net: inet_diag -- Return error code if protocol handler is missed

We've observed that in case if UDP diag module is not
supported in kernel the netlink returns NLMSG_DONE without
notifying a caller that handler is missed.

This patch makes __inet_diag_dump to return error code instead.

So as example it become possible to detect such situation
and handle it gracefully on userspace level.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: David Miller <davem@davemloft.net>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 535584c00f91..0c34bfabc11f 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -892,13 +892,16 @@ static int __inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
                 struct inet_diag_req_v2 *r, struct nlattr *bc)
 {
         const struct inet_diag_handler *handler;
+        int err = 0;
 
         handler = inet_diag_lock_handler(r->sdiag_protocol);
         if (!IS_ERR(handler))
                 handler->dump(skb, cb, r, bc);
+        else
+                err = PTR_ERR(handler);
         inet_diag_unlock_handler(handler);
 
-        return skb->len;
+        return err ? : skb->len;
 }
 
 static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)