Add 'teardown' action to veth-pair role

ansible/roles/veth-pair/README.md

@@ -2,7 +2,11 @@ Veth Pair
 =========
 
 This role creates a veth pair. It will plug one end into the specified OVS
-bridge and, optionally, can plug the other end into a source Linux bridge.
+bridge and, optionally, can plug the other end into a source Linux bridge. If
+`veth_pair_state` is `absent`, it will ensure the veth pair is not plugged into
+the OVS bridge; if `veth_pair_plug_into_source` is enabled, it will ensure the
+veth pair is not plugged into the source bridge; finally, it will ensure the
+veth pair itself does not exist.
 
 Requirements
 ------------
@@ -24,3 +28,5 @@ Role Variables
 - `veth_pair_plug_into_source`: Whether or not to plug the source end of the
   veth pair into a Linux bridge. If enabled, `veth_pair_source_bridge` must
   also be specified. Default is `false`.
+- `veth_pair_state`: Whether or not the veth pair should exist. Choose from
+  `present` or `absent`. Default is `present`.

ansible/roles/veth-pair/defaults/main.yml

@@ -1,3 +1,5 @@
 ---
 # Whether or not to plug the source end of the veth pair into a Linux bridge.
 veth_pair_plug_into_source: false
+# Whether the veth pair should be present or absent.
+veth_pair_state: present

ansible/roles/veth-pair/tasks/absent.yml

@@ -0,0 +1,33 @@
+---
+- name: Unplug veth from OVS bridge
+  openvswitch_port:
+    bridge: "{{ veth_pair_ovs_bridge }}"
+    port: "{{ veth_pair_ovs_link_name }}"
+    state: absent
+  become: true
+
+- name: Unplug veth from source bridge
+  command: >-
+    brctl delif {{ veth_pair_source_bridge }}
+    {{ veth_pair_source_link_name }}
+  register: res
+  failed_when:
+    - res.rc != 0
+    # Case where veth is already unplugged.
+    - not (res.rc == 1 and 'does not exist' in res.stderr)
+  changed_when: res.rc == 0
+  when: veth_pair_plug_into_source | bool
+  become: true
+
+- name: Delete veth pair
+  command: >-
+    ip link del dev {{ veth_pair_ovs_link_name }}
+    type veth
+    peer name {{ veth_pair_source_link_name }}
+  register: res
+  failed_when:
+    - res.rc != 0
+    # Case where veth pair is already absent.
+    - not (res.rc == 1 and 'Cannot find device' in res.stderr)
+  changed_when: res.rc == 0
+  become: true

ansible/roles/veth-pair/tasks/main.yml

@@ -1,29 +1,8 @@
 ---
-- name: Create veth pair
-  command: >-
-    ip link add dev {{ veth_pair_ovs_link_name }}
-    type veth
-    peer name {{ veth_pair_source_link_name }}
-  register: res
-  changed_when: res.rc == 0
-  # Return code 2 means the veth pair already exists
-  failed_when: res.rc not in [0, 2]
-  become: true
+- name: Ensure veth pair is absent
+  include_tasks: absent.yml
+  when: veth_pair_state == 'absent'
 
-- name: Plug veth into OVS bridge
-  openvswitch_port:
-    bridge: "{{ veth_pair_ovs_bridge }}"
-    port: "{{ veth_pair_ovs_link_name }}"
-  become: true
-
-- name: Plug veth into source bridge
-  command: >-
-    brctl addif {{ veth_pair_source_bridge }}
-    {{ veth_pair_source_link_name }}
-  register: res
-  failed_when:
-    - res.rc != 0
-    - "'already a member of a bridge' not in res.stderr"
-  changed_when: "'already a member of a bridge' not in res.stderr"
-  when: veth_pair_plug_into_source | bool
-  become: true
+- name: Ensure veth pair is present
+  include_tasks: present.yml
+  when: veth_pair_state != 'absent'

ansible/roles/veth-pair/tasks/present.yml

@@ -0,0 +1,29 @@
+---
+- name: Create veth pair
+  command: >-
+    ip link add dev {{ veth_pair_ovs_link_name }}
+    type veth
+    peer name {{ veth_pair_source_link_name }}
+  register: res
+  changed_when: res.rc == 0
+  # Return code 2 means the veth pair already exists
+  failed_when: res.rc not in [0, 2]
+  become: true
+
+- name: Plug veth into OVS bridge
+  openvswitch_port:
+    bridge: "{{ veth_pair_ovs_bridge }}"
+    port: "{{ veth_pair_ovs_link_name }}"
+  become: true
+
+- name: Plug veth into source bridge
+  command: >-
+    brctl addif {{ veth_pair_source_bridge }}
+    {{ veth_pair_source_link_name }}
+  register: res
+  failed_when:
+    - res.rc != 0
+    - "'already a member of a bridge' not in res.stderr"
+  changed_when: "'already a member of a bridge' not in res.stderr"
+  when: veth_pair_plug_into_source | bool
+  become: true