tcp: Add TIME_WAIT sockets in bhash2.

Jiri Slaby reported regression of bind() with a simple repro. [0]

The repro creates a TIME_WAIT socket and tries to bind() a new socket
with the same local address and port.  Before commit 28044fc1d495 ("net:
Add a bhash2 table hashed by port and address"), the bind() failed with
-EADDRINUSE, but now it succeeds.

The cited commit should have put TIME_WAIT sockets into bhash2; otherwise,
inet_bhash2_conflict() misses TIME_WAIT sockets when validating bind()
requests if the address is not a wildcard one.

The straight option is to move sk_bind2_node from struct sock to struct
sock_common to add twsk to bhash2 as implemented as RFC. [1]  However, the
binary layout change in the struct sock could affect performances moving
hot fields on different cachelines.

To avoid that, we add another TIME_WAIT list in inet_bind2_bucket and check
it while validating bind().

[0]: https://lore.kernel.org/netdev/6b971a4e-c7d8-411e-1f92-fda29b5b2fb9@kernel.org/
[1]: https://lore.kernel.org/netdev/20221221151258.25748-2-kuniyu@amazon.com/

Fixes: 28044fc1d495 ("net: Add a bhash2 table hashed by port and address")
Reported-by: Jiri Slaby <jirislaby@kernel.org>
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 9 insertions, 0 deletions

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 69174093078f..99bd823e97f6 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -108,6 +108,10 @@ struct inet_bind2_bucket {
 	struct hlist_node	node;
 	/* List of sockets hashed to this bucket */
 	struct hlist_head	owners;
+	/* bhash has twsk in owners, but bhash2 has twsk in
+	 * deathrow not to add a member in struct sock_common.
+	 */
+	struct hlist_head	deathrow;
 };
 
 static inline struct net *ib_net(const struct inet_bind_bucket *ib)
diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index 5b47545f22d3..4a8e578405cb 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -73,9 +73,14 @@ struct inet_timewait_sock {
 	u32			tw_priority;
 	struct timer_list	tw_timer;
 	struct inet_bind_bucket	*tw_tb;
+	struct inet_bind2_bucket	*tw_tb2;
+	struct hlist_node		tw_bind2_node;
 };
 #define tw_tclass tw_tos
 
+#define twsk_for_each_bound_bhash2(__tw, list) \
+	hlist_for_each_entry(__tw, list, tw_bind2_node)
+
 static inline struct inet_timewait_sock *inet_twsk(const struct sock *sk)
 {
 	return (struct inet_timewait_sock *)sk;