On Fri, Mar 25, 2016 at 10:35 AM, Ben Greear <gree...@candelatech.com> wrote: > > > On 03/24/2016 10:24 PM, Vijay Pandurangan wrote: >> >> On Fri, Mar 25, 2016 at 1:07 AM, Ben Greear <gree...@candelatech.com> >> wrote: >>> >>> On 03/24/2016 09:45 PM, Vijay Pandurangan wrote: >>>> >>>> >>>> Actually, maybe they should be set to CHECKSUM_PARTIAL if we want veth >>>> to drop the packets if they have bad checksums before they hit the >>>> application level. >>> >>> >>> >>> VETH is pretty special in that when you transmit a frame on one >>> device, it's pair receives it, and unless there is RAM corruption >>> or bugs in the kernel, then it cannot be corrupted. >> >> >> Yeah, you're right that that's an optimization. However, I think that >> we should first ensure that >> >> a->veth->b >> >> operates exactly like: >> >> a->physical eth 1 -> physical eth 2->b >> >> in all cases. Once we have that working everywhere we could think >> about optimizations. >> >> >> If we're willing to refactor, we could implement the optimization by >> allowing veth devices to know whether their immediate peer is. If a >> veth knows it's talking to another veth, it could under some >> circumstances elide checksum calculation and verification. I'm not >> sure what abstractions that would break, though. What do you guys >> think? > > > veth ALWAYS transmits to another VETH. The problem is that when veth is > given a packet to transmit, it is difficult to know where that packet > came from.
Yeah you're totally right – I guess what I was trying to express (but failed at) was that we might need to be able to track the original source of the packet for optimizations. > > And, adding software checksumming to veth for every frame would be a huge > performance hit. > > > Thanks, > Ben > > -- > Ben Greear <gree...@candelatech.com> > Candela Technologies Inc http://www.candelatech.com
