Re: [PATCH v2 06/25] linux: Add fallback for 64-bit time_t SO_TIMESTAMP{NS}

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 21/05/2021 15:38, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> On 20/05/2021 03:50, Florian Weimer wrote:
>>> * Adhemerval Zanella via Libc-alpha:
>>>
>>>> Calls with __TIMESIZE=32 will see the converted 64-bit time control
>>>> messages as spurious control message of unknown type.  Calls with
>>>> __TIMESIZE=64 running on pre-time64 kernels will see the original
>>>> message as a spurious control ones of unknown typ while running on
>>>> kernel with native 64-bit time support will only see the time64 version
>>>> of the control message.
>>>
>>> Does the mirror what the kernel does?  I have some concerns about
>>> backwards compatibility here, but if the kernel does it as well, that is
>>> likely a non-issue.
>>
>> The SO_TIMESTAMP{NS}_OLD to SO_TIMESTAMP{NS}_NEW for _TIME_BITS=64 is
>> what this patch does to add some compatibility. From kernel code:
>> net/socket.c
> 
> Will anything new show up for _TIME_BITS=32 on legacy architectures?

It will if a library setup a SO_TIMESTAMP{NS}_NEW (assuming running on
newer kernels), since afaik the timestamp is set on socket buffer within 
kernel (so my understanding is in theory one can see multiple different 
timestamps formats on same socket).