void
    silc_client_perform_key_agreement_fd(SilcClient client,
                                         SilcClientConnection conn,
                                         SilcClientEntry client_entry,
                                         int sock,
                                         char *hostname,
                                         SilcKeyAgreementCallback completion,
                                         void *context);

    Same as above but application has created already the connection to
    the remote host. The `sock' is the socket to the remote connection.
    Application can use this function if it does not want the client library
    to create the connection.