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