1 // Copyright (c) 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef NET_DNS_MDNS_CACHE_H_ 6 #define NET_DNS_MDNS_CACHE_H_ 7 8 #include <map> 9 #include <string> 10 #include <vector> 11 12 #include "base/callback.h" 13 #include "base/memory/scoped_ptr.h" 14 #include "base/time/time.h" 15 #include "net/base/net_export.h" 16 17 namespace net { 18 19 class ParsedDnsRecord; 20 class RecordParsed; 21 22 // mDNS Cache 23 // This is a cache of mDNS records. It keeps track of expiration times and is 24 // guaranteed not to return expired records. It also has facilities for timely 25 // record expiration. 26 class NET_EXPORT_PRIVATE MDnsCache { 27 public: 28 // Key type for the record map. It is a 3-tuple of type, name and optional 29 // value ordered by type, then name, then optional value. This allows us to 30 // query for all records of a certain type and name, while also allowing us 31 // to set records of a certain type, name and optionally value as unique. 32 class Key { 33 public: 34 Key(unsigned type, const std::string& name, const std::string& optional); 35 Key(const Key&); 36 Key& operator=(const Key&); 37 ~Key(); 38 bool operator<(const Key& key) const; 39 bool operator==(const Key& key) const; 40 41 unsigned type() const { return type_; } 42 const std::string& name() const { return name_; } 43 const std::string& optional() const { return optional_; } 44 45 // Create the cache key corresponding to |record|. 46 static Key CreateFor(const RecordParsed* record); 47 private: 48 unsigned type_; 49 std::string name_; 50 std::string optional_; 51 }; 52 53 typedef base::Callback<void(const RecordParsed*)> RecordRemovedCallback; 54 55 enum UpdateType { 56 RecordAdded, 57 RecordChanged, 58 RecordRemoved, 59 NoChange 60 }; 61 62 MDnsCache(); 63 ~MDnsCache(); 64 65 // Return value indicates whether the record was added, changed 66 // (existed previously with different value) or not changed (existed 67 // previously with same value). 68 UpdateType UpdateDnsRecord(scoped_ptr<const RecordParsed> record); 69 70 // Check cache for record with key |key|. Return the record if it exists, or 71 // NULL if it doesn't. 72 const RecordParsed* LookupKey(const Key& key); 73 74 // Return records with type |type| and name |name|. Expired records will not 75 // be returned. If |type| is zero, return all records with name |name|. 76 void FindDnsRecords(unsigned type, 77 const std::string& name, 78 std::vector<const RecordParsed*>* records, 79 base::Time now) const; 80 81 // Remove expired records, call |record_removed_callback| for every removed 82 // record. 83 void CleanupRecords(base::Time now, 84 const RecordRemovedCallback& record_removed_callback); 85 86 // Returns a time less than or equal to the next time a record will expire. 87 // Is updated when CleanupRecords or UpdateDnsRecord are called. Returns 88 // base::Time when the cache is empty. 89 base::Time next_expiration() const { return next_expiration_; } 90 91 // Remove a record from the cache. Returns a scoped version of the pointer 92 // passed in if it was removed, scoped null otherwise. 93 scoped_ptr<const RecordParsed> RemoveRecord(const RecordParsed* record); 94 95 void Clear(); 96 97 private: 98 typedef std::map<Key, const RecordParsed*> RecordMap; 99 100 // Get the effective expiration of a cache entry, based on its creation time 101 // and TTL. Does adjustments so entries with a TTL of zero will have a 102 // nonzero TTL, as explained in RFC 6762 Section 10.1. 103 static base::Time GetEffectiveExpiration(const RecordParsed* entry); 104 105 // Get optional part of the DNS key for shared records. For example, in PTR 106 // records this is the pointed domain, since multiple PTR records may exist 107 // for the same name. 108 static std::string GetOptionalFieldForRecord( 109 const RecordParsed* record); 110 111 RecordMap mdns_cache_; 112 113 base::Time next_expiration_; 114 115 DISALLOW_COPY_AND_ASSIGN(MDnsCache); 116 }; 117 118 } // namespace net 119 120 #endif // NET_DNS_MDNS_CACHE_H_ 121
