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

From: Simon Horman <[email-masked]>
Date: Tue, 6 Jan 2015 11:05:16 +0900

On Mon, Jan 05, 2015 at 05:19:26PM -0800, John Fastabend wrote:
> 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.

Thanks.

BTW, I think there are a few problems with net_flow_put_flow_action().

I am not quite to the bottom of it but it seems that:
* It loops over a->args[i] and then calls net_flow_put_act_types()
  which performs a similar loop. This outer-loop appears to be incorrect.
* It passes a[i].args instead of a->args[i] to net_flow_put_act_types()

I can post a fix once I've got it working to my satisfaction.
But if you are reworking that code anyway perhaps it is easier for
you to handle it then.