DnsConfigService and a posix implementation

net/dns/dns_config_service.h

Index: net/dns/dns_config_service.h
diff --git a/net/dns/dns_config_service.h b/net/dns/dns_config_service.h
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+// Copyright (c) 2011 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 NET_DNS_DNS_CONFIG_SERVICE_H_
+#define NET_DNS_DNS_CONFIG_SERVICE_H_
+#pragma once
+
+#include <list>
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/time.h"
+#include "net/base/net_export.h"
+
+namespace net {
+
+class IPEndPoint;
+
+// DnsConfig stores configuration of the system resolver.
+struct NET_EXPORT_PRIVATE DnsConfig {
+  DnsConfig();
+
+  bool Equals(const DnsConfig& d) const;
+
+  bool Valid() const {
+    return !nameservers.empty();
+  }
+
+  // List of name server addresses.
+  std::vector<IPEndPoint> nameservers;
+  // Suffix search list; used on first lookup when number of dots in given name
+  // is less than |ndots|.
+  std::vector<std::string> search;
+
+  // Resolver options; see man resolv.conf.
+  // TODO(szym): use |ndots| and |search| to determine the sequence of FQDNs
+  // to query given a specific name.
+
+  // Minimum number of dots before global resolution precedes |search|.
+  int ndots;
+  // Time between retransmissions, see res_state.retrans.
+  base::TimeDelta timeout;
+  // Maximum number of retries, see res_state.retry.
+  int attempts;
+  // Round robin entries in |nameservers| for subsequent requests.
+  bool rotate;
+  // Enable EDNS0 extensions.
+  bool edns0;
+};
+
+// Service for watching when the system DNS settings have changed.
+// Depending on the platform, watches files in /etc/ or win registry.
+class NET_EXPORT_PRIVATE DnsConfigService {
+ public:
+  // Callback interface for the client. The observer is called on the same
+  // thread as Watch(). Observer must outlive the service.
+  class Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Called only when |dns_config| is different from the last check.
+    virtual void OnConfigChanged(const DnsConfig& dns_config) = 0;
+  };
+
+  // Creates the platform-specific DnsConfigService.
+  static DnsConfigService* CreateSystemService();
+
+  DnsConfigService() {}
+  virtual ~DnsConfigService() {}
+
+  // Immediately starts watching system configuration for changes and attempts
+  // to read the configuration. For some platform implementations, the current
+  // thread must have an IO loop (for base::files::FilePathWatcher).
+  virtual void Watch() = 0;
+
+  // If a config is available, |observer| will immediately be called with
+  // OnConfigChanged.
+  virtual void AddObserver(Observer* observer) = 0;
+  virtual void RemoveObserver(Observer* observer) = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DnsConfigService);
+};
+
+}  // namespace net
+
+#endif  // NET_DNS_DNS_CONFIG_SERVICE_H_
+