From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH rdma-next 4/4] IB/core: Add IP to GID netlink offload Date: Wed, 4 May 2016 12:52:41 -0600 Message-ID: <20160504185241.GD20554@obsidianresearch.com> References: <1462376518-6725-1-git-send-email-leon@kernel.org> <1462376518-6725-5-git-send-email-leon@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1462376518-6725-5-git-send-email-leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Leon Romanovsky Cc: dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, markb-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org, majd-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org, matanb-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Wed, May 04, 2016 at 06:41:58PM +0300, Leon Romanovsky wrote: > From: Mark Bloch > > There is an assumption that rdmacm is used only between nodes > in the same IB subnet, this why ARP resolution can be used to turn > IP to GID in rdmacm. > > When dealing with IB communication between subnets this assumption > is no longer valid. ARP resolution will get us the next hop device > address and not the peer node's device address. > > To overcome this limitation, let's check user space if it can > provide the GID of the peer node, and fail if not. > > We add a sequence number to identify each request and fill in the GID > upon answer from user space. This description doesn't describe what this patch is trying to do. This patch is delegating IP to GID translation to user space if there is a route table entry for the destination. I have to say, I really don't like this at all. If we want to have proper routing support then the translation needs to be done somehow in-band. What is user space supposed to do? Jason -- 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