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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: releng/8.0/sys/netinet/tcp_output.c 196019 2009-08-01 19:26:27Z rwatson $"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/kernel.h> 44 #include <sys/lock.h> 45 #include <sys/mbuf.h> 46 #include <sys/mutex.h> 47 #include <sys/protosw.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/sysctl.h> 51 52 #include <net/if.h> 53 #include <net/route.h> 54 #include <net/vnet.h> 55 56 #include <netinet/in.h> 57 #include <netinet/in_systm.h> 58 #include <netinet/ip.h> 59 #include <netinet/in_pcb.h> 60 #include <netinet/ip_var.h> 61 #include <netinet/ip_options.h> 62 #ifdef INET6 63 #include <netinet6/in6_pcb.h> 64 #include <netinet/ip6.h> 65 #include <netinet6/ip6_var.h> 66 #endif 67 #include <netinet/tcp.h> 68 #define TCPOUTFLAGS 69 #include <netinet/tcp_fsm.h> 70 #include <netinet/tcp_seq.h> 71 #include <netinet/tcp_timer.h> 72 #include <netinet/tcp_var.h> 73 #include <netinet/tcpip.h> 74 #ifdef TCPDEBUG 75 #include <netinet/tcp_debug.h> 76 #endif 77 78 #ifdef IPSEC 79 #include <netipsec/ipsec.h> 80 #endif /*IPSEC*/ 81 82 #include <machine/in_cksum.h> 83 84 #include <security/mac/mac_framework.h> 85 86 #ifdef notyet 87 extern struct mbuf *m_copypack(); 88 #endif 89 90 VNET_DEFINE(int, path_mtu_discovery); 91 VNET_DEFINE(int, ss_fltsz); 92 VNET_DEFINE(int, ss_fltsz_local); 93 VNET_DEFINE(int, tcp_do_newreno); 94 VNET_DEFINE(int, tcp_do_tso); 95 VNET_DEFINE(int, tcp_do_autosndbuf); 96 VNET_DEFINE(int, tcp_autosndbuf_inc); 97 VNET_DEFINE(int, tcp_autosndbuf_max); 98 99 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 100 &VNET_NAME(path_mtu_discovery), 1, 101 "Enable Path MTU Discovery"); 102 103 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 104 &VNET_NAME(ss_fltsz), 1, 105 "Slow start flight size"); 106 107 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, 108 CTLFLAG_RW, &VNET_NAME(ss_fltsz_local), 1, 109 "Slow start flight size for local networks"); 110 111 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 112 &VNET_NAME(tcp_do_newreno), 0, 113 "Enable NewReno Algorithms"); 114 115 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 116 &VNET_NAME(tcp_do_tso), 0, 117 "Enable TCP Segmentation Offload"); 118 119 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 120 &VNET_NAME(tcp_do_autosndbuf), 0, 121 "Enable automatic send buffer sizing"); 122 123 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 124 &VNET_NAME(tcp_autosndbuf_inc), 0, 125 "Incrementor step size of automatic send buffer"); 126 127 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 128 &VNET_NAME(tcp_autosndbuf_max), 0, 129 "Max size of automatic send buffer"); 130 131 132 /* 133 * Tcp output routine: figure out what should be sent and send it. 134 */ 135 int 136 tcp_output(struct tcpcb *tp) 137 { 138 struct socket *so = tp->t_inpcb->inp_socket; 139 long len, recwin, sendwin; 140 int off, flags, error; 141 struct mbuf *m; 142 struct ip *ip = NULL; 143 struct ipovly *ipov = NULL; 144 struct tcphdr *th; 145 u_char opt[TCP_MAXOLEN]; 146 unsigned ipoptlen, optlen, hdrlen; 147 #ifdef IPSEC 148 unsigned ipsec_optlen = 0; 149 #endif 150 int idle, sendalot; 151 int sack_rxmit, sack_bytes_rxmt; 152 struct sackhole *p; 153 int tso = 0; 154 struct tcpopt to; 155 #if 0 156 int maxburst = TCP_MAXBURST; 157 #endif 158 #ifdef INET6 159 struct ip6_hdr *ip6 = NULL; 160 int isipv6; 161 162 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 163 #endif 164 165 INP_WLOCK_ASSERT(tp->t_inpcb); 166 167 /* 168 * Determine length of data that should be transmitted, 169 * and flags that will be used. 170 * If there is some data or critical controls (SYN, RST) 171 * to send, then transmit; otherwise, investigate further. 172 */ 173 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 174 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) { 175 /* 176 * We have been idle for "a while" and no acks are 177 * expected to clock out any data we send -- 178 * slow start to get ack "clock" running again. 179 * 180 * Set the slow-start flight size depending on whether 181 * this is a local network or not. 182 */ 183 int ss = V_ss_fltsz; 184 #ifdef INET6 185 if (isipv6) { 186 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 187 ss = V_ss_fltsz_local; 188 } else 189 #endif /* INET6 */ 190 if (in_localaddr(tp->t_inpcb->inp_faddr)) 191 ss = V_ss_fltsz_local; 192 tp->snd_cwnd = tp->t_maxseg * ss; 193 } 194 tp->t_flags &= ~TF_LASTIDLE; 195 if (idle) { 196 if (tp->t_flags & TF_MORETOCOME) { 197 tp->t_flags |= TF_LASTIDLE; 198 idle = 0; 199 } 200 } 201 again: 202 /* 203 * If we've recently taken a timeout, snd_max will be greater than 204 * snd_nxt. There may be SACK information that allows us to avoid 205 * resending already delivered data. Adjust snd_nxt accordingly. 206 */ 207 if ((tp->t_flags & TF_SACK_PERMIT) && 208 SEQ_LT(tp->snd_nxt, tp->snd_max)) 209 tcp_sack_adjust(tp); 210 sendalot = 0; 211 off = tp->snd_nxt - tp->snd_una; 212 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 213 sendwin = min(sendwin, tp->snd_bwnd); 214 215 flags = tcp_outflags[tp->t_state]; 216 /* 217 * Send any SACK-generated retransmissions. If we're explicitly trying 218 * to send out new data (when sendalot is 1), bypass this function. 219 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 220 * we're replacing a (future) new transmission with a retransmission 221 * now, and we previously incremented snd_cwnd in tcp_input(). 222 */ 223 /* 224 * Still in sack recovery , reset rxmit flag to zero. 225 */ 226 sack_rxmit = 0; 227 sack_bytes_rxmt = 0; 228 len = 0; 229 p = NULL; 230 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 231 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 232 long cwin; 233 234 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 235 if (cwin < 0) 236 cwin = 0; 237 /* Do not retransmit SACK segments beyond snd_recover */ 238 if (SEQ_GT(p->end, tp->snd_recover)) { 239 /* 240 * (At least) part of sack hole extends beyond 241 * snd_recover. Check to see if we can rexmit data 242 * for this hole. 243 */ 244 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 245 /* 246 * Can't rexmit any more data for this hole. 247 * That data will be rexmitted in the next 248 * sack recovery episode, when snd_recover 249 * moves past p->rxmit. 250 */ 251 p = NULL; 252 goto after_sack_rexmit; 253 } else 254 /* Can rexmit part of the current hole */ 255 len = ((long)ulmin(cwin, 256 tp->snd_recover - p->rxmit)); 257 } else 258 len = ((long)ulmin(cwin, p->end - p->rxmit)); 259 off = p->rxmit - tp->snd_una; 260 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 261 __func__, off)); 262 if (len > 0) { 263 sack_rxmit = 1; 264 sendalot = 1; 265 TCPSTAT_INC(tcps_sack_rexmits); 266 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 267 min(len, tp->t_maxseg)); 268 } 269 } 270 after_sack_rexmit: 271 /* 272 * Get standard flags, and add SYN or FIN if requested by 'hidden' 273 * state flags. 274 */ 275 if (tp->t_flags & TF_NEEDFIN) 276 flags |= TH_FIN; 277 if (tp->t_flags & TF_NEEDSYN) 278 flags |= TH_SYN; 279 280 SOCKBUF_LOCK(&so->so_snd); 281 /* 282 * If in persist timeout with window of 0, send 1 byte. 283 * Otherwise, if window is small but nonzero 284 * and timer expired, we will send what we can 285 * and go to transmit state. 286 */ 287 if (tp->t_flags & TF_FORCEDATA) { 288 if (sendwin == 0) { 289 /* 290 * If we still have some data to send, then 291 * clear the FIN bit. Usually this would 292 * happen below when it realizes that we 293 * aren't sending all the data. However, 294 * if we have exactly 1 byte of unsent data, 295 * then it won't clear the FIN bit below, 296 * and if we are in persist state, we wind 297 * up sending the packet without recording 298 * that we sent the FIN bit. 299 * 300 * We can't just blindly clear the FIN bit, 301 * because if we don't have any more data 302 * to send then the probe will be the FIN 303 * itself. 304 */ 305 if (off < so->so_snd.sb_cc) 306 flags &= ~TH_FIN; 307 sendwin = 1; 308 } else { 309 tcp_timer_activate(tp, TT_PERSIST, 0); 310 tp->t_rxtshift = 0; 311 } 312 } 313 314 /* 315 * If snd_nxt == snd_max and we have transmitted a FIN, the 316 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 317 * a negative length. This can also occur when TCP opens up 318 * its congestion window while receiving additional duplicate 319 * acks after fast-retransmit because TCP will reset snd_nxt 320 * to snd_max after the fast-retransmit. 321 * 322 * In the normal retransmit-FIN-only case, however, snd_nxt will 323 * be set to snd_una, the offset will be 0, and the length may 324 * wind up 0. 325 * 326 * If sack_rxmit is true we are retransmitting from the scoreboard 327 * in which case len is already set. 328 */ 329 if (sack_rxmit == 0) { 330 if (sack_bytes_rxmt == 0) 331 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 332 else { 333 long cwin; 334 335 /* 336 * We are inside of a SACK recovery episode and are 337 * sending new data, having retransmitted all the 338 * data possible in the scoreboard. 339 */ 340 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 341 - off); 342 /* 343 * Don't remove this (len > 0) check ! 344 * We explicitly check for len > 0 here (although it 345 * isn't really necessary), to work around a gcc 346 * optimization issue - to force gcc to compute 347 * len above. Without this check, the computation 348 * of len is bungled by the optimizer. 349 */ 350 if (len > 0) { 351 cwin = tp->snd_cwnd - 352 (tp->snd_nxt - tp->sack_newdata) - 353 sack_bytes_rxmt; 354 if (cwin < 0) 355 cwin = 0; 356 len = lmin(len, cwin); 357 } 358 } 359 } 360 361 /* 362 * Lop off SYN bit if it has already been sent. However, if this 363 * is SYN-SENT state and if segment contains data and if we don't 364 * know that foreign host supports TAO, suppress sending segment. 365 */ 366 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 367 if (tp->t_state != TCPS_SYN_RECEIVED) 368 flags &= ~TH_SYN; 369 off--, len++; 370 } 371 372 /* 373 * Be careful not to send data and/or FIN on SYN segments. 374 * This measure is needed to prevent interoperability problems 375 * with not fully conformant TCP implementations. 376 */ 377 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 378 len = 0; 379 flags &= ~TH_FIN; 380 } 381 382 if (len < 0) { 383 /* 384 * If FIN has been sent but not acked, 385 * but we haven't been called to retransmit, 386 * len will be < 0. Otherwise, window shrank 387 * after we sent into it. If window shrank to 0, 388 * cancel pending retransmit, pull snd_nxt back 389 * to (closed) window, and set the persist timer 390 * if it isn't already going. If the window didn't 391 * close completely, just wait for an ACK. 392 */ 393 len = 0; 394 if (sendwin == 0) { 395 tcp_timer_activate(tp, TT_REXMT, 0); 396 tp->t_rxtshift = 0; 397 tp->snd_nxt = tp->snd_una; 398 if (!tcp_timer_active(tp, TT_PERSIST)) 399 tcp_setpersist(tp); 400 } 401 } 402 403 /* len will be >= 0 after this point. */ 404 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 405 406 /* 407 * Automatic sizing of send socket buffer. Often the send buffer 408 * size is not optimally adjusted to the actual network conditions 409 * at hand (delay bandwidth product). Setting the buffer size too 410 * small limits throughput on links with high bandwidth and high 411 * delay (eg. trans-continental/oceanic links). Setting the 412 * buffer size too big consumes too much real kernel memory, 413 * especially with many connections on busy servers. 414 * 415 * The criteria to step up the send buffer one notch are: 416 * 1. receive window of remote host is larger than send buffer 417 * (with a fudge factor of 5/4th); 418 * 2. send buffer is filled to 7/8th with data (so we actually 419 * have data to make use of it); 420 * 3. send buffer fill has not hit maximal automatic size; 421 * 4. our send window (slow start and cogestion controlled) is 422 * larger than sent but unacknowledged data in send buffer. 423 * 424 * The remote host receive window scaling factor may limit the 425 * growing of the send buffer before it reaches its allowed 426 * maximum. 427 * 428 * It scales directly with slow start or congestion window 429 * and does at most one step per received ACK. This fast 430 * scaling has the drawback of growing the send buffer beyond 431 * what is strictly necessary to make full use of a given 432 * delay*bandwith product. However testing has shown this not 433 * to be much of an problem. At worst we are trading wasting 434 * of available bandwith (the non-use of it) for wasting some 435 * socket buffer memory. 436 * 437 * TODO: Shrink send buffer during idle periods together 438 * with congestion window. Requires another timer. Has to 439 * wait for upcoming tcp timer rewrite. 440 */ 441 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 442 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 443 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 444 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 445 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 446 if (!sbreserve_locked(&so->so_snd, 447 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 448 V_tcp_autosndbuf_max), so, curthread)) 449 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 450 } 451 } 452 453 /* 454 * Truncate to the maximum segment length or enable TCP Segmentation 455 * Offloading (if supported by hardware) and ensure that FIN is removed 456 * if the length no longer contains the last data byte. 457 * 458 * TSO may only be used if we are in a pure bulk sending state. The 459 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 460 * IP options prevent using TSO. With TSO the TCP header is the same 461 * (except for the sequence number) for all generated packets. This 462 * makes it impossible to transmit any options which vary per generated 463 * segment or packet. 464 * 465 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 466 * removal of FIN (if not already catched here) are handled later after 467 * the exact length of the TCP options are known. 468 */ 469 #ifdef IPSEC 470 /* 471 * Pre-calculate here as we save another lookup into the darknesses 472 * of IPsec that way and can actually decide if TSO is ok. 473 */ 474 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 475 #endif 476 if (len > tp->t_maxseg) { 477 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 478 ((tp->t_flags & TF_SIGNATURE) == 0) && 479 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 480 tp->t_inpcb->inp_options == NULL && 481 tp->t_inpcb->in6p_options == NULL 482 #ifdef IPSEC 483 && ipsec_optlen == 0 484 #endif 485 ) { 486 tso = 1; 487 } else { 488 len = tp->t_maxseg; 489 sendalot = 1; 490 tso = 0; 491 } 492 } 493 if (sack_rxmit) { 494 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 495 flags &= ~TH_FIN; 496 } else { 497 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 498 flags &= ~TH_FIN; 499 } 500 501 recwin = sbspace(&so->so_rcv); 502 503 /* 504 * Sender silly window avoidance. We transmit under the following 505 * conditions when len is non-zero: 506 * 507 * - We have a full segment (or more with TSO) 508 * - This is the last buffer in a write()/send() and we are 509 * either idle or running NODELAY 510 * - we've timed out (e.g. persist timer) 511 * - we have more then 1/2 the maximum send window's worth of 512 * data (receiver may be limited the window size) 513 * - we need to retransmit 514 */ 515 if (len) { 516 if (len >= tp->t_maxseg) 517 goto send; 518 /* 519 * NOTE! on localhost connections an 'ack' from the remote 520 * end may occur synchronously with the output and cause 521 * us to flush a buffer queued with moretocome. XXX 522 * 523 * note: the len + off check is almost certainly unnecessary. 524 */ 525 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 526 (idle || (tp->t_flags & TF_NODELAY)) && 527 len + off >= so->so_snd.sb_cc && 528 (tp->t_flags & TF_NOPUSH) == 0) { 529 goto send; 530 } 531 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 532 goto send; 533 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 534 goto send; 535 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 536 goto send; 537 if (sack_rxmit) 538 goto send; 539 } 540 541 /* 542 * Compare available window to amount of window 543 * known to peer (as advertised window less 544 * next expected input). If the difference is at least two 545 * max size segments, or at least 50% of the maximum possible 546 * window, then want to send a window update to peer. 547 * Skip this if the connection is in T/TCP half-open state. 548 * Don't send pure window updates when the peer has closed 549 * the connection and won't ever send more data. 550 */ 551 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 552 !TCPS_HAVERCVDFIN(tp->t_state)) { 553 /* 554 * "adv" is the amount we can increase the window, 555 * taking into account that we are limited by 556 * TCP_MAXWIN << tp->rcv_scale. 557 */ 558 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 559 (tp->rcv_adv - tp->rcv_nxt); 560 561 if (adv >= (long) (2 * tp->t_maxseg)) 562 goto send; 563 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 564 goto send; 565 } 566 567 /* 568 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 569 * is also a catch-all for the retransmit timer timeout case. 570 */ 571 if (tp->t_flags & TF_ACKNOW) 572 goto send; 573 if ((flags & TH_RST) || 574 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 575 goto send; 576 if (SEQ_GT(tp->snd_up, tp->snd_una)) 577 goto send; 578 /* 579 * If our state indicates that FIN should be sent 580 * and we have not yet done so, then we need to send. 581 */ 582 if (flags & TH_FIN && 583 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 584 goto send; 585 /* 586 * In SACK, it is possible for tcp_output to fail to send a segment 587 * after the retransmission timer has been turned off. Make sure 588 * that the retransmission timer is set. 589 */ 590 if ((tp->t_flags & TF_SACK_PERMIT) && 591 SEQ_GT(tp->snd_max, tp->snd_una) && 592 !tcp_timer_active(tp, TT_REXMT) && 593 !tcp_timer_active(tp, TT_PERSIST)) { 594 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 595 goto just_return; 596 } 597 /* 598 * TCP window updates are not reliable, rather a polling protocol 599 * using ``persist'' packets is used to insure receipt of window 600 * updates. The three ``states'' for the output side are: 601 * idle not doing retransmits or persists 602 * persisting to move a small or zero window 603 * (re)transmitting and thereby not persisting 604 * 605 * tcp_timer_active(tp, TT_PERSIST) 606 * is true when we are in persist state. 607 * (tp->t_flags & TF_FORCEDATA) 608 * is set when we are called to send a persist packet. 609 * tcp_timer_active(tp, TT_REXMT) 610 * is set when we are retransmitting 611 * The output side is idle when both timers are zero. 612 * 613 * If send window is too small, there is data to transmit, and no 614 * retransmit or persist is pending, then go to persist state. 615 * If nothing happens soon, send when timer expires: 616 * if window is nonzero, transmit what we can, 617 * otherwise force out a byte. 618 */ 619 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 620 !tcp_timer_active(tp, TT_PERSIST)) { 621 tp->t_rxtshift = 0; 622 tcp_setpersist(tp); 623 } 624 625 /* 626 * No reason to send a segment, just return. 627 */ 628 just_return: 629 SOCKBUF_UNLOCK(&so->so_snd); 630 return (0); 631 632 send: 633 SOCKBUF_LOCK_ASSERT(&so->so_snd); 634 /* 635 * Before ESTABLISHED, force sending of initial options 636 * unless TCP set not to do any options. 637 * NOTE: we assume that the IP/TCP header plus TCP options 638 * always fit in a single mbuf, leaving room for a maximum 639 * link header, i.e. 640 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 641 */ 642 optlen = 0; 643 #ifdef INET6 644 if (isipv6) 645 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 646 else 647 #endif 648 hdrlen = sizeof (struct tcpiphdr); 649 650 /* 651 * Compute options for segment. 652 * We only have to care about SYN and established connection 653 * segments. Options for SYN-ACK segments are handled in TCP 654 * syncache. 655 */ 656 if ((tp->t_flags & TF_NOOPT) == 0) { 657 to.to_flags = 0; 658 /* Maximum segment size. */ 659 if (flags & TH_SYN) { 660 tp->snd_nxt = tp->iss; 661 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 662 to.to_flags |= TOF_MSS; 663 } 664 /* Window scaling. */ 665 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 666 to.to_wscale = tp->request_r_scale; 667 to.to_flags |= TOF_SCALE; 668 } 669 /* Timestamps. */ 670 if ((tp->t_flags & TF_RCVD_TSTMP) || 671 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 672 to.to_tsval = ticks + tp->ts_offset; 673 to.to_tsecr = tp->ts_recent; 674 to.to_flags |= TOF_TS; 675 /* Set receive buffer autosizing timestamp. */ 676 if (tp->rfbuf_ts == 0 && 677 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 678 tp->rfbuf_ts = ticks; 679 } 680 /* Selective ACK's. */ 681 if (tp->t_flags & TF_SACK_PERMIT) { 682 if (flags & TH_SYN) 683 to.to_flags |= TOF_SACKPERM; 684 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 685 (tp->t_flags & TF_SACK_PERMIT) && 686 tp->rcv_numsacks > 0) { 687 to.to_flags |= TOF_SACK; 688 to.to_nsacks = tp->rcv_numsacks; 689 to.to_sacks = (u_char *)tp->sackblks; 690 } 691 } 692 #ifdef TCP_SIGNATURE 693 /* TCP-MD5 (RFC2385). */ 694 if (tp->t_flags & TF_SIGNATURE) 695 to.to_flags |= TOF_SIGNATURE; 696 #endif /* TCP_SIGNATURE */ 697 698 /* Processing the options. */ 699 hdrlen += optlen = tcp_addoptions(&to, opt); 700 } 701 702 #ifdef INET6 703 if (isipv6) 704 ipoptlen = ip6_optlen(tp->t_inpcb); 705 else 706 #endif 707 if (tp->t_inpcb->inp_options) 708 ipoptlen = tp->t_inpcb->inp_options->m_len - 709 offsetof(struct ipoption, ipopt_list); 710 else 711 ipoptlen = 0; 712 #ifdef IPSEC 713 ipoptlen += ipsec_optlen; 714 #endif 715 716 /* 717 * Adjust data length if insertion of options will 718 * bump the packet length beyond the t_maxopd length. 719 * Clear the FIN bit because we cut off the tail of 720 * the segment. 721 * 722 * When doing TSO limit a burst to TCP_MAXWIN minus the 723 * IP, TCP and Options length to keep ip->ip_len from 724 * overflowing. Prevent the last segment from being 725 * fractional thus making them all equal sized and set 726 * the flag to continue sending. TSO is disabled when 727 * IP options or IPSEC are present. 728 */ 729 if (len + optlen + ipoptlen > tp->t_maxopd) { 730 flags &= ~TH_FIN; 731 if (tso) { 732 if (len > TCP_MAXWIN - hdrlen - optlen) { 733 len = TCP_MAXWIN - hdrlen - optlen; 734 len = len - (len % (tp->t_maxopd - optlen)); 735 sendalot = 1; 736 } else if (tp->t_flags & TF_NEEDFIN) 737 sendalot = 1; 738 } else { 739 len = tp->t_maxopd - optlen - ipoptlen; 740 sendalot = 1; 741 } 742 } 743 744 /*#ifdef DIAGNOSTIC*/ 745 #ifdef INET6 746 if (max_linkhdr + hdrlen > MCLBYTES) 747 #else 748 if (max_linkhdr + hdrlen > MHLEN) 749 #endif 750 panic("tcphdr too big"); 751 /*#endif*/ 752 753 /* 754 * This KASSERT is here to catch edge cases at a well defined place. 755 * Before, those had triggered (random) panic conditions further down. 756 */ 757 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 758 759 /* 760 * Grab a header mbuf, attaching a copy of data to 761 * be transmitted, and initialize the header from 762 * the template for sends on this connection. 763 */ 764 if (len) { 765 struct mbuf *mb; 766 u_int moff; 767 768 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 769 TCPSTAT_INC(tcps_sndprobe); 770 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 771 TCPSTAT_INC(tcps_sndrexmitpack); 772 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 773 } else { 774 TCPSTAT_INC(tcps_sndpack); 775 TCPSTAT_ADD(tcps_sndbyte, len); 776 } 777 #ifdef notyet 778 if ((m = m_copypack(so->so_snd.sb_mb, off, 779 (int)len, max_linkhdr + hdrlen)) == 0) { 780 SOCKBUF_UNLOCK(&so->so_snd); 781 error = ENOBUFS; 782 goto out; 783 } 784 /* 785 * m_copypack left space for our hdr; use it. 786 */ 787 m->m_len += hdrlen; 788 m->m_data -= hdrlen; 789 #else 790 MGETHDR(m, M_DONTWAIT, MT_DATA); 791 if (m == NULL) { 792 SOCKBUF_UNLOCK(&so->so_snd); 793 error = ENOBUFS; 794 goto out; 795 } 796 #ifdef INET6 797 if (MHLEN < hdrlen + max_linkhdr) { 798 MCLGET(m, M_DONTWAIT); 799 if ((m->m_flags & M_EXT) == 0) { 800 SOCKBUF_UNLOCK(&so->so_snd); 801 m_freem(m); 802 error = ENOBUFS; 803 goto out; 804 } 805 } 806 #endif 807 m->m_data += max_linkhdr; 808 m->m_len = hdrlen; 809 810 /* 811 * Start the m_copy functions from the closest mbuf 812 * to the offset in the socket buffer chain. 813 */ 814 mb = sbsndptr(&so->so_snd, off, len, &moff); 815 816 if (len <= MHLEN - hdrlen - max_linkhdr) { 817 m_copydata(mb, moff, (int)len, 818 mtod(m, caddr_t) + hdrlen); 819 m->m_len += len; 820 } else { 821 m->m_next = m_copy(mb, moff, (int)len); 822 if (m->m_next == NULL) { 823 SOCKBUF_UNLOCK(&so->so_snd); 824 (void) m_free(m); 825 error = ENOBUFS; 826 goto out; 827 } 828 } 829 #endif 830 /* 831 * If we're sending everything we've got, set PUSH. 832 * (This will keep happy those implementations which only 833 * give data to the user when a buffer fills or 834 * a PUSH comes in.) 835 */ 836 if (off + len == so->so_snd.sb_cc) 837 flags |= TH_PUSH; 838 SOCKBUF_UNLOCK(&so->so_snd); 839 } else { 840 SOCKBUF_UNLOCK(&so->so_snd); 841 if (tp->t_flags & TF_ACKNOW) 842 TCPSTAT_INC(tcps_sndacks); 843 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 844 TCPSTAT_INC(tcps_sndctrl); 845 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 846 TCPSTAT_INC(tcps_sndurg); 847 else 848 TCPSTAT_INC(tcps_sndwinup); 849 850 MGETHDR(m, M_DONTWAIT, MT_DATA); 851 if (m == NULL) { 852 error = ENOBUFS; 853 goto out; 854 } 855 #ifdef INET6 856 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 857 MHLEN >= hdrlen) { 858 MH_ALIGN(m, hdrlen); 859 } else 860 #endif 861 m->m_data += max_linkhdr; 862 m->m_len = hdrlen; 863 } 864 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 865 m->m_pkthdr.rcvif = (struct ifnet *)0; 866 #ifdef MAC 867 mac_inpcb_create_mbuf(tp->t_inpcb, m); 868 #endif 869 #ifdef INET6 870 if (isipv6) { 871 ip6 = mtod(m, struct ip6_hdr *); 872 th = (struct tcphdr *)(ip6 + 1); 873 tcpip_fillheaders(tp->t_inpcb, ip6, th); 874 } else 875 #endif /* INET6 */ 876 { 877 ip = mtod(m, struct ip *); 878 ipov = (struct ipovly *)ip; 879 th = (struct tcphdr *)(ip + 1); 880 tcpip_fillheaders(tp->t_inpcb, ip, th); 881 } 882 883 /* 884 * Fill in fields, remembering maximum advertised 885 * window for use in delaying messages about window sizes. 886 * If resending a FIN, be sure not to use a new sequence number. 887 */ 888 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 889 tp->snd_nxt == tp->snd_max) 890 tp->snd_nxt--; 891 /* 892 * If we are starting a connection, send ECN setup 893 * SYN packet. If we are on a retransmit, we may 894 * resend those bits a number of times as per 895 * RFC 3168. 896 */ 897 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 898 if (tp->t_rxtshift >= 1) { 899 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 900 flags |= TH_ECE|TH_CWR; 901 } else 902 flags |= TH_ECE|TH_CWR; 903 } 904 905 if (tp->t_state == TCPS_ESTABLISHED && 906 (tp->t_flags & TF_ECN_PERMIT)) { 907 /* 908 * If the peer has ECN, mark data packets with 909 * ECN capable transmission (ECT). 910 * Ignore pure ack packets, retransmissions and window probes. 911 */ 912 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 913 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 914 #ifdef INET6 915 if (isipv6) 916 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 917 else 918 #endif 919 ip->ip_tos |= IPTOS_ECN_ECT0; 920 TCPSTAT_INC(tcps_ecn_ect0); 921 } 922 923 /* 924 * Reply with proper ECN notifications. 925 */ 926 if (tp->t_flags & TF_ECN_SND_CWR) { 927 flags |= TH_CWR; 928 tp->t_flags &= ~TF_ECN_SND_CWR; 929 } 930 if (tp->t_flags & TF_ECN_SND_ECE) 931 flags |= TH_ECE; 932 } 933 934 /* 935 * If we are doing retransmissions, then snd_nxt will 936 * not reflect the first unsent octet. For ACK only 937 * packets, we do not want the sequence number of the 938 * retransmitted packet, we want the sequence number 939 * of the next unsent octet. So, if there is no data 940 * (and no SYN or FIN), use snd_max instead of snd_nxt 941 * when filling in ti_seq. But if we are in persist 942 * state, snd_max might reflect one byte beyond the 943 * right edge of the window, so use snd_nxt in that 944 * case, since we know we aren't doing a retransmission. 945 * (retransmit and persist are mutually exclusive...) 946 */ 947 if (sack_rxmit == 0) { 948 if (len || (flags & (TH_SYN|TH_FIN)) || 949 tcp_timer_active(tp, TT_PERSIST)) 950 th->th_seq = htonl(tp->snd_nxt); 951 else 952 th->th_seq = htonl(tp->snd_max); 953 } else { 954 th->th_seq = htonl(p->rxmit); 955 p->rxmit += len; 956 tp->sackhint.sack_bytes_rexmit += len; 957 } 958 th->th_ack = htonl(tp->rcv_nxt); 959 if (optlen) { 960 bcopy(opt, th + 1, optlen); 961 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 962 } 963 th->th_flags = flags; 964 /* 965 * Calculate receive window. Don't shrink window, 966 * but avoid silly window syndrome. 967 */ 968 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 969 recwin < (long)tp->t_maxseg) 970 recwin = 0; 971 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 972 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 973 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 974 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 975 976 /* 977 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 978 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 979 * case is handled in syncache. 980 */ 981 if (flags & TH_SYN) 982 th->th_win = htons((u_short) 983 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 984 else 985 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 986 987 /* 988 * Adjust the RXWIN0SENT flag - indicate that we have advertised 989 * a 0 window. This may cause the remote transmitter to stall. This 990 * flag tells soreceive() to disable delayed acknowledgements when 991 * draining the buffer. This can occur if the receiver is attempting 992 * to read more data than can be buffered prior to transmitting on 993 * the connection. 994 */ 995 if (recwin == 0) 996 tp->t_flags |= TF_RXWIN0SENT; 997 else 998 tp->t_flags &= ~TF_RXWIN0SENT; 999 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1000 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1001 th->th_flags |= TH_URG; 1002 } else 1003 /* 1004 * If no urgent pointer to send, then we pull 1005 * the urgent pointer to the left edge of the send window 1006 * so that it doesn't drift into the send window on sequence 1007 * number wraparound. 1008 */ 1009 tp->snd_up = tp->snd_una; /* drag it along */ 1010 1011 #ifdef TCP_SIGNATURE 1012 if (tp->t_flags & TF_SIGNATURE) { 1013 int sigoff = to.to_signature - opt; 1014 tcp_signature_compute(m, 0, len, optlen, 1015 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1016 } 1017 #endif 1018 1019 /* 1020 * Put TCP length in extended header, and then 1021 * checksum extended header and data. 1022 */ 1023 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1024 #ifdef INET6 1025 if (isipv6) 1026 /* 1027 * ip6_plen is not need to be filled now, and will be filled 1028 * in ip6_output. 1029 */ 1030 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1031 sizeof(struct tcphdr) + optlen + len); 1032 else 1033 #endif /* INET6 */ 1034 { 1035 m->m_pkthdr.csum_flags = CSUM_TCP; 1036 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1037 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1038 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1039 1040 /* IP version must be set here for ipv4/ipv6 checking later */ 1041 KASSERT(ip->ip_v == IPVERSION, 1042 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1043 } 1044 1045 /* 1046 * Enable TSO and specify the size of the segments. 1047 * The TCP pseudo header checksum is always provided. 1048 * XXX: Fixme: This is currently not the case for IPv6. 1049 */ 1050 if (tso) { 1051 m->m_pkthdr.csum_flags = CSUM_TSO; 1052 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1053 } 1054 1055 /* 1056 * In transmit state, time the transmission and arrange for 1057 * the retransmit. In persist state, just set snd_max. 1058 */ 1059 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1060 !tcp_timer_active(tp, TT_PERSIST)) { 1061 tcp_seq startseq = tp->snd_nxt; 1062 1063 /* 1064 * Advance snd_nxt over sequence space of this segment. 1065 */ 1066 if (flags & (TH_SYN|TH_FIN)) { 1067 if (flags & TH_SYN) 1068 tp->snd_nxt++; 1069 if (flags & TH_FIN) { 1070 tp->snd_nxt++; 1071 tp->t_flags |= TF_SENTFIN; 1072 } 1073 } 1074 if (sack_rxmit) 1075 goto timer; 1076 tp->snd_nxt += len; 1077 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1078 tp->snd_max = tp->snd_nxt; 1079 /* 1080 * Time this transmission if not a retransmission and 1081 * not currently timing anything. 1082 */ 1083 if (tp->t_rtttime == 0) { 1084 tp->t_rtttime = ticks; 1085 tp->t_rtseq = startseq; 1086 TCPSTAT_INC(tcps_segstimed); 1087 } 1088 } 1089 1090 /* 1091 * Set retransmit timer if not currently set, 1092 * and not doing a pure ack or a keep-alive probe. 1093 * Initial value for retransmit timer is smoothed 1094 * round-trip time + 2 * round-trip time variance. 1095 * Initialize shift counter which is used for backoff 1096 * of retransmit time. 1097 */ 1098 timer: 1099 if (!tcp_timer_active(tp, TT_REXMT) && 1100 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1101 (tp->snd_nxt != tp->snd_una))) { 1102 if (tcp_timer_active(tp, TT_PERSIST)) { 1103 tcp_timer_activate(tp, TT_PERSIST, 0); 1104 tp->t_rxtshift = 0; 1105 } 1106 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1107 } 1108 } else { 1109 /* 1110 * Persist case, update snd_max but since we are in 1111 * persist mode (no window) we do not update snd_nxt. 1112 */ 1113 int xlen = len; 1114 if (flags & TH_SYN) 1115 ++xlen; 1116 if (flags & TH_FIN) { 1117 ++xlen; 1118 tp->t_flags |= TF_SENTFIN; 1119 } 1120 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1121 tp->snd_max = tp->snd_nxt + len; 1122 } 1123 1124 #ifdef TCPDEBUG 1125 /* 1126 * Trace. 1127 */ 1128 if (so->so_options & SO_DEBUG) { 1129 u_short save = 0; 1130 #ifdef INET6 1131 if (!isipv6) 1132 #endif 1133 { 1134 save = ipov->ih_len; 1135 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1136 } 1137 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1138 #ifdef INET6 1139 if (!isipv6) 1140 #endif 1141 ipov->ih_len = save; 1142 } 1143 #endif 1144 1145 /* 1146 * Fill in IP length and desired time to live and 1147 * send to IP level. There should be a better way 1148 * to handle ttl and tos; we could keep them in 1149 * the template, but need a way to checksum without them. 1150 */ 1151 /* 1152 * m->m_pkthdr.len should have been set before cksum calcuration, 1153 * because in6_cksum() need it. 1154 */ 1155 #ifdef INET6 1156 if (isipv6) { 1157 /* 1158 * we separately set hoplimit for every segment, since the 1159 * user might want to change the value via setsockopt. 1160 * Also, desired default hop limit might be changed via 1161 * Neighbor Discovery. 1162 */ 1163 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1164 1165 /* TODO: IPv6 IP6TOS_ECT bit on */ 1166 error = ip6_output(m, 1167 tp->t_inpcb->in6p_outputopts, NULL, 1168 ((so->so_options & SO_DONTROUTE) ? 1169 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1170 } else 1171 #endif /* INET6 */ 1172 { 1173 ip->ip_len = m->m_pkthdr.len; 1174 #ifdef INET6 1175 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1176 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1177 #endif /* INET6 */ 1178 /* 1179 * If we do path MTU discovery, then we set DF on every packet. 1180 * This might not be the best thing to do according to RFC3390 1181 * Section 2. However the tcp hostcache migitates the problem 1182 * so it affects only the first tcp connection with a host. 1183 */ 1184 if (V_path_mtu_discovery) 1185 ip->ip_off |= IP_DF; 1186 1187 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1188 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1189 tp->t_inpcb); 1190 } 1191 if (error) { 1192 1193 /* 1194 * We know that the packet was lost, so back out the 1195 * sequence number advance, if any. 1196 * 1197 * If the error is EPERM the packet got blocked by the 1198 * local firewall. Normally we should terminate the 1199 * connection but the blocking may have been spurious 1200 * due to a firewall reconfiguration cycle. So we treat 1201 * it like a packet loss and let the retransmit timer and 1202 * timeouts do their work over time. 1203 * XXX: It is a POLA question whether calling tcp_drop right 1204 * away would be the really correct behavior instead. 1205 */ 1206 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1207 !tcp_timer_active(tp, TT_PERSIST)) && 1208 ((flags & TH_SYN) == 0) && 1209 (error != EPERM)) { 1210 if (sack_rxmit) { 1211 p->rxmit -= len; 1212 tp->sackhint.sack_bytes_rexmit -= len; 1213 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1214 ("sackhint bytes rtx >= 0")); 1215 } else 1216 tp->snd_nxt -= len; 1217 } 1218 out: 1219 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1220 switch (error) { 1221 case EPERM: 1222 tp->t_softerror = error; 1223 return (error); 1224 case ENOBUFS: 1225 if (!tcp_timer_active(tp, TT_REXMT) && 1226 !tcp_timer_active(tp, TT_PERSIST)) 1227 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1228 tp->snd_cwnd = tp->t_maxseg; 1229 return (0); 1230 case EMSGSIZE: 1231 /* 1232 * For some reason the interface we used initially 1233 * to send segments changed to another or lowered 1234 * its MTU. 1235 * 1236 * tcp_mtudisc() will find out the new MTU and as 1237 * its last action, initiate retransmission, so it 1238 * is important to not do so here. 1239 * 1240 * If TSO was active we either got an interface 1241 * without TSO capabilits or TSO was turned off. 1242 * Disable it for this connection as too and 1243 * immediatly retry with MSS sized segments generated 1244 * by this function. 1245 */ 1246 if (tso) 1247 tp->t_flags &= ~TF_TSO; 1248 tcp_mtudisc(tp->t_inpcb, 0); 1249 return (0); 1250 case EHOSTDOWN: 1251 case EHOSTUNREACH: 1252 case ENETDOWN: 1253 case ENETUNREACH: 1254 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1255 tp->t_softerror = error; 1256 return (0); 1257 } 1258 /* FALLTHROUGH */ 1259 default: 1260 return (error); 1261 } 1262 } 1263 TCPSTAT_INC(tcps_sndtotal); 1264 1265 /* 1266 * Data sent (as far as we can tell). 1267 * If this advertises a larger window than any other segment, 1268 * then remember the size of the advertised window. 1269 * Any pending ACK has now been sent. 1270 */ 1271 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1272 tp->rcv_adv = tp->rcv_nxt + recwin; 1273 tp->last_ack_sent = tp->rcv_nxt; 1274 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1275 if (tcp_timer_active(tp, TT_DELACK)) 1276 tcp_timer_activate(tp, TT_DELACK, 0); 1277 #if 0 1278 /* 1279 * This completely breaks TCP if newreno is turned on. What happens 1280 * is that if delayed-acks are turned on on the receiver, this code 1281 * on the transmitter effectively destroys the TCP window, forcing 1282 * it to four packets (1.5Kx4 = 6K window). 1283 */ 1284 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1285 goto again; 1286 #endif 1287 if (sendalot) 1288 goto again; 1289 return (0); 1290 } 1291 1292 void 1293 tcp_setpersist(struct tcpcb *tp) 1294 { 1295 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1296 int tt; 1297 1298 if (tcp_timer_active(tp, TT_REXMT)) 1299 panic("tcp_setpersist: retransmit pending"); 1300 /* 1301 * Start/restart persistance timer. 1302 */ 1303 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1304 TCPTV_PERSMIN, TCPTV_PERSMAX); 1305 tcp_timer_activate(tp, TT_PERSIST, tt); 1306 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1307 tp->t_rxtshift++; 1308 } 1309 1310 /* 1311 * Insert TCP options according to the supplied parameters to the place 1312 * optp in a consistent way. Can handle unaligned destinations. 1313 * 1314 * The order of the option processing is crucial for optimal packing and 1315 * alignment for the scarce option space. 1316 * 1317 * The optimal order for a SYN/SYN-ACK segment is: 1318 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1319 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1320 * 1321 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1322 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1323 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1324 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1325 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1326 */ 1327 int 1328 tcp_addoptions(struct tcpopt *to, u_char *optp) 1329 { 1330 u_int mask, optlen = 0; 1331 1332 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1333 if ((to->to_flags & mask) != mask) 1334 continue; 1335 if (optlen == TCP_MAXOLEN) 1336 break; 1337 switch (to->to_flags & mask) { 1338 case TOF_MSS: 1339 while (optlen % 4) { 1340 optlen += TCPOLEN_NOP; 1341 *optp++ = TCPOPT_NOP; 1342 } 1343 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1344 continue; 1345 optlen += TCPOLEN_MAXSEG; 1346 *optp++ = TCPOPT_MAXSEG; 1347 *optp++ = TCPOLEN_MAXSEG; 1348 to->to_mss = htons(to->to_mss); 1349 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1350 optp += sizeof(to->to_mss); 1351 break; 1352 case TOF_SCALE: 1353 while (!optlen || optlen % 2 != 1) { 1354 optlen += TCPOLEN_NOP; 1355 *optp++ = TCPOPT_NOP; 1356 } 1357 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1358 continue; 1359 optlen += TCPOLEN_WINDOW; 1360 *optp++ = TCPOPT_WINDOW; 1361 *optp++ = TCPOLEN_WINDOW; 1362 *optp++ = to->to_wscale; 1363 break; 1364 case TOF_SACKPERM: 1365 while (optlen % 2) { 1366 optlen += TCPOLEN_NOP; 1367 *optp++ = TCPOPT_NOP; 1368 } 1369 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1370 continue; 1371 optlen += TCPOLEN_SACK_PERMITTED; 1372 *optp++ = TCPOPT_SACK_PERMITTED; 1373 *optp++ = TCPOLEN_SACK_PERMITTED; 1374 break; 1375 case TOF_TS: 1376 while (!optlen || optlen % 4 != 2) { 1377 optlen += TCPOLEN_NOP; 1378 *optp++ = TCPOPT_NOP; 1379 } 1380 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1381 continue; 1382 optlen += TCPOLEN_TIMESTAMP; 1383 *optp++ = TCPOPT_TIMESTAMP; 1384 *optp++ = TCPOLEN_TIMESTAMP; 1385 to->to_tsval = htonl(to->to_tsval); 1386 to->to_tsecr = htonl(to->to_tsecr); 1387 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1388 optp += sizeof(to->to_tsval); 1389 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1390 optp += sizeof(to->to_tsecr); 1391 break; 1392 case TOF_SIGNATURE: 1393 { 1394 int siglen = TCPOLEN_SIGNATURE - 2; 1395 1396 while (!optlen || optlen % 4 != 2) { 1397 optlen += TCPOLEN_NOP; 1398 *optp++ = TCPOPT_NOP; 1399 } 1400 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1401 continue; 1402 optlen += TCPOLEN_SIGNATURE; 1403 *optp++ = TCPOPT_SIGNATURE; 1404 *optp++ = TCPOLEN_SIGNATURE; 1405 to->to_signature = optp; 1406 while (siglen--) 1407 *optp++ = 0; 1408 break; 1409 } 1410 case TOF_SACK: 1411 { 1412 int sackblks = 0; 1413 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1414 tcp_seq sack_seq; 1415 1416 while (!optlen || optlen % 4 != 2) { 1417 optlen += TCPOLEN_NOP; 1418 *optp++ = TCPOPT_NOP; 1419 } 1420 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1421 continue; 1422 optlen += TCPOLEN_SACKHDR; 1423 *optp++ = TCPOPT_SACK; 1424 sackblks = min(to->to_nsacks, 1425 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1426 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1427 while (sackblks--) { 1428 sack_seq = htonl(sack->start); 1429 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1430 optp += sizeof(sack_seq); 1431 sack_seq = htonl(sack->end); 1432 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1433 optp += sizeof(sack_seq); 1434 optlen += TCPOLEN_SACK; 1435 sack++; 1436 } 1437 TCPSTAT_INC(tcps_sack_send_blocks); 1438 break; 1439 } 1440 default: 1441 panic("%s: unknown TCP option type", __func__); 1442 break; 1443 } 1444 } 1445 1446 /* Terminate and pad TCP options to a 4 byte boundary. */ 1447 if (optlen % 4) { 1448 optlen += TCPOLEN_EOL; 1449 *optp++ = TCPOPT_EOL; 1450 } 1451 /* 1452 * According to RFC 793 (STD0007): 1453 * "The content of the header beyond the End-of-Option option 1454 * must be header padding (i.e., zero)." 1455 * and later: "The padding is composed of zeros." 1456 */ 1457 while (optlen % 4) { 1458 optlen += TCPOLEN_PAD; 1459 *optp++ = TCPOPT_PAD; 1460 } 1461 1462 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1463 return (optlen); 1464 }
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