fix: 修复在非对应IP类型时进行无效检测依然输出的问题

cmd/main.go

@@ -7,9 +7,11 @@ import (
 	"net/http"
 	"os"
 	"runtime"
+	"time"
 
 	backtrace "github.com/oneclickvirt/backtrace/bk"
 	"github.com/oneclickvirt/backtrace/model"
+	"github.com/oneclickvirt/backtrace/utils"
 	. "github.com/oneclickvirt/defaultset"
 )
 
@@ -25,7 +27,7 @@ func main() {
 	go func() {
 		http.Get("https://hits.spiritlhl.net/backtrace.svg?action=hit&title=Hits&title_bg=%23555555&count_bg=%230eecf8&edge_flat=false")
 	}()
-	fmt.Println(Green("项目地址:"), Yellow("https://github.com/oneclickvirt/backtrace"))
+	fmt.Println(Green("Repo:"), Yellow("https://github.com/oneclickvirt/backtrace"))
 	var showVersion, showIpInfo, help, ipv6 bool
 	backtraceFlag := flag.NewFlagSet("backtrace", flag.ContinueOnError)
 	backtraceFlag.BoolVar(&help, "h", false, "Show help information")
@@ -58,7 +60,16 @@ func main() {
 			}
 		}
 	}
+	preCheck := utils.CheckPublicAccess(3 * time.Second)
+	if preCheck.Connected && preCheck.StackType == "DualStack" {
 		backtrace.BackTrace(ipv6)
+	} else if preCheck.Connected && preCheck.StackType == "IPv4" {
+		backtrace.BackTrace(false)
+	} else if preCheck.Connected && preCheck.StackType == "IPv6" {
+		backtrace.BackTrace(true)
+	} else {
+		fmt.Println(Red("PreCheck IP Type Failed"))
+	}
 	fmt.Println(Yellow("准确线路自行查看详细路由，本测试结果仅作参考"))
 	fmt.Println(Yellow("同一目标地址多个线路时，可能检测已越过汇聚层，除了第一个线路外，后续信息可能无效"))
 	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" {

utils/utils.go

@@ -0,0 +1,160 @@
+package utils
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+)
+
+type NetCheckResult struct {
+	HasIPv4   bool
+	HasIPv6   bool
+	Connected bool
+	StackType string // "IPv4", "IPv6", "DualStack", "None"
+}
+
+func makeResolver(proto, dnsAddr string) *net.Resolver {
+	return &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+			d := net.Dialer{
+				Timeout: 5 * time.Second,
+			}
+			return d.DialContext(ctx, proto, dnsAddr)
+		},
+	}
+}
+
+func CheckPublicAccess(timeout time.Duration) NetCheckResult {
+	if timeout < 2*time.Second {
+		timeout = 2 * time.Second
+	}
+	var wg sync.WaitGroup
+	resultChan := make(chan string, 8)
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+	checks := []struct {
+		Tag  string
+		Addr string
+		Kind string // udp4, udp6, http4, http6
+	}{
+		// UDP DNS
+		{"IPv4", "223.5.5.5:53", "udp4"},              // 阿里 DNS
+		{"IPv4", "8.8.8.8:53", "udp4"},                // Google DNS
+		{"IPv6", "[2400:3200::1]:53", "udp6"},         // 阿里 IPv6 DNS
+		{"IPv6", "[2001:4860:4860::8888]:53", "udp6"}, // Google IPv6 DNS
+		// HTTP HEAD
+		{"IPv4", "https://www.baidu.com", "http4"},     // 百度
+		{"IPv4", "https://1.1.1.1", "http4"},           // Cloudflare
+		{"IPv6", "https://[2400:3200::1]", "http6"},    // 阿里 IPv6
+		{"IPv6", "https://[2606:4700::1111]", "http6"}, // Cloudflare IPv6
+	}
+	for _, check := range checks {
+		wg.Add(1)
+		go func(tag, addr, kind string) {
+			defer wg.Done()
+			defer func() {
+				if r := recover(); r != nil {
+				}
+			}()
+			switch kind {
+			case "udp4", "udp6":
+				dialer := &net.Dialer{
+					Timeout: timeout / 4,
+				}
+				conn, err := dialer.DialContext(ctx, kind, addr)
+				if err == nil && conn != nil {
+					conn.Close()
+					select {
+					case resultChan <- tag:
+					case <-ctx.Done():
+						return
+					}
+				}
+			case "http4", "http6":
+				var resolver *net.Resolver
+				if kind == "http4" {
+					resolver = makeResolver("udp4", "223.5.5.5:53")
+				} else {
+					resolver = makeResolver("udp6", "[2400:3200::1]:53")
+				}
+				dialer := &net.Dialer{
+					Timeout:  timeout / 4,
+					Resolver: resolver,
+				}
+				transport := &http.Transport{
+					DialContext:           dialer.DialContext,
+					MaxIdleConns:          1,
+					MaxIdleConnsPerHost:   1,
+					IdleConnTimeout:       time.Second,
+					TLSHandshakeTimeout:   timeout / 4,
+					ResponseHeaderTimeout: timeout / 4,
+					DisableKeepAlives:     true,
+				}
+				client := &http.Client{
+					Timeout:   timeout / 4,
+					Transport: transport,
+					CheckRedirect: func(req *http.Request, via []*http.Request) error {
+						return http.ErrUseLastResponse
+					},
+				}
+				req, err := http.NewRequestWithContext(ctx, "HEAD", addr, nil)
+				if err != nil {
+					return
+				}
+				resp, err := client.Do(req)
+				if err == nil && resp != nil {
+					if resp.Body != nil {
+						resp.Body.Close()
+					}
+					if resp.StatusCode < 500 {
+						select {
+						case resultChan <- tag:
+						case <-ctx.Done():
+							return
+						}
+					}
+				}
+			}
+		}(check.Tag, check.Addr, check.Kind)
+	}
+	go func() {
+		wg.Wait()
+		close(resultChan)
+	}()
+	hasV4 := false
+	hasV6 := false
+	for {
+		select {
+		case res, ok := <-resultChan:
+			if !ok {
+				goto result
+			}
+			if res == "IPv4" {
+				hasV4 = true
+			}
+			if res == "IPv6" {
+				hasV6 = true
+			}
+		case <-ctx.Done():
+			goto result
+		}
+	}
+result:
+	stack := "None"
+	if hasV4 && hasV6 {
+		stack = "DualStack"
+	} else if hasV4 {
+		stack = "IPv4"
+	} else if hasV6 {
+		stack = "IPv6"
+	}
+	return NetCheckResult{
+		HasIPv4:   hasV4,
+		HasIPv6:   hasV6,
+		Connected: hasV4 || hasV6,
+		StackType: stack,
+	}
+}

utils/utils_test.go

@@ -0,0 +1,17 @@
+package utils
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestCheckPublicAccess(t *testing.T) {
+	timeout := 3 * time.Second
+	result := CheckPublicAccess(timeout)
+	if result.Connected {
+		fmt.Printf("✅ 本机有公网连接，类型: %s\n", result.StackType)
+	} else {
+		fmt.Println("❌ 本机未检测到公网连接")
+	}
+}