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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

1.8 KiB

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SPDX-License-Identifier

Title

Section

Source

Protocol

See-also

curl

CURLOPT_HTTPPROXYTUNNEL

libcurl

All

CURLOPT_PROXY (3)

CURLOPT_PROXYPORT (3)

CURLOPT_PROXYTYPE (3)

NAME

CURLOPT_HTTPPROXYTUNNEL - tunnel through HTTP proxy

SYNOPSIS

#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

EXAMPLE

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

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