Re: [dpdk-dev] [PATCH v1] net: fix TSO packet checksum incorrect

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

Hi,

On Tue, Jul 28, 2020 at 08:55:31AM +0000, Yuying Zhang wrote:
> The ol_flags check lacks of PKT_TX_IPV6 which causes checksum
> flag configuration error while IPv6/TCP TSO packet is sent.
> This patch fixes the issue using PKT_TX_OFFLOAD_MASK.
> 
> Fixes: 520059a41aa9 ("net: check fragmented headers in non-debug as well")
> 
> Signed-off-by: Yuying Zhang <yuying.zhang@intel.com>
> ---
>  lib/librte_net/rte_net.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/librte_net/rte_net.h b/lib/librte_net/rte_net.h
> index 1edc283a4..4b617ab4c 100644
> --- a/lib/librte_net/rte_net.h
> +++ b/lib/librte_net/rte_net.h
> @@ -125,7 +125,7 @@ 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)))
> +	if (!(ol_flags & PKT_TX_OFFLOAD_MASK))
>  		return 0;
>  
>  	if (ol_flags & (PKT_TX_OUTER_IPV4 | PKT_TX_OUTER_IPV6))
> -- 
> 2.25.1
> 

I think the PKT_TX_TCP_SEG flag is missing in the test above, it
should be like this:

 if (!(ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_L4_MASK | PKT_TX_TCP_SEG)))

It would be more precise than having the whole list of offload flags.

The reason is because in case of TSOv4, there is always the flag
PKT_TX_IP_CKSUM, so this test is always wrong and we continue in the
function. In case of TSOv6, there is neither PKT_TX_IP_CKSUM nor
PKT_TX_L4_TCP (which is not mandatory, the doc says that PKT_TX_TCP_SEG
implies PKT_TX_L4_TCP).

Thanks for spotting this. Can you please submit a v2 with
PKT_TX_TCP_SEG?

Olivier