Re: [Linuxptp-users] PTP4L daemon seems to have a problem with to a link local address for IPv6

[Richard C. <ric...@gm...>]

On Sun, Nov 25, 2012 at 06:38:01AM +0100, Mario Molitor wrote:
> >>For IPV6 tests I have changed PTP_PRIMARY_MCAST_IP6ADDR  to a
> >>link local address.
> >>(#define PTP_PRIMARY_MCAST_IP6ADDR "FF02:0:0:0:0:0:0:181")
> >
> >Why do you think this should be a link local address?
> 
> used the local scope in order to use only modules in a closed
> network segments.

But I think using link-local doesn't make sense for E2E.

Won't it prevent operation through a transparent switch or a non-BC
router?

Also, even if you are using directly connected PTP nodes, I would
think that using global scope should still work.

> >(I chose the global scope in order to maximise the chance of reaching
> >a master when running slave, and vice versa. I confess that I don't
> >really know what scope is correct to use here.
> 
> This is correct and makes sense.
> But in some cases maybe would like the user change this, but this is
> not the point at the moment.

If changing the scope is needed, then the udp6.c code will have to
behave differently depending on the scope. Setting the sin6_scope_id
non-zero only makes sense for link-local.

I read up on the scope field in IPv6 multicast addresses (Stevens, the
man page, and a bit of googling), and it might present a bit of a
problem. Each combination of scope and mcast addresses is a unqiue
group, so a general IPv6 client would have to join *all* of the groups
in order to find the server.

Thanks,
Richard