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

[Ethan Jackson]

33 it is!

I'm going to consider this patch reviewed.

Ethan

On Thu, Sep 15, 2011 at 17:11, Jesse Gross <jesse at nicira.com> wrote:
> I don't really think this all that important.  Neither moving the
> range that we allocate from nor making it discontinuous is that hard.
> Like I said before, I don't really care that much.  33 is fine.
>
> On Thu, Sep 15, 2011 at 5:06 PM, Ben Pfaff <blp at nicira.com> wrote:
>> I can't argue with that.  We could add a way to query it, I guess, if
>> really necessary.
>>
>> On Thu, Sep 15, 2011 at 05:04:16PM -0700, Jesse Gross wrote:
>>> I meant moving the group of fallback IDs would break things.
>>>
>>> On Thu, Sep 15, 2011 at 5:01 PM, Ben Pfaff <blp at nicira.com> wrote:
>>> > It wouldn't break the ABI to move either pool around, because those
>>> > aren't hardcoded in userspace, only in the kernel. ??A discontinuous
>>> > range would also work but wouldn't be necessary.
>>> >
>>> > On Thu, Sep 15, 2011 at 04:55:56PM -0700, Jesse Gross wrote:
>>> >> 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.
>>> >> >> >>
>>> >> >> >
>>> >> >
>>> >
>>
>