resolved: automatically forget all learnt DNS server information when the network configuration changes

When the network configuration changes we should relearn everything
there is to know about the configured DNS servers, because we might talk
to the same addresses, but there might be different servers behind them.

1 files changed, 19 insertions, 2 deletions

diff --git a/src/resolve/resolved-link.c b/src/resolve/resolved-link.c
index 21fd8465e6..3d26831b06 100644
--- a/src/resolve/resolved-link.c
+++ b/src/resolve/resolved-link.c
@@ -111,13 +111,30 @@ Link *link_free(Link *l) {
 }
 
 void link_allocate_scopes(Link *l) {
+        bool unicast_relevant;
         int r;
 
         assert(l);
 
-        if (link_relevant(l, AF_UNSPEC, false) &&
-            l->dns_servers) {
+        /* If a link that used to be relevant is no longer, or a link that did not use to be relevant now becomes
+         * relevant, let's reinit the learnt global DNS server information, since we might talk to different servers
+         * now, even if they have the same addresses as before. */
+
+        unicast_relevant = link_relevant(l, AF_UNSPEC, false);
+        if (unicast_relevant != l->unicast_relevant) {
+                l->unicast_relevant = unicast_relevant;
+
+                dns_server_reset_features_all(l->manager->fallback_dns_servers);
+                dns_server_reset_features_all(l->manager->dns_servers);
+        }
+
+        /* And now, allocate all scopes that makes sense now if we didn't have them yet, and drop those which we don't
+         * need anymore */
+
+        if (unicast_relevant && l->dns_servers) {
                 if (!l->unicast_scope) {
+                        dns_server_reset_features_all(l->dns_servers);
+
                         r = dns_scope_new(l->manager, &l->unicast_scope, l, DNS_PROTOCOL_DNS, AF_UNSPEC);
                         if (r < 0)
                                 log_warning_errno(r, "Failed to allocate DNS scope: %m");