Re: [dhcwg] Valid values for DHCPv6 option 18 (Interface ID)

[Simon Hobson <[e-mail]>]

Andre Kostur <[e-mail]> wrote:

> Has there been any changes as to how option 18 has been defined by us?
> I'm running into certain programs (Wireshark, in particular) and
> devices that appear to be doing both:
> - Assuming it's printable
> - Interpreting the content
> 
> Both appear to be strongly discouraged by 3315:
> 
>   The Interface-ID SHOULD be considered an opaque value, with policies
>   based on exact match only; that is, the Interface-ID SHOULD NOT be
>   internally parsed by the server.
> 
> According to my interpretation, that says that one should neither be
> attempting to interpret the contents, nor try to display it as a
> string.

I don't think the two are mutually exclusive.
The text you quote is about how the value is used for processing - ie you should not be looking into the value and using a subset of it for (eg) selecting address allocation policies.

Wireshark is a diagnostic tool, it make complete sense to display the content of packets/fields - that is the purpose of the tool. Just because we aren't allowed to delve into a field for processing purposes doesn't make the showing of the contents of that field invalid for diagnostic purposes.
It shouldn't be assuming a printable string though, and should take care to only use display safe methods (eg hex encode non-printable octets).