netdev - Re: [PATCH net-next] udp: expand SKB_DROP_REASON_UDP

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Message-ID: <67c9f10e7f7e8_1580029446@willemb.c.googlers.com.notmuch>
Date: Thu, 06 Mar 2025 14:01:34 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Eric Dumazet <edumazet@...gle.com>, 
 "David S . Miller" <davem@...emloft.net>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>
Cc: Willem de Bruijn <willemb@...gle.com>, 
 David Ahern <dsahern@...nel.org>, 
 Simon Horman <horms@...nel.org>, 
 netdev@...r.kernel.org, 
 eric.dumazet@...il.com, 
 Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next] udp: expand SKB_DROP_REASON_UDP_CSUM use

Eric Dumazet wrote:
> Use SKB_DROP_REASON_UDP_CSUM in __first_packet_length()
> and udp_read_skb() when dropping a packet because of
> a wrong UDP checksum.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  net/ipv4/udp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 17c7736d8349433ad2d4cbcc9414b2f8112610af..39c3adf333b5f02ca53f768c918c75f2fc7f93ac 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1848,7 +1848,7 @@ static struct sk_buff *__first_packet_length(struct sock *sk,
>  			atomic_inc(&sk->sk_drops);
>  			__skb_unlink(skb, rcvq);
>  			*total += skb->truesize;
> -			kfree_skb(skb);
> +			kfree_skb_reason(skb, SKB_DROP_REASON_UDP_CSUM);
>  		} else {
>  			udp_skb_csum_unnecessary_set(skb);
>  			break;
> @@ -2002,7 +2002,7 @@ int udp_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
>  		__UDP_INC_STATS(net, UDP_MIB_CSUMERRORS, is_udplite);
>  		__UDP_INC_STATS(net, UDP_MIB_INERRORS, is_udplite);
>  		atomic_inc(&sk->sk_drops);
> -		kfree_skb(skb);
> +		kfree_skb_reason(skb, SKB_DROP_REASON_UDP_CSUM);
>  		goto try_again;
>  	}

>From a quick search for UDP_MIB_CSUMERRORS, one more case with regular
kfree_skb:

csum_copy_err:
        if (!__sk_queue_drop_skb(sk, &udp_sk(sk)->reader_queue, skb, flags,
                                 udp_skb_destructor)) {
                UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
                UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
        }
        kfree_skb(skb);

And the same in net/ipv6/udp.c