Wireshark mailing list archives

Re: Undissected reserved fields


From: Michal Labedzki <michal.labedzki () tieto com>
Date: Sun, 1 Mar 2015 13:58:48 +0100

Personally, I always dissect reserved fields. Please do not forget
that there are many bit-reserved fields too. This probably implies
that we want to create filter for them (hf items), to keep the same
look for all fields in bitfield. I am not sure if _ws.reserved is fine
in bitfield. For other fields, I think also is good idea to create new
filters, because purpose of reserved field is to be used in future,
right? (in my practise... I think not...)

proto_tree_add_reserved_mbz()? (if use _ws.reserved)
Or maybe...
proto_tree_add_item(..., ENC_LITTLE_ENDIAN | ENC_MBZ)?  # ENC_MBZ,
seems to be similar format like ENC_ASCII, ENC_UTF8... By the way...
Add expert info if ENC_ASCII is not ASCII? The same for UTF8.

On 28 February 2015 at 00:08, Sean O. Stalley <sean.stalley () intel com> wrote:
+1. Would use this API if added (especially if it could be used for bitfields).

-Sean

On Fri, Feb 27, 2015 at 01:06:04PM -0800, Guy Harris wrote:

On Feb 27, 2015, at 10:28 AM, Jeff Morriss <jeff.morriss.ws () gmail com> wrote:

My opinion (which I've voiced on this list many times over the past ~10 years) is that such fields SHOULD be 
dissected.  Even better they should have an Expert Info if they are supposed to be 0 and aren't (Guy had suggested 
on a bug or somewhere that we should have an API with a name that includes "mbz"--for Must Be Zero--which would 
add the Expert Info automatically).

It was in the thread that started here:

      https://www.wireshark.org/lists/wireshark-dev/201402/msg00131.html

and I suggested both proto_tree_add_spare() (for fields that are spare and *not* required to be zero) and 
proto_tree_add_mbz() (for fields that *are* required to be zero) in

      https://www.wireshark.org/lists/wireshark-dev/201402/msg00135.html

Neither of those take an hf_ value as an argument, so they don't clutter the list of filterable fields with a bunch 
of individual values for each set of spare bits; to look for "must be zero but isn't", you'd look for the expert 
info.
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