Hostname conflict on macOS

[anlumo]

Not sure if this is even fixable.

When I publish a service running on macOS with this crate using the real hostname (obtained using the hostname crate for example), the operating system detects a duplicate hostname on the network and renames the host itself (so if the old name was "foo.local", it's renaming it to "foo-2.local").

I guess this is because Apple's implementation detects mdns-sd's broadcast packet containing the hostname and thinks that it's from a different host.

Unfortunately, this makes this crate pretty much unusable on macOS/iOS. For now, I'm just appending a prefix to the hostname so it doesn't conflict.

[keepsimple1]

Thanks for opening this issue. I wasn't aware of this until now. It seems like macOS has a default mDNS daemon running and doing probing. But I'm wondering why mdns-sd probing did not yield the hostname first. I have to look into more.

Meantime, could you try a not-perfect workaround: disable the multicast loopback? Like this:

   mdns.set_multicast_loop_v4(false).unwrap();
   mdns.set_multicast_loop_v6(false).unwrap();

see if it helps for your case?

[michaelklishin]

I want to second this behavior on macOS. I don't mean to disparage this library (thank you for developing and open sourcing it!) but the only thing that's worked for me was switching to zeroconf.

[keepsimple1]

I think the reason zeroconf doesn't have this problem is that, it wraps over the system Bonjour service on macOS, i.e. does not have its own responder, hence no conflict (Bonjour is the only responder).

I'm thinking of a possible solution for this issue: add a new API to ServiceInfo : set_skip_address_records(skip: bool), which if set to true, will not announce A/AAAA records.

I.e.: when the user decides the platform is macOS and they want to use the real hostname for mDNS service, they can call set_skip_address_records(true) so that mdns-sd will only announce non-address records, and the caller will resolve the address when getting A/AAAA records from Bonjour response. Will that work for you?

[anlumo]

Would that also get rid of the need to find out the local ip address and hostname? If so, that should fix the issue, yes.

[keepsimple1]

Would that also get rid of the need to find out the local ip address and hostname? If so, that should fix the issue, yes.

You would still need to provide host_name when registering your service. But you don't need to provide the local IP addresses assuming you're using the real hostname for host_name and call the new API to skip A/AAAA records.

I will try it out locally first.

[keepsimple1]

My original fix does not really work. It turns out the reason was really mdns-sd is publishing on more interfaces than Bonjour. I've created a PR #425 to address that, and my local testing seems to be good. Please give the PR branch a try when you have time. Thanks!

[keepsimple1]

I've updated the PR #425 to use a new API added in if-addrs. Tested it and seems to be good. If you have time, please give it a try. Thanks!

[keepsimple1]

Fix released in v0.18.0. If you still see the problem, please feel free to reopen this issue. Thanks!