net/dns/dns_client.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_CLIENT_H_
#define NET_DNS_DNS_CLIENT_H_

#include <memory>

#include "base/optional.h"
#include "base/time/time.h"
#include "net/base/net_export.h"
#include "net/base/rand_callback.h"
#include "net/dns/dns_config.h"
#include "net/dns/dns_hosts.h"
#include "net/dns/public/dns_config_overrides.h"

namespace net {

class AddressSorter;
class ClientSocketFactory;
class DnsSession;
class DnsTransactionFactory;
class NetLog;
class ResolveContext;

// Entry point for HostResolverManager to interact with the built-in async
// resolver, as implemented by DnsTransactionFactory. Manages configuration and
// status of the resolver.
class NET_EXPORT DnsClient {
 public:
  static const int kMaxInsecureFallbackFailures = 16;

  virtual ~DnsClient() {}

  // Returns true if the DnsClient is able and allowed to make secure DNS
  // transactions and DoH probe runners. If false, secure transactions and DoH
  // probe runners should not be created.
  virtual bool CanUseSecureDnsTransactions() const = 0;

  // Returns true if the DnsClient is able and allowed to make insecure DNS
  // transactions. If false, insecure transactions should not be created. Will
  // always be false unless SetInsecureEnabled(true) has been called.
  virtual bool CanUseInsecureDnsTransactions() const = 0;
  virtual void SetInsecureEnabled(bool enabled) = 0;

  // When true, DoH should not be used in AUTOMATIC mode since no DoH servers
  // have a successful probe state.
  virtual bool FallbackFromSecureTransactionPreferred(
      ResolveContext* context) const = 0;

  // When true, insecure DNS transactions should not be used when reasonable
  // fallback alternatives, e.g. system resolution can be used instead.
  virtual bool FallbackFromInsecureTransactionPreferred() const = 0;

  // Updates DNS config.  If effective config has changed, destroys the current
  // DnsTransactionFactory and creates a new one according to the effective
  // config, unless it is invalid or has |unhandled_options|.
  //
  // Returns whether or not the effective config changed.
  virtual bool SetSystemConfig(base::Optional<DnsConfig> system_config) = 0;
  virtual bool SetConfigOverrides(DnsConfigOverrides config_overrides) = 0;

  // If there is a current session, forces replacement with a new current
  // session with the same effective config, and creates a new
  // DnsTransactionFactory for the new session.
  virtual void ReplaceCurrentSession() = 0;

  // Used for tracking per-context-per-session data.
  // TODO(crbug.com/1022059): Once more per-context-per-session data has been
  // moved to ResolveContext and it doesn't need to call back into DnsSession,
  // convert this to a more limited session handle to prevent overuse of
  // DnsSession outside the DnsClient code.
  virtual DnsSession* GetCurrentSession() = 0;

  // Retrieve the current DNS configuration that would be used if transactions
  // were otherwise currently allowed. Returns null if configuration is
  // invalid or a configuration has not yet been read from the system.
  virtual const DnsConfig* GetEffectiveConfig() const = 0;
  virtual const DnsHosts* GetHosts() const = 0;

  // Returns null if the current config is not valid.
  virtual DnsTransactionFactory* GetTransactionFactory() = 0;

  virtual AddressSorter* GetAddressSorter() = 0;

  virtual void IncrementInsecureFallbackFailures() = 0;
  virtual void ClearInsecureFallbackFailures() = 0;

  virtual base::Optional<DnsConfig> GetSystemConfigForTesting() const = 0;
  virtual DnsConfigOverrides GetConfigOverridesForTesting() const = 0;

  virtual void SetTransactionFactoryForTesting(
      std::unique_ptr<DnsTransactionFactory> factory) = 0;

  // Creates default client.
  static std::unique_ptr<DnsClient> CreateClient(NetLog* net_log);

  // Creates a client for testing.  Allows using a mock ClientSocketFactory and
  // a deterministic random number generator. |socket_factory| must outlive
  // the returned DnsClient.
  static std::unique_ptr<DnsClient> CreateClientForTesting(
      NetLog* net_log,
      ClientSocketFactory* socket_factory,
      const RandIntCallback& rand_int_callback);
};

}  // namespace net

#endif  // NET_DNS_DNS_CLIENT_H_