[net/dns] Serve requests from HOSTS file if possible.

net/base/host_resolver_impl.cc

Index: net/base/host_resolver_impl.cc
diff --git a/net/base/host_resolver_impl.cc b/net/base/host_resolver_impl.cc
index ecbbd582a75879344fd00f2818483e55c5100466..d1f30855b7bbf5c98bdbb0e2a7776c4f4b750ae2 100644
--- a/net/base/host_resolver_impl.cc
+++ b/net/base/host_resolver_impl.cc
@@ -1205,6 +1205,17 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
                      base::TimeDelta());
   }
 
+  // Attempt to serve the job from hosts.
+  void ServeFromHosts() {

[szym, 2012/03/10 06:48:49]

Add a bool return so that the caller knows if this Job was destroyed or not.

+    DCHECK_GT(num_active_requests(), 0u);
+    AddressList addr_list;
+    if (resolver_->ServeFromHosts(key(),
+                                  requests_.front()->info(),
+                                  &addr_list)) {
+      CompleteRequests(OK, addr_list, base::TimeDelta());
+    }
+  }
+
  private:
   RequestPriority priority() const {
     return priority_tracker_.highest_priority();
@@ -1292,6 +1303,10 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
 
     if (net_error != OK) {
       dns_task_.reset();
+
+      // TODO(szym): Run ServeFromHosts now if nsswitch.conf says so.
+      // http://crbug.com/117655
+
       // TODO(szym): Some net errors indicate lack of connectivity. Starting
       // ProcTask in that case is a waste of time.
       StartProcTask();
@@ -1344,9 +1359,11 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB,
                                       net_error);
 
+    DCHECK(!requests_.empty());
+
     // We are the only consumer of |list|, so we can safely change the port
     // without copy-on-write. This pays off, when job has only one request.
-    if (net_error == OK && !requests_.empty())
+    if (net_error == OK)
       MutableSetPort(requests_.front()->info().port(), &list);
 
     if ((net_error != ERR_ABORTED) &&
@@ -1552,9 +1569,17 @@ int HostResolverImpl::ResolveHelper(const Key& key,
   int net_error = ERR_UNEXPECTED;
   if (ResolveAsIP(key, info, &net_error, addresses))
     return net_error;
-  net_error = ERR_DNS_CACHE_MISS;
-  ServeFromCache(key, info, request_net_log, &net_error, addresses);
-  return net_error;
+  if (ServeFromCache(key, info, &net_error, addresses)) {
+    request_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_CACHE_HIT, NULL);
+    return net_error;
+  }
+  // TODO(szym): Do not do this if nsswitch.conf instructs not to.
+  // http://crbug.com/117655
+  if (ServeFromHosts(key, info, addresses)) {
+    request_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_HOSTS_HIT, NULL);
+    return OK;
+  }
+  return ERR_DNS_CACHE_MISS;
 }
 
 int HostResolverImpl::ResolveFromCache(const RequestInfo& info,
@@ -1637,7 +1662,6 @@ bool HostResolverImpl::ResolveAsIP(const Key& key,
 
 bool HostResolverImpl::ServeFromCache(const Key& key,
                                       const RequestInfo& info,
-                                      const BoundNetLog& request_net_log,
                                       int* net_error,
                                       AddressList* addresses) {
   DCHECK(addresses);
@@ -1650,13 +1674,30 @@ bool HostResolverImpl::ServeFromCache(const Key& key,
   if (!cache_entry)
     return false;
 
-  request_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_CACHE_HIT, NULL);
+
   *net_error = cache_entry->error;
   if (*net_error == OK)
     *addresses = CreateAddressListUsingPort(cache_entry->addrlist, info.port());
   return true;
 }
 
+bool HostResolverImpl::ServeFromHosts(const Key& key,
+                                      const RequestInfo& info,
+                                      AddressList* addresses) {
+  DCHECK(addresses);
+  if (!dns_session_)
+    return false;
+
+  const DnsHosts& hosts = dns_session_->config().hosts;
+  DnsHosts::const_iterator it = hosts.find(DnsHostsKey(key.hostname,
+                                                       key.address_family));
+  if (it == hosts.end())
+    return false;
+
+  *addresses = AddressList::CreateFromIPAddress(it->second, info.port());
+  return true;
+}
+
 void HostResolverImpl::CacheResult(const Key& key,
                                    int net_error,
                                    const AddressList& addr_list,
@@ -1734,6 +1775,20 @@ void HostResolverImpl::AbortAllInProgressJobs() {
   }
 }
 
+void HostResolverImpl::TryServingAllJobsFromHosts() {
+  if (!dns_session_)
+    return;
+
+  // TODO(szym): Do not do this if nsswitch.conf instructs not to.
+  // http://crbug.com/117655
+
+  for (JobMap::iterator it = jobs_.begin(); it != jobs_.end(); ) {
+    Job* job = (it++)->second;
+    // This could remove |job| from |jobs_|, but iterators remain valid.
+    job->ServeFromHosts();

[szym, 2012/03/10 06:48:49]

HostResolverImpl could be destroyed in Request callback. Use self health check
as in AbortAllInProgressJobs.

+  }
+}
+
 void HostResolverImpl::OnIPAddressChanged() {
   if (cache_.get())
     cache_->clear();
@@ -1771,13 +1826,17 @@ void HostResolverImpl::OnConfigChanged(const DnsConfig& dns_config) {
   // newly started jobs use the new factory.
   bool had_factory = (dns_transaction_factory_.get() != NULL);
   if (dns_config.IsValid()) {
-    dns_transaction_factory_ = DnsTransactionFactory::CreateFactory(
-        new DnsSession(dns_config,
-                       ClientSocketFactory::GetDefaultFactory(),
-                       base::Bind(&base::RandInt),
-                       net_log_));
+    dns_session_ = new DnsSession(dns_config,
+                                  ClientSocketFactory::GetDefaultFactory(),
+                                  base::Bind(&base::RandInt),
+                                  net_log_);
+    dns_transaction_factory_ =
+        DnsTransactionFactory::CreateFactory(dns_session_);
+
+    TryServingAllJobsFromHosts();
   } else {
     dns_transaction_factory_.reset();
+    dns_session_.release();
   }
   // Don't Abort running Jobs unless they were running on DnsTransaction.
   // TODO(szym): This will change once http://crbug.com/114827 is fixed.