From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: [PATCH net v2] net: enable interface alias removal via rtnl Date: Tue, 10 Oct 2017 08:50:45 -0600 Message-ID: References: <1cccbbaa-455b-66e0-a447-7f7e3b3bb375@gmail.com> <20171010124138.27342-1-nicolas.dichtel@6wind.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, oliver@hartkopp.net, Stephen Hemminger To: Nicolas Dichtel , davem@davemloft.net Return-path: Received: from mail-pf0-f196.google.com ([209.85.192.196]:36067 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751385AbdJJOur (ORCPT ); Tue, 10 Oct 2017 10:50:47 -0400 Received: by mail-pf0-f196.google.com with SMTP id z11so18819924pfk.3 for ; Tue, 10 Oct 2017 07:50:47 -0700 (PDT) In-Reply-To: <20171010124138.27342-1-nicolas.dichtel@6wind.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: 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. > > Example: > $ ip l s dummy0 alias foo > $ ip l l dev dummy0 > 5: dummy0: 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: 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 > CC: Stephen Hemminger > Fixes: 96ca4a2cc145 ("net: remove ifalias on empty given alias") > Reported-by: Julien FLoret > Signed-off-by: Nicolas Dichtel > --- > > 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