In-browser DNS-based service discovery system

chrome/browser/local_discovery/service_discovery_client_impl.cc

+// Copyright (c) 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 <utility>
+
+#include "base/logging.h"
+#include "base/message_loop_proxy.h"
+#include "chrome/browser/local_discovery/service_discovery_client_impl.h"
+#include "net/dns/dns_protocol.h"
+#include "net/dns/record_rdata.h"
+
+namespace local_discovery {
+
+ServiceDiscoveryClientImpl::ServiceDiscoveryClientImpl() {
+}
+
+ServiceDiscoveryClientImpl::~ServiceDiscoveryClientImpl() {
+}
+
+scoped_ptr<ServiceTypeWatcher>
+ServiceDiscoveryClientImpl::CreateServiceTypeWatcher(
+    const std::string& service_type,
+    bool active,
+    bool alert_existing_services,
+    ServiceTypeWatcher::Delegate* delegate) {
+  return scoped_ptr<ServiceTypeWatcher>(new ServiceTypeWatcherImpl(
+      service_type, active, alert_existing_services, delegate));
+}
+
+scoped_ptr<ServiceReader> ServiceDiscoveryClientImpl::CreateServiceReader(
+    const std::string& service_name,
+    ServiceReader::Delegate* delegate) {
+  return scoped_ptr<ServiceReader>(new ServiceReaderImpl(
+      service_name, delegate));
+}
+
+ServiceTypeWatcherImpl::ServiceTypeWatcherImpl(
+    const std::string& service_type,
+    bool active,
+    bool alert_existing_services,
+    ServiceTypeWatcher::Delegate* delegate)
+    : service_type_(service_type), active_(active),
+      alert_existing_services_(alert_existing_services), delegate_(delegate),
+      started_(false) {
+}
+
+bool ServiceTypeWatcherImpl::Start() {
+  DCHECK(!started_);
+  listener_ = net::MDnsClient::GetInstance()->CreateListener(
+      net::dns_protocol::kTypePTR, service_type_, this);
+  if (!listener_->Start()) return false;

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

Chromium coding styles requires line break after condition.

[Noam Samuel, 2013/06/18 22:46:03]

Done.

+  if (!CreateTransaction(active_, alert_existing_services_, false))
+    return false;
+
+  started_ = true;
+  return true;
+}
+
+ServiceTypeWatcherImpl::~ServiceTypeWatcherImpl() {
+}
+
+void ServiceTypeWatcherImpl::GetAvailableServices(
+    std::vector<std::string>* services) const {
+  DCHECK(started_);
+  DCHECK(services);
+  services->insert(services->begin(), services_.begin(), services_.end());
+}
+
+void ServiceTypeWatcherImpl::DiscoverNewServices() {
+  DCHECK(started_);
+  CreateTransaction(true, false, false);
+}
+
+void ServiceTypeWatcherImpl::ForceUpdateServices() {
+  DCHECK(started_);
+  CreateTransaction(true, false, true);
+}
+
+bool ServiceTypeWatcherImpl::CreateTransaction(
+    bool active, bool alert_existing_services, bool force_refresh) {
+  int transaction_flags = 0;
+  if (active) transaction_flags |= net::MDnsTransaction::QUERY_NETWORK;

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

same

[Noam Samuel, 2013/06/18 22:46:03]

Done.

+
+  if (alert_existing_services) {
+    transaction_flags |= net::MDnsTransaction::QUERY_CACHE;
+  }
+
+  // TODO(noamsml): Add flag for force_refresh when support.
+
+  if (transaction_flags) {
+    transaction_ = net::MDnsClient::GetInstance()->CreateTransaction(
+        net::dns_protocol::kTypePTR, service_type_, transaction_flags,
+        base::Bind(&ServiceTypeWatcherImpl::OnTransactionResponse,
+                   base::Unretained(this)));
+    return transaction_->Start();
+  }
+
+  return true;
+}
+
+std::string ServiceTypeWatcherImpl::GetServiceType() const {
+  return listener_->GetName();
+}
+
+bool ServiceTypeWatcherImpl::IsActive() const {
+  return active_;
+}
+
+void ServiceTypeWatcherImpl::OnRecordUpdate(
+    net::MDnsListener::UpdateType update,
+    const net::RecordParsed* record) {
+  DCHECK(started_);
+  DCHECK(record->name() == GetServiceType());
+  DCHECK(record->type() == net::dns_protocol::kTypePTR);
+
+  const net::PtrRecordRdata* rdata = record->rdata<net::PtrRecordRdata>();
+
+  switch (update) {
+    case net::MDnsListener::RECORD_ADDED:
+      AddService(rdata->ptrdomain());
+      break;
+    case net::MDnsListener::RECORD_CHANGED:
+      NOTREACHED();
+      break;
+    case net::MDnsListener::RECORD_REMOVED:
+      RemoveService(rdata->ptrdomain());
+      break;
+  }
+}
+
+void ServiceTypeWatcherImpl::OnCachePurged() {
+  // Not yet implemented.
+}
+
+void ServiceTypeWatcherImpl::OnTransactionResponse(
+    net::MDnsTransaction::Result result,
+    const net::RecordParsed* record) {
+  DCHECK(started_);
+  if (result == net::MDnsTransaction::RESULT_RECORD) {
+    const net::PtrRecordRdata* rdata = record->rdata<net::PtrRecordRdata>();
+    DCHECK(rdata);
+    AddService(rdata->ptrdomain());
+  } else if (result == net::MDnsTransaction::RESULT_DONE) {
+    transaction_.reset();
+  }
+
+  // Do nothing for NSEC records. It is an error for hosts to broadcast an NSEC
+  // record for PTR records on any name.
+}
+
+void ServiceTypeWatcherImpl::AddService(const std::string& service) {
+  DCHECK(started_);
+  std::pair<std::set<std::string>::iterator, bool> found =
+      services_.insert(service);
+  if (found.second) {  // Newly inserted.
+    delegate_->OnServiceStatusChanged(true, service);
+  }
+}
+
+void ServiceTypeWatcherImpl::RemoveService(const std::string& service) {
+  DCHECK(started_);
+  if (services_.erase(service)) {
+    delegate_->OnServiceStatusChanged(false, service);
+  }
+}
+
+void ServiceTypeWatcherImpl::OnNsecRecord(const std::string& name,
+                                          unsigned rrtype) {
+  // Do nothing. It is an error for hosts to broadcast an NSEC record for PTR
+  // on any name.
+}
+
+ServiceReaderImpl::ServiceReaderImpl(
+    const std::string& service_name,
+    ServiceReader::Delegate* delegate)
+    : service_name_(service_name), delegate_(delegate),
+      has_address_(false), has_metadata_(false), started_(false) {
+  srv_listener_ = net::MDnsClient::GetInstance()->CreateListener(
+      net::dns_protocol::kTypeSRV, service_name, this);
+  txt_listener_ = net::MDnsClient::GetInstance()->CreateListener(
+      net::dns_protocol::kTypeTXT, service_name, this);
+}
+
+bool ServiceReaderImpl::Start() {
+  if (!srv_listener_->Start()) return false;

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

again

[Noam Samuel, 2013/06/18 22:46:03]

Done.

+  if (!txt_listener_->Start()) return false;
+
+  // Update initial values
+  if (!CreateTxtTransaction()) return false;
+  if (!CreateSrvTransaction()) return false;
+  started_ = true;
+  return true;
+}
+
+ServiceReaderImpl::~ServiceReaderImpl() {
+}
+
+bool ServiceReaderImpl::GetMetadata(
+    std::vector<std::string>* metadata) const {
+  DCHECK(started_);
+  if (has_metadata_) {
+    *metadata = metadata_;
+    return true;
+  }
+  return false;
+}
+
+void ServiceReaderImpl::ReadMetadata(const MetadataCallback& callback,
+                                     bool force_refresh) {
+  DCHECK(started_);
+  metadata_callbacks_.push_back(callback);
+  if (!txt_transaction_.get()) {
+    CreateTxtTransaction();
+  }
+}
+
+bool ServiceReaderImpl::CreateTxtTransaction() {
+  txt_transaction_ = net::MDnsClient::GetInstance()->CreateTransaction(
+      net::dns_protocol::kTypeTXT, service_name_,
+      net::MDnsTransaction::SINGLE_RESULT | net::MDnsTransaction::QUERY_CACHE |
+      net::MDnsTransaction::QUERY_NETWORK,
+      base::Bind(&ServiceReaderImpl::TxtRecordTransactionResponse,
+                 AsWeakPtr()));

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

don't need to break bind line

[Noam Samuel, 2013/06/18 22:46:03]

It doesn't fit by a couple of characters (at least, it doesn't now that it's
been renamed from Reader to Resolver).

+  return txt_transaction_->Start();
+}
+
+bool ServiceReaderImpl::GetAddress(net::HostPortPair* address) const {
+  DCHECK(started_);
+  if (has_address_) {
+    *address = address_;
+    return true;
+  }
+  return false;
+}
+
+void ServiceReaderImpl::ReadAddress(const AddressCallback& callback,
+                                    bool force_refresh) {
+  DCHECK(started_);
+  address_callbacks_.push_back(callback);
+  if (!srv_transaction_.get()) {
+    CreateSrvTransaction();
+  }
+}
+
+bool ServiceReaderImpl::CreateSrvTransaction() {
+  srv_transaction_ = net::MDnsClient::GetInstance()->CreateTransaction(
+      net::dns_protocol::kTypeSRV, service_name_,
+      net::MDnsTransaction::SINGLE_RESULT | net::MDnsTransaction::QUERY_CACHE |
+      net::MDnsTransaction::QUERY_NETWORK,
+      base::Bind(&ServiceReaderImpl::SrvRecordTransactionResponse,
+                 AsWeakPtr()));
+  return srv_transaction_->Start();
+}
+
+std::string ServiceReaderImpl::GetHumanReadableName() const {
+  // TODO(noamsml): Once we have escaping working, get this to
+  // parse escaped domains.
+  size_t first_period = service_name_.find_first_of('.');
+  return service_name_.substr(0, first_period);
+}
+
+std::string ServiceReaderImpl::GetType() const {
+  // TODO(noamsml): Once we have escaping working, get this to
+  // parse escaped domains.
+  size_t first_period = service_name_.find_first_of('.');
+  if (first_period == std::string::npos) return "";

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

more

[Noam Samuel, 2013/06/18 22:46:03]

Done.

+  return service_name_.substr(first_period+1);
+}
+
+std::string ServiceReaderImpl::GetName() const {
+  return service_name_;
+}
+
+bool ServiceReaderImpl::IsAvailable() const {
+  DCHECK(started_);
+  // TODO(noamsml): This should ideally be based on the PTR record.
+  return has_address_;
+}
+
+void ServiceReaderImpl::ReadLastSeen(
+    const ServiceReader::LastSeenCallback& callback) {
+  DCHECK(started_);
+  // HACK(noamsml): Because cache-based MDns transactions are currently
+  // synchronous, there can only be one last seen callback at a time, so
+  // no need to keep a callback list.
+
+  last_seen_transaction_ = net::MDnsClient::GetInstance()->CreateTransaction(
+      net::dns_protocol::kTypeSRV, service_name_,
+      net::MDnsTransaction::SINGLE_RESULT | net::MDnsTransaction::QUERY_CACHE,
+      base::Bind(&ServiceReaderImpl::LastSeenTransactionResponse,
+                 base::Unretained(this), callback));
+  last_seen_transaction_->Start();
+}
+
+void ServiceReaderImpl::LastSeenTransactionResponse(
+      const ServiceReader::LastSeenCallback& callback,
+      net::MDnsTransaction::Result status,
+      const net::RecordParsed* record) {
+  last_seen_transaction_.reset();
+  DCHECK(started_);
+  if (status == net::MDnsTransaction::RESULT_RECORD) {
+    DCHECK(record);
+    callback.Run(record->time_created());
+  } else {
+    callback.Run(base::Time());
+  }
+}
+
+void ServiceReaderImpl::OnRecordUpdate(net::MDnsListener::UpdateType update,
+                                       const net::RecordParsed* record) {
+  DCHECK(started_);
+  switch (record->type()) {
+    case net::dns_protocol::kTypeSRV: {
+      if (update == net::MDnsListener::RECORD_REMOVED) {
+        has_address_ = false;
+        address_ = net::HostPortPair();

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

same question as for has_metadata_ below

[Noam Samuel, 2013/06/18 22:46:03]

Code path removed.

+      } else {
+        has_address_ = true;
+        address_ = RecordToAddress(record);
+      }
+
+      if (delegate_) {
+        delegate_->OnAddressChanged(service_name_,
+                                    address_);
+      }
+      break;
+    }
+    case net::dns_protocol::kTypeTXT: {
+      if (update == net::MDnsListener::RECORD_REMOVED) {
+        has_metadata_ = false;

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

can you just use metadata_.empty() instead of has_metadata_

[Noam Samuel, 2013/06/15 00:42:06]

I think so. Technically, a service could have empty metadata, but I don't see
the distinction between having empty metadata and no metadata at all ever being
important.

+        metadata_ = std::vector<std::string>();
+      } else {
+        has_metadata_ = true;
+        metadata_ = RecordToMetadata(record);
+      }
+
+      if (delegate_) {
+        delegate_->OnMetadataChanged(service_name_,
+                                     metadata_);

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

one line

[Noam Samuel, 2013/06/18 22:46:03]

Deleted.

+      }
+      break;
+    }
+    default:
+      NOTREACHED();
+  }
+}
+
+void ServiceReaderImpl::OnCachePurged() {
+  // Not yet implemented.
+}
+
+void ServiceReaderImpl::SrvRecordTransactionResponse(
+    net::MDnsTransaction::Result status, const net::RecordParsed* record) {
+  DCHECK(started_);
+  srv_transaction_.reset();
+
+  if (record) {
+    address_ = RecordToAddress(record);
+    has_metadata_ = true;
+  }
+
+  std::vector<ServiceReader::AddressCallback> address_callbacks;
+  address_callbacks.swap(address_callbacks_);
+
+  ServiceReader::RequestStatus output_status = MDnsStatusToRequestStatus(
+      status);
+
+  for (std::vector<ServiceReader::AddressCallback>::iterator i =

[Vitaly Buka (NO REVIEWS), 2013/06/15 00:22:30]

SrvRecordTransactionResponse and TxtRecordTransactionResponse are very similar

[Noam Samuel, 2013/06/15 00:42:06]

Since they contain slightly different logic and types, I'm not sure how to merge
them short of using templates, which seems like overkill for this case.

[Noam Samuel, 2013/06/18 22:46:03]

Deleted.

+           address_callbacks.begin(); i != address_callbacks.end(); ++i) {
+    i->Run(output_status, address_);
+  }
+}
+
+void ServiceReaderImpl::TxtRecordTransactionResponse(
+    net::MDnsTransaction::Result status, const net::RecordParsed* record) {
+  DCHECK(started_);
+  txt_transaction_.reset();
+
+  std::vector<ServiceReader::MetadataCallback> metadata_callbacks;
+  metadata_callbacks.swap(metadata_callbacks_);
+
+  if (record) {
+    metadata_ = RecordToMetadata(record);
+    has_metadata_ = true;
+  }
+
+  ServiceReader::RequestStatus output_status = MDnsStatusToRequestStatus(
+      status);
+
+  for (std::vector<ServiceReader::MetadataCallback>::iterator i =
+           metadata_callbacks.begin(); i != metadata_callbacks.end(); ++i) {
+    i->Run(output_status, metadata_);
+  }
+}
+
+void ServiceReaderImpl::OnNsecRecord(const std::string& name,
+                                     unsigned rrtype) {
+  // TODO(noamsml): Logic NSEC in listener case.
+}
+
+ServiceReader::RequestStatus ServiceReaderImpl::MDnsStatusToRequestStatus(
+    net::MDnsTransaction::Result status) const {
+  switch (status) {
+    case net::MDnsTransaction::RESULT_RECORD:
+      return ServiceReader::STATUS_SUCCESS;
+    case net::MDnsTransaction::RESULT_NO_RESULTS:
+      return ServiceReader::STATUS_TIMEOUT;
+    case net::MDnsTransaction::RESULT_NSEC:
+      return ServiceReader::STATUS_KNOWN_NONEXISTENT;
+    case net::MDnsTransaction::RESULT_DONE:
+      NOTREACHED();
+      return ServiceReader::STATUS_TIMEOUT;
+  }
+}
+
+const std::vector<std::string>& ServiceReaderImpl::RecordToMetadata(
+    const net::RecordParsed* record) const {
+  DCHECK(record->type() == net::dns_protocol::kTypeTXT);
+  const net::TxtRecordRdata* txt_rdata = record->rdata<net::TxtRecordRdata>();
+  DCHECK(txt_rdata);
+  return txt_rdata->texts();
+}
+
+net::HostPortPair ServiceReaderImpl::RecordToAddress(
+    const net::RecordParsed* record) const {
+  DCHECK(record->type() == net::dns_protocol::kTypeSRV);
+  const net::SrvRecordRdata* srv_rdata = record->rdata<net::SrvRecordRdata>();
+  DCHECK(srv_rdata);
+  return net::HostPortPair(srv_rdata->target(), srv_rdata->port());
+}
+
+}  // namespace local_discovery