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// Copyright 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_QUIC_PORT_SUGGESTER_H_
#define NET_QUIC_PORT_SUGGESTER_H_
#include "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/sha1.h"
#include "net/base/net_export.h"
namespace net {
class HostPortPair;
// We provide a pseudo-random number generator that is always seeded the same
// way for a given destination host-port pair. The generator is used to
// consistently suggest (for that host-port pair) an ephemeral source port,
// and hence increase the likelihood that a server's load balancer will direct
// a repeated connection to the same server (with QUIC, further increasing the
// chance of connection establishment with 0-RTT).
class NET_EXPORT_PRIVATE PortSuggester
: public base::RefCounted<PortSuggester> {
public:
PortSuggester(const HostPortPair& server, uint64 seed);
// Generate a pseudo-random int in the inclusive range from |min| to |max|.
// Will (probably) return different numbers when called repeatedly.
int SuggestPort(int min, int max);
uint32 call_count() const { return call_count_; }
int previous_suggestion() const;
private:
friend class base::RefCounted<PortSuggester>;
virtual ~PortSuggester() {}
// We maintain the first 8 bytes of a hash as our seed_ state.
uint64 seed_;
uint32 call_count_; // Number of suggestions made.
int previous_suggestion_;
DISALLOW_COPY_AND_ASSIGN(PortSuggester);
};
} // namespace net
#endif // NET_QUIC_PORT_SUGGESTER_H_
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