Configuring network interfaces

Olsrd needs to fetch information about the network interfaces it is set up to use. This mainly includes fetching the unicast and broadcast IP addresses used by the network interface. To fetch such information various ioctl calls are made. They are documented in the netdevice(7) manual page. If using IPv6, some considerations have to be taken, this is discussed later. Most interface configuration in olsrd is done in the src/interface.c file. The ioctl commands are defined in various header-files, the most interesting commands regarding network interfaces, can be located in sys/ioctl.h^6.1. Here various ways to get and set network interface data is listed. Looking in the net/if.h header-file the data-structure needed for transmitting data, using the network interface related ioctl requests, can be found. The ifreq struct is the most used data-structure in network interface related ioctls.

Network interfaces are only set up for use with olsrd if certain criteria is met. The interface has to have the UP flag set, it has to be configured with and IP address and a broadcast address and it cannot a be special device such as the loopback interface.