Commit 2459b4c6 authored Oct 11, 2017 by Nicolas Dichtel Committed by David S. Miller Oct 16, 2017

net: enable interface alias removal via rtnl



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: 96ca4a2c ("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>

parent 2fd7c5ab

net/core/rtnetlink.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -1483,7 +1483,10 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
		[IFLA_LINKINFO] = { .type = NLA_NESTED },
		[IFLA_NET_NS_PID] = { .type = NLA_U32 },
		[IFLA_NET_NS_FD] = { .type = NLA_U32 },
		[IFLA_IFALIAS] = { .type = NLA_STRING, .len = IFALIASZ-1 },
		/* IFLA_IFALIAS is a string, but policy is set to NLA_BINARY to
		* allow 0-length string (needed to remove an alias).
		*/
		[IFLA_IFALIAS] = { .type = NLA_BINARY, .len = IFALIASZ - 1 },
		[IFLA_VFINFO_LIST] = {. type = NLA_NESTED },
		[IFLA_VF_PORTS] = { .type = NLA_NESTED },
		[IFLA_PORT_SELF] = { .type = NLA_NESTED },