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, recwin, sendwin; 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 tao; 129 #ifdef INET6 130 struct ip6_hdr *ip6 = NULL; 131 int isipv6; 132 133 bzero(&tao, sizeof(tao)); 134 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 135 #endif 136 137 INP_LOCK_ASSERT(tp->t_inpcb); 138 139 /* 140 * Determine length of data that should be transmitted, 141 * and flags that will be used. 142 * If there is some data or critical controls (SYN, RST) 143 * to send, then transmit; otherwise, investigate further. 144 */ 145 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 146 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 147 /* 148 * We have been idle for "a while" and no acks are 149 * expected to clock out any data we send -- 150 * slow start to get ack "clock" running again. 151 * 152 * Set the slow-start flight size depending on whether 153 * this is a local network or not. 154 */ 155 int ss = ss_fltsz; 156 #ifdef INET6 157 if (isipv6) { 158 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 159 ss = ss_fltsz_local; 160 } else 161 #endif /* INET6 */ 162 if (in_localaddr(tp->t_inpcb->inp_faddr)) 163 ss = ss_fltsz_local; 164 tp->snd_cwnd = tp->t_maxseg * ss; 165 } 166 tp->t_flags &= ~TF_LASTIDLE; 167 if (idle) { 168 if (tp->t_flags & TF_MORETOCOME) { 169 tp->t_flags |= TF_LASTIDLE; 170 idle = 0; 171 } 172 } 173 again: 174 sendalot = 0; 175 off = tp->snd_nxt - tp->snd_una; 176 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 177 sendwin = min(sendwin, tp->snd_bwnd); 178 179 flags = tcp_outflags[tp->t_state]; 180 /* 181 * Get standard flags, and add SYN or FIN if requested by 'hidden' 182 * state flags. 183 */ 184 if (tp->t_flags & TF_NEEDFIN) 185 flags |= TH_FIN; 186 if (tp->t_flags & TF_NEEDSYN) 187 flags |= TH_SYN; 188 189 /* 190 * If in persist timeout with window of 0, send 1 byte. 191 * Otherwise, if window is small but nonzero 192 * and timer expired, we will send what we can 193 * and go to transmit state. 194 */ 195 if (tp->t_force) { 196 if (sendwin == 0) { 197 /* 198 * If we still have some data to send, then 199 * clear the FIN bit. Usually this would 200 * happen below when it realizes that we 201 * aren't sending all the data. However, 202 * if we have exactly 1 byte of unsent data, 203 * then it won't clear the FIN bit below, 204 * and if we are in persist state, we wind 205 * up sending the packet without recording 206 * that we sent the FIN bit. 207 * 208 * We can't just blindly clear the FIN bit, 209 * because if we don't have any more data 210 * to send then the probe will be the FIN 211 * itself. 212 */ 213 if (off < so->so_snd.sb_cc) 214 flags &= ~TH_FIN; 215 sendwin = 1; 216 } else { 217 callout_stop(tp->tt_persist); 218 tp->t_rxtshift = 0; 219 } 220 } 221 222 /* 223 * If snd_nxt == snd_max and we have transmitted a FIN, the 224 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 225 * a negative length. This can also occur when TCP opens up 226 * its congestion window while receiving additional duplicate 227 * acks after fast-retransmit because TCP will reset snd_nxt 228 * to snd_max after the fast-retransmit. 229 * 230 * In the normal retransmit-FIN-only case, however, snd_nxt will 231 * be set to snd_una, the offset will be 0, and the length may 232 * wind up 0. 233 */ 234 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 235 236 237 /* 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 (tcp_do_rfc1644) 246 tcp_hc_gettao(&tp->t_inpcb->inp_inc, &tao); 247 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 248 tao.tao_ccsent == 0) 249 return 0; 250 } 251 252 /* 253 * Be careful not to send data and/or FIN on SYN segments 254 * in cases when no CC option will be sent. 255 * This measure is needed to prevent interoperability problems 256 * with not fully conformant TCP implementations. 257 */ 258 if ((flags & TH_SYN) && 259 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 260 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 261 len = 0; 262 flags &= ~TH_FIN; 263 } 264 265 if (len < 0) { 266 /* 267 * If FIN has been sent but not acked, 268 * but we haven't been called to retransmit, 269 * len will be < 0. Otherwise, window shrank 270 * after we sent into it. If window shrank to 0, 271 * cancel pending retransmit, pull snd_nxt back 272 * to (closed) window, and set the persist timer 273 * if it isn't already going. If the window didn't 274 * close completely, just wait for an ACK. 275 */ 276 len = 0; 277 if (sendwin == 0) { 278 callout_stop(tp->tt_rexmt); 279 tp->t_rxtshift = 0; 280 tp->snd_nxt = tp->snd_una; 281 if (!callout_active(tp->tt_persist)) 282 tcp_setpersist(tp); 283 } 284 } 285 286 /* 287 * len will be >= 0 after this point. Truncate to the maximum 288 * segment length and ensure that FIN is removed if the length 289 * no longer contains the last data byte. 290 */ 291 if (len > tp->t_maxseg) { 292 len = tp->t_maxseg; 293 sendalot = 1; 294 } 295 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 296 flags &= ~TH_FIN; 297 298 recwin = sbspace(&so->so_rcv); 299 300 /* 301 * Sender silly window avoidance. We transmit under the following 302 * conditions when len is non-zero: 303 * 304 * - We have a full segment 305 * - This is the last buffer in a write()/send() and we are 306 * either idle or running NODELAY 307 * - we've timed out (e.g. persist timer) 308 * - we have more then 1/2 the maximum send window's worth of 309 * data (receiver may be limited the window size) 310 * - we need to retransmit 311 */ 312 if (len) { 313 if (len == tp->t_maxseg) 314 goto send; 315 /* 316 * NOTE! on localhost connections an 'ack' from the remote 317 * end may occur synchronously with the output and cause 318 * us to flush a buffer queued with moretocome. XXX 319 * 320 * note: the len + off check is almost certainly unnecessary. 321 */ 322 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 323 (idle || (tp->t_flags & TF_NODELAY)) && 324 len + off >= so->so_snd.sb_cc && 325 (tp->t_flags & TF_NOPUSH) == 0) { 326 goto send; 327 } 328 if (tp->t_force) /* typ. timeout case */ 329 goto send; 330 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 331 goto send; 332 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 333 goto send; 334 } 335 336 /* 337 * Compare available window to amount of window 338 * known to peer (as advertised window less 339 * next expected input). If the difference is at least two 340 * max size segments, or at least 50% of the maximum possible 341 * window, then want to send a window update to peer. 342 * Skip this if the connection is in T/TCP half-open state. 343 */ 344 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN)) { 345 /* 346 * "adv" is the amount we can increase the window, 347 * taking into account that we are limited by 348 * TCP_MAXWIN << tp->rcv_scale. 349 */ 350 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 351 (tp->rcv_adv - tp->rcv_nxt); 352 353 if (adv >= (long) (2 * tp->t_maxseg)) 354 goto send; 355 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 356 goto send; 357 } 358 359 /* 360 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 361 * is also a catch-all for the retransmit timer timeout case. 362 */ 363 if (tp->t_flags & TF_ACKNOW) 364 goto send; 365 if ((flags & TH_RST) || 366 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 367 goto send; 368 if (SEQ_GT(tp->snd_up, tp->snd_una)) 369 goto send; 370 /* 371 * If our state indicates that FIN should be sent 372 * and we have not yet done so, then we need to send. 373 */ 374 if (flags & TH_FIN && 375 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 376 goto send; 377 378 /* 379 * TCP window updates are not reliable, rather a polling protocol 380 * using ``persist'' packets is used to insure receipt of window 381 * updates. The three ``states'' for the output side are: 382 * idle not doing retransmits or persists 383 * persisting to move a small or zero window 384 * (re)transmitting and thereby not persisting 385 * 386 * callout_active(tp->tt_persist) 387 * is true when we are in persist state. 388 * tp->t_force 389 * is set when we are called to send a persist packet. 390 * callout_active(tp->tt_rexmt) 391 * is set when we are retransmitting 392 * The output side is idle when both timers are zero. 393 * 394 * If send window is too small, there is data to transmit, and no 395 * retransmit or persist is pending, then go to persist state. 396 * If nothing happens soon, send when timer expires: 397 * if window is nonzero, transmit what we can, 398 * otherwise force out a byte. 399 */ 400 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 401 !callout_active(tp->tt_persist)) { 402 tp->t_rxtshift = 0; 403 tcp_setpersist(tp); 404 } 405 406 /* 407 * No reason to send a segment, just return. 408 */ 409 return (0); 410 411 send: 412 /* 413 * Before ESTABLISHED, force sending of initial options 414 * unless TCP set not to do any options. 415 * NOTE: we assume that the IP/TCP header plus TCP options 416 * always fit in a single mbuf, leaving room for a maximum 417 * link header, i.e. 418 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 419 */ 420 optlen = 0; 421 #ifdef INET6 422 if (isipv6) 423 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 424 else 425 #endif 426 hdrlen = sizeof (struct tcpiphdr); 427 if (flags & TH_SYN) { 428 tp->snd_nxt = tp->iss; 429 if ((tp->t_flags & TF_NOOPT) == 0) { 430 u_short mss; 431 432 opt[0] = TCPOPT_MAXSEG; 433 opt[1] = TCPOLEN_MAXSEG; 434 mss = htons((u_short) tcp_mssopt(&tp->t_inpcb->inp_inc)); 435 (void)memcpy(opt + 2, &mss, sizeof(mss)); 436 optlen = TCPOLEN_MAXSEG; 437 438 if ((tp->t_flags & TF_REQ_SCALE) && 439 ((flags & TH_ACK) == 0 || 440 (tp->t_flags & TF_RCVD_SCALE))) { 441 *((u_int32_t *)(opt + optlen)) = htonl( 442 TCPOPT_NOP << 24 | 443 TCPOPT_WINDOW << 16 | 444 TCPOLEN_WINDOW << 8 | 445 tp->request_r_scale); 446 optlen += 4; 447 } 448 } 449 } 450 451 /* 452 * Send a timestamp and echo-reply if this is a SYN and our side 453 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 454 * and our peer have sent timestamps in our SYN's. 455 */ 456 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 457 (flags & TH_RST) == 0 && 458 ((flags & TH_ACK) == 0 || 459 (tp->t_flags & TF_RCVD_TSTMP))) { 460 u_int32_t *lp = (u_int32_t *)(opt + optlen); 461 462 /* Form timestamp option as shown in appendix A of RFC 1323. */ 463 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 464 *lp++ = htonl(ticks); 465 *lp = htonl(tp->ts_recent); 466 optlen += TCPOLEN_TSTAMP_APPA; 467 } 468 469 /* 470 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 471 * options are allowed (!TF_NOOPT) and it's not a RST. 472 */ 473 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 474 (flags & TH_RST) == 0) { 475 switch (flags & (TH_SYN|TH_ACK)) { 476 /* 477 * This is a normal ACK, send CC if we received CC before 478 * from our peer. 479 */ 480 case TH_ACK: 481 if (!(tp->t_flags & TF_RCVD_CC)) 482 break; 483 /*FALLTHROUGH*/ 484 485 /* 486 * We can only get here in T/TCP's SYN_SENT* state, when 487 * we're a sending a non-SYN segment without waiting for 488 * the ACK of our SYN. A check above assures that we only 489 * do this if our peer understands T/TCP. 490 */ 491 case 0: 492 opt[optlen++] = TCPOPT_NOP; 493 opt[optlen++] = TCPOPT_NOP; 494 opt[optlen++] = TCPOPT_CC; 495 opt[optlen++] = TCPOLEN_CC; 496 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 497 498 optlen += 4; 499 break; 500 501 /* 502 * This is our initial SYN, check whether we have to use 503 * CC or CC.new. 504 */ 505 case TH_SYN: 506 opt[optlen++] = TCPOPT_NOP; 507 opt[optlen++] = TCPOPT_NOP; 508 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 509 TCPOPT_CCNEW : TCPOPT_CC; 510 opt[optlen++] = TCPOLEN_CC; 511 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 512 optlen += 4; 513 break; 514 515 /* 516 * This is a SYN,ACK; send CC and CC.echo if we received 517 * CC from our peer. 518 */ 519 case (TH_SYN|TH_ACK): 520 if (tp->t_flags & TF_RCVD_CC) { 521 opt[optlen++] = TCPOPT_NOP; 522 opt[optlen++] = TCPOPT_NOP; 523 opt[optlen++] = TCPOPT_CC; 524 opt[optlen++] = TCPOLEN_CC; 525 *(u_int32_t *)&opt[optlen] = 526 htonl(tp->cc_send); 527 optlen += 4; 528 opt[optlen++] = TCPOPT_NOP; 529 opt[optlen++] = TCPOPT_NOP; 530 opt[optlen++] = TCPOPT_CCECHO; 531 opt[optlen++] = TCPOLEN_CC; 532 *(u_int32_t *)&opt[optlen] = 533 htonl(tp->cc_recv); 534 optlen += 4; 535 } 536 break; 537 } 538 } 539 540 hdrlen += optlen; 541 542 #ifdef INET6 543 if (isipv6) 544 ipoptlen = ip6_optlen(tp->t_inpcb); 545 else 546 #endif 547 if (tp->t_inpcb->inp_options) 548 ipoptlen = tp->t_inpcb->inp_options->m_len - 549 offsetof(struct ipoption, ipopt_list); 550 else 551 ipoptlen = 0; 552 #ifdef IPSEC 553 ipoptlen += ipsec_hdrsiz_tcp(tp); 554 #endif 555 556 /* 557 * Adjust data length if insertion of options will 558 * bump the packet length beyond the t_maxopd length. 559 * Clear the FIN bit because we cut off the tail of 560 * the segment. 561 */ 562 if (len + optlen + ipoptlen > tp->t_maxopd) { 563 /* 564 * If there is still more to send, don't close the connection. 565 */ 566 flags &= ~TH_FIN; 567 len = tp->t_maxopd - optlen - ipoptlen; 568 sendalot = 1; 569 } 570 571 /*#ifdef DIAGNOSTIC*/ 572 #ifdef INET6 573 if (max_linkhdr + hdrlen > MCLBYTES) 574 #else 575 if (max_linkhdr + hdrlen > MHLEN) 576 #endif 577 panic("tcphdr too big"); 578 /*#endif*/ 579 580 /* 581 * Grab a header mbuf, attaching a copy of data to 582 * be transmitted, and initialize the header from 583 * the template for sends on this connection. 584 */ 585 if (len) { 586 if (tp->t_force && len == 1) 587 tcpstat.tcps_sndprobe++; 588 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 589 tcpstat.tcps_sndrexmitpack++; 590 tcpstat.tcps_sndrexmitbyte += len; 591 } else { 592 tcpstat.tcps_sndpack++; 593 tcpstat.tcps_sndbyte += len; 594 } 595 #ifdef notyet 596 if ((m = m_copypack(so->so_snd.sb_mb, off, 597 (int)len, max_linkhdr + hdrlen)) == 0) { 598 error = ENOBUFS; 599 goto out; 600 } 601 /* 602 * m_copypack left space for our hdr; use it. 603 */ 604 m->m_len += hdrlen; 605 m->m_data -= hdrlen; 606 #else 607 MGETHDR(m, M_DONTWAIT, MT_HEADER); 608 if (m == NULL) { 609 error = ENOBUFS; 610 goto out; 611 } 612 #ifdef INET6 613 if (MHLEN < hdrlen + max_linkhdr) { 614 MCLGET(m, M_DONTWAIT); 615 if ((m->m_flags & M_EXT) == 0) { 616 m_freem(m); 617 error = ENOBUFS; 618 goto out; 619 } 620 } 621 #endif 622 m->m_data += max_linkhdr; 623 m->m_len = hdrlen; 624 if (len <= MHLEN - hdrlen - max_linkhdr) { 625 m_copydata(so->so_snd.sb_mb, off, (int) len, 626 mtod(m, caddr_t) + hdrlen); 627 m->m_len += len; 628 } else { 629 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 630 if (m->m_next == 0) { 631 (void) m_free(m); 632 error = ENOBUFS; 633 goto out; 634 } 635 } 636 #endif 637 /* 638 * If we're sending everything we've got, set PUSH. 639 * (This will keep happy those implementations which only 640 * give data to the user when a buffer fills or 641 * a PUSH comes in.) 642 */ 643 if (off + len == so->so_snd.sb_cc) 644 flags |= TH_PUSH; 645 } else { 646 if (tp->t_flags & TF_ACKNOW) 647 tcpstat.tcps_sndacks++; 648 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 649 tcpstat.tcps_sndctrl++; 650 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 651 tcpstat.tcps_sndurg++; 652 else 653 tcpstat.tcps_sndwinup++; 654 655 MGETHDR(m, M_DONTWAIT, MT_HEADER); 656 if (m == NULL) { 657 error = ENOBUFS; 658 goto out; 659 } 660 #ifdef INET6 661 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 662 MHLEN >= hdrlen) { 663 MH_ALIGN(m, hdrlen); 664 } else 665 #endif 666 m->m_data += max_linkhdr; 667 m->m_len = hdrlen; 668 } 669 m->m_pkthdr.rcvif = (struct ifnet *)0; 670 #ifdef MAC 671 mac_create_mbuf_from_socket(so, m); 672 #endif 673 #ifdef INET6 674 if (isipv6) { 675 ip6 = mtod(m, struct ip6_hdr *); 676 th = (struct tcphdr *)(ip6 + 1); 677 tcpip_fillheaders(tp->t_inpcb, ip6, th); 678 } else 679 #endif /* INET6 */ 680 { 681 ip = mtod(m, struct ip *); 682 ipov = (struct ipovly *)ip; 683 th = (struct tcphdr *)(ip + 1); 684 tcpip_fillheaders(tp->t_inpcb, ip, th); 685 } 686 687 /* 688 * Fill in fields, remembering maximum advertised 689 * window for use in delaying messages about window sizes. 690 * If resending a FIN, be sure not to use a new sequence number. 691 */ 692 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 693 tp->snd_nxt == tp->snd_max) 694 tp->snd_nxt--; 695 /* 696 * If we are doing retransmissions, then snd_nxt will 697 * not reflect the first unsent octet. For ACK only 698 * packets, we do not want the sequence number of the 699 * retransmitted packet, we want the sequence number 700 * of the next unsent octet. So, if there is no data 701 * (and no SYN or FIN), use snd_max instead of snd_nxt 702 * when filling in ti_seq. But if we are in persist 703 * state, snd_max might reflect one byte beyond the 704 * right edge of the window, so use snd_nxt in that 705 * case, since we know we aren't doing a retransmission. 706 * (retransmit and persist are mutually exclusive...) 707 */ 708 if (len || (flags & (TH_SYN|TH_FIN)) 709 || callout_active(tp->tt_persist)) 710 th->th_seq = htonl(tp->snd_nxt); 711 else 712 th->th_seq = htonl(tp->snd_max); 713 th->th_ack = htonl(tp->rcv_nxt); 714 if (optlen) { 715 bcopy(opt, th + 1, optlen); 716 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 717 } 718 th->th_flags = flags; 719 /* 720 * Calculate receive window. Don't shrink window, 721 * but avoid silly window syndrome. 722 */ 723 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 724 recwin < (long)tp->t_maxseg) 725 recwin = 0; 726 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 727 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 728 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 729 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 730 th->th_win = htons((u_short) (recwin >> tp->rcv_scale)); 731 732 733 /* 734 * Adjust the RXWIN0SENT flag - indicate that we have advertised 735 * a 0 window. This may cause the remote transmitter to stall. This 736 * flag tells soreceive() to disable delayed acknowledgements when 737 * draining the buffer. This can occur if the receiver is attempting 738 * to read more data then can be buffered prior to transmitting on 739 * the connection. 740 */ 741 if (recwin == 0) 742 tp->t_flags |= TF_RXWIN0SENT; 743 else 744 tp->t_flags &= ~TF_RXWIN0SENT; 745 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 746 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 747 th->th_flags |= TH_URG; 748 } else 749 /* 750 * If no urgent pointer to send, then we pull 751 * the urgent pointer to the left edge of the send window 752 * so that it doesn't drift into the send window on sequence 753 * number wraparound. 754 */ 755 tp->snd_up = tp->snd_una; /* drag it along */ 756 757 /* 758 * Put TCP length in extended header, and then 759 * checksum extended header and data. 760 */ 761 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 762 #ifdef INET6 763 if (isipv6) 764 /* 765 * ip6_plen is not need to be filled now, and will be filled 766 * in ip6_output. 767 */ 768 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 769 sizeof(struct tcphdr) + optlen + len); 770 else 771 #endif /* INET6 */ 772 { 773 m->m_pkthdr.csum_flags = CSUM_TCP; 774 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 775 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 776 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 777 778 /* IP version must be set here for ipv4/ipv6 checking later */ 779 KASSERT(ip->ip_v == IPVERSION, 780 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 781 } 782 783 /* 784 * In transmit state, time the transmission and arrange for 785 * the retransmit. In persist state, just set snd_max. 786 */ 787 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 788 tcp_seq startseq = tp->snd_nxt; 789 790 /* 791 * Advance snd_nxt over sequence space of this segment. 792 */ 793 if (flags & (TH_SYN|TH_FIN)) { 794 if (flags & TH_SYN) 795 tp->snd_nxt++; 796 if (flags & TH_FIN) { 797 tp->snd_nxt++; 798 tp->t_flags |= TF_SENTFIN; 799 } 800 } 801 tp->snd_nxt += len; 802 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 803 tp->snd_max = tp->snd_nxt; 804 /* 805 * Time this transmission if not a retransmission and 806 * not currently timing anything. 807 */ 808 if (tp->t_rtttime == 0) { 809 tp->t_rtttime = ticks; 810 tp->t_rtseq = startseq; 811 tcpstat.tcps_segstimed++; 812 } 813 } 814 815 /* 816 * Set retransmit timer if not currently set, 817 * and not doing a pure ack or a keep-alive probe. 818 * Initial value for retransmit timer is smoothed 819 * round-trip time + 2 * round-trip time variance. 820 * Initialize shift counter which is used for backoff 821 * of retransmit time. 822 */ 823 if (!callout_active(tp->tt_rexmt) && 824 tp->snd_nxt != tp->snd_una) { 825 if (callout_active(tp->tt_persist)) { 826 callout_stop(tp->tt_persist); 827 tp->t_rxtshift = 0; 828 } 829 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 830 tcp_timer_rexmt, tp); 831 } 832 } else { 833 /* 834 * Persist case, update snd_max but since we are in 835 * persist mode (no window) we do not update snd_nxt. 836 */ 837 int xlen = len; 838 if (flags & TH_SYN) 839 ++xlen; 840 if (flags & TH_FIN) { 841 ++xlen; 842 tp->t_flags |= TF_SENTFIN; 843 } 844 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 845 tp->snd_max = tp->snd_nxt + len; 846 } 847 848 #ifdef TCPDEBUG 849 /* 850 * Trace. 851 */ 852 if (so->so_options & SO_DEBUG) { 853 u_short save = ipov->ih_len; 854 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 855 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 856 ipov->ih_len = save; 857 } 858 #endif 859 860 /* 861 * Fill in IP length and desired time to live and 862 * send to IP level. There should be a better way 863 * to handle ttl and tos; we could keep them in 864 * the template, but need a way to checksum without them. 865 */ 866 /* 867 * m->m_pkthdr.len should have been set before cksum calcuration, 868 * because in6_cksum() need it. 869 */ 870 #ifdef INET6 871 if (isipv6) { 872 /* 873 * we separately set hoplimit for every segment, since the 874 * user might want to change the value via setsockopt. 875 * Also, desired default hop limit might be changed via 876 * Neighbor Discovery. 877 */ 878 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, 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, NULL, 890 (so->so_options & SO_DONTROUTE), NULL, NULL, 891 tp->t_inpcb); 892 } else 893 #endif /* INET6 */ 894 { 895 ip->ip_len = m->m_pkthdr.len; 896 #ifdef INET6 897 if (INP_CHECK_SOCKAF(so, AF_INET6)) 898 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 899 #endif /* INET6 */ 900 /* 901 * If we do path MTU discovery, then we set DF on every packet. 902 * This might not be the best thing to do according to RFC3390 903 * Section 2. However the tcp hostcache migitates the problem 904 * so it affects only the first tcp connection with a host. 905 */ 906 if (path_mtu_discovery) 907 ip->ip_off |= IP_DF; 908 909 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 910 (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); 911 } 912 if (error) { 913 914 /* 915 * We know that the packet was lost, so back out the 916 * sequence number advance, if any. 917 */ 918 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 919 /* 920 * No need to check for TH_FIN here because 921 * the TF_SENTFIN flag handles that case. 922 */ 923 if ((flags & TH_SYN) == 0) 924 tp->snd_nxt -= len; 925 } 926 927 out: 928 if (error == ENOBUFS) { 929 if (!callout_active(tp->tt_rexmt) && 930 !callout_active(tp->tt_persist)) 931 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 932 tcp_timer_rexmt, tp); 933 tcp_quench(tp->t_inpcb, 0); 934 return (0); 935 } 936 if (error == EMSGSIZE) { 937 /* 938 * ip_output() will have already fixed the route 939 * for us. tcp_mtudisc() will, as its last action, 940 * initiate retransmission, so it is important to 941 * not do so here. 942 */ 943 tcp_mtudisc(tp->t_inpcb, 0); 944 return 0; 945 } 946 if ((error == EHOSTUNREACH || error == ENETDOWN) 947 && TCPS_HAVERCVDSYN(tp->t_state)) { 948 tp->t_softerror = error; 949 return (0); 950 } 951 return (error); 952 } 953 tcpstat.tcps_sndtotal++; 954 955 /* 956 * Data sent (as far as we can tell). 957 * If this advertises a larger window than any other segment, 958 * then remember the size of the advertised window. 959 * Any pending ACK has now been sent. 960 */ 961 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 962 tp->rcv_adv = tp->rcv_nxt + recwin; 963 tp->last_ack_sent = tp->rcv_nxt; 964 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 965 if (callout_active(tp->tt_delack)) 966 callout_stop(tp->tt_delack); 967 #if 0 968 /* 969 * This completely breaks TCP if newreno is turned on. What happens 970 * is that if delayed-acks are turned on on the receiver, this code 971 * on the transmitter effectively destroys the TCP window, forcing 972 * it to four packets (1.5Kx4 = 6K window). 973 */ 974 if (sendalot && (!tcp_do_newreno || --maxburst)) 975 goto again; 976 #endif 977 if (sendalot) 978 goto again; 979 return (0); 980 } 981 982 void 983 tcp_setpersist(tp) 984 register struct tcpcb *tp; 985 { 986 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 987 int tt; 988 989 if (callout_active(tp->tt_rexmt)) 990 panic("tcp_setpersist: retransmit pending"); 991 /* 992 * Start/restart persistance timer. 993 */ 994 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 995 TCPTV_PERSMIN, TCPTV_PERSMAX); 996 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 997 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 998 tp->t_rxtshift++; 999 } 1000