Subject: Re: [net-next-2.6 PATCH 02/10] ethtool: add ntuple flow specifier to network flow classifier

From: Alexander Duyck <[email-masked]>
Date: Fri, 04 Mar 2011 11:30:36 -0800

On 3/2/2011 12:03 PM, Dimitrios Michailidis wrote:
> Ben Hutchings wrote:
>> On Wed, 2011-03-02 at 11:11 -0800, Dimitrios Michailidis wrote:
>>> Ben Hutchings wrote:
>>>> /**
>>>>   * struct ethtool_flow_ext - flow spec common extension fields
>>>>   * @vlan_etype: EtherType for vlan tagged packet to match
>>>>   * @vlan_tci: VLAN tag to match
>>>>   * @data: Driver-dependent data to match
>>>>   *
>>>>   * Note: Additional fields may be inserted before @vlan_etype in future,
>>>>   * but the offset of the existing fields within the containing structure
>>>>   * (&struct ethtool_rx_flow_spec) will be stable.
>>>>   */
>>>> struct ethtool_flow_ext {
>>>> 	__be16	vlan_etype;
>>>> 	__be16	vlan_tci;
>>>> 	__be32	data[2];
>>>> };
>>>
>>> I am wondering about the semantics of these vlan_* fields.  Is vlan_etype the
>>> Ethertype in the VLAN header or the type after it?
>>
>> It would be the the type in the VLAN tag.  The nested ethertype is
>> normally implied by flow_type to be ETH_P_IP.
>>
>> This does leave the question of what this would mean:
>>
>> struct ethtool_rx_flow_spec fs = {
>> 	.flow_type = ... | FLOW_EXT,
>> 	...
>> 	.h_ext.vlan_tci = htons(0x1234),
>> 	.m_ext.vlan_etype = 0xffff,
>> };
>>
>> This says the TCI must be == 0x1234 but the type can be anything.  But
>> the type surely has to be be one assigned for use in VLAN tags.  Should
>> we leave it to the driver/hardware to determine what those valid types
>> are, or should we reject this as valid?
>
> Right.  Devices have some internal rules for what qualifies as a VLAN frame.
> If users are given the option to specify vlan_etype what do they get?
> At least we need to specify what is expected so drivers can decide if they can support it.

The basic idea I had is similar to what Ben described.  Basically the 
vlan_etype can be used to determine the Ethertype for the VLAN to be 
compared.  The reason for this is specifically the VLAN 0 case since 
without the VLAN Ethertype check VLAN 0 on ixgbe hardware will match an 
untagged frame and that may not be a desired result.  As such we can 
specify the VLAN Ethertype and then we will only match VLAN tagged 
frames without any false hits.

Thanks,

Alex