Did you try to bridge? Therefore I don’t believe that this is caused by firewall. So to make it simple, if your kernel receives a packet from the tun interface or any interface, for that matter whose destination IP address matches the IP address of the tun interface, contains a TCP segment with destination port 80, but there’s no process “owning” TCP port 80 in the system, then yes, the packet is dropped, and depending on the type of packet, the kernel may send back a TCP RST, or an ICMP error message. You must make sure you have TCP access from “a” to “b” on the port used by simpletun by default, can be changed with -p. Nut, when I create tap0 and tap1, then create bridge br0 and br1. This script is provided below.

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I don’t understand what you’re trying to say. 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. The interesting thing is that when I typed “ifconfig -a” tap2 RX packets was incremented when the ping is isssued.

At first I assumed this strange behavior could be explained by iptables handling tun interfaces in tun/tzp strange way, but from your explanations that is not case. From what I can understand, it looks like your issues are at the application level, not at the newtork level.

Each read returns a full packet or frame if using tap mode ; similarly, if we were to write, we would have to write an entire IP packet or ethernet frame in tap mode for each write. This will try to boot the nethead uml before the uml-switch is started.


You want that the kernel only send the traffic you’re interested in to the tap interface. I use now a line with: It seems that behavior was changed between 2. It may be better for somebody who is more experienced in using vde2 to update this page and show how to get more virtualization programs to attach to the same network.

Tun/Tap interface tutorial « \1

The module seems to exist, as there is a tun. And on the second computer: But as usual, it all depends on what you’re trying to achieve.

It also contains a link to a diagram which shows the big picture of iptables packet processing: The connections marked with can be direct port-to-port ethernet cables machineleft’s eth0 to NS3’s eth0 and machineright’s eth0 to NS3’s eth1or there can tyn/tap a switch in between.

Thursday, 27 December ARA: In order to simulate some network artefacts between the client and the server, i will use “Network Simulator NS3”.

I already expected that to happen because of the nature of UDP. I’m not running much more than the standard, plus dhcp3-server, bind9 and some extra stuff like xemacs, rsync, slay, etc.

If you want the kernel to send a frame with a MAC of This is the default setup with rootstrap. In your testcase, if you had eth5 instead of the tun tjn/tap, nothing would change.

I want to forward whatever ethernet frames comes to eth0 to tap0 and eth1 to tap1. In any case, no non-root user is allowed to configure the interface ie, assign an IP address and bring it upbut this is true of any regular interface too.


But when the data is in the program’s buffer it could be changed somehow before being transmitted, for example it could be encrypted and similarly decrypted at the other end. The dst IP of the packages is The program can start using the interface right away probably configuring it with at least an IP address beforeand, when it’s done, terminate and destroy the interface.

Even if the destination address is the local machine, the packets get lost.

Activate TUN/TAP

I found an alternate way of activating the tun module via insmod. April 22, at July 15, at Note that depending on the routing setup it’s quite likely that this error message will go out the same tun interface from which it came in, and your program that is connected to the tun file descriptor should be prepared to catch tnu/tap packets.

We’ll come back to this below. By the way, In ifconfig, the counter of drop and error are all 0. What happens if there is a rule to drop all from eth1, will it reach the tun after all the real interface is down?