Applied patch by James Smith to implement IPV6_V6ONLY support in

sockets and netconns.

Change-Id: I2ecd8e218703114890b2d678cc1ccf997a16f5e3

src/include/lwip/api.h

@@ -73,6 +73,12 @@ extern "C" {
 /** If a nonblocking write has been rejected before, poll_tcp needs to
     check if the netconn is writable again */
 #define NETCONN_FLAG_CHECK_WRITESPACE         0x10
+#if LWIP_IPV6
+/** If this flag is set then only IPv6 communication is allowed on the
+    netconn. As per RFC#3493 this features defaults to OFF allowing
+    dual-stack usage by default. */
+#define NETCONN_FLAG_IPV6_V6ONLY              0x20
+#endif /* LWIP_IPV6 */
 
 
 /* Helpers to process several netconn_types by the same code */

src/include/lwip/sockets.h

@@ -148,6 +148,9 @@ struct linger {
 #define IPPROTO_IP      0
 #define IPPROTO_TCP     6
 #define IPPROTO_UDP     17
+#if LWIP_IPV6
+#define IPPROTO_IPV6    41
+#endif /* LWIP_IPV6 */
 #define IPPROTO_UDPLITE 136
 
 /* Flags we can use with send and recv. */
@@ -175,6 +178,13 @@ struct linger {
 #define TCP_KEEPCNT    0x05    /* set pcb->keep_cnt   - Use number of probes sent for get/setsockopt */
 #endif /* LWIP_TCP */
 
+#if LWIP_IPV6
+/*
+ * Options for level IPPROTO_IPV6
+ */
+#define IPV6_V6ONLY 27 /* RFC3493: boolean control to restrict AF_INET6 sockets to IPv6 communications only. */
+#endif /* LWIP_IPV6 */
+
 #if LWIP_UDP && LWIP_UDPLITE
 /*
  * Options for level IPPROTO_UDPLITE