1 /* 2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 68 */ 69 70 #include "opt_inet.h" 71 #include "opt_inet6.h" 72 #include "opt_ipsec.h" 73 #include "opt_tcpdebug.h" 74 #include "opt_tcp_input.h" 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/sysctl.h> 80 #include <sys/malloc.h> 81 #include <sys/mbuf.h> 82 #include <sys/proc.h> /* for proc0 declaration */ 83 #include <sys/protosw.h> 84 #include <sys/socket.h> 85 #include <sys/socketvar.h> 86 #include <sys/syslog.h> 87 #include <sys/in_cksum.h> 88 89 #include <sys/socketvar2.h> 90 91 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 92 #include <machine/stdarg.h> 93 94 #include <net/if.h> 95 #include <net/route.h> 96 97 #include <netinet/in.h> 98 #include <netinet/in_systm.h> 99 #include <netinet/ip.h> 100 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 101 #include <netinet/in_var.h> 102 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 103 #include <netinet/in_pcb.h> 104 #include <netinet/ip_var.h> 105 #include <netinet/ip6.h> 106 #include <netinet/icmp6.h> 107 #include <netinet6/nd6.h> 108 #include <netinet6/ip6_var.h> 109 #include <netinet6/in6_pcb.h> 110 #include <netinet/tcp.h> 111 #include <netinet/tcp_fsm.h> 112 #include <netinet/tcp_seq.h> 113 #include <netinet/tcp_timer.h> 114 #include <netinet/tcp_timer2.h> 115 #include <netinet/tcp_var.h> 116 #include <netinet6/tcp6_var.h> 117 #include <netinet/tcpip.h> 118 119 #ifdef TCPDEBUG 120 #include <netinet/tcp_debug.h> 121 122 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 123 struct tcphdr tcp_savetcp; 124 #endif 125 126 #ifdef FAST_IPSEC 127 #include <netproto/ipsec/ipsec.h> 128 #include <netproto/ipsec/ipsec6.h> 129 #endif 130 131 #ifdef IPSEC 132 #include <netinet6/ipsec.h> 133 #include <netinet6/ipsec6.h> 134 #include <netproto/key/key.h> 135 #endif 136 137 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 138 139 static int log_in_vain = 0; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 141 &log_in_vain, 0, "Log all incoming TCP connections"); 142 143 static int blackhole = 0; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 145 &blackhole, 0, "Do not send RST when dropping refused connections"); 146 147 int tcp_delack_enabled = 1; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 149 &tcp_delack_enabled, 0, 150 "Delay ACK to try and piggyback it onto a data packet"); 151 152 #ifdef TCP_DROP_SYNFIN 153 static int drop_synfin = 0; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 156 #endif 157 158 static int tcp_do_limitedtransmit = 1; 159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 161 162 static int tcp_do_early_retransmit = 1; 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 164 &tcp_do_early_retransmit, 0, "Early retransmit"); 165 166 int tcp_aggregate_acks = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 169 170 static int tcp_do_eifel_detect = 1; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 172 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 173 174 static int tcp_do_abc = 1; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 176 &tcp_do_abc, 0, 177 "TCP Appropriate Byte Counting (RFC 3465)"); 178 179 /* 180 * The following value actually takes range [25ms, 250ms], 181 * given that most modern systems use 1ms ~ 10ms as the unit 182 * of timestamp option. 183 */ 184 static u_int tcp_paws_tolerance = 25; 185 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, paws_tolerance, CTLFLAG_RW, 186 &tcp_paws_tolerance, 0, "RFC1323 PAWS tolerance"); 187 188 /* 189 * Define as tunable for easy testing with SACK on and off. 190 * Warning: do not change setting in the middle of an existing active TCP flow, 191 * else strange things might happen to that flow. 192 */ 193 int tcp_do_sack = 1; 194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 195 &tcp_do_sack, 0, "Enable SACK Algorithms"); 196 197 int tcp_do_smartsack = 1; 198 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 199 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 200 201 int tcp_do_rescuesack = 1; 202 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW, 203 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK"); 204 205 int tcp_aggressive_rescuesack = 0; 206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW, 207 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK"); 208 209 static int tcp_force_sackrxt = 1; 210 SYSCTL_INT(_net_inet_tcp, OID_AUTO, force_sackrxt, CTLFLAG_RW, 211 &tcp_force_sackrxt, 0, "Allowed forced SACK retransmit burst"); 212 213 int tcp_do_rfc6675 = 1; 214 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675, CTLFLAG_RW, 215 &tcp_do_rfc6675, 0, "Enable RFC6675"); 216 217 int tcp_rfc6675_rxt = 0; 218 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_rxt, CTLFLAG_RW, 219 &tcp_rfc6675_rxt, 0, "Enable RFC6675 retransmit"); 220 221 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 222 "TCP Segment Reassembly Queue"); 223 224 int tcp_reass_maxseg = 0; 225 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 226 &tcp_reass_maxseg, 0, 227 "Global maximum number of TCP Segments in Reassembly Queue"); 228 229 int tcp_reass_qsize = 0; 230 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 231 &tcp_reass_qsize, 0, 232 "Global number of TCP Segments currently in Reassembly Queue"); 233 234 static int tcp_reass_overflows = 0; 235 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 236 &tcp_reass_overflows, 0, 237 "Global number of TCP Segment Reassembly Queue Overflows"); 238 239 int tcp_do_autorcvbuf = 1; 240 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 241 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 242 243 int tcp_autorcvbuf_inc = 16*1024; 244 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 245 &tcp_autorcvbuf_inc, 0, 246 "Incrementor step size of automatic receive buffer"); 247 248 int tcp_autorcvbuf_max = 2*1024*1024; 249 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 250 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 251 252 int tcp_sosend_agglim = 3; 253 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW, 254 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit"); 255 256 int tcp_sosend_async = 1; 257 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW, 258 &tcp_sosend_async, 0, "TCP asynchronized pru_send"); 259 260 static int tcp_ignore_redun_dsack = 1; 261 SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW, 262 &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK"); 263 264 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t, 265 tcp_seq); 266 static void tcp_pulloutofband(struct socket *, 267 struct tcphdr *, struct mbuf *, int); 268 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 269 struct mbuf *); 270 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq); 271 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 272 static void tcp_sack_rexmt(struct tcpcb *, boolean_t); 273 static boolean_t tcp_sack_limitedxmit(struct tcpcb *); 274 static int tcp_rmx_msl(const struct tcpcb *); 275 static void tcp_established(struct tcpcb *); 276 static boolean_t tcp_recv_dupack(struct tcpcb *, tcp_seq, u_int); 277 278 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 279 #ifdef INET6 280 #define ND6_HINT(tp) \ 281 do { \ 282 if ((tp) && (tp)->t_inpcb && \ 283 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 284 (tp)->t_inpcb->in6p_route.ro_rt) \ 285 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 286 } while (0) 287 #else 288 #define ND6_HINT(tp) 289 #endif 290 291 /* 292 * Indicate whether this ack should be delayed. We can delay the ack if 293 * - delayed acks are enabled and 294 * - there is no delayed ack timer in progress and 295 * - our last ack wasn't a 0-sized window. We never want to delay 296 * the ack that opens up a 0-sized window. 297 */ 298 #define DELAY_ACK(tp) \ 299 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 300 !(tp->t_flags & TF_RXWIN0SENT)) 301 302 #define acceptable_window_update(tp, th, tiwin) \ 303 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 304 (tp->snd_wl1 == th->th_seq && \ 305 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 306 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 307 308 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 309 #define need_early_retransmit(tp, ownd) \ 310 (tcp_do_early_retransmit && \ 311 (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \ 312 ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \ 313 tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \ 314 (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \ 315 tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg))) 316 317 /* 318 * Returns TRUE, if this segment can be merged with the last 319 * pending segment in the reassemble queue and this segment 320 * does not overlap with the pending segment immediately 321 * preceeding the last pending segment. 322 */ 323 static __inline boolean_t 324 tcp_paws_canreasslast(const struct tcpcb *tp, const struct tcphdr *th, int tlen) 325 { 326 const struct tseg_qent *last, *prev; 327 328 last = TAILQ_LAST(&tp->t_segq, tsegqe_head); 329 if (last == NULL) 330 return FALSE; 331 332 /* This segment comes immediately after the last pending segment */ 333 if (last->tqe_th->th_seq + last->tqe_len == th->th_seq) { 334 if (last->tqe_th->th_flags & TH_FIN) { 335 /* No segments should follow segment w/ FIN */ 336 return FALSE; 337 } 338 return TRUE; 339 } 340 341 if (th->th_seq + tlen != last->tqe_th->th_seq) 342 return FALSE; 343 /* This segment comes immediately before the last pending segment */ 344 345 prev = TAILQ_PREV(last, tsegqe_head, tqe_q); 346 if (prev == NULL) { 347 /* 348 * No pending preceeding segment, we assume this segment 349 * could be reassembled. 350 */ 351 return TRUE; 352 } 353 354 /* This segment does not overlap with the preceeding segment */ 355 if (SEQ_GEQ(th->th_seq, prev->tqe_th->th_seq + prev->tqe_len)) 356 return TRUE; 357 358 return FALSE; 359 } 360 361 static __inline void 362 tcp_ncr_update_rxtthresh(struct tcpcb *tp) 363 { 364 int old_rxtthresh = tp->t_rxtthresh; 365 uint32_t ownd = tp->snd_max - tp->snd_una; 366 367 tp->t_rxtthresh = max(tcprexmtthresh, ((ownd / tp->t_maxseg) >> 1)); 368 if (tp->t_rxtthresh != old_rxtthresh) { 369 tcp_sack_update_lostseq(&tp->scb, tp->snd_una, 370 tp->t_maxseg, tp->t_rxtthresh); 371 } 372 } 373 374 static int 375 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 376 { 377 struct tseg_qent *q; 378 struct tseg_qent *p = NULL; 379 struct tseg_qent *te; 380 struct socket *so = tp->t_inpcb->inp_socket; 381 int flags; 382 383 /* 384 * Call with th == NULL after become established to 385 * force pre-ESTABLISHED data up to user socket. 386 */ 387 if (th == NULL) 388 goto present; 389 390 /* 391 * Limit the number of segments in the reassembly queue to prevent 392 * holding on to too many segments (and thus running out of mbufs). 393 * Make sure to let the missing segment through which caused this 394 * queue. Always keep one global queue entry spare to be able to 395 * process the missing segment. 396 */ 397 if (th->th_seq != tp->rcv_nxt && 398 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 399 tcp_reass_overflows++; 400 tcpstat.tcps_rcvmemdrop++; 401 m_freem(m); 402 /* no SACK block to report */ 403 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 404 return (0); 405 } 406 407 /* Allocate a new queue entry. */ 408 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 409 if (te == NULL) { 410 tcpstat.tcps_rcvmemdrop++; 411 m_freem(m); 412 /* no SACK block to report */ 413 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 414 return (0); 415 } 416 atomic_add_int(&tcp_reass_qsize, 1); 417 418 if (th->th_flags & TH_FIN) 419 tp->t_flags |= TF_QUEDFIN; 420 421 /* 422 * Find a segment which begins after this one does. 423 */ 424 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) { 425 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 426 break; 427 p = q; 428 } 429 430 /* 431 * If there is a preceding segment, it may provide some of 432 * our data already. If so, drop the data from the incoming 433 * segment. If it provides all of our data, drop us. 434 */ 435 if (p != NULL) { 436 tcp_seq_diff_t i; 437 438 /* conversion to int (in i) handles seq wraparound */ 439 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 440 if (i > 0) { /* overlaps preceding segment */ 441 tp->sack_flags |= 442 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 443 /* enclosing block starts w/ preceding segment */ 444 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 445 if (i >= *tlenp) { 446 if (th->th_flags & TH_FIN) 447 p->tqe_th->th_flags |= TH_FIN; 448 449 /* preceding encloses incoming segment */ 450 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 451 p->tqe_th->th_seq + p->tqe_len, 452 p->tqe_th->th_flags); 453 tcpstat.tcps_rcvduppack++; 454 tcpstat.tcps_rcvdupbyte += *tlenp; 455 m_freem(m); 456 kfree(te, M_TSEGQ); 457 atomic_add_int(&tcp_reass_qsize, -1); 458 /* 459 * Try to present any queued data 460 * at the left window edge to the user. 461 * This is needed after the 3-WHS 462 * completes. 463 */ 464 goto present; /* ??? */ 465 } 466 m_adj(m, i); 467 *tlenp -= i; 468 th->th_seq += i; 469 /* incoming segment end is enclosing block end */ 470 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 471 th->th_seq + *tlenp, th->th_flags); 472 /* trim end of reported D-SACK block */ 473 tp->reportblk.rblk_end = th->th_seq; 474 } 475 } 476 tcpstat.tcps_rcvoopack++; 477 tcpstat.tcps_rcvoobyte += *tlenp; 478 479 /* 480 * While we overlap succeeding segments trim them or, 481 * if they are completely covered, dequeue them. 482 */ 483 while (q) { 484 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 485 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 486 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags); 487 struct tseg_qent *nq; 488 489 if (i <= 0) 490 break; 491 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 492 /* first time through */ 493 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 494 tp->encloseblk = tp->reportblk; 495 /* report trailing duplicate D-SACK segment */ 496 tp->reportblk.rblk_start = q->tqe_th->th_seq; 497 } 498 if ((tp->sack_flags & TSACK_F_ENCLOSESEG) && 499 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) { 500 /* extend enclosing block if one exists */ 501 tp->encloseblk.rblk_end = qend_sack; 502 } 503 if (i < q->tqe_len) { 504 q->tqe_th->th_seq += i; 505 q->tqe_len -= i; 506 m_adj(q->tqe_m, i); 507 break; 508 } 509 510 if (q->tqe_th->th_flags & TH_FIN) 511 th->th_flags |= TH_FIN; 512 513 nq = TAILQ_NEXT(q, tqe_q); 514 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 515 m_freem(q->tqe_m); 516 kfree(q, M_TSEGQ); 517 atomic_add_int(&tcp_reass_qsize, -1); 518 q = nq; 519 } 520 521 /* Insert the new segment queue entry into place. */ 522 te->tqe_m = m; 523 te->tqe_th = th; 524 te->tqe_len = *tlenp; 525 526 /* check if can coalesce with following segment */ 527 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 528 tcp_seq tend_sack; 529 530 te->tqe_len += q->tqe_len; 531 if (q->tqe_th->th_flags & TH_FIN) 532 te->tqe_th->th_flags |= TH_FIN; 533 tend_sack = TCP_SACK_BLKEND(te->tqe_th->th_seq + te->tqe_len, 534 te->tqe_th->th_flags); 535 536 m_cat(te->tqe_m, q->tqe_m); 537 tp->encloseblk.rblk_end = tend_sack; 538 /* 539 * When not reporting a duplicate segment, use 540 * the larger enclosing block as the SACK block. 541 */ 542 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 543 tp->reportblk.rblk_end = tend_sack; 544 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 545 kfree(q, M_TSEGQ); 546 atomic_add_int(&tcp_reass_qsize, -1); 547 } 548 549 if (p == NULL) { 550 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q); 551 } else { 552 /* check if can coalesce with preceding segment */ 553 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 554 if (te->tqe_th->th_flags & TH_FIN) 555 p->tqe_th->th_flags |= TH_FIN; 556 p->tqe_len += te->tqe_len; 557 m_cat(p->tqe_m, te->tqe_m); 558 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 559 /* 560 * When not reporting a duplicate segment, use 561 * the larger enclosing block as the SACK block. 562 */ 563 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 564 tp->reportblk.rblk_start = p->tqe_th->th_seq; 565 kfree(te, M_TSEGQ); 566 atomic_add_int(&tcp_reass_qsize, -1); 567 } else { 568 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q); 569 } 570 } 571 572 present: 573 /* 574 * Present data to user, advancing rcv_nxt through 575 * completed sequence space. 576 */ 577 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 578 return (0); 579 q = TAILQ_FIRST(&tp->t_segq); 580 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 581 return (0); 582 tp->rcv_nxt += q->tqe_len; 583 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 584 /* no SACK block to report since ACK advanced */ 585 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 586 } 587 /* no enclosing block to report since ACK advanced */ 588 tp->sack_flags &= ~TSACK_F_ENCLOSESEG; 589 flags = q->tqe_th->th_flags & TH_FIN; 590 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 591 KASSERT(TAILQ_EMPTY(&tp->t_segq) || 592 TAILQ_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 593 ("segment not coalesced")); 594 if (so->so_state & SS_CANTRCVMORE) { 595 m_freem(q->tqe_m); 596 } else { 597 lwkt_gettoken(&so->so_rcv.ssb_token); 598 ssb_appendstream(&so->so_rcv, q->tqe_m); 599 lwkt_reltoken(&so->so_rcv.ssb_token); 600 } 601 kfree(q, M_TSEGQ); 602 atomic_add_int(&tcp_reass_qsize, -1); 603 ND6_HINT(tp); 604 sorwakeup(so); 605 return (flags); 606 } 607 608 /* 609 * TCP input routine, follows pages 65-76 of the 610 * protocol specification dated September, 1981 very closely. 611 */ 612 #ifdef INET6 613 int 614 tcp6_input(struct mbuf **mp, int *offp, int proto) 615 { 616 struct mbuf *m = *mp; 617 struct in6_ifaddr *ia6; 618 619 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 620 621 /* 622 * draft-itojun-ipv6-tcp-to-anycast 623 * better place to put this in? 624 */ 625 ia6 = ip6_getdstifaddr(m); 626 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 627 struct ip6_hdr *ip6; 628 629 ip6 = mtod(m, struct ip6_hdr *); 630 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 631 offsetof(struct ip6_hdr, ip6_dst)); 632 return (IPPROTO_DONE); 633 } 634 635 tcp_input(mp, offp, proto); 636 return (IPPROTO_DONE); 637 } 638 #endif 639 640 int 641 tcp_input(struct mbuf **mp, int *offp, int proto) 642 { 643 int off0; 644 struct tcphdr *th; 645 struct ip *ip = NULL; 646 struct ipovly *ipov; 647 struct inpcb *inp = NULL; 648 u_char *optp = NULL; 649 int optlen = 0; 650 int tlen, off; 651 int len = 0; 652 int drop_hdrlen; 653 struct tcpcb *tp = NULL; 654 int thflags; 655 struct socket *so = NULL; 656 int todrop, acked; 657 boolean_t ourfinisacked, needoutput = FALSE, delayed_dupack = FALSE; 658 tcp_seq th_dupack = 0; /* XXX gcc warning */ 659 u_int to_flags = 0; /* XXX gcc warning */ 660 u_long tiwin; 661 int recvwin; 662 struct tcpopt to; /* options in this segment */ 663 struct sockaddr_in *next_hop = NULL; 664 int rstreason; /* For badport_bandlim accounting purposes */ 665 int cpu; 666 struct ip6_hdr *ip6 = NULL; 667 struct mbuf *m; 668 #ifdef INET6 669 boolean_t isipv6; 670 #else 671 const boolean_t isipv6 = FALSE; 672 #endif 673 #ifdef TCPDEBUG 674 short ostate = 0; 675 #endif 676 677 off0 = *offp; 678 m = *mp; 679 *mp = NULL; 680 681 tcpstat.tcps_rcvtotal++; 682 683 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 684 struct m_tag *mtag; 685 686 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 687 KKASSERT(mtag != NULL); 688 next_hop = m_tag_data(mtag); 689 } 690 691 #ifdef INET6 692 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 693 #endif 694 695 if (isipv6) { 696 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 697 ip6 = mtod(m, struct ip6_hdr *); 698 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 699 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 700 tcpstat.tcps_rcvbadsum++; 701 goto drop; 702 } 703 th = (struct tcphdr *)((caddr_t)ip6 + off0); 704 705 /* 706 * Be proactive about unspecified IPv6 address in source. 707 * As we use all-zero to indicate unbounded/unconnected pcb, 708 * unspecified IPv6 address can be used to confuse us. 709 * 710 * Note that packets with unspecified IPv6 destination is 711 * already dropped in ip6_input. 712 */ 713 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 714 /* XXX stat */ 715 goto drop; 716 } 717 } else { 718 /* 719 * Get IP and TCP header together in first mbuf. 720 * Note: IP leaves IP header in first mbuf. 721 */ 722 if (off0 > sizeof(struct ip)) { 723 ip_stripoptions(m); 724 off0 = sizeof(struct ip); 725 } 726 /* already checked and pulled up in ip_demux() */ 727 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 728 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 729 ip = mtod(m, struct ip *); 730 ipov = (struct ipovly *)ip; 731 th = (struct tcphdr *)((caddr_t)ip + off0); 732 tlen = ip->ip_len; 733 734 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 735 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 736 th->th_sum = m->m_pkthdr.csum_data; 737 else 738 th->th_sum = in_pseudo(ip->ip_src.s_addr, 739 ip->ip_dst.s_addr, 740 htonl(m->m_pkthdr.csum_data + 741 ip->ip_len + 742 IPPROTO_TCP)); 743 th->th_sum ^= 0xffff; 744 } else { 745 /* 746 * Checksum extended TCP header and data. 747 */ 748 len = sizeof(struct ip) + tlen; 749 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 750 ipov->ih_len = (u_short)tlen; 751 ipov->ih_len = htons(ipov->ih_len); 752 th->th_sum = in_cksum(m, len); 753 } 754 if (th->th_sum) { 755 tcpstat.tcps_rcvbadsum++; 756 goto drop; 757 } 758 #ifdef INET6 759 /* Re-initialization for later version check */ 760 ip->ip_v = IPVERSION; 761 #endif 762 } 763 764 /* 765 * Check that TCP offset makes sense, 766 * pull out TCP options and adjust length. XXX 767 */ 768 off = th->th_off << 2; 769 /* already checked and pulled up in ip_demux() */ 770 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 771 ("bad TCP data offset %d (tlen %d)", off, tlen)); 772 tlen -= off; /* tlen is used instead of ti->ti_len */ 773 if (off > sizeof(struct tcphdr)) { 774 if (isipv6) { 775 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 776 ip6 = mtod(m, struct ip6_hdr *); 777 th = (struct tcphdr *)((caddr_t)ip6 + off0); 778 } else { 779 /* already pulled up in ip_demux() */ 780 KASSERT(m->m_len >= sizeof(struct ip) + off, 781 ("TCP header and options not in one mbuf: " 782 "m_len %d, off %d", m->m_len, off)); 783 } 784 optlen = off - sizeof(struct tcphdr); 785 optp = (u_char *)(th + 1); 786 } 787 thflags = th->th_flags; 788 789 #ifdef TCP_DROP_SYNFIN 790 /* 791 * If the drop_synfin option is enabled, drop all packets with 792 * both the SYN and FIN bits set. This prevents e.g. nmap from 793 * identifying the TCP/IP stack. 794 * 795 * This is a violation of the TCP specification. 796 */ 797 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 798 goto drop; 799 #endif 800 801 /* 802 * Convert TCP protocol specific fields to host format. 803 */ 804 th->th_seq = ntohl(th->th_seq); 805 th->th_ack = ntohl(th->th_ack); 806 th->th_win = ntohs(th->th_win); 807 th->th_urp = ntohs(th->th_urp); 808 809 /* 810 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 811 * until after ip6_savecontrol() is called and before other functions 812 * which don't want those proto headers. 813 * Because ip6_savecontrol() is going to parse the mbuf to 814 * search for data to be passed up to user-land, it wants mbuf 815 * parameters to be unchanged. 816 * XXX: the call of ip6_savecontrol() has been obsoleted based on 817 * latest version of the advanced API (20020110). 818 */ 819 drop_hdrlen = off0 + off; 820 821 /* 822 * Locate pcb for segment. 823 */ 824 findpcb: 825 /* IPFIREWALL_FORWARD section */ 826 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 827 /* 828 * Transparently forwarded. Pretend to be the destination. 829 * already got one like this? 830 */ 831 cpu = mycpu->gd_cpuid; 832 inp = in_pcblookup_hash(&tcbinfo[cpu], 833 ip->ip_src, th->th_sport, 834 ip->ip_dst, th->th_dport, 835 0, m->m_pkthdr.rcvif); 836 if (!inp) { 837 /* 838 * It's new. Try to find the ambushing socket. 839 */ 840 841 /* 842 * The rest of the ipfw code stores the port in 843 * host order. XXX 844 * (The IP address is still in network order.) 845 */ 846 in_port_t dport = next_hop->sin_port ? 847 htons(next_hop->sin_port) : 848 th->th_dport; 849 850 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 851 next_hop->sin_addr.s_addr, dport); 852 inp = in_pcblookup_hash(&tcbinfo[cpu], 853 ip->ip_src, th->th_sport, 854 next_hop->sin_addr, dport, 855 1, m->m_pkthdr.rcvif); 856 } 857 } else { 858 if (isipv6) { 859 inp = in6_pcblookup_hash(&tcbinfo[0], 860 &ip6->ip6_src, th->th_sport, 861 &ip6->ip6_dst, th->th_dport, 862 1, m->m_pkthdr.rcvif); 863 } else { 864 cpu = mycpu->gd_cpuid; 865 inp = in_pcblookup_hash(&tcbinfo[cpu], 866 ip->ip_src, th->th_sport, 867 ip->ip_dst, th->th_dport, 868 1, m->m_pkthdr.rcvif); 869 } 870 } 871 872 /* 873 * If the state is CLOSED (i.e., TCB does not exist) then 874 * all data in the incoming segment is discarded. 875 * If the TCB exists but is in CLOSED state, it is embryonic, 876 * but should either do a listen or a connect soon. 877 */ 878 if (inp == NULL) { 879 if (log_in_vain) { 880 #ifdef INET6 881 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 882 #else 883 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 884 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 885 #endif 886 if (isipv6) { 887 strcpy(dbuf, "["); 888 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 889 strcat(dbuf, "]"); 890 strcpy(sbuf, "["); 891 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 892 strcat(sbuf, "]"); 893 } else { 894 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 895 strcpy(sbuf, inet_ntoa(ip->ip_src)); 896 } 897 switch (log_in_vain) { 898 case 1: 899 if (!(thflags & TH_SYN)) 900 break; 901 case 2: 902 log(LOG_INFO, 903 "Connection attempt to TCP %s:%d " 904 "from %s:%d flags:0x%02x\n", 905 dbuf, ntohs(th->th_dport), sbuf, 906 ntohs(th->th_sport), thflags); 907 break; 908 default: 909 break; 910 } 911 } 912 if (blackhole) { 913 switch (blackhole) { 914 case 1: 915 if (thflags & TH_SYN) 916 goto drop; 917 break; 918 case 2: 919 goto drop; 920 default: 921 goto drop; 922 } 923 } 924 rstreason = BANDLIM_RST_CLOSEDPORT; 925 goto dropwithreset; 926 } 927 928 #ifdef IPSEC 929 if (isipv6) { 930 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 931 ipsec6stat.in_polvio++; 932 goto drop; 933 } 934 } else { 935 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 936 ipsecstat.in_polvio++; 937 goto drop; 938 } 939 } 940 #endif 941 #ifdef FAST_IPSEC 942 if (isipv6) { 943 if (ipsec6_in_reject(m, inp)) 944 goto drop; 945 } else { 946 if (ipsec4_in_reject(m, inp)) 947 goto drop; 948 } 949 #endif 950 /* Check the minimum TTL for socket. */ 951 #ifdef INET6 952 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 953 goto drop; 954 #endif 955 956 tp = intotcpcb(inp); 957 if (tp == NULL) { 958 rstreason = BANDLIM_RST_CLOSEDPORT; 959 goto dropwithreset; 960 } 961 if (tp->t_state <= TCPS_CLOSED) 962 goto drop; 963 964 so = inp->inp_socket; 965 966 #ifdef TCPDEBUG 967 if (so->so_options & SO_DEBUG) { 968 ostate = tp->t_state; 969 if (isipv6) 970 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 971 else 972 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 973 tcp_savetcp = *th; 974 } 975 #endif 976 977 bzero(&to, sizeof to); 978 979 if (so->so_options & SO_ACCEPTCONN) { 980 struct in_conninfo inc; 981 982 #ifdef INET6 983 inc.inc_isipv6 = (isipv6 == TRUE); 984 #endif 985 if (isipv6) { 986 inc.inc6_faddr = ip6->ip6_src; 987 inc.inc6_laddr = ip6->ip6_dst; 988 inc.inc6_route.ro_rt = NULL; /* XXX */ 989 } else { 990 inc.inc_faddr = ip->ip_src; 991 inc.inc_laddr = ip->ip_dst; 992 inc.inc_route.ro_rt = NULL; /* XXX */ 993 } 994 inc.inc_fport = th->th_sport; 995 inc.inc_lport = th->th_dport; 996 997 /* 998 * If the state is LISTEN then ignore segment if it contains 999 * a RST. If the segment contains an ACK then it is bad and 1000 * send a RST. If it does not contain a SYN then it is not 1001 * interesting; drop it. 1002 * 1003 * If the state is SYN_RECEIVED (syncache) and seg contains 1004 * an ACK, but not for our SYN/ACK, send a RST. If the seg 1005 * contains a RST, check the sequence number to see if it 1006 * is a valid reset segment. 1007 */ 1008 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 1009 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 1010 if (!syncache_expand(&inc, th, &so, m)) { 1011 /* 1012 * No syncache entry, or ACK was not 1013 * for our SYN/ACK. Send a RST. 1014 */ 1015 tcpstat.tcps_badsyn++; 1016 rstreason = BANDLIM_RST_OPENPORT; 1017 goto dropwithreset; 1018 } 1019 1020 /* 1021 * Could not complete 3-way handshake, 1022 * connection is being closed down, and 1023 * syncache will free mbuf. 1024 */ 1025 if (so == NULL) 1026 return(IPPROTO_DONE); 1027 1028 /* 1029 * We must be in the correct protocol thread 1030 * for this connection. 1031 */ 1032 KKASSERT(so->so_port == &curthread->td_msgport); 1033 1034 /* 1035 * Socket is created in state SYN_RECEIVED. 1036 * Continue processing segment. 1037 */ 1038 inp = so->so_pcb; 1039 tp = intotcpcb(inp); 1040 /* 1041 * This is what would have happened in 1042 * tcp_output() when the SYN,ACK was sent. 1043 */ 1044 tp->snd_up = tp->snd_una; 1045 tp->snd_max = tp->snd_nxt = tp->iss + 1; 1046 tp->last_ack_sent = tp->rcv_nxt; 1047 1048 goto after_listen; 1049 } 1050 if (thflags & TH_RST) { 1051 syncache_chkrst(&inc, th); 1052 goto drop; 1053 } 1054 if (thflags & TH_ACK) { 1055 syncache_badack(&inc); 1056 tcpstat.tcps_badsyn++; 1057 rstreason = BANDLIM_RST_OPENPORT; 1058 goto dropwithreset; 1059 } 1060 goto drop; 1061 } 1062 1063 /* 1064 * Segment's flags are (SYN) or (SYN | FIN). 1065 */ 1066 #ifdef INET6 1067 /* 1068 * If deprecated address is forbidden, 1069 * we do not accept SYN to deprecated interface 1070 * address to prevent any new inbound connection from 1071 * getting established. 1072 * When we do not accept SYN, we send a TCP RST, 1073 * with deprecated source address (instead of dropping 1074 * it). We compromise it as it is much better for peer 1075 * to send a RST, and RST will be the final packet 1076 * for the exchange. 1077 * 1078 * If we do not forbid deprecated addresses, we accept 1079 * the SYN packet. RFC2462 does not suggest dropping 1080 * SYN in this case. 1081 * If we decipher RFC2462 5.5.4, it says like this: 1082 * 1. use of deprecated addr with existing 1083 * communication is okay - "SHOULD continue to be 1084 * used" 1085 * 2. use of it with new communication: 1086 * (2a) "SHOULD NOT be used if alternate address 1087 * with sufficient scope is available" 1088 * (2b) nothing mentioned otherwise. 1089 * Here we fall into (2b) case as we have no choice in 1090 * our source address selection - we must obey the peer. 1091 * 1092 * The wording in RFC2462 is confusing, and there are 1093 * multiple description text for deprecated address 1094 * handling - worse, they are not exactly the same. 1095 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1096 */ 1097 if (isipv6 && !ip6_use_deprecated) { 1098 struct in6_ifaddr *ia6; 1099 1100 if ((ia6 = ip6_getdstifaddr(m)) && 1101 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1102 tp = NULL; 1103 rstreason = BANDLIM_RST_OPENPORT; 1104 goto dropwithreset; 1105 } 1106 } 1107 #endif 1108 /* 1109 * If it is from this socket, drop it, it must be forged. 1110 * Don't bother responding if the destination was a broadcast. 1111 */ 1112 if (th->th_dport == th->th_sport) { 1113 if (isipv6) { 1114 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1115 &ip6->ip6_src)) 1116 goto drop; 1117 } else { 1118 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1119 goto drop; 1120 } 1121 } 1122 /* 1123 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1124 * 1125 * Note that it is quite possible to receive unicast 1126 * link-layer packets with a broadcast IP address. Use 1127 * in_broadcast() to find them. 1128 */ 1129 if (m->m_flags & (M_BCAST | M_MCAST)) 1130 goto drop; 1131 if (isipv6) { 1132 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1133 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1134 goto drop; 1135 } else { 1136 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1137 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1138 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1139 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1140 goto drop; 1141 } 1142 /* 1143 * SYN appears to be valid; create compressed TCP state 1144 * for syncache, or perform t/tcp connection. 1145 */ 1146 if (so->so_qlen <= so->so_qlimit) { 1147 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack); 1148 if (!syncache_add(&inc, &to, th, so, m)) 1149 goto drop; 1150 1151 /* 1152 * Entry added to syncache, mbuf used to 1153 * send SYN,ACK packet. 1154 */ 1155 return(IPPROTO_DONE); 1156 } 1157 goto drop; 1158 } 1159 1160 after_listen: 1161 /* 1162 * Should not happen - syncache should pick up these connections. 1163 * 1164 * Once we are past handling listen sockets we must be in the 1165 * correct protocol processing thread. 1166 */ 1167 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1168 KKASSERT(so->so_port == &curthread->td_msgport); 1169 1170 /* Unscale the window into a 32-bit value. */ 1171 if (!(thflags & TH_SYN)) 1172 tiwin = th->th_win << tp->snd_scale; 1173 else 1174 tiwin = th->th_win; 1175 1176 /* 1177 * This is the second part of the MSS DoS prevention code (after 1178 * minmss on the sending side) and it deals with too many too small 1179 * tcp packets in a too short timeframe (1 second). 1180 * 1181 * XXX Removed. This code was crap. It does not scale to network 1182 * speed, and default values break NFS. Gone. 1183 */ 1184 /* REMOVED */ 1185 1186 /* 1187 * Segment received on connection. 1188 * 1189 * Reset idle time and keep-alive timer. Don't waste time if less 1190 * then a second has elapsed. 1191 */ 1192 if ((int)(ticks - tp->t_rcvtime) > hz) 1193 tcp_timer_keep_activity(tp, thflags); 1194 1195 /* 1196 * Process options. 1197 * XXX this is tradtitional behavior, may need to be cleaned up. 1198 */ 1199 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack); 1200 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1201 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) { 1202 tp->t_flags |= TF_RCVD_SCALE; 1203 tp->snd_scale = to.to_requested_s_scale; 1204 } 1205 1206 /* 1207 * Initial send window; will be updated upon next ACK 1208 */ 1209 tp->snd_wnd = th->th_win; 1210 1211 if (to.to_flags & TOF_TS) { 1212 tp->t_flags |= TF_RCVD_TSTMP; 1213 tp->ts_recent = to.to_tsval; 1214 tp->ts_recent_age = ticks; 1215 } 1216 if (!(to.to_flags & TOF_MSS)) 1217 to.to_mss = 0; 1218 tcp_mss(tp, to.to_mss); 1219 /* 1220 * Only set the TF_SACK_PERMITTED per-connection flag 1221 * if we got a SACK_PERMITTED option from the other side 1222 * and the global tcp_do_sack variable is true. 1223 */ 1224 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1225 tp->t_flags |= TF_SACK_PERMITTED; 1226 } 1227 1228 /* 1229 * Header prediction: check for the two common cases 1230 * of a uni-directional data xfer. If the packet has 1231 * no control flags, is in-sequence, the window didn't 1232 * change and we're not retransmitting, it's a 1233 * candidate. If the length is zero and the ack moved 1234 * forward, we're the sender side of the xfer. Just 1235 * free the data acked & wake any higher level process 1236 * that was blocked waiting for space. If the length 1237 * is non-zero and the ack didn't move, we're the 1238 * receiver side. If we're getting packets in-order 1239 * (the reassembly queue is empty), add the data to 1240 * the socket buffer and note that we need a delayed ack. 1241 * Make sure that the hidden state-flags are also off. 1242 * Since we check for TCPS_ESTABLISHED above, it can only 1243 * be TH_NEEDSYN. 1244 */ 1245 if (tp->t_state == TCPS_ESTABLISHED && 1246 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1247 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1248 (!(to.to_flags & TOF_TS) || 1249 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1250 th->th_seq == tp->rcv_nxt && 1251 tp->snd_nxt == tp->snd_max) { 1252 1253 /* 1254 * If last ACK falls within this segment's sequence numbers, 1255 * record the timestamp. 1256 * NOTE that the test is modified according to the latest 1257 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1258 */ 1259 if ((to.to_flags & TOF_TS) && 1260 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1261 tp->ts_recent_age = ticks; 1262 tp->ts_recent = to.to_tsval; 1263 } 1264 1265 if (tlen == 0) { 1266 if (SEQ_GT(th->th_ack, tp->snd_una) && 1267 SEQ_LEQ(th->th_ack, tp->snd_max) && 1268 tp->snd_cwnd >= tp->snd_wnd && 1269 !IN_FASTRECOVERY(tp)) { 1270 /* 1271 * This is a pure ack for outstanding data. 1272 */ 1273 ++tcpstat.tcps_predack; 1274 /* 1275 * "bad retransmit" recovery 1276 * 1277 * If Eifel detection applies, then 1278 * it is deterministic, so use it 1279 * unconditionally over the old heuristic. 1280 * Otherwise, fall back to the old heuristic. 1281 */ 1282 if (tcp_do_eifel_detect && 1283 (to.to_flags & TOF_TS) && to.to_tsecr && 1284 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 1285 /* Eifel detection applicable. */ 1286 if (to.to_tsecr < tp->t_rexmtTS) { 1287 tcp_revert_congestion_state(tp); 1288 ++tcpstat.tcps_eifeldetected; 1289 if (tp->t_rxtshift != 1 || 1290 ticks >= tp->t_badrxtwin) 1291 ++tcpstat.tcps_rttcantdetect; 1292 } 1293 } else if (tp->t_rxtshift == 1 && 1294 ticks < tp->t_badrxtwin) { 1295 tcp_revert_congestion_state(tp); 1296 ++tcpstat.tcps_rttdetected; 1297 } 1298 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 1299 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 1300 /* 1301 * Recalculate the retransmit timer / rtt. 1302 * 1303 * Some machines (certain windows boxes) 1304 * send broken timestamp replies during the 1305 * SYN+ACK phase, ignore timestamps of 0. 1306 */ 1307 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1308 tcp_xmit_timer(tp, 1309 ticks - to.to_tsecr + 1, 1310 th->th_ack); 1311 } else if (tp->t_rtttime && 1312 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1313 tcp_xmit_timer(tp, 1314 ticks - tp->t_rtttime, 1315 th->th_ack); 1316 } 1317 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1318 acked = th->th_ack - tp->snd_una; 1319 tcpstat.tcps_rcvackpack++; 1320 tcpstat.tcps_rcvackbyte += acked; 1321 sbdrop(&so->so_snd.sb, acked); 1322 tp->snd_recover = th->th_ack - 1; 1323 tp->snd_una = th->th_ack; 1324 tp->t_dupacks = 0; 1325 /* 1326 * Update window information. 1327 */ 1328 if (tiwin != tp->snd_wnd && 1329 acceptable_window_update(tp, th, tiwin)) { 1330 /* keep track of pure window updates */ 1331 if (tp->snd_wl2 == th->th_ack && 1332 tiwin > tp->snd_wnd) 1333 tcpstat.tcps_rcvwinupd++; 1334 tp->snd_wnd = tiwin; 1335 tp->snd_wl1 = th->th_seq; 1336 tp->snd_wl2 = th->th_ack; 1337 if (tp->snd_wnd > tp->max_sndwnd) 1338 tp->max_sndwnd = tp->snd_wnd; 1339 } 1340 m_freem(m); 1341 ND6_HINT(tp); /* some progress has been done */ 1342 /* 1343 * If all outstanding data are acked, stop 1344 * retransmit timer, otherwise restart timer 1345 * using current (possibly backed-off) value. 1346 * If process is waiting for space, 1347 * wakeup/selwakeup/signal. If data 1348 * are ready to send, let tcp_output 1349 * decide between more output or persist. 1350 */ 1351 if (tp->snd_una == tp->snd_max) { 1352 tcp_callout_stop(tp, tp->tt_rexmt); 1353 } else if (!tcp_callout_active(tp, 1354 tp->tt_persist)) { 1355 tcp_callout_reset(tp, tp->tt_rexmt, 1356 tp->t_rxtcur, tcp_timer_rexmt); 1357 } 1358 sowwakeup(so); 1359 if (so->so_snd.ssb_cc > 0) 1360 tcp_output(tp); 1361 return(IPPROTO_DONE); 1362 } 1363 } else if (tiwin == tp->snd_wnd && 1364 th->th_ack == tp->snd_una && 1365 TAILQ_EMPTY(&tp->t_segq) && 1366 tlen <= ssb_space(&so->so_rcv)) { 1367 u_long newsize = 0; /* automatic sockbuf scaling */ 1368 /* 1369 * This is a pure, in-sequence data packet 1370 * with nothing on the reassembly queue and 1371 * we have enough buffer space to take it. 1372 */ 1373 ++tcpstat.tcps_preddat; 1374 tp->rcv_nxt += tlen; 1375 tcpstat.tcps_rcvpack++; 1376 tcpstat.tcps_rcvbyte += tlen; 1377 ND6_HINT(tp); /* some progress has been done */ 1378 /* 1379 * Automatic sizing of receive socket buffer. Often the send 1380 * buffer size is not optimally adjusted to the actual network 1381 * conditions at hand (delay bandwidth product). Setting the 1382 * buffer size too small limits throughput on links with high 1383 * bandwidth and high delay (eg. trans-continental/oceanic links). 1384 * 1385 * On the receive side the socket buffer memory is only rarely 1386 * used to any significant extent. This allows us to be much 1387 * more aggressive in scaling the receive socket buffer. For 1388 * the case that the buffer space is actually used to a large 1389 * extent and we run out of kernel memory we can simply drop 1390 * the new segments; TCP on the sender will just retransmit it 1391 * later. Setting the buffer size too big may only consume too 1392 * much kernel memory if the application doesn't read() from 1393 * the socket or packet loss or reordering makes use of the 1394 * reassembly queue. 1395 * 1396 * The criteria to step up the receive buffer one notch are: 1397 * 1. the number of bytes received during the time it takes 1398 * one timestamp to be reflected back to us (the RTT); 1399 * 2. received bytes per RTT is within seven eighth of the 1400 * current socket buffer size; 1401 * 3. receive buffer size has not hit maximal automatic size; 1402 * 1403 * This algorithm does one step per RTT at most and only if 1404 * we receive a bulk stream w/o packet losses or reorderings. 1405 * Shrinking the buffer during idle times is not necessary as 1406 * it doesn't consume any memory when idle. 1407 * 1408 * TODO: Only step up if the application is actually serving 1409 * the buffer to better manage the socket buffer resources. 1410 */ 1411 if (tcp_do_autorcvbuf && 1412 to.to_tsecr && 1413 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1414 if (to.to_tsecr > tp->rfbuf_ts && 1415 to.to_tsecr - tp->rfbuf_ts < hz) { 1416 if (tp->rfbuf_cnt > 1417 (so->so_rcv.ssb_hiwat / 8 * 7) && 1418 so->so_rcv.ssb_hiwat < 1419 tcp_autorcvbuf_max) { 1420 newsize = 1421 ulmin(so->so_rcv.ssb_hiwat + 1422 tcp_autorcvbuf_inc, 1423 tcp_autorcvbuf_max); 1424 } 1425 /* Start over with next RTT. */ 1426 tp->rfbuf_ts = 0; 1427 tp->rfbuf_cnt = 0; 1428 } else 1429 tp->rfbuf_cnt += tlen; /* add up */ 1430 } 1431 /* 1432 * Add data to socket buffer. 1433 */ 1434 if (so->so_state & SS_CANTRCVMORE) { 1435 m_freem(m); 1436 } else { 1437 /* 1438 * Set new socket buffer size, give up when 1439 * limit is reached. 1440 * 1441 * Adjusting the size can mess up ACK 1442 * sequencing when pure window updates are 1443 * being avoided (which is the default), 1444 * so force an ack. 1445 */ 1446 lwkt_gettoken(&so->so_rcv.ssb_token); 1447 if (newsize) { 1448 tp->t_flags |= TF_RXRESIZED; 1449 if (!ssb_reserve(&so->so_rcv, newsize, 1450 so, NULL)) { 1451 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1452 } 1453 if (newsize >= 1454 (TCP_MAXWIN << tp->rcv_scale)) { 1455 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1456 } 1457 } 1458 m_adj(m, drop_hdrlen); /* delayed header drop */ 1459 ssb_appendstream(&so->so_rcv, m); 1460 lwkt_reltoken(&so->so_rcv.ssb_token); 1461 } 1462 sorwakeup(so); 1463 /* 1464 * This code is responsible for most of the ACKs 1465 * the TCP stack sends back after receiving a data 1466 * packet. Note that the DELAY_ACK check fails if 1467 * the delack timer is already running, which results 1468 * in an ack being sent every other packet (which is 1469 * what we want). 1470 * 1471 * We then further aggregate acks by not actually 1472 * sending one until the protocol thread has completed 1473 * processing the current backlog of packets. This 1474 * does not delay the ack any further, but allows us 1475 * to take advantage of the packet aggregation that 1476 * high speed NICs do (usually blocks of 8-10 packets) 1477 * to send a single ack rather then four or five acks, 1478 * greatly reducing the ack rate, the return channel 1479 * bandwidth, and the protocol overhead on both ends. 1480 * 1481 * Since this also has the effect of slowing down 1482 * the exponential slow-start ramp-up, systems with 1483 * very large bandwidth-delay products might want 1484 * to turn the feature off. 1485 */ 1486 if (DELAY_ACK(tp)) { 1487 tcp_callout_reset(tp, tp->tt_delack, 1488 tcp_delacktime, tcp_timer_delack); 1489 } else if (tcp_aggregate_acks) { 1490 tp->t_flags |= TF_ACKNOW; 1491 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1492 tp->t_flags |= TF_ONOUTPUTQ; 1493 tp->tt_cpu = mycpu->gd_cpuid; 1494 TAILQ_INSERT_TAIL( 1495 &tcpcbackq[tp->tt_cpu], 1496 tp, t_outputq); 1497 } 1498 } else { 1499 tp->t_flags |= TF_ACKNOW; 1500 tcp_output(tp); 1501 } 1502 return(IPPROTO_DONE); 1503 } 1504 } 1505 1506 /* 1507 * Calculate amount of space in receive window, 1508 * and then do TCP input processing. 1509 * Receive window is amount of space in rcv queue, 1510 * but not less than advertised window. 1511 */ 1512 recvwin = ssb_space(&so->so_rcv); 1513 if (recvwin < 0) 1514 recvwin = 0; 1515 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1516 1517 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1518 tp->rfbuf_ts = 0; 1519 tp->rfbuf_cnt = 0; 1520 1521 switch (tp->t_state) { 1522 /* 1523 * If the state is SYN_RECEIVED: 1524 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1525 */ 1526 case TCPS_SYN_RECEIVED: 1527 if ((thflags & TH_ACK) && 1528 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1529 SEQ_GT(th->th_ack, tp->snd_max))) { 1530 rstreason = BANDLIM_RST_OPENPORT; 1531 goto dropwithreset; 1532 } 1533 break; 1534 1535 /* 1536 * If the state is SYN_SENT: 1537 * if seg contains an ACK, but not for our SYN, drop the input. 1538 * if seg contains a RST, then drop the connection. 1539 * if seg does not contain SYN, then drop it. 1540 * Otherwise this is an acceptable SYN segment 1541 * initialize tp->rcv_nxt and tp->irs 1542 * if seg contains ack then advance tp->snd_una 1543 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1544 * arrange for segment to be acked (eventually) 1545 * continue processing rest of data/controls, beginning with URG 1546 */ 1547 case TCPS_SYN_SENT: 1548 if ((thflags & TH_ACK) && 1549 (SEQ_LEQ(th->th_ack, tp->iss) || 1550 SEQ_GT(th->th_ack, tp->snd_max))) { 1551 rstreason = BANDLIM_UNLIMITED; 1552 goto dropwithreset; 1553 } 1554 if (thflags & TH_RST) { 1555 if (thflags & TH_ACK) 1556 tp = tcp_drop(tp, ECONNREFUSED); 1557 goto drop; 1558 } 1559 if (!(thflags & TH_SYN)) 1560 goto drop; 1561 1562 tp->irs = th->th_seq; 1563 tcp_rcvseqinit(tp); 1564 if (thflags & TH_ACK) { 1565 /* Our SYN was acked. */ 1566 tcpstat.tcps_connects++; 1567 soisconnected(so); 1568 /* Do window scaling on this connection? */ 1569 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1570 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1571 tp->rcv_scale = tp->request_r_scale; 1572 tp->rcv_adv += tp->rcv_wnd; 1573 tp->snd_una++; /* SYN is acked */ 1574 tcp_callout_stop(tp, tp->tt_rexmt); 1575 /* 1576 * If there's data, delay ACK; if there's also a FIN 1577 * ACKNOW will be turned on later. 1578 */ 1579 if (DELAY_ACK(tp) && tlen != 0) { 1580 tcp_callout_reset(tp, tp->tt_delack, 1581 tcp_delacktime, tcp_timer_delack); 1582 } else { 1583 tp->t_flags |= TF_ACKNOW; 1584 } 1585 /* 1586 * Received <SYN,ACK> in SYN_SENT[*] state. 1587 * Transitions: 1588 * SYN_SENT --> ESTABLISHED 1589 * SYN_SENT* --> FIN_WAIT_1 1590 */ 1591 tp->t_starttime = ticks; 1592 if (tp->t_flags & TF_NEEDFIN) { 1593 tp->t_state = TCPS_FIN_WAIT_1; 1594 tp->t_flags &= ~TF_NEEDFIN; 1595 thflags &= ~TH_SYN; 1596 } else { 1597 tcp_established(tp); 1598 } 1599 } else { 1600 /* 1601 * Received initial SYN in SYN-SENT[*] state => 1602 * simultaneous open. 1603 * Do 3-way handshake: 1604 * SYN-SENT -> SYN-RECEIVED 1605 * SYN-SENT* -> SYN-RECEIVED* 1606 */ 1607 tp->t_flags |= TF_ACKNOW; 1608 tcp_callout_stop(tp, tp->tt_rexmt); 1609 tp->t_state = TCPS_SYN_RECEIVED; 1610 } 1611 1612 /* 1613 * Advance th->th_seq to correspond to first data byte. 1614 * If data, trim to stay within window, 1615 * dropping FIN if necessary. 1616 */ 1617 th->th_seq++; 1618 if (tlen > tp->rcv_wnd) { 1619 todrop = tlen - tp->rcv_wnd; 1620 m_adj(m, -todrop); 1621 tlen = tp->rcv_wnd; 1622 thflags &= ~TH_FIN; 1623 tcpstat.tcps_rcvpackafterwin++; 1624 tcpstat.tcps_rcvbyteafterwin += todrop; 1625 } 1626 tp->snd_wl1 = th->th_seq - 1; 1627 tp->rcv_up = th->th_seq; 1628 /* 1629 * Client side of transaction: already sent SYN and data. 1630 * If the remote host used T/TCP to validate the SYN, 1631 * our data will be ACK'd; if so, enter normal data segment 1632 * processing in the middle of step 5, ack processing. 1633 * Otherwise, goto step 6. 1634 */ 1635 if (thflags & TH_ACK) 1636 goto process_ACK; 1637 1638 goto step6; 1639 1640 /* 1641 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1642 * do normal processing (we no longer bother with T/TCP). 1643 */ 1644 case TCPS_LAST_ACK: 1645 case TCPS_CLOSING: 1646 case TCPS_TIME_WAIT: 1647 break; /* continue normal processing */ 1648 } 1649 1650 /* 1651 * States other than LISTEN or SYN_SENT. 1652 * First check the RST flag and sequence number since reset segments 1653 * are exempt from the timestamp and connection count tests. This 1654 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1655 * below which allowed reset segments in half the sequence space 1656 * to fall though and be processed (which gives forged reset 1657 * segments with a random sequence number a 50 percent chance of 1658 * killing a connection). 1659 * Then check timestamp, if present. 1660 * Then check the connection count, if present. 1661 * Then check that at least some bytes of segment are within 1662 * receive window. If segment begins before rcv_nxt, 1663 * drop leading data (and SYN); if nothing left, just ack. 1664 * 1665 * 1666 * If the RST bit is set, check the sequence number to see 1667 * if this is a valid reset segment. 1668 * RFC 793 page 37: 1669 * In all states except SYN-SENT, all reset (RST) segments 1670 * are validated by checking their SEQ-fields. A reset is 1671 * valid if its sequence number is in the window. 1672 * Note: this does not take into account delayed ACKs, so 1673 * we should test against last_ack_sent instead of rcv_nxt. 1674 * The sequence number in the reset segment is normally an 1675 * echo of our outgoing acknowledgement numbers, but some hosts 1676 * send a reset with the sequence number at the rightmost edge 1677 * of our receive window, and we have to handle this case. 1678 * If we have multiple segments in flight, the intial reset 1679 * segment sequence numbers will be to the left of last_ack_sent, 1680 * but they will eventually catch up. 1681 * In any case, it never made sense to trim reset segments to 1682 * fit the receive window since RFC 1122 says: 1683 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1684 * 1685 * A TCP SHOULD allow a received RST segment to include data. 1686 * 1687 * DISCUSSION 1688 * It has been suggested that a RST segment could contain 1689 * ASCII text that encoded and explained the cause of the 1690 * RST. No standard has yet been established for such 1691 * data. 1692 * 1693 * If the reset segment passes the sequence number test examine 1694 * the state: 1695 * SYN_RECEIVED STATE: 1696 * If passive open, return to LISTEN state. 1697 * If active open, inform user that connection was refused. 1698 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1699 * Inform user that connection was reset, and close tcb. 1700 * CLOSING, LAST_ACK STATES: 1701 * Close the tcb. 1702 * TIME_WAIT STATE: 1703 * Drop the segment - see Stevens, vol. 2, p. 964 and 1704 * RFC 1337. 1705 */ 1706 if (thflags & TH_RST) { 1707 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1708 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1709 switch (tp->t_state) { 1710 1711 case TCPS_SYN_RECEIVED: 1712 so->so_error = ECONNREFUSED; 1713 goto close; 1714 1715 case TCPS_ESTABLISHED: 1716 case TCPS_FIN_WAIT_1: 1717 case TCPS_FIN_WAIT_2: 1718 case TCPS_CLOSE_WAIT: 1719 so->so_error = ECONNRESET; 1720 close: 1721 tp->t_state = TCPS_CLOSED; 1722 tcpstat.tcps_drops++; 1723 tp = tcp_close(tp); 1724 break; 1725 1726 case TCPS_CLOSING: 1727 case TCPS_LAST_ACK: 1728 tp = tcp_close(tp); 1729 break; 1730 1731 case TCPS_TIME_WAIT: 1732 break; 1733 } 1734 } 1735 goto drop; 1736 } 1737 1738 /* 1739 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1740 * and it's less than ts_recent, drop it. 1741 */ 1742 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1743 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1744 /* Check to see if ts_recent is over 24 days old. */ 1745 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1746 /* 1747 * Invalidate ts_recent. If this segment updates 1748 * ts_recent, the age will be reset later and ts_recent 1749 * will get a valid value. If it does not, setting 1750 * ts_recent to zero will at least satisfy the 1751 * requirement that zero be placed in the timestamp 1752 * echo reply when ts_recent isn't valid. The 1753 * age isn't reset until we get a valid ts_recent 1754 * because we don't want out-of-order segments to be 1755 * dropped when ts_recent is old. 1756 */ 1757 tp->ts_recent = 0; 1758 } else if (tcp_paws_tolerance && tlen != 0 && 1759 tp->t_state == TCPS_ESTABLISHED && 1760 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK&& 1761 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1762 th->th_ack == tp->snd_una && 1763 tiwin == tp->snd_wnd && 1764 TSTMP_GEQ(to.to_tsval + tcp_paws_tolerance, tp->ts_recent)&& 1765 (th->th_seq == tp->rcv_nxt || 1766 (SEQ_GT(th->th_seq, tp->rcv_nxt) && 1767 tcp_paws_canreasslast(tp, th, tlen)))) { 1768 /* 1769 * This tends to prevent valid new segments from being 1770 * dropped by the reordered segments sent by the fast 1771 * retransmission algorithm on the sending side, i.e. 1772 * the fast retransmitted segment w/ larger timestamp 1773 * arrives earlier than the previously sent new segments 1774 * w/ smaller timestamp. 1775 * 1776 * If following conditions are met, the segment is 1777 * accepted: 1778 * - The segment contains data 1779 * - The connection is established 1780 * - The header does not contain important flags 1781 * - SYN or FIN is not needed 1782 * - It does not acknowledge new data 1783 * - Receive window is not changed 1784 * - The timestamp is within "acceptable" range 1785 * - The new segment is what we are expecting or 1786 * the new segment could be merged w/ the last 1787 * pending segment on the reassemble queue 1788 */ 1789 tcpstat.tcps_pawsaccept++; 1790 tcpstat.tcps_pawsdrop++; 1791 } else { 1792 tcpstat.tcps_rcvduppack++; 1793 tcpstat.tcps_rcvdupbyte += tlen; 1794 tcpstat.tcps_pawsdrop++; 1795 if (tlen) 1796 goto dropafterack; 1797 goto drop; 1798 } 1799 } 1800 1801 /* 1802 * In the SYN-RECEIVED state, validate that the packet belongs to 1803 * this connection before trimming the data to fit the receive 1804 * window. Check the sequence number versus IRS since we know 1805 * the sequence numbers haven't wrapped. This is a partial fix 1806 * for the "LAND" DoS attack. 1807 */ 1808 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1809 rstreason = BANDLIM_RST_OPENPORT; 1810 goto dropwithreset; 1811 } 1812 1813 todrop = tp->rcv_nxt - th->th_seq; 1814 if (todrop > 0) { 1815 if (TCP_DO_SACK(tp)) { 1816 /* Report duplicate segment at head of packet. */ 1817 tp->reportblk.rblk_start = th->th_seq; 1818 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 1819 th->th_seq + tlen, thflags); 1820 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1821 tp->reportblk.rblk_end = tp->rcv_nxt; 1822 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT); 1823 tp->t_flags |= TF_ACKNOW; 1824 } 1825 if (thflags & TH_SYN) { 1826 thflags &= ~TH_SYN; 1827 th->th_seq++; 1828 if (th->th_urp > 1) 1829 th->th_urp--; 1830 else 1831 thflags &= ~TH_URG; 1832 todrop--; 1833 } 1834 /* 1835 * Following if statement from Stevens, vol. 2, p. 960. 1836 */ 1837 if (todrop > tlen || 1838 (todrop == tlen && !(thflags & TH_FIN))) { 1839 /* 1840 * Any valid FIN must be to the left of the window. 1841 * At this point the FIN must be a duplicate or out 1842 * of sequence; drop it. 1843 */ 1844 thflags &= ~TH_FIN; 1845 1846 /* 1847 * Send an ACK to resynchronize and drop any data. 1848 * But keep on processing for RST or ACK. 1849 */ 1850 tp->t_flags |= TF_ACKNOW; 1851 todrop = tlen; 1852 tcpstat.tcps_rcvduppack++; 1853 tcpstat.tcps_rcvdupbyte += todrop; 1854 } else { 1855 tcpstat.tcps_rcvpartduppack++; 1856 tcpstat.tcps_rcvpartdupbyte += todrop; 1857 } 1858 drop_hdrlen += todrop; /* drop from the top afterwards */ 1859 th->th_seq += todrop; 1860 tlen -= todrop; 1861 if (th->th_urp > todrop) 1862 th->th_urp -= todrop; 1863 else { 1864 thflags &= ~TH_URG; 1865 th->th_urp = 0; 1866 } 1867 } 1868 1869 /* 1870 * If new data are received on a connection after the 1871 * user processes are gone, then RST the other end. 1872 */ 1873 if ((so->so_state & SS_NOFDREF) && 1874 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1875 tp = tcp_close(tp); 1876 tcpstat.tcps_rcvafterclose++; 1877 rstreason = BANDLIM_UNLIMITED; 1878 goto dropwithreset; 1879 } 1880 1881 /* 1882 * If segment ends after window, drop trailing data 1883 * (and PUSH and FIN); if nothing left, just ACK. 1884 */ 1885 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1886 if (todrop > 0) { 1887 tcpstat.tcps_rcvpackafterwin++; 1888 if (todrop >= tlen) { 1889 tcpstat.tcps_rcvbyteafterwin += tlen; 1890 /* 1891 * If a new connection request is received 1892 * while in TIME_WAIT, drop the old connection 1893 * and start over if the sequence numbers 1894 * are above the previous ones. 1895 */ 1896 if (thflags & TH_SYN && 1897 tp->t_state == TCPS_TIME_WAIT && 1898 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1899 tp = tcp_close(tp); 1900 goto findpcb; 1901 } 1902 /* 1903 * If window is closed can only take segments at 1904 * window edge, and have to drop data and PUSH from 1905 * incoming segments. Continue processing, but 1906 * remember to ack. Otherwise, drop segment 1907 * and ack. 1908 */ 1909 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1910 tp->t_flags |= TF_ACKNOW; 1911 tcpstat.tcps_rcvwinprobe++; 1912 } else 1913 goto dropafterack; 1914 } else 1915 tcpstat.tcps_rcvbyteafterwin += todrop; 1916 m_adj(m, -todrop); 1917 tlen -= todrop; 1918 thflags &= ~(TH_PUSH | TH_FIN); 1919 } 1920 1921 /* 1922 * If last ACK falls within this segment's sequence numbers, 1923 * record its timestamp. 1924 * NOTE: 1925 * 1) That the test incorporates suggestions from the latest 1926 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1927 * 2) That updating only on newer timestamps interferes with 1928 * our earlier PAWS tests, so this check should be solely 1929 * predicated on the sequence space of this segment. 1930 * 3) That we modify the segment boundary check to be 1931 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1932 * instead of RFC1323's 1933 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1934 * This modified check allows us to overcome RFC1323's 1935 * limitations as described in Stevens TCP/IP Illustrated 1936 * Vol. 2 p.869. In such cases, we can still calculate the 1937 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1938 */ 1939 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1940 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1941 + ((thflags & TH_SYN) != 0) 1942 + ((thflags & TH_FIN) != 0)))) { 1943 tp->ts_recent_age = ticks; 1944 tp->ts_recent = to.to_tsval; 1945 } 1946 1947 /* 1948 * If a SYN is in the window, then this is an 1949 * error and we send an RST and drop the connection. 1950 */ 1951 if (thflags & TH_SYN) { 1952 tp = tcp_drop(tp, ECONNRESET); 1953 rstreason = BANDLIM_UNLIMITED; 1954 goto dropwithreset; 1955 } 1956 1957 /* 1958 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1959 * flag is on (half-synchronized state), then queue data for 1960 * later processing; else drop segment and return. 1961 */ 1962 if (!(thflags & TH_ACK)) { 1963 if (tp->t_state == TCPS_SYN_RECEIVED || 1964 (tp->t_flags & TF_NEEDSYN)) 1965 goto step6; 1966 else 1967 goto drop; 1968 } 1969 1970 /* 1971 * Ack processing. 1972 */ 1973 switch (tp->t_state) { 1974 /* 1975 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1976 * ESTABLISHED state and continue processing. 1977 * The ACK was checked above. 1978 */ 1979 case TCPS_SYN_RECEIVED: 1980 1981 tcpstat.tcps_connects++; 1982 soisconnected(so); 1983 /* Do window scaling? */ 1984 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1985 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1986 tp->rcv_scale = tp->request_r_scale; 1987 /* 1988 * Make transitions: 1989 * SYN-RECEIVED -> ESTABLISHED 1990 * SYN-RECEIVED* -> FIN-WAIT-1 1991 */ 1992 tp->t_starttime = ticks; 1993 if (tp->t_flags & TF_NEEDFIN) { 1994 tp->t_state = TCPS_FIN_WAIT_1; 1995 tp->t_flags &= ~TF_NEEDFIN; 1996 } else { 1997 tcp_established(tp); 1998 } 1999 /* 2000 * If segment contains data or ACK, will call tcp_reass() 2001 * later; if not, do so now to pass queued data to user. 2002 */ 2003 if (tlen == 0 && !(thflags & TH_FIN)) 2004 tcp_reass(tp, NULL, NULL, NULL); 2005 /* fall into ... */ 2006 2007 /* 2008 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2009 * ACKs. If the ack is in the range 2010 * tp->snd_una < th->th_ack <= tp->snd_max 2011 * then advance tp->snd_una to th->th_ack and drop 2012 * data from the retransmission queue. If this ACK reflects 2013 * more up to date window information we update our window information. 2014 */ 2015 case TCPS_ESTABLISHED: 2016 case TCPS_FIN_WAIT_1: 2017 case TCPS_FIN_WAIT_2: 2018 case TCPS_CLOSE_WAIT: 2019 case TCPS_CLOSING: 2020 case TCPS_LAST_ACK: 2021 case TCPS_TIME_WAIT: 2022 2023 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2024 boolean_t maynotdup = FALSE; 2025 2026 if (TCP_DO_SACK(tp)) 2027 tcp_sack_update_scoreboard(tp, &to); 2028 2029 if (tlen != 0 || tiwin != tp->snd_wnd || 2030 ((thflags & TH_FIN) && !(tp->t_flags & TF_SAWFIN))) 2031 maynotdup = TRUE; 2032 2033 if (!tcp_callout_active(tp, tp->tt_rexmt) || 2034 th->th_ack != tp->snd_una) { 2035 if (!maynotdup) 2036 tcpstat.tcps_rcvdupack++; 2037 tp->t_dupacks = 0; 2038 break; 2039 } 2040 2041 #define DELAY_DUPACK \ 2042 do { \ 2043 delayed_dupack = TRUE; \ 2044 th_dupack = th->th_ack; \ 2045 to_flags = to.to_flags; \ 2046 } while (0) 2047 if (maynotdup) { 2048 if (!tcp_do_rfc6675 || 2049 !TCP_DO_SACK(tp) || 2050 (to.to_flags & 2051 (TOF_SACK | TOF_SACK_REDUNDANT)) 2052 != TOF_SACK) { 2053 tp->t_dupacks = 0; 2054 } else { 2055 DELAY_DUPACK; 2056 } 2057 break; 2058 } 2059 if ((thflags & TH_FIN) && !(tp->t_flags & TF_QUEDFIN)) { 2060 /* 2061 * This could happen, if the reassemable 2062 * queue overflew or was drained. Don't 2063 * drop this FIN here; defer the duplicated 2064 * ACK processing until this FIN gets queued. 2065 */ 2066 DELAY_DUPACK; 2067 break; 2068 } 2069 #undef DELAY_DUPACK 2070 2071 if (tcp_recv_dupack(tp, th->th_ack, to.to_flags)) 2072 goto drop; 2073 else 2074 break; 2075 } 2076 2077 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2078 tp->t_dupacks = 0; 2079 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2080 /* 2081 * Detected optimistic ACK attack. 2082 * Force slow-start to de-synchronize attack. 2083 */ 2084 tp->snd_cwnd = tp->t_maxseg; 2085 tp->snd_wacked = 0; 2086 2087 tcpstat.tcps_rcvacktoomuch++; 2088 goto dropafterack; 2089 } 2090 /* 2091 * If we reach this point, ACK is not a duplicate, 2092 * i.e., it ACKs something we sent. 2093 */ 2094 if (tp->t_flags & TF_NEEDSYN) { 2095 /* 2096 * T/TCP: Connection was half-synchronized, and our 2097 * SYN has been ACK'd (so connection is now fully 2098 * synchronized). Go to non-starred state, 2099 * increment snd_una for ACK of SYN, and check if 2100 * we can do window scaling. 2101 */ 2102 tp->t_flags &= ~TF_NEEDSYN; 2103 tp->snd_una++; 2104 /* Do window scaling? */ 2105 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2106 (TF_RCVD_SCALE | TF_REQ_SCALE)) 2107 tp->rcv_scale = tp->request_r_scale; 2108 } 2109 2110 process_ACK: 2111 acked = th->th_ack - tp->snd_una; 2112 tcpstat.tcps_rcvackpack++; 2113 tcpstat.tcps_rcvackbyte += acked; 2114 2115 if (tcp_do_eifel_detect && acked > 0 && 2116 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2117 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 2118 /* Eifel detection applicable. */ 2119 if (to.to_tsecr < tp->t_rexmtTS) { 2120 ++tcpstat.tcps_eifeldetected; 2121 tcp_revert_congestion_state(tp); 2122 if (tp->t_rxtshift != 1 || 2123 ticks >= tp->t_badrxtwin) 2124 ++tcpstat.tcps_rttcantdetect; 2125 } 2126 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2127 /* 2128 * If we just performed our first retransmit, 2129 * and the ACK arrives within our recovery window, 2130 * then it was a mistake to do the retransmit 2131 * in the first place. Recover our original cwnd 2132 * and ssthresh, and proceed to transmit where we 2133 * left off. 2134 */ 2135 tcp_revert_congestion_state(tp); 2136 ++tcpstat.tcps_rttdetected; 2137 } 2138 2139 /* 2140 * If we have a timestamp reply, update smoothed 2141 * round trip time. If no timestamp is present but 2142 * transmit timer is running and timed sequence 2143 * number was acked, update smoothed round trip time. 2144 * Since we now have an rtt measurement, cancel the 2145 * timer backoff (cf., Phil Karn's retransmit alg.). 2146 * Recompute the initial retransmit timer. 2147 * 2148 * Some machines (certain windows boxes) send broken 2149 * timestamp replies during the SYN+ACK phase, ignore 2150 * timestamps of 0. 2151 */ 2152 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2153 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack); 2154 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2155 tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack); 2156 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2157 2158 /* 2159 * If no data (only SYN) was ACK'd, 2160 * skip rest of ACK processing. 2161 */ 2162 if (acked == 0) 2163 goto step6; 2164 2165 /* Stop looking for an acceptable ACK since one was received. */ 2166 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 2167 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 2168 2169 if (acked > so->so_snd.ssb_cc) { 2170 tp->snd_wnd -= so->so_snd.ssb_cc; 2171 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2172 ourfinisacked = TRUE; 2173 } else { 2174 sbdrop(&so->so_snd.sb, acked); 2175 tp->snd_wnd -= acked; 2176 ourfinisacked = FALSE; 2177 } 2178 sowwakeup(so); 2179 2180 /* 2181 * Update window information. 2182 */ 2183 if (acceptable_window_update(tp, th, tiwin)) { 2184 /* keep track of pure window updates */ 2185 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2186 tiwin > tp->snd_wnd) 2187 tcpstat.tcps_rcvwinupd++; 2188 tp->snd_wnd = tiwin; 2189 tp->snd_wl1 = th->th_seq; 2190 tp->snd_wl2 = th->th_ack; 2191 if (tp->snd_wnd > tp->max_sndwnd) 2192 tp->max_sndwnd = tp->snd_wnd; 2193 needoutput = TRUE; 2194 } 2195 2196 tp->snd_una = th->th_ack; 2197 if (TCP_DO_SACK(tp)) 2198 tcp_sack_update_scoreboard(tp, &to); 2199 if (IN_FASTRECOVERY(tp)) { 2200 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2201 EXIT_FASTRECOVERY(tp); 2202 needoutput = TRUE; 2203 /* 2204 * If the congestion window was inflated 2205 * to account for the other side's 2206 * cached packets, retract it. 2207 */ 2208 if (!TCP_DO_SACK(tp)) 2209 tp->snd_cwnd = tp->snd_ssthresh; 2210 2211 /* 2212 * Window inflation should have left us 2213 * with approximately snd_ssthresh outstanding 2214 * data. But, in case we would be inclined 2215 * to send a burst, better do it using 2216 * slow start. 2217 */ 2218 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2219 tp->snd_max + 2 * tp->t_maxseg)) 2220 tp->snd_cwnd = 2221 (tp->snd_max - tp->snd_una) + 2222 2 * tp->t_maxseg; 2223 2224 tp->snd_wacked = 0; 2225 } else { 2226 if (TCP_DO_SACK(tp)) { 2227 tp->snd_max_rexmt = tp->snd_max; 2228 tcp_sack_rexmt(tp, 2229 tp->snd_una == tp->rexmt_high); 2230 } else { 2231 tcp_newreno_partial_ack(tp, th, acked); 2232 } 2233 needoutput = FALSE; 2234 } 2235 } else { 2236 /* 2237 * Open the congestion window. When in slow-start, 2238 * open exponentially: maxseg per packet. Otherwise, 2239 * open linearly: maxseg per window. 2240 */ 2241 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2242 u_int abc_sslimit = 2243 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2244 tp->t_maxseg : 2 * tp->t_maxseg); 2245 2246 /* slow-start */ 2247 tp->snd_cwnd += tcp_do_abc ? 2248 min(acked, abc_sslimit) : tp->t_maxseg; 2249 } else { 2250 /* linear increase */ 2251 tp->snd_wacked += tcp_do_abc ? acked : 2252 tp->t_maxseg; 2253 if (tp->snd_wacked >= tp->snd_cwnd) { 2254 tp->snd_wacked -= tp->snd_cwnd; 2255 tp->snd_cwnd += tp->t_maxseg; 2256 } 2257 } 2258 tp->snd_cwnd = min(tp->snd_cwnd, 2259 TCP_MAXWIN << tp->snd_scale); 2260 tp->snd_recover = th->th_ack - 1; 2261 } 2262 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2263 tp->snd_nxt = tp->snd_una; 2264 2265 /* 2266 * If all outstanding data is acked, stop retransmit 2267 * timer and remember to restart (more output or persist). 2268 * If there is more data to be acked, restart retransmit 2269 * timer, using current (possibly backed-off) value. 2270 */ 2271 if (th->th_ack == tp->snd_max) { 2272 tcp_callout_stop(tp, tp->tt_rexmt); 2273 needoutput = TRUE; 2274 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2275 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2276 tcp_timer_rexmt); 2277 } 2278 2279 switch (tp->t_state) { 2280 /* 2281 * In FIN_WAIT_1 STATE in addition to the processing 2282 * for the ESTABLISHED state if our FIN is now acknowledged 2283 * then enter FIN_WAIT_2. 2284 */ 2285 case TCPS_FIN_WAIT_1: 2286 if (ourfinisacked) { 2287 /* 2288 * If we can't receive any more 2289 * data, then closing user can proceed. 2290 * Starting the timer is contrary to the 2291 * specification, but if we don't get a FIN 2292 * we'll hang forever. 2293 */ 2294 if (so->so_state & SS_CANTRCVMORE) { 2295 soisdisconnected(so); 2296 tcp_callout_reset(tp, tp->tt_2msl, 2297 tp->t_maxidle, tcp_timer_2msl); 2298 } 2299 tp->t_state = TCPS_FIN_WAIT_2; 2300 } 2301 break; 2302 2303 /* 2304 * In CLOSING STATE in addition to the processing for 2305 * the ESTABLISHED state if the ACK acknowledges our FIN 2306 * then enter the TIME-WAIT state, otherwise ignore 2307 * the segment. 2308 */ 2309 case TCPS_CLOSING: 2310 if (ourfinisacked) { 2311 tp->t_state = TCPS_TIME_WAIT; 2312 tcp_canceltimers(tp); 2313 tcp_callout_reset(tp, tp->tt_2msl, 2314 2 * tcp_rmx_msl(tp), 2315 tcp_timer_2msl); 2316 soisdisconnected(so); 2317 } 2318 break; 2319 2320 /* 2321 * In LAST_ACK, we may still be waiting for data to drain 2322 * and/or to be acked, as well as for the ack of our FIN. 2323 * If our FIN is now acknowledged, delete the TCB, 2324 * enter the closed state and return. 2325 */ 2326 case TCPS_LAST_ACK: 2327 if (ourfinisacked) { 2328 tp = tcp_close(tp); 2329 goto drop; 2330 } 2331 break; 2332 2333 /* 2334 * In TIME_WAIT state the only thing that should arrive 2335 * is a retransmission of the remote FIN. Acknowledge 2336 * it and restart the finack timer. 2337 */ 2338 case TCPS_TIME_WAIT: 2339 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2340 tcp_timer_2msl); 2341 goto dropafterack; 2342 } 2343 } 2344 2345 step6: 2346 /* 2347 * Update window information. 2348 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2349 */ 2350 if ((thflags & TH_ACK) && 2351 acceptable_window_update(tp, th, tiwin)) { 2352 /* keep track of pure window updates */ 2353 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2354 tiwin > tp->snd_wnd) 2355 tcpstat.tcps_rcvwinupd++; 2356 tp->snd_wnd = tiwin; 2357 tp->snd_wl1 = th->th_seq; 2358 tp->snd_wl2 = th->th_ack; 2359 if (tp->snd_wnd > tp->max_sndwnd) 2360 tp->max_sndwnd = tp->snd_wnd; 2361 needoutput = TRUE; 2362 } 2363 2364 /* 2365 * Process segments with URG. 2366 */ 2367 if ((thflags & TH_URG) && th->th_urp && 2368 !TCPS_HAVERCVDFIN(tp->t_state)) { 2369 /* 2370 * This is a kludge, but if we receive and accept 2371 * random urgent pointers, we'll crash in 2372 * soreceive. It's hard to imagine someone 2373 * actually wanting to send this much urgent data. 2374 */ 2375 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2376 th->th_urp = 0; /* XXX */ 2377 thflags &= ~TH_URG; /* XXX */ 2378 goto dodata; /* XXX */ 2379 } 2380 /* 2381 * If this segment advances the known urgent pointer, 2382 * then mark the data stream. This should not happen 2383 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2384 * a FIN has been received from the remote side. 2385 * In these states we ignore the URG. 2386 * 2387 * According to RFC961 (Assigned Protocols), 2388 * the urgent pointer points to the last octet 2389 * of urgent data. We continue, however, 2390 * to consider it to indicate the first octet 2391 * of data past the urgent section as the original 2392 * spec states (in one of two places). 2393 */ 2394 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2395 tp->rcv_up = th->th_seq + th->th_urp; 2396 so->so_oobmark = so->so_rcv.ssb_cc + 2397 (tp->rcv_up - tp->rcv_nxt) - 1; 2398 if (so->so_oobmark == 0) 2399 sosetstate(so, SS_RCVATMARK); 2400 sohasoutofband(so); 2401 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2402 } 2403 /* 2404 * Remove out of band data so doesn't get presented to user. 2405 * This can happen independent of advancing the URG pointer, 2406 * but if two URG's are pending at once, some out-of-band 2407 * data may creep in... ick. 2408 */ 2409 if (th->th_urp <= (u_long)tlen && 2410 !(so->so_options & SO_OOBINLINE)) { 2411 /* hdr drop is delayed */ 2412 tcp_pulloutofband(so, th, m, drop_hdrlen); 2413 } 2414 } else { 2415 /* 2416 * If no out of band data is expected, 2417 * pull receive urgent pointer along 2418 * with the receive window. 2419 */ 2420 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2421 tp->rcv_up = tp->rcv_nxt; 2422 } 2423 2424 dodata: /* XXX */ 2425 /* 2426 * Process the segment text, merging it into the TCP sequencing queue, 2427 * and arranging for acknowledgment of receipt if necessary. 2428 * This process logically involves adjusting tp->rcv_wnd as data 2429 * is presented to the user (this happens in tcp_usrreq.c, 2430 * case PRU_RCVD). If a FIN has already been received on this 2431 * connection then we just ignore the text. 2432 */ 2433 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2434 if (thflags & TH_FIN) 2435 tp->t_flags |= TF_SAWFIN; 2436 m_adj(m, drop_hdrlen); /* delayed header drop */ 2437 /* 2438 * Insert segment which includes th into TCP reassembly queue 2439 * with control block tp. Set thflags to whether reassembly now 2440 * includes a segment with FIN. This handles the common case 2441 * inline (segment is the next to be received on an established 2442 * connection, and the queue is empty), avoiding linkage into 2443 * and removal from the queue and repetition of various 2444 * conversions. 2445 * Set DELACK for segments received in order, but ack 2446 * immediately when segments are out of order (so 2447 * fast retransmit can work). 2448 */ 2449 if (th->th_seq == tp->rcv_nxt && 2450 TAILQ_EMPTY(&tp->t_segq) && 2451 TCPS_HAVEESTABLISHED(tp->t_state)) { 2452 if (thflags & TH_FIN) 2453 tp->t_flags |= TF_QUEDFIN; 2454 if (DELAY_ACK(tp)) { 2455 tcp_callout_reset(tp, tp->tt_delack, 2456 tcp_delacktime, tcp_timer_delack); 2457 } else { 2458 tp->t_flags |= TF_ACKNOW; 2459 } 2460 tp->rcv_nxt += tlen; 2461 thflags = th->th_flags & TH_FIN; 2462 tcpstat.tcps_rcvpack++; 2463 tcpstat.tcps_rcvbyte += tlen; 2464 ND6_HINT(tp); 2465 if (so->so_state & SS_CANTRCVMORE) { 2466 m_freem(m); 2467 } else { 2468 lwkt_gettoken(&so->so_rcv.ssb_token); 2469 ssb_appendstream(&so->so_rcv, m); 2470 lwkt_reltoken(&so->so_rcv.ssb_token); 2471 } 2472 sorwakeup(so); 2473 } else { 2474 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 2475 /* Initialize SACK report block. */ 2476 tp->reportblk.rblk_start = th->th_seq; 2477 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 2478 th->th_seq + tlen, thflags); 2479 } 2480 thflags = tcp_reass(tp, th, &tlen, m); 2481 tp->t_flags |= TF_ACKNOW; 2482 } 2483 2484 /* 2485 * Note the amount of data that peer has sent into 2486 * our window, in order to estimate the sender's 2487 * buffer size. 2488 */ 2489 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2490 } else { 2491 m_freem(m); 2492 thflags &= ~TH_FIN; 2493 } 2494 2495 /* 2496 * If FIN is received ACK the FIN and let the user know 2497 * that the connection is closing. 2498 */ 2499 if (thflags & TH_FIN) { 2500 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2501 socantrcvmore(so); 2502 /* 2503 * If connection is half-synchronized 2504 * (ie NEEDSYN flag on) then delay ACK, 2505 * so it may be piggybacked when SYN is sent. 2506 * Otherwise, since we received a FIN then no 2507 * more input can be expected, send ACK now. 2508 */ 2509 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2510 tcp_callout_reset(tp, tp->tt_delack, 2511 tcp_delacktime, tcp_timer_delack); 2512 } else { 2513 tp->t_flags |= TF_ACKNOW; 2514 } 2515 tp->rcv_nxt++; 2516 } 2517 2518 switch (tp->t_state) { 2519 /* 2520 * In SYN_RECEIVED and ESTABLISHED STATES 2521 * enter the CLOSE_WAIT state. 2522 */ 2523 case TCPS_SYN_RECEIVED: 2524 tp->t_starttime = ticks; 2525 /*FALLTHROUGH*/ 2526 case TCPS_ESTABLISHED: 2527 tp->t_state = TCPS_CLOSE_WAIT; 2528 break; 2529 2530 /* 2531 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2532 * enter the CLOSING state. 2533 */ 2534 case TCPS_FIN_WAIT_1: 2535 tp->t_state = TCPS_CLOSING; 2536 break; 2537 2538 /* 2539 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2540 * starting the time-wait timer, turning off the other 2541 * standard timers. 2542 */ 2543 case TCPS_FIN_WAIT_2: 2544 tp->t_state = TCPS_TIME_WAIT; 2545 tcp_canceltimers(tp); 2546 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2547 tcp_timer_2msl); 2548 soisdisconnected(so); 2549 break; 2550 2551 /* 2552 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2553 */ 2554 case TCPS_TIME_WAIT: 2555 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2556 tcp_timer_2msl); 2557 break; 2558 } 2559 } 2560 2561 #ifdef TCPDEBUG 2562 if (so->so_options & SO_DEBUG) 2563 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2564 #endif 2565 2566 /* 2567 * Delayed duplicated ACK processing 2568 */ 2569 if (delayed_dupack && tcp_recv_dupack(tp, th_dupack, to_flags)) 2570 needoutput = FALSE; 2571 2572 /* 2573 * Return any desired output. 2574 */ 2575 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2576 tcp_output(tp); 2577 tcp_sack_report_cleanup(tp); 2578 return(IPPROTO_DONE); 2579 2580 dropafterack: 2581 /* 2582 * Generate an ACK dropping incoming segment if it occupies 2583 * sequence space, where the ACK reflects our state. 2584 * 2585 * We can now skip the test for the RST flag since all 2586 * paths to this code happen after packets containing 2587 * RST have been dropped. 2588 * 2589 * In the SYN-RECEIVED state, don't send an ACK unless the 2590 * segment we received passes the SYN-RECEIVED ACK test. 2591 * If it fails send a RST. This breaks the loop in the 2592 * "LAND" DoS attack, and also prevents an ACK storm 2593 * between two listening ports that have been sent forged 2594 * SYN segments, each with the source address of the other. 2595 */ 2596 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2597 (SEQ_GT(tp->snd_una, th->th_ack) || 2598 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2599 rstreason = BANDLIM_RST_OPENPORT; 2600 goto dropwithreset; 2601 } 2602 #ifdef TCPDEBUG 2603 if (so->so_options & SO_DEBUG) 2604 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2605 #endif 2606 m_freem(m); 2607 tp->t_flags |= TF_ACKNOW; 2608 tcp_output(tp); 2609 tcp_sack_report_cleanup(tp); 2610 return(IPPROTO_DONE); 2611 2612 dropwithreset: 2613 /* 2614 * Generate a RST, dropping incoming segment. 2615 * Make ACK acceptable to originator of segment. 2616 * Don't bother to respond if destination was broadcast/multicast. 2617 */ 2618 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2619 goto drop; 2620 if (isipv6) { 2621 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2622 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2623 goto drop; 2624 } else { 2625 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2626 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2627 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2628 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2629 goto drop; 2630 } 2631 /* IPv6 anycast check is done at tcp6_input() */ 2632 2633 /* 2634 * Perform bandwidth limiting. 2635 */ 2636 #ifdef ICMP_BANDLIM 2637 if (badport_bandlim(rstreason) < 0) 2638 goto drop; 2639 #endif 2640 2641 #ifdef TCPDEBUG 2642 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2643 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2644 #endif 2645 if (thflags & TH_ACK) 2646 /* mtod() below is safe as long as hdr dropping is delayed */ 2647 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2648 TH_RST); 2649 else { 2650 if (thflags & TH_SYN) 2651 tlen++; 2652 /* mtod() below is safe as long as hdr dropping is delayed */ 2653 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2654 (tcp_seq)0, TH_RST | TH_ACK); 2655 } 2656 if (tp != NULL) 2657 tcp_sack_report_cleanup(tp); 2658 return(IPPROTO_DONE); 2659 2660 drop: 2661 /* 2662 * Drop space held by incoming segment and return. 2663 */ 2664 #ifdef TCPDEBUG 2665 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2666 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2667 #endif 2668 m_freem(m); 2669 if (tp != NULL) 2670 tcp_sack_report_cleanup(tp); 2671 return(IPPROTO_DONE); 2672 } 2673 2674 /* 2675 * Parse TCP options and place in tcpopt. 2676 */ 2677 static void 2678 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn, 2679 tcp_seq ack) 2680 { 2681 int opt, optlen, i; 2682 2683 to->to_flags = 0; 2684 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2685 opt = cp[0]; 2686 if (opt == TCPOPT_EOL) 2687 break; 2688 if (opt == TCPOPT_NOP) 2689 optlen = 1; 2690 else { 2691 if (cnt < 2) 2692 break; 2693 optlen = cp[1]; 2694 if (optlen < 2 || optlen > cnt) 2695 break; 2696 } 2697 switch (opt) { 2698 case TCPOPT_MAXSEG: 2699 if (optlen != TCPOLEN_MAXSEG) 2700 continue; 2701 if (!is_syn) 2702 continue; 2703 to->to_flags |= TOF_MSS; 2704 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2705 to->to_mss = ntohs(to->to_mss); 2706 break; 2707 case TCPOPT_WINDOW: 2708 if (optlen != TCPOLEN_WINDOW) 2709 continue; 2710 if (!is_syn) 2711 continue; 2712 to->to_flags |= TOF_SCALE; 2713 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2714 break; 2715 case TCPOPT_TIMESTAMP: 2716 if (optlen != TCPOLEN_TIMESTAMP) 2717 continue; 2718 to->to_flags |= TOF_TS; 2719 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2720 to->to_tsval = ntohl(to->to_tsval); 2721 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2722 to->to_tsecr = ntohl(to->to_tsecr); 2723 /* 2724 * If echoed timestamp is later than the current time, 2725 * fall back to non RFC1323 RTT calculation. 2726 */ 2727 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2728 to->to_tsecr = 0; 2729 break; 2730 case TCPOPT_SACK_PERMITTED: 2731 if (optlen != TCPOLEN_SACK_PERMITTED) 2732 continue; 2733 if (!is_syn) 2734 continue; 2735 to->to_flags |= TOF_SACK_PERMITTED; 2736 break; 2737 case TCPOPT_SACK: 2738 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2739 continue; 2740 to->to_nsackblocks = (optlen - 2) / 8; 2741 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2742 to->to_flags |= TOF_SACK; 2743 for (i = 0; i < to->to_nsackblocks; i++) { 2744 struct raw_sackblock *r = &to->to_sackblocks[i]; 2745 2746 r->rblk_start = ntohl(r->rblk_start); 2747 r->rblk_end = ntohl(r->rblk_end); 2748 2749 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { 2750 /* 2751 * Invalid SACK block; discard all 2752 * SACK blocks 2753 */ 2754 tcpstat.tcps_rcvbadsackopt++; 2755 to->to_nsackblocks = 0; 2756 to->to_sackblocks = NULL; 2757 to->to_flags &= ~TOF_SACK; 2758 break; 2759 } 2760 } 2761 if ((to->to_flags & TOF_SACK) && 2762 tcp_sack_ndsack_blocks(to->to_sackblocks, 2763 to->to_nsackblocks, ack)) 2764 to->to_flags |= TOF_DSACK; 2765 break; 2766 #ifdef TCP_SIGNATURE 2767 /* 2768 * XXX In order to reply to a host which has set the 2769 * TCP_SIGNATURE option in its initial SYN, we have to 2770 * record the fact that the option was observed here 2771 * for the syncache code to perform the correct response. 2772 */ 2773 case TCPOPT_SIGNATURE: 2774 if (optlen != TCPOLEN_SIGNATURE) 2775 continue; 2776 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2777 break; 2778 #endif /* TCP_SIGNATURE */ 2779 default: 2780 continue; 2781 } 2782 } 2783 } 2784 2785 /* 2786 * Pull out of band byte out of a segment so 2787 * it doesn't appear in the user's data queue. 2788 * It is still reflected in the segment length for 2789 * sequencing purposes. 2790 * "off" is the delayed to be dropped hdrlen. 2791 */ 2792 static void 2793 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2794 { 2795 int cnt = off + th->th_urp - 1; 2796 2797 while (cnt >= 0) { 2798 if (m->m_len > cnt) { 2799 char *cp = mtod(m, caddr_t) + cnt; 2800 struct tcpcb *tp = sototcpcb(so); 2801 2802 tp->t_iobc = *cp; 2803 tp->t_oobflags |= TCPOOB_HAVEDATA; 2804 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2805 m->m_len--; 2806 if (m->m_flags & M_PKTHDR) 2807 m->m_pkthdr.len--; 2808 return; 2809 } 2810 cnt -= m->m_len; 2811 m = m->m_next; 2812 if (m == NULL) 2813 break; 2814 } 2815 panic("tcp_pulloutofband"); 2816 } 2817 2818 /* 2819 * Collect new round-trip time estimate 2820 * and update averages and current timeout. 2821 */ 2822 static void 2823 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack) 2824 { 2825 int rebaserto = 0; 2826 2827 tcpstat.tcps_rttupdated++; 2828 tp->t_rttupdated++; 2829 if ((tp->rxt_flags & TRXT_F_REBASERTO) && 2830 SEQ_GT(ack, tp->snd_max_prev)) { 2831 #ifdef DEBUG_EIFEL_RESPONSE 2832 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ", 2833 tp->t_srtt_prev, tp->t_rttvar_prev, 2834 tp->t_srtt, tp->t_rttvar); 2835 #endif 2836 2837 tcpstat.tcps_eifelresponse++; 2838 rebaserto = 1; 2839 tp->rxt_flags &= ~TRXT_F_REBASERTO; 2840 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT)); 2841 tp->t_rttvar = max(tp->t_rttvar_prev, 2842 (rtt << (TCP_RTTVAR_SHIFT - 1))); 2843 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2844 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2845 2846 #ifdef DEBUG_EIFEL_RESPONSE 2847 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar); 2848 #endif 2849 } else if (tp->t_srtt != 0) { 2850 int delta; 2851 2852 /* 2853 * srtt is stored as fixed point with 5 bits after the 2854 * binary point (i.e., scaled by 8). The following magic 2855 * is equivalent to the smoothing algorithm in rfc793 with 2856 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2857 * point). Adjust rtt to origin 0. 2858 */ 2859 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2860 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2861 2862 if ((tp->t_srtt += delta) <= 0) 2863 tp->t_srtt = 1; 2864 2865 /* 2866 * We accumulate a smoothed rtt variance (actually, a 2867 * smoothed mean difference), then set the retransmit 2868 * timer to smoothed rtt + 4 times the smoothed variance. 2869 * rttvar is stored as fixed point with 4 bits after the 2870 * binary point (scaled by 16). The following is 2871 * equivalent to rfc793 smoothing with an alpha of .75 2872 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2873 * rfc793's wired-in beta. 2874 */ 2875 if (delta < 0) 2876 delta = -delta; 2877 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2878 if ((tp->t_rttvar += delta) <= 0) 2879 tp->t_rttvar = 1; 2880 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2881 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2882 } else { 2883 /* 2884 * No rtt measurement yet - use the unsmoothed rtt. 2885 * Set the variance to half the rtt (so our first 2886 * retransmit happens at 3*rtt). 2887 */ 2888 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2889 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2890 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2891 } 2892 tp->t_rtttime = 0; 2893 tp->t_rxtshift = 0; 2894 2895 #ifdef DEBUG_EIFEL_RESPONSE 2896 if (rebaserto) { 2897 kprintf("| rxtcur prev %d, old %d, ", 2898 tp->t_rxtcur_prev, tp->t_rxtcur); 2899 } 2900 #endif 2901 2902 /* 2903 * the retransmit should happen at rtt + 4 * rttvar. 2904 * Because of the way we do the smoothing, srtt and rttvar 2905 * will each average +1/2 tick of bias. When we compute 2906 * the retransmit timer, we want 1/2 tick of rounding and 2907 * 1 extra tick because of +-1/2 tick uncertainty in the 2908 * firing of the timer. The bias will give us exactly the 2909 * 1.5 tick we need. But, because the bias is 2910 * statistical, we have to test that we don't drop below 2911 * the minimum feasible timer (which is 2 ticks). 2912 */ 2913 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2914 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2915 2916 if (rebaserto) { 2917 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) { 2918 /* 2919 * RFC4015 requires that the new RTO is at least 2920 * 2*G (tcp_eifel_rtoinc) greater then the RTO 2921 * (t_rxtcur_prev) when the spurious retransmit 2922 * timeout happens. 2923 * 2924 * The above condition could be true, if the SRTT 2925 * and RTTVAR used to calculate t_rxtcur_prev 2926 * resulted in a value less than t_rttmin. So 2927 * simply increasing SRTT by tcp_eifel_rtoinc when 2928 * preparing for the Eifel response could not ensure 2929 * that the new RTO will be tcp_eifel_rtoinc greater 2930 * t_rxtcur_prev. 2931 */ 2932 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc; 2933 } 2934 #ifdef DEBUG_EIFEL_RESPONSE 2935 kprintf("new %d\n", tp->t_rxtcur); 2936 #endif 2937 } 2938 2939 /* 2940 * We received an ack for a packet that wasn't retransmitted; 2941 * it is probably safe to discard any error indications we've 2942 * received recently. This isn't quite right, but close enough 2943 * for now (a route might have failed after we sent a segment, 2944 * and the return path might not be symmetrical). 2945 */ 2946 tp->t_softerror = 0; 2947 } 2948 2949 /* 2950 * Determine a reasonable value for maxseg size. 2951 * If the route is known, check route for mtu. 2952 * If none, use an mss that can be handled on the outgoing 2953 * interface without forcing IP to fragment; if bigger than 2954 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2955 * to utilize large mbufs. If no route is found, route has no mtu, 2956 * or the destination isn't local, use a default, hopefully conservative 2957 * size (usually 512 or the default IP max size, but no more than the mtu 2958 * of the interface), as we can't discover anything about intervening 2959 * gateways or networks. We also initialize the congestion/slow start 2960 * window to be a single segment if the destination isn't local. 2961 * While looking at the routing entry, we also initialize other path-dependent 2962 * parameters from pre-set or cached values in the routing entry. 2963 * 2964 * Also take into account the space needed for options that we 2965 * send regularly. Make maxseg shorter by that amount to assure 2966 * that we can send maxseg amount of data even when the options 2967 * are present. Store the upper limit of the length of options plus 2968 * data in maxopd. 2969 * 2970 * NOTE that this routine is only called when we process an incoming 2971 * segment, for outgoing segments only tcp_mssopt is called. 2972 */ 2973 void 2974 tcp_mss(struct tcpcb *tp, int offer) 2975 { 2976 struct rtentry *rt; 2977 struct ifnet *ifp; 2978 int rtt, mss; 2979 u_long bufsize; 2980 struct inpcb *inp = tp->t_inpcb; 2981 struct socket *so; 2982 #ifdef INET6 2983 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2984 size_t min_protoh = isipv6 ? 2985 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2986 sizeof(struct tcpiphdr); 2987 #else 2988 const boolean_t isipv6 = FALSE; 2989 const size_t min_protoh = sizeof(struct tcpiphdr); 2990 #endif 2991 2992 if (isipv6) 2993 rt = tcp_rtlookup6(&inp->inp_inc); 2994 else 2995 rt = tcp_rtlookup(&inp->inp_inc); 2996 if (rt == NULL) { 2997 tp->t_maxopd = tp->t_maxseg = 2998 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2999 return; 3000 } 3001 ifp = rt->rt_ifp; 3002 so = inp->inp_socket; 3003 3004 /* 3005 * Offer == 0 means that there was no MSS on the SYN segment, 3006 * in this case we use either the interface mtu or tcp_mssdflt. 3007 * 3008 * An offer which is too large will be cut down later. 3009 */ 3010 if (offer == 0) { 3011 if (isipv6) { 3012 if (in6_localaddr(&inp->in6p_faddr)) { 3013 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 3014 min_protoh; 3015 } else { 3016 offer = tcp_v6mssdflt; 3017 } 3018 } else { 3019 if (in_localaddr(inp->inp_faddr)) 3020 offer = ifp->if_mtu - min_protoh; 3021 else 3022 offer = tcp_mssdflt; 3023 } 3024 } 3025 3026 /* 3027 * Prevent DoS attack with too small MSS. Round up 3028 * to at least minmss. 3029 * 3030 * Sanity check: make sure that maxopd will be large 3031 * enough to allow some data on segments even is the 3032 * all the option space is used (40bytes). Otherwise 3033 * funny things may happen in tcp_output. 3034 */ 3035 offer = max(offer, tcp_minmss); 3036 offer = max(offer, 64); 3037 3038 rt->rt_rmx.rmx_mssopt = offer; 3039 3040 /* 3041 * While we're here, check if there's an initial rtt 3042 * or rttvar. Convert from the route-table units 3043 * to scaled multiples of the slow timeout timer. 3044 */ 3045 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 3046 /* 3047 * XXX the lock bit for RTT indicates that the value 3048 * is also a minimum value; this is subject to time. 3049 */ 3050 if (rt->rt_rmx.rmx_locks & RTV_RTT) 3051 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 3052 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 3053 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3054 tcpstat.tcps_usedrtt++; 3055 if (rt->rt_rmx.rmx_rttvar) { 3056 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 3057 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 3058 tcpstat.tcps_usedrttvar++; 3059 } else { 3060 /* default variation is +- 1 rtt */ 3061 tp->t_rttvar = 3062 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3063 } 3064 TCPT_RANGESET(tp->t_rxtcur, 3065 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3066 tp->t_rttmin, TCPTV_REXMTMAX); 3067 } 3068 3069 /* 3070 * if there's an mtu associated with the route, use it 3071 * else, use the link mtu. Take the smaller of mss or offer 3072 * as our final mss. 3073 */ 3074 if (rt->rt_rmx.rmx_mtu) { 3075 mss = rt->rt_rmx.rmx_mtu - min_protoh; 3076 } else { 3077 if (isipv6) 3078 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 3079 else 3080 mss = ifp->if_mtu - min_protoh; 3081 } 3082 mss = min(mss, offer); 3083 3084 /* 3085 * maxopd stores the maximum length of data AND options 3086 * in a segment; maxseg is the amount of data in a normal 3087 * segment. We need to store this value (maxopd) apart 3088 * from maxseg, because now every segment carries options 3089 * and thus we normally have somewhat less data in segments. 3090 */ 3091 tp->t_maxopd = mss; 3092 3093 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3094 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3095 mss -= TCPOLEN_TSTAMP_APPA; 3096 3097 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3098 if (mss > MCLBYTES) 3099 mss &= ~(MCLBYTES-1); 3100 #else 3101 if (mss > MCLBYTES) 3102 mss = mss / MCLBYTES * MCLBYTES; 3103 #endif 3104 /* 3105 * If there's a pipesize, change the socket buffer 3106 * to that size. Make the socket buffers an integral 3107 * number of mss units; if the mss is larger than 3108 * the socket buffer, decrease the mss. 3109 */ 3110 #ifdef RTV_SPIPE 3111 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3112 #endif 3113 bufsize = so->so_snd.ssb_hiwat; 3114 if (bufsize < mss) 3115 mss = bufsize; 3116 else { 3117 bufsize = roundup(bufsize, mss); 3118 if (bufsize > sb_max) 3119 bufsize = sb_max; 3120 if (bufsize > so->so_snd.ssb_hiwat) 3121 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3122 } 3123 tp->t_maxseg = mss; 3124 3125 #ifdef RTV_RPIPE 3126 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3127 #endif 3128 bufsize = so->so_rcv.ssb_hiwat; 3129 if (bufsize > mss) { 3130 bufsize = roundup(bufsize, mss); 3131 if (bufsize > sb_max) 3132 bufsize = sb_max; 3133 if (bufsize > so->so_rcv.ssb_hiwat) { 3134 lwkt_gettoken(&so->so_rcv.ssb_token); 3135 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3136 lwkt_reltoken(&so->so_rcv.ssb_token); 3137 } 3138 } 3139 3140 /* 3141 * Set the slow-start flight size 3142 * 3143 * NOTE: t_maxseg must have been configured! 3144 */ 3145 tp->snd_cwnd = tcp_initial_window(tp); 3146 3147 if (rt->rt_rmx.rmx_ssthresh) { 3148 /* 3149 * There's some sort of gateway or interface 3150 * buffer limit on the path. Use this to set 3151 * the slow start threshhold, but set the 3152 * threshold to no less than 2*mss. 3153 */ 3154 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3155 tcpstat.tcps_usedssthresh++; 3156 } 3157 } 3158 3159 /* 3160 * Determine the MSS option to send on an outgoing SYN. 3161 */ 3162 int 3163 tcp_mssopt(struct tcpcb *tp) 3164 { 3165 struct rtentry *rt; 3166 #ifdef INET6 3167 boolean_t isipv6 = 3168 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3169 int min_protoh = isipv6 ? 3170 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3171 sizeof(struct tcpiphdr); 3172 #else 3173 const boolean_t isipv6 = FALSE; 3174 const size_t min_protoh = sizeof(struct tcpiphdr); 3175 #endif 3176 3177 if (isipv6) 3178 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3179 else 3180 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3181 if (rt == NULL) 3182 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3183 3184 return (rt->rt_ifp->if_mtu - min_protoh); 3185 } 3186 3187 /* 3188 * When a partial ack arrives, force the retransmission of the 3189 * next unacknowledged segment. Do not exit Fast Recovery. 3190 * 3191 * Implement the Slow-but-Steady variant of NewReno by restarting the 3192 * the retransmission timer. Turn it off here so it can be restarted 3193 * later in tcp_output(). 3194 */ 3195 static void 3196 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3197 { 3198 tcp_seq old_snd_nxt = tp->snd_nxt; 3199 u_long ocwnd = tp->snd_cwnd; 3200 3201 tcp_callout_stop(tp, tp->tt_rexmt); 3202 tp->t_rtttime = 0; 3203 tp->snd_nxt = th->th_ack; 3204 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3205 tp->snd_cwnd = tp->t_maxseg; 3206 tp->t_flags |= TF_ACKNOW; 3207 tcp_output(tp); 3208 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3209 tp->snd_nxt = old_snd_nxt; 3210 /* partial window deflation */ 3211 if (ocwnd > acked) 3212 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3213 else 3214 tp->snd_cwnd = tp->t_maxseg; 3215 } 3216 3217 /* 3218 * In contrast to the Slow-but-Steady NewReno variant, 3219 * we do not reset the retransmission timer for SACK retransmissions, 3220 * except when retransmitting snd_una. 3221 */ 3222 static void 3223 tcp_sack_rexmt(struct tcpcb *tp, boolean_t force) 3224 { 3225 tcp_seq old_snd_nxt = tp->snd_nxt; 3226 u_long ocwnd = tp->snd_cwnd; 3227 uint32_t pipe; 3228 int nseg = 0; /* consecutive new segments */ 3229 int nseg_rexmt = 0; /* retransmitted segments */ 3230 int maxrexmt = 0; 3231 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3232 3233 if (force) { 3234 uint32_t unsacked = tcp_sack_first_unsacked_len(tp); 3235 3236 /* 3237 * Try to fill the first hole in the receiver's 3238 * reassemble queue. 3239 */ 3240 maxrexmt = howmany(unsacked, tp->t_maxseg); 3241 if (maxrexmt > tcp_force_sackrxt) 3242 maxrexmt = tcp_force_sackrxt; 3243 } 3244 3245 tp->t_rtttime = 0; 3246 pipe = tcp_sack_compute_pipe(tp); 3247 while (((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg 3248 || (force && nseg_rexmt < maxrexmt && nseg == 0)) && 3249 (!tcp_do_smartsack || nseg < MAXBURST)) { 3250 tcp_seq old_snd_max, old_rexmt_high, nextrexmt; 3251 uint32_t sent, seglen; 3252 boolean_t rescue; 3253 int error; 3254 3255 old_rexmt_high = tp->rexmt_high; 3256 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) { 3257 tp->rexmt_high = old_rexmt_high; 3258 break; 3259 } 3260 3261 /* 3262 * If the next tranmission is a rescue retranmission, 3263 * we check whether we have already sent some data 3264 * (either new segments or retransmitted segments) 3265 * into the the network or not. Since the idea of rescue 3266 * retransmission is to sustain ACK clock, as long as 3267 * some segments are in the network, ACK clock will be 3268 * kept ticking. 3269 */ 3270 if (rescue && (nseg_rexmt > 0 || nseg > 0)) { 3271 tp->rexmt_high = old_rexmt_high; 3272 break; 3273 } 3274 3275 if (nextrexmt == tp->snd_max) 3276 ++nseg; 3277 else 3278 ++nseg_rexmt; 3279 tp->snd_nxt = nextrexmt; 3280 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3281 old_snd_max = tp->snd_max; 3282 if (nextrexmt == tp->snd_una) 3283 tcp_callout_stop(tp, tp->tt_rexmt); 3284 tp->t_flags |= TF_XMITNOW; 3285 error = tcp_output(tp); 3286 if (error != 0) { 3287 tp->rexmt_high = old_rexmt_high; 3288 break; 3289 } 3290 sent = tp->snd_nxt - nextrexmt; 3291 if (sent <= 0) { 3292 tp->rexmt_high = old_rexmt_high; 3293 break; 3294 } 3295 pipe += sent; 3296 tcpstat.tcps_sndsackpack++; 3297 tcpstat.tcps_sndsackbyte += sent; 3298 3299 if (rescue) { 3300 tcpstat.tcps_sackrescue++; 3301 tp->rexmt_rescue = tp->snd_nxt; 3302 tp->sack_flags |= TSACK_F_SACKRESCUED; 3303 break; 3304 } 3305 if (SEQ_LT(nextrexmt, old_snd_max) && 3306 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) { 3307 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3308 if (tcp_aggressive_rescuesack && 3309 (tp->sack_flags & TSACK_F_SACKRESCUED) && 3310 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) { 3311 /* Drag RescueRxt along with HighRxt */ 3312 tp->rexmt_rescue = tp->rexmt_high; 3313 } 3314 } 3315 } 3316 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3317 tp->snd_nxt = old_snd_nxt; 3318 tp->snd_cwnd = ocwnd; 3319 } 3320 3321 /* 3322 * Return TRUE, if some new segments are sent 3323 */ 3324 static boolean_t 3325 tcp_sack_limitedxmit(struct tcpcb *tp) 3326 { 3327 tcp_seq oldsndnxt = tp->snd_nxt; 3328 tcp_seq oldsndmax = tp->snd_max; 3329 u_long ocwnd = tp->snd_cwnd; 3330 uint32_t pipe, sent; 3331 boolean_t ret = FALSE; 3332 tcp_seq_diff_t cwnd_left; 3333 tcp_seq next; 3334 3335 tp->rexmt_high = tp->snd_una - 1; 3336 pipe = tcp_sack_compute_pipe(tp); 3337 cwnd_left = (tcp_seq_diff_t)(ocwnd - pipe); 3338 if (cwnd_left < (tcp_seq_diff_t)tp->t_maxseg) 3339 return FALSE; 3340 3341 next = tp->snd_nxt = tp->snd_max; 3342 tp->snd_cwnd = tp->snd_nxt - tp->snd_una + 3343 rounddown(cwnd_left, tp->t_maxseg); 3344 3345 tp->t_flags |= TF_XMITNOW; 3346 tcp_output(tp); 3347 3348 sent = tp->snd_nxt - next; 3349 if (sent > 0) { 3350 tcpstat.tcps_sndlimited += howmany(sent, tp->t_maxseg); 3351 ret = TRUE; 3352 } 3353 3354 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3355 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3356 ("snd_una moved in other threads")); 3357 tp->snd_nxt = oldsndnxt; 3358 } 3359 tp->snd_cwnd = ocwnd; 3360 3361 if (ret && TCP_DO_NCR(tp)) 3362 tcp_ncr_update_rxtthresh(tp); 3363 3364 return ret; 3365 } 3366 3367 /* 3368 * Reset idle time and keep-alive timer, typically called when a valid 3369 * tcp packet is received but may also be called when FASTKEEP is set 3370 * to prevent the previous long-timeout from calculating to a drop. 3371 * 3372 * Only update t_rcvtime for non-SYN packets. 3373 * 3374 * Handle the case where one side thinks the connection is established 3375 * but the other side has, say, rebooted without cleaning out the 3376 * connection. The SYNs could be construed as an attack and wind 3377 * up ignored, but in case it isn't an attack we can validate the 3378 * connection by forcing a keepalive. 3379 */ 3380 void 3381 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3382 { 3383 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3384 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3385 tp->t_flags |= TF_KEEPALIVE; 3386 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3387 tcp_timer_keep); 3388 } else { 3389 tp->t_rcvtime = ticks; 3390 tp->t_flags &= ~TF_KEEPALIVE; 3391 tcp_callout_reset(tp, tp->tt_keep, 3392 tp->t_keepidle, 3393 tcp_timer_keep); 3394 } 3395 } 3396 } 3397 3398 static int 3399 tcp_rmx_msl(const struct tcpcb *tp) 3400 { 3401 struct rtentry *rt; 3402 struct inpcb *inp = tp->t_inpcb; 3403 int msl; 3404 #ifdef INET6 3405 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3406 #else 3407 const boolean_t isipv6 = FALSE; 3408 #endif 3409 3410 if (isipv6) 3411 rt = tcp_rtlookup6(&inp->inp_inc); 3412 else 3413 rt = tcp_rtlookup(&inp->inp_inc); 3414 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3415 return tcp_msl; 3416 3417 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3418 if (msl == 0) 3419 msl = 1; 3420 3421 return msl; 3422 } 3423 3424 static void 3425 tcp_established(struct tcpcb *tp) 3426 { 3427 tp->t_state = TCPS_ESTABLISHED; 3428 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); 3429 3430 if (tp->t_rxtsyn > 0) { 3431 /* 3432 * RFC6298: 3433 * "If the timer expires awaiting the ACK of a SYN segment 3434 * and the TCP implementation is using an RTO less than 3 3435 * seconds, the RTO MUST be re-initialized to 3 seconds 3436 * when data transmission begins" 3437 */ 3438 if (tp->t_rxtcur < TCPTV_RTOBASE3) 3439 tp->t_rxtcur = TCPTV_RTOBASE3; 3440 } 3441 } 3442 3443 /* 3444 * Returns TRUE, if the ACK should be dropped 3445 */ 3446 static boolean_t 3447 tcp_recv_dupack(struct tcpcb *tp, tcp_seq th_ack, u_int to_flags) 3448 { 3449 boolean_t fast_sack_rexmt = TRUE; 3450 3451 tcpstat.tcps_rcvdupack++; 3452 3453 /* 3454 * We have outstanding data (other than a window probe), 3455 * this is a completely duplicate ack (ie, window info 3456 * didn't change), the ack is the biggest we've seen and 3457 * we've seen exactly our rexmt threshhold of them, so 3458 * assume a packet has been dropped and retransmit it. 3459 * Kludge snd_nxt & the congestion window so we send only 3460 * this one packet. 3461 */ 3462 if (IN_FASTRECOVERY(tp)) { 3463 if (TCP_DO_SACK(tp)) { 3464 boolean_t force = FALSE; 3465 3466 if (tp->snd_una == tp->rexmt_high && 3467 (to_flags & (TOF_SACK | TOF_SACK_REDUNDANT)) == 3468 TOF_SACK) { 3469 /* 3470 * New segments got SACKed and 3471 * no retransmit yet. 3472 */ 3473 force = TRUE; 3474 } 3475 3476 /* No artifical cwnd inflation. */ 3477 tcp_sack_rexmt(tp, force); 3478 } else { 3479 /* 3480 * Dup acks mean that packets have left 3481 * the network (they're now cached at the 3482 * receiver) so bump cwnd by the amount in 3483 * the receiver to keep a constant cwnd 3484 * packets in the network. 3485 */ 3486 tp->snd_cwnd += tp->t_maxseg; 3487 tcp_output(tp); 3488 } 3489 return TRUE; 3490 } else if (SEQ_LT(th_ack, tp->snd_recover)) { 3491 tp->t_dupacks = 0; 3492 return FALSE; 3493 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) && 3494 (to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) == 3495 (TOF_DSACK | TOF_SACK_REDUNDANT)) { 3496 /* 3497 * If the ACK carries DSACK and other SACK blocks 3498 * carry information that we have already known, 3499 * don't count this ACK as duplicate ACK. This 3500 * prevents spurious early retransmit and fast 3501 * retransmit. This also meets the requirement of 3502 * RFC3042 that new segments should not be sent if 3503 * the SACK blocks do not contain new information 3504 * (XXX we actually loosen the requirment that only 3505 * DSACK is checked here). 3506 * 3507 * This kind of ACKs are usually sent after spurious 3508 * retransmit. 3509 */ 3510 /* Do nothing; don't change t_dupacks */ 3511 return TRUE; 3512 } else if (tp->t_dupacks == 0 && TCP_DO_NCR(tp)) { 3513 tcp_ncr_update_rxtthresh(tp); 3514 } 3515 3516 if (++tp->t_dupacks == tp->t_rxtthresh) { 3517 tcp_seq old_snd_nxt; 3518 u_int win; 3519 3520 fastretransmit: 3521 if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) { 3522 tcp_save_congestion_state(tp); 3523 tp->rxt_flags |= TRXT_F_FASTREXMT; 3524 } 3525 /* 3526 * We know we're losing at the current window size, 3527 * so do congestion avoidance: set ssthresh to half 3528 * the current window and pull our congestion window 3529 * back to the new ssthresh. 3530 */ 3531 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 3532 if (win < 2) 3533 win = 2; 3534 tp->snd_ssthresh = win * tp->t_maxseg; 3535 ENTER_FASTRECOVERY(tp); 3536 tp->snd_recover = tp->snd_max; 3537 tcp_callout_stop(tp, tp->tt_rexmt); 3538 tp->t_rtttime = 0; 3539 old_snd_nxt = tp->snd_nxt; 3540 tp->snd_nxt = th_ack; 3541 if (TCP_DO_SACK(tp)) { 3542 uint32_t rxtlen; 3543 3544 rxtlen = tcp_sack_first_unsacked_len(tp); 3545 if (rxtlen > tp->t_maxseg) 3546 rxtlen = tp->t_maxseg; 3547 tp->snd_cwnd = rxtlen; 3548 } else { 3549 tp->snd_cwnd = tp->t_maxseg; 3550 } 3551 tcp_output(tp); 3552 ++tcpstat.tcps_sndfastrexmit; 3553 tp->snd_cwnd = tp->snd_ssthresh; 3554 tp->rexmt_high = tp->snd_nxt; 3555 tp->sack_flags &= ~TSACK_F_SACKRESCUED; 3556 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3557 tp->snd_nxt = old_snd_nxt; 3558 KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big")); 3559 if (TCP_DO_SACK(tp)) { 3560 if (fast_sack_rexmt) 3561 tcp_sack_rexmt(tp, FALSE); 3562 } else { 3563 tp->snd_cwnd += tp->t_maxseg * 3564 (tp->t_dupacks - tp->snd_limited); 3565 } 3566 } else if ((tcp_do_rfc6675 && TCP_DO_SACK(tp)) || TCP_DO_NCR(tp)) { 3567 /* 3568 * The RFC6675 recommends to reduce the byte threshold, 3569 * and enter fast retransmit if IsLost(snd_una). However, 3570 * if we use IsLost(snd_una) based fast retransmit here, 3571 * segments reordering will cause spurious retransmit. So 3572 * we defer the IsLost(snd_una) based fast retransmit until 3573 * the extended limited transmit can't send any segments and 3574 * early retransmit can't be done. 3575 */ 3576 if (tcp_rfc6675_rxt && tcp_do_rfc6675 && 3577 tcp_sack_islost(&tp->scb, tp->snd_una)) 3578 goto fastretransmit; 3579 3580 if (tcp_do_limitedtransmit || TCP_DO_NCR(tp)) { 3581 if (!tcp_sack_limitedxmit(tp)) { 3582 /* outstanding data */ 3583 uint32_t ownd = tp->snd_max - tp->snd_una; 3584 3585 if (need_early_retransmit(tp, ownd)) { 3586 ++tcpstat.tcps_sndearlyrexmit; 3587 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3588 goto fastretransmit; 3589 } else if (tcp_do_rfc6675 && 3590 tcp_sack_islost(&tp->scb, tp->snd_una)) { 3591 fast_sack_rexmt = FALSE; 3592 goto fastretransmit; 3593 } 3594 } 3595 } 3596 } else if (tcp_do_limitedtransmit) { 3597 u_long oldcwnd = tp->snd_cwnd; 3598 tcp_seq oldsndmax = tp->snd_max; 3599 tcp_seq oldsndnxt = tp->snd_nxt; 3600 /* outstanding data */ 3601 uint32_t ownd = tp->snd_max - tp->snd_una; 3602 u_int sent; 3603 3604 KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2, 3605 ("dupacks not 1 or 2")); 3606 if (tp->t_dupacks == 1) 3607 tp->snd_limited = 0; 3608 tp->snd_nxt = tp->snd_max; 3609 tp->snd_cwnd = ownd + 3610 (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg; 3611 tp->t_flags |= TF_XMITNOW; 3612 tcp_output(tp); 3613 3614 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3615 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3616 ("snd_una moved in other threads")); 3617 tp->snd_nxt = oldsndnxt; 3618 } 3619 tp->snd_cwnd = oldcwnd; 3620 sent = tp->snd_max - oldsndmax; 3621 if (sent > tp->t_maxseg) { 3622 KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) || 3623 (sent == tp->t_maxseg + 1 && 3624 (tp->t_flags & TF_SENTFIN)), 3625 ("sent too much")); 3626 KASSERT(sent <= tp->t_maxseg * 2, 3627 ("sent too many segments")); 3628 tp->snd_limited = 2; 3629 tcpstat.tcps_sndlimited += 2; 3630 } else if (sent > 0) { 3631 ++tp->snd_limited; 3632 ++tcpstat.tcps_sndlimited; 3633 } else if (need_early_retransmit(tp, ownd)) { 3634 ++tcpstat.tcps_sndearlyrexmit; 3635 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3636 goto fastretransmit; 3637 } 3638 } 3639 return TRUE; 3640 } 3641