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#!/bin/sh
# Copyright (c) 2025 Roy Marples
# All rights reserved
# resolvectl subscriber for resolvconf
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * 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
# OWNER 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.
[ -f "@SYSCONFDIR@"/resolvconf.conf ] || exit 0
. "@SYSCONFDIR@/resolvconf.conf" || exit 1
case "${resolvectl:-NO}" in
[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|[Oo][Nn]|1) ;;
*) exit 0;;
esac
# If we don't have resolvectl or systemd-resolved isn't running then
# we can't do much.
# We can't persist our data in /run/systemd/resolve/netif/$ifindex
# because systemd-resolved keeps it somehow, ie we can't change it
# once we have inserted it
if ! [ -d /sys/class/net ] || \
! type resolvectl >/dev/null 2>&1 || \
! pidof systemd-resolved >/dev/null
then
exit 1
fi
# resolvectl only accepts resolv.conf setup per physical interface
# although resolvconf has always hinted that the named configuration
# should be $interface.$protocol, this has never been a fixed requirement.
# Because resolvectl only accepts one configuration per interface we need
# to try and merge the resolv.conf's together.
# Luckily resolvconf makes this easy for us.
# Returns a list of resolvconf entries for a real interface
get_resolvconf_interfaces() {
IFACE="$1"
[ -d /sys/class/net/"$IFACE" ] || return 1
IFACES=
for IFACE_PROTO in $(@SBINDIR@/resolvconf -Li "$IFACE" "$IFACE.*" 2>/dev/null); do
# ens5 will work with ens5.dhcp and ens5.ra,
# but not ens5.5 or ens5.5.dhcp
if [ "$IFACE_PROTO" != "$IFACE" ]; then
# Ensure that ens5.5.dhcp doesn't work for ens5
if [ "${IFACE_PROTO%.*}" != "$IFACE" ]; then
continue
fi
# Ensure that ens5.dhcp isn't a real interface
# as ens5.5 likely is and the .5 matches the .dhcp
if [ -d /sys/class/net/"$IFACE_PROTO" ]; then
continue
fi
fi
IFACES="$IFACES${IFACES:+ }$IFACE_PROTO"
done
echo "$IFACES"
}
# For the given interface, apply a list of resolvconf entries
apply_resolvconf() {
IFACE="$1"
shift
if [ -z "$1" ]; then
resolvectl revert "$IFACE"
return
fi
# Set the default-route property first to avoid leakage.
# If any entry is private, the whole interface has to be private.
# If a more granular approach is needed, consider using the
# systemd-resolved subscriber instead which supports DNS delegates.
if [ -n "$(@SBINDIR@/resolvconf -p $@)" ]; then
resolvectl default-route "$IFACE" false
else
resolvectl default-route "$IFACE" true
fi
# Now set domain and dns
DOMAIN=$(@SBINDIR@/resolvconf -L $@ 2>/dev/null | sed -n -e "s/domain //p" -e "s/search //p")
NS=$(@SBINDIR@/resolvconf -L $@ 2>/dev/null | sed -n -e "s/nameserver //p")
if [ -n "$DOMAIN" ]; then
# If any entry is marked as not searchable, we mark all the
# domains as non searchable.
# If a more granular approach is needed, consider using the
# systemd-resolved subscriber instead which supports DNS delegates.
if [ -n "$(@SBINDIR@/resolvconf -pp $@)" ]; then
ND=
for d in $DOMAIN; do
ND="$ND${ND:+ }~$d"
done
DOMAIN="$ND"
fi
resolvectl domain "$IFACE" $DOMAIN
else
resolvectl domain "$IFACE" ""
fi
if [ -n "$NS" ]; then
resolvectl dns "$IFACE" $NS
else
resolvectl dns "$IFACE" ""
fi
}
# To get the full features of resolvconf, we need to work out each interface
# for every resolvconf addition and deletion
# This is because resolvconf.conf might have changed OR an exclusive
# interface deleted which makes other interfaces visible.
cd /sys/class/net
for IFACE in *; do
if [ "$IFACE" = lo ]; then
# systemd-resolved doesn't work with lo
continue
fi
IFACES=$(get_resolvconf_interfaces "$IFACE")
apply_resolvconf "$IFACE" $IFACES
done
# warn about resolv.conf with no matching interface
FAILED=
for IFACE_PROTO in $(@SBINDIR@/resolvconf -Li); do
IFACE="${IFACE_PROTO%.*}"
if [ "$IFACE" = lo ]; then
# Don't warn about loopback interface as that is typically
# used to configure libc for a nameserver on it and the libc
# subscriber will process that just fine.
continue
fi
if ! [ -d "/sys/class/net/$IFACE" ]; then
FAILED="$FAILED${FAILED:+ }$IFACE_PROTO"
fi
done
if [ -n "$FAILED" ]; then
echo "Could not apply resolv.conf to resolvectl: $FAILED" >&2
fi
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