Re: displaying header field without filtering

[Jeff Morriss <jeff.morriss.ws () gmail com>]

On 02/21/14 14:42, Guy Harris wrote:
> On Feb 21, 2014, at 8:15 AM, "John Dill" <John.Dill () greenfieldeng com> 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.

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