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/in.h> 86 #include <netinet/in_kdtrace.h> 87 #include <netinet/in_pcb.h> 88 #include <netinet/in_systm.h> 89 #include <netinet/ip.h> 90 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 91 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 92 #include <netinet/ip_var.h> 93 #include <netinet/ip_options.h> 94 #include <netinet/ip6.h> 95 #include <netinet/icmp6.h> 96 #include <netinet6/in6_pcb.h> 97 #include <netinet6/in6_var.h> 98 #include <netinet6/ip6_var.h> 99 #include <netinet6/nd6.h> 100 #ifdef TCP_RFC7413 101 #include <netinet/tcp_fastopen.h> 102 #endif 103 #include <netinet/tcp.h> 104 #include <netinet/tcp_fsm.h> 105 #include <netinet/tcp_seq.h> 106 #include <netinet/tcp_timer.h> 107 #include <netinet/tcp_var.h> 108 #include <netinet6/tcp6_var.h> 109 #include <netinet/tcpip.h> 110 #include <netinet/cc/cc.h> 111 #ifdef TCPPCAP 112 #include <netinet/tcp_pcap.h> 113 #endif 114 #include <netinet/tcp_syncache.h> 115 #ifdef TCPDEBUG 116 #include <netinet/tcp_debug.h> 117 #endif /* TCPDEBUG */ 118 #ifdef TCP_OFFLOAD 119 #include <netinet/tcp_offload.h> 120 #endif 121 122 #ifdef IPSEC 123 #include <netipsec/ipsec.h> 124 #include <netipsec/ipsec6.h> 125 #endif /*IPSEC*/ 126 127 #include <machine/in_cksum.h> 128 129 #include <security/mac/mac_framework.h> 130 131 const int tcprexmtthresh = 3; 132 133 int tcp_log_in_vain = 0; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 135 &tcp_log_in_vain, 0, 136 "Log all incoming TCP segments to closed ports"); 137 138 VNET_DEFINE(int, blackhole) = 0; 139 #define V_blackhole VNET(blackhole) 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 141 &VNET_NAME(blackhole), 0, 142 "Do not send RST on segments to closed ports"); 143 144 VNET_DEFINE(int, tcp_delack_enabled) = 1; 145 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 146 &VNET_NAME(tcp_delack_enabled), 0, 147 "Delay ACK to try and piggyback it onto a data packet"); 148 149 VNET_DEFINE(int, drop_synfin) = 0; 150 #define V_drop_synfin VNET(drop_synfin) 151 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 152 &VNET_NAME(drop_synfin), 0, 153 "Drop TCP packets with SYN+FIN set"); 154 155 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 157 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 158 "Use calculated pipe/in-flight bytes per RFC 6675"); 159 160 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 161 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) 162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 163 &VNET_NAME(tcp_do_rfc3042), 0, 164 "Enable RFC 3042 (Limited Transmit)"); 165 166 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 168 &VNET_NAME(tcp_do_rfc3390), 0, 169 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 170 171 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 172 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 173 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 174 "Slow-start flight size (initial congestion window) in number of segments"); 175 176 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 178 &VNET_NAME(tcp_do_rfc3465), 0, 179 "Enable RFC 3465 (Appropriate Byte Counting)"); 180 181 VNET_DEFINE(int, tcp_abc_l_var) = 2; 182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 183 &VNET_NAME(tcp_abc_l_var), 2, 184 "Cap the max cwnd increment during slow-start to this number of segments"); 185 186 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 187 188 VNET_DEFINE(int, tcp_do_ecn) = 0; 189 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 190 &VNET_NAME(tcp_do_ecn), 0, 191 "TCP ECN support"); 192 193 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 194 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 195 &VNET_NAME(tcp_ecn_maxretries), 0, 196 "Max retries before giving up on ECN"); 197 198 VNET_DEFINE(int, tcp_insecure_syn) = 0; 199 #define V_tcp_insecure_syn VNET(tcp_insecure_syn) 200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 201 &VNET_NAME(tcp_insecure_syn), 0, 202 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 203 204 VNET_DEFINE(int, tcp_insecure_rst) = 0; 205 #define V_tcp_insecure_rst VNET(tcp_insecure_rst) 206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 207 &VNET_NAME(tcp_insecure_rst), 0, 208 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 209 210 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 211 #define V_tcp_recvspace VNET(tcp_recvspace) 212 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 213 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 214 215 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 216 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) 217 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 218 &VNET_NAME(tcp_do_autorcvbuf), 0, 219 "Enable automatic receive buffer sizing"); 220 221 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 222 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) 223 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 224 &VNET_NAME(tcp_autorcvbuf_inc), 0, 225 "Incrementor step size of automatic receive buffer"); 226 227 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 228 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) 229 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 230 &VNET_NAME(tcp_autorcvbuf_max), 0, 231 "Max size of automatic receive buffer"); 232 233 VNET_DEFINE(struct inpcbhead, tcb); 234 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 235 VNET_DEFINE(struct inpcbinfo, tcbinfo); 236 237 /* 238 * TCP statistics are stored in an "array" of counter(9)s. 239 */ 240 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 241 VNET_PCPUSTAT_SYSINIT(tcpstat); 242 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 243 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 244 245 #ifdef VIMAGE 246 VNET_PCPUSTAT_SYSUNINIT(tcpstat); 247 #endif /* VIMAGE */ 248 /* 249 * Kernel module interface for updating tcpstat. The argument is an index 250 * into tcpstat treated as an array. 251 */ 252 void 253 kmod_tcpstat_inc(int statnum) 254 { 255 256 counter_u64_add(VNET(tcpstat)[statnum], 1); 257 } 258 259 /* 260 * Wrapper for the TCP established input helper hook. 261 */ 262 void 263 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 264 { 265 struct tcp_hhook_data hhook_data; 266 267 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 268 hhook_data.tp = tp; 269 hhook_data.th = th; 270 hhook_data.to = to; 271 272 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 273 tp->osd); 274 } 275 } 276 277 /* 278 * CC wrapper hook functions 279 */ 280 void 281 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type) 282 { 283 INP_WLOCK_ASSERT(tp->t_inpcb); 284 285 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 286 if (tp->snd_cwnd <= tp->snd_wnd) 287 tp->ccv->flags |= CCF_CWND_LIMITED; 288 else 289 tp->ccv->flags &= ~CCF_CWND_LIMITED; 290 291 if (type == CC_ACK) { 292 if (tp->snd_cwnd > tp->snd_ssthresh) { 293 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 294 V_tcp_abc_l_var * tcp_maxseg(tp)); 295 if (tp->t_bytes_acked >= tp->snd_cwnd) { 296 tp->t_bytes_acked -= tp->snd_cwnd; 297 tp->ccv->flags |= CCF_ABC_SENTAWND; 298 } 299 } else { 300 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 301 tp->t_bytes_acked = 0; 302 } 303 } 304 305 if (CC_ALGO(tp)->ack_received != NULL) { 306 /* XXXLAS: Find a way to live without this */ 307 tp->ccv->curack = th->th_ack; 308 CC_ALGO(tp)->ack_received(tp->ccv, type); 309 } 310 } 311 312 void 313 cc_conn_init(struct tcpcb *tp) 314 { 315 struct hc_metrics_lite metrics; 316 struct inpcb *inp = tp->t_inpcb; 317 u_int maxseg; 318 int rtt; 319 320 INP_WLOCK_ASSERT(tp->t_inpcb); 321 322 tcp_hc_get(&inp->inp_inc, &metrics); 323 maxseg = tcp_maxseg(tp); 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 * 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 * Support for user specified value for initial flight size. 359 * 360 * If a SYN or SYN/ACK was lost and retransmitted, we have to 361 * reduce the initial CWND to one segment as congestion is likely 362 * requiring us to be cautious. 363 */ 364 if (tp->snd_cwnd == 1) 365 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 366 else if (V_tcp_initcwnd_segments) 367 tp->snd_cwnd = min(V_tcp_initcwnd_segments * maxseg, 368 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 369 else if (V_tcp_do_rfc3390) 370 tp->snd_cwnd = min(4 * maxseg, max(2 * maxseg, 4380)); 371 else { 372 /* Per RFC5681 Section 3.1 */ 373 if (maxseg > 2190) 374 tp->snd_cwnd = 2 * maxseg; 375 else if (maxseg > 1095) 376 tp->snd_cwnd = 3 * maxseg; 377 else 378 tp->snd_cwnd = 4 * 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 u_int maxseg; 389 390 INP_WLOCK_ASSERT(tp->t_inpcb); 391 392 switch(type) { 393 case CC_NDUPACK: 394 if (!IN_FASTRECOVERY(tp->t_flags)) { 395 tp->snd_recover = tp->snd_max; 396 if (tp->t_flags & TF_ECN_PERMIT) 397 tp->t_flags |= TF_ECN_SND_CWR; 398 } 399 break; 400 case CC_ECN: 401 if (!IN_CONGRECOVERY(tp->t_flags)) { 402 TCPSTAT_INC(tcps_ecn_rcwnd); 403 tp->snd_recover = tp->snd_max; 404 if (tp->t_flags & TF_ECN_PERMIT) 405 tp->t_flags |= TF_ECN_SND_CWR; 406 } 407 break; 408 case CC_RTO: 409 maxseg = tcp_maxseg(tp); 410 tp->t_dupacks = 0; 411 tp->t_bytes_acked = 0; 412 EXIT_RECOVERY(tp->t_flags); 413 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 414 maxseg) * maxseg; 415 tp->snd_cwnd = maxseg; 416 break; 417 case CC_RTO_ERR: 418 TCPSTAT_INC(tcps_sndrexmitbad); 419 /* RTO was unnecessary, so reset everything. */ 420 tp->snd_cwnd = tp->snd_cwnd_prev; 421 tp->snd_ssthresh = tp->snd_ssthresh_prev; 422 tp->snd_recover = tp->snd_recover_prev; 423 if (tp->t_flags & TF_WASFRECOVERY) 424 ENTER_FASTRECOVERY(tp->t_flags); 425 if (tp->t_flags & TF_WASCRECOVERY) 426 ENTER_CONGRECOVERY(tp->t_flags); 427 tp->snd_nxt = tp->snd_max; 428 tp->t_flags &= ~TF_PREVVALID; 429 tp->t_badrxtwin = 0; 430 break; 431 } 432 433 if (CC_ALGO(tp)->cong_signal != NULL) { 434 if (th != NULL) 435 tp->ccv->curack = th->th_ack; 436 CC_ALGO(tp)->cong_signal(tp->ccv, type); 437 } 438 } 439 440 void inline 441 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 442 { 443 INP_WLOCK_ASSERT(tp->t_inpcb); 444 445 /* XXXLAS: KASSERT that we're in recovery? */ 446 447 if (CC_ALGO(tp)->post_recovery != NULL) { 448 tp->ccv->curack = th->th_ack; 449 CC_ALGO(tp)->post_recovery(tp->ccv); 450 } 451 /* XXXLAS: EXIT_RECOVERY ? */ 452 tp->t_bytes_acked = 0; 453 } 454 455 #ifdef TCP_SIGNATURE 456 static inline int 457 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, 458 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) 459 { 460 int ret; 461 462 tcp_fields_to_net(th); 463 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); 464 tcp_fields_to_host(th); 465 return (ret); 466 } 467 #endif 468 469 /* 470 * Indicate whether this ack should be delayed. We can delay the ack if 471 * following conditions are met: 472 * - There is no delayed ack timer in progress. 473 * - Our last ack wasn't a 0-sized window. We never want to delay 474 * the ack that opens up a 0-sized window. 475 * - LRO wasn't used for this segment. We make sure by checking that the 476 * segment size is not larger than the MSS. 477 */ 478 #define DELAY_ACK(tp, tlen) \ 479 ((!tcp_timer_active(tp, TT_DELACK) && \ 480 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 481 (tlen <= tp->t_maxseg) && \ 482 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 483 484 static void inline 485 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 486 { 487 INP_WLOCK_ASSERT(tp->t_inpcb); 488 489 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 490 switch (iptos & IPTOS_ECN_MASK) { 491 case IPTOS_ECN_CE: 492 tp->ccv->flags |= CCF_IPHDR_CE; 493 break; 494 case IPTOS_ECN_ECT0: 495 tp->ccv->flags &= ~CCF_IPHDR_CE; 496 break; 497 case IPTOS_ECN_ECT1: 498 tp->ccv->flags &= ~CCF_IPHDR_CE; 499 break; 500 } 501 502 if (th->th_flags & TH_CWR) 503 tp->ccv->flags |= CCF_TCPHDR_CWR; 504 else 505 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 506 507 if (tp->t_flags & TF_DELACK) 508 tp->ccv->flags |= CCF_DELACK; 509 else 510 tp->ccv->flags &= ~CCF_DELACK; 511 512 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 513 514 if (tp->ccv->flags & CCF_ACKNOW) 515 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 516 } 517 } 518 519 /* 520 * TCP input handling is split into multiple parts: 521 * tcp6_input is a thin wrapper around tcp_input for the extended 522 * ip6_protox[] call format in ip6_input 523 * tcp_input handles primary segment validation, inpcb lookup and 524 * SYN processing on listen sockets 525 * tcp_do_segment processes the ACK and text of the segment for 526 * establishing, established and closing connections 527 */ 528 #ifdef INET6 529 int 530 tcp6_input(struct mbuf **mp, int *offp, int proto) 531 { 532 struct mbuf *m = *mp; 533 struct in6_ifaddr *ia6; 534 struct ip6_hdr *ip6; 535 536 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 537 538 /* 539 * draft-itojun-ipv6-tcp-to-anycast 540 * better place to put this in? 541 */ 542 ip6 = mtod(m, struct ip6_hdr *); 543 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 544 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 545 struct ip6_hdr *ip6; 546 547 ifa_free(&ia6->ia_ifa); 548 ip6 = mtod(m, struct ip6_hdr *); 549 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 550 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 551 return (IPPROTO_DONE); 552 } 553 if (ia6) 554 ifa_free(&ia6->ia_ifa); 555 556 return (tcp_input(mp, offp, proto)); 557 } 558 #endif /* INET6 */ 559 560 int 561 tcp_input(struct mbuf **mp, int *offp, int proto) 562 { 563 struct mbuf *m = *mp; 564 struct tcphdr *th = NULL; 565 struct ip *ip = NULL; 566 struct inpcb *inp = NULL; 567 struct tcpcb *tp = NULL; 568 struct socket *so = NULL; 569 u_char *optp = NULL; 570 int off0; 571 int optlen = 0; 572 #ifdef INET 573 int len; 574 #endif 575 int tlen = 0, off; 576 int drop_hdrlen; 577 int thflags; 578 int rstreason = 0; /* For badport_bandlim accounting purposes */ 579 #ifdef TCP_SIGNATURE 580 uint8_t sig_checked = 0; 581 #endif 582 uint8_t iptos = 0; 583 struct m_tag *fwd_tag = NULL; 584 #ifdef INET6 585 struct ip6_hdr *ip6 = NULL; 586 int isipv6; 587 #else 588 const void *ip6 = NULL; 589 #endif /* INET6 */ 590 struct tcpopt to; /* options in this segment */ 591 char *s = NULL; /* address and port logging */ 592 int ti_locked; 593 #ifdef TCPDEBUG 594 /* 595 * The size of tcp_saveipgen must be the size of the max ip header, 596 * now IPv6. 597 */ 598 u_char tcp_saveipgen[IP6_HDR_LEN]; 599 struct tcphdr tcp_savetcp; 600 short ostate = 0; 601 #endif 602 603 #ifdef INET6 604 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 605 #endif 606 607 off0 = *offp; 608 m = *mp; 609 *mp = NULL; 610 to.to_flags = 0; 611 TCPSTAT_INC(tcps_rcvtotal); 612 613 #ifdef INET6 614 if (isipv6) { 615 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 616 617 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 618 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 619 if (m == NULL) { 620 TCPSTAT_INC(tcps_rcvshort); 621 return (IPPROTO_DONE); 622 } 623 } 624 625 ip6 = mtod(m, struct ip6_hdr *); 626 th = (struct tcphdr *)((caddr_t)ip6 + off0); 627 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 628 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 629 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 630 th->th_sum = m->m_pkthdr.csum_data; 631 else 632 th->th_sum = in6_cksum_pseudo(ip6, tlen, 633 IPPROTO_TCP, m->m_pkthdr.csum_data); 634 th->th_sum ^= 0xffff; 635 } else 636 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 637 if (th->th_sum) { 638 TCPSTAT_INC(tcps_rcvbadsum); 639 goto drop; 640 } 641 642 /* 643 * Be proactive about unspecified IPv6 address in source. 644 * As we use all-zero to indicate unbounded/unconnected pcb, 645 * unspecified IPv6 address can be used to confuse us. 646 * 647 * Note that packets with unspecified IPv6 destination is 648 * already dropped in ip6_input. 649 */ 650 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 651 /* XXX stat */ 652 goto drop; 653 } 654 } 655 #endif 656 #if defined(INET) && defined(INET6) 657 else 658 #endif 659 #ifdef INET 660 { 661 /* 662 * Get IP and TCP header together in first mbuf. 663 * Note: IP leaves IP header in first mbuf. 664 */ 665 if (off0 > sizeof (struct ip)) { 666 ip_stripoptions(m); 667 off0 = sizeof(struct ip); 668 } 669 if (m->m_len < sizeof (struct tcpiphdr)) { 670 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 671 == NULL) { 672 TCPSTAT_INC(tcps_rcvshort); 673 return (IPPROTO_DONE); 674 } 675 } 676 ip = mtod(m, struct ip *); 677 th = (struct tcphdr *)((caddr_t)ip + off0); 678 tlen = ntohs(ip->ip_len) - off0; 679 680 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 681 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 682 th->th_sum = m->m_pkthdr.csum_data; 683 else 684 th->th_sum = in_pseudo(ip->ip_src.s_addr, 685 ip->ip_dst.s_addr, 686 htonl(m->m_pkthdr.csum_data + tlen + 687 IPPROTO_TCP)); 688 th->th_sum ^= 0xffff; 689 } else { 690 struct ipovly *ipov = (struct ipovly *)ip; 691 692 /* 693 * Checksum extended TCP header and data. 694 */ 695 len = off0 + tlen; 696 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 697 ipov->ih_len = htons(tlen); 698 th->th_sum = in_cksum(m, len); 699 /* Reset length for SDT probes. */ 700 ip->ip_len = htons(tlen + off0); 701 } 702 703 if (th->th_sum) { 704 TCPSTAT_INC(tcps_rcvbadsum); 705 goto drop; 706 } 707 /* Re-initialization for later version check */ 708 ip->ip_v = IPVERSION; 709 } 710 #endif /* INET */ 711 712 #ifdef INET6 713 if (isipv6) 714 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 715 #endif 716 #if defined(INET) && defined(INET6) 717 else 718 #endif 719 #ifdef INET 720 iptos = ip->ip_tos; 721 #endif 722 723 /* 724 * Check that TCP offset makes sense, 725 * pull out TCP options and adjust length. XXX 726 */ 727 off = th->th_off << 2; 728 if (off < sizeof (struct tcphdr) || off > tlen) { 729 TCPSTAT_INC(tcps_rcvbadoff); 730 goto drop; 731 } 732 tlen -= off; /* tlen is used instead of ti->ti_len */ 733 if (off > sizeof (struct tcphdr)) { 734 #ifdef INET6 735 if (isipv6) { 736 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 737 ip6 = mtod(m, struct ip6_hdr *); 738 th = (struct tcphdr *)((caddr_t)ip6 + off0); 739 } 740 #endif 741 #if defined(INET) && defined(INET6) 742 else 743 #endif 744 #ifdef INET 745 { 746 if (m->m_len < sizeof(struct ip) + off) { 747 if ((m = m_pullup(m, sizeof (struct ip) + off)) 748 == NULL) { 749 TCPSTAT_INC(tcps_rcvshort); 750 return (IPPROTO_DONE); 751 } 752 ip = mtod(m, struct ip *); 753 th = (struct tcphdr *)((caddr_t)ip + off0); 754 } 755 } 756 #endif 757 optlen = off - sizeof (struct tcphdr); 758 optp = (u_char *)(th + 1); 759 } 760 thflags = th->th_flags; 761 762 /* 763 * Convert TCP protocol specific fields to host format. 764 */ 765 tcp_fields_to_host(th); 766 767 /* 768 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 769 */ 770 drop_hdrlen = off0 + off; 771 772 /* 773 * Locate pcb for segment; if we're likely to add or remove a 774 * connection then first acquire pcbinfo lock. There are three cases 775 * where we might discover later we need a write lock despite the 776 * flags: ACKs moving a connection out of the syncache, ACKs for a 777 * connection in TIMEWAIT and SYNs not targeting a listening socket. 778 */ 779 if ((thflags & (TH_FIN | TH_RST)) != 0) { 780 INP_INFO_RLOCK(&V_tcbinfo); 781 ti_locked = TI_RLOCKED; 782 } else 783 ti_locked = TI_UNLOCKED; 784 785 /* 786 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 787 */ 788 if ( 789 #ifdef INET6 790 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 791 #ifdef INET 792 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 793 #endif 794 #endif 795 #if defined(INET) && !defined(INET6) 796 (m->m_flags & M_IP_NEXTHOP) 797 #endif 798 ) 799 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 800 801 findpcb: 802 #ifdef INVARIANTS 803 if (ti_locked == TI_RLOCKED) { 804 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 805 } else { 806 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 807 } 808 #endif 809 #ifdef INET6 810 if (isipv6 && fwd_tag != NULL) { 811 struct sockaddr_in6 *next_hop6; 812 813 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 814 /* 815 * Transparently forwarded. Pretend to be the destination. 816 * Already got one like this? 817 */ 818 inp = in6_pcblookup_mbuf(&V_tcbinfo, 819 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 820 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 821 if (!inp) { 822 /* 823 * It's new. Try to find the ambushing socket. 824 * Because we've rewritten the destination address, 825 * any hardware-generated hash is ignored. 826 */ 827 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 828 th->th_sport, &next_hop6->sin6_addr, 829 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 830 th->th_dport, INPLOOKUP_WILDCARD | 831 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 832 } 833 } else if (isipv6) { 834 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 835 th->th_sport, &ip6->ip6_dst, th->th_dport, 836 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 837 m->m_pkthdr.rcvif, m); 838 } 839 #endif /* INET6 */ 840 #if defined(INET6) && defined(INET) 841 else 842 #endif 843 #ifdef INET 844 if (fwd_tag != NULL) { 845 struct sockaddr_in *next_hop; 846 847 next_hop = (struct sockaddr_in *)(fwd_tag+1); 848 /* 849 * Transparently forwarded. Pretend to be the destination. 850 * already got one like this? 851 */ 852 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 853 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 854 m->m_pkthdr.rcvif, m); 855 if (!inp) { 856 /* 857 * It's new. Try to find the ambushing socket. 858 * Because we've rewritten the destination address, 859 * any hardware-generated hash is ignored. 860 */ 861 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 862 th->th_sport, next_hop->sin_addr, 863 next_hop->sin_port ? ntohs(next_hop->sin_port) : 864 th->th_dport, INPLOOKUP_WILDCARD | 865 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 866 } 867 } else 868 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 869 th->th_sport, ip->ip_dst, th->th_dport, 870 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 871 m->m_pkthdr.rcvif, m); 872 #endif /* INET */ 873 874 /* 875 * If the INPCB does not exist then all data in the incoming 876 * segment is discarded and an appropriate RST is sent back. 877 * XXX MRT Send RST using which routing table? 878 */ 879 if (inp == NULL) { 880 /* 881 * Log communication attempts to ports that are not 882 * in use. 883 */ 884 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 885 tcp_log_in_vain == 2) { 886 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 887 log(LOG_INFO, "%s; %s: Connection attempt " 888 "to closed port\n", s, __func__); 889 } 890 /* 891 * When blackholing do not respond with a RST but 892 * completely ignore the segment and drop it. 893 */ 894 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 895 V_blackhole == 2) 896 goto dropunlock; 897 898 rstreason = BANDLIM_RST_CLOSEDPORT; 899 goto dropwithreset; 900 } 901 INP_WLOCK_ASSERT(inp); 902 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 903 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 904 ((inp->inp_socket == NULL) || 905 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 906 inp->inp_flowid = m->m_pkthdr.flowid; 907 inp->inp_flowtype = M_HASHTYPE_GET(m); 908 } 909 #ifdef IPSEC 910 #ifdef INET6 911 if (isipv6 && ipsec6_in_reject(m, inp)) { 912 goto dropunlock; 913 } else 914 #endif /* INET6 */ 915 if (ipsec4_in_reject(m, inp) != 0) { 916 goto dropunlock; 917 } 918 #endif /* IPSEC */ 919 920 /* 921 * Check the minimum TTL for socket. 922 */ 923 if (inp->inp_ip_minttl != 0) { 924 #ifdef INET6 925 if (isipv6) { 926 if (inp->inp_ip_minttl > ip6->ip6_hlim) 927 goto dropunlock; 928 } else 929 #endif 930 if (inp->inp_ip_minttl > ip->ip_ttl) 931 goto dropunlock; 932 } 933 934 /* 935 * A previous connection in TIMEWAIT state is supposed to catch stray 936 * or duplicate segments arriving late. If this segment was a 937 * legitimate new connection attempt, the old INPCB gets removed and 938 * we can try again to find a listening socket. 939 * 940 * At this point, due to earlier optimism, we may hold only an inpcb 941 * lock, and not the inpcbinfo write lock. If so, we need to try to 942 * acquire it, or if that fails, acquire a reference on the inpcb, 943 * drop all locks, acquire a global write lock, and then re-acquire 944 * the inpcb lock. We may at that point discover that another thread 945 * has tried to free the inpcb, in which case we need to loop back 946 * and try to find a new inpcb to deliver to. 947 * 948 * XXXRW: It may be time to rethink timewait locking. 949 */ 950 relocked: 951 if (inp->inp_flags & INP_TIMEWAIT) { 952 if (ti_locked == TI_UNLOCKED) { 953 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 954 in_pcbref(inp); 955 INP_WUNLOCK(inp); 956 INP_INFO_RLOCK(&V_tcbinfo); 957 ti_locked = TI_RLOCKED; 958 INP_WLOCK(inp); 959 if (in_pcbrele_wlocked(inp)) { 960 inp = NULL; 961 goto findpcb; 962 } 963 } else 964 ti_locked = TI_RLOCKED; 965 } 966 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 967 968 if (thflags & TH_SYN) 969 tcp_dooptions(&to, optp, optlen, TO_SYN); 970 /* 971 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 972 */ 973 if (tcp_twcheck(inp, &to, th, m, tlen)) 974 goto findpcb; 975 INP_INFO_RUNLOCK(&V_tcbinfo); 976 return (IPPROTO_DONE); 977 } 978 /* 979 * The TCPCB may no longer exist if the connection is winding 980 * down or it is in the CLOSED state. Either way we drop the 981 * segment and send an appropriate response. 982 */ 983 tp = intotcpcb(inp); 984 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 985 rstreason = BANDLIM_RST_CLOSEDPORT; 986 goto dropwithreset; 987 } 988 989 #ifdef TCP_OFFLOAD 990 if (tp->t_flags & TF_TOE) { 991 tcp_offload_input(tp, m); 992 m = NULL; /* consumed by the TOE driver */ 993 goto dropunlock; 994 } 995 #endif 996 997 /* 998 * We've identified a valid inpcb, but it could be that we need an 999 * inpcbinfo write lock but don't hold it. In this case, attempt to 1000 * acquire using the same strategy as the TIMEWAIT case above. If we 1001 * relock, we have to jump back to 'relocked' as the connection might 1002 * now be in TIMEWAIT. 1003 */ 1004 #ifdef INVARIANTS 1005 if ((thflags & (TH_FIN | TH_RST)) != 0) 1006 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1007 #endif 1008 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) || 1009 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN) && 1010 !(tp->t_flags & TF_FASTOPEN)))) { 1011 if (ti_locked == TI_UNLOCKED) { 1012 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 1013 in_pcbref(inp); 1014 INP_WUNLOCK(inp); 1015 INP_INFO_RLOCK(&V_tcbinfo); 1016 ti_locked = TI_RLOCKED; 1017 INP_WLOCK(inp); 1018 if (in_pcbrele_wlocked(inp)) { 1019 inp = NULL; 1020 goto findpcb; 1021 } 1022 goto relocked; 1023 } else 1024 ti_locked = TI_RLOCKED; 1025 } 1026 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1027 } 1028 1029 #ifdef MAC 1030 INP_WLOCK_ASSERT(inp); 1031 if (mac_inpcb_check_deliver(inp, m)) 1032 goto dropunlock; 1033 #endif 1034 so = inp->inp_socket; 1035 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1036 #ifdef TCPDEBUG 1037 if (so->so_options & SO_DEBUG) { 1038 ostate = tp->t_state; 1039 #ifdef INET6 1040 if (isipv6) { 1041 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1042 } else 1043 #endif 1044 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1045 tcp_savetcp = *th; 1046 } 1047 #endif /* TCPDEBUG */ 1048 /* 1049 * When the socket is accepting connections (the INPCB is in LISTEN 1050 * state) we look into the SYN cache if this is a new connection 1051 * attempt or the completion of a previous one. 1052 */ 1053 if (so->so_options & SO_ACCEPTCONN) { 1054 struct in_conninfo inc; 1055 1056 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 1057 "tp not listening", __func__)); 1058 bzero(&inc, sizeof(inc)); 1059 #ifdef INET6 1060 if (isipv6) { 1061 inc.inc_flags |= INC_ISIPV6; 1062 inc.inc6_faddr = ip6->ip6_src; 1063 inc.inc6_laddr = ip6->ip6_dst; 1064 } else 1065 #endif 1066 { 1067 inc.inc_faddr = ip->ip_src; 1068 inc.inc_laddr = ip->ip_dst; 1069 } 1070 inc.inc_fport = th->th_sport; 1071 inc.inc_lport = th->th_dport; 1072 inc.inc_fibnum = so->so_fibnum; 1073 1074 /* 1075 * Check for an existing connection attempt in syncache if 1076 * the flag is only ACK. A successful lookup creates a new 1077 * socket appended to the listen queue in SYN_RECEIVED state. 1078 */ 1079 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1080 1081 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1082 /* 1083 * Parse the TCP options here because 1084 * syncookies need access to the reflected 1085 * timestamp. 1086 */ 1087 tcp_dooptions(&to, optp, optlen, 0); 1088 /* 1089 * NB: syncache_expand() doesn't unlock 1090 * inp and tcpinfo locks. 1091 */ 1092 if (!syncache_expand(&inc, &to, th, &so, m)) { 1093 /* 1094 * No syncache entry or ACK was not 1095 * for our SYN/ACK. Send a RST. 1096 * NB: syncache did its own logging 1097 * of the failure cause. 1098 */ 1099 rstreason = BANDLIM_RST_OPENPORT; 1100 goto dropwithreset; 1101 } 1102 #ifdef TCP_RFC7413 1103 new_tfo_socket: 1104 #endif 1105 if (so == NULL) { 1106 /* 1107 * We completed the 3-way handshake 1108 * but could not allocate a socket 1109 * either due to memory shortage, 1110 * listen queue length limits or 1111 * global socket limits. Send RST 1112 * or wait and have the remote end 1113 * retransmit the ACK for another 1114 * try. 1115 */ 1116 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1117 log(LOG_DEBUG, "%s; %s: Listen socket: " 1118 "Socket allocation failed due to " 1119 "limits or memory shortage, %s\n", 1120 s, __func__, 1121 V_tcp_sc_rst_sock_fail ? 1122 "sending RST" : "try again"); 1123 if (V_tcp_sc_rst_sock_fail) { 1124 rstreason = BANDLIM_UNLIMITED; 1125 goto dropwithreset; 1126 } else 1127 goto dropunlock; 1128 } 1129 /* 1130 * Socket is created in state SYN_RECEIVED. 1131 * Unlock the listen socket, lock the newly 1132 * created socket and update the tp variable. 1133 */ 1134 INP_WUNLOCK(inp); /* listen socket */ 1135 inp = sotoinpcb(so); 1136 /* 1137 * New connection inpcb is already locked by 1138 * syncache_expand(). 1139 */ 1140 INP_WLOCK_ASSERT(inp); 1141 tp = intotcpcb(inp); 1142 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1143 ("%s: ", __func__)); 1144 #ifdef TCP_SIGNATURE 1145 if (sig_checked == 0) { 1146 tcp_dooptions(&to, optp, optlen, 1147 (thflags & TH_SYN) ? TO_SYN : 0); 1148 if (!tcp_signature_verify_input(m, off0, tlen, 1149 optlen, &to, th, tp->t_flags)) { 1150 1151 /* 1152 * In SYN_SENT state if it receives an 1153 * RST, it is allowed for further 1154 * processing. 1155 */ 1156 if ((thflags & TH_RST) == 0 || 1157 (tp->t_state == TCPS_SYN_SENT) == 0) 1158 goto dropunlock; 1159 } 1160 sig_checked = 1; 1161 } 1162 #endif 1163 1164 /* 1165 * Process the segment and the data it 1166 * contains. tcp_do_segment() consumes 1167 * the mbuf chain and unlocks the inpcb. 1168 */ 1169 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1170 iptos, ti_locked); 1171 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1172 return (IPPROTO_DONE); 1173 } 1174 /* 1175 * Segment flag validation for new connection attempts: 1176 * 1177 * Our (SYN|ACK) response was rejected. 1178 * Check with syncache and remove entry to prevent 1179 * retransmits. 1180 * 1181 * NB: syncache_chkrst does its own logging of failure 1182 * causes. 1183 */ 1184 if (thflags & TH_RST) { 1185 syncache_chkrst(&inc, th); 1186 goto dropunlock; 1187 } 1188 /* 1189 * We can't do anything without SYN. 1190 */ 1191 if ((thflags & TH_SYN) == 0) { 1192 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1193 log(LOG_DEBUG, "%s; %s: Listen socket: " 1194 "SYN is missing, segment ignored\n", 1195 s, __func__); 1196 TCPSTAT_INC(tcps_badsyn); 1197 goto dropunlock; 1198 } 1199 /* 1200 * (SYN|ACK) is bogus on a listen socket. 1201 */ 1202 if (thflags & TH_ACK) { 1203 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1204 log(LOG_DEBUG, "%s; %s: Listen socket: " 1205 "SYN|ACK invalid, segment rejected\n", 1206 s, __func__); 1207 syncache_badack(&inc); /* XXX: Not needed! */ 1208 TCPSTAT_INC(tcps_badsyn); 1209 rstreason = BANDLIM_RST_OPENPORT; 1210 goto dropwithreset; 1211 } 1212 /* 1213 * If the drop_synfin option is enabled, drop all 1214 * segments with both the SYN and FIN bits set. 1215 * This prevents e.g. nmap from identifying the 1216 * TCP/IP stack. 1217 * XXX: Poor reasoning. nmap has other methods 1218 * and is constantly refining its stack detection 1219 * strategies. 1220 * XXX: This is a violation of the TCP specification 1221 * and was used by RFC1644. 1222 */ 1223 if ((thflags & TH_FIN) && V_drop_synfin) { 1224 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1225 log(LOG_DEBUG, "%s; %s: Listen socket: " 1226 "SYN|FIN segment ignored (based on " 1227 "sysctl setting)\n", s, __func__); 1228 TCPSTAT_INC(tcps_badsyn); 1229 goto dropunlock; 1230 } 1231 /* 1232 * Segment's flags are (SYN) or (SYN|FIN). 1233 * 1234 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1235 * as they do not affect the state of the TCP FSM. 1236 * The data pointed to by TH_URG and th_urp is ignored. 1237 */ 1238 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1239 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1240 KASSERT(thflags & (TH_SYN), 1241 ("%s: Listen socket: TH_SYN not set", __func__)); 1242 #ifdef INET6 1243 /* 1244 * If deprecated address is forbidden, 1245 * we do not accept SYN to deprecated interface 1246 * address to prevent any new inbound connection from 1247 * getting established. 1248 * When we do not accept SYN, we send a TCP RST, 1249 * with deprecated source address (instead of dropping 1250 * it). We compromise it as it is much better for peer 1251 * to send a RST, and RST will be the final packet 1252 * for the exchange. 1253 * 1254 * If we do not forbid deprecated addresses, we accept 1255 * the SYN packet. RFC2462 does not suggest dropping 1256 * SYN in this case. 1257 * If we decipher RFC2462 5.5.4, it says like this: 1258 * 1. use of deprecated addr with existing 1259 * communication is okay - "SHOULD continue to be 1260 * used" 1261 * 2. use of it with new communication: 1262 * (2a) "SHOULD NOT be used if alternate address 1263 * with sufficient scope is available" 1264 * (2b) nothing mentioned otherwise. 1265 * Here we fall into (2b) case as we have no choice in 1266 * our source address selection - we must obey the peer. 1267 * 1268 * The wording in RFC2462 is confusing, and there are 1269 * multiple description text for deprecated address 1270 * handling - worse, they are not exactly the same. 1271 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1272 */ 1273 if (isipv6 && !V_ip6_use_deprecated) { 1274 struct in6_ifaddr *ia6; 1275 1276 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1277 if (ia6 != NULL && 1278 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1279 ifa_free(&ia6->ia_ifa); 1280 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1281 log(LOG_DEBUG, "%s; %s: Listen socket: " 1282 "Connection attempt to deprecated " 1283 "IPv6 address rejected\n", 1284 s, __func__); 1285 rstreason = BANDLIM_RST_OPENPORT; 1286 goto dropwithreset; 1287 } 1288 if (ia6) 1289 ifa_free(&ia6->ia_ifa); 1290 } 1291 #endif /* INET6 */ 1292 /* 1293 * Basic sanity checks on incoming SYN requests: 1294 * Don't respond if the destination is a link layer 1295 * broadcast according to RFC1122 4.2.3.10, p. 104. 1296 * If it is from this socket it must be forged. 1297 * Don't respond if the source or destination is a 1298 * global or subnet broad- or multicast address. 1299 * Note that it is quite possible to receive unicast 1300 * link-layer packets with a broadcast IP address. Use 1301 * in_broadcast() to find them. 1302 */ 1303 if (m->m_flags & (M_BCAST|M_MCAST)) { 1304 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1305 log(LOG_DEBUG, "%s; %s: Listen socket: " 1306 "Connection attempt from broad- or multicast " 1307 "link layer address ignored\n", s, __func__); 1308 goto dropunlock; 1309 } 1310 #ifdef INET6 1311 if (isipv6) { 1312 if (th->th_dport == th->th_sport && 1313 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1314 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1315 log(LOG_DEBUG, "%s; %s: Listen socket: " 1316 "Connection attempt to/from self " 1317 "ignored\n", s, __func__); 1318 goto dropunlock; 1319 } 1320 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1321 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1322 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1323 log(LOG_DEBUG, "%s; %s: Listen socket: " 1324 "Connection attempt from/to multicast " 1325 "address ignored\n", s, __func__); 1326 goto dropunlock; 1327 } 1328 } 1329 #endif 1330 #if defined(INET) && defined(INET6) 1331 else 1332 #endif 1333 #ifdef INET 1334 { 1335 if (th->th_dport == th->th_sport && 1336 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1337 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1338 log(LOG_DEBUG, "%s; %s: Listen socket: " 1339 "Connection attempt from/to self " 1340 "ignored\n", s, __func__); 1341 goto dropunlock; 1342 } 1343 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1344 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1345 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1346 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1347 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1348 log(LOG_DEBUG, "%s; %s: Listen socket: " 1349 "Connection attempt from/to broad- " 1350 "or multicast address ignored\n", 1351 s, __func__); 1352 goto dropunlock; 1353 } 1354 } 1355 #endif 1356 /* 1357 * SYN appears to be valid. Create compressed TCP state 1358 * for syncache. 1359 */ 1360 #ifdef TCPDEBUG 1361 if (so->so_options & SO_DEBUG) 1362 tcp_trace(TA_INPUT, ostate, tp, 1363 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1364 #endif 1365 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1366 tcp_dooptions(&to, optp, optlen, TO_SYN); 1367 #ifdef TCP_RFC7413 1368 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL)) 1369 goto new_tfo_socket; 1370 #else 1371 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); 1372 #endif 1373 /* 1374 * Entry added to syncache and mbuf consumed. 1375 * Only the listen socket is unlocked by syncache_add(). 1376 */ 1377 if (ti_locked == TI_RLOCKED) { 1378 INP_INFO_RUNLOCK(&V_tcbinfo); 1379 ti_locked = TI_UNLOCKED; 1380 } 1381 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1382 return (IPPROTO_DONE); 1383 } else if (tp->t_state == TCPS_LISTEN) { 1384 /* 1385 * When a listen socket is torn down the SO_ACCEPTCONN 1386 * flag is removed first while connections are drained 1387 * from the accept queue in a unlock/lock cycle of the 1388 * ACCEPT_LOCK, opening a race condition allowing a SYN 1389 * attempt go through unhandled. 1390 */ 1391 goto dropunlock; 1392 } 1393 1394 #ifdef TCP_SIGNATURE 1395 if (sig_checked == 0) { 1396 tcp_dooptions(&to, optp, optlen, 1397 (thflags & TH_SYN) ? TO_SYN : 0); 1398 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, 1399 th, tp->t_flags)) { 1400 1401 /* 1402 * In SYN_SENT state if it receives an RST, it is 1403 * allowed for further processing. 1404 */ 1405 if ((thflags & TH_RST) == 0 || 1406 (tp->t_state == TCPS_SYN_SENT) == 0) 1407 goto dropunlock; 1408 } 1409 sig_checked = 1; 1410 } 1411 #endif 1412 1413 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1414 1415 /* 1416 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1417 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1418 * the inpcb, and unlocks pcbinfo. 1419 */ 1420 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1421 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1422 return (IPPROTO_DONE); 1423 1424 dropwithreset: 1425 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1426 1427 if (ti_locked == TI_RLOCKED) { 1428 INP_INFO_RUNLOCK(&V_tcbinfo); 1429 ti_locked = TI_UNLOCKED; 1430 } 1431 #ifdef INVARIANTS 1432 else { 1433 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1434 "ti_locked: %d", __func__, ti_locked)); 1435 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1436 } 1437 #endif 1438 1439 if (inp != NULL) { 1440 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1441 INP_WUNLOCK(inp); 1442 } else 1443 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1444 m = NULL; /* mbuf chain got consumed. */ 1445 goto drop; 1446 1447 dropunlock: 1448 if (m != NULL) 1449 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1450 1451 if (ti_locked == TI_RLOCKED) { 1452 INP_INFO_RUNLOCK(&V_tcbinfo); 1453 ti_locked = TI_UNLOCKED; 1454 } 1455 #ifdef INVARIANTS 1456 else { 1457 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1458 "ti_locked: %d", __func__, ti_locked)); 1459 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1460 } 1461 #endif 1462 1463 if (inp != NULL) 1464 INP_WUNLOCK(inp); 1465 1466 drop: 1467 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1468 if (s != NULL) 1469 free(s, M_TCPLOG); 1470 if (m != NULL) 1471 m_freem(m); 1472 return (IPPROTO_DONE); 1473 } 1474 1475 void 1476 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1477 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1478 int ti_locked) 1479 { 1480 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1481 int rstreason, todrop, win; 1482 u_long tiwin; 1483 char *s; 1484 struct in_conninfo *inc; 1485 struct mbuf *mfree; 1486 struct tcpopt to; 1487 int tfo_syn; 1488 1489 #ifdef TCPDEBUG 1490 /* 1491 * The size of tcp_saveipgen must be the size of the max ip header, 1492 * now IPv6. 1493 */ 1494 u_char tcp_saveipgen[IP6_HDR_LEN]; 1495 struct tcphdr tcp_savetcp; 1496 short ostate = 0; 1497 #endif 1498 thflags = th->th_flags; 1499 inc = &tp->t_inpcb->inp_inc; 1500 tp->sackhint.last_sack_ack = 0; 1501 sack_changed = 0; 1502 1503 /* 1504 * If this is either a state-changing packet or current state isn't 1505 * established, we require a write lock on tcbinfo. Otherwise, we 1506 * allow the tcbinfo to be in either alocked or unlocked, as the 1507 * caller may have unnecessarily acquired a write lock due to a race. 1508 */ 1509 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1510 tp->t_state != TCPS_ESTABLISHED) { 1511 KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for " 1512 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1513 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1514 } else { 1515 #ifdef INVARIANTS 1516 if (ti_locked == TI_RLOCKED) 1517 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1518 else { 1519 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " 1520 "ti_locked: %d", __func__, ti_locked)); 1521 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1522 } 1523 #endif 1524 } 1525 INP_WLOCK_ASSERT(tp->t_inpcb); 1526 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1527 __func__)); 1528 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1529 __func__)); 1530 1531 #ifdef TCPPCAP 1532 /* Save segment, if requested. */ 1533 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1534 #endif 1535 1536 /* 1537 * Segment received on connection. 1538 * Reset idle time and keep-alive timer. 1539 * XXX: This should be done after segment 1540 * validation to ignore broken/spoofed segs. 1541 */ 1542 tp->t_rcvtime = ticks; 1543 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1544 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 1545 1546 /* 1547 * Scale up the window into a 32-bit value. 1548 * For the SYN_SENT state the scale is zero. 1549 */ 1550 tiwin = th->th_win << tp->snd_scale; 1551 1552 /* 1553 * TCP ECN processing. 1554 */ 1555 if (tp->t_flags & TF_ECN_PERMIT) { 1556 if (thflags & TH_CWR) 1557 tp->t_flags &= ~TF_ECN_SND_ECE; 1558 switch (iptos & IPTOS_ECN_MASK) { 1559 case IPTOS_ECN_CE: 1560 tp->t_flags |= TF_ECN_SND_ECE; 1561 TCPSTAT_INC(tcps_ecn_ce); 1562 break; 1563 case IPTOS_ECN_ECT0: 1564 TCPSTAT_INC(tcps_ecn_ect0); 1565 break; 1566 case IPTOS_ECN_ECT1: 1567 TCPSTAT_INC(tcps_ecn_ect1); 1568 break; 1569 } 1570 1571 /* Process a packet differently from RFC3168. */ 1572 cc_ecnpkt_handler(tp, th, iptos); 1573 1574 /* Congestion experienced. */ 1575 if (thflags & TH_ECE) { 1576 cc_cong_signal(tp, th, CC_ECN); 1577 } 1578 } 1579 1580 /* 1581 * Parse options on any incoming segment. 1582 */ 1583 tcp_dooptions(&to, (u_char *)(th + 1), 1584 (th->th_off << 2) - sizeof(struct tcphdr), 1585 (thflags & TH_SYN) ? TO_SYN : 0); 1586 1587 /* 1588 * If echoed timestamp is later than the current time, 1589 * fall back to non RFC1323 RTT calculation. Normalize 1590 * timestamp if syncookies were used when this connection 1591 * was established. 1592 */ 1593 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1594 to.to_tsecr -= tp->ts_offset; 1595 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1596 to.to_tsecr = 0; 1597 } 1598 /* 1599 * If timestamps were negotiated during SYN/ACK they should 1600 * appear on every segment during this session and vice versa. 1601 */ 1602 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1603 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1604 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1605 "no action\n", s, __func__); 1606 free(s, M_TCPLOG); 1607 } 1608 } 1609 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1610 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1611 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1612 "no action\n", s, __func__); 1613 free(s, M_TCPLOG); 1614 } 1615 } 1616 1617 /* 1618 * Process options only when we get SYN/ACK back. The SYN case 1619 * for incoming connections is handled in tcp_syncache. 1620 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1621 * or <SYN,ACK>) segment itself is never scaled. 1622 * XXX this is traditional behavior, may need to be cleaned up. 1623 */ 1624 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1625 if ((to.to_flags & TOF_SCALE) && 1626 (tp->t_flags & TF_REQ_SCALE)) { 1627 tp->t_flags |= TF_RCVD_SCALE; 1628 tp->snd_scale = to.to_wscale; 1629 } 1630 /* 1631 * Initial send window. It will be updated with 1632 * the next incoming segment to the scaled value. 1633 */ 1634 tp->snd_wnd = th->th_win; 1635 if (to.to_flags & TOF_TS) { 1636 tp->t_flags |= TF_RCVD_TSTMP; 1637 tp->ts_recent = to.to_tsval; 1638 tp->ts_recent_age = tcp_ts_getticks(); 1639 } 1640 if (to.to_flags & TOF_MSS) 1641 tcp_mss(tp, to.to_mss); 1642 if ((tp->t_flags & TF_SACK_PERMIT) && 1643 (to.to_flags & TOF_SACKPERM) == 0) 1644 tp->t_flags &= ~TF_SACK_PERMIT; 1645 } 1646 1647 /* 1648 * Header prediction: check for the two common cases 1649 * of a uni-directional data xfer. If the packet has 1650 * no control flags, is in-sequence, the window didn't 1651 * change and we're not retransmitting, it's a 1652 * candidate. If the length is zero and the ack moved 1653 * forward, we're the sender side of the xfer. Just 1654 * free the data acked & wake any higher level process 1655 * that was blocked waiting for space. If the length 1656 * is non-zero and the ack didn't move, we're the 1657 * receiver side. If we're getting packets in-order 1658 * (the reassembly queue is empty), add the data to 1659 * the socket buffer and note that we need a delayed ack. 1660 * Make sure that the hidden state-flags are also off. 1661 * Since we check for TCPS_ESTABLISHED first, it can only 1662 * be TH_NEEDSYN. 1663 */ 1664 if (tp->t_state == TCPS_ESTABLISHED && 1665 th->th_seq == tp->rcv_nxt && 1666 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1667 tp->snd_nxt == tp->snd_max && 1668 tiwin && tiwin == tp->snd_wnd && 1669 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1670 LIST_EMPTY(&tp->t_segq) && 1671 ((to.to_flags & TOF_TS) == 0 || 1672 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1673 1674 /* 1675 * If last ACK falls within this segment's sequence numbers, 1676 * record the timestamp. 1677 * NOTE that the test is modified according to the latest 1678 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1679 */ 1680 if ((to.to_flags & TOF_TS) != 0 && 1681 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1682 tp->ts_recent_age = tcp_ts_getticks(); 1683 tp->ts_recent = to.to_tsval; 1684 } 1685 1686 if (tlen == 0) { 1687 if (SEQ_GT(th->th_ack, tp->snd_una) && 1688 SEQ_LEQ(th->th_ack, tp->snd_max) && 1689 !IN_RECOVERY(tp->t_flags) && 1690 (to.to_flags & TOF_SACK) == 0 && 1691 TAILQ_EMPTY(&tp->snd_holes)) { 1692 /* 1693 * This is a pure ack for outstanding data. 1694 */ 1695 if (ti_locked == TI_RLOCKED) 1696 INP_INFO_RUNLOCK(&V_tcbinfo); 1697 ti_locked = TI_UNLOCKED; 1698 1699 TCPSTAT_INC(tcps_predack); 1700 1701 /* 1702 * "bad retransmit" recovery. 1703 */ 1704 if (tp->t_rxtshift == 1 && 1705 tp->t_flags & TF_PREVVALID && 1706 (int)(ticks - tp->t_badrxtwin) < 0) { 1707 cc_cong_signal(tp, th, CC_RTO_ERR); 1708 } 1709 1710 /* 1711 * Recalculate the transmit timer / rtt. 1712 * 1713 * Some boxes send broken timestamp replies 1714 * during the SYN+ACK phase, ignore 1715 * timestamps of 0 or we could calculate a 1716 * huge RTT and blow up the retransmit timer. 1717 */ 1718 if ((to.to_flags & TOF_TS) != 0 && 1719 to.to_tsecr) { 1720 u_int t; 1721 1722 t = tcp_ts_getticks() - to.to_tsecr; 1723 if (!tp->t_rttlow || tp->t_rttlow > t) 1724 tp->t_rttlow = t; 1725 tcp_xmit_timer(tp, 1726 TCP_TS_TO_TICKS(t) + 1); 1727 } else if (tp->t_rtttime && 1728 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1729 if (!tp->t_rttlow || 1730 tp->t_rttlow > ticks - tp->t_rtttime) 1731 tp->t_rttlow = ticks - tp->t_rtttime; 1732 tcp_xmit_timer(tp, 1733 ticks - tp->t_rtttime); 1734 } 1735 acked = BYTES_THIS_ACK(tp, th); 1736 1737 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1738 hhook_run_tcp_est_in(tp, th, &to); 1739 1740 TCPSTAT_INC(tcps_rcvackpack); 1741 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1742 sbdrop(&so->so_snd, acked); 1743 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1744 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1745 tp->snd_recover = th->th_ack - 1; 1746 1747 /* 1748 * Let the congestion control algorithm update 1749 * congestion control related information. This 1750 * typically means increasing the congestion 1751 * window. 1752 */ 1753 cc_ack_received(tp, th, CC_ACK); 1754 1755 tp->snd_una = th->th_ack; 1756 /* 1757 * Pull snd_wl2 up to prevent seq wrap relative 1758 * to th_ack. 1759 */ 1760 tp->snd_wl2 = th->th_ack; 1761 tp->t_dupacks = 0; 1762 m_freem(m); 1763 1764 /* 1765 * If all outstanding data are acked, stop 1766 * retransmit timer, otherwise restart timer 1767 * using current (possibly backed-off) value. 1768 * If process is waiting for space, 1769 * wakeup/selwakeup/signal. If data 1770 * are ready to send, let tcp_output 1771 * decide between more output or persist. 1772 */ 1773 #ifdef TCPDEBUG 1774 if (so->so_options & SO_DEBUG) 1775 tcp_trace(TA_INPUT, ostate, tp, 1776 (void *)tcp_saveipgen, 1777 &tcp_savetcp, 0); 1778 #endif 1779 TCP_PROBE3(debug__input, tp, th, 1780 mtod(m, const char *)); 1781 if (tp->snd_una == tp->snd_max) 1782 tcp_timer_activate(tp, TT_REXMT, 0); 1783 else if (!tcp_timer_active(tp, TT_PERSIST)) 1784 tcp_timer_activate(tp, TT_REXMT, 1785 tp->t_rxtcur); 1786 sowwakeup(so); 1787 if (sbavail(&so->so_snd)) 1788 (void) tp->t_fb->tfb_tcp_output(tp); 1789 goto check_delack; 1790 } 1791 } else if (th->th_ack == tp->snd_una && 1792 tlen <= sbspace(&so->so_rcv)) { 1793 int newsize = 0; /* automatic sockbuf scaling */ 1794 1795 /* 1796 * This is a pure, in-sequence data packet with 1797 * nothing on the reassembly queue and we have enough 1798 * buffer space to take it. 1799 */ 1800 if (ti_locked == TI_RLOCKED) 1801 INP_INFO_RUNLOCK(&V_tcbinfo); 1802 ti_locked = TI_UNLOCKED; 1803 1804 /* Clean receiver SACK report if present */ 1805 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1806 tcp_clean_sackreport(tp); 1807 TCPSTAT_INC(tcps_preddat); 1808 tp->rcv_nxt += tlen; 1809 /* 1810 * Pull snd_wl1 up to prevent seq wrap relative to 1811 * th_seq. 1812 */ 1813 tp->snd_wl1 = th->th_seq; 1814 /* 1815 * Pull rcv_up up to prevent seq wrap relative to 1816 * rcv_nxt. 1817 */ 1818 tp->rcv_up = tp->rcv_nxt; 1819 TCPSTAT_INC(tcps_rcvpack); 1820 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1821 #ifdef TCPDEBUG 1822 if (so->so_options & SO_DEBUG) 1823 tcp_trace(TA_INPUT, ostate, tp, 1824 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1825 #endif 1826 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1827 1828 /* 1829 * Automatic sizing of receive socket buffer. Often the send 1830 * buffer size is not optimally adjusted to the actual network 1831 * conditions at hand (delay bandwidth product). Setting the 1832 * buffer size too small limits throughput on links with high 1833 * bandwidth and high delay (eg. trans-continental/oceanic links). 1834 * 1835 * On the receive side the socket buffer memory is only rarely 1836 * used to any significant extent. This allows us to be much 1837 * more aggressive in scaling the receive socket buffer. For 1838 * the case that the buffer space is actually used to a large 1839 * extent and we run out of kernel memory we can simply drop 1840 * the new segments; TCP on the sender will just retransmit it 1841 * later. Setting the buffer size too big may only consume too 1842 * much kernel memory if the application doesn't read() from 1843 * the socket or packet loss or reordering makes use of the 1844 * reassembly queue. 1845 * 1846 * The criteria to step up the receive buffer one notch are: 1847 * 1. Application has not set receive buffer size with 1848 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1849 * 2. the number of bytes received during the time it takes 1850 * one timestamp to be reflected back to us (the RTT); 1851 * 3. received bytes per RTT is within seven eighth of the 1852 * current socket buffer size; 1853 * 4. receive buffer size has not hit maximal automatic size; 1854 * 1855 * This algorithm does one step per RTT at most and only if 1856 * we receive a bulk stream w/o packet losses or reorderings. 1857 * Shrinking the buffer during idle times is not necessary as 1858 * it doesn't consume any memory when idle. 1859 * 1860 * TODO: Only step up if the application is actually serving 1861 * the buffer to better manage the socket buffer resources. 1862 */ 1863 if (V_tcp_do_autorcvbuf && 1864 (to.to_flags & TOF_TS) && 1865 to.to_tsecr && 1866 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1867 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && 1868 to.to_tsecr - tp->rfbuf_ts < hz) { 1869 if (tp->rfbuf_cnt > 1870 (so->so_rcv.sb_hiwat / 8 * 7) && 1871 so->so_rcv.sb_hiwat < 1872 V_tcp_autorcvbuf_max) { 1873 newsize = 1874 min(so->so_rcv.sb_hiwat + 1875 V_tcp_autorcvbuf_inc, 1876 V_tcp_autorcvbuf_max); 1877 } 1878 /* Start over with next RTT. */ 1879 tp->rfbuf_ts = 0; 1880 tp->rfbuf_cnt = 0; 1881 } else 1882 tp->rfbuf_cnt += tlen; /* add up */ 1883 } 1884 1885 /* Add data to socket buffer. */ 1886 SOCKBUF_LOCK(&so->so_rcv); 1887 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1888 m_freem(m); 1889 } else { 1890 /* 1891 * Set new socket buffer size. 1892 * Give up when limit is reached. 1893 */ 1894 if (newsize) 1895 if (!sbreserve_locked(&so->so_rcv, 1896 newsize, so, NULL)) 1897 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1898 m_adj(m, drop_hdrlen); /* delayed header drop */ 1899 sbappendstream_locked(&so->so_rcv, m, 0); 1900 } 1901 /* NB: sorwakeup_locked() does an implicit unlock. */ 1902 sorwakeup_locked(so); 1903 if (DELAY_ACK(tp, tlen)) { 1904 tp->t_flags |= TF_DELACK; 1905 } else { 1906 tp->t_flags |= TF_ACKNOW; 1907 tp->t_fb->tfb_tcp_output(tp); 1908 } 1909 goto check_delack; 1910 } 1911 } 1912 1913 /* 1914 * Calculate amount of space in receive window, 1915 * and then do TCP input processing. 1916 * Receive window is amount of space in rcv queue, 1917 * but not less than advertised window. 1918 */ 1919 win = sbspace(&so->so_rcv); 1920 if (win < 0) 1921 win = 0; 1922 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1923 1924 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1925 tp->rfbuf_ts = 0; 1926 tp->rfbuf_cnt = 0; 1927 1928 switch (tp->t_state) { 1929 1930 /* 1931 * If the state is SYN_RECEIVED: 1932 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1933 */ 1934 case TCPS_SYN_RECEIVED: 1935 if ((thflags & TH_ACK) && 1936 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1937 SEQ_GT(th->th_ack, tp->snd_max))) { 1938 rstreason = BANDLIM_RST_OPENPORT; 1939 goto dropwithreset; 1940 } 1941 #ifdef TCP_RFC7413 1942 if (tp->t_flags & TF_FASTOPEN) { 1943 /* 1944 * When a TFO connection is in SYN_RECEIVED, the 1945 * only valid packets are the initial SYN, a 1946 * retransmit/copy of the initial SYN (possibly with 1947 * a subset of the original data), a valid ACK, a 1948 * FIN, or a RST. 1949 */ 1950 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1951 rstreason = BANDLIM_RST_OPENPORT; 1952 goto dropwithreset; 1953 } else if (thflags & TH_SYN) { 1954 /* non-initial SYN is ignored */ 1955 if ((tcp_timer_active(tp, TT_DELACK) || 1956 tcp_timer_active(tp, TT_REXMT))) 1957 goto drop; 1958 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1959 goto drop; 1960 } 1961 } 1962 #endif 1963 break; 1964 1965 /* 1966 * If the state is SYN_SENT: 1967 * if seg contains an ACK, but not for our SYN, drop the input. 1968 * if seg contains a RST, then drop the connection. 1969 * if seg does not contain SYN, then drop it. 1970 * Otherwise this is an acceptable SYN segment 1971 * initialize tp->rcv_nxt and tp->irs 1972 * if seg contains ack then advance tp->snd_una 1973 * if seg contains an ECE and ECN support is enabled, the stream 1974 * is ECN capable. 1975 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1976 * arrange for segment to be acked (eventually) 1977 * continue processing rest of data/controls, beginning with URG 1978 */ 1979 case TCPS_SYN_SENT: 1980 if ((thflags & TH_ACK) && 1981 (SEQ_LEQ(th->th_ack, tp->iss) || 1982 SEQ_GT(th->th_ack, tp->snd_max))) { 1983 rstreason = BANDLIM_UNLIMITED; 1984 goto dropwithreset; 1985 } 1986 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 1987 TCP_PROBE5(connect__refused, NULL, tp, 1988 mtod(m, const char *), tp, th); 1989 tp = tcp_drop(tp, ECONNREFUSED); 1990 } 1991 if (thflags & TH_RST) 1992 goto drop; 1993 if (!(thflags & TH_SYN)) 1994 goto drop; 1995 1996 tp->irs = th->th_seq; 1997 tcp_rcvseqinit(tp); 1998 if (thflags & TH_ACK) { 1999 TCPSTAT_INC(tcps_connects); 2000 soisconnected(so); 2001 #ifdef MAC 2002 mac_socketpeer_set_from_mbuf(m, so); 2003 #endif 2004 /* Do window scaling on this connection? */ 2005 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2006 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2007 tp->rcv_scale = tp->request_r_scale; 2008 } 2009 tp->rcv_adv += imin(tp->rcv_wnd, 2010 TCP_MAXWIN << tp->rcv_scale); 2011 tp->snd_una++; /* SYN is acked */ 2012 /* 2013 * If there's data, delay ACK; if there's also a FIN 2014 * ACKNOW will be turned on later. 2015 */ 2016 if (DELAY_ACK(tp, tlen) && tlen != 0) 2017 tcp_timer_activate(tp, TT_DELACK, 2018 tcp_delacktime); 2019 else 2020 tp->t_flags |= TF_ACKNOW; 2021 2022 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 2023 tp->t_flags |= TF_ECN_PERMIT; 2024 TCPSTAT_INC(tcps_ecn_shs); 2025 } 2026 2027 /* 2028 * Received <SYN,ACK> in SYN_SENT[*] state. 2029 * Transitions: 2030 * SYN_SENT --> ESTABLISHED 2031 * SYN_SENT* --> FIN_WAIT_1 2032 */ 2033 tp->t_starttime = ticks; 2034 if (tp->t_flags & TF_NEEDFIN) { 2035 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2036 tp->t_flags &= ~TF_NEEDFIN; 2037 thflags &= ~TH_SYN; 2038 } else { 2039 tcp_state_change(tp, TCPS_ESTABLISHED); 2040 TCP_PROBE5(connect__established, NULL, tp, 2041 mtod(m, const char *), tp, th); 2042 cc_conn_init(tp); 2043 tcp_timer_activate(tp, TT_KEEP, 2044 TP_KEEPIDLE(tp)); 2045 } 2046 } else { 2047 /* 2048 * Received initial SYN in SYN-SENT[*] state => 2049 * simultaneous open. 2050 * If it succeeds, connection is * half-synchronized. 2051 * Otherwise, do 3-way handshake: 2052 * SYN-SENT -> SYN-RECEIVED 2053 * SYN-SENT* -> SYN-RECEIVED* 2054 */ 2055 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2056 tcp_timer_activate(tp, TT_REXMT, 0); 2057 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2058 } 2059 2060 KASSERT(ti_locked == TI_RLOCKED, ("%s: trimthenstep6: " 2061 "ti_locked %d", __func__, ti_locked)); 2062 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2063 INP_WLOCK_ASSERT(tp->t_inpcb); 2064 2065 /* 2066 * Advance th->th_seq to correspond to first data byte. 2067 * If data, trim to stay within window, 2068 * dropping FIN if necessary. 2069 */ 2070 th->th_seq++; 2071 if (tlen > tp->rcv_wnd) { 2072 todrop = tlen - tp->rcv_wnd; 2073 m_adj(m, -todrop); 2074 tlen = tp->rcv_wnd; 2075 thflags &= ~TH_FIN; 2076 TCPSTAT_INC(tcps_rcvpackafterwin); 2077 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2078 } 2079 tp->snd_wl1 = th->th_seq - 1; 2080 tp->rcv_up = th->th_seq; 2081 /* 2082 * Client side of transaction: already sent SYN and data. 2083 * If the remote host used T/TCP to validate the SYN, 2084 * our data will be ACK'd; if so, enter normal data segment 2085 * processing in the middle of step 5, ack processing. 2086 * Otherwise, goto step 6. 2087 */ 2088 if (thflags & TH_ACK) 2089 goto process_ACK; 2090 2091 goto step6; 2092 2093 /* 2094 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2095 * do normal processing. 2096 * 2097 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2098 */ 2099 case TCPS_LAST_ACK: 2100 case TCPS_CLOSING: 2101 break; /* continue normal processing */ 2102 } 2103 2104 /* 2105 * States other than LISTEN or SYN_SENT. 2106 * First check the RST flag and sequence number since reset segments 2107 * are exempt from the timestamp and connection count tests. This 2108 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2109 * below which allowed reset segments in half the sequence space 2110 * to fall though and be processed (which gives forged reset 2111 * segments with a random sequence number a 50 percent chance of 2112 * killing a connection). 2113 * Then check timestamp, if present. 2114 * Then check the connection count, if present. 2115 * Then check that at least some bytes of segment are within 2116 * receive window. If segment begins before rcv_nxt, 2117 * drop leading data (and SYN); if nothing left, just ack. 2118 */ 2119 if (thflags & TH_RST) { 2120 /* 2121 * RFC5961 Section 3.2 2122 * 2123 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2124 * - If RST is in window, we send challenge ACK. 2125 * 2126 * Note: to take into account delayed ACKs, we should 2127 * test against last_ack_sent instead of rcv_nxt. 2128 * Note 2: we handle special case of closed window, not 2129 * covered by the RFC. 2130 */ 2131 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2132 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2133 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2134 2135 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2136 KASSERT(ti_locked == TI_RLOCKED, 2137 ("%s: TH_RST ti_locked %d, th %p tp %p", 2138 __func__, ti_locked, th, tp)); 2139 KASSERT(tp->t_state != TCPS_SYN_SENT, 2140 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2141 __func__, th, tp)); 2142 2143 if (V_tcp_insecure_rst || 2144 tp->last_ack_sent == th->th_seq) { 2145 TCPSTAT_INC(tcps_drops); 2146 /* Drop the connection. */ 2147 switch (tp->t_state) { 2148 case TCPS_SYN_RECEIVED: 2149 so->so_error = ECONNREFUSED; 2150 goto close; 2151 case TCPS_ESTABLISHED: 2152 case TCPS_FIN_WAIT_1: 2153 case TCPS_FIN_WAIT_2: 2154 case TCPS_CLOSE_WAIT: 2155 so->so_error = ECONNRESET; 2156 close: 2157 tcp_state_change(tp, TCPS_CLOSED); 2158 /* FALLTHROUGH */ 2159 default: 2160 tp = tcp_close(tp); 2161 } 2162 } else { 2163 TCPSTAT_INC(tcps_badrst); 2164 /* Send challenge ACK. */ 2165 tcp_respond(tp, mtod(m, void *), th, m, 2166 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2167 tp->last_ack_sent = tp->rcv_nxt; 2168 m = NULL; 2169 } 2170 } 2171 goto drop; 2172 } 2173 2174 /* 2175 * RFC5961 Section 4.2 2176 * Send challenge ACK for any SYN in synchronized state. 2177 */ 2178 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2179 tp->t_state != TCPS_SYN_RECEIVED) { 2180 KASSERT(ti_locked == TI_RLOCKED, 2181 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 2182 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2183 2184 TCPSTAT_INC(tcps_badsyn); 2185 if (V_tcp_insecure_syn && 2186 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2187 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2188 tp = tcp_drop(tp, ECONNRESET); 2189 rstreason = BANDLIM_UNLIMITED; 2190 } else { 2191 /* Send challenge ACK. */ 2192 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2193 tp->snd_nxt, TH_ACK); 2194 tp->last_ack_sent = tp->rcv_nxt; 2195 m = NULL; 2196 } 2197 goto drop; 2198 } 2199 2200 /* 2201 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2202 * and it's less than ts_recent, drop it. 2203 */ 2204 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2205 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2206 2207 /* Check to see if ts_recent is over 24 days old. */ 2208 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2209 /* 2210 * Invalidate ts_recent. If this segment updates 2211 * ts_recent, the age will be reset later and ts_recent 2212 * will get a valid value. If it does not, setting 2213 * ts_recent to zero will at least satisfy the 2214 * requirement that zero be placed in the timestamp 2215 * echo reply when ts_recent isn't valid. The 2216 * age isn't reset until we get a valid ts_recent 2217 * because we don't want out-of-order segments to be 2218 * dropped when ts_recent is old. 2219 */ 2220 tp->ts_recent = 0; 2221 } else { 2222 TCPSTAT_INC(tcps_rcvduppack); 2223 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2224 TCPSTAT_INC(tcps_pawsdrop); 2225 if (tlen) 2226 goto dropafterack; 2227 goto drop; 2228 } 2229 } 2230 2231 /* 2232 * In the SYN-RECEIVED state, validate that the packet belongs to 2233 * this connection before trimming the data to fit the receive 2234 * window. Check the sequence number versus IRS since we know 2235 * the sequence numbers haven't wrapped. This is a partial fix 2236 * for the "LAND" DoS attack. 2237 */ 2238 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2239 rstreason = BANDLIM_RST_OPENPORT; 2240 goto dropwithreset; 2241 } 2242 2243 todrop = tp->rcv_nxt - th->th_seq; 2244 if (todrop > 0) { 2245 if (thflags & TH_SYN) { 2246 thflags &= ~TH_SYN; 2247 th->th_seq++; 2248 if (th->th_urp > 1) 2249 th->th_urp--; 2250 else 2251 thflags &= ~TH_URG; 2252 todrop--; 2253 } 2254 /* 2255 * Following if statement from Stevens, vol. 2, p. 960. 2256 */ 2257 if (todrop > tlen 2258 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2259 /* 2260 * Any valid FIN must be to the left of the window. 2261 * At this point the FIN must be a duplicate or out 2262 * of sequence; drop it. 2263 */ 2264 thflags &= ~TH_FIN; 2265 2266 /* 2267 * Send an ACK to resynchronize and drop any data. 2268 * But keep on processing for RST or ACK. 2269 */ 2270 tp->t_flags |= TF_ACKNOW; 2271 todrop = tlen; 2272 TCPSTAT_INC(tcps_rcvduppack); 2273 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2274 } else { 2275 TCPSTAT_INC(tcps_rcvpartduppack); 2276 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2277 } 2278 drop_hdrlen += todrop; /* drop from the top afterwards */ 2279 th->th_seq += todrop; 2280 tlen -= todrop; 2281 if (th->th_urp > todrop) 2282 th->th_urp -= todrop; 2283 else { 2284 thflags &= ~TH_URG; 2285 th->th_urp = 0; 2286 } 2287 } 2288 2289 /* 2290 * If new data are received on a connection after the 2291 * user processes are gone, then RST the other end. 2292 */ 2293 if ((so->so_state & SS_NOFDREF) && 2294 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2295 KASSERT(ti_locked == TI_RLOCKED, ("%s: SS_NOFDEREF && " 2296 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 2297 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2298 2299 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2300 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2301 "after socket was closed, " 2302 "sending RST and removing tcpcb\n", 2303 s, __func__, tcpstates[tp->t_state], tlen); 2304 free(s, M_TCPLOG); 2305 } 2306 tp = tcp_close(tp); 2307 TCPSTAT_INC(tcps_rcvafterclose); 2308 rstreason = BANDLIM_UNLIMITED; 2309 goto dropwithreset; 2310 } 2311 2312 /* 2313 * If segment ends after window, drop trailing data 2314 * (and PUSH and FIN); if nothing left, just ACK. 2315 */ 2316 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2317 if (todrop > 0) { 2318 TCPSTAT_INC(tcps_rcvpackafterwin); 2319 if (todrop >= tlen) { 2320 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2321 /* 2322 * If window is closed can only take segments at 2323 * window edge, and have to drop data and PUSH from 2324 * incoming segments. Continue processing, but 2325 * remember to ack. Otherwise, drop segment 2326 * and ack. 2327 */ 2328 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2329 tp->t_flags |= TF_ACKNOW; 2330 TCPSTAT_INC(tcps_rcvwinprobe); 2331 } else 2332 goto dropafterack; 2333 } else 2334 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2335 m_adj(m, -todrop); 2336 tlen -= todrop; 2337 thflags &= ~(TH_PUSH|TH_FIN); 2338 } 2339 2340 /* 2341 * If last ACK falls within this segment's sequence numbers, 2342 * record its timestamp. 2343 * NOTE: 2344 * 1) That the test incorporates suggestions from the latest 2345 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2346 * 2) That updating only on newer timestamps interferes with 2347 * our earlier PAWS tests, so this check should be solely 2348 * predicated on the sequence space of this segment. 2349 * 3) That we modify the segment boundary check to be 2350 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2351 * instead of RFC1323's 2352 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2353 * This modified check allows us to overcome RFC1323's 2354 * limitations as described in Stevens TCP/IP Illustrated 2355 * Vol. 2 p.869. In such cases, we can still calculate the 2356 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2357 */ 2358 if ((to.to_flags & TOF_TS) != 0 && 2359 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2360 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2361 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2362 tp->ts_recent_age = tcp_ts_getticks(); 2363 tp->ts_recent = to.to_tsval; 2364 } 2365 2366 /* 2367 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2368 * flag is on (half-synchronized state), then queue data for 2369 * later processing; else drop segment and return. 2370 */ 2371 if ((thflags & TH_ACK) == 0) { 2372 if (tp->t_state == TCPS_SYN_RECEIVED || 2373 (tp->t_flags & TF_NEEDSYN)) { 2374 #ifdef TCP_RFC7413 2375 if (tp->t_state == TCPS_SYN_RECEIVED && 2376 tp->t_flags & TF_FASTOPEN) { 2377 tp->snd_wnd = tiwin; 2378 cc_conn_init(tp); 2379 } 2380 #endif 2381 goto step6; 2382 } else if (tp->t_flags & TF_ACKNOW) 2383 goto dropafterack; 2384 else 2385 goto drop; 2386 } 2387 2388 /* 2389 * Ack processing. 2390 */ 2391 switch (tp->t_state) { 2392 2393 /* 2394 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2395 * ESTABLISHED state and continue processing. 2396 * The ACK was checked above. 2397 */ 2398 case TCPS_SYN_RECEIVED: 2399 2400 TCPSTAT_INC(tcps_connects); 2401 soisconnected(so); 2402 /* Do window scaling? */ 2403 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2404 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2405 tp->rcv_scale = tp->request_r_scale; 2406 tp->snd_wnd = tiwin; 2407 } 2408 /* 2409 * Make transitions: 2410 * SYN-RECEIVED -> ESTABLISHED 2411 * SYN-RECEIVED* -> FIN-WAIT-1 2412 */ 2413 tp->t_starttime = ticks; 2414 if (tp->t_flags & TF_NEEDFIN) { 2415 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2416 tp->t_flags &= ~TF_NEEDFIN; 2417 } else { 2418 tcp_state_change(tp, TCPS_ESTABLISHED); 2419 TCP_PROBE5(accept__established, NULL, tp, 2420 mtod(m, const char *), tp, th); 2421 #ifdef TCP_RFC7413 2422 if (tp->t_tfo_pending) { 2423 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2424 tp->t_tfo_pending = NULL; 2425 2426 /* 2427 * Account for the ACK of our SYN prior to 2428 * regular ACK processing below. 2429 */ 2430 tp->snd_una++; 2431 } 2432 /* 2433 * TFO connections call cc_conn_init() during SYN 2434 * processing. Calling it again here for such 2435 * connections is not harmless as it would undo the 2436 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2437 * is retransmitted. 2438 */ 2439 if (!(tp->t_flags & TF_FASTOPEN)) 2440 #endif 2441 cc_conn_init(tp); 2442 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2443 } 2444 /* 2445 * If segment contains data or ACK, will call tcp_reass() 2446 * later; if not, do so now to pass queued data to user. 2447 */ 2448 if (tlen == 0 && (thflags & TH_FIN) == 0) 2449 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2450 (struct mbuf *)0); 2451 tp->snd_wl1 = th->th_seq - 1; 2452 /* FALLTHROUGH */ 2453 2454 /* 2455 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2456 * ACKs. If the ack is in the range 2457 * tp->snd_una < th->th_ack <= tp->snd_max 2458 * then advance tp->snd_una to th->th_ack and drop 2459 * data from the retransmission queue. If this ACK reflects 2460 * more up to date window information we update our window information. 2461 */ 2462 case TCPS_ESTABLISHED: 2463 case TCPS_FIN_WAIT_1: 2464 case TCPS_FIN_WAIT_2: 2465 case TCPS_CLOSE_WAIT: 2466 case TCPS_CLOSING: 2467 case TCPS_LAST_ACK: 2468 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2469 TCPSTAT_INC(tcps_rcvacktoomuch); 2470 goto dropafterack; 2471 } 2472 if ((tp->t_flags & TF_SACK_PERMIT) && 2473 ((to.to_flags & TOF_SACK) || 2474 !TAILQ_EMPTY(&tp->snd_holes))) 2475 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2476 else 2477 /* 2478 * Reset the value so that previous (valid) value 2479 * from the last ack with SACK doesn't get used. 2480 */ 2481 tp->sackhint.sacked_bytes = 0; 2482 2483 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2484 hhook_run_tcp_est_in(tp, th, &to); 2485 2486 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2487 u_int maxseg; 2488 2489 maxseg = tcp_maxseg(tp); 2490 if (tlen == 0 && 2491 (tiwin == tp->snd_wnd || 2492 (tp->t_flags & TF_SACK_PERMIT))) { 2493 /* 2494 * If this is the first time we've seen a 2495 * FIN from the remote, this is not a 2496 * duplicate and it needs to be processed 2497 * normally. This happens during a 2498 * simultaneous close. 2499 */ 2500 if ((thflags & TH_FIN) && 2501 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2502 tp->t_dupacks = 0; 2503 break; 2504 } 2505 TCPSTAT_INC(tcps_rcvdupack); 2506 /* 2507 * If we have outstanding data (other than 2508 * a window probe), this is a completely 2509 * duplicate ack (ie, window info didn't 2510 * change and FIN isn't set), 2511 * the ack is the biggest we've 2512 * seen and we've seen exactly our rexmt 2513 * threshhold of them, assume a packet 2514 * has been dropped and retransmit it. 2515 * Kludge snd_nxt & the congestion 2516 * window so we send only this one 2517 * packet. 2518 * 2519 * We know we're losing at the current 2520 * window size so do congestion avoidance 2521 * (set ssthresh to half the current window 2522 * and pull our congestion window back to 2523 * the new ssthresh). 2524 * 2525 * Dup acks mean that packets have left the 2526 * network (they're now cached at the receiver) 2527 * so bump cwnd by the amount in the receiver 2528 * to keep a constant cwnd packets in the 2529 * network. 2530 * 2531 * When using TCP ECN, notify the peer that 2532 * we reduced the cwnd. 2533 */ 2534 /* 2535 * Following 2 kinds of acks should not affect 2536 * dupack counting: 2537 * 1) Old acks 2538 * 2) Acks with SACK but without any new SACK 2539 * information in them. These could result from 2540 * any anomaly in the network like a switch 2541 * duplicating packets or a possible DoS attack. 2542 */ 2543 if (th->th_ack != tp->snd_una || 2544 ((tp->t_flags & TF_SACK_PERMIT) && 2545 !sack_changed)) 2546 break; 2547 else if (!tcp_timer_active(tp, TT_REXMT)) 2548 tp->t_dupacks = 0; 2549 else if (++tp->t_dupacks > tcprexmtthresh || 2550 IN_FASTRECOVERY(tp->t_flags)) { 2551 cc_ack_received(tp, th, CC_DUPACK); 2552 if ((tp->t_flags & TF_SACK_PERMIT) && 2553 IN_FASTRECOVERY(tp->t_flags)) { 2554 int awnd; 2555 2556 /* 2557 * Compute the amount of data in flight first. 2558 * We can inject new data into the pipe iff 2559 * we have less than 1/2 the original window's 2560 * worth of data in flight. 2561 */ 2562 if (V_tcp_do_rfc6675_pipe) 2563 awnd = tcp_compute_pipe(tp); 2564 else 2565 awnd = (tp->snd_nxt - tp->snd_fack) + 2566 tp->sackhint.sack_bytes_rexmit; 2567 2568 if (awnd < tp->snd_ssthresh) { 2569 tp->snd_cwnd += maxseg; 2570 if (tp->snd_cwnd > tp->snd_ssthresh) 2571 tp->snd_cwnd = tp->snd_ssthresh; 2572 } 2573 } else 2574 tp->snd_cwnd += maxseg; 2575 (void) tp->t_fb->tfb_tcp_output(tp); 2576 goto drop; 2577 } else if (tp->t_dupacks == tcprexmtthresh) { 2578 tcp_seq onxt = tp->snd_nxt; 2579 2580 /* 2581 * If we're doing sack, check to 2582 * see if we're already in sack 2583 * recovery. If we're not doing sack, 2584 * check to see if we're in newreno 2585 * recovery. 2586 */ 2587 if (tp->t_flags & TF_SACK_PERMIT) { 2588 if (IN_FASTRECOVERY(tp->t_flags)) { 2589 tp->t_dupacks = 0; 2590 break; 2591 } 2592 } else { 2593 if (SEQ_LEQ(th->th_ack, 2594 tp->snd_recover)) { 2595 tp->t_dupacks = 0; 2596 break; 2597 } 2598 } 2599 /* Congestion signal before ack. */ 2600 cc_cong_signal(tp, th, CC_NDUPACK); 2601 cc_ack_received(tp, th, CC_DUPACK); 2602 tcp_timer_activate(tp, TT_REXMT, 0); 2603 tp->t_rtttime = 0; 2604 if (tp->t_flags & TF_SACK_PERMIT) { 2605 TCPSTAT_INC( 2606 tcps_sack_recovery_episode); 2607 tp->sack_newdata = tp->snd_nxt; 2608 tp->snd_cwnd = maxseg; 2609 (void) tp->t_fb->tfb_tcp_output(tp); 2610 goto drop; 2611 } 2612 tp->snd_nxt = th->th_ack; 2613 tp->snd_cwnd = maxseg; 2614 (void) tp->t_fb->tfb_tcp_output(tp); 2615 KASSERT(tp->snd_limited <= 2, 2616 ("%s: tp->snd_limited too big", 2617 __func__)); 2618 tp->snd_cwnd = tp->snd_ssthresh + 2619 maxseg * 2620 (tp->t_dupacks - tp->snd_limited); 2621 if (SEQ_GT(onxt, tp->snd_nxt)) 2622 tp->snd_nxt = onxt; 2623 goto drop; 2624 } else if (V_tcp_do_rfc3042) { 2625 /* 2626 * Process first and second duplicate 2627 * ACKs. Each indicates a segment 2628 * leaving the network, creating room 2629 * for more. Make sure we can send a 2630 * packet on reception of each duplicate 2631 * ACK by increasing snd_cwnd by one 2632 * segment. Restore the original 2633 * snd_cwnd after packet transmission. 2634 */ 2635 cc_ack_received(tp, th, CC_DUPACK); 2636 u_long oldcwnd = tp->snd_cwnd; 2637 tcp_seq oldsndmax = tp->snd_max; 2638 u_int sent; 2639 int avail; 2640 2641 KASSERT(tp->t_dupacks == 1 || 2642 tp->t_dupacks == 2, 2643 ("%s: dupacks not 1 or 2", 2644 __func__)); 2645 if (tp->t_dupacks == 1) 2646 tp->snd_limited = 0; 2647 tp->snd_cwnd = 2648 (tp->snd_nxt - tp->snd_una) + 2649 (tp->t_dupacks - tp->snd_limited) * 2650 maxseg; 2651 /* 2652 * Only call tcp_output when there 2653 * is new data available to be sent. 2654 * Otherwise we would send pure ACKs. 2655 */ 2656 SOCKBUF_LOCK(&so->so_snd); 2657 avail = sbavail(&so->so_snd) - 2658 (tp->snd_nxt - tp->snd_una); 2659 SOCKBUF_UNLOCK(&so->so_snd); 2660 if (avail > 0) 2661 (void) tp->t_fb->tfb_tcp_output(tp); 2662 sent = tp->snd_max - oldsndmax; 2663 if (sent > maxseg) { 2664 KASSERT((tp->t_dupacks == 2 && 2665 tp->snd_limited == 0) || 2666 (sent == maxseg + 1 && 2667 tp->t_flags & TF_SENTFIN), 2668 ("%s: sent too much", 2669 __func__)); 2670 tp->snd_limited = 2; 2671 } else if (sent > 0) 2672 ++tp->snd_limited; 2673 tp->snd_cwnd = oldcwnd; 2674 goto drop; 2675 } 2676 } 2677 break; 2678 } else { 2679 /* 2680 * This ack is advancing the left edge, reset the 2681 * counter. 2682 */ 2683 tp->t_dupacks = 0; 2684 /* 2685 * If this ack also has new SACK info, increment the 2686 * counter as per rfc6675. 2687 */ 2688 if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed) 2689 tp->t_dupacks++; 2690 } 2691 2692 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2693 ("%s: th_ack <= snd_una", __func__)); 2694 2695 /* 2696 * If the congestion window was inflated to account 2697 * for the other side's cached packets, retract it. 2698 */ 2699 if (IN_FASTRECOVERY(tp->t_flags)) { 2700 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2701 if (tp->t_flags & TF_SACK_PERMIT) 2702 tcp_sack_partialack(tp, th); 2703 else 2704 tcp_newreno_partial_ack(tp, th); 2705 } else 2706 cc_post_recovery(tp, th); 2707 } 2708 /* 2709 * If we reach this point, ACK is not a duplicate, 2710 * i.e., it ACKs something we sent. 2711 */ 2712 if (tp->t_flags & TF_NEEDSYN) { 2713 /* 2714 * T/TCP: Connection was half-synchronized, and our 2715 * SYN has been ACK'd (so connection is now fully 2716 * synchronized). Go to non-starred state, 2717 * increment snd_una for ACK of SYN, and check if 2718 * we can do window scaling. 2719 */ 2720 tp->t_flags &= ~TF_NEEDSYN; 2721 tp->snd_una++; 2722 /* Do window scaling? */ 2723 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2724 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2725 tp->rcv_scale = tp->request_r_scale; 2726 /* Send window already scaled. */ 2727 } 2728 } 2729 2730 process_ACK: 2731 INP_WLOCK_ASSERT(tp->t_inpcb); 2732 2733 acked = BYTES_THIS_ACK(tp, th); 2734 TCPSTAT_INC(tcps_rcvackpack); 2735 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2736 2737 /* 2738 * If we just performed our first retransmit, and the ACK 2739 * arrives within our recovery window, then it was a mistake 2740 * to do the retransmit in the first place. Recover our 2741 * original cwnd and ssthresh, and proceed to transmit where 2742 * we left off. 2743 */ 2744 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && 2745 (int)(ticks - tp->t_badrxtwin) < 0) 2746 cc_cong_signal(tp, th, CC_RTO_ERR); 2747 2748 /* 2749 * If we have a timestamp reply, update smoothed 2750 * round trip time. If no timestamp is present but 2751 * transmit timer is running and timed sequence 2752 * number was acked, update smoothed round trip time. 2753 * Since we now have an rtt measurement, cancel the 2754 * timer backoff (cf., Phil Karn's retransmit alg.). 2755 * Recompute the initial retransmit timer. 2756 * 2757 * Some boxes send broken timestamp replies 2758 * during the SYN+ACK phase, ignore 2759 * timestamps of 0 or we could calculate a 2760 * huge RTT and blow up the retransmit timer. 2761 */ 2762 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2763 u_int t; 2764 2765 t = tcp_ts_getticks() - to.to_tsecr; 2766 if (!tp->t_rttlow || tp->t_rttlow > t) 2767 tp->t_rttlow = t; 2768 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2769 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2770 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2771 tp->t_rttlow = ticks - tp->t_rtttime; 2772 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2773 } 2774 2775 /* 2776 * If all outstanding data is acked, stop retransmit 2777 * timer and remember to restart (more output or persist). 2778 * If there is more data to be acked, restart retransmit 2779 * timer, using current (possibly backed-off) value. 2780 */ 2781 if (th->th_ack == tp->snd_max) { 2782 tcp_timer_activate(tp, TT_REXMT, 0); 2783 needoutput = 1; 2784 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2785 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2786 2787 /* 2788 * If no data (only SYN) was ACK'd, 2789 * skip rest of ACK processing. 2790 */ 2791 if (acked == 0) 2792 goto step6; 2793 2794 /* 2795 * Let the congestion control algorithm update congestion 2796 * control related information. This typically means increasing 2797 * the congestion window. 2798 */ 2799 cc_ack_received(tp, th, CC_ACK); 2800 2801 SOCKBUF_LOCK(&so->so_snd); 2802 if (acked > sbavail(&so->so_snd)) { 2803 tp->snd_wnd -= sbavail(&so->so_snd); 2804 mfree = sbcut_locked(&so->so_snd, 2805 (int)sbavail(&so->so_snd)); 2806 ourfinisacked = 1; 2807 } else { 2808 mfree = sbcut_locked(&so->so_snd, acked); 2809 tp->snd_wnd -= acked; 2810 ourfinisacked = 0; 2811 } 2812 /* NB: sowwakeup_locked() does an implicit unlock. */ 2813 sowwakeup_locked(so); 2814 m_freem(mfree); 2815 /* Detect una wraparound. */ 2816 if (!IN_RECOVERY(tp->t_flags) && 2817 SEQ_GT(tp->snd_una, tp->snd_recover) && 2818 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2819 tp->snd_recover = th->th_ack - 1; 2820 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2821 if (IN_RECOVERY(tp->t_flags) && 2822 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2823 EXIT_RECOVERY(tp->t_flags); 2824 } 2825 tp->snd_una = th->th_ack; 2826 if (tp->t_flags & TF_SACK_PERMIT) { 2827 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2828 tp->snd_recover = tp->snd_una; 2829 } 2830 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2831 tp->snd_nxt = tp->snd_una; 2832 2833 switch (tp->t_state) { 2834 2835 /* 2836 * In FIN_WAIT_1 STATE in addition to the processing 2837 * for the ESTABLISHED state if our FIN is now acknowledged 2838 * then enter FIN_WAIT_2. 2839 */ 2840 case TCPS_FIN_WAIT_1: 2841 if (ourfinisacked) { 2842 /* 2843 * If we can't receive any more 2844 * data, then closing user can proceed. 2845 * Starting the timer is contrary to the 2846 * specification, but if we don't get a FIN 2847 * we'll hang forever. 2848 * 2849 * XXXjl: 2850 * we should release the tp also, and use a 2851 * compressed state. 2852 */ 2853 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2854 soisdisconnected(so); 2855 tcp_timer_activate(tp, TT_2MSL, 2856 (tcp_fast_finwait2_recycle ? 2857 tcp_finwait2_timeout : 2858 TP_MAXIDLE(tp))); 2859 } 2860 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2861 } 2862 break; 2863 2864 /* 2865 * In CLOSING STATE in addition to the processing for 2866 * the ESTABLISHED state if the ACK acknowledges our FIN 2867 * then enter the TIME-WAIT state, otherwise ignore 2868 * the segment. 2869 */ 2870 case TCPS_CLOSING: 2871 if (ourfinisacked) { 2872 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2873 tcp_twstart(tp); 2874 INP_INFO_RUNLOCK(&V_tcbinfo); 2875 m_freem(m); 2876 return; 2877 } 2878 break; 2879 2880 /* 2881 * In LAST_ACK, we may still be waiting for data to drain 2882 * and/or to be acked, as well as for the ack of our FIN. 2883 * If our FIN is now acknowledged, delete the TCB, 2884 * enter the closed state and return. 2885 */ 2886 case TCPS_LAST_ACK: 2887 if (ourfinisacked) { 2888 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2889 tp = tcp_close(tp); 2890 goto drop; 2891 } 2892 break; 2893 } 2894 } 2895 2896 step6: 2897 INP_WLOCK_ASSERT(tp->t_inpcb); 2898 2899 /* 2900 * Update window information. 2901 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2902 */ 2903 if ((thflags & TH_ACK) && 2904 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2905 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2906 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2907 /* keep track of pure window updates */ 2908 if (tlen == 0 && 2909 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2910 TCPSTAT_INC(tcps_rcvwinupd); 2911 tp->snd_wnd = tiwin; 2912 tp->snd_wl1 = th->th_seq; 2913 tp->snd_wl2 = th->th_ack; 2914 if (tp->snd_wnd > tp->max_sndwnd) 2915 tp->max_sndwnd = tp->snd_wnd; 2916 needoutput = 1; 2917 } 2918 2919 /* 2920 * Process segments with URG. 2921 */ 2922 if ((thflags & TH_URG) && th->th_urp && 2923 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2924 /* 2925 * This is a kludge, but if we receive and accept 2926 * random urgent pointers, we'll crash in 2927 * soreceive. It's hard to imagine someone 2928 * actually wanting to send this much urgent data. 2929 */ 2930 SOCKBUF_LOCK(&so->so_rcv); 2931 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 2932 th->th_urp = 0; /* XXX */ 2933 thflags &= ~TH_URG; /* XXX */ 2934 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2935 goto dodata; /* XXX */ 2936 } 2937 /* 2938 * If this segment advances the known urgent pointer, 2939 * then mark the data stream. This should not happen 2940 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2941 * a FIN has been received from the remote side. 2942 * In these states we ignore the URG. 2943 * 2944 * According to RFC961 (Assigned Protocols), 2945 * the urgent pointer points to the last octet 2946 * of urgent data. We continue, however, 2947 * to consider it to indicate the first octet 2948 * of data past the urgent section as the original 2949 * spec states (in one of two places). 2950 */ 2951 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2952 tp->rcv_up = th->th_seq + th->th_urp; 2953 so->so_oobmark = sbavail(&so->so_rcv) + 2954 (tp->rcv_up - tp->rcv_nxt) - 1; 2955 if (so->so_oobmark == 0) 2956 so->so_rcv.sb_state |= SBS_RCVATMARK; 2957 sohasoutofband(so); 2958 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2959 } 2960 SOCKBUF_UNLOCK(&so->so_rcv); 2961 /* 2962 * Remove out of band data so doesn't get presented to user. 2963 * This can happen independent of advancing the URG pointer, 2964 * but if two URG's are pending at once, some out-of-band 2965 * data may creep in... ick. 2966 */ 2967 if (th->th_urp <= (u_long)tlen && 2968 !(so->so_options & SO_OOBINLINE)) { 2969 /* hdr drop is delayed */ 2970 tcp_pulloutofband(so, th, m, drop_hdrlen); 2971 } 2972 } else { 2973 /* 2974 * If no out of band data is expected, 2975 * pull receive urgent pointer along 2976 * with the receive window. 2977 */ 2978 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2979 tp->rcv_up = tp->rcv_nxt; 2980 } 2981 dodata: /* XXX */ 2982 INP_WLOCK_ASSERT(tp->t_inpcb); 2983 2984 /* 2985 * Process the segment text, merging it into the TCP sequencing queue, 2986 * and arranging for acknowledgment of receipt if necessary. 2987 * This process logically involves adjusting tp->rcv_wnd as data 2988 * is presented to the user (this happens in tcp_usrreq.c, 2989 * case PRU_RCVD). If a FIN has already been received on this 2990 * connection then we just ignore the text. 2991 */ 2992 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 2993 (tp->t_flags & TF_FASTOPEN)); 2994 if ((tlen || (thflags & TH_FIN) || tfo_syn) && 2995 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2996 tcp_seq save_start = th->th_seq; 2997 m_adj(m, drop_hdrlen); /* delayed header drop */ 2998 /* 2999 * Insert segment which includes th into TCP reassembly queue 3000 * with control block tp. Set thflags to whether reassembly now 3001 * includes a segment with FIN. This handles the common case 3002 * inline (segment is the next to be received on an established 3003 * connection, and the queue is empty), avoiding linkage into 3004 * and removal from the queue and repetition of various 3005 * conversions. 3006 * Set DELACK for segments received in order, but ack 3007 * immediately when segments are out of order (so 3008 * fast retransmit can work). 3009 */ 3010 if (th->th_seq == tp->rcv_nxt && 3011 LIST_EMPTY(&tp->t_segq) && 3012 (TCPS_HAVEESTABLISHED(tp->t_state) || 3013 tfo_syn)) { 3014 if (DELAY_ACK(tp, tlen) || tfo_syn) 3015 tp->t_flags |= TF_DELACK; 3016 else 3017 tp->t_flags |= TF_ACKNOW; 3018 tp->rcv_nxt += tlen; 3019 thflags = th->th_flags & TH_FIN; 3020 TCPSTAT_INC(tcps_rcvpack); 3021 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3022 SOCKBUF_LOCK(&so->so_rcv); 3023 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3024 m_freem(m); 3025 else 3026 sbappendstream_locked(&so->so_rcv, m, 0); 3027 /* NB: sorwakeup_locked() does an implicit unlock. */ 3028 sorwakeup_locked(so); 3029 } else { 3030 /* 3031 * XXX: Due to the header drop above "th" is 3032 * theoretically invalid by now. Fortunately 3033 * m_adj() doesn't actually frees any mbufs 3034 * when trimming from the head. 3035 */ 3036 thflags = tcp_reass(tp, th, &tlen, m); 3037 tp->t_flags |= TF_ACKNOW; 3038 } 3039 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 3040 tcp_update_sack_list(tp, save_start, save_start + tlen); 3041 #if 0 3042 /* 3043 * Note the amount of data that peer has sent into 3044 * our window, in order to estimate the sender's 3045 * buffer size. 3046 * XXX: Unused. 3047 */ 3048 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3049 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3050 else 3051 len = so->so_rcv.sb_hiwat; 3052 #endif 3053 } else { 3054 m_freem(m); 3055 thflags &= ~TH_FIN; 3056 } 3057 3058 /* 3059 * If FIN is received ACK the FIN and let the user know 3060 * that the connection is closing. 3061 */ 3062 if (thflags & TH_FIN) { 3063 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3064 socantrcvmore(so); 3065 /* 3066 * If connection is half-synchronized 3067 * (ie NEEDSYN flag on) then delay ACK, 3068 * so it may be piggybacked when SYN is sent. 3069 * Otherwise, since we received a FIN then no 3070 * more input can be expected, send ACK now. 3071 */ 3072 if (tp->t_flags & TF_NEEDSYN) 3073 tp->t_flags |= TF_DELACK; 3074 else 3075 tp->t_flags |= TF_ACKNOW; 3076 tp->rcv_nxt++; 3077 } 3078 switch (tp->t_state) { 3079 3080 /* 3081 * In SYN_RECEIVED and ESTABLISHED STATES 3082 * enter the CLOSE_WAIT state. 3083 */ 3084 case TCPS_SYN_RECEIVED: 3085 tp->t_starttime = ticks; 3086 /* FALLTHROUGH */ 3087 case TCPS_ESTABLISHED: 3088 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3089 break; 3090 3091 /* 3092 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3093 * enter the CLOSING state. 3094 */ 3095 case TCPS_FIN_WAIT_1: 3096 tcp_state_change(tp, TCPS_CLOSING); 3097 break; 3098 3099 /* 3100 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3101 * starting the time-wait timer, turning off the other 3102 * standard timers. 3103 */ 3104 case TCPS_FIN_WAIT_2: 3105 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 3106 KASSERT(ti_locked == TI_RLOCKED, ("%s: dodata " 3107 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 3108 ti_locked)); 3109 3110 tcp_twstart(tp); 3111 INP_INFO_RUNLOCK(&V_tcbinfo); 3112 return; 3113 } 3114 } 3115 if (ti_locked == TI_RLOCKED) 3116 INP_INFO_RUNLOCK(&V_tcbinfo); 3117 ti_locked = TI_UNLOCKED; 3118 3119 #ifdef TCPDEBUG 3120 if (so->so_options & SO_DEBUG) 3121 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3122 &tcp_savetcp, 0); 3123 #endif 3124 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3125 3126 /* 3127 * Return any desired output. 3128 */ 3129 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3130 (void) tp->t_fb->tfb_tcp_output(tp); 3131 3132 check_delack: 3133 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 3134 __func__, ti_locked)); 3135 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3136 INP_WLOCK_ASSERT(tp->t_inpcb); 3137 3138 if (tp->t_flags & TF_DELACK) { 3139 tp->t_flags &= ~TF_DELACK; 3140 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3141 } 3142 INP_WUNLOCK(tp->t_inpcb); 3143 return; 3144 3145 dropafterack: 3146 /* 3147 * Generate an ACK dropping incoming segment if it occupies 3148 * sequence space, where the ACK reflects our state. 3149 * 3150 * We can now skip the test for the RST flag since all 3151 * paths to this code happen after packets containing 3152 * RST have been dropped. 3153 * 3154 * In the SYN-RECEIVED state, don't send an ACK unless the 3155 * segment we received passes the SYN-RECEIVED ACK test. 3156 * If it fails send a RST. This breaks the loop in the 3157 * "LAND" DoS attack, and also prevents an ACK storm 3158 * between two listening ports that have been sent forged 3159 * SYN segments, each with the source address of the other. 3160 */ 3161 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3162 (SEQ_GT(tp->snd_una, th->th_ack) || 3163 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3164 rstreason = BANDLIM_RST_OPENPORT; 3165 goto dropwithreset; 3166 } 3167 #ifdef TCPDEBUG 3168 if (so->so_options & SO_DEBUG) 3169 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3170 &tcp_savetcp, 0); 3171 #endif 3172 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3173 if (ti_locked == TI_RLOCKED) 3174 INP_INFO_RUNLOCK(&V_tcbinfo); 3175 ti_locked = TI_UNLOCKED; 3176 3177 tp->t_flags |= TF_ACKNOW; 3178 (void) tp->t_fb->tfb_tcp_output(tp); 3179 INP_WUNLOCK(tp->t_inpcb); 3180 m_freem(m); 3181 return; 3182 3183 dropwithreset: 3184 if (ti_locked == TI_RLOCKED) 3185 INP_INFO_RUNLOCK(&V_tcbinfo); 3186 ti_locked = TI_UNLOCKED; 3187 3188 if (tp != NULL) { 3189 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3190 INP_WUNLOCK(tp->t_inpcb); 3191 } else 3192 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3193 return; 3194 3195 drop: 3196 if (ti_locked == TI_RLOCKED) { 3197 INP_INFO_RUNLOCK(&V_tcbinfo); 3198 ti_locked = TI_UNLOCKED; 3199 } 3200 #ifdef INVARIANTS 3201 else 3202 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3203 #endif 3204 3205 /* 3206 * Drop space held by incoming segment and return. 3207 */ 3208 #ifdef TCPDEBUG 3209 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3210 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3211 &tcp_savetcp, 0); 3212 #endif 3213 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3214 if (tp != NULL) 3215 INP_WUNLOCK(tp->t_inpcb); 3216 m_freem(m); 3217 } 3218 3219 /* 3220 * Issue RST and make ACK acceptable to originator of segment. 3221 * The mbuf must still include the original packet header. 3222 * tp may be NULL. 3223 */ 3224 void 3225 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3226 int tlen, int rstreason) 3227 { 3228 #ifdef INET 3229 struct ip *ip; 3230 #endif 3231 #ifdef INET6 3232 struct ip6_hdr *ip6; 3233 #endif 3234 3235 if (tp != NULL) { 3236 INP_WLOCK_ASSERT(tp->t_inpcb); 3237 } 3238 3239 /* Don't bother if destination was broadcast/multicast. */ 3240 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3241 goto drop; 3242 #ifdef INET6 3243 if (mtod(m, struct ip *)->ip_v == 6) { 3244 ip6 = mtod(m, struct ip6_hdr *); 3245 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3246 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3247 goto drop; 3248 /* IPv6 anycast check is done at tcp6_input() */ 3249 } 3250 #endif 3251 #if defined(INET) && defined(INET6) 3252 else 3253 #endif 3254 #ifdef INET 3255 { 3256 ip = mtod(m, struct ip *); 3257 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3258 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3259 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3260 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3261 goto drop; 3262 } 3263 #endif 3264 3265 /* Perform bandwidth limiting. */ 3266 if (badport_bandlim(rstreason) < 0) 3267 goto drop; 3268 3269 /* tcp_respond consumes the mbuf chain. */ 3270 if (th->th_flags & TH_ACK) { 3271 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3272 th->th_ack, TH_RST); 3273 } else { 3274 if (th->th_flags & TH_SYN) 3275 tlen++; 3276 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3277 (tcp_seq)0, TH_RST|TH_ACK); 3278 } 3279 return; 3280 drop: 3281 m_freem(m); 3282 } 3283 3284 /* 3285 * Parse TCP options and place in tcpopt. 3286 */ 3287 void 3288 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3289 { 3290 int opt, optlen; 3291 3292 to->to_flags = 0; 3293 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3294 opt = cp[0]; 3295 if (opt == TCPOPT_EOL) 3296 break; 3297 if (opt == TCPOPT_NOP) 3298 optlen = 1; 3299 else { 3300 if (cnt < 2) 3301 break; 3302 optlen = cp[1]; 3303 if (optlen < 2 || optlen > cnt) 3304 break; 3305 } 3306 switch (opt) { 3307 case TCPOPT_MAXSEG: 3308 if (optlen != TCPOLEN_MAXSEG) 3309 continue; 3310 if (!(flags & TO_SYN)) 3311 continue; 3312 to->to_flags |= TOF_MSS; 3313 bcopy((char *)cp + 2, 3314 (char *)&to->to_mss, sizeof(to->to_mss)); 3315 to->to_mss = ntohs(to->to_mss); 3316 break; 3317 case TCPOPT_WINDOW: 3318 if (optlen != TCPOLEN_WINDOW) 3319 continue; 3320 if (!(flags & TO_SYN)) 3321 continue; 3322 to->to_flags |= TOF_SCALE; 3323 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3324 break; 3325 case TCPOPT_TIMESTAMP: 3326 if (optlen != TCPOLEN_TIMESTAMP) 3327 continue; 3328 to->to_flags |= TOF_TS; 3329 bcopy((char *)cp + 2, 3330 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3331 to->to_tsval = ntohl(to->to_tsval); 3332 bcopy((char *)cp + 6, 3333 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3334 to->to_tsecr = ntohl(to->to_tsecr); 3335 break; 3336 #ifdef TCP_SIGNATURE 3337 /* 3338 * XXX In order to reply to a host which has set the 3339 * TCP_SIGNATURE option in its initial SYN, we have to 3340 * record the fact that the option was observed here 3341 * for the syncache code to perform the correct response. 3342 */ 3343 case TCPOPT_SIGNATURE: 3344 if (optlen != TCPOLEN_SIGNATURE) 3345 continue; 3346 to->to_flags |= TOF_SIGNATURE; 3347 to->to_signature = cp + 2; 3348 break; 3349 #endif 3350 case TCPOPT_SACK_PERMITTED: 3351 if (optlen != TCPOLEN_SACK_PERMITTED) 3352 continue; 3353 if (!(flags & TO_SYN)) 3354 continue; 3355 if (!V_tcp_do_sack) 3356 continue; 3357 to->to_flags |= TOF_SACKPERM; 3358 break; 3359 case TCPOPT_SACK: 3360 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3361 continue; 3362 if (flags & TO_SYN) 3363 continue; 3364 to->to_flags |= TOF_SACK; 3365 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3366 to->to_sacks = cp + 2; 3367 TCPSTAT_INC(tcps_sack_rcv_blocks); 3368 break; 3369 #ifdef TCP_RFC7413 3370 case TCPOPT_FAST_OPEN: 3371 if ((optlen != TCPOLEN_FAST_OPEN_EMPTY) && 3372 (optlen < TCPOLEN_FAST_OPEN_MIN) && 3373 (optlen > TCPOLEN_FAST_OPEN_MAX)) 3374 continue; 3375 if (!(flags & TO_SYN)) 3376 continue; 3377 if (!V_tcp_fastopen_enabled) 3378 continue; 3379 to->to_flags |= TOF_FASTOPEN; 3380 to->to_tfo_len = optlen - 2; 3381 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3382 break; 3383 #endif 3384 default: 3385 continue; 3386 } 3387 } 3388 } 3389 3390 /* 3391 * Pull out of band byte out of a segment so 3392 * it doesn't appear in the user's data queue. 3393 * It is still reflected in the segment length for 3394 * sequencing purposes. 3395 */ 3396 void 3397 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3398 int off) 3399 { 3400 int cnt = off + th->th_urp - 1; 3401 3402 while (cnt >= 0) { 3403 if (m->m_len > cnt) { 3404 char *cp = mtod(m, caddr_t) + cnt; 3405 struct tcpcb *tp = sototcpcb(so); 3406 3407 INP_WLOCK_ASSERT(tp->t_inpcb); 3408 3409 tp->t_iobc = *cp; 3410 tp->t_oobflags |= TCPOOB_HAVEDATA; 3411 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3412 m->m_len--; 3413 if (m->m_flags & M_PKTHDR) 3414 m->m_pkthdr.len--; 3415 return; 3416 } 3417 cnt -= m->m_len; 3418 m = m->m_next; 3419 if (m == NULL) 3420 break; 3421 } 3422 panic("tcp_pulloutofband"); 3423 } 3424 3425 /* 3426 * Collect new round-trip time estimate 3427 * and update averages and current timeout. 3428 */ 3429 void 3430 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3431 { 3432 int delta; 3433 3434 INP_WLOCK_ASSERT(tp->t_inpcb); 3435 3436 TCPSTAT_INC(tcps_rttupdated); 3437 tp->t_rttupdated++; 3438 if (tp->t_srtt != 0) { 3439 /* 3440 * srtt is stored as fixed point with 5 bits after the 3441 * binary point (i.e., scaled by 8). The following magic 3442 * is equivalent to the smoothing algorithm in rfc793 with 3443 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3444 * point). Adjust rtt to origin 0. 3445 */ 3446 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3447 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3448 3449 if ((tp->t_srtt += delta) <= 0) 3450 tp->t_srtt = 1; 3451 3452 /* 3453 * We accumulate a smoothed rtt variance (actually, a 3454 * smoothed mean difference), then set the retransmit 3455 * timer to smoothed rtt + 4 times the smoothed variance. 3456 * rttvar is stored as fixed point with 4 bits after the 3457 * binary point (scaled by 16). The following is 3458 * equivalent to rfc793 smoothing with an alpha of .75 3459 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3460 * rfc793's wired-in beta. 3461 */ 3462 if (delta < 0) 3463 delta = -delta; 3464 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3465 if ((tp->t_rttvar += delta) <= 0) 3466 tp->t_rttvar = 1; 3467 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3468 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3469 } else { 3470 /* 3471 * No rtt measurement yet - use the unsmoothed rtt. 3472 * Set the variance to half the rtt (so our first 3473 * retransmit happens at 3*rtt). 3474 */ 3475 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3476 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3477 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3478 } 3479 tp->t_rtttime = 0; 3480 tp->t_rxtshift = 0; 3481 3482 /* 3483 * the retransmit should happen at rtt + 4 * rttvar. 3484 * Because of the way we do the smoothing, srtt and rttvar 3485 * will each average +1/2 tick of bias. When we compute 3486 * the retransmit timer, we want 1/2 tick of rounding and 3487 * 1 extra tick because of +-1/2 tick uncertainty in the 3488 * firing of the timer. The bias will give us exactly the 3489 * 1.5 tick we need. But, because the bias is 3490 * statistical, we have to test that we don't drop below 3491 * the minimum feasible timer (which is 2 ticks). 3492 */ 3493 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3494 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3495 3496 /* 3497 * We received an ack for a packet that wasn't retransmitted; 3498 * it is probably safe to discard any error indications we've 3499 * received recently. This isn't quite right, but close enough 3500 * for now (a route might have failed after we sent a segment, 3501 * and the return path might not be symmetrical). 3502 */ 3503 tp->t_softerror = 0; 3504 } 3505 3506 /* 3507 * Determine a reasonable value for maxseg size. 3508 * If the route is known, check route for mtu. 3509 * If none, use an mss that can be handled on the outgoing interface 3510 * without forcing IP to fragment. If no route is found, route has no mtu, 3511 * or the destination isn't local, use a default, hopefully conservative 3512 * size (usually 512 or the default IP max size, but no more than the mtu 3513 * of the interface), as we can't discover anything about intervening 3514 * gateways or networks. We also initialize the congestion/slow start 3515 * window to be a single segment if the destination isn't local. 3516 * While looking at the routing entry, we also initialize other path-dependent 3517 * parameters from pre-set or cached values in the routing entry. 3518 * 3519 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3520 * IP options, e.g. IPSEC data, since length of this data may vary, and 3521 * thus it is calculated for every segment separately in tcp_output(). 3522 * 3523 * NOTE that this routine is only called when we process an incoming 3524 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3525 * settings are handled in tcp_mssopt(). 3526 */ 3527 void 3528 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3529 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3530 { 3531 int mss = 0; 3532 u_long maxmtu = 0; 3533 struct inpcb *inp = tp->t_inpcb; 3534 struct hc_metrics_lite metrics; 3535 #ifdef INET6 3536 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3537 size_t min_protoh = isipv6 ? 3538 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3539 sizeof (struct tcpiphdr); 3540 #else 3541 const size_t min_protoh = sizeof(struct tcpiphdr); 3542 #endif 3543 3544 INP_WLOCK_ASSERT(tp->t_inpcb); 3545 3546 if (mtuoffer != -1) { 3547 KASSERT(offer == -1, ("%s: conflict", __func__)); 3548 offer = mtuoffer - min_protoh; 3549 } 3550 3551 /* Initialize. */ 3552 #ifdef INET6 3553 if (isipv6) { 3554 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3555 tp->t_maxseg = V_tcp_v6mssdflt; 3556 } 3557 #endif 3558 #if defined(INET) && defined(INET6) 3559 else 3560 #endif 3561 #ifdef INET 3562 { 3563 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3564 tp->t_maxseg = V_tcp_mssdflt; 3565 } 3566 #endif 3567 3568 /* 3569 * No route to sender, stay with default mss and return. 3570 */ 3571 if (maxmtu == 0) { 3572 /* 3573 * In case we return early we need to initialize metrics 3574 * to a defined state as tcp_hc_get() would do for us 3575 * if there was no cache hit. 3576 */ 3577 if (metricptr != NULL) 3578 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3579 return; 3580 } 3581 3582 /* What have we got? */ 3583 switch (offer) { 3584 case 0: 3585 /* 3586 * Offer == 0 means that there was no MSS on the SYN 3587 * segment, in this case we use tcp_mssdflt as 3588 * already assigned to t_maxseg above. 3589 */ 3590 offer = tp->t_maxseg; 3591 break; 3592 3593 case -1: 3594 /* 3595 * Offer == -1 means that we didn't receive SYN yet. 3596 */ 3597 /* FALLTHROUGH */ 3598 3599 default: 3600 /* 3601 * Prevent DoS attack with too small MSS. Round up 3602 * to at least minmss. 3603 */ 3604 offer = max(offer, V_tcp_minmss); 3605 } 3606 3607 /* 3608 * rmx information is now retrieved from tcp_hostcache. 3609 */ 3610 tcp_hc_get(&inp->inp_inc, &metrics); 3611 if (metricptr != NULL) 3612 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3613 3614 /* 3615 * If there's a discovered mtu in tcp hostcache, use it. 3616 * Else, use the link mtu. 3617 */ 3618 if (metrics.rmx_mtu) 3619 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3620 else { 3621 #ifdef INET6 3622 if (isipv6) { 3623 mss = maxmtu - min_protoh; 3624 if (!V_path_mtu_discovery && 3625 !in6_localaddr(&inp->in6p_faddr)) 3626 mss = min(mss, V_tcp_v6mssdflt); 3627 } 3628 #endif 3629 #if defined(INET) && defined(INET6) 3630 else 3631 #endif 3632 #ifdef INET 3633 { 3634 mss = maxmtu - min_protoh; 3635 if (!V_path_mtu_discovery && 3636 !in_localaddr(inp->inp_faddr)) 3637 mss = min(mss, V_tcp_mssdflt); 3638 } 3639 #endif 3640 /* 3641 * XXX - The above conditional (mss = maxmtu - min_protoh) 3642 * probably violates the TCP spec. 3643 * The problem is that, since we don't know the 3644 * other end's MSS, we are supposed to use a conservative 3645 * default. But, if we do that, then MTU discovery will 3646 * never actually take place, because the conservative 3647 * default is much less than the MTUs typically seen 3648 * on the Internet today. For the moment, we'll sweep 3649 * this under the carpet. 3650 * 3651 * The conservative default might not actually be a problem 3652 * if the only case this occurs is when sending an initial 3653 * SYN with options and data to a host we've never talked 3654 * to before. Then, they will reply with an MSS value which 3655 * will get recorded and the new parameters should get 3656 * recomputed. For Further Study. 3657 */ 3658 } 3659 mss = min(mss, offer); 3660 3661 /* 3662 * Sanity check: make sure that maxseg will be large 3663 * enough to allow some data on segments even if the 3664 * all the option space is used (40bytes). Otherwise 3665 * funny things may happen in tcp_output. 3666 * 3667 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3668 */ 3669 mss = max(mss, 64); 3670 3671 tp->t_maxseg = mss; 3672 } 3673 3674 void 3675 tcp_mss(struct tcpcb *tp, int offer) 3676 { 3677 int mss; 3678 u_long bufsize; 3679 struct inpcb *inp; 3680 struct socket *so; 3681 struct hc_metrics_lite metrics; 3682 struct tcp_ifcap cap; 3683 3684 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3685 3686 bzero(&cap, sizeof(cap)); 3687 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3688 3689 mss = tp->t_maxseg; 3690 inp = tp->t_inpcb; 3691 3692 /* 3693 * If there's a pipesize, change the socket buffer to that size, 3694 * don't change if sb_hiwat is different than default (then it 3695 * has been changed on purpose with setsockopt). 3696 * Make the socket buffers an integral number of mss units; 3697 * if the mss is larger than the socket buffer, decrease the mss. 3698 */ 3699 so = inp->inp_socket; 3700 SOCKBUF_LOCK(&so->so_snd); 3701 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3702 bufsize = metrics.rmx_sendpipe; 3703 else 3704 bufsize = so->so_snd.sb_hiwat; 3705 if (bufsize < mss) 3706 mss = bufsize; 3707 else { 3708 bufsize = roundup(bufsize, mss); 3709 if (bufsize > sb_max) 3710 bufsize = sb_max; 3711 if (bufsize > so->so_snd.sb_hiwat) 3712 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3713 } 3714 SOCKBUF_UNLOCK(&so->so_snd); 3715 tp->t_maxseg = mss; 3716 3717 SOCKBUF_LOCK(&so->so_rcv); 3718 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3719 bufsize = metrics.rmx_recvpipe; 3720 else 3721 bufsize = so->so_rcv.sb_hiwat; 3722 if (bufsize > mss) { 3723 bufsize = roundup(bufsize, mss); 3724 if (bufsize > sb_max) 3725 bufsize = sb_max; 3726 if (bufsize > so->so_rcv.sb_hiwat) 3727 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3728 } 3729 SOCKBUF_UNLOCK(&so->so_rcv); 3730 3731 /* Check the interface for TSO capabilities. */ 3732 if (cap.ifcap & CSUM_TSO) { 3733 tp->t_flags |= TF_TSO; 3734 tp->t_tsomax = cap.tsomax; 3735 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3736 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3737 } 3738 } 3739 3740 /* 3741 * Determine the MSS option to send on an outgoing SYN. 3742 */ 3743 int 3744 tcp_mssopt(struct in_conninfo *inc) 3745 { 3746 int mss = 0; 3747 u_long maxmtu = 0; 3748 u_long thcmtu = 0; 3749 size_t min_protoh; 3750 3751 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3752 3753 #ifdef INET6 3754 if (inc->inc_flags & INC_ISIPV6) { 3755 mss = V_tcp_v6mssdflt; 3756 maxmtu = tcp_maxmtu6(inc, NULL); 3757 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3758 } 3759 #endif 3760 #if defined(INET) && defined(INET6) 3761 else 3762 #endif 3763 #ifdef INET 3764 { 3765 mss = V_tcp_mssdflt; 3766 maxmtu = tcp_maxmtu(inc, NULL); 3767 min_protoh = sizeof(struct tcpiphdr); 3768 } 3769 #endif 3770 #if defined(INET6) || defined(INET) 3771 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3772 #endif 3773 3774 if (maxmtu && thcmtu) 3775 mss = min(maxmtu, thcmtu) - min_protoh; 3776 else if (maxmtu || thcmtu) 3777 mss = max(maxmtu, thcmtu) - min_protoh; 3778 3779 return (mss); 3780 } 3781 3782 3783 /* 3784 * On a partial ack arrives, force the retransmission of the 3785 * next unacknowledged segment. Do not clear tp->t_dupacks. 3786 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3787 * be started again. 3788 */ 3789 void 3790 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3791 { 3792 tcp_seq onxt = tp->snd_nxt; 3793 u_long ocwnd = tp->snd_cwnd; 3794 u_int maxseg = tcp_maxseg(tp); 3795 3796 INP_WLOCK_ASSERT(tp->t_inpcb); 3797 3798 tcp_timer_activate(tp, TT_REXMT, 0); 3799 tp->t_rtttime = 0; 3800 tp->snd_nxt = th->th_ack; 3801 /* 3802 * Set snd_cwnd to one segment beyond acknowledged offset. 3803 * (tp->snd_una has not yet been updated when this function is called.) 3804 */ 3805 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3806 tp->t_flags |= TF_ACKNOW; 3807 (void) tp->t_fb->tfb_tcp_output(tp); 3808 tp->snd_cwnd = ocwnd; 3809 if (SEQ_GT(onxt, tp->snd_nxt)) 3810 tp->snd_nxt = onxt; 3811 /* 3812 * Partial window deflation. Relies on fact that tp->snd_una 3813 * not updated yet. 3814 */ 3815 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3816 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3817 else 3818 tp->snd_cwnd = 0; 3819 tp->snd_cwnd += maxseg; 3820 } 3821 3822 int 3823 tcp_compute_pipe(struct tcpcb *tp) 3824 { 3825 return (tp->snd_max - tp->snd_una + 3826 tp->sackhint.sack_bytes_rexmit - 3827 tp->sackhint.sacked_bytes); 3828 } 3829