resolved: add global config option to control mDNS stack

man/resolved.conf.xml

@@ -126,6 +126,21 @@
         global setting is on.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>MulticastDNS=</varname></term>
+        <listitem><para>Takes a boolean argument or
+        <literal>resolve</literal>. Controls Multicast DNS support (<ulink
+        url="https://tools.ietf.org/html/rfc6762">RFC 6762</ulink>) on
+        the local host. If true, enables full Multicast DNS responder and
+        resolver support. If false, disables both. If set to
+        <literal>resolve</literal>, only resolution support is enabled,
+        but responding is disabled. Note that
+        <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+        also maintains per-link Multicast DNS settings. Multicast DNS will be
+        enabled on a link only if the per-link and the
+        global setting is on.</para></listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><varname>DNSSEC=</varname></term>
         <listitem><para>Takes a boolean argument or

src/resolve/resolved-gperf.gperf

@@ -18,6 +18,7 @@ Resolve.DNS,             config_parse_dns_servers,            DNS_SERVER_SYSTEM,
 Resolve.FallbackDNS,     config_parse_dns_servers,            DNS_SERVER_FALLBACK, 0
 Resolve.Domains,         config_parse_search_domains,         0,                   0
 Resolve.LLMNR,           config_parse_resolve_support,        0,                   offsetof(Manager, llmnr_support)
+Resolve.MulticastDNS,    config_parse_resolve_support,        0,                   offsetof(Manager, mdns_support)
 Resolve.DNSSEC,          config_parse_dnssec_mode,            0,                   offsetof(Manager, dnssec_mode)
 Resolve.Cache,           config_parse_bool,                   0,                   offsetof(Manager, enable_cache)
 Resolve.DNSStubListener, config_parse_dns_stub_listener_mode, 0,                   offsetof(Manager, dns_stub_listener_mode)

src/resolve/resolved.conf.in

@@ -16,6 +16,7 @@
 #FallbackDNS=@DNS_SERVERS@
 #Domains=
 #LLMNR=yes
+#MulticastDNS=yes
 #DNSSEC=@DEFAULT_DNSSEC_MODE@
 #Cache=yes
 #DNSStubListener=udp