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sys/netinet/tcp_output.c
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1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/hhook.h> 44 #include <sys/kernel.h> 45 #include <sys/lock.h> 46 #include <sys/mbuf.h> 47 #include <sys/mutex.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/sysctl.h> 52 53 #include <net/if.h> 54 #include <net/route.h> 55 #include <net/vnet.h> 56 57 #include <netinet/cc.h> 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #include <netinet/ip_options.h> 64 #ifdef INET6 65 #include <netinet6/in6_pcb.h> 66 #include <netinet/ip6.h> 67 #include <netinet6/ip6_var.h> 68 #endif 69 #define TCPOUTFLAGS 70 #include <netinet/tcp_fsm.h> 71 #include <netinet/tcp_seq.h> 72 #include <netinet/tcp_timer.h> 73 #include <netinet/tcp_var.h> 74 #include <netinet/tcpip.h> 75 #ifdef TCPDEBUG 76 #include <netinet/tcp_debug.h> 77 #endif 78 #ifdef TCP_OFFLOAD 79 #include <netinet/tcp_offload.h> 80 #endif 81 82 #ifdef IPSEC 83 #include <netipsec/ipsec.h> 84 #endif /*IPSEC*/ 85 86 #include <machine/in_cksum.h> 87 88 #include <security/mac/mac_framework.h> 89 90 VNET_DEFINE(int, path_mtu_discovery) = 1; 91 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 92 &VNET_NAME(path_mtu_discovery), 1, 93 "Enable Path MTU Discovery"); 94 95 VNET_DEFINE(int, tcp_do_tso) = 1; 96 #define V_tcp_do_tso VNET(tcp_do_tso) 97 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 98 &VNET_NAME(tcp_do_tso), 0, 99 "Enable TCP Segmentation Offload"); 100 101 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 102 #define V_tcp_sendspace VNET(tcp_sendspace) 103 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW, 104 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 105 106 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 107 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 108 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 109 &VNET_NAME(tcp_do_autosndbuf), 0, 110 "Enable automatic send buffer sizing"); 111 112 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 113 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 114 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 115 &VNET_NAME(tcp_autosndbuf_inc), 0, 116 "Incrementor step size of automatic send buffer"); 117 118 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 119 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 120 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 121 &VNET_NAME(tcp_autosndbuf_max), 0, 122 "Max size of automatic send buffer"); 123 124 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 125 struct tcphdr *th, struct tcpopt *to, 126 long len, int tso); 127 static void inline cc_after_idle(struct tcpcb *tp); 128 129 /* 130 * Wrapper for the TCP established ouput helper hook. 131 */ 132 static void inline 133 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 134 struct tcpopt *to, long len, int tso) 135 { 136 struct tcp_hhook_data hhook_data; 137 138 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 139 hhook_data.tp = tp; 140 hhook_data.th = th; 141 hhook_data.to = to; 142 hhook_data.len = len; 143 hhook_data.tso = tso; 144 145 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 146 tp->osd); 147 } 148 } 149 150 /* 151 * CC wrapper hook functions 152 */ 153 static void inline 154 cc_after_idle(struct tcpcb *tp) 155 { 156 INP_WLOCK_ASSERT(tp->t_inpcb); 157 158 if (CC_ALGO(tp)->after_idle != NULL) 159 CC_ALGO(tp)->after_idle(tp->ccv); 160 } 161 162 /* 163 * Tcp output routine: figure out what should be sent and send it. 164 */ 165 int 166 tcp_output(struct tcpcb *tp) 167 { 168 struct socket *so = tp->t_inpcb->inp_socket; 169 long len, recwin, sendwin; 170 int off, flags, error = 0; /* Keep compiler happy */ 171 struct mbuf *m; 172 struct ip *ip = NULL; 173 struct ipovly *ipov = NULL; 174 struct tcphdr *th; 175 u_char opt[TCP_MAXOLEN]; 176 unsigned ipoptlen, optlen, hdrlen; 177 #ifdef IPSEC 178 unsigned ipsec_optlen = 0; 179 #endif 180 int idle, sendalot; 181 int sack_rxmit, sack_bytes_rxmt; 182 struct sackhole *p; 183 int tso, mtu; 184 struct tcpopt to; 185 #if 0 186 int maxburst = TCP_MAXBURST; 187 #endif 188 #ifdef INET6 189 struct ip6_hdr *ip6 = NULL; 190 int isipv6; 191 192 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 193 #endif 194 195 INP_WLOCK_ASSERT(tp->t_inpcb); 196 197 #ifdef TCP_OFFLOAD 198 if (tp->t_flags & TF_TOE) 199 return (tcp_offload_output(tp)); 200 #endif 201 202 /* 203 * Determine length of data that should be transmitted, 204 * and flags that will be used. 205 * If there is some data or critical controls (SYN, RST) 206 * to send, then transmit; otherwise, investigate further. 207 */ 208 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 209 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 210 cc_after_idle(tp); 211 tp->t_flags &= ~TF_LASTIDLE; 212 if (idle) { 213 if (tp->t_flags & TF_MORETOCOME) { 214 tp->t_flags |= TF_LASTIDLE; 215 idle = 0; 216 } 217 } 218 again: 219 /* 220 * If we've recently taken a timeout, snd_max will be greater than 221 * snd_nxt. There may be SACK information that allows us to avoid 222 * resending already delivered data. Adjust snd_nxt accordingly. 223 */ 224 if ((tp->t_flags & TF_SACK_PERMIT) && 225 SEQ_LT(tp->snd_nxt, tp->snd_max)) 226 tcp_sack_adjust(tp); 227 sendalot = 0; 228 tso = 0; 229 mtu = 0; 230 off = tp->snd_nxt - tp->snd_una; 231 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 232 233 flags = tcp_outflags[tp->t_state]; 234 /* 235 * Send any SACK-generated retransmissions. If we're explicitly trying 236 * to send out new data (when sendalot is 1), bypass this function. 237 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 238 * we're replacing a (future) new transmission with a retransmission 239 * now, and we previously incremented snd_cwnd in tcp_input(). 240 */ 241 /* 242 * Still in sack recovery , reset rxmit flag to zero. 243 */ 244 sack_rxmit = 0; 245 sack_bytes_rxmt = 0; 246 len = 0; 247 p = NULL; 248 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 249 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 250 long cwin; 251 252 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 253 if (cwin < 0) 254 cwin = 0; 255 /* Do not retransmit SACK segments beyond snd_recover */ 256 if (SEQ_GT(p->end, tp->snd_recover)) { 257 /* 258 * (At least) part of sack hole extends beyond 259 * snd_recover. Check to see if we can rexmit data 260 * for this hole. 261 */ 262 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 263 /* 264 * Can't rexmit any more data for this hole. 265 * That data will be rexmitted in the next 266 * sack recovery episode, when snd_recover 267 * moves past p->rxmit. 268 */ 269 p = NULL; 270 goto after_sack_rexmit; 271 } else 272 /* Can rexmit part of the current hole */ 273 len = ((long)ulmin(cwin, 274 tp->snd_recover - p->rxmit)); 275 } else 276 len = ((long)ulmin(cwin, p->end - p->rxmit)); 277 off = p->rxmit - tp->snd_una; 278 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 279 __func__, off)); 280 if (len > 0) { 281 sack_rxmit = 1; 282 sendalot = 1; 283 TCPSTAT_INC(tcps_sack_rexmits); 284 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 285 min(len, tp->t_maxseg)); 286 } 287 } 288 after_sack_rexmit: 289 /* 290 * Get standard flags, and add SYN or FIN if requested by 'hidden' 291 * state flags. 292 */ 293 if (tp->t_flags & TF_NEEDFIN) 294 flags |= TH_FIN; 295 if (tp->t_flags & TF_NEEDSYN) 296 flags |= TH_SYN; 297 298 SOCKBUF_LOCK(&so->so_snd); 299 /* 300 * If in persist timeout with window of 0, send 1 byte. 301 * Otherwise, if window is small but nonzero 302 * and timer expired, we will send what we can 303 * and go to transmit state. 304 */ 305 if (tp->t_flags & TF_FORCEDATA) { 306 if (sendwin == 0) { 307 /* 308 * If we still have some data to send, then 309 * clear the FIN bit. Usually this would 310 * happen below when it realizes that we 311 * aren't sending all the data. However, 312 * if we have exactly 1 byte of unsent data, 313 * then it won't clear the FIN bit below, 314 * and if we are in persist state, we wind 315 * up sending the packet without recording 316 * that we sent the FIN bit. 317 * 318 * We can't just blindly clear the FIN bit, 319 * because if we don't have any more data 320 * to send then the probe will be the FIN 321 * itself. 322 */ 323 if (off < so->so_snd.sb_cc) 324 flags &= ~TH_FIN; 325 sendwin = 1; 326 } else { 327 tcp_timer_activate(tp, TT_PERSIST, 0); 328 tp->t_rxtshift = 0; 329 } 330 } 331 332 /* 333 * If snd_nxt == snd_max and we have transmitted a FIN, the 334 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 335 * a negative length. This can also occur when TCP opens up 336 * its congestion window while receiving additional duplicate 337 * acks after fast-retransmit because TCP will reset snd_nxt 338 * to snd_max after the fast-retransmit. 339 * 340 * In the normal retransmit-FIN-only case, however, snd_nxt will 341 * be set to snd_una, the offset will be 0, and the length may 342 * wind up 0. 343 * 344 * If sack_rxmit is true we are retransmitting from the scoreboard 345 * in which case len is already set. 346 */ 347 if (sack_rxmit == 0) { 348 if (sack_bytes_rxmt == 0) 349 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 350 else { 351 long cwin; 352 353 /* 354 * We are inside of a SACK recovery episode and are 355 * sending new data, having retransmitted all the 356 * data possible in the scoreboard. 357 */ 358 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 359 - off); 360 /* 361 * Don't remove this (len > 0) check ! 362 * We explicitly check for len > 0 here (although it 363 * isn't really necessary), to work around a gcc 364 * optimization issue - to force gcc to compute 365 * len above. Without this check, the computation 366 * of len is bungled by the optimizer. 367 */ 368 if (len > 0) { 369 cwin = tp->snd_cwnd - 370 (tp->snd_nxt - tp->sack_newdata) - 371 sack_bytes_rxmt; 372 if (cwin < 0) 373 cwin = 0; 374 len = lmin(len, cwin); 375 } 376 } 377 } 378 379 /* 380 * Lop off SYN bit if it has already been sent. However, if this 381 * is SYN-SENT state and if segment contains data and if we don't 382 * know that foreign host supports TAO, suppress sending segment. 383 */ 384 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 385 if (tp->t_state != TCPS_SYN_RECEIVED) 386 flags &= ~TH_SYN; 387 off--, len++; 388 } 389 390 /* 391 * Be careful not to send data and/or FIN on SYN segments. 392 * This measure is needed to prevent interoperability problems 393 * with not fully conformant TCP implementations. 394 */ 395 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 396 len = 0; 397 flags &= ~TH_FIN; 398 } 399 400 if (len <= 0) { 401 /* 402 * If FIN has been sent but not acked, 403 * but we haven't been called to retransmit, 404 * len will be < 0. Otherwise, window shrank 405 * after we sent into it. If window shrank to 0, 406 * cancel pending retransmit, pull snd_nxt back 407 * to (closed) window, and set the persist timer 408 * if it isn't already going. If the window didn't 409 * close completely, just wait for an ACK. 410 * 411 * We also do a general check here to ensure that 412 * we will set the persist timer when we have data 413 * to send, but a 0-byte window. This makes sure 414 * the persist timer is set even if the packet 415 * hits one of the "goto send" lines below. 416 */ 417 len = 0; 418 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 419 (off < (int) so->so_snd.sb_cc)) { 420 tcp_timer_activate(tp, TT_REXMT, 0); 421 tp->t_rxtshift = 0; 422 tp->snd_nxt = tp->snd_una; 423 if (!tcp_timer_active(tp, TT_PERSIST)) 424 tcp_setpersist(tp); 425 } 426 } 427 428 /* len will be >= 0 after this point. */ 429 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 430 431 /* 432 * Automatic sizing of send socket buffer. Often the send buffer 433 * size is not optimally adjusted to the actual network conditions 434 * at hand (delay bandwidth product). Setting the buffer size too 435 * small limits throughput on links with high bandwidth and high 436 * delay (eg. trans-continental/oceanic links). Setting the 437 * buffer size too big consumes too much real kernel memory, 438 * especially with many connections on busy servers. 439 * 440 * The criteria to step up the send buffer one notch are: 441 * 1. receive window of remote host is larger than send buffer 442 * (with a fudge factor of 5/4th); 443 * 2. send buffer is filled to 7/8th with data (so we actually 444 * have data to make use of it); 445 * 3. send buffer fill has not hit maximal automatic size; 446 * 4. our send window (slow start and cogestion controlled) is 447 * larger than sent but unacknowledged data in send buffer. 448 * 449 * The remote host receive window scaling factor may limit the 450 * growing of the send buffer before it reaches its allowed 451 * maximum. 452 * 453 * It scales directly with slow start or congestion window 454 * and does at most one step per received ACK. This fast 455 * scaling has the drawback of growing the send buffer beyond 456 * what is strictly necessary to make full use of a given 457 * delay*bandwith product. However testing has shown this not 458 * to be much of an problem. At worst we are trading wasting 459 * of available bandwith (the non-use of it) for wasting some 460 * socket buffer memory. 461 * 462 * TODO: Shrink send buffer during idle periods together 463 * with congestion window. Requires another timer. Has to 464 * wait for upcoming tcp timer rewrite. 465 */ 466 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 467 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 468 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 469 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 470 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 471 if (!sbreserve_locked(&so->so_snd, 472 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 473 V_tcp_autosndbuf_max), so, curthread)) 474 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 475 } 476 } 477 478 /* 479 * Decide if we can use TCP Segmentation Offloading (if supported by 480 * hardware). 481 * 482 * TSO may only be used if we are in a pure bulk sending state. The 483 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 484 * IP options prevent using TSO. With TSO the TCP header is the same 485 * (except for the sequence number) for all generated packets. This 486 * makes it impossible to transmit any options which vary per generated 487 * segment or packet. 488 */ 489 #ifdef IPSEC 490 /* 491 * Pre-calculate here as we save another lookup into the darknesses 492 * of IPsec that way and can actually decide if TSO is ok. 493 */ 494 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 495 #endif 496 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 497 ((tp->t_flags & TF_SIGNATURE) == 0) && 498 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 499 #ifdef IPSEC 500 ipsec_optlen == 0 && 501 #endif 502 tp->t_inpcb->inp_options == NULL && 503 tp->t_inpcb->in6p_options == NULL) 504 tso = 1; 505 506 if (sack_rxmit) { 507 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 508 flags &= ~TH_FIN; 509 } else { 510 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 511 flags &= ~TH_FIN; 512 } 513 514 recwin = sbspace(&so->so_rcv); 515 516 /* 517 * Sender silly window avoidance. We transmit under the following 518 * conditions when len is non-zero: 519 * 520 * - We have a full segment (or more with TSO) 521 * - This is the last buffer in a write()/send() and we are 522 * either idle or running NODELAY 523 * - we've timed out (e.g. persist timer) 524 * - we have more then 1/2 the maximum send window's worth of 525 * data (receiver may be limited the window size) 526 * - we need to retransmit 527 */ 528 if (len) { 529 if (len >= tp->t_maxseg) 530 goto send; 531 /* 532 * NOTE! on localhost connections an 'ack' from the remote 533 * end may occur synchronously with the output and cause 534 * us to flush a buffer queued with moretocome. XXX 535 * 536 * note: the len + off check is almost certainly unnecessary. 537 */ 538 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 539 (idle || (tp->t_flags & TF_NODELAY)) && 540 len + off >= so->so_snd.sb_cc && 541 (tp->t_flags & TF_NOPUSH) == 0) { 542 goto send; 543 } 544 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 545 goto send; 546 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 547 goto send; 548 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 549 goto send; 550 if (sack_rxmit) 551 goto send; 552 } 553 554 /* 555 * Sending of standalone window updates. 556 * 557 * Window updates are important when we close our window due to a 558 * full socket buffer and are opening it again after the application 559 * reads data from it. Once the window has opened again and the 560 * remote end starts to send again the ACK clock takes over and 561 * provides the most current window information. 562 * 563 * We must avoid the silly window syndrome whereas every read 564 * from the receive buffer, no matter how small, causes a window 565 * update to be sent. We also should avoid sending a flurry of 566 * window updates when the socket buffer had queued a lot of data 567 * and the application is doing small reads. 568 * 569 * Prevent a flurry of pointless window updates by only sending 570 * an update when we can increase the advertized window by more 571 * than 1/4th of the socket buffer capacity. When the buffer is 572 * getting full or is very small be more aggressive and send an 573 * update whenever we can increase by two mss sized segments. 574 * In all other situations the ACK's to new incoming data will 575 * carry further window increases. 576 * 577 * Don't send an independent window update if a delayed 578 * ACK is pending (it will get piggy-backed on it) or the 579 * remote side already has done a half-close and won't send 580 * more data. Skip this if the connection is in T/TCP 581 * half-open state. 582 */ 583 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 584 !(tp->t_flags & TF_DELACK) && 585 !TCPS_HAVERCVDFIN(tp->t_state)) { 586 /* 587 * "adv" is the amount we could increase the window, 588 * taking into account that we are limited by 589 * TCP_MAXWIN << tp->rcv_scale. 590 */ 591 long adv; 592 int oldwin; 593 594 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 595 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 596 oldwin = (tp->rcv_adv - tp->rcv_nxt); 597 adv -= oldwin; 598 } else 599 oldwin = 0; 600 601 /* 602 * If the new window size ends up being the same as the old 603 * size when it is scaled, then don't force a window update. 604 */ 605 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 606 goto dontupdate; 607 608 if (adv >= (long)(2 * tp->t_maxseg) && 609 (adv >= (long)(so->so_rcv.sb_hiwat / 4) || 610 recwin <= (long)(so->so_rcv.sb_hiwat / 8) || 611 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 612 goto send; 613 } 614 dontupdate: 615 616 /* 617 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 618 * is also a catch-all for the retransmit timer timeout case. 619 */ 620 if (tp->t_flags & TF_ACKNOW) 621 goto send; 622 if ((flags & TH_RST) || 623 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 624 goto send; 625 if (SEQ_GT(tp->snd_up, tp->snd_una)) 626 goto send; 627 /* 628 * If our state indicates that FIN should be sent 629 * and we have not yet done so, then we need to send. 630 */ 631 if (flags & TH_FIN && 632 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 633 goto send; 634 /* 635 * In SACK, it is possible for tcp_output to fail to send a segment 636 * after the retransmission timer has been turned off. Make sure 637 * that the retransmission timer is set. 638 */ 639 if ((tp->t_flags & TF_SACK_PERMIT) && 640 SEQ_GT(tp->snd_max, tp->snd_una) && 641 !tcp_timer_active(tp, TT_REXMT) && 642 !tcp_timer_active(tp, TT_PERSIST)) { 643 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 644 goto just_return; 645 } 646 /* 647 * TCP window updates are not reliable, rather a polling protocol 648 * using ``persist'' packets is used to insure receipt of window 649 * updates. The three ``states'' for the output side are: 650 * idle not doing retransmits or persists 651 * persisting to move a small or zero window 652 * (re)transmitting and thereby not persisting 653 * 654 * tcp_timer_active(tp, TT_PERSIST) 655 * is true when we are in persist state. 656 * (tp->t_flags & TF_FORCEDATA) 657 * is set when we are called to send a persist packet. 658 * tcp_timer_active(tp, TT_REXMT) 659 * is set when we are retransmitting 660 * The output side is idle when both timers are zero. 661 * 662 * If send window is too small, there is data to transmit, and no 663 * retransmit or persist is pending, then go to persist state. 664 * If nothing happens soon, send when timer expires: 665 * if window is nonzero, transmit what we can, 666 * otherwise force out a byte. 667 */ 668 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 669 !tcp_timer_active(tp, TT_PERSIST)) { 670 tp->t_rxtshift = 0; 671 tcp_setpersist(tp); 672 } 673 674 /* 675 * No reason to send a segment, just return. 676 */ 677 just_return: 678 SOCKBUF_UNLOCK(&so->so_snd); 679 return (0); 680 681 send: 682 SOCKBUF_LOCK_ASSERT(&so->so_snd); 683 /* 684 * Before ESTABLISHED, force sending of initial options 685 * unless TCP set not to do any options. 686 * NOTE: we assume that the IP/TCP header plus TCP options 687 * always fit in a single mbuf, leaving room for a maximum 688 * link header, i.e. 689 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 690 */ 691 optlen = 0; 692 #ifdef INET6 693 if (isipv6) 694 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 695 else 696 #endif 697 hdrlen = sizeof (struct tcpiphdr); 698 699 /* 700 * Compute options for segment. 701 * We only have to care about SYN and established connection 702 * segments. Options for SYN-ACK segments are handled in TCP 703 * syncache. 704 */ 705 to.to_flags = 0; 706 if ((tp->t_flags & TF_NOOPT) == 0) { 707 /* Maximum segment size. */ 708 if (flags & TH_SYN) { 709 tp->snd_nxt = tp->iss; 710 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 711 to.to_flags |= TOF_MSS; 712 } 713 /* Window scaling. */ 714 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 715 to.to_wscale = tp->request_r_scale; 716 to.to_flags |= TOF_SCALE; 717 } 718 /* Timestamps. */ 719 if ((tp->t_flags & TF_RCVD_TSTMP) || 720 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 721 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 722 to.to_tsecr = tp->ts_recent; 723 to.to_flags |= TOF_TS; 724 /* Set receive buffer autosizing timestamp. */ 725 if (tp->rfbuf_ts == 0 && 726 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 727 tp->rfbuf_ts = tcp_ts_getticks(); 728 } 729 /* Selective ACK's. */ 730 if (tp->t_flags & TF_SACK_PERMIT) { 731 if (flags & TH_SYN) 732 to.to_flags |= TOF_SACKPERM; 733 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 734 (tp->t_flags & TF_SACK_PERMIT) && 735 tp->rcv_numsacks > 0) { 736 to.to_flags |= TOF_SACK; 737 to.to_nsacks = tp->rcv_numsacks; 738 to.to_sacks = (u_char *)tp->sackblks; 739 } 740 } 741 #ifdef TCP_SIGNATURE 742 /* TCP-MD5 (RFC2385). */ 743 if (tp->t_flags & TF_SIGNATURE) 744 to.to_flags |= TOF_SIGNATURE; 745 #endif /* TCP_SIGNATURE */ 746 747 /* Processing the options. */ 748 hdrlen += optlen = tcp_addoptions(&to, opt); 749 } 750 751 #ifdef INET6 752 if (isipv6) 753 ipoptlen = ip6_optlen(tp->t_inpcb); 754 else 755 #endif 756 if (tp->t_inpcb->inp_options) 757 ipoptlen = tp->t_inpcb->inp_options->m_len - 758 offsetof(struct ipoption, ipopt_list); 759 else 760 ipoptlen = 0; 761 #ifdef IPSEC 762 ipoptlen += ipsec_optlen; 763 #endif 764 765 /* 766 * Adjust data length if insertion of options will 767 * bump the packet length beyond the t_maxopd length. 768 * Clear the FIN bit because we cut off the tail of 769 * the segment. 770 */ 771 if (len + optlen + ipoptlen > tp->t_maxopd) { 772 flags &= ~TH_FIN; 773 774 if (tso) { 775 u_int if_hw_tsomax; 776 u_int if_hw_tsomaxsegcount; 777 u_int if_hw_tsomaxsegsize; 778 struct mbuf *mb; 779 u_int moff; 780 int max_len; 781 782 /* extract TSO information */ 783 if_hw_tsomax = tp->t_tsomax; 784 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 785 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 786 787 /* 788 * Limit a TSO burst to prevent it from 789 * overflowing or exceeding the maximum length 790 * allowed by the network interface: 791 */ 792 KASSERT(ipoptlen == 0, 793 ("%s: TSO can't do IP options", __func__)); 794 795 /* 796 * Check if we should limit by maximum payload 797 * length: 798 */ 799 if (if_hw_tsomax != 0) { 800 /* compute maximum TSO length */ 801 max_len = (if_hw_tsomax - hdrlen - 802 max_linkhdr); 803 if (max_len <= 0) { 804 len = 0; 805 } else if (len > max_len) { 806 sendalot = 1; 807 len = max_len; 808 } 809 } 810 811 /* 812 * Check if we should limit by maximum segment 813 * size and count: 814 */ 815 if (if_hw_tsomaxsegcount != 0 && 816 if_hw_tsomaxsegsize != 0) { 817 /* 818 * Subtract one segment for the LINK 819 * and TCP/IP headers mbuf that will 820 * be prepended to this mbuf chain 821 * after the code in this section 822 * limits the number of mbufs in the 823 * chain to if_hw_tsomaxsegcount. 824 */ 825 if_hw_tsomaxsegcount -= 1; 826 max_len = 0; 827 mb = sbsndmbuf(&so->so_snd, off, &moff); 828 829 while (mb != NULL && max_len < len) { 830 u_int mlen; 831 u_int frags; 832 833 /* 834 * Get length of mbuf fragment 835 * and how many hardware frags, 836 * rounded up, it would use: 837 */ 838 mlen = (mb->m_len - moff); 839 frags = howmany(mlen, 840 if_hw_tsomaxsegsize); 841 842 /* Handle special case: Zero Length Mbuf */ 843 if (frags == 0) 844 frags = 1; 845 846 /* 847 * Check if the fragment limit 848 * will be reached or exceeded: 849 */ 850 if (frags >= if_hw_tsomaxsegcount) { 851 max_len += min(mlen, 852 if_hw_tsomaxsegcount * 853 if_hw_tsomaxsegsize); 854 break; 855 } 856 max_len += mlen; 857 if_hw_tsomaxsegcount -= frags; 858 moff = 0; 859 mb = mb->m_next; 860 } 861 if (max_len <= 0) { 862 len = 0; 863 } else if (len > max_len) { 864 sendalot = 1; 865 len = max_len; 866 } 867 } 868 869 /* 870 * Prevent the last segment from being 871 * fractional unless the send sockbuf can be 872 * emptied: 873 */ 874 max_len = (tp->t_maxopd - optlen); 875 if ((off + len) < so->so_snd.sb_cc) { 876 moff = len % max_len; 877 if (moff != 0) { 878 len -= moff; 879 sendalot = 1; 880 } 881 } 882 883 /* 884 * In case there are too many small fragments 885 * don't use TSO: 886 */ 887 if (len <= max_len) { 888 len = max_len; 889 sendalot = 1; 890 tso = 0; 891 } 892 893 /* 894 * Send the FIN in a separate segment 895 * after the bulk sending is done. 896 * We don't trust the TSO implementations 897 * to clear the FIN flag on all but the 898 * last segment. 899 */ 900 if (tp->t_flags & TF_NEEDFIN) 901 sendalot = 1; 902 903 } else { 904 len = tp->t_maxopd - optlen - ipoptlen; 905 sendalot = 1; 906 } 907 } else 908 tso = 0; 909 910 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 911 ("%s: len > IP_MAXPACKET", __func__)); 912 913 /*#ifdef DIAGNOSTIC*/ 914 #ifdef INET6 915 if (max_linkhdr + hdrlen > MCLBYTES) 916 #else 917 if (max_linkhdr + hdrlen > MHLEN) 918 #endif 919 panic("tcphdr too big"); 920 /*#endif*/ 921 922 /* 923 * This KASSERT is here to catch edge cases at a well defined place. 924 * Before, those had triggered (random) panic conditions further down. 925 */ 926 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 927 928 /* 929 * Grab a header mbuf, attaching a copy of data to 930 * be transmitted, and initialize the header from 931 * the template for sends on this connection. 932 */ 933 if (len) { 934 struct mbuf *mb; 935 u_int moff; 936 937 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 938 TCPSTAT_INC(tcps_sndprobe); 939 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 940 tp->t_sndrexmitpack++; 941 TCPSTAT_INC(tcps_sndrexmitpack); 942 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 943 } else { 944 TCPSTAT_INC(tcps_sndpack); 945 TCPSTAT_ADD(tcps_sndbyte, len); 946 } 947 MGETHDR(m, M_DONTWAIT, MT_DATA); 948 if (m == NULL) { 949 SOCKBUF_UNLOCK(&so->so_snd); 950 error = ENOBUFS; 951 goto out; 952 } 953 #ifdef INET6 954 if (MHLEN < hdrlen + max_linkhdr) { 955 MCLGET(m, M_DONTWAIT); 956 if ((m->m_flags & M_EXT) == 0) { 957 SOCKBUF_UNLOCK(&so->so_snd); 958 m_freem(m); 959 error = ENOBUFS; 960 goto out; 961 } 962 } 963 #endif 964 m->m_data += max_linkhdr; 965 m->m_len = hdrlen; 966 967 /* 968 * Start the m_copy functions from the closest mbuf 969 * to the offset in the socket buffer chain. 970 */ 971 mb = sbsndptr(&so->so_snd, off, len, &moff); 972 973 if (len <= MHLEN - hdrlen - max_linkhdr) { 974 m_copydata(mb, moff, (int)len, 975 mtod(m, caddr_t) + hdrlen); 976 m->m_len += len; 977 } else { 978 m->m_next = m_copy(mb, moff, (int)len); 979 if (m->m_next == NULL) { 980 SOCKBUF_UNLOCK(&so->so_snd); 981 (void) m_free(m); 982 error = ENOBUFS; 983 goto out; 984 } 985 } 986 987 /* 988 * If we're sending everything we've got, set PUSH. 989 * (This will keep happy those implementations which only 990 * give data to the user when a buffer fills or 991 * a PUSH comes in.) 992 */ 993 if (off + len == so->so_snd.sb_cc) 994 flags |= TH_PUSH; 995 SOCKBUF_UNLOCK(&so->so_snd); 996 } else { 997 SOCKBUF_UNLOCK(&so->so_snd); 998 if (tp->t_flags & TF_ACKNOW) 999 TCPSTAT_INC(tcps_sndacks); 1000 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1001 TCPSTAT_INC(tcps_sndctrl); 1002 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1003 TCPSTAT_INC(tcps_sndurg); 1004 else 1005 TCPSTAT_INC(tcps_sndwinup); 1006 1007 MGETHDR(m, M_DONTWAIT, MT_DATA); 1008 if (m == NULL) { 1009 error = ENOBUFS; 1010 goto out; 1011 } 1012 #ifdef INET6 1013 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1014 MHLEN >= hdrlen) { 1015 MH_ALIGN(m, hdrlen); 1016 } else 1017 #endif 1018 m->m_data += max_linkhdr; 1019 m->m_len = hdrlen; 1020 } 1021 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1022 m->m_pkthdr.rcvif = (struct ifnet *)0; 1023 #ifdef MAC 1024 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1025 #endif 1026 #ifdef INET6 1027 if (isipv6) { 1028 ip6 = mtod(m, struct ip6_hdr *); 1029 th = (struct tcphdr *)(ip6 + 1); 1030 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1031 } else 1032 #endif /* INET6 */ 1033 { 1034 ip = mtod(m, struct ip *); 1035 ipov = (struct ipovly *)ip; 1036 th = (struct tcphdr *)(ip + 1); 1037 tcpip_fillheaders(tp->t_inpcb, ip, th); 1038 } 1039 1040 /* 1041 * Fill in fields, remembering maximum advertised 1042 * window for use in delaying messages about window sizes. 1043 * If resending a FIN, be sure not to use a new sequence number. 1044 */ 1045 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1046 tp->snd_nxt == tp->snd_max) 1047 tp->snd_nxt--; 1048 /* 1049 * If we are starting a connection, send ECN setup 1050 * SYN packet. If we are on a retransmit, we may 1051 * resend those bits a number of times as per 1052 * RFC 3168. 1053 */ 1054 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1055 if (tp->t_rxtshift >= 1) { 1056 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1057 flags |= TH_ECE|TH_CWR; 1058 } else 1059 flags |= TH_ECE|TH_CWR; 1060 } 1061 1062 if (tp->t_state == TCPS_ESTABLISHED && 1063 (tp->t_flags & TF_ECN_PERMIT)) { 1064 /* 1065 * If the peer has ECN, mark data packets with 1066 * ECN capable transmission (ECT). 1067 * Ignore pure ack packets, retransmissions and window probes. 1068 */ 1069 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1070 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1071 #ifdef INET6 1072 if (isipv6) 1073 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1074 else 1075 #endif 1076 ip->ip_tos |= IPTOS_ECN_ECT0; 1077 TCPSTAT_INC(tcps_ecn_ect0); 1078 } 1079 1080 /* 1081 * Reply with proper ECN notifications. 1082 */ 1083 if (tp->t_flags & TF_ECN_SND_CWR) { 1084 flags |= TH_CWR; 1085 tp->t_flags &= ~TF_ECN_SND_CWR; 1086 } 1087 if (tp->t_flags & TF_ECN_SND_ECE) 1088 flags |= TH_ECE; 1089 } 1090 1091 /* 1092 * If we are doing retransmissions, then snd_nxt will 1093 * not reflect the first unsent octet. For ACK only 1094 * packets, we do not want the sequence number of the 1095 * retransmitted packet, we want the sequence number 1096 * of the next unsent octet. So, if there is no data 1097 * (and no SYN or FIN), use snd_max instead of snd_nxt 1098 * when filling in ti_seq. But if we are in persist 1099 * state, snd_max might reflect one byte beyond the 1100 * right edge of the window, so use snd_nxt in that 1101 * case, since we know we aren't doing a retransmission. 1102 * (retransmit and persist are mutually exclusive...) 1103 */ 1104 if (sack_rxmit == 0) { 1105 if (len || (flags & (TH_SYN|TH_FIN)) || 1106 tcp_timer_active(tp, TT_PERSIST)) 1107 th->th_seq = htonl(tp->snd_nxt); 1108 else 1109 th->th_seq = htonl(tp->snd_max); 1110 } else { 1111 th->th_seq = htonl(p->rxmit); 1112 p->rxmit += len; 1113 tp->sackhint.sack_bytes_rexmit += len; 1114 } 1115 th->th_ack = htonl(tp->rcv_nxt); 1116 if (optlen) { 1117 bcopy(opt, th + 1, optlen); 1118 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1119 } 1120 th->th_flags = flags; 1121 /* 1122 * Calculate receive window. Don't shrink window, 1123 * but avoid silly window syndrome. 1124 */ 1125 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1126 recwin < (long)tp->t_maxseg) 1127 recwin = 0; 1128 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1129 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1130 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1131 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1132 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1133 1134 /* 1135 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1136 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1137 * case is handled in syncache. 1138 */ 1139 if (flags & TH_SYN) 1140 th->th_win = htons((u_short) 1141 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1142 else 1143 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1144 1145 /* 1146 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1147 * a 0 window. This may cause the remote transmitter to stall. This 1148 * flag tells soreceive() to disable delayed acknowledgements when 1149 * draining the buffer. This can occur if the receiver is attempting 1150 * to read more data than can be buffered prior to transmitting on 1151 * the connection. 1152 */ 1153 if (th->th_win == 0) { 1154 tp->t_sndzerowin++; 1155 tp->t_flags |= TF_RXWIN0SENT; 1156 } else 1157 tp->t_flags &= ~TF_RXWIN0SENT; 1158 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1159 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1160 th->th_flags |= TH_URG; 1161 } else 1162 /* 1163 * If no urgent pointer to send, then we pull 1164 * the urgent pointer to the left edge of the send window 1165 * so that it doesn't drift into the send window on sequence 1166 * number wraparound. 1167 */ 1168 tp->snd_up = tp->snd_una; /* drag it along */ 1169 1170 #ifdef TCP_SIGNATURE 1171 if (to.to_flags & TOF_SIGNATURE) { 1172 int sigoff = to.to_signature - opt; 1173 tcp_signature_compute(m, 0, len, optlen, 1174 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1175 } 1176 #endif 1177 1178 /* 1179 * Put TCP length in extended header, and then 1180 * checksum extended header and data. 1181 */ 1182 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1183 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1184 #ifdef INET6 1185 if (isipv6) { 1186 /* 1187 * ip6_plen is not need to be filled now, and will be filled 1188 * in ip6_output. 1189 */ 1190 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1191 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1192 optlen + len, IPPROTO_TCP, 0); 1193 } 1194 #endif 1195 #if defined(INET6) && defined(INET) 1196 else 1197 #endif 1198 #ifdef INET 1199 { 1200 m->m_pkthdr.csum_flags = CSUM_TCP; 1201 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1202 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1203 1204 /* IP version must be set here for ipv4/ipv6 checking later */ 1205 KASSERT(ip->ip_v == IPVERSION, 1206 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1207 } 1208 #endif 1209 1210 /* 1211 * Enable TSO and specify the size of the segments. 1212 * The TCP pseudo header checksum is always provided. 1213 * XXX: Fixme: This is currently not the case for IPv6. 1214 */ 1215 if (tso) { 1216 KASSERT(len > tp->t_maxopd - optlen, 1217 ("%s: len <= tso_segsz", __func__)); 1218 m->m_pkthdr.csum_flags |= CSUM_TSO; 1219 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1220 } 1221 1222 #ifdef IPSEC 1223 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1224 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", 1225 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1226 #else 1227 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1228 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", 1229 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1230 #endif 1231 1232 /* 1233 * In transmit state, time the transmission and arrange for 1234 * the retransmit. In persist state, just set snd_max. 1235 */ 1236 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1237 !tcp_timer_active(tp, TT_PERSIST)) { 1238 tcp_seq startseq = tp->snd_nxt; 1239 1240 /* 1241 * Advance snd_nxt over sequence space of this segment. 1242 */ 1243 if (flags & (TH_SYN|TH_FIN)) { 1244 if (flags & TH_SYN) 1245 tp->snd_nxt++; 1246 if (flags & TH_FIN) { 1247 tp->snd_nxt++; 1248 tp->t_flags |= TF_SENTFIN; 1249 } 1250 } 1251 if (sack_rxmit) 1252 goto timer; 1253 tp->snd_nxt += len; 1254 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1255 tp->snd_max = tp->snd_nxt; 1256 /* 1257 * Time this transmission if not a retransmission and 1258 * not currently timing anything. 1259 */ 1260 if (tp->t_rtttime == 0) { 1261 tp->t_rtttime = ticks; 1262 tp->t_rtseq = startseq; 1263 TCPSTAT_INC(tcps_segstimed); 1264 } 1265 } 1266 1267 /* 1268 * Set retransmit timer if not currently set, 1269 * and not doing a pure ack or a keep-alive probe. 1270 * Initial value for retransmit timer is smoothed 1271 * round-trip time + 2 * round-trip time variance. 1272 * Initialize shift counter which is used for backoff 1273 * of retransmit time. 1274 */ 1275 timer: 1276 if (!tcp_timer_active(tp, TT_REXMT) && 1277 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1278 (tp->snd_nxt != tp->snd_una))) { 1279 if (tcp_timer_active(tp, TT_PERSIST)) { 1280 tcp_timer_activate(tp, TT_PERSIST, 0); 1281 tp->t_rxtshift = 0; 1282 } 1283 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1284 } 1285 } else { 1286 /* 1287 * Persist case, update snd_max but since we are in 1288 * persist mode (no window) we do not update snd_nxt. 1289 */ 1290 int xlen = len; 1291 if (flags & TH_SYN) 1292 ++xlen; 1293 if (flags & TH_FIN) { 1294 ++xlen; 1295 tp->t_flags |= TF_SENTFIN; 1296 } 1297 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1298 tp->snd_max = tp->snd_nxt + len; 1299 } 1300 1301 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1302 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1303 1304 #ifdef TCPDEBUG 1305 /* 1306 * Trace. 1307 */ 1308 if (so->so_options & SO_DEBUG) { 1309 u_short save = 0; 1310 #ifdef INET6 1311 if (!isipv6) 1312 #endif 1313 { 1314 save = ipov->ih_len; 1315 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1316 } 1317 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1318 #ifdef INET6 1319 if (!isipv6) 1320 #endif 1321 ipov->ih_len = save; 1322 } 1323 #endif /* TCPDEBUG */ 1324 1325 /* 1326 * Fill in IP length and desired time to live and 1327 * send to IP level. There should be a better way 1328 * to handle ttl and tos; we could keep them in 1329 * the template, but need a way to checksum without them. 1330 */ 1331 /* 1332 * m->m_pkthdr.len should have been set before cksum calcuration, 1333 * because in6_cksum() need it. 1334 */ 1335 #ifdef INET6 1336 if (isipv6) { 1337 struct route_in6 ro; 1338 1339 bzero(&ro, sizeof(ro)); 1340 /* 1341 * we separately set hoplimit for every segment, since the 1342 * user might want to change the value via setsockopt. 1343 * Also, desired default hop limit might be changed via 1344 * Neighbor Discovery. 1345 */ 1346 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1347 1348 /* TODO: IPv6 IP6TOS_ECT bit on */ 1349 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1350 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1351 NULL, NULL, tp->t_inpcb); 1352 1353 if (error == EMSGSIZE && ro.ro_rt != NULL) 1354 mtu = ro.ro_rt->rt_rmx.rmx_mtu; 1355 RO_RTFREE(&ro); 1356 } 1357 #endif /* INET6 */ 1358 #if defined(INET) && defined(INET6) 1359 else 1360 #endif 1361 #ifdef INET 1362 { 1363 struct route ro; 1364 1365 bzero(&ro, sizeof(ro)); 1366 ip->ip_len = m->m_pkthdr.len; 1367 #ifdef INET6 1368 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1369 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1370 #endif /* INET6 */ 1371 /* 1372 * If we do path MTU discovery, then we set DF on every packet. 1373 * This might not be the best thing to do according to RFC3390 1374 * Section 2. However the tcp hostcache migitates the problem 1375 * so it affects only the first tcp connection with a host. 1376 * 1377 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1378 */ 1379 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1380 ip->ip_off |= IP_DF; 1381 1382 error = ip_output(m, tp->t_inpcb->inp_options, &ro, 1383 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1384 tp->t_inpcb); 1385 1386 if (error == EMSGSIZE && ro.ro_rt != NULL) 1387 mtu = ro.ro_rt->rt_rmx.rmx_mtu; 1388 RO_RTFREE(&ro); 1389 } 1390 #endif /* INET */ 1391 if (error) { 1392 1393 /* 1394 * We know that the packet was lost, so back out the 1395 * sequence number advance, if any. 1396 * 1397 * If the error is EPERM the packet got blocked by the 1398 * local firewall. Normally we should terminate the 1399 * connection but the blocking may have been spurious 1400 * due to a firewall reconfiguration cycle. So we treat 1401 * it like a packet loss and let the retransmit timer and 1402 * timeouts do their work over time. 1403 * XXX: It is a POLA question whether calling tcp_drop right 1404 * away would be the really correct behavior instead. 1405 */ 1406 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1407 !tcp_timer_active(tp, TT_PERSIST)) && 1408 ((flags & TH_SYN) == 0) && 1409 (error != EPERM)) { 1410 if (sack_rxmit) { 1411 p->rxmit -= len; 1412 tp->sackhint.sack_bytes_rexmit -= len; 1413 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1414 ("sackhint bytes rtx >= 0")); 1415 } else 1416 tp->snd_nxt -= len; 1417 } 1418 out: 1419 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1420 switch (error) { 1421 case EPERM: 1422 tp->t_softerror = error; 1423 return (error); 1424 case ENOBUFS: 1425 if (!tcp_timer_active(tp, TT_REXMT) && 1426 !tcp_timer_active(tp, TT_PERSIST)) 1427 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1428 tp->snd_cwnd = tp->t_maxseg; 1429 return (0); 1430 case EMSGSIZE: 1431 /* 1432 * For some reason the interface we used initially 1433 * to send segments changed to another or lowered 1434 * its MTU. 1435 * If TSO was active we either got an interface 1436 * without TSO capabilits or TSO was turned off. 1437 * If we obtained mtu from ip_output() then update 1438 * it and try again. 1439 */ 1440 if (tso) 1441 tp->t_flags &= ~TF_TSO; 1442 if (mtu != 0) { 1443 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1444 goto again; 1445 } 1446 return (error); 1447 case EHOSTDOWN: 1448 case EHOSTUNREACH: 1449 case ENETDOWN: 1450 case ENETUNREACH: 1451 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1452 tp->t_softerror = error; 1453 return (0); 1454 } 1455 /* FALLTHROUGH */ 1456 default: 1457 return (error); 1458 } 1459 } 1460 TCPSTAT_INC(tcps_sndtotal); 1461 1462 /* 1463 * Data sent (as far as we can tell). 1464 * If this advertises a larger window than any other segment, 1465 * then remember the size of the advertised window. 1466 * Any pending ACK has now been sent. 1467 */ 1468 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1469 tp->rcv_adv = tp->rcv_nxt + recwin; 1470 tp->last_ack_sent = tp->rcv_nxt; 1471 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1472 if (tcp_timer_active(tp, TT_DELACK)) 1473 tcp_timer_activate(tp, TT_DELACK, 0); 1474 #if 0 1475 /* 1476 * This completely breaks TCP if newreno is turned on. What happens 1477 * is that if delayed-acks are turned on on the receiver, this code 1478 * on the transmitter effectively destroys the TCP window, forcing 1479 * it to four packets (1.5Kx4 = 6K window). 1480 */ 1481 if (sendalot && --maxburst) 1482 goto again; 1483 #endif 1484 if (sendalot) 1485 goto again; 1486 return (0); 1487 } 1488 1489 void 1490 tcp_setpersist(struct tcpcb *tp) 1491 { 1492 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1493 int tt; 1494 1495 tp->t_flags &= ~TF_PREVVALID; 1496 if (tcp_timer_active(tp, TT_REXMT)) 1497 panic("tcp_setpersist: retransmit pending"); 1498 /* 1499 * Start/restart persistance timer. 1500 */ 1501 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1502 TCPTV_PERSMIN, TCPTV_PERSMAX); 1503 tcp_timer_activate(tp, TT_PERSIST, tt); 1504 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1505 tp->t_rxtshift++; 1506 } 1507 1508 /* 1509 * Insert TCP options according to the supplied parameters to the place 1510 * optp in a consistent way. Can handle unaligned destinations. 1511 * 1512 * The order of the option processing is crucial for optimal packing and 1513 * alignment for the scarce option space. 1514 * 1515 * The optimal order for a SYN/SYN-ACK segment is: 1516 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1517 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1518 * 1519 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1520 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1521 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1522 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1523 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1524 */ 1525 int 1526 tcp_addoptions(struct tcpopt *to, u_char *optp) 1527 { 1528 u_int mask, optlen = 0; 1529 1530 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1531 if ((to->to_flags & mask) != mask) 1532 continue; 1533 if (optlen == TCP_MAXOLEN) 1534 break; 1535 switch (to->to_flags & mask) { 1536 case TOF_MSS: 1537 while (optlen % 4) { 1538 optlen += TCPOLEN_NOP; 1539 *optp++ = TCPOPT_NOP; 1540 } 1541 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1542 continue; 1543 optlen += TCPOLEN_MAXSEG; 1544 *optp++ = TCPOPT_MAXSEG; 1545 *optp++ = TCPOLEN_MAXSEG; 1546 to->to_mss = htons(to->to_mss); 1547 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1548 optp += sizeof(to->to_mss); 1549 break; 1550 case TOF_SCALE: 1551 while (!optlen || optlen % 2 != 1) { 1552 optlen += TCPOLEN_NOP; 1553 *optp++ = TCPOPT_NOP; 1554 } 1555 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1556 continue; 1557 optlen += TCPOLEN_WINDOW; 1558 *optp++ = TCPOPT_WINDOW; 1559 *optp++ = TCPOLEN_WINDOW; 1560 *optp++ = to->to_wscale; 1561 break; 1562 case TOF_SACKPERM: 1563 while (optlen % 2) { 1564 optlen += TCPOLEN_NOP; 1565 *optp++ = TCPOPT_NOP; 1566 } 1567 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1568 continue; 1569 optlen += TCPOLEN_SACK_PERMITTED; 1570 *optp++ = TCPOPT_SACK_PERMITTED; 1571 *optp++ = TCPOLEN_SACK_PERMITTED; 1572 break; 1573 case TOF_TS: 1574 while (!optlen || optlen % 4 != 2) { 1575 optlen += TCPOLEN_NOP; 1576 *optp++ = TCPOPT_NOP; 1577 } 1578 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1579 continue; 1580 optlen += TCPOLEN_TIMESTAMP; 1581 *optp++ = TCPOPT_TIMESTAMP; 1582 *optp++ = TCPOLEN_TIMESTAMP; 1583 to->to_tsval = htonl(to->to_tsval); 1584 to->to_tsecr = htonl(to->to_tsecr); 1585 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1586 optp += sizeof(to->to_tsval); 1587 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1588 optp += sizeof(to->to_tsecr); 1589 break; 1590 #ifdef TCP_SIGNATURE 1591 case TOF_SIGNATURE: 1592 { 1593 int siglen = TCPOLEN_SIGNATURE - 2; 1594 1595 while (!optlen || optlen % 4 != 2) { 1596 optlen += TCPOLEN_NOP; 1597 *optp++ = TCPOPT_NOP; 1598 } 1599 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1600 continue; 1601 optlen += TCPOLEN_SIGNATURE; 1602 *optp++ = TCPOPT_SIGNATURE; 1603 *optp++ = TCPOLEN_SIGNATURE; 1604 to->to_signature = optp; 1605 while (siglen--) 1606 *optp++ = 0; 1607 break; 1608 } 1609 #endif 1610 case TOF_SACK: 1611 { 1612 int sackblks = 0; 1613 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1614 tcp_seq sack_seq; 1615 1616 while (!optlen || optlen % 4 != 2) { 1617 optlen += TCPOLEN_NOP; 1618 *optp++ = TCPOPT_NOP; 1619 } 1620 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1621 continue; 1622 optlen += TCPOLEN_SACKHDR; 1623 *optp++ = TCPOPT_SACK; 1624 sackblks = min(to->to_nsacks, 1625 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1626 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1627 while (sackblks--) { 1628 sack_seq = htonl(sack->start); 1629 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1630 optp += sizeof(sack_seq); 1631 sack_seq = htonl(sack->end); 1632 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1633 optp += sizeof(sack_seq); 1634 optlen += TCPOLEN_SACK; 1635 sack++; 1636 } 1637 TCPSTAT_INC(tcps_sack_send_blocks); 1638 break; 1639 } 1640 default: 1641 panic("%s: unknown TCP option type", __func__); 1642 break; 1643 } 1644 } 1645 1646 /* Terminate and pad TCP options to a 4 byte boundary. */ 1647 if (optlen % 4) { 1648 optlen += TCPOLEN_EOL; 1649 *optp++ = TCPOPT_EOL; 1650 } 1651 /* 1652 * According to RFC 793 (STD0007): 1653 * "The content of the header beyond the End-of-Option option 1654 * must be header padding (i.e., zero)." 1655 * and later: "The padding is composed of zeros." 1656 */ 1657 while (optlen % 4) { 1658 optlen += TCPOLEN_PAD; 1659 *optp++ = TCPOPT_PAD; 1660 } 1661 1662 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1663 return (optlen); 1664 }
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