> -----Original Message----- > From: Jakub Raczyński <j.raczyn...@elpromaelectronics.com> > Sent: Friday, February 18, 2022 1:08 AM > To: linuxptp-users@lists.sourceforge.net > Subject: Re: [Linuxptp-users] Multicast group (re)join issue vs IGMP snooping > > > 18.02.2022 00:51 Richard Cochran <richardcoch...@gmail.com> wrote: > > On Thu, Feb 17, 2022 at 05:26:15PM +0100, Janusz Użycki wrote: > > > > > 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. > > > > So their "IGMP snooping" feature is broken. Ask them to fix it. > > 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. We probably should assume that devices with older > kernel are all EOL but it is not uncommon for them to be still used. So maybe > some annotation on what kernel version will ptp4l work or what are required > kernel modules. > > > Cisco's PTP switch has issues. Have you looked at the residence > > times? I don't feel like implementing workarounds for buggy >hardware. > > And is depending on kernel features for ptp4l to work properly a good way? I > do > not think it is hardware issue here, but rather dependence on kernel version > and/or modules. >
ptp4l already has a lot of "it works better on newer kernel" bits, due to interfacing with Linux kernel interfaces so directly. I think the earliest technically working version is something from the 3.x series (3.5?) but I don't see a problem with documenting a newer version as recommended with the justifications of which features we rely on. I think I agree with Richard that this is the kernel's problem, and that we shouldn't try to forcibly re-send IGMP messages ourselves (in fact, there is no real interface to do this in the socket options.. There's simply a join and leave group option, but no mention of needing to re-join periodically or what attempting to join an already joined group would do). Thanks, Jake > Best regards > Jakub > > > _______________________________________________ > 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
