1 /* $OpenBSD: tcp_output.c,v 1.130 2021/02/08 19:37:15 jan Exp $ */ 2 /* $NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1988, 1990, 1993 6 * The Regents of the University of California. All rights reserved. 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 University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 33 * 34 * NRL grants permission for redistribution and use in source and binary 35 * forms, with or without modification, of the software and documentation 36 * created at NRL provided that the following conditions are met: 37 * 38 * 1. Redistributions of source code must retain the above copyright 39 * notice, this list of conditions and the following disclaimer. 40 * 2. Redistributions in binary form must reproduce the above copyright 41 * notice, this list of conditions and the following disclaimer in the 42 * documentation and/or other materials provided with the distribution. 43 * 3. All advertising materials mentioning features or use of this software 44 * must display the following acknowledgements: 45 * This product includes software developed by the University of 46 * California, Berkeley and its contributors. 47 * This product includes software developed at the Information 48 * Technology Division, US Naval Research Laboratory. 49 * 4. Neither the name of the NRL nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 54 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 55 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 56 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 57 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 58 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 59 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 60 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 61 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 62 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 63 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 64 * 65 * The views and conclusions contained in the software and documentation 66 * are those of the authors and should not be interpreted as representing 67 * official policies, either expressed or implied, of the US Naval 68 * Research Laboratory (NRL). 69 */ 70 71 #include "pf.h" 72 #include "stoeplitz.h" 73 74 #include <sys/param.h> 75 #include <sys/systm.h> 76 #include <sys/mbuf.h> 77 #include <sys/protosw.h> 78 #include <sys/socket.h> 79 #include <sys/socketvar.h> 80 #include <sys/kernel.h> 81 82 #include <net/if.h> 83 #include <net/route.h> 84 #if NPF > 0 85 #include <net/pfvar.h> 86 #endif 87 88 #include <netinet/in.h> 89 #include <netinet/ip.h> 90 #include <netinet/in_pcb.h> 91 #include <netinet/ip_var.h> 92 #include <netinet/tcp.h> 93 #define TCPOUTFLAGS 94 #include <netinet/tcp_fsm.h> 95 #include <netinet/tcp_seq.h> 96 #include <netinet/tcp_timer.h> 97 #include <netinet/tcp_var.h> 98 #include <netinet/tcp_debug.h> 99 100 #ifdef notyet 101 extern struct mbuf *m_copypack(); 102 #endif 103 104 extern int tcprexmtthresh; 105 106 #ifdef TCP_SACK_DEBUG 107 void tcp_print_holes(struct tcpcb *tp); 108 109 void 110 tcp_print_holes(struct tcpcb *tp) 111 { 112 struct sackhole *p = tp->snd_holes; 113 if (p == NULL) 114 return; 115 printf("Hole report: start--end dups rxmit\n"); 116 while (p) { 117 printf("%x--%x d %d r %x\n", p->start, p->end, p->dups, 118 p->rxmit); 119 p = p->next; 120 } 121 printf("\n"); 122 } 123 #endif /* TCP_SACK_DEBUG */ 124 125 /* 126 * Returns pointer to a sackhole if there are any pending retransmissions; 127 * NULL otherwise. 128 */ 129 struct sackhole * 130 tcp_sack_output(struct tcpcb *tp) 131 { 132 struct sackhole *p; 133 134 if (!tp->sack_enable) 135 return (NULL); 136 p = tp->snd_holes; 137 while (p) { 138 if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) { 139 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 140 p = p->next; 141 continue; 142 } 143 #ifdef TCP_SACK_DEBUG 144 if (p) 145 tcp_print_holes(tp); 146 #endif 147 return (p); 148 } 149 p = p->next; 150 } 151 return (NULL); 152 } 153 154 /* 155 * After a timeout, the SACK list may be rebuilt. This SACK information 156 * should be used to avoid retransmitting SACKed data. This function 157 * traverses the SACK list to see if snd_nxt should be moved forward. 158 */ 159 160 void 161 tcp_sack_adjust(struct tcpcb *tp) 162 { 163 struct sackhole *cur = tp->snd_holes; 164 if (cur == NULL) 165 return; /* No holes */ 166 if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack)) 167 return; /* We're already beyond any SACKed blocks */ 168 /* 169 * Two cases for which we want to advance snd_nxt: 170 * i) snd_nxt lies between end of one hole and beginning of another 171 * ii) snd_nxt lies between end of last hole and rcv_lastsack 172 */ 173 while (cur->next) { 174 if (SEQ_LT(tp->snd_nxt, cur->end)) 175 return; 176 if (SEQ_GEQ(tp->snd_nxt, cur->next->start)) 177 cur = cur->next; 178 else { 179 tp->snd_nxt = cur->next->start; 180 return; 181 } 182 } 183 if (SEQ_LT(tp->snd_nxt, cur->end)) 184 return; 185 tp->snd_nxt = tp->rcv_lastsack; 186 return; 187 } 188 189 /* 190 * Tcp output routine: figure out what should be sent and send it. 191 */ 192 int 193 tcp_output(struct tcpcb *tp) 194 { 195 struct socket *so = tp->t_inpcb->inp_socket; 196 long len, win, txmaxseg; 197 int off, flags, error; 198 struct mbuf *m; 199 struct tcphdr *th; 200 u_int32_t optbuf[howmany(MAX_TCPOPTLEN, sizeof(u_int32_t))]; 201 u_char *opt = (u_char *)optbuf; 202 unsigned int optlen, hdrlen, packetlen; 203 int idle, sendalot = 0; 204 int i, sack_rxmit = 0; 205 struct sackhole *p; 206 #ifdef TCP_SIGNATURE 207 unsigned int sigoff; 208 #endif /* TCP_SIGNATURE */ 209 #ifdef TCP_ECN 210 int needect; 211 #endif 212 213 if (tp->t_flags & TF_BLOCKOUTPUT) { 214 tp->t_flags |= TF_NEEDOUTPUT; 215 return (0); 216 } else 217 tp->t_flags &= ~TF_NEEDOUTPUT; 218 219 #if defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) 220 if (tp->sack_enable && (tp->t_flags & TF_SIGNATURE)) 221 return (EINVAL); 222 #endif /* defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */ 223 224 /* 225 * Determine length of data that should be transmitted, 226 * and flags that will be used. 227 * If there is some data or critical controls (SYN, RST) 228 * to send, then transmit; otherwise, investigate further. 229 */ 230 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 231 if (idle && (tcp_now - tp->t_rcvtime) >= tp->t_rxtcur) 232 /* 233 * We have been idle for "a while" and no acks are 234 * expected to clock out any data we send -- 235 * slow start to get ack "clock" running again. 236 */ 237 tp->snd_cwnd = 2 * tp->t_maxseg; 238 239 /* remember 'idle' for next invocation of tcp_output */ 240 if (idle && soissending(so)) { 241 tp->t_flags |= TF_LASTIDLE; 242 idle = 0; 243 } else 244 tp->t_flags &= ~TF_LASTIDLE; 245 246 again: 247 /* 248 * If we've recently taken a timeout, snd_max will be greater than 249 * snd_nxt. There may be SACK information that allows us to avoid 250 * resending already delivered data. Adjust snd_nxt accordingly. 251 */ 252 if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max)) 253 tcp_sack_adjust(tp); 254 off = tp->snd_nxt - tp->snd_una; 255 win = ulmin(tp->snd_wnd, tp->snd_cwnd); 256 257 flags = tcp_outflags[tp->t_state]; 258 259 /* 260 * Send any SACK-generated retransmissions. If we're explicitly trying 261 * to send out new data (when sendalot is 1), bypass this function. 262 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 263 * we're replacing a (future) new transmission with a retransmission 264 * now, and we previously incremented snd_cwnd in tcp_input(). 265 */ 266 if (tp->sack_enable && !sendalot) { 267 if (tp->t_dupacks >= tcprexmtthresh && 268 (p = tcp_sack_output(tp))) { 269 off = p->rxmit - tp->snd_una; 270 sack_rxmit = 1; 271 /* Coalesce holes into a single retransmission */ 272 len = min(tp->t_maxseg, p->end - p->rxmit); 273 if (SEQ_LT(tp->snd_una, tp->snd_last)) 274 tp->snd_cwnd -= tp->t_maxseg; 275 } 276 } 277 278 sendalot = 0; 279 /* 280 * If in persist timeout with window of 0, send 1 byte. 281 * Otherwise, if window is small but nonzero 282 * and timer expired, we will send what we can 283 * and go to transmit state. 284 */ 285 if (tp->t_force) { 286 if (win == 0) { 287 /* 288 * If we still have some data to send, then 289 * clear the FIN bit. Usually this would 290 * happen below when it realizes that we 291 * aren't sending all the data. However, 292 * if we have exactly 1 byte of unset data, 293 * then it won't clear the FIN bit below, 294 * and if we are in persist state, we wind 295 * up sending the packet without recording 296 * that we sent the FIN bit. 297 * 298 * We can't just blindly clear the FIN bit, 299 * because if we don't have any more data 300 * to send then the probe will be the FIN 301 * itself. 302 */ 303 if (off < so->so_snd.sb_cc) 304 flags &= ~TH_FIN; 305 win = 1; 306 } else { 307 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 308 tp->t_rxtshift = 0; 309 } 310 } 311 312 if (!sack_rxmit) { 313 len = ulmin(so->so_snd.sb_cc, win) - off; 314 } 315 316 if (len < 0) { 317 /* 318 * If FIN has been sent but not acked, 319 * but we haven't been called to retransmit, 320 * len will be -1. Otherwise, window shrank 321 * after we sent into it. If window shrank to 0, 322 * cancel pending retransmit, pull snd_nxt back 323 * to (closed) window, and set the persist timer 324 * if it isn't already going. If the window didn't 325 * close completely, just wait for an ACK. 326 */ 327 len = 0; 328 if (win == 0) { 329 TCP_TIMER_DISARM(tp, TCPT_REXMT); 330 tp->t_rxtshift = 0; 331 tp->snd_nxt = tp->snd_una; 332 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) 333 tcp_setpersist(tp); 334 } 335 } 336 337 /* 338 * Never send more than half a buffer full. This insures that we can 339 * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and 340 * therefore acks will never be delayed unless we run out of data to 341 * transmit. 342 */ 343 txmaxseg = ulmin(so->so_snd.sb_hiwat / 2, tp->t_maxseg); 344 345 if (len > txmaxseg) { 346 len = txmaxseg; 347 sendalot = 1; 348 } 349 if (off + len < so->so_snd.sb_cc) 350 flags &= ~TH_FIN; 351 352 win = sbspace(so, &so->so_rcv); 353 354 /* 355 * Sender silly window avoidance. If connection is idle 356 * and can send all data, a maximum segment, 357 * at least a maximum default-size segment do it, 358 * or are forced, do it; otherwise don't bother. 359 * If peer's buffer is tiny, then send 360 * when window is at least half open. 361 * If retransmitting (possibly after persist timer forced us 362 * to send into a small window), then must resend. 363 */ 364 if (len) { 365 if (len == txmaxseg) 366 goto send; 367 if ((idle || (tp->t_flags & TF_NODELAY)) && 368 len + off >= so->so_snd.sb_cc && !soissending(so) && 369 (tp->t_flags & TF_NOPUSH) == 0) 370 goto send; 371 if (tp->t_force) 372 goto send; 373 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 374 goto send; 375 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 376 goto send; 377 if (sack_rxmit) 378 goto send; 379 } 380 381 /* 382 * Compare available window to amount of window 383 * known to peer (as advertised window less 384 * next expected input). If the difference is at least two 385 * max size segments, or at least 50% of the maximum possible 386 * window, then want to send a window update to peer. 387 */ 388 if (win > 0) { 389 /* 390 * "adv" is the amount we can increase the window, 391 * taking into account that we are limited by 392 * TCP_MAXWIN << tp->rcv_scale. 393 */ 394 long adv = lmin(win, (long)TCP_MAXWIN << tp->rcv_scale) - 395 (tp->rcv_adv - tp->rcv_nxt); 396 397 if (adv >= (long) (2 * tp->t_maxseg)) 398 goto send; 399 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 400 goto send; 401 } 402 403 /* 404 * Send if we owe peer an ACK. 405 */ 406 if (tp->t_flags & TF_ACKNOW) 407 goto send; 408 if (flags & (TH_SYN|TH_RST)) 409 goto send; 410 if (SEQ_GT(tp->snd_up, tp->snd_una)) 411 goto send; 412 /* 413 * If our state indicates that FIN should be sent 414 * and we have not yet done so, or we're retransmitting the FIN, 415 * then we need to send. 416 */ 417 if (flags & TH_FIN && 418 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 419 goto send; 420 /* 421 * In SACK, it is possible for tcp_output to fail to send a segment 422 * after the retransmission timer has been turned off. Make sure 423 * that the retransmission timer is set. 424 */ 425 if (SEQ_GT(tp->snd_max, tp->snd_una) && 426 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 427 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 428 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 429 return (0); 430 } 431 432 /* 433 * TCP window updates are not reliable, rather a polling protocol 434 * using ``persist'' packets is used to insure receipt of window 435 * updates. The three ``states'' for the output side are: 436 * idle not doing retransmits or persists 437 * persisting to move a small or zero window 438 * (re)transmitting and thereby not persisting 439 * 440 * tp->t_timer[TCPT_PERSIST] 441 * is set when we are in persist state. 442 * tp->t_force 443 * is set when we are called to send a persist packet. 444 * tp->t_timer[TCPT_REXMT] 445 * is set when we are retransmitting 446 * The output side is idle when both timers are zero. 447 * 448 * If send window is too small, there is data to transmit, and no 449 * retransmit or persist is pending, then go to persist state. 450 * If nothing happens soon, send when timer expires: 451 * if window is nonzero, transmit what we can, 452 * otherwise force out a byte. 453 */ 454 if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 455 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 456 tp->t_rxtshift = 0; 457 tcp_setpersist(tp); 458 } 459 460 /* 461 * No reason to send a segment, just return. 462 */ 463 return (0); 464 465 send: 466 /* 467 * Before ESTABLISHED, force sending of initial options 468 * unless TCP set not to do any options. 469 * NOTE: we assume that the IP/TCP header plus TCP options 470 * always fit in a single mbuf, leaving room for a maximum 471 * link header, i.e. 472 * max_linkhdr + sizeof(network header) + sizeof(struct tcphdr + 473 * optlen <= MHLEN 474 */ 475 optlen = 0; 476 477 switch (tp->pf) { 478 case 0: /*default to PF_INET*/ 479 case PF_INET: 480 hdrlen = sizeof(struct ip) + sizeof(struct tcphdr); 481 break; 482 #ifdef INET6 483 case PF_INET6: 484 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 485 break; 486 #endif /* INET6 */ 487 default: 488 return (EPFNOSUPPORT); 489 } 490 491 if (flags & TH_SYN) { 492 tp->snd_nxt = tp->iss; 493 if ((tp->t_flags & TF_NOOPT) == 0) { 494 u_int16_t mss; 495 496 opt[0] = TCPOPT_MAXSEG; 497 opt[1] = 4; 498 mss = htons((u_int16_t) tcp_mss(tp, 0)); 499 memcpy(opt + 2, &mss, sizeof(mss)); 500 optlen = 4; 501 502 if (flags & TH_ACK) 503 tcp_mss_update(tp); 504 /* 505 * If this is the first SYN of connection (not a SYN 506 * ACK), include SACK_PERMIT_HDR option. If this is a 507 * SYN ACK, include SACK_PERMIT_HDR option if peer has 508 * already done so. 509 */ 510 if (tp->sack_enable && ((flags & TH_ACK) == 0 || 511 (tp->t_flags & TF_SACK_PERMIT))) { 512 *((u_int32_t *) (opt + optlen)) = 513 htonl(TCPOPT_SACK_PERMIT_HDR); 514 optlen += 4; 515 } 516 if ((tp->t_flags & TF_REQ_SCALE) && 517 ((flags & TH_ACK) == 0 || 518 (tp->t_flags & TF_RCVD_SCALE))) { 519 *((u_int32_t *) (opt + optlen)) = htonl( 520 TCPOPT_NOP << 24 | 521 TCPOPT_WINDOW << 16 | 522 TCPOLEN_WINDOW << 8 | 523 tp->request_r_scale); 524 optlen += 4; 525 } 526 } 527 } 528 529 /* 530 * Send a timestamp and echo-reply if this is a SYN and our side 531 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 532 * and our peer have sent timestamps in our SYN's. 533 */ 534 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 535 (flags & TH_RST) == 0 && 536 ((flags & (TH_SYN|TH_ACK)) == TH_SYN || 537 (tp->t_flags & TF_RCVD_TSTMP))) { 538 u_int32_t *lp = (u_int32_t *)(opt + optlen); 539 540 /* Form timestamp option as shown in appendix A of RFC 1323. */ 541 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 542 *lp++ = htonl(tcp_now + tp->ts_modulate); 543 *lp = htonl(tp->ts_recent); 544 optlen += TCPOLEN_TSTAMP_APPA; 545 546 /* Set receive buffer autosizing timestamp. */ 547 if (tp->rfbuf_ts == 0) 548 tp->rfbuf_ts = tcp_now; 549 550 } 551 552 #ifdef TCP_SIGNATURE 553 if (tp->t_flags & TF_SIGNATURE) { 554 u_int8_t *bp = (u_int8_t *)(opt + optlen); 555 556 /* Send signature option */ 557 *(bp++) = TCPOPT_SIGNATURE; 558 *(bp++) = TCPOLEN_SIGNATURE; 559 sigoff = optlen + 2; 560 561 { 562 unsigned int i; 563 564 for (i = 0; i < 16; i++) 565 *(bp++) = 0; 566 } 567 568 569 /* Pad options list to the next 32 bit boundary and 570 * terminate it. 571 */ 572 *bp++ = TCPOPT_NOP; 573 *bp++ = TCPOPT_NOP; 574 575 optlen += TCPOLEN_SIGLEN; 576 } 577 #endif /* TCP_SIGNATURE */ 578 579 /* 580 * Send SACKs if necessary. This should be the last option processed. 581 * Only as many SACKs are sent as are permitted by the maximum options 582 * size. No more than three SACKs are sent. 583 */ 584 if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED && 585 (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT && 586 tp->rcv_numsacks) { 587 u_int32_t *lp = (u_int32_t *)(opt + optlen); 588 u_int32_t *olp = lp++; 589 int count = 0; /* actual number of SACKs inserted */ 590 int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK; 591 592 tcpstat_inc(tcps_sack_snd_opts); 593 maxsack = min(maxsack, TCP_MAX_SACK); 594 for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) { 595 struct sackblk sack = tp->sackblks[i]; 596 if (sack.start == 0 && sack.end == 0) 597 continue; 598 *lp++ = htonl(sack.start); 599 *lp++ = htonl(sack.end); 600 count++; 601 } 602 *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2)); 603 optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */ 604 } 605 606 #ifdef DIAGNOSTIC 607 if (optlen > MAX_TCPOPTLEN) 608 panic("tcp_output: options too long"); 609 #endif /* DIAGNOSTIC */ 610 611 hdrlen += optlen; 612 613 /* 614 * Adjust data length if insertion of options will 615 * bump the packet length beyond the t_maxopd length. 616 */ 617 if (len > tp->t_maxopd - optlen) { 618 len = tp->t_maxopd - optlen; 619 sendalot = 1; 620 flags &= ~TH_FIN; 621 } 622 623 #ifdef DIAGNOSTIC 624 if (max_linkhdr + hdrlen > MCLBYTES) 625 panic("tcphdr too big"); 626 #endif 627 628 /* 629 * Grab a header mbuf, attaching a copy of data to 630 * be transmitted, and initialize the header from 631 * the template for sends on this connection. 632 */ 633 if (len) { 634 if (tp->t_force && len == 1) 635 tcpstat_inc(tcps_sndprobe); 636 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 637 tcpstat_pkt(tcps_sndrexmitpack, tcps_sndrexmitbyte, 638 len); 639 } else { 640 tcpstat_pkt(tcps_sndpack, tcps_sndbyte, len); 641 } 642 #ifdef notyet 643 if ((m = m_copypack(so->so_snd.sb_mb, off, 644 (int)len, max_linkhdr + hdrlen)) == 0) { 645 error = ENOBUFS; 646 goto out; 647 } 648 /* 649 * m_copypack left space for our hdr; use it. 650 */ 651 m->m_len += hdrlen; 652 m->m_data -= hdrlen; 653 #else 654 MGETHDR(m, M_DONTWAIT, MT_HEADER); 655 if (m != NULL && max_linkhdr + hdrlen > MHLEN) { 656 MCLGET(m, M_DONTWAIT); 657 if ((m->m_flags & M_EXT) == 0) { 658 m_freem(m); 659 m = NULL; 660 } 661 } 662 if (m == NULL) { 663 error = ENOBUFS; 664 goto out; 665 } 666 m->m_data += max_linkhdr; 667 m->m_len = hdrlen; 668 if (len <= m_trailingspace(m)) { 669 m_copydata(so->so_snd.sb_mb, off, (int) len, 670 mtod(m, caddr_t) + hdrlen); 671 m->m_len += len; 672 } else { 673 m->m_next = m_copym(so->so_snd.sb_mb, off, (int) len, 674 M_NOWAIT); 675 if (m->m_next == 0) { 676 (void) m_free(m); 677 error = ENOBUFS; 678 goto out; 679 } 680 } 681 if (so->so_snd.sb_mb->m_flags & M_PKTHDR) 682 m->m_pkthdr.ph_loopcnt = 683 so->so_snd.sb_mb->m_pkthdr.ph_loopcnt; 684 #endif 685 /* 686 * If we're sending everything we've got, set PUSH. 687 * (This will keep happy those implementations which only 688 * give data to the user when a buffer fills or 689 * a PUSH comes in.) 690 */ 691 if (off + len == so->so_snd.sb_cc && !soissending(so)) 692 flags |= TH_PUSH; 693 } else { 694 if (tp->t_flags & TF_ACKNOW) 695 tcpstat_inc(tcps_sndacks); 696 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 697 tcpstat_inc(tcps_sndctrl); 698 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 699 tcpstat_inc(tcps_sndurg); 700 else 701 tcpstat_inc(tcps_sndwinup); 702 703 MGETHDR(m, M_DONTWAIT, MT_HEADER); 704 if (m != NULL && max_linkhdr + hdrlen > MHLEN) { 705 MCLGET(m, M_DONTWAIT); 706 if ((m->m_flags & M_EXT) == 0) { 707 m_freem(m); 708 m = NULL; 709 } 710 } 711 if (m == NULL) { 712 error = ENOBUFS; 713 goto out; 714 } 715 m->m_data += max_linkhdr; 716 m->m_len = hdrlen; 717 } 718 m->m_pkthdr.ph_ifidx = 0; 719 m->m_pkthdr.len = hdrlen + len; 720 721 if (!tp->t_template) 722 panic("tcp_output"); 723 #ifdef DIAGNOSTIC 724 if (tp->t_template->m_len != hdrlen - optlen) 725 panic("tcp_output: template len != hdrlen - optlen"); 726 #endif /* DIAGNOSTIC */ 727 memcpy(mtod(m, caddr_t), mtod(tp->t_template, caddr_t), 728 tp->t_template->m_len); 729 th = (struct tcphdr *)(mtod(m, caddr_t) + tp->t_template->m_len - 730 sizeof(struct tcphdr)); 731 732 /* 733 * Fill in fields, remembering maximum advertised 734 * window for use in delaying messages about window sizes. 735 * If resending a FIN, be sure not to use a new sequence number. 736 */ 737 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && 738 (tp->snd_nxt == tp->snd_max)) 739 tp->snd_nxt--; 740 /* 741 * If we are doing retransmissions, then snd_nxt will 742 * not reflect the first unsent octet. For ACK only 743 * packets, we do not want the sequence number of the 744 * retransmitted packet, we want the sequence number 745 * of the next unsent octet. So, if there is no data 746 * (and no SYN or FIN), use snd_max instead of snd_nxt 747 * when filling in ti_seq. But if we are in persist 748 * state, snd_max might reflect one byte beyond the 749 * right edge of the window, so use snd_nxt in that 750 * case, since we know we aren't doing a retransmission. 751 * (retransmit and persist are mutually exclusive...) 752 */ 753 if (len || (flags & (TH_SYN|TH_FIN)) || TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) 754 th->th_seq = htonl(tp->snd_nxt); 755 else 756 th->th_seq = htonl(tp->snd_max); 757 758 if (sack_rxmit) { 759 /* 760 * If sendalot was turned on (due to option stuffing), turn it 761 * off. Properly set th_seq field. Advance the ret'x pointer 762 * by len. 763 */ 764 if (sendalot) 765 sendalot = 0; 766 th->th_seq = htonl(p->rxmit); 767 p->rxmit += len; 768 tcpstat_pkt(tcps_sack_rexmits, tcps_sack_rexmit_bytes, len); 769 } 770 771 th->th_ack = htonl(tp->rcv_nxt); 772 if (optlen) { 773 memcpy(th + 1, opt, optlen); 774 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 775 } 776 #ifdef TCP_ECN 777 if (tcp_do_ecn) { 778 /* 779 * if we have received congestion experienced segs, 780 * set ECE bit. 781 */ 782 if (tp->t_flags & TF_RCVD_CE) { 783 flags |= TH_ECE; 784 tcpstat_inc(tcps_ecn_sndece); 785 } 786 if (!(tp->t_flags & TF_DISABLE_ECN)) { 787 /* 788 * if this is a SYN seg, set ECE and CWR. 789 * set only ECE for SYN-ACK if peer supports ECN. 790 */ 791 if ((flags & (TH_SYN|TH_ACK)) == TH_SYN) 792 flags |= (TH_ECE|TH_CWR); 793 else if ((tp->t_flags & TF_ECN_PERMIT) && 794 (flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) 795 flags |= TH_ECE; 796 } 797 /* 798 * if we have reduced the congestion window, notify 799 * the peer by setting CWR bit. 800 */ 801 if ((tp->t_flags & TF_ECN_PERMIT) && 802 (tp->t_flags & TF_SEND_CWR)) { 803 flags |= TH_CWR; 804 tp->t_flags &= ~TF_SEND_CWR; 805 tcpstat_inc(tcps_ecn_sndcwr); 806 } 807 } 808 #endif 809 th->th_flags = flags; 810 811 /* 812 * Calculate receive window. Don't shrink window, 813 * but avoid silly window syndrome. 814 */ 815 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 816 win = 0; 817 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 818 win = (long)TCP_MAXWIN << tp->rcv_scale; 819 if (win < (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt)) 820 win = (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt); 821 if (flags & TH_RST) 822 win = 0; 823 th->th_win = htons((u_int16_t) (win>>tp->rcv_scale)); 824 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 825 u_int32_t urp = tp->snd_up - tp->snd_nxt; 826 if (urp > IP_MAXPACKET) 827 urp = IP_MAXPACKET; 828 th->th_urp = htons((u_int16_t)urp); 829 th->th_flags |= TH_URG; 830 } else 831 /* 832 * If no urgent pointer to send, then we pull 833 * the urgent pointer to the left edge of the send window 834 * so that it doesn't drift into the send window on sequence 835 * number wraparound. 836 */ 837 tp->snd_up = tp->snd_una; /* drag it along */ 838 839 #ifdef TCP_SIGNATURE 840 if (tp->t_flags & TF_SIGNATURE) { 841 int iphlen; 842 union sockaddr_union src, dst; 843 struct tdb *tdb; 844 845 bzero(&src, sizeof(union sockaddr_union)); 846 bzero(&dst, sizeof(union sockaddr_union)); 847 848 switch (tp->pf) { 849 case 0: /*default to PF_INET*/ 850 case AF_INET: 851 iphlen = sizeof(struct ip); 852 src.sa.sa_len = sizeof(struct sockaddr_in); 853 src.sa.sa_family = AF_INET; 854 src.sin.sin_addr = mtod(m, struct ip *)->ip_src; 855 dst.sa.sa_len = sizeof(struct sockaddr_in); 856 dst.sa.sa_family = AF_INET; 857 dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst; 858 break; 859 #ifdef INET6 860 case AF_INET6: 861 iphlen = sizeof(struct ip6_hdr); 862 src.sa.sa_len = sizeof(struct sockaddr_in6); 863 src.sa.sa_family = AF_INET6; 864 src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src; 865 dst.sa.sa_len = sizeof(struct sockaddr_in6); 866 dst.sa.sa_family = AF_INET6; 867 dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst; 868 break; 869 #endif /* INET6 */ 870 } 871 872 tdb = gettdbbysrcdst(rtable_l2(tp->t_inpcb->inp_rtableid), 873 0, &src, &dst, IPPROTO_TCP); 874 if (tdb == NULL) { 875 m_freem(m); 876 return (EPERM); 877 } 878 879 if (tcp_signature(tdb, tp->pf, m, th, iphlen, 0, 880 mtod(m, caddr_t) + hdrlen - optlen + sigoff) < 0) { 881 m_freem(m); 882 return (EINVAL); 883 } 884 } 885 #endif /* TCP_SIGNATURE */ 886 887 /* Defer checksumming until later (ip_output() or hardware) */ 888 m->m_pkthdr.csum_flags |= M_TCP_CSUM_OUT; 889 890 /* 891 * In transmit state, time the transmission and arrange for 892 * the retransmit. In persist state, just set snd_max. 893 */ 894 if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 895 tcp_seq startseq = tp->snd_nxt; 896 897 /* 898 * Advance snd_nxt over sequence space of this segment. 899 */ 900 if (flags & (TH_SYN|TH_FIN)) { 901 if (flags & TH_SYN) 902 tp->snd_nxt++; 903 if (flags & TH_FIN) { 904 tp->snd_nxt++; 905 tp->t_flags |= TF_SENTFIN; 906 } 907 } 908 if (tp->sack_enable) { 909 if (sack_rxmit && (p->rxmit != tp->snd_nxt)) { 910 goto timer; 911 } 912 } 913 tp->snd_nxt += len; 914 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 915 tp->snd_max = tp->snd_nxt; 916 /* 917 * Time this transmission if not a retransmission and 918 * not currently timing anything. 919 */ 920 if (tp->t_rtttime == 0) { 921 tp->t_rtttime = tcp_now; 922 tp->t_rtseq = startseq; 923 tcpstat_inc(tcps_segstimed); 924 } 925 } 926 927 /* 928 * Set retransmit timer if not currently set, 929 * and not doing an ack or a keep-alive probe. 930 * Initial value for retransmit timer is smoothed 931 * round-trip time + 2 * round-trip time variance. 932 * Initialize shift counter which is used for backoff 933 * of retransmit time. 934 */ 935 timer: 936 if (tp->sack_enable && sack_rxmit && 937 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 938 tp->snd_nxt != tp->snd_max) { 939 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 940 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 941 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 942 tp->t_rxtshift = 0; 943 } 944 } 945 946 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 947 tp->snd_nxt != tp->snd_una) { 948 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 949 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 950 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 951 tp->t_rxtshift = 0; 952 } 953 } 954 955 if (len == 0 && so->so_snd.sb_cc && 956 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 957 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 958 /* 959 * Avoid a situation where we do not set persist timer 960 * after a zero window condition. For example: 961 * 1) A -> B: packet with enough data to fill the window 962 * 2) B -> A: ACK for #1 + new data (0 window 963 * advertisement) 964 * 3) A -> B: ACK for #2, 0 len packet 965 * 966 * In this case, A will not activate the persist timer, 967 * because it chose to send a packet. Unless tcp_output 968 * is called for some other reason (delayed ack timer, 969 * another input packet from B, socket syscall), A will 970 * not send zero window probes. 971 * 972 * So, if you send a 0-length packet, but there is data 973 * in the socket buffer, and neither the rexmt or 974 * persist timer is already set, then activate the 975 * persist timer. 976 */ 977 tp->t_rxtshift = 0; 978 tcp_setpersist(tp); 979 } 980 } else 981 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 982 tp->snd_max = tp->snd_nxt + len; 983 984 tcp_update_sndspace(tp); 985 986 /* 987 * Trace. 988 */ 989 if (so->so_options & SO_DEBUG) 990 tcp_trace(TA_OUTPUT, tp->t_state, tp, tp, mtod(m, caddr_t), 0, 991 len); 992 993 /* 994 * Fill in IP length and desired time to live and 995 * send to IP level. There should be a better way 996 * to handle ttl and tos; we could keep them in 997 * the template, but need a way to checksum without them. 998 */ 999 1000 #ifdef TCP_ECN 1001 /* 1002 * if peer is ECN capable, set the ECT bit in the IP header. 1003 * but don't set ECT for a pure ack, a retransmit or a window probe. 1004 */ 1005 needect = 0; 1006 if (tcp_do_ecn && (tp->t_flags & TF_ECN_PERMIT)) { 1007 if (len == 0 || SEQ_LT(tp->snd_nxt, tp->snd_max) || 1008 (tp->t_force && len == 1)) { 1009 /* don't set ECT */ 1010 } else { 1011 needect = 1; 1012 tcpstat_inc(tcps_ecn_sndect); 1013 } 1014 } 1015 #endif 1016 1017 /* force routing table */ 1018 m->m_pkthdr.ph_rtableid = tp->t_inpcb->inp_rtableid; 1019 1020 #if NPF > 0 1021 pf_mbuf_link_inpcb(m, tp->t_inpcb); 1022 #endif 1023 1024 switch (tp->pf) { 1025 case 0: /*default to PF_INET*/ 1026 case AF_INET: 1027 { 1028 struct ip *ip; 1029 1030 ip = mtod(m, struct ip *); 1031 ip->ip_len = htons(m->m_pkthdr.len); 1032 packetlen = m->m_pkthdr.len; 1033 ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; 1034 ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos; 1035 #ifdef TCP_ECN 1036 if (needect) 1037 ip->ip_tos |= IPTOS_ECN_ECT0; 1038 #endif 1039 } 1040 #if NSTOEPLITZ > 0 1041 m->m_pkthdr.ph_flowid = tp->t_inpcb->inp_flowid; 1042 SET(m->m_pkthdr.csum_flags, M_FLOWID); 1043 #endif 1044 error = ip_output(m, tp->t_inpcb->inp_options, 1045 &tp->t_inpcb->inp_route, 1046 (ip_mtudisc ? IP_MTUDISC : 0), NULL, tp->t_inpcb, 0); 1047 break; 1048 #ifdef INET6 1049 case AF_INET6: 1050 { 1051 struct ip6_hdr *ip6; 1052 1053 ip6 = mtod(m, struct ip6_hdr *); 1054 ip6->ip6_plen = m->m_pkthdr.len - 1055 sizeof(struct ip6_hdr); 1056 packetlen = m->m_pkthdr.len; 1057 ip6->ip6_nxt = IPPROTO_TCP; 1058 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb); 1059 #ifdef TCP_ECN 1060 if (needect) 1061 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1062 #endif 1063 } 1064 error = ip6_output(m, tp->t_inpcb->inp_outputopts6, 1065 &tp->t_inpcb->inp_route6, 1066 0, NULL, tp->t_inpcb); 1067 break; 1068 #endif /* INET6 */ 1069 } 1070 1071 if (error) { 1072 out: 1073 if (error == ENOBUFS) { 1074 /* 1075 * If the interface queue is full, or IP cannot 1076 * get an mbuf, trigger TCP slow start. 1077 */ 1078 tp->snd_cwnd = tp->t_maxseg; 1079 return (0); 1080 } 1081 if (error == EMSGSIZE) { 1082 /* 1083 * ip_output() will have already fixed the route 1084 * for us. tcp_mtudisc() will, as its last action, 1085 * initiate retransmission, so it is important to 1086 * not do so here. 1087 */ 1088 tcp_mtudisc(tp->t_inpcb, -1); 1089 return (0); 1090 } 1091 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1092 TCPS_HAVERCVDSYN(tp->t_state)) { 1093 tp->t_softerror = error; 1094 return (0); 1095 } 1096 1097 /* Restart the delayed ACK timer, if necessary. */ 1098 if (TCP_TIMER_ISARMED(tp, TCPT_DELACK)) 1099 TCP_TIMER_ARM_MSEC(tp, TCPT_DELACK, tcp_delack_msecs); 1100 1101 return (error); 1102 } 1103 1104 if (packetlen > tp->t_pmtud_mtu_sent) 1105 tp->t_pmtud_mtu_sent = packetlen; 1106 1107 tcpstat_inc(tcps_sndtotal); 1108 if (TCP_TIMER_ISARMED(tp, TCPT_DELACK)) 1109 tcpstat_inc(tcps_delack); 1110 1111 /* 1112 * Data sent (as far as we can tell). 1113 * If this advertises a larger window than any other segment, 1114 * then remember the size of the advertised window. 1115 * Any pending ACK has now been sent. 1116 */ 1117 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 1118 tp->rcv_adv = tp->rcv_nxt + win; 1119 tp->last_ack_sent = tp->rcv_nxt; 1120 tp->t_flags &= ~TF_ACKNOW; 1121 TCP_TIMER_DISARM(tp, TCPT_DELACK); 1122 if (sendalot) 1123 goto again; 1124 return (0); 1125 } 1126 1127 void 1128 tcp_setpersist(struct tcpcb *tp) 1129 { 1130 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + TCP_RTT_BASE_SHIFT); 1131 int nticks; 1132 1133 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT)) 1134 panic("tcp_output REXMT"); 1135 /* 1136 * Start/restart persistence timer. 1137 */ 1138 if (t < tp->t_rttmin) 1139 t = tp->t_rttmin; 1140 TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift], 1141 TCPTV_PERSMIN, TCPTV_PERSMAX); 1142 TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks); 1143 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1144 tp->t_rxtshift++; 1145 } 1146