> On Fri, Feb 18, 2022 at 10:08:20AM +0100, Jakub Raczyński wrote: > > > I disagree. As far as I can tell, IGMP resending is done by kernel > > from version 4.9 upon notification. So basically, ptp4l will not > > work with any switch using IGMP in any way on older kernels. > > What do you mean? > > Are kernels 4.10+ working correctly, but 4.9 and earlier not working?
I cannot say on which precisely, would need more studying of Linux kernel. Seems that newer version of 4.9 has this implemented. Basically, problem originates from this https://unix.stackexchange.com/questions/523529/should-the-linux-kernel-perform-an-igmp-rejoin-on-link-up And ptp4l does not take care of that and neither are some kernel versions. So basically ptp4l will only work on switch with IGMP snooping if it has been started after the switch, while any restart of switch will cause all PTP traffic to be blocked permanently. The question is whether ptp4l should worry or that or not. I must agree that would be a bit of "voodoo engineering". But some products seem to have locked kernel version, that is EOL for some time, yet no updated are available. For user, it is hard to debug why is it a case (why PTP multicast, both L2 and L4, is blocked on switch), so at least some big warning about this would be appreciated. Best regards Jakub _______________________________________________ Linuxptp-users mailing list Linuxptp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-users
