ipv4: Return error for RTA_VIA attribute [Linux 5.0]

ipv4: Return error for RTA_VIA attribute [Linux 5.0]

This Linux kernel change "ipv4: Return error for RTA_VIA attribute" is included in the Linux 5.0 release. This change is authored by David Ahern <dsahern [at] gmail.com> on Tue Feb 26 09:00:02 2019 -0800. The commit for this change in Linux stable tree is b6e9e5d (patch).

ipv4: Return error for RTA_VIA attribute

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 via inet6 2001:db8:1::1 dev eth0
  $ ip ro ls
  ... dev eth0

Catch this and fail the route add:
  $ ip ro add 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 <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

There are 4 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 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 fe4f6a6..ed14ec2 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);
+       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);

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