CURLOPT_TCP_FASTOPEN(3)    Library Functions Manual    CURLOPT_TCP_FASTOPEN(3)

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.

SEE ALSO
       CURLOPT_SSL_FALSESTART(3)

libcurl                          April 26 2024         CURLOPT_TCP_FASTOPEN(3)