| 1 | /* $NetBSD: tcp_congctl.c,v 1.21 2016/04/26 08:44:44 ozaki-r Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 1997, 1998, 1999, 2001, 2005, 2006 The NetBSD Foundation, Inc. |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * This code is derived from software contributed to The NetBSD Foundation |
| 8 | * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation |
| 9 | * Facility, NASA Ames Research Center. |
| 10 | * This code is derived from software contributed to The NetBSD Foundation |
| 11 | * by Charles M. Hannum. |
| 12 | * This code is derived from software contributed to The NetBSD Foundation |
| 13 | * by Rui Paulo. |
| 14 | * |
| 15 | * Redistribution and use in source and binary forms, with or without |
| 16 | * modification, are permitted provided that the following conditions |
| 17 | * are met: |
| 18 | * 1. Redistributions of source code must retain the above copyright |
| 19 | * notice, this list of conditions and the following disclaimer. |
| 20 | * 2. Redistributions in binary form must reproduce the above copyright |
| 21 | * notice, this list of conditions and the following disclaimer in the |
| 22 | * documentation and/or other materials provided with the distribution. |
| 23 | * |
| 24 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
| 25 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| 26 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| 27 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
| 28 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 29 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 30 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 31 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 32 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 33 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 34 | * POSSIBILITY OF SUCH DAMAGE. |
| 35 | */ |
| 36 | |
| 37 | /* |
| 38 | * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. |
| 39 | * All rights reserved. |
| 40 | * |
| 41 | * Redistribution and use in source and binary forms, with or without |
| 42 | * modification, are permitted provided that the following conditions |
| 43 | * are met: |
| 44 | * 1. Redistributions of source code must retain the above copyright |
| 45 | * notice, this list of conditions and the following disclaimer. |
| 46 | * 2. Redistributions in binary form must reproduce the above copyright |
| 47 | * notice, this list of conditions and the following disclaimer in the |
| 48 | * documentation and/or other materials provided with the distribution. |
| 49 | * 3. Neither the name of the project nor the names of its contributors |
| 50 | * may be used to endorse or promote products derived from this software |
| 51 | * without specific prior written permission. |
| 52 | * |
| 53 | * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND |
| 54 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 55 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 56 | * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE |
| 57 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 58 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 59 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 60 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 61 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 62 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 63 | * SUCH DAMAGE. |
| 64 | */ |
| 65 | |
| 66 | /* |
| 67 | * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 |
| 68 | * |
| 69 | * NRL grants permission for redistribution and use in source and binary |
| 70 | * forms, with or without modification, of the software and documentation |
| 71 | * created at NRL provided that the following conditions are met: |
| 72 | * |
| 73 | * 1. Redistributions of source code must retain the above copyright |
| 74 | * notice, this list of conditions and the following disclaimer. |
| 75 | * 2. Redistributions in binary form must reproduce the above copyright |
| 76 | * notice, this list of conditions and the following disclaimer in the |
| 77 | * documentation and/or other materials provided with the distribution. |
| 78 | * 3. All advertising materials mentioning features or use of this software |
| 79 | * must display the following acknowledgements: |
| 80 | * This product includes software developed by the University of |
| 81 | * California, Berkeley and its contributors. |
| 82 | * This product includes software developed at the Information |
| 83 | * Technology Division, US Naval Research Laboratory. |
| 84 | * 4. Neither the name of the NRL nor the names of its contributors |
| 85 | * may be used to endorse or promote products derived from this software |
| 86 | * without specific prior written permission. |
| 87 | * |
| 88 | * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS |
| 89 | * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| 90 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A |
| 91 | * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR |
| 92 | * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| 93 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| 94 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| 95 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
| 96 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
| 97 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| 98 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 99 | * |
| 100 | * The views and conclusions contained in the software and documentation |
| 101 | * are those of the authors and should not be interpreted as representing |
| 102 | * official policies, either expressed or implied, of the US Naval |
| 103 | * Research Laboratory (NRL). |
| 104 | */ |
| 105 | |
| 106 | /* |
| 107 | * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 |
| 108 | * The Regents of the University of California. All rights reserved. |
| 109 | * |
| 110 | * Redistribution and use in source and binary forms, with or without |
| 111 | * modification, are permitted provided that the following conditions |
| 112 | * are met: |
| 113 | * 1. Redistributions of source code must retain the above copyright |
| 114 | * notice, this list of conditions and the following disclaimer. |
| 115 | * 2. Redistributions in binary form must reproduce the above copyright |
| 116 | * notice, this list of conditions and the following disclaimer in the |
| 117 | * documentation and/or other materials provided with the distribution. |
| 118 | * 3. Neither the name of the University nor the names of its contributors |
| 119 | * may be used to endorse or promote products derived from this software |
| 120 | * without specific prior written permission. |
| 121 | * |
| 122 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 123 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 124 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 125 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 126 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 127 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 128 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 129 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 130 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 131 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 132 | * SUCH DAMAGE. |
| 133 | * |
| 134 | * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 |
| 135 | */ |
| 136 | |
| 137 | #include <sys/cdefs.h> |
| 138 | __KERNEL_RCSID(0, "$NetBSD: tcp_congctl.c,v 1.21 2016/04/26 08:44:44 ozaki-r Exp $" ); |
| 139 | |
| 140 | #ifdef _KERNEL_OPT |
| 141 | #include "opt_inet.h" |
| 142 | #include "opt_tcp_debug.h" |
| 143 | #include "opt_tcp_congctl.h" |
| 144 | #endif |
| 145 | |
| 146 | #include <sys/param.h> |
| 147 | #include <sys/systm.h> |
| 148 | #include <sys/malloc.h> |
| 149 | #include <sys/mbuf.h> |
| 150 | #include <sys/protosw.h> |
| 151 | #include <sys/socket.h> |
| 152 | #include <sys/socketvar.h> |
| 153 | #include <sys/errno.h> |
| 154 | #include <sys/syslog.h> |
| 155 | #include <sys/pool.h> |
| 156 | #include <sys/domain.h> |
| 157 | #include <sys/kernel.h> |
| 158 | #include <sys/mutex.h> |
| 159 | |
| 160 | #include <net/if.h> |
| 161 | |
| 162 | #include <netinet/in.h> |
| 163 | #include <netinet/in_systm.h> |
| 164 | #include <netinet/ip.h> |
| 165 | #include <netinet/in_pcb.h> |
| 166 | #include <netinet/in_var.h> |
| 167 | #include <netinet/ip_var.h> |
| 168 | |
| 169 | #ifdef INET6 |
| 170 | #ifndef INET |
| 171 | #include <netinet/in.h> |
| 172 | #endif |
| 173 | #include <netinet/ip6.h> |
| 174 | #include <netinet6/ip6_var.h> |
| 175 | #include <netinet6/in6_pcb.h> |
| 176 | #include <netinet6/ip6_var.h> |
| 177 | #include <netinet6/in6_var.h> |
| 178 | #include <netinet/icmp6.h> |
| 179 | #include <netinet6/nd6.h> |
| 180 | #endif |
| 181 | |
| 182 | #include <netinet/tcp.h> |
| 183 | #include <netinet/tcp_fsm.h> |
| 184 | #include <netinet/tcp_seq.h> |
| 185 | #include <netinet/tcp_timer.h> |
| 186 | #include <netinet/tcp_var.h> |
| 187 | #include <netinet/tcpip.h> |
| 188 | #include <netinet/tcp_congctl.h> |
| 189 | #ifdef TCP_DEBUG |
| 190 | #include <netinet/tcp_debug.h> |
| 191 | #endif |
| 192 | |
| 193 | /* |
| 194 | * TODO: |
| 195 | * consider separating the actual implementations in another file. |
| 196 | */ |
| 197 | |
| 198 | static void tcp_common_congestion_exp(struct tcpcb *, int, int); |
| 199 | |
| 200 | static int tcp_reno_do_fast_retransmit(struct tcpcb *, const struct tcphdr *); |
| 201 | static int tcp_reno_fast_retransmit(struct tcpcb *, const struct tcphdr *); |
| 202 | static void tcp_reno_slow_retransmit(struct tcpcb *); |
| 203 | static void tcp_reno_fast_retransmit_newack(struct tcpcb *, |
| 204 | const struct tcphdr *); |
| 205 | static void tcp_reno_newack(struct tcpcb *, const struct tcphdr *); |
| 206 | static void tcp_reno_congestion_exp(struct tcpcb *tp); |
| 207 | |
| 208 | static int tcp_newreno_fast_retransmit(struct tcpcb *, const struct tcphdr *); |
| 209 | static void tcp_newreno_fast_retransmit_newack(struct tcpcb *, |
| 210 | const struct tcphdr *); |
| 211 | static void tcp_newreno_newack(struct tcpcb *, const struct tcphdr *); |
| 212 | |
| 213 | static int tcp_cubic_fast_retransmit(struct tcpcb *, const struct tcphdr *); |
| 214 | static void tcp_cubic_slow_retransmit(struct tcpcb *tp); |
| 215 | static void tcp_cubic_newack(struct tcpcb *, const struct tcphdr *); |
| 216 | static void tcp_cubic_congestion_exp(struct tcpcb *); |
| 217 | |
| 218 | static void tcp_congctl_fillnames(void); |
| 219 | |
| 220 | extern int tcprexmtthresh; |
| 221 | |
| 222 | MALLOC_DEFINE(M_TCPCONGCTL, "tcpcongctl" , "TCP congestion control structures" ); |
| 223 | |
| 224 | /* currently selected global congestion control */ |
| 225 | char tcp_congctl_global_name[TCPCC_MAXLEN]; |
| 226 | |
| 227 | /* available global congestion control algorithms */ |
| 228 | char tcp_congctl_avail[10 * TCPCC_MAXLEN]; |
| 229 | |
| 230 | /* |
| 231 | * Used to list the available congestion control algorithms. |
| 232 | */ |
| 233 | TAILQ_HEAD(, tcp_congctlent) tcp_congctlhd = |
| 234 | TAILQ_HEAD_INITIALIZER(tcp_congctlhd); |
| 235 | |
| 236 | static struct tcp_congctlent * tcp_congctl_global; |
| 237 | |
| 238 | static kmutex_t tcp_congctl_mtx; |
| 239 | |
| 240 | void |
| 241 | tcp_congctl_init(void) |
| 242 | { |
| 243 | int r __diagused; |
| 244 | |
| 245 | mutex_init(&tcp_congctl_mtx, MUTEX_DEFAULT, IPL_NONE); |
| 246 | |
| 247 | /* Base algorithms. */ |
| 248 | r = tcp_congctl_register("reno" , &tcp_reno_ctl); |
| 249 | KASSERT(r == 0); |
| 250 | r = tcp_congctl_register("newreno" , &tcp_newreno_ctl); |
| 251 | KASSERT(r == 0); |
| 252 | r = tcp_congctl_register("cubic" , &tcp_cubic_ctl); |
| 253 | KASSERT(r == 0); |
| 254 | |
| 255 | /* NewReno is the default. */ |
| 256 | #ifndef TCP_CONGCTL_DEFAULT |
| 257 | #define TCP_CONGCTL_DEFAULT "newreno" |
| 258 | #endif |
| 259 | |
| 260 | r = tcp_congctl_select(NULL, TCP_CONGCTL_DEFAULT); |
| 261 | KASSERT(r == 0); |
| 262 | } |
| 263 | |
| 264 | /* |
| 265 | * Register a congestion algorithm and select it if we have none. |
| 266 | */ |
| 267 | int |
| 268 | tcp_congctl_register(const char *name, const struct tcp_congctl *tcc) |
| 269 | { |
| 270 | struct tcp_congctlent *ntcc, *tccp; |
| 271 | |
| 272 | TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) |
| 273 | if (!strcmp(name, tccp->congctl_name)) { |
| 274 | /* name already registered */ |
| 275 | return EEXIST; |
| 276 | } |
| 277 | |
| 278 | ntcc = malloc(sizeof(*ntcc), M_TCPCONGCTL, M_WAITOK|M_ZERO); |
| 279 | |
| 280 | strlcpy(ntcc->congctl_name, name, sizeof(ntcc->congctl_name) - 1); |
| 281 | ntcc->congctl_ctl = tcc; |
| 282 | |
| 283 | TAILQ_INSERT_TAIL(&tcp_congctlhd, ntcc, congctl_ent); |
| 284 | tcp_congctl_fillnames(); |
| 285 | |
| 286 | if (TAILQ_FIRST(&tcp_congctlhd) == ntcc) |
| 287 | tcp_congctl_select(NULL, name); |
| 288 | |
| 289 | return 0; |
| 290 | } |
| 291 | |
| 292 | int |
| 293 | tcp_congctl_unregister(const char *name) |
| 294 | { |
| 295 | struct tcp_congctlent *tccp, *rtccp; |
| 296 | unsigned int size; |
| 297 | |
| 298 | rtccp = NULL; |
| 299 | size = 0; |
| 300 | TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) { |
| 301 | if (!strcmp(name, tccp->congctl_name)) |
| 302 | rtccp = tccp; |
| 303 | size++; |
| 304 | } |
| 305 | |
| 306 | if (!rtccp) |
| 307 | return ENOENT; |
| 308 | |
| 309 | if (size <= 1 || tcp_congctl_global == rtccp || rtccp->congctl_refcnt) |
| 310 | return EBUSY; |
| 311 | |
| 312 | TAILQ_REMOVE(&tcp_congctlhd, rtccp, congctl_ent); |
| 313 | free(rtccp, M_TCPCONGCTL); |
| 314 | tcp_congctl_fillnames(); |
| 315 | |
| 316 | return 0; |
| 317 | } |
| 318 | |
| 319 | /* |
| 320 | * Select a congestion algorithm by name. |
| 321 | */ |
| 322 | int |
| 323 | tcp_congctl_select(struct tcpcb *tp, const char *name) |
| 324 | { |
| 325 | struct tcp_congctlent *tccp, *old_tccp, *new_tccp; |
| 326 | bool old_found, new_found; |
| 327 | |
| 328 | KASSERT(name); |
| 329 | |
| 330 | old_found = (tp == NULL || tp->t_congctl == NULL); |
| 331 | old_tccp = NULL; |
| 332 | new_found = false; |
| 333 | new_tccp = NULL; |
| 334 | |
| 335 | TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) { |
| 336 | if (!old_found && tccp->congctl_ctl == tp->t_congctl) { |
| 337 | old_tccp = tccp; |
| 338 | old_found = true; |
| 339 | } |
| 340 | |
| 341 | if (!new_found && !strcmp(name, tccp->congctl_name)) { |
| 342 | new_tccp = tccp; |
| 343 | new_found = true; |
| 344 | } |
| 345 | |
| 346 | if (new_found && old_found) { |
| 347 | if (tp) { |
| 348 | mutex_enter(&tcp_congctl_mtx); |
| 349 | if (old_tccp) |
| 350 | old_tccp->congctl_refcnt--; |
| 351 | tp->t_congctl = new_tccp->congctl_ctl; |
| 352 | new_tccp->congctl_refcnt++; |
| 353 | mutex_exit(&tcp_congctl_mtx); |
| 354 | } else { |
| 355 | tcp_congctl_global = new_tccp; |
| 356 | strlcpy(tcp_congctl_global_name, |
| 357 | new_tccp->congctl_name, |
| 358 | sizeof(tcp_congctl_global_name) - 1); |
| 359 | } |
| 360 | return 0; |
| 361 | } |
| 362 | } |
| 363 | |
| 364 | return EINVAL; |
| 365 | } |
| 366 | |
| 367 | void |
| 368 | tcp_congctl_release(struct tcpcb *tp) |
| 369 | { |
| 370 | struct tcp_congctlent *tccp; |
| 371 | |
| 372 | KASSERT(tp->t_congctl); |
| 373 | |
| 374 | TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) { |
| 375 | if (tccp->congctl_ctl == tp->t_congctl) { |
| 376 | tccp->congctl_refcnt--; |
| 377 | return; |
| 378 | } |
| 379 | } |
| 380 | } |
| 381 | |
| 382 | /* |
| 383 | * Returns the name of a congestion algorithm. |
| 384 | */ |
| 385 | const char * |
| 386 | tcp_congctl_bystruct(const struct tcp_congctl *tcc) |
| 387 | { |
| 388 | struct tcp_congctlent *tccp; |
| 389 | |
| 390 | KASSERT(tcc); |
| 391 | |
| 392 | TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) |
| 393 | if (tccp->congctl_ctl == tcc) |
| 394 | return tccp->congctl_name; |
| 395 | |
| 396 | return NULL; |
| 397 | } |
| 398 | |
| 399 | static void |
| 400 | tcp_congctl_fillnames(void) |
| 401 | { |
| 402 | struct tcp_congctlent *tccp; |
| 403 | const char *delim = " " ; |
| 404 | |
| 405 | tcp_congctl_avail[0] = '\0'; |
| 406 | TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) { |
| 407 | strlcat(tcp_congctl_avail, tccp->congctl_name, |
| 408 | sizeof(tcp_congctl_avail) - 1); |
| 409 | if (TAILQ_NEXT(tccp, congctl_ent)) |
| 410 | strlcat(tcp_congctl_avail, delim, |
| 411 | sizeof(tcp_congctl_avail) - 1); |
| 412 | } |
| 413 | |
| 414 | } |
| 415 | |
| 416 | /* ------------------------------------------------------------------------ */ |
| 417 | |
| 418 | /* |
| 419 | * Common stuff |
| 420 | */ |
| 421 | |
| 422 | /* Window reduction (1-beta) for [New]Reno: 0.5 */ |
| 423 | #define RENO_BETAA 1 |
| 424 | #define RENO_BETAB 2 |
| 425 | /* Window reduction (1-beta) for Cubic: 0.8 */ |
| 426 | #define CUBIC_BETAA 4 |
| 427 | #define CUBIC_BETAB 5 |
| 428 | /* Draft Rhee Section 4.1 */ |
| 429 | #define CUBIC_CA 4 |
| 430 | #define CUBIC_CB 10 |
| 431 | |
| 432 | static void |
| 433 | tcp_common_congestion_exp(struct tcpcb *tp, int betaa, int betab) |
| 434 | { |
| 435 | u_int win; |
| 436 | |
| 437 | /* |
| 438 | * Reduce the congestion window and the slow start threshold. |
| 439 | */ |
| 440 | win = min(tp->snd_wnd, tp->snd_cwnd) * betaa / betab / tp->t_segsz; |
| 441 | if (win < 2) |
| 442 | win = 2; |
| 443 | |
| 444 | tp->snd_ssthresh = win * tp->t_segsz; |
| 445 | tp->snd_recover = tp->snd_max; |
| 446 | tp->snd_cwnd = tp->snd_ssthresh; |
| 447 | |
| 448 | /* |
| 449 | * When using TCP ECN, notify the peer that |
| 450 | * we reduced the cwnd. |
| 451 | */ |
| 452 | if (TCP_ECN_ALLOWED(tp)) |
| 453 | tp->t_flags |= TF_ECN_SND_CWR; |
| 454 | } |
| 455 | |
| 456 | |
| 457 | /* ------------------------------------------------------------------------ */ |
| 458 | |
| 459 | /* |
| 460 | * TCP/Reno congestion control. |
| 461 | */ |
| 462 | static void |
| 463 | tcp_reno_congestion_exp(struct tcpcb *tp) |
| 464 | { |
| 465 | |
| 466 | tcp_common_congestion_exp(tp, RENO_BETAA, RENO_BETAB); |
| 467 | } |
| 468 | |
| 469 | static int |
| 470 | tcp_reno_do_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th) |
| 471 | { |
| 472 | /* |
| 473 | * Dup acks mean that packets have left the |
| 474 | * network (they're now cached at the receiver) |
| 475 | * so bump cwnd by the amount in the receiver |
| 476 | * to keep a constant cwnd packets in the |
| 477 | * network. |
| 478 | * |
| 479 | * If we are using TCP/SACK, then enter |
| 480 | * Fast Recovery if the receiver SACKs |
| 481 | * data that is tcprexmtthresh * MSS |
| 482 | * bytes past the last ACKed segment, |
| 483 | * irrespective of the number of DupAcks. |
| 484 | */ |
| 485 | |
| 486 | tcp_seq onxt = tp->snd_nxt; |
| 487 | |
| 488 | tp->t_partialacks = 0; |
| 489 | TCP_TIMER_DISARM(tp, TCPT_REXMT); |
| 490 | tp->t_rtttime = 0; |
| 491 | if (TCP_SACK_ENABLED(tp)) { |
| 492 | tp->t_dupacks = tcprexmtthresh; |
| 493 | tp->sack_newdata = tp->snd_nxt; |
| 494 | tp->snd_cwnd = tp->t_segsz; |
| 495 | (void) tcp_output(tp); |
| 496 | return 0; |
| 497 | } |
| 498 | tp->snd_nxt = th->th_ack; |
| 499 | tp->snd_cwnd = tp->t_segsz; |
| 500 | (void) tcp_output(tp); |
| 501 | tp->snd_cwnd = tp->snd_ssthresh + tp->t_segsz * tp->t_dupacks; |
| 502 | if (SEQ_GT(onxt, tp->snd_nxt)) |
| 503 | tp->snd_nxt = onxt; |
| 504 | |
| 505 | return 0; |
| 506 | } |
| 507 | |
| 508 | static int |
| 509 | tcp_reno_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th) |
| 510 | { |
| 511 | |
| 512 | /* |
| 513 | * We know we're losing at the current |
| 514 | * window size so do congestion avoidance |
| 515 | * (set ssthresh to half the current window |
| 516 | * and pull our congestion window back to |
| 517 | * the new ssthresh). |
| 518 | */ |
| 519 | |
| 520 | tcp_reno_congestion_exp(tp); |
| 521 | return tcp_reno_do_fast_retransmit(tp, th); |
| 522 | } |
| 523 | |
| 524 | static void |
| 525 | tcp_reno_slow_retransmit(struct tcpcb *tp) |
| 526 | { |
| 527 | u_int win; |
| 528 | |
| 529 | /* |
| 530 | * Close the congestion window down to one segment |
| 531 | * (we'll open it by one segment for each ack we get). |
| 532 | * Since we probably have a window's worth of unacked |
| 533 | * data accumulated, this "slow start" keeps us from |
| 534 | * dumping all that data as back-to-back packets (which |
| 535 | * might overwhelm an intermediate gateway). |
| 536 | * |
| 537 | * There are two phases to the opening: Initially we |
| 538 | * open by one mss on each ack. This makes the window |
| 539 | * size increase exponentially with time. If the |
| 540 | * window is larger than the path can handle, this |
| 541 | * exponential growth results in dropped packet(s) |
| 542 | * almost immediately. To get more time between |
| 543 | * drops but still "push" the network to take advantage |
| 544 | * of improving conditions, we switch from exponential |
| 545 | * to linear window opening at some threshhold size. |
| 546 | * For a threshhold, we use half the current window |
| 547 | * size, truncated to a multiple of the mss. |
| 548 | * |
| 549 | * (the minimum cwnd that will give us exponential |
| 550 | * growth is 2 mss. We don't allow the threshhold |
| 551 | * to go below this.) |
| 552 | */ |
| 553 | |
| 554 | win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz; |
| 555 | if (win < 2) |
| 556 | win = 2; |
| 557 | /* Loss Window MUST be one segment. */ |
| 558 | tp->snd_cwnd = tp->t_segsz; |
| 559 | tp->snd_ssthresh = win * tp->t_segsz; |
| 560 | tp->t_partialacks = -1; |
| 561 | tp->t_dupacks = 0; |
| 562 | tp->t_bytes_acked = 0; |
| 563 | |
| 564 | if (TCP_ECN_ALLOWED(tp)) |
| 565 | tp->t_flags |= TF_ECN_SND_CWR; |
| 566 | } |
| 567 | |
| 568 | static void |
| 569 | tcp_reno_fast_retransmit_newack(struct tcpcb *tp, |
| 570 | const struct tcphdr *th) |
| 571 | { |
| 572 | if (tp->t_partialacks < 0) { |
| 573 | /* |
| 574 | * We were not in fast recovery. Reset the duplicate ack |
| 575 | * counter. |
| 576 | */ |
| 577 | tp->t_dupacks = 0; |
| 578 | } else { |
| 579 | /* |
| 580 | * Clamp the congestion window to the crossover point and |
| 581 | * exit fast recovery. |
| 582 | */ |
| 583 | if (tp->snd_cwnd > tp->snd_ssthresh) |
| 584 | tp->snd_cwnd = tp->snd_ssthresh; |
| 585 | tp->t_partialacks = -1; |
| 586 | tp->t_dupacks = 0; |
| 587 | tp->t_bytes_acked = 0; |
| 588 | if (TCP_SACK_ENABLED(tp) && SEQ_GT(th->th_ack, tp->snd_fack)) |
| 589 | tp->snd_fack = th->th_ack; |
| 590 | } |
| 591 | } |
| 592 | |
| 593 | static void |
| 594 | tcp_reno_newack(struct tcpcb *tp, const struct tcphdr *th) |
| 595 | { |
| 596 | /* |
| 597 | * When new data is acked, open the congestion window. |
| 598 | */ |
| 599 | |
| 600 | u_int cw = tp->snd_cwnd; |
| 601 | u_int incr = tp->t_segsz; |
| 602 | |
| 603 | if (tcp_do_abc) { |
| 604 | |
| 605 | /* |
| 606 | * RFC 3465 Appropriate Byte Counting (ABC) |
| 607 | */ |
| 608 | |
| 609 | int acked = th->th_ack - tp->snd_una; |
| 610 | |
| 611 | if (cw >= tp->snd_ssthresh) { |
| 612 | tp->t_bytes_acked += acked; |
| 613 | if (tp->t_bytes_acked >= cw) { |
| 614 | /* Time to increase the window. */ |
| 615 | tp->t_bytes_acked -= cw; |
| 616 | } else { |
| 617 | /* No need to increase yet. */ |
| 618 | incr = 0; |
| 619 | } |
| 620 | } else { |
| 621 | /* |
| 622 | * use 2*SMSS or 1*SMSS for the "L" param, |
| 623 | * depending on sysctl setting. |
| 624 | * |
| 625 | * (See RFC 3465 2.3 Choosing the Limit) |
| 626 | */ |
| 627 | u_int abc_lim; |
| 628 | |
| 629 | abc_lim = (tcp_abc_aggressive == 0 || |
| 630 | tp->snd_nxt != tp->snd_max) ? incr : incr * 2; |
| 631 | incr = min(acked, abc_lim); |
| 632 | } |
| 633 | } else { |
| 634 | |
| 635 | /* |
| 636 | * If the window gives us less than ssthresh packets |
| 637 | * in flight, open exponentially (segsz per packet). |
| 638 | * Otherwise open linearly: segsz per window |
| 639 | * (segsz^2 / cwnd per packet). |
| 640 | */ |
| 641 | |
| 642 | if (cw >= tp->snd_ssthresh) { |
| 643 | incr = incr * incr / cw; |
| 644 | } |
| 645 | } |
| 646 | |
| 647 | tp->snd_cwnd = min(cw + incr, TCP_MAXWIN << tp->snd_scale); |
| 648 | } |
| 649 | |
| 650 | const struct tcp_congctl tcp_reno_ctl = { |
| 651 | .fast_retransmit = tcp_reno_fast_retransmit, |
| 652 | .slow_retransmit = tcp_reno_slow_retransmit, |
| 653 | .fast_retransmit_newack = tcp_reno_fast_retransmit_newack, |
| 654 | .newack = tcp_reno_newack, |
| 655 | .cong_exp = tcp_reno_congestion_exp, |
| 656 | }; |
| 657 | |
| 658 | /* |
| 659 | * TCP/NewReno Congestion control. |
| 660 | */ |
| 661 | static int |
| 662 | tcp_newreno_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th) |
| 663 | { |
| 664 | |
| 665 | if (SEQ_LT(th->th_ack, tp->snd_high)) { |
| 666 | /* |
| 667 | * False fast retransmit after timeout. |
| 668 | * Do not enter fast recovery |
| 669 | */ |
| 670 | tp->t_dupacks = 0; |
| 671 | return 1; |
| 672 | } |
| 673 | /* |
| 674 | * Fast retransmit is same as reno. |
| 675 | */ |
| 676 | return tcp_reno_fast_retransmit(tp, th); |
| 677 | } |
| 678 | |
| 679 | /* |
| 680 | * Implement the NewReno response to a new ack, checking for partial acks in |
| 681 | * fast recovery. |
| 682 | */ |
| 683 | static void |
| 684 | tcp_newreno_fast_retransmit_newack(struct tcpcb *tp, const struct tcphdr *th) |
| 685 | { |
| 686 | if (tp->t_partialacks < 0) { |
| 687 | /* |
| 688 | * We were not in fast recovery. Reset the duplicate ack |
| 689 | * counter. |
| 690 | */ |
| 691 | tp->t_dupacks = 0; |
| 692 | } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { |
| 693 | /* |
| 694 | * This is a partial ack. Retransmit the first unacknowledged |
| 695 | * segment and deflate the congestion window by the amount of |
| 696 | * acknowledged data. Do not exit fast recovery. |
| 697 | */ |
| 698 | tcp_seq onxt = tp->snd_nxt; |
| 699 | u_long ocwnd = tp->snd_cwnd; |
| 700 | int sack_num_segs = 1, sack_bytes_rxmt = 0; |
| 701 | |
| 702 | /* |
| 703 | * snd_una has not yet been updated and the socket's send |
| 704 | * buffer has not yet drained off the ACK'd data, so we |
| 705 | * have to leave snd_una as it was to get the correct data |
| 706 | * offset in tcp_output(). |
| 707 | */ |
| 708 | tp->t_partialacks++; |
| 709 | TCP_TIMER_DISARM(tp, TCPT_REXMT); |
| 710 | tp->t_rtttime = 0; |
| 711 | tp->snd_nxt = th->th_ack; |
| 712 | |
| 713 | if (TCP_SACK_ENABLED(tp)) { |
| 714 | /* |
| 715 | * Partial ack handling within a sack recovery episode. |
| 716 | * Keeping this very simple for now. When a partial ack |
| 717 | * is received, force snd_cwnd to a value that will |
| 718 | * allow the sender to transmit no more than 2 segments. |
| 719 | * If necessary, a fancier scheme can be adopted at a |
| 720 | * later point, but for now, the goal is to prevent the |
| 721 | * sender from bursting a large amount of data in the |
| 722 | * midst of sack recovery. |
| 723 | */ |
| 724 | |
| 725 | /* |
| 726 | * send one or 2 segments based on how much |
| 727 | * new data was acked |
| 728 | */ |
| 729 | if (((th->th_ack - tp->snd_una) / tp->t_segsz) > 2) |
| 730 | sack_num_segs = 2; |
| 731 | (void)tcp_sack_output(tp, &sack_bytes_rxmt); |
| 732 | tp->snd_cwnd = sack_bytes_rxmt + |
| 733 | (tp->snd_nxt - tp->sack_newdata) + |
| 734 | sack_num_segs * tp->t_segsz; |
| 735 | tp->t_flags |= TF_ACKNOW; |
| 736 | (void) tcp_output(tp); |
| 737 | } else { |
| 738 | /* |
| 739 | * Set snd_cwnd to one segment beyond ACK'd offset |
| 740 | * snd_una is not yet updated when we're called |
| 741 | */ |
| 742 | tp->snd_cwnd = tp->t_segsz + (th->th_ack - tp->snd_una); |
| 743 | (void) tcp_output(tp); |
| 744 | tp->snd_cwnd = ocwnd; |
| 745 | if (SEQ_GT(onxt, tp->snd_nxt)) |
| 746 | tp->snd_nxt = onxt; |
| 747 | /* |
| 748 | * Partial window deflation. Relies on fact that |
| 749 | * tp->snd_una not updated yet. |
| 750 | */ |
| 751 | tp->snd_cwnd -= (th->th_ack - tp->snd_una - |
| 752 | tp->t_segsz); |
| 753 | } |
| 754 | } else { |
| 755 | /* |
| 756 | * Complete ack. Inflate the congestion window to ssthresh |
| 757 | * and exit fast recovery. |
| 758 | * |
| 759 | * Window inflation should have left us with approx. |
| 760 | * snd_ssthresh outstanding data. But in case we |
| 761 | * would be inclined to send a burst, better to do |
| 762 | * it via the slow start mechanism. |
| 763 | */ |
| 764 | if (SEQ_SUB(tp->snd_max, th->th_ack) < tp->snd_ssthresh) |
| 765 | tp->snd_cwnd = SEQ_SUB(tp->snd_max, th->th_ack) |
| 766 | + tp->t_segsz; |
| 767 | else |
| 768 | tp->snd_cwnd = tp->snd_ssthresh; |
| 769 | tp->t_partialacks = -1; |
| 770 | tp->t_dupacks = 0; |
| 771 | tp->t_bytes_acked = 0; |
| 772 | if (TCP_SACK_ENABLED(tp) && SEQ_GT(th->th_ack, tp->snd_fack)) |
| 773 | tp->snd_fack = th->th_ack; |
| 774 | } |
| 775 | } |
| 776 | |
| 777 | static void |
| 778 | tcp_newreno_newack(struct tcpcb *tp, const struct tcphdr *th) |
| 779 | { |
| 780 | /* |
| 781 | * If we are still in fast recovery (meaning we are using |
| 782 | * NewReno and we have only received partial acks), do not |
| 783 | * inflate the window yet. |
| 784 | */ |
| 785 | if (tp->t_partialacks < 0) |
| 786 | tcp_reno_newack(tp, th); |
| 787 | } |
| 788 | |
| 789 | |
| 790 | const struct tcp_congctl tcp_newreno_ctl = { |
| 791 | .fast_retransmit = tcp_newreno_fast_retransmit, |
| 792 | .slow_retransmit = tcp_reno_slow_retransmit, |
| 793 | .fast_retransmit_newack = tcp_newreno_fast_retransmit_newack, |
| 794 | .newack = tcp_newreno_newack, |
| 795 | .cong_exp = tcp_reno_congestion_exp, |
| 796 | }; |
| 797 | |
| 798 | /* |
| 799 | * CUBIC - http://tools.ietf.org/html/draft-rhee-tcpm-cubic-02 |
| 800 | */ |
| 801 | |
| 802 | /* Cubic prototypes */ |
| 803 | static void tcp_cubic_update_ctime(struct tcpcb *tp); |
| 804 | static uint32_t tcp_cubic_diff_ctime(struct tcpcb *); |
| 805 | static uint32_t tcp_cubic_cbrt(uint32_t); |
| 806 | static ulong tcp_cubic_getW(struct tcpcb *, uint32_t, uint32_t); |
| 807 | |
| 808 | /* Cubic TIME functions - XXX I don't like using timevals and microuptime */ |
| 809 | /* |
| 810 | * Set congestion timer to now |
| 811 | */ |
| 812 | static void |
| 813 | tcp_cubic_update_ctime(struct tcpcb *tp) |
| 814 | { |
| 815 | struct timeval now_timeval; |
| 816 | |
| 817 | getmicrouptime(&now_timeval); |
| 818 | tp->snd_cubic_ctime = now_timeval.tv_sec * 1000 + |
| 819 | now_timeval.tv_usec / 1000; |
| 820 | } |
| 821 | |
| 822 | /* |
| 823 | * miliseconds from last congestion |
| 824 | */ |
| 825 | static uint32_t |
| 826 | tcp_cubic_diff_ctime(struct tcpcb *tp) |
| 827 | { |
| 828 | struct timeval now_timeval; |
| 829 | |
| 830 | getmicrouptime(&now_timeval); |
| 831 | return now_timeval.tv_sec * 1000 + now_timeval.tv_usec / 1000 - |
| 832 | tp->snd_cubic_ctime; |
| 833 | } |
| 834 | |
| 835 | /* |
| 836 | * Approximate cubic root |
| 837 | */ |
| 838 | #define CBRT_ROUNDS 30 |
| 839 | static uint32_t |
| 840 | tcp_cubic_cbrt(uint32_t v) |
| 841 | { |
| 842 | int i, rounds = CBRT_ROUNDS; |
| 843 | uint64_t x = v / 3; |
| 844 | |
| 845 | /* We fail to calculate correct for small numbers */ |
| 846 | if (v == 0) |
| 847 | return 0; |
| 848 | else if (v < 4) |
| 849 | return 1; |
| 850 | |
| 851 | /* |
| 852 | * largest x that 2*x^3+3*x fits 64bit |
| 853 | * Avoid overflow for a time cost |
| 854 | */ |
| 855 | if (x > 2097151) |
| 856 | rounds += 10; |
| 857 | |
| 858 | for (i = 0; i < rounds; i++) |
| 859 | if (rounds == CBRT_ROUNDS) |
| 860 | x = (v + 2 * x * x * x) / (3 * x * x); |
| 861 | else |
| 862 | /* Avoid overflow */ |
| 863 | x = v / (3 * x * x) + 2 * x / 3; |
| 864 | |
| 865 | return (uint32_t)x; |
| 866 | } |
| 867 | |
| 868 | /* Draft Rhee Section 3.1 - get W(t+rtt) - Eq. 1 */ |
| 869 | static ulong |
| 870 | tcp_cubic_getW(struct tcpcb *tp, uint32_t ms_elapsed, uint32_t rtt) |
| 871 | { |
| 872 | uint32_t K; |
| 873 | long tK3; |
| 874 | |
| 875 | /* Section 3.1 Eq. 2 */ |
| 876 | K = tcp_cubic_cbrt(tp->snd_cubic_wmax / CUBIC_BETAB * |
| 877 | CUBIC_CB / CUBIC_CA); |
| 878 | /* (t-K)^3 - not clear why is the measure unit mattering */ |
| 879 | tK3 = (long)(ms_elapsed + rtt) - (long)K; |
| 880 | tK3 = tK3 * tK3 * tK3; |
| 881 | |
| 882 | return CUBIC_CA * tK3 / CUBIC_CB + tp->snd_cubic_wmax; |
| 883 | } |
| 884 | |
| 885 | static void |
| 886 | tcp_cubic_congestion_exp(struct tcpcb *tp) |
| 887 | { |
| 888 | |
| 889 | /* |
| 890 | * Congestion - Set WMax and shrink cwnd |
| 891 | */ |
| 892 | tcp_cubic_update_ctime(tp); |
| 893 | |
| 894 | /* Section 3.6 - Fast Convergence */ |
| 895 | if (tp->snd_cubic_wmax < tp->snd_cubic_wmax_last) { |
| 896 | tp->snd_cubic_wmax_last = tp->snd_cubic_wmax; |
| 897 | tp->snd_cubic_wmax = tp->snd_cubic_wmax / 2 + |
| 898 | tp->snd_cubic_wmax * CUBIC_BETAA / CUBIC_BETAB / 2; |
| 899 | } else { |
| 900 | tp->snd_cubic_wmax_last = tp->snd_cubic_wmax; |
| 901 | tp->snd_cubic_wmax = tp->snd_cwnd; |
| 902 | } |
| 903 | |
| 904 | tp->snd_cubic_wmax = max(tp->t_segsz, tp->snd_cubic_wmax); |
| 905 | |
| 906 | /* Shrink CWND */ |
| 907 | tcp_common_congestion_exp(tp, CUBIC_BETAA, CUBIC_BETAB); |
| 908 | } |
| 909 | |
| 910 | static int |
| 911 | tcp_cubic_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th) |
| 912 | { |
| 913 | |
| 914 | if (SEQ_LT(th->th_ack, tp->snd_high)) { |
| 915 | /* See newreno */ |
| 916 | tp->t_dupacks = 0; |
| 917 | return 1; |
| 918 | } |
| 919 | |
| 920 | /* |
| 921 | * mark WMax |
| 922 | */ |
| 923 | tcp_cubic_congestion_exp(tp); |
| 924 | |
| 925 | /* Do fast retransmit */ |
| 926 | return tcp_reno_do_fast_retransmit(tp, th); |
| 927 | } |
| 928 | |
| 929 | static void |
| 930 | tcp_cubic_newack(struct tcpcb *tp, const struct tcphdr *th) |
| 931 | { |
| 932 | uint32_t ms_elapsed, rtt; |
| 933 | u_long w_tcp; |
| 934 | |
| 935 | /* Congestion avoidance and not in fast recovery and usable rtt */ |
| 936 | if (tp->snd_cwnd > tp->snd_ssthresh && tp->t_partialacks < 0 && |
| 937 | /* |
| 938 | * t_srtt is 1/32 units of slow ticks |
| 939 | * converting it in ms would be equal to |
| 940 | * (t_srtt >> 5) * 1000 / PR_SLOWHZ ~= (t_srtt << 5) / PR_SLOWHZ |
| 941 | */ |
| 942 | (rtt = (tp->t_srtt << 5) / PR_SLOWHZ) > 0) { |
| 943 | ms_elapsed = tcp_cubic_diff_ctime(tp); |
| 944 | |
| 945 | /* Compute W_tcp(t) */ |
| 946 | w_tcp = tp->snd_cubic_wmax * CUBIC_BETAA / CUBIC_BETAB + |
| 947 | ms_elapsed / rtt / 3; |
| 948 | |
| 949 | if (tp->snd_cwnd > w_tcp) { |
| 950 | /* Not in TCP friendly mode */ |
| 951 | tp->snd_cwnd += (tcp_cubic_getW(tp, ms_elapsed, rtt) - |
| 952 | tp->snd_cwnd) / tp->snd_cwnd; |
| 953 | } else { |
| 954 | /* friendly TCP mode */ |
| 955 | tp->snd_cwnd = w_tcp; |
| 956 | } |
| 957 | |
| 958 | /* Make sure we are within limits */ |
| 959 | tp->snd_cwnd = max(tp->snd_cwnd, tp->t_segsz); |
| 960 | tp->snd_cwnd = min(tp->snd_cwnd, TCP_MAXWIN << tp->snd_scale); |
| 961 | } else { |
| 962 | /* Use New Reno */ |
| 963 | tcp_newreno_newack(tp, th); |
| 964 | } |
| 965 | } |
| 966 | |
| 967 | static void |
| 968 | tcp_cubic_slow_retransmit(struct tcpcb *tp) |
| 969 | { |
| 970 | |
| 971 | /* Timeout - Mark new congestion */ |
| 972 | tcp_cubic_congestion_exp(tp); |
| 973 | |
| 974 | /* Loss Window MUST be one segment. */ |
| 975 | tp->snd_cwnd = tp->t_segsz; |
| 976 | tp->t_partialacks = -1; |
| 977 | tp->t_dupacks = 0; |
| 978 | tp->t_bytes_acked = 0; |
| 979 | |
| 980 | if (TCP_ECN_ALLOWED(tp)) |
| 981 | tp->t_flags |= TF_ECN_SND_CWR; |
| 982 | } |
| 983 | |
| 984 | const struct tcp_congctl tcp_cubic_ctl = { |
| 985 | .fast_retransmit = tcp_cubic_fast_retransmit, |
| 986 | .slow_retransmit = tcp_cubic_slow_retransmit, |
| 987 | .fast_retransmit_newack = tcp_newreno_fast_retransmit_newack, |
| 988 | .newack = tcp_cubic_newack, |
| 989 | .cong_exp = tcp_cubic_congestion_exp, |
| 990 | }; |
| 991 | |