Re: [Qemu-devel] [PATCH] net: Silence 'has no peer' messages in testing mode

[Markus Armbruster <armbru@redhat.com>]

Thomas Huth <thuth@redhat.com> writes:

> On 07.05.2018 09:14, Markus Armbruster wrote:
> [...]
>> Two (possibly confused) questions:
>> 
>> 1. The user can add nics without convenience options:
>> 
>>     $ upstream-qemu -display none -nodefaults -device e1000
>>     upstream-qemu: warning: nic e1000.0 has no peer
>> 
>>    Shouldn't we silence the warning then, too?
>
> No, since that is certainly a mis-configuration in that case. Why would
> a user want to add a NIC without host backend?

Related:

    $ upstream-qemu -display none -nodefaults -net nic
    upstream-qemu: warning: vlan 0 is not connected to host network

The root of my confusion: I'm having difficulties making the connection
from the guard predicate (!qtest_enabled() || nd_table[0].used) to
"stupid default setup that isn't the test's fault".

In what scenarios exactly do we get unwanted "has no peer" messages?
Mandatory onboard NIC, perhaps?

Arguably, onboard NICs should default to a null backend that behaves
like "no carrier".  That's exactly what physical hardware does.  Could
even be useful outside tests once we support hot-plugging network
backends (we might already, I have no idea), just like physical hardware
supports plugging in network cables.

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