linux-kernel - Re: [Internet]Re: [PATCH net-next v4 4/4] net: tun: track dropped skb via kfree_skb

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Date:   Wed, 2 Mar 2022 04:16:01 +0000
From:   imagedong(董梦龙) <imagedong@...cent.com>
To:     David Ahern <dsahern@...il.com>, Jakub Kicinski <kuba@...nel.org>,
        "Dongli Zhang" <dongli.zhang@...cle.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "joao.m.martins@...cle.com" <joao.m.martins@...cle.com>,
        "joe.jin@...cle.com" <joe.jin@...cle.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>
Subject: Re: [Internet]Re: [PATCH net-next v4 4/4] net: tun: track dropped skb
 via kfree_skb_reason()



On 2022/3/2 AM 11:29，“David Ahern”<dsahern@...il.com> write:

>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 */
>> 
[...]
>>>  	SKB_DROP_REASON_DEV_HDR,	/* there is something wrong with
>>>  					 * device driver specific header
>>>  					 */
>>> +	SKB_DROP_REASON_DEV_READY,	/* device is not ready */
>> 
>> What is ready? link is not up? peer not connected? can we expand?
>
>As I recall in this case it is the tfile for a tun device disappeared -
>ie., a race condition.

This seems is that tun is not attached to a file (the tun device file
is not opened?) Maybe TAP_UNATTACHED is more suitable :)