Re: [PATCH net-next v1 01/03] net/macsec: Add MACsec skb extension Tx Data path support

[Paolo Abeni <pabeni@redhat.com>]

On Sun, 2022-05-08 at 12:09 +0300, Lior Nahmanson wrote:
> In the current MACsec offload implementation, MACsec interfaces are
> sharing the same MAC address of their parent interface by default.
> Therefore, HW can't distinguish if a packet was sent from MACsec
> interface and need to be offloaded or not.
> Also, it can't distinguish from which MACsec interface it was sent in
> case there are multiple MACsec interface with the same MAC address.
> 
> Used SKB extension, so SW can mark if a packet is needed to be offloaded
> and use the SCI, which is unique value for each MACsec interface,
> to notify the HW from which MACsec interface the packet is sent.
> 
> Signed-off-by: Lior Nahmanson <liorna@nvidia.com>
> Reviewed-by: Raed Salem <raeds@nvidia.com>
> Reviewed-by: Jiri Pirko <jiri@nvidia.com>
> Reviewed-by: Ben Ben-Ishay <benishay@nvidia.com>
> ---
>  drivers/net/Kconfig    | 1 +
>  drivers/net/macsec.c   | 5 +++++
>  include/linux/skbuff.h | 3 +++
>  include/net/macsec.h   | 6 ++++++
>  net/core/skbuff.c      | 7 +++++++
>  5 files changed, 22 insertions(+)
> 
> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> index b2a4f998c180..6c9a950b7010 100644
> --- a/drivers/net/Kconfig
> +++ b/drivers/net/Kconfig
> @@ -313,6 +313,7 @@ config MACSEC
>  	select CRYPTO_AES
>  	select CRYPTO_GCM
>  	select GRO_CELLS
> +	select SKB_EXTENSIONS
>  	help
>  	   MACsec is an encryption standard for Ethernet.
>  
> diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
> index 832f09ac075e..0960339e2442 100644
> --- a/drivers/net/macsec.c
> +++ b/drivers/net/macsec.c
> @@ -3377,6 +3377,11 @@ static netdev_tx_t macsec_start_xmit(struct sk_buff *skb,
>  	int ret, len;
>  
>  	if (macsec_is_offloaded(netdev_priv(dev))) {
> +		struct macsec_ext *secext = skb_ext_add(skb, SKB_EXT_MACSEC);
> +
> +		secext->sci = secy->sci;
> +		secext->offloaded = true;
> +
>  		skb->dev = macsec->real_dev;
>  		return dev_queue_xmit(skb);
>  	}
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 84d78df60453..4ee71c7848bf 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -4552,6 +4552,9 @@ enum skb_ext_id {
>  #endif
>  #if IS_ENABLED(CONFIG_MCTP_FLOWS)
>  	SKB_EXT_MCTP,
> +#endif
> +#if IS_ENABLED(CONFIG_MACSEC)
> +	SKB_EXT_MACSEC,
>  #endif
>  	SKB_EXT_NUM, /* must be last */
>  };
> diff --git a/include/net/macsec.h b/include/net/macsec.h
> index d6fa6b97f6ef..fcbca963c04d 100644
> --- a/include/net/macsec.h
> +++ b/include/net/macsec.h
> @@ -20,6 +20,12 @@
>  typedef u64 __bitwise sci_t;
>  typedef u32 __bitwise ssci_t;
>  
> +/* MACsec sk_buff extension data */
> +struct macsec_ext {
> +	sci_t sci;
> +	bool offloaded;

It looks like the bool is not used/it's always true when the extension
is attached? If so it's better to drop it and use the extension
presence as the flag.

BTW have you considered other options other then the skb extensions?
e.g. could you use skb_metadata() here?

Otherwise I think you need explicitly to take care of this extension at
the GRO layer, see commit 8550ff8d8c75

Thanks!

Paolo