refactor: Move kernel checking to cli

In order to simplify code of main.go, let us move code of kernel
checking to cli.

Furthermore, put kernel checking at pre-run phase of cli.

Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>

cli/cmd/env_detection.go

@@ -0,0 +1,54 @@
+// Copyright 2022 CFC4N <cfc4n.cs@gmail.com>. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"fmt"
+	"runtime"
+
+	"github.com/gojue/ecapture/pkg/util/kernel"
+)
+
+func detectKernel() error {
+	// 系统内核版本检测
+	kv, err := kernel.HostVersion()
+	if err != nil {
+		return fmt.Errorf("failed to get the host kernel version: %v", err)
+	}
+	switch runtime.GOARCH {
+	case "amd64":
+		if kv < kernel.VersionCode(4, 18, 0) {
+			return fmt.Errorf("the Linux/Android Kernel version %v (x86_64) is not supported. Requires a version greater than 4.18.", kv)
+		}
+	case "arm64":
+		if kv < kernel.VersionCode(5, 5, 0) {
+			return fmt.Errorf("the Linux/Android Kernel version %v (aarch64) is not supported. Requires a version greater than 5.5.", kv)
+		}
+	default:
+		return fmt.Errorf("unsupported CPU arch:%v", runtime.GOARCH)
+	}
+
+	return nil
+}
+
+func detectEnv() error {
+	// 环境检测
+
+	if err := detectKernel(); err != nil {
+		return err
+	}
+
+	return nil
+}

cli/cmd/root.go

@@ -17,11 +17,6 @@ package cmd
 import (
 	"context"
 	"fmt"
-	"github.com/gojue/ecapture/cli/cobrautl"
-	"github.com/gojue/ecapture/cli/http"
-	"github.com/gojue/ecapture/user/config"
-	"github.com/gojue/ecapture/user/module"
-	"github.com/rs/zerolog"
 	"io"
 	"net"
 	"os"
@@ -30,6 +25,11 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/gojue/ecapture/cli/cobrautl"
+	"github.com/gojue/ecapture/cli/http"
+	"github.com/gojue/ecapture/user/config"
+	"github.com/gojue/ecapture/user/module"
+	"github.com/rs/zerolog"
 	"github.com/spf13/cobra"
 )
 
@@ -69,9 +69,9 @@ var rootCmd = &cobra.Command{
 	Short:      CliDescription,
 	SuggestFor: []string{"ecapture"},
 
-	Long: `eCapture(旁观者) is a tool that can capture plaintext packets 
+	Long: `eCapture(旁观者) is a tool that can capture plaintext packets
 such as HTTPS and TLS without installing a CA certificate.
-It can also capture bash commands, which is suitable for 
+It can also capture bash commands, which is suitable for
 security auditing scenarios, such as database auditing of mysqld, etc (disabled on Android).
 Support Linux(Android)  X86_64 4.18/aarch64 5.5 or newer.
 Repository: https://github.com/gojue/ecapture
@@ -88,6 +88,14 @@ docker run --rm --privileged=true --net=host -v ${HOST_PATH}:${CONTAINER_PATH} g
 	// Uncomment the following line if your bare application
 	// has an action associated with it:
 	// Run: func(cmd *cobra.Command, args []string) { },
+
+	PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
+		if err := detectEnv(); err != nil {
+			return err
+		}
+
+		return nil
+	},
 }
 
 func usageFunc(c *cobra.Command) error {

main.go

@@ -2,32 +2,9 @@ package main
 
 import (
 	"github.com/gojue/ecapture/cli"
-	"github.com/gojue/ecapture/pkg/util/kernel"
 	_ "github.com/shuLhan/go-bindata" // add for bindata in Makefile
-	"log"
-	"runtime"
 )
 
 func main() {
-
-	// 环境检测
-	// 系统内核版本检测
-	kv, err := kernel.HostVersion()
-	if err != nil {
-		log.Fatal(err)
-	}
-	switch runtime.GOARCH {
-	case "amd64":
-		if kv < kernel.VersionCode(4, 18, 0) {
-			log.Fatalf("The Linux/Android Kernel version %v (x86_64) is not supported. Requires a version greater than 4.18.", kv)
-		}
-	case "arm64":
-		if kv < kernel.VersionCode(5, 5, 0) {
-			log.Fatalf("The Linux/Android Kernel version %v (aarch64) is not supported. Requires a version greater than 5.5.", kv)
-		}
-	default:
-		log.Fatalf("Unsupported CPU arch:%v. ", runtime.GOARCH)
-	}
-
 	cli.Start()
 }