Commit 64c83d83 authored by Jamal Hadi Salim's avatar Jamal Hadi Salim Committed by David S. Miller
Browse files

net netlink: Add new type NLA_BITFIELD32 



Generic bitflags attribute content sent to the kernel by user.
With this netlink attr type the user can either set or unset a
flag in the kernel.

The value is a bitmap that defines the bit values being set
The selector is a bitmask that defines which value bit is to be
considered.

A check is made to ensure the rules that a kernel subsystem always
conforms to bitflags the kernel already knows about. i.e
if the user tries to set a bit flag that is not understood then
the _it will be rejected_.

In the most basic form, the user specifies the attribute policy as:
[ATTR_GOO] = { .type = NLA_BITFIELD32, .validation_data = &myvalidflags },

where myvalidflags is the bit mask of the flags the kernel understands.

If the user _does not_ provide myvalidflags then the attribute will
also be rejected.

Examples:
value = 0x0, and selector = 0x1
implies we are selecting bit 1 and we want to set its value to 0.

value = 0x2, and selector = 0x2
implies we are selecting bit 2 and we want to set its value to 1.

Suggested-by: default avatarJiri Pirko <jiri@mellanox.com>
Signed-off-by: default avatarJamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fbbeefdd

include/net/netlink.h

+16 −0
Original line number Diff line number Diff line
@@ -178,6 +178,7 @@ enum { 
	NLA_S16,

	NLA_S32,

	NLA_S64,

	NLA_BITFIELD32,

	__NLA_TYPE_MAX,

};
@@ -206,6 +207,7 @@ enum { 
 *    NLA_MSECS            Leaving the length field zero will verify the

 *                         given type fits, using it verifies minimum length

 *                         just like "All other"

 *    NLA_BITFIELD32      A 32-bit bitmap/bitselector attribute

 *    All other            Minimum length of attribute payload

 *

 * Example:
@@ -213,11 +215,13 @@ enum { 
 * 	[ATTR_FOO] = { .type = NLA_U16 },

 *	[ATTR_BAR] = { .type = NLA_STRING, .len = BARSIZ },

 *	[ATTR_BAZ] = { .len = sizeof(struct mystruct) },

 *	[ATTR_GOO] = { .type = NLA_BITFIELD32, .validation_data = &myvalidflags },

 * };

 */

struct nla_policy {

	u16		type;

	u16		len;

	void            *validation_data;

};



/**
@@ -1202,6 +1206,18 @@ static inline struct in6_addr nla_get_in6_addr(const struct nlattr *nla) 
	return tmp;

}



/**

 * nla_get_bitfield32 - return payload of 32 bitfield attribute

 * @nla: nla_bitfield32 attribute

 */

static inline struct nla_bitfield32 nla_get_bitfield32(const struct nlattr *nla)

{

	struct nla_bitfield32 tmp;



	nla_memcpy(&tmp, nla, sizeof(tmp));

	return tmp;

}



/**

 * nla_memdup - duplicate attribute memory (kmemdup)

 * @src: netlink attribute to duplicate from

include/uapi/linux/netlink.h

+17 −0
Original line number Diff line number Diff line
@@ -226,5 +226,22 @@ struct nlattr { 
#define NLA_ALIGN(len)		(((len) + NLA_ALIGNTO - 1) & ~(NLA_ALIGNTO - 1))

#define NLA_HDRLEN		((int) NLA_ALIGN(sizeof(struct nlattr)))



/* Generic 32 bitflags attribute content sent to the kernel.

 *

 * The value is a bitmap that defines the values being set

 * The selector is a bitmask that defines which value is legit

 *

 * Examples:

 *  value = 0x0, and selector = 0x1

 *  implies we are selecting bit 1 and we want to set its value to 0.

 *

 *  value = 0x2, and selector = 0x2

 *  implies we are selecting bit 2 and we want to set its value to 1.

 *

 */

struct nla_bitfield32 {

	__u32 value;

	__u32 selector;

};



#endif /* _UAPI__LINUX_NETLINK_H */

lib/nlattr.c

+30 −0
Original line number Diff line number Diff line
@@ -27,6 +27,30 @@ static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = { 
	[NLA_S64]	= sizeof(s64),

};



static int validate_nla_bitfield32(const struct nlattr *nla,

				   u32 *valid_flags_allowed)

{

	const struct nla_bitfield32 *bf = nla_data(nla);

	u32 *valid_flags_mask = valid_flags_allowed;



	if (!valid_flags_allowed)

		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 validate_nla(const struct nlattr *nla, int maxtype,

			const struct nla_policy *policy)

{
@@ -46,6 +70,12 @@ static int validate_nla(const struct nlattr *nla, int maxtype, 
			return -ERANGE;

		break;



	case NLA_BITFIELD32:

		if (attrlen != sizeof(struct nla_bitfield32))

			return -ERANGE;



		return validate_nla_bitfield32(nla, pt->validation_data);



	case NLA_NUL_STRING:

		if (pt->len)

			minlen = min_t(int, attrlen, pt->len + 1);

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