* [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ
@ 2015-11-26 13:26 Phil Sutter
2015-11-26 13:56 ` Hannes Frederic Sowa
2015-11-29 20:07 ` Stephen Hemminger
0 siblings, 2 replies; 7+ messages in thread
From: Phil Sutter @ 2015-11-26 13:26 UTC (permalink / raw)
To: Stephen Hemminger; +Cc: netdev
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 <phil@nwl.cc>
---
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, \
+ .nlmsg_flags = NLM_F_REQUEST, \
+ }}
+
#endif /* __LIBNETLINK_H__ */
--
2.5.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ
2015-11-26 13:26 [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ Phil Sutter
@ 2015-11-26 13:56 ` Hannes Frederic Sowa
2015-11-26 14:00 ` Phil Sutter
2015-11-29 20:07 ` Stephen Hemminger
1 sibling, 1 reply; 7+ messages in thread
From: Hannes Frederic Sowa @ 2015-11-26 13:56 UTC (permalink / raw)
To: Phil Sutter, Stephen Hemminger; +Cc: netdev
Phil Sutter <phil@nwl.cc> 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 <phil@nwl.cc>
> ---
> 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) ?
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ
2015-11-26 13:56 ` Hannes Frederic Sowa
@ 2015-11-26 14:00 ` Phil Sutter
0 siblings, 0 replies; 7+ messages in thread
From: Phil Sutter @ 2015-11-26 14:00 UTC (permalink / raw)
To: Hannes Frederic Sowa; +Cc: Stephen Hemminger, netdev
On Thu, Nov 26, 2015 at 02:56:30PM +0100, Hannes Frederic Sowa wrote:
> > +#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) ?
Ah, thanks! I already considered offsetof(), but the fact it needs a
type name and the declared struct is anonymous appeared unsolvable to
me. Good to know typeof() can be used this way!
Thanks, Phil
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ
2015-11-26 13:26 [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ Phil Sutter
2015-11-26 13:56 ` Hannes Frederic Sowa
@ 2015-11-29 20:07 ` Stephen Hemminger
2015-11-29 21:40 ` Phil Sutter
2015-11-30 15:47 ` Phil Sutter
1 sibling, 2 replies; 7+ messages in thread
From: Stephen Hemminger @ 2015-11-29 20:07 UTC (permalink / raw)
To: Phil Sutter; +Cc: netdev
On Thu, 26 Nov 2015 14:26:05 +0100
Phil Sutter <phil@nwl.cc> wrote:
> 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 <phil@nwl.cc>
> ---
> 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(+)
I am not a fan of complex macros. But netlink seems to get lots of them.
You need to add more parens round arguments (like name).
Really longterm would rather iproute2 switched to a cleaner library like libmnl
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ
2015-11-29 20:07 ` Stephen Hemminger
@ 2015-11-29 21:40 ` Phil Sutter
2015-11-30 15:47 ` Phil Sutter
1 sibling, 0 replies; 7+ messages in thread
From: Phil Sutter @ 2015-11-29 21:40 UTC (permalink / raw)
To: Stephen Hemminger; +Cc: netdev
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On Sun, Nov 29, 2015 at 12:07:52PM -0800, Stephen Hemminger wrote:
> On Thu, 26 Nov 2015 14:26:05 +0100
> Phil Sutter <phil@nwl.cc> wrote:
>
> > 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 <phil@nwl.cc>
> > ---
> > 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(+)
>
> I am not a fan of complex macros. But netlink seems to get lots of them.
> You need to add more parens round arguments (like name).
>
> Really longterm would rather iproute2 switched to a cleaner library like libmnl
Ah, indeed! Someone else suggested that once, as well. I'll have a look
into that before continuing this path.
Thanks, Phil
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ
2015-11-29 20:07 ` Stephen Hemminger
2015-11-29 21:40 ` Phil Sutter
@ 2015-11-30 15:47 ` Phil Sutter
2015-11-30 17:20 ` Stephen Hemminger
1 sibling, 1 reply; 7+ messages in thread
From: Phil Sutter @ 2015-11-30 15:47 UTC (permalink / raw)
To: Stephen Hemminger; +Cc: netdev
On Sun, Nov 29, 2015 at 12:07:52PM -0800, Stephen Hemminger wrote:
> On Thu, 26 Nov 2015 14:26:05 +0100
> Phil Sutter <phil@nwl.cc> wrote:
>
> > 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 <phil@nwl.cc>
> > ---
> > 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(+)
>
> I am not a fan of complex macros. But netlink seems to get lots of them.
> You need to add more parens round arguments (like name).
>
> Really longterm would rather iproute2 switched to a cleaner library like libmnl
libmnl looks nice and simple (unlike libnl I was initially looking at by
accident). Now how to pull this off:
I don't think mandatorily depending on libmnl will be acceptable, do
you? So I can imagine two ways to do this:
A) Have a libmnl version of lib/libnetlink.c which is used instead of
the old one if libmnl is present.
B) Pull a copy of libmnl into iproute2 sources so it's always available
(as fallback) and make it replace lib/libnetlink.c. This sounds worse
than it is, using git-subtree allows to do this without imposing user
knowledge about it (like git-submodule does).
What do you think?
Cheers, Phil
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ
2015-11-30 15:47 ` Phil Sutter
@ 2015-11-30 17:20 ` Stephen Hemminger
0 siblings, 0 replies; 7+ messages in thread
From: Stephen Hemminger @ 2015-11-30 17:20 UTC (permalink / raw)
To: Phil Sutter; +Cc: netdev
On Mon, 30 Nov 2015 16:47:25 +0100
Phil Sutter <phil@nwl.cc> wrote:
> libmnl looks nice and simple (unlike libnl I was initially looking at by
> accident). Now how to pull this off:
>
> I don't think mandatorily depending on libmnl will be acceptable, do
> you? So I can imagine two ways to do this:
Having libmnl be mandatory is fine, but please put in net-next.
Every distro has libmnl and as long as it is documented not a big deal.
> A) Have a libmnl version of lib/libnetlink.c which is used instead of
> the old one if libmnl is present.
>
> B) Pull a copy of libmnl into iproute2 sources so it's always available
> (as fallback) and make it replace lib/libnetlink.c. This sounds worse
> than it is, using git-subtree allows to do this without imposing user
> knowledge about it (like git-submodule does).
Just incrementally change code to use libmnl instead of libnetlink.
Start with simple stuff.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2015-11-30 17:20 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-11-26 13:26 [iproute PATCH RFC] libnetlink: introduce DECLARE_NLREQ Phil Sutter
2015-11-26 13:56 ` Hannes Frederic Sowa
2015-11-26 14:00 ` Phil Sutter
2015-11-29 20:07 ` Stephen Hemminger
2015-11-29 21:40 ` Phil Sutter
2015-11-30 15:47 ` Phil Sutter
2015-11-30 17:20 ` Stephen Hemminger
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