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_inet.h" 54 #include "opt_inet6.h" 55 #include "opt_ipsec.h" 56 #include "opt_tcpdebug.h" 57 58 #include <sys/param.h> 59 #include <sys/kernel.h> 60 #ifdef TCP_HHOOK 61 #include <sys/hhook.h> 62 #endif 63 #include <sys/malloc.h> 64 #include <sys/mbuf.h> 65 #include <sys/proc.h> /* for proc0 declaration */ 66 #include <sys/protosw.h> 67 #include <sys/sdt.h> 68 #include <sys/signalvar.h> 69 #include <sys/socket.h> 70 #include <sys/socketvar.h> 71 #include <sys/sysctl.h> 72 #include <sys/syslog.h> 73 #include <sys/systm.h> 74 75 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 76 77 #include <vm/uma.h> 78 79 #include <net/if.h> 80 #include <net/if_var.h> 81 #include <net/route.h> 82 #include <net/vnet.h> 83 84 #define TCPSTATES /* for logging */ 85 86 #include <netinet/in.h> 87 #include <netinet/in_kdtrace.h> 88 #include <netinet/in_pcb.h> 89 #include <netinet/in_systm.h> 90 #include <netinet/ip.h> 91 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 92 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 93 #include <netinet/ip_var.h> 94 #include <netinet/ip_options.h> 95 #include <netinet/ip6.h> 96 #include <netinet/icmp6.h> 97 #include <netinet6/in6_pcb.h> 98 #include <netinet6/in6_var.h> 99 #include <netinet6/ip6_var.h> 100 #include <netinet6/nd6.h> 101 #ifdef TCP_RFC7413 102 #include <netinet/tcp_fastopen.h> 103 #endif 104 #include <netinet/tcp.h> 105 #include <netinet/tcp_fsm.h> 106 #include <netinet/tcp_seq.h> 107 #include <netinet/tcp_timer.h> 108 #include <netinet/tcp_var.h> 109 #include <netinet6/tcp6_var.h> 110 #include <netinet/tcpip.h> 111 #include <netinet/cc/cc.h> 112 #ifdef TCPPCAP 113 #include <netinet/tcp_pcap.h> 114 #endif 115 #include <netinet/tcp_syncache.h> 116 #ifdef TCPDEBUG 117 #include <netinet/tcp_debug.h> 118 #endif /* TCPDEBUG */ 119 #ifdef TCP_OFFLOAD 120 #include <netinet/tcp_offload.h> 121 #endif 122 123 #ifdef IPSEC 124 #include <netipsec/ipsec.h> 125 #include <netipsec/ipsec6.h> 126 #endif /*IPSEC*/ 127 128 #include <machine/in_cksum.h> 129 130 #include <security/mac/mac_framework.h> 131 132 const int tcprexmtthresh = 3; 133 134 int tcp_log_in_vain = 0; 135 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 136 &tcp_log_in_vain, 0, 137 "Log all incoming TCP segments to closed ports"); 138 139 VNET_DEFINE(int, blackhole) = 0; 140 #define V_blackhole VNET(blackhole) 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 142 &VNET_NAME(blackhole), 0, 143 "Do not send RST on segments to closed ports"); 144 145 VNET_DEFINE(int, tcp_delack_enabled) = 1; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 147 &VNET_NAME(tcp_delack_enabled), 0, 148 "Delay ACK to try and piggyback it onto a data packet"); 149 150 VNET_DEFINE(int, drop_synfin) = 0; 151 #define V_drop_synfin VNET(drop_synfin) 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 153 &VNET_NAME(drop_synfin), 0, 154 "Drop TCP packets with SYN+FIN set"); 155 156 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 158 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 159 "Use calculated pipe/in-flight bytes per RFC 6675"); 160 161 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 162 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 164 &VNET_NAME(tcp_do_rfc3042), 0, 165 "Enable RFC 3042 (Limited Transmit)"); 166 167 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 168 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 169 &VNET_NAME(tcp_do_rfc3390), 0, 170 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 171 172 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 174 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 175 "Slow-start flight size (initial congestion window) in number of segments"); 176 177 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 178 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 179 &VNET_NAME(tcp_do_rfc3465), 0, 180 "Enable RFC 3465 (Appropriate Byte Counting)"); 181 182 VNET_DEFINE(int, tcp_abc_l_var) = 2; 183 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 184 &VNET_NAME(tcp_abc_l_var), 2, 185 "Cap the max cwnd increment during slow-start to this number of segments"); 186 187 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 188 189 VNET_DEFINE(int, tcp_do_ecn) = 2; 190 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 191 &VNET_NAME(tcp_do_ecn), 0, 192 "TCP ECN support"); 193 194 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 195 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 196 &VNET_NAME(tcp_ecn_maxretries), 0, 197 "Max retries before giving up on ECN"); 198 199 VNET_DEFINE(int, tcp_insecure_syn) = 0; 200 #define V_tcp_insecure_syn VNET(tcp_insecure_syn) 201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 202 &VNET_NAME(tcp_insecure_syn), 0, 203 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 204 205 VNET_DEFINE(int, tcp_insecure_rst) = 0; 206 #define V_tcp_insecure_rst VNET(tcp_insecure_rst) 207 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 208 &VNET_NAME(tcp_insecure_rst), 0, 209 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 210 211 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 212 #define V_tcp_recvspace VNET(tcp_recvspace) 213 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 214 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 215 216 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 217 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) 218 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 219 &VNET_NAME(tcp_do_autorcvbuf), 0, 220 "Enable automatic receive buffer sizing"); 221 222 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 223 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) 224 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 225 &VNET_NAME(tcp_autorcvbuf_inc), 0, 226 "Incrementor step size of automatic receive buffer"); 227 228 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 229 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) 230 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 231 &VNET_NAME(tcp_autorcvbuf_max), 0, 232 "Max size of automatic receive buffer"); 233 234 VNET_DEFINE(struct inpcbhead, tcb); 235 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 236 VNET_DEFINE(struct inpcbinfo, tcbinfo); 237 238 /* 239 * TCP statistics are stored in an array of counter(9)s, which size matches 240 * size of struct tcpstat. TCP running connection count is a regular array. 241 */ 242 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 243 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 244 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 245 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 246 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 247 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 248 "TCP connection counts by TCP state"); 249 250 static void 251 tcp_vnet_init(const void *unused) 252 { 253 254 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK); 255 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK); 256 } 257 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 258 tcp_vnet_init, NULL); 259 260 #ifdef VIMAGE 261 static void 262 tcp_vnet_uninit(const void *unused) 263 { 264 265 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES); 266 VNET_PCPUSTAT_FREE(tcpstat); 267 } 268 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 269 tcp_vnet_uninit, NULL); 270 #endif /* VIMAGE */ 271 272 /* 273 * Kernel module interface for updating tcpstat. The argument is an index 274 * into tcpstat treated as an array. 275 */ 276 void 277 kmod_tcpstat_inc(int statnum) 278 { 279 280 counter_u64_add(VNET(tcpstat)[statnum], 1); 281 } 282 283 #ifdef TCP_HHOOK 284 /* 285 * Wrapper for the TCP established input helper hook. 286 */ 287 void 288 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 289 { 290 struct tcp_hhook_data hhook_data; 291 292 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 293 hhook_data.tp = tp; 294 hhook_data.th = th; 295 hhook_data.to = to; 296 297 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 298 tp->osd); 299 } 300 } 301 #endif 302 303 /* 304 * CC wrapper hook functions 305 */ 306 void 307 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 308 uint16_t type) 309 { 310 INP_WLOCK_ASSERT(tp->t_inpcb); 311 312 tp->ccv->nsegs = nsegs; 313 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 314 if (tp->snd_cwnd <= tp->snd_wnd) 315 tp->ccv->flags |= CCF_CWND_LIMITED; 316 else 317 tp->ccv->flags &= ~CCF_CWND_LIMITED; 318 319 if (type == CC_ACK) { 320 if (tp->snd_cwnd > tp->snd_ssthresh) { 321 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 322 nsegs * V_tcp_abc_l_var * tcp_maxseg(tp)); 323 if (tp->t_bytes_acked >= tp->snd_cwnd) { 324 tp->t_bytes_acked -= tp->snd_cwnd; 325 tp->ccv->flags |= CCF_ABC_SENTAWND; 326 } 327 } else { 328 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 329 tp->t_bytes_acked = 0; 330 } 331 } 332 333 if (CC_ALGO(tp)->ack_received != NULL) { 334 /* XXXLAS: Find a way to live without this */ 335 tp->ccv->curack = th->th_ack; 336 CC_ALGO(tp)->ack_received(tp->ccv, type); 337 } 338 } 339 340 void 341 cc_conn_init(struct tcpcb *tp) 342 { 343 struct hc_metrics_lite metrics; 344 struct inpcb *inp = tp->t_inpcb; 345 u_int maxseg; 346 int rtt; 347 348 INP_WLOCK_ASSERT(tp->t_inpcb); 349 350 tcp_hc_get(&inp->inp_inc, &metrics); 351 maxseg = tcp_maxseg(tp); 352 353 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 354 tp->t_srtt = rtt; 355 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 356 TCPSTAT_INC(tcps_usedrtt); 357 if (metrics.rmx_rttvar) { 358 tp->t_rttvar = metrics.rmx_rttvar; 359 TCPSTAT_INC(tcps_usedrttvar); 360 } else { 361 /* default variation is +- 1 rtt */ 362 tp->t_rttvar = 363 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 364 } 365 TCPT_RANGESET(tp->t_rxtcur, 366 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 367 tp->t_rttmin, TCPTV_REXMTMAX); 368 } 369 if (metrics.rmx_ssthresh) { 370 /* 371 * There's some sort of gateway or interface 372 * buffer limit on the path. Use this to set 373 * the slow start threshold, but set the 374 * threshold to no less than 2*mss. 375 */ 376 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 377 TCPSTAT_INC(tcps_usedssthresh); 378 } 379 380 /* 381 * Set the initial slow-start flight size. 382 * 383 * RFC5681 Section 3.1 specifies the default conservative values. 384 * RFC3390 specifies slightly more aggressive values. 385 * RFC6928 increases it to ten segments. 386 * Support for user specified value for initial flight size. 387 * 388 * If a SYN or SYN/ACK was lost and retransmitted, we have to 389 * reduce the initial CWND to one segment as congestion is likely 390 * requiring us to be cautious. 391 */ 392 if (tp->snd_cwnd == 1) 393 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 394 else if (V_tcp_initcwnd_segments) 395 tp->snd_cwnd = min(V_tcp_initcwnd_segments * maxseg, 396 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 397 else if (V_tcp_do_rfc3390) 398 tp->snd_cwnd = min(4 * maxseg, max(2 * maxseg, 4380)); 399 else { 400 /* Per RFC5681 Section 3.1 */ 401 if (maxseg > 2190) 402 tp->snd_cwnd = 2 * maxseg; 403 else if (maxseg > 1095) 404 tp->snd_cwnd = 3 * maxseg; 405 else 406 tp->snd_cwnd = 4 * maxseg; 407 } 408 409 if (CC_ALGO(tp)->conn_init != NULL) 410 CC_ALGO(tp)->conn_init(tp->ccv); 411 } 412 413 void inline 414 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 415 { 416 u_int maxseg; 417 418 INP_WLOCK_ASSERT(tp->t_inpcb); 419 420 switch(type) { 421 case CC_NDUPACK: 422 if (!IN_FASTRECOVERY(tp->t_flags)) { 423 tp->snd_recover = tp->snd_max; 424 if (tp->t_flags & TF_ECN_PERMIT) 425 tp->t_flags |= TF_ECN_SND_CWR; 426 } 427 break; 428 case CC_ECN: 429 if (!IN_CONGRECOVERY(tp->t_flags)) { 430 TCPSTAT_INC(tcps_ecn_rcwnd); 431 tp->snd_recover = tp->snd_max; 432 if (tp->t_flags & TF_ECN_PERMIT) 433 tp->t_flags |= TF_ECN_SND_CWR; 434 } 435 break; 436 case CC_RTO: 437 maxseg = tcp_maxseg(tp); 438 tp->t_dupacks = 0; 439 tp->t_bytes_acked = 0; 440 EXIT_RECOVERY(tp->t_flags); 441 if (CC_ALGO(tp)->cong_signal == NULL) { 442 /* 443 * RFC5681 Section 3.1 444 * ssthresh = max (FlightSize / 2, 2*SMSS) eq (4) 445 */ 446 tp->snd_ssthresh = 447 max((tp->snd_max - tp->snd_una) / 2 / maxseg, 2) 448 * maxseg; 449 tp->snd_cwnd = maxseg; 450 } 451 break; 452 case CC_RTO_ERR: 453 TCPSTAT_INC(tcps_sndrexmitbad); 454 /* RTO was unnecessary, so reset everything. */ 455 tp->snd_cwnd = tp->snd_cwnd_prev; 456 tp->snd_ssthresh = tp->snd_ssthresh_prev; 457 tp->snd_recover = tp->snd_recover_prev; 458 if (tp->t_flags & TF_WASFRECOVERY) 459 ENTER_FASTRECOVERY(tp->t_flags); 460 if (tp->t_flags & TF_WASCRECOVERY) 461 ENTER_CONGRECOVERY(tp->t_flags); 462 tp->snd_nxt = tp->snd_max; 463 tp->t_flags &= ~TF_PREVVALID; 464 tp->t_badrxtwin = 0; 465 break; 466 } 467 468 if (CC_ALGO(tp)->cong_signal != NULL) { 469 if (th != NULL) 470 tp->ccv->curack = th->th_ack; 471 CC_ALGO(tp)->cong_signal(tp->ccv, type); 472 } 473 } 474 475 void inline 476 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 477 { 478 INP_WLOCK_ASSERT(tp->t_inpcb); 479 480 /* XXXLAS: KASSERT that we're in recovery? */ 481 482 if (CC_ALGO(tp)->post_recovery != NULL) { 483 tp->ccv->curack = th->th_ack; 484 CC_ALGO(tp)->post_recovery(tp->ccv); 485 } 486 /* XXXLAS: EXIT_RECOVERY ? */ 487 tp->t_bytes_acked = 0; 488 } 489 490 #ifdef TCP_SIGNATURE 491 static inline int 492 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, 493 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) 494 { 495 int ret; 496 497 tcp_fields_to_net(th); 498 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); 499 tcp_fields_to_host(th); 500 return (ret); 501 } 502 #endif 503 504 /* 505 * Indicate whether this ack should be delayed. We can delay the ack if 506 * following conditions are met: 507 * - There is no delayed ack timer in progress. 508 * - Our last ack wasn't a 0-sized window. We never want to delay 509 * the ack that opens up a 0-sized window. 510 * - LRO wasn't used for this segment. We make sure by checking that the 511 * segment size is not larger than the MSS. 512 */ 513 #define DELAY_ACK(tp, tlen) \ 514 ((!tcp_timer_active(tp, TT_DELACK) && \ 515 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 516 (tlen <= tp->t_maxseg) && \ 517 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 518 519 static void inline 520 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 521 { 522 INP_WLOCK_ASSERT(tp->t_inpcb); 523 524 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 525 switch (iptos & IPTOS_ECN_MASK) { 526 case IPTOS_ECN_CE: 527 tp->ccv->flags |= CCF_IPHDR_CE; 528 break; 529 case IPTOS_ECN_ECT0: 530 tp->ccv->flags &= ~CCF_IPHDR_CE; 531 break; 532 case IPTOS_ECN_ECT1: 533 tp->ccv->flags &= ~CCF_IPHDR_CE; 534 break; 535 } 536 537 if (th->th_flags & TH_CWR) 538 tp->ccv->flags |= CCF_TCPHDR_CWR; 539 else 540 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 541 542 if (tp->t_flags & TF_DELACK) 543 tp->ccv->flags |= CCF_DELACK; 544 else 545 tp->ccv->flags &= ~CCF_DELACK; 546 547 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 548 549 if (tp->ccv->flags & CCF_ACKNOW) 550 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 551 } 552 } 553 554 /* 555 * TCP input handling is split into multiple parts: 556 * tcp6_input is a thin wrapper around tcp_input for the extended 557 * ip6_protox[] call format in ip6_input 558 * tcp_input handles primary segment validation, inpcb lookup and 559 * SYN processing on listen sockets 560 * tcp_do_segment processes the ACK and text of the segment for 561 * establishing, established and closing connections 562 */ 563 #ifdef INET6 564 int 565 tcp6_input(struct mbuf **mp, int *offp, int proto) 566 { 567 struct mbuf *m = *mp; 568 struct in6_ifaddr *ia6; 569 struct ip6_hdr *ip6; 570 571 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 572 573 /* 574 * draft-itojun-ipv6-tcp-to-anycast 575 * better place to put this in? 576 */ 577 ip6 = mtod(m, struct ip6_hdr *); 578 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 579 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 580 struct ip6_hdr *ip6; 581 582 ifa_free(&ia6->ia_ifa); 583 ip6 = mtod(m, struct ip6_hdr *); 584 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 585 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 586 return (IPPROTO_DONE); 587 } 588 if (ia6) 589 ifa_free(&ia6->ia_ifa); 590 591 return (tcp_input(mp, offp, proto)); 592 } 593 #endif /* INET6 */ 594 595 int 596 tcp_input(struct mbuf **mp, int *offp, int proto) 597 { 598 struct mbuf *m = *mp; 599 struct tcphdr *th = NULL; 600 struct ip *ip = NULL; 601 struct inpcb *inp = NULL; 602 struct tcpcb *tp = NULL; 603 struct socket *so = NULL; 604 u_char *optp = NULL; 605 int off0; 606 int optlen = 0; 607 #ifdef INET 608 int len; 609 #endif 610 int tlen = 0, off; 611 int drop_hdrlen; 612 int thflags; 613 int rstreason = 0; /* For badport_bandlim accounting purposes */ 614 #ifdef TCP_SIGNATURE 615 uint8_t sig_checked = 0; 616 #endif 617 uint8_t iptos; 618 struct m_tag *fwd_tag = NULL; 619 #ifdef INET6 620 struct ip6_hdr *ip6 = NULL; 621 int isipv6; 622 #else 623 const void *ip6 = NULL; 624 #endif /* INET6 */ 625 struct tcpopt to; /* options in this segment */ 626 char *s = NULL; /* address and port logging */ 627 int ti_locked; 628 #ifdef TCPDEBUG 629 /* 630 * The size of tcp_saveipgen must be the size of the max ip header, 631 * now IPv6. 632 */ 633 u_char tcp_saveipgen[IP6_HDR_LEN]; 634 struct tcphdr tcp_savetcp; 635 short ostate = 0; 636 #endif 637 638 #ifdef INET6 639 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 640 #endif 641 642 off0 = *offp; 643 m = *mp; 644 *mp = NULL; 645 to.to_flags = 0; 646 TCPSTAT_INC(tcps_rcvtotal); 647 648 #ifdef INET6 649 if (isipv6) { 650 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 651 652 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 653 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 654 if (m == NULL) { 655 TCPSTAT_INC(tcps_rcvshort); 656 return (IPPROTO_DONE); 657 } 658 } 659 660 ip6 = mtod(m, struct ip6_hdr *); 661 th = (struct tcphdr *)((caddr_t)ip6 + off0); 662 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 663 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 664 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 665 th->th_sum = m->m_pkthdr.csum_data; 666 else 667 th->th_sum = in6_cksum_pseudo(ip6, tlen, 668 IPPROTO_TCP, m->m_pkthdr.csum_data); 669 th->th_sum ^= 0xffff; 670 } else 671 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 672 if (th->th_sum) { 673 TCPSTAT_INC(tcps_rcvbadsum); 674 goto drop; 675 } 676 677 /* 678 * Be proactive about unspecified IPv6 address in source. 679 * As we use all-zero to indicate unbounded/unconnected pcb, 680 * unspecified IPv6 address can be used to confuse us. 681 * 682 * Note that packets with unspecified IPv6 destination is 683 * already dropped in ip6_input. 684 */ 685 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 686 /* XXX stat */ 687 goto drop; 688 } 689 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 690 } 691 #endif 692 #if defined(INET) && defined(INET6) 693 else 694 #endif 695 #ifdef INET 696 { 697 /* 698 * Get IP and TCP header together in first mbuf. 699 * Note: IP leaves IP header in first mbuf. 700 */ 701 if (off0 > sizeof (struct ip)) { 702 ip_stripoptions(m); 703 off0 = sizeof(struct ip); 704 } 705 if (m->m_len < sizeof (struct tcpiphdr)) { 706 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 707 == NULL) { 708 TCPSTAT_INC(tcps_rcvshort); 709 return (IPPROTO_DONE); 710 } 711 } 712 ip = mtod(m, struct ip *); 713 th = (struct tcphdr *)((caddr_t)ip + off0); 714 tlen = ntohs(ip->ip_len) - off0; 715 716 iptos = ip->ip_tos; 717 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 718 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 719 th->th_sum = m->m_pkthdr.csum_data; 720 else 721 th->th_sum = in_pseudo(ip->ip_src.s_addr, 722 ip->ip_dst.s_addr, 723 htonl(m->m_pkthdr.csum_data + tlen + 724 IPPROTO_TCP)); 725 th->th_sum ^= 0xffff; 726 } else { 727 struct ipovly *ipov = (struct ipovly *)ip; 728 729 /* 730 * Checksum extended TCP header and data. 731 */ 732 len = off0 + tlen; 733 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 734 ipov->ih_len = htons(tlen); 735 th->th_sum = in_cksum(m, len); 736 /* Reset length for SDT probes. */ 737 ip->ip_len = htons(len); 738 /* Reset TOS bits */ 739 ip->ip_tos = iptos; 740 /* Re-initialization for later version check */ 741 ip->ip_v = IPVERSION; 742 } 743 744 if (th->th_sum) { 745 TCPSTAT_INC(tcps_rcvbadsum); 746 goto drop; 747 } 748 } 749 #endif /* INET */ 750 751 /* 752 * Check that TCP offset makes sense, 753 * pull out TCP options and adjust length. XXX 754 */ 755 off = th->th_off << 2; 756 if (off < sizeof (struct tcphdr) || off > tlen) { 757 TCPSTAT_INC(tcps_rcvbadoff); 758 goto drop; 759 } 760 tlen -= off; /* tlen is used instead of ti->ti_len */ 761 if (off > sizeof (struct tcphdr)) { 762 #ifdef INET6 763 if (isipv6) { 764 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 765 ip6 = mtod(m, struct ip6_hdr *); 766 th = (struct tcphdr *)((caddr_t)ip6 + off0); 767 } 768 #endif 769 #if defined(INET) && defined(INET6) 770 else 771 #endif 772 #ifdef INET 773 { 774 if (m->m_len < sizeof(struct ip) + off) { 775 if ((m = m_pullup(m, sizeof (struct ip) + off)) 776 == NULL) { 777 TCPSTAT_INC(tcps_rcvshort); 778 return (IPPROTO_DONE); 779 } 780 ip = mtod(m, struct ip *); 781 th = (struct tcphdr *)((caddr_t)ip + off0); 782 } 783 } 784 #endif 785 optlen = off - sizeof (struct tcphdr); 786 optp = (u_char *)(th + 1); 787 } 788 thflags = th->th_flags; 789 790 /* 791 * Convert TCP protocol specific fields to host format. 792 */ 793 tcp_fields_to_host(th); 794 795 /* 796 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 797 */ 798 drop_hdrlen = off0 + off; 799 800 /* 801 * Locate pcb for segment; if we're likely to add or remove a 802 * connection then first acquire pcbinfo lock. There are three cases 803 * where we might discover later we need a write lock despite the 804 * flags: ACKs moving a connection out of the syncache, ACKs for a 805 * connection in TIMEWAIT and SYNs not targeting a listening socket. 806 */ 807 if ((thflags & (TH_FIN | TH_RST)) != 0) { 808 INP_INFO_RLOCK(&V_tcbinfo); 809 ti_locked = TI_RLOCKED; 810 } else 811 ti_locked = TI_UNLOCKED; 812 813 /* 814 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 815 */ 816 if ( 817 #ifdef INET6 818 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 819 #ifdef INET 820 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 821 #endif 822 #endif 823 #if defined(INET) && !defined(INET6) 824 (m->m_flags & M_IP_NEXTHOP) 825 #endif 826 ) 827 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 828 829 findpcb: 830 #ifdef INVARIANTS 831 if (ti_locked == TI_RLOCKED) { 832 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 833 } else { 834 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 835 } 836 #endif 837 #ifdef INET6 838 if (isipv6 && fwd_tag != NULL) { 839 struct sockaddr_in6 *next_hop6; 840 841 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 842 /* 843 * Transparently forwarded. Pretend to be the destination. 844 * Already got one like this? 845 */ 846 inp = in6_pcblookup_mbuf(&V_tcbinfo, 847 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 848 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 849 if (!inp) { 850 /* 851 * It's new. Try to find the ambushing socket. 852 * Because we've rewritten the destination address, 853 * any hardware-generated hash is ignored. 854 */ 855 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 856 th->th_sport, &next_hop6->sin6_addr, 857 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 858 th->th_dport, INPLOOKUP_WILDCARD | 859 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 860 } 861 } else if (isipv6) { 862 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 863 th->th_sport, &ip6->ip6_dst, th->th_dport, 864 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 865 m->m_pkthdr.rcvif, m); 866 } 867 #endif /* INET6 */ 868 #if defined(INET6) && defined(INET) 869 else 870 #endif 871 #ifdef INET 872 if (fwd_tag != NULL) { 873 struct sockaddr_in *next_hop; 874 875 next_hop = (struct sockaddr_in *)(fwd_tag+1); 876 /* 877 * Transparently forwarded. Pretend to be the destination. 878 * already got one like this? 879 */ 880 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 881 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 882 m->m_pkthdr.rcvif, m); 883 if (!inp) { 884 /* 885 * It's new. Try to find the ambushing socket. 886 * Because we've rewritten the destination address, 887 * any hardware-generated hash is ignored. 888 */ 889 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 890 th->th_sport, next_hop->sin_addr, 891 next_hop->sin_port ? ntohs(next_hop->sin_port) : 892 th->th_dport, INPLOOKUP_WILDCARD | 893 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 894 } 895 } else 896 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 897 th->th_sport, ip->ip_dst, th->th_dport, 898 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 899 m->m_pkthdr.rcvif, m); 900 #endif /* INET */ 901 902 /* 903 * If the INPCB does not exist then all data in the incoming 904 * segment is discarded and an appropriate RST is sent back. 905 * XXX MRT Send RST using which routing table? 906 */ 907 if (inp == NULL) { 908 /* 909 * Log communication attempts to ports that are not 910 * in use. 911 */ 912 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 913 tcp_log_in_vain == 2) { 914 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 915 log(LOG_INFO, "%s; %s: Connection attempt " 916 "to closed port\n", s, __func__); 917 } 918 /* 919 * When blackholing do not respond with a RST but 920 * completely ignore the segment and drop it. 921 */ 922 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 923 V_blackhole == 2) 924 goto dropunlock; 925 926 rstreason = BANDLIM_RST_CLOSEDPORT; 927 goto dropwithreset; 928 } 929 INP_WLOCK_ASSERT(inp); 930 /* 931 * While waiting for inp lock during the lookup, another thread 932 * can have dropped the inpcb, in which case we need to loop back 933 * and try to find a new inpcb to deliver to. 934 */ 935 if (inp->inp_flags & INP_DROPPED) { 936 INP_WUNLOCK(inp); 937 inp = NULL; 938 goto findpcb; 939 } 940 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 941 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 942 ((inp->inp_socket == NULL) || 943 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 944 inp->inp_flowid = m->m_pkthdr.flowid; 945 inp->inp_flowtype = M_HASHTYPE_GET(m); 946 } 947 #ifdef IPSEC 948 #ifdef INET6 949 if (isipv6 && ipsec6_in_reject(m, inp)) { 950 goto dropunlock; 951 } else 952 #endif /* INET6 */ 953 if (ipsec4_in_reject(m, inp) != 0) { 954 goto dropunlock; 955 } 956 #endif /* IPSEC */ 957 958 /* 959 * Check the minimum TTL for socket. 960 */ 961 if (inp->inp_ip_minttl != 0) { 962 #ifdef INET6 963 if (isipv6) { 964 if (inp->inp_ip_minttl > ip6->ip6_hlim) 965 goto dropunlock; 966 } else 967 #endif 968 if (inp->inp_ip_minttl > ip->ip_ttl) 969 goto dropunlock; 970 } 971 972 /* 973 * A previous connection in TIMEWAIT state is supposed to catch stray 974 * or duplicate segments arriving late. If this segment was a 975 * legitimate new connection attempt, the old INPCB gets removed and 976 * we can try again to find a listening socket. 977 * 978 * At this point, due to earlier optimism, we may hold only an inpcb 979 * lock, and not the inpcbinfo write lock. If so, we need to try to 980 * acquire it, or if that fails, acquire a reference on the inpcb, 981 * drop all locks, acquire a global write lock, and then re-acquire 982 * the inpcb lock. We may at that point discover that another thread 983 * has tried to free the inpcb, in which case we need to loop back 984 * and try to find a new inpcb to deliver to. 985 * 986 * XXXRW: It may be time to rethink timewait locking. 987 */ 988 relocked: 989 if (inp->inp_flags & INP_TIMEWAIT) { 990 if (ti_locked == TI_UNLOCKED) { 991 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 992 in_pcbref(inp); 993 INP_WUNLOCK(inp); 994 INP_INFO_RLOCK(&V_tcbinfo); 995 ti_locked = TI_RLOCKED; 996 INP_WLOCK(inp); 997 if (in_pcbrele_wlocked(inp)) { 998 inp = NULL; 999 goto findpcb; 1000 } else if (inp->inp_flags & INP_DROPPED) { 1001 INP_WUNLOCK(inp); 1002 inp = NULL; 1003 goto findpcb; 1004 } 1005 } else 1006 ti_locked = TI_RLOCKED; 1007 } 1008 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1009 1010 if (thflags & TH_SYN) 1011 tcp_dooptions(&to, optp, optlen, TO_SYN); 1012 /* 1013 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 1014 */ 1015 if (tcp_twcheck(inp, &to, th, m, tlen)) 1016 goto findpcb; 1017 INP_INFO_RUNLOCK(&V_tcbinfo); 1018 return (IPPROTO_DONE); 1019 } 1020 /* 1021 * The TCPCB may no longer exist if the connection is winding 1022 * down or it is in the CLOSED state. Either way we drop the 1023 * segment and send an appropriate response. 1024 */ 1025 tp = intotcpcb(inp); 1026 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 1027 rstreason = BANDLIM_RST_CLOSEDPORT; 1028 goto dropwithreset; 1029 } 1030 1031 #ifdef TCP_OFFLOAD 1032 if (tp->t_flags & TF_TOE) { 1033 tcp_offload_input(tp, m); 1034 m = NULL; /* consumed by the TOE driver */ 1035 goto dropunlock; 1036 } 1037 #endif 1038 1039 /* 1040 * We've identified a valid inpcb, but it could be that we need an 1041 * inpcbinfo write lock but don't hold it. In this case, attempt to 1042 * acquire using the same strategy as the TIMEWAIT case above. If we 1043 * relock, we have to jump back to 'relocked' as the connection might 1044 * now be in TIMEWAIT. 1045 */ 1046 #ifdef INVARIANTS 1047 if ((thflags & (TH_FIN | TH_RST)) != 0) 1048 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1049 #endif 1050 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) || 1051 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN) && 1052 !IS_FASTOPEN(tp->t_flags)))) { 1053 if (ti_locked == TI_UNLOCKED) { 1054 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 1055 in_pcbref(inp); 1056 INP_WUNLOCK(inp); 1057 INP_INFO_RLOCK(&V_tcbinfo); 1058 ti_locked = TI_RLOCKED; 1059 INP_WLOCK(inp); 1060 if (in_pcbrele_wlocked(inp)) { 1061 inp = NULL; 1062 goto findpcb; 1063 } else if (inp->inp_flags & INP_DROPPED) { 1064 INP_WUNLOCK(inp); 1065 inp = NULL; 1066 goto findpcb; 1067 } 1068 goto relocked; 1069 } else 1070 ti_locked = TI_RLOCKED; 1071 } 1072 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1073 } 1074 1075 #ifdef MAC 1076 INP_WLOCK_ASSERT(inp); 1077 if (mac_inpcb_check_deliver(inp, m)) 1078 goto dropunlock; 1079 #endif 1080 so = inp->inp_socket; 1081 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1082 #ifdef TCPDEBUG 1083 if (so->so_options & SO_DEBUG) { 1084 ostate = tp->t_state; 1085 #ifdef INET6 1086 if (isipv6) { 1087 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1088 } else 1089 #endif 1090 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1091 tcp_savetcp = *th; 1092 } 1093 #endif /* TCPDEBUG */ 1094 /* 1095 * When the socket is accepting connections (the INPCB is in LISTEN 1096 * state) we look into the SYN cache if this is a new connection 1097 * attempt or the completion of a previous one. 1098 */ 1099 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN), 1100 ("%s: so accepting but tp %p not listening", __func__, tp)); 1101 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) { 1102 struct in_conninfo inc; 1103 1104 bzero(&inc, sizeof(inc)); 1105 #ifdef INET6 1106 if (isipv6) { 1107 inc.inc_flags |= INC_ISIPV6; 1108 inc.inc6_faddr = ip6->ip6_src; 1109 inc.inc6_laddr = ip6->ip6_dst; 1110 } else 1111 #endif 1112 { 1113 inc.inc_faddr = ip->ip_src; 1114 inc.inc_laddr = ip->ip_dst; 1115 } 1116 inc.inc_fport = th->th_sport; 1117 inc.inc_lport = th->th_dport; 1118 inc.inc_fibnum = so->so_fibnum; 1119 1120 /* 1121 * Check for an existing connection attempt in syncache if 1122 * the flag is only ACK. A successful lookup creates a new 1123 * socket appended to the listen queue in SYN_RECEIVED state. 1124 */ 1125 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1126 1127 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1128 /* 1129 * Parse the TCP options here because 1130 * syncookies need access to the reflected 1131 * timestamp. 1132 */ 1133 tcp_dooptions(&to, optp, optlen, 0); 1134 /* 1135 * NB: syncache_expand() doesn't unlock 1136 * inp and tcpinfo locks. 1137 */ 1138 if (!syncache_expand(&inc, &to, th, &so, m)) { 1139 /* 1140 * No syncache entry or ACK was not 1141 * for our SYN/ACK. Send a RST. 1142 * NB: syncache did its own logging 1143 * of the failure cause. 1144 */ 1145 rstreason = BANDLIM_RST_OPENPORT; 1146 goto dropwithreset; 1147 } 1148 #ifdef TCP_RFC7413 1149 tfo_socket_result: 1150 #endif 1151 if (so == NULL) { 1152 /* 1153 * We completed the 3-way handshake 1154 * but could not allocate a socket 1155 * either due to memory shortage, 1156 * listen queue length limits or 1157 * global socket limits. Send RST 1158 * or wait and have the remote end 1159 * retransmit the ACK for another 1160 * try. 1161 */ 1162 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1163 log(LOG_DEBUG, "%s; %s: Listen socket: " 1164 "Socket allocation failed due to " 1165 "limits or memory shortage, %s\n", 1166 s, __func__, 1167 V_tcp_sc_rst_sock_fail ? 1168 "sending RST" : "try again"); 1169 if (V_tcp_sc_rst_sock_fail) { 1170 rstreason = BANDLIM_UNLIMITED; 1171 goto dropwithreset; 1172 } else 1173 goto dropunlock; 1174 } 1175 /* 1176 * Socket is created in state SYN_RECEIVED. 1177 * Unlock the listen socket, lock the newly 1178 * created socket and update the tp variable. 1179 */ 1180 INP_WUNLOCK(inp); /* listen socket */ 1181 inp = sotoinpcb(so); 1182 /* 1183 * New connection inpcb is already locked by 1184 * syncache_expand(). 1185 */ 1186 INP_WLOCK_ASSERT(inp); 1187 tp = intotcpcb(inp); 1188 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1189 ("%s: ", __func__)); 1190 #ifdef TCP_SIGNATURE 1191 if (sig_checked == 0) { 1192 tcp_dooptions(&to, optp, optlen, 1193 (thflags & TH_SYN) ? TO_SYN : 0); 1194 if (!tcp_signature_verify_input(m, off0, tlen, 1195 optlen, &to, th, tp->t_flags)) { 1196 1197 /* 1198 * In SYN_SENT state if it receives an 1199 * RST, it is allowed for further 1200 * processing. 1201 */ 1202 if ((thflags & TH_RST) == 0 || 1203 (tp->t_state == TCPS_SYN_SENT) == 0) 1204 goto dropunlock; 1205 } 1206 sig_checked = 1; 1207 } 1208 #endif 1209 1210 /* 1211 * Process the segment and the data it 1212 * contains. tcp_do_segment() consumes 1213 * the mbuf chain and unlocks the inpcb. 1214 */ 1215 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1216 iptos, ti_locked); 1217 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1218 return (IPPROTO_DONE); 1219 } 1220 /* 1221 * Segment flag validation for new connection attempts: 1222 * 1223 * Our (SYN|ACK) response was rejected. 1224 * Check with syncache and remove entry to prevent 1225 * retransmits. 1226 * 1227 * NB: syncache_chkrst does its own logging of failure 1228 * causes. 1229 */ 1230 if (thflags & TH_RST) { 1231 syncache_chkrst(&inc, th); 1232 goto dropunlock; 1233 } 1234 /* 1235 * We can't do anything without SYN. 1236 */ 1237 if ((thflags & TH_SYN) == 0) { 1238 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1239 log(LOG_DEBUG, "%s; %s: Listen socket: " 1240 "SYN is missing, segment ignored\n", 1241 s, __func__); 1242 TCPSTAT_INC(tcps_badsyn); 1243 goto dropunlock; 1244 } 1245 /* 1246 * (SYN|ACK) is bogus on a listen socket. 1247 */ 1248 if (thflags & TH_ACK) { 1249 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1250 log(LOG_DEBUG, "%s; %s: Listen socket: " 1251 "SYN|ACK invalid, segment rejected\n", 1252 s, __func__); 1253 syncache_badack(&inc); /* XXX: Not needed! */ 1254 TCPSTAT_INC(tcps_badsyn); 1255 rstreason = BANDLIM_RST_OPENPORT; 1256 goto dropwithreset; 1257 } 1258 /* 1259 * If the drop_synfin option is enabled, drop all 1260 * segments with both the SYN and FIN bits set. 1261 * This prevents e.g. nmap from identifying the 1262 * TCP/IP stack. 1263 * XXX: Poor reasoning. nmap has other methods 1264 * and is constantly refining its stack detection 1265 * strategies. 1266 * XXX: This is a violation of the TCP specification 1267 * and was used by RFC1644. 1268 */ 1269 if ((thflags & TH_FIN) && V_drop_synfin) { 1270 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1271 log(LOG_DEBUG, "%s; %s: Listen socket: " 1272 "SYN|FIN segment ignored (based on " 1273 "sysctl setting)\n", s, __func__); 1274 TCPSTAT_INC(tcps_badsyn); 1275 goto dropunlock; 1276 } 1277 /* 1278 * Segment's flags are (SYN) or (SYN|FIN). 1279 * 1280 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1281 * as they do not affect the state of the TCP FSM. 1282 * The data pointed to by TH_URG and th_urp is ignored. 1283 */ 1284 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1285 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1286 KASSERT(thflags & (TH_SYN), 1287 ("%s: Listen socket: TH_SYN not set", __func__)); 1288 #ifdef INET6 1289 /* 1290 * If deprecated address is forbidden, 1291 * we do not accept SYN to deprecated interface 1292 * address to prevent any new inbound connection from 1293 * getting established. 1294 * When we do not accept SYN, we send a TCP RST, 1295 * with deprecated source address (instead of dropping 1296 * it). We compromise it as it is much better for peer 1297 * to send a RST, and RST will be the final packet 1298 * for the exchange. 1299 * 1300 * If we do not forbid deprecated addresses, we accept 1301 * the SYN packet. RFC2462 does not suggest dropping 1302 * SYN in this case. 1303 * If we decipher RFC2462 5.5.4, it says like this: 1304 * 1. use of deprecated addr with existing 1305 * communication is okay - "SHOULD continue to be 1306 * used" 1307 * 2. use of it with new communication: 1308 * (2a) "SHOULD NOT be used if alternate address 1309 * with sufficient scope is available" 1310 * (2b) nothing mentioned otherwise. 1311 * Here we fall into (2b) case as we have no choice in 1312 * our source address selection - we must obey the peer. 1313 * 1314 * The wording in RFC2462 is confusing, and there are 1315 * multiple description text for deprecated address 1316 * handling - worse, they are not exactly the same. 1317 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1318 */ 1319 if (isipv6 && !V_ip6_use_deprecated) { 1320 struct in6_ifaddr *ia6; 1321 1322 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1323 if (ia6 != NULL && 1324 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1325 ifa_free(&ia6->ia_ifa); 1326 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1327 log(LOG_DEBUG, "%s; %s: Listen socket: " 1328 "Connection attempt to deprecated " 1329 "IPv6 address rejected\n", 1330 s, __func__); 1331 rstreason = BANDLIM_RST_OPENPORT; 1332 goto dropwithreset; 1333 } 1334 if (ia6) 1335 ifa_free(&ia6->ia_ifa); 1336 } 1337 #endif /* INET6 */ 1338 /* 1339 * Basic sanity checks on incoming SYN requests: 1340 * Don't respond if the destination is a link layer 1341 * broadcast according to RFC1122 4.2.3.10, p. 104. 1342 * If it is from this socket it must be forged. 1343 * Don't respond if the source or destination is a 1344 * global or subnet broad- or multicast address. 1345 * Note that it is quite possible to receive unicast 1346 * link-layer packets with a broadcast IP address. Use 1347 * in_broadcast() to find them. 1348 */ 1349 if (m->m_flags & (M_BCAST|M_MCAST)) { 1350 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1351 log(LOG_DEBUG, "%s; %s: Listen socket: " 1352 "Connection attempt from broad- or multicast " 1353 "link layer address ignored\n", s, __func__); 1354 goto dropunlock; 1355 } 1356 #ifdef INET6 1357 if (isipv6) { 1358 if (th->th_dport == th->th_sport && 1359 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1360 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1361 log(LOG_DEBUG, "%s; %s: Listen socket: " 1362 "Connection attempt to/from self " 1363 "ignored\n", s, __func__); 1364 goto dropunlock; 1365 } 1366 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1367 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1368 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1369 log(LOG_DEBUG, "%s; %s: Listen socket: " 1370 "Connection attempt from/to multicast " 1371 "address ignored\n", s, __func__); 1372 goto dropunlock; 1373 } 1374 } 1375 #endif 1376 #if defined(INET) && defined(INET6) 1377 else 1378 #endif 1379 #ifdef INET 1380 { 1381 if (th->th_dport == th->th_sport && 1382 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1383 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1384 log(LOG_DEBUG, "%s; %s: Listen socket: " 1385 "Connection attempt from/to self " 1386 "ignored\n", s, __func__); 1387 goto dropunlock; 1388 } 1389 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1390 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1391 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1392 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1393 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1394 log(LOG_DEBUG, "%s; %s: Listen socket: " 1395 "Connection attempt from/to broad- " 1396 "or multicast address ignored\n", 1397 s, __func__); 1398 goto dropunlock; 1399 } 1400 } 1401 #endif 1402 /* 1403 * SYN appears to be valid. Create compressed TCP state 1404 * for syncache. 1405 */ 1406 #ifdef TCPDEBUG 1407 if (so->so_options & SO_DEBUG) 1408 tcp_trace(TA_INPUT, ostate, tp, 1409 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1410 #endif 1411 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1412 tcp_dooptions(&to, optp, optlen, TO_SYN); 1413 #ifdef TCP_RFC7413 1414 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL)) 1415 goto tfo_socket_result; 1416 #else 1417 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); 1418 #endif 1419 /* 1420 * Entry added to syncache and mbuf consumed. 1421 * Only the listen socket is unlocked by syncache_add(). 1422 */ 1423 if (ti_locked == TI_RLOCKED) { 1424 INP_INFO_RUNLOCK(&V_tcbinfo); 1425 ti_locked = TI_UNLOCKED; 1426 } 1427 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1428 return (IPPROTO_DONE); 1429 } else if (tp->t_state == TCPS_LISTEN) { 1430 /* 1431 * When a listen socket is torn down the SO_ACCEPTCONN 1432 * flag is removed first while connections are drained 1433 * from the accept queue in a unlock/lock cycle of the 1434 * ACCEPT_LOCK, opening a race condition allowing a SYN 1435 * attempt go through unhandled. 1436 */ 1437 goto dropunlock; 1438 } 1439 1440 #ifdef TCP_SIGNATURE 1441 if (sig_checked == 0) { 1442 tcp_dooptions(&to, optp, optlen, 1443 (thflags & TH_SYN) ? TO_SYN : 0); 1444 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, 1445 th, tp->t_flags)) { 1446 1447 /* 1448 * In SYN_SENT state if it receives an RST, it is 1449 * allowed for further processing. 1450 */ 1451 if ((thflags & TH_RST) == 0 || 1452 (tp->t_state == TCPS_SYN_SENT) == 0) 1453 goto dropunlock; 1454 } 1455 sig_checked = 1; 1456 } 1457 #endif 1458 1459 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1460 1461 /* 1462 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1463 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1464 * the inpcb, and unlocks pcbinfo. 1465 */ 1466 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1467 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1468 return (IPPROTO_DONE); 1469 1470 dropwithreset: 1471 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1472 1473 if (ti_locked == TI_RLOCKED) { 1474 INP_INFO_RUNLOCK(&V_tcbinfo); 1475 ti_locked = TI_UNLOCKED; 1476 } 1477 #ifdef INVARIANTS 1478 else { 1479 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1480 "ti_locked: %d", __func__, ti_locked)); 1481 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1482 } 1483 #endif 1484 1485 if (inp != NULL) { 1486 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1487 INP_WUNLOCK(inp); 1488 } else 1489 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1490 m = NULL; /* mbuf chain got consumed. */ 1491 goto drop; 1492 1493 dropunlock: 1494 if (m != NULL) 1495 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1496 1497 if (ti_locked == TI_RLOCKED) { 1498 INP_INFO_RUNLOCK(&V_tcbinfo); 1499 ti_locked = TI_UNLOCKED; 1500 } 1501 #ifdef INVARIANTS 1502 else { 1503 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1504 "ti_locked: %d", __func__, ti_locked)); 1505 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1506 } 1507 #endif 1508 1509 if (inp != NULL) 1510 INP_WUNLOCK(inp); 1511 1512 drop: 1513 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1514 if (s != NULL) 1515 free(s, M_TCPLOG); 1516 if (m != NULL) 1517 m_freem(m); 1518 return (IPPROTO_DONE); 1519 } 1520 1521 void 1522 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1523 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1524 int ti_locked) 1525 { 1526 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1527 int rstreason, todrop, win; 1528 uint32_t tiwin; 1529 uint16_t nsegs; 1530 char *s; 1531 struct in_conninfo *inc; 1532 struct mbuf *mfree; 1533 struct tcpopt to; 1534 #ifdef TCP_RFC7413 1535 int tfo_syn; 1536 #endif 1537 1538 #ifdef TCPDEBUG 1539 /* 1540 * The size of tcp_saveipgen must be the size of the max ip header, 1541 * now IPv6. 1542 */ 1543 u_char tcp_saveipgen[IP6_HDR_LEN]; 1544 struct tcphdr tcp_savetcp; 1545 short ostate = 0; 1546 #endif 1547 thflags = th->th_flags; 1548 inc = &tp->t_inpcb->inp_inc; 1549 tp->sackhint.last_sack_ack = 0; 1550 sack_changed = 0; 1551 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1552 1553 /* 1554 * If this is either a state-changing packet or current state isn't 1555 * established, we require a write lock on tcbinfo. Otherwise, we 1556 * allow the tcbinfo to be in either alocked or unlocked, as the 1557 * caller may have unnecessarily acquired a write lock due to a race. 1558 */ 1559 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1560 tp->t_state != TCPS_ESTABLISHED) { 1561 KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for " 1562 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1563 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1564 } else { 1565 #ifdef INVARIANTS 1566 if (ti_locked == TI_RLOCKED) 1567 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1568 else { 1569 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " 1570 "ti_locked: %d", __func__, ti_locked)); 1571 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1572 } 1573 #endif 1574 } 1575 INP_WLOCK_ASSERT(tp->t_inpcb); 1576 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1577 __func__)); 1578 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1579 __func__)); 1580 1581 #ifdef TCPPCAP 1582 /* Save segment, if requested. */ 1583 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1584 #endif 1585 1586 /* 1587 * Segment received on connection. 1588 * Reset idle time and keep-alive timer. 1589 * XXX: This should be done after segment 1590 * validation to ignore broken/spoofed segs. 1591 */ 1592 tp->t_rcvtime = ticks; 1593 1594 /* 1595 * Scale up the window into a 32-bit value. 1596 * For the SYN_SENT state the scale is zero. 1597 */ 1598 tiwin = th->th_win << tp->snd_scale; 1599 1600 /* 1601 * TCP ECN processing. 1602 */ 1603 if (tp->t_flags & TF_ECN_PERMIT) { 1604 if (thflags & TH_CWR) 1605 tp->t_flags &= ~TF_ECN_SND_ECE; 1606 switch (iptos & IPTOS_ECN_MASK) { 1607 case IPTOS_ECN_CE: 1608 tp->t_flags |= TF_ECN_SND_ECE; 1609 TCPSTAT_INC(tcps_ecn_ce); 1610 break; 1611 case IPTOS_ECN_ECT0: 1612 TCPSTAT_INC(tcps_ecn_ect0); 1613 break; 1614 case IPTOS_ECN_ECT1: 1615 TCPSTAT_INC(tcps_ecn_ect1); 1616 break; 1617 } 1618 1619 /* Process a packet differently from RFC3168. */ 1620 cc_ecnpkt_handler(tp, th, iptos); 1621 1622 /* Congestion experienced. */ 1623 if (thflags & TH_ECE) { 1624 cc_cong_signal(tp, th, CC_ECN); 1625 } 1626 } 1627 1628 /* 1629 * Parse options on any incoming segment. 1630 */ 1631 tcp_dooptions(&to, (u_char *)(th + 1), 1632 (th->th_off << 2) - sizeof(struct tcphdr), 1633 (thflags & TH_SYN) ? TO_SYN : 0); 1634 1635 /* 1636 * If echoed timestamp is later than the current time, 1637 * fall back to non RFC1323 RTT calculation. Normalize 1638 * timestamp if syncookies were used when this connection 1639 * was established. 1640 */ 1641 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1642 to.to_tsecr -= tp->ts_offset; 1643 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1644 to.to_tsecr = 0; 1645 } 1646 /* 1647 * If timestamps were negotiated during SYN/ACK they should 1648 * appear on every segment during this session and vice versa. 1649 */ 1650 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1651 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1652 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1653 "no action\n", s, __func__); 1654 free(s, M_TCPLOG); 1655 } 1656 } 1657 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1658 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1659 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1660 "no action\n", s, __func__); 1661 free(s, M_TCPLOG); 1662 } 1663 } 1664 1665 /* 1666 * Process options only when we get SYN/ACK back. The SYN case 1667 * for incoming connections is handled in tcp_syncache. 1668 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1669 * or <SYN,ACK>) segment itself is never scaled. 1670 * XXX this is traditional behavior, may need to be cleaned up. 1671 */ 1672 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1673 if ((to.to_flags & TOF_SCALE) && 1674 (tp->t_flags & TF_REQ_SCALE)) { 1675 tp->t_flags |= TF_RCVD_SCALE; 1676 tp->snd_scale = to.to_wscale; 1677 } 1678 /* 1679 * Initial send window. It will be updated with 1680 * the next incoming segment to the scaled value. 1681 */ 1682 tp->snd_wnd = th->th_win; 1683 if (to.to_flags & TOF_TS) { 1684 tp->t_flags |= TF_RCVD_TSTMP; 1685 tp->ts_recent = to.to_tsval; 1686 tp->ts_recent_age = tcp_ts_getticks(); 1687 } 1688 if (to.to_flags & TOF_MSS) 1689 tcp_mss(tp, to.to_mss); 1690 if ((tp->t_flags & TF_SACK_PERMIT) && 1691 (to.to_flags & TOF_SACKPERM) == 0) 1692 tp->t_flags &= ~TF_SACK_PERMIT; 1693 } 1694 1695 /* 1696 * Header prediction: check for the two common cases 1697 * of a uni-directional data xfer. If the packet has 1698 * no control flags, is in-sequence, the window didn't 1699 * change and we're not retransmitting, it's a 1700 * candidate. If the length is zero and the ack moved 1701 * forward, we're the sender side of the xfer. Just 1702 * free the data acked & wake any higher level process 1703 * that was blocked waiting for space. If the length 1704 * is non-zero and the ack didn't move, we're the 1705 * receiver side. If we're getting packets in-order 1706 * (the reassembly queue is empty), add the data to 1707 * the socket buffer and note that we need a delayed ack. 1708 * Make sure that the hidden state-flags are also off. 1709 * Since we check for TCPS_ESTABLISHED first, it can only 1710 * be TH_NEEDSYN. 1711 */ 1712 if (tp->t_state == TCPS_ESTABLISHED && 1713 th->th_seq == tp->rcv_nxt && 1714 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1715 tp->snd_nxt == tp->snd_max && 1716 tiwin && tiwin == tp->snd_wnd && 1717 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1718 LIST_EMPTY(&tp->t_segq) && 1719 ((to.to_flags & TOF_TS) == 0 || 1720 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1721 1722 /* 1723 * If last ACK falls within this segment's sequence numbers, 1724 * record the timestamp. 1725 * NOTE that the test is modified according to the latest 1726 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1727 */ 1728 if ((to.to_flags & TOF_TS) != 0 && 1729 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1730 tp->ts_recent_age = tcp_ts_getticks(); 1731 tp->ts_recent = to.to_tsval; 1732 } 1733 1734 if (tlen == 0) { 1735 if (SEQ_GT(th->th_ack, tp->snd_una) && 1736 SEQ_LEQ(th->th_ack, tp->snd_max) && 1737 !IN_RECOVERY(tp->t_flags) && 1738 (to.to_flags & TOF_SACK) == 0 && 1739 TAILQ_EMPTY(&tp->snd_holes)) { 1740 /* 1741 * This is a pure ack for outstanding data. 1742 */ 1743 if (ti_locked == TI_RLOCKED) 1744 INP_INFO_RUNLOCK(&V_tcbinfo); 1745 ti_locked = TI_UNLOCKED; 1746 1747 TCPSTAT_INC(tcps_predack); 1748 1749 /* 1750 * "bad retransmit" recovery. 1751 */ 1752 if (tp->t_rxtshift == 1 && 1753 tp->t_flags & TF_PREVVALID && 1754 (int)(ticks - tp->t_badrxtwin) < 0) { 1755 cc_cong_signal(tp, th, CC_RTO_ERR); 1756 } 1757 1758 /* 1759 * Recalculate the transmit timer / rtt. 1760 * 1761 * Some boxes send broken timestamp replies 1762 * during the SYN+ACK phase, ignore 1763 * timestamps of 0 or we could calculate a 1764 * huge RTT and blow up the retransmit timer. 1765 */ 1766 if ((to.to_flags & TOF_TS) != 0 && 1767 to.to_tsecr) { 1768 uint32_t t; 1769 1770 t = tcp_ts_getticks() - to.to_tsecr; 1771 if (!tp->t_rttlow || tp->t_rttlow > t) 1772 tp->t_rttlow = t; 1773 tcp_xmit_timer(tp, 1774 TCP_TS_TO_TICKS(t) + 1); 1775 } else if (tp->t_rtttime && 1776 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1777 if (!tp->t_rttlow || 1778 tp->t_rttlow > ticks - tp->t_rtttime) 1779 tp->t_rttlow = ticks - tp->t_rtttime; 1780 tcp_xmit_timer(tp, 1781 ticks - tp->t_rtttime); 1782 } 1783 acked = BYTES_THIS_ACK(tp, th); 1784 1785 #ifdef TCP_HHOOK 1786 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1787 hhook_run_tcp_est_in(tp, th, &to); 1788 #endif 1789 1790 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1791 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1792 sbdrop(&so->so_snd, acked); 1793 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1794 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1795 tp->snd_recover = th->th_ack - 1; 1796 1797 /* 1798 * Let the congestion control algorithm update 1799 * congestion control related information. This 1800 * typically means increasing the congestion 1801 * window. 1802 */ 1803 cc_ack_received(tp, th, nsegs, CC_ACK); 1804 1805 tp->snd_una = th->th_ack; 1806 /* 1807 * Pull snd_wl2 up to prevent seq wrap relative 1808 * to th_ack. 1809 */ 1810 tp->snd_wl2 = th->th_ack; 1811 tp->t_dupacks = 0; 1812 m_freem(m); 1813 1814 /* 1815 * If all outstanding data are acked, stop 1816 * retransmit timer, otherwise restart timer 1817 * using current (possibly backed-off) value. 1818 * If process is waiting for space, 1819 * wakeup/selwakeup/signal. If data 1820 * are ready to send, let tcp_output 1821 * decide between more output or persist. 1822 */ 1823 #ifdef TCPDEBUG 1824 if (so->so_options & SO_DEBUG) 1825 tcp_trace(TA_INPUT, ostate, tp, 1826 (void *)tcp_saveipgen, 1827 &tcp_savetcp, 0); 1828 #endif 1829 TCP_PROBE3(debug__input, tp, th, 1830 mtod(m, const char *)); 1831 if (tp->snd_una == tp->snd_max) 1832 tcp_timer_activate(tp, TT_REXMT, 0); 1833 else if (!tcp_timer_active(tp, TT_PERSIST)) 1834 tcp_timer_activate(tp, TT_REXMT, 1835 tp->t_rxtcur); 1836 sowwakeup(so); 1837 if (sbavail(&so->so_snd)) 1838 (void) tp->t_fb->tfb_tcp_output(tp); 1839 goto check_delack; 1840 } 1841 } else if (th->th_ack == tp->snd_una && 1842 tlen <= sbspace(&so->so_rcv)) { 1843 int newsize = 0; /* automatic sockbuf scaling */ 1844 1845 /* 1846 * This is a pure, in-sequence data packet with 1847 * nothing on the reassembly queue and we have enough 1848 * buffer space to take it. 1849 */ 1850 if (ti_locked == TI_RLOCKED) 1851 INP_INFO_RUNLOCK(&V_tcbinfo); 1852 ti_locked = TI_UNLOCKED; 1853 1854 /* Clean receiver SACK report if present */ 1855 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1856 tcp_clean_sackreport(tp); 1857 TCPSTAT_INC(tcps_preddat); 1858 tp->rcv_nxt += tlen; 1859 /* 1860 * Pull snd_wl1 up to prevent seq wrap relative to 1861 * th_seq. 1862 */ 1863 tp->snd_wl1 = th->th_seq; 1864 /* 1865 * Pull rcv_up up to prevent seq wrap relative to 1866 * rcv_nxt. 1867 */ 1868 tp->rcv_up = tp->rcv_nxt; 1869 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1870 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1871 #ifdef TCPDEBUG 1872 if (so->so_options & SO_DEBUG) 1873 tcp_trace(TA_INPUT, ostate, tp, 1874 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1875 #endif 1876 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1877 1878 /* 1879 * Automatic sizing of receive socket buffer. Often the send 1880 * buffer size is not optimally adjusted to the actual network 1881 * conditions at hand (delay bandwidth product). Setting the 1882 * buffer size too small limits throughput on links with high 1883 * bandwidth and high delay (eg. trans-continental/oceanic links). 1884 * 1885 * On the receive side the socket buffer memory is only rarely 1886 * used to any significant extent. This allows us to be much 1887 * more aggressive in scaling the receive socket buffer. For 1888 * the case that the buffer space is actually used to a large 1889 * extent and we run out of kernel memory we can simply drop 1890 * the new segments; TCP on the sender will just retransmit it 1891 * later. Setting the buffer size too big may only consume too 1892 * much kernel memory if the application doesn't read() from 1893 * the socket or packet loss or reordering makes use of the 1894 * reassembly queue. 1895 * 1896 * The criteria to step up the receive buffer one notch are: 1897 * 1. Application has not set receive buffer size with 1898 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1899 * 2. the number of bytes received during the time it takes 1900 * one timestamp to be reflected back to us (the RTT); 1901 * 3. received bytes per RTT is within seven eighth of the 1902 * current socket buffer size; 1903 * 4. receive buffer size has not hit maximal automatic size; 1904 * 1905 * This algorithm does one step per RTT at most and only if 1906 * we receive a bulk stream w/o packet losses or reorderings. 1907 * Shrinking the buffer during idle times is not necessary as 1908 * it doesn't consume any memory when idle. 1909 * 1910 * TODO: Only step up if the application is actually serving 1911 * the buffer to better manage the socket buffer resources. 1912 */ 1913 if (V_tcp_do_autorcvbuf && 1914 (to.to_flags & TOF_TS) && 1915 to.to_tsecr && 1916 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1917 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && 1918 to.to_tsecr - tp->rfbuf_ts < hz) { 1919 if (tp->rfbuf_cnt > 1920 (so->so_rcv.sb_hiwat / 8 * 7) && 1921 so->so_rcv.sb_hiwat < 1922 V_tcp_autorcvbuf_max) { 1923 newsize = 1924 min(so->so_rcv.sb_hiwat + 1925 V_tcp_autorcvbuf_inc, 1926 V_tcp_autorcvbuf_max); 1927 } 1928 /* Start over with next RTT. */ 1929 tp->rfbuf_ts = 0; 1930 tp->rfbuf_cnt = 0; 1931 } else 1932 tp->rfbuf_cnt += tlen; /* add up */ 1933 } 1934 1935 /* Add data to socket buffer. */ 1936 SOCKBUF_LOCK(&so->so_rcv); 1937 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1938 m_freem(m); 1939 } else { 1940 /* 1941 * Set new socket buffer size. 1942 * Give up when limit is reached. 1943 */ 1944 if (newsize) 1945 if (!sbreserve_locked(&so->so_rcv, 1946 newsize, so, NULL)) 1947 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1948 m_adj(m, drop_hdrlen); /* delayed header drop */ 1949 sbappendstream_locked(&so->so_rcv, m, 0); 1950 } 1951 /* NB: sorwakeup_locked() does an implicit unlock. */ 1952 sorwakeup_locked(so); 1953 if (DELAY_ACK(tp, tlen)) { 1954 tp->t_flags |= TF_DELACK; 1955 } else { 1956 tp->t_flags |= TF_ACKNOW; 1957 tp->t_fb->tfb_tcp_output(tp); 1958 } 1959 goto check_delack; 1960 } 1961 } 1962 1963 /* 1964 * Calculate amount of space in receive window, 1965 * and then do TCP input processing. 1966 * Receive window is amount of space in rcv queue, 1967 * but not less than advertised window. 1968 */ 1969 win = sbspace(&so->so_rcv); 1970 if (win < 0) 1971 win = 0; 1972 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1973 1974 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1975 tp->rfbuf_ts = 0; 1976 tp->rfbuf_cnt = 0; 1977 1978 switch (tp->t_state) { 1979 1980 /* 1981 * If the state is SYN_RECEIVED: 1982 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1983 */ 1984 case TCPS_SYN_RECEIVED: 1985 if ((thflags & TH_ACK) && 1986 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1987 SEQ_GT(th->th_ack, tp->snd_max))) { 1988 rstreason = BANDLIM_RST_OPENPORT; 1989 goto dropwithreset; 1990 } 1991 #ifdef TCP_RFC7413 1992 if (IS_FASTOPEN(tp->t_flags)) { 1993 /* 1994 * When a TFO connection is in SYN_RECEIVED, the 1995 * only valid packets are the initial SYN, a 1996 * retransmit/copy of the initial SYN (possibly with 1997 * a subset of the original data), a valid ACK, a 1998 * FIN, or a RST. 1999 */ 2000 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 2001 rstreason = BANDLIM_RST_OPENPORT; 2002 goto dropwithreset; 2003 } else if (thflags & TH_SYN) { 2004 /* non-initial SYN is ignored */ 2005 if ((tcp_timer_active(tp, TT_DELACK) || 2006 tcp_timer_active(tp, TT_REXMT))) 2007 goto drop; 2008 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 2009 goto drop; 2010 } 2011 } 2012 #endif 2013 break; 2014 2015 /* 2016 * If the state is SYN_SENT: 2017 * if seg contains an ACK, but not for our SYN, drop the input. 2018 * if seg contains a RST, then drop the connection. 2019 * if seg does not contain SYN, then drop it. 2020 * Otherwise this is an acceptable SYN segment 2021 * initialize tp->rcv_nxt and tp->irs 2022 * if seg contains ack then advance tp->snd_una 2023 * if seg contains an ECE and ECN support is enabled, the stream 2024 * is ECN capable. 2025 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 2026 * arrange for segment to be acked (eventually) 2027 * continue processing rest of data/controls, beginning with URG 2028 */ 2029 case TCPS_SYN_SENT: 2030 if ((thflags & TH_ACK) && 2031 (SEQ_LEQ(th->th_ack, tp->iss) || 2032 SEQ_GT(th->th_ack, tp->snd_max))) { 2033 rstreason = BANDLIM_UNLIMITED; 2034 goto dropwithreset; 2035 } 2036 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 2037 TCP_PROBE5(connect__refused, NULL, tp, 2038 mtod(m, const char *), tp, th); 2039 tp = tcp_drop(tp, ECONNREFUSED); 2040 } 2041 if (thflags & TH_RST) 2042 goto drop; 2043 if (!(thflags & TH_SYN)) 2044 goto drop; 2045 2046 tp->irs = th->th_seq; 2047 tcp_rcvseqinit(tp); 2048 if (thflags & TH_ACK) { 2049 TCPSTAT_INC(tcps_connects); 2050 soisconnected(so); 2051 #ifdef MAC 2052 mac_socketpeer_set_from_mbuf(m, so); 2053 #endif 2054 /* Do window scaling on this connection? */ 2055 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2056 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2057 tp->rcv_scale = tp->request_r_scale; 2058 } 2059 tp->rcv_adv += min(tp->rcv_wnd, 2060 TCP_MAXWIN << tp->rcv_scale); 2061 tp->snd_una++; /* SYN is acked */ 2062 /* 2063 * If there's data, delay ACK; if there's also a FIN 2064 * ACKNOW will be turned on later. 2065 */ 2066 if (DELAY_ACK(tp, tlen) && tlen != 0) 2067 tcp_timer_activate(tp, TT_DELACK, 2068 tcp_delacktime); 2069 else 2070 tp->t_flags |= TF_ACKNOW; 2071 2072 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 2073 tp->t_flags |= TF_ECN_PERMIT; 2074 TCPSTAT_INC(tcps_ecn_shs); 2075 } 2076 2077 /* 2078 * Received <SYN,ACK> in SYN_SENT[*] state. 2079 * Transitions: 2080 * SYN_SENT --> ESTABLISHED 2081 * SYN_SENT* --> FIN_WAIT_1 2082 */ 2083 tp->t_starttime = ticks; 2084 if (tp->t_flags & TF_NEEDFIN) { 2085 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2086 tp->t_flags &= ~TF_NEEDFIN; 2087 thflags &= ~TH_SYN; 2088 } else { 2089 tcp_state_change(tp, TCPS_ESTABLISHED); 2090 TCP_PROBE5(connect__established, NULL, tp, 2091 mtod(m, const char *), tp, th); 2092 cc_conn_init(tp); 2093 tcp_timer_activate(tp, TT_KEEP, 2094 TP_KEEPIDLE(tp)); 2095 } 2096 } else { 2097 /* 2098 * Received initial SYN in SYN-SENT[*] state => 2099 * simultaneous open. 2100 * If it succeeds, connection is * half-synchronized. 2101 * Otherwise, do 3-way handshake: 2102 * SYN-SENT -> SYN-RECEIVED 2103 * SYN-SENT* -> SYN-RECEIVED* 2104 */ 2105 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2106 tcp_timer_activate(tp, TT_REXMT, 0); 2107 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2108 } 2109 2110 KASSERT(ti_locked == TI_RLOCKED, ("%s: trimthenstep6: " 2111 "ti_locked %d", __func__, ti_locked)); 2112 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2113 INP_WLOCK_ASSERT(tp->t_inpcb); 2114 2115 /* 2116 * Advance th->th_seq to correspond to first data byte. 2117 * If data, trim to stay within window, 2118 * dropping FIN if necessary. 2119 */ 2120 th->th_seq++; 2121 if (tlen > tp->rcv_wnd) { 2122 todrop = tlen - tp->rcv_wnd; 2123 m_adj(m, -todrop); 2124 tlen = tp->rcv_wnd; 2125 thflags &= ~TH_FIN; 2126 TCPSTAT_INC(tcps_rcvpackafterwin); 2127 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2128 } 2129 tp->snd_wl1 = th->th_seq - 1; 2130 tp->rcv_up = th->th_seq; 2131 /* 2132 * Client side of transaction: already sent SYN and data. 2133 * If the remote host used T/TCP to validate the SYN, 2134 * our data will be ACK'd; if so, enter normal data segment 2135 * processing in the middle of step 5, ack processing. 2136 * Otherwise, goto step 6. 2137 */ 2138 if (thflags & TH_ACK) 2139 goto process_ACK; 2140 2141 goto step6; 2142 2143 /* 2144 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2145 * do normal processing. 2146 * 2147 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2148 */ 2149 case TCPS_LAST_ACK: 2150 case TCPS_CLOSING: 2151 break; /* continue normal processing */ 2152 } 2153 2154 /* 2155 * States other than LISTEN or SYN_SENT. 2156 * First check the RST flag and sequence number since reset segments 2157 * are exempt from the timestamp and connection count tests. This 2158 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2159 * below which allowed reset segments in half the sequence space 2160 * to fall though and be processed (which gives forged reset 2161 * segments with a random sequence number a 50 percent chance of 2162 * killing a connection). 2163 * Then check timestamp, if present. 2164 * Then check the connection count, if present. 2165 * Then check that at least some bytes of segment are within 2166 * receive window. If segment begins before rcv_nxt, 2167 * drop leading data (and SYN); if nothing left, just ack. 2168 */ 2169 if (thflags & TH_RST) { 2170 /* 2171 * RFC5961 Section 3.2 2172 * 2173 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2174 * - If RST is in window, we send challenge ACK. 2175 * 2176 * Note: to take into account delayed ACKs, we should 2177 * test against last_ack_sent instead of rcv_nxt. 2178 * Note 2: we handle special case of closed window, not 2179 * covered by the RFC. 2180 */ 2181 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2182 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2183 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2184 2185 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2186 KASSERT(ti_locked == TI_RLOCKED, 2187 ("%s: TH_RST ti_locked %d, th %p tp %p", 2188 __func__, ti_locked, th, tp)); 2189 KASSERT(tp->t_state != TCPS_SYN_SENT, 2190 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2191 __func__, th, tp)); 2192 2193 if (V_tcp_insecure_rst || 2194 tp->last_ack_sent == th->th_seq) { 2195 TCPSTAT_INC(tcps_drops); 2196 /* Drop the connection. */ 2197 switch (tp->t_state) { 2198 case TCPS_SYN_RECEIVED: 2199 so->so_error = ECONNREFUSED; 2200 goto close; 2201 case TCPS_ESTABLISHED: 2202 case TCPS_FIN_WAIT_1: 2203 case TCPS_FIN_WAIT_2: 2204 case TCPS_CLOSE_WAIT: 2205 case TCPS_CLOSING: 2206 case TCPS_LAST_ACK: 2207 so->so_error = ECONNRESET; 2208 close: 2209 /* FALLTHROUGH */ 2210 default: 2211 tp = tcp_close(tp); 2212 } 2213 } else { 2214 TCPSTAT_INC(tcps_badrst); 2215 /* Send challenge ACK. */ 2216 tcp_respond(tp, mtod(m, void *), th, m, 2217 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2218 tp->last_ack_sent = tp->rcv_nxt; 2219 m = NULL; 2220 } 2221 } 2222 goto drop; 2223 } 2224 2225 /* 2226 * RFC5961 Section 4.2 2227 * Send challenge ACK for any SYN in synchronized state. 2228 */ 2229 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2230 tp->t_state != TCPS_SYN_RECEIVED) { 2231 KASSERT(ti_locked == TI_RLOCKED, 2232 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 2233 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2234 2235 TCPSTAT_INC(tcps_badsyn); 2236 if (V_tcp_insecure_syn && 2237 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2238 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2239 tp = tcp_drop(tp, ECONNRESET); 2240 rstreason = BANDLIM_UNLIMITED; 2241 } else { 2242 /* Send challenge ACK. */ 2243 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2244 tp->snd_nxt, TH_ACK); 2245 tp->last_ack_sent = tp->rcv_nxt; 2246 m = NULL; 2247 } 2248 goto drop; 2249 } 2250 2251 /* 2252 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2253 * and it's less than ts_recent, drop it. 2254 */ 2255 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2256 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2257 2258 /* Check to see if ts_recent is over 24 days old. */ 2259 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2260 /* 2261 * Invalidate ts_recent. If this segment updates 2262 * ts_recent, the age will be reset later and ts_recent 2263 * will get a valid value. If it does not, setting 2264 * ts_recent to zero will at least satisfy the 2265 * requirement that zero be placed in the timestamp 2266 * echo reply when ts_recent isn't valid. The 2267 * age isn't reset until we get a valid ts_recent 2268 * because we don't want out-of-order segments to be 2269 * dropped when ts_recent is old. 2270 */ 2271 tp->ts_recent = 0; 2272 } else { 2273 TCPSTAT_INC(tcps_rcvduppack); 2274 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2275 TCPSTAT_INC(tcps_pawsdrop); 2276 if (tlen) 2277 goto dropafterack; 2278 goto drop; 2279 } 2280 } 2281 2282 /* 2283 * In the SYN-RECEIVED state, validate that the packet belongs to 2284 * this connection before trimming the data to fit the receive 2285 * window. Check the sequence number versus IRS since we know 2286 * the sequence numbers haven't wrapped. This is a partial fix 2287 * for the "LAND" DoS attack. 2288 */ 2289 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2290 rstreason = BANDLIM_RST_OPENPORT; 2291 goto dropwithreset; 2292 } 2293 2294 todrop = tp->rcv_nxt - th->th_seq; 2295 if (todrop > 0) { 2296 if (thflags & TH_SYN) { 2297 thflags &= ~TH_SYN; 2298 th->th_seq++; 2299 if (th->th_urp > 1) 2300 th->th_urp--; 2301 else 2302 thflags &= ~TH_URG; 2303 todrop--; 2304 } 2305 /* 2306 * Following if statement from Stevens, vol. 2, p. 960. 2307 */ 2308 if (todrop > tlen 2309 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2310 /* 2311 * Any valid FIN must be to the left of the window. 2312 * At this point the FIN must be a duplicate or out 2313 * of sequence; drop it. 2314 */ 2315 thflags &= ~TH_FIN; 2316 2317 /* 2318 * Send an ACK to resynchronize and drop any data. 2319 * But keep on processing for RST or ACK. 2320 */ 2321 tp->t_flags |= TF_ACKNOW; 2322 todrop = tlen; 2323 TCPSTAT_INC(tcps_rcvduppack); 2324 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2325 } else { 2326 TCPSTAT_INC(tcps_rcvpartduppack); 2327 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2328 } 2329 drop_hdrlen += todrop; /* drop from the top afterwards */ 2330 th->th_seq += todrop; 2331 tlen -= todrop; 2332 if (th->th_urp > todrop) 2333 th->th_urp -= todrop; 2334 else { 2335 thflags &= ~TH_URG; 2336 th->th_urp = 0; 2337 } 2338 } 2339 2340 /* 2341 * If new data are received on a connection after the 2342 * user processes are gone, then RST the other end. 2343 */ 2344 if ((so->so_state & SS_NOFDREF) && 2345 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2346 KASSERT(ti_locked == TI_RLOCKED, ("%s: SS_NOFDEREF && " 2347 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 2348 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2349 2350 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2351 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2352 "after socket was closed, " 2353 "sending RST and removing tcpcb\n", 2354 s, __func__, tcpstates[tp->t_state], tlen); 2355 free(s, M_TCPLOG); 2356 } 2357 tp = tcp_close(tp); 2358 TCPSTAT_INC(tcps_rcvafterclose); 2359 rstreason = BANDLIM_UNLIMITED; 2360 goto dropwithreset; 2361 } 2362 2363 /* 2364 * If segment ends after window, drop trailing data 2365 * (and PUSH and FIN); if nothing left, just ACK. 2366 */ 2367 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2368 if (todrop > 0) { 2369 TCPSTAT_INC(tcps_rcvpackafterwin); 2370 if (todrop >= tlen) { 2371 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2372 /* 2373 * If window is closed can only take segments at 2374 * window edge, and have to drop data and PUSH from 2375 * incoming segments. Continue processing, but 2376 * remember to ack. Otherwise, drop segment 2377 * and ack. 2378 */ 2379 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2380 tp->t_flags |= TF_ACKNOW; 2381 TCPSTAT_INC(tcps_rcvwinprobe); 2382 } else 2383 goto dropafterack; 2384 } else 2385 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2386 m_adj(m, -todrop); 2387 tlen -= todrop; 2388 thflags &= ~(TH_PUSH|TH_FIN); 2389 } 2390 2391 /* 2392 * If last ACK falls within this segment's sequence numbers, 2393 * record its timestamp. 2394 * NOTE: 2395 * 1) That the test incorporates suggestions from the latest 2396 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2397 * 2) That updating only on newer timestamps interferes with 2398 * our earlier PAWS tests, so this check should be solely 2399 * predicated on the sequence space of this segment. 2400 * 3) That we modify the segment boundary check to be 2401 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2402 * instead of RFC1323's 2403 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2404 * This modified check allows us to overcome RFC1323's 2405 * limitations as described in Stevens TCP/IP Illustrated 2406 * Vol. 2 p.869. In such cases, we can still calculate the 2407 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2408 */ 2409 if ((to.to_flags & TOF_TS) != 0 && 2410 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2411 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2412 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2413 tp->ts_recent_age = tcp_ts_getticks(); 2414 tp->ts_recent = to.to_tsval; 2415 } 2416 2417 /* 2418 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2419 * flag is on (half-synchronized state), then queue data for 2420 * later processing; else drop segment and return. 2421 */ 2422 if ((thflags & TH_ACK) == 0) { 2423 if (tp->t_state == TCPS_SYN_RECEIVED || 2424 (tp->t_flags & TF_NEEDSYN)) { 2425 #ifdef TCP_RFC7413 2426 if (tp->t_state == TCPS_SYN_RECEIVED && 2427 IS_FASTOPEN(tp->t_flags)) { 2428 tp->snd_wnd = tiwin; 2429 cc_conn_init(tp); 2430 } 2431 #endif 2432 goto step6; 2433 } else if (tp->t_flags & TF_ACKNOW) 2434 goto dropafterack; 2435 else 2436 goto drop; 2437 } 2438 2439 /* 2440 * Ack processing. 2441 */ 2442 switch (tp->t_state) { 2443 2444 /* 2445 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2446 * ESTABLISHED state and continue processing. 2447 * The ACK was checked above. 2448 */ 2449 case TCPS_SYN_RECEIVED: 2450 2451 TCPSTAT_INC(tcps_connects); 2452 soisconnected(so); 2453 /* Do window scaling? */ 2454 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2455 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2456 tp->rcv_scale = tp->request_r_scale; 2457 tp->snd_wnd = tiwin; 2458 } 2459 /* 2460 * Make transitions: 2461 * SYN-RECEIVED -> ESTABLISHED 2462 * SYN-RECEIVED* -> FIN-WAIT-1 2463 */ 2464 tp->t_starttime = ticks; 2465 if (tp->t_flags & TF_NEEDFIN) { 2466 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2467 tp->t_flags &= ~TF_NEEDFIN; 2468 } else { 2469 tcp_state_change(tp, TCPS_ESTABLISHED); 2470 TCP_PROBE5(accept__established, NULL, tp, 2471 mtod(m, const char *), tp, th); 2472 #ifdef TCP_RFC7413 2473 if (tp->t_tfo_pending) { 2474 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2475 tp->t_tfo_pending = NULL; 2476 2477 /* 2478 * Account for the ACK of our SYN prior to 2479 * regular ACK processing below. 2480 */ 2481 tp->snd_una++; 2482 } 2483 /* 2484 * TFO connections call cc_conn_init() during SYN 2485 * processing. Calling it again here for such 2486 * connections is not harmless as it would undo the 2487 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2488 * is retransmitted. 2489 */ 2490 if (!IS_FASTOPEN(tp->t_flags)) 2491 #endif 2492 cc_conn_init(tp); 2493 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2494 } 2495 /* 2496 * If segment contains data or ACK, will call tcp_reass() 2497 * later; if not, do so now to pass queued data to user. 2498 */ 2499 if (tlen == 0 && (thflags & TH_FIN) == 0) 2500 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2501 (struct mbuf *)0); 2502 tp->snd_wl1 = th->th_seq - 1; 2503 /* FALLTHROUGH */ 2504 2505 /* 2506 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2507 * ACKs. If the ack is in the range 2508 * tp->snd_una < th->th_ack <= tp->snd_max 2509 * then advance tp->snd_una to th->th_ack and drop 2510 * data from the retransmission queue. If this ACK reflects 2511 * more up to date window information we update our window information. 2512 */ 2513 case TCPS_ESTABLISHED: 2514 case TCPS_FIN_WAIT_1: 2515 case TCPS_FIN_WAIT_2: 2516 case TCPS_CLOSE_WAIT: 2517 case TCPS_CLOSING: 2518 case TCPS_LAST_ACK: 2519 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2520 TCPSTAT_INC(tcps_rcvacktoomuch); 2521 goto dropafterack; 2522 } 2523 if ((tp->t_flags & TF_SACK_PERMIT) && 2524 ((to.to_flags & TOF_SACK) || 2525 !TAILQ_EMPTY(&tp->snd_holes))) 2526 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2527 else 2528 /* 2529 * Reset the value so that previous (valid) value 2530 * from the last ack with SACK doesn't get used. 2531 */ 2532 tp->sackhint.sacked_bytes = 0; 2533 2534 #ifdef TCP_HHOOK 2535 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2536 hhook_run_tcp_est_in(tp, th, &to); 2537 #endif 2538 2539 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2540 u_int maxseg; 2541 2542 maxseg = tcp_maxseg(tp); 2543 if (tlen == 0 && 2544 (tiwin == tp->snd_wnd || 2545 (tp->t_flags & TF_SACK_PERMIT))) { 2546 /* 2547 * If this is the first time we've seen a 2548 * FIN from the remote, this is not a 2549 * duplicate and it needs to be processed 2550 * normally. This happens during a 2551 * simultaneous close. 2552 */ 2553 if ((thflags & TH_FIN) && 2554 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2555 tp->t_dupacks = 0; 2556 break; 2557 } 2558 TCPSTAT_INC(tcps_rcvdupack); 2559 /* 2560 * If we have outstanding data (other than 2561 * a window probe), this is a completely 2562 * duplicate ack (ie, window info didn't 2563 * change and FIN isn't set), 2564 * the ack is the biggest we've 2565 * seen and we've seen exactly our rexmt 2566 * threshold of them, assume a packet 2567 * has been dropped and retransmit it. 2568 * Kludge snd_nxt & the congestion 2569 * window so we send only this one 2570 * packet. 2571 * 2572 * We know we're losing at the current 2573 * window size so do congestion avoidance 2574 * (set ssthresh to half the current window 2575 * and pull our congestion window back to 2576 * the new ssthresh). 2577 * 2578 * Dup acks mean that packets have left the 2579 * network (they're now cached at the receiver) 2580 * so bump cwnd by the amount in the receiver 2581 * to keep a constant cwnd packets in the 2582 * network. 2583 * 2584 * When using TCP ECN, notify the peer that 2585 * we reduced the cwnd. 2586 */ 2587 /* 2588 * Following 2 kinds of acks should not affect 2589 * dupack counting: 2590 * 1) Old acks 2591 * 2) Acks with SACK but without any new SACK 2592 * information in them. These could result from 2593 * any anomaly in the network like a switch 2594 * duplicating packets or a possible DoS attack. 2595 */ 2596 if (th->th_ack != tp->snd_una || 2597 ((tp->t_flags & TF_SACK_PERMIT) && 2598 !sack_changed)) 2599 break; 2600 else if (!tcp_timer_active(tp, TT_REXMT)) 2601 tp->t_dupacks = 0; 2602 else if (++tp->t_dupacks > tcprexmtthresh || 2603 IN_FASTRECOVERY(tp->t_flags)) { 2604 cc_ack_received(tp, th, nsegs, 2605 CC_DUPACK); 2606 if ((tp->t_flags & TF_SACK_PERMIT) && 2607 IN_FASTRECOVERY(tp->t_flags)) { 2608 int awnd; 2609 2610 /* 2611 * Compute the amount of data in flight first. 2612 * We can inject new data into the pipe iff 2613 * we have less than 1/2 the original window's 2614 * worth of data in flight. 2615 */ 2616 if (V_tcp_do_rfc6675_pipe) 2617 awnd = tcp_compute_pipe(tp); 2618 else 2619 awnd = (tp->snd_nxt - tp->snd_fack) + 2620 tp->sackhint.sack_bytes_rexmit; 2621 2622 if (awnd < tp->snd_ssthresh) { 2623 tp->snd_cwnd += maxseg; 2624 /* 2625 * RFC5681 Section 3.2 talks about cwnd 2626 * inflation on additional dupacks and 2627 * deflation on recovering from loss. 2628 * 2629 * We keep cwnd into check so that 2630 * we don't have to 'deflate' it when we 2631 * get out of recovery. 2632 */ 2633 if (tp->snd_cwnd > tp->snd_ssthresh) 2634 tp->snd_cwnd = tp->snd_ssthresh; 2635 } 2636 } else 2637 tp->snd_cwnd += maxseg; 2638 (void) tp->t_fb->tfb_tcp_output(tp); 2639 goto drop; 2640 } else if (tp->t_dupacks == tcprexmtthresh) { 2641 tcp_seq onxt = tp->snd_nxt; 2642 2643 /* 2644 * If we're doing sack, check to 2645 * see if we're already in sack 2646 * recovery. If we're not doing sack, 2647 * check to see if we're in newreno 2648 * recovery. 2649 */ 2650 if (tp->t_flags & TF_SACK_PERMIT) { 2651 if (IN_FASTRECOVERY(tp->t_flags)) { 2652 tp->t_dupacks = 0; 2653 break; 2654 } 2655 } else { 2656 if (SEQ_LEQ(th->th_ack, 2657 tp->snd_recover)) { 2658 tp->t_dupacks = 0; 2659 break; 2660 } 2661 } 2662 /* Congestion signal before ack. */ 2663 cc_cong_signal(tp, th, CC_NDUPACK); 2664 cc_ack_received(tp, th, nsegs, 2665 CC_DUPACK); 2666 tcp_timer_activate(tp, TT_REXMT, 0); 2667 tp->t_rtttime = 0; 2668 if (tp->t_flags & TF_SACK_PERMIT) { 2669 TCPSTAT_INC( 2670 tcps_sack_recovery_episode); 2671 tp->sack_newdata = tp->snd_nxt; 2672 if (CC_ALGO(tp)->cong_signal == NULL) 2673 tp->snd_cwnd = maxseg; 2674 (void) tp->t_fb->tfb_tcp_output(tp); 2675 goto drop; 2676 } 2677 tp->snd_nxt = th->th_ack; 2678 if (CC_ALGO(tp)->cong_signal == NULL) 2679 tp->snd_cwnd = maxseg; 2680 (void) tp->t_fb->tfb_tcp_output(tp); 2681 KASSERT(tp->snd_limited <= 2, 2682 ("%s: tp->snd_limited too big", 2683 __func__)); 2684 if (CC_ALGO(tp)->cong_signal == NULL) 2685 tp->snd_cwnd = tp->snd_ssthresh + 2686 maxseg * 2687 (tp->t_dupacks - tp->snd_limited); 2688 if (SEQ_GT(onxt, tp->snd_nxt)) 2689 tp->snd_nxt = onxt; 2690 goto drop; 2691 } else if (V_tcp_do_rfc3042) { 2692 /* 2693 * Process first and second duplicate 2694 * ACKs. Each indicates a segment 2695 * leaving the network, creating room 2696 * for more. Make sure we can send a 2697 * packet on reception of each duplicate 2698 * ACK by increasing snd_cwnd by one 2699 * segment. Restore the original 2700 * snd_cwnd after packet transmission. 2701 */ 2702 cc_ack_received(tp, th, nsegs, 2703 CC_DUPACK); 2704 uint32_t oldcwnd = tp->snd_cwnd; 2705 tcp_seq oldsndmax = tp->snd_max; 2706 u_int sent; 2707 int avail; 2708 2709 KASSERT(tp->t_dupacks == 1 || 2710 tp->t_dupacks == 2, 2711 ("%s: dupacks not 1 or 2", 2712 __func__)); 2713 if (tp->t_dupacks == 1) 2714 tp->snd_limited = 0; 2715 tp->snd_cwnd = 2716 (tp->snd_nxt - tp->snd_una) + 2717 (tp->t_dupacks - tp->snd_limited) * 2718 maxseg; 2719 /* 2720 * Only call tcp_output when there 2721 * is new data available to be sent. 2722 * Otherwise we would send pure ACKs. 2723 */ 2724 SOCKBUF_LOCK(&so->so_snd); 2725 avail = sbavail(&so->so_snd) - 2726 (tp->snd_nxt - tp->snd_una); 2727 SOCKBUF_UNLOCK(&so->so_snd); 2728 if (avail > 0) 2729 (void) tp->t_fb->tfb_tcp_output(tp); 2730 sent = tp->snd_max - oldsndmax; 2731 if (sent > maxseg) { 2732 KASSERT((tp->t_dupacks == 2 && 2733 tp->snd_limited == 0) || 2734 (sent == maxseg + 1 && 2735 tp->t_flags & TF_SENTFIN), 2736 ("%s: sent too much", 2737 __func__)); 2738 tp->snd_limited = 2; 2739 } else if (sent > 0) 2740 ++tp->snd_limited; 2741 tp->snd_cwnd = oldcwnd; 2742 goto drop; 2743 } 2744 } 2745 break; 2746 } else { 2747 /* 2748 * This ack is advancing the left edge, reset the 2749 * counter. 2750 */ 2751 tp->t_dupacks = 0; 2752 /* 2753 * If this ack also has new SACK info, increment the 2754 * counter as per rfc6675. 2755 */ 2756 if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed) 2757 tp->t_dupacks++; 2758 } 2759 2760 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2761 ("%s: th_ack <= snd_una", __func__)); 2762 2763 /* 2764 * If the congestion window was inflated to account 2765 * for the other side's cached packets, retract it. 2766 */ 2767 if (IN_FASTRECOVERY(tp->t_flags)) { 2768 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2769 if (tp->t_flags & TF_SACK_PERMIT) 2770 tcp_sack_partialack(tp, th); 2771 else 2772 tcp_newreno_partial_ack(tp, th); 2773 } else 2774 cc_post_recovery(tp, th); 2775 } 2776 /* 2777 * If we reach this point, ACK is not a duplicate, 2778 * i.e., it ACKs something we sent. 2779 */ 2780 if (tp->t_flags & TF_NEEDSYN) { 2781 /* 2782 * T/TCP: Connection was half-synchronized, and our 2783 * SYN has been ACK'd (so connection is now fully 2784 * synchronized). Go to non-starred state, 2785 * increment snd_una for ACK of SYN, and check if 2786 * we can do window scaling. 2787 */ 2788 tp->t_flags &= ~TF_NEEDSYN; 2789 tp->snd_una++; 2790 /* Do window scaling? */ 2791 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2792 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2793 tp->rcv_scale = tp->request_r_scale; 2794 /* Send window already scaled. */ 2795 } 2796 } 2797 2798 process_ACK: 2799 INP_WLOCK_ASSERT(tp->t_inpcb); 2800 2801 acked = BYTES_THIS_ACK(tp, th); 2802 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2803 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2804 tp->snd_una, th->th_ack, tp, m)); 2805 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2806 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2807 2808 /* 2809 * If we just performed our first retransmit, and the ACK 2810 * arrives within our recovery window, then it was a mistake 2811 * to do the retransmit in the first place. Recover our 2812 * original cwnd and ssthresh, and proceed to transmit where 2813 * we left off. 2814 */ 2815 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && 2816 (int)(ticks - tp->t_badrxtwin) < 0) 2817 cc_cong_signal(tp, th, CC_RTO_ERR); 2818 2819 /* 2820 * If we have a timestamp reply, update smoothed 2821 * round trip time. If no timestamp is present but 2822 * transmit timer is running and timed sequence 2823 * number was acked, update smoothed round trip time. 2824 * Since we now have an rtt measurement, cancel the 2825 * timer backoff (cf., Phil Karn's retransmit alg.). 2826 * Recompute the initial retransmit timer. 2827 * 2828 * Some boxes send broken timestamp replies 2829 * during the SYN+ACK phase, ignore 2830 * timestamps of 0 or we could calculate a 2831 * huge RTT and blow up the retransmit timer. 2832 */ 2833 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2834 uint32_t t; 2835 2836 t = tcp_ts_getticks() - to.to_tsecr; 2837 if (!tp->t_rttlow || tp->t_rttlow > t) 2838 tp->t_rttlow = t; 2839 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2840 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2841 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2842 tp->t_rttlow = ticks - tp->t_rtttime; 2843 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2844 } 2845 2846 /* 2847 * If all outstanding data is acked, stop retransmit 2848 * timer and remember to restart (more output or persist). 2849 * If there is more data to be acked, restart retransmit 2850 * timer, using current (possibly backed-off) value. 2851 */ 2852 if (th->th_ack == tp->snd_max) { 2853 tcp_timer_activate(tp, TT_REXMT, 0); 2854 needoutput = 1; 2855 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2856 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2857 2858 /* 2859 * If no data (only SYN) was ACK'd, 2860 * skip rest of ACK processing. 2861 */ 2862 if (acked == 0) 2863 goto step6; 2864 2865 /* 2866 * Let the congestion control algorithm update congestion 2867 * control related information. This typically means increasing 2868 * the congestion window. 2869 */ 2870 cc_ack_received(tp, th, nsegs, CC_ACK); 2871 2872 SOCKBUF_LOCK(&so->so_snd); 2873 if (acked > sbavail(&so->so_snd)) { 2874 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2875 tp->snd_wnd -= sbavail(&so->so_snd); 2876 else 2877 tp->snd_wnd = 0; 2878 mfree = sbcut_locked(&so->so_snd, 2879 (int)sbavail(&so->so_snd)); 2880 ourfinisacked = 1; 2881 } else { 2882 mfree = sbcut_locked(&so->so_snd, acked); 2883 if (tp->snd_wnd >= (uint32_t) acked) 2884 tp->snd_wnd -= acked; 2885 else 2886 tp->snd_wnd = 0; 2887 ourfinisacked = 0; 2888 } 2889 /* NB: sowwakeup_locked() does an implicit unlock. */ 2890 sowwakeup_locked(so); 2891 m_freem(mfree); 2892 /* Detect una wraparound. */ 2893 if (!IN_RECOVERY(tp->t_flags) && 2894 SEQ_GT(tp->snd_una, tp->snd_recover) && 2895 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2896 tp->snd_recover = th->th_ack - 1; 2897 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2898 if (IN_RECOVERY(tp->t_flags) && 2899 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2900 EXIT_RECOVERY(tp->t_flags); 2901 } 2902 tp->snd_una = th->th_ack; 2903 if (tp->t_flags & TF_SACK_PERMIT) { 2904 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2905 tp->snd_recover = tp->snd_una; 2906 } 2907 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2908 tp->snd_nxt = tp->snd_una; 2909 2910 switch (tp->t_state) { 2911 2912 /* 2913 * In FIN_WAIT_1 STATE in addition to the processing 2914 * for the ESTABLISHED state if our FIN is now acknowledged 2915 * then enter FIN_WAIT_2. 2916 */ 2917 case TCPS_FIN_WAIT_1: 2918 if (ourfinisacked) { 2919 /* 2920 * If we can't receive any more 2921 * data, then closing user can proceed. 2922 * Starting the timer is contrary to the 2923 * specification, but if we don't get a FIN 2924 * we'll hang forever. 2925 * 2926 * XXXjl: 2927 * we should release the tp also, and use a 2928 * compressed state. 2929 */ 2930 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2931 soisdisconnected(so); 2932 tcp_timer_activate(tp, TT_2MSL, 2933 (tcp_fast_finwait2_recycle ? 2934 tcp_finwait2_timeout : 2935 TP_MAXIDLE(tp))); 2936 } 2937 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2938 } 2939 break; 2940 2941 /* 2942 * In CLOSING STATE in addition to the processing for 2943 * the ESTABLISHED state if the ACK acknowledges our FIN 2944 * then enter the TIME-WAIT state, otherwise ignore 2945 * the segment. 2946 */ 2947 case TCPS_CLOSING: 2948 if (ourfinisacked) { 2949 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2950 tcp_twstart(tp); 2951 INP_INFO_RUNLOCK(&V_tcbinfo); 2952 m_freem(m); 2953 return; 2954 } 2955 break; 2956 2957 /* 2958 * In LAST_ACK, we may still be waiting for data to drain 2959 * and/or to be acked, as well as for the ack of our FIN. 2960 * If our FIN is now acknowledged, delete the TCB, 2961 * enter the closed state and return. 2962 */ 2963 case TCPS_LAST_ACK: 2964 if (ourfinisacked) { 2965 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2966 tp = tcp_close(tp); 2967 goto drop; 2968 } 2969 break; 2970 } 2971 } 2972 2973 step6: 2974 INP_WLOCK_ASSERT(tp->t_inpcb); 2975 2976 /* 2977 * Update window information. 2978 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2979 */ 2980 if ((thflags & TH_ACK) && 2981 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2982 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2983 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2984 /* keep track of pure window updates */ 2985 if (tlen == 0 && 2986 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2987 TCPSTAT_INC(tcps_rcvwinupd); 2988 tp->snd_wnd = tiwin; 2989 tp->snd_wl1 = th->th_seq; 2990 tp->snd_wl2 = th->th_ack; 2991 if (tp->snd_wnd > tp->max_sndwnd) 2992 tp->max_sndwnd = tp->snd_wnd; 2993 needoutput = 1; 2994 } 2995 2996 /* 2997 * Process segments with URG. 2998 */ 2999 if ((thflags & TH_URG) && th->th_urp && 3000 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3001 /* 3002 * This is a kludge, but if we receive and accept 3003 * random urgent pointers, we'll crash in 3004 * soreceive. It's hard to imagine someone 3005 * actually wanting to send this much urgent data. 3006 */ 3007 SOCKBUF_LOCK(&so->so_rcv); 3008 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 3009 th->th_urp = 0; /* XXX */ 3010 thflags &= ~TH_URG; /* XXX */ 3011 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 3012 goto dodata; /* XXX */ 3013 } 3014 /* 3015 * If this segment advances the known urgent pointer, 3016 * then mark the data stream. This should not happen 3017 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 3018 * a FIN has been received from the remote side. 3019 * In these states we ignore the URG. 3020 * 3021 * According to RFC961 (Assigned Protocols), 3022 * the urgent pointer points to the last octet 3023 * of urgent data. We continue, however, 3024 * to consider it to indicate the first octet 3025 * of data past the urgent section as the original 3026 * spec states (in one of two places). 3027 */ 3028 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 3029 tp->rcv_up = th->th_seq + th->th_urp; 3030 so->so_oobmark = sbavail(&so->so_rcv) + 3031 (tp->rcv_up - tp->rcv_nxt) - 1; 3032 if (so->so_oobmark == 0) 3033 so->so_rcv.sb_state |= SBS_RCVATMARK; 3034 sohasoutofband(so); 3035 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 3036 } 3037 SOCKBUF_UNLOCK(&so->so_rcv); 3038 /* 3039 * Remove out of band data so doesn't get presented to user. 3040 * This can happen independent of advancing the URG pointer, 3041 * but if two URG's are pending at once, some out-of-band 3042 * data may creep in... ick. 3043 */ 3044 if (th->th_urp <= (uint32_t)tlen && 3045 !(so->so_options & SO_OOBINLINE)) { 3046 /* hdr drop is delayed */ 3047 tcp_pulloutofband(so, th, m, drop_hdrlen); 3048 } 3049 } else { 3050 /* 3051 * If no out of band data is expected, 3052 * pull receive urgent pointer along 3053 * with the receive window. 3054 */ 3055 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 3056 tp->rcv_up = tp->rcv_nxt; 3057 } 3058 dodata: /* XXX */ 3059 INP_WLOCK_ASSERT(tp->t_inpcb); 3060 3061 /* 3062 * Process the segment text, merging it into the TCP sequencing queue, 3063 * and arranging for acknowledgment of receipt if necessary. 3064 * This process logically involves adjusting tp->rcv_wnd as data 3065 * is presented to the user (this happens in tcp_usrreq.c, 3066 * case PRU_RCVD). If a FIN has already been received on this 3067 * connection then we just ignore the text. 3068 */ 3069 #ifdef TCP_RFC7413 3070 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 3071 IS_FASTOPEN(tp->t_flags)); 3072 #else 3073 #define tfo_syn (false) 3074 #endif 3075 if ((tlen || (thflags & TH_FIN) || tfo_syn) && 3076 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3077 tcp_seq save_start = th->th_seq; 3078 m_adj(m, drop_hdrlen); /* delayed header drop */ 3079 /* 3080 * Insert segment which includes th into TCP reassembly queue 3081 * with control block tp. Set thflags to whether reassembly now 3082 * includes a segment with FIN. This handles the common case 3083 * inline (segment is the next to be received on an established 3084 * connection, and the queue is empty), avoiding linkage into 3085 * and removal from the queue and repetition of various 3086 * conversions. 3087 * Set DELACK for segments received in order, but ack 3088 * immediately when segments are out of order (so 3089 * fast retransmit can work). 3090 */ 3091 if (th->th_seq == tp->rcv_nxt && 3092 LIST_EMPTY(&tp->t_segq) && 3093 (TCPS_HAVEESTABLISHED(tp->t_state) || 3094 tfo_syn)) { 3095 if (DELAY_ACK(tp, tlen) || tfo_syn) 3096 tp->t_flags |= TF_DELACK; 3097 else 3098 tp->t_flags |= TF_ACKNOW; 3099 tp->rcv_nxt += tlen; 3100 thflags = th->th_flags & TH_FIN; 3101 TCPSTAT_INC(tcps_rcvpack); 3102 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3103 SOCKBUF_LOCK(&so->so_rcv); 3104 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3105 m_freem(m); 3106 else 3107 sbappendstream_locked(&so->so_rcv, m, 0); 3108 /* NB: sorwakeup_locked() does an implicit unlock. */ 3109 sorwakeup_locked(so); 3110 } else { 3111 /* 3112 * XXX: Due to the header drop above "th" is 3113 * theoretically invalid by now. Fortunately 3114 * m_adj() doesn't actually frees any mbufs 3115 * when trimming from the head. 3116 */ 3117 thflags = tcp_reass(tp, th, &tlen, m); 3118 tp->t_flags |= TF_ACKNOW; 3119 } 3120 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 3121 tcp_update_sack_list(tp, save_start, save_start + tlen); 3122 #if 0 3123 /* 3124 * Note the amount of data that peer has sent into 3125 * our window, in order to estimate the sender's 3126 * buffer size. 3127 * XXX: Unused. 3128 */ 3129 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3130 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3131 else 3132 len = so->so_rcv.sb_hiwat; 3133 #endif 3134 } else { 3135 m_freem(m); 3136 thflags &= ~TH_FIN; 3137 } 3138 3139 /* 3140 * If FIN is received ACK the FIN and let the user know 3141 * that the connection is closing. 3142 */ 3143 if (thflags & TH_FIN) { 3144 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3145 socantrcvmore(so); 3146 /* 3147 * If connection is half-synchronized 3148 * (ie NEEDSYN flag on) then delay ACK, 3149 * so it may be piggybacked when SYN is sent. 3150 * Otherwise, since we received a FIN then no 3151 * more input can be expected, send ACK now. 3152 */ 3153 if (tp->t_flags & TF_NEEDSYN) 3154 tp->t_flags |= TF_DELACK; 3155 else 3156 tp->t_flags |= TF_ACKNOW; 3157 tp->rcv_nxt++; 3158 } 3159 switch (tp->t_state) { 3160 3161 /* 3162 * In SYN_RECEIVED and ESTABLISHED STATES 3163 * enter the CLOSE_WAIT state. 3164 */ 3165 case TCPS_SYN_RECEIVED: 3166 tp->t_starttime = ticks; 3167 /* FALLTHROUGH */ 3168 case TCPS_ESTABLISHED: 3169 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3170 break; 3171 3172 /* 3173 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3174 * enter the CLOSING state. 3175 */ 3176 case TCPS_FIN_WAIT_1: 3177 tcp_state_change(tp, TCPS_CLOSING); 3178 break; 3179 3180 /* 3181 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3182 * starting the time-wait timer, turning off the other 3183 * standard timers. 3184 */ 3185 case TCPS_FIN_WAIT_2: 3186 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 3187 KASSERT(ti_locked == TI_RLOCKED, ("%s: dodata " 3188 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 3189 ti_locked)); 3190 3191 tcp_twstart(tp); 3192 INP_INFO_RUNLOCK(&V_tcbinfo); 3193 return; 3194 } 3195 } 3196 if (ti_locked == TI_RLOCKED) 3197 INP_INFO_RUNLOCK(&V_tcbinfo); 3198 ti_locked = TI_UNLOCKED; 3199 3200 #ifdef TCPDEBUG 3201 if (so->so_options & SO_DEBUG) 3202 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3203 &tcp_savetcp, 0); 3204 #endif 3205 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3206 3207 /* 3208 * Return any desired output. 3209 */ 3210 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3211 (void) tp->t_fb->tfb_tcp_output(tp); 3212 3213 check_delack: 3214 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 3215 __func__, ti_locked)); 3216 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3217 INP_WLOCK_ASSERT(tp->t_inpcb); 3218 3219 if (tp->t_flags & TF_DELACK) { 3220 tp->t_flags &= ~TF_DELACK; 3221 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3222 } 3223 INP_WUNLOCK(tp->t_inpcb); 3224 return; 3225 3226 dropafterack: 3227 /* 3228 * Generate an ACK dropping incoming segment if it occupies 3229 * sequence space, where the ACK reflects our state. 3230 * 3231 * We can now skip the test for the RST flag since all 3232 * paths to this code happen after packets containing 3233 * RST have been dropped. 3234 * 3235 * In the SYN-RECEIVED state, don't send an ACK unless the 3236 * segment we received passes the SYN-RECEIVED ACK test. 3237 * If it fails send a RST. This breaks the loop in the 3238 * "LAND" DoS attack, and also prevents an ACK storm 3239 * between two listening ports that have been sent forged 3240 * SYN segments, each with the source address of the other. 3241 */ 3242 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3243 (SEQ_GT(tp->snd_una, th->th_ack) || 3244 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3245 rstreason = BANDLIM_RST_OPENPORT; 3246 goto dropwithreset; 3247 } 3248 #ifdef TCPDEBUG 3249 if (so->so_options & SO_DEBUG) 3250 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3251 &tcp_savetcp, 0); 3252 #endif 3253 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3254 if (ti_locked == TI_RLOCKED) 3255 INP_INFO_RUNLOCK(&V_tcbinfo); 3256 ti_locked = TI_UNLOCKED; 3257 3258 tp->t_flags |= TF_ACKNOW; 3259 (void) tp->t_fb->tfb_tcp_output(tp); 3260 INP_WUNLOCK(tp->t_inpcb); 3261 m_freem(m); 3262 return; 3263 3264 dropwithreset: 3265 if (ti_locked == TI_RLOCKED) 3266 INP_INFO_RUNLOCK(&V_tcbinfo); 3267 ti_locked = TI_UNLOCKED; 3268 3269 if (tp != NULL) { 3270 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3271 INP_WUNLOCK(tp->t_inpcb); 3272 } else 3273 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3274 return; 3275 3276 drop: 3277 if (ti_locked == TI_RLOCKED) { 3278 INP_INFO_RUNLOCK(&V_tcbinfo); 3279 ti_locked = TI_UNLOCKED; 3280 } 3281 #ifdef INVARIANTS 3282 else 3283 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3284 #endif 3285 3286 /* 3287 * Drop space held by incoming segment and return. 3288 */ 3289 #ifdef TCPDEBUG 3290 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3291 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3292 &tcp_savetcp, 0); 3293 #endif 3294 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3295 if (tp != NULL) 3296 INP_WUNLOCK(tp->t_inpcb); 3297 m_freem(m); 3298 #ifndef TCP_RFC7413 3299 #undef tfo_syn 3300 #endif 3301 } 3302 3303 /* 3304 * Issue RST and make ACK acceptable to originator of segment. 3305 * The mbuf must still include the original packet header. 3306 * tp may be NULL. 3307 */ 3308 void 3309 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3310 int tlen, int rstreason) 3311 { 3312 #ifdef INET 3313 struct ip *ip; 3314 #endif 3315 #ifdef INET6 3316 struct ip6_hdr *ip6; 3317 #endif 3318 3319 if (tp != NULL) { 3320 INP_WLOCK_ASSERT(tp->t_inpcb); 3321 } 3322 3323 /* Don't bother if destination was broadcast/multicast. */ 3324 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3325 goto drop; 3326 #ifdef INET6 3327 if (mtod(m, struct ip *)->ip_v == 6) { 3328 ip6 = mtod(m, struct ip6_hdr *); 3329 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3330 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3331 goto drop; 3332 /* IPv6 anycast check is done at tcp6_input() */ 3333 } 3334 #endif 3335 #if defined(INET) && defined(INET6) 3336 else 3337 #endif 3338 #ifdef INET 3339 { 3340 ip = mtod(m, struct ip *); 3341 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3342 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3343 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3344 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3345 goto drop; 3346 } 3347 #endif 3348 3349 /* Perform bandwidth limiting. */ 3350 if (badport_bandlim(rstreason) < 0) 3351 goto drop; 3352 3353 /* tcp_respond consumes the mbuf chain. */ 3354 if (th->th_flags & TH_ACK) { 3355 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3356 th->th_ack, TH_RST); 3357 } else { 3358 if (th->th_flags & TH_SYN) 3359 tlen++; 3360 if (th->th_flags & TH_FIN) 3361 tlen++; 3362 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3363 (tcp_seq)0, TH_RST|TH_ACK); 3364 } 3365 return; 3366 drop: 3367 m_freem(m); 3368 } 3369 3370 /* 3371 * Parse TCP options and place in tcpopt. 3372 */ 3373 void 3374 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3375 { 3376 int opt, optlen; 3377 3378 to->to_flags = 0; 3379 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3380 opt = cp[0]; 3381 if (opt == TCPOPT_EOL) 3382 break; 3383 if (opt == TCPOPT_NOP) 3384 optlen = 1; 3385 else { 3386 if (cnt < 2) 3387 break; 3388 optlen = cp[1]; 3389 if (optlen < 2 || optlen > cnt) 3390 break; 3391 } 3392 switch (opt) { 3393 case TCPOPT_MAXSEG: 3394 if (optlen != TCPOLEN_MAXSEG) 3395 continue; 3396 if (!(flags & TO_SYN)) 3397 continue; 3398 to->to_flags |= TOF_MSS; 3399 bcopy((char *)cp + 2, 3400 (char *)&to->to_mss, sizeof(to->to_mss)); 3401 to->to_mss = ntohs(to->to_mss); 3402 break; 3403 case TCPOPT_WINDOW: 3404 if (optlen != TCPOLEN_WINDOW) 3405 continue; 3406 if (!(flags & TO_SYN)) 3407 continue; 3408 to->to_flags |= TOF_SCALE; 3409 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3410 break; 3411 case TCPOPT_TIMESTAMP: 3412 if (optlen != TCPOLEN_TIMESTAMP) 3413 continue; 3414 to->to_flags |= TOF_TS; 3415 bcopy((char *)cp + 2, 3416 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3417 to->to_tsval = ntohl(to->to_tsval); 3418 bcopy((char *)cp + 6, 3419 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3420 to->to_tsecr = ntohl(to->to_tsecr); 3421 break; 3422 #ifdef TCP_SIGNATURE 3423 /* 3424 * XXX In order to reply to a host which has set the 3425 * TCP_SIGNATURE option in its initial SYN, we have to 3426 * record the fact that the option was observed here 3427 * for the syncache code to perform the correct response. 3428 */ 3429 case TCPOPT_SIGNATURE: 3430 if (optlen != TCPOLEN_SIGNATURE) 3431 continue; 3432 to->to_flags |= TOF_SIGNATURE; 3433 to->to_signature = cp + 2; 3434 break; 3435 #endif 3436 case TCPOPT_SACK_PERMITTED: 3437 if (optlen != TCPOLEN_SACK_PERMITTED) 3438 continue; 3439 if (!(flags & TO_SYN)) 3440 continue; 3441 if (!V_tcp_do_sack) 3442 continue; 3443 to->to_flags |= TOF_SACKPERM; 3444 break; 3445 case TCPOPT_SACK: 3446 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3447 continue; 3448 if (flags & TO_SYN) 3449 continue; 3450 to->to_flags |= TOF_SACK; 3451 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3452 to->to_sacks = cp + 2; 3453 TCPSTAT_INC(tcps_sack_rcv_blocks); 3454 break; 3455 #ifdef TCP_RFC7413 3456 case TCPOPT_FAST_OPEN: 3457 if ((optlen != TCPOLEN_FAST_OPEN_EMPTY) && 3458 (optlen < TCPOLEN_FAST_OPEN_MIN) && 3459 (optlen > TCPOLEN_FAST_OPEN_MAX)) 3460 continue; 3461 if (!(flags & TO_SYN)) 3462 continue; 3463 if (!V_tcp_fastopen_enabled) 3464 continue; 3465 to->to_flags |= TOF_FASTOPEN; 3466 to->to_tfo_len = optlen - 2; 3467 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3468 break; 3469 #endif 3470 default: 3471 continue; 3472 } 3473 } 3474 } 3475 3476 /* 3477 * Pull out of band byte out of a segment so 3478 * it doesn't appear in the user's data queue. 3479 * It is still reflected in the segment length for 3480 * sequencing purposes. 3481 */ 3482 void 3483 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3484 int off) 3485 { 3486 int cnt = off + th->th_urp - 1; 3487 3488 while (cnt >= 0) { 3489 if (m->m_len > cnt) { 3490 char *cp = mtod(m, caddr_t) + cnt; 3491 struct tcpcb *tp = sototcpcb(so); 3492 3493 INP_WLOCK_ASSERT(tp->t_inpcb); 3494 3495 tp->t_iobc = *cp; 3496 tp->t_oobflags |= TCPOOB_HAVEDATA; 3497 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3498 m->m_len--; 3499 if (m->m_flags & M_PKTHDR) 3500 m->m_pkthdr.len--; 3501 return; 3502 } 3503 cnt -= m->m_len; 3504 m = m->m_next; 3505 if (m == NULL) 3506 break; 3507 } 3508 panic("tcp_pulloutofband"); 3509 } 3510 3511 /* 3512 * Collect new round-trip time estimate 3513 * and update averages and current timeout. 3514 */ 3515 void 3516 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3517 { 3518 int delta; 3519 3520 INP_WLOCK_ASSERT(tp->t_inpcb); 3521 3522 TCPSTAT_INC(tcps_rttupdated); 3523 tp->t_rttupdated++; 3524 if (tp->t_srtt != 0) { 3525 /* 3526 * srtt is stored as fixed point with 5 bits after the 3527 * binary point (i.e., scaled by 8). The following magic 3528 * is equivalent to the smoothing algorithm in rfc793 with 3529 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3530 * point). Adjust rtt to origin 0. 3531 */ 3532 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3533 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3534 3535 if ((tp->t_srtt += delta) <= 0) 3536 tp->t_srtt = 1; 3537 3538 /* 3539 * We accumulate a smoothed rtt variance (actually, a 3540 * smoothed mean difference), then set the retransmit 3541 * timer to smoothed rtt + 4 times the smoothed variance. 3542 * rttvar is stored as fixed point with 4 bits after the 3543 * binary point (scaled by 16). The following is 3544 * equivalent to rfc793 smoothing with an alpha of .75 3545 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3546 * rfc793's wired-in beta. 3547 */ 3548 if (delta < 0) 3549 delta = -delta; 3550 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3551 if ((tp->t_rttvar += delta) <= 0) 3552 tp->t_rttvar = 1; 3553 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3554 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3555 } else { 3556 /* 3557 * No rtt measurement yet - use the unsmoothed rtt. 3558 * Set the variance to half the rtt (so our first 3559 * retransmit happens at 3*rtt). 3560 */ 3561 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3562 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3563 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3564 } 3565 tp->t_rtttime = 0; 3566 tp->t_rxtshift = 0; 3567 3568 /* 3569 * the retransmit should happen at rtt + 4 * rttvar. 3570 * Because of the way we do the smoothing, srtt and rttvar 3571 * will each average +1/2 tick of bias. When we compute 3572 * the retransmit timer, we want 1/2 tick of rounding and 3573 * 1 extra tick because of +-1/2 tick uncertainty in the 3574 * firing of the timer. The bias will give us exactly the 3575 * 1.5 tick we need. But, because the bias is 3576 * statistical, we have to test that we don't drop below 3577 * the minimum feasible timer (which is 2 ticks). 3578 */ 3579 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3580 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3581 3582 /* 3583 * We received an ack for a packet that wasn't retransmitted; 3584 * it is probably safe to discard any error indications we've 3585 * received recently. This isn't quite right, but close enough 3586 * for now (a route might have failed after we sent a segment, 3587 * and the return path might not be symmetrical). 3588 */ 3589 tp->t_softerror = 0; 3590 } 3591 3592 /* 3593 * Determine a reasonable value for maxseg size. 3594 * If the route is known, check route for mtu. 3595 * If none, use an mss that can be handled on the outgoing interface 3596 * without forcing IP to fragment. If no route is found, route has no mtu, 3597 * or the destination isn't local, use a default, hopefully conservative 3598 * size (usually 512 or the default IP max size, but no more than the mtu 3599 * of the interface), as we can't discover anything about intervening 3600 * gateways or networks. We also initialize the congestion/slow start 3601 * window to be a single segment if the destination isn't local. 3602 * While looking at the routing entry, we also initialize other path-dependent 3603 * parameters from pre-set or cached values in the routing entry. 3604 * 3605 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3606 * IP options, e.g. IPSEC data, since length of this data may vary, and 3607 * thus it is calculated for every segment separately in tcp_output(). 3608 * 3609 * NOTE that this routine is only called when we process an incoming 3610 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3611 * settings are handled in tcp_mssopt(). 3612 */ 3613 void 3614 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3615 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3616 { 3617 int mss = 0; 3618 uint32_t maxmtu = 0; 3619 struct inpcb *inp = tp->t_inpcb; 3620 struct hc_metrics_lite metrics; 3621 #ifdef INET6 3622 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3623 size_t min_protoh = isipv6 ? 3624 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3625 sizeof (struct tcpiphdr); 3626 #else 3627 const size_t min_protoh = sizeof(struct tcpiphdr); 3628 #endif 3629 3630 INP_WLOCK_ASSERT(tp->t_inpcb); 3631 3632 if (mtuoffer != -1) { 3633 KASSERT(offer == -1, ("%s: conflict", __func__)); 3634 offer = mtuoffer - min_protoh; 3635 } 3636 3637 /* Initialize. */ 3638 #ifdef INET6 3639 if (isipv6) { 3640 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3641 tp->t_maxseg = V_tcp_v6mssdflt; 3642 } 3643 #endif 3644 #if defined(INET) && defined(INET6) 3645 else 3646 #endif 3647 #ifdef INET 3648 { 3649 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3650 tp->t_maxseg = V_tcp_mssdflt; 3651 } 3652 #endif 3653 3654 /* 3655 * No route to sender, stay with default mss and return. 3656 */ 3657 if (maxmtu == 0) { 3658 /* 3659 * In case we return early we need to initialize metrics 3660 * to a defined state as tcp_hc_get() would do for us 3661 * if there was no cache hit. 3662 */ 3663 if (metricptr != NULL) 3664 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3665 return; 3666 } 3667 3668 /* What have we got? */ 3669 switch (offer) { 3670 case 0: 3671 /* 3672 * Offer == 0 means that there was no MSS on the SYN 3673 * segment, in this case we use tcp_mssdflt as 3674 * already assigned to t_maxseg above. 3675 */ 3676 offer = tp->t_maxseg; 3677 break; 3678 3679 case -1: 3680 /* 3681 * Offer == -1 means that we didn't receive SYN yet. 3682 */ 3683 /* FALLTHROUGH */ 3684 3685 default: 3686 /* 3687 * Prevent DoS attack with too small MSS. Round up 3688 * to at least minmss. 3689 */ 3690 offer = max(offer, V_tcp_minmss); 3691 } 3692 3693 /* 3694 * rmx information is now retrieved from tcp_hostcache. 3695 */ 3696 tcp_hc_get(&inp->inp_inc, &metrics); 3697 if (metricptr != NULL) 3698 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3699 3700 /* 3701 * If there's a discovered mtu in tcp hostcache, use it. 3702 * Else, use the link mtu. 3703 */ 3704 if (metrics.rmx_mtu) 3705 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3706 else { 3707 #ifdef INET6 3708 if (isipv6) { 3709 mss = maxmtu - min_protoh; 3710 if (!V_path_mtu_discovery && 3711 !in6_localaddr(&inp->in6p_faddr)) 3712 mss = min(mss, V_tcp_v6mssdflt); 3713 } 3714 #endif 3715 #if defined(INET) && defined(INET6) 3716 else 3717 #endif 3718 #ifdef INET 3719 { 3720 mss = maxmtu - min_protoh; 3721 if (!V_path_mtu_discovery && 3722 !in_localaddr(inp->inp_faddr)) 3723 mss = min(mss, V_tcp_mssdflt); 3724 } 3725 #endif 3726 /* 3727 * XXX - The above conditional (mss = maxmtu - min_protoh) 3728 * probably violates the TCP spec. 3729 * The problem is that, since we don't know the 3730 * other end's MSS, we are supposed to use a conservative 3731 * default. But, if we do that, then MTU discovery will 3732 * never actually take place, because the conservative 3733 * default is much less than the MTUs typically seen 3734 * on the Internet today. For the moment, we'll sweep 3735 * this under the carpet. 3736 * 3737 * The conservative default might not actually be a problem 3738 * if the only case this occurs is when sending an initial 3739 * SYN with options and data to a host we've never talked 3740 * to before. Then, they will reply with an MSS value which 3741 * will get recorded and the new parameters should get 3742 * recomputed. For Further Study. 3743 */ 3744 } 3745 mss = min(mss, offer); 3746 3747 /* 3748 * Sanity check: make sure that maxseg will be large 3749 * enough to allow some data on segments even if the 3750 * all the option space is used (40bytes). Otherwise 3751 * funny things may happen in tcp_output. 3752 * 3753 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3754 */ 3755 mss = max(mss, 64); 3756 3757 tp->t_maxseg = mss; 3758 } 3759 3760 void 3761 tcp_mss(struct tcpcb *tp, int offer) 3762 { 3763 int mss; 3764 uint32_t bufsize; 3765 struct inpcb *inp; 3766 struct socket *so; 3767 struct hc_metrics_lite metrics; 3768 struct tcp_ifcap cap; 3769 3770 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3771 3772 bzero(&cap, sizeof(cap)); 3773 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3774 3775 mss = tp->t_maxseg; 3776 inp = tp->t_inpcb; 3777 3778 /* 3779 * If there's a pipesize, change the socket buffer to that size, 3780 * don't change if sb_hiwat is different than default (then it 3781 * has been changed on purpose with setsockopt). 3782 * Make the socket buffers an integral number of mss units; 3783 * if the mss is larger than the socket buffer, decrease the mss. 3784 */ 3785 so = inp->inp_socket; 3786 SOCKBUF_LOCK(&so->so_snd); 3787 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3788 bufsize = metrics.rmx_sendpipe; 3789 else 3790 bufsize = so->so_snd.sb_hiwat; 3791 if (bufsize < mss) 3792 mss = bufsize; 3793 else { 3794 bufsize = roundup(bufsize, mss); 3795 if (bufsize > sb_max) 3796 bufsize = sb_max; 3797 if (bufsize > so->so_snd.sb_hiwat) 3798 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3799 } 3800 SOCKBUF_UNLOCK(&so->so_snd); 3801 /* 3802 * Sanity check: make sure that maxseg will be large 3803 * enough to allow some data on segments even if the 3804 * all the option space is used (40bytes). Otherwise 3805 * funny things may happen in tcp_output. 3806 * 3807 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3808 */ 3809 tp->t_maxseg = max(mss, 64); 3810 3811 SOCKBUF_LOCK(&so->so_rcv); 3812 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3813 bufsize = metrics.rmx_recvpipe; 3814 else 3815 bufsize = so->so_rcv.sb_hiwat; 3816 if (bufsize > mss) { 3817 bufsize = roundup(bufsize, mss); 3818 if (bufsize > sb_max) 3819 bufsize = sb_max; 3820 if (bufsize > so->so_rcv.sb_hiwat) 3821 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3822 } 3823 SOCKBUF_UNLOCK(&so->so_rcv); 3824 3825 /* Check the interface for TSO capabilities. */ 3826 if (cap.ifcap & CSUM_TSO) { 3827 tp->t_flags |= TF_TSO; 3828 tp->t_tsomax = cap.tsomax; 3829 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3830 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3831 } 3832 } 3833 3834 /* 3835 * Determine the MSS option to send on an outgoing SYN. 3836 */ 3837 int 3838 tcp_mssopt(struct in_conninfo *inc) 3839 { 3840 int mss = 0; 3841 uint32_t thcmtu = 0; 3842 uint32_t maxmtu = 0; 3843 size_t min_protoh; 3844 3845 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3846 3847 #ifdef INET6 3848 if (inc->inc_flags & INC_ISIPV6) { 3849 mss = V_tcp_v6mssdflt; 3850 maxmtu = tcp_maxmtu6(inc, NULL); 3851 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3852 } 3853 #endif 3854 #if defined(INET) && defined(INET6) 3855 else 3856 #endif 3857 #ifdef INET 3858 { 3859 mss = V_tcp_mssdflt; 3860 maxmtu = tcp_maxmtu(inc, NULL); 3861 min_protoh = sizeof(struct tcpiphdr); 3862 } 3863 #endif 3864 #if defined(INET6) || defined(INET) 3865 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3866 #endif 3867 3868 if (maxmtu && thcmtu) 3869 mss = min(maxmtu, thcmtu) - min_protoh; 3870 else if (maxmtu || thcmtu) 3871 mss = max(maxmtu, thcmtu) - min_protoh; 3872 3873 return (mss); 3874 } 3875 3876 3877 /* 3878 * On a partial ack arrives, force the retransmission of the 3879 * next unacknowledged segment. Do not clear tp->t_dupacks. 3880 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3881 * be started again. 3882 */ 3883 void 3884 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3885 { 3886 tcp_seq onxt = tp->snd_nxt; 3887 uint32_t ocwnd = tp->snd_cwnd; 3888 u_int maxseg = tcp_maxseg(tp); 3889 3890 INP_WLOCK_ASSERT(tp->t_inpcb); 3891 3892 tcp_timer_activate(tp, TT_REXMT, 0); 3893 tp->t_rtttime = 0; 3894 tp->snd_nxt = th->th_ack; 3895 /* 3896 * Set snd_cwnd to one segment beyond acknowledged offset. 3897 * (tp->snd_una has not yet been updated when this function is called.) 3898 */ 3899 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3900 tp->t_flags |= TF_ACKNOW; 3901 (void) tp->t_fb->tfb_tcp_output(tp); 3902 tp->snd_cwnd = ocwnd; 3903 if (SEQ_GT(onxt, tp->snd_nxt)) 3904 tp->snd_nxt = onxt; 3905 /* 3906 * Partial window deflation. Relies on fact that tp->snd_una 3907 * not updated yet. 3908 */ 3909 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3910 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3911 else 3912 tp->snd_cwnd = 0; 3913 tp->snd_cwnd += maxseg; 3914 } 3915 3916 int 3917 tcp_compute_pipe(struct tcpcb *tp) 3918 { 3919 return (tp->snd_max - tp->snd_una + 3920 tp->sackhint.sack_bytes_rexmit - 3921 tp->sackhint.sacked_bytes); 3922 } 3923