Re: [PATCH net v2] net: enable interface alias removal via rtnl
From: David Ahern <hidden>
Date: 2017-10-10 14:50:47
On 10/10/17 6:41 AM, Nicolas Dichtel wrote:
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, so that the alias can be removed.not to be pedantic, but we need to be clear that the type is changed only for policy validation.
quoted hunk ↗ jump to hunk
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 <redacted> CC: Stephen Hemminger <stephen@networkplumber.org> Fixes: 96ca4a2cc145 ("net: remove ifalias on empty given alias") Reported-by: Julien FLoret <redacted> Signed-off-by: Nicolas Dichtel <redacted> --- 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 },
Seems like a reasonable solution. Acked-by: David Ahern <redacted>