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/*
* 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;
}
EXPORT_SYMBOL(nla_validate);

/**
* 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;
}
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
*
* 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))
pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
rem, current->comm);

err = 0;
errout:
return err;
}
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_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;
}
EXPORT_SYMBOL(nla_strlcpy);

/**
* 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;
}
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;

if (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 = (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
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