Re: [PATCH net] docs: tls: document the TLS_TX_ZEROCOPY_RO

[Maxim Mikityanskiy <maximmi@nvidia.com>]

On 2022-06-10 21:02, Jakub Kicinski wrote:
> Add missing documentation for the TLS_TX_ZEROCOPY_RO opt-in.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> CC: corbet@lwn.net
> CC: linux-doc@vger.kernel.org
> ---
>   Documentation/networking/tls.rst | 25 +++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
> 
> diff --git a/Documentation/networking/tls.rst b/Documentation/networking/tls.rst
> index 8cb2cd4e2a80..be8e10c14b05 100644
> --- a/Documentation/networking/tls.rst
> +++ b/Documentation/networking/tls.rst
> @@ -214,6 +214,31 @@ of calling send directly after a handshake using gnutls.
>   Since it doesn't implement a full record layer, control
>   messages are not supported.
>   
> +Optional optimizations
> +----------------------
> +
> +There are certain condition-specific optimizations the TLS ULP can make,
> +if requested. Those optimizations are either not universally beneficial
> +or may impact correctness, hence they require an opt-in.
> +All options are set per-socket using setsockopt(), and their
> +state can be checked using getsockopt() and via socket diag (``ss``).
> +
> +TLS_TX_ZEROCOPY_RO
> +~~~~~~~~~~~~~~~~~~
> +
> +For device offload only. Allow sendfile() data to be transmitted directly
> +to the NIC without making an in-kernel copy. This allows true zero-copy
> +behavior when device offload is enabled.
> +
> +The application must make sure that the data is not modified between being
> +submitted and transmission completing. In other words this is mostly
> +applicable if the data sent on a socket via sendfile() is read-only.
> +
> +Modifying the data may result in different versions of the data being used
> +for the original TCP transmission and TCP retransmissions. To the receiver
> +this will look like TLS records had been tampered with and will result
> +in record authentication failures.
> +
>   Statistics
>   ==========
>   

Acked-by: Maxim Mikityanskiy <maximmi@nvidia.com>