Add the ip_pool_select_addr4 function to select a random subnet of requested
size from an address space defined by a string list (for use with the
AP profile [IPv4].Address and the global [IPv4].APAddressPool settings),
avoiding those subnets that conflict with subnets in use. We take care
to give a similar weight to all subnets contained in the specified
ranges regardless of how many ranges contain each, basically so that
overlapping ranges don't affect the probabilities (debatable.)
Add the ip-pool submodule that tracks IPv4 addresses in use on the
system for use when selecting the address for a new AP. l_rtnl_address
is used internally because if we're going to return l_rtnl_address
objects it would be misleading if we didn't fill in all of their
properties like flags etc.
