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

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Nov 20, 2017 at 01:38:51PM +0100, Phil Sutter wrote:
> 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_*().

Oh, I see.

> 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.

As you prefer. For my usecase, the existing call is just fine.