On 2/17/2022 8:26 AM, Janusz Użycki wrote: > 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.
I think we at least need to re-send these when the link changes, though we perhaps were thinking that the kernel does this for us? Maybe thats a bug or maybe we have to set an option? There is no mention about whether we would need to re-issue this socket option in the "man 7 ip" manual page. > 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... > This sounds like what we should be doing as well. > best regards > Janusz > > > > > _______________________________________________ > Linuxptp-users mailing list > Linuxptp-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linuxptp-users _______________________________________________ Linuxptp-users mailing list Linuxptp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-users
