From: Olivier Matz <olivier.matz@6wind.com>
Date: Thu, 13 Oct 2016 14:16:03 +0000 (+0200)
Subject: net: add function to calculate checksum in mbuf
X-Git-Tag: spdx-start~5613
X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=c442fed81bb9;p=dpdk.git

net: add function to calculate checksum in mbuf

This function can be used to calculate the checksum of data embedded in
mbuf, that can be composed of several segments.

This function will be used by the virtio pmd in next commits to calculate
the checksum in software in case the protocol is not recognized.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Reviewed-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
---

diff --git a/doc/guides/rel_notes/release_16_11.rst b/doc/guides/rel_notes/release_16_11.rst
index 98914e3fe2..723479d20a 100644
--- a/doc/guides/rel_notes/release_16_11.rst
+++ b/doc/guides/rel_notes/release_16_11.rst
@@ -45,6 +45,11 @@ New Features
     in an mbuf chain and retrieve its packet type by software.
   * Added new functions ``rte_get_ptype_*()`` to dump a packet type as a string.
 
+* **Improved offloads support in mbuf.**
+
+  * Added a new function ``rte_raw_cksum_mbuf()`` to process the checksum of
+    data embedded in an mbuf chain.
+
 * **Added vhost-user dequeue zero copy support**
 
   The copy in dequeue path is saved, which is meant to improve the performance.
diff --git a/lib/librte_net/rte_ip.h b/lib/librte_net/rte_ip.h
index 5b7554ab8a..4491b86e27 100644
--- a/lib/librte_net/rte_ip.h
+++ b/lib/librte_net/rte_ip.h
@@ -229,6 +229,77 @@ rte_raw_cksum(const void *buf, size_t len)
 	return __rte_raw_cksum_reduce(sum);
 }
 
+/**
+ * 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 ckecksum.
+ * @param cksum
+ *   A pointer to the checksum, filled on success.
+ * @return
+ *   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;
+	}
+	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(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;
+}
+
 /**
  * Process the IPv4 checksum of an IPv4 header.
  *