Re: [net-next v4] tcp: add support for SO_PEEK_OFF socket option

[Eric Dumazet <edumazet@google.com>]

On Tue, Apr 9, 2024 at 5:28 PM <jmaloy@redhat.com> wrote:
>
> From: Jon Maloy <jmaloy@redhat.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@redhat.com>
> Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>

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