[net] HostResolverImpl + DnsTransaction + DnsConfigService = Asynchronous DNS ready for experiments.

net/dns/dns_transaction.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 "net/dns/dns_transaction.h"
 
 #include <deque>
 #include <string>
 #include <vector>
 
@@ skipping 193 matching lines @@
                          base::Bind(&DnsUDPAttempt::OnIOComplete,
                                     base::Unretained(this)));
   }
 
   int DoReadResponseComplete(int rv) {
     DCHECK_NE(ERR_IO_PENDING, rv);
     if (rv < 0)
       return rv;
 
     DCHECK(rv);
+    // TODO(szym): Consider making this check less aggressive.
+    // Other implementations simply ignore mismatched responses.
     if (!response_->InitParse(rv, *query_))
       return ERR_DNS_MALFORMED_RESPONSE;
     if (response_->flags() & dns_protocol::kFlagTC)
       return ERR_DNS_SERVER_REQUIRES_TCP;
     if (response_->rcode() != dns_protocol::kRcodeNOERROR &&
         response_->rcode() != dns_protocol::kRcodeNXDOMAIN) {
       return ERR_DNS_SERVER_FAILED;
     }
     if (response_->answer_count() == 0)
       return ERR_NAME_NOT_RESOLVED;
@@ skipping 304 matching lines @@
 
 // static
 scoped_ptr<DnsTransactionFactory> DnsTransactionFactory::CreateFactory(
     DnsSession* session) {
   return scoped_ptr<DnsTransactionFactory>(
       new DnsTransactionFactoryImpl(session));
 }
 
 }  // namespace net