homemade_firewall/filter.nft

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#!/usr/bin/nft
flush ruleset
include "./defines.nft"
table ip filter {
set allowed_tcp_ports {
type inet_service;
flags constant;
elements = { $SSH_PORT1, $SSH_PORT2, $DNS_PORT, $HTTP_PORT, $HTTPS_PORT };
}
set allowed_udp_ports_in {
type inet_service;
flags constant;
elements = { $DNS_PORT, $DHCP_IN_PORT }
}
set allowed_udp_ports_out {
type inet_service;
flags constant;
elements = { $DNS_PORT, $DHCP_OUT_PORT }
}
chain in {
type filter hook input priority filter; policy drop;
ct state invalid drop;
ct state {related,established} accept;
tcp dport @allowed_tcp_ports accept;
udp dport @allowed_udp_ports_in accept;
}
chain forward {
type filter hook forward priority filter; policy drop;
}
chain out {
type filter hook output priority filter; policy drop;
udp dport @allowed_udp_ports_out accept;
}
}