Merge branch 'netlink-auto-integers'

Jakub Kicinski says:

====================
netlink: add variable-length / auto integers

Add netlink support for "common" / variable-length / auto integers
which are carried at the message level as either 4B or 8B depending
on the exact value. This saves space and will hopefully decrease
the number of instances where we realize that we needed more bits
after uAPI is set is stone. It also loosens the alignment requirements,
avoiding the need for padding.

This mini-series is a fuller version of the previous RFC:
https://lore.kernel.org/netdev/20121204.130914.1457976839967676240.davem@davemloft.net/
No user included here. I have tested (and will use) it
in the upcoming page pool API but the assumption is that
it will be widely applicable. So sending without a user.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 72 insertions, 2 deletions

diff --git a/include/net/netlink.h b/include/net/netlink.h
index 8a7cd1170e1f..aba2b162a226 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -128,6 +128,8 @@
  *   nla_len(nla)			length of attribute payload
  *
  * Attribute Payload Access for Basic Types:
+ *   nla_get_uint(nla)			get payload for a uint attribute
+ *   nla_get_sint(nla)			get payload for a sint attribute
  *   nla_get_u8(nla)			get payload for a u8 attribute
  *   nla_get_u16(nla)			get payload for a u16 attribute
  *   nla_get_u32(nla)			get payload for a u32 attribute
@@ -183,6 +185,8 @@ enum {
 	NLA_REJECT,
 	NLA_BE16,
 	NLA_BE32,
+	NLA_SINT,
+	NLA_UINT,
 	__NLA_TYPE_MAX,
 };
 
@@ -229,6 +233,7 @@ enum nla_policy_validation {
  *                         nested header (or empty); len field is used if
  *                         nested_policy is also used, for the max attr
  *                         number in the nested policy.
+ *    NLA_SINT, NLA_UINT,
  *    NLA_U8, NLA_U16,
  *    NLA_U32, NLA_U64,
  *    NLA_S8, NLA_S16,
@@ -260,12 +265,14 @@ enum nla_policy_validation {
  *                         while an array has the nested attributes at another
  *                         level down and the attribute types directly in the
  *                         nesting don't matter.
+ *    NLA_UINT,
  *    NLA_U8,
  *    NLA_U16,
  *    NLA_U32,
  *    NLA_U64,
  *    NLA_BE16,
  *    NLA_BE32,
+ *    NLA_SINT,
  *    NLA_S8,
  *    NLA_S16,
  *    NLA_S32,
@@ -280,6 +287,7 @@ enum nla_policy_validation {
  *                         or NLA_POLICY_FULL_RANGE_SIGNED() macros instead.
  *                         Use the NLA_POLICY_MIN(), NLA_POLICY_MAX() and
  *                         NLA_POLICY_RANGE() macros.
+ *    NLA_UINT,
  *    NLA_U8,
  *    NLA_U16,
  *    NLA_U32,
@@ -288,6 +296,7 @@ enum nla_policy_validation {
  *                         to a struct netlink_range_validation that indicates
  *                         the min/max values.
  *                         Use NLA_POLICY_FULL_RANGE().
+ *    NLA_SINT,
  *    NLA_S8,
  *    NLA_S16,
  *    NLA_S32,
@@ -377,9 +386,11 @@ struct nla_policy {
 
 #define __NLA_IS_UINT_TYPE(tp)					\
 	(tp == NLA_U8 || tp == NLA_U16 || tp == NLA_U32 ||	\
-	 tp == NLA_U64 || tp == NLA_BE16 || tp == NLA_BE32)
+	 tp == NLA_U64 || tp == NLA_UINT ||			\
+	 tp == NLA_BE16 || tp == NLA_BE32)
 #define __NLA_IS_SINT_TYPE(tp)						\
-	(tp == NLA_S8 || tp == NLA_S16 || tp == NLA_S32 || tp == NLA_S64)
+	(tp == NLA_S8 || tp == NLA_S16 || tp == NLA_S32 || tp == NLA_S64 || \
+	 tp == NLA_SINT)
 
 #define __NLA_ENSURE(condition) BUILD_BUG_ON_ZERO(!(condition))
 #define NLA_ENSURE_UINT_TYPE(tp)			\
@@ -1358,6 +1369,22 @@ static inline int nla_put_u32(struct sk_buff *skb, int attrtype, u32 value)
 }
 
 /**
+ * nla_put_uint - Add a variable-size unsigned int to a socket buffer
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @value: numeric value
+ */
+static inline int nla_put_uint(struct sk_buff *skb, int attrtype, u64 value)
+{
+	u64 tmp64 = value;
+	u32 tmp32 = value;
+
+	if (tmp64 == tmp32)
+		return nla_put_u32(skb, attrtype, tmp32);
+	return nla_put(skb, attrtype, sizeof(u64), &tmp64);
+}
+
+/**
  * nla_put_be32 - Add a __be32 netlink attribute to a socket buffer
  * @skb: socket buffer to add attribute to
  * @attrtype: attribute type
@@ -1512,6 +1539,22 @@ static inline int nla_put_s64(struct sk_buff *skb, int attrtype, s64 value,
 }
 
 /**
+ * nla_put_sint - Add a variable-size signed int to a socket buffer
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @value: numeric value
+ */
+static inline int nla_put_sint(struct sk_buff *skb, int attrtype, s64 value)
+{
+	s64 tmp64 = value;
+	s32 tmp32 = value;
+
+	if (tmp64 == tmp32)
+		return nla_put_s32(skb, attrtype, tmp32);
+	return nla_put(skb, attrtype, sizeof(s64), &tmp64);
+}
+
+/**
  * nla_put_string - Add a string netlink attribute to a socket buffer
  * @skb: socket buffer to add attribute to
  * @attrtype: attribute type
@@ -1668,6 +1711,17 @@ static inline u64 nla_get_u64(const struct nlattr *nla)
 }
 
 /**
+ * nla_get_uint - return payload of uint attribute
+ * @nla: uint netlink attribute
+ */
+static inline u64 nla_get_uint(const struct nlattr *nla)
+{
+	if (nla_len(nla) == sizeof(u32))
+		return nla_get_u32(nla);
+	return nla_get_u64(nla);
+}
+
+/**
  * nla_get_be64 - return payload of __be64 attribute
  * @nla: __be64 netlink attribute
  */
@@ -1730,6 +1784,17 @@ static inline s64 nla_get_s64(const struct nlattr *nla)
 }
 
 /**
+ * nla_get_sint - return payload of uint attribute
+ * @nla: uint netlink attribute
+ */
+static inline s64 nla_get_sint(const struct nlattr *nla)
+{
+	if (nla_len(nla) == sizeof(s32))
+		return nla_get_s32(nla);
+	return nla_get_s64(nla);
+}
+
+/**
  * nla_get_flag - return payload of flag attribute
  * @nla: flag netlink attribute
  */
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index e2ae82e3f9f7..f87aaf28a649 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -298,6 +298,8 @@ struct nla_bitfield32 {
  *	entry has attributes again, the policy for those inner ones
  *	and the corresponding maxtype may be specified.
  * @NL_ATTR_TYPE_BITFIELD32: &struct nla_bitfield32 attribute
+ * @NL_ATTR_TYPE_SINT: 32-bit or 64-bit signed attribute, aligned to 4B
+ * @NL_ATTR_TYPE_UINT: 32-bit or 64-bit unsigned attribute, aligned to 4B
  */
 enum netlink_attribute_type {
 	NL_ATTR_TYPE_INVALID,
@@ -322,6 +324,9 @@ enum netlink_attribute_type {
 	NL_ATTR_TYPE_NESTED_ARRAY,
 
 	NL_ATTR_TYPE_BITFIELD32,
+
+	NL_ATTR_TYPE_SINT,
+	NL_ATTR_TYPE_UINT,
 };
 
 /**