[NETLINK]: Introduce nested and byteorder flag to netlink attribute

This change allows the generic attribute interface to be used within
the netfilter subsystem where this flag was initially introduced.

The byte-order flag is yet unused, it's intended use is to
allow automatic byte order convertions for all atomic types.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 23 insertions, 0 deletions

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index d2843ae4a83a..e638256ce472 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -131,6 +131,20 @@ struct nlattr
         __u16           nla_type;
 };
 
+/*
+ * nla_type (16 bits)
+ * +---+---+-------------------------------+
+ * | N | O | Attribute Type                |
+ * +---+---+-------------------------------+
+ * N := Carries nested attributes
+ * O := Payload stored in network byte order
+ *
+ * Note: The N and O flag are mutually exclusive.
+ */
+#define NLA_F_NESTED            (1 << 15)
+#define NLA_F_NET_BYTEORDER     (1 << 14)
+#define NLA_TYPE_MASK           ~(NLA_F_NESTED | NLA_F_NET_BYTEORDER)
+
 #define NLA_ALIGNTO             4
 #define NLA_ALIGN(len)          (((len) + NLA_ALIGNTO - 1) & ~(NLA_ALIGNTO - 1))
 #define NLA_HDRLEN              ((int) NLA_ALIGN(sizeof(struct nlattr)))
diff --git a/include/net/netlink.h b/include/net/netlink.h
index d7b824be5422..695e613a207b 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -667,6 +667,15 @@ static inline int nla_padlen(int payload)
 }
 
 /**
+ * nla_type - attribute type
+ * @nla: netlink attribute
+ */
+static inline int nla_type(const struct nlattr *nla)
+{
+        return nla->nla_type & NLA_TYPE_MASK;
+}
+
+/**
  * nla_data - head of payload
  * @nla: netlink attribute
  */