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