Section: gnutls (3)
gnutls_session_get_data2 - API function
int gnutls_session_get_data2(gnutls_session_t session, gnutls_datum_t * data);
- gnutls_session_t session
is a gnutls_session_t type.
- gnutls_datum_t * data
is a pointer to a datum that will hold the session.
Returns necessary parameters to support resumption. The client
should call this function and store the returned session data. A session
can be resumed later by calling gnutls_session_set_data()
with the returned
data. Note that under TLS 1.3, it is recommended for clients to use
session parameters only once, to prevent passive-observers from correlating
the different connections.
The returned data are allocated and must be released using gnutls_free().
This function will fail if called prior to handshake completion. In
case of false start TLS, the handshake completes only after data have
been successfully received from the peer.
Under TLS1.3 session resumption is possible only after a session ticket
is received by the client. To ensure that such a ticket has been received use
gnutls_session_get_flags() and check for flag GNUTLS_SFLAGS_SESSION_TICKET;
if this flag is not set, this function will wait for a new ticket within
an estimated rountrip, and if not received will return dummy data which
cannot lead to resumption.
To get notified when new tickets are received by the server
use gnutls_handshake_set_hook_function() to wait for GNUTLS_HANDSHAKE_NEW_SESSION_TICKET
messages. Each call of gnutls_session_get_data2() after a ticket is
received, will return session resumption data corresponding to the last
Note that this function under TLS1.3 requires a callback to be set with
gnutls_transport_set_pull_timeout_function() for successful operation. There
was a bug before 3.6.10 which could make this function fail if that callback
was not set. On later versions if not set, the function will return a successful
error code, but will return dummy data that cannot lead to a resumption.
On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
Report bugs to <firstname.lastname@example.org
Home page: https://www.gnutls.org
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