ipv4: Add helper inet_csk_update_pmtu().

This abstracts away the call to dst_ops->update_pmtu() so that we can
transparently handle the fact that, in the future, the dst itself can
be invalidated by the PMTU update (when we have non-host routes cached
in sockets).

So we try to rebuild the socket cached route after the method
invocation if necessary.

This isn't used by SCTP because it needs to cache dsts per-transport,
and thus will need it's own local version of this helper.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 9 deletions

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.
          */