Fix IPV6 detection

.travis.yml

@@ -5,6 +5,13 @@ sudo: required
 services:
   - docker
 
+# FIXME(#46924): these two commands are required to enable IPv6,
+# they shouldn't exist, please revert once more official solutions appeared.
+# see https://github.com/travis-ci/travis-ci/issues/8891#issuecomment-353403729
+before_install:
+  - echo '{"ipv6":true,"fixed-cidr-v6":"2001:db8:1::/64"}' | sudo tee /etc/docker/daemon.json
+  - sudo service docker restart
+
 language: generic
 
 notifications:

internal/net/net.go

@@ -24,7 +24,7 @@ import (
 
 // IsIPV6 checks if the input contains a valid IPV6 address
 func IsIPV6(ip _net.IP) bool {
-	return ip.To4() == nil
+	return ip != nil && ip.To4() == nil
 }
 
 // IsPortAvailable checks if a TCP port is available or not
@@ -37,8 +37,25 @@ func IsPortAvailable(p int) bool {
 	return false
 }
 
-// IsIPv6Enabled checks if IPV6 is enabled or not
+// IsIPv6Enabled checks if IPV6 is enabled or not and we have
+// at least one configured in the pod
 func IsIPv6Enabled() bool {
 	cmd := exec.Command("test", "-f", "/proc/net/if_inet6")
-	return cmd.Run() == nil
+	if cmd.Run() != nil {
+		return false
+	}
+
+	addrs, err := _net.InterfaceAddrs()
+	if err != nil {
+		return false
+	}
+
+	for _, addr := range addrs {
+		ip, _, _ := _net.ParseCIDR(addr.String())
+		if IsIPV6(ip) {
+			return true
+		}
+	}
+
+	return false
 }

internal/net/net_test.go

@@ -58,3 +58,10 @@ func TestIsPortAvailable(t *testing.T) {
 		t.Fatalf("expected port %v to not be available", p)
 	}
 }
+
+func TestIsIPv6Enabled(t *testing.T) {
+	isEnabled := IsIPv6Enabled()
+	if !isEnabled {
+		t.Fatalf("expected IPV6 be enabled")
+	}
+}