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/random.h>
  19 #include <linux/sched.h>
  20 #include <linux/slab.h>
  21 #include <linux/wait.h>
  22
  23 #include <net/inet_connection_sock.h>
  24 #include <net/inet_hashtables.h>
  25 #include <net/ip.h>
  26
  27 /*
  28  * Allocate and initialize a new local port bind bucket.
  29  * The bindhash mutex for snum's hash chain must be held here.
  30  */
  31 struct inet_bind_bucket *inet_bind_bucket_create(kmem_cache_t *cachep,
  32                                                  struct inet_bind_hashbucket *head,
  33                                                  const unsigned short snum)
  34 {
  35         struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, SLAB_ATOMIC);
  36
  37         if (tb != NULL) {
  38                 tb->port      = snum;
  39                 tb->fastreuse = 0;
  40                 INIT_HLIST_HEAD(&tb->owners);
  41                 hlist_add_head(&tb->node, &head->chain);
  42         }
  43         return tb;
  44 }
  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 /*
  66  * Get rid of any references to a local port held by the given sock.
  67  */
  68 static void __inet_put_port(struct inet_hashinfo *hashinfo, struct sock *sk)
  69 {
  70         const int bhash = inet_bhashfn(inet_sk(sk)->num, hashinfo->bhash_size);
  71         struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
  72         struct inet_bind_bucket *tb;
  73
  74         spin_lock(&head->lock);
  75         tb = inet_csk(sk)->icsk_bind_hash;
  76         __sk_del_bind_node(sk);
  77         inet_csk(sk)->icsk_bind_hash = NULL;
  78         inet_sk(sk)->num = 0;
  79         inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
  80         spin_unlock(&head->lock);
  81 }
  82
  83 void inet_put_port(struct inet_hashinfo *hashinfo, struct sock *sk)
  84 {
  85         local_bh_disable();
  86         __inet_put_port(hashinfo, sk);
  87         local_bh_enable();
  88 }
  89
  90 EXPORT_SYMBOL(inet_put_port);
  91
  92 /*
  93  * This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP.
  94  * Look, when several writers sleep and reader wakes them up, all but one
  95  * immediately hit write lock and grab all the cpus. Exclusive sleep solves
  96  * this, _but_ remember, it adds useless work on UP machines (wake up each
  97  * exclusive lock release). It should be ifdefed really.
  98  */
  99 void inet_listen_wlock(struct inet_hashinfo *hashinfo)
 100 {
 101         write_lock(&hashinfo->lhash_lock);
 102
 103         if (atomic_read(&hashinfo->lhash_users)) {
 104                 DEFINE_WAIT(wait);
 105
 106                 for (;;) {
 107                         prepare_to_wait_exclusive(&hashinfo->lhash_wait,
 108                                                   &wait, TASK_UNINTERRUPTIBLE);
 109                         if (!atomic_read(&hashinfo->lhash_users))
 110                                 break;
 111                         write_unlock_bh(&hashinfo->lhash_lock);
 112                         schedule();
 113                         write_lock_bh(&hashinfo->lhash_lock);
 114                 }
 115
 116                 finish_wait(&hashinfo->lhash_wait, &wait);
 117         }
 118 }
 119
 120 EXPORT_SYMBOL(inet_listen_wlock);
 121
 122 /*
 123  * Don't inline this cruft. Here are some nice properties to exploit here. The
 124  * BSD API does not allow a listening sock to specify the remote port nor the
 125  * remote address for the connection. So always assume those are both
 126  * wildcarded during the search since they can never be otherwise.
 127  */
 128 struct sock *__inet_lookup_listener(const struct hlist_head *head, const u32 daddr,
 129                                     const unsigned short hnum, const int dif)
 130 {
 131         struct sock *result = NULL, *sk;
 132         const struct hlist_node *node;
 133         int hiscore = -1;
 134
 135         sk_for_each(sk, node, head) {
 136                 const struct inet_sock *inet = inet_sk(sk);
 137
 138                 if (inet->num == hnum && !ipv6_only_sock(sk)) {
 139                         const __u32 rcv_saddr = inet->rcv_saddr;
 140                         int score = sk->sk_family == PF_INET ? 1 : 0;
 141
 142                         if (rcv_saddr) {
 143                                 if (rcv_saddr != daddr)
 144                                         continue;
 145                                 score += 2;
 146                         }
 147                         if (sk->sk_bound_dev_if) {
 148                                 if (sk->sk_bound_dev_if != dif)
 149                                         continue;
 150                                 score += 2;
 151                         }
 152                         if (score == 5)
 153                                 return sk;
 154                         if (score > hiscore) {
 155                                 hiscore = score;
 156                                 result  = sk;
 157                         }
 158                 }
 159         }
 160         return result;
 161 }
 162
 163 EXPORT_SYMBOL_GPL(__inet_lookup_listener);
 164
 165 /* called with local bh disabled */
 166 static int __inet_check_established(struct inet_timewait_death_row *death_row,
 167                                     struct sock *sk, __u16 lport,
 168                                     struct inet_timewait_sock **twp)
 169 {
 170         struct inet_hashinfo *hinfo = death_row->hashinfo;
 171         struct inet_sock *inet = inet_sk(sk);
 172         u32 daddr = inet->rcv_saddr;
 173         u32 saddr = inet->daddr;
 174         int dif = sk->sk_bound_dev_if;
 175         INET_ADDR_COOKIE(acookie, saddr, daddr)
 176         const __u32 ports = INET_COMBINED_PORTS(inet->dport, lport);
 177         unsigned int hash = inet_ehashfn(daddr, lport, saddr, inet->dport);
 178         struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
 179         struct sock *sk2;
 180         const struct hlist_node *node;
 181         struct inet_timewait_sock *tw;
 182
 183         prefetch(head->chain.first);
 184         write_lock(&head->lock);
 185
 186         /* Check TIME-WAIT sockets first. */
 187         sk_for_each(sk2, node, &(head + hinfo->ehash_size)->chain) {
 188                 tw = inet_twsk(sk2);
 189
 190                 if (INET_TW_MATCH(sk2, hash, acookie, saddr, daddr, ports, dif)) {
 191                         if (twsk_unique(sk, sk2, twp))
 192                                 goto unique;
 193                         else
 194                                 goto not_unique;
 195                 }
 196         }
 197         tw = NULL;
 198
 199         /* And established part... */
 200         sk_for_each(sk2, node, &head->chain) {
 201                 if (INET_MATCH(sk2, hash, acookie, saddr, daddr, ports, dif))
 202                         goto not_unique;
 203         }
 204
 205 unique:
 206         /* Must record num and sport now. Otherwise we will see
 207          * in hash table socket with a funny identity. */
 208         inet->num = lport;
 209         inet->sport = htons(lport);
 210         sk->sk_hash = hash;
 211         BUG_TRAP(sk_unhashed(sk));
 212         __sk_add_node(sk, &head->chain);
 213         sock_prot_inc_use(sk->sk_prot);
 214         write_unlock(&head->lock);
 215
 216         if (twp) {
 217                 *twp = tw;
 218                 NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);
 219         } else if (tw) {
 220                 /* Silly. Should hash-dance instead... */
 221                 inet_twsk_deschedule(tw, death_row);
 222                 NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);
 223
 224                 inet_twsk_put(tw);
 225         }
 226
 227         return 0;
 228
 229 not_unique:
 230         write_unlock(&head->lock);
 231         return -EADDRNOTAVAIL;
 232 }
 233
 234 static inline u32 inet_sk_port_offset(const struct sock *sk)
 235 {
 236         const struct inet_sock *inet = inet_sk(sk);
 237         return secure_ipv4_port_ephemeral(inet->rcv_saddr, inet->daddr,
 238                                           inet->dport);
 239 }
 240
 241 /*
 242  * Bind a port for a connect operation and hash it.
 243  */
 244 int inet_hash_connect(struct inet_timewait_death_row *death_row,
 245                       struct sock *sk)
 246 {
 247         struct inet_hashinfo *hinfo = death_row->hashinfo;
 248         const unsigned short snum = inet_sk(sk)->num;
 249         struct inet_bind_hashbucket *head;
 250         struct inet_bind_bucket *tb;
 251         int ret;
 252
 253         if (!snum) {
 254                 int low = sysctl_local_port_range[0];
 255                 int high = sysctl_local_port_range[1];
 256                 int range = high - low;
 257                 int i;
 258                 int port;
 259                 static u32 hint;
 260                 u32 offset = hint + inet_sk_port_offset(sk);
 261                 struct hlist_node *node;
 262                 struct inet_timewait_sock *tw = NULL;
 263
 264                 local_bh_disable();
 265                 for (i = 1; i <= range; i++) {
 266                         port = low + (i + offset) % range;
 267                         head = &hinfo->bhash[inet_bhashfn(port, hinfo->bhash_size)];
 268                         spin_lock(&head->lock);
 269
 270                         /* Does not bother with rcv_saddr checks,
 271                          * because the established check is already
 272                          * unique enough.
 273                          */
 274                         inet_bind_bucket_for_each(tb, node, &head->chain) {
 275                                 if (tb->port == port) {
 276                                         BUG_TRAP(!hlist_empty(&tb->owners));
 277                                         if (tb->fastreuse >= 0)
 278                                                 goto next_port;
 279                                         if (!__inet_check_established(death_row,
 280                                                                       sk, port,
 281                                                                       &tw))
 282                                                 goto ok;
 283                                         goto next_port;
 284                                 }
 285                         }
 286
 287                         tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep, head, port);
 288                         if (!tb) {
 289                                 spin_unlock(&head->lock);
 290                                 break;
 291                         }
 292                         tb->fastreuse = -1;
 293                         goto ok;
 294
 295                 next_port:
 296                         spin_unlock(&head->lock);
 297                 }
 298                 local_bh_enable();
 299
 300                 return -EADDRNOTAVAIL;
 301
 302 ok:
 303                 hint += i;
 304
 305                 /* Head lock still held and bh's disabled */
 306                 inet_bind_hash(sk, tb, port);
 307                 if (sk_unhashed(sk)) {
 308                         inet_sk(sk)->sport = htons(port);
 309                         __inet_hash(hinfo, sk, 0);
 310                 }
 311                 spin_unlock(&head->lock);
 312
 313                 if (tw) {
 314                         inet_twsk_deschedule(tw, death_row);
 315                         inet_twsk_put(tw);
 316                 }
 317
 318                 ret = 0;
 319                 goto out;
 320         }
 321
 322         head = &hinfo->bhash[inet_bhashfn(snum, hinfo->bhash_size)];
 323         tb  = inet_csk(sk)->icsk_bind_hash;
 324         spin_lock_bh(&head->lock);
 325         if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
 326                 __inet_hash(hinfo, sk, 0);
 327                 spin_unlock_bh(&head->lock);
 328                 return 0;
 329         } else {
 330                 spin_unlock(&head->lock);
 331                 /* No definite answer... Walk to established hash table */
 332                 ret = __inet_check_established(death_row, sk, snum, NULL);
 333 out:
 334                 local_bh_enable();
 335                 return ret;
 336         }
 337 }
 338
 339 EXPORT_SYMBOL_GPL(inet_hash_connect);