ipv6: udp: Do a route lookup and update during release_cb

This patch adds a release_cb for UDPv6.  It does a route lookup
and updates sk->sk_dst_cache if it is needed.  It picks up the
left-over job from ip6_sk_update_pmtu() if the sk was owned
by user during the pmtu update.

It takes a rcu_read_lock to protect the __sk_dst_get() operations
because another thread may do ip6_dst_store() without taking the
sk lock (e.g. sendmsg).

Fixes: 45e4fd26683c ("ipv6: Only create RTF_CACHE routes after encountering pmtu exception")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Reported-by: Wei Wang <weiwan@google.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Wei Wang <weiwan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 21 insertions, 0 deletions

diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 59e01f27db9f..9dd3882fe6bf 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -119,6 +119,26 @@ out:
         return err;
 }
 
+void ip6_datagram_release_cb(struct sock *sk)
+{
+        struct dst_entry *dst;
+
+        if (ipv6_addr_v4mapped(&sk->sk_v6_daddr))
+                return;
+
+        rcu_read_lock();
+        dst = __sk_dst_get(sk);
+        if (!dst || !dst->obsolete ||
+            dst->ops->check(dst, inet6_sk(sk)->dst_cookie)) {
+                rcu_read_unlock();
+                return;
+        }
+        rcu_read_unlock();
+
+        ip6_datagram_dst_update(sk, false);
+}
+EXPORT_SYMBOL_GPL(ip6_datagram_release_cb);
+
 static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 {
         struct sockaddr_in6     *usin = (struct sockaddr_in6 *) uaddr;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 8125931106be..6bc5c664fa46 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1539,6 +1539,7 @@ struct proto udpv6_prot = {
         .sendmsg           = udpv6_sendmsg,
         .recvmsg           = udpv6_recvmsg,
         .backlog_rcv       = __udpv6_queue_rcv_skb,
+        .release_cb        = ip6_datagram_release_cb,
         .hash              = udp_lib_hash,
         .unhash            = udp_lib_unhash,
         .rehash            = udp_v6_rehash,