Hi,

this is a shameless self-promotion :) I have posted about the Terrible
mDNS responder on Mastodon before, but not on this list, and I have
been making minor changes to it recently, so I thought I might as well
announce it here, perhaps it could be useful to someone.

Debian GNU/Hurd comes with Avahi in the default install (I believe).
Avahi has never worked for me (on the Hurd), and I doubt it has ever
worked for anyone else either. I *have* looked into the why (as in
spent hours debugging and patching it); I don't remember the
specifics, but I do remember that I concluded it won't be easy to make
it work. So, a dead end.

But I still wanted mDNS to work, for some definition of "work".
Namely, I wanted to be able to refer to my Hurd box by its symbolic
name, such as sergey-hurd-box.local (RIP) and hurdle.local, and not by
its DHCP-leased IP address, because that one is a chore to type and
remember, and could change in theory -- and it *did* change in
practice once I set up eth-multiplexer, which must have caused its MAC
to change (or something).

So I wrote the Terrible mDNS responder, named so because it's really
terrible and does not claim to be any good, quite the opposite, in
fact. So, caveat usor. But that being said, it works very well for me
in practice, does exactly what it was supposed to do (i.e. I can type "hurdle.local" and it works) and never once in the multiple years of
use has it caused me any issue, not even a minor one, so maybe it's
not that terrible after all.

To be very clear, this does *not* teach the system to do mDNS queries
(.local hostname lookups), this only makes it respond to other host's
queries. (Those other hosts may be running Avahi or sd-rd or Apple's mDNSResponder or LookupServer or ...)

The sources are over on GitHub [0]. There are no dependencies other
than a libc. It's built with Meson and licensed under AGPL v3+. It
even comes with an awkward attempt at a sysv init script! What's not
to like?

[0]: https://github.com/bugaevc/terrible-mdns-responder

Sergey

P.S. Something like this should get you up & running:
$ git clone git@github.com:bugaevc/terrible-mdns-responder.git
$ cd terrible-mdns-responder
$ meson setup build
$ ninja -C build
$ sudo ninja install -C build
$ sudo update-rc.d terrible-mdns-responder defaults
$ sudo update-rc.d avahi-daemon disable
$ sudo service terrible-mdns-responder start

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Sergey Bugaev <bugaevc@gmail.com> writes:

Hi,

this is a shameless self-promotion :) I have posted about the Terrible
mDNS responder on Mastodon before, but not on this list, and I have
been making minor changes to it recently, so I thought I might as well announce it here, perhaps it could be useful to someone.

Debian GNU/Hurd comes with Avahi in the default install (I believe).
Avahi has never worked for me (on the Hurd), and I doubt it has ever
worked for anyone else either. I *have* looked into the why (as in
spent hours debugging and patching it); I don't remember the
specifics, but I do remember that I concluded it won't be easy to make
it work. So, a dead end.

P.S. Something like this should get you up & running:
$ git clone git@github.com:bugaevc/terrible-mdns-responder.git
$ cd terrible-mdns-responder
$ meson setup build
$ ninja -C build
$ sudo ninja install -C build
$ sudo update-rc.d terrible-mdns-responder defaults
$ sudo update-rc.d avahi-daemon disable
$ sudo service terrible-mdns-responder start

Hmmm... How do you run the Hurd? Do you run linux on bare metal and
then Hurd on qemu? When you are typing "herd.local" what does that
mean?

I suppose that means on your linux machine you are typing "ssh
hurd.local"?

May I help you create your email into some kind of manual page/wiki article/blog post?

Thanks,

Joshua Branson
https://gnucode.me

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Hmmm... How do you run the Hurd? Do you run linux on bare metal and
then Hurd on qemu?

Yes. I run Hurd on a qemu/libvirt VM that itself runs on GNU/Linux.

When you are typing "herd.local" what does that
mean?

I suppose that means on your linux machine you are typing "ssh
hurd.local"?

Yes, on any machine that's on the same network as your Hurd machine,
you should be able to use "its-hostname.local" to refer to it (if the
machine's OS supports mDNS lookup). That's just how mDNS works, it's
not specific to the Hurd, my configuration (briefly described below),
or the Terrible mDNS responder (which is just one among all the mDNS
responder implementations, and a terrible one at that :D).

You can use its-hostname.local with ssh, or anywhere else where you'd
use a host, such as with ping or curl or git, etc. Specifically, on
Unix this is anything that uses gethostbyname() or getaddrinfo(). You
can try asking glibc about it: `getent hosts its-hostname.local`. If
you're running sd-rd, try `resolvectl query its-hostname.local`, and
for Avahi try `avahi-resolve-host-name its-hostname.local`.

In my case the network is the virtual network that libvirt creates;
all the (suitably configured) libvirt VMs and the host are connected
to this network and can all see & talk to each other. If you're using
libvirt too, see the file /usr/share/libvirt/networks/default.xml and
the output of `virsh --connect qemu:///system net-info default`.

One thing where mDNS will *not* work is if you use qemu with "user
networking" and pass hostfwd=tcp::5555-:22 or somesuch to get SSH
access. In this case, there is no real network created, at least as
far as the host is concerned, so it won't be able to talk to your VM
over mDNS.

May I help you create your email into some kind of manual page/wiki article/blog post?

Maybe?

But first, seeing that you're interested -- have you managed to build
/ install / use the Terrible mDNS responder? Does it work for you?

Sergey

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March 4, 2023 1:01 PM, "Sergey Bugaev" <bugaevc@gmail.com> wrote:

May I help you create your email into some kind of manual page/wiki
article/blog post?

Maybe?

But first, seeing that you're interested -- have you managed to build
/ install / use the Terrible mDNS responder? Does it work for you?

Sergey

I am probably one of the least experience Hurd enthusiasts. I currently have
a basic Hurd box (no X) running on a T46 (I think) with just 2 GB of RAM.

I will try to set up the Terrible mDNS responder. I will let you know.

Joshua

P.S. Please don't be too disappointed if I get busy and forget to actually
try it out. :(

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