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

[Ori Kam <orika@nvidia.com>]

Hi Gregory,

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Gregory Etelson
> Sent: Monday, July 19, 2021 11:33 AM
> 
> 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

Acked-by: Ori Kam <orika@nvidia.com>
Thanks,
Ori