source: lsb-bootscripts/sbin/ifdown@ 63a2c2d

#!/bin/sh
########################################################################
# Begin $NETWORK_DEVICES/ifdown
#
# Description : Interface Down
#
# Authors     : Nathan Coulson - nathan@linuxfromscratch.org
#               Kevin P. Fleming - kpfleming@linuxfromscratch.org
#
# Version     : 00.01
#
# Notes       : the IFCONFIG variable is passed to the scripts found
#               in the services directory, to indicate what file the
#               service should source to get environmental variables.
#
########################################################################

. /lib/lsb/init-functions

# Collect a list of configuration files for our interface
if [ -n "${2}" ]; then
    for file in ${@#$1}; do # All parameters except $1
        FILES="${FILES} /run/network/ifconfig.${1}/${file}"
    done
elif [ -d "/run/network/ifconfig.${1}" ]; then
    FILES=`echo /run/network/ifconfig.${1}/*`
else
    FILES="/run/network/ifconfig.${1}"
fi

# Reverse the order configuration files are processed in
for file in ${FILES}; do
    FILES2="${file} ${FILES2}"
done
FILES=${FILES2}

# Process each configuration file
for file in ${FILES}; do
    # skip backup files
    if [ "${file}" != "${file%""~""}" ]; then
        continue
    fi

    if [ ! -f "${file}" ]; then
        message="${file} is not a network configuration file or directory."
        log_warning_msg
    fi
    (
        if [ ! -d "${file}" ]; then
            . ${file}
        fi

        # Will not process this service if started by boot, and ONBOOT
        # is not set to yes
        if [ "${IN_BOOT}" = "1" -a "${ONBOOT}" != "yes" ]; then
            continue
        fi

        # Will not process this service if started by hotplug, and 
        # ONHOTPLUG is not set to yes
        if [ "${IN_HOTPLUG}" = "1" -a "${ONHOTPLUG}" != "yes" ]; then
            continue
        fi
    
        # This will run the service script, if SERVICE is set
        if [ -n "${SERVICE}" -a -x "/lib/network-services/${SERVICE}" ]; then
            if ip link show ${1} > /dev/null 2>&1
            then
                IFCONFIG=${file} /lib/network-services/${SERVICE} ${1} down &&
                if [ -f "${file}" ]; then
                    rm ${file}
                fi
            else
                message="Interface ${1} doesn't exist."
                log_warning_msg
            fi
        else
            echo -e "${FAILURE}Unable to process ${file}.  Either"
            echo -e "${FAILURE}the SERVICE variable was not set,"
            echo -e "${FAILURE}or the specified service cannot be executed."
            message=""
            log_failure_msg
        fi
    )
done

if [ -z "${2}" ]; then
    link_status=`ip link show $1`
    if [ -n "${link_status}" ]; then
        if echo "${link_status}" | grep -q UP; then
            message="Bringing down the ${1} interface..."
            ip link set ${1} down
            evaluate_retval standard
        fi
    fi
fi

# End $NETWORK_DEVICES/ifdown