netdev - Re: [net-next v4] tcp: add support for SO_PEEK

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Message-ID: <CANn89iKSO=P0Vr03ZaXn35-At+SRRvT=b3YrAuW7J5VR0hiFpQ@mail.gmail.com>
Date: Tue, 9 Apr 2024 17:59:39 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: jmaloy@...hat.com
Cc: netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org, 
	passt-dev@...st.top, sbrivio@...hat.com, lvivier@...hat.com, 
	dgibson@...hat.com, eric.dumazet@...il.com
Subject: Re: [net-next v4] tcp: add support for SO_PEEK_OFF socket option

On Tue, Apr 9, 2024 at 5:28 PM <jmaloy@...hat.com> wrote:
>
> From: Jon Maloy <jmaloy@...hat.com>
>
> When reading received messages from a socket with MSG_PEEK, we may want
> to read the contents with an offset, like we can do with pread/preadv()
> when reading files. Currently, it is not possible to do that.
>
> In this commit, we add support for the SO_PEEK_OFF socket option for TCP,
> in a similar way it is done for Unix Domain sockets.
>
> In the iperf3 log examples shown below, we can observe a throughput
> improvement of 15-20 % in the direction host->namespace when using the
> protocol splicer 'pasta' (https://passt.top).
> This is a consistent result.
>
> pasta(1) and passt(1) implement user-mode networking for network
> namespaces (containers) and virtual machines by means of a translation
> layer between Layer-2 network interface and native Layer-4 sockets
> (TCP, UDP, ICMP/ICMPv6 echo).
>
> Received, pending TCP data to the container/guest is kept in kernel
> buffers until acknowledged, so the tool routinely needs to fetch new
> data from socket, skipping data that was already sent.
>
> Suggested-by: Paolo Abeni <pabeni@...hat.com>
> Reviewed-by: Stefano Brivio <sbrivio@...hat.com>
> Signed-off-by: Jon Maloy <jmaloy@...hat.com>

Reviewed-by: Eric Dumazet <edumazet@...gle.com>