feat: make DNS domain configurable

Add a 'domain' option to the NixOS module and JSON config that
controls the domain suffix used for internal DNS names. Defaults to
'hyprspace' for backward compatibility. Supports multi-label domains
(e.g. 'vpn.internal').

- nixos/settings.nix: add 'domain' option
- config/config.go: read Domain from config, default to 'hyprspace'
- dns/server.go: use config.Domain instead of hard-coded value
- docs: document the new option
- dns/server_test.go: add tests for domainSuffix

config/config.go

@@ -29,6 +29,7 @@ type Config struct {
 	BuiltinAddr6           net.IP                `json:"-"`
 	Services               map[string]Service    `json:"-"`
 	FilterPrivateAddresses bool                  `json:"-"`
+	Domain                 string                `json:"-"`
 }
 
 // Peer defines a peer in the configuration. We might add more to this later.
@@ -195,6 +196,11 @@ func Read(path string) (*Config, error) {
 
 	result.FilterPrivateAddresses = input.FilterPrivateAddresses
 
+	result.Domain = input.Domain
+	if result.Domain == "" {
+		result.Domain = "hyprspace"
+	}
+
 	// Overwrite path of config to input.
 	result.Path = path
 	return &result, nil

dns/server.go

@@ -21,11 +21,14 @@ import (
 var logger = log.Logger("hyprspace/dns")
 
 func domainSuffix(config config.Config) string {
-	if config.Interface == "hyprspace" {
-		return "hyprspace."
-	} else {
-		return fmt.Sprintf("%s.hyprspace.", config.Interface)
+	domain := config.Domain
+	if domain == "" {
+		domain = "hyprspace"
 	}
+	if config.Interface == "hyprspace" {
+		return domain + "."
+	}
+	return fmt.Sprintf("%s.%s.", config.Interface, domain)
 }
 
 func withDomainSuffix(config config.Config, str string) string {

dns/server_test.go

@@ -0,0 +1,33 @@
+package dns
+
+import (
+	"testing"
+
+	"github.com/hyprspace/hyprspace/config"
+)
+
+func TestDomainSuffix(t *testing.T) {
+	tests := []struct {
+		name   string
+		iface  string
+		domain string
+		want   string
+	}{
+		{"default iface, default domain", "hyprspace", "hyprspace", "hyprspace."},
+		{"default iface, custom domain", "hyprspace", "vpn", "vpn."},
+		{"custom iface, default domain", "hs0", "hyprspace", "hs0.hyprspace."},
+		{"custom iface, custom domain", "hs0", "vpn", "hs0.vpn."},
+		{"multi-label domain", "hyprspace", "vpn.internal", "vpn.internal."},
+		{"custom iface, multi-label domain", "hs0", "vpn.internal", "hs0.vpn.internal."},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := config.Config{Interface: tt.iface, Domain: tt.domain}
+			got := domainSuffix(cfg)
+			if got != tt.want {
+				t.Errorf("domainSuffix() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}

docs/content/features/dns.md

@@ -4,7 +4,11 @@ Hyprspace runs a simple DNS server on the loopback interface for the purpose of
 
 ## Domain
 
-All DNS records are placed under a specific domain, based on the name of the network interface that Hyprspace controls. If the interface name is `hyprspace`, then the top-level domain `hyprspace.` is used. Otherwise, the domain `${interfaceName}.hyprspace.` is used. The rest of this document will assume that the domain is `hyprspace.`.
+All DNS records are placed under a specific domain, based on the `domain` config key (which defaults to `hyprspace`). If the interface name is `hyprspace` and the default `domain` is used, then the domain `hyprspace.` is used. Otherwise, the domain `${interfaceName}.${domain}.` is used. The rest of this document will assume that the domain is `hyprspace.`.
+
+## `domain` option
+
+The `domain` option in the JSON config file or the NixOS module controls the domain used for the internal DNS zone. The default is `hyprspace`. This may be a simple label (e.g. `vpn`) or a multi-label domain (e.g. `vpn.internal`). For example, setting `"domain": "vpn.internal"` would make all DNS names end in `.vpn.internal.` instead of `.hyprspace.`.
 
 ## Node lookup
 

docs/content/features/service-network.md

@@ -20,7 +20,9 @@ The config key `services` is used to configure the services a particular node sh
   }
 }
 ```
-This will make the services `example.mynode.hyprspace` and `other.mynode.hyrpspace` available. Upon connecting to the `example` service, the node establishes a connection to `/ip4/127.0.0.1/tcp/8080` and will relay all traffic between the service and the client.
+This will make the services `example.mynode.hyprspace` and `other.mynode.hyprspace` available. Upon connecting to the `example` service, the node establishes a connection to `/ip4/127.0.0.1/tcp/8080` and will relay all traffic between the service and the client.
+
+> **Note:** The `.hyprspace.` suffix follows the `domain` configuration option. If you change it (e.g. to `vpn.internal`), the hostnames will use that domain instead (e.g. `example.mynode.vpn.internal`).
 
 
 ## Implementation details

nixos/settings.nix

@@ -83,6 +83,13 @@ in
   options = {
     filterPrivateAddresses = mkEnableOption "filtering of private/link-local addresses from peer discovery. When enabled, the node will not attempt to connect to RFC1918, link-local, or loopback addresses advertised by other peers";
 
+    domain = mkOption {
+      type = types.str;
+      description = "Domain suffix used for DNS names within the Hyprspace network.";
+      default = "hyprspace";
+      example = "vpn.internal";
+    };
+
     listenAddresses = mkOption {
       type = types.listOf t.multiAddr;
       description = "List of addresses to listen on for libp2p traffic.";