isc-dhcp: detect whether ddns transfers are IPv4 only

If named is configured to not listen on any IPv6 interfaces,
then we should run 'nsupdate' with the '-4' argument.

Also:

* cleanup RFC-1918 address detection;
* don't generate PTR records for domain entries that aren't
  RFC-1918 addresses or these will generate NOTAUTH failures;

We're assuming that we're doing DNS split-horizon and that
internal addresses aren't routable.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

diff --git a/net/isc-dhcp/files/dhcpd.init b/net/isc-dhcp/files/dhcpd.init
index 4309d5af5b47ed1abb409c023711648ecb434728..e3dcdfdd2387eefc4f676d5c8a9e6096ec69bcc2 100755 (executable)
--- a/net/isc-dhcp/files/dhcpd.init
+++ b/net/isc-dhcp/files/dhcpd.init
@@ -46,13 +46,31 @@ time2seconds() {
        echo $(( number * multiplier ))
 }
 
-trim()
-{
+trim() {
        local arg="$1"
 
        echo "$arg" | sed -e 's/^ *//' -e 's/ *$//'
 }
 
+rfc1918_prefix() {
+       local octets="$(echo "${1%%/*}" | cut -d. -f1)"
+
+       [ "$octets" = "10" ] && { echo "$octets"; return; }
+
+       octets="$(echo "${1%%/*}" | cut -d. -f1-2)"
+
+       case "$octets" in
+       172.1[6789]|172.2[0-9]|172.3[01]|192.168)
+               echo "$octets"
+               ;;
+       esac
+}
+
+no_ipv6() {
+       [ -n "$(named-checkconf -px \
+               | sed -r -ne '1N; N; /^\tlisten-on-v6  ?\{\n\t\t"none";\n\t\};$/{ p; q; }; D')" ]
+}
+
 # duplicated from dnsmasq init script
 hex_to_hostid() {
        local var="$1"
@@ -200,7 +218,8 @@ static_domain_add() {
                revip="$(rev_str "$ip" ".")"
 
                update "$name.$domain." IN A "$ip"
-               update "$revip.in-addr.arpa." IN PTR "$name.$domain."
+               [ -n "$(rfc1918_prefix "$ip")" ] && \
+                       update "$revip.in-addr.arpa." IN PTR "$name.$domain."
        done
 }
 
@@ -377,15 +396,10 @@ dhcpd_add() {
 
        [ static = "$proto" ] || return 0
 
-       local pair="$(echo "${subnet%%/*}" | cut -d. -f1-2)"
-       case "$pair" in
-       10.*)
-               rfc1918_nets="$rfc1918_nets${rfc1918_nets:+ }10"
-               ;;
-       172.1[6789]|172.2[0-9]|172.3[01]|192.168)
-               rfc1918_nets="$rfc1918_nets${rfc1918_nets:+ }$pair"
-               ;;
-       esac
+       local octets="$(rfc1918_prefix "$subnet")"
+
+       [ -n "$octets" ] && rfc1918_nets="$rfc1918_nets${rfc1918_nets:+ }$octets"
+
        [ $synthesize -eq 0 ] && return
 
        config_get_bool dynamicdhcp "$cfg" "dynamicdhcp" 1
@@ -583,7 +597,12 @@ EOF
                static_srvhosts >> $config_file
 
                if [ $dynamicdns -eq 1 ]; then
-                       nsupdate -l -v $dyn_file
+                       local args=
+
+                       no_ipv6 && args="-4"
+
+                       nsupdate -l -v $args $dyn_file
+
                fi
 
                rm -f $dyn_file