net/ipv4/inet_connection_sock.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              Support for INET connection oriented protocols.
   7  *
   8  * Authors:     See the TCP sources
   9  *
  10  *              This program is free software; you can redistribute it and/or
  11  *              modify it under the terms of the GNU General Public License
  12  *              as published by the Free Software Foundation; either version
  13  *              2 of the License, or(at your option) any later version.
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/jhash.h>
  18
  19 #include <net/inet_connection_sock.h>
  20 #include <net/inet_hashtables.h>
  21 #include <net/inet_timewait_sock.h>
  22 #include <net/ip.h>
  23 #include <net/route.h>
  24 #include <net/tcp_states.h>
  25 #include <net/xfrm.h>
  26 #include <net/tcp.h>
  27 #include <net/sock_reuseport.h>
  28 #include <net/addrconf.h>
  29
  30 #if IS_ENABLED(CONFIG_IPV6)
  31 /* match_wildcard == true:  IPV6_ADDR_ANY equals to any IPv6 addresses if IPv6
  32  *                          only, and any IPv4 addresses if not IPv6 only
  33  * match_wildcard == false: addresses must be exactly the same, i.e.
  34  *                          IPV6_ADDR_ANY only equals to IPV6_ADDR_ANY,
  35  *                          and 0.0.0.0 equals to 0.0.0.0 only
  36  */
  37 static bool ipv6_rcv_saddr_equal(const struct in6_addr *sk1_rcv_saddr6,
  38                                  const struct in6_addr *sk2_rcv_saddr6,
  39                                  __be32 sk1_rcv_saddr, __be32 sk2_rcv_saddr,
  40                                  bool sk1_ipv6only, bool sk2_ipv6only,
  41                                  bool match_wildcard)
  42 {
  43         int addr_type = ipv6_addr_type(sk1_rcv_saddr6);
  44         int addr_type2 = sk2_rcv_saddr6 ? ipv6_addr_type(sk2_rcv_saddr6) : IPV6_ADDR_MAPPED;
  45
  46         /* if both are mapped, treat as IPv4 */
  47         if (addr_type == IPV6_ADDR_MAPPED && addr_type2 == IPV6_ADDR_MAPPED) {
  48                 if (!sk2_ipv6only) {
  49                         if (sk1_rcv_saddr == sk2_rcv_saddr)
  50                                 return true;
  51                         if (!sk1_rcv_saddr || !sk2_rcv_saddr)
  52                                 return match_wildcard;
  53                 }
  54                 return false;
  55         }
  56
  57         if (addr_type == IPV6_ADDR_ANY && addr_type2 == IPV6_ADDR_ANY)
  58                 return true;
  59
  60         if (addr_type2 == IPV6_ADDR_ANY && match_wildcard &&
  61             !(sk2_ipv6only && addr_type == IPV6_ADDR_MAPPED))
  62                 return true;
  63
  64         if (addr_type == IPV6_ADDR_ANY && match_wildcard &&
  65             !(sk1_ipv6only && addr_type2 == IPV6_ADDR_MAPPED))
  66                 return true;
  67
  68         if (sk2_rcv_saddr6 &&
  69             ipv6_addr_equal(sk1_rcv_saddr6, sk2_rcv_saddr6))
  70                 return true;
  71
  72         return false;
  73 }
  74 #endif
  75
  76 /* match_wildcard == true:  0.0.0.0 equals to any IPv4 addresses
  77  * match_wildcard == false: addresses must be exactly the same, i.e.
  78  *                          0.0.0.0 only equals to 0.0.0.0
  79  */
  80 static bool ipv4_rcv_saddr_equal(__be32 sk1_rcv_saddr, __be32 sk2_rcv_saddr,
  81                                  bool sk2_ipv6only, bool match_wildcard)
  82 {
  83         if (!sk2_ipv6only) {
  84                 if (sk1_rcv_saddr == sk2_rcv_saddr)
  85                         return true;
  86                 if (!sk1_rcv_saddr || !sk2_rcv_saddr)
  87                         return match_wildcard;
  88         }
  89         return false;
  90 }
  91
  92 bool inet_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2,
  93                           bool match_wildcard)
  94 {
  95 #if IS_ENABLED(CONFIG_IPV6)
  96         if (sk->sk_family == AF_INET6)
  97                 return ipv6_rcv_saddr_equal(&sk->sk_v6_rcv_saddr,
  98                                             inet6_rcv_saddr(sk2),
  99                                             sk->sk_rcv_saddr,
 100                                             sk2->sk_rcv_saddr,
 101                                             ipv6_only_sock(sk),
 102                                             ipv6_only_sock(sk2),
 103                                             match_wildcard);
 104 #endif
 105         return ipv4_rcv_saddr_equal(sk->sk_rcv_saddr, sk2->sk_rcv_saddr,
 106                                     ipv6_only_sock(sk2), match_wildcard);
 107 }
 108 EXPORT_SYMBOL(inet_rcv_saddr_equal);
 109
 110 bool inet_rcv_saddr_any(const struct sock *sk)
 111 {
 112 #if IS_ENABLED(CONFIG_IPV6)
 113         if (sk->sk_family == AF_INET6)
 114                 return ipv6_addr_any(&sk->sk_v6_rcv_saddr);
 115 #endif
 116         return !sk->sk_rcv_saddr;
 117 }
 118
 119 void inet_get_local_port_range(struct net *net, int *low, int *high)
 120 {
 121         unsigned int seq;
 122
 123         do {
 124                 seq = read_seqbegin(&net->ipv4.ip_local_ports.lock);
 125
 126                 *low = net->ipv4.ip_local_ports.range[0];
 127                 *high = net->ipv4.ip_local_ports.range[1];
 128         } while (read_seqretry(&net->ipv4.ip_local_ports.lock, seq));
 129 }
 130 EXPORT_SYMBOL(inet_get_local_port_range);
 131
 132 static int inet_csk_bind_conflict(const struct sock *sk,
 133                                   const struct inet_bind_bucket *tb,
 134                                   bool relax, bool reuseport_ok)
 135 {
 136         struct sock *sk2;
 137         bool reuse = sk->sk_reuse;
 138         bool reuseport = !!sk->sk_reuseport && reuseport_ok;
 139         kuid_t uid = sock_i_uid((struct sock *)sk);
 140
 141         /*
 142          * Unlike other sk lookup places we do not check
 143          * for sk_net here, since _all_ the socks listed
 144          * in tb->owners list belong to the same net - the
 145          * one this bucket belongs to.
 146          */
 147
 148         sk_for_each_bound(sk2, &tb->owners) {
 149                 if (sk != sk2 &&
 150                     (!sk->sk_bound_dev_if ||
 151                      !sk2->sk_bound_dev_if ||
 152                      sk->sk_bound_dev_if == sk2->sk_bound_dev_if)) {
 153                         if ((!reuse || !sk2->sk_reuse ||
 154                             sk2->sk_state == TCP_LISTEN) &&
 155                             (!reuseport || !sk2->sk_reuseport ||
 156                              rcu_access_pointer(sk->sk_reuseport_cb) ||
 157                              (sk2->sk_state != TCP_TIME_WAIT &&
 158                              !uid_eq(uid, sock_i_uid(sk2))))) {
 159                                 if (inet_rcv_saddr_equal(sk, sk2, true))
 160                                         break;
 161                         }
 162                         if (!relax && reuse && sk2->sk_reuse &&
 163                             sk2->sk_state != TCP_LISTEN) {
 164                                 if (inet_rcv_saddr_equal(sk, sk2, true))
 165                                         break;
 166                         }
 167                 }
 168         }
 169         return sk2 != NULL;
 170 }
 171
 172 /*
 173  * Find an open port number for the socket.  Returns with the
 174  * inet_bind_hashbucket lock held.
 175  */
 176 static struct inet_bind_hashbucket *
 177 inet_csk_find_open_port(struct sock *sk, struct inet_bind_bucket **tb_ret, int *port_ret)
 178 {
 179         struct inet_hashinfo *hinfo = sk->sk_prot->h.hashinfo;
 180         int port = 0;
 181         struct inet_bind_hashbucket *head;
 182         struct net *net = sock_net(sk);
 183         int i, low, high, attempt_half;
 184         struct inet_bind_bucket *tb;
 185         u32 remaining, offset;
 186         int l3mdev;
 187
 188         l3mdev = inet_sk_bound_l3mdev(sk);
 189         attempt_half = (sk->sk_reuse == SK_CAN_REUSE) ? 1 : 0;
 190 other_half_scan:
 191         inet_get_local_port_range(net, &low, &high);
 192         high++; /* [32768, 60999] -> [32768, 61000[ */
 193         if (high - low < 4)
 194                 attempt_half = 0;
 195         if (attempt_half) {
 196                 int half = low + (((high - low) >> 2) << 1);
 197
 198                 if (attempt_half == 1)
 199                         high = half;
 200                 else
 201                         low = half;
 202         }
 203         remaining = high - low;
 204         if (likely(remaining > 1))
 205                 remaining &= ~1U;
 206
 207         offset = prandom_u32() % remaining;
 208         /* __inet_hash_connect() favors ports having @low parity
 209          * We do the opposite to not pollute connect() users.
 210          */
 211         offset |= 1U;
 212
 213 other_parity_scan:
 214         port = low + offset;
 215         for (i = 0; i < remaining; i += 2, port += 2) {
 216                 if (unlikely(port >= high))
 217                         port -= remaining;
 218                 if (inet_is_local_reserved_port(net, port))
 219                         continue;
 220                 head = &hinfo->bhash[inet_bhashfn(net, port,
 221                                                   hinfo->bhash_size)];
 222                 spin_lock_bh(&head->lock);
 223                 inet_bind_bucket_for_each(tb, &head->chain)
 224                         if (net_eq(ib_net(tb), net) && tb->l3mdev == l3mdev &&
 225                             tb->port == port) {
 226                                 if (!inet_csk_bind_conflict(sk, tb, false, false))
 227                                         goto success;
 228                                 goto next_port;
 229                         }
 230                 tb = NULL;
 231                 goto success;
 232 next_port:
 233                 spin_unlock_bh(&head->lock);
 234                 cond_resched();
 235         }
 236
 237         offset--;
 238         if (!(offset & 1))
 239                 goto other_parity_scan;
 240
 241         if (attempt_half == 1) {
 242                 /* OK we now try the upper half of the range */
 243                 attempt_half = 2;
 244                 goto other_half_scan;
 245         }
 246         return NULL;
 247 success:
 248         *port_ret = port;
 249         *tb_ret = tb;
 250         return head;
 251 }
 252
 253 static inline int sk_reuseport_match(struct inet_bind_bucket *tb,
 254                                      struct sock *sk)
 255 {
 256         kuid_t uid = sock_i_uid(sk);
 257
 258         if (tb->fastreuseport <= 0)
 259                 return 0;
 260         if (!sk->sk_reuseport)
 261                 return 0;
 262         if (rcu_access_pointer(sk->sk_reuseport_cb))
 263                 return 0;
 264         if (!uid_eq(tb->fastuid, uid))
 265                 return 0;
 266         /* We only need to check the rcv_saddr if this tb was once marked
 267          * without fastreuseport and then was reset, as we can only know that
 268          * the fast_*rcv_saddr doesn't have any conflicts with the socks on the
 269          * owners list.
 270          */
 271         if (tb->fastreuseport == FASTREUSEPORT_ANY)
 272                 return 1;
 273 #if IS_ENABLED(CONFIG_IPV6)
 274         if (tb->fast_sk_family == AF_INET6)
 275                 return ipv6_rcv_saddr_equal(&tb->fast_v6_rcv_saddr,
 276                                             inet6_rcv_saddr(sk),
 277                                             tb->fast_rcv_saddr,
 278                                             sk->sk_rcv_saddr,
 279                                             tb->fast_ipv6_only,
 280                                             ipv6_only_sock(sk), true);
 281 #endif
 282         return ipv4_rcv_saddr_equal(tb->fast_rcv_saddr, sk->sk_rcv_saddr,
 283                                     ipv6_only_sock(sk), true);
 284 }
 285
 286 /* Obtain a reference to a local port for the given sock,
 287  * if snum is zero it means select any available local port.
 288  * We try to allocate an odd port (and leave even ports for connect())
 289  */
 290 int inet_csk_get_port(struct sock *sk, unsigned short snum)
 291 {
 292         bool reuse = sk->sk_reuse && sk->sk_state != TCP_LISTEN;
 293         struct inet_hashinfo *hinfo = sk->sk_prot->h.hashinfo;
 294         int ret = 1, port = snum;
 295         struct inet_bind_hashbucket *head;
 296         struct net *net = sock_net(sk);
 297         struct inet_bind_bucket *tb = NULL;
 298         kuid_t uid = sock_i_uid(sk);
 299         int l3mdev;
 300
 301         l3mdev = inet_sk_bound_l3mdev(sk);
 302
 303         if (!port) {
 304                 head = inet_csk_find_open_port(sk, &tb, &port);
 305                 if (!head)
 306                         return ret;
 307                 if (!tb)
 308                         goto tb_not_found;
 309                 goto success;
 310         }
 311         head = &hinfo->bhash[inet_bhashfn(net, port,
 312                                           hinfo->bhash_size)];
 313         spin_lock_bh(&head->lock);
 314         inet_bind_bucket_for_each(tb, &head->chain)
 315                 if (net_eq(ib_net(tb), net) && tb->l3mdev == l3mdev &&
 316                     tb->port == port)
 317                         goto tb_found;
 318 tb_not_found:
 319         tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep,
 320                                      net, head, port, l3mdev);
 321         if (!tb)
 322                 goto fail_unlock;
 323 tb_found:
 324         if (!hlist_empty(&tb->owners)) {
 325                 if (sk->sk_reuse == SK_FORCE_REUSE)
 326                         goto success;
 327
 328                 if ((tb->fastreuse > 0 && reuse) ||
 329                     sk_reuseport_match(tb, sk))
 330                         goto success;
 331                 if (inet_csk_bind_conflict(sk, tb, true, true))
 332                         goto fail_unlock;
 333         }
 334 success:
 335         if (hlist_empty(&tb->owners)) {
 336                 tb->fastreuse = reuse;
 337                 if (sk->sk_reuseport) {
 338                         tb->fastreuseport = FASTREUSEPORT_ANY;
 339                         tb->fastuid = uid;
 340                         tb->fast_rcv_saddr = sk->sk_rcv_saddr;
 341                         tb->fast_ipv6_only = ipv6_only_sock(sk);
 342                         tb->fast_sk_family = sk->sk_family;
 343 #if IS_ENABLED(CONFIG_IPV6)
 344                         tb->fast_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
 345 #endif
 346                 } else {
 347                         tb->fastreuseport = 0;
 348                 }
 349         } else {
 350                 if (!reuse)
 351                         tb->fastreuse = 0;
 352                 if (sk->sk_reuseport) {
 353                         /* We didn't match or we don't have fastreuseport set on
 354                          * the tb, but we have sk_reuseport set on this socket
 355                          * and we know that there are no bind conflicts with
 356                          * this socket in this tb, so reset our tb's reuseport
 357                          * settings so that any subsequent sockets that match
 358                          * our current socket will be put on the fast path.
 359                          *
 360                          * If we reset we need to set FASTREUSEPORT_STRICT so we
 361                          * do extra checking for all subsequent sk_reuseport
 362                          * socks.
 363                          */
 364                         if (!sk_reuseport_match(tb, sk)) {
 365                                 tb->fastreuseport = FASTREUSEPORT_STRICT;
 366                                 tb->fastuid = uid;
 367                                 tb->fast_rcv_saddr = sk->sk_rcv_saddr;
 368                                 tb->fast_ipv6_only = ipv6_only_sock(sk);
 369                                 tb->fast_sk_family = sk->sk_family;
 370 #if IS_ENABLED(CONFIG_IPV6)
 371                                 tb->fast_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
 372 #endif
 373                         }
 374                 } else {
 375                         tb->fastreuseport = 0;
 376                 }
 377         }
 378         if (!inet_csk(sk)->icsk_bind_hash)
 379                 inet_bind_hash(sk, tb, port);
 380         WARN_ON(inet_csk(sk)->icsk_bind_hash != tb);
 381         ret = 0;
 382
 383 fail_unlock:
 384         spin_unlock_bh(&head->lock);
 385         return ret;
 386 }
 387 EXPORT_SYMBOL_GPL(inet_csk_get_port);
 388
 389 /*
 390  * Wait for an incoming connection, avoid race conditions. This must be called
 391  * with the socket locked.
 392  */
 393 static int inet_csk_wait_for_connect(struct sock *sk, long timeo)
 394 {
 395         struct inet_connection_sock *icsk = inet_csk(sk);
 396         DEFINE_WAIT(wait);
 397         int err;
 398
 399         /*
 400          * True wake-one mechanism for incoming connections: only
 401          * one process gets woken up, not the 'whole herd'.
 402          * Since we do not 'race & poll' for established sockets
 403          * anymore, the common case will execute the loop only once.
 404          *
 405          * Subtle issue: "add_wait_queue_exclusive()" will be added
 406          * after any current non-exclusive waiters, and we know that
 407          * it will always _stay_ after any new non-exclusive waiters
 408          * because all non-exclusive waiters are added at the
 409          * beginning of the wait-queue. As such, it's ok to "drop"
 410          * our exclusiveness temporarily when we get woken up without
 411          * having to remove and re-insert us on the wait queue.
 412          */
 413         for (;;) {
 414                 prepare_to_wait_exclusive(sk_sleep(sk), &wait,
 415                                           TASK_INTERRUPTIBLE);
 416                 release_sock(sk);
 417                 if (reqsk_queue_empty(&icsk->icsk_accept_queue))
 418                         timeo = schedule_timeout(timeo);
 419                 sched_annotate_sleep();
 420                 lock_sock(sk);
 421                 err = 0;
 422                 if (!reqsk_queue_empty(&icsk->icsk_accept_queue))
 423                         break;
 424                 err = -EINVAL;
 425                 if (sk->sk_state != TCP_LISTEN)
 426                         break;
 427                 err = sock_intr_errno(timeo);
 428                 if (signal_pending(current))
 429                         break;
 430                 err = -EAGAIN;
 431                 if (!timeo)
 432                         break;
 433         }
 434         finish_wait(sk_sleep(sk), &wait);
 435         return err;
 436 }
 437
 438 /*
 439  * This will accept the next outstanding connection.
 440  */
 441 struct sock *inet_csk_accept(struct sock *sk, int flags, int *err, bool kern)
 442 {
 443         struct inet_connection_sock *icsk = inet_csk(sk);
 444         struct request_sock_queue *queue = &icsk->icsk_accept_queue;
 445         struct request_sock *req;
 446         struct sock *newsk;
 447         int error;
 448
 449         lock_sock(sk);
 450
 451         /* We need to make sure that this socket is listening,
 452          * and that it has something pending.
 453          */
 454         error = -EINVAL;
 455         if (sk->sk_state != TCP_LISTEN)
 456                 goto out_err;
 457
 458         /* Find already established connection */
 459         if (reqsk_queue_empty(queue)) {
 460                 long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);
 461
 462                 /* If this is a non blocking socket don't sleep */
 463                 error = -EAGAIN;
 464                 if (!timeo)
 465                         goto out_err;
 466
 467                 error = inet_csk_wait_for_connect(sk, timeo);
 468                 if (error)
 469                         goto out_err;
 470         }
 471         req = reqsk_queue_remove(queue, sk);
 472         newsk = req->sk;
 473
 474         if (sk->sk_protocol == IPPROTO_TCP &&
 475             tcp_rsk(req)->tfo_listener) {
 476                 spin_lock_bh(&queue->fastopenq.lock);
 477                 if (tcp_rsk(req)->tfo_listener) {
 478                         /* We are still waiting for the final ACK from 3WHS
 479                          * so can't free req now. Instead, we set req->sk to
 480                          * NULL to signify that the child socket is taken
 481                          * so reqsk_fastopen_remove() will free the req
 482                          * when 3WHS finishes (or is aborted).
 483                          */
 484                         req->sk = NULL;
 485                         req = NULL;
 486                 }
 487                 spin_unlock_bh(&queue->fastopenq.lock);
 488         }
 489 out:
 490         release_sock(sk);
 491         if (req)
 492                 reqsk_put(req);
 493         return newsk;
 494 out_err:
 495         newsk = NULL;
 496         req = NULL;
 497         *err = error;
 498         goto out;
 499 }
 500 EXPORT_SYMBOL(inet_csk_accept);
 501
 502 /*
 503  * Using different timers for retransmit, delayed acks and probes
 504  * We may wish use just one timer maintaining a list of expire jiffies
 505  * to optimize.
 506  */
 507 void inet_csk_init_xmit_timers(struct sock *sk,
 508                                void (*retransmit_handler)(struct timer_list *t),
 509                                void (*delack_handler)(struct timer_list *t),
 510                                void (*keepalive_handler)(struct timer_list *t))
 511 {
 512         struct inet_connection_sock *icsk = inet_csk(sk);
 513
 514         timer_setup(&icsk->icsk_retransmit_timer, retransmit_handler, 0);
 515         timer_setup(&icsk->icsk_delack_timer, delack_handler, 0);
 516         timer_setup(&sk->sk_timer, keepalive_handler, 0);
 517         icsk->icsk_pending = icsk->icsk_ack.pending = 0;
 518 }
 519 EXPORT_SYMBOL(inet_csk_init_xmit_timers);
 520
 521 void inet_csk_clear_xmit_timers(struct sock *sk)
 522 {
 523         struct inet_connection_sock *icsk = inet_csk(sk);
 524
 525         icsk->icsk_pending = icsk->icsk_ack.pending = icsk->icsk_ack.blocked = 0;
 526
 527         sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
 528         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 529         sk_stop_timer(sk, &sk->sk_timer);
 530 }
 531 EXPORT_SYMBOL(inet_csk_clear_xmit_timers);
 532
 533 void inet_csk_delete_keepalive_timer(struct sock *sk)
 534 {
 535         sk_stop_timer(sk, &sk->sk_timer);
 536 }
 537 EXPORT_SYMBOL(inet_csk_delete_keepalive_timer);
 538
 539 void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
 540 {
 541         sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
 542 }
 543 EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);
 544
 545 struct dst_entry *inet_csk_route_req(const struct sock *sk,
 546                                      struct flowi4 *fl4,
 547                                      const struct request_sock *req)
 548 {
 549         const struct inet_request_sock *ireq = inet_rsk(req);
 550         struct net *net = read_pnet(&ireq->ireq_net);
 551         struct ip_options_rcu *opt;
 552         struct rtable *rt;
 553
 554         rcu_read_lock();
 555         opt = rcu_dereference(ireq->ireq_opt);
 556
 557         flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,
 558                            RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
 559                            sk->sk_protocol, inet_sk_flowi_flags(sk),
 560                            (opt && opt->opt.srr) ? opt->opt.faddr : ireq->ir_rmt_addr,
 561                            ireq->ir_loc_addr, ireq->ir_rmt_port,
 562                            htons(ireq->ir_num), sk->sk_uid);
 563         security_req_classify_flow(req, flowi4_to_flowi(fl4));
 564         rt = ip_route_output_flow(net, fl4, sk);
 565         if (IS_ERR(rt))
 566                 goto no_route;
 567         if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
 568                 goto route_err;
 569         rcu_read_unlock();
 570         return &rt->dst;
 571
 572 route_err:
 573         ip_rt_put(rt);
 574 no_route:
 575         rcu_read_unlock();
 576         __IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
 577         return NULL;
 578 }
 579 EXPORT_SYMBOL_GPL(inet_csk_route_req);
 580
 581 struct dst_entry *inet_csk_route_child_sock(const struct sock *sk,
 582                                             struct sock *newsk,
 583                                             const struct request_sock *req)
 584 {
 585         const struct inet_request_sock *ireq = inet_rsk(req);
 586         struct net *net = read_pnet(&ireq->ireq_net);
 587         struct inet_sock *newinet = inet_sk(newsk);
 588         struct ip_options_rcu *opt;
 589         struct flowi4 *fl4;
 590         struct rtable *rt;
 591
 592         opt = rcu_dereference(ireq->ireq_opt);
 593         fl4 = &newinet->cork.fl.u.ip4;
 594
 595         flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,
 596                            RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
 597                            sk->sk_protocol, inet_sk_flowi_flags(sk),
 598                            (opt && opt->opt.srr) ? opt->opt.faddr : ireq->ir_rmt_addr,
 599                            ireq->ir_loc_addr, ireq->ir_rmt_port,
 600                            htons(ireq->ir_num), sk->sk_uid);
 601         security_req_classify_flow(req, flowi4_to_flowi(fl4));
 602         rt = ip_route_output_flow(net, fl4, sk);
 603         if (IS_ERR(rt))
 604                 goto no_route;
 605         if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
 606                 goto route_err;
 607         return &rt->dst;
 608
 609 route_err:
 610         ip_rt_put(rt);
 611 no_route:
 612         __IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
 613         return NULL;
 614 }
 615 EXPORT_SYMBOL_GPL(inet_csk_route_child_sock);
 616
 617 #if IS_ENABLED(CONFIG_IPV6)
 618 #define AF_INET_FAMILY(fam) ((fam) == AF_INET)
 619 #else
 620 #define AF_INET_FAMILY(fam) true
 621 #endif
 622
 623 /* Decide when to expire the request and when to resend SYN-ACK */
 624 static inline void syn_ack_recalc(struct request_sock *req, const int thresh,
 625                                   const int max_retries,
 626                                   const u8 rskq_defer_accept,
 627                                   int *expire, int *resend)
 628 {
 629         if (!rskq_defer_accept) {
 630                 *expire = req->num_timeout >= thresh;
 631                 *resend = 1;
 632                 return;
 633         }
 634         *expire = req->num_timeout >= thresh &&
 635                   (!inet_rsk(req)->acked || req->num_timeout >= max_retries);
 636         /*
 637          * Do not resend while waiting for data after ACK,
 638          * start to resend on end of deferring period to give
 639          * last chance for data or ACK to create established socket.
 640          */
 641         *resend = !inet_rsk(req)->acked ||
 642                   req->num_timeout >= rskq_defer_accept - 1;
 643 }
 644
 645 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req)
 646 {
 647         int err = req->rsk_ops->rtx_syn_ack(parent, req);
 648
 649         if (!err)
 650                 req->num_retrans++;
 651         return err;
 652 }
 653 EXPORT_SYMBOL(inet_rtx_syn_ack);
 654
 655 /* return true if req was found in the ehash table */
 656 static bool reqsk_queue_unlink(struct request_sock_queue *queue,
 657                                struct request_sock *req)
 658 {
 659         struct inet_hashinfo *hashinfo = req_to_sk(req)->sk_prot->h.hashinfo;
 660         bool found = false;
 661
 662         if (sk_hashed(req_to_sk(req))) {
 663                 spinlock_t *lock = inet_ehash_lockp(hashinfo, req->rsk_hash);
 664
 665                 spin_lock(lock);
 666                 found = __sk_nulls_del_node_init_rcu(req_to_sk(req));
 667                 spin_unlock(lock);
 668         }
 669         if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer))
 670                 reqsk_put(req);
 671         return found;
 672 }
 673
 674 void inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req)
 675 {
 676         if (reqsk_queue_unlink(&inet_csk(sk)->icsk_accept_queue, req)) {
 677                 reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
 678                 reqsk_put(req);
 679         }
 680 }
 681 EXPORT_SYMBOL(inet_csk_reqsk_queue_drop);
 682
 683 void inet_csk_reqsk_queue_drop_and_put(struct sock *sk, struct request_sock *req)
 684 {
 685         inet_csk_reqsk_queue_drop(sk, req);
 686         reqsk_put(req);
 687 }
 688 EXPORT_SYMBOL(inet_csk_reqsk_queue_drop_and_put);
 689
 690 static void reqsk_timer_handler(struct timer_list *t)
 691 {
 692         struct request_sock *req = from_timer(req, t, rsk_timer);
 693         struct sock *sk_listener = req->rsk_listener;
 694         struct net *net = sock_net(sk_listener);
 695         struct inet_connection_sock *icsk = inet_csk(sk_listener);
 696         struct request_sock_queue *queue = &icsk->icsk_accept_queue;
 697         int qlen, expire = 0, resend = 0;
 698         int max_retries, thresh;
 699         u8 defer_accept;
 700
 701         if (inet_sk_state_load(sk_listener) != TCP_LISTEN)
 702                 goto drop;
 703
 704         max_retries = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_synack_retries;
 705         thresh = max_retries;
 706         /* Normally all the openreqs are young and become mature
 707          * (i.e. converted to established socket) for first timeout.
 708          * If synack was not acknowledged for 1 second, it means
 709          * one of the following things: synack was lost, ack was lost,
 710          * rtt is high or nobody planned to ack (i.e. synflood).
 711          * When server is a bit loaded, queue is populated with old
 712          * open requests, reducing effective size of queue.
 713          * When server is well loaded, queue size reduces to zero
 714          * after several minutes of work. It is not synflood,
 715          * it is normal operation. The solution is pruning
 716          * too old entries overriding normal timeout, when
 717          * situation becomes dangerous.
 718          *
 719          * Essentially, we reserve half of room for young
 720          * embrions; and abort old ones without pity, if old
 721          * ones are about to clog our table.
 722          */
 723         qlen = reqsk_queue_len(queue);
 724         if ((qlen << 1) > max(8U, sk_listener->sk_max_ack_backlog)) {
 725                 int young = reqsk_queue_len_young(queue) << 1;
 726
 727                 while (thresh > 2) {
 728                         if (qlen < young)
 729                                 break;
 730                         thresh--;
 731                         young <<= 1;
 732                 }
 733         }
 734         defer_accept = READ_ONCE(queue->rskq_defer_accept);
 735         if (defer_accept)
 736                 max_retries = defer_accept;
 737         syn_ack_recalc(req, thresh, max_retries, defer_accept,
 738                        &expire, &resend);
 739         req->rsk_ops->syn_ack_timeout(req);
 740         if (!expire &&
 741             (!resend ||
 742              !inet_rtx_syn_ack(sk_listener, req) ||
 743              inet_rsk(req)->acked)) {
 744                 unsigned long timeo;
 745
 746                 if (req->num_timeout++ == 0)
 747                         atomic_dec(&queue->young);
 748                 timeo = min(TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
 749                 mod_timer(&req->rsk_timer, jiffies + timeo);
 750                 return;
 751         }
 752 drop:
 753         inet_csk_reqsk_queue_drop_and_put(sk_listener, req);
 754 }
 755
 756 static void reqsk_queue_hash_req(struct request_sock *req,
 757                                  unsigned long timeout)
 758 {
 759         req->num_retrans = 0;
 760         req->num_timeout = 0;
 761         req->sk = NULL;
 762
 763         timer_setup(&req->rsk_timer, reqsk_timer_handler, TIMER_PINNED);
 764         mod_timer(&req->rsk_timer, jiffies + timeout);
 765
 766         inet_ehash_insert(req_to_sk(req), NULL);
 767         /* before letting lookups find us, make sure all req fields
 768          * are committed to memory and refcnt initialized.
 769          */
 770         smp_wmb();
 771         refcount_set(&req->rsk_refcnt, 2 + 1);
 772 }
 773
 774 void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
 775                                    unsigned long timeout)
 776 {
 777         reqsk_queue_hash_req(req, timeout);
 778         inet_csk_reqsk_queue_added(sk);
 779 }
 780 EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_hash_add);
 781
 782 /**
 783  *      inet_csk_clone_lock - clone an inet socket, and lock its clone
 784  *      @sk: the socket to clone
 785  *      @req: request_sock
 786  *      @priority: for allocation (%GFP_KERNEL, %GFP_ATOMIC, etc)
 787  *
 788  *      Caller must unlock socket even in error path (bh_unlock_sock(newsk))
 789  */
 790 struct sock *inet_csk_clone_lock(const struct sock *sk,
 791                                  const struct request_sock *req,
 792                                  const gfp_t priority)
 793 {
 794         struct sock *newsk = sk_clone_lock(sk, priority);
 795
 796         if (newsk) {
 797                 struct inet_connection_sock *newicsk = inet_csk(newsk);
 798
 799                 inet_sk_set_state(newsk, TCP_SYN_RECV);
 800                 newicsk->icsk_bind_hash = NULL;
 801
 802                 inet_sk(newsk)->inet_dport = inet_rsk(req)->ir_rmt_port;
 803                 inet_sk(newsk)->inet_num = inet_rsk(req)->ir_num;
 804                 inet_sk(newsk)->inet_sport = htons(inet_rsk(req)->ir_num);
 805
 806                 /* listeners have SOCK_RCU_FREE, not the children */
 807                 sock_reset_flag(newsk, SOCK_RCU_FREE);
 808
 809                 inet_sk(newsk)->mc_list = NULL;
 810
 811                 newsk->sk_mark = inet_rsk(req)->ir_mark;
 812                 atomic64_set(&newsk->sk_cookie,
 813                              atomic64_read(&inet_rsk(req)->ir_cookie));
 814
 815                 newicsk->icsk_retransmits = 0;
 816                 newicsk->icsk_backoff     = 0;
 817                 newicsk->icsk_probes_out  = 0;
 818
 819                 /* Deinitialize accept_queue to trap illegal accesses. */
 820                 memset(&newicsk->icsk_accept_queue, 0, sizeof(newicsk->icsk_accept_queue));
 821
 822                 security_inet_csk_clone(newsk, req);
 823         }
 824         return newsk;
 825 }
 826 EXPORT_SYMBOL_GPL(inet_csk_clone_lock);
 827
 828 /*
 829  * At this point, there should be no process reference to this
 830  * socket, and thus no user references at all.  Therefore we
 831  * can assume the socket waitqueue is inactive and nobody will
 832  * try to jump onto it.
 833  */
 834 void inet_csk_destroy_sock(struct sock *sk)
 835 {
 836         WARN_ON(sk->sk_state != TCP_CLOSE);
 837         WARN_ON(!sock_flag(sk, SOCK_DEAD));
 838
 839         /* It cannot be in hash table! */
 840         WARN_ON(!sk_unhashed(sk));
 841
 842         /* If it has not 0 inet_sk(sk)->inet_num, it must be bound */
 843         WARN_ON(inet_sk(sk)->inet_num && !inet_csk(sk)->icsk_bind_hash);
 844
 845         sk->sk_prot->destroy(sk);
 846
 847         sk_stream_kill_queues(sk);
 848
 849         xfrm_sk_free_policy(sk);
 850
 851         sk_refcnt_debug_release(sk);
 852
 853         percpu_counter_dec(sk->sk_prot->orphan_count);
 854
 855         sock_put(sk);
 856 }
 857 EXPORT_SYMBOL(inet_csk_destroy_sock);
 858
 859 /* This function allows to force a closure of a socket after the call to
 860  * tcp/dccp_create_openreq_child().
 861  */
 862 void inet_csk_prepare_forced_close(struct sock *sk)
 863         __releases(&sk->sk_lock.slock)
 864 {
 865         /* sk_clone_lock locked the socket and set refcnt to 2 */
 866         bh_unlock_sock(sk);
 867         sock_put(sk);
 868
 869         /* The below has to be done to allow calling inet_csk_destroy_sock */
 870         sock_set_flag(sk, SOCK_DEAD);
 871         percpu_counter_inc(sk->sk_prot->orphan_count);
 872         inet_sk(sk)->inet_num = 0;
 873 }
 874 EXPORT_SYMBOL(inet_csk_prepare_forced_close);
 875
 876 int inet_csk_listen_start(struct sock *sk, int backlog)
 877 {
 878         struct inet_connection_sock *icsk = inet_csk(sk);
 879         struct inet_sock *inet = inet_sk(sk);
 880         int err = -EADDRINUSE;
 881
 882         reqsk_queue_alloc(&icsk->icsk_accept_queue);
 883
 884         sk->sk_ack_backlog = 0;
 885         inet_csk_delack_init(sk);
 886
 887         /* There is race window here: we announce ourselves listening,
 888          * but this transition is still not validated by get_port().
 889          * It is OK, because this socket enters to hash table only
 890          * after validation is complete.
 891          */
 892         inet_sk_state_store(sk, TCP_LISTEN);
 893         if (!sk->sk_prot->get_port(sk, inet->inet_num)) {
 894                 inet->inet_sport = htons(inet->inet_num);
 895
 896                 sk_dst_reset(sk);
 897                 err = sk->sk_prot->hash(sk);
 898
 899                 if (likely(!err))
 900                         return 0;
 901         }
 902
 903         inet_sk_set_state(sk, TCP_CLOSE);
 904         return err;
 905 }
 906 EXPORT_SYMBOL_GPL(inet_csk_listen_start);
 907
 908 static void inet_child_forget(struct sock *sk, struct request_sock *req,
 909                               struct sock *child)
 910 {
 911         sk->sk_prot->disconnect(child, O_NONBLOCK);
 912
 913         sock_orphan(child);
 914
 915         percpu_counter_inc(sk->sk_prot->orphan_count);
 916
 917         if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(req)->tfo_listener) {
 918                 BUG_ON(tcp_sk(child)->fastopen_rsk != req);
 919                 BUG_ON(sk != req->rsk_listener);
 920
 921                 /* Paranoid, to prevent race condition if
 922                  * an inbound pkt destined for child is
 923                  * blocked by sock lock in tcp_v4_rcv().
 924                  * Also to satisfy an assertion in
 925                  * tcp_v4_destroy_sock().
 926                  */
 927                 tcp_sk(child)->fastopen_rsk = NULL;
 928         }
 929         inet_csk_destroy_sock(child);
 930 }
 931
 932 struct sock *inet_csk_reqsk_queue_add(struct sock *sk,
 933                                       struct request_sock *req,
 934                                       struct sock *child)
 935 {
 936         struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 937
 938         spin_lock(&queue->rskq_lock);
 939         if (unlikely(sk->sk_state != TCP_LISTEN)) {
 940                 inet_child_forget(sk, req, child);
 941                 child = NULL;
 942         } else {
 943                 req->sk = child;
 944                 req->dl_next = NULL;
 945                 if (queue->rskq_accept_head == NULL)
 946                         queue->rskq_accept_head = req;
 947                 else
 948                         queue->rskq_accept_tail->dl_next = req;
 949                 queue->rskq_accept_tail = req;
 950                 sk_acceptq_added(sk);
 951         }
 952         spin_unlock(&queue->rskq_lock);
 953         return child;
 954 }
 955 EXPORT_SYMBOL(inet_csk_reqsk_queue_add);
 956
 957 struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,
 958                                          struct request_sock *req, bool own_req)
 959 {
 960         if (own_req) {
 961                 inet_csk_reqsk_queue_drop(sk, req);
 962                 reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
 963                 if (inet_csk_reqsk_queue_add(sk, req, child))
 964                         return child;
 965         }
 966         /* Too bad, another child took ownership of the request, undo. */
 967         bh_unlock_sock(child);
 968         sock_put(child);
 969         return NULL;
 970 }
 971 EXPORT_SYMBOL(inet_csk_complete_hashdance);
 972
 973 /*
 974  *      This routine closes sockets which have been at least partially
 975  *      opened, but not yet accepted.
 976  */
 977 void inet_csk_listen_stop(struct sock *sk)
 978 {
 979         struct inet_connection_sock *icsk = inet_csk(sk);
 980         struct request_sock_queue *queue = &icsk->icsk_accept_queue;
 981         struct request_sock *next, *req;
 982
 983         /* Following specs, it would be better either to send FIN
 984          * (and enter FIN-WAIT-1, it is normal close)
 985          * or to send active reset (abort).
 986          * Certainly, it is pretty dangerous while synflood, but it is
 987          * bad justification for our negligence 8)
 988          * To be honest, we are not able to make either
 989          * of the variants now.                 --ANK
 990          */
 991         while ((req = reqsk_queue_remove(queue, sk)) != NULL) {
 992                 struct sock *child = req->sk;
 993
 994                 local_bh_disable();
 995                 bh_lock_sock(child);
 996                 WARN_ON(sock_owned_by_user(child));
 997                 sock_hold(child);
 998
 999                 inet_child_forget(sk, req, child);
1000                 reqsk_put(req);
1001                 bh_unlock_sock(child);
1002                 local_bh_enable();
1003                 sock_put(child);
1004
1005                 cond_resched();
1006         }
1007         if (queue->fastopenq.rskq_rst_head) {
1008                 /* Free all the reqs queued in rskq_rst_head. */
1009                 spin_lock_bh(&queue->fastopenq.lock);
1010                 req = queue->fastopenq.rskq_rst_head;
1011                 queue->fastopenq.rskq_rst_head = NULL;
1012                 spin_unlock_bh(&queue->fastopenq.lock);
1013                 while (req != NULL) {
1014                         next = req->dl_next;
1015                         reqsk_put(req);
1016                         req = next;
1017                 }
1018         }
1019         WARN_ON_ONCE(sk->sk_ack_backlog);
1020 }
1021 EXPORT_SYMBOL_GPL(inet_csk_listen_stop);
1022
1023 void inet_csk_addr2sockaddr(struct sock *sk, struct sockaddr *uaddr)
1024 {
1025         struct sockaddr_in *sin = (struct sockaddr_in *)uaddr;
1026         const struct inet_sock *inet = inet_sk(sk);
1027
1028         sin->sin_family         = AF_INET;
1029         sin->sin_addr.s_addr    = inet->inet_daddr;
1030         sin->sin_port           = inet->inet_dport;
1031 }
1032 EXPORT_SYMBOL_GPL(inet_csk_addr2sockaddr);
1033
1034 #ifdef CONFIG_COMPAT
1035 int inet_csk_compat_getsockopt(struct sock *sk, int level, int optname,
1036                                char __user *optval, int __user *optlen)
1037 {
1038         const struct inet_connection_sock *icsk = inet_csk(sk);
1039
1040         if (icsk->icsk_af_ops->compat_getsockopt)
1041                 return icsk->icsk_af_ops->compat_getsockopt(sk, level, optname,
1042                                                             optval, optlen);
1043         return icsk->icsk_af_ops->getsockopt(sk, level, optname,
1044                                              optval, optlen);
1045 }
1046 EXPORT_SYMBOL_GPL(inet_csk_compat_getsockopt);
1047
1048 int inet_csk_compat_setsockopt(struct sock *sk, int level, int optname,
1049                                char __user *optval, unsigned int optlen)
1050 {
1051         const struct inet_connection_sock *icsk = inet_csk(sk);
1052
1053         if (icsk->icsk_af_ops->compat_setsockopt)
1054                 return icsk->icsk_af_ops->compat_setsockopt(sk, level, optname,
1055                                                             optval, optlen);
1056         return icsk->icsk_af_ops->setsockopt(sk, level, optname,
1057                                              optval, optlen);
1058 }
1059 EXPORT_SYMBOL_GPL(inet_csk_compat_setsockopt);
1060 #endif
1061
1062 static struct dst_entry *inet_csk_rebuild_route(struct sock *sk, struct flowi *fl)
1063 {
1064         const struct inet_sock *inet = inet_sk(sk);
1065         const struct ip_options_rcu *inet_opt;
1066         __be32 daddr = inet->inet_daddr;
1067         struct flowi4 *fl4;
1068         struct rtable *rt;
1069
1070         rcu_read_lock();
1071         inet_opt = rcu_dereference(inet->inet_opt);
1072         if (inet_opt && inet_opt->opt.srr)
1073                 daddr = inet_opt->opt.faddr;
1074         fl4 = &fl->u.ip4;
1075         rt = ip_route_output_ports(sock_net(sk), fl4, sk, daddr,
1076                                    inet->inet_saddr, inet->inet_dport,
1077                                    inet->inet_sport, sk->sk_protocol,
1078                                    RT_CONN_FLAGS(sk), sk->sk_bound_dev_if);
1079         if (IS_ERR(rt))
1080                 rt = NULL;
1081         if (rt)
1082                 sk_setup_caps(sk, &rt->dst);
1083         rcu_read_unlock();
1084
1085         return &rt->dst;
1086 }
1087
1088 struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu)
1089 {
1090         struct dst_entry *dst = __sk_dst_check(sk, 0);
1091         struct inet_sock *inet = inet_sk(sk);
1092
1093         if (!dst) {
1094                 dst = inet_csk_rebuild_route(sk, &inet->cork.fl);
1095                 if (!dst)
1096                         goto out;
1097         }
1098         dst->ops->update_pmtu(dst, sk, NULL, mtu);
1099
1100         dst = __sk_dst_check(sk, 0);
1101         if (!dst)
1102                 dst = inet_csk_rebuild_route(sk, &inet->cork.fl);
1103 out:
1104         return dst;
1105 }
1106 EXPORT_SYMBOL_GPL(inet_csk_update_pmtu);