netdev - Re: [PATCH 1/1] RDMA/rxe: Fetch skb packets from ethernet layer

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Message-ID: <20201109102518.6b3d92a5@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 9 Nov 2020 10:25:18 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Zhu Yanjun <zyjzyj2000@...il.com>
Cc:     Doug Ledford <dledford@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
        linux-rdma@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/1] RDMA/rxe: Fetch skb packets from ethernet layer

On Sun, 8 Nov 2020 13:27:32 +0800 Zhu Yanjun wrote:
> On Sun, Nov 8, 2020 at 1:24 PM Zhu Yanjun <zyjzyj2000@...il.com> wrote:
> > On Thu, 5 Nov 2020 19:12:01 +0800 Zhu Yanjun wrote:
> >
> > In the original design, in rx, skb packet would pass ethernet
> > layer and IP layer, eventually reach udp tunnel.
> >
> > Now rxe fetches the skb packets from the ethernet layer directly.
> > So this bypasses the IP and UDP layer. As such, the skb packets
> > are sent to the upper protocals directly from the ethernet layer.
> >
> > This increases bandwidth and decreases latency.
> >
> > Signed-off-by: Zhu Yanjun <yanjunz@...dia.com>
> >
> >
> > Nope, no stealing UDP packets with some random rx handlers.  
> 
> Why? Is there any risks?

Are there risks in layering violations? Yes.

For example - you do absolutely no protocol parsing, checksum
validation, only support IPv4, etc.

Besides it also makes the code far less maintainable, rx_handler is a
singleton, etc. etc.

> > The tunnel socket is a correct approach.