all: refactor router code to use interface

So the code is more modular, easier to read/maintain.

internal/router/firewalla/firewalla.go

@@ -0,0 +1,110 @@
+package firewalla
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/Control-D-Inc/ctrld/internal/router/dnsmasq"
+
+	"github.com/Control-D-Inc/ctrld"
+	"github.com/kardianos/service"
+)
+
+const (
+	Name = "firewalla"
+
+	firewallaDNSMasqConfigPath   = "/home/pi/.firewalla/config/dnsmasq_local/ctrld"
+	firewallaConfigPostMainDir   = "/home/pi/.firewalla/config/post_main.d"
+	firewallaCtrldInitScriptPath = "/home/pi/.firewalla/config/post_main.d/start_ctrld.sh"
+)
+
+type Firewalla struct {
+	cfg *ctrld.Config
+}
+
+// New returns a router.Router for configuring/setup/run ctrld on Firewalla routers.
+func New(cfg *ctrld.Config) *Firewalla {
+	return &Firewalla{cfg: cfg}
+}
+
+func (f *Firewalla) ConfigureService(_ *service.Config) error {
+	return nil
+}
+
+func (f *Firewalla) Install(_ *service.Config) error {
+	// Writing startup script.
+	if err := writeFirewallStartupScript(); err != nil {
+		return fmt.Errorf("writing startup script: %w", err)
+	}
+	return nil
+}
+
+func (f *Firewalla) Uninstall(_ *service.Config) error {
+	// Removing startup script.
+	if err := os.Remove(firewallaCtrldInitScriptPath); err != nil {
+		return fmt.Errorf("removing startup script: %w", err)
+	}
+	return nil
+}
+
+func (f *Firewalla) PreRun() error {
+	return nil
+}
+
+func (f *Firewalla) Configure() error {
+	f.cfg.Listener["0"].IP = "0.0.0.0"
+	f.cfg.Listener["0"].Port = 5354
+	return nil
+}
+
+func (f *Firewalla) Setup() error {
+	data, err := dnsmasq.FirewallaConfTmpl(dnsmasq.ConfigContentTmpl, f.cfg)
+	if err != nil {
+		return fmt.Errorf("generating dnsmasq config: %w", err)
+	}
+	if err := os.WriteFile(firewallaDNSMasqConfigPath, []byte(data), 0600); err != nil {
+		return fmt.Errorf("writing ctrld config: %w", err)
+	}
+
+	// Restart dnsmasq service.
+	if err := restartDNSMasq(); err != nil {
+		return fmt.Errorf("restartDNSMasq: %w", err)
+	}
+
+	return nil
+}
+
+func (f *Firewalla) Cleanup() error {
+	// Removing current config.
+	if err := os.Remove(firewallaDNSMasqConfigPath); err != nil {
+		return fmt.Errorf("removing ctrld config: %w", err)
+	}
+
+	// Restart dnsmasq service.
+	if err := restartDNSMasq(); err != nil {
+		return fmt.Errorf("restartDNSMasq: %w", err)
+	}
+
+	return nil
+}
+
+func writeFirewallStartupScript() error {
+	if err := os.MkdirAll(firewallaConfigPostMainDir, 0775); err != nil {
+		return err
+	}
+	exe, err := os.Executable()
+	if err != nil {
+		return err
+	}
+	// This is called when "ctrld start ..." runs, so recording
+	// the same command line arguments to use in startup script.
+	argStr := strings.Join(os.Args[1:], " ")
+	script := fmt.Sprintf("#!/bin/bash\n\nsudo %q %s\n", exe, argStr)
+	return os.WriteFile(firewallaCtrldInitScriptPath, []byte(script), 0755)
+}
+
+func restartDNSMasq() error {
+	return exec.Command("systemctl", "restart", "firerouter_dns").Run()
+}