NAME

       gnutls_transport_set_fastopen - API function

SYNOPSIS

       #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

       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

       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

       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

       3.5.3

REPORTING BUGS

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

COPYRIGHT

       Copyright © 2001-2022 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/share/doc/gnutls/
       directory does not contain the HTML form visit

       http://www.gnutls.org/manual/