@subheading gnutls_dtls_cookie_send

@anchor{gnutls_dtls_cookie_send}

@deftypefun {int} {gnutls_dtls_cookie_send} (gnutls_datum_t * @var{key}, void * @var{client_data}, size_t @var{client_data_size}, gnutls_dtls_prestate_st * @var{prestate}, gnutls_transport_ptr_t @var{ptr}, gnutls_push_func @var{push_func})

@var{key}: is a random key to be used at cookie generation

@var{client_data}: contains data identifying the client (i.e. address)

@var{client_data_size}: The size of client's data

@var{prestate}: The previous cookie returned by @code{gnutls_dtls_cookie_verify()} 

@var{ptr}: A transport pointer to be used by  @code{push_func} 

@var{push_func}: A function that will be used to reply

This function can be used to prevent denial of service

attacks to a DTLS server by requiring the client to

reply using a cookie sent by this function. That way

it can be ensured that a client we allocated resources

for (i.e. @code{gnutls_session_t} ) is the one that the 

original incoming packet was originated from.

This function must be called at the first incoming packet,

prior to allocating any resources and must be succeeded

by @code{gnutls_dtls_cookie_verify()} .

@strong{Returns:} the number of bytes sent, or a negative error code.  

@strong{Since:} 3.0

@end deftypefun

@subheading gnutls_dtls_cookie_verify

@anchor{gnutls_dtls_cookie_verify}

@deftypefun {int} {gnutls_dtls_cookie_verify} (gnutls_datum_t * @var{key}, void * @var{client_data}, size_t @var{client_data_size}, void * @var{_msg}, size_t @var{msg_size}, gnutls_dtls_prestate_st * @var{prestate})

@var{key}: is a random key to be used at cookie generation

@var{client_data}: contains data identifying the client (i.e. address)

@var{client_data_size}: The size of client's data

@var{_msg}: An incoming message that initiates a connection.

@var{msg_size}: The size of the message.

@var{prestate}: The cookie of this client.

This function will verify the received message for

a valid cookie. If a valid cookie is returned then

it should be associated with the session using

@code{gnutls_dtls_prestate_set()} ;

This function must be called after @code{gnutls_dtls_cookie_send()} .

@strong{Returns:} @code{GNUTLS_E_SUCCESS}  (0) on success, or a negative error code.  

@strong{Since:} 3.0

@end deftypefun

@subheading gnutls_dtls_get_data_mtu

@anchor{gnutls_dtls_get_data_mtu}

@deftypefun {unsigned int} {gnutls_dtls_get_data_mtu} (gnutls_session_t @var{session})

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

This function will return the actual maximum transfer unit for

application data. I.e. DTLS headers are subtracted from the

actual MTU which is set using @code{gnutls_dtls_set_mtu()} .

@strong{Returns:} the maximum allowed transfer unit.

@strong{Since:} 3.0

@end deftypefun

@subheading gnutls_dtls_get_mtu

@anchor{gnutls_dtls_get_mtu}

@deftypefun {unsigned int} {gnutls_dtls_get_mtu} (gnutls_session_t @var{session})

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

This function will return the MTU size as set with

@code{gnutls_dtls_set_mtu()} . This is not the actual MTU

of data you can transmit. Use @code{gnutls_dtls_get_data_mtu()} 

for that reason.

@strong{Returns:} the set maximum transfer unit.

@strong{Since:} 3.0

@end deftypefun

@subheading gnutls_dtls_get_timeout

@anchor{gnutls_dtls_get_timeout}

@deftypefun {unsigned int} {gnutls_dtls_get_timeout} (gnutls_session_t @var{session})

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

This function will return the milliseconds remaining

for a retransmission of the previously sent handshake

message. This function is useful when DTLS is used in

non-blocking mode, to estimate when to call @code{gnutls_handshake()} 

if no packets have been received.

@strong{Returns:} the remaining time in milliseconds.

@strong{Since:} 3.0

@end deftypefun

@subheading gnutls_dtls_prestate_set

@anchor{gnutls_dtls_prestate_set}

@deftypefun {void} {gnutls_dtls_prestate_set} (gnutls_session_t @var{session}, gnutls_dtls_prestate_st * @var{prestate})

@var{session}: a new session

@var{prestate}: contains the client's prestate

This function will associate the prestate acquired by

the cookie authentication with the client, with the newly 

established session.

This functions must be called after a successful @code{gnutls_dtls_cookie_verify()} 

and should be succeeded by the actual DTLS handshake using @code{gnutls_handshake()} .

@strong{Since:} 3.0

@end deftypefun

@subheading gnutls_dtls_set_data_mtu

@anchor{gnutls_dtls_set_data_mtu}

@deftypefun {int} {gnutls_dtls_set_data_mtu} (gnutls_session_t @var{session}, unsigned int @var{mtu})

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

@var{mtu}: The maximum unencrypted transfer unit of the session

This function will set the maximum size of the *unencrypted* records

which will be sent over a DTLS session. It is equivalent to calculating

the DTLS packet overhead with the current encryption parameters, and

calling @code{gnutls_dtls_set_mtu()}  with that value. In particular, this means

that you may need to call this function again after any negotiation or

renegotiation, in order to ensure that the MTU is still sufficient to

account for the new protocol overhead.

In most cases you only need to call @code{gnutls_dtls_set_mtu()}  with

the maximum MTU of your transport layer.

@strong{Returns:} @code{GNUTLS_E_SUCCESS}  (0) on success, or a negative error code.

@strong{Since:} 3.1

@end deftypefun

@subheading gnutls_dtls_set_mtu

@anchor{gnutls_dtls_set_mtu}

@deftypefun {void} {gnutls_dtls_set_mtu} (gnutls_session_t @var{session}, unsigned int @var{mtu})

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

@var{mtu}: The maximum transfer unit of the transport

This function will set the maximum transfer unit of the transport

that DTLS packets are sent over. Note that this should exclude

the IP (or IPv6) and UDP headers. So for DTLS over IPv6 on an

Ethernet device with MTU 1500, the DTLS MTU set with this function

would be 1500 - 40 (IPV6 header) - 8 (UDP header) = 1452.

@strong{Since:} 3.0

@end deftypefun

@subheading gnutls_dtls_set_timeouts

@anchor{gnutls_dtls_set_timeouts}

@deftypefun {void} {gnutls_dtls_set_timeouts} (gnutls_session_t @var{session}, unsigned int @var{retrans_timeout}, unsigned int @var{total_timeout})

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

@var{retrans_timeout}: The time at which a retransmission will occur in milliseconds

@var{total_timeout}: The time at which the connection will be aborted, in milliseconds.

This function will set the timeouts required for the DTLS handshake

protocol. The retransmission timeout is the time after which a

message from the peer is not received, the previous messages will

be retransmitted. The total timeout is the time after which the

handshake will be aborted with @code{GNUTLS_E_TIMEDOUT} .

The DTLS protocol recommends the values of 1 sec and 60 seconds

respectively, and these are the default values.

To disable retransmissions set a  @code{retrans_timeout} larger than the  @code{total_timeout} .

@strong{Since:} 3.0

@end deftypefun

@subheading gnutls_record_get_discarded

@anchor{gnutls_record_get_discarded}

@deftypefun {unsigned int} {gnutls_record_get_discarded} (gnutls_session_t @var{session})

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

Returns the number of discarded packets in a

DTLS connection.

@strong{Returns:} The number of discarded packets.

@strong{Since:} 3.0

@end deftypefun