rtcap destroys packet contents

rtcap destroys packet contents

[Lange Norbert]

Hi,

I have such a setup, where I push/pull ethernet traffic from an Application every millisecond:

[App] ---IDDP--> [RTSwitch] --ETH_P_ALL socket--> [rt_igp]
[App] <---IDDP-- [RTSwitch] <--ETH_P_ALL socket-- [rt_igp]
[Tun] <---tundev---/


Now I am sometimes missing packets that the other side should definitely have sent. I wanted to use rtcap
to inspect this issue, but unfortunately then I get messed up data so that I can't even finish some handshake procedures.

Is there some incompatibility between RTCAP and ETH_P_ALL (which makes its own copies of rtskb's)?
Btw, I can't unload rtap/rtnet once loaded.

Mit besten Grüßen / Kind regards

NORBERT LANGE

AT-RD3

ANDRITZ HYDRO GmbH
Eibesbrunnergasse 20
1120 Vienna / AUSTRIA
p: +43 50805 56684
norbert.lange@andritz.com
andritz.com

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Thank You
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Re: rtcap destroys packet contents

[Jan Kiszka]

On 16.12.19 13:36, Lange Norbert via Xenomai wrote:
> Hi,
> 
> I have such a setup, where I push/pull ethernet traffic from an Application every millisecond:
> 
> [App] ---IDDP--> [RTSwitch] --ETH_P_ALL socket--> [rt_igp]
> [App] <---IDDP-- [RTSwitch] <--ETH_P_ALL socket-- [rt_igp]
> [Tun] <---tundev---/
> 
> 
> Now I am sometimes missing packets that the other side should definitely have sent. I wanted to use rtcap
> to inspect this issue, but unfortunately then I get messed up data so that I can't even finish some handshake procedures.
> 
> Is there some incompatibility between RTCAP and ETH_P_ALL (which makes its own copies of rtskb's)?
> Btw, I can't unload rtap/rtnet once loaded.

There is at least no known incompatibility but it may simply have never 
been tested in that combination.

Do you see corruption on packets sent from the rtcap machine or received 
by it?

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

RE: rtcap destroys packet contents

[Lange Norbert]

> -----Original Message-----
> From: Jan Kiszka <jan.kiszka@siemens.com>
> Sent: Dienstag, 17. Dezember 2019 08:10
> To: Lange Norbert <norbert.lange@andritz.com>; Xenomai
> (xenomai@xenomai.org) <xenomai@xenomai.org>
> Subject: Re: rtcap destroys packet contents
>
> NON-ANDRITZ SOURCE: BE CAUTIOUS WITH CONTENT, LINKS OR
> ATTACHMENTS.
>
>
> On 16.12.19 13:36, Lange Norbert via Xenomai wrote:
> > Hi,
> >
> > I have such a setup, where I push/pull ethernet traffic from an Application
> every millisecond:
> >
> > [App] ---IDDP--> [RTSwitch] --ETH_P_ALL socket--> [rt_igp] [App]
> > <---IDDP-- [RTSwitch] <--ETH_P_ALL socket-- [rt_igp] [Tun]
> > <---tundev---/
> >
> >
> > Now I am sometimes missing packets that the other side should
> > definitely have sent. I wanted to use rtcap to inspect this issue, but
> unfortunately then I get messed up data so that I can't even finish some
> handshake procedures.
> >
> > Is there some incompatibility between RTCAP and ETH_P_ALL (which
> makes its own copies of rtskb's)?
> > Btw, I can't unload rtap/rtnet once loaded.
>
> There is at least no known incompatibility but it may simply have never been
> tested in that combination.
>
> Do you see corruption on packets sent from the rtcap machine or received by
> it?

I definitely see corruption from the "normal" reception over the raw packet socket (as soon as the rtcap module is active).
Seems like rtskb are reused before/while they are copied to userspace.

Analyzing the packets from the rtcap fake device for corruption would be time-consuming.

Norbert
________________________________

This message and any attachments are solely for the use of the intended recipients. They may contain privileged and/or confidential information or other information protected from disclosure. If you are not an intended recipient, you are hereby notified that you received this email in error and that any review, dissemination, distribution or copying of this email and any attachment is strictly prohibited. If you have received this email in error, please contact the sender and delete the message and any attachment from your system.

ANDRITZ HYDRO GmbH


Rechtsform/ Legal form: Gesellschaft mit beschränkter Haftung / Corporation

Firmensitz/ Registered seat: Wien

Firmenbuchgericht/ Court of registry: Handelsgericht Wien

Firmenbuchnummer/ Company registration: FN 61833 g

DVR: 0605077

UID-Nr.: ATU14756806


Thank You
________________________________