/*
 * NETLINK      Netlink attributes
 *
 *              Authors:        Thomas Graf <tgraf@suug.ch>
 *                              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/jiffies.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/types.h>
#include <net/netlink.h>

static const u16 nla_attr_minlen[NLA_TYPE_MAX+1] = {
        [NLA_U8]        = sizeof(u8),
        [NLA_U16]       = sizeof(u16),
        [NLA_U32]       = sizeof(u32),
        [NLA_U64]       = sizeof(u64),
        [NLA_NESTED]    = NLA_HDRLEN,
};

static int validate_nla(const struct nlattr *nla, int maxtype,
                        const struct nla_policy *policy)
{
        const struct nla_policy *pt;
        int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);

        if (type <= 0 || type > maxtype)
                return 0;

        pt = &policy[type];

        BUG_ON(pt->type > NLA_TYPE_MAX);

        switch (pt->type) {
        case NLA_FLAG:
                if (attrlen > 0)
                        return -ERANGE;
                break;

        case NLA_NUL_STRING:
                if (pt->len)
                        minlen = min_t(int, attrlen, pt->len + 1);
                else
                        minlen = attrlen;

                if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
                        return -EINVAL;
                /* fall through */

        case NLA_STRING:
                if (attrlen < 1)
                        return -ERANGE;

                if (pt->len) {
                        char *buf = nla_data(nla);

                        if (buf[attrlen - 1] == '\0')
                                attrlen--;

                        if (attrlen > pt->len)
                                return -ERANGE;
                }
                break;

        case NLA_BINARY:
                if (pt->len && attrlen > pt->len)
                        return -ERANGE;
                break;

        case NLA_NESTED_COMPAT:
                if (attrlen < pt->len)
                        return -ERANGE;
                if (attrlen < NLA_ALIGN(pt->len))
                        break;
                if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
                        return -ERANGE;
                nla = nla_data(nla) + NLA_ALIGN(pt->len);
                if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
                        return -ERANGE;
                break;
        case NLA_NESTED:
                /* a nested attributes is allowed to be empty; if its not,
                 * it must have a size of at least NLA_HDRLEN.
                 */
                if (attrlen == 0)
                        break;
        default:
                if (pt->len)
                        minlen = pt->len;
                else if (pt->type != NLA_UNSPEC)
                        minlen = nla_attr_minlen[pt->type];

                if (attrlen < minlen)
                        return -ERANGE;
        }

        return 0;
}

/**
 * nla_validate - Validate a stream of attributes
 * @head: head of attribute stream
 * @len: length of attribute stream
 * @maxtype: maximum attribute type to be expected
 * @policy: validation policy
 *
 * Validates all attributes in the specified attribute stream against the
 * specified policy. Attributes with a type exceeding maxtype will be
 * ignored. See documenation of struct nla_policy for more details.
 *
 * Returns 0 on success or a negative error code.
 */
int nla_validate(const struct nlattr *head, int len, int maxtype,
                 const struct nla_policy *policy)
{
        const struct nlattr *nla;
        int rem, err;

        nla_for_each_attr(nla, head, len, rem) {
                err = validate_nla(nla, maxtype, policy);
                if (err < 0)
                        goto errout;
        }

        err = 0;
errout:
        return err;
}

/**
 * nla_policy_len - Determin the max. length of a policy
 * @policy: policy to use
 * @n: number of policies
 *
 * Determines the max. length of the policy.  It is currently used
 * to allocated Netlink buffers roughly the size of the actual
 * message.
 *
 * Returns 0 on success or a negative error code.
 */
int
nla_policy_len(const struct nla_policy *p, int n)
{
        int i, len = 0;

        for (i = 0; i < n; i++, p++) {
                if (p->len)
                        len += nla_total_size(p->len);
                else if (nla_attr_minlen[p->type])
                        len += nla_total_size(nla_attr_minlen[p->type]);
        }

        return len;
}

/**
 * nla_parse - Parse a stream of attributes into a tb buffer
 * @tb: destination array with maxtype+1 elements
 * @maxtype: maximum attribute type to be expected
 * @head: head of attribute stream
 * @len: length of attribute stream
 * @policy: validation policy
 *
 * Parses a stream of attributes and stores a pointer to each attribute in
 * the tb array accessible via the attribute type. Attributes with a type
 * exceeding maxtype will be silently ignored for backwards compatibility
 * reasons. policy may be set to NULL if no validation is required.
 *
 * Returns 0 on success or a negative error code.
 */
int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
              int len, const struct nla_policy *policy)
{
        const struct nlattr *nla;
        int rem, err;

        memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));

        nla_for_each_attr(nla, head, len, rem) {
                u16 type = nla_type(nla);

                if (type > 0 && type <= maxtype) {
                        if (policy) {
                                err = validate_nla(nla, maxtype, policy);
                                if (err < 0)
                                        goto errout;
                        }

                        tb[type] = (struct nlattr *)nla;
                }
        }

        if (unlikely(rem > 0))
                printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
                       "attributes.\n", rem);

        err = 0;
errout:
        return err;
}

/**
 * nla_find - Find a specific attribute in a stream of attributes
 * @head: head of attribute stream
 * @len: length of attribute stream
 * @attrtype: type of attribute to look for
 *
 * Returns the first attribute in the stream matching the specified type.
 */
struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
{
        const struct nlattr *nla;
        int rem;

        nla_for_each_attr(nla, head, len, rem)
                if (nla_type(nla) == attrtype)
                        return (struct nlattr *)nla;

        return NULL;
}

/**
 * nla_strlcpy - Copy string attribute payload into a sized buffer
 * @dst: where to copy the string to
 * @nla: attribute to copy the string from
 * @dstsize: size of destination buffer
 *
 * Copies at most dstsize - 1 bytes into the destination buffer.
 * The result is always a valid NUL-terminated string. Unlike
 * strlcpy the destination buffer is always padded out.
 *
 * Returns the length of the source buffer.
 */
size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
{
        size_t srclen = nla_len(nla);
        char *src = nla_data(nla);

        if (srclen > 0 && src[srclen - 1] == '\0')
                srclen--;

        if (dstsize > 0) {
                size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;

                memset(dst, 0, dstsize);
                memcpy(dst, src, len);
        }

        return srclen;
}

/**
 * nla_memcpy - Copy a netlink attribute into another memory area
 * @dest: where to copy to memcpy
 * @src: netlink attribute to copy from
 * @count: size of the destination area
 *
 * Note: The number of bytes copied is limited by the length of
 *       attribute's payload. memcpy
 *
 * Returns the number of bytes copied.
 */
int nla_memcpy(void *dest, const struct nlattr *src, int count)
{
        int minlen = min_t(int, count, nla_len(src));

        memcpy(dest, nla_data(src), minlen);

        return minlen;
}

/**
 * nla_memcmp - Compare an attribute with sized memory area
 * @nla: netlink attribute
 * @data: memory area
 * @size: size of memory area
 */
int nla_memcmp(const struct nlattr *nla, const void *data,
                             size_t size)
{
        int d = nla_len(nla) - size;

        if (d == 0)
                d = memcmp(nla_data(nla), data, size);

        return d;
}

/**
 * nla_strcmp - Compare a string attribute against a string
 * @nla: netlink string attribute
 * @str: another string
 */
int nla_strcmp(const struct nlattr *nla, const char *str)
{
        int len = strlen(str) + 1;
        int d = nla_len(nla) - len;

        if (d == 0)
                d = memcmp(nla_data(nla), str, len);

        return d;
}

#ifdef CONFIG_NET
/**
 * __nla_reserve - reserve room for attribute on the skb
 * @skb: socket buffer to reserve room on
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 *
 * Adds a netlink attribute header to a socket buffer and reserves
 * room for the payload but does not copy it.
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute header and payload.
 */
struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
        struct nlattr *nla;

        nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
        nla->nla_type = attrtype;
        nla->nla_len = nla_attr_size(attrlen);

        memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));

        return nla;
}
EXPORT_SYMBOL(__nla_reserve);

/**
 * __nla_reserve_nohdr - reserve room for attribute without header
 * @skb: socket buffer to reserve room on
 * @attrlen: length of attribute payload
 *
 * Reserves room for attribute payload without a header.
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the payload.
 */
void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
        void *start;

        start = skb_put(skb, NLA_ALIGN(attrlen));
        memset(start, 0, NLA_ALIGN(attrlen));

        return start;
}
EXPORT_SYMBOL(__nla_reserve_nohdr);

/**
 * nla_reserve - reserve room for attribute on the skb
 * @skb: socket buffer to reserve room on
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 *
 * Adds a netlink attribute header to a socket buffer and reserves
 * room for the payload but does not copy it.
 *
 * Returns NULL if the tailroom of the skb is insufficient to store
 * the attribute header and payload.
 */
struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
        if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
                return NULL;

        return __nla_reserve(skb, attrtype, attrlen);
}
EXPORT_SYMBOL(nla_reserve);

/**
 * nla_reserve_nohdr - reserve room for attribute without header
 * @skb: socket buffer to reserve room on
 * @attrlen: length of attribute payload
 *
 * Reserves room for attribute payload without a header.
 *
 * Returns NULL if the tailroom of the skb is insufficient to store
 * the attribute payload.
 */
void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
        if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
                return NULL;

        return __nla_reserve_nohdr(skb, attrlen);
}
EXPORT_SYMBOL(nla_reserve_nohdr);

/**
 * __nla_put - Add a netlink attribute to a socket buffer
 * @skb: socket buffer to add attribute to
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute header and payload.
 */
void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
                             const void *data)
{
        struct nlattr *nla;

        nla = __nla_reserve(skb, attrtype, attrlen);
        memcpy(nla_data(nla), data, attrlen);
}
EXPORT_SYMBOL(__nla_put);

/**
 * __nla_put_nohdr - Add a netlink attribute without header
 * @skb: socket buffer to add attribute to
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute payload.
 */
void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
{
        void *start;

        start = __nla_reserve_nohdr(skb, attrlen);
        memcpy(start, data, attrlen);
}
EXPORT_SYMBOL(__nla_put_nohdr);

/**
 * nla_put - Add a netlink attribute to a socket buffer
 * @skb: socket buffer to add attribute to
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 * the attribute header and payload.
 */
int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
{
        if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
                return -EMSGSIZE;

        __nla_put(skb, attrtype, attrlen, data);
        return 0;
}
EXPORT_SYMBOL(nla_put);

/**
 * nla_put_nohdr - Add a netlink attribute without header
 * @skb: socket buffer to add attribute to
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 * the attribute payload.
 */
int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
{
        if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
                return -EMSGSIZE;

        __nla_put_nohdr(skb, attrlen, data);
        return 0;
}
EXPORT_SYMBOL(nla_put_nohdr);

/**
 * nla_append - Add a netlink attribute without header or padding
 * @skb: socket buffer to add attribute to
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 * the attribute payload.
 */
int nla_append(struct sk_buff *skb, int attrlen, const void *data)
{
        if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
                return -EMSGSIZE;

        memcpy(skb_put(skb, attrlen), data, attrlen);
        return 0;
}
EXPORT_SYMBOL(nla_append);
#endif

EXPORT_SYMBOL(nla_validate);
EXPORT_SYMBOL(nla_policy_len);
EXPORT_SYMBOL(nla_parse);
EXPORT_SYMBOL(nla_find);
EXPORT_SYMBOL(nla_strlcpy);
EXPORT_SYMBOL(nla_memcpy);
EXPORT_SYMBOL(nla_memcmp);
EXPORT_SYMBOL(nla_strcmp);