Re: [PATCH net 2/2] selftests: add openvswitch selftest suite

From: Ilya Maximets
Date: Thu Oct 20 2022 - 13:17:49 EST


On 10/20/22 18:33, Ilya Maximets wrote:
> On 10/20/22 17:32, Aaron Conole wrote:
>> Hi Ilya,
>>
>> Ilya Maximets <i.maximets@xxxxxxx> writes:
>>
>>> On 10/19/22 20:30, Aaron Conole wrote:
>>>> Previous commit resolves a WARN splat that can be difficult to reproduce,
>>>> but with the ovs-dpctl.py utility, it can be trivial. Introduce a test
>>>> case which creates a DP, and then downgrades the feature set. This will
>>>> include a utility 'ovs-dpctl.py' that can be extended to do additional
>>>> work.
>>>>
>>>> Signed-off-by: Aaron Conole <aconole@xxxxxxxxxx>
>>>> Signed-off-by: Kevin Sprague <ksprague0711@xxxxxxxxx>
>>>> ---
>>>> MAINTAINERS | 1 +
>>>> tools/testing/selftests/Makefile | 1 +
>>>> .../selftests/net/openvswitch/Makefile | 13 +
>>>> .../selftests/net/openvswitch/openvswitch.sh | 216 +++++++++
>>>> .../selftests/net/openvswitch/ovs-dpctl.py | 411 ++++++++++++++++++
>>>> 5 files changed, 642 insertions(+)
>>>> create mode 100644 tools/testing/selftests/net/openvswitch/Makefile
>>>> create mode 100755 tools/testing/selftests/net/openvswitch/openvswitch.sh
>>>> create mode 100644 tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>>>>
>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>> index abbe88e1c50b..295a6b0fbe26 100644
>>>> --- a/MAINTAINERS
>>>> +++ b/MAINTAINERS
>>>> @@ -15434,6 +15434,7 @@ S: Maintained
>>>> W: http://openvswitch.org
>>>> F: include/uapi/linux/openvswitch.h
>>>> F: net/openvswitch/
>>>> +F: tools/testing/selftests/net/openvswitch/
>>>>
>>>> OPERATING PERFORMANCE POINTS (OPP)
>>>> M: Viresh Kumar <vireshk@xxxxxxxxxx>
>>>
>>> ...
>>>
>>>> +exit ${exitcode}
>>>> diff --git a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>>>> b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>>>> new file mode 100644
>>>> index 000000000000..791d76b7adcd
>>>> --- /dev/null
>>>> +++ b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>>>> @@ -0,0 +1,411 @@
>>>> +#!/usr/bin/env python3
>>>> +# SPDX-License-Identifier: GPL-2.0
>>>> +
>>>> +# Controls the openvswitch module. Part of the kselftest suite, but
>>>> +# can be used for some diagnostic purpose as well.
>>>> +
>>>> +import logging
>>>> +import multiprocessing
>>>> +import socket
>>>> +import struct
>>>> +import sys
>>>> +
>>>> +try:
>>>> + from libnl.attr import NLA_NESTED, NLA_STRING, NLA_U32, NLA_UNSPEC
>>>> + from libnl.attr import nla_get_string, nla_get_u32
>>>> + from libnl.attr import nla_put, nla_put_string, nla_put_u32
>>>> + from libnl.attr import nla_policy
>>>> +
>>>> + from libnl.error import errmsg
>>>> +
>>>> + from libnl.genl.ctrl import genl_ctrl_resolve
>>>> + from libnl.genl.genl import genl_connect, genlmsg_parse, genlmsg_put
>>>> +
>>>> + from libnl.handlers import nl_cb_alloc, nl_cb_set
>>>> + from libnl.handlers import NL_CB_CUSTOM, NL_CB_MSG_IN, NL_CB_VALID
>>>> + from libnl.handlers import NL_OK, NL_STOP
>>>> +
>>>> + from libnl.linux_private.netlink import NLM_F_ACK, NLM_F_DUMP
>>>> + from libnl.linux_private.netlink import NLM_F_REQUEST, NLMSG_DONE
>>>> +
>>>> + from libnl.msg import NL_AUTO_SEQ, nlmsg_alloc, nlmsg_hdr
>>>> +
>>>> + from libnl.nl import NLMSG_ERROR, nl_recvmsgs_default, nl_send_auto
>>>> + from libnl.socket_ import nl_socket_alloc, nl_socket_set_cb
>>>> + from libnl.socket_ import nl_socket_get_local_port
>>>> +except ModuleNotFoundError:
>>>> + print("Need to install the python libnl3 library.")
>>>
>>>
>>> Hey, Aaron and Kevin. Selftests sounds like a very important and
>>> long overdue thing to add. Thanks for working on this!
>>>
>>> I have some worries about the libnl3 library though. It doesn't
>>> seem to be maintained well. It it maintained by a single person,
>>> it it was at least 3 different single persons over the last 7
>>> years via forks. It didn't get any significant development done
>>> since 2015 as well and no commits at all for a last 1.5 years.
>>> It is not packaged by any major distributions.
>>
>> :-/ On my fedora:
>>
>> 11:12:24 aconole@RHTPC1VM0NT ~$ dnf search python3-libnl3
>> Last metadata expiration check: 1 day, 0:25:11 ago on Wed 19 Oct 2022 10:47:21 AM EDT.
>> ===================== Name Exactly Matched: python3-libnl3 =====================
>> python3-libnl3.x86_64 : libnl3 binding for Python 3
>>
>>
>> And I can use it:
>>
>> 11:18:39 aconole@RHTPC1VM0NT {(6a5c83bdd991...)} ~/git/linux/tools/testing/selftests/net/openvswitch$ sudo python3 ./ovs-dpctl.py show
>> foop
>> Lookups: Hit: 0 Missed: 0 Lost: 0
>> Flows: 0
>> Masks: Hit: 0 Total: 0
>> Cache: Hit: 0
>> Caches:
>> Masks-cache: size: 256
>> Port 0: foop (internal)
>> 11:18:43 aconole@RHTPC1VM0NT {(6a5c83bdd991...)} ~/git/linux/tools/testing/selftests/net/openvswitch$ rpm -qa | grep python3-libnl3
>> python3-libnl3-3.5.0-6.fc34.x86_64
>> 11:19:01 aconole@RHTPC1VM0NT {(6a5c83bdd991...)} ~/git/linux/tools/testing/selftests/net/openvswitch$
>>
>> Was there some place you did not find it?
>
> You're right, I missed that somehow. But this is not an
> https://github.com/coolshou/libnl3 project. :)
> These are python bindings for the C libnl library:
>
> $ dnf info python3-libnl3
> Available Packages
> Name : python3-libnl3
> Version : 3.7.0
> Release : 1.fc36
> Architecture : x86_64
> Size : 153 k
> Source : libnl3-3.7.0-1.fc36.src.rpm
> Repository : updates
> Summary : libnl3 binding for Python 3
> URL : http://www.infradead.org/~tgr/libnl/
> License : LGPLv2
> Description : Python 3 bindings for libnl3

Actually, I can't find an equivalent package for Ubuntu 22.04.
And since pip is not an option (pip install libnl3 is a different
package), there is no way to install it there beside building
from sources.

Am I still missing something?

>
>>
>>> I'm talking about https://github.com/coolshou/libnl3 . Please,
>>> correct me if that is not the right one. There are too many
>>> libraies with the name libnl out there... That is also not a great
>>> sign.
>>
>> Yes, this is the project.
>
> Doensn't look like it...
>
>> We did look at some of the ones you
>> mentioned, but didn't find much.
>>
>> It is a sparse landscape of projects that provide netlink support in
>> python.
>>
>>> The C library libnl (https://github.com/thom311/libnl) seems to
>>> be well maintained in general. It has experimental python
>>> bindings which are not really supported much. Python bindings
>>> received only 2 actual code-changing commits in the last 7 years.
>>> Both of them are just python 2/3 compatibility changes.
>>> Maybe that is not that big of a deal since it's not really a
>>> real python library, but a wrapper on top of a main C library.
>>> However, I didn't find these python bindings to be packaged in
>>> distributions. And they seem to be not available in pip as well.
>>> So, building them is kind of a pain.
>>
>> Well, the python libnl3 should be installable via pip3. Ex:
>>
>> 11:27:15 aconole@RHTPC1VM0NT ~$ pip3 install libnl3
>> Defaulting to user installation because normal site-packages is not writeable
>> Collecting libnl3
>> Using cached libnl3-0.3.0-py3-none-any.whl (89 kB)
>> Installing collected packages: libnl3
>> Successfully installed libnl3-0.3.0
>
> And this is https://pypi.org/project/libnl3/, which is the
> https://github.com/coolshou/libnl3 project. So, by installing
> libnl3 via pip and installing python3-libnl3 from the fedora
> you're getting two completely different libraries.
>
> So, which one users should use?
>
> I can't find python bindings for the C libnl (which is the
> python3-libnl3 package) in pypi, so it can't be installed
> with pip.
>
>
>>
>> So I guess that is worth something.
>>
>> At least on Fedora it is installable from distribution as well.
>>
>>> There is another option which is pyroute2. It positions itself
>>> primarily as a netlink library and it does include an
>>> pyroute2.netlink module indeed:
>>> https://github.com/svinota/pyroute2/tree/master/pyroute2/netlink
>>> See the __init__.py for usage examples.
>>>
>>> This one looks to me like the most trustworthy. It is actively
>>> used by everyone in the python networking world, e.g. by OpenStack.
>>> And it is actively developed and maintained unlike other
>>> netlink-related python projects. It is also packaged in most of the
>>> main distributions, so it's easy to install and use. Many people
>>> already have it installed for other purposes.
>>>
>>> TBH, I didn't compare the functionality, but I'd expect that most
>>> of the things we need are implemented.
>>>
>>> What do you think?
>>
>> We can certainly look at switching, but having a quick glance, it seems
>> pyroute2 expects to provide the genl commands as well, so they would
>> want us to create an ovs module in pyroute2 that includes all of the ovs
>> family support. Of course, we can always do this just in our module,
>> but I think it isn't the way pyroute2 project wants to be structured.
>> More like a library that provides all the command functionality.
>
> What I was thinking is to import pyroute2.netlink and the
> pyroute2.netlink.generic and go from there. But I didn't
> look too deep on how to actually implement the functionality.
>
> The python bindings for the C libnl (python3-libnl3) sounds
> like a fine option since they are actually packaged in
> distributions (missed that in my initial reply). However,
> the fact that you can not install them via pip and actually
> you will install something but completely different is kind
> of weird. This has to be at least better documented, so
> users will know what to install and they will not try to use
> pip for that.
>
>>
>>> On the other note, I'm not a real python developer, but the code
>>> looks more like a C than a python even for me. Firstly, I'd say
>>> that it would be great to maintain some coding style, e.g. by
>>> checking with flake8 and/or black. See some issues/suggestions
>>> provided by these tools below.
>>
>> Agreed. BTW, on the rhel8 system I developed on:
>>
>> [root@wsfd-netdev60 openvswitch]# flake8 ./ovs-dpctl.py
>> [root@wsfd-netdev60 openvswitch]#
>>
>> So, I guess it is probably that I should have used a different system to
>> do the flake8 checks.
>
> Maybe the python version is different... I was running on f36
> with python 3.10. Also, the list of defaults might be different.
> flake8 doesn't use default ignore list if one is explicitly provided.
>
>>
>>> Secondly, we shouldd at least use argparse for argument parsing.
>>> It's part of the standard library since python 3.2, so doens't
>>> require any special dependencies to be installed.
>>
>> Okay - I can switch to argparse. TBH, I haven't kept up with python
>> standard library for some time.
>
> Well, 3.2 was released 11 years ago. :)
>
>>
>>> Some parts of the code can probably be re-written to be more
>>> "pythonic" as well, but I won't dive into that for now. I didn't
>>> review the code deep enough for that.
>>
>> I have difficulty sometimes understanding what it means to be "Real
>> Python (tm)" - I don't plan to change things too much. I can certainly
>> switch to using argparse, but unless you give something you want to
>> change, I would not change anything.
>
> I breifly looked through code and though I don't fully
> understand what this piece supposed to do:
>
> + segment = hdrval.find(":")
> + if segment == -1:
> + segment = len(hdrval)
> + hdrver = int(hdrval[:segment], 0)
> + if len(hdrval[:segment]):
> + userfeatures = int(hdrval[:segment], 0)
>
> but I have a strong feeling that this part can benefit
> from use of hdrval.split(':').
>
> I won't insist on that too much. :)
>
> Best regards, Ilya Maximets.