1 files changed, 328 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..00ec8d5d7
--- /dev/null
+++ b/net/ipv4/inet_timewait_sock.c
@@ -0,0 +1,328 @@
+/*
+ * 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 = tw->tw_dr->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);
+	atomic_dec(&tw->tw_dr->tw_count);
+	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 (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);
+
+void tw_timer_handler(unsigned long data)
+{
+	struct inet_timewait_sock *tw = (struct inet_timewait_sock *)data;
+
+	if (tw->tw_kill)
+		NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
+	else
+		NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED);
+	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 (atomic_read(&dr->tw_count) >= 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);
+
+		kmemcheck_annotate_bitfield(tw, flags);
+
+		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_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));
+		setup_timer(&tw->tw_timer, tw_timer_handler, (unsigned long)tw);
+		/*
+		 * 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);
+
+		__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. */
+void inet_twsk_deschedule(struct inet_timewait_sock *tw)
+{
+	if (del_timer_sync(&tw->tw_timer))
+		inet_twsk_kill(tw);
+}
+EXPORT_SYMBOL(inet_twsk_deschedule);
+
+void inet_twsk_schedule(struct inet_timewait_sock *tw, const int timeo)
+{
+	/* 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.
+	 */
+
+	tw->tw_kill = timeo <= 4*HZ;
+	if (!mod_timer_pinned(&tw->tw_timer, jiffies + timeo)) {
+		atomic_inc(&tw->tw_refcnt);
+		atomic_inc(&tw->tw_dr->tw_count);
+	}
+}
+EXPORT_SYMBOL_GPL(inet_twsk_schedule);
+
+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:
+		cond_resched();
+		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);
+			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);