netfilter: nfnetlink_queue: allow to attach expectations to conntracks

This patch adds the capability to attach expectations via nfnetlink_queue.
This is required by conntrack helpers that trigger expectations based on
the first packet seen like the TFTP and the DHCPv6 user-space helpers.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nfnetlink_queue.h

@@ -46,6 +46,7 @@ enum nfqnl_attr_type {
 	NFQA_CT_INFO,			/* enum ip_conntrack_info */
 	NFQA_CAP_LEN,			/* __u32 length of captured packet */
 	NFQA_SKB_INFO,			/* __u32 skb meta information */
+	NFQA_EXP,			/* nf_conntrack_netlink.h */
 
 	__NFQA_MAX
 };