netlink: add mmap'ed netlink helper functions

Add helper functions for looking up mmap'ed frame headers, reading and
writing their status, allocating skbs with mmap'ed data areas and a poll
function.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index d8e9264..07c4738 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -15,10 +15,17 @@
 	return (struct nlmsghdr *)skb->data;
 }
 
+enum netlink_skb_flags {
+	NETLINK_SKB_MMAPED	= 0x1,		/* Packet data is mmaped */
+	NETLINK_SKB_TX		= 0x2,		/* Packet was sent by userspace */
+	NETLINK_SKB_DELIVERED	= 0x4,		/* Packet was delivered */
+};
+
 struct netlink_skb_parms {
 	struct scm_creds	creds;		/* Skb credentials	*/
 	__u32			portid;
 	__u32			dst_group;
+	__u32			flags;
 	struct sock		*sk;
 };