[FR] Blackhole route for DHCPv6 delegated prefixes

[jlsnt]

Hello,

Would you please consider adding a flag (to the ia_pd option maybe ?) to add a "blackhole" route for delegated prefixes, rather than an "unreachable" one ? (current behavior - using Linux terms)

That would stop the host running dhcpcd from sending ICMPv6 unreachables back to port scanners and reveal the subnet is not routed.

Thank you for maintaining dhcpcd !