Re: [PATCH net v3 5/5] ptp: vclock: preserve missing hardware timestamps

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

On 13/10/2026 20:19, James Hilliard wrote:
> Socket timestamp delivery converts hardware timestamps to a bound
> virtual clock before checking whether a hardware timestamp is present.
> A zero timestamp means that the packet has no hardware timestamp, but
> timecounter_cyc2time() can turn that zero into a nonzero virtual time.
> The socket then reports a hardware timestamp which was never supplied.
> 
> Return zero without conversion when the input timestamp is absent.
> This also covers skb_get_tx_timestamp(), which checks for an absent
> timestamp after the same conversion.
> 
> This was identified during review of virtual clock sampling changes.
> 
> Fixes: d7c088265588 ("net: socket: support hardware timestamp conversion to PHC bound")
> Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
> ---
>   drivers/ptp/ptp_vclock.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/ptp/ptp_vclock.c b/drivers/ptp/ptp_vclock.c
> index 6675466bc307..4a62047f0ce0 100644
> --- a/drivers/ptp/ptp_vclock.c
> +++ b/drivers/ptp/ptp_vclock.c
> @@ -307,6 +307,8 @@ ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp, int vclock_index)
>   	u64 ns;
>   
>   	ns = ktime_to_ns(*hwtstamp);
> +	if (!ns)
> +		return 0;
>   
>   	srcu_idx = srcu_read_lock(&vclock_srcu);
>   
> 

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