[INET]: Generalise tcp_v4_lookup_listener

[safe/jmp/linux-2.6] / include / net / inet_hashtables.h

/*
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the BSD Socket
 *              interface as the means of communication with the user level.
 *
 * Authors:     Lotsa people, from code originally in tcp
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#ifndef _INET_HASHTABLES_H
#define _INET_HASHTABLES_H

#include <linux/interrupt.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/wait.h>

#include <net/sock.h>
#include <net/tcp_states.h>

#include <asm/atomic.h>

/* This is for all connections with a full identity, no wildcards.
 * New scheme, half the table is for TIME_WAIT, the other half is
 * for the rest.  I'll experiment with dynamic table growth later.
 */
struct inet_ehash_bucket {
        rwlock_t          lock;
        struct hlist_head chain;
} __attribute__((__aligned__(8)));

/* There are a few simple rules, which allow for local port reuse by
 * an application.  In essence:
 *
 *      1) Sockets bound to different interfaces may share a local port.
 *         Failing that, goto test 2.
 *      2) If all sockets have sk->sk_reuse set, and none of them are in
 *         TCP_LISTEN state, the port may be shared.
 *         Failing that, goto test 3.
 *      3) If all sockets are bound to a specific inet_sk(sk)->rcv_saddr local
 *         address, and none of them are the same, the port may be
 *         shared.
 *         Failing this, the port cannot be shared.
 *
 * The interesting point, is test #2.  This is what an FTP server does
 * all day.  To optimize this case we use a specific flag bit defined
 * below.  As we add sockets to a bind bucket list, we perform a
 * check of: (newsk->sk_reuse && (newsk->sk_state != TCP_LISTEN))
 * As long as all sockets added to a bind bucket pass this test,
 * the flag bit will be set.
 * The resulting situation is that tcp_v[46]_verify_bind() can just check
 * for this flag bit, if it is set and the socket trying to bind has
 * sk->sk_reuse set, we don't even have to walk the owners list at all,
 * we return that it is ok to bind this socket to the requested local port.
 *
 * Sounds like a lot of work, but it is worth it.  In a more naive
 * implementation (ie. current FreeBSD etc.) the entire list of ports
 * must be walked for each data port opened by an ftp server.  Needless
 * to say, this does not scale at all.  With a couple thousand FTP
 * users logged onto your box, isn't it nice to know that new data
 * ports are created in O(1) time?  I thought so. ;-)   -DaveM
 */
struct inet_bind_bucket {
        unsigned short          port;
        signed short            fastreuse;
        struct hlist_node       node;
        struct hlist_head       owners;
};

#define inet_bind_bucket_for_each(tb, node, head) \
        hlist_for_each_entry(tb, node, head, node)

struct inet_bind_hashbucket {
        spinlock_t              lock;
        struct hlist_head       chain;
};

/* This is for listening sockets, thus all sockets which possess wildcards. */
#define INET_LHTABLE_SIZE       32      /* Yes, really, this is all you need. */

struct inet_hashinfo {
        /* This is for sockets with full identity only.  Sockets here will
         * always be without wildcards and will have the following invariant:
         *
         *          TCP_ESTABLISHED <= sk->sk_state < TCP_CLOSE
         *
         * First half of the table is for sockets not in TIME_WAIT, second half
         * is for TIME_WAIT sockets only.
         */
        struct inet_ehash_bucket        *ehash;

        /* Ok, let's try this, I give up, we do need a local binding
         * TCP hash as well as the others for fast bind/connect.
         */
        struct inet_bind_hashbucket     *bhash;

        int                             bhash_size;
        int                             ehash_size;

        /* All sockets in TCP_LISTEN state will be in here.  This is the only
         * table where wildcard'd TCP sockets can exist.  Hash function here
         * is just local port number.
         */
        struct hlist_head               listening_hash[INET_LHTABLE_SIZE];

        /* All the above members are written once at bootup and
         * never written again _or_ are predominantly read-access.
         *
         * Now align to a new cache line as all the following members
         * are often dirty.
         */
        rwlock_t                        lhash_lock ____cacheline_aligned;
        atomic_t                        lhash_users;
        wait_queue_head_t               lhash_wait;
        spinlock_t                      portalloc_lock;
        kmem_cache_t                    *bind_bucket_cachep;
        int                             port_rover;
};

static inline int inet_ehashfn(const __u32 laddr, const __u16 lport,
                               const __u32 faddr, const __u16 fport,
                               const int ehash_size)
{
        int h = (laddr ^ lport) ^ (faddr ^ fport);
        h ^= h >> 16;
        h ^= h >> 8;
        return h & (ehash_size - 1);
}

static inline int inet_sk_ehashfn(const struct sock *sk, const int ehash_size)
{
        const struct inet_sock *inet = inet_sk(sk);
        const __u32 laddr = inet->rcv_saddr;
        const __u16 lport = inet->num;
        const __u32 faddr = inet->daddr;
        const __u16 fport = inet->dport;

        return inet_ehashfn(laddr, lport, faddr, fport, ehash_size);
}

extern struct inet_bind_bucket *
                    inet_bind_bucket_create(kmem_cache_t *cachep,
                                            struct inet_bind_hashbucket *head,
                                            const unsigned short snum);
extern void inet_bind_bucket_destroy(kmem_cache_t *cachep,
                                     struct inet_bind_bucket *tb);

static inline int inet_bhashfn(const __u16 lport, const int bhash_size)
{
        return lport & (bhash_size - 1);
}

extern void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
                           const unsigned short snum);

/* These can have wildcards, don't try too hard. */
static inline int inet_lhashfn(const unsigned short num)
{
        return num & (INET_LHTABLE_SIZE - 1);
}

static inline int inet_sk_listen_hashfn(const struct sock *sk)
{
        return inet_lhashfn(inet_sk(sk)->num);
}

/* Caller must disable local BH processing. */
static inline void __inet_inherit_port(struct inet_hashinfo *table,
                                       struct sock *sk, struct sock *child)
{
        const int bhash = inet_bhashfn(inet_sk(child)->num, table->bhash_size);
        struct inet_bind_hashbucket *head = &table->bhash[bhash];
        struct inet_bind_bucket *tb;

        spin_lock(&head->lock);
        tb = inet_sk(sk)->bind_hash;
        sk_add_bind_node(child, &tb->owners);
        inet_sk(child)->bind_hash = tb;
        spin_unlock(&head->lock);
}

static inline void inet_inherit_port(struct inet_hashinfo *table,
                                     struct sock *sk, struct sock *child)
{
        local_bh_disable();
        __inet_inherit_port(table, sk, child);
        local_bh_enable();
}

extern void inet_put_port(struct inet_hashinfo *table, struct sock *sk);

extern void inet_listen_wlock(struct inet_hashinfo *hashinfo);

/*
 * - We may sleep inside this lock.
 * - If sleeping is not required (or called from BH),
 *   use plain read_(un)lock(&inet_hashinfo.lhash_lock).
 */
static inline void inet_listen_lock(struct inet_hashinfo *hashinfo)
{
        /* read_lock synchronizes to candidates to writers */
        read_lock(&hashinfo->lhash_lock);
        atomic_inc(&hashinfo->lhash_users);
        read_unlock(&hashinfo->lhash_lock);
}

static inline void inet_listen_unlock(struct inet_hashinfo *hashinfo)
{
        if (atomic_dec_and_test(&hashinfo->lhash_users))
                wake_up(&hashinfo->lhash_wait);
}

static inline void __inet_hash(struct inet_hashinfo *hashinfo,
                               struct sock *sk, const int listen_possible)
{
        struct hlist_head *list;
        rwlock_t *lock;

        BUG_TRAP(sk_unhashed(sk));
        if (listen_possible && sk->sk_state == TCP_LISTEN) {
                list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
                lock = &hashinfo->lhash_lock;
                inet_listen_wlock(hashinfo);
        } else {
                sk->sk_hashent = inet_sk_ehashfn(sk, hashinfo->ehash_size);
                list = &hashinfo->ehash[sk->sk_hashent].chain;
                lock = &hashinfo->ehash[sk->sk_hashent].lock;
                write_lock(lock);
        }
        __sk_add_node(sk, list);
        sock_prot_inc_use(sk->sk_prot);
        write_unlock(lock);
        if (listen_possible && sk->sk_state == TCP_LISTEN)
                wake_up(&hashinfo->lhash_wait);
}

static inline void inet_hash(struct inet_hashinfo *hashinfo, struct sock *sk)
{
        if (sk->sk_state != TCP_CLOSE) {
                local_bh_disable();
                __inet_hash(hashinfo, sk, 1);
                local_bh_enable();
        }
}

static inline void inet_unhash(struct inet_hashinfo *hashinfo, struct sock *sk)
{
        rwlock_t *lock;

        if (sk_unhashed(sk))
                goto out;

        if (sk->sk_state == TCP_LISTEN) {
                local_bh_disable();
                inet_listen_wlock(hashinfo);
                lock = &hashinfo->lhash_lock;
        } else {
                struct inet_ehash_bucket *head = &hashinfo->ehash[sk->sk_hashent];
                lock = &head->lock;
                write_lock_bh(&head->lock);
        }

        if (__sk_del_node_init(sk))
                sock_prot_dec_use(sk->sk_prot);
        write_unlock_bh(lock);
out:
        if (sk->sk_state == TCP_LISTEN)
                wake_up(&hashinfo->lhash_wait);
}

extern struct sock *__inet_lookup_listener(const struct hlist_head *head,
                                           const u32 daddr,
                                           const unsigned short hnum,
                                           const int dif);

/* Optimize the common listener case. */
static inline struct sock *inet_lookup_listener(struct inet_hashinfo *hashinfo,
                                                const u32 daddr,
                                                const unsigned short hnum,
                                                const int dif)
{
        struct sock *sk = NULL;
        struct hlist_head *head;

        read_lock(&hashinfo->lhash_lock);
        head = &hashinfo->listening_hash[inet_lhashfn(hnum)];
        if (!hlist_empty(head)) {
                const struct inet_sock *inet = inet_sk((sk = __sk_head(head)));

                if (inet->num == hnum && !sk->sk_node.next &&
                    (!inet->rcv_saddr || inet->rcv_saddr == daddr) &&
                    (sk->sk_family == PF_INET || !ipv6_only_sock(sk)) &&
                    !sk->sk_bound_dev_if)
                        goto sherry_cache;
                sk = __inet_lookup_listener(head, daddr, hnum, dif);
        }
        if (sk) {
sherry_cache:
                sock_hold(sk);
        }
        read_unlock(&hashinfo->lhash_lock);
        return sk;
}
#endif /* _INET_HASHTABLES_H */