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Re: How can I get the Linux Synthetic Target to use DHCP?

[Redirected from ecos-devel]

On Wed, 5 Jan 2011, Michael Bergandi wrote:

> Sergei,
> > If you use an original 'ethernet.tdf' config file
> >
> > That is
> >
> > % egrep -v '(#|^\s*$)' $ECOS_REPOSITORY/devs/eth/synth/ecosynth/current/host/ethernet.tdf
> >
> > synth_device ethernet {
> > Â Âeth0 ethertap tap3 00:FE:42:63:84:A5
> > Â Âmax_buffer 32
> > }
> >
> > Let's notice that *ethertap* tap3 interface is used there.
> Yes, I get the tap3 created.
> tap3      Link encap:Ethernet  HWaddr b2:13:57:48:9e:f3
>           inet6 addr: fe80::b013:57ff:fe48:9ef3/64 Scope:Link
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:25 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:44 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:500
>           RX bytes:7650 (7.6 KB)  TX bytes:10945 (10.9 KB)
> > Have you configured 'tap3' interface?
> $ ifconfig tap3 up
> $ ifconfig tap3
> tap3      Link encap:Ethernet  HWaddr f6:9d:ca:9d:df:8c
>           inet6 addr: fe80::f49d:caff:fe9d:df8c/64 Scope:Link
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:14 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:500
>           RX bytes:4788 (4.7 KB)  TX bytes:308 (308.0 B)
> > Have you configured DHCP server on the interface? If you done it, Can you get IP address from DHCP pool on  the interface:
> This is the problem. I am on a network which is running a dhcp server.
> I don't have a specific dhcp server running on the host to handle only
> that interface. Is that required?
> Do I need to bridge the tap3 interface with an eth0/eth1 to get an
> address from the dhcp server on the network?
> > % sudo dhclient3 tap3
> This just does what the hello-net app is already doing. No surprise,
> it never gets an address either.
> > There should be no surprise for you that if you want to use DHCP for
> > synthetic target you have to configure and networking too.
> Yeah, I expected to have to configure the networking some how.
> Unfortunately, this is not in any of the documentation. I would expect
> that there would at least be some mention of using dhcp with a
> networked synthetic target app. Maybe even generalized steps for
> getting your host configured to get it working.
> > Well, I can guide how to get it working on Ubuntu, but I doubt that this
> > list is the appropriate place for this.
> That would be great.
> I do think that this and probably the user list is the appropriate
> place to address usage issue resulting from deficiencies in
> documentation. Perhaps I can contribute some documentation once we get
> this worked out.


I attach one-page SYNOPSYS (I wrote it in a past for myself to remember
details :-). Of course, I had the simplest environment (a standalone WS)





This is a short SYNOPSYS without any gory details!

Install User Mode Linux utilities

There is an utility (tunctl) to manage persistent TUN/TAP interfaces.

% sudo aptitude install uml-utilities

Configure TAP interface

  â Add to /etc/network/interfaces

    auto tap0
    iface tap0 inet static
            pre-up /usr/sbin/tunctl -t tap0

Test new TAP interface

 1. ifup

    % sudo ifup tap0
    Set 'tap0' persistent and owned by uid 0

 2. ifconfig

    % ifconfig -a tap0
    tap0     Link encap:Ethernet  HWaddr 5a:09:c7:66:88:8d
              inet addr:  Bcast:  Mask:

 3. ping

    % ping -c 4
    PING ( 56(84) bytes of data.
    64 bytes from icmp_seq=1 ttl=64 time=0.110 ms
    64 bytes from icmp_seq=2 ttl=64 time=0.097 ms
    64 bytes from icmp_seq=3 ttl=64 time=0.098 ms
    64 bytes from icmp_seq=4 ttl=64 time=0.094 ms

    --- ping statistics ---
    4 packets transmitted, 4 received, 0% packet loss, time 2999ms
    rtt min/avg/max/mdev = 0.094/0.099/0.110/0.013 ms

Install DHCP client and server

Perhaps, you have got it installed. Check that there is no listener for port #
67 (bootps port).

% netstat -lun | grep ":67"

If you have seen no output, intstall DHCP stuff:

% sudo aptitude install dhcp3-{server,client}

Configure DHCP server

  â Add to /etc/dhcp3/dhcpd.conf

    subnet netmask {

  â Either edit /etc/default/dhcp3-server and set


  â or use dpkg-reconfigure for that

    % sudo dpkg-reconfigure dhcp3-server

  â Restart DHCP server

    % sudo /etc/init.d/dhcp3-server restart

Test DHCP server from host

  â Reqest an address from server

    % sudo dhclient3 tap0
    Listening on LPF/tap0/5a:09:c7:66:88:8d
    Sending on   LPF/tap0/5a:09:c7:66:88:8d
    Sending on   Socket/fallback
    DHCPDISCOVER on tap0 to port 67 interval 8
    DHCPOFFER of from
    DHCPREQUEST of on tap0 to port 67
    DHCPACK of from
    bound to -- renewal in 255 seconds.

  â Release got address (optional)

    % sudo dhclient3 -r tap0
    Listening on LPF/tap0/5a:09:c7:66:88:8d
    Sending on   LPF/tap0/5a:09:c7:66:88:8d
    Sending on   Socket/fallback
    DHCPRELEASE on tap0 to port 67

Test DHCP server from eCos

 1. Configure eCos

    % ecosconfig -q new linux net

    create minimal config file (hw_test.ecm)

    ## minimal hw_test.ecm file
    cdl_option CYGPKG_NET_BUILD_HW_TESTS {
        user_value 1

    and import this file

    % ecosconfig import hw_test.ecm

 2. Build eCos

    % ecosconfig tree
    % make

 3. Build DHCP test

    % make -C net/common/current tests TESTS=tests/dhcp_test

 4. Create minimal target definition file (ethernet.tdf)

    ## minimal ethernet.tdf file
    synth_device ethernet {
        eth0 ethertap tap0 11:22:33:44:55:66
        max_buffer 32

 5. Run DHCP test as

    % ./install/tests/net/common/current/tests/dhcp_test \
            -io -nw -t ethernet.tdf

    and at the end you have to see in a terminal something like below

    BOOTP[eth0] op: REQUEST
           htype: Ethernet
            hlen: 6
            hops: 0
             xid: 0x1b535566
            secs: 24
           flags: 0x80
           hw_addr: 11:22:33:44:55:66
         client IP:
             my IP:
         server IP:
        gateway IP:
            DHCP message: 3 REQUEST
            DHCP server id:
            DHCP time 51: 600
            DHCP time 58: 300
            DHCP time 59: 525
            subnet mask:
            domain name:
            DHCP option: 37/55.9: 54 51 58 59 1 3 6 15 28
            DHCP option: 39/57.2: 576
            DHCP requested ip:
    $ PASS:<Dhcp test OK>

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