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The prototypes for the following functions lie in gnutls/dtls.h.
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_func
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. 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 gnutls_dtls_cookie_verify() .
Returns: the number of bytes sent, or a negative error code.
Since: 3.0
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.
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
gnutls_dtls_prestate_set() ;
This function must be called after gnutls_dtls_cookie_send() .
Returns: GNUTLS_E_SUCCESS (0) on success, or a negative error code.
Since: 3.0
session: is a 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 gnutls_dtls_set_mtu() .
Returns: the maximum allowed transfer unit.
Since: 3.0
session: is a gnutls_session_t type.
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. Use gnutls_dtls_get_data_mtu()
for that reason.
Returns: the set maximum transfer unit.
Since: 3.0
session: is a 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 gnutls_handshake()
if no packets have been received.
Returns: the remaining time in milliseconds.
Since: 3.0
session: a new session
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 gnutls_dtls_cookie_verify()
and should be succeeded by the actual DTLS handshake using gnutls_handshake() .
Since: 3.0
session: is a gnutls_session_t type.
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 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 gnutls_dtls_set_mtu() with
the maximum MTU of your transport layer.
Returns: GNUTLS_E_SUCCESS (0) on success, or a negative error code.
Since: 3.1
session: is a gnutls_session_t type.
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.
Since: 3.0
session: is a gnutls_session_t type.
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.
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, and these are the default values.
To disable retransmissions set a retrans_timeout larger than the total_timeout .
Since: 3.0
session: is a gnutls_session_t type.
Returns the number of discarded packets in a DTLS connection.
Returns: The number of discarded packets.
Since: 3.0
Next: X509 certificate API, Previous: Core TLS API, Up: API reference [Contents][Index]