From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve Wise Subject: Re: [PATCH v2] RDMA/CMA: fix iWARP adapter TCP port space usage Date: Wed, 23 Jun 2010 15:19:31 -0500 Message-ID: <4C226C53.7080802@opengridcomputing.com> References: <4C225078.6050001@opengridcomputing.com> <4C225697.6060702@opengridcomputing.com> <20100623192909.GT4630@obsidianresearch.com> <4C2263B3.9010608@opengridcomputing.com> <20100623195210.GU4630@obsidianresearch.com> <4C226A6F.4000801@opengridcomputing.com> <20100623200937.GV4630@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100623200937.GV4630-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Roland Dreier , Bernard Metzler , "Tung, Chien Tin" , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Peter P Waskiewicz Jr List-Id: linux-rdma@vger.kernel.org Jason Gunthorpe wrote: > On Wed, Jun 23, 2010 at 03:11:27PM -0500, Steve Wise wrote: > >> The IP address assigned for the cxgb3i iscsi device is _not_ assigned to >> a netdev interface via ifconfig, as far as I understand it (by looking >> at the cxgb3i code). So the host stack doesn't know about this address. >> There is an administrative requirement, I assume, that the secret iscsi >> ipaddr is within a subnet that is bound to the T3 ethX interface. >> Otherwise the routing lookup wouldn't work. >> > > So who responds to neighbor queries, and how do outgoing queries get > sent with the right IP? Sounds odd... > > The iscsi hba is only an initiator, so it doesn't need to respond to arp queries. I guess the Source Protocol Address in the outgoing ARP request will be the ipaddr of the outgoing interface. Its ok though because what is needed is the next-hop peer's hwaddr. So the ARP reply comes in, updates the host neigh entry, and a NEIGH_EVENT callout is performed to the offload device drivers. It is a little hackish, but that's the only way the netdev maintainers would allow iscsi offload in. They originally tried to use the src address from the ethX interface for the offload iscsi connections and that was rejected. Steve. -- 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