| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * 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. |
| * |
| * Generic TIME_WAIT sockets functions |
| * |
| * From code orinally in TCP |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/slab.h> |
| #include <linux/module.h> |
| #include <net/inet_hashtables.h> |
| #include <net/inet_timewait_sock.h> |
| #include <net/ip.h> |
| |
| |
| /** |
| * inet_twsk_bind_unhash - unhash a timewait socket from bind hash |
| * @tw: timewait socket |
| * @hashinfo: hashinfo pointer |
| * |
| * unhash a timewait socket from bind hash, if hashed. |
| * bind hash lock must be held by caller. |
| * Returns 1 if caller should call inet_twsk_put() after lock release. |
| */ |
| void inet_twsk_bind_unhash(struct inet_timewait_sock *tw, |
| struct inet_hashinfo *hashinfo) |
| { |
| struct inet_bind_bucket *tb = tw->tw_tb; |
| |
| if (!tb) |
| return; |
| |
| __hlist_del(&tw->tw_bind_node); |
| tw->tw_tb = NULL; |
| inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); |
| __sock_put((struct sock *)tw); |
| } |
| |
| /* Must be called with locally disabled BHs. */ |
| static void inet_twsk_kill(struct inet_timewait_sock *tw) |
| { |
| struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; |
| spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); |
| struct inet_bind_hashbucket *bhead; |
| |
| spin_lock(lock); |
| sk_nulls_del_node_init_rcu((struct sock *)tw); |
| spin_unlock(lock); |
| |
| /* Disassociate with bind bucket. */ |
| bhead = &hashinfo->bhash[tw->tw_bslot]; |
| |
| spin_lock(&bhead->lock); |
| inet_twsk_bind_unhash(tw, hashinfo); |
| spin_unlock(&bhead->lock); |
| |
| if (refcount_dec_and_test(&tw->tw_dr->tw_refcount)) |
| kfree(tw->tw_dr); |
| |
| inet_twsk_put(tw); |
| } |
| |
| void inet_twsk_free(struct inet_timewait_sock *tw) |
| { |
| struct module *owner = tw->tw_prot->owner; |
| twsk_destructor((struct sock *)tw); |
| #ifdef SOCK_REFCNT_DEBUG |
| pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw); |
| #endif |
| kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); |
| module_put(owner); |
| } |
| |
| void inet_twsk_put(struct inet_timewait_sock *tw) |
| { |
| if (refcount_dec_and_test(&tw->tw_refcnt)) |
| inet_twsk_free(tw); |
| } |
| EXPORT_SYMBOL_GPL(inet_twsk_put); |
| |
| static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw, |
| struct hlist_nulls_head *list) |
| { |
| hlist_nulls_add_head_rcu(&tw->tw_node, list); |
| } |
| |
| static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw, |
| struct hlist_head *list) |
| { |
| hlist_add_head(&tw->tw_bind_node, list); |
| } |
| |
| /* |
| * Enter the time wait state. This is called with locally disabled BH. |
| * Essentially we whip up a timewait bucket, copy the relevant info into it |
| * from the SK, and mess with hash chains and list linkage. |
| */ |
| void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, |
| struct inet_hashinfo *hashinfo) |
| { |
| const struct inet_sock *inet = inet_sk(sk); |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); |
| spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); |
| struct inet_bind_hashbucket *bhead; |
| /* Step 1: Put TW into bind hash. Original socket stays there too. |
| Note, that any socket with inet->num != 0 MUST be bound in |
| binding cache, even if it is closed. |
| */ |
| /* Cache inet_bhashfn(), because 'struct net' might be no longer |
| * available later in inet_twsk_kill(). |
| */ |
| tw->tw_bslot = inet_bhashfn(twsk_net(tw), inet->inet_num, |
| hashinfo->bhash_size); |
| bhead = &hashinfo->bhash[tw->tw_bslot]; |
| spin_lock(&bhead->lock); |
| tw->tw_tb = icsk->icsk_bind_hash; |
| WARN_ON(!icsk->icsk_bind_hash); |
| inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); |
| spin_unlock(&bhead->lock); |
| |
| spin_lock(lock); |
| |
| inet_twsk_add_node_rcu(tw, &ehead->chain); |
| |
| /* Step 3: Remove SK from hash chain */ |
| if (__sk_nulls_del_node_init_rcu(sk)) |
| sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); |
| |
| spin_unlock(lock); |
| |
| /* tw_refcnt is set to 3 because we have : |
| * - one reference for bhash chain. |
| * - one reference for ehash chain. |
| * - one reference for timer. |
| * We can use atomic_set() because prior spin_lock()/spin_unlock() |
| * committed into memory all tw fields. |
| * Also note that after this point, we lost our implicit reference |
| * so we are not allowed to use tw anymore. |
| */ |
| refcount_set(&tw->tw_refcnt, 3); |
| } |
| EXPORT_SYMBOL_GPL(inet_twsk_hashdance); |
| |
| static void tw_timer_handler(struct timer_list *t) |
| { |
| struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer); |
| |
| inet_twsk_kill(tw); |
| } |
| |
| struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, |
| struct inet_timewait_death_row *dr, |
| const int state) |
| { |
| struct inet_timewait_sock *tw; |
| |
| if (refcount_read(&dr->tw_refcount) - 1 >= dr->sysctl_max_tw_buckets) |
| return NULL; |
| |
| tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, |
| GFP_ATOMIC); |
| if (tw) { |
| const struct inet_sock *inet = inet_sk(sk); |
| |
| tw->tw_dr = dr; |
| /* Give us an identity. */ |
| tw->tw_daddr = inet->inet_daddr; |
| tw->tw_rcv_saddr = inet->inet_rcv_saddr; |
| tw->tw_bound_dev_if = sk->sk_bound_dev_if; |
| tw->tw_tos = inet->tos; |
| tw->tw_num = inet->inet_num; |
| tw->tw_state = TCP_TIME_WAIT; |
| tw->tw_substate = state; |
| tw->tw_sport = inet->inet_sport; |
| tw->tw_dport = inet->inet_dport; |
| tw->tw_family = sk->sk_family; |
| tw->tw_reuse = sk->sk_reuse; |
| tw->tw_reuseport = sk->sk_reuseport; |
| tw->tw_hash = sk->sk_hash; |
| tw->tw_ipv6only = 0; |
| tw->tw_transparent = inet->transparent; |
| tw->tw_prot = sk->sk_prot_creator; |
| atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); |
| twsk_net_set(tw, sock_net(sk)); |
| timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED); |
| /* |
| * Because we use RCU lookups, we should not set tw_refcnt |
| * to a non null value before everything is setup for this |
| * timewait socket. |
| */ |
| refcount_set(&tw->tw_refcnt, 0); |
| |
| __module_get(tw->tw_prot->owner); |
| } |
| |
| return tw; |
| } |
| EXPORT_SYMBOL_GPL(inet_twsk_alloc); |
| |
| /* These are always called from BH context. See callers in |
| * tcp_input.c to verify this. |
| */ |
| |
| /* This is for handling early-kills of TIME_WAIT sockets. |
| * Warning : consume reference. |
| * Caller should not access tw anymore. |
| */ |
| void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) |
| { |
| if (del_timer_sync(&tw->tw_timer)) |
| inet_twsk_kill(tw); |
| inet_twsk_put(tw); |
| } |
| EXPORT_SYMBOL(inet_twsk_deschedule_put); |
| |
| void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) |
| { |
| /* timeout := RTO * 3.5 |
| * |
| * 3.5 = 1+2+0.5 to wait for two retransmits. |
| * |
| * RATIONALE: if FIN arrived and we entered TIME-WAIT state, |
| * our ACK acking that FIN can be lost. If N subsequent retransmitted |
| * FINs (or previous seqments) are lost (probability of such event |
| * is p^(N+1), where p is probability to lose single packet and |
| * time to detect the loss is about RTO*(2^N - 1) with exponential |
| * backoff). Normal timewait length is calculated so, that we |
| * waited at least for one retransmitted FIN (maximal RTO is 120sec). |
| * [ BTW Linux. following BSD, violates this requirement waiting |
| * only for 60sec, we should wait at least for 240 secs. |
| * Well, 240 consumes too much of resources 8) |
| * ] |
| * This interval is not reduced to catch old duplicate and |
| * responces to our wandering segments living for two MSLs. |
| * However, if we use PAWS to detect |
| * old duplicates, we can reduce the interval to bounds required |
| * by RTO, rather than MSL. So, if peer understands PAWS, we |
| * kill tw bucket after 3.5*RTO (it is important that this number |
| * is greater than TS tick!) and detect old duplicates with help |
| * of PAWS. |
| */ |
| |
| if (!rearm) { |
| bool kill = timeo <= 4*HZ; |
| |
| __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : |
| LINUX_MIB_TIMEWAITED); |
| BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); |
| refcount_inc(&tw->tw_dr->tw_refcount); |
| } else { |
| mod_timer_pending(&tw->tw_timer, jiffies + timeo); |
| } |
| } |
| EXPORT_SYMBOL_GPL(__inet_twsk_schedule); |