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 ipovly *ipov; 178 struct tcphdr *th; 179 u_char opt[TCP_MAXOLEN]; 180 unsigned int ipoptlen, optlen, hdrlen; 181 int idle; 182 boolean_t sendalot; 183 struct ip6_hdr *ip6; 184 #ifdef INET6 185 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 186 #else 187 const boolean_t isipv6 = FALSE; 188 #endif 189 boolean_t can_tso = FALSE, use_tso; 190 boolean_t report_sack, idle_cwv = FALSE; 191 u_int segsz, tso_hlen; 192 193 KKASSERT(so->so_port == &curthread->td_msgport); 194 195 /* 196 * Determine length of data that should be transmitted, 197 * and flags that will be used. 198 * If there is some data or critical controls (SYN, RST) 199 * to send, then transmit; otherwise, investigate further. 200 */ 201 202 /* 203 * If we have been idle for a while, the send congestion window 204 * could be no longer representative of the current state of the 205 * link; need to validate congestion window. However, we should 206 * not perform congestion window validation here, since we could 207 * be asked to send pure ACK. 208 */ 209 if (tp->snd_max == tp->snd_una && 210 (ticks - tp->snd_last) >= tp->t_rxtcur && tcp_idle_restart) 211 idle_cwv = TRUE; 212 213 /* 214 * Calculate whether the transmit stream was previously idle 215 * and adjust TF_LASTIDLE for the next time. 216 */ 217 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 218 if (idle && (tp->t_flags & TF_MORETOCOME)) 219 tp->t_flags |= TF_LASTIDLE; 220 else 221 tp->t_flags &= ~TF_LASTIDLE; 222 223 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 224 !IN_FASTRECOVERY(tp)) 225 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); 226 227 /* 228 * Find out whether TSO could be used or not 229 * 230 * For TSO capable devices, the following assumptions apply to 231 * the processing of TCP flags: 232 * - If FIN is set on the large TCP segment, the device must set 233 * FIN on the last segment that it creates from the large TCP 234 * segment. 235 * - If PUSH is set on the large TCP segment, the device must set 236 * PUSH on the last segment that it creates from the large TCP 237 * segment. 238 */ 239 #if !defined(IPSEC) && !defined(FAST_IPSEC) 240 if (tcp_do_tso 241 #ifdef TCP_SIGNATURE 242 && (tp->t_flags & TF_SIGNATURE) == 0 243 #endif 244 ) { 245 if (!isipv6) { 246 struct rtentry *rt = inp->inp_route.ro_rt; 247 248 if (rt != NULL && (rt->rt_flags & RTF_UP) && 249 (rt->rt_ifp->if_hwassist & CSUM_TSO)) 250 can_tso = TRUE; 251 } 252 } 253 #endif /* !IPSEC && !FAST_IPSEC */ 254 255 again: 256 m = NULL; 257 ip = NULL; 258 ipov = NULL; 259 th = NULL; 260 ip6 = NULL; 261 262 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 263 TF_SACK_PERMITTED && 264 (!TAILQ_EMPTY(&tp->t_segq) || 265 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 266 report_sack = TRUE; 267 else 268 report_sack = FALSE; 269 270 /* Make use of SACK information when slow-starting after a RTO. */ 271 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 272 !IN_FASTRECOVERY(tp)) { 273 tcp_seq old_snd_nxt = tp->snd_nxt; 274 275 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 276 nsacked += tp->snd_nxt - old_snd_nxt; 277 } 278 279 sendalot = FALSE; 280 off = tp->snd_nxt - tp->snd_una; 281 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 282 sendwin = min(sendwin, tp->snd_bwnd); 283 284 flags = tcp_outflags[tp->t_state]; 285 /* 286 * Get standard flags, and add SYN or FIN if requested by 'hidden' 287 * state flags. 288 */ 289 if (tp->t_flags & TF_NEEDFIN) 290 flags |= TH_FIN; 291 if (tp->t_flags & TF_NEEDSYN) 292 flags |= TH_SYN; 293 294 /* 295 * If in persist timeout with window of 0, send 1 byte. 296 * Otherwise, if window is small but nonzero 297 * and timer expired, we will send what we can 298 * and go to transmit state. 299 */ 300 if (tp->t_flags & TF_FORCE) { 301 if (sendwin == 0) { 302 /* 303 * If we still have some data to send, then 304 * clear the FIN bit. Usually this would 305 * happen below when it realizes that we 306 * aren't sending all the data. However, 307 * if we have exactly 1 byte of unsent data, 308 * then it won't clear the FIN bit below, 309 * and if we are in persist state, we wind 310 * up sending the packet without recording 311 * that we sent the FIN bit. 312 * 313 * We can't just blindly clear the FIN bit, 314 * because if we don't have any more data 315 * to send then the probe will be the FIN 316 * itself. 317 */ 318 if (off < so->so_snd.ssb_cc) 319 flags &= ~TH_FIN; 320 sendwin = 1; 321 } else { 322 tcp_callout_stop(tp, tp->tt_persist); 323 tp->t_rxtshift = 0; 324 } 325 } 326 327 /* 328 * If snd_nxt == snd_max and we have transmitted a FIN, the 329 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in 330 * a negative length. This can also occur when TCP opens up 331 * its congestion window while receiving additional duplicate 332 * acks after fast-retransmit because TCP will reset snd_nxt 333 * to snd_max after the fast-retransmit. 334 * 335 * A negative length can also occur when we are in the 336 * TCPS_SYN_RECEIVED state due to a simultanious connect where 337 * our SYN has not been acked yet. 338 * 339 * In the normal retransmit-FIN-only case, however, snd_nxt will 340 * be set to snd_una, the offset will be 0, and the length may 341 * wind up 0. 342 */ 343 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; 344 345 /* 346 * Lop off SYN bit if it has already been sent. However, if this 347 * is SYN-SENT state and if segment contains data, suppress sending 348 * segment (sending the segment would be an option if we still 349 * did TAO and the remote host supported it). 350 */ 351 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 352 flags &= ~TH_SYN; 353 off--, len++; 354 if (len > 0 && tp->t_state == TCPS_SYN_SENT) { 355 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 356 return 0; 357 } 358 } 359 360 /* 361 * Be careful not to send data and/or FIN on SYN segments. 362 * This measure is needed to prevent interoperability problems 363 * with not fully conformant TCP implementations. 364 */ 365 if (flags & TH_SYN) { 366 len = 0; 367 flags &= ~TH_FIN; 368 } 369 370 if (len < 0) { 371 /* 372 * A negative len can occur if our FIN has been sent but not 373 * acked, or if we are in a simultanious connect in the 374 * TCPS_SYN_RECEIVED state with our SYN sent but not yet 375 * acked. 376 * 377 * If our window has contracted to 0 in the FIN case 378 * (which can only occur if we have NOT been called to 379 * retransmit as per code a few paragraphs up) then we 380 * want to shift the retransmit timer over to the 381 * persist timer. 382 * 383 * However, if we are in the TCPS_SYN_RECEIVED state 384 * (the SYN case) we will be in a simultanious connect and 385 * the window may be zero degeneratively. In this case we 386 * do not want to shift to the persist timer after the SYN 387 * or the SYN+ACK transmission. 388 */ 389 len = 0; 390 if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) { 391 tcp_callout_stop(tp, tp->tt_rexmt); 392 tp->t_rxtshift = 0; 393 tp->snd_nxt = tp->snd_una; 394 if (!tcp_callout_active(tp, tp->tt_persist)) 395 tcp_setpersist(tp); 396 } 397 } 398 399 KASSERT(len >= 0, ("%s: len < 0", __func__)); 400 /* 401 * Automatic sizing of send socket buffer. Often the send buffer 402 * size is not optimally adjusted to the actual network conditions 403 * at hand (delay bandwidth product). Setting the buffer size too 404 * small limits throughput on links with high bandwidth and high 405 * delay (eg. trans-continental/oceanic links). Setting the 406 * buffer size too big consumes too much real kernel memory, 407 * especially with many connections on busy servers. 408 * 409 * The criteria to step up the send buffer one notch are: 410 * 1. receive window of remote host is larger than send buffer 411 * (with a fudge factor of 5/4th); 412 * 2. send buffer is filled to 7/8th with data (so we actually 413 * have data to make use of it); 414 * 3. send buffer fill has not hit maximal automatic size; 415 * 4. our send window (slow start and cogestion controlled) is 416 * larger than sent but unacknowledged data in send buffer. 417 * 418 * The remote host receive window scaling factor may limit the 419 * growing of the send buffer before it reaches its allowed 420 * maximum. 421 * 422 * It scales directly with slow start or congestion window 423 * and does at most one step per received ACK. This fast 424 * scaling has the drawback of growing the send buffer beyond 425 * what is strictly necessary to make full use of a given 426 * delay*bandwith product. However testing has shown this not 427 * to be much of an problem. At worst we are trading wasting 428 * of available bandwith (the non-use of it) for wasting some 429 * socket buffer memory. 430 * 431 * TODO: Shrink send buffer during idle periods together 432 * with congestion window. Requires another timer. Has to 433 * wait for upcoming tcp timer rewrite. 434 */ 435 if (tcp_do_autosndbuf && so->so_snd.ssb_flags & SSB_AUTOSIZE) { 436 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.ssb_hiwat && 437 so->so_snd.ssb_cc >= (so->so_snd.ssb_hiwat / 8 * 7) && 438 so->so_snd.ssb_cc < tcp_autosndbuf_max && 439 sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) { 440 u_long newsize; 441 442 newsize = ulmin(so->so_snd.ssb_hiwat + 443 tcp_autosndbuf_inc, 444 tcp_autosndbuf_max); 445 if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) 446 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 447 if (newsize >= (TCP_MAXWIN << tp->snd_scale)) 448 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 449 } 450 } 451 452 /* 453 * Don't use TSO, if: 454 * - Congestion window needs validation 455 * - There are SACK blocks to report 456 * - RST or SYN flags is set 457 * - URG will be set 458 * 459 * XXX 460 * Checking for SYN|RST looks overkill, just to be safe than sorry 461 */ 462 use_tso = can_tso; 463 if (report_sack || idle_cwv || (flags & (TH_RST | TH_SYN))) 464 use_tso = FALSE; 465 if (use_tso) { 466 tcp_seq ugr_nxt = tp->snd_nxt; 467 468 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && 469 tp->snd_nxt == tp->snd_max) 470 --ugr_nxt; 471 472 if (SEQ_GT(tp->snd_up, ugr_nxt)) 473 use_tso = FALSE; 474 } 475 476 if (use_tso) { 477 /* 478 * Find out segment size and header length for TSO 479 */ 480 error = tcp_tso_getsize(tp, &segsz, &tso_hlen); 481 if (error) 482 use_tso = FALSE; 483 } 484 if (!use_tso) { 485 segsz = tp->t_maxseg; 486 tso_hlen = 0; /* not used */ 487 } 488 489 /* 490 * Truncate to the maximum segment length if not TSO, and ensure that 491 * FIN is removed if the length no longer contains the last data byte. 492 */ 493 if (len > segsz) { 494 if (!use_tso) { 495 len = segsz; 496 } else { 497 /* 498 * Truncate TSO transfers to (IP_MAXPACKET - iphlen - 499 * thoff), and make sure that we send equal size 500 * transfers down the stack (rather than big-small- 501 * big-small-...). 502 */ 503 len = (min(len, (IP_MAXPACKET - tso_hlen)) / segsz) * 504 segsz; 505 if (len <= segsz) 506 use_tso = FALSE; 507 } 508 sendalot = TRUE; 509 } else { 510 use_tso = FALSE; 511 } 512 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) 513 flags &= ~TH_FIN; 514 515 recvwin = ssb_space(&so->so_rcv); 516 517 /* 518 * Sender silly window avoidance. We transmit under the following 519 * conditions when len is non-zero: 520 * 521 * - We have a full segment 522 * - This is the last buffer in a write()/send() and we are 523 * either idle or running NODELAY 524 * - we've timed out (e.g. persist timer) 525 * - we have more then 1/2 the maximum send window's worth of 526 * data (receiver may be limiting the window size) 527 * - we need to retransmit 528 */ 529 if (len) { 530 if (len >= segsz) 531 goto send; 532 /* 533 * NOTE! on localhost connections an 'ack' from the remote 534 * end may occur synchronously with the output and cause 535 * us to flush a buffer queued with moretocome. XXX 536 * 537 * note: the len + off check is almost certainly unnecessary. 538 */ 539 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 540 (idle || (tp->t_flags & TF_NODELAY)) && 541 len + off >= so->so_snd.ssb_cc && 542 !(tp->t_flags & TF_NOPUSH)) { 543 goto send; 544 } 545 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 546 goto send; 547 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 548 goto send; 549 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 550 goto send; 551 if (tp->t_flags & TF_XMITNOW) 552 goto send; 553 } 554 555 /* 556 * Compare available window to amount of window 557 * known to peer (as advertised window less 558 * next expected input). If the difference is at least two 559 * max size segments, or at least 50% of the maximum possible 560 * window, then want to send a window update to peer. 561 */ 562 if (recvwin > 0) { 563 /* 564 * "adv" is the amount we can increase the window, 565 * taking into account that we are limited by 566 * TCP_MAXWIN << tp->rcv_scale. 567 */ 568 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 569 (tp->rcv_adv - tp->rcv_nxt); 570 long hiwat; 571 572 /* 573 * This ack case typically occurs when the user has drained 574 * the TCP socket buffer sufficiently to warrent an ack 575 * containing a 'pure window update'... that is, an ack that 576 * ONLY updates the tcp window. 577 * 578 * It is unclear why we would need to do a pure window update 579 * past 2 segments if we are going to do one at 1/2 the high 580 * water mark anyway, especially since under normal conditions 581 * the user program will drain the socket buffer quickly. 582 * The 2-segment pure window update will often add a large 583 * number of extra, unnecessary acks to the stream. 584 * 585 * avoid_pure_win_update now defaults to 1. 586 */ 587 if (avoid_pure_win_update == 0 || 588 (tp->t_flags & TF_RXRESIZED)) { 589 if (adv >= (long) (2 * segsz)) { 590 goto send; 591 } 592 } 593 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); 594 if (hiwat > (long)so->so_rcv.ssb_hiwat) 595 hiwat = (long)so->so_rcv.ssb_hiwat; 596 if (adv >= hiwat / 2) 597 goto send; 598 } 599 600 /* 601 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 602 * is also a catch-all for the retransmit timer timeout case. 603 */ 604 if (tp->t_flags & TF_ACKNOW) 605 goto send; 606 if ((flags & TH_RST) || 607 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 608 goto send; 609 if (SEQ_GT(tp->snd_up, tp->snd_una)) 610 goto send; 611 /* 612 * If our state indicates that FIN should be sent 613 * and we have not yet done so, then we need to send. 614 */ 615 if ((flags & TH_FIN) && 616 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 617 goto send; 618 619 /* 620 * TCP window updates are not reliable, rather a polling protocol 621 * using ``persist'' packets is used to insure receipt of window 622 * updates. The three ``states'' for the output side are: 623 * idle not doing retransmits or persists 624 * persisting to move a small or zero window 625 * (re)transmitting and thereby not persisting 626 * 627 * tcp_callout_active(tp, tp->tt_persist) 628 * is true when we are in persist state. 629 * The TF_FORCE flag in tp->t_flags 630 * is set when we are called to send a persist packet. 631 * tcp_callout_active(tp, tp->tt_rexmt) 632 * is set when we are retransmitting 633 * The output side is idle when both timers are zero. 634 * 635 * If send window is too small, there is data to transmit, and no 636 * retransmit or persist is pending, then go to persist state. 637 * 638 * If nothing happens soon, send when timer expires: 639 * if window is nonzero, transmit what we can, otherwise force out 640 * a byte. 641 * 642 * Don't try to set the persist state if we are in TCPS_SYN_RECEIVED 643 * with data pending. This situation can occur during a 644 * simultanious connect. 645 */ 646 if (so->so_snd.ssb_cc > 0 && 647 tp->t_state != TCPS_SYN_RECEIVED && 648 !tcp_callout_active(tp, tp->tt_rexmt) && 649 !tcp_callout_active(tp, tp->tt_persist)) { 650 tp->t_rxtshift = 0; 651 tcp_setpersist(tp); 652 } 653 654 /* 655 * No reason to send a segment, just return. 656 */ 657 tp->t_flags &= ~TF_XMITNOW; 658 return (0); 659 660 send: 661 /* 662 * Before ESTABLISHED, force sending of initial options 663 * unless TCP set not to do any options. 664 * NOTE: we assume that the IP/TCP header plus TCP options 665 * always fit in a single mbuf, leaving room for a maximum 666 * link header, i.e. 667 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 668 */ 669 optlen = 0; 670 if (isipv6) 671 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 672 else 673 hdrlen = sizeof(struct tcpiphdr); 674 if (flags & TH_SYN) { 675 tp->snd_nxt = tp->iss; 676 if (!(tp->t_flags & TF_NOOPT)) { 677 u_short mss; 678 679 opt[0] = TCPOPT_MAXSEG; 680 opt[1] = TCPOLEN_MAXSEG; 681 mss = htons((u_short) tcp_mssopt(tp)); 682 memcpy(opt + 2, &mss, sizeof mss); 683 optlen = TCPOLEN_MAXSEG; 684 685 if ((tp->t_flags & TF_REQ_SCALE) && 686 (!(flags & TH_ACK) || 687 (tp->t_flags & TF_RCVD_SCALE))) { 688 *((u_int32_t *)(opt + optlen)) = htonl( 689 TCPOPT_NOP << 24 | 690 TCPOPT_WINDOW << 16 | 691 TCPOLEN_WINDOW << 8 | 692 tp->request_r_scale); 693 optlen += 4; 694 } 695 696 if ((tcp_do_sack && !(flags & TH_ACK)) || 697 tp->t_flags & TF_SACK_PERMITTED) { 698 uint32_t *lp = (uint32_t *)(opt + optlen); 699 700 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 701 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 702 } 703 } 704 } 705 706 /* 707 * Send a timestamp and echo-reply if this is a SYN and our side 708 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 709 * and our peer have sent timestamps in our SYN's. 710 */ 711 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 712 !(flags & TH_RST) && 713 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 714 u_int32_t *lp = (u_int32_t *)(opt + optlen); 715 716 /* Form timestamp option as shown in appendix A of RFC 1323. */ 717 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 718 *lp++ = htonl(ticks); 719 *lp = htonl(tp->ts_recent); 720 optlen += TCPOLEN_TSTAMP_APPA; 721 } 722 723 /* Set receive buffer autosizing timestamp. */ 724 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) 725 tp->rfbuf_ts = ticks; 726 727 /* 728 * If this is a SACK connection and we have a block to report, 729 * fill in the SACK blocks in the TCP options. 730 */ 731 if (report_sack) 732 tcp_sack_fill_report(tp, opt, &optlen); 733 734 #ifdef TCP_SIGNATURE 735 if (tp->t_flags & TF_SIGNATURE) { 736 int i; 737 u_char *bp; 738 /* 739 * Initialize TCP-MD5 option (RFC2385) 740 */ 741 bp = (u_char *)opt + optlen; 742 *bp++ = TCPOPT_SIGNATURE; 743 *bp++ = TCPOLEN_SIGNATURE; 744 sigoff = optlen + 2; 745 for (i = 0; i < TCP_SIGLEN; i++) 746 *bp++ = 0; 747 optlen += TCPOLEN_SIGNATURE; 748 /* 749 * Terminate options list and maintain 32-bit alignment. 750 */ 751 *bp++ = TCPOPT_NOP; 752 *bp++ = TCPOPT_EOL; 753 optlen += 2; 754 } 755 #endif /* TCP_SIGNATURE */ 756 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 757 hdrlen += optlen; 758 759 if (isipv6) { 760 ipoptlen = ip6_optlen(inp); 761 } else { 762 if (inp->inp_options) { 763 ipoptlen = inp->inp_options->m_len - 764 offsetof(struct ipoption, ipopt_list); 765 } else { 766 ipoptlen = 0; 767 } 768 } 769 #ifdef IPSEC 770 ipoptlen += ipsec_hdrsiz_tcp(tp); 771 #endif 772 773 if (use_tso) { 774 /* TSO segment length must be multiple of segment size */ 775 KASSERT(len >= (2 * segsz) && (len % segsz == 0), 776 ("invalid TSO len %ld, segsz %u", len, segsz)); 777 } else { 778 KASSERT(len <= segsz, 779 ("invalid len %ld, segsz %u", len, segsz)); 780 781 /* 782 * Adjust data length if insertion of options will bump 783 * the packet length beyond the t_maxopd length. Clear 784 * FIN to prevent premature closure since there is still 785 * more data to send after this (now truncated) packet. 786 * 787 * If just the options do not fit we are in a no-win 788 * situation and we treat it as an unreachable host. 789 */ 790 if (len + optlen + ipoptlen > tp->t_maxopd) { 791 if (tp->t_maxopd <= optlen + ipoptlen) { 792 static time_t last_optlen_report; 793 794 if (last_optlen_report != time_second) { 795 last_optlen_report = time_second; 796 kprintf("tcpcb %p: MSS (%d) too " 797 "small to hold options!\n", 798 tp, tp->t_maxopd); 799 } 800 error = EHOSTUNREACH; 801 goto out; 802 } else { 803 flags &= ~TH_FIN; 804 len = tp->t_maxopd - optlen - ipoptlen; 805 sendalot = TRUE; 806 } 807 } 808 } 809 810 #ifdef INET6 811 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 812 #else 813 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 814 #endif 815 816 /* 817 * Grab a header mbuf, attaching a copy of data to 818 * be transmitted, and initialize the header from 819 * the template for sends on this connection. 820 */ 821 if (len) { 822 if ((tp->t_flags & TF_FORCE) && len == 1) 823 tcpstat.tcps_sndprobe++; 824 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 825 if (tp->snd_nxt == tp->snd_una) 826 tp->snd_max_rexmt = tp->snd_max; 827 if (nsacked) { 828 tcpstat.tcps_sndsackrtopack++; 829 tcpstat.tcps_sndsackrtobyte += len; 830 } 831 tcpstat.tcps_sndrexmitpack++; 832 tcpstat.tcps_sndrexmitbyte += len; 833 } else { 834 tcpstat.tcps_sndpack++; 835 tcpstat.tcps_sndbyte += len; 836 } 837 if (idle_cwv) { 838 idle_cwv = FALSE; 839 tcp_idle_cwnd_validate(tp); 840 } 841 /* Update last send time after CWV */ 842 tp->snd_last = ticks; 843 #ifdef notyet 844 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, 845 max_linkhdr + hdrlen)) == NULL) { 846 error = ENOBUFS; 847 goto after_th; 848 } 849 /* 850 * m_copypack left space for our hdr; use it. 851 */ 852 m->m_len += hdrlen; 853 m->m_data -= hdrlen; 854 #else 855 #ifndef INET6 856 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 857 #else 858 m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER, 859 M_PKTHDR, NULL); 860 #endif 861 if (m == NULL) { 862 error = ENOBUFS; 863 goto after_th; 864 } 865 m->m_data += max_linkhdr; 866 m->m_len = hdrlen; 867 if (len <= MHLEN - hdrlen - max_linkhdr) { 868 m_copydata(so->so_snd.ssb_mb, off, (int) len, 869 mtod(m, caddr_t) + hdrlen); 870 m->m_len += len; 871 } else { 872 m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len); 873 if (m->m_next == NULL) { 874 m_free(m); 875 m = NULL; 876 error = ENOBUFS; 877 goto after_th; 878 } 879 } 880 #endif 881 /* 882 * If we're sending everything we've got, set PUSH. 883 * (This will keep happy those implementations which only 884 * give data to the user when a buffer fills or 885 * a PUSH comes in.) 886 */ 887 if (off + len == so->so_snd.ssb_cc) 888 flags |= TH_PUSH; 889 } else { 890 if (tp->t_flags & TF_ACKNOW) 891 tcpstat.tcps_sndacks++; 892 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 893 tcpstat.tcps_sndctrl++; 894 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 895 tcpstat.tcps_sndurg++; 896 else 897 tcpstat.tcps_sndwinup++; 898 899 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 900 if (m == NULL) { 901 error = ENOBUFS; 902 goto after_th; 903 } 904 if (isipv6 && 905 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 906 MH_ALIGN(m, hdrlen); 907 else 908 m->m_data += max_linkhdr; 909 m->m_len = hdrlen; 910 } 911 m->m_pkthdr.rcvif = NULL; 912 if (isipv6) { 913 ip6 = mtod(m, struct ip6_hdr *); 914 th = (struct tcphdr *)(ip6 + 1); 915 tcp_fillheaders(tp, ip6, th, use_tso); 916 } else { 917 ip = mtod(m, struct ip *); 918 ipov = (struct ipovly *)ip; 919 th = (struct tcphdr *)(ip + 1); 920 /* this picks up the pseudo header (w/o the length) */ 921 tcp_fillheaders(tp, ip, th, use_tso); 922 } 923 after_th: 924 /* 925 * Fill in fields, remembering maximum advertised 926 * window for use in delaying messages about window sizes. 927 * If resending a FIN, be sure not to use a new sequence number. 928 */ 929 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 930 tp->snd_nxt == tp->snd_max) 931 tp->snd_nxt--; 932 933 if (th != NULL) { 934 /* 935 * If we are doing retransmissions, then snd_nxt will 936 * not reflect the first unsent octet. For ACK only 937 * packets, we do not want the sequence number of the 938 * retransmitted packet, we want the sequence number 939 * of the next unsent octet. So, if there is no data 940 * (and no SYN or FIN), use snd_max instead of snd_nxt 941 * when filling in ti_seq. But if we are in persist 942 * state, snd_max might reflect one byte beyond the 943 * right edge of the window, so use snd_nxt in that 944 * case, since we know we aren't doing a retransmission. 945 * (retransmit and persist are mutually exclusive...) 946 */ 947 if (len || (flags & (TH_SYN|TH_FIN)) || 948 tcp_callout_active(tp, tp->tt_persist)) 949 th->th_seq = htonl(tp->snd_nxt); 950 else 951 th->th_seq = htonl(tp->snd_max); 952 th->th_ack = htonl(tp->rcv_nxt); 953 if (optlen) { 954 bcopy(opt, th + 1, optlen); 955 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 956 } 957 th->th_flags = flags; 958 } 959 960 /* 961 * Calculate receive window. Don't shrink window, but avoid 962 * silly window syndrome by sending a 0 window if the actual 963 * window is less then one segment. 964 */ 965 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && 966 recvwin < (long)segsz) 967 recvwin = 0; 968 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt)) 969 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt); 970 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 971 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 972 973 /* 974 * Adjust the RXWIN0SENT flag - indicate that we have advertised 975 * a 0 window. This may cause the remote transmitter to stall. This 976 * flag tells soreceive() to disable delayed acknowledgements when 977 * draining the buffer. This can occur if the receiver is attempting 978 * to read more data then can be buffered prior to transmitting on 979 * the connection. 980 */ 981 if (recvwin == 0) 982 tp->t_flags |= TF_RXWIN0SENT; 983 else 984 tp->t_flags &= ~TF_RXWIN0SENT; 985 986 if (th != NULL) 987 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 988 989 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 990 KASSERT(!use_tso, ("URG with TSO")); 991 if (th != NULL) { 992 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 993 th->th_flags |= TH_URG; 994 } 995 } else { 996 /* 997 * If no urgent pointer to send, then we pull 998 * the urgent pointer to the left edge of the send window 999 * so that it doesn't drift into the send window on sequence 1000 * number wraparound. 1001 */ 1002 tp->snd_up = tp->snd_una; /* drag it along */ 1003 } 1004 1005 if (th != NULL) { 1006 #ifdef TCP_SIGNATURE 1007 if (tp->t_flags & TF_SIGNATURE) { 1008 tcpsignature_compute(m, len, optlen, 1009 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1010 } 1011 #endif /* TCP_SIGNATURE */ 1012 1013 /* 1014 * Put TCP length in extended header, and then 1015 * checksum extended header and data. 1016 */ 1017 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1018 if (isipv6) { 1019 /* 1020 * ip6_plen is not need to be filled now, and will be 1021 * filled in ip6_output(). 1022 */ 1023 th->th_sum = in6_cksum(m, IPPROTO_TCP, 1024 sizeof(struct ip6_hdr), 1025 sizeof(struct tcphdr) + optlen + len); 1026 } else { 1027 m->m_pkthdr.csum_thlen = sizeof(struct tcphdr) + optlen; 1028 if (use_tso) { 1029 m->m_pkthdr.csum_flags = CSUM_TSO; 1030 m->m_pkthdr.tso_segsz = segsz; 1031 } else { 1032 m->m_pkthdr.csum_flags = CSUM_TCP; 1033 m->m_pkthdr.csum_data = 1034 offsetof(struct tcphdr, th_sum); 1035 if (len + optlen) { 1036 th->th_sum = in_addword(th->th_sum, 1037 htons((u_short)(optlen + len))); 1038 } 1039 } 1040 1041 /* 1042 * IP version must be set here for ipv4/ipv6 checking 1043 * later 1044 */ 1045 KASSERT(ip->ip_v == IPVERSION, 1046 ("%s: IP version incorrect: %d", 1047 __func__, ip->ip_v)); 1048 } 1049 } 1050 1051 /* 1052 * In transmit state, time the transmission and arrange for 1053 * the retransmit. In persist state, just set snd_max. 1054 */ 1055 if (!(tp->t_flags & TF_FORCE) || 1056 !tcp_callout_active(tp, tp->tt_persist)) { 1057 tcp_seq startseq = tp->snd_nxt; 1058 1059 /* 1060 * Advance snd_nxt over sequence space of this segment. 1061 */ 1062 if (flags & (TH_SYN | TH_FIN)) { 1063 if (flags & TH_SYN) 1064 tp->snd_nxt++; 1065 if (flags & TH_FIN) { 1066 tp->snd_nxt++; 1067 tp->t_flags |= TF_SENTFIN; 1068 } 1069 } 1070 tp->snd_nxt += len; 1071 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1072 tp->snd_max = tp->snd_nxt; 1073 /* 1074 * Time this transmission if not a retransmission and 1075 * not currently timing anything. 1076 */ 1077 if (tp->t_rtttime == 0) { 1078 tp->t_rtttime = ticks; 1079 tp->t_rtseq = startseq; 1080 tcpstat.tcps_segstimed++; 1081 } 1082 } 1083 1084 /* 1085 * Set retransmit timer if not currently set, 1086 * and not doing a pure ack or a keep-alive probe. 1087 * Initial value for retransmit timer is smoothed 1088 * round-trip time + 2 * round-trip time variance. 1089 * Initialize shift counter which is used for backoff 1090 * of retransmit time. 1091 */ 1092 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1093 tp->snd_nxt != tp->snd_una) { 1094 if (tcp_callout_active(tp, tp->tt_persist)) { 1095 tcp_callout_stop(tp, tp->tt_persist); 1096 tp->t_rxtshift = 0; 1097 } 1098 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 1099 tcp_timer_rexmt); 1100 } 1101 } else { 1102 /* 1103 * Persist case, update snd_max but since we are in 1104 * persist mode (no window) we do not update snd_nxt. 1105 */ 1106 int xlen = len; 1107 if (flags & TH_SYN) 1108 panic("tcp_output: persist timer to send SYN"); 1109 if (flags & TH_FIN) { 1110 ++xlen; 1111 tp->t_flags |= TF_SENTFIN; 1112 } 1113 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1114 tp->snd_max = tp->snd_nxt + xlen; 1115 } 1116 1117 if (th != NULL) { 1118 #ifdef TCPDEBUG 1119 /* Trace. */ 1120 if (so->so_options & SO_DEBUG) { 1121 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1122 mtod(m, void *), th, 0); 1123 } 1124 #endif 1125 1126 /* 1127 * Fill in IP length and desired time to live and 1128 * send to IP level. There should be a better way 1129 * to handle ttl and tos; we could keep them in 1130 * the template, but need a way to checksum without them. 1131 */ 1132 /* 1133 * m->m_pkthdr.len should have been set before cksum 1134 * calcuration, because in6_cksum() need it. 1135 */ 1136 if (isipv6) { 1137 /* 1138 * we separately set hoplimit for every segment, 1139 * since the user might want to change the value 1140 * via setsockopt. Also, desired default hop 1141 * limit might be changed via Neighbor Discovery. 1142 */ 1143 ip6->ip6_hlim = in6_selecthlim(inp, 1144 (inp->in6p_route.ro_rt ? 1145 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1146 1147 /* TODO: IPv6 IP6TOS_ECT bit on */ 1148 error = ip6_output(m, inp->in6p_outputopts, 1149 &inp->in6p_route, (so->so_options & SO_DONTROUTE), 1150 NULL, NULL, inp); 1151 } else { 1152 struct rtentry *rt; 1153 ip->ip_len = m->m_pkthdr.len; 1154 #ifdef INET6 1155 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1156 ip->ip_ttl = in6_selecthlim(inp, 1157 (inp->in6p_route.ro_rt ? 1158 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1159 else 1160 #endif 1161 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1162 1163 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1164 /* 1165 * See if we should do MTU discovery. 1166 * We do it only if the following are true: 1167 * 1) we have a valid route to the destination 1168 * 2) the MTU is not locked (if it is, 1169 * then discovery has been disabled) 1170 */ 1171 if (path_mtu_discovery && 1172 (rt = inp->inp_route.ro_rt) && 1173 (rt->rt_flags & RTF_UP) && 1174 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 1175 ip->ip_off |= IP_DF; 1176 1177 error = ip_output(m, inp->inp_options, &inp->inp_route, 1178 (so->so_options & SO_DONTROUTE) | 1179 IP_DEBUGROUTE, NULL, inp); 1180 } 1181 } else { 1182 KASSERT(error != 0, ("no error, but th not set")); 1183 } 1184 if (error) { 1185 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1186 1187 /* 1188 * We know that the packet was lost, so back out the 1189 * sequence number advance, if any. 1190 */ 1191 if (!(tp->t_flags & TF_FORCE) || 1192 !tcp_callout_active(tp, tp->tt_persist)) { 1193 /* 1194 * No need to check for TH_FIN here because 1195 * the TF_SENTFIN flag handles that case. 1196 */ 1197 if (!(flags & TH_SYN)) 1198 tp->snd_nxt -= len; 1199 } 1200 1201 out: 1202 if (error == ENOBUFS) { 1203 /* 1204 * If we can't send, make sure there is something 1205 * to get us going again later. 1206 * 1207 * The persist timer isn't necessarily allowed in all 1208 * states, use the rexmt timer. 1209 */ 1210 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1211 !tcp_callout_active(tp, tp->tt_persist)) { 1212 tcp_callout_reset(tp, tp->tt_rexmt, 1213 tp->t_rxtcur, 1214 tcp_timer_rexmt); 1215 #if 0 1216 tp->t_rxtshift = 0; 1217 tcp_setpersist(tp); 1218 #endif 1219 } 1220 tcp_quench(inp, 0); 1221 return (0); 1222 } 1223 if (error == EMSGSIZE) { 1224 /* 1225 * ip_output() will have already fixed the route 1226 * for us. tcp_mtudisc() will, as its last action, 1227 * initiate retransmission, so it is important to 1228 * not do so here. 1229 */ 1230 tcp_mtudisc(inp, 0); 1231 return 0; 1232 } 1233 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1234 TCPS_HAVERCVDSYN(tp->t_state)) { 1235 tp->t_softerror = error; 1236 return (0); 1237 } 1238 return (error); 1239 } 1240 tcpstat.tcps_sndtotal++; 1241 1242 /* 1243 * Data sent (as far as we can tell). 1244 * 1245 * If this advertises a larger window than any other segment, 1246 * then remember the size of the advertised window. 1247 * 1248 * Any pending ACK has now been sent. 1249 */ 1250 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) { 1251 tp->rcv_adv = tp->rcv_nxt + recvwin; 1252 tp->t_flags &= ~TF_RXRESIZED; 1253 } 1254 tp->last_ack_sent = tp->rcv_nxt; 1255 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1256 if (tcp_delack_enabled) 1257 tcp_callout_stop(tp, tp->tt_delack); 1258 if (sendalot) 1259 goto again; 1260 return (0); 1261 } 1262 1263 void 1264 tcp_setpersist(struct tcpcb *tp) 1265 { 1266 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1267 int tt; 1268 1269 if (tp->t_state == TCPS_SYN_SENT || 1270 tp->t_state == TCPS_SYN_RECEIVED) { 1271 panic("tcp_setpersist: not established yet, current %s", 1272 tp->t_state == TCPS_SYN_SENT ? 1273 "SYN_SENT" : "SYN_RECEIVED"); 1274 } 1275 1276 if (tcp_callout_active(tp, tp->tt_rexmt)) 1277 panic("tcp_setpersist: retransmit pending"); 1278 /* 1279 * Start/restart persistance timer. 1280 */ 1281 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1282 TCPTV_PERSMAX); 1283 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist); 1284 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1285 tp->t_rxtshift++; 1286 } 1287 1288 static void 1289 tcp_idle_cwnd_validate(struct tcpcb *tp) 1290 { 1291 u_long initial_cwnd = tcp_initial_window(tp); 1292 u_long min_cwnd; 1293 1294 tcpstat.tcps_sndidle++; 1295 1296 /* According to RFC5681: RW=min(IW,cwnd) */ 1297 min_cwnd = min(tp->snd_cwnd, initial_cwnd); 1298 1299 if (tcp_idle_cwv) { 1300 u_long idle_time, decay_cwnd; 1301 1302 /* 1303 * RFC2861, but only after idle period. 1304 */ 1305 1306 /* 1307 * Before the congestion window is reduced, ssthresh 1308 * is set to the maximum of its current value and 3/4 1309 * cwnd. If the sender then has more data to send 1310 * than the decayed cwnd allows, the TCP will slow- 1311 * start (perform exponential increase) at least 1312 * half-way back up to the old value of cwnd. 1313 */ 1314 tp->snd_ssthresh = max(tp->snd_ssthresh, 1315 (3 * tp->snd_cwnd) / 4); 1316 1317 /* 1318 * Decay the congestion window by half for every RTT 1319 * that the flow remains inactive. 1320 * 1321 * The difference between our implementation and 1322 * RFC2861 is that we don't allow cwnd to go below 1323 * the value allowed by RFC5681 (min_cwnd). 1324 */ 1325 idle_time = ticks - tp->snd_last; 1326 decay_cwnd = tp->snd_cwnd; 1327 while (idle_time >= tp->t_rxtcur && 1328 decay_cwnd > min_cwnd) { 1329 decay_cwnd >>= 1; 1330 idle_time -= tp->t_rxtcur; 1331 } 1332 tp->snd_cwnd = max(decay_cwnd, min_cwnd); 1333 } else { 1334 /* 1335 * Slow-start from scratch to re-determine the send 1336 * congestion window. 1337 */ 1338 tp->snd_cwnd = min_cwnd; 1339 } 1340 1341 /* Restart ABC counting during congestion avoidance */ 1342 tp->snd_wacked = 0; 1343 } 1344 1345 static int 1346 tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen0) 1347 { 1348 struct inpcb * const inp = tp->t_inpcb; 1349 #ifdef INET6 1350 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 1351 #else 1352 const boolean_t isipv6 = FALSE; 1353 #endif 1354 unsigned int ipoptlen, optlen; 1355 u_int hlen; 1356 1357 hlen = sizeof(struct ip) + sizeof(struct tcphdr); 1358 1359 if (isipv6) { 1360 ipoptlen = ip6_optlen(inp); 1361 } else { 1362 if (inp->inp_options) { 1363 ipoptlen = inp->inp_options->m_len - 1364 offsetof(struct ipoption, ipopt_list); 1365 } else { 1366 ipoptlen = 0; 1367 } 1368 } 1369 #ifdef IPSEC 1370 ipoptlen += ipsec_hdrsiz_tcp(tp); 1371 #endif 1372 hlen += ipoptlen; 1373 1374 optlen = 0; 1375 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 1376 (tp->t_flags & TF_RCVD_TSTMP)) 1377 optlen += TCPOLEN_TSTAMP_APPA; 1378 hlen += optlen; 1379 1380 if (tp->t_maxopd <= optlen + ipoptlen) 1381 return EHOSTUNREACH; 1382 1383 *segsz = tp->t_maxopd - optlen - ipoptlen; 1384 *hlen0 = hlen; 1385 return 0; 1386 } 1387