Category: networking

dosemu networking issues.

I have decided to stick with WWIV 4.30 under dosemu for now, as there are a number of annoying bugs under WWIV5 compiled for Linux, and I know C much better than I know C++, so I can do a number of mods in the 4.30 code that I can’t in the 5.0 code 😉 So I thought I’d set up networking under dosemu, and I noticed something quite peculiar. I decided the easiest method to get things working would be to use bridging on my ethernet card. Keep in mind that I connect to this computer via wlan0. Here is the settings in my dosemu.conf:

$_vnet = "tap
$_netdev = "tap0"

And here is my

brctl addbr br0
ifconfig eth0 promisc up
brctl addif br0 eth0
ifconfig br0 netmask up
tunctl -u 1000
ifconfig tap0 promisc up
brctl addif br0 tap0

And I go into dosemu and set up a basic tcp.cfg for use with mTCP, and I can ping out to Google by both name and IP. Great! So, I exit the emulator and go back into Linux and try to download the Microsoft TCP/IP networking stuff for DOS. No go. I try to ping Google by name. Nope. By IP? Nope. OK. Reboot, since I don’t have the bridge coming up on boot. I double check everything, all look good, and I run my script again, but don’t go into dosemu. Can’t ping Google. I can ping my default gateway, though. Hmmm… Reboot again and lets try this a command at a time:

brctl addbr br0

I can still ping Google.

ifconfig eth0 promisc up

I can no longer ping Google.

ifconfig eth0 down
ifconfig eth0 up

I can ping Google again.

So, it appears that putting eth0 into promiscuous mode is causing me to not be able to ping Google via wlan0. But if I run the script and boot into dosemu, I can reach the Internet just fine. So instead of connecting via wlan0, I connect via eth0 and the exact same thing happens. Very strange that I can’t get out to the Internet from the my host OS, but can from the guest OS. Maybe if I connect via eth0 and disable wlan0 completely… Doesn’t make sense to me that having one nic in promiscuous mode should impact the other at all, unless my router is getting confused…


Today, I had the most bizarre phone call. Co-worker comes to me and says there is an abuse issue that needs addressed on line one. So, I pick up line one, and this guy is telling me about this guy who “uses your service” (I work for an ISP) who is making online threats, photoshopping nude photos and posting them online, and is involved in identity theft, all if which violate our usage agreement. The call definitely grabs my interest, because network security is fascinating. I start asking for information. The caller tells me that the police, sheriff, and FBI have all been contacted and are involved, so he cannot give me the IP address. At this point I’m thinking “Then why am I talking to you instead of a fed,” but I don’t say anything. Instead, I inform him that first, we would need a valid subpoena to release log files (not that our logs are particularly useful) and also state that we used to have a different upstream provider which provided IP address space to us, but we gave it back even though records still show those IP addresses as being assigned to us. I tell him the address space that is, and also our CIDR block, and he tells me that the address in question isn’t part of either network. How bizarre! I explain that I would need to talk to one of the three computer guys who told him that the activity traced to our network in order to investigate further, because an issue coming from that address could not have come from us. He finally relented and gave me the IP address, and a quick trip to ARIN shows that the IP address belongs to Road Runner! I do a traceroute and find out that this particular Road Runner customer is a business class account, and 22 hops away from us. The caller finally says that he’ll take what I’ve told him back to his computer guys (why is he handling this instead of the feds?!) and will get back to me. I told him that I’d be interested in knowing how the IP traces to us, so have one of the computer guys call me so I can help them figure out what’s going on.