netdev - Re: [RPI 3B+ / TSO / lan78xx ]

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Date:   Tue, 7 Jan 2020 09:04:23 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     RENARD Pierre-Francois <pfrenard@...il.com>,
        nsaenzjulienne@...e.de, woojung.huh@...rochip.com,
        UNGLinuxDriver@...rochip.com, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org, stefan.wahren@...e.com
Subject: Re: [RPI 3B+ / TSO / lan78xx ]



On 1/7/20 5:32 AM, RENARD Pierre-Francois wrote:
> 
> Hello all
> 
> I am facing an issue related to Raspberry PI 3B+ and onboard ethernet card.
> 
> When doing a huge transfer (more than 1GB) in a row, transfer hanges and failed after a few minutes.
> 
> 
> I have two ways to reproduce this issue
> 
> 
> using NFS (v3 or v4)
> 
>     dd if=/dev/zero of=/NFSPATH/file bs=4M count=1000 status=progress
> 
> 
>     we can see that at some point dd hangs and becomes non interrutible (no way to ctrl-c it or kill it)
> 
>     after afew minutes, dd dies and a bunch of NFS server not responding / NFS server is OK are seens into the journal
> 
> 
> Using SCP
> 
>     dd if=/dev/zero of=/tmp/file bs=4M count=1000
> 
>     scp /tmp/file user@...ver:/directory
> 
> 
>     scp hangs after 1GB and after a few minutes scp is failing with message "client_loop: send disconnect: Broken pipe lostconnection"
> 
> 
> 
> 
> It appears, this is a known bug relatted to TCP Segmentation Offload & Selective Acknowledge.
> 
> disabling this TSO (ethtool -K eth0 tso off & ethtool -K eth0 gso off) solves the issue.
> 
> A patch has been created to disable the feature by default by the raspberry team and is by default applied wihtin raspbian.
> 
> comment from the patch :
> 
> /* TSO seems to be having some issue with Selective Acknowledge (SACK) that
>  * results in lost data never being retransmitted.
>  * Disable it by default now, but adds a module parameter to enable it for
>  * debug purposes (the full cause is not currently understood).
>  */
> 
> 
> For reference you can find
> 
> a link to the issue I created yesterday : https://github.com/raspberrypi/linux/issues/3395
> 
> links to raspberry dev team : https://github.com/raspberrypi/linux/issues/2482 & https://github.com/raspberrypi/linux/issues/2449
> 
> 
> 
> If you need me to test things, or give you more informations, I ll be pleased to help.
>


I doubt TSO and SACK have a serious generic bug like that.

Most likely the TSO implementation on the driver/NIC has a bug .

Anyway you do not provide a kernel version, I am not sure what you expect from us.