tcpreplay for testing network stacks

[Chris Johns]

On 29/4/21 2:31 am, Vijay Kumar Banerjee wrote:
> On Wed, Apr 28, 2021 at 12:45 AM Chris Johns <chrisj at rtems.org> wrote:
>>
>> On 28/4/21 2:48 am, Vijay Kumar Banerjee wrote:
>>> I came across the tcpreplay tool and it looks like a nice tool for testing the
>>> network stacks. It can be used to capture network traffic and then play it back,
>>> this will help with testing the network packets from different network stacks.
>>>
>>> My proposal is to add the tcpreply as a host-side tool in rtems-tools and use it
>>> with the network interface where the network application is running. The only
>>> issue that I see with the whole idea is that the tcpreplay is GPLv3 licensed.
>>> Will that be compatible for rtems-tools? The github repository says that it's
>>> compatible with UNIX and Windows with cygwin.
>>>
>>> Source repository:https://github.com/appneta/tcpreplay
>>> <https://github.com/appneta/tcpreplay>
>>>
>>> Thoughts and suggestions are much appreciated.
>>
>> It is GPLv3 so it cannot be imported as source. It can be referenced as a
>> command if available for the host.
>>
> Ok.
> 
>> I also suggest you investigate VDE with qemu. This is what I use to avoid being
>> root.
>>
> VDE looks great, I haven't tried it before. Thanks for the suggestion!
> I'll try this out. 

No problem. Amar put me on to it years ago. I like it because I can run a few
qemu networked sessions and I do not need to be root to do this. My host set up
is simple...

>From /etc/rc.conf:

cloned_interfaces="bridge0 tap0 tap1 tap2"
autobridge_interfaces="bridge0"
ifconfig_bridge0="inet 10.10.5.2 netmask 255.255.255.0"
autobridge_bridge0="re0.3 tap0 tap1 tap2"

$ cat vde-start
#! /bin/sh
#
# vdeterm /tmp/mgmt1
#
sysctl net.link.tap.user_open=1
sysctl net.link.tap.up_on_open=1
chmod 660 /dev/tap0
vde_switch -d -s /tmp/vde1 -M /tmp/mgmt1 -tap tap0 -m 660 --mgmtmode 660

Note, I internally run a bridge that VDE attaches to and all this is layer 2.
The bridge is connected to a VLAN my engineering network runs on. You have to
expect varying levels of complexity in user networks.

> Can write some rtems-test recipes with VDE to
> automate the run? will that be feasible/possible?

This depends on the type of testing you are looking to perform and the type of
network architecture you are considering. My set up lets a qemu session see my
network. I am bridging across it via a single tap that is created when the OS
boots. I have attached some slides I put together last year on this topic.

The challenge is keeping the network infrastructure needed to a minimum, a
simple configuration, support for hardware and simulation targets and agnostic
network support.

Chris
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