Re: [Qemu-devel] tun/tap networking

["Jim C. Brown" <jma5@umd.edu>]

On Sat, Oct 01, 2005 at 10:12:41AM +0200, Jean-Christian de Rivaz wrote:
> Jim C. Brown a ?crit :
> 
> >Typically, tapX (tap0, tap1, etc) names are reserved for tap devices 
> >(ethernet
> >frames) and tunX (tun0, tun1, etc) are reserved for tun devices (IP 
> >frames).
> >
> >qemu breaks those rules and calls the tap device that it creates tun0. 
> >This is
> >done for reasons that Fabrice has not made clear. (I assume there is a 
> >reason
> >for it because he has refused to apply any of the patches that fix this.)
> 
> You point the real question: why it has been impossible to get accepted 
> any patch that fixed this. I has proposed one myself and I get no 
> comment at all. I see similar effort from others and obviousely there 
> failed almost the same way. No getting any valuable comment about why a 
> idea proposed by many peopoles is not applyed make this subject very hard.
> 

The change I was talking about is a one line patch...

It's annoying that Fabrice has said nothing about it. But it doesn't actually
mess anything up, it's just confusing for advanced users.

I presume that the device qemu makes is called tun0 because Fabrice wants to
make clear that he doesnt use (and wont support) the ethertap device. Not a
very good reason.

(Or maybe he wants to keep it tun0 because if he changed the name he'd have
to change the option -tun-fd to -tap-fd and that'd break some scripts.)

> I hope that we can resolve this subject, because in my point of view, 
> using a existing "tun" is far more simpler than create one the way quemu 
> do;

I never mentioned that. At all.

And qemu already supports that, via the -tun-fd option.

> and this open a lot of new uses in terme of the network managment of 
> the quemu instance. The very first one for me is to allow only root to 
> setup a DHCP server and to assign "tuns" interfaces to the users that 
> needs it, so there don't even have to think about the network setup, 
> ther just boot into quemu an OS with a DHCP client.
> 

That is a little tricky to do - but qemu can do it.

> Any comment this time ?
> -- 
> Jean-Christian de Rivaz
> 
> 
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-- 
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Infinite precision begets infinite perfection.