Subject: Re: [PATCH net-next V4 03/13] bridge: Validate that vlan is permitted on ingress

From: Vlad Yasevich <[email-masked]>
Date: Thu, 20 Dec 2012 10:41:28 -0500

On 12/20/2012 09:07 AM, Shmulik Ladkani wrote:
> Hi Vlad,
>
> On Wed, 19 Dec 2012 12:48:14 -0500 Vlad Yasevich <[email-masked]> wrote:
>> +static bool br_allowed_ingress(struct net_bridge_port *p, struct sk_buff *skb)
>> +{
>> +	struct net_port_vlan *pve;
>> +	u16 vid;
>> +
>> +	/* If there are no vlan in the permitted list, all packets are
>> +	 * permitted.
>> +	 */
>> +	if (list_empty(&p->vlan_list))
>> +		return true;
>
> I assumed the default policy would be Drop in such case, otherwise
> leaking between vlan domains is possible.
> Or maybe, ingress policy when port isn't a member of ingress VID should
> be configurable (drop/allow).

We have have to default to allow since we want to retain original bridge 
functionality if there is no configuration.

>
>> +	vid = br_get_vlan(skb);
>> +	pve = nbp_vlan_find(p, vid);
>
> Why search by iterating through NBP's vlan_list?
> You know the VID (hence may fetch the net_bridge_vlan from the hash), so
> why don't you directly consult the net_bridge_vlan's port_bitmap?

It's an alternative...  I am betting that this port isn't in too many 
vlans and that searching the list might be faster.

>
>> @@ -54,6 +74,9 @@ int br_handle_frame_finish(struct sk_buff *skb)
>>   	if (!p || p->state == BR_STATE_DISABLED)
>>   		goto drop;
>>
>> +	if (!br_allowed_ingress(p, skb))
>> +		goto drop;
>> +
>
> This condition should be also encorporated upon "ingress" at the "bridge
> master port" (that is, early at br_dev_xmit).
> Think of the "bridge master port" as yet another port:
> upon "ingress" (meaning, tx packets from the ip stack), we should
> also enforce any ingress permission rules.
>

I've tried that before and now can't think of a reason why I rejected 
it.  I'll try to remember...

Thanks
-vlad

> Regards,
> Shmulik