bsd/netinet/tcp_cc.c

   1 /*
   2  * Copyright (c) 2013-2014 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 #include <sys/param.h>
  30 #include <sys/systm.h>
  31 #include <sys/kernel.h>
  32 #include <sys/syslog.h>
  33 #include <sys/protosw.h>
  34 #include <sys/socketvar.h>
  35 #include <sys/kern_control.h>
  36 #include <sys/domain.h>
  37
  38 #include <netinet/in.h>
  39 #include <netinet/tcp.h>
  40 #include <netinet/tcp_var.h>
  41 #include <netinet/tcp_cc.h>
  42 #include <mach/sdt.h>
  43 #include <libkern/OSAtomic.h>
  44
  45 struct tcp_cc_debug_state {
  46         u_int64_t ccd_tsns;
  47         char ccd_srcaddr[INET6_ADDRSTRLEN];
  48         uint16_t ccd_srcport;
  49         char ccd_destaddr[INET6_ADDRSTRLEN];
  50         uint16_t ccd_destport;
  51         uint32_t ccd_snd_cwnd;
  52         uint32_t ccd_snd_wnd;
  53         uint32_t ccd_snd_ssthresh;
  54         uint32_t ccd_pipeack;
  55         uint32_t ccd_rttcur;
  56         uint32_t ccd_rxtcur;
  57         uint32_t ccd_srtt;
  58         uint32_t ccd_event;
  59         uint32_t ccd_sndcc;
  60         uint32_t ccd_sndhiwat;
  61         uint32_t ccd_bytes_acked;
  62         u_int8_t ccd_cc_index;
  63         u_int8_t ccd_unused_1__;
  64         u_int16_t ccd_unused_2__;
  65         union {
  66                 struct {
  67                         uint32_t ccd_last_max;
  68                         uint32_t ccd_tcp_win;
  69                         uint32_t ccd_target_win;
  70                         uint32_t ccd_avg_lastmax;
  71                         uint32_t ccd_mean_deviation;
  72                 } cubic_state;
  73                 struct {
  74                         u_int32_t led_base_rtt;
  75                 } ledbat_state;
  76         } u;
  77 };
  78
  79 int tcp_cc_debug = 0;
  80 SYSCTL_INT(_net_inet_tcp, OID_AUTO, cc_debug, CTLFLAG_RW | CTLFLAG_LOCKED,
  81         &tcp_cc_debug, 0, "Enable debug data collection");
  82
  83 extern struct tcp_cc_algo tcp_cc_newreno;
  84 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno_sockets,
  85         CTLFLAG_RD | CTLFLAG_LOCKED, &tcp_cc_newreno.num_sockets,
  86         0, "Number of sockets using newreno");
  87
  88 extern struct tcp_cc_algo tcp_cc_ledbat;
  89 SYSCTL_INT(_net_inet_tcp, OID_AUTO, background_sockets,
  90         CTLFLAG_RD | CTLFLAG_LOCKED, &tcp_cc_ledbat.num_sockets,
  91         0, "Number of sockets using background transport");
  92
  93 extern struct tcp_cc_algo tcp_cc_cubic;
  94 SYSCTL_INT(_net_inet_tcp, OID_AUTO, cubic_sockets,
  95         CTLFLAG_RD | CTLFLAG_LOCKED,&tcp_cc_cubic.num_sockets,
  96         0, "Number of sockets using cubic");
  97
  98 int tcp_use_newreno = 0;
  99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, use_newreno,
 100         CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_use_newreno, 0,
 101         "Use TCP NewReno by default");
 102
 103 static int tcp_check_cwnd_nonvalidated = 1;
 104 #if (DEBUG || DEVELOPMENT)
 105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, cwnd_nonvalidated,
 106     CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_check_cwnd_nonvalidated, 0,
 107     "Check if congestion window is non-validated");
 108 #endif /* (DEBUG || DEVELOPMENT) */
 109
 110  #define SET_SNDSB_IDEAL_SIZE(sndsb, size) \
 111         sndsb->sb_idealsize = min(max(tcp_sendspace, tp->snd_ssthresh), \
 112         tcp_autosndbuf_max);
 113
 114 /* Array containing pointers to currently implemented TCP CC algorithms */
 115 struct tcp_cc_algo* tcp_cc_algo_list[TCP_CC_ALGO_COUNT];
 116 struct zone *tcp_cc_zone;
 117
 118 /* Information for colelcting TCP debug information using control socket */
 119 #define TCP_CCDEBUG_CONTROL_NAME "com.apple.network.tcp_ccdebug"
 120 #define TCP_CCDBG_NOUNIT 0xffffffff
 121 static kern_ctl_ref tcp_ccdbg_ctlref = NULL;
 122 volatile UInt32 tcp_ccdbg_unit = TCP_CCDBG_NOUNIT;
 123
 124 void tcp_cc_init(void);
 125 static void tcp_cc_control_register(void);
 126 static errno_t tcp_ccdbg_control_connect(kern_ctl_ref kctl,
 127         struct sockaddr_ctl *sac, void **uinfo);
 128 static errno_t tcp_ccdbg_control_disconnect(kern_ctl_ref kctl,
 129         u_int32_t unit, void *uinfo);
 130 static struct tcp_cc_algo tcp_cc_algo_none;
 131 /*
 132  * Initialize TCP congestion control algorithms.
 133  */
 134
 135 void
 136 tcp_cc_init(void)
 137 {
 138         bzero(&tcp_cc_algo_list, sizeof(tcp_cc_algo_list));
 139         bzero(&tcp_cc_algo_none, sizeof(tcp_cc_algo_none));
 140
 141         tcp_cc_algo_list[TCP_CC_ALGO_NONE] = &tcp_cc_algo_none;
 142         tcp_cc_algo_list[TCP_CC_ALGO_NEWRENO_INDEX] = &tcp_cc_newreno;
 143         tcp_cc_algo_list[TCP_CC_ALGO_BACKGROUND_INDEX] = &tcp_cc_ledbat;
 144         tcp_cc_algo_list[TCP_CC_ALGO_CUBIC_INDEX] = &tcp_cc_cubic;
 145
 146         tcp_cc_control_register();
 147 }
 148
 149 static void
 150 tcp_cc_control_register(void)
 151 {
 152         struct kern_ctl_reg ccdbg_control;
 153         errno_t err;
 154
 155         bzero(&ccdbg_control, sizeof(ccdbg_control));
 156         strlcpy(ccdbg_control.ctl_name, TCP_CCDEBUG_CONTROL_NAME,
 157             sizeof(ccdbg_control.ctl_name));
 158         ccdbg_control.ctl_connect = tcp_ccdbg_control_connect;
 159         ccdbg_control.ctl_disconnect = tcp_ccdbg_control_disconnect;
 160         ccdbg_control.ctl_flags |= CTL_FLAG_PRIVILEGED;
 161         ccdbg_control.ctl_flags |= CTL_FLAG_REG_SOCK_STREAM;
 162
 163         err = ctl_register(&ccdbg_control, &tcp_ccdbg_ctlref);
 164         if (err != 0) {
 165                 log(LOG_ERR, "failed to register tcp_cc debug control");
 166         }
 167 }
 168
 169 /* Allow only one socket to connect at any time for debugging */
 170 static errno_t
 171 tcp_ccdbg_control_connect(kern_ctl_ref kctl, struct sockaddr_ctl *sac,
 172         void **uinfo)
 173 {
 174 #pragma unused(kctl)
 175 #pragma unused(uinfo)
 176
 177         UInt32 old_value = TCP_CCDBG_NOUNIT;
 178         UInt32 new_value = sac->sc_unit;
 179
 180         if (tcp_ccdbg_unit != old_value)
 181                 return (EALREADY);
 182
 183         if (OSCompareAndSwap(old_value, new_value, &tcp_ccdbg_unit))
 184                 return (0);
 185         else
 186                 return (EALREADY);
 187 }
 188
 189 static errno_t
 190 tcp_ccdbg_control_disconnect(kern_ctl_ref kctl, u_int32_t unit, void *uinfo)
 191 {
 192 #pragma unused(kctl, unit, uinfo)
 193
 194         if (unit == tcp_ccdbg_unit) {
 195                 UInt32 old_value = tcp_ccdbg_unit;
 196                 UInt32 new_value = TCP_CCDBG_NOUNIT;
 197                 if (tcp_ccdbg_unit == new_value)
 198                         return (0);
 199
 200                 if (!OSCompareAndSwap(old_value, new_value,
 201                         &tcp_ccdbg_unit))
 202                         log(LOG_DEBUG,
 203                             "failed to disconnect tcp_cc debug control");
 204         }
 205         return (0);
 206 }
 207
 208 inline void
 209 tcp_ccdbg_trace(struct tcpcb *tp, struct tcphdr *th, int32_t event)
 210 {
 211 #if !CONFIG_DTRACE
 212 #pragma unused(th)
 213 #endif /* !CONFIG_DTRACE */
 214         struct inpcb *inp = tp->t_inpcb;
 215
 216         if (tcp_cc_debug && tcp_ccdbg_unit > 0) {
 217                 struct tcp_cc_debug_state dbg_state;
 218                 struct timespec tv;
 219
 220                 bzero(&dbg_state, sizeof(dbg_state));
 221
 222                 nanotime(&tv);
 223                 /* Take time in seconds */
 224                 dbg_state.ccd_tsns = (tv.tv_sec * 1000000000) + tv.tv_nsec;
 225                 inet_ntop(SOCK_DOM(inp->inp_socket),
 226                     ((SOCK_DOM(inp->inp_socket) == PF_INET) ?
 227                     (void *)&inp->inp_laddr.s_addr :
 228                     (void *)&inp->in6p_laddr), dbg_state.ccd_srcaddr,
 229                     sizeof(dbg_state.ccd_srcaddr));
 230                 dbg_state.ccd_srcport = ntohs(inp->inp_lport);
 231                 inet_ntop(SOCK_DOM(inp->inp_socket),
 232                     ((SOCK_DOM(inp->inp_socket) == PF_INET) ?
 233                     (void *)&inp->inp_faddr.s_addr :
 234                     (void *)&inp->in6p_faddr), dbg_state.ccd_destaddr,
 235                     sizeof(dbg_state.ccd_destaddr));
 236                 dbg_state.ccd_destport = ntohs(inp->inp_fport);
 237
 238                 dbg_state.ccd_snd_cwnd = tp->snd_cwnd;
 239                 dbg_state.ccd_snd_wnd = tp->snd_wnd;
 240                 dbg_state.ccd_snd_ssthresh = tp->snd_ssthresh;
 241                 dbg_state.ccd_pipeack = tp->t_pipeack;
 242                 dbg_state.ccd_rttcur = tp->t_rttcur;
 243                 dbg_state.ccd_rxtcur = tp->t_rxtcur;
 244                 dbg_state.ccd_srtt = tp->t_srtt >> TCP_RTT_SHIFT;
 245                 dbg_state.ccd_event = event;
 246                 dbg_state.ccd_sndcc = inp->inp_socket->so_snd.sb_cc;
 247                 dbg_state.ccd_sndhiwat = inp->inp_socket->so_snd.sb_hiwat;
 248                 dbg_state.ccd_bytes_acked = tp->t_bytes_acked;
 249                 dbg_state.ccd_cc_index = tp->tcp_cc_index;
 250                 switch (tp->tcp_cc_index) {
 251                     case TCP_CC_ALGO_CUBIC_INDEX:
 252                         dbg_state.u.cubic_state.ccd_last_max =
 253                             tp->t_ccstate->cub_last_max;
 254                         dbg_state.u.cubic_state.ccd_tcp_win =
 255                             tp->t_ccstate->cub_tcp_win;
 256                         dbg_state.u.cubic_state.ccd_target_win =
 257                             tp->t_ccstate->cub_target_win;
 258                         dbg_state.u.cubic_state.ccd_avg_lastmax =
 259                             tp->t_ccstate->cub_avg_lastmax;
 260                         dbg_state.u.cubic_state.ccd_mean_deviation =
 261                             tp->t_ccstate->cub_mean_dev;
 262                         break;
 263                     case TCP_CC_ALGO_BACKGROUND_INDEX:
 264                         dbg_state.u.ledbat_state.led_base_rtt =
 265                             get_base_rtt(tp);
 266                         break;
 267                     default:
 268                         break;
 269                 }
 270
 271                 ctl_enqueuedata(tcp_ccdbg_ctlref, tcp_ccdbg_unit,
 272                         &dbg_state, sizeof(dbg_state), 0);
 273         }
 274         DTRACE_TCP5(cc, void, NULL, struct inpcb *, inp,
 275                 struct tcpcb *, tp, struct tcphdr *, th, int32_t, event);
 276 }
 277
 278 void tcp_cc_resize_sndbuf(struct tcpcb *tp)
 279 {
 280         struct sockbuf *sb;
 281         /*
 282          * If the send socket buffer size is bigger than ssthresh,
 283          * it is time to trim it because we do not want to hold
 284          * too many mbufs in the socket buffer
 285          */
 286         sb = &tp->t_inpcb->inp_socket->so_snd;
 287         if (sb->sb_hiwat > tp->snd_ssthresh &&
 288                 (sb->sb_flags & SB_AUTOSIZE)) {
 289                 if (sb->sb_idealsize > tp->snd_ssthresh) {
 290                         SET_SNDSB_IDEAL_SIZE(sb, tp->snd_ssthresh);
 291                 }
 292                 sb->sb_flags |= SB_TRIM;
 293         }
 294 }
 295
 296 void tcp_bad_rexmt_fix_sndbuf(struct tcpcb *tp)
 297 {
 298         struct sockbuf *sb;
 299         sb = &tp->t_inpcb->inp_socket->so_snd;
 300         if ((sb->sb_flags & (SB_TRIM|SB_AUTOSIZE)) == (SB_TRIM|SB_AUTOSIZE)) {
 301                 /*
 302                  * If there was a retransmission that was not necessary
 303                  * then the size of socket buffer can be restored to
 304                  * what it was before
 305                  */
 306                 SET_SNDSB_IDEAL_SIZE(sb, tp->snd_ssthresh);
 307                 if (sb->sb_hiwat <= sb->sb_idealsize) {
 308                         sbreserve(sb, sb->sb_idealsize);
 309                         sb->sb_flags &= ~SB_TRIM;
 310                 }
 311         }
 312 }
 313
 314 /*
 315  * Calculate initial cwnd according to RFC3390.
 316  *
 317  * Keep the old ss_fltsz sysctl for ABI compabitility issues.
 318  * but it will be overriden if tcp_do_rfc3390 sysctl when it is set.
 319  */
 320 void
 321 tcp_cc_cwnd_init_or_reset(struct tcpcb *tp)
 322 {
 323         if (tp->t_flags & TF_LOCAL) {
 324                 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local;
 325         } else {
 326                 /* initial congestion window according to RFC 3390 */
 327                 if (tcp_do_rfc3390)
 328                         tp->snd_cwnd = min(4 * tp->t_maxseg,
 329                                 max(2 * tp->t_maxseg, TCP_CC_CWND_INIT_BYTES));
 330                 else
 331                         tp->snd_cwnd = tp->t_maxseg * ss_fltsz;
 332         }
 333 }
 334
 335 /*
 336  * Indicate whether this ack should be delayed.
 337  * Here is the explanation for different settings of tcp_delack_enabled:
 338  *  - when set to 1, the bhavior is same as when set to 2. We kept this
 339  *    for binary compatibility.
 340  *  - when set to 2, will "ack every other packet"
 341  *      - if our last ack wasn't a 0-sized window.
 342  *      - if the peer hasn't sent us a TH_PUSH data packet (radar 3649245).
 343  *              If TH_PUSH is set, take this as a clue that we need to ACK
 344  *              with no delay. This helps higher level protocols who
 345  *              won't send us more data even if the window is open
 346  *              because their last "segment" hasn't been ACKed
 347  *  - when set to 3,  will do "streaming detection"
 348  *      - if we receive more than "maxseg_unacked" full packets
 349  *        in the last 100ms
 350  *      - if the connection is not in slow-start or idle or
 351  *        loss/recovery states
 352  *      - if those criteria aren't met, it will ack every other packet.
 353  */
 354 int
 355 tcp_cc_delay_ack(struct tcpcb *tp, struct tcphdr *th)
 356 {
 357         switch (tcp_delack_enabled) {
 358             case 1:
 359             case 2:
 360                 if ((tp->t_flags & TF_RXWIN0SENT) == 0 &&
 361                     (th->th_flags & TH_PUSH) == 0 &&
 362                     (tp->t_unacksegs == 1))
 363                         return(1);
 364                 break;
 365             case 3:
 366                 if ((tp->t_flags & TF_RXWIN0SENT) == 0 &&
 367                     (th->th_flags & TH_PUSH) == 0 &&
 368                     ((tp->t_unacksegs == 1) ||
 369                     ((tp->t_flags & TF_STRETCHACK) != 0 &&
 370                         tp->t_unacksegs < (maxseg_unacked))))
 371                         return(1);
 372                 break;
 373         }
 374         return(0);
 375 }
 376
 377 void
 378 tcp_cc_allocate_state(struct tcpcb *tp)
 379 {
 380         if (tp->tcp_cc_index == TCP_CC_ALGO_CUBIC_INDEX &&
 381                 tp->t_ccstate == NULL) {
 382                 tp->t_ccstate = (struct tcp_ccstate *)zalloc(tcp_cc_zone);
 383
 384                 /*
 385                  * If we could not allocate memory for congestion control
 386                  * state, revert to using TCP NewReno as it does not
 387                  * require any state
 388                  */
 389                 if (tp->t_ccstate == NULL)
 390                         tp->tcp_cc_index = TCP_CC_ALGO_NEWRENO_INDEX;
 391                 else
 392                         bzero(tp->t_ccstate, sizeof(*tp->t_ccstate));
 393         }
 394 }
 395
 396 /*
 397  * If stretch ack was disabled automatically on long standing connections,
 398  * re-evaluate the situation after 15 minutes to enable it.
 399  */
 400 #define TCP_STRETCHACK_DISABLE_WIN      (15 * 60 * TCP_RETRANSHZ)
 401 void
 402 tcp_cc_after_idle_stretchack(struct tcpcb *tp)
 403 {
 404         int32_t tdiff;
 405
 406         if (!(tp->t_flagsext & TF_DISABLE_STRETCHACK))
 407                 return;
 408
 409         tdiff = timer_diff(tcp_now, 0, tp->rcv_nostrack_ts, 0);
 410         if (tdiff < 0)
 411                 tdiff = -tdiff;
 412
 413         if (tdiff > TCP_STRETCHACK_DISABLE_WIN) {
 414                 tp->t_flagsext &= ~TF_DISABLE_STRETCHACK;
 415                 tp->t_stretchack_delayed = 0;
 416
 417                 tcp_reset_stretch_ack(tp);
 418         }
 419 }
 420
 421 /*
 422  * Detect if the congestion window is non-vlidated according to
 423  * draft-ietf-tcpm-newcwv-07
 424  */
 425
 426 inline uint32_t
 427 tcp_cc_is_cwnd_nonvalidated(struct tcpcb *tp)
 428 {
 429         if (tp->t_pipeack == 0 || tcp_check_cwnd_nonvalidated == 0) {
 430                 tp->t_flagsext &= ~TF_CWND_NONVALIDATED;
 431                 return (0);
 432         }
 433         if (tp->t_pipeack >= (tp->snd_cwnd) >> 1)
 434                 tp->t_flagsext &= ~TF_CWND_NONVALIDATED;
 435         else
 436                 tp->t_flagsext |= TF_CWND_NONVALIDATED;
 437         return (tp->t_flagsext & TF_CWND_NONVALIDATED);
 438 }
 439
 440 /*
 441  * Adjust congestion window in response to congestion in non-validated
 442  * phase.
 443  */
 444 inline void
 445 tcp_cc_adjust_nonvalidated_cwnd(struct tcpcb *tp)
 446 {
 447         tp->t_pipeack = tcp_get_max_pipeack(tp);
 448         tcp_clear_pipeack_state(tp);
 449         tp->snd_cwnd = (max(tp->t_pipeack, tp->t_lossflightsize) >> 1);
 450         tp->snd_cwnd = max(tp->snd_cwnd, TCP_CC_CWND_INIT_BYTES);
 451         tp->snd_cwnd += tp->t_maxseg * tcprexmtthresh;
 452         tp->t_flagsext &= ~TF_CWND_NONVALIDATED;
 453 }
 454
 455 /*
 456  * Return maximum of all the pipeack samples. Since the number of samples
 457  * TCP_PIPEACK_SAMPLE_COUNT is 3 at this time, it will be simpler to do
 458  * a comparision. We should change ths if the number of samples increases.
 459  */
 460 inline u_int32_t
 461 tcp_get_max_pipeack(struct tcpcb *tp)
 462 {
 463         u_int32_t max_pipeack = 0;
 464         max_pipeack = (tp->t_pipeack_sample[0] > tp->t_pipeack_sample[1]) ?
 465             tp->t_pipeack_sample[0] : tp->t_pipeack_sample[1];
 466         max_pipeack = (tp->t_pipeack_sample[2] > max_pipeack) ?
 467             tp->t_pipeack_sample[2] : max_pipeack;
 468
 469         return (max_pipeack);
 470 }
 471
 472 inline void
 473 tcp_clear_pipeack_state(struct tcpcb *tp)
 474 {
 475         bzero(tp->t_pipeack_sample, sizeof(tp->t_pipeack_sample));
 476         tp->t_pipeack_ind = 0;
 477         tp->t_lossflightsize = 0;
 478 }