1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 34 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 35 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.11 2004/04/07 17:01:25 dillon Exp $ 36 */ 37 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/kernel.h> 45 #include <sys/sysctl.h> 46 #include <sys/mbuf.h> 47 #include <sys/domain.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/in_cksum.h> 52 #include <sys/thread.h> 53 #include <sys/globaldata.h> 54 55 #include <net/route.h> 56 57 #include <netinet/in.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/in_pcb.h> 61 #include <netinet/ip_var.h> 62 #include <netinet6/in6_pcb.h> 63 #include <netinet/ip6.h> 64 #include <netinet6/ip6_var.h> 65 #include <netinet/tcp.h> 66 #define TCPOUTFLAGS 67 #include <netinet/tcp_fsm.h> 68 #include <netinet/tcp_seq.h> 69 #include <netinet/tcp_timer.h> 70 #include <netinet/tcp_var.h> 71 #include <netinet/tcpip.h> 72 #ifdef TCPDEBUG 73 #include <netinet/tcp_debug.h> 74 #endif 75 76 #ifdef IPSEC 77 #include <netinet6/ipsec.h> 78 #endif /*IPSEC*/ 79 80 #ifdef FAST_IPSEC 81 #include <netipsec/ipsec.h> 82 #define IPSEC 83 #endif /*FAST_IPSEC*/ 84 85 #ifdef notyet 86 extern struct mbuf *m_copypack(); 87 #endif 88 89 int path_mtu_discovery = 1; 90 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 91 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 92 93 int ss_fltsz = 1; 94 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 95 &ss_fltsz, 1, "Slow start flight size"); 96 97 int ss_fltsz_local = 4; 98 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 99 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 100 101 int tcp_do_newreno = 1; 102 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 103 0, "Enable NewReno Algorithms"); 104 105 /* 106 * Tcp output routine: figure out what should be sent and send it. 107 */ 108 int 109 tcp_output(tp) 110 struct tcpcb *tp; 111 { 112 struct inpcb * const inp = tp->t_inpcb; 113 struct socket *so = inp->inp_socket; 114 long len, recvwin, sendwin; 115 int off, flags, error; 116 struct mbuf *m; 117 struct ip *ip = NULL; 118 struct ipovly *ipov = NULL; 119 struct tcphdr *th; 120 u_char opt[TCP_MAXOLEN]; 121 unsigned ipoptlen, optlen, hdrlen; 122 int idle, sendalot; 123 struct ip6_hdr *ip6 = NULL; 124 #ifdef INET6 125 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 126 #else 127 const boolean_t isipv6 = FALSE; 128 #endif 129 struct rmxp_tao *taop; 130 131 /* 132 * Determine length of data that should be transmitted, 133 * and flags that will be used. 134 * If there is some data or critical controls (SYN, RST) 135 * to send, then transmit; otherwise, investigate further. 136 */ 137 if ((tp->snd_max == tp->snd_una) && 138 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 139 /* 140 * We have been idle for "a while" and no acks are 141 * expected to clock out any data we send -- 142 * slow start to get ack "clock" running again. 143 * 144 * Set the slow-start flight size depending on whether 145 * this is a local network or not. 146 */ 147 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 148 (!isipv6 && in_localaddr(inp->inp_faddr))) 149 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 150 else 151 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 152 } 153 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 154 if (idle && (tp->t_flags & TF_MORETOCOME)) 155 tp->t_flags |= TF_LASTIDLE; 156 else 157 tp->t_flags &= ~TF_LASTIDLE; 158 159 again: 160 sendalot = 0; 161 off = tp->snd_nxt - tp->snd_una; 162 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 163 sendwin = min(sendwin, tp->snd_bwnd); 164 165 flags = tcp_outflags[tp->t_state]; 166 /* 167 * Get standard flags, and add SYN or FIN if requested by 'hidden' 168 * state flags. 169 */ 170 if (tp->t_flags & TF_NEEDFIN) 171 flags |= TH_FIN; 172 if (tp->t_flags & TF_NEEDSYN) 173 flags |= TH_SYN; 174 175 /* 176 * If in persist timeout with window of 0, send 1 byte. 177 * Otherwise, if window is small but nonzero 178 * and timer expired, we will send what we can 179 * and go to transmit state. 180 */ 181 if (tp->t_force) { 182 if (sendwin == 0) { 183 /* 184 * If we still have some data to send, then 185 * clear the FIN bit. Usually this would 186 * happen below when it realizes that we 187 * aren't sending all the data. However, 188 * if we have exactly 1 byte of unsent data, 189 * then it won't clear the FIN bit below, 190 * and if we are in persist state, we wind 191 * up sending the packet without recording 192 * that we sent the FIN bit. 193 * 194 * We can't just blindly clear the FIN bit, 195 * because if we don't have any more data 196 * to send then the probe will be the FIN 197 * itself. 198 */ 199 if (off < so->so_snd.sb_cc) 200 flags &= ~TH_FIN; 201 sendwin = 1; 202 } else { 203 callout_stop(tp->tt_persist); 204 tp->t_rxtshift = 0; 205 } 206 } 207 208 /* 209 * If snd_nxt == snd_max and we have transmitted a FIN, the 210 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 211 * a negative length. This can also occur when TCP opens up 212 * its congestion window while receiving additional duplicate 213 * acks after fast-retransmit because TCP will reset snd_nxt 214 * to snd_max after the fast-retransmit. 215 * 216 * In the normal retransmit-FIN-only case, however, snd_nxt will 217 * be set to snd_una, the offset will be 0, and the length may 218 * wind up 0. 219 */ 220 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 221 222 /* 223 * Lop off SYN bit if it has already been sent. However, if this 224 * is SYN-SENT state and if segment contains data and if we don't 225 * know that foreign host supports TAO, suppress sending segment. 226 */ 227 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 228 flags &= ~TH_SYN; 229 off--, len++; 230 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 231 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 232 taop->tao_ccsent == 0)) 233 return 0; 234 } 235 236 /* 237 * Be careful not to send data and/or FIN on SYN segments 238 * in cases when no CC option will be sent. 239 * This measure is needed to prevent interoperability problems 240 * with not fully conformant TCP implementations. 241 */ 242 if ((flags & TH_SYN) && 243 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 244 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 245 len = 0; 246 flags &= ~TH_FIN; 247 } 248 249 if (len < 0) { 250 /* 251 * If FIN has been sent but not acked, 252 * but we haven't been called to retransmit, 253 * len will be < 0. Otherwise, window shrank 254 * after we sent into it. If window shrank to 0, 255 * cancel pending retransmit, pull snd_nxt back 256 * to (closed) window, and set the persist timer 257 * if it isn't already going. If the window didn't 258 * close completely, just wait for an ACK. 259 */ 260 len = 0; 261 if (sendwin == 0) { 262 callout_stop(tp->tt_rexmt); 263 tp->t_rxtshift = 0; 264 tp->snd_nxt = tp->snd_una; 265 if (!callout_active(tp->tt_persist)) 266 tcp_setpersist(tp); 267 } 268 } 269 270 /* 271 * len will be >= 0 after this point. Truncate to the maximum 272 * segment length and ensure that FIN is removed if the length 273 * no longer contains the last data byte. 274 */ 275 if (len > tp->t_maxseg) { 276 len = tp->t_maxseg; 277 sendalot = 1; 278 } 279 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 280 flags &= ~TH_FIN; 281 282 recvwin = sbspace(&so->so_rcv); 283 284 /* 285 * Sender silly window avoidance. We transmit under the following 286 * conditions when len is non-zero: 287 * 288 * - We have a full segment 289 * - This is the last buffer in a write()/send() and we are 290 * either idle or running NODELAY 291 * - we've timed out (e.g. persist timer) 292 * - we have more then 1/2 the maximum send window's worth of 293 * data (receiver may be limited the window size) 294 * - we need to retransmit 295 */ 296 if (len) { 297 if (len == tp->t_maxseg) 298 goto send; 299 /* 300 * NOTE! on localhost connections an 'ack' from the remote 301 * end may occur synchronously with the output and cause 302 * us to flush a buffer queued with moretocome. XXX 303 * 304 * note: the len + off check is almost certainly unnecessary. 305 */ 306 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 307 (idle || (tp->t_flags & TF_NODELAY)) && 308 len + off >= so->so_snd.sb_cc && 309 !(tp->t_flags & TF_NOPUSH)) { 310 goto send; 311 } 312 if (tp->t_force) /* typ. timeout case */ 313 goto send; 314 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 315 goto send; 316 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 317 goto send; 318 } 319 320 /* 321 * Compare available window to amount of window 322 * known to peer (as advertised window less 323 * next expected input). If the difference is at least two 324 * max size segments, or at least 50% of the maximum possible 325 * window, then want to send a window update to peer. 326 */ 327 if (recvwin > 0) { 328 /* 329 * "adv" is the amount we can increase the window, 330 * taking into account that we are limited by 331 * TCP_MAXWIN << tp->rcv_scale. 332 */ 333 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 334 (tp->rcv_adv - tp->rcv_nxt); 335 336 if (adv >= (long) (2 * tp->t_maxseg)) 337 goto send; 338 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 339 goto send; 340 } 341 342 /* 343 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 344 * is also a catch-all for the retransmit timer timeout case. 345 */ 346 if (tp->t_flags & TF_ACKNOW) 347 goto send; 348 if ((flags & TH_RST) || 349 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 350 goto send; 351 if (SEQ_GT(tp->snd_up, tp->snd_una)) 352 goto send; 353 /* 354 * If our state indicates that FIN should be sent 355 * and we have not yet done so, then we need to send. 356 */ 357 if (flags & TH_FIN && 358 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 359 goto send; 360 361 /* 362 * TCP window updates are not reliable, rather a polling protocol 363 * using ``persist'' packets is used to insure receipt of window 364 * updates. The three ``states'' for the output side are: 365 * idle not doing retransmits or persists 366 * persisting to move a small or zero window 367 * (re)transmitting and thereby not persisting 368 * 369 * callout_active(tp->tt_persist) 370 * is true when we are in persist state. 371 * tp->t_force 372 * is set when we are called to send a persist packet. 373 * callout_active(tp->tt_rexmt) 374 * is set when we are retransmitting 375 * The output side is idle when both timers are zero. 376 * 377 * If send window is too small, there is data to transmit, and no 378 * retransmit or persist is pending, then go to persist state. 379 * If nothing happens soon, send when timer expires: 380 * if window is nonzero, transmit what we can, 381 * otherwise force out a byte. 382 */ 383 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 384 !callout_active(tp->tt_persist)) { 385 tp->t_rxtshift = 0; 386 tcp_setpersist(tp); 387 } 388 389 /* 390 * No reason to send a segment, just return. 391 */ 392 return (0); 393 394 send: 395 /* 396 * Before ESTABLISHED, force sending of initial options 397 * unless TCP set not to do any options. 398 * NOTE: we assume that the IP/TCP header plus TCP options 399 * always fit in a single mbuf, leaving room for a maximum 400 * link header, i.e. 401 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 402 */ 403 optlen = 0; 404 if (isipv6) 405 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 406 else 407 hdrlen = sizeof(struct tcpiphdr); 408 if (flags & TH_SYN) { 409 tp->snd_nxt = tp->iss; 410 if (!(tp->t_flags & TF_NOOPT)) { 411 u_short mss; 412 413 opt[0] = TCPOPT_MAXSEG; 414 opt[1] = TCPOLEN_MAXSEG; 415 mss = htons((u_short) tcp_mssopt(tp)); 416 (void)memcpy(opt + 2, &mss, sizeof(mss)); 417 optlen = TCPOLEN_MAXSEG; 418 419 if ((tp->t_flags & TF_REQ_SCALE) && 420 (!(flags & TH_ACK) || 421 (tp->t_flags & TF_RCVD_SCALE))) { 422 *((u_int32_t *)(opt + optlen)) = htonl( 423 TCPOPT_NOP << 24 | 424 TCPOPT_WINDOW << 16 | 425 TCPOLEN_WINDOW << 8 | 426 tp->request_r_scale); 427 optlen += 4; 428 } 429 } 430 } 431 432 /* 433 * Send a timestamp and echo-reply if this is a SYN and our side 434 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 435 * and our peer have sent timestamps in our SYN's. 436 */ 437 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 438 !(flags & TH_RST) && 439 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 440 u_int32_t *lp = (u_int32_t *)(opt + optlen); 441 442 /* Form timestamp option as shown in appendix A of RFC 1323. */ 443 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 444 *lp++ = htonl(ticks); 445 *lp = htonl(tp->ts_recent); 446 optlen += TCPOLEN_TSTAMP_APPA; 447 } 448 449 /* 450 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 451 * options are allowed (!TF_NOOPT) and it's not a RST. 452 */ 453 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 454 !(flags & TH_RST)) { 455 switch (flags & (TH_SYN|TH_ACK)) { 456 /* 457 * This is a normal ACK, send CC if we received CC before 458 * from our peer. 459 */ 460 case TH_ACK: 461 if (!(tp->t_flags & TF_RCVD_CC)) 462 break; 463 /*FALLTHROUGH*/ 464 465 /* 466 * We can only get here in T/TCP's SYN_SENT* state, when 467 * we're a sending a non-SYN segment without waiting for 468 * the ACK of our SYN. A check above assures that we only 469 * do this if our peer understands T/TCP. 470 */ 471 case 0: 472 opt[optlen++] = TCPOPT_NOP; 473 opt[optlen++] = TCPOPT_NOP; 474 opt[optlen++] = TCPOPT_CC; 475 opt[optlen++] = TCPOLEN_CC; 476 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 477 478 optlen += 4; 479 break; 480 481 /* 482 * This is our initial SYN, check whether we have to use 483 * CC or CC.new. 484 */ 485 case TH_SYN: 486 opt[optlen++] = TCPOPT_NOP; 487 opt[optlen++] = TCPOPT_NOP; 488 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 489 TCPOPT_CCNEW : TCPOPT_CC; 490 opt[optlen++] = TCPOLEN_CC; 491 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 492 optlen += 4; 493 break; 494 495 /* 496 * This is a SYN,ACK; send CC and CC.echo if we received 497 * CC from our peer. 498 */ 499 case (TH_SYN|TH_ACK): 500 if (tp->t_flags & TF_RCVD_CC) { 501 opt[optlen++] = TCPOPT_NOP; 502 opt[optlen++] = TCPOPT_NOP; 503 opt[optlen++] = TCPOPT_CC; 504 opt[optlen++] = TCPOLEN_CC; 505 *(u_int32_t *)&opt[optlen] = 506 htonl(tp->cc_send); 507 optlen += 4; 508 opt[optlen++] = TCPOPT_NOP; 509 opt[optlen++] = TCPOPT_NOP; 510 opt[optlen++] = TCPOPT_CCECHO; 511 opt[optlen++] = TCPOLEN_CC; 512 *(u_int32_t *)&opt[optlen] = 513 htonl(tp->cc_recv); 514 optlen += 4; 515 } 516 break; 517 } 518 } 519 520 hdrlen += optlen; 521 522 if (isipv6) 523 ipoptlen = ip6_optlen(inp); 524 else { 525 if (inp->inp_options) { 526 ipoptlen = inp->inp_options->m_len - 527 offsetof(struct ipoption, ipopt_list); 528 } else { 529 ipoptlen = 0; 530 } 531 } 532 #ifdef IPSEC 533 ipoptlen += ipsec_hdrsiz_tcp(tp); 534 #endif 535 536 /* 537 * Adjust data length if insertion of options will 538 * bump the packet length beyond the t_maxopd length. 539 * Clear the FIN bit because we cut off the tail of 540 * the segment. 541 */ 542 if (len + optlen + ipoptlen > tp->t_maxopd) { 543 /* 544 * If there is still more to send, don't close the connection. 545 */ 546 flags &= ~TH_FIN; 547 len = tp->t_maxopd - optlen - ipoptlen; 548 sendalot = 1; 549 } 550 551 #ifdef INET6 552 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 553 #else 554 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 555 #endif 556 557 /* 558 * Grab a header mbuf, attaching a copy of data to 559 * be transmitted, and initialize the header from 560 * the template for sends on this connection. 561 */ 562 if (len) { 563 if (tp->t_force && len == 1) 564 tcpstat.tcps_sndprobe++; 565 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 566 tcpstat.tcps_sndrexmitpack++; 567 tcpstat.tcps_sndrexmitbyte += len; 568 } else { 569 tcpstat.tcps_sndpack++; 570 tcpstat.tcps_sndbyte += len; 571 } 572 #ifdef notyet 573 if ((m = m_copypack(so->so_snd.sb_mb, off, 574 (int)len, max_linkhdr + hdrlen)) == 0) { 575 error = ENOBUFS; 576 goto out; 577 } 578 /* 579 * m_copypack left space for our hdr; use it. 580 */ 581 m->m_len += hdrlen; 582 m->m_data -= hdrlen; 583 #else 584 MGETHDR(m, M_DONTWAIT, MT_HEADER); 585 if (m == NULL) { 586 error = ENOBUFS; 587 goto out; 588 } 589 #ifdef INET6 590 if (MHLEN < hdrlen + max_linkhdr) { 591 MCLGET(m, M_DONTWAIT); 592 if (!(m->m_flags & M_EXT)) { 593 m_freem(m); 594 error = ENOBUFS; 595 goto out; 596 } 597 } 598 #endif 599 m->m_data += max_linkhdr; 600 m->m_len = hdrlen; 601 if (len <= MHLEN - hdrlen - max_linkhdr) { 602 m_copydata(so->so_snd.sb_mb, off, (int) len, 603 mtod(m, caddr_t) + hdrlen); 604 m->m_len += len; 605 } else { 606 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 607 if (m->m_next == 0) { 608 (void) m_free(m); 609 error = ENOBUFS; 610 goto out; 611 } 612 } 613 #endif 614 /* 615 * If we're sending everything we've got, set PUSH. 616 * (This will keep happy those implementations which only 617 * give data to the user when a buffer fills or 618 * a PUSH comes in.) 619 */ 620 if (off + len == so->so_snd.sb_cc) 621 flags |= TH_PUSH; 622 } else { 623 if (tp->t_flags & TF_ACKNOW) 624 tcpstat.tcps_sndacks++; 625 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 626 tcpstat.tcps_sndctrl++; 627 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 628 tcpstat.tcps_sndurg++; 629 else 630 tcpstat.tcps_sndwinup++; 631 632 MGETHDR(m, M_DONTWAIT, MT_HEADER); 633 if (m == NULL) { 634 error = ENOBUFS; 635 goto out; 636 } 637 if (isipv6 && 638 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 639 MH_ALIGN(m, hdrlen); 640 else 641 m->m_data += max_linkhdr; 642 m->m_len = hdrlen; 643 } 644 m->m_pkthdr.rcvif = (struct ifnet *)0; 645 if (isipv6) { 646 ip6 = mtod(m, struct ip6_hdr *); 647 th = (struct tcphdr *)(ip6 + 1); 648 tcp_fillheaders(tp, ip6, th); 649 } else { 650 ip = mtod(m, struct ip *); 651 ipov = (struct ipovly *)ip; 652 th = (struct tcphdr *)(ip + 1); 653 /* this picks up the pseudo header (w/o the length) */ 654 tcp_fillheaders(tp, ip, th); 655 } 656 657 /* 658 * Fill in fields, remembering maximum advertised 659 * window for use in delaying messages about window sizes. 660 * If resending a FIN, be sure not to use a new sequence number. 661 */ 662 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 663 tp->snd_nxt == tp->snd_max) 664 tp->snd_nxt--; 665 /* 666 * If we are doing retransmissions, then snd_nxt will 667 * not reflect the first unsent octet. For ACK only 668 * packets, we do not want the sequence number of the 669 * retransmitted packet, we want the sequence number 670 * of the next unsent octet. So, if there is no data 671 * (and no SYN or FIN), use snd_max instead of snd_nxt 672 * when filling in ti_seq. But if we are in persist 673 * state, snd_max might reflect one byte beyond the 674 * right edge of the window, so use snd_nxt in that 675 * case, since we know we aren't doing a retransmission. 676 * (retransmit and persist are mutually exclusive...) 677 */ 678 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 679 th->th_seq = htonl(tp->snd_nxt); 680 else 681 th->th_seq = htonl(tp->snd_max); 682 th->th_ack = htonl(tp->rcv_nxt); 683 if (optlen) { 684 bcopy(opt, th + 1, optlen); 685 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 686 } 687 th->th_flags = flags; 688 /* 689 * Calculate receive window. Don't shrink window, 690 * but avoid silly window syndrome. 691 */ 692 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 693 recvwin < (long)tp->t_maxseg) 694 recvwin = 0; 695 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 696 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 697 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 698 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 699 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 700 701 /* 702 * Adjust the RXWIN0SENT flag - indicate that we have advertised 703 * a 0 window. This may cause the remote transmitter to stall. This 704 * flag tells soreceive() to disable delayed acknowledgements when 705 * draining the buffer. This can occur if the receiver is attempting 706 * to read more data then can be buffered prior to transmitting on 707 * the connection. 708 */ 709 if (recvwin == 0) 710 tp->t_flags |= TF_RXWIN0SENT; 711 else 712 tp->t_flags &= ~TF_RXWIN0SENT; 713 714 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 715 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 716 th->th_flags |= TH_URG; 717 } else { 718 /* 719 * If no urgent pointer to send, then we pull 720 * the urgent pointer to the left edge of the send window 721 * so that it doesn't drift into the send window on sequence 722 * number wraparound. 723 */ 724 tp->snd_up = tp->snd_una; /* drag it along */ 725 } 726 727 /* 728 * Put TCP length in extended header, and then 729 * checksum extended header and data. 730 */ 731 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 732 if (isipv6) { 733 /* 734 * ip6_plen is not need to be filled now, and will be filled 735 * in ip6_output. 736 */ 737 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 738 sizeof(struct tcphdr) + optlen + len); 739 } else { 740 m->m_pkthdr.csum_flags = CSUM_TCP; 741 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 742 if (len + optlen) 743 th->th_sum = in_addword(th->th_sum, 744 htons((u_short)(optlen + len))); 745 746 /* IP version must be set here for ipv4/ipv6 checking later */ 747 KASSERT(ip->ip_v == IPVERSION, 748 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 749 } 750 751 /* 752 * In transmit state, time the transmission and arrange for 753 * the retransmit. In persist state, just set snd_max. 754 */ 755 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 756 tcp_seq startseq = tp->snd_nxt; 757 758 /* 759 * Advance snd_nxt over sequence space of this segment. 760 */ 761 if (flags & (TH_SYN|TH_FIN)) { 762 if (flags & TH_SYN) 763 tp->snd_nxt++; 764 if (flags & TH_FIN) { 765 tp->snd_nxt++; 766 tp->t_flags |= TF_SENTFIN; 767 } 768 } 769 tp->snd_nxt += len; 770 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 771 tp->snd_max = tp->snd_nxt; 772 /* 773 * Time this transmission if not a retransmission and 774 * not currently timing anything. 775 */ 776 if (tp->t_rtttime == 0) { 777 tp->t_rtttime = ticks; 778 tp->t_rtseq = startseq; 779 tcpstat.tcps_segstimed++; 780 } 781 } 782 783 /* 784 * Set retransmit timer if not currently set, 785 * and not doing a pure ack or a keep-alive probe. 786 * Initial value for retransmit timer is smoothed 787 * round-trip time + 2 * round-trip time variance. 788 * Initialize shift counter which is used for backoff 789 * of retransmit time. 790 */ 791 if (!callout_active(tp->tt_rexmt) && 792 tp->snd_nxt != tp->snd_una) { 793 if (callout_active(tp->tt_persist)) { 794 callout_stop(tp->tt_persist); 795 tp->t_rxtshift = 0; 796 } 797 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 798 tcp_timer_rexmt, tp); 799 } 800 } else { 801 /* 802 * Persist case, update snd_max but since we are in 803 * persist mode (no window) we do not update snd_nxt. 804 */ 805 int xlen = len; 806 if (flags & TH_SYN) 807 ++xlen; 808 if (flags & TH_FIN) { 809 ++xlen; 810 tp->t_flags |= TF_SENTFIN; 811 } 812 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 813 tp->snd_max = tp->snd_nxt + xlen; 814 } 815 816 #ifdef TCPDEBUG 817 /* 818 * Trace. 819 */ 820 if (so->so_options & SO_DEBUG) 821 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 822 #endif 823 824 /* 825 * Fill in IP length and desired time to live and 826 * send to IP level. There should be a better way 827 * to handle ttl and tos; we could keep them in 828 * the template, but need a way to checksum without them. 829 */ 830 /* 831 * m->m_pkthdr.len should have been set before cksum calcuration, 832 * because in6_cksum() need it. 833 */ 834 if (isipv6) { 835 /* 836 * we separately set hoplimit for every segment, since the 837 * user might want to change the value via setsockopt. 838 * Also, desired default hop limit might be changed via 839 * Neighbor Discovery. 840 */ 841 ip6->ip6_hlim = in6_selecthlim(inp, 842 (inp->in6p_route.ro_rt ? 843 inp->in6p_route.ro_rt->rt_ifp : NULL)); 844 845 /* TODO: IPv6 IP6TOS_ECT bit on */ 846 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 847 (so->so_options & SO_DONTROUTE), NULL, NULL, inp); 848 } else { 849 struct rtentry *rt; 850 ip->ip_len = m->m_pkthdr.len; 851 #ifdef INET6 852 if (INP_CHECK_SOCKAF(so, AF_INET6)) 853 ip->ip_ttl = in6_selecthlim(inp, 854 (inp->in6p_route.ro_rt ? 855 inp->in6p_route.ro_rt->rt_ifp : NULL)); 856 else 857 #endif 858 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 859 860 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 861 /* 862 * See if we should do MTU discovery. 863 * We do it only if the following are true: 864 * 1) we have a valid route to the destination 865 * 2) the MTU is not locked (if it is, 866 * then discovery has been disabled) 867 */ 868 if (path_mtu_discovery && 869 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 870 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 871 ip->ip_off |= IP_DF; 872 873 error = ip_output(m, inp->inp_options, &inp->inp_route, 874 (so->so_options & SO_DONTROUTE), NULL, inp); 875 } 876 if (error) { 877 878 /* 879 * We know that the packet was lost, so back out the 880 * sequence number advance, if any. 881 */ 882 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 883 /* 884 * No need to check for TH_FIN here because 885 * the TF_SENTFIN flag handles that case. 886 */ 887 if (!(flags & TH_SYN)) 888 tp->snd_nxt -= len; 889 } 890 891 out: 892 if (error == ENOBUFS) { 893 /* 894 * If we can't send, make sure there is something 895 * to get us going again later. Persist state 896 * is not necessarily right, but it is close enough. 897 */ 898 if (!callout_active(tp->tt_rexmt) && 899 !callout_active(tp->tt_persist)) { 900 tp->t_rxtshift = 0; 901 tcp_setpersist(tp); 902 } 903 tcp_quench(inp, 0); 904 return (0); 905 } 906 if (error == EMSGSIZE) { 907 /* 908 * ip_output() will have already fixed the route 909 * for us. tcp_mtudisc() will, as its last action, 910 * initiate retransmission, so it is important to 911 * not do so here. 912 */ 913 tcp_mtudisc(inp, 0); 914 return 0; 915 } 916 if ((error == EHOSTUNREACH || error == ENETDOWN) && 917 TCPS_HAVERCVDSYN(tp->t_state)) { 918 tp->t_softerror = error; 919 return (0); 920 } 921 return (error); 922 } 923 tcpstat.tcps_sndtotal++; 924 925 /* 926 * Data sent (as far as we can tell). 927 * If this advertises a larger window than any other segment, 928 * then remember the size of the advertised window. 929 * Any pending ACK has now been sent. 930 */ 931 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 932 tp->rcv_adv = tp->rcv_nxt + recvwin; 933 tp->last_ack_sent = tp->rcv_nxt; 934 tp->t_flags &= ~TF_ACKNOW; 935 if (tcp_delack_enabled) 936 callout_stop(tp->tt_delack); 937 if (sendalot) 938 goto again; 939 return (0); 940 } 941 942 void 943 tcp_setpersist(tp) 944 struct tcpcb *tp; 945 { 946 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 947 int tt; 948 949 if (callout_active(tp->tt_rexmt)) 950 panic("tcp_setpersist: retransmit pending"); 951 /* 952 * Start/restart persistance timer. 953 */ 954 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 955 TCPTV_PERSMIN, TCPTV_PERSMAX); 956 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 957 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 958 tp->t_rxtshift++; 959 } 960