Re: [PATCH] rtnetlink: return the newly created link in response tonewlink

From: Thomas Graf
Date: Thu Jan 30 2014 - 09:46:11 EST


On 01/30/14 at 02:05pm, Tom Gundersen wrote:
> Userspace needs to reliably know the ifindex of the netdevs it creates,
> as we cannot rely on the ifname staying unchanged.
>
> Earlier, a simlpe NLMSG_ERROR would be returned, but this returns the
> corresponding RTM_NEWLINK on success instead.

This breaks existing Netlink applications in user space. User space
apps are not prepared to receive both a RTM_NEWLINK reply _and_
the ACK unless they have set NLM_F_ECHO in the original request.

You can already reliably retrieve the ifindex by listening to
RTNLGRP_LINK messages and be notified about the link created
including all follow-up renames.

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