Add DatagramClientSocket::BindToDefaultNetwork(),GetBoundNetwork()

net/udp/udp_socket_posix.cc

Index: net/udp/udp_socket_posix.cc
diff --git a/net/udp/udp_socket_posix.cc b/net/udp/udp_socket_posix.cc
index 5151f7b59807a6c399ec76bd3735edb120e8fc16..c395b88526269eb3b20756ee8a4668562327e7ae 100644
--- a/net/udp/udp_socket_posix.cc
+++ b/net/udp/udp_socket_posix.cc
@@ -326,10 +326,12 @@ int UDPSocketPosix::Bind(const IPEndPoint& address) {
 
 int UDPSocketPosix::BindToNetwork(
     NetworkChangeNotifier::NetworkHandle network) {
-#if defined(OS_ANDROID)
   DCHECK_NE(socket_, kInvalidSocket);
   DCHECK(CalledOnValidThread());
   DCHECK(!is_connected());
+  if (network == NetworkChangeNotifier::kInvalidNetworkHandle)
+    return ERR_INVALID_ARGUMENT;
+#if defined(OS_ANDROID)
   // Android prior to Lollipop didn't have support for binding sockets to
   // networks.
   if (base::android::BuildInfo::GetInstance()->sdk_int() <
@@ -353,7 +355,13 @@ int UDPSocketPosix::BindToNetwork(
   }
   if (setNetworkForSocket == nullptr)
     return ERR_NOT_IMPLEMENTED;
-  return MapSystemError(setNetworkForSocket(network, socket_));
+  int rv = setNetworkForSocket(network, socket_);
+  // If |network| has since disconnected, |rv| will be ENONET.  Surface this as
+  // ERR_NETWORK_CHANGED, rather than MapSystemError(ENONET) which gives back
+  // the less descriptive ERR_FAILED.
+  if (rv == ENONET)
+    return ERR_NETWORK_CHANGED;

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

This is probably fine, but shouldn't this be ERR_INTERNET_DISCONNECTED? (You
could loop a few times in the BindToDefaultNetwork() and not return immediately
on ERR_INTERNET_DISCONNECTED as well.)

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

ERR_INTERNET_DISCONNECTED means there are no networks connected at all (i.e.
completely disconnected).  Failing here with ENONET just means |network| has
gone away but does not imply anything about other networks.  Frequently the race
here will be encountered when we change from one default network to another, so
we may not be completely disconnected.

+  return MapSystemError(rv);
 #else
   NOTIMPLEMENTED();
   return ERR_NOT_IMPLEMENTED;