On Wed, 18 Nov 2015 22:47:02 +0100 David TAILLANDIER - DIGI VALUE <david.taillandier@xxxxxxxxxxxxx> wrote: > > Hi, > > according to the well-known netfilter schematic: > http://inai.de/images/nf-packet-flow.png > the "raw" table is processed before the "filter" table. > > I tested it with some usual commands without problem: > iptables --table raw --append PREROUTING --source 1.2.3.4 --jump REJECT > iptables --table raw --append PREROUTING --in-interface lo --jump ACCEPT > > - the packets are handled sooner, without the need to go though > conntrack+mangle+nat+routing. So less CPU/memory stress (and in turn > lightly compensated by the fact the iptable_raw module has to be > loaded ?) > - only one rule in case the box is also a router (won't be ok for > every rules, obviously) because there is no need to add the same rule > for filter/forward > > The documentations I found always describe the raw table to be used in > strict cases. But none give even the smallest justification. > > --> Is there any reasons not to use the raw table, apart dogmatic ones ? Don't have an answer, but I'll have to look into 'raw' for Smoothwall Express. I'll use pert near *anything* that will reduce 'wasteful' CPU load. Combined with ipset, it should be possible to drop all packets to and from 'banned' public IPs using fewer CPU cycles. I already drop INVALID in mangle:PREROUTING. Dropping packets to and from banned addresses in raw:PREROUTING and rejecting packets to banned IPs in raw:OUTPUT would reduce unneeded processing. Of course, this idea depends on whether ipset can be used in the raw table. One drawback is that NAT doesn't have a chance to re-address these packets. But this might not be too bad, since one doesn't want any traffic to or from banned IPs anyway. Neal -- To unsubscribe from this list: send the line "unsubscribe netfilter" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
