324 lines
9.4 KiB
C
324 lines
9.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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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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* Generic TIME_WAIT sockets functions
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*
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* From code orinally in TCP
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <net/inet_hashtables.h>
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#include <net/inet_timewait_sock.h>
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#include <net/ip.h>
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/**
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* inet_twsk_bind_unhash - unhash a timewait socket from bind hash
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* @tw: timewait socket
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* @hashinfo: hashinfo pointer
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*
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* unhash a timewait socket from bind hash, if hashed.
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* bind hash lock must be held by caller.
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* Returns 1 if caller should call inet_twsk_put() after lock release.
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*/
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void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
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struct inet_hashinfo *hashinfo)
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{
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struct inet_bind2_bucket *tb2 = tw->tw_tb2;
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struct inet_bind_bucket *tb = tw->tw_tb;
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if (!tb)
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return;
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__sk_del_bind_node((struct sock *)tw);
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tw->tw_tb = NULL;
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tw->tw_tb2 = NULL;
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inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2);
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inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
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__sock_put((struct sock *)tw);
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}
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/* Must be called with locally disabled BHs. */
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static void inet_twsk_kill(struct inet_timewait_sock *tw)
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{
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struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
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spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
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struct inet_bind_hashbucket *bhead, *bhead2;
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spin_lock(lock);
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sk_nulls_del_node_init_rcu((struct sock *)tw);
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spin_unlock(lock);
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/* Disassociate with bind bucket. */
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bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
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hashinfo->bhash_size)];
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bhead2 = inet_bhashfn_portaddr(hashinfo, (struct sock *)tw,
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twsk_net(tw), tw->tw_num);
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spin_lock(&bhead->lock);
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spin_lock(&bhead2->lock);
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inet_twsk_bind_unhash(tw, hashinfo);
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spin_unlock(&bhead2->lock);
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spin_unlock(&bhead->lock);
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refcount_dec(&tw->tw_dr->tw_refcount);
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inet_twsk_put(tw);
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}
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void inet_twsk_free(struct inet_timewait_sock *tw)
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{
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struct module *owner = tw->tw_prot->owner;
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twsk_destructor((struct sock *)tw);
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kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
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module_put(owner);
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}
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void inet_twsk_put(struct inet_timewait_sock *tw)
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{
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if (refcount_dec_and_test(&tw->tw_refcnt))
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inet_twsk_free(tw);
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}
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EXPORT_SYMBOL_GPL(inet_twsk_put);
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static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
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struct hlist_nulls_head *list)
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{
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hlist_nulls_add_head_rcu(&tw->tw_node, list);
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}
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/*
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* Enter the time wait state. This is called with locally disabled BH.
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* Essentially we whip up a timewait bucket, copy the relevant info into it
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* from the SK, and mess with hash chains and list linkage.
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*/
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void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
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struct inet_hashinfo *hashinfo)
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{
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const struct inet_sock *inet = inet_sk(sk);
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const struct inet_connection_sock *icsk = inet_csk(sk);
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struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
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spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
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struct inet_bind_hashbucket *bhead, *bhead2;
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/* Step 1: Put TW into bind hash. Original socket stays there too.
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Note, that any socket with inet->num != 0 MUST be bound in
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binding cache, even if it is closed.
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*/
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bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
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hashinfo->bhash_size)];
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bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num);
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spin_lock(&bhead->lock);
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spin_lock(&bhead2->lock);
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tw->tw_tb = icsk->icsk_bind_hash;
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WARN_ON(!icsk->icsk_bind_hash);
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tw->tw_tb2 = icsk->icsk_bind2_hash;
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WARN_ON(!icsk->icsk_bind2_hash);
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sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners);
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spin_unlock(&bhead2->lock);
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spin_unlock(&bhead->lock);
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spin_lock(lock);
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inet_twsk_add_node_rcu(tw, &ehead->chain);
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/* Step 3: Remove SK from hash chain */
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if (__sk_nulls_del_node_init_rcu(sk))
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sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
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spin_unlock(lock);
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/* tw_refcnt is set to 3 because we have :
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* - one reference for bhash chain.
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* - one reference for ehash chain.
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* - one reference for timer.
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* We can use atomic_set() because prior spin_lock()/spin_unlock()
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* committed into memory all tw fields.
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* Also note that after this point, we lost our implicit reference
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* so we are not allowed to use tw anymore.
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*/
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refcount_set(&tw->tw_refcnt, 3);
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}
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EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
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static void tw_timer_handler(struct timer_list *t)
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{
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struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);
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inet_twsk_kill(tw);
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}
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struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
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struct inet_timewait_death_row *dr,
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const int state)
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{
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struct inet_timewait_sock *tw;
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if (refcount_read(&dr->tw_refcount) - 1 >=
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READ_ONCE(dr->sysctl_max_tw_buckets))
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return NULL;
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tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
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GFP_ATOMIC);
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if (tw) {
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const struct inet_sock *inet = inet_sk(sk);
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tw->tw_dr = dr;
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/* Give us an identity. */
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tw->tw_daddr = inet->inet_daddr;
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tw->tw_rcv_saddr = inet->inet_rcv_saddr;
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tw->tw_bound_dev_if = sk->sk_bound_dev_if;
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tw->tw_tos = inet->tos;
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tw->tw_num = inet->inet_num;
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tw->tw_state = TCP_TIME_WAIT;
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tw->tw_substate = state;
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tw->tw_sport = inet->inet_sport;
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tw->tw_dport = inet->inet_dport;
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tw->tw_family = sk->sk_family;
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tw->tw_reuse = sk->sk_reuse;
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tw->tw_reuseport = sk->sk_reuseport;
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tw->tw_hash = sk->sk_hash;
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tw->tw_ipv6only = 0;
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tw->tw_transparent = inet_test_bit(TRANSPARENT, sk);
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tw->tw_prot = sk->sk_prot_creator;
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atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
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twsk_net_set(tw, sock_net(sk));
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timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED);
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/*
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* Because we use RCU lookups, we should not set tw_refcnt
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* to a non null value before everything is setup for this
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* timewait socket.
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*/
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refcount_set(&tw->tw_refcnt, 0);
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__module_get(tw->tw_prot->owner);
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}
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return tw;
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}
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EXPORT_SYMBOL_GPL(inet_twsk_alloc);
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/* These are always called from BH context. See callers in
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* tcp_input.c to verify this.
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*/
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/* This is for handling early-kills of TIME_WAIT sockets.
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* Warning : consume reference.
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* Caller should not access tw anymore.
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*/
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void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
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{
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if (del_timer_sync(&tw->tw_timer))
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inet_twsk_kill(tw);
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inet_twsk_put(tw);
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}
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EXPORT_SYMBOL(inet_twsk_deschedule_put);
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void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
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{
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/* timeout := RTO * 3.5
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*
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* 3.5 = 1+2+0.5 to wait for two retransmits.
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*
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* RATIONALE: if FIN arrived and we entered TIME-WAIT state,
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* our ACK acking that FIN can be lost. If N subsequent retransmitted
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* FINs (or previous seqments) are lost (probability of such event
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* is p^(N+1), where p is probability to lose single packet and
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* time to detect the loss is about RTO*(2^N - 1) with exponential
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* backoff). Normal timewait length is calculated so, that we
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* waited at least for one retransmitted FIN (maximal RTO is 120sec).
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* [ BTW Linux. following BSD, violates this requirement waiting
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* only for 60sec, we should wait at least for 240 secs.
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* Well, 240 consumes too much of resources 8)
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* ]
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* This interval is not reduced to catch old duplicate and
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* responces to our wandering segments living for two MSLs.
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* However, if we use PAWS to detect
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* old duplicates, we can reduce the interval to bounds required
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* by RTO, rather than MSL. So, if peer understands PAWS, we
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* kill tw bucket after 3.5*RTO (it is important that this number
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* is greater than TS tick!) and detect old duplicates with help
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* of PAWS.
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*/
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if (!rearm) {
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bool kill = timeo <= 4*HZ;
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__NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED :
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LINUX_MIB_TIMEWAITED);
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BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
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refcount_inc(&tw->tw_dr->tw_refcount);
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} else {
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mod_timer_pending(&tw->tw_timer, jiffies + timeo);
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}
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}
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EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
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/* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */
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void inet_twsk_purge(struct inet_hashinfo *hashinfo)
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{
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struct inet_ehash_bucket *head = &hashinfo->ehash[0];
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unsigned int ehash_mask = hashinfo->ehash_mask;
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struct hlist_nulls_node *node;
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unsigned int slot;
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struct sock *sk;
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for (slot = 0; slot <= ehash_mask; slot++, head++) {
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if (hlist_nulls_empty(&head->chain))
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continue;
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restart_rcu:
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cond_resched();
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rcu_read_lock();
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restart:
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sk_nulls_for_each_rcu(sk, node, &head->chain) {
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int state = inet_sk_state_load(sk);
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if ((1 << state) & ~(TCPF_TIME_WAIT |
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TCPF_NEW_SYN_RECV))
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continue;
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if (refcount_read(&sock_net(sk)->ns.count))
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continue;
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if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
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continue;
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if (refcount_read(&sock_net(sk)->ns.count)) {
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sock_gen_put(sk);
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goto restart;
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}
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rcu_read_unlock();
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local_bh_disable();
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if (state == TCP_TIME_WAIT) {
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inet_twsk_deschedule_put(inet_twsk(sk));
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} else {
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struct request_sock *req = inet_reqsk(sk);
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inet_csk_reqsk_queue_drop_and_put(req->rsk_listener,
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req);
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}
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local_bh_enable();
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goto restart_rcu;
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}
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/* If the nulls value we got at the end of this lookup is
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* not the expected one, we must restart lookup.
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* We probably met an item that was moved to another chain.
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*/
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if (get_nulls_value(node) != slot)
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goto restart;
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rcu_read_unlock();
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}
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}
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EXPORT_SYMBOL_GPL(inet_twsk_purge);
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