[Media Router] Add DialMediaSinkService and DeviceDescriptionService

chrome/browser/media/router/discovery/dial/device_description_service.cc

+// Copyright 2017 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 "chrome/browser/media/router/discovery/dial/device_description_service.h"
+
+#include "base/stl_util.h"
+#include "base/strings/string_util.h"
+#include "chrome/browser/media/router/discovery/dial/device_description_fetcher.h"
+#include "chrome/browser/media/router/discovery/dial/safe_dial_device_description_parser.h"
+#include "net/base/ip_address.h"
+#include "url/gurl.h"
+
+namespace {
+
+enum ErrorType {
+  NONE,
+  MISSING_UNIQUE_ID,
+  MISSING_FRIENDLY_NAME,
+  MISSING_APP_URL,
+  INVALID_APP_URL
+};
+
+// How long to cache a device description.
+const int kDeviceDescriptionCacheTimeMillis = 30 * 60 * 1000;

[mark a. foltz, 2017/04/18 18:16:26]

Per my earlier comment this could be much longer IMO.  We can be conservative
for now, but I would like to see this addressed.  I can start an email thread.

[zhaobin, 2017/04/21 23:12:58]

Done.

+
+// Time interval to clean up cache entries.
+const int kCacheCleanUpTimeoutMins = 30;
+
+// Maximum size on the number of cached entries.
+const int kCacheLimit = 256;

[mark a. foltz, 2017/04/18 18:16:26]

kCacheMaxEntries ?

[zhaobin, 2017/04/21 23:12:57]

Done.

+
+#ifndef NDEBUG
+// Replaces "<element_name>content</element_name>" with
+// "<element_name>***</element_name>"
+void Scrub(const std::string& element_name, std::string* xml_text) {
+  size_t pos = xml_text->find("<" + element_name + ">");
+  size_t end_pos = xml_text->find("</" + element_name + ">");
+
+  if (pos == std::string::npos || end_pos == std::string::npos)
+    return;
+
+  size_t start_pos = pos + element_name.length() + 2;
+  if (end_pos > start_pos)
+    xml_text->replace(start_pos, end_pos - start_pos, "***");
+}
+
+// Removes unique identifiers from the device description.
+// |xml_text|: The device description XML.
+// Returns original XML text if <UDN> or <serialNumber> field does not exist.
+std::string ScrubDeviceDescriptionXml(const std::string& xml_text) {
+  std::string scrubbed_xml(xml_text);
+  Scrub("UDN", &scrubbed_xml);
+  Scrub("serialNumber", &scrubbed_xml);
+  return scrubbed_xml;
+}
+
+std::string CachedDeviceDescriptionToString(
+    const media_router::DeviceDescriptionService::CacheEntry& cached_data) {
+  std::stringstream ss;

[mark a. foltz, 2017/04/18 18:16:26]

#ifndef NDEBUG
#include <sstream>
#endif

[zhaobin, 2017/04/21 23:12:58]

Done.

+  ss << "CachedDialDeviceDescription [unique_id]: "
+     << cached_data.description_data.unique_id
+     << " [friendly_name]: " << cached_data.description_data.friendly_name
+     << " [model_name]: " << cached_data.description_data.model_name
+     << " [app_url]: " << cached_data.description_data.app_url
+     << " [expire_time]: " << cached_data.expire_time
+     << " [config_id]: " << cached_data.config_id;
+
+  return ss.str();
+}
+#endif
+
+bool IsValidAppUrl(const GURL& app_url, const std::string& ip_address) {
+  return app_url.SchemeIs(url::kHttpScheme) && app_url.host() == ip_address;
+}
+
+// Checks mandatory fields. Returns ErrorType::NONE if device description is
+// valid; Otherwise returns specific error type.
+ErrorType ValidateParsedDeviceDescription(
+    const std::string& expected_ip_address,
+    const media_router::ParsedDialDeviceDescription& description_data) {
+  if (description_data.unique_id.empty()) {
+    return ErrorType::MISSING_UNIQUE_ID;
+  }
+  if (description_data.friendly_name.empty()) {
+    return ErrorType::MISSING_FRIENDLY_NAME;
+  }
+  if (!description_data.app_url.is_valid()) {
+    return ErrorType::MISSING_APP_URL;
+  }
+  if (!IsValidAppUrl(description_data.app_url, expected_ip_address)) {
+    return ErrorType::INVALID_APP_URL;
+  }
+  return ErrorType::NONE;
+}
+
+}  // namespace
+
+namespace media_router {
+
+DeviceDescriptionService::DeviceDescriptionService(
+    const DeviceDescriptionParseSuccessCallback& success_cb,
+    const DeviceDescriptionParseErrorCallback& error_cb)
+    : success_cb_(success_cb), error_cb_(error_cb) {}
+
+DeviceDescriptionService::~DeviceDescriptionService() = default;
+
+void DeviceDescriptionService::GetDeviceDescriptions(
+    const std::vector<DialDeviceData>& devices,
+    net::URLRequestContextGetter* request_context) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  std::map<std::string, std::unique_ptr<DeviceDescriptionFetcher>>
+      existing_fetcher_map;
+  for (auto& fetcher_it : device_description_fetcher_map_) {
+    std::string device_label = fetcher_it.first;
+    const auto& device_it =
+        std::find_if(devices.begin(), devices.end(),
+                     [&device_label](const DialDeviceData& device_data) {
+                       return device_data.label() == device_label;
+                     });
+    if (device_it == devices.end() ||
+        device_it->device_description_url() ==
+            fetcher_it.second->device_description_url()) {
+      existing_fetcher_map.insert(
+          std::make_pair(device_label, std::move(fetcher_it.second)));
+    }
+  }
+
+  // Remove all out dated fetchers.
+  device_description_fetcher_map_ = std::move(existing_fetcher_map);
+
+  for (const auto& device_data : devices) {
+    auto* cache_entry = CheckAndUpdateCache(device_data);
+    if (cache_entry) {
+      // Get device description from cache.
+      success_cb_.Run(device_data, cache_entry->description_data);
+      continue;
+    }
+
+    FetchDeviceDescription(device_data, request_context);
+  }
+
+  // Start a clean up timer.
+  if (!clean_up_timer_) {
+    clean_up_timer_.reset(new base::RepeatingTimer());
+    clean_up_timer_->Start(
+        FROM_HERE, base::TimeDelta::FromMinutes(kCacheCleanUpTimeoutMins), this,
+        &DeviceDescriptionService::CleanUpCacheEntries);
+  }
+}
+
+void DeviceDescriptionService::CleanUpCacheEntries() {
+  // TODO(zhaobin): instead of removing them directly, issue GET request to
+  // check if expired device descriptions are still alive.

[mark a. foltz, 2017/04/18 18:16:26]

This is probably okay - if the device is found through discovery again, it will
repopulate the cache entry.  So this TODO doesn't seem necessary.

[zhaobin, 2017/04/21 23:12:58]

Done.

+  DCHECK(thread_checker_.CalledOnValidThread());
+  base::Time now = GetNow();
+
+  DVLOG(2) << "Before clean up, cache size: " << description_map_.size();
+  base::EraseIf(description_map_,
+                [&now](const std::pair<std::string, CacheEntry>& cache_pair) {
+                  return cache_pair.second.expire_time < now;
+                });
+  DVLOG(2) << "After clean up, cache size: " << description_map_.size();

[mark a. foltz, 2017/04/18 18:16:26]

If the cache is emptied and there are no pending requests, you can cancel the
repeated timer.

[zhaobin, 2017/04/21 23:12:58]

Done.

+}
+
+base::Time DeviceDescriptionService::GetNow() {

[mark a. foltz, 2017/04/18 18:16:26]

Is this for unit testing?

[zhaobin, 2017/04/21 23:12:58]

Yes.

+  return base::Time::Now();
+}
+
+void DeviceDescriptionService::FetchDeviceDescription(
+    const DialDeviceData& device_data,
+    net::URLRequestContextGetter* request_context) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  auto device_description_fetcher = base::MakeUnique<DeviceDescriptionFetcher>(
+      device_data.device_description_url(), request_context,
+      base::BindOnce(
+          &DeviceDescriptionService::OnDeviceDescriptionFetchComplete,
+          base::Unretained(this), device_data),
+      base::BindOnce(&DeviceDescriptionService::OnDeviceDescriptionFetchError,
+                     base::Unretained(this), device_data));
+
+  device_description_fetcher->Start();
+  device_description_fetcher_map_.insert(std::make_pair(
+      device_data.label(), std::move(device_description_fetcher)));
+}
+
+const DeviceDescriptionService::CacheEntry*
+DeviceDescriptionService::CheckAndUpdateCache(
+    const DialDeviceData& device_data) {
+  const auto& it = description_map_.find(device_data.label());
+  if (it == description_map_.end())
+    return nullptr;
+
+  // If the entry's config_id does not match, or it has expired, remove it.
+  if (it->second.config_id != device_data.config_id() ||
+      GetNow() >= it->second.expire_time) {
+    DVLOG(2) << "Removing invalid entry " << it->first;
+    description_map_.erase(it);
+    return nullptr;
+  }
+
+  // Entry is valid.
+  return &it->second;
+}
+
+void DeviceDescriptionService::OnParsedDeviceDescription(
+    const DialDeviceData& device_data,
+    const GURL& app_url,
+    chrome::mojom::DialDeviceDescriptionPtr parsed_device_description) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  // Last callback for current utility process. Release |parser_| and
+  // SafeDialDeviceDescriptionParser object will be destroyed after this
+  // callback.
+  if (parser_ && parser_->GetPendingParsingRequests() == 0)

[mark a. foltz, 2017/04/18 18:16:26]

For a given list of devices, is it possible for one parse to complete before the
next one starts (because a HTTP request returned late)?  We may want to keep the
process alive until all fetches return, or move this check to the three second
timer in dial_media_sink_service.

[zhaobin, 2017/04/21 23:12:57]

Done.

+    parser_ = nullptr;
+
+  if (!parsed_device_description) {
+    error_cb_.Run(device_data, "Failed to parse device description xml");
+    return;
+  }
+
+  ParsedDialDeviceDescription description_data;
+  description_data.unique_id = parsed_device_description->unique_id;
+  description_data.friendly_name = parsed_device_description->friendly_name;
+  description_data.model_name = parsed_device_description->model_name;
+  description_data.app_url = app_url;
+
+  auto error = ValidateParsedDeviceDescription(
+      device_data.device_description_url().host(), description_data);
+
+  if (error != ErrorType::NONE) {
+    DLOG(WARNING) << "Device description failed to validate: " << error;
+    error_cb_.Run(device_data, "Failed to process fetch result");
+    return;
+  }
+
+  CacheEntry cached_description_data;
+  cached_description_data.expire_time =
+      GetNow() +
+      base::TimeDelta::FromMilliseconds(kDeviceDescriptionCacheTimeMillis);

[mark a. foltz, 2017/04/18 18:16:26]

Can you convert the cache timeout constant to use minutes (to be consistent with
the timer interval constant)?

[zhaobin, 2017/04/21 23:12:58]

Done.

+  cached_description_data.config_id = device_data.config_id();
+  cached_description_data.description_data = description_data;
+
+  DVLOG(2) << "Got device description for " << device_data.label()
+           << "... device description was: "
+           << CachedDeviceDescriptionToString(cached_description_data);
+
+  // Stick it in the cache if the description has a config (version) id.
+  // NOTE: We could cache descriptions without a config id and rely on the

[mark a. foltz, 2017/04/18 18:16:26]

Yes we should do this, to avoid repeatedly requesting descriptions from devices
that don't set a config id.

[zhaobin, 2017/04/21 23:12:58]

Done.

+  // timeout to eventually update the cache.
+  if (description_map_.size() < kCacheLimit &&

[mark a. foltz, 2017/04/18 18:16:26]

If the cache size limit has been hit, you can early return with description_data
without having to set up a cache entry.

[zhaobin, 2017/04/21 23:12:57]

Done.

+      cached_description_data.config_id) {
+    DVLOG(2) << "Caching device description for " << device_data.label();
+    description_map_.insert(
+        std::make_pair(device_data.label(), cached_description_data));
+  }
+
+  success_cb_.Run(device_data, description_data);
+}
+
+void DeviceDescriptionService::OnDeviceDescriptionFetchComplete(
+    const DialDeviceData& device_data,
+    const DialDeviceDescriptionData& description_data) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  if (!parser_)
+    parser_ = new SafeDialDeviceDescriptionParser();
+
+  parser_->Start(
+      description_data.device_description,
+      base::Bind(&DeviceDescriptionService::OnParsedDeviceDescription,
+                 base::Unretained(this), device_data,
+                 description_data.app_url));
+
+  DVLOG(2) << "Device description: "
+           << ScrubDeviceDescriptionXml(description_data.device_description);
+  device_description_fetcher_map_.erase(device_data.label());
+}
+
+void DeviceDescriptionService::OnDeviceDescriptionFetchError(
+    const DialDeviceData& device_data,
+    const std::string& error_message) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DVLOG(2) << "OnDeviceDescriptionFetchError [label]: " << device_data.label();
+
+  error_cb_.Run(device_data, error_message);
+  device_description_fetcher_map_.erase(device_data.label());
+}
+
+DeviceDescriptionService::CacheEntry::CacheEntry() : config_id(-1) {}
+DeviceDescriptionService::CacheEntry::CacheEntry(const CacheEntry& other) =
+    default;
+DeviceDescriptionService::CacheEntry::~CacheEntry() = default;
+
+}  // namespace media_router