Network topology discovery with Ansible and Skydive

Since Skydive already has a Python client library I thought it was “fun” to create an Ansible module leveraging it to add topology entities. In this blog post I will show how to use this module and how to use this module to provide real topology information.

Nodes and Links

The module is part of the Skydive repository, so the first thing is to prepare the Ansible environment by download the module in the proper place.

mkdir skydive-ansible
cd skydive-ansible
mkdir library
curl -Lo library/skydive_node.py https://raw.githubusercontent.com/skydive-project/skydive/master/contrib/ansible/library/skydive_node.py
curl -Lo library/skydive_edge.py https://raw.githubusercontent.com/skydive-project/skydive/master/contrib/ansible/library/skydive_edge.py

Now we have the module available, let’s write a really simple playbook creating two nodes, one will be a “Top of Rack” switch and the other one will be a port. Of course we will create a link between them.

vi playbook.yaml

- name: Skydive Ansible
  hosts: localhost
  tasks:

    - name: Create TOR
      skydive_node:
        name: 'TOR'
        type: "fabric"
        metadata:
          Model: My favorite Switch brand
          ManagementIP: 10.0.0.1
      register: tor_result

    - name: Create port
      skydive_node:
        name: 'PORT'
        type: 'fabric'
      register: port_result
    
    - name: Link TOR and port  
      skydive_edge:
        node1: "{{ tor_result.UUID }}"
        node2: "{{ port_result.UUID }}"
        relation_type: ownership
        metadata:
          Type: unknown

You can use the metadata dict to add any arbitrary information you want.

Once executed we’ll see the entities in the topology.

node1 and node2 can be either the ID of the nodes or a Gremlin expression. The following playbook shows a mix of ID and a Gremlin expression to link the switch port to a host interface.

- name: Skydive Ansible
  hosts: localhost
  tasks:

    - name: Create TOR
      skydive_node:
        name: 'TOR'
        type: "fabric"
        metadata:
          Model: My favorite Switch brand
          ManagementIP: 10.0.0.1
      register: tor_result

    - name: Create port
      skydive_node:
        name: 'PORT'
        type: 'fabric'
      register: port_result
    
    - name: Link TOR and port  
      skydive_edge:
        node1: "{{ tor_result.UUID }}"
        node2: "{{ port_result.UUID }}"
        relation_type: ownership

    - name: Link port and eth0  
      skydive_edge:
        node1: "{{ port_result.UUID }}"
        node2: "G.V().Has('Name', 'enp0s25')"
        relation_type: layer2

This gives the following topology.

Ansible, Skydive and LLDP

Finally the following example will be a bit more concrete. It uses LLDP to retrieve physical topology information and the Skydive module to inject them into the Skydive topology.

- name: Skydive Ansible
  hosts: localhost
  tasks:

  - name: Gather information from lldp
    lldp:
    become: true

  - name: Create TOR
    skydive_node:
      name: "TOR - {{ lldp[item]['chassis']['name'] }}"
      type: "fabric"
      seed: "{{ lldp[item]['chassis']['name'] }}:{{ lldp[item]['chassis']['mac'] }}"
      metadata:
        MAC: "{{ lldp[item]['chassis']['mac'] }}"
        Description: "{{ lldp[item]['chassis']['descr'] }}"
        Address: "{{ lldp[item]['chassis']['mgmt-ip'] }}"
    register: tors
    with_items: "{{ lldp.keys() }}"

  - name: Create port
    skydive_node:
      name: "{{ lldp[item]['port']['descr'] }}"
      type: "fabric"
      seed: "{{ lldp[item]['port']['descr'] }}:{{ lldp[item]['port']['mac'] }}"
      metadata:
        MAC: "{{ lldp[item]['port']['mac'] }}"
    register: ports
    with_items: "{{ lldp.keys() }}"
    
  - name: Link port to TOR
    skydive_edge:
      node1: "{{ item.0.UUID }}"
      node2: "{{ item.1.UUID }}"
      relation_type: ownership
    with_together:
      - "{{ tors.results }}"
      - "{{ ports.results }}"

  - name: Link port to host interface
    skydive_edge:
      node1: "{{ item.0.UUID }}"
      node2: "G.V().Has('Type', 'host').Out().Has('Name', '{{ item.1 }}')"
      relation_type: ownership
    with_together:
      - "{{ ports.results }}"
      - "{{ lldp.keys() }}"

conclusion

As we saw the Skydive module allows to leverage the the Network Automation Ansible ecosystem. The current Skydive module is a first version that surely needs to be improved. And, as usual, contributions are more than welcome :)