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fwl/examples/simple-router.fwl

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interface wan : WAN { dynamic; };
interface lan : LAN { cidr4 = { 10.0.0.0/24 }; };
zone lan_zone = { lan };
let rfc1918 : Set<IPv4> = { 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 };
-- Single IPv4 port forward: tcp:8080 -> 10.0.0.10:80
let forwards : Map<(Protocol, Port), (IP, Port)> = {
(tcp, :8080) -> (10.0.0.10, :80)
};
-- Open inbound ports on the router itself
let open_ports : Set<Port> = { :22 };
-- IPv6 forwarded destination: tcp . 2001:db8::1 . 22000
let forwards_v6 : Set<(Protocol, IP, Port)> = {
(tcp, 2001:db8::1, :22000)
};
policy input : Frame
on { hook = Input, table = Filter, priority = Filter }
= {
| _ if ct.state in { Established, Related } -> Allow;
| Frame(lo, _) -> Allow;
| Frame(_, IPv6(ip6, ICMPv6(_, _)))
if ip6.src in fe80::/10 -> Allow;
| Frame(_, IPv4(_, TCP(tcp, _)))
if tcp.dport in open_ports -> Allow;
| Frame(_, IPv4(_, UDP(udp, _)))
if udp.dport == :51944 -> Allow;
| _ -> Drop;
};
policy forward : Frame
on { hook = Forward, table = Filter, priority = Filter }
= {
| _ if ct.state in { Established, Related } -> Allow;
| _ if ct.status == DNAT -> Allow;
| Frame(iif in lan_zone -> wan, _) -> Allow;
| Frame(wan -> iif in lan_zone, IPv4(ip, TCP(th, _) | UDP(th, _)))
if (ip.protocol, th.dport) in forwards -> Allow;
| Frame(wan -> iif in lan_zone, IPv6(ip6, TCP(th, _) | UDP(th, _)))
if (ip6.protocol, ip6.dst, th.dport) in forwards_v6 -> Allow;
| _ -> Drop;
};
policy output : Frame
on { hook = Output, table = Filter, priority = Filter }
= {
| _ -> Allow;
};
policy nat_prerouting : Frame
on { hook = Prerouting, table = NAT, priority = DstNat }
= {
| Frame(_, IPv4(ip, TCP(th, _) | UDP(th, _))) ->
if perform FIB.daddrLocal(ip.dst)
then DNATMap((ip.protocol, th.dport), forwards)
else Allow;
| _ -> Allow;
};
policy nat_postrouting : Frame
on { hook = Postrouting, table = NAT, priority = SrcNat }
= {
| Frame(_ -> wan, IPv4(ip, _)) if ip.src in rfc1918 -> Masquerade;
| _ -> Allow;
};