localsubnetsetd maintains nftables sets for all subnets directly attached to the current machine. The original use case for localsubnetsetd was to give special access to traffic on an IPv6 subnet with an unpredictable network number (as is common with prefix delegations from consumer ISPs). More generally, localsubnetsetd allows you to treat local network traffic specially without involving a border firewall.
localsubnetsetd is written in Python 3 and requires the nftables and pyroute2
libraries. On Debian, you want the python3, python3-nftables, and
python3-pyroute2 packages.
localsubnetsetd requires that local_subnets4 and local_subnets6 sets exist
in the inet filter table. Create them with
nft add set inet filter local_subnets4 { type ipv4_addr; flags interval; }
nft add set inet filter local_subnets6 { type ipv6_addr; flags interval; }
This is not an official Google product.