netdev - Re: [PATCH 1/6] bridge: add support to parse multiple vlan info attributes in IFLA_AF

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Date:	Mon, 29 Dec 2014 16:07:12 -0800
From:	Scott Feldman <sfeldma@...il.com>
To:	roopa <roopa@...ulusnetworks.com>
Cc:	Netdev <netdev@...r.kernel.org>, shemminger@...tta.com,
	"vyasevic@...hat.com" <vyasevic@...hat.com>,
	Wilson Kok <wkok@...ulusnetworks.com>
Subject: Re: [PATCH 1/6] bridge: add support to parse multiple vlan info
 attributes in IFLA_AF_SPEC

On Mon, Dec 29, 2014 at 3:47 PM, Scott Feldman <sfeldma@...il.com> wrote:
> On Mon, Dec 29, 2014 at 2:10 PM, roopa <roopa@...ulusnetworks.com> wrote:
>> On 12/29/14, 1:40 PM, Scott Feldman wrote:
>>>
>>> On Mon, Dec 29, 2014 at 1:05 PM,  <roopa@...ulusnetworks.com> wrote:
>>>>
>>>> From: Roopa Prabhu <roopa@...ulusnetworks.com>
>>>>
>>>> This patch changes bridge IFLA_AF_SPEC netlink attribute parser to
>>>> look for more than one IFLA_BRIDGE_VLAN_INFO attribute. This allows
>>>> userspace to pack more than one vlan in the setlink msg.
>>>>
>>>> Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>
>>>> ---
>>>>   net/bridge/br_netlink.c |   18 +++++++++---------
>>>>   1 file changed, 9 insertions(+), 9 deletions(-)
>>>>
>>>> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
>>>> index 9f5eb55..75971b1 100644
>>>> --- a/net/bridge/br_netlink.c
>>>> +++ b/net/bridge/br_netlink.c
>>>> @@ -230,18 +230,18 @@ static int br_afspec(struct net_bridge *br,
>>>>                       struct nlattr *af_spec,
>>>>                       int cmd)
>>>>   {
>>>> -       struct nlattr *tb[IFLA_BRIDGE_MAX+1];
>>>> +       struct bridge_vlan_info *vinfo;
>>>>          int err = 0;
>>>> +       struct nlattr *attr;
>>>> +       int err = 0;
>>>> +       int rem;
>>>> +       u16 vid;
>>>>
>>>> -       err = nla_parse_nested(tb, IFLA_BRIDGE_MAX, af_spec,
>>>> ifla_br_policy);
>>>
>>> Removing this call orphans ifla_br_policy...should ifla_br_policy be
>>> removed?
>>
>>
>> good question. Its a good place to see the type. In-fact userspace programs
>> also copy the same policy to parse netlink attributes. hmmm..
>> I would like to keep it if it does not throw a warning.
>
> I don't know what the policy (sorry, no pun intended) on leaving dead
> code.  I say remove it.

You know, not using the policy seems like a step backwards, and maybe
it suggests a problem with the attr packing.

We had:

ifla_br_policy
   IFLA_BRIDGE_FLAGS
   IFLA_BRIDGE_MODE
   IFLA_BRIDGE_VLAN_INFO

This patch set makes it:

ifla_br_policy
   IFLA_BRIDGE_FLAGS
   IFLA_BRIDGE_MODE
   IFLA_BRIDGE_VLAN_INFO
   IFLA_BRIDGE_VLAN_RANGE_INFO

Which is fine, but now VLAN_INFO and VLAN_RANGE_INFO can be repeated.
I think you want some nesting to clarify:

ifla_br_policy
   IFLA_BRIDGE_FLAGS
   IFLA_BRIDGE_MODE
   IFLA_BRIDGE_VLAN_INFO
   IFLA_BRIDGE_VLAN_LIST_INFO    // nested array of
       IFLA_BRIDGE_VLAN_INFO
       IFLA_BRIDGE_VLAN_RANGE_INFO

Now you can keep the policy for the top-level parsing, and loop only
on the nested array VLAN_LIST_INFO.  Actually, now you can use just
RANGE_INFO in array and have:

ifla_br_policy
   IFLA_BRIDGE_FLAGS
   IFLA_BRIDGE_MODE
   IFLA_BRIDGE_VLAN_INFO
   IFLA_BRIDGE_VLAN_LIST_INFO    // nested array of
       IFLA_BRIDGE_VLAN_RANGE_INFO

And use VLAN_RANGE_INFO for both ranges of vids as well as single
vids.  That'll simplify your filling algo in patch 5.

-scott
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