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sys/netinet/tcp_output.c
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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 * $FreeBSD$ 35 */ 36 37 #include "opt_inet.h" 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 #ifdef TCP_SIGNATURE 117 int sigoff = 0; 118 #endif 119 register struct mbuf *m; 120 struct ip *ip = NULL; 121 register struct ipovly *ipov = NULL; 122 #ifdef INET6 123 struct ip6_hdr *ip6 = NULL; 124 #endif /* INET6 */ 125 register struct tcphdr *th; 126 u_char opt[TCP_MAXOLEN]; 127 unsigned ipoptlen, optlen, hdrlen; 128 int idle, sendalot; 129 #if 0 130 int maxburst = TCP_MAXBURST; 131 #endif 132 struct rmxp_tao *taop; 133 #ifdef INET6 134 int isipv6; 135 #endif 136 137 #ifdef INET6 138 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 139 #endif 140 141 /* 142 * Determine length of data that should be transmitted, 143 * and flags that will be used. 144 * If there is some data or critical controls (SYN, RST) 145 * to send, then transmit; otherwise, investigate further. 146 */ 147 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 148 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 149 /* 150 * We have been idle for "a while" and no acks are 151 * expected to clock out any data we send -- 152 * slow start to get ack "clock" running again. 153 * 154 * Set the slow-start flight size depending on whether 155 * this is a local network or not. 156 */ 157 if ( 158 #ifdef INET6 159 (isipv6 && in6_localaddr(&tp->t_inpcb->in6p_faddr)) || 160 (!isipv6 && 161 #endif 162 in_localaddr(tp->t_inpcb->inp_faddr) 163 #ifdef INET6 164 ) 165 #endif 166 ) 167 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 168 else 169 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 170 } 171 tp->t_flags &= ~TF_LASTIDLE; 172 if (idle) { 173 if (tp->t_flags & TF_MORETOCOME) { 174 tp->t_flags |= TF_LASTIDLE; 175 idle = 0; 176 } 177 } 178 again: 179 sendalot = 0; 180 off = tp->snd_nxt - tp->snd_una; 181 win = min(tp->snd_wnd, tp->snd_cwnd); 182 win = min(win, tp->snd_bwnd); 183 184 flags = tcp_outflags[tp->t_state]; 185 /* 186 * Get standard flags, and add SYN or FIN if requested by 'hidden' 187 * state flags. 188 */ 189 if (tp->t_flags & TF_NEEDFIN) 190 flags |= TH_FIN; 191 if (tp->t_flags & TF_NEEDSYN) 192 flags |= TH_SYN; 193 194 /* 195 * If in persist timeout with window of 0, send 1 byte. 196 * Otherwise, if window is small but nonzero 197 * and timer expired, we will send what we can 198 * and go to transmit state. 199 */ 200 if (tp->t_force) { 201 if (win == 0) { 202 /* 203 * If we still have some data to send, then 204 * clear the FIN bit. Usually this would 205 * happen below when it realizes that we 206 * aren't sending all the data. However, 207 * if we have exactly 1 byte of unsent data, 208 * then it won't clear the FIN bit below, 209 * and if we are in persist state, we wind 210 * up sending the packet without recording 211 * that we sent the FIN bit. 212 * 213 * We can't just blindly clear the FIN bit, 214 * because if we don't have any more data 215 * to send then the probe will be the FIN 216 * itself. 217 */ 218 if (off < so->so_snd.sb_cc) 219 flags &= ~TH_FIN; 220 win = 1; 221 } else { 222 callout_stop(tp->tt_persist); 223 tp->t_rxtshift = 0; 224 } 225 } 226 227 /* 228 * If snd_nxt == snd_max and we have transmitted a FIN, the 229 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 230 * a negative length. This can also occur when tcp opens up 231 * its congestion window while receiving additional duplicate 232 * acks after fast-retransmit because TCP will reset snd_nxt 233 * to snd_max after the fast-retransmit. 234 * 235 * In the normal retransmit-FIN-only case, however, snd_nxt will 236 * be set to snd_una, the offset will be 0, and the length may 237 * wind up 0. 238 */ 239 len = (long)ulmin(so->so_snd.sb_cc, win) - off; 240 241 taop = tcp_gettaocache(&tp->t_inpcb->inp_inc); 242 243 /* 244 * Lop off SYN bit if it has already been sent. However, if this 245 * is SYN-SENT state and if segment contains data and if we don't 246 * know that foreign host supports TAO, suppress sending segment. 247 */ 248 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 249 flags &= ~TH_SYN; 250 off--, len++; 251 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 252 (taop == NULL || taop->tao_ccsent == 0)) 253 return 0; 254 } 255 256 /* 257 * Be careful not to send data and/or FIN on SYN segments 258 * in cases when no CC option will be sent. 259 * This measure is needed to prevent interoperability problems 260 * with not fully conformant TCP implementations. 261 */ 262 if ((flags & TH_SYN) && 263 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 264 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 265 len = 0; 266 flags &= ~TH_FIN; 267 } 268 269 if (len < 0) { 270 /* 271 * If FIN has been sent but not acked, 272 * but we haven't been called to retransmit, 273 * len will be < 0. Otherwise, window shrank 274 * after we sent into it. If window shrank to 0, 275 * cancel pending retransmit, pull snd_nxt back 276 * to (closed) window, and set the persist timer 277 * if it isn't already going. If the window didn't 278 * close completely, just wait for an ACK. 279 */ 280 len = 0; 281 if (win == 0) { 282 callout_stop(tp->tt_rexmt); 283 tp->t_rxtshift = 0; 284 tp->snd_nxt = tp->snd_una; 285 if (!callout_active(tp->tt_persist)) 286 tcp_setpersist(tp); 287 } 288 } 289 290 /* 291 * len will be >= 0 after this point. Truncate to the maximum 292 * segment length and ensure that FIN is removed if the length 293 * no longer contains the last data byte. 294 */ 295 if (len > tp->t_maxseg) { 296 len = tp->t_maxseg; 297 sendalot = 1; 298 } 299 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 300 flags &= ~TH_FIN; 301 302 win = sbspace(&so->so_rcv); 303 304 /* 305 * Sender silly window avoidance. We transmit under the following 306 * conditions when len is non-zero: 307 * 308 * - We have a full segment 309 * - This is the last buffer in a write()/send() and we are 310 * either idle or running NODELAY 311 * - we've timed out (e.g. persist timer) 312 * - we have more then 1/2 the maximum send window's worth of 313 * data (receiver may be limited the window size) 314 * - we need to retransmit 315 */ 316 if (len) { 317 if (len == tp->t_maxseg) 318 goto send; 319 /* 320 * NOTE! on localhost connections an 'ack' from the remote 321 * end may occur synchronously with the output and cause 322 * us to flush a buffer queued with moretocome. XXX 323 * 324 * note: the len + off check is almost certainly unnecessary. 325 */ 326 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 327 (idle || (tp->t_flags & TF_NODELAY)) && 328 len + off >= so->so_snd.sb_cc && 329 (tp->t_flags & TF_NOPUSH) == 0) { 330 goto send; 331 } 332 if (tp->t_force) /* typ. timeout case */ 333 goto send; 334 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 335 goto send; 336 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 337 goto send; 338 } 339 340 /* 341 * Compare available window to amount of window 342 * known to peer (as advertised window less 343 * next expected input). If the difference is at least two 344 * max size segments, or at least 50% of the maximum possible 345 * window, then want to send a window update to peer. 346 */ 347 if (win > 0) { 348 /* 349 * "adv" is the amount we can increase the window, 350 * taking into account that we are limited by 351 * TCP_MAXWIN << tp->rcv_scale. 352 */ 353 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 354 (tp->rcv_adv - tp->rcv_nxt); 355 356 if (adv >= (long) (2 * tp->t_maxseg)) 357 goto send; 358 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 359 goto send; 360 } 361 362 /* 363 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 364 * is also a catch-all for the retransmit timer timeout case. 365 */ 366 if (tp->t_flags & TF_ACKNOW) 367 goto send; 368 if ((flags & TH_RST) || 369 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 370 goto send; 371 if (SEQ_GT(tp->snd_up, tp->snd_una)) 372 goto send; 373 /* 374 * If our state indicates that FIN should be sent 375 * and we have not yet done so, then we need to send. 376 */ 377 if (flags & TH_FIN && 378 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 379 goto send; 380 381 /* 382 * TCP window updates are not reliable, rather a polling protocol 383 * using ``persist'' packets is used to insure receipt of window 384 * updates. The three ``states'' for the output side are: 385 * idle not doing retransmits or persists 386 * persisting to move a small or zero window 387 * (re)transmitting and thereby not persisting 388 * 389 * callout_active(tp->tt_persist) 390 * is true when we are in persist state. 391 * tp->t_force 392 * is set when we are called to send a persist packet. 393 * callout_active(tp->tt_rexmt) 394 * is set when we are retransmitting 395 * The output side is idle when both timers are zero. 396 * 397 * If send window is too small, there is data to transmit, and no 398 * retransmit or persist is pending, then go to persist state. 399 * If nothing happens soon, send when timer expires: 400 * if window is nonzero, transmit what we can, 401 * otherwise force out a byte. 402 */ 403 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 404 !callout_active(tp->tt_persist)) { 405 tp->t_rxtshift = 0; 406 tcp_setpersist(tp); 407 } 408 409 /* 410 * No reason to send a segment, just return. 411 */ 412 return (0); 413 414 send: 415 /* 416 * Before ESTABLISHED, force sending of initial options 417 * unless TCP set not to do any options. 418 * NOTE: we assume that the IP/TCP header plus TCP options 419 * always fit in a single mbuf, leaving room for a maximum 420 * link header, i.e. 421 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 422 */ 423 optlen = 0; 424 #ifdef INET6 425 if (isipv6) 426 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 427 else 428 #endif 429 hdrlen = sizeof (struct tcpiphdr); 430 if (flags & TH_SYN) { 431 tp->snd_nxt = tp->iss; 432 if ((tp->t_flags & TF_NOOPT) == 0) { 433 u_short mss; 434 435 opt[0] = TCPOPT_MAXSEG; 436 opt[1] = TCPOLEN_MAXSEG; 437 mss = htons((u_short) tcp_mssopt(tp)); 438 (void)memcpy(opt + 2, &mss, sizeof(mss)); 439 optlen = TCPOLEN_MAXSEG; 440 441 if ((tp->t_flags & TF_REQ_SCALE) && 442 ((flags & TH_ACK) == 0 || 443 (tp->t_flags & TF_RCVD_SCALE))) { 444 *((u_int32_t *)(opt + optlen)) = htonl( 445 TCPOPT_NOP << 24 | 446 TCPOPT_WINDOW << 16 | 447 TCPOLEN_WINDOW << 8 | 448 tp->request_r_scale); 449 optlen += 4; 450 } 451 } 452 } 453 454 /* 455 * Send a timestamp and echo-reply if this is a SYN and our side 456 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 457 * and our peer have sent timestamps in our SYN's. 458 */ 459 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 460 (flags & TH_RST) == 0 && 461 ((flags & TH_ACK) == 0 || 462 (tp->t_flags & TF_RCVD_TSTMP))) { 463 u_int32_t *lp = (u_int32_t *)(opt + optlen); 464 465 /* Form timestamp option as shown in appendix A of RFC 1323. */ 466 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 467 *lp++ = htonl(ticks); 468 *lp = htonl(tp->ts_recent); 469 optlen += TCPOLEN_TSTAMP_APPA; 470 } 471 472 /* 473 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 474 * options are allowed (!TF_NOOPT) and it's not a RST. 475 */ 476 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 477 (flags & TH_RST) == 0) { 478 switch (flags & (TH_SYN|TH_ACK)) { 479 /* 480 * This is a normal ACK, send CC if we received CC before 481 * from our peer. 482 */ 483 case TH_ACK: 484 if (!(tp->t_flags & TF_RCVD_CC)) 485 break; 486 /*FALLTHROUGH*/ 487 488 /* 489 * We can only get here in T/TCP's SYN_SENT* state, when 490 * we're a sending a non-SYN segment without waiting for 491 * the ACK of our SYN. A check above assures that we only 492 * do this if our peer understands T/TCP. 493 */ 494 case 0: 495 opt[optlen++] = TCPOPT_NOP; 496 opt[optlen++] = TCPOPT_NOP; 497 opt[optlen++] = TCPOPT_CC; 498 opt[optlen++] = TCPOLEN_CC; 499 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 500 501 optlen += 4; 502 break; 503 504 /* 505 * This is our initial SYN, check whether we have to use 506 * CC or CC.new. 507 */ 508 case TH_SYN: 509 opt[optlen++] = TCPOPT_NOP; 510 opt[optlen++] = TCPOPT_NOP; 511 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 512 TCPOPT_CCNEW : TCPOPT_CC; 513 opt[optlen++] = TCPOLEN_CC; 514 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 515 optlen += 4; 516 break; 517 518 /* 519 * This is a SYN,ACK; send CC and CC.echo if we received 520 * CC from our peer. 521 */ 522 case (TH_SYN|TH_ACK): 523 if (tp->t_flags & TF_RCVD_CC) { 524 opt[optlen++] = TCPOPT_NOP; 525 opt[optlen++] = TCPOPT_NOP; 526 opt[optlen++] = TCPOPT_CC; 527 opt[optlen++] = TCPOLEN_CC; 528 *(u_int32_t *)&opt[optlen] = 529 htonl(tp->cc_send); 530 optlen += 4; 531 opt[optlen++] = TCPOPT_NOP; 532 opt[optlen++] = TCPOPT_NOP; 533 opt[optlen++] = TCPOPT_CCECHO; 534 opt[optlen++] = TCPOLEN_CC; 535 *(u_int32_t *)&opt[optlen] = 536 htonl(tp->cc_recv); 537 optlen += 4; 538 } 539 break; 540 } 541 } 542 543 #ifdef TCP_SIGNATURE 544 #ifdef INET6 545 if (!isipv6) 546 #endif 547 if (tp->t_flags & TF_SIGNATURE) { 548 int i; 549 u_char *bp; 550 /* 551 * Initialize TCP-MD5 option (RFC2385) 552 */ 553 bp = (u_char *)opt + optlen; 554 *bp++ = TCPOPT_SIGNATURE; 555 *bp++ = TCPOLEN_SIGNATURE; 556 sigoff = optlen + 2; 557 for (i = 0; i < TCP_SIGLEN; i++) 558 *bp++ = 0; 559 optlen += TCPOLEN_SIGNATURE; 560 /* 561 * Terminate options list and maintain 32-bit alignment. 562 */ 563 *bp++ = TCPOPT_NOP; 564 *bp++ = TCPOPT_EOL; 565 optlen += 2; 566 } 567 #endif /* TCP_SIGNATURE */ 568 569 hdrlen += optlen; 570 571 #ifdef INET6 572 if (isipv6) 573 ipoptlen = ip6_optlen(tp->t_inpcb); 574 else 575 #endif 576 { 577 if (tp->t_inpcb->inp_options) { 578 ipoptlen = tp->t_inpcb->inp_options->m_len - 579 offsetof(struct ipoption, ipopt_list); 580 } else { 581 ipoptlen = 0; 582 } 583 } 584 #ifdef IPSEC 585 ipoptlen += ipsec_hdrsiz_tcp(tp); 586 #endif 587 588 /* 589 * Adjust data length if insertion of options will 590 * bump the packet length beyond the t_maxopd length. 591 * Clear the FIN bit because we cut off the tail of 592 * the segment. 593 */ 594 if (len + optlen + ipoptlen > tp->t_maxopd) { 595 /* 596 * If there is still more to send, don't close the connection. 597 */ 598 flags &= ~TH_FIN; 599 len = tp->t_maxopd - optlen - ipoptlen; 600 sendalot = 1; 601 } 602 603 /*#ifdef DIAGNOSTIC*/ 604 #ifdef INET6 605 if (max_linkhdr + hdrlen > MCLBYTES) 606 panic("tcphdr too big"); 607 #else 608 if (max_linkhdr + hdrlen > MHLEN) 609 panic("tcphdr too big"); 610 #endif 611 /*#endif*/ 612 613 /* 614 * Grab a header mbuf, attaching a copy of data to 615 * be transmitted, and initialize the header from 616 * the template for sends on this connection. 617 */ 618 if (len) { 619 if (tp->t_force && len == 1) 620 tcpstat.tcps_sndprobe++; 621 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 622 tcpstat.tcps_sndrexmitpack++; 623 tcpstat.tcps_sndrexmitbyte += len; 624 } else { 625 tcpstat.tcps_sndpack++; 626 tcpstat.tcps_sndbyte += len; 627 } 628 #ifdef notyet 629 if ((m = m_copypack(so->so_snd.sb_mb, off, 630 (int)len, max_linkhdr + hdrlen)) == 0) { 631 error = ENOBUFS; 632 goto out; 633 } 634 /* 635 * m_copypack left space for our hdr; use it. 636 */ 637 m->m_len += hdrlen; 638 m->m_data -= hdrlen; 639 #else 640 MGETHDR(m, M_DONTWAIT, MT_HEADER); 641 if (m == NULL) { 642 error = ENOBUFS; 643 goto out; 644 } 645 #ifdef INET6 646 if (MHLEN < hdrlen + max_linkhdr) { 647 MCLGET(m, M_DONTWAIT); 648 if ((m->m_flags & M_EXT) == 0) { 649 m_freem(m); 650 error = ENOBUFS; 651 goto out; 652 } 653 } 654 #endif 655 m->m_data += max_linkhdr; 656 m->m_len = hdrlen; 657 if (len <= MHLEN - hdrlen - max_linkhdr) { 658 m_copydata(so->so_snd.sb_mb, off, (int) len, 659 mtod(m, caddr_t) + hdrlen); 660 m->m_len += len; 661 } else { 662 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 663 if (m->m_next == 0) { 664 (void) m_free(m); 665 error = ENOBUFS; 666 goto out; 667 } 668 } 669 #endif 670 /* 671 * If we're sending everything we've got, set PUSH. 672 * (This will keep happy those implementations which only 673 * give data to the user when a buffer fills or 674 * a PUSH comes in.) 675 */ 676 if (off + len == so->so_snd.sb_cc) 677 flags |= TH_PUSH; 678 } else { 679 if (tp->t_flags & TF_ACKNOW) 680 tcpstat.tcps_sndacks++; 681 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 682 tcpstat.tcps_sndctrl++; 683 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 684 tcpstat.tcps_sndurg++; 685 else 686 tcpstat.tcps_sndwinup++; 687 688 MGETHDR(m, M_DONTWAIT, MT_HEADER); 689 if (m == NULL) { 690 error = ENOBUFS; 691 goto out; 692 } 693 #ifdef INET6 694 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 695 MHLEN >= hdrlen) { 696 MH_ALIGN(m, hdrlen); 697 } else 698 #endif 699 m->m_data += max_linkhdr; 700 m->m_len = hdrlen; 701 } 702 m->m_pkthdr.rcvif = (struct ifnet *)0; 703 #ifdef INET6 704 if (isipv6) { 705 ip6 = mtod(m, struct ip6_hdr *); 706 th = (struct tcphdr *)(ip6 + 1); 707 tcp_fillheaders(tp, ip6, th); 708 } else 709 #endif /* INET6 */ 710 { 711 ip = mtod(m, struct ip *); 712 ipov = (struct ipovly *)ip; 713 th = (struct tcphdr *)(ip + 1); 714 /* this picks up the pseudo header (w/o the length) */ 715 tcp_fillheaders(tp, ip, th); 716 } 717 718 /* 719 * Fill in fields, remembering maximum advertised 720 * window for use in delaying messages about window sizes. 721 * If resending a FIN, be sure not to use a new sequence number. 722 */ 723 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 724 tp->snd_nxt == tp->snd_max) 725 tp->snd_nxt--; 726 /* 727 * If we are doing retransmissions, then snd_nxt will 728 * not reflect the first unsent octet. For ACK only 729 * packets, we do not want the sequence number of the 730 * retransmitted packet, we want the sequence number 731 * of the next unsent octet. So, if there is no data 732 * (and no SYN or FIN), use snd_max instead of snd_nxt 733 * when filling in ti_seq. But if we are in persist 734 * state, snd_max might reflect one byte beyond the 735 * right edge of the window, so use snd_nxt in that 736 * case, since we know we aren't doing a retransmission. 737 * (retransmit and persist are mutually exclusive...) 738 */ 739 if (len || (flags & (TH_SYN|TH_FIN)) 740 || callout_active(tp->tt_persist)) 741 th->th_seq = htonl(tp->snd_nxt); 742 else 743 th->th_seq = htonl(tp->snd_max); 744 th->th_ack = htonl(tp->rcv_nxt); 745 if (optlen) { 746 bcopy(opt, th + 1, optlen); 747 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 748 } 749 th->th_flags = flags; 750 /* 751 * Calculate receive window. Don't shrink window, 752 * but avoid silly window syndrome. 753 */ 754 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 755 win = 0; 756 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 757 win = (long)(tp->rcv_adv - tp->rcv_nxt); 758 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 759 win = (long)TCP_MAXWIN << tp->rcv_scale; 760 th->th_win = htons((u_short) (win>>tp->rcv_scale)); 761 762 /* 763 * Adjust the RXWIN0SENT flag - indicate that we have advertised 764 * a 0 window. This may cause the remote transmitter to stall. This 765 * flag tells soreceive() to disable delayed acknowledgements when 766 * draining the buffer. This can occur if the receiver is attempting 767 * to read more data then can be buffered prior to transmitting on 768 * the connection. 769 */ 770 if (win == 0) 771 tp->t_flags |= TF_RXWIN0SENT; 772 else 773 tp->t_flags &= ~TF_RXWIN0SENT; 774 775 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 776 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 777 th->th_flags |= TH_URG; 778 } else 779 /* 780 * If no urgent pointer to send, then we pull 781 * the urgent pointer to the left edge of the send window 782 * so that it doesn't drift into the send window on sequence 783 * number wraparound. 784 */ 785 tp->snd_up = tp->snd_una; /* drag it along */ 786 787 #ifdef TCP_SIGNATURE 788 #ifdef INET6 789 if (!isipv6) 790 #endif 791 if (tp->t_flags & TF_SIGNATURE) 792 tcp_signature_compute(m, sizeof(struct ip), len, optlen, 793 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 794 #endif 795 796 /* 797 * Put TCP length in extended header, and then 798 * checksum extended header and data. 799 */ 800 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 801 #ifdef INET6 802 if (isipv6) 803 /* 804 * ip6_plen is not need to be filled now, and will be filled 805 * in ip6_output. 806 */ 807 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 808 sizeof(struct tcphdr) + optlen + len); 809 else 810 #endif /* INET6 */ 811 { 812 m->m_pkthdr.csum_flags = CSUM_TCP; 813 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 814 if (len + optlen) 815 th->th_sum = in_addword(th->th_sum, 816 htons((u_short)(optlen + len))); 817 818 /* IP version must be set here for ipv4/ipv6 checking later */ 819 KASSERT(ip->ip_v == IPVERSION, 820 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 821 } 822 823 /* 824 * In transmit state, time the transmission and arrange for 825 * the retransmit. In persist state, just set snd_max. 826 */ 827 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 828 tcp_seq startseq = tp->snd_nxt; 829 830 /* 831 * Advance snd_nxt over sequence space of this segment. 832 */ 833 if (flags & (TH_SYN|TH_FIN)) { 834 if (flags & TH_SYN) 835 tp->snd_nxt++; 836 if (flags & TH_FIN) { 837 tp->snd_nxt++; 838 tp->t_flags |= TF_SENTFIN; 839 } 840 } 841 tp->snd_nxt += len; 842 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 843 tp->snd_max = tp->snd_nxt; 844 /* 845 * Time this transmission if not a retransmission and 846 * not currently timing anything. 847 */ 848 if (tp->t_rtttime == 0) { 849 tp->t_rtttime = ticks; 850 tp->t_rtseq = startseq; 851 tcpstat.tcps_segstimed++; 852 } 853 } 854 855 /* 856 * Set retransmit timer if not currently set, 857 * and not doing a pure ack or a keep-alive probe. 858 * Initial value for retransmit timer is smoothed 859 * round-trip time + 2 * round-trip time variance. 860 * Initialize shift counter which is used for backoff 861 * of retransmit time. 862 */ 863 if (!callout_active(tp->tt_rexmt) && 864 tp->snd_nxt != tp->snd_una) { 865 if (callout_active(tp->tt_persist)) { 866 callout_stop(tp->tt_persist); 867 tp->t_rxtshift = 0; 868 } 869 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 870 tcp_timer_rexmt, tp); 871 } 872 } else { 873 /* 874 * Persist case, update snd_max but since we are in 875 * persist mode (no window) we do not update snd_nxt. 876 */ 877 int xlen = len; 878 if (flags & TH_SYN) 879 ++xlen; 880 if (flags & TH_FIN) { 881 ++xlen; 882 tp->t_flags |= TF_SENTFIN; 883 } 884 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 885 tp->snd_max = tp->snd_nxt + xlen; 886 } 887 888 #ifdef TCPDEBUG 889 /* 890 * Trace. 891 */ 892 if (so->so_options & SO_DEBUG) 893 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 894 #endif 895 896 /* 897 * Fill in IP length and desired time to live and 898 * send to IP level. There should be a better way 899 * to handle ttl and tos; we could keep them in 900 * the template, but need a way to checksum without them. 901 */ 902 /* 903 * m->m_pkthdr.len should have been set before cksum calcuration, 904 * because in6_cksum() need it. 905 */ 906 #ifdef INET6 907 if (isipv6) { 908 /* 909 * we separately set hoplimit for every segment, since the 910 * user might want to change the value via setsockopt. 911 * Also, desired default hop limit might be changed via 912 * Neighbor Discovery. 913 */ 914 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, 915 tp->t_inpcb->in6p_route.ro_rt ? 916 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 917 : NULL); 918 919 /* TODO: IPv6 IP6TOS_ECT bit on */ 920 error = ip6_output(m, 921 tp->t_inpcb->in6p_outputopts, 922 &tp->t_inpcb->in6p_route, 923 (so->so_options & SO_DONTROUTE), NULL, NULL, 924 tp->t_inpcb); 925 } else 926 #endif /* INET6 */ 927 { 928 struct rtentry *rt; 929 ip->ip_len = m->m_pkthdr.len; 930 #ifdef INET6 931 if (INP_CHECK_SOCKAF(so, AF_INET6)) 932 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, 933 tp->t_inpcb->in6p_route.ro_rt ? 934 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 935 : NULL); 936 else 937 #endif /* INET6 */ 938 ip->ip_ttl = tp->t_inpcb->inp_ip_ttl; /* XXX */ 939 ip->ip_tos = tp->t_inpcb->inp_ip_tos; /* XXX */ 940 /* 941 * See if we should do MTU discovery. We do it only if the following 942 * are true: 943 * 1) we have a valid route to the destination 944 * 2) the MTU is not locked (if it is, then discovery has been 945 * disabled) 946 */ 947 if (path_mtu_discovery 948 && (rt = tp->t_inpcb->inp_route.ro_rt) 949 && rt->rt_flags & RTF_UP 950 && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { 951 ip->ip_off |= IP_DF; 952 } 953 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 954 (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); 955 } 956 if (error) { 957 958 /* 959 * We know that the packet was lost, so back out the 960 * sequence number advance, if any. 961 */ 962 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 963 /* 964 * No need to check for TH_FIN here because 965 * the TF_SENTFIN flag handles that case. 966 */ 967 if ((flags & TH_SYN) == 0) 968 tp->snd_nxt -= len; 969 } 970 971 out: 972 if (error == ENOBUFS) { 973 if (!callout_active(tp->tt_rexmt) && 974 !callout_active(tp->tt_persist)) 975 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 976 tcp_timer_rexmt, tp); 977 tcp_quench(tp->t_inpcb, 0); 978 return (0); 979 } 980 if (error == EMSGSIZE) { 981 /* 982 * ip_output() will have already fixed the route 983 * for us. tcp_mtudisc() will, as its last action, 984 * initiate retransmission, so it is important to 985 * not do so here. 986 */ 987 tcp_mtudisc(tp->t_inpcb, 0); 988 return 0; 989 } 990 if ((error == EHOSTUNREACH || error == ENETDOWN) 991 && TCPS_HAVERCVDSYN(tp->t_state)) { 992 tp->t_softerror = error; 993 return (0); 994 } 995 return (error); 996 } 997 tcpstat.tcps_sndtotal++; 998 999 /* 1000 * Data sent (as far as we can tell). 1001 * If this advertises a larger window than any other segment, 1002 * then remember the size of the advertised window. 1003 * Any pending ACK has now been sent. 1004 */ 1005 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 1006 tp->rcv_adv = tp->rcv_nxt + win; 1007 tp->last_ack_sent = tp->rcv_nxt; 1008 tp->t_flags &= ~TF_ACKNOW; 1009 if (tcp_delack_enabled) 1010 callout_stop(tp->tt_delack); 1011 #if 0 1012 /* 1013 * This completely breaks TCP if newreno is turned on. What happens 1014 * is that if delayed-acks are turned on on the receiver, this code 1015 * on the transmitter effectively destroys the TCP window, forcing 1016 * it to four packets (1.5Kx4 = 6K window). 1017 */ 1018 if (sendalot && (!tcp_do_newreno || --maxburst)) 1019 goto again; 1020 #endif 1021 if (sendalot) 1022 goto again; 1023 return (0); 1024 } 1025 1026 void 1027 tcp_setpersist(tp) 1028 register struct tcpcb *tp; 1029 { 1030 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1031 int tt; 1032 1033 if (callout_active(tp->tt_rexmt)) 1034 panic("tcp_setpersist: retransmit pending"); 1035 /* 1036 * Start/restart persistance timer. 1037 */ 1038 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1039 TCPTV_PERSMIN, TCPTV_PERSMAX); 1040 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1041 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1042 tp->t_rxtshift++; 1043 }
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