Add some documentation of SSL_CTX_set_tlsext_status_type()

=head1 NAME

SSL_CTX_set_tlsext_status_cb, SSL_CTX_set_tlsext_status_arg,

SSL_set_tlsext_status_type, SSL_get_tlsext_status_ocsp_resp,

SSL_set_tlsext_status_ocsp_resp - OCSP Certificate Status Request functions

SSL_CTX_set_tlsext_status_type, SSL_set_tlsext_status_type,

SSL_get_tlsext_status_ocsp_resp, SSL_set_tlsext_status_ocsp_resp - OCSP

Certificate Status Request functions

=head1 SYNOPSIS

                                   int (*callback)(SSL *, void *));

 long SSL_CTX_set_tlsext_status_arg(SSL_CTX *ctx, void *arg);

 long SSL_CTX_set_tlsext_status_type(SSL_CTX *ctx, int type);

 long SSL_set_tlsext_status_type(SSL *s, int type);

 long SSL_get_tlsext_status_ocsp_resp(ssl, unsigned char **resp);

A client application may request that a server send back an OCSP status response

(also known as OCSP stapling). To do so the client should call the

SSL_set_tlsext_status_type() function prior to the start of the handshake.

SSL_CTX_set_tlsext_status_type() function prior to the creation of any SSL

objects. Alternatively an application can call the SSL_set_tlsext_status_type()

function on an individual SSL object prior to the start of the handshake.

Currently the only supported type is B<TLSEXT_STATUSTYPE_ocsp>. This value

should be passed in the B<type> argument. The client should additionally provide

a callback function to decide what to do with the returned OCSP response by

calling SSL_CTX_set_tlsext_status_cb(). The callback function should determine

whether the returned OCSP response is acceptable or not. The callback will be

passed as an argument the value previously set via a call to

SSL_CTX_set_tlsext_status_arg(). Note that the callback will not be called in

the event of a handshake where session resumption occurs (because there are no

Certificates exchanged in such a handshake).

should be passed in the B<type> argument.

The client should additionally provide a callback function to decide what to do

with the returned OCSP response by calling SSL_CTX_set_tlsext_status_cb(). The

callback function should determine whether the returned OCSP response is

acceptable or not. The callback will be passed as an argument the value

previously set via a call to SSL_CTX_set_tlsext_status_arg(). Note that the

callback will not be called in the event of a handshake where session resumption

occurs (because there are no Certificates exchanged in such a handshake).

The response returned by the server can be obtained via a call to

SSL_get_tlsext_status_ocsp_resp(). The value B<*resp> will be updated to point

occurred).

SSL_CTX_set_tlsext_status_cb(), SSL_CTX_set_tlsext_status_arg(),

SSL_set_tlsext_status_type() and SSL_set_tlsext_status_ocsp_resp() return 0 on

error or 1 on success.

SSL_CTX_set_tlsext_status_type(), SSL_set_tlsext_status_type() and

SSL_set_tlsext_status_ocsp_resp() return 0 on error or 1 on success.

SSL_get_tlsext_status_ocsp_resp() returns the length of the OCSP response data

or -1 if there is no OCSP response data.

=head1 HISTORY

SSL_CTX_set_tlsext_status_type() was added in OpenSSL 1.1.0.

=cut