| 1 | /* |
| 2 | * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. |
| 3 | * Copyright (c) 2004 The DragonFly Project. All rights reserved. |
| 4 | * |
| 5 | * This code is derived from software contributed to The DragonFly Project |
| 6 | * by Jeffrey M. Hsu. |
| 7 | * |
| 8 | * Redistribution and use in source and binary forms, with or without |
| 9 | * modification, are permitted provided that the following conditions |
| 10 | * are met: |
| 11 | * 1. Redistributions of source code must retain the above copyright |
| 12 | * notice, this list of conditions and the following disclaimer. |
| 13 | * 2. Redistributions in binary form must reproduce the above copyright |
| 14 | * notice, this list of conditions and the following disclaimer in the |
| 15 | * documentation and/or other materials provided with the distribution. |
| 16 | * 3. Neither the name of The DragonFly Project nor the names of its |
| 17 | * contributors may be used to endorse or promote products derived |
| 18 | * from this software without specific, prior written permission. |
| 19 | * |
| 20 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 21 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 22 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| 23 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| 24 | * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 25 | * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| 26 | * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| 27 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| 28 | * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| 29 | * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| 30 | * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 31 | * SUCH DAMAGE. |
| 32 | */ |
| 33 | |
| 34 | /* |
| 35 | * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 |
| 36 | * The Regents of the University of California. All rights reserved. |
| 37 | * |
| 38 | * Redistribution and use in source and binary forms, with or without |
| 39 | * modification, are permitted provided that the following conditions |
| 40 | * are met: |
| 41 | * 1. Redistributions of source code must retain the above copyright |
| 42 | * notice, this list of conditions and the following disclaimer. |
| 43 | * 2. Redistributions in binary form must reproduce the above copyright |
| 44 | * notice, this list of conditions and the following disclaimer in the |
| 45 | * documentation and/or other materials provided with the distribution. |
| 46 | * 3. All advertising materials mentioning features or use of this software |
| 47 | * must display the following acknowledgement: |
| 48 | * This product includes software developed by the University of |
| 49 | * California, Berkeley and its contributors. |
| 50 | * 4. Neither the name of the University nor the names of its contributors |
| 51 | * may be used to endorse or promote products derived from this software |
| 52 | * without specific prior written permission. |
| 53 | * |
| 54 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 55 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 56 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 57 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 58 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 59 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 60 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 61 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 62 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 63 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 64 | * SUCH DAMAGE. |
| 65 | * |
| 66 | * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 |
| 67 | * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ |
| 68 | * $DragonFly: src/sys/netinet/tcp_output.c,v 1.34 2007/04/22 01:13:14 dillon Exp $ |
| 69 | */ |
| 70 | |
| 71 | #include "opt_inet.h" |
| 72 | #include "opt_inet6.h" |
| 73 | #include "opt_ipsec.h" |
| 74 | #include "opt_tcpdebug.h" |
| 75 | |
| 76 | #include <sys/param.h> |
| 77 | #include <sys/systm.h> |
| 78 | #include <sys/kernel.h> |
| 79 | #include <sys/sysctl.h> |
| 80 | #include <sys/mbuf.h> |
| 81 | #include <sys/domain.h> |
| 82 | #include <sys/protosw.h> |
| 83 | #include <sys/socket.h> |
| 84 | #include <sys/socketvar.h> |
| 85 | #include <sys/in_cksum.h> |
| 86 | #include <sys/thread.h> |
| 87 | #include <sys/globaldata.h> |
| 88 | |
| 89 | #include <net/route.h> |
| 90 | |
| 91 | #include <netinet/in.h> |
| 92 | #include <netinet/in_systm.h> |
| 93 | #include <netinet/ip.h> |
| 94 | #include <netinet/in_pcb.h> |
| 95 | #include <netinet/ip_var.h> |
| 96 | #include <netinet6/in6_pcb.h> |
| 97 | #include <netinet/ip6.h> |
| 98 | #include <netinet6/ip6_var.h> |
| 99 | #include <netinet/tcp.h> |
| 100 | #define TCPOUTFLAGS |
| 101 | #include <netinet/tcp_fsm.h> |
| 102 | #include <netinet/tcp_seq.h> |
| 103 | #include <netinet/tcp_timer.h> |
| 104 | #include <netinet/tcp_timer2.h> |
| 105 | #include <netinet/tcp_var.h> |
| 106 | #include <netinet/tcpip.h> |
| 107 | #ifdef TCPDEBUG |
| 108 | #include <netinet/tcp_debug.h> |
| 109 | #endif |
| 110 | |
| 111 | #ifdef IPSEC |
| 112 | #include <netinet6/ipsec.h> |
| 113 | #endif /*IPSEC*/ |
| 114 | |
| 115 | #ifdef FAST_IPSEC |
| 116 | #include <netproto/ipsec/ipsec.h> |
| 117 | #define IPSEC |
| 118 | #endif /*FAST_IPSEC*/ |
| 119 | |
| 120 | #ifdef notyet |
| 121 | extern struct mbuf *m_copypack(); |
| 122 | #endif |
| 123 | |
| 124 | int path_mtu_discovery = 0; |
| 125 | SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, |
| 126 | &path_mtu_discovery, 1, "Enable Path MTU Discovery"); |
| 127 | |
| 128 | static int avoid_pure_win_update = 1; |
| 129 | SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, |
| 130 | &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); |
| 131 | |
| 132 | int tcp_do_autosndbuf = 1; |
| 133 | SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, |
| 134 | &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); |
| 135 | |
| 136 | int tcp_autosndbuf_inc = 8*1024; |
| 137 | SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, |
| 138 | &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); |
| 139 | |
| 140 | int tcp_autosndbuf_max = 2*1024*1024; |
| 141 | SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, |
| 142 | &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); |
| 143 | |
| 144 | /* |
| 145 | * Tcp output routine: figure out what should be sent and send it. |
| 146 | */ |
| 147 | int |
| 148 | tcp_output(struct tcpcb *tp) |
| 149 | { |
| 150 | struct inpcb * const inp = tp->t_inpcb; |
| 151 | struct socket *so = inp->inp_socket; |
| 152 | long len, recvwin, sendwin; |
| 153 | int nsacked = 0; |
| 154 | int off, flags, error; |
| 155 | #ifdef TCP_SIGNATURE |
| 156 | int sigoff = 0; |
| 157 | #endif |
| 158 | struct mbuf *m; |
| 159 | struct ip *ip = NULL; |
| 160 | struct ipovly *ipov = NULL; |
| 161 | struct tcphdr *th; |
| 162 | u_char opt[TCP_MAXOLEN]; |
| 163 | unsigned int ipoptlen, optlen, hdrlen; |
| 164 | int idle; |
| 165 | boolean_t sendalot; |
| 166 | struct ip6_hdr *ip6 = NULL; |
| 167 | #ifdef INET6 |
| 168 | const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; |
| 169 | #else |
| 170 | const boolean_t isipv6 = FALSE; |
| 171 | #endif |
| 172 | |
| 173 | KKASSERT(so->so_port == &curthread->td_msgport); |
| 174 | |
| 175 | /* |
| 176 | * Determine length of data that should be transmitted, |
| 177 | * and flags that will be used. |
| 178 | * If there is some data or critical controls (SYN, RST) |
| 179 | * to send, then transmit; otherwise, investigate further. |
| 180 | */ |
| 181 | |
| 182 | /* |
| 183 | * If we have been idle for a while, the send congestion window |
| 184 | * could be no longer representative of the current state of the link. |
| 185 | * So unless we are expecting more acks to come in, slow-start from |
| 186 | * scratch to re-determine the send congestion window. |
| 187 | */ |
| 188 | if (tp->snd_max == tp->snd_una && |
| 189 | (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { |
| 190 | if (tcp_do_rfc3390) { |
| 191 | int initial_cwnd = |
| 192 | min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380)); |
| 193 | |
| 194 | tp->snd_cwnd = min(tp->snd_cwnd, initial_cwnd); |
| 195 | } else { |
| 196 | tp->snd_cwnd = tp->t_maxseg; |
| 197 | } |
| 198 | tp->snd_wacked = 0; |
| 199 | } |
| 200 | |
| 201 | /* |
| 202 | * Calculate whether the transmit stream was previously idle |
| 203 | * and adjust TF_LASTIDLE for the next time. |
| 204 | */ |
| 205 | idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); |
| 206 | if (idle && (tp->t_flags & TF_MORETOCOME)) |
| 207 | tp->t_flags |= TF_LASTIDLE; |
| 208 | else |
| 209 | tp->t_flags &= ~TF_LASTIDLE; |
| 210 | |
| 211 | if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && |
| 212 | !IN_FASTRECOVERY(tp)) |
| 213 | nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); |
| 214 | |
| 215 | again: |
| 216 | /* Make use of SACK information when slow-starting after a RTO. */ |
| 217 | if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && |
| 218 | !IN_FASTRECOVERY(tp)) { |
| 219 | tcp_seq old_snd_nxt = tp->snd_nxt; |
| 220 | |
| 221 | tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); |
| 222 | nsacked += tp->snd_nxt - old_snd_nxt; |
| 223 | } |
| 224 | |
| 225 | sendalot = FALSE; |
| 226 | off = tp->snd_nxt - tp->snd_una; |
| 227 | sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); |
| 228 | sendwin = min(sendwin, tp->snd_bwnd); |
| 229 | |
| 230 | flags = tcp_outflags[tp->t_state]; |
| 231 | /* |
| 232 | * Get standard flags, and add SYN or FIN if requested by 'hidden' |
| 233 | * state flags. |
| 234 | */ |
| 235 | if (tp->t_flags & TF_NEEDFIN) |
| 236 | flags |= TH_FIN; |
| 237 | if (tp->t_flags & TF_NEEDSYN) |
| 238 | flags |= TH_SYN; |
| 239 | |
| 240 | /* |
| 241 | * If in persist timeout with window of 0, send 1 byte. |
| 242 | * Otherwise, if window is small but nonzero |
| 243 | * and timer expired, we will send what we can |
| 244 | * and go to transmit state. |
| 245 | */ |
| 246 | if (tp->t_flags & TF_FORCE) { |
| 247 | if (sendwin == 0) { |
| 248 | /* |
| 249 | * If we still have some data to send, then |
| 250 | * clear the FIN bit. Usually this would |
| 251 | * happen below when it realizes that we |
| 252 | * aren't sending all the data. However, |
| 253 | * if we have exactly 1 byte of unsent data, |
| 254 | * then it won't clear the FIN bit below, |
| 255 | * and if we are in persist state, we wind |
| 256 | * up sending the packet without recording |
| 257 | * that we sent the FIN bit. |
| 258 | * |
| 259 | * We can't just blindly clear the FIN bit, |
| 260 | * because if we don't have any more data |
| 261 | * to send then the probe will be the FIN |
| 262 | * itself. |
| 263 | */ |
| 264 | if (off < so->so_snd.ssb_cc) |
| 265 | flags &= ~TH_FIN; |
| 266 | sendwin = 1; |
| 267 | } else { |
| 268 | tcp_callout_stop(tp, tp->tt_persist); |
| 269 | tp->t_rxtshift = 0; |
| 270 | } |
| 271 | } |
| 272 | |
| 273 | /* |
| 274 | * If snd_nxt == snd_max and we have transmitted a FIN, the |
| 275 | * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in |
| 276 | * a negative length. This can also occur when TCP opens up |
| 277 | * its congestion window while receiving additional duplicate |
| 278 | * acks after fast-retransmit because TCP will reset snd_nxt |
| 279 | * to snd_max after the fast-retransmit. |
| 280 | * |
| 281 | * A negative length can also occur when we are in the |
| 282 | * TCPS_SYN_RECEIVED state due to a simultanious connect where |
| 283 | * our SYN has not been acked yet. |
| 284 | * |
| 285 | * In the normal retransmit-FIN-only case, however, snd_nxt will |
| 286 | * be set to snd_una, the offset will be 0, and the length may |
| 287 | * wind up 0. |
| 288 | */ |
| 289 | len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; |
| 290 | |
| 291 | /* |
| 292 | * Lop off SYN bit if it has already been sent. However, if this |
| 293 | * is SYN-SENT state and if segment contains data, suppress sending |
| 294 | * segment (sending the segment would be an option if we still |
| 295 | * did TAO and the remote host supported it). |
| 296 | */ |
| 297 | if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { |
| 298 | flags &= ~TH_SYN; |
| 299 | off--, len++; |
| 300 | if (len > 0 && tp->t_state == TCPS_SYN_SENT) |
| 301 | return 0; |
| 302 | } |
| 303 | |
| 304 | /* |
| 305 | * Be careful not to send data and/or FIN on SYN segments. |
| 306 | * This measure is needed to prevent interoperability problems |
| 307 | * with not fully conformant TCP implementations. |
| 308 | */ |
| 309 | if (flags & TH_SYN) { |
| 310 | len = 0; |
| 311 | flags &= ~TH_FIN; |
| 312 | } |
| 313 | |
| 314 | if (len < 0) { |
| 315 | /* |
| 316 | * A negative len can occur if our FIN has been sent but not |
| 317 | * acked, or if we are in a simultanious connect in the |
| 318 | * TCPS_SYN_RECEIVED state with our SYN sent but not yet |
| 319 | * acked. |
| 320 | * |
| 321 | * If our window has contracted to 0 in the FIN case |
| 322 | * (which can only occur if we have NOT been called to |
| 323 | * retransmit as per code a few paragraphs up) then we |
| 324 | * want to shift the retransmit timer over to the |
| 325 | * persist timer. |
| 326 | * |
| 327 | * However, if we are in the TCPS_SYN_RECEIVED state |
| 328 | * (the SYN case) we will be in a simultanious connect and |
| 329 | * the window may be zero degeneratively. In this case we |
| 330 | * do not want to shift to the persist timer after the SYN |
| 331 | * or the SYN+ACK transmission. |
| 332 | */ |
| 333 | len = 0; |
| 334 | if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) { |
| 335 | tcp_callout_stop(tp, tp->tt_rexmt); |
| 336 | tp->t_rxtshift = 0; |
| 337 | tp->snd_nxt = tp->snd_una; |
| 338 | if (!tcp_callout_active(tp, tp->tt_persist)) |
| 339 | tcp_setpersist(tp); |
| 340 | } |
| 341 | } |
| 342 | |
| 343 | KASSERT(len >= 0, ("%s: len < 0", __func__)); |
| 344 | /* |
| 345 | * Automatic sizing of send socket buffer. Often the send buffer |
| 346 | * size is not optimally adjusted to the actual network conditions |
| 347 | * at hand (delay bandwidth product). Setting the buffer size too |
| 348 | * small limits throughput on links with high bandwidth and high |
| 349 | * delay (eg. trans-continental/oceanic links). Setting the |
| 350 | * buffer size too big consumes too much real kernel memory, |
| 351 | * especially with many connections on busy servers. |
| 352 | * |
| 353 | * The criteria to step up the send buffer one notch are: |
| 354 | * 1. receive window of remote host is larger than send buffer |
| 355 | * (with a fudge factor of 5/4th); |
| 356 | * 2. send buffer is filled to 7/8th with data (so we actually |
| 357 | * have data to make use of it); |
| 358 | * 3. send buffer fill has not hit maximal automatic size; |
| 359 | * 4. our send window (slow start and cogestion controlled) is |
| 360 | * larger than sent but unacknowledged data in send buffer. |
| 361 | * |
| 362 | * The remote host receive window scaling factor may limit the |
| 363 | * growing of the send buffer before it reaches its allowed |
| 364 | * maximum. |
| 365 | * |
| 366 | * It scales directly with slow start or congestion window |
| 367 | * and does at most one step per received ACK. This fast |
| 368 | * scaling has the drawback of growing the send buffer beyond |
| 369 | * what is strictly necessary to make full use of a given |
| 370 | * delay*bandwith product. However testing has shown this not |
| 371 | * to be much of an problem. At worst we are trading wasting |
| 372 | * of available bandwith (the non-use of it) for wasting some |
| 373 | * socket buffer memory. |
| 374 | * |
| 375 | * TODO: Shrink send buffer during idle periods together |
| 376 | * with congestion window. Requires another timer. Has to |
| 377 | * wait for upcoming tcp timer rewrite. |
| 378 | */ |
| 379 | if (tcp_do_autosndbuf && so->so_snd.ssb_flags & SSB_AUTOSIZE) { |
| 380 | if ((tp->snd_wnd / 4 * 5) >= so->so_snd.ssb_hiwat && |
| 381 | so->so_snd.ssb_cc >= (so->so_snd.ssb_hiwat / 8 * 7) && |
| 382 | so->so_snd.ssb_cc < tcp_autosndbuf_max && |
| 383 | sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) { |
| 384 | u_long newsize; |
| 385 | |
| 386 | newsize = ulmin(so->so_snd.ssb_hiwat + |
| 387 | tcp_autosndbuf_inc, |
| 388 | tcp_autosndbuf_max); |
| 389 | if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) |
| 390 | atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); |
| 391 | if (newsize >= (TCP_MAXWIN << tp->snd_scale)) |
| 392 | atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); |
| 393 | } |
| 394 | } |
| 395 | |
| 396 | /* |
| 397 | * Truncate to the maximum segment length and ensure that FIN is |
| 398 | * removed if the length no longer contains the last data byte. |
| 399 | */ |
| 400 | if (len > tp->t_maxseg) { |
| 401 | len = tp->t_maxseg; |
| 402 | sendalot = TRUE; |
| 403 | } |
| 404 | if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) |
| 405 | flags &= ~TH_FIN; |
| 406 | |
| 407 | recvwin = ssb_space(&so->so_rcv); |
| 408 | |
| 409 | /* |
| 410 | * Sender silly window avoidance. We transmit under the following |
| 411 | * conditions when len is non-zero: |
| 412 | * |
| 413 | * - We have a full segment |
| 414 | * - This is the last buffer in a write()/send() and we are |
| 415 | * either idle or running NODELAY |
| 416 | * - we've timed out (e.g. persist timer) |
| 417 | * - we have more then 1/2 the maximum send window's worth of |
| 418 | * data (receiver may be limiting the window size) |
| 419 | * - we need to retransmit |
| 420 | */ |
| 421 | if (len) { |
| 422 | if (len == tp->t_maxseg) |
| 423 | goto send; |
| 424 | /* |
| 425 | * NOTE! on localhost connections an 'ack' from the remote |
| 426 | * end may occur synchronously with the output and cause |
| 427 | * us to flush a buffer queued with moretocome. XXX |
| 428 | * |
| 429 | * note: the len + off check is almost certainly unnecessary. |
| 430 | */ |
| 431 | if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ |
| 432 | (idle || (tp->t_flags & TF_NODELAY)) && |
| 433 | len + off >= so->so_snd.ssb_cc && |
| 434 | !(tp->t_flags & TF_NOPUSH)) { |
| 435 | goto send; |
| 436 | } |
| 437 | if (tp->t_flags & TF_FORCE) /* typ. timeout case */ |
| 438 | goto send; |
| 439 | if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) |
| 440 | goto send; |
| 441 | if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ |
| 442 | goto send; |
| 443 | } |
| 444 | |
| 445 | /* |
| 446 | * Compare available window to amount of window |
| 447 | * known to peer (as advertised window less |
| 448 | * next expected input). If the difference is at least two |
| 449 | * max size segments, or at least 50% of the maximum possible |
| 450 | * window, then want to send a window update to peer. |
| 451 | */ |
| 452 | if (recvwin > 0) { |
| 453 | /* |
| 454 | * "adv" is the amount we can increase the window, |
| 455 | * taking into account that we are limited by |
| 456 | * TCP_MAXWIN << tp->rcv_scale. |
| 457 | */ |
| 458 | long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - |
| 459 | (tp->rcv_adv - tp->rcv_nxt); |
| 460 | long hiwat; |
| 461 | |
| 462 | /* |
| 463 | * This ack case typically occurs when the user has drained |
| 464 | * the TCP socket buffer sufficiently to warrent an ack |
| 465 | * containing a 'pure window update'... that is, an ack that |
| 466 | * ONLY updates the tcp window. |
| 467 | * |
| 468 | * It is unclear why we would need to do a pure window update |
| 469 | * past 2 segments if we are going to do one at 1/2 the high |
| 470 | * water mark anyway, especially since under normal conditions |
| 471 | * the user program will drain the socket buffer quickly. |
| 472 | * The 2-segment pure window update will often add a large |
| 473 | * number of extra, unnecessary acks to the stream. |
| 474 | * |
| 475 | * avoid_pure_win_update now defaults to 1. |
| 476 | */ |
| 477 | if (avoid_pure_win_update == 0 || |
| 478 | (tp->t_flags & TF_RXRESIZED)) { |
| 479 | if (adv >= (long) (2 * tp->t_maxseg)) { |
| 480 | goto send; |
| 481 | } |
| 482 | } |
| 483 | hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); |
| 484 | if (hiwat > (long)so->so_rcv.ssb_hiwat) |
| 485 | hiwat = (long)so->so_rcv.ssb_hiwat; |
| 486 | if (adv >= hiwat / 2) |
| 487 | goto send; |
| 488 | } |
| 489 | |
| 490 | /* |
| 491 | * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW |
| 492 | * is also a catch-all for the retransmit timer timeout case. |
| 493 | */ |
| 494 | if (tp->t_flags & TF_ACKNOW) |
| 495 | goto send; |
| 496 | if ((flags & TH_RST) || |
| 497 | ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) |
| 498 | goto send; |
| 499 | if (SEQ_GT(tp->snd_up, tp->snd_una)) |
| 500 | goto send; |
| 501 | /* |
| 502 | * If our state indicates that FIN should be sent |
| 503 | * and we have not yet done so, then we need to send. |
| 504 | */ |
| 505 | if (flags & TH_FIN && |
| 506 | (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) |
| 507 | goto send; |
| 508 | |
| 509 | /* |
| 510 | * TCP window updates are not reliable, rather a polling protocol |
| 511 | * using ``persist'' packets is used to insure receipt of window |
| 512 | * updates. The three ``states'' for the output side are: |
| 513 | * idle not doing retransmits or persists |
| 514 | * persisting to move a small or zero window |
| 515 | * (re)transmitting and thereby not persisting |
| 516 | * |
| 517 | * tcp_callout_active(tp, tp->tt_persist) |
| 518 | * is true when we are in persist state. |
| 519 | * The TF_FORCE flag in tp->t_flags |
| 520 | * is set when we are called to send a persist packet. |
| 521 | * tcp_callout_active(tp, tp->tt_rexmt) |
| 522 | * is set when we are retransmitting |
| 523 | * The output side is idle when both timers are zero. |
| 524 | * |
| 525 | * If send window is too small, there is data to transmit, and no |
| 526 | * retransmit or persist is pending, then go to persist state. |
| 527 | * If nothing happens soon, send when timer expires: |
| 528 | * if window is nonzero, transmit what we can, |
| 529 | * otherwise force out a byte. |
| 530 | */ |
| 531 | if (so->so_snd.ssb_cc > 0 && |
| 532 | !tcp_callout_active(tp, tp->tt_rexmt) && |
| 533 | !tcp_callout_active(tp, tp->tt_persist)) { |
| 534 | tp->t_rxtshift = 0; |
| 535 | tcp_setpersist(tp); |
| 536 | } |
| 537 | |
| 538 | /* |
| 539 | * No reason to send a segment, just return. |
| 540 | */ |
| 541 | return (0); |
| 542 | |
| 543 | send: |
| 544 | /* |
| 545 | * Before ESTABLISHED, force sending of initial options |
| 546 | * unless TCP set not to do any options. |
| 547 | * NOTE: we assume that the IP/TCP header plus TCP options |
| 548 | * always fit in a single mbuf, leaving room for a maximum |
| 549 | * link header, i.e. |
| 550 | * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES |
| 551 | */ |
| 552 | optlen = 0; |
| 553 | if (isipv6) |
| 554 | hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); |
| 555 | else |
| 556 | hdrlen = sizeof(struct tcpiphdr); |
| 557 | if (flags & TH_SYN) { |
| 558 | tp->snd_nxt = tp->iss; |
| 559 | if (!(tp->t_flags & TF_NOOPT)) { |
| 560 | u_short mss; |
| 561 | |
| 562 | opt[0] = TCPOPT_MAXSEG; |
| 563 | opt[1] = TCPOLEN_MAXSEG; |
| 564 | mss = htons((u_short) tcp_mssopt(tp)); |
| 565 | memcpy(opt + 2, &mss, sizeof mss); |
| 566 | optlen = TCPOLEN_MAXSEG; |
| 567 | |
| 568 | if ((tp->t_flags & TF_REQ_SCALE) && |
| 569 | (!(flags & TH_ACK) || |
| 570 | (tp->t_flags & TF_RCVD_SCALE))) { |
| 571 | *((u_int32_t *)(opt + optlen)) = htonl( |
| 572 | TCPOPT_NOP << 24 | |
| 573 | TCPOPT_WINDOW << 16 | |
| 574 | TCPOLEN_WINDOW << 8 | |
| 575 | tp->request_r_scale); |
| 576 | optlen += 4; |
| 577 | } |
| 578 | |
| 579 | if ((tcp_do_sack && !(flags & TH_ACK)) || |
| 580 | tp->t_flags & TF_SACK_PERMITTED) { |
| 581 | uint32_t *lp = (uint32_t *)(opt + optlen); |
| 582 | |
| 583 | *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); |
| 584 | optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; |
| 585 | } |
| 586 | } |
| 587 | } |
| 588 | |
| 589 | /* |
| 590 | * Send a timestamp and echo-reply if this is a SYN and our side |
| 591 | * wants to use timestamps (TF_REQ_TSTMP is set) or both our side |
| 592 | * and our peer have sent timestamps in our SYN's. |
| 593 | */ |
| 594 | if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && |
| 595 | !(flags & TH_RST) && |
| 596 | (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { |
| 597 | u_int32_t *lp = (u_int32_t *)(opt + optlen); |
| 598 | |
| 599 | /* Form timestamp option as shown in appendix A of RFC 1323. */ |
| 600 | *lp++ = htonl(TCPOPT_TSTAMP_HDR); |
| 601 | *lp++ = htonl(ticks); |
| 602 | *lp = htonl(tp->ts_recent); |
| 603 | optlen += TCPOLEN_TSTAMP_APPA; |
| 604 | } |
| 605 | |
| 606 | /* Set receive buffer autosizing timestamp. */ |
| 607 | if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) |
| 608 | tp->rfbuf_ts = ticks; |
| 609 | |
| 610 | /* |
| 611 | * If this is a SACK connection and we have a block to report, |
| 612 | * fill in the SACK blocks in the TCP options. |
| 613 | */ |
| 614 | if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == |
| 615 | TF_SACK_PERMITTED && |
| 616 | (!LIST_EMPTY(&tp->t_segq) || |
| 617 | tp->reportblk.rblk_start != tp->reportblk.rblk_end)) |
| 618 | tcp_sack_fill_report(tp, opt, &optlen); |
| 619 | |
| 620 | #ifdef TCP_SIGNATURE |
| 621 | if (tp->t_flags & TF_SIGNATURE) { |
| 622 | int i; |
| 623 | u_char *bp; |
| 624 | /* |
| 625 | * Initialize TCP-MD5 option (RFC2385) |
| 626 | */ |
| 627 | bp = (u_char *)opt + optlen; |
| 628 | *bp++ = TCPOPT_SIGNATURE; |
| 629 | *bp++ = TCPOLEN_SIGNATURE; |
| 630 | sigoff = optlen + 2; |
| 631 | for (i = 0; i < TCP_SIGLEN; i++) |
| 632 | *bp++ = 0; |
| 633 | optlen += TCPOLEN_SIGNATURE; |
| 634 | /* |
| 635 | * Terminate options list and maintain 32-bit alignment. |
| 636 | */ |
| 637 | *bp++ = TCPOPT_NOP; |
| 638 | *bp++ = TCPOPT_EOL; |
| 639 | optlen += 2; |
| 640 | } |
| 641 | #endif /* TCP_SIGNATURE */ |
| 642 | KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); |
| 643 | hdrlen += optlen; |
| 644 | |
| 645 | if (isipv6) { |
| 646 | ipoptlen = ip6_optlen(inp); |
| 647 | } else { |
| 648 | if (inp->inp_options) { |
| 649 | ipoptlen = inp->inp_options->m_len - |
| 650 | offsetof(struct ipoption, ipopt_list); |
| 651 | } else { |
| 652 | ipoptlen = 0; |
| 653 | } |
| 654 | } |
| 655 | #ifdef IPSEC |
| 656 | ipoptlen += ipsec_hdrsiz_tcp(tp); |
| 657 | #endif |
| 658 | |
| 659 | /* |
| 660 | * Adjust data length if insertion of options will bump the packet |
| 661 | * length beyond the t_maxopd length. Clear FIN to prevent premature |
| 662 | * closure since there is still more data to send after this (now |
| 663 | * truncated) packet. |
| 664 | * |
| 665 | * If just the options do not fit we are in a no-win situation and |
| 666 | * we treat it as an unreachable host. |
| 667 | */ |
| 668 | if (len + optlen + ipoptlen > tp->t_maxopd) { |
| 669 | if (tp->t_maxopd <= optlen + ipoptlen) { |
| 670 | static time_t last_optlen_report; |
| 671 | |
| 672 | if (last_optlen_report != time_second) { |
| 673 | last_optlen_report = time_second; |
| 674 | kprintf("tcpcb %p: MSS (%d) too small to hold options!\n", tp, tp->t_maxopd); |
| 675 | } |
| 676 | error = EHOSTUNREACH; |
| 677 | goto out; |
| 678 | } else { |
| 679 | flags &= ~TH_FIN; |
| 680 | len = tp->t_maxopd - optlen - ipoptlen; |
| 681 | sendalot = TRUE; |
| 682 | } |
| 683 | } |
| 684 | |
| 685 | #ifdef INET6 |
| 686 | KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); |
| 687 | #else |
| 688 | KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); |
| 689 | #endif |
| 690 | |
| 691 | /* |
| 692 | * Grab a header mbuf, attaching a copy of data to |
| 693 | * be transmitted, and initialize the header from |
| 694 | * the template for sends on this connection. |
| 695 | */ |
| 696 | if (len) { |
| 697 | if ((tp->t_flags & TF_FORCE) && len == 1) |
| 698 | tcpstat.tcps_sndprobe++; |
| 699 | else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { |
| 700 | if (tp->snd_nxt == tp->snd_una) |
| 701 | tp->snd_max_rexmt = tp->snd_max; |
| 702 | tcpstat.tcps_sndrexmitpack++; |
| 703 | tcpstat.tcps_sndrexmitbyte += len; |
| 704 | } else { |
| 705 | tcpstat.tcps_sndpack++; |
| 706 | tcpstat.tcps_sndbyte += len; |
| 707 | } |
| 708 | #ifdef notyet |
| 709 | if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, |
| 710 | max_linkhdr + hdrlen)) == NULL) { |
| 711 | error = ENOBUFS; |
| 712 | goto out; |
| 713 | } |
| 714 | /* |
| 715 | * m_copypack left space for our hdr; use it. |
| 716 | */ |
| 717 | m->m_len += hdrlen; |
| 718 | m->m_data -= hdrlen; |
| 719 | #else |
| 720 | #ifndef INET6 |
| 721 | m = m_gethdr(MB_DONTWAIT, MT_HEADER); |
| 722 | #else |
| 723 | m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER, |
| 724 | M_PKTHDR, NULL); |
| 725 | #endif |
| 726 | if (m == NULL) { |
| 727 | error = ENOBUFS; |
| 728 | goto out; |
| 729 | } |
| 730 | m->m_data += max_linkhdr; |
| 731 | m->m_len = hdrlen; |
| 732 | if (len <= MHLEN - hdrlen - max_linkhdr) { |
| 733 | m_copydata(so->so_snd.ssb_mb, off, (int) len, |
| 734 | mtod(m, caddr_t) + hdrlen); |
| 735 | m->m_len += len; |
| 736 | } else { |
| 737 | m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len); |
| 738 | if (m->m_next == NULL) { |
| 739 | m_free(m); |
| 740 | error = ENOBUFS; |
| 741 | goto out; |
| 742 | } |
| 743 | } |
| 744 | #endif |
| 745 | /* |
| 746 | * If we're sending everything we've got, set PUSH. |
| 747 | * (This will keep happy those implementations which only |
| 748 | * give data to the user when a buffer fills or |
| 749 | * a PUSH comes in.) |
| 750 | */ |
| 751 | if (off + len == so->so_snd.ssb_cc) |
| 752 | flags |= TH_PUSH; |
| 753 | } else { |
| 754 | if (tp->t_flags & TF_ACKNOW) |
| 755 | tcpstat.tcps_sndacks++; |
| 756 | else if (flags & (TH_SYN | TH_FIN | TH_RST)) |
| 757 | tcpstat.tcps_sndctrl++; |
| 758 | else if (SEQ_GT(tp->snd_up, tp->snd_una)) |
| 759 | tcpstat.tcps_sndurg++; |
| 760 | else |
| 761 | tcpstat.tcps_sndwinup++; |
| 762 | |
| 763 | MGETHDR(m, MB_DONTWAIT, MT_HEADER); |
| 764 | if (m == NULL) { |
| 765 | error = ENOBUFS; |
| 766 | goto out; |
| 767 | } |
| 768 | if (isipv6 && |
| 769 | (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) |
| 770 | MH_ALIGN(m, hdrlen); |
| 771 | else |
| 772 | m->m_data += max_linkhdr; |
| 773 | m->m_len = hdrlen; |
| 774 | } |
| 775 | m->m_pkthdr.rcvif = NULL; |
| 776 | if (isipv6) { |
| 777 | ip6 = mtod(m, struct ip6_hdr *); |
| 778 | th = (struct tcphdr *)(ip6 + 1); |
| 779 | tcp_fillheaders(tp, ip6, th); |
| 780 | } else { |
| 781 | ip = mtod(m, struct ip *); |
| 782 | ipov = (struct ipovly *)ip; |
| 783 | th = (struct tcphdr *)(ip + 1); |
| 784 | /* this picks up the pseudo header (w/o the length) */ |
| 785 | tcp_fillheaders(tp, ip, th); |
| 786 | } |
| 787 | |
| 788 | /* |
| 789 | * Fill in fields, remembering maximum advertised |
| 790 | * window for use in delaying messages about window sizes. |
| 791 | * If resending a FIN, be sure not to use a new sequence number. |
| 792 | */ |
| 793 | if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && |
| 794 | tp->snd_nxt == tp->snd_max) |
| 795 | tp->snd_nxt--; |
| 796 | /* |
| 797 | * If we are doing retransmissions, then snd_nxt will |
| 798 | * not reflect the first unsent octet. For ACK only |
| 799 | * packets, we do not want the sequence number of the |
| 800 | * retransmitted packet, we want the sequence number |
| 801 | * of the next unsent octet. So, if there is no data |
| 802 | * (and no SYN or FIN), use snd_max instead of snd_nxt |
| 803 | * when filling in ti_seq. But if we are in persist |
| 804 | * state, snd_max might reflect one byte beyond the |
| 805 | * right edge of the window, so use snd_nxt in that |
| 806 | * case, since we know we aren't doing a retransmission. |
| 807 | * (retransmit and persist are mutually exclusive...) |
| 808 | */ |
| 809 | if (len || (flags & (TH_SYN|TH_FIN)) || |
| 810 | tcp_callout_active(tp, tp->tt_persist)) |
| 811 | th->th_seq = htonl(tp->snd_nxt); |
| 812 | else |
| 813 | th->th_seq = htonl(tp->snd_max); |
| 814 | th->th_ack = htonl(tp->rcv_nxt); |
| 815 | if (optlen) { |
| 816 | bcopy(opt, th + 1, optlen); |
| 817 | th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; |
| 818 | } |
| 819 | th->th_flags = flags; |
| 820 | |
| 821 | /* |
| 822 | * Calculate receive window. Don't shrink window, but avoid |
| 823 | * silly window syndrome by sending a 0 window if the actual |
| 824 | * window is less then one segment. |
| 825 | */ |
| 826 | if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && |
| 827 | recvwin < (long)tp->t_maxseg) |
| 828 | recvwin = 0; |
| 829 | if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt)) |
| 830 | recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt); |
| 831 | if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) |
| 832 | recvwin = (long)TCP_MAXWIN << tp->rcv_scale; |
| 833 | th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); |
| 834 | |
| 835 | /* |
| 836 | * Adjust the RXWIN0SENT flag - indicate that we have advertised |
| 837 | * a 0 window. This may cause the remote transmitter to stall. This |
| 838 | * flag tells soreceive() to disable delayed acknowledgements when |
| 839 | * draining the buffer. This can occur if the receiver is attempting |
| 840 | * to read more data then can be buffered prior to transmitting on |
| 841 | * the connection. |
| 842 | */ |
| 843 | if (recvwin == 0) |
| 844 | tp->t_flags |= TF_RXWIN0SENT; |
| 845 | else |
| 846 | tp->t_flags &= ~TF_RXWIN0SENT; |
| 847 | |
| 848 | if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { |
| 849 | th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); |
| 850 | th->th_flags |= TH_URG; |
| 851 | } else { |
| 852 | /* |
| 853 | * If no urgent pointer to send, then we pull |
| 854 | * the urgent pointer to the left edge of the send window |
| 855 | * so that it doesn't drift into the send window on sequence |
| 856 | * number wraparound. |
| 857 | */ |
| 858 | tp->snd_up = tp->snd_una; /* drag it along */ |
| 859 | } |
| 860 | |
| 861 | #ifdef TCP_SIGNATURE |
| 862 | if (tp->t_flags & TF_SIGNATURE) |
| 863 | tcpsignature_compute(m, len, optlen, |
| 864 | (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); |
| 865 | #endif /* TCP_SIGNATURE */ |
| 866 | |
| 867 | /* |
| 868 | * Put TCP length in extended header, and then |
| 869 | * checksum extended header and data. |
| 870 | */ |
| 871 | m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ |
| 872 | if (isipv6) { |
| 873 | /* |
| 874 | * ip6_plen is not need to be filled now, and will be filled |
| 875 | * in ip6_output(). |
| 876 | */ |
| 877 | th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), |
| 878 | sizeof(struct tcphdr) + optlen + len); |
| 879 | } else { |
| 880 | m->m_pkthdr.csum_flags = CSUM_TCP; |
| 881 | m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); |
| 882 | if (len + optlen) |
| 883 | th->th_sum = in_addword(th->th_sum, |
| 884 | htons((u_short)(optlen + len))); |
| 885 | |
| 886 | /* IP version must be set here for ipv4/ipv6 checking later */ |
| 887 | KASSERT(ip->ip_v == IPVERSION, |
| 888 | ("%s: IP version incorrect: %d", __func__, ip->ip_v)); |
| 889 | } |
| 890 | |
| 891 | /* |
| 892 | * In transmit state, time the transmission and arrange for |
| 893 | * the retransmit. In persist state, just set snd_max. |
| 894 | */ |
| 895 | if (!(tp->t_flags & TF_FORCE) || |
| 896 | !tcp_callout_active(tp, tp->tt_persist)) { |
| 897 | tcp_seq startseq = tp->snd_nxt; |
| 898 | |
| 899 | /* |
| 900 | * Advance snd_nxt over sequence space of this segment. |
| 901 | */ |
| 902 | if (flags & (TH_SYN | TH_FIN)) { |
| 903 | if (flags & TH_SYN) |
| 904 | tp->snd_nxt++; |
| 905 | if (flags & TH_FIN) { |
| 906 | tp->snd_nxt++; |
| 907 | tp->t_flags |= TF_SENTFIN; |
| 908 | } |
| 909 | } |
| 910 | tp->snd_nxt += len; |
| 911 | if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { |
| 912 | tp->snd_max = tp->snd_nxt; |
| 913 | /* |
| 914 | * Time this transmission if not a retransmission and |
| 915 | * not currently timing anything. |
| 916 | */ |
| 917 | if (tp->t_rtttime == 0) { |
| 918 | tp->t_rtttime = ticks; |
| 919 | tp->t_rtseq = startseq; |
| 920 | tcpstat.tcps_segstimed++; |
| 921 | } |
| 922 | } |
| 923 | |
| 924 | /* |
| 925 | * Set retransmit timer if not currently set, |
| 926 | * and not doing a pure ack or a keep-alive probe. |
| 927 | * Initial value for retransmit timer is smoothed |
| 928 | * round-trip time + 2 * round-trip time variance. |
| 929 | * Initialize shift counter which is used for backoff |
| 930 | * of retransmit time. |
| 931 | */ |
| 932 | if (!tcp_callout_active(tp, tp->tt_rexmt) && |
| 933 | tp->snd_nxt != tp->snd_una) { |
| 934 | if (tcp_callout_active(tp, tp->tt_persist)) { |
| 935 | tcp_callout_stop(tp, tp->tt_persist); |
| 936 | tp->t_rxtshift = 0; |
| 937 | } |
| 938 | tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, |
| 939 | tcp_timer_rexmt); |
| 940 | } |
| 941 | } else { |
| 942 | /* |
| 943 | * Persist case, update snd_max but since we are in |
| 944 | * persist mode (no window) we do not update snd_nxt. |
| 945 | */ |
| 946 | int xlen = len; |
| 947 | if (flags & TH_SYN) |
| 948 | panic("tcp_output: persist timer to send SYN\n"); |
| 949 | if (flags & TH_FIN) { |
| 950 | ++xlen; |
| 951 | tp->t_flags |= TF_SENTFIN; |
| 952 | } |
| 953 | if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) |
| 954 | tp->snd_max = tp->snd_nxt + xlen; |
| 955 | } |
| 956 | |
| 957 | #ifdef TCPDEBUG |
| 958 | /* |
| 959 | * Trace. |
| 960 | */ |
| 961 | if (so->so_options & SO_DEBUG) |
| 962 | tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); |
| 963 | #endif |
| 964 | |
| 965 | /* |
| 966 | * Fill in IP length and desired time to live and |
| 967 | * send to IP level. There should be a better way |
| 968 | * to handle ttl and tos; we could keep them in |
| 969 | * the template, but need a way to checksum without them. |
| 970 | */ |
| 971 | /* |
| 972 | * m->m_pkthdr.len should have been set before cksum calcuration, |
| 973 | * because in6_cksum() need it. |
| 974 | */ |
| 975 | if (isipv6) { |
| 976 | /* |
| 977 | * we separately set hoplimit for every segment, since the |
| 978 | * user might want to change the value via setsockopt. |
| 979 | * Also, desired default hop limit might be changed via |
| 980 | * Neighbor Discovery. |
| 981 | */ |
| 982 | ip6->ip6_hlim = in6_selecthlim(inp, |
| 983 | (inp->in6p_route.ro_rt ? |
| 984 | inp->in6p_route.ro_rt->rt_ifp : NULL)); |
| 985 | |
| 986 | /* TODO: IPv6 IP6TOS_ECT bit on */ |
| 987 | error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, |
| 988 | (so->so_options & SO_DONTROUTE), NULL, NULL, |
| 989 | inp); |
| 990 | } else { |
| 991 | struct rtentry *rt; |
| 992 | ip->ip_len = m->m_pkthdr.len; |
| 993 | #ifdef INET6 |
| 994 | if (INP_CHECK_SOCKAF(so, AF_INET6)) |
| 995 | ip->ip_ttl = in6_selecthlim(inp, |
| 996 | (inp->in6p_route.ro_rt ? |
| 997 | inp->in6p_route.ro_rt->rt_ifp : NULL)); |
| 998 | else |
| 999 | #endif |
| 1000 | ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ |
| 1001 | |
| 1002 | ip->ip_tos = inp->inp_ip_tos; /* XXX */ |
| 1003 | /* |
| 1004 | * See if we should do MTU discovery. |
| 1005 | * We do it only if the following are true: |
| 1006 | * 1) we have a valid route to the destination |
| 1007 | * 2) the MTU is not locked (if it is, |
| 1008 | * then discovery has been disabled) |
| 1009 | */ |
| 1010 | if (path_mtu_discovery && |
| 1011 | (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && |
| 1012 | !(rt->rt_rmx.rmx_locks & RTV_MTU)) |
| 1013 | ip->ip_off |= IP_DF; |
| 1014 | |
| 1015 | error = ip_output(m, inp->inp_options, &inp->inp_route, |
| 1016 | (so->so_options & SO_DONTROUTE) | |
| 1017 | IP_DEBUGROUTE, NULL, inp); |
| 1018 | } |
| 1019 | if (error) { |
| 1020 | |
| 1021 | /* |
| 1022 | * We know that the packet was lost, so back out the |
| 1023 | * sequence number advance, if any. |
| 1024 | */ |
| 1025 | if (!(tp->t_flags & TF_FORCE) || |
| 1026 | !tcp_callout_active(tp, tp->tt_persist)) { |
| 1027 | /* |
| 1028 | * No need to check for TH_FIN here because |
| 1029 | * the TF_SENTFIN flag handles that case. |
| 1030 | */ |
| 1031 | if (!(flags & TH_SYN)) |
| 1032 | tp->snd_nxt -= len; |
| 1033 | } |
| 1034 | |
| 1035 | out: |
| 1036 | if (error == ENOBUFS) { |
| 1037 | /* |
| 1038 | * If we can't send, make sure there is something |
| 1039 | * to get us going again later. Persist state |
| 1040 | * is not necessarily right, but it is close enough. |
| 1041 | */ |
| 1042 | if (!tcp_callout_active(tp, tp->tt_rexmt) && |
| 1043 | !tcp_callout_active(tp, tp->tt_persist)) { |
| 1044 | tp->t_rxtshift = 0; |
| 1045 | tcp_setpersist(tp); |
| 1046 | } |
| 1047 | tcp_quench(inp, 0); |
| 1048 | return (0); |
| 1049 | } |
| 1050 | if (error == EMSGSIZE) { |
| 1051 | /* |
| 1052 | * ip_output() will have already fixed the route |
| 1053 | * for us. tcp_mtudisc() will, as its last action, |
| 1054 | * initiate retransmission, so it is important to |
| 1055 | * not do so here. |
| 1056 | */ |
| 1057 | tcp_mtudisc(inp, 0); |
| 1058 | return 0; |
| 1059 | } |
| 1060 | if ((error == EHOSTUNREACH || error == ENETDOWN) && |
| 1061 | TCPS_HAVERCVDSYN(tp->t_state)) { |
| 1062 | tp->t_softerror = error; |
| 1063 | return (0); |
| 1064 | } |
| 1065 | return (error); |
| 1066 | } |
| 1067 | tcpstat.tcps_sndtotal++; |
| 1068 | |
| 1069 | /* |
| 1070 | * Data sent (as far as we can tell). |
| 1071 | * |
| 1072 | * If this advertises a larger window than any other segment, |
| 1073 | * then remember the size of the advertised window. |
| 1074 | * |
| 1075 | * Any pending ACK has now been sent. |
| 1076 | */ |
| 1077 | if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) { |
| 1078 | tp->rcv_adv = tp->rcv_nxt + recvwin; |
| 1079 | tp->t_flags &= ~TF_RXRESIZED; |
| 1080 | } |
| 1081 | tp->last_ack_sent = tp->rcv_nxt; |
| 1082 | tp->t_flags &= ~TF_ACKNOW; |
| 1083 | if (tcp_delack_enabled) |
| 1084 | tcp_callout_stop(tp, tp->tt_delack); |
| 1085 | if (sendalot) |
| 1086 | goto again; |
| 1087 | return (0); |
| 1088 | } |
| 1089 | |
| 1090 | void |
| 1091 | tcp_setpersist(struct tcpcb *tp) |
| 1092 | { |
| 1093 | int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; |
| 1094 | int tt; |
| 1095 | |
| 1096 | if (tp->t_state == TCPS_SYN_SENT || |
| 1097 | tp->t_state == TCPS_SYN_RECEIVED) { |
| 1098 | panic("tcp_setpersist: not established yet, current %s\n", |
| 1099 | tp->t_state == TCPS_SYN_SENT ? |
| 1100 | "SYN_SENT" : "SYN_RECEIVED"); |
| 1101 | } |
| 1102 | |
| 1103 | if (tcp_callout_active(tp, tp->tt_rexmt)) |
| 1104 | panic("tcp_setpersist: retransmit pending"); |
| 1105 | /* |
| 1106 | * Start/restart persistance timer. |
| 1107 | */ |
| 1108 | TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, |
| 1109 | TCPTV_PERSMAX); |
| 1110 | tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist); |
| 1111 | if (tp->t_rxtshift < TCP_MAXRXTSHIFT) |
| 1112 | tp->t_rxtshift++; |
| 1113 | } |