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

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Date:   Wed, 10 Nov 2021 16:58:21 +0300
From:   Denis Kirjanov <dkirjanov@...e.de>
To:     Kumar Thangavel <kumarthangavel.hcl@...il.com>,
        Samuel Mendoza-Jonas <sam@...dozajonas.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     openbmc@...ts.ozlabs.org, linux-aspeed@...ts.ozlabs.org,
        patrickw3@...com, Amithash Prasad <amithash@...com>,
        velumanit@....com, sdasari@...com, netdev@...r.kernel.org
Subject: Re: [PATCH v4] Add payload to be 32-bit aligned to fix dropped
 packets



11/10/21 12:54 PM, Kumar Thangavel пишет:
> 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.

Please add Fixes tag
> 
> Signed-off-by: Kumar Thangavel <thangavel.k@....com>
> Acked-by: Samuel Mendoza-Jonas <sam@...dozajonas.com>
> Reviewed-by: Paul Menzel <pmenzel@...gen.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;
Would be nice to have a constant
> -	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);
>