UDP - impossible to receive 0 length udp packets

[txdv]

First of all: You can send UDP packets 0 content (no data at all, only udp headers) over the wire.

This issue has 3 bugs, I'll start with some code and the output and then explain what is wrong.

var dgram = require('dgram');
var s = dgram.createSocket('udp4');

s.bind(1234);

s.on('message', function (buffer, bytes) {
    console.log('recv:', buffer, bytes);
});

s.send(new Buffer(2), 0, 0, 1234, "127.0.0.1", function (err, bytes) {
    console.log('send:', err, bytes);
    s.send(new Buffer(0), 0, 0, 1234, "127.0.0.1", function (err, bytes) { });
});

The output:

send: null 2
dgram.js:249
    throw new RangeError('Offset into buffer too large');
          ^
RangeError: Offset into buffer too large
    at Socket.send (dgram.js:249:11)
    at Object.callback (/home/bentkus/Projects/c/node/udp.js:12:4)
    at Object.afterSend [as oncomplete] (dgram.js:322:8)

Let's start with

send: null 2

If you take a look on

s.send(new Buffer(2), 0, 0, 1234, "127.0.0.1", function (err, bytes) {

You see that we pass 0 as the length parameter, yet we get the length of the buffer in the callback even though we sent an empty packet over there wire (I checked with wireshark) we get a 2 in return (which is the size of the buffer).

Second bug:

The callback doesn't get called, because of this guard checking for nread == 0. It should actually check (nread == 0 && addr == NULL). Remember UDP packets can have no content, so 0 length.

Third bug:

s.send(new Buffer(0), 0, 0, 1234, "127.0.0.1", function (err, bytes) { });

is throwing:

dgram.js:249
    throw new RangeError('Offset into buffer too large');
          ^
RangeError: Offset into buffer too large
    at Socket.send (dgram.js:249:11)
    at Object.callback (/home/bentkus/Projects/c/node/udp.js:12:4)
    at Object.afterSend [as oncomplete] (dgram.js:322:8)

We have an offset of 0, length of 0 and the buffer length is 0. So this exception actually shouldn't occur.

[txdv]

Fix for Bug 1: #7885

[txdv]

All bugs fixed in that pull request.