Sunil Mohan Adapa 0817e7af45
names: Use systemd-resolved for DNS resolution
- Disable mDNS resolution. While we can migrate our DNS-SD service definition
files to systemd-resolved and switch from using avahi to systemd-resolved, many
programs still solely depend on avahi-daemon. Examples include cups and GNOME.
It is not clear if they will work any mDNS daemon or if they interact with
avahi-daemon in other ways that the mDNS protocol. So, for now, disable mDNS in
systemd-resolved and continue to use avahi-daemon for it. This is also Fedora's
default.

- Re-introduce Fallback DNS servers with the value same as the upstream systemd
project. Debian removes the default fallback DNS servers likely because they
could be considered a privacy violation. However, when systemd-resolved package
is first installed, the post install script recommends a reboot instead of
feeding the currently configured nameservers from /etc/resolve.conf into
systemd-resolved. Immediately, this causes the system not be able to connect to
any external servers. While this may be acceptable solution for interactive
systems and pre-built images, FreedomBox has to a) be available for remote
access b) perform upgrades without user intervention (and without reboot until a
day). To mitigate privacy concerns, an option to disable these fallback servers
will be provided in the UI.

- systemd-resolved's stub resolver runs on 127.0.0.53%lo:53 and 127.0.0.54. This
does not conflict either with shared connections which listen on 10.42.x.1 or
with bind which listens on 127.0.0.1 (and other IP addresses). This MR does not
address the existing conflict between bind and shared network connections.
However, it does not cause any further conflicts.

Tests:

* mDNS

- Avahi diagnostics works. daemon is running. mdns port is exposed in the
firewall.

- systemd-resolved does not listen on mDNS ports.

- Running avahi-browse shows freedombox on local network.

- Running avahi-browse shows the services ssh, sftp-ssh, http and ejabberd.

- Machine can be discovered in Gnome Files.

* NetworkManager shared connections

- After install/upgrade to systemd-resolved, 'shared' connections can be
created.

- With a 'shared' connection configured and active, it is possible to upgrade to
using systemd-resolved.

- Resolving domains from a machine on shared network goes via systemd-resolved
on FreedomBox.

* Bind

- Installing, running tests on bind works.

- Programs connecting from outside network can connect to bind as expected.

- Programs connecting from local machine can connect to bind as expected.

* Upgrading works

- Upgrading to new FreedomBox package works

- systemd-resolved is installed and running. 'resolvectl' shows a proper name
server (or fallback nameserver like 1.1.1.1).

- libnss-resolve is installed and configured in /etc/nsswitch.conf

- /etc/resolv.conf has proper link to /run/systemd/resolve/stub-resolv.conf.

- Programs using /etc/resolv.conf directly work. Install python3-pycares.
python3 -m pycares freedombox.org.

- NetworkManager has passed on proper DNS entries. In logs dns=systemd-resolved,
rc-manager=unmanaged, plugin=systemd-resolved

- DNS resolution works after first setup. Installing packages works.

- 'resolvectl query' resolution works.

- Programs using glibc API resolution such as 'ping' work.

* Fresh image

- Building an image with new freedombox package works without error.

- Booting from fresh images works.

- systemd-resolved is installed and running. 'resolvectl' show proper name
server.

- libnss-resolve is installed and configured in /etc/nsswitch.conf

- /etc/resolv.conf has proper link to /run/systemd/resolve/stub-resolv.conf

- Programs using /etc/resolv.conf directly work. Install python3-pycares.
python3 -m pycares wikipedia.org

- NetworkManager has passed on proper DNS entries. In logs dns=systemd-resolved,
rc-manager=unmanaged, plugin=systemd-resolved

- DNS resolution works after first setup. Installing packages works.

* Installing package on Debian

- Installing new freedombox package in Debian machine works.

- systemd-resolved is installed and running.

- libnss-resolve is installed and configured.

- /etc/resolv.conf has proper link to /run

- NetworkManager has passed on proper DNS entries to systemd-resolved using
'nmcli reload dns-rc'.

- Resolution works with fallback DNS servers when network interfaces are
configured with /etc/network/interfaces

* OpenVPNs works

- As a server, we don't push DNS servers to the client. So, a client continues
to use its old DNS servers. With systemd-resolved running on server, the client
is able to connect to OpenVPN server, route traffic to the internet, and resolve
DNS queries.

* WireGuard works

- As a server, we can't push DNS servers to the client. So, a client continues
to use its old DNS servers. With systemd-resolved running on server, the client
is able to connect to WireGuard server, route traffic to the internet, and
resolve DNS queries.

- As a client, server does not push DNS servers to the client. So, a client
continues to use its old DNS servers. With systemd-resolved running on the
client, the client is able to connect to WireGuard server, route traffic to the
internet, and resolve DNS queries.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Veiko Aasa <veiko17@disroot.org>
2024-09-04 10:28:47 +03:00
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