// 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. #ifndef NET_DNS_MDNS_CACHE_H_ #define NET_DNS_MDNS_CACHE_H_ #include #include #include #include #include "base/callback.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. class NET_EXPORT_PRIVATE MDnsCache { public: // 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 { public: Key(unsigned type, const std::string& name, const std::string& optional); Key(const Key&); Key& operator=(const Key&); ~Key(); bool operator<(const Key& key) const; bool operator==(const Key& key) const; unsigned type() const { return type_; } const std::string& name_lowercase() const { return name_lowercase_; } const std::string& optional() const { return optional_; } // Create the cache key corresponding to |record|. static Key CreateFor(const RecordParsed* record); private: unsigned type_; std::string name_lowercase_; std::string optional_; }; typedef base::RepeatingCallback RecordRemovedCallback; enum UpdateType { RecordAdded, RecordChanged, RecordRemoved, NoChange }; MDnsCache(); MDnsCache(const MDnsCache&) = delete; MDnsCache& operator=(const MDnsCache&) = delete; ~MDnsCache(); // 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 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* 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 RemoveRecord(const RecordParsed* record); bool IsCacheOverfilled() const; void set_entry_limit_for_testing(size_t entry_limit) { entry_limit_ = entry_limit; } private: typedef std::map> 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_; size_t entry_limit_; }; } // namespace net #endif // NET_DNS_MDNS_CACHE_H_