tcp_input.c revision 271667
1/*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 2007-2008,2010 5 * Swinburne University of Technology, Melbourne, Australia. 6 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> 7 * Copyright (c) 2010 The FreeBSD Foundation 8 * Copyright (c) 2010-2011 Juniper Networks, Inc. 9 * All rights reserved. 10 * 11 * Portions of this software were developed at the Centre for Advanced Internet 12 * Architectures, Swinburne University of Technology, by Lawrence Stewart, 13 * James Healy and David Hayes, made possible in part by a grant from the Cisco 14 * University Research Program Fund at Community Foundation Silicon Valley. 15 * 16 * Portions of this software were developed at the Centre for Advanced 17 * Internet Architectures, Swinburne University of Technology, Melbourne, 18 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 19 * 20 * Portions of this software were developed by Robert N. M. Watson under 21 * contract to Juniper Networks, Inc. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the above copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 4. Neither the name of the University nor the names of its contributors 32 * may be used to endorse or promote products derived from this software 33 * without specific prior written permission. 34 * 35 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 36 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 38 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 39 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 40 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 41 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 42 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 43 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 44 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 45 * SUCH DAMAGE. 46 * 47 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 48 */ 49 50#include <sys/cdefs.h> 51__FBSDID("$FreeBSD: stable/10/sys/netinet/tcp_input.c 271667 2014-09-16 09:48:35Z delphij $"); 52 53#include "opt_ipfw.h" /* for ipfw_fwd */ 54#include "opt_inet.h" 55#include "opt_inet6.h" 56#include "opt_ipsec.h" 57#include "opt_kdtrace.h" 58#include "opt_tcpdebug.h" 59 60#include <sys/param.h> 61#include <sys/kernel.h> 62#include <sys/hhook.h> 63#include <sys/malloc.h> 64#include <sys/mbuf.h> 65#include <sys/proc.h> /* for proc0 declaration */ 66#include <sys/protosw.h> 67#include <sys/sdt.h> 68#include <sys/signalvar.h> 69#include <sys/socket.h> 70#include <sys/socketvar.h> 71#include <sys/sysctl.h> 72#include <sys/syslog.h> 73#include <sys/systm.h> 74 75#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 76 77#include <vm/uma.h> 78 79#include <net/if.h> 80#include <net/route.h> 81#include <net/vnet.h> 82 83#define TCPSTATES /* for logging */ 84 85#include <netinet/cc.h> 86#include <netinet/in.h> 87#include <netinet/in_kdtrace.h> 88#include <netinet/in_pcb.h> 89#include <netinet/in_systm.h> 90#include <netinet/in_var.h> 91#include <netinet/ip.h> 92#include <netinet/ip_icmp.h> /* required for icmp_var.h */ 93#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 94#include <netinet/ip_var.h> 95#include <netinet/ip_options.h> 96#include <netinet/ip6.h> 97#include <netinet/icmp6.h> 98#include <netinet6/in6_pcb.h> 99#include <netinet6/ip6_var.h> 100#include <netinet6/nd6.h> 101#include <netinet/tcp_fsm.h> 102#include <netinet/tcp_seq.h> 103#include <netinet/tcp_timer.h> 104#include <netinet/tcp_var.h> 105#include <netinet6/tcp6_var.h> 106#include <netinet/tcpip.h> 107#include <netinet/tcp_syncache.h> 108#ifdef TCPDEBUG 109#include <netinet/tcp_debug.h> 110#endif /* TCPDEBUG */ 111#ifdef TCP_OFFLOAD 112#include <netinet/tcp_offload.h> 113#endif 114 115#ifdef IPSEC 116#include <netipsec/ipsec.h> 117#include <netipsec/ipsec6.h> 118#endif /*IPSEC*/ 119 120#include <machine/in_cksum.h> 121 122#include <security/mac/mac_framework.h> 123 124const int tcprexmtthresh = 3; 125 126int tcp_log_in_vain = 0; 127SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 128 &tcp_log_in_vain, 0, 129 "Log all incoming TCP segments to closed ports"); 130 131VNET_DEFINE(int, blackhole) = 0; 132#define V_blackhole VNET(blackhole) 133SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 134 &VNET_NAME(blackhole), 0, 135 "Do not send RST on segments to closed ports"); 136 137VNET_DEFINE(int, tcp_delack_enabled) = 1; 138SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 139 &VNET_NAME(tcp_delack_enabled), 0, 140 "Delay ACK to try and piggyback it onto a data packet"); 141 142VNET_DEFINE(int, drop_synfin) = 0; 143#define V_drop_synfin VNET(drop_synfin) 144SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 145 &VNET_NAME(drop_synfin), 0, 146 "Drop TCP packets with SYN+FIN set"); 147 148VNET_DEFINE(int, tcp_do_rfc3042) = 1; 149#define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) 150SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 151 &VNET_NAME(tcp_do_rfc3042), 0, 152 "Enable RFC 3042 (Limited Transmit)"); 153 154VNET_DEFINE(int, tcp_do_rfc3390) = 1; 155SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 156 &VNET_NAME(tcp_do_rfc3390), 0, 157 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 158 159SYSCTL_NODE(_net_inet_tcp, OID_AUTO, experimental, CTLFLAG_RW, 0, 160 "Experimental TCP extensions"); 161 162VNET_DEFINE(int, tcp_do_initcwnd10) = 1; 163SYSCTL_VNET_INT(_net_inet_tcp_experimental, OID_AUTO, initcwnd10, CTLFLAG_RW, 164 &VNET_NAME(tcp_do_initcwnd10), 0, 165 "Enable RFC 6928 (Increasing initial CWND to 10)"); 166 167VNET_DEFINE(int, tcp_do_rfc3465) = 1; 168SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW, 169 &VNET_NAME(tcp_do_rfc3465), 0, 170 "Enable RFC 3465 (Appropriate Byte Counting)"); 171 172VNET_DEFINE(int, tcp_abc_l_var) = 2; 173SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW, 174 &VNET_NAME(tcp_abc_l_var), 2, 175 "Cap the max cwnd increment during slow-start to this number of segments"); 176 177static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 178 179VNET_DEFINE(int, tcp_do_ecn) = 0; 180SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW, 181 &VNET_NAME(tcp_do_ecn), 0, 182 "TCP ECN support"); 183 184VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 185SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW, 186 &VNET_NAME(tcp_ecn_maxretries), 0, 187 "Max retries before giving up on ECN"); 188 189VNET_DEFINE(int, tcp_insecure_rst) = 0; 190#define V_tcp_insecure_rst VNET(tcp_insecure_rst) 191SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 192 &VNET_NAME(tcp_insecure_rst), 0, 193 "Follow the old (insecure) criteria for accepting RST packets"); 194 195VNET_DEFINE(int, tcp_recvspace) = 1024*64; 196#define V_tcp_recvspace VNET(tcp_recvspace) 197SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_RW, 198 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 199 200VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 201#define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) 202SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 203 &VNET_NAME(tcp_do_autorcvbuf), 0, 204 "Enable automatic receive buffer sizing"); 205 206VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 207#define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) 208SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 209 &VNET_NAME(tcp_autorcvbuf_inc), 0, 210 "Incrementor step size of automatic receive buffer"); 211 212VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 213#define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) 214SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 215 &VNET_NAME(tcp_autorcvbuf_max), 0, 216 "Max size of automatic receive buffer"); 217 218VNET_DEFINE(struct inpcbhead, tcb); 219#define tcb6 tcb /* for KAME src sync over BSD*'s */ 220VNET_DEFINE(struct inpcbinfo, tcbinfo); 221 222static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 223static void tcp_do_segment(struct mbuf *, struct tcphdr *, 224 struct socket *, struct tcpcb *, int, int, uint8_t, 225 int); 226static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, 227 struct tcpcb *, int, int); 228static void tcp_pulloutofband(struct socket *, 229 struct tcphdr *, struct mbuf *, int); 230static void tcp_xmit_timer(struct tcpcb *, int); 231static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 232static void inline cc_ack_received(struct tcpcb *tp, struct tcphdr *th, 233 uint16_t type); 234static void inline cc_conn_init(struct tcpcb *tp); 235static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th); 236static void inline hhook_run_tcp_est_in(struct tcpcb *tp, 237 struct tcphdr *th, struct tcpopt *to); 238 239/* 240 * TCP statistics are stored in an "array" of counter(9)s. 241 */ 242VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 243VNET_PCPUSTAT_SYSINIT(tcpstat); 244SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 245 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 246 247#ifdef VIMAGE 248VNET_PCPUSTAT_SYSUNINIT(tcpstat); 249#endif /* VIMAGE */ 250/* 251 * Kernel module interface for updating tcpstat. The argument is an index 252 * into tcpstat treated as an array. 253 */ 254void 255kmod_tcpstat_inc(int statnum) 256{ 257 258 counter_u64_add(VNET(tcpstat)[statnum], 1); 259} 260 261/* 262 * Wrapper for the TCP established input helper hook. 263 */ 264static void inline 265hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 266{ 267 struct tcp_hhook_data hhook_data; 268 269 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 270 hhook_data.tp = tp; 271 hhook_data.th = th; 272 hhook_data.to = to; 273 274 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 275 tp->osd); 276 } 277} 278 279/* 280 * CC wrapper hook functions 281 */ 282static void inline 283cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type) 284{ 285 INP_WLOCK_ASSERT(tp->t_inpcb); 286 287 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 288 if (tp->snd_cwnd <= tp->snd_wnd) 289 tp->ccv->flags |= CCF_CWND_LIMITED; 290 else 291 tp->ccv->flags &= ~CCF_CWND_LIMITED; 292 293 if (type == CC_ACK) { 294 if (tp->snd_cwnd > tp->snd_ssthresh) { 295 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 296 V_tcp_abc_l_var * tp->t_maxseg); 297 if (tp->t_bytes_acked >= tp->snd_cwnd) { 298 tp->t_bytes_acked -= tp->snd_cwnd; 299 tp->ccv->flags |= CCF_ABC_SENTAWND; 300 } 301 } else { 302 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 303 tp->t_bytes_acked = 0; 304 } 305 } 306 307 if (CC_ALGO(tp)->ack_received != NULL) { 308 /* XXXLAS: Find a way to live without this */ 309 tp->ccv->curack = th->th_ack; 310 CC_ALGO(tp)->ack_received(tp->ccv, type); 311 } 312} 313 314static void inline 315cc_conn_init(struct tcpcb *tp) 316{ 317 struct hc_metrics_lite metrics; 318 struct inpcb *inp = tp->t_inpcb; 319 int rtt; 320 321 INP_WLOCK_ASSERT(tp->t_inpcb); 322 323 tcp_hc_get(&inp->inp_inc, &metrics); 324 325 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 326 tp->t_srtt = rtt; 327 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 328 TCPSTAT_INC(tcps_usedrtt); 329 if (metrics.rmx_rttvar) { 330 tp->t_rttvar = metrics.rmx_rttvar; 331 TCPSTAT_INC(tcps_usedrttvar); 332 } else { 333 /* default variation is +- 1 rtt */ 334 tp->t_rttvar = 335 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 336 } 337 TCPT_RANGESET(tp->t_rxtcur, 338 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 339 tp->t_rttmin, TCPTV_REXMTMAX); 340 } 341 if (metrics.rmx_ssthresh) { 342 /* 343 * There's some sort of gateway or interface 344 * buffer limit on the path. Use this to set 345 * the slow start threshhold, but set the 346 * threshold to no less than 2*mss. 347 */ 348 tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh); 349 TCPSTAT_INC(tcps_usedssthresh); 350 } 351 352 /* 353 * Set the initial slow-start flight size. 354 * 355 * RFC5681 Section 3.1 specifies the default conservative values. 356 * RFC3390 specifies slightly more aggressive values. 357 * RFC6928 increases it to ten segments. 358 * 359 * If a SYN or SYN/ACK was lost and retransmitted, we have to 360 * reduce the initial CWND to one segment as congestion is likely 361 * requiring us to be cautious. 362 */ 363 if (tp->snd_cwnd == 1) 364 tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */ 365 else if (V_tcp_do_initcwnd10) 366 tp->snd_cwnd = min(10 * tp->t_maxseg, 367 max(2 * tp->t_maxseg, 14600)); 368 else if (V_tcp_do_rfc3390) 369 tp->snd_cwnd = min(4 * tp->t_maxseg, 370 max(2 * tp->t_maxseg, 4380)); 371 else { 372 /* Per RFC5681 Section 3.1 */ 373 if (tp->t_maxseg > 2190) 374 tp->snd_cwnd = 2 * tp->t_maxseg; 375 else if (tp->t_maxseg > 1095) 376 tp->snd_cwnd = 3 * tp->t_maxseg; 377 else 378 tp->snd_cwnd = 4 * tp->t_maxseg; 379 } 380 381 if (CC_ALGO(tp)->conn_init != NULL) 382 CC_ALGO(tp)->conn_init(tp->ccv); 383} 384 385void inline 386cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 387{ 388 INP_WLOCK_ASSERT(tp->t_inpcb); 389 390 switch(type) { 391 case CC_NDUPACK: 392 if (!IN_FASTRECOVERY(tp->t_flags)) { 393 tp->snd_recover = tp->snd_max; 394 if (tp->t_flags & TF_ECN_PERMIT) 395 tp->t_flags |= TF_ECN_SND_CWR; 396 } 397 break; 398 case CC_ECN: 399 if (!IN_CONGRECOVERY(tp->t_flags)) { 400 TCPSTAT_INC(tcps_ecn_rcwnd); 401 tp->snd_recover = tp->snd_max; 402 if (tp->t_flags & TF_ECN_PERMIT) 403 tp->t_flags |= TF_ECN_SND_CWR; 404 } 405 break; 406 case CC_RTO: 407 tp->t_dupacks = 0; 408 tp->t_bytes_acked = 0; 409 EXIT_RECOVERY(tp->t_flags); 410 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 411 tp->t_maxseg) * tp->t_maxseg; 412 tp->snd_cwnd = tp->t_maxseg; 413 break; 414 case CC_RTO_ERR: 415 TCPSTAT_INC(tcps_sndrexmitbad); 416 /* RTO was unnecessary, so reset everything. */ 417 tp->snd_cwnd = tp->snd_cwnd_prev; 418 tp->snd_ssthresh = tp->snd_ssthresh_prev; 419 tp->snd_recover = tp->snd_recover_prev; 420 if (tp->t_flags & TF_WASFRECOVERY) 421 ENTER_FASTRECOVERY(tp->t_flags); 422 if (tp->t_flags & TF_WASCRECOVERY) 423 ENTER_CONGRECOVERY(tp->t_flags); 424 tp->snd_nxt = tp->snd_max; 425 tp->t_flags &= ~TF_PREVVALID; 426 tp->t_badrxtwin = 0; 427 break; 428 } 429 430 if (CC_ALGO(tp)->cong_signal != NULL) { 431 if (th != NULL) 432 tp->ccv->curack = th->th_ack; 433 CC_ALGO(tp)->cong_signal(tp->ccv, type); 434 } 435} 436 437static void inline 438cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 439{ 440 INP_WLOCK_ASSERT(tp->t_inpcb); 441 442 /* XXXLAS: KASSERT that we're in recovery? */ 443 444 if (CC_ALGO(tp)->post_recovery != NULL) { 445 tp->ccv->curack = th->th_ack; 446 CC_ALGO(tp)->post_recovery(tp->ccv); 447 } 448 /* XXXLAS: EXIT_RECOVERY ? */ 449 tp->t_bytes_acked = 0; 450} 451 452#ifdef TCP_SIGNATURE 453static inline int 454tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, 455 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) 456{ 457 int ret; 458 459 tcp_fields_to_net(th); 460 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); 461 tcp_fields_to_host(th); 462 return (ret); 463} 464#endif 465 466/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 467#ifdef INET6 468#define ND6_HINT(tp) \ 469do { \ 470 if ((tp) && (tp)->t_inpcb && \ 471 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 472 nd6_nud_hint(NULL, NULL, 0); \ 473} while (0) 474#else 475#define ND6_HINT(tp) 476#endif 477 478/* 479 * Indicate whether this ack should be delayed. We can delay the ack if 480 * - there is no delayed ack timer in progress and 481 * - our last ack wasn't a 0-sized window. We never want to delay 482 * the ack that opens up a 0-sized window and 483 * - delayed acks are enabled or 484 * - this is a half-synchronized T/TCP connection. 485 * - the segment size is not larger than the MSS and LRO wasn't used 486 * for this segment. 487 */ 488#define DELAY_ACK(tp, tlen) \ 489 ((!tcp_timer_active(tp, TT_DELACK) && \ 490 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 491 (tlen <= tp->t_maxopd) && \ 492 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 493 494/* 495 * TCP input handling is split into multiple parts: 496 * tcp6_input is a thin wrapper around tcp_input for the extended 497 * ip6_protox[] call format in ip6_input 498 * tcp_input handles primary segment validation, inpcb lookup and 499 * SYN processing on listen sockets 500 * tcp_do_segment processes the ACK and text of the segment for 501 * establishing, established and closing connections 502 */ 503#ifdef INET6 504int 505tcp6_input(struct mbuf **mp, int *offp, int proto) 506{ 507 struct mbuf *m = *mp; 508 struct in6_ifaddr *ia6; 509 510 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 511 512 /* 513 * draft-itojun-ipv6-tcp-to-anycast 514 * better place to put this in? 515 */ 516 ia6 = ip6_getdstifaddr(m); 517 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 518 struct ip6_hdr *ip6; 519 520 ifa_free(&ia6->ia_ifa); 521 ip6 = mtod(m, struct ip6_hdr *); 522 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 523 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 524 return IPPROTO_DONE; 525 } 526 if (ia6) 527 ifa_free(&ia6->ia_ifa); 528 529 tcp_input(m, *offp); 530 return IPPROTO_DONE; 531} 532#endif /* INET6 */ 533 534void 535tcp_input(struct mbuf *m, int off0) 536{ 537 struct tcphdr *th = NULL; 538 struct ip *ip = NULL; 539 struct inpcb *inp = NULL; 540 struct tcpcb *tp = NULL; 541 struct socket *so = NULL; 542 u_char *optp = NULL; 543 int optlen = 0; 544#ifdef INET 545 int len; 546#endif 547 int tlen = 0, off; 548 int drop_hdrlen; 549 int thflags; 550 int rstreason = 0; /* For badport_bandlim accounting purposes */ 551#ifdef TCP_SIGNATURE 552 uint8_t sig_checked = 0; 553#endif 554 uint8_t iptos = 0; 555 struct m_tag *fwd_tag = NULL; 556#ifdef INET6 557 struct ip6_hdr *ip6 = NULL; 558 int isipv6; 559#else 560 const void *ip6 = NULL; 561#endif /* INET6 */ 562 struct tcpopt to; /* options in this segment */ 563 char *s = NULL; /* address and port logging */ 564 int ti_locked; 565#define TI_UNLOCKED 1 566#define TI_WLOCKED 2 567 568#ifdef TCPDEBUG 569 /* 570 * The size of tcp_saveipgen must be the size of the max ip header, 571 * now IPv6. 572 */ 573 u_char tcp_saveipgen[IP6_HDR_LEN]; 574 struct tcphdr tcp_savetcp; 575 short ostate = 0; 576#endif 577 578#ifdef INET6 579 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 580#endif 581 582 to.to_flags = 0; 583 TCPSTAT_INC(tcps_rcvtotal); 584 585#ifdef INET6 586 if (isipv6) { 587 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 588 589 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 590 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 591 if (m == NULL) { 592 TCPSTAT_INC(tcps_rcvshort); 593 return; 594 } 595 } 596 597 ip6 = mtod(m, struct ip6_hdr *); 598 th = (struct tcphdr *)((caddr_t)ip6 + off0); 599 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 600 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 601 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 602 th->th_sum = m->m_pkthdr.csum_data; 603 else 604 th->th_sum = in6_cksum_pseudo(ip6, tlen, 605 IPPROTO_TCP, m->m_pkthdr.csum_data); 606 th->th_sum ^= 0xffff; 607 } else 608 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 609 if (th->th_sum) { 610 TCPSTAT_INC(tcps_rcvbadsum); 611 goto drop; 612 } 613 614 /* 615 * Be proactive about unspecified IPv6 address in source. 616 * As we use all-zero to indicate unbounded/unconnected pcb, 617 * unspecified IPv6 address can be used to confuse us. 618 * 619 * Note that packets with unspecified IPv6 destination is 620 * already dropped in ip6_input. 621 */ 622 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 623 /* XXX stat */ 624 goto drop; 625 } 626 } 627#endif 628#if defined(INET) && defined(INET6) 629 else 630#endif 631#ifdef INET 632 { 633 /* 634 * Get IP and TCP header together in first mbuf. 635 * Note: IP leaves IP header in first mbuf. 636 */ 637 if (off0 > sizeof (struct ip)) { 638 ip_stripoptions(m); 639 off0 = sizeof(struct ip); 640 } 641 if (m->m_len < sizeof (struct tcpiphdr)) { 642 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 643 == NULL) { 644 TCPSTAT_INC(tcps_rcvshort); 645 return; 646 } 647 } 648 ip = mtod(m, struct ip *); 649 th = (struct tcphdr *)((caddr_t)ip + off0); 650 tlen = ntohs(ip->ip_len) - off0; 651 652 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 653 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 654 th->th_sum = m->m_pkthdr.csum_data; 655 else 656 th->th_sum = in_pseudo(ip->ip_src.s_addr, 657 ip->ip_dst.s_addr, 658 htonl(m->m_pkthdr.csum_data + tlen + 659 IPPROTO_TCP)); 660 th->th_sum ^= 0xffff; 661 } else { 662 struct ipovly *ipov = (struct ipovly *)ip; 663 664 /* 665 * Checksum extended TCP header and data. 666 */ 667 len = off0 + tlen; 668 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 669 ipov->ih_len = htons(tlen); 670 th->th_sum = in_cksum(m, len); 671 /* Reset length for SDT probes. */ 672 ip->ip_len = htons(tlen + off0); 673 } 674 675 if (th->th_sum) { 676 TCPSTAT_INC(tcps_rcvbadsum); 677 goto drop; 678 } 679 /* Re-initialization for later version check */ 680 ip->ip_v = IPVERSION; 681 } 682#endif /* INET */ 683 684#ifdef INET6 685 if (isipv6) 686 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 687#endif 688#if defined(INET) && defined(INET6) 689 else 690#endif 691#ifdef INET 692 iptos = ip->ip_tos; 693#endif 694 695 /* 696 * Check that TCP offset makes sense, 697 * pull out TCP options and adjust length. XXX 698 */ 699 off = th->th_off << 2; 700 if (off < sizeof (struct tcphdr) || off > tlen) { 701 TCPSTAT_INC(tcps_rcvbadoff); 702 goto drop; 703 } 704 tlen -= off; /* tlen is used instead of ti->ti_len */ 705 if (off > sizeof (struct tcphdr)) { 706#ifdef INET6 707 if (isipv6) { 708 IP6_EXTHDR_CHECK(m, off0, off, ); 709 ip6 = mtod(m, struct ip6_hdr *); 710 th = (struct tcphdr *)((caddr_t)ip6 + off0); 711 } 712#endif 713#if defined(INET) && defined(INET6) 714 else 715#endif 716#ifdef INET 717 { 718 if (m->m_len < sizeof(struct ip) + off) { 719 if ((m = m_pullup(m, sizeof (struct ip) + off)) 720 == NULL) { 721 TCPSTAT_INC(tcps_rcvshort); 722 return; 723 } 724 ip = mtod(m, struct ip *); 725 th = (struct tcphdr *)((caddr_t)ip + off0); 726 } 727 } 728#endif 729 optlen = off - sizeof (struct tcphdr); 730 optp = (u_char *)(th + 1); 731 } 732 thflags = th->th_flags; 733 734 /* 735 * Convert TCP protocol specific fields to host format. 736 */ 737 tcp_fields_to_host(th); 738 739 /* 740 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 741 */ 742 drop_hdrlen = off0 + off; 743 744 /* 745 * Locate pcb for segment; if we're likely to add or remove a 746 * connection then first acquire pcbinfo lock. There are two cases 747 * where we might discover later we need a write lock despite the 748 * flags: ACKs moving a connection out of the syncache, and ACKs for 749 * a connection in TIMEWAIT. 750 */ 751 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) { 752 INP_INFO_WLOCK(&V_tcbinfo); 753 ti_locked = TI_WLOCKED; 754 } else 755 ti_locked = TI_UNLOCKED; 756 757 /* 758 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 759 */ 760 if ( 761#ifdef INET6 762 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 763#ifdef INET 764 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 765#endif 766#endif 767#if defined(INET) && !defined(INET6) 768 (m->m_flags & M_IP_NEXTHOP) 769#endif 770 ) 771 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 772 773findpcb: 774#ifdef INVARIANTS 775 if (ti_locked == TI_WLOCKED) { 776 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 777 } else { 778 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 779 } 780#endif 781#ifdef INET6 782 if (isipv6 && fwd_tag != NULL) { 783 struct sockaddr_in6 *next_hop6; 784 785 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 786 /* 787 * Transparently forwarded. Pretend to be the destination. 788 * Already got one like this? 789 */ 790 inp = in6_pcblookup_mbuf(&V_tcbinfo, 791 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 792 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 793 if (!inp) { 794 /* 795 * It's new. Try to find the ambushing socket. 796 * Because we've rewritten the destination address, 797 * any hardware-generated hash is ignored. 798 */ 799 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 800 th->th_sport, &next_hop6->sin6_addr, 801 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 802 th->th_dport, INPLOOKUP_WILDCARD | 803 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 804 } 805 } else if (isipv6) { 806 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 807 th->th_sport, &ip6->ip6_dst, th->th_dport, 808 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 809 m->m_pkthdr.rcvif, m); 810 } 811#endif /* INET6 */ 812#if defined(INET6) && defined(INET) 813 else 814#endif 815#ifdef INET 816 if (fwd_tag != NULL) { 817 struct sockaddr_in *next_hop; 818 819 next_hop = (struct sockaddr_in *)(fwd_tag+1); 820 /* 821 * Transparently forwarded. Pretend to be the destination. 822 * already got one like this? 823 */ 824 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 825 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 826 m->m_pkthdr.rcvif, m); 827 if (!inp) { 828 /* 829 * It's new. Try to find the ambushing socket. 830 * Because we've rewritten the destination address, 831 * any hardware-generated hash is ignored. 832 */ 833 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 834 th->th_sport, next_hop->sin_addr, 835 next_hop->sin_port ? ntohs(next_hop->sin_port) : 836 th->th_dport, INPLOOKUP_WILDCARD | 837 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 838 } 839 } else 840 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 841 th->th_sport, ip->ip_dst, th->th_dport, 842 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 843 m->m_pkthdr.rcvif, m); 844#endif /* INET */ 845 846 /* 847 * If the INPCB does not exist then all data in the incoming 848 * segment is discarded and an appropriate RST is sent back. 849 * XXX MRT Send RST using which routing table? 850 */ 851 if (inp == NULL) { 852 /* 853 * Log communication attempts to ports that are not 854 * in use. 855 */ 856 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 857 tcp_log_in_vain == 2) { 858 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 859 log(LOG_INFO, "%s; %s: Connection attempt " 860 "to closed port\n", s, __func__); 861 } 862 /* 863 * When blackholing do not respond with a RST but 864 * completely ignore the segment and drop it. 865 */ 866 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 867 V_blackhole == 2) 868 goto dropunlock; 869 870 rstreason = BANDLIM_RST_CLOSEDPORT; 871 goto dropwithreset; 872 } 873 INP_WLOCK_ASSERT(inp); 874 if (!(inp->inp_flags & INP_HW_FLOWID) 875 && (m->m_flags & M_FLOWID) 876 && ((inp->inp_socket == NULL) 877 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) { 878 inp->inp_flags |= INP_HW_FLOWID; 879 inp->inp_flags &= ~INP_SW_FLOWID; 880 inp->inp_flowid = m->m_pkthdr.flowid; 881 } 882#ifdef IPSEC 883#ifdef INET6 884 if (isipv6 && ipsec6_in_reject(m, inp)) { 885 IPSEC6STAT_INC(ips_in_polvio); 886 goto dropunlock; 887 } else 888#endif /* INET6 */ 889 if (ipsec4_in_reject(m, inp) != 0) { 890 IPSECSTAT_INC(ips_in_polvio); 891 goto dropunlock; 892 } 893#endif /* IPSEC */ 894 895 /* 896 * Check the minimum TTL for socket. 897 */ 898 if (inp->inp_ip_minttl != 0) { 899#ifdef INET6 900 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 901 goto dropunlock; 902 else 903#endif 904 if (inp->inp_ip_minttl > ip->ip_ttl) 905 goto dropunlock; 906 } 907 908 /* 909 * A previous connection in TIMEWAIT state is supposed to catch stray 910 * or duplicate segments arriving late. If this segment was a 911 * legitimate new connection attempt, the old INPCB gets removed and 912 * we can try again to find a listening socket. 913 * 914 * At this point, due to earlier optimism, we may hold only an inpcb 915 * lock, and not the inpcbinfo write lock. If so, we need to try to 916 * acquire it, or if that fails, acquire a reference on the inpcb, 917 * drop all locks, acquire a global write lock, and then re-acquire 918 * the inpcb lock. We may at that point discover that another thread 919 * has tried to free the inpcb, in which case we need to loop back 920 * and try to find a new inpcb to deliver to. 921 * 922 * XXXRW: It may be time to rethink timewait locking. 923 */ 924relocked: 925 if (inp->inp_flags & INP_TIMEWAIT) { 926 if (ti_locked == TI_UNLOCKED) { 927 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) { 928 in_pcbref(inp); 929 INP_WUNLOCK(inp); 930 INP_INFO_WLOCK(&V_tcbinfo); 931 ti_locked = TI_WLOCKED; 932 INP_WLOCK(inp); 933 if (in_pcbrele_wlocked(inp)) { 934 inp = NULL; 935 goto findpcb; 936 } 937 } else 938 ti_locked = TI_WLOCKED; 939 } 940 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 941 942 if (thflags & TH_SYN) 943 tcp_dooptions(&to, optp, optlen, TO_SYN); 944 /* 945 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 946 */ 947 if (tcp_twcheck(inp, &to, th, m, tlen)) 948 goto findpcb; 949 INP_INFO_WUNLOCK(&V_tcbinfo); 950 return; 951 } 952 /* 953 * The TCPCB may no longer exist if the connection is winding 954 * down or it is in the CLOSED state. Either way we drop the 955 * segment and send an appropriate response. 956 */ 957 tp = intotcpcb(inp); 958 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 959 rstreason = BANDLIM_RST_CLOSEDPORT; 960 goto dropwithreset; 961 } 962 963#ifdef TCP_OFFLOAD 964 if (tp->t_flags & TF_TOE) { 965 tcp_offload_input(tp, m); 966 m = NULL; /* consumed by the TOE driver */ 967 goto dropunlock; 968 } 969#endif 970 971 /* 972 * We've identified a valid inpcb, but it could be that we need an 973 * inpcbinfo write lock but don't hold it. In this case, attempt to 974 * acquire using the same strategy as the TIMEWAIT case above. If we 975 * relock, we have to jump back to 'relocked' as the connection might 976 * now be in TIMEWAIT. 977 */ 978#ifdef INVARIANTS 979 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) 980 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 981#endif 982 if (tp->t_state != TCPS_ESTABLISHED) { 983 if (ti_locked == TI_UNLOCKED) { 984 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) { 985 in_pcbref(inp); 986 INP_WUNLOCK(inp); 987 INP_INFO_WLOCK(&V_tcbinfo); 988 ti_locked = TI_WLOCKED; 989 INP_WLOCK(inp); 990 if (in_pcbrele_wlocked(inp)) { 991 inp = NULL; 992 goto findpcb; 993 } 994 goto relocked; 995 } else 996 ti_locked = TI_WLOCKED; 997 } 998 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 999 } 1000 1001#ifdef MAC 1002 INP_WLOCK_ASSERT(inp); 1003 if (mac_inpcb_check_deliver(inp, m)) 1004 goto dropunlock; 1005#endif 1006 so = inp->inp_socket; 1007 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1008#ifdef TCPDEBUG 1009 if (so->so_options & SO_DEBUG) { 1010 ostate = tp->t_state; 1011#ifdef INET6 1012 if (isipv6) { 1013 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1014 } else 1015#endif 1016 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1017 tcp_savetcp = *th; 1018 } 1019#endif /* TCPDEBUG */ 1020 /* 1021 * When the socket is accepting connections (the INPCB is in LISTEN 1022 * state) we look into the SYN cache if this is a new connection 1023 * attempt or the completion of a previous one. Because listen 1024 * sockets are never in TCPS_ESTABLISHED, the V_tcbinfo lock will be 1025 * held in this case. 1026 */ 1027 if (so->so_options & SO_ACCEPTCONN) { 1028 struct in_conninfo inc; 1029 1030 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 1031 "tp not listening", __func__)); 1032 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1033 1034 bzero(&inc, sizeof(inc)); 1035#ifdef INET6 1036 if (isipv6) { 1037 inc.inc_flags |= INC_ISIPV6; 1038 inc.inc6_faddr = ip6->ip6_src; 1039 inc.inc6_laddr = ip6->ip6_dst; 1040 } else 1041#endif 1042 { 1043 inc.inc_faddr = ip->ip_src; 1044 inc.inc_laddr = ip->ip_dst; 1045 } 1046 inc.inc_fport = th->th_sport; 1047 inc.inc_lport = th->th_dport; 1048 inc.inc_fibnum = so->so_fibnum; 1049 1050 /* 1051 * Check for an existing connection attempt in syncache if 1052 * the flag is only ACK. A successful lookup creates a new 1053 * socket appended to the listen queue in SYN_RECEIVED state. 1054 */ 1055 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1056 /* 1057 * Parse the TCP options here because 1058 * syncookies need access to the reflected 1059 * timestamp. 1060 */ 1061 tcp_dooptions(&to, optp, optlen, 0); 1062 /* 1063 * NB: syncache_expand() doesn't unlock 1064 * inp and tcpinfo locks. 1065 */ 1066 if (!syncache_expand(&inc, &to, th, &so, m)) { 1067 /* 1068 * No syncache entry or ACK was not 1069 * for our SYN/ACK. Send a RST. 1070 * NB: syncache did its own logging 1071 * of the failure cause. 1072 */ 1073 rstreason = BANDLIM_RST_OPENPORT; 1074 goto dropwithreset; 1075 } 1076 if (so == NULL) { 1077 /* 1078 * We completed the 3-way handshake 1079 * but could not allocate a socket 1080 * either due to memory shortage, 1081 * listen queue length limits or 1082 * global socket limits. Send RST 1083 * or wait and have the remote end 1084 * retransmit the ACK for another 1085 * try. 1086 */ 1087 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1088 log(LOG_DEBUG, "%s; %s: Listen socket: " 1089 "Socket allocation failed due to " 1090 "limits or memory shortage, %s\n", 1091 s, __func__, 1092 V_tcp_sc_rst_sock_fail ? 1093 "sending RST" : "try again"); 1094 if (V_tcp_sc_rst_sock_fail) { 1095 rstreason = BANDLIM_UNLIMITED; 1096 goto dropwithreset; 1097 } else 1098 goto dropunlock; 1099 } 1100 /* 1101 * Socket is created in state SYN_RECEIVED. 1102 * Unlock the listen socket, lock the newly 1103 * created socket and update the tp variable. 1104 */ 1105 INP_WUNLOCK(inp); /* listen socket */ 1106 inp = sotoinpcb(so); 1107 INP_WLOCK(inp); /* new connection */ 1108 tp = intotcpcb(inp); 1109 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1110 ("%s: ", __func__)); 1111#ifdef TCP_SIGNATURE 1112 if (sig_checked == 0) { 1113 tcp_dooptions(&to, optp, optlen, 1114 (thflags & TH_SYN) ? TO_SYN : 0); 1115 if (!tcp_signature_verify_input(m, off0, tlen, 1116 optlen, &to, th, tp->t_flags)) { 1117 1118 /* 1119 * In SYN_SENT state if it receives an 1120 * RST, it is allowed for further 1121 * processing. 1122 */ 1123 if ((thflags & TH_RST) == 0 || 1124 (tp->t_state == TCPS_SYN_SENT) == 0) 1125 goto dropunlock; 1126 } 1127 sig_checked = 1; 1128 } 1129#endif 1130 1131 /* 1132 * Process the segment and the data it 1133 * contains. tcp_do_segment() consumes 1134 * the mbuf chain and unlocks the inpcb. 1135 */ 1136 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1137 iptos, ti_locked); 1138 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1139 return; 1140 } 1141 /* 1142 * Segment flag validation for new connection attempts: 1143 * 1144 * Our (SYN|ACK) response was rejected. 1145 * Check with syncache and remove entry to prevent 1146 * retransmits. 1147 * 1148 * NB: syncache_chkrst does its own logging of failure 1149 * causes. 1150 */ 1151 if (thflags & TH_RST) { 1152 syncache_chkrst(&inc, th); 1153 goto dropunlock; 1154 } 1155 /* 1156 * We can't do anything without SYN. 1157 */ 1158 if ((thflags & TH_SYN) == 0) { 1159 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1160 log(LOG_DEBUG, "%s; %s: Listen socket: " 1161 "SYN is missing, segment ignored\n", 1162 s, __func__); 1163 TCPSTAT_INC(tcps_badsyn); 1164 goto dropunlock; 1165 } 1166 /* 1167 * (SYN|ACK) is bogus on a listen socket. 1168 */ 1169 if (thflags & TH_ACK) { 1170 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1171 log(LOG_DEBUG, "%s; %s: Listen socket: " 1172 "SYN|ACK invalid, segment rejected\n", 1173 s, __func__); 1174 syncache_badack(&inc); /* XXX: Not needed! */ 1175 TCPSTAT_INC(tcps_badsyn); 1176 rstreason = BANDLIM_RST_OPENPORT; 1177 goto dropwithreset; 1178 } 1179 /* 1180 * If the drop_synfin option is enabled, drop all 1181 * segments with both the SYN and FIN bits set. 1182 * This prevents e.g. nmap from identifying the 1183 * TCP/IP stack. 1184 * XXX: Poor reasoning. nmap has other methods 1185 * and is constantly refining its stack detection 1186 * strategies. 1187 * XXX: This is a violation of the TCP specification 1188 * and was used by RFC1644. 1189 */ 1190 if ((thflags & TH_FIN) && V_drop_synfin) { 1191 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1192 log(LOG_DEBUG, "%s; %s: Listen socket: " 1193 "SYN|FIN segment ignored (based on " 1194 "sysctl setting)\n", s, __func__); 1195 TCPSTAT_INC(tcps_badsyn); 1196 goto dropunlock; 1197 } 1198 /* 1199 * Segment's flags are (SYN) or (SYN|FIN). 1200 * 1201 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1202 * as they do not affect the state of the TCP FSM. 1203 * The data pointed to by TH_URG and th_urp is ignored. 1204 */ 1205 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1206 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1207 KASSERT(thflags & (TH_SYN), 1208 ("%s: Listen socket: TH_SYN not set", __func__)); 1209#ifdef INET6 1210 /* 1211 * If deprecated address is forbidden, 1212 * we do not accept SYN to deprecated interface 1213 * address to prevent any new inbound connection from 1214 * getting established. 1215 * When we do not accept SYN, we send a TCP RST, 1216 * with deprecated source address (instead of dropping 1217 * it). We compromise it as it is much better for peer 1218 * to send a RST, and RST will be the final packet 1219 * for the exchange. 1220 * 1221 * If we do not forbid deprecated addresses, we accept 1222 * the SYN packet. RFC2462 does not suggest dropping 1223 * SYN in this case. 1224 * If we decipher RFC2462 5.5.4, it says like this: 1225 * 1. use of deprecated addr with existing 1226 * communication is okay - "SHOULD continue to be 1227 * used" 1228 * 2. use of it with new communication: 1229 * (2a) "SHOULD NOT be used if alternate address 1230 * with sufficient scope is available" 1231 * (2b) nothing mentioned otherwise. 1232 * Here we fall into (2b) case as we have no choice in 1233 * our source address selection - we must obey the peer. 1234 * 1235 * The wording in RFC2462 is confusing, and there are 1236 * multiple description text for deprecated address 1237 * handling - worse, they are not exactly the same. 1238 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1239 */ 1240 if (isipv6 && !V_ip6_use_deprecated) { 1241 struct in6_ifaddr *ia6; 1242 1243 ia6 = ip6_getdstifaddr(m); 1244 if (ia6 != NULL && 1245 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1246 ifa_free(&ia6->ia_ifa); 1247 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1248 log(LOG_DEBUG, "%s; %s: Listen socket: " 1249 "Connection attempt to deprecated " 1250 "IPv6 address rejected\n", 1251 s, __func__); 1252 rstreason = BANDLIM_RST_OPENPORT; 1253 goto dropwithreset; 1254 } 1255 if (ia6) 1256 ifa_free(&ia6->ia_ifa); 1257 } 1258#endif /* INET6 */ 1259 /* 1260 * Basic sanity checks on incoming SYN requests: 1261 * Don't respond if the destination is a link layer 1262 * broadcast according to RFC1122 4.2.3.10, p. 104. 1263 * If it is from this socket it must be forged. 1264 * Don't respond if the source or destination is a 1265 * global or subnet broad- or multicast address. 1266 * Note that it is quite possible to receive unicast 1267 * link-layer packets with a broadcast IP address. Use 1268 * in_broadcast() to find them. 1269 */ 1270 if (m->m_flags & (M_BCAST|M_MCAST)) { 1271 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1272 log(LOG_DEBUG, "%s; %s: Listen socket: " 1273 "Connection attempt from broad- or multicast " 1274 "link layer address ignored\n", s, __func__); 1275 goto dropunlock; 1276 } 1277#ifdef INET6 1278 if (isipv6) { 1279 if (th->th_dport == th->th_sport && 1280 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1281 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1282 log(LOG_DEBUG, "%s; %s: Listen socket: " 1283 "Connection attempt to/from self " 1284 "ignored\n", s, __func__); 1285 goto dropunlock; 1286 } 1287 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1288 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1289 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1290 log(LOG_DEBUG, "%s; %s: Listen socket: " 1291 "Connection attempt from/to multicast " 1292 "address ignored\n", s, __func__); 1293 goto dropunlock; 1294 } 1295 } 1296#endif 1297#if defined(INET) && defined(INET6) 1298 else 1299#endif 1300#ifdef INET 1301 { 1302 if (th->th_dport == th->th_sport && 1303 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1304 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1305 log(LOG_DEBUG, "%s; %s: Listen socket: " 1306 "Connection attempt from/to self " 1307 "ignored\n", s, __func__); 1308 goto dropunlock; 1309 } 1310 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1311 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1312 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1313 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1314 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1315 log(LOG_DEBUG, "%s; %s: Listen socket: " 1316 "Connection attempt from/to broad- " 1317 "or multicast address ignored\n", 1318 s, __func__); 1319 goto dropunlock; 1320 } 1321 } 1322#endif 1323 /* 1324 * SYN appears to be valid. Create compressed TCP state 1325 * for syncache. 1326 */ 1327#ifdef TCPDEBUG 1328 if (so->so_options & SO_DEBUG) 1329 tcp_trace(TA_INPUT, ostate, tp, 1330 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1331#endif 1332 tcp_dooptions(&to, optp, optlen, TO_SYN); 1333 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); 1334 /* 1335 * Entry added to syncache and mbuf consumed. 1336 * Everything already unlocked by syncache_add(). 1337 */ 1338 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1339 return; 1340 } else if (tp->t_state == TCPS_LISTEN) { 1341 /* 1342 * When a listen socket is torn down the SO_ACCEPTCONN 1343 * flag is removed first while connections are drained 1344 * from the accept queue in a unlock/lock cycle of the 1345 * ACCEPT_LOCK, opening a race condition allowing a SYN 1346 * attempt go through unhandled. 1347 */ 1348 goto dropunlock; 1349 } 1350 1351#ifdef TCP_SIGNATURE 1352 if (sig_checked == 0) { 1353 tcp_dooptions(&to, optp, optlen, 1354 (thflags & TH_SYN) ? TO_SYN : 0); 1355 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, 1356 th, tp->t_flags)) { 1357 1358 /* 1359 * In SYN_SENT state if it receives an RST, it is 1360 * allowed for further processing. 1361 */ 1362 if ((thflags & TH_RST) == 0 || 1363 (tp->t_state == TCPS_SYN_SENT) == 0) 1364 goto dropunlock; 1365 } 1366 sig_checked = 1; 1367 } 1368#endif 1369 1370 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1371 1372 /* 1373 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1374 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1375 * the inpcb, and unlocks pcbinfo. 1376 */ 1377 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1378 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1379 return; 1380 1381dropwithreset: 1382 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1383 1384 if (ti_locked == TI_WLOCKED) { 1385 INP_INFO_WUNLOCK(&V_tcbinfo); 1386 ti_locked = TI_UNLOCKED; 1387 } 1388#ifdef INVARIANTS 1389 else { 1390 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1391 "ti_locked: %d", __func__, ti_locked)); 1392 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1393 } 1394#endif 1395 1396 if (inp != NULL) { 1397 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1398 INP_WUNLOCK(inp); 1399 } else 1400 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1401 m = NULL; /* mbuf chain got consumed. */ 1402 goto drop; 1403 1404dropunlock: 1405 if (m != NULL) 1406 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1407 1408 if (ti_locked == TI_WLOCKED) { 1409 INP_INFO_WUNLOCK(&V_tcbinfo); 1410 ti_locked = TI_UNLOCKED; 1411 } 1412#ifdef INVARIANTS 1413 else { 1414 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1415 "ti_locked: %d", __func__, ti_locked)); 1416 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1417 } 1418#endif 1419 1420 if (inp != NULL) 1421 INP_WUNLOCK(inp); 1422 1423drop: 1424 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1425 if (s != NULL) 1426 free(s, M_TCPLOG); 1427 if (m != NULL) 1428 m_freem(m); 1429} 1430 1431static void 1432tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1433 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1434 int ti_locked) 1435{ 1436 int thflags, acked, ourfinisacked, needoutput = 0; 1437 int rstreason, todrop, win; 1438 u_long tiwin; 1439 char *s; 1440 struct in_conninfo *inc; 1441 struct mbuf *mfree; 1442 struct tcpopt to; 1443 1444#ifdef TCPDEBUG 1445 /* 1446 * The size of tcp_saveipgen must be the size of the max ip header, 1447 * now IPv6. 1448 */ 1449 u_char tcp_saveipgen[IP6_HDR_LEN]; 1450 struct tcphdr tcp_savetcp; 1451 short ostate = 0; 1452#endif 1453 thflags = th->th_flags; 1454 inc = &tp->t_inpcb->inp_inc; 1455 tp->sackhint.last_sack_ack = 0; 1456 1457 /* 1458 * If this is either a state-changing packet or current state isn't 1459 * established, we require a write lock on tcbinfo. Otherwise, we 1460 * allow the tcbinfo to be in either alocked or unlocked, as the 1461 * caller may have unnecessarily acquired a write lock due to a race. 1462 */ 1463 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1464 tp->t_state != TCPS_ESTABLISHED) { 1465 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for " 1466 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1467 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1468 } else { 1469#ifdef INVARIANTS 1470 if (ti_locked == TI_WLOCKED) 1471 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1472 else { 1473 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " 1474 "ti_locked: %d", __func__, ti_locked)); 1475 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1476 } 1477#endif 1478 } 1479 INP_WLOCK_ASSERT(tp->t_inpcb); 1480 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1481 __func__)); 1482 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1483 __func__)); 1484 1485 /* 1486 * Segment received on connection. 1487 * Reset idle time and keep-alive timer. 1488 * XXX: This should be done after segment 1489 * validation to ignore broken/spoofed segs. 1490 */ 1491 tp->t_rcvtime = ticks; 1492 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1493 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 1494 1495 /* 1496 * Unscale the window into a 32-bit value. 1497 * For the SYN_SENT state the scale is zero. 1498 */ 1499 tiwin = th->th_win << tp->snd_scale; 1500 1501 /* 1502 * TCP ECN processing. 1503 */ 1504 if (tp->t_flags & TF_ECN_PERMIT) { 1505 if (thflags & TH_CWR) 1506 tp->t_flags &= ~TF_ECN_SND_ECE; 1507 switch (iptos & IPTOS_ECN_MASK) { 1508 case IPTOS_ECN_CE: 1509 tp->t_flags |= TF_ECN_SND_ECE; 1510 TCPSTAT_INC(tcps_ecn_ce); 1511 break; 1512 case IPTOS_ECN_ECT0: 1513 TCPSTAT_INC(tcps_ecn_ect0); 1514 break; 1515 case IPTOS_ECN_ECT1: 1516 TCPSTAT_INC(tcps_ecn_ect1); 1517 break; 1518 } 1519 /* Congestion experienced. */ 1520 if (thflags & TH_ECE) { 1521 cc_cong_signal(tp, th, CC_ECN); 1522 } 1523 } 1524 1525 /* 1526 * Parse options on any incoming segment. 1527 */ 1528 tcp_dooptions(&to, (u_char *)(th + 1), 1529 (th->th_off << 2) - sizeof(struct tcphdr), 1530 (thflags & TH_SYN) ? TO_SYN : 0); 1531 1532 /* 1533 * If echoed timestamp is later than the current time, 1534 * fall back to non RFC1323 RTT calculation. Normalize 1535 * timestamp if syncookies were used when this connection 1536 * was established. 1537 */ 1538 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1539 to.to_tsecr -= tp->ts_offset; 1540 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1541 to.to_tsecr = 0; 1542 } 1543 /* 1544 * If timestamps were negotiated during SYN/ACK they should 1545 * appear on every segment during this session and vice versa. 1546 */ 1547 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1548 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1549 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1550 "no action\n", s, __func__); 1551 free(s, M_TCPLOG); 1552 } 1553 } 1554 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1555 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1556 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1557 "no action\n", s, __func__); 1558 free(s, M_TCPLOG); 1559 } 1560 } 1561 1562 /* 1563 * Process options only when we get SYN/ACK back. The SYN case 1564 * for incoming connections is handled in tcp_syncache. 1565 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1566 * or <SYN,ACK>) segment itself is never scaled. 1567 * XXX this is traditional behavior, may need to be cleaned up. 1568 */ 1569 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1570 if ((to.to_flags & TOF_SCALE) && 1571 (tp->t_flags & TF_REQ_SCALE)) { 1572 tp->t_flags |= TF_RCVD_SCALE; 1573 tp->snd_scale = to.to_wscale; 1574 } 1575 /* 1576 * Initial send window. It will be updated with 1577 * the next incoming segment to the scaled value. 1578 */ 1579 tp->snd_wnd = th->th_win; 1580 if (to.to_flags & TOF_TS) { 1581 tp->t_flags |= TF_RCVD_TSTMP; 1582 tp->ts_recent = to.to_tsval; 1583 tp->ts_recent_age = tcp_ts_getticks(); 1584 } 1585 if (to.to_flags & TOF_MSS) 1586 tcp_mss(tp, to.to_mss); 1587 if ((tp->t_flags & TF_SACK_PERMIT) && 1588 (to.to_flags & TOF_SACKPERM) == 0) 1589 tp->t_flags &= ~TF_SACK_PERMIT; 1590 } 1591 1592 /* 1593 * Header prediction: check for the two common cases 1594 * of a uni-directional data xfer. If the packet has 1595 * no control flags, is in-sequence, the window didn't 1596 * change and we're not retransmitting, it's a 1597 * candidate. If the length is zero and the ack moved 1598 * forward, we're the sender side of the xfer. Just 1599 * free the data acked & wake any higher level process 1600 * that was blocked waiting for space. If the length 1601 * is non-zero and the ack didn't move, we're the 1602 * receiver side. If we're getting packets in-order 1603 * (the reassembly queue is empty), add the data to 1604 * the socket buffer and note that we need a delayed ack. 1605 * Make sure that the hidden state-flags are also off. 1606 * Since we check for TCPS_ESTABLISHED first, it can only 1607 * be TH_NEEDSYN. 1608 */ 1609 if (tp->t_state == TCPS_ESTABLISHED && 1610 th->th_seq == tp->rcv_nxt && 1611 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1612 tp->snd_nxt == tp->snd_max && 1613 tiwin && tiwin == tp->snd_wnd && 1614 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1615 LIST_EMPTY(&tp->t_segq) && 1616 ((to.to_flags & TOF_TS) == 0 || 1617 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1618 1619 /* 1620 * If last ACK falls within this segment's sequence numbers, 1621 * record the timestamp. 1622 * NOTE that the test is modified according to the latest 1623 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1624 */ 1625 if ((to.to_flags & TOF_TS) != 0 && 1626 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1627 tp->ts_recent_age = tcp_ts_getticks(); 1628 tp->ts_recent = to.to_tsval; 1629 } 1630 1631 if (tlen == 0) { 1632 if (SEQ_GT(th->th_ack, tp->snd_una) && 1633 SEQ_LEQ(th->th_ack, tp->snd_max) && 1634 !IN_RECOVERY(tp->t_flags) && 1635 (to.to_flags & TOF_SACK) == 0 && 1636 TAILQ_EMPTY(&tp->snd_holes)) { 1637 /* 1638 * This is a pure ack for outstanding data. 1639 */ 1640 if (ti_locked == TI_WLOCKED) 1641 INP_INFO_WUNLOCK(&V_tcbinfo); 1642 ti_locked = TI_UNLOCKED; 1643 1644 TCPSTAT_INC(tcps_predack); 1645 1646 /* 1647 * "bad retransmit" recovery. 1648 */ 1649 if (tp->t_rxtshift == 1 && 1650 tp->t_flags & TF_PREVVALID && 1651 (int)(ticks - tp->t_badrxtwin) < 0) { 1652 cc_cong_signal(tp, th, CC_RTO_ERR); 1653 } 1654 1655 /* 1656 * Recalculate the transmit timer / rtt. 1657 * 1658 * Some boxes send broken timestamp replies 1659 * during the SYN+ACK phase, ignore 1660 * timestamps of 0 or we could calculate a 1661 * huge RTT and blow up the retransmit timer. 1662 */ 1663 if ((to.to_flags & TOF_TS) != 0 && 1664 to.to_tsecr) { 1665 u_int t; 1666 1667 t = tcp_ts_getticks() - to.to_tsecr; 1668 if (!tp->t_rttlow || tp->t_rttlow > t) 1669 tp->t_rttlow = t; 1670 tcp_xmit_timer(tp, 1671 TCP_TS_TO_TICKS(t) + 1); 1672 } else if (tp->t_rtttime && 1673 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1674 if (!tp->t_rttlow || 1675 tp->t_rttlow > ticks - tp->t_rtttime) 1676 tp->t_rttlow = ticks - tp->t_rtttime; 1677 tcp_xmit_timer(tp, 1678 ticks - tp->t_rtttime); 1679 } 1680 acked = BYTES_THIS_ACK(tp, th); 1681 1682 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1683 hhook_run_tcp_est_in(tp, th, &to); 1684 1685 TCPSTAT_INC(tcps_rcvackpack); 1686 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1687 sbdrop(&so->so_snd, acked); 1688 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1689 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1690 tp->snd_recover = th->th_ack - 1; 1691 1692 /* 1693 * Let the congestion control algorithm update 1694 * congestion control related information. This 1695 * typically means increasing the congestion 1696 * window. 1697 */ 1698 cc_ack_received(tp, th, CC_ACK); 1699 1700 tp->snd_una = th->th_ack; 1701 /* 1702 * Pull snd_wl2 up to prevent seq wrap relative 1703 * to th_ack. 1704 */ 1705 tp->snd_wl2 = th->th_ack; 1706 tp->t_dupacks = 0; 1707 m_freem(m); 1708 ND6_HINT(tp); /* Some progress has been made. */ 1709 1710 /* 1711 * If all outstanding data are acked, stop 1712 * retransmit timer, otherwise restart timer 1713 * using current (possibly backed-off) value. 1714 * If process is waiting for space, 1715 * wakeup/selwakeup/signal. If data 1716 * are ready to send, let tcp_output 1717 * decide between more output or persist. 1718 */ 1719#ifdef TCPDEBUG 1720 if (so->so_options & SO_DEBUG) 1721 tcp_trace(TA_INPUT, ostate, tp, 1722 (void *)tcp_saveipgen, 1723 &tcp_savetcp, 0); 1724#endif 1725 if (tp->snd_una == tp->snd_max) 1726 tcp_timer_activate(tp, TT_REXMT, 0); 1727 else if (!tcp_timer_active(tp, TT_PERSIST)) 1728 tcp_timer_activate(tp, TT_REXMT, 1729 tp->t_rxtcur); 1730 sowwakeup(so); 1731 if (so->so_snd.sb_cc) 1732 (void) tcp_output(tp); 1733 goto check_delack; 1734 } 1735 } else if (th->th_ack == tp->snd_una && 1736 tlen <= sbspace(&so->so_rcv)) { 1737 int newsize = 0; /* automatic sockbuf scaling */ 1738 1739 /* 1740 * This is a pure, in-sequence data packet with 1741 * nothing on the reassembly queue and we have enough 1742 * buffer space to take it. 1743 */ 1744 if (ti_locked == TI_WLOCKED) 1745 INP_INFO_WUNLOCK(&V_tcbinfo); 1746 ti_locked = TI_UNLOCKED; 1747 1748 /* Clean receiver SACK report if present */ 1749 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1750 tcp_clean_sackreport(tp); 1751 TCPSTAT_INC(tcps_preddat); 1752 tp->rcv_nxt += tlen; 1753 /* 1754 * Pull snd_wl1 up to prevent seq wrap relative to 1755 * th_seq. 1756 */ 1757 tp->snd_wl1 = th->th_seq; 1758 /* 1759 * Pull rcv_up up to prevent seq wrap relative to 1760 * rcv_nxt. 1761 */ 1762 tp->rcv_up = tp->rcv_nxt; 1763 TCPSTAT_INC(tcps_rcvpack); 1764 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1765 ND6_HINT(tp); /* Some progress has been made */ 1766#ifdef TCPDEBUG 1767 if (so->so_options & SO_DEBUG) 1768 tcp_trace(TA_INPUT, ostate, tp, 1769 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1770#endif 1771 /* 1772 * Automatic sizing of receive socket buffer. Often the send 1773 * buffer size is not optimally adjusted to the actual network 1774 * conditions at hand (delay bandwidth product). Setting the 1775 * buffer size too small limits throughput on links with high 1776 * bandwidth and high delay (eg. trans-continental/oceanic links). 1777 * 1778 * On the receive side the socket buffer memory is only rarely 1779 * used to any significant extent. This allows us to be much 1780 * more aggressive in scaling the receive socket buffer. For 1781 * the case that the buffer space is actually used to a large 1782 * extent and we run out of kernel memory we can simply drop 1783 * the new segments; TCP on the sender will just retransmit it 1784 * later. Setting the buffer size too big may only consume too 1785 * much kernel memory if the application doesn't read() from 1786 * the socket or packet loss or reordering makes use of the 1787 * reassembly queue. 1788 * 1789 * The criteria to step up the receive buffer one notch are: 1790 * 1. the number of bytes received during the time it takes 1791 * one timestamp to be reflected back to us (the RTT); 1792 * 2. received bytes per RTT is within seven eighth of the 1793 * current socket buffer size; 1794 * 3. receive buffer size has not hit maximal automatic size; 1795 * 1796 * This algorithm does one step per RTT at most and only if 1797 * we receive a bulk stream w/o packet losses or reorderings. 1798 * Shrinking the buffer during idle times is not necessary as 1799 * it doesn't consume any memory when idle. 1800 * 1801 * TODO: Only step up if the application is actually serving 1802 * the buffer to better manage the socket buffer resources. 1803 */ 1804 if (V_tcp_do_autorcvbuf && 1805 to.to_tsecr && 1806 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1807 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && 1808 to.to_tsecr - tp->rfbuf_ts < hz) { 1809 if (tp->rfbuf_cnt > 1810 (so->so_rcv.sb_hiwat / 8 * 7) && 1811 so->so_rcv.sb_hiwat < 1812 V_tcp_autorcvbuf_max) { 1813 newsize = 1814 min(so->so_rcv.sb_hiwat + 1815 V_tcp_autorcvbuf_inc, 1816 V_tcp_autorcvbuf_max); 1817 } 1818 /* Start over with next RTT. */ 1819 tp->rfbuf_ts = 0; 1820 tp->rfbuf_cnt = 0; 1821 } else 1822 tp->rfbuf_cnt += tlen; /* add up */ 1823 } 1824 1825 /* Add data to socket buffer. */ 1826 SOCKBUF_LOCK(&so->so_rcv); 1827 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1828 m_freem(m); 1829 } else { 1830 /* 1831 * Set new socket buffer size. 1832 * Give up when limit is reached. 1833 */ 1834 if (newsize) 1835 if (!sbreserve_locked(&so->so_rcv, 1836 newsize, so, NULL)) 1837 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1838 m_adj(m, drop_hdrlen); /* delayed header drop */ 1839 sbappendstream_locked(&so->so_rcv, m); 1840 } 1841 /* NB: sorwakeup_locked() does an implicit unlock. */ 1842 sorwakeup_locked(so); 1843 if (DELAY_ACK(tp, tlen)) { 1844 tp->t_flags |= TF_DELACK; 1845 } else { 1846 tp->t_flags |= TF_ACKNOW; 1847 tcp_output(tp); 1848 } 1849 goto check_delack; 1850 } 1851 } 1852 1853 /* 1854 * Calculate amount of space in receive window, 1855 * and then do TCP input processing. 1856 * Receive window is amount of space in rcv queue, 1857 * but not less than advertised window. 1858 */ 1859 win = sbspace(&so->so_rcv); 1860 if (win < 0) 1861 win = 0; 1862 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1863 1864 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1865 tp->rfbuf_ts = 0; 1866 tp->rfbuf_cnt = 0; 1867 1868 switch (tp->t_state) { 1869 1870 /* 1871 * If the state is SYN_RECEIVED: 1872 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1873 */ 1874 case TCPS_SYN_RECEIVED: 1875 if ((thflags & TH_ACK) && 1876 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1877 SEQ_GT(th->th_ack, tp->snd_max))) { 1878 rstreason = BANDLIM_RST_OPENPORT; 1879 goto dropwithreset; 1880 } 1881 break; 1882 1883 /* 1884 * If the state is SYN_SENT: 1885 * if seg contains an ACK, but not for our SYN, drop the input. 1886 * if seg contains a RST, then drop the connection. 1887 * if seg does not contain SYN, then drop it. 1888 * Otherwise this is an acceptable SYN segment 1889 * initialize tp->rcv_nxt and tp->irs 1890 * if seg contains ack then advance tp->snd_una 1891 * if seg contains an ECE and ECN support is enabled, the stream 1892 * is ECN capable. 1893 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1894 * arrange for segment to be acked (eventually) 1895 * continue processing rest of data/controls, beginning with URG 1896 */ 1897 case TCPS_SYN_SENT: 1898 if ((thflags & TH_ACK) && 1899 (SEQ_LEQ(th->th_ack, tp->iss) || 1900 SEQ_GT(th->th_ack, tp->snd_max))) { 1901 rstreason = BANDLIM_UNLIMITED; 1902 goto dropwithreset; 1903 } 1904 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 1905 TCP_PROBE5(connect__refused, NULL, tp, 1906 mtod(m, const char *), tp, th); 1907 tp = tcp_drop(tp, ECONNREFUSED); 1908 } 1909 if (thflags & TH_RST) 1910 goto drop; 1911 if (!(thflags & TH_SYN)) 1912 goto drop; 1913 1914 tp->irs = th->th_seq; 1915 tcp_rcvseqinit(tp); 1916 if (thflags & TH_ACK) { 1917 TCPSTAT_INC(tcps_connects); 1918 soisconnected(so); 1919#ifdef MAC 1920 mac_socketpeer_set_from_mbuf(m, so); 1921#endif 1922 /* Do window scaling on this connection? */ 1923 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1924 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1925 tp->rcv_scale = tp->request_r_scale; 1926 } 1927 tp->rcv_adv += imin(tp->rcv_wnd, 1928 TCP_MAXWIN << tp->rcv_scale); 1929 tp->snd_una++; /* SYN is acked */ 1930 /* 1931 * If there's data, delay ACK; if there's also a FIN 1932 * ACKNOW will be turned on later. 1933 */ 1934 if (DELAY_ACK(tp, tlen) && tlen != 0) 1935 tcp_timer_activate(tp, TT_DELACK, 1936 tcp_delacktime); 1937 else 1938 tp->t_flags |= TF_ACKNOW; 1939 1940 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 1941 tp->t_flags |= TF_ECN_PERMIT; 1942 TCPSTAT_INC(tcps_ecn_shs); 1943 } 1944 1945 /* 1946 * Received <SYN,ACK> in SYN_SENT[*] state. 1947 * Transitions: 1948 * SYN_SENT --> ESTABLISHED 1949 * SYN_SENT* --> FIN_WAIT_1 1950 */ 1951 tp->t_starttime = ticks; 1952 if (tp->t_flags & TF_NEEDFIN) { 1953 tcp_state_change(tp, TCPS_FIN_WAIT_1); 1954 tp->t_flags &= ~TF_NEEDFIN; 1955 thflags &= ~TH_SYN; 1956 } else { 1957 tcp_state_change(tp, TCPS_ESTABLISHED); 1958 TCP_PROBE5(connect__established, NULL, tp, 1959 mtod(m, const char *), tp, th); 1960 cc_conn_init(tp); 1961 tcp_timer_activate(tp, TT_KEEP, 1962 TP_KEEPIDLE(tp)); 1963 } 1964 } else { 1965 /* 1966 * Received initial SYN in SYN-SENT[*] state => 1967 * simultaneous open. If segment contains CC option 1968 * and there is a cached CC, apply TAO test. 1969 * If it succeeds, connection is * half-synchronized. 1970 * Otherwise, do 3-way handshake: 1971 * SYN-SENT -> SYN-RECEIVED 1972 * SYN-SENT* -> SYN-RECEIVED* 1973 * If there was no CC option, clear cached CC value. 1974 */ 1975 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1976 tcp_timer_activate(tp, TT_REXMT, 0); 1977 tcp_state_change(tp, TCPS_SYN_RECEIVED); 1978 } 1979 1980 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: " 1981 "ti_locked %d", __func__, ti_locked)); 1982 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1983 INP_WLOCK_ASSERT(tp->t_inpcb); 1984 1985 /* 1986 * Advance th->th_seq to correspond to first data byte. 1987 * If data, trim to stay within window, 1988 * dropping FIN if necessary. 1989 */ 1990 th->th_seq++; 1991 if (tlen > tp->rcv_wnd) { 1992 todrop = tlen - tp->rcv_wnd; 1993 m_adj(m, -todrop); 1994 tlen = tp->rcv_wnd; 1995 thflags &= ~TH_FIN; 1996 TCPSTAT_INC(tcps_rcvpackafterwin); 1997 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 1998 } 1999 tp->snd_wl1 = th->th_seq - 1; 2000 tp->rcv_up = th->th_seq; 2001 /* 2002 * Client side of transaction: already sent SYN and data. 2003 * If the remote host used T/TCP to validate the SYN, 2004 * our data will be ACK'd; if so, enter normal data segment 2005 * processing in the middle of step 5, ack processing. 2006 * Otherwise, goto step 6. 2007 */ 2008 if (thflags & TH_ACK) 2009 goto process_ACK; 2010 2011 goto step6; 2012 2013 /* 2014 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2015 * do normal processing. 2016 * 2017 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2018 */ 2019 case TCPS_LAST_ACK: 2020 case TCPS_CLOSING: 2021 break; /* continue normal processing */ 2022 } 2023 2024 /* 2025 * States other than LISTEN or SYN_SENT. 2026 * First check the RST flag and sequence number since reset segments 2027 * are exempt from the timestamp and connection count tests. This 2028 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2029 * below which allowed reset segments in half the sequence space 2030 * to fall though and be processed (which gives forged reset 2031 * segments with a random sequence number a 50 percent chance of 2032 * killing a connection). 2033 * Then check timestamp, if present. 2034 * Then check the connection count, if present. 2035 * Then check that at least some bytes of segment are within 2036 * receive window. If segment begins before rcv_nxt, 2037 * drop leading data (and SYN); if nothing left, just ack. 2038 * 2039 * 2040 * If the RST bit is set, check the sequence number to see 2041 * if this is a valid reset segment. 2042 * RFC 793 page 37: 2043 * In all states except SYN-SENT, all reset (RST) segments 2044 * are validated by checking their SEQ-fields. A reset is 2045 * valid if its sequence number is in the window. 2046 * Note: this does not take into account delayed ACKs, so 2047 * we should test against last_ack_sent instead of rcv_nxt. 2048 * The sequence number in the reset segment is normally an 2049 * echo of our outgoing acknowlegement numbers, but some hosts 2050 * send a reset with the sequence number at the rightmost edge 2051 * of our receive window, and we have to handle this case. 2052 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 2053 * that brute force RST attacks are possible. To combat this, 2054 * we use a much stricter check while in the ESTABLISHED state, 2055 * only accepting RSTs where the sequence number is equal to 2056 * last_ack_sent. In all other states (the states in which a 2057 * RST is more likely), the more permissive check is used. 2058 * If we have multiple segments in flight, the initial reset 2059 * segment sequence numbers will be to the left of last_ack_sent, 2060 * but they will eventually catch up. 2061 * In any case, it never made sense to trim reset segments to 2062 * fit the receive window since RFC 1122 says: 2063 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 2064 * 2065 * A TCP SHOULD allow a received RST segment to include data. 2066 * 2067 * DISCUSSION 2068 * It has been suggested that a RST segment could contain 2069 * ASCII text that encoded and explained the cause of the 2070 * RST. No standard has yet been established for such 2071 * data. 2072 * 2073 * If the reset segment passes the sequence number test examine 2074 * the state: 2075 * SYN_RECEIVED STATE: 2076 * If passive open, return to LISTEN state. 2077 * If active open, inform user that connection was refused. 2078 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 2079 * Inform user that connection was reset, and close tcb. 2080 * CLOSING, LAST_ACK STATES: 2081 * Close the tcb. 2082 * TIME_WAIT STATE: 2083 * Drop the segment - see Stevens, vol. 2, p. 964 and 2084 * RFC 1337. 2085 */ 2086 if (thflags & TH_RST) { 2087 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 2088 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2089 switch (tp->t_state) { 2090 2091 case TCPS_SYN_RECEIVED: 2092 so->so_error = ECONNREFUSED; 2093 goto close; 2094 2095 case TCPS_ESTABLISHED: 2096 if (V_tcp_insecure_rst == 0 && 2097 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && 2098 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && 2099 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 2100 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { 2101 TCPSTAT_INC(tcps_badrst); 2102 goto drop; 2103 } 2104 /* FALLTHROUGH */ 2105 case TCPS_FIN_WAIT_1: 2106 case TCPS_FIN_WAIT_2: 2107 case TCPS_CLOSE_WAIT: 2108 so->so_error = ECONNRESET; 2109 close: 2110 KASSERT(ti_locked == TI_WLOCKED, 2111 ("tcp_do_segment: TH_RST 1 ti_locked %d", 2112 ti_locked)); 2113 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2114 2115 tcp_state_change(tp, TCPS_CLOSED); 2116 TCPSTAT_INC(tcps_drops); 2117 tp = tcp_close(tp); 2118 break; 2119 2120 case TCPS_CLOSING: 2121 case TCPS_LAST_ACK: 2122 KASSERT(ti_locked == TI_WLOCKED, 2123 ("tcp_do_segment: TH_RST 2 ti_locked %d", 2124 ti_locked)); 2125 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2126 2127 tp = tcp_close(tp); 2128 break; 2129 } 2130 } 2131 goto drop; 2132 } 2133 2134 /* 2135 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2136 * and it's less than ts_recent, drop it. 2137 */ 2138 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2139 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2140 2141 /* Check to see if ts_recent is over 24 days old. */ 2142 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2143 /* 2144 * Invalidate ts_recent. If this segment updates 2145 * ts_recent, the age will be reset later and ts_recent 2146 * will get a valid value. If it does not, setting 2147 * ts_recent to zero will at least satisfy the 2148 * requirement that zero be placed in the timestamp 2149 * echo reply when ts_recent isn't valid. The 2150 * age isn't reset until we get a valid ts_recent 2151 * because we don't want out-of-order segments to be 2152 * dropped when ts_recent is old. 2153 */ 2154 tp->ts_recent = 0; 2155 } else { 2156 TCPSTAT_INC(tcps_rcvduppack); 2157 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2158 TCPSTAT_INC(tcps_pawsdrop); 2159 if (tlen) 2160 goto dropafterack; 2161 goto drop; 2162 } 2163 } 2164 2165 /* 2166 * In the SYN-RECEIVED state, validate that the packet belongs to 2167 * this connection before trimming the data to fit the receive 2168 * window. Check the sequence number versus IRS since we know 2169 * the sequence numbers haven't wrapped. This is a partial fix 2170 * for the "LAND" DoS attack. 2171 */ 2172 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2173 rstreason = BANDLIM_RST_OPENPORT; 2174 goto dropwithreset; 2175 } 2176 2177 todrop = tp->rcv_nxt - th->th_seq; 2178 if (todrop > 0) { 2179 if (thflags & TH_SYN) { 2180 thflags &= ~TH_SYN; 2181 th->th_seq++; 2182 if (th->th_urp > 1) 2183 th->th_urp--; 2184 else 2185 thflags &= ~TH_URG; 2186 todrop--; 2187 } 2188 /* 2189 * Following if statement from Stevens, vol. 2, p. 960. 2190 */ 2191 if (todrop > tlen 2192 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2193 /* 2194 * Any valid FIN must be to the left of the window. 2195 * At this point the FIN must be a duplicate or out 2196 * of sequence; drop it. 2197 */ 2198 thflags &= ~TH_FIN; 2199 2200 /* 2201 * Send an ACK to resynchronize and drop any data. 2202 * But keep on processing for RST or ACK. 2203 */ 2204 tp->t_flags |= TF_ACKNOW; 2205 todrop = tlen; 2206 TCPSTAT_INC(tcps_rcvduppack); 2207 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2208 } else { 2209 TCPSTAT_INC(tcps_rcvpartduppack); 2210 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2211 } 2212 drop_hdrlen += todrop; /* drop from the top afterwards */ 2213 th->th_seq += todrop; 2214 tlen -= todrop; 2215 if (th->th_urp > todrop) 2216 th->th_urp -= todrop; 2217 else { 2218 thflags &= ~TH_URG; 2219 th->th_urp = 0; 2220 } 2221 } 2222 2223 /* 2224 * If new data are received on a connection after the 2225 * user processes are gone, then RST the other end. 2226 */ 2227 if ((so->so_state & SS_NOFDREF) && 2228 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2229 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && " 2230 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 2231 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2232 2233 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2234 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2235 "after socket was closed, " 2236 "sending RST and removing tcpcb\n", 2237 s, __func__, tcpstates[tp->t_state], tlen); 2238 free(s, M_TCPLOG); 2239 } 2240 tp = tcp_close(tp); 2241 TCPSTAT_INC(tcps_rcvafterclose); 2242 rstreason = BANDLIM_UNLIMITED; 2243 goto dropwithreset; 2244 } 2245 2246 /* 2247 * If segment ends after window, drop trailing data 2248 * (and PUSH and FIN); if nothing left, just ACK. 2249 */ 2250 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2251 if (todrop > 0) { 2252 TCPSTAT_INC(tcps_rcvpackafterwin); 2253 if (todrop >= tlen) { 2254 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2255 /* 2256 * If window is closed can only take segments at 2257 * window edge, and have to drop data and PUSH from 2258 * incoming segments. Continue processing, but 2259 * remember to ack. Otherwise, drop segment 2260 * and ack. 2261 */ 2262 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2263 tp->t_flags |= TF_ACKNOW; 2264 TCPSTAT_INC(tcps_rcvwinprobe); 2265 } else 2266 goto dropafterack; 2267 } else 2268 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2269 m_adj(m, -todrop); 2270 tlen -= todrop; 2271 thflags &= ~(TH_PUSH|TH_FIN); 2272 } 2273 2274 /* 2275 * If last ACK falls within this segment's sequence numbers, 2276 * record its timestamp. 2277 * NOTE: 2278 * 1) That the test incorporates suggestions from the latest 2279 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2280 * 2) That updating only on newer timestamps interferes with 2281 * our earlier PAWS tests, so this check should be solely 2282 * predicated on the sequence space of this segment. 2283 * 3) That we modify the segment boundary check to be 2284 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2285 * instead of RFC1323's 2286 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2287 * This modified check allows us to overcome RFC1323's 2288 * limitations as described in Stevens TCP/IP Illustrated 2289 * Vol. 2 p.869. In such cases, we can still calculate the 2290 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2291 */ 2292 if ((to.to_flags & TOF_TS) != 0 && 2293 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2294 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2295 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2296 tp->ts_recent_age = tcp_ts_getticks(); 2297 tp->ts_recent = to.to_tsval; 2298 } 2299 2300 /* 2301 * If a SYN is in the window, then this is an 2302 * error and we send an RST and drop the connection. 2303 */ 2304 if (thflags & TH_SYN) { 2305 KASSERT(ti_locked == TI_WLOCKED, 2306 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 2307 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2308 2309 tp = tcp_drop(tp, ECONNRESET); 2310 rstreason = BANDLIM_UNLIMITED; 2311 goto drop; 2312 } 2313 2314 /* 2315 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2316 * flag is on (half-synchronized state), then queue data for 2317 * later processing; else drop segment and return. 2318 */ 2319 if ((thflags & TH_ACK) == 0) { 2320 if (tp->t_state == TCPS_SYN_RECEIVED || 2321 (tp->t_flags & TF_NEEDSYN)) 2322 goto step6; 2323 else if (tp->t_flags & TF_ACKNOW) 2324 goto dropafterack; 2325 else 2326 goto drop; 2327 } 2328 2329 /* 2330 * Ack processing. 2331 */ 2332 switch (tp->t_state) { 2333 2334 /* 2335 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2336 * ESTABLISHED state and continue processing. 2337 * The ACK was checked above. 2338 */ 2339 case TCPS_SYN_RECEIVED: 2340 2341 TCPSTAT_INC(tcps_connects); 2342 soisconnected(so); 2343 /* Do window scaling? */ 2344 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2345 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2346 tp->rcv_scale = tp->request_r_scale; 2347 tp->snd_wnd = tiwin; 2348 } 2349 /* 2350 * Make transitions: 2351 * SYN-RECEIVED -> ESTABLISHED 2352 * SYN-RECEIVED* -> FIN-WAIT-1 2353 */ 2354 tp->t_starttime = ticks; 2355 if (tp->t_flags & TF_NEEDFIN) { 2356 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2357 tp->t_flags &= ~TF_NEEDFIN; 2358 } else { 2359 tcp_state_change(tp, TCPS_ESTABLISHED); 2360 TCP_PROBE5(accept__established, NULL, tp, 2361 mtod(m, const char *), tp, th); 2362 cc_conn_init(tp); 2363 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2364 } 2365 /* 2366 * If segment contains data or ACK, will call tcp_reass() 2367 * later; if not, do so now to pass queued data to user. 2368 */ 2369 if (tlen == 0 && (thflags & TH_FIN) == 0) 2370 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2371 (struct mbuf *)0); 2372 tp->snd_wl1 = th->th_seq - 1; 2373 /* FALLTHROUGH */ 2374 2375 /* 2376 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2377 * ACKs. If the ack is in the range 2378 * tp->snd_una < th->th_ack <= tp->snd_max 2379 * then advance tp->snd_una to th->th_ack and drop 2380 * data from the retransmission queue. If this ACK reflects 2381 * more up to date window information we update our window information. 2382 */ 2383 case TCPS_ESTABLISHED: 2384 case TCPS_FIN_WAIT_1: 2385 case TCPS_FIN_WAIT_2: 2386 case TCPS_CLOSE_WAIT: 2387 case TCPS_CLOSING: 2388 case TCPS_LAST_ACK: 2389 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2390 TCPSTAT_INC(tcps_rcvacktoomuch); 2391 goto dropafterack; 2392 } 2393 if ((tp->t_flags & TF_SACK_PERMIT) && 2394 ((to.to_flags & TOF_SACK) || 2395 !TAILQ_EMPTY(&tp->snd_holes))) 2396 tcp_sack_doack(tp, &to, th->th_ack); 2397 2398 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2399 hhook_run_tcp_est_in(tp, th, &to); 2400 2401 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2402 if (tlen == 0 && tiwin == tp->snd_wnd) { 2403 TCPSTAT_INC(tcps_rcvdupack); 2404 /* 2405 * If we have outstanding data (other than 2406 * a window probe), this is a completely 2407 * duplicate ack (ie, window info didn't 2408 * change), the ack is the biggest we've 2409 * seen and we've seen exactly our rexmt 2410 * threshhold of them, assume a packet 2411 * has been dropped and retransmit it. 2412 * Kludge snd_nxt & the congestion 2413 * window so we send only this one 2414 * packet. 2415 * 2416 * We know we're losing at the current 2417 * window size so do congestion avoidance 2418 * (set ssthresh to half the current window 2419 * and pull our congestion window back to 2420 * the new ssthresh). 2421 * 2422 * Dup acks mean that packets have left the 2423 * network (they're now cached at the receiver) 2424 * so bump cwnd by the amount in the receiver 2425 * to keep a constant cwnd packets in the 2426 * network. 2427 * 2428 * When using TCP ECN, notify the peer that 2429 * we reduced the cwnd. 2430 */ 2431 if (!tcp_timer_active(tp, TT_REXMT) || 2432 th->th_ack != tp->snd_una) 2433 tp->t_dupacks = 0; 2434 else if (++tp->t_dupacks > tcprexmtthresh || 2435 IN_FASTRECOVERY(tp->t_flags)) { 2436 cc_ack_received(tp, th, CC_DUPACK); 2437 if ((tp->t_flags & TF_SACK_PERMIT) && 2438 IN_FASTRECOVERY(tp->t_flags)) { 2439 int awnd; 2440 2441 /* 2442 * Compute the amount of data in flight first. 2443 * We can inject new data into the pipe iff 2444 * we have less than 1/2 the original window's 2445 * worth of data in flight. 2446 */ 2447 awnd = (tp->snd_nxt - tp->snd_fack) + 2448 tp->sackhint.sack_bytes_rexmit; 2449 if (awnd < tp->snd_ssthresh) { 2450 tp->snd_cwnd += tp->t_maxseg; 2451 if (tp->snd_cwnd > tp->snd_ssthresh) 2452 tp->snd_cwnd = tp->snd_ssthresh; 2453 } 2454 } else 2455 tp->snd_cwnd += tp->t_maxseg; 2456 if ((thflags & TH_FIN) && 2457 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2458 /* 2459 * If its a fin we need to process 2460 * it to avoid a race where both 2461 * sides enter FIN-WAIT and send FIN|ACK 2462 * at the same time. 2463 */ 2464 break; 2465 } 2466 (void) tcp_output(tp); 2467 goto drop; 2468 } else if (tp->t_dupacks == tcprexmtthresh) { 2469 tcp_seq onxt = tp->snd_nxt; 2470 2471 /* 2472 * If we're doing sack, check to 2473 * see if we're already in sack 2474 * recovery. If we're not doing sack, 2475 * check to see if we're in newreno 2476 * recovery. 2477 */ 2478 if (tp->t_flags & TF_SACK_PERMIT) { 2479 if (IN_FASTRECOVERY(tp->t_flags)) { 2480 tp->t_dupacks = 0; 2481 break; 2482 } 2483 } else { 2484 if (SEQ_LEQ(th->th_ack, 2485 tp->snd_recover)) { 2486 tp->t_dupacks = 0; 2487 break; 2488 } 2489 } 2490 /* Congestion signal before ack. */ 2491 cc_cong_signal(tp, th, CC_NDUPACK); 2492 cc_ack_received(tp, th, CC_DUPACK); 2493 tcp_timer_activate(tp, TT_REXMT, 0); 2494 tp->t_rtttime = 0; 2495 if (tp->t_flags & TF_SACK_PERMIT) { 2496 TCPSTAT_INC( 2497 tcps_sack_recovery_episode); 2498 tp->sack_newdata = tp->snd_nxt; 2499 tp->snd_cwnd = tp->t_maxseg; 2500 (void) tcp_output(tp); 2501 goto drop; 2502 } 2503 tp->snd_nxt = th->th_ack; 2504 tp->snd_cwnd = tp->t_maxseg; 2505 if ((thflags & TH_FIN) && 2506 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2507 /* 2508 * If its a fin we need to process 2509 * it to avoid a race where both 2510 * sides enter FIN-WAIT and send FIN|ACK 2511 * at the same time. 2512 */ 2513 break; 2514 } 2515 (void) tcp_output(tp); 2516 KASSERT(tp->snd_limited <= 2, 2517 ("%s: tp->snd_limited too big", 2518 __func__)); 2519 tp->snd_cwnd = tp->snd_ssthresh + 2520 tp->t_maxseg * 2521 (tp->t_dupacks - tp->snd_limited); 2522 if (SEQ_GT(onxt, tp->snd_nxt)) 2523 tp->snd_nxt = onxt; 2524 goto drop; 2525 } else if (V_tcp_do_rfc3042) { 2526 cc_ack_received(tp, th, CC_DUPACK); 2527 u_long oldcwnd = tp->snd_cwnd; 2528 tcp_seq oldsndmax = tp->snd_max; 2529 u_int sent; 2530 int avail; 2531 2532 KASSERT(tp->t_dupacks == 1 || 2533 tp->t_dupacks == 2, 2534 ("%s: dupacks not 1 or 2", 2535 __func__)); 2536 if (tp->t_dupacks == 1) 2537 tp->snd_limited = 0; 2538 tp->snd_cwnd = 2539 (tp->snd_nxt - tp->snd_una) + 2540 (tp->t_dupacks - tp->snd_limited) * 2541 tp->t_maxseg; 2542 if ((thflags & TH_FIN) && 2543 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2544 /* 2545 * If its a fin we need to process 2546 * it to avoid a race where both 2547 * sides enter FIN-WAIT and send FIN|ACK 2548 * at the same time. 2549 */ 2550 break; 2551 } 2552 /* 2553 * Only call tcp_output when there 2554 * is new data available to be sent. 2555 * Otherwise we would send pure ACKs. 2556 */ 2557 SOCKBUF_LOCK(&so->so_snd); 2558 avail = so->so_snd.sb_cc - 2559 (tp->snd_nxt - tp->snd_una); 2560 SOCKBUF_UNLOCK(&so->so_snd); 2561 if (avail > 0) 2562 (void) tcp_output(tp); 2563 sent = tp->snd_max - oldsndmax; 2564 if (sent > tp->t_maxseg) { 2565 KASSERT((tp->t_dupacks == 2 && 2566 tp->snd_limited == 0) || 2567 (sent == tp->t_maxseg + 1 && 2568 tp->t_flags & TF_SENTFIN), 2569 ("%s: sent too much", 2570 __func__)); 2571 tp->snd_limited = 2; 2572 } else if (sent > 0) 2573 ++tp->snd_limited; 2574 tp->snd_cwnd = oldcwnd; 2575 goto drop; 2576 } 2577 } else 2578 tp->t_dupacks = 0; 2579 break; 2580 } 2581 2582 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2583 ("%s: th_ack <= snd_una", __func__)); 2584 2585 /* 2586 * If the congestion window was inflated to account 2587 * for the other side's cached packets, retract it. 2588 */ 2589 if (IN_FASTRECOVERY(tp->t_flags)) { 2590 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2591 if (tp->t_flags & TF_SACK_PERMIT) 2592 tcp_sack_partialack(tp, th); 2593 else 2594 tcp_newreno_partial_ack(tp, th); 2595 } else 2596 cc_post_recovery(tp, th); 2597 } 2598 tp->t_dupacks = 0; 2599 /* 2600 * If we reach this point, ACK is not a duplicate, 2601 * i.e., it ACKs something we sent. 2602 */ 2603 if (tp->t_flags & TF_NEEDSYN) { 2604 /* 2605 * T/TCP: Connection was half-synchronized, and our 2606 * SYN has been ACK'd (so connection is now fully 2607 * synchronized). Go to non-starred state, 2608 * increment snd_una for ACK of SYN, and check if 2609 * we can do window scaling. 2610 */ 2611 tp->t_flags &= ~TF_NEEDSYN; 2612 tp->snd_una++; 2613 /* Do window scaling? */ 2614 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2615 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2616 tp->rcv_scale = tp->request_r_scale; 2617 /* Send window already scaled. */ 2618 } 2619 } 2620 2621process_ACK: 2622 INP_WLOCK_ASSERT(tp->t_inpcb); 2623 2624 acked = BYTES_THIS_ACK(tp, th); 2625 TCPSTAT_INC(tcps_rcvackpack); 2626 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2627 2628 /* 2629 * If we just performed our first retransmit, and the ACK 2630 * arrives within our recovery window, then it was a mistake 2631 * to do the retransmit in the first place. Recover our 2632 * original cwnd and ssthresh, and proceed to transmit where 2633 * we left off. 2634 */ 2635 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && 2636 (int)(ticks - tp->t_badrxtwin) < 0) 2637 cc_cong_signal(tp, th, CC_RTO_ERR); 2638 2639 /* 2640 * If we have a timestamp reply, update smoothed 2641 * round trip time. If no timestamp is present but 2642 * transmit timer is running and timed sequence 2643 * number was acked, update smoothed round trip time. 2644 * Since we now have an rtt measurement, cancel the 2645 * timer backoff (cf., Phil Karn's retransmit alg.). 2646 * Recompute the initial retransmit timer. 2647 * 2648 * Some boxes send broken timestamp replies 2649 * during the SYN+ACK phase, ignore 2650 * timestamps of 0 or we could calculate a 2651 * huge RTT and blow up the retransmit timer. 2652 */ 2653 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2654 u_int t; 2655 2656 t = tcp_ts_getticks() - to.to_tsecr; 2657 if (!tp->t_rttlow || tp->t_rttlow > t) 2658 tp->t_rttlow = t; 2659 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2660 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2661 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2662 tp->t_rttlow = ticks - tp->t_rtttime; 2663 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2664 } 2665 2666 /* 2667 * If all outstanding data is acked, stop retransmit 2668 * timer and remember to restart (more output or persist). 2669 * If there is more data to be acked, restart retransmit 2670 * timer, using current (possibly backed-off) value. 2671 */ 2672 if (th->th_ack == tp->snd_max) { 2673 tcp_timer_activate(tp, TT_REXMT, 0); 2674 needoutput = 1; 2675 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2676 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2677 2678 /* 2679 * If no data (only SYN) was ACK'd, 2680 * skip rest of ACK processing. 2681 */ 2682 if (acked == 0) 2683 goto step6; 2684 2685 /* 2686 * Let the congestion control algorithm update congestion 2687 * control related information. This typically means increasing 2688 * the congestion window. 2689 */ 2690 cc_ack_received(tp, th, CC_ACK); 2691 2692 SOCKBUF_LOCK(&so->so_snd); 2693 if (acked > so->so_snd.sb_cc) { 2694 tp->snd_wnd -= so->so_snd.sb_cc; 2695 mfree = sbcut_locked(&so->so_snd, 2696 (int)so->so_snd.sb_cc); 2697 ourfinisacked = 1; 2698 } else { 2699 mfree = sbcut_locked(&so->so_snd, acked); 2700 tp->snd_wnd -= acked; 2701 ourfinisacked = 0; 2702 } 2703 /* NB: sowwakeup_locked() does an implicit unlock. */ 2704 sowwakeup_locked(so); 2705 m_freem(mfree); 2706 /* Detect una wraparound. */ 2707 if (!IN_RECOVERY(tp->t_flags) && 2708 SEQ_GT(tp->snd_una, tp->snd_recover) && 2709 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2710 tp->snd_recover = th->th_ack - 1; 2711 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2712 if (IN_RECOVERY(tp->t_flags) && 2713 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2714 EXIT_RECOVERY(tp->t_flags); 2715 } 2716 tp->snd_una = th->th_ack; 2717 if (tp->t_flags & TF_SACK_PERMIT) { 2718 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2719 tp->snd_recover = tp->snd_una; 2720 } 2721 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2722 tp->snd_nxt = tp->snd_una; 2723 2724 switch (tp->t_state) { 2725 2726 /* 2727 * In FIN_WAIT_1 STATE in addition to the processing 2728 * for the ESTABLISHED state if our FIN is now acknowledged 2729 * then enter FIN_WAIT_2. 2730 */ 2731 case TCPS_FIN_WAIT_1: 2732 if (ourfinisacked) { 2733 /* 2734 * If we can't receive any more 2735 * data, then closing user can proceed. 2736 * Starting the timer is contrary to the 2737 * specification, but if we don't get a FIN 2738 * we'll hang forever. 2739 * 2740 * XXXjl: 2741 * we should release the tp also, and use a 2742 * compressed state. 2743 */ 2744 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2745 soisdisconnected(so); 2746 tcp_timer_activate(tp, TT_2MSL, 2747 (tcp_fast_finwait2_recycle ? 2748 tcp_finwait2_timeout : 2749 TP_MAXIDLE(tp))); 2750 } 2751 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2752 } 2753 break; 2754 2755 /* 2756 * In CLOSING STATE in addition to the processing for 2757 * the ESTABLISHED state if the ACK acknowledges our FIN 2758 * then enter the TIME-WAIT state, otherwise ignore 2759 * the segment. 2760 */ 2761 case TCPS_CLOSING: 2762 if (ourfinisacked) { 2763 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2764 tcp_twstart(tp); 2765 INP_INFO_WUNLOCK(&V_tcbinfo); 2766 m_freem(m); 2767 return; 2768 } 2769 break; 2770 2771 /* 2772 * In LAST_ACK, we may still be waiting for data to drain 2773 * and/or to be acked, as well as for the ack of our FIN. 2774 * If our FIN is now acknowledged, delete the TCB, 2775 * enter the closed state and return. 2776 */ 2777 case TCPS_LAST_ACK: 2778 if (ourfinisacked) { 2779 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2780 tp = tcp_close(tp); 2781 goto drop; 2782 } 2783 break; 2784 } 2785 } 2786 2787step6: 2788 INP_WLOCK_ASSERT(tp->t_inpcb); 2789 2790 /* 2791 * Update window information. 2792 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2793 */ 2794 if ((thflags & TH_ACK) && 2795 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2796 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2797 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2798 /* keep track of pure window updates */ 2799 if (tlen == 0 && 2800 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2801 TCPSTAT_INC(tcps_rcvwinupd); 2802 tp->snd_wnd = tiwin; 2803 tp->snd_wl1 = th->th_seq; 2804 tp->snd_wl2 = th->th_ack; 2805 if (tp->snd_wnd > tp->max_sndwnd) 2806 tp->max_sndwnd = tp->snd_wnd; 2807 needoutput = 1; 2808 } 2809 2810 /* 2811 * Process segments with URG. 2812 */ 2813 if ((thflags & TH_URG) && th->th_urp && 2814 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2815 /* 2816 * This is a kludge, but if we receive and accept 2817 * random urgent pointers, we'll crash in 2818 * soreceive. It's hard to imagine someone 2819 * actually wanting to send this much urgent data. 2820 */ 2821 SOCKBUF_LOCK(&so->so_rcv); 2822 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2823 th->th_urp = 0; /* XXX */ 2824 thflags &= ~TH_URG; /* XXX */ 2825 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2826 goto dodata; /* XXX */ 2827 } 2828 /* 2829 * If this segment advances the known urgent pointer, 2830 * then mark the data stream. This should not happen 2831 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2832 * a FIN has been received from the remote side. 2833 * In these states we ignore the URG. 2834 * 2835 * According to RFC961 (Assigned Protocols), 2836 * the urgent pointer points to the last octet 2837 * of urgent data. We continue, however, 2838 * to consider it to indicate the first octet 2839 * of data past the urgent section as the original 2840 * spec states (in one of two places). 2841 */ 2842 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2843 tp->rcv_up = th->th_seq + th->th_urp; 2844 so->so_oobmark = so->so_rcv.sb_cc + 2845 (tp->rcv_up - tp->rcv_nxt) - 1; 2846 if (so->so_oobmark == 0) 2847 so->so_rcv.sb_state |= SBS_RCVATMARK; 2848 sohasoutofband(so); 2849 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2850 } 2851 SOCKBUF_UNLOCK(&so->so_rcv); 2852 /* 2853 * Remove out of band data so doesn't get presented to user. 2854 * This can happen independent of advancing the URG pointer, 2855 * but if two URG's are pending at once, some out-of-band 2856 * data may creep in... ick. 2857 */ 2858 if (th->th_urp <= (u_long)tlen && 2859 !(so->so_options & SO_OOBINLINE)) { 2860 /* hdr drop is delayed */ 2861 tcp_pulloutofband(so, th, m, drop_hdrlen); 2862 } 2863 } else { 2864 /* 2865 * If no out of band data is expected, 2866 * pull receive urgent pointer along 2867 * with the receive window. 2868 */ 2869 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2870 tp->rcv_up = tp->rcv_nxt; 2871 } 2872dodata: /* XXX */ 2873 INP_WLOCK_ASSERT(tp->t_inpcb); 2874 2875 /* 2876 * Process the segment text, merging it into the TCP sequencing queue, 2877 * and arranging for acknowledgment of receipt if necessary. 2878 * This process logically involves adjusting tp->rcv_wnd as data 2879 * is presented to the user (this happens in tcp_usrreq.c, 2880 * case PRU_RCVD). If a FIN has already been received on this 2881 * connection then we just ignore the text. 2882 */ 2883 if ((tlen || (thflags & TH_FIN)) && 2884 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2885 tcp_seq save_start = th->th_seq; 2886 m_adj(m, drop_hdrlen); /* delayed header drop */ 2887 /* 2888 * Insert segment which includes th into TCP reassembly queue 2889 * with control block tp. Set thflags to whether reassembly now 2890 * includes a segment with FIN. This handles the common case 2891 * inline (segment is the next to be received on an established 2892 * connection, and the queue is empty), avoiding linkage into 2893 * and removal from the queue and repetition of various 2894 * conversions. 2895 * Set DELACK for segments received in order, but ack 2896 * immediately when segments are out of order (so 2897 * fast retransmit can work). 2898 */ 2899 if (th->th_seq == tp->rcv_nxt && 2900 LIST_EMPTY(&tp->t_segq) && 2901 TCPS_HAVEESTABLISHED(tp->t_state)) { 2902 if (DELAY_ACK(tp, tlen)) 2903 tp->t_flags |= TF_DELACK; 2904 else 2905 tp->t_flags |= TF_ACKNOW; 2906 tp->rcv_nxt += tlen; 2907 thflags = th->th_flags & TH_FIN; 2908 TCPSTAT_INC(tcps_rcvpack); 2909 TCPSTAT_ADD(tcps_rcvbyte, tlen); 2910 ND6_HINT(tp); 2911 SOCKBUF_LOCK(&so->so_rcv); 2912 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2913 m_freem(m); 2914 else 2915 sbappendstream_locked(&so->so_rcv, m); 2916 /* NB: sorwakeup_locked() does an implicit unlock. */ 2917 sorwakeup_locked(so); 2918 } else { 2919 /* 2920 * XXX: Due to the header drop above "th" is 2921 * theoretically invalid by now. Fortunately 2922 * m_adj() doesn't actually frees any mbufs 2923 * when trimming from the head. 2924 */ 2925 thflags = tcp_reass(tp, th, &tlen, m); 2926 tp->t_flags |= TF_ACKNOW; 2927 } 2928 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 2929 tcp_update_sack_list(tp, save_start, save_start + tlen); 2930#if 0 2931 /* 2932 * Note the amount of data that peer has sent into 2933 * our window, in order to estimate the sender's 2934 * buffer size. 2935 * XXX: Unused. 2936 */ 2937 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 2938 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2939 else 2940 len = so->so_rcv.sb_hiwat; 2941#endif 2942 } else { 2943 m_freem(m); 2944 thflags &= ~TH_FIN; 2945 } 2946 2947 /* 2948 * If FIN is received ACK the FIN and let the user know 2949 * that the connection is closing. 2950 */ 2951 if (thflags & TH_FIN) { 2952 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2953 socantrcvmore(so); 2954 /* 2955 * If connection is half-synchronized 2956 * (ie NEEDSYN flag on) then delay ACK, 2957 * so it may be piggybacked when SYN is sent. 2958 * Otherwise, since we received a FIN then no 2959 * more input can be expected, send ACK now. 2960 */ 2961 if (tp->t_flags & TF_NEEDSYN) 2962 tp->t_flags |= TF_DELACK; 2963 else 2964 tp->t_flags |= TF_ACKNOW; 2965 tp->rcv_nxt++; 2966 } 2967 switch (tp->t_state) { 2968 2969 /* 2970 * In SYN_RECEIVED and ESTABLISHED STATES 2971 * enter the CLOSE_WAIT state. 2972 */ 2973 case TCPS_SYN_RECEIVED: 2974 tp->t_starttime = ticks; 2975 /* FALLTHROUGH */ 2976 case TCPS_ESTABLISHED: 2977 tcp_state_change(tp, TCPS_CLOSE_WAIT); 2978 break; 2979 2980 /* 2981 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2982 * enter the CLOSING state. 2983 */ 2984 case TCPS_FIN_WAIT_1: 2985 tcp_state_change(tp, TCPS_CLOSING); 2986 break; 2987 2988 /* 2989 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2990 * starting the time-wait timer, turning off the other 2991 * standard timers. 2992 */ 2993 case TCPS_FIN_WAIT_2: 2994 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2995 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata " 2996 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 2997 ti_locked)); 2998 2999 tcp_twstart(tp); 3000 INP_INFO_WUNLOCK(&V_tcbinfo); 3001 return; 3002 } 3003 } 3004 if (ti_locked == TI_WLOCKED) 3005 INP_INFO_WUNLOCK(&V_tcbinfo); 3006 ti_locked = TI_UNLOCKED; 3007 3008#ifdef TCPDEBUG 3009 if (so->so_options & SO_DEBUG) 3010 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3011 &tcp_savetcp, 0); 3012#endif 3013 3014 /* 3015 * Return any desired output. 3016 */ 3017 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3018 (void) tcp_output(tp); 3019 3020check_delack: 3021 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 3022 __func__, ti_locked)); 3023 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3024 INP_WLOCK_ASSERT(tp->t_inpcb); 3025 3026 if (tp->t_flags & TF_DELACK) { 3027 tp->t_flags &= ~TF_DELACK; 3028 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3029 } 3030 INP_WUNLOCK(tp->t_inpcb); 3031 return; 3032 3033dropafterack: 3034 /* 3035 * Generate an ACK dropping incoming segment if it occupies 3036 * sequence space, where the ACK reflects our state. 3037 * 3038 * We can now skip the test for the RST flag since all 3039 * paths to this code happen after packets containing 3040 * RST have been dropped. 3041 * 3042 * In the SYN-RECEIVED state, don't send an ACK unless the 3043 * segment we received passes the SYN-RECEIVED ACK test. 3044 * If it fails send a RST. This breaks the loop in the 3045 * "LAND" DoS attack, and also prevents an ACK storm 3046 * between two listening ports that have been sent forged 3047 * SYN segments, each with the source address of the other. 3048 */ 3049 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3050 (SEQ_GT(tp->snd_una, th->th_ack) || 3051 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3052 rstreason = BANDLIM_RST_OPENPORT; 3053 goto dropwithreset; 3054 } 3055#ifdef TCPDEBUG 3056 if (so->so_options & SO_DEBUG) 3057 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3058 &tcp_savetcp, 0); 3059#endif 3060 if (ti_locked == TI_WLOCKED) 3061 INP_INFO_WUNLOCK(&V_tcbinfo); 3062 ti_locked = TI_UNLOCKED; 3063 3064 tp->t_flags |= TF_ACKNOW; 3065 (void) tcp_output(tp); 3066 INP_WUNLOCK(tp->t_inpcb); 3067 m_freem(m); 3068 return; 3069 3070dropwithreset: 3071 if (ti_locked == TI_WLOCKED) 3072 INP_INFO_WUNLOCK(&V_tcbinfo); 3073 ti_locked = TI_UNLOCKED; 3074 3075 if (tp != NULL) { 3076 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3077 INP_WUNLOCK(tp->t_inpcb); 3078 } else 3079 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3080 return; 3081 3082drop: 3083 if (ti_locked == TI_WLOCKED) { 3084 INP_INFO_WUNLOCK(&V_tcbinfo); 3085 ti_locked = TI_UNLOCKED; 3086 } 3087#ifdef INVARIANTS 3088 else 3089 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3090#endif 3091 3092 /* 3093 * Drop space held by incoming segment and return. 3094 */ 3095#ifdef TCPDEBUG 3096 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3097 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3098 &tcp_savetcp, 0); 3099#endif 3100 if (tp != NULL) 3101 INP_WUNLOCK(tp->t_inpcb); 3102 m_freem(m); 3103} 3104 3105/* 3106 * Issue RST and make ACK acceptable to originator of segment. 3107 * The mbuf must still include the original packet header. 3108 * tp may be NULL. 3109 */ 3110static void 3111tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3112 int tlen, int rstreason) 3113{ 3114#ifdef INET 3115 struct ip *ip; 3116#endif 3117#ifdef INET6 3118 struct ip6_hdr *ip6; 3119#endif 3120 3121 if (tp != NULL) { 3122 INP_WLOCK_ASSERT(tp->t_inpcb); 3123 } 3124 3125 /* Don't bother if destination was broadcast/multicast. */ 3126 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3127 goto drop; 3128#ifdef INET6 3129 if (mtod(m, struct ip *)->ip_v == 6) { 3130 ip6 = mtod(m, struct ip6_hdr *); 3131 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3132 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3133 goto drop; 3134 /* IPv6 anycast check is done at tcp6_input() */ 3135 } 3136#endif 3137#if defined(INET) && defined(INET6) 3138 else 3139#endif 3140#ifdef INET 3141 { 3142 ip = mtod(m, struct ip *); 3143 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3144 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3145 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3146 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3147 goto drop; 3148 } 3149#endif 3150 3151 /* Perform bandwidth limiting. */ 3152 if (badport_bandlim(rstreason) < 0) 3153 goto drop; 3154 3155 /* tcp_respond consumes the mbuf chain. */ 3156 if (th->th_flags & TH_ACK) { 3157 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3158 th->th_ack, TH_RST); 3159 } else { 3160 if (th->th_flags & TH_SYN) 3161 tlen++; 3162 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3163 (tcp_seq)0, TH_RST|TH_ACK); 3164 } 3165 return; 3166drop: 3167 m_freem(m); 3168} 3169 3170/* 3171 * Parse TCP options and place in tcpopt. 3172 */ 3173static void 3174tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3175{ 3176 int opt, optlen; 3177 3178 to->to_flags = 0; 3179 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3180 opt = cp[0]; 3181 if (opt == TCPOPT_EOL) 3182 break; 3183 if (opt == TCPOPT_NOP) 3184 optlen = 1; 3185 else { 3186 if (cnt < 2) 3187 break; 3188 optlen = cp[1]; 3189 if (optlen < 2 || optlen > cnt) 3190 break; 3191 } 3192 switch (opt) { 3193 case TCPOPT_MAXSEG: 3194 if (optlen != TCPOLEN_MAXSEG) 3195 continue; 3196 if (!(flags & TO_SYN)) 3197 continue; 3198 to->to_flags |= TOF_MSS; 3199 bcopy((char *)cp + 2, 3200 (char *)&to->to_mss, sizeof(to->to_mss)); 3201 to->to_mss = ntohs(to->to_mss); 3202 break; 3203 case TCPOPT_WINDOW: 3204 if (optlen != TCPOLEN_WINDOW) 3205 continue; 3206 if (!(flags & TO_SYN)) 3207 continue; 3208 to->to_flags |= TOF_SCALE; 3209 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3210 break; 3211 case TCPOPT_TIMESTAMP: 3212 if (optlen != TCPOLEN_TIMESTAMP) 3213 continue; 3214 to->to_flags |= TOF_TS; 3215 bcopy((char *)cp + 2, 3216 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3217 to->to_tsval = ntohl(to->to_tsval); 3218 bcopy((char *)cp + 6, 3219 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3220 to->to_tsecr = ntohl(to->to_tsecr); 3221 break; 3222#ifdef TCP_SIGNATURE 3223 /* 3224 * XXX In order to reply to a host which has set the 3225 * TCP_SIGNATURE option in its initial SYN, we have to 3226 * record the fact that the option was observed here 3227 * for the syncache code to perform the correct response. 3228 */ 3229 case TCPOPT_SIGNATURE: 3230 if (optlen != TCPOLEN_SIGNATURE) 3231 continue; 3232 to->to_flags |= TOF_SIGNATURE; 3233 to->to_signature = cp + 2; 3234 break; 3235#endif 3236 case TCPOPT_SACK_PERMITTED: 3237 if (optlen != TCPOLEN_SACK_PERMITTED) 3238 continue; 3239 if (!(flags & TO_SYN)) 3240 continue; 3241 if (!V_tcp_do_sack) 3242 continue; 3243 to->to_flags |= TOF_SACKPERM; 3244 break; 3245 case TCPOPT_SACK: 3246 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3247 continue; 3248 if (flags & TO_SYN) 3249 continue; 3250 to->to_flags |= TOF_SACK; 3251 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3252 to->to_sacks = cp + 2; 3253 TCPSTAT_INC(tcps_sack_rcv_blocks); 3254 break; 3255 default: 3256 continue; 3257 } 3258 } 3259} 3260 3261/* 3262 * Pull out of band byte out of a segment so 3263 * it doesn't appear in the user's data queue. 3264 * It is still reflected in the segment length for 3265 * sequencing purposes. 3266 */ 3267static void 3268tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3269 int off) 3270{ 3271 int cnt = off + th->th_urp - 1; 3272 3273 while (cnt >= 0) { 3274 if (m->m_len > cnt) { 3275 char *cp = mtod(m, caddr_t) + cnt; 3276 struct tcpcb *tp = sototcpcb(so); 3277 3278 INP_WLOCK_ASSERT(tp->t_inpcb); 3279 3280 tp->t_iobc = *cp; 3281 tp->t_oobflags |= TCPOOB_HAVEDATA; 3282 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3283 m->m_len--; 3284 if (m->m_flags & M_PKTHDR) 3285 m->m_pkthdr.len--; 3286 return; 3287 } 3288 cnt -= m->m_len; 3289 m = m->m_next; 3290 if (m == NULL) 3291 break; 3292 } 3293 panic("tcp_pulloutofband"); 3294} 3295 3296/* 3297 * Collect new round-trip time estimate 3298 * and update averages and current timeout. 3299 */ 3300static void 3301tcp_xmit_timer(struct tcpcb *tp, int rtt) 3302{ 3303 int delta; 3304 3305 INP_WLOCK_ASSERT(tp->t_inpcb); 3306 3307 TCPSTAT_INC(tcps_rttupdated); 3308 tp->t_rttupdated++; 3309 if (tp->t_srtt != 0) { 3310 /* 3311 * srtt is stored as fixed point with 5 bits after the 3312 * binary point (i.e., scaled by 8). The following magic 3313 * is equivalent to the smoothing algorithm in rfc793 with 3314 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3315 * point). Adjust rtt to origin 0. 3316 */ 3317 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3318 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3319 3320 if ((tp->t_srtt += delta) <= 0) 3321 tp->t_srtt = 1; 3322 3323 /* 3324 * We accumulate a smoothed rtt variance (actually, a 3325 * smoothed mean difference), then set the retransmit 3326 * timer to smoothed rtt + 4 times the smoothed variance. 3327 * rttvar is stored as fixed point with 4 bits after the 3328 * binary point (scaled by 16). The following is 3329 * equivalent to rfc793 smoothing with an alpha of .75 3330 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3331 * rfc793's wired-in beta. 3332 */ 3333 if (delta < 0) 3334 delta = -delta; 3335 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3336 if ((tp->t_rttvar += delta) <= 0) 3337 tp->t_rttvar = 1; 3338 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3339 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3340 } else { 3341 /* 3342 * No rtt measurement yet - use the unsmoothed rtt. 3343 * Set the variance to half the rtt (so our first 3344 * retransmit happens at 3*rtt). 3345 */ 3346 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3347 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3348 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3349 } 3350 tp->t_rtttime = 0; 3351 tp->t_rxtshift = 0; 3352 3353 /* 3354 * the retransmit should happen at rtt + 4 * rttvar. 3355 * Because of the way we do the smoothing, srtt and rttvar 3356 * will each average +1/2 tick of bias. When we compute 3357 * the retransmit timer, we want 1/2 tick of rounding and 3358 * 1 extra tick because of +-1/2 tick uncertainty in the 3359 * firing of the timer. The bias will give us exactly the 3360 * 1.5 tick we need. But, because the bias is 3361 * statistical, we have to test that we don't drop below 3362 * the minimum feasible timer (which is 2 ticks). 3363 */ 3364 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3365 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3366 3367 /* 3368 * We received an ack for a packet that wasn't retransmitted; 3369 * it is probably safe to discard any error indications we've 3370 * received recently. This isn't quite right, but close enough 3371 * for now (a route might have failed after we sent a segment, 3372 * and the return path might not be symmetrical). 3373 */ 3374 tp->t_softerror = 0; 3375} 3376 3377/* 3378 * Determine a reasonable value for maxseg size. 3379 * If the route is known, check route for mtu. 3380 * If none, use an mss that can be handled on the outgoing interface 3381 * without forcing IP to fragment. If no route is found, route has no mtu, 3382 * or the destination isn't local, use a default, hopefully conservative 3383 * size (usually 512 or the default IP max size, but no more than the mtu 3384 * of the interface), as we can't discover anything about intervening 3385 * gateways or networks. We also initialize the congestion/slow start 3386 * window to be a single segment if the destination isn't local. 3387 * While looking at the routing entry, we also initialize other path-dependent 3388 * parameters from pre-set or cached values in the routing entry. 3389 * 3390 * Also take into account the space needed for options that we 3391 * send regularly. Make maxseg shorter by that amount to assure 3392 * that we can send maxseg amount of data even when the options 3393 * are present. Store the upper limit of the length of options plus 3394 * data in maxopd. 3395 * 3396 * NOTE that this routine is only called when we process an incoming 3397 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3398 * settings are handled in tcp_mssopt(). 3399 */ 3400void 3401tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3402 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3403{ 3404 int mss = 0; 3405 u_long maxmtu = 0; 3406 struct inpcb *inp = tp->t_inpcb; 3407 struct hc_metrics_lite metrics; 3408 int origoffer; 3409#ifdef INET6 3410 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3411 size_t min_protoh = isipv6 ? 3412 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3413 sizeof (struct tcpiphdr); 3414#else 3415 const size_t min_protoh = sizeof(struct tcpiphdr); 3416#endif 3417 3418 INP_WLOCK_ASSERT(tp->t_inpcb); 3419 3420 if (mtuoffer != -1) { 3421 KASSERT(offer == -1, ("%s: conflict", __func__)); 3422 offer = mtuoffer - min_protoh; 3423 } 3424 origoffer = offer; 3425 3426 /* Initialize. */ 3427#ifdef INET6 3428 if (isipv6) { 3429 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3430 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt; 3431 } 3432#endif 3433#if defined(INET) && defined(INET6) 3434 else 3435#endif 3436#ifdef INET 3437 { 3438 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3439 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt; 3440 } 3441#endif 3442 3443 /* 3444 * No route to sender, stay with default mss and return. 3445 */ 3446 if (maxmtu == 0) { 3447 /* 3448 * In case we return early we need to initialize metrics 3449 * to a defined state as tcp_hc_get() would do for us 3450 * if there was no cache hit. 3451 */ 3452 if (metricptr != NULL) 3453 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3454 return; 3455 } 3456 3457 /* What have we got? */ 3458 switch (offer) { 3459 case 0: 3460 /* 3461 * Offer == 0 means that there was no MSS on the SYN 3462 * segment, in this case we use tcp_mssdflt as 3463 * already assigned to t_maxopd above. 3464 */ 3465 offer = tp->t_maxopd; 3466 break; 3467 3468 case -1: 3469 /* 3470 * Offer == -1 means that we didn't receive SYN yet. 3471 */ 3472 /* FALLTHROUGH */ 3473 3474 default: 3475 /* 3476 * Prevent DoS attack with too small MSS. Round up 3477 * to at least minmss. 3478 */ 3479 offer = max(offer, V_tcp_minmss); 3480 } 3481 3482 /* 3483 * rmx information is now retrieved from tcp_hostcache. 3484 */ 3485 tcp_hc_get(&inp->inp_inc, &metrics); 3486 if (metricptr != NULL) 3487 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3488 3489 /* 3490 * If there's a discovered mtu int tcp hostcache, use it 3491 * else, use the link mtu. 3492 */ 3493 if (metrics.rmx_mtu) 3494 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3495 else { 3496#ifdef INET6 3497 if (isipv6) { 3498 mss = maxmtu - min_protoh; 3499 if (!V_path_mtu_discovery && 3500 !in6_localaddr(&inp->in6p_faddr)) 3501 mss = min(mss, V_tcp_v6mssdflt); 3502 } 3503#endif 3504#if defined(INET) && defined(INET6) 3505 else 3506#endif 3507#ifdef INET 3508 { 3509 mss = maxmtu - min_protoh; 3510 if (!V_path_mtu_discovery && 3511 !in_localaddr(inp->inp_faddr)) 3512 mss = min(mss, V_tcp_mssdflt); 3513 } 3514#endif 3515 /* 3516 * XXX - The above conditional (mss = maxmtu - min_protoh) 3517 * probably violates the TCP spec. 3518 * The problem is that, since we don't know the 3519 * other end's MSS, we are supposed to use a conservative 3520 * default. But, if we do that, then MTU discovery will 3521 * never actually take place, because the conservative 3522 * default is much less than the MTUs typically seen 3523 * on the Internet today. For the moment, we'll sweep 3524 * this under the carpet. 3525 * 3526 * The conservative default might not actually be a problem 3527 * if the only case this occurs is when sending an initial 3528 * SYN with options and data to a host we've never talked 3529 * to before. Then, they will reply with an MSS value which 3530 * will get recorded and the new parameters should get 3531 * recomputed. For Further Study. 3532 */ 3533 } 3534 mss = min(mss, offer); 3535 3536 /* 3537 * Sanity check: make sure that maxopd will be large 3538 * enough to allow some data on segments even if the 3539 * all the option space is used (40bytes). Otherwise 3540 * funny things may happen in tcp_output. 3541 */ 3542 mss = max(mss, 64); 3543 3544 /* 3545 * maxopd stores the maximum length of data AND options 3546 * in a segment; maxseg is the amount of data in a normal 3547 * segment. We need to store this value (maxopd) apart 3548 * from maxseg, because now every segment carries options 3549 * and thus we normally have somewhat less data in segments. 3550 */ 3551 tp->t_maxopd = mss; 3552 3553 /* 3554 * origoffer==-1 indicates that no segments were received yet. 3555 * In this case we just guess. 3556 */ 3557 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3558 (origoffer == -1 || 3559 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3560 mss -= TCPOLEN_TSTAMP_APPA; 3561 3562 tp->t_maxseg = mss; 3563} 3564 3565void 3566tcp_mss(struct tcpcb *tp, int offer) 3567{ 3568 int mss; 3569 u_long bufsize; 3570 struct inpcb *inp; 3571 struct socket *so; 3572 struct hc_metrics_lite metrics; 3573 struct tcp_ifcap cap; 3574 3575 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3576 3577 bzero(&cap, sizeof(cap)); 3578 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3579 3580 mss = tp->t_maxseg; 3581 inp = tp->t_inpcb; 3582 3583 /* 3584 * If there's a pipesize, change the socket buffer to that size, 3585 * don't change if sb_hiwat is different than default (then it 3586 * has been changed on purpose with setsockopt). 3587 * Make the socket buffers an integral number of mss units; 3588 * if the mss is larger than the socket buffer, decrease the mss. 3589 */ 3590 so = inp->inp_socket; 3591 SOCKBUF_LOCK(&so->so_snd); 3592 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3593 bufsize = metrics.rmx_sendpipe; 3594 else 3595 bufsize = so->so_snd.sb_hiwat; 3596 if (bufsize < mss) 3597 mss = bufsize; 3598 else { 3599 bufsize = roundup(bufsize, mss); 3600 if (bufsize > sb_max) 3601 bufsize = sb_max; 3602 if (bufsize > so->so_snd.sb_hiwat) 3603 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3604 } 3605 SOCKBUF_UNLOCK(&so->so_snd); 3606 tp->t_maxseg = mss; 3607 3608 SOCKBUF_LOCK(&so->so_rcv); 3609 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3610 bufsize = metrics.rmx_recvpipe; 3611 else 3612 bufsize = so->so_rcv.sb_hiwat; 3613 if (bufsize > mss) { 3614 bufsize = roundup(bufsize, mss); 3615 if (bufsize > sb_max) 3616 bufsize = sb_max; 3617 if (bufsize > so->so_rcv.sb_hiwat) 3618 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3619 } 3620 SOCKBUF_UNLOCK(&so->so_rcv); 3621 3622 /* Check the interface for TSO capabilities. */ 3623 if (cap.ifcap & CSUM_TSO) { 3624 tp->t_flags |= TF_TSO; 3625 tp->t_tsomax = cap.tsomax; 3626 } 3627} 3628 3629/* 3630 * Determine the MSS option to send on an outgoing SYN. 3631 */ 3632int 3633tcp_mssopt(struct in_conninfo *inc) 3634{ 3635 int mss = 0; 3636 u_long maxmtu = 0; 3637 u_long thcmtu = 0; 3638 size_t min_protoh; 3639 3640 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3641 3642#ifdef INET6 3643 if (inc->inc_flags & INC_ISIPV6) { 3644 mss = V_tcp_v6mssdflt; 3645 maxmtu = tcp_maxmtu6(inc, NULL); 3646 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3647 } 3648#endif 3649#if defined(INET) && defined(INET6) 3650 else 3651#endif 3652#ifdef INET 3653 { 3654 mss = V_tcp_mssdflt; 3655 maxmtu = tcp_maxmtu(inc, NULL); 3656 min_protoh = sizeof(struct tcpiphdr); 3657 } 3658#endif 3659#if defined(INET6) || defined(INET) 3660 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3661#endif 3662 3663 if (maxmtu && thcmtu) 3664 mss = min(maxmtu, thcmtu) - min_protoh; 3665 else if (maxmtu || thcmtu) 3666 mss = max(maxmtu, thcmtu) - min_protoh; 3667 3668 return (mss); 3669} 3670 3671 3672/* 3673 * On a partial ack arrives, force the retransmission of the 3674 * next unacknowledged segment. Do not clear tp->t_dupacks. 3675 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3676 * be started again. 3677 */ 3678static void 3679tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3680{ 3681 tcp_seq onxt = tp->snd_nxt; 3682 u_long ocwnd = tp->snd_cwnd; 3683 3684 INP_WLOCK_ASSERT(tp->t_inpcb); 3685 3686 tcp_timer_activate(tp, TT_REXMT, 0); 3687 tp->t_rtttime = 0; 3688 tp->snd_nxt = th->th_ack; 3689 /* 3690 * Set snd_cwnd to one segment beyond acknowledged offset. 3691 * (tp->snd_una has not yet been updated when this function is called.) 3692 */ 3693 tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th); 3694 tp->t_flags |= TF_ACKNOW; 3695 (void) tcp_output(tp); 3696 tp->snd_cwnd = ocwnd; 3697 if (SEQ_GT(onxt, tp->snd_nxt)) 3698 tp->snd_nxt = onxt; 3699 /* 3700 * Partial window deflation. Relies on fact that tp->snd_una 3701 * not updated yet. 3702 */ 3703 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3704 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3705 else 3706 tp->snd_cwnd = 0; 3707 tp->snd_cwnd += tp->t_maxseg; 3708} 3709