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