Re: The ieee802.11 dissector is a steaming pile of ordure

[Alexis La Goutte <alexis.lagoutte () gmail com>]

Hi Richard (and Bill)

It is historic... at the first, there is only limited fixed field and
tagged field...
and on last 802.11 spec, there is > 100 tagged field...

If you have a solution to avoid a big switch...
i have already think to put each case on separate function... but for some
case, there is only 5 lines of code...

Regards,

On Wed, Sep 9, 2015 at 6:11 PM, Bill Meier <wmeier () newsguy com> wrote:

> On 9/9/2015 12:03 PM, Bill Meier wrote:
>
> > On 9/9/2015 11:23 AM, Richard Sharpe wrote:
> >
> > > Take a look at epan/dissectors/packet-ieee80211.c!
> > >
> > > Specifically, add_tagged_field.
> > >
> > > That function is approximately 2,300 lines long and it consists of one
> > > big switch statement with every arm containing open-coded statements
> > > to add things to the proto tree.
> > It's even worse:
> >
> > add_fixed_field() given a "fixed field number" does a linear search thru
> > a (large) table to to find the number (and the associated function
> > address) and then calls the function ...
> >
> > One side effect: there are functions which aren't used but since they're
> > in the table, they're not flagged as unused by the compiler.
> >
> > In several cases there is (or was) duplicate code elsewhere doing a
> > dissection similar to the unused "fixed field functions".
> >
> > (I was working to fix all this but got a bit bored because I had to
> > spend time delving thru the 802211 spec trying to understand the code.
> > I guess I should at least do that work (unless you have a broader
> > solution in mind to handle both tagged and fixed fields ?)
>
> Actually, I guess add_tagged_field and add_fixed_field are sort of doing
> the same thing (just in different ways) with respect to the lookup.
>
>
>
>
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