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

net/dns/dns_session.cc

Index: net/dns/dns_session.cc
diff --git a/net/dns/dns_session.cc b/net/dns/dns_session.cc
index 15cbaa209a4eb81752df970af11dd31c60cda27c..6b2d02b27cdacb95c502cb420797ab817373468d 100644
--- a/net/dns/dns_session.cc
+++ b/net/dns/dns_session.cc
@@ -24,21 +24,21 @@ DnsSession::DnsSession(const DnsConfig& config,
       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) {
+  // The timeout doubles every full round (each nameserver once).
   // TODO(szym): Adapt timeout to observed RTT.
-  return config_.timeout * (attempt + 1);
+  return config_.timeout * (1 << (attempt / config_.nameservers.size()));
 }
 
 DnsSession::~DnsSession() {}