Subject: Re: [net-next PATCH v1 01/11] net: flow_table: create interface for hw match/action tables

From: John Fastabend <[email-masked]>
Date: Mon, 05 Jan 2015 17:19:26 -0800

On 01/05/2015 05:09 PM, Simon Horman wrote:
> On Mon, Jan 05, 2015 at 04:45:50PM -0800, John Fastabend wrote:
>> [...]
>>
>>>>> +/**
>>>>> + * @struct net_flow_field_ref
>>>>> + * @brief uniquely identify field as header:field tuple
>>>>> + */
>>>>> +struct net_flow_field_ref {
>>>>> +    int instance;
>>>>> +    int header;
>>>>> +    int field;
>>>>> +    int mask_type;
>>>>> +    int type;
>>>>> +    union {    /* Are these all the required data types */
>>>>> +        __u8 value_u8;
>>>>> +        __u16 value_u16;
>>>>> +        __u32 value_u32;
>>>>> +        __u64 value_u64;
>>>>> +    };
>>>>> +    union {    /* Are these all the required data types */
>>>>> +        __u8 mask_u8;
>>>>> +        __u16 mask_u16;
>>>>> +        __u32 mask_u32;
>>>>> +        __u64 mask_u64;
>>>>> +    };
>>>>> +};
>>>>
>>>> Does it make sense to write this as follows?
>>>
>>> Yes. I'll make this update it helps make it clear value/mask pairs are
>>> needed.
>>>
>>>>
>>>> union {
>>>>          struct {
>>>>                  __u8 value_u8;
>>>>                  __u8 mask_u8;
>>>>          };
>>>>          struct {
>>>>                  __u16 value_u16;
>>>>                  __u16 mask_u16;
>>>>          };
>>>>          ...
>>>> };
>>
>> Another thought is to pull this entirely out of the structure and hide
>> it from the UAPI so we can add more value/mask types as needed without
>> having to spin versions of net_flow_field_ref. On the other hand I've
>> been able to fit all my fields in these types so far and I can't think
>> of any additions we need at the moment.
>
> FWIW, I think it would be cleaner to break both field_ref and action_args
> out into attributes and not expose the structures to user-space. But
> perhaps there is an advantage to dealing with structures directly that
> I am missing.
>

I  came to the same conclusion just now as well. I'm reworking it now
for v2.

-- 
John Fastabend         Intel Corporation