Merge pull request #39837 from kdomanski/linked-ipv6

include IPv6 address of linked containers in /etc/hosts

daemon/container_operations.go

@@ -200,7 +200,14 @@ func (daemon *Daemon) buildSandboxOptions(container *container.Container) ([]lib
 		if alias != child.Name[1:] {
 			aliasList = aliasList + " " + child.Name[1:]
 		}
-		sboxOptions = append(sboxOptions, libnetwork.OptionExtraHost(aliasList, child.NetworkSettings.Networks[defaultNetName].IPAddress))
+		ipv4 := child.NetworkSettings.Networks[defaultNetName].IPAddress
+		ipv6 := child.NetworkSettings.Networks[defaultNetName].GlobalIPv6Address
+		if ipv4 != "" {
+			sboxOptions = append(sboxOptions, libnetwork.OptionExtraHost(aliasList, ipv4))
+		}
+		if ipv6 != "" {
+			sboxOptions = append(sboxOptions, libnetwork.OptionExtraHost(aliasList, ipv6))
+		}
 		cEndpointID = child.NetworkSettings.Networks[defaultNetName].EndpointID
 		if cEndpointID != "" {
 			childEndpoints = append(childEndpoints, cEndpointID)