tcp: fix tcp_release_cb() to dispatch via address family for mtu_reduced()

Make sure we use the correct address-family-specific function for
handling MTU reductions from within tcp_release_cb().

Previously AF_INET6 sockets were incorrectly always using the IPv6
code path when sometimes they were handling IPv4 traffic and thus had
an IPv4 dst.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Diagnosed-by: Willem de Bruijn <willemb@google.com>
Fixes: 563d34d057862 ("tcp: dont drop MTU reduction indications")
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 3 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index dceff5fe8e66..cd17f009aede 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -271,7 +271,7 @@ EXPORT_SYMBOL(tcp_v4_connect);
  * It can be called through tcp_release_cb() if socket was owned by user
  * at the time tcp_v4_err() was called to handle ICMP message.
  */
-static void tcp_v4_mtu_reduced(struct sock *sk)
+void tcp_v4_mtu_reduced(struct sock *sk)
 {
         struct dst_entry *dst;
         struct inet_sock *inet = inet_sk(sk);
@@ -302,6 +302,7 @@ static void tcp_v4_mtu_reduced(struct sock *sk)
                 tcp_simple_retransmit(sk);
         } /* else let the usual retransmit timer handle it */
 }
+EXPORT_SYMBOL(tcp_v4_mtu_reduced);
 
 static void do_redirect(struct sk_buff *skb, struct sock *sk)
 {
@@ -1787,6 +1788,7 @@ const struct inet_connection_sock_af_ops ipv4_specific = {
         .compat_setsockopt = compat_ip_setsockopt,
         .compat_getsockopt = compat_ip_getsockopt,
 #endif
+        .mtu_reduced       = tcp_v4_mtu_reduced,
 };
 EXPORT_SYMBOL(ipv4_specific);
 
@@ -2406,7 +2408,6 @@ struct proto tcp_prot = {
         .sendpage               = tcp_sendpage,
         .backlog_rcv            = tcp_v4_do_rcv,
         .release_cb             = tcp_release_cb,
-        .mtu_reduced            = tcp_v4_mtu_reduced,
         .hash                   = inet_hash,
         .unhash                 = inet_unhash,
         .get_port               = inet_csk_get_port,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ff3f0f75cc6c..5a7c41fbc6d3 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -800,7 +800,7 @@ void tcp_release_cb(struct sock *sk)
                 __sock_put(sk);
         }
         if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) {
-                sk->sk_prot->mtu_reduced(sk);
+                inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
                 __sock_put(sk);
         }
 }