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