[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>

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 */

include/net/genetlink.h

@@ -0,0 +1,154 @@
+#ifndef __NET_GENERIC_NETLINK_H
+#define __NET_GENERIC_NETLINK_H
+
+#include <linux/genetlink.h>
+#include <net/netlink.h>
+
+/**
+ * struct genl_family - generic netlink family
+ * @id: protocol family idenfitier
+ * @hdrsize: length of user specific header in bytes
+ * @name: name of family
+ * @version: protocol version
+ * @maxattr: maximum number of attributes supported
+ * @attrbuf: buffer to store parsed attributes
+ * @ops_list: list of all assigned operations
+ * @family_list: family list
+ */
+struct genl_family
+{
+	unsigned int		id;
+	unsigned int		hdrsize;
+	char			name[GENL_NAMSIZ];
+	unsigned int		version;
+	unsigned int		maxattr;
+	struct module *		owner;
+	struct nlattr **	attrbuf;	/* private */
+	struct list_head	ops_list;	/* private */
+	struct list_head	family_list;	/* private */
+};
+
+#define GENL_ADMIN_PERM		0x01
+
+/**
+ * struct genl_info - receiving information
+ * @snd_seq: sending sequence number
+ * @snd_pid: netlink pid of sender
+ * @nlhdr: netlink message header
+ * @genlhdr: generic netlink message header
+ * @userhdr: user specific header
+ * @attrs: netlink attributes
+ */
+struct genl_info
+{
+	u32			snd_seq;
+	u32			snd_pid;
+	struct nlmsghdr *	nlhdr;
+	struct genlmsghdr *	genlhdr;
+	void *			userhdr;
+	struct nlattr **	attrs;
+};
+
+/**
+ * struct genl_ops - generic netlink operations
+ * @cmd: command identifier
+ * @flags: flags
+ * @policy: attribute validation policy
+ * @doit: standard command callback
+ * @dumpit: callback for dumpers
+ * @ops_list: operations list
+ */
+struct genl_ops
+{
+	unsigned int		cmd;
+	unsigned int		flags;
+	struct nla_policy	*policy;
+	int		       (*doit)(struct sk_buff *skb,
+				       struct genl_info *info);
+	int		       (*dumpit)(struct sk_buff *skb,
+					 struct netlink_callback *cb);
+	struct list_head	ops_list;
+};
+
+extern int genl_register_family(struct genl_family *family);
+extern int genl_unregister_family(struct genl_family *family);
+extern int genl_register_ops(struct genl_family *, struct genl_ops *ops);
+extern int genl_unregister_ops(struct genl_family *, struct genl_ops *ops);
+
+extern struct sock *genl_sock;
+
+/**
+ * genlmsg_put - Add generic netlink header to netlink message
+ * @skb: socket buffer holding the message
+ * @pid: netlink pid the message is addressed to
+ * @seq: sequence number (usually the one of the sender)
+ * @type: netlink message type
+ * @hdrlen: length of the user specific header
+ * @flags netlink message flags
+ * @cmd: generic netlink command
+ * @version: version
+ *
+ * Returns pointer to user specific header
+ */
+static inline void *genlmsg_put(struct sk_buff *skb, u32 pid, u32 seq,
+				int type, int hdrlen, int flags,
+				u8 cmd, u8 version)
+{
+	struct nlmsghdr *nlh;
+	struct genlmsghdr *hdr;
+
+	nlh = nlmsg_put(skb, pid, seq, type, GENL_HDRLEN + hdrlen, flags);
+	if (nlh == NULL)
+		return NULL;
+
+	hdr = nlmsg_data(nlh);
+	hdr->cmd = cmd;
+	hdr->version = version;
+	hdr->reserved = 0;
+
+	return (char *) hdr + GENL_HDRLEN;
+}
+
+/**
+ * genlmsg_end - Finalize a generic netlink message
+ * @skb: socket buffer the message is stored in
+ * @hdr: user specific header
+ */
+static inline int genlmsg_end(struct sk_buff *skb, void *hdr)
+{
+	return nlmsg_end(skb, hdr - GENL_HDRLEN - NLMSG_HDRLEN);
+}
+
+/**
+ * genlmsg_cancel - Cancel construction of a generic netlink message
+ * @skb: socket buffer the message is stored in
+ * @hdr: generic netlink message header
+ */
+static inline int genlmsg_cancel(struct sk_buff *skb, void *hdr)
+{
+	return nlmsg_cancel(skb, hdr - GENL_HDRLEN - NLMSG_HDRLEN);
+}
+
+/**
+ * genlmsg_multicast - multicast a netlink message
+ * @skb: netlink message as socket buffer
+ * @pid: own netlink pid to avoid sending to yourself
+ * @group: multicast group id
+ */
+static inline int genlmsg_multicast(struct sk_buff *skb, u32 pid,
+				    unsigned int group)
+{
+	return nlmsg_multicast(genl_sock, skb, pid, group);
+}
+
+/**
+ * genlmsg_unicast - unicast a netlink message
+ * @skb: netlink message as socket buffer
+ * @pid: netlink pid of the destination socket
+ */
+static inline int genlmsg_unicast(struct sk_buff *skb, u32 pid)
+{
+	return nlmsg_unicast(genl_sock, skb, pid);
+}
+
+#endif	/* __NET_GENERIC_NETLINK_H */

net/netlink/Makefile

@@ -2,4 +2,4 @@
 # Makefile for the netlink driver.
 #
 
-obj-y  				:= af_netlink.o attr.o
+obj-y  				:= af_netlink.o attr.o genetlink.o

net/netlink/genetlink.c

@@ -0,0 +1,579 @@
+/*
+ * NETLINK      Generic Netlink Family
+ *
+ * 		Authors:	Jamal Hadi Salim
+ * 				Thomas Graf <tgraf@suug.ch>
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/string.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/genetlink.h>
+
+struct sock *genl_sock = NULL;
+
+static DECLARE_MUTEX(genl_sem); /* serialization of message processing */
+
+static void genl_lock(void)
+{
+	down(&genl_sem);
+}
+
+static int genl_trylock(void)
+{
+	return down_trylock(&genl_sem);
+}
+
+static void genl_unlock(void)
+{
+	up(&genl_sem);
+
+	if (genl_sock && genl_sock->sk_receive_queue.qlen)
+		genl_sock->sk_data_ready(genl_sock, 0);
+}
+
+#define GENL_FAM_TAB_SIZE	16
+#define GENL_FAM_TAB_MASK	(GENL_FAM_TAB_SIZE - 1)
+
+static struct list_head family_ht[GENL_FAM_TAB_SIZE];
+
+static int genl_ctrl_event(int event, void *data);
+
+static inline unsigned int genl_family_hash(unsigned int id)
+{
+	return id & GENL_FAM_TAB_MASK;
+}
+
+static inline struct list_head *genl_family_chain(unsigned int id)
+{
+	return &family_ht[genl_family_hash(id)];
+}
+
+static struct genl_family *genl_family_find_byid(unsigned int id)
+{
+	struct genl_family *f;
+
+	list_for_each_entry(f, genl_family_chain(id), family_list)
+		if (f->id == id)
+			return f;
+
+	return NULL;
+}
+
+static struct genl_family *genl_family_find_byname(char *name)
+{
+	struct genl_family *f;
+	int i;
+
+	for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
+		list_for_each_entry(f, genl_family_chain(i), family_list)
+			if (strcmp(f->name, name) == 0)
+				return f;
+
+	return NULL;
+}
+
+static struct genl_ops *genl_get_cmd(u8 cmd, struct genl_family *family)
+{
+	struct genl_ops *ops;
+
+	list_for_each_entry(ops, &family->ops_list, ops_list)
+		if (ops->cmd == cmd)
+			return ops;
+
+	return NULL;
+}
+
+/* Of course we are going to have problems once we hit
+ * 2^16 alive types, but that can only happen by year 2K
+*/
+static inline u16 genl_generate_id(void)
+{
+	static u16 id_gen_idx;
+	int overflowed = 0;
+
+	do {
+		if (id_gen_idx == 0)
+			id_gen_idx = GENL_MIN_ID;
+
+		if (++id_gen_idx > GENL_MAX_ID) {
+			if (!overflowed) {
+				overflowed = 1;
+				id_gen_idx = 0;
+				continue;
+			} else
+				return 0;
+		}
+
+	} while (genl_family_find_byid(id_gen_idx));
+
+	return id_gen_idx;
+}
+
+/**
+ * genl_register_ops - register generic netlink operations
+ * @family: generic netlink family
+ * @ops: operations to be registered
+ *
+ * Registers the specified operations and assigns them to the specified
+ * family. Either a doit or dumpit callback must be specified or the
+ * operation will fail. Only one operation structure per command
+ * identifier may be registered.
+ *
+ * See include/net/genetlink.h for more documenation on the operations
+ * structure.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int genl_register_ops(struct genl_family *family, struct genl_ops *ops)
+{
+	int err = -EINVAL;
+
+	if (ops->dumpit == NULL && ops->doit == NULL)
+		goto errout;
+
+	if (genl_get_cmd(ops->cmd, family)) {
+		err = -EEXIST;
+		goto errout;
+	}
+
+	genl_lock();
+	list_add_tail(&ops->ops_list, &family->ops_list);
+	genl_unlock();
+
+	genl_ctrl_event(CTRL_CMD_NEWOPS, ops);
+	err = 0;
+errout:
+	return err;
+}
+
+/**
+ * genl_unregister_ops - unregister generic netlink operations
+ * @family: generic netlink family
+ * @ops: operations to be unregistered
+ *
+ * Unregisters the specified operations and unassigns them from the
+ * specified family. The operation blocks until the current message
+ * processing has finished and doesn't start again until the
+ * unregister process has finished.
+ *
+ * Note: It is not necessary to unregister all operations before
+ *       unregistering the family, unregistering the family will cause
+ *       all assigned operations to be unregistered automatically.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int genl_unregister_ops(struct genl_family *family, struct genl_ops *ops)
+{
+	struct genl_ops *rc;
+
+	genl_lock();
+	list_for_each_entry(rc, &family->ops_list, ops_list) {
+		if (rc == ops) {
+			list_del(&ops->ops_list);
+			genl_unlock();
+			genl_ctrl_event(CTRL_CMD_DELOPS, ops);
+			return 0;
+		}
+	}
+	genl_unlock();
+
+	return -ENOENT;
+}
+
+/**
+ * genl_register_family - register a generic netlink family
+ * @family: generic netlink family
+ *
+ * Registers the specified family after validating it first. Only one
+ * family may be registered with the same family name or identifier.
+ * The family id may equal GENL_ID_GENERATE causing an unique id to
+ * be automatically generated and assigned.
+ *
+ * Return 0 on success or a negative error code.
+ */
+int genl_register_family(struct genl_family *family)
+{
+	int err = -EINVAL;
+
+	if (family->id && family->id < GENL_MIN_ID)
+		goto errout;
+
+	if (family->id > GENL_MAX_ID)
+		goto errout;
+
+	INIT_LIST_HEAD(&family->ops_list);
+
+	genl_lock();
+
+	if (genl_family_find_byname(family->name)) {
+		err = -EEXIST;
+		goto errout_locked;
+	}
+
+	if (genl_family_find_byid(family->id)) {
+		err = -EEXIST;
+		goto errout_locked;
+	}
+
+	if (!try_module_get(family->owner)) {
+		err = -EBUSY;
+		goto errout_locked;
+	}
+
+	if (family->id == GENL_ID_GENERATE) {
+		u16 newid = genl_generate_id();
+
+		if (!newid) {
+			err = -ENOMEM;
+			goto errout_locked;
+		}
+
+		family->id = newid;
+	}
+
+	if (family->maxattr) {
+		family->attrbuf = kmalloc((family->maxattr+1) *
+					sizeof(struct nlattr *), GFP_KERNEL);
+		if (family->attrbuf == NULL) {
+			err = -ENOMEM;
+			goto errout;
+		}
+	} else
+		family->attrbuf = NULL;
+
+	list_add_tail(&family->family_list, genl_family_chain(family->id));
+	genl_unlock();
+
+	genl_ctrl_event(CTRL_CMD_NEWFAMILY, family);
+
+	return 0;
+
+errout_locked:
+	genl_unlock();
+errout:
+	return err;
+}
+
+/**
+ * genl_unregister_family - unregister generic netlink family
+ * @family: generic netlink family
+ *
+ * Unregisters the specified family.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int genl_unregister_family(struct genl_family *family)
+{
+	struct genl_family *rc;
+
+	genl_lock();
+
+	list_for_each_entry(rc, genl_family_chain(family->id), family_list) {
+		if (family->id != rc->id || strcmp(rc->name, family->name))
+			continue;
+
+		list_del(&rc->family_list);
+		INIT_LIST_HEAD(&family->ops_list);
+		genl_unlock();
+
+		module_put(family->owner);
+		kfree(family->attrbuf);
+		genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
+		return 0;
+	}
+
+	genl_unlock();
+
+	return -ENOENT;
+}
+
+static inline int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			       int *errp)
+{
+	struct genl_ops *ops;
+	struct genl_family *family;
+	struct genl_info info;
+	struct genlmsghdr *hdr = nlmsg_data(nlh);
+	int hdrlen, err = -EINVAL;
+
+	if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
+		goto ignore;
+
+	if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
+		goto ignore;
+
+       	family = genl_family_find_byid(nlh->nlmsg_type);
+	if (family == NULL) {
+		err = -ENOENT;
+		goto errout;
+	}
+
+	hdrlen = GENL_HDRLEN + family->hdrsize;
+	if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
+		goto errout;
+
+	ops = genl_get_cmd(hdr->cmd, family);
+	if (ops == NULL) {
+		err = -EOPNOTSUPP;
+		goto errout;
+	}
+
+	if ((ops->flags & GENL_ADMIN_PERM) && security_netlink_recv(skb)) {
+		err = -EPERM;
+		goto errout;
+	}
+
+	if (nlh->nlmsg_flags & NLM_F_DUMP) {
+		if (ops->dumpit == NULL) {
+			err = -EOPNOTSUPP;
+			goto errout;
+		}
+
+		*errp = err = netlink_dump_start(genl_sock, skb, nlh,
+						 ops->dumpit, NULL);
+		if (err == 0)
+			skb_pull(skb, min(NLMSG_ALIGN(nlh->nlmsg_len),
+					  skb->len));
+		return -1;
+	}
+
+	if (ops->doit == NULL) {
+		err = -EOPNOTSUPP;
+		goto errout;
+	}
+
+	if (family->attrbuf) {
+		err = nlmsg_parse(nlh, hdrlen, family->attrbuf, family->maxattr,
+				  ops->policy);
+		if (err < 0)
+			goto errout;
+	}
+
+	info.snd_seq = nlh->nlmsg_seq;
+	info.snd_pid = NETLINK_CB(skb).pid;
+	info.nlhdr = nlh;
+	info.genlhdr = nlmsg_data(nlh);
+	info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
+	info.attrs = family->attrbuf;
+
+	*errp = err = ops->doit(skb, &info);
+	return err;
+
+ignore:
+	return 0;
+
+errout:
+	*errp = err;
+	return -1;
+}
+
+static void genl_rcv(struct sock *sk, int len)
+{
+	unsigned int qlen = 0;
+
+	do {
+		if (genl_trylock())
+			return;
+		netlink_run_queue(sk, &qlen, &genl_rcv_msg);
+		genl_unlock();
+	} while (qlen && genl_sock && genl_sock->sk_receive_queue.qlen);
+}
+
+/**************************************************************************
+ * Controller
+ **************************************************************************/
+
+static int ctrl_fill_info(struct genl_family *family, u32 pid, u32 seq,
+			  u32 flags, struct sk_buff *skb, u8 cmd)
+{
+	void *hdr;
+
+	hdr = genlmsg_put(skb, pid, seq, GENL_ID_CTRL, 0, flags, cmd,
+			  family->version);
+	if (hdr == NULL)
+		return -1;
+
+	NLA_PUT_STRING(skb, CTRL_ATTR_FAMILY_NAME, family->name);
+	NLA_PUT_U16(skb, CTRL_ATTR_FAMILY_ID, family->id);
+
+	return genlmsg_end(skb, hdr);
+
+nla_put_failure:
+	return genlmsg_cancel(skb, hdr);
+}
+
+static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
+{
+
+	int i, n = 0;
+	struct genl_family *rt;
+	int chains_to_skip = cb->args[0];
+	int fams_to_skip = cb->args[1];
+
+	for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
+		if (i < chains_to_skip)
+			continue;
+		n = 0;
+		list_for_each_entry(rt, genl_family_chain(i), family_list) {
+			if (++n < fams_to_skip)
+				continue;
+			if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).pid,
+					   cb->nlh->nlmsg_seq, NLM_F_MULTI,
+					   skb, CTRL_CMD_NEWFAMILY) < 0)
+				goto errout;
+		}
+
+		fams_to_skip = 0;
+	}
+
+errout:
+	cb->args[0] = i;
+	cb->args[1] = n;
+
+	return skb->len;
+}
+
+static struct sk_buff *ctrl_build_msg(struct genl_family *family, u32 pid,
+				      int seq, int cmd)
+{
+	struct sk_buff *skb;
+	int err;
+
+	skb = nlmsg_new(NLMSG_GOODSIZE);
+	if (skb == NULL)
+		return ERR_PTR(-ENOBUFS);
+
+	err = ctrl_fill_info(family, pid, seq, 0, skb, cmd);
+	if (err < 0) {
+		nlmsg_free(skb);
+		return ERR_PTR(err);
+	}
+
+	return skb;
+}
+
+static struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] __read_mostly = {
+	[CTRL_ATTR_FAMILY_ID]	= { .type = NLA_U16 },
+	[CTRL_ATTR_FAMILY_NAME]	= { .type = NLA_STRING },
+};
+
+static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
+{
+	struct sk_buff *msg;
+	struct genl_family *res = NULL;
+	int err = -EINVAL;
+
+	if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
+		u16 id = nla_get_u16(info->attrs[CTRL_ATTR_FAMILY_ID]);
+		res = genl_family_find_byid(id);
+	}
+
+	if (info->attrs[CTRL_ATTR_FAMILY_NAME]) {
+		char name[GENL_NAMSIZ];
+
+		if (nla_strlcpy(name, info->attrs[CTRL_ATTR_FAMILY_NAME],
+				GENL_NAMSIZ) >= GENL_NAMSIZ)
+			goto errout;
+
+		res = genl_family_find_byname(name);
+	}
+
+	if (res == NULL) {
+		err = -ENOENT;
+		goto errout;
+	}
+
+	msg = ctrl_build_msg(res, info->snd_pid, info->snd_seq,
+			     CTRL_CMD_NEWFAMILY);
+	if (IS_ERR(msg)) {
+		err = PTR_ERR(msg);
+		goto errout;
+	}
+
+	err = genlmsg_unicast(msg, info->snd_pid);
+errout:
+	return err;
+}
+
+static int genl_ctrl_event(int event, void *data)
+{
+	struct sk_buff *msg;
+
+	if (genl_sock == NULL)
+		return 0;
+
+	switch (event) {
+	case CTRL_CMD_NEWFAMILY:
+	case CTRL_CMD_DELFAMILY:
+		msg = ctrl_build_msg(data, 0, 0, event);
+		if (IS_ERR(msg))
+			return PTR_ERR(msg);
+
+		genlmsg_multicast(msg, 0, GENL_ID_CTRL);
+		break;
+	}
+
+	return 0;
+}
+
+static struct genl_ops genl_ctrl_ops = {
+	.cmd		= CTRL_CMD_GETFAMILY,
+	.doit		= ctrl_getfamily,
+	.dumpit		= ctrl_dumpfamily,
+	.policy		= ctrl_policy,
+};
+
+static struct genl_family genl_ctrl = {
+	.id = GENL_ID_CTRL,
+	.name = "nlctrl",
+	.version = 0x1,
+	.maxattr = CTRL_ATTR_MAX,
+	.owner = THIS_MODULE,
+};
+
+static int __init genl_init(void)
+{
+	int i, err;
+
+	for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
+		INIT_LIST_HEAD(&family_ht[i]);
+
+	err = genl_register_family(&genl_ctrl);
+	if (err < 0)
+		goto errout;
+
+	err = genl_register_ops(&genl_ctrl, &genl_ctrl_ops);
+	if (err < 0)
+		goto errout_register;
+
+	netlink_set_nonroot(NETLINK_GENERIC, NL_NONROOT_RECV);
+	genl_sock = netlink_kernel_create(NETLINK_GENERIC, GENL_MAX_ID,
+					  genl_rcv, THIS_MODULE);
+	if (genl_sock == NULL) {
+		panic("GENL: Cannot initialize generic netlink\n");
+		return -ENOMEM;
+	}
+
+	return 0;
+
+errout_register:
+	genl_unregister_family(&genl_ctrl);
+errout:
+	panic("GENL: Cannot register controller: %d\n", err);
+	return err;
+}
+
+subsys_initcall(genl_init);
+
+EXPORT_SYMBOL(genl_sock);
+EXPORT_SYMBOL(genl_register_ops);
+EXPORT_SYMBOL(genl_unregister_ops);
+EXPORT_SYMBOL(genl_register_family);
+EXPORT_SYMBOL(genl_unregister_family);