vring_avail
uint16_t hdrlen = offsetof(struct vring_avail, ring);
uint16_t hdrlen = offsetof(struct vring_avail, ring);
uint16_t hdrlen = offsetof(struct vring_avail, ring);
uint16_t hdrlen = offsetof(struct vring_avail, ring);
offsetof(struct vring_avail, ring[vq_num]));
struct vring_avail *vq_avail;