1 // Copyright (c) 2012 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_DNS_SESSION_H_ 6 #define NET_DNS_DNS_SESSION_H_ 7 8 #include <vector> 9 10 #include "base/lazy_instance.h" 11 #include "base/memory/ref_counted.h" 12 #include "base/memory/scoped_ptr.h" 13 #include "base/memory/scoped_vector.h" 14 #include "base/metrics/bucket_ranges.h" 15 #include "base/time/time.h" 16 #include "net/base/net_export.h" 17 #include "net/base/rand_callback.h" 18 #include "net/dns/dns_config_service.h" 19 #include "net/dns/dns_socket_pool.h" 20 21 namespace base { 22 class BucketRanges; 23 class SampleVector; 24 } 25 26 namespace net { 27 28 class ClientSocketFactory; 29 class DatagramClientSocket; 30 class NetLog; 31 class StreamSocket; 32 33 // Session parameters and state shared between DNS transactions. 34 // Ref-counted so that DnsClient::Request can keep working in absence of 35 // DnsClient. A DnsSession must be recreated when DnsConfig changes. 36 class NET_EXPORT_PRIVATE DnsSession NON_EXPORTED_BASE(public base::RefCounted<DnsSession>)37 : NON_EXPORTED_BASE(public base::RefCounted<DnsSession>) { 38 public: 39 typedef base::Callback<int()> RandCallback; 40 41 class NET_EXPORT_PRIVATE SocketLease { 42 public: 43 SocketLease(scoped_refptr<DnsSession> session, 44 unsigned server_index, 45 scoped_ptr<DatagramClientSocket> socket); 46 ~SocketLease(); 47 48 unsigned server_index() const { return server_index_; } 49 50 DatagramClientSocket* socket() { return socket_.get(); } 51 52 private: 53 scoped_refptr<DnsSession> session_; 54 unsigned server_index_; 55 scoped_ptr<DatagramClientSocket> socket_; 56 57 DISALLOW_COPY_AND_ASSIGN(SocketLease); 58 }; 59 60 DnsSession(const DnsConfig& config, 61 scoped_ptr<DnsSocketPool> socket_pool, 62 const RandIntCallback& rand_int_callback, 63 NetLog* net_log); 64 65 const DnsConfig& config() const { return config_; } 66 NetLog* net_log() const { return net_log_; } 67 68 // Return the next random query ID. 69 int NextQueryId() const; 70 71 // Return the index of the first configured server to use on first attempt. 72 unsigned NextFirstServerIndex(); 73 74 // Start with |server_index| and find the index of the next known good server 75 // to use on this attempt. Returns |server_index| if this server has no 76 // recorded failures, or if there are no other servers that have not failed 77 // or have failed longer time ago. 78 unsigned NextGoodServerIndex(unsigned server_index); 79 80 // Record that server failed to respond (due to SRV_FAIL or timeout). 81 void RecordServerFailure(unsigned server_index); 82 83 // Record that server responded successfully. 84 void RecordServerSuccess(unsigned server_index); 85 86 // Record how long it took to receive a response from the server. 87 void RecordRTT(unsigned server_index, base::TimeDelta rtt); 88 89 // Record suspected loss of a packet for a specific server. 90 void RecordLostPacket(unsigned server_index, int attempt); 91 92 // Record server stats before it is destroyed. 93 void RecordServerStats(); 94 95 // Return the timeout for the next query. |attempt| counts from 0 and is used 96 // for exponential backoff. 97 base::TimeDelta NextTimeout(unsigned server_index, int attempt); 98 99 // Allocate a socket, already connected to the server address. 100 // When the SocketLease is destroyed, the socket will be freed. 101 scoped_ptr<SocketLease> AllocateSocket(unsigned server_index, 102 const NetLog::Source& source); 103 104 // Creates a StreamSocket from the factory for a transaction over TCP. These 105 // sockets are not pooled. 106 scoped_ptr<StreamSocket> CreateTCPSocket(unsigned server_index, 107 const NetLog::Source& source); 108 109 private: 110 friend class base::RefCounted<DnsSession>; 111 ~DnsSession(); 112 113 // Release a socket. 114 void FreeSocket(unsigned server_index, 115 scoped_ptr<DatagramClientSocket> socket); 116 117 // Return the timeout using the TCP timeout method. 118 base::TimeDelta NextTimeoutFromJacobson(unsigned server_index, int attempt); 119 120 // Compute the timeout using the histogram method. 121 base::TimeDelta NextTimeoutFromHistogram(unsigned server_index, int attempt); 122 123 const DnsConfig config_; 124 scoped_ptr<DnsSocketPool> socket_pool_; 125 RandCallback rand_callback_; 126 NetLog* net_log_; 127 128 // Current index into |config_.nameservers| to begin resolution with. 129 int server_index_; 130 131 struct ServerStats; 132 133 // Track runtime statistics of each DNS server. 134 ScopedVector<ServerStats> server_stats_; 135 136 // Buckets shared for all |ServerStats::rtt_histogram|. 137 struct RttBuckets : public base::BucketRanges { 138 RttBuckets(); 139 }; 140 static base::LazyInstance<RttBuckets>::Leaky rtt_buckets_; 141 142 DISALLOW_COPY_AND_ASSIGN(DnsSession); 143 }; 144 145 } // namespace net 146 147 #endif // NET_DNS_DNS_SESSION_H_ 148