gnutls_transport_set_fastopen(3) — Linux manual page


gnutls_transport_set_fastopen(3) gnutls gnutls_transport_set_fastopen(3)

NAME         top

       gnutls_transport_set_fastopen - API function

SYNOPSIS         top

       #include <gnutls/socket.h>

       void gnutls_transport_set_fastopen(gnutls_session_t session, int
       fd, struct sockaddr * connect_addr, socklen_t connect_addrlen,
       unsigned int flags);

ARGUMENTS         top

       gnutls_session_t session
                   is a gnutls_session_t type.

       int fd      is the session's socket descriptor

       struct sockaddr * connect_addr
                   is the address we want to connect to

       socklen_t connect_addrlen
                   is the length of  connect_addr

       unsigned int flags
                   must be zero

DESCRIPTION         top

       Enables TCP Fast Open (TFO) for the specified TLS client session.
       That means that TCP connection establishment and the transmission
       of the first TLS client hello packet are combined. The peer's
       address must be  specified in  connect_addr and  connect_addrlen
       , and the socket specified by  fd should not be connected.

       TFO only works for TCP sockets of type AF_INET and AF_INET6.  If
       the OS doesn't support TCP fast open this function will result to
       gnutls using connect() transparently during the first write.

NOTE         top

       This function overrides all the transport callback functions.  If
       this is undesirable, TCP Fast Open must be implemented on the
       user callback functions without calling this function. When using
       this function, transport callbacks must not be set, and
       gnutls_transport_set_ptr() or gnutls_transport_set_int() must not
       be called.

       On GNU/Linux TFO has to be enabled at the system layer, that is
       in /proc/sys/net/ipv4/tcp_fastopen, bit 0 has to be set.

       This function has no effect on server sessions.

SINCE         top


REPORTING BUGS         top

       Report bugs to <>.
       Home page:

COPYRIGHT         top

       Copyright © 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         top

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

COLOPHON         top

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       Library) project.  Information about the project can be found at
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       manual page, send it to  This page was obtained
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gnutls                            3.8.0 gnutls_transport_set_fastopen(3)