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

[Ethan Jackson]

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.
>