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sys/netinet/tcp_output.c
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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 struct mbuf *m; 132 struct ip *ip = NULL; 133 struct ipovly *ipov = NULL; 134 struct tcphdr *th; 135 u_char opt[TCP_MAXOLEN]; 136 unsigned ipoptlen, optlen, hdrlen; 137 #ifdef IPSEC 138 unsigned ipsec_optlen = 0; 139 #endif 140 int idle, sendalot; 141 int sack_rxmit, sack_bytes_rxmt; 142 struct sackhole *p; 143 int tso = 0; 144 struct tcpopt to; 145 #if 0 146 int maxburst = TCP_MAXBURST; 147 #endif 148 #ifdef INET6 149 struct ip6_hdr *ip6 = NULL; 150 int isipv6; 151 152 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 153 #endif 154 155 INP_LOCK_ASSERT(tp->t_inpcb); 156 157 /* 158 * Determine length of data that should be transmitted, 159 * and flags that will be used. 160 * If there is some data or critical controls (SYN, RST) 161 * to send, then transmit; otherwise, investigate further. 162 */ 163 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 164 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 165 /* 166 * We have been idle for "a while" and no acks are 167 * expected to clock out any data we send -- 168 * slow start to get ack "clock" running again. 169 * 170 * Set the slow-start flight size depending on whether 171 * this is a local network or not. 172 */ 173 int ss = ss_fltsz; 174 #ifdef INET6 175 if (isipv6) { 176 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 177 ss = ss_fltsz_local; 178 } else 179 #endif /* INET6 */ 180 if (in_localaddr(tp->t_inpcb->inp_faddr)) 181 ss = ss_fltsz_local; 182 tp->snd_cwnd = tp->t_maxseg * ss; 183 } 184 tp->t_flags &= ~TF_LASTIDLE; 185 if (idle) { 186 if (tp->t_flags & TF_MORETOCOME) { 187 tp->t_flags |= TF_LASTIDLE; 188 idle = 0; 189 } 190 } 191 again: 192 /* 193 * If we've recently taken a timeout, snd_max will be greater than 194 * snd_nxt. There may be SACK information that allows us to avoid 195 * resending already delivered data. Adjust snd_nxt accordingly. 196 */ 197 if ((tp->t_flags & TF_SACK_PERMIT) && 198 SEQ_LT(tp->snd_nxt, tp->snd_max)) 199 tcp_sack_adjust(tp); 200 sendalot = 0; 201 off = tp->snd_nxt - tp->snd_una; 202 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 203 sendwin = min(sendwin, tp->snd_bwnd); 204 205 flags = tcp_outflags[tp->t_state]; 206 /* 207 * Send any SACK-generated retransmissions. If we're explicitly trying 208 * to send out new data (when sendalot is 1), bypass this function. 209 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 210 * we're replacing a (future) new transmission with a retransmission 211 * now, and we previously incremented snd_cwnd in tcp_input(). 212 */ 213 /* 214 * Still in sack recovery , reset rxmit flag to zero. 215 */ 216 sack_rxmit = 0; 217 sack_bytes_rxmt = 0; 218 len = 0; 219 p = NULL; 220 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 221 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 222 long cwin; 223 224 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 225 if (cwin < 0) 226 cwin = 0; 227 /* Do not retransmit SACK segments beyond snd_recover */ 228 if (SEQ_GT(p->end, tp->snd_recover)) { 229 /* 230 * (At least) part of sack hole extends beyond 231 * snd_recover. Check to see if we can rexmit data 232 * for this hole. 233 */ 234 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 235 /* 236 * Can't rexmit any more data for this hole. 237 * That data will be rexmitted in the next 238 * sack recovery episode, when snd_recover 239 * moves past p->rxmit. 240 */ 241 p = NULL; 242 goto after_sack_rexmit; 243 } else 244 /* Can rexmit part of the current hole */ 245 len = ((long)ulmin(cwin, 246 tp->snd_recover - p->rxmit)); 247 } else 248 len = ((long)ulmin(cwin, p->end - p->rxmit)); 249 off = p->rxmit - tp->snd_una; 250 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 251 __func__, off)); 252 if (len > 0) { 253 sack_rxmit = 1; 254 sendalot = 1; 255 tcpstat.tcps_sack_rexmits++; 256 tcpstat.tcps_sack_rexmit_bytes += 257 min(len, tp->t_maxseg); 258 } 259 } 260 after_sack_rexmit: 261 /* 262 * Get standard flags, and add SYN or FIN if requested by 'hidden' 263 * state flags. 264 */ 265 if (tp->t_flags & TF_NEEDFIN) 266 flags |= TH_FIN; 267 if (tp->t_flags & TF_NEEDSYN) 268 flags |= TH_SYN; 269 270 SOCKBUF_LOCK(&so->so_snd); 271 /* 272 * If in persist timeout with window of 0, send 1 byte. 273 * Otherwise, if window is small but nonzero 274 * and timer expired, we will send what we can 275 * and go to transmit state. 276 */ 277 if (tp->t_flags & TF_FORCEDATA) { 278 if (sendwin == 0) { 279 /* 280 * If we still have some data to send, then 281 * clear the FIN bit. Usually this would 282 * happen below when it realizes that we 283 * aren't sending all the data. However, 284 * if we have exactly 1 byte of unsent data, 285 * then it won't clear the FIN bit below, 286 * and if we are in persist state, we wind 287 * up sending the packet without recording 288 * that we sent the FIN bit. 289 * 290 * We can't just blindly clear the FIN bit, 291 * because if we don't have any more data 292 * to send then the probe will be the FIN 293 * itself. 294 */ 295 if (off < so->so_snd.sb_cc) 296 flags &= ~TH_FIN; 297 sendwin = 1; 298 } else { 299 tcp_timer_activate(tp, TT_PERSIST, 0); 300 tp->t_rxtshift = 0; 301 } 302 } 303 304 /* 305 * If snd_nxt == snd_max and we have transmitted a FIN, the 306 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 307 * a negative length. This can also occur when TCP opens up 308 * its congestion window while receiving additional duplicate 309 * acks after fast-retransmit because TCP will reset snd_nxt 310 * to snd_max after the fast-retransmit. 311 * 312 * In the normal retransmit-FIN-only case, however, snd_nxt will 313 * be set to snd_una, the offset will be 0, and the length may 314 * wind up 0. 315 * 316 * If sack_rxmit is true we are retransmitting from the scoreboard 317 * in which case len is already set. 318 */ 319 if (sack_rxmit == 0) { 320 if (sack_bytes_rxmt == 0) 321 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 322 else { 323 long cwin; 324 325 /* 326 * We are inside of a SACK recovery episode and are 327 * sending new data, having retransmitted all the 328 * data possible in the scoreboard. 329 */ 330 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 331 - off); 332 /* 333 * Don't remove this (len > 0) check ! 334 * We explicitly check for len > 0 here (although it 335 * isn't really necessary), to work around a gcc 336 * optimization issue - to force gcc to compute 337 * len above. Without this check, the computation 338 * of len is bungled by the optimizer. 339 */ 340 if (len > 0) { 341 cwin = tp->snd_cwnd - 342 (tp->snd_nxt - tp->sack_newdata) - 343 sack_bytes_rxmt; 344 if (cwin < 0) 345 cwin = 0; 346 len = lmin(len, cwin); 347 } 348 } 349 } 350 351 /* 352 * Lop off SYN bit if it has already been sent. However, if this 353 * is SYN-SENT state and if segment contains data and if we don't 354 * know that foreign host supports TAO, suppress sending segment. 355 */ 356 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 357 if (tp->t_state != TCPS_SYN_RECEIVED) 358 flags &= ~TH_SYN; 359 off--, len++; 360 } 361 362 /* 363 * Be careful not to send data and/or FIN on SYN segments. 364 * This measure is needed to prevent interoperability problems 365 * with not fully conformant TCP implementations. 366 */ 367 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 368 len = 0; 369 flags &= ~TH_FIN; 370 } 371 372 if (len < 0) { 373 /* 374 * If FIN has been sent but not acked, 375 * but we haven't been called to retransmit, 376 * len will be < 0. Otherwise, window shrank 377 * after we sent into it. If window shrank to 0, 378 * cancel pending retransmit, pull snd_nxt back 379 * to (closed) window, and set the persist timer 380 * if it isn't already going. If the window didn't 381 * close completely, just wait for an ACK. 382 */ 383 len = 0; 384 if (sendwin == 0) { 385 tcp_timer_activate(tp, TT_REXMT, 0); 386 tp->t_rxtshift = 0; 387 tp->snd_nxt = tp->snd_una; 388 if (!tcp_timer_active(tp, TT_PERSIST)) 389 tcp_setpersist(tp); 390 } 391 } 392 393 /* len will be >= 0 after this point. */ 394 KASSERT(len >= 0, ("%s: len < 0", __func__)); 395 396 /* 397 * Automatic sizing of send socket buffer. Often the send buffer 398 * size is not optimally adjusted to the actual network conditions 399 * at hand (delay bandwidth product). Setting the buffer size too 400 * small limits throughput on links with high bandwidth and high 401 * delay (eg. trans-continental/oceanic links). Setting the 402 * buffer size too big consumes too much real kernel memory, 403 * especially with many connections on busy servers. 404 * 405 * The criteria to step up the send buffer one notch are: 406 * 1. receive window of remote host is larger than send buffer 407 * (with a fudge factor of 5/4th); 408 * 2. send buffer is filled to 7/8th with data (so we actually 409 * have data to make use of it); 410 * 3. send buffer fill has not hit maximal automatic size; 411 * 4. our send window (slow start and cogestion controlled) is 412 * larger than sent but unacknowledged data in send buffer. 413 * 414 * The remote host receive window scaling factor may limit the 415 * growing of the send buffer before it reaches its allowed 416 * maximum. 417 * 418 * It scales directly with slow start or congestion window 419 * and does at most one step per received ACK. This fast 420 * scaling has the drawback of growing the send buffer beyond 421 * what is strictly necessary to make full use of a given 422 * delay*bandwith product. However testing has shown this not 423 * to be much of an problem. At worst we are trading wasting 424 * of available bandwith (the non-use of it) for wasting some 425 * socket buffer memory. 426 * 427 * TODO: Shrink send buffer during idle periods together 428 * with congestion window. Requires another timer. Has to 429 * wait for upcoming tcp timer rewrite. 430 */ 431 if (tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 432 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 433 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 434 so->so_snd.sb_cc < tcp_autosndbuf_max && 435 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 436 if (!sbreserve_locked(&so->so_snd, 437 min(so->so_snd.sb_hiwat + tcp_autosndbuf_inc, 438 tcp_autosndbuf_max), so, curthread)) 439 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 440 } 441 } 442 443 /* 444 * Truncate to the maximum segment length or enable TCP Segmentation 445 * Offloading (if supported by hardware) and ensure that FIN is removed 446 * if the length no longer contains the last data byte. 447 * 448 * TSO may only be used if we are in a pure bulk sending state. The 449 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 450 * IP options prevent using TSO. With TSO the TCP header is the same 451 * (except for the sequence number) for all generated packets. This 452 * makes it impossible to transmit any options which vary per generated 453 * segment or packet. 454 * 455 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 456 * removal of FIN (if not already catched here) are handled later after 457 * the exact length of the TCP options are known. 458 */ 459 #ifdef IPSEC 460 /* 461 * Pre-calculate here as we save another lookup into the darknesses 462 * of IPsec that way and can actually decide if TSO is ok. 463 */ 464 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 465 #endif 466 if (len > tp->t_maxseg) { 467 if ((tp->t_flags & TF_TSO) && tcp_do_tso && 468 ((tp->t_flags & TF_SIGNATURE) == 0) && 469 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 470 tp->t_inpcb->inp_options == NULL && 471 tp->t_inpcb->in6p_options == NULL 472 #ifdef IPSEC 473 && ipsec_optlen == 0 474 #endif 475 ) { 476 tso = 1; 477 } else { 478 len = tp->t_maxseg; 479 sendalot = 1; 480 tso = 0; 481 } 482 } 483 if (sack_rxmit) { 484 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 485 flags &= ~TH_FIN; 486 } else { 487 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 488 flags &= ~TH_FIN; 489 } 490 491 recwin = sbspace(&so->so_rcv); 492 493 /* 494 * Sender silly window avoidance. We transmit under the following 495 * conditions when len is non-zero: 496 * 497 * - We have a full segment (or more with TSO) 498 * - This is the last buffer in a write()/send() and we are 499 * either idle or running NODELAY 500 * - we've timed out (e.g. persist timer) 501 * - we have more then 1/2 the maximum send window's worth of 502 * data (receiver may be limited the window size) 503 * - we need to retransmit 504 */ 505 if (len) { 506 if (len >= tp->t_maxseg) 507 goto send; 508 /* 509 * NOTE! on localhost connections an 'ack' from the remote 510 * end may occur synchronously with the output and cause 511 * us to flush a buffer queued with moretocome. XXX 512 * 513 * note: the len + off check is almost certainly unnecessary. 514 */ 515 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 516 (idle || (tp->t_flags & TF_NODELAY)) && 517 len + off >= so->so_snd.sb_cc && 518 (tp->t_flags & TF_NOPUSH) == 0) { 519 goto send; 520 } 521 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 522 goto send; 523 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 524 goto send; 525 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 526 goto send; 527 if (sack_rxmit) 528 goto send; 529 } 530 531 /* 532 * Compare available window to amount of window 533 * known to peer (as advertised window less 534 * next expected input). If the difference is at least two 535 * max size segments, or at least 50% of the maximum possible 536 * window, then want to send a window update to peer. 537 * Skip this if the connection is in T/TCP half-open state. 538 * Don't send pure window updates when the peer has closed 539 * the connection and won't ever send more data. 540 */ 541 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 542 !TCPS_HAVERCVDFIN(tp->t_state)) { 543 /* 544 * "adv" is the amount we can increase the window, 545 * taking into account that we are limited by 546 * TCP_MAXWIN << tp->rcv_scale. 547 */ 548 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 549 (tp->rcv_adv - tp->rcv_nxt); 550 551 if (adv >= (long) (2 * tp->t_maxseg)) 552 goto send; 553 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 554 goto send; 555 } 556 557 /* 558 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 559 * is also a catch-all for the retransmit timer timeout case. 560 */ 561 if (tp->t_flags & TF_ACKNOW) 562 goto send; 563 if ((flags & TH_RST) || 564 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 565 goto send; 566 if (SEQ_GT(tp->snd_up, tp->snd_una)) 567 goto send; 568 /* 569 * If our state indicates that FIN should be sent 570 * and we have not yet done so, then we need to send. 571 */ 572 if (flags & TH_FIN && 573 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 574 goto send; 575 /* 576 * In SACK, it is possible for tcp_output to fail to send a segment 577 * after the retransmission timer has been turned off. Make sure 578 * that the retransmission timer is set. 579 */ 580 if ((tp->t_flags & TF_SACK_PERMIT) && 581 SEQ_GT(tp->snd_max, tp->snd_una) && 582 !tcp_timer_active(tp, TT_REXMT) && 583 !tcp_timer_active(tp, TT_PERSIST)) { 584 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 585 goto just_return; 586 } 587 /* 588 * TCP window updates are not reliable, rather a polling protocol 589 * using ``persist'' packets is used to insure receipt of window 590 * updates. The three ``states'' for the output side are: 591 * idle not doing retransmits or persists 592 * persisting to move a small or zero window 593 * (re)transmitting and thereby not persisting 594 * 595 * tcp_timer_active(tp, TT_PERSIST) 596 * is true when we are in persist state. 597 * (tp->t_flags & TF_FORCEDATA) 598 * is set when we are called to send a persist packet. 599 * tcp_timer_active(tp, TT_REXMT) 600 * is set when we are retransmitting 601 * The output side is idle when both timers are zero. 602 * 603 * If send window is too small, there is data to transmit, and no 604 * retransmit or persist is pending, then go to persist state. 605 * If nothing happens soon, send when timer expires: 606 * if window is nonzero, transmit what we can, 607 * otherwise force out a byte. 608 */ 609 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 610 !tcp_timer_active(tp, TT_PERSIST)) { 611 tp->t_rxtshift = 0; 612 tcp_setpersist(tp); 613 } 614 615 /* 616 * No reason to send a segment, just return. 617 */ 618 just_return: 619 SOCKBUF_UNLOCK(&so->so_snd); 620 return (0); 621 622 send: 623 SOCKBUF_LOCK_ASSERT(&so->so_snd); 624 /* 625 * Before ESTABLISHED, force sending of initial options 626 * unless TCP set not to do any options. 627 * NOTE: we assume that the IP/TCP header plus TCP options 628 * always fit in a single mbuf, leaving room for a maximum 629 * link header, i.e. 630 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 631 */ 632 optlen = 0; 633 #ifdef INET6 634 if (isipv6) 635 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 636 else 637 #endif 638 hdrlen = sizeof (struct tcpiphdr); 639 640 /* 641 * Compute options for segment. 642 * We only have to care about SYN and established connection 643 * segments. Options for SYN-ACK segments are handled in TCP 644 * syncache. 645 */ 646 if ((tp->t_flags & TF_NOOPT) == 0) { 647 to.to_flags = 0; 648 /* Maximum segment size. */ 649 if (flags & TH_SYN) { 650 tp->snd_nxt = tp->iss; 651 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 652 to.to_flags |= TOF_MSS; 653 } 654 /* Window scaling. */ 655 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 656 to.to_wscale = tp->request_r_scale; 657 to.to_flags |= TOF_SCALE; 658 } 659 /* Timestamps. */ 660 if ((tp->t_flags & TF_RCVD_TSTMP) || 661 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 662 to.to_tsval = ticks + tp->ts_offset; 663 to.to_tsecr = tp->ts_recent; 664 to.to_flags |= TOF_TS; 665 /* Set receive buffer autosizing timestamp. */ 666 if (tp->rfbuf_ts == 0 && 667 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 668 tp->rfbuf_ts = ticks; 669 } 670 /* Selective ACK's. */ 671 if (tp->t_flags & TF_SACK_PERMIT) { 672 if (flags & TH_SYN) 673 to.to_flags |= TOF_SACKPERM; 674 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 675 (tp->t_flags & TF_SACK_PERMIT) && 676 tp->rcv_numsacks > 0) { 677 to.to_flags |= TOF_SACK; 678 to.to_nsacks = tp->rcv_numsacks; 679 to.to_sacks = (u_char *)tp->sackblks; 680 } 681 } 682 #ifdef TCP_SIGNATURE 683 /* TCP-MD5 (RFC2385). */ 684 #ifdef INET6 685 if (!isipv6 && (tp->t_flags & TF_SIGNATURE)) 686 #else 687 if (tp->t_flags & TF_SIGNATURE) 688 #endif /* INET6 */ 689 to.to_flags |= TOF_SIGNATURE; 690 #endif /* TCP_SIGNATURE */ 691 692 /* Processing the options. */ 693 hdrlen += optlen = tcp_addoptions(&to, opt); 694 } 695 696 #ifdef INET6 697 if (isipv6) 698 ipoptlen = ip6_optlen(tp->t_inpcb); 699 else 700 #endif 701 if (tp->t_inpcb->inp_options) 702 ipoptlen = tp->t_inpcb->inp_options->m_len - 703 offsetof(struct ipoption, ipopt_list); 704 else 705 ipoptlen = 0; 706 #ifdef IPSEC 707 ipoptlen += ipsec_optlen; 708 #endif 709 710 /* 711 * Adjust data length if insertion of options will 712 * bump the packet length beyond the t_maxopd length. 713 * Clear the FIN bit because we cut off the tail of 714 * the segment. 715 * 716 * When doing TSO limit a burst to TCP_MAXWIN minus the 717 * IP, TCP and Options length to keep ip->ip_len from 718 * overflowing. Prevent the last segment from being 719 * fractional thus making them all equal sized and set 720 * the flag to continue sending. TSO is disabled when 721 * IP options or IPSEC are present. 722 */ 723 if (len + optlen + ipoptlen > tp->t_maxopd) { 724 flags &= ~TH_FIN; 725 if (tso) { 726 if (len > TCP_MAXWIN - hdrlen - optlen) { 727 len = TCP_MAXWIN - hdrlen - optlen; 728 len = len - (len % (tp->t_maxopd - optlen)); 729 sendalot = 1; 730 } else if (tp->t_flags & TF_NEEDFIN) 731 sendalot = 1; 732 } else { 733 len = tp->t_maxopd - optlen - ipoptlen; 734 sendalot = 1; 735 } 736 } 737 738 /*#ifdef DIAGNOSTIC*/ 739 #ifdef INET6 740 if (max_linkhdr + hdrlen > MCLBYTES) 741 #else 742 if (max_linkhdr + hdrlen > MHLEN) 743 #endif 744 panic("tcphdr too big"); 745 /*#endif*/ 746 747 /* 748 * Grab a header mbuf, attaching a copy of data to 749 * be transmitted, and initialize the header from 750 * the template for sends on this connection. 751 */ 752 if (len) { 753 struct mbuf *mb; 754 u_int moff; 755 756 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 757 tcpstat.tcps_sndprobe++; 758 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 759 tcpstat.tcps_sndrexmitpack++; 760 tcpstat.tcps_sndrexmitbyte += len; 761 } else { 762 tcpstat.tcps_sndpack++; 763 tcpstat.tcps_sndbyte += len; 764 } 765 #ifdef notyet 766 if ((m = m_copypack(so->so_snd.sb_mb, off, 767 (int)len, max_linkhdr + hdrlen)) == 0) { 768 SOCKBUF_UNLOCK(&so->so_snd); 769 error = ENOBUFS; 770 goto out; 771 } 772 /* 773 * m_copypack left space for our hdr; use it. 774 */ 775 m->m_len += hdrlen; 776 m->m_data -= hdrlen; 777 #else 778 MGETHDR(m, M_DONTWAIT, MT_DATA); 779 if (m == NULL) { 780 SOCKBUF_UNLOCK(&so->so_snd); 781 error = ENOBUFS; 782 goto out; 783 } 784 #ifdef INET6 785 if (MHLEN < hdrlen + max_linkhdr) { 786 MCLGET(m, M_DONTWAIT); 787 if ((m->m_flags & M_EXT) == 0) { 788 SOCKBUF_UNLOCK(&so->so_snd); 789 m_freem(m); 790 error = ENOBUFS; 791 goto out; 792 } 793 } 794 #endif 795 m->m_data += max_linkhdr; 796 m->m_len = hdrlen; 797 798 /* 799 * Start the m_copy functions from the closest mbuf 800 * to the offset in the socket buffer chain. 801 */ 802 mb = sbsndptr(&so->so_snd, off, len, &moff); 803 804 if (len <= MHLEN - hdrlen - max_linkhdr) { 805 m_copydata(mb, moff, (int)len, 806 mtod(m, caddr_t) + hdrlen); 807 m->m_len += len; 808 } else { 809 m->m_next = m_copy(mb, moff, (int)len); 810 if (m->m_next == NULL) { 811 SOCKBUF_UNLOCK(&so->so_snd); 812 (void) m_free(m); 813 error = ENOBUFS; 814 goto out; 815 } 816 } 817 #endif 818 /* 819 * If we're sending everything we've got, set PUSH. 820 * (This will keep happy those implementations which only 821 * give data to the user when a buffer fills or 822 * a PUSH comes in.) 823 */ 824 if (off + len == so->so_snd.sb_cc) 825 flags |= TH_PUSH; 826 SOCKBUF_UNLOCK(&so->so_snd); 827 } else { 828 SOCKBUF_UNLOCK(&so->so_snd); 829 if (tp->t_flags & TF_ACKNOW) 830 tcpstat.tcps_sndacks++; 831 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 832 tcpstat.tcps_sndctrl++; 833 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 834 tcpstat.tcps_sndurg++; 835 else 836 tcpstat.tcps_sndwinup++; 837 838 MGETHDR(m, M_DONTWAIT, MT_DATA); 839 if (m == NULL) { 840 error = ENOBUFS; 841 goto out; 842 } 843 #ifdef INET6 844 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 845 MHLEN >= hdrlen) { 846 MH_ALIGN(m, hdrlen); 847 } else 848 #endif 849 m->m_data += max_linkhdr; 850 m->m_len = hdrlen; 851 } 852 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 853 m->m_pkthdr.rcvif = (struct ifnet *)0; 854 #ifdef MAC 855 mac_create_mbuf_from_inpcb(tp->t_inpcb, m); 856 #endif 857 #ifdef INET6 858 if (isipv6) { 859 ip6 = mtod(m, struct ip6_hdr *); 860 th = (struct tcphdr *)(ip6 + 1); 861 tcpip_fillheaders(tp->t_inpcb, ip6, th); 862 } else 863 #endif /* INET6 */ 864 { 865 ip = mtod(m, struct ip *); 866 ipov = (struct ipovly *)ip; 867 th = (struct tcphdr *)(ip + 1); 868 tcpip_fillheaders(tp->t_inpcb, ip, th); 869 } 870 871 /* 872 * Fill in fields, remembering maximum advertised 873 * window for use in delaying messages about window sizes. 874 * If resending a FIN, be sure not to use a new sequence number. 875 */ 876 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 877 tp->snd_nxt == tp->snd_max) 878 tp->snd_nxt--; 879 /* 880 * If we are doing retransmissions, then snd_nxt will 881 * not reflect the first unsent octet. For ACK only 882 * packets, we do not want the sequence number of the 883 * retransmitted packet, we want the sequence number 884 * of the next unsent octet. So, if there is no data 885 * (and no SYN or FIN), use snd_max instead of snd_nxt 886 * when filling in ti_seq. But if we are in persist 887 * state, snd_max might reflect one byte beyond the 888 * right edge of the window, so use snd_nxt in that 889 * case, since we know we aren't doing a retransmission. 890 * (retransmit and persist are mutually exclusive...) 891 */ 892 if (sack_rxmit == 0) { 893 if (len || (flags & (TH_SYN|TH_FIN)) || 894 tcp_timer_active(tp, TT_PERSIST)) 895 th->th_seq = htonl(tp->snd_nxt); 896 else 897 th->th_seq = htonl(tp->snd_max); 898 } else { 899 th->th_seq = htonl(p->rxmit); 900 p->rxmit += len; 901 tp->sackhint.sack_bytes_rexmit += len; 902 } 903 th->th_ack = htonl(tp->rcv_nxt); 904 if (optlen) { 905 bcopy(opt, th + 1, optlen); 906 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 907 } 908 th->th_flags = flags; 909 /* 910 * Calculate receive window. Don't shrink window, 911 * but avoid silly window syndrome. 912 */ 913 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 914 recwin < (long)tp->t_maxseg) 915 recwin = 0; 916 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 917 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 918 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 919 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 920 921 /* 922 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 923 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 924 * case is handled in syncache. 925 */ 926 if (flags & TH_SYN) 927 th->th_win = htons((u_short) 928 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 929 else 930 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 931 932 /* 933 * Adjust the RXWIN0SENT flag - indicate that we have advertised 934 * a 0 window. This may cause the remote transmitter to stall. This 935 * flag tells soreceive() to disable delayed acknowledgements when 936 * draining the buffer. This can occur if the receiver is attempting 937 * to read more data then can be buffered prior to transmitting on 938 * the connection. 939 */ 940 if (recwin == 0) 941 tp->t_flags |= TF_RXWIN0SENT; 942 else 943 tp->t_flags &= ~TF_RXWIN0SENT; 944 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 945 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 946 th->th_flags |= TH_URG; 947 } else 948 /* 949 * If no urgent pointer to send, then we pull 950 * the urgent pointer to the left edge of the send window 951 * so that it doesn't drift into the send window on sequence 952 * number wraparound. 953 */ 954 tp->snd_up = tp->snd_una; /* drag it along */ 955 956 #ifdef TCP_SIGNATURE 957 #ifdef INET6 958 if (!isipv6) 959 #endif 960 if (tp->t_flags & TF_SIGNATURE) { 961 int sigoff = to.to_signature - opt; 962 tcp_signature_compute(m, sizeof(struct ip), len, optlen, 963 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 964 } 965 #endif 966 967 /* 968 * Put TCP length in extended header, and then 969 * checksum extended header and data. 970 */ 971 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 972 #ifdef INET6 973 if (isipv6) 974 /* 975 * ip6_plen is not need to be filled now, and will be filled 976 * in ip6_output. 977 */ 978 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 979 sizeof(struct tcphdr) + optlen + len); 980 else 981 #endif /* INET6 */ 982 { 983 m->m_pkthdr.csum_flags = CSUM_TCP; 984 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 985 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 986 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 987 988 /* IP version must be set here for ipv4/ipv6 checking later */ 989 KASSERT(ip->ip_v == IPVERSION, 990 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 991 } 992 993 /* 994 * Enable TSO and specify the size of the segments. 995 * The TCP pseudo header checksum is always provided. 996 * XXX: Fixme: This is currently not the case for IPv6. 997 */ 998 if (tso) { 999 m->m_pkthdr.csum_flags = CSUM_TSO; 1000 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1001 } 1002 1003 /* 1004 * In transmit state, time the transmission and arrange for 1005 * the retransmit. In persist state, just set snd_max. 1006 */ 1007 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1008 !tcp_timer_active(tp, TT_PERSIST)) { 1009 tcp_seq startseq = tp->snd_nxt; 1010 1011 /* 1012 * Advance snd_nxt over sequence space of this segment. 1013 */ 1014 if (flags & (TH_SYN|TH_FIN)) { 1015 if (flags & TH_SYN) 1016 tp->snd_nxt++; 1017 if (flags & TH_FIN) { 1018 tp->snd_nxt++; 1019 tp->t_flags |= TF_SENTFIN; 1020 } 1021 } 1022 if (sack_rxmit) 1023 goto timer; 1024 tp->snd_nxt += len; 1025 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1026 tp->snd_max = tp->snd_nxt; 1027 /* 1028 * Time this transmission if not a retransmission and 1029 * not currently timing anything. 1030 */ 1031 if (tp->t_rtttime == 0) { 1032 tp->t_rtttime = ticks; 1033 tp->t_rtseq = startseq; 1034 tcpstat.tcps_segstimed++; 1035 } 1036 } 1037 1038 /* 1039 * Set retransmit timer if not currently set, 1040 * and not doing a pure ack or a keep-alive probe. 1041 * Initial value for retransmit timer is smoothed 1042 * round-trip time + 2 * round-trip time variance. 1043 * Initialize shift counter which is used for backoff 1044 * of retransmit time. 1045 */ 1046 timer: 1047 if (!tcp_timer_active(tp, TT_REXMT) && 1048 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1049 (tp->snd_nxt != tp->snd_una))) { 1050 if (tcp_timer_active(tp, TT_PERSIST)) { 1051 tcp_timer_activate(tp, TT_PERSIST, 0); 1052 tp->t_rxtshift = 0; 1053 } 1054 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1055 } 1056 } else { 1057 /* 1058 * Persist case, update snd_max but since we are in 1059 * persist mode (no window) we do not update snd_nxt. 1060 */ 1061 int xlen = len; 1062 if (flags & TH_SYN) 1063 ++xlen; 1064 if (flags & TH_FIN) { 1065 ++xlen; 1066 tp->t_flags |= TF_SENTFIN; 1067 } 1068 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1069 tp->snd_max = tp->snd_nxt + len; 1070 } 1071 1072 #ifdef TCPDEBUG 1073 /* 1074 * Trace. 1075 */ 1076 if (so->so_options & SO_DEBUG) { 1077 u_short save = 0; 1078 #ifdef INET6 1079 if (!isipv6) 1080 #endif 1081 { 1082 save = ipov->ih_len; 1083 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1084 } 1085 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1086 #ifdef INET6 1087 if (!isipv6) 1088 #endif 1089 ipov->ih_len = save; 1090 } 1091 #endif 1092 1093 /* 1094 * Fill in IP length and desired time to live and 1095 * send to IP level. There should be a better way 1096 * to handle ttl and tos; we could keep them in 1097 * the template, but need a way to checksum without them. 1098 */ 1099 /* 1100 * m->m_pkthdr.len should have been set before cksum calcuration, 1101 * because in6_cksum() need it. 1102 */ 1103 #ifdef INET6 1104 if (isipv6) { 1105 /* 1106 * we separately set hoplimit for every segment, since the 1107 * user might want to change the value via setsockopt. 1108 * Also, desired default hop limit might be changed via 1109 * Neighbor Discovery. 1110 */ 1111 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1112 1113 /* TODO: IPv6 IP6TOS_ECT bit on */ 1114 error = ip6_output(m, 1115 tp->t_inpcb->in6p_outputopts, NULL, 1116 ((so->so_options & SO_DONTROUTE) ? 1117 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1118 } else 1119 #endif /* INET6 */ 1120 { 1121 ip->ip_len = m->m_pkthdr.len; 1122 #ifdef INET6 1123 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1124 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1125 #endif /* INET6 */ 1126 /* 1127 * If we do path MTU discovery, then we set DF on every packet. 1128 * This might not be the best thing to do according to RFC3390 1129 * Section 2. However the tcp hostcache migitates the problem 1130 * so it affects only the first tcp connection with a host. 1131 */ 1132 if (path_mtu_discovery) 1133 ip->ip_off |= IP_DF; 1134 1135 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1136 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1137 tp->t_inpcb); 1138 } 1139 if (error) { 1140 1141 /* 1142 * We know that the packet was lost, so back out the 1143 * sequence number advance, if any. 1144 * 1145 * If the error is EPERM the packet got blocked by the 1146 * local firewall. Normally we should terminate the 1147 * connection but the blocking may have been spurious 1148 * due to a firewall reconfiguration cycle. So we treat 1149 * it like a packet loss and let the retransmit timer and 1150 * timeouts do their work over time. 1151 * XXX: It is a POLA question whether calling tcp_drop right 1152 * away would be the really correct behavior instead. 1153 */ 1154 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1155 !tcp_timer_active(tp, TT_PERSIST)) && 1156 ((flags & TH_SYN) == 0) && 1157 (error != EPERM)) { 1158 if (sack_rxmit) { 1159 p->rxmit -= len; 1160 tp->sackhint.sack_bytes_rexmit -= len; 1161 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1162 ("sackhint bytes rtx >= 0")); 1163 } else 1164 tp->snd_nxt -= len; 1165 } 1166 out: 1167 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1168 switch (error) { 1169 case EPERM: 1170 tp->t_softerror = error; 1171 return (error); 1172 case ENOBUFS: 1173 if (!tcp_timer_active(tp, TT_REXMT) && 1174 !tcp_timer_active(tp, TT_PERSIST)) 1175 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1176 tp->snd_cwnd = tp->t_maxseg; 1177 return (0); 1178 case EMSGSIZE: 1179 /* 1180 * For some reason the interface we used initially 1181 * to send segments changed to another or lowered 1182 * its MTU. 1183 * 1184 * tcp_mtudisc() will find out the new MTU and as 1185 * its last action, initiate retransmission, so it 1186 * is important to not do so here. 1187 * 1188 * If TSO was active we either got an interface 1189 * without TSO capabilits or TSO was turned off. 1190 * Disable it for this connection as too and 1191 * immediatly retry with MSS sized segments generated 1192 * by this function. 1193 */ 1194 if (tso) 1195 tp->t_flags &= ~TF_TSO; 1196 tcp_mtudisc(tp->t_inpcb, 0); 1197 return (0); 1198 case EHOSTDOWN: 1199 case EHOSTUNREACH: 1200 case ENETDOWN: 1201 case ENETUNREACH: 1202 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1203 tp->t_softerror = error; 1204 return (0); 1205 } 1206 /* FALLTHROUGH */ 1207 default: 1208 return (error); 1209 } 1210 } 1211 tcpstat.tcps_sndtotal++; 1212 1213 /* 1214 * Data sent (as far as we can tell). 1215 * If this advertises a larger window than any other segment, 1216 * then remember the size of the advertised window. 1217 * Any pending ACK has now been sent. 1218 */ 1219 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1220 tp->rcv_adv = tp->rcv_nxt + recwin; 1221 tp->last_ack_sent = tp->rcv_nxt; 1222 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1223 if (tcp_timer_active(tp, TT_DELACK)) 1224 tcp_timer_activate(tp, TT_DELACK, 0); 1225 #if 0 1226 /* 1227 * This completely breaks TCP if newreno is turned on. What happens 1228 * is that if delayed-acks are turned on on the receiver, this code 1229 * on the transmitter effectively destroys the TCP window, forcing 1230 * it to four packets (1.5Kx4 = 6K window). 1231 */ 1232 if (sendalot && (!tcp_do_newreno || --maxburst)) 1233 goto again; 1234 #endif 1235 if (sendalot) 1236 goto again; 1237 return (0); 1238 } 1239 1240 void 1241 tcp_setpersist(struct tcpcb *tp) 1242 { 1243 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1244 int tt; 1245 1246 if (tcp_timer_active(tp, TT_REXMT)) 1247 panic("tcp_setpersist: retransmit pending"); 1248 /* 1249 * Start/restart persistance timer. 1250 */ 1251 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1252 TCPTV_PERSMIN, TCPTV_PERSMAX); 1253 tcp_timer_activate(tp, TT_PERSIST, tt); 1254 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1255 tp->t_rxtshift++; 1256 } 1257 1258 /* 1259 * Insert TCP options according to the supplied parameters to the place 1260 * optp in a consistent way. Can handle unaligned destinations. 1261 * 1262 * The order of the option processing is crucial for optimal packing and 1263 * alignment for the scarce option space. 1264 * 1265 * The optimal order for a SYN/SYN-ACK segment is: 1266 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1267 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1268 * 1269 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1270 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1271 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1272 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1273 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1274 */ 1275 int 1276 tcp_addoptions(struct tcpopt *to, u_char *optp) 1277 { 1278 u_int mask, optlen = 0; 1279 1280 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1281 if ((to->to_flags & mask) != mask) 1282 continue; 1283 if (optlen == TCP_MAXOLEN) 1284 break; 1285 switch (to->to_flags & mask) { 1286 case TOF_MSS: 1287 while (optlen % 4) { 1288 optlen += TCPOLEN_NOP; 1289 *optp++ = TCPOPT_NOP; 1290 } 1291 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1292 continue; 1293 optlen += TCPOLEN_MAXSEG; 1294 *optp++ = TCPOPT_MAXSEG; 1295 *optp++ = TCPOLEN_MAXSEG; 1296 to->to_mss = htons(to->to_mss); 1297 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1298 optp += sizeof(to->to_mss); 1299 break; 1300 case TOF_SCALE: 1301 while (!optlen || optlen % 2 != 1) { 1302 optlen += TCPOLEN_NOP; 1303 *optp++ = TCPOPT_NOP; 1304 } 1305 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1306 continue; 1307 optlen += TCPOLEN_WINDOW; 1308 *optp++ = TCPOPT_WINDOW; 1309 *optp++ = TCPOLEN_WINDOW; 1310 *optp++ = to->to_wscale; 1311 break; 1312 case TOF_SACKPERM: 1313 while (optlen % 2) { 1314 optlen += TCPOLEN_NOP; 1315 *optp++ = TCPOPT_NOP; 1316 } 1317 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1318 continue; 1319 optlen += TCPOLEN_SACK_PERMITTED; 1320 *optp++ = TCPOPT_SACK_PERMITTED; 1321 *optp++ = TCPOLEN_SACK_PERMITTED; 1322 break; 1323 case TOF_TS: 1324 while (!optlen || optlen % 4 != 2) { 1325 optlen += TCPOLEN_NOP; 1326 *optp++ = TCPOPT_NOP; 1327 } 1328 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1329 continue; 1330 optlen += TCPOLEN_TIMESTAMP; 1331 *optp++ = TCPOPT_TIMESTAMP; 1332 *optp++ = TCPOLEN_TIMESTAMP; 1333 to->to_tsval = htonl(to->to_tsval); 1334 to->to_tsecr = htonl(to->to_tsecr); 1335 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1336 optp += sizeof(to->to_tsval); 1337 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1338 optp += sizeof(to->to_tsecr); 1339 break; 1340 case TOF_SIGNATURE: 1341 { 1342 int siglen = TCPOLEN_SIGNATURE - 2; 1343 1344 while (!optlen || optlen % 4 != 2) { 1345 optlen += TCPOLEN_NOP; 1346 *optp++ = TCPOPT_NOP; 1347 } 1348 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1349 continue; 1350 optlen += TCPOLEN_SIGNATURE; 1351 *optp++ = TCPOPT_SIGNATURE; 1352 *optp++ = TCPOLEN_SIGNATURE; 1353 to->to_signature = optp; 1354 while (siglen--) 1355 *optp++ = 0; 1356 break; 1357 } 1358 case TOF_SACK: 1359 { 1360 int sackblks = 0; 1361 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1362 tcp_seq sack_seq; 1363 1364 while (!optlen || optlen % 4 != 2) { 1365 optlen += TCPOLEN_NOP; 1366 *optp++ = TCPOPT_NOP; 1367 } 1368 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1369 continue; 1370 optlen += TCPOLEN_SACKHDR; 1371 *optp++ = TCPOPT_SACK; 1372 sackblks = min(to->to_nsacks, 1373 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1374 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1375 while (sackblks--) { 1376 sack_seq = htonl(sack->start); 1377 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1378 optp += sizeof(sack_seq); 1379 sack_seq = htonl(sack->end); 1380 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1381 optp += sizeof(sack_seq); 1382 optlen += TCPOLEN_SACK; 1383 sack++; 1384 } 1385 tcpstat.tcps_sack_send_blocks++; 1386 break; 1387 } 1388 default: 1389 panic("%s: unknown TCP option type", __func__); 1390 break; 1391 } 1392 } 1393 1394 /* Terminate and pad TCP options to a 4 byte boundary. */ 1395 if (optlen % 4) { 1396 optlen += TCPOLEN_EOL; 1397 *optp++ = TCPOPT_EOL; 1398 } 1399 /* 1400 * According to RFC 793 (STD0007): 1401 * "The content of the header beyond the End-of-Option option 1402 * must be header padding (i.e., zero)." 1403 * and later: "The padding is composed of zeros." 1404 */ 1405 while (optlen % 4) { 1406 optlen += TCPOLEN_PAD; 1407 *optp++ = TCPOPT_PAD; 1408 } 1409 1410 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1411 return (optlen); 1412 }
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