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gnutls_handshake(3) gnutls gnutls_handshake(3)
gnutls_handshake - API function
int gnutls_handshake(gnutls_session_t session);
is a gnutls_session_t type.
This function performs the handshake of the TLS/SSL protocol, and
initializes the TLS session parameters.
The non-fatal errors expected by this function are:
GNUTLS_E_INTERRUPTED, GNUTLS_E_AGAIN, GNUTLS_E_WARNING_ALERT_RECEIVED.
When this function is called for re-handshake under TLS 1.2 or earlier,
the non-fatal error code GNUTLS_E_GOT_APPLICATION_DATA may also be
The former two interrupt the handshake procedure due to the transport
layer being interrupted, and the latter because of a "warning" alert
that was sent by the peer (it is always a good idea to check any
received alerts). On these non-fatal errors call this function again,
until it returns 0; cf. gnutls_record_get_direction() and
gnutls_error_is_fatal(). In DTLS sessions the non-fatal error
GNUTLS_E_LARGE_PACKET is also possible, and indicates that the MTU
should be adjusted.
When this function is called by a server after a rehandshake request
under TLS 1.2 or earlier the GNUTLS_E_GOT_APPLICATION_DATA error code
indicates that some data were pending prior to peer initiating the
handshake. Under TLS 1.3 this function when called after a successful
handshake, is a no-op and always succeeds in server side; in client
side this function is equivalent to gnutls_session_key_update() with
This function handles both full and abbreviated TLS handshakes
(resumption). For abbreviated handshakes, in client side, the
gnutls_session_set_data() should be called prior to this function to
set parameters from a previous session. In server side, resumption is
handled by either setting a DB back-end, or setting up keys for session
GNUTLS_E_SUCCESS on a successful handshake, otherwise a negative error
Report bugs to <firstname.lastname@example.org>.
Home page: https://www.gnutls.org
Copyright (C) 2001- Free Software Foundation, Inc., and others.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
The full documentation for gnutls is maintained as a Texinfo manual.
If the /usr/local/share/doc/gnutls/ directory does not contain the HTML
gnutls 3.7.8 gnutls_handshake(3)