[P4-dev] P4Runtime with bmv2 support

Antonin Bas antonin at barefootnetworks.com
Tue Jul 17 13:09:11 EDT 2018


If you want to use simple_switch_grpc, you need to follow the steps in the
README (
https://github.com/p4lang/behavioral-model/tree/master/targets/simple_switch_grpc)
and install PI without bmv2 support (I believe --without-bmv2 is the
default actually so the flag could simply be omitted).

All of your problems seem to come from the fact that you want to use the
tutorials repo with the latest versions of PI & bmv2 & p4c. When we release
a new version of the tutorials, we use a "frozen" version of the
dependencies. So if you want to use the tutorials you have to use the
appropriate versions, as advertised here:
https://github.com/p4lang/tutorials/blob/master/vm/user-bootstrap.sh#L8
If you want to develop your own control-plane code, feel free to use the
latest version of PI & bmv2 & p4c as they should work fine together, but
don't expect the tutorial exercises to work with these.

On Tue, Jul 17, 2018 at 8:21 AM, cs.lev <cs.lev at gmx.com> wrote:

> Dear all,
>
> I would like to have proper P4Runtime support on a bare-metal server, with
> all its python bindings to write my own controllers.
>
> I have run into the following issue during configuring and compiling
> related libraries.
>
> First of all, I found there is a cyclic dependency between bmv2 and PI
> (but correct me if I am wrong), as bmv2 can be compiled with PI support
> (--with-pi) which needs the PI libraries to be installed in order to
> compile afterwards the simple_switch_grpc binary.
> However, to support bmv2 in PI, during its installation, it requires bmv2
> and its libraries.
>
> As a workaround, first I compiled PI without bmv2 support, then compiled
> bmv2 with PI support, and finally I recompiled PI with bmv2 support.
> Everything seemed to be OK, as compilation ended without errors and
> simple_switch_grpc could have been run.
>
> After trying to test (a modified version of the) p4runtime example
> (originally tailored to the mininet environment) from p4lang/tutorial,
> the python based controller has complained about missing modules.
> After a lot of googling, debugging, and comparing ENV variables of the
> p4tutorial’s VM and my bare metal installation, I have found that the
> libraries the python modules are looking for should be in
> /usr/local/lib/python2.7/dist-packages/p4/.
>
> However, the PI installation on the bare metal put all libraries into
> /usr/local/lib/python2.7/dist-packages/p4*/v1*,
> even though the configure parameter --with-bmv2 should have indicated to
> the compilation process to not put the corresponding libraries in such a
> subdirectory (v1).
>
> In the beginning, it seemed a good idea to do the following:
>
> $ cp /usr/local/lib/python2.7/dist-packages/p4/v1/*
> /usr/local/lib/python2.7/dist-packages/p4/
>
> $ cp  /usr/local/lib/python2.7/dist-packages/p4/config/v1/*
> /usr/local/lib/python2.7/dist-packages/p4/config/
> Then, the controller application was now complaining about missing modules.
> So, it indeed seemed to be a good workaround...
>
>
> BUT, (if you are still with me :)), the interesting parts started to show
> up.
> The controller could connect to the switch and even the*
> readTableRules(p4info_helper,switch)* function could have been called and
> returned without errors.
>
> At this point, I still believed that everything is working, however when I
> tried to insert flow rules into my switch, the controller raised the
> following error:
>   File "controller.py", line 86, in main
>     output_port='0')
>   File "controller.py", line 23, in addIPforwardRule
>     "port": 1,
>   File "/home/csikor/p4/p4_vlan/p4runtime_controller/p4runtime_lib/helper.py",
> line 173, in buildTableEntry
>     for match_field_name, value in match_fields.iteritems()
>   File "/home/csikor/p4/p4_vlan/p4runtime_controller/p4runtime_lib/helper.py",
> line 100, in get_match_field_pb
>     if match_type == p4info_pb2.MatchField.VALID:
> AttributeError: type object 'MatchField' has no attribute 'VALID'
>
>
> The rule inserting source code had no issues in the mininet environment,
> but for a comprehensive view I include the relevant part of it below:
> def addIPforwardRule(p4info_helper, sw):
> table_entry = p4info_helper.buildTableEntry(
> table_name="MyIngress.ipv4_lpm",
> match_fields={
> "hdr.ipv4.dstAddr": ("10.0.0.1", 32)
> },
> action_name="MyIngress.ipv4_forward",
> action_params={
> "port": 1
> })
> sw.WriteTableEntry(table_entry)
>
>
> Later on, I have found out that in contrast to other python modules, the*
> p4info_pb2* library that I have used (copied from /usr/local/lib/
> python2.7/dist-packages/p4/config/v1) is not the same as it was in the
> p4lang/tutorial's VM's python modules, which of course is somewhat expected.
>
> In order to do a workaround again, as a last resort I have copied all the
> python libraries for P4runtime from the VM's
> /usr/local/lib/python2.7/dist-packages/p4/ directory to the same place at
> my bare metal server, but now I get a UNIMPLEMENTED error :)
>
>   File "controller.py", line 95, in main    s.SetForwardingPipelineConfig(p4info=p4info_helper.p4info,
> bmv2_json_file_path=bmv2_file_path)
>   File "/home/csikor/p4/p4_vlan/p4runtime_controller/p4runtime_lib/switch.py",
> line 45, in SetForwardingPipelineConfig    self.client_stub.
> SetForwardingPipelineConfig(request)
>   File "/usr/local/lib/python2.7/dist-packages/grpc/_channel.py", line
> 492, in __call__    return _end_unary_response_blocking(state, call,
> False, deadline)
>   File "/usr/local/lib/python2.7/dist-packages/grpc/_channel.py", line
> 440, in _end_unary_response_blocking
>
>   raise _Rendezvous(state, None, None, deadline)grpc._channel._Rendezvous:
> <_Rendezvous of RPC that terminated with (StatusCode.UNIMPLEMENTED, )>
>
> I guess some of the installation steps should be revisited, but can
> someone explain me in which order and how should I proceed with the
> installation of the libraries to have the same environment as the VM has?
> Or what else can I do?
>
> Thank you for considering my request.
>
> BR,
> Levi
>
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>


-- 
Antonin
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