netdev - Re: [PATCH net-next v2 07/12] net: vxlan: add skb drop reasons to vxlan

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Message-ID: <428563b5-acee-4320-9af9-883877903629@intel.com>
Date: Tue, 3 Sep 2024 14:32:14 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Menglong Dong <menglong8.dong@...il.com>
CC: <idosch@...dia.com>, <kuba@...nel.org>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <pabeni@...hat.com>, <dsahern@...nel.org>,
	<dongml2@...natelecom.cn>, <amcohen@...dia.com>, <gnault@...hat.com>,
	<bpoirier@...dia.com>, <b.galvani@...il.com>, <razor@...ckwall.org>,
	<petrm@...dia.com>, <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 07/12] net: vxlan: add skb drop reasons to
 vxlan_rcv()

From: Menglong Dong <menglong8.dong@...il.com>
Date: Sun, 1 Sep 2024 21:02:17 +0800

> On Fri, Aug 30, 2024 at 11:04 PM Alexander Lobakin
> <aleksander.lobakin@...el.com> wrote:

[...]

>>> @@ -1814,8 +1830,9 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
>>>       return 0;
>>>
>>>  drop:
>>> +     reason = reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
>>
>> Is this possible that @reason will be 0 (NOT_DROPPED_YET) here? At the
>> beginning of the function, it's not initialized, then each error path
>> sets it to a specific value. In most paths, you check for it being != 0
>> as a sign of error, so I doubt it can be 0 here.
>>
> 
> It can be 0 here, as we don't set a reason for every "goto drop"
> path. For example, in the line:
> 
>     if (!vs)
>         goto drop;
> 
> we don't set a reason, and the "reason" is 0 when we "goto drop",
> as I don't think that it is worth introducing a reason here.

Aaah okay, I didn't notice that, thanks for the explanation!

> 
> Thanks!
> Menglong Dong
> 
>>>       /* Consume bad packet */
>>> -     kfree_skb(skb);
>>> +     kfree_skb_reason(skb, reason);
>>>       return 0;
>>>  }

Thanks,
Olek