[libnftnl,v3] expr: add osf support

diff --git a/include/libnftnl/expr.h b/include/libnftnl/expr.h
index 219104e..6ec63ee 100644
--- a/include/libnftnl/expr.h
+++ b/include/libnftnl/expr.h
@@ -268,6 +268,10 @@  enum {
 	NFTNL_EXPR_OBJREF_SET_ID,
 };
 
+enum {
+	NFTNL_EXPR_OSF_DREG	= NFTNL_EXPR_BASE,
+};
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
diff --git a/include/linux/netfilter/nf_tables.h b/include/linux/netfilter/nf_tables.h
index 91449ef..51f9056 100644
--- a/include/linux/netfilter/nf_tables.h
+++ b/include/linux/netfilter/nf_tables.h
@@ -929,6 +929,18 @@  enum nft_socket_keys {
 };
 #define NFT_SOCKET_MAX	(__NFT_SOCKET_MAX - 1)
 
+/**
+ * enum nft_osf_attributes - nf_tables osf expression netlink attributes
+ *
+ * @NFTA_OSF_DREG: OS to match
+ */
+enum nft_osf_attributes {
+	NFTA_OSF_UNSPEC,
+	NFTA_OSF_DREG,
+	__NFTA_OSF_MAX,
+};
+#define NFTA_OSF_MAX (__NFTA_OSF_MAX - 1)
+
 /**
  * enum nft_ct_keys - nf_tables ct expression keys
  *
diff --git a/src/Makefile.am b/src/Makefile.am
index c66a257..bdc10f7 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -56,6 +56,7 @@  libnftnl_la_SOURCES = utils.c		\
 		      expr/redir.c	\
 		      expr/hash.c	\
 		      expr/socket.c	\
+		      expr/osf.c	\
 		      obj/counter.c	\
 		      obj/ct_helper.c	\
 		      obj/quota.c	\
diff --git a/src/expr/osf.c b/src/expr/osf.c
new file mode 100644
index 0000000..a005af8
--- /dev/null
+++ b/src/expr/osf.c
@@ -0,0 +1,174 @@ 
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <linux/netfilter/nf_tables.h>
+
+#include "internal.h"
+#include <libmnl/libmnl.h>
+#include <libnftnl/expr.h>
+#include <libnftnl/rule.h>
+
+#define OSF_GENRE_SIZE	32
+
+struct nftnl_expr_osf {
+	enum nft_registers	dreg;
+};
+
+static int nftnl_expr_osf_set(struct nftnl_expr *e, uint16_t type,
+			      const void *data, uint32_t data_len)
+{
+	struct nftnl_expr_osf *osf = nftnl_expr_data(e);
+
+	switch(type) {
+	case NFTNL_EXPR_OSF_DREG:
+		osf->dreg = *((uint32_t *)data);
+		break;
+	}
+	return 0;
+}
+
+static const void *
+nftnl_expr_osf_get(const struct nftnl_expr *e, uint16_t type,
+		   uint32_t *data_len)
+{
+	struct nftnl_expr_osf *osf = nftnl_expr_data(e);
+
+	switch(type) {
+	case NFTNL_EXPR_OSF_DREG:
+		*data_len = sizeof(osf->dreg);
+		return &osf->dreg;
+	}
+	return NULL;
+}
+
+static int nftnl_expr_osf_cb(const struct nlattr *attr, void *data)
+{
+	const struct nlattr **tb = data;
+	int type = mnl_attr_get_type(attr);
+
+	if (mnl_attr_type_valid(attr, NFTA_OSF_MAX) < 0)
+		return MNL_CB_OK;
+
+	switch(type) {
+	case NFTNL_EXPR_OSF_DREG:
+		if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
+			abi_breakage();
+		break;
+	}
+
+	tb[type] = attr;
+	return MNL_CB_OK;
+}
+
+static void
+nftnl_expr_osf_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
+{
+	struct nftnl_expr_osf *osf = nftnl_expr_data(e);
+
+	if (e->flags & (1 << NFTNL_EXPR_OSF_DREG))
+		mnl_attr_put_u32(nlh, NFTNL_EXPR_OSF_DREG, htonl(osf->dreg));
+}
+
+static int
+nftnl_expr_osf_parse(struct nftnl_expr *e, struct nlattr *attr)
+{
+	struct nftnl_expr_osf *osf = nftnl_expr_data(e);
+	struct nlattr *tb[NFTA_OSF_MAX + 1] = {};
+
+	if (mnl_attr_parse_nested(attr, nftnl_expr_osf_cb, tb) < 0)
+		return -1;
+
+	if (tb[NFTA_OSF_DREG]) {
+		osf->dreg = ntohl(mnl_attr_get_u32(tb[NFTA_OSF_DREG]));
+		e->flags |= (1 << NFTNL_EXPR_OSF_DREG);
+	}
+
+	return 0;
+}
+
+static int nftnl_expr_osf_json_parse(struct nftnl_expr *e, json_t *root,
+				     struct nftnl_parse_err *err)
+{
+#ifdef JSON_PARSING
+	__u32 dreg;
+
+	genre = nftnl_jansson_parse_u32(root, "dreg", err);
+	if (genre != NULL)
+		nftnl_expr_set_u32(e, NFTNL_EXPR_OSF_DREG, );
+
+	return 0;
+#else
+	errno = EOPNOTSUPP;
+	return -1;
+#endif
+}
+
+static int nftnl_expr_osf_snprintf_default(char *buf, size_t size,
+					   const struct nftnl_expr *e)
+{
+	struct nftnl_expr_osf *osf = nftnl_expr_data(e);
+	int ret, offset = 0, len = size;
+
+	if (e->flags & (1 << NFTNL_EXPR_OSF_DREG)) {
+		ret = snprintf(buf, len, "%u", osf->dreg);
+		SNPRINTF_BUFFER_SIZE(ret, len, offset);
+	}
+
+	return offset;
+}
+
+static int nftnl_expr_osf_export(char *buf, size_t size,
+				 const struct nftnl_expr *e, int type)
+{
+	struct nftnl_expr_osf *osf = nftnl_expr_data(e);
+	NFTNL_BUF_INIT(b, buf, size);
+
+	if (e->flags & (1 << NFTNL_EXPR_OSF_DREG))
+		nftnl_buf_u32(&b, type, osf->dreg, "dreg");
+
+	return nftnl_buf_done(&b);
+}
+
+static int
+nftnl_expr_osf_snprintf(char *buf, size_t len, uint32_t type,
+			uint32_t flags, const struct nftnl_expr *e)
+{
+	switch(type) {
+	case NFTNL_OUTPUT_DEFAULT:
+		return nftnl_expr_osf_snprintf_default(buf, len, e);
+	case NFTNL_OUTPUT_XML:
+	case NFTNL_OUTPUT_JSON:
+		return nftnl_expr_osf_export(buf, len, e, type);
+	default:
+		break;
+	}
+	return -1;
+}
+
+static bool nftnl_expr_osf_cmp(const struct nftnl_expr *e1,
+			       const struct nftnl_expr *e2)
+{
+	struct nftnl_expr_osf *l1 = nftnl_expr_data(e1);
+	struct nftnl_expr_osf *l2 = nftnl_expr_data(e2);
+	bool eq = true;
+
+	if (e1->flags & (1 << NFTNL_EXPR_OSF_DREG))
+		eq &= (l1->dreg == l2->dreg);
+
+	return eq;
+}
+
+struct expr_ops expr_ops_osf = {
+	.name		= "osf",
+	.alloc_len	= sizeof(struct nftnl_expr_osf),
+	.max_attr	= NFTA_OSF_MAX,
+	.cmp		= nftnl_expr_osf_cmp,
+	.set		= nftnl_expr_osf_set,
+	.get		= nftnl_expr_osf_get,
+	.parse		= nftnl_expr_osf_parse,
+	.build		= nftnl_expr_osf_build,
+	.snprintf	= nftnl_expr_osf_snprintf,
+	.json_parse	= nftnl_expr_osf_json_parse,
+};
diff --git a/src/expr_ops.c b/src/expr_ops.c
index cbb2a1b..f400246 100644
--- a/src/expr_ops.c
+++ b/src/expr_ops.c
@@ -36,6 +36,7 @@  extern struct expr_ops expr_ops_hash;
 extern struct expr_ops expr_ops_fib;
 extern struct expr_ops expr_ops_flow;
 extern struct expr_ops expr_ops_socket;
+extern struct expr_ops expr_ops_osf;
 
 static struct expr_ops expr_ops_notrack = {
 	.name	= "notrack",
@@ -75,6 +76,7 @@  static struct expr_ops *expr_ops[] = {
 	&expr_ops_objref,
 	&expr_ops_flow,
 	&expr_ops_socket,
+	&expr_ops_osf,
 	NULL,
 };