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