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 16:26:55 -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 4:07 PM, Scott Feldman <sfeldma@...il.com> wrote:
> 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.

Hmmmm...do you even need VLAN_RANGE_INFO?  How about just using
existing VLAN_INFO and add some more flags:

#define BRIDGE_VLAN_INFO_RANGE_START    (1<<3)
#define BRIDGE_VLAN_INFO_RANGE_END        (1<<4)

Now you can have:

   IFLA_BRIDGE_FLAGS
   IFLA_BRIDGE_MODE
   IFLA_BRIDGE_VLAN_INFO
   IFLA_BRIDGE_VLAN_INFO_LIST    // nested array of
       IFLA_BRIDGE_VLAN_INFO

Don't set START or END for single vids in list.
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