[time-nuts] Re: NIST NTP servers way off for anyone else?

[alec at unifiedmathematics.com]

Okay so "man cmsg"

I've seen cards (ethtool) that support several time options - what are 
they and how do I use them?

Also cmsg doesn't make it clear what these auxiliary headers might 
actually be, so that doesn't really leave me able to use this?

Is it ALWAYS there? What about receive offload?

Alec

---


On 2021-12-14 20:57, Hal Murray wrote:
> alec at unifiedmathematics.com said:
>> I've seen SO_TIMESTAMP and friends in ethtool but I have no idea what 
>> it  is
>> or how it works, can you point me in the right direction please?
> 
> man 7 socket on a Linux box.  Then man recvmsg and man cmsg
> 
> There are several variations on various OSes.
> 
> 
> The basic idea is that the OS input processing grabs a time stamp when 
> the
> packet arrives.  On Linux, that's done by the kernel thread that looks 
> in the
> packet headers to figure out which input queue the packet goes on.
> 
> The basic idea is that you get a time stamp when the packet arrives 
> rather
> than when the user program gets around to read/recv-ing it.