278 lines
8.5 KiB
C
278 lines
8.5 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Authors: Lotsa people, from code originally in tcp
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#ifndef _INET_HASHTABLES_H
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#define _INET_HASHTABLES_H
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#include <linux/interrupt.h>
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#include <linux/ip.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/types.h>
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#include <linux/wait.h>
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#include <net/sock.h>
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#include <net/tcp_states.h>
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#include <asm/atomic.h>
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/* This is for all connections with a full identity, no wildcards.
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* New scheme, half the table is for TIME_WAIT, the other half is
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* for the rest. I'll experiment with dynamic table growth later.
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*/
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struct inet_ehash_bucket {
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rwlock_t lock;
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struct hlist_head chain;
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} __attribute__((__aligned__(8)));
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/* There are a few simple rules, which allow for local port reuse by
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* an application. In essence:
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*
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* 1) Sockets bound to different interfaces may share a local port.
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* Failing that, goto test 2.
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* 2) If all sockets have sk->sk_reuse set, and none of them are in
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* TCP_LISTEN state, the port may be shared.
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* Failing that, goto test 3.
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* 3) If all sockets are bound to a specific inet_sk(sk)->rcv_saddr local
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* address, and none of them are the same, the port may be
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* shared.
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* Failing this, the port cannot be shared.
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*
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* The interesting point, is test #2. This is what an FTP server does
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* all day. To optimize this case we use a specific flag bit defined
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* below. As we add sockets to a bind bucket list, we perform a
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* check of: (newsk->sk_reuse && (newsk->sk_state != TCP_LISTEN))
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* As long as all sockets added to a bind bucket pass this test,
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* the flag bit will be set.
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* The resulting situation is that tcp_v[46]_verify_bind() can just check
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* for this flag bit, if it is set and the socket trying to bind has
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* sk->sk_reuse set, we don't even have to walk the owners list at all,
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* we return that it is ok to bind this socket to the requested local port.
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*
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* Sounds like a lot of work, but it is worth it. In a more naive
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* implementation (ie. current FreeBSD etc.) the entire list of ports
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* must be walked for each data port opened by an ftp server. Needless
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* to say, this does not scale at all. With a couple thousand FTP
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* users logged onto your box, isn't it nice to know that new data
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* ports are created in O(1) time? I thought so. ;-) -DaveM
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*/
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struct inet_bind_bucket {
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unsigned short port;
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signed short fastreuse;
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struct hlist_node node;
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struct hlist_head owners;
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};
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#define inet_bind_bucket_for_each(tb, node, head) \
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hlist_for_each_entry(tb, node, head, node)
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struct inet_bind_hashbucket {
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spinlock_t lock;
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struct hlist_head chain;
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};
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/* This is for listening sockets, thus all sockets which possess wildcards. */
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#define INET_LHTABLE_SIZE 32 /* Yes, really, this is all you need. */
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struct inet_hashinfo {
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/* This is for sockets with full identity only. Sockets here will
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* always be without wildcards and will have the following invariant:
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*
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* TCP_ESTABLISHED <= sk->sk_state < TCP_CLOSE
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*
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* First half of the table is for sockets not in TIME_WAIT, second half
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* is for TIME_WAIT sockets only.
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*/
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struct inet_ehash_bucket *ehash;
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/* Ok, let's try this, I give up, we do need a local binding
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* TCP hash as well as the others for fast bind/connect.
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*/
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struct inet_bind_hashbucket *bhash;
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int bhash_size;
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int ehash_size;
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/* All sockets in TCP_LISTEN state will be in here. This is the only
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* table where wildcard'd TCP sockets can exist. Hash function here
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* is just local port number.
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*/
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struct hlist_head listening_hash[INET_LHTABLE_SIZE];
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/* All the above members are written once at bootup and
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* never written again _or_ are predominantly read-access.
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*
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* Now align to a new cache line as all the following members
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* are often dirty.
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*/
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rwlock_t lhash_lock ____cacheline_aligned;
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atomic_t lhash_users;
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wait_queue_head_t lhash_wait;
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spinlock_t portalloc_lock;
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kmem_cache_t *bind_bucket_cachep;
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int port_rover;
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};
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static inline int inet_ehashfn(const __u32 laddr, const __u16 lport,
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const __u32 faddr, const __u16 fport,
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const int ehash_size)
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{
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int h = (laddr ^ lport) ^ (faddr ^ fport);
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h ^= h >> 16;
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h ^= h >> 8;
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return h & (ehash_size - 1);
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}
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static inline int inet_sk_ehashfn(const struct sock *sk, const int ehash_size)
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{
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const struct inet_sock *inet = inet_sk(sk);
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const __u32 laddr = inet->rcv_saddr;
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const __u16 lport = inet->num;
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const __u32 faddr = inet->daddr;
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const __u16 fport = inet->dport;
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return inet_ehashfn(laddr, lport, faddr, fport, ehash_size);
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}
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extern struct inet_bind_bucket *
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inet_bind_bucket_create(kmem_cache_t *cachep,
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struct inet_bind_hashbucket *head,
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const unsigned short snum);
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extern void inet_bind_bucket_destroy(kmem_cache_t *cachep,
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struct inet_bind_bucket *tb);
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static inline int inet_bhashfn(const __u16 lport, const int bhash_size)
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{
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return lport & (bhash_size - 1);
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}
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extern void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
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const unsigned short snum);
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/* These can have wildcards, don't try too hard. */
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static inline int inet_lhashfn(const unsigned short num)
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{
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return num & (INET_LHTABLE_SIZE - 1);
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}
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static inline int inet_sk_listen_hashfn(const struct sock *sk)
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{
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return inet_lhashfn(inet_sk(sk)->num);
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}
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/* Caller must disable local BH processing. */
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static inline void __inet_inherit_port(struct inet_hashinfo *table,
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struct sock *sk, struct sock *child)
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{
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const int bhash = inet_bhashfn(inet_sk(child)->num, table->bhash_size);
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struct inet_bind_hashbucket *head = &table->bhash[bhash];
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struct inet_bind_bucket *tb;
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spin_lock(&head->lock);
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tb = inet_sk(sk)->bind_hash;
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sk_add_bind_node(child, &tb->owners);
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inet_sk(child)->bind_hash = tb;
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spin_unlock(&head->lock);
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}
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static inline void inet_inherit_port(struct inet_hashinfo *table,
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struct sock *sk, struct sock *child)
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{
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local_bh_disable();
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__inet_inherit_port(table, sk, child);
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local_bh_enable();
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}
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extern void inet_put_port(struct inet_hashinfo *table, struct sock *sk);
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extern void inet_listen_wlock(struct inet_hashinfo *hashinfo);
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/*
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* - We may sleep inside this lock.
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* - If sleeping is not required (or called from BH),
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* use plain read_(un)lock(&inet_hashinfo.lhash_lock).
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*/
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static inline void inet_listen_lock(struct inet_hashinfo *hashinfo)
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{
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/* read_lock synchronizes to candidates to writers */
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read_lock(&hashinfo->lhash_lock);
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atomic_inc(&hashinfo->lhash_users);
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read_unlock(&hashinfo->lhash_lock);
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}
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static inline void inet_listen_unlock(struct inet_hashinfo *hashinfo)
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{
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if (atomic_dec_and_test(&hashinfo->lhash_users))
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wake_up(&hashinfo->lhash_wait);
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}
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static inline void __inet_hash(struct inet_hashinfo *hashinfo,
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struct sock *sk, const int listen_possible)
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{
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struct hlist_head *list;
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rwlock_t *lock;
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BUG_TRAP(sk_unhashed(sk));
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if (listen_possible && sk->sk_state == TCP_LISTEN) {
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list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
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lock = &hashinfo->lhash_lock;
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inet_listen_wlock(hashinfo);
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} else {
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sk->sk_hashent = inet_sk_ehashfn(sk, hashinfo->ehash_size);
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list = &hashinfo->ehash[sk->sk_hashent].chain;
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lock = &hashinfo->ehash[sk->sk_hashent].lock;
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write_lock(lock);
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}
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__sk_add_node(sk, list);
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sock_prot_inc_use(sk->sk_prot);
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write_unlock(lock);
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if (listen_possible && sk->sk_state == TCP_LISTEN)
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wake_up(&hashinfo->lhash_wait);
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}
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static inline void inet_hash(struct inet_hashinfo *hashinfo, struct sock *sk)
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{
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if (sk->sk_state != TCP_CLOSE) {
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local_bh_disable();
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__inet_hash(hashinfo, sk, 1);
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local_bh_enable();
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}
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}
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static inline void inet_unhash(struct inet_hashinfo *hashinfo, struct sock *sk)
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{
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rwlock_t *lock;
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if (sk_unhashed(sk))
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goto out;
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if (sk->sk_state == TCP_LISTEN) {
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local_bh_disable();
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inet_listen_wlock(hashinfo);
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lock = &hashinfo->lhash_lock;
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} else {
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struct inet_ehash_bucket *head = &hashinfo->ehash[sk->sk_hashent];
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lock = &head->lock;
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write_lock_bh(&head->lock);
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}
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if (__sk_del_node_init(sk))
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sock_prot_dec_use(sk->sk_prot);
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write_unlock_bh(lock);
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out:
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if (sk->sk_state == TCP_LISTEN)
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wake_up(&hashinfo->lhash_wait);
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}
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#endif /* _INET_HASHTABLES_H */
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