Subject: Re: [PATCH net-next v4 5/5] macsec: Add MACsec rx_handler change support

From: Sabrina Dubroca <[email-masked]>
Date: Wed, 12 Apr 2023 16:58:43 +0200

2023-04-08, 13:57:35 +0300, Emeel Hakim wrote:
> Offloading device drivers will mark offloaded MACsec SKBs with the
> corresponding SCI in the skb_metadata_dst so the macsec rx handler will
> know to which interface to divert those skbs, in case of a marked skb
> and a mismatch on the dst MAC address, divert the skb to the macsec
> net_device where the macsec rx_handler will be called.

Quoting my reply to v2:

========

Sorry, I don't understand what you're trying to say here and in the
subject line.

To me, "Add MACsec rx_handler change support" sounds like you're
changing what function is used as ->rx_handler, which is not what this
patch is doing.

========

> Example of such a case is having a MACsec with VLAN as an inner header
> ETHERNET | SECTAG | VLAN packet.
> 
> Signed-off-by: Emeel Hakim <[email-masked]>
> ---
>  drivers/net/macsec.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
> index 25616247d7a5..4e58d2b4f0e1 100644
> --- a/drivers/net/macsec.c
> +++ b/drivers/net/macsec.c
> @@ -1016,14 +1016,18 @@ static enum rx_handler_result handle_not_macsec(struct sk_buff *skb)
>  		struct sk_buff *nskb;
>  		struct pcpu_secy_stats *secy_stats = this_cpu_ptr(macsec->stats);
>  		struct net_device *ndev = macsec->secy.netdev;
> +		struct macsec_rx_sc *rx_sc_found = NULL;

I don't think "_found" is adding any information. "rx_sc" is
enough. And since it's only used in the if block below, it could be
defined down there.

And btw I don't think we even need to check "&& rx_sc_found" in the
code you're adding, but maybe I need more coffee. Anyway, I'd be fine
with saving the result of find_rx_sc and reusing it.

if (A && !rx_sc)
    continue;

[...]

if (A) // here we know rx_sc can't be NULL, otherwise we would have hit the continue earlier
    packet_host etc

>  		/* If h/w offloading is enabled, HW decodes frames and strips
>  		 * the SecTAG, so we have to deduce which port to deliver to.
>  		 */
>  		if (macsec_is_offloaded(macsec) && netif_running(ndev)) {
> -			if (md_dst && md_dst->type == METADATA_MACSEC &&
> -			    (!find_rx_sc(&macsec->secy, md_dst->u.macsec_info.sci)))
> +			rx_sc_found = (md_dst && md_dst->type == METADATA_MACSEC) ?
> +				      find_rx_sc(&macsec->secy, md_dst->u.macsec_info.sci) : NULL;
> +
> +			if (md_dst && md_dst->type == METADATA_MACSEC && !rx_sc_found) {
>  				continue;
> +			}

{} not needed around a single line.

>  
>  			if (ether_addr_equal_64bits(hdr->h_dest,
>  						    ndev->dev_addr)) {
> @@ -1048,6 +1052,14 @@ static enum rx_handler_result handle_not_macsec(struct sk_buff *skb)
>  
>  				__netif_rx(nskb);
>  			}
> +
> +			if (md_dst && md_dst->type == METADATA_MACSEC && rx_sc_found) {
> +				skb->dev = ndev;
> +				skb->pkt_type = PACKET_HOST;
> +				ret = RX_HANDLER_ANOTHER;
> +				goto out;
> +			}
> +
>  			continue;
>  		}
>  
> -- 
> 2.21.3
> 

-- 
Sabrina