[Chromoting] Hook up host talkgadget policy checks.

remoting/host/connection_block_checker.cc

Index: remoting/host/connection_block_checker.cc
diff --git a/remoting/host/connection_block_checker.cc b/remoting/host/connection_block_checker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8c4e76aa920b566d8354bb5a7357ceda1a4a9c68
--- /dev/null
+++ b/remoting/host/connection_block_checker.cc
@@ -0,0 +1,65 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/connection_block_checker.h"
+
+#include "googleurl/src/gurl.h"
+#include "net/url_request/url_fetcher.h"
+#include "remoting/host/chromoting_host_context.h"
+#include "remoting/host/constants.h"
+
+namespace remoting {
+
+const int kMaxConnectionBlockChecks = 5;
+
+ConnectionBlockChecker::ConnectionBlockChecker(
+    ChromotingHostContext* context,
+    std::string talkgadget_prefix)
+    : context_(context),
+      talkgadget_prefix_(talkgadget_prefix),
+      status_(UNKNOWN),
+      check_pending_(false),
+      reconnect_attempts_(0) {
+}
+
+// This is called in response to the TalkGadget http request initiated from
+// GetStatus().
+void ConnectionBlockChecker::OnURLFetchComplete(const net::URLFetcher* source) {
+  check_pending_ = false;
+  int response = source->GetResponseCode();
+  if (response == 200) {
+    LOG(INFO) << "Successfully connected to talkgadget.";
+    status_ = ALLOW;
+    url_fetcher_.reset(NULL);
+    return;
+  }
+  if (response == 404 || reconnect_attempts_ > kMaxConnectionBlockChecks) {

[Sergey Ulanov, 2012/08/28 00:33:42]

We may get 404 if there is a misbehaving proxy, so I'm not sure we can rely on
it.

[garykac, 2012/08/29 00:07:15]

Done.

+    LOG(INFO) << "Unable to connect to talkgadget.";
+    status_ = DENY;
+  } else {
+    LOG(INFO) << "Failed to find talkgadget. Retrying...";
+    reconnect_attempts_++;
+    status_ = UNKNOWN;
+  }
+}
+
+ConnectionBlockChecker::Status ConnectionBlockChecker::GetStatus() {

[Sergey Ulanov, 2012/08/28 00:33:42]

Here we check connection status only once when this code is called for the first
time. Problem is that if chromoting gets blocked later we will not know about
it. It's better to check before every single connection. It's even a bigger
problem if first kMaxConnectionBlockChecks connections fail just because of a
network failure. We will never be able to connect again, even after network
starts working. I suggest you make this method asynchronous and make a new URL
request every time it's called, e.g.
void GetBlockingState(const base::Callback<State>& callback);

[garykac, 2012/08/29 00:07:15]

Done.

+  if (status_ == UNKNOWN && !check_pending_) {
+    std::string talkgadget_url("https://");
+    if (talkgadget_prefix_.empty()) {
+      talkgadget_url += kDefaultHostTalkGadgetPrefix;
+    } else {
+      talkgadget_url += talkgadget_prefix_;
+    }
+    talkgadget_url += kTalkGadgetUrl;
+    LOG(INFO) << "Verifying connection to " << talkgadget_url;
+    url_fetcher_.reset(net::URLFetcher::Create(GURL(talkgadget_url),
+                                               net::URLFetcher::GET, this));
+    url_fetcher_->SetRequestContext(context_->url_request_context_getter());
+    url_fetcher_->Start();
+  }
+  return status_;
+}
+
+}  // namespace remoting