[Intel-wired-lan] [PATCH net-next v1 1/2] net: core: count drops from GRO

[Jacob Keller <jacob.e.keller@intel.com>]

On 1/6/2021 1:55 PM, Jesse Brandeburg wrote:
> When drivers call the various receive upcalls to receive an skb
> to the stack, sometimes that stack can drop the packet. The good
> news is that the return code is given to all the drivers of
> NET_RX_DROP or GRO_DROP. The bad news is that no drivers except
> the one "ice" driver that I changed, check the stat and increment
> the dropped count. This is currently leading to packets that
> arrive at the edge interface and are fully handled by the driver
> and then mysteriously disappear.
> 
> Rather than fix all drivers to increment the drop stat when
> handling the return code, emulate the already existing statistic
> update for NET_RX_DROP events for the two GRO_DROP locations, and
> increment the dev->rx_dropped associated with the skb.
> 
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> ---
>  net/core/dev.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 8fa739259041..ef34043a9550 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6071,6 +6071,7 @@ static gro_result_t napi_skb_finish(struct napi_struct *napi,
>  		break;
>  
>  	case GRO_DROP:
> +		atomic_long_inc(&skb->dev->rx_dropped);
>  		kfree_skb(skb);
>  		break;

Would it makes sense to have this be a different stat? or is it really
basically the same as the existing rx_dropped, so treating it
differently wouldn't make much sense..

>  
> @@ -6159,6 +6160,7 @@ static gro_result_t napi_frags_finish(struct napi_struct *napi,
>  		break;
>  
>  	case GRO_DROP:
> +		atomic_long_inc(&skb->dev->rx_dropped);
>  		napi_reuse_skb(napi, skb);
>  		break;
>  
>