netdev - Re: [iproute PATCH v3 1/2] libnetlink: add a variant of rtnl_send

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Date:	Wed, 23 Dec 2015 13:17:55 -0800
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Lorenzo Colitti <lorenzo@...gle.com>
Cc:	netdev@...r.kernel.org, eric.dumazet@...il.com,
	zenczykowski@...il.com
Subject: Re: [iproute PATCH v3 1/2] libnetlink: add a variant of
 rtnl_send_check that consumes ACKs

On Tue, 22 Dec 2015 17:31:33 +0900
Lorenzo Colitti <lorenzo@...gle.com> wrote:

> The new variant is identical to rtnl_send_check, except it also
> consumes the kernel response instead of using MSG_PEEK. This is
> useful for callers that send simple commands that never cause a
> response but only ACKs, and that expect to receive and deal
> with errors without printing them to stderr like rtnl_talk does.
> 
> Signed-off-by: Lorenzo Colitti <lorenzo@...gle.com>

Originally, iproute2 used netlink so that every request had an ACK and
this is the API in rtnl_talk. Then as an optimization it was observed
that ACK from kernel is not necessary (all error reports are handled in
send), but that for some asynchronous errors a check was necessary.

Therefore, I wonder why you need this, either:
 * don't ask kernel for ACK's (like most other ip commands),
 * or use rtnl_talk() and expect ACK.

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