Support proxy configuration in HttpClient

[sgjesse]

The HttpClient should support proxy configuration.

[sgjesse]

Marked this as blocking #5454.

[sgjesse]

I propose to make the proxy configuration be very much like the PAC scripts used for web browsers. Of cause using Dart code instead of JavaScript code. This could be done by having the ability to set proxy resolver function on an HttpClient, e.g.

abstract class HttpClient {

  ...

  void set findProxy(void finder(Uri url));
  
  ...
}

The function findProxy will return a string in the same format as is used by PAC scripts. We then need to make the functions available to PAC scripts (see http://findproxyforurl.com/pac-functions/) available in Dart.

The default, if findProxy is not set, will be not to use a proxy, which is the same as the following function:

HttpClient client = ...
client.findProxy = (_) => "DIRECT";

Always using the same proxy is also simple:

HttpClient client = ...
client.findProxy = (_) => "PROXY proxy.example.com:8080";

[sgjesse]

Set owner to @sgjesse.
Added Started label.

[sgjesse]

http://codereview.chromium.org/11066041/

[sgjesse]

https://codereview.chromium.org/11092044

[sgjesse]

Support for the findProxy approach described above is implemented in https://code.google.com/p/dart/source/detail?r=13348 and
https://code.google.com/p/dart/source/detail?r=13599.

What is now missing is support for tunneling using the CONNECT method when contacting the proxy. This is mostly required for HTTPS, but could also be supported for HTTP.

There is no specified way of configuring when to use a tunnel, but the simple heuristic is to use it for HTTPS connections only. If is should be supported for HTTP as well some kind of additional configuration will be required.

An additional issue is using secure transport between the HTTP client and the proxy server. For that the Chromium is using a extension of the PAC script, where HTTPS is used instead of PROXY, see http://www.chromium.org/developers/design-documents/secure-web-proxy and http://www.chromium.org/spdy/spdy-proxy.

Marking this as blocked on HTTPS support for now.

---

Marked this as being blocked by #3593.

[sgjesse]

Removed this from the M2 milestone.
Added this to the M3 milestone.
Unmarked this as being blocked by #3593.

[sgjesse]

Removed this from the M3 milestone.
Added this to the M4 milestone.

[sgjesse]

Added builtin support for using environment variables to configure the HTTP proxy in https://code.google.com/p/dart/source/detail?r=20202.

[DartBot]

This comment was originally written by geert.wl.clae...@gmail.com

---

When is M4 planned for because this is really a pita?

[sgjesse]

Made the environment configuration the default for HttpClient in https://code.google.com/p/dart/source/detail?r=21332.

[sgjesse]

Proposed change to proxies requiring authentication in https://codereview.chromium.org/13915007/.

[sgjesse]

Proxy authentication added in https://code.google.com/p/dart/source/detail?r=21417

Only CONNECT support is now missing.

---

Removed this from the M4 milestone.
Added this to the M5 milestone.

[sgjesse]

Support for the CONNECT method was added in https://code.google.com/p/dart/source/detail?r=22119.

---

Added Fixed label.

[DartBot]

This comment was originally written by zelenk...@gmail.com

---

I still get error even when https_proxy is configured and

curl -v https://pub.dartlang.org/packages/web_ui.json

works and I am using untested dart-sdk which includes r22119 change.

Here is the error:

$ pub.bat -v install
FINE: Pub 0.1.2+0.r23900
IO : Spawning cmd /c ver
IO : Finished ver. Exit code 0.stdout:Microsoft Windows [Version 6.1.7601]Nothing output on stderr.
Resolving dependencies...
SLVR: Solving dependencies:
    | - browser any from hosted (browser)
IO : Get versions from https://pub.dartlang.org/api/packages/browser.
FINE: HTTP GET https://pub.dartlang.org/api/packages/browser
    | Accept: application/vnd.pub.v2+json
Uncaught Error: SocketException: Failed host name lookup (OS Error: This is usually a temporary error during hostname resolution and means that the local server did not receive a response from an authoritative server.
, errno = 11002)
Stack Trace:
#­0 _NativeSocket.lookup.<anonymous closure> (dart:io-patch/socket_patch.dart:100:9)
#­1 _ThenFuture._sendValue (dart:async/future_impl.dart:316:24)
#­2 _FutureImpl._setValue (dart:async/future_impl.dart:153:26)
#­3 _SyncCompleter._setFutureValue (dart:async/future_impl.dart:43:21)
#­4 _Completer.complete (dart:async/future_impl.dart:12:20)
#­5 _SendPortImpl.call.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:106:27)
#­6 _ReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:81:92)

Unhandled exception:
SocketException: Failed host name lookup (OS Error: This is usually a temporary error during hostname resolution and means that the local server did not receive a response from an authoritative server.
, errno = 11002)
#­0 _FutureImpl._scheduleUnhandledError.<anonymous closure> (dart:async/future_impl.dart:192:9)
#­1 _asyncRunCallback._asyncRunCallback (dart:async/event_loop.dart:9:15)
#­2 _asyncRunCallback._asyncRunCallback (dart:async/event_loop.dart:13:7)
#­3 Timer.Timer.<anonymous closure> (dart:async-patch/timer_patch.dart:9:15)
#­4 _Timer._createTimerHandler._handleTimeout (timer_impl.dart:99:28)
#­5 _Timer._createTimerHandler._handleTimeout (timer_impl.dart:107:7)
#­6 _Timer._createTimerHandler.<anonymous closure> (timer_impl.dart:115:23)
#­7 _ReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:81:92)