linux-kernel - [PATCH net-next v2 01/10] netlink: Introduce nlmsg

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Message-Id: <20250414-nlmsg-v2-1-3d90cb42c6af@debian.org>
Date: Mon, 14 Apr 2025 06:24:07 -0700
From: Breno Leitao <leitao@...ian.org>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 David Ahern <dsahern@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Breno Leitao <leitao@...ian.org>, kernel-team@...a.com, 
 Kuniyuki Iwashima <kuniyu@...zon.com>
Subject: [PATCH net-next v2 01/10] netlink: Introduce nlmsg_payload helper

Create a new helper function, nlmsg_payload(), to simplify checking and
retrieving Netlink message payloads.

This reduces boilerplate code for users who need to verify the message
length before accessing its data.

Suggested-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Breno Leitao <leitao@...ian.org>
Reviewed-by: Jakub Kicinski <kuba@...nel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 include/net/netlink.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/net/netlink.h b/include/net/netlink.h
index 29e0db9403820..82e07e272290a 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -611,6 +611,22 @@ static inline int nlmsg_len(const struct nlmsghdr *nlh)
 	return nlh->nlmsg_len - NLMSG_HDRLEN;
 }

+/**
+ * nlmsg_payload - message payload if the data fits in the len
+ * @nlh: netlink message header
+ * @len: struct length
+ *
+ * Returns: The netlink message payload/data if the length is sufficient,
+ * otherwise NULL.
+ */
+static inline void *nlmsg_payload(const struct nlmsghdr *nlh, size_t len)
+{
+	if (nlh->nlmsg_len < nlmsg_msg_size(len))
+		return NULL;
+
+	return nlmsg_data(nlh);
+}
+
 /**
  * nlmsg_attrdata - head of attributes data
  * @nlh: netlink message header

-- 
2.47.1