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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.
- #ifndef NET_DNS_MDNS_CACHE_H_
- #define NET_DNS_MDNS_CACHE_H_
- #include <map>
- #include <memory>
- #include <string>
- #include <vector>
- #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<void(const RecordParsed*)>
- 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<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);
- bool IsCacheOverfilled() const;
- void set_entry_limit_for_testing(size_t entry_limit) {
- entry_limit_ = entry_limit;
- }
- private:
- 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_;
- size_t entry_limit_;
- };
- } // namespace net
- #endif // NET_DNS_MDNS_CACHE_H_
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