Re: [Linuxptp-users] ptp4l and network connectivity interruption

[Brian W. <br...@wa...>]

On Fri, 11 Dec 2015, Richard Cochran wrote:
> > It is an Intel 82574L. 8086:10d3
> 
> Ok, I have that card.  The driver is the e1000e (and not the e1000).
> Can you send me your iptables script so that I can try and reproduce
> the problem?

I am just dropping udp packets on INPUT for ports 319 and 320

iptables -A INPUT -p udp --dport 319 -j DROP
iptables -A INPUT -p udp --dport 320 -j DROP

After a few seconds I just delete those rules.
 
> > Looking again it appears it may be the opposite of what I thought.
> > ptp4l is maintaining the
> > offset value while the hardware clock has switched back to UTC time. I
> > am not seeing
> > anywhere that ptp4l is reseting the offset to 0 during this state.
> 
> Right, it is in the driver or HW.  I remember that card resetting the
> clock after link loss.  I complained about this, but Intel said it was
> as HW limitation, IIRC.
> 
> However, I wouldn't expect this to happen just from the action of the
> firewall.  That sounds more like a driver bug.
> 

I was looking at the linuxptp code to see if it could possibly detect the
condition. It does detect the initial jump when the hardware starts
receiving packets again. Maybe it could check the jump against the last
known offset value. Have it wait for a few packets while the device
settles before trusting that jump if it is close to the offset.

Brian