From: Jamal Hadi Salim <j...@mojatatu.com>
Generic bitflags attribute content sent to the kernel by user.
With this type the user can either set or unset a flag in the
kernel.
The nla_value is a bitmap that defines the values being set
The nla_selector is a bitmask that defines which value is legit.
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_BITFIELD_32, .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:
nla_value = 0x0, and nla_selector = 0x1
implies we are selecting bit 1 and we want to set its value to 0.
nla_value = 0x2, and nla_selector = 0x2
implies we are selecting bit 2 and we want to set its value to 1.
Signed-off-by: Jamal Hadi Salim <j...@mojatatu.com>
---
include/net/netlink.h | 4 ++++
include/uapi/linux/netlink.h | 17 +++++++++++++++++
lib/nlattr.c | 21 +++++++++++++++++++++
3 files changed, 42 insertions(+)
diff --git a/include/net/netlink.h b/include/net/netlink.h
index ef8e6c3..e33d1fb 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -178,6 +178,7 @@ enum {
NLA_S16,
NLA_S32,
NLA_S64,
+ NLA_BITFIELD_32,
__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_BITFIELD_32 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_BITFIELD_32, .validation_data =
&myvalidflags },
* };
*/
struct nla_policy {
u16 type;
u16 len;
+ void *validation_data;
};
/**
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index f86127a..0ac05a6 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -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 nla_value is a bitmap that defines the values being set
+ * The nla_selector is a bitmask that defines which value is legit
+ *
+ * Examples:
+ * nla_value = 0x0, and nla_selector = 0x1
+ * implies we are selecting bit 1 and we want to set its value to 0.
+ *
+ * nla_value = 0x2, and nla_selector = 0x2
+ * implies we are selecting bit 2 and we want to set its value to 1.
+ *
+ */
+struct nla_bitfield_32 {
+ __u32 nla_value;
+ __u32 nla_selector;
+};
#endif /* _UAPI__LINUX_NETLINK_H */
diff --git a/lib/nlattr.c b/lib/nlattr.c
index fb52435..c8aad7e 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -27,6 +27,20 @@
[NLA_S64] = sizeof(s64),
};
+static int validate_nla_bitfield_32(const struct nlattr *nla, void *valid_data)
+{
+ const struct nla_bitfield_32 *nbf = nla_data(nla);
+ u32 *valid_flags_mask = valid_data;
+
+ if (!valid_data)
+ return -EINVAL;
+
+ if (nbf->nla_value & ~*valid_flags_mask)
+ return -EINVAL;
+
+ return 0;
+}
+
static int validate_nla(const struct nlattr *nla, int maxtype,
const struct nla_policy *policy)
{
@@ -46,6 +60,13 @@ static int validate_nla(const struct nlattr *nla, int
maxtype,
return -ERANGE;
break;
+ case NLA_BITFIELD_32:
+ if (attrlen != sizeof(struct nla_bitfield_32))
+ return -ERANGE;
+
+ return validate_nla_bitfield_32(nla, pt->validation_data);
+ break;
+
case NLA_NUL_STRING:
if (pt->len)
minlen = min_t(int, attrlen, pt->len + 1);
--
1.9.1
