Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Tue, 15 Mar 2022 21:55:53 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     David Ahern <dsahern@kernel.org>
Cc:     menglong8.dong@gmail.com, rostedt@goodmis.org, mingo@redhat.com,
        xeb@mail.ru, davem@davemloft.net, yoshfuji@linux-ipv6.org,
        imagedong@tencent.com, edumazet@google.com, kafai@fb.com,
        talalahmad@google.com, keescook@chromium.org, alobakin@pm.me,
        flyingpeng@tencent.com, mengensun@tencent.com,
        dongli.zhang@oracle.com, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, Biao Jiang <benbjiang@tencent.com>
Subject: Re: [PATCH net-next 1/3] net: gre_demux: add skb drop reasons to
 gre_rcv()
Message-ID: <20220315215553.676a5d24@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
In-Reply-To: <daa287f3-fbed-515d-8f37-f2a36234cc8a@kernel.org>
References: <20220314133312.336653-1-imagedong@tencent.com>
        <20220314133312.336653-2-imagedong@tencent.com>
        <20220315200847.68c2efee@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
        <daa287f3-fbed-515d-8f37-f2a36234cc8a@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Tue, 15 Mar 2022 21:49:01 -0600 David Ahern wrote:
> >>  	ver = skb->data[1]&0x7f;
> >> -	if (ver >= GREPROTO_MAX)
> >> +	if (ver >= GREPROTO_MAX) {
> >> +		reason = SKB_DROP_REASON_GRE_VERSION;  
> > 
> > TBH I'm still not sure what level of granularity we should be shooting
> > for with the reasons. I'd throw all unexpected header values into one 
> > bucket, not go for a reason per field, per protocol. But as I'm said
> > I'm not sure myself, so we can keep what you have..  
> 
> I have stated before I do not believe every single drop point in the
> kernel needs a unique reason code. This is overkill. The reason augments
> information we already have -- the IP from kfree_skb tracepoint.

That's certainly true. I wonder if there is a systematic way of
approaching these additions that'd help us picking the points were 
we add reasons less of a judgment call.