1 // Copyright 2013 The Chromium Authors 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 <memory> 10 #include <string> 11 #include <vector> 12 13 #include "base/functional/callback.h" 14 #include "base/time/time.h" 15 #include "net/base/net_export.h" 16 17 namespace net { 18 19 class RecordParsed; 20 21 // mDNS Cache 22 // This is a cache of mDNS records. It keeps track of expiration times and is 23 // guaranteed not to return expired records. It also has facilities for timely 24 // record expiration. 25 class NET_EXPORT_PRIVATE MDnsCache { 26 public: 27 // Key type for the record map. It is a 3-tuple of type, name and optional 28 // value ordered by type, then name, then optional value. This allows us to 29 // query for all records of a certain type and name, while also allowing us 30 // to set records of a certain type, name and optionally value as unique. 31 class Key { 32 public: 33 Key(unsigned type, const std::string& name, const std::string& optional); 34 Key(const Key&); 35 Key& operator=(const Key&); 36 ~Key(); 37 bool operator<(const Key& key) const; 38 bool operator==(const Key& key) const; 39 type()40 unsigned type() const { return type_; } name_lowercase()41 const std::string& name_lowercase() const { return name_lowercase_; } optional()42 const std::string& optional() const { return optional_; } 43 44 // Create the cache key corresponding to |record|. 45 static Key CreateFor(const RecordParsed* record); 46 private: 47 unsigned type_; 48 std::string name_lowercase_; 49 std::string optional_; 50 }; 51 52 typedef base::RepeatingCallback<void(const RecordParsed*)> 53 RecordRemovedCallback; 54 55 enum UpdateType { 56 RecordAdded, 57 RecordChanged, 58 RecordRemoved, 59 NoChange 60 }; 61 62 MDnsCache(); 63 64 MDnsCache(const MDnsCache&) = delete; 65 MDnsCache& operator=(const MDnsCache&) = delete; 66 67 ~MDnsCache(); 68 69 // Return value indicates whether the record was added, changed 70 // (existed previously with different value) or not changed (existed 71 // previously with same value). 72 UpdateType UpdateDnsRecord(std::unique_ptr<const RecordParsed> record); 73 74 // Check cache for record with key |key|. Return the record if it exists, or 75 // NULL if it doesn't. 76 const RecordParsed* LookupKey(const Key& key); 77 78 // Return records with type |type| and name |name|. Expired records will not 79 // be returned. If |type| is zero, return all records with name |name|. 80 void FindDnsRecords(unsigned type, 81 const std::string& name, 82 std::vector<const RecordParsed*>* records, 83 base::Time now) const; 84 85 // Remove expired records, call |record_removed_callback| for every removed 86 // record. 87 void CleanupRecords(base::Time now, 88 const RecordRemovedCallback& record_removed_callback); 89 90 // Returns a time less than or equal to the next time a record will expire. 91 // Is updated when CleanupRecords or UpdateDnsRecord are called. Returns 92 // base::Time when the cache is empty. next_expiration()93 base::Time next_expiration() const { return next_expiration_; } 94 95 // Remove a record from the cache. Returns a scoped version of the pointer 96 // passed in if it was removed, scoped null otherwise. 97 std::unique_ptr<const RecordParsed> RemoveRecord(const RecordParsed* record); 98 99 bool IsCacheOverfilled() const; 100 set_entry_limit_for_testing(size_t entry_limit)101 void set_entry_limit_for_testing(size_t entry_limit) { 102 entry_limit_ = entry_limit; 103 } 104 105 private: 106 typedef std::map<Key, std::unique_ptr<const RecordParsed>> RecordMap; 107 108 // Get the effective expiration of a cache entry, based on its creation time 109 // and TTL. Does adjustments so entries with a TTL of zero will have a 110 // nonzero TTL, as explained in RFC 6762 Section 10.1. 111 static base::Time GetEffectiveExpiration(const RecordParsed* entry); 112 113 // Get optional part of the DNS key for shared records. For example, in PTR 114 // records this is the pointed domain, since multiple PTR records may exist 115 // for the same name. 116 static std::string GetOptionalFieldForRecord(const RecordParsed* record); 117 118 RecordMap mdns_cache_; 119 120 base::Time next_expiration_; 121 size_t entry_limit_; 122 }; 123 124 } // namespace net 125 126 #endif // NET_DNS_MDNS_CACHE_H_ 127