Re: Possible networking regression in 3.6.0

Eric Dumazet
2012-09-27T21:03:51Z

On Thu, 2012-09-27 at 19:05 +0100, Chris Clayton wrote:
> On 09/27/12 13:14, Eric Dumazet wrote:
> > On Thu, 2012-09-27 at 12:50 +0100, Chris Clayton wrote:
> >> Just for information - I've pulled Linus' tree this morning and the
> >> problem is still present. Also, Gunther Piaz has reported, via the
> >> bugzilla entry, that he too has hit this regression.
> >
> > I tried to reproduce the bug, and my kvm guests have no problem.
> >
> > I guess you need to precisely describe how you setup your network, so
> > that I can reproduce the problem and eventually fix it.
> >
>
> You've seen the bits from my firewall setup script that relate to this
> issue. I start the WinXP client with another script:
>
> #!/bin/sh
> if [ -e $HOME/kvm/var/run/kvm-winxp.pid ]; then
> echo "winxp is already running ..." > /dev/stderr
> exit 1
> fi
>
> # make sure the kvm modules are loaded
> if test -z "$(grep '\<kvm\>' /proc/misc)"; then
> sudo modprobe kvm-intel
> while test -z "$(grep '\<kvm\>' /proc/misc)"; do
> true
> done
> fi
>
> # make sure tun module is loaded
> if test ! -e /dev/net/tun; then
> sudo modprobe tun
> fi
>
> # figure out the cpu to use
> QVER=$(qemu-kvm --version | cut -d' ' -f 4 | sed 's/,/./')
> # assumes major version is 1
> MINORVER=$(echo $QVER | cut -d'.' -f 2)
> if [ $MINORVER -ge 1 ]; then
> CPU="host"
> else
> CPU="qemu64"
> fi
>
> # set up the network interface
> TAPDEV=$(sudo tunctl -b -u $(whoami))
> sudo ifconfig $TAPDEV 192.168.200.254 netmask 255.255.255.0 broadcast
> 192.168.200.255
>
> # start Windows XP
> qemu-kvm -drive file=$HOME/kvm/winxp.qcow2,index=0,cache=none,if=virtio
> -cpu $CPU -smp cores=1,threads=2 -soundhw es1370 \
> -m 768 -net nic,model=virtio,macaddr=$(getmacaddr) -net
> tap,ifname=$TAPDEV -startdate $(date +%Y-%m-%dT%H:%M:%S) \
> -name kxplaptop -pidfile $HOME/kvm/var/run/kvm-winxp.pid $*
>
> # stop the network interface
> sudo ifconfig $TAPDEV down
> sudo tunctl -d $TAPDEV &>/dev/null
>
> # tidy up
> rm -f $HOME/kvm/var/run/kvm-winxp.pid
>
>
> The call to getmacaddr just returns the next in a sequence of mac
> addresses. qemu-kvm is a symlink to /usr/bin/qemu-system-i386. I first
> found the problem whilst running qemu-kvm version 1.1.1 although I've
> since updated to 1.2.0.
>
> By the way, I doubt it will make a difference, but, although my laptop
> has a 64bit CPU, I am running a 32 bit kernel and, obviously, user space.
>
> Let me know if you need anything else.

It works for me.

Hmm, maybe your guest is using DHCP and DHCP fails ?

Could you check ?