package dns import ( "context" "fmt" "net" "strings" "github.com/Dreamacro/clash/component/dialer" "github.com/Dreamacro/clash/component/resolver" D "github.com/miekg/dns" ) type client struct { *D.Client r *Resolver port string host string } func (c *client) Exchange(m *D.Msg) (msg *D.Msg, err error) { return c.ExchangeContext(context.Background(), m) } func (c *client) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, err error) { var ip net.IP if c.r == nil { // a default ip dns ip = net.ParseIP(c.host) } else { if ip, err = resolver.ResolveIPWithResolver(c.host, c.r); err != nil { return nil, fmt.Errorf("use default dns resolve failed: %w", err) } } d, err := dialer.Dialer() if err != nil { return nil, err } if ip != nil && ip.IsGlobalUnicast() && dialer.DialHook != nil { network := "udp" if strings.HasPrefix(c.Client.Net, "tcp") { network = "tcp" } if err := dialer.DialHook(d, network, ip); err != nil { return nil, err } } c.Client.Dialer = d // miekg/dns ExchangeContext doesn't respond to context cancel. // this is a workaround type result struct { msg *D.Msg err error } ch := make(chan result, 1) go func() { msg, _, err := c.Client.Exchange(m, net.JoinHostPort(ip.String(), c.port)) ch <- result{msg, err} }() select { case <-ctx.Done(): return nil, ctx.Err() case ret := <-ch: return ret.msg, ret.err } }