Re: [PATCH v1 1/6] net: Generalize udp based tunnel offload
From: John W. Linville <hidden>
Date: 2015-12-01 16:15:16
On Tue, Dec 01, 2015 at 04:49:28PM +0100, Hannes Frederic Sowa wrote:
On Tue, Dec 1, 2015, at 16:44, John W. Linville wrote:quoted
On Mon, Nov 30, 2015 at 09:26:51PM -0800, Tom Herbert wrote:quoted
On Mon, Nov 30, 2015 at 5:28 PM, Jesse Gross [off-list ref] wrote:quoted
quoted
Based on what we can do today, I see only two real choices: do some refactoring to clean up the stack a bit or remove the existing VXLAN offloading altogether. I think this series is trying to do the former and the result is that the stack is cleaner after than before. That seems like a good thing.There is a third choice which is to do nothing. Creating an infrastructure that claims to "Generalize udp based tunnel offload" but actually doesn't generalize the mechanism is nothing more than window dressing-- this does nothing to help with the VXLAN to VXLAN-GPE transition for instance. If geneve specific offload is really needed now then that can be should with another ndo function, or alternatively ntuple filter with a device specific action would at least get the stack out of needing to be concerned with that. Regardless, we will work optimize the rest of the stack for devices that implement protocol agnostic mechanisms.Is there no concern about NDO proliferation? Does the size of the netdev_ops structure matter? Beyond that, I can see how a single entry point with an enum specifying the offload type isn't really any different in the grand scheme of things than having multiple NDOs, one per offload. Given the need to live with existing hardware offloads, I would lean toward a consolidated NDO. But if a different NDO per tunnel type is preferred, I can be satisified with that.Having per-offloading NDOs helps the stack to gather further information what kind of offloads the driver has even maybe without trying to call down into the layer (just by comparing to NULL). Checking this inside the driver offload function clearly does not have this feature. So we finally can have "ip tunnel please-recommend-type" feature. :)
That is a valuable insight! Maybe the per-offload NDO isn't such a bad idea afterall... :-) John -- John W. Linville Someday the world will need a hero, and you linville@tuxdriver.com might be all we have. Be ready.