netdev - Re: [PATCH net] qmi_wwan: Clone the skb when in pass-through mode

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Message-ID: <CAKfDRXjuCBj=jq+s93L3xHJAtAZbtEt0p4O5omrXgZfX1Xa6YQ@mail.gmail.com>
Date:   Wed, 16 Jun 2021 12:08:28 +0200
From:   Kristian Evensen <kristian.evensen@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Bjørn Mork <bjorn@...k.no>,
        Network Development <netdev@...r.kernel.org>,
        subashab@...eaurora.org
Subject: Re: [PATCH net] qmi_wwan: Clone the skb when in pass-through mode

Hi,

On Tue, Jun 15, 2021 at 9:26 PM Jakub Kicinski <kuba@...nel.org> wrote:
> Tricky piece of code. Perhaps we could add another return code
> to the rx_fixup call? Seems that we expect 0 or 1 today, maybe we
> can make 2 mean "data was copied out", and use that for the qmimux
> case?

I took another look at the qmi_wwan and usbnet code, and I think we
can solve the problem at hand with the current infrastructure. I
believe all we have to do, is to change qmimux_rx_fixup() to return 0
and not 1. When the rx_fixup() callback returns 0, rx_progress() will
jump to "done" and queue the skb for clean-up. This is the same
behavior as if FLAG_MULTI_PACKET was set. I will test and prepare a
patch changing the return value, assuming it works well. Looking at
the loop in qmimux_rx_fixup I also see room for some clean-up, I will
try to merge everything into one.

Kristian