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 1.10 2004/03/08 00:36:30 hsu 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 53 #include <net/route.h> 54 55 #include <netinet/in.h> 56 #include <netinet/in_systm.h> 57 #include <netinet/ip.h> 58 #include <netinet/in_pcb.h> 59 #include <netinet/ip_var.h> 60 #include <netinet6/in6_pcb.h> 61 #include <netinet/ip6.h> 62 #include <netinet6/ip6_var.h> 63 #include <netinet/tcp.h> 64 #define TCPOUTFLAGS 65 #include <netinet/tcp_fsm.h> 66 #include <netinet/tcp_seq.h> 67 #include <netinet/tcp_timer.h> 68 #include <netinet/tcp_var.h> 69 #include <netinet/tcpip.h> 70 #ifdef TCPDEBUG 71 #include <netinet/tcp_debug.h> 72 #endif 73 74 #ifdef IPSEC 75 #include <netinet6/ipsec.h> 76 #endif /*IPSEC*/ 77 78 #ifdef FAST_IPSEC 79 #include <netipsec/ipsec.h> 80 #define IPSEC 81 #endif /*FAST_IPSEC*/ 82 83 #ifdef notyet 84 extern struct mbuf *m_copypack(); 85 #endif 86 87 int path_mtu_discovery = 1; 88 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 89 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 90 91 int ss_fltsz = 1; 92 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 93 &ss_fltsz, 1, "Slow start flight size"); 94 95 int ss_fltsz_local = 4; 96 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 97 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 98 99 int tcp_do_newreno = 1; 100 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 101 0, "Enable NewReno Algorithms"); 102 103 /* 104 * Tcp output routine: figure out what should be sent and send it. 105 */ 106 int 107 tcp_output(tp) 108 struct tcpcb *tp; 109 { 110 struct inpcb * const inp = tp->t_inpcb; 111 struct socket *so = inp->inp_socket; 112 long len, recvwin, sendwin; 113 int off, flags, error; 114 struct mbuf *m; 115 struct ip *ip = NULL; 116 struct ipovly *ipov = NULL; 117 struct tcphdr *th; 118 u_char opt[TCP_MAXOLEN]; 119 unsigned ipoptlen, optlen, hdrlen; 120 int idle, sendalot; 121 struct ip6_hdr *ip6 = NULL; 122 #ifdef INET6 123 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 124 #else 125 const boolean_t isipv6 = FALSE; 126 #endif 127 struct rmxp_tao *taop; 128 129 /* 130 * Determine length of data that should be transmitted, 131 * and flags that will be used. 132 * If there is some data or critical controls (SYN, RST) 133 * to send, then transmit; otherwise, investigate further. 134 */ 135 if ((tp->snd_max == tp->snd_una) && 136 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 137 /* 138 * We have been idle for "a while" and no acks are 139 * expected to clock out any data we send -- 140 * slow start to get ack "clock" running again. 141 * 142 * Set the slow-start flight size depending on whether 143 * this is a local network or not. 144 */ 145 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 146 (!isipv6 && in_localaddr(inp->inp_faddr))) 147 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 148 else 149 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 150 } 151 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 152 if (idle && (tp->t_flags & TF_MORETOCOME)) 153 tp->t_flags |= TF_LASTIDLE; 154 else 155 tp->t_flags &= ~TF_LASTIDLE; 156 157 again: 158 sendalot = 0; 159 off = tp->snd_nxt - tp->snd_una; 160 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 161 sendwin = min(sendwin, tp->snd_bwnd); 162 163 flags = tcp_outflags[tp->t_state]; 164 /* 165 * Get standard flags, and add SYN or FIN if requested by 'hidden' 166 * state flags. 167 */ 168 if (tp->t_flags & TF_NEEDFIN) 169 flags |= TH_FIN; 170 if (tp->t_flags & TF_NEEDSYN) 171 flags |= TH_SYN; 172 173 /* 174 * If in persist timeout with window of 0, send 1 byte. 175 * Otherwise, if window is small but nonzero 176 * and timer expired, we will send what we can 177 * and go to transmit state. 178 */ 179 if (tp->t_force) { 180 if (sendwin == 0) { 181 /* 182 * If we still have some data to send, then 183 * clear the FIN bit. Usually this would 184 * happen below when it realizes that we 185 * aren't sending all the data. However, 186 * if we have exactly 1 byte of unsent data, 187 * then it won't clear the FIN bit below, 188 * and if we are in persist state, we wind 189 * up sending the packet without recording 190 * that we sent the FIN bit. 191 * 192 * We can't just blindly clear the FIN bit, 193 * because if we don't have any more data 194 * to send then the probe will be the FIN 195 * itself. 196 */ 197 if (off < so->so_snd.sb_cc) 198 flags &= ~TH_FIN; 199 sendwin = 1; 200 } else { 201 callout_stop(tp->tt_persist); 202 tp->t_rxtshift = 0; 203 } 204 } 205 206 /* 207 * If snd_nxt == snd_max and we have transmitted a FIN, the 208 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 209 * a negative length. This can also occur when TCP opens up 210 * its congestion window while receiving additional duplicate 211 * acks after fast-retransmit because TCP will reset snd_nxt 212 * to snd_max after the fast-retransmit. 213 * 214 * In the normal retransmit-FIN-only case, however, snd_nxt will 215 * be set to snd_una, the offset will be 0, and the length may 216 * wind up 0. 217 */ 218 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 219 220 /* 221 * Lop off SYN bit if it has already been sent. However, if this 222 * is SYN-SENT state and if segment contains data and if we don't 223 * know that foreign host supports TAO, suppress sending segment. 224 */ 225 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 226 flags &= ~TH_SYN; 227 off--, len++; 228 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 229 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 230 taop->tao_ccsent == 0)) 231 return 0; 232 } 233 234 /* 235 * Be careful not to send data and/or FIN on SYN segments 236 * in cases when no CC option will be sent. 237 * This measure is needed to prevent interoperability problems 238 * with not fully conformant TCP implementations. 239 */ 240 if ((flags & TH_SYN) && 241 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 242 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 243 len = 0; 244 flags &= ~TH_FIN; 245 } 246 247 if (len < 0) { 248 /* 249 * If FIN has been sent but not acked, 250 * but we haven't been called to retransmit, 251 * len will be < 0. Otherwise, window shrank 252 * after we sent into it. If window shrank to 0, 253 * cancel pending retransmit, pull snd_nxt back 254 * to (closed) window, and set the persist timer 255 * if it isn't already going. If the window didn't 256 * close completely, just wait for an ACK. 257 */ 258 len = 0; 259 if (sendwin == 0) { 260 callout_stop(tp->tt_rexmt); 261 tp->t_rxtshift = 0; 262 tp->snd_nxt = tp->snd_una; 263 if (!callout_active(tp->tt_persist)) 264 tcp_setpersist(tp); 265 } 266 } 267 268 /* 269 * len will be >= 0 after this point. Truncate to the maximum 270 * segment length and ensure that FIN is removed if the length 271 * no longer contains the last data byte. 272 */ 273 if (len > tp->t_maxseg) { 274 len = tp->t_maxseg; 275 sendalot = 1; 276 } 277 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 278 flags &= ~TH_FIN; 279 280 recvwin = sbspace(&so->so_rcv); 281 282 /* 283 * Sender silly window avoidance. We transmit under the following 284 * conditions when len is non-zero: 285 * 286 * - We have a full segment 287 * - This is the last buffer in a write()/send() and we are 288 * either idle or running NODELAY 289 * - we've timed out (e.g. persist timer) 290 * - we have more then 1/2 the maximum send window's worth of 291 * data (receiver may be limited the window size) 292 * - we need to retransmit 293 */ 294 if (len) { 295 if (len == tp->t_maxseg) 296 goto send; 297 /* 298 * NOTE! on localhost connections an 'ack' from the remote 299 * end may occur synchronously with the output and cause 300 * us to flush a buffer queued with moretocome. XXX 301 * 302 * note: the len + off check is almost certainly unnecessary. 303 */ 304 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 305 (idle || (tp->t_flags & TF_NODELAY)) && 306 len + off >= so->so_snd.sb_cc && 307 !(tp->t_flags & TF_NOPUSH)) { 308 goto send; 309 } 310 if (tp->t_force) /* typ. timeout case */ 311 goto send; 312 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 313 goto send; 314 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 315 goto send; 316 } 317 318 /* 319 * Compare available window to amount of window 320 * known to peer (as advertised window less 321 * next expected input). If the difference is at least two 322 * max size segments, or at least 50% of the maximum possible 323 * window, then want to send a window update to peer. 324 */ 325 if (recvwin > 0) { 326 /* 327 * "adv" is the amount we can increase the window, 328 * taking into account that we are limited by 329 * TCP_MAXWIN << tp->rcv_scale. 330 */ 331 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 332 (tp->rcv_adv - tp->rcv_nxt); 333 334 if (adv >= (long) (2 * tp->t_maxseg)) 335 goto send; 336 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 337 goto send; 338 } 339 340 /* 341 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 342 * is also a catch-all for the retransmit timer timeout case. 343 */ 344 if (tp->t_flags & TF_ACKNOW) 345 goto send; 346 if ((flags & TH_RST) || 347 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 348 goto send; 349 if (SEQ_GT(tp->snd_up, tp->snd_una)) 350 goto send; 351 /* 352 * If our state indicates that FIN should be sent 353 * and we have not yet done so, then we need to send. 354 */ 355 if (flags & TH_FIN && 356 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 357 goto send; 358 359 /* 360 * TCP window updates are not reliable, rather a polling protocol 361 * using ``persist'' packets is used to insure receipt of window 362 * updates. The three ``states'' for the output side are: 363 * idle not doing retransmits or persists 364 * persisting to move a small or zero window 365 * (re)transmitting and thereby not persisting 366 * 367 * callout_active(tp->tt_persist) 368 * is true when we are in persist state. 369 * tp->t_force 370 * is set when we are called to send a persist packet. 371 * callout_active(tp->tt_rexmt) 372 * is set when we are retransmitting 373 * The output side is idle when both timers are zero. 374 * 375 * If send window is too small, there is data to transmit, and no 376 * retransmit or persist is pending, then go to persist state. 377 * If nothing happens soon, send when timer expires: 378 * if window is nonzero, transmit what we can, 379 * otherwise force out a byte. 380 */ 381 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 382 !callout_active(tp->tt_persist)) { 383 tp->t_rxtshift = 0; 384 tcp_setpersist(tp); 385 } 386 387 /* 388 * No reason to send a segment, just return. 389 */ 390 return (0); 391 392 send: 393 /* 394 * Before ESTABLISHED, force sending of initial options 395 * unless TCP set not to do any options. 396 * NOTE: we assume that the IP/TCP header plus TCP options 397 * always fit in a single mbuf, leaving room for a maximum 398 * link header, i.e. 399 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 400 */ 401 optlen = 0; 402 if (isipv6) 403 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 404 else 405 hdrlen = sizeof(struct tcpiphdr); 406 if (flags & TH_SYN) { 407 tp->snd_nxt = tp->iss; 408 if (!(tp->t_flags & TF_NOOPT)) { 409 u_short mss; 410 411 opt[0] = TCPOPT_MAXSEG; 412 opt[1] = TCPOLEN_MAXSEG; 413 mss = htons((u_short) tcp_mssopt(tp)); 414 (void)memcpy(opt + 2, &mss, sizeof(mss)); 415 optlen = TCPOLEN_MAXSEG; 416 417 if ((tp->t_flags & TF_REQ_SCALE) && 418 (!(flags & TH_ACK) || 419 (tp->t_flags & TF_RCVD_SCALE))) { 420 *((u_int32_t *)(opt + optlen)) = htonl( 421 TCPOPT_NOP << 24 | 422 TCPOPT_WINDOW << 16 | 423 TCPOLEN_WINDOW << 8 | 424 tp->request_r_scale); 425 optlen += 4; 426 } 427 } 428 } 429 430 /* 431 * Send a timestamp and echo-reply if this is a SYN and our side 432 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 433 * and our peer have sent timestamps in our SYN's. 434 */ 435 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 436 !(flags & TH_RST) && 437 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 438 u_int32_t *lp = (u_int32_t *)(opt + optlen); 439 440 /* Form timestamp option as shown in appendix A of RFC 1323. */ 441 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 442 *lp++ = htonl(ticks); 443 *lp = htonl(tp->ts_recent); 444 optlen += TCPOLEN_TSTAMP_APPA; 445 } 446 447 /* 448 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 449 * options are allowed (!TF_NOOPT) and it's not a RST. 450 */ 451 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 452 !(flags & TH_RST)) { 453 switch (flags & (TH_SYN|TH_ACK)) { 454 /* 455 * This is a normal ACK, send CC if we received CC before 456 * from our peer. 457 */ 458 case TH_ACK: 459 if (!(tp->t_flags & TF_RCVD_CC)) 460 break; 461 /*FALLTHROUGH*/ 462 463 /* 464 * We can only get here in T/TCP's SYN_SENT* state, when 465 * we're a sending a non-SYN segment without waiting for 466 * the ACK of our SYN. A check above assures that we only 467 * do this if our peer understands T/TCP. 468 */ 469 case 0: 470 opt[optlen++] = TCPOPT_NOP; 471 opt[optlen++] = TCPOPT_NOP; 472 opt[optlen++] = TCPOPT_CC; 473 opt[optlen++] = TCPOLEN_CC; 474 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 475 476 optlen += 4; 477 break; 478 479 /* 480 * This is our initial SYN, check whether we have to use 481 * CC or CC.new. 482 */ 483 case TH_SYN: 484 opt[optlen++] = TCPOPT_NOP; 485 opt[optlen++] = TCPOPT_NOP; 486 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 487 TCPOPT_CCNEW : TCPOPT_CC; 488 opt[optlen++] = TCPOLEN_CC; 489 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 490 optlen += 4; 491 break; 492 493 /* 494 * This is a SYN,ACK; send CC and CC.echo if we received 495 * CC from our peer. 496 */ 497 case (TH_SYN|TH_ACK): 498 if (tp->t_flags & TF_RCVD_CC) { 499 opt[optlen++] = TCPOPT_NOP; 500 opt[optlen++] = TCPOPT_NOP; 501 opt[optlen++] = TCPOPT_CC; 502 opt[optlen++] = TCPOLEN_CC; 503 *(u_int32_t *)&opt[optlen] = 504 htonl(tp->cc_send); 505 optlen += 4; 506 opt[optlen++] = TCPOPT_NOP; 507 opt[optlen++] = TCPOPT_NOP; 508 opt[optlen++] = TCPOPT_CCECHO; 509 opt[optlen++] = TCPOLEN_CC; 510 *(u_int32_t *)&opt[optlen] = 511 htonl(tp->cc_recv); 512 optlen += 4; 513 } 514 break; 515 } 516 } 517 518 hdrlen += optlen; 519 520 if (isipv6) 521 ipoptlen = ip6_optlen(inp); 522 else { 523 if (inp->inp_options) { 524 ipoptlen = inp->inp_options->m_len - 525 offsetof(struct ipoption, ipopt_list); 526 } else { 527 ipoptlen = 0; 528 } 529 } 530 #ifdef IPSEC 531 ipoptlen += ipsec_hdrsiz_tcp(tp); 532 #endif 533 534 /* 535 * Adjust data length if insertion of options will 536 * bump the packet length beyond the t_maxopd length. 537 * Clear the FIN bit because we cut off the tail of 538 * the segment. 539 */ 540 if (len + optlen + ipoptlen > tp->t_maxopd) { 541 /* 542 * If there is still more to send, don't close the connection. 543 */ 544 flags &= ~TH_FIN; 545 len = tp->t_maxopd - optlen - ipoptlen; 546 sendalot = 1; 547 } 548 549 #ifdef INET6 550 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 551 #else 552 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 553 #endif 554 555 /* 556 * Grab a header mbuf, attaching a copy of data to 557 * be transmitted, and initialize the header from 558 * the template for sends on this connection. 559 */ 560 if (len) { 561 if (tp->t_force && len == 1) 562 tcpstat.tcps_sndprobe++; 563 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 564 tcpstat.tcps_sndrexmitpack++; 565 tcpstat.tcps_sndrexmitbyte += len; 566 } else { 567 tcpstat.tcps_sndpack++; 568 tcpstat.tcps_sndbyte += len; 569 } 570 #ifdef notyet 571 if ((m = m_copypack(so->so_snd.sb_mb, off, 572 (int)len, max_linkhdr + hdrlen)) == 0) { 573 error = ENOBUFS; 574 goto out; 575 } 576 /* 577 * m_copypack left space for our hdr; use it. 578 */ 579 m->m_len += hdrlen; 580 m->m_data -= hdrlen; 581 #else 582 MGETHDR(m, M_DONTWAIT, MT_HEADER); 583 if (m == NULL) { 584 error = ENOBUFS; 585 goto out; 586 } 587 #ifdef INET6 588 if (MHLEN < hdrlen + max_linkhdr) { 589 MCLGET(m, M_DONTWAIT); 590 if (!(m->m_flags & M_EXT)) { 591 m_freem(m); 592 error = ENOBUFS; 593 goto out; 594 } 595 } 596 #endif 597 m->m_data += max_linkhdr; 598 m->m_len = hdrlen; 599 if (len <= MHLEN - hdrlen - max_linkhdr) { 600 m_copydata(so->so_snd.sb_mb, off, (int) len, 601 mtod(m, caddr_t) + hdrlen); 602 m->m_len += len; 603 } else { 604 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 605 if (m->m_next == 0) { 606 (void) m_free(m); 607 error = ENOBUFS; 608 goto out; 609 } 610 } 611 #endif 612 /* 613 * If we're sending everything we've got, set PUSH. 614 * (This will keep happy those implementations which only 615 * give data to the user when a buffer fills or 616 * a PUSH comes in.) 617 */ 618 if (off + len == so->so_snd.sb_cc) 619 flags |= TH_PUSH; 620 } else { 621 if (tp->t_flags & TF_ACKNOW) 622 tcpstat.tcps_sndacks++; 623 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 624 tcpstat.tcps_sndctrl++; 625 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 626 tcpstat.tcps_sndurg++; 627 else 628 tcpstat.tcps_sndwinup++; 629 630 MGETHDR(m, M_DONTWAIT, MT_HEADER); 631 if (m == NULL) { 632 error = ENOBUFS; 633 goto out; 634 } 635 if (isipv6 && 636 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 637 MH_ALIGN(m, hdrlen); 638 else 639 m->m_data += max_linkhdr; 640 m->m_len = hdrlen; 641 } 642 m->m_pkthdr.rcvif = (struct ifnet *)0; 643 if (isipv6) { 644 ip6 = mtod(m, struct ip6_hdr *); 645 th = (struct tcphdr *)(ip6 + 1); 646 tcp_fillheaders(tp, ip6, th); 647 } else { 648 ip = mtod(m, struct ip *); 649 ipov = (struct ipovly *)ip; 650 th = (struct tcphdr *)(ip + 1); 651 /* this picks up the pseudo header (w/o the length) */ 652 tcp_fillheaders(tp, ip, th); 653 } 654 655 /* 656 * Fill in fields, remembering maximum advertised 657 * window for use in delaying messages about window sizes. 658 * If resending a FIN, be sure not to use a new sequence number. 659 */ 660 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 661 tp->snd_nxt == tp->snd_max) 662 tp->snd_nxt--; 663 /* 664 * If we are doing retransmissions, then snd_nxt will 665 * not reflect the first unsent octet. For ACK only 666 * packets, we do not want the sequence number of the 667 * retransmitted packet, we want the sequence number 668 * of the next unsent octet. So, if there is no data 669 * (and no SYN or FIN), use snd_max instead of snd_nxt 670 * when filling in ti_seq. But if we are in persist 671 * state, snd_max might reflect one byte beyond the 672 * right edge of the window, so use snd_nxt in that 673 * case, since we know we aren't doing a retransmission. 674 * (retransmit and persist are mutually exclusive...) 675 */ 676 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 677 th->th_seq = htonl(tp->snd_nxt); 678 else 679 th->th_seq = htonl(tp->snd_max); 680 th->th_ack = htonl(tp->rcv_nxt); 681 if (optlen) { 682 bcopy(opt, th + 1, optlen); 683 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 684 } 685 th->th_flags = flags; 686 /* 687 * Calculate receive window. Don't shrink window, 688 * but avoid silly window syndrome. 689 */ 690 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 691 recvwin < (long)tp->t_maxseg) 692 recvwin = 0; 693 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 694 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 695 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 696 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 697 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 698 699 /* 700 * Adjust the RXWIN0SENT flag - indicate that we have advertised 701 * a 0 window. This may cause the remote transmitter to stall. This 702 * flag tells soreceive() to disable delayed acknowledgements when 703 * draining the buffer. This can occur if the receiver is attempting 704 * to read more data then can be buffered prior to transmitting on 705 * the connection. 706 */ 707 if (recvwin == 0) 708 tp->t_flags |= TF_RXWIN0SENT; 709 else 710 tp->t_flags &= ~TF_RXWIN0SENT; 711 712 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 713 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 714 th->th_flags |= TH_URG; 715 } else { 716 /* 717 * If no urgent pointer to send, then we pull 718 * the urgent pointer to the left edge of the send window 719 * so that it doesn't drift into the send window on sequence 720 * number wraparound. 721 */ 722 tp->snd_up = tp->snd_una; /* drag it along */ 723 } 724 725 /* 726 * Put TCP length in extended header, and then 727 * checksum extended header and data. 728 */ 729 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 730 if (isipv6) { 731 /* 732 * ip6_plen is not need to be filled now, and will be filled 733 * in ip6_output. 734 */ 735 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 736 sizeof(struct tcphdr) + optlen + len); 737 } else { 738 m->m_pkthdr.csum_flags = CSUM_TCP; 739 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 740 if (len + optlen) 741 th->th_sum = in_addword(th->th_sum, 742 htons((u_short)(optlen + len))); 743 744 /* IP version must be set here for ipv4/ipv6 checking later */ 745 KASSERT(ip->ip_v == IPVERSION, 746 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 747 } 748 749 /* 750 * In transmit state, time the transmission and arrange for 751 * the retransmit. In persist state, just set snd_max. 752 */ 753 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 754 tcp_seq startseq = tp->snd_nxt; 755 756 /* 757 * Advance snd_nxt over sequence space of this segment. 758 */ 759 if (flags & (TH_SYN|TH_FIN)) { 760 if (flags & TH_SYN) 761 tp->snd_nxt++; 762 if (flags & TH_FIN) { 763 tp->snd_nxt++; 764 tp->t_flags |= TF_SENTFIN; 765 } 766 } 767 tp->snd_nxt += len; 768 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 769 tp->snd_max = tp->snd_nxt; 770 /* 771 * Time this transmission if not a retransmission and 772 * not currently timing anything. 773 */ 774 if (tp->t_rtttime == 0) { 775 tp->t_rtttime = ticks; 776 tp->t_rtseq = startseq; 777 tcpstat.tcps_segstimed++; 778 } 779 } 780 781 /* 782 * Set retransmit timer if not currently set, 783 * and not doing a pure ack or a keep-alive probe. 784 * Initial value for retransmit timer is smoothed 785 * round-trip time + 2 * round-trip time variance. 786 * Initialize shift counter which is used for backoff 787 * of retransmit time. 788 */ 789 if (!callout_active(tp->tt_rexmt) && 790 tp->snd_nxt != tp->snd_una) { 791 if (callout_active(tp->tt_persist)) { 792 callout_stop(tp->tt_persist); 793 tp->t_rxtshift = 0; 794 } 795 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 796 tcp_timer_rexmt, tp); 797 } 798 } else { 799 /* 800 * Persist case, update snd_max but since we are in 801 * persist mode (no window) we do not update snd_nxt. 802 */ 803 int xlen = len; 804 if (flags & TH_SYN) 805 ++xlen; 806 if (flags & TH_FIN) { 807 ++xlen; 808 tp->t_flags |= TF_SENTFIN; 809 } 810 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 811 tp->snd_max = tp->snd_nxt + xlen; 812 } 813 814 #ifdef TCPDEBUG 815 /* 816 * Trace. 817 */ 818 if (so->so_options & SO_DEBUG) 819 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 820 #endif 821 822 /* 823 * Fill in IP length and desired time to live and 824 * send to IP level. There should be a better way 825 * to handle ttl and tos; we could keep them in 826 * the template, but need a way to checksum without them. 827 */ 828 /* 829 * m->m_pkthdr.len should have been set before cksum calcuration, 830 * because in6_cksum() need it. 831 */ 832 if (isipv6) { 833 /* 834 * we separately set hoplimit for every segment, since the 835 * user might want to change the value via setsockopt. 836 * Also, desired default hop limit might be changed via 837 * Neighbor Discovery. 838 */ 839 ip6->ip6_hlim = in6_selecthlim(inp, 840 (inp->in6p_route.ro_rt ? 841 inp->in6p_route.ro_rt->rt_ifp : NULL)); 842 843 /* TODO: IPv6 IP6TOS_ECT bit on */ 844 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 845 (so->so_options & SO_DONTROUTE), NULL, NULL, inp); 846 } else { 847 struct rtentry *rt; 848 ip->ip_len = m->m_pkthdr.len; 849 #ifdef INET6 850 if (INP_CHECK_SOCKAF(so, AF_INET6)) 851 ip->ip_ttl = in6_selecthlim(inp, 852 (inp->in6p_route.ro_rt ? 853 inp->in6p_route.ro_rt->rt_ifp : NULL)); 854 else 855 #endif 856 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 857 858 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 859 /* 860 * See if we should do MTU discovery. 861 * We do it only if the following are true: 862 * 1) we have a valid route to the destination 863 * 2) the MTU is not locked (if it is, 864 * then discovery has been disabled) 865 */ 866 if (path_mtu_discovery && 867 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 868 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 869 ip->ip_off |= IP_DF; 870 871 error = ip_output(m, inp->inp_options, &inp->inp_route, 872 (so->so_options & SO_DONTROUTE), NULL, inp); 873 } 874 if (error) { 875 876 /* 877 * We know that the packet was lost, so back out the 878 * sequence number advance, if any. 879 */ 880 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 881 /* 882 * No need to check for TH_FIN here because 883 * the TF_SENTFIN flag handles that case. 884 */ 885 if (!(flags & TH_SYN)) 886 tp->snd_nxt -= len; 887 } 888 889 out: 890 if (error == ENOBUFS) { 891 /* 892 * If we can't send, make sure there is something 893 * to get us going again later. Persist state 894 * is not necessarily right, but it is close enough. 895 */ 896 if (!callout_active(tp->tt_rexmt) && 897 !callout_active(tp->tt_persist)) { 898 tp->t_rxtshift = 0; 899 tcp_setpersist(tp); 900 } 901 tcp_quench(inp, 0); 902 return (0); 903 } 904 if (error == EMSGSIZE) { 905 /* 906 * ip_output() will have already fixed the route 907 * for us. tcp_mtudisc() will, as its last action, 908 * initiate retransmission, so it is important to 909 * not do so here. 910 */ 911 tcp_mtudisc(inp, 0); 912 return 0; 913 } 914 if ((error == EHOSTUNREACH || error == ENETDOWN) && 915 TCPS_HAVERCVDSYN(tp->t_state)) { 916 tp->t_softerror = error; 917 return (0); 918 } 919 return (error); 920 } 921 tcpstat.tcps_sndtotal++; 922 923 /* 924 * Data sent (as far as we can tell). 925 * If this advertises a larger window than any other segment, 926 * then remember the size of the advertised window. 927 * Any pending ACK has now been sent. 928 */ 929 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 930 tp->rcv_adv = tp->rcv_nxt + recvwin; 931 tp->last_ack_sent = tp->rcv_nxt; 932 tp->t_flags &= ~TF_ACKNOW; 933 if (tcp_delack_enabled) 934 callout_stop(tp->tt_delack); 935 if (sendalot) 936 goto again; 937 return (0); 938 } 939 940 void 941 tcp_setpersist(tp) 942 struct tcpcb *tp; 943 { 944 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 945 int tt; 946 947 if (callout_active(tp->tt_rexmt)) 948 panic("tcp_setpersist: retransmit pending"); 949 /* 950 * Start/restart persistance timer. 951 */ 952 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 953 TCPTV_PERSMIN, TCPTV_PERSMAX); 954 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 955 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 956 tp->t_rxtshift++; 957 } 958