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 static int tcp_do_eifel_detect = 1; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 172 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 173 174 static int tcp_do_abc = 1; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 176 &tcp_do_abc, 0, 177 "TCP Appropriate Byte Counting (RFC 3465)"); 178 179 /* 180 * Define as tunable for easy testing with SACK on and off. 181 * Warning: do not change setting in the middle of an existing active TCP flow, 182 * else strange things might happen to that flow. 183 */ 184 int tcp_do_sack = 1; 185 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 186 &tcp_do_sack, 0, "Enable SACK Algorithms"); 187 188 int tcp_do_smartsack = 1; 189 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 190 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 191 192 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 193 "TCP Segment Reassembly Queue"); 194 195 int tcp_reass_maxseg = 0; 196 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 197 &tcp_reass_maxseg, 0, 198 "Global maximum number of TCP Segments in Reassembly Queue"); 199 200 int tcp_reass_qsize = 0; 201 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 202 &tcp_reass_qsize, 0, 203 "Global number of TCP Segments currently in Reassembly Queue"); 204 205 static int tcp_reass_overflows = 0; 206 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 207 &tcp_reass_overflows, 0, 208 "Global number of TCP Segment Reassembly Queue Overflows"); 209 210 int tcp_do_autorcvbuf = 1; 211 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 212 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 213 214 int tcp_autorcvbuf_inc = 16*1024; 215 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 216 &tcp_autorcvbuf_inc, 0, 217 "Incrementor step size of automatic receive buffer"); 218 219 int tcp_autorcvbuf_max = 2*1024*1024; 220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 221 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 222 223 int tcp_sosend_agglim = 2; 224 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW, 225 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit"); 226 227 int tcp_sosend_async = 1; 228 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW, 229 &tcp_sosend_async, 0, "TCP asynchronized pru_send"); 230 231 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 232 static void tcp_pulloutofband(struct socket *, 233 struct tcphdr *, struct mbuf *, int); 234 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 235 struct mbuf *); 236 static void tcp_xmit_timer(struct tcpcb *, int); 237 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 238 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 239 static int tcp_rmx_msl(const struct tcpcb *); 240 static void tcp_established(struct tcpcb *); 241 242 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 243 #ifdef INET6 244 #define ND6_HINT(tp) \ 245 do { \ 246 if ((tp) && (tp)->t_inpcb && \ 247 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 248 (tp)->t_inpcb->in6p_route.ro_rt) \ 249 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 250 } while (0) 251 #else 252 #define ND6_HINT(tp) 253 #endif 254 255 /* 256 * Indicate whether this ack should be delayed. We can delay the ack if 257 * - delayed acks are enabled and 258 * - there is no delayed ack timer in progress and 259 * - our last ack wasn't a 0-sized window. We never want to delay 260 * the ack that opens up a 0-sized window. 261 */ 262 #define DELAY_ACK(tp) \ 263 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 264 !(tp->t_flags & TF_RXWIN0SENT)) 265 266 #define acceptable_window_update(tp, th, tiwin) \ 267 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 268 (tp->snd_wl1 == th->th_seq && \ 269 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 270 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 271 272 static int 273 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 274 { 275 struct tseg_qent *q; 276 struct tseg_qent *p = NULL; 277 struct tseg_qent *te; 278 struct socket *so = tp->t_inpcb->inp_socket; 279 int flags; 280 281 /* 282 * Call with th == NULL after become established to 283 * force pre-ESTABLISHED data up to user socket. 284 */ 285 if (th == NULL) 286 goto present; 287 288 /* 289 * Limit the number of segments in the reassembly queue to prevent 290 * holding on to too many segments (and thus running out of mbufs). 291 * Make sure to let the missing segment through which caused this 292 * queue. Always keep one global queue entry spare to be able to 293 * process the missing segment. 294 */ 295 if (th->th_seq != tp->rcv_nxt && 296 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 297 tcp_reass_overflows++; 298 tcpstat.tcps_rcvmemdrop++; 299 m_freem(m); 300 /* no SACK block to report */ 301 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 302 return (0); 303 } 304 305 /* Allocate a new queue entry. */ 306 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 307 if (te == NULL) { 308 tcpstat.tcps_rcvmemdrop++; 309 m_freem(m); 310 /* no SACK block to report */ 311 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 312 return (0); 313 } 314 atomic_add_int(&tcp_reass_qsize, 1); 315 316 /* 317 * Find a segment which begins after this one does. 318 */ 319 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 320 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 321 break; 322 p = q; 323 } 324 325 /* 326 * If there is a preceding segment, it may provide some of 327 * our data already. If so, drop the data from the incoming 328 * segment. If it provides all of our data, drop us. 329 */ 330 if (p != NULL) { 331 tcp_seq_diff_t i; 332 333 /* conversion to int (in i) handles seq wraparound */ 334 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 335 if (i > 0) { /* overlaps preceding segment */ 336 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 337 /* enclosing block starts w/ preceding segment */ 338 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 339 if (i >= *tlenp) { 340 /* preceding encloses incoming segment */ 341 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 342 p->tqe_th->th_seq + p->tqe_len, 343 p->tqe_th->th_flags); 344 tcpstat.tcps_rcvduppack++; 345 tcpstat.tcps_rcvdupbyte += *tlenp; 346 m_freem(m); 347 kfree(te, M_TSEGQ); 348 atomic_add_int(&tcp_reass_qsize, -1); 349 /* 350 * Try to present any queued data 351 * at the left window edge to the user. 352 * This is needed after the 3-WHS 353 * completes. 354 */ 355 goto present; /* ??? */ 356 } 357 m_adj(m, i); 358 *tlenp -= i; 359 th->th_seq += i; 360 /* incoming segment end is enclosing block end */ 361 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 362 th->th_seq + *tlenp, th->th_flags); 363 /* trim end of reported D-SACK block */ 364 tp->reportblk.rblk_end = th->th_seq; 365 } 366 } 367 tcpstat.tcps_rcvoopack++; 368 tcpstat.tcps_rcvoobyte += *tlenp; 369 370 /* 371 * While we overlap succeeding segments trim them or, 372 * if they are completely covered, dequeue them. 373 */ 374 while (q) { 375 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 376 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 377 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags); 378 struct tseg_qent *nq; 379 380 if (i <= 0) 381 break; 382 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 383 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 384 tp->encloseblk = tp->reportblk; 385 /* report trailing duplicate D-SACK segment */ 386 tp->reportblk.rblk_start = q->tqe_th->th_seq; 387 } 388 if ((tp->t_flags & TF_ENCLOSESEG) && 389 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) { 390 /* extend enclosing block if one exists */ 391 tp->encloseblk.rblk_end = qend_sack; 392 } 393 if (i < q->tqe_len) { 394 q->tqe_th->th_seq += i; 395 q->tqe_len -= i; 396 m_adj(q->tqe_m, i); 397 break; 398 } 399 400 nq = LIST_NEXT(q, tqe_q); 401 LIST_REMOVE(q, tqe_q); 402 m_freem(q->tqe_m); 403 kfree(q, M_TSEGQ); 404 atomic_add_int(&tcp_reass_qsize, -1); 405 q = nq; 406 } 407 408 /* Insert the new segment queue entry into place. */ 409 te->tqe_m = m; 410 te->tqe_th = th; 411 te->tqe_len = *tlenp; 412 413 /* check if can coalesce with following segment */ 414 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 415 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 416 tcp_seq tend_sack = TCP_SACK_BLKEND(tend, te->tqe_th->th_flags); 417 418 te->tqe_len += q->tqe_len; 419 if (q->tqe_th->th_flags & TH_FIN) 420 te->tqe_th->th_flags |= TH_FIN; 421 m_cat(te->tqe_m, q->tqe_m); 422 tp->encloseblk.rblk_end = tend_sack; 423 /* 424 * When not reporting a duplicate segment, use 425 * the larger enclosing block as the SACK block. 426 */ 427 if (!(tp->t_flags & TF_DUPSEG)) 428 tp->reportblk.rblk_end = tend_sack; 429 LIST_REMOVE(q, tqe_q); 430 kfree(q, M_TSEGQ); 431 atomic_add_int(&tcp_reass_qsize, -1); 432 } 433 434 if (p == NULL) { 435 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 436 } else { 437 /* check if can coalesce with preceding segment */ 438 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 439 p->tqe_len += te->tqe_len; 440 m_cat(p->tqe_m, te->tqe_m); 441 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 442 /* 443 * When not reporting a duplicate segment, use 444 * the larger enclosing block as the SACK block. 445 */ 446 if (!(tp->t_flags & TF_DUPSEG)) 447 tp->reportblk.rblk_start = p->tqe_th->th_seq; 448 kfree(te, M_TSEGQ); 449 atomic_add_int(&tcp_reass_qsize, -1); 450 } else { 451 LIST_INSERT_AFTER(p, te, tqe_q); 452 } 453 } 454 455 present: 456 /* 457 * Present data to user, advancing rcv_nxt through 458 * completed sequence space. 459 */ 460 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 461 return (0); 462 q = LIST_FIRST(&tp->t_segq); 463 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 464 return (0); 465 tp->rcv_nxt += q->tqe_len; 466 if (!(tp->t_flags & TF_DUPSEG)) { 467 /* no SACK block to report since ACK advanced */ 468 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 469 } 470 /* no enclosing block to report since ACK advanced */ 471 tp->t_flags &= ~TF_ENCLOSESEG; 472 flags = q->tqe_th->th_flags & TH_FIN; 473 LIST_REMOVE(q, tqe_q); 474 KASSERT(LIST_EMPTY(&tp->t_segq) || 475 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 476 ("segment not coalesced")); 477 if (so->so_state & SS_CANTRCVMORE) { 478 m_freem(q->tqe_m); 479 } else { 480 lwkt_gettoken(&so->so_rcv.ssb_token); 481 ssb_appendstream(&so->so_rcv, q->tqe_m); 482 lwkt_reltoken(&so->so_rcv.ssb_token); 483 } 484 kfree(q, M_TSEGQ); 485 atomic_add_int(&tcp_reass_qsize, -1); 486 ND6_HINT(tp); 487 sorwakeup(so); 488 return (flags); 489 } 490 491 /* 492 * TCP input routine, follows pages 65-76 of the 493 * protocol specification dated September, 1981 very closely. 494 */ 495 #ifdef INET6 496 int 497 tcp6_input(struct mbuf **mp, int *offp, int proto) 498 { 499 struct mbuf *m = *mp; 500 struct in6_ifaddr *ia6; 501 502 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 503 504 /* 505 * draft-itojun-ipv6-tcp-to-anycast 506 * better place to put this in? 507 */ 508 ia6 = ip6_getdstifaddr(m); 509 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 510 struct ip6_hdr *ip6; 511 512 ip6 = mtod(m, struct ip6_hdr *); 513 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 514 offsetof(struct ip6_hdr, ip6_dst)); 515 return (IPPROTO_DONE); 516 } 517 518 tcp_input(mp, offp, proto); 519 return (IPPROTO_DONE); 520 } 521 #endif 522 523 int 524 tcp_input(struct mbuf **mp, int *offp, int proto) 525 { 526 int off0; 527 struct tcphdr *th; 528 struct ip *ip = NULL; 529 struct ipovly *ipov; 530 struct inpcb *inp = NULL; 531 u_char *optp = NULL; 532 int optlen = 0; 533 int tlen, off; 534 int len = 0; 535 int drop_hdrlen; 536 struct tcpcb *tp = NULL; 537 int thflags; 538 struct socket *so = NULL; 539 int todrop, acked; 540 boolean_t ourfinisacked, needoutput = FALSE; 541 u_long tiwin; 542 int recvwin; 543 struct tcpopt to; /* options in this segment */ 544 struct sockaddr_in *next_hop = NULL; 545 int rstreason; /* For badport_bandlim accounting purposes */ 546 int cpu; 547 struct ip6_hdr *ip6 = NULL; 548 struct mbuf *m; 549 #ifdef INET6 550 boolean_t isipv6; 551 #else 552 const boolean_t isipv6 = FALSE; 553 #endif 554 #ifdef TCPDEBUG 555 short ostate = 0; 556 #endif 557 558 off0 = *offp; 559 m = *mp; 560 *mp = NULL; 561 562 tcpstat.tcps_rcvtotal++; 563 564 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 565 struct m_tag *mtag; 566 567 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 568 KKASSERT(mtag != NULL); 569 next_hop = m_tag_data(mtag); 570 } 571 572 #ifdef INET6 573 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 574 #endif 575 576 if (isipv6) { 577 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 578 ip6 = mtod(m, struct ip6_hdr *); 579 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 580 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 581 tcpstat.tcps_rcvbadsum++; 582 goto drop; 583 } 584 th = (struct tcphdr *)((caddr_t)ip6 + off0); 585 586 /* 587 * Be proactive about unspecified IPv6 address in source. 588 * As we use all-zero to indicate unbounded/unconnected pcb, 589 * unspecified IPv6 address can be used to confuse us. 590 * 591 * Note that packets with unspecified IPv6 destination is 592 * already dropped in ip6_input. 593 */ 594 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 595 /* XXX stat */ 596 goto drop; 597 } 598 } else { 599 /* 600 * Get IP and TCP header together in first mbuf. 601 * Note: IP leaves IP header in first mbuf. 602 */ 603 if (off0 > sizeof(struct ip)) { 604 ip_stripoptions(m); 605 off0 = sizeof(struct ip); 606 } 607 /* already checked and pulled up in ip_demux() */ 608 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 609 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 610 ip = mtod(m, struct ip *); 611 ipov = (struct ipovly *)ip; 612 th = (struct tcphdr *)((caddr_t)ip + off0); 613 tlen = ip->ip_len; 614 615 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 616 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 617 th->th_sum = m->m_pkthdr.csum_data; 618 else 619 th->th_sum = in_pseudo(ip->ip_src.s_addr, 620 ip->ip_dst.s_addr, 621 htonl(m->m_pkthdr.csum_data + 622 ip->ip_len + 623 IPPROTO_TCP)); 624 th->th_sum ^= 0xffff; 625 } else { 626 /* 627 * Checksum extended TCP header and data. 628 */ 629 len = sizeof(struct ip) + tlen; 630 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 631 ipov->ih_len = (u_short)tlen; 632 ipov->ih_len = htons(ipov->ih_len); 633 th->th_sum = in_cksum(m, len); 634 } 635 if (th->th_sum) { 636 tcpstat.tcps_rcvbadsum++; 637 goto drop; 638 } 639 #ifdef INET6 640 /* Re-initialization for later version check */ 641 ip->ip_v = IPVERSION; 642 #endif 643 } 644 645 /* 646 * Check that TCP offset makes sense, 647 * pull out TCP options and adjust length. XXX 648 */ 649 off = th->th_off << 2; 650 /* already checked and pulled up in ip_demux() */ 651 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 652 ("bad TCP data offset %d (tlen %d)", off, tlen)); 653 tlen -= off; /* tlen is used instead of ti->ti_len */ 654 if (off > sizeof(struct tcphdr)) { 655 if (isipv6) { 656 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 657 ip6 = mtod(m, struct ip6_hdr *); 658 th = (struct tcphdr *)((caddr_t)ip6 + off0); 659 } else { 660 /* already pulled up in ip_demux() */ 661 KASSERT(m->m_len >= sizeof(struct ip) + off, 662 ("TCP header and options not in one mbuf: " 663 "m_len %d, off %d", m->m_len, off)); 664 } 665 optlen = off - sizeof(struct tcphdr); 666 optp = (u_char *)(th + 1); 667 } 668 thflags = th->th_flags; 669 670 #ifdef TCP_DROP_SYNFIN 671 /* 672 * If the drop_synfin option is enabled, drop all packets with 673 * both the SYN and FIN bits set. This prevents e.g. nmap from 674 * identifying the TCP/IP stack. 675 * 676 * This is a violation of the TCP specification. 677 */ 678 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 679 goto drop; 680 #endif 681 682 /* 683 * Convert TCP protocol specific fields to host format. 684 */ 685 th->th_seq = ntohl(th->th_seq); 686 th->th_ack = ntohl(th->th_ack); 687 th->th_win = ntohs(th->th_win); 688 th->th_urp = ntohs(th->th_urp); 689 690 /* 691 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 692 * until after ip6_savecontrol() is called and before other functions 693 * which don't want those proto headers. 694 * Because ip6_savecontrol() is going to parse the mbuf to 695 * search for data to be passed up to user-land, it wants mbuf 696 * parameters to be unchanged. 697 * XXX: the call of ip6_savecontrol() has been obsoleted based on 698 * latest version of the advanced API (20020110). 699 */ 700 drop_hdrlen = off0 + off; 701 702 /* 703 * Locate pcb for segment. 704 */ 705 findpcb: 706 /* IPFIREWALL_FORWARD section */ 707 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 708 /* 709 * Transparently forwarded. Pretend to be the destination. 710 * already got one like this? 711 */ 712 cpu = mycpu->gd_cpuid; 713 inp = in_pcblookup_hash(&tcbinfo[cpu], 714 ip->ip_src, th->th_sport, 715 ip->ip_dst, th->th_dport, 716 0, m->m_pkthdr.rcvif); 717 if (!inp) { 718 /* 719 * It's new. Try to find the ambushing socket. 720 */ 721 722 /* 723 * The rest of the ipfw code stores the port in 724 * host order. XXX 725 * (The IP address is still in network order.) 726 */ 727 in_port_t dport = next_hop->sin_port ? 728 htons(next_hop->sin_port) : 729 th->th_dport; 730 731 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 732 next_hop->sin_addr.s_addr, dport); 733 inp = in_pcblookup_hash(&tcbinfo[cpu], 734 ip->ip_src, th->th_sport, 735 next_hop->sin_addr, dport, 736 1, m->m_pkthdr.rcvif); 737 } 738 } else { 739 if (isipv6) { 740 inp = in6_pcblookup_hash(&tcbinfo[0], 741 &ip6->ip6_src, th->th_sport, 742 &ip6->ip6_dst, th->th_dport, 743 1, m->m_pkthdr.rcvif); 744 } else { 745 cpu = mycpu->gd_cpuid; 746 inp = in_pcblookup_hash(&tcbinfo[cpu], 747 ip->ip_src, th->th_sport, 748 ip->ip_dst, th->th_dport, 749 1, m->m_pkthdr.rcvif); 750 } 751 } 752 753 /* 754 * If the state is CLOSED (i.e., TCB does not exist) then 755 * all data in the incoming segment is discarded. 756 * If the TCB exists but is in CLOSED state, it is embryonic, 757 * but should either do a listen or a connect soon. 758 */ 759 if (inp == NULL) { 760 if (log_in_vain) { 761 #ifdef INET6 762 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 763 #else 764 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 765 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 766 #endif 767 if (isipv6) { 768 strcpy(dbuf, "["); 769 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 770 strcat(dbuf, "]"); 771 strcpy(sbuf, "["); 772 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 773 strcat(sbuf, "]"); 774 } else { 775 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 776 strcpy(sbuf, inet_ntoa(ip->ip_src)); 777 } 778 switch (log_in_vain) { 779 case 1: 780 if (!(thflags & TH_SYN)) 781 break; 782 case 2: 783 log(LOG_INFO, 784 "Connection attempt to TCP %s:%d " 785 "from %s:%d flags:0x%02x\n", 786 dbuf, ntohs(th->th_dport), sbuf, 787 ntohs(th->th_sport), thflags); 788 break; 789 default: 790 break; 791 } 792 } 793 if (blackhole) { 794 switch (blackhole) { 795 case 1: 796 if (thflags & TH_SYN) 797 goto drop; 798 break; 799 case 2: 800 goto drop; 801 default: 802 goto drop; 803 } 804 } 805 rstreason = BANDLIM_RST_CLOSEDPORT; 806 goto dropwithreset; 807 } 808 809 #ifdef IPSEC 810 if (isipv6) { 811 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 812 ipsec6stat.in_polvio++; 813 goto drop; 814 } 815 } else { 816 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 817 ipsecstat.in_polvio++; 818 goto drop; 819 } 820 } 821 #endif 822 #ifdef FAST_IPSEC 823 if (isipv6) { 824 if (ipsec6_in_reject(m, inp)) 825 goto drop; 826 } else { 827 if (ipsec4_in_reject(m, inp)) 828 goto drop; 829 } 830 #endif 831 /* Check the minimum TTL for socket. */ 832 #ifdef INET6 833 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 834 goto drop; 835 #endif 836 837 tp = intotcpcb(inp); 838 if (tp == NULL) { 839 rstreason = BANDLIM_RST_CLOSEDPORT; 840 goto dropwithreset; 841 } 842 if (tp->t_state <= TCPS_CLOSED) 843 goto drop; 844 845 /* Unscale the window into a 32-bit value. */ 846 if (!(thflags & TH_SYN)) 847 tiwin = th->th_win << tp->snd_scale; 848 else 849 tiwin = th->th_win; 850 851 so = inp->inp_socket; 852 853 #ifdef TCPDEBUG 854 if (so->so_options & SO_DEBUG) { 855 ostate = tp->t_state; 856 if (isipv6) 857 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 858 else 859 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 860 tcp_savetcp = *th; 861 } 862 #endif 863 864 bzero(&to, sizeof to); 865 866 if (so->so_options & SO_ACCEPTCONN) { 867 struct in_conninfo inc; 868 869 #ifdef INET6 870 inc.inc_isipv6 = (isipv6 == TRUE); 871 #endif 872 if (isipv6) { 873 inc.inc6_faddr = ip6->ip6_src; 874 inc.inc6_laddr = ip6->ip6_dst; 875 inc.inc6_route.ro_rt = NULL; /* XXX */ 876 } else { 877 inc.inc_faddr = ip->ip_src; 878 inc.inc_laddr = ip->ip_dst; 879 inc.inc_route.ro_rt = NULL; /* XXX */ 880 } 881 inc.inc_fport = th->th_sport; 882 inc.inc_lport = th->th_dport; 883 884 /* 885 * If the state is LISTEN then ignore segment if it contains 886 * a RST. If the segment contains an ACK then it is bad and 887 * send a RST. If it does not contain a SYN then it is not 888 * interesting; drop it. 889 * 890 * If the state is SYN_RECEIVED (syncache) and seg contains 891 * an ACK, but not for our SYN/ACK, send a RST. If the seg 892 * contains a RST, check the sequence number to see if it 893 * is a valid reset segment. 894 */ 895 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 896 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 897 if (!syncache_expand(&inc, th, &so, m)) { 898 /* 899 * No syncache entry, or ACK was not 900 * for our SYN/ACK. Send a RST. 901 */ 902 tcpstat.tcps_badsyn++; 903 rstreason = BANDLIM_RST_OPENPORT; 904 goto dropwithreset; 905 } 906 907 /* 908 * Could not complete 3-way handshake, 909 * connection is being closed down, and 910 * syncache will free mbuf. 911 */ 912 if (so == NULL) 913 return(IPPROTO_DONE); 914 915 /* 916 * We must be in the correct protocol thread 917 * for this connection. 918 */ 919 KKASSERT(so->so_port == &curthread->td_msgport); 920 921 /* 922 * Socket is created in state SYN_RECEIVED. 923 * Continue processing segment. 924 */ 925 inp = so->so_pcb; 926 tp = intotcpcb(inp); 927 /* 928 * This is what would have happened in 929 * tcp_output() when the SYN,ACK was sent. 930 */ 931 tp->snd_up = tp->snd_una; 932 tp->snd_max = tp->snd_nxt = tp->iss + 1; 933 tp->last_ack_sent = tp->rcv_nxt; 934 /* 935 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 936 * until the _second_ ACK is received: 937 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 938 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 939 * move to ESTAB, set snd_wnd to tiwin. 940 */ 941 tp->snd_wnd = tiwin; /* unscaled */ 942 goto after_listen; 943 } 944 if (thflags & TH_RST) { 945 syncache_chkrst(&inc, th); 946 goto drop; 947 } 948 if (thflags & TH_ACK) { 949 syncache_badack(&inc); 950 tcpstat.tcps_badsyn++; 951 rstreason = BANDLIM_RST_OPENPORT; 952 goto dropwithreset; 953 } 954 goto drop; 955 } 956 957 /* 958 * Segment's flags are (SYN) or (SYN | FIN). 959 */ 960 #ifdef INET6 961 /* 962 * If deprecated address is forbidden, 963 * we do not accept SYN to deprecated interface 964 * address to prevent any new inbound connection from 965 * getting established. 966 * When we do not accept SYN, we send a TCP RST, 967 * with deprecated source address (instead of dropping 968 * it). We compromise it as it is much better for peer 969 * to send a RST, and RST will be the final packet 970 * for the exchange. 971 * 972 * If we do not forbid deprecated addresses, we accept 973 * the SYN packet. RFC2462 does not suggest dropping 974 * SYN in this case. 975 * If we decipher RFC2462 5.5.4, it says like this: 976 * 1. use of deprecated addr with existing 977 * communication is okay - "SHOULD continue to be 978 * used" 979 * 2. use of it with new communication: 980 * (2a) "SHOULD NOT be used if alternate address 981 * with sufficient scope is available" 982 * (2b) nothing mentioned otherwise. 983 * Here we fall into (2b) case as we have no choice in 984 * our source address selection - we must obey the peer. 985 * 986 * The wording in RFC2462 is confusing, and there are 987 * multiple description text for deprecated address 988 * handling - worse, they are not exactly the same. 989 * I believe 5.5.4 is the best one, so we follow 5.5.4. 990 */ 991 if (isipv6 && !ip6_use_deprecated) { 992 struct in6_ifaddr *ia6; 993 994 if ((ia6 = ip6_getdstifaddr(m)) && 995 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 996 tp = NULL; 997 rstreason = BANDLIM_RST_OPENPORT; 998 goto dropwithreset; 999 } 1000 } 1001 #endif 1002 /* 1003 * If it is from this socket, drop it, it must be forged. 1004 * Don't bother responding if the destination was a broadcast. 1005 */ 1006 if (th->th_dport == th->th_sport) { 1007 if (isipv6) { 1008 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1009 &ip6->ip6_src)) 1010 goto drop; 1011 } else { 1012 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1013 goto drop; 1014 } 1015 } 1016 /* 1017 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1018 * 1019 * Note that it is quite possible to receive unicast 1020 * link-layer packets with a broadcast IP address. Use 1021 * in_broadcast() to find them. 1022 */ 1023 if (m->m_flags & (M_BCAST | M_MCAST)) 1024 goto drop; 1025 if (isipv6) { 1026 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1027 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1028 goto drop; 1029 } else { 1030 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1031 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1032 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1033 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1034 goto drop; 1035 } 1036 /* 1037 * SYN appears to be valid; create compressed TCP state 1038 * for syncache, or perform t/tcp connection. 1039 */ 1040 if (so->so_qlen <= so->so_qlimit) { 1041 tcp_dooptions(&to, optp, optlen, TRUE); 1042 if (!syncache_add(&inc, &to, th, so, m)) 1043 goto drop; 1044 1045 /* 1046 * Entry added to syncache, mbuf used to 1047 * send SYN,ACK packet. 1048 */ 1049 return(IPPROTO_DONE); 1050 } 1051 goto drop; 1052 } 1053 1054 after_listen: 1055 /* 1056 * Should not happen - syncache should pick up these connections. 1057 * 1058 * Once we are past handling listen sockets we must be in the 1059 * correct protocol processing thread. 1060 */ 1061 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1062 KKASSERT(so->so_port == &curthread->td_msgport); 1063 1064 /* 1065 * This is the second part of the MSS DoS prevention code (after 1066 * minmss on the sending side) and it deals with too many too small 1067 * tcp packets in a too short timeframe (1 second). 1068 * 1069 * XXX Removed. This code was crap. It does not scale to network 1070 * speed, and default values break NFS. Gone. 1071 */ 1072 /* REMOVED */ 1073 1074 /* 1075 * Segment received on connection. 1076 * 1077 * Reset idle time and keep-alive timer. Don't waste time if less 1078 * then a second has elapsed. 1079 */ 1080 if ((int)(ticks - tp->t_rcvtime) > hz) 1081 tcp_timer_keep_activity(tp, thflags); 1082 1083 /* 1084 * Process options. 1085 * XXX this is tradtitional behavior, may need to be cleaned up. 1086 */ 1087 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1088 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1089 if (to.to_flags & TOF_SCALE) { 1090 tp->t_flags |= TF_RCVD_SCALE; 1091 tp->requested_s_scale = to.to_requested_s_scale; 1092 } 1093 if (to.to_flags & TOF_TS) { 1094 tp->t_flags |= TF_RCVD_TSTMP; 1095 tp->ts_recent = to.to_tsval; 1096 tp->ts_recent_age = ticks; 1097 } 1098 if (!(to.to_flags & TOF_MSS)) 1099 to.to_mss = 0; 1100 tcp_mss(tp, to.to_mss); 1101 /* 1102 * Only set the TF_SACK_PERMITTED per-connection flag 1103 * if we got a SACK_PERMITTED option from the other side 1104 * and the global tcp_do_sack variable is true. 1105 */ 1106 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1107 tp->t_flags |= TF_SACK_PERMITTED; 1108 } 1109 1110 /* 1111 * Header prediction: check for the two common cases 1112 * of a uni-directional data xfer. If the packet has 1113 * no control flags, is in-sequence, the window didn't 1114 * change and we're not retransmitting, it's a 1115 * candidate. If the length is zero and the ack moved 1116 * forward, we're the sender side of the xfer. Just 1117 * free the data acked & wake any higher level process 1118 * that was blocked waiting for space. If the length 1119 * is non-zero and the ack didn't move, we're the 1120 * receiver side. If we're getting packets in-order 1121 * (the reassembly queue is empty), add the data to 1122 * the socket buffer and note that we need a delayed ack. 1123 * Make sure that the hidden state-flags are also off. 1124 * Since we check for TCPS_ESTABLISHED above, it can only 1125 * be TH_NEEDSYN. 1126 */ 1127 if (tp->t_state == TCPS_ESTABLISHED && 1128 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1129 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1130 (!(to.to_flags & TOF_TS) || 1131 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1132 th->th_seq == tp->rcv_nxt && 1133 tp->snd_nxt == tp->snd_max) { 1134 1135 /* 1136 * If last ACK falls within this segment's sequence numbers, 1137 * record the timestamp. 1138 * NOTE that the test is modified according to the latest 1139 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1140 */ 1141 if ((to.to_flags & TOF_TS) && 1142 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1143 tp->ts_recent_age = ticks; 1144 tp->ts_recent = to.to_tsval; 1145 } 1146 1147 if (tlen == 0) { 1148 if (SEQ_GT(th->th_ack, tp->snd_una) && 1149 SEQ_LEQ(th->th_ack, tp->snd_max) && 1150 tp->snd_cwnd >= tp->snd_wnd && 1151 !IN_FASTRECOVERY(tp)) { 1152 /* 1153 * This is a pure ack for outstanding data. 1154 */ 1155 ++tcpstat.tcps_predack; 1156 /* 1157 * "bad retransmit" recovery 1158 * 1159 * If Eifel detection applies, then 1160 * it is deterministic, so use it 1161 * unconditionally over the old heuristic. 1162 * Otherwise, fall back to the old heuristic. 1163 */ 1164 if (tcp_do_eifel_detect && 1165 (to.to_flags & TOF_TS) && to.to_tsecr && 1166 (tp->t_flags & TF_FIRSTACCACK)) { 1167 /* Eifel detection applicable. */ 1168 if (to.to_tsecr < tp->t_rexmtTS) { 1169 tcp_revert_congestion_state(tp); 1170 ++tcpstat.tcps_eifeldetected; 1171 if (tp->t_rxtshift != 1 || 1172 ticks >= tp->t_badrxtwin) 1173 ++tcpstat.tcps_rttcantdetect; 1174 } 1175 } else if (tp->t_rxtshift == 1 && 1176 ticks < tp->t_badrxtwin) { 1177 tcp_revert_congestion_state(tp); 1178 ++tcpstat.tcps_rttdetected; 1179 } 1180 tp->t_flags &= ~(TF_FIRSTACCACK | 1181 TF_FASTREXMT | TF_EARLYREXMT); 1182 /* 1183 * Recalculate the retransmit timer / rtt. 1184 * 1185 * Some machines (certain windows boxes) 1186 * send broken timestamp replies during the 1187 * SYN+ACK phase, ignore timestamps of 0. 1188 */ 1189 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1190 tcp_xmit_timer(tp, 1191 ticks - to.to_tsecr + 1); 1192 } else if (tp->t_rtttime && 1193 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1194 tcp_xmit_timer(tp, 1195 ticks - tp->t_rtttime); 1196 } 1197 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1198 acked = th->th_ack - tp->snd_una; 1199 tcpstat.tcps_rcvackpack++; 1200 tcpstat.tcps_rcvackbyte += acked; 1201 sbdrop(&so->so_snd.sb, acked); 1202 tp->snd_recover = th->th_ack - 1; 1203 tp->snd_una = th->th_ack; 1204 tp->t_dupacks = 0; 1205 /* 1206 * Update window information. 1207 */ 1208 if (tiwin != tp->snd_wnd && 1209 acceptable_window_update(tp, th, tiwin)) { 1210 /* keep track of pure window updates */ 1211 if (tp->snd_wl2 == th->th_ack && 1212 tiwin > tp->snd_wnd) 1213 tcpstat.tcps_rcvwinupd++; 1214 tp->snd_wnd = tiwin; 1215 tp->snd_wl1 = th->th_seq; 1216 tp->snd_wl2 = th->th_ack; 1217 if (tp->snd_wnd > tp->max_sndwnd) 1218 tp->max_sndwnd = tp->snd_wnd; 1219 } 1220 m_freem(m); 1221 ND6_HINT(tp); /* some progress has been done */ 1222 /* 1223 * If all outstanding data are acked, stop 1224 * retransmit timer, otherwise restart timer 1225 * using current (possibly backed-off) value. 1226 * If process is waiting for space, 1227 * wakeup/selwakeup/signal. If data 1228 * are ready to send, let tcp_output 1229 * decide between more output or persist. 1230 */ 1231 if (tp->snd_una == tp->snd_max) { 1232 tcp_callout_stop(tp, tp->tt_rexmt); 1233 } else if (!tcp_callout_active(tp, 1234 tp->tt_persist)) { 1235 tcp_callout_reset(tp, tp->tt_rexmt, 1236 tp->t_rxtcur, tcp_timer_rexmt); 1237 } 1238 sowwakeup(so); 1239 if (so->so_snd.ssb_cc > 0) 1240 tcp_output(tp); 1241 return(IPPROTO_DONE); 1242 } 1243 } else if (tiwin == tp->snd_wnd && 1244 th->th_ack == tp->snd_una && 1245 LIST_EMPTY(&tp->t_segq) && 1246 tlen <= ssb_space(&so->so_rcv)) { 1247 u_long newsize = 0; /* automatic sockbuf scaling */ 1248 /* 1249 * This is a pure, in-sequence data packet 1250 * with nothing on the reassembly queue and 1251 * we have enough buffer space to take it. 1252 */ 1253 ++tcpstat.tcps_preddat; 1254 tp->rcv_nxt += tlen; 1255 tcpstat.tcps_rcvpack++; 1256 tcpstat.tcps_rcvbyte += tlen; 1257 ND6_HINT(tp); /* some progress has been done */ 1258 /* 1259 * Automatic sizing of receive socket buffer. Often the send 1260 * buffer size is not optimally adjusted to the actual network 1261 * conditions at hand (delay bandwidth product). Setting the 1262 * buffer size too small limits throughput on links with high 1263 * bandwidth and high delay (eg. trans-continental/oceanic links). 1264 * 1265 * On the receive side the socket buffer memory is only rarely 1266 * used to any significant extent. This allows us to be much 1267 * more aggressive in scaling the receive socket buffer. For 1268 * the case that the buffer space is actually used to a large 1269 * extent and we run out of kernel memory we can simply drop 1270 * the new segments; TCP on the sender will just retransmit it 1271 * later. Setting the buffer size too big may only consume too 1272 * much kernel memory if the application doesn't read() from 1273 * the socket or packet loss or reordering makes use of the 1274 * reassembly queue. 1275 * 1276 * The criteria to step up the receive buffer one notch are: 1277 * 1. the number of bytes received during the time it takes 1278 * one timestamp to be reflected back to us (the RTT); 1279 * 2. received bytes per RTT is within seven eighth of the 1280 * current socket buffer size; 1281 * 3. receive buffer size has not hit maximal automatic size; 1282 * 1283 * This algorithm does one step per RTT at most and only if 1284 * we receive a bulk stream w/o packet losses or reorderings. 1285 * Shrinking the buffer during idle times is not necessary as 1286 * it doesn't consume any memory when idle. 1287 * 1288 * TODO: Only step up if the application is actually serving 1289 * the buffer to better manage the socket buffer resources. 1290 */ 1291 if (tcp_do_autorcvbuf && 1292 to.to_tsecr && 1293 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1294 if (to.to_tsecr > tp->rfbuf_ts && 1295 to.to_tsecr - tp->rfbuf_ts < hz) { 1296 if (tp->rfbuf_cnt > 1297 (so->so_rcv.ssb_hiwat / 8 * 7) && 1298 so->so_rcv.ssb_hiwat < 1299 tcp_autorcvbuf_max) { 1300 newsize = 1301 ulmin(so->so_rcv.ssb_hiwat + 1302 tcp_autorcvbuf_inc, 1303 tcp_autorcvbuf_max); 1304 } 1305 /* Start over with next RTT. */ 1306 tp->rfbuf_ts = 0; 1307 tp->rfbuf_cnt = 0; 1308 } else 1309 tp->rfbuf_cnt += tlen; /* add up */ 1310 } 1311 /* 1312 * Add data to socket buffer. 1313 */ 1314 if (so->so_state & SS_CANTRCVMORE) { 1315 m_freem(m); 1316 } else { 1317 /* 1318 * Set new socket buffer size, give up when 1319 * limit is reached. 1320 * 1321 * Adjusting the size can mess up ACK 1322 * sequencing when pure window updates are 1323 * being avoided (which is the default), 1324 * so force an ack. 1325 */ 1326 lwkt_gettoken(&so->so_rcv.ssb_token); 1327 if (newsize) { 1328 tp->t_flags |= TF_RXRESIZED; 1329 if (!ssb_reserve(&so->so_rcv, newsize, 1330 so, NULL)) { 1331 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1332 } 1333 if (newsize >= 1334 (TCP_MAXWIN << tp->rcv_scale)) { 1335 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1336 } 1337 } 1338 m_adj(m, drop_hdrlen); /* delayed header drop */ 1339 ssb_appendstream(&so->so_rcv, m); 1340 lwkt_reltoken(&so->so_rcv.ssb_token); 1341 } 1342 sorwakeup(so); 1343 /* 1344 * This code is responsible for most of the ACKs 1345 * the TCP stack sends back after receiving a data 1346 * packet. Note that the DELAY_ACK check fails if 1347 * the delack timer is already running, which results 1348 * in an ack being sent every other packet (which is 1349 * what we want). 1350 * 1351 * We then further aggregate acks by not actually 1352 * sending one until the protocol thread has completed 1353 * processing the current backlog of packets. This 1354 * does not delay the ack any further, but allows us 1355 * to take advantage of the packet aggregation that 1356 * high speed NICs do (usually blocks of 8-10 packets) 1357 * to send a single ack rather then four or five acks, 1358 * greatly reducing the ack rate, the return channel 1359 * bandwidth, and the protocol overhead on both ends. 1360 * 1361 * Since this also has the effect of slowing down 1362 * the exponential slow-start ramp-up, systems with 1363 * very large bandwidth-delay products might want 1364 * to turn the feature off. 1365 */ 1366 if (DELAY_ACK(tp)) { 1367 tcp_callout_reset(tp, tp->tt_delack, 1368 tcp_delacktime, tcp_timer_delack); 1369 } else if (tcp_aggregate_acks) { 1370 tp->t_flags |= TF_ACKNOW; 1371 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1372 tp->t_flags |= TF_ONOUTPUTQ; 1373 tp->tt_cpu = mycpu->gd_cpuid; 1374 TAILQ_INSERT_TAIL( 1375 &tcpcbackq[tp->tt_cpu], 1376 tp, t_outputq); 1377 } 1378 } else { 1379 tp->t_flags |= TF_ACKNOW; 1380 tcp_output(tp); 1381 } 1382 return(IPPROTO_DONE); 1383 } 1384 } 1385 1386 /* 1387 * Calculate amount of space in receive window, 1388 * and then do TCP input processing. 1389 * Receive window is amount of space in rcv queue, 1390 * but not less than advertised window. 1391 */ 1392 recvwin = ssb_space(&so->so_rcv); 1393 if (recvwin < 0) 1394 recvwin = 0; 1395 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1396 1397 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1398 tp->rfbuf_ts = 0; 1399 tp->rfbuf_cnt = 0; 1400 1401 switch (tp->t_state) { 1402 /* 1403 * If the state is SYN_RECEIVED: 1404 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1405 */ 1406 case TCPS_SYN_RECEIVED: 1407 if ((thflags & TH_ACK) && 1408 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1409 SEQ_GT(th->th_ack, tp->snd_max))) { 1410 rstreason = BANDLIM_RST_OPENPORT; 1411 goto dropwithreset; 1412 } 1413 break; 1414 1415 /* 1416 * If the state is SYN_SENT: 1417 * if seg contains an ACK, but not for our SYN, drop the input. 1418 * if seg contains a RST, then drop the connection. 1419 * if seg does not contain SYN, then drop it. 1420 * Otherwise this is an acceptable SYN segment 1421 * initialize tp->rcv_nxt and tp->irs 1422 * if seg contains ack then advance tp->snd_una 1423 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1424 * arrange for segment to be acked (eventually) 1425 * continue processing rest of data/controls, beginning with URG 1426 */ 1427 case TCPS_SYN_SENT: 1428 if ((thflags & TH_ACK) && 1429 (SEQ_LEQ(th->th_ack, tp->iss) || 1430 SEQ_GT(th->th_ack, tp->snd_max))) { 1431 rstreason = BANDLIM_UNLIMITED; 1432 goto dropwithreset; 1433 } 1434 if (thflags & TH_RST) { 1435 if (thflags & TH_ACK) 1436 tp = tcp_drop(tp, ECONNREFUSED); 1437 goto drop; 1438 } 1439 if (!(thflags & TH_SYN)) 1440 goto drop; 1441 tp->snd_wnd = th->th_win; /* initial send window */ 1442 1443 tp->irs = th->th_seq; 1444 tcp_rcvseqinit(tp); 1445 if (thflags & TH_ACK) { 1446 /* Our SYN was acked. */ 1447 tcpstat.tcps_connects++; 1448 soisconnected(so); 1449 /* Do window scaling on this connection? */ 1450 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1451 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1452 tp->snd_scale = tp->requested_s_scale; 1453 tp->rcv_scale = tp->request_r_scale; 1454 } 1455 tp->rcv_adv += tp->rcv_wnd; 1456 tp->snd_una++; /* SYN is acked */ 1457 tcp_callout_stop(tp, tp->tt_rexmt); 1458 /* 1459 * If there's data, delay ACK; if there's also a FIN 1460 * ACKNOW will be turned on later. 1461 */ 1462 if (DELAY_ACK(tp) && tlen != 0) { 1463 tcp_callout_reset(tp, tp->tt_delack, 1464 tcp_delacktime, tcp_timer_delack); 1465 } else { 1466 tp->t_flags |= TF_ACKNOW; 1467 } 1468 /* 1469 * Received <SYN,ACK> in SYN_SENT[*] state. 1470 * Transitions: 1471 * SYN_SENT --> ESTABLISHED 1472 * SYN_SENT* --> FIN_WAIT_1 1473 */ 1474 tp->t_starttime = ticks; 1475 if (tp->t_flags & TF_NEEDFIN) { 1476 tp->t_state = TCPS_FIN_WAIT_1; 1477 tp->t_flags &= ~TF_NEEDFIN; 1478 thflags &= ~TH_SYN; 1479 } else { 1480 tcp_established(tp); 1481 } 1482 } else { 1483 /* 1484 * Received initial SYN in SYN-SENT[*] state => 1485 * simultaneous open. 1486 * Do 3-way handshake: 1487 * SYN-SENT -> SYN-RECEIVED 1488 * SYN-SENT* -> SYN-RECEIVED* 1489 */ 1490 tp->t_flags |= TF_ACKNOW; 1491 tcp_callout_stop(tp, tp->tt_rexmt); 1492 tp->t_state = TCPS_SYN_RECEIVED; 1493 } 1494 1495 /* 1496 * Advance th->th_seq to correspond to first data byte. 1497 * If data, trim to stay within window, 1498 * dropping FIN if necessary. 1499 */ 1500 th->th_seq++; 1501 if (tlen > tp->rcv_wnd) { 1502 todrop = tlen - tp->rcv_wnd; 1503 m_adj(m, -todrop); 1504 tlen = tp->rcv_wnd; 1505 thflags &= ~TH_FIN; 1506 tcpstat.tcps_rcvpackafterwin++; 1507 tcpstat.tcps_rcvbyteafterwin += todrop; 1508 } 1509 tp->snd_wl1 = th->th_seq - 1; 1510 tp->rcv_up = th->th_seq; 1511 /* 1512 * Client side of transaction: already sent SYN and data. 1513 * If the remote host used T/TCP to validate the SYN, 1514 * our data will be ACK'd; if so, enter normal data segment 1515 * processing in the middle of step 5, ack processing. 1516 * Otherwise, goto step 6. 1517 */ 1518 if (thflags & TH_ACK) 1519 goto process_ACK; 1520 1521 goto step6; 1522 1523 /* 1524 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1525 * do normal processing (we no longer bother with T/TCP). 1526 */ 1527 case TCPS_LAST_ACK: 1528 case TCPS_CLOSING: 1529 case TCPS_TIME_WAIT: 1530 break; /* continue normal processing */ 1531 } 1532 1533 /* 1534 * States other than LISTEN or SYN_SENT. 1535 * First check the RST flag and sequence number since reset segments 1536 * are exempt from the timestamp and connection count tests. This 1537 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1538 * below which allowed reset segments in half the sequence space 1539 * to fall though and be processed (which gives forged reset 1540 * segments with a random sequence number a 50 percent chance of 1541 * killing a connection). 1542 * Then check timestamp, if present. 1543 * Then check the connection count, if present. 1544 * Then check that at least some bytes of segment are within 1545 * receive window. If segment begins before rcv_nxt, 1546 * drop leading data (and SYN); if nothing left, just ack. 1547 * 1548 * 1549 * If the RST bit is set, check the sequence number to see 1550 * if this is a valid reset segment. 1551 * RFC 793 page 37: 1552 * In all states except SYN-SENT, all reset (RST) segments 1553 * are validated by checking their SEQ-fields. A reset is 1554 * valid if its sequence number is in the window. 1555 * Note: this does not take into account delayed ACKs, so 1556 * we should test against last_ack_sent instead of rcv_nxt. 1557 * The sequence number in the reset segment is normally an 1558 * echo of our outgoing acknowledgement numbers, but some hosts 1559 * send a reset with the sequence number at the rightmost edge 1560 * of our receive window, and we have to handle this case. 1561 * If we have multiple segments in flight, the intial reset 1562 * segment sequence numbers will be to the left of last_ack_sent, 1563 * but they will eventually catch up. 1564 * In any case, it never made sense to trim reset segments to 1565 * fit the receive window since RFC 1122 says: 1566 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1567 * 1568 * A TCP SHOULD allow a received RST segment to include data. 1569 * 1570 * DISCUSSION 1571 * It has been suggested that a RST segment could contain 1572 * ASCII text that encoded and explained the cause of the 1573 * RST. No standard has yet been established for such 1574 * data. 1575 * 1576 * If the reset segment passes the sequence number test examine 1577 * the state: 1578 * SYN_RECEIVED STATE: 1579 * If passive open, return to LISTEN state. 1580 * If active open, inform user that connection was refused. 1581 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1582 * Inform user that connection was reset, and close tcb. 1583 * CLOSING, LAST_ACK STATES: 1584 * Close the tcb. 1585 * TIME_WAIT STATE: 1586 * Drop the segment - see Stevens, vol. 2, p. 964 and 1587 * RFC 1337. 1588 */ 1589 if (thflags & TH_RST) { 1590 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1591 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1592 switch (tp->t_state) { 1593 1594 case TCPS_SYN_RECEIVED: 1595 so->so_error = ECONNREFUSED; 1596 goto close; 1597 1598 case TCPS_ESTABLISHED: 1599 case TCPS_FIN_WAIT_1: 1600 case TCPS_FIN_WAIT_2: 1601 case TCPS_CLOSE_WAIT: 1602 so->so_error = ECONNRESET; 1603 close: 1604 tp->t_state = TCPS_CLOSED; 1605 tcpstat.tcps_drops++; 1606 tp = tcp_close(tp); 1607 break; 1608 1609 case TCPS_CLOSING: 1610 case TCPS_LAST_ACK: 1611 tp = tcp_close(tp); 1612 break; 1613 1614 case TCPS_TIME_WAIT: 1615 break; 1616 } 1617 } 1618 goto drop; 1619 } 1620 1621 /* 1622 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1623 * and it's less than ts_recent, drop it. 1624 */ 1625 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1626 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1627 1628 /* Check to see if ts_recent is over 24 days old. */ 1629 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1630 /* 1631 * Invalidate ts_recent. If this segment updates 1632 * ts_recent, the age will be reset later and ts_recent 1633 * will get a valid value. If it does not, setting 1634 * ts_recent to zero will at least satisfy the 1635 * requirement that zero be placed in the timestamp 1636 * echo reply when ts_recent isn't valid. The 1637 * age isn't reset until we get a valid ts_recent 1638 * because we don't want out-of-order segments to be 1639 * dropped when ts_recent is old. 1640 */ 1641 tp->ts_recent = 0; 1642 } else { 1643 tcpstat.tcps_rcvduppack++; 1644 tcpstat.tcps_rcvdupbyte += tlen; 1645 tcpstat.tcps_pawsdrop++; 1646 if (tlen) 1647 goto dropafterack; 1648 goto drop; 1649 } 1650 } 1651 1652 /* 1653 * In the SYN-RECEIVED state, validate that the packet belongs to 1654 * this connection before trimming the data to fit the receive 1655 * window. Check the sequence number versus IRS since we know 1656 * the sequence numbers haven't wrapped. This is a partial fix 1657 * for the "LAND" DoS attack. 1658 */ 1659 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1660 rstreason = BANDLIM_RST_OPENPORT; 1661 goto dropwithreset; 1662 } 1663 1664 todrop = tp->rcv_nxt - th->th_seq; 1665 if (todrop > 0) { 1666 if (TCP_DO_SACK(tp)) { 1667 /* Report duplicate segment at head of packet. */ 1668 tp->reportblk.rblk_start = th->th_seq; 1669 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 1670 th->th_seq + tlen, thflags); 1671 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1672 tp->reportblk.rblk_end = tp->rcv_nxt; 1673 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1674 } 1675 if (thflags & TH_SYN) { 1676 thflags &= ~TH_SYN; 1677 th->th_seq++; 1678 if (th->th_urp > 1) 1679 th->th_urp--; 1680 else 1681 thflags &= ~TH_URG; 1682 todrop--; 1683 } 1684 /* 1685 * Following if statement from Stevens, vol. 2, p. 960. 1686 */ 1687 if (todrop > tlen || 1688 (todrop == tlen && !(thflags & TH_FIN))) { 1689 /* 1690 * Any valid FIN must be to the left of the window. 1691 * At this point the FIN must be a duplicate or out 1692 * of sequence; drop it. 1693 */ 1694 thflags &= ~TH_FIN; 1695 1696 /* 1697 * Send an ACK to resynchronize and drop any data. 1698 * But keep on processing for RST or ACK. 1699 */ 1700 tp->t_flags |= TF_ACKNOW; 1701 todrop = tlen; 1702 tcpstat.tcps_rcvduppack++; 1703 tcpstat.tcps_rcvdupbyte += todrop; 1704 } else { 1705 tcpstat.tcps_rcvpartduppack++; 1706 tcpstat.tcps_rcvpartdupbyte += todrop; 1707 } 1708 drop_hdrlen += todrop; /* drop from the top afterwards */ 1709 th->th_seq += todrop; 1710 tlen -= todrop; 1711 if (th->th_urp > todrop) 1712 th->th_urp -= todrop; 1713 else { 1714 thflags &= ~TH_URG; 1715 th->th_urp = 0; 1716 } 1717 } 1718 1719 /* 1720 * If new data are received on a connection after the 1721 * user processes are gone, then RST the other end. 1722 */ 1723 if ((so->so_state & SS_NOFDREF) && 1724 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1725 tp = tcp_close(tp); 1726 tcpstat.tcps_rcvafterclose++; 1727 rstreason = BANDLIM_UNLIMITED; 1728 goto dropwithreset; 1729 } 1730 1731 /* 1732 * If segment ends after window, drop trailing data 1733 * (and PUSH and FIN); if nothing left, just ACK. 1734 */ 1735 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1736 if (todrop > 0) { 1737 tcpstat.tcps_rcvpackafterwin++; 1738 if (todrop >= tlen) { 1739 tcpstat.tcps_rcvbyteafterwin += tlen; 1740 /* 1741 * If a new connection request is received 1742 * while in TIME_WAIT, drop the old connection 1743 * and start over if the sequence numbers 1744 * are above the previous ones. 1745 */ 1746 if (thflags & TH_SYN && 1747 tp->t_state == TCPS_TIME_WAIT && 1748 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1749 tp = tcp_close(tp); 1750 goto findpcb; 1751 } 1752 /* 1753 * If window is closed can only take segments at 1754 * window edge, and have to drop data and PUSH from 1755 * incoming segments. Continue processing, but 1756 * remember to ack. Otherwise, drop segment 1757 * and ack. 1758 */ 1759 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1760 tp->t_flags |= TF_ACKNOW; 1761 tcpstat.tcps_rcvwinprobe++; 1762 } else 1763 goto dropafterack; 1764 } else 1765 tcpstat.tcps_rcvbyteafterwin += todrop; 1766 m_adj(m, -todrop); 1767 tlen -= todrop; 1768 thflags &= ~(TH_PUSH | TH_FIN); 1769 } 1770 1771 /* 1772 * If last ACK falls within this segment's sequence numbers, 1773 * record its timestamp. 1774 * NOTE: 1775 * 1) That the test incorporates suggestions from the latest 1776 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1777 * 2) That updating only on newer timestamps interferes with 1778 * our earlier PAWS tests, so this check should be solely 1779 * predicated on the sequence space of this segment. 1780 * 3) That we modify the segment boundary check to be 1781 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1782 * instead of RFC1323's 1783 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1784 * This modified check allows us to overcome RFC1323's 1785 * limitations as described in Stevens TCP/IP Illustrated 1786 * Vol. 2 p.869. In such cases, we can still calculate the 1787 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1788 */ 1789 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1790 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1791 + ((thflags & TH_SYN) != 0) 1792 + ((thflags & TH_FIN) != 0)))) { 1793 tp->ts_recent_age = ticks; 1794 tp->ts_recent = to.to_tsval; 1795 } 1796 1797 /* 1798 * If a SYN is in the window, then this is an 1799 * error and we send an RST and drop the connection. 1800 */ 1801 if (thflags & TH_SYN) { 1802 tp = tcp_drop(tp, ECONNRESET); 1803 rstreason = BANDLIM_UNLIMITED; 1804 goto dropwithreset; 1805 } 1806 1807 /* 1808 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1809 * flag is on (half-synchronized state), then queue data for 1810 * later processing; else drop segment and return. 1811 */ 1812 if (!(thflags & TH_ACK)) { 1813 if (tp->t_state == TCPS_SYN_RECEIVED || 1814 (tp->t_flags & TF_NEEDSYN)) 1815 goto step6; 1816 else 1817 goto drop; 1818 } 1819 1820 /* 1821 * Ack processing. 1822 */ 1823 switch (tp->t_state) { 1824 /* 1825 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1826 * ESTABLISHED state and continue processing. 1827 * The ACK was checked above. 1828 */ 1829 case TCPS_SYN_RECEIVED: 1830 1831 tcpstat.tcps_connects++; 1832 soisconnected(so); 1833 /* Do window scaling? */ 1834 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1835 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1836 tp->snd_scale = tp->requested_s_scale; 1837 tp->rcv_scale = tp->request_r_scale; 1838 } 1839 /* 1840 * Make transitions: 1841 * SYN-RECEIVED -> ESTABLISHED 1842 * SYN-RECEIVED* -> FIN-WAIT-1 1843 */ 1844 tp->t_starttime = ticks; 1845 if (tp->t_flags & TF_NEEDFIN) { 1846 tp->t_state = TCPS_FIN_WAIT_1; 1847 tp->t_flags &= ~TF_NEEDFIN; 1848 } else { 1849 tcp_established(tp); 1850 } 1851 /* 1852 * If segment contains data or ACK, will call tcp_reass() 1853 * later; if not, do so now to pass queued data to user. 1854 */ 1855 if (tlen == 0 && !(thflags & TH_FIN)) 1856 tcp_reass(tp, NULL, NULL, NULL); 1857 /* fall into ... */ 1858 1859 /* 1860 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1861 * ACKs. If the ack is in the range 1862 * tp->snd_una < th->th_ack <= tp->snd_max 1863 * then advance tp->snd_una to th->th_ack and drop 1864 * data from the retransmission queue. If this ACK reflects 1865 * more up to date window information we update our window information. 1866 */ 1867 case TCPS_ESTABLISHED: 1868 case TCPS_FIN_WAIT_1: 1869 case TCPS_FIN_WAIT_2: 1870 case TCPS_CLOSE_WAIT: 1871 case TCPS_CLOSING: 1872 case TCPS_LAST_ACK: 1873 case TCPS_TIME_WAIT: 1874 1875 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1876 if (TCP_DO_SACK(tp)) 1877 tcp_sack_update_scoreboard(tp, &to); 1878 if (tlen != 0 || tiwin != tp->snd_wnd) { 1879 tp->t_dupacks = 0; 1880 break; 1881 } 1882 tcpstat.tcps_rcvdupack++; 1883 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1884 th->th_ack != tp->snd_una) { 1885 tp->t_dupacks = 0; 1886 break; 1887 } 1888 /* 1889 * We have outstanding data (other than 1890 * a window probe), this is a completely 1891 * duplicate ack (ie, window info didn't 1892 * change), the ack is the biggest we've 1893 * seen and we've seen exactly our rexmt 1894 * threshhold of them, so assume a packet 1895 * has been dropped and retransmit it. 1896 * Kludge snd_nxt & the congestion 1897 * window so we send only this one 1898 * packet. 1899 */ 1900 if (IN_FASTRECOVERY(tp)) { 1901 if (TCP_DO_SACK(tp)) { 1902 /* No artifical cwnd inflation. */ 1903 tcp_sack_rexmt(tp, th); 1904 } else { 1905 /* 1906 * Dup acks mean that packets 1907 * have left the network 1908 * (they're now cached at the 1909 * receiver) so bump cwnd by 1910 * the amount in the receiver 1911 * to keep a constant cwnd 1912 * packets in the network. 1913 */ 1914 tp->snd_cwnd += tp->t_maxseg; 1915 tcp_output(tp); 1916 } 1917 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1918 tp->t_dupacks = 0; 1919 break; 1920 } else if (++tp->t_dupacks == tcprexmtthresh) { 1921 tcp_seq old_snd_nxt; 1922 u_int win; 1923 1924 fastretransmit: 1925 if (tcp_do_eifel_detect && 1926 (tp->t_flags & TF_RCVD_TSTMP)) { 1927 tcp_save_congestion_state(tp); 1928 tp->t_flags |= TF_FASTREXMT; 1929 } 1930 /* 1931 * We know we're losing at the current 1932 * window size, so do congestion avoidance: 1933 * set ssthresh to half the current window 1934 * and pull our congestion window back to the 1935 * new ssthresh. 1936 */ 1937 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1938 tp->t_maxseg; 1939 if (win < 2) 1940 win = 2; 1941 tp->snd_ssthresh = win * tp->t_maxseg; 1942 ENTER_FASTRECOVERY(tp); 1943 tp->snd_recover = tp->snd_max; 1944 tcp_callout_stop(tp, tp->tt_rexmt); 1945 tp->t_rtttime = 0; 1946 old_snd_nxt = tp->snd_nxt; 1947 tp->snd_nxt = th->th_ack; 1948 tp->snd_cwnd = tp->t_maxseg; 1949 tcp_output(tp); 1950 ++tcpstat.tcps_sndfastrexmit; 1951 tp->snd_cwnd = tp->snd_ssthresh; 1952 tp->rexmt_high = tp->snd_nxt; 1953 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1954 tp->snd_nxt = old_snd_nxt; 1955 KASSERT(tp->snd_limited <= 2, 1956 ("tp->snd_limited too big")); 1957 if (TCP_DO_SACK(tp)) 1958 tcp_sack_rexmt(tp, th); 1959 else 1960 tp->snd_cwnd += tp->t_maxseg * 1961 (tp->t_dupacks - tp->snd_limited); 1962 } else if (tcp_do_limitedtransmit) { 1963 u_long oldcwnd = tp->snd_cwnd; 1964 tcp_seq oldsndmax = tp->snd_max; 1965 tcp_seq oldsndnxt = tp->snd_nxt; 1966 /* outstanding data */ 1967 uint32_t ownd = tp->snd_max - tp->snd_una; 1968 u_int sent; 1969 1970 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1971 1972 KASSERT(tp->t_dupacks == 1 || 1973 tp->t_dupacks == 2, 1974 ("dupacks not 1 or 2")); 1975 if (tp->t_dupacks == 1) 1976 tp->snd_limited = 0; 1977 tp->snd_nxt = tp->snd_max; 1978 tp->snd_cwnd = ownd + 1979 (tp->t_dupacks - tp->snd_limited) * 1980 tp->t_maxseg; 1981 tcp_output(tp); 1982 1983 if (SEQ_LT(oldsndnxt, oldsndmax)) { 1984 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 1985 ("snd_una moved in other threads")); 1986 tp->snd_nxt = oldsndnxt; 1987 } 1988 tp->snd_cwnd = oldcwnd; 1989 sent = tp->snd_max - oldsndmax; 1990 if (sent > tp->t_maxseg) { 1991 KASSERT((tp->t_dupacks == 2 && 1992 tp->snd_limited == 0) || 1993 (sent == tp->t_maxseg + 1 && 1994 tp->t_flags & TF_SENTFIN), 1995 ("sent too much")); 1996 KASSERT(sent <= tp->t_maxseg * 2, 1997 ("sent too many segments")); 1998 tp->snd_limited = 2; 1999 tcpstat.tcps_sndlimited += 2; 2000 } else if (sent > 0) { 2001 ++tp->snd_limited; 2002 ++tcpstat.tcps_sndlimited; 2003 } else if (tcp_do_early_retransmit && 2004 (tcp_do_eifel_detect && 2005 (tp->t_flags & TF_RCVD_TSTMP)) && 2006 ownd < 4 * tp->t_maxseg && 2007 tp->t_dupacks + 1 >= 2008 iceildiv(ownd, tp->t_maxseg) && 2009 (!TCP_DO_SACK(tp) || 2010 ownd <= tp->t_maxseg || 2011 tcp_sack_has_sacked(&tp->scb, 2012 ownd - tp->t_maxseg))) { 2013 ++tcpstat.tcps_sndearlyrexmit; 2014 tp->t_flags |= TF_EARLYREXMT; 2015 goto fastretransmit; 2016 } 2017 } 2018 goto drop; 2019 } 2020 2021 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2022 tp->t_dupacks = 0; 2023 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2024 /* 2025 * Detected optimistic ACK attack. 2026 * Force slow-start to de-synchronize attack. 2027 */ 2028 tp->snd_cwnd = tp->t_maxseg; 2029 tp->snd_wacked = 0; 2030 2031 tcpstat.tcps_rcvacktoomuch++; 2032 goto dropafterack; 2033 } 2034 /* 2035 * If we reach this point, ACK is not a duplicate, 2036 * i.e., it ACKs something we sent. 2037 */ 2038 if (tp->t_flags & TF_NEEDSYN) { 2039 /* 2040 * T/TCP: Connection was half-synchronized, and our 2041 * SYN has been ACK'd (so connection is now fully 2042 * synchronized). Go to non-starred state, 2043 * increment snd_una for ACK of SYN, and check if 2044 * we can do window scaling. 2045 */ 2046 tp->t_flags &= ~TF_NEEDSYN; 2047 tp->snd_una++; 2048 /* Do window scaling? */ 2049 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2050 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2051 tp->snd_scale = tp->requested_s_scale; 2052 tp->rcv_scale = tp->request_r_scale; 2053 } 2054 } 2055 2056 process_ACK: 2057 acked = th->th_ack - tp->snd_una; 2058 tcpstat.tcps_rcvackpack++; 2059 tcpstat.tcps_rcvackbyte += acked; 2060 2061 if (tcp_do_eifel_detect && acked > 0 && 2062 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2063 (tp->t_flags & TF_FIRSTACCACK)) { 2064 /* Eifel detection applicable. */ 2065 if (to.to_tsecr < tp->t_rexmtTS) { 2066 ++tcpstat.tcps_eifeldetected; 2067 tcp_revert_congestion_state(tp); 2068 if (tp->t_rxtshift != 1 || 2069 ticks >= tp->t_badrxtwin) 2070 ++tcpstat.tcps_rttcantdetect; 2071 } 2072 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2073 /* 2074 * If we just performed our first retransmit, 2075 * and the ACK arrives within our recovery window, 2076 * then it was a mistake to do the retransmit 2077 * in the first place. Recover our original cwnd 2078 * and ssthresh, and proceed to transmit where we 2079 * left off. 2080 */ 2081 tcp_revert_congestion_state(tp); 2082 ++tcpstat.tcps_rttdetected; 2083 } 2084 2085 /* 2086 * If we have a timestamp reply, update smoothed 2087 * round trip time. If no timestamp is present but 2088 * transmit timer is running and timed sequence 2089 * number was acked, update smoothed round trip time. 2090 * Since we now have an rtt measurement, cancel the 2091 * timer backoff (cf., Phil Karn's retransmit alg.). 2092 * Recompute the initial retransmit timer. 2093 * 2094 * Some machines (certain windows boxes) send broken 2095 * timestamp replies during the SYN+ACK phase, ignore 2096 * timestamps of 0. 2097 */ 2098 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2099 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2100 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2101 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2102 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2103 2104 /* 2105 * If no data (only SYN) was ACK'd, 2106 * skip rest of ACK processing. 2107 */ 2108 if (acked == 0) 2109 goto step6; 2110 2111 /* Stop looking for an acceptable ACK since one was received. */ 2112 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2113 2114 if (acked > so->so_snd.ssb_cc) { 2115 tp->snd_wnd -= so->so_snd.ssb_cc; 2116 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2117 ourfinisacked = TRUE; 2118 } else { 2119 sbdrop(&so->so_snd.sb, acked); 2120 tp->snd_wnd -= acked; 2121 ourfinisacked = FALSE; 2122 } 2123 sowwakeup(so); 2124 2125 /* 2126 * Update window information. 2127 */ 2128 if (acceptable_window_update(tp, th, tiwin)) { 2129 /* keep track of pure window updates */ 2130 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2131 tiwin > tp->snd_wnd) 2132 tcpstat.tcps_rcvwinupd++; 2133 tp->snd_wnd = tiwin; 2134 tp->snd_wl1 = th->th_seq; 2135 tp->snd_wl2 = th->th_ack; 2136 if (tp->snd_wnd > tp->max_sndwnd) 2137 tp->max_sndwnd = tp->snd_wnd; 2138 needoutput = TRUE; 2139 } 2140 2141 tp->snd_una = th->th_ack; 2142 if (TCP_DO_SACK(tp)) 2143 tcp_sack_update_scoreboard(tp, &to); 2144 if (IN_FASTRECOVERY(tp)) { 2145 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2146 EXIT_FASTRECOVERY(tp); 2147 needoutput = TRUE; 2148 /* 2149 * If the congestion window was inflated 2150 * to account for the other side's 2151 * cached packets, retract it. 2152 */ 2153 if (!TCP_DO_SACK(tp)) 2154 tp->snd_cwnd = tp->snd_ssthresh; 2155 2156 /* 2157 * Window inflation should have left us 2158 * with approximately snd_ssthresh outstanding 2159 * data. But, in case we would be inclined 2160 * to send a burst, better do it using 2161 * slow start. 2162 */ 2163 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2164 tp->snd_max + 2 * tp->t_maxseg)) 2165 tp->snd_cwnd = 2166 (tp->snd_max - tp->snd_una) + 2167 2 * tp->t_maxseg; 2168 2169 tp->snd_wacked = 0; 2170 } else { 2171 if (TCP_DO_SACK(tp)) { 2172 tp->snd_max_rexmt = tp->snd_max; 2173 tcp_sack_rexmt(tp, th); 2174 } else { 2175 tcp_newreno_partial_ack(tp, th, acked); 2176 } 2177 needoutput = FALSE; 2178 } 2179 } else { 2180 /* 2181 * Open the congestion window. When in slow-start, 2182 * open exponentially: maxseg per packet. Otherwise, 2183 * open linearly: maxseg per window. 2184 */ 2185 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2186 u_int abc_sslimit = 2187 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2188 tp->t_maxseg : 2 * tp->t_maxseg); 2189 2190 /* slow-start */ 2191 tp->snd_cwnd += tcp_do_abc ? 2192 min(acked, abc_sslimit) : tp->t_maxseg; 2193 } else { 2194 /* linear increase */ 2195 tp->snd_wacked += tcp_do_abc ? acked : 2196 tp->t_maxseg; 2197 if (tp->snd_wacked >= tp->snd_cwnd) { 2198 tp->snd_wacked -= tp->snd_cwnd; 2199 tp->snd_cwnd += tp->t_maxseg; 2200 } 2201 } 2202 tp->snd_cwnd = min(tp->snd_cwnd, 2203 TCP_MAXWIN << tp->snd_scale); 2204 tp->snd_recover = th->th_ack - 1; 2205 } 2206 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2207 tp->snd_nxt = tp->snd_una; 2208 2209 /* 2210 * If all outstanding data is acked, stop retransmit 2211 * timer and remember to restart (more output or persist). 2212 * If there is more data to be acked, restart retransmit 2213 * timer, using current (possibly backed-off) value. 2214 */ 2215 if (th->th_ack == tp->snd_max) { 2216 tcp_callout_stop(tp, tp->tt_rexmt); 2217 needoutput = TRUE; 2218 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2219 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2220 tcp_timer_rexmt); 2221 } 2222 2223 switch (tp->t_state) { 2224 /* 2225 * In FIN_WAIT_1 STATE in addition to the processing 2226 * for the ESTABLISHED state if our FIN is now acknowledged 2227 * then enter FIN_WAIT_2. 2228 */ 2229 case TCPS_FIN_WAIT_1: 2230 if (ourfinisacked) { 2231 /* 2232 * If we can't receive any more 2233 * data, then closing user can proceed. 2234 * Starting the timer is contrary to the 2235 * specification, but if we don't get a FIN 2236 * we'll hang forever. 2237 */ 2238 if (so->so_state & SS_CANTRCVMORE) { 2239 soisdisconnected(so); 2240 tcp_callout_reset(tp, tp->tt_2msl, 2241 tp->t_maxidle, tcp_timer_2msl); 2242 } 2243 tp->t_state = TCPS_FIN_WAIT_2; 2244 } 2245 break; 2246 2247 /* 2248 * In CLOSING STATE in addition to the processing for 2249 * the ESTABLISHED state if the ACK acknowledges our FIN 2250 * then enter the TIME-WAIT state, otherwise ignore 2251 * the segment. 2252 */ 2253 case TCPS_CLOSING: 2254 if (ourfinisacked) { 2255 tp->t_state = TCPS_TIME_WAIT; 2256 tcp_canceltimers(tp); 2257 tcp_callout_reset(tp, tp->tt_2msl, 2258 2 * tcp_rmx_msl(tp), 2259 tcp_timer_2msl); 2260 soisdisconnected(so); 2261 } 2262 break; 2263 2264 /* 2265 * In LAST_ACK, we may still be waiting for data to drain 2266 * and/or to be acked, as well as for the ack of our FIN. 2267 * If our FIN is now acknowledged, delete the TCB, 2268 * enter the closed state and return. 2269 */ 2270 case TCPS_LAST_ACK: 2271 if (ourfinisacked) { 2272 tp = tcp_close(tp); 2273 goto drop; 2274 } 2275 break; 2276 2277 /* 2278 * In TIME_WAIT state the only thing that should arrive 2279 * is a retransmission of the remote FIN. Acknowledge 2280 * it and restart the finack timer. 2281 */ 2282 case TCPS_TIME_WAIT: 2283 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2284 tcp_timer_2msl); 2285 goto dropafterack; 2286 } 2287 } 2288 2289 step6: 2290 /* 2291 * Update window information. 2292 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2293 */ 2294 if ((thflags & TH_ACK) && 2295 acceptable_window_update(tp, th, tiwin)) { 2296 /* keep track of pure window updates */ 2297 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2298 tiwin > tp->snd_wnd) 2299 tcpstat.tcps_rcvwinupd++; 2300 tp->snd_wnd = tiwin; 2301 tp->snd_wl1 = th->th_seq; 2302 tp->snd_wl2 = th->th_ack; 2303 if (tp->snd_wnd > tp->max_sndwnd) 2304 tp->max_sndwnd = tp->snd_wnd; 2305 needoutput = TRUE; 2306 } 2307 2308 /* 2309 * Process segments with URG. 2310 */ 2311 if ((thflags & TH_URG) && th->th_urp && 2312 !TCPS_HAVERCVDFIN(tp->t_state)) { 2313 /* 2314 * This is a kludge, but if we receive and accept 2315 * random urgent pointers, we'll crash in 2316 * soreceive. It's hard to imagine someone 2317 * actually wanting to send this much urgent data. 2318 */ 2319 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2320 th->th_urp = 0; /* XXX */ 2321 thflags &= ~TH_URG; /* XXX */ 2322 goto dodata; /* XXX */ 2323 } 2324 /* 2325 * If this segment advances the known urgent pointer, 2326 * then mark the data stream. This should not happen 2327 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2328 * a FIN has been received from the remote side. 2329 * In these states we ignore the URG. 2330 * 2331 * According to RFC961 (Assigned Protocols), 2332 * the urgent pointer points to the last octet 2333 * of urgent data. We continue, however, 2334 * to consider it to indicate the first octet 2335 * of data past the urgent section as the original 2336 * spec states (in one of two places). 2337 */ 2338 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2339 tp->rcv_up = th->th_seq + th->th_urp; 2340 so->so_oobmark = so->so_rcv.ssb_cc + 2341 (tp->rcv_up - tp->rcv_nxt) - 1; 2342 if (so->so_oobmark == 0) 2343 sosetstate(so, SS_RCVATMARK); 2344 sohasoutofband(so); 2345 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2346 } 2347 /* 2348 * Remove out of band data so doesn't get presented to user. 2349 * This can happen independent of advancing the URG pointer, 2350 * but if two URG's are pending at once, some out-of-band 2351 * data may creep in... ick. 2352 */ 2353 if (th->th_urp <= (u_long)tlen && 2354 !(so->so_options & SO_OOBINLINE)) { 2355 /* hdr drop is delayed */ 2356 tcp_pulloutofband(so, th, m, drop_hdrlen); 2357 } 2358 } else { 2359 /* 2360 * If no out of band data is expected, 2361 * pull receive urgent pointer along 2362 * with the receive window. 2363 */ 2364 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2365 tp->rcv_up = tp->rcv_nxt; 2366 } 2367 2368 dodata: /* XXX */ 2369 /* 2370 * Process the segment text, merging it into the TCP sequencing queue, 2371 * and arranging for acknowledgment of receipt if necessary. 2372 * This process logically involves adjusting tp->rcv_wnd as data 2373 * is presented to the user (this happens in tcp_usrreq.c, 2374 * case PRU_RCVD). If a FIN has already been received on this 2375 * connection then we just ignore the text. 2376 */ 2377 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2378 m_adj(m, drop_hdrlen); /* delayed header drop */ 2379 /* 2380 * Insert segment which includes th into TCP reassembly queue 2381 * with control block tp. Set thflags to whether reassembly now 2382 * includes a segment with FIN. This handles the common case 2383 * inline (segment is the next to be received on an established 2384 * connection, and the queue is empty), avoiding linkage into 2385 * and removal from the queue and repetition of various 2386 * conversions. 2387 * Set DELACK for segments received in order, but ack 2388 * immediately when segments are out of order (so 2389 * fast retransmit can work). 2390 */ 2391 if (th->th_seq == tp->rcv_nxt && 2392 LIST_EMPTY(&tp->t_segq) && 2393 TCPS_HAVEESTABLISHED(tp->t_state)) { 2394 if (DELAY_ACK(tp)) { 2395 tcp_callout_reset(tp, tp->tt_delack, 2396 tcp_delacktime, tcp_timer_delack); 2397 } else { 2398 tp->t_flags |= TF_ACKNOW; 2399 } 2400 tp->rcv_nxt += tlen; 2401 thflags = th->th_flags & TH_FIN; 2402 tcpstat.tcps_rcvpack++; 2403 tcpstat.tcps_rcvbyte += tlen; 2404 ND6_HINT(tp); 2405 if (so->so_state & SS_CANTRCVMORE) { 2406 m_freem(m); 2407 } else { 2408 lwkt_gettoken(&so->so_rcv.ssb_token); 2409 ssb_appendstream(&so->so_rcv, m); 2410 lwkt_reltoken(&so->so_rcv.ssb_token); 2411 } 2412 sorwakeup(so); 2413 } else { 2414 if (!(tp->t_flags & TF_DUPSEG)) { 2415 /* Initialize SACK report block. */ 2416 tp->reportblk.rblk_start = th->th_seq; 2417 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 2418 th->th_seq + tlen, thflags); 2419 } 2420 thflags = tcp_reass(tp, th, &tlen, m); 2421 tp->t_flags |= TF_ACKNOW; 2422 } 2423 2424 /* 2425 * Note the amount of data that peer has sent into 2426 * our window, in order to estimate the sender's 2427 * buffer size. 2428 */ 2429 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2430 } else { 2431 m_freem(m); 2432 thflags &= ~TH_FIN; 2433 } 2434 2435 /* 2436 * If FIN is received ACK the FIN and let the user know 2437 * that the connection is closing. 2438 */ 2439 if (thflags & TH_FIN) { 2440 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2441 socantrcvmore(so); 2442 /* 2443 * If connection is half-synchronized 2444 * (ie NEEDSYN flag on) then delay ACK, 2445 * so it may be piggybacked when SYN is sent. 2446 * Otherwise, since we received a FIN then no 2447 * more input can be expected, send ACK now. 2448 */ 2449 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2450 tcp_callout_reset(tp, tp->tt_delack, 2451 tcp_delacktime, tcp_timer_delack); 2452 } else { 2453 tp->t_flags |= TF_ACKNOW; 2454 } 2455 tp->rcv_nxt++; 2456 } 2457 2458 switch (tp->t_state) { 2459 /* 2460 * In SYN_RECEIVED and ESTABLISHED STATES 2461 * enter the CLOSE_WAIT state. 2462 */ 2463 case TCPS_SYN_RECEIVED: 2464 tp->t_starttime = ticks; 2465 /*FALLTHROUGH*/ 2466 case TCPS_ESTABLISHED: 2467 tp->t_state = TCPS_CLOSE_WAIT; 2468 break; 2469 2470 /* 2471 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2472 * enter the CLOSING state. 2473 */ 2474 case TCPS_FIN_WAIT_1: 2475 tp->t_state = TCPS_CLOSING; 2476 break; 2477 2478 /* 2479 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2480 * starting the time-wait timer, turning off the other 2481 * standard timers. 2482 */ 2483 case TCPS_FIN_WAIT_2: 2484 tp->t_state = TCPS_TIME_WAIT; 2485 tcp_canceltimers(tp); 2486 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2487 tcp_timer_2msl); 2488 soisdisconnected(so); 2489 break; 2490 2491 /* 2492 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2493 */ 2494 case TCPS_TIME_WAIT: 2495 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2496 tcp_timer_2msl); 2497 break; 2498 } 2499 } 2500 2501 #ifdef TCPDEBUG 2502 if (so->so_options & SO_DEBUG) 2503 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2504 #endif 2505 2506 /* 2507 * Return any desired output. 2508 */ 2509 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2510 tcp_output(tp); 2511 tcp_sack_report_cleanup(tp); 2512 return(IPPROTO_DONE); 2513 2514 dropafterack: 2515 /* 2516 * Generate an ACK dropping incoming segment if it occupies 2517 * sequence space, where the ACK reflects our state. 2518 * 2519 * We can now skip the test for the RST flag since all 2520 * paths to this code happen after packets containing 2521 * RST have been dropped. 2522 * 2523 * In the SYN-RECEIVED state, don't send an ACK unless the 2524 * segment we received passes the SYN-RECEIVED ACK test. 2525 * If it fails send a RST. This breaks the loop in the 2526 * "LAND" DoS attack, and also prevents an ACK storm 2527 * between two listening ports that have been sent forged 2528 * SYN segments, each with the source address of the other. 2529 */ 2530 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2531 (SEQ_GT(tp->snd_una, th->th_ack) || 2532 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2533 rstreason = BANDLIM_RST_OPENPORT; 2534 goto dropwithreset; 2535 } 2536 #ifdef TCPDEBUG 2537 if (so->so_options & SO_DEBUG) 2538 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2539 #endif 2540 m_freem(m); 2541 tp->t_flags |= TF_ACKNOW; 2542 tcp_output(tp); 2543 tcp_sack_report_cleanup(tp); 2544 return(IPPROTO_DONE); 2545 2546 dropwithreset: 2547 /* 2548 * Generate a RST, dropping incoming segment. 2549 * Make ACK acceptable to originator of segment. 2550 * Don't bother to respond if destination was broadcast/multicast. 2551 */ 2552 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2553 goto drop; 2554 if (isipv6) { 2555 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2556 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2557 goto drop; 2558 } else { 2559 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2560 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2561 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2562 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2563 goto drop; 2564 } 2565 /* IPv6 anycast check is done at tcp6_input() */ 2566 2567 /* 2568 * Perform bandwidth limiting. 2569 */ 2570 #ifdef ICMP_BANDLIM 2571 if (badport_bandlim(rstreason) < 0) 2572 goto drop; 2573 #endif 2574 2575 #ifdef TCPDEBUG 2576 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2577 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2578 #endif 2579 if (thflags & TH_ACK) 2580 /* mtod() below is safe as long as hdr dropping is delayed */ 2581 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2582 TH_RST); 2583 else { 2584 if (thflags & TH_SYN) 2585 tlen++; 2586 /* mtod() below is safe as long as hdr dropping is delayed */ 2587 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2588 (tcp_seq)0, TH_RST | TH_ACK); 2589 } 2590 if (tp != NULL) 2591 tcp_sack_report_cleanup(tp); 2592 return(IPPROTO_DONE); 2593 2594 drop: 2595 /* 2596 * Drop space held by incoming segment and return. 2597 */ 2598 #ifdef TCPDEBUG 2599 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2600 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2601 #endif 2602 m_freem(m); 2603 if (tp != NULL) 2604 tcp_sack_report_cleanup(tp); 2605 return(IPPROTO_DONE); 2606 } 2607 2608 /* 2609 * Parse TCP options and place in tcpopt. 2610 */ 2611 static void 2612 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2613 { 2614 int opt, optlen, i; 2615 2616 to->to_flags = 0; 2617 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2618 opt = cp[0]; 2619 if (opt == TCPOPT_EOL) 2620 break; 2621 if (opt == TCPOPT_NOP) 2622 optlen = 1; 2623 else { 2624 if (cnt < 2) 2625 break; 2626 optlen = cp[1]; 2627 if (optlen < 2 || optlen > cnt) 2628 break; 2629 } 2630 switch (opt) { 2631 case TCPOPT_MAXSEG: 2632 if (optlen != TCPOLEN_MAXSEG) 2633 continue; 2634 if (!is_syn) 2635 continue; 2636 to->to_flags |= TOF_MSS; 2637 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2638 to->to_mss = ntohs(to->to_mss); 2639 break; 2640 case TCPOPT_WINDOW: 2641 if (optlen != TCPOLEN_WINDOW) 2642 continue; 2643 if (!is_syn) 2644 continue; 2645 to->to_flags |= TOF_SCALE; 2646 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2647 break; 2648 case TCPOPT_TIMESTAMP: 2649 if (optlen != TCPOLEN_TIMESTAMP) 2650 continue; 2651 to->to_flags |= TOF_TS; 2652 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2653 to->to_tsval = ntohl(to->to_tsval); 2654 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2655 to->to_tsecr = ntohl(to->to_tsecr); 2656 /* 2657 * If echoed timestamp is later than the current time, 2658 * fall back to non RFC1323 RTT calculation. 2659 */ 2660 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2661 to->to_tsecr = 0; 2662 break; 2663 case TCPOPT_SACK_PERMITTED: 2664 if (optlen != TCPOLEN_SACK_PERMITTED) 2665 continue; 2666 if (!is_syn) 2667 continue; 2668 to->to_flags |= TOF_SACK_PERMITTED; 2669 break; 2670 case TCPOPT_SACK: 2671 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2672 continue; 2673 to->to_nsackblocks = (optlen - 2) / 8; 2674 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2675 to->to_flags |= TOF_SACK; 2676 for (i = 0; i < to->to_nsackblocks; i++) { 2677 struct raw_sackblock *r = &to->to_sackblocks[i]; 2678 2679 r->rblk_start = ntohl(r->rblk_start); 2680 r->rblk_end = ntohl(r->rblk_end); 2681 2682 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { 2683 /* 2684 * Invalid SACK block; discard all 2685 * SACK blocks 2686 */ 2687 tcpstat.tcps_rcvbadsackopt++; 2688 to->to_nsackblocks = 0; 2689 to->to_sackblocks = NULL; 2690 to->to_flags &= ~TOF_SACK; 2691 break; 2692 } 2693 } 2694 break; 2695 #ifdef TCP_SIGNATURE 2696 /* 2697 * XXX In order to reply to a host which has set the 2698 * TCP_SIGNATURE option in its initial SYN, we have to 2699 * record the fact that the option was observed here 2700 * for the syncache code to perform the correct response. 2701 */ 2702 case TCPOPT_SIGNATURE: 2703 if (optlen != TCPOLEN_SIGNATURE) 2704 continue; 2705 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2706 break; 2707 #endif /* TCP_SIGNATURE */ 2708 default: 2709 continue; 2710 } 2711 } 2712 } 2713 2714 /* 2715 * Pull out of band byte out of a segment so 2716 * it doesn't appear in the user's data queue. 2717 * It is still reflected in the segment length for 2718 * sequencing purposes. 2719 * "off" is the delayed to be dropped hdrlen. 2720 */ 2721 static void 2722 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2723 { 2724 int cnt = off + th->th_urp - 1; 2725 2726 while (cnt >= 0) { 2727 if (m->m_len > cnt) { 2728 char *cp = mtod(m, caddr_t) + cnt; 2729 struct tcpcb *tp = sototcpcb(so); 2730 2731 tp->t_iobc = *cp; 2732 tp->t_oobflags |= TCPOOB_HAVEDATA; 2733 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2734 m->m_len--; 2735 if (m->m_flags & M_PKTHDR) 2736 m->m_pkthdr.len--; 2737 return; 2738 } 2739 cnt -= m->m_len; 2740 m = m->m_next; 2741 if (m == NULL) 2742 break; 2743 } 2744 panic("tcp_pulloutofband"); 2745 } 2746 2747 /* 2748 * Collect new round-trip time estimate 2749 * and update averages and current timeout. 2750 */ 2751 static void 2752 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2753 { 2754 int delta; 2755 2756 tcpstat.tcps_rttupdated++; 2757 tp->t_rttupdated++; 2758 if (tp->t_srtt != 0) { 2759 /* 2760 * srtt is stored as fixed point with 5 bits after the 2761 * binary point (i.e., scaled by 8). The following magic 2762 * is equivalent to the smoothing algorithm in rfc793 with 2763 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2764 * point). Adjust rtt to origin 0. 2765 */ 2766 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2767 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2768 2769 if ((tp->t_srtt += delta) <= 0) 2770 tp->t_srtt = 1; 2771 2772 /* 2773 * We accumulate a smoothed rtt variance (actually, a 2774 * smoothed mean difference), then set the retransmit 2775 * timer to smoothed rtt + 4 times the smoothed variance. 2776 * rttvar is stored as fixed point with 4 bits after the 2777 * binary point (scaled by 16). The following is 2778 * equivalent to rfc793 smoothing with an alpha of .75 2779 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2780 * rfc793's wired-in beta. 2781 */ 2782 if (delta < 0) 2783 delta = -delta; 2784 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2785 if ((tp->t_rttvar += delta) <= 0) 2786 tp->t_rttvar = 1; 2787 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2788 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2789 } else { 2790 /* 2791 * No rtt measurement yet - use the unsmoothed rtt. 2792 * Set the variance to half the rtt (so our first 2793 * retransmit happens at 3*rtt). 2794 */ 2795 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2796 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2797 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2798 } 2799 tp->t_rtttime = 0; 2800 tp->t_rxtshift = 0; 2801 2802 /* 2803 * the retransmit should happen at rtt + 4 * rttvar. 2804 * Because of the way we do the smoothing, srtt and rttvar 2805 * will each average +1/2 tick of bias. When we compute 2806 * the retransmit timer, we want 1/2 tick of rounding and 2807 * 1 extra tick because of +-1/2 tick uncertainty in the 2808 * firing of the timer. The bias will give us exactly the 2809 * 1.5 tick we need. But, because the bias is 2810 * statistical, we have to test that we don't drop below 2811 * the minimum feasible timer (which is 2 ticks). 2812 */ 2813 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2814 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2815 2816 /* 2817 * We received an ack for a packet that wasn't retransmitted; 2818 * it is probably safe to discard any error indications we've 2819 * received recently. This isn't quite right, but close enough 2820 * for now (a route might have failed after we sent a segment, 2821 * and the return path might not be symmetrical). 2822 */ 2823 tp->t_softerror = 0; 2824 } 2825 2826 /* 2827 * Determine a reasonable value for maxseg size. 2828 * If the route is known, check route for mtu. 2829 * If none, use an mss that can be handled on the outgoing 2830 * interface without forcing IP to fragment; if bigger than 2831 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2832 * to utilize large mbufs. If no route is found, route has no mtu, 2833 * or the destination isn't local, use a default, hopefully conservative 2834 * size (usually 512 or the default IP max size, but no more than the mtu 2835 * of the interface), as we can't discover anything about intervening 2836 * gateways or networks. We also initialize the congestion/slow start 2837 * window to be a single segment if the destination isn't local. 2838 * While looking at the routing entry, we also initialize other path-dependent 2839 * parameters from pre-set or cached values in the routing entry. 2840 * 2841 * Also take into account the space needed for options that we 2842 * send regularly. Make maxseg shorter by that amount to assure 2843 * that we can send maxseg amount of data even when the options 2844 * are present. Store the upper limit of the length of options plus 2845 * data in maxopd. 2846 * 2847 * NOTE that this routine is only called when we process an incoming 2848 * segment, for outgoing segments only tcp_mssopt is called. 2849 */ 2850 void 2851 tcp_mss(struct tcpcb *tp, int offer) 2852 { 2853 struct rtentry *rt; 2854 struct ifnet *ifp; 2855 int rtt, mss; 2856 u_long bufsize; 2857 struct inpcb *inp = tp->t_inpcb; 2858 struct socket *so; 2859 #ifdef INET6 2860 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2861 size_t min_protoh = isipv6 ? 2862 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2863 sizeof(struct tcpiphdr); 2864 #else 2865 const boolean_t isipv6 = FALSE; 2866 const size_t min_protoh = sizeof(struct tcpiphdr); 2867 #endif 2868 2869 if (isipv6) 2870 rt = tcp_rtlookup6(&inp->inp_inc); 2871 else 2872 rt = tcp_rtlookup(&inp->inp_inc); 2873 if (rt == NULL) { 2874 tp->t_maxopd = tp->t_maxseg = 2875 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2876 return; 2877 } 2878 ifp = rt->rt_ifp; 2879 so = inp->inp_socket; 2880 2881 /* 2882 * Offer == 0 means that there was no MSS on the SYN segment, 2883 * in this case we use either the interface mtu or tcp_mssdflt. 2884 * 2885 * An offer which is too large will be cut down later. 2886 */ 2887 if (offer == 0) { 2888 if (isipv6) { 2889 if (in6_localaddr(&inp->in6p_faddr)) { 2890 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 2891 min_protoh; 2892 } else { 2893 offer = tcp_v6mssdflt; 2894 } 2895 } else { 2896 if (in_localaddr(inp->inp_faddr)) 2897 offer = ifp->if_mtu - min_protoh; 2898 else 2899 offer = tcp_mssdflt; 2900 } 2901 } 2902 2903 /* 2904 * Prevent DoS attack with too small MSS. Round up 2905 * to at least minmss. 2906 * 2907 * Sanity check: make sure that maxopd will be large 2908 * enough to allow some data on segments even is the 2909 * all the option space is used (40bytes). Otherwise 2910 * funny things may happen in tcp_output. 2911 */ 2912 offer = max(offer, tcp_minmss); 2913 offer = max(offer, 64); 2914 2915 rt->rt_rmx.rmx_mssopt = offer; 2916 2917 /* 2918 * While we're here, check if there's an initial rtt 2919 * or rttvar. Convert from the route-table units 2920 * to scaled multiples of the slow timeout timer. 2921 */ 2922 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2923 /* 2924 * XXX the lock bit for RTT indicates that the value 2925 * is also a minimum value; this is subject to time. 2926 */ 2927 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2928 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2929 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2930 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2931 tcpstat.tcps_usedrtt++; 2932 if (rt->rt_rmx.rmx_rttvar) { 2933 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2934 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2935 tcpstat.tcps_usedrttvar++; 2936 } else { 2937 /* default variation is +- 1 rtt */ 2938 tp->t_rttvar = 2939 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2940 } 2941 TCPT_RANGESET(tp->t_rxtcur, 2942 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2943 tp->t_rttmin, TCPTV_REXMTMAX); 2944 } 2945 2946 /* 2947 * if there's an mtu associated with the route, use it 2948 * else, use the link mtu. Take the smaller of mss or offer 2949 * as our final mss. 2950 */ 2951 if (rt->rt_rmx.rmx_mtu) { 2952 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2953 } else { 2954 if (isipv6) 2955 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2956 else 2957 mss = ifp->if_mtu - min_protoh; 2958 } 2959 mss = min(mss, offer); 2960 2961 /* 2962 * maxopd stores the maximum length of data AND options 2963 * in a segment; maxseg is the amount of data in a normal 2964 * segment. We need to store this value (maxopd) apart 2965 * from maxseg, because now every segment carries options 2966 * and thus we normally have somewhat less data in segments. 2967 */ 2968 tp->t_maxopd = mss; 2969 2970 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 2971 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2972 mss -= TCPOLEN_TSTAMP_APPA; 2973 2974 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2975 if (mss > MCLBYTES) 2976 mss &= ~(MCLBYTES-1); 2977 #else 2978 if (mss > MCLBYTES) 2979 mss = mss / MCLBYTES * MCLBYTES; 2980 #endif 2981 /* 2982 * If there's a pipesize, change the socket buffer 2983 * to that size. Make the socket buffers an integral 2984 * number of mss units; if the mss is larger than 2985 * the socket buffer, decrease the mss. 2986 */ 2987 #ifdef RTV_SPIPE 2988 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2989 #endif 2990 bufsize = so->so_snd.ssb_hiwat; 2991 if (bufsize < mss) 2992 mss = bufsize; 2993 else { 2994 bufsize = roundup(bufsize, mss); 2995 if (bufsize > sb_max) 2996 bufsize = sb_max; 2997 if (bufsize > so->so_snd.ssb_hiwat) 2998 ssb_reserve(&so->so_snd, bufsize, so, NULL); 2999 } 3000 tp->t_maxseg = mss; 3001 3002 #ifdef RTV_RPIPE 3003 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3004 #endif 3005 bufsize = so->so_rcv.ssb_hiwat; 3006 if (bufsize > mss) { 3007 bufsize = roundup(bufsize, mss); 3008 if (bufsize > sb_max) 3009 bufsize = sb_max; 3010 if (bufsize > so->so_rcv.ssb_hiwat) { 3011 lwkt_gettoken(&so->so_rcv.ssb_token); 3012 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3013 lwkt_reltoken(&so->so_rcv.ssb_token); 3014 } 3015 } 3016 3017 /* 3018 * Set the slow-start flight size 3019 * 3020 * NOTE: t_maxseg must have been configured! 3021 */ 3022 tp->snd_cwnd = tcp_initial_window(tp); 3023 3024 if (rt->rt_rmx.rmx_ssthresh) { 3025 /* 3026 * There's some sort of gateway or interface 3027 * buffer limit on the path. Use this to set 3028 * the slow start threshhold, but set the 3029 * threshold to no less than 2*mss. 3030 */ 3031 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3032 tcpstat.tcps_usedssthresh++; 3033 } 3034 } 3035 3036 /* 3037 * Determine the MSS option to send on an outgoing SYN. 3038 */ 3039 int 3040 tcp_mssopt(struct tcpcb *tp) 3041 { 3042 struct rtentry *rt; 3043 #ifdef INET6 3044 boolean_t isipv6 = 3045 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3046 int min_protoh = isipv6 ? 3047 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3048 sizeof(struct tcpiphdr); 3049 #else 3050 const boolean_t isipv6 = FALSE; 3051 const size_t min_protoh = sizeof(struct tcpiphdr); 3052 #endif 3053 3054 if (isipv6) 3055 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3056 else 3057 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3058 if (rt == NULL) 3059 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3060 3061 return (rt->rt_ifp->if_mtu - min_protoh); 3062 } 3063 3064 /* 3065 * When a partial ack arrives, force the retransmission of the 3066 * next unacknowledged segment. Do not exit Fast Recovery. 3067 * 3068 * Implement the Slow-but-Steady variant of NewReno by restarting the 3069 * the retransmission timer. Turn it off here so it can be restarted 3070 * later in tcp_output(). 3071 */ 3072 static void 3073 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3074 { 3075 tcp_seq old_snd_nxt = tp->snd_nxt; 3076 u_long ocwnd = tp->snd_cwnd; 3077 3078 tcp_callout_stop(tp, tp->tt_rexmt); 3079 tp->t_rtttime = 0; 3080 tp->snd_nxt = th->th_ack; 3081 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3082 tp->snd_cwnd = tp->t_maxseg; 3083 tp->t_flags |= TF_ACKNOW; 3084 tcp_output(tp); 3085 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3086 tp->snd_nxt = old_snd_nxt; 3087 /* partial window deflation */ 3088 if (ocwnd > acked) 3089 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3090 else 3091 tp->snd_cwnd = tp->t_maxseg; 3092 } 3093 3094 /* 3095 * In contrast to the Slow-but-Steady NewReno variant, 3096 * we do not reset the retransmission timer for SACK retransmissions, 3097 * except when retransmitting snd_una. 3098 */ 3099 static void 3100 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3101 { 3102 uint32_t pipe, seglen; 3103 tcp_seq nextrexmt; 3104 boolean_t lostdup; 3105 tcp_seq old_snd_nxt = tp->snd_nxt; 3106 u_long ocwnd = tp->snd_cwnd; 3107 int nseg = 0; /* consecutive new segments */ 3108 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3109 3110 tp->t_rtttime = 0; 3111 pipe = tcp_sack_compute_pipe(tp); 3112 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3113 (!tcp_do_smartsack || nseg < MAXBURST) && 3114 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3115 uint32_t sent; 3116 tcp_seq old_snd_max; 3117 int error; 3118 3119 if (nextrexmt == tp->snd_max) 3120 ++nseg; 3121 tp->snd_nxt = nextrexmt; 3122 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3123 old_snd_max = tp->snd_max; 3124 if (nextrexmt == tp->snd_una) 3125 tcp_callout_stop(tp, tp->tt_rexmt); 3126 error = tcp_output(tp); 3127 if (error != 0) 3128 break; 3129 sent = tp->snd_nxt - nextrexmt; 3130 if (sent <= 0) 3131 break; 3132 if (!lostdup) 3133 pipe += sent; 3134 tcpstat.tcps_sndsackpack++; 3135 tcpstat.tcps_sndsackbyte += sent; 3136 if (SEQ_LT(nextrexmt, old_snd_max) && 3137 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3138 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3139 } 3140 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3141 tp->snd_nxt = old_snd_nxt; 3142 tp->snd_cwnd = ocwnd; 3143 } 3144 3145 /* 3146 * Reset idle time and keep-alive timer, typically called when a valid 3147 * tcp packet is received but may also be called when FASTKEEP is set 3148 * to prevent the previous long-timeout from calculating to a drop. 3149 * 3150 * Only update t_rcvtime for non-SYN packets. 3151 * 3152 * Handle the case where one side thinks the connection is established 3153 * but the other side has, say, rebooted without cleaning out the 3154 * connection. The SYNs could be construed as an attack and wind 3155 * up ignored, but in case it isn't an attack we can validate the 3156 * connection by forcing a keepalive. 3157 */ 3158 void 3159 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3160 { 3161 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3162 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3163 tp->t_flags |= TF_KEEPALIVE; 3164 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3165 tcp_timer_keep); 3166 } else { 3167 tp->t_rcvtime = ticks; 3168 tp->t_flags &= ~TF_KEEPALIVE; 3169 tcp_callout_reset(tp, tp->tt_keep, 3170 tp->t_keepidle, 3171 tcp_timer_keep); 3172 } 3173 } 3174 } 3175 3176 static int 3177 tcp_rmx_msl(const struct tcpcb *tp) 3178 { 3179 struct rtentry *rt; 3180 struct inpcb *inp = tp->t_inpcb; 3181 int msl; 3182 #ifdef INET6 3183 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3184 #else 3185 const boolean_t isipv6 = FALSE; 3186 #endif 3187 3188 if (isipv6) 3189 rt = tcp_rtlookup6(&inp->inp_inc); 3190 else 3191 rt = tcp_rtlookup(&inp->inp_inc); 3192 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3193 return tcp_msl; 3194 3195 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3196 if (msl == 0) 3197 msl = 1; 3198 3199 return msl; 3200 } 3201 3202 static void 3203 tcp_established(struct tcpcb *tp) 3204 { 3205 tp->t_state = TCPS_ESTABLISHED; 3206 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); 3207 3208 if (tp->t_rxtsyn > 0) { 3209 /* 3210 * RFC6298: 3211 * "If the timer expires awaiting the ACK of a SYN segment 3212 * and the TCP implementation is using an RTO less than 3 3213 * seconds, the RTO MUST be re-initialized to 3 seconds 3214 * when data transmission begins" 3215 */ 3216 if (tp->t_rxtcur < TCPTV_RTOBASE3) 3217 tp->t_rxtcur = TCPTV_RTOBASE3; 3218 } 3219 } 3220