And FYI I am using 2 virtual machines (sender, pass-through) and my host machine (receiver) just to start with. I am planning to have a physical setup similar to that later on. Thanks, Danushka On Tue, Dec 1, 2015 at 10:43 AM, Danushka Menikkumbura <danushka.menikkumbura@xxxxxxxxx> wrote: > Hello Martin, > > Thanks a lot for your quick reply. > > When I say "pass-through" node yes I mean the behavior of a router but > in this case my sender(s), pass-through node (i.e. router) and > receiver are all in the same subnet. In other words, the pass-through > node does not bridge two subnets. I hope you get the picture. > > Basically what I am trying to do is to stress the pass-through node to > test the performance of a Qdisc that I am currently working on. > > Can I follow the pointers given by you to have a setup like that?. > > I really appreciate your help as I am kind of stuck with this. > > Thanks, > Danushka > > On Tue, Dec 1, 2015 at 10:10 AM, Martin A. Brown <martin@xxxxxxxxxxxx> wrote: >> >> Hello Danushka, >> >>>I am trying to use a Linux box as a pass-through node using rinetd >>>as a port forwarding mechanism. I see that TOS is always zero on >>>the egress path so that my receiver does not receive the TOS values >>>I set on the sender. >> >> Do you need the TCP session to be terminated in userspace (and >> re-initiated)? That's what's happening with rinetd. You are using >> it as a TCP proxy. The Linux box is acting as a (TCP) receiver on >> one side, and initiating a brand new TCP connection outbound. >> That's why the ToS value is changing. >> >> Next question: When you say 'pass-through' node, I am not certain >> what you mean. Do you want your Linux box to act like a router? >> If so, then, that's very easy: >> >> sysctl -w net.ipv4.ip_forward=1 >> >> Now, you have a router. Send packets to the ultimate destination >> from your sender node. Make sure that you configure your routes >> properly (maybe that's already done). >> >>>Is there a way to solve this issue?. Maybe rinetd does not copy the >>>values properly?. >> >> I do not know rinetd. Perhaps somebody else does. >> >>>Probably there is a better/smarter way to do port forwarding (getting >>>my Linux box to work just as a pass-through node). Please let me know >>>if there is any other way to do that. >> >> How many values are you changing in the packet? Just the >> destination port? Also the destination address? >> >> I'm thinking that iptables NAT may provide you a solution. Assuming >> you are just messing with the destination address and port, you >> should be able to use iptables DNAT. I'd suggest reading these: >> >> http://linux-ip.net/html/nat-dnat.html >> https://www.frozentux.net/iptables-tutorial/chunkyhtml/x4033.html >> >> Good luck, >> >> -Martin >> >> -- >> Martin A. Brown >> http://linux-ip.net/ -- To unsubscribe from this list: send the line "unsubscribe lartc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
