[PATCH] i40e: fix ipv6 TSO issue for tx function

[Zhe Tao <zhe.tao@intel.com>]

Issue:
when using the following CLI in testpmd to enable ipv6 TSO feature
=============
set verbose 1
csum set ip hw 0
csum set udp hw 0
csum set tcp hw 0
csum set sctp hw 0
csum set outer-ip hw 0
csum parse_tunnel on 0
tso set 800 0
set fwd csum

start
=============

We will not get we want, the ipv6 packets sent out from IXIA can be received by
i40e, but cannot forward to another port.
The root cause is when HW doing the TSO offload for packets, it not only depends
on the context descriptor to define the MSS and TSO payload size, it also
need to know whether this packets is ipv4 or ipv6, ipv4 need the header csum,
but ipv6 doesn't need the csum. We need to use the i40e_txd_enable_checksum to
set the ipv6 type flag into the data descriptor when the packets are for
ipv6 TSO.  
 
Fixes: e3f0151f (i40e: enable Tx checksum only for offloaded packets)

Signed-off-by: Zhe Tao <zhe.tao@intel.com>
---
 drivers/net/i40e/i40e_rxtx.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c
index 1488f2f..ffd6dba 100644
--- a/drivers/net/i40e/i40e_rxtx.c
+++ b/drivers/net/i40e/i40e_rxtx.c
@@ -1545,6 +1545,7 @@ i40e_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 	uint16_t slen;
 	uint64_t buf_dma_addr;
 	union i40e_tx_offload tx_offload = {0};
+	bool enable_checksum = 0;
 
 	txq = tx_queue;
 	sw_ring = txq->sw_ring;
@@ -1620,7 +1621,13 @@ i40e_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 
 		/* Enable checksum offloading */
 		cd_tunneling_params = 0;
-		if (ol_flags & I40E_TX_CKSUM_OFFLOAD_MASK) {
+		/* Check whether need to do checksum or not */
+		if ((ol_flags & I40E_TX_CKSUM_OFFLOAD_MASK) ||
+		    ((ol_flags & PKT_TX_IPV6) && (ol_flags & PKT_TX_TCP_SEG))) {
+			enable_checksum = 1;
+		}
+
+		if (enable_checksum) {
 			i40e_txd_enable_checksum(ol_flags, &td_cmd, &td_offset,
 				tx_offload, &cd_tunneling_params);
 		}
-- 
2.1.4