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2019-01-31-network-dev.txt
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2019-01-31-network-dev.txt
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Getting started with Genode network developments
Yesterday afternoon I had to take care of duties that kept me away
from the office, so motivated by a
[https://lists.genode.org/pipermail/users/2019-January/006581.html - question]
on the mailing list last week, I decided to write down some handy tips
related to Genode developments and networking.
For many tasks in OS development like driver and kernel debugging a
dedicated test machine is essential, at least at a certain stage of
developments. But for the development of hardware-agnostic components,
for example network protocols or applications, the Genode/Linux
platform _base-linux_ perfectly fits most purposes. Keeping the
code-compile-test cycle on one PC rewards the developer with a quite
efficient workflow that takes boot times completely out of the loop
and also allows the use of powerful tools like GDB or even
[http://oprofile.sourceforge.net - OProfile].
Therefore, base-linux comes with a _linux_nic_drv_ that utilizes Linux
TUN/TAP devices to participate in a virtual ethernet. This approach
may sound familiar as it can also be applied with Qemu.
Static IP configuration
-----------------------
An init start node for linux_nic_drv looks is follows.
!<start name="linux_nic_drv" caps="130" ld="no">
! <resource name="RAM" quantum="20M"/>
! <provides><service name="Nic"/></provides>
! <config>
! <nic mac="02:00:00:00:00:01" tap="tap0"/> <!-- optional -->
! </config>
!</start>
As you can see the used MAC address and the TAP device name are
configurable in the '<config>' sub-node. Side node: linux_nic_drv is a
hybrid Genode component, which means it is part of the Genode system
running on Linux but also links to host libraries to access Linux
resources, in this case the TAP device. Therefore, the component is
required to be loaded by the Linux loader, e.g.
_/lib/x86_64-linux-gnu/ld-2.23.so_, which is expressed by the
'ld="no"' start-node attribute.
The ready to test run script _netperf_lwip.run_ can be found in
_repos/ports/run_. On base-linux, this scenario configures the
[https://hewlettpackard.github.io/netperf/ - Netperf] _netserver_ to
use the static IP configuration '10.0.2.55/24' and linux_nic_drv on
'tap0'. So before trying it out you have to setup the TAP device as
follows.
!dev=tap0
!user=developer
!
!ip tuntap add dev $dev mode tap user $user
!ip address flush dev $dev
!ip address add 10.0.2.1/24 brd 10.0.2.255 dev $dev
!ip link set dev $dev addr 02:00:00:ca:fe:01
!ip link set dev $dev up
I usually add the statements above to _/etc/rc.local_ of all my Ubuntu
development hosts during installation and immediately forget about
them. Now, you may try the scenario in an _x86_64_ build directory.
!make run/netperf_lwip KERNEL=linux
!...
![init -> nic_drv] no config provided, using tap0
![init -> netserver_genode] lwIP Nic interface up address=10.0.2.55...
!...
!Run script execution successful.
Let's make it dynamic
---------------------
The first step to a real dedicated development network is to replace
static IP configuration by DHCP. This is by far no sourcery and just
needs a small shell script and a configuration file for the dedicated
DHCP server, in my case the ISC DHCP server, which can be installed on
Ubuntu like follows.
!sudo apt install isc-dhcp-server
!sudo systemctl disable isc-dhcp-server
I disabled the system-wide configuration of the server because it can
be started on demand.
!# tap0-dhcpd.sh
!
!netdev=tap0
!dhcpd_conf=$netdev-dhcpd.conf
!dhcpd_conf_file=$(readlink -e "$dhcpd_conf")
!dhcpd_pid_file="/tmp/$netdev-dhcpd.pid"
!dhcpd_lease_file="/tmp/$netdev-dhcpd.lease"
!
!echo -n "" > $dhcpd_lease_file
!sudo chown dhcpd:dhcpd $dhcpd_lease_file
!
!sudo dhcpd -d -f -cf $dhcpd_conf_file \
! -pf $dhcpd_pid_file -lf $dhcpd_lease_file "$netdev"
The following configuration file provides a dynamic pool for virtual,
locally-administered MAC addresses beginning with '02:' and explicit
MAC-address-based host entries.
!# tap0-dhcpd.conf
!
!ddns-update-style none;
!authoritative;
!
!class "virtual" { match if (substring(hardware, 1,1) = 02); }
!
!subnet 10.0.2.0 netmask 255.255.255.0 {
! option broadcast-address 10.0.2.255;
!
! pool {
! max-lease-time 120;
! range 10.0.2.128 10.0.2.199;
! allow members of "virtual";
! }
!
! host test-host {
! hardware ethernet 12:00:00:00:00:01;
! fixed-address 10.0.2.99;
! }
!}
For testing the configuration, we enter the directory
_<build-dir>/var/run/netperf_lwip/genode_ and open the _config_ file
in our editor. First we apply the following change (remove lines
starting with *-* and add lines starting with *+*).
!-<lwip ip_addr="10.0.2.55" netmask="255.255.255.0" gateway="10.0.2.1"/>
!+<lwip dhcp="yes"/>
Now, run tap0-dhcp.sh in a separate terminal and restart the scenario
(without the actual netperf test).
!./core
!...
![init -> netserver_genode] lwIP Nic interface up address=10.0.2.128...
Great, netserver requested it's IP configuration via DHCP and was
offered a lease from the dynamic pool, which can also be seen in the
dhcpd terminal.
!DHCPDISCOVER from 02:00:00:00:00:01 via tap0
!DHCPOFFER on 10.0.2.128 to 02:00:00:00:00:01 via tap0
!DHCPREQUEST for 10.0.2.128 (10.0.2.1) from 02:00:00:00:00:01 via tap0
!DHCPACK on 10.0.2.128 to 02:00:00:00:00:01 via tap0
Not convinced? Okay let's ping the new host for testing.
!> ping -c 1 10.0.2.128
!PING 10.0.2.128 (10.0.2.128) 56(84) bytes of data.
!64 bytes from 10.0.2.128: icmp_seq=1 ttl=255 time=1.75 ms
!
!--- 10.0.2.128 ping statistics ---
!1 packets transmitted, 1 received, 0% packet loss, time 0ms
!rtt min/avg/max/mdev = 1.750/1.750/1.750/0.000 ms
Testing the dedicated configuration is equally simple by adding the
following line to the nic_drv start node in the config file and
restarting the scenario.
!<config> <nic mac="12:00:00:00:00:01"/> </config>
!./core
!...
![init -> netserver_genode] lwIP Nic interface up address=10.0.2.99...
!DHCPDISCOVER from 12:00:00:00:00:01 via tap0
!DHCPOFFER on 10.0.2.99 to 12:00:00:00:00:01 via tap0
!DHCPREQUEST for 10.0.2.99 (10.0.2.1) from 12:00:00:00:00:01 via tap0
!DHCPACK on 10.0.2.99 to 12:00:00:00:00:01 via tap0
!> ping -c 1 10.0.2.99
!PING 10.0.2.99 (10.0.2.99) 56(84) bytes of data.
!64 bytes from 10.0.2.99: icmp_seq=1 ttl=255 time=1.78 ms
!
!--- 10.0.2.99 ping statistics ---
!1 packets transmitted, 1 received, 0% packet loss, time 0ms
!rtt min/avg/max/mdev = 1.786/1.786/1.786/0.000 ms
Beyond toying
-------------
At some stage of network development it is time to move the scenario
to real hardware nodes in a dedicated development network. The simple
framework above is a good starting point and already enables to
configure nodes based on their MAC addresses and also supports virtual
ethernet devices like those behind the
[https://github.com/genodelabs/genode/tree/18.11/repos/os/src/server/nic_bridge - nic_bridge]
component. You only have to adapt the static IP configuration for the
NIC connected to the development network, set the 'netdev' in the DHCP
server script and the IP pools/entries in the DHCP server config
accordingly.
In the next post of this series I'll address the development-network
configuration including DHCP, network booting, and controlling
multiple test machines in parallel.
| networking debugging howto linux tooling