Re: [PATCH v2 net-next 2/2] tcp: add more DROP REASONs in receive process

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Jason Xing <kerneljasonxing@gmail.com>
Date: Fri,  9 Feb 2024 14:12:13 +0800
> From: Jason Xing <kernelxing@tencent.com>
> 
> As the title said, add more reasons to narrow down the range about
> why the skb should be dropped.
> 
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> ---
>  include/net/dropreason-core.h | 11 ++++++++++-
>  include/net/tcp.h             |  4 ++--
>  net/ipv4/tcp_input.c          | 26 +++++++++++++++++---------
>  net/ipv4/tcp_ipv4.c           | 19 ++++++++++++-------
>  net/ipv4/tcp_minisocks.c      | 10 +++++-----
>  net/ipv6/tcp_ipv6.c           | 19 ++++++++++++-------
>  6 files changed, 58 insertions(+), 31 deletions(-)
> 
> diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
> index efbc5dfd9e84..9a7643be9d07 100644
> --- a/include/net/dropreason-core.h
> +++ b/include/net/dropreason-core.h
> @@ -31,6 +31,8 @@
>  	FN(TCP_AOFAILURE)		\
>  	FN(SOCKET_BACKLOG)		\
>  	FN(TCP_FLAGS)			\
> +	FN(TCP_CONNREQNOTACCEPTABLE)	\
> +	FN(TCP_ABORTONDATA)		\
>  	FN(TCP_ZEROWINDOW)		\
>  	FN(TCP_OLD_DATA)		\
>  	FN(TCP_OVERWINDOW)		\
[...]
> @@ -6654,7 +6657,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
>  			rcu_read_unlock();
>  
>  			if (!acceptable)
> -				return 1;
> +				return SKB_DROP_REASON_TCP_CONNREQNOTACCEPTABLE;

This sounds a bit ambiguous, and I think it can be more specific
if tcp_conn_request() returns the drop reason and we change the
acceptable evaluation.

  acceptable = icsk->icsk_af_ops->conn_request(sk, skb) >= 0;


>  			consume_skb(skb);
>  			return 0;
>  		}