/* * 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/kmemcheck.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_unhash - unhash a timewait socket from established hash * @tw: timewait socket * * unhash a timewait socket from established hash, if hashed. * ehash lock must be held by caller. * Returns 1 if caller should call inet_twsk_put() after lock release. */ int inet_twsk_unhash(struct inet_timewait_sock *tw) { if (hlist_nulls_unhashed(&tw->tw_node)) return 0; hlist_nulls_del_rcu(&tw->tw_node); sk_nulls_node_init(&tw->tw_node); /* * We cannot call inet_twsk_put() ourself under lock, * caller must call it for us. */ return 1; } /** * 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. */ int inet_twsk_bind_unhash(struct inet_timewait_sock *tw, struct inet_hashinfo *hashinfo) { struct inet_bind_bucket *tb = tw->tw_tb; if (!tb) return 0; __hlist_del(&tw->tw_bind_node); tw->tw_tb = NULL; inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); /* * We cannot call inet_twsk_put() ourself under lock, * caller must call it for us. */ return 1; } /* Must be called with locally disabled BHs. */ static void __inet_twsk_kill(struct inet_timewait_sock *tw, struct inet_hashinfo *hashinfo) { struct inet_bind_hashbucket *bhead; int refcnt; /* Unlink from established hashes. */ spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); spin_lock(lock); refcnt = inet_twsk_unhash(tw); spin_unlock(lock); /* Disassociate with bind bucket. */ bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, hashinfo->bhash_size)]; spin_lock(&bhead->lock); refcnt += inet_twsk_bind_unhash(tw, hashinfo); spin_unlock(&bhead->lock); BUG_ON(refcnt >= atomic_read(&tw->tw_refcnt)); atomic_sub(refcnt, &tw->tw_refcnt); } 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 release_net(twsk_net(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 (atomic_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. */ bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, hashinfo->bhash_size)]; 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); /* * Step 2: Hash TW into tcp ehash chain. * Notes : * - tw_refcnt is set to 3 because : * - We have one reference from bhash chain. * - We have one reference from ehash chain. * We can use atomic_set() because prior spin_lock()/spin_unlock() * committed into memory all tw fields. */ atomic_set(&tw->tw_refcnt, 1 + 1 + 1); 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); } EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state) { struct inet_timewait_sock *tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, GFP_ATOMIC); if (tw != NULL) { const struct inet_sock *inet = inet_sk(sk); kmemcheck_annotate_bitfield(tw, flags); /* 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_hash = sk->sk_hash; tw->tw_ipv6only = 0; tw->tw_transparent = inet->transparent; tw->tw_prot = sk->sk_prot_creator; twsk_net_set(tw, hold_net(sock_net(sk))); /* * Because we use RCU lookups, we should not set tw_refcnt * to a non null value before everything is setup for this * timewait socket. */ atomic_set(&tw->tw_refcnt, 0); inet_twsk_dead_node_init(tw); __module_get(tw->tw_prot->owner); } return tw; } EXPORT_SYMBOL_GPL(inet_twsk_alloc); /* Returns non-zero if quota exceeded. */ static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr, const int slot) { struct inet_timewait_sock *tw; unsigned int killed; int ret; /* NOTE: compare this to previous version where lock * was released after detaching chain. It was racy, * because tw buckets are scheduled in not serialized context * in 2.3 (with netfilter), and with softnet it is common, because * soft irqs are not sequenced. */ killed = 0; ret = 0; rescan: inet_twsk_for_each_inmate(tw, &twdr->cells[slot]) { __inet_twsk_del_dead_node(tw); spin_unlock(&twdr->death_lock); __inet_twsk_kill(tw, twdr->hashinfo); #ifdef CONFIG_NET_NS NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED); #endif inet_twsk_put(tw); killed++; spin_lock(&twdr->death_lock); if (killed > INET_TWDR_TWKILL_QUOTA) { ret = 1; break; } /* While we dropped twdr->death_lock, another cpu may have * killed off the next TW bucket in the list, therefore * do a fresh re-read of the hlist head node with the * lock reacquired. We still use the hlist traversal * macro in order to get the prefetches. */ goto rescan; } twdr->tw_count -= killed; #ifndef CONFIG_NET_NS NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITED, killed); #endif return ret; } void inet_twdr_hangman(unsigned long data) { struct inet_timewait_death_row *twdr; unsigned int need_timer; twdr = (struct inet_timewait_death_row *)data; spin_lock(&twdr->death_lock); if (twdr->tw_count == 0) goto out; need_timer = 0; if (inet_twdr_do_twkill_work(twdr, twdr->slot)) { twdr->thread_slots |= (1 << twdr->slot); schedule_work(&twdr->twkill_work); need_timer = 1; } else { /* We purged the entire slot, anything left? */ if (twdr->tw_count) need_timer = 1; twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1)); } if (need_timer) mod_timer(&twdr->tw_timer, jiffies + twdr->period); out: spin_unlock(&twdr->death_lock); } EXPORT_SYMBOL_GPL(inet_twdr_hangman); void inet_twdr_twkill_work(struct work_struct *work) { struct inet_timewait_death_row *twdr = container_of(work, struct inet_timewait_death_row, twkill_work); int i; BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) > (sizeof(twdr->thread_slots) * 8)); while (twdr->thread_slots) { spin_lock_bh(&twdr->death_lock); for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) { if (!(twdr->thread_slots & (1 << i))) continue; while (inet_twdr_do_twkill_work(twdr, i) != 0) { if (need_resched()) { spin_unlock_bh(&twdr->death_lock); schedule(); spin_lock_bh(&twdr->death_lock); } } twdr->thread_slots &= ~(1 << i); } spin_unlock_bh(&twdr->death_lock); } } EXPORT_SYMBOL_GPL(inet_twdr_twkill_work); /* 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. */ void inet_twsk_deschedule(struct inet_timewait_sock *tw, struct inet_timewait_death_row *twdr) { spin_lock(&twdr->death_lock); if (inet_twsk_del_dead_node(tw)) { inet_twsk_put(tw); if (--twdr->tw_count == 0) del_timer(&twdr->tw_timer); } spin_unlock(&twdr->death_lock); __inet_twsk_kill(tw, twdr->hashinfo); } EXPORT_SYMBOL(inet_twsk_deschedule); void inet_twsk_schedule(struct inet_timewait_sock *tw, struct inet_timewait_death_row *twdr, const int timeo, const int timewait_len) { struct hlist_head *list; int slot; /* 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. */ slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK; spin_lock(&twdr->death_lock); /* Unlink it, if it was scheduled */ if (inet_twsk_del_dead_node(tw)) twdr->tw_count--; else atomic_inc(&tw->tw_refcnt); if (slot >= INET_TWDR_RECYCLE_SLOTS) { /* Schedule to slow timer */ if (timeo >= timewait_len) { slot = INET_TWDR_TWKILL_SLOTS - 1; } else { slot = DIV_ROUND_UP(timeo, twdr->period); if (slot >= INET_TWDR_TWKILL_SLOTS) slot = INET_TWDR_TWKILL_SLOTS - 1; } tw->tw_ttd = inet_tw_time_stamp() + timeo; slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1); list = &twdr->cells[slot]; } else { tw->tw_ttd = inet_tw_time_stamp() + (slot << INET_TWDR_RECYCLE_TICK); if (twdr->twcal_hand < 0) { twdr->twcal_hand = 0; twdr->twcal_jiffie = jiffies; twdr->twcal_timer.expires = twdr->twcal_jiffie + (slot << INET_TWDR_RECYCLE_TICK); add_timer(&twdr->twcal_timer); } else { if (time_after(twdr->twcal_timer.expires, jiffies + (slot << INET_TWDR_RECYCLE_TICK))) mod_timer(&twdr->twcal_timer, jiffies + (slot << INET_TWDR_RECYCLE_TICK)); slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1); } list = &twdr->twcal_row[slot]; } hlist_add_head(&tw->tw_death_node, list); if (twdr->tw_count++ == 0) mod_timer(&twdr->tw_timer, jiffies + twdr->period); spin_unlock(&twdr->death_lock); } EXPORT_SYMBOL_GPL(inet_twsk_schedule); void inet_twdr_twcal_tick(unsigned long data) { struct inet_timewait_death_row *twdr; int n, slot; unsigned long j; unsigned long now = jiffies; int killed = 0; int adv = 0; twdr = (struct inet_timewait_death_row *)data; spin_lock(&twdr->death_lock); if (twdr->twcal_hand < 0) goto out; slot = twdr->twcal_hand; j = twdr->twcal_jiffie; for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) { if (time_before_eq(j, now)) { struct hlist_node *safe; struct inet_timewait_sock *tw; inet_twsk_for_each_inmate_safe(tw, safe, &twdr->twcal_row[slot]) { __inet_twsk_del_dead_node(tw); __inet_twsk_kill(tw, twdr->hashinfo); #ifdef CONFIG_NET_NS NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED); #endif inet_twsk_put(tw); killed++; } } else { if (!adv) { adv = 1; twdr->twcal_jiffie = j; twdr->twcal_hand = slot; } if (!hlist_empty(&twdr->twcal_row[slot])) { mod_timer(&twdr->twcal_timer, j); goto out; } } j += 1 << INET_TWDR_RECYCLE_TICK; slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1); } twdr->twcal_hand = -1; out: if ((twdr->tw_count -= killed) == 0) del_timer(&twdr->tw_timer); #ifndef CONFIG_NET_NS NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITKILLED, killed); #endif spin_unlock(&twdr->death_lock); } EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick); void inet_twsk_purge(struct inet_hashinfo *hashinfo, struct inet_timewait_death_row *twdr, int family) { struct inet_timewait_sock *tw; struct sock *sk; struct hlist_nulls_node *node; unsigned int slot; for (slot = 0; slot <= hashinfo->ehash_mask; slot++) { struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; restart_rcu: rcu_read_lock(); restart: sk_nulls_for_each_rcu(sk, node, &head->chain) { if (sk->sk_state != TCP_TIME_WAIT) continue; tw = inet_twsk(sk); if ((tw->tw_family != family) || atomic_read(&twsk_net(tw)->count)) continue; if (unlikely(!atomic_inc_not_zero(&tw->tw_refcnt))) continue; if (unlikely((tw->tw_family != family) || atomic_read(&twsk_net(tw)->count))) { inet_twsk_put(tw); goto restart; } rcu_read_unlock(); local_bh_disable(); inet_twsk_deschedule(tw, twdr); local_bh_enable(); inet_twsk_put(tw); 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);