[dpdk-dev] [PATCH v3 04/13] mbuf: add help about TX checksum flags

[Olivier Matz <olivier.matz@6wind.com>]

Describe how to use hardware checksum API.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
---
 lib/librte_mbuf/rte_mbuf.h | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index d3eba44..0c96b00 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -98,14 +98,17 @@ extern "C" {
 /* add new TX flags here */
 #define PKT_TX_VXLAN_CKSUM   (1ULL << 50) /**< TX checksum of VXLAN computed by NIC */
 #define PKT_TX_IEEE1588_TMST (1ULL << 51) /**< TX IEEE1588 packet to timestamp. */
-/*
- * Bits 52+53 used for L4 packet type with checksum enabled.
- *     00: Reserved
- *     01: TCP checksum
- *     10: SCTP checksum
- *     11: UDP checksum
+
+/**
+ * Bits 52+53 used for L4 packet type with checksum enabled: 00: Reserved,
+ * 01: TCP checksum, 10: SCTP checksum, 11: UDP checksum. To use hardware
+ * L4 checksum offload, the user needs to:
+ *  - fill l2_len and l3_len in mbuf
+ *  - set the flags PKT_TX_TCP_CKSUM, PKT_TX_SCTP_CKSUM or PKT_TX_UDP_CKSUM
+ *  - calculate the pseudo header checksum and set it in the L4 header (only
+ *    for TCP or UDP). For SCTP, set the crc field to 0.
  */
-#define PKT_TX_L4_NO_CKSUM   (0ULL << 52) /**< Disable L4 cksum of TX pkt. */
+#define PKT_TX_L4_NO_CKSUM   (0ULL << 52) /* Disable L4 cksum of TX pkt. */
 #define PKT_TX_TCP_CKSUM     (1ULL << 52) /**< TCP cksum of TX pkt. computed by NIC. */
 #define PKT_TX_SCTP_CKSUM    (2ULL << 52) /**< SCTP cksum of TX pkt. computed by NIC. */
 #define PKT_TX_UDP_CKSUM     (3ULL << 52) /**< UDP cksum of TX pkt. computed by NIC. */
-- 
2.1.0