From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: [Qemu-devel] net packet storms with multiple NICs Date: Wed, 11 Nov 2009 12:23:01 +0300 Message-ID: <4AFA8275.2080306@msgid.tls.msk.ru> References: <4AE1D903.5030709@msgid.tls.msk.ru> <200911110119.18839.paul@codesourcery.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, KVM list To: Paul Brook Return-path: Received: from isrv.corpit.ru ([81.13.33.159]:33364 "EHLO isrv.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751349AbZKKJW6 (ORCPT ); Wed, 11 Nov 2009 04:22:58 -0500 In-Reply-To: <200911110119.18839.paul@codesourcery.com> Sender: kvm-owner@vger.kernel.org List-ID: Paul Brook wrote: >> I immediately reproduced the problem locally. It turns out that >> kvm reflects packets coming from one guest NIC on another guest >> NIC, and since both are connected to the same bridge we're getting >> endless packet storm. To a level when kvm process becomes 100% >> busy and does not respond to anything but `kill -9'. > > You created a network loop. It is working exactly as expected. > Create the same topology with a physical network hub and a pair of NICs and > you'll get the same end result. Paul, I know what the result is. But mind you, I talked about something different, namely: why, using "obvious" way, you get a packet storm/loop instead of a working network. And if that loop is useful in the first place. I've got answers to both already :) Thanks /mjt