Re: [Linuxptp-devel] unknown option ntpshm_segment at line 8 in eno1 section

[Jiri B. <jb...@re...>]

On Tue, 4 Aug 2015 10:34:17 +0200, Miroslav Lichvar wrote:
> When I run "ptp4l -6 -S -i ens5 -m", ss reports only IPv6 sockets for
> ptp4l:
> 
> # ss -lup | grep ptp4l
> UNCONN     0      0                 ::%ens5:ptp-event                 :::*        users:(("ptp4l",pid=5862,fd=10))
> UNCONN     0      0                 ::%ens5:ptp-general                 :::*        users:(("ptp4l",pid=5862,fd=11))

Sadly, ss does not report whether a given socket has IPV6_V6ONLY set or
not. By default (unless /proc/sys/net/ipv6/bindv6only is set), the IPv6
socket listens for both IPv6 and IPv4 connections, returning the latter
as v4-mapped IPv6 address.

linuxptp does not seem to set IPV6_V6ONLY, thus creating an UDP6 socket
indeed prevents creating an UDP4 one on the same UDP port.

Whether or not ptp4l should set IPV6_V6ONLY unconditionally needs some
more thinking, but my first impression is it would need to use IPv4
multicast addresses (v4-mapped to IPv6) to send the packets to the v4
hosts and not the IPv6 multicast addresses. This doesn't seem worth the
complications and IPV6_V6ONLY looks like to be appropriate here. But
somebody should think it through first :-)

 Jiri

-- 
Jiri Benc