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 <oli...@hartkopp.net>
CC: Stephen Hemminger <step...@networkplumber.org>
Fixes: 96ca4a2cc145 ("net: remove ifalias on empty given alias")
Reported-by: Julien FLoret <julien.flo...@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dich...@6wind.com>
---
David A., I hope that it is now clear and that a v4 will not be needed
for a so trivial patch.
v2 -> v3: reword the commit log
v1 -> v2: add the comment
net/core/rtnetlink.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index d4bcdcc68e92..5343565d88b7 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -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 },
--
2.13.2
