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Using lo interface for testing

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by kk_davey

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Hi

I've installed a kernel module that was written to enhance the TCP protocol for wireless networks by calculating network congestion at a wireless access point and passing this value on to the receiver.

To implement this enhancement I install a module at the router, and another at the receiver. I'd like to be able to test this on a stand alone computer, which I assume I use the lo interface for. Can my stand alone computer simulate a TCP connection using lo, meaning it would have to act as the sender, the router, and the receiver?

I.e. can I set up lo to simulate a connection (with limited transmission rate) whereby the packet travels down the protocol stack, to the wireless access point (where the router adds the congestion value to the TCP options), to the receiver, where it travels back up the stack, and the inserted congestion value can be interpreted appropriately.

Is this possible to simulate using lo?

5 replies

by jmgarvin

No. You have to use ath0 (or whatever your wireless card is) to actually transmit to the AP. lo is only your local interface.

by jmgarvin

If I understand this properly (and I probably don't, because I am pretty dense sometimes) you need a testbed for your firewall and a wireless connection.

Keep in mind your firewall will have nominal impact on your wireless security other than the actually wire going to the wall. Why? Anybody can connect to you ad-hoc (which means they can connect to your wireless card directly).

Anyway, on to the show. I think what you could do is create a ruleset for eth0 and then test it that way from another local box.

If you check out my blog https://www.techrepublic.com.com/5247-6257-0.html?id=4093177, you might glean some information from there.

Anyway, your best bet would be to put these rules (in order)
default policy incoming = drop
accept all lo
open the ports you need (eg DHCP, DNS, and HTTP)

Does that clarify any?

by kk_davey

Thanks very much. That did help - I'm sorry I took so long to get back to you (I only just noticed that rating function - looks like I can be a bit dense too!).

by kk_davey

Thanks for your response. I do understand that if I used something like the lo interface that it wouldn't be a wireless link. I was hoping to do some testing though (as I write/modify the code) before I transferred the code to the wireless test bed. As the testbed is a shared resource I don't want to have to transfer the code across everytime I make a change just to test that the change is ok.

Is there any other way I can test the code on a stand alone computer - remembering that it's a TCP change so the module code doesn't know if it's a wireless or a wireline link. It can therefore be used on an ethernet connection. The crucial part is that the receiver and the link/router before the receiver both have the appropriate modules installed on them.

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