The following return values can occur:
0
The SSL_clear() operation could not be performed. Check the error stack to find out the reason.
1
The SSL_clear() operation was successful.
SSL_new(3), SSL_free(3), SSL_shutdown(3), SSL_set_shutdown(3), SSL_CTX_set_options(3), ssl(3), SSL_CTX_set_client_cert_cb(3)