From 3d2913c30150f9e07f054a98265811c417b21f72 Mon Sep 17 00:00:00 2001
From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Date: Wed, 11 Oct 2017 16:24:48 +0200
Subject: [PATCH] net: enable interface alias removal via rtnl

commit 2459b4c635858094df78abb9ca87d99f89fe8ca5 upstream.

IFLA_IFALIAS is defined as NLA_STRING. It means that the minimal length of
the attribute is 1 ("\0"). However, to remove an alias, the attribute
length must be 0 (see dev_set_alias()).

Let's define the type to NLA_BINARY to allow 0-length string, so that the
alias can be removed.

Example:
$ ip l s dummy0 alias foo
$ ip l l dev dummy0
5: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether ae:20:30:4f:a7:f3 brd ff:ff:ff:ff:ff:ff
    alias foo

Before the patch:
$ ip l s dummy0 alias ""
RTNETLINK answers: Numerical result out of range

After the patch:
$ ip l s dummy0 alias ""
$ ip l l dev dummy0
5: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether ae:20:30:4f:a7:f3 brd ff:ff:ff:ff:ff:ff

CC: Oliver Hartkopp <oliver@hartkopp.net>
CC: Stephen Hemminger <stephen@networkplumber.org>
Fixes: 96ca4a2cc145 ("net: remove ifalias on empty given alias")
Reported-by: Julien FLoret <julien.floret@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
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