diff mbox series

[5.5,012/176] udp: rehash on disconnect

Message ID 20200303174305.990010916@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH March 3, 2020, 5:41 p.m. UTC 
From: Willem de Bruijn <willemb@google.com>

[ Upstream commit 303d0403b8c25e994e4a6e45389e173cf8706fb5 ]

As of the below commit, udp sockets bound to a specific address can
coexist with one bound to the any addr for the same port.

The commit also phased out the use of socket hashing based only on
port (hslot), in favor of always hashing on {addr, port} (hslot2).

The change broke the following behavior with disconnect (AF_UNSPEC):

    server binds to 0.0.0.0:1337
    server connects to 127.0.0.1:80
    server disconnects
    client connects to 127.0.0.1:1337
    client sends "hello"
    server reads "hello"	// times out, packet did not find sk

On connect the server acquires a specific source addr suitable for
routing to its destination. On disconnect it reverts to the any addr.

The connect call triggers a rehash to a different hslot2. On
disconnect, add the same to return to the original hslot2.

Skip this step if the socket is going to be unhashed completely.

Fixes: 4cdeeee9252a ("net: udp: prefer listeners bound to an address")
Reported-by: Pavel Roskin <plroskin@gmail.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/udp.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
diff mbox series

Patch

--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1856,8 +1856,12 @@  int __udp_disconnect(struct sock *sk, in
 	inet->inet_dport = 0;
 	sock_rps_reset_rxhash(sk);
 	sk->sk_bound_dev_if = 0;
-	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
+	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK)) {
 		inet_reset_saddr(sk);
+		if (sk->sk_prot->rehash &&
+		    (sk->sk_userlocks & SOCK_BINDPORT_LOCK))
+			sk->sk_prot->rehash(sk);
+	}
 
 	if (!(sk->sk_userlocks & SOCK_BINDPORT_LOCK)) {
 		sk->sk_prot->unhash(sk);