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
is the length of connect_addr
unsigned int flags
must be zero
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.
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
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.
This page is part of the GnuTLS (GnuTLS Transport Layer Security
Library) project. Information about the project can be found at
⟨http://www.gnutls.org/⟩. If you have a bug report for this
manual page, send it to email@example.com. This page was obtained
from the tarball gnutls-3.7.2.tar.xz fetched from
⟨http://www.gnutls.org/download.html⟩ on 2021-06-20. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
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gnutls 3.7.2 gnutls_transport_set_fastopen(3)