internal/router: support Ubios 4.3+

This change improves compatibility with newer UniFi OS versions while
maintaining backward compatibility with UniFi OS 4.2 and earlier.
The refactoring also reduces code duplication and improves maintainability
by centralizing dnsmasq configuration path logic.

internal/router/dnsmasq/dnsmasq.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"html/template"
 	"net"
+	"os"
 	"path/filepath"
 	"strings"
 
@@ -163,3 +164,27 @@ func FirewallaSelfInterfaces() []*net.Interface {
 	}
 	return ifaces
 }
+
+const (
+	ubios43ConfPath = "/run/dnsmasq.dhcp.conf.d"
+	ubios42ConfPath = "/run/dnsmasq.conf.d"
+	ubios43PidFile  = "/run/dnsmasq-main.pid"
+	ubios42PidFile  = "/run/dnsmasq.pid"
+	UbiosConfName   = "zzzctrld.conf"
+)
+
+// UbiosConfPath returns the appropriate configuration path based on the system's directory structure.
+func UbiosConfPath() string {
+	if st, _ := os.Stat(ubios43ConfPath); st != nil && st.IsDir() {
+		return ubios43ConfPath
+	}
+	return ubios42ConfPath
+}
+
+// UbiosPidFile returns the appropriate dnsmasq pid file based on the system's directory structure.
+func UbiosPidFile() string {
+	if st, _ := os.Stat(ubios43PidFile); st != nil && !st.IsDir() {
+		return ubios43PidFile
+	}
+	return ubios42PidFile
+}

internal/router/edgeos/edgeos.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 
 	"github.com/kardianos/service"
@@ -181,7 +182,7 @@ func ContentFilteringEnabled() bool {
 // DnsShieldEnabled reports whether DNS Shield is enabled.
 // See: https://community.ui.com/releases/UniFi-OS-Dream-Machines-3-2-7/251dfc1e-f4dd-4264-a080-3be9d8b9e02b
 func DnsShieldEnabled() bool {
-	buf, err := os.ReadFile("/var/run/dnsmasq.conf.d/dns.conf")
+	buf, err := os.ReadFile(filepath.Join(dnsmasq.UbiosConfPath(), "dns.conf"))
 	if err != nil {
 		return false
 	}

internal/router/service_ubios.go

@@ -13,14 +13,13 @@ import (
 	"time"
 
 	"github.com/kardianos/service"
+
+	"github.com/Control-D-Inc/ctrld/internal/router/dnsmasq"
 )
 
 // This is a copy of https://github.com/kardianos/service/blob/v1.2.1/service_sysv_linux.go,
 // with modification for supporting ubios v1 init system.
 
-// Keep in sync with ubios.ubiosDNSMasqConfigPath
-const ubiosDNSMasqConfigPath = "/run/dnsmasq.conf.d/zzzctrld.conf"
-
 type ubiosSvc struct {
 	i        service.Interface
 	platform string
@@ -86,7 +85,7 @@ func (s *ubiosSvc) Install() error {
 	}{
 		s.Config,
 		path,
-		ubiosDNSMasqConfigPath,
+		filepath.Join(dnsmasq.UbiosConfPath(), dnsmasq.UbiosConfName),
 	}
 
 	if err := s.template().Execute(f, to); err != nil {

internal/router/ubios/ubios.go

@@ -3,6 +3,7 @@ package ubios
 import (
 	"bytes"
 	"os"
+	"path/filepath"
 	"strconv"
 
 	"github.com/kardianos/service"
@@ -12,19 +13,19 @@ import (
 	"github.com/Control-D-Inc/ctrld/internal/router/edgeos"
 )
 
-const (
+const Name = "ubios"
-	Name                      = "ubios"
-	ubiosDNSMasqConfigPath    = "/run/dnsmasq.conf.d/zzzctrld.conf"
-	ubiosDNSMasqDnsConfigPath = "/run/dnsmasq.conf.d/dns.conf"
-)
 
 type Ubios struct {
-	cfg *ctrld.Config
+	cfg             *ctrld.Config
+	dnsmasqConfPath string
 }
 
 // New returns a router.Router for configuring/setup/run ctrld on Ubios routers.
 func New(cfg *ctrld.Config) *Ubios {
-	return &Ubios{cfg: cfg}
+	return &Ubios{
+		cfg:             cfg,
+		dnsmasqConfPath: filepath.Join(dnsmasq.UbiosConfPath(), dnsmasq.UbiosConfName),
+	}
 }
 
 func (u *Ubios) ConfigureService(config *service.Config) error {
@@ -59,7 +60,7 @@ func (u *Ubios) Setup() error {
 	if err != nil {
 		return err
 	}
-	if err := os.WriteFile(ubiosDNSMasqConfigPath, []byte(data), 0600); err != nil {
+	if err := os.WriteFile(u.dnsmasqConfPath, []byte(data), 0600); err != nil {
 		return err
 	}
 	// Restart dnsmasq service.
@@ -74,7 +75,7 @@ func (u *Ubios) Cleanup() error {
 		return nil
 	}
 	// Remove the custom dnsmasq config
-	if err := os.Remove(ubiosDNSMasqConfigPath); err != nil {
+	if err := os.Remove(u.dnsmasqConfPath); err != nil {
 		return err
 	}
 	// Restart dnsmasq service.
@@ -85,7 +86,7 @@ func (u *Ubios) Cleanup() error {
 }
 
 func restartDNSMasq() error {
-	buf, err := os.ReadFile("/run/dnsmasq.pid")
+	buf, err := os.ReadFile(dnsmasq.UbiosPidFile())
 	if err != nil {
 		return err
 	}