Finished DNS-SD server. Finished Privet-specified DNS-SD server.

Review URL: https://chromiumcodereview.appspot.com/16975004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@208064 0039d316-1c4b-4281-b951-d872f2087c98

12 files changed, 885 insertions, 68 deletions

diff --git a/cloud_print/gcp20/prototype/dns_packet_parser.cc b/cloud_print/gcp20/prototype/dns_packet_parser.cc
new file mode 100644
index 0000000..f85ffc7
--- /dev/null
+++ b/cloud_print/gcp20/prototype/dns_packet_parser.cc
@@ -0,0 +1,38 @@
+// 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_packet_parser.h"
+
+#include "net/base/big_endian.h"
+
+DnsPacketParser::DnsPacketParser(const char* packet, size_t length)
+    : packet_(packet),
+      length_(length),
+      record_parser_(packet, length, sizeof(header_)) {
+  net::BigEndianReader reader(packet, length);
+  is_header_read_ = reader.ReadU16(&header_.id) &&
+                    reader.ReadU16(&header_.flags) &&
+                    reader.ReadU16(&header_.qdcount) &&
+                    reader.ReadU16(&header_.ancount) &&
+                    reader.ReadU16(&header_.nscount) &&
+                    reader.ReadU16(&header_.arcount);
+}
+
+bool DnsPacketParser::ReadRecord(DnsQueryRecord* out) {
+  DCHECK(packet_);
+  DnsQueryRecord result;
+  size_t consumed = ReadName(&result.qname);
+  if (!consumed)
+    return false;
+  net::BigEndianReader reader(packet_ + GetOffset() + consumed,
+                              length_ - (GetOffset() + consumed));
+  if (reader.ReadU16(&result.qtype) && reader.ReadU16(&result.qclass) &&
+    record_parser_.SkipQuestion()) {  // instead of |cur_ = reader.ptr();|
+      *out = result;
+      return true;
+  }
+
+  return false;
+}
+
diff --git a/cloud_print/gcp20/prototype/dns_packet_parser.h b/cloud_print/gcp20/prototype/dns_packet_parser.h
new file mode 100644
index 0000000..88c6a03
--- /dev/null
+++ b/cloud_print/gcp20/prototype/dns_packet_parser.h
@@ -0,0 +1,78 @@
+// 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.
+
+#ifndef CLOUD_PRINT_GCP20_PROTOTYPE_DNS_PACKET_PARSER_H_
+#define CLOUD_PRINT_GCP20_PROTOTYPE_DNS_PACKET_PARSER_H_
+
+#include <string>
+
+#include "net/dns/dns_protocol.h"
+#include "net/dns/dns_response.h"
+
+// Parsed response record.
+struct DnsQueryRecord {
+  DnsQueryRecord() : qtype(0), qclass(0) {}
+  ~DnsQueryRecord() {}
+
+  std::string qname;  // in dotted form
+  uint16 qtype;
+  uint16 qclass;
+};
+
+// Iterator to walk over records of the DNS response packet. Encapsulates
+// |DnsRecordParser| object for using its functionality.
+class DnsPacketParser {
+ public:
+  // Constructs an iterator to process the |packet| of given |length|.
+  DnsPacketParser(const char* packet, size_t length);
+
+  // Destroys the object.
+  ~DnsPacketParser() {}
+
+  bool IsValid() const { return record_parser_.IsValid() && is_header_read_; }
+
+  // Returns |true| if no more bytes remain in the packet.
+  bool AtEnd() const { return record_parser_.AtEnd(); }
+
+  // Returns header of DNS packet.
+  const net::dns_protocol::Header& header() const { return header_; }
+
+  // Parses the next query record into |record|. Returns true if succeeded.
+  bool ReadRecord(DnsQueryRecord* record);
+
+  // Parses the next resource record into |record|. Returns true if succeeded.
+  bool ReadRecord(net::DnsResourceRecord* record) {
+    return record_parser_.ReadRecord(record);
+  }
+
+ private:
+  // Returns current offset into the packet.
+  size_t GetOffset() const { return record_parser_.GetOffset(); }
+
+  // Parses a (possibly compressed) DNS name from the packet starting at
+  // |pos|. Stores output (even partial) in |out| unless |out| is NULL. |out|
+  // is stored in the dotted form, e.g., "example.com". Returns number of bytes
+  // consumed or 0 on failure.
+  // This is exposed to allow parsing compressed names within RRDATA for TYPEs
+  // such as NS, CNAME, PTR, MX, SOA.
+  // See RFC 1035 section 4.1.4.
+  unsigned ReadName(std::string* out) const {
+    return record_parser_.ReadName(packet_ + GetOffset(), out);
+  }
+
+  const char* packet_;
+  size_t length_;
+
+  // Contents parsed header_;
+  net::dns_protocol::Header header_;
+  bool is_header_read_;
+
+  // Encapsulated parser.
+  net::DnsRecordParser record_parser_;
+
+  DISALLOW_COPY_AND_ASSIGN(DnsPacketParser);
+};
+
+#endif  // CLOUD_PRINT_GCP20_PROTOTYPE_DNS_PACKET_PARSER_H_
+
diff --git a/cloud_print/gcp20/prototype/dns_response_builder.cc b/cloud_print/gcp20/prototype/dns_response_builder.cc
new file mode 100644
index 0000000..2bcd43f
--- /dev/null
+++ b/cloud_print/gcp20/prototype/dns_response_builder.cc
@@ -0,0 +1,153 @@
+// 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_response_builder.h"
+
+#include "base/logging.h"
+#include "net/base/big_endian.h"
+#include "net/base/dns_util.h"
+#include "net/base/io_buffer.h"
+#include "net/base/ip_endpoint.h"
+#include "net/dns/dns_response.h"
+
+namespace {
+
+uint16 klass = net::dns_protocol::kClassIN;
+
+}  // namespace
+
+DnsResponseRecord::DnsResponseRecord() : type(0), klass(0), ttl(0) {
+}
+
+DnsResponseRecord::~DnsResponseRecord() {
+}
+
+DnsResponseBuilder::DnsResponseBuilder(uint16 id) {
+  header_.id = id;
+  // TODO(maksymb): Check do we need AA flag enabled.
+  header_.flags = net::dns_protocol::kFlagResponse |
+                  net::dns_protocol::kFlagAA;
+  header_.qdcount = 0;
+  header_.ancount = 0;
+  header_.nscount = 0;
+  header_.arcount = 0;
+}
+
+void DnsResponseBuilder::AppendPtr(const std::string& service_type, uint32 ttl,
+                                   const std::string& service_name) {
+  std::string rdata;
+  bool success = net::DNSDomainFromDot(service_name, &rdata);
+  DCHECK(success);
+
+  AddResponse(service_type, net::dns_protocol::kTypePTR, ttl, rdata);
+}
+
+void DnsResponseBuilder::AppendSrv(const std::string& service_name, uint32 ttl,
+                                   uint16 priority, uint16 weight,
+                                   uint16 http_port,
+                                   const std::string& service_domain_name) {
+  std::string domain_name;
+  bool success = net::DNSDomainFromDot(service_domain_name, &domain_name);
+  DCHECK(success);
+
+  std::vector<uint8> rdata(2 + 2 + 2 + domain_name.size());
+
+  net::BigEndianWriter writer(rdata.data(), rdata.size());
+  success = writer.WriteU16(priority) &&
+            writer.WriteU16(weight) &&
+            writer.WriteU16(http_port) &&
+            writer.WriteBytes(domain_name.data(), domain_name.size());
+  DCHECK(success);
+  DCHECK_EQ(writer.remaining(), 0);  // For warranty of correct size allocation.
+
+  AddResponse(service_name, net::dns_protocol::kTypeSRV, ttl,
+              std::string(rdata.begin(), rdata.end()));
+}
+
+void DnsResponseBuilder::AppendA(const std::string& service_domain_name,
+                                 uint32 ttl, net::IPAddressNumber http_ipv4) {
+  // TODO(maksymb): IP to send must depends on interface from where query was
+  // received.
+  if (http_ipv4.empty()) {
+    LOG(ERROR) << "Invalid IP";
+    return;
+  }
+
+  AddResponse(service_domain_name, net::dns_protocol::kTypeA, ttl,
+              std::string(http_ipv4.begin(), http_ipv4.end()));
+}
+
+void DnsResponseBuilder::AppendTxt(const std::string& service_name, uint32 ttl,
+                                   const std::vector<std::string>& metadata) {
+  std::string rdata;
+  for (std::vector<std::string>::const_iterator str = metadata.begin();
+       str != metadata.end(); ++str) {
+    int len = static_cast<int>(str->size());
+    DCHECK_LT(len, 256);
+    rdata += static_cast<char>(len);  // Set length byte.
+    rdata += *str;
+  }
+
+  AddResponse(service_name, net::dns_protocol::kTypeTXT, ttl, rdata);
+}
+
+scoped_refptr<net::IOBufferWithSize> DnsResponseBuilder::Build() {
+  size_t size = sizeof(header_);
+  for (std::vector<DnsResponseRecord>::const_iterator iter = responses_.begin();
+       iter != responses_.end(); ++iter) {
+    size += iter->name.size() + 2 +  // Two dots: first and last.
+            sizeof(iter->type) + sizeof(iter->klass) + sizeof(iter->ttl) +
+            2 +  // sizeof(RDLENGTH)
+            iter->rdata.size();
+  }
+
+  if (responses_.empty())
+    return NULL;  // No answer.
+
+  header_.ancount = static_cast<uint16>(responses_.size());
+
+  scoped_refptr<net::IOBufferWithSize> message(
+      new net::IOBufferWithSize(static_cast<int>(size)));
+  net::BigEndianWriter writer(message->data(), message->size());
+  bool success = writer.WriteU16(header_.id) &&
+                 writer.WriteU16(header_.flags) &&
+                 writer.WriteU16(header_.qdcount) &&
+                 writer.WriteU16(header_.ancount) &&
+                 writer.WriteU16(header_.nscount) &&
+                 writer.WriteU16(header_.arcount);
+  DCHECK(success);
+
+  std::string name_in_dns_format;
+  for (std::vector<DnsResponseRecord>::const_iterator iter = responses_.begin();
+       iter != responses_.end(); ++iter) {
+    success = net::DNSDomainFromDot(iter->name, &name_in_dns_format);
+    DCHECK(success);
+    DCHECK_EQ(name_in_dns_format.size(), iter->name.size() + 2);
+
+    success = writer.WriteBytes(name_in_dns_format.data(),
+                                name_in_dns_format.size()) &&
+              writer.WriteU16(iter->type) &&
+              writer.WriteU16(iter->klass) &&
+              writer.WriteU32(iter->ttl) &&
+              writer.WriteU16(static_cast<uint16>(iter->rdata.size())) &&
+              writer.WriteBytes(iter->rdata.data(), iter->rdata.size());
+    DCHECK(success);
+  }
+
+  DCHECK_EQ(writer.remaining(), 0);  // For warranty of correct size allocation.
+
+  return message;
+}
+
+void DnsResponseBuilder::AddResponse(const std::string& name, uint16 type,
+                                     uint32 ttl, const std::string& rdata) {
+  DnsResponseRecord response;
+  response.name = name;
+  response.klass = klass;
+  response.ttl = ttl;
+  response.type = type;
+  response.rdata = rdata;
+  responses_.push_back(response);
+}
+
diff --git a/cloud_print/gcp20/prototype/dns_response_builder.h b/cloud_print/gcp20/prototype/dns_response_builder.h
new file mode 100644
index 0000000..430a7e1
--- /dev/null
+++ b/cloud_print/gcp20/prototype/dns_response_builder.h
@@ -0,0 +1,68 @@
+// 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.
+
+#ifndef CLOUD_PRINT_GCP20_PROTOTYPE_DNS_RESPONSE_BUILDER_H_
+#define CLOUD_PRINT_GCP20_PROTOTYPE_DNS_RESPONSE_BUILDER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "net/base/net_util.h"
+#include "net/dns/dns_protocol.h"
+
+namespace net {
+  class IOBufferWithSize;
+}
+
+// Record for storing response data.
+struct DnsResponseRecord {
+  DnsResponseRecord();
+  ~DnsResponseRecord();
+
+  std::string name;  // in dotted form
+  uint16 type;
+  uint16 klass;
+  uint32 ttl;
+  std::string rdata;
+};
+
+// Class for building service-specified responses.
+class DnsResponseBuilder {
+ public:
+  // Initializes builder.
+  explicit DnsResponseBuilder(uint16 id);
+
+  // Destroys the object.
+  ~DnsResponseBuilder() {}
+
+  // Methods for appending different types of responses to packet.
+  void AppendPtr(const std::string& service_type, uint32 ttl,
+                 const std::string& service_name);
+  void AppendSrv(const std::string& service_name, uint32 ttl, uint16 priority,
+                 uint16 weight, uint16 http_port,
+                 const std::string& service_domain_name);
+  void AppendA(const std::string& service_domain_name, uint32 ttl,
+               net::IPAddressNumber http_ipv4);
+  void AppendTxt(const std::string& service_name, uint32 ttl,
+                 const std::vector<std::string>& metadata);
+
+  // Serializes packet to byte sequence.
+  scoped_refptr<net::IOBufferWithSize> Build();
+
+ private:
+  // Appends response to packet.
+  void AddResponse(const std::string& name, uint16 type, uint32 ttl,
+                   const std::string& rdata);
+
+  std::vector<DnsResponseRecord> responses_;
+
+  // Header of response package.
+  net::dns_protocol::Header header_;
+
+  DISALLOW_COPY_AND_ASSIGN(DnsResponseBuilder);
+};
+
+#endif  // CLOUD_PRINT_GCP20_PROTOTYPE_DNS_RESPONSE_BUILDER_H_
+
diff --git a/cloud_print/gcp20/prototype/dns_sd_server.cc b/cloud_print/gcp20/prototype/dns_sd_server.cc
index 0ca8b43..2d2716b 100644
--- a/cloud_print/gcp20/prototype/dns_sd_server.cc
+++ b/cloud_print/gcp20/prototype/dns_sd_server.cc
@@ -7,7 +7,15 @@
 #include <string.h>
 
 #include "base/basictypes.h"
+#include "base/bind.h"
+#include "base/command_line.h"
+#include "base/message_loop.h"
+#include "base/strings/stringprintf.h"
+#include "cloud_print/gcp20/prototype/dns_packet_parser.h"
+#include "cloud_print/gcp20/prototype/dns_response_builder.h"
 #include "net/base/big_endian.h"
+#include "net/base/dns_util.h"
+#include "net/base/net_errors.h"
 #include "net/base/net_util.h"
 #include "net/dns/dns_protocol.h"
 
@@ -16,53 +24,91 @@ 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
+const double kTimeToNextAnnouncement = 0.8;  // relatively to TTL
+const int kDnsBufSize = 65537;
+
+const uint16 kSrvPriority = 0;
+const uint16 kSrvWeight = 0;
+
+void DoNothingAfterSendToSocket(int /*val*/) {
+  NOTREACHED();
+  // TODO(maksymb): Delete this function once empty callback for SendTo() method
+  // will be allowed.
+}
 
 }  // namespace
 
-DnsSdServer::DnsSdServer() : is_online_(false) {
-  // Do nothing
+DnsSdServer::DnsSdServer()
+    : recv_buf_(new net::IOBufferWithSize(kDnsBufSize)),
+      full_ttl_(0) {
 }
 
 DnsSdServer::~DnsSdServer() {
   Shutdown();
 }
 
-bool DnsSdServer::Start() {
-  if (is_online_)
+bool DnsSdServer::Start(const ServiceParameters& serv_params, uint32 full_ttl,
+                        const std::vector<std::string>& metadata) {
+  if (IsOnline())
     return true;
 
   if (!CreateSocket())
     return false;
 
+  // Initializing server with parameters from arguments.
+  serv_params_ = serv_params;
+  full_ttl_ = full_ttl;
+  metadata_ = metadata;
+
   LOG(INFO) << "DNS server started";
+  LOG(WARNING) << "DNS server does not support probing";
 
-  SendAnnouncement(kDefaultTTL);
+  SendAnnouncement(full_ttl_);
+  base::MessageLoop::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&DnsSdServer::OnDatagramReceived, base::Unretained(this)));
 
-  is_online_ = true;
   return true;
 }
 
 void DnsSdServer::Update() {
-  if (!is_online_)
+  if (!IsOnline())
     return;
 
-  SendAnnouncement(kDefaultTTL);
+  SendAnnouncement(full_ttl_);
 }
 
 void DnsSdServer::Shutdown() {
-  if (!is_online_)
+  if (!IsOnline())
     return;
 
-  SendAnnouncement(0);  // ttl is 0
+  SendAnnouncement(0);  // TTL is 0
   socket_->Close();
-  is_online_ = false;
+  socket_.reset(NULL);
   LOG(INFO) << "DNS server stopped";
 }
 
-void DnsSdServer::ProcessMessages() {
-  NOTIMPLEMENTED();  // implement this
+void DnsSdServer::UpdateMetadata(const std::vector<std::string>& metadata) {
+  if (!IsOnline())
+    return;
+
+  metadata_ = metadata;
+
+  // TODO(maksymb): If less than 20% of full TTL left before next announcement
+  // then send it now.
+
+  uint32 current_ttl = GetCurrentTLL();
+  if (!CommandLine::ForCurrentProcess()->HasSwitch("no-announcement")) {
+    DnsResponseBuilder builder(current_ttl);
+
+    builder.AppendTxt(serv_params_.service_name_, current_ttl, metadata_);
+    scoped_refptr<net::IOBufferWithSize> buffer(builder.Build());
+
+    DCHECK(buffer.get() != NULL);
+
+    socket_->SendTo(buffer.get(), buffer.get()->size(), multicast_address_,
+                    base::Bind(&DoNothingAfterSendToSocket));
+  }
 }
 
 bool DnsSdServer::CreateSocket() {
@@ -77,8 +123,7 @@ bool DnsSdServer::CreateSocket() {
 
 
   socket_.reset(new net::UDPSocket(net::DatagramSocket::DEFAULT_BIND,
-                                   net::RandIntCallback(),
-                                   NULL,
+                                   net::RandIntCallback(), NULL,
                                    net::NetLog::Source()));
 
   net::IPEndPoint local_address = net::IPEndPoint(local_ip_any,
@@ -103,35 +148,153 @@ bool DnsSdServer::CreateSocket() {
   return true;
 }
 
-bool DnsSdServer::CheckPendingQueries() {
-  NOTIMPLEMENTED();  // implement this
-  return false;
+void DnsSdServer::ProcessMessage(int len, net::IOBufferWithSize* buf) {
+  VLOG(1) << "Received new message with length: " << len;
+
+  // Parse the message.
+  DnsPacketParser parser(buf->data(), len);
+
+  if (!parser.IsValid())  // Was unable to parse header.
+    return;
+
+  // TODO(maksymb): Handle truncated messages.
+  if (parser.header().flags & net::dns_protocol::kFlagResponse)  // Not a query.
+    return;
+
+  DnsResponseBuilder builder(parser.header().id);
+
+  uint32 current_ttl = GetCurrentTLL();
+
+  DnsQueryRecord query;
+  // TODO(maksymb): Check known answers.
+  for (int query_idx = 0; query_idx < parser.header().qdcount; ++query_idx) {
+    bool success = parser.ReadRecord(&query);
+    if (success) {
+      ProccessQuery(current_ttl, query, &builder);
+    } else {  // if (success)
+      LOG(INFO) << "Broken package";
+      break;
+    }
+  }
+
+  scoped_refptr<net::IOBufferWithSize> buffer(builder.Build());
+  if (buffer.get() == NULL)
+    return;  // No answers.
+
+  VLOG(1) << "Current TTL for respond: " << current_ttl;
+
+  bool multicast_respond =
+      CommandLine::ForCurrentProcess()->HasSwitch("multicast-respond");
+  socket_->SendTo(buffer.get(), buffer.get()->size(),
+                  multicast_respond ? multicast_address_ : recv_address_,
+                  base::Bind(&DoNothingAfterSendToSocket));
+  VLOG(1) << "Responded to "
+      << (multicast_respond ? multicast_address_ : recv_address_).ToString();
 }
 
-void DoNothing(int /*var*/) {
-  // Do nothing
+void DnsSdServer::ProccessQuery(uint32 current_ttl, const DnsQueryRecord& query,
+                                DnsResponseBuilder* builder) const {
+  std::string log;
+  bool responded = false;
+  switch (query.qtype) {
+    // TODO(maksymb): Add IPv6 support.
+    case net::dns_protocol::kTypePTR:
+      log = "Processing PTR query";
+      if (query.qname == serv_params_.service_type_) {
+        builder->AppendPtr(serv_params_.service_type_, current_ttl,
+                           serv_params_.service_name_);
+        responded = true;
+      }
+      break;
+    case net::dns_protocol::kTypeSRV:
+      log = "Processing SRV query";
+      if (query.qname == serv_params_.service_name_) {
+        builder->AppendSrv(serv_params_.service_name_, current_ttl,
+                           kSrvPriority, kSrvWeight, serv_params_.http_port_,
+                           serv_params_.service_domain_name_);
+        responded = true;
+      }
+      break;
+    case net::dns_protocol::kTypeA:
+      log = "Processing A query";
+      if (query.qname == serv_params_.service_domain_name_) {
+        builder->AppendA(serv_params_.service_domain_name_, current_ttl,
+                         serv_params_.http_ipv4_);
+        responded = true;
+      }
+      break;
+    case net::dns_protocol::kTypeTXT:
+      log = "Processing TXT query";
+      if (query.qname == serv_params_.service_name_) {
+        builder->AppendTxt(serv_params_.service_name_, current_ttl, metadata_);
+        responded = true;
+      }
+      break;
+    default:
+      base::SStringPrintf(&log, "Unknown query type (%d)", query.qtype);
+  }
+  log += responded ? ": responded" : ": ignored";
+  VLOG(1) << log;
+}
+
+void DnsSdServer::DoLoop(int rv) {
+  // TODO(maksymb): Check what happened if buffer will be overflowed
+  do {
+    if (rv > 0)
+      ProcessMessage(rv, recv_buf_);
+    rv = socket_->RecvFrom(recv_buf_, recv_buf_->size(), &recv_address_,
+                           base::Bind(&DnsSdServer::DoLoop,
+                                      base::Unretained(this)));
+  } while (rv > 0);
+
+  // TODO(maksymb): Add handler for errors
+  DCHECK(rv == net::ERR_IO_PENDING);
+}
+
+void DnsSdServer::OnDatagramReceived() {
+  DoLoop(0);
 }
 
 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;
+  if (!CommandLine::ForCurrentProcess()->HasSwitch("no-announcement")) {
+    DnsResponseBuilder builder(ttl);
+
+    builder.AppendPtr(serv_params_.service_type_, ttl,
+                      serv_params_.service_name_);
+    builder.AppendSrv(serv_params_.service_name_, ttl, kSrvPriority, kSrvWeight,
+                      serv_params_.http_port_,
+                      serv_params_.service_domain_name_);
+    builder.AppendA(serv_params_.service_domain_name_, ttl,
+                    serv_params_.http_ipv4_);
+    builder.AppendTxt(serv_params_.service_name_, ttl, metadata_);
+    scoped_refptr<net::IOBufferWithSize> buffer(builder.Build());
+
+    DCHECK(buffer.get() != NULL);
+
+    socket_->SendTo(buffer.get(), buffer.get()->size(), multicast_address_,
+                    base::Bind(&DoNothingAfterSendToSocket));
+
+    VLOG(1) << "Announcement was sent with TTL: " << ttl;
+  }
+
+  time_until_live_ = base::Time::Now() +
+      base::TimeDelta::FromSeconds(full_ttl_);
+
+  // Schedule next announcement.
+  base::MessageLoop::current()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&DnsSdServer::Update, base::Unretained(this)),
+      base::TimeDelta::FromSeconds(static_cast<int64>(
+          kTimeToNextAnnouncement*full_ttl_)));
+}
+
+uint32 DnsSdServer::GetCurrentTLL() const {
+  uint32 current_ttl = (time_until_live_ - base::Time::Now()).InSeconds();
+  if (time_until_live_ < base::Time::Now() || current_ttl == 0) {
+    // This should not be reachable. But still we don't need to fail.
+    current_ttl = 1;  // Service is still alive.
+    LOG(ERROR) << "|current_ttl| was equal to zero.";
+  }
+  return current_ttl;
 }
 
diff --git a/cloud_print/gcp20/prototype/dns_sd_server.h b/cloud_print/gcp20/prototype/dns_sd_server.h
index 9c8ed96..d5ef793 100644
--- a/cloud_print/gcp20/prototype/dns_sd_server.h
+++ b/cloud_print/gcp20/prototype/dns_sd_server.h
@@ -2,27 +2,40 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef GCP20_PROTOTYPE_DNS_SD_H_
-#define GCP20_PROTOTYPE_DNS_SD_H_
+#ifndef CLOUD_PRINT_GCP20_PROTOTYPE_DNS_SD_SERVER_H_
+#define CLOUD_PRINT_GCP20_PROTOTYPE_DNS_SD_SERVER_H_
 
+#include <string>
 #include <vector>
 
-#include "net/dns/dns_protocol.h"
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "cloud_print/gcp20/prototype/service_parameters.h"
+#include "net/base/ip_endpoint.h"
 #include "net/udp/udp_socket.h"
 
+namespace net {
+  class IOBufferWithSize;
+}
+
+struct DnsQueryRecord;
+class DnsResponseBuilder;
+
 // Class for sending multicast announcements, receiving queries and answering on
-// them. Client should call |ProccessMessages| periodically to make server work.
+// them.
+// TODO(maksymb): Implement probing.
 class DnsSdServer {
  public:
-  // Constructs unstarted server.
+  // Constructor does not start server.
   DnsSdServer();
 
-  // Stops server.
+  // Stops the server and destroys the object.
   ~DnsSdServer();
 
   // Starts the server. Returns |true| if server works. Also sends
   // announcement.
-  bool Start();
+  bool Start(const ServiceParameters& serv_params, uint32 full_ttl,
+             const std::vector<std::string>& metadata) WARN_UNUSED_RESULT;
 
   // Sends announcement if server works.
   void Update();
@@ -30,24 +43,35 @@ class DnsSdServer {
   // Stops server with announcement.
   void Shutdown();
 
-  // Process pending queries for the server.
-  void ProcessMessages();
-
   // Returns |true| if server works.
-  bool is_online() { return is_online_; }
+  bool IsOnline() { return !!socket_; }
+
+  // Updates data for TXT respond.
+  void UpdateMetadata(const std::vector<std::string>& metadata);
 
  private:
   // Binds a socket to multicast address. Returns |true| on success.
   bool CreateSocket();
 
+  // Processes single query.
+  void ProccessQuery(uint32 current_ttl, const DnsQueryRecord& query,
+                     DnsResponseBuilder* builder) const;
+
+  // Processes DNS message.
+  void ProcessMessage(int len, net::IOBufferWithSize* buf);
+
+  // CompletionCallback for receiving data from DNS.
+  void DoLoop(int rv);
+
+  // Function to start listening to socket (delegate to DoLoop function).
+  void OnDatagramReceived();
+
   // Sends announcement.
   void SendAnnouncement(uint32 ttl);
 
-  // Returns |true| if server received some questions.
-  bool CheckPendingQueries();
-
-  // Stores |true| if server was started.
-  bool is_online_;
+  // Calculates and returns current TTL (with accordance to last send
+  // announcement time.
+  uint32 GetCurrentTLL() const;
 
   // Stores socket to multicast address.
   scoped_ptr<net::UDPSocket> socket_;
@@ -55,8 +79,26 @@ class DnsSdServer {
   // Stores multicast address end point.
   net::IPEndPoint multicast_address_;
 
+  // Stores time until last announcement is live.
+  base::Time time_until_live_;
+
+  // Stores service parameters (like service-name and service-type etc.)
+  ServiceParameters serv_params_;
+
+  // Stores the buffer for receiving messages.
+  scoped_refptr<net::IOBufferWithSize> recv_buf_;
+
+  // Stores address from where last message was sent.
+  net::IPEndPoint recv_address_;
+
+  // Stores information for TXT respond.
+  std::vector<std::string> metadata_;
+
+  // TTL for announcements
+  uint32 full_ttl_;
+
   DISALLOW_COPY_AND_ASSIGN(DnsSdServer);
 };
 
-#endif  // GCP20_PROTOTYPE_DNS_SD_H_
+#endif  // CLOUD_PRINT_GCP20_PROTOTYPE_DNS_SD_SERVER_H_
 
diff --git a/cloud_print/gcp20/prototype/gcp20_device.cc b/cloud_print/gcp20/prototype/gcp20_device.cc
index 2ff1a2d..4eab248 100644
--- a/cloud_print/gcp20/prototype/gcp20_device.cc
+++ b/cloud_print/gcp20/prototype/gcp20_device.cc
@@ -2,12 +2,40 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <stdio.h>
+#include <signal.h>
 
+#include "base/at_exit.h"
+#include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
+#include "base/message_loop.h"
+#include "base/run_loop.h"
 #include "base/threading/platform_thread.h"
-#include "cloud_print/gcp20/prototype/dns_sd_server.h"
+#include "base/time.h"
+#include "cloud_print/gcp20/prototype/printer.h"
+
+namespace {
+
+Printer printer;
+base::AtExitManager at_exit;
+
+void StopPrinter() {
+  printer.Stop();
+}
+
+void StartPrinter() {
+  bool success = printer.Start();
+  DCHECK(success);
+
+  at_exit.RegisterTask(base::Bind(&StopPrinter));
+}
+
+void OnAbort(int val) {
+  StopPrinter();
+  base::MessageLoop::current()->Quit();
+}
+
+}  // namespace
 
 int main(int argc, char* argv[]) {
   CommandLine::Init(argc, argv);
@@ -16,11 +44,12 @@ int main(int argc, char* argv[]) {
   settings.logging_dest = logging::LOG_TO_SYSTEM_DEBUG_LOG;
   logging::InitLogging(settings);
 
-  DnsSdServer dns_sd_server;
-  dns_sd_server.Start();
-  base::PlatformThread::Sleep(base::TimeDelta::FromSeconds(2));
-  dns_sd_server.Shutdown();
+  signal(SIGINT, OnAbort);  // Handle Ctrl+C signal.
+
+  base::MessageLoop loop(base::MessageLoop::TYPE_IO);
+  base::MessageLoop::current()->PostTask(FROM_HERE, base::Bind(&StartPrinter));
+  base::RunLoop runner;
+  runner.Run();
 
   return 0;
 }
-
diff --git a/cloud_print/gcp20/prototype/gcp20_device.gyp b/cloud_print/gcp20/prototype/gcp20_device.gyp
index 7946960..8324b8b 100644
--- a/cloud_print/gcp20/prototype/gcp20_device.gyp
+++ b/cloud_print/gcp20/prototype/gcp20_device.gyp
@@ -16,14 +16,33 @@
   },
   'targets': [
     {
-      'target_name': 'gcp20_device',
-      'type': 'executable',
+      'target_name': 'gcp20_device_lib',
+      'type': 'static_library',
       'dependencies': [
         '<(DEPTH)/base/base.gyp:base',
         '<(DEPTH)/net/net.gyp:net',
       ],
       'sources': [
+        'dns_packet_parser.cc',
+        'dns_packet_parser.h',
+        'dns_response_builder.cc',
+        'dns_response_builder.h',
         'dns_sd_server.cc',
+        'dns_sd_server.h',
+        'gcp20_device.cc',
+        'printer.cc',
+        'printer.h',
+        'service_parameters.cc',
+        'service_parameters.h',
+      ],
+    },
+    {
+      'target_name': 'gcp20_device',
+      'type': 'executable',
+      'dependencies': [
+        'gcp20_device.gyp:gcp20_device_lib',
+      ],
+      'sources': [        
         'gcp20_device.cc',
       ],
       'msvs_settings': {
diff --git a/cloud_print/gcp20/prototype/printer.cc b/cloud_print/gcp20/prototype/printer.cc
new file mode 100644
index 0000000..4d39fe8
--- /dev/null
+++ b/cloud_print/gcp20/prototype/printer.cc
@@ -0,0 +1,131 @@
+// 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/printer.h"
+
+#include <string>
+#include <vector>
+
+#include "base/command_line.h"
+#include "base/strings/string_number_conversions.h"
+#include "cloud_print/gcp20/prototype/service_parameters.h"
+#include "net/base/net_util.h"
+
+namespace {
+
+const char* kServiceType = "_privet._tcp.local";
+const char* kServiceNamePrefix = "first_gcp20_device";
+const char* kServiceDomainName = "my-privet-device.local";
+
+const uint16 kDefaultTTL = 60*60;
+const uint16 kDefaultHttpPort = 10101;
+
+uint16 ReadHttpPortFromCommandLine() {
+  uint32 http_port_tmp = kDefaultHttpPort;
+
+  std::string http_port_string_tmp =
+      CommandLine::ForCurrentProcess()->GetSwitchValueASCII("http-port");
+  base::StringToUint(http_port_string_tmp, &http_port_tmp);
+
+  if (http_port_tmp > kuint16max) {
+    LOG(ERROR) << "Port " << http_port_tmp << " is too large (maximum is " <<
+        kDefaultHttpPort << "). Using default port.";
+
+    http_port_tmp = kDefaultHttpPort;
+  }
+
+  VLOG(1) << "HTTP port for responses: " << http_port_tmp;
+  return static_cast<uint16>(http_port_tmp);
+}
+
+uint16 ReadTtlFromCommandLine() {
+  uint32 ttl = kDefaultTTL;
+
+  base::StringToUint(
+      CommandLine::ForCurrentProcess()->GetSwitchValueASCII("ttl"), &ttl);
+
+  VLOG(1) << "TTL for announcements: " << ttl;
+  return ttl;
+}
+
+// Returns local IP address number of first interface found (except loopback).
+// Return value is empty if no interface found. Possible interfaces names are
+// "eth0", "wlan0" etc. If interface name is empty, function will return IP
+// address of first interface found.
+net::IPAddressNumber GetLocalIp(const std::string& interface_name,
+                                bool return_ipv6_number) {
+  net::NetworkInterfaceList interfaces;
+  bool success = net::GetNetworkList(&interfaces);
+  DCHECK(success);
+
+  size_t expected_address_size = return_ipv6_number ? net::kIPv6AddressSize
+                                                    : net::kIPv4AddressSize;
+
+  for (net::NetworkInterfaceList::iterator iter = interfaces.begin();
+       iter != interfaces.end(); ++iter) {
+    if (iter->address.size() == expected_address_size &&
+        (interface_name.empty() || interface_name == iter->name)) {
+      LOG(INFO) << net::IPAddressToString(iter->address);
+      return iter->address;
+    }
+  }
+
+  return net::IPAddressNumber();
+}
+
+}  // namespace
+
+Printer::Printer() : initialized_(false) {
+}
+
+Printer::~Printer() {
+  Stop();
+}
+
+bool Printer::Start() {
+  if (initialized_)
+    return true;
+
+  // TODO(maksymb): Add switch for command line to control interface name.
+  net::IPAddressNumber ip = GetLocalIp("", false);
+  if (ip.empty()) {
+    LOG(ERROR) << "No local IP found. Cannot start printer.";
+    return false;
+  }
+  VLOG(1) << "Local address: " << net::IPAddressToString(ip);
+
+  // Starting DNS-SD server.
+  initialized_ = dns_server_.Start(
+      ServiceParameters(kServiceType,
+                        kServiceNamePrefix,
+                        kServiceDomainName,
+                        ip,
+                        ReadHttpPortFromCommandLine()),
+      ReadTtlFromCommandLine(),
+      CreateTxt());
+
+  return initialized_;
+}
+
+void Printer::Stop() {
+  if (!initialized_)
+    return;
+
+  dns_server_.Shutdown();
+}
+
+std::vector<std::string> Printer::CreateTxt() const {
+  std::vector<std::string> txt;
+
+  txt.push_back("txtvers=1");
+  txt.push_back("ty=Google Cloud Ready Printer GCP2.0 Prototype");
+  txt.push_back("note=Virtual printer");
+  txt.push_back("url=https://www.google.com/cloudprint");
+  txt.push_back("type=printer");
+  txt.push_back("id=");
+  txt.push_back("cs=offline");
+
+  return txt;
+}
+
diff --git a/cloud_print/gcp20/prototype/printer.h b/cloud_print/gcp20/prototype/printer.h
new file mode 100644
index 0000000..d2d72b6
--- /dev/null
+++ b/cloud_print/gcp20/prototype/printer.h
@@ -0,0 +1,42 @@
+// 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.
+
+#ifndef GCP20_PROTOTYPE_PRINTER_H_
+#define GCP20_PROTOTYPE_PRINTER_H_
+
+#include <string>
+#include <vector>
+
+#include "cloud_print/gcp20/prototype/dns_sd_server.h"
+
+// This class will maintain work of DNS-SD server, HTTP server and others.
+class Printer {
+ public:
+  // Constructs uninitialized object.
+  Printer();
+
+  // Destroys the object.
+  ~Printer();
+
+  // Starts all servers.
+  bool Start();
+
+  // Stops all servers.
+  void Stop();
+
+ private:
+  // Creates data for DNS TXT respond.
+  std::vector<std::string> CreateTxt() const;
+
+  // Contains |true| if initialized.
+  bool initialized_;
+
+  // Contains DNS-SD server.
+  DnsSdServer dns_server_;
+
+  DISALLOW_COPY_AND_ASSIGN(Printer);
+};
+
+#endif  // GCP20_PROTOTYPE_PRINTER_H_
+
diff --git a/cloud_print/gcp20/prototype/service_parameters.cc b/cloud_print/gcp20/prototype/service_parameters.cc
new file mode 100644
index 0000000..e32581e
--- /dev/null
+++ b/cloud_print/gcp20/prototype/service_parameters.cc
@@ -0,0 +1,22 @@
+// 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/service_parameters.h"
+
+ServiceParameters::ServiceParameters() : http_port_(0) {
+}
+
+ServiceParameters::ServiceParameters(const std::string& service_type,
+                                     const std::string& service_name_prefix,
+                                     const std::string& service_domain_name,
+                                     const net::IPAddressNumber& http_ipv4,
+                                     uint16 http_port)
+    : service_type_(service_type),
+      service_name_(service_name_prefix + "." + service_type),
+      service_domain_name_(service_domain_name),
+      http_ipv4_(http_ipv4),
+      http_port_(http_port) {
+}
+
+
diff --git a/cloud_print/gcp20/prototype/service_parameters.h b/cloud_print/gcp20/prototype/service_parameters.h
new file mode 100644
index 0000000..79582ad
--- /dev/null
+++ b/cloud_print/gcp20/prototype/service_parameters.h
@@ -0,0 +1,32 @@
+// 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.
+
+#ifndef CLOUD_PRINT_GCP20_PROTOTYPE_SERVICE_PARAMETERS_H_
+#define CLOUD_PRINT_GCP20_PROTOTYPE_SERVICE_PARAMETERS_H_
+
+#include <string>
+
+#include "net/base/net_util.h"
+
+// Stores information about service.
+struct ServiceParameters {
+  ServiceParameters();
+
+  ~ServiceParameters() {}
+
+  ServiceParameters(const std::string& service_type,
+                    const std::string& service_name_prefix,
+                    const std::string& service_domain_name,
+                    const net::IPAddressNumber& http_ipv4,
+                    uint16 http_port);
+
+  std::string service_type_;
+  std::string service_name_;
+  std::string service_domain_name_;
+  net::IPAddressNumber http_ipv4_;
+  uint16 http_port_;
+};
+
+#endif  // CLOUD_PRINT_GCP20_PROTOTYPE_SERVICE_PARAMETERS_H_
+