This adds further netlink attribute validation: * min/max/range validation * validation through a custom function pointer This is useful to * reduce boilerplate code in command handling code, if attributes are used commonly across different commands * get more extended ACK error messages/attribute pointers * ensure attributes are valid even when ignored (though this might be a problem when converting existing code) Changes since v1: * split off validate_type from type and use that for min/max/range and function; this is better because the range is limited to the range of s16 and so things like "u16 with minimum value 1" couldn't be expressed earlier * add macros for this, e.g. NLA_POLICY_MIN(NLA_U16, 1) for the case mentioned in the previous bullet Using this pretty much in all places where applicable in nl80211 reduces the code size there by about 1.8KiB, with just a minimal code increase in lib/nlattr.o. johannes
