nixpkgs/nixos/modules/services/networking/nat.nix
Eelco Dolstra 29027fd1e1 Rewrite ‘with pkgs.lib’ -> ‘with lib’
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
2014-04-14 16:26:48 +02:00

133 lines
3.4 KiB
Nix

# This module enables Network Address Translation (NAT).
# XXX: todo: support multiple upstream links
# see http://yesican.chsoft.biz/lartc/MultihomedLinuxNetworking.html
{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.networking.nat;
dest = if cfg.externalIP == null then "-j MASQUERADE" else "-j SNAT --to-source ${cfg.externalIP}";
in
{
###### interface
options = {
networking.nat.enable = mkOption {
type = types.bool;
default = false;
description =
''
Whether to enable Network Address Translation (NAT).
'';
};
networking.nat.internalInterfaces = mkOption {
type = types.listOf types.str;
default = [];
example = [ "eth0" ];
description =
''
The interfaces for which to perform NAT. Packets coming from
these interface and destined for the external interface will
be rewritten.
'';
};
networking.nat.internalIPs = mkOption {
type = types.listOf types.str;
default = [];
example = [ "192.168.1.0/24" ];
description =
''
The IP address ranges for which to perform NAT. Packets
coming from these addresses (on any interface) 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 -w -t nat -F PREROUTING
iptables -w -t nat -F POSTROUTING
iptables -w -t nat -X
# We can't match on incoming interface in POSTROUTING, so
# mark packets coming from the external interfaces.
${concatMapStrings (iface: ''
iptables -w -t nat -A PREROUTING \
-i '${iface}' -j MARK --set-mark 1
'') cfg.internalInterfaces}
# NAT the marked packets.
${optionalString (cfg.internalInterfaces != []) ''
iptables -w -t nat -A POSTROUTING -m mark --mark 1 \
-o ${cfg.externalInterface} ${dest}
''}
# NAT packets coming from the internal IPs.
${concatMapStrings (range: ''
iptables -w -t nat -A POSTROUTING \
-s '${range}' -o ${cfg.externalInterface} ${dest}
'') cfg.internalIPs}
echo 1 > /proc/sys/net/ipv4/ip_forward
'';
postStop =
''
iptables -w -t nat -F PREROUTING
iptables -w -t nat -F POSTROUTING
iptables -w -t nat -X
'';
};
};
}