DnsConfigService and a posix implementation

net/dns/dns_config_service.h

+// 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_CONFIG_SERVICE_H_
+#define NET_DNS_CONFIG_SERVICE_H_
+#pragma once
+
+#include <list>
+#include <map>
+#include <string>
+#include <vector>
+
+#include "net/base/net_api.h"
+#include "net/base/net_util.h"
+
+namespace net {
+
+class IPEndPoint;
+
+// DnsConfig stores configuration of the system resolver.
+struct DnsConfig {
+  // Default values are taken from glibc resolv.h.
+  DnsConfig()
+    : ndots(1),
+      timeout(5),
+      attempts(2),
+      rotate(false),
+      edns0(false) {}
+
+  // List of name server addresses.
+  std::vector<IPEndPoint> nameservers;
+  // Suffix search list overrides |domain| and is 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.
+
+  // Min. number of dots before global resolution precedes |search|.

[cbentzel, 2011/08/05 19:11:39]

May as well spell out Minimum

[szym, 2011/08/15 14:27:42]

Done.

+  int ndots;
+  // Time (in seconds) between retransmissions, see res_state.retrans.
+  int timeout;

[cbentzel, 2011/08/05 19:11:39]

Probably better to use a base::TimeDelta from base/time.h here instead - and do
the conversion in ProxyConfigServiceLinux.  That way you don't need to worry
about unit conversion issues.

[szym, 2011/08/15 14:27:42]

Done.

+  // Max. number of retries, see res_state.retry.
+  int attempts;
+  // Round robin entries in |nameservers| for subsequent requests.
+  bool rotate;
+  // Enable EDNS0 extensions.
+  bool edns0;
+
+  bool Equals(const DnsConfig& d) const {
+    return (nameservers == d.nameservers) &&
+           (search == d.search) &&
+           (ndots == d.ndots) &&
+           (timeout == d.timeout) &&
+           (attempts == d.attempts) &&
+           (rotate == d.rotate) &&
+           (edns0 == d.edns0);
+  }
+
+  bool Valid() const {
+    return !nameservers.empty();
+  }
+};
+
+// Service for watching when the system DNS settings have changed.
+// Depending on the platform, watches files in /etc/ or win registry.
+class 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();
+
+  // Immediately starts watching system configuration for changes and attempts
+  // to read the configuration. The current thread must have an IO loop
+  // (for base::files::FilePathWatcher).
+  DnsConfigService() {}
+  virtual ~DnsConfigService() {}
+
+  virtual void AddObserver(Observer* observer) = 0;
+  virtual void RemoveObserver(Observer* observer) = 0;
+
+  const DnsConfig& dns_config() {
+    return dns_config_;
+  }
+
+ protected:

[cbentzel, 2011/08/05 19:11:39]

Why protected? In general I prefer public/private. Derived classes can always
use dns_config() if needed.

[szym, 2011/08/15 14:27:42]

The derived class needs to set dns_config_ but I don't want a public setter. Is
a protected setter better than a protected field? In the end I removed any
non-private access from dns_config_.

+  DnsConfig dns_config_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DnsConfigService);
+};
+
+}  // namespace net
+
+#endif  // NET_DNS_CONFIG_SERVICE_H_
+