I have installed the TAP-WIN32 Adapter V9 on my Windows 7 machine. I want to use TUN to read the IP packets out of the interface. I followed the C# sample from http://www.varsanofiev.com/inside/using_tuntap_under_windows.htm
I modified the code like below
IntPtr ptun = Marshal.AllocHGlobal(8);
Marshal.WriteInt32(ptun, 0, 0x0a030001);
Marshal.WriteInt32(ptun, 4, unchecked((int)0x00ffffFF));
bool val = DeviceIoControl (ptr, TAP_CONTROL_CODE (5, METHOD_BUFFERED) /*POINT TO POINT */, ptun, 8,ptun, 8, out len, IntPtr.Zero);
However, I still don't seem to get IP packets. I ran tcpdump on the other end and it complains "Wrong link layer encapsulation".
Is this the correct way of trying to get IP Packets out of TUN interface?
Answer
No, it is not the correct way. It's a pity, but tap/tun driver works only in tap mode in windows. It means that you can receive Ethernet packet, not IP. Let's consider the situation when you have some IP packet for destination address X. Before sending this packet on ethernet layer, OS creates an ARP query, hey, IP X, what is your MAC? In this case you have to implement an ARP layer. After ARP negotiations, system will send the Ethernet-encapsulated IP paket.