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Diffstat (limited to '')
| -rw-r--r-- | net/ipv4/inet_timewait_sock.c | 342 |
1 files changed, 342 insertions, 0 deletions
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c new file mode 100644 index 000000000..1d77d992e --- /dev/null +++ b/net/ipv4/inet_timewait_sock.c @@ -0,0 +1,342 @@ +// 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_bind2_bucket *tb2 = tw->tw_tb2; + 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); + + __hlist_del(&tw->tw_bind2_node); + tw->tw_tb2 = NULL; + inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2); + + __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); +#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); +} + +static void inet_twsk_add_bind2_node(struct inet_timewait_sock *tw, + struct hlist_head *list) +{ + hlist_add_head(&tw->tw_bind2_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, *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); + + spin_lock(&bhead->lock); + spin_lock(&bhead2->lock); + + tw->tw_tb = icsk->icsk_bind_hash; + WARN_ON(!icsk->icsk_bind_hash); + inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); + + tw->tw_tb2 = icsk->icsk_bind2_hash; + WARN_ON(!icsk->icsk_bind2_hash); + inet_twsk_add_bind2_node(tw, &tw->tw_tb2->deathrow); + + spin_unlock(&bhead2->lock); + 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 >= + 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->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); + +void inet_twsk_purge(struct inet_hashinfo *hashinfo, 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: + cond_resched(); + rcu_read_lock(); +restart: + sk_nulls_for_each_rcu(sk, node, &head->chain) { + if (sk->sk_state != TCP_TIME_WAIT) { + /* A kernel listener socket might not hold refcnt for net, + * so reqsk_timer_handler() could be fired after net is + * freed. Userspace listener and reqsk never exist here. + */ + if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV && + hashinfo->pernet)) { + struct request_sock *req = inet_reqsk(sk); + + inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req); + } + + continue; + } + + tw = inet_twsk(sk); + if ((tw->tw_family != family) || + refcount_read(&twsk_net(tw)->ns.count)) + continue; + + if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt))) + continue; + + if (unlikely((tw->tw_family != family) || + refcount_read(&twsk_net(tw)->ns.count))) { + inet_twsk_put(tw); + goto restart; + } + + rcu_read_unlock(); + local_bh_disable(); + inet_twsk_deschedule_put(tw); + 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); |