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![Eric Dumazet](/assets/img/avatar_default.png)
Multiple cpus can process duplicates of incoming ACK messages matching a SYN_RECV request socket. This is a rare event under normal operations, but definitely can happen. Only one must win the race, otherwise corruption would occur. To fix this without adding new atomic ops, we use logic in inet_ehash_nolisten() to detect the request was present in the same ehash bucket where we try to insert the new child. If request socket was not found, we have to undo the child creation. This actually removes a spin_lock()/spin_unlock() pair in reqsk_queue_unlink() for the fast path. Fixes:e994b2f0fb
("tcp: do not lock listener to process SYN packets") Fixes:079096f103
("tcp/dccp: install syn_recv requests into ehash table") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
374 lines
12 KiB
C
374 lines
12 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/ipv6.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/socket.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/inet_connection_sock.h>
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#include <net/inet_sock.h>
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#include <net/sock.h>
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#include <net/route.h>
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#include <net/tcp_states.h>
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#include <net/netns/hash.h>
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#include <linux/atomic.h>
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#include <asm/byteorder.h>
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/* This is for all connections with a full identity, no wildcards.
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* The 'e' prefix stands for Establish, but we really put all sockets
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* but LISTEN ones.
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*/
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struct inet_ehash_bucket {
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struct hlist_nulls_head chain;
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};
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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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possible_net_t ib_net;
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unsigned short port;
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signed char fastreuse;
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signed char fastreuseport;
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kuid_t fastuid;
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int num_owners;
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struct hlist_node node;
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struct hlist_head owners;
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};
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static inline struct net *ib_net(struct inet_bind_bucket *ib)
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{
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return read_pnet(&ib->ib_net);
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}
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#define inet_bind_bucket_for_each(tb, head) \
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hlist_for_each_entry(tb, 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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/*
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* Sockets can be hashed in established or listening table
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* We must use different 'nulls' end-of-chain value for listening
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* hash table, or we might find a socket that was closed and
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* reallocated/inserted into established hash table
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*/
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#define LISTENING_NULLS_BASE (1U << 29)
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struct inet_listen_hashbucket {
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spinlock_t lock;
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struct hlist_nulls_head head;
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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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*/
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struct inet_ehash_bucket *ehash;
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spinlock_t *ehash_locks;
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unsigned int ehash_mask;
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unsigned int ehash_locks_mask;
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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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unsigned int bhash_size;
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/* 4 bytes hole on 64 bit */
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struct kmem_cache *bind_bucket_cachep;
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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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* might be often dirty.
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*/
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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 inet_listen_hashbucket listening_hash[INET_LHTABLE_SIZE]
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____cacheline_aligned_in_smp;
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};
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static inline struct inet_ehash_bucket *inet_ehash_bucket(
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struct inet_hashinfo *hashinfo,
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unsigned int hash)
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{
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return &hashinfo->ehash[hash & hashinfo->ehash_mask];
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}
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static inline spinlock_t *inet_ehash_lockp(
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struct inet_hashinfo *hashinfo,
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unsigned int hash)
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{
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return &hashinfo->ehash_locks[hash & hashinfo->ehash_locks_mask];
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}
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int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo);
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static inline void inet_ehash_locks_free(struct inet_hashinfo *hashinfo)
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{
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kvfree(hashinfo->ehash_locks);
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hashinfo->ehash_locks = NULL;
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}
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struct inet_bind_bucket *
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inet_bind_bucket_create(struct kmem_cache *cachep, struct net *net,
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struct inet_bind_hashbucket *head,
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const unsigned short snum);
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void inet_bind_bucket_destroy(struct kmem_cache *cachep,
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struct inet_bind_bucket *tb);
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static inline u32 inet_bhashfn(const struct net *net, const __u16 lport,
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const u32 bhash_size)
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{
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return (lport + net_hash_mix(net)) & (bhash_size - 1);
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}
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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 u32 inet_lhashfn(const struct net *net, const unsigned short num)
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{
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return (num + net_hash_mix(net)) & (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(sock_net(sk), inet_sk(sk)->inet_num);
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}
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/* Caller must disable local BH processing. */
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int __inet_inherit_port(const struct sock *sk, struct sock *child);
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void inet_put_port(struct sock *sk);
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void inet_hashinfo_init(struct inet_hashinfo *h);
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bool inet_ehash_insert(struct sock *sk, struct sock *osk);
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bool inet_ehash_nolisten(struct sock *sk, struct sock *osk);
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void __inet_hash(struct sock *sk, struct sock *osk);
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void inet_hash(struct sock *sk);
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void inet_unhash(struct sock *sk);
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struct sock *__inet_lookup_listener(struct net *net,
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struct inet_hashinfo *hashinfo,
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const __be32 saddr, const __be16 sport,
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const __be32 daddr,
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const unsigned short hnum,
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const int dif);
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static inline struct sock *inet_lookup_listener(struct net *net,
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struct inet_hashinfo *hashinfo,
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__be32 saddr, __be16 sport,
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__be32 daddr, __be16 dport, int dif)
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{
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return __inet_lookup_listener(net, hashinfo, saddr, sport,
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daddr, ntohs(dport), dif);
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}
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/* Socket demux engine toys. */
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/* What happens here is ugly; there's a pair of adjacent fields in
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struct inet_sock; __be16 dport followed by __u16 num. We want to
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search by pair, so we combine the keys into a single 32bit value
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and compare with 32bit value read from &...->dport. Let's at least
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make sure that it's not mixed with anything else...
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On 64bit targets we combine comparisons with pair of adjacent __be32
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fields in the same way.
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*/
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#ifdef __BIG_ENDIAN
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#define INET_COMBINED_PORTS(__sport, __dport) \
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((__force __portpair)(((__force __u32)(__be16)(__sport) << 16) | (__u32)(__dport)))
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#else /* __LITTLE_ENDIAN */
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#define INET_COMBINED_PORTS(__sport, __dport) \
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((__force __portpair)(((__u32)(__dport) << 16) | (__force __u32)(__be16)(__sport)))
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#endif
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#if (BITS_PER_LONG == 64)
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#ifdef __BIG_ENDIAN
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#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
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const __addrpair __name = (__force __addrpair) ( \
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(((__force __u64)(__be32)(__saddr)) << 32) | \
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((__force __u64)(__be32)(__daddr)))
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#else /* __LITTLE_ENDIAN */
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#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
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const __addrpair __name = (__force __addrpair) ( \
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(((__force __u64)(__be32)(__daddr)) << 32) | \
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((__force __u64)(__be32)(__saddr)))
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#endif /* __BIG_ENDIAN */
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#define INET_MATCH(__sk, __net, __cookie, __saddr, __daddr, __ports, __dif) \
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(((__sk)->sk_portpair == (__ports)) && \
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((__sk)->sk_addrpair == (__cookie)) && \
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(!(__sk)->sk_bound_dev_if || \
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((__sk)->sk_bound_dev_if == (__dif))) && \
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net_eq(sock_net(__sk), (__net)))
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#else /* 32-bit arch */
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#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
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const int __name __deprecated __attribute__((unused))
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#define INET_MATCH(__sk, __net, __cookie, __saddr, __daddr, __ports, __dif) \
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(((__sk)->sk_portpair == (__ports)) && \
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((__sk)->sk_daddr == (__saddr)) && \
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((__sk)->sk_rcv_saddr == (__daddr)) && \
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(!(__sk)->sk_bound_dev_if || \
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((__sk)->sk_bound_dev_if == (__dif))) && \
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net_eq(sock_net(__sk), (__net)))
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#endif /* 64-bit arch */
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/*
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* Sockets in TCP_CLOSE state are _always_ taken out of the hash, so we need
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* not check it for lookups anymore, thanks Alexey. -DaveM
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*
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* Local BH must be disabled here.
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*/
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struct sock *__inet_lookup_established(struct net *net,
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struct inet_hashinfo *hashinfo,
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const __be32 saddr, const __be16 sport,
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const __be32 daddr, const u16 hnum,
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const int dif);
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static inline struct sock *
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inet_lookup_established(struct net *net, struct inet_hashinfo *hashinfo,
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const __be32 saddr, const __be16 sport,
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const __be32 daddr, const __be16 dport,
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const int dif)
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{
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return __inet_lookup_established(net, hashinfo, saddr, sport, daddr,
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ntohs(dport), dif);
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}
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static inline struct sock *__inet_lookup(struct net *net,
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struct inet_hashinfo *hashinfo,
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const __be32 saddr, const __be16 sport,
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const __be32 daddr, const __be16 dport,
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const int dif)
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{
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u16 hnum = ntohs(dport);
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struct sock *sk = __inet_lookup_established(net, hashinfo,
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saddr, sport, daddr, hnum, dif);
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return sk ? : __inet_lookup_listener(net, hashinfo, saddr, sport,
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daddr, hnum, dif);
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}
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static inline struct sock *inet_lookup(struct net *net,
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struct inet_hashinfo *hashinfo,
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const __be32 saddr, const __be16 sport,
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const __be32 daddr, const __be16 dport,
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const int dif)
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{
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struct sock *sk;
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local_bh_disable();
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sk = __inet_lookup(net, hashinfo, saddr, sport, daddr, dport, dif);
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local_bh_enable();
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return sk;
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}
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static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo,
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struct sk_buff *skb,
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const __be16 sport,
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const __be16 dport)
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{
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struct sock *sk = skb_steal_sock(skb);
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const struct iphdr *iph = ip_hdr(skb);
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if (sk)
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return sk;
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else
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return __inet_lookup(dev_net(skb_dst(skb)->dev), hashinfo,
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iph->saddr, sport,
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iph->daddr, dport, inet_iif(skb));
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}
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u32 sk_ehashfn(const struct sock *sk);
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u32 inet6_ehashfn(const struct net *net,
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const struct in6_addr *laddr, const u16 lport,
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const struct in6_addr *faddr, const __be16 fport);
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static inline void sk_daddr_set(struct sock *sk, __be32 addr)
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{
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sk->sk_daddr = addr; /* alias of inet_daddr */
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#if IS_ENABLED(CONFIG_IPV6)
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ipv6_addr_set_v4mapped(addr, &sk->sk_v6_daddr);
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#endif
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}
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static inline void sk_rcv_saddr_set(struct sock *sk, __be32 addr)
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{
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sk->sk_rcv_saddr = addr; /* alias of inet_rcv_saddr */
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#if IS_ENABLED(CONFIG_IPV6)
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ipv6_addr_set_v4mapped(addr, &sk->sk_v6_rcv_saddr);
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#endif
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}
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int __inet_hash_connect(struct inet_timewait_death_row *death_row,
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struct sock *sk, u32 port_offset,
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int (*check_established)(struct inet_timewait_death_row *,
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struct sock *, __u16,
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struct inet_timewait_sock **));
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int inet_hash_connect(struct inet_timewait_death_row *death_row,
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struct sock *sk);
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#endif /* _INET_HASHTABLES_H */
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