[geeks] Help: Network issue has me stumped

[Cory Smelosky]

This is a bit odd...

Can't for the life of me figure out what could be the cause.

I have a VM host, running Proxmox to do KVM VMs, inside one of the KVM VMs 
is some SIMH and KLH10 instances. Host NIC is e1000e

FTP TO these systems - never from - stalls for quite awhile every 65536 
(134320 if doing 9000-byte MTU across the board - even on the bridges) 
bytes.

VMs are doing virtio-net, changing has no effect.  Changing OS also has no effect. 
Nor does changing host OS or virt. software.  Nor does running KLH10 on 
the host itself.

Switch doesn't show any buffer failures, only buffer misses. Client 
doesn't show any packets dropped/lost.

TCPDUMP shows periodic (although regular) checksum fails and has the DF 
bit.

This seems to ONLY affect ftp.  No firewalls are in the way, SCP to the 
host is fine.

VDE attaching to FreeBSD tap, KLH10 attaching to Linux TAP, KLH10 
attaching to FreeBSD pcap...it doesn't matter.  FTP to the host is fine, 
FTP to the VMs themselves is also fine.

This issue HAS NOT always been present, and it does not appear for others.

Any ideas?  I'm completely stumped...and the only pointer was ... the 
number 65536 which refers only to a TCP/UDP window size.

Of note, I have an identical setup open TO THE PUBLIC INTERNET without 
issue.

-- 
Cory Smelosky
http://gewt.net Personal stuff
http://gimme-sympathy.org Projects