[PATCH net-next v5 1/3] netlink: Add nla_put_empty_nest helper

Joe Damato
2025-02-08T04:14:32Z

Creating empty nests is helpful when the exact attributes to be exposed
in the future are not known. Encapsulate the logic in a helper.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
---
v4:
- new in v4

include/net/netlink.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/include/net/netlink.h b/include/net/netlink.h
index e015ffbed819..29e0db940382 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -118,6 +118,7 @@
* nla_nest_start(skb, type) start a nested attribute
* nla_nest_end(skb, nla) finalize a nested attribute
* nla_nest_cancel(skb, nla) cancel nested attribute construction
+ * nla_put_empty_nest(skb, type) create an empty nest
*
* Attribute Length Calculations:
* nla_attr_size(payload) length of attribute w/o padding
@@ -2240,6 +2241,20 @@ static inline void nla_nest_cancel(struct sk_buff *skb, struct nlattr *start)
nlmsg_trim(skb, start);
}

+/**
+ * nla_put_empty_nest - Create an empty nest
+ * @skb: socket buffer the message is stored in
+ * @attrtype: attribute type of the container
+ *
+ * This function is a helper for creating empty nests.
+ *
+ * Returns: 0 when successful or -EMSGSIZE on failure.
+ */
+static inline int nla_put_empty_nest(struct sk_buff *skb, int attrtype)
+{
+ return nla_nest_start(skb, attrtype) ? 0 : -EMSGSIZE;
+}
+
/**
* __nla_validate_nested - Validate a stream of nested attributes
* @start: container attribute
--
2.43.0