Network

Local DNS Resolvers

There where lots of changes with DNS resolving in Ubuntu Desktop.

In the beginning there was just a /etc/resolve.conf file pointing to your LANs or ISP DNS resolvers, usually managed by your DHCP client.

Gnome Network-Manager came along and soon after DNSMasq would be installed as local cache.

Then resolveconf was introduced.

Not long after that all was moved out again in favor of systemd-resolved.

None of these worked particularly great, especially if you rely on DNSSEC.

Therefore I prefer to use unbound as local DNS resolver on the Desktop.

Together wit the help of dnssec-trigger the local LAN or your ISPs resolvers will be tested if they are able handle DNSSEC correctly.

If they do, they are used as upstream resolvers. If the don’t, the local unbound daemon will not use them and do all the resolving by itself.

Additionally some special cases like captive portals for WiFi networks are also handled.

Software Installation

$ sudo apt install unbound dnssec-trigger
$ sudo systemctl stop systemd-resolved.service resolvconf.service
$ sudo systemctl disable systemd-resolved.service resolvconf.service

Unbound Configuration

Unbound’s remote control must be enabled, for dnssec-trigger to be able to control it. Create a file called /etc/unbound/unbound.conf.d/remote-control.conf with the following content:

# Remote control config section.
remote-control:
        # Enable remote control with unbound-control(8) here.
        # set up the keys and certificates with unbound-control-setup.
        # Default: no
        control-enable: yes

Unbound’s remote control is protected by certificates. To setup the required key-files call the unbound-control-setup-command after saving and closing the configuration file and reloading the unbound server:

$> sudo systemctl reload unbound.service
$> sudo undbound-control-setup

DNSSEC-Trigger Configuration

Open the file /etc/dnssec-trigger.conf to set some general options:

# the domain example.com line (if any) to add to resolv.conf(5). default none.
# domain: "example.net"

# domain name search path to add to resolv.conf(5). default none.
# the search path from DHCP is not picked up, it could be used to misdirect.
# search: "example.com"

# Forward RFC 1918 private addresses to global forwarders
use-private-addresses: yes

Open the file /etc/dnssec.conf:

# Ensures that foward zones provided by NetworkManager connections will be
# validated by Unbound.
validate_connection_provided_zones=yes

#  - Domains provided by WiFi connection will be ignored.
add_wifi_provided_zones=no

# Enable or disable writing of search domains to `/etc/resolv.conf`.
set_search_domains=yes

# Enable or disable adding reverse name resolution zones derived from
# private IP addresses as defined in RFC 1918 and RFC 4193.
use_private_address_ranges=yes

Call dnssec-trigger-control-setup to setup keys and certificates for dnssec-trigger to securely interact with the unbound daemon and restart the service after that:

$> sudo dnssec-trigger-control-setup
$> sudo systemctl restart dnssec-triggerd.service

Warning

At the time of this writing there is a serious bug (#4218) in the current dnssec-triggerd daemon version 0.17.

dnssec-triggerd is very likely to crash soon after startup, leaving you without DNS resolution.

Here is a partial and temporary workaraound:

  1. Copy the file /lib/systemd/system/dnssec-triggerd.service to /etc/systemd/system/:

    $> sudo cp /lib/systemd/system/dnssec-triggerd.service /etc/systemd/system/
    
  2. Open the file /etc/systemd/system/dnssec-triggerd.service and comment out line 13 “ExecStartPost=-/usr/lib/dnssec-trigger/dnssec-trigger-script –update_all”:

    [Unit]
    Description=Reconfigure local DNSSEC resolver on connectivity changes
    After=NetworkManager.service unbound.service dnssec-triggerd-keygen.service
    Requires=unbound.service
    Wants=dnssec-triggerd-keygen.service
    
    [Service]
    PIDFile=/run/dnssec-triggerd.pid
    Type=simple
    Restart=always
    ExecStart=/usr/sbin/dnssec-triggerd -d
    ExecStartPre=-/usr/lib/dnssec-trigger/dnssec-trigger-script --prepare
    #ExecStartPost=-/usr/lib/dnssec-trigger/dnssec-trigger-script --update_all
    ExecStopPost=-/usr/lib/dnssec-trigger/dnssec-trigger-script --cleanup
    
    [Install]
    WantedBy=multi-user.target
    
  3. Save and close the file, then reload your services to activate the changes you just made:

    $> sudo systemctl daemon-reload
    
  4. Restart the dnssec-triggerd daemon:

    $> sudo systemctl restart dnssec-triggerd.service
    

Gnome Network Manager Configuration

This is how we create a perfect harmony between Gnome Network Manager, dnssec-trigger and unbound.

Tell network manager not to bother with systemd-resolved by creating the file /etc/NetworkManager/conf.d/no-systemd-resolved.conf:

[main]
systemd-resolved=false

Tell network manager that unbound and dnssec-trigger will be taking care of things. by creating the file /etc/NetworkManager/conf.d/unbound-dns.conf:

# Configuration file for NetworkManager.
# See "man 5 NetworkManager.conf" for details.
[main]

# NetworkManager will talk to unbound and dnssec-triggerd, using "Conditional
# Forwarding" with DNSSEC support. /etc/resolv.conf will be managed by
# dnssec-trigger daemon.
dns=unbound

# Don't touch /etc/resolv.conf
rc-manager=unmanaged

Restart the Network Manager service, after saving and closing the configuration file:

$> sudo systemctl restart NetworkManager.service

DNS Updates

Non-servers, like personal computers, desktop or laptops/notebooks usually get a dynamic temporary address. Portable devices might connect from different networks.

The nsupdate programm can contact your domain name server and update your hostname with the current address.

Nowadays NetworkManager is in charge of all these things, so updates should be managed by that too.

TBD

TSIG key

TBD

VPN

TBD