hi, this is potentially a dumb question, but I think not. I've been struggling with how to accomplish some basic networking from userland. I'm familiar with /dev/tun (i once moved it into bsd, so I understand how it works). And I'm familiar with AF_PACKET. I have a big application which emulates an entire computer. It wants to pretend it has a raw network interface. Right now it uses AF_PACKET. This works fine as long as you talk to a machine on the local wire. But it does *not* work if you want to talk to the computer which is running the application. A known problem. A raw socket write shoots the packet out to the ethernet driver and it never gets back into the local kernel. The 'typical' setup is to assign the emulator application an IP address which is on the local wire, often adjacent to the host which is running the application. i.e. if the linux host running the app is 192.168.1.1 the emulator app would be assigned 192.168.1.2. So, I thought about /dev/tun. This would work fine also, but would require some routing work. Both sides end up being a point-to-point link, so you could use a host netmask (i.e. 255.255.255.255) and burn one address but this is a pain. It requires proxy arp and a route to talk to hosts on the local wire. Also the /dev/tun is only really needed in the case where we are talking to the local host, so some 'switching' might be a solution (where switching==hack). It seems like the emulator network code could notice if it's talking to the local host and if so use the /dev/tun and if not use the AF_PACKET socket. seems like a pain. Not the first time I've run into this. Most emulators with network interfaces run into this on linux but not other os's. It seems freebsd does not have this problem. perhaps there is a little code in freebsd at the bottom of the AF_PACKET send code which notices if we are sending to the mac address of the local host? So, I was wondering if I'm missing something obvious. In a perfect world the emulator application could co-exist on the local ethernet interface *and* talk to the host computer as if it were another host on the same wire. any suggestions? -brad - : send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
