curl/docs/libcurl/opts/CURLOPT_TCP_FASTOPEN.md
Daniel Stenberg b935fd4a07
docs: make each libcurl man specify protocol(s)
The mandatory header now has a mandatory list of protocols for which the
manpage is relevant.

Most man pages already has a "PROTOCOLS" section, but this introduces a
stricter way to specify the relevant protocols.

cd2nroff verifies that at least one protocol is mentioned (which can be
`*`).

This information is not used just yet, but A) the PROTOCOLS section can
now instead get generated and get a unified wording across all manpages
and B) this allows us to more reliably filter/search for protocol
specific manpages/options.

Closes #13166
2024-03-21 15:27:06 +01:00

1.3 KiB

c: Copyright (C) Daniel Stenberg, daniel@haxx.se, et al. SPDX-License-Identifier: curl Title: CURLOPT_TCP_FASTOPEN Section: 3 Source: libcurl See-also: - CURLOPT_SSL_FALSESTART (3) Protocol: - *

NAME

CURLOPT_TCP_FASTOPEN - TCP Fast Open

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_FASTOPEN, long enable);

DESCRIPTION

Pass a long as parameter set to 1L to enable or 0 to disable.

TCP Fast Open (RFC 7413) is a mechanism that allows data to be carried in the SYN and SYN-ACK packets and consumed by the receiving end during the initial connection handshake, saving up to one full round-trip time (RTT).

Beware: the TLS session cache does not work when TCP Fast Open is enabled. TCP Fast Open is also known to be problematic on or across certain networks.

DEFAULT

0

PROTOCOLS

All

EXAMPLE

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    curl_easy_setopt(curl, CURLOPT_TCP_FASTOPEN, 1L);
    curl_easy_perform(curl);
  }
}

AVAILABILITY

Added in 7.49.0. This option is currently only supported on Linux and macOS 10.11 or later.

RETURN VALUE

Returns CURLE_OK if fast open is supported by the operating system, otherwise returns CURLE_NOT_BUILT_IN.