Re: [Qemu-devel] Question about tun/tap networking

Re: [Qemu-devel] Question about tun/tap networking

[Jim C. Brown]

I recommend using vde by Renzo Davoli instead of the default tuntap.
I am able to network 2 instances of windows 98 (in separate qemu's) and
minix 2.0.4 (in a hand-modified bochs). It worked without a hitch, and all
the machines are on the same subnet.

You still need forwarding to let the virtual machines see the lan or the
internet, however. The plus with vde is that you don't need to set up routing
for all these different tunN devices. (I use the Shorewall firewall, and using
tun was a pain...vde means I just have to set up routing and masquerading
for tap0, instead of for tun0, tun1, tun2, ...)

Available here btw: http://sourceforge.net/projects/vde/

On Mon, May 03, 2004 at 11:35:32AM +1000, nhand42@tpg.com.au wrote:
> Quoting Arne Bernin <arne@alamut.de>:
> 
> > Hi,
> > 
> > i am trying to set up two virtual machines with qemu 0.5.4. I have them
> > running, both with 2 network cards. I am able to ping all 4 interfaces
> > from the host they are running from but am not able to ping between both
> > virtual machines...
> > If i do a tcpdump on the corrsponding tun interfaces while trying to
> > ping i see a lot of arp who-has 172.16.0.254 tell 172.16.0.1 messages
> > (172.16.0.1 is the one machine, the other is 172.16.0.254). 
> > Is there something i have to do to get the arp responses right ??
> > Or am i totally wrong ?
> > 
> 
> You've stuck both virtual machines on the same subnet, so they think they're on the 
> same physical LAN. That's why they're doing ARPs and expecting replies. But you're 
> actually running two QEMU instances on two seperate TUN interfaces and they *aren't* 
> bridged. So the ARP on tun0 never gets seen on tun1 (and vice-versa). 
> 
> Set the second TUN interface to a different subnet (eg, 172.16.1.x) and enable ipv4 
> forwarding. Linux will then forward packets between tun0 and tun1.
> 
> You could also muck about with proxyarp or bridging but honestly, I wouldn't bother 
> with that. Routing is a lot easier to understand.
> 
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://mail.nongnu.org/mailman/listinfo/qemu-devel

-- 
Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.

Re: [Qemu-devel] Question about tun/tap networking

[Arne Bernin]

On Mon, 2004-05-03 at 05:09, Jim C. Brown wrote:

Hi Jim,

> I recommend using vde by Renzo Davoli instead of the default tuntap.
> I am able to network 2 instances of windows 98 (in separate qemu's) and
> minix 2.0.4 (in a hand-modified bochs). It worked without a hitch, and all
> the machines are on the same subnet.
> 
> You still need forwarding to let the virtual machines see the lan or the
> internet, however. The plus with vde is that you don't need to set up routing
> for all these different tunN devices. (I use the Shorewall firewall, and using
> tun was a pain...vde means I just have to set up routing and masquerading
> for tap0, instead of for tun0, tun1, tun2, ...)
> 
may you tell me how you set up your vde network ? I downloaded vde,
installed it, bootet 2 qemus (on the same subnet) and tried to ping each
other... I does not work, but i can ping the host they run on using a
tap0 device, and see the who-has... arp stuff while running tcpdump on
tap0. So it would be very interesting how you configured your vde_switch
qemu setup for multiple machines on the same vde_switch.

thanks,
          arne

Re: [Qemu-devel] Question about tun/tap networking

[Renzo Davoli]

On Mon, May 03, 2004 at 01:45:04PM +0200, Arne Bernin wrote:
> On Mon, 2004-05-03 at 05:09, Jim C. Brown wrote:
> Hi Jim,
> 
> > I recommend using vde by Renzo Davoli instead of the default tuntap.
> > I am able to network 2 instances of windows 98 (in separate qemu's) and
> > minix 2.0.4 (in a hand-modified bochs). It worked without a hitch, and all
> > the machines are on the same subnet.
Thank you for the advertisement ;-)
> > 
> > You still need forwarding to let the virtual machines see the lan or the
> > internet, however. The plus with vde is that you don't need to set up routing
> > for all these different tunN devices. (I use the Shorewall firewall, and using
> > tun was a pain...vde means I just have to set up routing and masquerading
> > for tap0, instead of for tun0, tun1, tun2, ...)
> > 
> may you tell me how you set up your vde network ? I downloaded vde,
> installed it, bootet 2 qemus (on the same subnet) and tried to ping each
> other... I does not work, but i can ping the host they run on using a
> tap0 device, and see the who-has... arp stuff while running tcpdump on
> tap0. So it would be very interesting how you configured your vde_switch
> qemu setup for multiple machines on the same vde_switch.

start your vde_switch

% vde_switch -daemon

to run qemu with vde you need to compile and install also the vdeq
utility (inside the qemu subdir of vde source code). Then run

% vdeq qemu ......

use all the other parameters for qemu at the end .... (but -n or
user-net obvsly). vdeq sets -tun-fd automatically.

I have coded also a shortcut to run qemu.
If you make a symbolic link of vdeq to vdesomething it runs "something"
so a symlink to vdeqemu let you write

% vdeqemu .....
instead of the previous command.

(if you have several versions of vde as I do, you can have several
symlinks with several suffixes).
> 

Just a final comment to say that I have just released the vde 1.5 with a
bugfix for qemu support (it missed some packets on very fast networks)
and slirp support for the entire vde network.

Fabrice, I have included your bootp mangement (with copyright and thanks
in the man page and in the README, GPL compliant).

ciao
	renzo

Re: [Qemu-devel] Question about tun/tap networking

[Renzo Davoli]

Errata-Corrige
> (if you have several versions of vde as I do, you can have several
> symlinks with several suffixes).
(if you have several versions of *qemu* as I do, you can have several
symlinks with several suffixes).

just for the sake of readability.

	renzo

Re: [Qemu-devel] Question about tun/tap networking

[Renzo Davoli]

> start your vde_switch
> % vde_switch -daemon

If you want a vde_switch connected to a tun interface the command is:
(you must be root!)

# vde_switch -daemon -tap tap0
# chmod 777 /tmp/vde.ctl

renzo

Sorry to be a bit OT, but this tool is used to run qemu....

Re: [Qemu-devel] Question about tun/tap networking

[Jim C. Brown]

On Mon, May 03, 2004 at 01:45:04PM +0200, Arne Bernin wrote:
> On Mon, 2004-05-03 at 05:09, Jim C. Brown wrote:
> 
> Hi Jim,
> 
> > I recommend using vde by Renzo Davoli instead of the default tuntap.
> > I am able to network 2 instances of windows 98 (in separate qemu's) and
> > minix 2.0.4 (in a hand-modified bochs). It worked without a hitch, and all
> > the machines are on the same subnet.
> > 
> > You still need forwarding to let the virtual machines see the lan or the
> > internet, however. The plus with vde is that you don't need to set up routing
> > for all these different tunN devices. (I use the Shorewall firewall, and using
> > tun was a pain...vde means I just have to set up routing and masquerading
> > for tap0, instead of for tun0, tun1, tun2, ...)
> > 
> may you tell me how you set up your vde network ? I downloaded vde,
> installed it, bootet 2 qemus (on the same subnet) and tried to ping each
> other... I does not work, but i can ping the host they run on using a
> tap0 device, and see the who-has... arp stuff while running tcpdump on
> tap0. So it would be very interesting how you configured your vde_switch
> qemu setup for multiple machines on the same vde_switch.
> 
> thanks,
>           arne
> 
> 

[/space/qemu/qemu-0.5.4/ $] su root
[/space/qemu/qemu-0.5.4/ #] vde_switch -daemon -tap tap0
[/space/qemu/qemu-0.5.4/ #] ifconfig tap0 192.168.1.254
[/space/qemu/qemu-0.5.4/ #] chmod 777 /tmp/vde.ctl
[/space/qemu/qemu-0.5.4/ #] exit
[/space/qemu/qemu-0.5.4/ $] vdeq qemu -hda disk1.img

This works, not only can I ping 2 different machines on the vde, I can also
ping the LAN from the vde, and vice versa. (ifconfig seems to set up
routing automagicly. Or was it something I put into shorewall...)

Note that for teh guest OS, you need to set up 192.168.1.254 as the default gateway
for just about everything.

> 
> 
> 
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://mail.nongnu.org/mailman/listinfo/qemu-devel

-- 
Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.

Re: [Qemu-devel] Question about tun/tap networking

[Arne Bernin]

On Mon, 2004-05-03 at 22:22, Jim C. Brown wrote:

> [/space/qemu/qemu-0.5.4/ $] su root
> [/space/qemu/qemu-0.5.4/ #] vde_switch -daemon -tap tap0
> [/space/qemu/qemu-0.5.4/ #] ifconfig tap0 192.168.1.254
> [/space/qemu/qemu-0.5.4/ #] chmod 777 /tmp/vde.ctl
> [/space/qemu/qemu-0.5.4/ #] exit
> [/space/qemu/qemu-0.5.4/ $] vdeq qemu -hda disk1.img
> 
> This works, not only can I ping 2 different machines on the vde, I can also
> ping the LAN from the vde, and vice versa. (ifconfig seems to set up
> routing automagicly. Or was it something I put into shorewall...)
> 
> Note that for teh guest OS, you need to set up 192.168.1.254 as the default gateway
> for just about everything.
> 

thanks, it is working now, just had some wrong firewall settings on the
guest OS linux boxes....

--arne

Re: [Qemu-devel] Question about tun/tap networking

[Jim C. Brown]

On Wed, Jun 23, 2004 at 07:54:07AM -0600, Phil Rasch wrote:
> I have been running a mixture of linux and windows machines, all real machines 
> on a LAN connected to the outside world through a router, which is acting as 
> my DHCP server, DNS server, and gateway machine. 
> 
> The LAN subnet is 192.168.0.*
> 
> Now I want to connect up the virtual machine running under QEMU. I want the 
> virtual machine to be on the same subnet as the real machines, and to use 
> DHCP from the router to get all the relevant info.

That is tricky. You will need to look into bridging.

> 
> Jim suggested the following commands for somebody else on the mailing list, 
> but I think that was headed towards devising a subnet that two virtual 
> machines could use to talk to each other.
> 
> [/space/qemu/qemu-0.5.4/ $] su root
> [/space/qemu/qemu-0.5.4/ #] vde_switch -daemon -tap tap0
> [/space/qemu/qemu-0.5.4/ #] ifconfig tap0 192.168.1.254
> [/space/qemu/qemu-0.5.4/ #] chmod 777 /tmp/vde.ctl
> [/space/qemu/qemu-0.5.4/ #] exit
> [/space/qemu/qemu-0.5.4/ $] vdeq qemu -hda disk1.img

That is correct. You now have 2 subnets, 198.168.0.* for the real network
and 192.168.1.* for qemu/VDE.

> 
> The thing I dont understand is whether the above command is setting up 
> seperate subnet for the virtual machines, or whether I can also set them up 
> on the same subnet as the real machines, and let them see the DHCP server,
> etc, and if so, then how to do it.  So far, I have never needed to learn the
> subtleties of ifconfig. Am I going to have to do so now? Do you have anymore 
> advice on using VDE and QEMU together for my purpose?

Like I said, you will need to use bridging. After you have loaded vde_switch,
skip the ifconfig step, and combine eth0 and tap0 into br0. Then you will need
to set up br0 properly. If you are going to use bridging however, I recommend
you use tuntap instead of VDE. (You don't really need VDE if you are going to
to use bridging.) If you decide to go with tuntap and bridging, you should look
in the qemu archives for assistance. There are several messages that appear
to have useful information on this topic, such as this one which tells you
step-by-step:

http://lists.gnu.org/archive/html/qemu-devel/2004-05/msg00032.html

(you'll need to do a 'brctl addif br0 eth0' and a 'ifconfig br0 192.168.0.XXX'
for the machine that will be running qemu (almost certainly in one of the startup
scripts, as eth0 must not have an ip yet) but otherwise the instructions are
exactly the same.)

I am curious though, why do you require that the virtual machines be on the same
subnet as the real ones?

> 
> Thanks
> 
> Phil

-- 
Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.

Re: [Qemu-devel] Question about tun/tap networking

[Phil Rasch]

Thanks Jim,

I dont really require everything to be on the same subnet. I just hate
having to figure out how to setup the nameservers, gateways, IP
numbers etc on each virtual machine I create. It would have been great
to just tell the virtual machine to "go get the relevant info from the
DHCP server". Maybe the alternative isnt really a big deal, but like I
said, I am a beginner at configuring networks.

Phil

On Wed, Jun 23, 2004 at 01:03:25PM -0400, Jim C. Brown wrote:
> On Wed, Jun 23, 2004 at 07:54:07AM -0600, Phil Rasch wrote:
> > I have been running a mixture of linux and windows machines, all real machines 
> > on a LAN connected to the outside world through a router, which is acting as 
> > my DHCP server, DNS server, and gateway machine. 
> > 
> > The LAN subnet is 192.168.0.*
> > 
> > Now I want to connect up the virtual machine running under QEMU. I want the 
> > virtual machine to be on the same subnet as the real machines, and to use 
> > DHCP from the router to get all the relevant info.
> 
> That is tricky. You will need to look into bridging.
> 
> > 
> > Jim suggested the following commands for somebody else on the mailing list, 
> > but I think that was headed towards devising a subnet that two virtual 
> > machines could use to talk to each other.
> > 
> > [/space/qemu/qemu-0.5.4/ $] su root
> > [/space/qemu/qemu-0.5.4/ #] vde_switch -daemon -tap tap0
> > [/space/qemu/qemu-0.5.4/ #] ifconfig tap0 192.168.1.254
> > [/space/qemu/qemu-0.5.4/ #] chmod 777 /tmp/vde.ctl
> > [/space/qemu/qemu-0.5.4/ #] exit
> > [/space/qemu/qemu-0.5.4/ $] vdeq qemu -hda disk1.img
> 
> That is correct. You now have 2 subnets, 198.168.0.* for the real network
> and 192.168.1.* for qemu/VDE.
> 
> > 
> > The thing I dont understand is whether the above command is setting up 
> > seperate subnet for the virtual machines, or whether I can also set them up 
> > on the same subnet as the real machines, and let them see the DHCP server,
> > etc, and if so, then how to do it.  So far, I have never needed to learn the
> > subtleties of ifconfig. Am I going to have to do so now? Do you have anymore 
> > advice on using VDE and QEMU together for my purpose?
> 
> Like I said, you will need to use bridging. After you have loaded vde_switch,
> skip the ifconfig step, and combine eth0 and tap0 into br0. Then you will need
> to set up br0 properly. If you are going to use bridging however, I recommend
> you use tuntap instead of VDE. (You don't really need VDE if you are going to
> to use bridging.) If you decide to go with tuntap and bridging, you should look
> in the qemu archives for assistance. There are several messages that appear
> to have useful information on this topic, such as this one which tells you
> step-by-step:
> 
> http://lists.gnu.org/archive/html/qemu-devel/2004-05/msg00032.html
> 
> (you'll need to do a 'brctl addif br0 eth0' and a 'ifconfig br0 192.168.0.XXX'
> for the machine that will be running qemu (almost certainly in one of the startup
> scripts, as eth0 must not have an ip yet) but otherwise the instructions are
> exactly the same.)
> 
> I am curious though, why do you require that the virtual machines be on the same
> subnet as the real ones?
> 
> > 
> > Thanks
> > 
> > Phil
> 
> -- 
> Infinite complexity begets infinite beauty.
> Infinite precision begets infinite perfection.

-- 
Phil Rasch, Climate Modeling Section, National Center for Atmospheric Research
Mail     --> P.O. Box 3000, Boulder CO 80307  
Shipping --> 1850 Table Mesa Dr, Boulder, CO 80305
email: pjr@ucar.edu, Web: http://www.cgd.ucar.edu/cms/pjr Phone: 303-497-1368, FAX: 303-497-1324 

Re: [Qemu-devel] Question about tun/tap networking

[Gianni Tedesco]

[-- Attachment #1: Type: text/plain, Size: 487 bytes --]

On Wed, 2004-06-23 at 13:03 -0400, Jim C. Brown wrote:
> That is tricky. You will need to look into bridging.

There are a few ways to do it:
 o static nat
 o iptables nat
 o bridging

Try this qemu-ifup for script for the iptables method:

	http://www.scaramanga.co.uk/stuff/qemu-ifup

-- 
// Gianni Tedesco (gianni at scaramanga dot co dot uk)
lynx --source www.scaramanga.co.uk/scaramanga.asc | gpg --import
8646BE7D: 6D9F 2287 870E A2C9 8F60 3A3C 91B5 7669 8646 BE7D

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 189 bytes --]

Re: [Qemu-devel] Question about tun/tap networking

[Jim C. Brown]

On Wed, Jun 23, 2004 at 06:16:32PM +0100, Gianni Tedesco wrote:
> On Wed, 2004-06-23 at 13:03 -0400, Jim C. Brown wrote:
> > That is tricky. You will need to look into bridging.
> 
> There are a few ways to do it:
>  o static nat
>  o iptables nat
>  o bridging
> 
> Try this qemu-ifup for script for the iptables method:
> 
> 	http://www.scaramanga.co.uk/stuff/qemu-ifup
> 

That's not what he asked for. AFAICT that script will set up a separate
subnet, 192.168.1.*, instead of using the 192.168.0.* subnet. It won't do
what he wants. (It looks like that to the outside world it will have an ip of
$qemu_ip, but from inside the guest OS he will still be on a separate subnet.)

In any case my recommendation is that he uses VDE and maintains all the virtual
machines on a separate subnet from his actual LAN (assuming thats possible,
of course some Windows machines will refuse to browse SMB network shares that
aren't on the same subnet ... but thats slightly off-topic).

> -- 
> // Gianni Tedesco (gianni at scaramanga dot co dot uk)
> lynx --source www.scaramanga.co.uk/scaramanga.asc | gpg --import
> 8646BE7D: 6D9F 2287 870E A2C9 8F60 3A3C 91B5 7669 8646 BE7D



> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel


-- 
Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.

[Qemu-devel] Question about tun/tap networking

[Arne Bernin]

Hi,

i am trying to set up two virtual machines with qemu 0.5.4. I have them
running, both with 2 network cards. I am able to ping all 4 interfaces
from the host they are running from but am not able to ping between both
virtual machines...
If i do a tcpdump on the corrsponding tun interfaces while trying to
ping i see a lot of arp who-has 172.16.0.254 tell 172.16.0.1 messages
(172.16.0.1 is the one machine, the other is 172.16.0.254). 
Is there something i have to do to get the arp responses right ??
Or am i totally wrong ?

thanks for any help,


--arne

Re: [Qemu-devel] Question about tun/tap networking

[nhand42]

Quoting Arne Bernin <arne@alamut.de>:

> Hi,
> 
> i am trying to set up two virtual machines with qemu 0.5.4. I have them
> running, both with 2 network cards. I am able to ping all 4 interfaces
> from the host they are running from but am not able to ping between both
> virtual machines...
> If i do a tcpdump on the corrsponding tun interfaces while trying to
> ping i see a lot of arp who-has 172.16.0.254 tell 172.16.0.1 messages
> (172.16.0.1 is the one machine, the other is 172.16.0.254). 
> Is there something i have to do to get the arp responses right ??
> Or am i totally wrong ?
> 

You've stuck both virtual machines on the same subnet, so they think they're on the 
same physical LAN. That's why they're doing ARPs and expecting replies. But you're 
actually running two QEMU instances on two seperate TUN interfaces and they *aren't* 
bridged. So the ARP on tun0 never gets seen on tun1 (and vice-versa). 

Set the second TUN interface to a different subnet (eg, 172.16.1.x) and enable ipv4 
forwarding. Linux will then forward packets between tun0 and tun1.

You could also muck about with proxyarp or bridging but honestly, I wouldn't bother 
with that. Routing is a lot easier to understand.

Re: [Qemu-devel] Question about tun/tap networking

[Carlos Valiente]

On Mon, 2004-05-03 at 02:35, nhand42@tpg.com.au wrote:
> You could also muck about with proxyarp or bridging but honestly, I wouldn't bother 
> with that. Routing is a lot easier to understand.

Bridging is not that difficult, either:

0. Get the userland bridge utils from http://bridge.sourceforge.net/ and
make sure your host Linux kernel is configured with CONFIG_BRIDGE

1. Create a bridge device (called 'br0', for instance):

# brctl addbr br0

2. Activate both TUN interfaces (but don't assign them IP addresses:
you'll do that for the bridge device instead)

# ifconfig tun0 0.0.0.0
# ifconfig tun1 0.0.0.0

3. Add both TUN interfaces to the bridge:

# brctl addif br0 tun0
# brctl addif br0 tun1

4. Set the bridge device IP address:

# ifconfig br0 172.16.1.1

C