From d75f871541c90be2660985fb8663a4a9df7e3e94 Mon Sep 17 00:00:00 2001
From: Cuong Manh Le <cuong@windscribe.com>
Date: Mon, 8 May 2023 22:54:05 +0700
Subject: [PATCH] internal/router: workaround problem with ntp bug on some
 Merlin routers

On some Merlin routers, due to ntp bug, after rebooing, dnsmasq config
was restored to default without ctrld changes, causing ctrld stop
working. Workaround this problem by catching restart diskmon event,
which is triggered by ntpd_synced, then restart dnsmasq.
---
 internal/router/service_merlin.go | 81 ++++++++++++++++++++++++-------
 1 file changed, 64 insertions(+), 17 deletions(-)

diff --git a/internal/router/service_merlin.go b/internal/router/service_merlin.go
index 7f40b0d..3878c71 100644
--- a/internal/router/service_merlin.go
+++ b/internal/router/service_merlin.go
@@ -15,7 +15,10 @@ import (
 	"github.com/kardianos/service"
 )
 
-const merlinJFFSScriptPath = "/jffs/scripts/services-start"
+const (
+	merlinJFFSScriptPath             = "/jffs/scripts/services-start"
+	merlinJFFSServiceEventScriptPath = "/jffs/scripts/service-event"
+)
 
 type merlinSvc struct {
 	i        service.Interface
@@ -101,14 +104,6 @@ func (s *merlinSvc) Install() error {
 	if err := os.MkdirAll(filepath.Dir(merlinJFFSScriptPath), 0755); err != nil {
 		return fmt.Errorf("os.MkdirAll: %w", err)
 	}
-	if _, err := os.Stat(merlinJFFSScriptPath); os.IsNotExist(err) {
-		if err := os.WriteFile(merlinJFFSScriptPath, []byte("#!/bin/sh\n"), 0755); err != nil {
-			return err
-		}
-	}
-	if err := os.Chmod(merlinJFFSScriptPath, 0755); err != nil {
-		return fmt.Errorf("os.Chmod: jffs script: %w", err)
-	}
 
 	tmpScript, err := os.CreateTemp("", "ctrld_install")
 	if err != nil {
@@ -117,14 +112,35 @@ func (s *merlinSvc) Install() error {
 	defer os.Remove(tmpScript.Name())
 	defer tmpScript.Close()
 
-	if _, err := tmpScript.WriteString(merlinAddStartupScript); err != nil {
+	if _, err := tmpScript.WriteString(merlinAddLineToScript); err != nil {
 		return fmt.Errorf("tmpScript.WriteString: %w", err)
 	}
 	if err := tmpScript.Close(); err != nil {
 		return fmt.Errorf("tmpScript.Close: %w", err)
 	}
-	if err := exec.Command("sh", tmpScript.Name(), s.configPath()+" start", merlinJFFSScriptPath).Run(); err != nil {
-		return fmt.Errorf("exec.Command: add startup script: %w", err)
+	addLineToScript := func(line, script string) error {
+		if _, err := os.Stat(script); os.IsNotExist(err) {
+			if err := os.WriteFile(script, []byte("#!/bin/sh\n"), 0755); err != nil {
+				return err
+			}
+		}
+		if err := os.Chmod(script, 0755); err != nil {
+			return fmt.Errorf("os.Chmod: jffs script: %w", err)
+		}
+
+		if err := exec.Command("sh", tmpScript.Name(), line, script).Run(); err != nil {
+			return fmt.Errorf("exec.Command: add startup script: %w", err)
+		}
+		return nil
+	}
+
+	for script, line := range map[string]string{
+		merlinJFFSScriptPath:             s.configPath() + " start",
+		merlinJFFSServiceEventScriptPath: s.configPath() + ` service_event "$1" "$2"`,
+	} {
+		if err := addLineToScript(line, script); err != nil {
+			return err
+		}
 	}
 
 	return nil
@@ -141,15 +157,37 @@ func (s *merlinSvc) Uninstall() error {
 	defer os.Remove(tmpScript.Name())
 	defer tmpScript.Close()
 
-	if _, err := tmpScript.WriteString(merlinRemoveStartupScript); err != nil {
+	if _, err := tmpScript.WriteString(merlinRemoveLineFromScript); err != nil {
 		return fmt.Errorf("tmpScript.WriteString: %w", err)
 	}
 	if err := tmpScript.Close(); err != nil {
 		return fmt.Errorf("tmpScript.Close: %w", err)
 	}
-	if err := exec.Command("sh", tmpScript.Name(), s.configPath()+" start", merlinJFFSScriptPath).Run(); err != nil {
-		return fmt.Errorf("exec.Command: %w", err)
+	removeLineFromScript := func(line, script string) error {
+		if _, err := os.Stat(script); os.IsNotExist(err) {
+			if err := os.WriteFile(script, []byte("#!/bin/sh\n"), 0755); err != nil {
+				return err
+			}
+		}
+		if err := os.Chmod(script, 0755); err != nil {
+			return fmt.Errorf("os.Chmod: jffs script: %w", err)
+		}
+
+		if err := exec.Command("sh", tmpScript.Name(), line, script).Run(); err != nil {
+			return fmt.Errorf("exec.Command: add startup script: %w", err)
+		}
+		return nil
 	}
+
+	for script, line := range map[string]string{
+		merlinJFFSScriptPath:             s.configPath() + " start",
+		merlinJFFSServiceEventScriptPath: s.configPath() + ` service_event "$1" "$2"`,
+	} {
+		if err := removeLineFromScript(line, script); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 
@@ -278,6 +316,15 @@ case "$1" in
       exit 1
     fi
   ;;
+  service_event)
+    event=$2
+    svc=$3
+    dnsmasq_pid_file=$(sed -n '/pid-file=/s///p' /etc/dnsmasq.conf)
+
+    if [ "$event" = "restart" ] && [ "$svc" = "diskmon" ]; then
+      kill "$(cat "$dnsmasq_pid_file")" >/dev/null 2>&1
+    fi
+  ;;
   *)
     echo "Usage: $0 {start|stop|restart|status}"
     exit 1
@@ -286,7 +333,7 @@ esac
 exit 0
 `
 
-const merlinAddStartupScript = `#!/bin/sh
+const merlinAddLineToScript = `#!/bin/sh
 
 line=$1
 file=$2
@@ -296,7 +343,7 @@ file=$2
 pc_append "$line" "$file" 
 `
 
-const merlinRemoveStartupScript = `#!/bin/sh
+const merlinRemoveLineFromScript = `#!/bin/sh
 
 line=$1
 file=$2