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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] accidental mistyping of command line kills networking |
Date: | Tue, 27 Oct 2009 16:44:03 -0500 |
User-agent: | Thunderbird 2.0.0.23 (X11/20090825) |
Beth Kon wrote:
Beth Kon wrote:A clarification... this command line is ok. But as it happens, windows datacenter does not have a driver for rtl8139. So somehow, this driverless adapter in windows is effectively causing an "extra" tap device to be specified on the qemu command line, wreaking havoc with the networking on the host.I accidentally entered a command line as follows:/usr/bin/qemu-kvm -drive file=/scratch/images/beth/windows/win2k3_32_R2.dat.10G.img,if=ide -m 2048 -boot cd -net nic,model=rtl8139 -net tap,script=/etc/qemu-ifup -vnc :12 -usbdevice tablet -monitor stdio -net nic,model=e1000 -net tap,script=/etc/qemu-ifupand the machine's networking broke, requiring a network restart to get it back in order. The second -net tap,script=/etc/qemu-ifup causes the problem./var/log/messages shows tap0: received packet with own address as source addressI don't have time at the moment to look into what's going wrong. Just wanted to make people aware.Beth Kon
It's actually not okay. You're creating a bridge with two tap devices on the bridge that happen to be connected in qemu by a vlan. If one tap device receives a packet, qemu is going to forward that packet to the other tap device, which will in turn send the packet to the bridge which in turn sends it to the first tap device.
Resulting in an infinite networking loop. Regards, Anthony Liguori
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