path: root/netwerk/dns/nsHostResolver.h

/* vim:set ts=4 sw=2 sts=2 et cin: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef nsHostResolver_h__
#define nsHostResolver_h__

#include "nscore.h"
#include "prnetdb.h"
#include "PLDHashTable.h"
#include "mozilla/CondVar.h"
#include "mozilla/DataMutex.h"
#include "mozilla/Mutex.h"
#include "nsISupportsImpl.h"
#include "nsIDNSListener.h"
#include "nsIDNSService.h"
#include "nsTArray.h"
#include "GetAddrInfo.h"
#include "mozilla/net/DNS.h"
#include "mozilla/net/DashboardTypes.h"
#include "mozilla/AtomicBitfields.h"
#include "mozilla/Atomics.h"
#include "mozilla/LinkedList.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/UniquePtr.h"
#include "nsRefPtrHashtable.h"
#include "nsIThreadPool.h"
#include "mozilla/net/NetworkConnectivityService.h"
#include "nsIDNSByTypeRecord.h"
#include "mozilla/net/DNSByTypeRecord.h"
#include "mozilla/Maybe.h"

class nsHostResolver;
class nsResolveHostCallback;
namespace mozilla {
namespace net {
class TRR;
class TRRQuery;
enum ResolverMode {
  MODE_NATIVEONLY,  // 0 - TRR OFF (by default)
  MODE_RESERVED1,   // 1 - Reserved value. Used to be parallel resolve.
  MODE_TRRFIRST,    // 2 - fallback to native on TRR failure
  MODE_TRRONLY,     // 3 - don't even fallback
  MODE_RESERVED4,   // 4 - Reserved value. Used to be race TRR with native.
  MODE_TRROFF       // 5 - identical to MODE_NATIVEONLY but explicitly selected
};
}  // namespace net
}  // namespace mozilla

#define TRR_DISABLED(x) (((x) == MODE_NATIVEONLY) || ((x) == MODE_TRROFF))

extern mozilla::Atomic<bool, mozilla::Relaxed> gNativeIsLocalhost;

#define MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY 3
#define MAX_RESOLVER_THREADS_FOR_HIGH_PRIORITY 5
#define MAX_NON_PRIORITY_REQUESTS 150

#define MAX_RESOLVER_THREADS               \
  (MAX_RESOLVER_THREADS_FOR_ANY_PRIORITY + \
   MAX_RESOLVER_THREADS_FOR_HIGH_PRIORITY)

struct nsHostKey {
  const nsCString host;
  const nsCString mTrrServer;
  uint16_t type;
  uint16_t flags;
  uint16_t af;
  bool pb;
  const nsCString originSuffix;
  explicit nsHostKey(const nsACString& host, const nsACString& aTrrServer,
                     uint16_t type, uint16_t flags, uint16_t af, bool pb,
                     const nsACString& originSuffix);
  bool operator==(const nsHostKey& other) const;
  size_t SizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
  PLDHashNumber Hash() const;
};

/**
 * nsHostRecord - ref counted object type stored in host resolver cache.
 */
class nsHostRecord : public mozilla::LinkedListElement<RefPtr<nsHostRecord>>,
                     public nsHostKey,
                     public nsISupports {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS

  virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
    return 0;
  }

  // Returns the TRR mode encoded by the flags
  nsIRequest::TRRMode TRRMode();

  // IMPORTANT: when adding new values, always add them to the end, otherwise
  // it will mess up telemetry.
  enum TRRSkippedReason : uint32_t {
    TRR_UNSET = 0,
    TRR_OK = 1,           // Only set when we actually got a positive TRR result
    TRR_NO_GSERVICE = 2,  // no gService
    TRR_PARENTAL_CONTROL = 3,         // parental control is on
    TRR_OFF_EXPLICIT = 4,             // user has set mode5
    TRR_REQ_MODE_DISABLED = 5,        // request  has disabled flags set
    TRR_MODE_NOT_ENABLED = 6,         // mode0
    TRR_FAILED = 7,                   // unknown failure
    TRR_MODE_UNHANDLED_DEFAULT = 8,   // Unhandled case in ComputeEffectiveMode
    TRR_MODE_UNHANDLED_DISABLED = 9,  // Unhandled case in ComputeEffectiveMode
    TRR_DISABLED_FLAG = 10,           // the DISABLE_TRR flag was set
    TRR_TIMEOUT = 11,                 // the TRR channel timed out
    TRR_CHANNEL_DNS_FAIL = 12,        // DoH server name failed to resolve
    TRR_IS_OFFLINE = 13,              // The browser is offline/no interfaces up
    TRR_NOT_CONFIRMED = 14,           // TRR confirmation is not done yet
    TRR_DID_NOT_MAKE_QUERY = 15,  // TrrLookup exited without doing a TRR query
    TRR_UNKNOWN_CHANNEL_FAILURE = 16,  // unknown channel failure reason
    TRR_HOST_BLOCKED_TEMPORARY = 17,   // host blocklisted
    TRR_SEND_FAILED = 18,          // The call to TRR::SendHTTPRequest failed
    TRR_NET_RESET = 19,            // NS_ERROR_NET_RESET
    TRR_NET_TIMEOUT = 20,          // NS_ERROR_NET_TIMEOUT
    TRR_NET_REFUSED = 21,          // NS_ERROR_CONNECTION_REFUSED
    TRR_NET_INTERRUPT = 22,        // NS_ERROR_NET_INTERRUPT
    TRR_NET_INADEQ_SEQURITY = 23,  // NS_ERROR_NET_INADEQUATE_SECURITY
    TRR_NO_ANSWERS = 24,           // TRR returned no answers
    TRR_DECODE_FAILED = 25,        // DohDecode failed
    TRR_EXCLUDED = 26,             // ExcludedFromTRR
    TRR_SERVER_RESPONSE_ERR = 27,  // Server responded with non-200 code
    TRR_RCODE_FAIL = 28,           // DNS response contains a non-NOERROR rcode
    TRR_NO_CONNECTIVITY = 29,      // Not confirmed because of no connectivity
  };

  // Records the first reason that caused TRR to be skipped or to fail.
  void RecordReason(TRRSkippedReason reason) {
    if (mTRRTRRSkippedReason == TRR_UNSET) {
      mTRRTRRSkippedReason = reason;
    }
  }

 protected:
  friend class nsHostResolver;
  friend class mozilla::net::TRR;
  friend class mozilla::net::TRRQuery;

  explicit nsHostRecord(const nsHostKey& key);
  virtual ~nsHostRecord() = default;

  // Mark hostrecord as not usable
  void Invalidate();

  enum ExpirationStatus {
    EXP_VALID,
    EXP_GRACE,
    EXP_EXPIRED,
  };

  ExpirationStatus CheckExpiration(const mozilla::TimeStamp& now) const;

  // Convenience function for setting the timestamps above (mValidStart,
  // mValidEnd, and mGraceStart). valid and grace are durations in seconds.
  void SetExpiration(const mozilla::TimeStamp& now, unsigned int valid,
                     unsigned int grace);
  void CopyExpirationTimesAndFlagsFrom(const nsHostRecord* aFromHostRecord);

  // Checks if the record is usable (not expired and has a value)
  bool HasUsableResult(const mozilla::TimeStamp& now,
                       uint16_t queryFlags = 0) const;

  enum DnsPriority {
    DNS_PRIORITY_LOW,
    DNS_PRIORITY_MEDIUM,
    DNS_PRIORITY_HIGH,
  };
  static DnsPriority GetPriority(uint16_t aFlags);

  virtual void Cancel();
  virtual bool HasUsableResultInternal() const { return false; }

  mozilla::LinkedList<RefPtr<nsResolveHostCallback>> mCallbacks;

  bool IsAddrRecord() const {
    return type == nsIDNSService::RESOLVE_TYPE_DEFAULT;
  }

  // When the record began being valid. Used mainly for bookkeeping.
  mozilla::TimeStamp mValidStart;

  // When the record is no longer valid (it's time of expiration)
  mozilla::TimeStamp mValidEnd;

  // When the record enters its grace period. This must be before mValidEnd.
  // If a record is in its grace period (and not expired), it will be used
  // but a request to refresh it will be made.
  mozilla::TimeStamp mGraceStart;

  // The computed TRR mode that is actually used by the request.
  // It is set in nsHostResolver::NameLookup and is based on the mode of the
  // default resolver and the TRRMode encoded in the flags.
  // The mode into account if the TRR service is disabled,
  // parental controls are on, domain matches exclusion list, etc.
  nsIRequest::TRRMode mEffectiveTRRMode;

  TRRSkippedReason mTRRTRRSkippedReason = TRR_UNSET;
  TRRSkippedReason mTRRAFailReason = TRR_UNSET;
  TRRSkippedReason mTRRAAAAFailReason = TRR_UNSET;

  mozilla::DataMutex<RefPtr<mozilla::net::TRRQuery>> mTRRQuery;

  mozilla::Atomic<int32_t>
      mResolving;  // counter of outstanding resolving calls

  uint8_t negative : 1; /* True if this record is a cache of a failed
                           lookup.  Negative cache entries are valid just
                           like any other (though never for more than 60
                           seconds), but a use of that negative entry
                           forces an asynchronous refresh. */
  uint8_t mDoomed : 1;  // explicitly expired
};

// b020e996-f6ab-45e5-9bf5-1da71dd0053a
#define ADDRHOSTRECORD_IID                           \
  {                                                  \
    0xb020e996, 0xf6ab, 0x45e5, {                    \
      0x9b, 0xf5, 0x1d, 0xa7, 0x1d, 0xd0, 0x05, 0x3a \
    }                                                \
  }

class AddrHostRecord final : public nsHostRecord {
  typedef mozilla::Mutex Mutex;

 public:
  NS_DECLARE_STATIC_IID_ACCESSOR(ADDRHOSTRECORD_IID)
  NS_DECL_ISUPPORTS_INHERITED

  /* a fully resolved host record has either a non-null |addr_info| or |addr|
   * field.  if |addr_info| is null, it implies that the |host| is an IP
   * address literal.  in which case, |addr| contains the parsed address.
   * otherwise, if |addr_info| is non-null, then it contains one or many
   * IP addresses corresponding to the given host name.  if both |addr_info|
   * and |addr| are null, then the given host has not yet been fully resolved.
   * |af| is the address family of the record we are querying for.
   */

  /* the lock protects |addr_info| and |addr_info_gencnt| because they
   * are mutable and accessed by the resolver worker thread and the
   * nsDNSService2 class.  |addr| doesn't change after it has been
   * assigned a value.  only the resolver worker thread modifies
   * nsHostRecord (and only in nsHostResolver::CompleteLookup);
   * the other threads just read it.  therefore the resolver worker
   * thread doesn't need to lock when reading |addr_info|.
   */
  Mutex addr_info_lock;
  int addr_info_gencnt; /* generation count of |addr_info| */
  RefPtr<mozilla::net::AddrInfo> addr_info;
  mozilla::UniquePtr<mozilla::net::NetAddr> addr;

  // hold addr_info_lock when calling the blocklist functions
  bool Blocklisted(const mozilla::net::NetAddr* query);
  void ResetBlocklist();
  void ReportUnusable(const mozilla::net::NetAddr* aAddress);

  size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const override;

  nsIRequest::TRRMode EffectiveTRRMode() const { return mEffectiveTRRMode; }

 private:
  friend class nsHostResolver;
  friend class mozilla::net::TRR;
  friend class mozilla::net::TRRQuery;

  explicit AddrHostRecord(const nsHostKey& key);
  ~AddrHostRecord();

  // Checks if the record is usable (not expired and has a value)
  bool HasUsableResultInternal() const override;

  bool RemoveOrRefresh(bool aTrrToo);  // Mark records currently being resolved
                                       // as needed to resolve again.

  void ResolveComplete();

  enum DnsPriority {
    DNS_PRIORITY_LOW,
    DNS_PRIORITY_MEDIUM,
    DNS_PRIORITY_HIGH,
  };
  static DnsPriority GetPriority(uint16_t aFlags);

  // true if pending and on the queue (not yet given to getaddrinfo())
  bool onQueue() { return LoadNative() && isInList(); }

  // When the lookups of this record started and their durations
  mozilla::TimeStamp mTrrStart;
  mozilla::TimeStamp mNativeStart;
  mozilla::TimeDuration mTrrDuration;
  mozilla::TimeDuration mNativeDuration;

  mozilla::Atomic<bool> mTRRUsed;  // TRR was used on this record
  uint8_t mTRRSuccess;             // number of successful TRR responses
  uint8_t mNativeSuccess;          // number of native lookup responses

  // clang-format off
  MOZ_ATOMIC_BITFIELDS(mAtomicBitfields, 8, (
    // true if this record is being resolved "natively", which means that
    // it is either on the pending queue or owned by one of the worker threads.
    (uint16_t, Native, 1),
    (uint16_t, NativeUsed, 1),
    // true if off queue and contributing to mActiveAnyThreadCount
    (uint16_t, UsingAnyThread, 1),
    (uint16_t, GetTtl, 1),
    (uint16_t, ResolveAgain, 1)
  ))
  // clang-format on

  // The number of times ReportUnusable() has been called in the record's
  // lifetime.
  uint32_t mUnusableCount = 0;

  // a list of addresses associated with this record that have been reported
  // as unusable. the list is kept as a set of strings to make it independent
  // of gencnt.
  nsTArray<nsCString> mUnusableItems;
};

NS_DEFINE_STATIC_IID_ACCESSOR(AddrHostRecord, ADDRHOSTRECORD_IID)

// 77b786a7-04be-44f2-987c-ab8aa96676e0
#define TYPEHOSTRECORD_IID                           \
  {                                                  \
    0x77b786a7, 0x04be, 0x44f2, {                    \
      0x98, 0x7c, 0xab, 0x8a, 0xa9, 0x66, 0x76, 0xe0 \
    }                                                \
  }

class TypeHostRecord final : public nsHostRecord,
                             public nsIDNSTXTRecord,
                             public nsIDNSHTTPSSVCRecord,
                             public mozilla::net::DNSHTTPSSVCRecordBase {
 public:
  NS_DECLARE_STATIC_IID_ACCESSOR(TYPEHOSTRECORD_IID)
  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_NSIDNSTXTRECORD
  NS_DECL_NSIDNSHTTPSSVCRECORD

  size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const override;
  uint32_t GetType();
  mozilla::net::TypeRecordResultType GetResults();

 private:
  friend class nsHostResolver;
  friend class mozilla::net::TRRQuery;

  explicit TypeHostRecord(const nsHostKey& key);
  ~TypeHostRecord();

  // Checks if the record is usable (not expired and has a value)
  bool HasUsableResultInternal() const override;

  bool HasUsableResult();

  mozilla::net::TypeRecordResultType mResults = AsVariant(mozilla::Nothing());
  mozilla::Mutex mResultsLock;

  // When the lookups of this record started (for telemetry).
  mozilla::TimeStamp mStart;
  bool mAllRecordsExcluded = false;
};

NS_DEFINE_STATIC_IID_ACCESSOR(TypeHostRecord, TYPEHOSTRECORD_IID)

/**
 * This class is used to notify listeners when a ResolveHost operation is
 * complete. Classes that derive it must implement threadsafe nsISupports
 * to be able to use RefPtr with this class.
 */
class nsResolveHostCallback
    : public mozilla::LinkedListElement<RefPtr<nsResolveHostCallback>>,
      public nsISupports {
 public:
  /**
   * OnResolveHostComplete
   *
   * this function is called to complete a host lookup initiated by
   * nsHostResolver::ResolveHost.  it may be invoked recursively from
   * ResolveHost or on an unspecified background thread.
   *
   * NOTE: it is the responsibility of the implementor of this method
   * to handle the callback in a thread safe manner.
   *
   * @param resolver
   *        nsHostResolver object associated with this result
   * @param record
   *        the host record containing the results of the lookup
   * @param status
   *        if successful, |record| contains non-null results
   */
  virtual void OnResolveHostComplete(nsHostResolver* resolver,
                                     nsHostRecord* record, nsresult status) = 0;
  /**
   * EqualsAsyncListener
   *
   * Determines if the listener argument matches the listener member var.
   * For subclasses not implementing a member listener, should return false.
   * For subclasses having a member listener, the function should check if
   * they are the same.  Used for cases where a pointer to an object
   * implementing nsResolveHostCallback is unknown, but a pointer to
   * the original listener is known.
   *
   * @param aListener
   *        nsIDNSListener object associated with the original request
   */
  virtual bool EqualsAsyncListener(nsIDNSListener* aListener) = 0;

  virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf) const = 0;

 protected:
  virtual ~nsResolveHostCallback() = default;
};

class AHostResolver {
 public:
  AHostResolver() = default;
  virtual ~AHostResolver() = default;
  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING

  enum LookupStatus {
    LOOKUP_OK,
    LOOKUP_RESOLVEAGAIN,
  };

  virtual LookupStatus CompleteLookup(
      nsHostRecord*, nsresult, mozilla::net::AddrInfo*, bool pb,
      const nsACString& aOriginsuffix,
      nsHostRecord::TRRSkippedReason aReason) = 0;
  virtual LookupStatus CompleteLookupByType(
      nsHostRecord*, nsresult, mozilla::net::TypeRecordResultType& aResult,
      uint32_t aTtl, bool pb) = 0;
  virtual nsresult GetHostRecord(const nsACString& host,
                                 const nsACString& aTrrServer, uint16_t type,
                                 uint16_t flags, uint16_t af, bool pb,
                                 const nsCString& originSuffix,
                                 nsHostRecord** result) {
    return NS_ERROR_FAILURE;
  }
  virtual nsresult TrrLookup_unlocked(nsHostRecord*,
                                      mozilla::net::TRR* pushedTRR = nullptr) {
    return NS_ERROR_FAILURE;
  }
  virtual void MaybeRenewHostRecord(nsHostRecord* aRec) {}
};

/**
 * nsHostResolver - an asynchronous host name resolver.
 */
class nsHostResolver : public nsISupports, public AHostResolver {
  using CondVar = mozilla::CondVar;
  using Mutex = mozilla::Mutex;

 public:
  NS_DECL_THREADSAFE_ISUPPORTS

  /**
   * creates an addref'd instance of a nsHostResolver object.
   */
  static nsresult Create(uint32_t maxCacheEntries,  // zero disables cache
                         uint32_t defaultCacheEntryLifetime,  // seconds
                         uint32_t defaultGracePeriod,         // seconds
                         nsHostResolver** result);

  /**
   * Set (new) cache limits.
   */
  void SetCacheLimits(uint32_t maxCacheEntries,  // zero disables cache
                      uint32_t defaultCacheEntryLifetime,  // seconds
                      uint32_t defaultGracePeriod);        // seconds

  /**
   * puts the resolver in the shutdown state, which will cause any pending
   * callbacks to be detached.  any future calls to ResolveHost will fail.
   */
  void Shutdown();

  /**
   * resolve the given hostname and originAttributes asynchronously.  the caller
   * can synthesize a synchronous host lookup using a lock and a cvar.  as noted
   * above the callback will occur re-entrantly from an unspecified thread.  the
   * host lookup cannot be canceled (cancelation can be layered above this by
   * having the callback implementation return without doing anything).
   */
  nsresult ResolveHost(const nsACString& aHost, const nsACString& trrServer,
                       uint16_t type,
                       const mozilla::OriginAttributes& aOriginAttributes,
                       uint16_t flags, uint16_t af,
                       nsResolveHostCallback* callback);

  nsHostRecord* InitRecord(const nsHostKey& key);
  mozilla::net::NetworkConnectivityService* GetNCS() { return mNCS; }

  /**
   * return a resolved hard coded loopback dns record for the specified key
   */
  already_AddRefed<nsHostRecord> InitLoopbackRecord(const nsHostKey& key,
                                                    nsresult* aRv);

  /**
   * removes the specified callback from the nsHostRecord for the given
   * hostname, originAttributes, flags, and address family.  these parameters
   * should correspond to the parameters passed to ResolveHost.  this function
   * executes the callback if the callback is still pending with the given
   * status.
   */
  void DetachCallback(const nsACString& hostname, const nsACString& trrServer,
                      uint16_t type,
                      const mozilla::OriginAttributes& aOriginAttributes,
                      uint16_t flags, uint16_t af,
                      nsResolveHostCallback* callback, nsresult status);

  /**
   * Cancels an async request associated with the hostname, originAttributes,
   * flags, address family and listener.  Cancels first callback found which
   * matches these criteria.  These parameters should correspond to the
   * parameters passed to ResolveHost.  If this is the last callback associated
   * with the host record, it is removed from any request queues it might be on.
   */
  void CancelAsyncRequest(const nsACString& host, const nsACString& trrServer,
                          uint16_t type,
                          const mozilla::OriginAttributes& aOriginAttributes,
                          uint16_t flags, uint16_t af,
                          nsIDNSListener* aListener, nsresult status);
  /**
   * values for the flags parameter passed to ResolveHost and DetachCallback
   * that may be bitwise OR'd together.
   *
   * NOTE: in this implementation, these flags correspond exactly in value
   *       to the flags defined on nsIDNSService.
   */
  enum {
    RES_BYPASS_CACHE = nsIDNSService::RESOLVE_BYPASS_CACHE,
    RES_CANON_NAME = nsIDNSService::RESOLVE_CANONICAL_NAME,
    RES_PRIORITY_MEDIUM = nsIDNSService::RESOLVE_PRIORITY_MEDIUM,
    RES_PRIORITY_LOW = nsIDNSService::RESOLVE_PRIORITY_LOW,
    RES_SPECULATE = nsIDNSService::RESOLVE_SPECULATE,
    // RES_DISABLE_IPV6 = nsIDNSService::RESOLVE_DISABLE_IPV6, // Not used
    RES_OFFLINE = nsIDNSService::RESOLVE_OFFLINE,
    // RES_DISABLE_IPv4 = nsIDNSService::RESOLVE_DISABLE_IPV4, // Not Used
    RES_ALLOW_NAME_COLLISION = nsIDNSService::RESOLVE_ALLOW_NAME_COLLISION,
    RES_DISABLE_TRR = nsIDNSService::RESOLVE_DISABLE_TRR,
    RES_REFRESH_CACHE = nsIDNSService::RESOLVE_REFRESH_CACHE,
    RES_IP_HINT = nsIDNSService::RESOLVE_IP_HINT
  };

  size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const;

  /**
   * Flush the DNS cache.
   */
  void FlushCache(bool aTrrToo);

  LookupStatus CompleteLookup(nsHostRecord*, nsresult, mozilla::net::AddrInfo*,
                              bool pb, const nsACString& aOriginsuffix,
                              nsHostRecord::TRRSkippedReason aReason) override;
  LookupStatus CompleteLookupByType(nsHostRecord*, nsresult,
                                    mozilla::net::TypeRecordResultType& aResult,
                                    uint32_t aTtl, bool pb) override;
  nsresult GetHostRecord(const nsACString& host, const nsACString& trrServer,
                         uint16_t type, uint16_t flags, uint16_t af, bool pb,
                         const nsCString& originSuffix,
                         nsHostRecord** result) override;
  nsresult TrrLookup_unlocked(nsHostRecord*,
                              mozilla::net::TRR* pushedTRR = nullptr) override;
  static mozilla::net::ResolverMode Mode();

  virtual void MaybeRenewHostRecord(nsHostRecord* aRec) override;

 private:
  explicit nsHostResolver(uint32_t maxCacheEntries,
                          uint32_t defaultCacheEntryLifetime,
                          uint32_t defaultGracePeriod);
  virtual ~nsHostResolver();

  nsresult Init();
  // In debug builds it asserts that the element is in the list.
  void AssertOnQ(nsHostRecord*, mozilla::LinkedList<RefPtr<nsHostRecord>>&);
  static void ComputeEffectiveTRRMode(nsHostRecord* aRec);
  nsresult NativeLookup(nsHostRecord*);
  nsresult TrrLookup(nsHostRecord*, mozilla::net::TRR* pushedTRR = nullptr);

  // Kick-off a name resolve operation, using native resolver and/or TRR
  nsresult NameLookup(nsHostRecord*);
  bool GetHostToLookup(AddrHostRecord** result);
  void MaybeRenewHostRecordLocked(nsHostRecord* aRec);

  // Removes the first element from the list and returns it AddRef-ed in aResult
  // Should not be called for an empty linked list.
  void DeQueue(mozilla::LinkedList<RefPtr<nsHostRecord>>& aQ,
               AddrHostRecord** aResult);
  // Cancels host records in the pending queue and also
  // calls CompleteLookup with the NS_ERROR_ABORT result code.
  void ClearPendingQueue(mozilla::LinkedList<RefPtr<nsHostRecord>>& aPendingQ);
  nsresult ConditionallyCreateThread(nsHostRecord* rec);

  /**
   * Starts a new lookup in the background for entries that are in the grace
   * period with a failed connect or all cached entries are negative.
   */
  nsresult ConditionallyRefreshRecord(nsHostRecord* rec,
                                      const nsACString& host);

  void AddToEvictionQ(nsHostRecord* rec);

  void ThreadFunc();

  enum {
    METHOD_HIT = 1,
    METHOD_RENEWAL = 2,
    METHOD_NEGATIVE_HIT = 3,
    METHOD_LITERAL = 4,
    METHOD_OVERFLOW = 5,
    METHOD_NETWORK_FIRST = 6,
    METHOD_NETWORK_SHARED = 7
  };

  uint32_t mMaxCacheEntries;
  uint32_t mDefaultCacheLifetime;  // granularity seconds
  uint32_t mDefaultGracePeriod;    // granularity seconds
  mutable Mutex mLock;  // mutable so SizeOfIncludingThis can be const
  CondVar mIdleTaskCV;
  nsRefPtrHashtable<nsGenericHashKey<nsHostKey>, nsHostRecord> mRecordDB;
  mozilla::LinkedList<RefPtr<nsHostRecord>> mHighQ;
  mozilla::LinkedList<RefPtr<nsHostRecord>> mMediumQ;
  mozilla::LinkedList<RefPtr<nsHostRecord>> mLowQ;
  mozilla::LinkedList<RefPtr<nsHostRecord>> mEvictionQ;
  uint32_t mEvictionQSize;
  PRTime mCreationTime;
  mozilla::TimeDuration mLongIdleTimeout;
  mozilla::TimeDuration mShortIdleTimeout;

  RefPtr<nsIThreadPool> mResolverThreads;
  RefPtr<mozilla::net::NetworkConnectivityService> mNCS;

  mozilla::Atomic<bool> mShutdown;
  mozilla::Atomic<uint32_t> mNumIdleTasks;
  mozilla::Atomic<uint32_t> mActiveTaskCount;
  mozilla::Atomic<uint32_t> mActiveAnyThreadCount;
  mozilla::Atomic<uint32_t> mPendingCount;

  // Set the expiration time stamps appropriately.
  void PrepareRecordExpirationAddrRecord(AddrHostRecord* rec) const;

 public:
  /*
   * Called by the networking dashboard via the DnsService2
   */
  void GetDNSCacheEntries(nsTArray<mozilla::net::DNSCacheEntries>*);
};

#endif  // nsHostResolver_h__