net: make writeAfterFIN() return false

[lpinca]

If false is not returned a readable stream piped into the socket
might continue reading indefinitely until the process goes out of
memory.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[lpinca]

'use strict';

const net = require('net');
const { Readable } = require('stream');

const chunk = Buffer.alloc(1024);

const readable = new Readable({
  read() {
    this.push(chunk);
  }
});

const server = net.createServer(function(socket) {
  server.close();
  socket.resume();
  setTimeout(function() {
    socket.end();
  }, 100);
});

server.listen(function() {
  const socket = net.connect(this.address().port, function() {
    socket.resume();
    socket.on('error', function() {});

    readable.pipe(socket);
  });
});

[Trott]

Does the documentation for socket.write() need an update to reflect this?

Returns true if the entire data was flushed successfully to the kernel
buffer. Returns false if all or part of the data was queued in user memory.
['drain'][] will be emitted when the buffer is again free.

[lpinca]

@Trott I think it's not needed. writeAfterFIN() replaces writeAfterEnd() to give the user a better error message.

When writeAfterEnd() is used writable.write() return false. An error is emitted to signal that the write has not been successful.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/23580/

[danbev]

Landed in 714a32c.