I’m not sure I understand what you’re trying to do. There is no traffic going through the interface. Android unfortunately has support only for tun. Here’s an example of how to do it. But for the writing internally, it doesn’t work. July 19, at Without knowing the details of the kernel bridge implementation, I would check, in random order:.

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Honestly I dont fully understand what it does If instead you need to do something special or specific to your task that cannot be accomplished with existing tools, then of course writing your own code C or otherwise is the way to go.

As a variation, the name of the virtual interface can be left unspecified, in which case the kernel will pick a name by trying to allocate the “next” device of that kind for example, if tap2 already exists, the kernel will try to allocate tap3, and so on. At this point, you will probably want to enable masquerading to get the tap network access to the local network or internet.

The virtual interfaces are destroyed by root, for example by scripts run at shutdown time, perhaps using tunctl -d or equivalent Let’s try it After this lengthy but necessary introduction, it’s time to do some work with it. The interesting thing is that when I typed “ifconfig -a” tap2 RX packets was incremented when the ping is isssued.

For the client, it’s ” Ah, I see, I was looking at an old version.

I was just trying to find a way to write to a tap interface when a user program constructs a frame. I create a user-mode tunnel using tunctl, but get a strange error message at run time. If the other end’s firewall is dropping IPv4 packets, it may look like the peers are connected whereas they are not.


August 14, at Do you know of a way to force tap0 to act as it did in earlier versions of the kernel? I have Linux version 3.

OpenVPN Overview

Another nice multipurpose network tool: Difficult to tell without seeing the real thing, but in my experience, ethernet frames you read from the tap interface do not have a preamble, if by that you mean the “” etc. Thanks much for taking the time to find all this out — I can make progress again! Is this a legitimate usage of tun at all? They are not the latest and greatest, but surely can provide a solid foundation and plenty of material to build upon. If I change the src IP of the intercepted packet,recalculate the required checksum and re-inject that packet, the packet gets forwarded to the proper interface.

So, I’m expecting that tap will forward the packet up in the layer. Installation Install the openvpn package on both client and server. This means that you can have 10 machines in London for instance and 50 in Berlin, and you can create a computer ethernet network using addresses from the How can I make it work as tap.

Since this machine will be set to run the whole time that the tap network is enabled, we want to make it’s memory footprint as small as possible. I guess the problem I’m having is that when I open the file descriptor as described in the article and write some ethernet frames to it using a tap interfacethe kernel doesn’t respond to the frames, like if the ethernet frames are ARP frames asking for the MAC address of the IP assigned to the tap0 interface, if I write them to tap0, I can see them with tcpdump, but the kernel does not send ARP replies back to my user application, like I would expect So no error is returned.


I just tested a code I found online to send and receive ethernet raw frames but I’ve not used it on a virtualinterface yet.

Enable Linux Tun Module for VPN Use on Ubuntu or Debian – Linuxsecrets

I have recalculated all the relevant checksums. This needs further investigation. It would be good reference as well as good agenda for me.

For some reason when I do a read I am always 8 bytes short in the value returned for the number of bytes read. As a shot-in-the-dark suggestion, see if you can use a bridge on the physical host as a “virtual switch” to which to connect the tin/tap interfaces of the guests.

Are you pinging a non-local IP address ie, one that would cause the kernel to actually send the data out, as opposed to replying directly? But that’s not enough to start using it to communicate with the interface.

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