Refactorings surrounding HostResolver:...

net/base/host_resolver_impl.cc

Index: net/base/host_resolver_impl.cc
===================================================================
--- net/base/host_resolver_impl.cc	(revision 20435)
+++ net/base/host_resolver_impl.cc	(working copy)
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "net/base/host_resolver.h"
+#include "net/base/host_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <ws2tcpip.h>
@@ -22,161 +22,36 @@
 #include "base/time.h"
 #include "base/worker_pool.h"
 #include "net/base/address_list.h"
+#include "net/base/host_resolver_proc.h"
 #include "net/base/net_errors.h"
 
-#if defined(OS_LINUX)
-#include "base/singleton.h"
-#include "base/thread_local_storage.h"
-#endif
-
 #if defined(OS_WIN)
 #include "net/base/winsock_init.h"
 #endif
 
 namespace net {
 
-//-----------------------------------------------------------------------------
-
-static HostMapper* host_mapper;
-
-std::string HostMapper::MapUsingPrevious(const std::string& host) {
-  return previous_mapper_.get() ? previous_mapper_->Map(host) : host;
+HostResolver* CreateSystemHostResolver() {
+  static const size_t kMaxHostCacheEntries = 100;
+  static const size_t kHostCacheExpirationMs = 60000;  // 1 minute.
+  return new HostResolverImpl(
+      NULL, kMaxHostCacheEntries, kHostCacheExpirationMs);
 }
 
-HostMapper* SetHostMapper(HostMapper* value) {
-  std::swap(host_mapper, value);
-  return value;
-}
-
-#if defined(OS_LINUX)
-// On Linux changes to /etc/resolv.conf can go unnoticed thus resulting in
-// DNS queries failing either because nameservers are unknown on startup
-// or because nameserver info has changed as a result of e.g. connecting to
-// a new network. Some distributions patch glibc to stat /etc/resolv.conf
-// to try to automatically detect such changes but these patches are not
-// universal and even patched systems such as Jaunty appear to need calls
-// to res_ninit to reload the nameserver information in different threads.
-//
-// We adopt the Mozilla solution here which is to call res_ninit when
-// lookups fail and to rate limit the reloading to once per second per
-// thread.
-
-// Keep a timer per calling thread to rate limit the calling of res_ninit.
-class DnsReloadTimer {
- public:
-  DnsReloadTimer() {
-    tls_index_.Initialize(SlotReturnFunction);
-  }
-
-  ~DnsReloadTimer() { }
-
-  // Check if the timer for the calling thread has expired. When no
-  // timer exists for the calling thread, create one.
-  bool Expired() {
-    const base::TimeDelta kRetryTime = base::TimeDelta::FromSeconds(1);
-    base::TimeTicks now = base::TimeTicks::Now();
-    base::TimeTicks* timer_ptr =
-      static_cast<base::TimeTicks*>(tls_index_.Get());
-
-    if (!timer_ptr) {
-      timer_ptr = new base::TimeTicks();
-      *timer_ptr = base::TimeTicks::Now();
-      tls_index_.Set(timer_ptr);
-      // Return true to reload dns info on the first call for each thread.
-      return true;
-    } else if (now - *timer_ptr > kRetryTime) {
-      *timer_ptr = now;
-      return true;
-    } else {
-      return false;
-    }
-  }
-
-  // Free the allocated timer.
-  static void SlotReturnFunction(void* data) {
-    base::TimeTicks* tls_data = static_cast<base::TimeTicks*>(data);
-    delete tls_data;
-  }
-
- private:
-  // We use thread local storage to identify which base::TimeTicks to
-  // interact with.
-  static ThreadLocalStorage::Slot tls_index_ ;
-
-  DISALLOW_COPY_AND_ASSIGN(DnsReloadTimer);
-};
-
-// A TLS slot to the TimeTicks for the current thread.
-// static
-ThreadLocalStorage::Slot DnsReloadTimer::tls_index_(base::LINKER_INITIALIZED);
-
-#endif  // defined(OS_LINUX)
-
-static int HostResolverProc(const std::string& host, struct addrinfo** out) {
-  struct addrinfo hints = {0};
-  hints.ai_family = AF_UNSPEC;
-
-#if defined(OS_WIN)
-  // DO NOT USE AI_ADDRCONFIG ON WINDOWS.
-  //
-  // The following comment in <winsock2.h> is the best documentation I found
-  // on AI_ADDRCONFIG for Windows:
-  //   Flags used in "hints" argument to getaddrinfo()
-  //       - AI_ADDRCONFIG is supported starting with Vista
-  //       - default is AI_ADDRCONFIG ON whether the flag is set or not
-  //         because the performance penalty in not having ADDRCONFIG in
-  //         the multi-protocol stack environment is severe;
-  //         this defaulting may be disabled by specifying the AI_ALL flag,
-  //         in that case AI_ADDRCONFIG must be EXPLICITLY specified to
-  //         enable ADDRCONFIG behavior
-  //
-  // Not only is AI_ADDRCONFIG unnecessary, but it can be harmful.  If the
-  // computer is not connected to a network, AI_ADDRCONFIG causes getaddrinfo
-  // to fail with WSANO_DATA (11004) for "localhost", probably because of the
-  // following note on AI_ADDRCONFIG in the MSDN getaddrinfo page:
-  //   The IPv4 or IPv6 loopback address is not considered a valid global
-  //   address.
-  // See http://crbug.com/5234.
-  hints.ai_flags = 0;
-#else
-  hints.ai_flags = AI_ADDRCONFIG;
-#endif
-
-  // Restrict result set to only this socket type to avoid duplicates.
-  hints.ai_socktype = SOCK_STREAM;
-
-  int err = getaddrinfo(host.c_str(), NULL, &hints, out);
-#if defined(OS_LINUX)
-  net::DnsReloadTimer* dns_timer = Singleton<net::DnsReloadTimer>::get();
-  // If we fail, re-initialise the resolver just in case there have been any
-  // changes to /etc/resolv.conf and retry. See http://crbug.com/11380 for info.
-  if (err && dns_timer->Expired()) {
-    res_nclose(&_res);
-    if (!res_ninit(&_res))
-      err = getaddrinfo(host.c_str(), NULL, &hints, out);
-  }
-#endif
-
-  return err ? ERR_NAME_NOT_RESOLVED : OK;
-}
-
-static int ResolveAddrInfo(HostMapper* mapper, const std::string& host,
-                           struct addrinfo** out) {
-  if (mapper) {
-    std::string mapped_host = mapper->Map(host);
-
-    if (mapped_host.empty())
-      return ERR_NAME_NOT_RESOLVED;
-
-    return HostResolverProc(mapped_host, out);
+static int ResolveAddrInfo(HostResolverProc* resolver_proc,
+                           const std::string& host, AddressList* out) {
+  if (resolver_proc) {
+    // Use the custom procedure.
+    return resolver_proc->Resolve(host, out);
   } else {
-    return HostResolverProc(host, out);
+    // Use the system procedure (getaddrinfo).
+    return SystemHostResolverProc(host, out);
   }
 }
 
 //-----------------------------------------------------------------------------
 
-class HostResolver::Request {
+class HostResolverImpl::Request {
  public:
   Request(int id, const RequestInfo& info, CompletionCallback* callback,
           AddressList* addresses)
@@ -245,28 +120,25 @@
 
 // This class represents a request to the worker pool for a "getaddrinfo()"
 // call.
-class HostResolver::Job : public base::RefCountedThreadSafe<HostResolver::Job> {
+class HostResolverImpl::Job
+    : public base::RefCountedThreadSafe<HostResolverImpl::Job> {
  public:
-  Job(HostResolver* resolver, const std::string& host)
+  Job(HostResolverImpl* resolver, const std::string& host)
       : host_(host),
         resolver_(resolver),
         origin_loop_(MessageLoop::current()),
-        host_mapper_(host_mapper),
-        error_(OK),
-        results_(NULL) {
+        resolver_proc_(resolver->effective_resolver_proc()),
+        error_(OK) {
   }
 
   ~Job() {
-    if (results_)
-      freeaddrinfo(results_);
-
     // Free the requests attached to this job.
     STLDeleteElements(&requests_);
   }
 
   // Attaches a request to this job. The job takes ownership of |req| and will
   // take care to delete it.
-  void AddRequest(HostResolver::Request* req) {
+  void AddRequest(Request* req) {
     req->set_job(this);
     requests_.push_back(req);
   }
@@ -301,11 +173,11 @@
 
     // We don't have to do anything further to actually cancel the requests
     // that were attached to this job (since they are unreachable now).
-    // But we will call HostResolver::CancelRequest(Request*) on each one
+    // But we will call HostResolverImpl::CancelRequest(Request*) on each one
     // in order to notify any observers.
     for (RequestsList::const_iterator it = requests_.begin();
          it != requests_.end(); ++it) {
-      HostResolver::Request* req = *it;
+      HostResolverImpl::Request* req = *it;
       if (!req->was_cancelled())
         resolver->CancelRequest(req);
     }
@@ -329,7 +201,7 @@
  private:
   void DoLookup() {
     // Running on the worker thread
-    error_ = ResolveAddrInfo(host_mapper_, host_, &results_);
+    error_ = ResolveAddrInfo(resolver_proc_, host_, &results_);
 
     Task* reply = NewRunnableMethod(this, &Job::OnLookupComplete);
 
@@ -353,59 +225,57 @@
     // TODO(eroman): this is being hit by URLRequestTest.CancelTest*,
     // because MessageLoop::current() == NULL.
     //DCHECK_EQ(origin_loop_, MessageLoop::current());
-    DCHECK(error_ || results_);
+    DCHECK(error_ || results_.head());
 
     if (was_cancelled())
       return;
 
     DCHECK(!requests_.empty());
 
-     // Adopt the address list using the port number of the first request.
-    AddressList addrlist;
-    if (error_ == OK) {
-      addrlist.Adopt(results_);
-      addrlist.SetPort(requests_[0]->port());
-      results_ = NULL;
-    }
+     // Use the port number of the first request.
+    if (error_ == OK)
+      results_.SetPort(requests_[0]->port());
 
-    resolver_->OnJobComplete(this, error_, addrlist);
+    resolver_->OnJobComplete(this, error_, results_);
   }
 
   // Set on the origin thread, read on the worker thread.
   std::string host_;
 
   // Only used on the origin thread (where Resolve was called).
-  HostResolver* resolver_;
+  HostResolverImpl* resolver_;
   RequestsList requests_;  // The requests waiting on this job.
 
   // Used to post ourselves onto the origin thread.
   Lock origin_loop_lock_;
   MessageLoop* origin_loop_;
 
-  // Hold an owning reference to the host mapper that we are going to use.
-  // This may not be the current host mapper by the time we call
+  // Hold an owning reference to the HostResolverProc that we are going to use.
+  // This may not be the current resolver procedure by the time we call
   // ResolveAddrInfo, but that's OK... we'll use it anyways, and the owning
   // reference ensures that it remains valid until we are done.
-  scoped_refptr<HostMapper> host_mapper_;
+  scoped_refptr<HostResolverProc> resolver_proc_;
 
   // Assigned on the worker thread, read on the origin thread.
   int error_;
-  struct addrinfo* results_;
+  AddressList results_;
 
   DISALLOW_COPY_AND_ASSIGN(Job);
 };
 
 //-----------------------------------------------------------------------------
 
-HostResolver::HostResolver(int max_cache_entries, int cache_duration_ms)
+HostResolverImpl::HostResolverImpl(HostResolverProc* resolver_proc,
+                                   int max_cache_entries,
+                                   int cache_duration_ms)
     : cache_(max_cache_entries, cache_duration_ms), next_request_id_(0),
-      shutdown_(false) {
+      resolver_proc_(resolver_proc), shutdown_(false) {
 #if defined(OS_WIN)
   EnsureWinsockInit();
 #endif
 }
 
-HostResolver::~HostResolver() {
+HostResolverImpl::~HostResolverImpl() {
   // Cancel the outstanding jobs. Those jobs may contain several attached
   // requests, which will also be cancelled.
   for (JobMap::iterator it = jobs_.begin(); it != jobs_.end(); ++it)
@@ -418,10 +288,10 @@
 
 // TODO(eroman): Don't create cache entries for hostnames which are simply IP
 // address literals.
-int HostResolver::Resolve(const RequestInfo& info,
-                          AddressList* addresses,
-                          CompletionCallback* callback,
-                          Request** out_req) {
+int HostResolverImpl::Resolve(const RequestInfo& info,
+                              AddressList* addresses,
+                              CompletionCallback* callback,
+                              RequestHandle* out_req) {
   if (shutdown_)
     return ERR_UNEXPECTED;
 
@@ -437,7 +307,7 @@
         info.hostname(), base::TimeTicks::Now());
     if (cache_entry) {
       addresses->SetFrom(cache_entry->addrlist, info.port());
-      int error = OK;
+      int error = cache_entry->error;
 
       // Notify registered observers.
       NotifyObserversFinishRequest(request_id, info, error);
@@ -448,13 +318,10 @@
 
   // If no callback was specified, do a synchronous resolution.
   if (!callback) {
-    struct addrinfo* results;
-    int error = ResolveAddrInfo(host_mapper, info.hostname(), &results);
-
-    // Adopt the address list.
     AddressList addrlist;
+    int error = ResolveAddrInfo(
+        effective_resolver_proc(), info.hostname(), &addrlist);
     if (error == OK) {
-      addrlist.Adopt(results);
       addrlist.SetPort(info.port());
       *addresses = addrlist;
     }
@@ -472,7 +339,7 @@
   // asked for it (out_req != NULL).
   Request* req = new Request(request_id, info, callback, addresses);
   if (out_req)
-    *out_req = req;
+    *out_req = reinterpret_cast<RequestHandle>(req);
 
   // Next we need to attach our request to a "job". This job is responsible for
   // calling "getaddrinfo(hostname)" on a worker thread.
@@ -499,7 +366,8 @@
 
 // See OnJobComplete(Job*) for why it is important not to clean out
 // cancelled requests from Job::requests_.
-void HostResolver::CancelRequest(Request* req) {
+void HostResolverImpl::CancelRequest(RequestHandle req_handle) {
+  Request* req = reinterpret_cast<Request*>(req_handle);
   DCHECK(req);
   DCHECK(req->job());
   // NULL out the fields of req, to mark it as cancelled.
@@ -507,11 +375,11 @@
   NotifyObserversCancelRequest(req->id(), req->info());
 }
 
-void HostResolver::AddObserver(Observer* observer) {
+void HostResolverImpl::AddObserver(Observer* observer) {
   observers_.push_back(observer);
 }
 
-void HostResolver::RemoveObserver(Observer* observer) {
+void HostResolverImpl::RemoveObserver(Observer* observer) {
   ObserversList::iterator it =
       std::find(observers_.begin(), observers_.end(), observer);
 
@@ -521,7 +389,7 @@
   observers_.erase(it);
 }
 
-void HostResolver::Shutdown() {
+void HostResolverImpl::Shutdown() {
   shutdown_ = true;
 
   // Cancel the outstanding jobs.
@@ -530,13 +398,13 @@
   jobs_.clear();
 }
 
-void HostResolver::AddOutstandingJob(Job* job) {
+void HostResolverImpl::AddOutstandingJob(Job* job) {
   scoped_refptr<Job>& found_job = jobs_[job->host()];
   DCHECK(!found_job);
   found_job = job;
 }
 
-HostResolver::Job* HostResolver::FindOutstandingJob(
+HostResolverImpl::Job* HostResolverImpl::FindOutstandingJob(
     const std::string& hostname) {
   JobMap::iterator it = jobs_.find(hostname);
   if (it != jobs_.end())
@@ -544,14 +412,14 @@
   return NULL;
 }
 
-void HostResolver::RemoveOutstandingJob(Job* job) {
+void HostResolverImpl::RemoveOutstandingJob(Job* job) {
   JobMap::iterator it = jobs_.find(job->host());
   DCHECK(it != jobs_.end());
   DCHECK_EQ(it->second.get(), job);
   jobs_.erase(it);
 }
 
-void HostResolver::OnJobComplete(Job* job,
+void HostResolverImpl::OnJobComplete(Job* job,
                                  int error,
                                  const AddressList& addrlist) {
   RemoveOutstandingJob(job);
@@ -586,7 +454,7 @@
   cur_completing_job_ = NULL;
 }
 
-void HostResolver::NotifyObserversStartRequest(int request_id,
+void HostResolverImpl::NotifyObserversStartRequest(int request_id,
                                                const RequestInfo& info) {
   for (ObserversList::iterator it = observers_.begin();
        it != observers_.end(); ++it) {
@@ -594,7 +462,7 @@
   }
 }
 
-void HostResolver::NotifyObserversFinishRequest(int request_id,
+void HostResolverImpl::NotifyObserversFinishRequest(int request_id,
                                                 const RequestInfo& info,
                                                 int error) {
   bool was_resolved = error == OK;
@@ -604,7 +472,7 @@
   }
 }
 
-void HostResolver::NotifyObserversCancelRequest(int request_id,
+void HostResolverImpl::NotifyObserversCancelRequest(int request_id,
                                                 const RequestInfo& info) {
   for (ObserversList::iterator it = observers_.begin();
        it != observers_.end(); ++it) {
@@ -612,56 +480,4 @@
   }
 }
 
-//-----------------------------------------------------------------------------
-
-SingleRequestHostResolver::SingleRequestHostResolver(HostResolver* resolver)
-    : resolver_(resolver),
-      cur_request_(NULL),
-      cur_request_callback_(NULL),
-      ALLOW_THIS_IN_INITIALIZER_LIST(
-          callback_(this, &SingleRequestHostResolver::OnResolveCompletion)) {
-  DCHECK(resolver_ != NULL);
-}
-
-SingleRequestHostResolver::~SingleRequestHostResolver() {
-  if (cur_request_) {
-    resolver_->CancelRequest(cur_request_);
-  }
-}
-
-int SingleRequestHostResolver::Resolve(const HostResolver::RequestInfo& info,
-                                       AddressList* addresses,
-                                       CompletionCallback* callback) {
-  DCHECK(!cur_request_ && !cur_request_callback_) << "resolver already in use";
-
-  HostResolver::Request* request = NULL;
-
-  // We need to be notified of completion before |callback| is called, so that
-  // we can clear out |cur_request_*|.
-  CompletionCallback* transient_callback = callback ? &callback_ : NULL;
-
-  int rv = resolver_->Resolve(info, addresses, transient_callback, &request);
-
-  if (rv == ERR_IO_PENDING) {
-    // Cleared in OnResolveCompletion().
-    cur_request_ = request;
-    cur_request_callback_ = callback;
-  }
-
-  return rv;
-}
-
-void SingleRequestHostResolver::OnResolveCompletion(int result) {
-  DCHECK(cur_request_ && cur_request_callback_);
-
-  CompletionCallback* callback = cur_request_callback_;
-
-  // Clear the outstanding request information.
-  cur_request_ = NULL;
-  cur_request_callback_ = NULL;
-
-  // Call the user's original callback.
-  callback->Run(result);
-}
-
 }  // namespace net