v4.19.13 snapshot.
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
new file mode 100644
index 0000000..88c5069
--- /dev/null
+++ b/net/ipv4/inet_timewait_sock.c
@@ -0,0 +1,301 @@
+/*
+ * 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[inet_bhashfn(twsk_net(tw), tw->tw_num,
+ hashinfo->bhash_size)];
+
+ spin_lock(&bhead->lock);
+ inet_twsk_bind_unhash(tw, hashinfo);
+ spin_unlock(&bhead->lock);
+
+ 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 (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.
+ */
+ 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);
+
+ 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);
+
+ if (tw->tw_kill)
+ __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
+ else
+ __NET_INC_STATS(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);
+
+ 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.
+ */
+
+ tw->tw_kill = timeo <= 4*HZ;
+ if (!rearm) {
+ BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
+ atomic_inc(&tw->tw_dr->tw_count);
+ } 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)
+ continue;
+ tw = inet_twsk(sk);
+ if ((tw->tw_family != family) ||
+ refcount_read(&twsk_net(tw)->count))
+ continue;
+
+ if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
+ continue;
+
+ if (unlikely((tw->tw_family != family) ||
+ refcount_read(&twsk_net(tw)->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);