Re: [PATCH] entry_data

[Massimiliano Hofer <max@nucleus.it>]

On Tuesday 20 June 2006 1:13 am, Patrick McHardy wrote:

> So I think we should introduce a .priv_size field or something in struct
> xt_match/xt_target and pass memory allocated by xtables to the matches
> and targets.

I changed the API on the (possibly wrong) assumption that most modules will 
need it for shared data (that's what I and at least some other modules need), 
but thinking about it there are other uses (multiple data with different 
sharing, non shared data that has no business in the userspace struct, etc.). 
In other words, you're right.

Following your suggestion I could add a .priv_size field and if it is non zero 
I allocate the requested memory and pass it as void * (the same type passed 
to (*checkentry)(), (*destroy)() and (*match)()).

We have 2 ways to implement this:
- we can allocate priv_size more bytes after data;
- we can separately allocate priv_size bytes and store a pointer in 
u.kernel.entry_data.

Seeing how the initialization code works, the first one is a bit hairy. The 
latter is really easy to implement, but if someone just needs 4 bytes we end 
up storing a pointer to a pointer with no good reason.

-- 
Saluti,
   Massimiliano Hofer
        Nucleus