Re: [PATCH v3 1/5] netlink: extended ACK reporting

[Johannes Berg <johannes@sipsolutions.net>]

On Tue, 2017-04-11 at 13:42 -0400, David Miller wrote:

> > Then, the library needs to be extended to enable this handling to
> > modify the way it needs to handle errors, together with the
> > setsockopt().

So I'd tend to agree, but

 * it was easy to solve this, with the flags I added
 * the flags reduce the amount of parsing dependencies, for example, it
   is then no longer necessary to check if error == 0 to know if the
   message was capped or not (when not requested), since the flag
   indicates it
 * having the flag that TLVs were set lets us not store if the
   setsockopt failed or not - this can be useful in the error report
   case (but not in the success/cookie case) since it avoids extra
   state that needs to be passed around
 * libnl, which seems pretty common, allows just passing a single
   pointer around as state, which is often already used for something
   else, meaning a bigger refactoring can be required to pass the extra
   state

So yes, in theory we don't need this, but in practice it does make the
userland parsing code quite a bit easier.

johannes