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authorDaniel Stenberg <daniel@haxx.se>2017-05-15 10:11:23 +0200
committerDaniel Stenberg <daniel@haxx.se>2017-05-15 10:11:23 +0200
commite366ca2b85a78a0ad8d663534bd462e61ad407b5 (patch)
tree2f2cd1317fb5cb6fa8aeb63274b1f015fc0058d3
parent180c75eb63ae95c41c692957ccd13321e44d4e9e (diff)
CURLOPT_HTTPPROXYTUNNEL: clarify, add example
-rw-r--r--docs/libcurl/opts/CURLOPT_HTTPPROXYTUNNEL.335
1 files changed, 23 insertions, 12 deletions
diff --git a/docs/libcurl/opts/CURLOPT_HTTPPROXYTUNNEL.3 b/docs/libcurl/opts/CURLOPT_HTTPPROXYTUNNEL.3
index bdd04dfff..5ded4d27a 100644
--- a/docs/libcurl/opts/CURLOPT_HTTPPROXYTUNNEL.3
+++ b/docs/libcurl/opts/CURLOPT_HTTPPROXYTUNNEL.3
@@ -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