net: Add a second bind table hashed by port and address

We currently have one tcp bind table (bhash) which hashes by port
number only. In the socket bind path, we check for bind conflicts by
traversing the specified port's inet_bind2_bucket while holding the
bucket's spinlock (see inet_csk_get_port() and inet_csk_bind_conflict()).

In instances where there are tons of sockets hashed to the same port
at different addresses, checking for a bind conflict is time-intensive
and can cause softirq cpu lockups, as well as stops new tcp connections
since __inet_inherit_port() also contests for the spinlock.

This patch proposes adding a second bind table, bhash2, that hashes by
port and ip address. Searching the bhash2 table leads to significantly
faster conflict resolution and less time holding the spinlock.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 67 insertions, 1 deletions

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index ebfa3df6f8dc..a0887b70967b 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -90,11 +90,32 @@ struct inet_bind_bucket {
 	struct hlist_head	owners;
 };
 
+struct inet_bind2_bucket {
+	possible_net_t		ib_net;
+	int			l3mdev;
+	unsigned short		port;
+	union {
+#if IS_ENABLED(CONFIG_IPV6)
+		struct in6_addr		v6_rcv_saddr;
+#endif
+		__be32			rcv_saddr;
+	};
+	/* Node in the inet2_bind_hashbucket chain */
+	struct hlist_node	node;
+	/* List of sockets hashed to this bucket */
+	struct hlist_head	owners;
+};
+
 static inline struct net *ib_net(struct inet_bind_bucket *ib)
 {
 	return read_pnet(&ib->ib_net);
 }
 
+static inline struct net *ib2_net(struct inet_bind2_bucket *ib)
+{
+	return read_pnet(&ib->ib_net);
+}
+
 #define inet_bind_bucket_for_each(tb, head) \
 	hlist_for_each_entry(tb, head, node)
 
@@ -103,6 +124,15 @@ struct inet_bind_hashbucket {
 	struct hlist_head	chain;
 };
 
+/* This is synchronized using the inet_bind_hashbucket's spinlock.
+ * Instead of having separate spinlocks, the inet_bind2_hashbucket can share
+ * the inet_bind_hashbucket's given that in every case where the bhash2 table
+ * is useful, a lookup in the bhash table also occurs.
+ */
+struct inet_bind2_hashbucket {
+	struct hlist_head	chain;
+};
+
 /* Sockets can be hashed in established or listening table.
  * We must use different 'nulls' end-of-chain value for all hash buckets :
  * A socket might transition from ESTABLISH to LISTEN state without
@@ -134,6 +164,12 @@ struct inet_hashinfo {
 	 */
 	struct kmem_cache		*bind_bucket_cachep;
 	struct inet_bind_hashbucket	*bhash;
+	/* The 2nd binding table hashed by port and address.
+	 * This is used primarily for expediting the resolution of bind
+	 * conflicts.
+	 */
+	struct kmem_cache		*bind2_bucket_cachep;
+	struct inet_bind2_hashbucket	*bhash2;
 	unsigned int			bhash_size;
 
 	/* The 2nd listener table hashed by local port and address */
@@ -193,6 +229,36 @@ inet_bind_bucket_create(struct kmem_cache *cachep, struct net *net,
 void inet_bind_bucket_destroy(struct kmem_cache *cachep,
 			      struct inet_bind_bucket *tb);
 
+static inline bool check_bind_bucket_match(struct inet_bind_bucket *tb,
+					   struct net *net,
+					   const unsigned short port,
+					   int l3mdev)
+{
+	return net_eq(ib_net(tb), net) && tb->port == port &&
+		tb->l3mdev == l3mdev;
+}
+
+struct inet_bind2_bucket *
+inet_bind2_bucket_create(struct kmem_cache *cachep, struct net *net,
+			 struct inet_bind2_hashbucket *head,
+			 const unsigned short port, int l3mdev,
+			 const struct sock *sk);
+
+void inet_bind2_bucket_destroy(struct kmem_cache *cachep,
+			       struct inet_bind2_bucket *tb);
+
+struct inet_bind2_bucket *
+inet_bind2_bucket_find(struct inet_hashinfo *hinfo, struct net *net,
+		       const unsigned short port, int l3mdev,
+		       struct sock *sk,
+		       struct inet_bind2_hashbucket **head);
+
+bool check_bind2_bucket_match_nulladdr(struct inet_bind2_bucket *tb,
+				       struct net *net,
+				       const unsigned short port,
+				       int l3mdev,
+				       const struct sock *sk);
+
 static inline u32 inet_bhashfn(const struct net *net, const __u16 lport,
 			       const u32 bhash_size)
 {
@@ -200,7 +266,7 @@ static inline u32 inet_bhashfn(const struct net *net, const __u16 lport,
 }
 
 void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
-		    const unsigned short snum);
+		    struct inet_bind2_bucket *tb2, const unsigned short snum);
 
 /* Caller must disable local BH processing. */
 int __inet_inherit_port(const struct sock *sk, struct sock *child);