netdev - Re: [PATCH net-next v5 1/2] net: mhi-net: Add re-aggregation of fragmented packets

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Message-ID: <20210206113121.52f27389@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Sat, 6 Feb 2021 11:31:21 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Loic Poulain <loic.poulain@...aro.org>
Cc:     davem@...emloft.net, willemdebruijn.kernel@...il.com,
        netdev@...r.kernel.org, stranche@...eaurora.org,
        subashab@...eaurora.org
Subject: Re: [PATCH net-next v5 1/2] net: mhi-net: Add re-aggregation of
 fragmented packets

On Thu,  4 Feb 2021 09:40:00 +0100 Loic Poulain wrote:
> When device side MTU is larger than host side MTU, the packets
> (typically rmnet packets) are split over multiple MHI transfers.
> In that case, fragments must be re-aggregated to recover the packet
> before forwarding to upper layer.
> 
> A fragmented packet result in -EOVERFLOW MHI transaction status for
> each of its fragments, except the final one. Such transfer was
> previously considered as error and fragments were simply dropped.
> 
> This change adds re-aggregation mechanism using skb chaining, via
> skb frag_list.
> 
> A warning (once) is printed since this behavior usually comes from
> a misconfiguration of the device (e.g. modem MTU).
> 
> Signed-off-by: Loic Poulain <loic.poulain@...aro.org>

Applied, thanks, but I had to invert the order of the patches.
Otherwise during bisection someone may hit a point in the tree
where mhi_net generates fragmented skbs but rmnet does not handle
them.