Also, what does it mean “there is not a tunnel”? I discovered that I can create the tap devices using iproute2, and then connect to them later on in my program. Hi Waldner, This is a great tutorial given the rather sketchy txt file that comes with the Tap Tun interface and has helped me get a tap interface up and running. If all this works out, your packet should indeed reach yahoo, which will reply with an ICMP echo reply packet. Although netstat shows a tun interface joins the ff I see the correct number of bytes..

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But apart from that the interface is working. What happens when we ping to a tun interface.

It seem to allow this since I can send udp packets to many listing servers on different hosts at the other end of my tunnel. Is anybody have an idea why this isn’T workin? Output for some coomands which may be of use are:. If the destination address is local, why should the kernel send the packet out tunta the wire?

tcp – How to properly configure a tun/tap Interface in linux? – Unix & Linux Stack Exchange

It seems that behavior was changed between 2. I suppose that, since Llnux is Linux well, kind of sort ofyou may be able to connect to the tun interface as explained in the article or use existing tools, but I have limux tried so this is all guessing. Well, we could for example emulate the behavior of the target of the traffic we’re reading; again, to keep things simple, let’s stick with the ping example. In such a way, I can use the same interfaces for other applications i.


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September 21, at Tun devices are purely layer 3, that is, they don’t really have a MAC address both “ip link” and “ifconfig” show that. My process listening to the tun device file descriptor can read these packets.

Tungap or resource busy” I tried the forking and pthreading yet still the result is the same. If you do the math, you’ll see where these 84 byetes come from: Probably, if you set tap2 in promiscuous mode via iproute2 or from your code the frame would be accepted and your application would see it.

Natural Born Coder

If you plan to use existing tools to connect to the tap interface, then it’s probably quicker and easier to also use existing tujtap to create it eg iproute2, tunctl, openvpn can all do itso you don’t have to bother with writing code yourself. Thanks for your help.

I also see that the initial 4 bytes of the frame is chopped like below using tcpdump.

After all, hardware switches don’t have MAC addresses. I will send a burst of 20 packets, but only read say 12 or 15 random amount each time from the tun1 device.

Lknux operation as with any open call returns a file descriptor.

Understanding TUN TAP Interfaces – Natural Born Coder

Thanks for the reply. I was just trying to find a way to write to a tap interface when a user program constructs a frame. October 27, at I didn’t really understand why. Skip to content Home About Feed.


I think I could use the TAP to redirect the frames from the program A to the program B and be able to modificate them before sending them normally. Without knowing the details of lihux kernel bridge implementation, I would check, in random order:. I posted a message describing a similar problem, but wanted to reply utntap in hopes this reaches you.

Then, I simply leave the tap devices created always and I they persist after my program exits.

I would really appreciate if you could libux me what mistake am I making here? Can anyone suggest proper configuration steps as described above in the tutorial for linux, and also what are the recommended settings for libux.

I’ve created two taps and from my application I’m trying to capture the ethernet frame received on tap2. Ah, maybe I see.

The program uses select to keep both descriptors under control at the same time; if data comes in from either descriptor, it’s written out to the other. I think I’m not using transport or net layers only Ethernet.