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/if.h> 55 #include <net/route.h> 56 57 #include <netinet/in.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/in_pcb.h> 61 #include <netinet/ip_var.h> 62 #include <netinet/ip_options.h> 63 #ifdef INET6 64 #include <netinet6/in6_pcb.h> 65 #include <netinet/ip6.h> 66 #include <netinet6/ip6_var.h> 67 #endif 68 #include <netinet/tcp.h> 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 #include <netinet/vinet.h> 79 80 #ifdef IPSEC 81 #include <netipsec/ipsec.h> 82 #endif /*IPSEC*/ 83 84 #include <machine/in_cksum.h> 85 86 #include <security/mac/mac_framework.h> 87 88 #ifdef notyet 89 extern struct mbuf *m_copypack(); 90 #endif 91 92 #ifdef VIMAGE_GLOBALS 93 int path_mtu_discovery; 94 int ss_fltsz; 95 int ss_fltsz_local; 96 int tcp_do_newreno; 97 int tcp_do_tso; 98 int tcp_do_autosndbuf; 99 int tcp_autosndbuf_inc; 100 int tcp_autosndbuf_max; 101 #endif 102 103 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, path_mtu_discovery, 104 CTLFLAG_RW, path_mtu_discovery, 1, "Enable Path MTU Discovery"); 105 106 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, 107 slowstart_flightsize, CTLFLAG_RW, 108 ss_fltsz, 1, "Slow start flight size"); 109 110 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, 111 local_slowstart_flightsize, CTLFLAG_RW, 112 ss_fltsz_local, 1, "Slow start flight size for local networks"); 113 114 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 115 tcp_do_newreno, 0, "Enable NewReno Algorithms"); 116 117 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 118 tcp_do_tso, 0, "Enable TCP Segmentation Offload"); 119 120 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_auto, 121 CTLFLAG_RW, 122 tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 123 124 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_inc, 125 CTLFLAG_RW, tcp_autosndbuf_inc, 0, 126 "Incrementor step size of automatic send buffer"); 127 128 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_max, 129 CTLFLAG_RW, tcp_autosndbuf_max, 0, 130 "Max size of automatic send buffer"); 131 132 133 /* 134 * Tcp output routine: figure out what should be sent and send it. 135 */ 136 int 137 tcp_output(struct tcpcb *tp) 138 { 139 INIT_VNET_INET(tp->t_inpcb->inp_vnet); 140 struct socket *so = tp->t_inpcb->inp_socket; 141 long len, recwin, sendwin; 142 int off, flags, error; 143 struct mbuf *m; 144 struct ip *ip = NULL; 145 struct ipovly *ipov = NULL; 146 struct tcphdr *th; 147 u_char opt[TCP_MAXOLEN]; 148 unsigned ipoptlen, optlen, hdrlen; 149 #ifdef IPSEC 150 unsigned ipsec_optlen = 0; 151 #endif 152 int idle, sendalot; 153 int sack_rxmit, sack_bytes_rxmt; 154 struct sackhole *p; 155 int tso = 0; 156 struct tcpopt to; 157 #if 0 158 int maxburst = TCP_MAXBURST; 159 #endif 160 #ifdef INET6 161 struct ip6_hdr *ip6 = NULL; 162 int isipv6; 163 164 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 165 #endif 166 167 INP_WLOCK_ASSERT(tp->t_inpcb); 168 169 /* 170 * Determine length of data that should be transmitted, 171 * and flags that will be used. 172 * If there is some data or critical controls (SYN, RST) 173 * to send, then transmit; otherwise, investigate further. 174 */ 175 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 176 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 177 /* 178 * We have been idle for "a while" and no acks are 179 * expected to clock out any data we send -- 180 * slow start to get ack "clock" running again. 181 * 182 * Set the slow-start flight size depending on whether 183 * this is a local network or not. 184 */ 185 int ss = V_ss_fltsz; 186 #ifdef INET6 187 if (isipv6) { 188 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 189 ss = V_ss_fltsz_local; 190 } else 191 #endif /* INET6 */ 192 if (in_localaddr(tp->t_inpcb->inp_faddr)) 193 ss = V_ss_fltsz_local; 194 tp->snd_cwnd = tp->t_maxseg * ss; 195 } 196 tp->t_flags &= ~TF_LASTIDLE; 197 if (idle) { 198 if (tp->t_flags & TF_MORETOCOME) { 199 tp->t_flags |= TF_LASTIDLE; 200 idle = 0; 201 } 202 } 203 again: 204 /* 205 * If we've recently taken a timeout, snd_max will be greater than 206 * snd_nxt. There may be SACK information that allows us to avoid 207 * resending already delivered data. Adjust snd_nxt accordingly. 208 */ 209 if ((tp->t_flags & TF_SACK_PERMIT) && 210 SEQ_LT(tp->snd_nxt, tp->snd_max)) 211 tcp_sack_adjust(tp); 212 sendalot = 0; 213 off = tp->snd_nxt - tp->snd_una; 214 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 215 sendwin = min(sendwin, tp->snd_bwnd); 216 217 flags = tcp_outflags[tp->t_state]; 218 /* 219 * Send any SACK-generated retransmissions. If we're explicitly trying 220 * to send out new data (when sendalot is 1), bypass this function. 221 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 222 * we're replacing a (future) new transmission with a retransmission 223 * now, and we previously incremented snd_cwnd in tcp_input(). 224 */ 225 /* 226 * Still in sack recovery , reset rxmit flag to zero. 227 */ 228 sack_rxmit = 0; 229 sack_bytes_rxmt = 0; 230 len = 0; 231 p = NULL; 232 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 233 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 234 long cwin; 235 236 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 237 if (cwin < 0) 238 cwin = 0; 239 /* Do not retransmit SACK segments beyond snd_recover */ 240 if (SEQ_GT(p->end, tp->snd_recover)) { 241 /* 242 * (At least) part of sack hole extends beyond 243 * snd_recover. Check to see if we can rexmit data 244 * for this hole. 245 */ 246 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 247 /* 248 * Can't rexmit any more data for this hole. 249 * That data will be rexmitted in the next 250 * sack recovery episode, when snd_recover 251 * moves past p->rxmit. 252 */ 253 p = NULL; 254 goto after_sack_rexmit; 255 } else 256 /* Can rexmit part of the current hole */ 257 len = ((long)ulmin(cwin, 258 tp->snd_recover - p->rxmit)); 259 } else 260 len = ((long)ulmin(cwin, p->end - p->rxmit)); 261 off = p->rxmit - tp->snd_una; 262 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 263 __func__, off)); 264 if (len > 0) { 265 sack_rxmit = 1; 266 sendalot = 1; 267 V_tcpstat.tcps_sack_rexmits++; 268 V_tcpstat.tcps_sack_rexmit_bytes += 269 min(len, tp->t_maxseg); 270 } 271 } 272 after_sack_rexmit: 273 /* 274 * Get standard flags, and add SYN or FIN if requested by 'hidden' 275 * state flags. 276 */ 277 if (tp->t_flags & TF_NEEDFIN) 278 flags |= TH_FIN; 279 if (tp->t_flags & TF_NEEDSYN) 280 flags |= TH_SYN; 281 282 SOCKBUF_LOCK(&so->so_snd); 283 /* 284 * If in persist timeout with window of 0, send 1 byte. 285 * Otherwise, if window is small but nonzero 286 * and timer expired, we will send what we can 287 * and go to transmit state. 288 */ 289 if (tp->t_flags & TF_FORCEDATA) { 290 if (sendwin == 0) { 291 /* 292 * If we still have some data to send, then 293 * clear the FIN bit. Usually this would 294 * happen below when it realizes that we 295 * aren't sending all the data. However, 296 * if we have exactly 1 byte of unsent data, 297 * then it won't clear the FIN bit below, 298 * and if we are in persist state, we wind 299 * up sending the packet without recording 300 * that we sent the FIN bit. 301 * 302 * We can't just blindly clear the FIN bit, 303 * because if we don't have any more data 304 * to send then the probe will be the FIN 305 * itself. 306 */ 307 if (off < so->so_snd.sb_cc) 308 flags &= ~TH_FIN; 309 sendwin = 1; 310 } else { 311 tcp_timer_activate(tp, TT_PERSIST, 0); 312 tp->t_rxtshift = 0; 313 } 314 } 315 316 /* 317 * If snd_nxt == snd_max and we have transmitted a FIN, the 318 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 319 * a negative length. This can also occur when TCP opens up 320 * its congestion window while receiving additional duplicate 321 * acks after fast-retransmit because TCP will reset snd_nxt 322 * to snd_max after the fast-retransmit. 323 * 324 * In the normal retransmit-FIN-only case, however, snd_nxt will 325 * be set to snd_una, the offset will be 0, and the length may 326 * wind up 0. 327 * 328 * If sack_rxmit is true we are retransmitting from the scoreboard 329 * in which case len is already set. 330 */ 331 if (sack_rxmit == 0) { 332 if (sack_bytes_rxmt == 0) 333 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 334 else { 335 long cwin; 336 337 /* 338 * We are inside of a SACK recovery episode and are 339 * sending new data, having retransmitted all the 340 * data possible in the scoreboard. 341 */ 342 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 343 - off); 344 /* 345 * Don't remove this (len > 0) check ! 346 * We explicitly check for len > 0 here (although it 347 * isn't really necessary), to work around a gcc 348 * optimization issue - to force gcc to compute 349 * len above. Without this check, the computation 350 * of len is bungled by the optimizer. 351 */ 352 if (len > 0) { 353 cwin = tp->snd_cwnd - 354 (tp->snd_nxt - tp->sack_newdata) - 355 sack_bytes_rxmt; 356 if (cwin < 0) 357 cwin = 0; 358 len = lmin(len, cwin); 359 } 360 } 361 } 362 363 /* 364 * Lop off SYN bit if it has already been sent. However, if this 365 * is SYN-SENT state and if segment contains data and if we don't 366 * know that foreign host supports TAO, suppress sending segment. 367 */ 368 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 369 if (tp->t_state != TCPS_SYN_RECEIVED) 370 flags &= ~TH_SYN; 371 off--, len++; 372 } 373 374 /* 375 * Be careful not to send data and/or FIN on SYN segments. 376 * This measure is needed to prevent interoperability problems 377 * with not fully conformant TCP implementations. 378 */ 379 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 380 len = 0; 381 flags &= ~TH_FIN; 382 } 383 384 if (len < 0) { 385 /* 386 * If FIN has been sent but not acked, 387 * but we haven't been called to retransmit, 388 * len will be < 0. Otherwise, window shrank 389 * after we sent into it. If window shrank to 0, 390 * cancel pending retransmit, pull snd_nxt back 391 * to (closed) window, and set the persist timer 392 * if it isn't already going. If the window didn't 393 * close completely, just wait for an ACK. 394 */ 395 len = 0; 396 if (sendwin == 0) { 397 tcp_timer_activate(tp, TT_REXMT, 0); 398 tp->t_rxtshift = 0; 399 tp->snd_nxt = tp->snd_una; 400 if (!tcp_timer_active(tp, TT_PERSIST)) 401 tcp_setpersist(tp); 402 } 403 } 404 405 /* len will be >= 0 after this point. */ 406 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 407 408 /* 409 * Automatic sizing of send socket buffer. Often the send buffer 410 * size is not optimally adjusted to the actual network conditions 411 * at hand (delay bandwidth product). Setting the buffer size too 412 * small limits throughput on links with high bandwidth and high 413 * delay (eg. trans-continental/oceanic links). Setting the 414 * buffer size too big consumes too much real kernel memory, 415 * especially with many connections on busy servers. 416 * 417 * The criteria to step up the send buffer one notch are: 418 * 1. receive window of remote host is larger than send buffer 419 * (with a fudge factor of 5/4th); 420 * 2. send buffer is filled to 7/8th with data (so we actually 421 * have data to make use of it); 422 * 3. send buffer fill has not hit maximal automatic size; 423 * 4. our send window (slow start and cogestion controlled) is 424 * larger than sent but unacknowledged data in send buffer. 425 * 426 * The remote host receive window scaling factor may limit the 427 * growing of the send buffer before it reaches its allowed 428 * maximum. 429 * 430 * It scales directly with slow start or congestion window 431 * and does at most one step per received ACK. This fast 432 * scaling has the drawback of growing the send buffer beyond 433 * what is strictly necessary to make full use of a given 434 * delay*bandwith product. However testing has shown this not 435 * to be much of an problem. At worst we are trading wasting 436 * of available bandwith (the non-use of it) for wasting some 437 * socket buffer memory. 438 * 439 * TODO: Shrink send buffer during idle periods together 440 * with congestion window. Requires another timer. Has to 441 * wait for upcoming tcp timer rewrite. 442 */ 443 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 444 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 445 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 446 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 447 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 448 if (!sbreserve_locked(&so->so_snd, 449 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 450 V_tcp_autosndbuf_max), so, curthread)) 451 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 452 } 453 } 454 455 /* 456 * Truncate to the maximum segment length or enable TCP Segmentation 457 * Offloading (if supported by hardware) and ensure that FIN is removed 458 * if the length no longer contains the last data byte. 459 * 460 * TSO may only be used if we are in a pure bulk sending state. The 461 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 462 * IP options prevent using TSO. With TSO the TCP header is the same 463 * (except for the sequence number) for all generated packets. This 464 * makes it impossible to transmit any options which vary per generated 465 * segment or packet. 466 * 467 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 468 * removal of FIN (if not already catched here) are handled later after 469 * the exact length of the TCP options are known. 470 */ 471 #ifdef IPSEC 472 /* 473 * Pre-calculate here as we save another lookup into the darknesses 474 * of IPsec that way and can actually decide if TSO is ok. 475 */ 476 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 477 #endif 478 if (len > tp->t_maxseg) { 479 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 480 ((tp->t_flags & TF_SIGNATURE) == 0) && 481 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 482 tp->t_inpcb->inp_options == NULL && 483 tp->t_inpcb->in6p_options == NULL 484 #ifdef IPSEC 485 && ipsec_optlen == 0 486 #endif 487 ) { 488 tso = 1; 489 } else { 490 len = tp->t_maxseg; 491 sendalot = 1; 492 tso = 0; 493 } 494 } 495 if (sack_rxmit) { 496 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 497 flags &= ~TH_FIN; 498 } else { 499 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 500 flags &= ~TH_FIN; 501 } 502 503 recwin = sbspace(&so->so_rcv); 504 505 /* 506 * Sender silly window avoidance. We transmit under the following 507 * conditions when len is non-zero: 508 * 509 * - We have a full segment (or more with TSO) 510 * - This is the last buffer in a write()/send() and we are 511 * either idle or running NODELAY 512 * - we've timed out (e.g. persist timer) 513 * - we have more then 1/2 the maximum send window's worth of 514 * data (receiver may be limited the window size) 515 * - we need to retransmit 516 */ 517 if (len) { 518 if (len >= tp->t_maxseg) 519 goto send; 520 /* 521 * NOTE! on localhost connections an 'ack' from the remote 522 * end may occur synchronously with the output and cause 523 * us to flush a buffer queued with moretocome. XXX 524 * 525 * note: the len + off check is almost certainly unnecessary. 526 */ 527 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 528 (idle || (tp->t_flags & TF_NODELAY)) && 529 len + off >= so->so_snd.sb_cc && 530 (tp->t_flags & TF_NOPUSH) == 0) { 531 goto send; 532 } 533 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 534 goto send; 535 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 536 goto send; 537 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 538 goto send; 539 if (sack_rxmit) 540 goto send; 541 } 542 543 /* 544 * Compare available window to amount of window 545 * known to peer (as advertised window less 546 * next expected input). If the difference is at least two 547 * max size segments, or at least 50% of the maximum possible 548 * window, then want to send a window update to peer. 549 * Skip this if the connection is in T/TCP half-open state. 550 * Don't send pure window updates when the peer has closed 551 * the connection and won't ever send more data. 552 */ 553 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 554 !TCPS_HAVERCVDFIN(tp->t_state)) { 555 /* 556 * "adv" is the amount we can increase the window, 557 * taking into account that we are limited by 558 * TCP_MAXWIN << tp->rcv_scale. 559 */ 560 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 561 (tp->rcv_adv - tp->rcv_nxt); 562 563 if (adv >= (long) (2 * tp->t_maxseg)) 564 goto send; 565 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 566 goto send; 567 } 568 569 /* 570 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 571 * is also a catch-all for the retransmit timer timeout case. 572 */ 573 if (tp->t_flags & TF_ACKNOW) 574 goto send; 575 if ((flags & TH_RST) || 576 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 577 goto send; 578 if (SEQ_GT(tp->snd_up, tp->snd_una)) 579 goto send; 580 /* 581 * If our state indicates that FIN should be sent 582 * and we have not yet done so, then we need to send. 583 */ 584 if (flags & TH_FIN && 585 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 586 goto send; 587 /* 588 * In SACK, it is possible for tcp_output to fail to send a segment 589 * after the retransmission timer has been turned off. Make sure 590 * that the retransmission timer is set. 591 */ 592 if ((tp->t_flags & TF_SACK_PERMIT) && 593 SEQ_GT(tp->snd_max, tp->snd_una) && 594 !tcp_timer_active(tp, TT_REXMT) && 595 !tcp_timer_active(tp, TT_PERSIST)) { 596 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 597 goto just_return; 598 } 599 /* 600 * TCP window updates are not reliable, rather a polling protocol 601 * using ``persist'' packets is used to insure receipt of window 602 * updates. The three ``states'' for the output side are: 603 * idle not doing retransmits or persists 604 * persisting to move a small or zero window 605 * (re)transmitting and thereby not persisting 606 * 607 * tcp_timer_active(tp, TT_PERSIST) 608 * is true when we are in persist state. 609 * (tp->t_flags & TF_FORCEDATA) 610 * is set when we are called to send a persist packet. 611 * tcp_timer_active(tp, TT_REXMT) 612 * is set when we are retransmitting 613 * The output side is idle when both timers are zero. 614 * 615 * If send window is too small, there is data to transmit, and no 616 * retransmit or persist is pending, then go to persist state. 617 * If nothing happens soon, send when timer expires: 618 * if window is nonzero, transmit what we can, 619 * otherwise force out a byte. 620 */ 621 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 622 !tcp_timer_active(tp, TT_PERSIST)) { 623 tp->t_rxtshift = 0; 624 tcp_setpersist(tp); 625 } 626 627 /* 628 * No reason to send a segment, just return. 629 */ 630 just_return: 631 SOCKBUF_UNLOCK(&so->so_snd); 632 return (0); 633 634 send: 635 SOCKBUF_LOCK_ASSERT(&so->so_snd); 636 /* 637 * Before ESTABLISHED, force sending of initial options 638 * unless TCP set not to do any options. 639 * NOTE: we assume that the IP/TCP header plus TCP options 640 * always fit in a single mbuf, leaving room for a maximum 641 * link header, i.e. 642 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 643 */ 644 optlen = 0; 645 #ifdef INET6 646 if (isipv6) 647 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 648 else 649 #endif 650 hdrlen = sizeof (struct tcpiphdr); 651 652 /* 653 * Compute options for segment. 654 * We only have to care about SYN and established connection 655 * segments. Options for SYN-ACK segments are handled in TCP 656 * syncache. 657 */ 658 if ((tp->t_flags & TF_NOOPT) == 0) { 659 to.to_flags = 0; 660 /* Maximum segment size. */ 661 if (flags & TH_SYN) { 662 tp->snd_nxt = tp->iss; 663 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 664 to.to_flags |= TOF_MSS; 665 } 666 /* Window scaling. */ 667 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 668 to.to_wscale = tp->request_r_scale; 669 to.to_flags |= TOF_SCALE; 670 } 671 /* Timestamps. */ 672 if ((tp->t_flags & TF_RCVD_TSTMP) || 673 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 674 to.to_tsval = ticks + tp->ts_offset; 675 to.to_tsecr = tp->ts_recent; 676 to.to_flags |= TOF_TS; 677 /* Set receive buffer autosizing timestamp. */ 678 if (tp->rfbuf_ts == 0 && 679 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 680 tp->rfbuf_ts = ticks; 681 } 682 /* Selective ACK's. */ 683 if (tp->t_flags & TF_SACK_PERMIT) { 684 if (flags & TH_SYN) 685 to.to_flags |= TOF_SACKPERM; 686 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 687 (tp->t_flags & TF_SACK_PERMIT) && 688 tp->rcv_numsacks > 0) { 689 to.to_flags |= TOF_SACK; 690 to.to_nsacks = tp->rcv_numsacks; 691 to.to_sacks = (u_char *)tp->sackblks; 692 } 693 } 694 #ifdef TCP_SIGNATURE 695 /* TCP-MD5 (RFC2385). */ 696 if (tp->t_flags & TF_SIGNATURE) 697 to.to_flags |= TOF_SIGNATURE; 698 #endif /* TCP_SIGNATURE */ 699 700 /* Processing the options. */ 701 hdrlen += optlen = tcp_addoptions(&to, opt); 702 } 703 704 #ifdef INET6 705 if (isipv6) 706 ipoptlen = ip6_optlen(tp->t_inpcb); 707 else 708 #endif 709 if (tp->t_inpcb->inp_options) 710 ipoptlen = tp->t_inpcb->inp_options->m_len - 711 offsetof(struct ipoption, ipopt_list); 712 else 713 ipoptlen = 0; 714 #ifdef IPSEC 715 ipoptlen += ipsec_optlen; 716 #endif 717 718 /* 719 * Adjust data length if insertion of options will 720 * bump the packet length beyond the t_maxopd length. 721 * Clear the FIN bit because we cut off the tail of 722 * the segment. 723 * 724 * When doing TSO limit a burst to TCP_MAXWIN minus the 725 * IP, TCP and Options length to keep ip->ip_len from 726 * overflowing. Prevent the last segment from being 727 * fractional thus making them all equal sized and set 728 * the flag to continue sending. TSO is disabled when 729 * IP options or IPSEC are present. 730 */ 731 if (len + optlen + ipoptlen > tp->t_maxopd) { 732 flags &= ~TH_FIN; 733 if (tso) { 734 if (len > TCP_MAXWIN - hdrlen - optlen) { 735 len = TCP_MAXWIN - hdrlen - optlen; 736 len = len - (len % (tp->t_maxopd - optlen)); 737 sendalot = 1; 738 } else if (tp->t_flags & TF_NEEDFIN) 739 sendalot = 1; 740 } else { 741 len = tp->t_maxopd - optlen - ipoptlen; 742 sendalot = 1; 743 } 744 } 745 746 /*#ifdef DIAGNOSTIC*/ 747 #ifdef INET6 748 if (max_linkhdr + hdrlen > MCLBYTES) 749 #else 750 if (max_linkhdr + hdrlen > MHLEN) 751 #endif 752 panic("tcphdr too big"); 753 /*#endif*/ 754 755 /* 756 * This KASSERT is here to catch edge cases at a well defined place. 757 * Before, those had triggered (random) panic conditions further down. 758 */ 759 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 760 761 /* 762 * Grab a header mbuf, attaching a copy of data to 763 * be transmitted, and initialize the header from 764 * the template for sends on this connection. 765 */ 766 if (len) { 767 struct mbuf *mb; 768 u_int moff; 769 770 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 771 V_tcpstat.tcps_sndprobe++; 772 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 773 V_tcpstat.tcps_sndrexmitpack++; 774 V_tcpstat.tcps_sndrexmitbyte += len; 775 } else { 776 V_tcpstat.tcps_sndpack++; 777 V_tcpstat.tcps_sndbyte += len; 778 } 779 #ifdef notyet 780 if ((m = m_copypack(so->so_snd.sb_mb, off, 781 (int)len, max_linkhdr + hdrlen)) == 0) { 782 SOCKBUF_UNLOCK(&so->so_snd); 783 error = ENOBUFS; 784 goto out; 785 } 786 /* 787 * m_copypack left space for our hdr; use it. 788 */ 789 m->m_len += hdrlen; 790 m->m_data -= hdrlen; 791 #else 792 MGETHDR(m, M_DONTWAIT, MT_DATA); 793 if (m == NULL) { 794 SOCKBUF_UNLOCK(&so->so_snd); 795 error = ENOBUFS; 796 goto out; 797 } 798 #ifdef INET6 799 if (MHLEN < hdrlen + max_linkhdr) { 800 MCLGET(m, M_DONTWAIT); 801 if ((m->m_flags & M_EXT) == 0) { 802 SOCKBUF_UNLOCK(&so->so_snd); 803 m_freem(m); 804 error = ENOBUFS; 805 goto out; 806 } 807 } 808 #endif 809 m->m_data += max_linkhdr; 810 m->m_len = hdrlen; 811 812 /* 813 * Start the m_copy functions from the closest mbuf 814 * to the offset in the socket buffer chain. 815 */ 816 mb = sbsndptr(&so->so_snd, off, len, &moff); 817 818 if (len <= MHLEN - hdrlen - max_linkhdr) { 819 m_copydata(mb, moff, (int)len, 820 mtod(m, caddr_t) + hdrlen); 821 m->m_len += len; 822 } else { 823 m->m_next = m_copy(mb, moff, (int)len); 824 if (m->m_next == NULL) { 825 SOCKBUF_UNLOCK(&so->so_snd); 826 (void) m_free(m); 827 error = ENOBUFS; 828 goto out; 829 } 830 } 831 #endif 832 /* 833 * If we're sending everything we've got, set PUSH. 834 * (This will keep happy those implementations which only 835 * give data to the user when a buffer fills or 836 * a PUSH comes in.) 837 */ 838 if (off + len == so->so_snd.sb_cc) 839 flags |= TH_PUSH; 840 SOCKBUF_UNLOCK(&so->so_snd); 841 } else { 842 SOCKBUF_UNLOCK(&so->so_snd); 843 if (tp->t_flags & TF_ACKNOW) 844 V_tcpstat.tcps_sndacks++; 845 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 846 V_tcpstat.tcps_sndctrl++; 847 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 848 V_tcpstat.tcps_sndurg++; 849 else 850 V_tcpstat.tcps_sndwinup++; 851 852 MGETHDR(m, M_DONTWAIT, MT_DATA); 853 if (m == NULL) { 854 error = ENOBUFS; 855 goto out; 856 } 857 #ifdef INET6 858 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 859 MHLEN >= hdrlen) { 860 MH_ALIGN(m, hdrlen); 861 } else 862 #endif 863 m->m_data += max_linkhdr; 864 m->m_len = hdrlen; 865 } 866 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 867 m->m_pkthdr.rcvif = (struct ifnet *)0; 868 #ifdef MAC 869 mac_inpcb_create_mbuf(tp->t_inpcb, m); 870 #endif 871 #ifdef INET6 872 if (isipv6) { 873 ip6 = mtod(m, struct ip6_hdr *); 874 th = (struct tcphdr *)(ip6 + 1); 875 tcpip_fillheaders(tp->t_inpcb, ip6, th); 876 } else 877 #endif /* INET6 */ 878 { 879 ip = mtod(m, struct ip *); 880 ipov = (struct ipovly *)ip; 881 th = (struct tcphdr *)(ip + 1); 882 tcpip_fillheaders(tp->t_inpcb, ip, th); 883 } 884 885 /* 886 * Fill in fields, remembering maximum advertised 887 * window for use in delaying messages about window sizes. 888 * If resending a FIN, be sure not to use a new sequence number. 889 */ 890 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 891 tp->snd_nxt == tp->snd_max) 892 tp->snd_nxt--; 893 /* 894 * If we are starting a connection, send ECN setup 895 * SYN packet. If we are on a retransmit, we may 896 * resend those bits a number of times as per 897 * RFC 3168. 898 */ 899 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 900 if (tp->t_rxtshift >= 1) { 901 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 902 flags |= TH_ECE|TH_CWR; 903 } else 904 flags |= TH_ECE|TH_CWR; 905 } 906 907 if (tp->t_state == TCPS_ESTABLISHED && 908 (tp->t_flags & TF_ECN_PERMIT)) { 909 /* 910 * If the peer has ECN, mark data packets with 911 * ECN capable transmission (ECT). 912 * Ignore pure ack packets, retransmissions and window probes. 913 */ 914 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 915 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 916 #ifdef INET6 917 if (isipv6) 918 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 919 else 920 #endif 921 ip->ip_tos |= IPTOS_ECN_ECT0; 922 V_tcpstat.tcps_ecn_ect0++; 923 } 924 925 /* 926 * Reply with proper ECN notifications. 927 */ 928 if (tp->t_flags & TF_ECN_SND_CWR) { 929 flags |= TH_CWR; 930 tp->t_flags &= ~TF_ECN_SND_CWR; 931 } 932 if (tp->t_flags & TF_ECN_SND_ECE) 933 flags |= TH_ECE; 934 } 935 936 /* 937 * If we are doing retransmissions, then snd_nxt will 938 * not reflect the first unsent octet. For ACK only 939 * packets, we do not want the sequence number of the 940 * retransmitted packet, we want the sequence number 941 * of the next unsent octet. So, if there is no data 942 * (and no SYN or FIN), use snd_max instead of snd_nxt 943 * when filling in ti_seq. But if we are in persist 944 * state, snd_max might reflect one byte beyond the 945 * right edge of the window, so use snd_nxt in that 946 * case, since we know we aren't doing a retransmission. 947 * (retransmit and persist are mutually exclusive...) 948 */ 949 if (sack_rxmit == 0) { 950 if (len || (flags & (TH_SYN|TH_FIN)) || 951 tcp_timer_active(tp, TT_PERSIST)) 952 th->th_seq = htonl(tp->snd_nxt); 953 else 954 th->th_seq = htonl(tp->snd_max); 955 } else { 956 th->th_seq = htonl(p->rxmit); 957 p->rxmit += len; 958 tp->sackhint.sack_bytes_rexmit += len; 959 } 960 th->th_ack = htonl(tp->rcv_nxt); 961 if (optlen) { 962 bcopy(opt, th + 1, optlen); 963 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 964 } 965 th->th_flags = flags; 966 /* 967 * Calculate receive window. Don't shrink window, 968 * but avoid silly window syndrome. 969 */ 970 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 971 recwin < (long)tp->t_maxseg) 972 recwin = 0; 973 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 974 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 975 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 976 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 977 978 /* 979 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 980 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 981 * case is handled in syncache. 982 */ 983 if (flags & TH_SYN) 984 th->th_win = htons((u_short) 985 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 986 else 987 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 988 989 /* 990 * Adjust the RXWIN0SENT flag - indicate that we have advertised 991 * a 0 window. This may cause the remote transmitter to stall. This 992 * flag tells soreceive() to disable delayed acknowledgements when 993 * draining the buffer. This can occur if the receiver is attempting 994 * to read more data than can be buffered prior to transmitting on 995 * the connection. 996 */ 997 if (recwin == 0) 998 tp->t_flags |= TF_RXWIN0SENT; 999 else 1000 tp->t_flags &= ~TF_RXWIN0SENT; 1001 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1002 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1003 th->th_flags |= TH_URG; 1004 } else 1005 /* 1006 * If no urgent pointer to send, then we pull 1007 * the urgent pointer to the left edge of the send window 1008 * so that it doesn't drift into the send window on sequence 1009 * number wraparound. 1010 */ 1011 tp->snd_up = tp->snd_una; /* drag it along */ 1012 1013 #ifdef TCP_SIGNATURE 1014 if (tp->t_flags & TF_SIGNATURE) { 1015 int sigoff = to.to_signature - opt; 1016 tcp_signature_compute(m, 0, len, optlen, 1017 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1018 } 1019 #endif 1020 1021 /* 1022 * Put TCP length in extended header, and then 1023 * checksum extended header and data. 1024 */ 1025 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1026 #ifdef INET6 1027 if (isipv6) 1028 /* 1029 * ip6_plen is not need to be filled now, and will be filled 1030 * in ip6_output. 1031 */ 1032 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1033 sizeof(struct tcphdr) + optlen + len); 1034 else 1035 #endif /* INET6 */ 1036 { 1037 m->m_pkthdr.csum_flags = CSUM_TCP; 1038 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1039 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1040 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1041 1042 /* IP version must be set here for ipv4/ipv6 checking later */ 1043 KASSERT(ip->ip_v == IPVERSION, 1044 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1045 } 1046 1047 /* 1048 * Enable TSO and specify the size of the segments. 1049 * The TCP pseudo header checksum is always provided. 1050 * XXX: Fixme: This is currently not the case for IPv6. 1051 */ 1052 if (tso) { 1053 m->m_pkthdr.csum_flags = CSUM_TSO; 1054 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1055 } 1056 1057 /* 1058 * In transmit state, time the transmission and arrange for 1059 * the retransmit. In persist state, just set snd_max. 1060 */ 1061 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1062 !tcp_timer_active(tp, TT_PERSIST)) { 1063 tcp_seq startseq = tp->snd_nxt; 1064 1065 /* 1066 * Advance snd_nxt over sequence space of this segment. 1067 */ 1068 if (flags & (TH_SYN|TH_FIN)) { 1069 if (flags & TH_SYN) 1070 tp->snd_nxt++; 1071 if (flags & TH_FIN) { 1072 tp->snd_nxt++; 1073 tp->t_flags |= TF_SENTFIN; 1074 } 1075 } 1076 if (sack_rxmit) 1077 goto timer; 1078 tp->snd_nxt += len; 1079 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1080 tp->snd_max = tp->snd_nxt; 1081 /* 1082 * Time this transmission if not a retransmission and 1083 * not currently timing anything. 1084 */ 1085 if (tp->t_rtttime == 0) { 1086 tp->t_rtttime = ticks; 1087 tp->t_rtseq = startseq; 1088 V_tcpstat.tcps_segstimed++; 1089 } 1090 } 1091 1092 /* 1093 * Set retransmit timer if not currently set, 1094 * and not doing a pure ack or a keep-alive probe. 1095 * Initial value for retransmit timer is smoothed 1096 * round-trip time + 2 * round-trip time variance. 1097 * Initialize shift counter which is used for backoff 1098 * of retransmit time. 1099 */ 1100 timer: 1101 if (!tcp_timer_active(tp, TT_REXMT) && 1102 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1103 (tp->snd_nxt != tp->snd_una))) { 1104 if (tcp_timer_active(tp, TT_PERSIST)) { 1105 tcp_timer_activate(tp, TT_PERSIST, 0); 1106 tp->t_rxtshift = 0; 1107 } 1108 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1109 } 1110 } else { 1111 /* 1112 * Persist case, update snd_max but since we are in 1113 * persist mode (no window) we do not update snd_nxt. 1114 */ 1115 int xlen = len; 1116 if (flags & TH_SYN) 1117 ++xlen; 1118 if (flags & TH_FIN) { 1119 ++xlen; 1120 tp->t_flags |= TF_SENTFIN; 1121 } 1122 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1123 tp->snd_max = tp->snd_nxt + len; 1124 } 1125 1126 #ifdef TCPDEBUG 1127 /* 1128 * Trace. 1129 */ 1130 if (so->so_options & SO_DEBUG) { 1131 u_short save = 0; 1132 #ifdef INET6 1133 if (!isipv6) 1134 #endif 1135 { 1136 save = ipov->ih_len; 1137 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1138 } 1139 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1140 #ifdef INET6 1141 if (!isipv6) 1142 #endif 1143 ipov->ih_len = save; 1144 } 1145 #endif 1146 1147 /* 1148 * Fill in IP length and desired time to live and 1149 * send to IP level. There should be a better way 1150 * to handle ttl and tos; we could keep them in 1151 * the template, but need a way to checksum without them. 1152 */ 1153 /* 1154 * m->m_pkthdr.len should have been set before cksum calcuration, 1155 * because in6_cksum() need it. 1156 */ 1157 #ifdef INET6 1158 if (isipv6) { 1159 /* 1160 * we separately set hoplimit for every segment, since the 1161 * user might want to change the value via setsockopt. 1162 * Also, desired default hop limit might be changed via 1163 * Neighbor Discovery. 1164 */ 1165 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1166 1167 /* TODO: IPv6 IP6TOS_ECT bit on */ 1168 error = ip6_output(m, 1169 tp->t_inpcb->in6p_outputopts, NULL, 1170 ((so->so_options & SO_DONTROUTE) ? 1171 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1172 } else 1173 #endif /* INET6 */ 1174 { 1175 ip->ip_len = m->m_pkthdr.len; 1176 #ifdef INET6 1177 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1178 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1179 #endif /* INET6 */ 1180 /* 1181 * If we do path MTU discovery, then we set DF on every packet. 1182 * This might not be the best thing to do according to RFC3390 1183 * Section 2. However the tcp hostcache migitates the problem 1184 * so it affects only the first tcp connection with a host. 1185 */ 1186 if (V_path_mtu_discovery) 1187 ip->ip_off |= IP_DF; 1188 1189 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1190 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1191 tp->t_inpcb); 1192 } 1193 if (error) { 1194 1195 /* 1196 * We know that the packet was lost, so back out the 1197 * sequence number advance, if any. 1198 * 1199 * If the error is EPERM the packet got blocked by the 1200 * local firewall. Normally we should terminate the 1201 * connection but the blocking may have been spurious 1202 * due to a firewall reconfiguration cycle. So we treat 1203 * it like a packet loss and let the retransmit timer and 1204 * timeouts do their work over time. 1205 * XXX: It is a POLA question whether calling tcp_drop right 1206 * away would be the really correct behavior instead. 1207 */ 1208 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1209 !tcp_timer_active(tp, TT_PERSIST)) && 1210 ((flags & TH_SYN) == 0) && 1211 (error != EPERM)) { 1212 if (sack_rxmit) { 1213 p->rxmit -= len; 1214 tp->sackhint.sack_bytes_rexmit -= len; 1215 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1216 ("sackhint bytes rtx >= 0")); 1217 } else 1218 tp->snd_nxt -= len; 1219 } 1220 out: 1221 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1222 switch (error) { 1223 case EPERM: 1224 tp->t_softerror = error; 1225 return (error); 1226 case ENOBUFS: 1227 if (!tcp_timer_active(tp, TT_REXMT) && 1228 !tcp_timer_active(tp, TT_PERSIST)) 1229 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1230 tp->snd_cwnd = tp->t_maxseg; 1231 return (0); 1232 case EMSGSIZE: 1233 /* 1234 * For some reason the interface we used initially 1235 * to send segments changed to another or lowered 1236 * its MTU. 1237 * 1238 * tcp_mtudisc() will find out the new MTU and as 1239 * its last action, initiate retransmission, so it 1240 * is important to not do so here. 1241 * 1242 * If TSO was active we either got an interface 1243 * without TSO capabilits or TSO was turned off. 1244 * Disable it for this connection as too and 1245 * immediatly retry with MSS sized segments generated 1246 * by this function. 1247 */ 1248 if (tso) 1249 tp->t_flags &= ~TF_TSO; 1250 tcp_mtudisc(tp->t_inpcb, 0); 1251 return (0); 1252 case EHOSTDOWN: 1253 case EHOSTUNREACH: 1254 case ENETDOWN: 1255 case ENETUNREACH: 1256 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1257 tp->t_softerror = error; 1258 return (0); 1259 } 1260 /* FALLTHROUGH */ 1261 default: 1262 return (error); 1263 } 1264 } 1265 V_tcpstat.tcps_sndtotal++; 1266 1267 /* 1268 * Data sent (as far as we can tell). 1269 * If this advertises a larger window than any other segment, 1270 * then remember the size of the advertised window. 1271 * Any pending ACK has now been sent. 1272 */ 1273 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1274 tp->rcv_adv = tp->rcv_nxt + recwin; 1275 tp->last_ack_sent = tp->rcv_nxt; 1276 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1277 if (tcp_timer_active(tp, TT_DELACK)) 1278 tcp_timer_activate(tp, TT_DELACK, 0); 1279 #if 0 1280 /* 1281 * This completely breaks TCP if newreno is turned on. What happens 1282 * is that if delayed-acks are turned on on the receiver, this code 1283 * on the transmitter effectively destroys the TCP window, forcing 1284 * it to four packets (1.5Kx4 = 6K window). 1285 */ 1286 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1287 goto again; 1288 #endif 1289 if (sendalot) 1290 goto again; 1291 return (0); 1292 } 1293 1294 void 1295 tcp_setpersist(struct tcpcb *tp) 1296 { 1297 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1298 int tt; 1299 1300 if (tcp_timer_active(tp, TT_REXMT)) 1301 panic("tcp_setpersist: retransmit pending"); 1302 /* 1303 * Start/restart persistance timer. 1304 */ 1305 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1306 TCPTV_PERSMIN, TCPTV_PERSMAX); 1307 tcp_timer_activate(tp, TT_PERSIST, tt); 1308 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1309 tp->t_rxtshift++; 1310 } 1311 1312 /* 1313 * Insert TCP options according to the supplied parameters to the place 1314 * optp in a consistent way. Can handle unaligned destinations. 1315 * 1316 * The order of the option processing is crucial for optimal packing and 1317 * alignment for the scarce option space. 1318 * 1319 * The optimal order for a SYN/SYN-ACK segment is: 1320 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1321 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1322 * 1323 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1324 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1325 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1326 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1327 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1328 */ 1329 int 1330 tcp_addoptions(struct tcpopt *to, u_char *optp) 1331 { 1332 INIT_VNET_INET(curvnet); 1333 u_int mask, optlen = 0; 1334 1335 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1336 if ((to->to_flags & mask) != mask) 1337 continue; 1338 if (optlen == TCP_MAXOLEN) 1339 break; 1340 switch (to->to_flags & mask) { 1341 case TOF_MSS: 1342 while (optlen % 4) { 1343 optlen += TCPOLEN_NOP; 1344 *optp++ = TCPOPT_NOP; 1345 } 1346 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1347 continue; 1348 optlen += TCPOLEN_MAXSEG; 1349 *optp++ = TCPOPT_MAXSEG; 1350 *optp++ = TCPOLEN_MAXSEG; 1351 to->to_mss = htons(to->to_mss); 1352 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1353 optp += sizeof(to->to_mss); 1354 break; 1355 case TOF_SCALE: 1356 while (!optlen || optlen % 2 != 1) { 1357 optlen += TCPOLEN_NOP; 1358 *optp++ = TCPOPT_NOP; 1359 } 1360 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1361 continue; 1362 optlen += TCPOLEN_WINDOW; 1363 *optp++ = TCPOPT_WINDOW; 1364 *optp++ = TCPOLEN_WINDOW; 1365 *optp++ = to->to_wscale; 1366 break; 1367 case TOF_SACKPERM: 1368 while (optlen % 2) { 1369 optlen += TCPOLEN_NOP; 1370 *optp++ = TCPOPT_NOP; 1371 } 1372 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1373 continue; 1374 optlen += TCPOLEN_SACK_PERMITTED; 1375 *optp++ = TCPOPT_SACK_PERMITTED; 1376 *optp++ = TCPOLEN_SACK_PERMITTED; 1377 break; 1378 case TOF_TS: 1379 while (!optlen || optlen % 4 != 2) { 1380 optlen += TCPOLEN_NOP; 1381 *optp++ = TCPOPT_NOP; 1382 } 1383 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1384 continue; 1385 optlen += TCPOLEN_TIMESTAMP; 1386 *optp++ = TCPOPT_TIMESTAMP; 1387 *optp++ = TCPOLEN_TIMESTAMP; 1388 to->to_tsval = htonl(to->to_tsval); 1389 to->to_tsecr = htonl(to->to_tsecr); 1390 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1391 optp += sizeof(to->to_tsval); 1392 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1393 optp += sizeof(to->to_tsecr); 1394 break; 1395 case TOF_SIGNATURE: 1396 { 1397 int siglen = TCPOLEN_SIGNATURE - 2; 1398 1399 while (!optlen || optlen % 4 != 2) { 1400 optlen += TCPOLEN_NOP; 1401 *optp++ = TCPOPT_NOP; 1402 } 1403 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1404 continue; 1405 optlen += TCPOLEN_SIGNATURE; 1406 *optp++ = TCPOPT_SIGNATURE; 1407 *optp++ = TCPOLEN_SIGNATURE; 1408 to->to_signature = optp; 1409 while (siglen--) 1410 *optp++ = 0; 1411 break; 1412 } 1413 case TOF_SACK: 1414 { 1415 int sackblks = 0; 1416 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1417 tcp_seq sack_seq; 1418 1419 while (!optlen || optlen % 4 != 2) { 1420 optlen += TCPOLEN_NOP; 1421 *optp++ = TCPOPT_NOP; 1422 } 1423 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1424 continue; 1425 optlen += TCPOLEN_SACKHDR; 1426 *optp++ = TCPOPT_SACK; 1427 sackblks = min(to->to_nsacks, 1428 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1429 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1430 while (sackblks--) { 1431 sack_seq = htonl(sack->start); 1432 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1433 optp += sizeof(sack_seq); 1434 sack_seq = htonl(sack->end); 1435 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1436 optp += sizeof(sack_seq); 1437 optlen += TCPOLEN_SACK; 1438 sack++; 1439 } 1440 V_tcpstat.tcps_sack_send_blocks++; 1441 break; 1442 } 1443 default: 1444 panic("%s: unknown TCP option type", __func__); 1445 break; 1446 } 1447 } 1448 1449 /* Terminate and pad TCP options to a 4 byte boundary. */ 1450 if (optlen % 4) { 1451 optlen += TCPOLEN_EOL; 1452 *optp++ = TCPOPT_EOL; 1453 } 1454 /* 1455 * According to RFC 793 (STD0007): 1456 * "The content of the header beyond the End-of-Option option 1457 * must be header padding (i.e., zero)." 1458 * and later: "The padding is composed of zeros." 1459 */ 1460 while (optlen % 4) { 1461 optlen += TCPOLEN_PAD; 1462 *optp++ = TCPOPT_PAD; 1463 } 1464 1465 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1466 return (optlen); 1467 } 1468