[PATCH v4] Add payload to be 32-bit aligned to fix dropped packets

[Kumar Thangavel]

Hi All,

    Could you please review the patch and provide your feedback?

Thanks,
Kumar.

On Thu, Oct 28, 2021 at 3:20 PM Kumar Thangavel <
kumarthangavel.hcl at gmail.com> wrote:

> Update NC-SI command handler (both standard and OEM) to take into
> account of payload paddings in allocating skb (in case of payload
> size is not 32-bit aligned).
>
> The checksum field follows payload field, without taking payload
> padding into account can cause checksum being truncated, leading to
> dropped packets.
>
> Signed-off-by: Kumar Thangavel <thangavel.k at hcl.com>
> Acked-by: Samuel Mendoza-Jonas <sam at mendozajonas.com>
> Reviewed-by: Paul Menzel <pmenzel at molgen.mpg.de>
>
> ---
>   v4:
>    - Updated existing macro for max function
>
>   v3:
>    - Added Macro for MAX
>    - Fixed the missed semicolon
>
>   v2:
>    - Added NC-SI spec version and section
>    - Removed blank line
>    - corrected spellings
>
>   v1:
>    - Initial draft
>
> ---
>  net/ncsi/ncsi-cmd.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/net/ncsi/ncsi-cmd.c b/net/ncsi/ncsi-cmd.c
> index ba9ae482141b..e44fe138c20f 100644
> --- a/net/ncsi/ncsi-cmd.c
> +++ b/net/ncsi/ncsi-cmd.c
> @@ -213,12 +213,16 @@ static int ncsi_cmd_handler_oem(struct sk_buff *skb,
>  {
>         struct ncsi_cmd_oem_pkt *cmd;
>         unsigned int len;
> +       /* NC-SI spec DSP_0222_1.2.0, section 8.2.2.2
> +        * requires payload to be padded with 0 to
> +        * 32-bit boundary before the checksum field.
> +        * Ensure the padding bytes are accounted for in
> +        * skb allocation
> +        */
>
> +       unsigned short payload = ALIGN(nca->payload, 4);
>         len = sizeof(struct ncsi_cmd_pkt_hdr) + 4;
> -       if (nca->payload < 26)
> -               len += 26;
> -       else
> -               len += nca->payload;
> +       len += max(payload, 26);
>
>         cmd = skb_put_zero(skb, len);
>         memcpy(&cmd->mfr_id, nca->data, nca->payload);
> @@ -272,6 +276,7 @@ static struct ncsi_request *ncsi_alloc_command(struct
> ncsi_cmd_arg *nca)
>         struct net_device *dev = nd->dev;
>         int hlen = LL_RESERVED_SPACE(dev);
>         int tlen = dev->needed_tailroom;
> +       int payload;
>         int len = hlen + tlen;
>         struct sk_buff *skb;
>         struct ncsi_request *nr;
> @@ -281,14 +286,14 @@ static struct ncsi_request
> *ncsi_alloc_command(struct ncsi_cmd_arg *nca)
>                 return NULL;
>
>         /* NCSI command packet has 16-bytes header, payload, 4 bytes
> checksum.
> +        * Payload needs padding so that the checksum field following
> payload is
> +        * aligned to 32-bit boundary.
>          * The packet needs padding if its payload is less than 26 bytes to
>          * meet 64 bytes minimal ethernet frame length.
>          */
>         len += sizeof(struct ncsi_cmd_pkt_hdr) + 4;
> -       if (nca->payload < 26)
> -               len += 26;
> -       else
> -               len += nca->payload;
> +       payload = ALIGN(nca->payload, 4);
> +       len += max(payload, 26);
>
>         /* Allocate skb */
>         skb = alloc_skb(len, GFP_ATOMIC);
> --
> 2.17.1
>
>
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