First the WinPcap library is used to enumerate the existing interfaces to make sure that only those are taken into account which the WinPcap library is able to actually work with. Their IP addresses are compaired against the one on the cmdline to find the desired interface.
Then the IP Helper API is used to enumerate the existing adapters to find out the the Ethernet address of the desired adapter. This Ethernet address is then used by Contiki too.
Network I/O is done using the usual suspect - which is WinPcap. There's no need for the WinPcap Developer's Pack! An ordinary WinPcap install - as it is i.e. part of Ethereal - is sufficient.
The code is still under development. But as I recently successfully opened HTML pages with the Contiki web browser I thought it might be the right time for an initial commit.