dhcpcq

#!/bin/sh
#
# Copyright (c) 2020 Kimmo Suominen
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer
#    in the documentation and/or other materials provided with the
#    distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#

#
# Report on dhcpcd(8) lease dump data
#
# 20201019  Kimmo Suominen
#

set -eu

PATH=/bin:/usr/bin:/sbin:/usr/sbin
export PATH

PROG="${0##*/}"
PDIR="${0%/*}"

dhcpcd=dhcpcd
case "${PDIR}" in
/*)
    if [ -x "${PDIR}/dhcpcd" ]
    then
	dhcpcd="${PDIR}/dhcpcd"
    fi
    ;;
esac

die()
{
    echo "${PROG}: ${*}" 1>&2
    exit 1
}

get_dhcpcd_dump()
{
    "${dhcpcd}" -U \
    | sed -n '
	/^reason=ROUTERADVERT$/,/^$/ {
	    p
	}
    '
}

get_interface_nd_data()
{
    local interface nd data
    interface="${1}"
    nd="${2}"
    data="${3}"

    echo "${data}" \
    | sed -n '
	/^interface='"${interface}"'$/,/^$/ {
	    /^nd'"${nd}"'_/ {
		s//_/
		p
	    }
	}
    '
}

get_interfaces()
{
    echo "${1}" \
    | sed -n '
	/^interface=/ {
	    s///
	    p
	}
    '
}

#
# Mimic "ndp -r" output from "dhcpcd -U" data
#

ndp_r()
{
    local data
    data="${1}"

    for int in $(get_interfaces "${data}")
    do
	i=1
	while :
	do
	    _from=
	    eval $(get_interface_nd_data "${int}" "${i}" "${data}")
	    if [ "${_from:+exists}" != "exists" ]
	    then
		break
	    fi

	    echo -n "${_from}"
	    case "${_from}" in
	    fe80:*)
		echo -n "%${int}"
		;;
	    esac
	    echo -n " if=${int}"

	    flags=
	    pref=medium
	    for flag in $(echo "${_flags}" | grep -i .)
	    do
		case "${flag}" in
		h)
		    pref=high
		    ;;
		*)
		    flags="${flags}${flag}"
		    ;;
		esac
	    done
	    echo -n ", flags=${flags}, pref=${pref}"

	    exp=$((${_lifetime} + ${_acquired} - ${_now}))
	    exp_minutes=$((${exp} / 60))
	    exp_seconds=$((${exp} % 60))
	    echo -n ", expire="
	    [ ${exp_minutes} -gt 0 ] && echo -n "${exp_minutes}m"
	    echo -n "${exp_seconds}s"

	    echo
	    i=$((${i} + 1))
	done
    done
}

usage()
{
    cat <<EOF

Usage:	${PROG} [-r] [-f file]
	${PROG} -h

Options:
-f	Read dhcpcd(8) lease dump data from a file
-h	Show this usage message
-r	Show default router list
EOF
}

# It is the only mode for now, so make it default
mode=ndp_r
source=

while getopts f:hr opt
do
    case "${opt}" in
    f)	source="${OPTARG}";;
    h)	usage; exit 0;;
    r)	mode=ndp_r;;
    n)	noop=true;;
    p)	mode=prune;;
    *)	usage 1>&2; exit 1;;
    esac
done
shift $((${OPTIND} - 1))

case "${source}" in
'')
    data="$(get_dhcpcd_dump)"
    ;;
*)
    if [ -r "${source}" ]
    then
	data="$(cat "${source}")"
    else
	die "Cannot read '${source}'"
    fi
    ;;
esac

case "${mode}" in
ndp_r)
    ndp_r "${data}"
    ;;
*)
    die "Unknown mode '${mode}'"
    ;;
esac