netdev - Re: [net-next] icmp: correct return value of icmp

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Date:   Wed, 07 Dec 2016 06:18:18 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Zhang Shengju <zhangshengju@...s.chinamobile.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [net-next] icmp: correct return value of icmp_rcv()

On Wed, 2016-12-07 at 14:52 +0800, Zhang Shengju wrote:
> Currently, icmp_rcv() always return zero on a packet delivery upcall.
> 
> To make its behavior more compliant with the way this API should be
> used, this patch changes this to let it return NET_RX_SUCCESS when the
> packet is proper handled, and NET_RX_DROP otherwise.
> 
> Signed-off-by: Zhang Shengju <zhangshengju@...s.chinamobile.com>
> ---
>  net/ipv4/icmp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
> index 691146a..f79d7a8 100644
> --- a/net/ipv4/icmp.c
> +++ b/net/ipv4/icmp.c
> @@ -1047,12 +1047,12 @@ int icmp_rcv(struct sk_buff *skb)
>  
>  	if (success)  {
>  		consume_skb(skb);
> -		return 0;
> +		return NET_RX_SUCCESS;
>  	}
>  
>  drop:
>  	kfree_skb(skb);
> -	return 0;
> +	return NET_RX_DROP;
>  csum_error:
>  	__ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
>  error:


I am curious, what external/visible effects do you expect from such a
change ?

We now have a very precise monitoring of where packets are dropped
(consume_skb()/kfree_skb())