[NETLINK]: Generic netlink family

The generic netlink family builds on top of netlink and provides
simplifies access for the less demanding netlink users. It solves
the problem of protocol numbers running out by introducing a so
called controller taking care of id management and name resolving.

Generic netlink modules register themself after filling out their
id card (struct genl_family), after successful registration the
modules are able to register callbacks to command numbers by
filling out a struct genl_ops and calling genl_register_op(). The
registered callbacks are invoked with attributes parsed making
life of simple modules a lot easier.

Although generic netlink modules can request static identifiers,
it is recommended to use GENL_ID_GENERATE and to let the controller
assign a unique identifier to the module. Userspace applications
will then ask the controller and lookup the idenfier by the module
name.

Due to the current multicast implementation of netlink, the number
of generic netlink modules is restricted to 1024 to avoid wasting
memory for the per socket multiacst subscription bitmask.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 51 insertions, 0 deletions

diff --git a/include/linux/genetlink.h b/include/linux/genetlink.h
new file mode 100644
index 000000000000..84f12a41dc01
--- /dev/null
+++ b/include/linux/genetlink.h
@@ -0,0 +1,51 @@
+#ifndef __LINUX_GENERIC_NETLINK_H
+#define __LINUX_GENERIC_NETLINK_H
+
+#include <linux/netlink.h>
+
+#define GENL_NAMSIZ	16	/* length of family name */
+
+#define GENL_MIN_ID	NLMSG_MIN_TYPE
+#define GENL_MAX_ID	1023
+
+struct genlmsghdr {
+	__u8	cmd;
+	__u8	version;
+	__u16	reserved;
+};
+
+#define GENL_HDRLEN	NLMSG_ALIGN(sizeof(struct genlmsghdr))
+
+/*
+ * List of reserved static generic netlink identifiers:
+ */
+#define GENL_ID_GENERATE	0
+#define GENL_ID_CTRL		NLMSG_MIN_TYPE
+
+/**************************************************************************
+ * Controller
+ **************************************************************************/
+
+enum {
+	CTRL_CMD_UNSPEC,
+	CTRL_CMD_NEWFAMILY,
+	CTRL_CMD_DELFAMILY,
+	CTRL_CMD_GETFAMILY,
+	CTRL_CMD_NEWOPS,
+	CTRL_CMD_DELOPS,
+	CTRL_CMD_GETOPS,
+	__CTRL_CMD_MAX,
+};
+
+#define CTRL_CMD_MAX (__CTRL_CMD_MAX - 1)
+
+enum {
+	CTRL_ATTR_UNSPEC,
+	CTRL_ATTR_FAMILY_ID,
+	CTRL_ATTR_FAMILY_NAME,
+	__CTRL_ATTR_MAX,
+};
+
+#define CTRL_ATTR_MAX (__CTRL_ATTR_MAX - 1)
+
+#endif	/* __LINUX_GENERIC_NETLINK_H */