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 1.2 2003/06/17 04:28:51 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 52 #include <net/route.h> 53 54 #include <netinet/in.h> 55 #include <netinet/in_systm.h> 56 #include <netinet/ip.h> 57 #include <netinet/in_pcb.h> 58 #include <netinet/ip_var.h> 59 #ifdef INET6 60 #include <netinet6/in6_pcb.h> 61 #include <netinet/ip6.h> 62 #include <netinet6/ip6_var.h> 63 #endif 64 #include <netinet/tcp.h> 65 #define TCPOUTFLAGS 66 #include <netinet/tcp_fsm.h> 67 #include <netinet/tcp_seq.h> 68 #include <netinet/tcp_timer.h> 69 #include <netinet/tcp_var.h> 70 #include <netinet/tcpip.h> 71 #ifdef TCPDEBUG 72 #include <netinet/tcp_debug.h> 73 #endif 74 75 #ifdef IPSEC 76 #include <netinet6/ipsec.h> 77 #endif /*IPSEC*/ 78 79 #ifdef FAST_IPSEC 80 #include <netipsec/ipsec.h> 81 #define IPSEC 82 #endif /*FAST_IPSEC*/ 83 84 #include <machine/in_cksum.h> 85 86 #ifdef notyet 87 extern struct mbuf *m_copypack(); 88 #endif 89 90 int path_mtu_discovery = 1; 91 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 92 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 93 94 int ss_fltsz = 1; 95 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 96 &ss_fltsz, 1, "Slow start flight size"); 97 98 int ss_fltsz_local = 4; 99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 100 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 101 102 int tcp_do_newreno = 1; 103 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 104 0, "Enable NewReno Algorithms"); 105 106 /* 107 * Tcp output routine: figure out what should be sent and send it. 108 */ 109 int 110 tcp_output(tp) 111 register struct tcpcb *tp; 112 { 113 register struct socket *so = tp->t_inpcb->inp_socket; 114 register long len, win; 115 int off, flags, error; 116 register struct mbuf *m; 117 struct ip *ip = NULL; 118 register struct ipovly *ipov = NULL; 119 #ifdef INET6 120 struct ip6_hdr *ip6 = NULL; 121 #endif /* INET6 */ 122 register struct tcphdr *th; 123 u_char opt[TCP_MAXOLEN]; 124 unsigned ipoptlen, optlen, hdrlen; 125 int idle, sendalot; 126 #if 0 127 int maxburst = TCP_MAXBURST; 128 #endif 129 struct rmxp_tao *taop; 130 #ifdef INET6 131 int isipv6; 132 #endif 133 134 #ifdef INET6 135 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 136 #endif 137 138 /* 139 * Determine length of data that should be transmitted, 140 * and flags that will be used. 141 * If there is some data or critical controls (SYN, RST) 142 * to send, then transmit; otherwise, investigate further. 143 */ 144 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 145 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 146 /* 147 * We have been idle for "a while" and no acks are 148 * expected to clock out any data we send -- 149 * slow start to get ack "clock" running again. 150 * 151 * Set the slow-start flight size depending on whether 152 * this is a local network or not. 153 */ 154 if ( 155 #ifdef INET6 156 (isipv6 && in6_localaddr(&tp->t_inpcb->in6p_faddr)) || 157 (!isipv6 && 158 #endif 159 in_localaddr(tp->t_inpcb->inp_faddr) 160 #ifdef INET6 161 ) 162 #endif 163 ) 164 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 165 else 166 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 167 } 168 tp->t_flags &= ~TF_LASTIDLE; 169 if (idle) { 170 if (tp->t_flags & TF_MORETOCOME) { 171 tp->t_flags |= TF_LASTIDLE; 172 idle = 0; 173 } 174 } 175 again: 176 sendalot = 0; 177 off = tp->snd_nxt - tp->snd_una; 178 win = min(tp->snd_wnd, tp->snd_cwnd); 179 win = min(win, tp->snd_bwnd); 180 181 flags = tcp_outflags[tp->t_state]; 182 /* 183 * Get standard flags, and add SYN or FIN if requested by 'hidden' 184 * state flags. 185 */ 186 if (tp->t_flags & TF_NEEDFIN) 187 flags |= TH_FIN; 188 if (tp->t_flags & TF_NEEDSYN) 189 flags |= TH_SYN; 190 191 /* 192 * If in persist timeout with window of 0, send 1 byte. 193 * Otherwise, if window is small but nonzero 194 * and timer expired, we will send what we can 195 * and go to transmit state. 196 */ 197 if (tp->t_force) { 198 if (win == 0) { 199 /* 200 * If we still have some data to send, then 201 * clear the FIN bit. Usually this would 202 * happen below when it realizes that we 203 * aren't sending all the data. However, 204 * if we have exactly 1 byte of unsent data, 205 * then it won't clear the FIN bit below, 206 * and if we are in persist state, we wind 207 * up sending the packet without recording 208 * that we sent the FIN bit. 209 * 210 * We can't just blindly clear the FIN bit, 211 * because if we don't have any more data 212 * to send then the probe will be the FIN 213 * itself. 214 */ 215 if (off < so->so_snd.sb_cc) 216 flags &= ~TH_FIN; 217 win = 1; 218 } else { 219 callout_stop(tp->tt_persist); 220 tp->t_rxtshift = 0; 221 } 222 } 223 224 /* 225 * If snd_nxt == snd_max and we have transmitted a FIN, the 226 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 227 * a negative length. This can also occur when tcp opens up 228 * its congestion window while receiving additional duplicate 229 * acks after fast-retransmit because TCP will reset snd_nxt 230 * to snd_max after the fast-retransmit. 231 * 232 * In the normal retransmit-FIN-only case, however, snd_nxt will 233 * be set to snd_una, the offset will be 0, and the length may 234 * wind up 0. 235 */ 236 len = (long)ulmin(so->so_snd.sb_cc, win) - off; 237 238 taop = tcp_gettaocache(&tp->t_inpcb->inp_inc); 239 240 /* 241 * Lop off SYN bit if it has already been sent. However, if this 242 * is SYN-SENT state and if segment contains data and if we don't 243 * know that foreign host supports TAO, suppress sending segment. 244 */ 245 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 246 flags &= ~TH_SYN; 247 off--, len++; 248 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 249 (taop == NULL || taop->tao_ccsent == 0)) 250 return 0; 251 } 252 253 /* 254 * Be careful not to send data and/or FIN on SYN segments 255 * in cases when no CC option will be sent. 256 * This measure is needed to prevent interoperability problems 257 * with not fully conformant TCP implementations. 258 */ 259 if ((flags & TH_SYN) && 260 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 261 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 262 len = 0; 263 flags &= ~TH_FIN; 264 } 265 266 if (len < 0) { 267 /* 268 * If FIN has been sent but not acked, 269 * but we haven't been called to retransmit, 270 * len will be < 0. Otherwise, window shrank 271 * after we sent into it. If window shrank to 0, 272 * cancel pending retransmit, pull snd_nxt back 273 * to (closed) window, and set the persist timer 274 * if it isn't already going. If the window didn't 275 * close completely, just wait for an ACK. 276 */ 277 len = 0; 278 if (win == 0) { 279 callout_stop(tp->tt_rexmt); 280 tp->t_rxtshift = 0; 281 tp->snd_nxt = tp->snd_una; 282 if (!callout_active(tp->tt_persist)) 283 tcp_setpersist(tp); 284 } 285 } 286 287 /* 288 * len will be >= 0 after this point. Truncate to the maximum 289 * segment length and ensure that FIN is removed if the length 290 * no longer contains the last data byte. 291 */ 292 if (len > tp->t_maxseg) { 293 len = tp->t_maxseg; 294 sendalot = 1; 295 } 296 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 297 flags &= ~TH_FIN; 298 299 win = sbspace(&so->so_rcv); 300 301 /* 302 * Sender silly window avoidance. We transmit under the following 303 * conditions when len is non-zero: 304 * 305 * - We have a full segment 306 * - This is the last buffer in a write()/send() and we are 307 * either idle or running NODELAY 308 * - we've timed out (e.g. persist timer) 309 * - we have more then 1/2 the maximum send window's worth of 310 * data (receiver may be limited the window size) 311 * - we need to retransmit 312 */ 313 if (len) { 314 if (len == tp->t_maxseg) 315 goto send; 316 /* 317 * NOTE! on localhost connections an 'ack' from the remote 318 * end may occur synchronously with the output and cause 319 * us to flush a buffer queued with moretocome. XXX 320 * 321 * note: the len + off check is almost certainly unnecessary. 322 */ 323 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 324 (idle || (tp->t_flags & TF_NODELAY)) && 325 len + off >= so->so_snd.sb_cc && 326 (tp->t_flags & TF_NOPUSH) == 0) { 327 goto send; 328 } 329 if (tp->t_force) /* typ. timeout case */ 330 goto send; 331 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 332 goto send; 333 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 334 goto send; 335 } 336 337 /* 338 * Compare available window to amount of window 339 * known to peer (as advertised window less 340 * next expected input). If the difference is at least two 341 * max size segments, or at least 50% of the maximum possible 342 * window, then want to send a window update to peer. 343 */ 344 if (win > 0) { 345 /* 346 * "adv" is the amount we can increase the window, 347 * taking into account that we are limited by 348 * TCP_MAXWIN << tp->rcv_scale. 349 */ 350 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 351 (tp->rcv_adv - tp->rcv_nxt); 352 353 if (adv >= (long) (2 * tp->t_maxseg)) 354 goto send; 355 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 356 goto send; 357 } 358 359 /* 360 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 361 * is also a catch-all for the retransmit timer timeout case. 362 */ 363 if (tp->t_flags & TF_ACKNOW) 364 goto send; 365 if ((flags & TH_RST) || 366 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 367 goto send; 368 if (SEQ_GT(tp->snd_up, tp->snd_una)) 369 goto send; 370 /* 371 * If our state indicates that FIN should be sent 372 * and we have not yet done so, then we need to send. 373 */ 374 if (flags & TH_FIN && 375 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 376 goto send; 377 378 /* 379 * TCP window updates are not reliable, rather a polling protocol 380 * using ``persist'' packets is used to insure receipt of window 381 * updates. The three ``states'' for the output side are: 382 * idle not doing retransmits or persists 383 * persisting to move a small or zero window 384 * (re)transmitting and thereby not persisting 385 * 386 * callout_active(tp->tt_persist) 387 * is true when we are in persist state. 388 * tp->t_force 389 * is set when we are called to send a persist packet. 390 * callout_active(tp->tt_rexmt) 391 * is set when we are retransmitting 392 * The output side is idle when both timers are zero. 393 * 394 * If send window is too small, there is data to transmit, and no 395 * retransmit or persist is pending, then go to persist state. 396 * If nothing happens soon, send when timer expires: 397 * if window is nonzero, transmit what we can, 398 * otherwise force out a byte. 399 */ 400 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 401 !callout_active(tp->tt_persist)) { 402 tp->t_rxtshift = 0; 403 tcp_setpersist(tp); 404 } 405 406 /* 407 * No reason to send a segment, just return. 408 */ 409 return (0); 410 411 send: 412 /* 413 * Before ESTABLISHED, force sending of initial options 414 * unless TCP set not to do any options. 415 * NOTE: we assume that the IP/TCP header plus TCP options 416 * always fit in a single mbuf, leaving room for a maximum 417 * link header, i.e. 418 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 419 */ 420 optlen = 0; 421 #ifdef INET6 422 if (isipv6) 423 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 424 else 425 #endif 426 hdrlen = sizeof (struct tcpiphdr); 427 if (flags & TH_SYN) { 428 tp->snd_nxt = tp->iss; 429 if ((tp->t_flags & TF_NOOPT) == 0) { 430 u_short mss; 431 432 opt[0] = TCPOPT_MAXSEG; 433 opt[1] = TCPOLEN_MAXSEG; 434 mss = htons((u_short) tcp_mssopt(tp)); 435 (void)memcpy(opt + 2, &mss, sizeof(mss)); 436 optlen = TCPOLEN_MAXSEG; 437 438 if ((tp->t_flags & TF_REQ_SCALE) && 439 ((flags & TH_ACK) == 0 || 440 (tp->t_flags & TF_RCVD_SCALE))) { 441 *((u_int32_t *)(opt + optlen)) = htonl( 442 TCPOPT_NOP << 24 | 443 TCPOPT_WINDOW << 16 | 444 TCPOLEN_WINDOW << 8 | 445 tp->request_r_scale); 446 optlen += 4; 447 } 448 } 449 } 450 451 /* 452 * Send a timestamp and echo-reply if this is a SYN and our side 453 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 454 * and our peer have sent timestamps in our SYN's. 455 */ 456 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 457 (flags & TH_RST) == 0 && 458 ((flags & TH_ACK) == 0 || 459 (tp->t_flags & TF_RCVD_TSTMP))) { 460 u_int32_t *lp = (u_int32_t *)(opt + optlen); 461 462 /* Form timestamp option as shown in appendix A of RFC 1323. */ 463 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 464 *lp++ = htonl(ticks); 465 *lp = htonl(tp->ts_recent); 466 optlen += TCPOLEN_TSTAMP_APPA; 467 } 468 469 /* 470 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 471 * options are allowed (!TF_NOOPT) and it's not a RST. 472 */ 473 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 474 (flags & TH_RST) == 0) { 475 switch (flags & (TH_SYN|TH_ACK)) { 476 /* 477 * This is a normal ACK, send CC if we received CC before 478 * from our peer. 479 */ 480 case TH_ACK: 481 if (!(tp->t_flags & TF_RCVD_CC)) 482 break; 483 /*FALLTHROUGH*/ 484 485 /* 486 * We can only get here in T/TCP's SYN_SENT* state, when 487 * we're a sending a non-SYN segment without waiting for 488 * the ACK of our SYN. A check above assures that we only 489 * do this if our peer understands T/TCP. 490 */ 491 case 0: 492 opt[optlen++] = TCPOPT_NOP; 493 opt[optlen++] = TCPOPT_NOP; 494 opt[optlen++] = TCPOPT_CC; 495 opt[optlen++] = TCPOLEN_CC; 496 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 497 498 optlen += 4; 499 break; 500 501 /* 502 * This is our initial SYN, check whether we have to use 503 * CC or CC.new. 504 */ 505 case TH_SYN: 506 opt[optlen++] = TCPOPT_NOP; 507 opt[optlen++] = TCPOPT_NOP; 508 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 509 TCPOPT_CCNEW : TCPOPT_CC; 510 opt[optlen++] = TCPOLEN_CC; 511 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 512 optlen += 4; 513 break; 514 515 /* 516 * This is a SYN,ACK; send CC and CC.echo if we received 517 * CC from our peer. 518 */ 519 case (TH_SYN|TH_ACK): 520 if (tp->t_flags & TF_RCVD_CC) { 521 opt[optlen++] = TCPOPT_NOP; 522 opt[optlen++] = TCPOPT_NOP; 523 opt[optlen++] = TCPOPT_CC; 524 opt[optlen++] = TCPOLEN_CC; 525 *(u_int32_t *)&opt[optlen] = 526 htonl(tp->cc_send); 527 optlen += 4; 528 opt[optlen++] = TCPOPT_NOP; 529 opt[optlen++] = TCPOPT_NOP; 530 opt[optlen++] = TCPOPT_CCECHO; 531 opt[optlen++] = TCPOLEN_CC; 532 *(u_int32_t *)&opt[optlen] = 533 htonl(tp->cc_recv); 534 optlen += 4; 535 } 536 break; 537 } 538 } 539 540 hdrlen += optlen; 541 542 #ifdef INET6 543 if (isipv6) 544 ipoptlen = ip6_optlen(tp->t_inpcb); 545 else 546 #endif 547 { 548 if (tp->t_inpcb->inp_options) { 549 ipoptlen = tp->t_inpcb->inp_options->m_len - 550 offsetof(struct ipoption, ipopt_list); 551 } else { 552 ipoptlen = 0; 553 } 554 } 555 #ifdef IPSEC 556 ipoptlen += ipsec_hdrsiz_tcp(tp); 557 #endif 558 559 /* 560 * Adjust data length if insertion of options will 561 * bump the packet length beyond the t_maxopd length. 562 * Clear the FIN bit because we cut off the tail of 563 * the segment. 564 */ 565 if (len + optlen + ipoptlen > tp->t_maxopd) { 566 /* 567 * If there is still more to send, don't close the connection. 568 */ 569 flags &= ~TH_FIN; 570 len = tp->t_maxopd - optlen - ipoptlen; 571 sendalot = 1; 572 } 573 574 /*#ifdef DIAGNOSTIC*/ 575 #ifdef INET6 576 if (max_linkhdr + hdrlen > MCLBYTES) 577 panic("tcphdr too big"); 578 #else 579 if (max_linkhdr + hdrlen > MHLEN) 580 panic("tcphdr too big"); 581 #endif 582 /*#endif*/ 583 584 /* 585 * Grab a header mbuf, attaching a copy of data to 586 * be transmitted, and initialize the header from 587 * the template for sends on this connection. 588 */ 589 if (len) { 590 if (tp->t_force && len == 1) 591 tcpstat.tcps_sndprobe++; 592 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 593 tcpstat.tcps_sndrexmitpack++; 594 tcpstat.tcps_sndrexmitbyte += len; 595 } else { 596 tcpstat.tcps_sndpack++; 597 tcpstat.tcps_sndbyte += len; 598 } 599 #ifdef notyet 600 if ((m = m_copypack(so->so_snd.sb_mb, off, 601 (int)len, max_linkhdr + hdrlen)) == 0) { 602 error = ENOBUFS; 603 goto out; 604 } 605 /* 606 * m_copypack left space for our hdr; use it. 607 */ 608 m->m_len += hdrlen; 609 m->m_data -= hdrlen; 610 #else 611 MGETHDR(m, M_DONTWAIT, MT_HEADER); 612 if (m == NULL) { 613 error = ENOBUFS; 614 goto out; 615 } 616 #ifdef INET6 617 if (MHLEN < hdrlen + max_linkhdr) { 618 MCLGET(m, M_DONTWAIT); 619 if ((m->m_flags & M_EXT) == 0) { 620 m_freem(m); 621 error = ENOBUFS; 622 goto out; 623 } 624 } 625 #endif 626 m->m_data += max_linkhdr; 627 m->m_len = hdrlen; 628 if (len <= MHLEN - hdrlen - max_linkhdr) { 629 m_copydata(so->so_snd.sb_mb, off, (int) len, 630 mtod(m, caddr_t) + hdrlen); 631 m->m_len += len; 632 } else { 633 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 634 if (m->m_next == 0) { 635 (void) m_free(m); 636 error = ENOBUFS; 637 goto out; 638 } 639 } 640 #endif 641 /* 642 * If we're sending everything we've got, set PUSH. 643 * (This will keep happy those implementations which only 644 * give data to the user when a buffer fills or 645 * a PUSH comes in.) 646 */ 647 if (off + len == so->so_snd.sb_cc) 648 flags |= TH_PUSH; 649 } else { 650 if (tp->t_flags & TF_ACKNOW) 651 tcpstat.tcps_sndacks++; 652 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 653 tcpstat.tcps_sndctrl++; 654 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 655 tcpstat.tcps_sndurg++; 656 else 657 tcpstat.tcps_sndwinup++; 658 659 MGETHDR(m, M_DONTWAIT, MT_HEADER); 660 if (m == NULL) { 661 error = ENOBUFS; 662 goto out; 663 } 664 #ifdef INET6 665 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 666 MHLEN >= hdrlen) { 667 MH_ALIGN(m, hdrlen); 668 } else 669 #endif 670 m->m_data += max_linkhdr; 671 m->m_len = hdrlen; 672 } 673 m->m_pkthdr.rcvif = (struct ifnet *)0; 674 #ifdef INET6 675 if (isipv6) { 676 ip6 = mtod(m, struct ip6_hdr *); 677 th = (struct tcphdr *)(ip6 + 1); 678 tcp_fillheaders(tp, ip6, th); 679 } else 680 #endif /* INET6 */ 681 { 682 ip = mtod(m, struct ip *); 683 ipov = (struct ipovly *)ip; 684 th = (struct tcphdr *)(ip + 1); 685 /* this picks up the pseudo header (w/o the length) */ 686 tcp_fillheaders(tp, ip, th); 687 } 688 689 /* 690 * Fill in fields, remembering maximum advertised 691 * window for use in delaying messages about window sizes. 692 * If resending a FIN, be sure not to use a new sequence number. 693 */ 694 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 695 tp->snd_nxt == tp->snd_max) 696 tp->snd_nxt--; 697 /* 698 * If we are doing retransmissions, then snd_nxt will 699 * not reflect the first unsent octet. For ACK only 700 * packets, we do not want the sequence number of the 701 * retransmitted packet, we want the sequence number 702 * of the next unsent octet. So, if there is no data 703 * (and no SYN or FIN), use snd_max instead of snd_nxt 704 * when filling in ti_seq. But if we are in persist 705 * state, snd_max might reflect one byte beyond the 706 * right edge of the window, so use snd_nxt in that 707 * case, since we know we aren't doing a retransmission. 708 * (retransmit and persist are mutually exclusive...) 709 */ 710 if (len || (flags & (TH_SYN|TH_FIN)) 711 || callout_active(tp->tt_persist)) 712 th->th_seq = htonl(tp->snd_nxt); 713 else 714 th->th_seq = htonl(tp->snd_max); 715 th->th_ack = htonl(tp->rcv_nxt); 716 if (optlen) { 717 bcopy(opt, th + 1, optlen); 718 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 719 } 720 th->th_flags = flags; 721 /* 722 * Calculate receive window. Don't shrink window, 723 * but avoid silly window syndrome. 724 */ 725 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 726 win = 0; 727 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 728 win = (long)(tp->rcv_adv - tp->rcv_nxt); 729 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 730 win = (long)TCP_MAXWIN << tp->rcv_scale; 731 th->th_win = htons((u_short) (win>>tp->rcv_scale)); 732 733 /* 734 * Adjust the RXWIN0SENT flag - indicate that we have advertised 735 * a 0 window. This may cause the remote transmitter to stall. This 736 * flag tells soreceive() to disable delayed acknowledgements when 737 * draining the buffer. This can occur if the receiver is attempting 738 * to read more data then can be buffered prior to transmitting on 739 * the connection. 740 */ 741 if (win == 0) 742 tp->t_flags |= TF_RXWIN0SENT; 743 else 744 tp->t_flags &= ~TF_RXWIN0SENT; 745 746 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 747 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 748 th->th_flags |= TH_URG; 749 } else 750 /* 751 * If no urgent pointer to send, then we pull 752 * the urgent pointer to the left edge of the send window 753 * so that it doesn't drift into the send window on sequence 754 * number wraparound. 755 */ 756 tp->snd_up = tp->snd_una; /* drag it along */ 757 758 /* 759 * Put TCP length in extended header, and then 760 * checksum extended header and data. 761 */ 762 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 763 #ifdef INET6 764 if (isipv6) 765 /* 766 * ip6_plen is not need to be filled now, and will be filled 767 * in ip6_output. 768 */ 769 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 770 sizeof(struct tcphdr) + optlen + len); 771 else 772 #endif /* INET6 */ 773 { 774 m->m_pkthdr.csum_flags = CSUM_TCP; 775 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 776 if (len + optlen) 777 th->th_sum = in_addword(th->th_sum, 778 htons((u_short)(optlen + len))); 779 780 /* IP version must be set here for ipv4/ipv6 checking later */ 781 KASSERT(ip->ip_v == IPVERSION, 782 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 783 } 784 785 /* 786 * In transmit state, time the transmission and arrange for 787 * the retransmit. In persist state, just set snd_max. 788 */ 789 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 790 tcp_seq startseq = tp->snd_nxt; 791 792 /* 793 * Advance snd_nxt over sequence space of this segment. 794 */ 795 if (flags & (TH_SYN|TH_FIN)) { 796 if (flags & TH_SYN) 797 tp->snd_nxt++; 798 if (flags & TH_FIN) { 799 tp->snd_nxt++; 800 tp->t_flags |= TF_SENTFIN; 801 } 802 } 803 tp->snd_nxt += len; 804 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 805 tp->snd_max = tp->snd_nxt; 806 /* 807 * Time this transmission if not a retransmission and 808 * not currently timing anything. 809 */ 810 if (tp->t_rtttime == 0) { 811 tp->t_rtttime = ticks; 812 tp->t_rtseq = startseq; 813 tcpstat.tcps_segstimed++; 814 } 815 } 816 817 /* 818 * Set retransmit timer if not currently set, 819 * and not doing a pure ack or a keep-alive probe. 820 * Initial value for retransmit timer is smoothed 821 * round-trip time + 2 * round-trip time variance. 822 * Initialize shift counter which is used for backoff 823 * of retransmit time. 824 */ 825 if (!callout_active(tp->tt_rexmt) && 826 tp->snd_nxt != tp->snd_una) { 827 if (callout_active(tp->tt_persist)) { 828 callout_stop(tp->tt_persist); 829 tp->t_rxtshift = 0; 830 } 831 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 832 tcp_timer_rexmt, tp); 833 } 834 } else { 835 /* 836 * Persist case, update snd_max but since we are in 837 * persist mode (no window) we do not update snd_nxt. 838 */ 839 int xlen = len; 840 if (flags & TH_SYN) 841 ++xlen; 842 if (flags & TH_FIN) { 843 ++xlen; 844 tp->t_flags |= TF_SENTFIN; 845 } 846 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 847 tp->snd_max = tp->snd_nxt + xlen; 848 } 849 850 #ifdef TCPDEBUG 851 /* 852 * Trace. 853 */ 854 if (so->so_options & SO_DEBUG) 855 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 856 #endif 857 858 /* 859 * Fill in IP length and desired time to live and 860 * send to IP level. There should be a better way 861 * to handle ttl and tos; we could keep them in 862 * the template, but need a way to checksum without them. 863 */ 864 /* 865 * m->m_pkthdr.len should have been set before cksum calcuration, 866 * because in6_cksum() need it. 867 */ 868 #ifdef INET6 869 if (isipv6) { 870 /* 871 * we separately set hoplimit for every segment, since the 872 * user might want to change the value via setsockopt. 873 * Also, desired default hop limit might be changed via 874 * Neighbor Discovery. 875 */ 876 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, 877 tp->t_inpcb->in6p_route.ro_rt ? 878 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 879 : NULL); 880 881 /* TODO: IPv6 IP6TOS_ECT bit on */ 882 error = ip6_output(m, 883 tp->t_inpcb->in6p_outputopts, 884 &tp->t_inpcb->in6p_route, 885 (so->so_options & SO_DONTROUTE), NULL, NULL, 886 tp->t_inpcb); 887 } else 888 #endif /* INET6 */ 889 { 890 struct rtentry *rt; 891 ip->ip_len = m->m_pkthdr.len; 892 #ifdef INET6 893 if (INP_CHECK_SOCKAF(so, AF_INET6)) 894 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, 895 tp->t_inpcb->in6p_route.ro_rt ? 896 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 897 : NULL); 898 else 899 #endif /* INET6 */ 900 ip->ip_ttl = tp->t_inpcb->inp_ip_ttl; /* XXX */ 901 ip->ip_tos = tp->t_inpcb->inp_ip_tos; /* XXX */ 902 /* 903 * See if we should do MTU discovery. We do it only if the following 904 * are true: 905 * 1) we have a valid route to the destination 906 * 2) the MTU is not locked (if it is, then discovery has been 907 * disabled) 908 */ 909 if (path_mtu_discovery 910 && (rt = tp->t_inpcb->inp_route.ro_rt) 911 && rt->rt_flags & RTF_UP 912 && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { 913 ip->ip_off |= IP_DF; 914 } 915 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 916 (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); 917 } 918 if (error) { 919 920 /* 921 * We know that the packet was lost, so back out the 922 * sequence number advance, if any. 923 */ 924 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 925 /* 926 * No need to check for TH_FIN here because 927 * the TF_SENTFIN flag handles that case. 928 */ 929 if ((flags & TH_SYN) == 0) 930 tp->snd_nxt -= len; 931 } 932 933 out: 934 if (error == ENOBUFS) { 935 if (!callout_active(tp->tt_rexmt) && 936 !callout_active(tp->tt_persist)) 937 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 938 tcp_timer_rexmt, tp); 939 tcp_quench(tp->t_inpcb, 0); 940 return (0); 941 } 942 if (error == EMSGSIZE) { 943 /* 944 * ip_output() will have already fixed the route 945 * for us. tcp_mtudisc() will, as its last action, 946 * initiate retransmission, so it is important to 947 * not do so here. 948 */ 949 tcp_mtudisc(tp->t_inpcb, 0); 950 return 0; 951 } 952 if ((error == EHOSTUNREACH || error == ENETDOWN) 953 && TCPS_HAVERCVDSYN(tp->t_state)) { 954 tp->t_softerror = error; 955 return (0); 956 } 957 return (error); 958 } 959 tcpstat.tcps_sndtotal++; 960 961 /* 962 * Data sent (as far as we can tell). 963 * If this advertises a larger window than any other segment, 964 * then remember the size of the advertised window. 965 * Any pending ACK has now been sent. 966 */ 967 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 968 tp->rcv_adv = tp->rcv_nxt + win; 969 tp->last_ack_sent = tp->rcv_nxt; 970 tp->t_flags &= ~TF_ACKNOW; 971 if (tcp_delack_enabled) 972 callout_stop(tp->tt_delack); 973 #if 0 974 /* 975 * This completely breaks TCP if newreno is turned on. What happens 976 * is that if delayed-acks are turned on on the receiver, this code 977 * on the transmitter effectively destroys the TCP window, forcing 978 * it to four packets (1.5Kx4 = 6K window). 979 */ 980 if (sendalot && (!tcp_do_newreno || --maxburst)) 981 goto again; 982 #endif 983 if (sendalot) 984 goto again; 985 return (0); 986 } 987 988 void 989 tcp_setpersist(tp) 990 register struct tcpcb *tp; 991 { 992 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 993 int tt; 994 995 if (callout_active(tp->tt_rexmt)) 996 panic("tcp_setpersist: retransmit pending"); 997 /* 998 * Start/restart persistance timer. 999 */ 1000 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1001 TCPTV_PERSMIN, TCPTV_PERSMAX); 1002 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1003 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1004 tp->t_rxtshift++; 1005 } 1006