Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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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_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/hhook.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/if.h> 54 #include <net/route.h> 55 #include <net/vnet.h> 56 57 #include <netinet/cc.h> 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #include <netinet/ip_options.h> 64 #ifdef INET6 65 #include <netinet6/in6_pcb.h> 66 #include <netinet/ip6.h> 67 #include <netinet6/ip6_var.h> 68 #endif 69 #define TCPOUTFLAGS 70 #include <netinet/tcp_fsm.h> 71 #include <netinet/tcp_seq.h> 72 #include <netinet/tcp_timer.h> 73 #include <netinet/tcp_var.h> 74 #include <netinet/tcpip.h> 75 #ifdef TCPDEBUG 76 #include <netinet/tcp_debug.h> 77 #endif 78 79 #ifdef IPSEC 80 #include <netipsec/ipsec.h> 81 #endif /*IPSEC*/ 82 83 #include <machine/in_cksum.h> 84 85 #include <security/mac/mac_framework.h> 86 87 #ifdef notyet 88 extern struct mbuf *m_copypack(); 89 #endif 90 91 VNET_DEFINE(int, path_mtu_discovery) = 1; 92 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 93 &VNET_NAME(path_mtu_discovery), 1, 94 "Enable Path MTU Discovery"); 95 96 VNET_DEFINE(int, ss_fltsz) = 1; 97 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 98 &VNET_NAME(ss_fltsz), 1, 99 "Slow start flight size"); 100 101 VNET_DEFINE(int, ss_fltsz_local) = 4; 102 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, 103 CTLFLAG_RW, &VNET_NAME(ss_fltsz_local), 1, 104 "Slow start flight size for local networks"); 105 106 VNET_DEFINE(int, tcp_do_tso) = 1; 107 #define V_tcp_do_tso VNET(tcp_do_tso) 108 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 109 &VNET_NAME(tcp_do_tso), 0, 110 "Enable TCP Segmentation Offload"); 111 112 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 113 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 114 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 115 &VNET_NAME(tcp_do_autosndbuf), 0, 116 "Enable automatic send buffer sizing"); 117 118 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 119 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 120 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 121 &VNET_NAME(tcp_autosndbuf_inc), 0, 122 "Incrementor step size of automatic send buffer"); 123 124 VNET_DEFINE(int, tcp_autosndbuf_max) = 256*1024; 125 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 126 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 127 &VNET_NAME(tcp_autosndbuf_max), 0, 128 "Max size of automatic send buffer"); 129 130 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 131 struct tcphdr *th, struct tcpopt *to, 132 long len, int tso); 133 static void inline cc_after_idle(struct tcpcb *tp); 134 135 /* 136 * Wrapper for the TCP established ouput helper hook. 137 */ 138 static void inline 139 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 140 struct tcpopt *to, long len, int tso) 141 { 142 struct tcp_hhook_data hhook_data; 143 144 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 145 hhook_data.tp = tp; 146 hhook_data.th = th; 147 hhook_data.to = to; 148 hhook_data.len = len; 149 hhook_data.tso = tso; 150 151 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 152 tp->osd); 153 } 154 } 155 156 /* 157 * CC wrapper hook functions 158 */ 159 static void inline 160 cc_after_idle(struct tcpcb *tp) 161 { 162 INP_WLOCK_ASSERT(tp->t_inpcb); 163 164 if (CC_ALGO(tp)->after_idle != NULL) 165 CC_ALGO(tp)->after_idle(tp->ccv); 166 } 167 168 /* 169 * Tcp output routine: figure out what should be sent and send it. 170 */ 171 int 172 tcp_output(struct tcpcb *tp) 173 { 174 struct socket *so = tp->t_inpcb->inp_socket; 175 long len, recwin, sendwin; 176 int off, flags, error; 177 struct mbuf *m; 178 struct ip *ip = NULL; 179 struct ipovly *ipov = NULL; 180 struct tcphdr *th; 181 u_char opt[TCP_MAXOLEN]; 182 unsigned ipoptlen, optlen, hdrlen; 183 #ifdef IPSEC 184 unsigned ipsec_optlen = 0; 185 #endif 186 int idle, sendalot; 187 int sack_rxmit, sack_bytes_rxmt; 188 struct sackhole *p; 189 int tso; 190 struct tcpopt to; 191 #if 0 192 int maxburst = TCP_MAXBURST; 193 #endif 194 #ifdef INET6 195 struct ip6_hdr *ip6 = NULL; 196 int isipv6; 197 198 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 199 #endif 200 201 INP_WLOCK_ASSERT(tp->t_inpcb); 202 203 /* 204 * Determine length of data that should be transmitted, 205 * and flags that will be used. 206 * If there is some data or critical controls (SYN, RST) 207 * to send, then transmit; otherwise, investigate further. 208 */ 209 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 210 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 211 cc_after_idle(tp); 212 tp->t_flags &= ~TF_LASTIDLE; 213 if (idle) { 214 if (tp->t_flags & TF_MORETOCOME) { 215 tp->t_flags |= TF_LASTIDLE; 216 idle = 0; 217 } 218 } 219 again: 220 /* 221 * If we've recently taken a timeout, snd_max will be greater than 222 * snd_nxt. There may be SACK information that allows us to avoid 223 * resending already delivered data. Adjust snd_nxt accordingly. 224 */ 225 if ((tp->t_flags & TF_SACK_PERMIT) && 226 SEQ_LT(tp->snd_nxt, tp->snd_max)) 227 tcp_sack_adjust(tp); 228 sendalot = 0; 229 tso = 0; 230 off = tp->snd_nxt - tp->snd_una; 231 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 232 sendwin = min(sendwin, tp->snd_bwnd); 233 234 flags = tcp_outflags[tp->t_state]; 235 /* 236 * Send any SACK-generated retransmissions. If we're explicitly trying 237 * to send out new data (when sendalot is 1), bypass this function. 238 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 239 * we're replacing a (future) new transmission with a retransmission 240 * now, and we previously incremented snd_cwnd in tcp_input(). 241 */ 242 /* 243 * Still in sack recovery , reset rxmit flag to zero. 244 */ 245 sack_rxmit = 0; 246 sack_bytes_rxmt = 0; 247 len = 0; 248 p = NULL; 249 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 250 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 251 long cwin; 252 253 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 254 if (cwin < 0) 255 cwin = 0; 256 /* Do not retransmit SACK segments beyond snd_recover */ 257 if (SEQ_GT(p->end, tp->snd_recover)) { 258 /* 259 * (At least) part of sack hole extends beyond 260 * snd_recover. Check to see if we can rexmit data 261 * for this hole. 262 */ 263 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 264 /* 265 * Can't rexmit any more data for this hole. 266 * That data will be rexmitted in the next 267 * sack recovery episode, when snd_recover 268 * moves past p->rxmit. 269 */ 270 p = NULL; 271 goto after_sack_rexmit; 272 } else 273 /* Can rexmit part of the current hole */ 274 len = ((long)ulmin(cwin, 275 tp->snd_recover - p->rxmit)); 276 } else 277 len = ((long)ulmin(cwin, p->end - p->rxmit)); 278 off = p->rxmit - tp->snd_una; 279 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 280 __func__, off)); 281 if (len > 0) { 282 sack_rxmit = 1; 283 sendalot = 1; 284 TCPSTAT_INC(tcps_sack_rexmits); 285 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 286 min(len, tp->t_maxseg)); 287 } 288 } 289 after_sack_rexmit: 290 /* 291 * Get standard flags, and add SYN or FIN if requested by 'hidden' 292 * state flags. 293 */ 294 if (tp->t_flags & TF_NEEDFIN) 295 flags |= TH_FIN; 296 if (tp->t_flags & TF_NEEDSYN) 297 flags |= TH_SYN; 298 299 SOCKBUF_LOCK(&so->so_snd); 300 /* 301 * If in persist timeout with window of 0, send 1 byte. 302 * Otherwise, if window is small but nonzero 303 * and timer expired, we will send what we can 304 * and go to transmit state. 305 */ 306 if (tp->t_flags & TF_FORCEDATA) { 307 if (sendwin == 0) { 308 /* 309 * If we still have some data to send, then 310 * clear the FIN bit. Usually this would 311 * happen below when it realizes that we 312 * aren't sending all the data. However, 313 * if we have exactly 1 byte of unsent data, 314 * then it won't clear the FIN bit below, 315 * and if we are in persist state, we wind 316 * up sending the packet without recording 317 * that we sent the FIN bit. 318 * 319 * We can't just blindly clear the FIN bit, 320 * because if we don't have any more data 321 * to send then the probe will be the FIN 322 * itself. 323 */ 324 if (off < so->so_snd.sb_cc) 325 flags &= ~TH_FIN; 326 sendwin = 1; 327 } else { 328 tcp_timer_activate(tp, TT_PERSIST, 0); 329 tp->t_rxtshift = 0; 330 } 331 } 332 333 /* 334 * If snd_nxt == snd_max and we have transmitted a FIN, the 335 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 336 * a negative length. This can also occur when TCP opens up 337 * its congestion window while receiving additional duplicate 338 * acks after fast-retransmit because TCP will reset snd_nxt 339 * to snd_max after the fast-retransmit. 340 * 341 * In the normal retransmit-FIN-only case, however, snd_nxt will 342 * be set to snd_una, the offset will be 0, and the length may 343 * wind up 0. 344 * 345 * If sack_rxmit is true we are retransmitting from the scoreboard 346 * in which case len is already set. 347 */ 348 if (sack_rxmit == 0) { 349 if (sack_bytes_rxmt == 0) 350 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 351 else { 352 long cwin; 353 354 /* 355 * We are inside of a SACK recovery episode and are 356 * sending new data, having retransmitted all the 357 * data possible in the scoreboard. 358 */ 359 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 360 - off); 361 /* 362 * Don't remove this (len > 0) check ! 363 * We explicitly check for len > 0 here (although it 364 * isn't really necessary), to work around a gcc 365 * optimization issue - to force gcc to compute 366 * len above. Without this check, the computation 367 * of len is bungled by the optimizer. 368 */ 369 if (len > 0) { 370 cwin = tp->snd_cwnd - 371 (tp->snd_nxt - tp->sack_newdata) - 372 sack_bytes_rxmt; 373 if (cwin < 0) 374 cwin = 0; 375 len = lmin(len, cwin); 376 } 377 } 378 } 379 380 /* 381 * Lop off SYN bit if it has already been sent. However, if this 382 * is SYN-SENT state and if segment contains data and if we don't 383 * know that foreign host supports TAO, suppress sending segment. 384 */ 385 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 386 if (tp->t_state != TCPS_SYN_RECEIVED) 387 flags &= ~TH_SYN; 388 off--, len++; 389 } 390 391 /* 392 * Be careful not to send data and/or FIN on SYN segments. 393 * This measure is needed to prevent interoperability problems 394 * with not fully conformant TCP implementations. 395 */ 396 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 397 len = 0; 398 flags &= ~TH_FIN; 399 } 400 401 if (len <= 0) { 402 /* 403 * If FIN has been sent but not acked, 404 * but we haven't been called to retransmit, 405 * len will be < 0. Otherwise, window shrank 406 * after we sent into it. If window shrank to 0, 407 * cancel pending retransmit, pull snd_nxt back 408 * to (closed) window, and set the persist timer 409 * if it isn't already going. If the window didn't 410 * close completely, just wait for an ACK. 411 * 412 * We also do a general check here to ensure that 413 * we will set the persist timer when we have data 414 * to send, but a 0-byte window. This makes sure 415 * the persist timer is set even if the packet 416 * hits one of the "goto send" lines below. 417 */ 418 len = 0; 419 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 420 (off < (int) so->so_snd.sb_cc)) { 421 tcp_timer_activate(tp, TT_REXMT, 0); 422 tp->t_rxtshift = 0; 423 tp->snd_nxt = tp->snd_una; 424 if (!tcp_timer_active(tp, TT_PERSIST)) 425 tcp_setpersist(tp); 426 } 427 } 428 429 /* len will be >= 0 after this point. */ 430 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 431 432 /* 433 * Automatic sizing of send socket buffer. Often the send buffer 434 * size is not optimally adjusted to the actual network conditions 435 * at hand (delay bandwidth product). Setting the buffer size too 436 * small limits throughput on links with high bandwidth and high 437 * delay (eg. trans-continental/oceanic links). Setting the 438 * buffer size too big consumes too much real kernel memory, 439 * especially with many connections on busy servers. 440 * 441 * The criteria to step up the send buffer one notch are: 442 * 1. receive window of remote host is larger than send buffer 443 * (with a fudge factor of 5/4th); 444 * 2. send buffer is filled to 7/8th with data (so we actually 445 * have data to make use of it); 446 * 3. send buffer fill has not hit maximal automatic size; 447 * 4. our send window (slow start and cogestion controlled) is 448 * larger than sent but unacknowledged data in send buffer. 449 * 450 * The remote host receive window scaling factor may limit the 451 * growing of the send buffer before it reaches its allowed 452 * maximum. 453 * 454 * It scales directly with slow start or congestion window 455 * and does at most one step per received ACK. This fast 456 * scaling has the drawback of growing the send buffer beyond 457 * what is strictly necessary to make full use of a given 458 * delay*bandwith product. However testing has shown this not 459 * to be much of an problem. At worst we are trading wasting 460 * of available bandwith (the non-use of it) for wasting some 461 * socket buffer memory. 462 * 463 * TODO: Shrink send buffer during idle periods together 464 * with congestion window. Requires another timer. Has to 465 * wait for upcoming tcp timer rewrite. 466 */ 467 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 468 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 469 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 470 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 471 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 472 if (!sbreserve_locked(&so->so_snd, 473 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 474 V_tcp_autosndbuf_max), so, curthread)) 475 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 476 } 477 } 478 479 /* 480 * Truncate to the maximum segment length or enable TCP Segmentation 481 * Offloading (if supported by hardware) and ensure that FIN is removed 482 * if the length no longer contains the last data byte. 483 * 484 * TSO may only be used if we are in a pure bulk sending state. The 485 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 486 * IP options prevent using TSO. With TSO the TCP header is the same 487 * (except for the sequence number) for all generated packets. This 488 * makes it impossible to transmit any options which vary per generated 489 * segment or packet. 490 * 491 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 492 * removal of FIN (if not already catched here) are handled later after 493 * the exact length of the TCP options are known. 494 */ 495 #ifdef IPSEC 496 /* 497 * Pre-calculate here as we save another lookup into the darknesses 498 * of IPsec that way and can actually decide if TSO is ok. 499 */ 500 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 501 #endif 502 if (len > tp->t_maxseg) { 503 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 504 ((tp->t_flags & TF_SIGNATURE) == 0) && 505 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 506 tp->t_inpcb->inp_options == NULL && 507 tp->t_inpcb->in6p_options == NULL 508 #ifdef IPSEC 509 && ipsec_optlen == 0 510 #endif 511 ) { 512 tso = 1; 513 } else { 514 len = tp->t_maxseg; 515 sendalot = 1; 516 } 517 } 518 519 if (sack_rxmit) { 520 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 521 flags &= ~TH_FIN; 522 } else { 523 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 524 flags &= ~TH_FIN; 525 } 526 527 recwin = sbspace(&so->so_rcv); 528 529 /* 530 * Sender silly window avoidance. We transmit under the following 531 * conditions when len is non-zero: 532 * 533 * - We have a full segment (or more with TSO) 534 * - This is the last buffer in a write()/send() and we are 535 * either idle or running NODELAY 536 * - we've timed out (e.g. persist timer) 537 * - we have more then 1/2 the maximum send window's worth of 538 * data (receiver may be limited the window size) 539 * - we need to retransmit 540 */ 541 if (len) { 542 if (len >= tp->t_maxseg) 543 goto send; 544 /* 545 * NOTE! on localhost connections an 'ack' from the remote 546 * end may occur synchronously with the output and cause 547 * us to flush a buffer queued with moretocome. XXX 548 * 549 * note: the len + off check is almost certainly unnecessary. 550 */ 551 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 552 (idle || (tp->t_flags & TF_NODELAY)) && 553 len + off >= so->so_snd.sb_cc && 554 (tp->t_flags & TF_NOPUSH) == 0) { 555 goto send; 556 } 557 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 558 goto send; 559 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 560 goto send; 561 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 562 goto send; 563 if (sack_rxmit) 564 goto send; 565 } 566 567 /* 568 * Compare available window to amount of window 569 * known to peer (as advertised window less 570 * next expected input). If the difference is at least two 571 * max size segments, or at least 50% of the maximum possible 572 * window, then want to send a window update to peer. 573 * Skip this if the connection is in T/TCP half-open state. 574 * Don't send pure window updates when the peer has closed 575 * the connection and won't ever send more data. 576 */ 577 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 578 !TCPS_HAVERCVDFIN(tp->t_state)) { 579 /* 580 * "adv" is the amount we can increase the window, 581 * taking into account that we are limited by 582 * TCP_MAXWIN << tp->rcv_scale. 583 */ 584 long adv; 585 int oldwin; 586 587 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 588 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 589 oldwin = (tp->rcv_adv - tp->rcv_nxt); 590 adv -= oldwin; 591 } else 592 oldwin = 0; 593 594 /* 595 * If the new window size ends up being the same as the old 596 * size when it is scaled, then don't force a window update. 597 */ 598 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 599 goto dontupdate; 600 if (adv >= (long) (2 * tp->t_maxseg)) 601 goto send; 602 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 603 goto send; 604 } 605 dontupdate: 606 607 /* 608 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 609 * is also a catch-all for the retransmit timer timeout case. 610 */ 611 if (tp->t_flags & TF_ACKNOW) 612 goto send; 613 if ((flags & TH_RST) || 614 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 615 goto send; 616 if (SEQ_GT(tp->snd_up, tp->snd_una)) 617 goto send; 618 /* 619 * If our state indicates that FIN should be sent 620 * and we have not yet done so, then we need to send. 621 */ 622 if (flags & TH_FIN && 623 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 624 goto send; 625 /* 626 * In SACK, it is possible for tcp_output to fail to send a segment 627 * after the retransmission timer has been turned off. Make sure 628 * that the retransmission timer is set. 629 */ 630 if ((tp->t_flags & TF_SACK_PERMIT) && 631 SEQ_GT(tp->snd_max, tp->snd_una) && 632 !tcp_timer_active(tp, TT_REXMT) && 633 !tcp_timer_active(tp, TT_PERSIST)) { 634 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 635 goto just_return; 636 } 637 /* 638 * TCP window updates are not reliable, rather a polling protocol 639 * using ``persist'' packets is used to insure receipt of window 640 * updates. The three ``states'' for the output side are: 641 * idle not doing retransmits or persists 642 * persisting to move a small or zero window 643 * (re)transmitting and thereby not persisting 644 * 645 * tcp_timer_active(tp, TT_PERSIST) 646 * is true when we are in persist state. 647 * (tp->t_flags & TF_FORCEDATA) 648 * is set when we are called to send a persist packet. 649 * tcp_timer_active(tp, TT_REXMT) 650 * is set when we are retransmitting 651 * The output side is idle when both timers are zero. 652 * 653 * If send window is too small, there is data to transmit, and no 654 * retransmit or persist is pending, then go to persist state. 655 * If nothing happens soon, send when timer expires: 656 * if window is nonzero, transmit what we can, 657 * otherwise force out a byte. 658 */ 659 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 660 !tcp_timer_active(tp, TT_PERSIST)) { 661 tp->t_rxtshift = 0; 662 tcp_setpersist(tp); 663 } 664 665 /* 666 * No reason to send a segment, just return. 667 */ 668 just_return: 669 SOCKBUF_UNLOCK(&so->so_snd); 670 return (0); 671 672 send: 673 SOCKBUF_LOCK_ASSERT(&so->so_snd); 674 /* 675 * Before ESTABLISHED, force sending of initial options 676 * unless TCP set not to do any options. 677 * NOTE: we assume that the IP/TCP header plus TCP options 678 * always fit in a single mbuf, leaving room for a maximum 679 * link header, i.e. 680 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 681 */ 682 optlen = 0; 683 #ifdef INET6 684 if (isipv6) 685 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 686 else 687 #endif 688 hdrlen = sizeof (struct tcpiphdr); 689 690 /* 691 * Compute options for segment. 692 * We only have to care about SYN and established connection 693 * segments. Options for SYN-ACK segments are handled in TCP 694 * syncache. 695 */ 696 if ((tp->t_flags & TF_NOOPT) == 0) { 697 to.to_flags = 0; 698 /* Maximum segment size. */ 699 if (flags & TH_SYN) { 700 tp->snd_nxt = tp->iss; 701 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 702 to.to_flags |= TOF_MSS; 703 } 704 /* Window scaling. */ 705 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 706 to.to_wscale = tp->request_r_scale; 707 to.to_flags |= TOF_SCALE; 708 } 709 /* Timestamps. */ 710 if ((tp->t_flags & TF_RCVD_TSTMP) || 711 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 712 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 713 to.to_tsecr = tp->ts_recent; 714 to.to_flags |= TOF_TS; 715 /* Set receive buffer autosizing timestamp. */ 716 if (tp->rfbuf_ts == 0 && 717 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 718 tp->rfbuf_ts = tcp_ts_getticks(); 719 } 720 /* Selective ACK's. */ 721 if (tp->t_flags & TF_SACK_PERMIT) { 722 if (flags & TH_SYN) 723 to.to_flags |= TOF_SACKPERM; 724 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 725 (tp->t_flags & TF_SACK_PERMIT) && 726 tp->rcv_numsacks > 0) { 727 to.to_flags |= TOF_SACK; 728 to.to_nsacks = tp->rcv_numsacks; 729 to.to_sacks = (u_char *)tp->sackblks; 730 } 731 } 732 #ifdef TCP_SIGNATURE 733 /* TCP-MD5 (RFC2385). */ 734 if (tp->t_flags & TF_SIGNATURE) 735 to.to_flags |= TOF_SIGNATURE; 736 #endif /* TCP_SIGNATURE */ 737 738 /* Processing the options. */ 739 hdrlen += optlen = tcp_addoptions(&to, opt); 740 } 741 742 #ifdef INET6 743 if (isipv6) 744 ipoptlen = ip6_optlen(tp->t_inpcb); 745 else 746 #endif 747 if (tp->t_inpcb->inp_options) 748 ipoptlen = tp->t_inpcb->inp_options->m_len - 749 offsetof(struct ipoption, ipopt_list); 750 else 751 ipoptlen = 0; 752 #ifdef IPSEC 753 ipoptlen += ipsec_optlen; 754 #endif 755 756 /* 757 * Adjust data length if insertion of options will 758 * bump the packet length beyond the t_maxopd length. 759 * Clear the FIN bit because we cut off the tail of 760 * the segment. 761 * 762 * When doing TSO limit a burst to TCP_MAXWIN minus the 763 * IP, TCP and Options length to keep ip->ip_len from 764 * overflowing. Prevent the last segment from being 765 * fractional thus making them all equal sized and set 766 * the flag to continue sending. TSO is disabled when 767 * IP options or IPSEC are present. 768 */ 769 if (len + optlen + ipoptlen > tp->t_maxopd) { 770 flags &= ~TH_FIN; 771 if (tso) { 772 if (len > TCP_MAXWIN - hdrlen - optlen) { 773 len = TCP_MAXWIN - hdrlen - optlen; 774 len = len - (len % (tp->t_maxopd - optlen)); 775 sendalot = 1; 776 } else if (tp->t_flags & TF_NEEDFIN) 777 sendalot = 1; 778 } else { 779 len = tp->t_maxopd - optlen - ipoptlen; 780 sendalot = 1; 781 } 782 } 783 784 /*#ifdef DIAGNOSTIC*/ 785 #ifdef INET6 786 if (max_linkhdr + hdrlen > MCLBYTES) 787 #else 788 if (max_linkhdr + hdrlen > MHLEN) 789 #endif 790 panic("tcphdr too big"); 791 /*#endif*/ 792 793 /* 794 * This KASSERT is here to catch edge cases at a well defined place. 795 * Before, those had triggered (random) panic conditions further down. 796 */ 797 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 798 799 /* 800 * Grab a header mbuf, attaching a copy of data to 801 * be transmitted, and initialize the header from 802 * the template for sends on this connection. 803 */ 804 if (len) { 805 struct mbuf *mb; 806 u_int moff; 807 808 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 809 TCPSTAT_INC(tcps_sndprobe); 810 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 811 tp->t_sndrexmitpack++; 812 TCPSTAT_INC(tcps_sndrexmitpack); 813 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 814 } else { 815 TCPSTAT_INC(tcps_sndpack); 816 TCPSTAT_ADD(tcps_sndbyte, len); 817 } 818 #ifdef notyet 819 if ((m = m_copypack(so->so_snd.sb_mb, off, 820 (int)len, max_linkhdr + hdrlen)) == 0) { 821 SOCKBUF_UNLOCK(&so->so_snd); 822 error = ENOBUFS; 823 goto out; 824 } 825 /* 826 * m_copypack left space for our hdr; use it. 827 */ 828 m->m_len += hdrlen; 829 m->m_data -= hdrlen; 830 #else 831 MGETHDR(m, M_DONTWAIT, MT_DATA); 832 if (m == NULL) { 833 SOCKBUF_UNLOCK(&so->so_snd); 834 error = ENOBUFS; 835 goto out; 836 } 837 #ifdef INET6 838 if (MHLEN < hdrlen + max_linkhdr) { 839 MCLGET(m, M_DONTWAIT); 840 if ((m->m_flags & M_EXT) == 0) { 841 SOCKBUF_UNLOCK(&so->so_snd); 842 m_freem(m); 843 error = ENOBUFS; 844 goto out; 845 } 846 } 847 #endif 848 m->m_data += max_linkhdr; 849 m->m_len = hdrlen; 850 851 /* 852 * Start the m_copy functions from the closest mbuf 853 * to the offset in the socket buffer chain. 854 */ 855 mb = sbsndptr(&so->so_snd, off, len, &moff); 856 857 if (len <= MHLEN - hdrlen - max_linkhdr) { 858 m_copydata(mb, moff, (int)len, 859 mtod(m, caddr_t) + hdrlen); 860 m->m_len += len; 861 } else { 862 m->m_next = m_copy(mb, moff, (int)len); 863 if (m->m_next == NULL) { 864 SOCKBUF_UNLOCK(&so->so_snd); 865 (void) m_free(m); 866 error = ENOBUFS; 867 goto out; 868 } 869 } 870 #endif 871 /* 872 * If we're sending everything we've got, set PUSH. 873 * (This will keep happy those implementations which only 874 * give data to the user when a buffer fills or 875 * a PUSH comes in.) 876 */ 877 if (off + len == so->so_snd.sb_cc) 878 flags |= TH_PUSH; 879 SOCKBUF_UNLOCK(&so->so_snd); 880 } else { 881 SOCKBUF_UNLOCK(&so->so_snd); 882 if (tp->t_flags & TF_ACKNOW) 883 TCPSTAT_INC(tcps_sndacks); 884 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 885 TCPSTAT_INC(tcps_sndctrl); 886 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 887 TCPSTAT_INC(tcps_sndurg); 888 else 889 TCPSTAT_INC(tcps_sndwinup); 890 891 MGETHDR(m, M_DONTWAIT, MT_DATA); 892 if (m == NULL) { 893 error = ENOBUFS; 894 goto out; 895 } 896 #ifdef INET6 897 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 898 MHLEN >= hdrlen) { 899 MH_ALIGN(m, hdrlen); 900 } else 901 #endif 902 m->m_data += max_linkhdr; 903 m->m_len = hdrlen; 904 } 905 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 906 m->m_pkthdr.rcvif = (struct ifnet *)0; 907 #ifdef MAC 908 mac_inpcb_create_mbuf(tp->t_inpcb, m); 909 #endif 910 #ifdef INET6 911 if (isipv6) { 912 ip6 = mtod(m, struct ip6_hdr *); 913 th = (struct tcphdr *)(ip6 + 1); 914 tcpip_fillheaders(tp->t_inpcb, ip6, th); 915 } else 916 #endif /* INET6 */ 917 { 918 ip = mtod(m, struct ip *); 919 ipov = (struct ipovly *)ip; 920 th = (struct tcphdr *)(ip + 1); 921 tcpip_fillheaders(tp->t_inpcb, ip, th); 922 } 923 924 /* 925 * Fill in fields, remembering maximum advertised 926 * window for use in delaying messages about window sizes. 927 * If resending a FIN, be sure not to use a new sequence number. 928 */ 929 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 930 tp->snd_nxt == tp->snd_max) 931 tp->snd_nxt--; 932 /* 933 * If we are starting a connection, send ECN setup 934 * SYN packet. If we are on a retransmit, we may 935 * resend those bits a number of times as per 936 * RFC 3168. 937 */ 938 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 939 if (tp->t_rxtshift >= 1) { 940 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 941 flags |= TH_ECE|TH_CWR; 942 } else 943 flags |= TH_ECE|TH_CWR; 944 } 945 946 if (tp->t_state == TCPS_ESTABLISHED && 947 (tp->t_flags & TF_ECN_PERMIT)) { 948 /* 949 * If the peer has ECN, mark data packets with 950 * ECN capable transmission (ECT). 951 * Ignore pure ack packets, retransmissions and window probes. 952 */ 953 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 954 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 955 #ifdef INET6 956 if (isipv6) 957 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 958 else 959 #endif 960 ip->ip_tos |= IPTOS_ECN_ECT0; 961 TCPSTAT_INC(tcps_ecn_ect0); 962 } 963 964 /* 965 * Reply with proper ECN notifications. 966 */ 967 if (tp->t_flags & TF_ECN_SND_CWR) { 968 flags |= TH_CWR; 969 tp->t_flags &= ~TF_ECN_SND_CWR; 970 } 971 if (tp->t_flags & TF_ECN_SND_ECE) 972 flags |= TH_ECE; 973 } 974 975 /* 976 * If we are doing retransmissions, then snd_nxt will 977 * not reflect the first unsent octet. For ACK only 978 * packets, we do not want the sequence number of the 979 * retransmitted packet, we want the sequence number 980 * of the next unsent octet. So, if there is no data 981 * (and no SYN or FIN), use snd_max instead of snd_nxt 982 * when filling in ti_seq. But if we are in persist 983 * state, snd_max might reflect one byte beyond the 984 * right edge of the window, so use snd_nxt in that 985 * case, since we know we aren't doing a retransmission. 986 * (retransmit and persist are mutually exclusive...) 987 */ 988 if (sack_rxmit == 0) { 989 if (len || (flags & (TH_SYN|TH_FIN)) || 990 tcp_timer_active(tp, TT_PERSIST)) 991 th->th_seq = htonl(tp->snd_nxt); 992 else 993 th->th_seq = htonl(tp->snd_max); 994 } else { 995 th->th_seq = htonl(p->rxmit); 996 p->rxmit += len; 997 tp->sackhint.sack_bytes_rexmit += len; 998 } 999 th->th_ack = htonl(tp->rcv_nxt); 1000 if (optlen) { 1001 bcopy(opt, th + 1, optlen); 1002 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1003 } 1004 th->th_flags = flags; 1005 /* 1006 * Calculate receive window. Don't shrink window, 1007 * but avoid silly window syndrome. 1008 */ 1009 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1010 recwin < (long)tp->t_maxseg) 1011 recwin = 0; 1012 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1013 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1014 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1015 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1016 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1017 1018 /* 1019 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1020 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1021 * case is handled in syncache. 1022 */ 1023 if (flags & TH_SYN) 1024 th->th_win = htons((u_short) 1025 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1026 else 1027 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1028 1029 /* 1030 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1031 * a 0 window. This may cause the remote transmitter to stall. This 1032 * flag tells soreceive() to disable delayed acknowledgements when 1033 * draining the buffer. This can occur if the receiver is attempting 1034 * to read more data than can be buffered prior to transmitting on 1035 * the connection. 1036 */ 1037 if (th->th_win == 0) { 1038 tp->t_sndzerowin++; 1039 tp->t_flags |= TF_RXWIN0SENT; 1040 } else 1041 tp->t_flags &= ~TF_RXWIN0SENT; 1042 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1043 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1044 th->th_flags |= TH_URG; 1045 } else 1046 /* 1047 * If no urgent pointer to send, then we pull 1048 * the urgent pointer to the left edge of the send window 1049 * so that it doesn't drift into the send window on sequence 1050 * number wraparound. 1051 */ 1052 tp->snd_up = tp->snd_una; /* drag it along */ 1053 1054 #ifdef TCP_SIGNATURE 1055 if (tp->t_flags & TF_SIGNATURE) { 1056 int sigoff = to.to_signature - opt; 1057 tcp_signature_compute(m, 0, len, optlen, 1058 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1059 } 1060 #endif 1061 1062 /* 1063 * Put TCP length in extended header, and then 1064 * checksum extended header and data. 1065 */ 1066 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1067 #ifdef INET6 1068 if (isipv6) 1069 /* 1070 * ip6_plen is not need to be filled now, and will be filled 1071 * in ip6_output. 1072 */ 1073 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1074 sizeof(struct tcphdr) + optlen + len); 1075 else 1076 #endif /* INET6 */ 1077 { 1078 m->m_pkthdr.csum_flags = CSUM_TCP; 1079 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1080 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1081 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1082 1083 /* IP version must be set here for ipv4/ipv6 checking later */ 1084 KASSERT(ip->ip_v == IPVERSION, 1085 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1086 } 1087 1088 /* 1089 * Enable TSO and specify the size of the segments. 1090 * The TCP pseudo header checksum is always provided. 1091 * XXX: Fixme: This is currently not the case for IPv6. 1092 */ 1093 if (tso) { 1094 KASSERT(len > tp->t_maxopd - optlen, 1095 ("%s: len <= tso_segsz", __func__)); 1096 m->m_pkthdr.csum_flags |= CSUM_TSO; 1097 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1098 } 1099 1100 /* 1101 * In transmit state, time the transmission and arrange for 1102 * the retransmit. In persist state, just set snd_max. 1103 */ 1104 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1105 !tcp_timer_active(tp, TT_PERSIST)) { 1106 tcp_seq startseq = tp->snd_nxt; 1107 1108 /* 1109 * Advance snd_nxt over sequence space of this segment. 1110 */ 1111 if (flags & (TH_SYN|TH_FIN)) { 1112 if (flags & TH_SYN) 1113 tp->snd_nxt++; 1114 if (flags & TH_FIN) { 1115 tp->snd_nxt++; 1116 tp->t_flags |= TF_SENTFIN; 1117 } 1118 } 1119 if (sack_rxmit) 1120 goto timer; 1121 tp->snd_nxt += len; 1122 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1123 tp->snd_max = tp->snd_nxt; 1124 /* 1125 * Time this transmission if not a retransmission and 1126 * not currently timing anything. 1127 */ 1128 if (tp->t_rtttime == 0) { 1129 tp->t_rtttime = ticks; 1130 tp->t_rtseq = startseq; 1131 TCPSTAT_INC(tcps_segstimed); 1132 } 1133 } 1134 1135 /* 1136 * Set retransmit timer if not currently set, 1137 * and not doing a pure ack or a keep-alive probe. 1138 * Initial value for retransmit timer is smoothed 1139 * round-trip time + 2 * round-trip time variance. 1140 * Initialize shift counter which is used for backoff 1141 * of retransmit time. 1142 */ 1143 timer: 1144 if (!tcp_timer_active(tp, TT_REXMT) && 1145 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1146 (tp->snd_nxt != tp->snd_una))) { 1147 if (tcp_timer_active(tp, TT_PERSIST)) { 1148 tcp_timer_activate(tp, TT_PERSIST, 0); 1149 tp->t_rxtshift = 0; 1150 } 1151 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1152 } 1153 } else { 1154 /* 1155 * Persist case, update snd_max but since we are in 1156 * persist mode (no window) we do not update snd_nxt. 1157 */ 1158 int xlen = len; 1159 if (flags & TH_SYN) 1160 ++xlen; 1161 if (flags & TH_FIN) { 1162 ++xlen; 1163 tp->t_flags |= TF_SENTFIN; 1164 } 1165 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1166 tp->snd_max = tp->snd_nxt + len; 1167 } 1168 1169 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1170 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1171 1172 #ifdef TCPDEBUG 1173 /* 1174 * Trace. 1175 */ 1176 if (so->so_options & SO_DEBUG) { 1177 u_short save = 0; 1178 #ifdef INET6 1179 if (!isipv6) 1180 #endif 1181 { 1182 save = ipov->ih_len; 1183 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1184 } 1185 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1186 #ifdef INET6 1187 if (!isipv6) 1188 #endif 1189 ipov->ih_len = save; 1190 } 1191 #endif 1192 1193 /* 1194 * Fill in IP length and desired time to live and 1195 * send to IP level. There should be a better way 1196 * to handle ttl and tos; we could keep them in 1197 * the template, but need a way to checksum without them. 1198 */ 1199 /* 1200 * m->m_pkthdr.len should have been set before cksum calcuration, 1201 * because in6_cksum() need it. 1202 */ 1203 #ifdef INET6 1204 if (isipv6) { 1205 /* 1206 * we separately set hoplimit for every segment, since the 1207 * user might want to change the value via setsockopt. 1208 * Also, desired default hop limit might be changed via 1209 * Neighbor Discovery. 1210 */ 1211 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1212 1213 /* TODO: IPv6 IP6TOS_ECT bit on */ 1214 error = ip6_output(m, 1215 tp->t_inpcb->in6p_outputopts, NULL, 1216 ((so->so_options & SO_DONTROUTE) ? 1217 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1218 } else 1219 #endif /* INET6 */ 1220 { 1221 ip->ip_len = m->m_pkthdr.len; 1222 #ifdef INET6 1223 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1224 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1225 #endif /* INET6 */ 1226 /* 1227 * If we do path MTU discovery, then we set DF on every packet. 1228 * This might not be the best thing to do according to RFC3390 1229 * Section 2. However the tcp hostcache migitates the problem 1230 * so it affects only the first tcp connection with a host. 1231 * 1232 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1233 */ 1234 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1235 ip->ip_off |= IP_DF; 1236 1237 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1238 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1239 tp->t_inpcb); 1240 } 1241 if (error) { 1242 1243 /* 1244 * We know that the packet was lost, so back out the 1245 * sequence number advance, if any. 1246 * 1247 * If the error is EPERM the packet got blocked by the 1248 * local firewall. Normally we should terminate the 1249 * connection but the blocking may have been spurious 1250 * due to a firewall reconfiguration cycle. So we treat 1251 * it like a packet loss and let the retransmit timer and 1252 * timeouts do their work over time. 1253 * XXX: It is a POLA question whether calling tcp_drop right 1254 * away would be the really correct behavior instead. 1255 */ 1256 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1257 !tcp_timer_active(tp, TT_PERSIST)) && 1258 ((flags & TH_SYN) == 0) && 1259 (error != EPERM)) { 1260 if (sack_rxmit) { 1261 p->rxmit -= len; 1262 tp->sackhint.sack_bytes_rexmit -= len; 1263 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1264 ("sackhint bytes rtx >= 0")); 1265 } else 1266 tp->snd_nxt -= len; 1267 } 1268 out: 1269 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1270 switch (error) { 1271 case EPERM: 1272 tp->t_softerror = error; 1273 return (error); 1274 case ENOBUFS: 1275 if (!tcp_timer_active(tp, TT_REXMT) && 1276 !tcp_timer_active(tp, TT_PERSIST)) 1277 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1278 tp->snd_cwnd = tp->t_maxseg; 1279 return (0); 1280 case EMSGSIZE: 1281 /* 1282 * For some reason the interface we used initially 1283 * to send segments changed to another or lowered 1284 * its MTU. 1285 * 1286 * tcp_mtudisc() will find out the new MTU and as 1287 * its last action, initiate retransmission, so it 1288 * is important to not do so here. 1289 * 1290 * If TSO was active we either got an interface 1291 * without TSO capabilits or TSO was turned off. 1292 * Disable it for this connection as too and 1293 * immediatly retry with MSS sized segments generated 1294 * by this function. 1295 */ 1296 if (tso) 1297 tp->t_flags &= ~TF_TSO; 1298 tcp_mtudisc(tp->t_inpcb, -1); 1299 return (0); 1300 case EHOSTDOWN: 1301 case EHOSTUNREACH: 1302 case ENETDOWN: 1303 case ENETUNREACH: 1304 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1305 tp->t_softerror = error; 1306 return (0); 1307 } 1308 /* FALLTHROUGH */ 1309 default: 1310 return (error); 1311 } 1312 } 1313 TCPSTAT_INC(tcps_sndtotal); 1314 1315 /* 1316 * Data sent (as far as we can tell). 1317 * If this advertises a larger window than any other segment, 1318 * then remember the size of the advertised window. 1319 * Any pending ACK has now been sent. 1320 */ 1321 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1322 tp->rcv_adv = tp->rcv_nxt + recwin; 1323 tp->last_ack_sent = tp->rcv_nxt; 1324 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1325 if (tcp_timer_active(tp, TT_DELACK)) 1326 tcp_timer_activate(tp, TT_DELACK, 0); 1327 #if 0 1328 /* 1329 * This completely breaks TCP if newreno is turned on. What happens 1330 * is that if delayed-acks are turned on on the receiver, this code 1331 * on the transmitter effectively destroys the TCP window, forcing 1332 * it to four packets (1.5Kx4 = 6K window). 1333 */ 1334 if (sendalot && --maxburst) 1335 goto again; 1336 #endif 1337 if (sendalot) 1338 goto again; 1339 return (0); 1340 } 1341 1342 void 1343 tcp_setpersist(struct tcpcb *tp) 1344 { 1345 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1346 int tt; 1347 1348 tp->t_flags &= ~TF_PREVVALID; 1349 if (tcp_timer_active(tp, TT_REXMT)) 1350 panic("tcp_setpersist: retransmit pending"); 1351 /* 1352 * Start/restart persistance timer. 1353 */ 1354 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1355 TCPTV_PERSMIN, TCPTV_PERSMAX); 1356 tcp_timer_activate(tp, TT_PERSIST, tt); 1357 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1358 tp->t_rxtshift++; 1359 } 1360 1361 /* 1362 * Insert TCP options according to the supplied parameters to the place 1363 * optp in a consistent way. Can handle unaligned destinations. 1364 * 1365 * The order of the option processing is crucial for optimal packing and 1366 * alignment for the scarce option space. 1367 * 1368 * The optimal order for a SYN/SYN-ACK segment is: 1369 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1370 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1371 * 1372 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1373 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1374 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1375 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1376 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1377 */ 1378 int 1379 tcp_addoptions(struct tcpopt *to, u_char *optp) 1380 { 1381 u_int mask, optlen = 0; 1382 1383 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1384 if ((to->to_flags & mask) != mask) 1385 continue; 1386 if (optlen == TCP_MAXOLEN) 1387 break; 1388 switch (to->to_flags & mask) { 1389 case TOF_MSS: 1390 while (optlen % 4) { 1391 optlen += TCPOLEN_NOP; 1392 *optp++ = TCPOPT_NOP; 1393 } 1394 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1395 continue; 1396 optlen += TCPOLEN_MAXSEG; 1397 *optp++ = TCPOPT_MAXSEG; 1398 *optp++ = TCPOLEN_MAXSEG; 1399 to->to_mss = htons(to->to_mss); 1400 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1401 optp += sizeof(to->to_mss); 1402 break; 1403 case TOF_SCALE: 1404 while (!optlen || optlen % 2 != 1) { 1405 optlen += TCPOLEN_NOP; 1406 *optp++ = TCPOPT_NOP; 1407 } 1408 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1409 continue; 1410 optlen += TCPOLEN_WINDOW; 1411 *optp++ = TCPOPT_WINDOW; 1412 *optp++ = TCPOLEN_WINDOW; 1413 *optp++ = to->to_wscale; 1414 break; 1415 case TOF_SACKPERM: 1416 while (optlen % 2) { 1417 optlen += TCPOLEN_NOP; 1418 *optp++ = TCPOPT_NOP; 1419 } 1420 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1421 continue; 1422 optlen += TCPOLEN_SACK_PERMITTED; 1423 *optp++ = TCPOPT_SACK_PERMITTED; 1424 *optp++ = TCPOLEN_SACK_PERMITTED; 1425 break; 1426 case TOF_TS: 1427 while (!optlen || optlen % 4 != 2) { 1428 optlen += TCPOLEN_NOP; 1429 *optp++ = TCPOPT_NOP; 1430 } 1431 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1432 continue; 1433 optlen += TCPOLEN_TIMESTAMP; 1434 *optp++ = TCPOPT_TIMESTAMP; 1435 *optp++ = TCPOLEN_TIMESTAMP; 1436 to->to_tsval = htonl(to->to_tsval); 1437 to->to_tsecr = htonl(to->to_tsecr); 1438 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1439 optp += sizeof(to->to_tsval); 1440 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1441 optp += sizeof(to->to_tsecr); 1442 break; 1443 case TOF_SIGNATURE: 1444 { 1445 int siglen = TCPOLEN_SIGNATURE - 2; 1446 1447 while (!optlen || optlen % 4 != 2) { 1448 optlen += TCPOLEN_NOP; 1449 *optp++ = TCPOPT_NOP; 1450 } 1451 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1452 continue; 1453 optlen += TCPOLEN_SIGNATURE; 1454 *optp++ = TCPOPT_SIGNATURE; 1455 *optp++ = TCPOLEN_SIGNATURE; 1456 to->to_signature = optp; 1457 while (siglen--) 1458 *optp++ = 0; 1459 break; 1460 } 1461 case TOF_SACK: 1462 { 1463 int sackblks = 0; 1464 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1465 tcp_seq sack_seq; 1466 1467 while (!optlen || optlen % 4 != 2) { 1468 optlen += TCPOLEN_NOP; 1469 *optp++ = TCPOPT_NOP; 1470 } 1471 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1472 continue; 1473 optlen += TCPOLEN_SACKHDR; 1474 *optp++ = TCPOPT_SACK; 1475 sackblks = min(to->to_nsacks, 1476 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1477 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1478 while (sackblks--) { 1479 sack_seq = htonl(sack->start); 1480 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1481 optp += sizeof(sack_seq); 1482 sack_seq = htonl(sack->end); 1483 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1484 optp += sizeof(sack_seq); 1485 optlen += TCPOLEN_SACK; 1486 sack++; 1487 } 1488 TCPSTAT_INC(tcps_sack_send_blocks); 1489 break; 1490 } 1491 default: 1492 panic("%s: unknown TCP option type", __func__); 1493 break; 1494 } 1495 } 1496 1497 /* Terminate and pad TCP options to a 4 byte boundary. */ 1498 if (optlen % 4) { 1499 optlen += TCPOLEN_EOL; 1500 *optp++ = TCPOPT_EOL; 1501 } 1502 /* 1503 * According to RFC 793 (STD0007): 1504 * "The content of the header beyond the End-of-Option option 1505 * must be header padding (i.e., zero)." 1506 * and later: "The padding is composed of zeros." 1507 */ 1508 while (optlen % 4) { 1509 optlen += TCPOLEN_PAD; 1510 *optp++ = TCPOPT_PAD; 1511 } 1512 1513 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1514 return (optlen); 1515 }
Cache object: b12d8c39f1a538bd651aec4a16918896
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