path: root/net/netlink/genetlink.c

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

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

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

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

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

#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];
/*
 * Bitmap of multicast groups that are currently in use.
 *
 * To avoid an allocation at boot of just one unsigned long,
 * declare it global instead.
 * Bit 0 is marked as already used since group 0 is invalid.
 */
static unsigned long mc_group_start = 0x1;
static unsigned long *mc_groups = &mc_group_start;
static unsigned long mc_groups_longs = 1;

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 = GENL_MIN_ID;
	int i;

	for (i = 0; i <= GENL_MAX_ID - GENL_MIN_ID; i++) {
		if (!genl_family_find_byid(id_gen_idx))
			return id_gen_idx;
		if (++id_gen_idx > GENL_MAX_ID)
			id_gen_idx = GENL_MIN_ID;
	}

	return 0;
}

static struct genl_multicast_group notify_grp;

/**
 * genl_register_mc_group - register a multicast group
 *
 * Registers the specified multicast group and notifies userspace
 * about the new group.
 *
 * Returns 0 on success or a negative error code.
 *
 * @family: The generic netlink family the group shall be registered for.
 * @grp: The group to register, must have a name.
 */
int genl_register_mc_group(struct genl_family *family,
			   struct genl_multicast_group *grp)
{
	int id;
	unsigned long *new_groups;
	int err = 0;

	BUG_ON(grp->name[0] == '\0');

	genl_lock();

	/* special-case our own group */
	if (grp == &notify_grp)
		id = GENL_ID_CTRL;
	else
		id = find_first_zero_bit(mc_groups,
					 mc_groups_longs * BITS_PER_LONG);


	if (id >= mc_groups_longs * BITS_PER_LONG) {
		size_t nlen = (mc_groups_longs + 1) * sizeof(unsigned long);

		if (mc_groups == &mc_group_start) {
			new_groups = kzalloc(nlen, GFP_KERNEL);
			if (!new_groups) {
				err = -ENOMEM;
				goto out;
			}
			mc_groups = new_groups;
			*mc_groups = mc_group_start;
		} else {
			new_groups = krealloc(mc_groups, nlen, GFP_KERNEL);
			if (!new_groups) {
				err = -ENOMEM;
				goto out;
			}
			mc_groups = new_groups;
			mc_groups[mc_groups_longs] = 0;
		}
		mc_groups_longs++;
	}

	if (family->netnsok) {
		struct net *net;

		netlink_table_grab();
		rcu_read_lock();
		for_each_net_rcu(net) {
			err = __netlink_change_ngroups(net->genl_sock,
					mc_groups_longs * BITS_PER_LONG);
			if (err) {
				/*
				 * No need to roll back, can only fail if
				 * memory allocation fails and then the
				 * number of _possible_ groups has been
				 * increased on some sockets which is ok.
				 */
				rcu_read_unlock();
				netlink_table_ungrab();
				goto out;
			}
		}
		rcu_read_unlock();
		netlink_table_ungrab();