sockets: OutOfBand bytes/packets are not supported

[clshortfuse]

Node v6.3.0
Linux localhost 3.14.0 #1 SMP PREEMPT Thu Aug 25 01:02:56 PDT 2016 x86_64 Intel(R) Core(TM) i7-5500U CPU @ 2.40GHz GenuineIntel GNU/Linux
net

When a TCP client, that connects to a NodeJS server, sends an OutOfBand/Urgent byte, the packet is completely dropped.

Full disclosure, I'm migrating an Android (client) /.NET (server) application that uses OutOfBand/Urgent bytes and have hit a wall. If the client send a packet with OutOfBand flag set, there's no way for me to receive it on the server (nodeJS).

I can understand if the default implementation is to drop them, but there should be an option to allow these packets to come in.

[clshortfuse]

ffi to the rescue:

var ffi = require('ffi');
var ref = require('ref');
var lib = new ffi.DynamicLibrary();
var setsockopt = ffi.ForeignFunction(lib.get('setsockopt'), 
  ref.types.int, 
  [ref.types.int, ref.types.int, ref.types.int, ref.refType(ref.types.void), ref.refType(ref.types.uint32)]);

var SOL_SOCKET = 0x1;
var SO_OOBINLINE = 0xA;

setsockopt(socket._handle.fd, 
  SOL_SOCKET, 
  SO_OOBINLINE, 
  ref.alloc(ref.types.bool, true), 
  ref.alloc(ref.types.int, ref.types.bool.size));

My only concern is that SOL_SOCKET and SO_OOBINLINE may differ based on architecture.

[clshortfuse]

Should I open another issue for the fact the packets are dropped? Having them inline would be a feature I can understand, but the packets shouldn't be dropped because of the header. I'm unclear because libuv seems to send it as a another packet and not dropping it, but for some reason nodejs drops them?

[Trott]

@bnoordhuis, @indutny, @nodejs/streams: Thoughts on this one? (Close? Keep open? Any answer to @clshortfuse's question in the last comment?)

[addaleax]

I’m not sure about libuv, I guess this would have to be implemented there first. This doesn’t seem like an unreasonable feature, just something where somebody needs to invest their time to actually do it.

[bnoordhuis]

There is an in-progress pull request (libuv/libuv#1040) that lets uv_poll_t handles poll with POLLPRI in order to receive notifications for OOB data.

Apropos SO_OOBINLINE, libuv sets it on MacOS but that's a mitigation technique for a denial-of-service that platform is (or was) vulnerable to.

[bnoordhuis]

libuv/libuv#1040 was merged sometime ago so it's now possible - at least in theory - to teach node.js about the UV_PRIORITIZED flag to uv_poll_start().

Having said that, it's something of an uphill battle because node.js currently doesn't use¹ or expose uv_poll_start(). (You could use ffi to access it though.)

Unless someone is willing to work on it, I suggest we close this. The fact that this issue has been open for a year without attracting much comment or activity is, I think, a good indicator that it's not much in use. That it wasn't raised until 2016 is too.

¹ Except internally in one place.

[mcollina]

Closing, feel free to reopen if you want to work on this!

[iamakulov]

For the reference, @clshortfuse also created a library to get a crossplatform socket ID: https://github.com/clshortfuse/node-getsockethandleaddress. (Useful with the code from #8282 (comment))