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/sysctl.h> 74 #include <sys/mbuf.h> 75 #include <sys/domain.h> 76 #include <sys/protosw.h> 77 #include <sys/socket.h> 78 #include <sys/socketvar.h> 79 #include <sys/in_cksum.h> 80 #include <sys/thread.h> 81 #include <sys/globaldata.h> 82 83 #include <net/if.h> 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 notyet 110 extern struct mbuf *m_copypack(); 111 #endif 112 113 int path_mtu_discovery = 1; 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 115 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 116 117 static int avoid_pure_win_update = 1; 118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, 119 &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); 120 121 /* 122 * 1 - enabled for increasing and decreasing the buffer size 123 * 2 - enabled only for increasing the buffer size 124 */ 125 int tcp_do_autosndbuf = 1; 126 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 127 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 128 129 int tcp_autosndbuf_inc = 8*1024; 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 131 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 132 133 int tcp_autosndbuf_min = 32768; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_min, CTLFLAG_RW, 135 &tcp_autosndbuf_min, 0, "Min size of automatic send buffer"); 136 137 int tcp_autosndbuf_max = 2*1024*1024; 138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 139 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 140 141 int tcp_prio_synack = 1; 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, prio_synack, CTLFLAG_RW, 143 &tcp_prio_synack, 0, "Prioritize SYN, SYN|ACK and pure ACK"); 144 145 static int tcp_idle_cwv = 1; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_cwv, CTLFLAG_RW, 147 &tcp_idle_cwv, 0, 148 "Congestion window validation after idle period (part of RFC2861)"); 149 150 static int tcp_idle_restart = 1; 151 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_restart, CTLFLAG_RW, 152 &tcp_idle_restart, 0, "Reset congestion window after idle period"); 153 154 static int tcp_do_tso = 1; 155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 156 &tcp_do_tso, 0, "Enable TCP Segmentation Offload (TSO)"); 157 158 static int tcp_fairsend = 4; 159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fairsend, CTLFLAG_RW, 160 &tcp_fairsend, 0, 161 "Amount of segments sent before yield to other senders or receivers"); 162 163 static void tcp_idle_cwnd_validate(struct tcpcb *); 164 165 static int tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen); 166 static void tcp_output_sched(struct tcpcb *tp); 167 168 /* 169 * Tcp output routine: figure out what should be sent and send it. 170 */ 171 int 172 tcp_output(struct tcpcb *tp) 173 { 174 struct inpcb * const inp = tp->t_inpcb; 175 struct socket *so = inp->inp_socket; 176 long len, recvwin, sendwin; 177 int nsacked = 0; 178 int off, flags, error = 0; 179 #ifdef TCP_SIGNATURE 180 int sigoff = 0; 181 #endif 182 struct mbuf *m; 183 struct ip *ip; 184 struct tcphdr *th; 185 u_char opt[TCP_MAXOLEN]; 186 unsigned int ipoptlen, optlen, hdrlen; 187 int idle; 188 boolean_t sendalot; 189 struct ip6_hdr *ip6; 190 #ifdef INET6 191 const boolean_t isipv6 = INP_ISIPV6(inp); 192 #else 193 const boolean_t isipv6 = FALSE; 194 #endif 195 boolean_t can_tso = FALSE, use_tso; 196 boolean_t report_sack, idle_cwv = FALSE; 197 u_int segsz, tso_hlen, tso_lenmax = 0; 198 int segcnt = 0; 199 boolean_t need_sched = FALSE; 200 201 KKASSERT(so->so_port == &curthread->td_msgport); 202 203 /* 204 * Determine length of data that should be transmitted, 205 * and flags that will be used. 206 * If there is some data or critical controls (SYN, RST) 207 * to send, then transmit; otherwise, investigate further. 208 */ 209 210 /* 211 * If we have been idle for a while, the send congestion window 212 * could be no longer representative of the current state of the 213 * link; need to validate congestion window. However, we should 214 * not perform congestion window validation here, since we could 215 * be asked to send pure ACK. 216 */ 217 if (tp->snd_max == tp->snd_una && 218 (ticks - tp->snd_last) >= tp->t_rxtcur && tcp_idle_restart) 219 idle_cwv = TRUE; 220 221 /* 222 * Calculate whether the transmit stream was previously idle 223 * and adjust TF_LASTIDLE for the next time. 224 */ 225 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 226 if (idle && (tp->t_flags & TF_MORETOCOME)) 227 tp->t_flags |= TF_LASTIDLE; 228 else 229 tp->t_flags &= ~TF_LASTIDLE; 230 231 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 232 !IN_FASTRECOVERY(tp)) 233 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); 234 235 /* 236 * Find out whether TSO could be used or not 237 * 238 * For TSO capable devices, the following assumptions apply to 239 * the processing of TCP flags: 240 * - If FIN is set on the large TCP segment, the device must set 241 * FIN on the last segment that it creates from the large TCP 242 * segment. 243 * - If PUSH is set on the large TCP segment, the device must set 244 * PUSH on the last segment that it creates from the large TCP 245 * segment. 246 */ 247 if (tcp_do_tso 248 #ifdef TCP_SIGNATURE 249 && (tp->t_flags & TF_SIGNATURE) == 0 250 #endif 251 ) { 252 if (!isipv6) { 253 struct rtentry *rt = inp->inp_route.ro_rt; 254 255 if (rt != NULL && (rt->rt_flags & RTF_UP) && 256 (rt->rt_ifp->if_hwassist & CSUM_TSO)) { 257 can_tso = TRUE; 258 tso_lenmax = rt->rt_ifp->if_tsolen; 259 } 260 } 261 } 262 263 again: 264 m = NULL; 265 ip = NULL; 266 th = NULL; 267 ip6 = NULL; 268 269 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 270 TF_SACK_PERMITTED && 271 (!TAILQ_EMPTY(&tp->t_segq) || 272 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 273 report_sack = TRUE; 274 else 275 report_sack = FALSE; 276 277 /* Make use of SACK information when slow-starting after a RTO. */ 278 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 279 !IN_FASTRECOVERY(tp)) { 280 tcp_seq old_snd_nxt = tp->snd_nxt; 281 282 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 283 nsacked += tp->snd_nxt - old_snd_nxt; 284 } 285 286 sendalot = FALSE; 287 off = tp->snd_nxt - tp->snd_una; 288 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 289 sendwin = min(sendwin, tp->snd_bwnd); 290 291 flags = tcp_outflags[tp->t_state]; 292 /* 293 * Get standard flags, and add SYN or FIN if requested by 'hidden' 294 * state flags. 295 */ 296 if (tp->t_flags & TF_NEEDFIN) 297 flags |= TH_FIN; 298 if (tp->t_flags & TF_NEEDSYN) 299 flags |= TH_SYN; 300 301 /* 302 * If in persist timeout with window of 0, send 1 byte. 303 * Otherwise, if window is small but nonzero 304 * and timer expired, we will send what we can 305 * and go to transmit state. 306 */ 307 if (tp->t_flags & TF_FORCE) { 308 if (sendwin == 0) { 309 /* 310 * If we still have some data to send, then 311 * clear the FIN bit. Usually this would 312 * happen below when it realizes that we 313 * aren't sending all the data. However, 314 * if we have exactly 1 byte of unsent data, 315 * then it won't clear the FIN bit below, 316 * and if we are in persist state, we wind 317 * up sending the packet without recording 318 * that we sent the FIN bit. 319 * 320 * We can't just blindly clear the FIN bit, 321 * because if we don't have any more data 322 * to send then the probe will be the FIN 323 * itself. 324 */ 325 if (off < so->so_snd.ssb_cc) 326 flags &= ~TH_FIN; 327 sendwin = 1; 328 } else { 329 tcp_callout_stop(tp, tp->tt_persist); 330 tp->t_rxtshift = 0; 331 } 332 } 333 334 /* 335 * If snd_nxt == snd_max and we have transmitted a FIN, the 336 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in 337 * a negative length. This can also occur when TCP opens up 338 * its congestion window while receiving additional duplicate 339 * acks after fast-retransmit because TCP will reset snd_nxt 340 * to snd_max after the fast-retransmit. 341 * 342 * A negative length can also occur when we are in the 343 * TCPS_SYN_RECEIVED state due to a simultanious connect where 344 * our SYN has not been acked yet. 345 * 346 * In the normal retransmit-FIN-only case, however, snd_nxt will 347 * be set to snd_una, the offset will be 0, and the length may 348 * wind up 0. 349 */ 350 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; 351 352 /* 353 * Lop off SYN bit if it has already been sent. However, if this 354 * is SYN-SENT state and if segment contains data, suppress sending 355 * segment (sending the segment would be an option if we still 356 * did TAO and the remote host supported it). 357 */ 358 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 359 flags &= ~TH_SYN; 360 off--, len++; 361 if (len > 0 && tp->t_state == TCPS_SYN_SENT) { 362 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 363 return 0; 364 } 365 } 366 367 /* 368 * Be careful not to send data and/or FIN on SYN segments. 369 * This measure is needed to prevent interoperability problems 370 * with not fully conformant TCP implementations. 371 */ 372 if (flags & TH_SYN) { 373 len = 0; 374 flags &= ~TH_FIN; 375 } 376 377 if (len < 0) { 378 /* 379 * A negative len can occur if our FIN has been sent but not 380 * acked, or if we are in a simultanious connect in the 381 * TCPS_SYN_RECEIVED state with our SYN sent but not yet 382 * acked. 383 * 384 * If our window has contracted to 0 in the FIN case 385 * (which can only occur if we have NOT been called to 386 * retransmit as per code a few paragraphs up) then we 387 * want to shift the retransmit timer over to the 388 * persist timer. 389 * 390 * However, if we are in the TCPS_SYN_RECEIVED state 391 * (the SYN case) we will be in a simultanious connect and 392 * the window may be zero degeneratively. In this case we 393 * do not want to shift to the persist timer after the SYN 394 * or the SYN+ACK transmission. 395 */ 396 len = 0; 397 if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) { 398 tcp_callout_stop(tp, tp->tt_rexmt); 399 tp->t_rxtshift = 0; 400 tp->snd_nxt = tp->snd_una; 401 if (!tcp_callout_active(tp, tp->tt_persist)) 402 tcp_setpersist(tp); 403 } 404 } 405 406 KASSERT(len >= 0, ("%s: len < 0", __func__)); 407 /* 408 * Automatic sizing of send socket buffer. Often the send buffer 409 * size is not optimally adjusted to the actual network conditions 410 * at hand (delay bandwidth product). Setting the buffer size too 411 * small limits throughput on links with high bandwidth and high 412 * delay (eg. trans-continental/oceanic links). Setting the 413 * buffer size too big consumes too much real kernel memory, 414 * especially with many connections on busy servers. 415 * 416 * The criteria to step up the send buffer one notch are: 417 * 1. receive window of remote host is larger than send buffer 418 * (with a fudge factor of 5/4th); 419 * 2. hiwat has not significantly exceeded bwnd (inflight) 420 * (bwnd is a maximal value if inflight is disabled). 421 * 3. send buffer is filled to 7/8th with data (so we actually 422 * have data to make use of it); 423 * 4. hiwat has not hit maximal automatic size; 424 * 5. our send window (slow start and cogestion controlled) is 425 * larger than sent but unacknowledged data in send buffer. 426 * 427 * The remote host receive window scaling factor may limit the 428 * growing of the send buffer before it reaches its allowed 429 * maximum. 430 * 431 * It scales directly with slow start or congestion window 432 * and does at most one step per received ACK. This fast 433 * scaling has the drawback of growing the send buffer beyond 434 * what is strictly necessary to make full use of a given 435 * delay*bandwith product. However testing has shown this not 436 * to be much of an problem. At worst we are trading wasting 437 * of available bandwith (the non-use of it) for wasting some 438 * socket buffer memory. 439 * 440 * The criteria for shrinking the buffer is based solely on 441 * the inflight code (snd_bwnd). If inflight is disabled, 442 * the buffer will not be shrinked. Note that snd_bwnd already 443 * has a fudge factor. Our test adds a little hysteresis. 444 */ 445 if (tcp_do_autosndbuf && (so->so_snd.ssb_flags & SSB_AUTOSIZE)) { 446 const int asbinc = tcp_autosndbuf_inc; 447 const int hiwat = so->so_snd.ssb_hiwat; 448 const int lowat = so->so_snd.ssb_lowat; 449 u_long newsize; 450 451 if ((tp->snd_wnd / 4 * 5) >= hiwat && 452 so->so_snd.ssb_cc >= (hiwat / 8 * 7) && 453 hiwat < tp->snd_bwnd + hiwat / 10 && 454 hiwat + asbinc < tcp_autosndbuf_max && 455 hiwat < (TCP_MAXWIN << tp->snd_scale) && 456 sendwin >= (so->so_snd.ssb_cc - 457 (tp->snd_nxt - tp->snd_una))) { 458 newsize = ulmin(hiwat + asbinc, tcp_autosndbuf_max); 459 if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) 460 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 461 #if 0 462 if (newsize >= (TCP_MAXWIN << tp->snd_scale)) 463 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 464 #endif 465 } else if ((long)tp->snd_bwnd < 466 (long)(hiwat * 3 / 4 - lowat - asbinc) && 467 hiwat > tp->t_maxseg * 2 + asbinc && 468 hiwat + asbinc >= tcp_autosndbuf_min && 469 tcp_do_autosndbuf == 1) { 470 newsize = ulmax(hiwat - asbinc, tp->t_maxseg * 2); 471 ssb_reserve(&so->so_snd, newsize, so, NULL); 472 } 473 } 474 475 /* 476 * Don't use TSO, if: 477 * - Congestion window needs validation 478 * - There are SACK blocks to report 479 * - RST or SYN flags is set 480 * - URG will be set 481 * 482 * XXX 483 * Checking for SYN|RST looks overkill, just to be safe than sorry 484 */ 485 use_tso = can_tso; 486 if (report_sack || idle_cwv || (flags & (TH_RST | TH_SYN))) 487 use_tso = FALSE; 488 if (use_tso) { 489 tcp_seq ugr_nxt = tp->snd_nxt; 490 491 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && 492 tp->snd_nxt == tp->snd_max) 493 --ugr_nxt; 494 495 if (SEQ_GT(tp->snd_up, ugr_nxt)) 496 use_tso = FALSE; 497 } 498 499 if (use_tso) { 500 /* 501 * Find out segment size and header length for TSO 502 */ 503 error = tcp_tso_getsize(tp, &segsz, &tso_hlen); 504 if (error) 505 use_tso = FALSE; 506 } 507 if (!use_tso) { 508 segsz = tp->t_maxseg; 509 tso_hlen = 0; /* not used */ 510 } 511 512 /* 513 * Truncate to the maximum segment length if not TSO, and ensure that 514 * FIN is removed if the length no longer contains the last data byte. 515 */ 516 if (len > segsz) { 517 if (!use_tso) { 518 len = segsz; 519 ++segcnt; 520 } else { 521 int nsegs; 522 523 if (__predict_false(tso_lenmax < segsz)) 524 tso_lenmax = segsz << 1; 525 526 /* 527 * Truncate TSO transfers to (IP_MAXPACKET - iphlen - 528 * thoff), and make sure that we send equal size 529 * transfers down the stack (rather than big-small- 530 * big-small-...). 531 */ 532 len = min(len, tso_lenmax); 533 nsegs = min(len, (IP_MAXPACKET - tso_hlen)) / segsz; 534 KKASSERT(nsegs > 0); 535 536 len = nsegs * segsz; 537 538 if (len <= segsz) { 539 use_tso = FALSE; 540 ++segcnt; 541 } else { 542 segcnt += nsegs; 543 } 544 } 545 sendalot = TRUE; 546 } else { 547 use_tso = FALSE; 548 if (len > 0) 549 ++segcnt; 550 } 551 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) 552 flags &= ~TH_FIN; 553 554 recvwin = ssb_space(&so->so_rcv); 555 556 /* 557 * Sender silly window avoidance. We transmit under the following 558 * conditions when len is non-zero: 559 * 560 * - We have a full segment 561 * - This is the last buffer in a write()/send() and we are 562 * either idle or running NODELAY 563 * - we've timed out (e.g. persist timer) 564 * - we have more then 1/2 the maximum send window's worth of 565 * data (receiver may be limiting the window size) 566 * - we need to retransmit 567 */ 568 if (len) { 569 if (len >= segsz) 570 goto send; 571 /* 572 * NOTE! on localhost connections an 'ack' from the remote 573 * end may occur synchronously with the output and cause 574 * us to flush a buffer queued with moretocome. XXX 575 * 576 * note: the len + off check is almost certainly unnecessary. 577 */ 578 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 579 (idle || (tp->t_flags & TF_NODELAY)) && 580 len + off >= so->so_snd.ssb_cc && 581 !(tp->t_flags & TF_NOPUSH)) { 582 goto send; 583 } 584 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 585 goto send; 586 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 587 goto send; 588 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 589 goto send; 590 if (tp->t_flags & TF_XMITNOW) 591 goto send; 592 } 593 594 /* 595 * Compare available window to amount of window 596 * known to peer (as advertised window less 597 * next expected input). If the difference is at least two 598 * max size segments, or at least 50% of the maximum possible 599 * window, then want to send a window update to peer. 600 */ 601 if (recvwin > 0) { 602 /* 603 * "adv" is the amount we can increase the window, 604 * taking into account that we are limited by 605 * TCP_MAXWIN << tp->rcv_scale. 606 */ 607 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 608 (tp->rcv_adv - tp->rcv_nxt); 609 long hiwat; 610 611 /* 612 * This ack case typically occurs when the user has drained 613 * the TCP socket buffer sufficiently to warrent an ack 614 * containing a 'pure window update'... that is, an ack that 615 * ONLY updates the tcp window. 616 * 617 * It is unclear why we would need to do a pure window update 618 * past 2 segments if we are going to do one at 1/2 the high 619 * water mark anyway, especially since under normal conditions 620 * the user program will drain the socket buffer quickly. 621 * The 2-segment pure window update will often add a large 622 * number of extra, unnecessary acks to the stream. 623 * 624 * avoid_pure_win_update now defaults to 1. 625 */ 626 if (avoid_pure_win_update == 0 || 627 (tp->t_flags & TF_RXRESIZED)) { 628 if (adv >= (long) (2 * segsz)) { 629 goto send; 630 } 631 } 632 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); 633 if (hiwat > (long)so->so_rcv.ssb_hiwat) 634 hiwat = (long)so->so_rcv.ssb_hiwat; 635 if (adv >= hiwat / 2) 636 goto send; 637 } 638 639 /* 640 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 641 * is also a catch-all for the retransmit timer timeout case. 642 */ 643 if (tp->t_flags & TF_ACKNOW) 644 goto send; 645 if ((flags & TH_RST) || 646 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 647 goto send; 648 if (SEQ_GT(tp->snd_up, tp->snd_una)) 649 goto send; 650 /* 651 * If our state indicates that FIN should be sent 652 * and we have not yet done so, then we need to send. 653 */ 654 if ((flags & TH_FIN) && 655 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 656 goto send; 657 658 /* 659 * TCP window updates are not reliable, rather a polling protocol 660 * using ``persist'' packets is used to insure receipt of window 661 * updates. The three ``states'' for the output side are: 662 * idle not doing retransmits or persists 663 * persisting to move a small or zero window 664 * (re)transmitting and thereby not persisting 665 * 666 * tcp_callout_active(tp, tp->tt_persist) 667 * is true when we are in persist state. 668 * The TF_FORCE flag in tp->t_flags 669 * is set when we are called to send a persist packet. 670 * tcp_callout_active(tp, tp->tt_rexmt) 671 * is set when we are retransmitting 672 * The output side is idle when both timers are zero. 673 * 674 * If send window is too small, there is data to transmit, and no 675 * retransmit or persist is pending, then go to persist state. 676 * 677 * If nothing happens soon, send when timer expires: 678 * if window is nonzero, transmit what we can, otherwise force out 679 * a byte. 680 * 681 * Don't try to set the persist state if we are in TCPS_SYN_RECEIVED 682 * with data pending. This situation can occur during a 683 * simultanious connect. 684 */ 685 if (so->so_snd.ssb_cc > 0 && 686 tp->t_state != TCPS_SYN_RECEIVED && 687 !tcp_callout_active(tp, tp->tt_rexmt) && 688 !tcp_callout_active(tp, tp->tt_persist)) { 689 tp->t_rxtshift = 0; 690 tcp_setpersist(tp); 691 } 692 693 /* 694 * No reason to send a segment, just return. 695 */ 696 tp->t_flags &= ~TF_XMITNOW; 697 return (0); 698 699 send: 700 if (need_sched && len > 0) { 701 tcp_output_sched(tp); 702 return 0; 703 } 704 705 /* 706 * Before ESTABLISHED, force sending of initial options 707 * unless TCP set not to do any options. 708 * NOTE: we assume that the IP/TCP header plus TCP options 709 * always fit in a single mbuf, leaving room for a maximum 710 * link header, i.e. 711 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 712 */ 713 optlen = 0; 714 if (isipv6) 715 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 716 else 717 hdrlen = sizeof(struct tcpiphdr); 718 if (flags & TH_SYN) { 719 tp->snd_nxt = tp->iss; 720 if (!(tp->t_flags & TF_NOOPT)) { 721 u_short mss; 722 723 opt[0] = TCPOPT_MAXSEG; 724 opt[1] = TCPOLEN_MAXSEG; 725 mss = htons((u_short) tcp_mssopt(tp)); 726 memcpy(opt + 2, &mss, sizeof mss); 727 optlen = TCPOLEN_MAXSEG; 728 729 if ((tp->t_flags & TF_REQ_SCALE) && 730 (!(flags & TH_ACK) || 731 (tp->t_flags & TF_RCVD_SCALE))) { 732 *((u_int32_t *)(opt + optlen)) = htonl( 733 TCPOPT_NOP << 24 | 734 TCPOPT_WINDOW << 16 | 735 TCPOLEN_WINDOW << 8 | 736 tp->request_r_scale); 737 optlen += 4; 738 } 739 740 if ((tcp_do_sack && !(flags & TH_ACK)) || 741 tp->t_flags & TF_SACK_PERMITTED) { 742 uint32_t *lp = (uint32_t *)(opt + optlen); 743 744 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 745 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 746 } 747 } 748 } 749 750 /* 751 * Send a timestamp and echo-reply if this is a SYN and our side 752 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 753 * and our peer have sent timestamps in our SYN's. 754 */ 755 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 756 !(flags & TH_RST) && 757 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 758 u_int32_t *lp = (u_int32_t *)(opt + optlen); 759 760 /* Form timestamp option as shown in appendix A of RFC 1323. */ 761 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 762 *lp++ = htonl(ticks); 763 *lp = htonl(tp->ts_recent); 764 optlen += TCPOLEN_TSTAMP_APPA; 765 } 766 767 /* Set receive buffer autosizing timestamp. */ 768 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) 769 tp->rfbuf_ts = ticks; 770 771 /* 772 * If this is a SACK connection and we have a block to report, 773 * fill in the SACK blocks in the TCP options. 774 */ 775 if (report_sack) 776 tcp_sack_fill_report(tp, opt, &optlen); 777 778 #ifdef TCP_SIGNATURE 779 if (tp->t_flags & TF_SIGNATURE) { 780 int i; 781 u_char *bp; 782 /* 783 * Initialize TCP-MD5 option (RFC2385) 784 */ 785 bp = (u_char *)opt + optlen; 786 *bp++ = TCPOPT_SIGNATURE; 787 *bp++ = TCPOLEN_SIGNATURE; 788 sigoff = optlen + 2; 789 for (i = 0; i < TCP_SIGLEN; i++) 790 *bp++ = 0; 791 optlen += TCPOLEN_SIGNATURE; 792 /* 793 * Terminate options list and maintain 32-bit alignment. 794 */ 795 *bp++ = TCPOPT_NOP; 796 *bp++ = TCPOPT_EOL; 797 optlen += 2; 798 } 799 #endif /* TCP_SIGNATURE */ 800 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 801 hdrlen += optlen; 802 803 if (isipv6) { 804 ipoptlen = ip6_optlen(inp); 805 } else { 806 if (inp->inp_options) { 807 ipoptlen = inp->inp_options->m_len - 808 offsetof(struct ipoption, ipopt_list); 809 } else { 810 ipoptlen = 0; 811 } 812 } 813 814 if (use_tso) { 815 /* TSO segment length must be multiple of segment size */ 816 KASSERT(len >= (2 * segsz) && (len % segsz == 0), 817 ("invalid TSO len %ld, segsz %u", len, segsz)); 818 } else { 819 KASSERT(len <= segsz, 820 ("invalid len %ld, segsz %u", len, segsz)); 821 822 /* 823 * Adjust data length if insertion of options will bump 824 * the packet length beyond the t_maxopd length. Clear 825 * FIN to prevent premature closure since there is still 826 * more data to send after this (now truncated) packet. 827 * 828 * If just the options do not fit we are in a no-win 829 * situation and we treat it as an unreachable host. 830 */ 831 if (len + optlen + ipoptlen > tp->t_maxopd) { 832 if (tp->t_maxopd <= optlen + ipoptlen) { 833 static time_t last_optlen_report; 834 835 if (last_optlen_report != time_uptime) { 836 last_optlen_report = time_uptime; 837 kprintf("tcpcb %p: MSS (%d) too " 838 "small to hold options!\n", 839 tp, tp->t_maxopd); 840 } 841 error = EHOSTUNREACH; 842 goto out; 843 } else { 844 flags &= ~TH_FIN; 845 len = tp->t_maxopd - optlen - ipoptlen; 846 sendalot = TRUE; 847 } 848 } 849 } 850 851 #ifdef INET6 852 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 853 #else 854 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 855 #endif 856 857 /* 858 * Grab a header mbuf, attaching a copy of data to 859 * be transmitted, and initialize the header from 860 * the template for sends on this connection. 861 */ 862 if (len) { 863 if ((tp->t_flags & TF_FORCE) && len == 1) 864 tcpstat.tcps_sndprobe++; 865 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 866 if (tp->snd_nxt == tp->snd_una) 867 tp->snd_max_rexmt = tp->snd_max; 868 if (nsacked) { 869 tcpstat.tcps_sndsackrtopack++; 870 tcpstat.tcps_sndsackrtobyte += len; 871 } 872 tcpstat.tcps_sndrexmitpack++; 873 tcpstat.tcps_sndrexmitbyte += len; 874 } else { 875 tcpstat.tcps_sndpack++; 876 tcpstat.tcps_sndbyte += len; 877 } 878 if (idle_cwv) { 879 idle_cwv = FALSE; 880 tcp_idle_cwnd_validate(tp); 881 } 882 /* Update last send time after CWV */ 883 tp->snd_last = ticks; 884 #ifdef notyet 885 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, 886 max_linkhdr + hdrlen)) == NULL) { 887 error = ENOBUFS; 888 goto after_th; 889 } 890 /* 891 * m_copypack left space for our hdr; use it. 892 */ 893 m->m_len += hdrlen; 894 m->m_data -= hdrlen; 895 #else 896 #ifndef INET6 897 m = m_gethdr(M_NOWAIT, MT_HEADER); 898 #else 899 m = m_getl(hdrlen + max_linkhdr, M_NOWAIT, MT_HEADER, 900 M_PKTHDR, NULL); 901 #endif 902 if (m == NULL) { 903 error = ENOBUFS; 904 goto after_th; 905 } 906 m->m_data += max_linkhdr; 907 m->m_len = hdrlen; 908 if (len <= MHLEN - hdrlen - max_linkhdr) { 909 m_copydata(so->so_snd.ssb_mb, off, (int) len, 910 mtod(m, caddr_t) + hdrlen); 911 m->m_len += len; 912 } else { 913 m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len); 914 if (m->m_next == NULL) { 915 m_free(m); 916 m = NULL; 917 error = ENOBUFS; 918 goto after_th; 919 } 920 } 921 #endif 922 /* 923 * If we're sending everything we've got, set PUSH. 924 * (This will keep happy those implementations which only 925 * give data to the user when a buffer fills or 926 * a PUSH comes in.) 927 */ 928 if (off + len == so->so_snd.ssb_cc) 929 flags |= TH_PUSH; 930 } else { 931 if (tp->t_flags & TF_ACKNOW) 932 tcpstat.tcps_sndacks++; 933 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 934 tcpstat.tcps_sndctrl++; 935 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 936 tcpstat.tcps_sndurg++; 937 else 938 tcpstat.tcps_sndwinup++; 939 940 MGETHDR(m, M_NOWAIT, MT_HEADER); 941 if (m == NULL) { 942 error = ENOBUFS; 943 goto after_th; 944 } 945 if (isipv6 && 946 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 947 MH_ALIGN(m, hdrlen); 948 else 949 m->m_data += max_linkhdr; 950 m->m_len = hdrlen; 951 952 /* 953 * Prioritize SYN, SYN|ACK and pure ACK. 954 * Leave FIN and RST as they are. 955 */ 956 if (tcp_prio_synack && (flags & (TH_FIN | TH_RST)) == 0) 957 m->m_flags |= M_PRIO; 958 } 959 m->m_pkthdr.rcvif = NULL; 960 if (isipv6) { 961 ip6 = mtod(m, struct ip6_hdr *); 962 th = (struct tcphdr *)(ip6 + 1); 963 tcp_fillheaders(tp, ip6, th, use_tso); 964 } else { 965 ip = mtod(m, struct ip *); 966 th = (struct tcphdr *)(ip + 1); 967 /* this picks up the pseudo header (w/o the length) */ 968 tcp_fillheaders(tp, ip, th, use_tso); 969 } 970 after_th: 971 /* 972 * Fill in fields, remembering maximum advertised 973 * window for use in delaying messages about window sizes. 974 * If resending a FIN, be sure not to use a new sequence number. 975 */ 976 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 977 tp->snd_nxt == tp->snd_max) 978 tp->snd_nxt--; 979 980 if (th != NULL) { 981 /* 982 * If we are doing retransmissions, then snd_nxt will 983 * not reflect the first unsent octet. For ACK only 984 * packets, we do not want the sequence number of the 985 * retransmitted packet, we want the sequence number 986 * of the next unsent octet. So, if there is no data 987 * (and no SYN or FIN), use snd_max instead of snd_nxt 988 * when filling in ti_seq. But if we are in persist 989 * state, snd_max might reflect one byte beyond the 990 * right edge of the window, so use snd_nxt in that 991 * case, since we know we aren't doing a retransmission. 992 * (retransmit and persist are mutually exclusive...) 993 */ 994 if (len || (flags & (TH_SYN|TH_FIN)) || 995 tcp_callout_active(tp, tp->tt_persist)) 996 th->th_seq = htonl(tp->snd_nxt); 997 else 998 th->th_seq = htonl(tp->snd_max); 999 th->th_ack = htonl(tp->rcv_nxt); 1000 if (optlen) { 1001 bcopy(opt, th + 1, optlen); 1002 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1003 } 1004 th->th_flags = flags; 1005 } 1006 1007 /* 1008 * Calculate receive window. Don't shrink window, but avoid 1009 * silly window syndrome by sending a 0 window if the actual 1010 * window is less then one segment. 1011 */ 1012 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && 1013 recvwin < (long)segsz) 1014 recvwin = 0; 1015 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt)) 1016 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt); 1017 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 1018 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 1019 1020 /* 1021 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1022 * a 0 window. This may cause the remote transmitter to stall. This 1023 * flag tells soreceive() to disable delayed acknowledgements when 1024 * draining the buffer. This can occur if the receiver is attempting 1025 * to read more data then can be buffered prior to transmitting on 1026 * the connection. 1027 */ 1028 if (recvwin == 0) 1029 tp->t_flags |= TF_RXWIN0SENT; 1030 else 1031 tp->t_flags &= ~TF_RXWIN0SENT; 1032 1033 if (th != NULL) 1034 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 1035 1036 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1037 KASSERT(!use_tso, ("URG with TSO")); 1038 if (th != NULL) { 1039 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1040 th->th_flags |= TH_URG; 1041 } 1042 } else { 1043 /* 1044 * If no urgent pointer to send, then we pull 1045 * the urgent pointer to the left edge of the send window 1046 * so that it doesn't drift into the send window on sequence 1047 * number wraparound. 1048 */ 1049 tp->snd_up = tp->snd_una; /* drag it along */ 1050 } 1051 1052 if (th != NULL) { 1053 #ifdef TCP_SIGNATURE 1054 if (tp->t_flags & TF_SIGNATURE) { 1055 tcpsignature_compute(m, len, optlen, 1056 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1057 } 1058 #endif /* TCP_SIGNATURE */ 1059 1060 /* 1061 * Put TCP length in extended header, and then 1062 * checksum extended header and data. 1063 */ 1064 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1065 if (isipv6) { 1066 /* 1067 * ip6_plen is not need to be filled now, and will be 1068 * filled in ip6_output(). 1069 */ 1070 th->th_sum = in6_cksum(m, IPPROTO_TCP, 1071 sizeof(struct ip6_hdr), 1072 sizeof(struct tcphdr) + optlen + len); 1073 } else { 1074 m->m_pkthdr.csum_thlen = sizeof(struct tcphdr) + optlen; 1075 if (use_tso) { 1076 m->m_pkthdr.csum_flags = CSUM_TSO; 1077 m->m_pkthdr.tso_segsz = segsz; 1078 } else { 1079 m->m_pkthdr.csum_flags = CSUM_TCP; 1080 m->m_pkthdr.csum_data = 1081 offsetof(struct tcphdr, th_sum); 1082 if (len + optlen) { 1083 th->th_sum = in_addword(th->th_sum, 1084 htons((u_short)(optlen + len))); 1085 } 1086 } 1087 1088 /* 1089 * IP version must be set here for ipv4/ipv6 checking 1090 * later 1091 */ 1092 KASSERT(ip->ip_v == IPVERSION, 1093 ("%s: IP version incorrect: %d", 1094 __func__, ip->ip_v)); 1095 } 1096 } 1097 1098 /* 1099 * In transmit state, time the transmission and arrange for 1100 * the retransmit. In persist state, just set snd_max. 1101 */ 1102 if (!(tp->t_flags & TF_FORCE) || 1103 !tcp_callout_active(tp, tp->tt_persist)) { 1104 tcp_seq startseq = tp->snd_nxt; 1105 1106 /* 1107 * Advance snd_nxt over sequence space of this segment. 1108 */ 1109 if (flags & (TH_SYN | TH_FIN)) { 1110 if (flags & TH_SYN) 1111 tp->snd_nxt++; 1112 if (flags & TH_FIN) { 1113 tp->snd_nxt++; 1114 tp->t_flags |= TF_SENTFIN; 1115 } 1116 } 1117 tp->snd_nxt += len; 1118 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1119 tp->snd_max = tp->snd_nxt; 1120 /* 1121 * Time this transmission if not a retransmission and 1122 * not currently timing anything. 1123 */ 1124 if (tp->t_rtttime == 0) { 1125 tp->t_rtttime = ticks; 1126 tp->t_rtseq = startseq; 1127 tcpstat.tcps_segstimed++; 1128 } 1129 } 1130 1131 /* 1132 * Set retransmit timer if not currently set, 1133 * and not doing a pure ack or a keep-alive probe. 1134 * Initial value for retransmit timer is smoothed 1135 * round-trip time + 2 * round-trip time variance. 1136 * Initialize shift counter which is used for backoff 1137 * of retransmit time. 1138 */ 1139 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1140 tp->snd_nxt != tp->snd_una) { 1141 if (tcp_callout_active(tp, tp->tt_persist)) { 1142 tcp_callout_stop(tp, tp->tt_persist); 1143 tp->t_rxtshift = 0; 1144 } 1145 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 1146 tcp_timer_rexmt); 1147 } else if (len == 0 && so->so_snd.ssb_cc && 1148 tp->t_state > TCPS_SYN_RECEIVED && 1149 !tcp_callout_active(tp, tp->tt_rexmt) && 1150 !tcp_callout_active(tp, tp->tt_persist)) { 1151 /* 1152 * Avoid a situation where we do not set persist timer 1153 * after a zero window condition. For example: 1154 * 1) A -> B: packet with enough data to fill the window 1155 * 2) B -> A: ACK for #1 + new data (0 window 1156 * advertisement) 1157 * 3) A -> B: ACK for #2, 0 len packet 1158 * 1159 * In this case, A will not activate the persist timer, 1160 * because it chose to send a packet. Unless tcp_output 1161 * is called for some other reason (delayed ack timer, 1162 * another input packet from B, socket syscall), A will 1163 * not send zero window probes. 1164 * 1165 * So, if you send a 0-length packet, but there is data 1166 * in the socket buffer, and neither the rexmt or 1167 * persist timer is already set, then activate the 1168 * persist timer. 1169 */ 1170 tp->t_rxtshift = 0; 1171 tcp_setpersist(tp); 1172 } 1173 } else { 1174 /* 1175 * Persist case, update snd_max but since we are in 1176 * persist mode (no window) we do not update snd_nxt. 1177 */ 1178 int xlen = len; 1179 if (flags & TH_SYN) 1180 panic("tcp_output: persist timer to send SYN"); 1181 if (flags & TH_FIN) { 1182 ++xlen; 1183 tp->t_flags |= TF_SENTFIN; 1184 } 1185 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1186 tp->snd_max = tp->snd_nxt + xlen; 1187 } 1188 1189 if (th != NULL) { 1190 #ifdef TCPDEBUG 1191 /* Trace. */ 1192 if (so->so_options & SO_DEBUG) { 1193 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1194 mtod(m, void *), th, 0); 1195 } 1196 #endif 1197 1198 /* 1199 * Fill in IP length and desired time to live and 1200 * send to IP level. There should be a better way 1201 * to handle ttl and tos; we could keep them in 1202 * the template, but need a way to checksum without them. 1203 */ 1204 /* 1205 * m->m_pkthdr.len should have been set before cksum 1206 * calcuration, because in6_cksum() need it. 1207 */ 1208 if (isipv6) { 1209 /* 1210 * we separately set hoplimit for every segment, 1211 * since the user might want to change the value 1212 * via setsockopt. Also, desired default hop 1213 * limit might be changed via Neighbor Discovery. 1214 */ 1215 ip6->ip6_hlim = in6_selecthlim(inp, 1216 (inp->in6p_route.ro_rt ? 1217 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1218 1219 /* TODO: IPv6 IP6TOS_ECT bit on */ 1220 error = ip6_output(m, inp->in6p_outputopts, 1221 &inp->in6p_route, (so->so_options & SO_DONTROUTE), 1222 NULL, NULL, inp); 1223 } else { 1224 struct rtentry *rt; 1225 1226 KASSERT(!INP_CHECK_SOCKAF(so, AF_INET6), ("inet6 pcb")); 1227 1228 ip->ip_len = m->m_pkthdr.len; 1229 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1230 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1231 /* 1232 * See if we should do MTU discovery. 1233 * We do it only if the following are true: 1234 * 1) we have a valid route to the destination 1235 * 2) the MTU is not locked (if it is, 1236 * then discovery has been disabled) 1237 */ 1238 if (path_mtu_discovery && 1239 (rt = inp->inp_route.ro_rt) && 1240 (rt->rt_flags & RTF_UP) && 1241 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 1242 ip->ip_off |= IP_DF; 1243 1244 KASSERT(inp->inp_flags & INP_HASH, 1245 ("inpcb has no hash")); 1246 m_sethash(m, inp->inp_hashval); 1247 error = ip_output(m, inp->inp_options, &inp->inp_route, 1248 (so->so_options & SO_DONTROUTE) | 1249 IP_DEBUGROUTE, NULL, inp); 1250 } 1251 } else { 1252 KASSERT(error != 0, ("no error, but th not set")); 1253 } 1254 if (error) { 1255 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1256 1257 /* 1258 * We know that the packet was lost, so back out the 1259 * sequence number advance, if any. 1260 */ 1261 if (!(tp->t_flags & TF_FORCE) || 1262 !tcp_callout_active(tp, tp->tt_persist)) { 1263 /* 1264 * No need to check for TH_FIN here because 1265 * the TF_SENTFIN flag handles that case. 1266 */ 1267 if (!(flags & TH_SYN)) 1268 tp->snd_nxt -= len; 1269 } 1270 1271 out: 1272 if (error == ENOBUFS) { 1273 KASSERT((len == 0 && (flags & (TH_SYN | TH_FIN)) == 0) || 1274 tcp_callout_active(tp, tp->tt_rexmt) || 1275 tcp_callout_active(tp, tp->tt_persist), 1276 ("neither rexmt nor persist timer is set")); 1277 return (0); 1278 } 1279 if (error == EMSGSIZE) { 1280 /* 1281 * ip_output() will have already fixed the route 1282 * for us. tcp_mtudisc() will, as its last action, 1283 * initiate retransmission, so it is important to 1284 * not do so here. 1285 */ 1286 tcp_mtudisc(inp, 0); 1287 return 0; 1288 } 1289 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1290 TCPS_HAVERCVDSYN(tp->t_state)) { 1291 tp->t_softerror = error; 1292 return (0); 1293 } 1294 return (error); 1295 } 1296 tcpstat.tcps_sndtotal++; 1297 1298 /* 1299 * Data sent (as far as we can tell). 1300 * 1301 * If this advertises a larger window than any other segment, 1302 * then remember the size of the advertised window. 1303 * 1304 * Any pending ACK has now been sent. 1305 */ 1306 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) { 1307 tp->rcv_adv = tp->rcv_nxt + recvwin; 1308 tp->t_flags &= ~TF_RXRESIZED; 1309 } 1310 tp->last_ack_sent = tp->rcv_nxt; 1311 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW); 1312 if (tcp_delack_enabled) 1313 tcp_callout_stop(tp, tp->tt_delack); 1314 if (sendalot) { 1315 if (tcp_fairsend > 0 && (tp->t_flags & TF_FAIRSEND) && 1316 segcnt >= tcp_fairsend) 1317 need_sched = TRUE; 1318 goto again; 1319 } 1320 return (0); 1321 } 1322 1323 void 1324 tcp_setpersist(struct tcpcb *tp) 1325 { 1326 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1327 int tt; 1328 1329 if (tp->t_state == TCPS_SYN_SENT || 1330 tp->t_state == TCPS_SYN_RECEIVED) { 1331 panic("tcp_setpersist: not established yet, current %s", 1332 tp->t_state == TCPS_SYN_SENT ? 1333 "SYN_SENT" : "SYN_RECEIVED"); 1334 } 1335 1336 if (tcp_callout_active(tp, tp->tt_rexmt)) 1337 panic("tcp_setpersist: retransmit pending"); 1338 /* 1339 * Start/restart persistance timer. 1340 */ 1341 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1342 TCPTV_PERSMAX); 1343 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist); 1344 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1345 tp->t_rxtshift++; 1346 } 1347 1348 static void 1349 tcp_idle_cwnd_validate(struct tcpcb *tp) 1350 { 1351 u_long initial_cwnd = tcp_initial_window(tp); 1352 u_long min_cwnd; 1353 1354 tcpstat.tcps_sndidle++; 1355 1356 /* According to RFC5681: RW=min(IW,cwnd) */ 1357 min_cwnd = min(tp->snd_cwnd, initial_cwnd); 1358 1359 if (tcp_idle_cwv) { 1360 u_long idle_time, decay_cwnd; 1361 1362 /* 1363 * RFC2861, but only after idle period. 1364 */ 1365 1366 /* 1367 * Before the congestion window is reduced, ssthresh 1368 * is set to the maximum of its current value and 3/4 1369 * cwnd. If the sender then has more data to send 1370 * than the decayed cwnd allows, the TCP will slow- 1371 * start (perform exponential increase) at least 1372 * half-way back up to the old value of cwnd. 1373 */ 1374 tp->snd_ssthresh = max(tp->snd_ssthresh, 1375 (3 * tp->snd_cwnd) / 4); 1376 1377 /* 1378 * Decay the congestion window by half for every RTT 1379 * that the flow remains inactive. 1380 * 1381 * The difference between our implementation and 1382 * RFC2861 is that we don't allow cwnd to go below 1383 * the value allowed by RFC5681 (min_cwnd). 1384 */ 1385 idle_time = ticks - tp->snd_last; 1386 decay_cwnd = tp->snd_cwnd; 1387 while (idle_time >= tp->t_rxtcur && 1388 decay_cwnd > min_cwnd) { 1389 decay_cwnd >>= 1; 1390 idle_time -= tp->t_rxtcur; 1391 } 1392 tp->snd_cwnd = max(decay_cwnd, min_cwnd); 1393 } else { 1394 /* 1395 * Slow-start from scratch to re-determine the send 1396 * congestion window. 1397 */ 1398 tp->snd_cwnd = min_cwnd; 1399 } 1400 1401 /* Restart ABC counting during congestion avoidance */ 1402 tp->snd_wacked = 0; 1403 } 1404 1405 static int 1406 tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen0) 1407 { 1408 struct inpcb * const inp = tp->t_inpcb; 1409 #ifdef INET6 1410 const boolean_t isipv6 = INP_ISIPV6(inp); 1411 #else 1412 const boolean_t isipv6 = FALSE; 1413 #endif 1414 unsigned int ipoptlen, optlen; 1415 u_int hlen; 1416 1417 hlen = sizeof(struct ip) + sizeof(struct tcphdr); 1418 1419 if (isipv6) { 1420 ipoptlen = ip6_optlen(inp); 1421 } else { 1422 if (inp->inp_options) { 1423 ipoptlen = inp->inp_options->m_len - 1424 offsetof(struct ipoption, ipopt_list); 1425 } else { 1426 ipoptlen = 0; 1427 } 1428 } 1429 hlen += ipoptlen; 1430 1431 optlen = 0; 1432 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 1433 (tp->t_flags & TF_RCVD_TSTMP)) 1434 optlen += TCPOLEN_TSTAMP_APPA; 1435 hlen += optlen; 1436 1437 if (tp->t_maxopd <= optlen + ipoptlen) 1438 return EHOSTUNREACH; 1439 1440 *segsz = tp->t_maxopd - optlen - ipoptlen; 1441 *hlen0 = hlen; 1442 return 0; 1443 } 1444 1445 static void 1446 tcp_output_sched_handler(netmsg_t nmsg) 1447 { 1448 struct tcpcb *tp = nmsg->lmsg.u.ms_resultp; 1449 1450 /* Reply ASAP */ 1451 crit_enter(); 1452 lwkt_replymsg(&nmsg->lmsg, 0); 1453 crit_exit(); 1454 1455 tcp_output_fair(tp); 1456 } 1457 1458 void 1459 tcp_output_init(struct tcpcb *tp) 1460 { 1461 netmsg_init(tp->tt_sndmore, NULL, &netisr_adone_rport, MSGF_DROPABLE, 1462 tcp_output_sched_handler); 1463 tp->tt_sndmore->lmsg.u.ms_resultp = tp; 1464 } 1465 1466 void 1467 tcp_output_cancel(struct tcpcb *tp) 1468 { 1469 /* 1470 * This message is still pending to be processed; 1471 * drop it. Optimized. 1472 */ 1473 crit_enter(); 1474 if ((tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) == 0) { 1475 lwkt_dropmsg(&tp->tt_sndmore->lmsg); 1476 } 1477 crit_exit(); 1478 } 1479 1480 boolean_t 1481 tcp_output_pending(struct tcpcb *tp) 1482 { 1483 if ((tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) == 0) 1484 return TRUE; 1485 else 1486 return FALSE; 1487 } 1488 1489 static void 1490 tcp_output_sched(struct tcpcb *tp) 1491 { 1492 crit_enter(); 1493 if (tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) 1494 lwkt_sendmsg(netisr_cpuport(mycpuid), &tp->tt_sndmore->lmsg); 1495 crit_exit(); 1496 } 1497 1498 /* 1499 * Fairsend 1500 * 1501 * Yield to other senders or receivers on the same netisr if the current 1502 * TCP stream has sent tcp_fairsend segments and is going to burst more 1503 * segments. Bursting large amount of segements in a single TCP stream 1504 * could delay other senders' segments and receivers' ACKs quite a lot, 1505 * if others segments and ACKs are queued on to the same hardware transmit 1506 * queue; thus cause unfairness between senders and suppress receiving 1507 * performance. 1508 * 1509 * Fairsend should be performed at the places that do not affect segment 1510 * sending during congestion control, e.g. 1511 * - User requested output 1512 * - ACK input triggered output 1513 * 1514 * NOTE: 1515 * For devices that are TSO capable, their TSO aggregation size limit could 1516 * affect fairsend. 1517 */ 1518 int 1519 tcp_output_fair(struct tcpcb *tp) 1520 { 1521 int ret; 1522 1523 tp->t_flags |= TF_FAIRSEND; 1524 ret = tcp_output(tp); 1525 tp->t_flags &= ~TF_FAIRSEND; 1526 1527 return ret; 1528 } 1529