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/module.h>
  17 #include <linux/random.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 #include <net/ip.h>
  25
  26 /*
  27  * Allocate and initialize a new local port bind bucket.
  28  * The bindhash mutex for snum's hash chain must be held here.
  29  */
  30 struct inet_bind_bucket *inet_bind_bucket_create(kmem_cache_t *cachep,
  31                                                  struct inet_bind_hashbucket *head,
  32                                                  const unsigned short snum)
  33 {
  34         struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, SLAB_ATOMIC);
  35
  36         if (tb != NULL) {
  37                 tb->port      = snum;
  38                 tb->fastreuse = 0;
  39                 INIT_HLIST_HEAD(&tb->owners);
  40                 hlist_add_head(&tb->node, &head->chain);
  41         }
  42         return tb;
  43 }
  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         inet_sk(sk)->num = snum;
  60         sk_add_bind_node(sk, &tb->owners);
  61         inet_csk(sk)->icsk_bind_hash = tb;
  62 }
  63
  64 /*
  65  * Get rid of any references to a local port held by the given sock.
  66  */
  67 static void __inet_put_port(struct inet_hashinfo *hashinfo, struct sock *sk)
  68 {
  69         const int bhash = inet_bhashfn(inet_sk(sk)->num, hashinfo->bhash_size);
  70         struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
  71         struct inet_bind_bucket *tb;
  72
  73         spin_lock(&head->lock);
  74         tb = inet_csk(sk)->icsk_bind_hash;
  75         __sk_del_bind_node(sk);
  76         inet_csk(sk)->icsk_bind_hash = NULL;
  77         inet_sk(sk)->num = 0;
  78         inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
  79         spin_unlock(&head->lock);
  80 }
  81
  82 void inet_put_port(struct inet_hashinfo *hashinfo, struct sock *sk)
  83 {
  84         local_bh_disable();
  85         __inet_put_port(hashinfo, sk);
  86         local_bh_enable();
  87 }
  88
  89 EXPORT_SYMBOL(inet_put_port);
  90
  91 /*
  92  * This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP.
  93  * Look, when several writers sleep and reader wakes them up, all but one
  94  * immediately hit write lock and grab all the cpus. Exclusive sleep solves
  95  * this, _but_ remember, it adds useless work on UP machines (wake up each
  96  * exclusive lock release). It should be ifdefed really.
  97  */
  98 void inet_listen_wlock(struct inet_hashinfo *hashinfo)
  99 {
 100         write_lock(&hashinfo->lhash_lock);
 101
 102         if (atomic_read(&hashinfo->lhash_users)) {
 103                 DEFINE_WAIT(wait);
 104
 105                 for (;;) {
 106                         prepare_to_wait_exclusive(&hashinfo->lhash_wait,
 107                                                   &wait, TASK_UNINTERRUPTIBLE);
 108                         if (!atomic_read(&hashinfo->lhash_users))
 109                                 break;
 110                         write_unlock_bh(&hashinfo->lhash_lock);
 111                         schedule();
 112                         write_lock_bh(&hashinfo->lhash_lock);
 113                 }
 114
 115                 finish_wait(&hashinfo->lhash_wait, &wait);
 116         }
 117 }
 118
 119 EXPORT_SYMBOL(inet_listen_wlock);
 120
 121 /*
 122  * Don't inline this cruft. Here are some nice properties to exploit here. The
 123  * BSD API does not allow a listening sock to specify the remote port nor the
 124  * remote address for the connection. So always assume those are both
 125  * wildcarded during the search since they can never be otherwise.
 126  */
 127 struct sock *__inet_lookup_listener(const struct hlist_head *head, const u32 daddr,
 128                                     const unsigned short hnum, const int dif)
 129 {
 130         struct sock *result = NULL, *sk;
 131         const struct hlist_node *node;
 132         int hiscore = -1;
 133
 134         sk_for_each(sk, node, head) {
 135                 const struct inet_sock *inet = inet_sk(sk);
 136
 137                 if (inet->num == hnum && !ipv6_only_sock(sk)) {
 138                         const __u32 rcv_saddr = inet->rcv_saddr;
 139                         int score = sk->sk_family == PF_INET ? 1 : 0;
 140
 141                         if (rcv_saddr) {
 142                                 if (rcv_saddr != daddr)
 143                                         continue;
 144                                 score += 2;
 145                         }
 146                         if (sk->sk_bound_dev_if) {
 147                                 if (sk->sk_bound_dev_if != dif)
 148                                         continue;
 149                                 score += 2;
 150                         }
 151                         if (score == 5)
 152                                 return sk;
 153                         if (score > hiscore) {
 154                                 hiscore = score;
 155                                 result  = sk;
 156                         }
 157                 }
 158         }
 159         return result;
 160 }
 161
 162 EXPORT_SYMBOL_GPL(__inet_lookup_listener);
 163
 164 /* called with local bh disabled */
 165 static int __inet_check_established(struct inet_timewait_death_row *death_row,
 166                                     struct sock *sk, __u16 lport,
 167                                     struct inet_timewait_sock **twp)
 168 {
 169         struct inet_hashinfo *hinfo = death_row->hashinfo;
 170         struct inet_sock *inet = inet_sk(sk);
 171         u32 daddr = inet->rcv_saddr;
 172         u32 saddr = inet->daddr;
 173         int dif = sk->sk_bound_dev_if;
 174         INET_ADDR_COOKIE(acookie, saddr, daddr)
 175         const __u32 ports = INET_COMBINED_PORTS(inet->dport, lport);
 176         unsigned int hash = inet_ehashfn(daddr, lport, saddr, inet->dport);
 177         struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
 178         struct sock *sk2;
 179         const struct hlist_node *node;
 180         struct inet_timewait_sock *tw;
 181
 182         prefetch(head->chain.first);
 183         write_lock(&head->lock);
 184
 185         /* Check TIME-WAIT sockets first. */
 186         sk_for_each(sk2, node, &(head + hinfo->ehash_size)->chain) {
 187                 tw = inet_twsk(sk2);
 188
 189                 if (INET_TW_MATCH(sk2, hash, acookie, saddr, daddr, ports, dif)) {
 190                         if (twsk_unique(sk, sk2, twp))
 191                                 goto unique;
 192                         else
 193                                 goto not_unique;
 194                 }
 195         }
 196         tw = NULL;
 197
 198         /* And established part... */
 199         sk_for_each(sk2, node, &head->chain) {
 200                 if (INET_MATCH(sk2, hash, acookie, saddr, daddr, ports, dif))
 201                         goto not_unique;
 202         }
 203
 204 unique:
 205         /* Must record num and sport now. Otherwise we will see
 206          * in hash table socket with a funny identity. */
 207         inet->num = lport;
 208         inet->sport = htons(lport);
 209         sk->sk_hash = hash;
 210         BUG_TRAP(sk_unhashed(sk));
 211         __sk_add_node(sk, &head->chain);
 212         sock_prot_inc_use(sk->sk_prot);
 213         write_unlock(&head->lock);
 214
 215         if (twp) {
 216                 *twp = tw;
 217                 NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);
 218         } else if (tw) {
 219                 /* Silly. Should hash-dance instead... */
 220                 inet_twsk_deschedule(tw, death_row);
 221                 NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);
 222
 223                 inet_twsk_put(tw);
 224         }
 225
 226         return 0;
 227
 228 not_unique:
 229         write_unlock(&head->lock);
 230         return -EADDRNOTAVAIL;
 231 }
 232
 233 static inline u32 inet_sk_port_offset(const struct sock *sk)
 234 {
 235         const struct inet_sock *inet = inet_sk(sk);
 236         return secure_ipv4_port_ephemeral(inet->rcv_saddr, inet->daddr,
 237                                           inet->dport);
 238 }
 239
 240 /*
 241  * Bind a port for a connect operation and hash it.
 242  */
 243 int inet_hash_connect(struct inet_timewait_death_row *death_row,
 244                       struct sock *sk)
 245 {
 246         struct inet_hashinfo *hinfo = death_row->hashinfo;
 247         const unsigned short snum = inet_sk(sk)->num;
 248         struct inet_bind_hashbucket *head;
 249         struct inet_bind_bucket *tb;
 250         int ret;
 251
 252         if (!snum) {
 253                 int low = sysctl_local_port_range[0];
 254                 int high = sysctl_local_port_range[1];
 255                 int range = high - low;
 256                 int i;
 257                 int port;
 258                 static u32 hint;
 259                 u32 offset = hint + inet_sk_port_offset(sk);
 260                 struct hlist_node *node;
 261                 struct inet_timewait_sock *tw = NULL;
 262
 263                 local_bh_disable();
 264                 for (i = 1; i <= range; i++) {
 265                         port = low + (i + offset) % range;
 266                         head = &hinfo->bhash[inet_bhashfn(port, hinfo->bhash_size)];
 267                         spin_lock(&head->lock);
 268
 269                         /* Does not bother with rcv_saddr checks,
 270                          * because the established check is already
 271                          * unique enough.
 272                          */
 273                         inet_bind_bucket_for_each(tb, node, &head->chain) {
 274                                 if (tb->port == port) {
 275                                         BUG_TRAP(!hlist_empty(&tb->owners));
 276                                         if (tb->fastreuse >= 0)
 277                                                 goto next_port;
 278                                         if (!__inet_check_established(death_row,
 279                                                                       sk, port,
 280                                                                       &tw))
 281                                                 goto ok;
 282                                         goto next_port;
 283                                 }
 284                         }
 285
 286                         tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep, head, port);
 287                         if (!tb) {
 288                                 spin_unlock(&head->lock);
 289                                 break;
 290                         }
 291                         tb->fastreuse = -1;
 292                         goto ok;
 293
 294                 next_port:
 295                         spin_unlock(&head->lock);
 296                 }
 297                 local_bh_enable();
 298
 299                 return -EADDRNOTAVAIL;
 300
 301 ok:
 302                 hint += i;
 303
 304                 /* Head lock still held and bh's disabled */
 305                 inet_bind_hash(sk, tb, port);
 306                 if (sk_unhashed(sk)) {
 307                         inet_sk(sk)->sport = htons(port);
 308                         __inet_hash(hinfo, sk, 0);
 309                 }
 310                 spin_unlock(&head->lock);
 311
 312                 if (tw) {
 313                         inet_twsk_deschedule(tw, death_row);
 314                         inet_twsk_put(tw);
 315                 }
 316
 317                 ret = 0;
 318                 goto out;
 319         }
 320
 321         head = &hinfo->bhash[inet_bhashfn(snum, hinfo->bhash_size)];
 322         tb  = inet_csk(sk)->icsk_bind_hash;
 323         spin_lock_bh(&head->lock);
 324         if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
 325                 __inet_hash(hinfo, sk, 0);
 326                 spin_unlock_bh(&head->lock);
 327                 return 0;
 328         } else {
 329                 spin_unlock(&head->lock);
 330                 /* No definite answer... Walk to established hash table */
 331                 ret = __inet_check_established(death_row, sk, snum, NULL);
 332 out:
 333                 local_bh_enable();
 334                 return ret;
 335         }
 336 }
 337
 338 EXPORT_SYMBOL_GPL(inet_hash_connect);