mirror of
https://github.com/fankes/komari-agent.git
synced 2025-10-18 10:39:24 +08:00
278 lines
7.5 KiB
Go
278 lines
7.5 KiB
Go
package dnsresolver
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import (
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"context"
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"crypto/tls"
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"fmt"
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"log"
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"net"
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"net/http"
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"sort"
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"strings"
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"sync"
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"time"
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"github.com/komari-monitor/komari-agent/cmd/flags"
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)
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var (
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DNSServers = []string{
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"[2606:4700:4700::1111]:53", // Cloudflare IPv6
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"[2606:4700:4700::1001]:53", // Cloudflare IPv6 备用
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"[2001:4860:4860::8888]:53", // Google IPv6
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"[2001:4860:4860::8844]:53", // Google IPv6 备用
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"114.114.114.114:53", // 114DNS，中国大陆
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"1.1.1.1:53", // Cloudflare IPv4
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"8.8.8.8:53", // Google IPv4
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"8.8.4.4:53", // Google IPv4 备用
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"223.5.5.5:53", // 阿里DNS，中国大陆
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"119.29.29.29:53", // DNSPod，中国大陆
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}
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// CustomDNSServer 自定义DNS服务器，可以通过命令行参数设置
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CustomDNSServer string
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preferV4Once sync.Once
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hasIPv4 bool
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)
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// SetCustomDNSServer 设置自定义DNS服务器
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func SetCustomDNSServer(dnsServer string) {
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if dnsServer == "" {
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return
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}
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CustomDNSServer = normalizeDNSServer(dnsServer)
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}
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// normalizeDNSServer 将输入的 DNS 服务器字符串规范化为 host:port 形式：
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// - IPv6 地址自动加方括号并补全端口 :53（若未提供）
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// - IPv4/域名未提供端口时补全 :53
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func normalizeDNSServer(s string) string {
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s = strings.TrimSpace(s)
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// 已是 [ipv6]:port 或 host:port 形式
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if (strings.HasPrefix(s, "[") && strings.Contains(s, "]:")) || (strings.Count(s, ":") == 1 && !strings.Contains(s, "]")) {
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return s
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}
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// 纯 IPv6（未加端口/括号）
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if strings.Count(s, ":") >= 2 && !strings.Contains(s, "]") {
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return "[" + s + "]:53"
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}
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// 其它情况：若未包含端口则补 53
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if !strings.Contains(s, ":") {
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return s + ":53"
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}
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return s
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}
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// getCurrentDNSServer 获取当前要使用的DNS服务器
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func getCurrentDNSServer() string {
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if CustomDNSServer != "" {
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return CustomDNSServer
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}
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// 如果没有设置自定义DNS，返回空字符串，表示应使用系统默认解析器
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return ""
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}
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// GetCustomResolver 返回一个解析器：
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// - 若设置了自定义 DNS：使用该服务器（并在失败时尝试内置列表作为兜底）。
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// - 若未设置自定义 DNS：返回系统默认解析器（不使用内置列表）。
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func GetCustomResolver() *net.Resolver {
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// 未设置自定义 DNS，直接使用系统默认解析器
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if getCurrentDNSServer() == "" {
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return net.DefaultResolver
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}
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// 设置了自定义 DNS，则构造使用自定义 DNS 的解析器
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return &net.Resolver{
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PreferGo: true,
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Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
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d := net.Dialer{Timeout: 10 * time.Second}
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// 优先使用自定义 DNS 服务器
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dnsServer := getCurrentDNSServer()
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if dnsServer != "" {
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if conn, err := d.DialContext(ctx, "udp", dnsServer); err == nil {
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return conn, nil
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}
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}
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log.Printf("Custom DNS server %s is unreachable, trying fallback servers", dnsServer)
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// 如果自定义DNS不可用，则尝试内置列表作为兜底
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for _, server := range DNSServers {
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if server == dnsServer {
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continue
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}
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if conn, err := d.DialContext(ctx, "udp", server); err == nil {
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return conn, nil
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}
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}
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return nil, fmt.Errorf("no available DNS server")
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},
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}
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}
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// GetHTTPClient 返回一个使用自定义DNS解析器的HTTP客户端
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// buildTransport 构建带有自定义解析/拨号策略的 HTTP 传输层，可注入 TLS 配置
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func buildTransport(timeout time.Duration, tlsConfig *tls.Config) *http.Transport {
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if timeout <= 0 {
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timeout = 30 * time.Second
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}
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customResolver := GetCustomResolver()
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return &http.Transport{
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Proxy: http.ProxyFromEnvironment,
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DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
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host, port, err := net.SplitHostPort(addr)
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if err != nil {
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return nil, err
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}
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ips, err := customResolver.LookupHost(ctx, host)
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if err != nil {
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return nil, err
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}
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// 根据本机是否具备 IPv4 动态排序
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preferIPv4 := preferIPv4First()
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sort.SliceStable(ips, func(i, j int) bool {
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ip1 := net.ParseIP(ips[i])
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ip2 := net.ParseIP(ips[j])
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if ip1 == nil || ip2 == nil {
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return false
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}
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if preferIPv4 {
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return ip1.To4() != nil && ip2.To4() == nil
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}
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// IPv6 优先
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return ip1.To4() == nil && ip2.To4() != nil
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})
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for _, ip := range ips {
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dialer := &net.Dialer{
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Timeout: timeout,
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KeepAlive: 30 * time.Second,
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DualStack: true,
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}
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conn, err := dialer.DialContext(ctx, network, net.JoinHostPort(ip, port))
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if err == nil {
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return conn, nil
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}
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}
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return nil, fmt.Errorf("failed to dial to any of the resolved IPs")
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},
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MaxIdleConns: 10,
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IdleConnTimeout: 90 * time.Second,
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TLSHandshakeTimeout: 10 * time.Second,
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ExpectContinueTimeout: 1 * time.Second,
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TLSClientConfig: tlsConfig,
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ForceAttemptHTTP2: true,
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}
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}
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func GetHTTPClient(timeout time.Duration) *http.Client {
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return &http.Client{
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Transport: buildTransport(timeout, &tls.Config{
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InsecureSkipVerify: flags.IgnoreUnsafeCert,
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}),
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Timeout: timeout,
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}
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}
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// GetNetDialer 返回一个使用自定义DNS解析器的网络拨号器
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func GetNetDialer(timeout time.Duration) *net.Dialer {
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if timeout <= 0 {
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timeout = 5 * time.Second
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}
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return &net.Dialer{
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Timeout: timeout,
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KeepAlive: 30 * time.Second,
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Resolver: GetCustomResolver(),
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}
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}
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// GetDialContext 返回一个自定义 DialContext：
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// - 使用自定义解析器解析主机名
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// - 优先尝试 IPv4，再尝试 IPv6
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// - 逐个 IP 进行连接尝试，直到成功或全部失败
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func GetDialContext(timeout time.Duration) func(ctx context.Context, network, addr string) (net.Conn, error) {
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if timeout <= 0 {
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timeout = 15 * time.Second
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}
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resolver := GetCustomResolver()
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return func(ctx context.Context, network, addr string) (net.Conn, error) {
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host, port, err := net.SplitHostPort(addr)
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if err != nil {
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return nil, err
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}
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// 为解析设置一个带超时的子 context，避免整体拨号过快超时
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lookupCtx, cancel := context.WithTimeout(ctx, timeout)
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defer cancel()
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ips, err := resolver.LookupHost(lookupCtx, host)
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if err != nil {
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return nil, err
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}
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// 根据本机是否具备 IPv4 动态排序
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preferIPv4 := preferIPv4First()
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sort.SliceStable(ips, func(i, j int) bool {
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ip1 := net.ParseIP(ips[i])
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ip2 := net.ParseIP(ips[j])
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if ip1 == nil || ip2 == nil {
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return false
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}
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if preferIPv4 {
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return ip1.To4() != nil && ip2.To4() == nil
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}
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// IPv6 优先
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return ip1.To4() == nil && ip2.To4() != nil
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})
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// 逐个 IP 尝试连接
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for _, ip := range ips {
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d := &net.Dialer{
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Timeout: timeout,
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KeepAlive: 30 * time.Second,
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DualStack: true,
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}
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c, err := d.DialContext(ctx, network, net.JoinHostPort(ip, port))
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if err == nil {
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return c, nil
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}
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}
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return nil, fmt.Errorf("failed to dial to any of the resolved IPs")
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}
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}
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// preferIPv4First 检测本机是否存在可用的 IPv4 地址，若没有则在连接尝试中优先 IPv6
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func preferIPv4First() bool {
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preferV4Once.Do(func() {
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ifaces, _ := net.Interfaces()
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for _, iface := range ifaces {
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if (iface.Flags&net.FlagUp) == 0 || (iface.Flags&net.FlagLoopback) != 0 {
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continue
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}
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addrs, _ := iface.Addrs()
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for _, a := range addrs {
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var ip net.IP
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switch v := a.(type) {
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case *net.IPNet:
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ip = v.IP
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case *net.IPAddr:
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ip = v.IP
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}
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if ip == nil || ip.IsLoopback() {
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continue
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}
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if ip.To4() != nil {
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hasIPv4 = true
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return
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}
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}
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}
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hasIPv4 = false
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})
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return hasIPv4
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}
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