Modules/Docker: Add networks option

system/modules/docker/default.nix

@@ -15,6 +15,8 @@ in {
       })
     ];
 
+    networking.firewall.trustedInterfaces = ["docker0" "podman0"];
+
     virtualisation = {
       docker = {
         enable = !docker.podman;
@@ -61,5 +63,74 @@ in {
         else "docker"; # "docker" or "podman"
       libvirtd.enable = true;
     };
+
+    systemd.services = let
+      cli =
+        if docker.podman
+        then "${config.virtualisation.podman.package}/bin/podman"
+        else "${config.virtualisation.docker.package}/bin/docker";
+
+      mkDockerNetwork = name: options:
+        builtins.concatStringsSep "\n" [
+          # Make sure to return true on fail to not crash
+          ''
+            check=$(${cli} network inspect ${name} || true)
+            if [ -z "$check" ]; then
+          ''
+
+          (builtins.concatStringsSep " " [
+            "${cli} network create"
+
+            # Disable masquerading
+            (lib.mkIf
+              options.disable_masquerade
+              ''-o "com.docker.network.bridge.enable_ip_masquerade"="false"'')
+
+            # Enable ipv6
+            (lib.mkIf
+              options.ipv6.enable
+              "--ipv6")
+            (lib.mkIf
+              (builtins.hasAttr "gateway" options.ipv6)
+              ''--gateway="${options.ipv6.gateway}"'')
+            (lib.mkIf
+              (builtins.hasAttrs "subnet" options.ipv6)
+              ''--subnet="${options.ipv6.subnet}"'')
+
+            "${name}"
+          ])
+
+          ''
+            else
+              echo "${name} already exists!"
+            fi
+          ''
+        ];
+
+      mkPodmanNetwork = name: options:
+        builtins.concatStringsSep "\n" [
+          ''
+            ehco "Can't create Podman networks (yet)!"
+          ''
+        ];
+
+      mkSystemdNetworkService = name: options: let
+        toolName =
+          if docker.podman
+          then "Podman"
+          else "Docker";
+      in {
+        description = "Creates the ${toolName} network \"${name}\"";
+        after = ["network.target"];
+        wantedBy = ["multi-user.target"];
+
+        serviceConfig.Type = "oneshot";
+        script =
+          if docker.podman
+          then (mkPodmanNetwork name options)
+          else (mkDockerNetwork name options);
+      };
+    in
+      lib.mkMerge (builtins.mapAttrs mkSystemdNetworkService docker.networks);
   };
 }