/usr/lib/avahi/avahi-daemon-check-dns.sh is in avahi-daemon 0.6.31-4ubuntu1.3.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 | #!/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
}
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 ! $(egrep -q "nameserver 127.0.0.1|::1" /etc/resolv.conf); then
# Get addresses of all running interfaces
ADDRS=$(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=$(route -n | grep '^0.0.0.0 ')
if [ -z "${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
OUT=`LC_ALL=C 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 [ -x "`which invoke-rc.d 2>/dev/null`" ]; then
invoke-rc.d avahi-daemon start || true
else
if [ -x "/etc/init.d/avahi-daemon" ]; then
/etc/init.d/avahi-daemon start || true
fi
fi
fi
}
disable_avahi () {
[ -e ${DISABLE_TAG} ] && return
if [ -x /etc/init.d/avahi-daemon ]; then
if [ -x "`which invoke-rc.d 2>/dev/null`" ]; then
invoke-rc.d --force avahi-daemon stop || true
else
if [ -x "/etc/init.d/avahi-daemon" ]; then
/etc/init.d/avahi-daemon stop || true
fi
fi
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 disabled 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
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
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