1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 2007-2008,2010 7 * Swinburne University of Technology, Melbourne, Australia. 8 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> 9 * Copyright (c) 2010 The FreeBSD Foundation 10 * Copyright (c) 2010-2011 Juniper Networks, Inc. 11 * All rights reserved. 12 * 13 * Portions of this software were developed at the Centre for Advanced Internet 14 * Architectures, Swinburne University of Technology, by Lawrence Stewart, 15 * James Healy and David Hayes, made possible in part by a grant from the Cisco 16 * University Research Program Fund at Community Foundation Silicon Valley. 17 * 18 * Portions of this software were developed at the Centre for Advanced 19 * Internet Architectures, Swinburne University of Technology, Melbourne, 20 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 21 * 22 * Portions of this software were developed by Robert N. M. Watson under 23 * contract to Juniper Networks, Inc. 24 * 25 * Redistribution and use in source and binary forms, with or without 26 * modification, are permitted provided that the following conditions 27 * are met: 28 * 1. Redistributions of source code must retain the above copyright 29 * notice, this list of conditions and the following disclaimer. 30 * 2. Redistributions in binary form must reproduce the above copyright 31 * notice, this list of conditions and the following disclaimer in the 32 * documentation and/or other materials provided with the distribution. 33 * 3. Neither the name of the University nor the names of its contributors 34 * may be used to endorse or promote products derived from this software 35 * without specific prior written permission. 36 * 37 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 38 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 40 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 41 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 42 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 43 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 45 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 46 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 47 * SUCH DAMAGE. 48 * 49 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 50 */ 51 52 #include <sys/cdefs.h> 53 __FBSDID("$FreeBSD$"); 54 55 #include "opt_inet.h" 56 #include "opt_inet6.h" 57 #include "opt_ipsec.h" 58 #include "opt_tcpdebug.h" 59 60 #include <sys/param.h> 61 #include <sys/arb.h> 62 #include <sys/kernel.h> 63 #ifdef TCP_HHOOK 64 #include <sys/hhook.h> 65 #endif 66 #include <sys/malloc.h> 67 #include <sys/mbuf.h> 68 #include <sys/proc.h> /* for proc0 declaration */ 69 #include <sys/protosw.h> 70 #include <sys/qmath.h> 71 #include <sys/sdt.h> 72 #include <sys/signalvar.h> 73 #include <sys/socket.h> 74 #include <sys/socketvar.h> 75 #include <sys/sysctl.h> 76 #include <sys/syslog.h> 77 #include <sys/systm.h> 78 #include <sys/stats.h> 79 80 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 81 82 #include <vm/uma.h> 83 84 #include <net/if.h> 85 #include <net/if_var.h> 86 #include <net/route.h> 87 #include <net/vnet.h> 88 89 #define TCPSTATES /* for logging */ 90 91 #include <netinet/in.h> 92 #include <netinet/in_kdtrace.h> 93 #include <netinet/in_pcb.h> 94 #include <netinet/in_systm.h> 95 #include <netinet/ip.h> 96 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 97 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 98 #include <netinet/ip_var.h> 99 #include <netinet/ip_options.h> 100 #include <netinet/ip6.h> 101 #include <netinet/icmp6.h> 102 #include <netinet6/in6_pcb.h> 103 #include <netinet6/in6_var.h> 104 #include <netinet6/ip6_var.h> 105 #include <netinet6/nd6.h> 106 #include <netinet/tcp.h> 107 #include <netinet/tcp_fsm.h> 108 #include <netinet/tcp_log_buf.h> 109 #include <netinet/tcp_seq.h> 110 #include <netinet/tcp_timer.h> 111 #include <netinet/tcp_var.h> 112 #include <netinet6/tcp6_var.h> 113 #include <netinet/tcpip.h> 114 #include <netinet/cc/cc.h> 115 #include <netinet/tcp_fastopen.h> 116 #ifdef TCPPCAP 117 #include <netinet/tcp_pcap.h> 118 #endif 119 #include <netinet/tcp_syncache.h> 120 #ifdef TCPDEBUG 121 #include <netinet/tcp_debug.h> 122 #endif /* TCPDEBUG */ 123 #ifdef TCP_OFFLOAD 124 #include <netinet/tcp_offload.h> 125 #endif 126 127 #include <netipsec/ipsec_support.h> 128 129 #include <machine/in_cksum.h> 130 131 #include <security/mac/mac_framework.h> 132 133 const int tcprexmtthresh = 3; 134 135 VNET_DEFINE(int, tcp_log_in_vain) = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_VNET | CTLFLAG_RW, 137 &VNET_NAME(tcp_log_in_vain), 0, 138 "Log all incoming TCP segments to closed ports"); 139 140 VNET_DEFINE(int, blackhole) = 0; 141 #define V_blackhole VNET(blackhole) 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 143 &VNET_NAME(blackhole), 0, 144 "Do not send RST on segments to closed ports"); 145 146 VNET_DEFINE(int, tcp_delack_enabled) = 1; 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 148 &VNET_NAME(tcp_delack_enabled), 0, 149 "Delay ACK to try and piggyback it onto a data packet"); 150 151 VNET_DEFINE(int, drop_synfin) = 0; 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_newcwv) = 0; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newcwv, CTLFLAG_VNET | CTLFLAG_RW, 158 &VNET_NAME(tcp_do_newcwv), 0, 159 "Enable New Congestion Window Validation per RFC7661"); 160 161 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 163 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 164 "Use calculated pipe/in-flight bytes per RFC 6675"); 165 166 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 168 &VNET_NAME(tcp_do_rfc3042), 0, 169 "Enable RFC 3042 (Limited Transmit)"); 170 171 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 172 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 173 &VNET_NAME(tcp_do_rfc3390), 0, 174 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 175 176 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 178 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 179 "Slow-start flight size (initial congestion window) in number of segments"); 180 181 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 183 &VNET_NAME(tcp_do_rfc3465), 0, 184 "Enable RFC 3465 (Appropriate Byte Counting)"); 185 186 VNET_DEFINE(int, tcp_abc_l_var) = 2; 187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 188 &VNET_NAME(tcp_abc_l_var), 2, 189 "Cap the max cwnd increment during slow-start to this number of segments"); 190 191 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, 192 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 193 "TCP ECN"); 194 195 VNET_DEFINE(int, tcp_do_ecn) = 2; 196 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 197 &VNET_NAME(tcp_do_ecn), 0, 198 "TCP ECN support"); 199 200 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 201 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 202 &VNET_NAME(tcp_ecn_maxretries), 0, 203 "Max retries before giving up on ECN"); 204 205 VNET_DEFINE(int, tcp_insecure_syn) = 0; 206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 207 &VNET_NAME(tcp_insecure_syn), 0, 208 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 209 210 VNET_DEFINE(int, tcp_insecure_rst) = 0; 211 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 212 &VNET_NAME(tcp_insecure_rst), 0, 213 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 214 215 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 216 #define V_tcp_recvspace VNET(tcp_recvspace) 217 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 218 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 219 220 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 221 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 222 &VNET_NAME(tcp_do_autorcvbuf), 0, 223 "Enable automatic receive buffer sizing"); 224 225 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 226 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 227 &VNET_NAME(tcp_autorcvbuf_max), 0, 228 "Max size of automatic receive buffer"); 229 230 VNET_DEFINE(struct inpcbhead, tcb); 231 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 232 VNET_DEFINE(struct inpcbinfo, tcbinfo); 233 234 /* 235 * TCP statistics are stored in an array of counter(9)s, which size matches 236 * size of struct tcpstat. TCP running connection count is a regular array. 237 */ 238 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 239 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 240 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 241 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 242 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 243 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 244 "TCP connection counts by TCP state"); 245 246 static void 247 tcp_vnet_init(const void *unused) 248 { 249 250 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK); 251 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK); 252 } 253 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 254 tcp_vnet_init, NULL); 255 256 #ifdef VIMAGE 257 static void 258 tcp_vnet_uninit(const void *unused) 259 { 260 261 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES); 262 VNET_PCPUSTAT_FREE(tcpstat); 263 } 264 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 265 tcp_vnet_uninit, NULL); 266 #endif /* VIMAGE */ 267 268 /* 269 * Kernel module interface for updating tcpstat. The first argument is an index 270 * into tcpstat treated as an array. 271 */ 272 void 273 kmod_tcpstat_add(int statnum, int val) 274 { 275 276 counter_u64_add(VNET(tcpstat)[statnum], val); 277 } 278 279 #ifdef TCP_HHOOK 280 /* 281 * Wrapper for the TCP established input helper hook. 282 */ 283 void 284 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 285 { 286 struct tcp_hhook_data hhook_data; 287 288 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 289 hhook_data.tp = tp; 290 hhook_data.th = th; 291 hhook_data.to = to; 292 293 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 294 tp->osd); 295 } 296 } 297 #endif 298 299 /* 300 * CC wrapper hook functions 301 */ 302 void 303 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 304 uint16_t type) 305 { 306 #ifdef STATS 307 int32_t gput; 308 #endif 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 ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) || 315 (V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) && 316 (tp->snd_cwnd < (tcp_compute_pipe(tp) * 2)))) 317 tp->ccv->flags |= CCF_CWND_LIMITED; 318 else 319 tp->ccv->flags &= ~CCF_CWND_LIMITED; 320 321 if (type == CC_ACK) { 322 #ifdef STATS 323 stats_voi_update_abs_s32(tp->t_stats, VOI_TCP_CALCFRWINDIFF, 324 ((int32_t)tp->snd_cwnd) - tp->snd_wnd); 325 if (!IN_RECOVERY(tp->t_flags)) 326 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_ACKLEN, 327 tp->ccv->bytes_this_ack / (tcp_maxseg(tp) * nsegs)); 328 if ((tp->t_flags & TF_GPUTINPROG) && 329 SEQ_GEQ(th->th_ack, tp->gput_ack)) { 330 /* 331 * Compute goodput in bits per millisecond. 332 */ 333 gput = (((int64_t)(th->th_ack - tp->gput_seq)) << 3) / 334 max(1, tcp_ts_getticks() - tp->gput_ts); 335 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_GPUT, 336 gput); 337 /* 338 * XXXLAS: This is a temporary hack, and should be 339 * chained off VOI_TCP_GPUT when stats(9) grows an API 340 * to deal with chained VOIs. 341 */ 342 if (tp->t_stats_gput_prev > 0) 343 stats_voi_update_abs_s32(tp->t_stats, 344 VOI_TCP_GPUT_ND, 345 ((gput - tp->t_stats_gput_prev) * 100) / 346 tp->t_stats_gput_prev); 347 tp->t_flags &= ~TF_GPUTINPROG; 348 tp->t_stats_gput_prev = gput; 349 } 350 #endif /* STATS */ 351 if (tp->snd_cwnd > tp->snd_ssthresh) { 352 tp->t_bytes_acked += tp->ccv->bytes_this_ack; 353 if (tp->t_bytes_acked >= tp->snd_cwnd) { 354 tp->t_bytes_acked -= tp->snd_cwnd; 355 tp->ccv->flags |= CCF_ABC_SENTAWND; 356 } 357 } else { 358 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 359 tp->t_bytes_acked = 0; 360 } 361 } 362 363 if (CC_ALGO(tp)->ack_received != NULL) { 364 /* XXXLAS: Find a way to live without this */ 365 tp->ccv->curack = th->th_ack; 366 CC_ALGO(tp)->ack_received(tp->ccv, type); 367 } 368 #ifdef STATS 369 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_LCWIN, tp->snd_cwnd); 370 #endif 371 } 372 373 void 374 cc_conn_init(struct tcpcb *tp) 375 { 376 struct hc_metrics_lite metrics; 377 struct inpcb *inp = tp->t_inpcb; 378 u_int maxseg; 379 int rtt; 380 381 INP_WLOCK_ASSERT(tp->t_inpcb); 382 383 tcp_hc_get(&inp->inp_inc, &metrics); 384 maxseg = tcp_maxseg(tp); 385 386 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 387 tp->t_srtt = rtt; 388 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 389 TCPSTAT_INC(tcps_usedrtt); 390 if (metrics.rmx_rttvar) { 391 tp->t_rttvar = metrics.rmx_rttvar; 392 TCPSTAT_INC(tcps_usedrttvar); 393 } else { 394 /* default variation is +- 1 rtt */ 395 tp->t_rttvar = 396 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 397 } 398 TCPT_RANGESET(tp->t_rxtcur, 399 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 400 tp->t_rttmin, TCPTV_REXMTMAX); 401 } 402 if (metrics.rmx_ssthresh) { 403 /* 404 * There's some sort of gateway or interface 405 * buffer limit on the path. Use this to set 406 * the slow start threshold, but set the 407 * threshold to no less than 2*mss. 408 */ 409 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 410 TCPSTAT_INC(tcps_usedssthresh); 411 } 412 413 /* 414 * Set the initial slow-start flight size. 415 * 416 * If a SYN or SYN/ACK was lost and retransmitted, we have to 417 * reduce the initial CWND to one segment as congestion is likely 418 * requiring us to be cautious. 419 */ 420 if (tp->snd_cwnd == 1) 421 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 422 else 423 tp->snd_cwnd = tcp_compute_initwnd(maxseg); 424 425 if (CC_ALGO(tp)->conn_init != NULL) 426 CC_ALGO(tp)->conn_init(tp->ccv); 427 } 428 429 void inline 430 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 431 { 432 u_int maxseg; 433 434 INP_WLOCK_ASSERT(tp->t_inpcb); 435 436 #ifdef STATS 437 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_CSIG, type); 438 #endif 439 440 switch(type) { 441 case CC_NDUPACK: 442 if (!IN_FASTRECOVERY(tp->t_flags)) { 443 tp->snd_recover = tp->snd_max; 444 if (tp->t_flags2 & TF2_ECN_PERMIT) 445 tp->t_flags2 |= TF2_ECN_SND_CWR; 446 } 447 break; 448 case CC_ECN: 449 if (!IN_CONGRECOVERY(tp->t_flags) || 450 /* 451 * Allow ECN reaction on ACK to CWR, if 452 * that data segment was also CE marked. 453 */ 454 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 455 EXIT_CONGRECOVERY(tp->t_flags); 456 TCPSTAT_INC(tcps_ecn_rcwnd); 457 tp->snd_recover = tp->snd_max + 1; 458 if (tp->t_flags2 & TF2_ECN_PERMIT) 459 tp->t_flags2 |= TF2_ECN_SND_CWR; 460 } 461 break; 462 case CC_RTO: 463 maxseg = tcp_maxseg(tp); 464 tp->t_dupacks = 0; 465 tp->t_bytes_acked = 0; 466 EXIT_RECOVERY(tp->t_flags); 467 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 468 maxseg) * maxseg; 469 tp->snd_cwnd = maxseg; 470 if (tp->t_flags2 & TF2_ECN_PERMIT) 471 tp->t_flags2 |= TF2_ECN_SND_CWR; 472 break; 473 case CC_RTO_ERR: 474 TCPSTAT_INC(tcps_sndrexmitbad); 475 /* RTO was unnecessary, so reset everything. */ 476 tp->snd_cwnd = tp->snd_cwnd_prev; 477 tp->snd_ssthresh = tp->snd_ssthresh_prev; 478 tp->snd_recover = tp->snd_recover_prev; 479 if (tp->t_flags & TF_WASFRECOVERY) 480 ENTER_FASTRECOVERY(tp->t_flags); 481 if (tp->t_flags & TF_WASCRECOVERY) 482 ENTER_CONGRECOVERY(tp->t_flags); 483 tp->snd_nxt = tp->snd_max; 484 tp->t_flags &= ~TF_PREVVALID; 485 tp->t_badrxtwin = 0; 486 break; 487 } 488 489 if (CC_ALGO(tp)->cong_signal != NULL) { 490 if (th != NULL) 491 tp->ccv->curack = th->th_ack; 492 CC_ALGO(tp)->cong_signal(tp->ccv, type); 493 } 494 } 495 496 void inline 497 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 498 { 499 INP_WLOCK_ASSERT(tp->t_inpcb); 500 501 /* XXXLAS: KASSERT that we're in recovery? */ 502 503 if (CC_ALGO(tp)->post_recovery != NULL) { 504 tp->ccv->curack = th->th_ack; 505 CC_ALGO(tp)->post_recovery(tp->ccv); 506 } 507 /* XXXLAS: EXIT_RECOVERY ? */ 508 tp->t_bytes_acked = 0; 509 } 510 511 /* 512 * Indicate whether this ack should be delayed. We can delay the ack if 513 * following conditions are met: 514 * - There is no delayed ack timer in progress. 515 * - Our last ack wasn't a 0-sized window. We never want to delay 516 * the ack that opens up a 0-sized window. 517 * - LRO wasn't used for this segment. We make sure by checking that the 518 * segment size is not larger than the MSS. 519 */ 520 #define DELAY_ACK(tp, tlen) \ 521 ((!tcp_timer_active(tp, TT_DELACK) && \ 522 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 523 (tlen <= tp->t_maxseg) && \ 524 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 525 526 void inline 527 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 528 { 529 INP_WLOCK_ASSERT(tp->t_inpcb); 530 531 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 532 switch (iptos & IPTOS_ECN_MASK) { 533 case IPTOS_ECN_CE: 534 tp->ccv->flags |= CCF_IPHDR_CE; 535 break; 536 case IPTOS_ECN_ECT0: 537 /* FALLTHROUGH */ 538 case IPTOS_ECN_ECT1: 539 /* FALLTHROUGH */ 540 case IPTOS_ECN_NOTECT: 541 tp->ccv->flags &= ~CCF_IPHDR_CE; 542 break; 543 } 544 545 if (th->th_flags & TH_CWR) 546 tp->ccv->flags |= CCF_TCPHDR_CWR; 547 else 548 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 549 550 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 551 552 if (tp->ccv->flags & CCF_ACKNOW) { 553 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 554 tp->t_flags |= TF_ACKNOW; 555 } 556 } 557 } 558 559 /* 560 * TCP input handling is split into multiple parts: 561 * tcp6_input is a thin wrapper around tcp_input for the extended 562 * ip6_protox[] call format in ip6_input 563 * tcp_input handles primary segment validation, inpcb lookup and 564 * SYN processing on listen sockets 565 * tcp_do_segment processes the ACK and text of the segment for 566 * establishing, established and closing connections 567 */ 568 #ifdef INET6 569 int 570 tcp6_input(struct mbuf **mp, int *offp, int proto) 571 { 572 struct mbuf *m; 573 struct in6_ifaddr *ia6; 574 struct ip6_hdr *ip6; 575 576 m = *mp; 577 if (m->m_len < *offp + sizeof(struct tcphdr)) { 578 m = m_pullup(m, *offp + sizeof(struct tcphdr)); 579 if (m == NULL) { 580 *mp = m; 581 TCPSTAT_INC(tcps_rcvshort); 582 return (IPPROTO_DONE); 583 } 584 } 585 586 /* 587 * draft-itojun-ipv6-tcp-to-anycast 588 * better place to put this in? 589 */ 590 ip6 = mtod(m, struct ip6_hdr *); 591 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 592 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 593 ifa_free(&ia6->ia_ifa); 594 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 595 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 596 *mp = NULL; 597 return (IPPROTO_DONE); 598 } 599 if (ia6) 600 ifa_free(&ia6->ia_ifa); 601 602 *mp = m; 603 return (tcp_input(mp, offp, proto)); 604 } 605 #endif /* INET6 */ 606 607 int 608 tcp_input(struct mbuf **mp, int *offp, int proto) 609 { 610 struct mbuf *m = *mp; 611 struct tcphdr *th = NULL; 612 struct ip *ip = NULL; 613 struct inpcb *inp = NULL; 614 struct tcpcb *tp = NULL; 615 struct socket *so = NULL; 616 u_char *optp = NULL; 617 int off0; 618 int optlen = 0; 619 #ifdef INET 620 int len; 621 uint8_t ipttl; 622 #endif 623 int tlen = 0, off; 624 int drop_hdrlen; 625 int thflags; 626 int rstreason = 0; /* For badport_bandlim accounting purposes */ 627 uint8_t iptos; 628 struct m_tag *fwd_tag = NULL; 629 #ifdef INET6 630 struct ip6_hdr *ip6 = NULL; 631 int isipv6; 632 #else 633 const void *ip6 = NULL; 634 #endif /* INET6 */ 635 struct tcpopt to; /* options in this segment */ 636 char *s = NULL; /* address and port logging */ 637 #ifdef TCPDEBUG 638 /* 639 * The size of tcp_saveipgen must be the size of the max ip header, 640 * now IPv6. 641 */ 642 u_char tcp_saveipgen[IP6_HDR_LEN]; 643 struct tcphdr tcp_savetcp; 644 short ostate = 0; 645 #endif 646 647 NET_EPOCH_ASSERT(); 648 649 #ifdef INET6 650 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 651 #endif 652 653 off0 = *offp; 654 m = *mp; 655 *mp = NULL; 656 to.to_flags = 0; 657 TCPSTAT_INC(tcps_rcvtotal); 658 659 #ifdef INET6 660 if (isipv6) { 661 ip6 = mtod(m, struct ip6_hdr *); 662 th = (struct tcphdr *)((caddr_t)ip6 + off0); 663 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 664 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 665 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 666 th->th_sum = m->m_pkthdr.csum_data; 667 else 668 th->th_sum = in6_cksum_pseudo(ip6, tlen, 669 IPPROTO_TCP, m->m_pkthdr.csum_data); 670 th->th_sum ^= 0xffff; 671 } else 672 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 673 if (th->th_sum) { 674 TCPSTAT_INC(tcps_rcvbadsum); 675 goto drop; 676 } 677 678 /* 679 * Be proactive about unspecified IPv6 address in source. 680 * As we use all-zero to indicate unbounded/unconnected pcb, 681 * unspecified IPv6 address can be used to confuse us. 682 * 683 * Note that packets with unspecified IPv6 destination is 684 * already dropped in ip6_input. 685 */ 686 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 687 /* XXX stat */ 688 goto drop; 689 } 690 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 691 } 692 #endif 693 #if defined(INET) && defined(INET6) 694 else 695 #endif 696 #ifdef INET 697 { 698 /* 699 * Get IP and TCP header together in first mbuf. 700 * Note: IP leaves IP header in first mbuf. 701 */ 702 if (off0 > sizeof (struct ip)) { 703 ip_stripoptions(m); 704 off0 = sizeof(struct ip); 705 } 706 if (m->m_len < sizeof (struct tcpiphdr)) { 707 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 708 == NULL) { 709 TCPSTAT_INC(tcps_rcvshort); 710 return (IPPROTO_DONE); 711 } 712 } 713 ip = mtod(m, struct ip *); 714 th = (struct tcphdr *)((caddr_t)ip + off0); 715 tlen = ntohs(ip->ip_len) - off0; 716 717 iptos = ip->ip_tos; 718 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 719 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 720 th->th_sum = m->m_pkthdr.csum_data; 721 else 722 th->th_sum = in_pseudo(ip->ip_src.s_addr, 723 ip->ip_dst.s_addr, 724 htonl(m->m_pkthdr.csum_data + tlen + 725 IPPROTO_TCP)); 726 th->th_sum ^= 0xffff; 727 } else { 728 struct ipovly *ipov = (struct ipovly *)ip; 729 730 /* 731 * Checksum extended TCP header and data. 732 */ 733 len = off0 + tlen; 734 ipttl = ip->ip_ttl; 735 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 736 ipov->ih_len = htons(tlen); 737 th->th_sum = in_cksum(m, len); 738 /* Reset length for SDT probes. */ 739 ip->ip_len = htons(len); 740 /* Reset TOS bits */ 741 ip->ip_tos = iptos; 742 /* Re-initialization for later version check */ 743 ip->ip_ttl = ipttl; 744 ip->ip_v = IPVERSION; 745 ip->ip_hl = off0 >> 2; 746 } 747 748 if (th->th_sum) { 749 TCPSTAT_INC(tcps_rcvbadsum); 750 goto drop; 751 } 752 } 753 #endif /* INET */ 754 755 /* 756 * Check that TCP offset makes sense, 757 * pull out TCP options and adjust length. XXX 758 */ 759 off = th->th_off << 2; 760 if (off < sizeof (struct tcphdr) || off > tlen) { 761 TCPSTAT_INC(tcps_rcvbadoff); 762 goto drop; 763 } 764 tlen -= off; /* tlen is used instead of ti->ti_len */ 765 if (off > sizeof (struct tcphdr)) { 766 #ifdef INET6 767 if (isipv6) { 768 if (m->m_len < off0 + off) { 769 m = m_pullup(m, off0 + off); 770 if (m == NULL) { 771 TCPSTAT_INC(tcps_rcvshort); 772 return (IPPROTO_DONE); 773 } 774 } 775 ip6 = mtod(m, struct ip6_hdr *); 776 th = (struct tcphdr *)((caddr_t)ip6 + off0); 777 } 778 #endif 779 #if defined(INET) && defined(INET6) 780 else 781 #endif 782 #ifdef INET 783 { 784 if (m->m_len < sizeof(struct ip) + off) { 785 if ((m = m_pullup(m, sizeof (struct ip) + off)) 786 == NULL) { 787 TCPSTAT_INC(tcps_rcvshort); 788 return (IPPROTO_DONE); 789 } 790 ip = mtod(m, struct ip *); 791 th = (struct tcphdr *)((caddr_t)ip + off0); 792 } 793 } 794 #endif 795 optlen = off - sizeof (struct tcphdr); 796 optp = (u_char *)(th + 1); 797 } 798 thflags = th->th_flags; 799 800 /* 801 * Convert TCP protocol specific fields to host format. 802 */ 803 tcp_fields_to_host(th); 804 805 /* 806 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 807 */ 808 drop_hdrlen = off0 + off; 809 810 /* 811 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 812 */ 813 if ( 814 #ifdef INET6 815 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 816 #ifdef INET 817 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 818 #endif 819 #endif 820 #if defined(INET) && !defined(INET6) 821 (m->m_flags & M_IP_NEXTHOP) 822 #endif 823 ) 824 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 825 826 findpcb: 827 #ifdef INET6 828 if (isipv6 && fwd_tag != NULL) { 829 struct sockaddr_in6 *next_hop6; 830 831 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 832 /* 833 * Transparently forwarded. Pretend to be the destination. 834 * Already got one like this? 835 */ 836 inp = in6_pcblookup_mbuf(&V_tcbinfo, 837 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 838 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 839 if (!inp) { 840 /* 841 * It's new. Try to find the ambushing socket. 842 * Because we've rewritten the destination address, 843 * any hardware-generated hash is ignored. 844 */ 845 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 846 th->th_sport, &next_hop6->sin6_addr, 847 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 848 th->th_dport, INPLOOKUP_WILDCARD | 849 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 850 } 851 } else if (isipv6) { 852 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 853 th->th_sport, &ip6->ip6_dst, th->th_dport, 854 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 855 m->m_pkthdr.rcvif, m); 856 } 857 #endif /* INET6 */ 858 #if defined(INET6) && defined(INET) 859 else 860 #endif 861 #ifdef INET 862 if (fwd_tag != NULL) { 863 struct sockaddr_in *next_hop; 864 865 next_hop = (struct sockaddr_in *)(fwd_tag+1); 866 /* 867 * Transparently forwarded. Pretend to be the destination. 868 * already got one like this? 869 */ 870 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 871 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 872 m->m_pkthdr.rcvif, m); 873 if (!inp) { 874 /* 875 * It's new. Try to find the ambushing socket. 876 * Because we've rewritten the destination address, 877 * any hardware-generated hash is ignored. 878 */ 879 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 880 th->th_sport, next_hop->sin_addr, 881 next_hop->sin_port ? ntohs(next_hop->sin_port) : 882 th->th_dport, INPLOOKUP_WILDCARD | 883 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 884 } 885 } else 886 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 887 th->th_sport, ip->ip_dst, th->th_dport, 888 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 889 m->m_pkthdr.rcvif, m); 890 #endif /* INET */ 891 892 /* 893 * If the INPCB does not exist then all data in the incoming 894 * segment is discarded and an appropriate RST is sent back. 895 * XXX MRT Send RST using which routing table? 896 */ 897 if (inp == NULL) { 898 /* 899 * Log communication attempts to ports that are not 900 * in use. 901 */ 902 if ((V_tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 903 V_tcp_log_in_vain == 2) { 904 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 905 log(LOG_INFO, "%s; %s: Connection attempt " 906 "to closed port\n", s, __func__); 907 } 908 /* 909 * When blackholing do not respond with a RST but 910 * completely ignore the segment and drop it. 911 */ 912 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 913 V_blackhole == 2) 914 goto dropunlock; 915 916 rstreason = BANDLIM_RST_CLOSEDPORT; 917 goto dropwithreset; 918 } 919 INP_WLOCK_ASSERT(inp); 920 /* 921 * While waiting for inp lock during the lookup, another thread 922 * can have dropped the inpcb, in which case we need to loop back 923 * and try to find a new inpcb to deliver to. 924 */ 925 if (inp->inp_flags & INP_DROPPED) { 926 INP_WUNLOCK(inp); 927 inp = NULL; 928 goto findpcb; 929 } 930 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 931 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 932 ((inp->inp_socket == NULL) || 933 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 934 inp->inp_flowid = m->m_pkthdr.flowid; 935 inp->inp_flowtype = M_HASHTYPE_GET(m); 936 } 937 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 938 #ifdef INET6 939 if (isipv6 && IPSEC_ENABLED(ipv6) && 940 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) { 941 goto dropunlock; 942 } 943 #ifdef INET 944 else 945 #endif 946 #endif /* INET6 */ 947 #ifdef INET 948 if (IPSEC_ENABLED(ipv4) && 949 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) { 950 goto dropunlock; 951 } 952 #endif /* INET */ 953 #endif /* IPSEC */ 954 955 /* 956 * Check the minimum TTL for socket. 957 */ 958 if (inp->inp_ip_minttl != 0) { 959 #ifdef INET6 960 if (isipv6) { 961 if (inp->inp_ip_minttl > ip6->ip6_hlim) 962 goto dropunlock; 963 } else 964 #endif 965 if (inp->inp_ip_minttl > ip->ip_ttl) 966 goto dropunlock; 967 } 968 969 /* 970 * A previous connection in TIMEWAIT state is supposed to catch stray 971 * or duplicate segments arriving late. If this segment was a 972 * legitimate new connection attempt, the old INPCB gets removed and 973 * we can try again to find a listening socket. 974 * 975 * At this point, due to earlier optimism, we may hold only an inpcb 976 * lock, and not the inpcbinfo write lock. If so, we need to try to 977 * acquire it, or if that fails, acquire a reference on the inpcb, 978 * drop all locks, acquire a global write lock, and then re-acquire 979 * the inpcb lock. We may at that point discover that another thread 980 * has tried to free the inpcb, in which case we need to loop back 981 * and try to find a new inpcb to deliver to. 982 * 983 * XXXRW: It may be time to rethink timewait locking. 984 */ 985 if (inp->inp_flags & INP_TIMEWAIT) { 986 if (thflags & TH_SYN) 987 tcp_dooptions(&to, optp, optlen, TO_SYN); 988 /* 989 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 990 */ 991 if (tcp_twcheck(inp, &to, th, m, tlen)) 992 goto findpcb; 993 return (IPPROTO_DONE); 994 } 995 /* 996 * The TCPCB may no longer exist if the connection is winding 997 * down or it is in the CLOSED state. Either way we drop the 998 * segment and send an appropriate response. 999 */ 1000 tp = intotcpcb(inp); 1001 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 1002 rstreason = BANDLIM_RST_CLOSEDPORT; 1003 goto dropwithreset; 1004 } 1005 1006 #ifdef TCP_OFFLOAD 1007 if (tp->t_flags & TF_TOE) { 1008 tcp_offload_input(tp, m); 1009 m = NULL; /* consumed by the TOE driver */ 1010 goto dropunlock; 1011 } 1012 #endif 1013 1014 #ifdef MAC 1015 INP_WLOCK_ASSERT(inp); 1016 if (mac_inpcb_check_deliver(inp, m)) 1017 goto dropunlock; 1018 #endif 1019 so = inp->inp_socket; 1020 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1021 #ifdef TCPDEBUG 1022 if (so->so_options & SO_DEBUG) { 1023 ostate = tp->t_state; 1024 #ifdef INET6 1025 if (isipv6) { 1026 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1027 } else 1028 #endif 1029 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1030 tcp_savetcp = *th; 1031 } 1032 #endif /* TCPDEBUG */ 1033 /* 1034 * When the socket is accepting connections (the INPCB is in LISTEN 1035 * state) we look into the SYN cache if this is a new connection 1036 * attempt or the completion of a previous one. 1037 */ 1038 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN), 1039 ("%s: so accepting but tp %p not listening", __func__, tp)); 1040 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) { 1041 struct in_conninfo inc; 1042 1043 bzero(&inc, sizeof(inc)); 1044 #ifdef INET6 1045 if (isipv6) { 1046 inc.inc_flags |= INC_ISIPV6; 1047 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU) 1048 inc.inc_flags |= INC_IPV6MINMTU; 1049 inc.inc6_faddr = ip6->ip6_src; 1050 inc.inc6_laddr = ip6->ip6_dst; 1051 } else 1052 #endif 1053 { 1054 inc.inc_faddr = ip->ip_src; 1055 inc.inc_laddr = ip->ip_dst; 1056 } 1057 inc.inc_fport = th->th_sport; 1058 inc.inc_lport = th->th_dport; 1059 inc.inc_fibnum = so->so_fibnum; 1060 1061 /* 1062 * Check for an existing connection attempt in syncache if 1063 * the flag is only ACK. A successful lookup creates a new 1064 * socket appended to the listen queue in SYN_RECEIVED state. 1065 */ 1066 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1067 /* 1068 * Parse the TCP options here because 1069 * syncookies need access to the reflected 1070 * timestamp. 1071 */ 1072 tcp_dooptions(&to, optp, optlen, 0); 1073 /* 1074 * NB: syncache_expand() doesn't unlock 1075 * inp and tcpinfo locks. 1076 */ 1077 rstreason = syncache_expand(&inc, &to, th, &so, m); 1078 if (rstreason < 0) { 1079 /* 1080 * A failing TCP MD5 signature comparison 1081 * must result in the segment being dropped 1082 * and must not produce any response back 1083 * to the sender. 1084 */ 1085 goto dropunlock; 1086 } else if (rstreason == 0) { 1087 /* 1088 * No syncache entry or ACK was not 1089 * for our SYN/ACK. Send a RST. 1090 * NB: syncache did its own logging 1091 * of the failure cause. 1092 */ 1093 rstreason = BANDLIM_RST_OPENPORT; 1094 goto dropwithreset; 1095 } 1096 tfo_socket_result: 1097 if (so == NULL) { 1098 /* 1099 * We completed the 3-way handshake 1100 * but could not allocate a socket 1101 * either due to memory shortage, 1102 * listen queue length limits or 1103 * global socket limits. Send RST 1104 * or wait and have the remote end 1105 * retransmit the ACK for another 1106 * try. 1107 */ 1108 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1109 log(LOG_DEBUG, "%s; %s: Listen socket: " 1110 "Socket allocation failed due to " 1111 "limits or memory shortage, %s\n", 1112 s, __func__, 1113 V_tcp_sc_rst_sock_fail ? 1114 "sending RST" : "try again"); 1115 if (V_tcp_sc_rst_sock_fail) { 1116 rstreason = BANDLIM_UNLIMITED; 1117 goto dropwithreset; 1118 } else 1119 goto dropunlock; 1120 } 1121 /* 1122 * Socket is created in state SYN_RECEIVED. 1123 * Unlock the listen socket, lock the newly 1124 * created socket and update the tp variable. 1125 */ 1126 INP_WUNLOCK(inp); /* listen socket */ 1127 inp = sotoinpcb(so); 1128 /* 1129 * New connection inpcb is already locked by 1130 * syncache_expand(). 1131 */ 1132 INP_WLOCK_ASSERT(inp); 1133 tp = intotcpcb(inp); 1134 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1135 ("%s: ", __func__)); 1136 /* 1137 * Process the segment and the data it 1138 * contains. tcp_do_segment() consumes 1139 * the mbuf chain and unlocks the inpcb. 1140 */ 1141 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1142 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1143 iptos); 1144 return (IPPROTO_DONE); 1145 } 1146 /* 1147 * Segment flag validation for new connection attempts: 1148 * 1149 * Our (SYN|ACK) response was rejected. 1150 * Check with syncache and remove entry to prevent 1151 * retransmits. 1152 * 1153 * NB: syncache_chkrst does its own logging of failure 1154 * causes. 1155 */ 1156 if (thflags & TH_RST) { 1157 syncache_chkrst(&inc, th, m); 1158 goto dropunlock; 1159 } 1160 /* 1161 * We can't do anything without SYN. 1162 */ 1163 if ((thflags & TH_SYN) == 0) { 1164 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1165 log(LOG_DEBUG, "%s; %s: Listen socket: " 1166 "SYN is missing, segment ignored\n", 1167 s, __func__); 1168 TCPSTAT_INC(tcps_badsyn); 1169 goto dropunlock; 1170 } 1171 /* 1172 * (SYN|ACK) is bogus on a listen socket. 1173 */ 1174 if (thflags & TH_ACK) { 1175 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1176 log(LOG_DEBUG, "%s; %s: Listen socket: " 1177 "SYN|ACK invalid, segment rejected\n", 1178 s, __func__); 1179 syncache_badack(&inc); /* XXX: Not needed! */ 1180 TCPSTAT_INC(tcps_badsyn); 1181 rstreason = BANDLIM_RST_OPENPORT; 1182 goto dropwithreset; 1183 } 1184 /* 1185 * If the drop_synfin option is enabled, drop all 1186 * segments with both the SYN and FIN bits set. 1187 * This prevents e.g. nmap from identifying the 1188 * TCP/IP stack. 1189 * XXX: Poor reasoning. nmap has other methods 1190 * and is constantly refining its stack detection 1191 * strategies. 1192 * XXX: This is a violation of the TCP specification 1193 * and was used by RFC1644. 1194 */ 1195 if ((thflags & TH_FIN) && V_drop_synfin) { 1196 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1197 log(LOG_DEBUG, "%s; %s: Listen socket: " 1198 "SYN|FIN segment ignored (based on " 1199 "sysctl setting)\n", s, __func__); 1200 TCPSTAT_INC(tcps_badsyn); 1201 goto dropunlock; 1202 } 1203 /* 1204 * Segment's flags are (SYN) or (SYN|FIN). 1205 * 1206 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1207 * as they do not affect the state of the TCP FSM. 1208 * The data pointed to by TH_URG and th_urp is ignored. 1209 */ 1210 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1211 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1212 KASSERT(thflags & (TH_SYN), 1213 ("%s: Listen socket: TH_SYN not set", __func__)); 1214 #ifdef INET6 1215 /* 1216 * If deprecated address is forbidden, 1217 * we do not accept SYN to deprecated interface 1218 * address to prevent any new inbound connection from 1219 * getting established. 1220 * When we do not accept SYN, we send a TCP RST, 1221 * with deprecated source address (instead of dropping 1222 * it). We compromise it as it is much better for peer 1223 * to send a RST, and RST will be the final packet 1224 * for the exchange. 1225 * 1226 * If we do not forbid deprecated addresses, we accept 1227 * the SYN packet. RFC2462 does not suggest dropping 1228 * SYN in this case. 1229 * If we decipher RFC2462 5.5.4, it says like this: 1230 * 1. use of deprecated addr with existing 1231 * communication is okay - "SHOULD continue to be 1232 * used" 1233 * 2. use of it with new communication: 1234 * (2a) "SHOULD NOT be used if alternate address 1235 * with sufficient scope is available" 1236 * (2b) nothing mentioned otherwise. 1237 * Here we fall into (2b) case as we have no choice in 1238 * our source address selection - we must obey the peer. 1239 * 1240 * The wording in RFC2462 is confusing, and there are 1241 * multiple description text for deprecated address 1242 * handling - worse, they are not exactly the same. 1243 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1244 */ 1245 if (isipv6 && !V_ip6_use_deprecated) { 1246 struct in6_ifaddr *ia6; 1247 1248 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1249 if (ia6 != NULL && 1250 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1251 ifa_free(&ia6->ia_ifa); 1252 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1253 log(LOG_DEBUG, "%s; %s: Listen socket: " 1254 "Connection attempt to deprecated " 1255 "IPv6 address rejected\n", 1256 s, __func__); 1257 rstreason = BANDLIM_RST_OPENPORT; 1258 goto dropwithreset; 1259 } 1260 if (ia6) 1261 ifa_free(&ia6->ia_ifa); 1262 } 1263 #endif /* INET6 */ 1264 /* 1265 * Basic sanity checks on incoming SYN requests: 1266 * Don't respond if the destination is a link layer 1267 * broadcast according to RFC1122 4.2.3.10, p. 104. 1268 * If it is from this socket it must be forged. 1269 * Don't respond if the source or destination is a 1270 * global or subnet broad- or multicast address. 1271 * Note that it is quite possible to receive unicast 1272 * link-layer packets with a broadcast IP address. Use 1273 * in_broadcast() to find them. 1274 */ 1275 if (m->m_flags & (M_BCAST|M_MCAST)) { 1276 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1277 log(LOG_DEBUG, "%s; %s: Listen socket: " 1278 "Connection attempt from broad- or multicast " 1279 "link layer address ignored\n", s, __func__); 1280 goto dropunlock; 1281 } 1282 #ifdef INET6 1283 if (isipv6) { 1284 if (th->th_dport == th->th_sport && 1285 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1286 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1287 log(LOG_DEBUG, "%s; %s: Listen socket: " 1288 "Connection attempt to/from self " 1289 "ignored\n", s, __func__); 1290 goto dropunlock; 1291 } 1292 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1293 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1294 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1295 log(LOG_DEBUG, "%s; %s: Listen socket: " 1296 "Connection attempt from/to multicast " 1297 "address ignored\n", s, __func__); 1298 goto dropunlock; 1299 } 1300 } 1301 #endif 1302 #if defined(INET) && defined(INET6) 1303 else 1304 #endif 1305 #ifdef INET 1306 { 1307 if (th->th_dport == th->th_sport && 1308 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1309 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1310 log(LOG_DEBUG, "%s; %s: Listen socket: " 1311 "Connection attempt from/to self " 1312 "ignored\n", s, __func__); 1313 goto dropunlock; 1314 } 1315 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1316 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1317 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1318 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1319 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1320 log(LOG_DEBUG, "%s; %s: Listen socket: " 1321 "Connection attempt from/to broad- " 1322 "or multicast address ignored\n", 1323 s, __func__); 1324 goto dropunlock; 1325 } 1326 } 1327 #endif 1328 /* 1329 * SYN appears to be valid. Create compressed TCP state 1330 * for syncache. 1331 */ 1332 #ifdef TCPDEBUG 1333 if (so->so_options & SO_DEBUG) 1334 tcp_trace(TA_INPUT, ostate, tp, 1335 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1336 #endif 1337 TCP_PROBE3(debug__input, tp, th, m); 1338 tcp_dooptions(&to, optp, optlen, TO_SYN); 1339 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL, iptos)) 1340 goto tfo_socket_result; 1341 1342 /* 1343 * Entry added to syncache and mbuf consumed. 1344 * Only the listen socket is unlocked by syncache_add(). 1345 */ 1346 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1347 return (IPPROTO_DONE); 1348 } else if (tp->t_state == TCPS_LISTEN) { 1349 /* 1350 * When a listen socket is torn down the SO_ACCEPTCONN 1351 * flag is removed first while connections are drained 1352 * from the accept queue in a unlock/lock cycle of the 1353 * ACCEPT_LOCK, opening a race condition allowing a SYN 1354 * attempt go through unhandled. 1355 */ 1356 goto dropunlock; 1357 } 1358 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1359 if (tp->t_flags & TF_SIGNATURE) { 1360 tcp_dooptions(&to, optp, optlen, thflags); 1361 if ((to.to_flags & TOF_SIGNATURE) == 0) { 1362 TCPSTAT_INC(tcps_sig_err_nosigopt); 1363 goto dropunlock; 1364 } 1365 if (!TCPMD5_ENABLED() || 1366 TCPMD5_INPUT(m, th, to.to_signature) != 0) 1367 goto dropunlock; 1368 } 1369 #endif 1370 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1371 1372 /* 1373 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1374 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1375 * the inpcb, and unlocks pcbinfo. 1376 */ 1377 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos); 1378 return (IPPROTO_DONE); 1379 1380 dropwithreset: 1381 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1382 1383 if (inp != NULL) { 1384 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1385 INP_WUNLOCK(inp); 1386 } else 1387 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1388 m = NULL; /* mbuf chain got consumed. */ 1389 goto drop; 1390 1391 dropunlock: 1392 if (m != NULL) 1393 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1394 1395 if (inp != NULL) 1396 INP_WUNLOCK(inp); 1397 1398 drop: 1399 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1400 if (s != NULL) 1401 free(s, M_TCPLOG); 1402 if (m != NULL) 1403 m_freem(m); 1404 return (IPPROTO_DONE); 1405 } 1406 1407 /* 1408 * Automatic sizing of receive socket buffer. Often the send 1409 * buffer size is not optimally adjusted to the actual network 1410 * conditions at hand (delay bandwidth product). Setting the 1411 * buffer size too small limits throughput on links with high 1412 * bandwidth and high delay (eg. trans-continental/oceanic links). 1413 * 1414 * On the receive side the socket buffer memory is only rarely 1415 * used to any significant extent. This allows us to be much 1416 * more aggressive in scaling the receive socket buffer. For 1417 * the case that the buffer space is actually used to a large 1418 * extent and we run out of kernel memory we can simply drop 1419 * the new segments; TCP on the sender will just retransmit it 1420 * later. Setting the buffer size too big may only consume too 1421 * much kernel memory if the application doesn't read() from 1422 * the socket or packet loss or reordering makes use of the 1423 * reassembly queue. 1424 * 1425 * The criteria to step up the receive buffer one notch are: 1426 * 1. Application has not set receive buffer size with 1427 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1428 * 2. the number of bytes received during 1/2 of an sRTT 1429 * is at least 3/8 of the current socket buffer size. 1430 * 3. receive buffer size has not hit maximal automatic size; 1431 * 1432 * If all of the criteria are met we increaset the socket buffer 1433 * by a 1/2 (bounded by the max). This allows us to keep ahead 1434 * of slow-start but also makes it so our peer never gets limited 1435 * by our rwnd which we then open up causing a burst. 1436 * 1437 * This algorithm does two steps per RTT at most and only if 1438 * we receive a bulk stream w/o packet losses or reorderings. 1439 * Shrinking the buffer during idle times is not necessary as 1440 * it doesn't consume any memory when idle. 1441 * 1442 * TODO: Only step up if the application is actually serving 1443 * the buffer to better manage the socket buffer resources. 1444 */ 1445 int 1446 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so, 1447 struct tcpcb *tp, int tlen) 1448 { 1449 int newsize = 0; 1450 1451 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) && 1452 tp->t_srtt != 0 && tp->rfbuf_ts != 0 && 1453 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) > 1454 ((tp->t_srtt >> TCP_RTT_SHIFT)/2)) { 1455 if (tp->rfbuf_cnt > ((so->so_rcv.sb_hiwat / 2)/ 4 * 3) && 1456 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) { 1457 newsize = min((so->so_rcv.sb_hiwat + (so->so_rcv.sb_hiwat/2)), V_tcp_autorcvbuf_max); 1458 } 1459 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize); 1460 1461 /* Start over with next RTT. */ 1462 tp->rfbuf_ts = 0; 1463 tp->rfbuf_cnt = 0; 1464 } else { 1465 tp->rfbuf_cnt += tlen; /* add up */ 1466 } 1467 return (newsize); 1468 } 1469 1470 void 1471 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1472 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos) 1473 { 1474 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1475 int rstreason, todrop, win, incforsyn = 0; 1476 uint32_t tiwin; 1477 uint16_t nsegs; 1478 char *s; 1479 struct in_conninfo *inc; 1480 struct mbuf *mfree; 1481 struct tcpopt to; 1482 int tfo_syn; 1483 1484 #ifdef TCPDEBUG 1485 /* 1486 * The size of tcp_saveipgen must be the size of the max ip header, 1487 * now IPv6. 1488 */ 1489 u_char tcp_saveipgen[IP6_HDR_LEN]; 1490 struct tcphdr tcp_savetcp; 1491 short ostate = 0; 1492 #endif 1493 thflags = th->th_flags; 1494 inc = &tp->t_inpcb->inp_inc; 1495 tp->sackhint.last_sack_ack = 0; 1496 sack_changed = 0; 1497 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1498 1499 NET_EPOCH_ASSERT(); 1500 INP_WLOCK_ASSERT(tp->t_inpcb); 1501 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1502 __func__)); 1503 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1504 __func__)); 1505 1506 #ifdef TCPPCAP 1507 /* Save segment, if requested. */ 1508 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1509 #endif 1510 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0, 1511 tlen, NULL, true); 1512 1513 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 1514 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1515 log(LOG_DEBUG, "%s; %s: " 1516 "SYN|FIN segment ignored (based on " 1517 "sysctl setting)\n", s, __func__); 1518 free(s, M_TCPLOG); 1519 } 1520 goto drop; 1521 } 1522 1523 /* 1524 * If a segment with the ACK-bit set arrives in the SYN-SENT state 1525 * check SEQ.ACK first. 1526 */ 1527 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) && 1528 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { 1529 rstreason = BANDLIM_UNLIMITED; 1530 goto dropwithreset; 1531 } 1532 1533 /* 1534 * Segment received on connection. 1535 * Reset idle time and keep-alive timer. 1536 * XXX: This should be done after segment 1537 * validation to ignore broken/spoofed segs. 1538 */ 1539 tp->t_rcvtime = ticks; 1540 1541 /* 1542 * Scale up the window into a 32-bit value. 1543 * For the SYN_SENT state the scale is zero. 1544 */ 1545 tiwin = th->th_win << tp->snd_scale; 1546 #ifdef STATS 1547 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_FRWIN, tiwin); 1548 #endif 1549 1550 /* 1551 * TCP ECN processing. 1552 */ 1553 if (tp->t_flags2 & TF2_ECN_PERMIT) { 1554 if (thflags & TH_CWR) { 1555 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1556 tp->t_flags |= TF_ACKNOW; 1557 } 1558 switch (iptos & IPTOS_ECN_MASK) { 1559 case IPTOS_ECN_CE: 1560 tp->t_flags2 |= TF2_ECN_SND_ECE; 1561 TCPSTAT_INC(tcps_ecn_ce); 1562 break; 1563 case IPTOS_ECN_ECT0: 1564 TCPSTAT_INC(tcps_ecn_ect0); 1565 break; 1566 case IPTOS_ECN_ECT1: 1567 TCPSTAT_INC(tcps_ecn_ect1); 1568 break; 1569 } 1570 1571 /* Process a packet differently from RFC3168. */ 1572 cc_ecnpkt_handler(tp, th, iptos); 1573 1574 /* Congestion experienced. */ 1575 if (thflags & TH_ECE) { 1576 cc_cong_signal(tp, th, CC_ECN); 1577 } 1578 } 1579 1580 /* 1581 * Parse options on any incoming segment. 1582 */ 1583 tcp_dooptions(&to, (u_char *)(th + 1), 1584 (th->th_off << 2) - sizeof(struct tcphdr), 1585 (thflags & TH_SYN) ? TO_SYN : 0); 1586 1587 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1588 if ((tp->t_flags & TF_SIGNATURE) != 0 && 1589 (to.to_flags & TOF_SIGNATURE) == 0) { 1590 TCPSTAT_INC(tcps_sig_err_sigopt); 1591 /* XXX: should drop? */ 1592 } 1593 #endif 1594 /* 1595 * If echoed timestamp is later than the current time, 1596 * fall back to non RFC1323 RTT calculation. Normalize 1597 * timestamp if syncookies were used when this connection 1598 * was established. 1599 */ 1600 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1601 to.to_tsecr -= tp->ts_offset; 1602 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1603 to.to_tsecr = 0; 1604 else if (tp->t_flags & TF_PREVVALID && 1605 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 1606 cc_cong_signal(tp, th, CC_RTO_ERR); 1607 } 1608 /* 1609 * Process options only when we get SYN/ACK back. The SYN case 1610 * for incoming connections is handled in tcp_syncache. 1611 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1612 * or <SYN,ACK>) segment itself is never scaled. 1613 * XXX this is traditional behavior, may need to be cleaned up. 1614 */ 1615 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1616 /* Handle parallel SYN for ECN */ 1617 if (!(thflags & TH_ACK) && 1618 ((thflags & (TH_CWR | TH_ECE)) == (TH_CWR | TH_ECE)) && 1619 ((V_tcp_do_ecn == 1) || (V_tcp_do_ecn == 2))) { 1620 tp->t_flags2 |= TF2_ECN_PERMIT; 1621 tp->t_flags2 |= TF2_ECN_SND_ECE; 1622 TCPSTAT_INC(tcps_ecn_shs); 1623 } 1624 if ((to.to_flags & TOF_SCALE) && 1625 (tp->t_flags & TF_REQ_SCALE)) { 1626 tp->t_flags |= TF_RCVD_SCALE; 1627 tp->snd_scale = to.to_wscale; 1628 } else 1629 tp->t_flags &= ~TF_REQ_SCALE; 1630 /* 1631 * Initial send window. It will be updated with 1632 * the next incoming segment to the scaled value. 1633 */ 1634 tp->snd_wnd = th->th_win; 1635 if ((to.to_flags & TOF_TS) && 1636 (tp->t_flags & TF_REQ_TSTMP)) { 1637 tp->t_flags |= TF_RCVD_TSTMP; 1638 tp->ts_recent = to.to_tsval; 1639 tp->ts_recent_age = tcp_ts_getticks(); 1640 } else 1641 tp->t_flags &= ~TF_REQ_TSTMP; 1642 if (to.to_flags & TOF_MSS) 1643 tcp_mss(tp, to.to_mss); 1644 if ((tp->t_flags & TF_SACK_PERMIT) && 1645 (to.to_flags & TOF_SACKPERM) == 0) 1646 tp->t_flags &= ~TF_SACK_PERMIT; 1647 if (IS_FASTOPEN(tp->t_flags)) { 1648 if (to.to_flags & TOF_FASTOPEN) { 1649 uint16_t mss; 1650 1651 if (to.to_flags & TOF_MSS) 1652 mss = to.to_mss; 1653 else 1654 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 1655 mss = TCP6_MSS; 1656 else 1657 mss = TCP_MSS; 1658 tcp_fastopen_update_cache(tp, mss, 1659 to.to_tfo_len, to.to_tfo_cookie); 1660 } else 1661 tcp_fastopen_disable_path(tp); 1662 } 1663 } 1664 1665 /* 1666 * If timestamps were negotiated during SYN/ACK they should 1667 * appear on every segment during this session and vice versa. 1668 */ 1669 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1670 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1671 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1672 "no action\n", s, __func__); 1673 free(s, M_TCPLOG); 1674 } 1675 } 1676 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1677 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1678 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1679 "no action\n", s, __func__); 1680 free(s, M_TCPLOG); 1681 } 1682 } 1683 1684 /* 1685 * Header prediction: check for the two common cases 1686 * of a uni-directional data xfer. If the packet has 1687 * no control flags, is in-sequence, the window didn't 1688 * change and we're not retransmitting, it's a 1689 * candidate. If the length is zero and the ack moved 1690 * forward, we're the sender side of the xfer. Just 1691 * free the data acked & wake any higher level process 1692 * that was blocked waiting for space. If the length 1693 * is non-zero and the ack didn't move, we're the 1694 * receiver side. If we're getting packets in-order 1695 * (the reassembly queue is empty), add the data to 1696 * the socket buffer and note that we need a delayed ack. 1697 * Make sure that the hidden state-flags are also off. 1698 * Since we check for TCPS_ESTABLISHED first, it can only 1699 * be TH_NEEDSYN. 1700 */ 1701 if (tp->t_state == TCPS_ESTABLISHED && 1702 th->th_seq == tp->rcv_nxt && 1703 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1704 tp->snd_nxt == tp->snd_max && 1705 tiwin && tiwin == tp->snd_wnd && 1706 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1707 SEGQ_EMPTY(tp) && 1708 ((to.to_flags & TOF_TS) == 0 || 1709 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1710 /* 1711 * If last ACK falls within this segment's sequence numbers, 1712 * record the timestamp. 1713 * NOTE that the test is modified according to the latest 1714 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1715 */ 1716 if ((to.to_flags & TOF_TS) != 0 && 1717 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1718 tp->ts_recent_age = tcp_ts_getticks(); 1719 tp->ts_recent = to.to_tsval; 1720 } 1721 1722 if (tlen == 0) { 1723 if (SEQ_GT(th->th_ack, tp->snd_una) && 1724 SEQ_LEQ(th->th_ack, tp->snd_max) && 1725 !IN_RECOVERY(tp->t_flags) && 1726 (to.to_flags & TOF_SACK) == 0 && 1727 TAILQ_EMPTY(&tp->snd_holes)) { 1728 /* 1729 * This is a pure ack for outstanding data. 1730 */ 1731 TCPSTAT_INC(tcps_predack); 1732 1733 /* 1734 * "bad retransmit" recovery without timestamps. 1735 */ 1736 if ((to.to_flags & TOF_TS) == 0 && 1737 tp->t_rxtshift == 1 && 1738 tp->t_flags & TF_PREVVALID && 1739 (int)(ticks - tp->t_badrxtwin) < 0) { 1740 cc_cong_signal(tp, th, CC_RTO_ERR); 1741 } 1742 1743 /* 1744 * Recalculate the transmit timer / rtt. 1745 * 1746 * Some boxes send broken timestamp replies 1747 * during the SYN+ACK phase, ignore 1748 * timestamps of 0 or we could calculate a 1749 * huge RTT and blow up the retransmit timer. 1750 */ 1751 if ((to.to_flags & TOF_TS) != 0 && 1752 to.to_tsecr) { 1753 uint32_t t; 1754 1755 t = tcp_ts_getticks() - to.to_tsecr; 1756 if (!tp->t_rttlow || tp->t_rttlow > t) 1757 tp->t_rttlow = t; 1758 tcp_xmit_timer(tp, 1759 TCP_TS_TO_TICKS(t) + 1); 1760 } else if (tp->t_rtttime && 1761 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1762 if (!tp->t_rttlow || 1763 tp->t_rttlow > ticks - tp->t_rtttime) 1764 tp->t_rttlow = ticks - tp->t_rtttime; 1765 tcp_xmit_timer(tp, 1766 ticks - tp->t_rtttime); 1767 } 1768 acked = BYTES_THIS_ACK(tp, th); 1769 1770 #ifdef TCP_HHOOK 1771 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1772 hhook_run_tcp_est_in(tp, th, &to); 1773 #endif 1774 1775 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1776 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1777 sbdrop(&so->so_snd, acked); 1778 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1779 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1780 tp->snd_recover = th->th_ack - 1; 1781 1782 /* 1783 * Let the congestion control algorithm update 1784 * congestion control related information. This 1785 * typically means increasing the congestion 1786 * window. 1787 */ 1788 cc_ack_received(tp, th, nsegs, CC_ACK); 1789 1790 tp->snd_una = th->th_ack; 1791 /* 1792 * Pull snd_wl2 up to prevent seq wrap relative 1793 * to th_ack. 1794 */ 1795 tp->snd_wl2 = th->th_ack; 1796 tp->t_dupacks = 0; 1797 m_freem(m); 1798 1799 /* 1800 * If all outstanding data are acked, stop 1801 * retransmit timer, otherwise restart timer 1802 * using current (possibly backed-off) value. 1803 * If process is waiting for space, 1804 * wakeup/selwakeup/signal. If data 1805 * are ready to send, let tcp_output 1806 * decide between more output or persist. 1807 */ 1808 #ifdef TCPDEBUG 1809 if (so->so_options & SO_DEBUG) 1810 tcp_trace(TA_INPUT, ostate, tp, 1811 (void *)tcp_saveipgen, 1812 &tcp_savetcp, 0); 1813 #endif 1814 TCP_PROBE3(debug__input, tp, th, m); 1815 if (tp->snd_una == tp->snd_max) 1816 tcp_timer_activate(tp, TT_REXMT, 0); 1817 else if (!tcp_timer_active(tp, TT_PERSIST)) 1818 tcp_timer_activate(tp, TT_REXMT, 1819 tp->t_rxtcur); 1820 sowwakeup(so); 1821 if (sbavail(&so->so_snd)) 1822 (void) tp->t_fb->tfb_tcp_output(tp); 1823 goto check_delack; 1824 } 1825 } else if (th->th_ack == tp->snd_una && 1826 tlen <= sbspace(&so->so_rcv)) { 1827 int newsize = 0; /* automatic sockbuf scaling */ 1828 1829 /* 1830 * This is a pure, in-sequence data packet with 1831 * nothing on the reassembly queue and we have enough 1832 * buffer space to take it. 1833 */ 1834 /* Clean receiver SACK report if present */ 1835 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1836 tcp_clean_sackreport(tp); 1837 TCPSTAT_INC(tcps_preddat); 1838 tp->rcv_nxt += tlen; 1839 if (tlen && 1840 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 1841 (tp->t_fbyte_in == 0)) { 1842 tp->t_fbyte_in = ticks; 1843 if (tp->t_fbyte_in == 0) 1844 tp->t_fbyte_in = 1; 1845 if (tp->t_fbyte_out && tp->t_fbyte_in) 1846 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 1847 } 1848 /* 1849 * Pull snd_wl1 up to prevent seq wrap relative to 1850 * th_seq. 1851 */ 1852 tp->snd_wl1 = th->th_seq; 1853 /* 1854 * Pull rcv_up up to prevent seq wrap relative to 1855 * rcv_nxt. 1856 */ 1857 tp->rcv_up = tp->rcv_nxt; 1858 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1859 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1860 #ifdef TCPDEBUG 1861 if (so->so_options & SO_DEBUG) 1862 tcp_trace(TA_INPUT, ostate, tp, 1863 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1864 #endif 1865 TCP_PROBE3(debug__input, tp, th, m); 1866 1867 newsize = tcp_autorcvbuf(m, th, so, tp, tlen); 1868 1869 /* Add data to socket buffer. */ 1870 SOCKBUF_LOCK(&so->so_rcv); 1871 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1872 m_freem(m); 1873 } else { 1874 /* 1875 * Set new socket buffer size. 1876 * Give up when limit is reached. 1877 */ 1878 if (newsize) 1879 if (!sbreserve_locked(&so->so_rcv, 1880 newsize, so, NULL)) 1881 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1882 m_adj(m, drop_hdrlen); /* delayed header drop */ 1883 sbappendstream_locked(&so->so_rcv, m, 0); 1884 } 1885 /* NB: sorwakeup_locked() does an implicit unlock. */ 1886 sorwakeup_locked(so); 1887 if (DELAY_ACK(tp, tlen)) { 1888 tp->t_flags |= TF_DELACK; 1889 } else { 1890 tp->t_flags |= TF_ACKNOW; 1891 tp->t_fb->tfb_tcp_output(tp); 1892 } 1893 goto check_delack; 1894 } 1895 } 1896 1897 /* 1898 * Calculate amount of space in receive window, 1899 * and then do TCP input processing. 1900 * Receive window is amount of space in rcv queue, 1901 * but not less than advertised window. 1902 */ 1903 win = sbspace(&so->so_rcv); 1904 if (win < 0) 1905 win = 0; 1906 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1907 1908 switch (tp->t_state) { 1909 /* 1910 * If the state is SYN_RECEIVED: 1911 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1912 */ 1913 case TCPS_SYN_RECEIVED: 1914 if ((thflags & TH_ACK) && 1915 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1916 SEQ_GT(th->th_ack, tp->snd_max))) { 1917 rstreason = BANDLIM_RST_OPENPORT; 1918 goto dropwithreset; 1919 } 1920 if (IS_FASTOPEN(tp->t_flags)) { 1921 /* 1922 * When a TFO connection is in SYN_RECEIVED, the 1923 * only valid packets are the initial SYN, a 1924 * retransmit/copy of the initial SYN (possibly with 1925 * a subset of the original data), a valid ACK, a 1926 * FIN, or a RST. 1927 */ 1928 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1929 rstreason = BANDLIM_RST_OPENPORT; 1930 goto dropwithreset; 1931 } else if (thflags & TH_SYN) { 1932 /* non-initial SYN is ignored */ 1933 if ((tcp_timer_active(tp, TT_DELACK) || 1934 tcp_timer_active(tp, TT_REXMT))) 1935 goto drop; 1936 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1937 goto drop; 1938 } 1939 } 1940 break; 1941 1942 /* 1943 * If the state is SYN_SENT: 1944 * if seg contains a RST with valid ACK (SEQ.ACK has already 1945 * been verified), then drop the connection. 1946 * if seg contains a RST without an ACK, drop the seg. 1947 * if seg does not contain SYN, then drop the seg. 1948 * Otherwise this is an acceptable SYN segment 1949 * initialize tp->rcv_nxt and tp->irs 1950 * if seg contains ack then advance tp->snd_una 1951 * if seg contains an ECE and ECN support is enabled, the stream 1952 * is ECN capable. 1953 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1954 * arrange for segment to be acked (eventually) 1955 * continue processing rest of data/controls, beginning with URG 1956 */ 1957 case TCPS_SYN_SENT: 1958 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 1959 TCP_PROBE5(connect__refused, NULL, tp, 1960 m, tp, th); 1961 tp = tcp_drop(tp, ECONNREFUSED); 1962 } 1963 if (thflags & TH_RST) 1964 goto drop; 1965 if (!(thflags & TH_SYN)) 1966 goto drop; 1967 1968 tp->irs = th->th_seq; 1969 tcp_rcvseqinit(tp); 1970 if (thflags & TH_ACK) { 1971 int tfo_partial_ack = 0; 1972 1973 TCPSTAT_INC(tcps_connects); 1974 soisconnected(so); 1975 #ifdef MAC 1976 mac_socketpeer_set_from_mbuf(m, so); 1977 #endif 1978 /* Do window scaling on this connection? */ 1979 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1980 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1981 tp->rcv_scale = tp->request_r_scale; 1982 } 1983 tp->rcv_adv += min(tp->rcv_wnd, 1984 TCP_MAXWIN << tp->rcv_scale); 1985 tp->snd_una++; /* SYN is acked */ 1986 /* 1987 * If not all the data that was sent in the TFO SYN 1988 * has been acked, resend the remainder right away. 1989 */ 1990 if (IS_FASTOPEN(tp->t_flags) && 1991 (tp->snd_una != tp->snd_max)) { 1992 tp->snd_nxt = th->th_ack; 1993 tfo_partial_ack = 1; 1994 } 1995 /* 1996 * If there's data, delay ACK; if there's also a FIN 1997 * ACKNOW will be turned on later. 1998 */ 1999 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack) 2000 tcp_timer_activate(tp, TT_DELACK, 2001 tcp_delacktime); 2002 else 2003 tp->t_flags |= TF_ACKNOW; 2004 2005 if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) && 2006 (V_tcp_do_ecn == 1)) { 2007 tp->t_flags2 |= TF2_ECN_PERMIT; 2008 TCPSTAT_INC(tcps_ecn_shs); 2009 } 2010 2011 /* 2012 * Received <SYN,ACK> in SYN_SENT[*] state. 2013 * Transitions: 2014 * SYN_SENT --> ESTABLISHED 2015 * SYN_SENT* --> FIN_WAIT_1 2016 */ 2017 tp->t_starttime = ticks; 2018 if (tp->t_flags & TF_NEEDFIN) { 2019 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2020 tp->t_flags &= ~TF_NEEDFIN; 2021 thflags &= ~TH_SYN; 2022 } else { 2023 tcp_state_change(tp, TCPS_ESTABLISHED); 2024 TCP_PROBE5(connect__established, NULL, tp, 2025 m, tp, th); 2026 cc_conn_init(tp); 2027 tcp_timer_activate(tp, TT_KEEP, 2028 TP_KEEPIDLE(tp)); 2029 } 2030 } else { 2031 /* 2032 * Received initial SYN in SYN-SENT[*] state => 2033 * simultaneous open. 2034 * If it succeeds, connection is * half-synchronized. 2035 * Otherwise, do 3-way handshake: 2036 * SYN-SENT -> SYN-RECEIVED 2037 * SYN-SENT* -> SYN-RECEIVED* 2038 */ 2039 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2040 tcp_timer_activate(tp, TT_REXMT, 0); 2041 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2042 } 2043 2044 INP_WLOCK_ASSERT(tp->t_inpcb); 2045 2046 /* 2047 * Advance th->th_seq to correspond to first data byte. 2048 * If data, trim to stay within window, 2049 * dropping FIN if necessary. 2050 */ 2051 th->th_seq++; 2052 if (tlen > tp->rcv_wnd) { 2053 todrop = tlen - tp->rcv_wnd; 2054 m_adj(m, -todrop); 2055 tlen = tp->rcv_wnd; 2056 thflags &= ~TH_FIN; 2057 TCPSTAT_INC(tcps_rcvpackafterwin); 2058 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2059 } 2060 tp->snd_wl1 = th->th_seq - 1; 2061 tp->rcv_up = th->th_seq; 2062 /* 2063 * Client side of transaction: already sent SYN and data. 2064 * If the remote host used T/TCP to validate the SYN, 2065 * our data will be ACK'd; if so, enter normal data segment 2066 * processing in the middle of step 5, ack processing. 2067 * Otherwise, goto step 6. 2068 */ 2069 if (thflags & TH_ACK) 2070 goto process_ACK; 2071 2072 goto step6; 2073 2074 /* 2075 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2076 * do normal processing. 2077 * 2078 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2079 */ 2080 case TCPS_LAST_ACK: 2081 case TCPS_CLOSING: 2082 break; /* continue normal processing */ 2083 } 2084 2085 /* 2086 * States other than LISTEN or SYN_SENT. 2087 * First check the RST flag and sequence number since reset segments 2088 * are exempt from the timestamp and connection count tests. This 2089 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2090 * below which allowed reset segments in half the sequence space 2091 * to fall though and be processed (which gives forged reset 2092 * segments with a random sequence number a 50 percent chance of 2093 * killing a connection). 2094 * Then check timestamp, if present. 2095 * Then check the connection count, if present. 2096 * Then check that at least some bytes of segment are within 2097 * receive window. If segment begins before rcv_nxt, 2098 * drop leading data (and SYN); if nothing left, just ack. 2099 */ 2100 if (thflags & TH_RST) { 2101 /* 2102 * RFC5961 Section 3.2 2103 * 2104 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2105 * - If RST is in window, we send challenge ACK. 2106 * 2107 * Note: to take into account delayed ACKs, we should 2108 * test against last_ack_sent instead of rcv_nxt. 2109 * Note 2: we handle special case of closed window, not 2110 * covered by the RFC. 2111 */ 2112 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2113 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2114 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2115 KASSERT(tp->t_state != TCPS_SYN_SENT, 2116 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2117 __func__, th, tp)); 2118 2119 if (V_tcp_insecure_rst || 2120 tp->last_ack_sent == th->th_seq) { 2121 TCPSTAT_INC(tcps_drops); 2122 /* Drop the connection. */ 2123 switch (tp->t_state) { 2124 case TCPS_SYN_RECEIVED: 2125 so->so_error = ECONNREFUSED; 2126 goto close; 2127 case TCPS_ESTABLISHED: 2128 case TCPS_FIN_WAIT_1: 2129 case TCPS_FIN_WAIT_2: 2130 case TCPS_CLOSE_WAIT: 2131 case TCPS_CLOSING: 2132 case TCPS_LAST_ACK: 2133 so->so_error = ECONNRESET; 2134 close: 2135 /* FALLTHROUGH */ 2136 default: 2137 tp = tcp_close(tp); 2138 } 2139 } else { 2140 TCPSTAT_INC(tcps_badrst); 2141 /* Send challenge ACK. */ 2142 tcp_respond(tp, mtod(m, void *), th, m, 2143 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2144 tp->last_ack_sent = tp->rcv_nxt; 2145 m = NULL; 2146 } 2147 } 2148 goto drop; 2149 } 2150 2151 /* 2152 * RFC5961 Section 4.2 2153 * Send challenge ACK for any SYN in synchronized state. 2154 */ 2155 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2156 tp->t_state != TCPS_SYN_RECEIVED) { 2157 TCPSTAT_INC(tcps_badsyn); 2158 if (V_tcp_insecure_syn && 2159 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2160 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2161 tp = tcp_drop(tp, ECONNRESET); 2162 rstreason = BANDLIM_UNLIMITED; 2163 } else { 2164 /* Send challenge ACK. */ 2165 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2166 tp->snd_nxt, TH_ACK); 2167 tp->last_ack_sent = tp->rcv_nxt; 2168 m = NULL; 2169 } 2170 goto drop; 2171 } 2172 2173 /* 2174 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2175 * and it's less than ts_recent, drop it. 2176 */ 2177 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2178 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2179 /* Check to see if ts_recent is over 24 days old. */ 2180 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2181 /* 2182 * Invalidate ts_recent. If this segment updates 2183 * ts_recent, the age will be reset later and ts_recent 2184 * will get a valid value. If it does not, setting 2185 * ts_recent to zero will at least satisfy the 2186 * requirement that zero be placed in the timestamp 2187 * echo reply when ts_recent isn't valid. The 2188 * age isn't reset until we get a valid ts_recent 2189 * because we don't want out-of-order segments to be 2190 * dropped when ts_recent is old. 2191 */ 2192 tp->ts_recent = 0; 2193 } else { 2194 TCPSTAT_INC(tcps_rcvduppack); 2195 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2196 TCPSTAT_INC(tcps_pawsdrop); 2197 if (tlen) 2198 goto dropafterack; 2199 goto drop; 2200 } 2201 } 2202 2203 /* 2204 * In the SYN-RECEIVED state, validate that the packet belongs to 2205 * this connection before trimming the data to fit the receive 2206 * window. Check the sequence number versus IRS since we know 2207 * the sequence numbers haven't wrapped. This is a partial fix 2208 * for the "LAND" DoS attack. 2209 */ 2210 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2211 rstreason = BANDLIM_RST_OPENPORT; 2212 goto dropwithreset; 2213 } 2214 2215 todrop = tp->rcv_nxt - th->th_seq; 2216 if (todrop > 0) { 2217 if (thflags & TH_SYN) { 2218 thflags &= ~TH_SYN; 2219 th->th_seq++; 2220 if (th->th_urp > 1) 2221 th->th_urp--; 2222 else 2223 thflags &= ~TH_URG; 2224 todrop--; 2225 } 2226 /* 2227 * Following if statement from Stevens, vol. 2, p. 960. 2228 */ 2229 if (todrop > tlen 2230 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2231 /* 2232 * Any valid FIN must be to the left of the window. 2233 * At this point the FIN must be a duplicate or out 2234 * of sequence; drop it. 2235 */ 2236 thflags &= ~TH_FIN; 2237 2238 /* 2239 * Send an ACK to resynchronize and drop any data. 2240 * But keep on processing for RST or ACK. 2241 */ 2242 tp->t_flags |= TF_ACKNOW; 2243 todrop = tlen; 2244 TCPSTAT_INC(tcps_rcvduppack); 2245 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2246 } else { 2247 TCPSTAT_INC(tcps_rcvpartduppack); 2248 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2249 } 2250 /* 2251 * DSACK - add SACK block for dropped range 2252 */ 2253 if ((todrop > 0) && (tp->t_flags & TF_SACK_PERMIT)) { 2254 tcp_update_sack_list(tp, th->th_seq, 2255 th->th_seq + todrop); 2256 /* 2257 * ACK now, as the next in-sequence segment 2258 * will clear the DSACK block again 2259 */ 2260 tp->t_flags |= TF_ACKNOW; 2261 } 2262 drop_hdrlen += todrop; /* drop from the top afterwards */ 2263 th->th_seq += todrop; 2264 tlen -= todrop; 2265 if (th->th_urp > todrop) 2266 th->th_urp -= todrop; 2267 else { 2268 thflags &= ~TH_URG; 2269 th->th_urp = 0; 2270 } 2271 } 2272 2273 /* 2274 * If new data are received on a connection after the 2275 * user processes are gone, then RST the other end. 2276 */ 2277 if ((so->so_state & SS_NOFDREF) && 2278 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2279 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2280 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2281 "after socket was closed, " 2282 "sending RST and removing tcpcb\n", 2283 s, __func__, tcpstates[tp->t_state], tlen); 2284 free(s, M_TCPLOG); 2285 } 2286 tp = tcp_close(tp); 2287 TCPSTAT_INC(tcps_rcvafterclose); 2288 rstreason = BANDLIM_UNLIMITED; 2289 goto dropwithreset; 2290 } 2291 2292 /* 2293 * If segment ends after window, drop trailing data 2294 * (and PUSH and FIN); if nothing left, just ACK. 2295 */ 2296 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2297 if (todrop > 0) { 2298 TCPSTAT_INC(tcps_rcvpackafterwin); 2299 if (todrop >= tlen) { 2300 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2301 /* 2302 * If window is closed can only take segments at 2303 * window edge, and have to drop data and PUSH from 2304 * incoming segments. Continue processing, but 2305 * remember to ack. Otherwise, drop segment 2306 * and ack. 2307 */ 2308 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2309 tp->t_flags |= TF_ACKNOW; 2310 TCPSTAT_INC(tcps_rcvwinprobe); 2311 } else 2312 goto dropafterack; 2313 } else 2314 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2315 m_adj(m, -todrop); 2316 tlen -= todrop; 2317 thflags &= ~(TH_PUSH|TH_FIN); 2318 } 2319 2320 /* 2321 * If last ACK falls within this segment's sequence numbers, 2322 * record its timestamp. 2323 * NOTE: 2324 * 1) That the test incorporates suggestions from the latest 2325 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2326 * 2) That updating only on newer timestamps interferes with 2327 * our earlier PAWS tests, so this check should be solely 2328 * predicated on the sequence space of this segment. 2329 * 3) That we modify the segment boundary check to be 2330 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2331 * instead of RFC1323's 2332 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2333 * This modified check allows us to overcome RFC1323's 2334 * limitations as described in Stevens TCP/IP Illustrated 2335 * Vol. 2 p.869. In such cases, we can still calculate the 2336 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2337 */ 2338 if ((to.to_flags & TOF_TS) != 0 && 2339 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2340 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2341 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2342 tp->ts_recent_age = tcp_ts_getticks(); 2343 tp->ts_recent = to.to_tsval; 2344 } 2345 2346 /* 2347 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2348 * flag is on (half-synchronized state), then queue data for 2349 * later processing; else drop segment and return. 2350 */ 2351 if ((thflags & TH_ACK) == 0) { 2352 if (tp->t_state == TCPS_SYN_RECEIVED || 2353 (tp->t_flags & TF_NEEDSYN)) { 2354 if (tp->t_state == TCPS_SYN_RECEIVED && 2355 IS_FASTOPEN(tp->t_flags)) { 2356 tp->snd_wnd = tiwin; 2357 cc_conn_init(tp); 2358 } 2359 goto step6; 2360 } else if (tp->t_flags & TF_ACKNOW) 2361 goto dropafterack; 2362 else 2363 goto drop; 2364 } 2365 2366 /* 2367 * Ack processing. 2368 */ 2369 switch (tp->t_state) { 2370 /* 2371 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2372 * ESTABLISHED state and continue processing. 2373 * The ACK was checked above. 2374 */ 2375 case TCPS_SYN_RECEIVED: 2376 2377 TCPSTAT_INC(tcps_connects); 2378 soisconnected(so); 2379 /* Do window scaling? */ 2380 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2381 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2382 tp->rcv_scale = tp->request_r_scale; 2383 } 2384 tp->snd_wnd = tiwin; 2385 /* 2386 * Make transitions: 2387 * SYN-RECEIVED -> ESTABLISHED 2388 * SYN-RECEIVED* -> FIN-WAIT-1 2389 */ 2390 tp->t_starttime = ticks; 2391 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) { 2392 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2393 tp->t_tfo_pending = NULL; 2394 } 2395 if (tp->t_flags & TF_NEEDFIN) { 2396 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2397 tp->t_flags &= ~TF_NEEDFIN; 2398 } else { 2399 tcp_state_change(tp, TCPS_ESTABLISHED); 2400 TCP_PROBE5(accept__established, NULL, tp, 2401 m, tp, th); 2402 /* 2403 * TFO connections call cc_conn_init() during SYN 2404 * processing. Calling it again here for such 2405 * connections is not harmless as it would undo the 2406 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2407 * is retransmitted. 2408 */ 2409 if (!IS_FASTOPEN(tp->t_flags)) 2410 cc_conn_init(tp); 2411 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2412 } 2413 /* 2414 * Account for the ACK of our SYN prior to 2415 * regular ACK processing below, except for 2416 * simultaneous SYN, which is handled later. 2417 */ 2418 if (SEQ_GT(th->th_ack, tp->snd_una) && !(tp->t_flags & TF_NEEDSYN)) 2419 incforsyn = 1; 2420 /* 2421 * If segment contains data or ACK, will call tcp_reass() 2422 * later; if not, do so now to pass queued data to user. 2423 */ 2424 if (tlen == 0 && (thflags & TH_FIN) == 0) 2425 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0, 2426 (struct mbuf *)0); 2427 tp->snd_wl1 = th->th_seq - 1; 2428 /* FALLTHROUGH */ 2429 2430 /* 2431 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2432 * ACKs. If the ack is in the range 2433 * tp->snd_una < th->th_ack <= tp->snd_max 2434 * then advance tp->snd_una to th->th_ack and drop 2435 * data from the retransmission queue. If this ACK reflects 2436 * more up to date window information we update our window information. 2437 */ 2438 case TCPS_ESTABLISHED: 2439 case TCPS_FIN_WAIT_1: 2440 case TCPS_FIN_WAIT_2: 2441 case TCPS_CLOSE_WAIT: 2442 case TCPS_CLOSING: 2443 case TCPS_LAST_ACK: 2444 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2445 TCPSTAT_INC(tcps_rcvacktoomuch); 2446 goto dropafterack; 2447 } 2448 if ((tp->t_flags & TF_SACK_PERMIT) && 2449 ((to.to_flags & TOF_SACK) || 2450 !TAILQ_EMPTY(&tp->snd_holes))) 2451 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2452 else 2453 /* 2454 * Reset the value so that previous (valid) value 2455 * from the last ack with SACK doesn't get used. 2456 */ 2457 tp->sackhint.sacked_bytes = 0; 2458 2459 #ifdef TCP_HHOOK 2460 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2461 hhook_run_tcp_est_in(tp, th, &to); 2462 #endif 2463 2464 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2465 u_int maxseg; 2466 2467 maxseg = tcp_maxseg(tp); 2468 if (tlen == 0 && 2469 (tiwin == tp->snd_wnd || 2470 (tp->t_flags & TF_SACK_PERMIT))) { 2471 /* 2472 * If this is the first time we've seen a 2473 * FIN from the remote, this is not a 2474 * duplicate and it needs to be processed 2475 * normally. This happens during a 2476 * simultaneous close. 2477 */ 2478 if ((thflags & TH_FIN) && 2479 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2480 tp->t_dupacks = 0; 2481 break; 2482 } 2483 TCPSTAT_INC(tcps_rcvdupack); 2484 /* 2485 * If we have outstanding data (other than 2486 * a window probe), this is a completely 2487 * duplicate ack (ie, window info didn't 2488 * change and FIN isn't set), 2489 * the ack is the biggest we've 2490 * seen and we've seen exactly our rexmt 2491 * threshold of them, assume a packet 2492 * has been dropped and retransmit it. 2493 * Kludge snd_nxt & the congestion 2494 * window so we send only this one 2495 * packet. 2496 * 2497 * We know we're losing at the current 2498 * window size so do congestion avoidance 2499 * (set ssthresh to half the current window 2500 * and pull our congestion window back to 2501 * the new ssthresh). 2502 * 2503 * Dup acks mean that packets have left the 2504 * network (they're now cached at the receiver) 2505 * so bump cwnd by the amount in the receiver 2506 * to keep a constant cwnd packets in the 2507 * network. 2508 * 2509 * When using TCP ECN, notify the peer that 2510 * we reduced the cwnd. 2511 */ 2512 /* 2513 * Following 2 kinds of acks should not affect 2514 * dupack counting: 2515 * 1) Old acks 2516 * 2) Acks with SACK but without any new SACK 2517 * information in them. These could result from 2518 * any anomaly in the network like a switch 2519 * duplicating packets or a possible DoS attack. 2520 */ 2521 if (th->th_ack != tp->snd_una || 2522 ((tp->t_flags & TF_SACK_PERMIT) && 2523 !sack_changed)) 2524 break; 2525 else if (!tcp_timer_active(tp, TT_REXMT)) 2526 tp->t_dupacks = 0; 2527 else if (++tp->t_dupacks > tcprexmtthresh || 2528 IN_FASTRECOVERY(tp->t_flags)) { 2529 cc_ack_received(tp, th, nsegs, 2530 CC_DUPACK); 2531 if ((tp->t_flags & TF_SACK_PERMIT) && 2532 IN_FASTRECOVERY(tp->t_flags)) { 2533 int awnd; 2534 2535 /* 2536 * Compute the amount of data in flight first. 2537 * We can inject new data into the pipe iff 2538 * we have less than 1/2 the original window's 2539 * worth of data in flight. 2540 */ 2541 if (V_tcp_do_rfc6675_pipe) 2542 awnd = tcp_compute_pipe(tp); 2543 else 2544 awnd = (tp->snd_nxt - tp->snd_fack) + 2545 tp->sackhint.sack_bytes_rexmit; 2546 2547 if (awnd < tp->snd_ssthresh) { 2548 tp->snd_cwnd += maxseg; 2549 if (tp->snd_cwnd > tp->snd_ssthresh) 2550 tp->snd_cwnd = tp->snd_ssthresh; 2551 } 2552 } else 2553 tp->snd_cwnd += maxseg; 2554 (void) tp->t_fb->tfb_tcp_output(tp); 2555 goto drop; 2556 } else if (tp->t_dupacks == tcprexmtthresh) { 2557 tcp_seq onxt = tp->snd_nxt; 2558 2559 /* 2560 * If we're doing sack, check to 2561 * see if we're already in sack 2562 * recovery. If we're not doing sack, 2563 * check to see if we're in newreno 2564 * recovery. 2565 */ 2566 if (tp->t_flags & TF_SACK_PERMIT) { 2567 if (IN_FASTRECOVERY(tp->t_flags)) { 2568 tp->t_dupacks = 0; 2569 break; 2570 } 2571 } else { 2572 if (SEQ_LEQ(th->th_ack, 2573 tp->snd_recover)) { 2574 tp->t_dupacks = 0; 2575 break; 2576 } 2577 } 2578 /* Congestion signal before ack. */ 2579 cc_cong_signal(tp, th, CC_NDUPACK); 2580 cc_ack_received(tp, th, nsegs, 2581 CC_DUPACK); 2582 tcp_timer_activate(tp, TT_REXMT, 0); 2583 tp->t_rtttime = 0; 2584 if (tp->t_flags & TF_SACK_PERMIT) { 2585 TCPSTAT_INC( 2586 tcps_sack_recovery_episode); 2587 tp->snd_recover = tp->snd_nxt; 2588 tp->snd_cwnd = maxseg; 2589 (void) tp->t_fb->tfb_tcp_output(tp); 2590 goto drop; 2591 } 2592 tp->snd_nxt = th->th_ack; 2593 tp->snd_cwnd = maxseg; 2594 (void) tp->t_fb->tfb_tcp_output(tp); 2595 KASSERT(tp->snd_limited <= 2, 2596 ("%s: tp->snd_limited too big", 2597 __func__)); 2598 tp->snd_cwnd = tp->snd_ssthresh + 2599 maxseg * 2600 (tp->t_dupacks - tp->snd_limited); 2601 if (SEQ_GT(onxt, tp->snd_nxt)) 2602 tp->snd_nxt = onxt; 2603 goto drop; 2604 } else if (V_tcp_do_rfc3042) { 2605 /* 2606 * Process first and second duplicate 2607 * ACKs. Each indicates a segment 2608 * leaving the network, creating room 2609 * for more. Make sure we can send a 2610 * packet on reception of each duplicate 2611 * ACK by increasing snd_cwnd by one 2612 * segment. Restore the original 2613 * snd_cwnd after packet transmission. 2614 */ 2615 cc_ack_received(tp, th, nsegs, 2616 CC_DUPACK); 2617 uint32_t oldcwnd = tp->snd_cwnd; 2618 tcp_seq oldsndmax = tp->snd_max; 2619 u_int sent; 2620 int avail; 2621 2622 KASSERT(tp->t_dupacks == 1 || 2623 tp->t_dupacks == 2, 2624 ("%s: dupacks not 1 or 2", 2625 __func__)); 2626 if (tp->t_dupacks == 1) 2627 tp->snd_limited = 0; 2628 tp->snd_cwnd = 2629 (tp->snd_nxt - tp->snd_una) + 2630 (tp->t_dupacks - tp->snd_limited) * 2631 maxseg; 2632 /* 2633 * Only call tcp_output when there 2634 * is new data available to be sent. 2635 * Otherwise we would send pure ACKs. 2636 */ 2637 SOCKBUF_LOCK(&so->so_snd); 2638 avail = sbavail(&so->so_snd) - 2639 (tp->snd_nxt - tp->snd_una); 2640 SOCKBUF_UNLOCK(&so->so_snd); 2641 if (avail > 0) 2642 (void) tp->t_fb->tfb_tcp_output(tp); 2643 sent = tp->snd_max - oldsndmax; 2644 if (sent > maxseg) { 2645 KASSERT((tp->t_dupacks == 2 && 2646 tp->snd_limited == 0) || 2647 (sent == maxseg + 1 && 2648 tp->t_flags & TF_SENTFIN), 2649 ("%s: sent too much", 2650 __func__)); 2651 tp->snd_limited = 2; 2652 } else if (sent > 0) 2653 ++tp->snd_limited; 2654 tp->snd_cwnd = oldcwnd; 2655 goto drop; 2656 } 2657 } 2658 break; 2659 } else { 2660 /* 2661 * This ack is advancing the left edge, reset the 2662 * counter. 2663 */ 2664 tp->t_dupacks = 0; 2665 /* 2666 * If this ack also has new SACK info, increment the 2667 * counter as per rfc6675. The variable 2668 * sack_changed tracks all changes to the SACK 2669 * scoreboard, including when partial ACKs without 2670 * SACK options are received, and clear the scoreboard 2671 * from the left side. Such partial ACKs should not be 2672 * counted as dupacks here. 2673 */ 2674 if ((tp->t_flags & TF_SACK_PERMIT) && 2675 (to.to_flags & TOF_SACK) && 2676 sack_changed) 2677 tp->t_dupacks++; 2678 } 2679 2680 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2681 ("%s: th_ack <= snd_una", __func__)); 2682 2683 /* 2684 * If the congestion window was inflated to account 2685 * for the other side's cached packets, retract it. 2686 */ 2687 if (IN_FASTRECOVERY(tp->t_flags)) { 2688 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2689 if (tp->t_flags & TF_SACK_PERMIT) 2690 tcp_sack_partialack(tp, th); 2691 else 2692 tcp_newreno_partial_ack(tp, th); 2693 } else 2694 cc_post_recovery(tp, th); 2695 } 2696 /* 2697 * If we reach this point, ACK is not a duplicate, 2698 * i.e., it ACKs something we sent. 2699 */ 2700 if (tp->t_flags & TF_NEEDSYN) { 2701 /* 2702 * T/TCP: Connection was half-synchronized, and our 2703 * SYN has been ACK'd (so connection is now fully 2704 * synchronized). Go to non-starred state, 2705 * increment snd_una for ACK of SYN, and check if 2706 * we can do window scaling. 2707 */ 2708 tp->t_flags &= ~TF_NEEDSYN; 2709 tp->snd_una++; 2710 /* Do window scaling? */ 2711 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2712 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2713 tp->rcv_scale = tp->request_r_scale; 2714 /* Send window already scaled. */ 2715 } 2716 } 2717 2718 process_ACK: 2719 INP_WLOCK_ASSERT(tp->t_inpcb); 2720 2721 /* 2722 * Adjust for the SYN bit in sequence space, 2723 * but don't account for it in cwnd calculations. 2724 * This is for the SYN_RECEIVED, non-simultaneous 2725 * SYN case. SYN_SENT and simultaneous SYN are 2726 * treated elsewhere. 2727 */ 2728 if (incforsyn) 2729 tp->snd_una++; 2730 acked = BYTES_THIS_ACK(tp, th); 2731 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2732 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2733 tp->snd_una, th->th_ack, tp, m)); 2734 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2735 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2736 2737 /* 2738 * If we just performed our first retransmit, and the ACK 2739 * arrives within our recovery window, then it was a mistake 2740 * to do the retransmit in the first place. Recover our 2741 * original cwnd and ssthresh, and proceed to transmit where 2742 * we left off. 2743 */ 2744 if (tp->t_rxtshift == 1 && 2745 tp->t_flags & TF_PREVVALID && 2746 tp->t_badrxtwin && 2747 SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 2748 cc_cong_signal(tp, th, CC_RTO_ERR); 2749 2750 /* 2751 * If we have a timestamp reply, update smoothed 2752 * round trip time. If no timestamp is present but 2753 * transmit timer is running and timed sequence 2754 * number was acked, update smoothed round trip time. 2755 * Since we now have an rtt measurement, cancel the 2756 * timer backoff (cf., Phil Karn's retransmit alg.). 2757 * Recompute the initial retransmit timer. 2758 * 2759 * Some boxes send broken timestamp replies 2760 * during the SYN+ACK phase, ignore 2761 * timestamps of 0 or we could calculate a 2762 * huge RTT and blow up the retransmit timer. 2763 */ 2764 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2765 uint32_t t; 2766 2767 t = tcp_ts_getticks() - to.to_tsecr; 2768 if (!tp->t_rttlow || tp->t_rttlow > t) 2769 tp->t_rttlow = t; 2770 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2771 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2772 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2773 tp->t_rttlow = ticks - tp->t_rtttime; 2774 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2775 } 2776 2777 /* 2778 * If all outstanding data is acked, stop retransmit 2779 * timer and remember to restart (more output or persist). 2780 * If there is more data to be acked, restart retransmit 2781 * timer, using current (possibly backed-off) value. 2782 */ 2783 if (th->th_ack == tp->snd_max) { 2784 tcp_timer_activate(tp, TT_REXMT, 0); 2785 needoutput = 1; 2786 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2787 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2788 2789 /* 2790 * If no data (only SYN) was ACK'd, 2791 * skip rest of ACK processing. 2792 */ 2793 if (acked == 0) 2794 goto step6; 2795 2796 /* 2797 * Let the congestion control algorithm update congestion 2798 * control related information. This typically means increasing 2799 * the congestion window. 2800 */ 2801 cc_ack_received(tp, th, nsegs, CC_ACK); 2802 2803 SOCKBUF_LOCK(&so->so_snd); 2804 if (acked > sbavail(&so->so_snd)) { 2805 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2806 tp->snd_wnd -= sbavail(&so->so_snd); 2807 else 2808 tp->snd_wnd = 0; 2809 mfree = sbcut_locked(&so->so_snd, 2810 (int)sbavail(&so->so_snd)); 2811 ourfinisacked = 1; 2812 } else { 2813 mfree = sbcut_locked(&so->so_snd, acked); 2814 if (tp->snd_wnd >= (uint32_t) acked) 2815 tp->snd_wnd -= acked; 2816 else 2817 tp->snd_wnd = 0; 2818 ourfinisacked = 0; 2819 } 2820 /* NB: sowwakeup_locked() does an implicit unlock. */ 2821 sowwakeup_locked(so); 2822 m_freem(mfree); 2823 /* Detect una wraparound. */ 2824 if (!IN_RECOVERY(tp->t_flags) && 2825 SEQ_GT(tp->snd_una, tp->snd_recover) && 2826 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2827 tp->snd_recover = th->th_ack - 1; 2828 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2829 if (IN_RECOVERY(tp->t_flags) && 2830 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2831 EXIT_RECOVERY(tp->t_flags); 2832 } 2833 tp->snd_una = th->th_ack; 2834 if (tp->t_flags & TF_SACK_PERMIT) { 2835 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2836 tp->snd_recover = tp->snd_una; 2837 } 2838 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2839 tp->snd_nxt = tp->snd_una; 2840 2841 switch (tp->t_state) { 2842 /* 2843 * In FIN_WAIT_1 STATE in addition to the processing 2844 * for the ESTABLISHED state if our FIN is now acknowledged 2845 * then enter FIN_WAIT_2. 2846 */ 2847 case TCPS_FIN_WAIT_1: 2848 if (ourfinisacked) { 2849 /* 2850 * If we can't receive any more 2851 * data, then closing user can proceed. 2852 * Starting the timer is contrary to the 2853 * specification, but if we don't get a FIN 2854 * we'll hang forever. 2855 * 2856 * XXXjl: 2857 * we should release the tp also, and use a 2858 * compressed state. 2859 */ 2860 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2861 soisdisconnected(so); 2862 tcp_timer_activate(tp, TT_2MSL, 2863 (tcp_fast_finwait2_recycle ? 2864 tcp_finwait2_timeout : 2865 TP_MAXIDLE(tp))); 2866 } 2867 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2868 } 2869 break; 2870 2871 /* 2872 * In CLOSING STATE in addition to the processing for 2873 * the ESTABLISHED state if the ACK acknowledges our FIN 2874 * then enter the TIME-WAIT state, otherwise ignore 2875 * the segment. 2876 */ 2877 case TCPS_CLOSING: 2878 if (ourfinisacked) { 2879 tcp_twstart(tp); 2880 m_freem(m); 2881 return; 2882 } 2883 break; 2884 2885 /* 2886 * In LAST_ACK, we may still be waiting for data to drain 2887 * and/or to be acked, as well as for the ack of our FIN. 2888 * If our FIN is now acknowledged, delete the TCB, 2889 * enter the closed state and return. 2890 */ 2891 case TCPS_LAST_ACK: 2892 if (ourfinisacked) { 2893 tp = tcp_close(tp); 2894 goto drop; 2895 } 2896 break; 2897 } 2898 } 2899 2900 step6: 2901 INP_WLOCK_ASSERT(tp->t_inpcb); 2902 2903 /* 2904 * Update window information. 2905 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2906 */ 2907 if ((thflags & TH_ACK) && 2908 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2909 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2910 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2911 /* keep track of pure window updates */ 2912 if (tlen == 0 && 2913 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2914 TCPSTAT_INC(tcps_rcvwinupd); 2915 tp->snd_wnd = tiwin; 2916 tp->snd_wl1 = th->th_seq; 2917 tp->snd_wl2 = th->th_ack; 2918 if (tp->snd_wnd > tp->max_sndwnd) 2919 tp->max_sndwnd = tp->snd_wnd; 2920 needoutput = 1; 2921 } 2922 2923 /* 2924 * Process segments with URG. 2925 */ 2926 if ((thflags & TH_URG) && th->th_urp && 2927 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2928 /* 2929 * This is a kludge, but if we receive and accept 2930 * random urgent pointers, we'll crash in 2931 * soreceive. It's hard to imagine someone 2932 * actually wanting to send this much urgent data. 2933 */ 2934 SOCKBUF_LOCK(&so->so_rcv); 2935 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 2936 th->th_urp = 0; /* XXX */ 2937 thflags &= ~TH_URG; /* XXX */ 2938 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2939 goto dodata; /* XXX */ 2940 } 2941 /* 2942 * If this segment advances the known urgent pointer, 2943 * then mark the data stream. This should not happen 2944 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2945 * a FIN has been received from the remote side. 2946 * In these states we ignore the URG. 2947 * 2948 * According to RFC961 (Assigned Protocols), 2949 * the urgent pointer points to the last octet 2950 * of urgent data. We continue, however, 2951 * to consider it to indicate the first octet 2952 * of data past the urgent section as the original 2953 * spec states (in one of two places). 2954 */ 2955 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2956 tp->rcv_up = th->th_seq + th->th_urp; 2957 so->so_oobmark = sbavail(&so->so_rcv) + 2958 (tp->rcv_up - tp->rcv_nxt) - 1; 2959 if (so->so_oobmark == 0) 2960 so->so_rcv.sb_state |= SBS_RCVATMARK; 2961 sohasoutofband(so); 2962 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2963 } 2964 SOCKBUF_UNLOCK(&so->so_rcv); 2965 /* 2966 * Remove out of band data so doesn't get presented to user. 2967 * This can happen independent of advancing the URG pointer, 2968 * but if two URG's are pending at once, some out-of-band 2969 * data may creep in... ick. 2970 */ 2971 if (th->th_urp <= (uint32_t)tlen && 2972 !(so->so_options & SO_OOBINLINE)) { 2973 /* hdr drop is delayed */ 2974 tcp_pulloutofband(so, th, m, drop_hdrlen); 2975 } 2976 } else { 2977 /* 2978 * If no out of band data is expected, 2979 * pull receive urgent pointer along 2980 * with the receive window. 2981 */ 2982 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2983 tp->rcv_up = tp->rcv_nxt; 2984 } 2985 dodata: /* XXX */ 2986 INP_WLOCK_ASSERT(tp->t_inpcb); 2987 2988 /* 2989 * Process the segment text, merging it into the TCP sequencing queue, 2990 * and arranging for acknowledgment of receipt if necessary. 2991 * This process logically involves adjusting tp->rcv_wnd as data 2992 * is presented to the user (this happens in tcp_usrreq.c, 2993 * case PRU_RCVD). If a FIN has already been received on this 2994 * connection then we just ignore the text. 2995 */ 2996 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 2997 IS_FASTOPEN(tp->t_flags)); 2998 if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) && 2999 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3000 tcp_seq save_start = th->th_seq; 3001 tcp_seq save_rnxt = tp->rcv_nxt; 3002 int save_tlen = tlen; 3003 m_adj(m, drop_hdrlen); /* delayed header drop */ 3004 /* 3005 * Insert segment which includes th into TCP reassembly queue 3006 * with control block tp. Set thflags to whether reassembly now 3007 * includes a segment with FIN. This handles the common case 3008 * inline (segment is the next to be received on an established 3009 * connection, and the queue is empty), avoiding linkage into 3010 * and removal from the queue and repetition of various 3011 * conversions. 3012 * Set DELACK for segments received in order, but ack 3013 * immediately when segments are out of order (so 3014 * fast retransmit can work). 3015 */ 3016 if (th->th_seq == tp->rcv_nxt && 3017 SEGQ_EMPTY(tp) && 3018 (TCPS_HAVEESTABLISHED(tp->t_state) || 3019 tfo_syn)) { 3020 if (DELAY_ACK(tp, tlen) || tfo_syn) 3021 tp->t_flags |= TF_DELACK; 3022 else 3023 tp->t_flags |= TF_ACKNOW; 3024 tp->rcv_nxt += tlen; 3025 if (tlen && 3026 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 3027 (tp->t_fbyte_in == 0)) { 3028 tp->t_fbyte_in = ticks; 3029 if (tp->t_fbyte_in == 0) 3030 tp->t_fbyte_in = 1; 3031 if (tp->t_fbyte_out && tp->t_fbyte_in) 3032 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 3033 } 3034 thflags = th->th_flags & TH_FIN; 3035 TCPSTAT_INC(tcps_rcvpack); 3036 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3037 SOCKBUF_LOCK(&so->so_rcv); 3038 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3039 m_freem(m); 3040 else 3041 sbappendstream_locked(&so->so_rcv, m, 0); 3042 /* NB: sorwakeup_locked() does an implicit unlock. */ 3043 sorwakeup_locked(so); 3044 } else { 3045 /* 3046 * XXX: Due to the header drop above "th" is 3047 * theoretically invalid by now. Fortunately 3048 * m_adj() doesn't actually frees any mbufs 3049 * when trimming from the head. 3050 */ 3051 tcp_seq temp = save_start; 3052 thflags = tcp_reass(tp, th, &temp, &tlen, m); 3053 tp->t_flags |= TF_ACKNOW; 3054 } 3055 if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) { 3056 if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) { 3057 /* 3058 * DSACK actually handled in the fastpath 3059 * above. 3060 */ 3061 tcp_update_sack_list(tp, save_start, 3062 save_start + save_tlen); 3063 } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) { 3064 if ((tp->rcv_numsacks >= 1) && 3065 (tp->sackblks[0].end == save_start)) { 3066 /* 3067 * Partial overlap, recorded at todrop 3068 * above. 3069 */ 3070 tcp_update_sack_list(tp, 3071 tp->sackblks[0].start, 3072 tp->sackblks[0].end); 3073 } else { 3074 tcp_update_dsack_list(tp, save_start, 3075 save_start + save_tlen); 3076 } 3077 } else if (tlen >= save_tlen) { 3078 /* Update of sackblks. */ 3079 tcp_update_dsack_list(tp, save_start, 3080 save_start + save_tlen); 3081 } else if (tlen > 0) { 3082 tcp_update_dsack_list(tp, save_start, 3083 save_start + tlen); 3084 } 3085 } 3086 #if 0 3087 /* 3088 * Note the amount of data that peer has sent into 3089 * our window, in order to estimate the sender's 3090 * buffer size. 3091 * XXX: Unused. 3092 */ 3093 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3094 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3095 else 3096 len = so->so_rcv.sb_hiwat; 3097 #endif 3098 } else { 3099 m_freem(m); 3100 thflags &= ~TH_FIN; 3101 } 3102 3103 /* 3104 * If FIN is received ACK the FIN and let the user know 3105 * that the connection is closing. 3106 */ 3107 if (thflags & TH_FIN) { 3108 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3109 socantrcvmore(so); 3110 /* 3111 * If connection is half-synchronized 3112 * (ie NEEDSYN flag on) then delay ACK, 3113 * so it may be piggybacked when SYN is sent. 3114 * Otherwise, since we received a FIN then no 3115 * more input can be expected, send ACK now. 3116 */ 3117 if (tp->t_flags & TF_NEEDSYN) 3118 tp->t_flags |= TF_DELACK; 3119 else 3120 tp->t_flags |= TF_ACKNOW; 3121 tp->rcv_nxt++; 3122 } 3123 switch (tp->t_state) { 3124 /* 3125 * In SYN_RECEIVED and ESTABLISHED STATES 3126 * enter the CLOSE_WAIT state. 3127 */ 3128 case TCPS_SYN_RECEIVED: 3129 tp->t_starttime = ticks; 3130 /* FALLTHROUGH */ 3131 case TCPS_ESTABLISHED: 3132 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3133 break; 3134 3135 /* 3136 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3137 * enter the CLOSING state. 3138 */ 3139 case TCPS_FIN_WAIT_1: 3140 tcp_state_change(tp, TCPS_CLOSING); 3141 break; 3142 3143 /* 3144 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3145 * starting the time-wait timer, turning off the other 3146 * standard timers. 3147 */ 3148 case TCPS_FIN_WAIT_2: 3149 tcp_twstart(tp); 3150 return; 3151 } 3152 } 3153 #ifdef TCPDEBUG 3154 if (so->so_options & SO_DEBUG) 3155 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3156 &tcp_savetcp, 0); 3157 #endif 3158 TCP_PROBE3(debug__input, tp, th, m); 3159 3160 /* 3161 * Return any desired output. 3162 */ 3163 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3164 (void) tp->t_fb->tfb_tcp_output(tp); 3165 3166 check_delack: 3167 INP_WLOCK_ASSERT(tp->t_inpcb); 3168 3169 if (tp->t_flags & TF_DELACK) { 3170 tp->t_flags &= ~TF_DELACK; 3171 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3172 } 3173 INP_WUNLOCK(tp->t_inpcb); 3174 return; 3175 3176 dropafterack: 3177 /* 3178 * Generate an ACK dropping incoming segment if it occupies 3179 * sequence space, where the ACK reflects our state. 3180 * 3181 * We can now skip the test for the RST flag since all 3182 * paths to this code happen after packets containing 3183 * RST have been dropped. 3184 * 3185 * In the SYN-RECEIVED state, don't send an ACK unless the 3186 * segment we received passes the SYN-RECEIVED ACK test. 3187 * If it fails send a RST. This breaks the loop in the 3188 * "LAND" DoS attack, and also prevents an ACK storm 3189 * between two listening ports that have been sent forged 3190 * SYN segments, each with the source address of the other. 3191 */ 3192 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3193 (SEQ_GT(tp->snd_una, th->th_ack) || 3194 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3195 rstreason = BANDLIM_RST_OPENPORT; 3196 goto dropwithreset; 3197 } 3198 #ifdef TCPDEBUG 3199 if (so->so_options & SO_DEBUG) 3200 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3201 &tcp_savetcp, 0); 3202 #endif 3203 TCP_PROBE3(debug__input, tp, th, m); 3204 tp->t_flags |= TF_ACKNOW; 3205 (void) tp->t_fb->tfb_tcp_output(tp); 3206 INP_WUNLOCK(tp->t_inpcb); 3207 m_freem(m); 3208 return; 3209 3210 dropwithreset: 3211 if (tp != NULL) { 3212 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3213 INP_WUNLOCK(tp->t_inpcb); 3214 } else 3215 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3216 return; 3217 3218 drop: 3219 /* 3220 * Drop space held by incoming segment and return. 3221 */ 3222 #ifdef TCPDEBUG 3223 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3224 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3225 &tcp_savetcp, 0); 3226 #endif 3227 TCP_PROBE3(debug__input, tp, th, m); 3228 if (tp != NULL) 3229 INP_WUNLOCK(tp->t_inpcb); 3230 m_freem(m); 3231 } 3232 3233 /* 3234 * Issue RST and make ACK acceptable to originator of segment. 3235 * The mbuf must still include the original packet header. 3236 * tp may be NULL. 3237 */ 3238 void 3239 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3240 int tlen, int rstreason) 3241 { 3242 #ifdef INET 3243 struct ip *ip; 3244 #endif 3245 #ifdef INET6 3246 struct ip6_hdr *ip6; 3247 #endif 3248 3249 if (tp != NULL) { 3250 INP_WLOCK_ASSERT(tp->t_inpcb); 3251 } 3252 3253 /* Don't bother if destination was broadcast/multicast. */ 3254 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3255 goto drop; 3256 #ifdef INET6 3257 if (mtod(m, struct ip *)->ip_v == 6) { 3258 ip6 = mtod(m, struct ip6_hdr *); 3259 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3260 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3261 goto drop; 3262 /* IPv6 anycast check is done at tcp6_input() */ 3263 } 3264 #endif 3265 #if defined(INET) && defined(INET6) 3266 else 3267 #endif 3268 #ifdef INET 3269 { 3270 ip = mtod(m, struct ip *); 3271 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3272 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3273 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3274 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3275 goto drop; 3276 } 3277 #endif 3278 3279 /* Perform bandwidth limiting. */ 3280 if (badport_bandlim(rstreason) < 0) 3281 goto drop; 3282 3283 /* tcp_respond consumes the mbuf chain. */ 3284 if (th->th_flags & TH_ACK) { 3285 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3286 th->th_ack, TH_RST); 3287 } else { 3288 if (th->th_flags & TH_SYN) 3289 tlen++; 3290 if (th->th_flags & TH_FIN) 3291 tlen++; 3292 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3293 (tcp_seq)0, TH_RST|TH_ACK); 3294 } 3295 return; 3296 drop: 3297 m_freem(m); 3298 } 3299 3300 /* 3301 * Parse TCP options and place in tcpopt. 3302 */ 3303 void 3304 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3305 { 3306 int opt, optlen; 3307 3308 to->to_flags = 0; 3309 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3310 opt = cp[0]; 3311 if (opt == TCPOPT_EOL) 3312 break; 3313 if (opt == TCPOPT_NOP) 3314 optlen = 1; 3315 else { 3316 if (cnt < 2) 3317 break; 3318 optlen = cp[1]; 3319 if (optlen < 2 || optlen > cnt) 3320 break; 3321 } 3322 switch (opt) { 3323 case TCPOPT_MAXSEG: 3324 if (optlen != TCPOLEN_MAXSEG) 3325 continue; 3326 if (!(flags & TO_SYN)) 3327 continue; 3328 to->to_flags |= TOF_MSS; 3329 bcopy((char *)cp + 2, 3330 (char *)&to->to_mss, sizeof(to->to_mss)); 3331 to->to_mss = ntohs(to->to_mss); 3332 break; 3333 case TCPOPT_WINDOW: 3334 if (optlen != TCPOLEN_WINDOW) 3335 continue; 3336 if (!(flags & TO_SYN)) 3337 continue; 3338 to->to_flags |= TOF_SCALE; 3339 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3340 break; 3341 case TCPOPT_TIMESTAMP: 3342 if (optlen != TCPOLEN_TIMESTAMP) 3343 continue; 3344 to->to_flags |= TOF_TS; 3345 bcopy((char *)cp + 2, 3346 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3347 to->to_tsval = ntohl(to->to_tsval); 3348 bcopy((char *)cp + 6, 3349 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3350 to->to_tsecr = ntohl(to->to_tsecr); 3351 break; 3352 case TCPOPT_SIGNATURE: 3353 /* 3354 * In order to reply to a host which has set the 3355 * TCP_SIGNATURE option in its initial SYN, we have 3356 * to record the fact that the option was observed 3357 * here for the syncache code to perform the correct 3358 * response. 3359 */ 3360 if (optlen != TCPOLEN_SIGNATURE) 3361 continue; 3362 to->to_flags |= TOF_SIGNATURE; 3363 to->to_signature = cp + 2; 3364 break; 3365 case TCPOPT_SACK_PERMITTED: 3366 if (optlen != TCPOLEN_SACK_PERMITTED) 3367 continue; 3368 if (!(flags & TO_SYN)) 3369 continue; 3370 if (!V_tcp_do_sack) 3371 continue; 3372 to->to_flags |= TOF_SACKPERM; 3373 break; 3374 case TCPOPT_SACK: 3375 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3376 continue; 3377 if (flags & TO_SYN) 3378 continue; 3379 to->to_flags |= TOF_SACK; 3380 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3381 to->to_sacks = cp + 2; 3382 TCPSTAT_INC(tcps_sack_rcv_blocks); 3383 break; 3384 case TCPOPT_FAST_OPEN: 3385 /* 3386 * Cookie length validation is performed by the 3387 * server side cookie checking code or the client 3388 * side cookie cache update code. 3389 */ 3390 if (!(flags & TO_SYN)) 3391 continue; 3392 if (!V_tcp_fastopen_client_enable && 3393 !V_tcp_fastopen_server_enable) 3394 continue; 3395 to->to_flags |= TOF_FASTOPEN; 3396 to->to_tfo_len = optlen - 2; 3397 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3398 break; 3399 default: 3400 continue; 3401 } 3402 } 3403 } 3404 3405 /* 3406 * Pull out of band byte out of a segment so 3407 * it doesn't appear in the user's data queue. 3408 * It is still reflected in the segment length for 3409 * sequencing purposes. 3410 */ 3411 void 3412 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3413 int off) 3414 { 3415 int cnt = off + th->th_urp - 1; 3416 3417 while (cnt >= 0) { 3418 if (m->m_len > cnt) { 3419 char *cp = mtod(m, caddr_t) + cnt; 3420 struct tcpcb *tp = sototcpcb(so); 3421 3422 INP_WLOCK_ASSERT(tp->t_inpcb); 3423 3424 tp->t_iobc = *cp; 3425 tp->t_oobflags |= TCPOOB_HAVEDATA; 3426 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3427 m->m_len--; 3428 if (m->m_flags & M_PKTHDR) 3429 m->m_pkthdr.len--; 3430 return; 3431 } 3432 cnt -= m->m_len; 3433 m = m->m_next; 3434 if (m == NULL) 3435 break; 3436 } 3437 panic("tcp_pulloutofband"); 3438 } 3439 3440 /* 3441 * Collect new round-trip time estimate 3442 * and update averages and current timeout. 3443 */ 3444 void 3445 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3446 { 3447 int delta; 3448 3449 INP_WLOCK_ASSERT(tp->t_inpcb); 3450 3451 TCPSTAT_INC(tcps_rttupdated); 3452 tp->t_rttupdated++; 3453 #ifdef STATS 3454 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT, 3455 imax(0, rtt * 1000 / hz)); 3456 #endif 3457 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) { 3458 /* 3459 * srtt is stored as fixed point with 5 bits after the 3460 * binary point (i.e., scaled by 8). The following magic 3461 * is equivalent to the smoothing algorithm in rfc793 with 3462 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3463 * point). Adjust rtt to origin 0. 3464 */ 3465 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3466 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3467 3468 if ((tp->t_srtt += delta) <= 0) 3469 tp->t_srtt = 1; 3470 3471 /* 3472 * We accumulate a smoothed rtt variance (actually, a 3473 * smoothed mean difference), then set the retransmit 3474 * timer to smoothed rtt + 4 times the smoothed variance. 3475 * rttvar is stored as fixed point with 4 bits after the 3476 * binary point (scaled by 16). The following is 3477 * equivalent to rfc793 smoothing with an alpha of .75 3478 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3479 * rfc793's wired-in beta. 3480 */ 3481 if (delta < 0) 3482 delta = -delta; 3483 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3484 if ((tp->t_rttvar += delta) <= 0) 3485 tp->t_rttvar = 1; 3486 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3487 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3488 } else { 3489 /* 3490 * No rtt measurement yet - use the unsmoothed rtt. 3491 * Set the variance to half the rtt (so our first 3492 * retransmit happens at 3*rtt). 3493 */ 3494 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3495 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3496 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3497 } 3498 tp->t_rtttime = 0; 3499 tp->t_rxtshift = 0; 3500 3501 /* 3502 * the retransmit should happen at rtt + 4 * rttvar. 3503 * Because of the way we do the smoothing, srtt and rttvar 3504 * will each average +1/2 tick of bias. When we compute 3505 * the retransmit timer, we want 1/2 tick of rounding and 3506 * 1 extra tick because of +-1/2 tick uncertainty in the 3507 * firing of the timer. The bias will give us exactly the 3508 * 1.5 tick we need. But, because the bias is 3509 * statistical, we have to test that we don't drop below 3510 * the minimum feasible timer (which is 2 ticks). 3511 */ 3512 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3513 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3514 3515 /* 3516 * We received an ack for a packet that wasn't retransmitted; 3517 * it is probably safe to discard any error indications we've 3518 * received recently. This isn't quite right, but close enough 3519 * for now (a route might have failed after we sent a segment, 3520 * and the return path might not be symmetrical). 3521 */ 3522 tp->t_softerror = 0; 3523 } 3524 3525 /* 3526 * Determine a reasonable value for maxseg size. 3527 * If the route is known, check route for mtu. 3528 * If none, use an mss that can be handled on the outgoing interface 3529 * without forcing IP to fragment. If no route is found, route has no mtu, 3530 * or the destination isn't local, use a default, hopefully conservative 3531 * size (usually 512 or the default IP max size, but no more than the mtu 3532 * of the interface), as we can't discover anything about intervening 3533 * gateways or networks. We also initialize the congestion/slow start 3534 * window to be a single segment if the destination isn't local. 3535 * While looking at the routing entry, we also initialize other path-dependent 3536 * parameters from pre-set or cached values in the routing entry. 3537 * 3538 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3539 * IP options, e.g. IPSEC data, since length of this data may vary, and 3540 * thus it is calculated for every segment separately in tcp_output(). 3541 * 3542 * NOTE that this routine is only called when we process an incoming 3543 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3544 * settings are handled in tcp_mssopt(). 3545 */ 3546 void 3547 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3548 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3549 { 3550 int mss = 0; 3551 uint32_t maxmtu = 0; 3552 struct inpcb *inp = tp->t_inpcb; 3553 struct hc_metrics_lite metrics; 3554 #ifdef INET6 3555 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3556 size_t min_protoh = isipv6 ? 3557 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3558 sizeof (struct tcpiphdr); 3559 #else 3560 const size_t min_protoh = sizeof(struct tcpiphdr); 3561 #endif 3562 3563 INP_WLOCK_ASSERT(tp->t_inpcb); 3564 3565 if (mtuoffer != -1) { 3566 KASSERT(offer == -1, ("%s: conflict", __func__)); 3567 offer = mtuoffer - min_protoh; 3568 } 3569 3570 /* Initialize. */ 3571 #ifdef INET6 3572 if (isipv6) { 3573 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3574 tp->t_maxseg = V_tcp_v6mssdflt; 3575 } 3576 #endif 3577 #if defined(INET) && defined(INET6) 3578 else 3579 #endif 3580 #ifdef INET 3581 { 3582 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3583 tp->t_maxseg = V_tcp_mssdflt; 3584 } 3585 #endif 3586 3587 /* 3588 * No route to sender, stay with default mss and return. 3589 */ 3590 if (maxmtu == 0) { 3591 /* 3592 * In case we return early we need to initialize metrics 3593 * to a defined state as tcp_hc_get() would do for us 3594 * if there was no cache hit. 3595 */ 3596 if (metricptr != NULL) 3597 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3598 return; 3599 } 3600 3601 /* What have we got? */ 3602 switch (offer) { 3603 case 0: 3604 /* 3605 * Offer == 0 means that there was no MSS on the SYN 3606 * segment, in this case we use tcp_mssdflt as 3607 * already assigned to t_maxseg above. 3608 */ 3609 offer = tp->t_maxseg; 3610 break; 3611 3612 case -1: 3613 /* 3614 * Offer == -1 means that we didn't receive SYN yet. 3615 */ 3616 /* FALLTHROUGH */ 3617 3618 default: 3619 /* 3620 * Prevent DoS attack with too small MSS. Round up 3621 * to at least minmss. 3622 */ 3623 offer = max(offer, V_tcp_minmss); 3624 } 3625 3626 /* 3627 * rmx information is now retrieved from tcp_hostcache. 3628 */ 3629 tcp_hc_get(&inp->inp_inc, &metrics); 3630 if (metricptr != NULL) 3631 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3632 3633 /* 3634 * If there's a discovered mtu in tcp hostcache, use it. 3635 * Else, use the link mtu. 3636 */ 3637 if (metrics.rmx_mtu) 3638 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3639 else { 3640 #ifdef INET6 3641 if (isipv6) { 3642 mss = maxmtu - min_protoh; 3643 if (!V_path_mtu_discovery && 3644 !in6_localaddr(&inp->in6p_faddr)) 3645 mss = min(mss, V_tcp_v6mssdflt); 3646 } 3647 #endif 3648 #if defined(INET) && defined(INET6) 3649 else 3650 #endif 3651 #ifdef INET 3652 { 3653 mss = maxmtu - min_protoh; 3654 if (!V_path_mtu_discovery && 3655 !in_localaddr(inp->inp_faddr)) 3656 mss = min(mss, V_tcp_mssdflt); 3657 } 3658 #endif 3659 /* 3660 * XXX - The above conditional (mss = maxmtu - min_protoh) 3661 * probably violates the TCP spec. 3662 * The problem is that, since we don't know the 3663 * other end's MSS, we are supposed to use a conservative 3664 * default. But, if we do that, then MTU discovery will 3665 * never actually take place, because the conservative 3666 * default is much less than the MTUs typically seen 3667 * on the Internet today. For the moment, we'll sweep 3668 * this under the carpet. 3669 * 3670 * The conservative default might not actually be a problem 3671 * if the only case this occurs is when sending an initial 3672 * SYN with options and data to a host we've never talked 3673 * to before. Then, they will reply with an MSS value which 3674 * will get recorded and the new parameters should get 3675 * recomputed. For Further Study. 3676 */ 3677 } 3678 mss = min(mss, offer); 3679 3680 /* 3681 * Sanity check: make sure that maxseg will be large 3682 * enough to allow some data on segments even if the 3683 * all the option space is used (40bytes). Otherwise 3684 * funny things may happen in tcp_output. 3685 * 3686 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3687 */ 3688 mss = max(mss, 64); 3689 3690 tp->t_maxseg = mss; 3691 } 3692 3693 void 3694 tcp_mss(struct tcpcb *tp, int offer) 3695 { 3696 int mss; 3697 uint32_t bufsize; 3698 struct inpcb *inp; 3699 struct socket *so; 3700 struct hc_metrics_lite metrics; 3701 struct tcp_ifcap cap; 3702 3703 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3704 3705 bzero(&cap, sizeof(cap)); 3706 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3707 3708 mss = tp->t_maxseg; 3709 inp = tp->t_inpcb; 3710 3711 /* 3712 * If there's a pipesize, change the socket buffer to that size, 3713 * don't change if sb_hiwat is different than default (then it 3714 * has been changed on purpose with setsockopt). 3715 * Make the socket buffers an integral number of mss units; 3716 * if the mss is larger than the socket buffer, decrease the mss. 3717 */ 3718 so = inp->inp_socket; 3719 SOCKBUF_LOCK(&so->so_snd); 3720 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3721 bufsize = metrics.rmx_sendpipe; 3722 else 3723 bufsize = so->so_snd.sb_hiwat; 3724 if (bufsize < mss) 3725 mss = bufsize; 3726 else { 3727 bufsize = roundup(bufsize, mss); 3728 if (bufsize > sb_max) 3729 bufsize = sb_max; 3730 if (bufsize > so->so_snd.sb_hiwat) 3731 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3732 } 3733 SOCKBUF_UNLOCK(&so->so_snd); 3734 /* 3735 * Sanity check: make sure that maxseg will be large 3736 * enough to allow some data on segments even if the 3737 * all the option space is used (40bytes). Otherwise 3738 * funny things may happen in tcp_output. 3739 * 3740 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3741 */ 3742 tp->t_maxseg = max(mss, 64); 3743 3744 SOCKBUF_LOCK(&so->so_rcv); 3745 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3746 bufsize = metrics.rmx_recvpipe; 3747 else 3748 bufsize = so->so_rcv.sb_hiwat; 3749 if (bufsize > mss) { 3750 bufsize = roundup(bufsize, mss); 3751 if (bufsize > sb_max) 3752 bufsize = sb_max; 3753 if (bufsize > so->so_rcv.sb_hiwat) 3754 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3755 } 3756 SOCKBUF_UNLOCK(&so->so_rcv); 3757 3758 /* Check the interface for TSO capabilities. */ 3759 if (cap.ifcap & CSUM_TSO) { 3760 tp->t_flags |= TF_TSO; 3761 tp->t_tsomax = cap.tsomax; 3762 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3763 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3764 } 3765 } 3766 3767 /* 3768 * Determine the MSS option to send on an outgoing SYN. 3769 */ 3770 int 3771 tcp_mssopt(struct in_conninfo *inc) 3772 { 3773 int mss = 0; 3774 uint32_t thcmtu = 0; 3775 uint32_t maxmtu = 0; 3776 size_t min_protoh; 3777 3778 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3779 3780 #ifdef INET6 3781 if (inc->inc_flags & INC_ISIPV6) { 3782 mss = V_tcp_v6mssdflt; 3783 maxmtu = tcp_maxmtu6(inc, NULL); 3784 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3785 } 3786 #endif 3787 #if defined(INET) && defined(INET6) 3788 else 3789 #endif 3790 #ifdef INET 3791 { 3792 mss = V_tcp_mssdflt; 3793 maxmtu = tcp_maxmtu(inc, NULL); 3794 min_protoh = sizeof(struct tcpiphdr); 3795 } 3796 #endif 3797 #if defined(INET6) || defined(INET) 3798 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3799 #endif 3800 3801 if (maxmtu && thcmtu) 3802 mss = min(maxmtu, thcmtu) - min_protoh; 3803 else if (maxmtu || thcmtu) 3804 mss = max(maxmtu, thcmtu) - min_protoh; 3805 3806 return (mss); 3807 } 3808 3809 /* 3810 * On a partial ack arrives, force the retransmission of the 3811 * next unacknowledged segment. Do not clear tp->t_dupacks. 3812 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3813 * be started again. 3814 */ 3815 void 3816 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3817 { 3818 tcp_seq onxt = tp->snd_nxt; 3819 uint32_t ocwnd = tp->snd_cwnd; 3820 u_int maxseg = tcp_maxseg(tp); 3821 3822 INP_WLOCK_ASSERT(tp->t_inpcb); 3823 3824 tcp_timer_activate(tp, TT_REXMT, 0); 3825 tp->t_rtttime = 0; 3826 tp->snd_nxt = th->th_ack; 3827 /* 3828 * Set snd_cwnd to one segment beyond acknowledged offset. 3829 * (tp->snd_una has not yet been updated when this function is called.) 3830 */ 3831 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3832 tp->t_flags |= TF_ACKNOW; 3833 (void) tp->t_fb->tfb_tcp_output(tp); 3834 tp->snd_cwnd = ocwnd; 3835 if (SEQ_GT(onxt, tp->snd_nxt)) 3836 tp->snd_nxt = onxt; 3837 /* 3838 * Partial window deflation. Relies on fact that tp->snd_una 3839 * not updated yet. 3840 */ 3841 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3842 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3843 else 3844 tp->snd_cwnd = 0; 3845 tp->snd_cwnd += maxseg; 3846 } 3847 3848 int 3849 tcp_compute_pipe(struct tcpcb *tp) 3850 { 3851 return (tp->snd_max - tp->snd_una + 3852 tp->sackhint.sack_bytes_rexmit - 3853 tp->sackhint.sacked_bytes); 3854 } 3855 3856 uint32_t 3857 tcp_compute_initwnd(uint32_t maxseg) 3858 { 3859 /* 3860 * Calculate the Initial Window, also used as Restart Window 3861 * 3862 * RFC5681 Section 3.1 specifies the default conservative values. 3863 * RFC3390 specifies slightly more aggressive values. 3864 * RFC6928 increases it to ten segments. 3865 * Support for user specified value for initial flight size. 3866 */ 3867 if (V_tcp_initcwnd_segments) 3868 return min(V_tcp_initcwnd_segments * maxseg, 3869 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 3870 else if (V_tcp_do_rfc3390) 3871 return min(4 * maxseg, max(2 * maxseg, 4380)); 3872 else { 3873 /* Per RFC5681 Section 3.1 */ 3874 if (maxseg > 2190) 3875 return (2 * maxseg); 3876 else if (maxseg > 1095) 3877 return (3 * maxseg); 3878 else 3879 return (4 * maxseg); 3880 } 3881 } 3882