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Re: [Qemu-discuss] Unable to establish TCP sessions between guests using

From: Peter Kieser
Subject: Re: [Qemu-discuss] Unable to establish TCP sessions between guests using virtio-net on Linux 3.12 and above
Date: Fri, 27 Jun 2014 12:53:47 -0700
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0

On 2014-06-27 12:19 PM, Peter Kieser wrote:

Kernel versions tested: 3.13, 3.14, 3.15
Related debian bug report: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=738863

I'm not sure if this is a problem specific to openvswitch or KVM. I have a network setup where I have one openvswitch bridge setup, with various ports with VLAN tags and a firewall running as a guest. After upgrading to Linux 3.13, all guests with virtio interfaces with TSO enabled (the default) are unable to establish TCP connections via the guest firewall. ICMP ping works fine. If I disable TSO on the vnet interfaces (as outlined in the bug report above) guests are then able to communicate with each other.

Is there a patch for this issue that hasn't made it into mainline that I should test out? Is this an issue specific to KVM, or is it an openvswitch issue?

Than kyou,



Some further testing:

* Disabling vhost-net (vhost=off) for a particular VM has no effect to this issue
* Changing from virtio to e1000 for the NIC completely resolves this issue


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