package dialer import ( "context" "errors" "net" "github.com/Dreamacro/clash/component/resolver" ) func Dialer() *net.Dialer { dialer := &net.Dialer{} if DialerHook != nil { DialerHook(dialer) } return dialer } func ListenConfig() *net.ListenConfig { cfg := &net.ListenConfig{} if ListenConfigHook != nil { ListenConfigHook(cfg) } return cfg } func Dial(network, address string) (net.Conn, error) { return DialContext(context.Background(), network, address) } func DialContext(ctx context.Context, network, address string) (net.Conn, error) { switch network { case "tcp4", "tcp6", "udp4", "udp6": host, port, err := net.SplitHostPort(address) if err != nil { return nil, err } dialer := Dialer() 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 } if DialHook != nil { DialHook(dialer, network, ip) } return dialer.DialContext(ctx, network, net.JoinHostPort(ip.String(), port)) case "tcp", "udp": return dualStackDailContext(ctx, network, address) default: return nil, errors.New("network invalid") } } func ListenPacket(network, address string) (net.PacketConn, error) { lc := ListenConfig() if ListenPacketHook != nil && address == "" { ip := ListenPacketHook() if ip != nil { address = net.JoinHostPort(ip.String(), "0") } } return lc.ListenPacket(context.Background(), network, address) } func dualStackDailContext(ctx context.Context, network, address string) (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) { dialer := Dialer() 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 if DialHook != nil { DialHook(dialer, network, ip) } result.Conn, result.error = dialer.DialContext(ctx, network, net.JoinHostPort(ip.String(), port)) } go startRacer(ctx, network+"4", host, false) go startRacer(ctx, network+"6", host, true) for { select { case res := <-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 } } } } }