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 output 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 len = 0; 412 if (sendwin == 0) { 413 tcp_timer_activate(tp, TT_REXMT, 0); 414 tp->t_rxtshift = 0; 415 tp->snd_nxt = tp->snd_una; 416 if (!tcp_timer_active(tp, TT_PERSIST)) 417 tcp_setpersist(tp); 418 } 419 } 420 421 /* len will be >= 0 after this point. */ 422 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 423 424 /* 425 * Automatic sizing of send socket buffer. Often the send buffer 426 * size is not optimally adjusted to the actual network conditions 427 * at hand (delay bandwidth product). Setting the buffer size too 428 * small limits throughput on links with high bandwidth and high 429 * delay (eg. trans-continental/oceanic links). Setting the 430 * buffer size too big consumes too much real kernel memory, 431 * especially with many connections on busy servers. 432 * 433 * The criteria to step up the send buffer one notch are: 434 * 1. receive window of remote host is larger than send buffer 435 * (with a fudge factor of 5/4th); 436 * 2. send buffer is filled to 7/8th with data (so we actually 437 * have data to make use of it); 438 * 3. send buffer fill has not hit maximal automatic size; 439 * 4. our send window (slow start and cogestion controlled) is 440 * larger than sent but unacknowledged data in send buffer. 441 * 442 * The remote host receive window scaling factor may limit the 443 * growing of the send buffer before it reaches its allowed 444 * maximum. 445 * 446 * It scales directly with slow start or congestion window 447 * and does at most one step per received ACK. This fast 448 * scaling has the drawback of growing the send buffer beyond 449 * what is strictly necessary to make full use of a given 450 * delay*bandwith product. However testing has shown this not 451 * to be much of an problem. At worst we are trading wasting 452 * of available bandwith (the non-use of it) for wasting some 453 * socket buffer memory. 454 * 455 * TODO: Shrink send buffer during idle periods together 456 * with congestion window. Requires another timer. Has to 457 * wait for upcoming tcp timer rewrite. 458 */ 459 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 460 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 461 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 462 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 463 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 464 if (!sbreserve_locked(&so->so_snd, 465 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 466 V_tcp_autosndbuf_max), so, curthread)) 467 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 468 } 469 } 470 471 /* 472 * Decide if we can use TCP Segmentation Offloading (if supported by 473 * hardware). 474 * 475 * TSO may only be used if we are in a pure bulk sending state. The 476 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 477 * IP options prevent using TSO. With TSO the TCP header is the same 478 * (except for the sequence number) for all generated packets. This 479 * makes it impossible to transmit any options which vary per generated 480 * segment or packet. 481 */ 482 #ifdef IPSEC 483 /* 484 * Pre-calculate here as we save another lookup into the darknesses 485 * of IPsec that way and can actually decide if TSO is ok. 486 */ 487 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 488 #endif 489 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 490 ((tp->t_flags & TF_SIGNATURE) == 0) && 491 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 492 #ifdef IPSEC 493 ipsec_optlen == 0 && 494 #endif 495 tp->t_inpcb->inp_options == NULL && 496 tp->t_inpcb->in6p_options == NULL) 497 tso = 1; 498 499 if (sack_rxmit) { 500 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 501 flags &= ~TH_FIN; 502 } else { 503 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 504 flags &= ~TH_FIN; 505 } 506 507 recwin = sbspace(&so->so_rcv); 508 509 /* 510 * Sender silly window avoidance. We transmit under the following 511 * conditions when len is non-zero: 512 * 513 * - We have a full segment (or more with TSO) 514 * - This is the last buffer in a write()/send() and we are 515 * either idle or running NODELAY 516 * - we've timed out (e.g. persist timer) 517 * - we have more then 1/2 the maximum send window's worth of 518 * data (receiver may be limited the window size) 519 * - we need to retransmit 520 */ 521 if (len) { 522 if (len >= tp->t_maxseg) 523 goto send; 524 /* 525 * NOTE! on localhost connections an 'ack' from the remote 526 * end may occur synchronously with the output and cause 527 * us to flush a buffer queued with moretocome. XXX 528 * 529 * note: the len + off check is almost certainly unnecessary. 530 */ 531 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 532 (idle || (tp->t_flags & TF_NODELAY)) && 533 len + off >= so->so_snd.sb_cc && 534 (tp->t_flags & TF_NOPUSH) == 0) { 535 goto send; 536 } 537 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 538 goto send; 539 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 540 goto send; 541 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 542 goto send; 543 if (sack_rxmit) 544 goto send; 545 } 546 547 /* 548 * Sending of standalone window updates. 549 * 550 * Window updates are important when we close our window due to a 551 * full socket buffer and are opening it again after the application 552 * reads data from it. Once the window has opened again and the 553 * remote end starts to send again the ACK clock takes over and 554 * provides the most current window information. 555 * 556 * We must avoid the silly window syndrome whereas every read 557 * from the receive buffer, no matter how small, causes a window 558 * update to be sent. We also should avoid sending a flurry of 559 * window updates when the socket buffer had queued a lot of data 560 * and the application is doing small reads. 561 * 562 * Prevent a flurry of pointless window updates by only sending 563 * an update when we can increase the advertized window by more 564 * than 1/4th of the socket buffer capacity. When the buffer is 565 * getting full or is very small be more aggressive and send an 566 * update whenever we can increase by two mss sized segments. 567 * In all other situations the ACK's to new incoming data will 568 * carry further window increases. 569 * 570 * Don't send an independent window update if a delayed 571 * ACK is pending (it will get piggy-backed on it) or the 572 * remote side already has done a half-close and won't send 573 * more data. Skip this if the connection is in T/TCP 574 * half-open state. 575 */ 576 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 577 !(tp->t_flags & TF_DELACK) && 578 !TCPS_HAVERCVDFIN(tp->t_state)) { 579 /* 580 * "adv" is the amount we could increase the window, 581 * taking into account that we are limited by 582 * TCP_MAXWIN << tp->rcv_scale. 583 */ 584 long adv; 585 int oldwin; 586 587 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 588 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 589 oldwin = (tp->rcv_adv - tp->rcv_nxt); 590 adv -= oldwin; 591 } else 592 oldwin = 0; 593 594 /* 595 * If the new window size ends up being the same as the old 596 * size when it is scaled, then don't force a window update. 597 */ 598 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 599 goto dontupdate; 600 601 if (adv >= (long)(2 * tp->t_maxseg) && 602 (adv >= (long)(so->so_rcv.sb_hiwat / 4) || 603 recwin <= (long)(so->so_rcv.sb_hiwat / 8) || 604 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 605 goto send; 606 } 607 dontupdate: 608 609 /* 610 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 611 * is also a catch-all for the retransmit timer timeout case. 612 */ 613 if (tp->t_flags & TF_ACKNOW) 614 goto send; 615 if ((flags & TH_RST) || 616 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 617 goto send; 618 if (SEQ_GT(tp->snd_up, tp->snd_una)) 619 goto send; 620 /* 621 * If our state indicates that FIN should be sent 622 * and we have not yet done so, then we need to send. 623 */ 624 if (flags & TH_FIN && 625 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 626 goto send; 627 /* 628 * In SACK, it is possible for tcp_output to fail to send a segment 629 * after the retransmission timer has been turned off. Make sure 630 * that the retransmission timer is set. 631 */ 632 if ((tp->t_flags & TF_SACK_PERMIT) && 633 SEQ_GT(tp->snd_max, tp->snd_una) && 634 !tcp_timer_active(tp, TT_REXMT) && 635 !tcp_timer_active(tp, TT_PERSIST)) { 636 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 637 goto just_return; 638 } 639 /* 640 * TCP window updates are not reliable, rather a polling protocol 641 * using ``persist'' packets is used to insure receipt of window 642 * updates. The three ``states'' for the output side are: 643 * idle not doing retransmits or persists 644 * persisting to move a small or zero window 645 * (re)transmitting and thereby not persisting 646 * 647 * tcp_timer_active(tp, TT_PERSIST) 648 * is true when we are in persist state. 649 * (tp->t_flags & TF_FORCEDATA) 650 * is set when we are called to send a persist packet. 651 * tcp_timer_active(tp, TT_REXMT) 652 * is set when we are retransmitting 653 * The output side is idle when both timers are zero. 654 * 655 * If send window is too small, there is data to transmit, and no 656 * retransmit or persist is pending, then go to persist state. 657 * If nothing happens soon, send when timer expires: 658 * if window is nonzero, transmit what we can, 659 * otherwise force out a byte. 660 */ 661 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 662 !tcp_timer_active(tp, TT_PERSIST)) { 663 tp->t_rxtshift = 0; 664 tcp_setpersist(tp); 665 } 666 667 /* 668 * No reason to send a segment, just return. 669 */ 670 just_return: 671 SOCKBUF_UNLOCK(&so->so_snd); 672 return (0); 673 674 send: 675 SOCKBUF_LOCK_ASSERT(&so->so_snd); 676 /* 677 * Before ESTABLISHED, force sending of initial options 678 * unless TCP set not to do any options. 679 * NOTE: we assume that the IP/TCP header plus TCP options 680 * always fit in a single mbuf, leaving room for a maximum 681 * link header, i.e. 682 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 683 */ 684 optlen = 0; 685 #ifdef INET6 686 if (isipv6) 687 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 688 else 689 #endif 690 hdrlen = sizeof (struct tcpiphdr); 691 692 /* 693 * Compute options for segment. 694 * We only have to care about SYN and established connection 695 * segments. Options for SYN-ACK segments are handled in TCP 696 * syncache. 697 */ 698 if ((tp->t_flags & TF_NOOPT) == 0) { 699 to.to_flags = 0; 700 /* Maximum segment size. */ 701 if (flags & TH_SYN) { 702 tp->snd_nxt = tp->iss; 703 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 704 to.to_flags |= TOF_MSS; 705 } 706 /* Window scaling. */ 707 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 708 to.to_wscale = tp->request_r_scale; 709 to.to_flags |= TOF_SCALE; 710 } 711 /* Timestamps. */ 712 if ((tp->t_flags & TF_RCVD_TSTMP) || 713 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 714 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 715 to.to_tsecr = tp->ts_recent; 716 to.to_flags |= TOF_TS; 717 /* Set receive buffer autosizing timestamp. */ 718 if (tp->rfbuf_ts == 0 && 719 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 720 tp->rfbuf_ts = tcp_ts_getticks(); 721 } 722 /* Selective ACK's. */ 723 if (tp->t_flags & TF_SACK_PERMIT) { 724 if (flags & TH_SYN) 725 to.to_flags |= TOF_SACKPERM; 726 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 727 (tp->t_flags & TF_SACK_PERMIT) && 728 tp->rcv_numsacks > 0) { 729 to.to_flags |= TOF_SACK; 730 to.to_nsacks = tp->rcv_numsacks; 731 to.to_sacks = (u_char *)tp->sackblks; 732 } 733 } 734 #ifdef TCP_SIGNATURE 735 /* TCP-MD5 (RFC2385). */ 736 if (tp->t_flags & TF_SIGNATURE) 737 to.to_flags |= TOF_SIGNATURE; 738 #endif /* TCP_SIGNATURE */ 739 740 /* Processing the options. */ 741 hdrlen += optlen = tcp_addoptions(&to, opt); 742 } 743 744 #ifdef INET6 745 if (isipv6) 746 ipoptlen = ip6_optlen(tp->t_inpcb); 747 else 748 #endif 749 if (tp->t_inpcb->inp_options) 750 ipoptlen = tp->t_inpcb->inp_options->m_len - 751 offsetof(struct ipoption, ipopt_list); 752 else 753 ipoptlen = 0; 754 #ifdef IPSEC 755 ipoptlen += ipsec_optlen; 756 #endif 757 758 /* 759 * Adjust data length if insertion of options will 760 * bump the packet length beyond the t_maxopd length. 761 * Clear the FIN bit because we cut off the tail of 762 * the segment. 763 */ 764 if (len + optlen + ipoptlen > tp->t_maxopd) { 765 flags &= ~TH_FIN; 766 767 if (tso) { 768 KASSERT(ipoptlen == 0, 769 ("%s: TSO can't do IP options", __func__)); 770 771 /* 772 * Limit a burst to IP_MAXPACKET minus IP, 773 * TCP and options length to keep ip->ip_len 774 * from overflowing. 775 */ 776 if (len > IP_MAXPACKET - hdrlen) { 777 len = IP_MAXPACKET - hdrlen; 778 sendalot = 1; 779 } 780 781 /* 782 * Prevent the last segment from being 783 * fractional unless the send sockbuf can 784 * be emptied. 785 */ 786 if (sendalot && off + len < so->so_snd.sb_cc) { 787 len -= len % (tp->t_maxopd - optlen); 788 sendalot = 1; 789 } 790 791 /* 792 * Send the FIN in a separate segment 793 * after the bulk sending is done. 794 * We don't trust the TSO implementations 795 * to clear the FIN flag on all but the 796 * last segment. 797 */ 798 if (tp->t_flags & TF_NEEDFIN) 799 sendalot = 1; 800 801 } else { 802 len = tp->t_maxopd - optlen - ipoptlen; 803 sendalot = 1; 804 } 805 } else 806 tso = 0; 807 808 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 809 ("%s: len > IP_MAXPACKET", __func__)); 810 811 /*#ifdef DIAGNOSTIC*/ 812 #ifdef INET6 813 if (max_linkhdr + hdrlen > MCLBYTES) 814 #else 815 if (max_linkhdr + hdrlen > MHLEN) 816 #endif 817 panic("tcphdr too big"); 818 /*#endif*/ 819 820 /* 821 * This KASSERT is here to catch edge cases at a well defined place. 822 * Before, those had triggered (random) panic conditions further down. 823 */ 824 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 825 826 /* 827 * Grab a header mbuf, attaching a copy of data to 828 * be transmitted, and initialize the header from 829 * the template for sends on this connection. 830 */ 831 if (len) { 832 struct mbuf *mb; 833 u_int moff; 834 835 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 836 TCPSTAT_INC(tcps_sndprobe); 837 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 838 tp->t_sndrexmitpack++; 839 TCPSTAT_INC(tcps_sndrexmitpack); 840 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 841 } else { 842 TCPSTAT_INC(tcps_sndpack); 843 TCPSTAT_ADD(tcps_sndbyte, len); 844 } 845 #ifdef INET6 846 if (MHLEN < hdrlen + max_linkhdr) 847 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 848 else 849 #endif 850 m = m_gethdr(M_NOWAIT, MT_DATA); 851 852 if (m == NULL) { 853 SOCKBUF_UNLOCK(&so->so_snd); 854 error = ENOBUFS; 855 sack_rxmit = 0; 856 goto out; 857 } 858 859 m->m_data += max_linkhdr; 860 m->m_len = hdrlen; 861 862 /* 863 * Start the m_copy functions from the closest mbuf 864 * to the offset in the socket buffer chain. 865 */ 866 mb = sbsndptr(&so->so_snd, off, len, &moff); 867 868 if (len <= MHLEN - hdrlen - max_linkhdr) { 869 m_copydata(mb, moff, (int)len, 870 mtod(m, caddr_t) + hdrlen); 871 m->m_len += len; 872 } else { 873 m->m_next = m_copy(mb, moff, (int)len); 874 if (m->m_next == NULL) { 875 SOCKBUF_UNLOCK(&so->so_snd); 876 (void) m_free(m); 877 error = ENOBUFS; 878 sack_rxmit = 0; 879 goto out; 880 } 881 } 882 883 /* 884 * If we're sending everything we've got, set PUSH. 885 * (This will keep happy those implementations which only 886 * give data to the user when a buffer fills or 887 * a PUSH comes in.) 888 */ 889 if (off + len == so->so_snd.sb_cc) 890 flags |= TH_PUSH; 891 SOCKBUF_UNLOCK(&so->so_snd); 892 } else { 893 SOCKBUF_UNLOCK(&so->so_snd); 894 if (tp->t_flags & TF_ACKNOW) 895 TCPSTAT_INC(tcps_sndacks); 896 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 897 TCPSTAT_INC(tcps_sndctrl); 898 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 899 TCPSTAT_INC(tcps_sndurg); 900 else 901 TCPSTAT_INC(tcps_sndwinup); 902 903 m = m_gethdr(M_NOWAIT, MT_DATA); 904 if (m == NULL) { 905 error = ENOBUFS; 906 sack_rxmit = 0; 907 goto out; 908 } 909 #ifdef INET6 910 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 911 MHLEN >= hdrlen) { 912 MH_ALIGN(m, hdrlen); 913 } else 914 #endif 915 m->m_data += max_linkhdr; 916 m->m_len = hdrlen; 917 } 918 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 919 m->m_pkthdr.rcvif = (struct ifnet *)0; 920 #ifdef MAC 921 mac_inpcb_create_mbuf(tp->t_inpcb, m); 922 #endif 923 #ifdef INET6 924 if (isipv6) { 925 ip6 = mtod(m, struct ip6_hdr *); 926 th = (struct tcphdr *)(ip6 + 1); 927 tcpip_fillheaders(tp->t_inpcb, ip6, th); 928 } else 929 #endif /* INET6 */ 930 { 931 ip = mtod(m, struct ip *); 932 ipov = (struct ipovly *)ip; 933 th = (struct tcphdr *)(ip + 1); 934 tcpip_fillheaders(tp->t_inpcb, ip, th); 935 } 936 937 /* 938 * Fill in fields, remembering maximum advertised 939 * window for use in delaying messages about window sizes. 940 * If resending a FIN, be sure not to use a new sequence number. 941 */ 942 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 943 tp->snd_nxt == tp->snd_max) 944 tp->snd_nxt--; 945 /* 946 * If we are starting a connection, send ECN setup 947 * SYN packet. If we are on a retransmit, we may 948 * resend those bits a number of times as per 949 * RFC 3168. 950 */ 951 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 952 if (tp->t_rxtshift >= 1) { 953 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 954 flags |= TH_ECE|TH_CWR; 955 } else 956 flags |= TH_ECE|TH_CWR; 957 } 958 959 if (tp->t_state == TCPS_ESTABLISHED && 960 (tp->t_flags & TF_ECN_PERMIT)) { 961 /* 962 * If the peer has ECN, mark data packets with 963 * ECN capable transmission (ECT). 964 * Ignore pure ack packets, retransmissions and window probes. 965 */ 966 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 967 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 968 #ifdef INET6 969 if (isipv6) 970 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 971 else 972 #endif 973 ip->ip_tos |= IPTOS_ECN_ECT0; 974 TCPSTAT_INC(tcps_ecn_ect0); 975 } 976 977 /* 978 * Reply with proper ECN notifications. 979 */ 980 if (tp->t_flags & TF_ECN_SND_CWR) { 981 flags |= TH_CWR; 982 tp->t_flags &= ~TF_ECN_SND_CWR; 983 } 984 if (tp->t_flags & TF_ECN_SND_ECE) 985 flags |= TH_ECE; 986 } 987 988 /* 989 * If we are doing retransmissions, then snd_nxt will 990 * not reflect the first unsent octet. For ACK only 991 * packets, we do not want the sequence number of the 992 * retransmitted packet, we want the sequence number 993 * of the next unsent octet. So, if there is no data 994 * (and no SYN or FIN), use snd_max instead of snd_nxt 995 * when filling in ti_seq. But if we are in persist 996 * state, snd_max might reflect one byte beyond the 997 * right edge of the window, so use snd_nxt in that 998 * case, since we know we aren't doing a retransmission. 999 * (retransmit and persist are mutually exclusive...) 1000 */ 1001 if (sack_rxmit == 0) { 1002 if (len || (flags & (TH_SYN|TH_FIN)) || 1003 tcp_timer_active(tp, TT_PERSIST)) 1004 th->th_seq = htonl(tp->snd_nxt); 1005 else 1006 th->th_seq = htonl(tp->snd_max); 1007 } else { 1008 th->th_seq = htonl(p->rxmit); 1009 p->rxmit += len; 1010 tp->sackhint.sack_bytes_rexmit += len; 1011 } 1012 th->th_ack = htonl(tp->rcv_nxt); 1013 if (optlen) { 1014 bcopy(opt, th + 1, optlen); 1015 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1016 } 1017 th->th_flags = flags; 1018 /* 1019 * Calculate receive window. Don't shrink window, 1020 * but avoid silly window syndrome. 1021 */ 1022 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1023 recwin < (long)tp->t_maxseg) 1024 recwin = 0; 1025 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1026 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1027 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1028 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1029 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1030 1031 /* 1032 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1033 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1034 * case is handled in syncache. 1035 */ 1036 if (flags & TH_SYN) 1037 th->th_win = htons((u_short) 1038 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1039 else 1040 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1041 1042 /* 1043 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1044 * a 0 window. This may cause the remote transmitter to stall. This 1045 * flag tells soreceive() to disable delayed acknowledgements when 1046 * draining the buffer. This can occur if the receiver is attempting 1047 * to read more data than can be buffered prior to transmitting on 1048 * the connection. 1049 */ 1050 if (th->th_win == 0) { 1051 tp->t_sndzerowin++; 1052 tp->t_flags |= TF_RXWIN0SENT; 1053 } else 1054 tp->t_flags &= ~TF_RXWIN0SENT; 1055 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1056 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1057 th->th_flags |= TH_URG; 1058 } else 1059 /* 1060 * If no urgent pointer to send, then we pull 1061 * the urgent pointer to the left edge of the send window 1062 * so that it doesn't drift into the send window on sequence 1063 * number wraparound. 1064 */ 1065 tp->snd_up = tp->snd_una; /* drag it along */ 1066 1067 #ifdef TCP_SIGNATURE 1068 if (tp->t_flags & TF_SIGNATURE) { 1069 int sigoff = to.to_signature - opt; 1070 tcp_signature_compute(m, 0, len, optlen, 1071 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1072 } 1073 #endif 1074 1075 /* 1076 * Put TCP length in extended header, and then 1077 * checksum extended header and data. 1078 */ 1079 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1080 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1081 #ifdef INET6 1082 if (isipv6) { 1083 /* 1084 * ip6_plen is not need to be filled now, and will be filled 1085 * in ip6_output. 1086 */ 1087 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1088 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1089 optlen + len, IPPROTO_TCP, 0); 1090 } 1091 #endif 1092 #if defined(INET6) && defined(INET) 1093 else 1094 #endif 1095 #ifdef INET 1096 { 1097 m->m_pkthdr.csum_flags = CSUM_TCP; 1098 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1099 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1100 1101 /* IP version must be set here for ipv4/ipv6 checking later */ 1102 KASSERT(ip->ip_v == IPVERSION, 1103 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1104 } 1105 #endif 1106 1107 /* 1108 * Enable TSO and specify the size of the segments. 1109 * The TCP pseudo header checksum is always provided. 1110 * XXX: Fixme: This is currently not the case for IPv6. 1111 */ 1112 if (tso) { 1113 KASSERT(len > tp->t_maxopd - optlen, 1114 ("%s: len <= tso_segsz", __func__)); 1115 m->m_pkthdr.csum_flags |= CSUM_TSO; 1116 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1117 } 1118 1119 #ifdef IPSEC 1120 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1121 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", 1122 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1123 #else 1124 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1125 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", 1126 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1127 #endif 1128 1129 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1130 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1131 1132 #ifdef TCPDEBUG 1133 /* 1134 * Trace. 1135 */ 1136 if (so->so_options & SO_DEBUG) { 1137 u_short save = 0; 1138 #ifdef INET6 1139 if (!isipv6) 1140 #endif 1141 { 1142 save = ipov->ih_len; 1143 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1144 } 1145 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1146 #ifdef INET6 1147 if (!isipv6) 1148 #endif 1149 ipov->ih_len = save; 1150 } 1151 #endif /* TCPDEBUG */ 1152 1153 /* 1154 * Fill in IP length and desired time to live and 1155 * send to IP level. There should be a better way 1156 * to handle ttl and tos; we could keep them in 1157 * the template, but need a way to checksum without them. 1158 */ 1159 /* 1160 * m->m_pkthdr.len should have been set before cksum calcuration, 1161 * because in6_cksum() need it. 1162 */ 1163 #ifdef INET6 1164 if (isipv6) { 1165 struct route_in6 ro; 1166 1167 bzero(&ro, sizeof(ro)); 1168 /* 1169 * we separately set hoplimit for every segment, since the 1170 * user might want to change the value via setsockopt. 1171 * Also, desired default hop limit might be changed via 1172 * Neighbor Discovery. 1173 */ 1174 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1175 1176 /* TODO: IPv6 IP6TOS_ECT bit on */ 1177 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1178 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1179 NULL, NULL, tp->t_inpcb); 1180 1181 if (error == EMSGSIZE && ro.ro_rt != NULL) 1182 mtu = ro.ro_rt->rt_rmx.rmx_mtu; 1183 RO_RTFREE(&ro); 1184 } 1185 #endif /* INET6 */ 1186 #if defined(INET) && defined(INET6) 1187 else 1188 #endif 1189 #ifdef INET 1190 { 1191 struct route ro; 1192 1193 bzero(&ro, sizeof(ro)); 1194 ip->ip_len = htons(m->m_pkthdr.len); 1195 #ifdef INET6 1196 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1197 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1198 #endif /* INET6 */ 1199 /* 1200 * If we do path MTU discovery, then we set DF on every packet. 1201 * This might not be the best thing to do according to RFC3390 1202 * Section 2. However the tcp hostcache migitates the problem 1203 * so it affects only the first tcp connection with a host. 1204 * 1205 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1206 */ 1207 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1208 ip->ip_off |= htons(IP_DF); 1209 1210 error = ip_output(m, tp->t_inpcb->inp_options, &ro, 1211 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1212 tp->t_inpcb); 1213 1214 if (error == EMSGSIZE && ro.ro_rt != NULL) 1215 mtu = ro.ro_rt->rt_rmx.rmx_mtu; 1216 RO_RTFREE(&ro); 1217 } 1218 #endif /* INET */ 1219 1220 out: 1221 /* 1222 * In transmit state, time the transmission and arrange for 1223 * the retransmit. In persist state, just set snd_max. 1224 */ 1225 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1226 !tcp_timer_active(tp, TT_PERSIST)) { 1227 tcp_seq startseq = tp->snd_nxt; 1228 1229 /* 1230 * Advance snd_nxt over sequence space of this segment. 1231 */ 1232 if (flags & (TH_SYN|TH_FIN)) { 1233 if (flags & TH_SYN) 1234 tp->snd_nxt++; 1235 if (flags & TH_FIN) { 1236 tp->snd_nxt++; 1237 tp->t_flags |= TF_SENTFIN; 1238 } 1239 } 1240 if (sack_rxmit) 1241 goto timer; 1242 tp->snd_nxt += len; 1243 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1244 tp->snd_max = tp->snd_nxt; 1245 /* 1246 * Time this transmission if not a retransmission and 1247 * not currently timing anything. 1248 */ 1249 if (tp->t_rtttime == 0) { 1250 tp->t_rtttime = ticks; 1251 tp->t_rtseq = startseq; 1252 TCPSTAT_INC(tcps_segstimed); 1253 } 1254 } 1255 1256 /* 1257 * Set retransmit timer if not currently set, 1258 * and not doing a pure ack or a keep-alive probe. 1259 * Initial value for retransmit timer is smoothed 1260 * round-trip time + 2 * round-trip time variance. 1261 * Initialize shift counter which is used for backoff 1262 * of retransmit time. 1263 */ 1264 timer: 1265 if (!tcp_timer_active(tp, TT_REXMT) && 1266 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1267 (tp->snd_nxt != tp->snd_una))) { 1268 if (tcp_timer_active(tp, TT_PERSIST)) { 1269 tcp_timer_activate(tp, TT_PERSIST, 0); 1270 tp->t_rxtshift = 0; 1271 } 1272 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1273 } 1274 } else { 1275 /* 1276 * Persist case, update snd_max but since we are in 1277 * persist mode (no window) we do not update snd_nxt. 1278 */ 1279 int xlen = len; 1280 if (flags & TH_SYN) 1281 ++xlen; 1282 if (flags & TH_FIN) { 1283 ++xlen; 1284 tp->t_flags |= TF_SENTFIN; 1285 } 1286 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1287 tp->snd_max = tp->snd_nxt + len; 1288 } 1289 1290 if (error) { 1291 1292 /* 1293 * We know that the packet was lost, so back out the 1294 * sequence number advance, if any. 1295 * 1296 * If the error is EPERM the packet got blocked by the 1297 * local firewall. Normally we should terminate the 1298 * connection but the blocking may have been spurious 1299 * due to a firewall reconfiguration cycle. So we treat 1300 * it like a packet loss and let the retransmit timer and 1301 * timeouts do their work over time. 1302 * XXX: It is a POLA question whether calling tcp_drop right 1303 * away would be the really correct behavior instead. 1304 */ 1305 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1306 !tcp_timer_active(tp, TT_PERSIST)) && 1307 ((flags & TH_SYN) == 0) && 1308 (error != EPERM)) { 1309 if (sack_rxmit) { 1310 p->rxmit -= len; 1311 tp->sackhint.sack_bytes_rexmit -= len; 1312 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1313 ("sackhint bytes rtx >= 0")); 1314 } else 1315 tp->snd_nxt -= len; 1316 } 1317 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1318 switch (error) { 1319 case EPERM: 1320 tp->t_softerror = error; 1321 return (error); 1322 case ENOBUFS: 1323 if (!tcp_timer_active(tp, TT_REXMT) && 1324 !tcp_timer_active(tp, TT_PERSIST)) 1325 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1326 tp->snd_cwnd = tp->t_maxseg; 1327 return (0); 1328 case EMSGSIZE: 1329 /* 1330 * For some reason the interface we used initially 1331 * to send segments changed to another or lowered 1332 * its MTU. 1333 * If TSO was active we either got an interface 1334 * without TSO capabilits or TSO was turned off. 1335 * If we obtained mtu from ip_output() then update 1336 * it and try again. 1337 */ 1338 if (tso) 1339 tp->t_flags &= ~TF_TSO; 1340 if (mtu != 0) { 1341 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1342 goto again; 1343 } 1344 return (error); 1345 case EHOSTDOWN: 1346 case EHOSTUNREACH: 1347 case ENETDOWN: 1348 case ENETUNREACH: 1349 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1350 tp->t_softerror = error; 1351 return (0); 1352 } 1353 /* FALLTHROUGH */ 1354 default: 1355 return (error); 1356 } 1357 } 1358 TCPSTAT_INC(tcps_sndtotal); 1359 1360 /* 1361 * Data sent (as far as we can tell). 1362 * If this advertises a larger window than any other segment, 1363 * then remember the size of the advertised window. 1364 * Any pending ACK has now been sent. 1365 */ 1366 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1367 tp->rcv_adv = tp->rcv_nxt + recwin; 1368 tp->last_ack_sent = tp->rcv_nxt; 1369 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1370 if (tcp_timer_active(tp, TT_DELACK)) 1371 tcp_timer_activate(tp, TT_DELACK, 0); 1372 #if 0 1373 /* 1374 * This completely breaks TCP if newreno is turned on. What happens 1375 * is that if delayed-acks are turned on on the receiver, this code 1376 * on the transmitter effectively destroys the TCP window, forcing 1377 * it to four packets (1.5Kx4 = 6K window). 1378 */ 1379 if (sendalot && --maxburst) 1380 goto again; 1381 #endif 1382 if (sendalot) 1383 goto again; 1384 return (0); 1385 } 1386 1387 void 1388 tcp_setpersist(struct tcpcb *tp) 1389 { 1390 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1391 int tt; 1392 1393 tp->t_flags &= ~TF_PREVVALID; 1394 if (tcp_timer_active(tp, TT_REXMT)) 1395 panic("tcp_setpersist: retransmit pending"); 1396 /* 1397 * Start/restart persistance timer. 1398 */ 1399 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1400 TCPTV_PERSMIN, TCPTV_PERSMAX); 1401 tcp_timer_activate(tp, TT_PERSIST, tt); 1402 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1403 tp->t_rxtshift++; 1404 } 1405 1406 /* 1407 * Insert TCP options according to the supplied parameters to the place 1408 * optp in a consistent way. Can handle unaligned destinations. 1409 * 1410 * The order of the option processing is crucial for optimal packing and 1411 * alignment for the scarce option space. 1412 * 1413 * The optimal order for a SYN/SYN-ACK segment is: 1414 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1415 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1416 * 1417 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1418 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1419 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1420 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1421 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1422 */ 1423 int 1424 tcp_addoptions(struct tcpopt *to, u_char *optp) 1425 { 1426 u_int mask, optlen = 0; 1427 1428 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1429 if ((to->to_flags & mask) != mask) 1430 continue; 1431 if (optlen == TCP_MAXOLEN) 1432 break; 1433 switch (to->to_flags & mask) { 1434 case TOF_MSS: 1435 while (optlen % 4) { 1436 optlen += TCPOLEN_NOP; 1437 *optp++ = TCPOPT_NOP; 1438 } 1439 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1440 continue; 1441 optlen += TCPOLEN_MAXSEG; 1442 *optp++ = TCPOPT_MAXSEG; 1443 *optp++ = TCPOLEN_MAXSEG; 1444 to->to_mss = htons(to->to_mss); 1445 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1446 optp += sizeof(to->to_mss); 1447 break; 1448 case TOF_SCALE: 1449 while (!optlen || optlen % 2 != 1) { 1450 optlen += TCPOLEN_NOP; 1451 *optp++ = TCPOPT_NOP; 1452 } 1453 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1454 continue; 1455 optlen += TCPOLEN_WINDOW; 1456 *optp++ = TCPOPT_WINDOW; 1457 *optp++ = TCPOLEN_WINDOW; 1458 *optp++ = to->to_wscale; 1459 break; 1460 case TOF_SACKPERM: 1461 while (optlen % 2) { 1462 optlen += TCPOLEN_NOP; 1463 *optp++ = TCPOPT_NOP; 1464 } 1465 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1466 continue; 1467 optlen += TCPOLEN_SACK_PERMITTED; 1468 *optp++ = TCPOPT_SACK_PERMITTED; 1469 *optp++ = TCPOLEN_SACK_PERMITTED; 1470 break; 1471 case TOF_TS: 1472 while (!optlen || optlen % 4 != 2) { 1473 optlen += TCPOLEN_NOP; 1474 *optp++ = TCPOPT_NOP; 1475 } 1476 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1477 continue; 1478 optlen += TCPOLEN_TIMESTAMP; 1479 *optp++ = TCPOPT_TIMESTAMP; 1480 *optp++ = TCPOLEN_TIMESTAMP; 1481 to->to_tsval = htonl(to->to_tsval); 1482 to->to_tsecr = htonl(to->to_tsecr); 1483 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1484 optp += sizeof(to->to_tsval); 1485 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1486 optp += sizeof(to->to_tsecr); 1487 break; 1488 case TOF_SIGNATURE: 1489 { 1490 int siglen = TCPOLEN_SIGNATURE - 2; 1491 1492 while (!optlen || optlen % 4 != 2) { 1493 optlen += TCPOLEN_NOP; 1494 *optp++ = TCPOPT_NOP; 1495 } 1496 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1497 continue; 1498 optlen += TCPOLEN_SIGNATURE; 1499 *optp++ = TCPOPT_SIGNATURE; 1500 *optp++ = TCPOLEN_SIGNATURE; 1501 to->to_signature = optp; 1502 while (siglen--) 1503 *optp++ = 0; 1504 break; 1505 } 1506 case TOF_SACK: 1507 { 1508 int sackblks = 0; 1509 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1510 tcp_seq sack_seq; 1511 1512 while (!optlen || optlen % 4 != 2) { 1513 optlen += TCPOLEN_NOP; 1514 *optp++ = TCPOPT_NOP; 1515 } 1516 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1517 continue; 1518 optlen += TCPOLEN_SACKHDR; 1519 *optp++ = TCPOPT_SACK; 1520 sackblks = min(to->to_nsacks, 1521 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1522 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1523 while (sackblks--) { 1524 sack_seq = htonl(sack->start); 1525 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1526 optp += sizeof(sack_seq); 1527 sack_seq = htonl(sack->end); 1528 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1529 optp += sizeof(sack_seq); 1530 optlen += TCPOLEN_SACK; 1531 sack++; 1532 } 1533 TCPSTAT_INC(tcps_sack_send_blocks); 1534 break; 1535 } 1536 default: 1537 panic("%s: unknown TCP option type", __func__); 1538 break; 1539 } 1540 } 1541 1542 /* Terminate and pad TCP options to a 4 byte boundary. */ 1543 if (optlen % 4) { 1544 optlen += TCPOLEN_EOL; 1545 *optp++ = TCPOPT_EOL; 1546 } 1547 /* 1548 * According to RFC 793 (STD0007): 1549 * "The content of the header beyond the End-of-Option option 1550 * must be header padding (i.e., zero)." 1551 * and later: "The padding is composed of zeros." 1552 */ 1553 while (optlen % 4) { 1554 optlen += TCPOLEN_PAD; 1555 *optp++ = TCPOPT_PAD; 1556 } 1557 1558 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1559 return (optlen); 1560 } 1561