CURLOPT_HAPROXYPROTOCOL - Man Page

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HAPROXYPROTOCOL,
                          long haproxy_protocol);

A long parameter set to 1 tells the library to send an HAProxy PROXY protocol v1 header at beginning of the connection. The default action is not to send this header.

This option is primarily useful when sending test requests to a service that expects this header.

Most applications do not need this option.

0, do not send any HAProxy PROXY protocol header

This functionality affects all supported protocols

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

Added in curl 7.60.0

Returns CURLE_OK if HTTP is enabled, and CURLE_UNKNOWN_OPTION if not.

CURLOPT_PROXY(3)

curl_easy_setopt(3), CURLOPT_HAPROXY_CLIENT_IP(3), libcurl-symbols(3).