Johannes Berg wrote: > On Wed, 2007-07-04 at 16:12 +0200, Patrick McHardy wrote: > >>Johannes Berg wrote: >> >>>Hey, >>> >>>Looking through the code that uses NL_NONROOT_SEND I just realised that >>>it's impossible to send multicast messages from userspace to multicast >>>groups with IDs higher than 31. That's not really good given that >>>everywhere else we handle multicast groups up to 2^32-1 :/ >> >> >>Why do you want to send to a multicast group from userspace? > > > Why not, what's wrong with that?
The kernel doesn't have any multicast listeners (yet). > Actually, I think I mentioned this earlier, I was thinking about doing > wireless configuration as a group where both the kernel and possibly a > userspace process listen on that multicast group and processes that want > to configure a device just send to that group. Then the kernel ignores > the message if a userspace process is handling the specific device > completely. For example changing the BSSID: if the kernel is doing MLME > then it changes the BSSID, but if a userspace process is doing it then > the kernel doesn't do anything since BSSID changing is a pure MLME > function, but for consistency it'd be nice if both could be done the > same way, hence a multicast group. > > This was actually suggested by Herbert since it's easy to find out if > that multicast group has a listener and not so easy if a special generic > netlink socket in userspace is (still) open. I wonder if thats really a good idea to use multicast for device configuration. Unicast transmissions from userspace to kernel are reliable when you don't use MSG_DONTWAIT. For multicasts doing the same would mean blocking on each receiver when the receive queue is full. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
