@deftypefun {void} {gnutls_handshake_set_hook_function} (gnutls_session_t @var{session}, unsigned int @var{htype}, int @var{when}, gnutls_handshake_hook_func @var{func})

@var{session}: is a @code{gnutls_session_t}  type

@var{htype}: the @code{gnutls_handshake_description_t}  of the message to hook at

@var{when}: @code{GNUTLS_HOOK_} * depending on when the hook function should be called

@var{func}: is the function to be called

This function will set a callback to be called after or before the specified

handshake message has been received or generated. This is a

generalization of @code{gnutls_handshake_set_post_client_hello_function()} .

To call the hook function prior to the message being generated or processed

use @code{GNUTLS_HOOK_PRE}  as  @code{when} parameter, @code{GNUTLS_HOOK_POST}  to call

after, and @code{GNUTLS_HOOK_BOTH}  for both cases.

This callback must return 0 on success or a gnutls error code to

terminate the handshake.

To hook at all handshake messages use an  @code{htype} of @code{GNUTLS_HANDSHAKE_ANY} .

@strong{Warning:} You should not use this function to terminate the

handshake based on client input unless you know what you are

doing. Before the handshake is finished there is no way to know if

there is a man-in-the-middle attack being performed.

@end deftypefun