[Chromoting] Hook up host talkgadget policy checks.

remoting/host/dns_blackhole_checker.cc

Index: remoting/host/dns_blackhole_checker.cc
diff --git a/remoting/host/dns_blackhole_checker.cc b/remoting/host/dns_blackhole_checker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fb4ae03f2ed5723c916da6ef8a83f3dd4639ea31
--- /dev/null
+++ b/remoting/host/dns_blackhole_checker.cc
@@ -0,0 +1,70 @@
+// 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/dns_blackhole_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 {
+
+// Default prefix added to the base talkgadget URL.
+const char kDefaultHostTalkGadgetPrefix[] = "chromoting-host";
+
+// The base talkgadget URL.
+const char kTalkGadgetUrl[] = ".talkgadget.google.com/talkgadget/"
+                              "oauth/chrome-remote-desktop-host";
+
+DnsBlackholeChecker::DnsBlackholeChecker(
+    ChromotingHostContext* context,
+    std::string talkgadget_prefix)
+    : context_(context),
+      talkgadget_prefix_(talkgadget_prefix) {
+}
+
+DnsBlackholeChecker::~DnsBlackholeChecker() {
+}
+
+// This is called in response to the TalkGadget http request initiated from
+// CheckStatus().
+void DnsBlackholeChecker::OnURLFetchComplete(const net::URLFetcher* source) {
+  int response = source->GetResponseCode();
+  bool allow = false;
+  if (source->GetResponseCode() == 200) {
+    LOG(INFO) << "Successfully connected to host talkgadget.";
+    allow = true;
+  } else {
+    LOG(INFO) << "Unable to connect to host talkgadget (" << response << ")";
+  }
+  url_fetcher_.reset(NULL);
+  callback_.Run(allow);
+  callback_.Reset();
+}
+
+void DnsBlackholeChecker::CheckForDnsBlackhole(
+    const base::Callback<void(bool)>& callback) {
+  // Make sure we're not currently in the middle of a connection check.
+  if (!url_fetcher_.get()) {
+    DCHECK(callback_.is_null());
+    callback_ = callback;
+    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();
+  } else {
+    LOG(INFO) << "Pending connection check";
+  }
+}
+
+}  // namespace remoting