FreeBSD/Linux Kernel Cross Reference
sys/lib/nlattr.c

     /*
      * 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/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,
            [NLA_S8]        = sizeof(s8),
            [NLA_S16]       = sizeof(s16),
            [NLA_S32]       = sizeof(s32),
            [NLA_S64]       = sizeof(s64),
    };
    
    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);

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