ipv6: Return error for RTA_VIA attribute [Linux 5.0]

ipv6: Return error for RTA_VIA attribute [Linux 5.0]

This Linux kernel change "ipv6: 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 09:00:03 2019 -0800. The commit for this change in Linux stable tree is e381854 (patch).

ipv6: Return error for RTA_VIA attribute

IPv6 currently does not support nexthops outside of the AF_INET6 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 -6 ro add 2001:db8:2::/64 via inet dev eth0
  $ ip ro ls
  2001:db8:2::/64 dev eth0 metric 1024 pref medium

Catch this and fail the route add:
  $ ip -6 ro add 2001:db8:2::/64 via inet dev eth0
  Error: IPv6 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/ipv6/route.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index ce15dc4..b7a6200 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -4182,6 +4182,10 @@ static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
        cfg->fc_gateway = nla_get_in6_addr(tb[RTA_GATEWAY]);
        cfg->fc_flags |= RTF_GATEWAY;
+   if (tb[RTA_VIA]) {
+       NL_SET_ERR_MSG(extack, "IPv6 does not support RTA_VIA attribute");
+       goto errout;
+   }

    if (tb[RTA_DST]) {
        int plen = (rtm->rtm_dst_len + 7) >> 3;

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