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 NoChange 59 }; 60 61 MDnsCache(); 62 ~MDnsCache(); 63 64 // Return value indicates whether the record was added, changed 65 // (existed previously with different value) or not changed (existed 66 // previously with same value). 67 UpdateType UpdateDnsRecord(scoped_ptr<const RecordParsed> record); 68 69 // Check cache for record with key |key|. Return the record if it exists, or 70 // NULL if it doesn't. 71 const RecordParsed* LookupKey(const Key& key); 72 73 // Return records with type |type| and name |name|. Expired records will not 74 // be returned. If |type| is zero, return all records with name |name|. 75 void FindDnsRecords(unsigned type, 76 const std::string& name, 77 std::vector<const RecordParsed*>* records, 78 base::Time now) const; 79 80 // Remove expired records, call |record_removed_callback| for every removed 81 // record. 82 void CleanupRecords(base::Time now, 83 const RecordRemovedCallback& record_removed_callback); 84 85 // Returns a time less than or equal to the next time a record will expire. 86 // Is updated when CleanupRecords or UpdateDnsRecord are called. Returns 87 // base::Time when the cache is empty. 88 base::Time next_expiration() const { return next_expiration_; } 89 90 // Remove a record from the cache. Returns a scoped version of the pointer 91 // passed in if it was removed, scoped null otherwise. 92 scoped_ptr<const RecordParsed> RemoveRecord(const RecordParsed* record); 93 94 void Clear(); 95 96 private: 97 typedef std::map<Key, const RecordParsed*> RecordMap; 98 99 // Get the effective expiration of a cache entry, based on its creation time 100 // and TTL. Does adjustments so entries with a TTL of zero will have a 101 // nonzero TTL, as explained in RFC 6762 Section 10.1. 102 static base::Time GetEffectiveExpiration(const RecordParsed* entry); 103 104 // Get optional part of the DNS key for shared records. For example, in PTR 105 // records this is the pointed domain, since multiple PTR records may exist 106 // for the same name. 107 static std::string GetOptionalFieldForRecord( 108 const RecordParsed* record); 109 110 RecordMap mdns_cache_; 111 112 base::Time next_expiration_; 113 114 DISALLOW_COPY_AND_ASSIGN(MDnsCache); 115 }; 116 117 } // namespace net 118 119 #endif // NET_DNS_MDNS_CACHE_H_ 120