curl-w32/docs/libcurl/opts/CURLOPT_SSL_FALSESTART.md

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---
c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_SSL_FALSESTART
Section: 3
Source: libcurl
See-also:
- CURLOPT_TCP_FASTOPEN (3)
---
# NAME
CURLOPT_SSL_FALSESTART - TLS false start
# SYNOPSIS
~~~c
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_FALSESTART, long enable);
~~~
# DESCRIPTION
Pass a long as parameter set to 1L to enable or 0 to disable.
This option determines whether libcurl should use false start during the TLS
handshake. False start is a mode where a TLS client starts sending application
data before verifying the server's Finished message, thus saving a round trip
when performing a full handshake.
# DEFAULT
0
# PROTOCOLS
All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.
# EXAMPLE
~~~c
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
curl_easy_setopt(curl, CURLOPT_SSL_FALSESTART, 1L);
curl_easy_perform(curl);
}
}
~~~
# AVAILABILITY
Added in 7.42.0. This option is currently only supported by the Secure
Transport (on iOS 7.0 or later, or OS X 10.9 or later) TLS backend.
# RETURN VALUE
Returns CURLE_OK if false start is supported by the SSL backend, otherwise
returns CURLE_NOT_BUILT_IN.