Add a Dns preresolve interface in //content

chrome/browser/net/predictor.cc

 // Copyright (c) 2012 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/net/predictor.h"
 
 #include <algorithm>
 #include <cmath>
 #include <set>
 #include <sstream>
@@ skipping 86 matching lines @@
 
 static int g_max_queueing_delay_ms =
     Predictor::kMaxSpeculativeResolveQueueDelayMs;
 static size_t g_max_parallel_resolves =
     Predictor::kMaxSpeculativeParallelResolves;
 
 // A version number for prefs that are saved. This should be incremented when
 // we change the format so that we discard old data.
 static const int kPredictorStartupFormatVersion = 1;
 
-class Predictor::LookupRequest {
- public:
-  LookupRequest(Predictor* predictor,
-                net::HostResolver* host_resolver,
-                const GURL& url)
-      : predictor_(predictor),
-        url_(url),
-        resolver_(host_resolver) {
-  }
-
-  // Return underlying network resolver status.
-  // net::OK ==> Host was found synchronously.
-  // net:ERR_IO_PENDING ==> Network will callback later with result.
-  // anything else ==> Host was not found synchronously.
-  int Start() {
-    net::HostResolver::RequestInfo resolve_info(
-        net::HostPortPair::FromURL(url_));
-
-    // Make a note that this is a speculative resolve request. This allows us
-    // to separate it from real navigations in the observer's callback, and
-    // lets the HostResolver know it can de-prioritize it.
-    resolve_info.set_is_speculative(true);
-    return resolver_.Resolve(
-        resolve_info,
-        net::DEFAULT_PRIORITY,
-        &addresses_,
-        base::Bind(&LookupRequest::OnLookupFinished, base::Unretained(this)),
-        net::BoundNetLog());
-  }
-
- private:
-  void OnLookupFinished(int result) {
-    predictor_->OnLookupFinished(this, url_, result == net::OK);
-  }
-
-  Predictor* predictor_;  // The predictor which started us.
-
-  const GURL url_;  // Hostname to resolve.
-  net::SingleRequestHostResolver resolver_;
-  net::AddressList addresses_;
-
-  DISALLOW_COPY_AND_ASSIGN(LookupRequest);
-};
-
 Predictor::Predictor(bool preconnect_enabled, bool predictor_enabled)
     : url_request_context_getter_(NULL),
       predictor_enabled_(predictor_enabled),
       user_prefs_(NULL),
       profile_io_data_(NULL),
+      num_pending_lookups_(0),
       peak_pending_lookups_(0),
       shutdown_(false),
       max_concurrent_dns_lookups_(g_max_parallel_resolves),
       max_dns_queue_delay_(
           TimeDelta::FromMilliseconds(g_max_queueing_delay_ms)),
-      host_resolver_(NULL),
       transport_security_state_(NULL),
       ssl_config_service_(NULL),
       proxy_service_(NULL),
       preconnect_enabled_(preconnect_enabled),
       consecutive_omnibox_preconnect_count_(0),
       next_trim_time_(base::TimeTicks::Now() +
                       TimeDelta::FromHours(kDurationBetweenTrimmingsHours)),
       observer_(NULL) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 }
@@ skipping 219 matching lines @@
 }
 
 // ---------------------- End UI methods. -------------------------------------
 
 // --------------------- Start IO methods. ------------------------------------
 
 void Predictor::Shutdown() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DCHECK(!shutdown_);
   shutdown_ = true;
-
-  STLDeleteElements(&pending_lookups_);
 }
 
 void Predictor::DiscardAllResults() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   // Delete anything listed so far in this session that shows in about:dns.
   referrers_.clear();
 
 
   // Try to delete anything in our work queue.
   while (!work_queue_.IsEmpty()) {
     // Emulate processing cycle as though host was not found.
     GURL url = work_queue_.Pop();
     UrlInfo* info = &results_[url];
     DCHECK(info->HasUrl(url));
     info->SetAssignedState();
     info->SetNoSuchNameState();
   }
-  // Now every result_ is either resolved, or is being resolved
-  // (see LookupRequest).
+  // Now every result_ is either resolved, or is being resolved.
 
   // Step through result_, recording names of all hosts that can't be erased.
   // We can't erase anything being worked on.
   Results assignees;
   for (Results::iterator it = results_.begin(); results_.end() != it; ++it) {
     GURL url(it->first);
     UrlInfo* info = &it->second;
     DCHECK(info->HasUrl(url));
     if (info->is_assigned()) {
       info->SetPendingDeleteState();
@@ skipping 254 matching lines @@
 
 void Predictor::FinalizeInitializationOnIOThread(
     const UrlList& startup_urls,
     base::ListValue* referral_list,
     IOThread* io_thread,
     ProfileIOData* profile_io_data) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
   profile_io_data_ = profile_io_data;
   initial_observer_.reset(new InitialObserver());
-  host_resolver_ = io_thread->globals()->host_resolver.get();
 
   net::URLRequestContext* context =
       url_request_context_getter_->GetURLRequestContext();
   transport_security_state_ = context->transport_security_state();
   ssl_config_service_ = context->ssl_config_service();
   proxy_service_ = context->proxy_service();
 
   // base::WeakPtrFactory instances need to be created and destroyed
   // on the same thread. The predictor lives on the IO thread and will die
   // from there so now that we're on the IO thread we need to properly
@@ skipping 162 matching lines @@
 void Predictor::PreconnectUrlOnIOThread(
     const GURL& original_url,
     const GURL& first_party_for_cookies,
     UrlInfo::ResolutionMotivation motivation,
     bool allow_credentials,
     int count) {
   // Skip the HSTS redirect.
   GURL url = GetHSTSRedirectOnIOThread(original_url);
 
   // TODO(csharrison): The observer should only be notified after the null check
-  // for the URLRequestContextGetter. The predictor tests should be fixed to
-  // allow for this, as they currently expect a callback with no getter.
-  // URLRequestContextGetter is null. Tests rely on this behavior.
+  // for the ProfileIOData. The predictor tests should be fixed to allow for
+  // this, as they currently expect a callback with no getter.
   if (observer_) {
     observer_->OnPreconnectUrl(
         url, first_party_for_cookies, motivation, count);
   }
 
-  net::URLRequestContextGetter* getter = url_request_context_getter_.get();
-  if (!getter)
+  if (!profile_io_data_)
     return;
 
   // Translate the motivation from UrlRequest motivations to HttpRequest
   // motivations.
   net::HttpRequestInfo::RequestMotivation request_motivation =
       net::HttpRequestInfo::NORMAL_MOTIVATION;
   switch (motivation) {
     case UrlInfo::OMNIBOX_MOTIVATED:
       request_motivation = net::HttpRequestInfo::OMNIBOX_MOTIVATED;
       break;
     case UrlInfo::LEARNED_REFERAL_MOTIVATED:
       request_motivation = net::HttpRequestInfo::PRECONNECT_MOTIVATED;
       break;
     case UrlInfo::MOUSE_OVER_MOTIVATED:
     case UrlInfo::SELF_REFERAL_MOTIVATED:
     case UrlInfo::EARLY_LOAD_MOTIVATED:
       request_motivation = net::HttpRequestInfo::EARLY_LOAD_MOTIVATED;
       break;
     default:
       // Other motivations should never happen here.
       NOTREACHED();
       break;
   }
   UMA_HISTOGRAM_ENUMERATION("Net.PreconnectMotivation", motivation,
                             UrlInfo::MAX_MOTIVATED);
-  content::PreconnectUrl(getter, url, first_party_for_cookies, count,
-                         allow_credentials, request_motivation);
+  content::PreconnectUrl(profile_io_data_->GetResourceContext(), url,
+                         first_party_for_cookies, count, allow_credentials,
+                         request_motivation);
 }
 
 void Predictor::PredictFrameSubresources(const GURL& url,
                                          const GURL& first_party_for_cookies) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI) ||
          BrowserThread::CurrentlyOn(BrowserThread::IO));
   if (!predictor_enabled_)
     return;
   if (!CanPreresolveAndPreconnect())
     return;
@@ skipping 90 matching lines @@
       UrlInfo* queued_info = AppendToResolutionQueue(future_url->first,
                                                      motivation);
       if (queued_info)
         queued_info->SetReferringHostname(url);
     }
     UMA_HISTOGRAM_ENUMERATION("Net.PreconnectSubresourceEval", evalution,
                               SUBRESOURCE_VALUE_MAX);
   }
 }
 
-void Predictor::OnLookupFinished(LookupRequest* request, const GURL& url,
-                                 bool found) {
+void Predictor::OnLookupFinished(const GURL& url, int result) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
-  LookupFinished(request, url, found);
-  pending_lookups_.erase(request);
-  delete request;
-
+  LookupFinished(url, result == net::OK);
+  DCHECK_GT(num_pending_lookups_, 0u);
+  num_pending_lookups_--;
   StartSomeQueuedResolutions();
 }
 
-void Predictor::LookupFinished(LookupRequest* request, const GURL& url,
-                               bool found) {
+void Predictor::LookupFinished(const GURL& url, bool found) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   UrlInfo* info = &results_[url];
   DCHECK(info->HasUrl(url));
   if (info->is_marked_to_delete()) {
     results_.erase(url);
   } else {
     if (found)
       info->SetFoundState();
     else
       info->SetNoSuchNameState();
@@ skipping 59 matching lines @@
       break;
     info = &results_[work_queue_.Pop()];
     info->SetAssignedState();
   }
   return true;
 }
 
 void Predictor::StartSomeQueuedResolutions() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
-  // If the queue is disabled, just make LookupRequests for all entries.
+  // If the queue is disabled, just make requests for all entries.
   bool enable_queue = base::FeatureList::IsEnabled(kUsePredictorDNSQueue);
-  while (!work_queue_.IsEmpty() &&
-         (!enable_queue ||
-          pending_lookups_.size() < max_concurrent_dns_lookups_)) {
+  while (
+      !work_queue_.IsEmpty() &&
+      (!enable_queue || num_pending_lookups_ < max_concurrent_dns_lookups_)) {
     const GURL url(work_queue_.Pop());
     UrlInfo* info = &results_[url];
     DCHECK(info->HasUrl(url));
     info->SetAssignedState();
 
     // Only perform congestion control if the queue is enabled.
     if (enable_queue && CongestionControlPerformed(info)) {
       DCHECK(work_queue_.IsEmpty());
       return;
     }
 
-    LookupRequest* request = new LookupRequest(this, host_resolver_, url);
-
-    int status = request->Start();
+    int status = content::PreresolveUrl(
+        profile_io_data_->GetResourceContext(), url,
+        base::Bind(&Predictor::OnLookupFinished, base::Unretained(this), url));

[kinuko, 2016/05/24 09:15:27]

Who guarantees the callback is called while |this| is alive?

[Charlie Harrison, 2016/05/24 13:14:22]

Good question. The semantics shouldn't be changed from the previous version of
the code, and in fact we do see a small amount of crashes for OnLookupFinished
today. I filed crbug.com/614350 that hopefully this patch will fix.

I'm not sure what the best way to fix it is. Possibly we could add an
intermediate object scoped to the callback that is notified of predictor
destruction. I'd hate to add that after we've removed the LookupRequest here
though :(.

[kinuko, 2016/05/24 14:38:34]

If we just want to disallow running the callback when |this| gets destructed we
could possibly just use weak ptr here (and in the other place too)..?  (Note
that I'm naively writing this without looking into the detailed object
relationship around this code)

[Charlie Harrison, 2016/05/24 16:06:36]

That works :) I scanned through the ownership and it all looks good. The only
thing we mutate in OnLookupFinished is the results_ map which should be
destructed fine when the Predictor goes away. Thanks for the suggestion.

     if (status == net::ERR_IO_PENDING) {
       // Will complete asynchronously.
-      pending_lookups_.insert(request);
-      peak_pending_lookups_ = std::max(peak_pending_lookups_,
-                                       pending_lookups_.size());
+      num_pending_lookups_++;
+      peak_pending_lookups_ =
+          std::max(peak_pending_lookups_, num_pending_lookups_);
     } else {
       // Completed synchronously (was already cached by HostResolver), or else
       // there was (equivalently) some network error that prevents us from
       // finding the name.  Status net::OK means it was "found."
-      LookupFinished(request, url, status == net::OK);
-      delete request;
+      LookupFinished(url, status == net::OK);
     }
   }
 }
 
 void Predictor::TrimReferrers() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!urls_being_trimmed_.empty())
     return;   // There is incremental trimming in progress already.
 
   // Check to see if it is time to trim yet.
@@ skipping 201 matching lines @@
 }
 
 void SimplePredictor::ShutdownOnUIThread() {
   SetShutdown(true);
 }
 
 bool SimplePredictor::CanPrefetchAndPrerender() const { return true; }
 bool SimplePredictor::CanPreresolveAndPreconnect() const { return true; }
 
 }  // namespace chrome_browser_net