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_tcpdebug.h" 69 70 #include <sys/param.h> 71 #include <sys/systm.h> 72 #include <sys/kernel.h> 73 #include <sys/malloc.h> /* for M_NOWAIT */ 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.h> 85 #include <net/if_var.h> 86 #include <net/route.h> 87 #include <net/netmsg2.h> 88 #include <net/netisr2.h> 89 90 #include <netinet/in.h> 91 #include <netinet/in_systm.h> 92 #include <netinet/ip.h> 93 #include <netinet/in_pcb.h> 94 #include <netinet/ip_var.h> 95 #include <netinet6/in6_pcb.h> 96 #include <netinet/ip6.h> 97 #include <netinet6/ip6_var.h> 98 #include <netinet/tcp.h> 99 #define TCPOUTFLAGS 100 #include <netinet/tcp_fsm.h> 101 #include <netinet/tcp_seq.h> 102 #include <netinet/tcp_timer.h> 103 #include <netinet/tcp_timer2.h> 104 #include <netinet/tcp_var.h> 105 #include <netinet/tcpip.h> 106 #ifdef TCPDEBUG 107 #include <netinet/tcp_debug.h> 108 #endif 109 110 #ifdef notyet 111 extern struct mbuf *m_copypack(); 112 #endif 113 114 int path_mtu_discovery = 1; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 116 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 117 118 static int avoid_pure_win_update = 1; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, 120 &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); 121 122 /* 123 * 1 - enabled for increasing and decreasing the buffer size 124 * 2 - enabled only for increasing the buffer size 125 */ 126 int tcp_do_autosndbuf = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 128 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 129 130 int tcp_autosndbuf_inc = 8*1024; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 132 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 133 134 int tcp_autosndbuf_min = 32768; 135 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_min, CTLFLAG_RW, 136 &tcp_autosndbuf_min, 0, "Min size of automatic send buffer"); 137 138 int tcp_autosndbuf_max = 2*1024*1024; 139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 140 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 141 142 int tcp_prio_synack = 1; 143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, prio_synack, CTLFLAG_RW, 144 &tcp_prio_synack, 0, "Prioritize SYN, SYN|ACK and pure ACK"); 145 146 static int tcp_idle_cwv = 1; 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_cwv, CTLFLAG_RW, 148 &tcp_idle_cwv, 0, 149 "Congestion window validation after idle period (part of RFC2861)"); 150 151 static int tcp_idle_restart = 1; 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_restart, CTLFLAG_RW, 153 &tcp_idle_restart, 0, "Reset congestion window after idle period"); 154 155 static int tcp_do_tso = 1; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 157 &tcp_do_tso, 0, "Enable TCP Segmentation Offload (TSO)"); 158 159 static int tcp_fairsend = 4; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fairsend, CTLFLAG_RW, 161 &tcp_fairsend, 0, 162 "Amount of segments sent before yield to other senders or receivers"); 163 164 static void tcp_idle_cwnd_validate(struct tcpcb *); 165 166 static int tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen); 167 static void tcp_output_sched(struct tcpcb *tp); 168 169 /* 170 * Tcp output routine: figure out what should be sent and send it. 171 */ 172 int 173 tcp_output(struct tcpcb *tp) 174 { 175 struct inpcb * const inp = tp->t_inpcb; 176 struct socket *so = inp->inp_socket; 177 long len, recvwin, sendwin; 178 int nsacked = 0; 179 int off, flags, error = 0; 180 #ifdef TCP_SIGNATURE 181 int sigoff = 0; 182 #endif 183 struct mbuf *m; 184 struct ip *ip; 185 struct tcphdr *th; 186 u_char opt[TCP_MAXOLEN]; 187 unsigned int ipoptlen, optlen, hdrlen; 188 int idle; 189 boolean_t sendalot; 190 struct ip6_hdr *ip6; 191 #ifdef INET6 192 const boolean_t isipv6 = INP_ISIPV6(inp); 193 #else 194 const boolean_t isipv6 = FALSE; 195 #endif 196 boolean_t can_tso = FALSE, use_tso; 197 boolean_t report_sack, idle_cwv = FALSE; 198 u_int segsz, tso_hlen, tso_lenmax = 0; 199 int segcnt = 0; 200 boolean_t need_sched = FALSE; 201 202 KKASSERT(so->so_port == &curthread->td_msgport); 203 204 /* 205 * Determine length of data that should be transmitted, 206 * and flags that will be used. 207 * If there is some data or critical controls (SYN, RST) 208 * to send, then transmit; otherwise, investigate further. 209 */ 210 211 /* 212 * If we have been idle for a while, the send congestion window 213 * could be no longer representative of the current state of the 214 * link; need to validate congestion window. However, we should 215 * not perform congestion window validation here, since we could 216 * be asked to send pure ACK. 217 */ 218 if (tp->snd_max == tp->snd_una && 219 (ticks - tp->snd_last) >= tp->t_rxtcur && tcp_idle_restart) 220 idle_cwv = TRUE; 221 222 /* 223 * Calculate whether the transmit stream was previously idle 224 * and adjust TF_LASTIDLE for the next time. 225 */ 226 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 227 if (idle && (tp->t_flags & TF_MORETOCOME)) 228 tp->t_flags |= TF_LASTIDLE; 229 else 230 tp->t_flags &= ~TF_LASTIDLE; 231 232 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 233 !IN_FASTRECOVERY(tp)) 234 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); 235 236 /* 237 * Find out whether TSO could be used or not 238 * 239 * For TSO capable devices, the following assumptions apply to 240 * the processing of TCP flags: 241 * - If FIN is set on the large TCP segment, the device must set 242 * FIN on the last segment that it creates from the large TCP 243 * segment. 244 * - If PUSH is set on the large TCP segment, the device must set 245 * PUSH on the last segment that it creates from the large TCP 246 * segment. 247 */ 248 if (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 } 263 264 again: 265 m = NULL; 266 ip = NULL; 267 th = NULL; 268 ip6 = NULL; 269 270 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 271 TF_SACK_PERMITTED && 272 (!TAILQ_EMPTY(&tp->t_segq) || 273 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 274 report_sack = TRUE; 275 else 276 report_sack = FALSE; 277 278 /* Make use of SACK information when slow-starting after a RTO. */ 279 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 280 !IN_FASTRECOVERY(tp)) { 281 tcp_seq old_snd_nxt = tp->snd_nxt; 282 283 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 284 nsacked += tp->snd_nxt - old_snd_nxt; 285 } 286 287 sendalot = FALSE; 288 off = tp->snd_nxt - tp->snd_una; 289 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 290 sendwin = min(sendwin, tp->snd_bwnd); 291 292 flags = tcp_outflags[tp->t_state]; 293 /* 294 * Get standard flags, and add SYN or FIN if requested by 'hidden' 295 * state flags. 296 */ 297 if (tp->t_flags & TF_NEEDFIN) 298 flags |= TH_FIN; 299 if (tp->t_flags & TF_NEEDSYN) 300 flags |= TH_SYN; 301 302 /* 303 * If in persist timeout with window of 0, send 1 byte. 304 * Otherwise, if window is small but nonzero 305 * and timer expired, we will send what we can 306 * and go to transmit state. 307 */ 308 if (tp->t_flags & TF_FORCE) { 309 if (sendwin == 0) { 310 /* 311 * If we still have some data to send, then 312 * clear the FIN bit. Usually this would 313 * happen below when it realizes that we 314 * aren't sending all the data. However, 315 * if we have exactly 1 byte of unsent data, 316 * then it won't clear the FIN bit below, 317 * and if we are in persist state, we wind 318 * up sending the packet without recording 319 * that we sent the FIN bit. 320 * 321 * We can't just blindly clear the FIN bit, 322 * because if we don't have any more data 323 * to send then the probe will be the FIN 324 * itself. 325 */ 326 if (off < so->so_snd.ssb_cc) 327 flags &= ~TH_FIN; 328 sendwin = 1; 329 } else { 330 tcp_callout_stop(tp, tp->tt_persist); 331 tp->t_rxtshift = 0; 332 } 333 } 334 335 /* 336 * If snd_nxt == snd_max and we have transmitted a FIN, the 337 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in 338 * a negative length. This can also occur when TCP opens up 339 * its congestion window while receiving additional duplicate 340 * acks after fast-retransmit because TCP will reset snd_nxt 341 * to snd_max after the fast-retransmit. 342 * 343 * A negative length can also occur when we are in the 344 * TCPS_SYN_RECEIVED state due to a simultanious connect where 345 * our SYN has not been acked yet. 346 * 347 * In the normal retransmit-FIN-only case, however, snd_nxt will 348 * be set to snd_una, the offset will be 0, and the length may 349 * wind up 0. 350 */ 351 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; 352 353 /* 354 * Lop off SYN bit if it has already been sent. However, if this 355 * is SYN-SENT state and if segment contains data, suppress sending 356 * segment (sending the segment would be an option if we still 357 * did TAO and the remote host supported it). 358 */ 359 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 360 flags &= ~TH_SYN; 361 off--, len++; 362 if (len > 0 && tp->t_state == TCPS_SYN_SENT) { 363 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 364 return 0; 365 } 366 } 367 368 /* 369 * Be careful not to send data and/or FIN on SYN segments. 370 * This measure is needed to prevent interoperability problems 371 * with not fully conformant TCP implementations. 372 */ 373 if (flags & TH_SYN) { 374 len = 0; 375 flags &= ~TH_FIN; 376 } 377 378 if (len < 0) { 379 /* 380 * A negative len can occur if our FIN has been sent but not 381 * acked, or if we are in a simultanious connect in the 382 * TCPS_SYN_RECEIVED state with our SYN sent but not yet 383 * acked. 384 * 385 * If our window has contracted to 0 in the FIN case 386 * (which can only occur if we have NOT been called to 387 * retransmit as per code a few paragraphs up) then we 388 * want to shift the retransmit timer over to the 389 * persist timer. 390 * 391 * However, if we are in the TCPS_SYN_RECEIVED state 392 * (the SYN case) we will be in a simultanious connect and 393 * the window may be zero degeneratively. In this case we 394 * do not want to shift to the persist timer after the SYN 395 * or the SYN+ACK transmission. 396 */ 397 len = 0; 398 if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) { 399 tcp_callout_stop(tp, tp->tt_rexmt); 400 tp->t_rxtshift = 0; 401 tp->snd_nxt = tp->snd_una; 402 if (!tcp_callout_active(tp, tp->tt_persist)) 403 tcp_setpersist(tp); 404 } 405 } 406 407 KASSERT(len >= 0, ("%s: len < 0", __func__)); 408 /* 409 * Automatic sizing of send socket buffer. Often the send buffer 410 * size is not optimally adjusted to the actual network conditions 411 * at hand (delay bandwidth product). Setting the buffer size too 412 * small limits throughput on links with high bandwidth and high 413 * delay (eg. trans-continental/oceanic links). Setting the 414 * buffer size too big consumes too much real kernel memory, 415 * especially with many connections on busy servers. 416 * 417 * The criteria to step up the send buffer one notch are: 418 * 1. receive window of remote host is larger than send buffer 419 * (with a fudge factor of 5/4th); 420 * 2. hiwat has not significantly exceeded bwnd (inflight) 421 * (bwnd is a maximal value if inflight is disabled). 422 * 3. send buffer is filled to 7/8th with data (so we actually 423 * have data to make use of it); 424 * 4. hiwat has not hit maximal automatic size; 425 * 5. our send window (slow start and cogestion controlled) is 426 * larger than sent but unacknowledged data in send buffer. 427 * 428 * The remote host receive window scaling factor may limit the 429 * growing of the send buffer before it reaches its allowed 430 * maximum. 431 * 432 * It scales directly with slow start or congestion window 433 * and does at most one step per received ACK. This fast 434 * scaling has the drawback of growing the send buffer beyond 435 * what is strictly necessary to make full use of a given 436 * delay*bandwith product. However testing has shown this not 437 * to be much of an problem. At worst we are trading wasting 438 * of available bandwith (the non-use of it) for wasting some 439 * socket buffer memory. 440 * 441 * The criteria for shrinking the buffer is based solely on 442 * the inflight code (snd_bwnd). If inflight is disabled, 443 * the buffer will not be shrinked. Note that snd_bwnd already 444 * has a fudge factor. Our test adds a little hysteresis. 445 */ 446 if (tcp_do_autosndbuf && (so->so_snd.ssb_flags & SSB_AUTOSIZE)) { 447 const int asbinc = tcp_autosndbuf_inc; 448 const int hiwat = so->so_snd.ssb_hiwat; 449 const int lowat = so->so_snd.ssb_lowat; 450 u_long newsize; 451 452 if ((tp->snd_wnd / 4 * 5) >= hiwat && 453 so->so_snd.ssb_cc >= (hiwat / 8 * 7) && 454 hiwat < tp->snd_bwnd + hiwat / 10 && 455 hiwat + asbinc < tcp_autosndbuf_max && 456 hiwat < (TCP_MAXWIN << tp->snd_scale) && 457 sendwin >= (so->so_snd.ssb_cc - 458 (tp->snd_nxt - tp->snd_una))) { 459 newsize = ulmin(hiwat + asbinc, tcp_autosndbuf_max); 460 if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) 461 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 462 #if 0 463 if (newsize >= (TCP_MAXWIN << tp->snd_scale)) 464 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 465 #endif 466 } else if ((long)tp->snd_bwnd < 467 (long)(hiwat * 3 / 4 - lowat - asbinc) && 468 hiwat > tp->t_maxseg * 2 + asbinc && 469 hiwat + asbinc >= tcp_autosndbuf_min && 470 tcp_do_autosndbuf == 1) { 471 newsize = ulmax(hiwat - asbinc, tp->t_maxseg * 2); 472 ssb_reserve(&so->so_snd, newsize, so, NULL); 473 } 474 } 475 476 /* 477 * Don't use TSO, if: 478 * - Congestion window needs validation 479 * - There are SACK blocks to report 480 * - RST or SYN flags is set 481 * - URG will be set 482 * 483 * XXX 484 * Checking for SYN|RST looks overkill, just to be safe than sorry 485 */ 486 use_tso = can_tso; 487 if (report_sack || idle_cwv || (flags & (TH_RST | TH_SYN))) 488 use_tso = FALSE; 489 if (use_tso) { 490 tcp_seq ugr_nxt = tp->snd_nxt; 491 492 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && 493 tp->snd_nxt == tp->snd_max) 494 --ugr_nxt; 495 496 if (SEQ_GT(tp->snd_up, ugr_nxt)) 497 use_tso = FALSE; 498 } 499 500 if (use_tso) { 501 /* 502 * Find out segment size and header length for TSO 503 */ 504 error = tcp_tso_getsize(tp, &segsz, &tso_hlen); 505 if (error) 506 use_tso = FALSE; 507 } 508 if (!use_tso) { 509 segsz = tp->t_maxseg; 510 tso_hlen = 0; /* not used */ 511 } 512 513 /* 514 * Truncate to the maximum segment length if not TSO, and ensure that 515 * FIN is removed if the length no longer contains the last data byte. 516 */ 517 if (len > segsz) { 518 if (!use_tso) { 519 len = segsz; 520 ++segcnt; 521 } else { 522 int nsegs; 523 524 if (__predict_false(tso_lenmax < segsz)) 525 tso_lenmax = segsz << 1; 526 527 /* 528 * Truncate TSO transfers to (IP_MAXPACKET - iphlen - 529 * thoff), and make sure that we send equal size 530 * transfers down the stack (rather than big-small- 531 * big-small-...). 532 */ 533 len = min(len, tso_lenmax); 534 nsegs = min(len, (IP_MAXPACKET - tso_hlen)) / segsz; 535 KKASSERT(nsegs > 0); 536 537 len = nsegs * segsz; 538 539 if (len <= segsz) { 540 use_tso = FALSE; 541 ++segcnt; 542 } else { 543 segcnt += nsegs; 544 } 545 } 546 sendalot = TRUE; 547 } else { 548 use_tso = FALSE; 549 if (len > 0) 550 ++segcnt; 551 } 552 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) 553 flags &= ~TH_FIN; 554 555 recvwin = ssb_space(&so->so_rcv); 556 557 /* 558 * Sender silly window avoidance. We transmit under the following 559 * conditions when len is non-zero: 560 * 561 * - We have a full segment 562 * - This is the last buffer in a write()/send() and we are 563 * either idle or running NODELAY 564 * - we've timed out (e.g. persist timer) 565 * - we have more then 1/2 the maximum send window's worth of 566 * data (receiver may be limiting the window size) 567 * - we need to retransmit 568 */ 569 if (len) { 570 if (len >= segsz) 571 goto send; 572 /* 573 * NOTE! on localhost connections an 'ack' from the remote 574 * end may occur synchronously with the output and cause 575 * us to flush a buffer queued with moretocome. XXX 576 * 577 * note: the len + off check is almost certainly unnecessary. 578 */ 579 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 580 (idle || (tp->t_flags & TF_NODELAY)) && 581 len + off >= so->so_snd.ssb_cc && 582 !(tp->t_flags & TF_NOPUSH)) { 583 goto send; 584 } 585 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 586 goto send; 587 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 588 goto send; 589 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 590 goto send; 591 if (tp->t_flags & TF_XMITNOW) 592 goto send; 593 } 594 595 /* 596 * Compare available window to amount of window 597 * known to peer (as advertised window less 598 * next expected input). If the difference is at least two 599 * max size segments, or at least 50% of the maximum possible 600 * window, then want to send a window update to peer. 601 */ 602 if (recvwin > 0) { 603 /* 604 * "adv" is the amount we can increase the window, 605 * taking into account that we are limited by 606 * TCP_MAXWIN << tp->rcv_scale. 607 */ 608 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 609 (tp->rcv_adv - tp->rcv_nxt); 610 long hiwat; 611 612 /* 613 * This ack case typically occurs when the user has drained 614 * the TCP socket buffer sufficiently to warrent an ack 615 * containing a 'pure window update'... that is, an ack that 616 * ONLY updates the tcp window. 617 * 618 * It is unclear why we would need to do a pure window update 619 * past 2 segments if we are going to do one at 1/2 the high 620 * water mark anyway, especially since under normal conditions 621 * the user program will drain the socket buffer quickly. 622 * The 2-segment pure window update will often add a large 623 * number of extra, unnecessary acks to the stream. 624 * 625 * avoid_pure_win_update now defaults to 1. 626 */ 627 if (avoid_pure_win_update == 0 || 628 (tp->t_flags & TF_RXRESIZED)) { 629 if (adv >= (long) (2 * segsz)) { 630 goto send; 631 } 632 } 633 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); 634 if (hiwat > (long)so->so_rcv.ssb_hiwat) 635 hiwat = (long)so->so_rcv.ssb_hiwat; 636 if (adv >= hiwat / 2) 637 goto send; 638 } 639 640 /* 641 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 642 * is also a catch-all for the retransmit timer timeout case. 643 */ 644 if (tp->t_flags & TF_ACKNOW) 645 goto send; 646 if ((flags & TH_RST) || 647 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 648 goto send; 649 if (SEQ_GT(tp->snd_up, tp->snd_una)) 650 goto send; 651 /* 652 * If our state indicates that FIN should be sent 653 * and we have not yet done so, then we need to send. 654 */ 655 if ((flags & TH_FIN) && 656 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 657 goto send; 658 659 /* 660 * TCP window updates are not reliable, rather a polling protocol 661 * using ``persist'' packets is used to insure receipt of window 662 * updates. The three ``states'' for the output side are: 663 * idle not doing retransmits or persists 664 * persisting to move a small or zero window 665 * (re)transmitting and thereby not persisting 666 * 667 * tcp_callout_active(tp, tp->tt_persist) 668 * is true when we are in persist state. 669 * The TF_FORCE flag in tp->t_flags 670 * is set when we are called to send a persist packet. 671 * tcp_callout_active(tp, tp->tt_rexmt) 672 * is set when we are retransmitting 673 * The output side is idle when both timers are zero. 674 * 675 * If send window is too small, there is data to transmit, and no 676 * retransmit or persist is pending, then go to persist state. 677 * 678 * If nothing happens soon, send when timer expires: 679 * if window is nonzero, transmit what we can, otherwise force out 680 * a byte. 681 * 682 * Don't try to set the persist state if we are in TCPS_SYN_RECEIVED 683 * with data pending. This situation can occur during a 684 * simultanious connect. 685 */ 686 if (so->so_snd.ssb_cc > 0 && 687 tp->t_state != TCPS_SYN_RECEIVED && 688 !tcp_callout_active(tp, tp->tt_rexmt) && 689 !tcp_callout_active(tp, tp->tt_persist)) { 690 tp->t_rxtshift = 0; 691 tcp_setpersist(tp); 692 } 693 694 /* 695 * No reason to send a segment, just return. 696 */ 697 tp->t_flags &= ~TF_XMITNOW; 698 return (0); 699 700 send: 701 if (need_sched && len > 0) { 702 tcp_output_sched(tp); 703 return 0; 704 } 705 706 /* 707 * Before ESTABLISHED, force sending of initial options 708 * unless TCP set not to do any options. 709 * NOTE: we assume that the IP/TCP header plus TCP options 710 * always fit in a single mbuf, leaving room for a maximum 711 * link header, i.e. 712 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 713 */ 714 optlen = 0; 715 if (isipv6) 716 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 717 else 718 hdrlen = sizeof(struct tcpiphdr); 719 if (flags & TH_SYN) { 720 tp->snd_nxt = tp->iss; 721 if (!(tp->t_flags & TF_NOOPT)) { 722 u_short mss; 723 724 opt[0] = TCPOPT_MAXSEG; 725 opt[1] = TCPOLEN_MAXSEG; 726 mss = htons((u_short) tcp_mssopt(tp)); 727 memcpy(opt + 2, &mss, sizeof mss); 728 optlen = TCPOLEN_MAXSEG; 729 730 if ((tp->t_flags & TF_REQ_SCALE) && 731 (!(flags & TH_ACK) || 732 (tp->t_flags & TF_RCVD_SCALE))) { 733 *((u_int32_t *)(opt + optlen)) = htonl( 734 TCPOPT_NOP << 24 | 735 TCPOPT_WINDOW << 16 | 736 TCPOLEN_WINDOW << 8 | 737 tp->request_r_scale); 738 optlen += 4; 739 } 740 741 if ((tcp_do_sack && !(flags & TH_ACK)) || 742 tp->t_flags & TF_SACK_PERMITTED) { 743 uint32_t *lp = (uint32_t *)(opt + optlen); 744 745 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 746 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 747 } 748 } 749 } 750 751 /* 752 * Send a timestamp and echo-reply if this is a SYN and our side 753 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 754 * and our peer have sent timestamps in our SYN's. 755 */ 756 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 757 !(flags & TH_RST) && 758 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 759 u_int32_t *lp = (u_int32_t *)(opt + optlen); 760 761 /* Form timestamp option as shown in appendix A of RFC 1323. */ 762 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 763 *lp++ = htonl(ticks); 764 *lp = htonl(tp->ts_recent); 765 optlen += TCPOLEN_TSTAMP_APPA; 766 } 767 768 /* Set receive buffer autosizing timestamp. */ 769 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) 770 tp->rfbuf_ts = ticks; 771 772 /* 773 * If this is a SACK connection and we have a block to report, 774 * fill in the SACK blocks in the TCP options. 775 */ 776 if (report_sack) 777 tcp_sack_fill_report(tp, opt, &optlen); 778 779 #ifdef TCP_SIGNATURE 780 if (tp->t_flags & TF_SIGNATURE) { 781 int i; 782 u_char *bp; 783 /* 784 * Initialize TCP-MD5 option (RFC2385) 785 */ 786 bp = (u_char *)opt + optlen; 787 *bp++ = TCPOPT_SIGNATURE; 788 *bp++ = TCPOLEN_SIGNATURE; 789 sigoff = optlen + 2; 790 for (i = 0; i < TCP_SIGLEN; i++) 791 *bp++ = 0; 792 optlen += TCPOLEN_SIGNATURE; 793 /* 794 * Terminate options list and maintain 32-bit alignment. 795 */ 796 *bp++ = TCPOPT_NOP; 797 *bp++ = TCPOPT_EOL; 798 optlen += 2; 799 } 800 #endif /* TCP_SIGNATURE */ 801 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 802 hdrlen += optlen; 803 804 if (isipv6) { 805 ipoptlen = ip6_optlen(inp); 806 } else { 807 if (inp->inp_options) { 808 ipoptlen = inp->inp_options->m_len - 809 offsetof(struct ipoption, ipopt_list); 810 } else { 811 ipoptlen = 0; 812 } 813 } 814 815 if (use_tso) { 816 /* TSO segment length must be multiple of segment size */ 817 KASSERT(len >= (2 * segsz) && (len % segsz == 0), 818 ("invalid TSO len %ld, segsz %u", len, segsz)); 819 } else { 820 KASSERT(len <= segsz, 821 ("invalid len %ld, segsz %u", len, segsz)); 822 823 /* 824 * Adjust data length if insertion of options will bump 825 * the packet length beyond the t_maxopd length. Clear 826 * FIN to prevent premature closure since there is still 827 * more data to send after this (now truncated) packet. 828 * 829 * If just the options do not fit we are in a no-win 830 * situation and we treat it as an unreachable host. 831 */ 832 if (len + optlen + ipoptlen > tp->t_maxopd) { 833 if (tp->t_maxopd <= optlen + ipoptlen) { 834 static time_t last_optlen_report; 835 836 if (last_optlen_report != time_uptime) { 837 last_optlen_report = time_uptime; 838 kprintf("tcpcb %p: MSS (%d) too " 839 "small to hold options!\n", 840 tp, tp->t_maxopd); 841 } 842 error = EHOSTUNREACH; 843 goto out; 844 } else { 845 flags &= ~TH_FIN; 846 len = tp->t_maxopd - optlen - ipoptlen; 847 sendalot = TRUE; 848 } 849 } 850 } 851 852 #ifdef INET6 853 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 854 #else 855 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 856 #endif 857 858 /* 859 * Grab a header mbuf, attaching a copy of data to 860 * be transmitted, and initialize the header from 861 * the template for sends on this connection. 862 */ 863 if (len) { 864 if ((tp->t_flags & TF_FORCE) && len == 1) 865 tcpstat.tcps_sndprobe++; 866 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 867 if (tp->snd_nxt == tp->snd_una) 868 tp->snd_max_rexmt = tp->snd_max; 869 if (nsacked) { 870 tcpstat.tcps_sndsackrtopack++; 871 tcpstat.tcps_sndsackrtobyte += len; 872 } 873 tcpstat.tcps_sndrexmitpack++; 874 tcpstat.tcps_sndrexmitbyte += len; 875 } else { 876 tcpstat.tcps_sndpack++; 877 tcpstat.tcps_sndbyte += len; 878 } 879 if (idle_cwv) { 880 idle_cwv = FALSE; 881 tcp_idle_cwnd_validate(tp); 882 } 883 /* Update last send time after CWV */ 884 tp->snd_last = ticks; 885 #ifdef notyet 886 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, 887 max_linkhdr + hdrlen)) == NULL) { 888 error = ENOBUFS; 889 goto after_th; 890 } 891 /* 892 * m_copypack left space for our hdr; use it. 893 */ 894 m->m_len += hdrlen; 895 m->m_data -= hdrlen; 896 #else 897 #ifndef INET6 898 m = m_gethdr(M_NOWAIT, MT_HEADER); 899 #else 900 m = m_getl(hdrlen + max_linkhdr, M_NOWAIT, MT_HEADER, 901 M_PKTHDR, NULL); 902 #endif 903 if (m == NULL) { 904 error = ENOBUFS; 905 goto after_th; 906 } 907 m->m_data += max_linkhdr; 908 m->m_len = hdrlen; 909 if (len <= MHLEN - hdrlen - max_linkhdr) { 910 m_copydata(so->so_snd.ssb_mb, off, (int) len, 911 mtod(m, caddr_t) + hdrlen); 912 m->m_len += len; 913 } else { 914 m->m_next = m_copym(so->so_snd.ssb_mb, off, 915 (int) len, M_NOWAIT); 916 if (m->m_next == NULL) { 917 m_free(m); 918 m = NULL; 919 error = ENOBUFS; 920 goto after_th; 921 } 922 } 923 #endif 924 /* 925 * If we're sending everything we've got, set PUSH. 926 * (This will keep happy those implementations which only 927 * give data to the user when a buffer fills or 928 * a PUSH comes in.) 929 */ 930 if (off + len == so->so_snd.ssb_cc) 931 flags |= TH_PUSH; 932 } else { 933 if (tp->t_flags & TF_ACKNOW) 934 tcpstat.tcps_sndacks++; 935 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 936 tcpstat.tcps_sndctrl++; 937 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 938 tcpstat.tcps_sndurg++; 939 else 940 tcpstat.tcps_sndwinup++; 941 942 MGETHDR(m, M_NOWAIT, MT_HEADER); 943 if (m == NULL) { 944 error = ENOBUFS; 945 goto after_th; 946 } 947 if (isipv6 && 948 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 949 MH_ALIGN(m, hdrlen); 950 else 951 m->m_data += max_linkhdr; 952 m->m_len = hdrlen; 953 954 /* 955 * Prioritize SYN, SYN|ACK and pure ACK. 956 * Leave FIN and RST as they are. 957 */ 958 if (tcp_prio_synack && (flags & (TH_FIN | TH_RST)) == 0) 959 m->m_flags |= M_PRIO; 960 } 961 m->m_pkthdr.rcvif = NULL; 962 if (isipv6) { 963 ip6 = mtod(m, struct ip6_hdr *); 964 th = (struct tcphdr *)(ip6 + 1); 965 tcp_fillheaders(tp, ip6, th, use_tso); 966 } else { 967 ip = mtod(m, struct ip *); 968 th = (struct tcphdr *)(ip + 1); 969 /* this picks up the pseudo header (w/o the length) */ 970 tcp_fillheaders(tp, ip, th, use_tso); 971 } 972 after_th: 973 /* 974 * Fill in fields, remembering maximum advertised 975 * window for use in delaying messages about window sizes. 976 * If resending a FIN, be sure not to use a new sequence number. 977 */ 978 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 979 tp->snd_nxt == tp->snd_max) 980 tp->snd_nxt--; 981 982 if (th != NULL) { 983 /* 984 * If we are doing retransmissions, then snd_nxt will 985 * not reflect the first unsent octet. For ACK only 986 * packets, we do not want the sequence number of the 987 * retransmitted packet, we want the sequence number 988 * of the next unsent octet. So, if there is no data 989 * (and no SYN or FIN), use snd_max instead of snd_nxt 990 * when filling in ti_seq. But if we are in persist 991 * state, snd_max might reflect one byte beyond the 992 * right edge of the window, so use snd_nxt in that 993 * case, since we know we aren't doing a retransmission. 994 * (retransmit and persist are mutually exclusive...) 995 */ 996 if (len || (flags & (TH_SYN|TH_FIN)) || 997 tcp_callout_active(tp, tp->tt_persist)) 998 th->th_seq = htonl(tp->snd_nxt); 999 else 1000 th->th_seq = htonl(tp->snd_max); 1001 th->th_ack = htonl(tp->rcv_nxt); 1002 if (optlen) { 1003 bcopy(opt, th + 1, optlen); 1004 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1005 } 1006 th->th_flags = flags; 1007 } 1008 1009 /* 1010 * Calculate receive window. Don't shrink window, but avoid 1011 * silly window syndrome by sending a 0 window if the actual 1012 * window is less then one segment. 1013 */ 1014 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && 1015 recvwin < (long)segsz) 1016 recvwin = 0; 1017 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt)) 1018 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt); 1019 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 1020 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 1021 1022 /* 1023 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1024 * a 0 window. This may cause the remote transmitter to stall. This 1025 * flag tells soreceive() to disable delayed acknowledgements when 1026 * draining the buffer. This can occur if the receiver is attempting 1027 * to read more data then can be buffered prior to transmitting on 1028 * the connection. 1029 */ 1030 if (recvwin == 0) 1031 tp->t_flags |= TF_RXWIN0SENT; 1032 else 1033 tp->t_flags &= ~TF_RXWIN0SENT; 1034 1035 if (th != NULL) 1036 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 1037 1038 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1039 KASSERT(!use_tso, ("URG with TSO")); 1040 if (th != NULL) { 1041 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1042 th->th_flags |= TH_URG; 1043 } 1044 } else { 1045 /* 1046 * If no urgent pointer to send, then we pull 1047 * the urgent pointer to the left edge of the send window 1048 * so that it doesn't drift into the send window on sequence 1049 * number wraparound. 1050 */ 1051 tp->snd_up = tp->snd_una; /* drag it along */ 1052 } 1053 1054 if (th != NULL) { 1055 #ifdef TCP_SIGNATURE 1056 if (tp->t_flags & TF_SIGNATURE) { 1057 tcpsignature_compute(m, len, optlen, 1058 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1059 } 1060 #endif /* TCP_SIGNATURE */ 1061 1062 /* 1063 * Put TCP length in extended header, and then 1064 * checksum extended header and data. 1065 */ 1066 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1067 if (isipv6) { 1068 /* 1069 * ip6_plen is not need to be filled now, and will be 1070 * filled in ip6_output(). 1071 */ 1072 th->th_sum = in6_cksum(m, IPPROTO_TCP, 1073 sizeof(struct ip6_hdr), 1074 sizeof(struct tcphdr) + optlen + len); 1075 } else { 1076 m->m_pkthdr.csum_thlen = sizeof(struct tcphdr) + optlen; 1077 if (use_tso) { 1078 m->m_pkthdr.csum_flags = CSUM_TSO; 1079 m->m_pkthdr.tso_segsz = segsz; 1080 } else { 1081 m->m_pkthdr.csum_flags = CSUM_TCP; 1082 m->m_pkthdr.csum_data = 1083 offsetof(struct tcphdr, th_sum); 1084 if (len + optlen) { 1085 th->th_sum = in_addword(th->th_sum, 1086 htons((u_short)(optlen + len))); 1087 } 1088 } 1089 1090 /* 1091 * IP version must be set here for ipv4/ipv6 checking 1092 * later 1093 */ 1094 KASSERT(ip->ip_v == IPVERSION, 1095 ("%s: IP version incorrect: %d", 1096 __func__, ip->ip_v)); 1097 } 1098 } 1099 1100 /* 1101 * In transmit state, time the transmission and arrange for 1102 * the retransmit. In persist state, just set snd_max. 1103 */ 1104 if (!(tp->t_flags & TF_FORCE) || 1105 !tcp_callout_active(tp, tp->tt_persist)) { 1106 tcp_seq startseq = tp->snd_nxt; 1107 1108 /* 1109 * Advance snd_nxt over sequence space of this segment. 1110 */ 1111 if (flags & (TH_SYN | TH_FIN)) { 1112 if (flags & TH_SYN) 1113 tp->snd_nxt++; 1114 if (flags & TH_FIN) { 1115 tp->snd_nxt++; 1116 tp->t_flags |= TF_SENTFIN; 1117 } 1118 } 1119 tp->snd_nxt += len; 1120 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1121 tp->snd_max = tp->snd_nxt; 1122 /* 1123 * Time this transmission if not a retransmission and 1124 * not currently timing anything. 1125 */ 1126 if (tp->t_rtttime == 0) { 1127 tp->t_rtttime = ticks; 1128 tp->t_rtseq = startseq; 1129 tcpstat.tcps_segstimed++; 1130 } 1131 } 1132 1133 /* 1134 * Set retransmit timer if not currently set, 1135 * and not doing a pure ack or a keep-alive probe. 1136 * Initial value for retransmit timer is smoothed 1137 * round-trip time + 2 * round-trip time variance. 1138 * Initialize shift counter which is used for backoff 1139 * of retransmit time. 1140 */ 1141 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1142 tp->snd_nxt != tp->snd_una) { 1143 if (tcp_callout_active(tp, tp->tt_persist)) { 1144 tcp_callout_stop(tp, tp->tt_persist); 1145 tp->t_rxtshift = 0; 1146 } 1147 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 1148 tcp_timer_rexmt); 1149 } else if (len == 0 && so->so_snd.ssb_cc && 1150 tp->t_state > TCPS_SYN_RECEIVED && 1151 !tcp_callout_active(tp, tp->tt_rexmt) && 1152 !tcp_callout_active(tp, tp->tt_persist)) { 1153 /* 1154 * Avoid a situation where we do not set persist timer 1155 * after a zero window condition. For example: 1156 * 1) A -> B: packet with enough data to fill the window 1157 * 2) B -> A: ACK for #1 + new data (0 window 1158 * advertisement) 1159 * 3) A -> B: ACK for #2, 0 len packet 1160 * 1161 * In this case, A will not activate the persist timer, 1162 * because it chose to send a packet. Unless tcp_output 1163 * is called for some other reason (delayed ack timer, 1164 * another input packet from B, socket syscall), A will 1165 * not send zero window probes. 1166 * 1167 * So, if you send a 0-length packet, but there is data 1168 * in the socket buffer, and neither the rexmt or 1169 * persist timer is already set, then activate the 1170 * persist timer. 1171 */ 1172 tp->t_rxtshift = 0; 1173 tcp_setpersist(tp); 1174 } 1175 } else { 1176 /* 1177 * Persist case, update snd_max but since we are in 1178 * persist mode (no window) we do not update snd_nxt. 1179 */ 1180 int xlen = len; 1181 if (flags & TH_SYN) 1182 panic("tcp_output: persist timer to send SYN"); 1183 if (flags & TH_FIN) { 1184 ++xlen; 1185 tp->t_flags |= TF_SENTFIN; 1186 } 1187 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1188 tp->snd_max = tp->snd_nxt + xlen; 1189 } 1190 1191 if (th != NULL) { 1192 #ifdef TCPDEBUG 1193 /* Trace. */ 1194 if (so->so_options & SO_DEBUG) { 1195 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1196 mtod(m, void *), th, 0); 1197 } 1198 #endif 1199 1200 /* 1201 * Fill in IP length and desired time to live and 1202 * send to IP level. There should be a better way 1203 * to handle ttl and tos; we could keep them in 1204 * the template, but need a way to checksum without them. 1205 */ 1206 /* 1207 * m->m_pkthdr.len should have been set before cksum 1208 * calcuration, because in6_cksum() need it. 1209 */ 1210 if (isipv6) { 1211 /* 1212 * we separately set hoplimit for every segment, 1213 * since the user might want to change the value 1214 * via setsockopt. Also, desired default hop 1215 * limit might be changed via Neighbor Discovery. 1216 */ 1217 ip6->ip6_hlim = in6_selecthlim(inp, 1218 (inp->in6p_route.ro_rt ? 1219 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1220 1221 /* TODO: IPv6 IP6TOS_ECT bit on */ 1222 error = ip6_output(m, inp->in6p_outputopts, 1223 &inp->in6p_route, (so->so_options & SO_DONTROUTE), 1224 NULL, NULL, inp); 1225 } else { 1226 struct rtentry *rt; 1227 1228 KASSERT(!INP_CHECK_SOCKAF(so, AF_INET6), ("inet6 pcb")); 1229 1230 ip->ip_len = htons(m->m_pkthdr.len); 1231 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1232 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1233 /* 1234 * See if we should do MTU discovery. 1235 * We do it only if the following are true: 1236 * 1) we have a valid route to the destination 1237 * 2) the MTU is not locked (if it is, 1238 * then discovery has been disabled) 1239 */ 1240 if (path_mtu_discovery && 1241 (rt = inp->inp_route.ro_rt) && 1242 (rt->rt_flags & RTF_UP) && 1243 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 1244 { 1245 ip->ip_off |= htons(IP_DF); 1246 } 1247 1248 KASSERT(inp->inp_flags & INP_HASH, 1249 ("inpcb has no hash")); 1250 m_sethash(m, inp->inp_hashval); 1251 error = ip_output(m, inp->inp_options, &inp->inp_route, 1252 (so->so_options & SO_DONTROUTE) | 1253 IP_DEBUGROUTE, NULL, inp); 1254 } 1255 } else { 1256 KASSERT(error != 0, ("no error, but th not set")); 1257 } 1258 if (error) { 1259 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1260 1261 /* 1262 * We know that the packet was lost, so back out the 1263 * sequence number advance, if any. 1264 */ 1265 if (!(tp->t_flags & TF_FORCE) || 1266 !tcp_callout_active(tp, tp->tt_persist)) { 1267 /* 1268 * No need to check for TH_FIN here because 1269 * the TF_SENTFIN flag handles that case. 1270 */ 1271 if (!(flags & TH_SYN)) 1272 tp->snd_nxt -= len; 1273 } 1274 1275 out: 1276 if (error == ENOBUFS) { 1277 KASSERT((len == 0 && (flags & (TH_SYN | TH_FIN)) == 0) || 1278 tcp_callout_active(tp, tp->tt_rexmt) || 1279 tcp_callout_active(tp, tp->tt_persist), 1280 ("neither rexmt nor persist timer is set")); 1281 return (0); 1282 } 1283 if (error == EMSGSIZE) { 1284 /* 1285 * ip_output() will have already fixed the route 1286 * for us. tcp_mtudisc() will, as its last action, 1287 * initiate retransmission, so it is important to 1288 * not do so here. 1289 */ 1290 tcp_mtudisc(inp, 0); 1291 return 0; 1292 } 1293 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1294 TCPS_HAVERCVDSYN(tp->t_state)) { 1295 tp->t_softerror = error; 1296 return (0); 1297 } 1298 return (error); 1299 } 1300 tcpstat.tcps_sndtotal++; 1301 1302 /* 1303 * Data sent (as far as we can tell). 1304 * 1305 * If this advertises a larger window than any other segment, 1306 * then remember the size of the advertised window. 1307 * 1308 * Any pending ACK has now been sent. 1309 */ 1310 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) { 1311 tp->rcv_adv = tp->rcv_nxt + recvwin; 1312 tp->t_flags &= ~TF_RXRESIZED; 1313 } 1314 tp->last_ack_sent = tp->rcv_nxt; 1315 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1316 if (tcp_delack_enabled) 1317 tcp_callout_stop(tp, tp->tt_delack); 1318 if (sendalot) { 1319 if (tcp_fairsend > 0 && (tp->t_flags & TF_FAIRSEND) && 1320 segcnt >= tcp_fairsend) 1321 need_sched = TRUE; 1322 goto again; 1323 } 1324 return (0); 1325 } 1326 1327 void 1328 tcp_setpersist(struct tcpcb *tp) 1329 { 1330 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1331 int tt; 1332 1333 if (tp->t_state == TCPS_SYN_SENT || 1334 tp->t_state == TCPS_SYN_RECEIVED) { 1335 panic("tcp_setpersist: not established yet, current %s", 1336 tp->t_state == TCPS_SYN_SENT ? 1337 "SYN_SENT" : "SYN_RECEIVED"); 1338 } 1339 1340 if (tcp_callout_active(tp, tp->tt_rexmt)) 1341 panic("tcp_setpersist: retransmit pending"); 1342 /* 1343 * Start/restart persistance timer. 1344 */ 1345 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1346 TCPTV_PERSMAX); 1347 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist); 1348 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1349 tp->t_rxtshift++; 1350 } 1351 1352 static void 1353 tcp_idle_cwnd_validate(struct tcpcb *tp) 1354 { 1355 u_long initial_cwnd = tcp_initial_window(tp); 1356 u_long min_cwnd; 1357 1358 tcpstat.tcps_sndidle++; 1359 1360 /* According to RFC5681: RW=min(IW,cwnd) */ 1361 min_cwnd = min(tp->snd_cwnd, initial_cwnd); 1362 1363 if (tcp_idle_cwv) { 1364 u_long idle_time, decay_cwnd; 1365 1366 /* 1367 * RFC2861, but only after idle period. 1368 */ 1369 1370 /* 1371 * Before the congestion window is reduced, ssthresh 1372 * is set to the maximum of its current value and 3/4 1373 * cwnd. If the sender then has more data to send 1374 * than the decayed cwnd allows, the TCP will slow- 1375 * start (perform exponential increase) at least 1376 * half-way back up to the old value of cwnd. 1377 */ 1378 tp->snd_ssthresh = max(tp->snd_ssthresh, 1379 (3 * tp->snd_cwnd) / 4); 1380 1381 /* 1382 * Decay the congestion window by half for every RTT 1383 * that the flow remains inactive. 1384 * 1385 * The difference between our implementation and 1386 * RFC2861 is that we don't allow cwnd to go below 1387 * the value allowed by RFC5681 (min_cwnd). 1388 */ 1389 idle_time = ticks - tp->snd_last; 1390 decay_cwnd = tp->snd_cwnd; 1391 while (idle_time >= tp->t_rxtcur && 1392 decay_cwnd > min_cwnd) { 1393 decay_cwnd >>= 1; 1394 idle_time -= tp->t_rxtcur; 1395 } 1396 tp->snd_cwnd = max(decay_cwnd, min_cwnd); 1397 } else { 1398 /* 1399 * Slow-start from scratch to re-determine the send 1400 * congestion window. 1401 */ 1402 tp->snd_cwnd = min_cwnd; 1403 } 1404 1405 /* Restart ABC counting during congestion avoidance */ 1406 tp->snd_wacked = 0; 1407 } 1408 1409 static int 1410 tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen0) 1411 { 1412 struct inpcb * const inp = tp->t_inpcb; 1413 #ifdef INET6 1414 const boolean_t isipv6 = INP_ISIPV6(inp); 1415 #else 1416 const boolean_t isipv6 = FALSE; 1417 #endif 1418 unsigned int ipoptlen, optlen; 1419 u_int hlen; 1420 1421 hlen = sizeof(struct ip) + sizeof(struct tcphdr); 1422 1423 if (isipv6) { 1424 ipoptlen = ip6_optlen(inp); 1425 } else { 1426 if (inp->inp_options) { 1427 ipoptlen = inp->inp_options->m_len - 1428 offsetof(struct ipoption, ipopt_list); 1429 } else { 1430 ipoptlen = 0; 1431 } 1432 } 1433 hlen += ipoptlen; 1434 1435 optlen = 0; 1436 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 1437 (tp->t_flags & TF_RCVD_TSTMP)) 1438 optlen += TCPOLEN_TSTAMP_APPA; 1439 hlen += optlen; 1440 1441 if (tp->t_maxopd <= optlen + ipoptlen) 1442 return EHOSTUNREACH; 1443 1444 *segsz = tp->t_maxopd - optlen - ipoptlen; 1445 *hlen0 = hlen; 1446 return 0; 1447 } 1448 1449 static void 1450 tcp_output_sched_handler(netmsg_t nmsg) 1451 { 1452 struct tcpcb *tp = nmsg->lmsg.u.ms_resultp; 1453 1454 /* Reply ASAP */ 1455 crit_enter(); 1456 lwkt_replymsg(&nmsg->lmsg, 0); 1457 crit_exit(); 1458 1459 tcp_output_fair(tp); 1460 } 1461 1462 void 1463 tcp_output_init(struct tcpcb *tp) 1464 { 1465 netmsg_init(tp->tt_sndmore, NULL, &netisr_adone_rport, MSGF_DROPABLE, 1466 tcp_output_sched_handler); 1467 tp->tt_sndmore->lmsg.u.ms_resultp = tp; 1468 } 1469 1470 void 1471 tcp_output_cancel(struct tcpcb *tp) 1472 { 1473 /* 1474 * This message is still pending to be processed; 1475 * drop it. Optimized. 1476 */ 1477 crit_enter(); 1478 if ((tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) == 0) { 1479 lwkt_dropmsg(&tp->tt_sndmore->lmsg); 1480 } 1481 crit_exit(); 1482 } 1483 1484 boolean_t 1485 tcp_output_pending(struct tcpcb *tp) 1486 { 1487 if ((tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) == 0) 1488 return TRUE; 1489 else 1490 return FALSE; 1491 } 1492 1493 static void 1494 tcp_output_sched(struct tcpcb *tp) 1495 { 1496 crit_enter(); 1497 if (tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) 1498 lwkt_sendmsg(netisr_cpuport(mycpuid), &tp->tt_sndmore->lmsg); 1499 crit_exit(); 1500 } 1501 1502 /* 1503 * Fairsend 1504 * 1505 * Yield to other senders or receivers on the same netisr if the current 1506 * TCP stream has sent tcp_fairsend segments and is going to burst more 1507 * segments. Bursting large amount of segements in a single TCP stream 1508 * could delay other senders' segments and receivers' ACKs quite a lot, 1509 * if others segments and ACKs are queued on to the same hardware transmit 1510 * queue; thus cause unfairness between senders and suppress receiving 1511 * performance. 1512 * 1513 * Fairsend should be performed at the places that do not affect segment 1514 * sending during congestion control, e.g. 1515 * - User requested output 1516 * - ACK input triggered output 1517 * 1518 * NOTE: 1519 * For devices that are TSO capable, their TSO aggregation size limit could 1520 * affect fairsend. 1521 */ 1522 int 1523 tcp_output_fair(struct tcpcb *tp) 1524 { 1525 int ret; 1526 1527 tp->t_flags |= TF_FAIRSEND; 1528 ret = tcp_output(tp); 1529 tp->t_flags &= ~TF_FAIRSEND; 1530 1531 return ret; 1532 } 1533