From 020000433be30a3f68fa8dd3adb7202110e5b28c Mon Sep 17 00:00:00 2001
From: Thomas Haller <thaller@redhat.com>
Date: Mon, 18 Feb 2019 12:09:49 +0100
Subject: [PATCH] platform/netlink: add nla_data_as() macro

This macro casts the return pointer and asserts that the netlink attribute
is suitably large.
---
 src/platform/nm-netlink.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/platform/nm-netlink.h b/src/platform/nm-netlink.h
index d9ba93738..6d71562d9 100644
--- a/src/platform/nm-netlink.h
+++ b/src/platform/nm-netlink.h
@@ -154,6 +154,20 @@ nla_data (const struct nlattr *nla)
 	return &(((char *) nla)[NLA_HDRLEN]);
 }
 
+#define nla_data_as(type, nla) \
+	({ \
+		const struct nlattr *_nla = (nla); \
+		\
+		nm_assert (nla_len (_nla) >= sizeof (type)); \
+		\
+		/* note that casting the pointer is undefined behavior in C, if
+		 * the data has wrong alignment. Netlink data is aligned to 4 bytes,
+		 * that means, if the alignment is larger than 4, this is invalid. */ \
+		G_STATIC_ASSERT_EXPR (_nm_alignof (type) <= NLA_ALIGNTO); \
+		\
+		(type *) nla_data (_nla); \
+	})
+
 static inline uint8_t
 nla_get_u8 (const struct nlattr *nla)
 {