Helpers

You will probably find yourself in a situation where you want to add multiple external devices to your topology. You can of course just define new nodes for them manually, but there are some helper functions that you can use to quickly define switches, routers or other external devices (for example "The Internet").

These helpers are available under config.lib.topology, regardless of whether you are within a topology module, or a NixOS modules.

mkConnection & mkConnectionRev

A small helper that allows you to write mkConection "host" "lan" instead of the longer form:

{ node = "host"; interface = "lan"; }

Also comes in a reversed variant mkConnectionRev, that marks the connection as reversed to the renderer. See the chapter on connections for why this is sometimes needed.

mkInternet

A small utility that creates a cloud image to represent the internet. It already has an interface called * where you can connect stuff. An optional parameter connections can take either a single connection or a list of connections for this interface.

Example:

nodes.internet = mkInternet {
  connections = mkConnection "node1" "interface1";
};

mkSwitch

This function simplifies creation of a switch. It accepts the name of the switch as the first argument and then some optional arguments in an attrset. It particular, it will:

• Set the device type to switch
• Set hardware image and info if given
• Accept a list called interfaceGroups. This list itself contains multiple lists of interface names. All interfaces are created, regardless of the list in which they appear. All interfaces that stand together in one list will automatically share their network with other interfaces in that specific list, like a dumb switch would.
• Accepts an attrset connections where you can specify additional connections for each interface in the form of a single connection or list of connections. ``.

Example:

nodes.switch1 = mkSwitch "Switch 1" {
  info = "D-Link DGS-105";
  image = ./image-dlink-dgs105.png;
  interfaceGroups = [["eth1" "eth2" "eth3" "eth4" "eth5"]];
  connections.eth1 = mkConnection "host1" "lan";
  connections.eth2 = [(mkConnection "host2" "wan") (mkConnection "host3" "eth0")];

  # any other attributes specified here are directly forwarded to the node:
  interfaces.eth1.network = "home";
};

mkRouter

Exactly the same as mkSwitch, but sets the device type to router instead of switch, which changes the icon to the right.

Example:

nodes.router = mkRouter "Router" {
  info = "Some Router Type XY";
  # eth1-4 are switched, wan1 is the external DSL connection
  interfaceGroups = [["eth1" "eth2" "eth3" "eth4"] ["wan1"]];
  connections.wan1 = mkConnection "host1" "wan";
};

mkDevice

Exactly the same as mkSwitch, but sets the device type to device instead of switch, which has no icon to the right by default.