gnutls_transport_set_fastopen(3)

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: https://www.gnutls.org

COPYRIGHT
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
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

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