connectivity: honor "main.systemd-resolved" setting to not resolve names first

If the user disabled systemd-resolved, two things seem apparent:

 - the user does not want us to use systemd-resolved

 - NetworkManager is not pushing the DNS configuration to
   systemd-resoved.

It seems to me, we should not consult systemd-resolved in that case.

4 files changed, 74 insertions, 36 deletions

diff --git a/man/NetworkManager.conf.xml b/man/NetworkManager.conf.xml
index 26de6f275a..65ebe013ad 100644
--- a/man/NetworkManager.conf.xml
+++ b/man/NetworkManager.conf.xml
@@ -402,11 +402,13 @@ no-auto-default=*
         <literal>systemd-resolved</literal>. Defaults to "<literal>true</literal>".
         </para>
         <para>Note that this setting is complementary to the
-        <varname>dns</varname> setting. You can keep this enable while using
+        <varname>dns</varname> setting. You can keep this enabled while using
         <varname>dns</varname> set to another DNS plugin alongside
         <literal>systemd-resolved</literal>, or <varname>dns</varname> set to
         <literal>systemd-resolved</literal> to configure the system resolver to use
         <literal>systemd-resolved</literal>.</para>
+        <para>If systemd-resolved is enabled, the connectivity check resolves the
+        hostname per-device.</para>
         </listitem>
       </varlistentry>
 
diff --git a/src/dns/nm-dns-manager.c b/src/dns/nm-dns-manager.c
index 5b02edb92d..1f1fe21317 100644
--- a/src/dns/nm-dns-manager.c
+++ b/src/dns/nm-dns-manager.c
@@ -344,6 +344,21 @@ _ip_config_lst_head (NMDnsManager *self)
 
 /*****************************************************************************/
 
+gboolean
+nm_dns_manager_has_systemd_resolved (NMDnsManager *self)
+{
+	NMDnsManagerPrivate *priv;
+
+	g_return_val_if_fail (NM_IS_DNS_MANAGER (self), FALSE);
+
+	priv = NM_DNS_MANAGER_GET_PRIVATE (self);
+
+	return    priv->sd_resolve_plugin
+	       || NM_IS_DNS_SYSTEMD_RESOLVED (priv->plugin);
+}
+
+/*****************************************************************************/
+
 static void
 add_string_item (GPtrArray *array, const char *str, gboolean dup)
 {
diff --git a/src/dns/nm-dns-manager.h b/src/dns/nm-dns-manager.h
index a3e9472e5f..7f6ed3edc6 100644
--- a/src/dns/nm-dns-manager.h
+++ b/src/dns/nm-dns-manager.h
@@ -129,6 +129,8 @@ typedef enum {
 
 void nm_dns_manager_stop (NMDnsManager *self);
 
+gboolean nm_dns_manager_has_systemd_resolved (NMDnsManager *self);
+
 /*****************************************************************************/
 
 char *nmtst_dns_create_resolv_conf (const char *const*searches,
diff --git a/src/nm-connectivity.c b/src/nm-connectivity.c
index ea4ea7189e..3703f7f269 100644
--- a/src/nm-connectivity.c
+++ b/src/nm-connectivity.c
@@ -23,7 +23,6 @@
 #include "nm-default.h"
 
 #include "nm-connectivity.h"
-#include "nm-dbus-manager.h"
 
 #include <string.h>
 
@@ -34,6 +33,8 @@
 #include "c-list/src/c-list.h"
 #include "nm-config.h"
 #include "NetworkManagerUtils.h"
+#include "nm-dbus-manager.h"
+#include "dns/nm-dns-manager.h"
 
 #define HEADER_STATUS_ONLINE "X-NetworkManager-Status: online\r\n"
 
@@ -114,9 +115,10 @@ typedef struct {
 	char *host;
 	char *port;
 	char *response;
-	gboolean enabled;
-	guint interval;
 	NMConfig *config;
+	guint interval;
+
+	bool enabled:1;
 } NMConnectivityPrivate;
 
 struct _NMConnectivity {
@@ -728,43 +730,60 @@ nm_connectivity_check_start (NMConnectivity *self,
 
 #if WITH_CONCHECK
 	if (iface && ifindex > 0 && priv->enabled && priv->host) {
-		GDBusConnection *dbus_connection;
+		gboolean has_systemd_resolved;
 
 		cb_data->concheck.ifindex = ifindex;
 
-		dbus_connection = nm_dbus_manager_get_dbus_connection (nm_dbus_manager_get ());
-		if (!dbus_connection) {
-			/* we have no D-Bus connection? That might happen in configure and quit mode.
-			 *
-			 * Anyway, something is very odd, just fail connectivity check. */
-			_LOG2D ("start fake request (fail due to no D-Bus connection)");
-			cb_data->fail_reason_no_dbus_connection = TRUE;
-			cb_data->timeout_id = g_idle_add (_idle_cb, cb_data);
-			return cb_data;
+		/* note that we pick up support for systemd-resolved right away when we need it.
+		 * We don't need to remember the setting, because we can (cheaply) check anew
+		 * on each request.
+		 *
+		 * Yes, this makes NMConnectivity singleton dependent on NMDnsManager singleton.
+		 * Well, not really: it makes connectivity-check-start dependent on NMDnsManager
+		 * which merely means, not to start a connectivity check, late during shutdown. */
+		has_systemd_resolved = nm_dns_manager_has_systemd_resolved (nm_dns_manager_get ());
+
+		if (has_systemd_resolved) {
+			GDBusConnection *dbus_connection;
+
+			dbus_connection = nm_dbus_manager_get_dbus_connection (nm_dbus_manager_get ());
+			if (!dbus_connection) {
+				/* we have no D-Bus connection? That might happen in configure and quit mode.
+				 *
+				 * Anyway, something is very odd, just fail connectivity check. */
+				_LOG2D ("start fake request (fail due to no D-Bus connection)");
+				cb_data->fail_reason_no_dbus_connection = TRUE;
+				cb_data->timeout_id = g_idle_add (_idle_cb, cb_data);
+				return cb_data;
+			}
+
+			cb_data->concheck.resolve_cancellable = g_cancellable_new ();
+
+			g_dbus_connection_call (nm_dbus_manager_get_dbus_connection (nm_dbus_manager_get ()),
+			                        "org.freedesktop.resolve1",
+			                        "/org/freedesktop/resolve1",
+			                        "org.freedesktop.resolve1.Manager",
+			                        "ResolveHostname",
+			                        g_variant_new ("(isit)",
+			                                       (gint32) cb_data->concheck.ifindex,
+			                                       priv->host,
+			                                       (gint32) cb_data->addr_family,
+			                                       SD_RESOLVED_DNS),
+			                        G_VARIANT_TYPE ("(a(iiay)st)"),
+			                        G_DBUS_CALL_FLAGS_NONE,
+			                        -1,
+			                        cb_data->concheck.resolve_cancellable,
+			                        resolve_cb,
+			                        cb_data);
+			_LOG2D ("start request to '%s' (try resolving '%s' using systemd-resolved)",
+			        priv->uri,
+			        priv->host);
+		} else {
+			_LOG2D ("start request to '%s' (systemd-resolved not available)",
+			        priv->uri);
+			do_curl_request (cb_data);
 		}
 
-		cb_data->concheck.resolve_cancellable = g_cancellable_new ();
-
-		g_dbus_connection_call (nm_dbus_manager_get_dbus_connection (nm_dbus_manager_get ()),
-		                        "org.freedesktop.resolve1",
-		                        "/org/freedesktop/resolve1",
-		                        "org.freedesktop.resolve1.Manager",
-		                        "ResolveHostname",
-		                        g_variant_new ("(isit)",
-		                                       (gint32) cb_data->concheck.ifindex,
-		                                       priv->host,
-		                                       (gint32) cb_data->addr_family,
-		                                       SD_RESOLVED_DNS),
-		                        G_VARIANT_TYPE ("(a(iiay)st)"),
-		                        G_DBUS_CALL_FLAGS_NONE,
-		                        -1,
-		                        cb_data->concheck.resolve_cancellable,
-		                        resolve_cb,
-		                        cb_data);
-
-		_LOG2D ("start request to '%s' (try resolving '%s' using systemd-resolved)",
-		        priv->uri,
-		        priv->host);
 		return cb_data;
 	}
 #endif