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_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_mac.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/domain.h> 45 #include <sys/kernel.h> 46 #include <sys/lock.h> 47 #include <sys/mac.h> 48 #include <sys/mbuf.h> 49 #include <sys/mutex.h> 50 #include <sys/protosw.h> 51 #include <sys/socket.h> 52 #include <sys/socketvar.h> 53 #include <sys/sysctl.h> 54 55 #include <net/route.h> 56 57 #include <netinet/in.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/in_pcb.h> 61 #include <netinet/ip_var.h> 62 #ifdef INET6 63 #include <netinet6/in6_pcb.h> 64 #include <netinet/ip6.h> 65 #include <netinet6/ip6_var.h> 66 #endif 67 #include <netinet/tcp.h> 68 #define TCPOUTFLAGS 69 #include <netinet/tcp_fsm.h> 70 #include <netinet/tcp_seq.h> 71 #include <netinet/tcp_timer.h> 72 #include <netinet/tcp_var.h> 73 #include <netinet/tcpip.h> 74 #ifdef TCPDEBUG 75 #include <netinet/tcp_debug.h> 76 #endif 77 78 #ifdef IPSEC 79 #include <netinet6/ipsec.h> 80 #endif /*IPSEC*/ 81 82 #ifdef FAST_IPSEC 83 #include <netipsec/ipsec.h> 84 #define IPSEC 85 #endif /*FAST_IPSEC*/ 86 87 #include <machine/in_cksum.h> 88 89 #ifdef notyet 90 extern struct mbuf *m_copypack(); 91 #endif 92 93 int path_mtu_discovery = 1; 94 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 95 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 96 97 int ss_fltsz = 1; 98 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 99 &ss_fltsz, 1, "Slow start flight size"); 100 101 int ss_fltsz_local = 4; 102 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 103 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 104 105 int tcp_do_newreno = 1; 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 107 0, "Enable NewReno Algorithms"); 108 109 /* 110 * Tcp output routine: figure out what should be sent and send it. 111 */ 112 int 113 tcp_output(struct tcpcb *tp) 114 { 115 struct socket *so = tp->t_inpcb->inp_socket; 116 long len, win; 117 int off, flags, error; 118 struct mbuf *m; 119 struct ip *ip = NULL; 120 struct ipovly *ipov = NULL; 121 struct tcphdr *th; 122 u_char opt[TCP_MAXOLEN]; 123 unsigned ipoptlen, optlen, hdrlen; 124 int idle, sendalot; 125 #if 0 126 int maxburst = TCP_MAXBURST; 127 #endif 128 struct rmxp_tao *taop; 129 #ifdef INET6 130 struct ip6_hdr *ip6 = NULL; 131 int isipv6; 132 133 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 134 #endif 135 136 INP_LOCK_ASSERT(tp->t_inpcb); 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 int ss = ss_fltsz; 155 #ifdef INET6 156 if (isipv6) { 157 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 158 ss = ss_fltsz_local; 159 } else 160 #endif /* INET6 */ 161 if (in_localaddr(tp->t_inpcb->inp_faddr)) 162 ss = ss_fltsz_local; 163 tp->snd_cwnd = tp->t_maxseg * ss; 164 } 165 tp->t_flags &= ~TF_LASTIDLE; 166 if (idle) { 167 if (tp->t_flags & TF_MORETOCOME) { 168 tp->t_flags |= TF_LASTIDLE; 169 idle = 0; 170 } 171 } 172 again: 173 sendalot = 0; 174 off = tp->snd_nxt - tp->snd_una; 175 win = min(tp->snd_wnd, tp->snd_cwnd); 176 win = min(win, tp->snd_bwnd); 177 178 flags = tcp_outflags[tp->t_state]; 179 /* 180 * Get standard flags, and add SYN or FIN if requested by 'hidden' 181 * state flags. 182 */ 183 if (tp->t_flags & TF_NEEDFIN) 184 flags |= TH_FIN; 185 if (tp->t_flags & TF_NEEDSYN) 186 flags |= TH_SYN; 187 188 /* 189 * If in persist timeout with window of 0, send 1 byte. 190 * Otherwise, if window is small but nonzero 191 * and timer expired, we will send what we can 192 * and go to transmit state. 193 */ 194 if (tp->t_force) { 195 if (win == 0) { 196 /* 197 * If we still have some data to send, then 198 * clear the FIN bit. Usually this would 199 * happen below when it realizes that we 200 * aren't sending all the data. However, 201 * if we have exactly 1 byte of unsent data, 202 * then it won't clear the FIN bit below, 203 * and if we are in persist state, we wind 204 * up sending the packet without recording 205 * that we sent the FIN bit. 206 * 207 * We can't just blindly clear the FIN bit, 208 * because if we don't have any more data 209 * to send then the probe will be the FIN 210 * itself. 211 */ 212 if (off < so->so_snd.sb_cc) 213 flags &= ~TH_FIN; 214 win = 1; 215 } else { 216 callout_stop(tp->tt_persist); 217 tp->t_rxtshift = 0; 218 } 219 } 220 221 /* 222 * If snd_nxt == snd_max and we have transmitted a FIN, the 223 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 224 * a negative length. This can also occur when tcp opens up 225 * its congestion window while receiving additional duplicate 226 * acks after fast-retransmit because TCP will reset snd_nxt 227 * to snd_max after the fast-retransmit. 228 * 229 * In the normal retransmit-FIN-only case, however, snd_nxt will 230 * be set to snd_una, the offset will be 0, and the length may 231 * wind up 0. 232 */ 233 len = (long)ulmin(so->so_snd.sb_cc, win) - off; 234 235 taop = tcp_gettaocache(&tp->t_inpcb->inp_inc); 236 237 /* 238 * Lop off SYN bit if it has already been sent. However, if this 239 * is SYN-SENT state and if segment contains data and if we don't 240 * know that foreign host supports TAO, suppress sending segment. 241 */ 242 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 243 flags &= ~TH_SYN; 244 off--, len++; 245 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 246 (taop == NULL || taop->tao_ccsent == 0)) 247 return 0; 248 } 249 250 /* 251 * Be careful not to send data and/or FIN on SYN segments 252 * in cases when no CC option will be sent. 253 * This measure is needed to prevent interoperability problems 254 * with not fully conformant TCP implementations. 255 */ 256 if ((flags & TH_SYN) && 257 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 258 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 259 len = 0; 260 flags &= ~TH_FIN; 261 } 262 263 if (len < 0) { 264 /* 265 * If FIN has been sent but not acked, 266 * but we haven't been called to retransmit, 267 * len will be < 0. Otherwise, window shrank 268 * after we sent into it. If window shrank to 0, 269 * cancel pending retransmit, pull snd_nxt back 270 * to (closed) window, and set the persist timer 271 * if it isn't already going. If the window didn't 272 * close completely, just wait for an ACK. 273 */ 274 len = 0; 275 if (win == 0) { 276 callout_stop(tp->tt_rexmt); 277 tp->t_rxtshift = 0; 278 tp->snd_nxt = tp->snd_una; 279 if (!callout_active(tp->tt_persist)) 280 tcp_setpersist(tp); 281 } 282 } 283 284 /* 285 * len will be >= 0 after this point. Truncate to the maximum 286 * segment length and ensure that FIN is removed if the length 287 * no longer contains the last data byte. 288 */ 289 if (len > tp->t_maxseg) { 290 len = tp->t_maxseg; 291 sendalot = 1; 292 } 293 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 294 flags &= ~TH_FIN; 295 296 win = sbspace(&so->so_rcv); 297 298 /* 299 * Sender silly window avoidance. We transmit under the following 300 * conditions when len is non-zero: 301 * 302 * - We have a full segment 303 * - This is the last buffer in a write()/send() and we are 304 * either idle or running NODELAY 305 * - we've timed out (e.g. persist timer) 306 * - we have more then 1/2 the maximum send window's worth of 307 * data (receiver may be limited the window size) 308 * - we need to retransmit 309 */ 310 if (len) { 311 if (len == tp->t_maxseg) 312 goto send; 313 /* 314 * NOTE! on localhost connections an 'ack' from the remote 315 * end may occur synchronously with the output and cause 316 * us to flush a buffer queued with moretocome. XXX 317 * 318 * note: the len + off check is almost certainly unnecessary. 319 */ 320 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 321 (idle || (tp->t_flags & TF_NODELAY)) && 322 len + off >= so->so_snd.sb_cc && 323 (tp->t_flags & TF_NOPUSH) == 0) { 324 goto send; 325 } 326 if (tp->t_force) /* typ. timeout case */ 327 goto send; 328 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 329 goto send; 330 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 331 goto send; 332 } 333 334 /* 335 * Compare available window to amount of window 336 * known to peer (as advertised window less 337 * next expected input). If the difference is at least two 338 * max size segments, or at least 50% of the maximum possible 339 * window, then want to send a window update to peer. 340 * Skip this if the connection is in T/TCP half-open state. 341 */ 342 if (win > 0 && !(tp->t_flags & TF_NEEDSYN)) { 343 /* 344 * "adv" is the amount we can increase the window, 345 * taking into account that we are limited by 346 * TCP_MAXWIN << tp->rcv_scale. 347 */ 348 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 349 (tp->rcv_adv - tp->rcv_nxt); 350 351 if (adv >= (long) (2 * tp->t_maxseg)) 352 goto send; 353 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 354 goto send; 355 } 356 357 /* 358 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 359 * is also a catch-all for the retransmit timer timeout case. 360 */ 361 if (tp->t_flags & TF_ACKNOW) 362 goto send; 363 if ((flags & TH_RST) || 364 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 365 goto send; 366 if (SEQ_GT(tp->snd_up, tp->snd_una)) 367 goto send; 368 /* 369 * If our state indicates that FIN should be sent 370 * and we have not yet done so, then we need to send. 371 */ 372 if (flags & TH_FIN && 373 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 374 goto send; 375 376 /* 377 * TCP window updates are not reliable, rather a polling protocol 378 * using ``persist'' packets is used to insure receipt of window 379 * updates. The three ``states'' for the output side are: 380 * idle not doing retransmits or persists 381 * persisting to move a small or zero window 382 * (re)transmitting and thereby not persisting 383 * 384 * callout_active(tp->tt_persist) 385 * is true when we are in persist state. 386 * tp->t_force 387 * is set when we are called to send a persist packet. 388 * callout_active(tp->tt_rexmt) 389 * is set when we are retransmitting 390 * The output side is idle when both timers are zero. 391 * 392 * If send window is too small, there is data to transmit, and no 393 * retransmit or persist is pending, then go to persist state. 394 * If nothing happens soon, send when timer expires: 395 * if window is nonzero, transmit what we can, 396 * otherwise force out a byte. 397 */ 398 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 399 !callout_active(tp->tt_persist)) { 400 tp->t_rxtshift = 0; 401 tcp_setpersist(tp); 402 } 403 404 /* 405 * No reason to send a segment, just return. 406 */ 407 return (0); 408 409 send: 410 /* 411 * Before ESTABLISHED, force sending of initial options 412 * unless TCP set not to do any options. 413 * NOTE: we assume that the IP/TCP header plus TCP options 414 * always fit in a single mbuf, leaving room for a maximum 415 * link header, i.e. 416 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 417 */ 418 optlen = 0; 419 #ifdef INET6 420 if (isipv6) 421 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 422 else 423 #endif 424 hdrlen = sizeof (struct tcpiphdr); 425 if (flags & TH_SYN) { 426 tp->snd_nxt = tp->iss; 427 if ((tp->t_flags & TF_NOOPT) == 0) { 428 u_short mss; 429 430 opt[0] = TCPOPT_MAXSEG; 431 opt[1] = TCPOLEN_MAXSEG; 432 mss = htons((u_short) tcp_mssopt(tp)); 433 (void)memcpy(opt + 2, &mss, sizeof(mss)); 434 optlen = TCPOLEN_MAXSEG; 435 436 if ((tp->t_flags & TF_REQ_SCALE) && 437 ((flags & TH_ACK) == 0 || 438 (tp->t_flags & TF_RCVD_SCALE))) { 439 *((u_int32_t *)(opt + optlen)) = htonl( 440 TCPOPT_NOP << 24 | 441 TCPOPT_WINDOW << 16 | 442 TCPOLEN_WINDOW << 8 | 443 tp->request_r_scale); 444 optlen += 4; 445 } 446 } 447 } 448 449 /* 450 * Send a timestamp and echo-reply if this is a SYN and our side 451 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 452 * and our peer have sent timestamps in our SYN's. 453 */ 454 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 455 (flags & TH_RST) == 0 && 456 ((flags & TH_ACK) == 0 || 457 (tp->t_flags & TF_RCVD_TSTMP))) { 458 u_int32_t *lp = (u_int32_t *)(opt + optlen); 459 460 /* Form timestamp option as shown in appendix A of RFC 1323. */ 461 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 462 *lp++ = htonl(ticks); 463 *lp = htonl(tp->ts_recent); 464 optlen += TCPOLEN_TSTAMP_APPA; 465 } 466 467 /* 468 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 469 * options are allowed (!TF_NOOPT) and it's not a RST. 470 */ 471 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 472 (flags & TH_RST) == 0) { 473 switch (flags & (TH_SYN|TH_ACK)) { 474 /* 475 * This is a normal ACK, send CC if we received CC before 476 * from our peer. 477 */ 478 case TH_ACK: 479 if (!(tp->t_flags & TF_RCVD_CC)) 480 break; 481 /*FALLTHROUGH*/ 482 483 /* 484 * We can only get here in T/TCP's SYN_SENT* state, when 485 * we're a sending a non-SYN segment without waiting for 486 * the ACK of our SYN. A check above assures that we only 487 * do this if our peer understands T/TCP. 488 */ 489 case 0: 490 opt[optlen++] = TCPOPT_NOP; 491 opt[optlen++] = TCPOPT_NOP; 492 opt[optlen++] = TCPOPT_CC; 493 opt[optlen++] = TCPOLEN_CC; 494 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 495 496 optlen += 4; 497 break; 498 499 /* 500 * This is our initial SYN, check whether we have to use 501 * CC or CC.new. 502 */ 503 case TH_SYN: 504 opt[optlen++] = TCPOPT_NOP; 505 opt[optlen++] = TCPOPT_NOP; 506 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 507 TCPOPT_CCNEW : TCPOPT_CC; 508 opt[optlen++] = TCPOLEN_CC; 509 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 510 optlen += 4; 511 break; 512 513 /* 514 * This is a SYN,ACK; send CC and CC.echo if we received 515 * CC from our peer. 516 */ 517 case (TH_SYN|TH_ACK): 518 if (tp->t_flags & TF_RCVD_CC) { 519 opt[optlen++] = TCPOPT_NOP; 520 opt[optlen++] = TCPOPT_NOP; 521 opt[optlen++] = TCPOPT_CC; 522 opt[optlen++] = TCPOLEN_CC; 523 *(u_int32_t *)&opt[optlen] = 524 htonl(tp->cc_send); 525 optlen += 4; 526 opt[optlen++] = TCPOPT_NOP; 527 opt[optlen++] = TCPOPT_NOP; 528 opt[optlen++] = TCPOPT_CCECHO; 529 opt[optlen++] = TCPOLEN_CC; 530 *(u_int32_t *)&opt[optlen] = 531 htonl(tp->cc_recv); 532 optlen += 4; 533 } 534 break; 535 } 536 } 537 538 hdrlen += optlen; 539 540 #ifdef INET6 541 if (isipv6) 542 ipoptlen = ip6_optlen(tp->t_inpcb); 543 else 544 #endif 545 if (tp->t_inpcb->inp_options) 546 ipoptlen = tp->t_inpcb->inp_options->m_len - 547 offsetof(struct ipoption, ipopt_list); 548 else 549 ipoptlen = 0; 550 #ifdef IPSEC 551 ipoptlen += ipsec_hdrsiz_tcp(tp); 552 #endif 553 554 /* 555 * Adjust data length if insertion of options will 556 * bump the packet length beyond the t_maxopd length. 557 * Clear the FIN bit because we cut off the tail of 558 * the segment. 559 */ 560 if (len + optlen + ipoptlen > tp->t_maxopd) { 561 /* 562 * If there is still more to send, don't close the connection. 563 */ 564 flags &= ~TH_FIN; 565 len = tp->t_maxopd - optlen - ipoptlen; 566 sendalot = 1; 567 } 568 569 /*#ifdef DIAGNOSTIC*/ 570 #ifdef INET6 571 if (max_linkhdr + hdrlen > MCLBYTES) 572 #else 573 if (max_linkhdr + hdrlen > MHLEN) 574 #endif 575 panic("tcphdr too big"); 576 /*#endif*/ 577 578 /* 579 * Grab a header mbuf, attaching a copy of data to 580 * be transmitted, and initialize the header from 581 * the template for sends on this connection. 582 */ 583 if (len) { 584 if (tp->t_force && len == 1) 585 tcpstat.tcps_sndprobe++; 586 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 587 tcpstat.tcps_sndrexmitpack++; 588 tcpstat.tcps_sndrexmitbyte += len; 589 } else { 590 tcpstat.tcps_sndpack++; 591 tcpstat.tcps_sndbyte += len; 592 } 593 #ifdef notyet 594 if ((m = m_copypack(so->so_snd.sb_mb, off, 595 (int)len, max_linkhdr + hdrlen)) == 0) { 596 error = ENOBUFS; 597 goto out; 598 } 599 /* 600 * m_copypack left space for our hdr; use it. 601 */ 602 m->m_len += hdrlen; 603 m->m_data -= hdrlen; 604 #else 605 MGETHDR(m, M_DONTWAIT, MT_HEADER); 606 if (m == NULL) { 607 error = ENOBUFS; 608 goto out; 609 } 610 #ifdef INET6 611 if (MHLEN < hdrlen + max_linkhdr) { 612 MCLGET(m, M_DONTWAIT); 613 if ((m->m_flags & M_EXT) == 0) { 614 m_freem(m); 615 error = ENOBUFS; 616 goto out; 617 } 618 } 619 #endif 620 m->m_data += max_linkhdr; 621 m->m_len = hdrlen; 622 if (len <= MHLEN - hdrlen - max_linkhdr) { 623 m_copydata(so->so_snd.sb_mb, off, (int) len, 624 mtod(m, caddr_t) + hdrlen); 625 m->m_len += len; 626 } else { 627 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 628 if (m->m_next == 0) { 629 (void) m_free(m); 630 error = ENOBUFS; 631 goto out; 632 } 633 } 634 #endif 635 /* 636 * If we're sending everything we've got, set PUSH. 637 * (This will keep happy those implementations which only 638 * give data to the user when a buffer fills or 639 * a PUSH comes in.) 640 */ 641 if (off + len == so->so_snd.sb_cc) 642 flags |= TH_PUSH; 643 } else { 644 if (tp->t_flags & TF_ACKNOW) 645 tcpstat.tcps_sndacks++; 646 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 647 tcpstat.tcps_sndctrl++; 648 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 649 tcpstat.tcps_sndurg++; 650 else 651 tcpstat.tcps_sndwinup++; 652 653 MGETHDR(m, M_DONTWAIT, MT_HEADER); 654 if (m == NULL) { 655 error = ENOBUFS; 656 goto out; 657 } 658 #ifdef INET6 659 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 660 MHLEN >= hdrlen) { 661 MH_ALIGN(m, hdrlen); 662 } else 663 #endif 664 m->m_data += max_linkhdr; 665 m->m_len = hdrlen; 666 } 667 m->m_pkthdr.rcvif = (struct ifnet *)0; 668 #ifdef MAC 669 mac_create_mbuf_from_socket(so, m); 670 #endif 671 #ifdef INET6 672 if (isipv6) { 673 ip6 = mtod(m, struct ip6_hdr *); 674 th = (struct tcphdr *)(ip6 + 1); 675 tcpip_fillheaders(tp->t_inpcb, ip6, th); 676 } else 677 #endif /* INET6 */ 678 { 679 ip = mtod(m, struct ip *); 680 ipov = (struct ipovly *)ip; 681 th = (struct tcphdr *)(ip + 1); 682 tcpip_fillheaders(tp->t_inpcb, ip, th); 683 } 684 685 /* 686 * Fill in fields, remembering maximum advertised 687 * window for use in delaying messages about window sizes. 688 * If resending a FIN, be sure not to use a new sequence number. 689 */ 690 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 691 tp->snd_nxt == tp->snd_max) 692 tp->snd_nxt--; 693 /* 694 * If we are doing retransmissions, then snd_nxt will 695 * not reflect the first unsent octet. For ACK only 696 * packets, we do not want the sequence number of the 697 * retransmitted packet, we want the sequence number 698 * of the next unsent octet. So, if there is no data 699 * (and no SYN or FIN), use snd_max instead of snd_nxt 700 * when filling in ti_seq. But if we are in persist 701 * state, snd_max might reflect one byte beyond the 702 * right edge of the window, so use snd_nxt in that 703 * case, since we know we aren't doing a retransmission. 704 * (retransmit and persist are mutually exclusive...) 705 */ 706 if (len || (flags & (TH_SYN|TH_FIN)) 707 || callout_active(tp->tt_persist)) 708 th->th_seq = htonl(tp->snd_nxt); 709 else 710 th->th_seq = htonl(tp->snd_max); 711 th->th_ack = htonl(tp->rcv_nxt); 712 if (optlen) { 713 bcopy(opt, th + 1, optlen); 714 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 715 } 716 th->th_flags = flags; 717 /* 718 * Calculate receive window. Don't shrink window, 719 * but avoid silly window syndrome. 720 */ 721 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 722 win = 0; 723 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 724 win = (long)(tp->rcv_adv - tp->rcv_nxt); 725 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 726 win = (long)TCP_MAXWIN << tp->rcv_scale; 727 th->th_win = htons((u_short) (win>>tp->rcv_scale)); 728 729 730 /* 731 * Adjust the RXWIN0SENT flag - indicate that we have advertised 732 * a 0 window. This may cause the remote transmitter to stall. This 733 * flag tells soreceive() to disable delayed acknowledgements when 734 * draining the buffer. This can occur if the receiver is attempting 735 * to read more data then can be buffered prior to transmitting on 736 * the connection. 737 */ 738 if (win == 0) 739 tp->t_flags |= TF_RXWIN0SENT; 740 else 741 tp->t_flags &= ~TF_RXWIN0SENT; 742 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 743 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 744 th->th_flags |= TH_URG; 745 } else 746 /* 747 * If no urgent pointer to send, then we pull 748 * the urgent pointer to the left edge of the send window 749 * so that it doesn't drift into the send window on sequence 750 * number wraparound. 751 */ 752 tp->snd_up = tp->snd_una; /* drag it along */ 753 754 /* 755 * Put TCP length in extended header, and then 756 * checksum extended header and data. 757 */ 758 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 759 #ifdef INET6 760 if (isipv6) 761 /* 762 * ip6_plen is not need to be filled now, and will be filled 763 * in ip6_output. 764 */ 765 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 766 sizeof(struct tcphdr) + optlen + len); 767 else 768 #endif /* INET6 */ 769 { 770 m->m_pkthdr.csum_flags = CSUM_TCP; 771 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 772 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 773 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 774 775 /* IP version must be set here for ipv4/ipv6 checking later */ 776 KASSERT(ip->ip_v == IPVERSION, 777 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 778 } 779 780 /* 781 * In transmit state, time the transmission and arrange for 782 * the retransmit. In persist state, just set snd_max. 783 */ 784 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 785 tcp_seq startseq = tp->snd_nxt; 786 787 /* 788 * Advance snd_nxt over sequence space of this segment. 789 */ 790 if (flags & (TH_SYN|TH_FIN)) { 791 if (flags & TH_SYN) 792 tp->snd_nxt++; 793 if (flags & TH_FIN) { 794 tp->snd_nxt++; 795 tp->t_flags |= TF_SENTFIN; 796 } 797 } 798 tp->snd_nxt += len; 799 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 800 tp->snd_max = tp->snd_nxt; 801 /* 802 * Time this transmission if not a retransmission and 803 * not currently timing anything. 804 */ 805 if (tp->t_rtttime == 0) { 806 tp->t_rtttime = ticks; 807 tp->t_rtseq = startseq; 808 tcpstat.tcps_segstimed++; 809 } 810 } 811 812 /* 813 * Set retransmit timer if not currently set, 814 * and not doing a pure ack or a keep-alive probe. 815 * Initial value for retransmit timer is smoothed 816 * round-trip time + 2 * round-trip time variance. 817 * Initialize shift counter which is used for backoff 818 * of retransmit time. 819 */ 820 if (!callout_active(tp->tt_rexmt) && 821 tp->snd_nxt != tp->snd_una) { 822 if (callout_active(tp->tt_persist)) { 823 callout_stop(tp->tt_persist); 824 tp->t_rxtshift = 0; 825 } 826 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 827 tcp_timer_rexmt, tp); 828 } 829 } else { 830 /* 831 * Persist case, update snd_max but since we are in 832 * persist mode (no window) we do not update snd_nxt. 833 */ 834 int xlen = len; 835 if (flags & TH_SYN) 836 ++xlen; 837 if (flags & TH_FIN) { 838 ++xlen; 839 tp->t_flags |= TF_SENTFIN; 840 } 841 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 842 tp->snd_max = tp->snd_nxt + len; 843 } 844 845 #ifdef TCPDEBUG 846 /* 847 * Trace. 848 */ 849 if (so->so_options & SO_DEBUG) { 850 u_short save = ipov->ih_len; 851 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 852 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 853 ipov->ih_len = save; 854 } 855 #endif 856 857 /* 858 * Fill in IP length and desired time to live and 859 * send to IP level. There should be a better way 860 * to handle ttl and tos; we could keep them in 861 * the template, but need a way to checksum without them. 862 */ 863 /* 864 * m->m_pkthdr.len should have been set before cksum calcuration, 865 * because in6_cksum() need it. 866 */ 867 #ifdef INET6 868 if (isipv6) { 869 /* 870 * we separately set hoplimit for every segment, since the 871 * user might want to change the value via setsockopt. 872 * Also, desired default hop limit might be changed via 873 * Neighbor Discovery. 874 */ 875 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, 876 tp->t_inpcb->in6p_route.ro_rt ? 877 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 878 : NULL); 879 880 /* TODO: IPv6 IP6TOS_ECT bit on */ 881 #if defined(IPSEC) && !defined(FAST_IPSEC) 882 if (ipsec_setsocket(m, so) != 0) { 883 m_freem(m); 884 error = ENOBUFS; 885 goto out; 886 } 887 #endif /*IPSEC*/ 888 error = ip6_output(m, 889 tp->t_inpcb->in6p_outputopts, 890 &tp->t_inpcb->in6p_route, 891 (so->so_options & SO_DONTROUTE), NULL, NULL, 892 tp->t_inpcb); 893 } else 894 #endif /* INET6 */ 895 { 896 struct rtentry *rt; 897 ip->ip_len = m->m_pkthdr.len; 898 #ifdef INET6 899 if (INP_CHECK_SOCKAF(so, AF_INET6)) 900 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, 901 tp->t_inpcb->in6p_route.ro_rt ? 902 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 903 : NULL); 904 #endif /* INET6 */ 905 /* 906 * See if we should do MTU discovery. We do it only if the following 907 * are true: 908 * 1) we have a valid route to the destination 909 * 2) the MTU is not locked (if it is, then discovery has been 910 * disabled) 911 */ 912 if (path_mtu_discovery 913 && (rt = tp->t_inpcb->inp_route.ro_rt) 914 && rt->rt_flags & RTF_UP 915 && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { 916 ip->ip_off |= IP_DF; 917 } 918 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 919 (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); 920 } 921 if (error) { 922 923 /* 924 * We know that the packet was lost, so back out the 925 * sequence number advance, if any. 926 */ 927 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 928 /* 929 * No need to check for TH_FIN here because 930 * the TF_SENTFIN flag handles that case. 931 */ 932 if ((flags & TH_SYN) == 0) 933 tp->snd_nxt -= len; 934 } 935 936 out: 937 if (error == ENOBUFS) { 938 if (!callout_active(tp->tt_rexmt) && 939 !callout_active(tp->tt_persist)) 940 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 941 tcp_timer_rexmt, tp); 942 tcp_quench(tp->t_inpcb, 0); 943 return (0); 944 } 945 if (error == EMSGSIZE) { 946 /* 947 * ip_output() will have already fixed the route 948 * for us. tcp_mtudisc() will, as its last action, 949 * initiate retransmission, so it is important to 950 * not do so here. 951 */ 952 tcp_mtudisc(tp->t_inpcb, 0); 953 return 0; 954 } 955 if ((error == EHOSTUNREACH || error == ENETDOWN) 956 && TCPS_HAVERCVDSYN(tp->t_state)) { 957 tp->t_softerror = error; 958 return (0); 959 } 960 return (error); 961 } 962 tcpstat.tcps_sndtotal++; 963 964 /* 965 * Data sent (as far as we can tell). 966 * If this advertises a larger window than any other segment, 967 * then remember the size of the advertised window. 968 * Any pending ACK has now been sent. 969 */ 970 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 971 tp->rcv_adv = tp->rcv_nxt + win; 972 tp->last_ack_sent = tp->rcv_nxt; 973 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 974 if (callout_active(tp->tt_delack)) 975 callout_stop(tp->tt_delack); 976 #if 0 977 /* 978 * This completely breaks TCP if newreno is turned on. What happens 979 * is that if delayed-acks are turned on on the receiver, this code 980 * on the transmitter effectively destroys the TCP window, forcing 981 * it to four packets (1.5Kx4 = 6K window). 982 */ 983 if (sendalot && (!tcp_do_newreno || --maxburst)) 984 goto again; 985 #endif 986 if (sendalot) 987 goto again; 988 return (0); 989 } 990 991 void 992 tcp_setpersist(tp) 993 register struct tcpcb *tp; 994 { 995 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 996 int tt; 997 998 if (callout_active(tp->tt_rexmt)) 999 panic("tcp_setpersist: retransmit pending"); 1000 /* 1001 * Start/restart persistance timer. 1002 */ 1003 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1004 TCPTV_PERSMIN, TCPTV_PERSMAX); 1005 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1006 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1007 tp->t_rxtshift++; 1008 } 1009