Fix check for CMake not detecting struct cmsg

This check seems to have never worked and on Linux we hard coded
the check instead. Remove this hard coded assumption and use a
working check based on check_struct_has_member instead.

This is has the side-effect of port-sharing being enabled on macOS
when compiled with cmake.

Change-Id: Ia020c696f63a2a317f001c061b2ab4da69977750
Signed-off-by: Arne Schwabe <arne-openvpn@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20240925151342.13307-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg29448.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6271574d1b680433cf13ed0680b3f30c9cdfcc3d..5db207d31a451b8b7eb1f681239e6be1924d5686 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -131,7 +131,6 @@ if (${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
     set(ENABLE_FEATURE_TUN_PERSIST 1)
     set(HAVE_LINUX_TYPES_H 1)
     set(ENABLE_DCO YES)
-    set(HAVE_CMSGHDR YES)
 elseif (${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD")
     set(TARGET_FREEBSD YES)
     set(ENABLE_DCO YES)
@@ -185,7 +184,6 @@ check_symbol_exists(mlockall sys/mman.h HAVE_MLOCKALL)
 
 check_symbol_exists(sendmsg sys/socket.h HAVE_SENDMSG)
 check_symbol_exists(recvmsg sys/socket.h HAVE_RECVMSG)
-check_symbol_exists(cmsghdr sys/socket.h HAVE_CMSGHDR)
 check_symbol_exists(openlog syslog.h HAVE_OPENLOG)
 check_symbol_exists(syslog syslog.h HAVE_SYSLOG)
 check_symbol_exists(getgrnam grp.h HAVE_GETGRNAM)
@@ -193,6 +191,11 @@ check_symbol_exists(getpwnam pwd.h HAVE_GETPWNAM)
 check_symbol_exists(getsockname sys/socket.h HAVE_GETSOCKNAME)
 check_symbol_exists(getrlimit "sys/time.h;sys/resource.h" HAVE_GETRLIMIT)
 
+# Checking for existence of structs with check_symbol_exists does not work,
+# so we use check_struct_hash_member with a member instead
+check_struct_has_member("struct cmsghdr" cmsg_len sys/socket.h HAVE_CMSGHDR)
+
+
 # Some OS (e.g. FreeBSD) need some basic headers to allow
 # including network headers
 set(NETEXTRA sys/types.h)