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Commit 1092cb21 authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
Browse files

[NETLINK]: attr: add nested compat attribute type 



Add a nested compat attribute type that can be used to convert
attributes that contain a structure to nested attributes in a
backwards compatible way.

Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 334a8132

include/net/netlink.h

+84 −0
Original line number Diff line number Diff line
@@ -118,6 +118,9 @@ 
 * Nested Attributes Construction:

 *   nla_nest_start(skb, type)		start a nested attribute

 *   nla_nest_end(skb, nla)		finalize a nested attribute

 *   nla_nest_compat_start(skb, type,	start a nested compat attribute

 *			   len, data)

 *   nla_nest_compat_end(skb, type)	finalize a nested compat attribute

 *   nla_nest_cancel(skb, nla)		cancel nested attribute construction

 *

 * Attribute Length Calculations:
@@ -152,6 +155,7 @@ 
 *   nla_find_nested()			find attribute in nested attributes

 *   nla_parse()			parse and validate stream of attrs

 *   nla_parse_nested()			parse nested attribuets

 *   nla_parse_nested_compat()		parse nested compat attributes

 *   nla_for_each_attr()		loop over all attributes

 *   nla_for_each_nested()		loop over the nested attributes

 *=========================================================================
@@ -170,6 +174,7 @@ enum { 
	NLA_FLAG,

	NLA_MSECS,

	NLA_NESTED,

	NLA_NESTED_COMPAT,

	NLA_NUL_STRING,

	NLA_BINARY,

	__NLA_TYPE_MAX,
@@ -190,6 +195,7 @@ enum { 
 *    NLA_NUL_STRING       Maximum length of string (excluding NUL)

 *    NLA_FLAG             Unused

 *    NLA_BINARY           Maximum length of attribute payload

 *    NLA_NESTED_COMPAT    Exact length of structure payload

 *    All other            Exact length of attribute payload

 *

 * Example:
@@ -733,6 +739,39 @@ static inline int nla_parse_nested(struct nlattr *tb[], int maxtype, 
{

	return nla_parse(tb, maxtype, nla_data(nla), nla_len(nla), policy);

}



/**

 * nla_parse_nested_compat - parse nested compat attributes

 * @tb: destination array with maxtype+1 elements

 * @maxtype: maximum attribute type to be expected

 * @nla: attribute containing the nested attributes

 * @data: pointer to point to contained structure

 * @len: length of contained structure

 * @policy: validation policy

 *

 * Parse a nested compat attribute. The compat attribute contains a structure

 * and optionally a set of nested attributes. On success the data pointer

 * points to the nested data and tb contains the parsed attributes

 * (see nla_parse).

 */

static inline int __nla_parse_nested_compat(struct nlattr *tb[], int maxtype,

					    struct nlattr *nla,

					    const struct nla_policy *policy,

					    int len)

{

	if (nla_len(nla) < len)

		return -1;

	if (nla_len(nla) >= NLA_ALIGN(len) + sizeof(struct nlattr))

		return nla_parse_nested(tb, maxtype,

					nla_data(nla) + NLA_ALIGN(len),

					policy);

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

	return 0;

}



#define nla_parse_nested_compat(tb, maxtype, nla, policy, data, len) \

({	data = nla_len(nla) >= len ? nla_data(nla) : NULL; \

	__nla_parse_nested_compat(tb, maxtype, nla, policy, len); })

/**

 * nla_put_u8 - Add a u16 netlink attribute to a socket buffer

 * @skb: socket buffer to add attribute to
@@ -964,6 +1003,51 @@ static inline int nla_nest_end(struct sk_buff *skb, struct nlattr *start) 
	return skb->len;

}



/**

 * nla_nest_compat_start - Start a new level of nested compat attributes

 * @skb: socket buffer to add attributes to

 * @attrtype: attribute type of container

 * @attrlen: length of structure

 * @data: pointer to structure

 *

 * Start a nested compat attribute that contains both a structure and

 * a set of nested attributes.

 *

 * Returns the container attribute

 */

static inline struct nlattr *nla_nest_compat_start(struct sk_buff *skb,

						   int attrtype, int attrlen,

						   const void *data)

{

	struct nlattr *start = (struct nlattr *)skb_tail_pointer(skb);



	if (nla_put(skb, attrtype, attrlen, data) < 0)

		return NULL;

	if (nla_nest_start(skb, attrtype) == NULL) {

		nlmsg_trim(skb, start);

		return NULL;

	}

	return start;

}



/**

 * nla_nest_compat_end - Finalize nesting of compat attributes

 * @skb: socket buffer the attribtues are stored in

 * @start: container attribute

 *

 * Corrects the container attribute header to include the all

 * appeneded attributes.

 *

 * Returns the total data length of the skb.

 */

static inline int nla_nest_compat_end(struct sk_buff *skb, struct nlattr *start)

{

	struct nlattr *nest = (void *)start + NLMSG_ALIGN(start->nla_len);



	start->nla_len = skb_tail_pointer(skb) - (unsigned char *)start;

	return nla_nest_end(skb, nest);

}



/**

 * nla_nest_cancel - Cancel nesting of attributes

 * @skb: socket buffer the message is stored in

net/netlink/attr.c

+11 −0
Original line number Diff line number Diff line
@@ -72,6 +72,17 @@ static int validate_nla(struct nlattr *nla, int maxtype, 
			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;

	default:

		if (pt->len)

			minlen = pt->len;