Method tryOneName

tun/netstack/tun.go:746–811

(ctx context.Context, name string, qtype dnsmessage.Type)

}

func (tnet *Net) tryOneName(ctx context.Context, name string, qtype dnsmessage.Type) (dnsmessage.Parser, string, error) {
	var lastErr error

	n, err := dnsmessage.NewName(name)
	if err != nil {
		return dnsmessage.Parser{}, "", errCannotMarshalDNSMessage
	}
	q := dnsmessage.Question{
		Name:  n,
		Type:  qtype,
		Class: dnsmessage.ClassINET,
	}

	for i := 0; i < 2; i++ {
		for _, server := range tnet.dnsServers {
			p, h, err := tnet.exchange(ctx, server, q, time.Second*5)
			if err != nil {
				dnsErr := &net.DNSError{
					Err:    err.Error(),
					Name:   name,
					Server: server.String(),
				}
				if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
					dnsErr.IsTimeout = true
				}
				if _, ok := err.(*net.OpError); ok {
					dnsErr.IsTemporary = true
				}
				lastErr = dnsErr
				continue
			}

			if err := checkHeader(&p, h); err != nil {
				dnsErr := &net.DNSError{
					Err:    err.Error(),
					Name:   name,
					Server: server.String(),
				}
				if err == errServerTemporarilyMisbehaving {
					dnsErr.IsTemporary = true
				}
				if err == errNoSuchHost {
					dnsErr.IsNotFound = true
					return p, server.String(), dnsErr
				}
				lastErr = dnsErr
				continue
			}

			err = skipToAnswer(&p, qtype)
			if err == nil {
				return p, server.String(), nil
			}
			lastErr = &net.DNSError{
				Err:    err.Error(),
				Name:   name,
				Server: server.String(),
			}