Subject: [PATCH net-next v2 3/6] netlink: add helpers for extack attr presence checking

From: Jakub Kicinski <[email-masked]>
Date: Wed, 24 Aug 2022 19:41:19 -0700

Being able to check attribute presence and set extack
if not on one line is handy, add helpers.

Signed-off-by: Jakub Kicinski <[email-masked]>
--
v2: squash old genetlink and netlink patches now that
    we don't need special handling of fixed headers (Johannes)
---
CC: [email-masked]
---
 include/linux/netlink.h | 11 +++++++++++
 include/net/genetlink.h |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 2e647157f383..f30b66996058 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -139,6 +139,17 @@ struct netlink_ext_ack {
 	}						\
 } while (0)
 
+#define NL_REQ_ATTR_CHECK(extack, nest, tb, type) ({		\
+	struct nlattr **__tb = (tb);				\
+	u32 __attr = (type);					\
+	int __retval;						\
+								\
+	__retval = !__tb[__attr];				\
+	if (__retval)						\
+		NL_SET_ERR_ATTR_MISS((extack), (nest), __attr);	\
+	__retval;						\
+})
+
 static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
 					    u64 cookie)
 {
diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 56a50e1c51b9..c41b20783ad0 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -107,6 +107,13 @@ static inline void genl_info_net_set(struct genl_info *info, struct net *net)
 
 #define GENL_SET_ERR_MSG(info, msg) NL_SET_ERR_MSG((info)->extack, msg)
 
+/* Report that a root attribute is missing */
+#define GENL_REQ_ATTR_CHECK(info, attr) ({				\
+	struct genl_info *__info = (info);				\
+									\
+	NL_REQ_ATTR_CHECK(__info->extack, NULL, __info->attrs, (attr)); \
+})
+
 enum genl_validate_flags {
 	GENL_DONT_VALIDATE_STRICT		= BIT(0),
 	GENL_DONT_VALIDATE_DUMP			= BIT(1),
-- 
2.37.2