#!/bin/sh
#
# This file is part of the resolvconf package.
#

set -e

echo_usage() { echo "Usage: resolvconf (-d IFACE|-a IFACE|-u|--enable-updates|--disable-updates|--updates-are-enabled|--create-runtime-directories|--wipe-runtime-directories)" ; }

PATH=/sbin:/bin
MYNAME="${0##*/}"
RUN_DIR=/run/resolvconf
IFACE_DIR="${RUN_DIR}/interface"
ENABLE_UPDATES_FLAGFILE="${RUN_DIR}/enable-updates"
POSTPONED_UPDATE_FLAGFILE="${RUN_DIR}/postponed-update"

report_err() { echo "${MYNAME}: Error: $*" >&2 ; }

# Check arguments
CMD="$1"
case "$CMD" in
-a|-d)
IFACE="$2"
if [ ! "$IFACE" ] ; then
report_err "No interface name specified"
echo_usage >&2
exit 1
fi
report_iface_err() {
report_err "$* not allowed in interface record name"
}
case "$IFACE" in
*/*) report_iface_err "Slash" ; exit 1 ;;
*" "*) report_iface_err "Space" ; exit 1 ;;
.*) report_iface_err "Initial dot" ; exit 1 ;;
-*) report_iface_err "Initial hyphen" ; exit 1 ;;
~*) report_iface_err "Initial tilde" ; exit 1 ;;
esac
;;
-u|--enable-updates|--disable-updates|--updates-are-enabled|--create-runtime-directories|--wipe-runtime-directories)
if [ "$2" ] ; then
report_err "The $CMD option does not take an argument"
echo_usage >&2
exit 1
fi
;;
*)
report_err "Command not recognized"
echo_usage >&2
exit 99
;;
esac

# Handle creation and wiping of run-time directories
case "$CMD" in
--create-runtime-directories)
umask 022
if [ ! -d "$RUN_DIR" ] ; then
# Create directory at the target
mkdir "$RUN_CANONICALDIR" || { report_err "Error creating directory $RUN_CANONICALDIR" ; exit 1 ; }
fi
# The resolvconf run directory now exists.
if [ ! -d "${RUN_DIR}/interface" ] ; then
mkdir "${RUN_DIR}/interface" || { report_err "Error creating directory ${RUN_DIR}/interface" ; exit 1 ; }
fi
# The interface directory now exists. We are done.
exit 0
;;
--wipe-runtime-directories)
# Delete files in the resolvconf run directory (target) but not the directory itself
[ -d "$RUN_DIR" ] || exit 0
rm -f "$RUN_DIR"/resolv.conf
rm -f "$ENABLE_UPDATES_FLAGFILE"
rm -f "$POSTPONED_UPDATE_FLAGFILE"
rm -rf "$IFACE_DIR"
exit 0
;;
esac

[ -d "$IFACE_DIR" ] || { report_err "$IFACE_DIR either does not exist or is not a directory" ; exit 1 ; }
cd "$IFACE_DIR"

update_and_exit()
{
rm -f "$POSTPONED_UPDATE_FLAGFILE"
exec run-parts ${1:+--arg="$1"} ${2:+--arg="$2"} /etc/resolvconf/update.d
}

# Handle commands that don't require normalized_stdin()

case "$CMD" in
-d)
if [ ! -e "$IFACE" ] ; then
exit 0
fi
if [ ! -s "$IFACE" ] ; then
rm -f "$IFACE"
exit 0
fi
rm -f "$IFACE"
if [ -e "$ENABLE_UPDATES_FLAGFILE" ] ; then
update_and_exit -d "$IFACE"
else
: >| "$POSTPONED_UPDATE_FLAGFILE"
exit 0
fi
;;
-u)
if [ -e "$ENABLE_UPDATES_FLAGFILE" ] ; then
update_and_exit -u
else
: >| "$POSTPONED_UPDATE_FLAGFILE"
exit 0
fi
;;
--enable-updates)
: >| "$ENABLE_UPDATES_FLAGFILE" || exit 1
if [ -e "$POSTPONED_UPDATE_FLAGFILE" ] ; then
(update_and_exit -u) || :
fi
exit 0
;;
--disable-updates)
rm -f "$POSTPONED_UPDATE_FLAGFILE" || :
rm -f "$ENABLE_UPDATES_FLAGFILE" || exit 1
exit 0
;;
--updates-are-enabled)
if [ -e "$ENABLE_UPDATES_FLAGFILE" ] ; then
exit 0
else
exit 1
fi
;;
esac

#
# The following function must EXACTLY the same in the resolvconf
# and test-normalization scripts. And the test must pass!
#
### BEGIN FUNCTION TO COPY TO THE test-normalization SCRIPT ###
#
# Echo stdin with:
# comments removed;
# initial and terminal whitespace removed;
# whitespace strings replaced by single blanks;
# leading zeroes removed from nameserver address fields;
# first set of zero fields in an IPv6 address collapsed to '::';
# empty lines removed.
normalized_stdin() {
sed \
-e 's/#.*$//' \
-e 's/[[:blank:]]\+$//' \
-e 's/^[[:blank:]]\+//' \
-e 's/[[:blank:]]\+/ /g' \
-e '/^nameserver/!b ENDOFCYCLE' \
-e 's/$/ /' \
-e 's/\([:. ]\)0\+/\10/g' \
-e 's/\([:. ]\)0\([123456789abcdefABCDEF][[:xdigit:]]*\)/\1\2/g' \
-e '/::/b ENDOFCYCLE; s/ \(0[: ]\)\+/ ::/' \
-e '/::/b ENDOFCYCLE; s/:\(0[: ]\)\+/::/' \
-e ': ENDOFCYCLE' \
- | \
sed \
-e 's/[[:blank:]]\+$//' \
-e '/^$/d'
}
### END FUNCTION TO COPY TO THE test-normalization SCRIPT ###

case "$CMD" in
-a)
OLD_CONTENT=""
[ -f "$IFACE" ] && OLD_CONTENT="$(cat "$IFACE")"
NEW_CONTENT="$(normalized_stdin)"
# Proceed only if content has changed. The test here can't
# eliminate 100% of redundant invocations of update scripts
# because we don't do any locking; however it certainly does
# eliminate most of them.
if [ "$NEW_CONTENT" = "$OLD_CONTENT" ] ; then
exit 0
fi
IFACE_TMPFILE="${IFACE}_new.$$"
cleanup() { rm -f "$IFACE_TMPFILE" ; }
trap cleanup EXIT
echo "$NEW_CONTENT" > "$IFACE_TMPFILE"
mv -f "$IFACE_TMPFILE" "$IFACE"

if [ -e "$ENABLE_UPDATES_FLAGFILE" ] ; then
update_and_exit -a "$IFACE"
else
: >| "$POSTPONED_UPDATE_FLAGFILE"
exit 0
fi
;;
esac

# Don't reach here
exit 99