include/net/inet_hashtables.h

   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  * Authors:     Lotsa people, from code originally in tcp
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  */
  13
  14 #ifndef _INET_HASHTABLES_H
  15 #define _INET_HASHTABLES_H
  16
  17
  18 #include <linux/interrupt.h>
  19 #include <linux/ipv6.h>
  20 #include <linux/list.h>
  21 #include <linux/slab.h>
  22 #include <linux/socket.h>
  23 #include <linux/spinlock.h>
  24 #include <linux/types.h>
  25 #include <linux/wait.h>
  26
  27 #include <net/inet_connection_sock.h>
  28 #include <net/inet_sock.h>
  29 #include <net/route.h>
  30 #include <net/sock.h>
  31 #include <net/tcp_states.h>
  32
  33 #include <asm/atomic.h>
  34 #include <asm/byteorder.h>
  35
  36 /* This is for all connections with a full identity, no wildcards.
  37  * New scheme, half the table is for TIME_WAIT, the other half is
  38  * for the rest.  I'll experiment with dynamic table growth later.
  39  */
  40 struct inet_ehash_bucket {
  41         rwlock_t          lock;
  42         struct hlist_head chain;
  43 };
  44
  45 /* There are a few simple rules, which allow for local port reuse by
  46  * an application.  In essence:
  47  *
  48  *      1) Sockets bound to different interfaces may share a local port.
  49  *         Failing that, goto test 2.
  50  *      2) If all sockets have sk->sk_reuse set, and none of them are in
  51  *         TCP_LISTEN state, the port may be shared.
  52  *         Failing that, goto test 3.
  53  *      3) If all sockets are bound to a specific inet_sk(sk)->rcv_saddr local
  54  *         address, and none of them are the same, the port may be
  55  *         shared.
  56  *         Failing this, the port cannot be shared.
  57  *
  58  * The interesting point, is test #2.  This is what an FTP server does
  59  * all day.  To optimize this case we use a specific flag bit defined
  60  * below.  As we add sockets to a bind bucket list, we perform a
  61  * check of: (newsk->sk_reuse && (newsk->sk_state != TCP_LISTEN))
  62  * As long as all sockets added to a bind bucket pass this test,
  63  * the flag bit will be set.
  64  * The resulting situation is that tcp_v[46]_verify_bind() can just check
  65  * for this flag bit, if it is set and the socket trying to bind has
  66  * sk->sk_reuse set, we don't even have to walk the owners list at all,
  67  * we return that it is ok to bind this socket to the requested local port.
  68  *
  69  * Sounds like a lot of work, but it is worth it.  In a more naive
  70  * implementation (ie. current FreeBSD etc.) the entire list of ports
  71  * must be walked for each data port opened by an ftp server.  Needless
  72  * to say, this does not scale at all.  With a couple thousand FTP
  73  * users logged onto your box, isn't it nice to know that new data
  74  * ports are created in O(1) time?  I thought so. ;-)   -DaveM
  75  */
  76 struct inet_bind_bucket {
  77         unsigned short          port;
  78         signed short            fastreuse;
  79         struct hlist_node       node;
  80         struct hlist_head       owners;
  81 };
  82
  83 #define inet_bind_bucket_for_each(tb, node, head) \
  84         hlist_for_each_entry(tb, node, head, node)
  85
  86 struct inet_bind_hashbucket {
  87         spinlock_t              lock;
  88         struct hlist_head       chain;
  89 };
  90
  91 /* This is for listening sockets, thus all sockets which possess wildcards. */
  92 #define INET_LHTABLE_SIZE       32      /* Yes, really, this is all you need. */
  93
  94 struct inet_hashinfo {
  95         /* This is for sockets with full identity only.  Sockets here will
  96          * always be without wildcards and will have the following invariant:
  97          *
  98          *          TCP_ESTABLISHED <= sk->sk_state < TCP_CLOSE
  99          *
 100          * First half of the table is for sockets not in TIME_WAIT, second half
 101          * is for TIME_WAIT sockets only.
 102          */
 103         struct inet_ehash_bucket        *ehash;
 104
 105         /* Ok, let's try this, I give up, we do need a local binding
 106          * TCP hash as well as the others for fast bind/connect.
 107          */
 108         struct inet_bind_hashbucket     *bhash;
 109
 110         int                             bhash_size;
 111         unsigned int                    ehash_size;
 112
 113         /* All sockets in TCP_LISTEN state will be in here.  This is the only
 114          * table where wildcard'd TCP sockets can exist.  Hash function here
 115          * is just local port number.
 116          */
 117         struct hlist_head               listening_hash[INET_LHTABLE_SIZE];
 118
 119         /* All the above members are written once at bootup and
 120          * never written again _or_ are predominantly read-access.
 121          *
 122          * Now align to a new cache line as all the following members
 123          * are often dirty.
 124          */
 125         rwlock_t                        lhash_lock ____cacheline_aligned;
 126         atomic_t                        lhash_users;
 127         wait_queue_head_t               lhash_wait;
 128         struct kmem_cache                       *bind_bucket_cachep;
 129 };
 130
 131 static inline struct inet_ehash_bucket *inet_ehash_bucket(
 132         struct inet_hashinfo *hashinfo,
 133         unsigned int hash)
 134 {
 135         return &hashinfo->ehash[hash & (hashinfo->ehash_size - 1)];
 136 }
 137
 138 extern struct inet_bind_bucket *
 139                     inet_bind_bucket_create(struct kmem_cache *cachep,
 140                                             struct inet_bind_hashbucket *head,
 141                                             const unsigned short snum);
 142 extern void inet_bind_bucket_destroy(struct kmem_cache *cachep,
 143                                      struct inet_bind_bucket *tb);
 144
 145 static inline int inet_bhashfn(const __u16 lport, const int bhash_size)
 146 {
 147         return lport & (bhash_size - 1);
 148 }
 149
 150 extern void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
 151                            const unsigned short snum);
 152
 153 /* These can have wildcards, don't try too hard. */
 154 static inline int inet_lhashfn(const unsigned short num)
 155 {
 156         return num & (INET_LHTABLE_SIZE - 1);
 157 }
 158
 159 static inline int inet_sk_listen_hashfn(const struct sock *sk)
 160 {
 161         return inet_lhashfn(inet_sk(sk)->num);
 162 }
 163
 164 /* Caller must disable local BH processing. */
 165 static inline void __inet_inherit_port(struct inet_hashinfo *table,
 166                                        struct sock *sk, struct sock *child)
 167 {
 168         const int bhash = inet_bhashfn(inet_sk(child)->num, table->bhash_size);
 169         struct inet_bind_hashbucket *head = &table->bhash[bhash];
 170         struct inet_bind_bucket *tb;
 171
 172         spin_lock(&head->lock);
 173         tb = inet_csk(sk)->icsk_bind_hash;
 174         sk_add_bind_node(child, &tb->owners);
 175         inet_csk(child)->icsk_bind_hash = tb;
 176         spin_unlock(&head->lock);
 177 }
 178
 179 static inline void inet_inherit_port(struct inet_hashinfo *table,
 180                                      struct sock *sk, struct sock *child)
 181 {
 182         local_bh_disable();
 183         __inet_inherit_port(table, sk, child);
 184         local_bh_enable();
 185 }
 186
 187 extern void inet_put_port(struct inet_hashinfo *table, struct sock *sk);
 188
 189 extern void inet_listen_wlock(struct inet_hashinfo *hashinfo);
 190
 191 /*
 192  * - We may sleep inside this lock.
 193  * - If sleeping is not required (or called from BH),
 194  *   use plain read_(un)lock(&inet_hashinfo.lhash_lock).
 195  */
 196 static inline void inet_listen_lock(struct inet_hashinfo *hashinfo)
 197 {
 198         /* read_lock synchronizes to candidates to writers */
 199         read_lock(&hashinfo->lhash_lock);
 200         atomic_inc(&hashinfo->lhash_users);
 201         read_unlock(&hashinfo->lhash_lock);
 202 }
 203
 204 static inline void inet_listen_unlock(struct inet_hashinfo *hashinfo)
 205 {
 206         if (atomic_dec_and_test(&hashinfo->lhash_users))
 207                 wake_up(&hashinfo->lhash_wait);
 208 }
 209
 210 static inline void __inet_hash(struct inet_hashinfo *hashinfo,
 211                                struct sock *sk, const int listen_possible)
 212 {
 213         struct hlist_head *list;
 214         rwlock_t *lock;
 215
 216         BUG_TRAP(sk_unhashed(sk));
 217         if (listen_possible && sk->sk_state == TCP_LISTEN) {
 218                 list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
 219                 lock = &hashinfo->lhash_lock;
 220                 inet_listen_wlock(hashinfo);
 221         } else {
 222                 struct inet_ehash_bucket *head;
 223                 sk->sk_hash = inet_sk_ehashfn(sk);
 224                 head = inet_ehash_bucket(hashinfo, sk->sk_hash);
 225                 list = &head->chain;
 226                 lock = &head->lock;
 227                 write_lock(lock);
 228         }
 229         __sk_add_node(sk, list);
 230         sock_prot_inc_use(sk->sk_prot);
 231         write_unlock(lock);
 232         if (listen_possible && sk->sk_state == TCP_LISTEN)
 233                 wake_up(&hashinfo->lhash_wait);
 234 }
 235
 236 static inline void inet_hash(struct inet_hashinfo *hashinfo, struct sock *sk)
 237 {
 238         if (sk->sk_state != TCP_CLOSE) {
 239                 local_bh_disable();
 240                 __inet_hash(hashinfo, sk, 1);
 241                 local_bh_enable();
 242         }
 243 }
 244
 245 static inline void inet_unhash(struct inet_hashinfo *hashinfo, struct sock *sk)
 246 {
 247         rwlock_t *lock;
 248
 249         if (sk_unhashed(sk))
 250                 goto out;
 251
 252         if (sk->sk_state == TCP_LISTEN) {
 253                 local_bh_disable();
 254                 inet_listen_wlock(hashinfo);
 255                 lock = &hashinfo->lhash_lock;
 256         } else {
 257                 lock = &inet_ehash_bucket(hashinfo, sk->sk_hash)->lock;
 258                 write_lock_bh(lock);
 259         }
 260
 261         if (__sk_del_node_init(sk))
 262                 sock_prot_dec_use(sk->sk_prot);
 263         write_unlock_bh(lock);
 264 out:
 265         if (sk->sk_state == TCP_LISTEN)
 266                 wake_up(&hashinfo->lhash_wait);
 267 }
 268
 269 static inline int inet_iif(const struct sk_buff *skb)
 270 {
 271         return ((struct rtable *)skb->dst)->rt_iif;
 272 }
 273
 274 extern struct sock *__inet_lookup_listener(struct inet_hashinfo *hashinfo,
 275                                            const __be32 daddr,
 276                                            const unsigned short hnum,
 277                                            const int dif);
 278
 279 static inline struct sock *inet_lookup_listener(struct inet_hashinfo *hashinfo,
 280                                                 __be32 daddr, __be16 dport, int dif)
 281 {
 282         return __inet_lookup_listener(hashinfo, daddr, ntohs(dport), dif);
 283 }
 284
 285 /* Socket demux engine toys. */
 286 /* What happens here is ugly; there's a pair of adjacent fields in
 287    struct inet_sock; __be16 dport followed by __u16 num.  We want to
 288    search by pair, so we combine the keys into a single 32bit value
 289    and compare with 32bit value read from &...->dport.  Let's at least
 290    make sure that it's not mixed with anything else...
 291    On 64bit targets we combine comparisons with pair of adjacent __be32
 292    fields in the same way.
 293 */
 294 typedef __u32 __bitwise __portpair;
 295 #ifdef __BIG_ENDIAN
 296 #define INET_COMBINED_PORTS(__sport, __dport) \
 297         ((__force __portpair)(((__force __u32)(__be16)(__sport) << 16) | (__u32)(__dport)))
 298 #else /* __LITTLE_ENDIAN */
 299 #define INET_COMBINED_PORTS(__sport, __dport) \
 300         ((__force __portpair)(((__u32)(__dport) << 16) | (__force __u32)(__be16)(__sport)))
 301 #endif
 302
 303 #if (BITS_PER_LONG == 64)
 304 typedef __u64 __bitwise __addrpair;
 305 #ifdef __BIG_ENDIAN
 306 #define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
 307         const __addrpair __name = (__force __addrpair) ( \
 308                                    (((__force __u64)(__be32)(__saddr)) << 32) | \
 309                                    ((__force __u64)(__be32)(__daddr)));
 310 #else /* __LITTLE_ENDIAN */
 311 #define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
 312         const __addrpair __name = (__force __addrpair) ( \
 313                                    (((__force __u64)(__be32)(__daddr)) << 32) | \
 314                                    ((__force __u64)(__be32)(__saddr)));
 315 #endif /* __BIG_ENDIAN */
 316 #define INET_MATCH(__sk, __hash, __cookie, __saddr, __daddr, __ports, __dif)\
 317         (((__sk)->sk_hash == (__hash))                          &&      \
 318          ((*((__addrpair *)&(inet_sk(__sk)->daddr))) == (__cookie))     &&      \
 319          ((*((__portpair *)&(inet_sk(__sk)->dport))) == (__ports))      &&      \
 320          (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
 321 #define INET_TW_MATCH(__sk, __hash, __cookie, __saddr, __daddr, __ports, __dif)\
 322         (((__sk)->sk_hash == (__hash))                          &&      \
 323          ((*((__addrpair *)&(inet_twsk(__sk)->tw_daddr))) == (__cookie)) &&     \
 324          ((*((__portpair *)&(inet_twsk(__sk)->tw_dport))) == (__ports)) &&      \
 325          (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
 326 #else /* 32-bit arch */
 327 #define INET_ADDR_COOKIE(__name, __saddr, __daddr)
 328 #define INET_MATCH(__sk, __hash, __cookie, __saddr, __daddr, __ports, __dif)    \
 329         (((__sk)->sk_hash == (__hash))                          &&      \
 330          (inet_sk(__sk)->daddr          == (__saddr))           &&      \
 331          (inet_sk(__sk)->rcv_saddr      == (__daddr))           &&      \
 332          ((*((__portpair *)&(inet_sk(__sk)->dport))) == (__ports))      &&      \
 333          (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
 334 #define INET_TW_MATCH(__sk, __hash,__cookie, __saddr, __daddr, __ports, __dif)  \
 335         (((__sk)->sk_hash == (__hash))                          &&      \
 336          (inet_twsk(__sk)->tw_daddr     == (__saddr))           &&      \
 337          (inet_twsk(__sk)->tw_rcv_saddr == (__daddr))           &&      \
 338          ((*((__portpair *)&(inet_twsk(__sk)->tw_dport))) == (__ports)) &&      \
 339          (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
 340 #endif /* 64-bit arch */
 341
 342 /*
 343  * Sockets in TCP_CLOSE state are _always_ taken out of the hash, so we need
 344  * not check it for lookups anymore, thanks Alexey. -DaveM
 345  *
 346  * Local BH must be disabled here.
 347  */
 348 static inline struct sock *
 349         __inet_lookup_established(struct inet_hashinfo *hashinfo,
 350                                   const __be32 saddr, const __be16 sport,
 351                                   const __be32 daddr, const u16 hnum,
 352                                   const int dif)
 353 {
 354         INET_ADDR_COOKIE(acookie, saddr, daddr)
 355         const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
 356         struct sock *sk;
 357         const struct hlist_node *node;
 358         /* Optimize here for direct hit, only listening connections can
 359          * have wildcards anyways.
 360          */
 361         unsigned int hash = inet_ehashfn(daddr, hnum, saddr, sport);
 362         struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
 363
 364         prefetch(head->chain.first);
 365         read_lock(&head->lock);
 366         sk_for_each(sk, node, &head->chain) {
 367                 if (INET_MATCH(sk, hash, acookie, saddr, daddr, ports, dif))
 368                         goto hit; /* You sunk my battleship! */
 369         }
 370
 371         /* Must check for a TIME_WAIT'er before going to listener hash. */
 372         sk_for_each(sk, node, &(head + hashinfo->ehash_size)->chain) {
 373                 if (INET_TW_MATCH(sk, hash, acookie, saddr, daddr, ports, dif))
 374                         goto hit;
 375         }
 376         sk = NULL;
 377 out:
 378         read_unlock(&head->lock);
 379         return sk;
 380 hit:
 381         sock_hold(sk);
 382         goto out;
 383 }
 384
 385 static inline struct sock *
 386         inet_lookup_established(struct inet_hashinfo *hashinfo,
 387                                 const __be32 saddr, const __be16 sport,
 388                                 const __be32 daddr, const __be16 dport,
 389                                 const int dif)
 390 {
 391         return __inet_lookup_established(hashinfo, saddr, sport, daddr,
 392                                          ntohs(dport), dif);
 393 }
 394
 395 static inline struct sock *__inet_lookup(struct inet_hashinfo *hashinfo,
 396                                          const __be32 saddr, const __be16 sport,
 397                                          const __be32 daddr, const __be16 dport,
 398                                          const int dif)
 399 {
 400         u16 hnum = ntohs(dport);
 401         struct sock *sk = __inet_lookup_established(hashinfo, saddr, sport, daddr,
 402                                                     hnum, dif);
 403         return sk ? : __inet_lookup_listener(hashinfo, daddr, hnum, dif);
 404 }
 405
 406 static inline struct sock *inet_lookup(struct inet_hashinfo *hashinfo,
 407                                        const __be32 saddr, const __be16 sport,
 408                                        const __be32 daddr, const __be16 dport,
 409                                        const int dif)
 410 {
 411         struct sock *sk;
 412
 413         local_bh_disable();
 414         sk = __inet_lookup(hashinfo, saddr, sport, daddr, dport, dif);
 415         local_bh_enable();
 416
 417         return sk;
 418 }
 419
 420 extern int inet_hash_connect(struct inet_timewait_death_row *death_row,
 421                              struct sock *sk);
 422 #endif /* _INET_HASHTABLES_H */