bpf_zbuf_header
(struct bpf_zbuf_header *)sf_buf_kva(zb->zb_pages[0]);
offset += sizeof(struct bpf_zbuf_header);
offset += sizeof(struct bpf_zbuf_header);
d->bd_bufsize = bz->bz_buflen - sizeof(struct bpf_zbuf_header);
struct bpf_zbuf_header *zb_header; /* Shared header. */