Re: Specifying names for tap interfaces

[buhrow%lothlorien.nfbcal.org@localhost (Brian Buhrow)]

        Hello.  I know nothing here either, but I have a couple of questions.
Who is it that's launching the guests?  Can't who ever it is, have a
locking protocol that says,  I'm now fetching a network interface, please
don't fetch one until I'm certain my client is up or dead?  Then we know we
won't have a race for the interface name, and we're done.
        I'm a little with Darren on the issue of alias names in that an 
interface
should be known by one name during the life of its existence.  It seems to
me the issue here is who controls the name of an interface and how does
that knowledge get passed around?  So far I've not seen anything that makes
me feel comfortable with the proposed solutions.  If I'm writing firewall
rules, I need to know the name of the interface I'm using well before Qemu
gets into the picture and as long as that's true, I fail to understand the
problem we face.  I think it would be helpful,even though it may seem
extremely elementary to those that know, if someone who understands both
how hvm hosts used to get their interface names and what changed.
-thanks
-Brian

On Jun 21, 12:16pm, Roger Pau Monne wrote:
} Subject: Re: Specifying names for tap interfaces
} Martin Husemann wrote:
} > On Thu, Jun 21, 2012 at 11:24:37AM +0100, Roger Pau Monne wrote:
} >> Then we end up with the same problem, since xl needs to know the name of
} >> the created device (to launch the appropriate hotplug scripts), and
} >> there's not way to fetch that from Qemu.
} >
} > I thought I saw command line options to invoke qemu that pass the tap
} > ifname, or even open a fd and just pass the number?
} >
} > Something like:
} >
} >     qemu -net tap,ifname=tap14
} > or
} >     qemu -net tap,fd=4
} >
} > and you could pass the name to the script vie environment vars.
} 
} As I said on a previous email, how can you guarantee that the name you 
} chose and pass to Qemu will not be taken by someone else while you are 
} calling Qemu?
} 
} You might even be launching several guests at the same time, which will 
} lead you to a race.
} 
>-- End of excerpt from Roger Pau Monne