macOS: test udp_multicast_join fails on macOS 13 and above

[mizvekov]

Fails with:

not ok 403 - udp_multicast_join
# exit code 6
# Output from process `udp_multicast_join`:
# Assertion failed in test/test-udp-multicast-join.c on line 163: `r == 0` (-8 == 0)

Failure happens on udp_set_membership / setsockopt call.

For reference, see: https://github.com/libuv/libuv/actions/runs/7277757514/job/19830481286#step:5:508

[bnoordhuis]

It's probably a firewall issue (common issue with the multicast tests) but that -8 error code is kind of odd, that's ENOEXEC.

[juanarbol]

I could work on this.

[bnoordhuis]

You're welcome to. Do you know what the root cause is?

[juanarbol]

No yet... I'm investigating

[juanarbol]

I think I found the problem, but I'm not sure why is happening:

diff --git a/src/unix/udp.c b/src/unix/udp.c
index c2814512..29742136 100644
--- a/src/unix/udp.c
+++ b/src/unix/udp.c
@@ -811,7 +811,7 @@ static int uv__udp_set_membership4(uv_udp_t* handle,
     mreq.imr_interface.s_addr = htonl(INADDR_ANY);
   }
 
-  mreq.imr_multiaddr.s_addr = multicast_addr->sin_addr.s_addr;
+  mreq.imr_multiaddr.s_addr = inet_addr("239.255.255.250");
 
   switch (membership) {
   case UV_JOIN_GROUP:

That diff will make the setsockopt works, but sure the test runner will hang.

Maybe the problem is in uv_ip4_addr(multicast_addr...)

libuv/src/unix/udp.c

Line 1060 in 7b9e37c

if (uv_ip4_addr(multicast_addr, 0, &addr4) == 0) {

, is the only function touching the multicast_addr struct.

Any hints? Or ideas?

[bnoordhuis]

The test tries to join the multicast group with address 239.255.0.1.

My best guess is that address is completely blocked off, whereas 239.255.255.250 is available(ish) but not able to send or receive datagrams.

See if starts working when you disable the macos firewall completely.

[juanarbol]

I have my firewall disabled, It has been disabled this whole time

[bnoordhuis]

Ah, okay. I don't have a good hypothesis then. Do local subnet addresses (224.0.0.x) work?

[juanarbol]

Ok, this is really weird; I'm using the next Node.js UDP server

const dgram = require('dgram');

const MULTICAST_ADDR = '224.0.0.4';
const PORT = 1234;

const socket = dgram.createSocket({ type: 'udp4', reuseAddr: true });

socket.on('error', (err) => {
  console.error(`Socket error: ${err}`);
  socket.close();
});

socket.on('listening', () => {
  console.log(`Socket listening on ${socket.address().address}:${socket.address().port}`);
});

socket.on('message', (msg, rinfo) => {
  console.log(`Received message from ${rinfo.address}:${rinfo.port}: ${msg}`);
});

socket.bind(PORT, () => {
  socket.addMembership(MULTICAST_ADDR);
  console.log(`Joined multicast group ${MULTICAST_ADDR}`);
});

If I run that, and change the test to use that address, the test passes, normally. Now, If I kill that server and try to run that server again, I get the same -8 error code that I get in libuv. Anyway, the test won't pass unless a run a UDP server.

[juanarbol]

It is a firewall issue.

#4314 (comment)