On Thu, Nov 16, 2017 at 03:12:06PM +0100, Pablo Neira Ayuso wrote:
> On Thu, Nov 16, 2017 at 02:58:21PM +0100, Phil Sutter wrote:
> > On Thu, Nov 16, 2017 at 02:54:44PM +0100, Pablo Neira Ayuso wrote:
> > > On Thu, Nov 16, 2017 at 02:38:24PM +0100, Pablo Neira Ayuso wrote:
> > > > On Thu, Nov 16, 2017 at 09:06:29AM +0100, Phil Sutter wrote:
> > > > > This introduces a rather nasty macro to call nftnl_*_fprintf() only if
> > > > > output_fp is valid. On the other hand, it allows to pull the common
> > > > > parts (format argument, event conversion) into a single place.
> > > > >
> > > > > Signed-off-by: Phil Sutter <phil@xxxxxx>
> > > > > ---
> > > > > src/netlink.c | 38 ++++++++++++++++++--------------------
> > > > > 1 file changed, 18 insertions(+), 20 deletions(-)
> > > > >
> > > > > diff --git a/src/netlink.c b/src/netlink.c
> > > > > index 845eeeffd7387..81b92ac1e2d7c 100644
> > > > > --- a/src/netlink.c
> > > > > +++ b/src/netlink.c
> > > > > @@ -40,6 +40,12 @@
> > > > > #include <iface.h>
> > > > >
> > > > > #define nft_mon_print(monh, ...) nft_print(monh->ctx->octx, __VA_ARGS__)
> > > > > +#define nftnl_mon_print(monh, type, obj, event) \
> > > > > + if (monh->ctx->octx->output_fp) { \
> > > > > + nftnl_##type##_fprintf(monh->ctx->octx->output_fp, \
> > > > > + obj, monh->format, \
> > > > > + netlink_msg2nftnl_of(event)); \
> > > > > + }
> > > >
> > > > Wait.
> > > >
> > > > Can't we just change nftnl_*_fprintf to do nothing if output_fp is
> > > > NULL.
> > > >
> > > > That should be safe.
> > >
> > > Or we just save all these branches by always setting output_fp to
> > > stdout. It should simplify things a bit.
> > >
> > > What am I missing here?
> >
> > output_fp is under application control (via nft_ctx_set_output()), and I
> > think it's a valid use-case for applications to call
> > 'nft_ctx_set_output(NULL)' to disable all output.
>
> We can set a dummy file descriptor that point to /dev/null, right?
Which we would have to acquire using 'open()', correct? What if that
call fails?
I could think of a static FILE *devnull in nft_ctx_set_output() which is
opened if needed, and closed if the program exits. Would that work?
Cheers, Phil
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