t_flags |= TF_KEEPALIVE; 3174 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3175 tcp_timer_keep); 3176 } else { 3177 tp->t_rcvtime = ticks; 3178 tp->t_flags &= ~TF_KEEPALIVE; 3179 tcp_callout_reset(tp, tp->tt_keep, 3180 tcp_getkeepidle(tp), 3181 tcp_timer_keep); 3182 } 3183 } 3184 } 3185 3186 static int 3187 tcp_rmx_msl(const struct tcpcb *tp) 3188 { 3189 struct rtentry *rt; 3190 struct inpcb *inp = tp->t_inpcb; 3191 int msl; 3192 #ifdef INET6 3193 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3194 #else 3195 const boolean_t isipv6 = FALSE; 3196 #endif 3197 3198 if (isipv6) 3199 rt = tcp_rtlookup6(&inp->inp_inc); 3200 else 3201 rt = tcp_rtlookup(&inp->inp_inc); 3202 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3203 return tcp_msl; 3204 3205 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3206 if (msl == 0) 3207 msl = 1; 3208 3209 return msl; 3210 } 3211 3212 static void 3213 tcp_established(struct tcpcb *tp) 3214 { 3215 tp->t_state = TCPS_ESTABLISHED; 3216 tcp_callout_reset(tp, tp->tt_keep, tcp_getkeepidle(tp), tcp_timer_keep); 3217 3218 if (tp->t_flags & TF_SYN_WASLOST) { 3219 /* 3220 * RFC3390: 3221 * "If the SYN or SYN/ACK is lost, the initial window used by 3222 * a sender after a correctly transmitted SYN MUST be one 3223 * segment consisting of MSS bytes." 3224 */ 3225 tp->snd_cwnd = tp->t_maxseg; 3226 3227 /* 3228 * RFC6298: 3229 * "If the timer expires awaiting the ACK of a SYN segment 3230 * and the TCP implementation is using an RTO less than 3 3231 * seconds, the RTO MUST be re-initialized to 3 seconds 3232 * when data transmission begins" 3233 */ 3234 if (tp->t_rxtcur < TCPTV_RTOBASE3) 3235 tp->t_rxtcur = TCPTV_RTOBASE3; 3236 } 3237 } 3238