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