On Sun, 2007-06-03 at 19:18 +0200, Jan Engelhardt wrote: > On Jun 3 2007 18:00, Andrew Beverley wrote: > >On Sun, 2007-06-03 at 13:12 +0200, Jan Engelhardt wrote: > >> Adds the connlimit match that has been in POM-NG for a long time. > >> > >> * works with 2.6.22, xtables'ified and all that > >> > >> * will request nf_conntrack_ipv4 upon load > >> (otherwise it hotdrops every packet - a glitch that goes back > >> to at least 2.6.20.2) > > > >Excellent! This has been at the back of my mind for a while. > > > >Is there any chance of getting UDP flows added as well as TCP > >connections? > > I dare to say it's easy. The real problem is rather, that UDP is > connectionless, so for one, connlimit can, by definition of the word > 'connectionless', not apply to UDP, though it is technically > possible. Understood. > Second, because UDP "connections" "fly" (timeout after 30 > seconds), just spewing one UDP packet out may kill another connection > (e.g. if you use connlimit in conjunction with DROP or REJECT). I see what you mean, although I personally would use this with an IPSET target, and I would argue it is the responsibility of the administrator to ensure it is used correctly. > What's more, UDP packets can be easily forged, much more than TCP, so > anyone on the same subtree (not subnet, because that's something > different) can send a bogus UDP packet and stop your connections from > working. I didn't know that, but I doubt anyone where I would use it would be able to do that :-) > Let's see how to implement UDP counting... The alternative, as I see it, is to adapt hashlimit to have an option to limit by number of different concurrent streams to different port numbers (but same source/destination IP address). However, I personally think it would sit better in connlimit, even if UDP is not a connection by strict definition. Is it something you would consider, or shall I look at it myself? With regards to Patrick's comment, IIRC this was one of the points he originally raised. Regards, Andy Beverley
