Function rte_raw_cksum_mbuf

dpdk/lib/net/rte_ip.h:234–292

* Compute the raw (non complemented) checksum of a packet. * * @param m * The pointer to the mbuf. * @param off * The offset in bytes to start the checksum. * @param len * The length in bytes of the data to checksum. * @param cksum * A pointer to the checksum, filled on success. * @return * 0 on success, -1 on error (bad length or offset). */

 *   0 on success, -1 on error (bad length or offset).
 */
static inline int
rte_raw_cksum_mbuf(const struct rte_mbuf *m, uint32_t off, uint32_t len,
	uint16_t *cksum)
{
	const struct rte_mbuf *seg;
	const char *buf;
	uint32_t sum, tmp;
	uint32_t seglen, done;

	/* easy case: all data in the first segment */
	if (off + len <= rte_pktmbuf_data_len(m)) {
		*cksum = rte_raw_cksum(rte_pktmbuf_mtod_offset(m,
				const char *, off), len);
		return 0;
	}

	if (unlikely(off + len > rte_pktmbuf_pkt_len(m)))
		return -1; /* invalid params, return a dummy value */

	/* else browse the segment to find offset */
	seglen = 0;
	for (seg = m; seg != NULL; seg = seg->next) {
		seglen = rte_pktmbuf_data_len(seg);
		if (off < seglen)
			break;
		off -= seglen;
	}
	RTE_ASSERT(seg != NULL);
	if (seg == NULL)
		return -1;
	seglen -= off;
	buf = rte_pktmbuf_mtod_offset(seg, const char *, off);
	if (seglen >= len) {
		/* all in one segment */
		*cksum = rte_raw_cksum(buf, len);
		return 0;
	}

	/* hard case: process checksum of several segments */
	sum = 0;
	done = 0;
	for (;;) {
		tmp = __rte_raw_cksum(buf, seglen, 0);
		if (done & 1)
			tmp = rte_bswap16((uint16_t)tmp);
		sum += tmp;
		done += seglen;
		if (done == len)
			break;
		seg = seg->next;
		buf = rte_pktmbuf_mtod(seg, const char *);
		seglen = rte_pktmbuf_data_len(seg);
		if (seglen > len - done)
			seglen = len - done;
	}

	*cksum = __rte_raw_cksum_reduce(sum);
	return 0;