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CURLOPT_HTTPPROXYTUNNEL: clarify, add example

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Daniel Stenberg 2017-05-15 10:11:23 +02:00
parent 180c75eb63
commit e366ca2b85
1 changed files with 23 additions and 12 deletions
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docs/libcurl/opts/CURLOPT_HTTPPROXYTUNNEL.3
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@ -5,7 +5,7 @@
.\" * | (__| |_| | _ <| |___
.\" * \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
@ -28,27 +28,38 @@ CURLOPT_HTTPPROXYTUNNEL \- tunnel through HTTP proxy
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPPROXYTUNNEL, long tunnel);
.SH DESCRIPTION
Set the parameter to 1 to make libcurl tunnel all operations through the HTTP
proxy. There is a big difference between using a proxy and to tunnel through
it. If you don't know what this means, you probably don't want this tunneling
option.
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 essentially means that a CONNECT 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 whitelist specific port numbers
Tunneling means that a 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.
When using this, it only makes sense to use \fICURLOPT_PROXYTYPE(3)\fP set to
a HTTP proxy.
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 will make libcurl send an FTP URL in a 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
All network protocols
.SH EXAMPLE
TODO
.nf
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
Always
.SH RETURN VALUE