… a utility class

…t relying on external dependencies

…CommandTransport optimized implementation

- The original implementation we had could not access some of the required methods due to being outside of the `hudson.remoting` package, so we didn't need these wrappers

- Some of the tests require JUnit 4.12

…occurs in "fast" protocols

… filter layer

- Resurected from history as we will be forced to diverge to map against the JNLPProtocol APIs rather than follow the nicer implementation path from CJOC

…c within remoting

- rather than having one half of the protocol in jenkins and the other half in remoting.
- I need to write tests for this and then remote the old classes

…rQueueInputStream

- Also causes commands that span multiple frames to be corrupted

…onnects

- Don't think this affected any real protocols, but better to fix after finding

- Avoids intermediate String representation. Could probably get faster still with BigInteger and zero-left-pad but it becomes harder to understand

…et concurrent modification exceptions

- They'll recover, but better is not to have to worry about it at all

…ave been tried

- Also better setup of the SSLContext

…for writing

…efused connections

…ict validation

…ceive and send sides without bombing out.

Prevents stack traces such as

```
Exception in thread "main" java.lang.IllegalStateException: Filter has already been completed
	at org.jenkinsci.remoting.protocol.FilterLayer.completed(FilterLayer.java:106)
	at org.jenkinsci.remoting.protocol.impl.ConnectionHeadersFilterLayer.complete(ConnectionHeadersFilterLayer.java:365)
	at org.jenkinsci.remoting.protocol.impl.ConnectionHeadersFilterLayer.doSend(ConnectionHeadersFilterLayer.java:498)
	at org.jenkinsci.remoting.protocol.ProtocolStack$Ptr.doSend(ProtocolStack.java:691)
	at org.jenkinsci.remoting.protocol.ApplicationLayer.write(ApplicationLayer.java:157)
	at org.jenkinsci.remoting.protocol.impl.ChannelApplicationLayer.start(ChannelApplicationLayer.java:226)
	at org.jenkinsci.remoting.protocol.ProtocolStack.init(ProtocolStack.java:202)
	at org.jenkinsci.remoting.protocol.ProtocolStack.access$700(ProtocolStack.java:107)
	at org.jenkinsci.remoting.protocol.ProtocolStack$Builder.build(ProtocolStack.java:555)
	at org.jenkinsci.remoting.engine.JnlpProtocol4PlainHandler.connect(JnlpProtocol4PlainHandler.java:149)
	at org.jenkinsci.remoting.engine.JnlpProtocolHandler.connect(JnlpProtocolHandler.java:140)
	at org.jenkinsci.remoting.engine.HandlerLoopbackLoadStress.startClient(HandlerLoopbackLoadStress.java:466)
	at org.jenkinsci.remoting.engine.HandlerLoopbackLoadStress.main(HandlerLoopbackLoadStress.java:426)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
```

… method

…tStream implementation

- Drops support for mark and unbounded read in return for faster performance

- We don't need the general purpose mark support or unbounded reads, so lets get more performance

…ions, so allow preference declaration

- You'll see why I spotted this next

- This needs its own LICENSE and NOTICE files as it includes things like JUnit

…build agents

…e command line

- though this technically is OK as protected or package scope as any derived classes can implement and Enum is a public class so there is a parent type that people can reference

- Of course we are now weakening the equality test, but since this has come through the cipher
  this shouldn't be too bad.

- Found another set of cases where the cookie gets mangled, as the EngineUtil.readLine does a `.trim()`
  If the encrypted cookie happens to being or end with a whitespace character... boom
  A first order analysis looks only at the single bytes that could be whitespace.
  There are 9 such bytecodes, but that includes `\n` which we have already tested for
  So there is an 8 in 256 or 1 in 32 chance that the first character is whitespace
  There is a 31 in 32 chance that it is not and a 1 in 32 chance that the last is whitespace
  Thus (1/32 + 32/32*1/32) = 6%... or in total 28% of the time the generated cookies will
  be unusable with the current handshaking ciphers

- Also stop creating throw-away instances of `SecureRandom` because that is a waste

…s introduced bug

- We don't want to synchronize as that will cause issues during the close. We can rely on the stack for ensuring that reads are serialized and writes are serialized and the `channel` field is write once with the write guarded by the synchronized setup method

 - On machines with fewer cores than my machine, the selector thread may not have processed the interest removal and hence the test can fail randomly for lower spec machines