CURLOPT_SUPPRESS_CONNECT_HEADERS - Man Page

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SUPPRESS_CONNECT_HEADERS, long onoff);

When CURLOPT_HTTPPROXYTUNNEL(3) is used and a CONNECT request is made, suppress proxy CONNECT response headers from the user callback functions CURLOPT_HEADERFUNCTION(3) and CURLOPT_WRITEFUNCTION(3).

Proxy CONNECT response headers can complicate header processing since it is essentially a separate set of headers. You can enable this option to suppress those headers.

For example let's assume an HTTPS URL is to be retrieved via CONNECT. On success there would normally be two sets of headers, and each header line sent to the header function and/or the write function. The data given to the callbacks would look like this:

HTTP/1.1 200 Connection established
{headers}
...

HTTP/1.1 200 OK
Content-Type: application/json
{headers}
...

{body}
...

However by enabling this option the CONNECT response headers are suppressed, so the data given to the callbacks would look like this:

HTTP/1.1 200 OK
Content-Type: application/json
{headers}
...

{body}
...

0

This functionality affects all supported protocols

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

    curl_easy_setopt(curl, CURLOPT_HEADER, 1L);
    curl_easy_setopt(curl, CURLOPT_PROXY, "http://foo:3128");
    curl_easy_setopt(curl, CURLOPT_HTTPPROXYTUNNEL, 1L);
    curl_easy_setopt(curl, CURLOPT_SUPPRESS_CONNECT_HEADERS, 1L);

    curl_easy_perform(curl);

    /* always cleanup */
    curl_easy_cleanup(curl);
  }
}

Added in curl 7.54.0

CURLE_OK or an error such as CURLE_UNKNOWN_OPTION.

CURLOPT_HEADER(3), CURLOPT_HTTPPROXYTUNNEL(3), CURLOPT_PROXY(3)

curl_easy_setopt(3), CURLINFO_HEADER_SIZE(3), CURLOPT_HTTPPROXYTUNNEL(3), libcurl-symbols(3).