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nixpkgs/nixos/modules/services/networking/nat.nix
2013-10-30 18:47:43 +01:00

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Nix

# This module enables Network Address Translation (NAT).
# XXX: todo: support multiple upstream links
# see http://yesican.chsoft.biz/lartc/MultihomedLinuxNetworking.html
{ config, pkgs, ... }:
with pkgs.lib;
let
cfg = config.networking.nat;
in
{
###### interface
options = {
networking.nat.enable = mkOption {
type = types.bool;
default = false;
description =
''
Whether to enable Network Address Translation (NAT).
'';
};
networking.nat.internalIPs = mkOption {
type = types.listOf types.str;
example = [ "192.168.1.0/24" ] ;
description =
''
The IP address ranges for which to perform NAT. Packets
coming from these networks and destined for the external
interface will be rewritten.
'';
};
networking.nat.externalInterface = mkOption {
type = types.str;
example = "eth1";
description =
''
The name of the external network interface.
'';
};
networking.nat.externalIP = mkOption {
type = types.nullOr types.str;
default = null;
example = "203.0.113.123";
description =
''
The public IP address to which packets from the local
network are to be rewritten. If this is left empty, the
IP address associated with the external interface will be
used.
'';
};
};
###### implementation
config = mkIf config.networking.nat.enable {
environment.systemPackages = [ pkgs.iptables ];
boot.kernelModules = [ "nf_nat_ftp" ];
jobs.nat =
{ description = "Network Address Translation";
startOn = "started network-interfaces";
path = [ pkgs.iptables ];
preStart =
''
iptables -t nat -F POSTROUTING
iptables -t nat -X
''
+ (concatMapStrings (network:
''
iptables -t nat -A POSTROUTING \
-s ${network} -o ${cfg.externalInterface} \
${if cfg.externalIP == null
then "-j MASQUERADE"
else "-j SNAT --to-source ${cfg.externalIP}"}
''
) cfg.internalIPs) +
''
echo 1 > /proc/sys/net/ipv4/ip_forward
'';
postStop =
''
iptables -t nat -F POSTROUTING
'';
};
};
}