net/ipv4/tcp_metrics.c

   1 #include <linux/rcupdate.h>
   2 #include <linux/spinlock.h>
   3 #include <linux/jiffies.h>
   4 #include <linux/bootmem.h>
   5 #include <linux/module.h>
   6 #include <linux/cache.h>
   7 #include <linux/slab.h>
   8 #include <linux/init.h>
   9 #include <linux/tcp.h>
  10 #include <linux/hash.h>
  11
  12 #include <net/inet_connection_sock.h>
  13 #include <net/net_namespace.h>
  14 #include <net/request_sock.h>
  15 #include <net/inetpeer.h>
  16 #include <net/sock.h>
  17 #include <net/ipv6.h>
  18 #include <net/dst.h>
  19 #include <net/tcp.h>
  20
  21 int sysctl_tcp_nometrics_save __read_mostly;
  22
  23 enum tcp_metric_index {
  24         TCP_METRIC_RTT,
  25         TCP_METRIC_RTTVAR,
  26         TCP_METRIC_SSTHRESH,
  27         TCP_METRIC_CWND,
  28         TCP_METRIC_REORDERING,
  29
  30         /* Always last.  */
  31         TCP_METRIC_MAX,
  32 };
  33
  34 struct tcp_fastopen_metrics {
  35         u16     mss;
  36         u16     syn_loss:10;            /* Recurring Fast Open SYN losses */
  37         unsigned long   last_syn_loss;  /* Last Fast Open SYN loss */
  38         struct  tcp_fastopen_cookie     cookie;
  39 };
  40
  41 struct tcp_metrics_block {
  42         struct tcp_metrics_block __rcu  *tcpm_next;
  43         struct inetpeer_addr            tcpm_addr;
  44         unsigned long                   tcpm_stamp;
  45         u32                             tcpm_ts;
  46         u32                             tcpm_ts_stamp;
  47         u32                             tcpm_lock;
  48         u32                             tcpm_vals[TCP_METRIC_MAX];
  49         struct tcp_fastopen_metrics     tcpm_fastopen;
  50 };
  51
  52 static bool tcp_metric_locked(struct tcp_metrics_block *tm,
  53                               enum tcp_metric_index idx)
  54 {
  55         return tm->tcpm_lock & (1 << idx);
  56 }
  57
  58 static u32 tcp_metric_get(struct tcp_metrics_block *tm,
  59                           enum tcp_metric_index idx)
  60 {
  61         return tm->tcpm_vals[idx];
  62 }
  63
  64 static u32 tcp_metric_get_jiffies(struct tcp_metrics_block *tm,
  65                                   enum tcp_metric_index idx)
  66 {
  67         return msecs_to_jiffies(tm->tcpm_vals[idx]);
  68 }
  69
  70 static void tcp_metric_set(struct tcp_metrics_block *tm,
  71                            enum tcp_metric_index idx,
  72                            u32 val)
  73 {
  74         tm->tcpm_vals[idx] = val;
  75 }
  76
  77 static void tcp_metric_set_msecs(struct tcp_metrics_block *tm,
  78                                  enum tcp_metric_index idx,
  79                                  u32 val)
  80 {
  81         tm->tcpm_vals[idx] = jiffies_to_msecs(val);
  82 }
  83
  84 static bool addr_same(const struct inetpeer_addr *a,
  85                       const struct inetpeer_addr *b)
  86 {
  87         const struct in6_addr *a6, *b6;
  88
  89         if (a->family != b->family)
  90                 return false;
  91         if (a->family == AF_INET)
  92                 return a->addr.a4 == b->addr.a4;
  93
  94         a6 = (const struct in6_addr *) &a->addr.a6[0];
  95         b6 = (const struct in6_addr *) &b->addr.a6[0];
  96
  97         return ipv6_addr_equal(a6, b6);
  98 }
  99
 100 struct tcpm_hash_bucket {
 101         struct tcp_metrics_block __rcu  *chain;
 102 };
 103
 104 static DEFINE_SPINLOCK(tcp_metrics_lock);
 105
 106 static void tcpm_suck_dst(struct tcp_metrics_block *tm, struct dst_entry *dst)
 107 {
 108         u32 val;
 109
 110         val = 0;
 111         if (dst_metric_locked(dst, RTAX_RTT))
 112                 val |= 1 << TCP_METRIC_RTT;
 113         if (dst_metric_locked(dst, RTAX_RTTVAR))
 114                 val |= 1 << TCP_METRIC_RTTVAR;
 115         if (dst_metric_locked(dst, RTAX_SSTHRESH))
 116                 val |= 1 << TCP_METRIC_SSTHRESH;
 117         if (dst_metric_locked(dst, RTAX_CWND))
 118                 val |= 1 << TCP_METRIC_CWND;
 119         if (dst_metric_locked(dst, RTAX_REORDERING))
 120                 val |= 1 << TCP_METRIC_REORDERING;
 121         tm->tcpm_lock = val;
 122
 123         tm->tcpm_vals[TCP_METRIC_RTT] = dst_metric_raw(dst, RTAX_RTT);
 124         tm->tcpm_vals[TCP_METRIC_RTTVAR] = dst_metric_raw(dst, RTAX_RTTVAR);
 125         tm->tcpm_vals[TCP_METRIC_SSTHRESH] = dst_metric_raw(dst, RTAX_SSTHRESH);
 126         tm->tcpm_vals[TCP_METRIC_CWND] = dst_metric_raw(dst, RTAX_CWND);
 127         tm->tcpm_vals[TCP_METRIC_REORDERING] = dst_metric_raw(dst, RTAX_REORDERING);
 128         tm->tcpm_ts = 0;
 129         tm->tcpm_ts_stamp = 0;
 130         tm->tcpm_fastopen.mss = 0;
 131         tm->tcpm_fastopen.syn_loss = 0;
 132         tm->tcpm_fastopen.cookie.len = 0;
 133 }
 134
 135 static struct tcp_metrics_block *tcpm_new(struct dst_entry *dst,
 136                                           struct inetpeer_addr *addr,
 137                                           unsigned int hash,
 138                                           bool reclaim)
 139 {
 140         struct tcp_metrics_block *tm;
 141         struct net *net;
 142
 143         spin_lock_bh(&tcp_metrics_lock);
 144         net = dev_net(dst->dev);
 145         if (unlikely(reclaim)) {
 146                 struct tcp_metrics_block *oldest;
 147
 148                 oldest = rcu_dereference(net->ipv4.tcp_metrics_hash[hash].chain);
 149                 for (tm = rcu_dereference(oldest->tcpm_next); tm;
 150                      tm = rcu_dereference(tm->tcpm_next)) {
 151                         if (time_before(tm->tcpm_stamp, oldest->tcpm_stamp))
 152                                 oldest = tm;
 153                 }
 154                 tm = oldest;
 155         } else {
 156                 tm = kmalloc(sizeof(*tm), GFP_ATOMIC);
 157                 if (!tm)
 158                         goto out_unlock;
 159         }
 160         tm->tcpm_addr = *addr;
 161         tm->tcpm_stamp = jiffies;
 162
 163         tcpm_suck_dst(tm, dst);
 164
 165         if (likely(!reclaim)) {
 166                 tm->tcpm_next = net->ipv4.tcp_metrics_hash[hash].chain;
 167                 rcu_assign_pointer(net->ipv4.tcp_metrics_hash[hash].chain, tm);
 168         }
 169
 170 out_unlock:
 171         spin_unlock_bh(&tcp_metrics_lock);
 172         return tm;
 173 }
 174
 175 #define TCP_METRICS_TIMEOUT             (60 * 60 * HZ)
 176
 177 static void tcpm_check_stamp(struct tcp_metrics_block *tm, struct dst_entry *dst)
 178 {
 179         if (tm && unlikely(time_after(jiffies, tm->tcpm_stamp + TCP_METRICS_TIMEOUT)))
 180                 tcpm_suck_dst(tm, dst);
 181 }
 182
 183 #define TCP_METRICS_RECLAIM_DEPTH       5
 184 #define TCP_METRICS_RECLAIM_PTR         (struct tcp_metrics_block *) 0x1UL
 185
 186 static struct tcp_metrics_block *tcp_get_encode(struct tcp_metrics_block *tm, int depth)
 187 {
 188         if (tm)
 189                 return tm;
 190         if (depth > TCP_METRICS_RECLAIM_DEPTH)
 191                 return TCP_METRICS_RECLAIM_PTR;
 192         return NULL;
 193 }
 194
 195 static struct tcp_metrics_block *__tcp_get_metrics(const struct inetpeer_addr *addr,
 196                                                    struct net *net, unsigned int hash)
 197 {
 198         struct tcp_metrics_block *tm;
 199         int depth = 0;
 200
 201         for (tm = rcu_dereference(net->ipv4.tcp_metrics_hash[hash].chain); tm;
 202              tm = rcu_dereference(tm->tcpm_next)) {
 203                 if (addr_same(&tm->tcpm_addr, addr))
 204                         break;
 205                 depth++;
 206         }
 207         return tcp_get_encode(tm, depth);
 208 }
 209
 210 static struct tcp_metrics_block *__tcp_get_metrics_req(struct request_sock *req,
 211                                                        struct dst_entry *dst)
 212 {
 213         struct tcp_metrics_block *tm;
 214         struct inetpeer_addr addr;
 215         unsigned int hash;
 216         struct net *net;
 217
 218         addr.family = req->rsk_ops->family;
 219         switch (addr.family) {
 220         case AF_INET:
 221                 addr.addr.a4 = inet_rsk(req)->rmt_addr;
 222                 hash = (__force unsigned int) addr.addr.a4;
 223                 break;
 224         case AF_INET6:
 225                 *(struct in6_addr *)addr.addr.a6 = inet6_rsk(req)->rmt_addr;
 226                 hash = ipv6_addr_hash(&inet6_rsk(req)->rmt_addr);
 227                 break;
 228         default:
 229                 return NULL;
 230         }
 231
 232         net = dev_net(dst->dev);
 233         hash = hash_32(hash, net->ipv4.tcp_metrics_hash_log);
 234
 235         for (tm = rcu_dereference(net->ipv4.tcp_metrics_hash[hash].chain); tm;
 236              tm = rcu_dereference(tm->tcpm_next)) {
 237                 if (addr_same(&tm->tcpm_addr, &addr))
 238                         break;
 239         }
 240         tcpm_check_stamp(tm, dst);
 241         return tm;
 242 }
 243
 244 static struct tcp_metrics_block *__tcp_get_metrics_tw(struct inet_timewait_sock *tw)
 245 {
 246         struct inet6_timewait_sock *tw6;
 247         struct tcp_metrics_block *tm;
 248         struct inetpeer_addr addr;
 249         unsigned int hash;
 250         struct net *net;
 251
 252         addr.family = tw->tw_family;
 253         switch (addr.family) {
 254         case AF_INET:
 255                 addr.addr.a4 = tw->tw_daddr;
 256                 hash = (__force unsigned int) addr.addr.a4;
 257                 break;
 258         case AF_INET6:
 259                 tw6 = inet6_twsk((struct sock *)tw);
 260                 *(struct in6_addr *)addr.addr.a6 = tw6->tw_v6_daddr;
 261                 hash = ipv6_addr_hash(&tw6->tw_v6_daddr);
 262                 break;
 263         default:
 264                 return NULL;
 265         }
 266
 267         net = twsk_net(tw);
 268         hash = hash_32(hash, net->ipv4.tcp_metrics_hash_log);
 269
 270         for (tm = rcu_dereference(net->ipv4.tcp_metrics_hash[hash].chain); tm;
 271              tm = rcu_dereference(tm->tcpm_next)) {
 272                 if (addr_same(&tm->tcpm_addr, &addr))
 273                         break;
 274         }
 275         return tm;
 276 }
 277
 278 static struct tcp_metrics_block *tcp_get_metrics(struct sock *sk,
 279                                                  struct dst_entry *dst,
 280                                                  bool create)
 281 {
 282         struct tcp_metrics_block *tm;
 283         struct inetpeer_addr addr;
 284         unsigned int hash;
 285         struct net *net;
 286         bool reclaim;
 287
 288         addr.family = sk->sk_family;
 289         switch (addr.family) {
 290         case AF_INET:
 291                 addr.addr.a4 = inet_sk(sk)->inet_daddr;
 292                 hash = (__force unsigned int) addr.addr.a4;
 293                 break;
 294         case AF_INET6:
 295                 *(struct in6_addr *)addr.addr.a6 = inet6_sk(sk)->daddr;
 296                 hash = ipv6_addr_hash(&inet6_sk(sk)->daddr);
 297                 break;
 298         default:
 299                 return NULL;
 300         }
 301
 302         net = dev_net(dst->dev);
 303         hash = hash_32(hash, net->ipv4.tcp_metrics_hash_log);
 304
 305         tm = __tcp_get_metrics(&addr, net, hash);
 306         reclaim = false;
 307         if (tm == TCP_METRICS_RECLAIM_PTR) {
 308                 reclaim = true;
 309                 tm = NULL;
 310         }
 311         if (!tm && create)
 312                 tm = tcpm_new(dst, &addr, hash, reclaim);
 313         else
 314                 tcpm_check_stamp(tm, dst);
 315
 316         return tm;
 317 }
 318
 319 /* Save metrics learned by this TCP session.  This function is called
 320  * only, when TCP finishes successfully i.e. when it enters TIME-WAIT
 321  * or goes from LAST-ACK to CLOSE.
 322  */
 323 void tcp_update_metrics(struct sock *sk)
 324 {
 325         const struct inet_connection_sock *icsk = inet_csk(sk);
 326         struct dst_entry *dst = __sk_dst_get(sk);
 327         struct tcp_sock *tp = tcp_sk(sk);
 328         struct tcp_metrics_block *tm;
 329         unsigned long rtt;
 330         u32 val;
 331         int m;
 332
 333         if (sysctl_tcp_nometrics_save || !dst)
 334                 return;
 335
 336         if (dst->flags & DST_HOST)
 337                 dst_confirm(dst);
 338
 339         rcu_read_lock();
 340         if (icsk->icsk_backoff || !tp->srtt) {
 341                 /* This session failed to estimate rtt. Why?
 342                  * Probably, no packets returned in time.  Reset our
 343                  * results.
 344                  */
 345                 tm = tcp_get_metrics(sk, dst, false);
 346                 if (tm && !tcp_metric_locked(tm, TCP_METRIC_RTT))
 347                         tcp_metric_set(tm, TCP_METRIC_RTT, 0);
 348                 goto out_unlock;
 349         } else
 350                 tm = tcp_get_metrics(sk, dst, true);
 351
 352         if (!tm)
 353                 goto out_unlock;
 354
 355         rtt = tcp_metric_get_jiffies(tm, TCP_METRIC_RTT);
 356         m = rtt - tp->srtt;
 357
 358         /* If newly calculated rtt larger than stored one, store new
 359          * one. Otherwise, use EWMA. Remember, rtt overestimation is
 360          * always better than underestimation.
 361          */
 362         if (!tcp_metric_locked(tm, TCP_METRIC_RTT)) {
 363                 if (m <= 0)
 364                         rtt = tp->srtt;
 365                 else
 366                         rtt -= (m >> 3);
 367                 tcp_metric_set_msecs(tm, TCP_METRIC_RTT, rtt);
 368         }
 369
 370         if (!tcp_metric_locked(tm, TCP_METRIC_RTTVAR)) {
 371                 unsigned long var;
 372
 373                 if (m < 0)
 374                         m = -m;
 375
 376                 /* Scale deviation to rttvar fixed point */
 377                 m >>= 1;
 378                 if (m < tp->mdev)
 379                         m = tp->mdev;
 380
 381                 var = tcp_metric_get_jiffies(tm, TCP_METRIC_RTTVAR);
 382                 if (m >= var)
 383                         var = m;
 384                 else
 385                         var -= (var - m) >> 2;
 386
 387                 tcp_metric_set_msecs(tm, TCP_METRIC_RTTVAR, var);
 388         }
 389
 390         if (tcp_in_initial_slowstart(tp)) {
 391                 /* Slow start still did not finish. */
 392                 if (!tcp_metric_locked(tm, TCP_METRIC_SSTHRESH)) {
 393                         val = tcp_metric_get(tm, TCP_METRIC_SSTHRESH);
 394                         if (val && (tp->snd_cwnd >> 1) > val)
 395                                 tcp_metric_set(tm, TCP_METRIC_SSTHRESH,
 396                                                tp->snd_cwnd >> 1);
 397                 }
 398                 if (!tcp_metric_locked(tm, TCP_METRIC_CWND)) {
 399                         val = tcp_metric_get(tm, TCP_METRIC_CWND);
 400                         if (tp->snd_cwnd > val)
 401                                 tcp_metric_set(tm, TCP_METRIC_CWND,
 402                                                tp->snd_cwnd);
 403                 }
 404         } else if (tp->snd_cwnd > tp->snd_ssthresh &&
 405                    icsk->icsk_ca_state == TCP_CA_Open) {
 406                 /* Cong. avoidance phase, cwnd is reliable. */
 407                 if (!tcp_metric_locked(tm, TCP_METRIC_SSTHRESH))
 408                         tcp_metric_set(tm, TCP_METRIC_SSTHRESH,
 409                                        max(tp->snd_cwnd >> 1, tp->snd_ssthresh));
 410                 if (!tcp_metric_locked(tm, TCP_METRIC_CWND)) {
 411                         val = tcp_metric_get(tm, TCP_METRIC_CWND);
 412                         tcp_metric_set(tm, TCP_METRIC_CWND, (val + tp->snd_cwnd) >> 1);
 413                 }
 414         } else {
 415                 /* Else slow start did not finish, cwnd is non-sense,
 416                  * ssthresh may be also invalid.
 417                  */
 418                 if (!tcp_metric_locked(tm, TCP_METRIC_CWND)) {
 419                         val = tcp_metric_get(tm, TCP_METRIC_CWND);
 420                         tcp_metric_set(tm, TCP_METRIC_CWND,
 421                                        (val + tp->snd_ssthresh) >> 1);
 422                 }
 423                 if (!tcp_metric_locked(tm, TCP_METRIC_SSTHRESH)) {
 424                         val = tcp_metric_get(tm, TCP_METRIC_SSTHRESH);
 425                         if (val && tp->snd_ssthresh > val)
 426                                 tcp_metric_set(tm, TCP_METRIC_SSTHRESH,
 427                                                tp->snd_ssthresh);
 428                 }
 429                 if (!tcp_metric_locked(tm, TCP_METRIC_REORDERING)) {
 430                         val = tcp_metric_get(tm, TCP_METRIC_REORDERING);
 431                         if (val < tp->reordering &&
 432                             tp->reordering != sysctl_tcp_reordering)
 433                                 tcp_metric_set(tm, TCP_METRIC_REORDERING,
 434                                                tp->reordering);
 435                 }
 436         }
 437         tm->tcpm_stamp = jiffies;
 438 out_unlock:
 439         rcu_read_unlock();
 440 }
 441
 442 /* Initialize metrics on socket. */
 443
 444 void tcp_init_metrics(struct sock *sk)
 445 {
 446         struct dst_entry *dst = __sk_dst_get(sk);
 447         struct tcp_sock *tp = tcp_sk(sk);
 448         struct tcp_metrics_block *tm;
 449         u32 val;
 450
 451         if (dst == NULL)
 452                 goto reset;
 453
 454         dst_confirm(dst);
 455
 456         rcu_read_lock();
 457         tm = tcp_get_metrics(sk, dst, true);
 458         if (!tm) {
 459                 rcu_read_unlock();
 460                 goto reset;
 461         }
 462
 463         if (tcp_metric_locked(tm, TCP_METRIC_CWND))
 464                 tp->snd_cwnd_clamp = tcp_metric_get(tm, TCP_METRIC_CWND);
 465
 466         val = tcp_metric_get(tm, TCP_METRIC_SSTHRESH);
 467         if (val) {
 468                 tp->snd_ssthresh = val;
 469                 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
 470                         tp->snd_ssthresh = tp->snd_cwnd_clamp;
 471         } else {
 472                 /* ssthresh may have been reduced unnecessarily during.
 473                  * 3WHS. Restore it back to its initial default.
 474                  */
 475                 tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
 476         }
 477         val = tcp_metric_get(tm, TCP_METRIC_REORDERING);
 478         if (val && tp->reordering != val) {
 479                 tcp_disable_fack(tp);
 480                 tcp_disable_early_retrans(tp);
 481                 tp->reordering = val;
 482         }
 483
 484         val = tcp_metric_get(tm, TCP_METRIC_RTT);
 485         if (val == 0 || tp->srtt == 0) {
 486                 rcu_read_unlock();
 487                 goto reset;
 488         }
 489         /* Initial rtt is determined from SYN,SYN-ACK.
 490          * The segment is small and rtt may appear much
 491          * less than real one. Use per-dst memory
 492          * to make it more realistic.
 493          *
 494          * A bit of theory. RTT is time passed after "normal" sized packet
 495          * is sent until it is ACKed. In normal circumstances sending small
 496          * packets force peer to delay ACKs and calculation is correct too.
 497          * The algorithm is adaptive and, provided we follow specs, it
 498          * NEVER underestimate RTT. BUT! If peer tries to make some clever
 499          * tricks sort of "quick acks" for time long enough to decrease RTT
 500          * to low value, and then abruptly stops to do it and starts to delay
 501          * ACKs, wait for troubles.
 502          */
 503         val = msecs_to_jiffies(val);
 504         if (val > tp->srtt) {
 505                 tp->srtt = val;
 506                 tp->rtt_seq = tp->snd_nxt;
 507         }
 508         val = tcp_metric_get_jiffies(tm, TCP_METRIC_RTTVAR);
 509         if (val > tp->mdev) {
 510                 tp->mdev = val;
 511                 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
 512         }
 513         rcu_read_unlock();
 514
 515         tcp_set_rto(sk);
 516 reset:
 517         if (tp->srtt == 0) {
 518                 /* RFC6298: 5.7 We've failed to get a valid RTT sample from
 519                  * 3WHS. This is most likely due to retransmission,
 520                  * including spurious one. Reset the RTO back to 3secs
 521                  * from the more aggressive 1sec to avoid more spurious
 522                  * retransmission.
 523                  */
 524                 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_FALLBACK;
 525                 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_FALLBACK;
 526         }
 527         /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
 528          * retransmitted. In light of RFC6298 more aggressive 1sec
 529          * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
 530          * retransmission has occurred.
 531          */
 532         if (tp->total_retrans > 1)
 533                 tp->snd_cwnd = 1;
 534         else
 535                 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
 536         tp->snd_cwnd_stamp = tcp_time_stamp;
 537 }
 538
 539 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst, bool paws_check)
 540 {
 541         struct tcp_metrics_block *tm;
 542         bool ret;
 543
 544         if (!dst)
 545                 return false;
 546
 547         rcu_read_lock();
 548         tm = __tcp_get_metrics_req(req, dst);
 549         if (paws_check) {
 550                 if (tm &&
 551                     (u32)get_seconds() - tm->tcpm_ts_stamp < TCP_PAWS_MSL &&
 552                     (s32)(tm->tcpm_ts - req->ts_recent) > TCP_PAWS_WINDOW)
 553                         ret = false;
 554                 else
 555                         ret = true;
 556         } else {
 557                 if (tm && tcp_metric_get(tm, TCP_METRIC_RTT) && tm->tcpm_ts_stamp)
 558                         ret = true;
 559                 else
 560                         ret = false;
 561         }
 562         rcu_read_unlock();
 563
 564         return ret;
 565 }
 566 EXPORT_SYMBOL_GPL(tcp_peer_is_proven);
 567
 568 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst)
 569 {
 570         struct tcp_metrics_block *tm;
 571
 572         rcu_read_lock();
 573         tm = tcp_get_metrics(sk, dst, true);
 574         if (tm) {
 575                 struct tcp_sock *tp = tcp_sk(sk);
 576
 577                 if ((u32)get_seconds() - tm->tcpm_ts_stamp <= TCP_PAWS_MSL) {
 578                         tp->rx_opt.ts_recent_stamp = tm->tcpm_ts_stamp;
 579                         tp->rx_opt.ts_recent = tm->tcpm_ts;
 580                 }
 581         }
 582         rcu_read_unlock();
 583 }
 584 EXPORT_SYMBOL_GPL(tcp_fetch_timewait_stamp);
 585
 586 /* VJ's idea. Save last timestamp seen from this destination and hold
 587  * it at least for normal timewait interval to use for duplicate
 588  * segment detection in subsequent connections, before they enter
 589  * synchronized state.
 590  */
 591 bool tcp_remember_stamp(struct sock *sk)
 592 {
 593         struct dst_entry *dst = __sk_dst_get(sk);
 594         bool ret = false;
 595
 596         if (dst) {
 597                 struct tcp_metrics_block *tm;
 598
 599                 rcu_read_lock();
 600                 tm = tcp_get_metrics(sk, dst, true);
 601                 if (tm) {
 602                         struct tcp_sock *tp = tcp_sk(sk);
 603
 604                         if ((s32)(tm->tcpm_ts - tp->rx_opt.ts_recent) <= 0 ||
 605                             ((u32)get_seconds() - tm->tcpm_ts_stamp > TCP_PAWS_MSL &&
 606                              tm->tcpm_ts_stamp <= (u32)tp->rx_opt.ts_recent_stamp)) {
 607                                 tm->tcpm_ts_stamp = (u32)tp->rx_opt.ts_recent_stamp;
 608                                 tm->tcpm_ts = tp->rx_opt.ts_recent;
 609                         }
 610                         ret = true;
 611                 }
 612                 rcu_read_unlock();
 613         }
 614         return ret;
 615 }
 616
 617 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw)
 618 {
 619         struct tcp_metrics_block *tm;
 620         bool ret = false;
 621
 622         rcu_read_lock();
 623         tm = __tcp_get_metrics_tw(tw);
 624         if (tw) {
 625                 const struct tcp_timewait_sock *tcptw;
 626                 struct sock *sk = (struct sock *) tw;
 627
 628                 tcptw = tcp_twsk(sk);
 629                 if ((s32)(tm->tcpm_ts - tcptw->tw_ts_recent) <= 0 ||
 630                     ((u32)get_seconds() - tm->tcpm_ts_stamp > TCP_PAWS_MSL &&
 631                      tm->tcpm_ts_stamp <= (u32)tcptw->tw_ts_recent_stamp)) {
 632                         tm->tcpm_ts_stamp = (u32)tcptw->tw_ts_recent_stamp;
 633                         tm->tcpm_ts        = tcptw->tw_ts_recent;
 634                 }
 635                 ret = true;
 636         }
 637         rcu_read_unlock();
 638
 639         return ret;
 640 }
 641
 642 static DEFINE_SEQLOCK(fastopen_seqlock);
 643
 644 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
 645                             struct tcp_fastopen_cookie *cookie,
 646                             int *syn_loss, unsigned long *last_syn_loss)
 647 {
 648         struct tcp_metrics_block *tm;
 649
 650         rcu_read_lock();
 651         tm = tcp_get_metrics(sk, __sk_dst_get(sk), false);
 652         if (tm) {
 653                 struct tcp_fastopen_metrics *tfom = &tm->tcpm_fastopen;
 654                 unsigned int seq;
 655
 656                 do {
 657                         seq = read_seqbegin(&fastopen_seqlock);
 658                         if (tfom->mss)
 659                                 *mss = tfom->mss;
 660                         *cookie = tfom->cookie;
 661                         *syn_loss = tfom->syn_loss;
 662                         *last_syn_loss = *syn_loss ? tfom->last_syn_loss : 0;
 663                 } while (read_seqretry(&fastopen_seqlock, seq));
 664         }
 665         rcu_read_unlock();
 666 }
 667
 668 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
 669                             struct tcp_fastopen_cookie *cookie, bool syn_lost)
 670 {
 671         struct tcp_metrics_block *tm;
 672
 673         rcu_read_lock();
 674         tm = tcp_get_metrics(sk, __sk_dst_get(sk), true);
 675         if (tm) {
 676                 struct tcp_fastopen_metrics *tfom = &tm->tcpm_fastopen;
 677
 678                 write_seqlock_bh(&fastopen_seqlock);
 679                 tfom->mss = mss;
 680                 if (cookie->len > 0)
 681                         tfom->cookie = *cookie;
 682                 if (syn_lost) {
 683                         ++tfom->syn_loss;
 684                         tfom->last_syn_loss = jiffies;
 685                 } else
 686                         tfom->syn_loss = 0;
 687                 write_sequnlock_bh(&fastopen_seqlock);
 688         }
 689         rcu_read_unlock();
 690 }
 691
 692 static unsigned int tcpmhash_entries;
 693 static int __init set_tcpmhash_entries(char *str)
 694 {
 695         ssize_t ret;
 696
 697         if (!str)
 698                 return 0;
 699
 700         ret = kstrtouint(str, 0, &tcpmhash_entries);
 701         if (ret)
 702                 return 0;
 703
 704         return 1;
 705 }
 706 __setup("tcpmhash_entries=", set_tcpmhash_entries);
 707
 708 static int __net_init tcp_net_metrics_init(struct net *net)
 709 {
 710         size_t size;
 711         unsigned int slots;
 712
 713         slots = tcpmhash_entries;
 714         if (!slots) {
 715                 if (totalram_pages >= 128 * 1024)
 716                         slots = 16 * 1024;
 717                 else
 718                         slots = 8 * 1024;
 719         }
 720
 721         net->ipv4.tcp_metrics_hash_log = order_base_2(slots);
 722         size = sizeof(struct tcpm_hash_bucket) << net->ipv4.tcp_metrics_hash_log;
 723
 724         net->ipv4.tcp_metrics_hash = kzalloc(size, GFP_KERNEL);
 725         if (!net->ipv4.tcp_metrics_hash)
 726                 return -ENOMEM;
 727
 728         return 0;
 729 }
 730
 731 static void __net_exit tcp_net_metrics_exit(struct net *net)
 732 {
 733         kfree(net->ipv4.tcp_metrics_hash);
 734 }
 735
 736 static __net_initdata struct pernet_operations tcp_net_metrics_ops = {
 737         .init   =       tcp_net_metrics_init,
 738         .exit   =       tcp_net_metrics_exit,
 739 };
 740
 741 void __init tcp_metrics_init(void)
 742 {
 743         register_pernet_subsys(&tcp_net_metrics_ops);
 744 }