From 612a8bf34e7d48164506fb968792b22f62c6411b Mon Sep 17 00:00:00 2001
From: MickLesk <mickey.leskowitz@gmail.com>
Date: Sun, 22 Mar 2026 20:43:28 +0100
Subject: [PATCH] fix(build): guard against empty IPv6 address in static mode

Prevents 'net0: invalid format' when IPv6 method is static but
IPV6_ADDR is empty. Fixes #13178.
---
 misc/build.func | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/misc/build.func b/misc/build.func
index 6819744b4..40881d795 100644
--- a/misc/build.func
+++ b/misc/build.func
@@ -3544,8 +3544,10 @@ build_container() {
   auto) NET_STRING="$NET_STRING,ip6=auto" ;;
   dhcp) NET_STRING="$NET_STRING,ip6=dhcp" ;;
   static)
-    NET_STRING="$NET_STRING,ip6=$IPV6_ADDR"
-    [ -n "$IPV6_GATE" ] && NET_STRING="$NET_STRING,gw6=$IPV6_GATE"
+    if [[ -n "$IPV6_ADDR" ]]; then
+      NET_STRING="$NET_STRING,ip6=$IPV6_ADDR"
+      [ -n "$IPV6_GATE" ] && NET_STRING="$NET_STRING,gw6=$IPV6_GATE"
+    fi
     ;;
   none) ;;
   esac