curl/docs/libcurl/opts/CURLOPT_HTTPPROXYTUNNEL.md
Daniel Stenberg e3fe020089
docs/libcurl: generate PROTOCOLS from meta-data
Remove the PROTOCOLS section from the source files completely and
instead generate them based on the header data in the curldown files.

It also generates TLS backend information for options marked for TLS as
protocol.

Closes #13175
2024-03-23 18:13:03 +01:00

74 lines
1.8 KiB
Markdown

---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_HTTPPROXYTUNNEL
Section: 3
Source: libcurl
Protocol:
- All
See-also:
- CURLOPT_PROXY (3)
- CURLOPT_PROXYPORT (3)
- CURLOPT_PROXYTYPE (3)
---
# NAME
CURLOPT_HTTPPROXYTUNNEL - tunnel through HTTP proxy
# SYNOPSIS
~~~c
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPPROXYTUNNEL, long tunnel);
~~~
# DESCRIPTION
Set the **tunnel** parameter to 1L to make libcurl tunnel all operations
through the HTTP proxy (set with CURLOPT_PROXY(3)). 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
CURLOPT_SUPPRESS_CONNECT_HEADERS(3).
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).
# DEFAULT
0
# EXAMPLE
~~~c
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);
}
}
~~~
# AVAILABILITY
Always
# RETURN VALUE
Returns CURLE_OK