IPv6 blackhole route

[Slavko <linux@slavino.sk>]

Hi,

i play with blackhole route on IPv6 and i either did something wrong or
i am somewhat confused... I am in really using on somewhat old OpenWRT
router (Linux 4.4.92 mips, with iptables v1.4.21), but my investigation
was on Debian oldstable (Linux 6.1.0-42-amd64 x86_64, with iptables
v1.8.9 (nf_tables)), inside privileged LXC container (if that matter).

I tried to use TRACE target on Debian, but it fails on rule with match
module, thus no luck to investigate it in more depth on machine with
iptables (with real rules):

    ...
    Error: match extension not found
    xtables-monitor v1.8.9 (nf_tables): Parsing nftables rule failed
    Perhaps xtables-monitor or your kernel needs to be upgraded.
    ...

When i add IPv4 blackhole route, the packet seems to be dropped at
routing decision, at least counters in filter/INPUT chain doesn't grows,
i don't get response for ping and in kernel log (i log from all network
namespaces) i see:

    IPv4: martian source 10.0.0.2 from 10.0.0.3, on dev eth0

But when i try to same with IPv6, eg.:

    ip route add blackhole fd16:b::3/64

(it works even without -6) i do not get ping response, but counters in
filter/INPUT continues to grow and nothing is logged in kernel log, thus
i guess that packet goes behind routing decision.

Please, did i it wrongly or it is expected behavior on IPv6 or ...?

regards

-- 
Slavko
https://www.slavino.sk