[IPV6] MIP6: Add socket option and ancillary data interface of routing header type 2.

Add socket option and ancillary data interface of routing header type
2.  Mobile IPv6 application will use this to send binding
acknowledgement with the header without relation of confirmed route
optimization (binding).

Based on MIPL2 kernel patch.

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 8561b9d..7206747 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -648,10 +648,13 @@
 
 			rthdr = (struct ipv6_rt_hdr *)CMSG_DATA(cmsg);
 
-			/*
-			 *	TYPE 0
-			 */
-			if (rthdr->type) {
+			switch (rthdr->type) {
+			case IPV6_SRCRT_TYPE_0:
+#ifdef CONFIG_IPV6_MIP6
+			case IPV6_SRCRT_TYPE_2:
+#endif
+				break;
+			default:
 				err = -EINVAL;
 				goto exit_f;
 			}