[PATCH net 1/3] ipv4: Return error for RTA_VIA attribute

[David Ahern]

From: David Ahern <dsah...@gmail.com>

IPv4 currently does not support nexthops outside of the AF_INET family.
Specifically, it does not handle RTA_VIA attribute. If it is passed
in a route add request, the actual route added only uses the device
which is clearly not what the user intended:

  $ ip ro add 172.16.1.0/24 via inet6 2001:db8:1::1 dev eth0
  $ ip ro ls
  ...
  172.16.1.0/24 dev eth0

Catch this and fail the route add:
  $ ip ro add 172.16.1.0/24 via inet6 2001:db8:1::1 dev eth0
  Error: IPv4 does not support RTA_VIA attribute.

Fixes: 03c0566542f4c ("mpls: Netlink commands to add, remove, and dump routes")
Signed-off-by: David Ahern <dsah...@gmail.com>
---
 net/ipv4/fib_frontend.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index fe4f6a624238..ed14ec245584 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -710,6 +710,10 @@ static int rtm_to_fib_config(struct net *net, struct 
sk_buff *skb,
                case RTA_GATEWAY:
                        cfg->fc_gw = nla_get_be32(attr);
                        break;
+               case RTA_VIA:
+                       NL_SET_ERR_MSG(extack, "IPv4 does not support RTA_VIA 
attribute");
+                       err = -EINVAL;
+                       goto errout;
                case RTA_PRIORITY:
                        cfg->fc_priority = nla_get_u32(attr);
                        break;
-- 
2.11.0