tcp_terminal on linux

Christian Helmuth christian.helmuth at ...1...
Fri Feb 3 09:16:20 CET 2017

Hello Prashanth,

On Thu, Feb 02, 2017 at 05:19:46PM -0800, Prashanth Mundkur wrote:
> After disabling the have_spec check, I can compile and run it.  After
> setting the suid bit on drivers/nic/spec/linux/nic_drv to allow it to
> access /dev/net/tun, I get the following output:

Just a remark to prevent setting suid: I setup my tap0 device so that
in can be used by my user ID like follows in /etc/rc.local on Ubuntu.

  # Setup tap device for base-linux tests
  user=<YOUR USER ID>

  ip tuntap add dev $dev mode tap user $user
  ip address flush dev $dev
  ip address add brd dev $dev
  ip link set dev $dev addr 02:00:00:ca:fe:01
  ip link set dev $dev up

But now to your question...

> Though I can see the tap device,
> 15: tap0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
>     link/ether c2:60:31:f8:52:fc brd ff:ff:ff:ff:ff:ff
> I don't see any listening socket on port 8888.
> So clearly there is some missing plumbing.  What do I need to do to
> fill that in?

If you mean you can't see any listening program on port 8888 on your
host machine that's expected. Genode is running in a virtual network
behind the tap0 device. Additionally, the log states that the
tcp_terminal uses DHCP for network configuration but you may not run a
DHCP server on tap0. Now you have two option: Configure a DHCP server
to serve a private network behind tap, e.g.,, or (much
simpler) configure tcp_terminal statically. Therefore you apply the
following changes to the run script (assuming the example network

    <start name="tcp_terminal">
  -     <libc stdout="/dev/log">
  +     <libc ip_addr="" netmask="" gateway=""
  +           stdout="/dev/log" stderr="/dev/log"/>

The terminal should then be accessible at

Christian Helmuth
Genode Labs · · /ˈdʒiː.nəʊd/

Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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