[ovs-dev] [mcgroup 4/4] dpif-linux: Handle nl_lookup_genl_mcgroup() failures.

[Ben Pfaff]

On Wed, Sep 14, 2011 at 05:55:34PM -0700, Ethan Jackson wrote:
> The nl_lookup_genl_mcgroup() function can fail on older kernels
> which do not support the required netlink interface.  Before this
> patch, dpif-linux would refuse to create a datapath when this
> happened.  With this patch, it attempts to use a workaround.  If
> the workaround fails it simply disables the affected features
> without completely disabling the dpif.

In the future, it is possible that we will want a fallback for other
multicast groups as well.  Would it make sense to make the fallback
group an argument to nl_lookup_genl_mcgroup(), with zero to disable
fallback?  (Of course nl_lookup_genl_mcgroup() would still log a
message that the fallback was in use.)  Then it will simplify later
work, if there is any.

Thanks,

Ben.