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189 lines
5.3 KiB
Nix
189 lines
5.3 KiB
Nix
# This module enables Network Address Translation (NAT).
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# XXX: todo: support multiple upstream links
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# see http://yesican.chsoft.biz/lartc/MultihomedLinuxNetworking.html
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{ config, lib, pkgs, ... }:
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with lib;
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let
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cfg = config.networking.nat;
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dest = if cfg.externalIP == null then "-j MASQUERADE" else "-j SNAT --to-source ${cfg.externalIP}";
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flushNat = ''
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iptables -w -t nat -D PREROUTING -j nixos-nat-pre 2>/dev/null|| true
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iptables -w -t nat -F nixos-nat-pre 2>/dev/null || true
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iptables -w -t nat -X nixos-nat-pre 2>/dev/null || true
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iptables -w -t nat -D POSTROUTING -j nixos-nat-post 2>/dev/null || true
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iptables -w -t nat -F nixos-nat-post 2>/dev/null || true
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iptables -w -t nat -X nixos-nat-post 2>/dev/null || true
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'';
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setupNat = ''
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# Create subchain where we store rules
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iptables -w -t nat -N nixos-nat-pre
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iptables -w -t nat -N nixos-nat-post
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# We can't match on incoming interface in POSTROUTING, so
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# mark packets coming from the external interfaces.
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${concatMapStrings (iface: ''
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iptables -w -t nat -A nixos-nat-pre \
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-i '${iface}' -j MARK --set-mark 1
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'') cfg.internalInterfaces}
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# NAT the marked packets.
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${optionalString (cfg.internalInterfaces != []) ''
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iptables -w -t nat -A nixos-nat-post -m mark --mark 1 \
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-o ${cfg.externalInterface} ${dest}
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''}
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# NAT packets coming from the internal IPs.
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${concatMapStrings (range: ''
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iptables -w -t nat -A nixos-nat-post \
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-s '${range}' -o ${cfg.externalInterface} ${dest}
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'') cfg.internalIPs}
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# NAT from external ports to internal ports.
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${concatMapStrings (fwd: ''
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iptables -w -t nat -A nixos-nat-pre \
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-i ${cfg.externalInterface} -p tcp \
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--dport ${builtins.toString fwd.sourcePort} \
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-j DNAT --to-destination ${fwd.destination}
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'') cfg.forwardPorts}
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# Append our chains to the nat tables
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iptables -w -t nat -A PREROUTING -j nixos-nat-pre
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iptables -w -t nat -A POSTROUTING -j nixos-nat-post
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'';
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in
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{
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###### interface
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options = {
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networking.nat.enable = mkOption {
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type = types.bool;
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default = false;
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description =
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''
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Whether to enable Network Address Translation (NAT).
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'';
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};
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networking.nat.internalInterfaces = mkOption {
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type = types.listOf types.str;
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default = [];
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example = [ "eth0" ];
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description =
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''
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The interfaces for which to perform NAT. Packets coming from
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these interface and destined for the external interface will
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be rewritten.
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'';
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};
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networking.nat.internalIPs = mkOption {
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type = types.listOf types.str;
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default = [];
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example = [ "192.168.1.0/24" ];
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description =
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''
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The IP address ranges for which to perform NAT. Packets
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coming from these addresses (on any interface) and destined
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for the external interface will be rewritten.
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'';
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};
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networking.nat.externalInterface = mkOption {
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type = types.str;
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example = "eth1";
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description =
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''
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The name of the external network interface.
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'';
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};
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networking.nat.externalIP = mkOption {
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type = types.nullOr types.str;
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default = null;
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example = "203.0.113.123";
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description =
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''
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The public IP address to which packets from the local
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network are to be rewritten. If this is left empty, the
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IP address associated with the external interface will be
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used.
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'';
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};
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networking.nat.forwardPorts = mkOption {
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type = types.listOf types.optionSet;
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default = [];
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example = [ { sourcePort = 8080; destination = "10.0.0.1:80"; } ];
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options = {
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sourcePort = mkOption {
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type = types.int;
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example = 8080;
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description = "Source port of the external interface";
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};
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destination = mkOption {
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type = types.str;
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example = "10.0.0.1:80";
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description = "Forward tcp connection to destination ip:port";
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};
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};
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description =
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''
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List of forwarded ports from the external interface to
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internal destinations by using DNAT.
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'';
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};
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};
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###### implementation
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config = mkIf config.networking.nat.enable {
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environment.systemPackages = [ pkgs.iptables ];
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boot = {
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kernelModules = [ "nf_nat_ftp" ];
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kernel.sysctl = {
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"net.ipv4.conf.all.forwarding" = mkOverride 99 true;
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"net.ipv4.conf.default.forwarding" = mkOverride 99 true;
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};
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};
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networking.firewall = mkIf config.networking.firewall.enable {
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extraCommands = mkMerge [ (mkBefore flushNat) setupNat ];
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extraStopCommands = flushNat;
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};
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systemd.services = mkIf (!config.networking.firewall.enable) { nat = {
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description = "Network Address Translation";
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wantedBy = [ "network.target" ];
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after = [ "network-interfaces.target" "systemd-modules-load.service" ];
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path = [ pkgs.iptables ];
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unitConfig.ConditionCapability = "CAP_NET_ADMIN";
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = true;
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};
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script = flushNat + setupNat;
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postStop = flushNat;
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}; };
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};
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}
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