netdev - RE: [PATCH net 1/2] r8152: fix the sw rx checksum is unavailable

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Date:   Fri, 25 Nov 2016 06:11:18 +0000
From:   Hayes Wang <hayeswang@...ltek.com>
To:     Mark Lord <mlord@...ox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     nic_swsd <nic_swsd@...ltek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: RE: [PATCH net 1/2] r8152: fix the sw rx checksum is unavailable

Mark Lord [mailto:mlord@...ox.com]
> Sent: Thursday, November 24, 2016 11:25 PM
[...]
> x86 has near fully-coherent memory, so it is the "easy" platform
> to get things working on.  But Linux supports a very diverse number
> of platforms, with varying degrees of cache/memory coherency,
> and it can be tricky for things to work correctly on all of them.

However, I have test iperf on raspberry pi v1 which you suggest
for more than one day. I still couldn't reproduce your issue.

> If you are testing with the driver as currently in 4.4.34,
> then you won't even notice when things are screwing up,
> because the driver just silently drops packets.
> Or it passes them on without noticing that they have bad data.

I only drop the packet silently when the rx descriptor outside
the urb buffer. Then, I check the rx descriptor before checking
the length of the packet.

> Here (attached) is the instrumented driver I am using here now.
> I suggest you use it or something similar when testing,
> and not the stock driver.

I would test it again with your driver.

[...]
> Also, unrelated, but inside r8152_submit_rx() there is this code:
> 
>          /* The rx would be stopped, so skip submitting */
>          if (test_bit(RTL8152_UNPLUG, &tp->flags) ||
>              !test_bit(WORK_ENABLE, &tp->flags)
> || !netif_carrier_ok(tp->netdev))
>                 return 0;
> 
> If that "return 0" statement is ever executed, doesn't it result
> in the loss/leak of a buffer?

They would be found back by calling rtl_start_rx(), when the rx
is restarted.

Best Regards,
Hayes