[Avocado-devel] Using network sniffer in avocado-vt

[Xu Han]

On 9/12/18 5:41 PM, Sergey Bronnikov wrote:
>
>
> ср, 12 сент. 2018 г. в 12:09, Xu Han <xuhan at redhat.com 
> <mailto:xuhan at redhat.com>>:
>
>
>     On 9/12/18 7:58 AM, Cleber Rosa wrote:
>>     On 9/11/18 5:43 AM, Sergey Bronnikov wrote:
>>>     Hello!
>>>
>>>     avocado-vt uses network sniffer (tshark or tcpdump) for getting
>>>     IP address of running guest OS. QEMU has an option to dump network
>>>     traffic to a file. Using this option looks simpler than using of
>>>     external sniffer . I believe there were reasons to prefer sniffer
>>>     instead of qemu dump option. Can someone tell about them?
>>>
>>>     Sergey
>>     Sergey,
>>
>>     It'd be nice to try to rewrite the "sniffing" code in terms of "-object
>>     filter-dump" (AKA "-net dump").
>>
>>     I see that there are some limitations in the QEMU builtin network dump,
>>     but we can always use such an implementation when appropriate.
>
>     It's a good idea to use '-net dump' functionality for getting IP
>     addresses, parsing pcap format files is always be easy than
>     parsing plain text generated by those sniffer tools.
>
>     However, my concern is that this method is a little bit
>     aggressive, I'm not sure if enabling this function  for a guest
>     would affect the other part of the network function. And please be
>     noted that a well functioning QEMU is the guarantee for us to get
>     the correct IP addresses, while the QEMU is the box that we are
>     testing.
>
> Please take into account that there are many projects (including mine) 
> where Avocado-VT used not for testing QEMU but for testing software 
> _inside_ QEMU.

Sergey,

OK, I see. So I'd suggest to make "-net dump" be the third sniffing 
method, and keep the previous two for QEMU testing. Thanks.


Cleber,

Is there a better way in Avocado to do this kind of test rather than 
using Avocado-VT?


Thanks,
Xu
>
>>     Xu has written the tshak backend, so I bet he knows more about it.
>
>     Honestly speaking, I have no idea about why it used tcpdump not
>     others.. The reason of adding the tshark(wireshark) support is,
>     sometimes, tcpdump has the problem to get the right informaion
>     (see https://github.com/avocado-framework/avocado-vt/pull/1463).
>
>     We can also get IP adresses by using the function provided by
>     qemu-guest-agent, it can work with both dhcp and static network.
>     But, for me, it is an "aggressive" way as well.
>
> This method may not work when OS inside QEMU is under test.
>
>     Thanks,
>     Xu
>
>
>>     FIY, we're trying a different approach of getting guest information on
>>     Avocado (not on Avocado-VT), by using the "cloudinit" feature when the
>>     guest has support for it:
>>
>>     https://avocado-framework.readthedocs.io/en/64.0/api/utils/avocado.utils.html#module-avocado.utils.cloudinit
>>
>>     It's simplistic at the moment, but it's possible to check for the
>>     instance id used, and get the IP address from the the "phone home" HTTP
>>     connection.
>>
>>     Regards,
>>
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