net/netlink/genetlink.c - arm/linux-arm64-legacy - Git at Google

 /*
  * NETLINK      Generic Netlink Family
  *
  * 		Authors:	Jamal Hadi Salim
  * 				Thomas Graf <tgraf@suug.ch>
  */

 #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 <linux/mutex.h>
 #include <net/sock.h>
 #include <net/genetlink.h>

 struct sock *genl_sock = NULL;

 static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */

 static void genl_lock(void)
 {
 	mutex_lock(&genl_mutex);
 }

 static int genl_trylock(void)
 {
 	return !mutex_trylock(&genl_mutex);
 }

 static void genl_unlock(void)
 {
 	mutex_unlock(&genl_mutex);

 	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 (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_locked;
 		}
 	} 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();

 		kfree(family->attrbuf);
 		genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
 		return 0;
 	}

 	genl_unlock();

 	return -ENOENT;
 }

 static 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, CAP_NET_ADMIN)) {
 		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, u8 cmd)
 {
 	struct sk_buff *skb;
 	int err;

 	skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
 	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, GFP_KERNEL);
 		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,
 };

 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 0;

 errout_register:
 	genl_unregister_family(&genl_ctrl);
 errout:
 	panic("GENL: Cannot register controller: %d\n", 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);
	/*
	* NETLINK Generic Netlink Family
	*
	* Authors: Jamal Hadi Salim
	* Thomas Graf <tgraf@suug.ch>
	*/

	#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 <linux/mutex.h>
	#include <net/sock.h>
	#include <net/genetlink.h>

	struct sock *genl_sock = NULL;

	static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */

	static void genl_lock(void)
	{
	mutex_lock(&genl_mutex);
	}

	static int genl_trylock(void)
	{
	return !mutex_trylock(&genl_mutex);
	}

	static void genl_unlock(void)
	{
	mutex_unlock(&genl_mutex);

	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 (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_locked;
	}
	} 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();

	kfree(family->attrbuf);
	genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
	return 0;
	}

	genl_unlock();

	return -ENOENT;
	}

	static 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, CAP_NET_ADMIN)) {
	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, u8 cmd)
	{
	struct sk_buff *skb;
	int err;

	skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
	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, GFP_KERNEL);
	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,
	};

	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 0;

	errout_register:
	genl_unregister_family(&genl_ctrl);
	errout:
	panic("GENL: Cannot register controller: %d\n", 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);