[RFC] dropping network hotplug support from network service

[Don Dutile]

On 06/21/2011 01:52 PM, Bill Nottingham wrote:
> Don Dutile (ddutile at redhat.com) said:
>> On 06/20/2011 05:09 PM, Bill Nottingham wrote:
>>> I'm considering drop the network hotplug support from the 'network'
>>> service. This is the code that would automatically run ifup when a new
>>> network device appeared, if there was a configuration for it.
>>>
>>> The supported solution would be to use NetworkManager for these usage
>>> cases (or wicd, or netplugd, or conman...) Alternatively, just run
>>> ifup yourself.
>>>
>>> Currently, this would happen in the following cases:
>>> 1. USB and/or expresscard hotplugged ethernet/wireless
>>> 2. PCI hotswap of a network card
>>> 3. Runtime addition of network interfaces in virtual system
>>> 4. Admin manually removes and reloads a driver module
>>>
>>> For #1, those systems are generally better served by NM.
>>> For #2, this is something with such heavy admin interaction that I
>>> would suspect that it would be preferred to handle it manually. (Also,
>>> swapping hardware likely invalidates the configuration in any case.)
>>> For #3, you're unlikely to have a configuration written for a freshly
>>> available device.
>> sorry, I don't understand this statement....
>> but has me worried for virt hot add/remove of assigned devices
>
> Essentially, hot-adding a virtual device would not bring the device
> up automatically if you're using the old network service; you'd have
> to run 'ifup' by hand.
>
hot-adding a VF-nic to a Linux kvm guest brings up the hot-added (VF) 
nic in the guest today.... am I missing what you mean?

>>> For #4, bringing up the device automatically can cause more issues
>>> than it solves. (We've seen this happen for vlans, for example.)
>> This is done all the time (on KVM hosts) to take down PF driver&  load
>> PF+VF drivers for SRIOV-capable devices.
>
> This would be a different device with a different hardware address,
> correct?
>
Nope; typically start up an SRIOV device in PF-only mode (igb, for 
example), then do an rmmod igb; modprobe igb max_vfs=7;  same PF mac;
new VF mac's.

and as VF's are added & removed from guests, they may be removed & added
back to host.

> Bill