GnuTLS: use gnutls_transport_set_int if available

gnutls_transport_set_ptr may cause problems on some platforms,
therefore the replacement gnutls_transport_set_int is used
when available (since GnuTLS >= 3.1.9).

autoconf/configure.in

@@ -1275,6 +1275,10 @@ if test "x$support_crypto" != "xno" -o "x$support_tls" != "xno"; then
 
       if test "$have_gnutls" = "yes"; then
          AC_DEFINE(HAVE_GNUTLS, 1, [Define to 1 if GNUTLS library is available])
+         # gnutls_transport_set_ptr may cause problems on some platforms,
+         # therefore the replacement gnutls_transport_set_int is used
+         # when available (since GnuTLS >= 3.1.9)
+         AC_CHECK_FUNCS(gnutls_transport_set_int)
       fi
 
       if test "$support_tls" != "no" -a "$have_gnutls" = "yes"; then

src/lib/tls_gnutls.c

@@ -490,8 +490,15 @@ TLS_CONNECTION *new_tls_connection(TLS_CONTEXT *ctx, int fd, bool server)
 
    /*
     * Link the TLS session and the filedescriptor of the socket used.
+    * gnutls_transport_set_ptr may cause problems on some platforms,
+    * therefore the replacement gnutls_transport_set_int is used,
+    * when available (since GnuTLS >= 3.1.9)
     */
+#ifdef HAVE_GNUTLS_TRANSPORT_SET_INT
+   gnutls_transport_set_int(tls->gnutls_state, fd);
+#else
    gnutls_transport_set_ptr(tls->gnutls_state, (gnutls_transport_ptr_t)fd);
+#endif
 
    /*
     * Server specific settings.