Very slow and inconsistent internal network speed (between, VM's on the same host) for FreeBSD 11.0+ as guest on, XCP-ng/XenServer

[Roger Pau Monné]

There's a mistake in my reply below.

On Tue, Jun 25, 2019 at 04:56:43PM +0200, Roger Pau Monné wrote:
> On Tue, Jun 25, 2019 at 01:55:40PM +0200, Christian M wrote:
> > I've made two tests while running tcpdump on the xcp-ng host. I'm not at
> > all qualified to interpret the .pcap files from tcpdump, but I've put them
> > on Google Drive and linked them below the two tests. Perhaps someone more
> > qualified could have a look for anything useful in there. Please note the
> > extremely uneven throughput for test 2 below. It's almost like the
> > throughput increased when running tcpdump simultaneously.
> > 
> > Host: XCP-ng 7.6.0
> > Network: Private Network on host, not connected to any PIF.
> > VM1: 12.0-RELEASE (1 VIF, 172.31.16.125)
> > VM2: 12.0-RELEASE (1 VIF, 172.31.15.126)
> > 
> > On the host I listen with tcpdump on the VIF for VM1 in both tests.
> > 
> > VM1 as client:
> > 
> > On XCP-ng: tcpdump -i vif42.0 -s 0 -w xcp-ng-vm1-client.pcap
> 
> Can you check the capabilities of vif42.0? (ie: whether csum
> offloading is actually disabled on the host?)
> 
> > xcp-ng-vm1-client.pcap (80M):
> > https://drive.google.com/open?id=1eR3fetvKRz3vFSXCxDKuJYFrQ3wLqjrU
> > On VM1: iperf3 -c 172.31.16.126
> > On VM2: iperf3 -s
> 
> I've taken a look at the dump and the checksum is wrong (or maybe
> missing) for all? packets.
> 
> Packets with source 172.31.16.125 all have the TCP checksum set to
> 0x7f80 and all packets with source 172.31.16.125 have the TCP checksum
                                     ^ 172.31.16.126