fix: 拆分main函数，分函数方便后续维护，添加前置检测自动切换离线模式

utils/utils.go

@@ -3,13 +3,11 @@ package utils
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"fmt"
-	"github.com/imroc/req/v3"
-	"github.com/oneclickvirt/UnlockTests/uts"
-	"github.com/oneclickvirt/basics/system"
-	. "github.com/oneclickvirt/defaultset"
-	"github.com/oneclickvirt/security/network"
 	"io"
+	"net"
+	"net/http"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -17,6 +15,12 @@ import (
 	"sync"
 	"time"
 	"unicode/utf8"
+
+	"github.com/imroc/req/v3"
+	"github.com/oneclickvirt/UnlockTests/uts"
+	"github.com/oneclickvirt/basics/system"
+	. "github.com/oneclickvirt/defaultset"
+	"github.com/oneclickvirt/security/network"
 )
 
 // PrintCenteredTitle 根据指定的宽度打印居中标题
@@ -95,14 +99,14 @@ func CheckChina(enableLogger bool) bool {
 }
 
 // BasicsAndSecurityCheck 执行安全检查
-func BasicsAndSecurityCheck(language, nt3CheckType string, securtyCheckStatus bool) (string, string, string) {
+func BasicsAndSecurityCheck(language, nt3CheckType string, securityCheckStatus bool) (string, string, string) {
 	var wgt sync.WaitGroup
 	var ipInfo, securityInfo, systemInfo string
 	var err error
 	wgt.Add(1)
 	go func() {
 		defer wgt.Done()
-		ipInfo, securityInfo, err = network.NetworkCheck("both", securtyCheckStatus, language)
+		ipInfo, securityInfo, err = network.NetworkCheck("both", securityCheckStatus, language)
 		if err != nil {
 			fmt.Println(err.Error())
 		}
@@ -330,3 +334,159 @@ func ProcessAndUpload(output string, filePath string, enableUplaod bool) (string
 	}
 	return "", ""
 }
+
+// ============================= 前置联网能力检测 =============================
+
+var StackType string
+
+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"
+	}
+	StackType = stack
+	return NetCheckResult{
+		HasIPv4:   hasV4,
+		HasIPv6:   hasV6,
+		Connected: hasV4 || hasV6,
+		StackType: stack,
+	}
+}