3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Neal Cardwell <ncardw...@google.com>

[ Upstream commit 4fab9071950c2021d846e18351e0f46a1cffd67b ]

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 <ncardw...@google.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Diagnosed-by: Willem de Bruijn <will...@google.com>
Fixes: 563d34d057862 ("tcp: dont drop MTU reduction indications")
Reviewed-by: Hannes Frederic Sowa <han...@stressinduktion.org>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 include/net/inet_connection_sock.h |    1 +
 include/net/sock.h                 |    1 -
 include/net/tcp.h                  |    1 +
 net/ipv4/tcp_ipv4.c                |    5 +++--
 net/ipv4/tcp_output.c              |    2 +-
 net/ipv6/tcp_ipv6.c                |    3 ++-
 6 files changed, 8 insertions(+), 5 deletions(-)

--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -62,6 +62,7 @@ struct inet_connection_sock_af_ops {
        void        (*addr2sockaddr)(struct sock *sk, struct sockaddr *);
        int         (*bind_conflict)(const struct sock *sk,
                                     const struct inet_bind_bucket *tb, bool 
relax);
+       void        (*mtu_reduced)(struct sock *sk);
 };
 
 /** inet_connection_sock - INET connection oriented sock
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -971,7 +971,6 @@ struct proto {
                                                struct sk_buff *skb);
 
        void            (*release_cb)(struct sock *sk);
-       void            (*mtu_reduced)(struct sock *sk);
 
        /* Keeping track of sk's, looking them up, and port selection methods. 
*/
        void                    (*hash)(struct sock *sk);
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -448,6 +448,7 @@ const u8 *tcp_parse_md5sig_option(const
  */
 
 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
+void tcp_v4_mtu_reduced(struct sock *sk);
 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
 struct sock *tcp_create_openreq_child(struct sock *sk,
                                      struct request_sock *req,
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -269,7 +269,7 @@ 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);
@@ -300,6 +300,7 @@ static void tcp_v4_mtu_reduced(struct so
                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)
 {
@@ -1880,6 +1881,7 @@ const struct inet_connection_sock_af_ops
        .compat_setsockopt = compat_ip_setsockopt,
        .compat_getsockopt = compat_ip_getsockopt,
 #endif
+       .mtu_reduced       = tcp_v4_mtu_reduced,
 };
 EXPORT_SYMBOL(ipv4_specific);
 
@@ -2499,7 +2501,6 @@ 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,
--- 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);
        }
 }
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1681,6 +1681,7 @@ static const struct inet_connection_sock
        .compat_setsockopt = compat_ipv6_setsockopt,
        .compat_getsockopt = compat_ipv6_getsockopt,
 #endif
+       .mtu_reduced       = tcp_v6_mtu_reduced,
 };
 
 #ifdef CONFIG_TCP_MD5SIG
@@ -1711,6 +1712,7 @@ static const struct inet_connection_sock
        .compat_setsockopt = compat_ipv6_setsockopt,
        .compat_getsockopt = compat_ipv6_getsockopt,
 #endif
+       .mtu_reduced       = tcp_v4_mtu_reduced,
 };
 
 #ifdef CONFIG_TCP_MD5SIG
@@ -1950,7 +1952,6 @@ struct proto tcpv6_prot = {
        .sendpage               = tcp_sendpage,
        .backlog_rcv            = tcp_v6_do_rcv,
        .release_cb             = tcp_release_cb,
-       .mtu_reduced            = tcp_v6_mtu_reduced,
        .hash                   = tcp_v6_hash,
        .unhash                 = inet_unhash,
        .get_port               = inet_csk_get_port,


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