netfilter: ipset: Introduce new operation to get both setname and family

ip[6]tables set match and SET target need to know the family of the set
in order to reject adding rules which refer to a set with a non-mathcing
family. Currently such rules are silently accepted and then ignored
instead of generating a clear error message to the user, which is not
helpful.
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

include/uapi/linux/netfilter/ipset/ip_set.h

@@ -250,6 +250,14 @@ struct ip_set_req_get_set {
 #define IP_SET_OP_GET_BYINDEX	0x00000007	/* Get set name by index */
 /* Uses ip_set_req_get_set */
 
+#define IP_SET_OP_GET_FNAME	0x00000008	/* Get set index and family */
+struct ip_set_req_get_set_family {
+	unsigned int op;
+	unsigned int version;
+	unsigned int family;
+	union ip_set_name_index set;
+};
+
 #define IP_SET_OP_VERSION	0x00000100	/* Ask kernel version */
 struct ip_set_req_version {
 	unsigned int op;

net/netfilter/ipset/ip_set_core.c

@@ -1788,6 +1788,23 @@ ip_set_sockfn_get(struct sock *sk, int optval, void __user *user, int *len)
 		nfnl_unlock(NFNL_SUBSYS_IPSET);
 		goto copy;
 	}
+	case IP_SET_OP_GET_FNAME: {
+		struct ip_set_req_get_set_family *req_get = data;
+		ip_set_id_t id;
+
+		if (*len != sizeof(struct ip_set_req_get_set_family)) {
+			ret = -EINVAL;
+			goto done;
+		}
+		req_get->set.name[IPSET_MAXNAMELEN - 1] = '\0';
+		nfnl_lock(NFNL_SUBSYS_IPSET);
+		find_set_and_id(req_get->set.name, &id);
+		req_get->set.index = id;
+		if (id != IPSET_INVALID_ID)
+			req_get->family = nfnl_set(id)->family;
+		nfnl_unlock(NFNL_SUBSYS_IPSET);
+		goto copy;
+	}
 	case IP_SET_OP_GET_BYINDEX: {
 		struct ip_set_req_get_set *req_get = data;
 		struct ip_set *set;