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C.2 Datagram TLS API
The prototypes for the following functions lie in ‘gnutls/dtls.h’.
gnutls_dtls_cookie_send
- Function: int gnutls_dtls_cookie_send (gnutls_datum_t* key, void* client_data, size_t client_data_size, gnutls_dtls_prestate_st* prestate, gnutls_transport_ptr_t ptr, gnutls_push_func push_func)
key: is a random key to be used at cookie generation
client_data: contains data identifying the client (i.e. address)
client_data_size: The size of client’s data
prestate: The previous cookie returned by
gnutls_dtls_cookie_verify()ptr: A transport pointer to be used by
push_funcpush_func: A function that will be used to reply
Description: 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.
gnutls_session_t) is the one that the original incoming packet was originated from.Returns: the number of bytes sent, or a negative error code.
Since: 3.0.0
gnutls_dtls_cookie_verify
- Function: int gnutls_dtls_cookie_verify (gnutls_datum_t* key, void* client_data, size_t client_data_size, void* _msg, size_t msg_size, gnutls_dtls_prestate_st* prestate)
key: is a random key to be used at cookie generation
client_data: contains data identifying the client (i.e. address)
client_data_size: The size of client’s data
_msg: An incoming message that initiates a connection.
msg_size: The size of the message.
prestate: The cookie of this client.
Description: This function will verify an incoming message for a valid cookie. If a valid cookie is returned then it should be associated with the session using
gnutls_dtls_prestate_set();Returns:
GNUTLS_E_SUCCESS(0) on success, or a negative error code.Since: 3.0.0
gnutls_dtls_get_data_mtu
- Function: unsigned int gnutls_dtls_get_data_mtu (gnutls_session_t session)
session: is a
gnutls_session_tstructure.Description: This function will return the actual maximum transfer unit for application data. I.e. DTLS headers are subtracted from the actual MTU.
Returns: the maximum allowed transfer unit.
Since: 3.0.0
gnutls_dtls_get_mtu
- Function: unsigned int gnutls_dtls_get_mtu (gnutls_session_t session)
session: is a
gnutls_session_tstructure.Description: This function will return the MTU size as set with
gnutls_dtls_set_mtu(). This is not the actual MTU of data you can transmit. Usegnutls_dtls_get_data_mtu()for that reason.Returns: the set maximum transfer unit.
Since: 3.0.0
gnutls_dtls_prestate_set
- Function: void gnutls_dtls_prestate_set (gnutls_session_t session, gnutls_dtls_prestate_st* prestate)
session: a new session
prestate: contains the client’s prestate
Description: This function will associate the prestate acquired by the cookie authentication with the client, with the newly established session.
Since: 3.0.0
gnutls_dtls_set_mtu
- Function: void gnutls_dtls_set_mtu (gnutls_session_t session, unsigned int mtu)
session: is a
gnutls_session_tstructure.mtu: The maximum transfer unit of the interface
Description: This function will set the maximum transfer unit of the interface that DTLS packets are expected to leave from.
Since: 3.0.0
gnutls_dtls_set_timeouts
- Function: void gnutls_dtls_set_timeouts (gnutls_session_t session, unsigned int retrans_timeout, unsigned int total_timeout)
session: is a
gnutls_session_tstructure.retrans_timeout: The time at which a retransmission will occur in milliseconds
total_timeout: The time at which the connection will be aborted, in milliseconds.
Description: 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
GNUTLS_E_TIMEDOUT.The DTLS protocol recommends the values of 1 sec and 60 seconds respectively.
If the retransmission timeout is zero then the handshake will operate in a non-blocking way, i.e., return
GNUTLS_E_AGAIN.Since: 3.0.0
gnutls_record_get_discarded
- Function: unsigned int gnutls_record_get_discarded (gnutls_session_t session)
session: is a
gnutls_session_tstructure.Description: Returns the number of discarded packets in a DTLS connection.
Returns: The number of discarded packets.
Since: 3.0.0
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