From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ Date: Thu, 26 Nov 2015 14:56:30 +0100 Message-ID: <87oaegx3sh.fsf@stressinduktion.org> References: <1448544365-23153-1-git-send-email-phil@nwl.cc> Mime-Version: 1.0 Content-Type: text/plain Cc: netdev@vger.kernel.org To: Phil Sutter , Stephen Hemminger Return-path: Received: from out2-smtp.messagingengine.com ([66.111.4.26]:55417 "EHLO out2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751570AbbKZN4c (ORCPT ); Thu, 26 Nov 2015 08:56:32 -0500 Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailout.nyi.internal (Postfix) with ESMTP id BAB2F20B58 for ; Thu, 26 Nov 2015 08:56:31 -0500 (EST) In-Reply-To: <1448544365-23153-1-git-send-email-phil@nwl.cc> Sender: netdev-owner@vger.kernel.org List-ID: Phil Sutter writes: > This macro aims to simplify most netlink users' pattern to prepare a > request, which is to create an unnamed struct and initialize it: > > | struct { > | struct nlmsghdr n; > | struct whatever foo; > | char buf[arbitrary number]; > | } req; > | > | memset(&req, 0, sizeof(req)); > | req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct whatever)); > | req.n.nlmsg_flags = NLM_F_REQUEST; > > Having this patch applied, the above can be replaced by a static > initializer like so: > > | DECLARE_NLREQ(req, n, struct whatever foo, arbitrary number); > > There is an added benefit, as well: Due to explicit alignment, the > requested tailroom is really as big as requested no matter what size > struct whatever really is. > > Signed-off-by: Phil Sutter > --- > This patch is RFC because I want to wait for peer review and upstream > acceptance before sending in the big refactoring patch itself. > --- > include/libnetlink.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/libnetlink.h b/include/libnetlink.h > index 2280c39c670a4..7e12a7b12b55d 100644 > --- a/include/libnetlink.h > +++ b/include/libnetlink.h > @@ -196,5 +196,16 @@ int rtnl_from_file(FILE *, rtnl_listen_filter_t handler, > * messages from dump file */ > #define NLMSG_TSTAMP 15 > > +/* declare a netlink request with initial payload */ > +#define DECLARE_NLREQ(name, hdrname, payload, tailroom) \ > + struct { \ > + struct nlmsghdr hdrname; \ > + payload; \ > + char __b[tailroom] __attribute__((aligned(NLMSG_ALIGNTO))); \ > + } name = { .hdrname = { \ > + .nlmsg_len = (unsigned long)&name.__b - (unsigned long)&name, \ offsetof(typeof(name), __b) ?