SPLICE_F_GIFT
if (flags & SPLICE_F_GIFT)
#define SPLICE_F_ALL (SPLICE_F_MOVE|SPLICE_F_NONBLOCK|SPLICE_F_MORE|SPLICE_F_GIFT)
ret = vmsplice(zerocopy[1], &iov, 1, SPLICE_F_GIFT);
vmsplice_ret = vmsplice(pipe_fds[1], &iov, 1, SPLICE_F_GIFT);
unsigned int f = SPLICE_F_NONBLOCK | SPLICE_F_MORE | SPLICE_F_GIFT;