netdev - Re: skb_shared_hwstamps ability to handle 64 bit seconds and nanoseconds

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Message-ID: <f1d80992b806213e63fe1d6c62c0081c4a24ca62.camel@inf.elte.hu>
Date: Sat, 28 Sep 2024 08:48:02 +0200
From: Ferenc Fejes <fejes@....elte.hu>
To: Greg Dowd <dowdgreg@...il.com>, netdev@...r.kernel.org
Subject: Re: skb_shared_hwstamps ability to handle 64 bit seconds and
 nanoseconds

Hello,

On Fri, 2024-09-27 at 09:35 -0700, Greg Dowd wrote:
> Hello all,
> I am not sure if this is the right list but I posted this in newbies
> and got referred here.  Anyone have any insight?
> 
> 
> I had a question regarding kernel timestamping.  I see definitions
> for
> SO_TIMESTAMPING_NEW in networking options to allow use of time
> structures containing 64bit timestamps.  However, I don't see any way
> for skbuff timestamps to pass around structures with 64 bits as the
> skb_shared_hwstamps use a typedef ktime_t which stacks the seconds
> and
> nanoseconds into a single 64bit value.

I'm not sure I get your question. There are functions in
kernel/time/timekeeping.c for conversions between ktime_t and struct
timespec back and forth.

>From userspace, you can only use struct timespec, which has sec and
nanosec attributes, all prepared as a CMSG on RX. Same for TX but thats
less interesting unless you want to use SO_TXTIME.

Could you rephrase your question or define the problem you want to
solve?


> I am not sure who maintains this section of the code.  Any ideas?
> 
> thanks...Greg

Thanks,
Ferenc