feat(lite): Add support for hostname parameter routing in backend addresses (minekube#603)

- Introduced the ability to use wildcard parameters in backend addresses, allowing dynamic routing based on hostname segments.
- Updated configuration files to include examples of the new routing feature.
- Enhanced documentation to explain the usage of hostname parameters and provide real-world examples.
- Implemented tests to validate the new parameter substitution functionality and ensure correct behavior in various scenarios.

Author: robinbraemer

.web/docs/guide/lite.md

@@ -45,6 +45,89 @@ config:
         backend: [10.0.0.2:25566]
 ```
 
+## Hostname Parameter Routing
+
+Gate Lite supports extracting parts of hostnames using wildcard patterns and using them in backend addresses via `$1`, `$2`, etc. parameters. This enables dynamic routing where parts of the hostname are used to construct the backend address.
+
+:::: code-group
+
+```yaml [Basic Usage]
+lite:
+  routes:
+    # Extract subdomain and use it in backend address
+    - host: '*.domain.com'
+      backend: '$1.servers.svc:25565'
+    # Example: abc.domain.com → abc.servers.svc:25565
+```
+
+```yaml [Multiple Parameters]
+lite:
+  routes:
+    # Capture multiple parts
+    - host: '*.*.example.com'
+      backend: '$1-$2.servers.svc:25565'
+    # Example: abc.def.example.com → abc-def.servers.svc:25565
+
+    # Use parameters in different order
+    - host: '*.subdomain.*'
+      backend: '$2.$1.backend:25565'
+    # Example: abc.subdomain.com → com.abc.backend:25565
+```
+
+```yaml [Question Mark Wildcard]
+lite:
+  routes:
+    # Using ? for single character matching
+    - host: '?.example.com'
+      backend: 'server-$1:25565'
+    # Example: a.example.com → server-a:25565
+```
+
+```yaml [Real-World Example]
+lite:
+  routes:
+    # Route abc.domain.com to abc.servers.svc:25565
+    - host: '*.domain.com'
+      backend: '$1.servers.svc:25565'
+
+    # Route abc.def.domain.com to abc-def.servers.svc:25565
+    - host: '*.*.domain.com'
+      backend: '$1-$2.servers.svc:25565'
+```
+
+::::
+
+### Parameter Indexing
+
+- `$1` refers to the first wildcard match (`*` or `?`)
+- `$2` refers to the second wildcard match
+- `$3` refers to the third wildcard match
+- And so on...
+
+Wildcards are numbered in the order they appear in the pattern from left to right.
+
+### Wildcard Types
+
+- `*` matches any sequence of characters (including empty) and captures it
+- `?` matches any single character and captures it
+
+### Edge Cases
+
+- If a parameter index is out of range (e.g., `$99` when only 2 groups are captured), it remains as-is in the backend address
+- If no wildcards are present in the pattern, parameters in the backend address are not substituted
+- Empty captures (e.g., `*` matching empty string) result in empty strings in the backend address
+
+::: tip Config Validation
+
+Gate validates your configuration and will warn you about invalid parameter usage:
+
+- **Parameters without wildcards**: If you use `$1` in a backend address but the host pattern has no wildcards, Gate will warn that parameters won't be substituted
+- **Out-of-range parameters**: If you use `$2` but the pattern only has one wildcard, Gate will warn that the parameter exceeds available wildcards
+
+These are warnings, not errors - your configuration will still work, but parameters will remain as literal text (e.g., `$1.servers.svc:25565` instead of being substituted).
+
+:::
+
 ## Load Balancing Strategies
 
 When multiple backends are configured, Gate Lite can distribute connections using different strategies.
@@ -274,4 +357,4 @@ If you use Lite mode and your backend servers do player authentication,
 you do not need to worry.
 
 Checkout the [Anti-DDoS](/guide/security/ddos) guide for how
-to protect your Minecraft servers from DDoS attacks.
+to protect your Minecraft servers from DDoS attacks.

config-lite.yml

@@ -45,6 +45,10 @@ config:
         backend: 172.16.0.12:25566
         proxyProtocol: true # Use proxy protocol to connect to backend.
         tcpShieldRealIP: true # Optionally you can also use TCPShield's RealIP protocol.
+      # Use hostname parameters in backend addresses with $1, $2, etc.
+      # Example: abc.domain.com → abc.servers.svc:25565
+      - host: '*.domain.com'
+        backend: '$1.servers.svc:25565'
       # You can also match to multiple hosts to one or multiple backends.
       - host: [127.0.0.1, localhost]
         backend: [172.16.0.12:25566, backend.example.com:25566]

config.yml

@@ -185,6 +185,11 @@ config:
         backend: 172.16.0.12:25566
         proxyProtocol: true # Use proxy protocol to connect to backend.
         tcpShieldRealIP: true # Optionally you can also use TCPShield's RealIP protocol.
+      # Use hostname parameters in backend addresses with $1, $2, etc.
+      # Extract parts of the hostname and use them in the backend address.
+      # Example: abc.domain.com → abc.servers.svc:25565
+      - host: '*.domain.com'
+        backend: '$1.servers.svc:25565'
       # You can also match to multiple hosts to one or multiple backends.
       - host: [127.0.0.1, localhost]
         backend: [172.16.0.12:25566, backend.example.com:25566]

go.mod

@@ -52,7 +52,6 @@ require (
 
 require (
 	buf.build/gen/go/minekube/connect/protocolbuffers/go v1.36.10-20240220124425-904ce30425c9.1 // indirect
-	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
 	github.com/cenkalti/backoff/v5 v5.0.3 // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.7 // indirect
 	github.com/ebitengine/purego v0.9.0 // indirect
@@ -77,8 +76,6 @@ require (
 	github.com/segmentio/fasthash v1.0.3 // indirect
 	github.com/sethvargo/go-envconfig v1.3.0 // indirect
 	github.com/shirou/gopsutil/v4 v4.25.9 // indirect
-	github.com/shoenig/go-m1cpu v0.1.7 // indirect
-	github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 // indirect
 	github.com/spf13/afero v1.15.0 // indirect
 	github.com/spf13/cast v1.10.0 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect