IPv6 BIRD filters

[Marek Królikowski]

Hello Guys,
Anyone create maybe a good filters for BIRD IPv6 upstreams?
I just add this to my import filter:
import filter {
if bgp_path.len > 49 then reject;
if (net.len < 16) || (net.len > 48) then reject;
accept;
};
But i saw i get strange routing:
root@it-bgp:~# birdc6 show route 2404:1710::/28
BIRD 1.6.3 ready.
2404:1710::/28     via 2a02:XXXX:XXXX:1 on eth0 [Italy 13:52:47 from 
2a02:XXXX:XXXX::2] * (100/?) [AS65332i]

Anyone got any good filter to block something like this?

Best Regards
Marek