From: Xie He <xie.he.0141@gmail.com>
To: Martin Schiller <ms@dev.tdt.de>
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, 1 Feb 2021 02:49:09 -0800 [thread overview]
Message-ID: <CAJht_EPGk871aqK-1+=W7vGZrX8QY8LDVF26jkFjm3veeQmPWw@mail.gmail.com> (raw)
In-Reply-To: <204c18e95caf2ae84fb567dd4be0c3ac@dev.tdt.de>
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.
next prev parent reply other threads:[~2021-02-01 10:50 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 [this message]
2021-02-01 12:47 ` Martin Schiller
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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