Consistently suggest ephemeral port for QUIC client

net/quic/port_suggester.h

Index: net/quic/port_suggester.h
diff --git a/net/quic/port_suggester.h b/net/quic/port_suggester.h
new file mode 100644
index 0000000000000000000000000000000000000000..6e265bf63b00baca89961c7332d84462a0b06a3b
--- /dev/null
+++ b/net/quic/port_suggester.h
@@ -0,0 +1,45 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[wtc, 2013/12/06 23:36:44]

Nit: this should say 2013. And "(c)" is now not needed.

Also fix the other new files.

[jar (doing other things), 2013/12/07 00:47:58]

Done.

+// 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/host_port_pair.h"

[wtc, 2013/12/06 23:36:44]

Nit: you may be able to get by with a forward declaration of HostPortPair.

[jar (doing other things), 2013/12/07 00:47:58]

Done.

+
+namespace net {
+
+// 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 PortSuggester
+    : public base::RefCountedThreadSafe<PortSuggester> {
+ public:
+  // |per_profile_randomness| is used to prevent (reduce probability of) one
+  // profile's suggestions from matching that of another.
+  PortSuggester(const HostPortPair& hostport, uint64 per_profile_randomness);

[wtc, 2013/12/06 23:36:44]

Nit: you should explain whose host and port |hostport| is. Alternatively you can
probably just name the parameter |server|.

[jar (doing other things), 2013/12/07 00:47:58]

Done (switched to |server|)

+
+  // Generate a pseudo-random int in the given range. Will (probably) return

[wtc, 2013/12/06 23:36:44]

Nit: please specify whether the range is inclusive.

[jar (doing other things), 2013/12/07 00:47:58]

Done.

+  // different numbers when called repeatedly.
+  int SuggestPort(int min, int max);
+
+ private:
+  friend class base::RefCountedThreadSafe<PortSuggester>;
+
+  virtual ~PortSuggester();
+
+  unsigned char seed_[base::kSHA1Length];
+  int count_;  // Number of suggestions made.
+
+  DISALLOW_COPY_AND_ASSIGN(PortSuggester);
+};
+
+}  // namespace net
+
+#endif  // NET_QUIC_PORT_SUGGESTER_H_