On Fri, Jan 22, 2010 at 11:09:43AM +0100, Patrick McHardy wrote: > Fredrik Ax wrote: > > Hi guys, > > > > I'm a pretty experienced Linux / network developer and administrator, > > but I can't get my head around this one. > > > > The long story is that I have a box used as router/fw/proxy running > > Debian Squeeze with a customized 2.6.32 x86_64 kernel having three > > interfaces (eth2,eth3,eth4) on the same external subnet. One of the > > interfaces is used for doing masquerading of other > > subnets. Masquerading (not snat) is chosen because the interfaces are > > on dhcp, and I don't want to have to rewrite the fw rules each time I > > get a new addr ... already have enough with dhclient-hooks for fixing > > the routing tables dns-updates, etc ;-) What I basically want to do is > > make the proxy's request to go out the same ifc as the masqueraded > > packets getting a src addr of s41.s42.s43.s44. Other locally generated > > packets should get a src addr s21.s22.s23.s24. > > > > To accomplish this I'm using iptables to mark all, to port 80, locally > > generated tcp packets: > > > > % iptables -t mangle -vnL OUTPUT > > Chain OUTPUT (policy ACCEPT 3234 packets, 2254K bytes) > > pkts bytes target prot opt in out source destination > > 1114 181K MARK tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 MARK set 0x4 > > > > I have verified that the iptables rule marks them fine enough. > > > > Then the ip rule with prio 99 below should then catch them and route > > according to table eth4 below. That rule however does, for some reason > > not match those packets, instead they are routed according to table > > eth2 below (prio 200 rule), getting src addr s21.s22.s23.s24. If I > > disable that rule they are routed according the the prio 300 rule > > (getting src addr s31.s32.s33.s34). > > > > ... > > > > > > What am I doing wrong here? > > Source address selection happens before the packet is even generated, > so iptables marking in OUTPUT can't affect it. So, to accomplish this I would have to oute it through a dummy interface to make iptables able to mark it before it goes out? TIA, /frax ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ -- 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
