Function bpf_zerocopy_append_bytes

freebsd/net/bpf_zerocopy.c:240–283

* Copy bytes from a source into the specified zbuf. The caller is * responsible for performing bounds checking, etc. */

 * responsible for performing bounds checking, etc.
 */
void
bpf_zerocopy_append_bytes(struct bpf_d *d, caddr_t buf, u_int offset,
    void *src, u_int len)
{
	u_int count, page, poffset;
	u_char *src_bytes;
	struct zbuf *zb;

	KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
	    ("bpf_zerocopy_append_bytes: not in zbuf mode"));
	KASSERT(buf != NULL, ("bpf_zerocopy_append_bytes: NULL buf"));

	src_bytes = (u_char *)src;
	zb = (struct zbuf *)buf;

	KASSERT((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0,
	    ("bpf_zerocopy_append_bytes: ZBUF_FLAG_ASSIGNED"));

	/*
	 * Scatter-gather copy to user pages mapped into kernel address space
	 * using sf_bufs: copy up to a page at a time.
	 */
	offset += sizeof(struct bpf_zbuf_header);
	page = offset / PAGE_SIZE;
	poffset = offset % PAGE_SIZE;
	while (len > 0) {
		KASSERT(page < zb->zb_numpages, ("bpf_zerocopy_append_bytes:"
		   " page overflow (%d p %d np)\n", page, zb->zb_numpages));

		count = min(len, PAGE_SIZE - poffset);
		bcopy(src_bytes, ((u_char *)sf_buf_kva(zb->zb_pages[page])) +
		    poffset, count);
		poffset += count;
		if (poffset == PAGE_SIZE) {
			poffset = 0;
			page++;
		}
		KASSERT(poffset < PAGE_SIZE,
		    ("bpf_zerocopy_append_bytes: page offset overflow (%d)",
		    poffset));
		len -= count;
		src_bytes += count;
	}
}

/*
 * Copy bytes from an mbuf chain to the specified zbuf: copying will be