On Mon, 2013-04-29 at 11:52 -0400, David Miller wrote:

From: Cong Wang <redacted>
Date: Wed, 24 Apr 2013 13:54:33 +0800

quoted

+	rc = sock_create_kern(AF_INET6, SOCK_DGRAM, IPPROTO_UDP, &vn->sock);
+	if (rc < 0) {
+		pr_debug("UDP socket create failed\n");
+		return rc;
+	}

You have to fall back to creating and using an ipv4 socket if making
the ipv6 one fails.

IPV6 being enabled does not mean it is guaranteed the one can
successfully create ipv6 sockets.

You also must handle /proc/sys/net/ipv6/conf/${DEV}/disable_ipv6
correctly as far as this stuff goes as well.

Right, we should detect the run-time IPv6 support too.