src/net/dns/dns_transaction.h

// 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.

#ifndef NET_DNS_DNS_TRANSACTION_H_
#define NET_DNS_DNS_TRANSACTION_H_

#include <string>

#include "base/basictypes.h"
#include "base/callback_forward.h"
#include "base/memory/scoped_ptr.h"
#include "net/base/net_export.h"

namespace net {

class BoundNetLog;
class DnsResponse;
class DnsSession;

// DnsTransaction implements a stub DNS resolver as defined in RFC 1034.
// The DnsTransaction takes care of retransmissions, name server fallback (or
// round-robin), suffix search, and simple response validation ("does it match
// the query") to fight poisoning.
//
// Destroying DnsTransaction cancels the underlying network effort.
class NET_EXPORT_PRIVATE DnsTransaction {
 public:
  virtual ~DnsTransaction() {}

  // Returns the original |hostname|.
  virtual const std::string& GetHostname() const = 0;

  // Returns the |qtype|.
  virtual uint16 GetType() const = 0;

  // Starts the transaction. Returns the net error on synchronous failure or
  // ERR_IO_PENDING in which case the result will be passed via the callback.
  // Can be called at most once.
  virtual int Start() = 0;
};

// Creates DnsTransaction which performs asynchronous DNS search.
// It does NOT perform caching, aggregation or prioritization of transactions.
//
// Destroying the factory does NOT affect any already created DnsTransactions.
class NET_EXPORT_PRIVATE DnsTransactionFactory {
 public:
  // Called with the response or NULL if no matching response was received.
  // Note that the |GetDottedName()| of the response may be different than the
  // original |hostname| as a result of suffix search.
  typedef base::Callback<void(DnsTransaction* transaction,
                              int neterror,
                              const DnsResponse* response)> CallbackType;

  virtual ~DnsTransactionFactory() {}

  // Creates DnsTransaction for the given |hostname| and |qtype| (assuming
  // QCLASS is IN). |hostname| should be in the dotted form. A dot at the end
  // implies the domain name is fully-qualified and will be exempt from suffix
  // search. |hostname| should not be an IP literal.
  //
  // The transaction will run |callback| upon asynchronous completion.
  // The |net_log| is used as the parent log.
  virtual scoped_ptr<DnsTransaction> CreateTransaction(
      const std::string& hostname,
      uint16 qtype,
      const CallbackType& callback,
      const BoundNetLog& net_log) WARN_UNUSED_RESULT = 0;

  // Creates a DnsTransactionFactory which creates DnsTransactionImpl using the
  // |session|.
  static scoped_ptr<DnsTransactionFactory> CreateFactory(
      DnsSession* session) WARN_UNUSED_RESULT;
};

}  // namespace net

#endif  // NET_DNS_DNS_TRANSACTION_H_