I would like to consult you about a problem related to virt-manager and Qemu. I am trying to use this program to create a virtual machine with Qemu from Gentoo, but I have problems to establish the network connection.
As I have read, in order for virtual machines to use the host's network connection, I need to create a virtual network, which will be associated with a host computer interface and selected as a device associated with the network card of the host. virtual machine.
But it turns out that when I try to create a virtual network from the "details" window, the option to add networks appears to me disabled 
I have tried to activate the interfaces from the "network interfaces" tab, but it gives me this error 
Error setting interface startmode: esta función no está soportada por el controlador de conexión: virInterfaceDefineXML
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/host.py", line 788, in interface_apply
interface.set_startmode(newmode)
File "/usr/share/virt-manager/virtManager/interface.py", line 109, in set_startmode
self._redefine_xmlobj(xmlobj)
File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 389, in _redefine_xmlobj
self._define(newxml)
File "/usr/share/virt-manager/virtManager/interface.py", line 44, in _define
return self.conn.define_interface(xml)
File "/usr/share/virt-manager/virtManager/connection.py", line 684, in define_interface
return self._backend.interfaceDefineXML(xml, 0)
File "/usr/lib64/python2.7/site-packages/libvirt.py", line 3801, in interfaceDefineXML
if ret is None:raise libvirtError('virInterfaceDefineXML() failed', conn=self)
libvirtError: esta función no está soportada por el controlador de conexión: virInterfaceDefineXML´
I followed all the steps indicated in the Gentoo wiki, activating all the elements of the kernel that are indicated there, and loading the necessary modules, but it still does not work.
I have even tried to start virt-manager with root permission, but without success
Any idea how I can solve it?