net: allow reading data into a static buffer

Co-Authored-By: Anna Henningsen <anna@addaleax.net>

PR-URL: https://github.com/nodejs/node/pull/25436
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

benchmark/net/net-s2c.js

@@ -5,33 +5,68 @@ const common = require('../common.js');
 const PORT = common.PORT;
 
 const bench = common.createBenchmark(main, {
-  len: [64, 102400, 1024 * 1024 * 16],
+  sendchunklen: [256, 32 * 1024, 128 * 1024, 16 * 1024 * 1024],
   type: ['utf', 'asc', 'buf'],
+  recvbuflen: [0, 64 * 1024, 1024 * 1024],
+  recvbufgenfn: ['true', 'false'],
   dur: [5]
 });
 
 var chunk;
 var encoding;
+var recvbuf;
+var received = 0;
+
+function main({ dur, sendchunklen, type, recvbuflen, recvbufgenfn }) {
+  if (isFinite(recvbuflen) && recvbuflen > 0)
+    recvbuf = Buffer.alloc(recvbuflen);
 
-function main({ dur, len, type }) {
   switch (type) {
     case 'buf':
-      chunk = Buffer.alloc(len, 'x');
+      chunk = Buffer.alloc(sendchunklen, 'x');
       break;
     case 'utf':
       encoding = 'utf8';
-      chunk = 'ü'.repeat(len / 2);
+      chunk = 'ü'.repeat(sendchunklen / 2);
       break;
     case 'asc':
       encoding = 'ascii';
-      chunk = 'x'.repeat(len);
+      chunk = 'x'.repeat(sendchunklen);
       break;
     default:
       throw new Error(`invalid type: ${type}`);
   }
 
   const reader = new Reader();
-  const writer = new Writer();
+  var writer;
+  var socketOpts;
+  if (recvbuf === undefined) {
+    writer = new Writer();
+    socketOpts = { port: PORT };
+  } else {
+    let buffer = recvbuf;
+    if (recvbufgenfn === 'true') {
+      let bufidx = -1;
+      const bufpool = [
+        recvbuf,
+        Buffer.from(recvbuf),
+        Buffer.from(recvbuf),
+      ];
+      buffer = () => {
+        bufidx = (bufidx + 1) % bufpool.length;
+        return bufpool[bufidx];
+      };
+    }
+    socketOpts = {
+      port: PORT,
+      onread: {
+        buffer,
+        callback: function(nread, buf) {
+          received += nread;
+        }
+      }
+    };
+  }
 
   // The actual benchmark.
   const server = net.createServer((socket) => {
@@ -39,14 +74,15 @@ function main({ dur, len, type }) {
   });
 
   server.listen(PORT, () => {
-    const socket = net.connect(PORT);
+    const socket = net.connect(socketOpts);
     socket.on('connect', () => {
       bench.start();
 
-      socket.pipe(writer);
+      if (recvbuf === undefined)
+        socket.pipe(writer);
 
       setTimeout(() => {
-        const bytes = writer.received;
+        const bytes = received;
         const gbits = (bytes * 8) / (1024 * 1024 * 1024);
         bench.end(gbits);
         process.exit(0);
@@ -58,12 +94,11 @@ function main({ dur, len, type }) {
 const net = require('net');
 
 function Writer() {
-  this.received = 0;
   this.writable = true;
 }
 
 Writer.prototype.write = function(chunk, encoding, cb) {
-  this.received += chunk.length;
+  received += chunk.length;
 
   if (typeof encoding === 'function')
     encoding();

doc/api/net.md

@@ -593,6 +593,9 @@ for the [`'connect'`][] event **once**.
 <!-- YAML
 added: v0.1.90
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/25436
+    description: Added `onread` option.
   - version: v6.0.0
     pr-url: https://github.com/nodejs/node/pull/6021
     description: The `hints` option defaults to `0` in all cases now.
@@ -629,6 +632,39 @@ For [IPC][] connections, available `options` are:
   See [Identifying paths for IPC connections][]. If provided, the TCP-specific
   options above are ignored.
 
+For both types, available `options` include:
+
+* `onread` {Object} - If specified, incoming data is stored in a single `buffer`
+  and passed to the supplied `callback` when data arrives on the socket.
+  Note: this will cause the streaming functionality to not provide any data,
+  however events like `'error'`, `'end'`, and `'close'` will still be emitted
+  as normal and methods like `pause()` and `resume()` will also behave as
+  expected.
+  * `buffer` {Buffer|Uint8Array|Function} - Either a reusable chunk of memory to
+    use for storing incoming data or a function that returns such.
+  * `callback` {Function} This function is called for every chunk of incoming
+    data. Two arguments are passed to it: the number of bytes written to
+    `buffer` and a reference to `buffer`. Return `false` from this function to
+    implicitly `pause()` the socket. This function will be executed in the
+    global context.
+
+Following is an example of a client using the `onread` option:
+
+```js
+const net = require('net');
+net.connect({
+  port: 80,
+  onread: {
+    // Reuses a 4KiB Buffer for every read from the socket
+    buffer: Buffer.alloc(4 * 1024),
+    callback: function(nread, buf) {
+      // Received data is available in `buf` from 0 to `nread`
+      console.log(buf.toString('utf8', 0, nread));
+    }
+  }
+});
+```
+
 #### socket.connect(path[, connectListener])
 
 * `path` {string} Path the client should connect to. See

lib/internal/stream_base_commons.js

@@ -23,6 +23,7 @@ const {
   setUnrefTimeout,
   getTimerDuration
 } = require('internal/timers');
+const { isUint8Array } = require('internal/util/types');
 const { clearTimeout } = require('timers');
 
 const kMaybeDestroy = Symbol('kMaybeDestroy');
@@ -32,6 +33,9 @@ const kHandle = Symbol('kHandle');
 const kSession = Symbol('kSession');
 
 const debug = require('internal/util/debuglog').debuglog('stream');
+const kBuffer = Symbol('kBuffer');
+const kBufferGen = Symbol('kBufferGen');
+const kBufferCb = Symbol('kBufferCb');
 
 function handleWriteReq(req, data, encoding) {
   const { handle } = req;
@@ -161,9 +165,23 @@ function onStreamRead(arrayBuffer) {
   stream[kUpdateTimer]();
 
   if (nread > 0 && !stream.destroyed) {
-    const offset = streamBaseState[kArrayBufferOffset];
+    let ret;
-    const buf = new FastBuffer(arrayBuffer, offset, nread);
+    let result;
-    if (!stream.push(buf)) {
+    const userBuf = stream[kBuffer];
+    if (userBuf) {
+      result = (stream[kBufferCb](nread, userBuf) !== false);
+      const bufGen = stream[kBufferGen];
+      if (bufGen !== null) {
+        const nextBuf = bufGen();
+        if (isUint8Array(nextBuf))
+          stream[kBuffer] = ret = nextBuf;
+      }
+    } else {
+      const offset = streamBaseState[kArrayBufferOffset];
+      const buf = new FastBuffer(arrayBuffer, offset, nread);
+      result = stream.push(buf);
+    }
+    if (!result) {
       handle.reading = false;
       if (!stream.destroyed) {
         const err = handle.readStop();
@@ -172,7 +190,7 @@ function onStreamRead(arrayBuffer) {
       }
     }
 
-    return;
+    return ret;
   }
 
   if (nread === 0) {
@@ -241,5 +259,8 @@ module.exports = {
   kUpdateTimer,
   kHandle,
   kSession,
-  setStreamTimeout
+  setStreamTimeout,
+  kBuffer,
+  kBufferCb,
+  kBufferGen
 };

lib/net.js

@@ -67,7 +67,10 @@ const {
   kAfterAsyncWrite,
   kHandle,
   kUpdateTimer,
-  setStreamTimeout
+  setStreamTimeout,
+  kBuffer,
+  kBufferCb,
+  kBufferGen
 } = require('internal/stream_base_commons');
 const {
   codes: {
@@ -86,6 +89,7 @@ const {
   exceptionWithHostPort,
   uvExceptionWithHostPort
 } = require('internal/errors');
+const { isUint8Array } = require('internal/util/types');
 const { validateInt32, validateString } = require('internal/validators');
 const kLastWriteQueueSize = Symbol('lastWriteQueueSize');
 const {
@@ -225,6 +229,18 @@ function initSocketHandle(self) {
     self._handle[owner_symbol] = self;
     self._handle.onread = onStreamRead;
     self[async_id_symbol] = getNewAsyncId(self._handle);
+
+    let userBuf = self[kBuffer];
+    if (userBuf) {
+      const bufGen = self[kBufferGen];
+      if (bufGen !== null) {
+        userBuf = bufGen();
+        if (!isUint8Array(userBuf))
+          return;
+        self[kBuffer] = userBuf;
+      }
+      self._handle.useUserBuffer(userBuf);
+    }
   }
 }
 
@@ -247,6 +263,9 @@ function Socket(options) {
   this._host = null;
   this[kLastWriteQueueSize] = 0;
   this[kTimeout] = null;
+  this[kBuffer] = null;
+  this[kBufferCb] = null;
+  this[kBufferGen] = null;
 
   if (typeof options === 'number')
     options = { fd: options }; // Legacy interface.
@@ -271,40 +290,55 @@ function Socket(options) {
   if (options.handle) {
     this._handle = options.handle; // private
     this[async_id_symbol] = getNewAsyncId(this._handle);
-  } else if (options.fd !== undefined) {
+  } else {
-    const { fd } = options;
+    const onread = options.onread;
-    let err;
+    if (onread !== null && typeof onread === 'object' &&
+        (isUint8Array(onread.buffer) || typeof onread.buffer === 'function') &&
+        typeof onread.callback === 'function') {
+      if (typeof onread.buffer === 'function') {
+        this[kBuffer] = true;
+        this[kBufferGen] = onread.buffer;
+      } else {
+        this[kBuffer] = onread.buffer;
+      }
+      this[kBufferCb] = onread.callback;
+    }
+    if (options.fd !== undefined) {
+      const { fd } = options;
+      let err;
 
-    // createHandle will throw ERR_INVALID_FD_TYPE if `fd` is not
+      // createHandle will throw ERR_INVALID_FD_TYPE if `fd` is not
-    // a valid `PIPE` or `TCP` descriptor
+      // a valid `PIPE` or `TCP` descriptor
-    this._handle = createHandle(fd, false);
+      this._handle = createHandle(fd, false);
 
-    err = this._handle.open(fd);
+      err = this._handle.open(fd);
 
-    // While difficult to fabricate, in some architectures
+      // While difficult to fabricate, in some architectures
-    // `open` may return an error code for valid file descriptors
+      // `open` may return an error code for valid file descriptors
-    // which cannot be opened. This is difficult to test as most
+      // which cannot be opened. This is difficult to test as most
-    // un-openable fds will throw on `createHandle`
+      // un-openable fds will throw on `createHandle`
-    if (err)
-      throw errnoException(err, 'open');
-
-    this[async_id_symbol] = this._handle.getAsyncId();
-
-    if ((fd === 1 || fd === 2) &&
-        (this._handle instanceof Pipe) &&
-        process.platform === 'win32') {
-      // Make stdout and stderr blocking on Windows
-      err = this._handle.setBlocking(true);
       if (err)
-        throw errnoException(err, 'setBlocking');
+        throw errnoException(err, 'open');
 
-      this._writev = null;
+      this[async_id_symbol] = this._handle.getAsyncId();
-      this._write = makeSyncWrite(fd);
+
-      // makeSyncWrite adjusts this value like the original handle would, so
+      if ((fd === 1 || fd === 2) &&
-      // we need to let it do that by turning it into a writable, own property.
+          (this._handle instanceof Pipe) &&
-      Object.defineProperty(this._handle, 'bytesWritten', {
+          process.platform === 'win32') {
-        value: 0, writable: true
+        // Make stdout and stderr blocking on Windows
-      });
+        err = this._handle.setBlocking(true);
+        if (err)
+          throw errnoException(err, 'setBlocking');
+
+        this._writev = null;
+        this._write = makeSyncWrite(fd);
+        // makeSyncWrite adjusts this value like the original handle would, so
+        // we need to let it do that by turning it into a writable, own
+        // property.
+        Object.defineProperty(this._handle, 'bytesWritten', {
+          value: 0, writable: true
+        });
+      }
     }
   }
 
@@ -514,6 +548,15 @@ Object.defineProperty(Socket.prototype, kUpdateTimer, {
 });
 
 
+function tryReadStart(socket) {
+  // Not already reading, start the flow
+  debug('Socket._handle.readStart');
+  socket._handle.reading = true;
+  var err = socket._handle.readStart();
+  if (err)
+    socket.destroy(errnoException(err, 'read'));
+}
+
 // Just call handle.readStart until we have enough in the buffer
 Socket.prototype._read = function(n) {
   debug('_read');
@@ -522,12 +565,7 @@ Socket.prototype._read = function(n) {
     debug('_read wait for connection');
     this.once('connect', () => this._read(n));
   } else if (!this._handle.reading) {
-    // Not already reading, start the flow
+    tryReadStart(this);
-    debug('Socket._read readStart');
-    this._handle.reading = true;
-    var err = this._handle.readStart();
-    if (err)
-      this.destroy(errnoException(err, 'read'));
   }
 };
 
@@ -539,6 +577,38 @@ Socket.prototype.end = function(data, encoding, callback) {
 };
 
 
+Socket.prototype.pause = function() {
+  if (this[kBuffer] && !this.connecting && this._handle &&
+      this._handle.reading) {
+    this._handle.reading = false;
+    if (!this.destroyed) {
+      const err = this._handle.readStop();
+      if (err)
+        this.destroy(errnoException(err, 'read'));
+    }
+  }
+  return stream.Duplex.prototype.pause.call(this);
+};
+
+
+Socket.prototype.resume = function() {
+  if (this[kBuffer] && !this.connecting && this._handle &&
+      !this._handle.reading) {
+    tryReadStart(this);
+  }
+  return stream.Duplex.prototype.resume.call(this);
+};
+
+
+Socket.prototype.read = function(n) {
+  if (this[kBuffer] && !this.connecting && this._handle &&
+      !this._handle.reading) {
+    tryReadStart(this);
+  }
+  return stream.Duplex.prototype.read.call(this, n);
+};
+
+
 // Called when the 'end' event is emitted.
 function onReadableStreamEnd() {
   if (!this.allowHalfOpen) {

src/stream_base.cc

@@ -26,6 +26,7 @@ using v8::FunctionCallbackInfo;
 using v8::HandleScope;
 using v8::Integer;
 using v8::Local;
+using v8::MaybeLocal;
 using v8::Object;
 using v8::ReadOnly;
 using v8::String;
@@ -50,6 +51,13 @@ int StreamBase::ReadStopJS(const FunctionCallbackInfo<Value>& args) {
   return ReadStop();
 }
 
+int StreamBase::UseUserBuffer(const FunctionCallbackInfo<Value>& args) {
+  CHECK(Buffer::HasInstance(args[0]));
+
+  uv_buf_t buf = uv_buf_init(Buffer::Data(args[0]), Buffer::Length(args[0]));
+  PushStreamListener(new CustomBufferJSListener(buf));
+  return 0;
+}
 
 int StreamBase::Shutdown(const FunctionCallbackInfo<Value>& args) {
   CHECK(args[0]->IsObject());
@@ -291,19 +299,22 @@ int StreamBase::WriteString(const FunctionCallbackInfo<Value>& args) {
 }
 
 
-void StreamBase::CallJSOnreadMethod(ssize_t nread,
+MaybeLocal<Value> StreamBase::CallJSOnreadMethod(ssize_t nread,
-                                    Local<ArrayBuffer> ab,
+                                                 Local<ArrayBuffer> ab,
-                                    size_t offset) {
+                                                 size_t offset,
+                                                 StreamBaseJSChecks checks) {
   Environment* env = env_;
 
   DCHECK_EQ(static_cast<int32_t>(nread), nread);
   DCHECK_LE(offset, INT32_MAX);
 
-  if (ab.IsEmpty()) {
+  if (checks == DONT_SKIP_NREAD_CHECKS) {
-    DCHECK_EQ(offset, 0);
+    if (ab.IsEmpty()) {
-    DCHECK_LE(nread, 0);
+      DCHECK_EQ(offset, 0);
-  } else {
+      DCHECK_LE(nread, 0);
-    DCHECK_GE(nread, 0);
+    } else {
+      DCHECK_GE(nread, 0);
+    }
   }
 
   env->stream_base_state()[kReadBytesOrError] = nread;
@@ -317,7 +328,7 @@ void StreamBase::CallJSOnreadMethod(ssize_t nread,
   CHECK_NOT_NULL(wrap);
   Local<Value> onread = wrap->object()->GetInternalField(kOnReadFunctionField);
   CHECK(onread->IsFunction());
-  wrap->MakeCallback(onread.As<Function>(), arraysize(argv), argv);
+  return wrap->MakeCallback(onread.As<Function>(), arraysize(argv), argv);
 }
 
 
@@ -366,6 +377,9 @@ void StreamBase::AddMethods(Environment* env, Local<FunctionTemplate> t) {
   env->SetProtoMethod(t, "readStart", JSMethod<&StreamBase::ReadStartJS>);
   env->SetProtoMethod(t, "readStop", JSMethod<&StreamBase::ReadStopJS>);
   env->SetProtoMethod(t, "shutdown", JSMethod<&StreamBase::Shutdown>);
+  env->SetProtoMethod(t,
+                      "useUserBuffer",
+                      JSMethod<&StreamBase::UseUserBuffer>);
   env->SetProtoMethod(t, "writev", JSMethod<&StreamBase::Writev>);
   env->SetProtoMethod(t, "writeBuffer", JSMethod<&StreamBase::WriteBuffer>);
   env->SetProtoMethod(
@@ -445,6 +459,7 @@ void StreamResource::ClearError() {
   // No-op
 }
 
+
 uv_buf_t EmitToJSStreamListener::OnStreamAlloc(size_t suggested_size) {
   CHECK_NOT_NULL(stream_);
   Environment* env = static_cast<StreamBase*>(stream_)->stream_env();
@@ -472,6 +487,32 @@ void EmitToJSStreamListener::OnStreamRead(ssize_t nread, const uv_buf_t& buf_) {
 }
 
 
+uv_buf_t CustomBufferJSListener::OnStreamAlloc(size_t suggested_size) {
+  return buffer_;
+}
+
+
+void CustomBufferJSListener::OnStreamRead(ssize_t nread, const uv_buf_t& buf) {
+  CHECK_NOT_NULL(stream_);
+  CHECK_EQ(buf.base, buffer_.base);
+
+  StreamBase* stream = static_cast<StreamBase*>(stream_);
+  Environment* env = stream->stream_env();
+  HandleScope handle_scope(env->isolate());
+  Context::Scope context_scope(env->context());
+
+  MaybeLocal<Value> ret = stream->CallJSOnreadMethod(nread,
+                             Local<ArrayBuffer>(),
+                             0,
+                             StreamBase::SKIP_NREAD_CHECKS);
+  Local<Value> next_buf_v;
+  if (ret.ToLocal(&next_buf_v) && !next_buf_v->IsUndefined()) {
+    buffer_.base = Buffer::Data(next_buf_v);
+    buffer_.len = Buffer::Length(next_buf_v);
+  }
+}
+
+
 void ReportWritesToJSStreamListener::OnStreamAfterReqFinished(
     StreamReq* req_wrap, int status) {
   StreamBase* stream = static_cast<StreamBase*>(stream_);

src/stream_base.h

@@ -180,6 +180,21 @@ class EmitToJSStreamListener : public ReportWritesToJSStreamListener {
 };
 
 
+// An alternative listener that uses a custom, user-provided buffer
+// for reading data.
+class CustomBufferJSListener : public ReportWritesToJSStreamListener {
+ public:
+  uv_buf_t OnStreamAlloc(size_t suggested_size) override;
+  void OnStreamRead(ssize_t nread, const uv_buf_t& buf) override;
+  void OnStreamDestroy() override { delete this; }
+
+  explicit CustomBufferJSListener(uv_buf_t buffer) : buffer_(buffer) {}
+
+ private:
+  uv_buf_t buffer_;
+};
+
+
 // A generic stream, comparable to JS land’s `Duplex` streams.
 // A stream is always controlled through one `StreamListener` instance.
 class StreamResource {
@@ -273,9 +288,13 @@ class StreamBase : public StreamResource {
   virtual bool IsIPCPipe();
   virtual int GetFD();
 
-  void CallJSOnreadMethod(ssize_t nread,
+  enum StreamBaseJSChecks { DONT_SKIP_NREAD_CHECKS, SKIP_NREAD_CHECKS };
-                          v8::Local<v8::ArrayBuffer> ab,
+
-                          size_t offset = 0);
+  v8::MaybeLocal<v8::Value> CallJSOnreadMethod(
+      ssize_t nread,
+      v8::Local<v8::ArrayBuffer> ab,
+      size_t offset = 0,
+      StreamBaseJSChecks checks = DONT_SKIP_NREAD_CHECKS);
 
   // This is named `stream_env` to avoid name clashes, because a lot of
   // subclasses are also `BaseObject`s.
@@ -323,6 +342,7 @@ class StreamBase : public StreamResource {
   int WriteBuffer(const v8::FunctionCallbackInfo<v8::Value>& args);
   template <enum encoding enc>
   int WriteString(const v8::FunctionCallbackInfo<v8::Value>& args);
+  int UseUserBuffer(const v8::FunctionCallbackInfo<v8::Value>& args);
 
   static void GetFD(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void GetExternal(const v8::FunctionCallbackInfo<v8::Value>& args);

test/parallel/test-net-onread-static-buffer.js

@@ -0,0 +1,186 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
+
+const message = Buffer.from('hello world');
+
+// Test typical usage
+net.createServer(common.mustCall(function(socket) {
+  this.close();
+  socket.end(message);
+})).listen(0, function() {
+  let received = 0;
+  const buffers = [];
+  const sockBuf = Buffer.alloc(8);
+  net.connect({
+    port: this.address().port,
+    onread: {
+      buffer: sockBuf,
+      callback: function(nread, buf) {
+        assert.strictEqual(buf, sockBuf);
+        received += nread;
+        buffers.push(Buffer.from(buf.slice(0, nread)));
+      }
+    }
+  }).on('data', common.mustNotCall()).on('end', common.mustCall(() => {
+    assert.strictEqual(received, message.length);
+    assert.deepStrictEqual(Buffer.concat(buffers), message);
+  }));
+});
+
+// Test Uint8Array support
+net.createServer(common.mustCall(function(socket) {
+  this.close();
+  socket.end(message);
+})).listen(0, function() {
+  let received = 0;
+  let incoming = new Uint8Array(0);
+  const sockBuf = new Uint8Array(8);
+  net.connect({
+    port: this.address().port,
+    onread: {
+      buffer: sockBuf,
+      callback: function(nread, buf) {
+        assert.strictEqual(buf, sockBuf);
+        received += nread;
+        const newIncoming = new Uint8Array(incoming.length + nread);
+        newIncoming.set(incoming);
+        newIncoming.set(buf.slice(0, nread), incoming.length);
+        incoming = newIncoming;
+      }
+    }
+  }).on('data', common.mustNotCall()).on('end', common.mustCall(() => {
+    assert.strictEqual(received, message.length);
+    assert.deepStrictEqual(incoming, new Uint8Array(message));
+  }));
+});
+
+// Test Buffer callback usage
+net.createServer(common.mustCall(function(socket) {
+  this.close();
+  socket.end(message);
+})).listen(0, function() {
+  let received = 0;
+  const incoming = [];
+  const bufPool = [ Buffer.alloc(2), Buffer.alloc(2), Buffer.alloc(2) ];
+  let bufPoolIdx = -1;
+  let bufPoolUsage = 0;
+  net.connect({
+    port: this.address().port,
+    onread: {
+      buffer: () => {
+        ++bufPoolUsage;
+        bufPoolIdx = (bufPoolIdx + 1) % bufPool.length;
+        return bufPool[bufPoolIdx];
+      },
+      callback: function(nread, buf) {
+        assert.strictEqual(buf, bufPool[bufPoolIdx]);
+        received += nread;
+        incoming.push(Buffer.from(buf.slice(0, nread)));
+      }
+    }
+  }).on('data', common.mustNotCall()).on('end', common.mustCall(() => {
+    assert.strictEqual(received, message.length);
+    assert.deepStrictEqual(Buffer.concat(incoming), message);
+    assert.strictEqual(bufPoolUsage, 7);
+  }));
+});
+
+// Test Uint8Array callback support
+net.createServer(common.mustCall(function(socket) {
+  this.close();
+  socket.end(message);
+})).listen(0, function() {
+  let received = 0;
+  let incoming = new Uint8Array(0);
+  const bufPool = [ new Uint8Array(2), new Uint8Array(2), new Uint8Array(2) ];
+  let bufPoolIdx = -1;
+  let bufPoolUsage = 0;
+  net.connect({
+    port: this.address().port,
+    onread: {
+      buffer: () => {
+        ++bufPoolUsage;
+        bufPoolIdx = (bufPoolIdx + 1) % bufPool.length;
+        return bufPool[bufPoolIdx];
+      },
+      callback: function(nread, buf) {
+        assert.strictEqual(buf, bufPool[bufPoolIdx]);
+        received += nread;
+        const newIncoming = new Uint8Array(incoming.length + nread);
+        newIncoming.set(incoming);
+        newIncoming.set(buf.slice(0, nread), incoming.length);
+        incoming = newIncoming;
+      }
+    }
+  }).on('data', common.mustNotCall()).on('end', common.mustCall(() => {
+    assert.strictEqual(received, message.length);
+    assert.deepStrictEqual(incoming, new Uint8Array(message));
+    assert.strictEqual(bufPoolUsage, 7);
+  }));
+});
+
+// Test explicit socket pause
+net.createServer(common.mustCall(function(socket) {
+  this.close();
+  socket.end(message);
+})).listen(0, function() {
+  let received = 0;
+  const buffers = [];
+  const sockBuf = Buffer.alloc(8);
+  let paused = false;
+  net.connect({
+    port: this.address().port,
+    onread: {
+      buffer: sockBuf,
+      callback: function(nread, buf) {
+        assert.strictEqual(paused, false);
+        assert.strictEqual(buf, sockBuf);
+        received += nread;
+        buffers.push(Buffer.from(buf.slice(0, nread)));
+        paused = true;
+        this.pause();
+        setTimeout(() => {
+          paused = false;
+          this.resume();
+        }, 100);
+      }
+    }
+  }).on('data', common.mustNotCall()).on('end', common.mustCall(() => {
+    assert.strictEqual(received, message.length);
+    assert.deepStrictEqual(Buffer.concat(buffers), message);
+  }));
+});
+
+// Test implicit socket pause
+net.createServer(common.mustCall(function(socket) {
+  this.close();
+  socket.end(message);
+})).listen(0, function() {
+  let received = 0;
+  const buffers = [];
+  const sockBuf = Buffer.alloc(8);
+  let paused = false;
+  net.connect({
+    port: this.address().port,
+    onread: {
+      buffer: sockBuf,
+      callback: function(nread, buf) {
+        assert.strictEqual(paused, false);
+        assert.strictEqual(buf, sockBuf);
+        received += nread;
+        buffers.push(Buffer.from(buf.slice(0, nread)));
+        paused = true;
+        setTimeout(() => {
+          paused = false;
+          this.resume();
+        }, 100);
+        return false;
+      }
+    }
+  }).on('data', common.mustNotCall()).on('end', common.mustCall(() => {
+    assert.strictEqual(received, message.length);
+    assert.deepStrictEqual(Buffer.concat(buffers), message);
+  }));
+});