qubes-mirage-firewall/packet.ml

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(* Copyright (C) 2015, Thomas Leonard <thomas.leonard@unikernel.com>
See the README file for details. *)
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open Fw_utils
type port = int
type ports = {
sport : port; (* Source port *)
dport : port; (* Destination *)
}
type host =
[ `Client of client_link | `Firewall | `NetVM | `External of Ipaddr.t ]
type ('src, 'dst) info = {
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packet : Nat_packet.t;
src : 'src;
dst : 'dst;
proto : [ `UDP of ports | `TCP of ports | `ICMP | `Unknown ];
}
(* The first message in a TCP connection has SYN set and ACK clear. *)
let is_tcp_start = function
| `IPv4 (_ip, `TCP (hdr, _body)) -> Tcp.Tcp_packet.(hdr.syn && not hdr.ack)
| _ -> false
(* The possible actions we can take for a packet: *)
type action = [
| `Accept (* Send the packet to its destination. *)
| `NAT (* Rewrite the packet's source field so packet appears to
have come from the firewall, via an unused port.
Also, add NAT rules so related packets will be translated accordingly. *)
| `NAT_to of host * port (* As for [`NAT], but also rewrite the packet's
destination fields so it will be sent to [host:port]. *)
| `Drop of string (* Drop the packet and log the given reason. *)
]