[P4-dev] bmv2: "Error when requesting config md5 sum from switch"

Andy Fingerhut andy.fingerhut at gmail.com
Sun Sep 16 18:43:02 EDT 2018


Thanks for the detailed reports, David.  I suspect you are an Ubuntu
18.04 + P4 tools "early adopter" and may be one of the first to investigate
this deeply into these issues.

I had tried Thrift 0.11.0 on Ubuntu 18.04 as well, but did not try mininet,
nor multiple physical devices each running their own bmv2 simple_switch
connected by physical Ethernet ports.  There is an issue here suggesting
perhaps updating Thrift to version 0.11.0 for behavioral-model, but I have
added a comment to that issue linking to your message:
https://github.com/p4lang/behavioral-model/issues/597

I believe one long term answer is that Thrift will become no-longer-used at
some point, once the P4Runtime API using Google Protobufs instead of Thrift
becomes more tested and used.

That said, if someone does figure out a way to get existing Thrift-based
APIs working on Ubuntu 18.04, that would be nice to have.

Andy Fingerhut

On Sun, Sep 16, 2018 at 2:36 PM David Hancock <dhancock at cs.utah.edu> wrote:

> I have confirmed that Thrift 0.9.2 on Ubuntu 14.04 works in my environment.
>
> I was trying 0.11.0 on Ubuntu 18.04 because during installation of 0.9.2
> I got an error claiming libcrypto was missing, which is supposed to be
> included with libssl-dev but installing libssl-dev didn't fix the
> problem.  Googling reveals this is a known problem but I couldn't tell
> what the best solution was of many suggested.
>
> Hence 0.11.0, which presented no errors during installation, but when I
> call runtime_CLI.load_json_config eventually it ends up in Thrift's
> recv_bm_get_config_md5() -> read(), which has that extra check on
> sys.version_info triggering iprot.readString().decode('utf-8'), which
> fails with UnicodeDecodeError.
>
> To me this seems like a bug with Thrift but I'm no Thrift expert.
> 'iprot' in my case is of type
> thrift.protocol.TBinaryProtocol.TBinaryProtocol.  I don't know what
> message is being sent that starts with 0xed and I don't understand the
> logic for why Thrift wants to decode it as utf-8.
>
> So I downgraded to Ubuntu 14.04 and Thrift 0.9.2 because that was my
> setup when doing experiments in mininet.
>
> --David
>
>
> On 09/16/2018 12:15 AM, David Hancock wrote:
> > It appears the issue is with Thrift.  I am running version 0.11.0.  I
> > traced the error to std_client.bm_get_config_md5() -> ... ->
> > recv_bm_get_config_md5 -> ...; here's the full stack trace:
> >
> > bm_md5sum = std_client.bm_get_config_md5()
> > Traceback (most recent call last):
> >   File "<console>", line 1, in <module>
> >   File
> >
> "/usr/local/lib/python2.7/dist-packages/bm_runtime/standard/Standard.py",
> > line 2864, in bm_get_config_md5
> >     return self.recv_bm_get_config_md5()
> >   File
> >
> "/usr/local/lib/python2.7/dist-packages/bm_runtime/standard/Standard.py",
> > line 2882, in recv_bm_get_config_md5
> >     result.read(iprot)
> >   File
> >
> "/usr/local/lib/python2.7/dist-packages/bm_runtime/standard/Standard.py",
> > line 14572, in read
> >     self.success = iprot.readString().decode('utf-8') if
> > sys.version_info[0] == 2 else iprot.readString()
> >   File "/usr/lib/python2.7/encodings/utf_8.py", line 16, in decode
> >     return codecs.utf_8_decode(input, errors, True)
> > UnicodeDecodeError: 'utf8' codec can't decode byte 0xed in position 0:
> > invalid continuation byte
> >
> > --David
> >
> >
> > On 09/15/2018 09:23 PM, David Hancock wrote:
> >> Hello,
> >>
> >> I get "Error when requesting config md5 sum from switch" when executing:
> >>
> >> runtime_CLI.load_json_config(<bm_runtime.standard.Standard.Client
> >> object>, <JSON path>)
> >>
> >> in my python-based controller that connects to a bmv2 simple_switch.
> >> I did not get this error in mininet experiments; I'm only getting it
> >> now that I'm trying to experiment on a physical cluster.
> >>
> >> Is there a common reason for that error?
> >>
> >> Here is some of the code preceding the statement that results in the
> >> error:
> >>
> >>     ip = 'localhost'
> >>     port = 9090
> >>
> >>     services =
> >>
> runtime_CLI.RuntimeAPI.get_thrift_services(runtime_CLI.PreType.SimplePre)
> >>     services.extend(SimpleSwitchAPI.get_thrift_services())
> >>
> >>     try:
> >>       std_client, mc_client, sswitch_client =
> >> runtime_CLI.thrift_connect(ip, port, services)
> >>     except:
> >>         return "Error - create_device(" + dev_name + "): " +
> >> str(sys.exc_info()[0])
> >>
> >>     json = <path to JSON>
> >>     runtime_CLI.load_json_config(std_client, json)
> >>
> >> I can break right before the load_json_config call and everything
> >> looks in order - in particular, get_thrift_services and
> >> thrift_connect executed successfully.
> >>
> >> Thank you for any ideas you may have,
> >>
> >> David
> >>
> >>
> >> _______________________________________________
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> >> P4-dev at lists.p4.org
> >> http://lists.p4.org/mailman/listinfo/p4-dev_lists.p4.org
> >
> >
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