Hi,
Does the issue still concern PTP for Linux:
"Dear IEEE 1588 implementers: don't forget about IGMP if you do
multicast! « The PTP guy (logdown.com) "
http://theptpguy.logdown.com/posts/2015/08/31/dear-ieee-1588-implementers-remember-about-igmp
?
From our observations for IPv4 (L4) E2E it still applies to ptp4l. On
Cisco and Netgear switches (even L3 set as L2 switch) IGMP snooping must
be disabled for proper PTP multicast work.
ptp4l joins to multicast group once on start (only once, ie. it triggers
Linux kernel once to send IGMP packet):
udp.c: err = setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &req,
sizeof(req));
What is impact such implementation when interface goes down and up
again, or on network recrossing? There is no periodic rejoin package
observed.
For IPv6 likely there is no problem but we have not tested.
Maybe it is Linux kernel issue. However for comparison ptpd2 implements
periodic multicast group (re)join (optionmaster_igmp_refresh_interval):
src/dep/net.c:netInitMulticastIPv4()
https://github.com/ptpd/ptpd/blob/master/src/dep/net.c#L605
https://github.com/ptpd/ptpd/blob/master/src/dep/net.c#L2278
https://github.com/ptpd/ptpd/blob/master/src/protocol.c#L607
https://github.com/ptpd/ptpd/blob/master/src/protocol.c#L1120 Other
proprietary PTP devices send IGMP packets periodically every 1-2s and
work with the switches despite IGMP snooping enabled...
best regards
Janusz
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