resolved: allocate DNS scope for links only if the interface is up

For mDNS and LLMNR we already created the scopes only if the specific interfaces where actually up and suitable for
Multicasting. Add a similar (but weaker) logic for unicast DNS as well.

1 files changed, 20 insertions, 12 deletions

diff --git a/src/resolve/resolved-link.c b/src/resolve/resolved-link.c
index 1e8f88024b..a5033e322a 100644
--- a/src/resolve/resolved-link.c
+++ b/src/resolve/resolved-link.c
@@ -93,7 +93,8 @@ static void link_allocate_scopes(Link *l) {
 
         assert(l);
 
-        if (l->dns_servers) {
+        if (link_relevant(l, AF_UNSPEC, false) &&
+            l->dns_servers) {
                 if (!l->unicast_scope) {
                         r = dns_scope_new(l->manager, &l->unicast_scope, l, DNS_PROTOCOL_DNS, AF_UNSPEC);
                         if (r < 0)
@@ -102,7 +103,7 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->unicast_scope = dns_scope_free(l->unicast_scope);
 
-        if (link_relevant(l, AF_INET) &&
+        if (link_relevant(l, AF_INET, true) &&
             l->llmnr_support != RESOLVE_SUPPORT_NO &&
             l->manager->llmnr_support != RESOLVE_SUPPORT_NO) {
                 if (!l->llmnr_ipv4_scope) {
@@ -113,7 +114,7 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->llmnr_ipv4_scope = dns_scope_free(l->llmnr_ipv4_scope);
 
-        if (link_relevant(l, AF_INET6) &&
+        if (link_relevant(l, AF_INET6, true) &&
             l->llmnr_support != RESOLVE_SUPPORT_NO &&
             l->manager->llmnr_support != RESOLVE_SUPPORT_NO &&
             socket_ipv6_is_supported()) {
@@ -125,7 +126,7 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->llmnr_ipv6_scope = dns_scope_free(l->llmnr_ipv6_scope);
 
-        if (link_relevant(l, AF_INET) &&
+        if (link_relevant(l, AF_INET, true) &&
             l->mdns_support != RESOLVE_SUPPORT_NO &&
             l->manager->mdns_support != RESOLVE_SUPPORT_NO) {
                 if (!l->mdns_ipv4_scope) {
@@ -136,7 +137,7 @@ static void link_allocate_scopes(Link *l) {
         } else
                 l->mdns_ipv4_scope = dns_scope_free(l->mdns_ipv4_scope);
 
-        if (link_relevant(l, AF_INET6) &&
+        if (link_relevant(l, AF_INET6, true) &&
             l->mdns_support != RESOLVE_SUPPORT_NO &&
             l->manager->mdns_support != RESOLVE_SUPPORT_NO) {
                 if (!l->mdns_ipv6_scope) {
@@ -430,28 +431,35 @@ int link_update_monitor(Link *l) {
         return 0;
 }
 
-bool link_relevant(Link *l, int family) {
+bool link_relevant(Link *l, int family, bool multicast) {
         _cleanup_free_ char *state = NULL;
         LinkAddress *a;
 
         assert(l);
 
-        /* A link is relevant if it isn't a loopback or pointopoint
-         * device, has a link beat, can do multicast and has at least
-         * one relevant IP address */
+        /* A link is relevant for multicast traffic if it isn't a loopback or pointopoint device, has a link beat, can
+         * do multicast and has at least one relevant IP address */
 
-        if (l->flags & (IFF_LOOPBACK|IFF_POINTOPOINT|IFF_DORMANT))
+        if (l->flags & (IFF_LOOPBACK|IFF_DORMANT))
                 return false;
 
-        if ((l->flags & (IFF_UP|IFF_LOWER_UP|IFF_MULTICAST)) != (IFF_UP|IFF_LOWER_UP|IFF_MULTICAST))
+        if ((l->flags & (IFF_UP|IFF_LOWER_UP)) != (IFF_UP|IFF_LOWER_UP))
                 return false;
 
+        if (multicast) {
+                if (l->flags & IFF_POINTOPOINT)
+                        return false;
+
+                if ((l->flags & IFF_MULTICAST) != IFF_MULTICAST)
+                        return false;
+        }
+
         sd_network_link_get_operational_state(l->ifindex, &state);
         if (state && !STR_IN_SET(state, "unknown", "degraded", "routable"))
                 return false;
 
         LIST_FOREACH(addresses, a, l->addresses)
-                if (a->family == family && link_address_relevant(a))
+                if ((family == AF_UNSPEC || a->family == family) && link_address_relevant(a))
                         return true;
 
         return false;