resolved: add code to join/leave mDNS multicast groups

Per link, join the mDNS multicast groups when the scope is created, and
leave it again when the scope goes away.

3 files changed, 25 insertions, 7 deletions

diff --git a/src/resolve/resolved-dns-packet.h b/src/resolve/resolved-dns-packet.h
index 1d275f8110..48b3572cb4 100644
--- a/src/resolve/resolved-dns-packet.h
+++ b/src/resolve/resolved-dns-packet.h
@@ -225,6 +225,9 @@ DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 #define LLMNR_MULTICAST_IPV6_ADDRESS ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x03 } })
 
+#define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
+#define MDNS_MULTICAST_IPV6_ADDRESS  ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0xfb } })
+
 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
         uint64_t f;
 
diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index a90692cdf4..10148cb08e 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -59,6 +59,7 @@ int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int
         LIST_PREPEND(scopes, m->dns_scopes, s);
 
         dns_scope_llmnr_membership(s, true);
+        dns_scope_mdns_membership(s, true);
 
         log_debug("New scope on link %s, protocol %s, family %s", l ? l->name : "*", dns_protocol_to_string(protocol), family == AF_UNSPEC ? "*" : af_to_name(family));
 
@@ -95,6 +96,7 @@ DnsScope* dns_scope_free(DnsScope *s) {
         log_debug("Removing scope on link %s, protocol %s, family %s", s->link ? s->link->name : "*", dns_protocol_to_string(s->protocol), s->family == AF_UNSPEC ? "*" : af_to_name(s->family));
 
         dns_scope_llmnr_membership(s, false);
+        dns_scope_mdns_membership(s, false);
         dns_scope_abort_transactions(s);
 
         while (s->query_candidates)
@@ -477,19 +479,15 @@ int dns_scope_good_key(DnsScope *s, DnsResourceKey *key) {
         return true;
 }
 
-int dns_scope_llmnr_membership(DnsScope *s, bool b) {
+static int dns_scope_multicast_membership(DnsScope *s, bool b, struct in_addr in, struct in6_addr in6) {
         int fd;
 
         assert(s);
-
-        if (s->protocol != DNS_PROTOCOL_LLMNR)
-                return 0;
-
         assert(s->link);
 
         if (s->family == AF_INET) {
                 struct ip_mreqn mreqn = {
-                        .imr_multiaddr = LLMNR_MULTICAST_IPV4_ADDRESS,
+                        .imr_multiaddr = in,
                         .imr_ifindex = s->link->ifindex,
                 };
 
@@ -508,7 +506,7 @@ int dns_scope_llmnr_membership(DnsScope *s, bool b) {
 
         } else if (s->family == AF_INET6) {
                 struct ipv6_mreq mreq = {
-                        .ipv6mr_multiaddr = LLMNR_MULTICAST_IPV6_ADDRESS,
+                        .ipv6mr_multiaddr = in6,
                         .ipv6mr_interface = s->link->ifindex,
                 };
 
@@ -527,6 +525,22 @@ int dns_scope_llmnr_membership(DnsScope *s, bool b) {
         return 0;
 }
 
+int dns_scope_llmnr_membership(DnsScope *s, bool b) {
+
+        if (s->protocol != DNS_PROTOCOL_LLMNR)
+                return 0;
+
+        return dns_scope_multicast_membership(s, b, LLMNR_MULTICAST_IPV4_ADDRESS, LLMNR_MULTICAST_IPV6_ADDRESS);
+}
+
+int dns_scope_mdns_membership(DnsScope *s, bool b) {
+
+        if (s->protocol != DNS_PROTOCOL_MDNS)
+                return 0;
+
+        return dns_scope_multicast_membership(s, b, MDNS_MULTICAST_IPV4_ADDRESS, MDNS_MULTICAST_IPV6_ADDRESS);
+}
+
 static int dns_scope_make_reply_packet(
                 DnsScope *s,
                 uint16_t id,
diff --git a/src/resolve/resolved-dns-scope.h b/src/resolve/resolved-dns-scope.h
index 15d9a1fd6f..2fc2e07deb 100644
--- a/src/resolve/resolved-dns-scope.h
+++ b/src/resolve/resolved-dns-scope.h
@@ -93,6 +93,7 @@ DnsServer *dns_scope_get_dns_server(DnsScope *s);
 void dns_scope_next_dns_server(DnsScope *s);
 
 int dns_scope_llmnr_membership(DnsScope *s, bool b);
+int dns_scope_mdns_membership(DnsScope *s, bool b);
 
 void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p);