1 /* 2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 68 */ 69 70 #include "opt_inet.h" 71 #include "opt_inet6.h" 72 #include "opt_ipsec.h" 73 #include "opt_tcpdebug.h" 74 #include "opt_tcp_input.h" 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/sysctl.h> 80 #include <sys/malloc.h> 81 #include <sys/mbuf.h> 82 #include <sys/proc.h> /* for proc0 declaration */ 83 #include <sys/protosw.h> 84 #include <sys/socket.h> 85 #include <sys/socketvar.h> 86 #include <sys/syslog.h> 87 #include <sys/in_cksum.h> 88 89 #include <sys/socketvar2.h> 90 91 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 92 #include <machine/stdarg.h> 93 94 #include <net/if.h> 95 #include <net/route.h> 96 97 #include <netinet/in.h> 98 #include <netinet/in_systm.h> 99 #include <netinet/ip.h> 100 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 101 #include <netinet/in_var.h> 102 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 103 #include <netinet/in_pcb.h> 104 #include <netinet/ip_var.h> 105 #include <netinet/ip6.h> 106 #include <netinet/icmp6.h> 107 #include <netinet6/nd6.h> 108 #include <netinet6/ip6_var.h> 109 #include <netinet6/in6_pcb.h> 110 #include <netinet/tcp.h> 111 #include <netinet/tcp_fsm.h> 112 #include <netinet/tcp_seq.h> 113 #include <netinet/tcp_timer.h> 114 #include <netinet/tcp_timer2.h> 115 #include <netinet/tcp_var.h> 116 #include <netinet6/tcp6_var.h> 117 #include <netinet/tcpip.h> 118 119 #ifdef TCPDEBUG 120 #include <netinet/tcp_debug.h> 121 122 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 123 struct tcphdr tcp_savetcp; 124 #endif 125 126 #ifdef FAST_IPSEC 127 #include <netproto/ipsec/ipsec.h> 128 #include <netproto/ipsec/ipsec6.h> 129 #endif 130 131 #ifdef IPSEC 132 #include <netinet6/ipsec.h> 133 #include <netinet6/ipsec6.h> 134 #include <netproto/key/key.h> 135 #endif 136 137 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 138 139 static int log_in_vain = 0; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 141 &log_in_vain, 0, "Log all incoming TCP connections"); 142 143 static int blackhole = 0; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 145 &blackhole, 0, "Do not send RST when dropping refused connections"); 146 147 int tcp_delack_enabled = 1; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 149 &tcp_delack_enabled, 0, 150 "Delay ACK to try and piggyback it onto a data packet"); 151 152 #ifdef TCP_DROP_SYNFIN 153 static int drop_synfin = 0; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 156 #endif 157 158 static int tcp_do_limitedtransmit = 1; 159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 161 162 static int tcp_do_early_retransmit = 1; 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 164 &tcp_do_early_retransmit, 0, "Early retransmit"); 165 166 int tcp_aggregate_acks = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 169 170 int tcp_do_rfc3390 = 1; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 172 &tcp_do_rfc3390, 0, 173 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 174 175 static int tcp_do_eifel_detect = 1; 176 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 177 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 178 179 static int tcp_do_abc = 1; 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 181 &tcp_do_abc, 0, 182 "TCP Appropriate Byte Counting (RFC 3465)"); 183 184 /* 185 * Define as tunable for easy testing with SACK on and off. 186 * Warning: do not change setting in the middle of an existing active TCP flow, 187 * else strange things might happen to that flow. 188 */ 189 int tcp_do_sack = 1; 190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 191 &tcp_do_sack, 0, "Enable SACK Algorithms"); 192 193 int tcp_do_smartsack = 1; 194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 195 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 196 197 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 198 "TCP Segment Reassembly Queue"); 199 200 int tcp_reass_maxseg = 0; 201 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 202 &tcp_reass_maxseg, 0, 203 "Global maximum number of TCP Segments in Reassembly Queue"); 204 205 int tcp_reass_qsize = 0; 206 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 207 &tcp_reass_qsize, 0, 208 "Global number of TCP Segments currently in Reassembly Queue"); 209 210 static int tcp_reass_overflows = 0; 211 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 212 &tcp_reass_overflows, 0, 213 "Global number of TCP Segment Reassembly Queue Overflows"); 214 215 int tcp_do_autorcvbuf = 1; 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 217 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 218 219 int tcp_autorcvbuf_inc = 16*1024; 220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 221 &tcp_autorcvbuf_inc, 0, 222 "Incrementor step size of automatic receive buffer"); 223 224 int tcp_autorcvbuf_max = 2*1024*1024; 225 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 226 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 227 228 int tcp_sosnd_agglim = 2; 229 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_agglim, CTLFLAG_RW, 230 &tcp_sosnd_agglim, 0, "TCP sosend mbuf aggregation limit"); 231 232 int tcp_sosnd_async = 1; 233 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_async, CTLFLAG_RW, 234 &tcp_sosnd_async, 0, "TCP asynchronized pru_send"); 235 236 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 237 static void tcp_pulloutofband(struct socket *, 238 struct tcphdr *, struct mbuf *, int); 239 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 240 struct mbuf *); 241 static void tcp_xmit_timer(struct tcpcb *, int); 242 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 243 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 244 static int tcp_rmx_msl(const struct tcpcb *); 245 246 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 247 #ifdef INET6 248 #define ND6_HINT(tp) \ 249 do { \ 250 if ((tp) && (tp)->t_inpcb && \ 251 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 252 (tp)->t_inpcb->in6p_route.ro_rt) \ 253 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 254 } while (0) 255 #else 256 #define ND6_HINT(tp) 257 #endif 258 259 /* 260 * Indicate whether this ack should be delayed. We can delay the ack if 261 * - delayed acks are enabled and 262 * - there is no delayed ack timer in progress and 263 * - our last ack wasn't a 0-sized window. We never want to delay 264 * the ack that opens up a 0-sized window. 265 */ 266 #define DELAY_ACK(tp) \ 267 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 268 !(tp->t_flags & TF_RXWIN0SENT)) 269 270 #define acceptable_window_update(tp, th, tiwin) \ 271 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 272 (tp->snd_wl1 == th->th_seq && \ 273 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 274 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 275 276 static int 277 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 278 { 279 struct tseg_qent *q; 280 struct tseg_qent *p = NULL; 281 struct tseg_qent *te; 282 struct socket *so = tp->t_inpcb->inp_socket; 283 int flags; 284 285 /* 286 * Call with th == NULL after become established to 287 * force pre-ESTABLISHED data up to user socket. 288 */ 289 if (th == NULL) 290 goto present; 291 292 /* 293 * Limit the number of segments in the reassembly queue to prevent 294 * holding on to too many segments (and thus running out of mbufs). 295 * Make sure to let the missing segment through which caused this 296 * queue. Always keep one global queue entry spare to be able to 297 * process the missing segment. 298 */ 299 if (th->th_seq != tp->rcv_nxt && 300 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 301 tcp_reass_overflows++; 302 tcpstat.tcps_rcvmemdrop++; 303 m_freem(m); 304 /* no SACK block to report */ 305 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 306 return (0); 307 } 308 309 /* Allocate a new queue entry. */ 310 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 311 if (te == NULL) { 312 tcpstat.tcps_rcvmemdrop++; 313 m_freem(m); 314 /* no SACK block to report */ 315 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 316 return (0); 317 } 318 atomic_add_int(&tcp_reass_qsize, 1); 319 320 /* 321 * Find a segment which begins after this one does. 322 */ 323 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 324 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 325 break; 326 p = q; 327 } 328 329 /* 330 * If there is a preceding segment, it may provide some of 331 * our data already. If so, drop the data from the incoming 332 * segment. If it provides all of our data, drop us. 333 */ 334 if (p != NULL) { 335 tcp_seq_diff_t i; 336 337 /* conversion to int (in i) handles seq wraparound */ 338 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 339 if (i > 0) { /* overlaps preceding segment */ 340 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 341 /* enclosing block starts w/ preceding segment */ 342 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 343 if (i >= *tlenp) { 344 /* preceding encloses incoming segment */ 345 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 346 p->tqe_len; 347 tcpstat.tcps_rcvduppack++; 348 tcpstat.tcps_rcvdupbyte += *tlenp; 349 m_freem(m); 350 kfree(te, M_TSEGQ); 351 atomic_add_int(&tcp_reass_qsize, -1); 352 /* 353 * Try to present any queued data 354 * at the left window edge to the user. 355 * This is needed after the 3-WHS 356 * completes. 357 */ 358 goto present; /* ??? */ 359 } 360 m_adj(m, i); 361 *tlenp -= i; 362 th->th_seq += i; 363 /* incoming segment end is enclosing block end */ 364 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 365 ((th->th_flags & TH_FIN) != 0); 366 /* trim end of reported D-SACK block */ 367 tp->reportblk.rblk_end = th->th_seq; 368 } 369 } 370 tcpstat.tcps_rcvoopack++; 371 tcpstat.tcps_rcvoobyte += *tlenp; 372 373 /* 374 * While we overlap succeeding segments trim them or, 375 * if they are completely covered, dequeue them. 376 */ 377 while (q) { 378 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 379 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 380 struct tseg_qent *nq; 381 382 if (i <= 0) 383 break; 384 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 385 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 386 tp->encloseblk = tp->reportblk; 387 /* report trailing duplicate D-SACK segment */ 388 tp->reportblk.rblk_start = q->tqe_th->th_seq; 389 } 390 if ((tp->t_flags & TF_ENCLOSESEG) && 391 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 392 /* extend enclosing block if one exists */ 393 tp->encloseblk.rblk_end = qend; 394 } 395 if (i < q->tqe_len) { 396 q->tqe_th->th_seq += i; 397 q->tqe_len -= i; 398 m_adj(q->tqe_m, i); 399 break; 400 } 401 402 nq = LIST_NEXT(q, tqe_q); 403 LIST_REMOVE(q, tqe_q); 404 m_freem(q->tqe_m); 405 kfree(q, M_TSEGQ); 406 atomic_add_int(&tcp_reass_qsize, -1); 407 q = nq; 408 } 409 410 /* Insert the new segment queue entry into place. */ 411 te->tqe_m = m; 412 te->tqe_th = th; 413 te->tqe_len = *tlenp; 414 415 /* check if can coalesce with following segment */ 416 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 417 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 418 419 te->tqe_len += q->tqe_len; 420 if (q->tqe_th->th_flags & TH_FIN) 421 te->tqe_th->th_flags |= TH_FIN; 422 m_cat(te->tqe_m, q->tqe_m); 423 tp->encloseblk.rblk_end = tend; 424 /* 425 * When not reporting a duplicate segment, use 426 * the larger enclosing block as the SACK block. 427 */ 428 if (!(tp->t_flags & TF_DUPSEG)) 429 tp->reportblk.rblk_end = tend; 430 LIST_REMOVE(q, tqe_q); 431 kfree(q, M_TSEGQ); 432 atomic_add_int(&tcp_reass_qsize, -1); 433 } 434 435 if (p == NULL) { 436 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 437 } else { 438 /* check if can coalesce with preceding segment */ 439 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 440 p->tqe_len += te->tqe_len; 441 m_cat(p->tqe_m, te->tqe_m); 442 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 443 /* 444 * When not reporting a duplicate segment, use 445 * the larger enclosing block as the SACK block. 446 */ 447 if (!(tp->t_flags & TF_DUPSEG)) 448 tp->reportblk.rblk_start = p->tqe_th->th_seq; 449 kfree(te, M_TSEGQ); 450 atomic_add_int(&tcp_reass_qsize, -1); 451 } else { 452 LIST_INSERT_AFTER(p, te, tqe_q); 453 } 454 } 455 456 present: 457 /* 458 * Present data to user, advancing rcv_nxt through 459 * completed sequence space. 460 */ 461 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 462 return (0); 463 q = LIST_FIRST(&tp->t_segq); 464 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 465 return (0); 466 tp->rcv_nxt += q->tqe_len; 467 if (!(tp->t_flags & TF_DUPSEG)) { 468 /* no SACK block to report since ACK advanced */ 469 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 470 } 471 /* no enclosing block to report since ACK advanced */ 472 tp->t_flags &= ~TF_ENCLOSESEG; 473 flags = q->tqe_th->th_flags & TH_FIN; 474 LIST_REMOVE(q, tqe_q); 475 KASSERT(LIST_EMPTY(&tp->t_segq) || 476 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 477 ("segment not coalesced")); 478 if (so->so_state & SS_CANTRCVMORE) { 479 m_freem(q->tqe_m); 480 } else { 481 lwkt_gettoken(&so->so_rcv.ssb_token); 482 ssb_appendstream(&so->so_rcv, q->tqe_m); 483 lwkt_reltoken(&so->so_rcv.ssb_token); 484 } 485 kfree(q, M_TSEGQ); 486 atomic_add_int(&tcp_reass_qsize, -1); 487 ND6_HINT(tp); 488 sorwakeup(so); 489 return (flags); 490 } 491 492 /* 493 * TCP input routine, follows pages 65-76 of the 494 * protocol specification dated September, 1981 very closely. 495 */ 496 #ifdef INET6 497 int 498 tcp6_input(struct mbuf **mp, int *offp, int proto) 499 { 500 struct mbuf *m = *mp; 501 struct in6_ifaddr *ia6; 502 503 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 504 505 /* 506 * draft-itojun-ipv6-tcp-to-anycast 507 * better place to put this in? 508 */ 509 ia6 = ip6_getdstifaddr(m); 510 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 511 struct ip6_hdr *ip6; 512 513 ip6 = mtod(m, struct ip6_hdr *); 514 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 515 offsetof(struct ip6_hdr, ip6_dst)); 516 return (IPPROTO_DONE); 517 } 518 519 tcp_input(mp, offp, proto); 520 return (IPPROTO_DONE); 521 } 522 #endif 523 524 int 525 tcp_input(struct mbuf **mp, int *offp, int proto) 526 { 527 int off0; 528 struct tcphdr *th; 529 struct ip *ip = NULL; 530 struct ipovly *ipov; 531 struct inpcb *inp = NULL; 532 u_char *optp = NULL; 533 int optlen = 0; 534 int tlen, off; 535 int len = 0; 536 int drop_hdrlen; 537 struct tcpcb *tp = NULL; 538 int thflags; 539 struct socket *so = NULL; 540 int todrop, acked; 541 boolean_t ourfinisacked, needoutput = FALSE; 542 u_long tiwin; 543 int recvwin; 544 struct tcpopt to; /* options in this segment */ 545 struct sockaddr_in *next_hop = NULL; 546 int rstreason; /* For badport_bandlim accounting purposes */ 547 int cpu; 548 struct ip6_hdr *ip6 = NULL; 549 struct mbuf *m; 550 #ifdef INET6 551 boolean_t isipv6; 552 #else 553 const boolean_t isipv6 = FALSE; 554 #endif 555 #ifdef TCPDEBUG 556 short ostate = 0; 557 #endif 558 559 off0 = *offp; 560 m = *mp; 561 *mp = NULL; 562 563 tcpstat.tcps_rcvtotal++; 564 565 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 566 struct m_tag *mtag; 567 568 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 569 KKASSERT(mtag != NULL); 570 next_hop = m_tag_data(mtag); 571 } 572 573 #ifdef INET6 574 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 575 #endif 576 577 if (isipv6) { 578 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 579 ip6 = mtod(m, struct ip6_hdr *); 580 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 581 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 582 tcpstat.tcps_rcvbadsum++; 583 goto drop; 584 } 585 th = (struct tcphdr *)((caddr_t)ip6 + off0); 586 587 /* 588 * Be proactive about unspecified IPv6 address in source. 589 * As we use all-zero to indicate unbounded/unconnected pcb, 590 * unspecified IPv6 address can be used to confuse us. 591 * 592 * Note that packets with unspecified IPv6 destination is 593 * already dropped in ip6_input. 594 */ 595 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 596 /* XXX stat */ 597 goto drop; 598 } 599 } else { 600 /* 601 * Get IP and TCP header together in first mbuf. 602 * Note: IP leaves IP header in first mbuf. 603 */ 604 if (off0 > sizeof(struct ip)) { 605 ip_stripoptions(m); 606 off0 = sizeof(struct ip); 607 } 608 /* already checked and pulled up in ip_demux() */ 609 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 610 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 611 ip = mtod(m, struct ip *); 612 ipov = (struct ipovly *)ip; 613 th = (struct tcphdr *)((caddr_t)ip + off0); 614 tlen = ip->ip_len; 615 616 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 617 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 618 th->th_sum = m->m_pkthdr.csum_data; 619 else 620 th->th_sum = in_pseudo(ip->ip_src.s_addr, 621 ip->ip_dst.s_addr, 622 htonl(m->m_pkthdr.csum_data + 623 ip->ip_len + 624 IPPROTO_TCP)); 625 th->th_sum ^= 0xffff; 626 } else { 627 /* 628 * Checksum extended TCP header and data. 629 */ 630 len = sizeof(struct ip) + tlen; 631 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 632 ipov->ih_len = (u_short)tlen; 633 ipov->ih_len = htons(ipov->ih_len); 634 th->th_sum = in_cksum(m, len); 635 } 636 if (th->th_sum) { 637 tcpstat.tcps_rcvbadsum++; 638 goto drop; 639 } 640 #ifdef INET6 641 /* Re-initialization for later version check */ 642 ip->ip_v = IPVERSION; 643 #endif 644 } 645 646 /* 647 * Check that TCP offset makes sense, 648 * pull out TCP options and adjust length. XXX 649 */ 650 off = th->th_off << 2; 651 /* already checked and pulled up in ip_demux() */ 652 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 653 ("bad TCP data offset %d (tlen %d)", off, tlen)); 654 tlen -= off; /* tlen is used instead of ti->ti_len */ 655 if (off > sizeof(struct tcphdr)) { 656 if (isipv6) { 657 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 658 ip6 = mtod(m, struct ip6_hdr *); 659 th = (struct tcphdr *)((caddr_t)ip6 + off0); 660 } else { 661 /* already pulled up in ip_demux() */ 662 KASSERT(m->m_len >= sizeof(struct ip) + off, 663 ("TCP header and options not in one mbuf: " 664 "m_len %d, off %d", m->m_len, off)); 665 } 666 optlen = off - sizeof(struct tcphdr); 667 optp = (u_char *)(th + 1); 668 } 669 thflags = th->th_flags; 670 671 #ifdef TCP_DROP_SYNFIN 672 /* 673 * If the drop_synfin option is enabled, drop all packets with 674 * both the SYN and FIN bits set. This prevents e.g. nmap from 675 * identifying the TCP/IP stack. 676 * 677 * This is a violation of the TCP specification. 678 */ 679 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 680 goto drop; 681 #endif 682 683 /* 684 * Convert TCP protocol specific fields to host format. 685 */ 686 th->th_seq = ntohl(th->th_seq); 687 th->th_ack = ntohl(th->th_ack); 688 th->th_win = ntohs(th->th_win); 689 th->th_urp = ntohs(th->th_urp); 690 691 /* 692 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 693 * until after ip6_savecontrol() is called and before other functions 694 * which don't want those proto headers. 695 * Because ip6_savecontrol() is going to parse the mbuf to 696 * search for data to be passed up to user-land, it wants mbuf 697 * parameters to be unchanged. 698 * XXX: the call of ip6_savecontrol() has been obsoleted based on 699 * latest version of the advanced API (20020110). 700 */ 701 drop_hdrlen = off0 + off; 702 703 /* 704 * Locate pcb for segment. 705 */ 706 findpcb: 707 /* IPFIREWALL_FORWARD section */ 708 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 709 /* 710 * Transparently forwarded. Pretend to be the destination. 711 * already got one like this? 712 */ 713 cpu = mycpu->gd_cpuid; 714 inp = in_pcblookup_hash(&tcbinfo[cpu], 715 ip->ip_src, th->th_sport, 716 ip->ip_dst, th->th_dport, 717 0, m->m_pkthdr.rcvif); 718 if (!inp) { 719 /* 720 * It's new. Try to find the ambushing socket. 721 */ 722 723 /* 724 * The rest of the ipfw code stores the port in 725 * host order. XXX 726 * (The IP address is still in network order.) 727 */ 728 in_port_t dport = next_hop->sin_port ? 729 htons(next_hop->sin_port) : 730 th->th_dport; 731 732 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 733 next_hop->sin_addr.s_addr, dport); 734 inp = in_pcblookup_hash(&tcbinfo[cpu], 735 ip->ip_src, th->th_sport, 736 next_hop->sin_addr, dport, 737 1, m->m_pkthdr.rcvif); 738 } 739 } else { 740 if (isipv6) { 741 inp = in6_pcblookup_hash(&tcbinfo[0], 742 &ip6->ip6_src, th->th_sport, 743 &ip6->ip6_dst, th->th_dport, 744 1, m->m_pkthdr.rcvif); 745 } else { 746 cpu = mycpu->gd_cpuid; 747 inp = in_pcblookup_hash(&tcbinfo[cpu], 748 ip->ip_src, th->th_sport, 749 ip->ip_dst, th->th_dport, 750 1, m->m_pkthdr.rcvif); 751 } 752 } 753 754 /* 755 * If the state is CLOSED (i.e., TCB does not exist) then 756 * all data in the incoming segment is discarded. 757 * If the TCB exists but is in CLOSED state, it is embryonic, 758 * but should either do a listen or a connect soon. 759 */ 760 if (inp == NULL) { 761 if (log_in_vain) { 762 #ifdef INET6 763 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 764 #else 765 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 766 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 767 #endif 768 if (isipv6) { 769 strcpy(dbuf, "["); 770 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 771 strcat(dbuf, "]"); 772 strcpy(sbuf, "["); 773 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 774 strcat(sbuf, "]"); 775 } else { 776 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 777 strcpy(sbuf, inet_ntoa(ip->ip_src)); 778 } 779 switch (log_in_vain) { 780 case 1: 781 if (!(thflags & TH_SYN)) 782 break; 783 case 2: 784 log(LOG_INFO, 785 "Connection attempt to TCP %s:%d " 786 "from %s:%d flags:0x%02x\n", 787 dbuf, ntohs(th->th_dport), sbuf, 788 ntohs(th->th_sport), thflags); 789 break; 790 default: 791 break; 792 } 793 } 794 if (blackhole) { 795 switch (blackhole) { 796 case 1: 797 if (thflags & TH_SYN) 798 goto drop; 799 break; 800 case 2: 801 goto drop; 802 default: 803 goto drop; 804 } 805 } 806 rstreason = BANDLIM_RST_CLOSEDPORT; 807 goto dropwithreset; 808 } 809 810 #ifdef IPSEC 811 if (isipv6) { 812 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 813 ipsec6stat.in_polvio++; 814 goto drop; 815 } 816 } else { 817 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 818 ipsecstat.in_polvio++; 819 goto drop; 820 } 821 } 822 #endif 823 #ifdef FAST_IPSEC 824 if (isipv6) { 825 if (ipsec6_in_reject(m, inp)) 826 goto drop; 827 } else { 828 if (ipsec4_in_reject(m, inp)) 829 goto drop; 830 } 831 #endif 832 /* Check the minimum TTL for socket. */ 833 #ifdef INET6 834 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 835 goto drop; 836 #endif 837 838 tp = intotcpcb(inp); 839 if (tp == NULL) { 840 rstreason = BANDLIM_RST_CLOSEDPORT; 841 goto dropwithreset; 842 } 843 if (tp->t_state <= TCPS_CLOSED) 844 goto drop; 845 846 /* Unscale the window into a 32-bit value. */ 847 if (!(thflags & TH_SYN)) 848 tiwin = th->th_win << tp->snd_scale; 849 else 850 tiwin = th->th_win; 851 852 so = inp->inp_socket; 853 854 #ifdef TCPDEBUG 855 if (so->so_options & SO_DEBUG) { 856 ostate = tp->t_state; 857 if (isipv6) 858 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 859 else 860 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 861 tcp_savetcp = *th; 862 } 863 #endif 864 865 bzero(&to, sizeof to); 866 867 if (so->so_options & SO_ACCEPTCONN) { 868 struct in_conninfo inc; 869 870 #ifdef INET6 871 inc.inc_isipv6 = (isipv6 == TRUE); 872 #endif 873 if (isipv6) { 874 inc.inc6_faddr = ip6->ip6_src; 875 inc.inc6_laddr = ip6->ip6_dst; 876 inc.inc6_route.ro_rt = NULL; /* XXX */ 877 } else { 878 inc.inc_faddr = ip->ip_src; 879 inc.inc_laddr = ip->ip_dst; 880 inc.inc_route.ro_rt = NULL; /* XXX */ 881 } 882 inc.inc_fport = th->th_sport; 883 inc.inc_lport = th->th_dport; 884 885 /* 886 * If the state is LISTEN then ignore segment if it contains 887 * a RST. If the segment contains an ACK then it is bad and 888 * send a RST. If it does not contain a SYN then it is not 889 * interesting; drop it. 890 * 891 * If the state is SYN_RECEIVED (syncache) and seg contains 892 * an ACK, but not for our SYN/ACK, send a RST. If the seg 893 * contains a RST, check the sequence number to see if it 894 * is a valid reset segment. 895 */ 896 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 897 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 898 if (!syncache_expand(&inc, th, &so, m)) { 899 /* 900 * No syncache entry, or ACK was not 901 * for our SYN/ACK. Send a RST. 902 */ 903 tcpstat.tcps_badsyn++; 904 rstreason = BANDLIM_RST_OPENPORT; 905 goto dropwithreset; 906 } 907 908 /* 909 * Could not complete 3-way handshake, 910 * connection is being closed down, and 911 * syncache will free mbuf. 912 */ 913 if (so == NULL) 914 return(IPPROTO_DONE); 915 916 /* 917 * We must be in the correct protocol thread 918 * for this connection. 919 */ 920 KKASSERT(so->so_port == &curthread->td_msgport); 921 922 /* 923 * Socket is created in state SYN_RECEIVED. 924 * Continue processing segment. 925 */ 926 inp = so->so_pcb; 927 tp = intotcpcb(inp); 928 /* 929 * This is what would have happened in 930 * tcp_output() when the SYN,ACK was sent. 931 */ 932 tp->snd_up = tp->snd_una; 933 tp->snd_max = tp->snd_nxt = tp->iss + 1; 934 tp->last_ack_sent = tp->rcv_nxt; 935 /* 936 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 937 * until the _second_ ACK is received: 938 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 939 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 940 * move to ESTAB, set snd_wnd to tiwin. 941 */ 942 tp->snd_wnd = tiwin; /* unscaled */ 943 goto after_listen; 944 } 945 if (thflags & TH_RST) { 946 syncache_chkrst(&inc, th); 947 goto drop; 948 } 949 if (thflags & TH_ACK) { 950 syncache_badack(&inc); 951 tcpstat.tcps_badsyn++; 952 rstreason = BANDLIM_RST_OPENPORT; 953 goto dropwithreset; 954 } 955 goto drop; 956 } 957 958 /* 959 * Segment's flags are (SYN) or (SYN | FIN). 960 */ 961 #ifdef INET6 962 /* 963 * If deprecated address is forbidden, 964 * we do not accept SYN to deprecated interface 965 * address to prevent any new inbound connection from 966 * getting established. 967 * When we do not accept SYN, we send a TCP RST, 968 * with deprecated source address (instead of dropping 969 * it). We compromise it as it is much better for peer 970 * to send a RST, and RST will be the final packet 971 * for the exchange. 972 * 973 * If we do not forbid deprecated addresses, we accept 974 * the SYN packet. RFC2462 does not suggest dropping 975 * SYN in this case. 976 * If we decipher RFC2462 5.5.4, it says like this: 977 * 1. use of deprecated addr with existing 978 * communication is okay - "SHOULD continue to be 979 * used" 980 * 2. use of it with new communication: 981 * (2a) "SHOULD NOT be used if alternate address 982 * with sufficient scope is available" 983 * (2b) nothing mentioned otherwise. 984 * Here we fall into (2b) case as we have no choice in 985 * our source address selection - we must obey the peer. 986 * 987 * The wording in RFC2462 is confusing, and there are 988 * multiple description text for deprecated address 989 * handling - worse, they are not exactly the same. 990 * I believe 5.5.4 is the best one, so we follow 5.5.4. 991 */ 992 if (isipv6 && !ip6_use_deprecated) { 993 struct in6_ifaddr *ia6; 994 995 if ((ia6 = ip6_getdstifaddr(m)) && 996 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 997 tp = NULL; 998 rstreason = BANDLIM_RST_OPENPORT; 999 goto dropwithreset; 1000 } 1001 } 1002 #endif 1003 /* 1004 * If it is from this socket, drop it, it must be forged. 1005 * Don't bother responding if the destination was a broadcast. 1006 */ 1007 if (th->th_dport == th->th_sport) { 1008 if (isipv6) { 1009 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1010 &ip6->ip6_src)) 1011 goto drop; 1012 } else { 1013 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1014 goto drop; 1015 } 1016 } 1017 /* 1018 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1019 * 1020 * Note that it is quite possible to receive unicast 1021 * link-layer packets with a broadcast IP address. Use 1022 * in_broadcast() to find them. 1023 */ 1024 if (m->m_flags & (M_BCAST | M_MCAST)) 1025 goto drop; 1026 if (isipv6) { 1027 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1028 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1029 goto drop; 1030 } else { 1031 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1032 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1033 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1034 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1035 goto drop; 1036 } 1037 /* 1038 * SYN appears to be valid; create compressed TCP state 1039 * for syncache, or perform t/tcp connection. 1040 */ 1041 if (so->so_qlen <= so->so_qlimit) { 1042 tcp_dooptions(&to, optp, optlen, TRUE); 1043 if (!syncache_add(&inc, &to, th, &so, m)) 1044 goto drop; 1045 1046 /* 1047 * Entry added to syncache, mbuf used to 1048 * send SYN,ACK packet. 1049 */ 1050 if (so == NULL) 1051 return(IPPROTO_DONE); 1052 1053 /* 1054 * We must be in the correct protocol thread for 1055 * this connection. 1056 */ 1057 KKASSERT(so->so_port == &curthread->td_msgport); 1058 1059 inp = so->so_pcb; 1060 tp = intotcpcb(inp); 1061 tp->snd_wnd = tiwin; 1062 tp->t_starttime = ticks; 1063 tp->t_state = TCPS_ESTABLISHED; 1064 1065 /* 1066 * If there is a FIN, or if there is data and the 1067 * connection is local, then delay SYN,ACK(SYN) in 1068 * the hope of piggy-backing it on a response 1069 * segment. Otherwise must send ACK now in case 1070 * the other side is slow starting. 1071 */ 1072 if (DELAY_ACK(tp) && 1073 ((thflags & TH_FIN) || 1074 (tlen != 0 && 1075 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1076 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1077 tcp_callout_reset(tp, tp->tt_delack, 1078 tcp_delacktime, tcp_timer_delack); 1079 tp->t_flags |= TF_NEEDSYN; 1080 } else { 1081 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1082 } 1083 1084 tcpstat.tcps_connects++; 1085 soisconnected(so); 1086 goto trimthenstep6; 1087 } 1088 goto drop; 1089 } 1090 1091 after_listen: 1092 /* 1093 * Should not happen - syncache should pick up these connections. 1094 * 1095 * Once we are past handling listen sockets we must be in the 1096 * correct protocol processing thread. 1097 */ 1098 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1099 KKASSERT(so->so_port == &curthread->td_msgport); 1100 1101 /* 1102 * This is the second part of the MSS DoS prevention code (after 1103 * minmss on the sending side) and it deals with too many too small 1104 * tcp packets in a too short timeframe (1 second). 1105 * 1106 * XXX Removed. This code was crap. It does not scale to network 1107 * speed, and default values break NFS. Gone. 1108 */ 1109 /* REMOVED */ 1110 1111 /* 1112 * Segment received on connection. 1113 * 1114 * Reset idle time and keep-alive timer. Don't waste time if less 1115 * then a second has elapsed. 1116 */ 1117 if ((int)(ticks - tp->t_rcvtime) > hz) 1118 tcp_timer_keep_activity(tp, thflags); 1119 1120 /* 1121 * Process options. 1122 * XXX this is tradtitional behavior, may need to be cleaned up. 1123 */ 1124 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1125 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1126 if (to.to_flags & TOF_SCALE) { 1127 tp->t_flags |= TF_RCVD_SCALE; 1128 tp->requested_s_scale = to.to_requested_s_scale; 1129 } 1130 if (to.to_flags & TOF_TS) { 1131 tp->t_flags |= TF_RCVD_TSTMP; 1132 tp->ts_recent = to.to_tsval; 1133 tp->ts_recent_age = ticks; 1134 } 1135 if (to.to_flags & TOF_MSS) 1136 tcp_mss(tp, to.to_mss); 1137 /* 1138 * Only set the TF_SACK_PERMITTED per-connection flag 1139 * if we got a SACK_PERMITTED option from the other side 1140 * and the global tcp_do_sack variable is true. 1141 */ 1142 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1143 tp->t_flags |= TF_SACK_PERMITTED; 1144 } 1145 1146 /* 1147 * Header prediction: check for the two common cases 1148 * of a uni-directional data xfer. If the packet has 1149 * no control flags, is in-sequence, the window didn't 1150 * change and we're not retransmitting, it's a 1151 * candidate. If the length is zero and the ack moved 1152 * forward, we're the sender side of the xfer. Just 1153 * free the data acked & wake any higher level process 1154 * that was blocked waiting for space. If the length 1155 * is non-zero and the ack didn't move, we're the 1156 * receiver side. If we're getting packets in-order 1157 * (the reassembly queue is empty), add the data to 1158 * the socket buffer and note that we need a delayed ack. 1159 * Make sure that the hidden state-flags are also off. 1160 * Since we check for TCPS_ESTABLISHED above, it can only 1161 * be TH_NEEDSYN. 1162 */ 1163 if (tp->t_state == TCPS_ESTABLISHED && 1164 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1165 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1166 (!(to.to_flags & TOF_TS) || 1167 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1168 th->th_seq == tp->rcv_nxt && 1169 tp->snd_nxt == tp->snd_max) { 1170 1171 /* 1172 * If last ACK falls within this segment's sequence numbers, 1173 * record the timestamp. 1174 * NOTE that the test is modified according to the latest 1175 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1176 */ 1177 if ((to.to_flags & TOF_TS) && 1178 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1179 tp->ts_recent_age = ticks; 1180 tp->ts_recent = to.to_tsval; 1181 } 1182 1183 if (tlen == 0) { 1184 if (SEQ_GT(th->th_ack, tp->snd_una) && 1185 SEQ_LEQ(th->th_ack, tp->snd_max) && 1186 tp->snd_cwnd >= tp->snd_wnd && 1187 !IN_FASTRECOVERY(tp)) { 1188 /* 1189 * This is a pure ack for outstanding data. 1190 */ 1191 ++tcpstat.tcps_predack; 1192 /* 1193 * "bad retransmit" recovery 1194 * 1195 * If Eifel detection applies, then 1196 * it is deterministic, so use it 1197 * unconditionally over the old heuristic. 1198 * Otherwise, fall back to the old heuristic. 1199 */ 1200 if (tcp_do_eifel_detect && 1201 (to.to_flags & TOF_TS) && to.to_tsecr && 1202 (tp->t_flags & TF_FIRSTACCACK)) { 1203 /* Eifel detection applicable. */ 1204 if (to.to_tsecr < tp->t_rexmtTS) { 1205 tcp_revert_congestion_state(tp); 1206 ++tcpstat.tcps_eifeldetected; 1207 } 1208 } else if (tp->t_rxtshift == 1 && 1209 ticks < tp->t_badrxtwin) { 1210 tcp_revert_congestion_state(tp); 1211 ++tcpstat.tcps_rttdetected; 1212 } 1213 tp->t_flags &= ~(TF_FIRSTACCACK | 1214 TF_FASTREXMT | TF_EARLYREXMT); 1215 /* 1216 * Recalculate the retransmit timer / rtt. 1217 * 1218 * Some machines (certain windows boxes) 1219 * send broken timestamp replies during the 1220 * SYN+ACK phase, ignore timestamps of 0. 1221 */ 1222 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1223 tcp_xmit_timer(tp, 1224 ticks - to.to_tsecr + 1); 1225 } else if (tp->t_rtttime && 1226 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1227 tcp_xmit_timer(tp, 1228 ticks - tp->t_rtttime); 1229 } 1230 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1231 acked = th->th_ack - tp->snd_una; 1232 tcpstat.tcps_rcvackpack++; 1233 tcpstat.tcps_rcvackbyte += acked; 1234 sbdrop(&so->so_snd.sb, acked); 1235 tp->snd_recover = th->th_ack - 1; 1236 tp->snd_una = th->th_ack; 1237 tp->t_dupacks = 0; 1238 /* 1239 * Update window information. 1240 */ 1241 if (tiwin != tp->snd_wnd && 1242 acceptable_window_update(tp, th, tiwin)) { 1243 /* keep track of pure window updates */ 1244 if (tp->snd_wl2 == th->th_ack && 1245 tiwin > tp->snd_wnd) 1246 tcpstat.tcps_rcvwinupd++; 1247 tp->snd_wnd = tiwin; 1248 tp->snd_wl1 = th->th_seq; 1249 tp->snd_wl2 = th->th_ack; 1250 if (tp->snd_wnd > tp->max_sndwnd) 1251 tp->max_sndwnd = tp->snd_wnd; 1252 } 1253 m_freem(m); 1254 ND6_HINT(tp); /* some progress has been done */ 1255 /* 1256 * If all outstanding data are acked, stop 1257 * retransmit timer, otherwise restart timer 1258 * using current (possibly backed-off) value. 1259 * If process is waiting for space, 1260 * wakeup/selwakeup/signal. If data 1261 * are ready to send, let tcp_output 1262 * decide between more output or persist. 1263 */ 1264 if (tp->snd_una == tp->snd_max) { 1265 tcp_callout_stop(tp, tp->tt_rexmt); 1266 } else if (!tcp_callout_active(tp, 1267 tp->tt_persist)) { 1268 tcp_callout_reset(tp, tp->tt_rexmt, 1269 tp->t_rxtcur, tcp_timer_rexmt); 1270 } 1271 sowwakeup(so); 1272 if (so->so_snd.ssb_cc > 0) 1273 tcp_output(tp); 1274 return(IPPROTO_DONE); 1275 } 1276 } else if (tiwin == tp->snd_wnd && 1277 th->th_ack == tp->snd_una && 1278 LIST_EMPTY(&tp->t_segq) && 1279 tlen <= ssb_space(&so->so_rcv)) { 1280 u_long newsize = 0; /* automatic sockbuf scaling */ 1281 /* 1282 * This is a pure, in-sequence data packet 1283 * with nothing on the reassembly queue and 1284 * we have enough buffer space to take it. 1285 */ 1286 ++tcpstat.tcps_preddat; 1287 tp->rcv_nxt += tlen; 1288 tcpstat.tcps_rcvpack++; 1289 tcpstat.tcps_rcvbyte += tlen; 1290 ND6_HINT(tp); /* some progress has been done */ 1291 /* 1292 * Automatic sizing of receive socket buffer. Often the send 1293 * buffer size is not optimally adjusted to the actual network 1294 * conditions at hand (delay bandwidth product). Setting the 1295 * buffer size too small limits throughput on links with high 1296 * bandwidth and high delay (eg. trans-continental/oceanic links). 1297 * 1298 * On the receive side the socket buffer memory is only rarely 1299 * used to any significant extent. This allows us to be much 1300 * more aggressive in scaling the receive socket buffer. For 1301 * the case that the buffer space is actually used to a large 1302 * extent and we run out of kernel memory we can simply drop 1303 * the new segments; TCP on the sender will just retransmit it 1304 * later. Setting the buffer size too big may only consume too 1305 * much kernel memory if the application doesn't read() from 1306 * the socket or packet loss or reordering makes use of the 1307 * reassembly queue. 1308 * 1309 * The criteria to step up the receive buffer one notch are: 1310 * 1. the number of bytes received during the time it takes 1311 * one timestamp to be reflected back to us (the RTT); 1312 * 2. received bytes per RTT is within seven eighth of the 1313 * current socket buffer size; 1314 * 3. receive buffer size has not hit maximal automatic size; 1315 * 1316 * This algorithm does one step per RTT at most and only if 1317 * we receive a bulk stream w/o packet losses or reorderings. 1318 * Shrinking the buffer during idle times is not necessary as 1319 * it doesn't consume any memory when idle. 1320 * 1321 * TODO: Only step up if the application is actually serving 1322 * the buffer to better manage the socket buffer resources. 1323 */ 1324 if (tcp_do_autorcvbuf && 1325 to.to_tsecr && 1326 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1327 if (to.to_tsecr > tp->rfbuf_ts && 1328 to.to_tsecr - tp->rfbuf_ts < hz) { 1329 if (tp->rfbuf_cnt > 1330 (so->so_rcv.ssb_hiwat / 8 * 7) && 1331 so->so_rcv.ssb_hiwat < 1332 tcp_autorcvbuf_max) { 1333 newsize = 1334 ulmin(so->so_rcv.ssb_hiwat + 1335 tcp_autorcvbuf_inc, 1336 tcp_autorcvbuf_max); 1337 } 1338 /* Start over with next RTT. */ 1339 tp->rfbuf_ts = 0; 1340 tp->rfbuf_cnt = 0; 1341 } else 1342 tp->rfbuf_cnt += tlen; /* add up */ 1343 } 1344 /* 1345 * Add data to socket buffer. 1346 */ 1347 if (so->so_state & SS_CANTRCVMORE) { 1348 m_freem(m); 1349 } else { 1350 /* 1351 * Set new socket buffer size, give up when 1352 * limit is reached. 1353 * 1354 * Adjusting the size can mess up ACK 1355 * sequencing when pure window updates are 1356 * being avoided (which is the default), 1357 * so force an ack. 1358 */ 1359 lwkt_gettoken(&so->so_rcv.ssb_token); 1360 if (newsize) { 1361 tp->t_flags |= TF_RXRESIZED; 1362 if (!ssb_reserve(&so->so_rcv, newsize, 1363 so, NULL)) { 1364 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1365 } 1366 if (newsize >= 1367 (TCP_MAXWIN << tp->rcv_scale)) { 1368 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1369 } 1370 } 1371 m_adj(m, drop_hdrlen); /* delayed header drop */ 1372 ssb_appendstream(&so->so_rcv, m); 1373 lwkt_reltoken(&so->so_rcv.ssb_token); 1374 } 1375 sorwakeup(so); 1376 /* 1377 * This code is responsible for most of the ACKs 1378 * the TCP stack sends back after receiving a data 1379 * packet. Note that the DELAY_ACK check fails if 1380 * the delack timer is already running, which results 1381 * in an ack being sent every other packet (which is 1382 * what we want). 1383 * 1384 * We then further aggregate acks by not actually 1385 * sending one until the protocol thread has completed 1386 * processing the current backlog of packets. This 1387 * does not delay the ack any further, but allows us 1388 * to take advantage of the packet aggregation that 1389 * high speed NICs do (usually blocks of 8-10 packets) 1390 * to send a single ack rather then four or five acks, 1391 * greatly reducing the ack rate, the return channel 1392 * bandwidth, and the protocol overhead on both ends. 1393 * 1394 * Since this also has the effect of slowing down 1395 * the exponential slow-start ramp-up, systems with 1396 * very large bandwidth-delay products might want 1397 * to turn the feature off. 1398 */ 1399 if (DELAY_ACK(tp)) { 1400 tcp_callout_reset(tp, tp->tt_delack, 1401 tcp_delacktime, tcp_timer_delack); 1402 } else if (tcp_aggregate_acks) { 1403 tp->t_flags |= TF_ACKNOW; 1404 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1405 tp->t_flags |= TF_ONOUTPUTQ; 1406 tp->tt_cpu = mycpu->gd_cpuid; 1407 TAILQ_INSERT_TAIL( 1408 &tcpcbackq[tp->tt_cpu], 1409 tp, t_outputq); 1410 } 1411 } else { 1412 tp->t_flags |= TF_ACKNOW; 1413 tcp_output(tp); 1414 } 1415 return(IPPROTO_DONE); 1416 } 1417 } 1418 1419 /* 1420 * Calculate amount of space in receive window, 1421 * and then do TCP input processing. 1422 * Receive window is amount of space in rcv queue, 1423 * but not less than advertised window. 1424 */ 1425 recvwin = ssb_space(&so->so_rcv); 1426 if (recvwin < 0) 1427 recvwin = 0; 1428 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1429 1430 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1431 tp->rfbuf_ts = 0; 1432 tp->rfbuf_cnt = 0; 1433 1434 switch (tp->t_state) { 1435 /* 1436 * If the state is SYN_RECEIVED: 1437 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1438 */ 1439 case TCPS_SYN_RECEIVED: 1440 if ((thflags & TH_ACK) && 1441 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1442 SEQ_GT(th->th_ack, tp->snd_max))) { 1443 rstreason = BANDLIM_RST_OPENPORT; 1444 goto dropwithreset; 1445 } 1446 break; 1447 1448 /* 1449 * If the state is SYN_SENT: 1450 * if seg contains an ACK, but not for our SYN, drop the input. 1451 * if seg contains a RST, then drop the connection. 1452 * if seg does not contain SYN, then drop it. 1453 * Otherwise this is an acceptable SYN segment 1454 * initialize tp->rcv_nxt and tp->irs 1455 * if seg contains ack then advance tp->snd_una 1456 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1457 * arrange for segment to be acked (eventually) 1458 * continue processing rest of data/controls, beginning with URG 1459 */ 1460 case TCPS_SYN_SENT: 1461 if ((thflags & TH_ACK) && 1462 (SEQ_LEQ(th->th_ack, tp->iss) || 1463 SEQ_GT(th->th_ack, tp->snd_max))) { 1464 rstreason = BANDLIM_UNLIMITED; 1465 goto dropwithreset; 1466 } 1467 if (thflags & TH_RST) { 1468 if (thflags & TH_ACK) 1469 tp = tcp_drop(tp, ECONNREFUSED); 1470 goto drop; 1471 } 1472 if (!(thflags & TH_SYN)) 1473 goto drop; 1474 tp->snd_wnd = th->th_win; /* initial send window */ 1475 1476 tp->irs = th->th_seq; 1477 tcp_rcvseqinit(tp); 1478 if (thflags & TH_ACK) { 1479 /* Our SYN was acked. */ 1480 tcpstat.tcps_connects++; 1481 soisconnected(so); 1482 /* Do window scaling on this connection? */ 1483 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1484 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1485 tp->snd_scale = tp->requested_s_scale; 1486 tp->rcv_scale = tp->request_r_scale; 1487 } 1488 tp->rcv_adv += tp->rcv_wnd; 1489 tp->snd_una++; /* SYN is acked */ 1490 tcp_callout_stop(tp, tp->tt_rexmt); 1491 /* 1492 * If there's data, delay ACK; if there's also a FIN 1493 * ACKNOW will be turned on later. 1494 */ 1495 if (DELAY_ACK(tp) && tlen != 0) { 1496 tcp_callout_reset(tp, tp->tt_delack, 1497 tcp_delacktime, tcp_timer_delack); 1498 } else { 1499 tp->t_flags |= TF_ACKNOW; 1500 } 1501 /* 1502 * Received <SYN,ACK> in SYN_SENT[*] state. 1503 * Transitions: 1504 * SYN_SENT --> ESTABLISHED 1505 * SYN_SENT* --> FIN_WAIT_1 1506 */ 1507 tp->t_starttime = ticks; 1508 if (tp->t_flags & TF_NEEDFIN) { 1509 tp->t_state = TCPS_FIN_WAIT_1; 1510 tp->t_flags &= ~TF_NEEDFIN; 1511 thflags &= ~TH_SYN; 1512 } else { 1513 tp->t_state = TCPS_ESTABLISHED; 1514 tcp_callout_reset(tp, tp->tt_keep, 1515 tcp_getkeepidle(tp), 1516 tcp_timer_keep); 1517 } 1518 } else { 1519 /* 1520 * Received initial SYN in SYN-SENT[*] state => 1521 * simultaneous open. 1522 * Do 3-way handshake: 1523 * SYN-SENT -> SYN-RECEIVED 1524 * SYN-SENT* -> SYN-RECEIVED* 1525 */ 1526 tp->t_flags |= TF_ACKNOW; 1527 tcp_callout_stop(tp, tp->tt_rexmt); 1528 tp->t_state = TCPS_SYN_RECEIVED; 1529 } 1530 1531 trimthenstep6: 1532 /* 1533 * Advance th->th_seq to correspond to first data byte. 1534 * If data, trim to stay within window, 1535 * dropping FIN if necessary. 1536 */ 1537 th->th_seq++; 1538 if (tlen > tp->rcv_wnd) { 1539 todrop = tlen - tp->rcv_wnd; 1540 m_adj(m, -todrop); 1541 tlen = tp->rcv_wnd; 1542 thflags &= ~TH_FIN; 1543 tcpstat.tcps_rcvpackafterwin++; 1544 tcpstat.tcps_rcvbyteafterwin += todrop; 1545 } 1546 tp->snd_wl1 = th->th_seq - 1; 1547 tp->rcv_up = th->th_seq; 1548 /* 1549 * Client side of transaction: already sent SYN and data. 1550 * If the remote host used T/TCP to validate the SYN, 1551 * our data will be ACK'd; if so, enter normal data segment 1552 * processing in the middle of step 5, ack processing. 1553 * Otherwise, goto step 6. 1554 */ 1555 if (thflags & TH_ACK) 1556 goto process_ACK; 1557 1558 goto step6; 1559 1560 /* 1561 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1562 * do normal processing (we no longer bother with T/TCP). 1563 */ 1564 case TCPS_LAST_ACK: 1565 case TCPS_CLOSING: 1566 case TCPS_TIME_WAIT: 1567 break; /* continue normal processing */ 1568 } 1569 1570 /* 1571 * States other than LISTEN or SYN_SENT. 1572 * First check the RST flag and sequence number since reset segments 1573 * are exempt from the timestamp and connection count tests. This 1574 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1575 * below which allowed reset segments in half the sequence space 1576 * to fall though and be processed (which gives forged reset 1577 * segments with a random sequence number a 50 percent chance of 1578 * killing a connection). 1579 * Then check timestamp, if present. 1580 * Then check the connection count, if present. 1581 * Then check that at least some bytes of segment are within 1582 * receive window. If segment begins before rcv_nxt, 1583 * drop leading data (and SYN); if nothing left, just ack. 1584 * 1585 * 1586 * If the RST bit is set, check the sequence number to see 1587 * if this is a valid reset segment. 1588 * RFC 793 page 37: 1589 * In all states except SYN-SENT, all reset (RST) segments 1590 * are validated by checking their SEQ-fields. A reset is 1591 * valid if its sequence number is in the window. 1592 * Note: this does not take into account delayed ACKs, so 1593 * we should test against last_ack_sent instead of rcv_nxt. 1594 * The sequence number in the reset segment is normally an 1595 * echo of our outgoing acknowledgement numbers, but some hosts 1596 * send a reset with the sequence number at the rightmost edge 1597 * of our receive window, and we have to handle this case. 1598 * If we have multiple segments in flight, the intial reset 1599 * segment sequence numbers will be to the left of last_ack_sent, 1600 * but they will eventually catch up. 1601 * In any case, it never made sense to trim reset segments to 1602 * fit the receive window since RFC 1122 says: 1603 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1604 * 1605 * A TCP SHOULD allow a received RST segment to include data. 1606 * 1607 * DISCUSSION 1608 * It has been suggested that a RST segment could contain 1609 * ASCII text that encoded and explained the cause of the 1610 * RST. No standard has yet been established for such 1611 * data. 1612 * 1613 * If the reset segment passes the sequence number test examine 1614 * the state: 1615 * SYN_RECEIVED STATE: 1616 * If passive open, return to LISTEN state. 1617 * If active open, inform user that connection was refused. 1618 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1619 * Inform user that connection was reset, and close tcb. 1620 * CLOSING, LAST_ACK STATES: 1621 * Close the tcb. 1622 * TIME_WAIT STATE: 1623 * Drop the segment - see Stevens, vol. 2, p. 964 and 1624 * RFC 1337. 1625 */ 1626 if (thflags & TH_RST) { 1627 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1628 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1629 switch (tp->t_state) { 1630 1631 case TCPS_SYN_RECEIVED: 1632 so->so_error = ECONNREFUSED; 1633 goto close; 1634 1635 case TCPS_ESTABLISHED: 1636 case TCPS_FIN_WAIT_1: 1637 case TCPS_FIN_WAIT_2: 1638 case TCPS_CLOSE_WAIT: 1639 so->so_error = ECONNRESET; 1640 close: 1641 tp->t_state = TCPS_CLOSED; 1642 tcpstat.tcps_drops++; 1643 tp = tcp_close(tp); 1644 break; 1645 1646 case TCPS_CLOSING: 1647 case TCPS_LAST_ACK: 1648 tp = tcp_close(tp); 1649 break; 1650 1651 case TCPS_TIME_WAIT: 1652 break; 1653 } 1654 } 1655 goto drop; 1656 } 1657 1658 /* 1659 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1660 * and it's less than ts_recent, drop it. 1661 */ 1662 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1663 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1664 1665 /* Check to see if ts_recent is over 24 days old. */ 1666 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1667 /* 1668 * Invalidate ts_recent. If this segment updates 1669 * ts_recent, the age will be reset later and ts_recent 1670 * will get a valid value. If it does not, setting 1671 * ts_recent to zero will at least satisfy the 1672 * requirement that zero be placed in the timestamp 1673 * echo reply when ts_recent isn't valid. The 1674 * age isn't reset until we get a valid ts_recent 1675 * because we don't want out-of-order segments to be 1676 * dropped when ts_recent is old. 1677 */ 1678 tp->ts_recent = 0; 1679 } else { 1680 tcpstat.tcps_rcvduppack++; 1681 tcpstat.tcps_rcvdupbyte += tlen; 1682 tcpstat.tcps_pawsdrop++; 1683 if (tlen) 1684 goto dropafterack; 1685 goto drop; 1686 } 1687 } 1688 1689 /* 1690 * In the SYN-RECEIVED state, validate that the packet belongs to 1691 * this connection before trimming the data to fit the receive 1692 * window. Check the sequence number versus IRS since we know 1693 * the sequence numbers haven't wrapped. This is a partial fix 1694 * for the "LAND" DoS attack. 1695 */ 1696 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1697 rstreason = BANDLIM_RST_OPENPORT; 1698 goto dropwithreset; 1699 } 1700 1701 todrop = tp->rcv_nxt - th->th_seq; 1702 if (todrop > 0) { 1703 if (TCP_DO_SACK(tp)) { 1704 /* Report duplicate segment at head of packet. */ 1705 tp->reportblk.rblk_start = th->th_seq; 1706 tp->reportblk.rblk_end = th->th_seq + tlen; 1707 if (thflags & TH_FIN) 1708 ++tp->reportblk.rblk_end; 1709 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1710 tp->reportblk.rblk_end = tp->rcv_nxt; 1711 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1712 } 1713 if (thflags & TH_SYN) { 1714 thflags &= ~TH_SYN; 1715 th->th_seq++; 1716 if (th->th_urp > 1) 1717 th->th_urp--; 1718 else 1719 thflags &= ~TH_URG; 1720 todrop--; 1721 } 1722 /* 1723 * Following if statement from Stevens, vol. 2, p. 960. 1724 */ 1725 if (todrop > tlen || 1726 (todrop == tlen && !(thflags & TH_FIN))) { 1727 /* 1728 * Any valid FIN must be to the left of the window. 1729 * At this point the FIN must be a duplicate or out 1730 * of sequence; drop it. 1731 */ 1732 thflags &= ~TH_FIN; 1733 1734 /* 1735 * Send an ACK to resynchronize and drop any data. 1736 * But keep on processing for RST or ACK. 1737 */ 1738 tp->t_flags |= TF_ACKNOW; 1739 todrop = tlen; 1740 tcpstat.tcps_rcvduppack++; 1741 tcpstat.tcps_rcvdupbyte += todrop; 1742 } else { 1743 tcpstat.tcps_rcvpartduppack++; 1744 tcpstat.tcps_rcvpartdupbyte += todrop; 1745 } 1746 drop_hdrlen += todrop; /* drop from the top afterwards */ 1747 th->th_seq += todrop; 1748 tlen -= todrop; 1749 if (th->th_urp > todrop) 1750 th->th_urp -= todrop; 1751 else { 1752 thflags &= ~TH_URG; 1753 th->th_urp = 0; 1754 } 1755 } 1756 1757 /* 1758 * If new data are received on a connection after the 1759 * user processes are gone, then RST the other end. 1760 */ 1761 if ((so->so_state & SS_NOFDREF) && 1762 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1763 tp = tcp_close(tp); 1764 tcpstat.tcps_rcvafterclose++; 1765 rstreason = BANDLIM_UNLIMITED; 1766 goto dropwithreset; 1767 } 1768 1769 /* 1770 * If segment ends after window, drop trailing data 1771 * (and PUSH and FIN); if nothing left, just ACK. 1772 */ 1773 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1774 if (todrop > 0) { 1775 tcpstat.tcps_rcvpackafterwin++; 1776 if (todrop >= tlen) { 1777 tcpstat.tcps_rcvbyteafterwin += tlen; 1778 /* 1779 * If a new connection request is received 1780 * while in TIME_WAIT, drop the old connection 1781 * and start over if the sequence numbers 1782 * are above the previous ones. 1783 */ 1784 if (thflags & TH_SYN && 1785 tp->t_state == TCPS_TIME_WAIT && 1786 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1787 tp = tcp_close(tp); 1788 goto findpcb; 1789 } 1790 /* 1791 * If window is closed can only take segments at 1792 * window edge, and have to drop data and PUSH from 1793 * incoming segments. Continue processing, but 1794 * remember to ack. Otherwise, drop segment 1795 * and ack. 1796 */ 1797 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1798 tp->t_flags |= TF_ACKNOW; 1799 tcpstat.tcps_rcvwinprobe++; 1800 } else 1801 goto dropafterack; 1802 } else 1803 tcpstat.tcps_rcvbyteafterwin += todrop; 1804 m_adj(m, -todrop); 1805 tlen -= todrop; 1806 thflags &= ~(TH_PUSH | TH_FIN); 1807 } 1808 1809 /* 1810 * If last ACK falls within this segment's sequence numbers, 1811 * record its timestamp. 1812 * NOTE: 1813 * 1) That the test incorporates suggestions from the latest 1814 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1815 * 2) That updating only on newer timestamps interferes with 1816 * our earlier PAWS tests, so this check should be solely 1817 * predicated on the sequence space of this segment. 1818 * 3) That we modify the segment boundary check to be 1819 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1820 * instead of RFC1323's 1821 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1822 * This modified check allows us to overcome RFC1323's 1823 * limitations as described in Stevens TCP/IP Illustrated 1824 * Vol. 2 p.869. In such cases, we can still calculate the 1825 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1826 */ 1827 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1828 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1829 + ((thflags & TH_SYN) != 0) 1830 + ((thflags & TH_FIN) != 0)))) { 1831 tp->ts_recent_age = ticks; 1832 tp->ts_recent = to.to_tsval; 1833 } 1834 1835 /* 1836 * If a SYN is in the window, then this is an 1837 * error and we send an RST and drop the connection. 1838 */ 1839 if (thflags & TH_SYN) { 1840 tp = tcp_drop(tp, ECONNRESET); 1841 rstreason = BANDLIM_UNLIMITED; 1842 goto dropwithreset; 1843 } 1844 1845 /* 1846 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1847 * flag is on (half-synchronized state), then queue data for 1848 * later processing; else drop segment and return. 1849 */ 1850 if (!(thflags & TH_ACK)) { 1851 if (tp->t_state == TCPS_SYN_RECEIVED || 1852 (tp->t_flags & TF_NEEDSYN)) 1853 goto step6; 1854 else 1855 goto drop; 1856 } 1857 1858 /* 1859 * Ack processing. 1860 */ 1861 switch (tp->t_state) { 1862 /* 1863 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1864 * ESTABLISHED state and continue processing. 1865 * The ACK was checked above. 1866 */ 1867 case TCPS_SYN_RECEIVED: 1868 1869 tcpstat.tcps_connects++; 1870 soisconnected(so); 1871 /* Do window scaling? */ 1872 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1873 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1874 tp->snd_scale = tp->requested_s_scale; 1875 tp->rcv_scale = tp->request_r_scale; 1876 } 1877 /* 1878 * Make transitions: 1879 * SYN-RECEIVED -> ESTABLISHED 1880 * SYN-RECEIVED* -> FIN-WAIT-1 1881 */ 1882 tp->t_starttime = ticks; 1883 if (tp->t_flags & TF_NEEDFIN) { 1884 tp->t_state = TCPS_FIN_WAIT_1; 1885 tp->t_flags &= ~TF_NEEDFIN; 1886 } else { 1887 tp->t_state = TCPS_ESTABLISHED; 1888 tcp_callout_reset(tp, tp->tt_keep, 1889 tcp_getkeepidle(tp), 1890 tcp_timer_keep); 1891 } 1892 /* 1893 * If segment contains data or ACK, will call tcp_reass() 1894 * later; if not, do so now to pass queued data to user. 1895 */ 1896 if (tlen == 0 && !(thflags & TH_FIN)) 1897 tcp_reass(tp, NULL, NULL, NULL); 1898 /* fall into ... */ 1899 1900 /* 1901 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1902 * ACKs. If the ack is in the range 1903 * tp->snd_una < th->th_ack <= tp->snd_max 1904 * then advance tp->snd_una to th->th_ack and drop 1905 * data from the retransmission queue. If this ACK reflects 1906 * more up to date window information we update our window information. 1907 */ 1908 case TCPS_ESTABLISHED: 1909 case TCPS_FIN_WAIT_1: 1910 case TCPS_FIN_WAIT_2: 1911 case TCPS_CLOSE_WAIT: 1912 case TCPS_CLOSING: 1913 case TCPS_LAST_ACK: 1914 case TCPS_TIME_WAIT: 1915 1916 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1917 if (TCP_DO_SACK(tp)) 1918 tcp_sack_update_scoreboard(tp, &to); 1919 if (tlen != 0 || tiwin != tp->snd_wnd) { 1920 tp->t_dupacks = 0; 1921 break; 1922 } 1923 tcpstat.tcps_rcvdupack++; 1924 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1925 th->th_ack != tp->snd_una) { 1926 tp->t_dupacks = 0; 1927 break; 1928 } 1929 /* 1930 * We have outstanding data (other than 1931 * a window probe), this is a completely 1932 * duplicate ack (ie, window info didn't 1933 * change), the ack is the biggest we've 1934 * seen and we've seen exactly our rexmt 1935 * threshhold of them, so assume a packet 1936 * has been dropped and retransmit it. 1937 * Kludge snd_nxt & the congestion 1938 * window so we send only this one 1939 * packet. 1940 */ 1941 if (IN_FASTRECOVERY(tp)) { 1942 if (TCP_DO_SACK(tp)) { 1943 /* No artifical cwnd inflation. */ 1944 tcp_sack_rexmt(tp, th); 1945 } else { 1946 /* 1947 * Dup acks mean that packets 1948 * have left the network 1949 * (they're now cached at the 1950 * receiver) so bump cwnd by 1951 * the amount in the receiver 1952 * to keep a constant cwnd 1953 * packets in the network. 1954 */ 1955 tp->snd_cwnd += tp->t_maxseg; 1956 tcp_output(tp); 1957 } 1958 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1959 tp->t_dupacks = 0; 1960 break; 1961 } else if (++tp->t_dupacks == tcprexmtthresh) { 1962 tcp_seq old_snd_nxt; 1963 u_int win; 1964 1965 fastretransmit: 1966 if (tcp_do_eifel_detect && 1967 (tp->t_flags & TF_RCVD_TSTMP)) { 1968 tcp_save_congestion_state(tp); 1969 tp->t_flags |= TF_FASTREXMT; 1970 } 1971 /* 1972 * We know we're losing at the current 1973 * window size, so do congestion avoidance: 1974 * set ssthresh to half the current window 1975 * and pull our congestion window back to the 1976 * new ssthresh. 1977 */ 1978 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1979 tp->t_maxseg; 1980 if (win < 2) 1981 win = 2; 1982 tp->snd_ssthresh = win * tp->t_maxseg; 1983 ENTER_FASTRECOVERY(tp); 1984 tp->snd_recover = tp->snd_max; 1985 tcp_callout_stop(tp, tp->tt_rexmt); 1986 tp->t_rtttime = 0; 1987 old_snd_nxt = tp->snd_nxt; 1988 tp->snd_nxt = th->th_ack; 1989 tp->snd_cwnd = tp->t_maxseg; 1990 tcp_output(tp); 1991 ++tcpstat.tcps_sndfastrexmit; 1992 tp->snd_cwnd = tp->snd_ssthresh; 1993 tp->rexmt_high = tp->snd_nxt; 1994 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1995 tp->snd_nxt = old_snd_nxt; 1996 KASSERT(tp->snd_limited <= 2, 1997 ("tp->snd_limited too big")); 1998 if (TCP_DO_SACK(tp)) 1999 tcp_sack_rexmt(tp, th); 2000 else 2001 tp->snd_cwnd += tp->t_maxseg * 2002 (tp->t_dupacks - tp->snd_limited); 2003 } else if (tcp_do_limitedtransmit) { 2004 u_long oldcwnd = tp->snd_cwnd; 2005 tcp_seq oldsndmax = tp->snd_max; 2006 tcp_seq oldsndnxt = tp->snd_nxt; 2007 /* outstanding data */ 2008 uint32_t ownd = tp->snd_max - tp->snd_una; 2009 u_int sent; 2010 2011 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 2012 2013 KASSERT(tp->t_dupacks == 1 || 2014 tp->t_dupacks == 2, 2015 ("dupacks not 1 or 2")); 2016 if (tp->t_dupacks == 1) 2017 tp->snd_limited = 0; 2018 tp->snd_nxt = tp->snd_max; 2019 tp->snd_cwnd = ownd + 2020 (tp->t_dupacks - tp->snd_limited) * 2021 tp->t_maxseg; 2022 tcp_output(tp); 2023 2024 /* 2025 * Other acks may have been processed, 2026 * snd_nxt cannot be reset to a value less 2027 * then snd_una. 2028 */ 2029 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2030 if (SEQ_GT(oldsndnxt, tp->snd_una)) 2031 tp->snd_nxt = oldsndnxt; 2032 else 2033 tp->snd_nxt = tp->snd_una; 2034 } 2035 tp->snd_cwnd = oldcwnd; 2036 sent = tp->snd_max - oldsndmax; 2037 if (sent > tp->t_maxseg) { 2038 KASSERT((tp->t_dupacks == 2 && 2039 tp->snd_limited == 0) || 2040 (sent == tp->t_maxseg + 1 && 2041 tp->t_flags & TF_SENTFIN), 2042 ("sent too much")); 2043 KASSERT(sent <= tp->t_maxseg * 2, 2044 ("sent too many segments")); 2045 tp->snd_limited = 2; 2046 tcpstat.tcps_sndlimited += 2; 2047 } else if (sent > 0) { 2048 ++tp->snd_limited; 2049 ++tcpstat.tcps_sndlimited; 2050 } else if (tcp_do_early_retransmit && 2051 (tcp_do_eifel_detect && 2052 (tp->t_flags & TF_RCVD_TSTMP)) && 2053 ownd < 4 * tp->t_maxseg && 2054 tp->t_dupacks + 1 >= 2055 iceildiv(ownd, tp->t_maxseg) && 2056 (!TCP_DO_SACK(tp) || 2057 ownd <= tp->t_maxseg || 2058 tcp_sack_has_sacked(&tp->scb, 2059 ownd - tp->t_maxseg))) { 2060 ++tcpstat.tcps_sndearlyrexmit; 2061 tp->t_flags |= TF_EARLYREXMT; 2062 goto fastretransmit; 2063 } 2064 } 2065 goto drop; 2066 } 2067 2068 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2069 tp->t_dupacks = 0; 2070 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2071 /* 2072 * Detected optimistic ACK attack. 2073 * Force slow-start to de-synchronize attack. 2074 */ 2075 tp->snd_cwnd = tp->t_maxseg; 2076 tp->snd_wacked = 0; 2077 2078 tcpstat.tcps_rcvacktoomuch++; 2079 goto dropafterack; 2080 } 2081 /* 2082 * If we reach this point, ACK is not a duplicate, 2083 * i.e., it ACKs something we sent. 2084 */ 2085 if (tp->t_flags & TF_NEEDSYN) { 2086 /* 2087 * T/TCP: Connection was half-synchronized, and our 2088 * SYN has been ACK'd (so connection is now fully 2089 * synchronized). Go to non-starred state, 2090 * increment snd_una for ACK of SYN, and check if 2091 * we can do window scaling. 2092 */ 2093 tp->t_flags &= ~TF_NEEDSYN; 2094 tp->snd_una++; 2095 /* Do window scaling? */ 2096 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2097 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2098 tp->snd_scale = tp->requested_s_scale; 2099 tp->rcv_scale = tp->request_r_scale; 2100 } 2101 } 2102 2103 process_ACK: 2104 acked = th->th_ack - tp->snd_una; 2105 tcpstat.tcps_rcvackpack++; 2106 tcpstat.tcps_rcvackbyte += acked; 2107 2108 if (tcp_do_eifel_detect && acked > 0 && 2109 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2110 (tp->t_flags & TF_FIRSTACCACK)) { 2111 /* Eifel detection applicable. */ 2112 if (to.to_tsecr < tp->t_rexmtTS) { 2113 ++tcpstat.tcps_eifeldetected; 2114 tcp_revert_congestion_state(tp); 2115 if (tp->t_rxtshift == 1 && 2116 ticks >= tp->t_badrxtwin) 2117 ++tcpstat.tcps_rttcantdetect; 2118 } 2119 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2120 /* 2121 * If we just performed our first retransmit, 2122 * and the ACK arrives within our recovery window, 2123 * then it was a mistake to do the retransmit 2124 * in the first place. Recover our original cwnd 2125 * and ssthresh, and proceed to transmit where we 2126 * left off. 2127 */ 2128 tcp_revert_congestion_state(tp); 2129 ++tcpstat.tcps_rttdetected; 2130 } 2131 2132 /* 2133 * If we have a timestamp reply, update smoothed 2134 * round trip time. If no timestamp is present but 2135 * transmit timer is running and timed sequence 2136 * number was acked, update smoothed round trip time. 2137 * Since we now have an rtt measurement, cancel the 2138 * timer backoff (cf., Phil Karn's retransmit alg.). 2139 * Recompute the initial retransmit timer. 2140 * 2141 * Some machines (certain windows boxes) send broken 2142 * timestamp replies during the SYN+ACK phase, ignore 2143 * timestamps of 0. 2144 */ 2145 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2146 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2147 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2148 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2149 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2150 2151 /* 2152 * If no data (only SYN) was ACK'd, 2153 * skip rest of ACK processing. 2154 */ 2155 if (acked == 0) 2156 goto step6; 2157 2158 /* Stop looking for an acceptable ACK since one was received. */ 2159 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2160 2161 if (acked > so->so_snd.ssb_cc) { 2162 tp->snd_wnd -= so->so_snd.ssb_cc; 2163 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2164 ourfinisacked = TRUE; 2165 } else { 2166 sbdrop(&so->so_snd.sb, acked); 2167 tp->snd_wnd -= acked; 2168 ourfinisacked = FALSE; 2169 } 2170 sowwakeup(so); 2171 2172 /* 2173 * Update window information. 2174 * Don't look at window if no ACK: 2175 * TAC's send garbage on first SYN. 2176 */ 2177 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2178 (tp->snd_wl1 == th->th_seq && 2179 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2180 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2181 /* keep track of pure window updates */ 2182 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2183 tiwin > tp->snd_wnd) 2184 tcpstat.tcps_rcvwinupd++; 2185 tp->snd_wnd = tiwin; 2186 tp->snd_wl1 = th->th_seq; 2187 tp->snd_wl2 = th->th_ack; 2188 if (tp->snd_wnd > tp->max_sndwnd) 2189 tp->max_sndwnd = tp->snd_wnd; 2190 needoutput = TRUE; 2191 } 2192 2193 tp->snd_una = th->th_ack; 2194 if (TCP_DO_SACK(tp)) 2195 tcp_sack_update_scoreboard(tp, &to); 2196 if (IN_FASTRECOVERY(tp)) { 2197 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2198 EXIT_FASTRECOVERY(tp); 2199 needoutput = TRUE; 2200 /* 2201 * If the congestion window was inflated 2202 * to account for the other side's 2203 * cached packets, retract it. 2204 */ 2205 if (!TCP_DO_SACK(tp)) 2206 tp->snd_cwnd = tp->snd_ssthresh; 2207 2208 /* 2209 * Window inflation should have left us 2210 * with approximately snd_ssthresh outstanding 2211 * data. But, in case we would be inclined 2212 * to send a burst, better do it using 2213 * slow start. 2214 */ 2215 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2216 tp->snd_max + 2 * tp->t_maxseg)) 2217 tp->snd_cwnd = 2218 (tp->snd_max - tp->snd_una) + 2219 2 * tp->t_maxseg; 2220 2221 tp->snd_wacked = 0; 2222 } else { 2223 if (TCP_DO_SACK(tp)) { 2224 tp->snd_max_rexmt = tp->snd_max; 2225 tcp_sack_rexmt(tp, th); 2226 } else { 2227 tcp_newreno_partial_ack(tp, th, acked); 2228 } 2229 needoutput = FALSE; 2230 } 2231 } else { 2232 /* 2233 * Open the congestion window. When in slow-start, 2234 * open exponentially: maxseg per packet. Otherwise, 2235 * open linearly: maxseg per window. 2236 */ 2237 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2238 u_int abc_sslimit = 2239 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2240 tp->t_maxseg : 2 * tp->t_maxseg); 2241 2242 /* slow-start */ 2243 tp->snd_cwnd += tcp_do_abc ? 2244 min(acked, abc_sslimit) : tp->t_maxseg; 2245 } else { 2246 /* linear increase */ 2247 tp->snd_wacked += tcp_do_abc ? acked : 2248 tp->t_maxseg; 2249 if (tp->snd_wacked >= tp->snd_cwnd) { 2250 tp->snd_wacked -= tp->snd_cwnd; 2251 tp->snd_cwnd += tp->t_maxseg; 2252 } 2253 } 2254 tp->snd_cwnd = min(tp->snd_cwnd, 2255 TCP_MAXWIN << tp->snd_scale); 2256 tp->snd_recover = th->th_ack - 1; 2257 } 2258 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2259 tp->snd_nxt = tp->snd_una; 2260 2261 /* 2262 * If all outstanding data is acked, stop retransmit 2263 * timer and remember to restart (more output or persist). 2264 * If there is more data to be acked, restart retransmit 2265 * timer, using current (possibly backed-off) value. 2266 */ 2267 if (th->th_ack == tp->snd_max) { 2268 tcp_callout_stop(tp, tp->tt_rexmt); 2269 needoutput = TRUE; 2270 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2271 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2272 tcp_timer_rexmt); 2273 } 2274 2275 switch (tp->t_state) { 2276 /* 2277 * In FIN_WAIT_1 STATE in addition to the processing 2278 * for the ESTABLISHED state if our FIN is now acknowledged 2279 * then enter FIN_WAIT_2. 2280 */ 2281 case TCPS_FIN_WAIT_1: 2282 if (ourfinisacked) { 2283 /* 2284 * If we can't receive any more 2285 * data, then closing user can proceed. 2286 * Starting the timer is contrary to the 2287 * specification, but if we don't get a FIN 2288 * we'll hang forever. 2289 */ 2290 if (so->so_state & SS_CANTRCVMORE) { 2291 soisdisconnected(so); 2292 tcp_callout_reset(tp, tp->tt_2msl, 2293 tp->t_maxidle, tcp_timer_2msl); 2294 } 2295 tp->t_state = TCPS_FIN_WAIT_2; 2296 } 2297 break; 2298 2299 /* 2300 * In CLOSING STATE in addition to the processing for 2301 * the ESTABLISHED state if the ACK acknowledges our FIN 2302 * then enter the TIME-WAIT state, otherwise ignore 2303 * the segment. 2304 */ 2305 case TCPS_CLOSING: 2306 if (ourfinisacked) { 2307 tp->t_state = TCPS_TIME_WAIT; 2308 tcp_canceltimers(tp); 2309 tcp_callout_reset(tp, tp->tt_2msl, 2310 2 * tcp_rmx_msl(tp), 2311 tcp_timer_2msl); 2312 soisdisconnected(so); 2313 } 2314 break; 2315 2316 /* 2317 * In LAST_ACK, we may still be waiting for data to drain 2318 * and/or to be acked, as well as for the ack of our FIN. 2319 * If our FIN is now acknowledged, delete the TCB, 2320 * enter the closed state and return. 2321 */ 2322 case TCPS_LAST_ACK: 2323 if (ourfinisacked) { 2324 tp = tcp_close(tp); 2325 goto drop; 2326 } 2327 break; 2328 2329 /* 2330 * In TIME_WAIT state the only thing that should arrive 2331 * is a retransmission of the remote FIN. Acknowledge 2332 * it and restart the finack timer. 2333 */ 2334 case TCPS_TIME_WAIT: 2335 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2336 tcp_timer_2msl); 2337 goto dropafterack; 2338 } 2339 } 2340 2341 step6: 2342 /* 2343 * Update window information. 2344 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2345 */ 2346 if ((thflags & TH_ACK) && 2347 acceptable_window_update(tp, th, tiwin)) { 2348 /* keep track of pure window updates */ 2349 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2350 tiwin > tp->snd_wnd) 2351 tcpstat.tcps_rcvwinupd++; 2352 tp->snd_wnd = tiwin; 2353 tp->snd_wl1 = th->th_seq; 2354 tp->snd_wl2 = th->th_ack; 2355 if (tp->snd_wnd > tp->max_sndwnd) 2356 tp->max_sndwnd = tp->snd_wnd; 2357 needoutput = TRUE; 2358 } 2359 2360 /* 2361 * Process segments with URG. 2362 */ 2363 if ((thflags & TH_URG) && th->th_urp && 2364 !TCPS_HAVERCVDFIN(tp->t_state)) { 2365 /* 2366 * This is a kludge, but if we receive and accept 2367 * random urgent pointers, we'll crash in 2368 * soreceive. It's hard to imagine someone 2369 * actually wanting to send this much urgent data. 2370 */ 2371 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2372 th->th_urp = 0; /* XXX */ 2373 thflags &= ~TH_URG; /* XXX */ 2374 goto dodata; /* XXX */ 2375 } 2376 /* 2377 * If this segment advances the known urgent pointer, 2378 * then mark the data stream. This should not happen 2379 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2380 * a FIN has been received from the remote side. 2381 * In these states we ignore the URG. 2382 * 2383 * According to RFC961 (Assigned Protocols), 2384 * the urgent pointer points to the last octet 2385 * of urgent data. We continue, however, 2386 * to consider it to indicate the first octet 2387 * of data past the urgent section as the original 2388 * spec states (in one of two places). 2389 */ 2390 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2391 tp->rcv_up = th->th_seq + th->th_urp; 2392 so->so_oobmark = so->so_rcv.ssb_cc + 2393 (tp->rcv_up - tp->rcv_nxt) - 1; 2394 if (so->so_oobmark == 0) 2395 sosetstate(so, SS_RCVATMARK); 2396 sohasoutofband(so); 2397 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2398 } 2399 /* 2400 * Remove out of band data so doesn't get presented to user. 2401 * This can happen independent of advancing the URG pointer, 2402 * but if two URG's are pending at once, some out-of-band 2403 * data may creep in... ick. 2404 */ 2405 if (th->th_urp <= (u_long)tlen && 2406 !(so->so_options & SO_OOBINLINE)) { 2407 /* hdr drop is delayed */ 2408 tcp_pulloutofband(so, th, m, drop_hdrlen); 2409 } 2410 } else { 2411 /* 2412 * If no out of band data is expected, 2413 * pull receive urgent pointer along 2414 * with the receive window. 2415 */ 2416 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2417 tp->rcv_up = tp->rcv_nxt; 2418 } 2419 2420 dodata: /* XXX */ 2421 /* 2422 * Process the segment text, merging it into the TCP sequencing queue, 2423 * and arranging for acknowledgment of receipt if necessary. 2424 * This process logically involves adjusting tp->rcv_wnd as data 2425 * is presented to the user (this happens in tcp_usrreq.c, 2426 * case PRU_RCVD). If a FIN has already been received on this 2427 * connection then we just ignore the text. 2428 */ 2429 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2430 m_adj(m, drop_hdrlen); /* delayed header drop */ 2431 /* 2432 * Insert segment which includes th into TCP reassembly queue 2433 * with control block tp. Set thflags to whether reassembly now 2434 * includes a segment with FIN. This handles the common case 2435 * inline (segment is the next to be received on an established 2436 * connection, and the queue is empty), avoiding linkage into 2437 * and removal from the queue and repetition of various 2438 * conversions. 2439 * Set DELACK for segments received in order, but ack 2440 * immediately when segments are out of order (so 2441 * fast retransmit can work). 2442 */ 2443 if (th->th_seq == tp->rcv_nxt && 2444 LIST_EMPTY(&tp->t_segq) && 2445 TCPS_HAVEESTABLISHED(tp->t_state)) { 2446 if (DELAY_ACK(tp)) { 2447 tcp_callout_reset(tp, tp->tt_delack, 2448 tcp_delacktime, tcp_timer_delack); 2449 } else { 2450 tp->t_flags |= TF_ACKNOW; 2451 } 2452 tp->rcv_nxt += tlen; 2453 thflags = th->th_flags & TH_FIN; 2454 tcpstat.tcps_rcvpack++; 2455 tcpstat.tcps_rcvbyte += tlen; 2456 ND6_HINT(tp); 2457 if (so->so_state & SS_CANTRCVMORE) { 2458 m_freem(m); 2459 } else { 2460 lwkt_gettoken(&so->so_rcv.ssb_token); 2461 ssb_appendstream(&so->so_rcv, m); 2462 lwkt_reltoken(&so->so_rcv.ssb_token); 2463 } 2464 sorwakeup(so); 2465 } else { 2466 if (!(tp->t_flags & TF_DUPSEG)) { 2467 /* Initialize SACK report block. */ 2468 tp->reportblk.rblk_start = th->th_seq; 2469 tp->reportblk.rblk_end = th->th_seq + tlen + 2470 ((thflags & TH_FIN) != 0); 2471 } 2472 thflags = tcp_reass(tp, th, &tlen, m); 2473 tp->t_flags |= TF_ACKNOW; 2474 } 2475 2476 /* 2477 * Note the amount of data that peer has sent into 2478 * our window, in order to estimate the sender's 2479 * buffer size. 2480 */ 2481 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2482 } else { 2483 m_freem(m); 2484 thflags &= ~TH_FIN; 2485 } 2486 2487 /* 2488 * If FIN is received ACK the FIN and let the user know 2489 * that the connection is closing. 2490 */ 2491 if (thflags & TH_FIN) { 2492 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2493 socantrcvmore(so); 2494 /* 2495 * If connection is half-synchronized 2496 * (ie NEEDSYN flag on) then delay ACK, 2497 * so it may be piggybacked when SYN is sent. 2498 * Otherwise, since we received a FIN then no 2499 * more input can be expected, send ACK now. 2500 */ 2501 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2502 tcp_callout_reset(tp, tp->tt_delack, 2503 tcp_delacktime, tcp_timer_delack); 2504 } else { 2505 tp->t_flags |= TF_ACKNOW; 2506 } 2507 tp->rcv_nxt++; 2508 } 2509 2510 switch (tp->t_state) { 2511 /* 2512 * In SYN_RECEIVED and ESTABLISHED STATES 2513 * enter the CLOSE_WAIT state. 2514 */ 2515 case TCPS_SYN_RECEIVED: 2516 tp->t_starttime = ticks; 2517 /*FALLTHROUGH*/ 2518 case TCPS_ESTABLISHED: 2519 tp->t_state = TCPS_CLOSE_WAIT; 2520 break; 2521 2522 /* 2523 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2524 * enter the CLOSING state. 2525 */ 2526 case TCPS_FIN_WAIT_1: 2527 tp->t_state = TCPS_CLOSING; 2528 break; 2529 2530 /* 2531 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2532 * starting the time-wait timer, turning off the other 2533 * standard timers. 2534 */ 2535 case TCPS_FIN_WAIT_2: 2536 tp->t_state = TCPS_TIME_WAIT; 2537 tcp_canceltimers(tp); 2538 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2539 tcp_timer_2msl); 2540 soisdisconnected(so); 2541 break; 2542 2543 /* 2544 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2545 */ 2546 case TCPS_TIME_WAIT: 2547 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2548 tcp_timer_2msl); 2549 break; 2550 } 2551 } 2552 2553 #ifdef TCPDEBUG 2554 if (so->so_options & SO_DEBUG) 2555 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2556 #endif 2557 2558 /* 2559 * Return any desired output. 2560 */ 2561 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2562 tcp_output(tp); 2563 return(IPPROTO_DONE); 2564 2565 dropafterack: 2566 /* 2567 * Generate an ACK dropping incoming segment if it occupies 2568 * sequence space, where the ACK reflects our state. 2569 * 2570 * We can now skip the test for the RST flag since all 2571 * paths to this code happen after packets containing 2572 * RST have been dropped. 2573 * 2574 * In the SYN-RECEIVED state, don't send an ACK unless the 2575 * segment we received passes the SYN-RECEIVED ACK test. 2576 * If it fails send a RST. This breaks the loop in the 2577 * "LAND" DoS attack, and also prevents an ACK storm 2578 * between two listening ports that have been sent forged 2579 * SYN segments, each with the source address of the other. 2580 */ 2581 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2582 (SEQ_GT(tp->snd_una, th->th_ack) || 2583 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2584 rstreason = BANDLIM_RST_OPENPORT; 2585 goto dropwithreset; 2586 } 2587 #ifdef TCPDEBUG 2588 if (so->so_options & SO_DEBUG) 2589 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2590 #endif 2591 m_freem(m); 2592 tp->t_flags |= TF_ACKNOW; 2593 tcp_output(tp); 2594 return(IPPROTO_DONE); 2595 2596 dropwithreset: 2597 /* 2598 * Generate a RST, dropping incoming segment. 2599 * Make ACK acceptable to originator of segment. 2600 * Don't bother to respond if destination was broadcast/multicast. 2601 */ 2602 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2603 goto drop; 2604 if (isipv6) { 2605 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2606 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2607 goto drop; 2608 } else { 2609 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2610 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2611 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2612 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2613 goto drop; 2614 } 2615 /* IPv6 anycast check is done at tcp6_input() */ 2616 2617 /* 2618 * Perform bandwidth limiting. 2619 */ 2620 #ifdef ICMP_BANDLIM 2621 if (badport_bandlim(rstreason) < 0) 2622 goto drop; 2623 #endif 2624 2625 #ifdef TCPDEBUG 2626 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2627 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2628 #endif 2629 if (thflags & TH_ACK) 2630 /* mtod() below is safe as long as hdr dropping is delayed */ 2631 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2632 TH_RST); 2633 else { 2634 if (thflags & TH_SYN) 2635 tlen++; 2636 /* mtod() below is safe as long as hdr dropping is delayed */ 2637 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2638 (tcp_seq)0, TH_RST | TH_ACK); 2639 } 2640 return(IPPROTO_DONE); 2641 2642 drop: 2643 /* 2644 * Drop space held by incoming segment and return. 2645 */ 2646 #ifdef TCPDEBUG 2647 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2648 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2649 #endif 2650 m_freem(m); 2651 return(IPPROTO_DONE); 2652 } 2653 2654 /* 2655 * Parse TCP options and place in tcpopt. 2656 */ 2657 static void 2658 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2659 { 2660 int opt, optlen, i; 2661 2662 to->to_flags = 0; 2663 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2664 opt = cp[0]; 2665 if (opt == TCPOPT_EOL) 2666 break; 2667 if (opt == TCPOPT_NOP) 2668 optlen = 1; 2669 else { 2670 if (cnt < 2) 2671 break; 2672 optlen = cp[1]; 2673 if (optlen < 2 || optlen > cnt) 2674 break; 2675 } 2676 switch (opt) { 2677 case TCPOPT_MAXSEG: 2678 if (optlen != TCPOLEN_MAXSEG) 2679 continue; 2680 if (!is_syn) 2681 continue; 2682 to->to_flags |= TOF_MSS; 2683 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2684 to->to_mss = ntohs(to->to_mss); 2685 break; 2686 case TCPOPT_WINDOW: 2687 if (optlen != TCPOLEN_WINDOW) 2688 continue; 2689 if (!is_syn) 2690 continue; 2691 to->to_flags |= TOF_SCALE; 2692 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2693 break; 2694 case TCPOPT_TIMESTAMP: 2695 if (optlen != TCPOLEN_TIMESTAMP) 2696 continue; 2697 to->to_flags |= TOF_TS; 2698 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2699 to->to_tsval = ntohl(to->to_tsval); 2700 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2701 to->to_tsecr = ntohl(to->to_tsecr); 2702 /* 2703 * If echoed timestamp is later than the current time, 2704 * fall back to non RFC1323 RTT calculation. 2705 */ 2706 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2707 to->to_tsecr = 0; 2708 break; 2709 case TCPOPT_SACK_PERMITTED: 2710 if (optlen != TCPOLEN_SACK_PERMITTED) 2711 continue; 2712 if (!is_syn) 2713 continue; 2714 to->to_flags |= TOF_SACK_PERMITTED; 2715 break; 2716 case TCPOPT_SACK: 2717 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2718 continue; 2719 to->to_nsackblocks = (optlen - 2) / 8; 2720 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2721 to->to_flags |= TOF_SACK; 2722 for (i = 0; i < to->to_nsackblocks; i++) { 2723 struct raw_sackblock *r = &to->to_sackblocks[i]; 2724 2725 r->rblk_start = ntohl(r->rblk_start); 2726 r->rblk_end = ntohl(r->rblk_end); 2727 } 2728 break; 2729 #ifdef TCP_SIGNATURE 2730 /* 2731 * XXX In order to reply to a host which has set the 2732 * TCP_SIGNATURE option in its initial SYN, we have to 2733 * record the fact that the option was observed here 2734 * for the syncache code to perform the correct response. 2735 */ 2736 case TCPOPT_SIGNATURE: 2737 if (optlen != TCPOLEN_SIGNATURE) 2738 continue; 2739 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2740 break; 2741 #endif /* TCP_SIGNATURE */ 2742 default: 2743 continue; 2744 } 2745 } 2746 } 2747 2748 /* 2749 * Pull out of band byte out of a segment so 2750 * it doesn't appear in the user's data queue. 2751 * It is still reflected in the segment length for 2752 * sequencing purposes. 2753 * "off" is the delayed to be dropped hdrlen. 2754 */ 2755 static void 2756 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2757 { 2758 int cnt = off + th->th_urp - 1; 2759 2760 while (cnt >= 0) { 2761 if (m->m_len > cnt) { 2762 char *cp = mtod(m, caddr_t) + cnt; 2763 struct tcpcb *tp = sototcpcb(so); 2764 2765 tp->t_iobc = *cp; 2766 tp->t_oobflags |= TCPOOB_HAVEDATA; 2767 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2768 m->m_len--; 2769 if (m->m_flags & M_PKTHDR) 2770 m->m_pkthdr.len--; 2771 return; 2772 } 2773 cnt -= m->m_len; 2774 m = m->m_next; 2775 if (m == NULL) 2776 break; 2777 } 2778 panic("tcp_pulloutofband"); 2779 } 2780 2781 /* 2782 * Collect new round-trip time estimate 2783 * and update averages and current timeout. 2784 */ 2785 static void 2786 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2787 { 2788 int delta; 2789 2790 tcpstat.tcps_rttupdated++; 2791 tp->t_rttupdated++; 2792 if (tp->t_srtt != 0) { 2793 /* 2794 * srtt is stored as fixed point with 5 bits after the 2795 * binary point (i.e., scaled by 8). The following magic 2796 * is equivalent to the smoothing algorithm in rfc793 with 2797 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2798 * point). Adjust rtt to origin 0. 2799 */ 2800 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2801 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2802 2803 if ((tp->t_srtt += delta) <= 0) 2804 tp->t_srtt = 1; 2805 2806 /* 2807 * We accumulate a smoothed rtt variance (actually, a 2808 * smoothed mean difference), then set the retransmit 2809 * timer to smoothed rtt + 4 times the smoothed variance. 2810 * rttvar is stored as fixed point with 4 bits after the 2811 * binary point (scaled by 16). The following is 2812 * equivalent to rfc793 smoothing with an alpha of .75 2813 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2814 * rfc793's wired-in beta. 2815 */ 2816 if (delta < 0) 2817 delta = -delta; 2818 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2819 if ((tp->t_rttvar += delta) <= 0) 2820 tp->t_rttvar = 1; 2821 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2822 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2823 } else { 2824 /* 2825 * No rtt measurement yet - use the unsmoothed rtt. 2826 * Set the variance to half the rtt (so our first 2827 * retransmit happens at 3*rtt). 2828 */ 2829 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2830 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2831 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2832 } 2833 tp->t_rtttime = 0; 2834 tp->t_rxtshift = 0; 2835 2836 /* 2837 * the retransmit should happen at rtt + 4 * rttvar. 2838 * Because of the way we do the smoothing, srtt and rttvar 2839 * will each average +1/2 tick of bias. When we compute 2840 * the retransmit timer, we want 1/2 tick of rounding and 2841 * 1 extra tick because of +-1/2 tick uncertainty in the 2842 * firing of the timer. The bias will give us exactly the 2843 * 1.5 tick we need. But, because the bias is 2844 * statistical, we have to test that we don't drop below 2845 * the minimum feasible timer (which is 2 ticks). 2846 */ 2847 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2848 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2849 2850 /* 2851 * We received an ack for a packet that wasn't retransmitted; 2852 * it is probably safe to discard any error indications we've 2853 * received recently. This isn't quite right, but close enough 2854 * for now (a route might have failed after we sent a segment, 2855 * and the return path might not be symmetrical). 2856 */ 2857 tp->t_softerror = 0; 2858 } 2859 2860 /* 2861 * Determine a reasonable value for maxseg size. 2862 * If the route is known, check route for mtu. 2863 * If none, use an mss that can be handled on the outgoing 2864 * interface without forcing IP to fragment; if bigger than 2865 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2866 * to utilize large mbufs. If no route is found, route has no mtu, 2867 * or the destination isn't local, use a default, hopefully conservative 2868 * size (usually 512 or the default IP max size, but no more than the mtu 2869 * of the interface), as we can't discover anything about intervening 2870 * gateways or networks. We also initialize the congestion/slow start 2871 * window to be a single segment if the destination isn't local. 2872 * While looking at the routing entry, we also initialize other path-dependent 2873 * parameters from pre-set or cached values in the routing entry. 2874 * 2875 * Also take into account the space needed for options that we 2876 * send regularly. Make maxseg shorter by that amount to assure 2877 * that we can send maxseg amount of data even when the options 2878 * are present. Store the upper limit of the length of options plus 2879 * data in maxopd. 2880 * 2881 * NOTE that this routine is only called when we process an incoming 2882 * segment, for outgoing segments only tcp_mssopt is called. 2883 */ 2884 void 2885 tcp_mss(struct tcpcb *tp, int offer) 2886 { 2887 struct rtentry *rt; 2888 struct ifnet *ifp; 2889 int rtt, mss; 2890 u_long bufsize; 2891 struct inpcb *inp = tp->t_inpcb; 2892 struct socket *so; 2893 #ifdef INET6 2894 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2895 size_t min_protoh = isipv6 ? 2896 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2897 sizeof(struct tcpiphdr); 2898 #else 2899 const boolean_t isipv6 = FALSE; 2900 const size_t min_protoh = sizeof(struct tcpiphdr); 2901 #endif 2902 2903 if (isipv6) 2904 rt = tcp_rtlookup6(&inp->inp_inc); 2905 else 2906 rt = tcp_rtlookup(&inp->inp_inc); 2907 if (rt == NULL) { 2908 tp->t_maxopd = tp->t_maxseg = 2909 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2910 return; 2911 } 2912 ifp = rt->rt_ifp; 2913 so = inp->inp_socket; 2914 2915 /* 2916 * Offer == 0 means that there was no MSS on the SYN segment, 2917 * in this case we use either the interface mtu or tcp_mssdflt. 2918 * 2919 * An offer which is too large will be cut down later. 2920 */ 2921 if (offer == 0) { 2922 if (isipv6) { 2923 if (in6_localaddr(&inp->in6p_faddr)) { 2924 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 2925 min_protoh; 2926 } else { 2927 offer = tcp_v6mssdflt; 2928 } 2929 } else { 2930 if (in_localaddr(inp->inp_faddr)) 2931 offer = ifp->if_mtu - min_protoh; 2932 else 2933 offer = tcp_mssdflt; 2934 } 2935 } 2936 2937 /* 2938 * Prevent DoS attack with too small MSS. Round up 2939 * to at least minmss. 2940 * 2941 * Sanity check: make sure that maxopd will be large 2942 * enough to allow some data on segments even is the 2943 * all the option space is used (40bytes). Otherwise 2944 * funny things may happen in tcp_output. 2945 */ 2946 offer = max(offer, tcp_minmss); 2947 offer = max(offer, 64); 2948 2949 rt->rt_rmx.rmx_mssopt = offer; 2950 2951 /* 2952 * While we're here, check if there's an initial rtt 2953 * or rttvar. Convert from the route-table units 2954 * to scaled multiples of the slow timeout timer. 2955 */ 2956 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2957 /* 2958 * XXX the lock bit for RTT indicates that the value 2959 * is also a minimum value; this is subject to time. 2960 */ 2961 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2962 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2963 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2964 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2965 tcpstat.tcps_usedrtt++; 2966 if (rt->rt_rmx.rmx_rttvar) { 2967 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2968 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2969 tcpstat.tcps_usedrttvar++; 2970 } else { 2971 /* default variation is +- 1 rtt */ 2972 tp->t_rttvar = 2973 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2974 } 2975 TCPT_RANGESET(tp->t_rxtcur, 2976 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2977 tp->t_rttmin, TCPTV_REXMTMAX); 2978 } 2979 2980 /* 2981 * if there's an mtu associated with the route, use it 2982 * else, use the link mtu. Take the smaller of mss or offer 2983 * as our final mss. 2984 */ 2985 if (rt->rt_rmx.rmx_mtu) { 2986 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2987 } else { 2988 if (isipv6) 2989 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2990 else 2991 mss = ifp->if_mtu - min_protoh; 2992 } 2993 mss = min(mss, offer); 2994 2995 /* 2996 * maxopd stores the maximum length of data AND options 2997 * in a segment; maxseg is the amount of data in a normal 2998 * segment. We need to store this value (maxopd) apart 2999 * from maxseg, because now every segment carries options 3000 * and thus we normally have somewhat less data in segments. 3001 */ 3002 tp->t_maxopd = mss; 3003 3004 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3005 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3006 mss -= TCPOLEN_TSTAMP_APPA; 3007 3008 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3009 if (mss > MCLBYTES) 3010 mss &= ~(MCLBYTES-1); 3011 #else 3012 if (mss > MCLBYTES) 3013 mss = mss / MCLBYTES * MCLBYTES; 3014 #endif 3015 /* 3016 * If there's a pipesize, change the socket buffer 3017 * to that size. Make the socket buffers an integral 3018 * number of mss units; if the mss is larger than 3019 * the socket buffer, decrease the mss. 3020 */ 3021 #ifdef RTV_SPIPE 3022 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3023 #endif 3024 bufsize = so->so_snd.ssb_hiwat; 3025 if (bufsize < mss) 3026 mss = bufsize; 3027 else { 3028 bufsize = roundup(bufsize, mss); 3029 if (bufsize > sb_max) 3030 bufsize = sb_max; 3031 if (bufsize > so->so_snd.ssb_hiwat) 3032 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3033 } 3034 tp->t_maxseg = mss; 3035 3036 #ifdef RTV_RPIPE 3037 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3038 #endif 3039 bufsize = so->so_rcv.ssb_hiwat; 3040 if (bufsize > mss) { 3041 bufsize = roundup(bufsize, mss); 3042 if (bufsize > sb_max) 3043 bufsize = sb_max; 3044 if (bufsize > so->so_rcv.ssb_hiwat) { 3045 lwkt_gettoken(&so->so_rcv.ssb_token); 3046 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3047 lwkt_reltoken(&so->so_rcv.ssb_token); 3048 } 3049 } 3050 3051 /* 3052 * Set the slow-start flight size depending on whether this 3053 * is a local network or not. 3054 */ 3055 if (tcp_do_rfc3390) 3056 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3057 else 3058 tp->snd_cwnd = mss; 3059 3060 if (rt->rt_rmx.rmx_ssthresh) { 3061 /* 3062 * There's some sort of gateway or interface 3063 * buffer limit on the path. Use this to set 3064 * the slow start threshhold, but set the 3065 * threshold to no less than 2*mss. 3066 */ 3067 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3068 tcpstat.tcps_usedssthresh++; 3069 } 3070 } 3071 3072 /* 3073 * Determine the MSS option to send on an outgoing SYN. 3074 */ 3075 int 3076 tcp_mssopt(struct tcpcb *tp) 3077 { 3078 struct rtentry *rt; 3079 #ifdef INET6 3080 boolean_t isipv6 = 3081 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3082 int min_protoh = isipv6 ? 3083 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3084 sizeof(struct tcpiphdr); 3085 #else 3086 const boolean_t isipv6 = FALSE; 3087 const size_t min_protoh = sizeof(struct tcpiphdr); 3088 #endif 3089 3090 if (isipv6) 3091 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3092 else 3093 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3094 if (rt == NULL) 3095 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3096 3097 return (rt->rt_ifp->if_mtu - min_protoh); 3098 } 3099 3100 /* 3101 * When a partial ack arrives, force the retransmission of the 3102 * next unacknowledged segment. Do not exit Fast Recovery. 3103 * 3104 * Implement the Slow-but-Steady variant of NewReno by restarting the 3105 * the retransmission timer. Turn it off here so it can be restarted 3106 * later in tcp_output(). 3107 */ 3108 static void 3109 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3110 { 3111 tcp_seq old_snd_nxt = tp->snd_nxt; 3112 u_long ocwnd = tp->snd_cwnd; 3113 3114 tcp_callout_stop(tp, tp->tt_rexmt); 3115 tp->t_rtttime = 0; 3116 tp->snd_nxt = th->th_ack; 3117 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3118 tp->snd_cwnd = tp->t_maxseg; 3119 tp->t_flags |= TF_ACKNOW; 3120 tcp_output(tp); 3121 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3122 tp->snd_nxt = old_snd_nxt; 3123 /* partial window deflation */ 3124 if (ocwnd > acked) 3125 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3126 else 3127 tp->snd_cwnd = tp->t_maxseg; 3128 } 3129 3130 /* 3131 * In contrast to the Slow-but-Steady NewReno variant, 3132 * we do not reset the retransmission timer for SACK retransmissions, 3133 * except when retransmitting snd_una. 3134 */ 3135 static void 3136 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3137 { 3138 uint32_t pipe, seglen; 3139 tcp_seq nextrexmt; 3140 boolean_t lostdup; 3141 tcp_seq old_snd_nxt = tp->snd_nxt; 3142 u_long ocwnd = tp->snd_cwnd; 3143 int nseg = 0; /* consecutive new segments */ 3144 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3145 3146 tp->t_rtttime = 0; 3147 pipe = tcp_sack_compute_pipe(tp); 3148 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3149 (!tcp_do_smartsack || nseg < MAXBURST) && 3150 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3151 uint32_t sent; 3152 tcp_seq old_snd_max; 3153 int error; 3154 3155 if (nextrexmt == tp->snd_max) 3156 ++nseg; 3157 tp->snd_nxt = nextrexmt; 3158 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3159 old_snd_max = tp->snd_max; 3160 if (nextrexmt == tp->snd_una) 3161 tcp_callout_stop(tp, tp->tt_rexmt); 3162 error = tcp_output(tp); 3163 if (error != 0) 3164 break; 3165 sent = tp->snd_nxt - nextrexmt; 3166 if (sent <= 0) 3167 break; 3168 if (!lostdup) 3169 pipe += sent; 3170 tcpstat.tcps_sndsackpack++; 3171 tcpstat.tcps_sndsackbyte += sent; 3172 if (SEQ_LT(nextrexmt, old_snd_max) && 3173 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3174 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3175 } 3176 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3177 tp->snd_nxt = old_snd_nxt; 3178 tp->snd_cwnd = ocwnd; 3179 } 3180 3181 /* 3182 * Reset idle time and keep-alive timer, typically called when a valid 3183 * tcp packet is received but may also be called when FASTKEEP is set 3184 * to prevent the previous long-timeout from calculating to a drop. 3185 * 3186 * Only update t_rcvtime for non-SYN packets. 3187 * 3188 * Handle the case where one side thinks the connection is established 3189 * but the other side has, say, rebooted without cleaning out the 3190 * connection. The SYNs could be construed as an attack and wind 3191 * up ignored, but in case it isn't an attack we can validate the 3192 * connection by forcing a keepalive. 3193 */ 3194 void 3195 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3196 { 3197 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3198 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3199 tp->t_flags |= TF_KEEPALIVE; 3200 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3201 tcp_timer_keep); 3202 } else { 3203 tp->t_rcvtime = ticks; 3204 tp->t_flags &= ~TF_KEEPALIVE; 3205 tcp_callout_reset(tp, tp->tt_keep, 3206 tcp_getkeepidle(tp), 3207 tcp_timer_keep); 3208 } 3209 } 3210 } 3211 3212 static int 3213 tcp_rmx_msl(const struct tcpcb *tp) 3214 { 3215 struct rtentry *rt; 3216 struct inpcb *inp = tp->t_inpcb; 3217 int msl; 3218 #ifdef INET6 3219 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3220 #else 3221 const boolean_t isipv6 = FALSE; 3222 #endif 3223 3224 if (isipv6) 3225 rt = tcp_rtlookup6(&inp->inp_inc); 3226 else 3227 rt = tcp_rtlookup(&inp->inp_inc); 3228 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3229 return tcp_msl; 3230 3231 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3232 if (msl == 0) 3233 msl = 1; 3234 3235 return msl; 3236 } 3237