+/* This callback type is used inside SSL_CTX, SSL, and in the functions that set
+ * them. It is used to override the generation of SSL/TLS session IDs in a
+ * server. Return value should be zero on an error, non-zero to proceed. Also,
+ * callbacks should themselves check if the id they generate is unique otherwise
+ * the SSL handshake will fail with an error - callbacks can do this using the
+ * 'ssl' value they're passed by;
+ * SSL_has_matching_session_id(ssl, id, *id_len)
+ * The length value passed in is set at the maximum size the session ID can be.
+ * In SSLv2 this is 16 bytes, whereas SSLv3/TLSv1 it is 32 bytes. The callback
+ * can alter this length to be less if desired, but under SSLv2 session IDs are
+ * supposed to be fixed at 16 bytes so the id will be padded after the callback
+ * returns in this case. It is also an error for the callback to set the size to
+ * zero. */
+typedef int (*GEN_SESSION_CB)(const SSL *ssl, unsigned char *id,
+ unsigned int *id_len);
+