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. Neither the name of the University nor the names of its contributors 47 * may be used to endorse or promote products derived from this software 48 * without specific prior written permission. 49 * 50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 60 * SUCH DAMAGE. 61 * 62 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 63 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 64 */ 65 66 #include "opt_inet.h" 67 #include "opt_inet6.h" 68 #include "opt_ipsec.h" 69 #include "opt_tcpdebug.h" 70 #include "opt_tcp_input.h" 71 72 #include <sys/param.h> 73 #include <sys/systm.h> 74 #include <sys/kernel.h> 75 #include <sys/sysctl.h> 76 #include <sys/malloc.h> 77 #include <sys/mbuf.h> 78 #include <sys/proc.h> /* for proc0 declaration */ 79 #include <sys/protosw.h> 80 #include <sys/socket.h> 81 #include <sys/socketvar.h> 82 #include <sys/syslog.h> 83 #include <sys/in_cksum.h> 84 85 #include <sys/socketvar2.h> 86 87 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 88 #include <machine/stdarg.h> 89 90 #include <net/if.h> 91 #include <net/route.h> 92 93 #include <netinet/in.h> 94 #include <netinet/in_systm.h> 95 #include <netinet/ip.h> 96 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 97 #include <netinet/in_var.h> 98 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 99 #include <netinet/in_pcb.h> 100 #include <netinet/ip_var.h> 101 #include <netinet/ip6.h> 102 #include <netinet/icmp6.h> 103 #include <netinet6/nd6.h> 104 #include <netinet6/ip6_var.h> 105 #include <netinet6/in6_pcb.h> 106 #include <netinet/tcp.h> 107 #include <netinet/tcp_fsm.h> 108 #include <netinet/tcp_seq.h> 109 #include <netinet/tcp_timer.h> 110 #include <netinet/tcp_timer2.h> 111 #include <netinet/tcp_var.h> 112 #include <netinet6/tcp6_var.h> 113 #include <netinet/tcpip.h> 114 115 #ifdef TCPDEBUG 116 #include <netinet/tcp_debug.h> 117 118 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 119 struct tcphdr tcp_savetcp; 120 #endif 121 122 #ifdef FAST_IPSEC 123 #include <netproto/ipsec/ipsec.h> 124 #include <netproto/ipsec/ipsec6.h> 125 #endif 126 127 #ifdef IPSEC 128 #include <netinet6/ipsec.h> 129 #include <netinet6/ipsec6.h> 130 #include <netproto/key/key.h> 131 #endif 132 133 /* 134 * Limit burst of new packets during SACK based fast recovery 135 * or extended limited transmit. 136 */ 137 #define TCP_SACK_MAXBURST 4 138 139 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 140 141 static int log_in_vain = 0; 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 143 &log_in_vain, 0, "Log all incoming TCP connections"); 144 145 static int blackhole = 0; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 147 &blackhole, 0, "Do not send RST when dropping refused connections"); 148 149 int tcp_delack_enabled = 1; 150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 151 &tcp_delack_enabled, 0, 152 "Delay ACK to try and piggyback it onto a data packet"); 153 154 #ifdef TCP_DROP_SYNFIN 155 static int drop_synfin = 0; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 157 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 158 #endif 159 160 static int tcp_do_limitedtransmit = 1; 161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 162 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 163 164 static int tcp_do_early_retransmit = 1; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 166 &tcp_do_early_retransmit, 0, "Early retransmit"); 167 168 int tcp_aggregate_acks = 1; 169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 170 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 171 172 static int tcp_do_eifel_detect = 1; 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 174 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 175 176 static int tcp_do_abc = 1; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 178 &tcp_do_abc, 0, 179 "TCP Appropriate Byte Counting (RFC 3465)"); 180 181 /* 182 * The following value actually takes range [25ms, 250ms], 183 * given that most modern systems use 1ms ~ 10ms as the unit 184 * of timestamp option. 185 */ 186 static u_int tcp_paws_tolerance = 25; 187 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, paws_tolerance, CTLFLAG_RW, 188 &tcp_paws_tolerance, 0, "RFC1323 PAWS tolerance"); 189 190 /* 191 * Define as tunable for easy testing with SACK on and off. 192 * Warning: do not change setting in the middle of an existing active TCP flow, 193 * else strange things might happen to that flow. 194 */ 195 int tcp_do_sack = 1; 196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 197 &tcp_do_sack, 0, "Enable SACK Algorithms"); 198 199 int tcp_do_smartsack = 1; 200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 201 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 202 203 int tcp_do_rescuesack = 1; 204 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW, 205 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK"); 206 207 int tcp_aggressive_rescuesack = 0; 208 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW, 209 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK"); 210 211 static int tcp_force_sackrxt = 1; 212 SYSCTL_INT(_net_inet_tcp, OID_AUTO, force_sackrxt, CTLFLAG_RW, 213 &tcp_force_sackrxt, 0, "Allowed forced SACK retransmit burst"); 214 215 int tcp_do_rfc6675 = 1; 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675, CTLFLAG_RW, 217 &tcp_do_rfc6675, 0, "Enable RFC6675"); 218 219 int tcp_rfc6675_rxt = 0; 220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_rxt, CTLFLAG_RW, 221 &tcp_rfc6675_rxt, 0, "Enable RFC6675 retransmit"); 222 223 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 224 "TCP Segment Reassembly Queue"); 225 226 int tcp_reass_maxseg = 0; 227 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 228 &tcp_reass_maxseg, 0, 229 "Global maximum number of TCP Segments in Reassembly Queue"); 230 231 int tcp_reass_qsize = 0; 232 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 233 &tcp_reass_qsize, 0, 234 "Global number of TCP Segments currently in Reassembly Queue"); 235 236 static int tcp_reass_overflows = 0; 237 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 238 &tcp_reass_overflows, 0, 239 "Global number of TCP Segment Reassembly Queue Overflows"); 240 241 int tcp_do_autorcvbuf = 1; 242 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 243 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 244 245 int tcp_autorcvbuf_inc = 16*1024; 246 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 247 &tcp_autorcvbuf_inc, 0, 248 "Incrementor step size of automatic receive buffer"); 249 250 int tcp_autorcvbuf_max = 2*1024*1024; 251 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 252 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 253 254 int tcp_sosend_agglim = 3; 255 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW, 256 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit"); 257 258 int tcp_sosend_async = 1; 259 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW, 260 &tcp_sosend_async, 0, "TCP asynchronized pru_send"); 261 262 static int tcp_ignore_redun_dsack = 1; 263 SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW, 264 &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK"); 265 266 static int tcp_reuseport_ext = 1; 267 SYSCTL_INT(_net_inet_tcp, OID_AUTO, reuseport_ext, CTLFLAG_RW, 268 &tcp_reuseport_ext, 0, "SO_REUSEPORT extension"); 269 270 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t, 271 tcp_seq); 272 static void tcp_pulloutofband(struct socket *, 273 struct tcphdr *, struct mbuf *, int); 274 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 275 struct mbuf *); 276 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq); 277 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 278 static void tcp_sack_rexmt(struct tcpcb *, boolean_t); 279 static boolean_t tcp_sack_limitedxmit(struct tcpcb *); 280 static int tcp_rmx_msl(const struct tcpcb *); 281 static void tcp_established(struct tcpcb *); 282 static boolean_t tcp_recv_dupack(struct tcpcb *, tcp_seq, u_int); 283 284 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 285 #ifdef INET6 286 #define ND6_HINT(tp) \ 287 do { \ 288 if ((tp) && (tp)->t_inpcb && \ 289 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 290 (tp)->t_inpcb->in6p_route.ro_rt) \ 291 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 292 } while (0) 293 #else 294 #define ND6_HINT(tp) 295 #endif 296 297 /* 298 * Indicate whether this ack should be delayed. We can delay the ack if 299 * - delayed acks are enabled and 300 * - there is no delayed ack timer in progress and 301 * - our last ack wasn't a 0-sized window. We never want to delay 302 * the ack that opens up a 0-sized window. 303 */ 304 #define DELAY_ACK(tp) \ 305 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 306 !(tp->t_flags & TF_RXWIN0SENT)) 307 308 #define acceptable_window_update(tp, th, tiwin) \ 309 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 310 (tp->snd_wl1 == th->th_seq && \ 311 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 312 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 313 314 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 315 #define need_early_retransmit(tp, ownd) \ 316 (tcp_do_early_retransmit && \ 317 (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \ 318 ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \ 319 tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \ 320 (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \ 321 tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg))) 322 323 /* 324 * Returns TRUE, if this segment can be merged with the last 325 * pending segment in the reassemble queue and this segment 326 * does not overlap with the pending segment immediately 327 * preceeding the last pending segment. 328 */ 329 static __inline boolean_t 330 tcp_paws_canreasslast(const struct tcpcb *tp, const struct tcphdr *th, int tlen) 331 { 332 const struct tseg_qent *last, *prev; 333 334 last = TAILQ_LAST(&tp->t_segq, tsegqe_head); 335 if (last == NULL) 336 return FALSE; 337 338 /* This segment comes immediately after the last pending segment */ 339 if (last->tqe_th->th_seq + last->tqe_len == th->th_seq) { 340 if (last->tqe_th->th_flags & TH_FIN) { 341 /* No segments should follow segment w/ FIN */ 342 return FALSE; 343 } 344 return TRUE; 345 } 346 347 if (th->th_seq + tlen != last->tqe_th->th_seq) 348 return FALSE; 349 /* This segment comes immediately before the last pending segment */ 350 351 prev = TAILQ_PREV(last, tsegqe_head, tqe_q); 352 if (prev == NULL) { 353 /* 354 * No pending preceeding segment, we assume this segment 355 * could be reassembled. 356 */ 357 return TRUE; 358 } 359 360 /* This segment does not overlap with the preceeding segment */ 361 if (SEQ_GEQ(th->th_seq, prev->tqe_th->th_seq + prev->tqe_len)) 362 return TRUE; 363 364 return FALSE; 365 } 366 367 static __inline void 368 tcp_ncr_update_rxtthresh(struct tcpcb *tp) 369 { 370 int old_rxtthresh = tp->t_rxtthresh; 371 uint32_t ownd = tp->snd_max - tp->snd_una; 372 373 tp->t_rxtthresh = max(tcprexmtthresh, ((ownd / tp->t_maxseg) >> 1)); 374 if (tp->t_rxtthresh != old_rxtthresh) { 375 tcp_sack_update_lostseq(&tp->scb, tp->snd_una, 376 tp->t_maxseg, tp->t_rxtthresh); 377 } 378 } 379 380 static int 381 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 382 { 383 struct tseg_qent *q; 384 struct tseg_qent *p = NULL; 385 struct tseg_qent *te; 386 struct socket *so = tp->t_inpcb->inp_socket; 387 int flags; 388 389 /* 390 * Call with th == NULL after become established to 391 * force pre-ESTABLISHED data up to user socket. 392 */ 393 if (th == NULL) 394 goto present; 395 396 /* 397 * Limit the number of segments in the reassembly queue to prevent 398 * holding on to too many segments (and thus running out of mbufs). 399 * Make sure to let the missing segment through which caused this 400 * queue. Always keep one global queue entry spare to be able to 401 * process the missing segment. 402 */ 403 if (th->th_seq != tp->rcv_nxt && 404 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 405 tcp_reass_overflows++; 406 tcpstat.tcps_rcvmemdrop++; 407 m_freem(m); 408 /* no SACK block to report */ 409 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 410 return (0); 411 } 412 413 /* Allocate a new queue entry. */ 414 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 415 if (te == NULL) { 416 tcpstat.tcps_rcvmemdrop++; 417 m_freem(m); 418 /* no SACK block to report */ 419 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 420 return (0); 421 } 422 atomic_add_int(&tcp_reass_qsize, 1); 423 424 if (th->th_flags & TH_FIN) 425 tp->t_flags |= TF_QUEDFIN; 426 427 /* 428 * Find a segment which begins after this one does. 429 */ 430 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) { 431 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 432 break; 433 p = q; 434 } 435 436 /* 437 * If there is a preceding segment, it may provide some of 438 * our data already. If so, drop the data from the incoming 439 * segment. If it provides all of our data, drop us. 440 */ 441 if (p != NULL) { 442 tcp_seq_diff_t i; 443 444 /* conversion to int (in i) handles seq wraparound */ 445 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 446 if (i > 0) { /* overlaps preceding segment */ 447 tp->sack_flags |= 448 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 449 /* enclosing block starts w/ preceding segment */ 450 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 451 if (i >= *tlenp) { 452 if (th->th_flags & TH_FIN) 453 p->tqe_th->th_flags |= TH_FIN; 454 455 /* preceding encloses incoming segment */ 456 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 457 p->tqe_th->th_seq + p->tqe_len, 458 p->tqe_th->th_flags); 459 tcpstat.tcps_rcvduppack++; 460 tcpstat.tcps_rcvdupbyte += *tlenp; 461 m_freem(m); 462 kfree(te, M_TSEGQ); 463 atomic_add_int(&tcp_reass_qsize, -1); 464 /* 465 * Try to present any queued data 466 * at the left window edge to the user. 467 * This is needed after the 3-WHS 468 * completes. 469 */ 470 goto present; /* ??? */ 471 } 472 m_adj(m, i); 473 *tlenp -= i; 474 th->th_seq += i; 475 /* incoming segment end is enclosing block end */ 476 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 477 th->th_seq + *tlenp, th->th_flags); 478 /* trim end of reported D-SACK block */ 479 tp->reportblk.rblk_end = th->th_seq; 480 } 481 } 482 tcpstat.tcps_rcvoopack++; 483 tcpstat.tcps_rcvoobyte += *tlenp; 484 485 /* 486 * While we overlap succeeding segments trim them or, 487 * if they are completely covered, dequeue them. 488 */ 489 while (q) { 490 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 491 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 492 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags); 493 struct tseg_qent *nq; 494 495 if (i <= 0) 496 break; 497 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 498 /* first time through */ 499 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 500 tp->encloseblk = tp->reportblk; 501 /* report trailing duplicate D-SACK segment */ 502 tp->reportblk.rblk_start = q->tqe_th->th_seq; 503 } 504 if ((tp->sack_flags & TSACK_F_ENCLOSESEG) && 505 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) { 506 /* extend enclosing block if one exists */ 507 tp->encloseblk.rblk_end = qend_sack; 508 } 509 if (i < q->tqe_len) { 510 q->tqe_th->th_seq += i; 511 q->tqe_len -= i; 512 m_adj(q->tqe_m, i); 513 break; 514 } 515 516 if (q->tqe_th->th_flags & TH_FIN) 517 th->th_flags |= TH_FIN; 518 519 nq = TAILQ_NEXT(q, tqe_q); 520 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 521 m_freem(q->tqe_m); 522 kfree(q, M_TSEGQ); 523 atomic_add_int(&tcp_reass_qsize, -1); 524 q = nq; 525 } 526 527 /* Insert the new segment queue entry into place. */ 528 te->tqe_m = m; 529 te->tqe_th = th; 530 te->tqe_len = *tlenp; 531 532 /* check if can coalesce with following segment */ 533 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 534 tcp_seq tend_sack; 535 536 te->tqe_len += q->tqe_len; 537 if (q->tqe_th->th_flags & TH_FIN) 538 te->tqe_th->th_flags |= TH_FIN; 539 tend_sack = TCP_SACK_BLKEND(te->tqe_th->th_seq + te->tqe_len, 540 te->tqe_th->th_flags); 541 542 m_cat(te->tqe_m, q->tqe_m); 543 tp->encloseblk.rblk_end = tend_sack; 544 /* 545 * When not reporting a duplicate segment, use 546 * the larger enclosing block as the SACK block. 547 */ 548 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 549 tp->reportblk.rblk_end = tend_sack; 550 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 551 kfree(q, M_TSEGQ); 552 atomic_add_int(&tcp_reass_qsize, -1); 553 } 554 555 if (p == NULL) { 556 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q); 557 } else { 558 /* check if can coalesce with preceding segment */ 559 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 560 if (te->tqe_th->th_flags & TH_FIN) 561 p->tqe_th->th_flags |= TH_FIN; 562 p->tqe_len += te->tqe_len; 563 m_cat(p->tqe_m, te->tqe_m); 564 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 565 /* 566 * When not reporting a duplicate segment, use 567 * the larger enclosing block as the SACK block. 568 */ 569 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 570 tp->reportblk.rblk_start = p->tqe_th->th_seq; 571 kfree(te, M_TSEGQ); 572 atomic_add_int(&tcp_reass_qsize, -1); 573 } else { 574 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q); 575 } 576 } 577 578 present: 579 /* 580 * Present data to user, advancing rcv_nxt through 581 * completed sequence space. 582 */ 583 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 584 return (0); 585 q = TAILQ_FIRST(&tp->t_segq); 586 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 587 return (0); 588 tp->rcv_nxt += q->tqe_len; 589 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 590 /* no SACK block to report since ACK advanced */ 591 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 592 } 593 /* no enclosing block to report since ACK advanced */ 594 tp->sack_flags &= ~TSACK_F_ENCLOSESEG; 595 flags = q->tqe_th->th_flags & TH_FIN; 596 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 597 KASSERT(TAILQ_EMPTY(&tp->t_segq) || 598 TAILQ_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 599 ("segment not coalesced")); 600 if (so->so_state & SS_CANTRCVMORE) { 601 m_freem(q->tqe_m); 602 } else { 603 lwkt_gettoken(&so->so_rcv.ssb_token); 604 ssb_appendstream(&so->so_rcv, q->tqe_m); 605 lwkt_reltoken(&so->so_rcv.ssb_token); 606 } 607 kfree(q, M_TSEGQ); 608 atomic_add_int(&tcp_reass_qsize, -1); 609 ND6_HINT(tp); 610 sorwakeup(so); 611 return (flags); 612 } 613 614 /* 615 * TCP input routine, follows pages 65-76 of the 616 * protocol specification dated September, 1981 very closely. 617 */ 618 #ifdef INET6 619 int 620 tcp6_input(struct mbuf **mp, int *offp, int proto) 621 { 622 struct mbuf *m = *mp; 623 struct in6_ifaddr *ia6; 624 625 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 626 627 /* 628 * draft-itojun-ipv6-tcp-to-anycast 629 * better place to put this in? 630 */ 631 ia6 = ip6_getdstifaddr(m); 632 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 633 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 634 offsetof(struct ip6_hdr, ip6_dst)); 635 return (IPPROTO_DONE); 636 } 637 638 tcp_input(mp, offp, proto); 639 return (IPPROTO_DONE); 640 } 641 #endif 642 643 int 644 tcp_input(struct mbuf **mp, int *offp, int proto) 645 { 646 int off0; 647 struct tcphdr *th; 648 struct ip *ip = NULL; 649 struct ipovly *ipov; 650 struct inpcb *inp = NULL; 651 u_char *optp = NULL; 652 int optlen = 0; 653 int tlen, off; 654 int len = 0; 655 int drop_hdrlen; 656 struct tcpcb *tp = NULL; 657 int thflags; 658 struct socket *so = NULL; 659 int todrop, acked; 660 boolean_t ourfinisacked, needoutput = FALSE, delayed_dupack = FALSE; 661 tcp_seq th_dupack = 0; /* XXX gcc warning */ 662 u_int to_flags = 0; /* XXX gcc warning */ 663 u_long tiwin; 664 int recvwin; 665 struct tcpopt to; /* options in this segment */ 666 struct sockaddr_in *next_hop = NULL; 667 int rstreason; /* For badport_bandlim accounting purposes */ 668 int cpu; 669 struct ip6_hdr *ip6 = NULL; 670 struct mbuf *m; 671 #ifdef INET6 672 boolean_t isipv6; 673 #else 674 const boolean_t isipv6 = FALSE; 675 #endif 676 #ifdef TCPDEBUG 677 short ostate = 0; 678 #endif 679 680 off0 = *offp; 681 m = *mp; 682 *mp = NULL; 683 684 tcpstat.tcps_rcvtotal++; 685 686 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 687 struct m_tag *mtag; 688 689 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 690 KKASSERT(mtag != NULL); 691 next_hop = m_tag_data(mtag); 692 } 693 694 #ifdef INET6 695 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 696 #endif 697 698 if (isipv6) { 699 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 700 ip6 = mtod(m, struct ip6_hdr *); 701 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 702 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 703 tcpstat.tcps_rcvbadsum++; 704 goto drop; 705 } 706 th = (struct tcphdr *)((caddr_t)ip6 + off0); 707 708 /* 709 * Be proactive about unspecified IPv6 address in source. 710 * As we use all-zero to indicate unbounded/unconnected pcb, 711 * unspecified IPv6 address can be used to confuse us. 712 * 713 * Note that packets with unspecified IPv6 destination is 714 * already dropped in ip6_input. 715 */ 716 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 717 /* XXX stat */ 718 goto drop; 719 } 720 } else { 721 /* 722 * Get IP and TCP header together in first mbuf. 723 * Note: IP leaves IP header in first mbuf. 724 */ 725 if (off0 > sizeof(struct ip)) { 726 ip_stripoptions(m); 727 off0 = sizeof(struct ip); 728 } 729 /* already checked and pulled up in ip_demux() */ 730 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 731 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 732 ip = mtod(m, struct ip *); 733 ipov = (struct ipovly *)ip; 734 th = (struct tcphdr *)((caddr_t)ip + off0); 735 tlen = ip->ip_len; 736 737 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 738 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 739 th->th_sum = m->m_pkthdr.csum_data; 740 else 741 th->th_sum = in_pseudo(ip->ip_src.s_addr, 742 ip->ip_dst.s_addr, 743 htonl(m->m_pkthdr.csum_data + 744 ip->ip_len + 745 IPPROTO_TCP)); 746 th->th_sum ^= 0xffff; 747 } else { 748 /* 749 * Checksum extended TCP header and data. 750 */ 751 len = sizeof(struct ip) + tlen; 752 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 753 ipov->ih_len = (u_short)tlen; 754 ipov->ih_len = htons(ipov->ih_len); 755 th->th_sum = in_cksum(m, len); 756 } 757 if (th->th_sum) { 758 tcpstat.tcps_rcvbadsum++; 759 goto drop; 760 } 761 #ifdef INET6 762 /* Re-initialization for later version check */ 763 ip->ip_v = IPVERSION; 764 #endif 765 } 766 767 /* 768 * Check that TCP offset makes sense, 769 * pull out TCP options and adjust length. XXX 770 */ 771 off = th->th_off << 2; 772 /* already checked and pulled up in ip_demux() */ 773 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 774 ("bad TCP data offset %d (tlen %d)", off, tlen)); 775 tlen -= off; /* tlen is used instead of ti->ti_len */ 776 if (off > sizeof(struct tcphdr)) { 777 if (isipv6) { 778 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 779 ip6 = mtod(m, struct ip6_hdr *); 780 th = (struct tcphdr *)((caddr_t)ip6 + off0); 781 } else { 782 /* already pulled up in ip_demux() */ 783 KASSERT(m->m_len >= sizeof(struct ip) + off, 784 ("TCP header and options not in one mbuf: " 785 "m_len %d, off %d", m->m_len, off)); 786 } 787 optlen = off - sizeof(struct tcphdr); 788 optp = (u_char *)(th + 1); 789 } 790 thflags = th->th_flags; 791 792 #ifdef TCP_DROP_SYNFIN 793 /* 794 * If the drop_synfin option is enabled, drop all packets with 795 * both the SYN and FIN bits set. This prevents e.g. nmap from 796 * identifying the TCP/IP stack. 797 * 798 * This is a violation of the TCP specification. 799 */ 800 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 801 goto drop; 802 #endif 803 804 /* 805 * Convert TCP protocol specific fields to host format. 806 */ 807 th->th_seq = ntohl(th->th_seq); 808 th->th_ack = ntohl(th->th_ack); 809 th->th_win = ntohs(th->th_win); 810 th->th_urp = ntohs(th->th_urp); 811 812 /* 813 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 814 * until after ip6_savecontrol() is called and before other functions 815 * which don't want those proto headers. 816 * Because ip6_savecontrol() is going to parse the mbuf to 817 * search for data to be passed up to user-land, it wants mbuf 818 * parameters to be unchanged. 819 * XXX: the call of ip6_savecontrol() has been obsoleted based on 820 * latest version of the advanced API (20020110). 821 */ 822 drop_hdrlen = off0 + off; 823 824 /* 825 * Locate pcb for segment. 826 */ 827 findpcb: 828 /* IPFIREWALL_FORWARD section */ 829 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 830 /* 831 * Transparently forwarded. Pretend to be the destination. 832 * already got one like this? 833 */ 834 cpu = mycpu->gd_cpuid; 835 inp = in_pcblookup_hash(&tcbinfo[cpu], 836 ip->ip_src, th->th_sport, 837 ip->ip_dst, th->th_dport, 838 0, m->m_pkthdr.rcvif); 839 if (!inp) { 840 /* 841 * It's new. Try to find the ambushing socket. 842 */ 843 844 /* 845 * The rest of the ipfw code stores the port in 846 * host order. XXX 847 * (The IP address is still in network order.) 848 */ 849 in_port_t dport = next_hop->sin_port ? 850 htons(next_hop->sin_port) : 851 th->th_dport; 852 853 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 854 next_hop->sin_addr.s_addr, dport); 855 inp = in_pcblookup_hash(&tcbinfo[cpu], 856 ip->ip_src, th->th_sport, 857 next_hop->sin_addr, dport, 858 1, m->m_pkthdr.rcvif); 859 } 860 } else { 861 if (isipv6) { 862 inp = in6_pcblookup_hash(&tcbinfo[0], 863 &ip6->ip6_src, th->th_sport, 864 &ip6->ip6_dst, th->th_dport, 865 1, m->m_pkthdr.rcvif); 866 } else { 867 cpu = mycpu->gd_cpuid; 868 inp = in_pcblookup_pkthash(&tcbinfo[cpu], 869 ip->ip_src, th->th_sport, 870 ip->ip_dst, th->th_dport, 871 1, m->m_pkthdr.rcvif, 872 tcp_reuseport_ext ? m : NULL); 873 } 874 } 875 876 /* 877 * If the state is CLOSED (i.e., TCB does not exist) then 878 * all data in the incoming segment is discarded. 879 * If the TCB exists but is in CLOSED state, it is embryonic, 880 * but should either do a listen or a connect soon. 881 */ 882 if (inp == NULL) { 883 if (log_in_vain) { 884 #ifdef INET6 885 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 886 #else 887 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 888 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 889 #endif 890 if (isipv6) { 891 strcpy(dbuf, "["); 892 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 893 strcat(dbuf, "]"); 894 strcpy(sbuf, "["); 895 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 896 strcat(sbuf, "]"); 897 } else { 898 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 899 strcpy(sbuf, inet_ntoa(ip->ip_src)); 900 } 901 switch (log_in_vain) { 902 case 1: 903 if (!(thflags & TH_SYN)) 904 break; 905 case 2: 906 log(LOG_INFO, 907 "Connection attempt to TCP %s:%d " 908 "from %s:%d flags:0x%02x\n", 909 dbuf, ntohs(th->th_dport), sbuf, 910 ntohs(th->th_sport), thflags); 911 break; 912 default: 913 break; 914 } 915 } 916 if (blackhole) { 917 switch (blackhole) { 918 case 1: 919 if (thflags & TH_SYN) 920 goto drop; 921 break; 922 case 2: 923 goto drop; 924 default: 925 goto drop; 926 } 927 } 928 rstreason = BANDLIM_RST_CLOSEDPORT; 929 goto dropwithreset; 930 } 931 932 #ifdef IPSEC 933 if (isipv6) { 934 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 935 ipsec6stat.in_polvio++; 936 goto drop; 937 } 938 } else { 939 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 940 ipsecstat.in_polvio++; 941 goto drop; 942 } 943 } 944 #endif 945 #ifdef FAST_IPSEC 946 if (isipv6) { 947 if (ipsec6_in_reject(m, inp)) 948 goto drop; 949 } else { 950 if (ipsec4_in_reject(m, inp)) 951 goto drop; 952 } 953 #endif 954 /* Check the minimum TTL for socket. */ 955 #ifdef INET6 956 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 957 goto drop; 958 #endif 959 960 tp = intotcpcb(inp); 961 if (tp == NULL) { 962 rstreason = BANDLIM_RST_CLOSEDPORT; 963 goto dropwithreset; 964 } 965 if (tp->t_state <= TCPS_CLOSED) 966 goto drop; 967 968 so = inp->inp_socket; 969 970 #ifdef TCPDEBUG 971 if (so->so_options & SO_DEBUG) { 972 ostate = tp->t_state; 973 if (isipv6) 974 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 975 else 976 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 977 tcp_savetcp = *th; 978 } 979 #endif 980 981 bzero(&to, sizeof to); 982 983 if (so->so_options & SO_ACCEPTCONN) { 984 struct in_conninfo inc; 985 986 #ifdef INET6 987 inc.inc_isipv6 = (isipv6 == TRUE); 988 #endif 989 if (isipv6) { 990 inc.inc6_faddr = ip6->ip6_src; 991 inc.inc6_laddr = ip6->ip6_dst; 992 inc.inc6_route.ro_rt = NULL; /* XXX */ 993 } else { 994 inc.inc_faddr = ip->ip_src; 995 inc.inc_laddr = ip->ip_dst; 996 inc.inc_route.ro_rt = NULL; /* XXX */ 997 } 998 inc.inc_fport = th->th_sport; 999 inc.inc_lport = th->th_dport; 1000 1001 /* 1002 * If the state is LISTEN then ignore segment if it contains 1003 * a RST. If the segment contains an ACK then it is bad and 1004 * send a RST. If it does not contain a SYN then it is not 1005 * interesting; drop it. 1006 * 1007 * If the state is SYN_RECEIVED (syncache) and seg contains 1008 * an ACK, but not for our SYN/ACK, send a RST. If the seg 1009 * contains a RST, check the sequence number to see if it 1010 * is a valid reset segment. 1011 */ 1012 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 1013 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 1014 if (!syncache_expand(&inc, th, &so, m)) { 1015 /* 1016 * No syncache entry, or ACK was not 1017 * for our SYN/ACK. Send a RST. 1018 */ 1019 tcpstat.tcps_badsyn++; 1020 rstreason = BANDLIM_RST_OPENPORT; 1021 goto dropwithreset; 1022 } 1023 1024 /* 1025 * Could not complete 3-way handshake, 1026 * connection is being closed down, and 1027 * syncache will free mbuf. 1028 */ 1029 if (so == NULL) 1030 return(IPPROTO_DONE); 1031 1032 /* 1033 * We must be in the correct protocol thread 1034 * for this connection. 1035 */ 1036 KKASSERT(so->so_port == &curthread->td_msgport); 1037 1038 /* 1039 * Socket is created in state SYN_RECEIVED. 1040 * Continue processing segment. 1041 */ 1042 inp = so->so_pcb; 1043 tp = intotcpcb(inp); 1044 /* 1045 * This is what would have happened in 1046 * tcp_output() when the SYN,ACK was sent. 1047 */ 1048 tp->snd_up = tp->snd_una; 1049 tp->snd_max = tp->snd_nxt = tp->iss + 1; 1050 tp->last_ack_sent = tp->rcv_nxt; 1051 1052 goto after_listen; 1053 } 1054 if (thflags & TH_RST) { 1055 syncache_chkrst(&inc, th); 1056 goto drop; 1057 } 1058 if (thflags & TH_ACK) { 1059 syncache_badack(&inc); 1060 tcpstat.tcps_badsyn++; 1061 rstreason = BANDLIM_RST_OPENPORT; 1062 goto dropwithreset; 1063 } 1064 goto drop; 1065 } 1066 1067 /* 1068 * Segment's flags are (SYN) or (SYN | FIN). 1069 */ 1070 #ifdef INET6 1071 /* 1072 * If deprecated address is forbidden, 1073 * we do not accept SYN to deprecated interface 1074 * address to prevent any new inbound connection from 1075 * getting established. 1076 * When we do not accept SYN, we send a TCP RST, 1077 * with deprecated source address (instead of dropping 1078 * it). We compromise it as it is much better for peer 1079 * to send a RST, and RST will be the final packet 1080 * for the exchange. 1081 * 1082 * If we do not forbid deprecated addresses, we accept 1083 * the SYN packet. RFC2462 does not suggest dropping 1084 * SYN in this case. 1085 * If we decipher RFC2462 5.5.4, it says like this: 1086 * 1. use of deprecated addr with existing 1087 * communication is okay - "SHOULD continue to be 1088 * used" 1089 * 2. use of it with new communication: 1090 * (2a) "SHOULD NOT be used if alternate address 1091 * with sufficient scope is available" 1092 * (2b) nothing mentioned otherwise. 1093 * Here we fall into (2b) case as we have no choice in 1094 * our source address selection - we must obey the peer. 1095 * 1096 * The wording in RFC2462 is confusing, and there are 1097 * multiple description text for deprecated address 1098 * handling - worse, they are not exactly the same. 1099 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1100 */ 1101 if (isipv6 && !ip6_use_deprecated) { 1102 struct in6_ifaddr *ia6; 1103 1104 if ((ia6 = ip6_getdstifaddr(m)) && 1105 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1106 tp = NULL; 1107 rstreason = BANDLIM_RST_OPENPORT; 1108 goto dropwithreset; 1109 } 1110 } 1111 #endif 1112 /* 1113 * If it is from this socket, drop it, it must be forged. 1114 * Don't bother responding if the destination was a broadcast. 1115 */ 1116 if (th->th_dport == th->th_sport) { 1117 if (isipv6) { 1118 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1119 &ip6->ip6_src)) 1120 goto drop; 1121 } else { 1122 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1123 goto drop; 1124 } 1125 } 1126 /* 1127 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1128 * 1129 * Note that it is quite possible to receive unicast 1130 * link-layer packets with a broadcast IP address. Use 1131 * in_broadcast() to find them. 1132 */ 1133 if (m->m_flags & (M_BCAST | M_MCAST)) 1134 goto drop; 1135 if (isipv6) { 1136 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1137 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1138 goto drop; 1139 } else { 1140 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1141 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1142 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1143 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1144 goto drop; 1145 } 1146 /* 1147 * SYN appears to be valid; create compressed TCP state 1148 * for syncache, or perform t/tcp connection. 1149 */ 1150 if (so->so_qlen <= so->so_qlimit) { 1151 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack); 1152 if (!syncache_add(&inc, &to, th, so, m)) 1153 goto drop; 1154 1155 /* 1156 * Entry added to syncache, mbuf used to 1157 * send SYN,ACK packet. 1158 */ 1159 return(IPPROTO_DONE); 1160 } 1161 goto drop; 1162 } 1163 1164 after_listen: 1165 /* 1166 * Should not happen - syncache should pick up these connections. 1167 * 1168 * Once we are past handling listen sockets we must be in the 1169 * correct protocol processing thread. 1170 */ 1171 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1172 KKASSERT(so->so_port == &curthread->td_msgport); 1173 1174 /* Unscale the window into a 32-bit value. */ 1175 if (!(thflags & TH_SYN)) 1176 tiwin = th->th_win << tp->snd_scale; 1177 else 1178 tiwin = th->th_win; 1179 1180 /* 1181 * This is the second part of the MSS DoS prevention code (after 1182 * minmss on the sending side) and it deals with too many too small 1183 * tcp packets in a too short timeframe (1 second). 1184 * 1185 * XXX Removed. This code was crap. It does not scale to network 1186 * speed, and default values break NFS. Gone. 1187 */ 1188 /* REMOVED */ 1189 1190 /* 1191 * Segment received on connection. 1192 * 1193 * Reset idle time and keep-alive timer. Don't waste time if less 1194 * then a second has elapsed. 1195 */ 1196 if ((int)(ticks - tp->t_rcvtime) > hz) 1197 tcp_timer_keep_activity(tp, thflags); 1198 1199 /* 1200 * Process options. 1201 * XXX this is tradtitional behavior, may need to be cleaned up. 1202 */ 1203 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack); 1204 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1205 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) { 1206 tp->t_flags |= TF_RCVD_SCALE; 1207 tp->snd_scale = to.to_requested_s_scale; 1208 } 1209 1210 /* 1211 * Initial send window; will be updated upon next ACK 1212 */ 1213 tp->snd_wnd = th->th_win; 1214 1215 if (to.to_flags & TOF_TS) { 1216 tp->t_flags |= TF_RCVD_TSTMP; 1217 tp->ts_recent = to.to_tsval; 1218 tp->ts_recent_age = ticks; 1219 } 1220 if (!(to.to_flags & TOF_MSS)) 1221 to.to_mss = 0; 1222 tcp_mss(tp, to.to_mss); 1223 /* 1224 * Only set the TF_SACK_PERMITTED per-connection flag 1225 * if we got a SACK_PERMITTED option from the other side 1226 * and the global tcp_do_sack variable is true. 1227 */ 1228 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1229 tp->t_flags |= TF_SACK_PERMITTED; 1230 } 1231 1232 /* 1233 * Header prediction: check for the two common cases 1234 * of a uni-directional data xfer. If the packet has 1235 * no control flags, is in-sequence, the window didn't 1236 * change and we're not retransmitting, it's a 1237 * candidate. If the length is zero and the ack moved 1238 * forward, we're the sender side of the xfer. Just 1239 * free the data acked & wake any higher level process 1240 * that was blocked waiting for space. If the length 1241 * is non-zero and the ack didn't move, we're the 1242 * receiver side. If we're getting packets in-order 1243 * (the reassembly queue is empty), add the data to 1244 * the socket buffer and note that we need a delayed ack. 1245 * Make sure that the hidden state-flags are also off. 1246 * Since we check for TCPS_ESTABLISHED above, it can only 1247 * be TH_NEEDSYN. 1248 */ 1249 if (tp->t_state == TCPS_ESTABLISHED && 1250 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1251 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1252 (!(to.to_flags & TOF_TS) || 1253 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1254 th->th_seq == tp->rcv_nxt && 1255 tp->snd_nxt == tp->snd_max) { 1256 1257 /* 1258 * If last ACK falls within this segment's sequence numbers, 1259 * record the timestamp. 1260 * NOTE that the test is modified according to the latest 1261 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1262 */ 1263 if ((to.to_flags & TOF_TS) && 1264 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1265 tp->ts_recent_age = ticks; 1266 tp->ts_recent = to.to_tsval; 1267 } 1268 1269 if (tlen == 0) { 1270 if (SEQ_GT(th->th_ack, tp->snd_una) && 1271 SEQ_LEQ(th->th_ack, tp->snd_max) && 1272 tp->snd_cwnd >= tp->snd_wnd && 1273 !IN_FASTRECOVERY(tp)) { 1274 /* 1275 * This is a pure ack for outstanding data. 1276 */ 1277 ++tcpstat.tcps_predack; 1278 /* 1279 * "bad retransmit" recovery 1280 * 1281 * If Eifel detection applies, then 1282 * it is deterministic, so use it 1283 * unconditionally over the old heuristic. 1284 * Otherwise, fall back to the old heuristic. 1285 */ 1286 if (tcp_do_eifel_detect && 1287 (to.to_flags & TOF_TS) && to.to_tsecr && 1288 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 1289 /* Eifel detection applicable. */ 1290 if (to.to_tsecr < tp->t_rexmtTS) { 1291 tcp_revert_congestion_state(tp); 1292 ++tcpstat.tcps_eifeldetected; 1293 if (tp->t_rxtshift != 1 || 1294 ticks >= tp->t_badrxtwin) 1295 ++tcpstat.tcps_rttcantdetect; 1296 } 1297 } else if (tp->t_rxtshift == 1 && 1298 ticks < tp->t_badrxtwin) { 1299 tcp_revert_congestion_state(tp); 1300 ++tcpstat.tcps_rttdetected; 1301 } 1302 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 1303 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 1304 /* 1305 * Recalculate the retransmit timer / rtt. 1306 * 1307 * Some machines (certain windows boxes) 1308 * send broken timestamp replies during the 1309 * SYN+ACK phase, ignore timestamps of 0. 1310 */ 1311 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1312 tcp_xmit_timer(tp, 1313 ticks - to.to_tsecr + 1, 1314 th->th_ack); 1315 } else if (tp->t_rtttime && 1316 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1317 tcp_xmit_timer(tp, 1318 ticks - tp->t_rtttime, 1319 th->th_ack); 1320 } 1321 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1322 acked = th->th_ack - tp->snd_una; 1323 tcpstat.tcps_rcvackpack++; 1324 tcpstat.tcps_rcvackbyte += acked; 1325 sbdrop(&so->so_snd.sb, acked); 1326 tp->snd_recover = th->th_ack - 1; 1327 tp->snd_una = th->th_ack; 1328 tp->t_dupacks = 0; 1329 /* 1330 * Update window information. 1331 */ 1332 if (tiwin != tp->snd_wnd && 1333 acceptable_window_update(tp, th, tiwin)) { 1334 /* keep track of pure window updates */ 1335 if (tp->snd_wl2 == th->th_ack && 1336 tiwin > tp->snd_wnd) 1337 tcpstat.tcps_rcvwinupd++; 1338 tp->snd_wnd = tiwin; 1339 tp->snd_wl1 = th->th_seq; 1340 tp->snd_wl2 = th->th_ack; 1341 if (tp->snd_wnd > tp->max_sndwnd) 1342 tp->max_sndwnd = tp->snd_wnd; 1343 } 1344 m_freem(m); 1345 ND6_HINT(tp); /* some progress has been done */ 1346 /* 1347 * If all outstanding data are acked, stop 1348 * retransmit timer, otherwise restart timer 1349 * using current (possibly backed-off) value. 1350 * If process is waiting for space, 1351 * wakeup/selwakeup/signal. If data 1352 * are ready to send, let tcp_output 1353 * decide between more output or persist. 1354 */ 1355 if (tp->snd_una == tp->snd_max) { 1356 tcp_callout_stop(tp, tp->tt_rexmt); 1357 } else if (!tcp_callout_active(tp, 1358 tp->tt_persist)) { 1359 tcp_callout_reset(tp, tp->tt_rexmt, 1360 tp->t_rxtcur, tcp_timer_rexmt); 1361 } 1362 sowwakeup(so); 1363 if (so->so_snd.ssb_cc > 0 && 1364 !tcp_output_pending(tp)) 1365 tcp_output_fair(tp); 1366 return(IPPROTO_DONE); 1367 } 1368 } else if (tiwin == tp->snd_wnd && 1369 th->th_ack == tp->snd_una && 1370 TAILQ_EMPTY(&tp->t_segq) && 1371 tlen <= ssb_space(&so->so_rcv)) { 1372 u_long newsize = 0; /* automatic sockbuf scaling */ 1373 /* 1374 * This is a pure, in-sequence data packet 1375 * with nothing on the reassembly queue and 1376 * we have enough buffer space to take it. 1377 */ 1378 ++tcpstat.tcps_preddat; 1379 tp->rcv_nxt += tlen; 1380 tcpstat.tcps_rcvpack++; 1381 tcpstat.tcps_rcvbyte += tlen; 1382 ND6_HINT(tp); /* some progress has been done */ 1383 /* 1384 * Automatic sizing of receive socket buffer. Often the send 1385 * buffer size is not optimally adjusted to the actual network 1386 * conditions at hand (delay bandwidth product). Setting the 1387 * buffer size too small limits throughput on links with high 1388 * bandwidth and high delay (eg. trans-continental/oceanic links). 1389 * 1390 * On the receive side the socket buffer memory is only rarely 1391 * used to any significant extent. This allows us to be much 1392 * more aggressive in scaling the receive socket buffer. For 1393 * the case that the buffer space is actually used to a large 1394 * extent and we run out of kernel memory we can simply drop 1395 * the new segments; TCP on the sender will just retransmit it 1396 * later. Setting the buffer size too big may only consume too 1397 * much kernel memory if the application doesn't read() from 1398 * the socket or packet loss or reordering makes use of the 1399 * reassembly queue. 1400 * 1401 * The criteria to step up the receive buffer one notch are: 1402 * 1. the number of bytes received during the time it takes 1403 * one timestamp to be reflected back to us (the RTT); 1404 * 2. received bytes per RTT is within seven eighth of the 1405 * current socket buffer size; 1406 * 3. receive buffer size has not hit maximal automatic size; 1407 * 1408 * This algorithm does one step per RTT at most and only if 1409 * we receive a bulk stream w/o packet losses or reorderings. 1410 * Shrinking the buffer during idle times is not necessary as 1411 * it doesn't consume any memory when idle. 1412 * 1413 * TODO: Only step up if the application is actually serving 1414 * the buffer to better manage the socket buffer resources. 1415 */ 1416 if (tcp_do_autorcvbuf && 1417 to.to_tsecr && 1418 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1419 if (to.to_tsecr > tp->rfbuf_ts && 1420 to.to_tsecr - tp->rfbuf_ts < hz) { 1421 if (tp->rfbuf_cnt > 1422 (so->so_rcv.ssb_hiwat / 8 * 7) && 1423 so->so_rcv.ssb_hiwat < 1424 tcp_autorcvbuf_max) { 1425 newsize = 1426 ulmin(so->so_rcv.ssb_hiwat + 1427 tcp_autorcvbuf_inc, 1428 tcp_autorcvbuf_max); 1429 } 1430 /* Start over with next RTT. */ 1431 tp->rfbuf_ts = 0; 1432 tp->rfbuf_cnt = 0; 1433 } else 1434 tp->rfbuf_cnt += tlen; /* add up */ 1435 } 1436 /* 1437 * Add data to socket buffer. 1438 */ 1439 if (so->so_state & SS_CANTRCVMORE) { 1440 m_freem(m); 1441 } else { 1442 /* 1443 * Set new socket buffer size, give up when 1444 * limit is reached. 1445 * 1446 * Adjusting the size can mess up ACK 1447 * sequencing when pure window updates are 1448 * being avoided (which is the default), 1449 * so force an ack. 1450 */ 1451 lwkt_gettoken(&so->so_rcv.ssb_token); 1452 if (newsize) { 1453 tp->t_flags |= TF_RXRESIZED; 1454 if (!ssb_reserve(&so->so_rcv, newsize, 1455 so, NULL)) { 1456 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1457 } 1458 if (newsize >= 1459 (TCP_MAXWIN << tp->rcv_scale)) { 1460 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1461 } 1462 } 1463 m_adj(m, drop_hdrlen); /* delayed header drop */ 1464 ssb_appendstream(&so->so_rcv, m); 1465 lwkt_reltoken(&so->so_rcv.ssb_token); 1466 } 1467 sorwakeup(so); 1468 /* 1469 * This code is responsible for most of the ACKs 1470 * the TCP stack sends back after receiving a data 1471 * packet. Note that the DELAY_ACK check fails if 1472 * the delack timer is already running, which results 1473 * in an ack being sent every other packet (which is 1474 * what we want). 1475 * 1476 * We then further aggregate acks by not actually 1477 * sending one until the protocol thread has completed 1478 * processing the current backlog of packets. This 1479 * does not delay the ack any further, but allows us 1480 * to take advantage of the packet aggregation that 1481 * high speed NICs do (usually blocks of 8-10 packets) 1482 * to send a single ack rather then four or five acks, 1483 * greatly reducing the ack rate, the return channel 1484 * bandwidth, and the protocol overhead on both ends. 1485 * 1486 * Since this also has the effect of slowing down 1487 * the exponential slow-start ramp-up, systems with 1488 * very large bandwidth-delay products might want 1489 * to turn the feature off. 1490 */ 1491 if (DELAY_ACK(tp)) { 1492 tcp_callout_reset(tp, tp->tt_delack, 1493 tcp_delacktime, tcp_timer_delack); 1494 } else if (tcp_aggregate_acks) { 1495 tp->t_flags |= TF_ACKNOW; 1496 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1497 tp->t_flags |= TF_ONOUTPUTQ; 1498 tp->tt_cpu = mycpu->gd_cpuid; 1499 TAILQ_INSERT_TAIL( 1500 &tcpcbackq[tp->tt_cpu], 1501 tp, t_outputq); 1502 } 1503 } else { 1504 tp->t_flags |= TF_ACKNOW; 1505 tcp_output(tp); 1506 } 1507 return(IPPROTO_DONE); 1508 } 1509 } 1510 1511 /* 1512 * Calculate amount of space in receive window, 1513 * and then do TCP input processing. 1514 * Receive window is amount of space in rcv queue, 1515 * but not less than advertised window. 1516 */ 1517 recvwin = ssb_space(&so->so_rcv); 1518 if (recvwin < 0) 1519 recvwin = 0; 1520 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1521 1522 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1523 tp->rfbuf_ts = 0; 1524 tp->rfbuf_cnt = 0; 1525 1526 switch (tp->t_state) { 1527 /* 1528 * If the state is SYN_RECEIVED: 1529 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1530 */ 1531 case TCPS_SYN_RECEIVED: 1532 if ((thflags & TH_ACK) && 1533 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1534 SEQ_GT(th->th_ack, tp->snd_max))) { 1535 rstreason = BANDLIM_RST_OPENPORT; 1536 goto dropwithreset; 1537 } 1538 break; 1539 1540 /* 1541 * If the state is SYN_SENT: 1542 * if seg contains an ACK, but not for our SYN, drop the input. 1543 * if seg contains a RST, then drop the connection. 1544 * if seg does not contain SYN, then drop it. 1545 * Otherwise this is an acceptable SYN segment 1546 * initialize tp->rcv_nxt and tp->irs 1547 * if seg contains ack then advance tp->snd_una 1548 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1549 * arrange for segment to be acked (eventually) 1550 * continue processing rest of data/controls, beginning with URG 1551 */ 1552 case TCPS_SYN_SENT: 1553 if ((thflags & TH_ACK) && 1554 (SEQ_LEQ(th->th_ack, tp->iss) || 1555 SEQ_GT(th->th_ack, tp->snd_max))) { 1556 rstreason = BANDLIM_UNLIMITED; 1557 goto dropwithreset; 1558 } 1559 if (thflags & TH_RST) { 1560 if (thflags & TH_ACK) 1561 tp = tcp_drop(tp, ECONNREFUSED); 1562 goto drop; 1563 } 1564 if (!(thflags & TH_SYN)) 1565 goto drop; 1566 1567 tp->irs = th->th_seq; 1568 tcp_rcvseqinit(tp); 1569 if (thflags & TH_ACK) { 1570 /* Our SYN was acked. */ 1571 tcpstat.tcps_connects++; 1572 soisconnected(so); 1573 /* Do window scaling on this connection? */ 1574 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1575 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1576 tp->rcv_scale = tp->request_r_scale; 1577 tp->rcv_adv += tp->rcv_wnd; 1578 tp->snd_una++; /* SYN is acked */ 1579 tcp_callout_stop(tp, tp->tt_rexmt); 1580 /* 1581 * If there's data, delay ACK; if there's also a FIN 1582 * ACKNOW will be turned on later. 1583 */ 1584 if (DELAY_ACK(tp) && tlen != 0) { 1585 tcp_callout_reset(tp, tp->tt_delack, 1586 tcp_delacktime, tcp_timer_delack); 1587 } else { 1588 tp->t_flags |= TF_ACKNOW; 1589 } 1590 /* 1591 * Received <SYN,ACK> in SYN_SENT[*] state. 1592 * Transitions: 1593 * SYN_SENT --> ESTABLISHED 1594 * SYN_SENT* --> FIN_WAIT_1 1595 */ 1596 tp->t_starttime = ticks; 1597 if (tp->t_flags & TF_NEEDFIN) { 1598 tp->t_state = TCPS_FIN_WAIT_1; 1599 tp->t_flags &= ~TF_NEEDFIN; 1600 thflags &= ~TH_SYN; 1601 } else { 1602 tcp_established(tp); 1603 } 1604 } else { 1605 /* 1606 * Received initial SYN in SYN-SENT[*] state => 1607 * simultaneous open. 1608 * Do 3-way handshake: 1609 * SYN-SENT -> SYN-RECEIVED 1610 * SYN-SENT* -> SYN-RECEIVED* 1611 */ 1612 tp->t_flags |= TF_ACKNOW; 1613 tcp_callout_stop(tp, tp->tt_rexmt); 1614 tp->t_state = TCPS_SYN_RECEIVED; 1615 } 1616 1617 /* 1618 * Advance th->th_seq to correspond to first data byte. 1619 * If data, trim to stay within window, 1620 * dropping FIN if necessary. 1621 */ 1622 th->th_seq++; 1623 if (tlen > tp->rcv_wnd) { 1624 todrop = tlen - tp->rcv_wnd; 1625 m_adj(m, -todrop); 1626 tlen = tp->rcv_wnd; 1627 thflags &= ~TH_FIN; 1628 tcpstat.tcps_rcvpackafterwin++; 1629 tcpstat.tcps_rcvbyteafterwin += todrop; 1630 } 1631 tp->snd_wl1 = th->th_seq - 1; 1632 tp->rcv_up = th->th_seq; 1633 /* 1634 * Client side of transaction: already sent SYN and data. 1635 * If the remote host used T/TCP to validate the SYN, 1636 * our data will be ACK'd; if so, enter normal data segment 1637 * processing in the middle of step 5, ack processing. 1638 * Otherwise, goto step 6. 1639 */ 1640 if (thflags & TH_ACK) 1641 goto process_ACK; 1642 1643 goto step6; 1644 1645 /* 1646 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1647 * do normal processing (we no longer bother with T/TCP). 1648 */ 1649 case TCPS_LAST_ACK: 1650 case TCPS_CLOSING: 1651 case TCPS_TIME_WAIT: 1652 break; /* continue normal processing */ 1653 } 1654 1655 /* 1656 * States other than LISTEN or SYN_SENT. 1657 * First check the RST flag and sequence number since reset segments 1658 * are exempt from the timestamp and connection count tests. This 1659 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1660 * below which allowed reset segments in half the sequence space 1661 * to fall though and be processed (which gives forged reset 1662 * segments with a random sequence number a 50 percent chance of 1663 * killing a connection). 1664 * Then check timestamp, if present. 1665 * Then check the connection count, if present. 1666 * Then check that at least some bytes of segment are within 1667 * receive window. If segment begins before rcv_nxt, 1668 * drop leading data (and SYN); if nothing left, just ack. 1669 * 1670 * 1671 * If the RST bit is set, check the sequence number to see 1672 * if this is a valid reset segment. 1673 * RFC 793 page 37: 1674 * In all states except SYN-SENT, all reset (RST) segments 1675 * are validated by checking their SEQ-fields. A reset is 1676 * valid if its sequence number is in the window. 1677 * Note: this does not take into account delayed ACKs, so 1678 * we should test against last_ack_sent instead of rcv_nxt. 1679 * The sequence number in the reset segment is normally an 1680 * echo of our outgoing acknowledgement numbers, but some hosts 1681 * send a reset with the sequence number at the rightmost edge 1682 * of our receive window, and we have to handle this case. 1683 * If we have multiple segments in flight, the intial reset 1684 * segment sequence numbers will be to the left of last_ack_sent, 1685 * but they will eventually catch up. 1686 * In any case, it never made sense to trim reset segments to 1687 * fit the receive window since RFC 1122 says: 1688 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1689 * 1690 * A TCP SHOULD allow a received RST segment to include data. 1691 * 1692 * DISCUSSION 1693 * It has been suggested that a RST segment could contain 1694 * ASCII text that encoded and explained the cause of the 1695 * RST. No standard has yet been established for such 1696 * data. 1697 * 1698 * If the reset segment passes the sequence number test examine 1699 * the state: 1700 * SYN_RECEIVED STATE: 1701 * If passive open, return to LISTEN state. 1702 * If active open, inform user that connection was refused. 1703 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1704 * Inform user that connection was reset, and close tcb. 1705 * CLOSING, LAST_ACK STATES: 1706 * Close the tcb. 1707 * TIME_WAIT STATE: 1708 * Drop the segment - see Stevens, vol. 2, p. 964 and 1709 * RFC 1337. 1710 */ 1711 if (thflags & TH_RST) { 1712 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1713 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1714 switch (tp->t_state) { 1715 1716 case TCPS_SYN_RECEIVED: 1717 so->so_error = ECONNREFUSED; 1718 goto close; 1719 1720 case TCPS_ESTABLISHED: 1721 case TCPS_FIN_WAIT_1: 1722 case TCPS_FIN_WAIT_2: 1723 case TCPS_CLOSE_WAIT: 1724 so->so_error = ECONNRESET; 1725 close: 1726 tp->t_state = TCPS_CLOSED; 1727 tcpstat.tcps_drops++; 1728 tp = tcp_close(tp); 1729 break; 1730 1731 case TCPS_CLOSING: 1732 case TCPS_LAST_ACK: 1733 tp = tcp_close(tp); 1734 break; 1735 1736 case TCPS_TIME_WAIT: 1737 break; 1738 } 1739 } 1740 goto drop; 1741 } 1742 1743 /* 1744 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1745 * and it's less than ts_recent, drop it. 1746 */ 1747 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1748 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1749 /* Check to see if ts_recent is over 24 days old. */ 1750 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1751 /* 1752 * Invalidate ts_recent. If this segment updates 1753 * ts_recent, the age will be reset later and ts_recent 1754 * will get a valid value. If it does not, setting 1755 * ts_recent to zero will at least satisfy the 1756 * requirement that zero be placed in the timestamp 1757 * echo reply when ts_recent isn't valid. The 1758 * age isn't reset until we get a valid ts_recent 1759 * because we don't want out-of-order segments to be 1760 * dropped when ts_recent is old. 1761 */ 1762 tp->ts_recent = 0; 1763 } else if (tcp_paws_tolerance && tlen != 0 && 1764 tp->t_state == TCPS_ESTABLISHED && 1765 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK&& 1766 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1767 th->th_ack == tp->snd_una && 1768 tiwin == tp->snd_wnd && 1769 TSTMP_GEQ(to.to_tsval + tcp_paws_tolerance, tp->ts_recent)&& 1770 (th->th_seq == tp->rcv_nxt || 1771 (SEQ_GT(th->th_seq, tp->rcv_nxt) && 1772 tcp_paws_canreasslast(tp, th, tlen)))) { 1773 /* 1774 * This tends to prevent valid new segments from being 1775 * dropped by the reordered segments sent by the fast 1776 * retransmission algorithm on the sending side, i.e. 1777 * the fast retransmitted segment w/ larger timestamp 1778 * arrives earlier than the previously sent new segments 1779 * w/ smaller timestamp. 1780 * 1781 * If following conditions are met, the segment is 1782 * accepted: 1783 * - The segment contains data 1784 * - The connection is established 1785 * - The header does not contain important flags 1786 * - SYN or FIN is not needed 1787 * - It does not acknowledge new data 1788 * - Receive window is not changed 1789 * - The timestamp is within "acceptable" range 1790 * - The new segment is what we are expecting or 1791 * the new segment could be merged w/ the last 1792 * pending segment on the reassemble queue 1793 */ 1794 tcpstat.tcps_pawsaccept++; 1795 tcpstat.tcps_pawsdrop++; 1796 } else { 1797 tcpstat.tcps_rcvduppack++; 1798 tcpstat.tcps_rcvdupbyte += tlen; 1799 tcpstat.tcps_pawsdrop++; 1800 if (tlen) 1801 goto dropafterack; 1802 goto drop; 1803 } 1804 } 1805 1806 /* 1807 * In the SYN-RECEIVED state, validate that the packet belongs to 1808 * this connection before trimming the data to fit the receive 1809 * window. Check the sequence number versus IRS since we know 1810 * the sequence numbers haven't wrapped. This is a partial fix 1811 * for the "LAND" DoS attack. 1812 */ 1813 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1814 rstreason = BANDLIM_RST_OPENPORT; 1815 goto dropwithreset; 1816 } 1817 1818 todrop = tp->rcv_nxt - th->th_seq; 1819 if (todrop > 0) { 1820 if (TCP_DO_SACK(tp)) { 1821 /* Report duplicate segment at head of packet. */ 1822 tp->reportblk.rblk_start = th->th_seq; 1823 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 1824 th->th_seq + tlen, thflags); 1825 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1826 tp->reportblk.rblk_end = tp->rcv_nxt; 1827 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT); 1828 tp->t_flags |= TF_ACKNOW; 1829 } 1830 if (thflags & TH_SYN) { 1831 thflags &= ~TH_SYN; 1832 th->th_seq++; 1833 if (th->th_urp > 1) 1834 th->th_urp--; 1835 else 1836 thflags &= ~TH_URG; 1837 todrop--; 1838 } 1839 /* 1840 * Following if statement from Stevens, vol. 2, p. 960. 1841 */ 1842 if (todrop > tlen || 1843 (todrop == tlen && !(thflags & TH_FIN))) { 1844 /* 1845 * Any valid FIN must be to the left of the window. 1846 * At this point the FIN must be a duplicate or out 1847 * of sequence; drop it. 1848 */ 1849 thflags &= ~TH_FIN; 1850 1851 /* 1852 * Send an ACK to resynchronize and drop any data. 1853 * But keep on processing for RST or ACK. 1854 */ 1855 tp->t_flags |= TF_ACKNOW; 1856 todrop = tlen; 1857 tcpstat.tcps_rcvduppack++; 1858 tcpstat.tcps_rcvdupbyte += todrop; 1859 } else { 1860 tcpstat.tcps_rcvpartduppack++; 1861 tcpstat.tcps_rcvpartdupbyte += todrop; 1862 } 1863 drop_hdrlen += todrop; /* drop from the top afterwards */ 1864 th->th_seq += todrop; 1865 tlen -= todrop; 1866 if (th->th_urp > todrop) 1867 th->th_urp -= todrop; 1868 else { 1869 thflags &= ~TH_URG; 1870 th->th_urp = 0; 1871 } 1872 } 1873 1874 /* 1875 * If new data are received on a connection after the 1876 * user processes are gone, then RST the other end. 1877 */ 1878 if ((so->so_state & SS_NOFDREF) && 1879 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1880 tp = tcp_close(tp); 1881 tcpstat.tcps_rcvafterclose++; 1882 rstreason = BANDLIM_UNLIMITED; 1883 goto dropwithreset; 1884 } 1885 1886 /* 1887 * If segment ends after window, drop trailing data 1888 * (and PUSH and FIN); if nothing left, just ACK. 1889 */ 1890 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1891 if (todrop > 0) { 1892 tcpstat.tcps_rcvpackafterwin++; 1893 if (todrop >= tlen) { 1894 tcpstat.tcps_rcvbyteafterwin += tlen; 1895 /* 1896 * If a new connection request is received 1897 * while in TIME_WAIT, drop the old connection 1898 * and start over if the sequence numbers 1899 * are above the previous ones. 1900 */ 1901 if (thflags & TH_SYN && 1902 tp->t_state == TCPS_TIME_WAIT && 1903 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1904 tp = tcp_close(tp); 1905 goto findpcb; 1906 } 1907 /* 1908 * If window is closed can only take segments at 1909 * window edge, and have to drop data and PUSH from 1910 * incoming segments. Continue processing, but 1911 * remember to ack. Otherwise, drop segment 1912 * and ack. 1913 */ 1914 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1915 tp->t_flags |= TF_ACKNOW; 1916 tcpstat.tcps_rcvwinprobe++; 1917 } else 1918 goto dropafterack; 1919 } else 1920 tcpstat.tcps_rcvbyteafterwin += todrop; 1921 m_adj(m, -todrop); 1922 tlen -= todrop; 1923 thflags &= ~(TH_PUSH | TH_FIN); 1924 } 1925 1926 /* 1927 * If last ACK falls within this segment's sequence numbers, 1928 * record its timestamp. 1929 * NOTE: 1930 * 1) That the test incorporates suggestions from the latest 1931 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1932 * 2) That updating only on newer timestamps interferes with 1933 * our earlier PAWS tests, so this check should be solely 1934 * predicated on the sequence space of this segment. 1935 * 3) That we modify the segment boundary check to be 1936 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1937 * instead of RFC1323's 1938 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1939 * This modified check allows us to overcome RFC1323's 1940 * limitations as described in Stevens TCP/IP Illustrated 1941 * Vol. 2 p.869. In such cases, we can still calculate the 1942 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1943 */ 1944 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1945 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1946 + ((thflags & TH_SYN) != 0) 1947 + ((thflags & TH_FIN) != 0)))) { 1948 tp->ts_recent_age = ticks; 1949 tp->ts_recent = to.to_tsval; 1950 } 1951 1952 /* 1953 * If a SYN is in the window, then this is an 1954 * error and we send an RST and drop the connection. 1955 */ 1956 if (thflags & TH_SYN) { 1957 tp = tcp_drop(tp, ECONNRESET); 1958 rstreason = BANDLIM_UNLIMITED; 1959 goto dropwithreset; 1960 } 1961 1962 /* 1963 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1964 * flag is on (half-synchronized state), then queue data for 1965 * later processing; else drop segment and return. 1966 */ 1967 if (!(thflags & TH_ACK)) { 1968 if (tp->t_state == TCPS_SYN_RECEIVED || 1969 (tp->t_flags & TF_NEEDSYN)) 1970 goto step6; 1971 else 1972 goto drop; 1973 } 1974 1975 /* 1976 * Ack processing. 1977 */ 1978 switch (tp->t_state) { 1979 /* 1980 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1981 * ESTABLISHED state and continue processing. 1982 * The ACK was checked above. 1983 */ 1984 case TCPS_SYN_RECEIVED: 1985 1986 tcpstat.tcps_connects++; 1987 soisconnected(so); 1988 /* Do window scaling? */ 1989 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1990 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1991 tp->rcv_scale = tp->request_r_scale; 1992 /* 1993 * Make transitions: 1994 * SYN-RECEIVED -> ESTABLISHED 1995 * SYN-RECEIVED* -> FIN-WAIT-1 1996 */ 1997 tp->t_starttime = ticks; 1998 if (tp->t_flags & TF_NEEDFIN) { 1999 tp->t_state = TCPS_FIN_WAIT_1; 2000 tp->t_flags &= ~TF_NEEDFIN; 2001 } else { 2002 tcp_established(tp); 2003 } 2004 /* 2005 * If segment contains data or ACK, will call tcp_reass() 2006 * later; if not, do so now to pass queued data to user. 2007 */ 2008 if (tlen == 0 && !(thflags & TH_FIN)) 2009 tcp_reass(tp, NULL, NULL, NULL); 2010 /* fall into ... */ 2011 2012 /* 2013 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2014 * ACKs. If the ack is in the range 2015 * tp->snd_una < th->th_ack <= tp->snd_max 2016 * then advance tp->snd_una to th->th_ack and drop 2017 * data from the retransmission queue. If this ACK reflects 2018 * more up to date window information we update our window information. 2019 */ 2020 case TCPS_ESTABLISHED: 2021 case TCPS_FIN_WAIT_1: 2022 case TCPS_FIN_WAIT_2: 2023 case TCPS_CLOSE_WAIT: 2024 case TCPS_CLOSING: 2025 case TCPS_LAST_ACK: 2026 case TCPS_TIME_WAIT: 2027 2028 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2029 boolean_t maynotdup = FALSE; 2030 2031 if (TCP_DO_SACK(tp)) 2032 tcp_sack_update_scoreboard(tp, &to); 2033 2034 if (tlen != 0 || tiwin != tp->snd_wnd || 2035 ((thflags & TH_FIN) && !(tp->t_flags & TF_SAWFIN))) 2036 maynotdup = TRUE; 2037 2038 if (!tcp_callout_active(tp, tp->tt_rexmt) || 2039 th->th_ack != tp->snd_una) { 2040 if (!maynotdup) 2041 tcpstat.tcps_rcvdupack++; 2042 tp->t_dupacks = 0; 2043 break; 2044 } 2045 2046 #define DELAY_DUPACK \ 2047 do { \ 2048 delayed_dupack = TRUE; \ 2049 th_dupack = th->th_ack; \ 2050 to_flags = to.to_flags; \ 2051 } while (0) 2052 if (maynotdup) { 2053 if (!tcp_do_rfc6675 || 2054 !TCP_DO_SACK(tp) || 2055 (to.to_flags & 2056 (TOF_SACK | TOF_SACK_REDUNDANT)) 2057 != TOF_SACK) { 2058 tp->t_dupacks = 0; 2059 } else { 2060 DELAY_DUPACK; 2061 } 2062 break; 2063 } 2064 if ((thflags & TH_FIN) && !(tp->t_flags & TF_QUEDFIN)) { 2065 /* 2066 * This could happen, if the reassemable 2067 * queue overflew or was drained. Don't 2068 * drop this FIN here; defer the duplicated 2069 * ACK processing until this FIN gets queued. 2070 */ 2071 DELAY_DUPACK; 2072 break; 2073 } 2074 #undef DELAY_DUPACK 2075 2076 if (tcp_recv_dupack(tp, th->th_ack, to.to_flags)) 2077 goto drop; 2078 else 2079 break; 2080 } 2081 2082 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2083 tp->t_dupacks = 0; 2084 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2085 /* 2086 * Detected optimistic ACK attack. 2087 * Force slow-start to de-synchronize attack. 2088 */ 2089 tp->snd_cwnd = tp->t_maxseg; 2090 tp->snd_wacked = 0; 2091 2092 tcpstat.tcps_rcvacktoomuch++; 2093 goto dropafterack; 2094 } 2095 /* 2096 * If we reach this point, ACK is not a duplicate, 2097 * i.e., it ACKs something we sent. 2098 */ 2099 if (tp->t_flags & TF_NEEDSYN) { 2100 /* 2101 * T/TCP: Connection was half-synchronized, and our 2102 * SYN has been ACK'd (so connection is now fully 2103 * synchronized). Go to non-starred state, 2104 * increment snd_una for ACK of SYN, and check if 2105 * we can do window scaling. 2106 */ 2107 tp->t_flags &= ~TF_NEEDSYN; 2108 tp->snd_una++; 2109 /* Do window scaling? */ 2110 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2111 (TF_RCVD_SCALE | TF_REQ_SCALE)) 2112 tp->rcv_scale = tp->request_r_scale; 2113 } 2114 2115 process_ACK: 2116 acked = th->th_ack - tp->snd_una; 2117 tcpstat.tcps_rcvackpack++; 2118 tcpstat.tcps_rcvackbyte += acked; 2119 2120 if (tcp_do_eifel_detect && acked > 0 && 2121 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2122 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 2123 /* Eifel detection applicable. */ 2124 if (to.to_tsecr < tp->t_rexmtTS) { 2125 ++tcpstat.tcps_eifeldetected; 2126 tcp_revert_congestion_state(tp); 2127 if (tp->t_rxtshift != 1 || 2128 ticks >= tp->t_badrxtwin) 2129 ++tcpstat.tcps_rttcantdetect; 2130 } 2131 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2132 /* 2133 * If we just performed our first retransmit, 2134 * and the ACK arrives within our recovery window, 2135 * then it was a mistake to do the retransmit 2136 * in the first place. Recover our original cwnd 2137 * and ssthresh, and proceed to transmit where we 2138 * left off. 2139 */ 2140 tcp_revert_congestion_state(tp); 2141 ++tcpstat.tcps_rttdetected; 2142 } 2143 2144 /* 2145 * If we have a timestamp reply, update smoothed 2146 * round trip time. If no timestamp is present but 2147 * transmit timer is running and timed sequence 2148 * number was acked, update smoothed round trip time. 2149 * Since we now have an rtt measurement, cancel the 2150 * timer backoff (cf., Phil Karn's retransmit alg.). 2151 * Recompute the initial retransmit timer. 2152 * 2153 * Some machines (certain windows boxes) send broken 2154 * timestamp replies during the SYN+ACK phase, ignore 2155 * timestamps of 0. 2156 */ 2157 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2158 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack); 2159 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2160 tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack); 2161 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2162 2163 /* 2164 * If no data (only SYN) was ACK'd, 2165 * skip rest of ACK processing. 2166 */ 2167 if (acked == 0) 2168 goto step6; 2169 2170 /* Stop looking for an acceptable ACK since one was received. */ 2171 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 2172 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 2173 2174 if (acked > so->so_snd.ssb_cc) { 2175 tp->snd_wnd -= so->so_snd.ssb_cc; 2176 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2177 ourfinisacked = TRUE; 2178 } else { 2179 sbdrop(&so->so_snd.sb, acked); 2180 tp->snd_wnd -= acked; 2181 ourfinisacked = FALSE; 2182 } 2183 sowwakeup(so); 2184 2185 /* 2186 * Update window information. 2187 */ 2188 if (acceptable_window_update(tp, th, tiwin)) { 2189 /* keep track of pure window updates */ 2190 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2191 tiwin > tp->snd_wnd) 2192 tcpstat.tcps_rcvwinupd++; 2193 tp->snd_wnd = tiwin; 2194 tp->snd_wl1 = th->th_seq; 2195 tp->snd_wl2 = th->th_ack; 2196 if (tp->snd_wnd > tp->max_sndwnd) 2197 tp->max_sndwnd = tp->snd_wnd; 2198 needoutput = TRUE; 2199 } 2200 2201 tp->snd_una = th->th_ack; 2202 if (TCP_DO_SACK(tp)) 2203 tcp_sack_update_scoreboard(tp, &to); 2204 if (IN_FASTRECOVERY(tp)) { 2205 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2206 EXIT_FASTRECOVERY(tp); 2207 needoutput = TRUE; 2208 /* 2209 * If the congestion window was inflated 2210 * to account for the other side's 2211 * cached packets, retract it. 2212 */ 2213 if (!TCP_DO_SACK(tp)) 2214 tp->snd_cwnd = tp->snd_ssthresh; 2215 2216 /* 2217 * Window inflation should have left us 2218 * with approximately snd_ssthresh outstanding 2219 * data. But, in case we would be inclined 2220 * to send a burst, better do it using 2221 * slow start. 2222 */ 2223 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2224 tp->snd_max + 2 * tp->t_maxseg)) 2225 tp->snd_cwnd = 2226 (tp->snd_max - tp->snd_una) + 2227 2 * tp->t_maxseg; 2228 2229 tp->snd_wacked = 0; 2230 } else { 2231 if (TCP_DO_SACK(tp)) { 2232 tp->snd_max_rexmt = tp->snd_max; 2233 tcp_sack_rexmt(tp, 2234 tp->snd_una == tp->rexmt_high); 2235 } else { 2236 tcp_newreno_partial_ack(tp, th, acked); 2237 } 2238 needoutput = FALSE; 2239 } 2240 } else { 2241 /* 2242 * Open the congestion window. When in slow-start, 2243 * open exponentially: maxseg per packet. Otherwise, 2244 * open linearly: maxseg per window. 2245 */ 2246 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2247 u_int abc_sslimit = 2248 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2249 tp->t_maxseg : 2 * tp->t_maxseg); 2250 2251 /* slow-start */ 2252 tp->snd_cwnd += tcp_do_abc ? 2253 min(acked, abc_sslimit) : tp->t_maxseg; 2254 } else { 2255 /* linear increase */ 2256 tp->snd_wacked += tcp_do_abc ? acked : 2257 tp->t_maxseg; 2258 if (tp->snd_wacked >= tp->snd_cwnd) { 2259 tp->snd_wacked -= tp->snd_cwnd; 2260 tp->snd_cwnd += tp->t_maxseg; 2261 } 2262 } 2263 tp->snd_cwnd = min(tp->snd_cwnd, 2264 TCP_MAXWIN << tp->snd_scale); 2265 tp->snd_recover = th->th_ack - 1; 2266 } 2267 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2268 tp->snd_nxt = tp->snd_una; 2269 2270 /* 2271 * If all outstanding data is acked, stop retransmit 2272 * timer and remember to restart (more output or persist). 2273 * If there is more data to be acked, restart retransmit 2274 * timer, using current (possibly backed-off) value. 2275 */ 2276 if (th->th_ack == tp->snd_max) { 2277 tcp_callout_stop(tp, tp->tt_rexmt); 2278 needoutput = TRUE; 2279 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2280 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2281 tcp_timer_rexmt); 2282 } 2283 2284 switch (tp->t_state) { 2285 /* 2286 * In FIN_WAIT_1 STATE in addition to the processing 2287 * for the ESTABLISHED state if our FIN is now acknowledged 2288 * then enter FIN_WAIT_2. 2289 */ 2290 case TCPS_FIN_WAIT_1: 2291 if (ourfinisacked) { 2292 /* 2293 * If we can't receive any more 2294 * data, then closing user can proceed. 2295 * Starting the timer is contrary to the 2296 * specification, but if we don't get a FIN 2297 * we'll hang forever. 2298 */ 2299 if (so->so_state & SS_CANTRCVMORE) { 2300 soisdisconnected(so); 2301 tcp_callout_reset(tp, tp->tt_2msl, 2302 tp->t_maxidle, tcp_timer_2msl); 2303 } 2304 tp->t_state = TCPS_FIN_WAIT_2; 2305 } 2306 break; 2307 2308 /* 2309 * In CLOSING STATE in addition to the processing for 2310 * the ESTABLISHED state if the ACK acknowledges our FIN 2311 * then enter the TIME-WAIT state, otherwise ignore 2312 * the segment. 2313 */ 2314 case TCPS_CLOSING: 2315 if (ourfinisacked) { 2316 tp->t_state = TCPS_TIME_WAIT; 2317 tcp_canceltimers(tp); 2318 tcp_callout_reset(tp, tp->tt_2msl, 2319 2 * tcp_rmx_msl(tp), 2320 tcp_timer_2msl); 2321 soisdisconnected(so); 2322 } 2323 break; 2324 2325 /* 2326 * In LAST_ACK, we may still be waiting for data to drain 2327 * and/or to be acked, as well as for the ack of our FIN. 2328 * If our FIN is now acknowledged, delete the TCB, 2329 * enter the closed state and return. 2330 */ 2331 case TCPS_LAST_ACK: 2332 if (ourfinisacked) { 2333 tp = tcp_close(tp); 2334 goto drop; 2335 } 2336 break; 2337 2338 /* 2339 * In TIME_WAIT state the only thing that should arrive 2340 * is a retransmission of the remote FIN. Acknowledge 2341 * it and restart the finack timer. 2342 */ 2343 case TCPS_TIME_WAIT: 2344 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2345 tcp_timer_2msl); 2346 goto dropafterack; 2347 } 2348 } 2349 2350 step6: 2351 /* 2352 * Update window information. 2353 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2354 */ 2355 if ((thflags & TH_ACK) && 2356 acceptable_window_update(tp, th, tiwin)) { 2357 /* keep track of pure window updates */ 2358 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2359 tiwin > tp->snd_wnd) 2360 tcpstat.tcps_rcvwinupd++; 2361 tp->snd_wnd = tiwin; 2362 tp->snd_wl1 = th->th_seq; 2363 tp->snd_wl2 = th->th_ack; 2364 if (tp->snd_wnd > tp->max_sndwnd) 2365 tp->max_sndwnd = tp->snd_wnd; 2366 needoutput = TRUE; 2367 } 2368 2369 /* 2370 * Process segments with URG. 2371 */ 2372 if ((thflags & TH_URG) && th->th_urp && 2373 !TCPS_HAVERCVDFIN(tp->t_state)) { 2374 /* 2375 * This is a kludge, but if we receive and accept 2376 * random urgent pointers, we'll crash in 2377 * soreceive. It's hard to imagine someone 2378 * actually wanting to send this much urgent data. 2379 */ 2380 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2381 th->th_urp = 0; /* XXX */ 2382 thflags &= ~TH_URG; /* XXX */ 2383 goto dodata; /* XXX */ 2384 } 2385 /* 2386 * If this segment advances the known urgent pointer, 2387 * then mark the data stream. This should not happen 2388 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2389 * a FIN has been received from the remote side. 2390 * In these states we ignore the URG. 2391 * 2392 * According to RFC961 (Assigned Protocols), 2393 * the urgent pointer points to the last octet 2394 * of urgent data. We continue, however, 2395 * to consider it to indicate the first octet 2396 * of data past the urgent section as the original 2397 * spec states (in one of two places). 2398 */ 2399 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2400 tp->rcv_up = th->th_seq + th->th_urp; 2401 so->so_oobmark = so->so_rcv.ssb_cc + 2402 (tp->rcv_up - tp->rcv_nxt) - 1; 2403 if (so->so_oobmark == 0) 2404 sosetstate(so, SS_RCVATMARK); 2405 sohasoutofband(so); 2406 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2407 } 2408 /* 2409 * Remove out of band data so doesn't get presented to user. 2410 * This can happen independent of advancing the URG pointer, 2411 * but if two URG's are pending at once, some out-of-band 2412 * data may creep in... ick. 2413 */ 2414 if (th->th_urp <= (u_long)tlen && 2415 !(so->so_options & SO_OOBINLINE)) { 2416 /* hdr drop is delayed */ 2417 tcp_pulloutofband(so, th, m, drop_hdrlen); 2418 } 2419 } else { 2420 /* 2421 * If no out of band data is expected, 2422 * pull receive urgent pointer along 2423 * with the receive window. 2424 */ 2425 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2426 tp->rcv_up = tp->rcv_nxt; 2427 } 2428 2429 dodata: /* XXX */ 2430 /* 2431 * Process the segment text, merging it into the TCP sequencing queue, 2432 * and arranging for acknowledgment of receipt if necessary. 2433 * This process logically involves adjusting tp->rcv_wnd as data 2434 * is presented to the user (this happens in tcp_usrreq.c, 2435 * case PRU_RCVD). If a FIN has already been received on this 2436 * connection then we just ignore the text. 2437 */ 2438 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2439 if (thflags & TH_FIN) 2440 tp->t_flags |= TF_SAWFIN; 2441 m_adj(m, drop_hdrlen); /* delayed header drop */ 2442 /* 2443 * Insert segment which includes th into TCP reassembly queue 2444 * with control block tp. Set thflags to whether reassembly now 2445 * includes a segment with FIN. This handles the common case 2446 * inline (segment is the next to be received on an established 2447 * connection, and the queue is empty), avoiding linkage into 2448 * and removal from the queue and repetition of various 2449 * conversions. 2450 * Set DELACK for segments received in order, but ack 2451 * immediately when segments are out of order (so 2452 * fast retransmit can work). 2453 */ 2454 if (th->th_seq == tp->rcv_nxt && 2455 TAILQ_EMPTY(&tp->t_segq) && 2456 TCPS_HAVEESTABLISHED(tp->t_state)) { 2457 if (thflags & TH_FIN) 2458 tp->t_flags |= TF_QUEDFIN; 2459 if (DELAY_ACK(tp)) { 2460 tcp_callout_reset(tp, tp->tt_delack, 2461 tcp_delacktime, tcp_timer_delack); 2462 } else { 2463 tp->t_flags |= TF_ACKNOW; 2464 } 2465 tp->rcv_nxt += tlen; 2466 thflags = th->th_flags & TH_FIN; 2467 tcpstat.tcps_rcvpack++; 2468 tcpstat.tcps_rcvbyte += tlen; 2469 ND6_HINT(tp); 2470 if (so->so_state & SS_CANTRCVMORE) { 2471 m_freem(m); 2472 } else { 2473 lwkt_gettoken(&so->so_rcv.ssb_token); 2474 ssb_appendstream(&so->so_rcv, m); 2475 lwkt_reltoken(&so->so_rcv.ssb_token); 2476 } 2477 sorwakeup(so); 2478 } else { 2479 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 2480 /* Initialize SACK report block. */ 2481 tp->reportblk.rblk_start = th->th_seq; 2482 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 2483 th->th_seq + tlen, thflags); 2484 } 2485 thflags = tcp_reass(tp, th, &tlen, m); 2486 tp->t_flags |= TF_ACKNOW; 2487 } 2488 2489 /* 2490 * Note the amount of data that peer has sent into 2491 * our window, in order to estimate the sender's 2492 * buffer size. 2493 */ 2494 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2495 } else { 2496 m_freem(m); 2497 thflags &= ~TH_FIN; 2498 } 2499 2500 /* 2501 * If FIN is received ACK the FIN and let the user know 2502 * that the connection is closing. 2503 */ 2504 if (thflags & TH_FIN) { 2505 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2506 socantrcvmore(so); 2507 /* 2508 * If connection is half-synchronized 2509 * (ie NEEDSYN flag on) then delay ACK, 2510 * so it may be piggybacked when SYN is sent. 2511 * Otherwise, since we received a FIN then no 2512 * more input can be expected, send ACK now. 2513 */ 2514 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2515 tcp_callout_reset(tp, tp->tt_delack, 2516 tcp_delacktime, tcp_timer_delack); 2517 } else { 2518 tp->t_flags |= TF_ACKNOW; 2519 } 2520 tp->rcv_nxt++; 2521 } 2522 2523 switch (tp->t_state) { 2524 /* 2525 * In SYN_RECEIVED and ESTABLISHED STATES 2526 * enter the CLOSE_WAIT state. 2527 */ 2528 case TCPS_SYN_RECEIVED: 2529 tp->t_starttime = ticks; 2530 /*FALLTHROUGH*/ 2531 case TCPS_ESTABLISHED: 2532 tp->t_state = TCPS_CLOSE_WAIT; 2533 break; 2534 2535 /* 2536 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2537 * enter the CLOSING state. 2538 */ 2539 case TCPS_FIN_WAIT_1: 2540 tp->t_state = TCPS_CLOSING; 2541 break; 2542 2543 /* 2544 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2545 * starting the time-wait timer, turning off the other 2546 * standard timers. 2547 */ 2548 case TCPS_FIN_WAIT_2: 2549 tp->t_state = TCPS_TIME_WAIT; 2550 tcp_canceltimers(tp); 2551 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2552 tcp_timer_2msl); 2553 soisdisconnected(so); 2554 break; 2555 2556 /* 2557 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2558 */ 2559 case TCPS_TIME_WAIT: 2560 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2561 tcp_timer_2msl); 2562 break; 2563 } 2564 } 2565 2566 #ifdef TCPDEBUG 2567 if (so->so_options & SO_DEBUG) 2568 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2569 #endif 2570 2571 /* 2572 * Delayed duplicated ACK processing 2573 */ 2574 if (delayed_dupack && tcp_recv_dupack(tp, th_dupack, to_flags)) 2575 needoutput = FALSE; 2576 2577 /* 2578 * Return any desired output. 2579 */ 2580 if ((tp->t_flags & TF_ACKNOW) || 2581 (needoutput && tcp_sack_report_needed(tp))) { 2582 tcp_output_cancel(tp); 2583 tcp_output_fair(tp); 2584 } else if (needoutput && !tcp_output_pending(tp)) { 2585 tcp_output_fair(tp); 2586 } 2587 tcp_sack_report_cleanup(tp); 2588 return(IPPROTO_DONE); 2589 2590 dropafterack: 2591 /* 2592 * Generate an ACK dropping incoming segment if it occupies 2593 * sequence space, where the ACK reflects our state. 2594 * 2595 * We can now skip the test for the RST flag since all 2596 * paths to this code happen after packets containing 2597 * RST have been dropped. 2598 * 2599 * In the SYN-RECEIVED state, don't send an ACK unless the 2600 * segment we received passes the SYN-RECEIVED ACK test. 2601 * If it fails send a RST. This breaks the loop in the 2602 * "LAND" DoS attack, and also prevents an ACK storm 2603 * between two listening ports that have been sent forged 2604 * SYN segments, each with the source address of the other. 2605 */ 2606 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2607 (SEQ_GT(tp->snd_una, th->th_ack) || 2608 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2609 rstreason = BANDLIM_RST_OPENPORT; 2610 goto dropwithreset; 2611 } 2612 #ifdef TCPDEBUG 2613 if (so->so_options & SO_DEBUG) 2614 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2615 #endif 2616 m_freem(m); 2617 tp->t_flags |= TF_ACKNOW; 2618 tcp_output(tp); 2619 tcp_sack_report_cleanup(tp); 2620 return(IPPROTO_DONE); 2621 2622 dropwithreset: 2623 /* 2624 * Generate a RST, dropping incoming segment. 2625 * Make ACK acceptable to originator of segment. 2626 * Don't bother to respond if destination was broadcast/multicast. 2627 */ 2628 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2629 goto drop; 2630 if (isipv6) { 2631 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2632 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2633 goto drop; 2634 } else { 2635 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2636 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2637 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2638 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2639 goto drop; 2640 } 2641 /* IPv6 anycast check is done at tcp6_input() */ 2642 2643 /* 2644 * Perform bandwidth limiting. 2645 */ 2646 #ifdef ICMP_BANDLIM 2647 if (badport_bandlim(rstreason) < 0) 2648 goto drop; 2649 #endif 2650 2651 #ifdef TCPDEBUG 2652 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2653 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2654 #endif 2655 if (thflags & TH_ACK) 2656 /* mtod() below is safe as long as hdr dropping is delayed */ 2657 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2658 TH_RST); 2659 else { 2660 if (thflags & TH_SYN) 2661 tlen++; 2662 /* mtod() below is safe as long as hdr dropping is delayed */ 2663 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2664 (tcp_seq)0, TH_RST | TH_ACK); 2665 } 2666 if (tp != NULL) 2667 tcp_sack_report_cleanup(tp); 2668 return(IPPROTO_DONE); 2669 2670 drop: 2671 /* 2672 * Drop space held by incoming segment and return. 2673 */ 2674 #ifdef TCPDEBUG 2675 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2676 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2677 #endif 2678 m_freem(m); 2679 if (tp != NULL) 2680 tcp_sack_report_cleanup(tp); 2681 return(IPPROTO_DONE); 2682 } 2683 2684 /* 2685 * Parse TCP options and place in tcpopt. 2686 */ 2687 static void 2688 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn, 2689 tcp_seq ack) 2690 { 2691 int opt, optlen, i; 2692 2693 to->to_flags = 0; 2694 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2695 opt = cp[0]; 2696 if (opt == TCPOPT_EOL) 2697 break; 2698 if (opt == TCPOPT_NOP) 2699 optlen = 1; 2700 else { 2701 if (cnt < 2) 2702 break; 2703 optlen = cp[1]; 2704 if (optlen < 2 || optlen > cnt) 2705 break; 2706 } 2707 switch (opt) { 2708 case TCPOPT_MAXSEG: 2709 if (optlen != TCPOLEN_MAXSEG) 2710 continue; 2711 if (!is_syn) 2712 continue; 2713 to->to_flags |= TOF_MSS; 2714 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2715 to->to_mss = ntohs(to->to_mss); 2716 break; 2717 case TCPOPT_WINDOW: 2718 if (optlen != TCPOLEN_WINDOW) 2719 continue; 2720 if (!is_syn) 2721 continue; 2722 to->to_flags |= TOF_SCALE; 2723 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2724 break; 2725 case TCPOPT_TIMESTAMP: 2726 if (optlen != TCPOLEN_TIMESTAMP) 2727 continue; 2728 to->to_flags |= TOF_TS; 2729 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2730 to->to_tsval = ntohl(to->to_tsval); 2731 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2732 to->to_tsecr = ntohl(to->to_tsecr); 2733 /* 2734 * If echoed timestamp is later than the current time, 2735 * fall back to non RFC1323 RTT calculation. 2736 */ 2737 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2738 to->to_tsecr = 0; 2739 break; 2740 case TCPOPT_SACK_PERMITTED: 2741 if (optlen != TCPOLEN_SACK_PERMITTED) 2742 continue; 2743 if (!is_syn) 2744 continue; 2745 to->to_flags |= TOF_SACK_PERMITTED; 2746 break; 2747 case TCPOPT_SACK: 2748 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2749 continue; 2750 to->to_nsackblocks = (optlen - 2) / 8; 2751 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2752 to->to_flags |= TOF_SACK; 2753 for (i = 0; i < to->to_nsackblocks; i++) { 2754 struct raw_sackblock *r = &to->to_sackblocks[i]; 2755 2756 r->rblk_start = ntohl(r->rblk_start); 2757 r->rblk_end = ntohl(r->rblk_end); 2758 2759 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { 2760 /* 2761 * Invalid SACK block; discard all 2762 * SACK blocks 2763 */ 2764 tcpstat.tcps_rcvbadsackopt++; 2765 to->to_nsackblocks = 0; 2766 to->to_sackblocks = NULL; 2767 to->to_flags &= ~TOF_SACK; 2768 break; 2769 } 2770 } 2771 if ((to->to_flags & TOF_SACK) && 2772 tcp_sack_ndsack_blocks(to->to_sackblocks, 2773 to->to_nsackblocks, ack)) 2774 to->to_flags |= TOF_DSACK; 2775 break; 2776 #ifdef TCP_SIGNATURE 2777 /* 2778 * XXX In order to reply to a host which has set the 2779 * TCP_SIGNATURE option in its initial SYN, we have to 2780 * record the fact that the option was observed here 2781 * for the syncache code to perform the correct response. 2782 */ 2783 case TCPOPT_SIGNATURE: 2784 if (optlen != TCPOLEN_SIGNATURE) 2785 continue; 2786 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2787 break; 2788 #endif /* TCP_SIGNATURE */ 2789 default: 2790 continue; 2791 } 2792 } 2793 } 2794 2795 /* 2796 * Pull out of band byte out of a segment so 2797 * it doesn't appear in the user's data queue. 2798 * It is still reflected in the segment length for 2799 * sequencing purposes. 2800 * "off" is the delayed to be dropped hdrlen. 2801 */ 2802 static void 2803 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2804 { 2805 int cnt = off + th->th_urp - 1; 2806 2807 while (cnt >= 0) { 2808 if (m->m_len > cnt) { 2809 char *cp = mtod(m, caddr_t) + cnt; 2810 struct tcpcb *tp = sototcpcb(so); 2811 2812 tp->t_iobc = *cp; 2813 tp->t_oobflags |= TCPOOB_HAVEDATA; 2814 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2815 m->m_len--; 2816 if (m->m_flags & M_PKTHDR) 2817 m->m_pkthdr.len--; 2818 return; 2819 } 2820 cnt -= m->m_len; 2821 m = m->m_next; 2822 if (m == NULL) 2823 break; 2824 } 2825 panic("tcp_pulloutofband"); 2826 } 2827 2828 /* 2829 * Collect new round-trip time estimate 2830 * and update averages and current timeout. 2831 */ 2832 static void 2833 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack) 2834 { 2835 int rebaserto = 0; 2836 2837 tcpstat.tcps_rttupdated++; 2838 tp->t_rttupdated++; 2839 if ((tp->rxt_flags & TRXT_F_REBASERTO) && 2840 SEQ_GT(ack, tp->snd_max_prev)) { 2841 #ifdef DEBUG_EIFEL_RESPONSE 2842 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ", 2843 tp->t_srtt_prev, tp->t_rttvar_prev, 2844 tp->t_srtt, tp->t_rttvar); 2845 #endif 2846 2847 tcpstat.tcps_eifelresponse++; 2848 rebaserto = 1; 2849 tp->rxt_flags &= ~TRXT_F_REBASERTO; 2850 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT)); 2851 tp->t_rttvar = max(tp->t_rttvar_prev, 2852 (rtt << (TCP_RTTVAR_SHIFT - 1))); 2853 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2854 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2855 2856 #ifdef DEBUG_EIFEL_RESPONSE 2857 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar); 2858 #endif 2859 } else if (tp->t_srtt != 0) { 2860 int delta; 2861 2862 /* 2863 * srtt is stored as fixed point with 5 bits after the 2864 * binary point (i.e., scaled by 8). The following magic 2865 * is equivalent to the smoothing algorithm in rfc793 with 2866 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2867 * point). Adjust rtt to origin 0. 2868 */ 2869 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2870 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2871 2872 if ((tp->t_srtt += delta) <= 0) 2873 tp->t_srtt = 1; 2874 2875 /* 2876 * We accumulate a smoothed rtt variance (actually, a 2877 * smoothed mean difference), then set the retransmit 2878 * timer to smoothed rtt + 4 times the smoothed variance. 2879 * rttvar is stored as fixed point with 4 bits after the 2880 * binary point (scaled by 16). The following is 2881 * equivalent to rfc793 smoothing with an alpha of .75 2882 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2883 * rfc793's wired-in beta. 2884 */ 2885 if (delta < 0) 2886 delta = -delta; 2887 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2888 if ((tp->t_rttvar += delta) <= 0) 2889 tp->t_rttvar = 1; 2890 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2891 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2892 } else { 2893 /* 2894 * No rtt measurement yet - use the unsmoothed rtt. 2895 * Set the variance to half the rtt (so our first 2896 * retransmit happens at 3*rtt). 2897 */ 2898 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2899 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2900 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2901 } 2902 tp->t_rtttime = 0; 2903 tp->t_rxtshift = 0; 2904 2905 #ifdef DEBUG_EIFEL_RESPONSE 2906 if (rebaserto) { 2907 kprintf("| rxtcur prev %d, old %d, ", 2908 tp->t_rxtcur_prev, tp->t_rxtcur); 2909 } 2910 #endif 2911 2912 /* 2913 * the retransmit should happen at rtt + 4 * rttvar. 2914 * Because of the way we do the smoothing, srtt and rttvar 2915 * will each average +1/2 tick of bias. When we compute 2916 * the retransmit timer, we want 1/2 tick of rounding and 2917 * 1 extra tick because of +-1/2 tick uncertainty in the 2918 * firing of the timer. The bias will give us exactly the 2919 * 1.5 tick we need. But, because the bias is 2920 * statistical, we have to test that we don't drop below 2921 * the minimum feasible timer (which is 2 ticks). 2922 */ 2923 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2924 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2925 2926 if (rebaserto) { 2927 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) { 2928 /* 2929 * RFC4015 requires that the new RTO is at least 2930 * 2*G (tcp_eifel_rtoinc) greater then the RTO 2931 * (t_rxtcur_prev) when the spurious retransmit 2932 * timeout happens. 2933 * 2934 * The above condition could be true, if the SRTT 2935 * and RTTVAR used to calculate t_rxtcur_prev 2936 * resulted in a value less than t_rttmin. So 2937 * simply increasing SRTT by tcp_eifel_rtoinc when 2938 * preparing for the Eifel response could not ensure 2939 * that the new RTO will be tcp_eifel_rtoinc greater 2940 * t_rxtcur_prev. 2941 */ 2942 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc; 2943 } 2944 #ifdef DEBUG_EIFEL_RESPONSE 2945 kprintf("new %d\n", tp->t_rxtcur); 2946 #endif 2947 } 2948 2949 /* 2950 * We received an ack for a packet that wasn't retransmitted; 2951 * it is probably safe to discard any error indications we've 2952 * received recently. This isn't quite right, but close enough 2953 * for now (a route might have failed after we sent a segment, 2954 * and the return path might not be symmetrical). 2955 */ 2956 tp->t_softerror = 0; 2957 } 2958 2959 /* 2960 * Determine a reasonable value for maxseg size. 2961 * If the route is known, check route for mtu. 2962 * If none, use an mss that can be handled on the outgoing 2963 * interface without forcing IP to fragment; if bigger than 2964 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2965 * to utilize large mbufs. If no route is found, route has no mtu, 2966 * or the destination isn't local, use a default, hopefully conservative 2967 * size (usually 512 or the default IP max size, but no more than the mtu 2968 * of the interface), as we can't discover anything about intervening 2969 * gateways or networks. We also initialize the congestion/slow start 2970 * window to be a single segment if the destination isn't local. 2971 * While looking at the routing entry, we also initialize other path-dependent 2972 * parameters from pre-set or cached values in the routing entry. 2973 * 2974 * Also take into account the space needed for options that we 2975 * send regularly. Make maxseg shorter by that amount to assure 2976 * that we can send maxseg amount of data even when the options 2977 * are present. Store the upper limit of the length of options plus 2978 * data in maxopd. 2979 * 2980 * NOTE that this routine is only called when we process an incoming 2981 * segment, for outgoing segments only tcp_mssopt is called. 2982 */ 2983 void 2984 tcp_mss(struct tcpcb *tp, int offer) 2985 { 2986 struct rtentry *rt; 2987 struct ifnet *ifp; 2988 int rtt, mss; 2989 u_long bufsize; 2990 struct inpcb *inp = tp->t_inpcb; 2991 struct socket *so; 2992 #ifdef INET6 2993 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2994 size_t min_protoh = isipv6 ? 2995 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2996 sizeof(struct tcpiphdr); 2997 #else 2998 const boolean_t isipv6 = FALSE; 2999 const size_t min_protoh = sizeof(struct tcpiphdr); 3000 #endif 3001 3002 if (isipv6) 3003 rt = tcp_rtlookup6(&inp->inp_inc); 3004 else 3005 rt = tcp_rtlookup(&inp->inp_inc); 3006 if (rt == NULL) { 3007 tp->t_maxopd = tp->t_maxseg = 3008 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3009 return; 3010 } 3011 ifp = rt->rt_ifp; 3012 so = inp->inp_socket; 3013 3014 /* 3015 * Offer == 0 means that there was no MSS on the SYN segment, 3016 * in this case we use either the interface mtu or tcp_mssdflt. 3017 * 3018 * An offer which is too large will be cut down later. 3019 */ 3020 if (offer == 0) { 3021 if (isipv6) { 3022 if (in6_localaddr(&inp->in6p_faddr)) { 3023 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 3024 min_protoh; 3025 } else { 3026 offer = tcp_v6mssdflt; 3027 } 3028 } else { 3029 if (in_localaddr(inp->inp_faddr)) 3030 offer = ifp->if_mtu - min_protoh; 3031 else 3032 offer = tcp_mssdflt; 3033 } 3034 } 3035 3036 /* 3037 * Prevent DoS attack with too small MSS. Round up 3038 * to at least minmss. 3039 * 3040 * Sanity check: make sure that maxopd will be large 3041 * enough to allow some data on segments even is the 3042 * all the option space is used (40bytes). Otherwise 3043 * funny things may happen in tcp_output. 3044 */ 3045 offer = max(offer, tcp_minmss); 3046 offer = max(offer, 64); 3047 3048 rt->rt_rmx.rmx_mssopt = offer; 3049 3050 /* 3051 * While we're here, check if there's an initial rtt 3052 * or rttvar. Convert from the route-table units 3053 * to scaled multiples of the slow timeout timer. 3054 */ 3055 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 3056 /* 3057 * XXX the lock bit for RTT indicates that the value 3058 * is also a minimum value; this is subject to time. 3059 */ 3060 if (rt->rt_rmx.rmx_locks & RTV_RTT) 3061 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 3062 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 3063 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3064 tcpstat.tcps_usedrtt++; 3065 if (rt->rt_rmx.rmx_rttvar) { 3066 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 3067 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 3068 tcpstat.tcps_usedrttvar++; 3069 } else { 3070 /* default variation is +- 1 rtt */ 3071 tp->t_rttvar = 3072 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3073 } 3074 TCPT_RANGESET(tp->t_rxtcur, 3075 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3076 tp->t_rttmin, TCPTV_REXMTMAX); 3077 } 3078 3079 /* 3080 * if there's an mtu associated with the route, use it 3081 * else, use the link mtu. Take the smaller of mss or offer 3082 * as our final mss. 3083 */ 3084 if (rt->rt_rmx.rmx_mtu) { 3085 mss = rt->rt_rmx.rmx_mtu - min_protoh; 3086 } else { 3087 if (isipv6) 3088 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 3089 else 3090 mss = ifp->if_mtu - min_protoh; 3091 } 3092 mss = min(mss, offer); 3093 3094 /* 3095 * maxopd stores the maximum length of data AND options 3096 * in a segment; maxseg is the amount of data in a normal 3097 * segment. We need to store this value (maxopd) apart 3098 * from maxseg, because now every segment carries options 3099 * and thus we normally have somewhat less data in segments. 3100 */ 3101 tp->t_maxopd = mss; 3102 3103 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3104 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3105 mss -= TCPOLEN_TSTAMP_APPA; 3106 3107 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3108 if (mss > MCLBYTES) 3109 mss &= ~(MCLBYTES-1); 3110 #else 3111 if (mss > MCLBYTES) 3112 mss = mss / MCLBYTES * MCLBYTES; 3113 #endif 3114 /* 3115 * If there's a pipesize, change the socket buffer 3116 * to that size. Make the socket buffers an integral 3117 * number of mss units; if the mss is larger than 3118 * the socket buffer, decrease the mss. 3119 */ 3120 #ifdef RTV_SPIPE 3121 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3122 #endif 3123 bufsize = so->so_snd.ssb_hiwat; 3124 if (bufsize < mss) 3125 mss = bufsize; 3126 else { 3127 bufsize = roundup(bufsize, mss); 3128 if (bufsize > sb_max) 3129 bufsize = sb_max; 3130 if (bufsize > so->so_snd.ssb_hiwat) 3131 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3132 } 3133 tp->t_maxseg = mss; 3134 3135 #ifdef RTV_RPIPE 3136 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3137 #endif 3138 bufsize = so->so_rcv.ssb_hiwat; 3139 if (bufsize > mss) { 3140 bufsize = roundup(bufsize, mss); 3141 if (bufsize > sb_max) 3142 bufsize = sb_max; 3143 if (bufsize > so->so_rcv.ssb_hiwat) { 3144 lwkt_gettoken(&so->so_rcv.ssb_token); 3145 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3146 lwkt_reltoken(&so->so_rcv.ssb_token); 3147 } 3148 } 3149 3150 /* 3151 * Set the slow-start flight size 3152 * 3153 * NOTE: t_maxseg must have been configured! 3154 */ 3155 tp->snd_cwnd = tcp_initial_window(tp); 3156 3157 if (rt->rt_rmx.rmx_ssthresh) { 3158 /* 3159 * There's some sort of gateway or interface 3160 * buffer limit on the path. Use this to set 3161 * the slow start threshhold, but set the 3162 * threshold to no less than 2*mss. 3163 */ 3164 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3165 tcpstat.tcps_usedssthresh++; 3166 } 3167 } 3168 3169 /* 3170 * Determine the MSS option to send on an outgoing SYN. 3171 */ 3172 int 3173 tcp_mssopt(struct tcpcb *tp) 3174 { 3175 struct rtentry *rt; 3176 #ifdef INET6 3177 boolean_t isipv6 = 3178 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3179 int min_protoh = isipv6 ? 3180 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3181 sizeof(struct tcpiphdr); 3182 #else 3183 const boolean_t isipv6 = FALSE; 3184 const size_t min_protoh = sizeof(struct tcpiphdr); 3185 #endif 3186 3187 if (isipv6) 3188 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3189 else 3190 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3191 if (rt == NULL) 3192 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3193 3194 return (rt->rt_ifp->if_mtu - min_protoh); 3195 } 3196 3197 /* 3198 * When a partial ack arrives, force the retransmission of the 3199 * next unacknowledged segment. Do not exit Fast Recovery. 3200 * 3201 * Implement the Slow-but-Steady variant of NewReno by restarting the 3202 * the retransmission timer. Turn it off here so it can be restarted 3203 * later in tcp_output(). 3204 */ 3205 static void 3206 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3207 { 3208 tcp_seq old_snd_nxt = tp->snd_nxt; 3209 u_long ocwnd = tp->snd_cwnd; 3210 3211 tcp_callout_stop(tp, tp->tt_rexmt); 3212 tp->t_rtttime = 0; 3213 tp->snd_nxt = th->th_ack; 3214 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3215 tp->snd_cwnd = tp->t_maxseg; 3216 tp->t_flags |= TF_ACKNOW; 3217 tcp_output(tp); 3218 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3219 tp->snd_nxt = old_snd_nxt; 3220 /* partial window deflation */ 3221 if (ocwnd > acked) 3222 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3223 else 3224 tp->snd_cwnd = tp->t_maxseg; 3225 } 3226 3227 /* 3228 * In contrast to the Slow-but-Steady NewReno variant, 3229 * we do not reset the retransmission timer for SACK retransmissions, 3230 * except when retransmitting snd_una. 3231 */ 3232 static void 3233 tcp_sack_rexmt(struct tcpcb *tp, boolean_t force) 3234 { 3235 tcp_seq old_snd_nxt = tp->snd_nxt; 3236 u_long ocwnd = tp->snd_cwnd; 3237 uint32_t pipe; 3238 int nseg = 0; /* consecutive new segments */ 3239 int nseg_rexmt = 0; /* retransmitted segments */ 3240 int maxrexmt = 0; 3241 3242 if (force) { 3243 uint32_t unsacked = tcp_sack_first_unsacked_len(tp); 3244 3245 /* 3246 * Try to fill the first hole in the receiver's 3247 * reassemble queue. 3248 */ 3249 maxrexmt = howmany(unsacked, tp->t_maxseg); 3250 if (maxrexmt > tcp_force_sackrxt) 3251 maxrexmt = tcp_force_sackrxt; 3252 } 3253 3254 tp->t_rtttime = 0; 3255 pipe = tcp_sack_compute_pipe(tp); 3256 while (((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg 3257 || (force && nseg_rexmt < maxrexmt && nseg == 0)) && 3258 (!tcp_do_smartsack || nseg < TCP_SACK_MAXBURST)) { 3259 tcp_seq old_snd_max, old_rexmt_high, nextrexmt; 3260 uint32_t sent, seglen; 3261 boolean_t rescue; 3262 int error; 3263 3264 old_rexmt_high = tp->rexmt_high; 3265 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) { 3266 tp->rexmt_high = old_rexmt_high; 3267 break; 3268 } 3269 3270 /* 3271 * If the next tranmission is a rescue retranmission, 3272 * we check whether we have already sent some data 3273 * (either new segments or retransmitted segments) 3274 * into the the network or not. Since the idea of rescue 3275 * retransmission is to sustain ACK clock, as long as 3276 * some segments are in the network, ACK clock will be 3277 * kept ticking. 3278 */ 3279 if (rescue && (nseg_rexmt > 0 || nseg > 0)) { 3280 tp->rexmt_high = old_rexmt_high; 3281 break; 3282 } 3283 3284 if (nextrexmt == tp->snd_max) 3285 ++nseg; 3286 else 3287 ++nseg_rexmt; 3288 tp->snd_nxt = nextrexmt; 3289 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3290 old_snd_max = tp->snd_max; 3291 if (nextrexmt == tp->snd_una) 3292 tcp_callout_stop(tp, tp->tt_rexmt); 3293 tp->t_flags |= TF_XMITNOW; 3294 error = tcp_output(tp); 3295 if (error != 0) { 3296 tp->rexmt_high = old_rexmt_high; 3297 break; 3298 } 3299 sent = tp->snd_nxt - nextrexmt; 3300 if (sent <= 0) { 3301 tp->rexmt_high = old_rexmt_high; 3302 break; 3303 } 3304 pipe += sent; 3305 tcpstat.tcps_sndsackpack++; 3306 tcpstat.tcps_sndsackbyte += sent; 3307 3308 if (rescue) { 3309 tcpstat.tcps_sackrescue++; 3310 tp->rexmt_rescue = tp->snd_nxt; 3311 tp->sack_flags |= TSACK_F_SACKRESCUED; 3312 break; 3313 } 3314 if (SEQ_LT(nextrexmt, old_snd_max) && 3315 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) { 3316 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3317 if (tcp_aggressive_rescuesack && 3318 (tp->sack_flags & TSACK_F_SACKRESCUED) && 3319 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) { 3320 /* Drag RescueRxt along with HighRxt */ 3321 tp->rexmt_rescue = tp->rexmt_high; 3322 } 3323 } 3324 } 3325 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3326 tp->snd_nxt = old_snd_nxt; 3327 tp->snd_cwnd = ocwnd; 3328 } 3329 3330 /* 3331 * Return TRUE, if some new segments are sent 3332 */ 3333 static boolean_t 3334 tcp_sack_limitedxmit(struct tcpcb *tp) 3335 { 3336 tcp_seq oldsndnxt = tp->snd_nxt; 3337 tcp_seq oldsndmax = tp->snd_max; 3338 u_long ocwnd = tp->snd_cwnd; 3339 uint32_t pipe, sent; 3340 boolean_t ret = FALSE; 3341 tcp_seq_diff_t cwnd_left; 3342 tcp_seq next; 3343 3344 tp->rexmt_high = tp->snd_una - 1; 3345 pipe = tcp_sack_compute_pipe(tp); 3346 cwnd_left = (tcp_seq_diff_t)(ocwnd - pipe); 3347 if (cwnd_left < (tcp_seq_diff_t)tp->t_maxseg) 3348 return FALSE; 3349 3350 if (tcp_do_smartsack) 3351 cwnd_left = ulmin(cwnd_left, tp->t_maxseg * TCP_SACK_MAXBURST); 3352 3353 next = tp->snd_nxt = tp->snd_max; 3354 tp->snd_cwnd = tp->snd_nxt - tp->snd_una + 3355 rounddown(cwnd_left, tp->t_maxseg); 3356 3357 tp->t_flags |= TF_XMITNOW; 3358 tcp_output(tp); 3359 3360 sent = tp->snd_nxt - next; 3361 if (sent > 0) { 3362 tcpstat.tcps_sndlimited += howmany(sent, tp->t_maxseg); 3363 ret = TRUE; 3364 } 3365 3366 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3367 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3368 ("snd_una moved in other threads")); 3369 tp->snd_nxt = oldsndnxt; 3370 } 3371 tp->snd_cwnd = ocwnd; 3372 3373 if (ret && TCP_DO_NCR(tp)) 3374 tcp_ncr_update_rxtthresh(tp); 3375 3376 return ret; 3377 } 3378 3379 /* 3380 * Reset idle time and keep-alive timer, typically called when a valid 3381 * tcp packet is received but may also be called when FASTKEEP is set 3382 * to prevent the previous long-timeout from calculating to a drop. 3383 * 3384 * Only update t_rcvtime for non-SYN packets. 3385 * 3386 * Handle the case where one side thinks the connection is established 3387 * but the other side has, say, rebooted without cleaning out the 3388 * connection. The SYNs could be construed as an attack and wind 3389 * up ignored, but in case it isn't an attack we can validate the 3390 * connection by forcing a keepalive. 3391 */ 3392 void 3393 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3394 { 3395 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3396 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3397 tp->t_flags |= TF_KEEPALIVE; 3398 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3399 tcp_timer_keep); 3400 } else { 3401 tp->t_rcvtime = ticks; 3402 tp->t_flags &= ~TF_KEEPALIVE; 3403 tcp_callout_reset(tp, tp->tt_keep, 3404 tp->t_keepidle, 3405 tcp_timer_keep); 3406 } 3407 } 3408 } 3409 3410 static int 3411 tcp_rmx_msl(const struct tcpcb *tp) 3412 { 3413 struct rtentry *rt; 3414 struct inpcb *inp = tp->t_inpcb; 3415 int msl; 3416 #ifdef INET6 3417 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3418 #else 3419 const boolean_t isipv6 = FALSE; 3420 #endif 3421 3422 if (isipv6) 3423 rt = tcp_rtlookup6(&inp->inp_inc); 3424 else 3425 rt = tcp_rtlookup(&inp->inp_inc); 3426 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3427 return tcp_msl; 3428 3429 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3430 if (msl == 0) 3431 msl = 1; 3432 3433 return msl; 3434 } 3435 3436 static void 3437 tcp_established(struct tcpcb *tp) 3438 { 3439 tp->t_state = TCPS_ESTABLISHED; 3440 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); 3441 3442 if (tp->t_rxtsyn > 0) { 3443 /* 3444 * RFC6298: 3445 * "If the timer expires awaiting the ACK of a SYN segment 3446 * and the TCP implementation is using an RTO less than 3 3447 * seconds, the RTO MUST be re-initialized to 3 seconds 3448 * when data transmission begins" 3449 */ 3450 if (tp->t_rxtcur < TCPTV_RTOBASE3) 3451 tp->t_rxtcur = TCPTV_RTOBASE3; 3452 } 3453 } 3454 3455 /* 3456 * Returns TRUE, if the ACK should be dropped 3457 */ 3458 static boolean_t 3459 tcp_recv_dupack(struct tcpcb *tp, tcp_seq th_ack, u_int to_flags) 3460 { 3461 boolean_t fast_sack_rexmt = TRUE; 3462 3463 tcpstat.tcps_rcvdupack++; 3464 3465 /* 3466 * We have outstanding data (other than a window probe), 3467 * this is a completely duplicate ack (ie, window info 3468 * didn't change), the ack is the biggest we've seen and 3469 * we've seen exactly our rexmt threshhold of them, so 3470 * assume a packet has been dropped and retransmit it. 3471 * Kludge snd_nxt & the congestion window so we send only 3472 * this one packet. 3473 */ 3474 if (IN_FASTRECOVERY(tp)) { 3475 if (TCP_DO_SACK(tp)) { 3476 boolean_t force = FALSE; 3477 3478 if (tp->snd_una == tp->rexmt_high && 3479 (to_flags & (TOF_SACK | TOF_SACK_REDUNDANT)) == 3480 TOF_SACK) { 3481 /* 3482 * New segments got SACKed and 3483 * no retransmit yet. 3484 */ 3485 force = TRUE; 3486 } 3487 3488 /* No artifical cwnd inflation. */ 3489 tcp_sack_rexmt(tp, force); 3490 } else { 3491 /* 3492 * Dup acks mean that packets have left 3493 * the network (they're now cached at the 3494 * receiver) so bump cwnd by the amount in 3495 * the receiver to keep a constant cwnd 3496 * packets in the network. 3497 */ 3498 tp->snd_cwnd += tp->t_maxseg; 3499 tcp_output(tp); 3500 } 3501 return TRUE; 3502 } else if (SEQ_LT(th_ack, tp->snd_recover)) { 3503 tp->t_dupacks = 0; 3504 return FALSE; 3505 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) && 3506 (to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) == 3507 (TOF_DSACK | TOF_SACK_REDUNDANT)) { 3508 /* 3509 * If the ACK carries DSACK and other SACK blocks 3510 * carry information that we have already known, 3511 * don't count this ACK as duplicate ACK. This 3512 * prevents spurious early retransmit and fast 3513 * retransmit. This also meets the requirement of 3514 * RFC3042 that new segments should not be sent if 3515 * the SACK blocks do not contain new information 3516 * (XXX we actually loosen the requirment that only 3517 * DSACK is checked here). 3518 * 3519 * This kind of ACKs are usually sent after spurious 3520 * retransmit. 3521 */ 3522 /* Do nothing; don't change t_dupacks */ 3523 return TRUE; 3524 } else if (tp->t_dupacks == 0 && TCP_DO_NCR(tp)) { 3525 tcp_ncr_update_rxtthresh(tp); 3526 } 3527 3528 if (++tp->t_dupacks == tp->t_rxtthresh) { 3529 tcp_seq old_snd_nxt; 3530 u_int win; 3531 3532 fastretransmit: 3533 if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) { 3534 tcp_save_congestion_state(tp); 3535 tp->rxt_flags |= TRXT_F_FASTREXMT; 3536 } 3537 /* 3538 * We know we're losing at the current window size, 3539 * so do congestion avoidance: set ssthresh to half 3540 * the current window and pull our congestion window 3541 * back to the new ssthresh. 3542 */ 3543 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 3544 if (win < 2) 3545 win = 2; 3546 tp->snd_ssthresh = win * tp->t_maxseg; 3547 ENTER_FASTRECOVERY(tp); 3548 tp->snd_recover = tp->snd_max; 3549 tcp_callout_stop(tp, tp->tt_rexmt); 3550 tp->t_rtttime = 0; 3551 old_snd_nxt = tp->snd_nxt; 3552 tp->snd_nxt = th_ack; 3553 if (TCP_DO_SACK(tp)) { 3554 uint32_t rxtlen; 3555 3556 rxtlen = tcp_sack_first_unsacked_len(tp); 3557 if (rxtlen > tp->t_maxseg) 3558 rxtlen = tp->t_maxseg; 3559 tp->snd_cwnd = rxtlen; 3560 } else { 3561 tp->snd_cwnd = tp->t_maxseg; 3562 } 3563 tcp_output(tp); 3564 ++tcpstat.tcps_sndfastrexmit; 3565 tp->snd_cwnd = tp->snd_ssthresh; 3566 tp->rexmt_high = tp->snd_nxt; 3567 tp->sack_flags &= ~TSACK_F_SACKRESCUED; 3568 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3569 tp->snd_nxt = old_snd_nxt; 3570 KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big")); 3571 if (TCP_DO_SACK(tp)) { 3572 if (fast_sack_rexmt) 3573 tcp_sack_rexmt(tp, FALSE); 3574 } else { 3575 tp->snd_cwnd += tp->t_maxseg * 3576 (tp->t_dupacks - tp->snd_limited); 3577 } 3578 } else if ((tcp_do_rfc6675 && TCP_DO_SACK(tp)) || TCP_DO_NCR(tp)) { 3579 /* 3580 * The RFC6675 recommends to reduce the byte threshold, 3581 * and enter fast retransmit if IsLost(snd_una). However, 3582 * if we use IsLost(snd_una) based fast retransmit here, 3583 * segments reordering will cause spurious retransmit. So 3584 * we defer the IsLost(snd_una) based fast retransmit until 3585 * the extended limited transmit can't send any segments and 3586 * early retransmit can't be done. 3587 */ 3588 if (tcp_rfc6675_rxt && tcp_do_rfc6675 && 3589 tcp_sack_islost(&tp->scb, tp->snd_una)) 3590 goto fastretransmit; 3591 3592 if (tcp_do_limitedtransmit || TCP_DO_NCR(tp)) { 3593 if (!tcp_sack_limitedxmit(tp)) { 3594 /* outstanding data */ 3595 uint32_t ownd = tp->snd_max - tp->snd_una; 3596 3597 if (need_early_retransmit(tp, ownd)) { 3598 ++tcpstat.tcps_sndearlyrexmit; 3599 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3600 goto fastretransmit; 3601 } else if (tcp_do_rfc6675 && 3602 tcp_sack_islost(&tp->scb, tp->snd_una)) { 3603 fast_sack_rexmt = FALSE; 3604 goto fastretransmit; 3605 } 3606 } 3607 } 3608 } else if (tcp_do_limitedtransmit) { 3609 u_long oldcwnd = tp->snd_cwnd; 3610 tcp_seq oldsndmax = tp->snd_max; 3611 tcp_seq oldsndnxt = tp->snd_nxt; 3612 /* outstanding data */ 3613 uint32_t ownd = tp->snd_max - tp->snd_una; 3614 u_int sent; 3615 3616 KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2, 3617 ("dupacks not 1 or 2")); 3618 if (tp->t_dupacks == 1) 3619 tp->snd_limited = 0; 3620 tp->snd_nxt = tp->snd_max; 3621 tp->snd_cwnd = ownd + 3622 (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg; 3623 tp->t_flags |= TF_XMITNOW; 3624 tcp_output(tp); 3625 3626 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3627 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3628 ("snd_una moved in other threads")); 3629 tp->snd_nxt = oldsndnxt; 3630 } 3631 tp->snd_cwnd = oldcwnd; 3632 sent = tp->snd_max - oldsndmax; 3633 if (sent > tp->t_maxseg) { 3634 KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) || 3635 (sent == tp->t_maxseg + 1 && 3636 (tp->t_flags & TF_SENTFIN)), 3637 ("sent too much")); 3638 KASSERT(sent <= tp->t_maxseg * 2, 3639 ("sent too many segments")); 3640 tp->snd_limited = 2; 3641 tcpstat.tcps_sndlimited += 2; 3642 } else if (sent > 0) { 3643 ++tp->snd_limited; 3644 ++tcpstat.tcps_sndlimited; 3645 } else if (need_early_retransmit(tp, ownd)) { 3646 ++tcpstat.tcps_sndearlyrexmit; 3647 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3648 goto fastretransmit; 3649 } 3650 } 3651 return TRUE; 3652 } 3653