Comment 37 for bug 1432599
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#37 |
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bbfa235
(Get the code!)
When an interface is configured outside of NetworkManager's knowledge (like libvirt's or docker's bridge), then NetworkManager generates an in-memory connection profile and pretends(!) that this is active. This is to show that something is going on with the device, and NetworkManager is supposed to touch that device.
Whether this pretend mode is of any use is a good question. It's obviously confusing. I actually do make use of this behaviour to have a dispatcher script that does something for such external devices, so it's not entirely useless. Also, it causes the output of `nmcli device` to show that *something* is going on there. Although, maybe that's more confusing than helpful. In any case, NetworkManager needs a way to express that something is happening with this devices, and this is the way it does that. It doesn't mean that NetworkManager actually touches the device.
Comment 26 does not say what actual problem NetworkManager causes by this (aside the confusion to the user).
Comment 26 also explains that `nm-online` gives wrong results. I think nm-online has one real use-case: to implement `NetworkManager
Without the `--startup` option, I don't think it's of any use at all. It can only return "online" or "offline". It maps the NetworkManager's states "local", "site", and "global" to "online". I think that is is sensible, if you connect to a libvirt bridge some network is configured and nm-online considers that as "online". However I don't think that describing the online state in two words is meaningful and calling `nm-online` is not useful.
For a while NetworkManager had a udev rule to automatically unmanage docker bridges. But that was dropped, because docker bridges are nothing special. It's a common thing that something aside NetworkManager configures an interface and NetworkManager must not interfere. So, what actual problems are causes by this?
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> 1) You should never need to create (actually *shouldn't* create) an ifcfg-* file for a libvirt-created bridge. If proper operation requires this, then there is definitely a bug.
Right. NM doesn't.
> 2) NetworkManager should never mess around with bridge devices created by other entities (e.g. libvirt, but really anyone else), and no special plugin should be required to make that happen. If we (libvirt) wanted NM to manage the bridge, we would create it via NM.
Right. NM shouldn't. Does it?