net/dns/mdns_cache.h

   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_