4 files changed, 52 insertions, 18 deletions

diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index 291e7cee14e7..2cf44b4ed2e6 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -337,4 +337,6 @@ extern int inet_csk_compat_getsockopt(struct sock *sk, int level, int optname,
                                       char __user *optval, int __user *optlen);
 extern int inet_csk_compat_setsockopt(struct sock *sk, int level, int optname,
                                       char __user *optval, unsigned int optlen);
+
+extern struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu);
 #endif /* _INET_CONNECTION_SOCK_H */
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 129ed8f74138..683902fcc8ed 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -161,17 +161,10 @@ static inline void dccp_do_pmtu_discovery(struct sock *sk,
         if (sk->sk_state == DCCP_LISTEN)
                 return;
 
-        /* We don't check in the destentry if pmtu discovery is forbidden
-         * on this route. We just assume that no packet_to_big packets
-         * are send back when pmtu discovery is not active.
-         * There is a small race when the user changes this flag in the
-         * route, but I think that's acceptable.
-         */
-        if ((dst = __sk_dst_check(sk, 0)) == NULL)
+        dst = inet_csk_update_pmtu(sk, mtu);
+        if (!dst)
                 return;
 
-        dst->ops->update_pmtu(dst, mtu);
-
         /* Something is about to be wrong... Remember soft error
          * for the case, if this connection will not able to recover.
          */
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 76825be3b643..200d21809379 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -803,3 +803,49 @@ int inet_csk_compat_setsockopt(struct sock *sk, int level, int optname,
 }
 EXPORT_SYMBOL_GPL(inet_csk_compat_setsockopt);
 #endif
+
+static struct dst_entry *inet_csk_rebuild_route(struct sock *sk, struct flowi *fl)
+{
+        struct inet_sock *inet = inet_sk(sk);
+        struct ip_options_rcu *inet_opt;
+        __be32 daddr = inet->inet_daddr;
+        struct flowi4 *fl4;
+        struct rtable *rt;
+
+        rcu_read_lock();
+        inet_opt = rcu_dereference(inet->inet_opt);
+        if (inet_opt && inet_opt->opt.srr)
+                daddr = inet_opt->opt.faddr;
+        fl4 = &fl->u.ip4;
+        rt = ip_route_output_ports(sock_net(sk), fl4, sk, daddr,
+                                   inet->inet_saddr, inet->inet_dport,
+                                   inet->inet_sport, sk->sk_protocol,
+                                   RT_CONN_FLAGS(sk), sk->sk_bound_dev_if);
+        if (IS_ERR(rt))
+                rt = NULL;
+        if (rt)
+                sk_setup_caps(sk, &rt->dst);
+        rcu_read_unlock();
+
+        return &rt->dst;
+}
+
+struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu)
+{
+        struct dst_entry *dst = __sk_dst_check(sk, 0);
+        struct inet_sock *inet = inet_sk(sk);
+
+        if (!dst) {
+                dst = inet_csk_rebuild_route(sk, &inet->cork.fl);
+                if (!dst)
+                        goto out;
+        }
+        dst->ops->update_pmtu(dst, mtu);
+
+        dst = __sk_dst_check(sk, 0);
+        if (!dst)
+                dst = inet_csk_rebuild_route(sk, &inet->cork.fl);
+out:
+        return dst;
+}
+EXPORT_SYMBOL_GPL(inet_csk_update_pmtu);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 7a0062cb4ed0..b8e7e0595407 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -289,17 +289,10 @@ static void do_pmtu_discovery(struct sock *sk, const struct iphdr *iph, u32 mtu)
         if (sk->sk_state == TCP_LISTEN)
                 return;
 
-        /* We don't check in the destentry if pmtu discovery is forbidden
-         * on this route. We just assume that no packet_to_big packets
-         * are send back when pmtu discovery is not active.
-         * There is a small race when the user changes this flag in the
-         * route, but I think that's acceptable.
-         */
-        if ((dst = __sk_dst_check(sk, 0)) == NULL)
+        dst = inet_csk_update_pmtu(sk, mtu);
+        if (!dst)
                 return;
 
-        dst->ops->update_pmtu(dst, mtu);
-
         /* Something is about to be wrong... Remember soft error
          * for the case, if this connection will not able to recover.
          */