Motivation:
How we did the mapping from native code to AbstractKQueueChannel was not safe and could lead to heap corruption. This then sometimes produced ClassCastExceptions or could also lead to crashes. This happened sometimes when running the testsuite.
Modifications:
Use a Map for the mapping (just as we do in the native epoll transport).
Result:
No more heap corruption / crashes.
Motivation:
Most of the maven modules do not explicitly declare their
dependencies and rely on transitivity, which is not always correct.
Modifications:
For all maven modules, add all of their dependencies to pom.xml
Result:
All of the (essentially non-transitive) depepdencies of the modules are explicitly declared in pom.xml
Motivation:
MACOSX_DEPLOYMENT_TARGET=10.6 needs to be used as everything before is not supported in 10.14 anymore. 10.6 was released 2009 so this should be a safe thing to do.
Modifications:
Use MACOSX_DEPLOYMENT_TARGET=10.6
Result:
Be able to compile on MacOS 10.14
Motivation:
Add an option (through a SelectStrategy return code) to have the Netty event loop thread to do busy-wait on the epoll.
The reason for this change is to avoid the context switch cost that comes when the event loop thread is blocked on the epoll_wait() call.
On average, the context switch has a penalty of ~13usec.
This benefits both:
The latency when reading from a socket
Scheduling tasks to be executed on the event loop thread.
The tradeoff, when enabling this feature, is that the event loop thread will be using 100% cpu, even when inactive.
Modification:
Added SelectStrategy option to return BUSY_WAIT
Epoll loop will do a epoll_wait() with no timeout
Use pause instruction to hint to processor that we're in a busy loop
Result:
When enabled, minimizes impact of context switch in the critical path
Motivation
The EpollChannelConfig (same for KQueues) and its subclasses repeatetly declare their own channel field which leads to a 3x repetition for each config instance. Given the fields are protected or package-private it's exposing the code code to "field hiding" bugs.
Modifications
Use the the existing protected channel field from the DefaultChannelConfig class and simply cast it when needed.
Result
Fixes#8331
Motivation:
We should ensure we call *UnLoad when we detect an error during calling *OnLoad and previous *OnLoad calls were succesfull.
Modifications:
Correctly call *UnLoad when needed.
Result:
More correct code and no leaks when an error happens during loading the native lib.
* Allow to use native transports when sun.misc.Unsafe is not present on the system
Motivation:
We should be able to use the native transports (epoll / kqueue) even when sun.misc.Unsafe is not present on the system. This is especially important as Java11 will be released soon and does not allow access to it by default.
Modifications:
- Correctly disable usage of sun.misc.Unsafe when -PnoUnsafe is used while running the build
- Correctly increment metric when UnpooledDirectByteBuf is allocated. This was uncovered once -PnoUnsafe usage was fixed.
- Implement fallbacks in all our native transport code for when sun.misc.Unsafe is not present.
Result:
Fixes https://github.com/netty/netty/issues/8229.
Motivation:
We should support to load multiple shaded versions of the same netty artifact as netty is often used in multiple dependencies.
This is related to https://github.com/netty/netty/issues/7272.
Modifications:
- Use -fvisibility=hidden when compiling and use JNIEXPORT for things we really want to have exported
- Ensure fields are declared as static so these are not exported
- Adjust testsuite-shading to use install_name_tool on MacOS to change the id of the lib. Otherwise the wrong may be used.
Result:
Be able to use multiple shaded versions of the same netty artifact.
Motivation:
Epoll and Kqueue channels have internal state which forces
a single read operation after channel construction. This
violates the Channel#read() interface which indicates that
data shouldn't be delivered until this method is called.
The behavior is also inconsistent with the NIO transport.
Modifications:
- Epoll and Kqueue shouldn't unconditionally read upon
initialization, and instead should rely upon Channel#read()
or auto_read.
Result:
Epoll and Kqueue are more consistent with NIO.
Motivation:
We should allow to schedule tasks with a delay up to Long.MAX_VALUE as we did pre 4.1.25.Final.
Modifications:
Just ensure we not overflow and put the correct max limits in place when schedule a timer. At worse we will get a wakeup to early and then schedule a new timeout.
Result:
Fixes https://github.com/netty/netty/issues/7970.
* Read until all data is consumed when EOF is detected even if readPending is false and auto-read is disabled.
Motivation:
We should better always notify the user of EOF even if the user did not request any data as otherwise we may never be notified when the remote peer closes the connection. This should be ok as the amount of extra data we may read and so fire through the pipeline is limited by SO_RECVBUF.
Modifications:
- Always drain the socket when EOF is detected.
- Add testcase
Result:
No risk for the user to be not notified of EOF.
Motivation:
Sometimes it's useful to disable native transports / native ssl to debug a problem. We should allow to do so with a system property so people not need to adjust code for this.
Modifications:
Add system properties which allow to disable native transport and native ssl.
Result:
Easier to disable native code usage without code changes.
Motivation:
Using a very huge delay when calling schedule(...) may cause an Selector error when calling select(...) later on. We should gaurd against such a big value.
Modifications:
- Add guard against a very huge value.
- Added tests.
Result:
Fixes [#7365]
Motivation:
AbstractNioByteChannel will detect that the remote end of the socket has
been closed and propagate a user event through the pipeline. However if
the user has auto read on, or calls read again, we may propagate the
same user events again. If the underlying transport continuously
notifies us that there is read activity this will happen in a spin loop
which consumes unnecessary CPU.
Modifications:
- AbstractNioByteChannel's unsafe read() should check if the input side
of the socket has been shutdown before processing the event. This is
consistent with EPOLL and KQUEUE transports.
- add unit test with @normanmaurer's help, and make transports consistent with respect to user events
Result:
No more read spin loop in NIO when the channel is half closed.
Motivation:
The flush task is currently using flush() which will have the affect of have the flush traverse the whole ChannelPipeline and also flush messages that were written since we gave up flushing. This is not really correct as we should only continue to flush messages that were flushed at the point in time when the flush task was submitted for execution if the user not explicit call flush() by him/herself.
Modification:
Call *Unsafe.flush0() via the flush task which will only continue flushing messages that were marked as flushed before.
Result:
More correct behaviour when the flush task is used.
Motivation:
KQueue implementations current have inconsistent behavior with Epoll implementations with respect to asynchronous sockets and connecting. In the Epoll transport we attempt to connect, if the connect call does not synchornously fail/succeed we set the EPOLLOUT which will be triggered by the kernel if the connection attempt succeeds or an error occurs. The connect API provides no way to asynchronously communicate an error so the Epoll implementation fires a EPOLLOUT event and puts the connect status in getsockopt(SO_ERROR). KQueue provides the same APIs but different behavior. If the EVFILT_WRITE is not enabled and the EVFILT_READ is enabled before connect is called, and there is an error the kernel may fire the EVFILT_READ filter and provide the Connection Refused error via read(). This is even true if we set the EVFILT_WRITE filter after calling connect because connect didn't synchornously complete. After the error has been delievered via read() a call to getsockopt(SO_ERROR) will return 0 indicating there is no error. This means we cannot rely upon the KQueue based kernel to deliver connection errors via the EVFILT_WRITE filter in the same way that the linux kernel does with the EPOLLOUT flag.
ce241bd introduced a change which depends upon the behavior of the EVFILT_WRITE being set and may prematurely stop writing to the OS as a result, becaues we assume the OS will notify us when the socket is writable. However the current work around for the above described behavior is to initialize the EVFILT_WRITE to true for connection oriented protocols. This leads to prematurely exiting from the flush() which may lead to deadlock.
Modifications:
- KQueue should check when an error is obtained from read() if the connectPromise has not yet been completed, and if not complete it with a ConnectException
Result:
No more deadlock in KQueue due to asynchronous connect workaround.
Motivation:
b215794de3 recently introduced a change in behavior where writeSpinCount provided a limit for how many write operations were attempted per flush operation. However when the write quantum was meet the selector write flag was not cleared, and the channel unsafe flush0 method has an optimization which prematurely exits if the write flag is set. This may lead to no write progress being made under the following scenario:
- flush is called, but the socket can't accept all data, we set the write flag
- the selector wakes us up because the socket is writable, we write data and use the writeSpinCount quantum
- we then schedule a flush() on the EventLoop to execute later, however it the flush0 optimization prematurely exits because the write flag is still set
In this scenario the socket is still writable so the EventLoop may never notify us that the socket is writable, and therefore we may never attempt to flush data to the OS.
Modifications:
- When the writeSpinCount quantum is exceeded we should clear the selector write flag
Result:
Fixes https://github.com/netty/netty/issues/7729
Motivation:
IovArray implements MessageProcessor, and the processMessage method will continue to be called during iteration until it returns true. A recent commit b215794de3 changed the return value to only return true if any component of a CompositeByteBuf was added as a result of the method call. However this results in the iteration continuing, and potentially subsequent smaller buffers maybe added, which will result in out of order writes and generally corrupts data.
Modifications:
- IovArray#add should return false so that the MessageProcessor#processMessage will stop iterating.
Result:
Native transports which use IovArray will not corrupt data during gathering writes of CompositeByteBuf objects.
Motivation:
FileDescriptor#writev calls JNI code, and that JNI code dereferences a NULL pointer which crashes the application. This occurs when writing a single CompositeByteBuf object with more than one component.
Modifications:
- Initialize the iovec iterator properly to avoid the core dump
- Fix the array length calculation if we aren't able to fit all the ByteBuffer objects in the iovec array
Result:
No more core dump.
Motivation:
The writeSpinCount currently loops over the same buffer, gathering
write, file write, or other write operation multiple times but will
continue writing until there is nothing left or the OS doesn't accept
any data for that specific write. However if the OS keeps accepting
writes there is no way to limit how much time we spend on a specific
socket. This can lead to unfair consumption of resources dedicated to a
single socket.
We currently don't limit the amount of bytes we attempt to write per
gathering write. If there are many more bytes pending relative to the
SO_SNDBUF size we will end up building iov arrays with more elements
than can be written, which results in extra iteration, conditionals,
and book keeping.
Modifications:
- writeSpinCount should limit the number of system calls we make to
write data, instead of applying to individual write operations
- IovArray should support a maximum number of bytes
- IovArray should support composite buffers of greater than size 1024
- We should auto-scale the amount of data that we attempt to write per
gathering write operation relative to SO_SNDBUF and how much data is
successfully written
- The non-unsafe path should also support a maximum number of bytes,
and respect the IOV_MAX limit
Result:
Write resource consumption can be bounded and gathering writes have
a limit relative to the amount of data which can actually be accepted
by the socket.
Motivation:
We used NetUtil.isIpV4StackPreferred() when loading JNI code which tries to load NetworkInterface in its static initializer. Unfortunally a lock on the NetworkInterface class init may be already hold somewhere else which may cause a loader deadlock.
Modifications:
Add a new Socket.initialize() method that will be called when init the library and pass everything needed to the JNI level so we not need to call back to java.
Result:
Fixes [#7458].
Motivation:
AbstractChannel attempts to "filter" messages which are written [1]. A goal of this process is to copy from heap to direct if necessary. However implementations of this method [2][3] may translate a buffer with 0 readable bytes to EMPTY_BUFFER. This may mask a user error where an empty buffer is written but already released.
Modifications:
Replace safeRelease(...) with release(...) to ensure we propagate reference count issues.
Result:
Fixes [#7383]
Automatic-Module-Name entry provides a stable JDK9 module name, when Netty is used in a modular JDK9 applications. More info: http://blog.joda.org/2017/05/java-se-9-jpms-automatic-modules.html
When Netty migrates to JDK9 in the future, the entry can be replaced by actual module-info descriptor.
Modification:
The POM-s are configured to put the correct module names to the manifest.
Result:
Fixes#7218.
Motivation:
We need to set readPending to false when we detect a EOF while issue a read as otherwise we may not unregister from the Selector / Epoll / KQueue and so keep on receving wakeups.
The important bit is that we may even get a wakeup for a read event but will still will only be able to read 0 bytes from the socket, so we need to be very careful when we clear the readPending. This can happen because we generally using edge-triggered mode for our native transports and because of the nature of edge-triggered we may schedule an read event just to find out there is nothing left to read atm (because we completely drained the socket on the previous read).
Modifications:
Set readPending to false when EOF is detected.
Result:
Fixes [#7255].
This reverts commit 413c7c2cd8 as it introduced an regression when edge-triggered mode is used which is true for our native transports by default. With 413c7c2cd8 included it was possible that we set readPending to false by mistake even if we would be interested in read more.
Motivation:
readPending is currently only set to false if data is delivered to the application, however this may result in duplicate events being received from the selector in the event that the socket was closed.
Modifications:
- We should set readPending to false before each read attempt for all
transports besides NIO.
- Based upon the Javadocs it is possible that NIO may have spurious
wakeups [1]. In this case we should be more cautious and only set
readPending to false if data was actually read.
[1] https://docs.oracle.com/javase/7/docs/api/java/nio/channels/SelectionKey.html
That a selection key's ready set indicates that its channel is ready for some operation category is a hint, but not a guarantee, that an operation in such a category may be performed by a thread without causing the thread to block.
Result:
Notification from the selector (or simulated events from kqueue/epoll ET) in the event of socket closure.
Fixes https://github.com/netty/netty/issues/7255
Motivation:
Even if it's a super micro-optimization (most JVM could optimize such
cases in runtime), in theory (and according to some perf tests) it
may help a bit. It also makes a code more clear and allows you to
access such methods in the test scope directly, without instance of
the class.
Modifications:
Add 'static' modifier for all methods, where it possible. Mostly in
test scope.
Result:
Cleaner code with proper 'static' modifiers.
Motivation:
Due a bug we happen to sometimes fail the connectPromise with a ClosedChannelException when using the kqueue transport and the remote peer refuses the connection. We need to ensure we fail it with the correct exception.
Modifications:
Call finishConnect() before calling close() to ensure we preserve the correct exception.
Result:
KQueueSocketConnectionAttemptTest.testConnectionRefused will pass always on macOS.
Motivation:
There are 2 motivations, the first depends on the second:
Loading Netty Epoll statically stopped working in 4.1.16, due to
`Native` always loading the arch specific shared object. In a
static binary, there is no arch specific SO.
Second, there are a ton of exceptions that can happen when loading
a native library. When loading native code, Netty tries a bunch of
different paths but a failure in any given may not be fatal.
Additionally: turning on debug logging is not always feasible so
exceptions get silently swallowed.
Modifications:
* Change Epoll and Kqueue to try the static load second
* Modify NativeLibraryLoader to record all the locations where
exceptions occur.
* Attempt to use `addSuppressed` from Java 7 if available.
Alternatives Considered:
An alternative would be to record log messages at each failure. If
all load attempts fail, the log messages are printed as warning,
else as debug. The problem with this is there is no `LogRecord` to
create like in java.util.logging. Buffering the args to
logger.log() at the end of the method loses the call site, and
changes the order of events to be confusing.
Another alternative is to teach NativeLibraryLoader about loading
the SO first, and then the static version. This would consolidate
the code fore Epoll, Kqueue, and TCNative. I think this is the
long term better option, but this PR is changing a lot already.
Someone else can take a crack at it later
Results:
Epoll Still Loads and easier debugging.
Motivation:
When SO_LINGER is used we run doClose() on the GlobalEventExecutor by default so we need to ensure we schedule all code that needs to be run on the EventLoop on the EventLoop in doClose. Beside this there are also threading issues when calling shutdownOutput(...)
Modifications:
- Schedule removal from EventLoop to the EventLoop
- Correctly handle shutdownOutput and shutdown in respect with threading-model
- Add unit tests
Result:
Fixes [#7159].
Motivation:
We need to ensure we use the correct osname in the Bundle-NativeCode declaration as declared in:
https://www.osgi.org/developer/specifications/reference/
Modifications:
Update osname to match the spec.
Result:
Correct Bundle-NativeCode entry in the MANIFEST
Motivation:
We should only try to load the native artifacts if the architecture we are currently running on is the same as the one the native libraries were compiled for.
Modifications:
Include architecture in native lib name and append the current arch when trying to load these. This will fail then if its not the same as the arch of the compiled arch.
Result:
Fixes [#7150].
Motivation:
PD and PD0 Both try to find and use Unsafe. If unavailable, they
try to log why and continue on. However, it is not always east to
enable this logging. Chaining exceptions together is much easier
to reach, and the original exception is relevant when Unsafe is
needed.
Modifications:
* Make PD log why PD0 could not be loaded with a trace level log
* Make PD0 remember why Unsafe wasn't available
* Expose unavailability cause through PD for higher level use.
* Make Epoll and KQueue include the reason when failing
Result:
Easier debugging in hard to reconfigure environments
Motivation:
If AutoClose is false and there is a IoException then AbstractChannel will not close the channel but instead just fail flushed element in the ChannelOutboundBuffer. AbstractChannel also notifies of writability changes, which may lead to an infinite loop if the peer has closed its read side of the socket because we will keep accepting more data but continuously fail because the peer isn't accepting writes.
Modifications:
- If the transport throws on a write we should acknowledge that the output side of the channel has been shutdown and cleanup. If the channel can't accept more data because it is full, and still healthy it is not expected to throw. However if the channel is not healthy it will throw and is not expected to accept any more writes. In this case we should shutdown the output for Channels that support this feature and otherwise just close.
- Connection-less protocols like UDP can remain the same because the channel may disconnected temporarily.
- Make sure AbstractUnsafe#shutdownOutput is called because the shutdown on the socket may throw an exception.
Result:
More correct handling of write failure when AutoClose is false.
Motivation:
As noticed in https://stackoverflow.com/questions/45700277/
compilation can fail if the definition of a method doesn't
match the declaration. It's easy enough to add this in, and make
it easy to compile.
Modifications:
Add JNIEXPORT to the entry points.
* On Windows this adds: `__declspec(dllexport)`
* On Mac this adds: `__attribute__((visibility("default")))`
* On Linux (GCC 4.2+) this adds: ` __attribute__((visibility("default")))`
* On other it doesn't add anything.
Result:
Easier compilation
Motivation:
KQueueEventLoop and EpollEventLoop implement different approaches to applying a timeout of their respective poll calls. Epoll attempts to ensure the desired timeout is satisfied at the java layer and at the JNI layer, but it should be sufficient to account for spurious wakups at the JNI layer. Epoll timeout granularity is also limited to milliseconds which may be too large for some latency sensitive applications.
Modifications:
- Make EpollEventLoop wait method look like KQueueEventLoop
- Epoll should support a finer timeout granularity via timerfd_create. We can hide most of these details behind the epollWait0 JNI call to avoid crossing additional JNI boundaries.
Result:
More consistent timeout approach between KQueue and Epoll.
Motivation:
The EPOLL transport uses EPOLLRDHUP to detect when the peer closes the write side of the socket. Currently KQueue is not able to mimic this behavior and the only way to detect if the peer has closed is to read. It may not always be appropriate to read for backpressure and other reasons at the application level.
Modifications:
- Support EVFILT_SOCK filter which provides notification when the peer closes the socket
Result:
KQueue transport has more consistent behavior with Epoll transport for detecting peer closure.
Motivation:
Due to an oversight (by myself), linking two JNI modules with
duplicate symbols fails in linking. This only seems to happen
some of the time (the behavior seems to be different between GCC
and Clang toolchains). For instance, including both netty tcnative
and netty epoll fails to link because of duplicate JNI_OnLoad
symobols.
Modification:
Do not define the JNI_OnLoad and JNI_OnUnload symbols when
compiling for static linkage, as indicated by the NETTY_BUILD_STATIC
preprocessor define. They are never directly called when
statically linked.
Result:
Able to statically compile epoll and tcnative code into a single
binary.
Motivation:
At the moment we try to load the library using multiple names which includes names using - but also _ . We should just use _ all the time.
Modifications:
Replace - with _
Result:
Fixes [#7069]
Motivation:
Implementations of DuplexChannel delegate the shutdownOutput to the underlying transport, but do not take any action on the ChannelOutboundBuffer. In the event of a write failure due to the underlying transport failing and application may attempt to shutdown the output and allow the read side the transport to finish and detect the close. However this may result in an issue where writes are failed, this generates a writability change, we continue to write more data, and this may lead to another writability change, and this loop may continue. Shutting down the output should fail all pending writes and not allow any future writes to avoid this scenario.
Modifications:
- Implementations of DuplexChannel should null out the ChannelOutboundBuffer and fail all pending writes
Result:
More controlled sequencing for shutting down the output side of a channel.
Motivation:
We did not correctly handle connect() and disconnect() in EpollDatagramChannel / KQueueDatagramChannel and so the behavior was different compared to NioDatagramChannel.
Modifications:
- Correct implement connect and disconnect methods
- Share connect and related code
- Add tests
Result:
EpollDatagramChannel / KQueueDatagramChannel also supports correctly connect() and disconnect() methods.
Motivation:
`Epoll.ensureAvailability()` is called multiple times, once in
static initialization and in a couple of the constructors. This is
redundant and confusing to read.
Modifications:
Move `Epoll.ensureAvailability()` call into an instance initializer
and remove all other references. This ensures that every EELG
checks availability, while still delaying the check until
construction. This pattern is used when there are multiple ctors,
as in this class.
Result:
Easier to read code.
Motivation:
We should not try to detect a free port in tests put just use 0 when bind so there is no race in which the system my bind something to the port we choosen before.
Modifications:
- Remove the usage of TestUtils.getFreePort() in the testsuite
- Remove hack to workaround bind errors which will not happen anymore now
Result:
Less flacky tests.
Motivation:
JCTools 2.0.2 provides an unbounded MPSC linked queue. Before we shaded JCTools we had our own unbounded MPSC linked queue and used it in various places but gave this up because there was no public equivalent available in JCTools at the time.
Modifications:
- Use JCTool's MPSC linked queue when no upper bound is specified
Result:
Fixes https://github.com/netty/netty/issues/5951
Motivation:
We used an intermediate collection to store the read DatagramPackets and only fired these through the pipeline once wewere done with the reading loop. This is not needed and can also increase memory usage.
Modifications:
Remove intermediate collection
Result:
Less overhead and possible less memory usage during read loop.
Motivation:
The kqueue documentation states that 'Calling close() on a file descriptor will remove any kevents that reference the descriptor.' [1], but doesn't mention if this cleanup will be done synchronously. Under some circumstances it has been observed that cleanup was not done immediately and when KQueueEventLoop attempted to access the channel associated with the event the JVM would crash, a ClassCastException, or generally undefined behavior would occur because of invalid pointer references.
[1] https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2
Modifications:
- AbstractKqueueChannel#doClose should not rely upon this assumption and instead should call doDeregister() to ensure cleanup is done synchronously.
- Deleting a kevent should also set the jniSelfPtr stored in the udata of that kevent to NULL, to ensure we will not dereference it later.
Result:
No more kqueue crash due to close/cleanup sequencing.
Motivation:
We rely upon the linker being non-lazy to test compatibility the native library compatibility for kqueue, but the default mode of operation is to lazy link.
Modifications:
- We should modify the build scripts to inform the linker that this library should not be lazy linked
- Error messages changes
dyld: lazy symbol binding failed: Symbol not found: _clock_gettime
java.lang.UnsatisfiedLinkError: unsupported JNI version 0xFFFFFFFF required by .../libnetty-transport-native-kqueue.dylib
Result:
Link errors are detected upon library load time.
Motivation:
Enable static linking for Java 8. These commits are the same as those introduced to netty tcnative. The goal is to allow lots of JNI libraries to be statically linked together without having conflict `JNI_OnLoad` methods.
Modification:
* add JNI_OnLoad suffixes to enable static linking
* Add static names to the list of libraries that try to be loaded
* Enable compiling with JNI 1.8
* Sort includes
Result:
Enable statically linked JNI code.
Motivation:
We should not force autoconf and compile as this will result in multiple executions and so slow down the build.
Modifications:
Remove force declarations
Result:
Faster build of native modules
Motivation:
1. special handling of ByteBuf with multi nioBuffer rather than type of CompositeByteBuf (eg. DuplicatedByteBuf with CompositeByteBuf)
2. EpollDatagramUnicastTest and KQueueDatagramUnicastTest passed because CompositeByteBuf is converted to DuplicatedByteBuf before write to channel
3. uninitalized struct msghdr will raise error
Modifications:
1. isBufferCopyNeededForWrite(like isSingleDirectBuffer in NioDatgramChannel) checks wether a new direct buffer is needed
2. special handling of ByteBuf with multi nioBuffer in EpollDatagramChannel, AbstractEpollStreamChannel, KQueueDatagramChannel, AbstractKQueueStreamChannel and IovArray
3. initalize struct msghdr
Result:
handle of ByteBuf with multi nioBuffer in EpollDatagramChannel and KQueueDatagramChannel are ok
Motivation:
We only can call eventLoop() if we are registered on an EventLoop yet. As we just did this without checking we spammed the log with an error that was harmless.
Modifications:
Check if registered on eventLoop before try to deregister on close.
Result:
Fixes [#6770]
Motivation:
The native epoll transport allows to wrap an existing filedescriptor, we should support the same in the native kqueue transport.
Modifications:
Add constructors that allow to wrap and existing filedescriptor.
Result:
Featureset of native transports more on par.
