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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "chrome/browser/extensions/api/dial/dial_service.h"
      6 
      7 #include <algorithm>
      8 #include <set>
      9 #include <utility>
     10 
     11 #include "base/basictypes.h"
     12 #include "base/callback.h"
     13 #include "base/logging.h"
     14 #include "base/rand_util.h"
     15 #include "base/strings/string_number_conversions.h"
     16 #include "base/strings/stringprintf.h"
     17 #include "base/time/time.h"
     18 #include "chrome/browser/extensions/api/dial/dial_device_data.h"
     19 #include "chrome/common/chrome_version_info.h"
     20 #include "content/public/browser/browser_thread.h"
     21 #include "net/base/completion_callback.h"
     22 #include "net/base/io_buffer.h"
     23 #include "net/base/ip_endpoint.h"
     24 #include "net/base/net_errors.h"
     25 #include "net/base/net_util.h"
     26 #include "net/http/http_response_headers.h"
     27 #include "net/http/http_util.h"
     28 #include "url/gurl.h"
     29 #if defined(OS_CHROMEOS)
     30 #include "chromeos/network/network_state.h"
     31 #include "chromeos/network/network_state_handler.h"
     32 #include "third_party/cros_system_api/dbus/service_constants.h"
     33 #endif
     34 
     35 using base::Time;
     36 using base::TimeDelta;
     37 using content::BrowserThread;
     38 using net::HttpResponseHeaders;
     39 using net::HttpUtil;
     40 using net::IOBufferWithSize;
     41 using net::IPAddressNumber;
     42 using net::IPEndPoint;
     43 using net::NetworkInterface;
     44 using net::NetworkInterfaceList;
     45 using net::StringIOBuffer;
     46 using net::UDPSocket;
     47 
     48 namespace extensions {
     49 
     50 namespace {
     51 
     52 // The total number of requests to make per discovery cycle.
     53 const int kDialMaxRequests = 4;
     54 
     55 // The interval to wait between successive requests.
     56 const int kDialRequestIntervalMillis = 1000;
     57 
     58 // The maximum delay a device may wait before responding (MX).
     59 const int kDialMaxResponseDelaySecs = 1;
     60 
     61 // The maximum time a response is expected after a M-SEARCH request.
     62 const int kDialResponseTimeoutSecs = 2;
     63 
     64 // The multicast IP address for discovery.
     65 const char kDialRequestAddress[] = "239.255.255.250";
     66 
     67 // The UDP port number for discovery.
     68 const int kDialRequestPort = 1900;
     69 
     70 // The DIAL service type as part of the search request.
     71 const char kDialSearchType[] = "urn:dial-multiscreen-org:service:dial:1";
     72 
     73 // SSDP headers parsed from the response.
     74 const char kSsdpLocationHeader[] = "LOCATION";
     75 const char kSsdpCacheControlHeader[] = "CACHE-CONTROL";
     76 const char kSsdpConfigIdHeader[] = "CONFIGID.UPNP.ORG";
     77 const char kSsdpUsnHeader[] = "USN";
     78 
     79 // The receive buffer size, in bytes.
     80 const int kDialRecvBufferSize = 1500;
     81 
     82 // Gets a specific header from |headers| and puts it in |value|.
     83 bool GetHeader(HttpResponseHeaders* headers, const char* name,
     84                std::string* value) {
     85   return headers->EnumerateHeader(NULL, std::string(name), value);
     86 }
     87 
     88 // Returns the request string.
     89 std::string BuildRequest() {
     90   // Extra line at the end to make UPnP lib happy.
     91   chrome::VersionInfo version;
     92   std::string request(base::StringPrintf(
     93       "M-SEARCH * HTTP/1.1\r\n"
     94       "HOST: %s:%i\r\n"
     95       "MAN: \"ssdp:discover\"\r\n"
     96       "MX: %d\r\n"
     97       "ST: %s\r\n"
     98       "USER-AGENT: %s/%s %s\r\n"
     99       "\r\n",
    100       kDialRequestAddress,
    101       kDialRequestPort,
    102       kDialMaxResponseDelaySecs,
    103       kDialSearchType,
    104       version.Name().c_str(),
    105       version.Version().c_str(),
    106       version.OSType().c_str()));
    107   // 1500 is a good MTU value for most Ethernet LANs.
    108   DCHECK(request.size() <= 1500);
    109   return request;
    110 }
    111 
    112 #if !defined(OS_CHROMEOS)
    113 void GetNetworkListOnFileThread(
    114     const scoped_refptr<base::MessageLoopProxy>& loop,
    115     const base::Callback<void(const NetworkInterfaceList& networks)>& cb) {
    116   NetworkInterfaceList list;
    117   bool success = net::GetNetworkList(
    118       &list, net::INCLUDE_HOST_SCOPE_VIRTUAL_INTERFACES);
    119   if (!success)
    120     DVLOG(1) << "Could not retrieve network list!";
    121 
    122   loop->PostTask(FROM_HERE, base::Bind(cb, list));
    123 }
    124 
    125 #else
    126 
    127 // Finds the IP address of the preferred interface of network type |type|
    128 // to bind the socket and inserts the address into |bind_address_list|. This
    129 // ChromeOS version can prioritize wifi and ethernet interfaces.
    130 void InsertBestBindAddressChromeOS(
    131     const chromeos::NetworkTypePattern& type,
    132     std::vector<IPAddressNumber>* bind_address_list) {
    133   const chromeos::NetworkState* state = chromeos::NetworkHandler::Get()
    134       ->network_state_handler()->ConnectedNetworkByType(type);
    135   IPAddressNumber bind_ip_address;
    136   if (state
    137       && net::ParseIPLiteralToNumber(state->ip_address(), &bind_ip_address)
    138       && bind_ip_address.size() == net::kIPv4AddressSize) {
    139     DVLOG(1) << "Found " << state->type() << ", " << state->name() << ": "
    140              << state->ip_address();
    141     bind_address_list->push_back(bind_ip_address);
    142   }
    143 }
    144 #endif  // !defined(OS_CHROMEOS)
    145 
    146 }  // namespace
    147 
    148 DialServiceImpl::DialSocket::DialSocket(
    149     const base::Closure& discovery_request_cb,
    150     const base::Callback<void(const DialDeviceData&)>& device_discovered_cb,
    151     const base::Closure& on_error_cb)
    152     : discovery_request_cb_(discovery_request_cb),
    153       device_discovered_cb_(device_discovered_cb),
    154       on_error_cb_(on_error_cb),
    155       is_writing_(false),
    156       is_reading_(false) {
    157 }
    158 
    159 DialServiceImpl::DialSocket::~DialSocket() {
    160   DCHECK(thread_checker_.CalledOnValidThread());
    161 }
    162 
    163 bool DialServiceImpl::DialSocket::CreateAndBindSocket(
    164     const IPAddressNumber& bind_ip_address,
    165     net::NetLog* net_log,
    166     net::NetLog::Source net_log_source) {
    167   DCHECK(thread_checker_.CalledOnValidThread());
    168   DCHECK(!socket_.get());
    169   DCHECK(bind_ip_address.size() == net::kIPv4AddressSize);
    170 
    171   net::RandIntCallback rand_cb = base::Bind(&base::RandInt);
    172   socket_.reset(new UDPSocket(net::DatagramSocket::RANDOM_BIND,
    173                               rand_cb,
    174                               net_log,
    175                               net_log_source));
    176   socket_->AllowBroadcast();
    177 
    178   // 0 means bind a random port
    179   IPEndPoint address(bind_ip_address, 0);
    180 
    181   if (!CheckResult("Bind", socket_->Bind(address)))
    182     return false;
    183 
    184   DCHECK(socket_.get());
    185 
    186   recv_buffer_ = new IOBufferWithSize(kDialRecvBufferSize);
    187   return ReadSocket();
    188 }
    189 
    190 void DialServiceImpl::DialSocket::SendOneRequest(
    191     const net::IPEndPoint& send_address,
    192     const scoped_refptr<net::StringIOBuffer>& send_buffer) {
    193   if (!socket_.get()) {
    194     DLOG(WARNING) << "Socket not connected.";
    195     return;
    196   }
    197 
    198   if (is_writing_) {
    199     VLOG(2) << "Already writing.";
    200     return;
    201   }
    202 
    203   is_writing_ = true;
    204   int result = socket_->SendTo(
    205       send_buffer.get(), send_buffer->size(), send_address,
    206       base::Bind(&DialServiceImpl::DialSocket::OnSocketWrite,
    207                  base::Unretained(this),
    208                  send_buffer->size()));
    209   bool result_ok = CheckResult("SendTo", result);
    210   if (result_ok && result > 0) {
    211     // Synchronous write.
    212     OnSocketWrite(send_buffer->size(), result);
    213   }
    214 }
    215 
    216 bool DialServiceImpl::DialSocket::IsClosed() {
    217   DCHECK(thread_checker_.CalledOnValidThread());
    218   return !socket_.get();
    219 }
    220 
    221 bool DialServiceImpl::DialSocket::CheckResult(const char* operation,
    222                                               int result) {
    223   DCHECK(thread_checker_.CalledOnValidThread());
    224   VLOG(2) << "Operation " << operation << " result " << result;
    225   if (result < net::OK && result != net::ERR_IO_PENDING) {
    226     Close();
    227     std::string error_str(net::ErrorToString(result));
    228     DVLOG(0) << "dial socket error: " << error_str;
    229     on_error_cb_.Run();
    230     return false;
    231   }
    232   return true;
    233 }
    234 
    235 void DialServiceImpl::DialSocket::Close() {
    236   DCHECK(thread_checker_.CalledOnValidThread());
    237   is_reading_ = false;
    238   is_writing_ = false;
    239   socket_.reset();
    240 }
    241 
    242 void DialServiceImpl::DialSocket::OnSocketWrite(int send_buffer_size,
    243                                                 int result) {
    244   DCHECK(thread_checker_.CalledOnValidThread());
    245   is_writing_ = false;
    246   if (!CheckResult("OnSocketWrite", result))
    247     return;
    248   if (result != send_buffer_size) {
    249     DLOG(ERROR) << "Sent " << result << " chars, expected "
    250                 << send_buffer_size << " chars";
    251   }
    252   discovery_request_cb_.Run();
    253 }
    254 
    255 bool DialServiceImpl::DialSocket::ReadSocket() {
    256   DCHECK(thread_checker_.CalledOnValidThread());
    257   if (!socket_.get()) {
    258     DLOG(WARNING) << "Socket not connected.";
    259     return false;
    260   }
    261 
    262   if (is_reading_) {
    263     VLOG(2) << "Already reading.";
    264     return false;
    265   }
    266 
    267   int result = net::OK;
    268   bool result_ok = true;
    269   do {
    270     is_reading_ = true;
    271     result = socket_->RecvFrom(
    272         recv_buffer_.get(),
    273         kDialRecvBufferSize, &recv_address_,
    274         base::Bind(&DialServiceImpl::DialSocket::OnSocketRead,
    275                    base::Unretained(this)));
    276     result_ok = CheckResult("RecvFrom", result);
    277     if (result != net::ERR_IO_PENDING)
    278       is_reading_ = false;
    279     if (result_ok && result > 0) {
    280       // Synchronous read.
    281       HandleResponse(result);
    282     }
    283   } while (result_ok && result != net::OK && result != net::ERR_IO_PENDING);
    284   return result_ok;
    285 }
    286 
    287 void DialServiceImpl::DialSocket::OnSocketRead(int result) {
    288   DCHECK(thread_checker_.CalledOnValidThread());
    289   is_reading_ = false;
    290   if (!CheckResult("OnSocketRead", result))
    291     return;
    292   if (result > 0)
    293     HandleResponse(result);
    294 
    295   // Await next response.
    296   ReadSocket();
    297 }
    298 
    299 void DialServiceImpl::DialSocket::HandleResponse(int bytes_read) {
    300   DCHECK(thread_checker_.CalledOnValidThread());
    301   DCHECK_GT(bytes_read, 0);
    302   if (bytes_read > kDialRecvBufferSize) {
    303     DLOG(ERROR) << bytes_read << " > " << kDialRecvBufferSize << "!?";
    304     return;
    305   }
    306   VLOG(2) << "Read " << bytes_read << " bytes from "
    307           << recv_address_.ToString();
    308 
    309   std::string response(recv_buffer_->data(), bytes_read);
    310   Time response_time = Time::Now();
    311 
    312   // Attempt to parse response, notify observers if successful.
    313   DialDeviceData parsed_device;
    314   if (ParseResponse(response, response_time, &parsed_device))
    315     device_discovered_cb_.Run(parsed_device);
    316 }
    317 
    318 // static
    319 bool DialServiceImpl::DialSocket::ParseResponse(
    320     const std::string& response,
    321     const base::Time& response_time,
    322     DialDeviceData* device) {
    323   int headers_end = HttpUtil::LocateEndOfHeaders(response.c_str(),
    324                                                  response.size());
    325   if (headers_end < 1) {
    326     VLOG(2) << "Headers invalid or empty, ignoring: " << response;
    327     return false;
    328   }
    329   std::string raw_headers =
    330       HttpUtil::AssembleRawHeaders(response.c_str(), headers_end);
    331   VLOG(2) << "raw_headers: " << raw_headers << "\n";
    332   scoped_refptr<HttpResponseHeaders> headers =
    333       new HttpResponseHeaders(raw_headers);
    334 
    335   std::string device_url_str;
    336   if (!GetHeader(headers.get(), kSsdpLocationHeader, &device_url_str) ||
    337       device_url_str.empty()) {
    338     VLOG(2) << "No LOCATION header found.";
    339     return false;
    340   }
    341 
    342   GURL device_url(device_url_str);
    343   if (!DialDeviceData::IsDeviceDescriptionUrl(device_url)) {
    344     VLOG(2) << "URL " << device_url_str << " not valid.";
    345     return false;
    346   }
    347 
    348   std::string device_id;
    349   if (!GetHeader(headers.get(), kSsdpUsnHeader, &device_id) ||
    350       device_id.empty()) {
    351     VLOG(2) << "No USN header found.";
    352     return false;
    353   }
    354 
    355   device->set_device_id(device_id);
    356   device->set_device_description_url(device_url);
    357   device->set_response_time(response_time);
    358 
    359   // TODO(mfoltz): Parse the max-age value from the cache control header.
    360   // http://crbug.com/165289
    361   std::string cache_control;
    362   GetHeader(headers.get(), kSsdpCacheControlHeader, &cache_control);
    363 
    364   std::string config_id;
    365   int config_id_int;
    366   if (GetHeader(headers.get(), kSsdpConfigIdHeader, &config_id) &&
    367       base::StringToInt(config_id, &config_id_int)) {
    368     device->set_config_id(config_id_int);
    369   } else {
    370     VLOG(2) << "Malformed or missing " << kSsdpConfigIdHeader << ": "
    371             << config_id;
    372   }
    373 
    374   return true;
    375 }
    376 
    377 DialServiceImpl::DialServiceImpl(net::NetLog* net_log)
    378     : discovery_active_(false),
    379       num_requests_sent_(0),
    380       max_requests_(kDialMaxRequests),
    381       finish_delay_(TimeDelta::FromMilliseconds((kDialMaxRequests - 1) *
    382                                                 kDialRequestIntervalMillis) +
    383                     TimeDelta::FromSeconds(kDialResponseTimeoutSecs)),
    384       request_interval_(
    385           TimeDelta::FromMilliseconds(kDialRequestIntervalMillis)) {
    386   IPAddressNumber address;
    387   bool success = net::ParseIPLiteralToNumber(kDialRequestAddress, &address);
    388   DCHECK(success);
    389   send_address_ = IPEndPoint(address, kDialRequestPort);
    390   send_buffer_ = new StringIOBuffer(BuildRequest());
    391   net_log_ = net_log;
    392   net_log_source_.type = net::NetLog::SOURCE_UDP_SOCKET;
    393   net_log_source_.id = net_log_->NextID();
    394 }
    395 
    396 DialServiceImpl::~DialServiceImpl() {
    397   DCHECK(thread_checker_.CalledOnValidThread());
    398 }
    399 
    400 void DialServiceImpl::AddObserver(Observer* observer) {
    401   DCHECK(thread_checker_.CalledOnValidThread());
    402   observer_list_.AddObserver(observer);
    403 }
    404 
    405 void DialServiceImpl::RemoveObserver(Observer* observer) {
    406   DCHECK(thread_checker_.CalledOnValidThread());
    407   observer_list_.RemoveObserver(observer);
    408 }
    409 
    410 bool DialServiceImpl::HasObserver(Observer* observer) {
    411   DCHECK(thread_checker_.CalledOnValidThread());
    412   return observer_list_.HasObserver(observer);
    413 }
    414 
    415 bool DialServiceImpl::Discover() {
    416   DCHECK(thread_checker_.CalledOnValidThread());
    417   if (discovery_active_) {
    418     VLOG(2) << "Discovery is already active - returning.";
    419     return false;
    420   }
    421   discovery_active_ = true;
    422 
    423   VLOG(2) << "Discovery started.";
    424 
    425   StartDiscovery();
    426   return true;
    427 }
    428 
    429 void DialServiceImpl::StartDiscovery() {
    430   DCHECK(thread_checker_.CalledOnValidThread());
    431   DCHECK(discovery_active_);
    432   if (HasOpenSockets()) {
    433     VLOG(2) << "Calling StartDiscovery() with open sockets. Returning.";
    434     return;
    435   }
    436 
    437 #if defined(OS_CHROMEOS)
    438   // The ChromeOS specific version of getting network interfaces does not
    439   // require trampolining to another thread, and contains additional interface
    440   // information such as interface types (i.e. wifi vs cellular).
    441   std::vector<IPAddressNumber> chrome_os_address_list;
    442   InsertBestBindAddressChromeOS(chromeos::NetworkTypePattern::Ethernet(),
    443                                 &chrome_os_address_list);
    444   InsertBestBindAddressChromeOS(chromeos::NetworkTypePattern::WiFi(),
    445                                 &chrome_os_address_list);
    446   DiscoverOnAddresses(chrome_os_address_list);
    447 
    448 #else
    449   BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE, base::Bind(
    450       &GetNetworkListOnFileThread,
    451       base::MessageLoopProxy::current(), base::Bind(
    452           &DialServiceImpl::SendNetworkList, AsWeakPtr())));
    453 #endif
    454 }
    455 
    456 void DialServiceImpl::SendNetworkList(const NetworkInterfaceList& networks) {
    457   DCHECK(thread_checker_.CalledOnValidThread());
    458   typedef std::pair<uint32, net::AddressFamily> InterfaceIndexAddressFamily;
    459   std::set<InterfaceIndexAddressFamily> interface_index_addr_family_seen;
    460   std::vector<IPAddressNumber> ip_addresses;
    461 
    462   // Binds a socket to each IPv4 network interface found. Note that
    463   // there may be duplicates in |networks|, so address family + interface index
    464   // is used to identify unique interfaces.
    465   // TODO(mfoltz): Support IPV6 multicast.  http://crbug.com/165286
    466   for (NetworkInterfaceList::const_iterator iter = networks.begin();
    467        iter != networks.end(); ++iter) {
    468     net::AddressFamily addr_family = net::GetAddressFamily(iter->address);
    469     DVLOG(1) << "Found " << iter->name << ", "
    470              << net::IPAddressToString(iter->address)
    471              << ", address family: " << addr_family;
    472     if (addr_family == net::ADDRESS_FAMILY_IPV4) {
    473       InterfaceIndexAddressFamily interface_index_addr_family =
    474           std::make_pair(iter->interface_index, addr_family);
    475       bool inserted = interface_index_addr_family_seen
    476           .insert(interface_index_addr_family)
    477           .second;
    478       // We have not seen this interface before, so add its IP address to the
    479       // discovery list.
    480       if (inserted) {
    481         VLOG(2) << "Encountered "
    482                 << "interface index: " << iter->interface_index << ", "
    483                 << "address family: " << addr_family << " for the first time, "
    484                 << "adding IP address " << net::IPAddressToString(iter->address)
    485                 << " to list.";
    486         ip_addresses.push_back(iter->address);
    487       } else {
    488         VLOG(2) << "Already encountered "
    489                 << "interface index: " << iter->interface_index << ", "
    490                 << "address family: " << addr_family << " before, not adding.";
    491       }
    492     }
    493   }
    494 
    495   DiscoverOnAddresses(ip_addresses);
    496 }
    497 
    498 void DialServiceImpl::DiscoverOnAddresses(
    499     const std::vector<IPAddressNumber>& ip_addresses) {
    500   if (ip_addresses.empty()) {
    501     DVLOG(1) << "Could not find a valid interface to bind. Finishing discovery";
    502     FinishDiscovery();
    503     return;
    504   }
    505 
    506   // Schedule a timer to finish the discovery process (and close the sockets).
    507   if (finish_delay_ > TimeDelta::FromSeconds(0)) {
    508     VLOG(2) << "Starting timer to finish discovery.";
    509     finish_timer_.Start(FROM_HERE,
    510                         finish_delay_,
    511                         this,
    512                         &DialServiceImpl::FinishDiscovery);
    513   }
    514 
    515   for (std::vector<IPAddressNumber>::const_iterator iter = ip_addresses.begin();
    516        iter != ip_addresses.end();
    517        ++iter)
    518     BindAndAddSocket(*iter);
    519 
    520   SendOneRequest();
    521 }
    522 
    523 void DialServiceImpl::BindAndAddSocket(const IPAddressNumber& bind_ip_address) {
    524   scoped_ptr<DialServiceImpl::DialSocket> dial_socket(CreateDialSocket());
    525   if (dial_socket->CreateAndBindSocket(bind_ip_address, net_log_,
    526                                        net_log_source_))
    527     dial_sockets_.push_back(dial_socket.release());
    528 }
    529 
    530 scoped_ptr<DialServiceImpl::DialSocket> DialServiceImpl::CreateDialSocket() {
    531   scoped_ptr<DialServiceImpl::DialSocket> dial_socket(
    532       new DialServiceImpl::DialSocket(
    533           base::Bind(&DialServiceImpl::NotifyOnDiscoveryRequest, AsWeakPtr()),
    534           base::Bind(&DialServiceImpl::NotifyOnDeviceDiscovered, AsWeakPtr()),
    535           base::Bind(&DialServiceImpl::NotifyOnError, AsWeakPtr())));
    536   return dial_socket.Pass();
    537 }
    538 
    539 void DialServiceImpl::SendOneRequest() {
    540   DCHECK(thread_checker_.CalledOnValidThread());
    541   if (num_requests_sent_ == max_requests_) {
    542     VLOG(2) << "Reached max requests; stopping request timer.";
    543     request_timer_.Stop();
    544     return;
    545   }
    546   num_requests_sent_++;
    547   VLOG(2) << "Sending request " << num_requests_sent_ << "/"
    548           << max_requests_;
    549   for (ScopedVector<DialServiceImpl::DialSocket>::iterator iter =
    550            dial_sockets_.begin();
    551        iter != dial_sockets_.end();
    552        ++iter) {
    553     if (!((*iter)->IsClosed()))
    554       (*iter)->SendOneRequest(send_address_, send_buffer_);
    555   }
    556 }
    557 
    558 void DialServiceImpl::NotifyOnDiscoveryRequest() {
    559   DCHECK(thread_checker_.CalledOnValidThread());
    560   // If discovery is inactive, no reason to notify observers.
    561   if (!discovery_active_) {
    562     VLOG(2) << "Request sent after discovery finished.  Ignoring.";
    563     return;
    564   }
    565 
    566   VLOG(2) << "Notifying observers of discovery request";
    567   FOR_EACH_OBSERVER(Observer, observer_list_, OnDiscoveryRequest(this));
    568   // If we need to send additional requests, schedule a timer to do so.
    569   if (num_requests_sent_ < max_requests_ && num_requests_sent_ == 1) {
    570     VLOG(2) << "Scheduling timer to send additional requests";
    571     // TODO(imcheng): Move this to SendOneRequest() once the implications are
    572     // understood.
    573     request_timer_.Start(FROM_HERE,
    574                          request_interval_,
    575                          this,
    576                          &DialServiceImpl::SendOneRequest);
    577   }
    578 }
    579 
    580 void DialServiceImpl::NotifyOnDeviceDiscovered(
    581     const DialDeviceData& device_data) {
    582   DCHECK(thread_checker_.CalledOnValidThread());
    583   if (!discovery_active_) {
    584     VLOG(2) << "Got response after discovery finished.  Ignoring.";
    585     return;
    586   }
    587   FOR_EACH_OBSERVER(Observer, observer_list_,
    588                     OnDeviceDiscovered(this, device_data));
    589 }
    590 
    591 void DialServiceImpl::NotifyOnError() {
    592   DCHECK(thread_checker_.CalledOnValidThread());
    593   // TODO(imcheng): Modify upstream so that the device list is not cleared
    594   // when it could still potentially discover devices on other sockets.
    595   FOR_EACH_OBSERVER(Observer, observer_list_,
    596                     OnError(this,
    597                             HasOpenSockets() ? DIAL_SERVICE_SOCKET_ERROR
    598                                              : DIAL_SERVICE_NO_INTERFACES));
    599 }
    600 
    601 void DialServiceImpl::FinishDiscovery() {
    602   DCHECK(thread_checker_.CalledOnValidThread());
    603   DCHECK(discovery_active_);
    604   VLOG(2) << "Discovery finished.";
    605   // Close all open sockets.
    606   dial_sockets_.clear();
    607   finish_timer_.Stop();
    608   request_timer_.Stop();
    609   discovery_active_ = false;
    610   num_requests_sent_ = 0;
    611   FOR_EACH_OBSERVER(Observer, observer_list_, OnDiscoveryFinished(this));
    612 }
    613 
    614 bool DialServiceImpl::HasOpenSockets() {
    615   for (ScopedVector<DialSocket>::const_iterator iter = dial_sockets_.begin();
    616        iter != dial_sockets_.end();
    617        ++iter) {
    618     if (!((*iter)->IsClosed()))
    619       return true;
    620   }
    621   return false;
    622 }
    623 
    624 }  // namespace extensions
    625