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