Re: [RFC] Vendor-specific dissector extension for EtherNet/IP

[Phil Turmel <pturmel () automation-pros com>]

On 08/30/2017 10:49 AM, Michael Mann via Wireshark-dev wrote:

> > > 2. There is no support currently for "classless" service codes (like
> > > those used in Rockwell Automation PLCs), which is what
> > > _https://www.wireshark.org/lists/ethereal-dev/200601/msg00174.html_ appears
> > > to be talking about.
>
> > As I understand it the service codes mentioned in that thread are class specific.
> > I have never encountered "classless" service codes until now, I didn't even know that
> > existed (as CIP doesn't implement this behaviour, or at least I couldn't find it in the documentation).
>  
> To me, in layman's terms, the format of a CIP message is <service code><identifier>
> In the CIP specs, they focus on <identifier> being an object class and instance, but
> for some Rockwell PLCs, the <identifier> is just a string (and there is no class in the message).
> That's what I mean when I refer to "classless" requests.

Sorry to jump in, but I thought I'd clarify this part.  The
specification does mandate support for class/instance and
class/instance/attribute EPATHs in compliant devices for spec'd classes,
but doesn't require that for vendor-specific objects.

The spec *does* call out Message Router-specific service code 0x4B for
Symbolic Translation, offering a spec-standard way to convert symbolic
EPATHs to corresponding class/instance EPATHs.

Given the specification's treatment of this, I'd suggest keeping the
dissection of non-class EPATHs in place.

{ FWIW, I'm a ODVA spec subscriber and registered vendor... }

Regards,

Phil Turmel, Owner
-- 
Automation Professionals, LLC
97 Howell Ave
Fairburn, GA 30213
Office: (678) 817-4261 x24
Mobile: (404) 713-7284
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