[net/dns] Removes locking from DnsConfigServiceWin and adds local computer name.

net/dns/dns_config_service_win.cc

 // 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 "net/dns/dns_config_service_win.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/string_split.h"
 #include "base/string_util.h"
 #include "base/synchronization/lock.h"
+#include "base/threading/non_thread_safe.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/utf_string_conversions.h"
 #include "base/win/object_watcher.h"
 #include "base/win/registry.h"
 #include "base/win/windows_version.h"
 #include "googleurl/src/url_canon.h"
 #include "net/base/net_util.h"
+#include "net/base/network_change_notifier.h"
 #include "net/dns/dns_protocol.h"
 #include "net/dns/file_path_watcher_wrapper.h"
 #include "net/dns/serial_worker.h"
 
 #pragma comment(lib, "iphlpapi.lib")
 
 namespace net {
 
 namespace internal {
 
 namespace {
 
-// Watches a single registry key for changes. Thread-safe.
-class RegistryWatcher : public base::win::ObjectWatcher::Delegate {
+// Registry key paths.
+const wchar_t* const kTcpipPath =
+    L"SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters";
+const wchar_t* const kTcpip6Path =
+    L"SYSTEM\\CurrentControlSet\\Services\\Tcpip6\\Parameters";
+const wchar_t* const kDnscachePath =
+    L"SYSTEM\\CurrentControlSet\\Services\\Dnscache\\Parameters";
+const wchar_t* const kPolicyPath =
+    L"SOFTWARE\\Policies\\Microsoft\\Windows NT\\DNSClient";
+
+// Convenience for reading values using RegKey.
+class RegistryReader : public base::NonThreadSafe {
  public:
-  typedef base::Callback<void(bool succeeded)> CallbackType;
-  RegistryWatcher() {}
-
-  bool Watch(const wchar_t* key, const CallbackType& callback) {
-    base::AutoLock lock(lock_);
-    DCHECK(!callback.is_null());
-    CancelLocked();
-    if (key_.Open(HKEY_LOCAL_MACHINE, key,
-                  KEY_NOTIFY | KEY_QUERY_VALUE) != ERROR_SUCCESS)
-      return false;
-    if (key_.StartWatching() != ERROR_SUCCESS)
-      return false;
-    if (!watcher_.StartWatching(key_.watch_event(), this))
-      return false;
-    callback_ = callback;
-    return true;
-  }
-
-  void Cancel() {
-    base::AutoLock lock(lock_);
-    CancelLocked();
-  }
-
-  virtual void OnObjectSignaled(HANDLE object) OVERRIDE {
-    base::AutoLock lock(lock_);
-    bool succeeded = (key_.StartWatching() == ERROR_SUCCESS) &&
-                     watcher_.StartWatching(key_.watch_event(), this);
-    if (!callback_.is_null())
-      callback_.Run(succeeded);
+  explicit RegistryReader(const wchar_t* key) {
+    // Ignoring the result. |key_.Valid()| will catch failures.
+    key_.Open(HKEY_LOCAL_MACHINE, key, KEY_QUERY_VALUE);
   }
 
   bool ReadString(const wchar_t* name,
                   DnsSystemSettings::RegString* out) const {
-    base::AutoLock lock(lock_);
+    DCHECK(CalledOnValidThread());
     out->set = false;
     if (!key_.Valid()) {
       // Assume that if the |key_| is invalid then the key is missing.
       return true;
     }
     LONG result = key_.ReadValue(name, &out->value);
     if (result == ERROR_SUCCESS) {
       out->set = true;
       return true;
     }
     return (result == ERROR_FILE_NOT_FOUND);
   }
 
   bool ReadDword(const wchar_t* name,
                  DnsSystemSettings::RegDword* out) const {
-    base::AutoLock lock(lock_);
+    DCHECK(CalledOnValidThread());
     out->set = false;
     if (!key_.Valid()) {
       // Assume that if the |key_| is invalid then the key is missing.
       return true;
     }
     LONG result = key_.ReadValueDW(name, &out->value);
     if (result == ERROR_SUCCESS) {
       out->set = true;
       return true;
     }
     return (result == ERROR_FILE_NOT_FOUND);
   }
 
  private:
-  void CancelLocked() {
-    lock_.AssertAcquired();
+  base::win::RegKey key_;
+
+  DISALLOW_COPY_AND_ASSIGN(RegistryReader);
+};
+
+
+// Watches a single registry key for changes.
+class RegistryWatcher : public base::win::ObjectWatcher::Delegate,
+                        public base::NonThreadSafe {
+ public:
+  typedef base::Callback<void(bool succeeded)> CallbackType;
+  RegistryWatcher() {}
+
+  bool Watch(const wchar_t* key, const CallbackType& callback) {
+    DCHECK(CalledOnValidThread());
+    DCHECK(!callback.is_null());
+    Cancel();
+    if (key_.Open(HKEY_LOCAL_MACHINE, key, KEY_NOTIFY) != ERROR_SUCCESS)
+      return false;
+    if (key_.StartWatching() != ERROR_SUCCESS)
+      return false;
+    if (!watcher_.StartWatching(key_.watch_event(), this))
+      return false;
+    callback_ = callback;
+    return true;
+  }
+
+  bool IsWatching() const {
+    DCHECK(CalledOnValidThread());
+    return !callback_.is_null();
+  }
+
+  void Cancel() {
+    DCHECK(CalledOnValidThread());
     callback_.Reset();
     if (key_.Valid()) {
       watcher_.StopWatching();
       key_.StopWatching();
+      key_.Close();
     }
   }
 
-  mutable base::Lock lock_;
+  virtual void OnObjectSignaled(HANDLE object) OVERRIDE {
+    DCHECK(CalledOnValidThread());
+    bool succeeded = (key_.StartWatching() == ERROR_SUCCESS) &&
+                      watcher_.StartWatching(key_.watch_event(), this);
+    CallbackType callback = callback_;
+    if (!succeeded)
+      Cancel();
+    if (!callback.is_null())
+      callback.Run(succeeded);
+  }
+
+ private:
   CallbackType callback_;
   base::win::RegKey key_;
   base::win::ObjectWatcher watcher_;
 
   DISALLOW_COPY_AND_ASSIGN(RegistryWatcher);
 };
 
+// Returns NULL if failed.
+scoped_ptr_malloc<IP_ADAPTER_ADDRESSES> ReadIpHelper(ULONG flags) {
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  scoped_ptr_malloc<IP_ADAPTER_ADDRESSES> out;
+  ULONG len = 15000;  // As recommended by MSDN for GetAdaptersAddresses.
+  UINT rv = ERROR_BUFFER_OVERFLOW;
+  // Try up to three times.
+  for (unsigned tries = 0;
+        (tries < 3) && (rv == ERROR_BUFFER_OVERFLOW);
+        tries++) {
+    out.reset(
+        reinterpret_cast<PIP_ADAPTER_ADDRESSES>(malloc(len)));

[mmenke, 2012/03/22 19:36:08]

nit:  Think this will all fit on one line.  Next line might, too.

+    rv = GetAdaptersAddresses(AF_UNSPEC, flags, NULL,
+                              out.get(), &len);
+  }
+  if (rv != NO_ERROR)
+    out.reset();
+  return out.Pass();
+}
+
 // Converts a string16 domain name to ASCII, possibly using punycode.
 // Returns true if the conversion succeeds and output is not empty. In case of
 // failure, |domain| might become dirty.
 bool ParseDomainASCII(const string16& widestr, std::string* domain) {
   DCHECK(domain);
   if (widestr.empty())
     return false;
 
   // Check if already ASCII.
   if (IsStringASCII(widestr)) {
@@ skipping 184 matching lines @@
       : service_(service),
         success_(false) {}
 
   bool Watch() {
     DCHECK(loop()->BelongsToCurrentThread());
 
     RegistryWatcher::CallbackType callback =
         base::Bind(&ConfigReader::OnChange, base::Unretained(this));
 
     // The Tcpip key must be present.
-    if (!tcpip_watcher_.Watch(
-        L"SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters",
-        callback))
+    if (!tcpip_watcher_.Watch(kTcpipPath, callback))
       return false;
 
     // Watch for IPv6 nameservers.
-    tcpip6_watcher_.Watch(
-        L"SYSTEM\\CurrentControlSet\\Services\\Tcpip6\\Parameters",
-        callback);
+    tcpip6_watcher_.Watch(kTcpip6Path, callback);
 
     // DNS suffix search list and devolution can be configured via group
     // policy which sets this registry key. If the key is missing, the policy
     // does not apply, and the DNS client uses Tcpip and Dnscache settings.
     // If a policy is installed, DnsConfigService will need to be restarted.
     // BUG=99509
 
-    dnscache_watcher_.Watch(
-        L"SYSTEM\\CurrentControlSet\\Services\\Dnscache\\Parameters",
-        callback);
-
-    policy_watcher_.Watch(
-        L"SOFTWARE\\Policies\\Microsoft\\Windows NT\\DNSClient",
-        callback);
+    dnscache_watcher_.Watch(kDnscachePath, callback);
+    policy_watcher_.Watch(kPolicyPath, callback);
 
     WorkNow();
     return true;
   }
 
   void Cancel() {
     DCHECK(loop()->BelongsToCurrentThread());
     SerialWorker::Cancel();
     policy_watcher_.Cancel();
     dnscache_watcher_.Cancel();
@@ skipping 11 matching lines @@
     if (!IsCancelled())
       service_->InvalidateConfig();
     // We don't trust a config that we cannot watch in the future.
     // TODO(szym): re-start watcher if that makes sense. http://crbug.com/116139
     if (succeeded)
       WorkNow();
     else
       LOG(ERROR) << "Failed to watch DNS config";
   }
 
-  bool ReadIpHelper(DnsSystemSettings* settings) {
-    base::ThreadRestrictions::AssertIOAllowed();
-
-    ULONG flags = GAA_FLAG_SKIP_ANYCAST |
-                  GAA_FLAG_SKIP_UNICAST |
-                  GAA_FLAG_SKIP_MULTICAST |
-                  GAA_FLAG_SKIP_FRIENDLY_NAME;
-    ULONG len = 15000;  // As recommended by MSDN for GetAdaptersAddresses.
-    UINT rv = ERROR_BUFFER_OVERFLOW;
-    // Try up to three times.
-    for (unsigned tries = 0;
-         (tries < 3) && (rv == ERROR_BUFFER_OVERFLOW);
-         tries++) {
-      settings->addresses.reset(
-          reinterpret_cast<PIP_ADAPTER_ADDRESSES>(malloc(len)));
-      rv = GetAdaptersAddresses(AF_UNSPEC, flags, NULL,
-                                settings->addresses.get(), &len);
-    }
-    return (rv == NO_ERROR);
-  }
-
-  bool ReadDevolutionSetting(const RegistryWatcher& watcher,
+  bool ReadDevolutionSetting(const RegistryReader& reader,
                              DnsSystemSettings::DevolutionSetting& setting) {
-    return watcher.ReadDword(L"UseDomainNameDevolution", &setting.enabled) &&
-           watcher.ReadDword(L"DomainNameDevolutionLevel", &setting.level);
+    return reader.ReadDword(L"UseDomainNameDevolution", &setting.enabled) &&
+           reader.ReadDword(L"DomainNameDevolutionLevel", &setting.level);
   }
 
   virtual void DoWork() OVERRIDE {
     // Should be called on WorkerPool.
     success_ = false;
 
     DnsSystemSettings settings;
     memset(&settings, 0, sizeof(settings));
-    if (!ReadIpHelper(&settings))
+    settings.addresses = ReadIpHelper(GAA_FLAG_SKIP_ANYCAST |
+                                      GAA_FLAG_SKIP_UNICAST |
+                                      GAA_FLAG_SKIP_MULTICAST |
+                                      GAA_FLAG_SKIP_FRIENDLY_NAME);
+    if (!settings.addresses.get())
       return;  // no point reading the rest
 
-    if (!policy_watcher_.ReadString(L"SearchList",
-                                    &settings.policy_search_list))
+    RegistryReader tcpip_reader(kTcpipPath);
+    RegistryReader tcpip6_reader(kTcpip6Path);
+    RegistryReader dnscache_reader(kDnscachePath);
+    RegistryReader policy_reader(kPolicyPath);
+
+    if (!policy_reader.ReadString(L"SearchList",
+                                  &settings.policy_search_list))
       return;
 
-    if (!tcpip_watcher_.ReadString(L"SearchList", &settings.tcpip_search_list))
+    if (!tcpip_reader.ReadString(L"SearchList", &settings.tcpip_search_list))
       return;
 
-    if (!tcpip_watcher_.ReadString(L"Domain", &settings.tcpip_domain))
+    if (!tcpip_reader.ReadString(L"Domain", &settings.tcpip_domain))
       return;
 
-    if (!ReadDevolutionSetting(policy_watcher_, settings.policy_devolution))
+    if (!ReadDevolutionSetting(policy_reader, settings.policy_devolution))
       return;
 
-    if (!ReadDevolutionSetting(dnscache_watcher_,
+    if (!ReadDevolutionSetting(dnscache_reader,
                                settings.dnscache_devolution))
       return;
 
-    if (!ReadDevolutionSetting(tcpip_watcher_, settings.tcpip_devolution))
+    if (!ReadDevolutionSetting(tcpip_reader, settings.tcpip_devolution))
       return;
 
-    if (!policy_watcher_.ReadDword(L"AppendToMultiLabelName",
-                                   &settings.append_to_multi_label_name))
+    if (!policy_reader.ReadDword(L"AppendToMultiLabelName",
+                                 &settings.append_to_multi_label_name))
       return;
 
     success_ = ConvertSettingsToDnsConfig(settings, &dns_config_);
   }
 
   virtual void OnWorkFinished() OVERRIDE {
     DCHECK(loop()->BelongsToCurrentThread());
     DCHECK(!IsCancelled());
     if (success_) {
       service_->OnConfigRead(dns_config_);
     } else {
       LOG(WARNING) << "Failed to read config.";
     }
   }
 
   DnsConfigServiceWin* service_;
   // Written in DoRead(), read in OnReadFinished(). No locking required.
   DnsConfig dns_config_;
   bool success_;
 
   RegistryWatcher tcpip_watcher_;
   RegistryWatcher tcpip6_watcher_;
   RegistryWatcher dnscache_watcher_;
   RegistryWatcher policy_watcher_;
 };
 
+FilePath GetHostsPath() {
+  TCHAR buffer[MAX_PATH];
+  UINT rc = GetSystemDirectory(buffer, MAX_PATH);
+  DCHECK(0 < rc && rc < MAX_PATH);
+  return FilePath(buffer).Append(FILE_PATH_LITERAL("drivers\\etc\\hosts"));
+}
+
+// An extension for DnsHostsReader which also watches the HOSTS file,
+// reads local name from GetComputerNameEx, local IP from GetAdaptersAddresses,
+// and observes changes to local IP address.
+class DnsConfigServiceWin::HostsReader
+    : public DnsHostsReader,
+      public NetworkChangeNotifier::IPAddressObserver {
+ public:
+  explicit HostsReader(DnsConfigServiceWin* service)
+      : DnsHostsReader(GetHostsPath()), service_(service) {
+  }
+
+  bool Watch() {
+    DCHECK(loop()->BelongsToCurrentThread());
+    DCHECK(!IsCancelled());
+
+    // In case the reader is restarted, remove it from the observer list.
+    NetworkChangeNotifier::RemoveIPAddressObserver(this);
+
+    if (!hosts_watcher_.Watch(path(),
+                              base::Bind(&HostsReader::OnHostsChanged,
+                                         base::Unretained(this)))) {
+      return false;
+    }
+    NetworkChangeNotifier::AddIPAddressObserver(this);
+    WorkNow();
+    return true;
+  }
+
+  // Cancels the underlying SerialWorker. Cannot be undone.
+  void Cancel() {
+    DnsHostsReader::Cancel();
+    hosts_watcher_.Cancel();
+    NetworkChangeNotifier::RemoveIPAddressObserver(this);
+  }
+
+ private:
+  virtual void OnIPAddressChanged() OVERRIDE {
+    DCHECK(loop()->BelongsToCurrentThread());
+    service_->InvalidateHosts();
+    if (!hosts_watcher_.IsWatching())
+      return;
+    WorkNow();
+  }
+
+  void OnHostsChanged(bool succeeded) {
+    DCHECK(loop()->BelongsToCurrentThread());
+    service_->InvalidateHosts();
+    if (succeeded)
+      WorkNow();
+    else
+      LOG(ERROR) << "Failed to watch DNS hosts";
+  }
+
+  virtual void DoWork() OVERRIDE {
+    DnsHostsReader::DoWork();
+
+    if (!success_)
+      return;
+
+    // Default address of local computer name and "localhost" can be overridden
+    // by the HOSTS file, but if it's not there, then we need to fill it in.
+
+    success_ = false;
+
+    WCHAR buffer[MAX_PATH];
+    DWORD size = MAX_PATH;
+    std::string localname;
+    if (!GetComputerNameExW(ComputerNameDnsHostname, buffer, &size) ||
+        !ParseDomainASCII(buffer, &localname)) {
+      LOG(ERROR) << "Failed to read local computer name";
+      return;
+    }
+    StringToLowerASCII(&localname);
+
+    scoped_ptr_malloc<IP_ADAPTER_ADDRESSES> addresses =
+        ReadIpHelper(GAA_FLAG_SKIP_ANYCAST |
+                     GAA_FLAG_SKIP_DNS_SERVER |
+                     GAA_FLAG_SKIP_MULTICAST |
+                     GAA_FLAG_SKIP_FRIENDLY_NAME);
+    if (!addresses.get())
+      return;
+
+    // The order of adapters is the network binding order, so stick to the
+    // first good adapter for each family.
+    bool have_ipv4 =
+        dns_hosts_.count(DnsHostsKey(localname, ADDRESS_FAMILY_IPV4)) > 0;
+    bool have_ipv6 =
+        dns_hosts_.count(DnsHostsKey(localname, ADDRESS_FAMILY_IPV6)) > 0;
+    for (const IP_ADAPTER_ADDRESSES* adapter = addresses.get();
+         adapter != NULL && !(have_ipv4 && have_ipv6);

[mmenke, 2012/03/22 19:36:08]

nit:  Think (!have_ipv4 || !have_ipv6) is a little easier to cognitively follow.
 If you disagree, feel free to leave as-is.

+         adapter = adapter->Next) {
+      if (adapter->OperStatus != IfOperStatusUp)
+        continue;
+      if (adapter->IfType == IF_TYPE_SOFTWARE_LOOPBACK)
+        continue;
+
+      for (const IP_ADAPTER_UNICAST_ADDRESS* address =
+               adapter->FirstUnicastAddress;
+           address != NULL;
+           address = address->Next) {
+        IPEndPoint ipe;
+        if (!ipe.FromSockAddr(address->Address.lpSockaddr,
+                              address->Address.iSockaddrLength)) {
+          return;
+        }
+        if (!have_ipv4 && (ipe.GetFamily() == AF_INET)) {
+          have_ipv4 = true;
+          dns_hosts_[DnsHostsKey(localname, ADDRESS_FAMILY_IPV4)] =
+              ipe.address();
+        } else if (!have_ipv6 && (ipe.GetFamily() == AF_INET6)) {
+          have_ipv6 = true;
+          dns_hosts_[DnsHostsKey(localname, ADDRESS_FAMILY_IPV6)] =
+              ipe.address();
+        }

[mmenke, 2012/03/22 19:36:08]

You could simplify this as well.  I don't think the speed difference matters if
we just use insert here as well, and ditch have_ipv4 and have_ipv6 entirely,
though it wouldn't really simplify things that much.

+      }
+    }
+
+    const unsigned char kIPv4Localhost[] = { 127, 0, 0, 1 };
+    const unsigned char kIPv6Localhost[] = { 0, 0, 0, 0, 0, 0, 0, 0,
+                                             0, 0, 0, 0, 0, 0, 0, 1 };
+    IPAddressNumber loopback_ipv4(kIPv4Localhost,
+                                  kIPv4Localhost + arraysize(kIPv4Localhost));
+    IPAddressNumber loopback_ipv6(kIPv6Localhost,
+                                  kIPv6Localhost + arraysize(kIPv6Localhost));
+    dns_hosts_.insert(

[mmenke, 2012/03/22 19:36:08]

You should add a comment that this will not overwrite any pre-existing entries
from the HOSTs file.

+        std::make_pair(DnsHostsKey("localhost", ADDRESS_FAMILY_IPV4),
+                       loopback_ipv4));
+    dns_hosts_.insert(
+        std::make_pair(DnsHostsKey("localhost", ADDRESS_FAMILY_IPV6),
+                       loopback_ipv6));
+    success_ = true;
+  }
+
+  virtual void OnWorkFinished() OVERRIDE {
+    DCHECK(loop()->BelongsToCurrentThread());
+    if (!success_ || !hosts_watcher_.IsWatching())
+      return;
+    service_->OnHostsRead(dns_hosts_);
+  }
+
+  DnsConfigServiceWin* service_;
+  FilePathWatcherWrapper hosts_watcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(HostsReader);
+};
+
+
 DnsConfigServiceWin::DnsConfigServiceWin()
     : config_reader_(new ConfigReader(this)),
-      hosts_watcher_(new FilePathWatcherWrapper()) {}
+      hosts_reader_(new HostsReader(this)) {}
 
 DnsConfigServiceWin::~DnsConfigServiceWin() {
   DCHECK(CalledOnValidThread());
   config_reader_->Cancel();
-  if (hosts_reader_)
-    hosts_reader_->Cancel();
+  hosts_reader_->Cancel();
 }
 
 void DnsConfigServiceWin::Watch(const CallbackType& callback) {
   DCHECK(CalledOnValidThread());
   DCHECK(!callback.is_null());
   set_callback(callback);
 
   // This is done only once per lifetime so open the keys and file watcher
   // handles on this thread.
   // TODO(szym): Should/can this be avoided? http://crbug.com/114223
   base::ThreadRestrictions::ScopedAllowIO allow_io;
 
   if (!config_reader_->Watch()) {
     LOG(ERROR) << "Failed to start watching DNS config";
     InvalidateConfig();
   }
 
-  TCHAR buffer[MAX_PATH];
-  UINT rc = GetSystemDirectory(buffer, MAX_PATH);
-  DCHECK(0 < rc && rc < MAX_PATH);
-  FilePath hosts_path = FilePath(buffer).
-      Append(FILE_PATH_LITERAL("drivers\\etc\\hosts"));
-  hosts_reader_ = new DnsHostsReader(
-      hosts_path,
-      base::Bind(&DnsConfigServiceWin::OnHostsRead, base::Unretained(this)));
-  if (hosts_watcher_->Watch(hosts_path,
-                            base::Bind(&DnsConfigServiceWin::OnHostsChanged,
-                                       base::Unretained(this)))) {
-    OnHostsChanged(true);
-  } else {
-    OnHostsChanged(false);
+  if (!hosts_reader_->Watch()) {
+    LOG(ERROR) << "Failed to start watching HOSTS";
+    InvalidateHosts();
   }
 }
 
-void DnsConfigServiceWin::OnHostsChanged(bool succeeded) {
-  InvalidateHosts();
-  if (succeeded)
-    hosts_reader_->WorkNow();
-  else
-    LOG(ERROR) << "Failed to watch DNS hosts";
-}
-
 }  // namespace internal
 
 // static
 scoped_ptr<DnsConfigService> DnsConfigService::CreateSystemService() {
   return scoped_ptr<DnsConfigService>(new internal::DnsConfigServiceWin());
 }
 
 }  // namespace net