1 // Copyright 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_QUIC_PORT_SUGGESTER_H_ 6 #define NET_QUIC_PORT_SUGGESTER_H_ 7 8 #include "base/basictypes.h" 9 #include "base/memory/ref_counted.h" 10 #include "base/sha1.h" 11 #include "net/base/net_export.h" 12 13 namespace net { 14 15 class HostPortPair; 16 17 // We provide a pseudo-random number generator that is always seeded the same 18 // way for a given destination host-port pair. The generator is used to 19 // consistently suggest (for that host-port pair) an ephemeral source port, 20 // and hence increase the likelihood that a server's load balancer will direct 21 // a repeated connection to the same server (with QUIC, further increasing the 22 // chance of connection establishment with 0-RTT). 23 class NET_EXPORT_PRIVATE PortSuggester 24 : public base::RefCounted<PortSuggester> { 25 public: 26 PortSuggester(const HostPortPair& server, uint64 seed); 27 28 // Generate a pseudo-random int in the inclusive range from |min| to |max|. 29 // Will (probably) return different numbers when called repeatedly. 30 int SuggestPort(int min, int max); 31 call_count()32 uint32 call_count() const { return call_count_; } 33 int previous_suggestion() const; 34 35 private: 36 friend class base::RefCounted<PortSuggester>; 37 ~PortSuggester()38 virtual ~PortSuggester() {} 39 40 // We maintain the first 8 bytes of a hash as our seed_ state. 41 uint64 seed_; 42 uint32 call_count_; // Number of suggestions made. 43 int previous_suggestion_; 44 45 DISALLOW_COPY_AND_ASSIGN(PortSuggester); 46 }; 47 48 } // namespace net 49 50 #endif // NET_QUIC_PORT_SUGGESTER_H_ 51