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sony / nmos-cpp

An NMOS (Networked Media Open Specifications) Registry and Node in C++ (IS-04, IS-05)

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Debian 11 mdns broken

TobiasThierolf opened this issue · comments

commented

Hello all,

I am not sure if this is the right place for my question, but maybe you have an idea.
We've recently updated our OS from Debian 9 (avahi 0.6.32) to Debian 11 (avahi 0.8) and encountered some issues with the avahi mdns in combination with the nmos-cpp.
Right now we are not able to detect an nmos-registry via mdns. Even though avahi-discover shows the nmos-registry and other services correctly. Other services are working as expected, like NDI.

I've compared the configuration on both systems and it looks fine as far as I can tell (mainly /etc/nsswitch.conf and /etc/avahi/avahi-daemon.conf).

Since it works on other applications, my question is if there is anything specific that I've to take care of for nmos-cpp?

Thanks in advance
Tobias

commented

Hi Tobias. I'm not sure what the problem could be. I've been using Avahi 0.8 locally for some time and the GitHub Actions has an Ubuntu 22.04 runner that is using Avahi 0.8 and seems to be passing all tests in mDNS mode.

commented

Hello Gareth,

sorry for the late reply, we had public holiday in germany. I will try to do some more tests and gather some information and keep you updated.

Thanks,
Tobias

commented

Hello Gareth,

after a lot of google and try and error I finally resolved my issue at least on my local workstation here.
Basically this https://unix.stackexchange.com/questions/352237/avahi-daemon-and-local-domain-issues discussion over here had the solution that made it finally work.

First I've changed the nsswitch.conf file (replaced the mdns4_minimal with mdns4), the issue was still there. Than I've added /etc/mdns.allow with the two entries .local and .local. and the applications immediately found the registry after restarting the avahi-daemon. Both changes are mandatory it seems, I've tried both file changes without the other, but it never worked.

--> Update here: I had to move the dns entry in front of the mdns4. Otherwise the standard DNS name resolution didn't work correctly anymore.

I am not really familiar with mdns or avahi, so I don't really know exactly why this resolved the issues I had. The weird thing is that my configuration on Debian 9 didn't have the mdns.allow file nor the changes of the nsswitch.conf.

I have to test it tomorrow on the target machines as well, but I think this should resolve it the same way.

Thanks,
Tobias

commented

That's a good investigation and a really helpful link. Thanks!

Do you know if your local network has a local unicast domain maybe??

@lo-simon I suggest reopening this and adding the Documentation label.

commented

That's a good investigation and a really helpful link. Thanks!

Do you know if your local network has a local unicast domain maybe??

@lo-simon I suggest reopening this and adding the Documentation label.

The domain specified in the resolv.conf is not local if this answers your question, sorry I am not so familiar with this topic.