MDEV-8743: mysqld port/socket - FD_CLOEXEC if no SOCK_CLOEXEC

In MDEV-8743, the port/socket of mysqld was changed to set FD_CLOEXEC.
The existing mysql_socket_socket function already set that with
SOCK_CLOEXEC when the socket was created. So here we move the fcntl
functionality to the mysql_socket_socket as port/socket are the only
callers.

Preprocessor checks of SOCK_CLOEXEC cannot be done as its a 0 if not
there and SOCK_CLOEXEC (being the value of the enum in bits/socket_type.h)
Preprocesssor logic for arithmetic and non-arithmetic defines are
hard/nonportable/ugly to read. As such we just check in my_global.h
and define HAVE_SOCK_CLOEXEC if we have it.

There was a disparity in behaviour between defined(WITH_WSREP) and
not depending on the OS, so the WITH_WSREP condition was removed
from setting calling fcntl.

All sockets are now maked SOCK_CLOEXEC/FD_CLOEXEC.

strace of mysqld with SOCK_CLOEXEC:

socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC, IPPROTO_TCP) = 10
write(2, "180419 14:52:40 [Note] Server socket created on IP: '127.0.0.1'.\n", 65180419 14:52:40 [Note] Server socket created on IP: '127.0.0.1'.
) = 65
setsockopt(10, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
bind(10, {sa_family=AF_INET, sin_port=htons(16020), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
listen(10, 150)                         = 0
socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC, IPPROTO_TCP) = 11
write(2, "180419 14:52:40 [Note] Server socket created on IP: '127.0.0.1'.\n", 65180419 14:52:40 [Note] Server socket created on IP: '127.0.0.1'.
) = 65
setsockopt(11, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
bind(11, {sa_family=AF_INET, sin_port=htons(16021), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
listen(11, 150)                         = 0
socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0) = 12
unlink("/home/dan/repos/build-mariadb-server-10.0/mysql-test/var/tmp/mysqld.1.sock") = -1 ENOENT (No such file or directory)
setsockopt(12, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
umask(000)                              = 006
bind(12, {sa_family=AF_UNIX, sun_path="/home/dan/repos/build-mariadb-server-10.0/mysql-test/var/tmp/mysqld.1.sock"}, 110) = 0
umask(006)                              = 000
listen(12, 150)                         = 0

2 files changed, 8 insertions, 0 deletions

diff --git a/include/my_global.h b/include/my_global.h
index ad1527d7b37..057c613d64c 100644
--- a/include/my_global.h
+++ b/include/my_global.h
@@ -608,6 +608,8 @@ typedef SOCKET_SIZE_TYPE size_socket;
 #endif
 #ifndef SOCK_CLOEXEC
 #define SOCK_CLOEXEC    0
+#else
+#define HAVE_SOCK_CLOEXEC
 #endif
 
 /* additional file share flags for win32 */
diff --git a/include/mysql/psi/mysql_socket.h b/include/mysql/psi/mysql_socket.h
index bd05ef9b8a9..70700a733d8 100644
--- a/include/mysql/psi/mysql_socket.h
+++ b/include/mysql/psi/mysql_socket.h
@@ -562,6 +562,12 @@ inline_mysql_socket_socket
       (key, (const my_socket*)&mysql_socket.fd, NULL, 0);
   }
 #endif
+
+  /* SOCK_CLOEXEC isn't always a number - can't preprocessor compare */
+#if defined(HAVE_FCNTL) && defined(FD_CLOEXEC) && !defined(HAVE_SOCK_CLOEXEC)
+  (void) fcntl(mysql_socket.fd, F_SETFD, FD_CLOEXEC);
+#endif
+
   return mysql_socket;
 }