source: bootscripts/contrib/lsb-v3/sbin/ifup@ cb95d5f

#!/bin/sh
########################################################################
# Begin $NETWORK_DEVICES/ifup
#
# Description : Interface Up
#
# Authors     : Nathan Coulson - nathan@linuxfromscratch.org
#               Kevin P. Fleming - kpfleming@linuxfromscratch.org
#
# Version     : 00.00
#
# 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} # All parameters except $1
  do
        FILES="${FILES} ${NETWORK_DEVICES}/ifconfig.${1}/${file}"
    done
elif [ -d "${NETWORK_DEVICES}/ifconfig.${1}" ]; then
    FILES=`echo ${NETWORK_DEVICES}/ifconfig.${1}/*`
else 
    FILES="${NETWORK_DEVICES}/ifconfig.${1}"
fi

message="Bringing up the ${1} interface..."

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

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

    (
        . ${file}

        # 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" -a "${HOSTNAME}" != "(none)" ]; then
             continue
        fi

        if [ -n "${SERVICE}" -a -x "${NETWORK_DEVICES}/services/${SERVICE}" ]; then
            if [ -z "${CHECK_LINK}" -o "${CHECK_LINK}" = "y" -o "${CHECK_LINK}" = "yes" -o "${CHECK_LINK}" = "1" ]; then
                if ip link show ${1} > /dev/null 2>&1; then
                    link_status=`ip link show ${1}`
                    if [ -n "${link_status}" ]; then
                        if ! echo "${link_status}" | grep -q UP; then
                            ip link set ${1} up
                            evaluate_retval standard
                        fi
                    fi
                else
                    message="${message}Interface ${1} doesn't exist."
                    log_warning_msg
                fi
            fi
            IFCONFIG=${file} ${NETWORK_DEVICES}/services/${SERVICE} ${1} up
        else
            echo -e "${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

# End $NETWORK_DEVICES/ifup