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

[Ben Pfaff]

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.