/*
 * 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>

struct sock *genl_sock = NULL;

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;
        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;
}

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;

        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++;
        }

        err = netlink_change_ngroups(genl_sock,
                                     mc_groups_longs * BITS_PER_LONG);
        if (err)
                goto out;

        grp->id = id;
        set_bit(id, mc_groups);
        list_add_tail(&grp->list, &family->mcast_groups);
        grp->family = family;

        genl_ctrl_event(CTRL_CMD_NEWMCAST_GRP, grp);
 out:
        genl_unlock();
        return err;
}
EXPORT_SYMBOL(genl_register_mc_group);

static void __genl_unregister_mc_group(struct genl_family *family,
                                       struct genl_multicast_group *grp)
{
        BUG_ON(grp->family != family);
        netlink_clear_multicast_users(genl_sock, grp->id);
        clear_bit(grp->id, mc_groups);
        list_del(&grp->list);
        genl_ctrl_event(CTRL_CMD_DELMCAST_GRP, grp);
        grp->id = 0;
        grp->family = NULL;
}

/**
 * genl_unregister_mc_group - unregister a multicast group
 *
 * Unregisters the specified multicast group and notifies userspace
 * about it. All current listeners on the group are removed.
 *
 * Note: It is not necessary to unregister all multicast groups before
 *       unregistering the family, unregistering the family will cause
 *       all assigned multicast groups to be unregistered automatically.
 *
 * @family: Generic netlink family the group belongs to.
 * @grp: The group to unregister, must have been registered successfully
 *       previously.
 */
void genl_unregister_mc_group(struct genl_family *family,
                              struct genl_multicast_group *grp)
{
        genl_lock();
        __genl_unregister_mc_group(family, grp);
        genl_unlock();
}

static void genl_unregister_mc_groups(struct genl_family *family)
{
        struct genl_multicast_group *grp, *tmp;

        list_for_each_entry_safe(grp, tmp, &family->mcast_groups, list)
                __genl_unregister_mc_group(family, grp);
}

/**
 * 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;
        }

        if (ops->dumpit)
                ops->flags |= GENL_CMD_CAP_DUMP;
        if (ops->doit)
                ops->flags |= GENL_CMD_CAP_DO;
        if (ops->policy)
                ops->flags |= GENL_CMD_CAP_HASPOL;

        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);
        INIT_LIST_HEAD(&family->mcast_groups);

        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();

        genl_unregister_mc_groups(family);

        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)
{
        struct genl_ops *ops;
        struct genl_family *family;
        struct genl_info info;
        struct genlmsghdr *hdr = nlmsg_data(nlh);
        int hdrlen, err;

        family = genl_family_find_byid(nlh->nlmsg_type);
        if (family == NULL)
                return -ENOENT;

        hdrlen = GENL_HDRLEN + family->hdrsize;
        if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
                return -EINVAL;

        ops = genl_get_cmd(hdr->cmd, family);
        if (ops == NULL)
                return -EOPNOTSUPP;

        if ((ops->flags & GENL_ADMIN_PERM) &&
            security_netlink_recv(skb, CAP_NET_ADMIN))
                return -EPERM;

        if (nlh->nlmsg_flags & NLM_F_DUMP) {
                if (ops->dumpit == NULL)
                        return -EOPNOTSUPP;

                genl_unlock();
                err = netlink_dump_start(genl_sock, skb, nlh,
                                         ops->dumpit, ops->done);
                genl_lock();
                return err;
        }

        if (ops->doit == NULL)
                return -EOPNOTSUPP;

        if (family->attrbuf) {
                err = nlmsg_parse(nlh, hdrlen, family->attrbuf, family->maxattr,
                                  ops->policy);
                if (err < 0)
                        return err;
        }

        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;

        return ops->doit(skb, &info);
}

static void genl_rcv(struct sk_buff *skb)
{
        genl_lock();
        netlink_rcv_skb(skb, &genl_rcv_msg);
        genl_unlock();
}

/**************************************************************************
 * Controller
 **************************************************************************/

static struct genl_family genl_ctrl = {
        .id = GENL_ID_CTRL,
        .name = "nlctrl",
        .version = 0x2,
        .maxattr = CTRL_ATTR_MAX,
};

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_ctrl, flags, cmd);
        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);
        NLA_PUT_U32(skb, CTRL_ATTR_VERSION, family->version);
        NLA_PUT_U32(skb, CTRL_ATTR_HDRSIZE, family->hdrsize);
        NLA_PUT_U32(skb, CTRL_ATTR_MAXATTR, family->maxattr);

        if (!list_empty(&family->ops_list)) {
                struct nlattr *nla_ops;
                struct genl_ops *ops;
                int idx = 1;

                nla_ops = nla_nest_start(skb, CTRL_ATTR_OPS);
                if (nla_ops == NULL)
                        goto nla_put_failure;

                list_for_each_entry(ops, &family->ops_list, ops_list) {
                        struct nlattr *nest;

                        nest = nla_nest_start(skb, idx++);
                        if (nest == NULL)
                                goto nla_put_failure;

                        NLA_PUT_U32(skb, CTRL_ATTR_OP_ID, ops->cmd);
                        NLA_PUT_U32(skb, CTRL_ATTR_OP_FLAGS, ops->flags);

                        nla_nest_end(skb, nest);
                }

                nla_nest_end(skb, nla_ops);
        }

        if (!list_empty(&family->mcast_groups)) {
                struct genl_multicast_group *grp;
                struct nlattr *nla_grps;
                int idx = 1;

                nla_grps = nla_nest_start(skb, CTRL_ATTR_MCAST_GROUPS);
                if (nla_grps == NULL)
                        goto nla_put_failure;

                list_for_each_entry(grp, &family->mcast_groups, list) {
                        struct nlattr *nest;

                        nest = nla_nest_start(skb, idx++);
                        if (nest == NULL)
                                goto nla_put_failure;

                        NLA_PUT_U32(skb, CTRL_ATTR_MCAST_GRP_ID, grp->id);
                        NLA_PUT_STRING(skb, CTRL_ATTR_MCAST_GRP_NAME,
                                       grp->name);

                        nla_nest_end(skb, nest);
                }
                nla_nest_end(skb, nla_grps);
        }

        return genlmsg_end(skb, hdr);

nla_put_failure:
        genlmsg_cancel(skb, hdr);
        return -EMSGSIZE;
}

static int ctrl_fill_mcgrp_info(struct genl_multicast_group *grp, u32 pid,
                                u32 seq, u32 flags, struct sk_buff *skb,
                                u8 cmd)
{
        void *hdr;
        struct nlattr *nla_grps;
        struct nlattr *nest;

        hdr = genlmsg_put(skb, pid, seq, &genl_ctrl, flags, cmd);
        if (hdr == NULL)
                return -1;

        NLA_PUT_STRING(skb, CTRL_ATTR_FAMILY_NAME, grp->family->name);
        NLA_PUT_U16(skb, CTRL_ATTR_FAMILY_ID, grp->family->id);

        nla_grps = nla_nest_start(skb, CTRL_ATTR_MCAST_GROUPS);
        if (nla_grps == NULL)
                goto nla_put_failure;

        nest = nla_nest_start(skb, 1);
        if (nest == NULL)
                goto nla_put_failure;

        NLA_PUT_U32(skb, CTRL_ATTR_MCAST_GRP_ID, grp->id);
        NLA_PUT_STRING(skb, CTRL_ATTR_MCAST_GRP_NAME,
                       grp->name);

        nla_nest_end(skb, nest);
        nla_nest_end(skb, nla_grps);

        return genlmsg_end(skb, hdr);

nla_put_failure:
        genlmsg_cancel(skb, hdr);
        return -EMSGSIZE;
}

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_family_msg(struct genl_family *family,
                                             u32 pid, int seq, u8 cmd)
{
        struct sk_buff *skb;
        int err;

        skb = nlmsg_new(NLMSG_DEFAULT_SIZE, 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 sk_buff *ctrl_build_mcgrp_msg(struct genl_multicast_group *grp,
                                            u32 pid, int seq, u8 cmd)
{
        struct sk_buff *skb;
        int err;

        skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (skb == NULL)
                return ERR_PTR(-ENOBUFS);

        err = ctrl_fill_mcgrp_info(grp, pid, seq, 0, skb, cmd);
        if (err < 0) {
                nlmsg_free(skb);
                return ERR_PTR(err);
        }

        return skb;
}

static const struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] = {
        [CTRL_ATTR_FAMILY_ID]   = { .type = NLA_U16 },
        [CTRL_ATTR_FAMILY_NAME] = { .type = NLA_NUL_STRING,
                                    .len = GENL_NAMSIZ - 1 },
};

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;

                name = nla_data(info->attrs[CTRL_ATTR_FAMILY_NAME]);
                res = genl_family_find_byname(name);
        }

        if (res == NULL) {
                err = -ENOENT;
                goto errout;
        }

        msg = ctrl_build_family_msg(res, info->snd_pid, info->snd_seq,
                                    CTRL_CMD_NEWFAMILY);
        if (IS_ERR(msg)) {
                err = PTR_ERR(msg);
                goto errout;
        }

        err = genlmsg_reply(msg, info);
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_family_msg(data, 0, 0, event);
                if (IS_ERR(msg))
                        return PTR_ERR(msg);

                genlmsg_multicast(msg, 0, GENL_ID_CTRL, GFP_KERNEL);
                break;
        case CTRL_CMD_NEWMCAST_GRP:
        case CTRL_CMD_DELMCAST_GRP:
                msg = ctrl_build_mcgrp_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_multicast_group notify_grp = {
        .name           = "notify",
};

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);

        /* we'll bump the group number right afterwards */
        genl_sock = netlink_kernel_create(&init_net, NETLINK_GENERIC, 0,
                                          genl_rcv, &genl_mutex, THIS_MODULE);
        if (genl_sock == NULL)
                panic("GENL: Cannot initialize generic netlink\n");

        err = genl_register_mc_group(&genl_ctrl, &notify_grp);
        if (err < 0)
                goto errout_register;

        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);