// 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 #include #include #include #include #include /** * 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_bind2_bucket *tb2 = tw->tw_tb2; struct inet_bind_bucket *tb = tw->tw_tb; if (!tb) return; __sk_del_bind_node((struct sock *)tw); tw->tw_tb = NULL; tw->tw_tb2 = NULL; inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2); 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, *bhead2; spin_lock(lock); sk_nulls_del_node_init_rcu((struct sock *)tw); spin_unlock(lock); /* Disassociate with bind bucket. */ bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, hashinfo->bhash_size)]; bhead2 = inet_bhashfn_portaddr(hashinfo, (struct sock *)tw, twsk_net(tw), tw->tw_num); spin_lock(&bhead->lock); spin_lock(&bhead2->lock); inet_twsk_bind_unhash(tw, hashinfo); spin_unlock(&bhead2->lock); spin_unlock(&bhead->lock); refcount_dec(&tw->tw_dr->tw_refcount); 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); 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_schedule(struct inet_timewait_sock *tw, int timeo) { __inet_twsk_schedule(tw, timeo, false); } /* * Enter the time wait state. * Essentially we whip up a timewait bucket, copy the relevant info into it * from the SK, and mess with hash chains and list linkage. * * The caller must not access @tw anymore after this function returns. */ void inet_twsk_hashdance_schedule(struct inet_timewait_sock *tw, struct sock *sk, struct inet_hashinfo *hashinfo, int timeo) { 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, *bhead2; /* 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. */ bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, hashinfo->bhash_size)]; bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num); local_bh_disable(); spin_lock(&bhead->lock); spin_lock(&bhead2->lock); tw->tw_tb = icsk->icsk_bind_hash; WARN_ON(!icsk->icsk_bind_hash); tw->tw_tb2 = icsk->icsk_bind2_hash; WARN_ON(!icsk->icsk_bind2_hash); sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners); spin_unlock(&bhead2->lock); spin_unlock(&bhead->lock); spin_lock(lock); /* Step 2: Hash TW into tcp ehash chain */ 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); /* Ensure above writes are committed into memory before updating the * refcount. * Provides ordering vs later refcount_inc(). */ smp_wmb(); /* tw_refcnt is set to 3 because we have : * - one reference for bhash chain. * - one reference for ehash chain. * - one reference for timer. * 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); inet_twsk_schedule(tw, timeo); spin_unlock(lock); local_bh_enable(); } EXPORT_SYMBOL_GPL(inet_twsk_hashdance_schedule); 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 >= READ_ONCE(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_test_bit(TRANSPARENT, sk); 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, 0); /* * 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) { struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); /* inet_twsk_purge() walks over all sockets, including tw ones, * and removes them via inet_twsk_deschedule_put() after a * refcount_inc_not_zero(). * * inet_twsk_hashdance_schedule() must (re)init the refcount before * arming the timer, i.e. inet_twsk_purge can obtain a reference to * a twsk that did not yet schedule the timer. * * The ehash lock synchronizes these two: * After acquiring the lock, the timer is always scheduled (else * timer_shutdown returns false), because hashdance_schedule releases * the ehash lock only after completing the timer initialization. * * Without grabbing the ehash lock, we get: * 1) cpu x sets twsk refcount to 3 * 2) cpu y bumps refcount to 4 * 3) cpu y calls inet_twsk_deschedule_put() and shuts timer down * 4) cpu x tries to start timer, but mod_timer is a noop post-shutdown * -> timer refcount is never decremented. */ spin_lock(lock); /* Makes sure hashdance_schedule() has completed */ spin_unlock(lock); if (timer_shutdown_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); /* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */ void inet_twsk_purge(struct inet_hashinfo *hashinfo) { struct inet_ehash_bucket *head = &hashinfo->ehash[0]; unsigned int ehash_mask = hashinfo->ehash_mask; struct hlist_nulls_node *node; unsigned int slot; struct sock *sk; for (slot = 0; slot <= ehash_mask; slot++, head++) { if (hlist_nulls_empty(&head->chain)) continue; restart_rcu: cond_resched(); rcu_read_lock(); restart: sk_nulls_for_each_rcu(sk, node, &head->chain) { int state = inet_sk_state_load(sk); if ((1 << state) & ~(TCPF_TIME_WAIT | TCPF_NEW_SYN_RECV)) continue; if (refcount_read(&sock_net(sk)->ns.count)) continue; if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) continue; if (refcount_read(&sock_net(sk)->ns.count)) { sock_gen_put(sk); goto restart; } rcu_read_unlock(); local_bh_disable(); if (state == TCP_TIME_WAIT) { inet_twsk_deschedule_put(inet_twsk(sk)); } else { struct request_sock *req = inet_reqsk(sk); inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req); } local_bh_enable(); goto restart_rcu; } /* If the nulls value we got at the end of this lookup is * not the expected one, we must restart lookup. * We probably met an item that was moved to another chain. */ if (get_nulls_value(node) != slot) goto restart; rcu_read_unlock(); } } EXPORT_SYMBOL_GPL(inet_twsk_purge);