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/sdt.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 54 #include <net/if.h> 55 #include <net/route.h> 56 #include <net/vnet.h> 57 58 #include <netinet/cc.h> 59 #include <netinet/in.h> 60 #include <netinet/in_kdtrace.h> 61 #include <netinet/in_systm.h> 62 #include <netinet/ip.h> 63 #include <netinet/in_pcb.h> 64 #include <netinet/ip_var.h> 65 #include <netinet/ip_options.h> 66 #ifdef INET6 67 #include <netinet6/in6_pcb.h> 68 #include <netinet/ip6.h> 69 #include <netinet6/ip6_var.h> 70 #endif 71 #define TCPOUTFLAGS 72 #include <netinet/tcp_fsm.h> 73 #include <netinet/tcp_seq.h> 74 #include <netinet/tcp_timer.h> 75 #include <netinet/tcp_var.h> 76 #include <netinet/tcpip.h> 77 #ifdef TCPDEBUG 78 #include <netinet/tcp_debug.h> 79 #endif 80 #ifdef TCP_OFFLOAD 81 #include <netinet/tcp_offload.h> 82 #endif 83 84 #ifdef IPSEC 85 #include <netipsec/ipsec.h> 86 #endif /*IPSEC*/ 87 88 #include <machine/in_cksum.h> 89 90 #include <security/mac/mac_framework.h> 91 92 VNET_DEFINE(int, path_mtu_discovery) = 1; 93 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 94 &VNET_NAME(path_mtu_discovery), 1, 95 "Enable Path MTU Discovery"); 96 97 VNET_DEFINE(int, tcp_do_tso) = 1; 98 #define V_tcp_do_tso VNET(tcp_do_tso) 99 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 100 &VNET_NAME(tcp_do_tso), 0, 101 "Enable TCP Segmentation Offload"); 102 103 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 104 #define V_tcp_sendspace VNET(tcp_sendspace) 105 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW, 106 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 107 108 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 109 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 110 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 111 &VNET_NAME(tcp_do_autosndbuf), 0, 112 "Enable automatic send buffer sizing"); 113 114 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 115 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 116 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 117 &VNET_NAME(tcp_autosndbuf_inc), 0, 118 "Incrementor step size of automatic send buffer"); 119 120 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 121 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 122 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 123 &VNET_NAME(tcp_autosndbuf_max), 0, 124 "Max size of automatic send buffer"); 125 126 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 127 struct tcphdr *th, struct tcpopt *to, 128 long len, int tso); 129 static void inline cc_after_idle(struct tcpcb *tp); 130 131 /* 132 * Wrapper for the TCP established output helper hook. 133 */ 134 static void inline 135 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 136 struct tcpopt *to, long len, int tso) 137 { 138 struct tcp_hhook_data hhook_data; 139 140 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 141 hhook_data.tp = tp; 142 hhook_data.th = th; 143 hhook_data.to = to; 144 hhook_data.len = len; 145 hhook_data.tso = tso; 146 147 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 148 tp->osd); 149 } 150 } 151 152 /* 153 * CC wrapper hook functions 154 */ 155 static void inline 156 cc_after_idle(struct tcpcb *tp) 157 { 158 INP_WLOCK_ASSERT(tp->t_inpcb); 159 160 if (CC_ALGO(tp)->after_idle != NULL) 161 CC_ALGO(tp)->after_idle(tp->ccv); 162 } 163 164 /* 165 * Tcp output routine: figure out what should be sent and send it. 166 */ 167 int 168 tcp_output(struct tcpcb *tp) 169 { 170 struct socket *so = tp->t_inpcb->inp_socket; 171 long len, recwin, sendwin; 172 int off, flags, error = 0; /* Keep compiler happy */ 173 struct mbuf *m; 174 struct ip *ip = NULL; 175 struct ipovly *ipov = NULL; 176 struct tcphdr *th; 177 u_char opt[TCP_MAXOLEN]; 178 unsigned ipoptlen, optlen, hdrlen; 179 #ifdef IPSEC 180 unsigned ipsec_optlen = 0; 181 #endif 182 int idle, sendalot; 183 int sack_rxmit, sack_bytes_rxmt; 184 struct sackhole *p; 185 int tso, mtu; 186 struct tcpopt to; 187 #if 0 188 int maxburst = TCP_MAXBURST; 189 #endif 190 #ifdef INET6 191 struct ip6_hdr *ip6 = NULL; 192 int isipv6; 193 194 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 195 #endif 196 197 INP_WLOCK_ASSERT(tp->t_inpcb); 198 199 #ifdef TCP_OFFLOAD 200 if (tp->t_flags & TF_TOE) 201 return (tcp_offload_output(tp)); 202 #endif 203 204 /* 205 * Determine length of data that should be transmitted, 206 * and flags that will be used. 207 * If there is some data or critical controls (SYN, RST) 208 * to send, then transmit; otherwise, investigate further. 209 */ 210 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 211 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 212 cc_after_idle(tp); 213 tp->t_flags &= ~TF_LASTIDLE; 214 if (idle) { 215 if (tp->t_flags & TF_MORETOCOME) { 216 tp->t_flags |= TF_LASTIDLE; 217 idle = 0; 218 } 219 } 220 again: 221 /* 222 * If we've recently taken a timeout, snd_max will be greater than 223 * snd_nxt. There may be SACK information that allows us to avoid 224 * resending already delivered data. Adjust snd_nxt accordingly. 225 */ 226 if ((tp->t_flags & TF_SACK_PERMIT) && 227 SEQ_LT(tp->snd_nxt, tp->snd_max)) 228 tcp_sack_adjust(tp); 229 sendalot = 0; 230 tso = 0; 231 mtu = 0; 232 off = tp->snd_nxt - tp->snd_una; 233 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 234 235 flags = tcp_outflags[tp->t_state]; 236 /* 237 * Send any SACK-generated retransmissions. If we're explicitly trying 238 * to send out new data (when sendalot is 1), bypass this function. 239 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 240 * we're replacing a (future) new transmission with a retransmission 241 * now, and we previously incremented snd_cwnd in tcp_input(). 242 */ 243 /* 244 * Still in sack recovery , reset rxmit flag to zero. 245 */ 246 sack_rxmit = 0; 247 sack_bytes_rxmt = 0; 248 len = 0; 249 p = NULL; 250 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 251 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 252 long cwin; 253 254 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 255 if (cwin < 0) 256 cwin = 0; 257 /* Do not retransmit SACK segments beyond snd_recover */ 258 if (SEQ_GT(p->end, tp->snd_recover)) { 259 /* 260 * (At least) part of sack hole extends beyond 261 * snd_recover. Check to see if we can rexmit data 262 * for this hole. 263 */ 264 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 265 /* 266 * Can't rexmit any more data for this hole. 267 * That data will be rexmitted in the next 268 * sack recovery episode, when snd_recover 269 * moves past p->rxmit. 270 */ 271 p = NULL; 272 goto after_sack_rexmit; 273 } else 274 /* Can rexmit part of the current hole */ 275 len = ((long)ulmin(cwin, 276 tp->snd_recover - p->rxmit)); 277 } else 278 len = ((long)ulmin(cwin, p->end - p->rxmit)); 279 off = p->rxmit - tp->snd_una; 280 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 281 __func__, off)); 282 if (len > 0) { 283 sack_rxmit = 1; 284 sendalot = 1; 285 TCPSTAT_INC(tcps_sack_rexmits); 286 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 287 min(len, tp->t_maxseg)); 288 } 289 } 290 after_sack_rexmit: 291 /* 292 * Get standard flags, and add SYN or FIN if requested by 'hidden' 293 * state flags. 294 */ 295 if (tp->t_flags & TF_NEEDFIN) 296 flags |= TH_FIN; 297 if (tp->t_flags & TF_NEEDSYN) 298 flags |= TH_SYN; 299 300 SOCKBUF_LOCK(&so->so_snd); 301 /* 302 * If in persist timeout with window of 0, send 1 byte. 303 * Otherwise, if window is small but nonzero 304 * and timer expired, we will send what we can 305 * and go to transmit state. 306 */ 307 if (tp->t_flags & TF_FORCEDATA) { 308 if (sendwin == 0) { 309 /* 310 * If we still have some data to send, then 311 * clear the FIN bit. Usually this would 312 * happen below when it realizes that we 313 * aren't sending all the data. However, 314 * if we have exactly 1 byte of unsent data, 315 * then it won't clear the FIN bit below, 316 * and if we are in persist state, we wind 317 * up sending the packet without recording 318 * that we sent the FIN bit. 319 * 320 * We can't just blindly clear the FIN bit, 321 * because if we don't have any more data 322 * to send then the probe will be the FIN 323 * itself. 324 */ 325 if (off < so->so_snd.sb_cc) 326 flags &= ~TH_FIN; 327 sendwin = 1; 328 } else { 329 tcp_timer_activate(tp, TT_PERSIST, 0); 330 tp->t_rxtshift = 0; 331 } 332 } 333 334 /* 335 * If snd_nxt == snd_max and we have transmitted a FIN, the 336 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 337 * a negative length. This can also occur when TCP opens up 338 * its congestion window while receiving additional duplicate 339 * acks after fast-retransmit because TCP will reset snd_nxt 340 * to snd_max after the fast-retransmit. 341 * 342 * In the normal retransmit-FIN-only case, however, snd_nxt will 343 * be set to snd_una, the offset will be 0, and the length may 344 * wind up 0. 345 * 346 * If sack_rxmit is true we are retransmitting from the scoreboard 347 * in which case len is already set. 348 */ 349 if (sack_rxmit == 0) { 350 if (sack_bytes_rxmt == 0) 351 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 352 else { 353 long cwin; 354 355 /* 356 * We are inside of a SACK recovery episode and are 357 * sending new data, having retransmitted all the 358 * data possible in the scoreboard. 359 */ 360 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 361 - off); 362 /* 363 * Don't remove this (len > 0) check ! 364 * We explicitly check for len > 0 here (although it 365 * isn't really necessary), to work around a gcc 366 * optimization issue - to force gcc to compute 367 * len above. Without this check, the computation 368 * of len is bungled by the optimizer. 369 */ 370 if (len > 0) { 371 cwin = tp->snd_cwnd - 372 (tp->snd_nxt - tp->sack_newdata) - 373 sack_bytes_rxmt; 374 if (cwin < 0) 375 cwin = 0; 376 len = lmin(len, cwin); 377 } 378 } 379 } 380 381 /* 382 * Lop off SYN bit if it has already been sent. However, if this 383 * is SYN-SENT state and if segment contains data and if we don't 384 * know that foreign host supports TAO, suppress sending segment. 385 */ 386 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 387 if (tp->t_state != TCPS_SYN_RECEIVED) 388 flags &= ~TH_SYN; 389 off--, len++; 390 } 391 392 /* 393 * Be careful not to send data and/or FIN on SYN segments. 394 * This measure is needed to prevent interoperability problems 395 * with not fully conformant TCP implementations. 396 */ 397 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 398 len = 0; 399 flags &= ~TH_FIN; 400 } 401 402 if (len < 0) { 403 /* 404 * If FIN has been sent but not acked, 405 * but we haven't been called to retransmit, 406 * len will be < 0. Otherwise, window shrank 407 * after we sent into it. If window shrank to 0, 408 * cancel pending retransmit, pull snd_nxt back 409 * to (closed) window, and set the persist timer 410 * if it isn't already going. If the window didn't 411 * close completely, just wait for an ACK. 412 */ 413 len = 0; 414 if (sendwin == 0) { 415 tcp_timer_activate(tp, TT_REXMT, 0); 416 tp->t_rxtshift = 0; 417 tp->snd_nxt = tp->snd_una; 418 if (!tcp_timer_active(tp, TT_PERSIST)) 419 tcp_setpersist(tp); 420 } 421 } 422 423 /* len will be >= 0 after this point. */ 424 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 425 426 /* 427 * Automatic sizing of send socket buffer. Often the send buffer 428 * size is not optimally adjusted to the actual network conditions 429 * at hand (delay bandwidth product). Setting the buffer size too 430 * small limits throughput on links with high bandwidth and high 431 * delay (eg. trans-continental/oceanic links). Setting the 432 * buffer size too big consumes too much real kernel memory, 433 * especially with many connections on busy servers. 434 * 435 * The criteria to step up the send buffer one notch are: 436 * 1. receive window of remote host is larger than send buffer 437 * (with a fudge factor of 5/4th); 438 * 2. send buffer is filled to 7/8th with data (so we actually 439 * have data to make use of it); 440 * 3. send buffer fill has not hit maximal automatic size; 441 * 4. our send window (slow start and cogestion controlled) is 442 * larger than sent but unacknowledged data in send buffer. 443 * 444 * The remote host receive window scaling factor may limit the 445 * growing of the send buffer before it reaches its allowed 446 * maximum. 447 * 448 * It scales directly with slow start or congestion window 449 * and does at most one step per received ACK. This fast 450 * scaling has the drawback of growing the send buffer beyond 451 * what is strictly necessary to make full use of a given 452 * delay*bandwith product. However testing has shown this not 453 * to be much of an problem. At worst we are trading wasting 454 * of available bandwith (the non-use of it) for wasting some 455 * socket buffer memory. 456 * 457 * TODO: Shrink send buffer during idle periods together 458 * with congestion window. Requires another timer. Has to 459 * wait for upcoming tcp timer rewrite. 460 */ 461 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 462 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 463 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 464 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 465 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 466 if (!sbreserve_locked(&so->so_snd, 467 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 468 V_tcp_autosndbuf_max), so, curthread)) 469 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 470 } 471 } 472 473 /* 474 * Decide if we can use TCP Segmentation Offloading (if supported by 475 * hardware). 476 * 477 * TSO may only be used if we are in a pure bulk sending state. The 478 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 479 * IP options prevent using TSO. With TSO the TCP header is the same 480 * (except for the sequence number) for all generated packets. This 481 * makes it impossible to transmit any options which vary per generated 482 * segment or packet. 483 */ 484 #ifdef IPSEC 485 /* 486 * Pre-calculate here as we save another lookup into the darknesses 487 * of IPsec that way and can actually decide if TSO is ok. 488 */ 489 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 490 #endif 491 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 492 ((tp->t_flags & TF_SIGNATURE) == 0) && 493 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 494 #ifdef IPSEC 495 ipsec_optlen == 0 && 496 #endif 497 tp->t_inpcb->inp_options == NULL && 498 tp->t_inpcb->in6p_options == NULL) 499 tso = 1; 500 501 if (sack_rxmit) { 502 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 503 flags &= ~TH_FIN; 504 } else { 505 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 506 flags &= ~TH_FIN; 507 } 508 509 recwin = sbspace(&so->so_rcv); 510 511 /* 512 * Sender silly window avoidance. We transmit under the following 513 * conditions when len is non-zero: 514 * 515 * - We have a full segment (or more with TSO) 516 * - This is the last buffer in a write()/send() and we are 517 * either idle or running NODELAY 518 * - we've timed out (e.g. persist timer) 519 * - we have more then 1/2 the maximum send window's worth of 520 * data (receiver may be limited the window size) 521 * - we need to retransmit 522 */ 523 if (len) { 524 if (len >= tp->t_maxseg) 525 goto send; 526 /* 527 * NOTE! on localhost connections an 'ack' from the remote 528 * end may occur synchronously with the output and cause 529 * us to flush a buffer queued with moretocome. XXX 530 * 531 * note: the len + off check is almost certainly unnecessary. 532 */ 533 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 534 (idle || (tp->t_flags & TF_NODELAY)) && 535 len + off >= so->so_snd.sb_cc && 536 (tp->t_flags & TF_NOPUSH) == 0) { 537 goto send; 538 } 539 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 540 goto send; 541 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 542 goto send; 543 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 544 goto send; 545 if (sack_rxmit) 546 goto send; 547 } 548 549 /* 550 * Sending of standalone window updates. 551 * 552 * Window updates are important when we close our window due to a 553 * full socket buffer and are opening it again after the application 554 * reads data from it. Once the window has opened again and the 555 * remote end starts to send again the ACK clock takes over and 556 * provides the most current window information. 557 * 558 * We must avoid the silly window syndrome whereas every read 559 * from the receive buffer, no matter how small, causes a window 560 * update to be sent. We also should avoid sending a flurry of 561 * window updates when the socket buffer had queued a lot of data 562 * and the application is doing small reads. 563 * 564 * Prevent a flurry of pointless window updates by only sending 565 * an update when we can increase the advertized window by more 566 * than 1/4th of the socket buffer capacity. When the buffer is 567 * getting full or is very small be more aggressive and send an 568 * update whenever we can increase by two mss sized segments. 569 * In all other situations the ACK's to new incoming data will 570 * carry further window increases. 571 * 572 * Don't send an independent window update if a delayed 573 * ACK is pending (it will get piggy-backed on it) or the 574 * remote side already has done a half-close and won't send 575 * more data. Skip this if the connection is in T/TCP 576 * half-open state. 577 */ 578 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 579 !(tp->t_flags & TF_DELACK) && 580 !TCPS_HAVERCVDFIN(tp->t_state)) { 581 /* 582 * "adv" is the amount we could increase the window, 583 * taking into account that we are limited by 584 * TCP_MAXWIN << tp->rcv_scale. 585 */ 586 long adv; 587 int oldwin; 588 589 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 590 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 591 oldwin = (tp->rcv_adv - tp->rcv_nxt); 592 adv -= oldwin; 593 } else 594 oldwin = 0; 595 596 /* 597 * If the new window size ends up being the same as the old 598 * size when it is scaled, then don't force a window update. 599 */ 600 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 601 goto dontupdate; 602 603 if (adv >= (long)(2 * tp->t_maxseg) && 604 (adv >= (long)(so->so_rcv.sb_hiwat / 4) || 605 recwin <= (long)(so->so_rcv.sb_hiwat / 8) || 606 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 607 goto send; 608 } 609 dontupdate: 610 611 /* 612 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 613 * is also a catch-all for the retransmit timer timeout case. 614 */ 615 if (tp->t_flags & TF_ACKNOW) 616 goto send; 617 if ((flags & TH_RST) || 618 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 619 goto send; 620 if (SEQ_GT(tp->snd_up, tp->snd_una)) 621 goto send; 622 /* 623 * If our state indicates that FIN should be sent 624 * and we have not yet done so, then we need to send. 625 */ 626 if (flags & TH_FIN && 627 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 628 goto send; 629 /* 630 * In SACK, it is possible for tcp_output to fail to send a segment 631 * after the retransmission timer has been turned off. Make sure 632 * that the retransmission timer is set. 633 */ 634 if ((tp->t_flags & TF_SACK_PERMIT) && 635 SEQ_GT(tp->snd_max, tp->snd_una) && 636 !tcp_timer_active(tp, TT_REXMT) && 637 !tcp_timer_active(tp, TT_PERSIST)) { 638 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 639 goto just_return; 640 } 641 /* 642 * TCP window updates are not reliable, rather a polling protocol 643 * using ``persist'' packets is used to insure receipt of window 644 * updates. The three ``states'' for the output side are: 645 * idle not doing retransmits or persists 646 * persisting to move a small or zero window 647 * (re)transmitting and thereby not persisting 648 * 649 * tcp_timer_active(tp, TT_PERSIST) 650 * is true when we are in persist state. 651 * (tp->t_flags & TF_FORCEDATA) 652 * is set when we are called to send a persist packet. 653 * tcp_timer_active(tp, TT_REXMT) 654 * is set when we are retransmitting 655 * The output side is idle when both timers are zero. 656 * 657 * If send window is too small, there is data to transmit, and no 658 * retransmit or persist is pending, then go to persist state. 659 * If nothing happens soon, send when timer expires: 660 * if window is nonzero, transmit what we can, 661 * otherwise force out a byte. 662 */ 663 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 664 !tcp_timer_active(tp, TT_PERSIST)) { 665 tp->t_rxtshift = 0; 666 tcp_setpersist(tp); 667 } 668 669 /* 670 * No reason to send a segment, just return. 671 */ 672 just_return: 673 SOCKBUF_UNLOCK(&so->so_snd); 674 return (0); 675 676 send: 677 SOCKBUF_LOCK_ASSERT(&so->so_snd); 678 if (len > 0) { 679 if (len >= tp->t_maxseg) 680 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 681 else 682 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 683 } 684 /* 685 * Before ESTABLISHED, force sending of initial options 686 * unless TCP set not to do any options. 687 * NOTE: we assume that the IP/TCP header plus TCP options 688 * always fit in a single mbuf, leaving room for a maximum 689 * link header, i.e. 690 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 691 */ 692 optlen = 0; 693 #ifdef INET6 694 if (isipv6) 695 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 696 else 697 #endif 698 hdrlen = sizeof (struct tcpiphdr); 699 700 /* 701 * Compute options for segment. 702 * We only have to care about SYN and established connection 703 * segments. Options for SYN-ACK segments are handled in TCP 704 * syncache. 705 */ 706 if ((tp->t_flags & TF_NOOPT) == 0) { 707 to.to_flags = 0; 708 /* Maximum segment size. */ 709 if (flags & TH_SYN) { 710 tp->snd_nxt = tp->iss; 711 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 712 to.to_flags |= TOF_MSS; 713 } 714 /* Window scaling. */ 715 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 716 to.to_wscale = tp->request_r_scale; 717 to.to_flags |= TOF_SCALE; 718 } 719 /* Timestamps. */ 720 if ((tp->t_flags & TF_RCVD_TSTMP) || 721 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 722 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 723 to.to_tsecr = tp->ts_recent; 724 to.to_flags |= TOF_TS; 725 /* Set receive buffer autosizing timestamp. */ 726 if (tp->rfbuf_ts == 0 && 727 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 728 tp->rfbuf_ts = tcp_ts_getticks(); 729 } 730 /* Selective ACK's. */ 731 if (tp->t_flags & TF_SACK_PERMIT) { 732 if (flags & TH_SYN) 733 to.to_flags |= TOF_SACKPERM; 734 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 735 (tp->t_flags & TF_SACK_PERMIT) && 736 tp->rcv_numsacks > 0) { 737 to.to_flags |= TOF_SACK; 738 to.to_nsacks = tp->rcv_numsacks; 739 to.to_sacks = (u_char *)tp->sackblks; 740 } 741 } 742 #ifdef TCP_SIGNATURE 743 /* TCP-MD5 (RFC2385). */ 744 if (tp->t_flags & TF_SIGNATURE) 745 to.to_flags |= TOF_SIGNATURE; 746 #endif /* TCP_SIGNATURE */ 747 748 /* Processing the options. */ 749 hdrlen += optlen = tcp_addoptions(&to, opt); 750 } 751 752 #ifdef INET6 753 if (isipv6) 754 ipoptlen = ip6_optlen(tp->t_inpcb); 755 else 756 #endif 757 if (tp->t_inpcb->inp_options) 758 ipoptlen = tp->t_inpcb->inp_options->m_len - 759 offsetof(struct ipoption, ipopt_list); 760 else 761 ipoptlen = 0; 762 #ifdef IPSEC 763 ipoptlen += ipsec_optlen; 764 #endif 765 766 /* 767 * Adjust data length if insertion of options will 768 * bump the packet length beyond the t_maxopd length. 769 * Clear the FIN bit because we cut off the tail of 770 * the segment. 771 */ 772 if (len + optlen + ipoptlen > tp->t_maxopd) { 773 flags &= ~TH_FIN; 774 775 if (tso) { 776 u_int if_hw_tsomax; 777 u_int if_hw_tsomaxsegcount; 778 u_int if_hw_tsomaxsegsize; 779 struct mbuf *mb; 780 u_int moff; 781 int max_len; 782 783 /* extract TSO information */ 784 if_hw_tsomax = tp->t_tsomax; 785 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 786 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 787 788 /* 789 * Limit a TSO burst to prevent it from 790 * overflowing or exceeding the maximum length 791 * allowed by the network interface: 792 */ 793 KASSERT(ipoptlen == 0, 794 ("%s: TSO can't do IP options", __func__)); 795 796 /* 797 * Check if we should limit by maximum payload 798 * length: 799 */ 800 if (if_hw_tsomax != 0) { 801 /* compute maximum TSO length */ 802 max_len = (if_hw_tsomax - hdrlen); 803 if (max_len <= 0) { 804 len = 0; 805 } else if (len > (u_int)max_len) { 806 sendalot = 1; 807 len = (u_int)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 max_len = 0; 818 mb = sbsndmbuf(&so->so_snd, off, &moff); 819 820 while (mb != NULL && (u_int)max_len < len) { 821 u_int mlen; 822 u_int frags; 823 824 /* 825 * Get length of mbuf fragment 826 * and how many hardware frags, 827 * rounded up, it would use: 828 */ 829 mlen = (mb->m_len - moff); 830 frags = howmany(mlen, 831 if_hw_tsomaxsegsize); 832 833 /* Handle special case: Zero Length Mbuf */ 834 if (frags == 0) 835 frags = 1; 836 837 /* 838 * Check if the fragment limit 839 * will be reached or exceeded: 840 */ 841 if (frags >= if_hw_tsomaxsegcount) { 842 max_len += min(mlen, 843 if_hw_tsomaxsegcount * 844 if_hw_tsomaxsegsize); 845 break; 846 } 847 max_len += mlen; 848 if_hw_tsomaxsegcount -= frags; 849 moff = 0; 850 mb = mb->m_next; 851 } 852 if (max_len <= 0) { 853 len = 0; 854 } else if (len > (u_int)max_len) { 855 sendalot = 1; 856 len = (u_int)max_len; 857 } 858 } 859 860 /* 861 * Prevent the last segment from being 862 * fractional unless the send sockbuf can be 863 * emptied: 864 */ 865 max_len = (tp->t_maxopd - optlen); 866 if ((off + len) < so->so_snd.sb_cc) { 867 moff = len % (u_int)max_len; 868 if (moff != 0) { 869 len -= moff; 870 sendalot = 1; 871 } 872 } 873 874 /* 875 * In case there are too many small fragments 876 * don't use TSO: 877 */ 878 if (len <= (u_int)max_len) { 879 len = (u_int)max_len; 880 sendalot = 1; 881 tso = 0; 882 } 883 884 /* 885 * Send the FIN in a separate segment 886 * after the bulk sending is done. 887 * We don't trust the TSO implementations 888 * to clear the FIN flag on all but the 889 * last segment. 890 */ 891 if (tp->t_flags & TF_NEEDFIN) 892 sendalot = 1; 893 894 } else { 895 len = tp->t_maxopd - optlen - ipoptlen; 896 sendalot = 1; 897 } 898 } else 899 tso = 0; 900 901 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 902 ("%s: len > IP_MAXPACKET", __func__)); 903 904 /*#ifdef DIAGNOSTIC*/ 905 #ifdef INET6 906 if (max_linkhdr + hdrlen > MCLBYTES) 907 #else 908 if (max_linkhdr + hdrlen > MHLEN) 909 #endif 910 panic("tcphdr too big"); 911 /*#endif*/ 912 913 /* 914 * This KASSERT is here to catch edge cases at a well defined place. 915 * Before, those had triggered (random) panic conditions further down. 916 */ 917 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 918 919 /* 920 * Grab a header mbuf, attaching a copy of data to 921 * be transmitted, and initialize the header from 922 * the template for sends on this connection. 923 */ 924 if (len) { 925 struct mbuf *mb; 926 u_int moff; 927 928 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 929 TCPSTAT_INC(tcps_sndprobe); 930 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 931 tp->t_sndrexmitpack++; 932 TCPSTAT_INC(tcps_sndrexmitpack); 933 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 934 } else { 935 TCPSTAT_INC(tcps_sndpack); 936 TCPSTAT_ADD(tcps_sndbyte, len); 937 } 938 #ifdef INET6 939 if (MHLEN < hdrlen + max_linkhdr) 940 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 941 else 942 #endif 943 m = m_gethdr(M_NOWAIT, MT_DATA); 944 945 if (m == NULL) { 946 SOCKBUF_UNLOCK(&so->so_snd); 947 error = ENOBUFS; 948 sack_rxmit = 0; 949 goto out; 950 } 951 952 m->m_data += max_linkhdr; 953 m->m_len = hdrlen; 954 955 /* 956 * Start the m_copy functions from the closest mbuf 957 * to the offset in the socket buffer chain. 958 */ 959 mb = sbsndptr(&so->so_snd, off, len, &moff); 960 961 if (len <= MHLEN - hdrlen - max_linkhdr) { 962 m_copydata(mb, moff, (int)len, 963 mtod(m, caddr_t) + hdrlen); 964 m->m_len += len; 965 } else { 966 m->m_next = m_copy(mb, moff, (int)len); 967 if (m->m_next == NULL) { 968 SOCKBUF_UNLOCK(&so->so_snd); 969 (void) m_free(m); 970 error = ENOBUFS; 971 sack_rxmit = 0; 972 goto out; 973 } 974 } 975 976 /* 977 * If we're sending everything we've got, set PUSH. 978 * (This will keep happy those implementations which only 979 * give data to the user when a buffer fills or 980 * a PUSH comes in.) 981 */ 982 if (off + len == so->so_snd.sb_cc) 983 flags |= TH_PUSH; 984 SOCKBUF_UNLOCK(&so->so_snd); 985 } else { 986 SOCKBUF_UNLOCK(&so->so_snd); 987 if (tp->t_flags & TF_ACKNOW) 988 TCPSTAT_INC(tcps_sndacks); 989 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 990 TCPSTAT_INC(tcps_sndctrl); 991 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 992 TCPSTAT_INC(tcps_sndurg); 993 else 994 TCPSTAT_INC(tcps_sndwinup); 995 996 m = m_gethdr(M_NOWAIT, MT_DATA); 997 if (m == NULL) { 998 error = ENOBUFS; 999 sack_rxmit = 0; 1000 goto out; 1001 } 1002 #ifdef INET6 1003 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1004 MHLEN >= hdrlen) { 1005 MH_ALIGN(m, hdrlen); 1006 } else 1007 #endif 1008 m->m_data += max_linkhdr; 1009 m->m_len = hdrlen; 1010 } 1011 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1012 m->m_pkthdr.rcvif = (struct ifnet *)0; 1013 #ifdef MAC 1014 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1015 #endif 1016 #ifdef INET6 1017 if (isipv6) { 1018 ip6 = mtod(m, struct ip6_hdr *); 1019 th = (struct tcphdr *)(ip6 + 1); 1020 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1021 } else 1022 #endif /* INET6 */ 1023 { 1024 ip = mtod(m, struct ip *); 1025 ipov = (struct ipovly *)ip; 1026 th = (struct tcphdr *)(ip + 1); 1027 tcpip_fillheaders(tp->t_inpcb, ip, th); 1028 } 1029 1030 /* 1031 * Fill in fields, remembering maximum advertised 1032 * window for use in delaying messages about window sizes. 1033 * If resending a FIN, be sure not to use a new sequence number. 1034 */ 1035 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1036 tp->snd_nxt == tp->snd_max) 1037 tp->snd_nxt--; 1038 /* 1039 * If we are starting a connection, send ECN setup 1040 * SYN packet. If we are on a retransmit, we may 1041 * resend those bits a number of times as per 1042 * RFC 3168. 1043 */ 1044 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1045 if (tp->t_rxtshift >= 1) { 1046 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1047 flags |= TH_ECE|TH_CWR; 1048 } else 1049 flags |= TH_ECE|TH_CWR; 1050 } 1051 1052 if (tp->t_state == TCPS_ESTABLISHED && 1053 (tp->t_flags & TF_ECN_PERMIT)) { 1054 /* 1055 * If the peer has ECN, mark data packets with 1056 * ECN capable transmission (ECT). 1057 * Ignore pure ack packets, retransmissions and window probes. 1058 */ 1059 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1060 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1061 #ifdef INET6 1062 if (isipv6) 1063 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1064 else 1065 #endif 1066 ip->ip_tos |= IPTOS_ECN_ECT0; 1067 TCPSTAT_INC(tcps_ecn_ect0); 1068 } 1069 1070 /* 1071 * Reply with proper ECN notifications. 1072 */ 1073 if (tp->t_flags & TF_ECN_SND_CWR) { 1074 flags |= TH_CWR; 1075 tp->t_flags &= ~TF_ECN_SND_CWR; 1076 } 1077 if (tp->t_flags & TF_ECN_SND_ECE) 1078 flags |= TH_ECE; 1079 } 1080 1081 /* 1082 * If we are doing retransmissions, then snd_nxt will 1083 * not reflect the first unsent octet. For ACK only 1084 * packets, we do not want the sequence number of the 1085 * retransmitted packet, we want the sequence number 1086 * of the next unsent octet. So, if there is no data 1087 * (and no SYN or FIN), use snd_max instead of snd_nxt 1088 * when filling in ti_seq. But if we are in persist 1089 * state, snd_max might reflect one byte beyond the 1090 * right edge of the window, so use snd_nxt in that 1091 * case, since we know we aren't doing a retransmission. 1092 * (retransmit and persist are mutually exclusive...) 1093 */ 1094 if (sack_rxmit == 0) { 1095 if (len || (flags & (TH_SYN|TH_FIN)) || 1096 tcp_timer_active(tp, TT_PERSIST)) 1097 th->th_seq = htonl(tp->snd_nxt); 1098 else 1099 th->th_seq = htonl(tp->snd_max); 1100 } else { 1101 th->th_seq = htonl(p->rxmit); 1102 p->rxmit += len; 1103 tp->sackhint.sack_bytes_rexmit += len; 1104 } 1105 th->th_ack = htonl(tp->rcv_nxt); 1106 if (optlen) { 1107 bcopy(opt, th + 1, optlen); 1108 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1109 } 1110 th->th_flags = flags; 1111 /* 1112 * Calculate receive window. Don't shrink window, 1113 * but avoid silly window syndrome. 1114 */ 1115 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1116 recwin < (long)tp->t_maxseg) 1117 recwin = 0; 1118 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1119 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1120 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1121 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1122 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1123 1124 /* 1125 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1126 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1127 * case is handled in syncache. 1128 */ 1129 if (flags & TH_SYN) 1130 th->th_win = htons((u_short) 1131 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1132 else 1133 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1134 1135 /* 1136 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1137 * a 0 window. This may cause the remote transmitter to stall. This 1138 * flag tells soreceive() to disable delayed acknowledgements when 1139 * draining the buffer. This can occur if the receiver is attempting 1140 * to read more data than can be buffered prior to transmitting on 1141 * the connection. 1142 */ 1143 if (th->th_win == 0) { 1144 tp->t_sndzerowin++; 1145 tp->t_flags |= TF_RXWIN0SENT; 1146 } else 1147 tp->t_flags &= ~TF_RXWIN0SENT; 1148 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1149 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1150 th->th_flags |= TH_URG; 1151 } else 1152 /* 1153 * If no urgent pointer to send, then we pull 1154 * the urgent pointer to the left edge of the send window 1155 * so that it doesn't drift into the send window on sequence 1156 * number wraparound. 1157 */ 1158 tp->snd_up = tp->snd_una; /* drag it along */ 1159 1160 #ifdef TCP_SIGNATURE 1161 if (tp->t_flags & TF_SIGNATURE) { 1162 int sigoff = to.to_signature - opt; 1163 tcp_signature_compute(m, 0, len, optlen, 1164 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1165 } 1166 #endif 1167 1168 /* 1169 * Put TCP length in extended header, and then 1170 * checksum extended header and data. 1171 */ 1172 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1173 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1174 #ifdef INET6 1175 if (isipv6) { 1176 /* 1177 * ip6_plen is not need to be filled now, and will be filled 1178 * in ip6_output. 1179 */ 1180 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1181 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1182 optlen + len, IPPROTO_TCP, 0); 1183 } 1184 #endif 1185 #if defined(INET6) && defined(INET) 1186 else 1187 #endif 1188 #ifdef INET 1189 { 1190 m->m_pkthdr.csum_flags = CSUM_TCP; 1191 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1192 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1193 1194 /* IP version must be set here for ipv4/ipv6 checking later */ 1195 KASSERT(ip->ip_v == IPVERSION, 1196 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1197 } 1198 #endif 1199 1200 /* 1201 * Enable TSO and specify the size of the segments. 1202 * The TCP pseudo header checksum is always provided. 1203 * XXX: Fixme: This is currently not the case for IPv6. 1204 */ 1205 if (tso) { 1206 KASSERT(len > tp->t_maxopd - optlen, 1207 ("%s: len <= tso_segsz", __func__)); 1208 m->m_pkthdr.csum_flags |= CSUM_TSO; 1209 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1210 } 1211 1212 #ifdef IPSEC 1213 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1214 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", 1215 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1216 #else 1217 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1218 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", 1219 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1220 #endif 1221 1222 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1223 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1224 1225 #ifdef TCPDEBUG 1226 /* 1227 * Trace. 1228 */ 1229 if (so->so_options & SO_DEBUG) { 1230 u_short save = 0; 1231 #ifdef INET6 1232 if (!isipv6) 1233 #endif 1234 { 1235 save = ipov->ih_len; 1236 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1237 } 1238 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1239 #ifdef INET6 1240 if (!isipv6) 1241 #endif 1242 ipov->ih_len = save; 1243 } 1244 #endif /* TCPDEBUG */ 1245 1246 /* 1247 * Fill in IP length and desired time to live and 1248 * send to IP level. There should be a better way 1249 * to handle ttl and tos; we could keep them in 1250 * the template, but need a way to checksum without them. 1251 */ 1252 /* 1253 * m->m_pkthdr.len should have been set before checksum calculation, 1254 * because in6_cksum() need it. 1255 */ 1256 #ifdef INET6 1257 if (isipv6) { 1258 struct route_in6 ro; 1259 1260 bzero(&ro, sizeof(ro)); 1261 /* 1262 * we separately set hoplimit for every segment, since the 1263 * user might want to change the value via setsockopt. 1264 * Also, desired default hop limit might be changed via 1265 * Neighbor Discovery. 1266 */ 1267 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1268 1269 /* 1270 * Set the packet size here for the benefit of DTrace probes. 1271 * ip6_output() will set it properly; it's supposed to include 1272 * the option header lengths as well. 1273 */ 1274 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1275 1276 if (tp->t_state == TCPS_SYN_SENT) 1277 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1278 1279 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1280 1281 /* TODO: IPv6 IP6TOS_ECT bit on */ 1282 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1283 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1284 NULL, NULL, tp->t_inpcb); 1285 1286 if (error == EMSGSIZE && ro.ro_rt != NULL) 1287 mtu = ro.ro_rt->rt_mtu; 1288 RO_RTFREE(&ro); 1289 } 1290 #endif /* INET6 */ 1291 #if defined(INET) && defined(INET6) 1292 else 1293 #endif 1294 #ifdef INET 1295 { 1296 struct route ro; 1297 1298 bzero(&ro, sizeof(ro)); 1299 ip->ip_len = htons(m->m_pkthdr.len); 1300 #ifdef INET6 1301 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1302 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1303 #endif /* INET6 */ 1304 /* 1305 * If we do path MTU discovery, then we set DF on every packet. 1306 * This might not be the best thing to do according to RFC3390 1307 * Section 2. However the tcp hostcache migitates the problem 1308 * so it affects only the first tcp connection with a host. 1309 * 1310 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1311 */ 1312 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) { 1313 ip->ip_off |= htons(IP_DF); 1314 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1315 } else { 1316 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1317 } 1318 1319 if (tp->t_state == TCPS_SYN_SENT) 1320 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1321 1322 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1323 1324 error = ip_output(m, tp->t_inpcb->inp_options, &ro, 1325 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1326 tp->t_inpcb); 1327 1328 if (error == EMSGSIZE && ro.ro_rt != NULL) 1329 mtu = ro.ro_rt->rt_mtu; 1330 RO_RTFREE(&ro); 1331 } 1332 #endif /* INET */ 1333 1334 out: 1335 /* 1336 * In transmit state, time the transmission and arrange for 1337 * the retransmit. In persist state, just set snd_max. 1338 */ 1339 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1340 !tcp_timer_active(tp, TT_PERSIST)) { 1341 tcp_seq startseq = tp->snd_nxt; 1342 1343 /* 1344 * Advance snd_nxt over sequence space of this segment. 1345 */ 1346 if (flags & (TH_SYN|TH_FIN)) { 1347 if (flags & TH_SYN) 1348 tp->snd_nxt++; 1349 if (flags & TH_FIN) { 1350 tp->snd_nxt++; 1351 tp->t_flags |= TF_SENTFIN; 1352 } 1353 } 1354 if (sack_rxmit) 1355 goto timer; 1356 tp->snd_nxt += len; 1357 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1358 tp->snd_max = tp->snd_nxt; 1359 /* 1360 * Time this transmission if not a retransmission and 1361 * not currently timing anything. 1362 */ 1363 if (tp->t_rtttime == 0) { 1364 tp->t_rtttime = ticks; 1365 tp->t_rtseq = startseq; 1366 TCPSTAT_INC(tcps_segstimed); 1367 } 1368 } 1369 1370 /* 1371 * Set retransmit timer if not currently set, 1372 * and not doing a pure ack or a keep-alive probe. 1373 * Initial value for retransmit timer is smoothed 1374 * round-trip time + 2 * round-trip time variance. 1375 * Initialize shift counter which is used for backoff 1376 * of retransmit time. 1377 */ 1378 timer: 1379 if (!tcp_timer_active(tp, TT_REXMT) && 1380 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1381 (tp->snd_nxt != tp->snd_una))) { 1382 if (tcp_timer_active(tp, TT_PERSIST)) { 1383 tcp_timer_activate(tp, TT_PERSIST, 0); 1384 tp->t_rxtshift = 0; 1385 } 1386 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1387 } 1388 } else { 1389 /* 1390 * Persist case, update snd_max but since we are in 1391 * persist mode (no window) we do not update snd_nxt. 1392 */ 1393 int xlen = len; 1394 if (flags & TH_SYN) 1395 ++xlen; 1396 if (flags & TH_FIN) { 1397 ++xlen; 1398 tp->t_flags |= TF_SENTFIN; 1399 } 1400 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1401 tp->snd_max = tp->snd_nxt + len; 1402 } 1403 1404 if (error) { 1405 1406 /* 1407 * We know that the packet was lost, so back out the 1408 * sequence number advance, if any. 1409 * 1410 * If the error is EPERM the packet got blocked by the 1411 * local firewall. Normally we should terminate the 1412 * connection but the blocking may have been spurious 1413 * due to a firewall reconfiguration cycle. So we treat 1414 * it like a packet loss and let the retransmit timer and 1415 * timeouts do their work over time. 1416 * XXX: It is a POLA question whether calling tcp_drop right 1417 * away would be the really correct behavior instead. 1418 */ 1419 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1420 !tcp_timer_active(tp, TT_PERSIST)) && 1421 ((flags & TH_SYN) == 0) && 1422 (error != EPERM)) { 1423 if (sack_rxmit) { 1424 p->rxmit -= len; 1425 tp->sackhint.sack_bytes_rexmit -= len; 1426 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1427 ("sackhint bytes rtx >= 0")); 1428 } else 1429 tp->snd_nxt -= len; 1430 } 1431 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1432 switch (error) { 1433 case EPERM: 1434 tp->t_softerror = error; 1435 return (error); 1436 case ENOBUFS: 1437 if (!tcp_timer_active(tp, TT_REXMT) && 1438 !tcp_timer_active(tp, TT_PERSIST)) 1439 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1440 tp->snd_cwnd = tp->t_maxseg; 1441 return (0); 1442 case EMSGSIZE: 1443 /* 1444 * For some reason the interface we used initially 1445 * to send segments changed to another or lowered 1446 * its MTU. 1447 * If TSO was active we either got an interface 1448 * without TSO capabilits or TSO was turned off. 1449 * If we obtained mtu from ip_output() then update 1450 * it and try again. 1451 */ 1452 if (tso) 1453 tp->t_flags &= ~TF_TSO; 1454 if (mtu != 0) { 1455 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1456 goto again; 1457 } 1458 return (error); 1459 case EHOSTDOWN: 1460 case EHOSTUNREACH: 1461 case ENETDOWN: 1462 case ENETUNREACH: 1463 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1464 tp->t_softerror = error; 1465 return (0); 1466 } 1467 /* FALLTHROUGH */ 1468 default: 1469 return (error); 1470 } 1471 } 1472 TCPSTAT_INC(tcps_sndtotal); 1473 1474 /* 1475 * Data sent (as far as we can tell). 1476 * If this advertises a larger window than any other segment, 1477 * then remember the size of the advertised window. 1478 * Any pending ACK has now been sent. 1479 */ 1480 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1481 tp->rcv_adv = tp->rcv_nxt + recwin; 1482 tp->last_ack_sent = tp->rcv_nxt; 1483 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1484 if (tcp_timer_active(tp, TT_DELACK)) 1485 tcp_timer_activate(tp, TT_DELACK, 0); 1486 #if 0 1487 /* 1488 * This completely breaks TCP if newreno is turned on. What happens 1489 * is that if delayed-acks are turned on on the receiver, this code 1490 * on the transmitter effectively destroys the TCP window, forcing 1491 * it to four packets (1.5Kx4 = 6K window). 1492 */ 1493 if (sendalot && --maxburst) 1494 goto again; 1495 #endif 1496 if (sendalot) 1497 goto again; 1498 return (0); 1499 } 1500 1501 void 1502 tcp_setpersist(struct tcpcb *tp) 1503 { 1504 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1505 int tt; 1506 1507 tp->t_flags &= ~TF_PREVVALID; 1508 if (tcp_timer_active(tp, TT_REXMT)) 1509 panic("tcp_setpersist: retransmit pending"); 1510 /* 1511 * Start/restart persistance timer. 1512 */ 1513 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1514 TCPTV_PERSMIN, TCPTV_PERSMAX); 1515 tcp_timer_activate(tp, TT_PERSIST, tt); 1516 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1517 tp->t_rxtshift++; 1518 } 1519 1520 /* 1521 * Insert TCP options according to the supplied parameters to the place 1522 * optp in a consistent way. Can handle unaligned destinations. 1523 * 1524 * The order of the option processing is crucial for optimal packing and 1525 * alignment for the scarce option space. 1526 * 1527 * The optimal order for a SYN/SYN-ACK segment is: 1528 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1529 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1530 * 1531 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1532 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1533 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1534 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1535 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1536 */ 1537 int 1538 tcp_addoptions(struct tcpopt *to, u_char *optp) 1539 { 1540 u_int mask, optlen = 0; 1541 1542 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1543 if ((to->to_flags & mask) != mask) 1544 continue; 1545 if (optlen == TCP_MAXOLEN) 1546 break; 1547 switch (to->to_flags & mask) { 1548 case TOF_MSS: 1549 while (optlen % 4) { 1550 optlen += TCPOLEN_NOP; 1551 *optp++ = TCPOPT_NOP; 1552 } 1553 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1554 continue; 1555 optlen += TCPOLEN_MAXSEG; 1556 *optp++ = TCPOPT_MAXSEG; 1557 *optp++ = TCPOLEN_MAXSEG; 1558 to->to_mss = htons(to->to_mss); 1559 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1560 optp += sizeof(to->to_mss); 1561 break; 1562 case TOF_SCALE: 1563 while (!optlen || optlen % 2 != 1) { 1564 optlen += TCPOLEN_NOP; 1565 *optp++ = TCPOPT_NOP; 1566 } 1567 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1568 continue; 1569 optlen += TCPOLEN_WINDOW; 1570 *optp++ = TCPOPT_WINDOW; 1571 *optp++ = TCPOLEN_WINDOW; 1572 *optp++ = to->to_wscale; 1573 break; 1574 case TOF_SACKPERM: 1575 while (optlen % 2) { 1576 optlen += TCPOLEN_NOP; 1577 *optp++ = TCPOPT_NOP; 1578 } 1579 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1580 continue; 1581 optlen += TCPOLEN_SACK_PERMITTED; 1582 *optp++ = TCPOPT_SACK_PERMITTED; 1583 *optp++ = TCPOLEN_SACK_PERMITTED; 1584 break; 1585 case TOF_TS: 1586 while (!optlen || optlen % 4 != 2) { 1587 optlen += TCPOLEN_NOP; 1588 *optp++ = TCPOPT_NOP; 1589 } 1590 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1591 continue; 1592 optlen += TCPOLEN_TIMESTAMP; 1593 *optp++ = TCPOPT_TIMESTAMP; 1594 *optp++ = TCPOLEN_TIMESTAMP; 1595 to->to_tsval = htonl(to->to_tsval); 1596 to->to_tsecr = htonl(to->to_tsecr); 1597 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1598 optp += sizeof(to->to_tsval); 1599 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1600 optp += sizeof(to->to_tsecr); 1601 break; 1602 case TOF_SIGNATURE: 1603 { 1604 int siglen = TCPOLEN_SIGNATURE - 2; 1605 1606 while (!optlen || optlen % 4 != 2) { 1607 optlen += TCPOLEN_NOP; 1608 *optp++ = TCPOPT_NOP; 1609 } 1610 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1611 continue; 1612 optlen += TCPOLEN_SIGNATURE; 1613 *optp++ = TCPOPT_SIGNATURE; 1614 *optp++ = TCPOLEN_SIGNATURE; 1615 to->to_signature = optp; 1616 while (siglen--) 1617 *optp++ = 0; 1618 break; 1619 } 1620 case TOF_SACK: 1621 { 1622 int sackblks = 0; 1623 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1624 tcp_seq sack_seq; 1625 1626 while (!optlen || optlen % 4 != 2) { 1627 optlen += TCPOLEN_NOP; 1628 *optp++ = TCPOPT_NOP; 1629 } 1630 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1631 continue; 1632 optlen += TCPOLEN_SACKHDR; 1633 *optp++ = TCPOPT_SACK; 1634 sackblks = min(to->to_nsacks, 1635 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1636 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1637 while (sackblks--) { 1638 sack_seq = htonl(sack->start); 1639 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1640 optp += sizeof(sack_seq); 1641 sack_seq = htonl(sack->end); 1642 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1643 optp += sizeof(sack_seq); 1644 optlen += TCPOLEN_SACK; 1645 sack++; 1646 } 1647 TCPSTAT_INC(tcps_sack_send_blocks); 1648 break; 1649 } 1650 default: 1651 panic("%s: unknown TCP option type", __func__); 1652 break; 1653 } 1654 } 1655 1656 /* Terminate and pad TCP options to a 4 byte boundary. */ 1657 if (optlen % 4) { 1658 optlen += TCPOLEN_EOL; 1659 *optp++ = TCPOPT_EOL; 1660 } 1661 /* 1662 * According to RFC 793 (STD0007): 1663 * "The content of the header beyond the End-of-Option option 1664 * must be header padding (i.e., zero)." 1665 * and later: "The padding is composed of zeros." 1666 */ 1667 while (optlen % 4) { 1668 optlen += TCPOLEN_PAD; 1669 *optp++ = TCPOPT_PAD; 1670 } 1671 1672 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1673 return (optlen); 1674 } 1675