net/quic/port_suggester.h

   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
  32   uint32 call_count() const { return call_count_; }
  33   int previous_suggestion() const;
  34
  35  private:
  36   friend class base::RefCounted<PortSuggester>;
  37
  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_