Re: [dpdk-dev] [PATCH v3] net: fix Intel-specific Prepare the outer ipv4 hdr for checksum

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 7/7/21 12:40 PM, Mohsin Kazmi wrote:
> Preparation the headers for the hardware offload
> misses the outer ipv4 checksum offload.
> It results in bad checksum computed by hardware NIC.
> 
> This patch fixes the issue by setting the outer ipv4
> checksum field to 0.
> 
> Fixes: 4fb7e803eb1a ("ethdev: add Tx preparation")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Mohsin Kazmi <mohsin.kazmi14@gmail.com>
> Acked-by: Qi Zhang <qi.z.zhang@intel.com>
> ---
> v3:
>     * Update the conditional test with PKT_TX_OUTER_IP_CKSUM.
>     * Update the commit title with "Intel-specific".
> 
> v2:
>     * Update the commit message with Fixes.
> 
>   lib/net/rte_net.h | 15 +++++++++++++--
>   1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/net/rte_net.h b/lib/net/rte_net.h
> index 434435ffa2..3f4c8c58b9 100644
> --- a/lib/net/rte_net.h
> +++ b/lib/net/rte_net.h
> @@ -125,11 +125,22 @@ rte_net_intel_cksum_flags_prepare(struct rte_mbuf *m, uint64_t ol_flags)
>   	 * Mainly it is required to avoid fragmented headers check if
>   	 * no offloads are requested.
>   	 */
> -	if (!(ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_L4_MASK | PKT_TX_TCP_SEG)))
> +	if (!(ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_L4_MASK | PKT_TX_TCP_SEG |
> +			  PKT_TX_OUTER_IP_CKSUM)))
>   		return 0;
>   
> -	if (ol_flags & (PKT_TX_OUTER_IPV4 | PKT_TX_OUTER_IPV6))
> +	if (ol_flags & (PKT_TX_OUTER_IPV4 | PKT_TX_OUTER_IPV6)) {
>   		inner_l3_offset += m->outer_l2_len + m->outer_l3_len;
> +		/*
> +		 * prepare outer ipv4 header checksum by setting it to 0,
> +		 * in order to be computed by hardware NICs.
> +		 */
> +		if (ol_flags & PKT_TX_OUTER_IP_CKSUM) {
> +			ipv4_hdr = rte_pktmbuf_mtod_offset(m,
> +					struct rte_ipv4_hdr *, m->outer_l2_len);
> +			ipv4_hdr->hdr_checksum = 0;

Here we assume that the field is located in the first segment.
Unlikely but it still could be false. We must handle it properly.

> +		}
> +	}
>   
>   	/*
>   	 * Check if headers are fragmented.
>