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From: Martin Schiller <ms@dev.tdt.de>
To: Xie He <xie.he.0141@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Linux X25 <linux-x25@vger.kernel.org>,
	Linux Kernel Network Developers <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net] net: lapb: Copy the skb before sending a packet
Date: Mon, 01 Feb 2021 13:47:54 +0100	[thread overview]
Message-ID: <abe3a003ad7fd68d3ecae5246e8d5137@dev.tdt.de> (raw)
In-Reply-To: <CAJht_EPGk871aqK-1+=W7vGZrX8QY8LDVF26jkFjm3veeQmPWw@mail.gmail.com>

On 2021-02-01 11:49, Xie He wrote:
> On Mon, Feb 1, 2021 at 2:05 AM Martin Schiller <ms@dev.tdt.de> wrote:
>> 
>> What kind of packages do you mean are corrupted?
>> ETH_P_X25 or ETH_P_HDLC?
> 
> I mean ETH_P_X25. I was using "lapbether.c" to test so there was no 
> ETH_P_HDLC.
> 
>> I have also sent a patch here in the past that addressed corrupted
>> ETH_P_X25 frames on an AF_PACKET socket:
>> 
>> https://lkml.org/lkml/2020/1/13/388
>> 
>> Unfortunately I could not track and describe exactly where the problem
>> was.
> 
> Ah... Looks like we had the same problem.
> 
>> I just wonder when/where is the logically correct place to copy the 
>> skb.
>> Shouldn't it be copied before removing the pseudo header (as I did in 
>> my
>> patch)?
> 
> I think it's not necessary to copy it before removing the pseudo
> header, because "skb_pull" will not change any data in the data
> buffer. "skb_pull" will only change the values of "skb->data" and
> "skb->len". These values are not shared between clones of skbs, so
> it's safe to change them without affecting other clones of the skb.
> 
> I also choose to copy the skb in the LAPB module (rather than in the
> drivers) because I see all drivers have this problem (including the
> recently deleted x25_asy.c driver), so it'd be better to fix this
> issue in the LAPB module, for all drivers.

OK.

Acked-by: Martin Schiller <ms@dev.tdt.de>


  reply	other threads:[~2021-02-01 12:50 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-01  5:57 [PATCH net] net: lapb: Copy the skb before sending a packet Xie He
2021-02-01 10:05 ` Martin Schiller
2021-02-01 10:49   ` Xie He
2021-02-01 12:47     ` Martin Schiller [this message]
2021-02-01 14:10 ` Julian Wiedmann
2021-02-01 16:14   ` Xie He
2021-02-02  4:42     ` Jakub Kicinski
2021-02-02  6:25       ` Xie He
2021-02-02 16:41         ` Jakub Kicinski
2021-02-02  9:04     ` David Laight
2021-02-02 16:50 ` patchwork-bot+netdevbpf

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