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

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Date:   Tue, 11 Apr 2017 21:43:29 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     David Miller <davem@...emloft.net>, pablo@...filter.org
Cc:     dsa@...ulusnetworks.com, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, jhs@...atatu.com, jbenc@...hat.com,
        jiri@...nulli.us
Subject: Re: [PATCH v3 1/5] netlink: extended ACK reporting

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