Re: [nft PATCH RFC] libnftables: Make output_fp default to /dev/null

[Phil Sutter <phil@nwl.cc>]

On Mon, Nov 20, 2017 at 01:33:13PM +0100, Pablo Neira Ayuso wrote:
> On Mon, Nov 20, 2017 at 01:32:04PM +0100, Pablo Neira Ayuso wrote:
> > Hi Phil,
> > 
> > On Thu, Nov 16, 2017 at 08:14:15PM +0100, Phil Sutter wrote:
> > > Ensure output_fp is never NULL which allows to drop all respective
> > > checks.
> > > 
> > > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > > ---
> > > Hi Pablo,
> > > 
> > > This is how I understood your suggestion to use /dev/null. While
> > > implementing it though, I had an idea for a much simpler solution,
> > > namely just rejecting NULL in nft_set_output() and therefore forcing the
> > > application to deal with opening /dev/null if no output is desired. What
> > > do you think about that?
> > 
> > I like your idea of rejecting NULL.

OK, cool.

> BTW, why does nft_set_output() return FILE *? Is there any usecase for
> this?

It's a quick way to change output_fp and store its old value. Current
users are nft_run_cmd_from_*().

I could introduce nft_get_output() to make the return value a dedicated
success/fail indicator if you prefer that, otherwise I'd just make
nft_set_output() return NULL in error case.

Cheers, Phil