From 767d814636706aea175f7b5faf1dbe433d30c950 Mon Sep 17 00:00:00 2001
From: Franco Fichtner <franco@opnsense.org>
Date: Tue, 23 Nov 2021 16:16:47 +0100
Subject: [PATCH] interfaces: on a device node there is no parent to use

Seems to have been in the code for a while.  dhcp6usev4iface should
have probably been the default all along since otherwise this seeps
into the default mode on IPv6 causing it to fail.
---
 src/etc/inc/interfaces.inc | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/etc/inc/interfaces.inc b/src/etc/inc/interfaces.inc
index fead5d8ae..b306eed50 100644
--- a/src/etc/inc/interfaces.inc
+++ b/src/etc/inc/interfaces.inc
@@ -3713,10 +3713,10 @@ function get_real_interface($interface = 'wan', $family = 'all')
                             case 'ppp':
                             case 'l2tp':
                             case 'pptp':
-                                if (isset($cfg['dhcp6usev4iface'])) {
+                                list ($realif) = get_parent_interface($interface);
+                                if (isset($cfg['dhcp6usev4iface']) || strpos($realif, '/') === 0) {
+                                    /* parent interface not usable on user request or if device node */
                                     $realif = $cfg['if'];
-                                } else {
-                                    list ($realif) = get_parent_interface($interface);
                                 }
                                 break;
                             default: