WebRTC should generate default private address even when adapter enumeration is disabled.

webrtc/base/network.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 133 matching lines @@
   // Any MAC based IPv6 should be avoided to prevent the MAC tracking.
   if (IPIsMacBased(ip)) {
     return true;
   }
 
   return false;
 }
 
 }  // namespace
 
+// These addresses are used as the targets to find out the default local address
+// on a multi-homed endpoint. They are actually DNS servers.
+const char kPublicIPv4Host[] = "8.8.8.8";
+const char kPublicIPv6Host[] = "2001:4860:4860::8888";
+const int kPublicPort = 53;  // DNS port.
+
 std::string MakeNetworkKey(const std::string& name, const IPAddress& prefix,
                            int prefix_length) {
   std::ostringstream ost;
   ost << name << "%" << prefix.ToString() << "/" << prefix_length;
   return ost.str();
 }
 
 NetworkManager::NetworkManager() {
 }
 
 NetworkManager::~NetworkManager() {
 }
 
 NetworkManager::EnumerationPermission NetworkManager::enumeration_permission()
     const {
   return ENUMERATION_ALLOWED;
 }
 
+bool NetworkManager::GetDefaultLocalAddress(int family, IPAddress* addr) const {
+  return false;
+}
+
 NetworkManagerBase::NetworkManagerBase()
     : enumeration_permission_(NetworkManager::ENUMERATION_ALLOWED),
       max_ipv6_networks_(kMaxIPv6Networks),
       ipv6_enabled_(true) {
 }
 
 NetworkManagerBase::~NetworkManagerBase() {
   for (const auto& kv : networks_map_) {
     delete kv.second;
   }
 }
 
 NetworkManager::EnumerationPermission
 NetworkManagerBase::enumeration_permission() const {
   return enumeration_permission_;
 }
 
 void NetworkManagerBase::GetAnyAddressNetworks(NetworkList* networks) {
   if (!ipv4_any_address_network_) {
     const rtc::IPAddress ipv4_any_address(INADDR_ANY);
     ipv4_any_address_network_.reset(
         new rtc::Network("any", "any", ipv4_any_address, 0));
+    ipv4_any_address_network_->set_default_address_provider(this);

[pthatcher1, 2015/11/10 18:52:34]

Why not just set the provider at the very beginning when the classes are
constructed?

[guoweis_webrtc, 2015/11/10 20:37:29]

Because chromium code calls the constructor as well and I can't modify them in
one batch.

     ipv4_any_address_network_->AddIP(ipv4_any_address);
   }
   networks->push_back(ipv4_any_address_network_.get());
 
   if (ipv6_enabled()) {
     if (!ipv6_any_address_network_) {
       const rtc::IPAddress ipv6_any_address(in6addr_any);
       ipv6_any_address_network_.reset(
           new rtc::Network("any", "any", ipv6_any_address, 0));
+      ipv6_any_address_network_->set_default_address_provider(this);
       ipv6_any_address_network_->AddIP(ipv6_any_address);
     }
     networks->push_back(ipv6_any_address_network_.get());
   }
 }
 
 void NetworkManagerBase::GetNetworks(NetworkList* result) const {
   int ipv6_networks = 0;
   result->clear();
   for (Network* network : networks_) {
@@ skipping 101 matching lines @@
       if (pref > 0) {
         --pref;
       } else {
         LOG(LS_ERROR) << "Too many network interfaces to handle!";
         break;
       }
     }
   }
 }
 
+void NetworkManagerBase::set_default_local_address(const IPAddress& ip) {
+  if (ip.family() == AF_INET) {
+    default_ipv4_address_ = ip;
+  } else if (ip.family() == AF_INET6) {
+    default_ipv6_address_ = ip;
+  }
+}
+
+bool NetworkManagerBase::GetDefaultLocalAddress(int family,
+                                                IPAddress* ipaddr) const {
+  if (family == AF_INET) {
+    *ipaddr = default_ipv4_address_;
+    return true;
+  } else if (family == AF_INET6) {
+    *ipaddr = default_ipv6_address_;
+    return true;
+  }
+  return false;
+}
+
 BasicNetworkManager::BasicNetworkManager()
     : thread_(NULL), sent_first_update_(false), start_count_(0),
       network_ignore_mask_(kDefaultNetworkIgnoreMask),
       ignore_non_default_routes_(false) {
 }
 
 BasicNetworkManager::~BasicNetworkManager() {
 }
 
 void BasicNetworkManager::OnNetworksChanged() {
@@ skipping 68 matching lines @@
         adapter_type = ADAPTER_TYPE_LOOPBACK;
       }
 #if defined(WEBRTC_IOS)
       // Cell networks are pdp_ipN on iOS.
       if (strncmp(cursor->ifa_name, "pdp_ip", 6) == 0) {
         adapter_type = ADAPTER_TYPE_CELLULAR;
       }
 #endif
       // TODO(phoglund): Need to recognize other types as well.
       scoped_ptr<Network> network(new Network(cursor->ifa_name,
-                                              cursor->ifa_name,
-                                              prefix,
-                                              prefix_length,
-                                              adapter_type));
+                                              cursor->ifa_name, prefix,
+                                              prefix_length, adapter_type));
+      network->set_default_address_provider(this);
       network->set_scope_id(scope_id);
       network->AddIP(ip);
       network->set_ignored(IsIgnoredNetwork(*network));
       if (include_ignored || !network->ignored()) {
         networks->push_back(network.release());
       }
     } else {
       (*existing_network).second->AddIP(ip);
     }
   }
@@ skipping 130 matching lines @@
         IPAddress prefix;
         int prefix_length = GetPrefix(prefixlist, ip, &prefix);
         std::string key = MakeNetworkKey(name, prefix, prefix_length);
         auto existing_network = current_networks.find(key);
         if (existing_network == current_networks.end()) {
           AdapterType adapter_type = ADAPTER_TYPE_UNKNOWN;
           if (adapter_addrs->IfType == IF_TYPE_SOFTWARE_LOOPBACK) {
             // TODO(phoglund): Need to recognize other types as well.
             adapter_type = ADAPTER_TYPE_LOOPBACK;
           }
-          scoped_ptr<Network> network(new Network(name,
-                                                  description,
-                                                  prefix,
-                                                  prefix_length,
-                                                  adapter_type));
+          scoped_ptr<Network> network(new Network(name, description, prefix,
+                                                  prefix_length, adapter_type));
+          network->set_default_address_provider(this);
           network->set_scope_id(scope_id);
           network->AddIP(ip);
           bool ignored = IsIgnoredNetwork(*network);
           network->set_ignored(ignored);
           if (include_ignored || !network->ignored()) {
             networks->push_back(network.release());
           }
         } else {
           (*existing_network).second->AddIP(ip);
         }
@@ skipping 136 matching lines @@
     }
     case kSignalNetworksMessage:  {
       SignalNetworksChanged();
       break;
     }
     default:
       ASSERT(false);
   }
 }
 
+IPAddress BasicNetworkManager::QueryDefaultAddress(int family) const {
+  ASSERT(thread_ == Thread::Current());
+  ASSERT(thread_->socketserver() != nullptr);
+  ASSERT(family == AF_INET || family == AF_INET6);
+
+  scoped_ptr<AsyncSocket> socket(
+      thread_->socketserver()->CreateAsyncSocket(family, SOCK_DGRAM));
+  if (socket &&
+      socket->Connect(
+          SocketAddress(family == AF_INET ? kPublicIPv4Host : kPublicIPv6Host,
+                        kPublicPort)) == 0) {
+    return socket->GetLocalAddress().ipaddr();
+  }

[pthatcher1, 2015/11/10 18:52:34]

It might be more clear as:

if (!socket) {
  return IPAddress();
}

auto remote_address = family == AF_INET ? kPublicIPv4Host : kPublicIPv6Host;
if (!socket->Connect(remote_address, kPublicPort)) {
  return IPAddress();
}

return socket->GetLocalAddress().ipaddr();

[guoweis_webrtc, 2015/11/10 20:37:29]

Done.

+
+  return IPAddress();
+}
+
 void BasicNetworkManager::UpdateNetworksOnce() {
   if (!start_count_)
     return;
 
   ASSERT(Thread::Current() == thread_);
 
   NetworkList list;
   if (!CreateNetworks(false, &list)) {
     SignalError();
   } else {
     bool changed;
-    MergeNetworkList(list, &changed);
+    NetworkManager::Stats stats;
+    MergeNetworkList(list, &changed, &stats);
+    if (stats.ipv6_network_count) {
+      set_default_local_address(QueryDefaultAddress(AF_INET6));

[pthatcher1, 2015/11/10 18:52:34]

Why bother checking the stats?  Why not just query both all the time?

[guoweis_webrtc, 2015/11/10 20:37:29]

If there is no ipv6 address at all, there is no point to query interface here
for that address family.

+    }
+    if (stats.ipv4_network_count) {
+      set_default_local_address(QueryDefaultAddress(AF_INET));
+    }
     if (changed || !sent_first_update_) {
       SignalNetworksChanged();
       sent_first_update_ = true;
     }
   }
 }
 
 void BasicNetworkManager::UpdateNetworksContinually() {
   UpdateNetworksOnce();
   thread_->PostDelayed(kNetworksUpdateIntervalMs, this, kUpdateNetworksMessage);
@@ skipping 10 matching lines @@
                    << ((network->ignored()) ? ", Ignored" : "");
     }
   }
   // Release the network list created previously.
   // Do this in a seperated for loop for better readability.
   for (Network* network : list) {
     delete network;
   }
 }
 
-Network::Network(const std::string& name, const std::string& desc,
-                 const IPAddress& prefix, int prefix_length)
-    : name_(name), description_(desc), prefix_(prefix),
+Network::Network(const std::string& name,
+                 const std::string& desc,
+                 const IPAddress& prefix,
+                 int prefix_length)
+    : name_(name),
+      description_(desc),
+      prefix_(prefix),
       prefix_length_(prefix_length),
-      key_(MakeNetworkKey(name, prefix, prefix_length)), scope_id_(0),
-      ignored_(false), type_(ADAPTER_TYPE_UNKNOWN), preference_(0) {
-}
+      key_(MakeNetworkKey(name, prefix, prefix_length)),
+      scope_id_(0),
+      ignored_(false),
+      type_(ADAPTER_TYPE_UNKNOWN),
+      preference_(0) {}
 
-Network::Network(const std::string& name, const std::string& desc,
-                 const IPAddress& prefix, int prefix_length, AdapterType type)
-    : name_(name), description_(desc), prefix_(prefix),
+Network::Network(const std::string& name,
+                 const std::string& desc,
+                 const IPAddress& prefix,
+                 int prefix_length,
+                 AdapterType type)
+    : name_(name),
+      description_(desc),
+      prefix_(prefix),
       prefix_length_(prefix_length),
-      key_(MakeNetworkKey(name, prefix, prefix_length)), scope_id_(0),
-      ignored_(false), type_(type), preference_(0) {
-}
+      key_(MakeNetworkKey(name, prefix, prefix_length)),
+      scope_id_(0),
+      ignored_(false),
+      type_(type),
+      preference_(0) {}
 
 Network::~Network() = default;
 
 // Sets the addresses of this network. Returns true if the address set changed.
 // Change detection is short circuited if the changed argument is true.
 bool Network::SetIPs(const std::vector<InterfaceAddress>& ips, bool changed) {
   // Detect changes with a nested loop; n-squared but we expect on the order
   // of 2-3 addresses per network.
   changed = changed || ips.size() != ips_.size();
   if (!changed) {
@@ skipping 51 matching lines @@
   std::stringstream ss;
   // Print out the first space-terminated token of the network desc, plus
   // the IP address.
   ss << "Net[" << description_.substr(0, description_.find(' '))
      << ":" << prefix_.ToSensitiveString() << "/" << prefix_length_
      << ":" << AdapterTypeToString(type_) << "]";
   return ss.str();
 }
 
 }  // namespace rtc