[ovs-dev] [mcgroup 2/4] datapath: Hardcode vport multicast group ID on older kernels.

[Jesse Gross]

I guess the other thing is if we want to increase our pool of
preallocated multicast groups, we have to either break the ABI or make
the current pool discontinuous.

On Thu, Sep 15, 2011 at 4:48 PM, Ben Pfaff <blp at nicira.com> wrote:
> Personally I'd suggest 33 for this one and increment for each
> succeeding family.  No one's ever mentioned a problem with our use of
> genetlink groups.  Since RHEL5 is probably declining rather than
> increasing in deployment, my guess is that no one ever will.
>
> On Thu, Sep 15, 2011 at 04:44:53PM -0700, Jesse Gross wrote:
>> Not really, I don't have any particular opinion on the actual number.
>> The only thing that I was concerned about is what it would look like
>> if we want to do this with the multicast groups for other families.
>>
>> On Thu, Sep 15, 2011 at 4:40 PM, Ethan Jackson <ethan at nicira.com> wrote:
>> > Based on my offline discussions with Jesse I arrived, rather
>> > arbitrarily, at the number 214. ??I don't know enough about the kernel
>> > to judge what a good number choice would be. ??Jesse seemed to think
>> > larger was better. ??I'll use whatever the two of you think is best.
>> >
>> > Ethan
>> >
>> >
>> > On Thu, Sep 15, 2011 at 16:31, Ben Pfaff <blp at nicira.com> wrote:
>> >> On Thu, Sep 15, 2011 at 04:10:55PM -0700, Ethan Jackson wrote:
>> >>> > Where does the number 214 come from?
>> >>>
>> >>> Experimentally I found that the number had to be fairly small. ??I
>> >>> wanted it to be large enough to be unlikely conflict to values the
>> >>> proper way. ??I also wanted a number which was arbitrary to avoid
>> >>> conflicting with other people who may be improperly hardcoding values
>> >>> like this.
>> >>
>> >> We already use genetlink groups 16 through 31 (see
>> >> datapath/linux/compat/genetlink-openvswitch.c) and group 32 (see
>> >> datapath/linux/compat/genetlink-brcompat.c). ??I don't think it makes
>> >> sense to skip all the way to 214. ??Even in 2.6.37 I only see a total
>> >> of 11 defined genetlink multicast groups, so I doubt that anyone's
>> >> going to backport a bunch of them to RHEL 5.
>> >>
>> >
>