From e5e2e46300e263e9364a93807742004e95c3bc56 Mon Sep 17 00:00:00 2001
From: Franco Fichtner <franco@opnsense.org>
Date: Fri, 22 Oct 2021 10:03:13 +0200
Subject: [PATCH] dhcp: clarify code around is_linklocal() conditional

---
 src/etc/inc/plugins.inc.d/dhcpd.inc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/etc/inc/plugins.inc.d/dhcpd.inc b/src/etc/inc/plugins.inc.d/dhcpd.inc
index 28c17f963..8ce0b1b08 100644
--- a/src/etc/inc/plugins.inc.d/dhcpd.inc
+++ b/src/etc/inc/plugins.inc.d/dhcpd.inc
@@ -308,11 +308,17 @@ function dhcpd_radvd_configure($verbose = false, $blacklist = array())
             $radvdconf .= "\tAdvDefaultLifetime 0;\n";
         }
 
+        /*
+         * Only a CARP VIP can inject a link-local address and it
+         * means we need to force that address into the RA message
+         * for failover to work.
+         */
         if (is_linklocal($ifcfgipv6)) {
-            $radvdconf .= "\tAdvSourceLLAddress off;\n";
             $radvdconf .= "\tAdvRASrcAddress {\n";
             $radvdconf .= "\t\t{$ifcfgipv6};\n";
             $radvdconf .= "\t};\n";
+            /* to avoid wrong MAC being stuck in failover case only */
+            $radvdconf .= "\tAdvSourceLLAddress off;\n";
         }
 
         $stanzas = array();