1 /* 2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 53 * The Regents of the University of California. All rights reserved. 54 * 55 * Redistribution and use in source and binary forms, with or without 56 * modification, are permitted provided that the following conditions 57 * are met: 58 * 1. Redistributions of source code must retain the above copyright 59 * notice, this list of conditions and the following disclaimer. 60 * 2. Redistributions in binary form must reproduce the above copyright 61 * notice, this list of conditions and the following disclaimer in the 62 * documentation and/or other materials provided with the distribution. 63 * 3. All advertising materials mentioning features or use of this software 64 * must display the following acknowledgement: 65 * This product includes software developed by the University of 66 * California, Berkeley and its contributors. 67 * 4. Neither the name of the University nor the names of its contributors 68 * may be used to endorse or promote products derived from this software 69 * without specific prior written permission. 70 * 71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 81 * SUCH DAMAGE. 82 * 83 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 84 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 85 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.15 2004/07/08 22:07:35 hsu Exp $ 86 */ 87 88 #include "opt_inet6.h" 89 #include "opt_ipsec.h" 90 #include "opt_tcpdebug.h" 91 92 #include <sys/param.h> 93 #include <sys/systm.h> 94 #include <sys/kernel.h> 95 #include <sys/sysctl.h> 96 #include <sys/mbuf.h> 97 #include <sys/domain.h> 98 #include <sys/protosw.h> 99 #include <sys/socket.h> 100 #include <sys/socketvar.h> 101 #include <sys/in_cksum.h> 102 #include <sys/thread.h> 103 #include <sys/globaldata.h> 104 105 #include <net/route.h> 106 107 #include <netinet/in.h> 108 #include <netinet/in_systm.h> 109 #include <netinet/ip.h> 110 #include <netinet/in_pcb.h> 111 #include <netinet/ip_var.h> 112 #include <netinet6/in6_pcb.h> 113 #include <netinet/ip6.h> 114 #include <netinet6/ip6_var.h> 115 #include <netinet/tcp.h> 116 #define TCPOUTFLAGS 117 #include <netinet/tcp_fsm.h> 118 #include <netinet/tcp_seq.h> 119 #include <netinet/tcp_timer.h> 120 #include <netinet/tcp_var.h> 121 #include <netinet/tcpip.h> 122 #ifdef TCPDEBUG 123 #include <netinet/tcp_debug.h> 124 #endif 125 126 #ifdef IPSEC 127 #include <netinet6/ipsec.h> 128 #endif /*IPSEC*/ 129 130 #ifdef FAST_IPSEC 131 #include <netipsec/ipsec.h> 132 #define IPSEC 133 #endif /*FAST_IPSEC*/ 134 135 #ifdef notyet 136 extern struct mbuf *m_copypack(); 137 #endif 138 139 int path_mtu_discovery = 1; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 141 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 142 143 int ss_fltsz = 1; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 145 &ss_fltsz, 1, "Slow start flight size"); 146 147 int ss_fltsz_local = 4; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 149 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 150 151 int tcp_do_newreno = 1; 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 153 0, "Enable NewReno Algorithms"); 154 155 /* 156 * Tcp output routine: figure out what should be sent and send it. 157 */ 158 int 159 tcp_output(tp) 160 struct tcpcb *tp; 161 { 162 struct inpcb * const inp = tp->t_inpcb; 163 struct socket *so = inp->inp_socket; 164 long len, recvwin, sendwin; 165 int off, flags, error; 166 struct mbuf *m; 167 struct ip *ip = NULL; 168 struct ipovly *ipov = NULL; 169 struct tcphdr *th; 170 u_char opt[TCP_MAXOLEN]; 171 unsigned ipoptlen, optlen, hdrlen; 172 int idle, sendalot; 173 struct ip6_hdr *ip6 = NULL; 174 #ifdef INET6 175 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 176 #else 177 const boolean_t isipv6 = FALSE; 178 #endif 179 struct rmxp_tao *taop; 180 181 /* 182 * Determine length of data that should be transmitted, 183 * and flags that will be used. 184 * If there is some data or critical controls (SYN, RST) 185 * to send, then transmit; otherwise, investigate further. 186 */ 187 if ((tp->snd_max == tp->snd_una) && 188 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 189 /* 190 * We have been idle for "a while" and no acks are 191 * expected to clock out any data we send -- 192 * slow start to get ack "clock" running again. 193 * 194 * Set the slow-start flight size depending on whether 195 * this is a local network or not. 196 */ 197 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 198 (!isipv6 && in_localaddr(inp->inp_faddr))) 199 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 200 else 201 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 202 } 203 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 204 if (idle && (tp->t_flags & TF_MORETOCOME)) 205 tp->t_flags |= TF_LASTIDLE; 206 else 207 tp->t_flags &= ~TF_LASTIDLE; 208 209 again: 210 sendalot = 0; 211 off = tp->snd_nxt - tp->snd_una; 212 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 213 sendwin = min(sendwin, tp->snd_bwnd); 214 215 flags = tcp_outflags[tp->t_state]; 216 /* 217 * Get standard flags, and add SYN or FIN if requested by 'hidden' 218 * state flags. 219 */ 220 if (tp->t_flags & TF_NEEDFIN) 221 flags |= TH_FIN; 222 if (tp->t_flags & TF_NEEDSYN) 223 flags |= TH_SYN; 224 225 /* 226 * If in persist timeout with window of 0, send 1 byte. 227 * Otherwise, if window is small but nonzero 228 * and timer expired, we will send what we can 229 * and go to transmit state. 230 */ 231 if (tp->t_flags & TF_FORCE) { 232 if (sendwin == 0) { 233 /* 234 * If we still have some data to send, then 235 * clear the FIN bit. Usually this would 236 * happen below when it realizes that we 237 * aren't sending all the data. However, 238 * if we have exactly 1 byte of unsent data, 239 * then it won't clear the FIN bit below, 240 * and if we are in persist state, we wind 241 * up sending the packet without recording 242 * that we sent the FIN bit. 243 * 244 * We can't just blindly clear the FIN bit, 245 * because if we don't have any more data 246 * to send then the probe will be the FIN 247 * itself. 248 */ 249 if (off < so->so_snd.sb_cc) 250 flags &= ~TH_FIN; 251 sendwin = 1; 252 } else { 253 callout_stop(tp->tt_persist); 254 tp->t_rxtshift = 0; 255 } 256 } 257 258 /* 259 * If snd_nxt == snd_max and we have transmitted a FIN, the 260 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 261 * a negative length. This can also occur when TCP opens up 262 * its congestion window while receiving additional duplicate 263 * acks after fast-retransmit because TCP will reset snd_nxt 264 * to snd_max after the fast-retransmit. 265 * 266 * In the normal retransmit-FIN-only case, however, snd_nxt will 267 * be set to snd_una, the offset will be 0, and the length may 268 * wind up 0. 269 */ 270 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 271 272 /* 273 * Lop off SYN bit if it has already been sent. However, if this 274 * is SYN-SENT state and if segment contains data and if we don't 275 * know that foreign host supports TAO, suppress sending segment. 276 */ 277 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 278 flags &= ~TH_SYN; 279 off--, len++; 280 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 281 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 282 taop->tao_ccsent == 0)) 283 return 0; 284 } 285 286 /* 287 * Be careful not to send data and/or FIN on SYN segments 288 * in cases when no CC option will be sent. 289 * This measure is needed to prevent interoperability problems 290 * with not fully conformant TCP implementations. 291 */ 292 if ((flags & TH_SYN) && 293 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 294 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 295 len = 0; 296 flags &= ~TH_FIN; 297 } 298 299 if (len < 0) { 300 /* 301 * If FIN has been sent but not acked, 302 * but we haven't been called to retransmit, 303 * len will be < 0. Otherwise, window shrank 304 * after we sent into it. If window shrank to 0, 305 * cancel pending retransmit, pull snd_nxt back 306 * to (closed) window, and set the persist timer 307 * if it isn't already going. If the window didn't 308 * close completely, just wait for an ACK. 309 */ 310 len = 0; 311 if (sendwin == 0) { 312 callout_stop(tp->tt_rexmt); 313 tp->t_rxtshift = 0; 314 tp->snd_nxt = tp->snd_una; 315 if (!callout_active(tp->tt_persist)) 316 tcp_setpersist(tp); 317 } 318 } 319 320 /* 321 * len will be >= 0 after this point. Truncate to the maximum 322 * segment length and ensure that FIN is removed if the length 323 * no longer contains the last data byte. 324 */ 325 if (len > tp->t_maxseg) { 326 len = tp->t_maxseg; 327 sendalot = 1; 328 } 329 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 330 flags &= ~TH_FIN; 331 332 recvwin = sbspace(&so->so_rcv); 333 334 /* 335 * Sender silly window avoidance. We transmit under the following 336 * conditions when len is non-zero: 337 * 338 * - We have a full segment 339 * - This is the last buffer in a write()/send() and we are 340 * either idle or running NODELAY 341 * - we've timed out (e.g. persist timer) 342 * - we have more then 1/2 the maximum send window's worth of 343 * data (receiver may be limited the window size) 344 * - we need to retransmit 345 */ 346 if (len) { 347 if (len == tp->t_maxseg) 348 goto send; 349 /* 350 * NOTE! on localhost connections an 'ack' from the remote 351 * end may occur synchronously with the output and cause 352 * us to flush a buffer queued with moretocome. XXX 353 * 354 * note: the len + off check is almost certainly unnecessary. 355 */ 356 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 357 (idle || (tp->t_flags & TF_NODELAY)) && 358 len + off >= so->so_snd.sb_cc && 359 !(tp->t_flags & TF_NOPUSH)) { 360 goto send; 361 } 362 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 363 goto send; 364 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 365 goto send; 366 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 367 goto send; 368 } 369 370 /* 371 * Compare available window to amount of window 372 * known to peer (as advertised window less 373 * next expected input). If the difference is at least two 374 * max size segments, or at least 50% of the maximum possible 375 * window, then want to send a window update to peer. 376 */ 377 if (recvwin > 0) { 378 /* 379 * "adv" is the amount we can increase the window, 380 * taking into account that we are limited by 381 * TCP_MAXWIN << tp->rcv_scale. 382 */ 383 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 384 (tp->rcv_adv - tp->rcv_nxt); 385 386 if (adv >= (long) (2 * tp->t_maxseg)) 387 goto send; 388 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 389 goto send; 390 } 391 392 /* 393 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 394 * is also a catch-all for the retransmit timer timeout case. 395 */ 396 if (tp->t_flags & TF_ACKNOW) 397 goto send; 398 if ((flags & TH_RST) || 399 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 400 goto send; 401 if (SEQ_GT(tp->snd_up, tp->snd_una)) 402 goto send; 403 /* 404 * If our state indicates that FIN should be sent 405 * and we have not yet done so, then we need to send. 406 */ 407 if (flags & TH_FIN && 408 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 409 goto send; 410 411 /* 412 * TCP window updates are not reliable, rather a polling protocol 413 * using ``persist'' packets is used to insure receipt of window 414 * updates. The three ``states'' for the output side are: 415 * idle not doing retransmits or persists 416 * persisting to move a small or zero window 417 * (re)transmitting and thereby not persisting 418 * 419 * callout_active(tp->tt_persist) 420 * is true when we are in persist state. 421 * The TF_FORCE flag in tp->t_flags 422 * is set when we are called to send a persist packet. 423 * callout_active(tp->tt_rexmt) 424 * is set when we are retransmitting 425 * The output side is idle when both timers are zero. 426 * 427 * If send window is too small, there is data to transmit, and no 428 * retransmit or persist is pending, then go to persist state. 429 * If nothing happens soon, send when timer expires: 430 * if window is nonzero, transmit what we can, 431 * otherwise force out a byte. 432 */ 433 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 434 !callout_active(tp->tt_persist)) { 435 tp->t_rxtshift = 0; 436 tcp_setpersist(tp); 437 } 438 439 /* 440 * No reason to send a segment, just return. 441 */ 442 return (0); 443 444 send: 445 /* 446 * Before ESTABLISHED, force sending of initial options 447 * unless TCP set not to do any options. 448 * NOTE: we assume that the IP/TCP header plus TCP options 449 * always fit in a single mbuf, leaving room for a maximum 450 * link header, i.e. 451 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 452 */ 453 optlen = 0; 454 if (isipv6) 455 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 456 else 457 hdrlen = sizeof(struct tcpiphdr); 458 if (flags & TH_SYN) { 459 tp->snd_nxt = tp->iss; 460 if (!(tp->t_flags & TF_NOOPT)) { 461 u_short mss; 462 463 opt[0] = TCPOPT_MAXSEG; 464 opt[1] = TCPOLEN_MAXSEG; 465 mss = htons((u_short) tcp_mssopt(tp)); 466 (void)memcpy(opt + 2, &mss, sizeof(mss)); 467 optlen = TCPOLEN_MAXSEG; 468 469 if ((tp->t_flags & TF_REQ_SCALE) && 470 (!(flags & TH_ACK) || 471 (tp->t_flags & TF_RCVD_SCALE))) { 472 *((u_int32_t *)(opt + optlen)) = htonl( 473 TCPOPT_NOP << 24 | 474 TCPOPT_WINDOW << 16 | 475 TCPOLEN_WINDOW << 8 | 476 tp->request_r_scale); 477 optlen += 4; 478 } 479 } 480 } 481 482 /* 483 * Send a timestamp and echo-reply if this is a SYN and our side 484 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 485 * and our peer have sent timestamps in our SYN's. 486 */ 487 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 488 !(flags & TH_RST) && 489 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 490 u_int32_t *lp = (u_int32_t *)(opt + optlen); 491 492 /* Form timestamp option as shown in appendix A of RFC 1323. */ 493 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 494 *lp++ = htonl(ticks); 495 *lp = htonl(tp->ts_recent); 496 optlen += TCPOLEN_TSTAMP_APPA; 497 } 498 499 /* 500 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 501 * options are allowed (!TF_NOOPT) and it's not a RST. 502 */ 503 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 504 !(flags & TH_RST)) { 505 switch (flags & (TH_SYN|TH_ACK)) { 506 /* 507 * This is a normal ACK, send CC if we received CC before 508 * from our peer. 509 */ 510 case TH_ACK: 511 if (!(tp->t_flags & TF_RCVD_CC)) 512 break; 513 /*FALLTHROUGH*/ 514 515 /* 516 * We can only get here in T/TCP's SYN_SENT* state, when 517 * we're a sending a non-SYN segment without waiting for 518 * the ACK of our SYN. A check above assures that we only 519 * do this if our peer understands T/TCP. 520 */ 521 case 0: 522 opt[optlen++] = TCPOPT_NOP; 523 opt[optlen++] = TCPOPT_NOP; 524 opt[optlen++] = TCPOPT_CC; 525 opt[optlen++] = TCPOLEN_CC; 526 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 527 528 optlen += 4; 529 break; 530 531 /* 532 * This is our initial SYN, check whether we have to use 533 * CC or CC.new. 534 */ 535 case TH_SYN: 536 opt[optlen++] = TCPOPT_NOP; 537 opt[optlen++] = TCPOPT_NOP; 538 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 539 TCPOPT_CCNEW : TCPOPT_CC; 540 opt[optlen++] = TCPOLEN_CC; 541 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 542 optlen += 4; 543 break; 544 545 /* 546 * This is a SYN,ACK; send CC and CC.echo if we received 547 * CC from our peer. 548 */ 549 case (TH_SYN|TH_ACK): 550 if (tp->t_flags & TF_RCVD_CC) { 551 opt[optlen++] = TCPOPT_NOP; 552 opt[optlen++] = TCPOPT_NOP; 553 opt[optlen++] = TCPOPT_CC; 554 opt[optlen++] = TCPOLEN_CC; 555 *(u_int32_t *)&opt[optlen] = 556 htonl(tp->cc_send); 557 optlen += 4; 558 opt[optlen++] = TCPOPT_NOP; 559 opt[optlen++] = TCPOPT_NOP; 560 opt[optlen++] = TCPOPT_CCECHO; 561 opt[optlen++] = TCPOLEN_CC; 562 *(u_int32_t *)&opt[optlen] = 563 htonl(tp->cc_recv); 564 optlen += 4; 565 } 566 break; 567 } 568 } 569 570 hdrlen += optlen; 571 572 if (isipv6) 573 ipoptlen = ip6_optlen(inp); 574 else { 575 if (inp->inp_options) { 576 ipoptlen = inp->inp_options->m_len - 577 offsetof(struct ipoption, ipopt_list); 578 } else { 579 ipoptlen = 0; 580 } 581 } 582 #ifdef IPSEC 583 ipoptlen += ipsec_hdrsiz_tcp(tp); 584 #endif 585 586 /* 587 * Adjust data length if insertion of options will 588 * bump the packet length beyond the t_maxopd length. 589 * Clear the FIN bit because we cut off the tail of 590 * the segment. 591 */ 592 if (len + optlen + ipoptlen > tp->t_maxopd) { 593 /* 594 * If there is still more to send, don't close the connection. 595 */ 596 flags &= ~TH_FIN; 597 len = tp->t_maxopd - optlen - ipoptlen; 598 sendalot = 1; 599 } 600 601 #ifdef INET6 602 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 603 #else 604 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 605 #endif 606 607 /* 608 * Grab a header mbuf, attaching a copy of data to 609 * be transmitted, and initialize the header from 610 * the template for sends on this connection. 611 */ 612 if (len) { 613 if ((tp->t_flags & TF_FORCE) && len == 1) 614 tcpstat.tcps_sndprobe++; 615 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 616 tcpstat.tcps_sndrexmitpack++; 617 tcpstat.tcps_sndrexmitbyte += len; 618 } else { 619 tcpstat.tcps_sndpack++; 620 tcpstat.tcps_sndbyte += len; 621 } 622 #ifdef notyet 623 if ((m = m_copypack(so->so_snd.sb_mb, off, 624 (int)len, max_linkhdr + hdrlen)) == 0) { 625 error = ENOBUFS; 626 goto out; 627 } 628 /* 629 * m_copypack left space for our hdr; use it. 630 */ 631 m->m_len += hdrlen; 632 m->m_data -= hdrlen; 633 #else 634 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 635 if (m == NULL) { 636 error = ENOBUFS; 637 goto out; 638 } 639 #ifdef INET6 640 if (MHLEN < hdrlen + max_linkhdr) { 641 MCLGET(m, MB_DONTWAIT); 642 if (!(m->m_flags & M_EXT)) { 643 m_freem(m); 644 error = ENOBUFS; 645 goto out; 646 } 647 } 648 #endif 649 m->m_data += max_linkhdr; 650 m->m_len = hdrlen; 651 if (len <= MHLEN - hdrlen - max_linkhdr) { 652 m_copydata(so->so_snd.sb_mb, off, (int) len, 653 mtod(m, caddr_t) + hdrlen); 654 m->m_len += len; 655 } else { 656 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 657 if (m->m_next == 0) { 658 (void) m_free(m); 659 error = ENOBUFS; 660 goto out; 661 } 662 } 663 #endif 664 /* 665 * If we're sending everything we've got, set PUSH. 666 * (This will keep happy those implementations which only 667 * give data to the user when a buffer fills or 668 * a PUSH comes in.) 669 */ 670 if (off + len == so->so_snd.sb_cc) 671 flags |= TH_PUSH; 672 } else { 673 if (tp->t_flags & TF_ACKNOW) 674 tcpstat.tcps_sndacks++; 675 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 676 tcpstat.tcps_sndctrl++; 677 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 678 tcpstat.tcps_sndurg++; 679 else 680 tcpstat.tcps_sndwinup++; 681 682 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 683 if (m == NULL) { 684 error = ENOBUFS; 685 goto out; 686 } 687 if (isipv6 && 688 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 689 MH_ALIGN(m, hdrlen); 690 else 691 m->m_data += max_linkhdr; 692 m->m_len = hdrlen; 693 } 694 m->m_pkthdr.rcvif = (struct ifnet *)0; 695 if (isipv6) { 696 ip6 = mtod(m, struct ip6_hdr *); 697 th = (struct tcphdr *)(ip6 + 1); 698 tcp_fillheaders(tp, ip6, th); 699 } else { 700 ip = mtod(m, struct ip *); 701 ipov = (struct ipovly *)ip; 702 th = (struct tcphdr *)(ip + 1); 703 /* this picks up the pseudo header (w/o the length) */ 704 tcp_fillheaders(tp, ip, th); 705 } 706 707 /* 708 * Fill in fields, remembering maximum advertised 709 * window for use in delaying messages about window sizes. 710 * If resending a FIN, be sure not to use a new sequence number. 711 */ 712 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 713 tp->snd_nxt == tp->snd_max) 714 tp->snd_nxt--; 715 /* 716 * If we are doing retransmissions, then snd_nxt will 717 * not reflect the first unsent octet. For ACK only 718 * packets, we do not want the sequence number of the 719 * retransmitted packet, we want the sequence number 720 * of the next unsent octet. So, if there is no data 721 * (and no SYN or FIN), use snd_max instead of snd_nxt 722 * when filling in ti_seq. But if we are in persist 723 * state, snd_max might reflect one byte beyond the 724 * right edge of the window, so use snd_nxt in that 725 * case, since we know we aren't doing a retransmission. 726 * (retransmit and persist are mutually exclusive...) 727 */ 728 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 729 th->th_seq = htonl(tp->snd_nxt); 730 else 731 th->th_seq = htonl(tp->snd_max); 732 th->th_ack = htonl(tp->rcv_nxt); 733 if (optlen) { 734 bcopy(opt, th + 1, optlen); 735 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 736 } 737 th->th_flags = flags; 738 /* 739 * Calculate receive window. Don't shrink window, 740 * but avoid silly window syndrome. 741 */ 742 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 743 recvwin < (long)tp->t_maxseg) 744 recvwin = 0; 745 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 746 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 747 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 748 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 749 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 750 751 /* 752 * Adjust the RXWIN0SENT flag - indicate that we have advertised 753 * a 0 window. This may cause the remote transmitter to stall. This 754 * flag tells soreceive() to disable delayed acknowledgements when 755 * draining the buffer. This can occur if the receiver is attempting 756 * to read more data then can be buffered prior to transmitting on 757 * the connection. 758 */ 759 if (recvwin == 0) 760 tp->t_flags |= TF_RXWIN0SENT; 761 else 762 tp->t_flags &= ~TF_RXWIN0SENT; 763 764 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 765 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 766 th->th_flags |= TH_URG; 767 } else { 768 /* 769 * If no urgent pointer to send, then we pull 770 * the urgent pointer to the left edge of the send window 771 * so that it doesn't drift into the send window on sequence 772 * number wraparound. 773 */ 774 tp->snd_up = tp->snd_una; /* drag it along */ 775 } 776 777 /* 778 * Put TCP length in extended header, and then 779 * checksum extended header and data. 780 */ 781 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 782 if (isipv6) { 783 /* 784 * ip6_plen is not need to be filled now, and will be filled 785 * in ip6_output. 786 */ 787 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 788 sizeof(struct tcphdr) + optlen + len); 789 } else { 790 m->m_pkthdr.csum_flags = CSUM_TCP; 791 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 792 if (len + optlen) 793 th->th_sum = in_addword(th->th_sum, 794 htons((u_short)(optlen + len))); 795 796 /* IP version must be set here for ipv4/ipv6 checking later */ 797 KASSERT(ip->ip_v == IPVERSION, 798 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 799 } 800 801 /* 802 * In transmit state, time the transmission and arrange for 803 * the retransmit. In persist state, just set snd_max. 804 */ 805 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { 806 tcp_seq startseq = tp->snd_nxt; 807 808 /* 809 * Advance snd_nxt over sequence space of this segment. 810 */ 811 if (flags & (TH_SYN|TH_FIN)) { 812 if (flags & TH_SYN) 813 tp->snd_nxt++; 814 if (flags & TH_FIN) { 815 tp->snd_nxt++; 816 tp->t_flags |= TF_SENTFIN; 817 } 818 } 819 tp->snd_nxt += len; 820 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 821 tp->snd_max = tp->snd_nxt; 822 /* 823 * Time this transmission if not a retransmission and 824 * not currently timing anything. 825 */ 826 if (tp->t_rtttime == 0) { 827 tp->t_rtttime = ticks; 828 tp->t_rtseq = startseq; 829 tcpstat.tcps_segstimed++; 830 } 831 } 832 833 /* 834 * Set retransmit timer if not currently set, 835 * and not doing a pure ack or a keep-alive probe. 836 * Initial value for retransmit timer is smoothed 837 * round-trip time + 2 * round-trip time variance. 838 * Initialize shift counter which is used for backoff 839 * of retransmit time. 840 */ 841 if (!callout_active(tp->tt_rexmt) && 842 tp->snd_nxt != tp->snd_una) { 843 if (callout_active(tp->tt_persist)) { 844 callout_stop(tp->tt_persist); 845 tp->t_rxtshift = 0; 846 } 847 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 848 tcp_timer_rexmt, tp); 849 } 850 } else { 851 /* 852 * Persist case, update snd_max but since we are in 853 * persist mode (no window) we do not update snd_nxt. 854 */ 855 int xlen = len; 856 if (flags & TH_SYN) 857 ++xlen; 858 if (flags & TH_FIN) { 859 ++xlen; 860 tp->t_flags |= TF_SENTFIN; 861 } 862 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 863 tp->snd_max = tp->snd_nxt + xlen; 864 } 865 866 #ifdef TCPDEBUG 867 /* 868 * Trace. 869 */ 870 if (so->so_options & SO_DEBUG) 871 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 872 #endif 873 874 /* 875 * Fill in IP length and desired time to live and 876 * send to IP level. There should be a better way 877 * to handle ttl and tos; we could keep them in 878 * the template, but need a way to checksum without them. 879 */ 880 /* 881 * m->m_pkthdr.len should have been set before cksum calcuration, 882 * because in6_cksum() need it. 883 */ 884 if (isipv6) { 885 /* 886 * we separately set hoplimit for every segment, since the 887 * user might want to change the value via setsockopt. 888 * Also, desired default hop limit might be changed via 889 * Neighbor Discovery. 890 */ 891 ip6->ip6_hlim = in6_selecthlim(inp, 892 (inp->in6p_route.ro_rt ? 893 inp->in6p_route.ro_rt->rt_ifp : NULL)); 894 895 /* TODO: IPv6 IP6TOS_ECT bit on */ 896 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 897 (so->so_options & SO_DONTROUTE), NULL, NULL, inp); 898 } else { 899 struct rtentry *rt; 900 ip->ip_len = m->m_pkthdr.len; 901 #ifdef INET6 902 if (INP_CHECK_SOCKAF(so, AF_INET6)) 903 ip->ip_ttl = in6_selecthlim(inp, 904 (inp->in6p_route.ro_rt ? 905 inp->in6p_route.ro_rt->rt_ifp : NULL)); 906 else 907 #endif 908 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 909 910 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 911 /* 912 * See if we should do MTU discovery. 913 * We do it only if the following are true: 914 * 1) we have a valid route to the destination 915 * 2) the MTU is not locked (if it is, 916 * then discovery has been disabled) 917 */ 918 if (path_mtu_discovery && 919 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 920 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 921 ip->ip_off |= IP_DF; 922 923 error = ip_output(m, inp->inp_options, &inp->inp_route, 924 (so->so_options & SO_DONTROUTE), NULL, inp); 925 } 926 if (error) { 927 928 /* 929 * We know that the packet was lost, so back out the 930 * sequence number advance, if any. 931 */ 932 if (!(tp->t_flags & TF_FORCE) || 933 !callout_active(tp->tt_persist)) { 934 /* 935 * No need to check for TH_FIN here because 936 * the TF_SENTFIN flag handles that case. 937 */ 938 if (!(flags & TH_SYN)) 939 tp->snd_nxt -= len; 940 } 941 942 out: 943 if (error == ENOBUFS) { 944 /* 945 * If we can't send, make sure there is something 946 * to get us going again later. Persist state 947 * is not necessarily right, but it is close enough. 948 */ 949 if (!callout_active(tp->tt_rexmt) && 950 !callout_active(tp->tt_persist)) { 951 tp->t_rxtshift = 0; 952 tcp_setpersist(tp); 953 } 954 tcp_quench(inp, 0); 955 return (0); 956 } 957 if (error == EMSGSIZE) { 958 /* 959 * ip_output() will have already fixed the route 960 * for us. tcp_mtudisc() will, as its last action, 961 * initiate retransmission, so it is important to 962 * not do so here. 963 */ 964 tcp_mtudisc(inp, 0); 965 return 0; 966 } 967 if ((error == EHOSTUNREACH || error == ENETDOWN) && 968 TCPS_HAVERCVDSYN(tp->t_state)) { 969 tp->t_softerror = error; 970 return (0); 971 } 972 return (error); 973 } 974 tcpstat.tcps_sndtotal++; 975 976 /* 977 * Data sent (as far as we can tell). 978 * If this advertises a larger window than any other segment, 979 * then remember the size of the advertised window. 980 * Any pending ACK has now been sent. 981 */ 982 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 983 tp->rcv_adv = tp->rcv_nxt + recvwin; 984 tp->last_ack_sent = tp->rcv_nxt; 985 tp->t_flags &= ~TF_ACKNOW; 986 if (tcp_delack_enabled) 987 callout_stop(tp->tt_delack); 988 if (sendalot) 989 goto again; 990 return (0); 991 } 992 993 void 994 tcp_setpersist(tp) 995 struct tcpcb *tp; 996 { 997 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 998 int tt; 999 1000 if (callout_active(tp->tt_rexmt)) 1001 panic("tcp_setpersist: retransmit pending"); 1002 /* 1003 * Start/restart persistance timer. 1004 */ 1005 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1006 TCPTV_PERSMIN, TCPTV_PERSMAX); 1007 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1008 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1009 tp->t_rxtshift++; 1010 } 1011