From f95cdedfaab81d783d641b7bc74e82bdafa0504b Mon Sep 17 00:00:00 2001
From: Lars Ekman <lars.g.ekman@est.tech>
Date: Sat, 27 Oct 2018 05:51:38 +0200
Subject: [PATCH] Improved detect in ipv6IsEnabled() (#555)

* Improved detect in ipv6IsEnabled()

* Added comments in ipv6IsEnabled.

Problem described in #155
---
 pkg/controllers/routing/utils.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/pkg/controllers/routing/utils.go b/pkg/controllers/routing/utils.go
index 2bf53d25..c05dc13a 100644
--- a/pkg/controllers/routing/utils.go
+++ b/pkg/controllers/routing/utils.go
@@ -83,7 +83,14 @@ func ipv4IsEnabled() bool {
 }
 
 func ipv6IsEnabled() bool {
-	l, err := net.Listen("tcp6", "")
+	// If ipv6 is disabled with;
+	//
+	//  sysctl -w net.ipv6.conf.all.disable_ipv6=1
+	//
+	// It is still possible to listen on the any-address "::". So this
+	// function tries the loopback address "::1" which must be present
+	// if ipv6 is enabled.
+	l, err := net.Listen("tcp6", "[::1]:0")
 	if err != nil {
 		return false
 	}