linux: import nf_tables and nfnetlink headers from Linux 5.8

Will be used/needed in the upcoming nfnetlink/nftables support.
This follows existing model where kernel uapi headers are cached
locally.

src/basic/linux/netfilter/nfnetlink.h

@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _NFNETLINK_H
+#define _NFNETLINK_H
+#include <linux/types.h>
+#include <linux/netfilter/nfnetlink_compat.h>
+
+enum nfnetlink_groups {
+	NFNLGRP_NONE,
+#define NFNLGRP_NONE			NFNLGRP_NONE
+	NFNLGRP_CONNTRACK_NEW,
+#define NFNLGRP_CONNTRACK_NEW		NFNLGRP_CONNTRACK_NEW
+	NFNLGRP_CONNTRACK_UPDATE,
+#define NFNLGRP_CONNTRACK_UPDATE	NFNLGRP_CONNTRACK_UPDATE
+	NFNLGRP_CONNTRACK_DESTROY,
+#define NFNLGRP_CONNTRACK_DESTROY	NFNLGRP_CONNTRACK_DESTROY
+	NFNLGRP_CONNTRACK_EXP_NEW,
+#define	NFNLGRP_CONNTRACK_EXP_NEW	NFNLGRP_CONNTRACK_EXP_NEW
+	NFNLGRP_CONNTRACK_EXP_UPDATE,
+#define NFNLGRP_CONNTRACK_EXP_UPDATE	NFNLGRP_CONNTRACK_EXP_UPDATE
+	NFNLGRP_CONNTRACK_EXP_DESTROY,
+#define NFNLGRP_CONNTRACK_EXP_DESTROY	NFNLGRP_CONNTRACK_EXP_DESTROY
+	NFNLGRP_NFTABLES,
+#define NFNLGRP_NFTABLES                NFNLGRP_NFTABLES
+	NFNLGRP_ACCT_QUOTA,
+#define NFNLGRP_ACCT_QUOTA		NFNLGRP_ACCT_QUOTA
+	NFNLGRP_NFTRACE,
+#define NFNLGRP_NFTRACE			NFNLGRP_NFTRACE
+	__NFNLGRP_MAX,
+};
+#define NFNLGRP_MAX	(__NFNLGRP_MAX - 1)
+
+/* General form of address family dependent message.
+ */
+struct nfgenmsg {
+	__u8  nfgen_family;		/* AF_xxx */
+	__u8  version;		/* nfnetlink version */
+	__be16    res_id;		/* resource id */
+};
+
+#define NFNETLINK_V0	0
+
+/* netfilter netlink message types are split in two pieces:
+ * 8 bit subsystem, 8bit operation.
+ */
+
+#define NFNL_SUBSYS_ID(x)	((x & 0xff00) >> 8)
+#define NFNL_MSG_TYPE(x)	(x & 0x00ff)
+
+/* No enum here, otherwise __stringify() trick of MODULE_ALIAS_NFNL_SUBSYS()
+ * won't work anymore */
+#define NFNL_SUBSYS_NONE 		0
+#define NFNL_SUBSYS_CTNETLINK		1
+#define NFNL_SUBSYS_CTNETLINK_EXP	2
+#define NFNL_SUBSYS_QUEUE		3
+#define NFNL_SUBSYS_ULOG		4
+#define NFNL_SUBSYS_OSF			5
+#define NFNL_SUBSYS_IPSET		6
+#define NFNL_SUBSYS_ACCT		7
+#define NFNL_SUBSYS_CTNETLINK_TIMEOUT	8
+#define NFNL_SUBSYS_CTHELPER		9
+#define NFNL_SUBSYS_NFTABLES		10
+#define NFNL_SUBSYS_NFT_COMPAT		11
+#define NFNL_SUBSYS_COUNT		12
+
+/* Reserved control nfnetlink messages */
+#define NFNL_MSG_BATCH_BEGIN		NLMSG_MIN_TYPE
+#define NFNL_MSG_BATCH_END		NLMSG_MIN_TYPE+1
+
+/**
+ * enum nfnl_batch_attributes - nfnetlink batch netlink attributes
+ *
+ * @NFNL_BATCH_GENID: generation ID for this changeset (NLA_U32)
+ */
+enum nfnl_batch_attributes {
+        NFNL_BATCH_UNSPEC,
+        NFNL_BATCH_GENID,
+        __NFNL_BATCH_MAX
+};
+#define NFNL_BATCH_MAX			(__NFNL_BATCH_MAX - 1)
+
+#endif /* _NFNETLINK_H */