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|
#!/bin/sh
# Check if the (default) gateway configured for the interface is
# present in our network
#
# This script should be installed in /etc/network/if-up.d/
# It can also be used as a standalone script by setting up
# its environment:
# IFACE=eth0 IF_GATEWAY=192.168.0.1 check-gateway
#
# NOTE: If IF_GATEWAY is not provided the script will try to test
# the default gateway.
#
# TODO:
#
# - Support non-default gateways that might have been set at the
# same time the interface was enabled.
#
# ------------------------------------------------------------------------
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
# You can also find a copy of the GNU General Public License at
# http://www.gnu.org/licenses/licenses.html#TOCLGPL
# Check if an IP we are going to assign to an Ethernet interface
# is already in use by another system.
#
# Read system default file
[ -r /etc/default/network-test ] && . /etc/default/network-test
# Defaults
ARPING=/usr/bin/arping
ARP_COUNT=${ARP_COUNT:-2}
ARP_TIMEOUT=${ARP_TIMEOUT:-3}
DO_SYSLOG=${DO_SYSLOG:-yes}
VERBOSITY=${VERBOSITY:-0}
# Do not continue if ARPING is not available
[ ! -x "$ARPING" ] && exit 0
# or if the user has told us to not do arpings
[ "$DO_ARPING" = "no" ] && exit 0
# Break out if we don't have an interface to work with
[ -z "$IFACE" ] && exit 0
# Check our IFACE name
case "$IFACE" in
sl* | lo*) exit 0;; # if it is a serial line or loopback skip it as ARP ping is not possible there
--all) exit 0;; # do nothing with --all as we do not know where to operate
*) ;;
esac
if [ "$DO_SYSLOG" = "yes" ] ; then
OUTPUT="logger -i -p daemon.err -s"
else
OUTPUT="echo"
fi
# Try to obtain the IP address of our gateway (DHCP case)
if [ -z "$IF_GATEWAY" ] ; then
IF_GATEWAY=$(ip route list | grep "^default " | grep "dev $IFACE" | awk '{print $3}')
# Warn if there are multiple gateways
echo $IF_GATEWAY | grep -q " " && [ "$VERBOSITY" -eq 1 ] && $OUTPUT "Found multiple gateways as default routes for $IFACE"
fi
# Still no IP? Bail out
[ -z "$IF_GATEWAY" ] && exit 0
# Set up our environment
LC_ALL=C
export LC_ALL
do_arping() {
# Send ARP pings to detect if the default gateway is "out there"
# Curiously enough, the script will return faster if there *is* a system
# with the same IP address and will take ${ARP_TIMEOUT}*${ARP_COUNT} seconds
# to return if there is none.
# Do not do the check if ethtool (if installed) tells us the interface
# does not have link, notice that ARPING will try to send the ARP requests
# even if there is no link so we use this to speed things up
local GATEWAY=$1
local ARPING_OPTIONS="-q -c $ARP_COUNT -w $ARP_TIMEOUT -f -I $IFACE"
local GATEWAY_FOUND=1
# Check if the interface is up
if [ -z "`ip link show $real_iface up 2>/dev/null`" ]; then
return 0
fi
[ "$VERBOSITY" -eq 1 ] && $OUTPUT "DEBUG: Sending arp pings through $IFACE to detect if the gateway $GATEWAY is present"
if [ "`id -u`" = 0 ] ; then
if $ARPING $ARPING_OPTIONS $GATEWAY ; then
GATEWAY_FOUND=0
fi
else
# If we are not root we can only use arping in DAD mode
# in this case we negate the check as it will return 1
# if there is an answer
if ! $ARPING $ARPING_OPTIONS -D $GATEWAY ; then
GATEWAY_FOUND=0
fi
fi
if [ "$GATEWAY_FOUND" = 1 ] ; then
$OUTPUT "ERROR: Cannot find default gateway $GATEWAY in the network where $IFACE is connected to"
fi
}
for gateway in $IF_GATEWAY ; do
do_arping $gateway
done
exit 0
|
