Detect FreeBSD versions with broken MSG_CMSG_CLOEXEC

If we are compiling against a version of FreeBSD where MSG_CMSG_CLOEXEC
does not work, use the fallback directly. This was only fixed recently
(in https://cgit.freebsd.org/src/commit/?id=6ceacebdf52211).

Signed-off-by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>

3 files changed, 33 insertions, 1 deletions

diff --git a/meson.build b/meson.build
index a116d9d..5cd978f 100644
--- a/meson.build
+++ b/meson.build
@@ -43,6 +43,22 @@ foreach f: have_funcs
 	config_h.set('HAVE_' + f.underscorify().to_upper(), cc.has_function(f))
 endforeach
 config_h.set10('HAVE_XUCRED_CR_PID', cc.has_member('struct xucred', 'cr_pid', prefix : '#include <sys/ucred.h>'))
+have_broken_msg_cmsg_cloexec = false
+if host_machine.system() == 'freebsd'
+	have_broken_msg_cmsg_cloexec = not cc.compiles('''
+#include <sys/param.h> /* To get __FreeBSD_version. */
+#if __FreeBSD_version < 1300502 || \
+    (__FreeBSD_version >= 1400000 && __FreeBSD_version < 1400006)
+/*
+ * FreeBSD had a broken implementation of MSG_CMSG_CLOEXEC between 2015 and
+ * 2021. Check if we are compiling against a version that includes the fix
+ * (https://cgit.freebsd.org/src/commit/?id=6ceacebdf52211).
+ */
+#error "Broken MSG_CMSG_CLOEXEC"
+#endif
+''', name : 'MSG_CMSG_CLOEXEC works correctly')
+endif
+config_h.set10('HAVE_BROKEN_MSG_CMSG_CLOEXEC', have_broken_msg_cmsg_cloexec)
 
 if get_option('libraries')
 	if host_machine.system() == 'freebsd'
diff --git a/src/wayland-os.c b/src/wayland-os.c
index 44d4e72..27c6035 100644
--- a/src/wayland-os.c
+++ b/src/wayland-os.c
@@ -168,6 +168,15 @@ recvmsg_cloexec_fallback(int sockfd, struct msghdr *msg, int flags)
 ssize_t
 wl_os_recvmsg_cloexec(int sockfd, struct msghdr *msg, int flags)
 {
+#if HAVE_BROKEN_MSG_CMSG_CLOEXEC
+	/*
+	 * FreeBSD had a broken implementation of MSG_CMSG_CLOEXEC between 2015
+	 * and 2021, so we have to use the non-MSG_CMSG_CLOEXEC fallback
+	 * directly when compiling against a version that does not include the
+	 * fix (https://cgit.freebsd.org/src/commit/?id=6ceacebdf52211).
+	 */
+#pragma message("Using fallback directly since MSG_CMSG_CLOEXEC is broken.")
+#else
 	ssize_t len;
 
 	len = recvmsg(sockfd, msg, flags | MSG_CMSG_CLOEXEC);
@@ -175,7 +184,7 @@ wl_os_recvmsg_cloexec(int sockfd, struct msghdr *msg, int flags)
 		return len;
 	if (errno != EINVAL)
 		return -1;
-
+#endif
 	return recvmsg_cloexec_fallback(sockfd, msg, flags);
 }
 
diff --git a/tests/os-wrappers-test.c b/tests/os-wrappers-test.c
index 51eaa29..aadb93b 100644
--- a/tests/os-wrappers-test.c
+++ b/tests/os-wrappers-test.c
@@ -23,6 +23,7 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+#include "../config.h"
 
 #define _GNU_SOURCE
 
@@ -341,7 +342,13 @@ do_os_wrappers_recvmsg_cloexec(int n)
 	struct marshal_data data;
 
 	data.nr_fds_begin = count_open_fds();
+#if HAVE_BROKEN_MSG_CMSG_CLOEXEC
+	/* We call the fallback directly on FreeBSD versions with a broken
+	 * MSG_CMSG_CLOEXEC, so we don't call the local recvmsg() wrapper. */
+	data.wrapped_calls = 0;
+#else
 	data.wrapped_calls = n;
+#endif
 
 	setup_marshal_data(&data);
 	data.nr_fds_conn = count_open_fds();