netdev - Re: [net PATCH] octeontx2-pf: Reduce minimum mtu size to 60

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Message-ID: <CO1PR18MB46665FA74B25A50E98BE32FFA1999@CO1PR18MB4666.namprd18.prod.outlook.com>
Date:   Fri, 29 Jul 2022 09:33:03 +0000
From:   Subbaraya Sundeep Bhatta <sbhatta@...vell.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Naveen Mamindlapalli <naveenm@...vell.com>,
        "richardcochran@...il.com" <richardcochran@...il.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sunil Kovvuri Goutham <sgoutham@...vell.com>
Subject: Re: [net PATCH] octeontx2-pf: Reduce minimum mtu size to 60

Hi Andrew,

Added PTP maintainer also in v2. We fixed this to work with latest ptp4l since after debugging we found
ptp4l complains bad message for Sync packets. 
Lets hear from Richard.

Thanks,
Sundeep

________________________________________
From: Andrew Lunn <andrew@...n.ch>
Sent: Friday, July 29, 2022 3:27 AM
To: Naveen Mamindlapalli
Cc: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org; pabeni@...hat.com; netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Sunil Kovvuri Goutham; Subbaraya Sundeep Bhatta
Re: [net PATCH] octeontx2-pf: Reduce minimum mtu size to 60

----------------------------------------------------------------------
On Thu, Jul 28, 2022 at 06:08:12PM +0530, Naveen Mamindlapalli wrote:
> From: Subbaraya Sundeep <sbhatta@...vell.com>
>
> PTP messages like SYNC, FOLLOW_UP, DELAY_REQ are of size 58 bytes.
> Using a minimum packet length as 64 makes NIX to pad 6 bytes of
> zeroes while transmission. This is causing latest ptp4l application to
> emit errors since length in PTP header and received packet are not same.
> Padding upto 3 bytes is fine but more than that makes ptp4l to assume
> the pad bytes as a TLV. Hence reduce the size to 60 from 64.

Please Cc: the PTP maintainer for changes like this.

I also don't follow your explanation. At least for the original 802.3,
you had to pad packets shorter than 64 bytes, otherwise CSMA/CD did
not work. So i would expect PTP messages should be padded to 64?

Or is you hardware doing the padding wrong, and this is a workaround
for that bug?

    Andrew