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// Copyright (c) 2013 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.
#include <map>
#include <memory>
#include <string>
#include <vector>
#include "base/callback.h"
#include "base/macros.h"
#include "base/time/time.h"
#include "net/base/net_export.h"
namespace net {
class RecordParsed;
// mDNS Cache
// This is a cache of mDNS records. It keeps track of expiration times and is
// guaranteed not to return expired records. It also has facilities for timely
// record expiration.
// Key type for the record map. It is a 3-tuple of type, name and optional
// value ordered by type, then name, then optional value. This allows us to
// query for all records of a certain type and name, while also allowing us
// to set records of a certain type, name and optionally value as unique.
class Key {
Key(unsigned type, const std::string& name, const std::string& optional);
Key(const Key&);
Key& operator=(const Key&);
bool operator<(const Key& key) const;
bool operator==(const Key& key) const;
unsigned type() const { return type_; }
const std::string& name() const { return name_; }
const std::string& optional() const { return optional_; }
// Create the cache key corresponding to |record|.
static Key CreateFor(const RecordParsed* record);
unsigned type_;
std::string name_;
std::string optional_;
typedef base::Callback<void(const RecordParsed*)> RecordRemovedCallback;
enum UpdateType {
// Return value indicates whether the record was added, changed
// (existed previously with different value) or not changed (existed
// previously with same value).
UpdateType UpdateDnsRecord(std::unique_ptr<const RecordParsed> record);
// Check cache for record with key |key|. Return the record if it exists, or
// NULL if it doesn't.
const RecordParsed* LookupKey(const Key& key);
// Return records with type |type| and name |name|. Expired records will not
// be returned. If |type| is zero, return all records with name |name|.
void FindDnsRecords(unsigned type,
const std::string& name,
std::vector<const RecordParsed*>* records,
base::Time now) const;
// Remove expired records, call |record_removed_callback| for every removed
// record.
void CleanupRecords(base::Time now,
const RecordRemovedCallback& record_removed_callback);
// Returns a time less than or equal to the next time a record will expire.
// Is updated when CleanupRecords or UpdateDnsRecord are called. Returns
// base::Time when the cache is empty.
base::Time next_expiration() const { return next_expiration_; }
// Remove a record from the cache. Returns a scoped version of the pointer
// passed in if it was removed, scoped null otherwise.
std::unique_ptr<const RecordParsed> RemoveRecord(const RecordParsed* record);
typedef std::map<Key, std::unique_ptr<const RecordParsed>> RecordMap;
// Get the effective expiration of a cache entry, based on its creation time
// and TTL. Does adjustments so entries with a TTL of zero will have a
// nonzero TTL, as explained in RFC 6762 Section 10.1.
static base::Time GetEffectiveExpiration(const RecordParsed* entry);
// Get optional part of the DNS key for shared records. For example, in PTR
// records this is the pointed domain, since multiple PTR records may exist
// for the same name.
static std::string GetOptionalFieldForRecord(const RecordParsed* record);
RecordMap mdns_cache_;
base::Time next_expiration_;
} // namespace net