Unable to decode message length

[Valentin David]

I have found the issue. So I just reply to archive the solution in case 
others have the same issue.

I had both portablexdr and litirpc available at build time. I removed 
portablexdr for it to link to libtirpc, and now it works.

On Thu, Jul 16, 2020 at 11:48, Valentin David 
<valentin.david at codethink.co.uk> wrote:
> Thank you for the help. But here I get exactly the same data as you. 
> So I suppose the issue is on the server side only. I will try with 
> gdb now.
> 
> On Wed, Jul 15, 2020 at 16:02, Michal Privoznik <mprivozn at redhat.com> 
> wrote:
>> On 7/14/20 7:42 PM, Valentin David wrote:
>>> Hello all,
>>> 
>>> I have been trying to get libvirtd to work but when I connect to it 
>>> with virsh, I get "error : virNetMessageDecodeLength:131 : Unable 
>>> to decode message length"
>>> 
>>> This happens with libvirt 6.1.0, libtirpc 1.2.6, rpcsvc-proto 
>>> 1.4.1. I have tried with other versions, but I still get the same 
>>> error.
>>> 
>>> If anybody has any tip on what to try next, that would be helpful. 
>>> Thank you in advance.
>>> 
>>> Here is the debug log of libvirtd when I try to connect with virsh:
>>> 
>> 
>>> 2020-07-14 16:29:58.220+0000: 5352: error : 
>>> virNetMessageDecodeLength:131 : Unable to decode message length
>> 
>> This is interesting. The error message is reported when xdr_u_int() 
>> fails. It is trying to decode first 4 bytes of incoming message to 
>> see how long it is. I can think of two possible reasons for this:
>> 
>> 1) the client did not send 4 bytes
>> 2) the rpcgen generated some wrong code that libtirpc is unable to 
>> decode.
>> 
>> I suggest using wireshark to check what data is send (don't forget 
>> to use plain TCP transport in URI, for instance 'virsh -c 
>> qemu+tcp://localhost/system'). The first call that virsh does is 
>> AUTH_LIST procedure and it should look like this:
>> 
>> 0000   00 00 00 00 00 00 00 00 00 00 00 00 86 dd 60 04
>> 0010   52 cc 00 3c 06 40 00 00 00 00 00 00 00 00 00 00
>> 0020   00 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00
>> 0030   00 00 00 00 00 01 df 6c 40 7d fd e7 38 94 09 92
>> 0040   bf 48 80 18 02 00 00 44 00 00 01 01 08 0a c9 4f
>> 0050   f4 f2 c9 4f f4 f2 00 00 00 1c 20 00 80 86 00 00
>> 0060   00 01 00 00 00 42 00 00 00 00 00 00 00 00 00 00
>> 0070   00 00
>> 
>> bytes 0x56-0x59 contain 0x1c (= 28) which is the length of the 
>> packet (28 bytes). This is how our dissector decodes it:
>> 
>> Libvirt
>>     length: 28
>>     program: REMOTE (0x20008086)
>>     version: 1
>>     procedure: AUTH_LIST (66)
>>     type: CALL (0)
>>     serial: 0
>>     status: OK (0)
>> 
>> 
>> Michal
>> 
>> 

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