start: unify and simplify network creation

Make sure that network creation happens at the same time for containers started
by privileged and unprivileged users. The only reason we didn't do this so far
was to avoid sending network device ifindices around in the privileged case.

Link: #3066
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/conf.c

@@ -3563,16 +3563,19 @@ int lxc_setup(struct lxc_handler *handler)
 	if (ret < 0)
 		return -1;
 
-	ret = lxc_setup_network_in_child_namespaces(lxc_conf, &lxc_conf->network);
-	if (ret < 0) {
-		ERROR("Failed to setup network");
-		return -1;
-	}
+	if (handler->ns_clone_flags & CLONE_NEWNET) {
+		ret = lxc_setup_network_in_child_namespaces(lxc_conf,
+							    &lxc_conf->network);
+		if (ret < 0) {
+			ERROR("Failed to setup network");
+			return -1;
+		}
 
-	ret = lxc_network_send_name_and_ifindex_to_parent(handler);
-	if (ret < 0) {
-		ERROR("Failed to send network device names and ifindices to parent");
-		return -1;
+		ret = lxc_network_send_name_and_ifindex_to_parent(handler);
+		if (ret < 0) {
+			ERROR("Failed to send network device names and ifindices to parent");
+			return -1;
+		}
 	}
 
 	if (lxc_conf->autodev > 0) {