Re: [dpdk-dev] [PATCH v2] net: prepare the outer ipv4 hdr for checksum

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

Hi Mohsin,

Hope you are fine!
Please see my comments below.

On Wed, Jun 30, 2021 at 01:04:04PM +0200, Mohsin Kazmi wrote:
> Re: [PATCH v2] net: prepare the outer ipv4 hdr for checksum

I suggest to highlight that it this is the Intel-specific tx-prepare
function in the commit title. What about:

  net: fix Intel-specific Tx preparation for outer checksums

> 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>
> ---
> 
> v2:
> * Update the commit message with Fixes.
> ---
>  lib/net/rte_net.h | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/net/rte_net.h b/lib/net/rte_net.h
> index 434435ffa2..e47365099e 100644
> --- a/lib/net/rte_net.h
> +++ b/lib/net/rte_net.h
> @@ -128,8 +128,18 @@ rte_net_intel_cksum_flags_prepare(struct rte_mbuf *m, uint64_t ol_flags)
>  	if (!(ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_L4_MASK | PKT_TX_TCP_SEG)))
>  		return 0;

I think this test should be updated too with PKT_TX_OUTER_IP_CKSUM.

>  
> -	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;
> +		}
> +	}

What about outer L4 checksum? Does it requires the same than inner?

>  
>  	/*
>  	 * Check if headers are fragmented.
> -- 
> 2.17.1
>