nft-simple-fw/fw.nft

#!/usr/bin/env nft -f

table inet fw {
	include "./conf.def"

	# invalid packets
	counter ct-invalid { packets 0 bytes 0 }
	# !(tcp|udp) protocol packets dropped
	counter catchall { packets 0 bytes 0 }
	# iifgroup != IIFGROUP_ETHERNET | IIFGROUP_VPN
	counter iif-other { packets 0 bytes 0 }
	# non-unicast
	counter non-unicast { packets 0 bytes 0 }
	# no reverse path
	counter no-reverse-path { packets 0 bytes 0 }
	# ipv6 type 0 routing headers
	counter type0-header { packets 0 bytes 0 }
	# dropped icmp packets
	counter unwanted-icmp { packets 0 bytes 0 }
	counter unwanted-icmpv6 { packets 0 bytes 0 }
	# reject total
	counter reject-total { packets 0 bytes 0 }
	# dropped total
	counter drop-total { packets 0 bytes 0 }

	set set_private_net4 {
		type ipv4_addr
		flags constant,interval
		elements = $SET_PRIVATE_NETS_V4
	}

	set set_private_net6 {
		type ipv6_addr
		flags constant,interval
		elements = $SET_PRIVATE_NETS_V6
	}

	set set_icmpv4 {
		type icmp_type
		flags constant
		elements = $SET_ALLOW_ICMP_V4
	}

	set set_icmpv6 {
		type icmpv6_type
		flags constant
		elements = $SET_ALLOW_ICMP_V6
	}

	chain iif-dispatch {
		type filter hook input priority filter; policy drop;
		iif "lo" accept
		jump ct-state-filter
		iifgroup vmap {
			$IIFGROUP_ETHERNET : goto input-zone-dispatch,
			$IIFGROUP_VPN : goto vpn
		}
		# basic filtering of unhandled iifgroups
		counter name "iif-other" jump proto-filter
		goto reject-verdict
	}

	chain input-zone-dispatch {
		ip saddr @set_private_net4 goto private
		ip6 saddr @set_private_net6 goto private
		goto public
	}

	chain icmp-dispatch {
		ip6 nexthdr ipv6-icmp goto icmpv6-filter
		ip protocol icmp goto icmpv4-filter
	}

	chain proto-filter {
		jump icmp-dispatch
		ip protocol igmp goto log-drop
		# drop unsolicited broadcast/multicast
		meta pkttype { broadcast, multicast } counter name "non-unicast" goto log-drop
		# disallow ipv6 type 0 routing headers
		rt type 0 counter name "type0-header" goto log6-reject-addr-unreachable
	}

	chain ct-state-filter {
		# stateful filtering and packet fastpath
		ct state established,related accept
		ct state invalid counter name "ct-invalid" goto log-drop
	}

	chain rp-filter {
		# reverse path filter for ipv6
		type filter hook prerouting priority raw; policy drop;
		fib saddr . iif oif exists accept
		counter name "no-reverse-path" goto log-drop
	}

	chain icmpv6-filter {
		# allow configured types
		icmpv6 type @set_icmpv6 accept
		# and all essential types according to rfc4890
		jump rfc4890
		counter name "unwanted-icmpv6" goto log-drop 
	}

	chain icmpv4-filter {
		icmp type @set_icmpv4 accept
		counter name "unwanted-icmp" goto log-drop
	}

	chain rfc4890 {
		# https://tools.ietf.org/html/rfc4890
		# https://github.com/intel/intel-iot-refkit/blob/master/meta-refkit-core/recipes-security/nftables-settings-default/files/firewall.template

		# allow basic IPv6 functionality.
		icmpv6 type {
			destination-unreachable,
			packet-too-big,
			time-exceeded,
			parameter-problem,
			echo-request,
			echo-reply
		} accept;

		# allow auto configuration support.
		icmpv6 type {
			nd-neighbor-solicit,
			nd-neighbor-advert,
			nd-router-advert,
			nd-router-solicit
		} ip6 hoplimit 255 accept;

		# allow multicast listener discovery on link-local addresses.
		icmpv6 type {
			mld-listener-query,
			mld-listener-report,
			mld-listener-reduction
		} ip6 saddr $NET_V6_LINK_LOCAL accept;

		# allow multicast router discovery messages on link-local
		# addresses (hop limit 1).
		icmpv6 type {
			nd-router-advert,
			nd-router-solicit
		} ip6 hoplimit 1 ip6 saddr $NET_V6_LINK_LOCAL accept;
	}

	chain reject-verdict {
		meta l4proto vmap {
			udp : goto logx-reject-port-unreachable,
			tcp : goto logx-reject-tcp-reset
		}
		counter name "catchall" goto logx-reject-port-unreachable
	}

	chain log-reject {
		# if called, the subsequent rules *must* include an absolute reject verdict
		# this allows specifying a reject method on return
		counter name "reject-total" comment "total packets rejected"
		limit rate 5/minute burst 5 packets \
			log prefix "sfw (reject): " level debug flags ip options
	}

	chain log-drop {
		counter name "drop-total" comment "total packets dropped"
		limit rate 5/minute burst 5 packets \
			log prefix "sfw (drop): " level debug flags ip options
		drop comment "drop packet"
		# end of rule traversal
	}

	chain log6-reject-addr-unreachable {
		jump log-reject
		reject with icmpv6 type addr-unreachable comment "icmpv6 addr-unreachable"
		# end of rule traversal
	}

	chain logx-reject-port-unreachable {
		jump log-reject
		reject comment "icmpx port-unreachable"
		# end of rule traversal
	}

	chain logx-reject-tcp-reset {
		jump log-reject
		reject with tcp reset comment "icmpx tcp reset"
		# end of rule traversal
	}

	chain vpn-zone-svc     { include "./services.d/vpn/*.nft";     }
	chain private-zone-svc { include "./services.d/private/*.nft"; }
	chain public-zone-svc  { include "./services.d/public/*.nft";  }
	chain forward-zone-svc { include "./services.d/forward/*.nft"; }
	chain output-zone-svc  { include "./services.d/output/*.nft";  }

	include "./zones/vpn.nft"
	include "./zones/private.nft"
	include "./zones/public.nft"
	include "./zones/forward.nft"
	include "./zones/output.nft"
}