Custom links with MAC address

[Azmodeszer]

I'm trying to set up a custom link that incorporates a device's MAC address in order to link to an external monitoring GUI. I have this so far:

{% set mac_address = '' %}
{% if object.interfaces.get(name='GigabitEthernet0/2') %}
    {% set mac_address = object.interfaces.get(name='GigabitEthernet0/2').mac_address %}
{% elif object.interfaces.get(name='GigabitEthernet0') %}
    {% set mac_address = object.interfaces.get(name='GigabitEthernet0').mac_address %}
{% endif %}

{% if mac_address %}
    https://<webguiIP>/screens/dashboard.html#!/APTable/APView/{{ mac_address }}
{% else %}
    No MAC address found for specified interfaces.
{% endif %}

This almost works, but there are two hurdles:

1. It doesn't seem to parse the elif condition, i.e. unless the interface is named "GigabitEthernet0/2", it says that no interface was found, even if there is an interface named "GigabitEthernet0". Either way this isn't very elegant. Ideally, it should just iterate through all the attached interfaces and select the MAC address where the value is not NULL or similar (the relevant interface should always be the one with a MAC address entered). I'm not a coder and mostly got the code above from ChatGPT and some basic logic/trial&error, so any guidance appreciated. The official documentation does not go into enough detail to help me with this, it seems.

2. The ! in the URL is always encoded as "%21" in the resulting link, which renders it useless. Is there a way to enforce the "!"?

[candlerb]

The ! in the URL is always encoded as "%21" in the resulting link, which renders it useless. Is there a way to enforce the "!"?

What's your Netbox version? I remember seeing there was a change in URL encoding recently. I think it's #13011. Maybe you need to make a feature request to allow this character as well. (FWIW, exclamation mark is a "sub-delim" in rfc3986. I think reserved character escaping should be done inside {{ .. }} expansions, but not in the static part of a URL)

Regarding database queries: the interface you are using is the Django ORM, so you can look at the Django documentation for this.

For finding the first interface with a MAC address you probably want something like object.interfaces.filter(mac_address__isnull=False).first() (although if there are multiple interfaces like this it may be indeterminate which one is picked)

The reason your elif clause isn't being used is probably because the first get() which doesn't find any object raises an exception, rather than returning None, so your whole template execution will abort.

The best way to test all this interactively is using nbshell.

# /opt/netbox/venv/bin/python /opt/netbox/netbox/manage.py nbshell
### NetBox interactive shell (netbox3)
### Python 3.8.10 | Django 4.2.8 | NetBox 3.6.7
### lsmodels() will show available models. Use help(<model>) for more info.
>>> o = Device.objects.get(name="nuc1")
>>> o.interfaces.filter(mac_address__isnull=False).first()
<Interface: br255>
>>> o.interfaces.filter(mac_address__isnull=False).first().mac_address
EUI('AA:BB:CC:DD:EE:FF')
>>>

but:

>>> o.interfaces.get(name="nonexistent")
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/opt/netbox/venv/lib/python3.8/site-packages/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/opt/netbox/venv/lib/python3.8/site-packages/django/db/models/query.py", line 637, in get
    raise self.model.DoesNotExist(
dcim.models.device_components.Interface.DoesNotExist: Interface matching query does not exist.

Note that unlike get(), first() returns None if there is no match, which makes it easier to use.

>>> o.interfaces.filter(mac_address="ff:ff:ff:ff:ff:ff").first()
>>>

[Azmodeszer]

I'm using v3.6.6.

Thanks for the response, I'll have a look at your suggestions.

[Azmodeszer]

Cheers, seems to work fine for my purposes with

https://<URL>/{{ object.interfaces.filter(mac_address__isnull=False).first().mac_address }}

Apart from the ! thing, of course. Should I open an issue/feature request?

[candlerb]

Yes I think a feature request is the right thing here.

[Azmodeszer]

Done.

One more thing: Is there a way to add a condition so that the Custom Link only shows up for devices with a specific Device Role?

[candlerb]

https://docs.netbox.dev/en/stable/customization/custom-links/#conditional-rendering

(Note: that means you need to use Jinja2 template for the link text as well as the link URL)