65 lines
1.3 KiB
Markdown
65 lines
1.3 KiB
Markdown
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---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_TCP_FASTOPEN
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_SSL_FALSESTART (3)
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---
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# NAME
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CURLOPT_TCP_FASTOPEN - TCP Fast Open
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_FASTOPEN, long enable);
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~~~
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# DESCRIPTION
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Pass a long as parameter set to 1L to enable or 0 to disable.
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TCP Fast Open (RFC 7413) is a mechanism that allows data to be carried in the
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SYN and SYN-ACK packets and consumed by the receiving end during the initial
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connection handshake, saving up to one full round-trip time (RTT).
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Beware: the TLS session cache does not work when TCP Fast Open is enabled. TCP
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Fast Open is also known to be problematic on or across certain networks.
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# DEFAULT
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0
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# PROTOCOLS
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All
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# EXAMPLE
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~~~c
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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curl_easy_setopt(curl, CURLOPT_TCP_FASTOPEN, 1L);
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curl_easy_perform(curl);
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}
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}
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~~~
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# AVAILABILITY
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Added in 7.49.0. This option is currently only supported on Linux and macOS
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10.11 or later.
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# RETURN VALUE
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Returns CURLE_OK if fast open is supported by the operating system, otherwise
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returns CURLE_NOT_BUILT_IN.
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