On Tuesday, July 8, 2025 9:45 AM, Jakub Kicinski kuba@kernel.org wrote:
On Tue, 8 Jul 2025 01:34:13 +0000 Song, Yoong Siang wrote:
For normal XDP my understanding is that its the driver's responsibility to move the "reserved" stuff out of place before presenting the frame to program.
Is it means that driver needs to move out the "reserved" stuff before XDP program and then move back the stuff after XDP program for certain situation, like
XDP_PASS?
Why would the driver need to move it back? On XDP_PASS an skb is constructed, so the metadata should be transferred to the skb. There is no need to copy it back as a prepend.
I said so because I thought need to put back the timestamp as prepend and then point skb_shared_hwtstamps.netdev_data to it to support the ndo_get_tstamp().
I haven't study the code flow in detail, so I might be missing something.