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# 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 ${cfg.externalIP}";
externalInterfaceFilter = param:
optionalString (cfg.externalInterface != null) "${param} ${cfg.externalInterface}";
flushNat = ''
iptables -w -t nat -D PREROUTING -j nixos-nat-pre 2>/dev/null|| true
iptables -w -t nat -F nixos-nat-pre 2>/dev/null || true
iptables -w -t nat -X nixos-nat-pre 2>/dev/null || true
iptables -w -t nat -D POSTROUTING -j nixos-nat-post 2>/dev/null || true
iptables -w -t nat -F nixos-nat-post 2>/dev/null || true
iptables -w -t nat -X nixos-nat-post 2>/dev/null || true
'';
setupNat = ''
# Create subchain where we store rules
iptables -w -t nat -N nixos-nat-pre
iptables -w -t nat -N nixos-nat-post
# We can't match on incoming interface in POSTROUTING, so
# mark packets coming from the external interfaces.
${concatMapStrings (iface: ''
iptables -w -t nat -A nixos-nat-pre \
-i '${iface}' -j MARK --set-mark 1
'') cfg.internalInterfaces}
# NAT the marked packets.
${optionalString (cfg.internalInterfaces != []) ''
iptables -w -t nat -A nixos-nat-post -m mark --mark 1 \
${externalInterfaceFilter "-o"} ${dest}
''}
# NAT packets coming from the internal IPs.
${concatMapStrings (range: ''
iptables -w -t nat -A nixos-nat-post \
-s '${range}' \! -d '${range}'
${externalInterfaceFilter "-o"} ${dest}
'') cfg.internalIPs}
# NAT from external ports to internal ports.
${concatMapStrings (fwd: ''
iptables -w -t nat -A nixos-nat-pre \
${externalInterfaceFilter "-i"} -p tcp \
--dport ${builtins.toString fwd.sourcePort} \
-j DNAT --to-destination ${fwd.destination}
'') cfg.forwardPorts}
# Append our chains to the nat tables
iptables -w -t nat -A PREROUTING -j nixos-nat-pre
iptables -w -t nat -A POSTROUTING -j nixos-nat-post
'';
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.nullOr types.str;
default = null;
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.
'';
};
networking.nat.forwardPorts = mkOption {
type = types.listOf types.optionSet;
default = [];
example = [ { sourcePort = 8080; destination = "10.0.0.1:80"; } ];
options = {
sourcePort = mkOption {
type = types.int;
example = 8080;
description = "Source port of the external interface";
};
destination = mkOption {
type = types.str;
example = "10.0.0.1:80";
description = "Forward tcp connection to destination ip:port";
};
};
description =
''
List of forwarded ports from the external interface to
internal destinations by using DNAT.
'';
};
};
###### implementation
config = mkIf config.networking.nat.enable {
environment.systemPackages = [ pkgs.iptables ];
boot = {
kernelModules = [ "nf_nat_ftp" ];
kernel.sysctl = {
"net.ipv4.conf.all.forwarding" = mkOverride 99 true;
"net.ipv4.conf.default.forwarding" = mkOverride 99 true;
};
};
networking.firewall = mkIf config.networking.firewall.enable {
extraCommands = mkMerge [ (mkBefore flushNat) setupNat ];
extraStopCommands = flushNat;
};
systemd.services = mkIf (!config.networking.firewall.enable) { nat = {
description = "Network Address Translation";
wantedBy = [ "network.target" ];
after = [ "network-interfaces.target" "systemd-modules-load.service" ];
path = [ pkgs.iptables ];
unitConfig.ConditionCapability = "CAP_NET_ADMIN";
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
};
script = flushNat + setupNat;
postStop = flushNat;
}; };
};
}
|
