[PATCH v7] Add payload to be 32-bit aligned to fix dropped packets
Eric Dumazet
eric.dumazet at gmail.com
Fri Nov 19 04:14:00 AEDT 2021
On 11/18/21 8:03 AM, Kumar Thangavel 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.
>
Patch title should start with a prefix, identifying which layer/driver is
involved.
Probably in this case
net/ncsi: Add payload to be 32-bit aligned to fix dropped packets
> Fixes: fb4ee67529ff ("net/ncsi: Add NCSI OEM command support")
> 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>
>
> ---
> v7:
> - Updated padding_bytes as const static int variable
>
> v6:
> - Updated type of padding_bytes variable
> - Updated type of payload
> - Seperated variable declarations and code
>
> v5:
> - Added Fixes tag
> - Added const variable for padding_bytes
>
> v4:
> - Used 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 | 24 ++++++++++++++++--------
> 1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/net/ncsi/ncsi-cmd.c b/net/ncsi/ncsi-cmd.c
> index ba9ae482141b..9a6f10f4833e 100644
> --- a/net/ncsi/ncsi-cmd.c
> +++ b/net/ncsi/ncsi-cmd.c
> @@ -18,6 +18,8 @@
> #include "internal.h"
> #include "ncsi-pkt.h"
>
> +const static int padding_bytes = 26;
It would be nice to have some kind of reference, to explain
what is this magic value.
Moving the comment [1] here might make sense.
> +
> u32 ncsi_calculate_checksum(unsigned char *data, int len)
> {
> u32 checksum = 0;
> @@ -213,12 +215,17 @@ static int ncsi_cmd_handler_oem(struct sk_buff *skb,
> {
> struct ncsi_cmd_oem_pkt *cmd;
> unsigned int len;
> + int payload;
[1] This comment could be moved before @padding_bytes
> + /* 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
> + */
>
> + 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, padding_bytes);
>
> cmd = skb_put_zero(skb, len);
> memcpy(&cmd->mfr_id, nca->data, nca->payload);
> @@ -272,6 +279,7 @@ 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 +289,14 @@ 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, padding_bytes);
>
> /* Allocate skb */
> skb = alloc_skb(len, GFP_ATOMIC);
>
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