From cdd56ba07e221ec3dff4a36baa73f99980fdfe7e Mon Sep 17 00:00:00 2001
From: Alessandro Boch <aboch@docker.com>
Date: Tue, 3 Jan 2017 11:39:04 -0800
Subject: [PATCH] Prioritize nw endpoint which can provide both v4 and v6
 connectivity

- when selecting sandbox's default gw

Signed-off-by: Alessandro Boch <aboch@docker.com>
---
 libnetwork/sandbox.go | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/libnetwork/sandbox.go b/libnetwork/sandbox.go
index 48b95f66e1..6767026369 100644
--- a/libnetwork/sandbox.go
+++ b/libnetwork/sandbox.go
@@ -1174,6 +1174,17 @@ func (eh epHeap) Less(i, j int) bool {
 		return true
 	}
 
+	if epi.joinInfo != nil && epj.joinInfo != nil {
+		if (epi.joinInfo.gw != nil && epi.joinInfo.gw6 != nil) &&
+			(epj.joinInfo.gw == nil || epj.joinInfo.gw6 == nil) {
+			return true
+		}
+		if (epj.joinInfo.gw != nil && epj.joinInfo.gw6 != nil) &&
+			(epi.joinInfo.gw == nil || epi.joinInfo.gw6 == nil) {
+			return false
+		}
+	}
+
 	if ci != nil {
 		cip, ok = ci.epPriority[eh[i].ID()]
 		if !ok {