Re: Step by step instructions for KVM networking

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

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Daniel Qarras wrote:
> Hi!
>
>   
>> In general the setup is exactly like qemu, so any howto for qemu is 
>> applicable.
>>
>> Here's what I do:
>>
>> - copy scripts/kvm from the kvm tarball to /etc/init.d, chkconfig and
>> start the kvm service. that sets up a bridge
>> - copy scripts/qemu-ifup into a new directory /etc/kvm.  make sure it
>> is executable.
>> - run qemu like this:
>>
>>    qemu-system-x86_64 -net nic -net tap,script=/etc/kvm/qemu-ifup
>> [other options]...
>>     
>
> Thanks for your kind answer but unfortunately I cannot find the scripts
> you mentioned from the kvm tar ball:
>
> sh-3.1$ find kvm-14 | grep scripts
> kvm-14/scripts
> kvm-14/scripts/run_img
> kvm-14/scripts/65-kvm.rules
> kvm-14/scripts/mkbootdisk
> sh-3.1$ 
>
> There is kvm-14/kvm script but that doesn't look at all like a Red Hat
> init script, it a Python script. I googled for qemu-ifup and found
> about dozen different kind of versions so I'm not sure which one I
> should use. But definetely the scripts you mentioned would be just what
> I was looking for!
>
>   

Sorry, the scripts didn't make it into the release.  I'm attaching them 
here.

If you're running Fedora, it looks like there's some bridging support in 
initscripts (I haven't tried it though).


-- 
error compiling committee.c: too many arguments to function


[-- Attachment #2: kvm --]
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#!/bin/sh
# kvm init script              Takes care for all VMM tasks
#
# chkconfig: - 99 01
# description: The KVM is a kernel level Virtual Machine Monitor.  \
#              Currently it starts a bridge and attached eth0 for it

dir=$(dirname "$0")

ifnum=${ifnum:-$(ip route list | awk '/^default / { print $NF }' | sed 's/^[^0-9]*//')}
ifnum=${ifnum:-0}
switch=${sw0:-sw${ifnum}}
pif=${pif:-eth${ifnum}}
antispoof=${antispoof:-no}
command=$1

if [ -f /etc/sysconfig/network-scripts/ifcfg-${pif} ]; then
    . /etc/sysconfig/network-scripts/ifcfg-${pif}
fi

get_ip_info() {
    addr=`ip addr show dev $1 | egrep '^ *inet' | sed -e 's/ *inet //' -e 's/ .*//'`
    gateway=$(ip route list | awk '/^default / { print $3 }')
}
    
do_ifup() {
     if [ ${addr} ] ; then
        ip addr flush $1 
        ip addr add ${addr} dev $1 
        ip link set dev $1 up 
     fi
}

link_exists()
{
    if ip link show "$1" >/dev/null 2>/dev/null
    then
        return 0
    else
        return 1
    fi
}

create_switch () {
    local switch=$1

    if [ ! -e "/sys/class/net/${switch}/bridge" ]; then
	brctl addbr ${switch} >/dev/null 2>&1
	brctl stp ${switch} off >/dev/null 2>&1
	brctl setfd ${switch} 0.1 >/dev/null 2>&1
    fi
    ip link set ${switch} up >/dev/null 2>&1
}

add_to_switch () {
    local switch=$1
    local dev=$2

    if [ -e "/sys/class/net/${switch}/brif/${dev}" ]; then
	ip link set ${dev} up >/dev/null 2>&1 || true
	return
    fi
    brctl addif ${switch} ${dev} >/dev/null 2>&1
    ip link set ${dev} up >/dev/null 2>&1
}

#taken from Xen
transfer_routes () {
    local src=$1
    local dst=$2
    # List all routes and grep the ones with $src in.
    # Stick 'ip route del' on the front to delete.
    # Change $src to $dst and use 'ip route add' to add.
    ip route list | sed -ne "
/dev ${src}\( \|$\)/ {
  h
  s/^/ip route del /
  P
  g
  s/${src}/${dst}/
  s/^/ip route add /
  P
  d
}" | sh -e
}


change_ips() {
    local src=$1
    local dst=$2

    #take care also for case we do not have /etc/sysconfig data (the switch as a src case)
    if [ -x $BOOTPROTO ]; then
        if [ -x $(pgrep dhclient) ];then
           BOOTPROTO="null"
        else
            BOOTPROTO="dhcp"
        fi
    fi

    if [ $BOOTPROTO = "dhcp" ]; then
        ifdown ${src} >/dev/null 2>&1 || true
        ip link set ${src} up >/dev/null 2>&1
        pkill dhclient >/dev/null 2>&1
	for ((i=0;i<3;i++)); do
	    pgrep dhclient >/dev/null 2>&1 || i=4	
   	    sleep 1
	done
        dhclient ${dst} >/dev/null 2>&1
    else
        get_ip_info ${src}
        ifdown ${src} >/dev/null 2>&1 || true
        ip link set ${src} up >/dev/null 2>&1
        do_ifup ${dst}
        transfer_routes ${src} ${dst}
        ip route add default via ${gateway} dev ${dst}
    fi
}
               
antispoofing () {
    iptables -P FORWARD DROP >/dev/null 2>&1
    iptables -F FORWARD >/dev/null 2>&1
    iptables -A FORWARD -m physdev --physdev-in ${dev} -j ACCEPT >/dev/null 2>&1
}

status () {
    local dev=$1
    local sw=$2
    
    echo '============================================================'
    ip addr show ${dev}
    ip addr show ${sw}
    echo ' '
    brctl show ${sw}
    echo ' '
    ip route list
    echo ' '
    route -n
    echo '============================================================'
    gateway=$(ip route list | awk '/^default / { print $3 }')
    ping -c 1 ${gateway} || true
    echo '============================================================'
}

start () {
    if [ "${switch}" = "null" ] ; then
	return
    fi

    create_switch ${switch}
    add_to_switch ${switch} ${pif}
    change_ips ${pif} ${switch}

    if [ ${antispoof} = 'yes' ] ; then
	antispoofing
    fi

    grep -q GenuineIntel /proc/cpuinfo && /sbin/modprobe kvm-intel
    grep -q AuthenticAMD /proc/cpuinfo && /sbin/modprobe kvm-amd
}

stop () {
    if [ "${switch}" = "null" ]; then
	return
    fi
    if ! link_exists "$switch"; then
	return
    fi

    change_ips ${switch} ${pif}
    ip link set ${switch} down
    brctl delbr ${switch}

    grep -q GenuineIntel /proc/cpuinfo && /sbin/modprobe -r kvm-intel
    grep -q AuthenticAMD /proc/cpuinfo && /sbin/modprobe -r kvm-amd
    /sbin/modprobe -r kvm
}


case "$command" in
    start)
	echo -n $"Starting KVM: "
	start
	echo
	;;
    
    stop)
	echo -n $"Shutting down KVM: "
	stop
	echo
	;;

    status)
	status ${pif} ${switch}
	;;

    *)
	echo "Unknown command: $command" >&2
	echo 'Valid commands are: start, stop, status' >&2
	exit 1
esac

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#!/bin/sh

switch=$(ip route list | awk '/^default / { print $NF }')
ifconfig $1 0.0.0.0 up
brctl addif ${switch} $1

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