File avahi-daemon-check-dns.sh of Package avahi.31309
#!/bin/sh
#
# If we have an unicast .local domain, we immediately disable avahi to avoid
# conflicts with the multicast IP4LL .local domain
PATH=/bin:/usr/bin:/sbin:/usr/sbin
RUNDIR="/var/run/avahi-daemon/"
DISABLE_TAG="$RUNDIR/disabled-for-unicast-local"
NS_CACHE="$RUNDIR/checked_nameservers"
AVAHI_DAEMON_DETECT_LOCAL=1
test -f /etc/default/avahi-daemon && . /etc/default/avahi-daemon
if [ "$AVAHI_DAEMON_DETECT_LOCAL" != "1" ]; then
exit 0
fi
ensure_rundir() {
if [ ! -d ${RUNDIR} ] ; then
mkdir -m 0755 -p ${RUNDIR}
chown avahi:avahi ${RUNDIR}
fi
}
log_disable_warning() {
if [ -x /usr/bin/logger ]; then
logger -p daemon.warning -t avahi <<EOF
Avahi detected that your currently configured local DNS server serves
a domain .local. This is inherently incompatible with Avahi and thus
Avahi stopped itself. If you want to use Avahi in this network, please
contact your administrator and convince him to use a different DNS domain,
since .local should be used exclusively for Zeroconf technology.
For more information, see http://avahi.org/wiki/AvahiAndUnicastDotLocal
EOF
fi
}
dns_reachable() {
# If there are no nameserver entries in resolv.conf there is no dns reachable
$(grep -q nameserver /etc/resolv.conf) || return 1;
# If there is no local nameserver and no we have no global ip addresses
# then we can't reach any nameservers
if ! $(egrep -q "nameserver 127.0.0.1|::1" /etc/resolv.conf); then
if [ -x "$(which ip)" ]; then
ADDRS=$(ip addr show scope global | grep inet)
ROUTES=$(ip route show 0.0.0.0/0)
elif [ -x "$(which ifconfig)" -a -x "$(which route)" ]; then
# Get addresses of all running interfaces
ADDRS=$(LC_ALL=C ifconfig | grep ' addr:')
# Filter out all local addresses
ADDRS=$(echo "${ADDRS}" | egrep -v ':127|Scope:Host|Scope:Link')
# Check we have a default route
ROUTES=$(route -n | grep '^0.0.0.0 ')
fi
if [ -z "${ADDRS}" -o -z "${ROUTES}" ] ; then
return 1;
fi
fi
return 0
}
dns_has_local() {
# Some magic to do tests
if [ -n "${FAKE_HOST_RETURN}" ] ; then
if [ "${FAKE_HOST_RETURN}" = "true" ]; then
return 0;
else
return 1;
fi
fi
# Use timeout when calling host as workaround for LP: #1752411
OUT=`LC_ALL=C timeout 5 host -t soa local. 2>&1`
if [ $? -eq 0 ] ; then
if echo "$OUT" | egrep -vq 'has no|not found'; then
return 0
fi
else
# Checking the dns servers failed. Assuming no .local unicast dns, but
# remove the nameserver cache so we recheck the next time we're triggered
rm -f ${NS_CACHE}
fi
return 1
}
dns_needs_check() {
TMP_CACHE="${NS_CACHE}.$$"
RET=0
ensure_rundir
cat /etc/resolv.conf | grep "nameserver" | sort > ${TMP_CACHE} || return 0
if [ -e ${NS_CACHE} ]; then
DIFFERENCE=$(diff -w ${NS_CACHE} ${TMP_CACHE})
echo "${DIFFERENCE}" | grep -q '^>'
ADDED=$?
echo "${DIFFERENCE}" | grep -q '^<'
REMOVED=$?
# Avahi was disabled and no servers were removed, no need to recheck
[ -e ${DISABLE_TAG} ] && [ ${REMOVED} -ne 0 ] && RET=1
# Avahi was enabled and no servers were added, no need to recheck
[ ! -e ${DISABLE_TAG} ] && [ ${ADDED} -ne 0 ] && RET=1
fi
mv ${TMP_CACHE} ${NS_CACHE}
return ${RET};
}
enable_avahi () {
# no unicast .local conflict, so remove the tag and start avahi again
if [ -e ${DISABLE_TAG} ]; then
rm -f ${DISABLE_TAG}
if [ -d /run/systemd/system ]; then
systemctl start avahi-daemon.socket avahi-daemon.service || true
elif [ -x "/etc/init.d/avahi-daemon" ]; then
/etc/init.d/avahi-daemon start || true
fi
fi
}
disable_avahi () {
[ -e ${DISABLE_TAG} ] && return
if [ -d /run/systemd/system ]; then
systemctl stop avahi-daemon.socket avahi-daemon.service || true
log_disable_warning
elif [ -x "/etc/init.d/avahi-daemon" ]; then
/etc/init.d/avahi-daemon stop || true
log_disable_warning
fi
ensure_rundir
touch ${DISABLE_TAG}
}
if ! dns_reachable ; then
# No unicast dns server reachable, so enable avahi
enable_avahi
# And blow away the dns cache, so we force a recheck when the interface comes
# up again
rm -f ${NS_CACHE}
exit 0
fi
# Check if the dns needs checking..
dns_needs_check || exit 0
if dns_has_local ; then
# .local from dns server, disabling avahi
disable_avahi
else
# no .local from dns server, enabling avahi
enable_avahi
fi
exit 0