Soft delete BGP Groups, IX's and BGP Sessions to allow for idempotent configs

[mngan]

Proposed Functionality

Currently, there is no way to safely remove a BGP group or Peering session from an EOS (possibly IOS too) style config. This is because objects are hard deleted. There is no information passed to the template that can tell it to remove a group or session that had previously been configured. By soft deleting these objects, the deleted objects can be passed down to the template, and appropriately handled.

The package django-safedelete handles this pretty well. It even handles some of the edge cases (e.g re-add a session that was previously deleted, and cascading soft deletes).

Use Case

Deploy a bgp group with a session

local ip = 1.1.1.1
peer ip = 1.1.1.2
local as = 32590
peer as = 1234
bgp_group = AS1234-DUMMY

Which generates something like this:

router bgp 32590
  no bgp default ipv4-unicast
  !
  neighbor as1234-dummy-v4 peer group
  neighbor as1234-dummy-v4 next-hop-self
  !
  address-family ipv4
    neighbor as1234-dummy-v4 activate
  !
  neighbor 1.1.1.2 peer group as1234-dummy-v4
  neighbor 1.1.1.2 remote-as 1234
  neighbor 1.1.1.2 description "Dummy Corp"
  no neighbor 1.1.1.2 shutdown
!

But if I delete the BGP session, the generated config looks like this

router bgp 32590
  no bgp default ipv4-unicast
  !
  neighbor as1234-dummy-v4 peer group
  neighbor as1234-dummy-v4 next-hop-self
  !
  address-family ipv4
    neighbor as1234-dummy-v4 activate
  !
!

which leaves the neighbor 1.1.1.2 still configured. With the deleted added to the soft deletable objects, you can detect these and add in the appropriate config like so:

router bgp 32590
  no bgp default ipv4-unicast
  !
  neighbor as1234-dummy-v4 peer group
  neighbor as1234-dummy-v4 next-hop-self
  !
  address-family ipv4
    neighbor as1234-dummy-v4 activate
  !
  no neighbor 1.1.1.2
!

Example template code

{% if session.deleted %}
  no neighbor {{ session.ip_address }}
{% else %}
  neighbor {{ session.ip_address }} peer group {{ bgp_group.slug }}
  neighbor {{ session.ip_address }} remote-as {{ session.autonomous_system.asn }}
  neighbor {{ session.ip_address }} description "{{ session.autonomous_system.name }}"
  {% if session.enabled %}
  no neighbor {{ session.ip_address }} shutdown
  {% else %}
  neighbor {{ session.ip_address }} shutdown
  {% endif %} 
{% endif %}

External Dependencies

django-safedelete

[gmazoyer]

Same FR as #86 (mentioned for tracking)