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sys/netinet/tcp_output.c
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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. Neither the name of the University nor the names of its contributors 47 * may be used to endorse or promote products derived from this software 48 * without specific prior written permission. 49 * 50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 60 * SUCH DAMAGE. 61 * 62 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 63 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 64 */ 65 66 #include "opt_inet.h" 67 #include "opt_inet6.h" 68 #include "opt_ipsec.h" 69 #include "opt_tcpdebug.h" 70 71 #include <sys/param.h> 72 #include <sys/systm.h> 73 #include <sys/kernel.h> 74 #include <sys/sysctl.h> 75 #include <sys/mbuf.h> 76 #include <sys/domain.h> 77 #include <sys/protosw.h> 78 #include <sys/socket.h> 79 #include <sys/socketvar.h> 80 #include <sys/in_cksum.h> 81 #include <sys/thread.h> 82 #include <sys/globaldata.h> 83 84 #include <net/if_var.h> 85 #include <net/route.h> 86 #include <net/netmsg2.h> 87 #include <net/netisr2.h> 88 89 #include <netinet/in.h> 90 #include <netinet/in_systm.h> 91 #include <netinet/ip.h> 92 #include <netinet/in_pcb.h> 93 #include <netinet/ip_var.h> 94 #include <netinet6/in6_pcb.h> 95 #include <netinet/ip6.h> 96 #include <netinet6/ip6_var.h> 97 #include <netinet/tcp.h> 98 #define TCPOUTFLAGS 99 #include <netinet/tcp_fsm.h> 100 #include <netinet/tcp_seq.h> 101 #include <netinet/tcp_timer.h> 102 #include <netinet/tcp_timer2.h> 103 #include <netinet/tcp_var.h> 104 #include <netinet/tcpip.h> 105 #ifdef TCPDEBUG 106 #include <netinet/tcp_debug.h> 107 #endif 108 109 #ifdef IPSEC 110 #include <netinet6/ipsec.h> 111 #endif /*IPSEC*/ 112 113 #ifdef FAST_IPSEC 114 #include <netproto/ipsec/ipsec.h> 115 #define IPSEC 116 #endif /*FAST_IPSEC*/ 117 118 #ifdef notyet 119 extern struct mbuf *m_copypack(); 120 #endif 121 122 int path_mtu_discovery = 0; 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 124 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 125 126 static int avoid_pure_win_update = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, 128 &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); 129 130 int tcp_do_autosndbuf = 1; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 132 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 133 134 int tcp_autosndbuf_inc = 8*1024; 135 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 136 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 137 138 int tcp_autosndbuf_max = 2*1024*1024; 139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 140 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 141 142 int tcp_prio_synack = 1; 143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, prio_synack, CTLFLAG_RW, 144 &tcp_prio_synack, 0, "Prioritize SYN, SYN|ACK and pure ACK"); 145 146 static int tcp_idle_cwv = 1; 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_cwv, CTLFLAG_RW, 148 &tcp_idle_cwv, 0, 149 "Congestion window validation after idle period (part of RFC2861)"); 150 151 static int tcp_idle_restart = 1; 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_restart, CTLFLAG_RW, 153 &tcp_idle_restart, 0, "Reset congestion window after idle period"); 154 155 static int tcp_do_tso = 1; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 157 &tcp_do_tso, 0, "Enable TCP Segmentation Offload (TSO)"); 158 159 static int tcp_fairsend = 4; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fairsend, CTLFLAG_RW, 161 &tcp_fairsend, 0, 162 "Amount of segments sent before yield to other senders or receivers"); 163 164 static void tcp_idle_cwnd_validate(struct tcpcb *); 165 166 static int tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen); 167 static void tcp_output_sched(struct tcpcb *tp); 168 169 /* 170 * Tcp output routine: figure out what should be sent and send it. 171 */ 172 int 173 tcp_output(struct tcpcb *tp) 174 { 175 struct inpcb * const inp = tp->t_inpcb; 176 struct socket *so = inp->inp_socket; 177 long len, recvwin, sendwin; 178 int nsacked = 0; 179 int off, flags, error = 0; 180 #ifdef TCP_SIGNATURE 181 int sigoff = 0; 182 #endif 183 struct mbuf *m; 184 struct ip *ip; 185 struct tcphdr *th; 186 u_char opt[TCP_MAXOLEN]; 187 unsigned int ipoptlen, optlen, hdrlen; 188 int idle; 189 boolean_t sendalot; 190 struct ip6_hdr *ip6; 191 #ifdef INET6 192 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 193 #else 194 const boolean_t isipv6 = FALSE; 195 #endif 196 boolean_t can_tso = FALSE, use_tso; 197 boolean_t report_sack, idle_cwv = FALSE; 198 u_int segsz, tso_hlen, tso_lenmax = 0; 199 int segcnt = 0; 200 boolean_t need_sched = FALSE; 201 202 KKASSERT(so->so_port == &curthread->td_msgport); 203 204 /* 205 * Determine length of data that should be transmitted, 206 * and flags that will be used. 207 * If there is some data or critical controls (SYN, RST) 208 * to send, then transmit; otherwise, investigate further. 209 */ 210 211 /* 212 * If we have been idle for a while, the send congestion window 213 * could be no longer representative of the current state of the 214 * link; need to validate congestion window. However, we should 215 * not perform congestion window validation here, since we could 216 * be asked to send pure ACK. 217 */ 218 if (tp->snd_max == tp->snd_una && 219 (ticks - tp->snd_last) >= tp->t_rxtcur && tcp_idle_restart) 220 idle_cwv = TRUE; 221 222 /* 223 * Calculate whether the transmit stream was previously idle 224 * and adjust TF_LASTIDLE for the next time. 225 */ 226 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 227 if (idle && (tp->t_flags & TF_MORETOCOME)) 228 tp->t_flags |= TF_LASTIDLE; 229 else 230 tp->t_flags &= ~TF_LASTIDLE; 231 232 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 233 !IN_FASTRECOVERY(tp)) 234 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); 235 236 /* 237 * Find out whether TSO could be used or not 238 * 239 * For TSO capable devices, the following assumptions apply to 240 * the processing of TCP flags: 241 * - If FIN is set on the large TCP segment, the device must set 242 * FIN on the last segment that it creates from the large TCP 243 * segment. 244 * - If PUSH is set on the large TCP segment, the device must set 245 * PUSH on the last segment that it creates from the large TCP 246 * segment. 247 */ 248 #if !defined(IPSEC) && !defined(FAST_IPSEC) 249 if (tcp_do_tso 250 #ifdef TCP_SIGNATURE 251 && (tp->t_flags & TF_SIGNATURE) == 0 252 #endif 253 ) { 254 if (!isipv6) { 255 struct rtentry *rt = inp->inp_route.ro_rt; 256 257 if (rt != NULL && (rt->rt_flags & RTF_UP) && 258 (rt->rt_ifp->if_hwassist & CSUM_TSO)) { 259 can_tso = TRUE; 260 tso_lenmax = rt->rt_ifp->if_tsolen; 261 } 262 } 263 } 264 #endif /* !IPSEC && !FAST_IPSEC */ 265 266 again: 267 m = NULL; 268 ip = NULL; 269 th = NULL; 270 ip6 = NULL; 271 272 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 273 TF_SACK_PERMITTED && 274 (!TAILQ_EMPTY(&tp->t_segq) || 275 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 276 report_sack = TRUE; 277 else 278 report_sack = FALSE; 279 280 /* Make use of SACK information when slow-starting after a RTO. */ 281 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 282 !IN_FASTRECOVERY(tp)) { 283 tcp_seq old_snd_nxt = tp->snd_nxt; 284 285 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 286 nsacked += tp->snd_nxt - old_snd_nxt; 287 } 288 289 sendalot = FALSE; 290 off = tp->snd_nxt - tp->snd_una; 291 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 292 sendwin = min(sendwin, tp->snd_bwnd); 293 294 flags = tcp_outflags[tp->t_state]; 295 /* 296 * Get standard flags, and add SYN or FIN if requested by 'hidden' 297 * state flags. 298 */ 299 if (tp->t_flags & TF_NEEDFIN) 300 flags |= TH_FIN; 301 if (tp->t_flags & TF_NEEDSYN) 302 flags |= TH_SYN; 303 304 /* 305 * If in persist timeout with window of 0, send 1 byte. 306 * Otherwise, if window is small but nonzero 307 * and timer expired, we will send what we can 308 * and go to transmit state. 309 */ 310 if (tp->t_flags & TF_FORCE) { 311 if (sendwin == 0) { 312 /* 313 * If we still have some data to send, then 314 * clear the FIN bit. Usually this would 315 * happen below when it realizes that we 316 * aren't sending all the data. However, 317 * if we have exactly 1 byte of unsent data, 318 * then it won't clear the FIN bit below, 319 * and if we are in persist state, we wind 320 * up sending the packet without recording 321 * that we sent the FIN bit. 322 * 323 * We can't just blindly clear the FIN bit, 324 * because if we don't have any more data 325 * to send then the probe will be the FIN 326 * itself. 327 */ 328 if (off < so->so_snd.ssb_cc) 329 flags &= ~TH_FIN; 330 sendwin = 1; 331 } else { 332 tcp_callout_stop(tp, tp->tt_persist); 333 tp->t_rxtshift = 0; 334 } 335 } 336 337 /* 338 * If snd_nxt == snd_max and we have transmitted a FIN, the 339 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in 340 * a negative length. This can also occur when TCP opens up 341 * its congestion window while receiving additional duplicate 342 * acks after fast-retransmit because TCP will reset snd_nxt 343 * to snd_max after the fast-retransmit. 344 * 345 * A negative length can also occur when we are in the 346 * TCPS_SYN_RECEIVED state due to a simultanious connect where 347 * our SYN has not been acked yet. 348 * 349 * In the normal retransmit-FIN-only case, however, snd_nxt will 350 * be set to snd_una, the offset will be 0, and the length may 351 * wind up 0. 352 */ 353 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; 354 355 /* 356 * Lop off SYN bit if it has already been sent. However, if this 357 * is SYN-SENT state and if segment contains data, suppress sending 358 * segment (sending the segment would be an option if we still 359 * did TAO and the remote host supported it). 360 */ 361 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 362 flags &= ~TH_SYN; 363 off--, len++; 364 if (len > 0 && tp->t_state == TCPS_SYN_SENT) { 365 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 366 return 0; 367 } 368 } 369 370 /* 371 * Be careful not to send data and/or FIN on SYN segments. 372 * This measure is needed to prevent interoperability problems 373 * with not fully conformant TCP implementations. 374 */ 375 if (flags & TH_SYN) { 376 len = 0; 377 flags &= ~TH_FIN; 378 } 379 380 if (len < 0) { 381 /* 382 * A negative len can occur if our FIN has been sent but not 383 * acked, or if we are in a simultanious connect in the 384 * TCPS_SYN_RECEIVED state with our SYN sent but not yet 385 * acked. 386 * 387 * If our window has contracted to 0 in the FIN case 388 * (which can only occur if we have NOT been called to 389 * retransmit as per code a few paragraphs up) then we 390 * want to shift the retransmit timer over to the 391 * persist timer. 392 * 393 * However, if we are in the TCPS_SYN_RECEIVED state 394 * (the SYN case) we will be in a simultanious connect and 395 * the window may be zero degeneratively. In this case we 396 * do not want to shift to the persist timer after the SYN 397 * or the SYN+ACK transmission. 398 */ 399 len = 0; 400 if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) { 401 tcp_callout_stop(tp, tp->tt_rexmt); 402 tp->t_rxtshift = 0; 403 tp->snd_nxt = tp->snd_una; 404 if (!tcp_callout_active(tp, tp->tt_persist)) 405 tcp_setpersist(tp); 406 } 407 } 408 409 KASSERT(len >= 0, ("%s: len < 0", __func__)); 410 /* 411 * Automatic sizing of send socket buffer. Often the send buffer 412 * size is not optimally adjusted to the actual network conditions 413 * at hand (delay bandwidth product). Setting the buffer size too 414 * small limits throughput on links with high bandwidth and high 415 * delay (eg. trans-continental/oceanic links). Setting the 416 * buffer size too big consumes too much real kernel memory, 417 * especially with many connections on busy servers. 418 * 419 * The criteria to step up the send buffer one notch are: 420 * 1. receive window of remote host is larger than send buffer 421 * (with a fudge factor of 5/4th); 422 * 2. send buffer is filled to 7/8th with data (so we actually 423 * have data to make use of it); 424 * 3. send buffer fill has not hit maximal automatic size; 425 * 4. our send window (slow start and cogestion controlled) is 426 * larger than sent but unacknowledged data in send buffer. 427 * 428 * The remote host receive window scaling factor may limit the 429 * growing of the send buffer before it reaches its allowed 430 * maximum. 431 * 432 * It scales directly with slow start or congestion window 433 * and does at most one step per received ACK. This fast 434 * scaling has the drawback of growing the send buffer beyond 435 * what is strictly necessary to make full use of a given 436 * delay*bandwith product. However testing has shown this not 437 * to be much of an problem. At worst we are trading wasting 438 * of available bandwith (the non-use of it) for wasting some 439 * socket buffer memory. 440 * 441 * TODO: Shrink send buffer during idle periods together 442 * with congestion window. Requires another timer. Has to 443 * wait for upcoming tcp timer rewrite. 444 */ 445 if (tcp_do_autosndbuf && so->so_snd.ssb_flags & SSB_AUTOSIZE) { 446 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.ssb_hiwat && 447 so->so_snd.ssb_cc >= (so->so_snd.ssb_hiwat / 8 * 7) && 448 so->so_snd.ssb_cc < tcp_autosndbuf_max && 449 sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) { 450 u_long newsize; 451 452 newsize = ulmin(so->so_snd.ssb_hiwat + 453 tcp_autosndbuf_inc, 454 tcp_autosndbuf_max); 455 if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) 456 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 457 if (newsize >= (TCP_MAXWIN << tp->snd_scale)) 458 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 459 } 460 } 461 462 /* 463 * Don't use TSO, if: 464 * - Congestion window needs validation 465 * - There are SACK blocks to report 466 * - RST or SYN flags is set 467 * - URG will be set 468 * 469 * XXX 470 * Checking for SYN|RST looks overkill, just to be safe than sorry 471 */ 472 use_tso = can_tso; 473 if (report_sack || idle_cwv || (flags & (TH_RST | TH_SYN))) 474 use_tso = FALSE; 475 if (use_tso) { 476 tcp_seq ugr_nxt = tp->snd_nxt; 477 478 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && 479 tp->snd_nxt == tp->snd_max) 480 --ugr_nxt; 481 482 if (SEQ_GT(tp->snd_up, ugr_nxt)) 483 use_tso = FALSE; 484 } 485 486 if (use_tso) { 487 /* 488 * Find out segment size and header length for TSO 489 */ 490 error = tcp_tso_getsize(tp, &segsz, &tso_hlen); 491 if (error) 492 use_tso = FALSE; 493 } 494 if (!use_tso) { 495 segsz = tp->t_maxseg; 496 tso_hlen = 0; /* not used */ 497 } 498 499 /* 500 * Truncate to the maximum segment length if not TSO, and ensure that 501 * FIN is removed if the length no longer contains the last data byte. 502 */ 503 if (len > segsz) { 504 if (!use_tso) { 505 len = segsz; 506 ++segcnt; 507 } else { 508 int nsegs; 509 510 if (__predict_false(tso_lenmax < segsz)) 511 tso_lenmax = segsz << 1; 512 513 /* 514 * Truncate TSO transfers to (IP_MAXPACKET - iphlen - 515 * thoff), and make sure that we send equal size 516 * transfers down the stack (rather than big-small- 517 * big-small-...). 518 */ 519 len = min(len, tso_lenmax); 520 nsegs = min(len, (IP_MAXPACKET - tso_hlen)) / segsz; 521 KKASSERT(nsegs > 0); 522 523 len = nsegs * segsz; 524 525 if (len <= segsz) { 526 use_tso = FALSE; 527 ++segcnt; 528 } else { 529 segcnt += nsegs; 530 } 531 } 532 sendalot = TRUE; 533 } else { 534 use_tso = FALSE; 535 if (len > 0) 536 ++segcnt; 537 } 538 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) 539 flags &= ~TH_FIN; 540 541 recvwin = ssb_space(&so->so_rcv); 542 543 /* 544 * Sender silly window avoidance. We transmit under the following 545 * conditions when len is non-zero: 546 * 547 * - We have a full segment 548 * - This is the last buffer in a write()/send() and we are 549 * either idle or running NODELAY 550 * - we've timed out (e.g. persist timer) 551 * - we have more then 1/2 the maximum send window's worth of 552 * data (receiver may be limiting the window size) 553 * - we need to retransmit 554 */ 555 if (len) { 556 if (len >= segsz) 557 goto send; 558 /* 559 * NOTE! on localhost connections an 'ack' from the remote 560 * end may occur synchronously with the output and cause 561 * us to flush a buffer queued with moretocome. XXX 562 * 563 * note: the len + off check is almost certainly unnecessary. 564 */ 565 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 566 (idle || (tp->t_flags & TF_NODELAY)) && 567 len + off >= so->so_snd.ssb_cc && 568 !(tp->t_flags & TF_NOPUSH)) { 569 goto send; 570 } 571 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 572 goto send; 573 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 574 goto send; 575 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 576 goto send; 577 if (tp->t_flags & TF_XMITNOW) 578 goto send; 579 } 580 581 /* 582 * Compare available window to amount of window 583 * known to peer (as advertised window less 584 * next expected input). If the difference is at least two 585 * max size segments, or at least 50% of the maximum possible 586 * window, then want to send a window update to peer. 587 */ 588 if (recvwin > 0) { 589 /* 590 * "adv" is the amount we can increase the window, 591 * taking into account that we are limited by 592 * TCP_MAXWIN << tp->rcv_scale. 593 */ 594 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 595 (tp->rcv_adv - tp->rcv_nxt); 596 long hiwat; 597 598 /* 599 * This ack case typically occurs when the user has drained 600 * the TCP socket buffer sufficiently to warrent an ack 601 * containing a 'pure window update'... that is, an ack that 602 * ONLY updates the tcp window. 603 * 604 * It is unclear why we would need to do a pure window update 605 * past 2 segments if we are going to do one at 1/2 the high 606 * water mark anyway, especially since under normal conditions 607 * the user program will drain the socket buffer quickly. 608 * The 2-segment pure window update will often add a large 609 * number of extra, unnecessary acks to the stream. 610 * 611 * avoid_pure_win_update now defaults to 1. 612 */ 613 if (avoid_pure_win_update == 0 || 614 (tp->t_flags & TF_RXRESIZED)) { 615 if (adv >= (long) (2 * segsz)) { 616 goto send; 617 } 618 } 619 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); 620 if (hiwat > (long)so->so_rcv.ssb_hiwat) 621 hiwat = (long)so->so_rcv.ssb_hiwat; 622 if (adv >= hiwat / 2) 623 goto send; 624 } 625 626 /* 627 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 628 * is also a catch-all for the retransmit timer timeout case. 629 */ 630 if (tp->t_flags & TF_ACKNOW) 631 goto send; 632 if ((flags & TH_RST) || 633 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 634 goto send; 635 if (SEQ_GT(tp->snd_up, tp->snd_una)) 636 goto send; 637 /* 638 * If our state indicates that FIN should be sent 639 * and we have not yet done so, then we need to send. 640 */ 641 if ((flags & TH_FIN) && 642 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 643 goto send; 644 645 /* 646 * TCP window updates are not reliable, rather a polling protocol 647 * using ``persist'' packets is used to insure receipt of window 648 * updates. The three ``states'' for the output side are: 649 * idle not doing retransmits or persists 650 * persisting to move a small or zero window 651 * (re)transmitting and thereby not persisting 652 * 653 * tcp_callout_active(tp, tp->tt_persist) 654 * is true when we are in persist state. 655 * The TF_FORCE flag in tp->t_flags 656 * is set when we are called to send a persist packet. 657 * tcp_callout_active(tp, tp->tt_rexmt) 658 * is set when we are retransmitting 659 * The output side is idle when both timers are zero. 660 * 661 * If send window is too small, there is data to transmit, and no 662 * retransmit or persist is pending, then go to persist state. 663 * 664 * If nothing happens soon, send when timer expires: 665 * if window is nonzero, transmit what we can, otherwise force out 666 * a byte. 667 * 668 * Don't try to set the persist state if we are in TCPS_SYN_RECEIVED 669 * with data pending. This situation can occur during a 670 * simultanious connect. 671 */ 672 if (so->so_snd.ssb_cc > 0 && 673 tp->t_state != TCPS_SYN_RECEIVED && 674 !tcp_callout_active(tp, tp->tt_rexmt) && 675 !tcp_callout_active(tp, tp->tt_persist)) { 676 tp->t_rxtshift = 0; 677 tcp_setpersist(tp); 678 } 679 680 /* 681 * No reason to send a segment, just return. 682 */ 683 tp->t_flags &= ~TF_XMITNOW; 684 return (0); 685 686 send: 687 if (need_sched && len > 0) { 688 tcp_output_sched(tp); 689 return 0; 690 } 691 692 /* 693 * Before ESTABLISHED, force sending of initial options 694 * unless TCP set not to do any options. 695 * NOTE: we assume that the IP/TCP header plus TCP options 696 * always fit in a single mbuf, leaving room for a maximum 697 * link header, i.e. 698 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 699 */ 700 optlen = 0; 701 if (isipv6) 702 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 703 else 704 hdrlen = sizeof(struct tcpiphdr); 705 if (flags & TH_SYN) { 706 tp->snd_nxt = tp->iss; 707 if (!(tp->t_flags & TF_NOOPT)) { 708 u_short mss; 709 710 opt[0] = TCPOPT_MAXSEG; 711 opt[1] = TCPOLEN_MAXSEG; 712 mss = htons((u_short) tcp_mssopt(tp)); 713 memcpy(opt + 2, &mss, sizeof mss); 714 optlen = TCPOLEN_MAXSEG; 715 716 if ((tp->t_flags & TF_REQ_SCALE) && 717 (!(flags & TH_ACK) || 718 (tp->t_flags & TF_RCVD_SCALE))) { 719 *((u_int32_t *)(opt + optlen)) = htonl( 720 TCPOPT_NOP << 24 | 721 TCPOPT_WINDOW << 16 | 722 TCPOLEN_WINDOW << 8 | 723 tp->request_r_scale); 724 optlen += 4; 725 } 726 727 if ((tcp_do_sack && !(flags & TH_ACK)) || 728 tp->t_flags & TF_SACK_PERMITTED) { 729 uint32_t *lp = (uint32_t *)(opt + optlen); 730 731 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 732 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 733 } 734 } 735 } 736 737 /* 738 * Send a timestamp and echo-reply if this is a SYN and our side 739 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 740 * and our peer have sent timestamps in our SYN's. 741 */ 742 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 743 !(flags & TH_RST) && 744 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 745 u_int32_t *lp = (u_int32_t *)(opt + optlen); 746 747 /* Form timestamp option as shown in appendix A of RFC 1323. */ 748 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 749 *lp++ = htonl(ticks); 750 *lp = htonl(tp->ts_recent); 751 optlen += TCPOLEN_TSTAMP_APPA; 752 } 753 754 /* Set receive buffer autosizing timestamp. */ 755 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) 756 tp->rfbuf_ts = ticks; 757 758 /* 759 * If this is a SACK connection and we have a block to report, 760 * fill in the SACK blocks in the TCP options. 761 */ 762 if (report_sack) 763 tcp_sack_fill_report(tp, opt, &optlen); 764 765 #ifdef TCP_SIGNATURE 766 if (tp->t_flags & TF_SIGNATURE) { 767 int i; 768 u_char *bp; 769 /* 770 * Initialize TCP-MD5 option (RFC2385) 771 */ 772 bp = (u_char *)opt + optlen; 773 *bp++ = TCPOPT_SIGNATURE; 774 *bp++ = TCPOLEN_SIGNATURE; 775 sigoff = optlen + 2; 776 for (i = 0; i < TCP_SIGLEN; i++) 777 *bp++ = 0; 778 optlen += TCPOLEN_SIGNATURE; 779 /* 780 * Terminate options list and maintain 32-bit alignment. 781 */ 782 *bp++ = TCPOPT_NOP; 783 *bp++ = TCPOPT_EOL; 784 optlen += 2; 785 } 786 #endif /* TCP_SIGNATURE */ 787 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 788 hdrlen += optlen; 789 790 if (isipv6) { 791 ipoptlen = ip6_optlen(inp); 792 } else { 793 if (inp->inp_options) { 794 ipoptlen = inp->inp_options->m_len - 795 offsetof(struct ipoption, ipopt_list); 796 } else { 797 ipoptlen = 0; 798 } 799 } 800 #ifdef IPSEC 801 ipoptlen += ipsec_hdrsiz_tcp(tp); 802 #endif 803 804 if (use_tso) { 805 /* TSO segment length must be multiple of segment size */ 806 KASSERT(len >= (2 * segsz) && (len % segsz == 0), 807 ("invalid TSO len %ld, segsz %u", len, segsz)); 808 } else { 809 KASSERT(len <= segsz, 810 ("invalid len %ld, segsz %u", len, segsz)); 811 812 /* 813 * Adjust data length if insertion of options will bump 814 * the packet length beyond the t_maxopd length. Clear 815 * FIN to prevent premature closure since there is still 816 * more data to send after this (now truncated) packet. 817 * 818 * If just the options do not fit we are in a no-win 819 * situation and we treat it as an unreachable host. 820 */ 821 if (len + optlen + ipoptlen > tp->t_maxopd) { 822 if (tp->t_maxopd <= optlen + ipoptlen) { 823 static time_t last_optlen_report; 824 825 if (last_optlen_report != time_uptime) { 826 last_optlen_report = time_uptime; 827 kprintf("tcpcb %p: MSS (%d) too " 828 "small to hold options!\n", 829 tp, tp->t_maxopd); 830 } 831 error = EHOSTUNREACH; 832 goto out; 833 } else { 834 flags &= ~TH_FIN; 835 len = tp->t_maxopd - optlen - ipoptlen; 836 sendalot = TRUE; 837 } 838 } 839 } 840 841 #ifdef INET6 842 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 843 #else 844 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 845 #endif 846 847 /* 848 * Grab a header mbuf, attaching a copy of data to 849 * be transmitted, and initialize the header from 850 * the template for sends on this connection. 851 */ 852 if (len) { 853 if ((tp->t_flags & TF_FORCE) && len == 1) 854 tcpstat.tcps_sndprobe++; 855 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 856 if (tp->snd_nxt == tp->snd_una) 857 tp->snd_max_rexmt = tp->snd_max; 858 if (nsacked) { 859 tcpstat.tcps_sndsackrtopack++; 860 tcpstat.tcps_sndsackrtobyte += len; 861 } 862 tcpstat.tcps_sndrexmitpack++; 863 tcpstat.tcps_sndrexmitbyte += len; 864 } else { 865 tcpstat.tcps_sndpack++; 866 tcpstat.tcps_sndbyte += len; 867 } 868 if (idle_cwv) { 869 idle_cwv = FALSE; 870 tcp_idle_cwnd_validate(tp); 871 } 872 /* Update last send time after CWV */ 873 tp->snd_last = ticks; 874 #ifdef notyet 875 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, 876 max_linkhdr + hdrlen)) == NULL) { 877 error = ENOBUFS; 878 goto after_th; 879 } 880 /* 881 * m_copypack left space for our hdr; use it. 882 */ 883 m->m_len += hdrlen; 884 m->m_data -= hdrlen; 885 #else 886 #ifndef INET6 887 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 888 #else 889 m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER, 890 M_PKTHDR, NULL); 891 #endif 892 if (m == NULL) { 893 error = ENOBUFS; 894 goto after_th; 895 } 896 m->m_data += max_linkhdr; 897 m->m_len = hdrlen; 898 if (len <= MHLEN - hdrlen - max_linkhdr) { 899 m_copydata(so->so_snd.ssb_mb, off, (int) len, 900 mtod(m, caddr_t) + hdrlen); 901 m->m_len += len; 902 } else { 903 m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len); 904 if (m->m_next == NULL) { 905 m_free(m); 906 m = NULL; 907 error = ENOBUFS; 908 goto after_th; 909 } 910 } 911 #endif 912 /* 913 * If we're sending everything we've got, set PUSH. 914 * (This will keep happy those implementations which only 915 * give data to the user when a buffer fills or 916 * a PUSH comes in.) 917 */ 918 if (off + len == so->so_snd.ssb_cc) 919 flags |= TH_PUSH; 920 } else { 921 if (tp->t_flags & TF_ACKNOW) 922 tcpstat.tcps_sndacks++; 923 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 924 tcpstat.tcps_sndctrl++; 925 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 926 tcpstat.tcps_sndurg++; 927 else 928 tcpstat.tcps_sndwinup++; 929 930 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 931 if (m == NULL) { 932 error = ENOBUFS; 933 goto after_th; 934 } 935 if (isipv6 && 936 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 937 MH_ALIGN(m, hdrlen); 938 else 939 m->m_data += max_linkhdr; 940 m->m_len = hdrlen; 941 942 /* 943 * Prioritize SYN, SYN|ACK and pure ACK. 944 * Leave FIN and RST as they are. 945 */ 946 if (tcp_prio_synack && (flags & (TH_FIN | TH_RST)) == 0) 947 m->m_flags |= M_PRIO; 948 } 949 m->m_pkthdr.rcvif = NULL; 950 if (isipv6) { 951 ip6 = mtod(m, struct ip6_hdr *); 952 th = (struct tcphdr *)(ip6 + 1); 953 tcp_fillheaders(tp, ip6, th, use_tso); 954 } else { 955 ip = mtod(m, struct ip *); 956 th = (struct tcphdr *)(ip + 1); 957 /* this picks up the pseudo header (w/o the length) */ 958 tcp_fillheaders(tp, ip, th, use_tso); 959 } 960 after_th: 961 /* 962 * Fill in fields, remembering maximum advertised 963 * window for use in delaying messages about window sizes. 964 * If resending a FIN, be sure not to use a new sequence number. 965 */ 966 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 967 tp->snd_nxt == tp->snd_max) 968 tp->snd_nxt--; 969 970 if (th != NULL) { 971 /* 972 * If we are doing retransmissions, then snd_nxt will 973 * not reflect the first unsent octet. For ACK only 974 * packets, we do not want the sequence number of the 975 * retransmitted packet, we want the sequence number 976 * of the next unsent octet. So, if there is no data 977 * (and no SYN or FIN), use snd_max instead of snd_nxt 978 * when filling in ti_seq. But if we are in persist 979 * state, snd_max might reflect one byte beyond the 980 * right edge of the window, so use snd_nxt in that 981 * case, since we know we aren't doing a retransmission. 982 * (retransmit and persist are mutually exclusive...) 983 */ 984 if (len || (flags & (TH_SYN|TH_FIN)) || 985 tcp_callout_active(tp, tp->tt_persist)) 986 th->th_seq = htonl(tp->snd_nxt); 987 else 988 th->th_seq = htonl(tp->snd_max); 989 th->th_ack = htonl(tp->rcv_nxt); 990 if (optlen) { 991 bcopy(opt, th + 1, optlen); 992 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 993 } 994 th->th_flags = flags; 995 } 996 997 /* 998 * Calculate receive window. Don't shrink window, but avoid 999 * silly window syndrome by sending a 0 window if the actual 1000 * window is less then one segment. 1001 */ 1002 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && 1003 recvwin < (long)segsz) 1004 recvwin = 0; 1005 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt)) 1006 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt); 1007 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 1008 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 1009 1010 /* 1011 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1012 * a 0 window. This may cause the remote transmitter to stall. This 1013 * flag tells soreceive() to disable delayed acknowledgements when 1014 * draining the buffer. This can occur if the receiver is attempting 1015 * to read more data then can be buffered prior to transmitting on 1016 * the connection. 1017 */ 1018 if (recvwin == 0) 1019 tp->t_flags |= TF_RXWIN0SENT; 1020 else 1021 tp->t_flags &= ~TF_RXWIN0SENT; 1022 1023 if (th != NULL) 1024 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 1025 1026 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1027 KASSERT(!use_tso, ("URG with TSO")); 1028 if (th != NULL) { 1029 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1030 th->th_flags |= TH_URG; 1031 } 1032 } else { 1033 /* 1034 * If no urgent pointer to send, then we pull 1035 * the urgent pointer to the left edge of the send window 1036 * so that it doesn't drift into the send window on sequence 1037 * number wraparound. 1038 */ 1039 tp->snd_up = tp->snd_una; /* drag it along */ 1040 } 1041 1042 if (th != NULL) { 1043 #ifdef TCP_SIGNATURE 1044 if (tp->t_flags & TF_SIGNATURE) { 1045 tcpsignature_compute(m, len, optlen, 1046 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1047 } 1048 #endif /* TCP_SIGNATURE */ 1049 1050 /* 1051 * Put TCP length in extended header, and then 1052 * checksum extended header and data. 1053 */ 1054 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1055 if (isipv6) { 1056 /* 1057 * ip6_plen is not need to be filled now, and will be 1058 * filled in ip6_output(). 1059 */ 1060 th->th_sum = in6_cksum(m, IPPROTO_TCP, 1061 sizeof(struct ip6_hdr), 1062 sizeof(struct tcphdr) + optlen + len); 1063 } else { 1064 m->m_pkthdr.csum_thlen = sizeof(struct tcphdr) + optlen; 1065 if (use_tso) { 1066 m->m_pkthdr.csum_flags = CSUM_TSO; 1067 m->m_pkthdr.tso_segsz = segsz; 1068 } else { 1069 m->m_pkthdr.csum_flags = CSUM_TCP; 1070 m->m_pkthdr.csum_data = 1071 offsetof(struct tcphdr, th_sum); 1072 if (len + optlen) { 1073 th->th_sum = in_addword(th->th_sum, 1074 htons((u_short)(optlen + len))); 1075 } 1076 } 1077 1078 /* 1079 * IP version must be set here for ipv4/ipv6 checking 1080 * later 1081 */ 1082 KASSERT(ip->ip_v == IPVERSION, 1083 ("%s: IP version incorrect: %d", 1084 __func__, ip->ip_v)); 1085 } 1086 } 1087 1088 /* 1089 * In transmit state, time the transmission and arrange for 1090 * the retransmit. In persist state, just set snd_max. 1091 */ 1092 if (!(tp->t_flags & TF_FORCE) || 1093 !tcp_callout_active(tp, tp->tt_persist)) { 1094 tcp_seq startseq = tp->snd_nxt; 1095 1096 /* 1097 * Advance snd_nxt over sequence space of this segment. 1098 */ 1099 if (flags & (TH_SYN | TH_FIN)) { 1100 if (flags & TH_SYN) 1101 tp->snd_nxt++; 1102 if (flags & TH_FIN) { 1103 tp->snd_nxt++; 1104 tp->t_flags |= TF_SENTFIN; 1105 } 1106 } 1107 tp->snd_nxt += len; 1108 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1109 tp->snd_max = tp->snd_nxt; 1110 /* 1111 * Time this transmission if not a retransmission and 1112 * not currently timing anything. 1113 */ 1114 if (tp->t_rtttime == 0) { 1115 tp->t_rtttime = ticks; 1116 tp->t_rtseq = startseq; 1117 tcpstat.tcps_segstimed++; 1118 } 1119 } 1120 1121 /* 1122 * Set retransmit timer if not currently set, 1123 * and not doing a pure ack or a keep-alive probe. 1124 * Initial value for retransmit timer is smoothed 1125 * round-trip time + 2 * round-trip time variance. 1126 * Initialize shift counter which is used for backoff 1127 * of retransmit time. 1128 */ 1129 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1130 tp->snd_nxt != tp->snd_una) { 1131 if (tcp_callout_active(tp, tp->tt_persist)) { 1132 tcp_callout_stop(tp, tp->tt_persist); 1133 tp->t_rxtshift = 0; 1134 } 1135 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 1136 tcp_timer_rexmt); 1137 } 1138 } else { 1139 /* 1140 * Persist case, update snd_max but since we are in 1141 * persist mode (no window) we do not update snd_nxt. 1142 */ 1143 int xlen = len; 1144 if (flags & TH_SYN) 1145 panic("tcp_output: persist timer to send SYN"); 1146 if (flags & TH_FIN) { 1147 ++xlen; 1148 tp->t_flags |= TF_SENTFIN; 1149 } 1150 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1151 tp->snd_max = tp->snd_nxt + xlen; 1152 } 1153 1154 if (th != NULL) { 1155 #ifdef TCPDEBUG 1156 /* Trace. */ 1157 if (so->so_options & SO_DEBUG) { 1158 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1159 mtod(m, void *), th, 0); 1160 } 1161 #endif 1162 1163 /* 1164 * Fill in IP length and desired time to live and 1165 * send to IP level. There should be a better way 1166 * to handle ttl and tos; we could keep them in 1167 * the template, but need a way to checksum without them. 1168 */ 1169 /* 1170 * m->m_pkthdr.len should have been set before cksum 1171 * calcuration, because in6_cksum() need it. 1172 */ 1173 if (isipv6) { 1174 /* 1175 * we separately set hoplimit for every segment, 1176 * since the user might want to change the value 1177 * via setsockopt. Also, desired default hop 1178 * limit might be changed via Neighbor Discovery. 1179 */ 1180 ip6->ip6_hlim = in6_selecthlim(inp, 1181 (inp->in6p_route.ro_rt ? 1182 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1183 1184 /* TODO: IPv6 IP6TOS_ECT bit on */ 1185 error = ip6_output(m, inp->in6p_outputopts, 1186 &inp->in6p_route, (so->so_options & SO_DONTROUTE), 1187 NULL, NULL, inp); 1188 } else { 1189 struct rtentry *rt; 1190 ip->ip_len = m->m_pkthdr.len; 1191 #ifdef INET6 1192 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1193 ip->ip_ttl = in6_selecthlim(inp, 1194 (inp->in6p_route.ro_rt ? 1195 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1196 else 1197 #endif 1198 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1199 1200 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1201 /* 1202 * See if we should do MTU discovery. 1203 * We do it only if the following are true: 1204 * 1) we have a valid route to the destination 1205 * 2) the MTU is not locked (if it is, 1206 * then discovery has been disabled) 1207 */ 1208 if (path_mtu_discovery && 1209 (rt = inp->inp_route.ro_rt) && 1210 (rt->rt_flags & RTF_UP) && 1211 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 1212 ip->ip_off |= IP_DF; 1213 1214 error = ip_output(m, inp->inp_options, &inp->inp_route, 1215 (so->so_options & SO_DONTROUTE) | 1216 IP_DEBUGROUTE, NULL, inp); 1217 } 1218 } else { 1219 KASSERT(error != 0, ("no error, but th not set")); 1220 } 1221 if (error) { 1222 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1223 1224 /* 1225 * We know that the packet was lost, so back out the 1226 * sequence number advance, if any. 1227 */ 1228 if (!(tp->t_flags & TF_FORCE) || 1229 !tcp_callout_active(tp, tp->tt_persist)) { 1230 /* 1231 * No need to check for TH_FIN here because 1232 * the TF_SENTFIN flag handles that case. 1233 */ 1234 if (!(flags & TH_SYN)) 1235 tp->snd_nxt -= len; 1236 } 1237 1238 out: 1239 if (error == ENOBUFS) { 1240 /* 1241 * If we can't send, make sure there is something 1242 * to get us going again later. 1243 * 1244 * The persist timer isn't necessarily allowed in all 1245 * states, use the rexmt timer. 1246 */ 1247 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1248 !tcp_callout_active(tp, tp->tt_persist)) { 1249 tcp_callout_reset(tp, tp->tt_rexmt, 1250 tp->t_rxtcur, 1251 tcp_timer_rexmt); 1252 #if 0 1253 tp->t_rxtshift = 0; 1254 tcp_setpersist(tp); 1255 #endif 1256 } 1257 tcp_quench(inp, 0); 1258 return (0); 1259 } 1260 if (error == EMSGSIZE) { 1261 /* 1262 * ip_output() will have already fixed the route 1263 * for us. tcp_mtudisc() will, as its last action, 1264 * initiate retransmission, so it is important to 1265 * not do so here. 1266 */ 1267 tcp_mtudisc(inp, 0); 1268 return 0; 1269 } 1270 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1271 TCPS_HAVERCVDSYN(tp->t_state)) { 1272 tp->t_softerror = error; 1273 return (0); 1274 } 1275 return (error); 1276 } 1277 tcpstat.tcps_sndtotal++; 1278 1279 /* 1280 * Data sent (as far as we can tell). 1281 * 1282 * If this advertises a larger window than any other segment, 1283 * then remember the size of the advertised window. 1284 * 1285 * Any pending ACK has now been sent. 1286 */ 1287 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) { 1288 tp->rcv_adv = tp->rcv_nxt + recvwin; 1289 tp->t_flags &= ~TF_RXRESIZED; 1290 } 1291 tp->last_ack_sent = tp->rcv_nxt; 1292 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1293 if (tcp_delack_enabled) 1294 tcp_callout_stop(tp, tp->tt_delack); 1295 if (sendalot) { 1296 if (tcp_fairsend > 0 && (tp->t_flags & TF_FAIRSEND) && 1297 segcnt >= tcp_fairsend) 1298 need_sched = TRUE; 1299 goto again; 1300 } 1301 return (0); 1302 } 1303 1304 void 1305 tcp_setpersist(struct tcpcb *tp) 1306 { 1307 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1308 int tt; 1309 1310 if (tp->t_state == TCPS_SYN_SENT || 1311 tp->t_state == TCPS_SYN_RECEIVED) { 1312 panic("tcp_setpersist: not established yet, current %s", 1313 tp->t_state == TCPS_SYN_SENT ? 1314 "SYN_SENT" : "SYN_RECEIVED"); 1315 } 1316 1317 if (tcp_callout_active(tp, tp->tt_rexmt)) 1318 panic("tcp_setpersist: retransmit pending"); 1319 /* 1320 * Start/restart persistance timer. 1321 */ 1322 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1323 TCPTV_PERSMAX); 1324 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist); 1325 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1326 tp->t_rxtshift++; 1327 } 1328 1329 static void 1330 tcp_idle_cwnd_validate(struct tcpcb *tp) 1331 { 1332 u_long initial_cwnd = tcp_initial_window(tp); 1333 u_long min_cwnd; 1334 1335 tcpstat.tcps_sndidle++; 1336 1337 /* According to RFC5681: RW=min(IW,cwnd) */ 1338 min_cwnd = min(tp->snd_cwnd, initial_cwnd); 1339 1340 if (tcp_idle_cwv) { 1341 u_long idle_time, decay_cwnd; 1342 1343 /* 1344 * RFC2861, but only after idle period. 1345 */ 1346 1347 /* 1348 * Before the congestion window is reduced, ssthresh 1349 * is set to the maximum of its current value and 3/4 1350 * cwnd. If the sender then has more data to send 1351 * than the decayed cwnd allows, the TCP will slow- 1352 * start (perform exponential increase) at least 1353 * half-way back up to the old value of cwnd. 1354 */ 1355 tp->snd_ssthresh = max(tp->snd_ssthresh, 1356 (3 * tp->snd_cwnd) / 4); 1357 1358 /* 1359 * Decay the congestion window by half for every RTT 1360 * that the flow remains inactive. 1361 * 1362 * The difference between our implementation and 1363 * RFC2861 is that we don't allow cwnd to go below 1364 * the value allowed by RFC5681 (min_cwnd). 1365 */ 1366 idle_time = ticks - tp->snd_last; 1367 decay_cwnd = tp->snd_cwnd; 1368 while (idle_time >= tp->t_rxtcur && 1369 decay_cwnd > min_cwnd) { 1370 decay_cwnd >>= 1; 1371 idle_time -= tp->t_rxtcur; 1372 } 1373 tp->snd_cwnd = max(decay_cwnd, min_cwnd); 1374 } else { 1375 /* 1376 * Slow-start from scratch to re-determine the send 1377 * congestion window. 1378 */ 1379 tp->snd_cwnd = min_cwnd; 1380 } 1381 1382 /* Restart ABC counting during congestion avoidance */ 1383 tp->snd_wacked = 0; 1384 } 1385 1386 static int 1387 tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen0) 1388 { 1389 struct inpcb * const inp = tp->t_inpcb; 1390 #ifdef INET6 1391 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 1392 #else 1393 const boolean_t isipv6 = FALSE; 1394 #endif 1395 unsigned int ipoptlen, optlen; 1396 u_int hlen; 1397 1398 hlen = sizeof(struct ip) + sizeof(struct tcphdr); 1399 1400 if (isipv6) { 1401 ipoptlen = ip6_optlen(inp); 1402 } else { 1403 if (inp->inp_options) { 1404 ipoptlen = inp->inp_options->m_len - 1405 offsetof(struct ipoption, ipopt_list); 1406 } else { 1407 ipoptlen = 0; 1408 } 1409 } 1410 #ifdef IPSEC 1411 ipoptlen += ipsec_hdrsiz_tcp(tp); 1412 #endif 1413 hlen += ipoptlen; 1414 1415 optlen = 0; 1416 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 1417 (tp->t_flags & TF_RCVD_TSTMP)) 1418 optlen += TCPOLEN_TSTAMP_APPA; 1419 hlen += optlen; 1420 1421 if (tp->t_maxopd <= optlen + ipoptlen) 1422 return EHOSTUNREACH; 1423 1424 *segsz = tp->t_maxopd - optlen - ipoptlen; 1425 *hlen0 = hlen; 1426 return 0; 1427 } 1428 1429 static void 1430 tcp_output_sched_handler(netmsg_t nmsg) 1431 { 1432 struct tcpcb *tp = nmsg->lmsg.u.ms_resultp; 1433 1434 /* Reply ASAP */ 1435 crit_enter(); 1436 lwkt_replymsg(&nmsg->lmsg, 0); 1437 crit_exit(); 1438 1439 tcp_output_fair(tp); 1440 } 1441 1442 void 1443 tcp_output_init(struct tcpcb *tp) 1444 { 1445 netmsg_init(tp->tt_sndmore, NULL, &netisr_adone_rport, MSGF_DROPABLE, 1446 tcp_output_sched_handler); 1447 tp->tt_sndmore->lmsg.u.ms_resultp = tp; 1448 } 1449 1450 void 1451 tcp_output_cancel(struct tcpcb *tp) 1452 { 1453 /* 1454 * This message is still pending to be processed; 1455 * drop it. Optimized. 1456 */ 1457 crit_enter(); 1458 if ((tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) == 0) { 1459 lwkt_dropmsg(&tp->tt_sndmore->lmsg); 1460 } 1461 crit_exit(); 1462 } 1463 1464 boolean_t 1465 tcp_output_pending(struct tcpcb *tp) 1466 { 1467 if ((tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) == 0) 1468 return TRUE; 1469 else 1470 return FALSE; 1471 } 1472 1473 static void 1474 tcp_output_sched(struct tcpcb *tp) 1475 { 1476 crit_enter(); 1477 if (tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) 1478 lwkt_sendmsg(netisr_cpuport(mycpuid), &tp->tt_sndmore->lmsg); 1479 crit_exit(); 1480 } 1481 1482 /* 1483 * Fairsend 1484 * 1485 * Yield to other senders or receivers on the same netisr if the current 1486 * TCP stream has sent tcp_fairsend segments and is going to burst more 1487 * segments. Bursting large amount of segements in a single TCP stream 1488 * could delay other senders' segments and receivers' ACKs quite a lot, 1489 * if others segments and ACKs are queued on to the same hardware transmit 1490 * queue; thus cause unfairness between senders and suppress receiving 1491 * performance. 1492 * 1493 * Fairsend should be performed at the places that do not affect segment 1494 * sending during congestion control, e.g. 1495 * - User requested output 1496 * - ACK input triggered output 1497 * 1498 * NOTE: 1499 * For devices that are TSO capable, their TSO aggregation size limit could 1500 * affect fairsend. 1501 */ 1502 int 1503 tcp_output_fair(struct tcpcb *tp) 1504 { 1505 int ret; 1506 1507 tp->t_flags |= TF_FAIRSEND; 1508 ret = tcp_output(tp); 1509 tp->t_flags &= ~TF_FAIRSEND; 1510 1511 return ret; 1512 }
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