[PATCH net 0/1] Prevent DSA tags from breaking COE

[Household Cang]

> On Dec 22, 2023, at 7:30 AM, Vladimir Oltean <olteanv at gmail.com> wrote:
> 
> Is "rx off" actually required, or just "tx off”?

Before adjusted the ethtool -K, the client upload speed is 880Mbps (download speed 0.6Mbps). RK3568 is acting as a router, so client is sending to eth1 via DSA user port, rx used here, and then tx on eth0. So this might suggest only tx needs to be turned off on eth1.

> 
> The MT7531BE switch requires transmitted packets to have an additional
> header which indicates what switch port is targeted. So the packet
> structure is not the same as what eth0 transmits.
> 

I understand. How many bytes are the DSA header for MT, 8 bytes?

> Your GMAC datasheet should explain what packets it is able to offload
> L4 checksumming for, quite plainly. Probably MAC + IP + TCP yes, but
> MAC + MTK DSA + IP + TCP no.

I hardly could find this in the data sheet for RK3568. From the DMA mapping, it insinuates a correct ether type needs to be detected after the MAC header, besides an inner and an outer VLAN tag, if there are any.

>  The driver still declares
> the NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM features because it is able to
> offload checksumming for _some_ packets, but it falls back to the
> software checksum helper for the rest. This includes your MTK DSA tagged
> packets.

I guess the end verdict regarding whether the hardware supports checksum offloading on DSA frames is a NO. So this is going to use some precious CPU power I am looking to fully dedicate to ipsec. Though I am pursuing crypto hw offloading at the same time with baylibre.

Lucas.