From 303d0403b8c25e994e4a6e45389e173cf8706fb5 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Wed, 19 Feb 2020 14:16:32 -0500 Subject: udp: rehash on disconnect 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 Signed-off-by: Willem de Bruijn Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/udp.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index db76b9609299..08a41f1e1cd2 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1857,8 +1857,12 @@ int __udp_disconnect(struct sock *sk, int flags) 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); -- cgit v1.2.3-59-g8ed1b