+/* Set the GCM invocation field, decrypt only */
+#define EVP_CTRL_GCM_SET_IV_INV 0x18
+
+/* GCM TLS constants */
+/* Length of fixed part of IV derived from PRF */
+#define EVP_GCM_TLS_FIXED_IV_LEN 4
+/* Length of explicit part of IV part of TLS records */
+#define EVP_GCM_TLS_EXPLICIT_IV_LEN 8
+/* Length of tag for TLS */
+#define EVP_GCM_TLS_TAG_LEN 16