10.9 Multi-stage mapping

Suppose your network adapters are hotplugged and you enable automatic configuration as described in Triggering network configuration – hotplug, Section 10.8.2. Suppose further that you need to map logical interfaces to "physical" interfaces depending both on the adapter underlying the physical interface (as described in Dealing with inconsistent naming of interfaces by the kernel, Section 10.7) and on the network connected to the interface (as described, for example, in Logical interface selection using guessnet, Section 10.6.3.1). You can accomplish this with multi-stage mapping.

The first mapping stage takes the hotplug group name and outputs the kernel-assigned interface name if the interface is to be hot plugged. The second mapping stage takes a kernel-assigned interface name and outputs an adapter name. The third mapping stage maps adapter names to logical interface names based on the network environment.

     # Allow hotplug to bring up interfaces
     mapping hotplug
     	script echo
     
     # Determine whether interface is wired or Wi-Fi
     mapping eth?
             script /usr/local/sbin/get-mac-address.sh
             map 02:23:45:3C:45:3C wired
             map 00:A3:03:63:26:93 wifi
     
     # Detect which wired network is available
     mapping wired
             script guessnet-ifupdown
             map work-wired
             map home
     
     # Detect which Wi-Fi network is available
     mapping wifi
             script ifscout
             map starbucks
             map work-wireless
     
     iface work-wired inet static
     	...