Merge pull request oasisprotocol#2349 from oasisprotocol/amela/docs-rofl-proxy-custom-domains

docs: Document ROFL proxy custom domains

Author: matevz

docs/rofl/features/proxy.mdx

@@ -1,16 +1,17 @@
 # Port Proxy
 
-Port proxy for your ROFL automatically generates public HTTPS URLs for
-services in your app. Simply publish a port in your `compose.yaml` and the
-proxy handles TLS certificates and routing.
+The ROFL proxy automatically makes your services accessible via public URLs.
+Simply publish a port in your `compose.yaml` and the proxy will make sure
+the traffic is correctly routed.
 
-TLS is terminated inside the app, providing end-to-end encryption so that
-even the provider cannot see the traffic.
+TLS is required and it is terminated inside your ROFL enclave, providing
+confidentiality and integrity protection so that even the provider cannot see or
+modify the traffic. The default `terminate-tls` mode will also generate and
+configure a Let's Encrypt certificate in ROFL to authenticate your services.
 
 ## Enabling the Proxy
 
-To expose a port from your container, publish it in
-your `compose.yaml` file:
+To expose a port from your container, publish it in your `compose.yaml` file:
 
 ```yaml title="compose.yaml"
 services:
@@ -20,14 +21,15 @@ services:
       - "5678:5678" # Expose container port 5678 on host port 5678
 ```
 
-After deploying your app, you can find the generated URL by
-running `oasis rofl machine show`:
+After deploying your app, you can find the generated URL by running `oasis
+rofl machine show`:
 
 ```shell
 oasis rofl machine show
 ```
 
-The output will contain a `Proxy` section with the URL for each published port:
+The output will contain a `Proxy` section with the public URL for each
+published port:
 
 ```
 Proxy:
@@ -38,30 +40,87 @@ Proxy:
 
 ## Configuration
 
-The proxy behavior can be configured using annotations in
-your `compose.yaml` file.
+The proxy behavior can be configured using [annotations] in your
+`compose.yaml` file.
 
-The annotation key is `net.oasis.proxy.ports.<published_port>.mode`.
+[annotations]: https://docs.docker.com/reference/compose-file/services/#annotations
 
-Supported modes are:
+### Overview
 
-- `terminate-tls` (default): The proxy terminates the TLS connection and
-  forwards the unencrypted traffic to your container.
-  This is suitable for HTTPS services.
-- `passthrough`: The proxy forwards the raw TCP connection to your container.
-  This is suitable for services that handle their own TLS or
-  use other TCP-based protocols.
-- `ignore`: The proxy will ignore this port, and it will
-  not be exposed publicly.
+Each annotation follows this general format:
 
-Example of configuring a port for TCP passthrough:
+`net.oasis.proxy.ports.<published_port>.<setting>: <value>`
+
+Where:
+
+- `<published_port>`: The external port exposed in your compose.yaml
+- `<setting>`: The specific proxy configuration (e.g., `mode`, `custom_domain`)
+
+### Example Configuration
+
+The following example configures port 80 to use `terminate-tls` mode (the
+default) with a custom domain and port 8080 to use TCP `passthrough`.
 
 ```yaml title="compose.yaml"
 services:
   myservice:
     image: docker.io/my/service:latest
     ports:
+      - "80:80"
       - "8080:8080"
     annotations:
+      net.oasis.proxy.ports.80.custom_domain: mydomain.com
       net.oasis.proxy.ports.8080.mode: passthrough
 ```
+
+What this configuration does:
+
+- The application container exposes ports 80 and 8080.
+- On port 80 the proxy terminates TLS for mydomain.com and forwards traffic to
+  the application container.
+- On port 8080 the proxy forwards the raw TCP connection to your application
+  container (`mode: passthrough`).
+
+### Annotation Reference
+
+#### `net.oasis.proxy.ports.<published_port>.mode`
+
+Defines how the proxy should handle connections for the specified port.
+
+| Mode                      | Description                                                                 | Typical Use Case                                                     |
+| ------------------------- | --------------------------------------------------------------------------- | -------------------------------------------------------------------- |
+| `terminate-tls` (default) | The proxy terminates TLS and forwards traffic to the container (all within the TEE). | Standard HTTPS web applications.                                     |
+| `passthrough`             | The proxy forwards raw TCP traffic directly to the container.               | Services that handle their own TLS or use other TCP-based protocols. |
+| `ignore`                  | The proxy ignores this port entirely and does not expose it publicly.       | Internal or non-public service ports.                                |
+
+#### `net.oasis.proxy.ports.<published_port>.custom_domain`
+
+Assigns a custom domain name to the published port.
+
+- When using `terminate-tls` mode (the default), you need to use special
+  configuration for your custom domain to route through the proxy.
+
+  After your app is deployed, use the Oasis CLI to obtain instructions to
+  configure `A` and `TXT` records in your DNS:
+
+  ```shell
+  oasis rofl machine show
+  ```
+
+  ```
+  Proxy:
+    Domain: m897.opf-testnet-rofl-25.rofl.app
+    Ports from compose file:
+      5678 (frontend): https://demo.rofl.build
+        * Point the A record of your domain to: 131.153.241.25
+        * Add a TXT record to your domain:
+  oasis-rofl-verification=4SKHCn4E2SNDB5tXayQeHZsvH/+kJSNGuQaTAPepYJc=
+  ```
+
+- If you're using `passthrough` mode, the proxy doesn't terminate TLS and your
+  app needs to handle it directly. In this case, the `custom_domain` setting
+  is not needed. Instead, configure your domain to point directly to the ROFL
+  instance's address.
+
+- If you're using `ignore` mode, the port isn't published, so the
+  `custom_domain` setting has no effect.