"www.GetIPv6.info decal" from Phil Wolff on Flickr

Hurricane Electric IPv6 Gateway on Raspbian for Raspberry Pi

NOTE: This article was replaced on 2019-03-12 by a github repository where I now use Vagrant instead of a Raspberry Pi, because I was having some power issues with my Raspberry Pi. Also, using this method means I can easily use an Ansible Playbook. The following config will still work(!) however I prefer this Vagrant/Ansible workflow for this, so won’t update this blog post any further.

Following an off-hand remark from a colleague at work, I decided I wanted to set up a Raspberry Pi as a Hurricane Electric IPv6 6in4 tunnel router. Most of the advice around (in particular, this post about setting up IPv6 on the Raspberry Pi Forums) related to earlier version of Raspbian, so I thought I’d bring it up-to-date.

I installed the latest available version of Raspbian Stretch Lite (2018-11-13) and transferred it to a MicroSD card. I added the file ssh to the boot volume and unmounted it. I then fitted it into my Raspberry Pi, and booted it. While it was booting, I set a static IPv4 address on my router (192.168.1.252) for the Raspberry Pi, so I knew what IP address it would be on my network.

I logged into my Hurricane Electric (HE) account at tunnelbroker.net and created a new tunnel, specifying my public IP address, and selecting my closest HE endpoint. When the new tunnel was created, I went to the “Example Configurations” tab, and selected “Debian/Ubuntu” from the list of available OS options. I copied this configuration into my clipboard.

I SSH’d into the Pi, and gave it a basic config (changed the password, expanded the disk, turned off “predictable network names”, etc) and then rebooted it.

After this was done, I created a file in /etc/network/interfaces.d/he-ipv6 and pasted in the config from the HE website. I had to change the “local” line from the public IP I’d provided HE with, to the real IP address of this box. Note that any public IPs (that is, not 192.168.x.x addresses) in the config files and settings I’ve noted refer to documentation addressing (TEST-NET-2 and the IPv6 documentation address ranges)

auto he-ipv6
iface he-ipv6 inet6 v4tunnel
        address 2001:db8:123c:abd::2
        netmask 64
        endpoint 198.51.100.100
        local 192.168.1.252
        ttl 255
        gateway 2001:db8:123c:abd::1

Next, I created a file in /etc/network/interfaces.d/eth0 and put the following configuration in, using the first IPv6 address in the “routed /64” range listed on the HE site:

auto eth0
iface eth0 inet static
    address 192.168.1.252
    gateway 192.168.1.254
    netmask 24
    dns-nameserver 8.8.8.8
    dns-nameserver 8.8.4.4

iface eth0 inet6 static
    address 2001:db8:123d:abc::1
    netmask 64

Next, I disabled the DHCPd service by issuing systemctl stop dhcpcd.service Late edit (2019-01-22): Note, a colleague mentioned that this should have actually been systemctl stop dhcpcd.service && systemctl disable dhcpcd.service – good spot! Thanks!! This ensures that if, for some crazy reason, the router stops offering the right DHCP address to me, I can still access this box on this IP. Huzzah!

I accessed another host which had IPv6 access, and performed both a ping and an SSH attempt. Both worked. Fab. However, this now needs to be blocked, as we shouldn’t permit anything to be visible downstream from this gateway.

I’m using the Uncomplicated Firewall (ufw) which is a simple wrapper around IPTables. Let’s create our policy.

# First install the software
sudo apt update && sudo apt install ufw -y

# Permits inbound IPv4 SSH to this host - which should be internal only. 
# These rules allow tailored access in to our managed services
ufw allow in on eth0 app DNS
ufw allow in on eth0 app OpenSSH

# These rules accept all broadcast and multicast traffic
ufw allow in on eth0 to 224.0.0.0/4 # Multicast addresses
ufw allow in on eth0 to 255.255.255.255 # Global broadcast
ufw allow in on eth0 to 192.168.1.255 # Local broadcast

# Alternatively, accept everything coming in on eth0
# If you do this one, you don't need the lines above
ufw allow in on eth0

# Setup the default rules - deny inbound and routed, permit outbound
ufw default deny incoming 
ufw default deny routed
ufw default allow outgoing

# Prevent inbound IPv6 to the network
# Also, log any drops so we can spot them if we have an issue
ufw route deny log from ::/0 to 2001:db8:123d:abc::/64

# Permit outbound IPv6 from the network
ufw route allow from 2001:db8:123d:abc::/64

# Start the firewall!
ufw enable

# Check the policy
ufw status verbose
ufw status numbered

Most of the documentation I found suggested running radvd for IPv6 address allocation. This basically just allocates on a random basis, and, as far as I can make out, each renewal gives the host a new IPv6 address. To make that work, I performed apt-get update && apt-get install radvd -y and then created this file as /etc/radvd.conf. If all you want is a floating IP address with no static assignment – this will do it…

interface eth0
{
    AdvSendAdvert on;
    MinRtrAdvInterval 3;
    MaxRtrAdvInterval 10;
    prefix 2001:db8:123d:abc::/64
    {
        AdvOnLink on;
        AdvAutonomous on;
    };
   route ::/0 {
   };
};

However, this doesn’t give me the ability to statically assign IPv6 addresses to hosts. I found that a different IPv6 allocation method will do static addressing, based on your MAC address called SLAAC (note there are some privacy issues with this, but I’m OK with them for now…) In this mode assuming the prefix as before – 2001:db8:123d:abc:: and a MAC address of de:ad:be:ef:01:23, your IPv6 address will be something like: 2001:db8:123d:abc:dead:beff:feef:0123and this will be repeatably so – because you’re unlikely to change your MAC address (hopefully!!).

This SLAAC allocation mode is available in DNSMasq, which I’ve consumed before (in a Pi-Hole). To use this, I installed DNSMasq with apt-get update && apt-get install dnsmasq -y and then configured it as follows:

interface=eth0
listen-address=127.0.0.1
# DHCPv6 - Hurricane Electric Resolver and Google's
dhcp-option=option6:dns-server,[2001:470:20::2],[2001:4860:4860::8888]
# IPv6 DHCP scope
dhcp-range=2001:db8:123d:abc::, slaac

I decided to move from using my router as a DHCP server, to using this same host, so expanded that config as follows, based on several posts, but mostly centred around the MAN page (I’m happy to have this DNSMasq config improved if you’ve got any suggestions ;) )

# Stuff for DNS resolution
domain-needed
bogus-priv
no-resolv
filterwin2k
expand-hosts
domain=localnet
local=/localnet/
log-queries

# Global options
interface=eth0
listen-address=127.0.0.1

# Set these hosts as the DNS server for your network
# Hurricane Electric and Google
dhcp-option=option6:dns-server,[2001:470:20::2],2001:4860:4860::8888]

# My DNS servers are:
server=1.1.1.1                # Cloudflare's DNS server
server=8.8.8.8                # Google's DNS server

# IPv4 DHCP scope
dhcp-range=192.168.1.10,192.168.1.210,12h
# IPv6 DHCP scope
dhcp-range=2001:db8:123d:abc::, slaac

# Record the DHCP leases here
dhcp-leasefile=/run/dnsmasq/dhcp-lease

# DHCPv4 Router
dhcp-option=3,192.168.1.254

So, that’s what I’m doing now! Hope it helps you!

Late edit (2019-01-22): In issue 129 of the “Awesome Self Hosted Newsletter“, I found a post called “My New Years Resolution: Learn IPv6“… which uses a pfSense box and a Hurricane Electric tunnel too. Fab!

Header image is “www.GetIPv6.info decal” by “Phil Wolff” on Flickr and is released under a CC-BY-SA license. Used with thanks!

"Zenith Z-19 Terminal" from ajmexico on Flickr

Some things I learned this week while coding extensions to Ansible!

If you follow any of the content I post around the internet, you might have seen me asking questions about trying to get data out of azure_rm_*_facts into something that’s usable. I can’t go into why I needed that data yet (it’s a little project I’m working on), but the upshot is that trying to manipulate data using “set_fact” with jinja is *doable* but *messy*. In the end, I decided to hand it all off to a new ansible module I’m writing. So, here are the things I learned about this.

  1. There’s lots more documentation about writing a module (a plugin that let’s you do stuff) than there is about writing filters (things that change text inline) or lookups (things that let you search other data stores). In the end, while I could have spent the time to figure out how better to write a filter or a lookup, it actually makes more sense in my context to hand a module all my data, and say “Parse this” and register the result than it would have done to have the playbook constantly check whether things were in other things. I still might have to do that, but… you know, for now, I’ve got the bits I want! :)
  2. I did start looking at writing a filter, and discovered that the “debugging advice” on the ansible site is all geared up to enable more modules than enabling filters… but I did discover that modules execute on their target (e.g. WebHost01) while filters and lookups execute on the local machine. Why does this matter? Well…..
  3. While I was looking for documentation about debugging Ansible code, I stumbled over this page on debugging modules that makes it all look easy. Except, it’s only for debugging *MODULES* (very frustrating. Well, what does it actually mean? The modules get zipped up and sent to the host that will be executing the code, which means that with an extra flag to your playbook (ANSIBLE_KEEP_REMOTE_FILES – even if it’s going to be run on “localhost”), you get the combined output of the script placed into a path on your machine, which means you can debug that specific play. That doesn’t work for filters…
  4. SOO, I jumped into #ansible on Freenode and asked for help. They in turn couldn’t help me (it’s more about writing playbooks than writing filters, modules, etc), so they directed me to #ansible-devel, where I was advised to use a python library called “q” (Edit, same day: my friend @mohclips pointed me to this youtube video from 2003 of the guy who wrote q explaining about it. Thanks Nick! I learned something *else* about this library).
  5. Oh man, this is the motherlode. So, q makes life *VERY* easy. Assuming this is valid code: All you’d need to do would be to add two lines, as you’ll see here: This then dumps the output from each of the q(something) lines into /tmp/q for you to read at your leisure! (To be fair, I’d probably remove it after you’ve finished, so you don’t fill a disk :) )
  6. And that’s when I discovered that it’s actually easier to use q() for all my python debugging purposes than it is to follow the advice above about debugging modules. Yehr, it’s basically a load of print statements, so you don’t get to see stack traces, or read all the variables, and you don’t get to step through code to see why decisions were taken… but for the rubbish code I produce, it’s easily enough for me!

Header image is “Zenith Z-19 Terminal” by “ajmexico” on Flickr and is released under a CC-BY license. Used with thanks!

"LEGO Factory Playset" from Brickset on Flickr

Building Azure Environments in Ansible

Recently, I’ve been migrating my POV (proof of value) and POC (proof of concept) environment from K5 to Azure to be able to test vendor products inside Azure. I ran a few tests to build the environment using the native tools (the powershell scripts) and found that the Powershell way of delivering Azure environments seems overly complicated… particularly as I’m comfortable with how Ansible works.

To be fair, I also need to look at Terraform, but that isn’t what I’m looking at today :)

So, let’s start with the scaffolding. Any Ansible Playbook which deals with creating virtual machines needs to have some extra modules installed. Make sure you’ve got ansible 2.7 or later and the python azure library 2.0.0 or later (you can get both with pip for python).

Next, let’s look at the group_vars for this playbook.

This file has several pieces. We define the project settings (anything prefixed project_ is a project setting), including the prefix used for all resources we create (in this case “env01“), and a standard password used for all VMs we create (in this case “My$uper$ecret$Passw0rd“).

Next we define the standard images to load from the Marketplace. You can extend this with other images, these are just the “easiest” ones that I’m most familiar with (your mileage may vary). Next up is the networks to build inside the VNet, and lastly we define the actual machines we want to build. If you’ve got questions about any of the values we define here, just let me know in the comments below :)

Next, we’ll start looking at the playbook (this has been exploded out – the full playbook is also in the gist).

Here we start by pulling in the variables we might want to override, and we do this by reading system environment variables (ANSIBLE_PREFIX and BREAKGLASS) and using them if they’re set. If they’re not, use the project defaults, and if that hasn’t been set, use some pre-defined values… and then tell us what they are when we’re running the tasks (those are the debug: lines).

This block is where we create our “Static Assets” – individual items that we will be consuming later. This shows a clear win here over the Powershell methods endorsed by Microsoft – here you can create a Resource Group (RG) as part of the playbook! We also create a single Storage Account for this RG and a single VNET too.

These creation rules are not suitable for production use, as this defines an “Any-Any” Security group! You should tailor your security groups for your need, not for blanket access in!

This is where things start to get a bit more interesting – We’re using the “async/async_status” pattern here (and the rest of these sections) to start creating the resources in parallel. As far as I can tell, sometimes you’ll get a case where the async doesn’t quite get set up fast enough, then the async_status can’t track the resources properly, but re-running the playbook should be enough to sort that out, without slowing things down too much.

But what are we actually doing with this block of code? A UDR is a “User Defined Route” or routing table for Azure. Effectively, you treat each network interface as being plumbed directly to the router (none of this “same subnet broadcast” stuff works here!) so you can do routing at the router for all the networks.

By default there are some existing network routes (stuff to the internet flows to the internet, RFC1918 addresses are dropped with the exception of any RFC1918 addresses you have covered in your VNETs, and each of your subnets can reach each other “directly”). Adding a UDR overrides this routing table. The UDRs we’re creating here are applied at a subnet level, but currently don’t override any of the existing routes (they’re blank). We’ll start putting routes in after we’ve added the UDRs to the subnets. Talking of which….

Again, this block is not really suitable for production use, and assumes the VNET supernet of /8 will be broken down into several /24’s. In the “real world” you might deliver a handful of /26’s in a /24 VNET… or you might even have lots of disparate /24’s in the VNET which are then allocated exactly as individual /24 subnets… this is not what this model delivers but you might wish to investigate further!

Now that we’ve created our subnets, we can start adding the routing table to the UDR. This is a basic one – add a 0.0.0.0/0 route (internet access) from the “protected” network via the firewall. You can get a lot more specific than this – most people are likely to want to add the VNET range (in this case 10.0.0.0/8) via the firewall as well, except for this subnet (because otherwise, for example, 10.0.0.100 trying to reach 10.0.0.101 will go via the firewall too).

Without going too much into the intricacies of network architecture, if you are routing your traffic between subnets to the firewall, it’s probably better to get an appliance with more interfaces, so you can route traffic across the appliance, rather than going across a single interface as this will halve your traffic bandwidth (it’s currently capped 1Gb/s – so 500Mb/s).

Having mentioned “The Internet” – let’s give our firewall a public IP address, and create the rest of the interfaces as well.

This script creates a public IP address by default for each interface unless you explicitly tell it not to (see lines 40, 53 and 62 in the group_vars file I rendered above). You could easily turn this around by changing the lines which contain this:

item.1.public is not defined or (item.1.public is defined and item.1.public == 'true')

into lines which contain this:

item.1.public is defined and item.1.public == 'true'

OK, having done all that, we’re now ready to build our virtual machines. I’ve introduced a “Priority system” here – VMs with priority 0 go first, then 1, and 2 go last. The code snippet below is just for priority 0, but you can easily see how you’d extrapolate that out (and in fact, the full code sample does just that).

There are a few blocks here to draw attention to :) I’ve re-jigged them a bit here so it’s clearer to understand, but when you see them in the main playbook they’re a bit more compact. Let’s start with looking at the Network Interfaces section!

network_interfaces: |
  [
    {%- for nw in item.value.ports -%}
      '{{ prefix }}{{ item.value.name }}port{{ nw.subnet.name }}'
      {%- if not loop.last -%}, {%- endif -%} 
    {%- endfor -%}
  ]

In this part, we loop over the ports defined for the virtual machine. This is because one device may have 1 interface, or four interfaces. YAML is parsed to make a JSON variable, so here we can create a JSON variable, that when the YAML is parsed it will just drop in. We’ve previously created all the interfaces to have names like this PREFIXhostnamePORTsubnetname (or aFW01portWAN in more conventional terms), so here we construct a JSON array, like this: ['aFW01portWAN'] but that could just as easily have been ['aFW01portWAN', 'aFW01portProtect', 'aFW01portMGMT', 'aFW01portSync']. This will then attach those interfaces to the virtual machine.

Next up, custom_data. This section is sometimes known externally as userdata or config_disk. My code has always referred to it as a “Provision Script” – hence the variable name in the code below!

custom_data: |
  {%- if item.value.provision_script is defined and item.value.provision_script != '' -%}
    {%- include(item.value.provision_script) -%}
  {%- elif item.value.image.provision_script is defined and item.value.image.provision_script != '' -%}
    {%- include(item.value.image.provision_script) -%}
  {%- else -%}
    {{ omit }}
  {%- endif -%}

Let’s pick this one apart too. If we’ve defined a provisioning script file for the VM, include it, if we’ve defined a provisioning script file for the image (or marketplace entry), then include that instead… otherwise, pretend that there’s no “custom_data” field before you submit this to Azure.

One last quirk to Azure, is that some images require a “plan” to go with it, and others don’t.

plan: |
  {%- if item.value.image.plan is not defined -%}{{ omit }}{%- else -%}
    {'name': '{{ item.value.image.sku }}',
     'publisher': '{{ item.value.image.publisher }}',
     'product': '{{ item.value.image.offer }}'
    }
  {%- endif -%}

So, here we say “if we’ve not got a plan, omit the value being passed to Azure, otherwise use these fields we previously specified. Weird huh?

The very last thing we do in the script is to re-render the standard password we’ve used for all these builds, so that we can check them out!

Want to review this all in one place?

Here’s the link to the full playbook, as well as the group variables (which should be in ./group_vars/all.yml) and two sample userdata files (which should be in ./userdata) for an Ubuntu machine (using cloud-init) and one for a FortiGate Firewall.

All the other files in that gist (prefixes from 10-16 and 00) are for this blog post only, and aren’t likely to work!

If you do end up using this, please drop me a note below, or star the gist! That’d be awesome!!

Image credit: “Lego Factory Playset” from Flickr by “Brickset” released under a CC-BY license. Used with Thanks!

Troubleshooting FortiGate API issues with the CLI?

One of my colleagues has asked me for some help with an Ansible script he’s writing to push some policy to a cloud hosted FortiGate appliance. Unfortunately, he kept getting some very weird error messages, like this one:

fatal: [localhost]: FAILED! => {"changed": false, "meta": {"build": 200, "error": -651, "http_method": "PUT", "http_status": 500, "mkey": "vip8080", "name": "vip", "path": "firewall", "revision": "36.0.0.10745196634707694665.1544442857", "serial": "CENSORED", "status": "error", "vdom": "root", "version": "v6.0.3"}, "msg": "Error in repo"}

This is using Fortinet’s own Ansible Modules, which, in turn use the fortiosapi python module.

This same colleague came across a post on the Fortinet Developer Network site (access to the site requires vendor approval), which said “this might be an internal bug, but to debug it, use the following”

fgt # diagnose debug enable

fgt # diagnose debug cli 8
Debug messages will be on for 30 minutes.

And then run your API commands. Your error message will be surfaced there… so here’s mine! (Mapped port doesn’t match extport in a vip).

0: config firewall vip
0: edit "vip8080"
0: unset src-filter
0: unset service
0: set extintf "port1"
0: set portforward enable
0: unset srcintf-filter
0: set mappedip "192.0.2.1-192.0.2.1"
0: unset extport
0: set extport 8080-8081
0: unset mappedport
0: set mappedport 8080
-651: end

Creating Self Signed certificates in Ansible

In my day job, I sometimes need to use a self-signed certificate when building a box. As I love using Ansible, I wanted to make the self-signed certificate piece something that was part of my Ansible workflow.

Here follows a bit of basic code that you could use to work through how the process of creating a self-signed certificate would work. I would strongly recommend using something more production-ready (e.g. LetsEncrypt) when you’re looking to move from “development” to “production” :)

---
- hosts: localhost
  vars:
  - dnsname: your.dns.name
  - tmppath: "./tmp/"
  - crtpath: "{{ tmppath }}{{ dnsname }}.crt"
  - pempath: "{{ tmppath }}{{ dnsname }}.pem"
  - csrpath: "{{ tmppath }}{{ dnsname }}.csr"
  - pfxpath: "{{ tmppath }}{{ dnsname }}.pfx"
  - private_key_password: "password"
  tasks:
  - file:
      path: "{{ tmppath }}"
      state: absent
  - file:
      path: "{{ tmppath }}"
      state: directory
  - name: "Generate the private key file to sign the CSR"
    openssl_privatekey:
      path: "{{ pempath }}"
      passphrase: "{{ private_key_password }}"
      cipher: aes256
  - name: "Generate the CSR file signed with the private key"
    openssl_csr:
      path: "{{ csrpath }}"
      privatekey_path: "{{ pempath }}"
      privatekey_passphrase: "{{ private_key_password }}"
      common_name: "{{ dnsname }}"
  - name: "Sign the CSR file as a CA to turn it into a certificate"
    openssl_certificate:
      path: "{{ crtpath }}"
      privatekey_path: "{{ pempath }}"
      privatekey_passphrase: "{{ private_key_password }}"
      csr_path: "{{ csrpath }}"
      provider: selfsigned
  - name: "Convert the signed certificate into a PKCS12 file with the attached private key"
    openssl_pkcs12:
      action: export
      path: "{{ pfxpath }}"
      name: "{{ dnsname }}"
      privatekey_path: "{{ pempath }}"
      privatekey_passphrase: "{{ private_key_password }}"
      passphrase: password
      certificate_path: "{{ crtpath }}"
      state: present

“You can’t run multiple commands in sudo” – and how to work around this

At work, we share tips and tricks, and one of my colleagues recently called me out on the following stanza I posted:

I like this [ansible] one for Debian based systems:
  - name: "Apt update, Full-upgrade, autoremove, autoclean"
    become: yes
    apt:
      upgrade: full
      update_cache: yes
      autoremove: yes
      autoclean: yes

And if you’re trying to figure out how to do that in Shell:
apt-get update && apt-get full-update -y && apt-get autoremove -y && apt-get autoclean -y

His response was “Surely you’re not logging into bash as root”. I said “I normally sudo -i as soon as I’ve logged in. I can’t recall offhand how one does a sudo for a string of command && command statements”

Well, as a result of this, I looked into it. Here’s one comment from the first Stack Overflow page I found:

You can’t run multiple commands from sudo – you always need to trick it into executing a shell which may accept multiple commands to run as parameters

So here are a few options on how to do that:

  1. sudo -s whoami \; whoami (link to answer)
  2. sudo sh -c "whoami ; whoami" (link to answer)
  3. But, my favourite is from this answer:

    An alternative using eval so avoiding use of a subshell: sudo -s eval 'whoami; whoami'

Why do I prefer the last one? Well, I already use eval for other purposes – mostly for starting my ssh-agent over SSH, like this: eval `ssh-agent` ; ssh-add

Ansible Behaviour Change

For those of you who are working with #Ansible… Ansible 2.5 is out, and has an unusual documentation change around a key Ansible concept – `with_` loops Where you previously had:

with_dict: "{{ your_fact }}"
or
with_subelements:
- "{{ your_fact }}"
- some_subkey

This now should be written like this:

loop: "{{ lookup('dict', your_fact) }}"
and
loop: "{{ lookup('subelements', your_fact, 'some_subkey') }}"

Fear not, I hear you say, It’s fine, of course the documentation suggests that this is “how it’s always been”…… HA HA HA Nope. This behaviour is new as of 2.5, and needs ansible to be updated to the latest version. As far as I can tell, there’s no way to indicate to Ansible “Oh, BTW, this needs to be running on 2.5 or later”… so I wrote a role that does that for you.

ansible-galaxy install JonTheNiceGuy.version-check

You’re welcome :)

More useful URLs:

Creating OpenStack “Allowed Address Pairs” for Clusters with Ansible

This post came about after a couple of hours of iterations, so I can’t necessarily quote all the sources I worked from, but I’ll do my best!

In OpenStack (particularly in the “Kilo” release I’m working with), if you have a networking device that will pass traffic on behalf of something else (e.g. Firewall, IDS, Router, Transparent Proxy) you need to tell the virtual NIC that the interface is allowed to pass traffic for other IP addresses, as OpenStack applies by default a “Same Origin” firewall rule to the interface. Defining this in OpenStack is more complex than it could be, because for some reason, you can’t define 0.0.0.0/0 as this allowed address pair, so instead you have to define 0.0.0.0/1 and 128.0.0.0/1.

Here’s how you define those allowed address pairs (note, this assumes you’ve got some scaffolding in place to define things like “network_appliance”):

allowed_address_pairs: "{% if (item.0.network_appliance|default('false')|lower() == 'true') or (item.1.network_appliance|default('false')|lower() == 'true') %}[{'ip_address': '0.0.0.0/1'}, {'ip_address': '128.0.0.0/1'}]{% else %}{{ item.0.allowed_address_pairs|default(omit) }}{% endif %}"

OK, so we’ve defined the allowed address pairs! We can pass traffic across our firewall. But (and there’s always a but), the product I’m working with at the moment has a floating MAC address in a cluster, when you define an HA pair. They have a standard schedule for how each port’s floating MAC is assigned… so here’s what I’ve ended up with (and yes, I know it’s a mess!)

allowed_address_pairs: "{% if (item.0.network_appliance|default('false')|lower() == 'true') or (item.1.network_appliance|default('false')|lower() == 'true') %}[{'ip_address': '0.0.0.0/1'},{'ip_address': '128.0.0.0/1'}{% if item.0.ha is defined and item.0.ha != '' %}{% for vdom in range(0,40, 10) %},{'ip_address': '0.0.0.0/1','mac_address': '{{ item.0.floating_mac_prefix|default(item.0.image.floating_mac_prefix|default(floating_mac_prefix)) }}:{% if item.0.ha.group_id|default(0) < 16 %}0{% endif %}{{ '%0x' | format(item.0.ha.group_id|default(0)|int) }}:{% if vdom+(item.1.interface|default('1')|replace('port', '')|int)-1 < 16 %}0{% endif %}{{ '%0x' | format(vdom+(item.1.interface|default('1')|replace('port', '')|int)-1) }}'}, {'ip_address': '128.0.0.0/1','mac_address': '{{ item.0.floating_mac_prefix|default(item.0.image.floating_mac_prefix|default(floating_mac_prefix)) }}:{% if item.0.ha.group_id|default(0) < 16 %}0{% endif %}{{ '%0x' | format(item.0.ha.group_id|default(0)|int) }}:{% if vdom+(item.1.interface|default('0')|replace('port', '')|int)-1 < 16 %}0{% endif %}{{ '%0x' | format(vdom+(item.1.interface|default('1')|replace('port', '')|int)-1) }}'}{% endfor %}{% endif %}]{% else %}{{ item.0.allowed_address_pairs|default(omit) }}{% endif %}"

Let's break this down a bit. The vendor says that each port gets a standard prefix, (e.g. DE:CA:FB:AD) then the penultimate octet is the "Cluster ID" number in hex, and then the last octet is the sum of the port number (zero-indexed) added to a VDOM number, which increments in 10's. We're only allowed to assign 10 "allowed address pairs" to an interface, so I've got the two originals (which are assigned to "whatever" the defined mac address is of the interface), and four passes around. Other vendors (e.g. this one) do things differently, so I'll probably need to revisit this once I know how the next one (and the next one... etc.) works!

So, we have here a few parts to make that happen.

The penultimate octet, which is the group ID in hex needs to be two hex digits long, and without adding more python modules to our default machines, we can't use a "pad" filter (to add 0's to the beginning of the mac octets), so we do that by hand:

{% if item.0.ha.group_id|default(0) < 16 %}0{% endif %}

And here's how to convert the group ID into a hex number:

{{ '%0x' | format(item.0.ha.group_id|default(0)|int) }}

Then the next octet is the sum of the VDOM and PortID. First we need to loop around the VDOMs. We don't always know whether we're going to be adding VDOMs until after deployment has started, so here we will assume we've got 3 VDOMs (plus VDOM "0" for management) as it doesn't really matter if we don't end up using them. We create the vdom variable like this:

{% for vdom in range(0, 40, 10) %} STUFF {% endfor %}

We need to put the actual port ID in there too. As we're using a with_subelement loop we can't create an increment, but what we can do is ensure we're recording the interface number. This only works here because the vendor has a sequential port number (port1, port2, etc). We'll need to experiment further with other vendors! So, here's how we're doing this. We already know how to create a hex number, but we do need to use some other Jinja2 filters here:

{{ '%0x' | format(vdom+(item.1.interface|default('1')|replace('port', '')|int)-1) }}

Let's pull this apart a bit further. item.1.interface is the name of the interface, and if it doesn't exist (using the |default('1') part) we replace it with the string "1". So, let's replace that variable with a "normal" value.

{{ '%0x' | format(vdom+("port1"|replace('port', '')|int)-1) }}

Next, we need to remove the word "port" from the string "port1" to make it just "1", so we use the replace filter to strip part of that value out. Let's do that:

{{ '%0x' | format(vdom+("1"|int)-1) }}

After that, we need to turn the string "1" into the literal number 1:

{{ '%0x' | format(vdom+1-1) }}

We loop through vdom several times, but let's pick one instance of that at random - 30 (the fourth iteration of the vdom for-loop):

{{ '%0x' | format(30+1-1) }}

And then we resolve the maths:

{{ '%0x' | format(30) }}

And then the |format(30) turns the '%0x' into the value "1e"

Assuming the vendor prefix is, as I mentioned, 'de:ca:fb:ad:' and the cluster ID is 0, this gives us the following resulting allowed address pairs:

[
{"ip_address": "0.0.0.0/1"},
{"ip_address": "128.0.0.0/1"},
{"ip_address": "0.0.0.0/1", "mac_address": "de:ca:fb:ad:00:00"},
{"ip_address": "128.0.0.0/1", "mac_address": "de:ca:fb:ad:00:00"},
{"ip_address": "0.0.0.0/1", "mac_address": "de:ca:fb:ad:00:0a"},
{"ip_address": "128.0.0.0/1", "mac_address": "de:ca:fb:ad:00:0a"},
{"ip_address": "0.0.0.0/1", "mac_address": "de:ca:fb:ad:00:14"},
{"ip_address": "128.0.0.0/1", "mac_address": "de:ca:fb:ad:00:14"},
{"ip_address": "0.0.0.0/1", "mac_address": "de:ca:fb:ad:00:1e"},
{"ip_address": "128.0.0.0/1", "mac_address": "de:ca:fb:ad:00:1e"}
]

I hope this has helped you!

Sources of information:

Defining Networks with Ansible

In my day job, I’m using Ansible to provision networks in OpenStack. One of the complaints I’ve had about the way I now define them is that the person implementing the network has to spell out all the network elements – the subnet size, DHCP pool, the addresses of the firewalls and names of those items. This works for a manual implementation process, but is seriously broken when you try to hand that over to someone else to implement. Most people just want something which says “Here is the network I want to implement – 192.0.2.0/24″… and let the system make it for you.

So, I wrote some code to make that happen. It’s not perfect, and it’s not what’s in production (we have lots more things I need to add for that!) but it should do OK with an IPv4 network.

Hope this makes sense!

---
- hosts: localhost
  vars:
  - networks:
      # Defined as a subnet with specific router and firewall addressing
      external:
        subnet: "192.0.2.0/24"
        firewall: "192.0.2.1"
        router: "192.0.2.254"
      # Defined as an IP address and CIDR prefix, rather than a proper network address and CIDR prefix
      internal_1:
        subnet: "198.51.100.64/24"
      # A valid smaller network and CIDR prefix
      internal_2:
        subnet: "203.0.113.0/27"
      # A tiny CIDR network
      internal_3:
        subnet: "203.0.113.64/30"
      # These two CIDR networks are unusable for this environment
      internal_4:
        subnet: "203.0.113.128/31"
      internal_5:
        subnet: "203.0.113.192/32"
      # A massive CIDR network
      internal_6:
        subnet: "10.0.0.0/8"
  tasks:
  # Based on https://stackoverflow.com/a/47631963/5738 with serious help from mgedmin and apollo13 via #ansible on Freenode
  - name: Add router and firewall addressing for CIDR prefixes < 30     set_fact:       networks: >
        {{ networks | default({}) | combine(
          {item.key: {
            'subnet': item.value.subnet | ipv4('network'),
            'router': item.value.router | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 1) | ipv4),
            'firewall': item.value.firewall | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 1) | ipv4),
            'dhcp_start': item.value.dhcp_start | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 2) | ipv4),
            'dhcp_end': item.value.dhcp_end | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 2) | ipv4)
          }
        }) }}
    with_dict: "{{ networks }}"
    when: item.value.subnet | ipv4('prefix') < 30   - name: Add router and firewall addressing for CIDR prefixes = 30     set_fact:       networks: >
        {{ networks | default({}) | combine(
          {item.key: {
            'subnet': item.value.subnet | ipv4('network'),
            'router': item.value.router | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 1) | ipv4),
            'firewall': item.value.firewall | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 1) | ipv4)
          }
        }) }}
    with_dict: "{{ networks }}"
    when: item.value.subnet | ipv4('prefix') == 30
  - debug:
      var: networks