net/ipv4/inet_hashtables.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  *              Generic INET transport hashtables
   7  *
   8  * Authors:     Lotsa people, from code originally in tcp
   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/config.h>
  17 #include <linux/module.h>
  18 #include <linux/sched.h>
  19 #include <linux/slab.h>
  20 #include <linux/wait.h>
  21
  22 #include <net/inet_connection_sock.h>
  23 #include <net/inet_hashtables.h>
  24
  25 /*
  26  * Allocate and initialize a new local port bind bucket.
  27  * The bindhash mutex for snum's hash chain must be held here.
  28  */
  29 struct inet_bind_bucket *inet_bind_bucket_create(kmem_cache_t *cachep,
  30                                                  struct inet_bind_hashbucket *head,
  31                                                  const unsigned short snum)
  32 {
  33         struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, SLAB_ATOMIC);
  34
  35         if (tb != NULL) {
  36                 tb->port      = snum;
  37                 tb->fastreuse = 0;
  38                 INIT_HLIST_HEAD(&tb->owners);
  39                 hlist_add_head(&tb->node, &head->chain);
  40         }
  41         return tb;
  42 }
  43
  44 EXPORT_SYMBOL(inet_bind_bucket_create);
  45
  46 /*
  47  * Caller must hold hashbucket lock for this tb with local BH disabled
  48  */
  49 void inet_bind_bucket_destroy(kmem_cache_t *cachep, struct inet_bind_bucket *tb)
  50 {
  51         if (hlist_empty(&tb->owners)) {
  52                 __hlist_del(&tb->node);
  53                 kmem_cache_free(cachep, tb);
  54         }
  55 }
  56
  57 void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
  58                     const unsigned short snum)
  59 {
  60         inet_sk(sk)->num = snum;
  61         sk_add_bind_node(sk, &tb->owners);
  62         inet_csk(sk)->icsk_bind_hash = tb;
  63 }
  64
  65 EXPORT_SYMBOL(inet_bind_hash);
  66
  67 /*
  68  * Get rid of any references to a local port held by the given sock.
  69  */
  70 static void __inet_put_port(struct inet_hashinfo *hashinfo, struct sock *sk)
  71 {
  72         const int bhash = inet_bhashfn(inet_sk(sk)->num, hashinfo->bhash_size);
  73         struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
  74         struct inet_bind_bucket *tb;
  75
  76         spin_lock(&head->lock);
  77         tb = inet_csk(sk)->icsk_bind_hash;
  78         __sk_del_bind_node(sk);
  79         inet_csk(sk)->icsk_bind_hash = NULL;
  80         inet_sk(sk)->num = 0;
  81         inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
  82         spin_unlock(&head->lock);
  83 }
  84
  85 void inet_put_port(struct inet_hashinfo *hashinfo, struct sock *sk)
  86 {
  87         local_bh_disable();
  88         __inet_put_port(hashinfo, sk);
  89         local_bh_enable();
  90 }
  91
  92 EXPORT_SYMBOL(inet_put_port);
  93
  94 /*
  95  * This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP.
  96  * Look, when several writers sleep and reader wakes them up, all but one
  97  * immediately hit write lock and grab all the cpus. Exclusive sleep solves
  98  * this, _but_ remember, it adds useless work on UP machines (wake up each
  99  * exclusive lock release). It should be ifdefed really.
 100  */
 101 void inet_listen_wlock(struct inet_hashinfo *hashinfo)
 102 {
 103         write_lock(&hashinfo->lhash_lock);
 104
 105         if (atomic_read(&hashinfo->lhash_users)) {
 106                 DEFINE_WAIT(wait);
 107
 108                 for (;;) {
 109                         prepare_to_wait_exclusive(&hashinfo->lhash_wait,
 110                                                   &wait, TASK_UNINTERRUPTIBLE);
 111                         if (!atomic_read(&hashinfo->lhash_users))
 112                                 break;
 113                         write_unlock_bh(&hashinfo->lhash_lock);
 114                         schedule();
 115                         write_lock_bh(&hashinfo->lhash_lock);
 116                 }
 117
 118                 finish_wait(&hashinfo->lhash_wait, &wait);
 119         }
 120 }
 121
 122 EXPORT_SYMBOL(inet_listen_wlock);
 123
 124 /*
 125  * Don't inline this cruft. Here are some nice properties to exploit here. The
 126  * BSD API does not allow a listening sock to specify the remote port nor the
 127  * remote address for the connection. So always assume those are both
 128  * wildcarded during the search since they can never be otherwise.
 129  */
 130 struct sock *__inet_lookup_listener(const struct hlist_head *head, const u32 daddr,
 131                                     const unsigned short hnum, const int dif)
 132 {
 133         struct sock *result = NULL, *sk;
 134         const struct hlist_node *node;
 135         int hiscore = -1;
 136
 137         sk_for_each(sk, node, head) {
 138                 const struct inet_sock *inet = inet_sk(sk);
 139
 140                 if (inet->num == hnum && !ipv6_only_sock(sk)) {
 141                         const __u32 rcv_saddr = inet->rcv_saddr;
 142                         int score = sk->sk_family == PF_INET ? 1 : 0;
 143
 144                         if (rcv_saddr) {
 145                                 if (rcv_saddr != daddr)
 146                                         continue;
 147                                 score += 2;
 148                         }
 149                         if (sk->sk_bound_dev_if) {
 150                                 if (sk->sk_bound_dev_if != dif)
 151                                         continue;
 152                                 score += 2;
 153                         }
 154                         if (score == 5)
 155                                 return sk;
 156                         if (score > hiscore) {
 157                                 hiscore = score;
 158                                 result  = sk;
 159                         }
 160                 }
 161         }
 162         return result;
 163 }
 164
 165 EXPORT_SYMBOL_GPL(__inet_lookup_listener);