[PATCH v2 4/6] wg: Check sockaddr_inet field offsets against system sockaddr

[Daniel Gröber]

Some systems may have the sockaddr fields in a different arrangement and
need #ifdef'ing this makes this obvious to any future porters.

Signed-off-by: Daniel Gröber <dxld at darkboxed.org>
---
 src/containers.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/containers.h b/src/containers.h
index 2f3d88f..357df77 100644
--- a/src/containers.h
+++ b/src/containers.h
@@ -8,6 +8,8 @@
 
 #include <stdint.h>
 #include <stdlib.h>
+#include <stddef.h>
+#include <assert.h>
 #include <time.h>
 #include <sys/socket.h>
 #include <net/if.h>
@@ -44,6 +46,25 @@ struct sockaddr_inet {
 	};
 };
 
+#if defined(_MSC_VER)
+#define static_assert(x) static_assert(x, #x)
+#elif !defined(static_assert)
+#define static_assert(x) _Static_assert((x), #x)
+#endif
+
+static_assert(offsetof(struct sockaddr_in, sin_port) ==
+	      offsetof(struct sockaddr_inet, sinet_port));
+static_assert(offsetof(struct sockaddr_in6, sin6_port) ==
+	      offsetof(struct sockaddr_inet, sinet_port));
+
+#define assert_offsets_match(tyx, tyy, field) \
+	static_assert(offsetof(tyx, field) == offsetof(tyy, field))
+
+assert_offsets_match(struct sockaddr_in, struct sockaddr_inet, sin_addr);
+assert_offsets_match(struct sockaddr_in6, struct sockaddr_inet, sin6_flowinfo);
+assert_offsets_match(struct sockaddr_in6, struct sockaddr_inet, sin6_addr);
+assert_offsets_match(struct sockaddr_in6, struct sockaddr_inet, sin6_scope_id);
+
 struct wgallowedip {
 	uint16_t family;
 	union {
-- 
2.39.2