1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_mac.h" 39 #include "opt_tcpdebug.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/domain.h> 44 #include <sys/kernel.h> 45 #include <sys/lock.h> 46 #include <sys/mbuf.h> 47 #include <sys/mutex.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/sysctl.h> 52 #include <sys/vimage.h> 53 54 #include <net/route.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 int path_mtu_discovery = 1; 91 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 92 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 93 94 int ss_fltsz = 1; 95 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 96 &ss_fltsz, 1, "Slow start flight size"); 97 98 int ss_fltsz_local = 4; 99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 100 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 101 102 int tcp_do_newreno = 1; 103 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 104 &tcp_do_newreno, 0, "Enable NewReno Algorithms"); 105 106 int tcp_do_tso = 1; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 108 &tcp_do_tso, 0, "Enable TCP Segmentation Offload"); 109 110 int tcp_do_autosndbuf = 1; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 112 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 113 114 int tcp_autosndbuf_inc = 8*1024; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 116 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 117 118 int tcp_autosndbuf_max = 256*1024; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 120 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 121 122 123 /* 124 * Tcp output routine: figure out what should be sent and send it. 125 */ 126 int 127 tcp_output(struct tcpcb *tp) 128 { 129 struct socket *so = tp->t_inpcb->inp_socket; 130 long len, recwin, sendwin; 131 int off, flags, error; 132 struct mbuf *m; 133 struct ip *ip = NULL; 134 struct ipovly *ipov = NULL; 135 struct tcphdr *th; 136 u_char opt[TCP_MAXOLEN]; 137 unsigned ipoptlen, optlen, hdrlen; 138 #ifdef IPSEC 139 unsigned ipsec_optlen = 0; 140 #endif 141 int idle, sendalot; 142 int sack_rxmit, sack_bytes_rxmt; 143 struct sackhole *p; 144 int tso = 0; 145 struct tcpopt to; 146 #if 0 147 int maxburst = TCP_MAXBURST; 148 #endif 149 #ifdef INET6 150 struct ip6_hdr *ip6 = NULL; 151 int isipv6; 152 153 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 154 #endif 155 156 INP_WLOCK_ASSERT(tp->t_inpcb); 157 158 /* 159 * Determine length of data that should be transmitted, 160 * and flags that will be used. 161 * If there is some data or critical controls (SYN, RST) 162 * to send, then transmit; otherwise, investigate further. 163 */ 164 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 165 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 166 /* 167 * We have been idle for "a while" and no acks are 168 * expected to clock out any data we send -- 169 * slow start to get ack "clock" running again. 170 * 171 * Set the slow-start flight size depending on whether 172 * this is a local network or not. 173 */ 174 int ss = V_ss_fltsz; 175 #ifdef INET6 176 if (isipv6) { 177 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 178 ss = V_ss_fltsz_local; 179 } else 180 #endif /* INET6 */ 181 if (in_localaddr(tp->t_inpcb->inp_faddr)) 182 ss = V_ss_fltsz_local; 183 tp->snd_cwnd = tp->t_maxseg * ss; 184 } 185 tp->t_flags &= ~TF_LASTIDLE; 186 if (idle) { 187 if (tp->t_flags & TF_MORETOCOME) { 188 tp->t_flags |= TF_LASTIDLE; 189 idle = 0; 190 } 191 } 192 again: 193 /* 194 * If we've recently taken a timeout, snd_max will be greater than 195 * snd_nxt. There may be SACK information that allows us to avoid 196 * resending already delivered data. Adjust snd_nxt accordingly. 197 */ 198 if ((tp->t_flags & TF_SACK_PERMIT) && 199 SEQ_LT(tp->snd_nxt, tp->snd_max)) 200 tcp_sack_adjust(tp); 201 sendalot = 0; 202 off = tp->snd_nxt - tp->snd_una; 203 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 204 sendwin = min(sendwin, tp->snd_bwnd); 205 206 flags = tcp_outflags[tp->t_state]; 207 /* 208 * Send any SACK-generated retransmissions. If we're explicitly trying 209 * to send out new data (when sendalot is 1), bypass this function. 210 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 211 * we're replacing a (future) new transmission with a retransmission 212 * now, and we previously incremented snd_cwnd in tcp_input(). 213 */ 214 /* 215 * Still in sack recovery , reset rxmit flag to zero. 216 */ 217 sack_rxmit = 0; 218 sack_bytes_rxmt = 0; 219 len = 0; 220 p = NULL; 221 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 222 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 223 long cwin; 224 225 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 226 if (cwin < 0) 227 cwin = 0; 228 /* Do not retransmit SACK segments beyond snd_recover */ 229 if (SEQ_GT(p->end, tp->snd_recover)) { 230 /* 231 * (At least) part of sack hole extends beyond 232 * snd_recover. Check to see if we can rexmit data 233 * for this hole. 234 */ 235 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 236 /* 237 * Can't rexmit any more data for this hole. 238 * That data will be rexmitted in the next 239 * sack recovery episode, when snd_recover 240 * moves past p->rxmit. 241 */ 242 p = NULL; 243 goto after_sack_rexmit; 244 } else 245 /* Can rexmit part of the current hole */ 246 len = ((long)ulmin(cwin, 247 tp->snd_recover - p->rxmit)); 248 } else 249 len = ((long)ulmin(cwin, p->end - p->rxmit)); 250 off = p->rxmit - tp->snd_una; 251 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 252 __func__, off)); 253 if (len > 0) { 254 sack_rxmit = 1; 255 sendalot = 1; 256 V_tcpstat.tcps_sack_rexmits++; 257 V_tcpstat.tcps_sack_rexmit_bytes += 258 min(len, tp->t_maxseg); 259 } 260 } 261 after_sack_rexmit: 262 /* 263 * Get standard flags, and add SYN or FIN if requested by 'hidden' 264 * state flags. 265 */ 266 if (tp->t_flags & TF_NEEDFIN) 267 flags |= TH_FIN; 268 if (tp->t_flags & TF_NEEDSYN) 269 flags |= TH_SYN; 270 271 SOCKBUF_LOCK(&so->so_snd); 272 /* 273 * If in persist timeout with window of 0, send 1 byte. 274 * Otherwise, if window is small but nonzero 275 * and timer expired, we will send what we can 276 * and go to transmit state. 277 */ 278 if (tp->t_flags & TF_FORCEDATA) { 279 if (sendwin == 0) { 280 /* 281 * If we still have some data to send, then 282 * clear the FIN bit. Usually this would 283 * happen below when it realizes that we 284 * aren't sending all the data. However, 285 * if we have exactly 1 byte of unsent data, 286 * then it won't clear the FIN bit below, 287 * and if we are in persist state, we wind 288 * up sending the packet without recording 289 * that we sent the FIN bit. 290 * 291 * We can't just blindly clear the FIN bit, 292 * because if we don't have any more data 293 * to send then the probe will be the FIN 294 * itself. 295 */ 296 if (off < so->so_snd.sb_cc) 297 flags &= ~TH_FIN; 298 sendwin = 1; 299 } else { 300 tcp_timer_activate(tp, TT_PERSIST, 0); 301 tp->t_rxtshift = 0; 302 } 303 } 304 305 /* 306 * If snd_nxt == snd_max and we have transmitted a FIN, the 307 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 308 * a negative length. This can also occur when TCP opens up 309 * its congestion window while receiving additional duplicate 310 * acks after fast-retransmit because TCP will reset snd_nxt 311 * to snd_max after the fast-retransmit. 312 * 313 * In the normal retransmit-FIN-only case, however, snd_nxt will 314 * be set to snd_una, the offset will be 0, and the length may 315 * wind up 0. 316 * 317 * If sack_rxmit is true we are retransmitting from the scoreboard 318 * in which case len is already set. 319 */ 320 if (sack_rxmit == 0) { 321 if (sack_bytes_rxmt == 0) 322 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 323 else { 324 long cwin; 325 326 /* 327 * We are inside of a SACK recovery episode and are 328 * sending new data, having retransmitted all the 329 * data possible in the scoreboard. 330 */ 331 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 332 - off); 333 /* 334 * Don't remove this (len > 0) check ! 335 * We explicitly check for len > 0 here (although it 336 * isn't really necessary), to work around a gcc 337 * optimization issue - to force gcc to compute 338 * len above. Without this check, the computation 339 * of len is bungled by the optimizer. 340 */ 341 if (len > 0) { 342 cwin = tp->snd_cwnd - 343 (tp->snd_nxt - tp->sack_newdata) - 344 sack_bytes_rxmt; 345 if (cwin < 0) 346 cwin = 0; 347 len = lmin(len, cwin); 348 } 349 } 350 } 351 352 /* 353 * Lop off SYN bit if it has already been sent. However, if this 354 * is SYN-SENT state and if segment contains data and if we don't 355 * know that foreign host supports TAO, suppress sending segment. 356 */ 357 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 358 if (tp->t_state != TCPS_SYN_RECEIVED) 359 flags &= ~TH_SYN; 360 off--, len++; 361 } 362 363 /* 364 * Be careful not to send data and/or FIN on SYN segments. 365 * This measure is needed to prevent interoperability problems 366 * with not fully conformant TCP implementations. 367 */ 368 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 369 len = 0; 370 flags &= ~TH_FIN; 371 } 372 373 if (len < 0) { 374 /* 375 * If FIN has been sent but not acked, 376 * but we haven't been called to retransmit, 377 * len will be < 0. Otherwise, window shrank 378 * after we sent into it. If window shrank to 0, 379 * cancel pending retransmit, pull snd_nxt back 380 * to (closed) window, and set the persist timer 381 * if it isn't already going. If the window didn't 382 * close completely, just wait for an ACK. 383 */ 384 len = 0; 385 if (sendwin == 0) { 386 tcp_timer_activate(tp, TT_REXMT, 0); 387 tp->t_rxtshift = 0; 388 tp->snd_nxt = tp->snd_una; 389 if (!tcp_timer_active(tp, TT_PERSIST)) 390 tcp_setpersist(tp); 391 } 392 } 393 394 /* len will be >= 0 after this point. */ 395 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 396 397 /* 398 * Automatic sizing of send socket buffer. Often the send buffer 399 * size is not optimally adjusted to the actual network conditions 400 * at hand (delay bandwidth product). Setting the buffer size too 401 * small limits throughput on links with high bandwidth and high 402 * delay (eg. trans-continental/oceanic links). Setting the 403 * buffer size too big consumes too much real kernel memory, 404 * especially with many connections on busy servers. 405 * 406 * The criteria to step up the send buffer one notch are: 407 * 1. receive window of remote host is larger than send buffer 408 * (with a fudge factor of 5/4th); 409 * 2. send buffer is filled to 7/8th with data (so we actually 410 * have data to make use of it); 411 * 3. send buffer fill has not hit maximal automatic size; 412 * 4. our send window (slow start and cogestion controlled) is 413 * larger than sent but unacknowledged data in send buffer. 414 * 415 * The remote host receive window scaling factor may limit the 416 * growing of the send buffer before it reaches its allowed 417 * maximum. 418 * 419 * It scales directly with slow start or congestion window 420 * and does at most one step per received ACK. This fast 421 * scaling has the drawback of growing the send buffer beyond 422 * what is strictly necessary to make full use of a given 423 * delay*bandwith product. However testing has shown this not 424 * to be much of an problem. At worst we are trading wasting 425 * of available bandwith (the non-use of it) for wasting some 426 * socket buffer memory. 427 * 428 * TODO: Shrink send buffer during idle periods together 429 * with congestion window. Requires another timer. Has to 430 * wait for upcoming tcp timer rewrite. 431 */ 432 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 433 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 434 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 435 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 436 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 437 if (!sbreserve_locked(&so->so_snd, 438 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 439 V_tcp_autosndbuf_max), so, curthread)) 440 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 441 } 442 } 443 444 /* 445 * Truncate to the maximum segment length or enable TCP Segmentation 446 * Offloading (if supported by hardware) and ensure that FIN is removed 447 * if the length no longer contains the last data byte. 448 * 449 * TSO may only be used if we are in a pure bulk sending state. The 450 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 451 * IP options prevent using TSO. With TSO the TCP header is the same 452 * (except for the sequence number) for all generated packets. This 453 * makes it impossible to transmit any options which vary per generated 454 * segment or packet. 455 * 456 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 457 * removal of FIN (if not already catched here) are handled later after 458 * the exact length of the TCP options are known. 459 */ 460 #ifdef IPSEC 461 /* 462 * Pre-calculate here as we save another lookup into the darknesses 463 * of IPsec that way and can actually decide if TSO is ok. 464 */ 465 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 466 #endif 467 if (len > tp->t_maxseg) { 468 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 469 ((tp->t_flags & TF_SIGNATURE) == 0) && 470 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 471 tp->t_inpcb->inp_options == NULL && 472 tp->t_inpcb->in6p_options == NULL 473 #ifdef IPSEC 474 && ipsec_optlen == 0 475 #endif 476 ) { 477 tso = 1; 478 } else { 479 len = tp->t_maxseg; 480 sendalot = 1; 481 tso = 0; 482 } 483 } 484 if (sack_rxmit) { 485 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 486 flags &= ~TH_FIN; 487 } else { 488 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 489 flags &= ~TH_FIN; 490 } 491 492 recwin = sbspace(&so->so_rcv); 493 494 /* 495 * Sender silly window avoidance. We transmit under the following 496 * conditions when len is non-zero: 497 * 498 * - We have a full segment (or more with TSO) 499 * - This is the last buffer in a write()/send() and we are 500 * either idle or running NODELAY 501 * - we've timed out (e.g. persist timer) 502 * - we have more then 1/2 the maximum send window's worth of 503 * data (receiver may be limited the window size) 504 * - we need to retransmit 505 */ 506 if (len) { 507 if (len >= tp->t_maxseg) 508 goto send; 509 /* 510 * NOTE! on localhost connections an 'ack' from the remote 511 * end may occur synchronously with the output and cause 512 * us to flush a buffer queued with moretocome. XXX 513 * 514 * note: the len + off check is almost certainly unnecessary. 515 */ 516 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 517 (idle || (tp->t_flags & TF_NODELAY)) && 518 len + off >= so->so_snd.sb_cc && 519 (tp->t_flags & TF_NOPUSH) == 0) { 520 goto send; 521 } 522 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 523 goto send; 524 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 525 goto send; 526 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 527 goto send; 528 if (sack_rxmit) 529 goto send; 530 } 531 532 /* 533 * Compare available window to amount of window 534 * known to peer (as advertised window less 535 * next expected input). If the difference is at least two 536 * max size segments, or at least 50% of the maximum possible 537 * window, then want to send a window update to peer. 538 * Skip this if the connection is in T/TCP half-open state. 539 * Don't send pure window updates when the peer has closed 540 * the connection and won't ever send more data. 541 */ 542 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 543 !TCPS_HAVERCVDFIN(tp->t_state)) { 544 /* 545 * "adv" is the amount we can increase the window, 546 * taking into account that we are limited by 547 * TCP_MAXWIN << tp->rcv_scale. 548 */ 549 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 550 (tp->rcv_adv - tp->rcv_nxt); 551 552 if (adv >= (long) (2 * tp->t_maxseg)) 553 goto send; 554 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 555 goto send; 556 } 557 558 /* 559 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 560 * is also a catch-all for the retransmit timer timeout case. 561 */ 562 if (tp->t_flags & TF_ACKNOW) 563 goto send; 564 if ((flags & TH_RST) || 565 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 566 goto send; 567 if (SEQ_GT(tp->snd_up, tp->snd_una)) 568 goto send; 569 /* 570 * If our state indicates that FIN should be sent 571 * and we have not yet done so, then we need to send. 572 */ 573 if (flags & TH_FIN && 574 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 575 goto send; 576 /* 577 * In SACK, it is possible for tcp_output to fail to send a segment 578 * after the retransmission timer has been turned off. Make sure 579 * that the retransmission timer is set. 580 */ 581 if ((tp->t_flags & TF_SACK_PERMIT) && 582 SEQ_GT(tp->snd_max, tp->snd_una) && 583 !tcp_timer_active(tp, TT_REXMT) && 584 !tcp_timer_active(tp, TT_PERSIST)) { 585 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 586 goto just_return; 587 } 588 /* 589 * TCP window updates are not reliable, rather a polling protocol 590 * using ``persist'' packets is used to insure receipt of window 591 * updates. The three ``states'' for the output side are: 592 * idle not doing retransmits or persists 593 * persisting to move a small or zero window 594 * (re)transmitting and thereby not persisting 595 * 596 * tcp_timer_active(tp, TT_PERSIST) 597 * is true when we are in persist state. 598 * (tp->t_flags & TF_FORCEDATA) 599 * is set when we are called to send a persist packet. 600 * tcp_timer_active(tp, TT_REXMT) 601 * is set when we are retransmitting 602 * The output side is idle when both timers are zero. 603 * 604 * If send window is too small, there is data to transmit, and no 605 * retransmit or persist is pending, then go to persist state. 606 * If nothing happens soon, send when timer expires: 607 * if window is nonzero, transmit what we can, 608 * otherwise force out a byte. 609 */ 610 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 611 !tcp_timer_active(tp, TT_PERSIST)) { 612 tp->t_rxtshift = 0; 613 tcp_setpersist(tp); 614 } 615 616 /* 617 * No reason to send a segment, just return. 618 */ 619 just_return: 620 SOCKBUF_UNLOCK(&so->so_snd); 621 return (0); 622 623 send: 624 SOCKBUF_LOCK_ASSERT(&so->so_snd); 625 /* 626 * Before ESTABLISHED, force sending of initial options 627 * unless TCP set not to do any options. 628 * NOTE: we assume that the IP/TCP header plus TCP options 629 * always fit in a single mbuf, leaving room for a maximum 630 * link header, i.e. 631 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 632 */ 633 optlen = 0; 634 #ifdef INET6 635 if (isipv6) 636 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 637 else 638 #endif 639 hdrlen = sizeof (struct tcpiphdr); 640 641 /* 642 * Compute options for segment. 643 * We only have to care about SYN and established connection 644 * segments. Options for SYN-ACK segments are handled in TCP 645 * syncache. 646 */ 647 if ((tp->t_flags & TF_NOOPT) == 0) { 648 to.to_flags = 0; 649 /* Maximum segment size. */ 650 if (flags & TH_SYN) { 651 tp->snd_nxt = tp->iss; 652 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 653 to.to_flags |= TOF_MSS; 654 } 655 /* Window scaling. */ 656 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 657 to.to_wscale = tp->request_r_scale; 658 to.to_flags |= TOF_SCALE; 659 } 660 /* Timestamps. */ 661 if ((tp->t_flags & TF_RCVD_TSTMP) || 662 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 663 to.to_tsval = ticks + tp->ts_offset; 664 to.to_tsecr = tp->ts_recent; 665 to.to_flags |= TOF_TS; 666 /* Set receive buffer autosizing timestamp. */ 667 if (tp->rfbuf_ts == 0 && 668 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 669 tp->rfbuf_ts = ticks; 670 } 671 /* Selective ACK's. */ 672 if (tp->t_flags & TF_SACK_PERMIT) { 673 if (flags & TH_SYN) 674 to.to_flags |= TOF_SACKPERM; 675 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 676 (tp->t_flags & TF_SACK_PERMIT) && 677 tp->rcv_numsacks > 0) { 678 to.to_flags |= TOF_SACK; 679 to.to_nsacks = tp->rcv_numsacks; 680 to.to_sacks = (u_char *)tp->sackblks; 681 } 682 } 683 #ifdef TCP_SIGNATURE 684 /* TCP-MD5 (RFC2385). */ 685 if (tp->t_flags & TF_SIGNATURE) 686 to.to_flags |= TOF_SIGNATURE; 687 #endif /* TCP_SIGNATURE */ 688 689 /* Processing the options. */ 690 hdrlen += optlen = tcp_addoptions(&to, opt); 691 } 692 693 #ifdef INET6 694 if (isipv6) 695 ipoptlen = ip6_optlen(tp->t_inpcb); 696 else 697 #endif 698 if (tp->t_inpcb->inp_options) 699 ipoptlen = tp->t_inpcb->inp_options->m_len - 700 offsetof(struct ipoption, ipopt_list); 701 else 702 ipoptlen = 0; 703 #ifdef IPSEC 704 ipoptlen += ipsec_optlen; 705 #endif 706 707 /* 708 * Adjust data length if insertion of options will 709 * bump the packet length beyond the t_maxopd length. 710 * Clear the FIN bit because we cut off the tail of 711 * the segment. 712 * 713 * When doing TSO limit a burst to TCP_MAXWIN minus the 714 * IP, TCP and Options length to keep ip->ip_len from 715 * overflowing. Prevent the last segment from being 716 * fractional thus making them all equal sized and set 717 * the flag to continue sending. TSO is disabled when 718 * IP options or IPSEC are present. 719 */ 720 if (len + optlen + ipoptlen > tp->t_maxopd) { 721 flags &= ~TH_FIN; 722 if (tso) { 723 if (len > TCP_MAXWIN - hdrlen - optlen) { 724 len = TCP_MAXWIN - hdrlen - optlen; 725 len = len - (len % (tp->t_maxopd - optlen)); 726 sendalot = 1; 727 } else if (tp->t_flags & TF_NEEDFIN) 728 sendalot = 1; 729 } else { 730 len = tp->t_maxopd - optlen - ipoptlen; 731 sendalot = 1; 732 } 733 } 734 735 /*#ifdef DIAGNOSTIC*/ 736 #ifdef INET6 737 if (max_linkhdr + hdrlen > MCLBYTES) 738 #else 739 if (max_linkhdr + hdrlen > MHLEN) 740 #endif 741 panic("tcphdr too big"); 742 /*#endif*/ 743 744 /* 745 * This KASSERT is here to catch edge cases at a well defined place. 746 * Before, those had triggered (random) panic conditions further down. 747 */ 748 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 749 750 /* 751 * Grab a header mbuf, attaching a copy of data to 752 * be transmitted, and initialize the header from 753 * the template for sends on this connection. 754 */ 755 if (len) { 756 struct mbuf *mb; 757 u_int moff; 758 759 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 760 V_tcpstat.tcps_sndprobe++; 761 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 762 V_tcpstat.tcps_sndrexmitpack++; 763 V_tcpstat.tcps_sndrexmitbyte += len; 764 } else { 765 V_tcpstat.tcps_sndpack++; 766 V_tcpstat.tcps_sndbyte += len; 767 } 768 #ifdef notyet 769 if ((m = m_copypack(so->so_snd.sb_mb, off, 770 (int)len, max_linkhdr + hdrlen)) == 0) { 771 SOCKBUF_UNLOCK(&so->so_snd); 772 error = ENOBUFS; 773 goto out; 774 } 775 /* 776 * m_copypack left space for our hdr; use it. 777 */ 778 m->m_len += hdrlen; 779 m->m_data -= hdrlen; 780 #else 781 MGETHDR(m, M_DONTWAIT, MT_DATA); 782 if (m == NULL) { 783 SOCKBUF_UNLOCK(&so->so_snd); 784 error = ENOBUFS; 785 goto out; 786 } 787 #ifdef INET6 788 if (MHLEN < hdrlen + max_linkhdr) { 789 MCLGET(m, M_DONTWAIT); 790 if ((m->m_flags & M_EXT) == 0) { 791 SOCKBUF_UNLOCK(&so->so_snd); 792 m_freem(m); 793 error = ENOBUFS; 794 goto out; 795 } 796 } 797 #endif 798 m->m_data += max_linkhdr; 799 m->m_len = hdrlen; 800 801 /* 802 * Start the m_copy functions from the closest mbuf 803 * to the offset in the socket buffer chain. 804 */ 805 mb = sbsndptr(&so->so_snd, off, len, &moff); 806 807 if (len <= MHLEN - hdrlen - max_linkhdr) { 808 m_copydata(mb, moff, (int)len, 809 mtod(m, caddr_t) + hdrlen); 810 m->m_len += len; 811 } else { 812 m->m_next = m_copy(mb, moff, (int)len); 813 if (m->m_next == NULL) { 814 SOCKBUF_UNLOCK(&so->so_snd); 815 (void) m_free(m); 816 error = ENOBUFS; 817 goto out; 818 } 819 } 820 #endif 821 /* 822 * If we're sending everything we've got, set PUSH. 823 * (This will keep happy those implementations which only 824 * give data to the user when a buffer fills or 825 * a PUSH comes in.) 826 */ 827 if (off + len == so->so_snd.sb_cc) 828 flags |= TH_PUSH; 829 SOCKBUF_UNLOCK(&so->so_snd); 830 } else { 831 SOCKBUF_UNLOCK(&so->so_snd); 832 if (tp->t_flags & TF_ACKNOW) 833 V_tcpstat.tcps_sndacks++; 834 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 835 V_tcpstat.tcps_sndctrl++; 836 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 837 V_tcpstat.tcps_sndurg++; 838 else 839 V_tcpstat.tcps_sndwinup++; 840 841 MGETHDR(m, M_DONTWAIT, MT_DATA); 842 if (m == NULL) { 843 error = ENOBUFS; 844 goto out; 845 } 846 #ifdef INET6 847 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 848 MHLEN >= hdrlen) { 849 MH_ALIGN(m, hdrlen); 850 } else 851 #endif 852 m->m_data += max_linkhdr; 853 m->m_len = hdrlen; 854 } 855 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 856 m->m_pkthdr.rcvif = (struct ifnet *)0; 857 #ifdef MAC 858 mac_inpcb_create_mbuf(tp->t_inpcb, m); 859 #endif 860 #ifdef INET6 861 if (isipv6) { 862 ip6 = mtod(m, struct ip6_hdr *); 863 th = (struct tcphdr *)(ip6 + 1); 864 tcpip_fillheaders(tp->t_inpcb, ip6, th); 865 } else 866 #endif /* INET6 */ 867 { 868 ip = mtod(m, struct ip *); 869 ipov = (struct ipovly *)ip; 870 th = (struct tcphdr *)(ip + 1); 871 tcpip_fillheaders(tp->t_inpcb, ip, th); 872 } 873 874 /* 875 * Fill in fields, remembering maximum advertised 876 * window for use in delaying messages about window sizes. 877 * If resending a FIN, be sure not to use a new sequence number. 878 */ 879 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 880 tp->snd_nxt == tp->snd_max) 881 tp->snd_nxt--; 882 /* 883 * If we are starting a connection, send ECN setup 884 * SYN packet. If we are on a retransmit, we may 885 * resend those bits a number of times as per 886 * RFC 3168. 887 */ 888 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 889 if (tp->t_rxtshift >= 1) { 890 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 891 flags |= TH_ECE|TH_CWR; 892 } else 893 flags |= TH_ECE|TH_CWR; 894 } 895 896 if (tp->t_state == TCPS_ESTABLISHED && 897 (tp->t_flags & TF_ECN_PERMIT)) { 898 /* 899 * If the peer has ECN, mark data packets with 900 * ECN capable transmission (ECT). 901 * Ignore pure ack packets, retransmissions and window probes. 902 */ 903 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 904 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 905 #ifdef INET6 906 if (isipv6) 907 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 908 else 909 #endif 910 ip->ip_tos |= IPTOS_ECN_ECT0; 911 V_tcpstat.tcps_ecn_ect0++; 912 } 913 914 /* 915 * Reply with proper ECN notifications. 916 */ 917 if (tp->t_flags & TF_ECN_SND_CWR) { 918 flags |= TH_CWR; 919 tp->t_flags &= ~TF_ECN_SND_CWR; 920 } 921 if (tp->t_flags & TF_ECN_SND_ECE) 922 flags |= TH_ECE; 923 } 924 925 /* 926 * If we are doing retransmissions, then snd_nxt will 927 * not reflect the first unsent octet. For ACK only 928 * packets, we do not want the sequence number of the 929 * retransmitted packet, we want the sequence number 930 * of the next unsent octet. So, if there is no data 931 * (and no SYN or FIN), use snd_max instead of snd_nxt 932 * when filling in ti_seq. But if we are in persist 933 * state, snd_max might reflect one byte beyond the 934 * right edge of the window, so use snd_nxt in that 935 * case, since we know we aren't doing a retransmission. 936 * (retransmit and persist are mutually exclusive...) 937 */ 938 if (sack_rxmit == 0) { 939 if (len || (flags & (TH_SYN|TH_FIN)) || 940 tcp_timer_active(tp, TT_PERSIST)) 941 th->th_seq = htonl(tp->snd_nxt); 942 else 943 th->th_seq = htonl(tp->snd_max); 944 } else { 945 th->th_seq = htonl(p->rxmit); 946 p->rxmit += len; 947 tp->sackhint.sack_bytes_rexmit += len; 948 } 949 th->th_ack = htonl(tp->rcv_nxt); 950 if (optlen) { 951 bcopy(opt, th + 1, optlen); 952 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 953 } 954 th->th_flags = flags; 955 /* 956 * Calculate receive window. Don't shrink window, 957 * but avoid silly window syndrome. 958 */ 959 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 960 recwin < (long)tp->t_maxseg) 961 recwin = 0; 962 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 963 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 964 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 965 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 966 967 /* 968 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 969 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 970 * case is handled in syncache. 971 */ 972 if (flags & TH_SYN) 973 th->th_win = htons((u_short) 974 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 975 else 976 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 977 978 /* 979 * Adjust the RXWIN0SENT flag - indicate that we have advertised 980 * a 0 window. This may cause the remote transmitter to stall. This 981 * flag tells soreceive() to disable delayed acknowledgements when 982 * draining the buffer. This can occur if the receiver is attempting 983 * to read more data than can be buffered prior to transmitting on 984 * the connection. 985 */ 986 if (recwin == 0) 987 tp->t_flags |= TF_RXWIN0SENT; 988 else 989 tp->t_flags &= ~TF_RXWIN0SENT; 990 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 991 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 992 th->th_flags |= TH_URG; 993 } else 994 /* 995 * If no urgent pointer to send, then we pull 996 * the urgent pointer to the left edge of the send window 997 * so that it doesn't drift into the send window on sequence 998 * number wraparound. 999 */ 1000 tp->snd_up = tp->snd_una; /* drag it along */ 1001 1002 #ifdef TCP_SIGNATURE 1003 if (tp->t_flags & TF_SIGNATURE) { 1004 int sigoff = to.to_signature - opt; 1005 tcp_signature_compute(m, 0, len, optlen, 1006 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1007 } 1008 #endif 1009 1010 /* 1011 * Put TCP length in extended header, and then 1012 * checksum extended header and data. 1013 */ 1014 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1015 #ifdef INET6 1016 if (isipv6) 1017 /* 1018 * ip6_plen is not need to be filled now, and will be filled 1019 * in ip6_output. 1020 */ 1021 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1022 sizeof(struct tcphdr) + optlen + len); 1023 else 1024 #endif /* INET6 */ 1025 { 1026 m->m_pkthdr.csum_flags = CSUM_TCP; 1027 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1028 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1029 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1030 1031 /* IP version must be set here for ipv4/ipv6 checking later */ 1032 KASSERT(ip->ip_v == IPVERSION, 1033 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1034 } 1035 1036 /* 1037 * Enable TSO and specify the size of the segments. 1038 * The TCP pseudo header checksum is always provided. 1039 * XXX: Fixme: This is currently not the case for IPv6. 1040 */ 1041 if (tso) { 1042 m->m_pkthdr.csum_flags = CSUM_TSO; 1043 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1044 } 1045 1046 /* 1047 * In transmit state, time the transmission and arrange for 1048 * the retransmit. In persist state, just set snd_max. 1049 */ 1050 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1051 !tcp_timer_active(tp, TT_PERSIST)) { 1052 tcp_seq startseq = tp->snd_nxt; 1053 1054 /* 1055 * Advance snd_nxt over sequence space of this segment. 1056 */ 1057 if (flags & (TH_SYN|TH_FIN)) { 1058 if (flags & TH_SYN) 1059 tp->snd_nxt++; 1060 if (flags & TH_FIN) { 1061 tp->snd_nxt++; 1062 tp->t_flags |= TF_SENTFIN; 1063 } 1064 } 1065 if (sack_rxmit) 1066 goto timer; 1067 tp->snd_nxt += len; 1068 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1069 tp->snd_max = tp->snd_nxt; 1070 /* 1071 * Time this transmission if not a retransmission and 1072 * not currently timing anything. 1073 */ 1074 if (tp->t_rtttime == 0) { 1075 tp->t_rtttime = ticks; 1076 tp->t_rtseq = startseq; 1077 V_tcpstat.tcps_segstimed++; 1078 } 1079 } 1080 1081 /* 1082 * Set retransmit timer if not currently set, 1083 * and not doing a pure ack or a keep-alive probe. 1084 * Initial value for retransmit timer is smoothed 1085 * round-trip time + 2 * round-trip time variance. 1086 * Initialize shift counter which is used for backoff 1087 * of retransmit time. 1088 */ 1089 timer: 1090 if (!tcp_timer_active(tp, TT_REXMT) && 1091 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1092 (tp->snd_nxt != tp->snd_una))) { 1093 if (tcp_timer_active(tp, TT_PERSIST)) { 1094 tcp_timer_activate(tp, TT_PERSIST, 0); 1095 tp->t_rxtshift = 0; 1096 } 1097 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1098 } 1099 } else { 1100 /* 1101 * Persist case, update snd_max but since we are in 1102 * persist mode (no window) we do not update snd_nxt. 1103 */ 1104 int xlen = len; 1105 if (flags & TH_SYN) 1106 ++xlen; 1107 if (flags & TH_FIN) { 1108 ++xlen; 1109 tp->t_flags |= TF_SENTFIN; 1110 } 1111 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1112 tp->snd_max = tp->snd_nxt + len; 1113 } 1114 1115 #ifdef TCPDEBUG 1116 /* 1117 * Trace. 1118 */ 1119 if (so->so_options & SO_DEBUG) { 1120 u_short save = 0; 1121 #ifdef INET6 1122 if (!isipv6) 1123 #endif 1124 { 1125 save = ipov->ih_len; 1126 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1127 } 1128 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1129 #ifdef INET6 1130 if (!isipv6) 1131 #endif 1132 ipov->ih_len = save; 1133 } 1134 #endif 1135 1136 /* 1137 * Fill in IP length and desired time to live and 1138 * send to IP level. There should be a better way 1139 * to handle ttl and tos; we could keep them in 1140 * the template, but need a way to checksum without them. 1141 */ 1142 /* 1143 * m->m_pkthdr.len should have been set before cksum calcuration, 1144 * because in6_cksum() need it. 1145 */ 1146 #ifdef INET6 1147 if (isipv6) { 1148 /* 1149 * we separately set hoplimit for every segment, since the 1150 * user might want to change the value via setsockopt. 1151 * Also, desired default hop limit might be changed via 1152 * Neighbor Discovery. 1153 */ 1154 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1155 1156 /* TODO: IPv6 IP6TOS_ECT bit on */ 1157 error = ip6_output(m, 1158 tp->t_inpcb->in6p_outputopts, NULL, 1159 ((so->so_options & SO_DONTROUTE) ? 1160 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1161 } else 1162 #endif /* INET6 */ 1163 { 1164 ip->ip_len = m->m_pkthdr.len; 1165 #ifdef INET6 1166 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1167 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1168 #endif /* INET6 */ 1169 /* 1170 * If we do path MTU discovery, then we set DF on every packet. 1171 * This might not be the best thing to do according to RFC3390 1172 * Section 2. However the tcp hostcache migitates the problem 1173 * so it affects only the first tcp connection with a host. 1174 */ 1175 if (V_path_mtu_discovery) 1176 ip->ip_off |= IP_DF; 1177 1178 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1179 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1180 tp->t_inpcb); 1181 } 1182 if (error) { 1183 1184 /* 1185 * We know that the packet was lost, so back out the 1186 * sequence number advance, if any. 1187 * 1188 * If the error is EPERM the packet got blocked by the 1189 * local firewall. Normally we should terminate the 1190 * connection but the blocking may have been spurious 1191 * due to a firewall reconfiguration cycle. So we treat 1192 * it like a packet loss and let the retransmit timer and 1193 * timeouts do their work over time. 1194 * XXX: It is a POLA question whether calling tcp_drop right 1195 * away would be the really correct behavior instead. 1196 */ 1197 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1198 !tcp_timer_active(tp, TT_PERSIST)) && 1199 ((flags & TH_SYN) == 0) && 1200 (error != EPERM)) { 1201 if (sack_rxmit) { 1202 p->rxmit -= len; 1203 tp->sackhint.sack_bytes_rexmit -= len; 1204 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1205 ("sackhint bytes rtx >= 0")); 1206 } else 1207 tp->snd_nxt -= len; 1208 } 1209 out: 1210 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1211 switch (error) { 1212 case EPERM: 1213 tp->t_softerror = error; 1214 return (error); 1215 case ENOBUFS: 1216 if (!tcp_timer_active(tp, TT_REXMT) && 1217 !tcp_timer_active(tp, TT_PERSIST)) 1218 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1219 tp->snd_cwnd = tp->t_maxseg; 1220 return (0); 1221 case EMSGSIZE: 1222 /* 1223 * For some reason the interface we used initially 1224 * to send segments changed to another or lowered 1225 * its MTU. 1226 * 1227 * tcp_mtudisc() will find out the new MTU and as 1228 * its last action, initiate retransmission, so it 1229 * is important to not do so here. 1230 * 1231 * If TSO was active we either got an interface 1232 * without TSO capabilits or TSO was turned off. 1233 * Disable it for this connection as too and 1234 * immediatly retry with MSS sized segments generated 1235 * by this function. 1236 */ 1237 if (tso) 1238 tp->t_flags &= ~TF_TSO; 1239 tcp_mtudisc(tp->t_inpcb, 0); 1240 return (0); 1241 case EHOSTDOWN: 1242 case EHOSTUNREACH: 1243 case ENETDOWN: 1244 case ENETUNREACH: 1245 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1246 tp->t_softerror = error; 1247 return (0); 1248 } 1249 /* FALLTHROUGH */ 1250 default: 1251 return (error); 1252 } 1253 } 1254 V_tcpstat.tcps_sndtotal++; 1255 1256 /* 1257 * Data sent (as far as we can tell). 1258 * If this advertises a larger window than any other segment, 1259 * then remember the size of the advertised window. 1260 * Any pending ACK has now been sent. 1261 */ 1262 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1263 tp->rcv_adv = tp->rcv_nxt + recwin; 1264 tp->last_ack_sent = tp->rcv_nxt; 1265 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1266 if (tcp_timer_active(tp, TT_DELACK)) 1267 tcp_timer_activate(tp, TT_DELACK, 0); 1268 #if 0 1269 /* 1270 * This completely breaks TCP if newreno is turned on. What happens 1271 * is that if delayed-acks are turned on on the receiver, this code 1272 * on the transmitter effectively destroys the TCP window, forcing 1273 * it to four packets (1.5Kx4 = 6K window). 1274 */ 1275 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1276 goto again; 1277 #endif 1278 if (sendalot) 1279 goto again; 1280 return (0); 1281 } 1282 1283 void 1284 tcp_setpersist(struct tcpcb *tp) 1285 { 1286 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1287 int tt; 1288 1289 if (tcp_timer_active(tp, TT_REXMT)) 1290 panic("tcp_setpersist: retransmit pending"); 1291 /* 1292 * Start/restart persistance timer. 1293 */ 1294 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1295 TCPTV_PERSMIN, TCPTV_PERSMAX); 1296 tcp_timer_activate(tp, TT_PERSIST, tt); 1297 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1298 tp->t_rxtshift++; 1299 } 1300 1301 /* 1302 * Insert TCP options according to the supplied parameters to the place 1303 * optp in a consistent way. Can handle unaligned destinations. 1304 * 1305 * The order of the option processing is crucial for optimal packing and 1306 * alignment for the scarce option space. 1307 * 1308 * The optimal order for a SYN/SYN-ACK segment is: 1309 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1310 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1311 * 1312 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1313 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1314 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1315 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1316 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1317 */ 1318 int 1319 tcp_addoptions(struct tcpopt *to, u_char *optp) 1320 { 1321 u_int mask, optlen = 0; 1322 1323 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1324 if ((to->to_flags & mask) != mask) 1325 continue; 1326 if (optlen == TCP_MAXOLEN) 1327 break; 1328 switch (to->to_flags & mask) { 1329 case TOF_MSS: 1330 while (optlen % 4) { 1331 optlen += TCPOLEN_NOP; 1332 *optp++ = TCPOPT_NOP; 1333 } 1334 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1335 continue; 1336 optlen += TCPOLEN_MAXSEG; 1337 *optp++ = TCPOPT_MAXSEG; 1338 *optp++ = TCPOLEN_MAXSEG; 1339 to->to_mss = htons(to->to_mss); 1340 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1341 optp += sizeof(to->to_mss); 1342 break; 1343 case TOF_SCALE: 1344 while (!optlen || optlen % 2 != 1) { 1345 optlen += TCPOLEN_NOP; 1346 *optp++ = TCPOPT_NOP; 1347 } 1348 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1349 continue; 1350 optlen += TCPOLEN_WINDOW; 1351 *optp++ = TCPOPT_WINDOW; 1352 *optp++ = TCPOLEN_WINDOW; 1353 *optp++ = to->to_wscale; 1354 break; 1355 case TOF_SACKPERM: 1356 while (optlen % 2) { 1357 optlen += TCPOLEN_NOP; 1358 *optp++ = TCPOPT_NOP; 1359 } 1360 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1361 continue; 1362 optlen += TCPOLEN_SACK_PERMITTED; 1363 *optp++ = TCPOPT_SACK_PERMITTED; 1364 *optp++ = TCPOLEN_SACK_PERMITTED; 1365 break; 1366 case TOF_TS: 1367 while (!optlen || optlen % 4 != 2) { 1368 optlen += TCPOLEN_NOP; 1369 *optp++ = TCPOPT_NOP; 1370 } 1371 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1372 continue; 1373 optlen += TCPOLEN_TIMESTAMP; 1374 *optp++ = TCPOPT_TIMESTAMP; 1375 *optp++ = TCPOLEN_TIMESTAMP; 1376 to->to_tsval = htonl(to->to_tsval); 1377 to->to_tsecr = htonl(to->to_tsecr); 1378 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1379 optp += sizeof(to->to_tsval); 1380 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1381 optp += sizeof(to->to_tsecr); 1382 break; 1383 case TOF_SIGNATURE: 1384 { 1385 int siglen = TCPOLEN_SIGNATURE - 2; 1386 1387 while (!optlen || optlen % 4 != 2) { 1388 optlen += TCPOLEN_NOP; 1389 *optp++ = TCPOPT_NOP; 1390 } 1391 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1392 continue; 1393 optlen += TCPOLEN_SIGNATURE; 1394 *optp++ = TCPOPT_SIGNATURE; 1395 *optp++ = TCPOLEN_SIGNATURE; 1396 to->to_signature = optp; 1397 while (siglen--) 1398 *optp++ = 0; 1399 break; 1400 } 1401 case TOF_SACK: 1402 { 1403 int sackblks = 0; 1404 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1405 tcp_seq sack_seq; 1406 1407 while (!optlen || optlen % 4 != 2) { 1408 optlen += TCPOLEN_NOP; 1409 *optp++ = TCPOPT_NOP; 1410 } 1411 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1412 continue; 1413 optlen += TCPOLEN_SACKHDR; 1414 *optp++ = TCPOPT_SACK; 1415 sackblks = min(to->to_nsacks, 1416 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1417 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1418 while (sackblks--) { 1419 sack_seq = htonl(sack->start); 1420 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1421 optp += sizeof(sack_seq); 1422 sack_seq = htonl(sack->end); 1423 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1424 optp += sizeof(sack_seq); 1425 optlen += TCPOLEN_SACK; 1426 sack++; 1427 } 1428 V_tcpstat.tcps_sack_send_blocks++; 1429 break; 1430 } 1431 default: 1432 panic("%s: unknown TCP option type", __func__); 1433 break; 1434 } 1435 } 1436 1437 /* Terminate and pad TCP options to a 4 byte boundary. */ 1438 if (optlen % 4) { 1439 optlen += TCPOLEN_EOL; 1440 *optp++ = TCPOPT_EOL; 1441 } 1442 /* 1443 * According to RFC 793 (STD0007): 1444 * "The content of the header beyond the End-of-Option option 1445 * must be header padding (i.e., zero)." 1446 * and later: "The padding is composed of zeros." 1447 */ 1448 while (optlen % 4) { 1449 optlen += TCPOLEN_PAD; 1450 *optp++ = TCPOPT_PAD; 1451 } 1452 1453 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1454 return (optlen); 1455 } 1456