DnsClient refactoring + features (timeout, suffix search, server rotation).

net/dns/dns_session.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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_session.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/time.h"
 #include "net/base/ip_endpoint.h"
 #include "net/dns/dns_config_service.h"
 #include "net/socket/client_socket_factory.h"
 
 namespace net {
 
 DnsSession::DnsSession(const DnsConfig& config,
                        ClientSocketFactory* factory,
                        const RandIntCallback& rand_int_callback,
                        NetLog* net_log)
     : config_(config),
       socket_factory_(factory),
       rand_callback_(base::Bind(rand_int_callback, 0, kuint16max)),
       net_log_(net_log),
       server_index_(0) {
 }
 
-int DnsSession::NextId() const {
+int DnsSession::NextQueryId() const {
   return rand_callback_.Run();
 }
 
-const IPEndPoint& DnsSession::NextServer() {
-  // TODO(szym): Rotate servers on failures.
-  const IPEndPoint& ipe = config_.nameservers[server_index_];
+int DnsSession::NextFirstServerIndex() {
+  int index = server_index_;
   if (config_.rotate)
     server_index_ = (server_index_ + 1) % config_.nameservers.size();
-  return ipe;
+  return index;
 }
 
 base::TimeDelta DnsSession::NextTimeout(int attempt) {
-  // TODO(szym): Adapt timeout to observed RTT.
-  return config_.timeout * (attempt + 1);
+  // The timeout doubles every full round (each nameserver once).
+  // TODO(szym): Adapt timeout to observed RTT. http://crbug.com/110197
+  return config_.timeout * (1 << (attempt / config_.nameservers.size()));
 }
 
 DnsSession::~DnsSession() {}
 
 }  // namespace net