lwtunnel: valid encap attr check should return 0 when lwtunnel is disabled

An error was reported upgrading to 4.9.8:
    root@Typhoon:~# ip route add default table 210 nexthop dev eth0 via 10.68.64.1
    weight 1 nexthop dev eth0 via 10.68.64.2 weight 1
    RTNETLINK answers: Operation not supported

The problem occurs when CONFIG_LWTUNNEL is not enabled and a multipath
route is submitted.

The point of lwtunnel_valid_encap_type_attr is catch modules that
need to be loaded before any references are taken with rntl held. With
CONFIG_LWTUNNEL disabled, there will be no modules to load so the
lwtunnel_valid_encap_type_attr stub should just return 0.

Fixes: 9ed59592e3e3 ("lwtunnel: fix autoload of lwt modules")
Reported-by: pupilla@libero.it
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/lwtunnel.h b/include/net/lwtunnel.h
index 73dd8764746069d48cd9ed6863f54c53864bb47a..0388b9c5f5e2c7257cc0eb19be469974becab5ed 100644 (file)
--- a/include/net/lwtunnel.h
+++ b/include/net/lwtunnel.h
@@ -178,7 +178,10 @@ static inline int lwtunnel_valid_encap_type(u16 encap_type)
 }
 static inline int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int len)
 {
-       return -EOPNOTSUPP;
+       /* return 0 since we are not walking attr looking for
+        * RTA_ENCAP_TYPE attribute on nexthops.
+        */
+       return 0;
 }
 
 static inline int lwtunnel_build_state(struct net_device *dev, u16 encap_type,