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Date: Fri, 28 Sep 2012 10:22:18 +0100 From: Chris Clayton <chris2553@...glemail.com> To: Eric Dumazet <eric.dumazet@...il.com> CC: David Miller <davem@...emloft.net>, netdev@...r.kernel.org, gpiez@....de Subject: Re: Possible networking regression in 3.6.0 On 09/27/12 22:17, Eric Dumazet wrote: > On Thu, 2012-09-27 at 23:03 +0200, Eric Dumazet wrote: >> 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 ? No, the WinXP guest is configured with a fixed IP address (192.168.200.1). Subnet mask is 255.255.255.0, and default gateway is 192.168.200.254. DNS is 192.168.0.1. > > Yes it seems the problem. On the host I tried : > > # ip ro get 8.8.8.8 from 192.168.200.1 iif tap1 > 8.8.8.8 from 192.168.200.1 via 172.30.42.1 dev eth0 > cache iif * > > So if the guest tries to send a frame to 8.8.8.8 we are going to forward > the packet to eth0 > > But if the guest tries to send to 255.255.255.255, we try to deliver the > packet to the host itself, instead of broadcasting to eth0 > > # ip ro get 255.255.255.255 from 192.168.200.1 iif tap1 > broadcast 255.255.255.255 from 192.168.200.1 dev lo > cache <local,brd> iif * > > > David, maybe you'll have an idea ? > > Thanks > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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