CURLOPT_TCP_FASTOPEN

Section: curl_easy_setopt options (3)
Updated: November 04, 2020
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NAME

CURLOPT_TCP_FASTOPEN - enable TCP Fast Open

SYNOPSIS

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 (RFC7413) 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).

DEFAULT

PROTOCOLS

All

EXAMPLE

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 OS X El Capitan.

RETURN VALUE

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