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Author SHA1 Message Date
226fe6577f minor fixes 2025-09-30 18:18:38 +00:00
376aa0c9b6 remove empty .sops.yaml and secrets files 2025-09-30 22:09:11 +05:30
2f5f746492 update README with a more detailed setup guide 2025-09-30 21:16:36 +05:30
01a77e65a6 update overall module structure, remove host-specific config files
- update flake.nix to reflect new structure
- update modules/default.nix imports
- update modules/network.nix and wireguard.nix
- remove config/configuration.nix and hardware-configuration.nix
- remove modules/access.nix from this module's scope
2025-09-30 21:14:06 +05:30
10 changed files with 322 additions and 254 deletions

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145
README.md
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@@ -1,34 +1,125 @@
# sixnix
My ISP provides me a single `/64` and it's dynamically assigned. I cannot have multiple networks with functional autoconfiguration. One solution to this is use one of 4to6 [tunnel brokers](https://tunnelbroker.services/) like the one offered by [Hurricane Electric](https://tunnelbroker.net/). Since my ISP uses CGNAT this setup is tricky if not impossible.
IPv6 WireGuard tunnels with optional BGP failover.
Fortunately Linode provides free `/56` to customers and the cheapest VPS costs just $5/month. You get 256 `/64` subnets. The following table provides an example where you can have 15 delegations of `/60` and use the 16th `/60` for the wireguard peer addressing.
## Motivation
| Client subnet | WireGuard subnet | |
|--------------------|---------------------|----|
| 2001:db8::/60 | 2001:db8:0:f0::/64 | 1 |
| 2001:db8:0:10::/60 | 2001:db8:0:f1::/64 | 2 |
| 2001:db8:0:20::/60 | 2001:db8:0:f2::/64 | 3 |
| 2001:db8:0:30::/60 | 2001:db8:0:f3::/64 | 4 |
| 2001:db8:0:40::/60 | 2001:db8:0:f4::/64 | 5 |
| 2001:db8:0:50::/60 | 2001:db8:0:f5::/64 | 6 |
| 2001:db8:0:60::/60 | 2001:db8:0:f6::/64 | 7 |
| 2001:db8:0:70::/60 | 2001:db8:0:f7::/64 | 8 |
| 2001:db8:0:80::/60 | 2001:db8:0:f8::/64 | 9 |
| 2001:db8:0:90::/60 | 2001:db8:0:f9::/64 | 10 |
| 2001:db8:0:a0::/60 | 2001:db8:0:fa::/64 | 11 |
| 2001:db8:0:b0::/60 | 2001:db8:0:fb::/64 | 12 |
| 2001:db8:0:c0::/60 | 2001:db8:0:fc::/64 | 13 |
| 2001:db8:0:d0::/60 | 2001:db8:0:fd::/64 | 14 |
| 2001:db8:0:e0::/60 | 2001:db8:0:fe::/64 | 15 |
My ISP gives me a single `/64` and it's dynamically assigned. Can't have multiple networks with functional autoconfiguration. Tunnel brokers like [Hurricane Electric](https://tunnelbroker.net/) would work but my ISP uses CGNAT which makes that setup tricky if not impossible. They also do not have any exit nodes in the region I want.
| Host | Subnet |
|-----------------------|-----------------------------|
| wireguard.example.com | 2001:0db8:0:ff::/64 |
Linode provides a routed `/56` and 1TB traffic at 1 Gbit/s for with their cheapest $5/month VPS. That's 256 `/64` subnets.
You can follow the linode's [nixos installation guide](https://www.linode.com/docs/guides/install-nixos-on-linode/) and/or use this repo as a reference to set up your wireguard tunnels.
## Solution 1: Simple WireGuard tunnels
- set up sops using the [docs here](https://github.com/Mic92/sops-nix)
- add root password, wireguard server private keys and peer public keys
- add ssh public keys and configure any additional user accounts in `modules/access.nix`
- configure egress, firewall, wireguard tunnels etc in `modules/network.nix`
Just a plain WireGuard tunnel to route the `/56` to your home network.
With a `/56` you can carve out a `/60` for WireGuard endpoints and you're left with 15 `/60` subnets. Share it with friends!
| Client subnet | WireGuard subnet | |
|--------------------|----------------------|----|
| 2001:db8::/60 | 2001:db8:0:f0::a/127 | 1 |
| 2001:db8:0:10::/60 | 2001:db8:0:f1::a/127 | 2 |
| 2001:db8:0:20::/60 | 2001:db8:0:f2::a/127 | 3 |
| 2001:db8:0:30::/60 | 2001:db8:0:f3::a/127 | 4 |
| 2001:db8:0:40::/60 | 2001:db8:0:f4::a/127 | 5 |
| 2001:db8:0:50::/60 | 2001:db8:0:f5::a/127 | 6 |
| 2001:db8:0:60::/60 | 2001:db8:0:f6::a/127 | 7 |
| 2001:db8:0:70::/60 | 2001:db8:0:f7::a/127 | 8 |
| 2001:db8:0:80::/60 | 2001:db8:0:f8::a/127 | 9 |
| 2001:db8:0:90::/60 | 2001:db8:0:f9::a/127 | 10 |
| 2001:db8:0:a0::/60 | 2001:db8:0:fa::a/127 | 11 |
| 2001:db8:0:b0::/60 | 2001:db8:0:fb::a/127 | 12 |
| 2001:db8:0:c0::/60 | 2001:db8:0:fc::a/127 | 13 |
| 2001:db8:0:d0::/60 | 2001:db8:0:fd::a/127 | 14 |
| 2001:db8:0:e0::/60 | 2001:db8:0:fe::a/127 | 15 |
### Basic configuration
```nix
{
inputs.sixnix.url = "git+https://code.planet-express.in/konarak/sixnix.git";
outputs = { nixpkgs, sixnix, ... }: {
nixosConfigurations.tunnel-server = nixpkgs.lib.nixosSystem {
modules = [
sixnix.nixosModules.default
{
sixnix = {
enable = true;
hostname = "tunnel-server";
domain = "example.com";
};
wireguard.interfaces = [{
interface = "wg0";
serverPort = 51820;
serverAddress = "2001:db8:a7c4:0:f0::a/127";
clientAddress = "2001:db8:a7c4:0:f0::b/127";
clientSubnet = "2001:db8:a7c4::/60";
serverPrivateKeyFile = "/run/secrets/wg0-server-private";
clientPublicKeyFile = "/run/secrets/wg0-client-public";
}];
}
];
};
};
}
```
How it works:
- Your router uses the ISP-provided IPv6 to connect to the WireGuard server
- Interfaces get `/64`s from the delegated `/60` with router advertisement enabled
- All traffic from clients goes out to the internet via Linode
## Solution 2: WireGuard tunnels with BGP for failover
Want redundancy? Run two Linodes in the same datacenter and use BGP to share a single `/56` between them. If one server goes down, BGP automatically fails over to the other.
Cost: $10/month + tax for two Linodes with pooled 2TB traffic quota.
### BGP configuration
```nix
{
sixnix = {
enable = true;
hostname = "tunnel-primary";
domain = "example.com";
bgp = {
enable = true;
peers = [
"2001:db8:9f2b::1" # BGP peer addresses (e.g., Linode route servers)
"2001:db8:9f2b::2"
"2001:db8:9f2b::3"
"2001:db8:9f2b::4"
];
advertisedSubnets = [ "2001:db8:a7c4::/56" ];
routeMap = "primary"; # or "secondary" for the backup server
};
};
wireguard.interfaces = [{
interface = "wg0";
serverPort = 51820;
serverAddress = "2001:db8:a7c4:0:f0::a/127";
clientAddress = "2001:db8:a7c4:0:f0::b/127";
clientSubnet = "2001:db8:a7c4::/60";
serverPrivateKeyFile = "/run/secrets/wg0-server-private";
clientPublicKeyFile = "/run/secrets/wg0-client-public";
}];
}
```
The BGP setup creates:
- A shared dummy interface with a VIP that both servers announce
- Route servers configured automatically based on datacenter ID
- Blackhole routes for the advertised subnet
- Primary/secondary route maps for failover priority
## Notes
- BGP peers and advertised subnets are fully configurable
- The FRR configuration template may need adjustments for providers other than Linode (AS numbers, communities, etc.)
- For Linode: use route servers `2600:3c0f:<dcId>:34::{1,2,3,4}` where `<dcId>` is your datacenter ID (e.g., 25 for in-maa)
- See Linode's [BGP documentation](https://techdocs.akamai.com/cloud-computing/docs/configuring-ip-failover-over-bgp-using-frr-advanced) for more details
- See [`modules/network.nix`](modules/network.nix) and [`modules/wireguard.nix`](modules/wireguard.nix) for all available options

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@@ -1,45 +0,0 @@
{ config, lib, pkgs, ... }:
{
sops.defaultSopsFile = ../secrets/secrets.yaml;
imports = [
# Include the results of the hardware scan.
./hardware-configuration.nix
../modules/sixnix
];
# Use the GRUB 2 boot loader.
boot.loader.grub.enable = true;
# Enable the Flakes feature and the accompanying new nix command-line tool
nix.settings.experimental-features = [ "nix-command" "flakes" ];
environment.systemPackages = with pkgs; [ git curl btop emacs-nox ];
# Copy the NixOS configuration file and link it from the resulting system
# (/run/current-system/configuration.nix). This is useful in case you
# accidentally delete configuration.nix.
# system.copySystemConfiguration = true;
# This option defines the first version of NixOS you have installed on this particular machine,
# and is used to maintain compatibility with application data (e.g. databases) created on older NixOS versions.
#
# Most users should NEVER change this value after the initial install, for any reason,
# even if you've upgraded your system to a new NixOS release.
#
# This value does NOT affect the Nixpkgs version your packages and OS are pulled from,
# so changing it will NOT upgrade your system - see https://nixos.org/manual/nixos/stable/#sec-upgrading for how
# to actually do that.
#
# This value being lower than the current NixOS release does NOT mean your system is
# out of date, out of support, or vulnerable.
#
# Do NOT change this value unless you have manually inspected all the changes it would make to your configuration,
# and migrated your data accordingly.
#
# For more information, see `man configuration.nix` or https://nixos.org/manual/nixos/stable/options#opt-system.stateVersion .
system.stateVersion = "25.05"; # Did you read the comment?
}

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@@ -1,41 +0,0 @@
# Do not modify this file! It was generated by nixos-generate-config
# and may be overwritten by future invocations. Please make changes
# to /etc/nixos/configuration.nix instead.
{ config, lib, pkgs, modulesPath, ... }:
{
imports = [ (modulesPath + "/profiles/qemu-guest.nix") ];
boot.initrd.availableKernelModules =
[ "virtio_pci" "virtio_scsi" "ahci" "sd_mod" ];
boot.initrd.kernelModules = [ ];
boot.kernelModules = [ "wireguard" ];
boot.extraModulePackages = [ ];
fileSystems."/" = {
device = "/dev/sda";
fsType = "ext4";
};
swapDevices = [ ];
# Enables DHCP on each ethernet and wireless interface. In case of scripted networking
# (the default) this is the recommended approach. When using systemd-networkd it's
# still possible to use this option, but it's recommended to use it in conjunction
# with explicit per-interface declarations with `networking.interfaces.<interface>.useDHCP`.
# networking.useDHCP = lib.mkDefault true;
# networking.interfaces.enp0s4.useDHCP = lib.mkDefault true;
nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
boot.kernelParams = [ "console=ttyS0,19200n8" ];
boot.loader.grub.extraConfig = ''
serial --speed=19200 --unit=0 --word=8 --parity=no --stop=1;
terminal_input serial;
terminal_output serial;
'';
boot.loader.grub.forceInstall = true;
boot.loader.grub.device = "nodev";
boot.loader.timeout = 10;
}

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@@ -1,25 +1,12 @@
{
description = "Server Configuration for WireGuard provider";
description = "Simple WireGuard tunnelbroker, with optional failover using BGP";
inputs = {
nixpkgs.url = "nixpkgs/nixos-25.05";
nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixos-unstable";
sops-nix.url = "github:Mic92/sops-nix";
sops-nix.inputs.nixpkgs.follows = "nixpkgs";
nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
};
outputs = { self, nixpkgs, nixpkgs-unstable, sops-nix, }@attrs: {
nixosConfigurations = {
"tunnels" = nixpkgs.lib.nixosSystem {
system = "x86_64-linux";
specialArgs = attrs;
modules = [
(import ./config/maa1-ops/configuration.nix)
sops-nix.nixosModules.sops
];
};
};
outputs = { self, nixpkgs }: {
nixosModules.default = import ./modules;
nixosModules.sixnix = import ./modules;
};
}

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@@ -1,44 +0,0 @@
{ config, pkgs, ... }:
let
keys = [
];
root.password = config.sops.secrets.password-root.path;
in {
sops.secrets = let def = { neededForUsers = true; };
in {
"password-root" = def;
};
services.openssh = {
enable = true;
settings.PermitRootLogin = "no";
};
# protect from ssh spammers
services.sshguard.enable = true;
# disable kernel from logging REFUSED CONNECTIONS messages when we actually drop this traffic
networking.firewall.logRefusedConnections = false;
# enable mosh and open firewall ports
programs.mosh.enable = true;
security.sudo.wheelNeedsPassword = false;
users.mutableUsers = false;
users.users.root = {
hashedPasswordFile = root.password;
openssh.authorizedKeys.keys = keys;
};
# users.users.<username> = {
# isNormalUser = true;
# extraGroups = [ "wheel" ];
# hashedPasswordFile = <username.password>;
# openssh.authorizedKeys.keys = <username.keys>;
# };
}

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@@ -1 +1 @@
{ config, pkgs, ... }: { imports = [ ./access.nix ./network.nix ]; }
{ config, pkgs, ... }: { imports = [ ./network.nix ./wireguard.nix ]; }

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@@ -1,63 +1,188 @@
{ config, pkgs, ... }:
let
hostname = "tunnels";
domain = "example.com";
{ config, pkgs, lib, ... }:
resolvers = [ "9.9.9.9" "2620:fe::fe" ];
with lib;
egress = {
interface = "eth0";
ipv4.gateway = "198.51.100.10";
ipv4.address = "198.51.100.1/24";
ipv6.gateway = "fe80::1";
ipv6.address = "2001:DB8:10:cafe:dcaf::3210/64";
};
tunnels = [{
interface = "wg0";
serverPort = 51820;
serverAddress = "2001:db8:de:ff0::1/128";
clientAddress = "2001:db8:de:ff0::2/128";
clientSubnet = "2001:db8:de:f00::/60";
serverPrivateKeyFile = "wg0-server-private";
clientPublicKeyFile = "wg0-client-public";
}];
let cfg = config.sixnix;
in {
options.sixnix = {
enable = mkEnableOption "sixnix networking configuration";
networking.hostName = hostname;
networking.domain = domain;
# Enable systemd-networkd
systemd.network.enable = true;
networking.useNetworkd = true;
# Tools for monitoring/key generation
environment.systemPackages = with pkgs; [ wireguard-tools tcpdump ];
# Configure Ethernet interface (eth0)
systemd.network.networks."10-egress" = {
matchConfig.Name = egress.interface;
networkConfig = {
DHCP = "no";
IPv6AcceptRA = "no";
IPv6PrivacyExtensions = "yes";
IPv6Forwarding = "yes";
hostname = mkOption {
type = types.str;
description = "Server hostname";
};
address = [ egress.ipv4.address egress.ipv6.address ];
gateway = [ egress.ipv4.gateway egress.ipv6.gateway ];
domain = mkOption {
type = types.str;
default = "notwork.in";
description = "Domain name";
};
dns = resolvers;
interface = mkOption {
type = types.str;
default = "enp0s3";
description = "Network interface name";
};
dns = mkOption {
type = types.listOf types.str;
default = [ "9.9.9.9" "2620:fe::fe" ];
description = "DNS resolvers for systemd-networkd";
};
ipv4 = {
address = mkOption {
type = types.nullOr types.str;
default = null;
description = "IPv4 address with CIDR (documentation only - using DHCP)";
};
gateway = mkOption {
type = types.nullOr types.str;
default = null;
description = "IPv4 gateway (documentation only - using DHCP)";
};
};
ipv6 = {
address = mkOption {
type = types.nullOr types.str;
default = null;
description = "IPv6 address with CIDR (documentation only - using SLAAC)";
};
gateway = mkOption {
type = types.str;
default = "fe80::1";
description = "IPv6 gateway (documentation only - using SLAAC)";
};
};
bgp = {
enable = mkOption {
type = types.bool;
default = false;
description = "Enable BGP/FRR for shared IP failover";
};
peers = mkOption {
type = types.listOf types.str;
default = [];
example = [ "2001:db8::1" "2001:db8::2" "2001:db8::3" "2001:db8::4" ];
description = "List of BGP peer addresses (e.g., Linode route servers)";
};
advertisedSubnets = mkOption {
type = types.listOf types.str;
default = [];
example = [ "2001:db8:1234::/56" ];
description = "List of IPv6 subnets to advertise via BGP";
};
routeMap = mkOption {
type = types.enum [ "primary" "secondary" ];
description = "BGP route map type (primary/secondary for HA)";
};
};
wireguard = {
enable = mkOption {
type = types.bool;
default = false;
description = "Enable WireGuard configuration";
};
};
};
boot.kernel.sysctl = { "net.ipv6.conf.all.forwarding" = 1; };
imports = [ ./wireguard.nix ];
wireguard.interfaces = tunnels;
config = mkIf cfg.enable {
networking.hostName = cfg.hostname;
networking.domain = cfg.domain;
networking.nftables.enable = true;
networking.firewall = { allowedUDPPorts = map (x: x.serverPort) tunnels; };
# Enable systemd-networkd
systemd.network.enable = true;
networking.useNetworkd = true;
}
# Tools for monitoring/key generation
environment.systemPackages = with pkgs; [ wireguard-tools tcpdump ];
# Configure network interface - pure SLAAC/DHCP
systemd.network.networks."10-egress" = {
matchConfig.Name = cfg.interface;
networkConfig = {
DHCP = "yes"; # Enable both IPv4 and IPv6 DHCP
IPv6AcceptRA = "yes";
IPv6PrivacyExtensions = "no";
IPv6Forwarding = "yes";
};
dns = cfg.dns;
};
# Add blackhole routes for advertised subnets on loopback
systemd.network.networks."10-loopback" = mkIf cfg.bgp.enable {
matchConfig.Name = "lo";
routes = map (subnet: {
Destination = subnet;
Type = "blackhole";
}) cfg.bgp.advertisedSubnets;
};
# Create dummy interface for shared WireGuard endpoint IP (HA setup)
systemd.network.netdevs."20-shared-dummy" = mkIf cfg.bgp.enable {
netdevConfig = {
Kind = "dummy";
Name = "shared0";
};
};
systemd.network.networks."20-shared-dummy" = mkIf cfg.bgp.enable {
matchConfig.Name = "shared0";
address = [ "2600:3c08:e002:6cff::1/128" ];
};
boot.kernel.sysctl = {
"net.ipv6.conf.all.forwarding" = 1;
"net.ipv6.conf.${cfg.interface}.accept_ra" = 2;
# Accept prefix info
"net.ipv6.conf.${cfg.interface}.accept_ra_pinfo" = 1;
# Accept default router
"net.ipv6.conf.${cfg.interface}.accept_ra_defrtr" = 1;
};
# BGP configuration
# Reference: https://techdocs.akamai.com/cloud-computing/docs/configuring-ip-failover-over-bgp-using-frr-advanced
services.frr.bgpd.enable = cfg.bgp.enable;
services.frr.config = mkIf cfg.bgp.enable (let
peerConfig = concatMapStringsSep "\n" (peer: " neighbor ${peer} peer-group RS") cfg.bgp.peers;
networkConfig = concatMapStringsSep "\n" (subnet: " network ${subnet} route-map ${cfg.bgp.routeMap}") cfg.bgp.advertisedSubnets;
in ''
hostname ${cfg.hostname}
router bgp 65001
no bgp ebgp-requires-policy
coalesce-time 1000
bgp bestpath as-path multipath-relax
neighbor RS peer-group
neighbor RS remote-as external
neighbor RS ebgp-multihop 10
neighbor RS capability extended-nexthop
${peerConfig}
address-family ipv6 unicast
${networkConfig}
redistribute static
neighbor RS activate
exit-address-family
route-map primary permit 10
set community 65000:1
route-map secondary permit 10
set community 65000:2
ipv6 nht resolve-via-default
'');
};
}

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@@ -12,7 +12,7 @@ let
serverAddress = mkOption {
type = types.str;
description =
"IPv6 address with CIDR prefix to bind WireGuard (e.g., 2001:db8::1/64).";
"IPv6 address/prefix to bind WireGuard (e.g., 2001:db8::1/64).";
};
serverPort = mkOption {
type = types.port;
@@ -20,19 +20,19 @@ let
};
clientAddress = mkOption {
type = types.str;
description = "Peer IPv6 address with CIDR (e.g., 2001:db8::2/128).";
description = "Peer IPv6 address/prefix (e.g., 2001:db8::2/128).";
};
clientSubnet = mkOption {
type = types.str;
description = "Peer subnet IPv6 CIDR (e.g., 2001:db8::/64).";
description = "Peer IPv6 subnet (e.g., 2001:db8::/64).";
};
serverPrivateKeyFile = mkOption {
type = types.str;
description = "Name of the sops secret containing server private key.";
type = types.path;
description = "Path to server private key file.";
};
clientPublicKeyFile = mkOption {
type = types.str;
description = "Name of the sops secret containing client public key.";
type = types.path;
description = "Path to client public key file.";
};
};
});
@@ -47,14 +47,14 @@ let
"Duplicate values found for '${name}': ${builtins.toString values}";
};
secretAssertions = lib.flatten (map (cfg: [
fileAssertions = lib.flatten (map (cfg: [
{
assertion = builtins.hasAttr cfg.serverPrivateKeyFile config.sops.secrets;
message = "Missing sops secret: ${cfg.serverPrivateKeyFile}";
assertion = cfg.serverPrivateKeyFile != null;
message = "serverPrivateKeyFile must be provided for interface ${cfg.interface}";
}
{
assertion = builtins.hasAttr cfg.clientPublicKeyFile config.sops.secrets;
message = "Missing sops secret: ${cfg.clientPublicKeyFile}";
assertion = cfg.clientPublicKeyFile != null;
message = "clientPublicKeyFile must be provided for interface ${cfg.interface}";
}
]) interfaces);
@@ -69,34 +69,28 @@ let
in {
options.wireguard.interfaces = mkOption {
type = wgConfigType;
default = [];
description = "List of WireGuard interface configurations.";
};
config = {
sops.secrets = let
def = {
owner = "systemd-network";
group = "systemd-network";
};
in lib.mkMerge (map (cfg: {
"${cfg.serverPrivateKeyFile}" = def;
"${cfg.clientPublicKeyFile}" = def;
}) interfaces);
assertions = lib.mkAfter (fileAssertions ++ uniquenessAssertions);
assertions = lib.mkAfter (secretAssertions ++ uniquenessAssertions);
systemd.network.enable = true;
systemd.network.netdevs = lib.mkMerge (map (cfg: {
"${cfg.interface}" = {
netdevConfig = {
Kind = "wireguard";
MTUBytes = "1412";
Name = cfg.interface;
};
wireguardConfig = {
PrivateKeyFile = config.sops.secrets.${cfg.serverPrivateKeyFile}.path;
PrivateKeyFile = cfg.serverPrivateKeyFile;
ListenPort = cfg.serverPort;
};
wireguardPeers = [{
PublicKeyFile = config.sops.secrets.${cfg.clientPublicKeyFile}.path;
PublicKeyFile = cfg.clientPublicKeyFile;
AllowedIPs = [ cfg.clientAddress cfg.clientSubnet ];
}];
};
@@ -105,13 +99,11 @@ in {
systemd.network.networks = lib.mkMerge (map (cfg: {
"${cfg.interface}" = {
matchConfig = { Name = cfg.interface; };
networkConfig = { IPv6Forwarding = "yes"; };
address = [ cfg.serverAddress ];
routes = [
{
Destination = cfg.clientAddress;
Scope = "link";
}
{
Destination = cfg.clientSubnet;
Scope = "link";
@@ -119,5 +111,8 @@ in {
];
};
}) interfaces);
# Automatically open firewall ports for WireGuard
networking.firewall.allowedUDPPorts = map (cfg: cfg.serverPort) interfaces;
};
}

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