// SPDX-License-Identifier: GPL-2.0
/*
 * NETLINK      Netlink attributes
 *
 *              Authors:        Thomas Graf <tgraf@suug.ch>
 *                              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
 */

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

/* For these data types, attribute length should be exactly the given
 * size. However, to maintain compatibility with broken commands, if the
 * attribute length does not match the expected size a warning is emitted
 * to the user that the command is sending invalid data and needs to be fixed.
 */
static const u8 nla_attr_len[NLA_TYPE_MAX+1] = {
        [NLA_U8]        = sizeof(u8),
        [NLA_U16]       = sizeof(u16),
        [NLA_U32]       = sizeof(u32),
        [NLA_U64]       = sizeof(u64),
        [NLA_S8]        = sizeof(s8),
        [NLA_S16]       = sizeof(s16),
        [NLA_S32]       = sizeof(s32),
        [NLA_S64]       = sizeof(s64),
        [NLA_BE16]      = sizeof(__be16),
        [NLA_BE32]      = sizeof(__be32),
};

static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
        [NLA_U8]        = sizeof(u8),
        [NLA_U16]       = sizeof(u16),
        [NLA_U32]       = sizeof(u32),
        [NLA_U64]       = sizeof(u64),
        [NLA_MSECS]     = sizeof(u64),
        [NLA_NESTED]    = NLA_HDRLEN,
        [NLA_S8]        = sizeof(s8),
        [NLA_S16]       = sizeof(s16),
        [NLA_S32]       = sizeof(s32),
        [NLA_S64]       = sizeof(s64),
        [NLA_BE16]      = sizeof(__be16),
        [NLA_BE32]      = sizeof(__be32),
};

/*
 * Nested policies might refer back to the original
 * policy in some cases, and userspace could try to
 * abuse that and recurse by nesting in the right
 * ways. Limit recursion to avoid this problem.
 */
#define MAX_POLICY_RECURSION_DEPTH      10

static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
                                const struct nla_policy *policy,
                                unsigned int validate,
                                struct netlink_ext_ack *extack,
                                struct nlattr **tb, unsigned int depth);

static int validate_nla_bitfield32(const struct nlattr *nla,
                                   const u32 valid_flags_mask)
{
        const struct nla_bitfield32 *bf = nla_data(nla);

        if (!valid_flags_mask)
                return -EINVAL;

        /*disallow invalid bit selector */
        if (bf->selector & ~valid_flags_mask)
                return -EINVAL;

        /*disallow invalid bit values */
        if (bf->value & ~valid_flags_mask)
                return -EINVAL;

        /*disallow valid bit values that are not selected*/
        if (bf->value & ~bf->selector)
                return -EINVAL;

        return 0;
}

static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
                              const struct nla_policy *policy,
                              struct netlink_ext_ack *extack,
                              unsigned int validate, unsigned int depth)
{
        const struct nlattr *entry;
        int rem;

        nla_for_each_attr(entry, head, len, rem) {
                int ret;

                if (nla_len(entry) == 0)
                        continue;

                if (nla_len(entry) < NLA_HDRLEN) {
                        NL_SET_ERR_MSG_ATTR_POL(extack, entry, policy,
                                                "Array element too short");
                        return -ERANGE;
                }

                ret = __nla_validate_parse(nla_data(entry), nla_len(entry),
                                           maxtype, policy, validate, extack,
                                           NULL, depth + 1);
                if (ret < 0)
                        return ret;
        }

        return 0;
}

void nla_get_range_unsigned(const struct nla_policy *pt,
                            struct netlink_range_validation *range)
{
        WARN_ON_ONCE(pt->validation_type != NLA_VALIDATE_RANGE_PTR &&
                     (pt->min < 0 || pt->max < 0));

        range->min = 0;

        switch (pt->type) {
        case NLA_U8:
                range->max = U8_MAX;
                break;
        case NLA_U16:
        case NLA_BE16:
        case NLA_BINARY:
                range->max = U16_MAX;
                break;
        case NLA_U32:
        case NLA_BE32:
                range->max = U32_MAX;
                break;
        case NLA_U64:
        case NLA_UINT:
        case NLA_MSECS:
                range->max = U64_MAX;
                break;
        default:
                WARN_ON_ONCE(1);
                return;
        }

        switch (pt->validation_type) {
        case NLA_VALIDATE_RANGE:
        case NLA_VALIDATE_RANGE_WARN_TOO_LONG:
                range->min = pt->min;
                range->max = pt->max;
                break;
        case NLA_VALIDATE_RANGE_PTR:
                *range = *pt->range;
                break;
        case NLA_VALIDATE_MIN:
                range->min = pt->min;
                break;
        case NLA_VALIDATE_MAX:
                range->max = pt->max;
                break;
        default:
                break;
        }
}

static int nla_validate_range_unsigned(const struct nla_policy *pt,
                                       const struct nlattr *nla,
                                       struct netlink_ext_ack *extack,
                                       unsigned int validate)
{
        struct netlink_range_validation range;
        u64 value;

        switch (pt->type) {
        case NLA_U8:
                value = nla_get_u8(nla);
                break;
        case NLA_U16:
                value = nla_get_u16(nla);
                break;
        case NLA_U32:
                value = nla_get_u32(nla);
                break;
        case NLA_U64:
                value = nla_get_u64(nla);
                break;
        case NLA_UINT:
                value = nla_get_uint(nla);
                break;
        case NLA_MSECS:
                value = nla_get_u64(nla);
                break;
        case NLA_BINARY:
                value = nla_len(nla);
                break;
        case NLA_BE16:
                value = ntohs(nla_get_be16(nla));
                break;
        case NLA_BE32:
                value = ntohl(nla_get_be32(nla));
                break;
        default:
                return -EINVAL;
        }

        nla_get_range_unsigned(pt, &range);

        if (pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG &&
            pt->type == NLA_BINARY && value > range.max) {
                pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
                                    current->comm, pt->type);
                if (validate & NL_VALIDATE_STRICT_ATTRS) {
                        NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                                "invalid attribute length");
                        return -EINVAL;
                }

                /* this assumes min <= max (don't validate against min) */
                return 0;
        }

        if (value < range.min || value > range.max) {
                bool binary = pt->type == NLA_BINARY;

                if (binary)
                        NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                                "binary attribute size out of range");
                else
                        NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                                "integer out of range");

                return -ERANGE;
        }

        return 0;
}

void nla_get_range_signed(const struct nla_policy *pt,
                          struct netlink_range_validation_signed *range)
{
        switch (pt->type) {
        case NLA_S8:
                range->min = S8_MIN;
                range->max = S8_MAX;
                break;
        case NLA_S16:
                range->min = S16_MIN;
                range->max = S16_MAX;
                break;
        case NLA_S32:
                range->min = S32_MIN;
                range->max = S32_MAX;
                break;
        case NLA_S64:
        case NLA_SINT:
                range->min = S64_MIN;
                range->max = S64_MAX;
                break;
        default:
                WARN_ON_ONCE(1);
                return;
        }

        switch (pt->validation_type) {
        case NLA_VALIDATE_RANGE:
                range->min = pt->min;
                range->max = pt->max;
                break;
        case NLA_VALIDATE_RANGE_PTR:
                *range = *pt->range_signed;
                break;
        case NLA_VALIDATE_MIN:
                range->min = pt->min;
                break;
        case NLA_VALIDATE_MAX:
                range->max = pt->max;
                break;
        default:
                break;
        }
}

static int nla_validate_int_range_signed(const struct nla_policy *pt,
                                         const struct nlattr *nla,
                                         struct netlink_ext_ack *extack)
{
        struct netlink_range_validation_signed range;
        s64 value;

        switch (pt->type) {
        case NLA_S8:
                value = nla_get_s8(nla);
                break;
        case NLA_S16:
                value = nla_get_s16(nla);
                break;
        case NLA_S32:
                value = nla_get_s32(nla);
                break;
        case NLA_S64:
                value = nla_get_s64(nla);
                break;
        case NLA_SINT:
                value = nla_get_sint(nla);
                break;
        default:
                return -EINVAL;
        }

        nla_get_range_signed(pt, &range);

        if (value < range.min || value > range.max) {
                NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                        "integer out of range");
                return -ERANGE;
        }

        return 0;
}

static int nla_validate_int_range(const struct nla_policy *pt,
                                  const struct nlattr *nla,
                                  struct netlink_ext_ack *extack,
                                  unsigned int validate)
{
        switch (pt->type) {
        case NLA_U8:
        case NLA_U16:
        case NLA_U32:
        case NLA_U64:
        case NLA_UINT:
        case NLA_MSECS:
        case NLA_BINARY:
        case NLA_BE16:
        case NLA_BE32:
                return nla_validate_range_unsigned(pt, nla, extack, validate);
        case NLA_S8:
        case NLA_S16:
        case NLA_S32:
        case NLA_S64:
        case NLA_SINT:
                return nla_validate_int_range_signed(pt, nla, extack);
        default:
                WARN_ON(1);
                return -EINVAL;
        }
}

static int nla_validate_mask(const struct nla_policy *pt,
                             const struct nlattr *nla,
                             struct netlink_ext_ack *extack)
{
        u64 value;

        switch (pt->type) {
        case NLA_U8:
                value = nla_get_u8(nla);
                break;
        case NLA_U16:
                value = nla_get_u16(nla);
                break;
        case NLA_U32:
                value = nla_get_u32(nla);
                break;
        case NLA_U64:
                value = nla_get_u64(nla);
                break;
        case NLA_UINT:
                value = nla_get_uint(nla);
                break;
        case NLA_BE16:
                value = ntohs(nla_get_be16(nla));
                break;
        case NLA_BE32:
                value = ntohl(nla_get_be32(nla));
                break;
        default:
                return -EINVAL;
        }

        if (value & ~(u64)pt->mask) {
                NL_SET_ERR_MSG_ATTR(extack, nla, "reserved bit set");
                return -EINVAL;
        }

        return 0;
}

static int validate_nla(const struct nlattr *nla, int maxtype,
                        const struct nla_policy *policy, unsigned int validate,
                        struct netlink_ext_ack *extack, unsigned int depth)
{
        u16 strict_start_type = policy[0].strict_start_type;
        const struct nla_policy *pt;
        int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
        int err = -ERANGE;

        if (strict_start_type && type >= strict_start_type)
                validate |= NL_VALIDATE_STRICT;

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

        type = array_index_nospec(type, maxtype + 1);
        pt = &policy[type];

        BUG_ON(pt->type > NLA_TYPE_MAX);

        if (nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) {
                pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
                                    current->comm, type);
                if (validate & NL_VALIDATE_STRICT_ATTRS) {
                        NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                                "invalid attribute length");
                        return -EINVAL;
                }
        }

        if (validate & NL_VALIDATE_NESTED) {
                if ((pt->type == NLA_NESTED || pt->type == NLA_NESTED_ARRAY) &&
                    !(nla->nla_type & NLA_F_NESTED)) {
                        NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                                "NLA_F_NESTED is missing");
                        return -EINVAL;
                }
                if (pt->type != NLA_NESTED && pt->type != NLA_NESTED_ARRAY &&
                    pt->type != NLA_UNSPEC && (nla->nla_type & NLA_F_NESTED)) {
                        NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                                "NLA_F_NESTED not expected");
                        return -EINVAL;
                }
        }

        switch (pt->type) {
        case NLA_REJECT:
                if (extack && pt->reject_message) {
                        NL_SET_BAD_ATTR(extack, nla);
                        extack->_msg = pt->reject_message;
                        return -EINVAL;
                }
                err = -EINVAL;
                goto out_err;

        case NLA_FLAG:
                if (attrlen > 0)
                        goto out_err;
                break;

        case NLA_SINT:
        case NLA_UINT:
                if (attrlen != sizeof(u32) && attrlen != sizeof(u64)) {
                        NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                                "invalid attribute length");
                        return -EINVAL;
                }
                break;

        case NLA_BITFIELD32:
                if (attrlen != sizeof(struct nla_bitfield32))
                        goto out_err;

                err = validate_nla_bitfield32(nla, pt->bitfield32_valid);
                if (err)
                        goto out_err;
                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) {
                        err = -EINVAL;
                        goto out_err;
                }
                fallthrough;

        case NLA_STRING:
                if (attrlen < 1)
                        goto out_err;

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

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

                        if (attrlen > pt->len)
                                goto out_err;
                }
                break;

        case NLA_BINARY:
                if (pt->len && attrlen > pt->len)
                        goto out_err;
                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;
                if (attrlen < NLA_HDRLEN)
                        goto out_err;
                if (pt->nested_policy) {
                        err = __nla_validate_parse(nla_data(nla), nla_len(nla),
                                                   pt->len, pt->nested_policy,
                                                   validate, extack, NULL,
                                                   depth + 1);
                        if (err < 0) {
                                /*
                                 * return directly to preserve the inner
                                 * error message/attribute pointer
                                 */
                                return err;
                        }
                }
                break;
        case NLA_NESTED_ARRAY:
                /* a nested array attribute is allowed to be empty; if its not,
                 * it must have a size of at least NLA_HDRLEN.
                 */
                if (attrlen == 0)
                        break;
                if (attrlen < NLA_HDRLEN)
                        goto out_err;
                if (pt->nested_policy) {
                        int err;

                        err = nla_validate_array(nla_data(nla), nla_len(nla),
                                                 pt->len, pt->nested_policy,
                                                 extack, validate, depth);
                        if (err < 0) {
                                /*
                                 * return directly to preserve the inner
                                 * error message/attribute pointer
                                 */
                                return err;
                        }
                }
                break;

        case NLA_UNSPEC:
                if (validate & NL_VALIDATE_UNSPEC) {
                        NL_SET_ERR_MSG_ATTR(extack, nla,
                                            "Unsupported attribute");
                        return -EINVAL;
                }
                if (attrlen < pt->len)
                        goto out_err;
                break;

        default:
                if (pt->len)
                        minlen = pt->len;
                else
                        minlen = nla_attr_minlen[pt->type];

                if (attrlen < minlen)
                        goto out_err;
        }

        /* further validation */
        switch (pt->validation_type) {
        case NLA_VALIDATE_NONE:
                /* nothing to do */
                break;
        case NLA_VALIDATE_RANGE_PTR:
        case NLA_VALIDATE_RANGE:
        case NLA_VALIDATE_RANGE_WARN_TOO_LONG:
        case NLA_VALIDATE_MIN:
        case NLA_VALIDATE_MAX:
                err = nla_validate_int_range(pt, nla, extack, validate);
                if (err)
                        return err;
                break;
        case NLA_VALIDATE_MASK:
                err = nla_validate_mask(pt, nla, extack);
                if (err)
                        return err;
                break;
        case NLA_VALIDATE_FUNCTION:
                if (pt->validate) {
                        err = pt->validate(nla, extack);
                        if (err)
                                return err;
                }
                break;
        }

        return 0;
out_err:
        NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
                                "Attribute failed policy validation");
        return err;
}

static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
                                const struct nla_policy *policy,
                                unsigned int validate,
                                struct netlink_ext_ack *extack,
                                struct nlattr **tb, unsigned int depth)
{
        const struct nlattr *nla;
        int rem;

        if (depth >= MAX_POLICY_RECURSION_DEPTH) {
                NL_SET_ERR_MSG(extack,
                               "allowed policy recursion depth exceeded");
                return -EINVAL;
        }

        if (tb)
                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 (validate & NL_VALIDATE_MAXTYPE) {
                                NL_SET_ERR_MSG_ATTR(extack, nla,
                                                    "Unknown attribute type");
                                return -EINVAL;
                        }
                        continue;
                }
                type = array_index_nospec(type, maxtype + 1);
                if (policy) {
                        int err = validate_nla(nla, maxtype, policy,
                                               validate, extack, depth);

                        if (err < 0)
                                return err;
                }

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

        if (unlikely(rem > 0)) {
                pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
                                    rem, current->comm);
                NL_SET_ERR_MSG(extack, "bytes leftover after parsing attributes");
                if (validate & NL_VALIDATE_TRAILING)
                        return -EINVAL;
        }

        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
 * @validate: validation strictness
 * @extack: extended ACK report struct
 *
 * Validates all attributes in the specified attribute stream against the
 * specified policy. Validation depends on the validate flags passed, see
 * &enum netlink_validation for more details on that.
 * See documentation 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, unsigned int validate,
                   struct netlink_ext_ack *extack)
{
        return __nla_validate_parse(head, len, maxtype, policy, validate,
                                    extack, NULL, 0);
}
EXPORT_SYMBOL(__nla_validate);

/**
 * nla_policy_len - Determine the max. length of a policy
 * @p: 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_len[p->type])
                        len += nla_total_size(nla_attr_len[p->type]);
                else if (nla_attr_minlen[p->type])
                        len += nla_total_size(nla_attr_minlen[p->type]);
        }

        return len;
}
EXPORT_SYMBOL(nla_policy_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
 * @validate: validation strictness
 * @extack: extended ACK pointer
 *
 * Parses a stream of attributes and stores a pointer to each attribute in
 * the tb array accessible via the attribute type.
 * Validation is controlled by the @validate parameter.
 *
 * 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, unsigned int validate,
                struct netlink_ext_ack *extack)
{
        return __nla_validate_parse(head, len, maxtype, policy, validate,
                                    extack, tb, 0);
}
EXPORT_SYMBOL(__nla_parse);

/**
 * 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;
}
EXPORT_SYMBOL(nla_find);

/**
 * nla_strscpy - 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.
 * Unlike strscpy() the destination buffer is always padded out.
 *
 * Return:
 * * srclen - Returns @nla length (not including the trailing %NUL).
 * * -E2BIG - If @dstsize is 0 or greater than U16_MAX or @nla length greater
 *            than @dstsize.
 */
ssize_t nla_strscpy(char *dst, const struct nlattr *nla, size_t dstsize)
{
        size_t srclen = nla_len(nla);
        char *src = nla_data(nla);
        ssize_t ret;
        size_t len;

        if (dstsize == 0 || WARN_ON_ONCE(dstsize > U16_MAX))
                return -E2BIG;

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

        if (srclen >= dstsize) {
                len = dstsize - 1;
                ret = -E2BIG;
        } else {
                len = srclen;
                ret = len;
        }

        memcpy(dst, src, len);
        /* Zero pad end of dst. */
        memset(dst + len, 0, dstsize - len);

        return ret;
}
EXPORT_SYMBOL(nla_strscpy);

/**
 * nla_strdup - Copy string attribute payload into a newly allocated buffer
 * @nla: attribute to copy the string from
 * @flags: the type of memory to allocate (see kmalloc).
 *
 * Returns a pointer to the allocated buffer or NULL on error.
 */
char *nla_strdup(const struct nlattr *nla, gfp_t flags)
{
        size_t srclen = nla_len(nla);
        char *src = nla_data(nla), *dst;

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

        dst = kmalloc(srclen + 1, flags);
        if (dst != NULL) {
                memcpy(dst, src, srclen);
                dst[srclen] = '\0';
        }
        return dst;
}
EXPORT_SYMBOL(nla_strdup);

/**
 * 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);
        if (count > minlen)
                memset(dest + minlen, 0, count - minlen);

        return minlen;
}
EXPORT_SYMBOL(nla_memcpy);

/**
 * 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;
}
EXPORT_SYMBOL(nla_memcmp);

/**
 * 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);
        char *buf = nla_data(nla);
        int attrlen = nla_len(nla);
        int d;

        while (attrlen > 0 && buf[attrlen - 1] == '\0')
                attrlen--;

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

        return d;
}
EXPORT_SYMBOL(nla_strcmp);

#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 = 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_64bit - reserve room for attribute on the skb and align it
 * @skb: socket buffer to reserve room on
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @padattr: attribute type for the padding
 *
 * Adds a netlink attribute header to a socket buffer and reserves
 * room for the payload but does not copy it. It also ensure that this
 * attribute will have a 64-bit aligned nla_data() area.
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute header and payload.
 */
struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
                                   int attrlen, int padattr)
{
        nla_align_64bit(skb, padattr);

        return __nla_reserve(skb, attrtype, attrlen);
}
EXPORT_SYMBOL(__nla_reserve_64bit);

/**
 * __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)
{
        return skb_put_zero(skb, NLA_ALIGN(attrlen));
}
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_64bit - reserve room for attribute on the skb and align it
 * @skb: socket buffer to reserve room on
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @padattr: attribute type for the padding
 *
 * Adds a netlink attribute header to a socket buffer and reserves
 * room for the payload but does not copy it. It also ensure that this
 * attribute will have a 64-bit aligned nla_data() area.
 *
 * Returns NULL if the tailroom of the skb is insufficient to store
 * the attribute header and payload.
 */
struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
                                 int padattr)
{
        size_t len;

        if (nla_need_padding_for_64bit(skb))
                len = nla_total_size_64bit(attrlen);
        else
                len = nla_total_size(attrlen);
        if (unlikely(skb_tailroom(skb) < len))
                return NULL;

        return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
}
EXPORT_SYMBOL(nla_reserve_64bit);

/**
 * 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_64bit - Add a netlink attribute to a socket buffer and align it
 * @skb: socket buffer to add attribute to
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 * @padattr: attribute type for the padding
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute header and payload.
 */
void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
                     const void *data, int padattr)
{
        struct nlattr *nla;

        nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
        memcpy(nla_data(nla), data, attrlen);
}
EXPORT_SYMBOL(__nla_put_64bit);

/**
 * __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_64bit - Add a netlink attribute to a socket buffer and align it
 * @skb: socket buffer to add attribute to
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 * @padattr: attribute type for the padding
 *
 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 * the attribute header and payload.
 */
int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
                  const void *data, int padattr)
{
        size_t len;

        if (nla_need_padding_for_64bit(skb))
                len = nla_total_size_64bit(attrlen);
        else
                len = nla_total_size(attrlen);
        if (unlikely(skb_tailroom(skb) < len))
                return -EMSGSIZE;

        __nla_put_64bit(skb, attrtype, attrlen, data, padattr);
        return 0;
}
EXPORT_SYMBOL(nla_put_64bit);

/**
 * 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;

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