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_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, path_mtu_discovery, 92 CTLFLAG_RW, path_mtu_discovery, 1, "Enable Path MTU Discovery"); 93 94 int ss_fltsz = 1; 95 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, 96 slowstart_flightsize, CTLFLAG_RW, 97 ss_fltsz, 1, "Slow start flight size"); 98 99 int ss_fltsz_local = 4; 100 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, 101 local_slowstart_flightsize, CTLFLAG_RW, 102 ss_fltsz_local, 1, "Slow start flight size for local networks"); 103 104 int tcp_do_newreno = 1; 105 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 106 tcp_do_newreno, 0, "Enable NewReno Algorithms"); 107 108 int tcp_do_tso = 1; 109 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 110 tcp_do_tso, 0, "Enable TCP Segmentation Offload"); 111 112 int tcp_do_autosndbuf = 1; 113 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_auto, 114 CTLFLAG_RW, 115 tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 116 117 int tcp_autosndbuf_inc = 8*1024; 118 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_inc, 119 CTLFLAG_RW, tcp_autosndbuf_inc, 0, 120 "Incrementor step size of automatic send buffer"); 121 122 int tcp_autosndbuf_max = 256*1024; 123 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, sendbuf_max, 124 CTLFLAG_RW, tcp_autosndbuf_max, 0, 125 "Max size of automatic send buffer"); 126 127 128 /* 129 * Tcp output routine: figure out what should be sent and send it. 130 */ 131 int 132 tcp_output(struct tcpcb *tp) 133 { 134 INIT_VNET_INET(tp->t_inpcb->inp_vnet); 135 struct socket *so = tp->t_inpcb->inp_socket; 136 long len, recwin, sendwin; 137 int off, flags, error; 138 struct mbuf *m; 139 struct ip *ip = NULL; 140 struct ipovly *ipov = NULL; 141 struct tcphdr *th; 142 u_char opt[TCP_MAXOLEN]; 143 unsigned ipoptlen, optlen, hdrlen; 144 #ifdef IPSEC 145 unsigned ipsec_optlen = 0; 146 #endif 147 int idle, sendalot; 148 int sack_rxmit, sack_bytes_rxmt; 149 struct sackhole *p; 150 int tso = 0; 151 struct tcpopt to; 152 #if 0 153 int maxburst = TCP_MAXBURST; 154 #endif 155 #ifdef INET6 156 struct ip6_hdr *ip6 = NULL; 157 int isipv6; 158 159 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 160 #endif 161 162 INP_WLOCK_ASSERT(tp->t_inpcb); 163 164 /* 165 * Determine length of data that should be transmitted, 166 * and flags that will be used. 167 * If there is some data or critical controls (SYN, RST) 168 * to send, then transmit; otherwise, investigate further. 169 */ 170 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 171 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 172 /* 173 * We have been idle for "a while" and no acks are 174 * expected to clock out any data we send -- 175 * slow start to get ack "clock" running again. 176 * 177 * Set the slow-start flight size depending on whether 178 * this is a local network or not. 179 */ 180 int ss = V_ss_fltsz; 181 #ifdef INET6 182 if (isipv6) { 183 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 184 ss = V_ss_fltsz_local; 185 } else 186 #endif /* INET6 */ 187 if (in_localaddr(tp->t_inpcb->inp_faddr)) 188 ss = V_ss_fltsz_local; 189 tp->snd_cwnd = tp->t_maxseg * ss; 190 } 191 tp->t_flags &= ~TF_LASTIDLE; 192 if (idle) { 193 if (tp->t_flags & TF_MORETOCOME) { 194 tp->t_flags |= TF_LASTIDLE; 195 idle = 0; 196 } 197 } 198 again: 199 /* 200 * If we've recently taken a timeout, snd_max will be greater than 201 * snd_nxt. There may be SACK information that allows us to avoid 202 * resending already delivered data. Adjust snd_nxt accordingly. 203 */ 204 if ((tp->t_flags & TF_SACK_PERMIT) && 205 SEQ_LT(tp->snd_nxt, tp->snd_max)) 206 tcp_sack_adjust(tp); 207 sendalot = 0; 208 off = tp->snd_nxt - tp->snd_una; 209 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 210 sendwin = min(sendwin, tp->snd_bwnd); 211 212 flags = tcp_outflags[tp->t_state]; 213 /* 214 * Send any SACK-generated retransmissions. If we're explicitly trying 215 * to send out new data (when sendalot is 1), bypass this function. 216 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 217 * we're replacing a (future) new transmission with a retransmission 218 * now, and we previously incremented snd_cwnd in tcp_input(). 219 */ 220 /* 221 * Still in sack recovery , reset rxmit flag to zero. 222 */ 223 sack_rxmit = 0; 224 sack_bytes_rxmt = 0; 225 len = 0; 226 p = NULL; 227 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 228 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 229 long cwin; 230 231 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 232 if (cwin < 0) 233 cwin = 0; 234 /* Do not retransmit SACK segments beyond snd_recover */ 235 if (SEQ_GT(p->end, tp->snd_recover)) { 236 /* 237 * (At least) part of sack hole extends beyond 238 * snd_recover. Check to see if we can rexmit data 239 * for this hole. 240 */ 241 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 242 /* 243 * Can't rexmit any more data for this hole. 244 * That data will be rexmitted in the next 245 * sack recovery episode, when snd_recover 246 * moves past p->rxmit. 247 */ 248 p = NULL; 249 goto after_sack_rexmit; 250 } else 251 /* Can rexmit part of the current hole */ 252 len = ((long)ulmin(cwin, 253 tp->snd_recover - p->rxmit)); 254 } else 255 len = ((long)ulmin(cwin, p->end - p->rxmit)); 256 off = p->rxmit - tp->snd_una; 257 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 258 __func__, off)); 259 if (len > 0) { 260 sack_rxmit = 1; 261 sendalot = 1; 262 V_tcpstat.tcps_sack_rexmits++; 263 V_tcpstat.tcps_sack_rexmit_bytes += 264 min(len, tp->t_maxseg); 265 } 266 } 267 after_sack_rexmit: 268 /* 269 * Get standard flags, and add SYN or FIN if requested by 'hidden' 270 * state flags. 271 */ 272 if (tp->t_flags & TF_NEEDFIN) 273 flags |= TH_FIN; 274 if (tp->t_flags & TF_NEEDSYN) 275 flags |= TH_SYN; 276 277 SOCKBUF_LOCK(&so->so_snd); 278 /* 279 * If in persist timeout with window of 0, send 1 byte. 280 * Otherwise, if window is small but nonzero 281 * and timer expired, we will send what we can 282 * and go to transmit state. 283 */ 284 if (tp->t_flags & TF_FORCEDATA) { 285 if (sendwin == 0) { 286 /* 287 * If we still have some data to send, then 288 * clear the FIN bit. Usually this would 289 * happen below when it realizes that we 290 * aren't sending all the data. However, 291 * if we have exactly 1 byte of unsent data, 292 * then it won't clear the FIN bit below, 293 * and if we are in persist state, we wind 294 * up sending the packet without recording 295 * that we sent the FIN bit. 296 * 297 * We can't just blindly clear the FIN bit, 298 * because if we don't have any more data 299 * to send then the probe will be the FIN 300 * itself. 301 */ 302 if (off < so->so_snd.sb_cc) 303 flags &= ~TH_FIN; 304 sendwin = 1; 305 } else { 306 tcp_timer_activate(tp, TT_PERSIST, 0); 307 tp->t_rxtshift = 0; 308 } 309 } 310 311 /* 312 * If snd_nxt == snd_max and we have transmitted a FIN, the 313 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 314 * a negative length. This can also occur when TCP opens up 315 * its congestion window while receiving additional duplicate 316 * acks after fast-retransmit because TCP will reset snd_nxt 317 * to snd_max after the fast-retransmit. 318 * 319 * In the normal retransmit-FIN-only case, however, snd_nxt will 320 * be set to snd_una, the offset will be 0, and the length may 321 * wind up 0. 322 * 323 * If sack_rxmit is true we are retransmitting from the scoreboard 324 * in which case len is already set. 325 */ 326 if (sack_rxmit == 0) { 327 if (sack_bytes_rxmt == 0) 328 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 329 else { 330 long cwin; 331 332 /* 333 * We are inside of a SACK recovery episode and are 334 * sending new data, having retransmitted all the 335 * data possible in the scoreboard. 336 */ 337 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 338 - off); 339 /* 340 * Don't remove this (len > 0) check ! 341 * We explicitly check for len > 0 here (although it 342 * isn't really necessary), to work around a gcc 343 * optimization issue - to force gcc to compute 344 * len above. Without this check, the computation 345 * of len is bungled by the optimizer. 346 */ 347 if (len > 0) { 348 cwin = tp->snd_cwnd - 349 (tp->snd_nxt - tp->sack_newdata) - 350 sack_bytes_rxmt; 351 if (cwin < 0) 352 cwin = 0; 353 len = lmin(len, cwin); 354 } 355 } 356 } 357 358 /* 359 * Lop off SYN bit if it has already been sent. However, if this 360 * is SYN-SENT state and if segment contains data and if we don't 361 * know that foreign host supports TAO, suppress sending segment. 362 */ 363 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 364 if (tp->t_state != TCPS_SYN_RECEIVED) 365 flags &= ~TH_SYN; 366 off--, len++; 367 } 368 369 /* 370 * Be careful not to send data and/or FIN on SYN segments. 371 * This measure is needed to prevent interoperability problems 372 * with not fully conformant TCP implementations. 373 */ 374 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 375 len = 0; 376 flags &= ~TH_FIN; 377 } 378 379 if (len < 0) { 380 /* 381 * If FIN has been sent but not acked, 382 * but we haven't been called to retransmit, 383 * len will be < 0. Otherwise, window shrank 384 * after we sent into it. If window shrank to 0, 385 * cancel pending retransmit, pull snd_nxt back 386 * to (closed) window, and set the persist timer 387 * if it isn't already going. If the window didn't 388 * close completely, just wait for an ACK. 389 */ 390 len = 0; 391 if (sendwin == 0) { 392 tcp_timer_activate(tp, TT_REXMT, 0); 393 tp->t_rxtshift = 0; 394 tp->snd_nxt = tp->snd_una; 395 if (!tcp_timer_active(tp, TT_PERSIST)) 396 tcp_setpersist(tp); 397 } 398 } 399 400 /* len will be >= 0 after this point. */ 401 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 402 403 /* 404 * Automatic sizing of send socket buffer. Often the send buffer 405 * size is not optimally adjusted to the actual network conditions 406 * at hand (delay bandwidth product). Setting the buffer size too 407 * small limits throughput on links with high bandwidth and high 408 * delay (eg. trans-continental/oceanic links). Setting the 409 * buffer size too big consumes too much real kernel memory, 410 * especially with many connections on busy servers. 411 * 412 * The criteria to step up the send buffer one notch are: 413 * 1. receive window of remote host is larger than send buffer 414 * (with a fudge factor of 5/4th); 415 * 2. send buffer is filled to 7/8th with data (so we actually 416 * have data to make use of it); 417 * 3. send buffer fill has not hit maximal automatic size; 418 * 4. our send window (slow start and cogestion controlled) is 419 * larger than sent but unacknowledged data in send buffer. 420 * 421 * The remote host receive window scaling factor may limit the 422 * growing of the send buffer before it reaches its allowed 423 * maximum. 424 * 425 * It scales directly with slow start or congestion window 426 * and does at most one step per received ACK. This fast 427 * scaling has the drawback of growing the send buffer beyond 428 * what is strictly necessary to make full use of a given 429 * delay*bandwith product. However testing has shown this not 430 * to be much of an problem. At worst we are trading wasting 431 * of available bandwith (the non-use of it) for wasting some 432 * socket buffer memory. 433 * 434 * TODO: Shrink send buffer during idle periods together 435 * with congestion window. Requires another timer. Has to 436 * wait for upcoming tcp timer rewrite. 437 */ 438 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 439 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 440 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 441 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 442 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 443 if (!sbreserve_locked(&so->so_snd, 444 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 445 V_tcp_autosndbuf_max), so, curthread)) 446 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 447 } 448 } 449 450 /* 451 * Truncate to the maximum segment length or enable TCP Segmentation 452 * Offloading (if supported by hardware) and ensure that FIN is removed 453 * if the length no longer contains the last data byte. 454 * 455 * TSO may only be used if we are in a pure bulk sending state. The 456 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 457 * IP options prevent using TSO. With TSO the TCP header is the same 458 * (except for the sequence number) for all generated packets. This 459 * makes it impossible to transmit any options which vary per generated 460 * segment or packet. 461 * 462 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 463 * removal of FIN (if not already catched here) are handled later after 464 * the exact length of the TCP options are known. 465 */ 466 #ifdef IPSEC 467 /* 468 * Pre-calculate here as we save another lookup into the darknesses 469 * of IPsec that way and can actually decide if TSO is ok. 470 */ 471 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 472 #endif 473 if (len > tp->t_maxseg) { 474 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 475 ((tp->t_flags & TF_SIGNATURE) == 0) && 476 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 477 tp->t_inpcb->inp_options == NULL && 478 tp->t_inpcb->in6p_options == NULL 479 #ifdef IPSEC 480 && ipsec_optlen == 0 481 #endif 482 ) { 483 tso = 1; 484 } else { 485 len = tp->t_maxseg; 486 sendalot = 1; 487 tso = 0; 488 } 489 } 490 if (sack_rxmit) { 491 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 492 flags &= ~TH_FIN; 493 } else { 494 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 495 flags &= ~TH_FIN; 496 } 497 498 recwin = sbspace(&so->so_rcv); 499 500 /* 501 * Sender silly window avoidance. We transmit under the following 502 * conditions when len is non-zero: 503 * 504 * - We have a full segment (or more with TSO) 505 * - This is the last buffer in a write()/send() and we are 506 * either idle or running NODELAY 507 * - we've timed out (e.g. persist timer) 508 * - we have more then 1/2 the maximum send window's worth of 509 * data (receiver may be limited the window size) 510 * - we need to retransmit 511 */ 512 if (len) { 513 if (len >= tp->t_maxseg) 514 goto send; 515 /* 516 * NOTE! on localhost connections an 'ack' from the remote 517 * end may occur synchronously with the output and cause 518 * us to flush a buffer queued with moretocome. XXX 519 * 520 * note: the len + off check is almost certainly unnecessary. 521 */ 522 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 523 (idle || (tp->t_flags & TF_NODELAY)) && 524 len + off >= so->so_snd.sb_cc && 525 (tp->t_flags & TF_NOPUSH) == 0) { 526 goto send; 527 } 528 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 529 goto send; 530 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 531 goto send; 532 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 533 goto send; 534 if (sack_rxmit) 535 goto send; 536 } 537 538 /* 539 * Compare available window to amount of window 540 * known to peer (as advertised window less 541 * next expected input). If the difference is at least two 542 * max size segments, or at least 50% of the maximum possible 543 * window, then want to send a window update to peer. 544 * Skip this if the connection is in T/TCP half-open state. 545 * Don't send pure window updates when the peer has closed 546 * the connection and won't ever send more data. 547 */ 548 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 549 !TCPS_HAVERCVDFIN(tp->t_state)) { 550 /* 551 * "adv" is the amount we can increase the window, 552 * taking into account that we are limited by 553 * TCP_MAXWIN << tp->rcv_scale. 554 */ 555 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 556 (tp->rcv_adv - tp->rcv_nxt); 557 558 if (adv >= (long) (2 * tp->t_maxseg)) 559 goto send; 560 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 561 goto send; 562 } 563 564 /* 565 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 566 * is also a catch-all for the retransmit timer timeout case. 567 */ 568 if (tp->t_flags & TF_ACKNOW) 569 goto send; 570 if ((flags & TH_RST) || 571 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 572 goto send; 573 if (SEQ_GT(tp->snd_up, tp->snd_una)) 574 goto send; 575 /* 576 * If our state indicates that FIN should be sent 577 * and we have not yet done so, then we need to send. 578 */ 579 if (flags & TH_FIN && 580 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 581 goto send; 582 /* 583 * In SACK, it is possible for tcp_output to fail to send a segment 584 * after the retransmission timer has been turned off. Make sure 585 * that the retransmission timer is set. 586 */ 587 if ((tp->t_flags & TF_SACK_PERMIT) && 588 SEQ_GT(tp->snd_max, tp->snd_una) && 589 !tcp_timer_active(tp, TT_REXMT) && 590 !tcp_timer_active(tp, TT_PERSIST)) { 591 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 592 goto just_return; 593 } 594 /* 595 * TCP window updates are not reliable, rather a polling protocol 596 * using ``persist'' packets is used to insure receipt of window 597 * updates. The three ``states'' for the output side are: 598 * idle not doing retransmits or persists 599 * persisting to move a small or zero window 600 * (re)transmitting and thereby not persisting 601 * 602 * tcp_timer_active(tp, TT_PERSIST) 603 * is true when we are in persist state. 604 * (tp->t_flags & TF_FORCEDATA) 605 * is set when we are called to send a persist packet. 606 * tcp_timer_active(tp, TT_REXMT) 607 * is set when we are retransmitting 608 * The output side is idle when both timers are zero. 609 * 610 * If send window is too small, there is data to transmit, and no 611 * retransmit or persist is pending, then go to persist state. 612 * If nothing happens soon, send when timer expires: 613 * if window is nonzero, transmit what we can, 614 * otherwise force out a byte. 615 */ 616 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 617 !tcp_timer_active(tp, TT_PERSIST)) { 618 tp->t_rxtshift = 0; 619 tcp_setpersist(tp); 620 } 621 622 /* 623 * No reason to send a segment, just return. 624 */ 625 just_return: 626 SOCKBUF_UNLOCK(&so->so_snd); 627 return (0); 628 629 send: 630 SOCKBUF_LOCK_ASSERT(&so->so_snd); 631 /* 632 * Before ESTABLISHED, force sending of initial options 633 * unless TCP set not to do any options. 634 * NOTE: we assume that the IP/TCP header plus TCP options 635 * always fit in a single mbuf, leaving room for a maximum 636 * link header, i.e. 637 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 638 */ 639 optlen = 0; 640 #ifdef INET6 641 if (isipv6) 642 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 643 else 644 #endif 645 hdrlen = sizeof (struct tcpiphdr); 646 647 /* 648 * Compute options for segment. 649 * We only have to care about SYN and established connection 650 * segments. Options for SYN-ACK segments are handled in TCP 651 * syncache. 652 */ 653 if ((tp->t_flags & TF_NOOPT) == 0) { 654 to.to_flags = 0; 655 /* Maximum segment size. */ 656 if (flags & TH_SYN) { 657 tp->snd_nxt = tp->iss; 658 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 659 to.to_flags |= TOF_MSS; 660 } 661 /* Window scaling. */ 662 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 663 to.to_wscale = tp->request_r_scale; 664 to.to_flags |= TOF_SCALE; 665 } 666 /* Timestamps. */ 667 if ((tp->t_flags & TF_RCVD_TSTMP) || 668 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 669 to.to_tsval = ticks + tp->ts_offset; 670 to.to_tsecr = tp->ts_recent; 671 to.to_flags |= TOF_TS; 672 /* Set receive buffer autosizing timestamp. */ 673 if (tp->rfbuf_ts == 0 && 674 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 675 tp->rfbuf_ts = ticks; 676 } 677 /* Selective ACK's. */ 678 if (tp->t_flags & TF_SACK_PERMIT) { 679 if (flags & TH_SYN) 680 to.to_flags |= TOF_SACKPERM; 681 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 682 (tp->t_flags & TF_SACK_PERMIT) && 683 tp->rcv_numsacks > 0) { 684 to.to_flags |= TOF_SACK; 685 to.to_nsacks = tp->rcv_numsacks; 686 to.to_sacks = (u_char *)tp->sackblks; 687 } 688 } 689 #ifdef TCP_SIGNATURE 690 /* TCP-MD5 (RFC2385). */ 691 if (tp->t_flags & TF_SIGNATURE) 692 to.to_flags |= TOF_SIGNATURE; 693 #endif /* TCP_SIGNATURE */ 694 695 /* Processing the options. */ 696 hdrlen += optlen = tcp_addoptions(&to, opt); 697 } 698 699 #ifdef INET6 700 if (isipv6) 701 ipoptlen = ip6_optlen(tp->t_inpcb); 702 else 703 #endif 704 if (tp->t_inpcb->inp_options) 705 ipoptlen = tp->t_inpcb->inp_options->m_len - 706 offsetof(struct ipoption, ipopt_list); 707 else 708 ipoptlen = 0; 709 #ifdef IPSEC 710 ipoptlen += ipsec_optlen; 711 #endif 712 713 /* 714 * Adjust data length if insertion of options will 715 * bump the packet length beyond the t_maxopd length. 716 * Clear the FIN bit because we cut off the tail of 717 * the segment. 718 * 719 * When doing TSO limit a burst to TCP_MAXWIN minus the 720 * IP, TCP and Options length to keep ip->ip_len from 721 * overflowing. Prevent the last segment from being 722 * fractional thus making them all equal sized and set 723 * the flag to continue sending. TSO is disabled when 724 * IP options or IPSEC are present. 725 */ 726 if (len + optlen + ipoptlen > tp->t_maxopd) { 727 flags &= ~TH_FIN; 728 if (tso) { 729 if (len > TCP_MAXWIN - hdrlen - optlen) { 730 len = TCP_MAXWIN - hdrlen - optlen; 731 len = len - (len % (tp->t_maxopd - optlen)); 732 sendalot = 1; 733 } else if (tp->t_flags & TF_NEEDFIN) 734 sendalot = 1; 735 } else { 736 len = tp->t_maxopd - optlen - ipoptlen; 737 sendalot = 1; 738 } 739 } 740 741 /*#ifdef DIAGNOSTIC*/ 742 #ifdef INET6 743 if (max_linkhdr + hdrlen > MCLBYTES) 744 #else 745 if (max_linkhdr + hdrlen > MHLEN) 746 #endif 747 panic("tcphdr too big"); 748 /*#endif*/ 749 750 /* 751 * This KASSERT is here to catch edge cases at a well defined place. 752 * Before, those had triggered (random) panic conditions further down. 753 */ 754 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 755 756 /* 757 * Grab a header mbuf, attaching a copy of data to 758 * be transmitted, and initialize the header from 759 * the template for sends on this connection. 760 */ 761 if (len) { 762 struct mbuf *mb; 763 u_int moff; 764 765 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 766 V_tcpstat.tcps_sndprobe++; 767 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 768 V_tcpstat.tcps_sndrexmitpack++; 769 V_tcpstat.tcps_sndrexmitbyte += len; 770 } else { 771 V_tcpstat.tcps_sndpack++; 772 V_tcpstat.tcps_sndbyte += len; 773 } 774 #ifdef notyet 775 if ((m = m_copypack(so->so_snd.sb_mb, off, 776 (int)len, max_linkhdr + hdrlen)) == 0) { 777 SOCKBUF_UNLOCK(&so->so_snd); 778 error = ENOBUFS; 779 goto out; 780 } 781 /* 782 * m_copypack left space for our hdr; use it. 783 */ 784 m->m_len += hdrlen; 785 m->m_data -= hdrlen; 786 #else 787 MGETHDR(m, M_DONTWAIT, MT_DATA); 788 if (m == NULL) { 789 SOCKBUF_UNLOCK(&so->so_snd); 790 error = ENOBUFS; 791 goto out; 792 } 793 #ifdef INET6 794 if (MHLEN < hdrlen + max_linkhdr) { 795 MCLGET(m, M_DONTWAIT); 796 if ((m->m_flags & M_EXT) == 0) { 797 SOCKBUF_UNLOCK(&so->so_snd); 798 m_freem(m); 799 error = ENOBUFS; 800 goto out; 801 } 802 } 803 #endif 804 m->m_data += max_linkhdr; 805 m->m_len = hdrlen; 806 807 /* 808 * Start the m_copy functions from the closest mbuf 809 * to the offset in the socket buffer chain. 810 */ 811 mb = sbsndptr(&so->so_snd, off, len, &moff); 812 813 if (len <= MHLEN - hdrlen - max_linkhdr) { 814 m_copydata(mb, moff, (int)len, 815 mtod(m, caddr_t) + hdrlen); 816 m->m_len += len; 817 } else { 818 m->m_next = m_copy(mb, moff, (int)len); 819 if (m->m_next == NULL) { 820 SOCKBUF_UNLOCK(&so->so_snd); 821 (void) m_free(m); 822 error = ENOBUFS; 823 goto out; 824 } 825 } 826 #endif 827 /* 828 * If we're sending everything we've got, set PUSH. 829 * (This will keep happy those implementations which only 830 * give data to the user when a buffer fills or 831 * a PUSH comes in.) 832 */ 833 if (off + len == so->so_snd.sb_cc) 834 flags |= TH_PUSH; 835 SOCKBUF_UNLOCK(&so->so_snd); 836 } else { 837 SOCKBUF_UNLOCK(&so->so_snd); 838 if (tp->t_flags & TF_ACKNOW) 839 V_tcpstat.tcps_sndacks++; 840 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 841 V_tcpstat.tcps_sndctrl++; 842 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 843 V_tcpstat.tcps_sndurg++; 844 else 845 V_tcpstat.tcps_sndwinup++; 846 847 MGETHDR(m, M_DONTWAIT, MT_DATA); 848 if (m == NULL) { 849 error = ENOBUFS; 850 goto out; 851 } 852 #ifdef INET6 853 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 854 MHLEN >= hdrlen) { 855 MH_ALIGN(m, hdrlen); 856 } else 857 #endif 858 m->m_data += max_linkhdr; 859 m->m_len = hdrlen; 860 } 861 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 862 m->m_pkthdr.rcvif = (struct ifnet *)0; 863 #ifdef MAC 864 mac_inpcb_create_mbuf(tp->t_inpcb, m); 865 #endif 866 #ifdef INET6 867 if (isipv6) { 868 ip6 = mtod(m, struct ip6_hdr *); 869 th = (struct tcphdr *)(ip6 + 1); 870 tcpip_fillheaders(tp->t_inpcb, ip6, th); 871 } else 872 #endif /* INET6 */ 873 { 874 ip = mtod(m, struct ip *); 875 ipov = (struct ipovly *)ip; 876 th = (struct tcphdr *)(ip + 1); 877 tcpip_fillheaders(tp->t_inpcb, ip, th); 878 } 879 880 /* 881 * Fill in fields, remembering maximum advertised 882 * window for use in delaying messages about window sizes. 883 * If resending a FIN, be sure not to use a new sequence number. 884 */ 885 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 886 tp->snd_nxt == tp->snd_max) 887 tp->snd_nxt--; 888 /* 889 * If we are starting a connection, send ECN setup 890 * SYN packet. If we are on a retransmit, we may 891 * resend those bits a number of times as per 892 * RFC 3168. 893 */ 894 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 895 if (tp->t_rxtshift >= 1) { 896 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 897 flags |= TH_ECE|TH_CWR; 898 } else 899 flags |= TH_ECE|TH_CWR; 900 } 901 902 if (tp->t_state == TCPS_ESTABLISHED && 903 (tp->t_flags & TF_ECN_PERMIT)) { 904 /* 905 * If the peer has ECN, mark data packets with 906 * ECN capable transmission (ECT). 907 * Ignore pure ack packets, retransmissions and window probes. 908 */ 909 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 910 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 911 #ifdef INET6 912 if (isipv6) 913 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 914 else 915 #endif 916 ip->ip_tos |= IPTOS_ECN_ECT0; 917 V_tcpstat.tcps_ecn_ect0++; 918 } 919 920 /* 921 * Reply with proper ECN notifications. 922 */ 923 if (tp->t_flags & TF_ECN_SND_CWR) { 924 flags |= TH_CWR; 925 tp->t_flags &= ~TF_ECN_SND_CWR; 926 } 927 if (tp->t_flags & TF_ECN_SND_ECE) 928 flags |= TH_ECE; 929 } 930 931 /* 932 * If we are doing retransmissions, then snd_nxt will 933 * not reflect the first unsent octet. For ACK only 934 * packets, we do not want the sequence number of the 935 * retransmitted packet, we want the sequence number 936 * of the next unsent octet. So, if there is no data 937 * (and no SYN or FIN), use snd_max instead of snd_nxt 938 * when filling in ti_seq. But if we are in persist 939 * state, snd_max might reflect one byte beyond the 940 * right edge of the window, so use snd_nxt in that 941 * case, since we know we aren't doing a retransmission. 942 * (retransmit and persist are mutually exclusive...) 943 */ 944 if (sack_rxmit == 0) { 945 if (len || (flags & (TH_SYN|TH_FIN)) || 946 tcp_timer_active(tp, TT_PERSIST)) 947 th->th_seq = htonl(tp->snd_nxt); 948 else 949 th->th_seq = htonl(tp->snd_max); 950 } else { 951 th->th_seq = htonl(p->rxmit); 952 p->rxmit += len; 953 tp->sackhint.sack_bytes_rexmit += len; 954 } 955 th->th_ack = htonl(tp->rcv_nxt); 956 if (optlen) { 957 bcopy(opt, th + 1, optlen); 958 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 959 } 960 th->th_flags = flags; 961 /* 962 * Calculate receive window. Don't shrink window, 963 * but avoid silly window syndrome. 964 */ 965 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 966 recwin < (long)tp->t_maxseg) 967 recwin = 0; 968 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 969 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 970 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 971 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 972 973 /* 974 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 975 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 976 * case is handled in syncache. 977 */ 978 if (flags & TH_SYN) 979 th->th_win = htons((u_short) 980 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 981 else 982 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 983 984 /* 985 * Adjust the RXWIN0SENT flag - indicate that we have advertised 986 * a 0 window. This may cause the remote transmitter to stall. This 987 * flag tells soreceive() to disable delayed acknowledgements when 988 * draining the buffer. This can occur if the receiver is attempting 989 * to read more data than can be buffered prior to transmitting on 990 * the connection. 991 */ 992 if (recwin == 0) 993 tp->t_flags |= TF_RXWIN0SENT; 994 else 995 tp->t_flags &= ~TF_RXWIN0SENT; 996 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 997 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 998 th->th_flags |= TH_URG; 999 } else 1000 /* 1001 * If no urgent pointer to send, then we pull 1002 * the urgent pointer to the left edge of the send window 1003 * so that it doesn't drift into the send window on sequence 1004 * number wraparound. 1005 */ 1006 tp->snd_up = tp->snd_una; /* drag it along */ 1007 1008 #ifdef TCP_SIGNATURE 1009 if (tp->t_flags & TF_SIGNATURE) { 1010 int sigoff = to.to_signature - opt; 1011 tcp_signature_compute(m, 0, len, optlen, 1012 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1013 } 1014 #endif 1015 1016 /* 1017 * Put TCP length in extended header, and then 1018 * checksum extended header and data. 1019 */ 1020 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1021 #ifdef INET6 1022 if (isipv6) 1023 /* 1024 * ip6_plen is not need to be filled now, and will be filled 1025 * in ip6_output. 1026 */ 1027 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1028 sizeof(struct tcphdr) + optlen + len); 1029 else 1030 #endif /* INET6 */ 1031 { 1032 m->m_pkthdr.csum_flags = CSUM_TCP; 1033 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1034 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1035 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1036 1037 /* IP version must be set here for ipv4/ipv6 checking later */ 1038 KASSERT(ip->ip_v == IPVERSION, 1039 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1040 } 1041 1042 /* 1043 * Enable TSO and specify the size of the segments. 1044 * The TCP pseudo header checksum is always provided. 1045 * XXX: Fixme: This is currently not the case for IPv6. 1046 */ 1047 if (tso) { 1048 m->m_pkthdr.csum_flags = CSUM_TSO; 1049 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1050 } 1051 1052 /* 1053 * In transmit state, time the transmission and arrange for 1054 * the retransmit. In persist state, just set snd_max. 1055 */ 1056 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1057 !tcp_timer_active(tp, TT_PERSIST)) { 1058 tcp_seq startseq = tp->snd_nxt; 1059 1060 /* 1061 * Advance snd_nxt over sequence space of this segment. 1062 */ 1063 if (flags & (TH_SYN|TH_FIN)) { 1064 if (flags & TH_SYN) 1065 tp->snd_nxt++; 1066 if (flags & TH_FIN) { 1067 tp->snd_nxt++; 1068 tp->t_flags |= TF_SENTFIN; 1069 } 1070 } 1071 if (sack_rxmit) 1072 goto timer; 1073 tp->snd_nxt += len; 1074 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1075 tp->snd_max = tp->snd_nxt; 1076 /* 1077 * Time this transmission if not a retransmission and 1078 * not currently timing anything. 1079 */ 1080 if (tp->t_rtttime == 0) { 1081 tp->t_rtttime = ticks; 1082 tp->t_rtseq = startseq; 1083 V_tcpstat.tcps_segstimed++; 1084 } 1085 } 1086 1087 /* 1088 * Set retransmit timer if not currently set, 1089 * and not doing a pure ack or a keep-alive probe. 1090 * Initial value for retransmit timer is smoothed 1091 * round-trip time + 2 * round-trip time variance. 1092 * Initialize shift counter which is used for backoff 1093 * of retransmit time. 1094 */ 1095 timer: 1096 if (!tcp_timer_active(tp, TT_REXMT) && 1097 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1098 (tp->snd_nxt != tp->snd_una))) { 1099 if (tcp_timer_active(tp, TT_PERSIST)) { 1100 tcp_timer_activate(tp, TT_PERSIST, 0); 1101 tp->t_rxtshift = 0; 1102 } 1103 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1104 } 1105 } else { 1106 /* 1107 * Persist case, update snd_max but since we are in 1108 * persist mode (no window) we do not update snd_nxt. 1109 */ 1110 int xlen = len; 1111 if (flags & TH_SYN) 1112 ++xlen; 1113 if (flags & TH_FIN) { 1114 ++xlen; 1115 tp->t_flags |= TF_SENTFIN; 1116 } 1117 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1118 tp->snd_max = tp->snd_nxt + len; 1119 } 1120 1121 #ifdef TCPDEBUG 1122 /* 1123 * Trace. 1124 */ 1125 if (so->so_options & SO_DEBUG) { 1126 u_short save = 0; 1127 #ifdef INET6 1128 if (!isipv6) 1129 #endif 1130 { 1131 save = ipov->ih_len; 1132 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1133 } 1134 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1135 #ifdef INET6 1136 if (!isipv6) 1137 #endif 1138 ipov->ih_len = save; 1139 } 1140 #endif 1141 1142 /* 1143 * Fill in IP length and desired time to live and 1144 * send to IP level. There should be a better way 1145 * to handle ttl and tos; we could keep them in 1146 * the template, but need a way to checksum without them. 1147 */ 1148 /* 1149 * m->m_pkthdr.len should have been set before cksum calcuration, 1150 * because in6_cksum() need it. 1151 */ 1152 #ifdef INET6 1153 if (isipv6) { 1154 /* 1155 * we separately set hoplimit for every segment, since the 1156 * user might want to change the value via setsockopt. 1157 * Also, desired default hop limit might be changed via 1158 * Neighbor Discovery. 1159 */ 1160 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1161 1162 /* TODO: IPv6 IP6TOS_ECT bit on */ 1163 error = ip6_output(m, 1164 tp->t_inpcb->in6p_outputopts, NULL, 1165 ((so->so_options & SO_DONTROUTE) ? 1166 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1167 } else 1168 #endif /* INET6 */ 1169 { 1170 ip->ip_len = m->m_pkthdr.len; 1171 #ifdef INET6 1172 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1173 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1174 #endif /* INET6 */ 1175 /* 1176 * If we do path MTU discovery, then we set DF on every packet. 1177 * This might not be the best thing to do according to RFC3390 1178 * Section 2. However the tcp hostcache migitates the problem 1179 * so it affects only the first tcp connection with a host. 1180 */ 1181 if (V_path_mtu_discovery) 1182 ip->ip_off |= IP_DF; 1183 1184 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1185 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1186 tp->t_inpcb); 1187 } 1188 if (error) { 1189 1190 /* 1191 * We know that the packet was lost, so back out the 1192 * sequence number advance, if any. 1193 * 1194 * If the error is EPERM the packet got blocked by the 1195 * local firewall. Normally we should terminate the 1196 * connection but the blocking may have been spurious 1197 * due to a firewall reconfiguration cycle. So we treat 1198 * it like a packet loss and let the retransmit timer and 1199 * timeouts do their work over time. 1200 * XXX: It is a POLA question whether calling tcp_drop right 1201 * away would be the really correct behavior instead. 1202 */ 1203 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1204 !tcp_timer_active(tp, TT_PERSIST)) && 1205 ((flags & TH_SYN) == 0) && 1206 (error != EPERM)) { 1207 if (sack_rxmit) { 1208 p->rxmit -= len; 1209 tp->sackhint.sack_bytes_rexmit -= len; 1210 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1211 ("sackhint bytes rtx >= 0")); 1212 } else 1213 tp->snd_nxt -= len; 1214 } 1215 out: 1216 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1217 switch (error) { 1218 case EPERM: 1219 tp->t_softerror = error; 1220 return (error); 1221 case ENOBUFS: 1222 if (!tcp_timer_active(tp, TT_REXMT) && 1223 !tcp_timer_active(tp, TT_PERSIST)) 1224 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1225 tp->snd_cwnd = tp->t_maxseg; 1226 return (0); 1227 case EMSGSIZE: 1228 /* 1229 * For some reason the interface we used initially 1230 * to send segments changed to another or lowered 1231 * its MTU. 1232 * 1233 * tcp_mtudisc() will find out the new MTU and as 1234 * its last action, initiate retransmission, so it 1235 * is important to not do so here. 1236 * 1237 * If TSO was active we either got an interface 1238 * without TSO capabilits or TSO was turned off. 1239 * Disable it for this connection as too and 1240 * immediatly retry with MSS sized segments generated 1241 * by this function. 1242 */ 1243 if (tso) 1244 tp->t_flags &= ~TF_TSO; 1245 tcp_mtudisc(tp->t_inpcb, 0); 1246 return (0); 1247 case EHOSTDOWN: 1248 case EHOSTUNREACH: 1249 case ENETDOWN: 1250 case ENETUNREACH: 1251 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1252 tp->t_softerror = error; 1253 return (0); 1254 } 1255 /* FALLTHROUGH */ 1256 default: 1257 return (error); 1258 } 1259 } 1260 V_tcpstat.tcps_sndtotal++; 1261 1262 /* 1263 * Data sent (as far as we can tell). 1264 * If this advertises a larger window than any other segment, 1265 * then remember the size of the advertised window. 1266 * Any pending ACK has now been sent. 1267 */ 1268 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1269 tp->rcv_adv = tp->rcv_nxt + recwin; 1270 tp->last_ack_sent = tp->rcv_nxt; 1271 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1272 if (tcp_timer_active(tp, TT_DELACK)) 1273 tcp_timer_activate(tp, TT_DELACK, 0); 1274 #if 0 1275 /* 1276 * This completely breaks TCP if newreno is turned on. What happens 1277 * is that if delayed-acks are turned on on the receiver, this code 1278 * on the transmitter effectively destroys the TCP window, forcing 1279 * it to four packets (1.5Kx4 = 6K window). 1280 */ 1281 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1282 goto again; 1283 #endif 1284 if (sendalot) 1285 goto again; 1286 return (0); 1287 } 1288 1289 void 1290 tcp_setpersist(struct tcpcb *tp) 1291 { 1292 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1293 int tt; 1294 1295 if (tcp_timer_active(tp, TT_REXMT)) 1296 panic("tcp_setpersist: retransmit pending"); 1297 /* 1298 * Start/restart persistance timer. 1299 */ 1300 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1301 TCPTV_PERSMIN, TCPTV_PERSMAX); 1302 tcp_timer_activate(tp, TT_PERSIST, tt); 1303 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1304 tp->t_rxtshift++; 1305 } 1306 1307 /* 1308 * Insert TCP options according to the supplied parameters to the place 1309 * optp in a consistent way. Can handle unaligned destinations. 1310 * 1311 * The order of the option processing is crucial for optimal packing and 1312 * alignment for the scarce option space. 1313 * 1314 * The optimal order for a SYN/SYN-ACK segment is: 1315 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1316 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1317 * 1318 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1319 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1320 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1321 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1322 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1323 */ 1324 int 1325 tcp_addoptions(struct tcpopt *to, u_char *optp) 1326 { 1327 INIT_VNET_INET(curvnet); 1328 u_int mask, optlen = 0; 1329 1330 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1331 if ((to->to_flags & mask) != mask) 1332 continue; 1333 if (optlen == TCP_MAXOLEN) 1334 break; 1335 switch (to->to_flags & mask) { 1336 case TOF_MSS: 1337 while (optlen % 4) { 1338 optlen += TCPOLEN_NOP; 1339 *optp++ = TCPOPT_NOP; 1340 } 1341 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1342 continue; 1343 optlen += TCPOLEN_MAXSEG; 1344 *optp++ = TCPOPT_MAXSEG; 1345 *optp++ = TCPOLEN_MAXSEG; 1346 to->to_mss = htons(to->to_mss); 1347 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1348 optp += sizeof(to->to_mss); 1349 break; 1350 case TOF_SCALE: 1351 while (!optlen || optlen % 2 != 1) { 1352 optlen += TCPOLEN_NOP; 1353 *optp++ = TCPOPT_NOP; 1354 } 1355 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1356 continue; 1357 optlen += TCPOLEN_WINDOW; 1358 *optp++ = TCPOPT_WINDOW; 1359 *optp++ = TCPOLEN_WINDOW; 1360 *optp++ = to->to_wscale; 1361 break; 1362 case TOF_SACKPERM: 1363 while (optlen % 2) { 1364 optlen += TCPOLEN_NOP; 1365 *optp++ = TCPOPT_NOP; 1366 } 1367 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1368 continue; 1369 optlen += TCPOLEN_SACK_PERMITTED; 1370 *optp++ = TCPOPT_SACK_PERMITTED; 1371 *optp++ = TCPOLEN_SACK_PERMITTED; 1372 break; 1373 case TOF_TS: 1374 while (!optlen || optlen % 4 != 2) { 1375 optlen += TCPOLEN_NOP; 1376 *optp++ = TCPOPT_NOP; 1377 } 1378 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1379 continue; 1380 optlen += TCPOLEN_TIMESTAMP; 1381 *optp++ = TCPOPT_TIMESTAMP; 1382 *optp++ = TCPOLEN_TIMESTAMP; 1383 to->to_tsval = htonl(to->to_tsval); 1384 to->to_tsecr = htonl(to->to_tsecr); 1385 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1386 optp += sizeof(to->to_tsval); 1387 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1388 optp += sizeof(to->to_tsecr); 1389 break; 1390 case TOF_SIGNATURE: 1391 { 1392 int siglen = TCPOLEN_SIGNATURE - 2; 1393 1394 while (!optlen || optlen % 4 != 2) { 1395 optlen += TCPOLEN_NOP; 1396 *optp++ = TCPOPT_NOP; 1397 } 1398 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1399 continue; 1400 optlen += TCPOLEN_SIGNATURE; 1401 *optp++ = TCPOPT_SIGNATURE; 1402 *optp++ = TCPOLEN_SIGNATURE; 1403 to->to_signature = optp; 1404 while (siglen--) 1405 *optp++ = 0; 1406 break; 1407 } 1408 case TOF_SACK: 1409 { 1410 int sackblks = 0; 1411 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1412 tcp_seq sack_seq; 1413 1414 while (!optlen || optlen % 4 != 2) { 1415 optlen += TCPOLEN_NOP; 1416 *optp++ = TCPOPT_NOP; 1417 } 1418 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1419 continue; 1420 optlen += TCPOLEN_SACKHDR; 1421 *optp++ = TCPOPT_SACK; 1422 sackblks = min(to->to_nsacks, 1423 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1424 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1425 while (sackblks--) { 1426 sack_seq = htonl(sack->start); 1427 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1428 optp += sizeof(sack_seq); 1429 sack_seq = htonl(sack->end); 1430 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1431 optp += sizeof(sack_seq); 1432 optlen += TCPOLEN_SACK; 1433 sack++; 1434 } 1435 V_tcpstat.tcps_sack_send_blocks++; 1436 break; 1437 } 1438 default: 1439 panic("%s: unknown TCP option type", __func__); 1440 break; 1441 } 1442 } 1443 1444 /* Terminate and pad TCP options to a 4 byte boundary. */ 1445 if (optlen % 4) { 1446 optlen += TCPOLEN_EOL; 1447 *optp++ = TCPOPT_EOL; 1448 } 1449 /* 1450 * According to RFC 793 (STD0007): 1451 * "The content of the header beyond the End-of-Option option 1452 * must be header padding (i.e., zero)." 1453 * and later: "The padding is composed of zeros." 1454 */ 1455 while (optlen % 4) { 1456 optlen += TCPOLEN_PAD; 1457 *optp++ = TCPOPT_PAD; 1458 } 1459 1460 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1461 return (optlen); 1462 } 1463