lib: set addr in myrecvfrom6

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
add support for Route Information Option (rfc4191)

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
add support for Default Router Preference in RA msg (rfc4191)

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
lib: remove unused fields from RA struct

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
lib: introduce option validity checks

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
lib: move msg validity check into separate function

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
lib: introcude option validity check callback for separate option types

Signed-off-by: Jiri Pirko <jiri@resnulli.us>