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_flag_values is a bitmap that defines the values being set
The nla_flag_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. Example
if the user tries to set a bit flag that is not understood then
the _it will be rejected_.
The user specifies the attribute policy as:
[ATTR_GOO] = { .type = NLA_FLAG_BITS, .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_flag_values = 0x0, and nla_flag_selector = 0x1
implies we are selecting bit 1 and we want to set its value to 0.
nla_flag_values = 0x2, and nla_flag_selector = 0x2
implies we are selecting bit 2 and we want to set its value to 1.
This patch also provides an extra feature (which should be a separate
pach): a validation callback that could be speaciliazed for other types.
So a kernel subsystem could specify validation rules of the following
nature:
[ATTR_GOO] = { .type = MYTYPE,
.validation_data = &myvalidation_data,
.validate_content = mycontent_validator },
With validator callback looking like:
int mycontent_validator(const struct nlattr *nla, void *valid_data)
{
const struct myattribute *user_data = nla_data(nla);
struct myvalidation_struct *valid_data_constraint = valid_data;
... validate user_data against valid_data_constraint ...
... return appropriate error code etc ...
}
Only compile tested to float the idea.
Signed-off-by: Jamal Hadi Salim <j...@mojatatu.com>
---
include/net/netlink.h | 11 +++++++++++
include/uapi/linux/rtnetlink.h | 17 +++++++++++++++++
lib/nlattr.c | 25 +++++++++++++++++++++++++
3 files changed, 53 insertions(+)
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 0170917..8ab9784 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -6,6 +6,11 @@
#include <linux/jiffies.h>
#include <linux/in6.h>
+struct nla_bit_flags {
+ u32 nla_flag_values;
+ u32 nla_flag_selector;
+};
+
/* ========================================================================
* Netlink Messages and Attributes Interface (As Seen On TV)
* ------------------------------------------------------------------------
@@ -178,6 +183,7 @@ enum {
NLA_S16,
NLA_S32,
NLA_S64,
+ NLA_FLAG_BITS,
__NLA_TYPE_MAX,
};
@@ -206,6 +212,7 @@ enum {
* NLA_MSECS Leaving the length field zero will verify the
* given type fits, using it verifies minimum length
* just like "All other"
+ * NLA_FLAG_BITS A bitmap/bitselector attribute
* All other Minimum length of attribute payload
*
* Example:
@@ -213,11 +220,15 @@ enum {
* [ATTR_FOO] = { .type = NLA_U16 },
* [ATTR_BAR] = { .type = NLA_STRING, .len = BARSIZ },
* [ATTR_BAZ] = { .len = sizeof(struct mystruct) },
+ * [ATTR_GOO] = { .type = NLA_FLAG_BITS, .validation_data = &myvalidflags
},
* };
*/
struct nla_policy {
u16 type;
u16 len;
+ void *validation_data;
+ int (*validate_content)(const struct nlattr *nla,
+ const void *validation_data);
};
/**
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index cce0613..3691d8d 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -179,6 +179,23 @@ struct rtattr {
#define RTA_DATA(rta) ((void*)(((char*)(rta)) + RTA_LENGTH(0)))
#define RTA_PAYLOAD(rta) ((int)((rta)->rta_len) - RTA_LENGTH(0))
+/* Generic bitflags attribute content sent to the kernel.
+ *
+ * The nla_flag_values is a bitmap that defines the values being set
+ * The nla_flag_selector is a bitmask that defines which value is legit
+ *
+ * Examples:
+ * nla_flag_values = 0x0, and nla_flag_selector = 0x1
+ * implies we are selecting bit 1 and we want to set its value to 0.
+ *
+ * nla_flag_values = 0x2, and nla_flag_selector = 0x2
+ * implies we are selecting bit 2 and we want to set its value to 1.
+ *
+ */
+struct __nla_bit_flags {
+ __u32 nla_flag_values;
+ __u32 nla_flag_selector;
+};
diff --git a/lib/nlattr.c b/lib/nlattr.c
index a7e0b16..78fed43 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -27,6 +27,21 @@
[NLA_S64] = sizeof(s64),
};
+static int validate_nla_bit_flags(const struct nlattr *nla, void *valid_data)
+{
+ const struct nla_bit_flags *nbf = nla_data(nla);
+ u32 *valid_flags_mask = valid_data;
+
+ if (!valid_data)
+ return -EINVAL;
+
+
+ if (nbf->nla_flag_values & ~*valid_flags_mask)
+ return -EINVAL;
+
+ return 0;
+}
+
static int validate_nla(const struct nlattr *nla, int maxtype,
const struct nla_policy *policy)
{
@@ -46,6 +61,13 @@ static int validate_nla(const struct nlattr *nla, int
maxtype,
return -ERANGE;
break;
+ case NLA_FLAG_BITS:
+ if (attrlen != 8) /* 2 x 32 bits */
+ return -ERANGE;
+
+ return validate_nla_bit_flags(nla, pt->validation_data);
+ break;
+
case NLA_NUL_STRING:
if (pt->len)
minlen = min_t(int, attrlen, pt->len + 1);
@@ -103,6 +125,9 @@ static int validate_nla(const struct nlattr *nla, int
maxtype,
return -ERANGE;
}
+ if (pt->validate_content)
+ return pt->validate_content(nla, pt->validation_data);
+
return 0;
}
--
1.9.1
