kldload() returns a positive integer when it loads a ko, so check that the
return value is -1 to detect error cases, not that it's different from zero.
MFC after: 3 days
X-MFC-With: r357234
kldload() returns an error (EEXIST) if the module is already loaded.
That's not a problem for us, so ignore that error.
While here also clean up include statements.
MFC after: 3 days
X-MFC-With: r357234
if_epair abused the ifr_data field to insert its second interface in
IFC_IFLIST. If userspace provides a value for ifr_data it would get
dereferenced by the kernel leading to a panic.
Reported by: Ilja Van Sprundel <ivansprundel@ioactive.com>
MFC after: 3 days
