Wireshark-dev: Re: [Wireshark-dev] displaying header field without filtering
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From: Jeff Morriss <jeff.morriss.ws@xxxxxxxxx>
Date: Mon, 24 Feb 2014 16:34:21 -0500
On 02/21/14 14:42, Guy Harris wrote:


On Feb 21, 2014, at 8:15 AM, "John Dill" <John.Dill@xxxxxxxxxxxxxxxxx> wrote:


 From the topic discussion, I got the impression that not
putting hf_register_info entries for Spare or Reserved fields
was considered bad practice.


Some might consider it bad practice; I don't.


I'm one who has said it is bad practice.  But... (more below)


The only advantage to having it be a named field would be to be able to filter for a specific value for the field, or to check whether it's non-zero.

I'm not sure there's any point in filtering for specific values.

There might be some use for checking for non-zero values *if* the spare bits are supposed to be zero; that's why I suggested proto_tree_add_mbz(), if, for a given collection of spare bits, those bits Must Be Zero.
That's true: in fact the only real use case I've had for it is filtering "xxx.yyy.spare != 0" because that helps me prove that implementation A is violating the law (which says the bits must be 0).
Personally I'd probably still err on the side of "add a [filterable] field for spare bytes" because I like to filter for them but there's no reason I couldn't do that and others could use these APIs.