Multicast DNS implementation (initial)

net/dns/mdns_listener_impl.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_LISTENER_IMPL_H_
+#define NET_DNS_MDNS_LISTENER_IMPL_H_
+
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/time/clock.h"
+#include "base/task_runner.h"
+#include "base/cancelable_callback.h"
+#include "net/base/io_buffer.h"
+#include "net/base/ip_endpoint.h"
+#include "net/dns/mdns_cache.h"
+#include "net/dns/mdns_listener.h"
+#include "net/udp/udp_socket.h"
+
+namespace net {
+
+class MDnsListenerImpl;
+
+class MDnsListenerFactoryImpl : public MDnsListenerFactory {
+ public:
+  class Core : public base::SupportsWeakPtr<Core> {

[szym, 2013/05/24 15:32:22]

Needs comment regarding lifetime. When is Core created? Who can hold weak
pointers to it?

[Noam Samuel, 2013/05/24 19:00:49]

The weak pointer-ability of these classes is mostly used to allow scheduling
methods on them through the message loop.

[szym, 2013/05/25 02:51:01]

Still needs a comment in the code.

On 2013/05/24 19:00:49, Noam Samuel wrote:

[Noam Samuel, 2013/05/29 21:25:16]

Done.

+   public:
+    explicit Core(MDnsListenerFactoryImpl* factory);
+    ~Core();
+
+    // Initialize the core. Returns true on success.
+    bool Init();
+
+    // Send a query with a specific rrtype and name. Returns true on success.
+    bool SendQuery(uint16 rrtype, std::string name);
+
+    // Add/remove a listener to the list of listener. May cause network traffic
+    // if listener is active.
+    void AddListener(MDnsListenerImpl* listener, bool alert_existing_records);
+    void RemoveListener(MDnsListenerImpl* listener);
+
+    // Query the cache for records of a specific type and name.
+    void QueryCache(uint16 rrtype, const std::string& name,
+                    std::vector<const RecordParsed*>* records) const;
+
+   private:
+    typedef std::pair<uint16, std::string> ListenerKey;
+
+    typedef std::multimap<ListenerKey, MDnsListenerImpl*>::iterator
+        ListenersIterator;
+
+    // Bind a socket with a specific address size to a specific multicast group
+    // and port 5353.
+    bool BindSocket(UDPSocket* socket,
+                    int addr_size,
+                    const char* multicast_group);
+
+    // Callback for handling a datagram being recieved on either ipv4 or ipv6.
+    // Responsible for ensuring we request another packet from the network.
+    void OnDatagramRecieved(UDPSocket* socket,

[szym, 2013/05/24 15:32:22]

Throughout the file: s/Recieve/Receive/

[Noam Samuel, 2013/05/29 21:25:16]

Done.

+                            DnsResponse* response,
+                            IPEndPoint* recv_addr,
+                            int bytes_read);
+
+    // Request another packet from the network.

[szym, 2013/05/24 15:32:22]

The implementation shows that this calls RecvFrom without sending anything out.
Why would anyone send us a packet? Can it wait indefinitely?

What does this return?

[Noam Samuel, 2013/05/24 19:00:49]

It does wait indefinitely. It does so in an asynchronous fashion. Since every
MDns client has to act as a server, this is actually part of a listening loop
that continually listens for packets sent to the mDNS multicast group.

On 2013/05/24 15:32:22, szym wrote:

+    bool RecieveOnePacket(UDPSocket* socket,
+                          DnsResponse* response,
+                          IPEndPoint* recv_addr);
+
+    // Parse the response and alert relevant listeners.
+    void HandlePacket(DnsResponse* response, int bytes_read);
+
+    // Alert listeners of an update to the cache.
+    void AlertListeners(MDnsUpdateType update_type,
+                        const ListenerKey& key, const RecordParsed* record);
+
+    // Schedule a cleanup to a specific time, cancelling other cleanups.
+    void ScheduleCleanup(base::Time cleanup);
+
+    // Clean up the cache and schedule a new cleanup.
+    void DoCleanup();
+
+    // Callback for when sending a query has finished.
+    void SendDone(int sent);
+
+    // Callback for when a record is removed from the cache.
+    void OnRecordRemoved(const RecordParsed* record);
+
+    std::multimap<ListenerKey, MDnsListenerImpl*> listeners_;
+
+    scoped_ptr<UDPSocket> socket_ipv4_;
+    scoped_ptr<UDPSocket> socket_ipv6_;
+
+    scoped_ptr<DnsResponse> response_ipv4_;
+    scoped_ptr<DnsResponse> response_ipv6_;
+
+    // The address from which the last packet was recieved.
+    IPEndPoint recv_addr_ipv4_;
+    IPEndPoint recv_addr_ipv6_;
+
+    MDnsListenerFactoryImpl* factory_;
+    MDnsCache cache_;
+
+    base::CancelableCallback<void()> cleanup_callback_;
+    base::Time scheduled_cleanup_;

[szym, 2013/05/24 15:32:22]

DISALLOW_COPY_AND_ASSIGN.

[Noam Samuel, 2013/05/29 21:25:16]

Done.

+  };
+
+  MDnsListenerFactoryImpl();
+
+  // Used only for testing. Lets users of this class decouple it from time
+  // dependence.
+  MDnsListenerFactoryImpl(base::Clock* clock, base::TaskRunner* task_runner);
+  virtual ~MDnsListenerFactoryImpl();
+
+  // Add delegate for RRType |rrtype| and name |name|.
+  // If |name| is an empty string, listen to all notification of type
+  // |rrtype|.
+  virtual scoped_ptr<MDnsListener> CreateListener(
+      uint16 rrtype,
+      const std::string& name,
+      bool active,
+      bool alert_existing_records,
+      MDnsListenerFactory::Delegate* delegate) OVERRIDE;

[szym, 2013/05/24 15:32:22]

You don't need MDnsListenerFactory:: here and elsewhere in this file.

[Noam Samuel, 2013/05/29 21:25:16]

Moved all the delegates and callbacks to their respective objects.

On 2013/05/24 15:32:22, szym wrote:

+
+  // 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 MDnsListenerFactory::QueryCallback& callback) OVERRIDE;
+
+  // Functions for testing only.
+  bool IsListeningForTests();
+
+ protected:
+  // These are couplings to multicast networking that tests will need to
+  // override in order to ensure the tests run only on the loopback network.
+
+  // Tests will need to redirect multicast queries to a unicast destination.
+  virtual IPEndPoint GetIPv4SendEndpoint();
+  virtual IPEndPoint GetIPv6SendEndpoint();
+
+  // Tests will need to control the binding behavior of sockets
+  // (e.g. not use REUSEADDR and not join the multicast group).
+  virtual bool BindToAddressAndMulticastGroup(UDPSocket* socket,
+                                              const IPEndPoint& address,
+                                              const IPAddressNumber& group);
+
+ private:
+  bool AddListenRef();
+  void SubtractListenRef();
+
+  scoped_ptr<Core> core_;
+  int listen_refs_;
+
+  // Since we can either own or not own clock, use both a scoped_ptr and a ptr.
+  scoped_ptr<base::Clock> clock_owned_;
+  base::Clock* clock_;
+
+  scoped_refptr<base::TaskRunner> task_runner_;
+};
+
+class MDnsListenerImpl : public MDnsListener,
+                         public base::SupportsWeakPtr<MDnsListenerImpl> {
+ public:
+  MDnsListenerImpl(uint16 rrtype,
+                   const std::string& name,
+                   bool active,
+                   bool alert_existing_records,
+                   MDnsListenerFactory::Delegate* delegate,
+                   MDnsListenerFactoryImpl::Core* core);
+
+  // Destroying the listener stops listening.
+  virtual ~MDnsListenerImpl();
+
+  // Get the host or service name for this query.
+  // Return an empty string for no name.
+  virtual const std::string& GetName() const OVERRIDE;
+
+  // Get the type for this query (SRV, TXT, A, AAA, etc)
+  virtual uint16 GetType() const OVERRIDE;
+
+  virtual bool IsActive() const OVERRIDE;
+
+  // 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) OVERRIDE;
+
+  // 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 OVERRIDE;
+
+  MDnsListenerFactory::Delegate* delegate() { return delegate_; }
+
+  void AlertDelegate(MDnsUpdateType update_type,
+                     const RecordParsed* record_parsed);
+ private:
+  uint16 rrtype_;
+  std::string name_;
+  bool active_;
+  MDnsListenerFactoryImpl::Core* parent_;
+  MDnsListenerFactory::Delegate* delegate_;
+};
+
+class MDnsTransactionImpl : public MDnsTransaction,
+                            public base::SupportsWeakPtr<MDnsTransactionImpl>,
+                            public MDnsListenerFactoryImpl::Delegate {
+ public:
+  MDnsTransactionImpl(uint16 rrtype,
+                      const std::string& name,
+                      const MDnsListenerFactory::QueryCallback& callback,
+                      base::TaskRunner* task_runner);
+  virtual ~MDnsTransactionImpl();
+
+  // Start the transaction. Returns true on success.
+  bool Init(MDnsListenerFactoryImpl* factory,
+            MDnsListenerFactoryImpl::Core* core);
+
+  // MDnsListenerFactoryImpl::Delegate implementation
+  virtual void OnRecordUpdate(MDnsUpdateType update,
+                              const RecordParsed* record) OVERRIDE;
+  virtual void OnNSecRecord(const std::string& name, unsigned type) OVERRIDE;
+
+
+  virtual const std::string& GetName() const OVERRIDE;
+  virtual uint16 GetType() const OVERRIDE;
+
+ private:
+  // Trigger the callback and reset all related variables.
+  void TriggerCallback(MDnsTransactionResult result,
+                       const RecordParsed* record);
+
+  // Internal callback for when a cache record is found.
+  void CacheRecordFound(const RecordParsed* record);
+
+  // Callback for when the transaction times out.
+  void OnTimedOut();
+
+  uint16 rrtype_;
+  std::string name_;
+  MDnsListenerFactory::QueryCallback callback_;
+
+  bool triggered_;
+  scoped_ptr<MDnsListener> listener_;
+  base::CancelableCallback<void()> timeout_;
+  scoped_refptr<base::TaskRunner> task_runner_;
+};
+}
+#endif  // NET_DNS_MDNS_LISTENER_IMPL_H_