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Date:   Wed, 2 Mar 2022 11:22:55 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     David Ahern <dsahern@gmail.com>
Cc:     Dongli Zhang <dongli.zhang@oracle.com>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
        davem@davemloft.net, rostedt@goodmis.org, mingo@redhat.com,
        ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
        imagedong@tencent.com, joao.m.martins@oracle.com,
        joe.jin@oracle.com, edumazet@google.com
Subject: Re: [PATCH net-next v4 4/4] net: tun: track dropped skb via
 kfree_skb_reason()
Message-ID: <20220302112255.545618dd@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
In-Reply-To: <2071f8a0-148d-96fa-75b9-8277c2f87287@gmail.com>
References: <20220226084929.6417-1-dongli.zhang@oracle.com>
        <20220226084929.6417-5-dongli.zhang@oracle.com>
        <20220301185021.7cba195d@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
        <2071f8a0-148d-96fa-75b9-8277c2f87287@gmail.com>
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On Tue, 1 Mar 2022 20:29:37 -0700 David Ahern wrote:
> On 3/1/22 7:50 PM, Jakub Kicinski wrote:
> > On Sat, 26 Feb 2022 00:49:29 -0800 Dongli Zhang wrote:  
> >> +	SKB_DROP_REASON_SKB_PULL,	/* failed to pull sk_buff data */
> >> +	SKB_DROP_REASON_SKB_TRIM,	/* failed to trim sk_buff data */  
> > 
> > IDK if these are not too low level and therefore lacking meaning.
> > 
> > What are your thoughts David?  
> 
> I agree. Not every kfree_skb is worthy of a reason. "Internal
> housekeeping" errors are random and nothing a user / admin can do about
> drops.
> 
> IMHO, the value of the reason code is when it aligns with SNMP counters
> (original motivation for this direction) and relevant details like TCP
> or UDP checksum mismatch, packets for a socket that is not open, socket
> is full, ring buffer is full, packets for "other host", etc.

Agreed :(