/*
   * 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_MSECS]	= 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.
  ", 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);