dns: fix negative ipv4.dns-priority for systemd-resolved

A negative ipv4.dns-priority and ipv6.dns-priority has the meaning to configure
the DNS information of the connection exclusively. With systemd-resolved, that means
we must explicitly unset the configuration from other interfaces.

https://bugzilla.gnome.org/show_bug.cgi?id=783569
(cherry picked from commit 70792e51d94a5e7790b3e65b7d6cf591b251f4cd)

4 files changed, 30 insertions, 14 deletions

diff --git a/src/dns/nm-dns-dnsmasq.c b/src/dns/nm-dns-dnsmasq.c
index 33cda8371b..67aae6f431 100644
--- a/src/dns/nm-dns-dnsmasq.c
+++ b/src/dns/nm-dns-dnsmasq.c
@@ -561,6 +561,8 @@ update (NMDnsPlugin *plugin,
 	NMDnsDnsmasq *self = NM_DNS_DNSMASQ (plugin);
 	NMDnsDnsmasqPrivate *priv = NM_DNS_DNSMASQ_GET_PRIVATE (self);
 	GVariantBuilder servers;
+	guint i;
+	int prio, first_prio;
 
 	start_dnsmasq (self);
 
@@ -569,9 +571,13 @@ update (NMDnsPlugin *plugin,
 	if (global_config)
 		add_global_config (self, &servers, global_config);
 	else {
-		while (*configs) {
-			add_ip_config_data (self, &servers, *configs);
-			configs++;
+		for (i = 0; configs[i]; i++) {
+			prio = nm_dns_ip_config_data_get_dns_priority (configs[i]);
+			if (i == 0)
+				first_prio = prio;
+			else if (first_prio < 0 && first_prio != prio)
+				break;
+			add_ip_config_data (self, &servers, configs[i]);
 		}
 	}
 
diff --git a/src/dns/nm-dns-manager.c b/src/dns/nm-dns-manager.c
index 6e567e5d4a..c99ed112d4 100644
--- a/src/dns/nm-dns-manager.c
+++ b/src/dns/nm-dns-manager.c
@@ -1041,10 +1041,10 @@ _collect_resolv_conf_data (NMDnsManager *self, /* only for logging context, no o
 				       get_nameserver_list (current->config, &tmp_gstring));
 			}
 
-			if (!skip) {
+			if (!skip)
 				merge_one_ip_config_data (&rc, current);
-				plugin_confs[j++] = current;
-			}
+
+			plugin_confs[j++] = current;
 		}
 		plugin_confs[j++] = NULL;
 	}
diff --git a/src/dns/nm-dns-plugin.c b/src/dns/nm-dns-plugin.c
index 460093440c..740ff26bab 100644
--- a/src/dns/nm-dns-plugin.c
+++ b/src/dns/nm-dns-plugin.c
@@ -84,7 +84,7 @@ nm_dns_plugin_update (NMDnsPlugin *self,
 	g_return_val_if_fail (NM_DNS_PLUGIN_GET_CLASS (self)->update != NULL, FALSE);
 
 	return NM_DNS_PLUGIN_GET_CLASS (self)->update (self,
-	                                               configs,
+	                                               configs ?: NM_PTRARRAY_EMPTY (const NMDnsIPConfigData *),
 	                                               global_config,
 	                                               hostname);
 }
diff --git a/src/dns/nm-dns-systemd-resolved.c b/src/dns/nm-dns-systemd-resolved.c
index a943e572d9..f49aed57da 100644
--- a/src/dns/nm-dns-systemd-resolved.c
+++ b/src/dns/nm-dns-systemd-resolved.c
@@ -102,7 +102,8 @@ call_done (GObject *source, GAsyncResult *r, gpointer user_data)
 static void
 add_interface_configuration (NMDnsSystemdResolved *self,
                              GArray *interfaces,
-                             const NMDnsIPConfigData *data)
+                             const NMDnsIPConfigData *data,
+                             gboolean skip)
 {
 	int i;
 	InterfaceConfig *ic = NULL;
@@ -130,7 +131,8 @@ add_interface_configuration (NMDnsSystemdResolved *self,
 		ic->ifindex = ifindex;
 	}
 
-	ic->configs = g_list_append (ic->configs, data->config);
+	if (!skip)
+		ic->configs = g_list_append (ic->configs, data->config);
 }
 
 static void
@@ -294,11 +296,19 @@ update (NMDnsPlugin *plugin,
 {
 	NMDnsSystemdResolved *self = NM_DNS_SYSTEMD_RESOLVED (plugin);
 	GArray *interfaces = g_array_new (TRUE, TRUE, sizeof (InterfaceConfig));
-	const NMDnsIPConfigData *const*c;
-	int i;
-
-	for (c = configs; *c != NULL; c++)
-		add_interface_configuration (self, interfaces, *c);
+	guint i;
+	int prio, first_prio = 0;
+
+	for (i = 0; configs[i]; i++) {
+		gboolean skip = FALSE;
+
+		prio = nm_dns_ip_config_data_get_dns_priority (configs[i]);
+		if (i == 0)
+			first_prio = prio;
+		else if (first_prio < 0 && first_prio != prio)
+			skip = TRUE;
+		add_interface_configuration (self, interfaces, configs[i], skip);
+	}
 
 	free_pending_updates (self);