Re: [dpdk-dev] Wrong TCP checksum of packets sent by Linux guest (virtIO/vhost)

["Gray, Mark D" <mark.d.gray@intel.com>]

> > >
> > > Hi Franck,
> > >
> > > 2014-09-02 13:20, Franck BAUDIN:
> > > > I am using dpdk-ovs 1.1.0 (latest release) as follow :
> > > >
> > > > linux-guest (no DPKD) <---  virtIO ---> OVDK 1.1.0 (with latest
> > > > DPDK [*]) < --
> > > - Niantic --- > linux-native
> > > >
> > > [...]
> > > > UDP/ICMP connectivity is fine, but TCP checksum of packet sent by
> > > > the
> > > guest are incorrect, as showed with tcpdump on linux-native.
> > >
> > > Thanks for reporting.
> > > Could you try virtio without vhost?
> > >
> > >
> >
> > Looping in the dpdk-ovs list.
> >
> > * Does the new vhost API allow a user to know if all the relevant
> > offloads have been turned on/off for that interface? It seems that
> > this is possible through the virtio_net structure but it would be good
> > to get some feedback from the relevant person working on DPDK
> > (Huawei?).
> >
> > * If this is the case, then it is probably in the realm of the vswitch
> > do the actual checksum (for VM-VM) or correctly configure the NIC when
> > sending out through the physical interface.
> >
> > Comments?
> 
> 
> Mark:
> So far not supported. This is important as well in VxLan case. For the packet

Ok 

> flow Guest A->  virtio -> ..->OVDK->.. -> Guest B.
> 1) If guest A and B are on different host machines, say A and B respectively,
> and if the nic on A supports vxlan checksum offload, then both guest and
> host needn't generate checksum, the nic will generate checksum for both
> inner and outer packet.

The vswitch would need to support this

> 2) In VM2VM case, as it is trusted communication channel, could we
> negotiate with the guest tcp stack not to verify checksum for received
> packet?

Perhaps

> 
> >
> > Mark