static iBGP IPv4 route with link-local IPv6 next-hop

[Banerjee, Debabrata]

Hello, I’m trying to use RFC 5549 and RFC 2545 to do this route advertisement, 
and it seems it should work according to the bird documentation. However, bird 
is sending an empty NLRI whenever I use a v6 next-hop, either link-local or 
global. I've tried various combinations of specifying the route "via" or "next 
hop address" with the global or link-local address, I haven't found a 
combination that it likes. In any case, bird would need to figure out the right 
tuple (global, link-local) to send in the extended next hop message.

Tcpdump:
        Update Message (2), length: 29
          Multi-Protocol Unreach NLRI (15), length: 3, Flags [O]: 
            AFI: IPv6 (2), SAFI: Unicast (1)
              End-of-Rib Marker (empty NLRI)
            0x0000:  0002 01

bird> show static 
198.18.235.70/32
        via 2001:4878:c1e1:4015::c612:ea44%eth0

Example config:
router id 192.18.234.68;

protocol device {
}

protocol kernel {
        ipv4 {
                import none;
                export none;
        };
}

protocol static static2 {
        ipv4;
        route 198.18.235.70/32 via 2001:4878:c1e1:4015::c612:ea44 % eth0;
}

protocol bgp uplink1 {
        local 198.18.234.68 as 20940;
        neighbor 198.18.234.65 as 20940;

        ipv4 {
                export all;
                next hop address fe80::216:3eff:fe3c:e58;
                extended next hop;
        };
};