package dialer import ( "context" "errors" "net" "github.com/Dreamacro/clash/component/resolver" ) func DialContext(ctx context.Context, network, address string, options ...Option) (net.Conn, error) { switch network { case "tcp4", "tcp6", "udp4", "udp6": host, port, err := net.SplitHostPort(address) if err != nil { return nil, err } var ip net.IP switch network { case "tcp4", "udp4": ip, err = resolver.ResolveIPv4(host) default: ip, err = resolver.ResolveIPv6(host) } if err != nil { return nil, err } return dialContext(ctx, network, ip, port, options) case "tcp", "udp": return dualStackDialContext(ctx, network, address, options) default: return nil, errors.New("network invalid") } } func ListenPacket(ctx context.Context, network, address string, options ...Option) (net.PacketConn, error) { cfg := &config{} if !cfg.skipDefault { for _, o := range DefaultOptions { o(cfg) } } for _, o := range options { o(cfg) } lc := &net.ListenConfig{} if cfg.interfaceName != "" { addr, err := bindIfaceToListenConfig(cfg.interfaceName, lc, network, address) if err != nil { return nil, err } address = addr } if cfg.addrReuse { addrReuseToListenConfig(lc) } return lc.ListenPacket(ctx, network, address) } func dialContext(ctx context.Context, network string, destination net.IP, port string, options []Option) (net.Conn, error) { opt := &config{} if !opt.skipDefault { for _, o := range DefaultOptions { o(opt) } } for _, o := range options { o(opt) } dialer := &net.Dialer{} if opt.interfaceName != "" { if err := bindIfaceToDialer(opt.interfaceName, dialer, network, destination); err != nil { return nil, err } } return dialer.DialContext(ctx, network, net.JoinHostPort(destination.String(), port)) } func dualStackDialContext(ctx context.Context, network, address string, options []Option) (net.Conn, error) { host, port, err := net.SplitHostPort(address) if err != nil { return nil, err } returned := make(chan struct{}) defer close(returned) type dialResult struct { net.Conn error resolved bool ipv6 bool done bool } results := make(chan dialResult) var primary, fallback dialResult startRacer := func(ctx context.Context, network, host string, ipv6 bool) { result := dialResult{ipv6: ipv6, done: true} defer func() { select { case results <- result: case <-returned: if result.Conn != nil { result.Conn.Close() } } }() var ip net.IP if ipv6 { ip, result.error = resolver.ResolveIPv6(host) } else { ip, result.error = resolver.ResolveIPv4(host) } if result.error != nil { return } result.resolved = true result.Conn, result.error = dialContext(ctx, network, ip, port, options) } go startRacer(ctx, network+"4", host, false) go startRacer(ctx, network+"6", host, true) for res := range results { if res.error == nil { return res.Conn, nil } if !res.ipv6 { primary = res } else { fallback = res } if primary.done && fallback.done { if primary.resolved { return nil, primary.error } else if fallback.resolved { return nil, fallback.error } else { return nil, primary.error } } } return nil, errors.New("never touched") }