From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leon Romanovsky Subject: Re: Netlink messages without NLM_F_REQUEST flag Date: Wed, 7 Jun 2017 20:00:37 +0300 Message-ID: <20170607170037.GG1127@mtr-leonro.local> References: <20170607161901.GD1127@mtr-leonro.local> <20170607163758.GA25313@obsidianresearch.com> <20170607164750.GA7507@obsidianresearch.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="YH9Qf6Fh2G5kB/85" Return-path: Content-Disposition: inline In-Reply-To: <20170607164750.GA7507-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Kaike Wan , John Fleck , Ira Weiny , Thomas Graf , Doug Ledford , Jiri Pirko , RDMA mailing list , linux-netdev List-Id: linux-rdma@vger.kernel.org --YH9Qf6Fh2G5kB/85 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Jun 07, 2017 at 10:47:50AM -0600, Jason Gunthorpe wrote: > On Wed, Jun 07, 2017 at 07:43:44PM +0300, Leon Romanovsky wrote: > > On Wed, Jun 7, 2017 at 7:37 PM, Jason Gunthorpe > > wrote: > > > On Wed, Jun 07, 2017 at 07:19:01PM +0300, Leon Romanovsky wrote: > > >> It makes me wonder if it is expected behavior for > > >> ibnl_rcv_reply_skb() to handle !NLM_F_REQUEST messages and do we > > >> really need it? What are the scenarios? In my use case, which is > > >> for sure different from yours, I'm always setting NLM_F_REQUEST > > >> while communicating with kernel. > > > > > > If I recall the user space SA code issues REQUESTS from the kernel to > > > userspace, so userspace returns with the response format. This is > > > abnormal for netlink hence the special function. > > > > In netlink semantics, kernel side is supposed to send netlink > > notification message and userspace is supposed to send REQUEST. > > That pattern is for async communications, the SA stuff needs a sync > protocol, unfortunately. There is special flag NLM_F_ACK for it and userspace will set NLM_F_REQUEST | NLM_F_ACK once synchronization is needed. > > Jason --YH9Qf6Fh2G5kB/85 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkhr/r4Op1/04yqaB5GN7iDZyWKcFAlk4MTUACgkQ5GN7iDZy WKf/PQ//TuTB8yVW1rT8ya0bcJBhuJpuaLR7LJWuWi6S1FKisuhBE53zK5mVlGiJ Lmga4nxAfJuCk+8OpXPaDspbq68ZazZI2/Mn4DHBxTgG5jKokCuWERxUr+WDokMK wq5I1Om7JCiRaXNbGURZnkLZ+lGlI/Qv/UbhZpNEYFHSNsblt6HuqnoDyCFmF5bQ egohnb/tCqSHP1aufhQjy3R+ghlwk1nAIqbKG/eOaNc7HFeLxXYAut0lOSuTun1t df3GQ5X/3qyB6nLPb/CqEtyWff1/z7ChVTPc+Fl57EzyKGm1rOySSW3nZC8rRpNK MGNj60FAhN9wwluojrgjlKRUe0aDiQcvs34yLirke1WcxNkcKLttSVW/dN0s37Om +JqpR2fq3XiSJRS+3OgIdxYYPfNqTnwkEWE1jyVk0PB7mQmIxlrLGKmzZ9iXHkiU o3YF7g6ANs3+7zSTz8wWMJuyFFnasC01FlJQ7U3D12tf++fVJSAvDQ3tDjSjeTz5 V8SFH9yoNsFWomxRnJYo+UmVNNuXgFMFbt12SWfXOutPieLKcDBau5RVwhiRbJOF gQK7fIyQSwph3reThy9fwEEdWwX2fQo8+pNHo4b8v+B7HBSO0oFnC4QRglcRRWEl NMbeUzvkSZIy9ivFPOHNZpr23nA/OMQARTsNo3HES8ibOuUGlMo= =d3N2 -----END PGP SIGNATURE----- --YH9Qf6Fh2G5kB/85-- -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html