datalink2iov
if (datalink2iov(NULL, iov, &niov, SCATTER_SEGMENTS, NULL, NULL) == -1) {
if (datalink2iov(NULL, iov, &niov, SCATTER_SEGMENTS, NULL, NULL) == -1) {
fd[0] = datalink2iov(dl, iov, &niov, SCATTER_SEGMENTS, fd + 2, &nfd);
extern int datalink2iov(struct datalink *, struct iovec *, int *, int, int *,