Re: [Resend PATCH net] bridge: uapi: mrp: Fix MRP_PORT_ROLE

[David Miller]

From: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>
Date: Sat, 20 Jun 2020 15:14:03 +0200

> Currently the MRP_PORT_ROLE_NONE has the value 0x2 but this is in conflict
> with the IEC 62439-2 standard. The standard defines the following port
> roles: primary (0x0), secondary(0x1), interconnect(0x2).
> Therefore remove the port role none.
> 
> Fixes: 4714d13791f831 ("bridge: uapi: mrp: Add mrp attributes.")
> Signed-off-by: Horatiu Vultur <horatiu.vultur@xxxxxxxxxxxxx>

The code accepts arbitrary 32-bit values for the role in a configuration
but only PRIMARY and SECONDARY seem to be valid.

There is no validation that the value used makes sense.

In the future if we handle type interconnect, and we add checks, it will
break any existing applications.  Because they can validly pass any
non-zero valid and the code treats that as SECONDARY currently.

So you really can't just remove NONE, you have to add validation code
too so we don't run into problem in the future.

Thanks.