// 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_HOST_RESOLVER_IMPL_H_
#define NET_DNS_HOST_RESOLVER_IMPL_H_
#include <map>
#include "base/basictypes.h"
#include "base/gtest_prod_util.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/scoped_vector.h"
#include "base/memory/weak_ptr.h"
#include "base/threading/non_thread_safe.h"
#include "base/time/time.h"
#include "net/base/capturing_net_log.h"
#include "net/base/net_export.h"
#include "net/base/network_change_notifier.h"
#include "net/base/prioritized_dispatcher.h"
#include "net/dns/host_cache.h"
#include "net/dns/host_resolver.h"
#include "net/dns/host_resolver_proc.h"
namespace net {
class BoundNetLog;
class DnsClient;
class NetLog;
// For each hostname that is requested, HostResolver creates a
// HostResolverImpl::Job. When this job gets dispatched it creates a ProcTask
// which runs the given HostResolverProc on a WorkerPool thread. If requests for
// that same host are made during the job's lifetime, they are attached to the
// existing job rather than creating a new one. This avoids doing parallel
// resolves for the same host.
//
// The way these classes fit together is illustrated by:
//
//
// +----------- HostResolverImpl -------------+
// | | |
// Job Job Job
// (for host1, fam1) (for host2, fam2) (for hostx, famx)
// / | | / | | / | |
// Request ... Request Request ... Request Request ... Request
// (port1) (port2) (port3) (port4) (port5) (portX)
//
// When a HostResolverImpl::Job finishes, the callbacks of each waiting request
// are run on the origin thread.
//
// Thread safety: This class is not threadsafe, and must only be called
// from one thread!
//
// The HostResolverImpl enforces limits on the maximum number of concurrent
// threads using PrioritizedDispatcher::Limits.
//
// Jobs are ordered in the queue based on their priority and order of arrival.
class NET_EXPORT HostResolverImpl
: public HostResolver,
NON_EXPORTED_BASE(public base::NonThreadSafe),
public NetworkChangeNotifier::IPAddressObserver,
public NetworkChangeNotifier::DNSObserver {
public:
// Parameters for ProcTask which resolves hostnames using HostResolveProc.
//
// |resolver_proc| is used to perform the actual resolves; it must be
// thread-safe since it is run from multiple worker threads. If
// |resolver_proc| is NULL then the default host resolver procedure is
// used (which is SystemHostResolverProc except if overridden).
//
// For each attempt, we could start another attempt if host is not resolved
// within |unresponsive_delay| time. We keep attempting to resolve the host
// for |max_retry_attempts|. For every retry attempt, we grow the
// |unresponsive_delay| by the |retry_factor| amount (that is retry interval
// is multiplied by the retry factor each time). Once we have retried
// |max_retry_attempts|, we give up on additional attempts.
//
struct NET_EXPORT_PRIVATE ProcTaskParams {
// Sets up defaults.
ProcTaskParams(HostResolverProc* resolver_proc, size_t max_retry_attempts);
~ProcTaskParams();
// The procedure to use for resolving host names. This will be NULL, except
// in the case of unit-tests which inject custom host resolving behaviors.
scoped_refptr<HostResolverProc> resolver_proc;
// Maximum number retry attempts to resolve the hostname.
// Pass HostResolver::kDefaultRetryAttempts to choose a default value.
size_t max_retry_attempts;
// This is the limit after which we make another attempt to resolve the host
// if the worker thread has not responded yet.
base::TimeDelta unresponsive_delay;
// Factor to grow |unresponsive_delay| when we re-re-try.
uint32 retry_factor;
};
// Creates a HostResolver that first uses the local cache |cache|, and then
// falls back to |proc_params.resolver_proc|.
//
// If |cache| is NULL, then no caching is used. Otherwise we take
// ownership of the |cache| pointer, and will free it during destruction.
//
// |job_limits| specifies the maximum number of jobs that the resolver will
// run at once. This upper-bounds the total number of outstanding
// DNS transactions (not counting retransmissions and retries).
//
// |net_log| must remain valid for the life of the HostResolverImpl.
HostResolverImpl(scoped_ptr<HostCache> cache,
const PrioritizedDispatcher::Limits& job_limits,
const ProcTaskParams& proc_params,
NetLog* net_log);
// If any completion callbacks are pending when the resolver is destroyed,
// the host resolutions are cancelled, and the completion callbacks will not
// be called.
virtual ~HostResolverImpl();
// Configures maximum number of Jobs in the queue. Exposed for testing.
// Only allowed when the queue is empty.
void SetMaxQueuedJobs(size_t value);
// Set the DnsClient to be used for resolution. In case of failure, the
// HostResolverProc from ProcTaskParams will be queried. If the DnsClient is
// not pre-configured with a valid DnsConfig, a new config is fetched from
// NetworkChangeNotifier.
void SetDnsClient(scoped_ptr<DnsClient> dns_client);
// HostResolver methods:
virtual int Resolve(const RequestInfo& info,
RequestPriority priority,
AddressList* addresses,
const CompletionCallback& callback,
RequestHandle* out_req,
const BoundNetLog& source_net_log) OVERRIDE;
virtual int ResolveFromCache(const RequestInfo& info,
AddressList* addresses,
const BoundNetLog& source_net_log) OVERRIDE;
virtual void CancelRequest(RequestHandle req) OVERRIDE;
virtual void SetDefaultAddressFamily(AddressFamily address_family) OVERRIDE;
virtual AddressFamily GetDefaultAddressFamily() const OVERRIDE;
virtual void SetDnsClientEnabled(bool enabled) OVERRIDE;
virtual HostCache* GetHostCache() OVERRIDE;
virtual base::Value* GetDnsConfigAsValue() const OVERRIDE;
private:
friend class HostResolverImplTest;
class Job;
class ProcTask;
class LoopbackProbeJob;
class DnsTask;
class Request;
typedef HostCache::Key Key;
typedef std::map<Key, Job*> JobMap;
typedef ScopedVector<Request> RequestsList;
// Number of consecutive failures of DnsTask (with successful fallback to
// ProcTask) before the DnsClient is disabled until the next DNS change.
static const unsigned kMaximumDnsFailures;
// Helper used by |Resolve()| and |ResolveFromCache()|. Performs IP
// literal, cache and HOSTS lookup (if enabled), returns OK if successful,
// ERR_NAME_NOT_RESOLVED if either hostname is invalid or IP literal is
// incompatible, ERR_DNS_CACHE_MISS if entry was not found in cache and HOSTS.
int ResolveHelper(const Key& key,
const RequestInfo& info,
AddressList* addresses,
const BoundNetLog& request_net_log);
// Tries to resolve |key| as an IP, returns true and sets |net_error| if
// succeeds, returns false otherwise.
bool ResolveAsIP(const Key& key,
const RequestInfo& info,
int* net_error,
AddressList* addresses);
// If |key| is not found in cache returns false, otherwise returns
// true, sets |net_error| to the cached error code and fills |addresses|
// if it is a positive entry.
bool ServeFromCache(const Key& key,
const RequestInfo& info,
int* net_error,
AddressList* addresses);
// If we have a DnsClient with a valid DnsConfig, and |key| is found in the
// HOSTS file, returns true and fills |addresses|. Otherwise returns false.
bool ServeFromHosts(const Key& key,
const RequestInfo& info,
AddressList* addresses);
// Callback from HaveOnlyLoopbackAddresses probe.
void SetHaveOnlyLoopbackAddresses(bool result);
// Returns the (hostname, address_family) key to use for |info|, choosing an
// "effective" address family by inheriting the resolver's default address
// family when the request leaves it unspecified.
Key GetEffectiveKeyForRequest(const RequestInfo& info,
const BoundNetLog& net_log) const;
// Records the result in cache if cache is present.
void CacheResult(const Key& key,
const HostCache::Entry& entry,
base::TimeDelta ttl);
// Removes |job| from |jobs_|, only if it exists.
void RemoveJob(Job* job);
// Aborts all in progress jobs with ERR_NETWORK_CHANGED and notifies their
// requests. Might start new jobs.
void AbortAllInProgressJobs();
// Aborts all in progress DnsTasks. In-progress jobs will fall back to
// ProcTasks. Might start new jobs, if any jobs were taking up two dispatcher
// slots.
void AbortDnsTasks();
// Attempts to serve each Job in |jobs_| from the HOSTS file if we have
// a DnsClient with a valid DnsConfig.
void TryServingAllJobsFromHosts();
// NetworkChangeNotifier::IPAddressObserver:
virtual void OnIPAddressChanged() OVERRIDE;
// NetworkChangeNotifier::DNSObserver:
virtual void OnDNSChanged() OVERRIDE;
// True if have a DnsClient with a valid DnsConfig.
bool HaveDnsConfig() const;
// Called when a host name is successfully resolved and DnsTask was run on it
// and resulted in |net_error|.
void OnDnsTaskResolve(int net_error);
// Allows the tests to catch slots leaking out of the dispatcher. One
// HostResolverImpl::Job could occupy multiple PrioritizedDispatcher job
// slots.
size_t num_running_dispatcher_jobs_for_tests() const {
return dispatcher_.num_running_jobs();
}
// Cache of host resolution results.
scoped_ptr<HostCache> cache_;
// Map from HostCache::Key to a Job.
JobMap jobs_;
// Starts Jobs according to their priority and the configured limits.
PrioritizedDispatcher dispatcher_;
// Limit on the maximum number of jobs queued in |dispatcher_|.
size_t max_queued_jobs_;
// Parameters for ProcTask.
ProcTaskParams proc_params_;
NetLog* net_log_;
// Address family to use when the request doesn't specify one.
AddressFamily default_address_family_;
base::WeakPtrFactory<HostResolverImpl> weak_ptr_factory_;
base::WeakPtrFactory<HostResolverImpl> probe_weak_ptr_factory_;
// If present, used by DnsTask and ServeFromHosts to resolve requests.
scoped_ptr<DnsClient> dns_client_;
// True if received valid config from |dns_config_service_|. Temporary, used
// to measure performance of DnsConfigService: http://crbug.com/125599
bool received_dns_config_;
// Number of consecutive failures of DnsTask, counted when fallback succeeds.
unsigned num_dns_failures_;
// True if probing is done for each Request to set address family. When false,
// explicit setting in |default_address_family_| is used.
bool probe_ipv6_support_;
// True if DnsConfigService detected that system configuration depends on
// local IPv6 connectivity. Disables probing.
bool use_local_ipv6_;
// True iff ProcTask has successfully resolved a hostname known to have IPv6
// addresses using ADDRESS_FAMILY_UNSPECIFIED. Reset on IP address change.
bool resolved_known_ipv6_hostname_;
// Any resolver flags that should be added to a request by default.
HostResolverFlags additional_resolver_flags_;
// Allow fallback to ProcTask if DnsTask fails.
bool fallback_to_proctask_;
DISALLOW_COPY_AND_ASSIGN(HostResolverImpl);
};
} // namespace net
#endif // NET_DNS_HOST_RESOLVER_IMPL_H_