// cgo_unix.go (cgoLookupServicePort).
		if e == _WSATYPE_NOT_FOUND || e == _WSAHOST_NOT_FOUND {
			return 0, newDNSError(errUnknownPort, network+"/"+service, "")
		}
		return 0, newDNSError(winError("getaddrinfow", e), network+"/"+service, "")
	}
	defer syscall.FreeAddrInfoW(result)
	if result == nil {
		return 0, newDNSError(syscall.EINVAL, network+"/"+service, "")
	}
	addr := unsafe.Pointer(result.Addr)
	switch result.Family {

		case _C_EAI_SYSTEM:
			if err == nil { // see golang.org/issue/6232
				err = syscall.EMFILE
			}
			return 0, newDNSError(err, network+"/"+service, "")
		case _C_EAI_SERVICE, _C_EAI_NONAME: // Darwin returns EAI_NONAME.
			return 0, newDNSError(errUnknownPort, network+"/"+service, "")
		default:
			return 0, newDNSError(addrinfoErrno(gerrno), network+"/"+service, "")
		}
	}
	defer _C_freeaddrinfo(res)

					// another server won't help.
					return p, server, newDNSError(errNoSuchHost, name, server)
				}
				lastErr = newDNSError(err, name, server)
				continue
			}

			if err := skipToAnswer(&p, qtype); err != nil {
				if err == errNoSuchHost {
					// The name does not exist, so trying
					// another server won't help.
					return p, server, newDNSError(errNoSuchHost, name, server)
				}

			go dnsWaitGroupDone(ch, lookupGroupCancel)
		}
		err := newDNSError(mapErr(ctx.Err()), host, "")
		if trace != nil && trace.DNSDone != nil {
			trace.DNSDone(nil, false, err)
		}
		return nil, err
	case r := <-ch:
		dnsWaitGroup.Done()
		lookupGroupCancel()
		err := r.Err
		if err != nil {
			if _, ok := err.(*DNSError); !ok {
				err = newDNSError(mapErr(err), host, "")
			}
		}

	// contain any records of the requested type (data not found),
	// or the name itself was not found (NXDOMAIN).
	IsNotFound bool
}

// newDNSError creates a new *DNSError.
// Based on the err, it sets the UnwrapErr, IsTimeout, IsTemporary, IsNotFound fields.
func newDNSError(err error, name, server string) *DNSError {
	var (
		isTimeout   bool
		isTemporary bool
		unwrapErr   error
	)

		stringslite.HasSuffix(err.Error(), "dns: resource does not exist; negrcode") ||
		stringslite.HasSuffix(err.Error(), "dns failure") {
		err = errNoSuchHost
	}
	return newDNSError(err, name, "")
}

// toLower returns a lower-case version of in. Restricting us to
// ASCII is sufficient to handle the IP protocol names and allow
// us to not depend on the strings and unicode packages.