repo/core/curl/files/CURLOPT_HTTPPROXYTUNNEL.3

.\" generated by cd2nroff 0.1 from CURLOPT_HTTPPROXYTUNNEL.md
.TH CURLOPT_HTTPPROXYTUNNEL 3 "2024-08-02" libcurl
.SH NAME
CURLOPT_HTTPPROXYTUNNEL \- tunnel through HTTP proxy
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPPROXYTUNNEL, long tunnel);
.fi
.SH DESCRIPTION
Set the \fBtunnel\fP parameter to 1L to make libcurl tunnel all operations
through the HTTP proxy (set with \fICURLOPT_PROXY(3)\fP). There is a big
difference between using a proxy and to tunnel through it.

Tunneling means that an HTTP CONNECT request is sent to the proxy, asking it
to connect to a remote host on a specific port number and then the traffic is
just passed through the proxy. Proxies tend to white\-list specific port numbers
it allows CONNECT requests to and often only port 80 and 443 are allowed.

To suppress proxy CONNECT response headers from user callbacks use
\fICURLOPT_SUPPRESS_CONNECT_HEADERS(3)\fP.

HTTP proxies can generally only speak HTTP (for obvious reasons), which makes
libcurl convert non\-HTTP requests to HTTP when using an HTTP proxy without
this tunnel option set. For example, asking for an FTP URL and specifying an
HTTP proxy makes libcurl send an FTP URL in an HTTP GET request to the
proxy. By instead tunneling through the proxy, you avoid that conversion (that
rarely works through the proxy anyway).
.SH DEFAULT
0
.SH PROTOCOLS
This functionality affects all supported protocols
.SH EXAMPLE
.nf
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/file.txt");
    curl_easy_setopt(curl, CURLOPT_PROXY, "http://127.0.0.1:80");
    curl_easy_setopt(curl, CURLOPT_HTTPPROXYTUNNEL, 1L);
    curl_easy_perform(curl);
  }
}
.fi
.SH AVAILABILITY
Added in curl 7.3
.SH RETURN VALUE
Returns CURLE_OK
.SH SEE ALSO
.BR CURLOPT_PROXY (3),
.BR CURLOPT_PROXYPORT (3),
.BR CURLOPT_PROXYTYPE (3)