[ovs-dev] [PATCH 14/18] keep "kernel name" for each netdev

Ben Pfaff blp at nicira.com
Fri Feb 1 05:06:09 UTC 2013


On Fri, Feb 01, 2013 at 12:23:00PM +0900, YAMAMOTO Takashi wrote:
> hi,
> 
> >> >         * ovs-vswitchd starts up and creates some tap devices.  It knows
> >> >           the mapping between the user-requested name and the kernel
> >> >           name.
> >> > 
> >> >         * Admin restarts ovs-vswitchd.
> >> > 
> >> >         * New instance of ovs-vswitchd creates new tap devices because
> >> >           it does not know the kernel names of the existing ones and
> >> >           does not have a way to discover them.  The existing ones are
> >> >           effectively leaked.
> >> 
> >> there isn't a leak as ovs-vswitchd destroys the old one when stopping.
> > 
> > OK.  But this may cause a different inconvenience to the user: if the
> > user configured an IP address on the tap device, then restarting
> > ovs-vswitchd will drop that IP address and the user will have to add it
> > back.  This doesn't happen with the Linux kernel datapath, and I don't
> > think it happens with the Linux userspace datapath (I can't say for the
> > FreeBSD one).  But if that issue does not bother you, then I will not
> > worry about it.
> 
> are you sure about the linux userspace datapath behaviour?
> a casual looking at linux's Documentation/networking/tuntap.txt and
> netdev-linux.c made me think otherwise.

Hmm.  I think you are right.  This is not the way I remember this code
working, but it is pretty old.  Never mind.


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