[dpdk-dev] [PATCH] app/testpmd: fix TX checksum calculation for tunnel

[Gregory Etelson <getelson@nvidia.com>]

TX checksum of a tunnelled packet can be calculated for outer headers
only or for both outer and inner parts. The calculation method is
determined by application.
If TX checksum calculation can be offloaded, hardware ignores
existing checksum value and replaces it with an updated result.
If TX checksum is calculated by a software, existing value must be
zeroed first.
The testpmd checksum forwarding engine always zeroed inner checksums.
If inner checksum calculation was offloaded, that header was left
with 0 checksum value.
Following outer software checksum calculation produced wrong value.
The patch zeroes inner IPv4 checksum only before software calculation.

Fixes: 51f694dd40f5 ("app/testpmd: rework checksum forward engine")

Cc: stable@dpdk.org

Signed-off-by: Gregory Etelson <getelson@nvidia.com>
Reviewed-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
---
 app/test-pmd/csumonly.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/app/test-pmd/csumonly.c b/app/test-pmd/csumonly.c
index 089936587b..a658cd5389 100644
--- a/app/test-pmd/csumonly.c
+++ b/app/test-pmd/csumonly.c
@@ -480,17 +480,18 @@ process_inner_cksums(void *l3_hdr, const struct testpmd_offload_info *info,
 
 	if (info->ethertype == _htons(RTE_ETHER_TYPE_IPV4)) {
 		ipv4_hdr = l3_hdr;
-		ipv4_hdr->hdr_checksum = 0;
 
 		ol_flags |= PKT_TX_IPV4;
 		if (info->l4_proto == IPPROTO_TCP && tso_segsz) {
 			ol_flags |= PKT_TX_IP_CKSUM;
 		} else {
-			if (tx_offloads & DEV_TX_OFFLOAD_IPV4_CKSUM)
+			if (tx_offloads & DEV_TX_OFFLOAD_IPV4_CKSUM) {
 				ol_flags |= PKT_TX_IP_CKSUM;
-			else
+			} else if (ipv4_hdr->hdr_checksum) {
+				ipv4_hdr->hdr_checksum = 0;
 				ipv4_hdr->hdr_checksum =
 					rte_ipv4_cksum(ipv4_hdr);
+			}
 		}
 	} else if (info->ethertype == _htons(RTE_ETHER_TYPE_IPV6))
 		ol_flags |= PKT_TX_IPV6;
@@ -501,10 +502,10 @@ process_inner_cksums(void *l3_hdr, const struct testpmd_offload_info *info,
 		udp_hdr = (struct rte_udp_hdr *)((char *)l3_hdr + info->l3_len);
 		/* do not recalculate udp cksum if it was 0 */
 		if (udp_hdr->dgram_cksum != 0) {
-			udp_hdr->dgram_cksum = 0;
-			if (tx_offloads & DEV_TX_OFFLOAD_UDP_CKSUM)
+			if (tx_offloads & DEV_TX_OFFLOAD_UDP_CKSUM) {
 				ol_flags |= PKT_TX_UDP_CKSUM;
-			else {
+			} else if (udp_hdr->dgram_cksum) {
+				udp_hdr->dgram_cksum = 0;
 				udp_hdr->dgram_cksum =
 					get_udptcp_checksum(l3_hdr, udp_hdr,
 						info->ethertype);
@@ -514,12 +515,12 @@ process_inner_cksums(void *l3_hdr, const struct testpmd_offload_info *info,
 			ol_flags |= PKT_TX_UDP_SEG;
 	} else if (info->l4_proto == IPPROTO_TCP) {
 		tcp_hdr = (struct rte_tcp_hdr *)((char *)l3_hdr + info->l3_len);
-		tcp_hdr->cksum = 0;
 		if (tso_segsz)
 			ol_flags |= PKT_TX_TCP_SEG;
-		else if (tx_offloads & DEV_TX_OFFLOAD_TCP_CKSUM)
+		else if (tx_offloads & DEV_TX_OFFLOAD_TCP_CKSUM) {
 			ol_flags |= PKT_TX_TCP_CKSUM;
-		else {
+		} else if (tcp_hdr->cksum) {
+			tcp_hdr->cksum = 0;
 			tcp_hdr->cksum =
 				get_udptcp_checksum(l3_hdr, tcp_hdr,
 					info->ethertype);
@@ -529,13 +530,13 @@ process_inner_cksums(void *l3_hdr, const struct testpmd_offload_info *info,
 	} else if (info->l4_proto == IPPROTO_SCTP) {
 		sctp_hdr = (struct rte_sctp_hdr *)
 			((char *)l3_hdr + info->l3_len);
-		sctp_hdr->cksum = 0;
 		/* sctp payload must be a multiple of 4 to be
 		 * offloaded */
 		if ((tx_offloads & DEV_TX_OFFLOAD_SCTP_CKSUM) &&
 			((ipv4_hdr->total_length & 0x3) == 0)) {
 			ol_flags |= PKT_TX_SCTP_CKSUM;
-		} else {
+		} else if (sctp_hdr->cksum) {
+			sctp_hdr->cksum = 0;
 			/* XXX implement CRC32c, example available in
 			 * RFC3309 */
 		}
-- 
2.31.1