netdev - Re: [PATCH net-next 2/2] net: skb: use kfree_skb_with_reason() in tcp_v4

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Date:   Wed, 29 Dec 2021 13:18:36 -0700
From:   David Ahern <dsahern@...il.com>
To:     menglong8.dong@...il.com, rostedt@...dmis.org, dsahern@...nel.org
Cc:     mingo@...hat.com, davem@...emloft.net, kuba@...nel.org,
        nhorman@...driver.com, edumazet@...gle.com,
        yoshfuji@...ux-ipv6.org, jonathan.lemon@...il.com, alobakin@...me,
        cong.wang@...edance.com, pabeni@...hat.com, talalahmad@...gle.com,
        haokexin@...il.com, keescook@...omium.org, imagedong@...cent.com,
        atenart@...nel.org, bigeasy@...utronix.de, weiwan@...gle.com,
        arnd@...db.de, vvs@...tuozzo.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] net: skb: use kfree_skb_with_reason() in
 tcp_v4_rcv()

On 12/29/21 7:32 AM, menglong8.dong@...il.com wrote:
> From: Menglong Dong <imagedong@...cent.com>
> 
> Replace kfree_skb() with kfree_skb_with_reason() in tcp_v4_rcv().
> Following drop reason are added:
> 
> SKB_DROP_REASON_NO_SOCK
> SKB_DROP_REASON_BAD_PACKET
> SKB_DROP_REASON_TCP_CSUM
> 
> After this patch, 'kfree_skb' event will print message like this:
> 
> $           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
> $              | |         |   |||||     |         |
>           <idle>-0       [000] ..s1.    36.113438: kfree_skb: skbaddr=(____ptrval____) protocol=2048 location=(____ptrval____) reason: NO_SOCK
> 
> The reason of skb drop is printed too.
> 
> Signed-off-by: Menglong Dong <imagedong@...cent.com>
> ---
>  include/linux/skbuff.h     |  3 +++
>  include/trace/events/skb.h |  3 +++
>  net/ipv4/tcp_ipv4.c        | 10 ++++++++--

your first patch set was targeting UDP and now you are starting with tcp?


>  3 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 3620b3ff2154..f85db6c035d1 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -313,6 +313,9 @@ struct sk_buff;
>   */
>  enum skb_drop_reason {
>  	SKB_DROP_REASON_NOT_SPECIFIED,
> +	SKB_DROP_REASON_NO_SOCK,

SKB_DROP_REASON_NO_SOCKET

> +	SKB_DROP_REASON_BAD_PACKET,

SKB_DROP_REASON_PKT_TOO_SMALL

User oriented messages, not code based.


> +	SKB_DROP_REASON_TCP_CSUM,
>  	SKB_DROP_REASON_MAX,
>  };
>  
> diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
> index cab1c08a30cd..b9ea6b4ed7ec 100644
> --- a/include/trace/events/skb.h
> +++ b/include/trace/events/skb.h
> @@ -11,6 +11,9 @@
>  
>  #define TRACE_SKB_DROP_REASON					\
>  	EM(SKB_DROP_REASON_NOT_SPECIFIED, NOT_SPECIFIED)	\
> +	EM(SKB_DROP_REASON_NO_SOCK, NO_SOCK)			\
> +	EM(SKB_DROP_REASON_BAD_PACKET, BAD_PACKET)		\
> +	EM(SKB_DROP_REASON_TCP_CSUM, TCP_CSUM)			\
>  	EMe(SKB_DROP_REASON_MAX, HAHA_MAX)
>  
>  #undef EM
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index ac10e4cdd8d0..03dc4c79b84b 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1971,8 +1971,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
>  	const struct tcphdr *th;
>  	bool refcounted;
>  	struct sock *sk;
> +	int drop_reason;
>  	int ret;
>  
> +	drop_reason = 0;

	drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;