configs: replace krebs.iptables with the nftables firewall
Every machine now uses networking.firewall on networking.nftables with
the same defaults krebs.iptables had: input and forward drop, all ICMP
accepted, no reverse path filter. Open ports and trusted interfaces are
unchanged on all machines.
- interface port rules become firewall.interfaces.<if>.allowed*Ports,
interface-wide accepts trustedInterfaces
- forwarding goes through extraForwardRules; yellow keeps forward
unfiltered for the transmission namespace
- NAT rules become per-module networking.nftables.tables
- ssh-redirect: 45621 redirects to 22, new connections to 22 are reset
unless they come from lo, retiolum or wiregrill
- xerxes: the JOOL xtables target is added by jool-iptables through
ip6tables-nft, with XTABLES_LIBDIR pointing at jool's extension
- flushRuleset = false so libvirt/podman/jool tables survive reloads;
extraDeletions drops the iptables-nft tables krebs.iptables left
Rules that were silently ignored while networking.firewall was disabled,
such as clan's yggdrasil filter, now take effect.