Public bug reported:
Binary package hint: kvm
Serious networking problems with KVM running a Windows XP x64 host using
bridged networking. This may be a KVM bug, or a bridged-networking or
ethernet driver bug; I unfortunately don't have the skills to tell the
difference but will do what I can to help pinpoint the problem.
My Setup:
- Lucid 64bit installed on dual quad-core (Intel) Dell Precision R710,
32Gb RAM.
- One KVM instance running Windows XP x64 with 16Gb RAM, using bridged
networking. Symptoms occur with both standard "-net nic" KVM network
drivers (rtl8139?) and virtio network drivers on Windows. Either way I
am also using "-net tap" so I can get out to the real network.
- I'm starting KVM from the command line instead of using libvirt &
virt-manager, because I need to specify sockets/cores/threads for my
CPU. Otherwise Windows XP only uses 2 CPUs. I don't think this is
relevant but who knows.
The Problem:
The KVM windows image starts up fine, and at first works properly. But
after a very short duration, usually less than two minutes, the
networking freezes up. Can't get to the internet, can't access local
shares, nothing. Sometimes it magically comes back; sometimes it's gone
forever.
An interesting, possibly related detail: If I shut down the Windows
image, the host machine's networking freezes up for many seconds just as
the image is exiting. After the exit is complete and KVM is completely
shut down, I can ssh or VNC back into the host machine again without
problems.
So, after restarting the KVM image I try running the "iperf" network
performance tool in two modes.
1) From a separate PC on my LAN, I can run iperf between the Lucid
*host* and that PC, and never have any problems. I can consistently get
800 Mbits/sec up and 200 MBits/sec down. (I've run it about 50 times)
2) From the separate PC to the KVM Windows image running on the Lucid host:
- it sometimes runs successfully with 130Mbit/sec in both directions;
- other times gets just 25-40Mbit/sec;
- and sometimes it fails completely with the error message "write
failed: Connection reset by peer. read on server close failed: Connection
reset by peer".
What can I do to help pinpoint this bug? My hunch is the error is in
the bridging or the ethernet driver, but I don't know how to test that
since I only use bridging for KVM clients! Any ideas on what I can do?
I really want to help diagnose this.
** Affects: kvm (Ubuntu)
Importance: Undecided
Status: New
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kvm images losing connectivity w/bridged network
https://bugs.launchpad.net/bugs/584048
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