netdev - Re: [PATCH net] rtnetlink: fix userspace API breakage for iproute2

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Message-Id: <20140530.174248.715408523447246496.davem@davemloft.net>
Date:	Fri, 30 May 2014 17:42:48 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	mschmidt@...hat.com
Cc:	netdev@...r.kernel.org, stephen@...workplumber.org,
	alexander.h.duyck@...el.com, michael.riesch@...cron.at
Subject: Re: [PATCH net] rtnetlink: fix userspace API breakage for iproute2
 < v3.9.0

From: Michal Schmidt <mschmidt@...hat.com>
Date: Wed, 28 May 2014 14:15:19 +0200

> When running RHEL6 userspace on a current upstream kernel, "ip link"
> fails to show VF information.
> 
> The reason is a kernel<->userspace API change introduced by commit
> 88c5b5ce5cb57 ("rtnetlink: Call nlmsg_parse() with correct header length"),
> after which the kernel does not see iproute2's IFLA_EXT_MASK attribute
> in the netlink request.
> 
> iproute2 adjusted for the API change in its commit 63338dca4513
> ("libnetlink: Use ifinfomsg instead of rtgenmsg in rtnl_wilddump_req_filter").
> 
> The problem has been noticed before:
> http://marc.info/?l=linux-netdev&m=136692296022182&w=2
> (Subject: Re: getting VF link info seems to be broken in 3.9-rc8)
> 
> We can do better than tell those with old userspace to upgrade. We can
> recognize the old iproute2 in the kernel by checking the netlink message
> length. Even when including the IFLA_EXT_MASK attribute, its netlink
> message is shorter than struct ifinfomsg.
> 
> With this patch "ip link" shows VF information in both old and new
> iproute2 versions.
> 
> Signed-off-by: Michal Schmidt <mschmidt@...hat.com>

The userspace tool should be fixed on the system, rather than having the
kernel cater to a user tool bug.

I'm not applying this, sorry.
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