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_mac.h" 41 #include "opt_tcpdebug.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/domain.h> 46 #include <sys/kernel.h> 47 #include <sys/lock.h> 48 #include <sys/mac.h> 49 #include <sys/mbuf.h> 50 #include <sys/mutex.h> 51 #include <sys/protosw.h> 52 #include <sys/socket.h> 53 #include <sys/socketvar.h> 54 #include <sys/sysctl.h> 55 56 #include <net/route.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #ifdef INET6 64 #include <netinet6/in6_pcb.h> 65 #include <netinet/ip6.h> 66 #include <netinet6/ip6_var.h> 67 #endif 68 #include <netinet/tcp.h> 69 #define TCPOUTFLAGS 70 #include <netinet/tcp_fsm.h> 71 #include <netinet/tcp_seq.h> 72 #include <netinet/tcp_timer.h> 73 #include <netinet/tcp_var.h> 74 #include <netinet/tcpip.h> 75 #ifdef TCPDEBUG 76 #include <netinet/tcp_debug.h> 77 #endif 78 79 #ifdef IPSEC 80 #include <netinet6/ipsec.h> 81 #endif /*IPSEC*/ 82 83 #ifdef FAST_IPSEC 84 #include <netipsec/ipsec.h> 85 #define IPSEC 86 #endif /*FAST_IPSEC*/ 87 88 #include <machine/in_cksum.h> 89 90 #ifdef notyet 91 extern struct mbuf *m_copypack(); 92 #endif 93 94 int path_mtu_discovery = 1; 95 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 96 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 97 98 int ss_fltsz = 1; 99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 100 &ss_fltsz, 1, "Slow start flight size"); 101 102 int ss_fltsz_local = 4; 103 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 104 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 105 106 int tcp_do_newreno = 1; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 108 0, "Enable NewReno Algorithms"); 109 110 /* 111 * Tcp output routine: figure out what should be sent and send it. 112 */ 113 int 114 tcp_output(struct tcpcb *tp) 115 { 116 struct socket *so = tp->t_inpcb->inp_socket; 117 long len, recwin, sendwin; 118 int off, flags, error; 119 #ifdef TCP_SIGNATURE 120 int sigoff = 0; 121 #endif 122 struct mbuf *m; 123 struct ip *ip = NULL; 124 struct ipovly *ipov = NULL; 125 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 tao; 133 #ifdef INET6 134 struct ip6_hdr *ip6 = NULL; 135 int isipv6; 136 137 bzero(&tao, sizeof(tao)); 138 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 139 #endif 140 141 INP_LOCK_ASSERT(tp->t_inpcb); 142 143 /* 144 * Determine length of data that should be transmitted, 145 * and flags that will be used. 146 * If there is some data or critical controls (SYN, RST) 147 * to send, then transmit; otherwise, investigate further. 148 */ 149 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 150 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 151 /* 152 * We have been idle for "a while" and no acks are 153 * expected to clock out any data we send -- 154 * slow start to get ack "clock" running again. 155 * 156 * Set the slow-start flight size depending on whether 157 * this is a local network or not. 158 */ 159 int ss = ss_fltsz; 160 #ifdef INET6 161 if (isipv6) { 162 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 163 ss = ss_fltsz_local; 164 } else 165 #endif /* INET6 */ 166 if (in_localaddr(tp->t_inpcb->inp_faddr)) 167 ss = ss_fltsz_local; 168 tp->snd_cwnd = tp->t_maxseg * ss; 169 } 170 tp->t_flags &= ~TF_LASTIDLE; 171 if (idle) { 172 if (tp->t_flags & TF_MORETOCOME) { 173 tp->t_flags |= TF_LASTIDLE; 174 idle = 0; 175 } 176 } 177 again: 178 sendalot = 0; 179 off = tp->snd_nxt - tp->snd_una; 180 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 181 sendwin = min(sendwin, tp->snd_bwnd); 182 183 flags = tcp_outflags[tp->t_state]; 184 /* 185 * Get standard flags, and add SYN or FIN if requested by 'hidden' 186 * state flags. 187 */ 188 if (tp->t_flags & TF_NEEDFIN) 189 flags |= TH_FIN; 190 if (tp->t_flags & TF_NEEDSYN) 191 flags |= TH_SYN; 192 193 /* 194 * If in persist timeout with window of 0, send 1 byte. 195 * Otherwise, if window is small but nonzero 196 * and timer expired, we will send what we can 197 * and go to transmit state. 198 */ 199 if (tp->t_force) { 200 if (sendwin == 0) { 201 /* 202 * If we still have some data to send, then 203 * clear the FIN bit. Usually this would 204 * happen below when it realizes that we 205 * aren't sending all the data. However, 206 * if we have exactly 1 byte of unsent data, 207 * then it won't clear the FIN bit below, 208 * and if we are in persist state, we wind 209 * up sending the packet without recording 210 * that we sent the FIN bit. 211 * 212 * We can't just blindly clear the FIN bit, 213 * because if we don't have any more data 214 * to send then the probe will be the FIN 215 * itself. 216 */ 217 if (off < so->so_snd.sb_cc) 218 flags &= ~TH_FIN; 219 sendwin = 1; 220 } else { 221 callout_stop(tp->tt_persist); 222 tp->t_rxtshift = 0; 223 } 224 } 225 226 /* 227 * If snd_nxt == snd_max and we have transmitted a FIN, the 228 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 229 * a negative length. This can also occur when TCP opens up 230 * its congestion window while receiving additional duplicate 231 * acks after fast-retransmit because TCP will reset snd_nxt 232 * to snd_max after the fast-retransmit. 233 * 234 * In the normal retransmit-FIN-only case, however, snd_nxt will 235 * be set to snd_una, the offset will be 0, and the length may 236 * wind up 0. 237 */ 238 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 239 240 241 /* 242 * Lop off SYN bit if it has already been sent. However, if this 243 * is SYN-SENT state and if segment contains data and if we don't 244 * know that foreign host supports TAO, suppress sending segment. 245 */ 246 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 247 flags &= ~TH_SYN; 248 off--, len++; 249 if (tcp_do_rfc1644) 250 tcp_hc_gettao(&tp->t_inpcb->inp_inc, &tao); 251 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 252 tao.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 (sendwin == 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 recwin = 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 * Skip this if the connection is in T/TCP half-open state. 347 */ 348 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN)) { 349 /* 350 * "adv" is the amount we can increase the window, 351 * taking into account that we are limited by 352 * TCP_MAXWIN << tp->rcv_scale. 353 */ 354 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 355 (tp->rcv_adv - tp->rcv_nxt); 356 357 if (adv >= (long) (2 * tp->t_maxseg)) 358 goto send; 359 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 360 goto send; 361 } 362 363 /* 364 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 365 * is also a catch-all for the retransmit timer timeout case. 366 */ 367 if (tp->t_flags & TF_ACKNOW) 368 goto send; 369 if ((flags & TH_RST) || 370 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 371 goto send; 372 if (SEQ_GT(tp->snd_up, tp->snd_una)) 373 goto send; 374 /* 375 * If our state indicates that FIN should be sent 376 * and we have not yet done so, then we need to send. 377 */ 378 if (flags & TH_FIN && 379 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 380 goto send; 381 382 /* 383 * TCP window updates are not reliable, rather a polling protocol 384 * using ``persist'' packets is used to insure receipt of window 385 * updates. The three ``states'' for the output side are: 386 * idle not doing retransmits or persists 387 * persisting to move a small or zero window 388 * (re)transmitting and thereby not persisting 389 * 390 * callout_active(tp->tt_persist) 391 * is true when we are in persist state. 392 * tp->t_force 393 * is set when we are called to send a persist packet. 394 * callout_active(tp->tt_rexmt) 395 * is set when we are retransmitting 396 * The output side is idle when both timers are zero. 397 * 398 * If send window is too small, there is data to transmit, and no 399 * retransmit or persist is pending, then go to persist state. 400 * If nothing happens soon, send when timer expires: 401 * if window is nonzero, transmit what we can, 402 * otherwise force out a byte. 403 */ 404 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 405 !callout_active(tp->tt_persist)) { 406 tp->t_rxtshift = 0; 407 tcp_setpersist(tp); 408 } 409 410 /* 411 * No reason to send a segment, just return. 412 */ 413 return (0); 414 415 send: 416 /* 417 * Before ESTABLISHED, force sending of initial options 418 * unless TCP set not to do any options. 419 * NOTE: we assume that the IP/TCP header plus TCP options 420 * always fit in a single mbuf, leaving room for a maximum 421 * link header, i.e. 422 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 423 */ 424 optlen = 0; 425 #ifdef INET6 426 if (isipv6) 427 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 428 else 429 #endif 430 hdrlen = sizeof (struct tcpiphdr); 431 if (flags & TH_SYN) { 432 tp->snd_nxt = tp->iss; 433 if ((tp->t_flags & TF_NOOPT) == 0) { 434 u_short mss; 435 436 opt[0] = TCPOPT_MAXSEG; 437 opt[1] = TCPOLEN_MAXSEG; 438 mss = htons((u_short) tcp_mssopt(&tp->t_inpcb->inp_inc)); 439 (void)memcpy(opt + 2, &mss, sizeof(mss)); 440 optlen = TCPOLEN_MAXSEG; 441 442 if ((tp->t_flags & TF_REQ_SCALE) && 443 ((flags & TH_ACK) == 0 || 444 (tp->t_flags & TF_RCVD_SCALE))) { 445 *((u_int32_t *)(opt + optlen)) = htonl( 446 TCPOPT_NOP << 24 | 447 TCPOPT_WINDOW << 16 | 448 TCPOLEN_WINDOW << 8 | 449 tp->request_r_scale); 450 optlen += 4; 451 } 452 } 453 } 454 455 /* 456 * Send a timestamp and echo-reply if this is a SYN and our side 457 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 458 * and our peer have sent timestamps in our SYN's. 459 */ 460 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 461 (flags & TH_RST) == 0 && 462 ((flags & TH_ACK) == 0 || 463 (tp->t_flags & TF_RCVD_TSTMP))) { 464 u_int32_t *lp = (u_int32_t *)(opt + optlen); 465 466 /* Form timestamp option as shown in appendix A of RFC 1323. */ 467 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 468 *lp++ = htonl(ticks); 469 *lp = htonl(tp->ts_recent); 470 optlen += TCPOLEN_TSTAMP_APPA; 471 } 472 473 /* 474 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 475 * options are allowed (!TF_NOOPT) and it's not a RST. 476 */ 477 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 478 (flags & TH_RST) == 0) { 479 switch (flags & (TH_SYN|TH_ACK)) { 480 /* 481 * This is a normal ACK, send CC if we received CC before 482 * from our peer. 483 */ 484 case TH_ACK: 485 if (!(tp->t_flags & TF_RCVD_CC)) 486 break; 487 /*FALLTHROUGH*/ 488 489 /* 490 * We can only get here in T/TCP's SYN_SENT* state, when 491 * we're a sending a non-SYN segment without waiting for 492 * the ACK of our SYN. A check above assures that we only 493 * do this if our peer understands T/TCP. 494 */ 495 case 0: 496 opt[optlen++] = TCPOPT_NOP; 497 opt[optlen++] = TCPOPT_NOP; 498 opt[optlen++] = TCPOPT_CC; 499 opt[optlen++] = TCPOLEN_CC; 500 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 501 502 optlen += 4; 503 break; 504 505 /* 506 * This is our initial SYN, check whether we have to use 507 * CC or CC.new. 508 */ 509 case TH_SYN: 510 opt[optlen++] = TCPOPT_NOP; 511 opt[optlen++] = TCPOPT_NOP; 512 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 513 TCPOPT_CCNEW : TCPOPT_CC; 514 opt[optlen++] = TCPOLEN_CC; 515 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 516 optlen += 4; 517 break; 518 519 /* 520 * This is a SYN,ACK; send CC and CC.echo if we received 521 * CC from our peer. 522 */ 523 case (TH_SYN|TH_ACK): 524 if (tp->t_flags & TF_RCVD_CC) { 525 opt[optlen++] = TCPOPT_NOP; 526 opt[optlen++] = TCPOPT_NOP; 527 opt[optlen++] = TCPOPT_CC; 528 opt[optlen++] = TCPOLEN_CC; 529 *(u_int32_t *)&opt[optlen] = 530 htonl(tp->cc_send); 531 optlen += 4; 532 opt[optlen++] = TCPOPT_NOP; 533 opt[optlen++] = TCPOPT_NOP; 534 opt[optlen++] = TCPOPT_CCECHO; 535 opt[optlen++] = TCPOLEN_CC; 536 *(u_int32_t *)&opt[optlen] = 537 htonl(tp->cc_recv); 538 optlen += 4; 539 } 540 break; 541 } 542 } 543 544 #ifdef TCP_SIGNATURE 545 #ifdef INET6 546 if (!isipv6) 547 #endif 548 if (tp->t_flags & TF_SIGNATURE) { 549 int i; 550 u_char *bp; 551 552 /* Initialize TCP-MD5 option (RFC2385) */ 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 *bp++ = TCPOPT_NOP; 563 *bp++ = TCPOPT_EOL; 564 optlen += 2; 565 } 566 #endif /* TCP_SIGNATURE */ 567 568 hdrlen += optlen; 569 570 #ifdef INET6 571 if (isipv6) 572 ipoptlen = ip6_optlen(tp->t_inpcb); 573 else 574 #endif 575 if (tp->t_inpcb->inp_options) 576 ipoptlen = tp->t_inpcb->inp_options->m_len - 577 offsetof(struct ipoption, ipopt_list); 578 else 579 ipoptlen = 0; 580 #ifdef IPSEC 581 ipoptlen += ipsec_hdrsiz_tcp(tp); 582 #endif 583 584 /* 585 * Adjust data length if insertion of options will 586 * bump the packet length beyond the t_maxopd length. 587 * Clear the FIN bit because we cut off the tail of 588 * the segment. 589 */ 590 if (len + optlen + ipoptlen > tp->t_maxopd) { 591 /* 592 * If there is still more to send, don't close the connection. 593 */ 594 flags &= ~TH_FIN; 595 len = tp->t_maxopd - optlen - ipoptlen; 596 sendalot = 1; 597 } 598 599 /*#ifdef DIAGNOSTIC*/ 600 #ifdef INET6 601 if (max_linkhdr + hdrlen > MCLBYTES) 602 #else 603 if (max_linkhdr + hdrlen > MHLEN) 604 #endif 605 panic("tcphdr too big"); 606 /*#endif*/ 607 608 /* 609 * Grab a header mbuf, attaching a copy of data to 610 * be transmitted, and initialize the header from 611 * the template for sends on this connection. 612 */ 613 if (len) { 614 if (tp->t_force && len == 1) 615 tcpstat.tcps_sndprobe++; 616 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 617 tcpstat.tcps_sndrexmitpack++; 618 tcpstat.tcps_sndrexmitbyte += len; 619 } else { 620 tcpstat.tcps_sndpack++; 621 tcpstat.tcps_sndbyte += len; 622 } 623 #ifdef notyet 624 if ((m = m_copypack(so->so_snd.sb_mb, off, 625 (int)len, max_linkhdr + hdrlen)) == 0) { 626 error = ENOBUFS; 627 goto out; 628 } 629 /* 630 * m_copypack left space for our hdr; use it. 631 */ 632 m->m_len += hdrlen; 633 m->m_data -= hdrlen; 634 #else 635 MGETHDR(m, M_DONTWAIT, MT_HEADER); 636 if (m == NULL) { 637 error = ENOBUFS; 638 goto out; 639 } 640 #ifdef INET6 641 if (MHLEN < hdrlen + max_linkhdr) { 642 MCLGET(m, M_DONTWAIT); 643 if ((m->m_flags & M_EXT) == 0) { 644 m_freem(m); 645 error = ENOBUFS; 646 goto out; 647 } 648 } 649 #endif 650 m->m_data += max_linkhdr; 651 m->m_len = hdrlen; 652 if (len <= MHLEN - hdrlen - max_linkhdr) { 653 m_copydata(so->so_snd.sb_mb, off, (int) len, 654 mtod(m, caddr_t) + hdrlen); 655 m->m_len += len; 656 } else { 657 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 658 if (m->m_next == 0) { 659 (void) m_free(m); 660 error = ENOBUFS; 661 goto out; 662 } 663 } 664 #endif 665 /* 666 * If we're sending everything we've got, set PUSH. 667 * (This will keep happy those implementations which only 668 * give data to the user when a buffer fills or 669 * a PUSH comes in.) 670 */ 671 if (off + len == so->so_snd.sb_cc) 672 flags |= TH_PUSH; 673 } else { 674 if (tp->t_flags & TF_ACKNOW) 675 tcpstat.tcps_sndacks++; 676 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 677 tcpstat.tcps_sndctrl++; 678 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 679 tcpstat.tcps_sndurg++; 680 else 681 tcpstat.tcps_sndwinup++; 682 683 MGETHDR(m, M_DONTWAIT, MT_HEADER); 684 if (m == NULL) { 685 error = ENOBUFS; 686 goto out; 687 } 688 #ifdef INET6 689 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 690 MHLEN >= hdrlen) { 691 MH_ALIGN(m, hdrlen); 692 } else 693 #endif 694 m->m_data += max_linkhdr; 695 m->m_len = hdrlen; 696 } 697 m->m_pkthdr.rcvif = (struct ifnet *)0; 698 #ifdef MAC 699 mac_create_mbuf_from_socket(so, m); 700 #endif 701 #ifdef INET6 702 if (isipv6) { 703 ip6 = mtod(m, struct ip6_hdr *); 704 th = (struct tcphdr *)(ip6 + 1); 705 tcpip_fillheaders(tp->t_inpcb, ip6, th); 706 } else 707 #endif /* INET6 */ 708 { 709 ip = mtod(m, struct ip *); 710 ipov = (struct ipovly *)ip; 711 th = (struct tcphdr *)(ip + 1); 712 tcpip_fillheaders(tp->t_inpcb, ip, th); 713 } 714 715 /* 716 * Fill in fields, remembering maximum advertised 717 * window for use in delaying messages about window sizes. 718 * If resending a FIN, be sure not to use a new sequence number. 719 */ 720 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 721 tp->snd_nxt == tp->snd_max) 722 tp->snd_nxt--; 723 /* 724 * If we are doing retransmissions, then snd_nxt will 725 * not reflect the first unsent octet. For ACK only 726 * packets, we do not want the sequence number of the 727 * retransmitted packet, we want the sequence number 728 * of the next unsent octet. So, if there is no data 729 * (and no SYN or FIN), use snd_max instead of snd_nxt 730 * when filling in ti_seq. But if we are in persist 731 * state, snd_max might reflect one byte beyond the 732 * right edge of the window, so use snd_nxt in that 733 * case, since we know we aren't doing a retransmission. 734 * (retransmit and persist are mutually exclusive...) 735 */ 736 if (len || (flags & (TH_SYN|TH_FIN)) 737 || callout_active(tp->tt_persist)) 738 th->th_seq = htonl(tp->snd_nxt); 739 else 740 th->th_seq = htonl(tp->snd_max); 741 th->th_ack = htonl(tp->rcv_nxt); 742 if (optlen) { 743 bcopy(opt, th + 1, optlen); 744 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 745 } 746 th->th_flags = flags; 747 /* 748 * Calculate receive window. Don't shrink window, 749 * but avoid silly window syndrome. 750 */ 751 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 752 recwin < (long)tp->t_maxseg) 753 recwin = 0; 754 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 755 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 756 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 757 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 758 th->th_win = htons((u_short) (recwin >> tp->rcv_scale)); 759 760 761 /* 762 * Adjust the RXWIN0SENT flag - indicate that we have advertised 763 * a 0 window. This may cause the remote transmitter to stall. This 764 * flag tells soreceive() to disable delayed acknowledgements when 765 * draining the buffer. This can occur if the receiver is attempting 766 * to read more data then can be buffered prior to transmitting on 767 * the connection. 768 */ 769 if (recwin == 0) 770 tp->t_flags |= TF_RXWIN0SENT; 771 else 772 tp->t_flags &= ~TF_RXWIN0SENT; 773 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 774 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 775 th->th_flags |= TH_URG; 776 } else 777 /* 778 * If no urgent pointer to send, then we pull 779 * the urgent pointer to the left edge of the send window 780 * so that it doesn't drift into the send window on sequence 781 * number wraparound. 782 */ 783 tp->snd_up = tp->snd_una; /* drag it along */ 784 785 #ifdef TCP_SIGNATURE 786 #ifdef INET6 787 if (!isipv6) 788 #endif 789 if (tp->t_flags & TF_SIGNATURE) 790 tcp_signature_compute(m, sizeof(struct ip), len, optlen, 791 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 792 #endif 793 794 /* 795 * Put TCP length in extended header, and then 796 * checksum extended header and data. 797 */ 798 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 799 #ifdef INET6 800 if (isipv6) 801 /* 802 * ip6_plen is not need to be filled now, and will be filled 803 * in ip6_output. 804 */ 805 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 806 sizeof(struct tcphdr) + optlen + len); 807 else 808 #endif /* INET6 */ 809 { 810 m->m_pkthdr.csum_flags = CSUM_TCP; 811 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 812 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 813 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 814 815 /* IP version must be set here for ipv4/ipv6 checking later */ 816 KASSERT(ip->ip_v == IPVERSION, 817 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 818 } 819 820 /* 821 * In transmit state, time the transmission and arrange for 822 * the retransmit. In persist state, just set snd_max. 823 */ 824 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 825 tcp_seq startseq = tp->snd_nxt; 826 827 /* 828 * Advance snd_nxt over sequence space of this segment. 829 */ 830 if (flags & (TH_SYN|TH_FIN)) { 831 if (flags & TH_SYN) 832 tp->snd_nxt++; 833 if (flags & TH_FIN) { 834 tp->snd_nxt++; 835 tp->t_flags |= TF_SENTFIN; 836 } 837 } 838 tp->snd_nxt += len; 839 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 840 tp->snd_max = tp->snd_nxt; 841 /* 842 * Time this transmission if not a retransmission and 843 * not currently timing anything. 844 */ 845 if (tp->t_rtttime == 0) { 846 tp->t_rtttime = ticks; 847 tp->t_rtseq = startseq; 848 tcpstat.tcps_segstimed++; 849 } 850 } 851 852 /* 853 * Set retransmit timer if not currently set, 854 * and not doing a pure ack or a keep-alive probe. 855 * Initial value for retransmit timer is smoothed 856 * round-trip time + 2 * round-trip time variance. 857 * Initialize shift counter which is used for backoff 858 * of retransmit time. 859 */ 860 if (!callout_active(tp->tt_rexmt) && 861 tp->snd_nxt != tp->snd_una) { 862 if (callout_active(tp->tt_persist)) { 863 callout_stop(tp->tt_persist); 864 tp->t_rxtshift = 0; 865 } 866 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 867 tcp_timer_rexmt, tp); 868 } 869 } else { 870 /* 871 * Persist case, update snd_max but since we are in 872 * persist mode (no window) we do not update snd_nxt. 873 */ 874 int xlen = len; 875 if (flags & TH_SYN) 876 ++xlen; 877 if (flags & TH_FIN) { 878 ++xlen; 879 tp->t_flags |= TF_SENTFIN; 880 } 881 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 882 tp->snd_max = tp->snd_nxt + len; 883 } 884 885 #ifdef TCPDEBUG 886 /* 887 * Trace. 888 */ 889 if (so->so_options & SO_DEBUG) { 890 u_short save = ipov->ih_len; 891 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 892 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 893 ipov->ih_len = save; 894 } 895 #endif 896 897 /* 898 * Fill in IP length and desired time to live and 899 * send to IP level. There should be a better way 900 * to handle ttl and tos; we could keep them in 901 * the template, but need a way to checksum without them. 902 */ 903 /* 904 * m->m_pkthdr.len should have been set before cksum calcuration, 905 * because in6_cksum() need it. 906 */ 907 #ifdef INET6 908 if (isipv6) { 909 /* 910 * we separately set hoplimit for every segment, since the 911 * user might want to change the value via setsockopt. 912 * Also, desired default hop limit might be changed via 913 * Neighbor Discovery. 914 */ 915 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 916 917 /* TODO: IPv6 IP6TOS_ECT bit on */ 918 error = ip6_output(m, 919 tp->t_inpcb->in6p_outputopts, NULL, 920 (so->so_options & SO_DONTROUTE), NULL, NULL, 921 tp->t_inpcb); 922 } else 923 #endif /* INET6 */ 924 { 925 ip->ip_len = m->m_pkthdr.len; 926 #ifdef INET6 927 if (INP_CHECK_SOCKAF(so, AF_INET6)) 928 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 929 #endif /* INET6 */ 930 /* 931 * If we do path MTU discovery, then we set DF on every packet. 932 * This might not be the best thing to do according to RFC3390 933 * Section 2. However the tcp hostcache migitates the problem 934 * so it affects only the first tcp connection with a host. 935 */ 936 if (path_mtu_discovery) 937 ip->ip_off |= IP_DF; 938 939 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 940 (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); 941 } 942 if (error) { 943 944 /* 945 * We know that the packet was lost, so back out the 946 * sequence number advance, if any. 947 */ 948 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 949 /* 950 * No need to check for TH_FIN here because 951 * the TF_SENTFIN flag handles that case. 952 */ 953 if ((flags & TH_SYN) == 0) 954 tp->snd_nxt -= len; 955 } 956 957 out: 958 if (error == ENOBUFS) { 959 if (!callout_active(tp->tt_rexmt) && 960 !callout_active(tp->tt_persist)) 961 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 962 tcp_timer_rexmt, tp); 963 tcp_quench(tp->t_inpcb, 0); 964 return (0); 965 } 966 if (error == EMSGSIZE) { 967 /* 968 * ip_output() will have already fixed the route 969 * for us. tcp_mtudisc() will, as its last action, 970 * initiate retransmission, so it is important to 971 * not do so here. 972 */ 973 tcp_mtudisc(tp->t_inpcb, 0); 974 return 0; 975 } 976 if ((error == EHOSTUNREACH || error == ENETDOWN) 977 && TCPS_HAVERCVDSYN(tp->t_state)) { 978 tp->t_softerror = error; 979 return (0); 980 } 981 return (error); 982 } 983 tcpstat.tcps_sndtotal++; 984 985 /* 986 * Data sent (as far as we can tell). 987 * If this advertises a larger window than any other segment, 988 * then remember the size of the advertised window. 989 * Any pending ACK has now been sent. 990 */ 991 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 992 tp->rcv_adv = tp->rcv_nxt + recwin; 993 tp->last_ack_sent = tp->rcv_nxt; 994 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 995 if (callout_active(tp->tt_delack)) 996 callout_stop(tp->tt_delack); 997 #if 0 998 /* 999 * This completely breaks TCP if newreno is turned on. What happens 1000 * is that if delayed-acks are turned on on the receiver, this code 1001 * on the transmitter effectively destroys the TCP window, forcing 1002 * it to four packets (1.5Kx4 = 6K window). 1003 */ 1004 if (sendalot && (!tcp_do_newreno || --maxburst)) 1005 goto again; 1006 #endif 1007 if (sendalot) 1008 goto again; 1009 return (0); 1010 } 1011 1012 void 1013 tcp_setpersist(tp) 1014 register struct tcpcb *tp; 1015 { 1016 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1017 int tt; 1018 1019 if (callout_active(tp->tt_rexmt)) 1020 panic("tcp_setpersist: retransmit pending"); 1021 /* 1022 * Start/restart persistance timer. 1023 */ 1024 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1025 TCPTV_PERSMIN, TCPTV_PERSMAX); 1026 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1027 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1028 tp->t_rxtshift++; 1029 } 1030