Now that it's working, here's the first draft of the code to expose the netlink policy to userspace.
One thing I didn't think I would do but did anyway now is to map the NLA_* type to a new attribute, and translate it for userspace. This may not be the most convenient, but I think we would prefer to have more flexibility with the NLA_* types in the future. For example, there's no real reason to have NLA_MSECS vs. NLA_U64, and we may want to remove one. Similarly, we have a lot of types for binary: * NLA_UNSPEC - min length * NLA_BINARY - max length * NLA_MIN_LEN - min length * NLA_EXACT_LEN - min & max length are equal And obviously we may want to expand that in the future to have *both* max and min length (we could easily do it using the range we have now already, in fact.) As we can expose both min and max length to userspace in optional attributes, these can just be the same NL_ATTR_TYPE_BINARY. I have a very hacky (and full of warnings) change to iproute2, I've put it here but don't look closely: https://p.sipsolutions.net/4c674acaf8d6ca71.txt It will print out things like (for nl80211): ID: 0x18 policy[0]:attr[4]: type=NUL_STRING max len:15 ID: 0x18 policy[0]:attr[5]: type=U32 range:[0,12] ID: 0x18 policy[0]:attr[15]: type=BINARY max len:2304 ID: 0x18 policy[0]:attr[16]: type=U16 range:[1,2007] ID: 0x18 policy[0]:attr[273]: type=NESTED policy:2 maxattr:5 ID: 0x18 policy[2]:attr[5]: type=NESTED_ARRAY policy:3 maxattr:4 ID: 0x18 policy[3]:attr[1]: type=BINARY min len:6 max len:6 ID: 0x18 policy[3]:attr[2]: type=NESTED ID: 0x18 policy[3]:attr[3]: type=NESTED policy:4 maxattr:2 [...] I've omitted lots of lines, I get close to 200 entries for the current nl80211 policy. As far as mechanics go, this is based on my previous patchset to allow making validation strict. In principle, it's orthogonal, but I suspect it would have some conflicts to apply. The combined code is also available in mac80211-next (kernel.org) in the `netlink-policy-export' branch. johannes
