Re: [PATCH v12 net-next 2/3] netdevsim: Implement basic ptp support

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 08/11/2026 20:15, Maciek Machnikowski wrote:
> Add support for virtual timestamping inside the netdevsim driver.
> The implementation uses two attached ptp_mock clocks, reads the timestamps
> of the ones attached either to the netdevsim or its peer and returns
> timestamps using standard timestamps APIs.
> 
> This implementation enables running ptp4l on netdevsim adapters and
> introduces a new ptp selftest.
> 
> skb_hwtstamps(skb)->hwtstamp aliases with skb_shinfo(skb)->xsk_meta in
> the skb_shared_info union. For an AF_XDP generic-xmit skb forwarded to
> a peer with RX timestamping enabled, writing the RX timestamp into
> that union turns xsk_meta.tx_timestamp into a PHC-derived value that
> the AF_XDP destructor (xsk_destruct_skb()) later dereferences as a
> pointer, corrupting memory. Orphan the skb before writing the RX
> timestamp so any pending destructor (e.g. the AF_XDP completion) runs
> against the original, unmodified union contents first.
> 
> Co-developed-by: Milena Olech <milena.olech@intel.com>
> Signed-off-by: Milena Olech <milena.olech@intel.com>
> Reviewed-by: Mina Almasry <almasrymina@google.com>
> Signed-off-by: Maciek Machnikowski <maciek@machnikowski.net>

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>