> -----Original Message-----
> From: Richard Cochran <richardcoch...@gmail.com>
> Sent: Friday, February 18, 2022 2:13 PM
> To: Jakub Raczyński <j.raczyn...@elpromaelectronics.com>
> Cc: linuxptp-users@lists.sourceforge.net
> Subject: Re: [Linuxptp-users] Multicast group (re)join issue vs IGMP snooping
>
> 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?
>
> Thanks,
> Richard
>
FWIW, it looks like there are some sysctls for this, from ip sysctl
documentation:
igmpv2_unsolicited_report_interval - INTEGER
The interval in milliseconds in which the next unsolicited
IGMPv1 or IGMPv2 report retransmit will take place.
Default: 10000 (10 seconds)
igmpv3_unsolicited_report_interval - INTEGER
The interval in milliseconds in which the next unsolicited
IGMPv3 report retransmit will take place.
Default: 1000 (1 seconds)
It looks like the default for IGMPv3 was changed from 10 to 1second in
cab70040dfd9 ("net: igmp: Reduce Unsolicited report interval to 1s when using
IGMPv3") and made configurable in 2690048c01f3 ("net: igmp: Allow user-space
configuration of igmp unsolicited report interval")
As far as I can tell, the default settings since a long time is to re-transmit
an unsolicited join request with a random interval between 0 and 10 seconds as
of the 2.6 git history. I couldn't find any data from before that.
So I think Richard is quite right, if there is a bug, it is in the kernel, and
as far as I can tell it is at least intended that the kernel will re-transmit
these as necessary.
Thanks,
Jake
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