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gnutls_handshake(3)                 gnutls                 gnutls_handshake(3)


NAME

       gnutls_handshake - API function


SYNOPSIS

       #include <gnutls/gnutls.h>

       int gnutls_handshake(gnutls_session_t session);


ARGUMENTS

       gnutls_session_t session
                   is a gnutls_session_t type.


DESCRIPTION

       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
       returned.

       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
       GNUTLS_KU_PEER flag.

       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
       tickets.


RETURNS

       GNUTLS_E_SUCCESS on a successful handshake, otherwise a negative error
       code.


REPORTING BUGS

       Report bugs to <bugs@gnutls.org>.
       Home page: https://www.gnutls.org


COPYRIGHT

       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.


SEE ALSO

       The full documentation for gnutls is maintained as a Texinfo manual.
       If the /usr/local/share/doc/gnutls/ directory does not contain the HTML
       form visit

       https://www.gnutls.org/manual/

gnutls                               3.7.9                 gnutls_handshake(3)

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