infra/roles/bind-role

Ansible role bind

An Ansible role for setting up BIND ISC as an authoritative DNS server for a single domain on EL7 or Ubuntu Server. Specifically, the responsibilities of this role are to:

• install BIND
• set up the main configuration file
  • master server
  • slave server
• set up forward and reverse lookup zone files

This role supports multiple reverse zones. IPv6 lookups are also supported, both forward and reverse.

Configuring the firewall is not a concern of this role, so you should do this using another role (e.g. bertvv.rh-base).

If you like/use this role, please consider giving it a star. Thanks!

Requirements

• The package python-ipaddr should be installed on the management node (since v3.7.0)

Role Variables

Variables are not required, unless specified.

Variable	Default	Comments (type)
bind_acls	[]	A list of ACL definitions, which are dicts with fields name and match_list. See below for an example.
bind_allow_query	['localhost']	A list of hosts that are allowed to query this DNS server. Set to ['any'] to allow all hosts
bind_allow_update	['none']	A list of hosts that are allowed to dynamically update this DNS server.
bind_check_names	[]	Check host names for compliance with RFC 952 and RFC 1123 and take the defined actioni (e.g. warn, ignore, fail).
bind_forwarders	[]	A list of name servers to forward DNS requests to.
bind_forward_only	false	If true, BIND is set up as a caching name server
bind_listen_ipv4	['127.0.0.1']	A list of the IPv4 address of the network interface(s) to listen on. Set to ['any'] to listen on all interfaces.
bind_listen_ipv6	['::1']	A list of the IPv6 address of the network interface(s) to listen on
bind_log	data/named.run	Path to the log file
bind_other_name_servers	[]	A list of nameservers outside of the domain. For each one, an NS record will be created.
bind_recursion	false	Determines whether requests for which the DNS server is not authoritative should be forwarded†.
bind_allow_recursion	['any']	Similar to bind_allow_query, this option applies to recursive queries.
bind_rrset_order	random	Defines order for DNS round robin (either random or cyclic)
bind_dnssec_enable	true	Is DNSSEC enabled
bind_dnssec_validation	true	Is DNSSEC validation enabled
bind_zone_also_notify	-	A list of servers that will receive a notification when the master zone file is reloaded.
bind_zone_hostmaster_email	hostmaster	The e-mail address of the system administrator
bind_zone_hosts	[]	Host definitions. See below this table for examples.
bind_zone_delegate	[]	Zone delegation. See below this table for examples.
bind_zone_mail_servers	[{name: mail, preference: 10}]	A list of dicts (with fields name and preference) specifying the mail servers for this domain.
bind_zone_master_server_ip	-	(Required) The IP address of the master DNS server.
bind_zone_minimum_ttl	1D	Minimum TTL field in the SOA record.
bind_zone_name_servers	[ansible_hostname]	A list of the DNS servers for this domain.
bind_zone_name	example.com	The domain name
bind_zone_networks	['10.0.2']	A list of the networks that are part of the domain
bind_zone_ipv6_networks	[]	A list of the IPv6 networks that are part of the domain, in CIDR notation (e.g. 2001:db8::/48)
bind_zone_other_name_servers	[]	A list of the DNS servers outside of this domain.
bind_zone_services	[]	A list of services to be advertized by SRV records
bind_zone_text	[]	A list of dicts with fields name and text, specifying TXT records. text can be a list or string.
bind_zone_time_to_expire	1W	Time to expire field in the SOA record.
bind_zone_time_to_refresh	1D	Time to refresh field in the SOA record.
bind_zone_time_to_retry	1H	Time to retry field in the SOA record.
bind_zone_ttl	1W	Time to Live field in the SOA record.

† Best practice for an authoritative name server is to leave recursion turned off. However, for some cases it may be necessary to have recursion turned on.

Minimal variables for a working zone

Even thoug only variable bind_zone_master_server_ip is required for the role to run without errors, this is not sufficient to get a working zone. In order to set up an authoritative name server that is available to clients, you should also at least define the following variables:

Variable	Master	Slave
bind_zone_name	V	V
bind_zone_networks	V	V
bind_zone_name_servers	V	V
bind_zone_hosts	V	--
bind_listen_ipv4	V	V
bind_allow_query	V	V

Host definitions

Host names that this DNS server should resolve can be specified with the variable bind_zone_hosts as a list of dicts with fields name, ip and aliases, e.g.:

bind_zone_hosts:
  - name: pub01
    ip: 192.0.2.1
    ipv6: 2001:db8::1
    aliases:
      - ns
  - name: '@'
    ip:
      - 192.0.2.2
      - 192.0.2.3
    ipv6:
      - 2001:db8::2
      - 2001:db8::3
    aliases:
      - www
  - name: priv01
    ip: 10.0.0.1

To allow to surf to http://example.com/, set the host name of your web server to '@' (must be quoted!). In BIND syntax, @ indicates the domain name itself.

IP addresses (both IPv4 and IPv6) can be specified as a string or as a list. This results in a single or multiple A/AAAA records for the host, respectively. This enables DNS round robin, a simple load balancing technique. The order in which the IP addresses are returned can be configured with role variable bind_rrset_order.

As you can see, not all hosts are in the same network. This is perfectly acceptable, and supported by this role. All networks should be specified in bind_zone_networks, though, or the host will not get a PTR record for reverse lookup:

bind_zone_networks:
  - '192.0.2'
  - '10'
  - '172.16'

Remark that only the network part should be specified here! When specifying a class B IP address (e.g. "172.16") in a variable file, it must be quoted. Otherwise, the Yaml parser will interpret it as a float.

Based on the idea and examples detailed at https://linuxmonk.ch/wordpress/index.php/2016/managing-dns-zones-with-ansible/ for the gdnsd package, the zonefiles are fully idempotent, and thus only get updated if "real" content changes.

Zone delgation

To delegate a zone to a DNS, it is enough to create a NS record with:

bind_zone_delegate:
  - zone: foo
    dns: 192.0.2.1

which is the equivalent of:

foo IN NS 192.0.2.1

Service records

Service (SRV) records can be added with the variable bind_zone_services, e.g.:

bind_zone_services:
  - name: _ldap._tcp
    weight: 100
    port: 88
    target: dc001

This is a list of dicts with mandatory fields name (service name), target (host providing the service), port (TCP/UDP port of the service) and optional fields priority (default = 0) and weight (default = 0).

ACLs

ACLs can be defined like this:

bind_acls:
  - name: acl1
    match_list:
      - 192.0.2.0/24
      - 10.0.0.0/8

The names of the ACLs will be added to the allow-transfer clause in global options.

Dependencies

No dependencies. If you want to configure the firewall, do this through another role (e.g. bertvv.rh-base).

Example Playbook

See the test playbook test.yml for an elaborate example that shows all features.

Testing

There are two test environments for this role, one based on Vagrant, the other on Docker. The latter powers the Travis-CI tests. The tests are kept in a separate (orphan) branch so as not to clutter the actual code of the role. git-worktree(1) is used to include the test code into the working directory. Remark that this requires at least Git v2.5.0.

Running Docker tests

1. Fetch the test branch: git fetch origin docker-tests
2. Create a Git worktree for the test code: git worktree add docker-tests docker-tests. This will create a directory docker-tests/

The script docker-tests.sh will create a Docker container, and apply this role from a playbook test.yml. The Docker images are configured for testing Ansible roles and are published at https://hub.docker.com/r/bertvv/ansible-testing/. There are images available for several distributions and versions. The distribution and version should be specified outside the script using environment variables:

DISTRIBUTION=centos VERSION=7 ./tests/docker-tests.sh

The specific combinations of distributions and versions that are supported by this role are specified in .travis.yml.

The first time the test script is run, a container will be created that is assigned the IP address 172.17.0.2. This will be the master DNS-server. The server is still running after the script finishes and can be queried from the command line, e.g.:

$ dig @172.17.0.2 www.acme-inc.com +short
srv001.acme-inc.com.
172.17.1.1

If you run the script again, a new container is launched with IP address 172.17.0.3 that will be set up as a slave DNS-server. After a few seconds, it will have received updates from the master server and can be queried as well.

$ dig @172.17.0.3 www.acme-inc.com +short
srv001.acme-inc.com.
172.17.1.1

The script tests/functional-tests.sh will run a BATS test suite, dns.bats that performs a number of different queries. Specify the server IP address as the environment variable ${SUT_IP} (short for System Under Test).

$ SUT_IP=172.17.0.2 ./tests/functional-tests.sh
### Using BATS executable at: /usr/local/bin/bats
### Running test /home/bert/CfgMgmt/roles/bind/tests/dns.bats
 ✓ Forward lookups public servers
 ✓ Reverse lookups
 ✓ Alias lookups public servers
 ✓ IPv6 forward lookups
 ✓ NS record lookup
 ✓ Mail server lookup
 ✓ Service record lookup
 ✓ TXT record lookup

8 tests, 0 failures
$ SUT_IP=172.17.0.3 ./tests/functional-tests.sh
[...]

Running Vagrant tests

1. Fetch the tests branch: git fetch origin vagrant-tests
2. Create a Git worktree for the test code: git worktree add vagrant-tests vagrant-tests. This will create a directory vagrant-tests/.
3. cd vagrant-tests/
4. vagrant up will then create two VMs and apply a test playbook (test.yml).

The command vagrant up results in a setup with two DNS servers, a master and a slave, set up according to playbook test.yml.

Hostname	ip
testbindmaster	192.168.56.53
testbindslave	192.168.56.54

IP addresses are in the subnet of the default VirtualBox Host Only network interface (192.168.56.0/24). You should be able to query the servers from your host system. For example, to verify if the slave is updated correctly, you can do the following:

$ dig @192.168.56.54 ns1.example.com +short
testbindmaster.example.com.
192.168.56.53
$ dig @192.168.56.54 example.com www.example.com +short
web.example.com.
192.168.56.20
192.168.56.21
$ dig @192.168.56.54 MX example.com +short
10 mail.example.com.

An automated acceptance test written in BATS is provided that checks most settings specified in tests/test.yml. You can run it by executing the shell script tests/runtests.sh. The script can be run on either your host system (assuming you have a Bash shell), or one of the VMs. The script will download BATS if needed and run the test script tests/dns.bats on both the master and the slave DNS server.

$ cd vagrant-tests
$ vagrant up
[...]
$ ./runtests.sh
Testing 192.168.56.53
✓ The `dig` command should be installed
✓ It should return the NS record(s)
✓ It should be able to resolve host names
✓ It should be able to resolve IPv6 addresses
✓ It should be able to do reverse lookups
✓ It should be able to resolve aliases
✓ It should return the MX record(s)

6 tests, 0 failures
Testing 192.168.56.54
✓ The `dig` command should be installed
✓ It should return the NS record(s)
✓ It should be able to resolve host names
✓ It should be able to resolve IPv6 addresses
✓ It should be able to do reverse lookups
✓ It should be able to resolve aliases
✓ It should return the MX record(s)

6 tests, 0 failures

Running from the VM:

$ vagrant ssh testbindmaster
Last login: Sun Jun 14 18:52:35 2015 from 10.0.2.2
Welcome to your Packer-built virtual machine.
[vagrant@testbindmaster ~]$ /vagrant/runtests.sh
Testing 192.168.56.53
 ✓ The `dig` command should be installed
[...]

License

BSD

Contributors

Issues, feature requests, ideas, suggestions, etc. are appreciated and can be posted in the Issues section.

Pull requests are also very welcome. Please create a topic branch for your proposed changes. If you don't, this will create conflicts in your fork after the merge. Don't hesitate to add yourself to the contributor list below in your PR!

• Bert Van Vreckem (Maintainer)
• B. Verschueren
• Greg Cockburn
• Guillaume Darmont
• Joanna Delaporte
• Jose Taas
• Peter Janes
• Mario Ciccarelli
• Rafael Bodill
• Stuart Knight
• Loic Dachary