netfilter: nf_tables: add nft_expr_type_request_module()

This helper function makes sure the family specific extension is loaded.

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

net/netfilter/nf_tables_api.c

@@ -2019,6 +2019,19 @@ static const struct nft_expr_type *__nft_expr_type_get(u8 family,
 	return NULL;
 }
 
+#ifdef CONFIG_MODULES
+static int nft_expr_type_request_module(struct net *net, u8 family,
+					struct nlattr *nla)
+{
+	nft_request_module(net, "nft-expr-%u-%.*s", family,
+			   nla_len(nla), (char *)nla_data(nla));
+	if (__nft_expr_type_get(family, nla))
+		return -EAGAIN;
+
+	return 0;
+}
+#endif
+
 static const struct nft_expr_type *nft_expr_type_get(struct net *net,
 						     u8 family,
 						     struct nlattr *nla)
@@ -2035,9 +2048,7 @@ static const struct nft_expr_type *nft_expr_type_get(struct net *net,
 	lockdep_nfnl_nft_mutex_not_held();
 #ifdef CONFIG_MODULES
 	if (type == NULL) {
-		nft_request_module(net, "nft-expr-%u-%.*s", family,
-				   nla_len(nla), (char *)nla_data(nla));
-		if (__nft_expr_type_get(family, nla))
+		if (nft_expr_type_request_module(net, family, nla) == -EAGAIN)
 			return ERR_PTR(-EAGAIN);
 
 		nft_request_module(net, "nft-expr-%.*s",