Add DatagramClientSocket::BindToDefaultNetwork(),GetBoundNetwork()

net/udp/udp_client_socket.cc

Index: net/udp/udp_client_socket.cc
diff --git a/net/udp/udp_client_socket.cc b/net/udp/udp_client_socket.cc
index a991f10bd0c527a4cf211867a975f1778e7a1507..6b66fe1b08c555c10876a5afff500ec36b1bce70 100644
--- a/net/udp/udp_client_socket.cc
+++ b/net/udp/udp_client_socket.cc
@@ -13,15 +13,49 @@ UDPClientSocket::UDPClientSocket(DatagramSocket::BindType bind_type,
                                  const RandIntCallback& rand_int_cb,
                                  net::NetLog* net_log,
                                  const net::NetLog::Source& source)
-    : socket_(bind_type, rand_int_cb, net_log, source) {
-}
+    : socket_(bind_type, rand_int_cb, net_log, source),
+      network_(NetworkChangeNotifier::kInvalidNetworkHandle) {}
 
 UDPClientSocket::~UDPClientSocket() {
 }
 
 int UDPClientSocket::BindToNetwork(
     NetworkChangeNotifier::NetworkHandle network) {
-  return socket_.BindToNetwork(network);
+  int rv = socket_.BindToNetwork(network);
+  if (rv == OK)
+    network_ = network;
+  return rv;
+}
+
+int UDPClientSocket::BindToDefaultNetwork() {
+  if (!NetworkChangeNotifier::AreNetworkHandlesSupported())
+    return ERR_NOT_IMPLEMENTED;
+  int rv;
+  // Calling connect() will bind a socket to the default network, however there
+  // is no way to determine what network the socket got bound to.  The
+  // alternative is to query what the default network is and bind the socket to
+  // that network explicitly, however this is racy because the default network
+  // can change in between when we query it and when we bind to it.  This is
+  // rare but should be accounted for.  Since changes of the default network
+  // should not come in quick succession, we can simply try again.  Loop up to
+  // three times for good measure.
+  for (int attempt = 0; attempt < 3; attempt++) {

[Jana, 2015/12/04 20:30:16]

attempt < 2 should be enough for this, right? is it possible for this to go to
the attempt = 2?

[pauljensen, 2015/12/07 13:05:55]

I think 2 might be enough but as I said in the comment "Loop up to three times
for good measure."  I see little cost in this as all calls here should be very
fast.

[Jana, 2015/12/07 17:30:52]

I don't think it's a matter of cost; it's a matter of code readability. Given
that the loop is to protect against the specific race that should _never_ take
more than 2 iterations, why do more than 2 iterations?

[pauljensen, 2015/12/08 14:31:19]

I changed it to 2.

+    NetworkChangeNotifier::NetworkHandle network =
+        NetworkChangeNotifier::GetDefaultNetwork();
+    if (network == NetworkChangeNotifier::kInvalidNetworkHandle)
+      return ERR_INTERNET_DISCONNECTED;
+    rv = BindToNetwork(network);
+    // |network| may have disconnected between the call to GetDefaultNetwork()
+    // and the call to BindToNetwork(). Loop if this is the case (|rv| will be
+    // ERR_NETWORK_CHANGED).
+    if (rv != ERR_NETWORK_CHANGED)
+      return rv;
+  }
+  return rv;
+}
+
+NetworkChangeNotifier::NetworkHandle UDPClientSocket::GetBoundNetwork() {
+  return network_;
 }
 
 int UDPClientSocket::Connect(const IPEndPoint& address) {