netdev - Re: [ PATCH v1 2/2] ibmveth: Identify ingress large send packets.

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Date:   Sat, 10 Oct 2020 12:40:12 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     David Wilder <dwilder@...ibm.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        tlfalcon@...ux.ibm.com, cris.forno@....com,
        pradeeps@...ux.vnet.ibm.com, wilder@...ibm.com
Subject: Re: [ PATCH v1 2/2] ibmveth: Identify ingress large send packets.

On Thu, Oct 8, 2020 at 3:06 PM David Wilder <dwilder@...ibm.com> wrote:
>
> Ingress large send packets are identified by either:
> The IBMVETH_RXQ_LRG_PKT flag in the receive buffer
> or with a -1 placed in the ip header checksum.
> The method used depends on firmware version.
>
> Signed-off-by: David Wilder <dwilder@...ibm.com>
> Reviewed-by: Thomas Falcon <tlfalcon@...ux.ibm.com>
> Reviewed-by: Cristobal Forno <cris.forno@....com>
> Reviewed-by: Pradeep Satyanarayana <pradeeps@...ux.vnet.ibm.com>
> ---
>  drivers/net/ethernet/ibm/ibmveth.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
> index 3935a7e..e357cbe 100644
> --- a/drivers/net/ethernet/ibm/ibmveth.c
> +++ b/drivers/net/ethernet/ibm/ibmveth.c
> @@ -1349,6 +1349,7 @@ static int ibmveth_poll(struct napi_struct *napi, int budget)
>                         int offset = ibmveth_rxq_frame_offset(adapter);
>                         int csum_good = ibmveth_rxq_csum_good(adapter);
>                         int lrg_pkt = ibmveth_rxq_large_packet(adapter);
> +                       __sum16 iph_check = 0;
>
>                         skb = ibmveth_rxq_get_buffer(adapter);
>
> @@ -1385,7 +1386,17 @@ static int ibmveth_poll(struct napi_struct *napi, int budget)
>                         skb_put(skb, length);
>                         skb->protocol = eth_type_trans(skb, netdev);
>
> -                       if (length > netdev->mtu + ETH_HLEN) {
> +                       /* PHYP without PLSO support places a -1 in the ip
> +                        * checksum for large send frames.
> +                        */
> +                       if (be16_to_cpu(skb->protocol) == ETH_P_IP) {
> +                               struct iphdr *iph = (struct iphdr *)skb->data;
> +
> +                               iph_check = iph->check;

Check against truncated/bad packets.