rycks' corner

1. Installer les paquets

apt-get install vde

2. lancer la commande suivante pour que tun apparaisse dans la liste des interfaces lors d'un ifconfig

vde_switch -tap tun -daemon

3. avoir le bon fichier /etc/qemu-ifup (je ne sais plus qui est l'auteur original de ce script, probablement Olivier mais ce n'est pas certain)

#!/bin/bash
#
###########################################################################
# Configuration of the tunN devices for usage with QEMU.
#
# Based on the tunconfig script from MOL.
#
# This script should be named /etc/qemu-ifup-sudo
#
# To use this script you must have...
#
#   0) kernel support for TUN devices
#
#   1) the device node /dev/net/tun with read/write permissions
#
#   2) invoked qemu with TUN support (this is the default)
#
#   3) configured /etc/sudoers to let you run this script
#
# An example /etc/sudoers entry for (3) would be:
#
#   myself    ALL=/etc/qemu-ifup-sudo
#
# If your linux box is configured as a firewall or a DHCP server or a
# router then you don't want to be running this script.
#
# Fabrice is working on a user-net implementation that will eventually
# obsolete this script.
#
#############################################################################

PROVIDE_DHCP=yes
DNS_REDIRECT=yes

IFCONFIG=/sbin/ifconfig
IPTABLES=/sbin/iptables
DHCPD=/usr/sbin/dhcpd

# uncomment to override nameserver autodetection
# NAMESERVER=10.0.0.1


####################################################################

TUN_DEV=${1:-tun}
ACTION=${2:-up}

TUN_NUM=0
NET_NUM=`expr 40 + $TUN_NUM`
TUN_NET=192.168.$NET_NUM.0
TUN_HOST=192.168.$NET_NUM.1


#########################################################
# Misc Checks
#########################################################

-x $IFCONFIG || {
    echo "---> fatal: $IFCONFIG not installed" 1>&2
    exit 1
}

-x $DHCPD || {
    echo "---> warning: $DHCPD not installed" 1>&2
    PROVIDE_DHCP=no
}

-x $IPTABLES || {
    echo "---> fatal: $IPTABLES not installed" 1>&2
    exit 1
}

$IPTABLES -L -n -t nat > /dev/null || {
    echo "---> fatal: $IPTABLES indicates no NAT support" 1>&2
    exit 1
}

-e /proc/sys/net/ipv4/ip_forward || {
    echo "---> fatal: you don't have /proc/sys/net/ipv4/ip_forward" 1>&2
    exit 1
}

#########################################################
# Remove old (possibly stale) ruleset
#########################################################
{
    $IPTABLES -t nat -D POSTROUTING -s $TUN_NET/24 -d ! $TUN_NET/24 -j MASQUERADE
    $IPTABLES -t nat -D PREROUTING -p tcp -i $TUN_DEV -d $TUN_HOST --dport 53 -j qemu-dns
    $IPTABLES -t nat -D PREROUTING -p udp -i $TUN_DEV -d $TUN_HOST --dport 53 -j qemu-dns
    $IPTABLES -t nat -F qemu-dns
} >& /dev/null


#########################################################
# Bring down interface
#########################################################

"$ACTION" = down && {
    $IFCONFIG $TUN_DEV down
}


#########################################################
# Configure interface
#########################################################

"$ACTION" = up && {
    # the dhcpd server can get stuck if the QEMU side of the
    # tun device is shutdown uncleanly
    -f /var/run/dhcpd.pid -a "$PROVIDE_... && {
        echo "kill -9 stale dhcpd server"
        kill -9 `cat /var/run/dhcpd.pid` > /dev/null 2>&1
    }

    # configure the interface
    $IFCONFIG $TUN_DEV $TUN_HOST

    # masquerade the tun network
    $IPTABLES -t nat -A POSTROUTING -s $TUN_NET/24 -d ! $TUN_NET/24 -j MASQUERADE

    # DNS redirection
    "$DNS_REDIRECT" = yes && {
        ! "$NAMESERVER" && {
            NAMESERVER=`grep ^nameserver /etc/resolv.conf | awk -- '{ print $2 ; exit 0; }'`
            ! "$NAMESERVER" && {
                echo "Could not determine the nameserver (localhost is used)."
                NAMESERVER=$TUN_HOST
            }
        }

        # create a table for DNS redirection
        $IPTABLES -t nat -N qemu-dns 2> /dev/null
        $IPTABLES -t nat -A qemu-dns -j DNAT --to $NAMESERVER

        # redirect tcp/udp port 53 (nameserver queries)
        $IPTABLES -t nat -A PREROUTING -p tcp -i $TUN_DEV -d $TUN_HOST --dport 53 -j qemu-dns
        $IPTABLES -t nat -A PREROUTING -p udp -i $TUN_DEV -d $TUN_HOST --dport 53 -j qemu-dns
    }
}


#########################################################
# Generate DHCP configuration file
#########################################################

for N in `seq 40 50` ; do
    T_NET=192.168.$N.0
    T_HOST=192.168.$N.1
    T_RANGE="192.168.$N.2 192.168.$N.100"

    echo "subnet $T_NET netmask 255.255.255.0 {"
    echo "      option domain-name-servers      $T_HOST;"
    echo "      option routers                  $T_HOST;"
    echo "      range                           $T_RANGE;"
    echo "}"
done > /tmp/qemu-dhcpd-$$.conf

#########################################################
# Start the DHCP and IP forwarding
#########################################################

IFACES=`netstat -i | sed -n -e 's/^\(tun0-9\).*/\1/gp'`

if "$IFACES" ; then
    "$PROVIDE_DHCP" = yes && $DHCPD -q -cf /tmp/qemu-dhcpd-$$.conf $IFACES
    echo 1 > /proc/sys/net/ipv4/ip_forward
else
    $IPTABLES -t nat -X qemu-dns >& /dev/null
    echo 0 > /proc/sys/net/ipv4/ip_forward
fi

exit 0