zebra: fix showing nexthop vrf for ipv6 blackhole

For some reasons the Linux kernel associates the ipv6 blackhole of non
default table the lo interface.

> root@r1# ip -6 route show table 100
> root@r1# ip -6 route add unreachable default metric 4278198272 table 100
> root@r1# ip -6 route show table 100
> unreachable default dev lo metric 4278198272 pref medium

As a consequence, the VRF default that owns the lo interface is shown as
the nexthop VRF:

> r1# show ipv6 route table 20
> Table 20:
> K>* ::/0 [255/8192] unreachable (ICMP unreachable) (vrf default), 00:18:12

Do not display the nexthop VRF of a blackhole. It does not make sense
for a blackhole and it was not displayed in the past.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

0 files changed, 0 insertions, 0 deletions