[Feature]: Supper for Layer4 app

[BenRLange]

Preflight checks

• I searched existing issues and discussions and did not find a duplicate.

Problem / use case

Howdy,
We are wanting to implement some advanced features using the layer4 app (https://github.com/mholt/caddy-l4)

Looks like there isn't really a way to add this in.

When using an advanced route it gets confused because the settings are applied at the server level and we don't have access to that.

Proposed solution

Add in an option to handle layer4 app settings. Probably best for advanced routes only.

Alternatives considered

No response

Additional context

No response

[BenRLange]

So, my apologies for throwing the somewhat poorly outlined feature request up there, I did it in the midst of other things.

After thinking about it some more it would perhaps make sense to treat this a request to modify caddy global server options as defined here: https://caddyserver.com/docs/caddyfile/options

This would include creating things like custom code snippets that could be reused in other advanced routes, or things such as layer4 apps, trusted proxies and other global server options.

This could be done simply as a caddyfile entry so that users would be able to customize the config based on whatever their current caddy build allows. Doing so would reduce the need for UI work on your part and also increase the flexibility that is offered. Perhaps adding a new section (under the "Configure" section on the left side bar) would seem to be a great place to keep this. Of course offering the option to replicate it across the caddy fleet as well as the standard validation check.

Hopefully this makes sense, let me know if you have any questions.

[X4Applegate]

Thanks for coming back with more detail @BenRLange — that's really helpful.

I dug into this and confirmed something important: adapting a Caddyfile that contains only a global options block (no site addresses) silently drops anything inside the servers { } sub-block — trusted_proxies, listener_wrappers, protocols, etc. never make it into the resulting JSON, because those settings only mean something attached to an actual apps.http.servers.* entry, and CaddyUI generates its own server blocks separately from anything pasted in. So a fully general "paste any global option" box isn't as clean as it sounds — it would silently eat half of what gets pasted into it.

layer4 doesn't have that problem — it's a standalone top-level app (apps.layer4), independent of apps.http.servers, so it survives isolated adaptation just fine.

So here's the scoped plan for v1: a per-server field where you paste your layer4 { ... } Caddyfile block, which CaddyUI sends to that Caddy's own /adapt endpoint and merges the resulting apps.layer4 into the config it pushes — validated the same way everything else is before it's applied, with fleet replication to copy the same block to other nodes. We're also adding the caddy-l4 module to our published Caddy image so it's available out of the box.

Broader "any global server option" support (snippets, trusted_proxies, etc.) is a genuinely harder problem for the reasons above and isn't part of this pass — may revisit separately if there's demand. Building the layer4 piece now.

[X4Applegate]

Shipped in v2.56.0.

Added a Layer4 app field to the Caddy server edit form: paste a complete layer4 { ... } Caddyfile block, and CaddyUI adapts it through that server's own admin API and merges only the resulting apps.layer4 subtree into the config it pushes on every sync. A few details that might matter for your setup:

• The block is validated against the server's own admin API at save time, so a typo or a Caddy build without the module surfaces immediately rather than breaking the next scheduled sync.
• A server running layer4 with no proxy hosts/redirects/routes/certs of its own now syncs normally instead of being refused as "nothing to push."
• There's an "Also copy to" picker to replicate the same block across fleet nodes — each target is checked against its own admin API independently, so one node missing the module doesn't block the others.
• The published applegater/caddyui-caddy image now ships with caddy-l4 compiled in, so it works out of the box if you're using that image.

As discussed in the thread above, this pass covers layer4 specifically rather than the fully general "any Caddyfile global option" request — I confirmed that a general global-options box would silently drop anything in a servers { } sub-block (trusted_proxies, etc.) since those only mean something attached to an actual http server entry. layer4 doesn't have that problem since it's a standalone top-level app.

• Release: https://github.com/X4Applegate/caddyui/releases/tag/v2.56.0
• Docker: applegater/caddyui:v2.56.0 + applegater/caddyui-caddy:v2.56.0 (both :latest/:stable too)

Let us know how it works for your routing setup.