Multicast: membership to (*, G) group after leaving a (S, G) group

[Hans Petter Selasky]

On 2020-07-07 12:01, Fabrice Colliot wrote:
> Hi,
> 
> I'm using smcroute to join and leave multicast groups and I don't
> understand the behavior of FreeBSD when the group is left.
> 
> Here is what I do:
> 
> smcroute join em1 10.3.4.5 224.0.55.55
> ifmcstat -i em1
> em1:
>          inet 10.10.0.1
>          igmpv3 rv 2 qi 125 qri 10 uri 3
>                  group 224.0.55.55 mode include
>                          mcast-macaddr 01:00:5e:00:37:37
>                  group 224.0.0.1 mode exclude
>                          mcast-macaddr 01:00:5e:00:00:01
> 
> smcroute leave em1 10.3.4.5 224.0.55.55
> ifmcstat -i em1
> em1:
>          inet 10.10.0.1
>          igmpv3 rv 2 qi 125 qri 10 uri 3
>                  group 224.0.55.55 mode undefined
>                          mcast-macaddr 01:00:5e:00:37:37
>                  group 224.0.0.1 mode exclude
>                          mcast-macaddr 01:00:5e:00:00:01
> 
> At this point, I expected to have no membership left on em1 for 224.0.55.55
> but ifmcstat shows that the interface is still a member of the group but in
> undefined mode.
> 
> I was wondering if anybody could tell me why the group membership seems to
> be transitioned to a (*, G) membership when all the (S, G) memberships are
> removed.
> 

Which version of FreeBSD is this?

--HPS