Re: setting flow spec rules under vswitch configuration

[Or Gerlitz <ogerlitz@mellanox.com>]

On 09/10/2012 18:48, Ben Hutchings wrote:
> On Tue, 2012-10-09 at 11:37 +0200, Or Gerlitz wrote:
>> Hi Ben,
>>
>> Looking on kernel ethtool flow steering APIs in the context of a device
>> which is used as the uplink of a virtual switch, the admin should be able
>> to provide flow specification and action (e.g drop) that relates to traffic
>> coming from a specific port of the switch e.g that relates to a certain
>> VM,etc.
>>
>> For that end, we need to be able to specify both the L3/L4 attributes of
>> the flow and an L2 spec, that is the L2 spec containing the destination MAC
>> can't be assumed as the one of that device.
>>
>> Specifically, in struct ethtool_rx_ntuple_flow_spec, I think we should
>> let the
>> to provide an ethhdr even when L3/L4 spec is given, make sense?
> Yes, but the ethertype looks redundant - the inner type is implied by
> the L3 flow type and the outer type for a VLAN-encapsulated packet
> should be matched against ethtool_flow_ext::vlan_etype.  Might be better
> to avoid confusion by just specifying the L2 addresses.
>
>> if yes, how
>> would you like to see this change, add a union entry that contains both,
>> or in
>> another way?
> struct ethtool_rx_ntuple_flow_spec is obsolete; struct
> ethtool_rx_flow_spec is what we have to consider.  That effectively has:
>
> 	union ethtool_flow_union {
> 		struct ethtool_tcpip4_spec		tcp_ip4_spec;
> 		struct ethtool_tcpip4_spec		udp_ip4_spec;
> 		struct ethtool_tcpip4_spec		sctp_ip4_spec;
> 		struct ethtool_ah_espip4_spec		ah_ip4_spec;
> 		struct ethtool_ah_espip4_spec		esp_ip4_spec;
> 		struct ethtool_usrip4_spec		usr_ip4_spec;
> 		struct ethhdr				ether_spec;
> 		/* above are up to 16 bytes long */
> 		__u8					hdata[60];
> 	} h_u;
> 	struct ethtool_flow_ext {
> 		__be16	vlan_etype;
> 		__be16	vlan_tci;
> 		__be32	data[2];
> 	} h_ext;
> 	union ethtool_flow_union m_u;
> 	struct ethtool_flow_ext m_ext;
>
> So ethtool_flow_union::hdata currently provides 44 bytes of padding
> between the per-protocol flow specs and ethtool_flow_ext, which can be
> reallocated to the *beginning* of ethtool_flow_ext.  At some point we'll
> presumably want to add IPv6 flow specs, which will use up 24 bytes of
> that padding at the front.  So we can potentially extend
> ethtool_flow_ext by up to 20 bytes.
>
> Ben.
>

Ben,

Thanks for setting the sketch of a plan here... so if we go little bit 
into details, we can safely move 20 bytes from the hadata[60] field into 
the beginning of struct ethtool_flow_ext, which will still allow old
user space to work with newer kernels. As for newer uses space that 
would like to set mac addresses within
ethtool_flow_ext, how are they supposed to identify if the kernel 
supports this extension (of the extension...)? this might be newbee 
question, I didn't made many ethtool patches so far.

Also on a related note, what does the 64bit data field of 
ethtool_flow_ext used for?

Or.