1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/domain.h> 45 #ifdef TCP_HHOOK 46 #include <sys/hhook.h> 47 #endif 48 #include <sys/kernel.h> 49 #include <sys/lock.h> 50 #include <sys/mbuf.h> 51 #include <sys/mutex.h> 52 #include <sys/protosw.h> 53 #include <sys/sdt.h> 54 #include <sys/socket.h> 55 #include <sys/socketvar.h> 56 #include <sys/sysctl.h> 57 58 #include <net/if.h> 59 #include <net/route.h> 60 #include <net/vnet.h> 61 62 #include <netinet/in.h> 63 #include <netinet/in_kdtrace.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/ip.h> 66 #include <netinet/in_pcb.h> 67 #include <netinet/ip_var.h> 68 #include <netinet/ip_options.h> 69 #ifdef INET6 70 #include <netinet6/in6_pcb.h> 71 #include <netinet/ip6.h> 72 #include <netinet6/ip6_var.h> 73 #endif 74 #include <netinet/tcp.h> 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_log_buf.h> 77 #include <netinet/tcp_seq.h> 78 #include <netinet/tcp_timer.h> 79 #include <netinet/tcp_var.h> 80 #include <netinet/tcpip.h> 81 #include <netinet/cc/cc.h> 82 #include <netinet/tcp_fastopen.h> 83 #ifdef TCPPCAP 84 #include <netinet/tcp_pcap.h> 85 #endif 86 #ifdef TCPDEBUG 87 #include <netinet/tcp_debug.h> 88 #endif 89 #ifdef TCP_OFFLOAD 90 #include <netinet/tcp_offload.h> 91 #endif 92 93 #include <netipsec/ipsec_support.h> 94 95 #include <machine/in_cksum.h> 96 97 #include <security/mac/mac_framework.h> 98 99 VNET_DEFINE(int, path_mtu_discovery) = 1; 100 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 101 &VNET_NAME(path_mtu_discovery), 1, 102 "Enable Path MTU Discovery"); 103 104 VNET_DEFINE(int, tcp_do_tso) = 1; 105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 106 &VNET_NAME(tcp_do_tso), 0, 107 "Enable TCP Segmentation Offload"); 108 109 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 110 #define V_tcp_sendspace VNET(tcp_sendspace) 111 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 112 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 113 114 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 116 &VNET_NAME(tcp_do_autosndbuf), 0, 117 "Enable automatic send buffer sizing"); 118 119 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 120 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 121 &VNET_NAME(tcp_autosndbuf_inc), 0, 122 "Incrementor step size of automatic send buffer"); 123 124 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 126 &VNET_NAME(tcp_autosndbuf_max), 0, 127 "Max size of automatic send buffer"); 128 129 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 130 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 132 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 133 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 134 135 /* 136 * Make sure that either retransmit or persist timer is set for SYN, FIN and 137 * non-ACK. 138 */ 139 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 140 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 141 tcp_timer_active((tp), TT_REXMT) || \ 142 tcp_timer_active((tp), TT_PERSIST), \ 143 ("neither rexmt nor persist timer is set")) 144 145 static void inline cc_after_idle(struct tcpcb *tp); 146 147 #ifdef TCP_HHOOK 148 /* 149 * Wrapper for the TCP established output helper hook. 150 */ 151 void 152 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 153 struct tcpopt *to, uint32_t len, int tso) 154 { 155 struct tcp_hhook_data hhook_data; 156 157 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 158 hhook_data.tp = tp; 159 hhook_data.th = th; 160 hhook_data.to = to; 161 hhook_data.len = len; 162 hhook_data.tso = tso; 163 164 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 165 tp->osd); 166 } 167 } 168 #endif 169 170 /* 171 * Flags used when sending segments in tcp_output. Basic flags (TH_RST, 172 * TH_ACK,TH_SYN,TH_FIN) are totally determined by state, with the proviso 173 * that TH_FIN is sent only if all data queued for output is included in the 174 * segment. 175 */ 176 u_char tcp_outflags[TCP_NSTATES] = { 177 TH_RST|TH_ACK, /* 0, CLOSED */ 178 0, /* 1, LISTEN */ 179 TH_SYN, /* 2, SYN_SENT */ 180 TH_SYN|TH_ACK, /* 3, SYN_RECEIVED */ 181 TH_ACK, /* 4, ESTABLISHED */ 182 TH_ACK, /* 5, CLOSE_WAIT */ 183 TH_FIN|TH_ACK, /* 6, FIN_WAIT_1 */ 184 TH_FIN|TH_ACK, /* 7, CLOSING */ 185 TH_FIN|TH_ACK, /* 8, LAST_ACK */ 186 TH_ACK, /* 9, FIN_WAIT_2 */ 187 TH_ACK, /* 10, TIME_WAIT */ 188 }; 189 190 /* 191 * CC wrapper hook functions 192 */ 193 static void inline 194 cc_after_idle(struct tcpcb *tp) 195 { 196 INP_WLOCK_ASSERT(tp->t_inpcb); 197 198 if (CC_ALGO(tp)->after_idle != NULL) 199 CC_ALGO(tp)->after_idle(tp->ccv); 200 } 201 202 /* 203 * Tcp output routine: figure out what should be sent and send it. 204 */ 205 int 206 tcp_output(struct tcpcb *tp) 207 { 208 struct socket *so = tp->t_inpcb->inp_socket; 209 int32_t len; 210 uint32_t recwin, sendwin; 211 int off, flags, error = 0; /* Keep compiler happy */ 212 struct mbuf *m; 213 struct ip *ip = NULL; 214 #ifdef TCPDEBUG 215 struct ipovly *ipov = NULL; 216 #endif 217 struct tcphdr *th; 218 u_char opt[TCP_MAXOLEN]; 219 unsigned ipoptlen, optlen, hdrlen; 220 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 221 unsigned ipsec_optlen = 0; 222 #endif 223 int idle, sendalot, curticks; 224 int sack_rxmit, sack_bytes_rxmt; 225 struct sackhole *p; 226 int tso, mtu; 227 struct tcpopt to; 228 unsigned int wanted_cookie = 0; 229 unsigned int dont_sendalot = 0; 230 #if 0 231 int maxburst = TCP_MAXBURST; 232 #endif 233 #ifdef INET6 234 struct ip6_hdr *ip6 = NULL; 235 int isipv6; 236 237 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 238 #endif 239 240 INP_WLOCK_ASSERT(tp->t_inpcb); 241 242 #ifdef TCP_OFFLOAD 243 if (tp->t_flags & TF_TOE) 244 return (tcp_offload_output(tp)); 245 #endif 246 247 /* 248 * For TFO connections in SYN_RECEIVED, only allow the initial 249 * SYN|ACK and those sent by the retransmit timer. 250 */ 251 if (IS_FASTOPEN(tp->t_flags) && 252 (tp->t_state == TCPS_SYN_RECEIVED) && 253 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */ 254 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 255 return (0); 256 257 /* 258 * Determine length of data that should be transmitted, 259 * and flags that will be used. 260 * If there is some data or critical controls (SYN, RST) 261 * to send, then transmit; otherwise, investigate further. 262 */ 263 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 264 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 265 cc_after_idle(tp); 266 tp->t_flags &= ~TF_LASTIDLE; 267 if (idle) { 268 if (tp->t_flags & TF_MORETOCOME) { 269 tp->t_flags |= TF_LASTIDLE; 270 idle = 0; 271 } 272 } 273 again: 274 /* 275 * If we've recently taken a timeout, snd_max will be greater than 276 * snd_nxt. There may be SACK information that allows us to avoid 277 * resending already delivered data. Adjust snd_nxt accordingly. 278 */ 279 if ((tp->t_flags & TF_SACK_PERMIT) && 280 SEQ_LT(tp->snd_nxt, tp->snd_max)) 281 tcp_sack_adjust(tp); 282 sendalot = 0; 283 tso = 0; 284 mtu = 0; 285 off = tp->snd_nxt - tp->snd_una; 286 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 287 288 flags = tcp_outflags[tp->t_state]; 289 /* 290 * Send any SACK-generated retransmissions. If we're explicitly trying 291 * to send out new data (when sendalot is 1), bypass this function. 292 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 293 * we're replacing a (future) new transmission with a retransmission 294 * now, and we previously incremented snd_cwnd in tcp_input(). 295 */ 296 /* 297 * Still in sack recovery , reset rxmit flag to zero. 298 */ 299 sack_rxmit = 0; 300 sack_bytes_rxmt = 0; 301 len = 0; 302 p = NULL; 303 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 304 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 305 uint32_t cwin; 306 307 cwin = 308 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 309 /* Do not retransmit SACK segments beyond snd_recover */ 310 if (SEQ_GT(p->end, tp->snd_recover)) { 311 /* 312 * (At least) part of sack hole extends beyond 313 * snd_recover. Check to see if we can rexmit data 314 * for this hole. 315 */ 316 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 317 /* 318 * Can't rexmit any more data for this hole. 319 * That data will be rexmitted in the next 320 * sack recovery episode, when snd_recover 321 * moves past p->rxmit. 322 */ 323 p = NULL; 324 goto after_sack_rexmit; 325 } else 326 /* Can rexmit part of the current hole */ 327 len = ((int32_t)ulmin(cwin, 328 tp->snd_recover - p->rxmit)); 329 } else 330 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 331 off = p->rxmit - tp->snd_una; 332 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 333 __func__, off)); 334 if (len > 0) { 335 sack_rxmit = 1; 336 sendalot = 1; 337 TCPSTAT_INC(tcps_sack_rexmits); 338 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 339 min(len, tp->t_maxseg)); 340 } 341 } 342 after_sack_rexmit: 343 /* 344 * Get standard flags, and add SYN or FIN if requested by 'hidden' 345 * state flags. 346 */ 347 if (tp->t_flags & TF_NEEDFIN) 348 flags |= TH_FIN; 349 if (tp->t_flags & TF_NEEDSYN) 350 flags |= TH_SYN; 351 352 SOCKBUF_LOCK(&so->so_snd); 353 /* 354 * If in persist timeout with window of 0, send 1 byte. 355 * Otherwise, if window is small but nonzero 356 * and timer expired, we will send what we can 357 * and go to transmit state. 358 */ 359 if (tp->t_flags & TF_FORCEDATA) { 360 if (sendwin == 0) { 361 /* 362 * If we still have some data to send, then 363 * clear the FIN bit. Usually this would 364 * happen below when it realizes that we 365 * aren't sending all the data. However, 366 * if we have exactly 1 byte of unsent data, 367 * then it won't clear the FIN bit below, 368 * and if we are in persist state, we wind 369 * up sending the packet without recording 370 * that we sent the FIN bit. 371 * 372 * We can't just blindly clear the FIN bit, 373 * because if we don't have any more data 374 * to send then the probe will be the FIN 375 * itself. 376 */ 377 if (off < sbused(&so->so_snd)) 378 flags &= ~TH_FIN; 379 sendwin = 1; 380 } else { 381 tcp_timer_activate(tp, TT_PERSIST, 0); 382 tp->t_rxtshift = 0; 383 } 384 } 385 386 /* 387 * If snd_nxt == snd_max and we have transmitted a FIN, the 388 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 389 * a negative length. This can also occur when TCP opens up 390 * its congestion window while receiving additional duplicate 391 * acks after fast-retransmit because TCP will reset snd_nxt 392 * to snd_max after the fast-retransmit. 393 * 394 * In the normal retransmit-FIN-only case, however, snd_nxt will 395 * be set to snd_una, the offset will be 0, and the length may 396 * wind up 0. 397 * 398 * If sack_rxmit is true we are retransmitting from the scoreboard 399 * in which case len is already set. 400 */ 401 if (sack_rxmit == 0) { 402 if (sack_bytes_rxmt == 0) 403 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 404 off); 405 else { 406 int32_t cwin; 407 408 /* 409 * We are inside of a SACK recovery episode and are 410 * sending new data, having retransmitted all the 411 * data possible in the scoreboard. 412 */ 413 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 414 off); 415 /* 416 * Don't remove this (len > 0) check ! 417 * We explicitly check for len > 0 here (although it 418 * isn't really necessary), to work around a gcc 419 * optimization issue - to force gcc to compute 420 * len above. Without this check, the computation 421 * of len is bungled by the optimizer. 422 */ 423 if (len > 0) { 424 cwin = tp->snd_cwnd - 425 (tp->snd_nxt - tp->sack_newdata) - 426 sack_bytes_rxmt; 427 if (cwin < 0) 428 cwin = 0; 429 len = imin(len, cwin); 430 } 431 } 432 } 433 434 /* 435 * Lop off SYN bit if it has already been sent. However, if this 436 * is SYN-SENT state and if segment contains data and if we don't 437 * know that foreign host supports TAO, suppress sending segment. 438 */ 439 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 440 if (tp->t_state != TCPS_SYN_RECEIVED) 441 flags &= ~TH_SYN; 442 /* 443 * When sending additional segments following a TFO SYN|ACK, 444 * do not include the SYN bit. 445 */ 446 if (IS_FASTOPEN(tp->t_flags) && 447 (tp->t_state == TCPS_SYN_RECEIVED)) 448 flags &= ~TH_SYN; 449 off--, len++; 450 } 451 452 /* 453 * Be careful not to send data and/or FIN on SYN segments. 454 * This measure is needed to prevent interoperability problems 455 * with not fully conformant TCP implementations. 456 */ 457 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 458 len = 0; 459 flags &= ~TH_FIN; 460 } 461 462 /* 463 * On TFO sockets, ensure no data is sent in the following cases: 464 * 465 * - When retransmitting SYN|ACK on a passively-created socket 466 * 467 * - When retransmitting SYN on an actively created socket 468 * 469 * - When sending a zero-length cookie (cookie request) on an 470 * actively created socket 471 * 472 * - When the socket is in the CLOSED state (RST is being sent) 473 */ 474 if (IS_FASTOPEN(tp->t_flags) && 475 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 476 ((tp->t_state == TCPS_SYN_SENT) && 477 (tp->t_tfo_client_cookie_len == 0)) || 478 (flags & TH_RST))) 479 len = 0; 480 if (len <= 0) { 481 /* 482 * If FIN has been sent but not acked, 483 * but we haven't been called to retransmit, 484 * len will be < 0. Otherwise, window shrank 485 * after we sent into it. If window shrank to 0, 486 * cancel pending retransmit, pull snd_nxt back 487 * to (closed) window, and set the persist timer 488 * if it isn't already going. If the window didn't 489 * close completely, just wait for an ACK. 490 * 491 * We also do a general check here to ensure that 492 * we will set the persist timer when we have data 493 * to send, but a 0-byte window. This makes sure 494 * the persist timer is set even if the packet 495 * hits one of the "goto send" lines below. 496 */ 497 len = 0; 498 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 499 (off < (int) sbavail(&so->so_snd))) { 500 tcp_timer_activate(tp, TT_REXMT, 0); 501 tp->t_rxtshift = 0; 502 tp->snd_nxt = tp->snd_una; 503 if (!tcp_timer_active(tp, TT_PERSIST)) 504 tcp_setpersist(tp); 505 } 506 } 507 508 /* len will be >= 0 after this point. */ 509 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 510 511 tcp_sndbuf_autoscale(tp, so, sendwin); 512 513 /* 514 * Decide if we can use TCP Segmentation Offloading (if supported by 515 * hardware). 516 * 517 * TSO may only be used if we are in a pure bulk sending state. The 518 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 519 * IP options prevent using TSO. With TSO the TCP header is the same 520 * (except for the sequence number) for all generated packets. This 521 * makes it impossible to transmit any options which vary per generated 522 * segment or packet. 523 * 524 * IPv4 handling has a clear separation of ip options and ip header 525 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 526 * the right thing below to provide length of just ip options and thus 527 * checking for ipoptlen is enough to decide if ip options are present. 528 */ 529 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 530 /* 531 * Pre-calculate here as we save another lookup into the darknesses 532 * of IPsec that way and can actually decide if TSO is ok. 533 */ 534 #ifdef INET6 535 if (isipv6 && IPSEC_ENABLED(ipv6)) 536 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 537 #ifdef INET 538 else 539 #endif 540 #endif /* INET6 */ 541 #ifdef INET 542 if (IPSEC_ENABLED(ipv4)) 543 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 544 #endif /* INET */ 545 #endif /* IPSEC */ 546 #ifdef INET6 547 if (isipv6) 548 ipoptlen = ip6_optlen(tp->t_inpcb); 549 else 550 #endif 551 if (tp->t_inpcb->inp_options) 552 ipoptlen = tp->t_inpcb->inp_options->m_len - 553 offsetof(struct ipoption, ipopt_list); 554 else 555 ipoptlen = 0; 556 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 557 ipoptlen += ipsec_optlen; 558 #endif 559 560 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 561 ((tp->t_flags & TF_SIGNATURE) == 0) && 562 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 563 ipoptlen == 0 && !(flags & TH_SYN)) 564 tso = 1; 565 566 if (sack_rxmit) { 567 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 568 flags &= ~TH_FIN; 569 } else { 570 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 571 sbused(&so->so_snd))) 572 flags &= ~TH_FIN; 573 } 574 575 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 576 (long)TCP_MAXWIN << tp->rcv_scale); 577 578 /* 579 * Sender silly window avoidance. We transmit under the following 580 * conditions when len is non-zero: 581 * 582 * - We have a full segment (or more with TSO) 583 * - This is the last buffer in a write()/send() and we are 584 * either idle or running NODELAY 585 * - we've timed out (e.g. persist timer) 586 * - we have more then 1/2 the maximum send window's worth of 587 * data (receiver may be limited the window size) 588 * - we need to retransmit 589 */ 590 if (len) { 591 if (len >= tp->t_maxseg) 592 goto send; 593 /* 594 * NOTE! on localhost connections an 'ack' from the remote 595 * end may occur synchronously with the output and cause 596 * us to flush a buffer queued with moretocome. XXX 597 * 598 * note: the len + off check is almost certainly unnecessary. 599 */ 600 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 601 (idle || (tp->t_flags & TF_NODELAY)) && 602 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 603 (tp->t_flags & TF_NOPUSH) == 0) { 604 goto send; 605 } 606 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 607 goto send; 608 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 609 goto send; 610 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 611 goto send; 612 if (sack_rxmit) 613 goto send; 614 } 615 616 /* 617 * Sending of standalone window updates. 618 * 619 * Window updates are important when we close our window due to a 620 * full socket buffer and are opening it again after the application 621 * reads data from it. Once the window has opened again and the 622 * remote end starts to send again the ACK clock takes over and 623 * provides the most current window information. 624 * 625 * We must avoid the silly window syndrome whereas every read 626 * from the receive buffer, no matter how small, causes a window 627 * update to be sent. We also should avoid sending a flurry of 628 * window updates when the socket buffer had queued a lot of data 629 * and the application is doing small reads. 630 * 631 * Prevent a flurry of pointless window updates by only sending 632 * an update when we can increase the advertized window by more 633 * than 1/4th of the socket buffer capacity. When the buffer is 634 * getting full or is very small be more aggressive and send an 635 * update whenever we can increase by two mss sized segments. 636 * In all other situations the ACK's to new incoming data will 637 * carry further window increases. 638 * 639 * Don't send an independent window update if a delayed 640 * ACK is pending (it will get piggy-backed on it) or the 641 * remote side already has done a half-close and won't send 642 * more data. Skip this if the connection is in T/TCP 643 * half-open state. 644 */ 645 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 646 !(tp->t_flags & TF_DELACK) && 647 !TCPS_HAVERCVDFIN(tp->t_state)) { 648 /* 649 * "adv" is the amount we could increase the window, 650 * taking into account that we are limited by 651 * TCP_MAXWIN << tp->rcv_scale. 652 */ 653 int32_t adv; 654 int oldwin; 655 656 adv = recwin; 657 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 658 oldwin = (tp->rcv_adv - tp->rcv_nxt); 659 adv -= oldwin; 660 } else 661 oldwin = 0; 662 663 /* 664 * If the new window size ends up being the same as or less 665 * than the old size when it is scaled, then don't force 666 * a window update. 667 */ 668 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 669 goto dontupdate; 670 671 if (adv >= (int32_t)(2 * tp->t_maxseg) && 672 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 673 recwin <= (so->so_rcv.sb_hiwat / 8) || 674 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 675 goto send; 676 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 677 goto send; 678 } 679 dontupdate: 680 681 /* 682 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 683 * is also a catch-all for the retransmit timer timeout case. 684 */ 685 if (tp->t_flags & TF_ACKNOW) 686 goto send; 687 if ((flags & TH_RST) || 688 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 689 goto send; 690 if (SEQ_GT(tp->snd_up, tp->snd_una)) 691 goto send; 692 /* 693 * If our state indicates that FIN should be sent 694 * and we have not yet done so, then we need to send. 695 */ 696 if (flags & TH_FIN && 697 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 698 goto send; 699 /* 700 * In SACK, it is possible for tcp_output to fail to send a segment 701 * after the retransmission timer has been turned off. Make sure 702 * that the retransmission timer is set. 703 */ 704 if ((tp->t_flags & TF_SACK_PERMIT) && 705 SEQ_GT(tp->snd_max, tp->snd_una) && 706 !tcp_timer_active(tp, TT_REXMT) && 707 !tcp_timer_active(tp, TT_PERSIST)) { 708 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 709 goto just_return; 710 } 711 /* 712 * TCP window updates are not reliable, rather a polling protocol 713 * using ``persist'' packets is used to insure receipt of window 714 * updates. The three ``states'' for the output side are: 715 * idle not doing retransmits or persists 716 * persisting to move a small or zero window 717 * (re)transmitting and thereby not persisting 718 * 719 * tcp_timer_active(tp, TT_PERSIST) 720 * is true when we are in persist state. 721 * (tp->t_flags & TF_FORCEDATA) 722 * is set when we are called to send a persist packet. 723 * tcp_timer_active(tp, TT_REXMT) 724 * is set when we are retransmitting 725 * The output side is idle when both timers are zero. 726 * 727 * If send window is too small, there is data to transmit, and no 728 * retransmit or persist is pending, then go to persist state. 729 * If nothing happens soon, send when timer expires: 730 * if window is nonzero, transmit what we can, 731 * otherwise force out a byte. 732 */ 733 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 734 !tcp_timer_active(tp, TT_PERSIST)) { 735 tp->t_rxtshift = 0; 736 tcp_setpersist(tp); 737 } 738 739 /* 740 * No reason to send a segment, just return. 741 */ 742 just_return: 743 SOCKBUF_UNLOCK(&so->so_snd); 744 return (0); 745 746 send: 747 SOCKBUF_LOCK_ASSERT(&so->so_snd); 748 if (len > 0) { 749 if (len >= tp->t_maxseg) 750 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 751 else 752 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 753 } 754 /* 755 * Before ESTABLISHED, force sending of initial options 756 * unless TCP set not to do any options. 757 * NOTE: we assume that the IP/TCP header plus TCP options 758 * always fit in a single mbuf, leaving room for a maximum 759 * link header, i.e. 760 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 761 */ 762 optlen = 0; 763 #ifdef INET6 764 if (isipv6) 765 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 766 else 767 #endif 768 hdrlen = sizeof (struct tcpiphdr); 769 770 /* 771 * Compute options for segment. 772 * We only have to care about SYN and established connection 773 * segments. Options for SYN-ACK segments are handled in TCP 774 * syncache. 775 */ 776 to.to_flags = 0; 777 if ((tp->t_flags & TF_NOOPT) == 0) { 778 /* Maximum segment size. */ 779 if (flags & TH_SYN) { 780 tp->snd_nxt = tp->iss; 781 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 782 to.to_flags |= TOF_MSS; 783 784 /* 785 * On SYN or SYN|ACK transmits on TFO connections, 786 * only include the TFO option if it is not a 787 * retransmit, as the presence of the TFO option may 788 * have caused the original SYN or SYN|ACK to have 789 * been dropped by a middlebox. 790 */ 791 if (IS_FASTOPEN(tp->t_flags) && 792 (tp->t_rxtshift == 0)) { 793 if (tp->t_state == TCPS_SYN_RECEIVED) { 794 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 795 to.to_tfo_cookie = 796 (u_int8_t *)&tp->t_tfo_cookie.server; 797 to.to_flags |= TOF_FASTOPEN; 798 wanted_cookie = 1; 799 } else if (tp->t_state == TCPS_SYN_SENT) { 800 to.to_tfo_len = 801 tp->t_tfo_client_cookie_len; 802 to.to_tfo_cookie = 803 tp->t_tfo_cookie.client; 804 to.to_flags |= TOF_FASTOPEN; 805 wanted_cookie = 1; 806 /* 807 * If we wind up having more data to 808 * send with the SYN than can fit in 809 * one segment, don't send any more 810 * until the SYN|ACK comes back from 811 * the other end. 812 */ 813 dont_sendalot = 1; 814 } 815 } 816 } 817 /* Window scaling. */ 818 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 819 to.to_wscale = tp->request_r_scale; 820 to.to_flags |= TOF_SCALE; 821 } 822 /* Timestamps. */ 823 if ((tp->t_flags & TF_RCVD_TSTMP) || 824 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 825 curticks = tcp_ts_getticks(); 826 to.to_tsval = curticks + tp->ts_offset; 827 to.to_tsecr = tp->ts_recent; 828 to.to_flags |= TOF_TS; 829 if (tp->t_rxtshift == 1) 830 tp->t_badrxtwin = curticks; 831 } 832 833 /* Set receive buffer autosizing timestamp. */ 834 if (tp->rfbuf_ts == 0 && 835 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 836 tp->rfbuf_ts = tcp_ts_getticks(); 837 838 /* Selective ACK's. */ 839 if (tp->t_flags & TF_SACK_PERMIT) { 840 if (flags & TH_SYN) 841 to.to_flags |= TOF_SACKPERM; 842 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 843 (tp->t_flags & TF_SACK_PERMIT) && 844 tp->rcv_numsacks > 0) { 845 to.to_flags |= TOF_SACK; 846 to.to_nsacks = tp->rcv_numsacks; 847 to.to_sacks = (u_char *)tp->sackblks; 848 } 849 } 850 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 851 /* TCP-MD5 (RFC2385). */ 852 /* 853 * Check that TCP_MD5SIG is enabled in tcpcb to 854 * account the size needed to set this TCP option. 855 */ 856 if (tp->t_flags & TF_SIGNATURE) 857 to.to_flags |= TOF_SIGNATURE; 858 #endif /* TCP_SIGNATURE */ 859 860 /* Processing the options. */ 861 hdrlen += optlen = tcp_addoptions(&to, opt); 862 /* 863 * If we wanted a TFO option to be added, but it was unable 864 * to fit, ensure no data is sent. 865 */ 866 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 867 !(to.to_flags & TOF_FASTOPEN)) 868 len = 0; 869 } 870 871 /* 872 * Adjust data length if insertion of options will 873 * bump the packet length beyond the t_maxseg length. 874 * Clear the FIN bit because we cut off the tail of 875 * the segment. 876 */ 877 if (len + optlen + ipoptlen > tp->t_maxseg) { 878 flags &= ~TH_FIN; 879 880 if (tso) { 881 u_int if_hw_tsomax; 882 u_int if_hw_tsomaxsegcount; 883 u_int if_hw_tsomaxsegsize; 884 struct mbuf *mb; 885 u_int moff; 886 int max_len; 887 888 /* extract TSO information */ 889 if_hw_tsomax = tp->t_tsomax; 890 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 891 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 892 893 /* 894 * Limit a TSO burst to prevent it from 895 * overflowing or exceeding the maximum length 896 * allowed by the network interface: 897 */ 898 KASSERT(ipoptlen == 0, 899 ("%s: TSO can't do IP options", __func__)); 900 901 /* 902 * Check if we should limit by maximum payload 903 * length: 904 */ 905 if (if_hw_tsomax != 0) { 906 /* compute maximum TSO length */ 907 max_len = (if_hw_tsomax - hdrlen - 908 max_linkhdr); 909 if (max_len <= 0) { 910 len = 0; 911 } else if (len > max_len) { 912 sendalot = 1; 913 len = max_len; 914 } 915 } 916 917 /* 918 * Check if we should limit by maximum segment 919 * size and count: 920 */ 921 if (if_hw_tsomaxsegcount != 0 && 922 if_hw_tsomaxsegsize != 0) { 923 /* 924 * Subtract one segment for the LINK 925 * and TCP/IP headers mbuf that will 926 * be prepended to this mbuf chain 927 * after the code in this section 928 * limits the number of mbufs in the 929 * chain to if_hw_tsomaxsegcount. 930 */ 931 if_hw_tsomaxsegcount -= 1; 932 max_len = 0; 933 mb = sbsndmbuf(&so->so_snd, off, &moff); 934 935 while (mb != NULL && max_len < len) { 936 u_int mlen; 937 u_int frags; 938 939 /* 940 * Get length of mbuf fragment 941 * and how many hardware frags, 942 * rounded up, it would use: 943 */ 944 mlen = (mb->m_len - moff); 945 frags = howmany(mlen, 946 if_hw_tsomaxsegsize); 947 948 /* Handle special case: Zero Length Mbuf */ 949 if (frags == 0) 950 frags = 1; 951 952 /* 953 * Check if the fragment limit 954 * will be reached or exceeded: 955 */ 956 if (frags >= if_hw_tsomaxsegcount) { 957 max_len += min(mlen, 958 if_hw_tsomaxsegcount * 959 if_hw_tsomaxsegsize); 960 break; 961 } 962 max_len += mlen; 963 if_hw_tsomaxsegcount -= frags; 964 moff = 0; 965 mb = mb->m_next; 966 } 967 if (max_len <= 0) { 968 len = 0; 969 } else if (len > max_len) { 970 sendalot = 1; 971 len = max_len; 972 } 973 } 974 975 /* 976 * Prevent the last segment from being 977 * fractional unless the send sockbuf can be 978 * emptied: 979 */ 980 max_len = (tp->t_maxseg - optlen); 981 if (((uint32_t)off + (uint32_t)len) < 982 sbavail(&so->so_snd)) { 983 moff = len % max_len; 984 if (moff != 0) { 985 len -= moff; 986 sendalot = 1; 987 } 988 } 989 990 /* 991 * In case there are too many small fragments 992 * don't use TSO: 993 */ 994 if (len <= max_len) { 995 len = max_len; 996 sendalot = 1; 997 tso = 0; 998 } 999 1000 /* 1001 * Send the FIN in a separate segment 1002 * after the bulk sending is done. 1003 * We don't trust the TSO implementations 1004 * to clear the FIN flag on all but the 1005 * last segment. 1006 */ 1007 if (tp->t_flags & TF_NEEDFIN) 1008 sendalot = 1; 1009 1010 } else { 1011 len = tp->t_maxseg - optlen - ipoptlen; 1012 sendalot = 1; 1013 if (dont_sendalot) 1014 sendalot = 0; 1015 } 1016 } else 1017 tso = 0; 1018 1019 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1020 ("%s: len > IP_MAXPACKET", __func__)); 1021 1022 /*#ifdef DIAGNOSTIC*/ 1023 #ifdef INET6 1024 if (max_linkhdr + hdrlen > MCLBYTES) 1025 #else 1026 if (max_linkhdr + hdrlen > MHLEN) 1027 #endif 1028 panic("tcphdr too big"); 1029 /*#endif*/ 1030 1031 /* 1032 * This KASSERT is here to catch edge cases at a well defined place. 1033 * Before, those had triggered (random) panic conditions further down. 1034 */ 1035 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1036 1037 /* 1038 * Grab a header mbuf, attaching a copy of data to 1039 * be transmitted, and initialize the header from 1040 * the template for sends on this connection. 1041 */ 1042 if (len) { 1043 struct mbuf *mb; 1044 u_int moff; 1045 1046 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1047 TCPSTAT_INC(tcps_sndprobe); 1048 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1049 tp->t_sndrexmitpack++; 1050 TCPSTAT_INC(tcps_sndrexmitpack); 1051 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1052 } else { 1053 TCPSTAT_INC(tcps_sndpack); 1054 TCPSTAT_ADD(tcps_sndbyte, len); 1055 } 1056 #ifdef INET6 1057 if (MHLEN < hdrlen + max_linkhdr) 1058 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1059 else 1060 #endif 1061 m = m_gethdr(M_NOWAIT, MT_DATA); 1062 1063 if (m == NULL) { 1064 SOCKBUF_UNLOCK(&so->so_snd); 1065 error = ENOBUFS; 1066 sack_rxmit = 0; 1067 goto out; 1068 } 1069 1070 m->m_data += max_linkhdr; 1071 m->m_len = hdrlen; 1072 1073 /* 1074 * Start the m_copy functions from the closest mbuf 1075 * to the offset in the socket buffer chain. 1076 */ 1077 mb = sbsndptr(&so->so_snd, off, len, &moff); 1078 1079 if (len <= MHLEN - hdrlen - max_linkhdr) { 1080 m_copydata(mb, moff, len, 1081 mtod(m, caddr_t) + hdrlen); 1082 m->m_len += len; 1083 } else { 1084 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1085 if (m->m_next == NULL) { 1086 SOCKBUF_UNLOCK(&so->so_snd); 1087 (void) m_free(m); 1088 error = ENOBUFS; 1089 sack_rxmit = 0; 1090 goto out; 1091 } 1092 } 1093 1094 /* 1095 * If we're sending everything we've got, set PUSH. 1096 * (This will keep happy those implementations which only 1097 * give data to the user when a buffer fills or 1098 * a PUSH comes in.) 1099 */ 1100 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1101 !(flags & TH_SYN)) 1102 flags |= TH_PUSH; 1103 SOCKBUF_UNLOCK(&so->so_snd); 1104 } else { 1105 SOCKBUF_UNLOCK(&so->so_snd); 1106 if (tp->t_flags & TF_ACKNOW) 1107 TCPSTAT_INC(tcps_sndacks); 1108 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1109 TCPSTAT_INC(tcps_sndctrl); 1110 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1111 TCPSTAT_INC(tcps_sndurg); 1112 else 1113 TCPSTAT_INC(tcps_sndwinup); 1114 1115 m = m_gethdr(M_NOWAIT, MT_DATA); 1116 if (m == NULL) { 1117 error = ENOBUFS; 1118 sack_rxmit = 0; 1119 goto out; 1120 } 1121 #ifdef INET6 1122 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1123 MHLEN >= hdrlen) { 1124 M_ALIGN(m, hdrlen); 1125 } else 1126 #endif 1127 m->m_data += max_linkhdr; 1128 m->m_len = hdrlen; 1129 } 1130 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1131 m->m_pkthdr.rcvif = (struct ifnet *)0; 1132 #ifdef MAC 1133 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1134 #endif 1135 #ifdef INET6 1136 if (isipv6) { 1137 ip6 = mtod(m, struct ip6_hdr *); 1138 th = (struct tcphdr *)(ip6 + 1); 1139 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1140 } else 1141 #endif /* INET6 */ 1142 { 1143 ip = mtod(m, struct ip *); 1144 #ifdef TCPDEBUG 1145 ipov = (struct ipovly *)ip; 1146 #endif 1147 th = (struct tcphdr *)(ip + 1); 1148 tcpip_fillheaders(tp->t_inpcb, ip, th); 1149 } 1150 1151 /* 1152 * Fill in fields, remembering maximum advertised 1153 * window for use in delaying messages about window sizes. 1154 * If resending a FIN, be sure not to use a new sequence number. 1155 */ 1156 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1157 tp->snd_nxt == tp->snd_max) 1158 tp->snd_nxt--; 1159 /* 1160 * If we are starting a connection, send ECN setup 1161 * SYN packet. If we are on a retransmit, we may 1162 * resend those bits a number of times as per 1163 * RFC 3168. 1164 */ 1165 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1166 if (tp->t_rxtshift >= 1) { 1167 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1168 flags |= TH_ECE|TH_CWR; 1169 } else 1170 flags |= TH_ECE|TH_CWR; 1171 } 1172 1173 if (tp->t_state == TCPS_ESTABLISHED && 1174 (tp->t_flags & TF_ECN_PERMIT)) { 1175 /* 1176 * If the peer has ECN, mark data packets with 1177 * ECN capable transmission (ECT). 1178 * Ignore pure ack packets, retransmissions and window probes. 1179 */ 1180 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1181 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1182 #ifdef INET6 1183 if (isipv6) 1184 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1185 else 1186 #endif 1187 ip->ip_tos |= IPTOS_ECN_ECT0; 1188 TCPSTAT_INC(tcps_ecn_ect0); 1189 } 1190 1191 /* 1192 * Reply with proper ECN notifications. 1193 */ 1194 if (tp->t_flags & TF_ECN_SND_CWR) { 1195 flags |= TH_CWR; 1196 tp->t_flags &= ~TF_ECN_SND_CWR; 1197 } 1198 if (tp->t_flags & TF_ECN_SND_ECE) 1199 flags |= TH_ECE; 1200 } 1201 1202 /* 1203 * If we are doing retransmissions, then snd_nxt will 1204 * not reflect the first unsent octet. For ACK only 1205 * packets, we do not want the sequence number of the 1206 * retransmitted packet, we want the sequence number 1207 * of the next unsent octet. So, if there is no data 1208 * (and no SYN or FIN), use snd_max instead of snd_nxt 1209 * when filling in ti_seq. But if we are in persist 1210 * state, snd_max might reflect one byte beyond the 1211 * right edge of the window, so use snd_nxt in that 1212 * case, since we know we aren't doing a retransmission. 1213 * (retransmit and persist are mutually exclusive...) 1214 */ 1215 if (sack_rxmit == 0) { 1216 if (len || (flags & (TH_SYN|TH_FIN)) || 1217 tcp_timer_active(tp, TT_PERSIST)) 1218 th->th_seq = htonl(tp->snd_nxt); 1219 else 1220 th->th_seq = htonl(tp->snd_max); 1221 } else { 1222 th->th_seq = htonl(p->rxmit); 1223 p->rxmit += len; 1224 tp->sackhint.sack_bytes_rexmit += len; 1225 } 1226 th->th_ack = htonl(tp->rcv_nxt); 1227 if (optlen) { 1228 bcopy(opt, th + 1, optlen); 1229 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1230 } 1231 th->th_flags = flags; 1232 /* 1233 * Calculate receive window. Don't shrink window, 1234 * but avoid silly window syndrome. 1235 */ 1236 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1237 recwin < tp->t_maxseg) 1238 recwin = 0; 1239 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1240 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1241 recwin = (tp->rcv_adv - tp->rcv_nxt); 1242 1243 /* 1244 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1245 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1246 * case is handled in syncache. 1247 */ 1248 if (flags & TH_SYN) 1249 th->th_win = htons((u_short) 1250 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1251 else 1252 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1253 1254 /* 1255 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1256 * a 0 window. This may cause the remote transmitter to stall. This 1257 * flag tells soreceive() to disable delayed acknowledgements when 1258 * draining the buffer. This can occur if the receiver is attempting 1259 * to read more data than can be buffered prior to transmitting on 1260 * the connection. 1261 */ 1262 if (th->th_win == 0) { 1263 tp->t_sndzerowin++; 1264 tp->t_flags |= TF_RXWIN0SENT; 1265 } else 1266 tp->t_flags &= ~TF_RXWIN0SENT; 1267 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1268 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1269 th->th_flags |= TH_URG; 1270 } else 1271 /* 1272 * If no urgent pointer to send, then we pull 1273 * the urgent pointer to the left edge of the send window 1274 * so that it doesn't drift into the send window on sequence 1275 * number wraparound. 1276 */ 1277 tp->snd_up = tp->snd_una; /* drag it along */ 1278 1279 /* 1280 * Put TCP length in extended header, and then 1281 * checksum extended header and data. 1282 */ 1283 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1284 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1285 1286 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1287 if (to.to_flags & TOF_SIGNATURE) { 1288 /* 1289 * Calculate MD5 signature and put it into the place 1290 * determined before. 1291 * NOTE: since TCP options buffer doesn't point into 1292 * mbuf's data, calculate offset and use it. 1293 */ 1294 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1295 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1296 /* 1297 * Do not send segment if the calculation of MD5 1298 * digest has failed. 1299 */ 1300 m_freem(m); 1301 goto out; 1302 } 1303 } 1304 #endif 1305 #ifdef INET6 1306 if (isipv6) { 1307 /* 1308 * There is no need to fill in ip6_plen right now. 1309 * It will be filled later by ip6_output. 1310 */ 1311 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1312 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1313 optlen + len, IPPROTO_TCP, 0); 1314 } 1315 #endif 1316 #if defined(INET6) && defined(INET) 1317 else 1318 #endif 1319 #ifdef INET 1320 { 1321 m->m_pkthdr.csum_flags = CSUM_TCP; 1322 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1323 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1324 1325 /* IP version must be set here for ipv4/ipv6 checking later */ 1326 KASSERT(ip->ip_v == IPVERSION, 1327 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1328 } 1329 #endif 1330 1331 /* 1332 * Enable TSO and specify the size of the segments. 1333 * The TCP pseudo header checksum is always provided. 1334 */ 1335 if (tso) { 1336 KASSERT(len > tp->t_maxseg - optlen, 1337 ("%s: len <= tso_segsz", __func__)); 1338 m->m_pkthdr.csum_flags |= CSUM_TSO; 1339 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1340 } 1341 1342 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 1343 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1344 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1345 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1346 #else 1347 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1348 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1349 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1350 #endif 1351 1352 #ifdef TCP_HHOOK 1353 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1354 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1355 #endif 1356 1357 #ifdef TCPDEBUG 1358 /* 1359 * Trace. 1360 */ 1361 if (so->so_options & SO_DEBUG) { 1362 u_short save = 0; 1363 #ifdef INET6 1364 if (!isipv6) 1365 #endif 1366 { 1367 save = ipov->ih_len; 1368 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1369 } 1370 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1371 #ifdef INET6 1372 if (!isipv6) 1373 #endif 1374 ipov->ih_len = save; 1375 } 1376 #endif /* TCPDEBUG */ 1377 TCP_PROBE3(debug__output, tp, th, m); 1378 1379 /* We're getting ready to send; log now. */ 1380 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1381 len, NULL, false); 1382 1383 /* 1384 * Fill in IP length and desired time to live and 1385 * send to IP level. There should be a better way 1386 * to handle ttl and tos; we could keep them in 1387 * the template, but need a way to checksum without them. 1388 */ 1389 /* 1390 * m->m_pkthdr.len should have been set before checksum calculation, 1391 * because in6_cksum() need it. 1392 */ 1393 #ifdef INET6 1394 if (isipv6) { 1395 /* 1396 * we separately set hoplimit for every segment, since the 1397 * user might want to change the value via setsockopt. 1398 * Also, desired default hop limit might be changed via 1399 * Neighbor Discovery. 1400 */ 1401 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1402 1403 /* 1404 * Set the packet size here for the benefit of DTrace probes. 1405 * ip6_output() will set it properly; it's supposed to include 1406 * the option header lengths as well. 1407 */ 1408 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1409 1410 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1411 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1412 else 1413 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1414 1415 if (tp->t_state == TCPS_SYN_SENT) 1416 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1417 1418 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1419 1420 #ifdef TCPPCAP 1421 /* Save packet, if requested. */ 1422 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1423 #endif 1424 1425 /* TODO: IPv6 IP6TOS_ECT bit on */ 1426 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1427 &tp->t_inpcb->inp_route6, 1428 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1429 NULL, NULL, tp->t_inpcb); 1430 1431 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1432 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1433 } 1434 #endif /* INET6 */ 1435 #if defined(INET) && defined(INET6) 1436 else 1437 #endif 1438 #ifdef INET 1439 { 1440 ip->ip_len = htons(m->m_pkthdr.len); 1441 #ifdef INET6 1442 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1443 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1444 #endif /* INET6 */ 1445 /* 1446 * If we do path MTU discovery, then we set DF on every packet. 1447 * This might not be the best thing to do according to RFC3390 1448 * Section 2. However the tcp hostcache migitates the problem 1449 * so it affects only the first tcp connection with a host. 1450 * 1451 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1452 */ 1453 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1454 ip->ip_off |= htons(IP_DF); 1455 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1456 } else { 1457 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1458 } 1459 1460 if (tp->t_state == TCPS_SYN_SENT) 1461 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1462 1463 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1464 1465 #ifdef TCPPCAP 1466 /* Save packet, if requested. */ 1467 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1468 #endif 1469 1470 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1471 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1472 tp->t_inpcb); 1473 1474 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1475 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1476 } 1477 #endif /* INET */ 1478 1479 out: 1480 /* 1481 * In transmit state, time the transmission and arrange for 1482 * the retransmit. In persist state, just set snd_max. 1483 */ 1484 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1485 !tcp_timer_active(tp, TT_PERSIST)) { 1486 tcp_seq startseq = tp->snd_nxt; 1487 1488 /* 1489 * Advance snd_nxt over sequence space of this segment. 1490 */ 1491 if (flags & (TH_SYN|TH_FIN)) { 1492 if (flags & TH_SYN) 1493 tp->snd_nxt++; 1494 if (flags & TH_FIN) { 1495 tp->snd_nxt++; 1496 tp->t_flags |= TF_SENTFIN; 1497 } 1498 } 1499 if (sack_rxmit) 1500 goto timer; 1501 tp->snd_nxt += len; 1502 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1503 tp->snd_max = tp->snd_nxt; 1504 /* 1505 * Time this transmission if not a retransmission and 1506 * not currently timing anything. 1507 */ 1508 if (tp->t_rtttime == 0) { 1509 tp->t_rtttime = ticks; 1510 tp->t_rtseq = startseq; 1511 TCPSTAT_INC(tcps_segstimed); 1512 } 1513 } 1514 1515 /* 1516 * Set retransmit timer if not currently set, 1517 * and not doing a pure ack or a keep-alive probe. 1518 * Initial value for retransmit timer is smoothed 1519 * round-trip time + 2 * round-trip time variance. 1520 * Initialize shift counter which is used for backoff 1521 * of retransmit time. 1522 */ 1523 timer: 1524 if (!tcp_timer_active(tp, TT_REXMT) && 1525 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1526 (tp->snd_nxt != tp->snd_una))) { 1527 if (tcp_timer_active(tp, TT_PERSIST)) { 1528 tcp_timer_activate(tp, TT_PERSIST, 0); 1529 tp->t_rxtshift = 0; 1530 } 1531 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1532 } else if (len == 0 && sbavail(&so->so_snd) && 1533 !tcp_timer_active(tp, TT_REXMT) && 1534 !tcp_timer_active(tp, TT_PERSIST)) { 1535 /* 1536 * Avoid a situation where we do not set persist timer 1537 * after a zero window condition. For example: 1538 * 1) A -> B: packet with enough data to fill the window 1539 * 2) B -> A: ACK for #1 + new data (0 window 1540 * advertisement) 1541 * 3) A -> B: ACK for #2, 0 len packet 1542 * 1543 * In this case, A will not activate the persist timer, 1544 * because it chose to send a packet. Unless tcp_output 1545 * is called for some other reason (delayed ack timer, 1546 * another input packet from B, socket syscall), A will 1547 * not send zero window probes. 1548 * 1549 * So, if you send a 0-length packet, but there is data 1550 * in the socket buffer, and neither the rexmt or 1551 * persist timer is already set, then activate the 1552 * persist timer. 1553 */ 1554 tp->t_rxtshift = 0; 1555 tcp_setpersist(tp); 1556 } 1557 } else { 1558 /* 1559 * Persist case, update snd_max but since we are in 1560 * persist mode (no window) we do not update snd_nxt. 1561 */ 1562 int xlen = len; 1563 if (flags & TH_SYN) 1564 ++xlen; 1565 if (flags & TH_FIN) { 1566 ++xlen; 1567 tp->t_flags |= TF_SENTFIN; 1568 } 1569 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1570 tp->snd_max = tp->snd_nxt + xlen; 1571 } 1572 1573 if (error) { 1574 /* Record the error. */ 1575 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1576 error, 0, NULL, false); 1577 1578 /* 1579 * We know that the packet was lost, so back out the 1580 * sequence number advance, if any. 1581 * 1582 * If the error is EPERM the packet got blocked by the 1583 * local firewall. Normally we should terminate the 1584 * connection but the blocking may have been spurious 1585 * due to a firewall reconfiguration cycle. So we treat 1586 * it like a packet loss and let the retransmit timer and 1587 * timeouts do their work over time. 1588 * XXX: It is a POLA question whether calling tcp_drop right 1589 * away would be the really correct behavior instead. 1590 */ 1591 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1592 !tcp_timer_active(tp, TT_PERSIST)) && 1593 ((flags & TH_SYN) == 0) && 1594 (error != EPERM)) { 1595 if (sack_rxmit) { 1596 p->rxmit -= len; 1597 tp->sackhint.sack_bytes_rexmit -= len; 1598 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1599 ("sackhint bytes rtx >= 0")); 1600 } else 1601 tp->snd_nxt -= len; 1602 } 1603 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1604 switch (error) { 1605 case EACCES: 1606 case EPERM: 1607 tp->t_softerror = error; 1608 return (error); 1609 case ENOBUFS: 1610 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1611 tp->snd_cwnd = tp->t_maxseg; 1612 return (0); 1613 case EMSGSIZE: 1614 /* 1615 * For some reason the interface we used initially 1616 * to send segments changed to another or lowered 1617 * its MTU. 1618 * If TSO was active we either got an interface 1619 * without TSO capabilits or TSO was turned off. 1620 * If we obtained mtu from ip_output() then update 1621 * it and try again. 1622 */ 1623 if (tso) 1624 tp->t_flags &= ~TF_TSO; 1625 if (mtu != 0) { 1626 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1627 goto again; 1628 } 1629 return (error); 1630 case EHOSTDOWN: 1631 case EHOSTUNREACH: 1632 case ENETDOWN: 1633 case ENETUNREACH: 1634 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1635 tp->t_softerror = error; 1636 return (0); 1637 } 1638 /* FALLTHROUGH */ 1639 default: 1640 return (error); 1641 } 1642 } 1643 TCPSTAT_INC(tcps_sndtotal); 1644 1645 /* 1646 * Data sent (as far as we can tell). 1647 * If this advertises a larger window than any other segment, 1648 * then remember the size of the advertised window. 1649 * Any pending ACK has now been sent. 1650 */ 1651 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1652 tp->rcv_adv = tp->rcv_nxt + recwin; 1653 tp->last_ack_sent = tp->rcv_nxt; 1654 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1655 if (tcp_timer_active(tp, TT_DELACK)) 1656 tcp_timer_activate(tp, TT_DELACK, 0); 1657 #if 0 1658 /* 1659 * This completely breaks TCP if newreno is turned on. What happens 1660 * is that if delayed-acks are turned on on the receiver, this code 1661 * on the transmitter effectively destroys the TCP window, forcing 1662 * it to four packets (1.5Kx4 = 6K window). 1663 */ 1664 if (sendalot && --maxburst) 1665 goto again; 1666 #endif 1667 if (sendalot) 1668 goto again; 1669 return (0); 1670 } 1671 1672 void 1673 tcp_setpersist(struct tcpcb *tp) 1674 { 1675 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1676 int tt; 1677 1678 tp->t_flags &= ~TF_PREVVALID; 1679 if (tcp_timer_active(tp, TT_REXMT)) 1680 panic("tcp_setpersist: retransmit pending"); 1681 /* 1682 * Start/restart persistence timer. 1683 */ 1684 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1685 tcp_persmin, tcp_persmax); 1686 tcp_timer_activate(tp, TT_PERSIST, tt); 1687 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1688 tp->t_rxtshift++; 1689 } 1690 1691 /* 1692 * Insert TCP options according to the supplied parameters to the place 1693 * optp in a consistent way. Can handle unaligned destinations. 1694 * 1695 * The order of the option processing is crucial for optimal packing and 1696 * alignment for the scarce option space. 1697 * 1698 * The optimal order for a SYN/SYN-ACK segment is: 1699 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1700 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1701 * 1702 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1703 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1704 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1705 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1706 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1707 */ 1708 int 1709 tcp_addoptions(struct tcpopt *to, u_char *optp) 1710 { 1711 u_int32_t mask, optlen = 0; 1712 1713 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1714 if ((to->to_flags & mask) != mask) 1715 continue; 1716 if (optlen == TCP_MAXOLEN) 1717 break; 1718 switch (to->to_flags & mask) { 1719 case TOF_MSS: 1720 while (optlen % 4) { 1721 optlen += TCPOLEN_NOP; 1722 *optp++ = TCPOPT_NOP; 1723 } 1724 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1725 continue; 1726 optlen += TCPOLEN_MAXSEG; 1727 *optp++ = TCPOPT_MAXSEG; 1728 *optp++ = TCPOLEN_MAXSEG; 1729 to->to_mss = htons(to->to_mss); 1730 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1731 optp += sizeof(to->to_mss); 1732 break; 1733 case TOF_SCALE: 1734 while (!optlen || optlen % 2 != 1) { 1735 optlen += TCPOLEN_NOP; 1736 *optp++ = TCPOPT_NOP; 1737 } 1738 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1739 continue; 1740 optlen += TCPOLEN_WINDOW; 1741 *optp++ = TCPOPT_WINDOW; 1742 *optp++ = TCPOLEN_WINDOW; 1743 *optp++ = to->to_wscale; 1744 break; 1745 case TOF_SACKPERM: 1746 while (optlen % 2) { 1747 optlen += TCPOLEN_NOP; 1748 *optp++ = TCPOPT_NOP; 1749 } 1750 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1751 continue; 1752 optlen += TCPOLEN_SACK_PERMITTED; 1753 *optp++ = TCPOPT_SACK_PERMITTED; 1754 *optp++ = TCPOLEN_SACK_PERMITTED; 1755 break; 1756 case TOF_TS: 1757 while (!optlen || optlen % 4 != 2) { 1758 optlen += TCPOLEN_NOP; 1759 *optp++ = TCPOPT_NOP; 1760 } 1761 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1762 continue; 1763 optlen += TCPOLEN_TIMESTAMP; 1764 *optp++ = TCPOPT_TIMESTAMP; 1765 *optp++ = TCPOLEN_TIMESTAMP; 1766 to->to_tsval = htonl(to->to_tsval); 1767 to->to_tsecr = htonl(to->to_tsecr); 1768 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1769 optp += sizeof(to->to_tsval); 1770 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1771 optp += sizeof(to->to_tsecr); 1772 break; 1773 case TOF_SIGNATURE: 1774 { 1775 int siglen = TCPOLEN_SIGNATURE - 2; 1776 1777 while (!optlen || optlen % 4 != 2) { 1778 optlen += TCPOLEN_NOP; 1779 *optp++ = TCPOPT_NOP; 1780 } 1781 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1782 to->to_flags &= ~TOF_SIGNATURE; 1783 continue; 1784 } 1785 optlen += TCPOLEN_SIGNATURE; 1786 *optp++ = TCPOPT_SIGNATURE; 1787 *optp++ = TCPOLEN_SIGNATURE; 1788 to->to_signature = optp; 1789 while (siglen--) 1790 *optp++ = 0; 1791 break; 1792 } 1793 case TOF_SACK: 1794 { 1795 int sackblks = 0; 1796 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1797 tcp_seq sack_seq; 1798 1799 while (!optlen || optlen % 4 != 2) { 1800 optlen += TCPOLEN_NOP; 1801 *optp++ = TCPOPT_NOP; 1802 } 1803 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1804 continue; 1805 optlen += TCPOLEN_SACKHDR; 1806 *optp++ = TCPOPT_SACK; 1807 sackblks = min(to->to_nsacks, 1808 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1809 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1810 while (sackblks--) { 1811 sack_seq = htonl(sack->start); 1812 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1813 optp += sizeof(sack_seq); 1814 sack_seq = htonl(sack->end); 1815 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1816 optp += sizeof(sack_seq); 1817 optlen += TCPOLEN_SACK; 1818 sack++; 1819 } 1820 TCPSTAT_INC(tcps_sack_send_blocks); 1821 break; 1822 } 1823 case TOF_FASTOPEN: 1824 { 1825 int total_len; 1826 1827 /* XXX is there any point to aligning this option? */ 1828 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1829 if (TCP_MAXOLEN - optlen < total_len) { 1830 to->to_flags &= ~TOF_FASTOPEN; 1831 continue; 1832 } 1833 *optp++ = TCPOPT_FAST_OPEN; 1834 *optp++ = total_len; 1835 if (to->to_tfo_len > 0) { 1836 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1837 optp += to->to_tfo_len; 1838 } 1839 optlen += total_len; 1840 break; 1841 } 1842 default: 1843 panic("%s: unknown TCP option type", __func__); 1844 break; 1845 } 1846 } 1847 1848 /* Terminate and pad TCP options to a 4 byte boundary. */ 1849 if (optlen % 4) { 1850 optlen += TCPOLEN_EOL; 1851 *optp++ = TCPOPT_EOL; 1852 } 1853 /* 1854 * According to RFC 793 (STD0007): 1855 * "The content of the header beyond the End-of-Option option 1856 * must be header padding (i.e., zero)." 1857 * and later: "The padding is composed of zeros." 1858 */ 1859 while (optlen % 4) { 1860 optlen += TCPOLEN_PAD; 1861 *optp++ = TCPOPT_PAD; 1862 } 1863 1864 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1865 return (optlen); 1866 } 1867 1868 /* 1869 * This is a copy of m_copym(), taking the TSO segment size/limit 1870 * constraints into account, and advancing the sndptr as it goes. 1871 */ 1872 struct mbuf * 1873 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1874 int32_t seglimit, int32_t segsize, struct sockbuf *sb) 1875 { 1876 struct mbuf *n, **np; 1877 struct mbuf *top; 1878 int32_t off = off0; 1879 int32_t len = *plen; 1880 int32_t fragsize; 1881 int32_t len_cp = 0; 1882 int32_t *pkthdrlen; 1883 uint32_t mlen, frags; 1884 bool copyhdr; 1885 1886 1887 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1888 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1889 if (off == 0 && m->m_flags & M_PKTHDR) 1890 copyhdr = true; 1891 else 1892 copyhdr = false; 1893 while (off > 0) { 1894 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1895 if (off < m->m_len) 1896 break; 1897 off -= m->m_len; 1898 if ((sb) && (m == sb->sb_sndptr)) { 1899 sb->sb_sndptroff += m->m_len; 1900 sb->sb_sndptr = m->m_next; 1901 } 1902 m = m->m_next; 1903 } 1904 np = ⊤ 1905 top = NULL; 1906 pkthdrlen = NULL; 1907 while (len > 0) { 1908 if (m == NULL) { 1909 KASSERT(len == M_COPYALL, 1910 ("tcp_m_copym, length > size of mbuf chain")); 1911 *plen = len_cp; 1912 if (pkthdrlen != NULL) 1913 *pkthdrlen = len_cp; 1914 break; 1915 } 1916 mlen = min(len, m->m_len - off); 1917 if (seglimit) { 1918 /* 1919 * For M_NOMAP mbufs, add 3 segments 1920 * + 1 in case we are crossing page boundaries 1921 * + 2 in case the TLS hdr/trailer are used 1922 * It is cheaper to just add the segments 1923 * than it is to take the cache miss to look 1924 * at the mbuf ext_pgs state in detail. 1925 */ 1926 if (m->m_flags & M_NOMAP) { 1927 fragsize = min(segsize, PAGE_SIZE); 1928 frags = 3; 1929 } else { 1930 fragsize = segsize; 1931 frags = 0; 1932 } 1933 1934 /* Break if we really can't fit anymore. */ 1935 if ((frags + 1) >= seglimit) { 1936 *plen = len_cp; 1937 if (pkthdrlen != NULL) 1938 *pkthdrlen = len_cp; 1939 break; 1940 } 1941 1942 /* 1943 * Reduce size if you can't copy the whole 1944 * mbuf. If we can't copy the whole mbuf, also 1945 * adjust len so the loop will end after this 1946 * mbuf. 1947 */ 1948 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 1949 mlen = (seglimit - frags - 1) * fragsize; 1950 len = mlen; 1951 *plen = len_cp + len; 1952 if (pkthdrlen != NULL) 1953 *pkthdrlen = *plen; 1954 } 1955 frags += howmany(mlen, fragsize); 1956 if (frags == 0) 1957 frags++; 1958 seglimit -= frags; 1959 KASSERT(seglimit > 0, 1960 ("%s: seglimit went too low", __func__)); 1961 } 1962 if (copyhdr) 1963 n = m_gethdr(M_NOWAIT, m->m_type); 1964 else 1965 n = m_get(M_NOWAIT, m->m_type); 1966 *np = n; 1967 if (n == NULL) 1968 goto nospace; 1969 if (copyhdr) { 1970 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 1971 goto nospace; 1972 if (len == M_COPYALL) 1973 n->m_pkthdr.len -= off0; 1974 else 1975 n->m_pkthdr.len = len; 1976 pkthdrlen = &n->m_pkthdr.len; 1977 copyhdr = false; 1978 } 1979 n->m_len = mlen; 1980 len_cp += n->m_len; 1981 if (m->m_flags & M_EXT) { 1982 n->m_data = m->m_data + off; 1983 mb_dupcl(n, m); 1984 } else 1985 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 1986 (u_int)n->m_len); 1987 1988 if (sb && (sb->sb_sndptr == m) && 1989 ((n->m_len + off) >= m->m_len) && m->m_next) { 1990 sb->sb_sndptroff += m->m_len; 1991 sb->sb_sndptr = m->m_next; 1992 } 1993 off = 0; 1994 if (len != M_COPYALL) { 1995 len -= n->m_len; 1996 } 1997 m = m->m_next; 1998 np = &n->m_next; 1999 } 2000 return (top); 2001 nospace: 2002 m_freem(top); 2003 return (NULL); 2004 } 2005 2006 void 2007 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2008 { 2009 2010 /* 2011 * Automatic sizing of send socket buffer. Often the send buffer 2012 * size is not optimally adjusted to the actual network conditions 2013 * at hand (delay bandwidth product). Setting the buffer size too 2014 * small limits throughput on links with high bandwidth and high 2015 * delay (eg. trans-continental/oceanic links). Setting the 2016 * buffer size too big consumes too much real kernel memory, 2017 * especially with many connections on busy servers. 2018 * 2019 * The criteria to step up the send buffer one notch are: 2020 * 1. receive window of remote host is larger than send buffer 2021 * (with a fudge factor of 5/4th); 2022 * 2. send buffer is filled to 7/8th with data (so we actually 2023 * have data to make use of it); 2024 * 3. send buffer fill has not hit maximal automatic size; 2025 * 4. our send window (slow start and cogestion controlled) is 2026 * larger than sent but unacknowledged data in send buffer. 2027 * 2028 * The remote host receive window scaling factor may limit the 2029 * growing of the send buffer before it reaches its allowed 2030 * maximum. 2031 * 2032 * It scales directly with slow start or congestion window 2033 * and does at most one step per received ACK. This fast 2034 * scaling has the drawback of growing the send buffer beyond 2035 * what is strictly necessary to make full use of a given 2036 * delay*bandwidth product. However testing has shown this not 2037 * to be much of an problem. At worst we are trading wasting 2038 * of available bandwidth (the non-use of it) for wasting some 2039 * socket buffer memory. 2040 * 2041 * TODO: Shrink send buffer during idle periods together 2042 * with congestion window. Requires another timer. Has to 2043 * wait for upcoming tcp timer rewrite. 2044 * 2045 * XXXGL: should there be used sbused() or sbavail()? 2046 */ 2047 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2048 int lowat; 2049 2050 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2051 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2052 sbused(&so->so_snd) >= 2053 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2054 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2055 sendwin >= (sbused(&so->so_snd) - 2056 (tp->snd_nxt - tp->snd_una))) { 2057 if (!sbreserve_locked(&so->so_snd, 2058 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2059 V_tcp_autosndbuf_max), so, curthread)) 2060 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2061 } 2062 } 2063 } 2064