From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: [nft PATCH 2/2] monitor: Make JSON output respect output_fp Date: Thu, 16 Nov 2017 14:57:42 +0100 Message-ID: <20171116135742.GA13598@salvia> References: <20171116080629.30564-1-phil@nwl.cc> <20171116080629.30564-3-phil@nwl.cc> <20171116133824.GA5926@salvia> <20171116135402.GJ32305@orbyte.nwl.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: Phil Sutter , netfilter-devel@vger.kernel.org Return-path: Received: from mail.us.es ([193.147.175.20]:53206 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964976AbdKPN5s (ORCPT ); Thu, 16 Nov 2017 08:57:48 -0500 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 7DBDF2EFEBE for ; Thu, 16 Nov 2017 14:57:46 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 672A9DA876 for ; Thu, 16 Nov 2017 14:57:46 +0100 (CET) Content-Disposition: inline In-Reply-To: <20171116135402.GJ32305@orbyte.nwl.cc> Sender: netfilter-devel-owner@vger.kernel.org List-ID: On Thu, Nov 16, 2017 at 02:54:02PM +0100, Phil Sutter 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 > > > --- > > > 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 > > > > > > #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. > > Looks like you just caught me trying to avoid changing libnftnl. :D > > Yet I still consider the macro valuable since it avoids the nasty > pointer deref chain. > > I'll prepare a patch to libnftnl and then provide v2 of this patch with > simplified nftnl_mon_print() macro. ACK? I wonder if we can just avoid such change by making sure that monh->ctx->octx->output_fp is always set. May that work too?