GCP2.0 Device: mDNS basics

cloud_print/gcp20/prototype/dns_sd_server.cc

Index: cloud_print/gcp20/prototype/dns_sd_server.cc
diff --git a/cloud_print/gcp20/prototype/dns_sd_server.cc b/cloud_print/gcp20/prototype/dns_sd_server.cc
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+++ b/cloud_print/gcp20/prototype/dns_sd_server.cc
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+// Copyright 2013 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 "cloud_print/gcp20/prototype/dns_sd_server.h"
+
+#include <string.h>
+
+#include "base/basictypes.h"
+#include "net/base/big_endian.h"
+#include "net/base/net_util.h"
+#include "net/dns/dns_protocol.h"
+
+namespace {
+
+const char* kDefaultIpAddressMulticast = "224.0.0.251";
+const uint16 kDefaultPortMulticast = 5353;
+
+// TODO(maksymb): Add possibility to set constants via command line arguments
+const uint32 kDefaultTTL = 60*60;  // in seconds
+
+}  // namespace
+
+DnsSdServer::DnsSdServer() : is_online_(false) {
+  // Do nothing
+}
+
+DnsSdServer::~DnsSdServer() {
+  Shutdown();
+}
+
+bool DnsSdServer::Start() {
+  if (is_online_)
+    return true;
+
+  if (!CreateSocket())
+    return false;
+
+  LOG(INFO) << "DNS server started";
+
+  SendAnnouncement(kDefaultTTL);
+
+  is_online_ = true;
+  return true;
+}
+
+void DnsSdServer::Update() {
+  if (!is_online_)
+    return;
+
+  SendAnnouncement(kDefaultTTL);
+}
+
+void DnsSdServer::Shutdown() {
+  if (!is_online_)
+    return;
+
+  SendAnnouncement(0);  // ttl is 0
+  socket_->Close();
+  is_online_ = false;
+  LOG(INFO) << "DNS server stopped";
+}
+
+void DnsSdServer::ProcessMessages() {
+  NOTIMPLEMENTED();  // implement this
+}
+
+bool DnsSdServer::CreateSocket() {
+  net::IPAddressNumber local_ip_any;
+  bool success = net::ParseIPLiteralToNumber("0.0.0.0", &local_ip_any);
+  DCHECK(success);
+
+  net::IPAddressNumber multicast_dns_ip_address;
+  success = net::ParseIPLiteralToNumber(kDefaultIpAddressMulticast,
+                                        &multicast_dns_ip_address);
+  DCHECK(success);
+
+
+  socket_.reset(new net::UDPSocket(net::DatagramSocket::DEFAULT_BIND,
+                                   net::RandIntCallback(),
+                                   NULL,
+                                   net::NetLog::Source()));
+
+  net::IPEndPoint local_address = net::IPEndPoint(local_ip_any,
+                                                  kDefaultPortMulticast);
+  multicast_address_ = net::IPEndPoint(multicast_dns_ip_address,
+                                       kDefaultPortMulticast);
+
+  socket_->AllowAddressReuse();
+
+  int status = socket_->Bind(local_address);
+  if (status < 0)
+    return false;
+
+  socket_->SetMulticastLoopbackMode(false);
+  status = socket_->JoinGroup(multicast_dns_ip_address);
+
+  if (status < 0)
+    return false;
+
+  DCHECK(socket_->is_connected());
+
+  return true;
+}
+
+bool DnsSdServer::CheckPendingQueries() {
+  NOTIMPLEMENTED();  // implement this
+  return false;
+}
+
+void DoNothing(int /*var*/) {
+  // Do nothing
+}
+
+void DnsSdServer::SendAnnouncement(uint32 ttl) {
+  // Create a message with allocated space for header.
+  // DNS header is temporary empty.
+  scoped_ptr<std::vector<uint8> > message(
+    new std::vector<uint8>(sizeof(net::dns_protocol::Header), 0));  // all is 0
+
+  // TODO(maksymb): Create and implement DnsResponse class
+
+  // Preparing for sending
+  scoped_refptr<net::IOBufferWithSize> buffer =
+    new net::IOBufferWithSize(static_cast<int>(message.get()->size()));
+  memcpy(buffer.get()->data(), message.get()->data(), message.get()->size());
+
+  // Create empty callback (we don't need it at all) and send packet
+  net::CompletionCallback callback = base::Bind(DoNothing);
+  socket_->SendTo(buffer.get(),
+                  buffer.get()->size(),
+                  multicast_address_,
+                  callback);
+
+  LOG(INFO) << "Announcement was sent with TTL: " << ttl;
+}
+