1 /* 2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 68 */ 69 70 #include "opt_inet.h" 71 #include "opt_inet6.h" 72 #include "opt_ipsec.h" 73 #include "opt_tcpdebug.h" 74 75 #include <sys/param.h> 76 #include <sys/systm.h> 77 #include <sys/kernel.h> 78 #include <sys/sysctl.h> 79 #include <sys/mbuf.h> 80 #include <sys/domain.h> 81 #include <sys/protosw.h> 82 #include <sys/socket.h> 83 #include <sys/socketvar.h> 84 #include <sys/in_cksum.h> 85 #include <sys/thread.h> 86 #include <sys/globaldata.h> 87 88 #include <net/if_var.h> 89 #include <net/route.h> 90 91 #include <netinet/in.h> 92 #include <netinet/in_systm.h> 93 #include <netinet/ip.h> 94 #include <netinet/in_pcb.h> 95 #include <netinet/ip_var.h> 96 #include <netinet6/in6_pcb.h> 97 #include <netinet/ip6.h> 98 #include <netinet6/ip6_var.h> 99 #include <netinet/tcp.h> 100 #define TCPOUTFLAGS 101 #include <netinet/tcp_fsm.h> 102 #include <netinet/tcp_seq.h> 103 #include <netinet/tcp_timer.h> 104 #include <netinet/tcp_timer2.h> 105 #include <netinet/tcp_var.h> 106 #include <netinet/tcpip.h> 107 #ifdef TCPDEBUG 108 #include <netinet/tcp_debug.h> 109 #endif 110 111 #ifdef IPSEC 112 #include <netinet6/ipsec.h> 113 #endif /*IPSEC*/ 114 115 #ifdef FAST_IPSEC 116 #include <netproto/ipsec/ipsec.h> 117 #define IPSEC 118 #endif /*FAST_IPSEC*/ 119 120 #ifdef notyet 121 extern struct mbuf *m_copypack(); 122 #endif 123 124 int path_mtu_discovery = 0; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 126 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 127 128 static int avoid_pure_win_update = 1; 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, 130 &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); 131 132 int tcp_do_autosndbuf = 1; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 134 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 135 136 int tcp_autosndbuf_inc = 8*1024; 137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 138 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 139 140 int tcp_autosndbuf_max = 2*1024*1024; 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 142 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 143 144 static int tcp_idle_cwv = 1; 145 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_cwv, CTLFLAG_RW, 146 &tcp_idle_cwv, 0, 147 "Congestion window validation after idle period (part of RFC2861)"); 148 149 static int tcp_idle_restart = 1; 150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_restart, CTLFLAG_RW, 151 &tcp_idle_restart, 0, "Reset congestion window after idle period"); 152 153 static int tcp_do_tso = 1; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 155 &tcp_do_tso, 0, "Enable TCP Segmentation Offload (TSO)"); 156 157 static void tcp_idle_cwnd_validate(struct tcpcb *); 158 159 static int tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen); 160 161 /* 162 * Tcp output routine: figure out what should be sent and send it. 163 */ 164 int 165 tcp_output(struct tcpcb *tp) 166 { 167 struct inpcb * const inp = tp->t_inpcb; 168 struct socket *so = inp->inp_socket; 169 long len, recvwin, sendwin; 170 int nsacked = 0; 171 int off, flags, error = 0; 172 #ifdef TCP_SIGNATURE 173 int sigoff = 0; 174 #endif 175 struct mbuf *m; 176 struct ip *ip; 177 struct tcphdr *th; 178 u_char opt[TCP_MAXOLEN]; 179 unsigned int ipoptlen, optlen, hdrlen; 180 int idle; 181 boolean_t sendalot; 182 struct ip6_hdr *ip6; 183 #ifdef INET6 184 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 185 #else 186 const boolean_t isipv6 = FALSE; 187 #endif 188 boolean_t can_tso = FALSE, use_tso; 189 boolean_t report_sack, idle_cwv = FALSE; 190 u_int segsz, tso_hlen; 191 192 KKASSERT(so->so_port == &curthread->td_msgport); 193 194 /* 195 * Determine length of data that should be transmitted, 196 * and flags that will be used. 197 * If there is some data or critical controls (SYN, RST) 198 * to send, then transmit; otherwise, investigate further. 199 */ 200 201 /* 202 * If we have been idle for a while, the send congestion window 203 * could be no longer representative of the current state of the 204 * link; need to validate congestion window. However, we should 205 * not perform congestion window validation here, since we could 206 * be asked to send pure ACK. 207 */ 208 if (tp->snd_max == tp->snd_una && 209 (ticks - tp->snd_last) >= tp->t_rxtcur && tcp_idle_restart) 210 idle_cwv = TRUE; 211 212 /* 213 * Calculate whether the transmit stream was previously idle 214 * and adjust TF_LASTIDLE for the next time. 215 */ 216 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 217 if (idle && (tp->t_flags & TF_MORETOCOME)) 218 tp->t_flags |= TF_LASTIDLE; 219 else 220 tp->t_flags &= ~TF_LASTIDLE; 221 222 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 223 !IN_FASTRECOVERY(tp)) 224 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); 225 226 /* 227 * Find out whether TSO could be used or not 228 * 229 * For TSO capable devices, the following assumptions apply to 230 * the processing of TCP flags: 231 * - If FIN is set on the large TCP segment, the device must set 232 * FIN on the last segment that it creates from the large TCP 233 * segment. 234 * - If PUSH is set on the large TCP segment, the device must set 235 * PUSH on the last segment that it creates from the large TCP 236 * segment. 237 */ 238 #if !defined(IPSEC) && !defined(FAST_IPSEC) 239 if (tcp_do_tso 240 #ifdef TCP_SIGNATURE 241 && (tp->t_flags & TF_SIGNATURE) == 0 242 #endif 243 ) { 244 if (!isipv6) { 245 struct rtentry *rt = inp->inp_route.ro_rt; 246 247 if (rt != NULL && (rt->rt_flags & RTF_UP) && 248 (rt->rt_ifp->if_hwassist & CSUM_TSO)) 249 can_tso = TRUE; 250 } 251 } 252 #endif /* !IPSEC && !FAST_IPSEC */ 253 254 again: 255 m = NULL; 256 ip = NULL; 257 th = NULL; 258 ip6 = NULL; 259 260 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 261 TF_SACK_PERMITTED && 262 (!TAILQ_EMPTY(&tp->t_segq) || 263 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 264 report_sack = TRUE; 265 else 266 report_sack = FALSE; 267 268 /* Make use of SACK information when slow-starting after a RTO. */ 269 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 270 !IN_FASTRECOVERY(tp)) { 271 tcp_seq old_snd_nxt = tp->snd_nxt; 272 273 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 274 nsacked += tp->snd_nxt - old_snd_nxt; 275 } 276 277 sendalot = FALSE; 278 off = tp->snd_nxt - tp->snd_una; 279 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 280 sendwin = min(sendwin, tp->snd_bwnd); 281 282 flags = tcp_outflags[tp->t_state]; 283 /* 284 * Get standard flags, and add SYN or FIN if requested by 'hidden' 285 * state flags. 286 */ 287 if (tp->t_flags & TF_NEEDFIN) 288 flags |= TH_FIN; 289 if (tp->t_flags & TF_NEEDSYN) 290 flags |= TH_SYN; 291 292 /* 293 * If in persist timeout with window of 0, send 1 byte. 294 * Otherwise, if window is small but nonzero 295 * and timer expired, we will send what we can 296 * and go to transmit state. 297 */ 298 if (tp->t_flags & TF_FORCE) { 299 if (sendwin == 0) { 300 /* 301 * If we still have some data to send, then 302 * clear the FIN bit. Usually this would 303 * happen below when it realizes that we 304 * aren't sending all the data. However, 305 * if we have exactly 1 byte of unsent data, 306 * then it won't clear the FIN bit below, 307 * and if we are in persist state, we wind 308 * up sending the packet without recording 309 * that we sent the FIN bit. 310 * 311 * We can't just blindly clear the FIN bit, 312 * because if we don't have any more data 313 * to send then the probe will be the FIN 314 * itself. 315 */ 316 if (off < so->so_snd.ssb_cc) 317 flags &= ~TH_FIN; 318 sendwin = 1; 319 } else { 320 tcp_callout_stop(tp, tp->tt_persist); 321 tp->t_rxtshift = 0; 322 } 323 } 324 325 /* 326 * If snd_nxt == snd_max and we have transmitted a FIN, the 327 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in 328 * a negative length. This can also occur when TCP opens up 329 * its congestion window while receiving additional duplicate 330 * acks after fast-retransmit because TCP will reset snd_nxt 331 * to snd_max after the fast-retransmit. 332 * 333 * A negative length can also occur when we are in the 334 * TCPS_SYN_RECEIVED state due to a simultanious connect where 335 * our SYN has not been acked yet. 336 * 337 * In the normal retransmit-FIN-only case, however, snd_nxt will 338 * be set to snd_una, the offset will be 0, and the length may 339 * wind up 0. 340 */ 341 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; 342 343 /* 344 * Lop off SYN bit if it has already been sent. However, if this 345 * is SYN-SENT state and if segment contains data, suppress sending 346 * segment (sending the segment would be an option if we still 347 * did TAO and the remote host supported it). 348 */ 349 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 350 flags &= ~TH_SYN; 351 off--, len++; 352 if (len > 0 && tp->t_state == TCPS_SYN_SENT) { 353 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 354 return 0; 355 } 356 } 357 358 /* 359 * Be careful not to send data and/or FIN on SYN segments. 360 * This measure is needed to prevent interoperability problems 361 * with not fully conformant TCP implementations. 362 */ 363 if (flags & TH_SYN) { 364 len = 0; 365 flags &= ~TH_FIN; 366 } 367 368 if (len < 0) { 369 /* 370 * A negative len can occur if our FIN has been sent but not 371 * acked, or if we are in a simultanious connect in the 372 * TCPS_SYN_RECEIVED state with our SYN sent but not yet 373 * acked. 374 * 375 * If our window has contracted to 0 in the FIN case 376 * (which can only occur if we have NOT been called to 377 * retransmit as per code a few paragraphs up) then we 378 * want to shift the retransmit timer over to the 379 * persist timer. 380 * 381 * However, if we are in the TCPS_SYN_RECEIVED state 382 * (the SYN case) we will be in a simultanious connect and 383 * the window may be zero degeneratively. In this case we 384 * do not want to shift to the persist timer after the SYN 385 * or the SYN+ACK transmission. 386 */ 387 len = 0; 388 if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) { 389 tcp_callout_stop(tp, tp->tt_rexmt); 390 tp->t_rxtshift = 0; 391 tp->snd_nxt = tp->snd_una; 392 if (!tcp_callout_active(tp, tp->tt_persist)) 393 tcp_setpersist(tp); 394 } 395 } 396 397 KASSERT(len >= 0, ("%s: len < 0", __func__)); 398 /* 399 * Automatic sizing of send socket buffer. Often the send buffer 400 * size is not optimally adjusted to the actual network conditions 401 * at hand (delay bandwidth product). Setting the buffer size too 402 * small limits throughput on links with high bandwidth and high 403 * delay (eg. trans-continental/oceanic links). Setting the 404 * buffer size too big consumes too much real kernel memory, 405 * especially with many connections on busy servers. 406 * 407 * The criteria to step up the send buffer one notch are: 408 * 1. receive window of remote host is larger than send buffer 409 * (with a fudge factor of 5/4th); 410 * 2. send buffer is filled to 7/8th with data (so we actually 411 * have data to make use of it); 412 * 3. send buffer fill has not hit maximal automatic size; 413 * 4. our send window (slow start and cogestion controlled) is 414 * larger than sent but unacknowledged data in send buffer. 415 * 416 * The remote host receive window scaling factor may limit the 417 * growing of the send buffer before it reaches its allowed 418 * maximum. 419 * 420 * It scales directly with slow start or congestion window 421 * and does at most one step per received ACK. This fast 422 * scaling has the drawback of growing the send buffer beyond 423 * what is strictly necessary to make full use of a given 424 * delay*bandwith product. However testing has shown this not 425 * to be much of an problem. At worst we are trading wasting 426 * of available bandwith (the non-use of it) for wasting some 427 * socket buffer memory. 428 * 429 * TODO: Shrink send buffer during idle periods together 430 * with congestion window. Requires another timer. Has to 431 * wait for upcoming tcp timer rewrite. 432 */ 433 if (tcp_do_autosndbuf && so->so_snd.ssb_flags & SSB_AUTOSIZE) { 434 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.ssb_hiwat && 435 so->so_snd.ssb_cc >= (so->so_snd.ssb_hiwat / 8 * 7) && 436 so->so_snd.ssb_cc < tcp_autosndbuf_max && 437 sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) { 438 u_long newsize; 439 440 newsize = ulmin(so->so_snd.ssb_hiwat + 441 tcp_autosndbuf_inc, 442 tcp_autosndbuf_max); 443 if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) 444 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 445 if (newsize >= (TCP_MAXWIN << tp->snd_scale)) 446 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 447 } 448 } 449 450 /* 451 * Don't use TSO, if: 452 * - Congestion window needs validation 453 * - There are SACK blocks to report 454 * - RST or SYN flags is set 455 * - URG will be set 456 * 457 * XXX 458 * Checking for SYN|RST looks overkill, just to be safe than sorry 459 */ 460 use_tso = can_tso; 461 if (report_sack || idle_cwv || (flags & (TH_RST | TH_SYN))) 462 use_tso = FALSE; 463 if (use_tso) { 464 tcp_seq ugr_nxt = tp->snd_nxt; 465 466 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && 467 tp->snd_nxt == tp->snd_max) 468 --ugr_nxt; 469 470 if (SEQ_GT(tp->snd_up, ugr_nxt)) 471 use_tso = FALSE; 472 } 473 474 if (use_tso) { 475 /* 476 * Find out segment size and header length for TSO 477 */ 478 error = tcp_tso_getsize(tp, &segsz, &tso_hlen); 479 if (error) 480 use_tso = FALSE; 481 } 482 if (!use_tso) { 483 segsz = tp->t_maxseg; 484 tso_hlen = 0; /* not used */ 485 } 486 487 /* 488 * Truncate to the maximum segment length if not TSO, and ensure that 489 * FIN is removed if the length no longer contains the last data byte. 490 */ 491 if (len > segsz) { 492 if (!use_tso) { 493 len = segsz; 494 } else { 495 /* 496 * Truncate TSO transfers to (IP_MAXPACKET - iphlen - 497 * thoff), and make sure that we send equal size 498 * transfers down the stack (rather than big-small- 499 * big-small-...). 500 */ 501 len = (min(len, (IP_MAXPACKET - tso_hlen)) / segsz) * 502 segsz; 503 if (len <= segsz) 504 use_tso = FALSE; 505 } 506 sendalot = TRUE; 507 } else { 508 use_tso = FALSE; 509 } 510 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) 511 flags &= ~TH_FIN; 512 513 recvwin = ssb_space(&so->so_rcv); 514 515 /* 516 * Sender silly window avoidance. We transmit under the following 517 * conditions when len is non-zero: 518 * 519 * - We have a full segment 520 * - This is the last buffer in a write()/send() and we are 521 * either idle or running NODELAY 522 * - we've timed out (e.g. persist timer) 523 * - we have more then 1/2 the maximum send window's worth of 524 * data (receiver may be limiting the window size) 525 * - we need to retransmit 526 */ 527 if (len) { 528 if (len >= segsz) 529 goto send; 530 /* 531 * NOTE! on localhost connections an 'ack' from the remote 532 * end may occur synchronously with the output and cause 533 * us to flush a buffer queued with moretocome. XXX 534 * 535 * note: the len + off check is almost certainly unnecessary. 536 */ 537 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 538 (idle || (tp->t_flags & TF_NODELAY)) && 539 len + off >= so->so_snd.ssb_cc && 540 !(tp->t_flags & TF_NOPUSH)) { 541 goto send; 542 } 543 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 544 goto send; 545 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 546 goto send; 547 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 548 goto send; 549 if (tp->t_flags & TF_XMITNOW) 550 goto send; 551 } 552 553 /* 554 * Compare available window to amount of window 555 * known to peer (as advertised window less 556 * next expected input). If the difference is at least two 557 * max size segments, or at least 50% of the maximum possible 558 * window, then want to send a window update to peer. 559 */ 560 if (recvwin > 0) { 561 /* 562 * "adv" is the amount we can increase the window, 563 * taking into account that we are limited by 564 * TCP_MAXWIN << tp->rcv_scale. 565 */ 566 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 567 (tp->rcv_adv - tp->rcv_nxt); 568 long hiwat; 569 570 /* 571 * This ack case typically occurs when the user has drained 572 * the TCP socket buffer sufficiently to warrent an ack 573 * containing a 'pure window update'... that is, an ack that 574 * ONLY updates the tcp window. 575 * 576 * It is unclear why we would need to do a pure window update 577 * past 2 segments if we are going to do one at 1/2 the high 578 * water mark anyway, especially since under normal conditions 579 * the user program will drain the socket buffer quickly. 580 * The 2-segment pure window update will often add a large 581 * number of extra, unnecessary acks to the stream. 582 * 583 * avoid_pure_win_update now defaults to 1. 584 */ 585 if (avoid_pure_win_update == 0 || 586 (tp->t_flags & TF_RXRESIZED)) { 587 if (adv >= (long) (2 * segsz)) { 588 goto send; 589 } 590 } 591 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); 592 if (hiwat > (long)so->so_rcv.ssb_hiwat) 593 hiwat = (long)so->so_rcv.ssb_hiwat; 594 if (adv >= hiwat / 2) 595 goto send; 596 } 597 598 /* 599 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 600 * is also a catch-all for the retransmit timer timeout case. 601 */ 602 if (tp->t_flags & TF_ACKNOW) 603 goto send; 604 if ((flags & TH_RST) || 605 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 606 goto send; 607 if (SEQ_GT(tp->snd_up, tp->snd_una)) 608 goto send; 609 /* 610 * If our state indicates that FIN should be sent 611 * and we have not yet done so, then we need to send. 612 */ 613 if ((flags & TH_FIN) && 614 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 615 goto send; 616 617 /* 618 * TCP window updates are not reliable, rather a polling protocol 619 * using ``persist'' packets is used to insure receipt of window 620 * updates. The three ``states'' for the output side are: 621 * idle not doing retransmits or persists 622 * persisting to move a small or zero window 623 * (re)transmitting and thereby not persisting 624 * 625 * tcp_callout_active(tp, tp->tt_persist) 626 * is true when we are in persist state. 627 * The TF_FORCE flag in tp->t_flags 628 * is set when we are called to send a persist packet. 629 * tcp_callout_active(tp, tp->tt_rexmt) 630 * is set when we are retransmitting 631 * The output side is idle when both timers are zero. 632 * 633 * If send window is too small, there is data to transmit, and no 634 * retransmit or persist is pending, then go to persist state. 635 * 636 * If nothing happens soon, send when timer expires: 637 * if window is nonzero, transmit what we can, otherwise force out 638 * a byte. 639 * 640 * Don't try to set the persist state if we are in TCPS_SYN_RECEIVED 641 * with data pending. This situation can occur during a 642 * simultanious connect. 643 */ 644 if (so->so_snd.ssb_cc > 0 && 645 tp->t_state != TCPS_SYN_RECEIVED && 646 !tcp_callout_active(tp, tp->tt_rexmt) && 647 !tcp_callout_active(tp, tp->tt_persist)) { 648 tp->t_rxtshift = 0; 649 tcp_setpersist(tp); 650 } 651 652 /* 653 * No reason to send a segment, just return. 654 */ 655 tp->t_flags &= ~TF_XMITNOW; 656 return (0); 657 658 send: 659 /* 660 * Before ESTABLISHED, force sending of initial options 661 * unless TCP set not to do any options. 662 * NOTE: we assume that the IP/TCP header plus TCP options 663 * always fit in a single mbuf, leaving room for a maximum 664 * link header, i.e. 665 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 666 */ 667 optlen = 0; 668 if (isipv6) 669 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 670 else 671 hdrlen = sizeof(struct tcpiphdr); 672 if (flags & TH_SYN) { 673 tp->snd_nxt = tp->iss; 674 if (!(tp->t_flags & TF_NOOPT)) { 675 u_short mss; 676 677 opt[0] = TCPOPT_MAXSEG; 678 opt[1] = TCPOLEN_MAXSEG; 679 mss = htons((u_short) tcp_mssopt(tp)); 680 memcpy(opt + 2, &mss, sizeof mss); 681 optlen = TCPOLEN_MAXSEG; 682 683 if ((tp->t_flags & TF_REQ_SCALE) && 684 (!(flags & TH_ACK) || 685 (tp->t_flags & TF_RCVD_SCALE))) { 686 *((u_int32_t *)(opt + optlen)) = htonl( 687 TCPOPT_NOP << 24 | 688 TCPOPT_WINDOW << 16 | 689 TCPOLEN_WINDOW << 8 | 690 tp->request_r_scale); 691 optlen += 4; 692 } 693 694 if ((tcp_do_sack && !(flags & TH_ACK)) || 695 tp->t_flags & TF_SACK_PERMITTED) { 696 uint32_t *lp = (uint32_t *)(opt + optlen); 697 698 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 699 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 700 } 701 } 702 } 703 704 /* 705 * Send a timestamp and echo-reply if this is a SYN and our side 706 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 707 * and our peer have sent timestamps in our SYN's. 708 */ 709 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 710 !(flags & TH_RST) && 711 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 712 u_int32_t *lp = (u_int32_t *)(opt + optlen); 713 714 /* Form timestamp option as shown in appendix A of RFC 1323. */ 715 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 716 *lp++ = htonl(ticks); 717 *lp = htonl(tp->ts_recent); 718 optlen += TCPOLEN_TSTAMP_APPA; 719 } 720 721 /* Set receive buffer autosizing timestamp. */ 722 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) 723 tp->rfbuf_ts = ticks; 724 725 /* 726 * If this is a SACK connection and we have a block to report, 727 * fill in the SACK blocks in the TCP options. 728 */ 729 if (report_sack) 730 tcp_sack_fill_report(tp, opt, &optlen); 731 732 #ifdef TCP_SIGNATURE 733 if (tp->t_flags & TF_SIGNATURE) { 734 int i; 735 u_char *bp; 736 /* 737 * Initialize TCP-MD5 option (RFC2385) 738 */ 739 bp = (u_char *)opt + optlen; 740 *bp++ = TCPOPT_SIGNATURE; 741 *bp++ = TCPOLEN_SIGNATURE; 742 sigoff = optlen + 2; 743 for (i = 0; i < TCP_SIGLEN; i++) 744 *bp++ = 0; 745 optlen += TCPOLEN_SIGNATURE; 746 /* 747 * Terminate options list and maintain 32-bit alignment. 748 */ 749 *bp++ = TCPOPT_NOP; 750 *bp++ = TCPOPT_EOL; 751 optlen += 2; 752 } 753 #endif /* TCP_SIGNATURE */ 754 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 755 hdrlen += optlen; 756 757 if (isipv6) { 758 ipoptlen = ip6_optlen(inp); 759 } else { 760 if (inp->inp_options) { 761 ipoptlen = inp->inp_options->m_len - 762 offsetof(struct ipoption, ipopt_list); 763 } else { 764 ipoptlen = 0; 765 } 766 } 767 #ifdef IPSEC 768 ipoptlen += ipsec_hdrsiz_tcp(tp); 769 #endif 770 771 if (use_tso) { 772 /* TSO segment length must be multiple of segment size */ 773 KASSERT(len >= (2 * segsz) && (len % segsz == 0), 774 ("invalid TSO len %ld, segsz %u", len, segsz)); 775 } else { 776 KASSERT(len <= segsz, 777 ("invalid len %ld, segsz %u", len, segsz)); 778 779 /* 780 * Adjust data length if insertion of options will bump 781 * the packet length beyond the t_maxopd length. Clear 782 * FIN to prevent premature closure since there is still 783 * more data to send after this (now truncated) packet. 784 * 785 * If just the options do not fit we are in a no-win 786 * situation and we treat it as an unreachable host. 787 */ 788 if (len + optlen + ipoptlen > tp->t_maxopd) { 789 if (tp->t_maxopd <= optlen + ipoptlen) { 790 static time_t last_optlen_report; 791 792 if (last_optlen_report != time_second) { 793 last_optlen_report = time_second; 794 kprintf("tcpcb %p: MSS (%d) too " 795 "small to hold options!\n", 796 tp, tp->t_maxopd); 797 } 798 error = EHOSTUNREACH; 799 goto out; 800 } else { 801 flags &= ~TH_FIN; 802 len = tp->t_maxopd - optlen - ipoptlen; 803 sendalot = TRUE; 804 } 805 } 806 } 807 808 #ifdef INET6 809 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 810 #else 811 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 812 #endif 813 814 /* 815 * Grab a header mbuf, attaching a copy of data to 816 * be transmitted, and initialize the header from 817 * the template for sends on this connection. 818 */ 819 if (len) { 820 if ((tp->t_flags & TF_FORCE) && len == 1) 821 tcpstat.tcps_sndprobe++; 822 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 823 if (tp->snd_nxt == tp->snd_una) 824 tp->snd_max_rexmt = tp->snd_max; 825 if (nsacked) { 826 tcpstat.tcps_sndsackrtopack++; 827 tcpstat.tcps_sndsackrtobyte += len; 828 } 829 tcpstat.tcps_sndrexmitpack++; 830 tcpstat.tcps_sndrexmitbyte += len; 831 } else { 832 tcpstat.tcps_sndpack++; 833 tcpstat.tcps_sndbyte += len; 834 } 835 if (idle_cwv) { 836 idle_cwv = FALSE; 837 tcp_idle_cwnd_validate(tp); 838 } 839 /* Update last send time after CWV */ 840 tp->snd_last = ticks; 841 #ifdef notyet 842 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, 843 max_linkhdr + hdrlen)) == NULL) { 844 error = ENOBUFS; 845 goto after_th; 846 } 847 /* 848 * m_copypack left space for our hdr; use it. 849 */ 850 m->m_len += hdrlen; 851 m->m_data -= hdrlen; 852 #else 853 #ifndef INET6 854 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 855 #else 856 m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER, 857 M_PKTHDR, NULL); 858 #endif 859 if (m == NULL) { 860 error = ENOBUFS; 861 goto after_th; 862 } 863 m->m_data += max_linkhdr; 864 m->m_len = hdrlen; 865 if (len <= MHLEN - hdrlen - max_linkhdr) { 866 m_copydata(so->so_snd.ssb_mb, off, (int) len, 867 mtod(m, caddr_t) + hdrlen); 868 m->m_len += len; 869 } else { 870 m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len); 871 if (m->m_next == NULL) { 872 m_free(m); 873 m = NULL; 874 error = ENOBUFS; 875 goto after_th; 876 } 877 } 878 #endif 879 /* 880 * If we're sending everything we've got, set PUSH. 881 * (This will keep happy those implementations which only 882 * give data to the user when a buffer fills or 883 * a PUSH comes in.) 884 */ 885 if (off + len == so->so_snd.ssb_cc) 886 flags |= TH_PUSH; 887 } else { 888 if (tp->t_flags & TF_ACKNOW) 889 tcpstat.tcps_sndacks++; 890 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 891 tcpstat.tcps_sndctrl++; 892 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 893 tcpstat.tcps_sndurg++; 894 else 895 tcpstat.tcps_sndwinup++; 896 897 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 898 if (m == NULL) { 899 error = ENOBUFS; 900 goto after_th; 901 } 902 if (isipv6 && 903 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 904 MH_ALIGN(m, hdrlen); 905 else 906 m->m_data += max_linkhdr; 907 m->m_len = hdrlen; 908 } 909 m->m_pkthdr.rcvif = NULL; 910 if (isipv6) { 911 ip6 = mtod(m, struct ip6_hdr *); 912 th = (struct tcphdr *)(ip6 + 1); 913 tcp_fillheaders(tp, ip6, th, use_tso); 914 } else { 915 ip = mtod(m, struct ip *); 916 th = (struct tcphdr *)(ip + 1); 917 /* this picks up the pseudo header (w/o the length) */ 918 tcp_fillheaders(tp, ip, th, use_tso); 919 } 920 after_th: 921 /* 922 * Fill in fields, remembering maximum advertised 923 * window for use in delaying messages about window sizes. 924 * If resending a FIN, be sure not to use a new sequence number. 925 */ 926 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 927 tp->snd_nxt == tp->snd_max) 928 tp->snd_nxt--; 929 930 if (th != NULL) { 931 /* 932 * If we are doing retransmissions, then snd_nxt will 933 * not reflect the first unsent octet. For ACK only 934 * packets, we do not want the sequence number of the 935 * retransmitted packet, we want the sequence number 936 * of the next unsent octet. So, if there is no data 937 * (and no SYN or FIN), use snd_max instead of snd_nxt 938 * when filling in ti_seq. But if we are in persist 939 * state, snd_max might reflect one byte beyond the 940 * right edge of the window, so use snd_nxt in that 941 * case, since we know we aren't doing a retransmission. 942 * (retransmit and persist are mutually exclusive...) 943 */ 944 if (len || (flags & (TH_SYN|TH_FIN)) || 945 tcp_callout_active(tp, tp->tt_persist)) 946 th->th_seq = htonl(tp->snd_nxt); 947 else 948 th->th_seq = htonl(tp->snd_max); 949 th->th_ack = htonl(tp->rcv_nxt); 950 if (optlen) { 951 bcopy(opt, th + 1, optlen); 952 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 953 } 954 th->th_flags = flags; 955 } 956 957 /* 958 * Calculate receive window. Don't shrink window, but avoid 959 * silly window syndrome by sending a 0 window if the actual 960 * window is less then one segment. 961 */ 962 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && 963 recvwin < (long)segsz) 964 recvwin = 0; 965 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt)) 966 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt); 967 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 968 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 969 970 /* 971 * Adjust the RXWIN0SENT flag - indicate that we have advertised 972 * a 0 window. This may cause the remote transmitter to stall. This 973 * flag tells soreceive() to disable delayed acknowledgements when 974 * draining the buffer. This can occur if the receiver is attempting 975 * to read more data then can be buffered prior to transmitting on 976 * the connection. 977 */ 978 if (recvwin == 0) 979 tp->t_flags |= TF_RXWIN0SENT; 980 else 981 tp->t_flags &= ~TF_RXWIN0SENT; 982 983 if (th != NULL) 984 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 985 986 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 987 KASSERT(!use_tso, ("URG with TSO")); 988 if (th != NULL) { 989 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 990 th->th_flags |= TH_URG; 991 } 992 } else { 993 /* 994 * If no urgent pointer to send, then we pull 995 * the urgent pointer to the left edge of the send window 996 * so that it doesn't drift into the send window on sequence 997 * number wraparound. 998 */ 999 tp->snd_up = tp->snd_una; /* drag it along */ 1000 } 1001 1002 if (th != NULL) { 1003 #ifdef TCP_SIGNATURE 1004 if (tp->t_flags & TF_SIGNATURE) { 1005 tcpsignature_compute(m, len, optlen, 1006 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1007 } 1008 #endif /* TCP_SIGNATURE */ 1009 1010 /* 1011 * Put TCP length in extended header, and then 1012 * checksum extended header and data. 1013 */ 1014 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1015 if (isipv6) { 1016 /* 1017 * ip6_plen is not need to be filled now, and will be 1018 * filled in ip6_output(). 1019 */ 1020 th->th_sum = in6_cksum(m, IPPROTO_TCP, 1021 sizeof(struct ip6_hdr), 1022 sizeof(struct tcphdr) + optlen + len); 1023 } else { 1024 m->m_pkthdr.csum_thlen = sizeof(struct tcphdr) + optlen; 1025 if (use_tso) { 1026 m->m_pkthdr.csum_flags = CSUM_TSO; 1027 m->m_pkthdr.tso_segsz = segsz; 1028 } else { 1029 m->m_pkthdr.csum_flags = CSUM_TCP; 1030 m->m_pkthdr.csum_data = 1031 offsetof(struct tcphdr, th_sum); 1032 if (len + optlen) { 1033 th->th_sum = in_addword(th->th_sum, 1034 htons((u_short)(optlen + len))); 1035 } 1036 } 1037 1038 /* 1039 * IP version must be set here for ipv4/ipv6 checking 1040 * later 1041 */ 1042 KASSERT(ip->ip_v == IPVERSION, 1043 ("%s: IP version incorrect: %d", 1044 __func__, ip->ip_v)); 1045 } 1046 } 1047 1048 /* 1049 * In transmit state, time the transmission and arrange for 1050 * the retransmit. In persist state, just set snd_max. 1051 */ 1052 if (!(tp->t_flags & TF_FORCE) || 1053 !tcp_callout_active(tp, tp->tt_persist)) { 1054 tcp_seq startseq = tp->snd_nxt; 1055 1056 /* 1057 * Advance snd_nxt over sequence space of this segment. 1058 */ 1059 if (flags & (TH_SYN | TH_FIN)) { 1060 if (flags & TH_SYN) 1061 tp->snd_nxt++; 1062 if (flags & TH_FIN) { 1063 tp->snd_nxt++; 1064 tp->t_flags |= TF_SENTFIN; 1065 } 1066 } 1067 tp->snd_nxt += len; 1068 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1069 tp->snd_max = tp->snd_nxt; 1070 /* 1071 * Time this transmission if not a retransmission and 1072 * not currently timing anything. 1073 */ 1074 if (tp->t_rtttime == 0) { 1075 tp->t_rtttime = ticks; 1076 tp->t_rtseq = startseq; 1077 tcpstat.tcps_segstimed++; 1078 } 1079 } 1080 1081 /* 1082 * Set retransmit timer if not currently set, 1083 * and not doing a pure ack or a keep-alive probe. 1084 * Initial value for retransmit timer is smoothed 1085 * round-trip time + 2 * round-trip time variance. 1086 * Initialize shift counter which is used for backoff 1087 * of retransmit time. 1088 */ 1089 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1090 tp->snd_nxt != tp->snd_una) { 1091 if (tcp_callout_active(tp, tp->tt_persist)) { 1092 tcp_callout_stop(tp, tp->tt_persist); 1093 tp->t_rxtshift = 0; 1094 } 1095 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 1096 tcp_timer_rexmt); 1097 } 1098 } else { 1099 /* 1100 * Persist case, update snd_max but since we are in 1101 * persist mode (no window) we do not update snd_nxt. 1102 */ 1103 int xlen = len; 1104 if (flags & TH_SYN) 1105 panic("tcp_output: persist timer to send SYN"); 1106 if (flags & TH_FIN) { 1107 ++xlen; 1108 tp->t_flags |= TF_SENTFIN; 1109 } 1110 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1111 tp->snd_max = tp->snd_nxt + xlen; 1112 } 1113 1114 if (th != NULL) { 1115 #ifdef TCPDEBUG 1116 /* Trace. */ 1117 if (so->so_options & SO_DEBUG) { 1118 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1119 mtod(m, void *), th, 0); 1120 } 1121 #endif 1122 1123 /* 1124 * Fill in IP length and desired time to live and 1125 * send to IP level. There should be a better way 1126 * to handle ttl and tos; we could keep them in 1127 * the template, but need a way to checksum without them. 1128 */ 1129 /* 1130 * m->m_pkthdr.len should have been set before cksum 1131 * calcuration, because in6_cksum() need it. 1132 */ 1133 if (isipv6) { 1134 /* 1135 * we separately set hoplimit for every segment, 1136 * since the user might want to change the value 1137 * via setsockopt. Also, desired default hop 1138 * limit might be changed via Neighbor Discovery. 1139 */ 1140 ip6->ip6_hlim = in6_selecthlim(inp, 1141 (inp->in6p_route.ro_rt ? 1142 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1143 1144 /* TODO: IPv6 IP6TOS_ECT bit on */ 1145 error = ip6_output(m, inp->in6p_outputopts, 1146 &inp->in6p_route, (so->so_options & SO_DONTROUTE), 1147 NULL, NULL, inp); 1148 } else { 1149 struct rtentry *rt; 1150 ip->ip_len = m->m_pkthdr.len; 1151 #ifdef INET6 1152 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1153 ip->ip_ttl = in6_selecthlim(inp, 1154 (inp->in6p_route.ro_rt ? 1155 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1156 else 1157 #endif 1158 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1159 1160 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1161 /* 1162 * See if we should do MTU discovery. 1163 * We do it only if the following are true: 1164 * 1) we have a valid route to the destination 1165 * 2) the MTU is not locked (if it is, 1166 * then discovery has been disabled) 1167 */ 1168 if (path_mtu_discovery && 1169 (rt = inp->inp_route.ro_rt) && 1170 (rt->rt_flags & RTF_UP) && 1171 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 1172 ip->ip_off |= IP_DF; 1173 1174 error = ip_output(m, inp->inp_options, &inp->inp_route, 1175 (so->so_options & SO_DONTROUTE) | 1176 IP_DEBUGROUTE, NULL, inp); 1177 } 1178 } else { 1179 KASSERT(error != 0, ("no error, but th not set")); 1180 } 1181 if (error) { 1182 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1183 1184 /* 1185 * We know that the packet was lost, so back out the 1186 * sequence number advance, if any. 1187 */ 1188 if (!(tp->t_flags & TF_FORCE) || 1189 !tcp_callout_active(tp, tp->tt_persist)) { 1190 /* 1191 * No need to check for TH_FIN here because 1192 * the TF_SENTFIN flag handles that case. 1193 */ 1194 if (!(flags & TH_SYN)) 1195 tp->snd_nxt -= len; 1196 } 1197 1198 out: 1199 if (error == ENOBUFS) { 1200 /* 1201 * If we can't send, make sure there is something 1202 * to get us going again later. 1203 * 1204 * The persist timer isn't necessarily allowed in all 1205 * states, use the rexmt timer. 1206 */ 1207 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1208 !tcp_callout_active(tp, tp->tt_persist)) { 1209 tcp_callout_reset(tp, tp->tt_rexmt, 1210 tp->t_rxtcur, 1211 tcp_timer_rexmt); 1212 #if 0 1213 tp->t_rxtshift = 0; 1214 tcp_setpersist(tp); 1215 #endif 1216 } 1217 tcp_quench(inp, 0); 1218 return (0); 1219 } 1220 if (error == EMSGSIZE) { 1221 /* 1222 * ip_output() will have already fixed the route 1223 * for us. tcp_mtudisc() will, as its last action, 1224 * initiate retransmission, so it is important to 1225 * not do so here. 1226 */ 1227 tcp_mtudisc(inp, 0); 1228 return 0; 1229 } 1230 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1231 TCPS_HAVERCVDSYN(tp->t_state)) { 1232 tp->t_softerror = error; 1233 return (0); 1234 } 1235 return (error); 1236 } 1237 tcpstat.tcps_sndtotal++; 1238 1239 /* 1240 * Data sent (as far as we can tell). 1241 * 1242 * If this advertises a larger window than any other segment, 1243 * then remember the size of the advertised window. 1244 * 1245 * Any pending ACK has now been sent. 1246 */ 1247 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) { 1248 tp->rcv_adv = tp->rcv_nxt + recvwin; 1249 tp->t_flags &= ~TF_RXRESIZED; 1250 } 1251 tp->last_ack_sent = tp->rcv_nxt; 1252 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1253 if (tcp_delack_enabled) 1254 tcp_callout_stop(tp, tp->tt_delack); 1255 if (sendalot) 1256 goto again; 1257 return (0); 1258 } 1259 1260 void 1261 tcp_setpersist(struct tcpcb *tp) 1262 { 1263 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1264 int tt; 1265 1266 if (tp->t_state == TCPS_SYN_SENT || 1267 tp->t_state == TCPS_SYN_RECEIVED) { 1268 panic("tcp_setpersist: not established yet, current %s", 1269 tp->t_state == TCPS_SYN_SENT ? 1270 "SYN_SENT" : "SYN_RECEIVED"); 1271 } 1272 1273 if (tcp_callout_active(tp, tp->tt_rexmt)) 1274 panic("tcp_setpersist: retransmit pending"); 1275 /* 1276 * Start/restart persistance timer. 1277 */ 1278 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1279 TCPTV_PERSMAX); 1280 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist); 1281 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1282 tp->t_rxtshift++; 1283 } 1284 1285 static void 1286 tcp_idle_cwnd_validate(struct tcpcb *tp) 1287 { 1288 u_long initial_cwnd = tcp_initial_window(tp); 1289 u_long min_cwnd; 1290 1291 tcpstat.tcps_sndidle++; 1292 1293 /* According to RFC5681: RW=min(IW,cwnd) */ 1294 min_cwnd = min(tp->snd_cwnd, initial_cwnd); 1295 1296 if (tcp_idle_cwv) { 1297 u_long idle_time, decay_cwnd; 1298 1299 /* 1300 * RFC2861, but only after idle period. 1301 */ 1302 1303 /* 1304 * Before the congestion window is reduced, ssthresh 1305 * is set to the maximum of its current value and 3/4 1306 * cwnd. If the sender then has more data to send 1307 * than the decayed cwnd allows, the TCP will slow- 1308 * start (perform exponential increase) at least 1309 * half-way back up to the old value of cwnd. 1310 */ 1311 tp->snd_ssthresh = max(tp->snd_ssthresh, 1312 (3 * tp->snd_cwnd) / 4); 1313 1314 /* 1315 * Decay the congestion window by half for every RTT 1316 * that the flow remains inactive. 1317 * 1318 * The difference between our implementation and 1319 * RFC2861 is that we don't allow cwnd to go below 1320 * the value allowed by RFC5681 (min_cwnd). 1321 */ 1322 idle_time = ticks - tp->snd_last; 1323 decay_cwnd = tp->snd_cwnd; 1324 while (idle_time >= tp->t_rxtcur && 1325 decay_cwnd > min_cwnd) { 1326 decay_cwnd >>= 1; 1327 idle_time -= tp->t_rxtcur; 1328 } 1329 tp->snd_cwnd = max(decay_cwnd, min_cwnd); 1330 } else { 1331 /* 1332 * Slow-start from scratch to re-determine the send 1333 * congestion window. 1334 */ 1335 tp->snd_cwnd = min_cwnd; 1336 } 1337 1338 /* Restart ABC counting during congestion avoidance */ 1339 tp->snd_wacked = 0; 1340 } 1341 1342 static int 1343 tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen0) 1344 { 1345 struct inpcb * const inp = tp->t_inpcb; 1346 #ifdef INET6 1347 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 1348 #else 1349 const boolean_t isipv6 = FALSE; 1350 #endif 1351 unsigned int ipoptlen, optlen; 1352 u_int hlen; 1353 1354 hlen = sizeof(struct ip) + sizeof(struct tcphdr); 1355 1356 if (isipv6) { 1357 ipoptlen = ip6_optlen(inp); 1358 } else { 1359 if (inp->inp_options) { 1360 ipoptlen = inp->inp_options->m_len - 1361 offsetof(struct ipoption, ipopt_list); 1362 } else { 1363 ipoptlen = 0; 1364 } 1365 } 1366 #ifdef IPSEC 1367 ipoptlen += ipsec_hdrsiz_tcp(tp); 1368 #endif 1369 hlen += ipoptlen; 1370 1371 optlen = 0; 1372 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 1373 (tp->t_flags & TF_RCVD_TSTMP)) 1374 optlen += TCPOLEN_TSTAMP_APPA; 1375 hlen += optlen; 1376 1377 if (tp->t_maxopd <= optlen + ipoptlen) 1378 return EHOSTUNREACH; 1379 1380 *segsz = tp->t_maxopd - optlen - ipoptlen; 1381 *hlen0 = hlen; 1382 return 0; 1383 } 1384