HostResolverImpl will return ERR_NAME_NOT_RESOLVED instead of Ok if address list is empty

net/dns/host_resolver_impl.cc

Index: net/dns/host_resolver_impl.cc
diff --git a/net/dns/host_resolver_impl.cc b/net/dns/host_resolver_impl.cc
index 0aed70d6b75deb230261d520cd742f2f9bcb3ea1..e7f7d4b9e867e063fda96a4ba03e24f29c9d5a6c 100644
--- a/net/dns/host_resolver_impl.cc
+++ b/net/dns/host_resolver_impl.cc
@@ -682,7 +682,11 @@ class HostResolverImpl::ProcTask
                         int error,
                         const int os_error) {
     DCHECK(origin_loop_->BelongsToCurrentThread());
-    DCHECK(error || !results.empty());
+    // If results are empty, we should return an error.
+    bool empty_list_on_ok = (error == OK && results.empty());
+    UMA_HISTOGRAM_BOOLEAN("DNS.EmptyAddressListAndNoError1", empty_list_on_ok);
+    if (empty_list_on_ok)
+      error = ERR_NAME_NOT_RESOLVED;
 
     bool was_retry_attempt = attempt_number > 1;
 
@@ -1437,6 +1441,11 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
       }
     }
 
+    bool empty_list_on_ok = (net_error == OK && addr_list.empty());

[szym, 2013/05/06 20:07:02]

As I pointed out before, I don't think this can ever be true.

In line 689 you overwrite |error|. OnProcTaskComplete is actually called in line
745 (via callback_.Run) with the overwritten value.

My suggestion was to remove it from here entirely and leave it in
OnLookupComplete only.

[mef, 2013/05/07 14:53:40]

Done. I left it here because my previous experiment with unit test showed it to
be effective, but I guess it was done after I removed DCHECK but before I've
added the same logic to OnLookupComplete.

On 2013/05/06 20:07:02, szym wrote:

+    UMA_HISTOGRAM_BOOLEAN("DNS.EmptyAddressListAndNoError2", empty_list_on_ok);
+    if (empty_list_on_ok)
+      net_error = ERR_NAME_NOT_RESOLVED;
+
     if (dns_task_error_ != OK) {
       base::TimeDelta duration = base::TimeTicks::Now() - start_time;
       if (net_error == OK) {