Multicast DNS implementation (initial)

net/dns/mdns_client.h

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_DNS_MDNS_CLIENT_H_
+#define NET_DNS_MDNS_CLIENT_H_
+
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "net/dns/dns_query.h"
+#include "net/dns/dns_response.h"
+#include "net/dns/record_parsed.h"
+
+namespace net {
+
+class RecordParsed;
+
+enum MDnsUpdateType {
+  kMDnsRecordAdded,
+  kMDnsRecordChanged,
+  kMDnsRecordRemoved
+};
+
+enum MDnsTransactionResult {
+  kMDnsTransactionSuccess,
+  kMDnsTransactionTimeout,
+  kMDnsTransactionNsec
+};
+
+// A class representing a one-time unique-record lookup. A transaction takes one
+// associated callback (see |MDnsClient::CreateTransaction|) and calls it when
+// a matching record has been found, either from the cache or by querying the
+// network. Transactions will time out after a reasonable number of seconds.
+class MDnsTransaction {
+ public:
+  typedef base::Callback<void(MDnsTransactionResult, const RecordParsed*)>
+  ResultCallback;
+
+  // Destroying the transaction cancels it.
+  virtual ~MDnsTransaction() {}
+
+  // Get the host or service name for the transaction.
+  virtual const std::string& GetName() const = 0;
+
+  // Get the type for this transaction (SRV, TXT, A, AAA, etc)
+  virtual uint16 GetType() const = 0;
+};
+
+// A listener listens for updates regarding a specific record or set of records.
+// If a listener is active (determined at its creation) it will send queries
+// when appropriate.
+class MDnsListener {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // Called when a record is added, removed or updated.
+    virtual void OnRecordUpdate(MDnsUpdateType update,
+                                const RecordParsed* record) = 0;
+
+    // Called when a record is marked nonexistent by an NSEC record.
+    virtual void OnNsecRecord(const std::string& name, unsigned type) = 0;
+  };
+
+  // Destroying the listener stops listening.
+  virtual ~MDnsListener() {}
+
+  // Get the host or service name for this query.
+  // Return an empty string for no name.
+  virtual const std::string& GetName() const = 0;
+
+  // Get the type for this query (SRV, TXT, A, AAA, etc)
+  virtual uint16 GetType() const = 0;
+
+  // Whether this listener is active (true) or passive (false)
+  virtual bool IsActive() const = 0;
+
+  // Applies only to listeners with names. Will send out a query for new
+  // information. |force_refresh_cache| will force a refresh of all cached
+  // entities.
+  virtual bool SendQuery(bool force_refresh_cache) = 0;
+
+  // Applies only to listeners with names. Query mDNS cache synchronously for
+  // either single- or multi- valued records.
+  virtual bool QueryCache(std::vector<const RecordParsed*>* records) const = 0;
+};
+
+// This class listens for Multicast DNS on the local network. You can access
+// information regarding multicast DNS either by creating an |MDnsListener| to
+// be notified of new records, or by creating an |MDnsTransaction| to look up
+// the value of a specific records.
+class MDnsClient {
+ public:
+  virtual ~MDnsClient() {}
+
+  // Create listener object for RRType |rrtype| and name |name|.
+  // If |name| is an empty string, listen to all notification of type
+  // |rrtype|. If a listener is |active|, it will send queries when the client
+  // thinks they are needed. If |alert_existing_records| is true, a listener's
+  // delegate will be alerted for records already in the cache when it is
+  // created.
+  virtual scoped_ptr<MDnsListener> CreateListener(
+      uint16 rrtype,
+      const std::string& name,
+      bool active,
+      bool alert_existing_records,
+      MDnsListener::Delegate* delegate) = 0;
+
+  // Create a transaction to Query MDNS for a single-value query
+  // (A, AAAA, TXT, and SRV) asynchronously. May defer to cache.
+  virtual scoped_ptr<MDnsTransaction> CreateTransaction(
+      uint16 rrtype,
+      const std::string& name,
+      const MDnsTransaction::ResultCallback& callback) = 0;
+
+  // Lazily create and return static instance for MDnsClient.
+  static MDnsClient* GetInstance();
+
+  // Set the global instance (for testing). MUST be called before the first call
+  // to GetInstance.
+  static void SetInstance(MDnsClient* instance);
+};
+
+}  // net
+#endif  // NET_DNS_MDNS_CLIENT_H_