tree 50c7e303026871c65ffbfd8480a8aa20524cee98
parent bef1909ee3ed1ca39231b260a8d3b4544ecd0c8f
author Michal Schmidt <mschmidt@redhat.com> 1401279319 +0200
committer David S. Miller <davem@davemloft.net> 1402596462 -0700

rtnetlink: fix userspace API breakage for iproute2 < v3.9.0

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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>