[Chromoting] Hook up host talkgadget policy checks.

remoting/host/dns_blackhole_checker.h

+// 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.
+
+#ifndef REMOTING_HOST_DNS_BLACKHOLE_CHECKER_H_
+#define REMOTING_HOST_DNS_BLACKHOLE_CHECKER_H_
+
+#include "net/url_request/url_fetcher_delegate.h"
+
+#include "base/callback.h"
+
+namespace remoting {
+
+class ChromotingHostContext;
+
+class DnsBlackholeChecker : public net::URLFetcherDelegate {

[Sergey Ulanov, 2012/08/30 18:05:01]

I'm not fan for of this name for the same reason I didn't like
TalkReachableChecker that Wez suggested previously. But it's a minor concern -
feel free to keep it as is. 

[Wez, 2012/08/30 20:43:38]

Given that we have no better ideas for naming, and that we have only a single
implementation that checks for a DNS blackhole, I'd prefer that we re-name this
if/when we need to, but I agree with you in principle!

+ public:
+  DnsBlackholeChecker(ChromotingHostContext* context,
+                      std::string talkgadget_prefix);
+  virtual ~DnsBlackholeChecker();
+
+  // net::URLFetcherDelegate interface.
+  virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;
+
+  // Initiates a check the verify that the host talkgadget has not been "DNS
+  // blackholed" to prevent connections.
+  void CheckForDnsBlackhole(const base::Callback<void(bool)>& callback);

[Sergey Ulanov, 2012/08/30 18:05:01]

Please add comment saying that if this method is called again before the
callback is called, then the pending check is cancelled.

[garykac, 2012/08/31 18:28:23]

Done.

+
+ private:
+  ChromotingHostContext* context_;
+
+  // URL fetcher used to verify access to the host talkgadget.
+  scoped_ptr<net::URLFetcher> url_fetcher_;
+
+  // The string pre-pended to '.talkgadget.google.com' to create the full
+  // talkgadget domain name for the host.
+  std::string talkgadget_prefix_;
+
+  // Called with the results of the connection check.
+  base::Callback<void(bool)> callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(DnsBlackholeChecker);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_DNS_BLACKHOLE_CHECKER_H_