#!/usr/bin/nft -f

# IPv4/IPv6 Simple & Safe firewall ruleset.
# More examples in /usr/share/nftables/ and /usr/share/doc/nftables/examples/.

# references, some codes from:
# https://wiki.archlinux.org/title/Nftables
# https://www.procustodibus.com/blog/2021/11/wireguard-nftables
# https://wiki.gentoo.org/wiki/Nftables/Examples#Basic_NAT

# needed for reload config using `sudo systemctl restart nftables` or `sudo nft -f /etc/nftables.conf`
flush ruleset

define pub_iface = "eth0"
define wg_iface = "wg0"

table inet my_table {

	chain my_input {
		type filter hook input priority filter
		policy drop

		ct state invalid drop comment "early drop of invalid connections"
		ct state {established, related} accept comment "allow tracked connections"
		iifname lo accept comment "allow from loopback"
		iifname $wg_iface accept comment "allow from wireguard"
		ip protocol icmp accept
		meta l4proto ipv6-icmp accept

		tcp dport ssh accept
		#tcp dport qbt-nox accept
		#tcp dport qbt accept
		#udp dport qbt accept
		#tcp dport iperf3 accept
		udp dport wireguard accept
		# for acme.sh standalone mode builtin webserver to renew ssl cert
		tcp dport http accept
		# email related ports
		tcp dport smtp accept
		tcp dport pop3 accept
		tcp dport imap accept
		tcp dport submissions accept
		tcp dport submission accept
		tcp dport imaps accept
		tcp dport pop3s accept

		pkttype host limit rate 5/second counter reject with icmpx type admin-prohibited
		counter comment "count any other traffic"
	}

	chain my_forward {
		type filter hook forward priority filter
		policy drop
		# Drop everything forwarded to us. We do not forward. That is routers job.

		# needed for wireguard?
		#iifname $wg_iface oifname $pub_iface accept
		#iifname $pub_iface oifname $wg_iface accept
		iifname $wg_iface accept
		oifname $wg_iface accept
	}

	chain my_output {
		type filter hook output priority filter
		policy accept
		# Accept every outbound connection
	}
}

# needed to wireguard NAT masquerade VPN traffic
# Need inet to masquerade both ipv4 and ipv6? If use ip it will only masquerade ipv4? If use ip6 it will only masquerade ipv6?
# https://wiki.nftables.org/wiki-nftables/index.php/Nftables_families
table inet nat {
	# newer kernel no need for `chain prerouting { type nat hook prerouting priority -100; policy accept; }`, more see https://www.procustodibus.com/blog/2021/11/wireguard-nftables/
	# for all packets to $pub_iface, after routing, replace source address with primary IP of $pub_iface interface
	chain postrouting {
		type nat hook postrouting priority 100
		policy accept
		oifname $pub_iface masquerade
	}
}