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