From bf4fd2c82d8697618d7bcb6148704d142701a7aa Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@fri.uni-lj.si>
Date: Thu, 15 May 2025 14:55:43 +0200
Subject: [PATCH] alpine: support non-VM hosts in interfaces template

Ignore OOB management interface, allow configuring loopback interface
with NetBox data, and setting MTU.
---
 filter_plugins/util.py               | 21 +++++++++++++++++++++
 roles/alpine/templates/interfaces.j2 | 20 +++++++++++++++++---
 2 files changed, 38 insertions(+), 3 deletions(-)
 create mode 100644 filter_plugins/util.py

diff --git a/filter_plugins/util.py b/filter_plugins/util.py
new file mode 100644
index 0000000..af5d1b7
--- /dev/null
+++ b/filter_plugins/util.py
@@ -0,0 +1,21 @@
+#!/usr/bin/python
+
+class FilterModule(object):
+    '''Helper filters to make Ansible less unpleasant'''
+    def filters(self):
+        return {
+            'defaultattr': self.defaultattr,
+            'list2dict': self.list2dict,
+        }
+
+    def defaultattr(self, objects, attr, val=None):
+        '''
+        Set a default value if the given attribute is not defined for an object.
+        '''
+        yield from (obj | { attr: obj.get(attr, val) } for obj in objects)
+
+    def list2dict(self, items, key):
+        '''
+        Like items2dict but keep entire dictionaries as values.
+        '''
+        return {item[key]: item for item in items}
diff --git a/roles/alpine/templates/interfaces.j2 b/roles/alpine/templates/interfaces.j2
index 2c883ed..021e564 100644
--- a/roles/alpine/templates/interfaces.j2
+++ b/roles/alpine/templates/interfaces.j2
@@ -1,9 +1,21 @@
+{# Loopback interface must be present so define it here if none exists. #}
+{% if interfaces | rejectattr("name", "==", "lo") %}
 auto lo
 iface lo inet loopback
 
-{% for iface in interfaces | selectattr('enabled') %}
+{% endif -%}
+
+{# Skip disabled and OOB management interfaces. #}
+{# For VMs we have to set the attribute manually (to false) so rejectattr works. #}
+{% for iface in interfaces
+    | defaultattr('mgmt_only')
+    | rejectattr('mgmt_only')
+    | selectattr('enabled') %}
 auto {{ iface.name }}
-iface {{ iface.name }} inet static
+iface {{ iface.name }} inet {% if iface.name == "lo" %}loopback{% else %}static{% endif +%}
+{% if iface.mtu %}
+    mtu {{ iface.mtu }}
+{% endif %}
 {% for address in iface.ip_addresses %}
     address {{ address.address }}
 {% if address.family.value == 4 %}
@@ -21,4 +33,6 @@ iface {{ iface.name }} inet static
     pre-up echo 0 > /proc/sys/net/ipv6/conf/$IFACE/autoconf
 {% endif %}
 
-{% endfor %}
+{% endfor -%}
+
+source-directory /etc/network/interfaces.d