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