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 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_mac.h" 39 #include "opt_tcpdebug.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/domain.h> 44 #include <sys/kernel.h> 45 #include <sys/lock.h> 46 #include <sys/mbuf.h> 47 #include <sys/mutex.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/sysctl.h> 52 53 #include <net/route.h> 54 55 #include <netinet/in.h> 56 #include <netinet/in_systm.h> 57 #include <netinet/ip.h> 58 #include <netinet/in_pcb.h> 59 #include <netinet/ip_var.h> 60 #include <netinet/ip_options.h> 61 #ifdef INET6 62 #include <netinet6/in6_pcb.h> 63 #include <netinet/ip6.h> 64 #include <netinet6/ip6_var.h> 65 #endif 66 #include <netinet/tcp.h> 67 #define TCPOUTFLAGS 68 #include <netinet/tcp_fsm.h> 69 #include <netinet/tcp_seq.h> 70 #include <netinet/tcp_timer.h> 71 #include <netinet/tcp_var.h> 72 #include <netinet/tcpip.h> 73 #ifdef TCPDEBUG 74 #include <netinet/tcp_debug.h> 75 #endif 76 77 #ifdef IPSEC 78 #include <netipsec/ipsec.h> 79 #endif /*IPSEC*/ 80 81 #include <machine/in_cksum.h> 82 83 #include <security/mac/mac_framework.h> 84 85 #ifdef notyet 86 extern struct mbuf *m_copypack(); 87 #endif 88 89 int path_mtu_discovery = 1; 90 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 91 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 92 93 int ss_fltsz = 1; 94 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 95 &ss_fltsz, 1, "Slow start flight size"); 96 97 int ss_fltsz_local = 4; 98 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 99 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 100 101 int tcp_do_newreno = 1; 102 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 103 &tcp_do_newreno, 0, "Enable NewReno Algorithms"); 104 105 int tcp_do_tso = 1; 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 107 &tcp_do_tso, 0, "Enable TCP Segmentation Offload"); 108 109 int tcp_do_autosndbuf = 1; 110 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 111 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 112 113 int tcp_autosndbuf_inc = 8*1024; 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 115 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 116 117 int tcp_autosndbuf_max = 256*1024; 118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 119 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 120 121 122 /* 123 * Tcp output routine: figure out what should be sent and send it. 124 */ 125 int 126 tcp_output(struct tcpcb *tp) 127 { 128 struct socket *so = tp->t_inpcb->inp_socket; 129 long len, recwin, sendwin; 130 int off, flags, error; 131 #ifdef TCP_SIGNATURE 132 int sigoff = 0; 133 #endif 134 struct mbuf *m; 135 struct ip *ip = NULL; 136 struct ipovly *ipov = NULL; 137 struct tcphdr *th; 138 u_char opt[TCP_MAXOLEN]; 139 unsigned ipoptlen, optlen, hdrlen; 140 #ifdef IPSEC 141 unsigned ipsec_optlen = 0; 142 #endif 143 int idle, sendalot; 144 int sack_rxmit, sack_bytes_rxmt; 145 struct sackhole *p; 146 int tso = 0; 147 struct tcpopt to; 148 #if 0 149 int maxburst = TCP_MAXBURST; 150 #endif 151 #ifdef INET6 152 struct ip6_hdr *ip6 = NULL; 153 int isipv6; 154 155 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 156 #endif 157 158 INP_LOCK_ASSERT(tp->t_inpcb); 159 160 /* 161 * Determine length of data that should be transmitted, 162 * and flags that will be used. 163 * If there is some data or critical controls (SYN, RST) 164 * to send, then transmit; otherwise, investigate further. 165 */ 166 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 167 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 168 /* 169 * We have been idle for "a while" and no acks are 170 * expected to clock out any data we send -- 171 * slow start to get ack "clock" running again. 172 * 173 * Set the slow-start flight size depending on whether 174 * this is a local network or not. 175 */ 176 int ss = ss_fltsz; 177 #ifdef INET6 178 if (isipv6) { 179 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 180 ss = ss_fltsz_local; 181 } else 182 #endif /* INET6 */ 183 if (in_localaddr(tp->t_inpcb->inp_faddr)) 184 ss = ss_fltsz_local; 185 tp->snd_cwnd = tp->t_maxseg * ss; 186 } 187 tp->t_flags &= ~TF_LASTIDLE; 188 if (idle) { 189 if (tp->t_flags & TF_MORETOCOME) { 190 tp->t_flags |= TF_LASTIDLE; 191 idle = 0; 192 } 193 } 194 again: 195 /* 196 * If we've recently taken a timeout, snd_max will be greater than 197 * snd_nxt. There may be SACK information that allows us to avoid 198 * resending already delivered data. Adjust snd_nxt accordingly. 199 */ 200 if ((tp->t_flags & TF_SACK_PERMIT) && 201 SEQ_LT(tp->snd_nxt, tp->snd_max)) 202 tcp_sack_adjust(tp); 203 sendalot = 0; 204 off = tp->snd_nxt - tp->snd_una; 205 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 206 sendwin = min(sendwin, tp->snd_bwnd); 207 208 flags = tcp_outflags[tp->t_state]; 209 /* 210 * Send any SACK-generated retransmissions. If we're explicitly trying 211 * to send out new data (when sendalot is 1), bypass this function. 212 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 213 * we're replacing a (future) new transmission with a retransmission 214 * now, and we previously incremented snd_cwnd in tcp_input(). 215 */ 216 /* 217 * Still in sack recovery , reset rxmit flag to zero. 218 */ 219 sack_rxmit = 0; 220 sack_bytes_rxmt = 0; 221 len = 0; 222 p = NULL; 223 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 224 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 225 long cwin; 226 227 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 228 if (cwin < 0) 229 cwin = 0; 230 /* Do not retransmit SACK segments beyond snd_recover */ 231 if (SEQ_GT(p->end, tp->snd_recover)) { 232 /* 233 * (At least) part of sack hole extends beyond 234 * snd_recover. Check to see if we can rexmit data 235 * for this hole. 236 */ 237 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 238 /* 239 * Can't rexmit any more data for this hole. 240 * That data will be rexmitted in the next 241 * sack recovery episode, when snd_recover 242 * moves past p->rxmit. 243 */ 244 p = NULL; 245 goto after_sack_rexmit; 246 } else 247 /* Can rexmit part of the current hole */ 248 len = ((long)ulmin(cwin, 249 tp->snd_recover - p->rxmit)); 250 } else 251 len = ((long)ulmin(cwin, p->end - p->rxmit)); 252 off = p->rxmit - tp->snd_una; 253 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 254 __func__, off)); 255 if (len > 0) { 256 sack_rxmit = 1; 257 sendalot = 1; 258 tcpstat.tcps_sack_rexmits++; 259 tcpstat.tcps_sack_rexmit_bytes += 260 min(len, tp->t_maxseg); 261 } 262 } 263 after_sack_rexmit: 264 /* 265 * Get standard flags, and add SYN or FIN if requested by 'hidden' 266 * state flags. 267 */ 268 if (tp->t_flags & TF_NEEDFIN) 269 flags |= TH_FIN; 270 if (tp->t_flags & TF_NEEDSYN) 271 flags |= TH_SYN; 272 273 SOCKBUF_LOCK(&so->so_snd); 274 /* 275 * If in persist timeout with window of 0, send 1 byte. 276 * Otherwise, if window is small but nonzero 277 * and timer expired, we will send what we can 278 * and go to transmit state. 279 */ 280 if (tp->t_flags & TF_FORCEDATA) { 281 if (sendwin == 0) { 282 /* 283 * If we still have some data to send, then 284 * clear the FIN bit. Usually this would 285 * happen below when it realizes that we 286 * aren't sending all the data. However, 287 * if we have exactly 1 byte of unsent data, 288 * then it won't clear the FIN bit below, 289 * and if we are in persist state, we wind 290 * up sending the packet without recording 291 * that we sent the FIN bit. 292 * 293 * We can't just blindly clear the FIN bit, 294 * because if we don't have any more data 295 * to send then the probe will be the FIN 296 * itself. 297 */ 298 if (off < so->so_snd.sb_cc) 299 flags &= ~TH_FIN; 300 sendwin = 1; 301 } else { 302 tcp_timer_activate(tp, TT_PERSIST, 0); 303 tp->t_rxtshift = 0; 304 } 305 } 306 307 /* 308 * If snd_nxt == snd_max and we have transmitted a FIN, the 309 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 310 * a negative length. This can also occur when TCP opens up 311 * its congestion window while receiving additional duplicate 312 * acks after fast-retransmit because TCP will reset snd_nxt 313 * to snd_max after the fast-retransmit. 314 * 315 * In the normal retransmit-FIN-only case, however, snd_nxt will 316 * be set to snd_una, the offset will be 0, and the length may 317 * wind up 0. 318 * 319 * If sack_rxmit is true we are retransmitting from the scoreboard 320 * in which case len is already set. 321 */ 322 if (sack_rxmit == 0) { 323 if (sack_bytes_rxmt == 0) 324 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 325 else { 326 long cwin; 327 328 /* 329 * We are inside of a SACK recovery episode and are 330 * sending new data, having retransmitted all the 331 * data possible in the scoreboard. 332 */ 333 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 334 - off); 335 /* 336 * Don't remove this (len > 0) check ! 337 * We explicitly check for len > 0 here (although it 338 * isn't really necessary), to work around a gcc 339 * optimization issue - to force gcc to compute 340 * len above. Without this check, the computation 341 * of len is bungled by the optimizer. 342 */ 343 if (len > 0) { 344 cwin = tp->snd_cwnd - 345 (tp->snd_nxt - tp->sack_newdata) - 346 sack_bytes_rxmt; 347 if (cwin < 0) 348 cwin = 0; 349 len = lmin(len, cwin); 350 } 351 } 352 } 353 354 /* 355 * Lop off SYN bit if it has already been sent. However, if this 356 * is SYN-SENT state and if segment contains data and if we don't 357 * know that foreign host supports TAO, suppress sending segment. 358 */ 359 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 360 if (tp->t_state != TCPS_SYN_RECEIVED) 361 flags &= ~TH_SYN; 362 off--, len++; 363 } 364 365 /* 366 * Be careful not to send data and/or FIN on SYN segments. 367 * This measure is needed to prevent interoperability problems 368 * with not fully conformant TCP implementations. 369 */ 370 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 371 len = 0; 372 flags &= ~TH_FIN; 373 } 374 375 if (len < 0) { 376 /* 377 * If FIN has been sent but not acked, 378 * but we haven't been called to retransmit, 379 * len will be < 0. Otherwise, window shrank 380 * after we sent into it. If window shrank to 0, 381 * cancel pending retransmit, pull snd_nxt back 382 * to (closed) window, and set the persist timer 383 * if it isn't already going. If the window didn't 384 * close completely, just wait for an ACK. 385 */ 386 len = 0; 387 if (sendwin == 0) { 388 tcp_timer_activate(tp, TT_REXMT, 0); 389 tp->t_rxtshift = 0; 390 tp->snd_nxt = tp->snd_una; 391 if (!tcp_timer_active(tp, TT_PERSIST)) 392 tcp_setpersist(tp); 393 } 394 } 395 396 /* len will be >= 0 after this point. */ 397 KASSERT(len >= 0, ("%s: len < 0", __func__)); 398 399 /* 400 * Automatic sizing of send socket buffer. Often the send buffer 401 * size is not optimally adjusted to the actual network conditions 402 * at hand (delay bandwidth product). Setting the buffer size too 403 * small limits throughput on links with high bandwidth and high 404 * delay (eg. trans-continental/oceanic links). Setting the 405 * buffer size too big consumes too much real kernel memory, 406 * especially with many connections on busy servers. 407 * 408 * The criteria to step up the send buffer one notch are: 409 * 1. receive window of remote host is larger than send buffer 410 * (with a fudge factor of 5/4th); 411 * 2. send buffer is filled to 7/8th with data (so we actually 412 * have data to make use of it); 413 * 3. send buffer fill has not hit maximal automatic size; 414 * 4. our send window (slow start and cogestion controlled) is 415 * larger than sent but unacknowledged data in send buffer. 416 * 417 * The remote host receive window scaling factor may limit the 418 * growing of the send buffer before it reaches its allowed 419 * maximum. 420 * 421 * It scales directly with slow start or congestion window 422 * and does at most one step per received ACK. This fast 423 * scaling has the drawback of growing the send buffer beyond 424 * what is strictly necessary to make full use of a given 425 * delay*bandwith product. However testing has shown this not 426 * to be much of an problem. At worst we are trading wasting 427 * of available bandwith (the non-use of it) for wasting some 428 * socket buffer memory. 429 * 430 * TODO: Shrink send buffer during idle periods together 431 * with congestion window. Requires another timer. Has to 432 * wait for upcoming tcp timer rewrite. 433 */ 434 if (tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 435 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 436 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 437 so->so_snd.sb_cc < tcp_autosndbuf_max && 438 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 439 if (!sbreserve_locked(&so->so_snd, 440 min(so->so_snd.sb_hiwat + tcp_autosndbuf_inc, 441 tcp_autosndbuf_max), so, curthread)) 442 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 443 } 444 } 445 446 /* 447 * Truncate to the maximum segment length or enable TCP Segmentation 448 * Offloading (if supported by hardware) and ensure that FIN is removed 449 * if the length no longer contains the last data byte. 450 * 451 * TSO may only be used if we are in a pure bulk sending state. The 452 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 453 * IP options prevent using TSO. With TSO the TCP header is the same 454 * (except for the sequence number) for all generated packets. This 455 * makes it impossible to transmit any options which vary per generated 456 * segment or packet. 457 * 458 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 459 * removal of FIN (if not already catched here) are handled later after 460 * the exact length of the TCP options are known. 461 */ 462 #ifdef IPSEC 463 /* 464 * Pre-calculate here as we save another lookup into the darknesses 465 * of IPsec that way and can actually decide if TSO is ok. 466 */ 467 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 468 #endif 469 if (len > tp->t_maxseg) { 470 if ((tp->t_flags & TF_TSO) && tcp_do_tso && 471 ((tp->t_flags & TF_SIGNATURE) == 0) && 472 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 473 tp->t_inpcb->inp_options == NULL && 474 tp->t_inpcb->in6p_options == NULL 475 #ifdef IPSEC 476 && ipsec_optlen == 0 477 #endif 478 ) { 479 tso = 1; 480 } else { 481 len = tp->t_maxseg; 482 sendalot = 1; 483 tso = 0; 484 } 485 } 486 if (sack_rxmit) { 487 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 488 flags &= ~TH_FIN; 489 } else { 490 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 491 flags &= ~TH_FIN; 492 } 493 494 recwin = sbspace(&so->so_rcv); 495 496 /* 497 * Sender silly window avoidance. We transmit under the following 498 * conditions when len is non-zero: 499 * 500 * - We have a full segment (or more with TSO) 501 * - This is the last buffer in a write()/send() and we are 502 * either idle or running NODELAY 503 * - we've timed out (e.g. persist timer) 504 * - we have more then 1/2 the maximum send window's worth of 505 * data (receiver may be limited the window size) 506 * - we need to retransmit 507 */ 508 if (len) { 509 if (len >= tp->t_maxseg) 510 goto send; 511 /* 512 * NOTE! on localhost connections an 'ack' from the remote 513 * end may occur synchronously with the output and cause 514 * us to flush a buffer queued with moretocome. XXX 515 * 516 * note: the len + off check is almost certainly unnecessary. 517 */ 518 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 519 (idle || (tp->t_flags & TF_NODELAY)) && 520 len + off >= so->so_snd.sb_cc && 521 (tp->t_flags & TF_NOPUSH) == 0) { 522 goto send; 523 } 524 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 525 goto send; 526 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 527 goto send; 528 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 529 goto send; 530 if (sack_rxmit) 531 goto send; 532 } 533 534 /* 535 * Compare available window to amount of window 536 * known to peer (as advertised window less 537 * next expected input). If the difference is at least two 538 * max size segments, or at least 50% of the maximum possible 539 * window, then want to send a window update to peer. 540 * Skip this if the connection is in T/TCP half-open state. 541 * Don't send pure window updates when the peer has closed 542 * the connection and won't ever send more data. 543 */ 544 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 545 !TCPS_HAVERCVDFIN(tp->t_state)) { 546 /* 547 * "adv" is the amount we can increase the window, 548 * taking into account that we are limited by 549 * TCP_MAXWIN << tp->rcv_scale. 550 */ 551 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 552 (tp->rcv_adv - tp->rcv_nxt); 553 554 if (adv >= (long) (2 * tp->t_maxseg)) 555 goto send; 556 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 557 goto send; 558 } 559 560 /* 561 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 562 * is also a catch-all for the retransmit timer timeout case. 563 */ 564 if (tp->t_flags & TF_ACKNOW) 565 goto send; 566 if ((flags & TH_RST) || 567 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 568 goto send; 569 if (SEQ_GT(tp->snd_up, tp->snd_una)) 570 goto send; 571 /* 572 * If our state indicates that FIN should be sent 573 * and we have not yet done so, then we need to send. 574 */ 575 if (flags & TH_FIN && 576 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 577 goto send; 578 /* 579 * In SACK, it is possible for tcp_output to fail to send a segment 580 * after the retransmission timer has been turned off. Make sure 581 * that the retransmission timer is set. 582 */ 583 if ((tp->t_flags & TF_SACK_PERMIT) && 584 SEQ_GT(tp->snd_max, tp->snd_una) && 585 !tcp_timer_active(tp, TT_REXMT) && 586 !tcp_timer_active(tp, TT_PERSIST)) { 587 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 588 goto just_return; 589 } 590 /* 591 * TCP window updates are not reliable, rather a polling protocol 592 * using ``persist'' packets is used to insure receipt of window 593 * updates. The three ``states'' for the output side are: 594 * idle not doing retransmits or persists 595 * persisting to move a small or zero window 596 * (re)transmitting and thereby not persisting 597 * 598 * tcp_timer_active(tp, TT_PERSIST) 599 * is true when we are in persist state. 600 * (tp->t_flags & TF_FORCEDATA) 601 * is set when we are called to send a persist packet. 602 * tcp_timer_active(tp, TT_REXMT) 603 * is set when we are retransmitting 604 * The output side is idle when both timers are zero. 605 * 606 * If send window is too small, there is data to transmit, and no 607 * retransmit or persist is pending, then go to persist state. 608 * If nothing happens soon, send when timer expires: 609 * if window is nonzero, transmit what we can, 610 * otherwise force out a byte. 611 */ 612 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 613 !tcp_timer_active(tp, TT_PERSIST)) { 614 tp->t_rxtshift = 0; 615 tcp_setpersist(tp); 616 } 617 618 /* 619 * No reason to send a segment, just return. 620 */ 621 just_return: 622 SOCKBUF_UNLOCK(&so->so_snd); 623 return (0); 624 625 send: 626 SOCKBUF_LOCK_ASSERT(&so->so_snd); 627 /* 628 * Before ESTABLISHED, force sending of initial options 629 * unless TCP set not to do any options. 630 * NOTE: we assume that the IP/TCP header plus TCP options 631 * always fit in a single mbuf, leaving room for a maximum 632 * link header, i.e. 633 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 634 */ 635 optlen = 0; 636 #ifdef INET6 637 if (isipv6) 638 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 639 else 640 #endif 641 hdrlen = sizeof (struct tcpiphdr); 642 643 /* 644 * Compute options for segment. 645 * We only have to care about SYN and established connection 646 * segments. Options for SYN-ACK segments are handled in TCP 647 * syncache. 648 */ 649 if ((tp->t_flags & TF_NOOPT) == 0) { 650 to.to_flags = 0; 651 /* Maximum segment size. */ 652 if (flags & TH_SYN) { 653 tp->snd_nxt = tp->iss; 654 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 655 to.to_flags |= TOF_MSS; 656 } 657 /* Window scaling. */ 658 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 659 to.to_wscale = tp->request_r_scale; 660 to.to_flags |= TOF_SCALE; 661 } 662 /* Timestamps. */ 663 if ((tp->t_flags & TF_RCVD_TSTMP) || 664 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 665 to.to_tsval = ticks + tp->ts_offset; 666 to.to_tsecr = tp->ts_recent; 667 to.to_flags |= TOF_TS; 668 /* Set receive buffer autosizing timestamp. */ 669 if (tp->rfbuf_ts == 0 && 670 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 671 tp->rfbuf_ts = ticks; 672 } 673 /* Selective ACK's. */ 674 if (tp->t_flags & TF_SACK_PERMIT) { 675 if (flags & TH_SYN) 676 to.to_flags |= TOF_SACKPERM; 677 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 678 (tp->t_flags & TF_SACK_PERMIT) && 679 tp->rcv_numsacks > 0) { 680 to.to_flags |= TOF_SACK; 681 to.to_nsacks = tp->rcv_numsacks; 682 to.to_sacks = (u_char *)tp->sackblks; 683 } 684 } 685 #ifdef TCP_SIGNATURE 686 /* TCP-MD5 (RFC2385). */ 687 #ifdef INET6 688 if (!isipv6 && (tp->t_flags & TF_SIGNATURE)) 689 #else 690 if (tp->t_flags & TF_SIGNATURE) 691 #endif /* INET6 */ 692 to.to_flags |= TOF_SIGNATURE; 693 #endif /* TCP_SIGNATURE */ 694 695 /* Processing the options. */ 696 hdrlen += optlen = tcp_addoptions(&to, opt); 697 698 #ifdef TCP_SIGNATURE 699 sigoff = to.to_signature - (u_char *)&to; 700 #endif /* TCP_SIGNATURE */ 701 } 702 703 #ifdef INET6 704 if (isipv6) 705 ipoptlen = ip6_optlen(tp->t_inpcb); 706 else 707 #endif 708 if (tp->t_inpcb->inp_options) 709 ipoptlen = tp->t_inpcb->inp_options->m_len - 710 offsetof(struct ipoption, ipopt_list); 711 else 712 ipoptlen = 0; 713 #ifdef IPSEC 714 ipoptlen += ipsec_optlen; 715 #endif 716 717 /* 718 * Adjust data length if insertion of options will 719 * bump the packet length beyond the t_maxopd length. 720 * Clear the FIN bit because we cut off the tail of 721 * the segment. 722 * 723 * When doing TSO limit a burst to TCP_MAXWIN minus the 724 * IP, TCP and Options length to keep ip->ip_len from 725 * overflowing. Prevent the last segment from being 726 * fractional thus making them all equal sized and set 727 * the flag to continue sending. TSO is disabled when 728 * IP options or IPSEC are present. 729 */ 730 if (len + optlen + ipoptlen > tp->t_maxopd) { 731 flags &= ~TH_FIN; 732 if (tso) { 733 if (len > TCP_MAXWIN - hdrlen - optlen) { 734 len = TCP_MAXWIN - hdrlen - optlen; 735 len = len - (len % (tp->t_maxopd - optlen)); 736 sendalot = 1; 737 } else if (tp->t_flags & TF_NEEDFIN) 738 sendalot = 1; 739 } else { 740 len = tp->t_maxopd - optlen - ipoptlen; 741 sendalot = 1; 742 } 743 } 744 745 /*#ifdef DIAGNOSTIC*/ 746 #ifdef INET6 747 if (max_linkhdr + hdrlen > MCLBYTES) 748 #else 749 if (max_linkhdr + hdrlen > MHLEN) 750 #endif 751 panic("tcphdr too big"); 752 /*#endif*/ 753 754 /* 755 * Grab a header mbuf, attaching a copy of data to 756 * be transmitted, and initialize the header from 757 * the template for sends on this connection. 758 */ 759 if (len) { 760 struct mbuf *mb; 761 u_int moff; 762 763 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 764 tcpstat.tcps_sndprobe++; 765 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 766 tcpstat.tcps_sndrexmitpack++; 767 tcpstat.tcps_sndrexmitbyte += len; 768 } else { 769 tcpstat.tcps_sndpack++; 770 tcpstat.tcps_sndbyte += len; 771 } 772 #ifdef notyet 773 if ((m = m_copypack(so->so_snd.sb_mb, off, 774 (int)len, max_linkhdr + hdrlen)) == 0) { 775 SOCKBUF_UNLOCK(&so->so_snd); 776 error = ENOBUFS; 777 goto out; 778 } 779 /* 780 * m_copypack left space for our hdr; use it. 781 */ 782 m->m_len += hdrlen; 783 m->m_data -= hdrlen; 784 #else 785 MGETHDR(m, M_DONTWAIT, MT_DATA); 786 if (m == NULL) { 787 SOCKBUF_UNLOCK(&so->so_snd); 788 error = ENOBUFS; 789 goto out; 790 } 791 #ifdef INET6 792 if (MHLEN < hdrlen + max_linkhdr) { 793 MCLGET(m, M_DONTWAIT); 794 if ((m->m_flags & M_EXT) == 0) { 795 SOCKBUF_UNLOCK(&so->so_snd); 796 m_freem(m); 797 error = ENOBUFS; 798 goto out; 799 } 800 } 801 #endif 802 m->m_data += max_linkhdr; 803 m->m_len = hdrlen; 804 805 /* 806 * Start the m_copy functions from the closest mbuf 807 * to the offset in the socket buffer chain. 808 */ 809 mb = sbsndptr(&so->so_snd, off, len, &moff); 810 811 if (len <= MHLEN - hdrlen - max_linkhdr) { 812 m_copydata(mb, moff, (int)len, 813 mtod(m, caddr_t) + hdrlen); 814 m->m_len += len; 815 } else { 816 m->m_next = m_copy(mb, moff, (int)len); 817 if (m->m_next == NULL) { 818 SOCKBUF_UNLOCK(&so->so_snd); 819 (void) m_free(m); 820 error = ENOBUFS; 821 goto out; 822 } 823 } 824 #endif 825 /* 826 * If we're sending everything we've got, set PUSH. 827 * (This will keep happy those implementations which only 828 * give data to the user when a buffer fills or 829 * a PUSH comes in.) 830 */ 831 if (off + len == so->so_snd.sb_cc) 832 flags |= TH_PUSH; 833 SOCKBUF_UNLOCK(&so->so_snd); 834 } else { 835 SOCKBUF_UNLOCK(&so->so_snd); 836 if (tp->t_flags & TF_ACKNOW) 837 tcpstat.tcps_sndacks++; 838 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 839 tcpstat.tcps_sndctrl++; 840 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 841 tcpstat.tcps_sndurg++; 842 else 843 tcpstat.tcps_sndwinup++; 844 845 MGETHDR(m, M_DONTWAIT, MT_DATA); 846 if (m == NULL) { 847 error = ENOBUFS; 848 goto out; 849 } 850 #ifdef INET6 851 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 852 MHLEN >= hdrlen) { 853 MH_ALIGN(m, hdrlen); 854 } else 855 #endif 856 m->m_data += max_linkhdr; 857 m->m_len = hdrlen; 858 } 859 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 860 m->m_pkthdr.rcvif = (struct ifnet *)0; 861 #ifdef MAC 862 mac_inpcb_create_mbuf(tp->t_inpcb, m); 863 #endif 864 #ifdef INET6 865 if (isipv6) { 866 ip6 = mtod(m, struct ip6_hdr *); 867 th = (struct tcphdr *)(ip6 + 1); 868 tcpip_fillheaders(tp->t_inpcb, ip6, th); 869 } else 870 #endif /* INET6 */ 871 { 872 ip = mtod(m, struct ip *); 873 ipov = (struct ipovly *)ip; 874 th = (struct tcphdr *)(ip + 1); 875 tcpip_fillheaders(tp->t_inpcb, ip, th); 876 } 877 878 /* 879 * Fill in fields, remembering maximum advertised 880 * window for use in delaying messages about window sizes. 881 * If resending a FIN, be sure not to use a new sequence number. 882 */ 883 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 884 tp->snd_nxt == tp->snd_max) 885 tp->snd_nxt--; 886 /* 887 * If we are doing retransmissions, then snd_nxt will 888 * not reflect the first unsent octet. For ACK only 889 * packets, we do not want the sequence number of the 890 * retransmitted packet, we want the sequence number 891 * of the next unsent octet. So, if there is no data 892 * (and no SYN or FIN), use snd_max instead of snd_nxt 893 * when filling in ti_seq. But if we are in persist 894 * state, snd_max might reflect one byte beyond the 895 * right edge of the window, so use snd_nxt in that 896 * case, since we know we aren't doing a retransmission. 897 * (retransmit and persist are mutually exclusive...) 898 */ 899 if (sack_rxmit == 0) { 900 if (len || (flags & (TH_SYN|TH_FIN)) || 901 tcp_timer_active(tp, TT_PERSIST)) 902 th->th_seq = htonl(tp->snd_nxt); 903 else 904 th->th_seq = htonl(tp->snd_max); 905 } else { 906 th->th_seq = htonl(p->rxmit); 907 p->rxmit += len; 908 tp->sackhint.sack_bytes_rexmit += len; 909 } 910 th->th_ack = htonl(tp->rcv_nxt); 911 if (optlen) { 912 bcopy(opt, th + 1, optlen); 913 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 914 } 915 th->th_flags = flags; 916 /* 917 * Calculate receive window. Don't shrink window, 918 * but avoid silly window syndrome. 919 */ 920 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 921 recwin < (long)tp->t_maxseg) 922 recwin = 0; 923 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 924 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 925 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 926 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 927 928 /* 929 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 930 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 931 * case is handled in syncache. 932 */ 933 if (flags & TH_SYN) 934 th->th_win = htons((u_short) 935 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 936 else 937 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 938 939 /* 940 * Adjust the RXWIN0SENT flag - indicate that we have advertised 941 * a 0 window. This may cause the remote transmitter to stall. This 942 * flag tells soreceive() to disable delayed acknowledgements when 943 * draining the buffer. This can occur if the receiver is attempting 944 * to read more data then can be buffered prior to transmitting on 945 * the connection. 946 */ 947 if (recwin == 0) 948 tp->t_flags |= TF_RXWIN0SENT; 949 else 950 tp->t_flags &= ~TF_RXWIN0SENT; 951 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 952 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 953 th->th_flags |= TH_URG; 954 } else 955 /* 956 * If no urgent pointer to send, then we pull 957 * the urgent pointer to the left edge of the send window 958 * so that it doesn't drift into the send window on sequence 959 * number wraparound. 960 */ 961 tp->snd_up = tp->snd_una; /* drag it along */ 962 963 #ifdef TCP_SIGNATURE 964 #ifdef INET6 965 if (!isipv6) 966 #endif 967 if (tp->t_flags & TF_SIGNATURE) 968 tcp_signature_compute(m, sizeof(struct ip), len, optlen, 969 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 970 #endif 971 972 /* 973 * Put TCP length in extended header, and then 974 * checksum extended header and data. 975 */ 976 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 977 #ifdef INET6 978 if (isipv6) 979 /* 980 * ip6_plen is not need to be filled now, and will be filled 981 * in ip6_output. 982 */ 983 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 984 sizeof(struct tcphdr) + optlen + len); 985 else 986 #endif /* INET6 */ 987 { 988 m->m_pkthdr.csum_flags = CSUM_TCP; 989 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 990 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 991 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 992 993 /* IP version must be set here for ipv4/ipv6 checking later */ 994 KASSERT(ip->ip_v == IPVERSION, 995 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 996 } 997 998 /* 999 * Enable TSO and specify the size of the segments. 1000 * The TCP pseudo header checksum is always provided. 1001 * XXX: Fixme: This is currently not the case for IPv6. 1002 */ 1003 if (tso) { 1004 m->m_pkthdr.csum_flags = CSUM_TSO; 1005 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1006 } 1007 1008 /* 1009 * In transmit state, time the transmission and arrange for 1010 * the retransmit. In persist state, just set snd_max. 1011 */ 1012 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1013 !tcp_timer_active(tp, TT_PERSIST)) { 1014 tcp_seq startseq = tp->snd_nxt; 1015 1016 /* 1017 * Advance snd_nxt over sequence space of this segment. 1018 */ 1019 if (flags & (TH_SYN|TH_FIN)) { 1020 if (flags & TH_SYN) 1021 tp->snd_nxt++; 1022 if (flags & TH_FIN) { 1023 tp->snd_nxt++; 1024 tp->t_flags |= TF_SENTFIN; 1025 } 1026 } 1027 if (sack_rxmit) 1028 goto timer; 1029 tp->snd_nxt += len; 1030 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1031 tp->snd_max = tp->snd_nxt; 1032 /* 1033 * Time this transmission if not a retransmission and 1034 * not currently timing anything. 1035 */ 1036 if (tp->t_rtttime == 0) { 1037 tp->t_rtttime = ticks; 1038 tp->t_rtseq = startseq; 1039 tcpstat.tcps_segstimed++; 1040 } 1041 } 1042 1043 /* 1044 * Set retransmit timer if not currently set, 1045 * and not doing a pure ack or a keep-alive probe. 1046 * Initial value for retransmit timer is smoothed 1047 * round-trip time + 2 * round-trip time variance. 1048 * Initialize shift counter which is used for backoff 1049 * of retransmit time. 1050 */ 1051 timer: 1052 if (!tcp_timer_active(tp, TT_REXMT) && 1053 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1054 (tp->snd_nxt != tp->snd_una))) { 1055 if (tcp_timer_active(tp, TT_PERSIST)) { 1056 tcp_timer_activate(tp, TT_PERSIST, 0); 1057 tp->t_rxtshift = 0; 1058 } 1059 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1060 } 1061 } else { 1062 /* 1063 * Persist case, update snd_max but since we are in 1064 * persist mode (no window) we do not update snd_nxt. 1065 */ 1066 int xlen = len; 1067 if (flags & TH_SYN) 1068 ++xlen; 1069 if (flags & TH_FIN) { 1070 ++xlen; 1071 tp->t_flags |= TF_SENTFIN; 1072 } 1073 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1074 tp->snd_max = tp->snd_nxt + len; 1075 } 1076 1077 #ifdef TCPDEBUG 1078 /* 1079 * Trace. 1080 */ 1081 if (so->so_options & SO_DEBUG) { 1082 u_short save = 0; 1083 #ifdef INET6 1084 if (!isipv6) 1085 #endif 1086 { 1087 save = ipov->ih_len; 1088 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1089 } 1090 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1091 #ifdef INET6 1092 if (!isipv6) 1093 #endif 1094 ipov->ih_len = save; 1095 } 1096 #endif 1097 1098 /* 1099 * Fill in IP length and desired time to live and 1100 * send to IP level. There should be a better way 1101 * to handle ttl and tos; we could keep them in 1102 * the template, but need a way to checksum without them. 1103 */ 1104 /* 1105 * m->m_pkthdr.len should have been set before cksum calcuration, 1106 * because in6_cksum() need it. 1107 */ 1108 #ifdef INET6 1109 if (isipv6) { 1110 /* 1111 * we separately set hoplimit for every segment, since the 1112 * user might want to change the value via setsockopt. 1113 * Also, desired default hop limit might be changed via 1114 * Neighbor Discovery. 1115 */ 1116 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1117 1118 /* TODO: IPv6 IP6TOS_ECT bit on */ 1119 error = ip6_output(m, 1120 tp->t_inpcb->in6p_outputopts, NULL, 1121 ((so->so_options & SO_DONTROUTE) ? 1122 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1123 } else 1124 #endif /* INET6 */ 1125 { 1126 ip->ip_len = m->m_pkthdr.len; 1127 #ifdef INET6 1128 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1129 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1130 #endif /* INET6 */ 1131 /* 1132 * If we do path MTU discovery, then we set DF on every packet. 1133 * This might not be the best thing to do according to RFC3390 1134 * Section 2. However the tcp hostcache migitates the problem 1135 * so it affects only the first tcp connection with a host. 1136 */ 1137 if (path_mtu_discovery) 1138 ip->ip_off |= IP_DF; 1139 1140 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1141 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1142 tp->t_inpcb); 1143 } 1144 if (error) { 1145 1146 /* 1147 * We know that the packet was lost, so back out the 1148 * sequence number advance, if any. 1149 * 1150 * If the error is EPERM the packet got blocked by the 1151 * local firewall. Normally we should terminate the 1152 * connection but the blocking may have been spurious 1153 * due to a firewall reconfiguration cycle. So we treat 1154 * it like a packet loss and let the retransmit timer and 1155 * timeouts do their work over time. 1156 * XXX: It is a POLA question whether calling tcp_drop right 1157 * away would be the really correct behavior instead. 1158 */ 1159 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1160 !tcp_timer_active(tp, TT_PERSIST)) && 1161 ((flags & TH_SYN) == 0) && 1162 (error != EPERM)) { 1163 if (sack_rxmit) { 1164 p->rxmit -= len; 1165 tp->sackhint.sack_bytes_rexmit -= len; 1166 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1167 ("sackhint bytes rtx >= 0")); 1168 } else 1169 tp->snd_nxt -= len; 1170 } 1171 out: 1172 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1173 switch (error) { 1174 case EPERM: 1175 tp->t_softerror = error; 1176 return (error); 1177 case ENOBUFS: 1178 if (!tcp_timer_active(tp, TT_REXMT) && 1179 !tcp_timer_active(tp, TT_PERSIST)) 1180 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1181 tp->snd_cwnd = tp->t_maxseg; 1182 return (0); 1183 case EMSGSIZE: 1184 /* 1185 * For some reason the interface we used initially 1186 * to send segments changed to another or lowered 1187 * its MTU. 1188 * 1189 * tcp_mtudisc() will find out the new MTU and as 1190 * its last action, initiate retransmission, so it 1191 * is important to not do so here. 1192 * 1193 * If TSO was active we either got an interface 1194 * without TSO capabilits or TSO was turned off. 1195 * Disable it for this connection as too and 1196 * immediatly retry with MSS sized segments generated 1197 * by this function. 1198 */ 1199 if (tso) 1200 tp->t_flags &= ~TF_TSO; 1201 tcp_mtudisc(tp->t_inpcb, 0); 1202 return (0); 1203 case EHOSTDOWN: 1204 case EHOSTUNREACH: 1205 case ENETDOWN: 1206 case ENETUNREACH: 1207 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1208 tp->t_softerror = error; 1209 return (0); 1210 } 1211 /* FALLTHROUGH */ 1212 default: 1213 return (error); 1214 } 1215 } 1216 tcpstat.tcps_sndtotal++; 1217 1218 /* 1219 * Data sent (as far as we can tell). 1220 * If this advertises a larger window than any other segment, 1221 * then remember the size of the advertised window. 1222 * Any pending ACK has now been sent. 1223 */ 1224 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1225 tp->rcv_adv = tp->rcv_nxt + recwin; 1226 tp->last_ack_sent = tp->rcv_nxt; 1227 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1228 if (tcp_timer_active(tp, TT_DELACK)) 1229 tcp_timer_activate(tp, TT_DELACK, 0); 1230 #if 0 1231 /* 1232 * This completely breaks TCP if newreno is turned on. What happens 1233 * is that if delayed-acks are turned on on the receiver, this code 1234 * on the transmitter effectively destroys the TCP window, forcing 1235 * it to four packets (1.5Kx4 = 6K window). 1236 */ 1237 if (sendalot && (!tcp_do_newreno || --maxburst)) 1238 goto again; 1239 #endif 1240 if (sendalot) 1241 goto again; 1242 return (0); 1243 } 1244 1245 void 1246 tcp_setpersist(struct tcpcb *tp) 1247 { 1248 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1249 int tt; 1250 1251 if (tcp_timer_active(tp, TT_REXMT)) 1252 panic("tcp_setpersist: retransmit pending"); 1253 /* 1254 * Start/restart persistance timer. 1255 */ 1256 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1257 TCPTV_PERSMIN, TCPTV_PERSMAX); 1258 tcp_timer_activate(tp, TT_PERSIST, tt); 1259 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1260 tp->t_rxtshift++; 1261 } 1262 1263 /* 1264 * Insert TCP options according to the supplied parameters to the place 1265 * optp in a consistent way. Can handle unaligned destinations. 1266 * 1267 * The order of the option processing is crucial for optimal packing and 1268 * alignment for the scarce option space. 1269 * 1270 * The optimal order for a SYN/SYN-ACK segment is: 1271 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1272 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1273 * 1274 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1275 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1276 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1277 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1278 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1279 */ 1280 int 1281 tcp_addoptions(struct tcpopt *to, u_char *optp) 1282 { 1283 u_int mask, optlen = 0; 1284 1285 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1286 if ((to->to_flags & mask) != mask) 1287 continue; 1288 switch (to->to_flags & mask) { 1289 case TOF_MSS: 1290 while (optlen % 4) { 1291 optlen += TCPOLEN_NOP; 1292 *optp++ = TCPOPT_NOP; 1293 } 1294 optlen += TCPOLEN_MAXSEG; 1295 *optp++ = TCPOPT_MAXSEG; 1296 *optp++ = TCPOLEN_MAXSEG; 1297 to->to_mss = htons(to->to_mss); 1298 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1299 optp += sizeof(to->to_mss); 1300 break; 1301 case TOF_SCALE: 1302 while (!optlen || optlen % 2 != 1) { 1303 optlen += TCPOLEN_NOP; 1304 *optp++ = TCPOPT_NOP; 1305 } 1306 optlen += TCPOLEN_WINDOW; 1307 *optp++ = TCPOPT_WINDOW; 1308 *optp++ = TCPOLEN_WINDOW; 1309 *optp++ = to->to_wscale; 1310 break; 1311 case TOF_SACKPERM: 1312 while (optlen % 2) { 1313 optlen += TCPOLEN_NOP; 1314 *optp++ = TCPOPT_NOP; 1315 } 1316 optlen += TCPOLEN_SACK_PERMITTED; 1317 *optp++ = TCPOPT_SACK_PERMITTED; 1318 *optp++ = TCPOLEN_SACK_PERMITTED; 1319 break; 1320 case TOF_TS: 1321 while (!optlen || optlen % 4 != 2) { 1322 optlen += TCPOLEN_NOP; 1323 *optp++ = TCPOPT_NOP; 1324 } 1325 optlen += TCPOLEN_TIMESTAMP; 1326 *optp++ = TCPOPT_TIMESTAMP; 1327 *optp++ = TCPOLEN_TIMESTAMP; 1328 to->to_tsval = htonl(to->to_tsval); 1329 to->to_tsecr = htonl(to->to_tsecr); 1330 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1331 optp += sizeof(to->to_tsval); 1332 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1333 optp += sizeof(to->to_tsecr); 1334 break; 1335 case TOF_SIGNATURE: 1336 { 1337 int siglen = TCPOLEN_SIGNATURE - 2; 1338 1339 while (!optlen || optlen % 4 != 2) { 1340 optlen += TCPOLEN_NOP; 1341 *optp++ = TCPOPT_NOP; 1342 } 1343 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1344 continue; 1345 optlen += TCPOLEN_SIGNATURE; 1346 *optp++ = TCPOPT_SIGNATURE; 1347 *optp++ = TCPOLEN_SIGNATURE; 1348 to->to_signature = optp; 1349 while (siglen--) 1350 *optp++ = 0; 1351 break; 1352 } 1353 case TOF_SACK: 1354 { 1355 int sackblks = 0; 1356 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1357 tcp_seq sack_seq; 1358 1359 while (!optlen || optlen % 4 != 2) { 1360 optlen += TCPOLEN_NOP; 1361 *optp++ = TCPOPT_NOP; 1362 } 1363 if (TCP_MAXOLEN - optlen < 2 + TCPOLEN_SACK) 1364 continue; 1365 optlen += TCPOLEN_SACKHDR; 1366 *optp++ = TCPOPT_SACK; 1367 sackblks = min(to->to_nsacks, 1368 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1369 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1370 while (sackblks--) { 1371 sack_seq = htonl(sack->start); 1372 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1373 optp += sizeof(sack_seq); 1374 sack_seq = htonl(sack->end); 1375 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1376 optp += sizeof(sack_seq); 1377 optlen += TCPOLEN_SACK; 1378 sack++; 1379 } 1380 tcpstat.tcps_sack_send_blocks++; 1381 break; 1382 } 1383 default: 1384 panic("%s: unknown TCP option type", __func__); 1385 break; 1386 } 1387 } 1388 1389 /* Terminate and pad TCP options to a 4 byte boundary. */ 1390 if (optlen % 4) { 1391 optlen += TCPOLEN_EOL; 1392 *optp++ = TCPOPT_EOL; 1393 } 1394 while (optlen % 4) { 1395 optlen += TCPOLEN_NOP; 1396 *optp++ = TCPOPT_NOP; 1397 } 1398 1399 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1400 return (optlen); 1401 } 1402