[Qemu-devel] Dynamic bridging

[Qemu-devel] Dynamic bridging

[Ben Taylor]

I was trying to get the bridging working (with the help
of pbrook and nox- on the irc #qemu channel) and
eventually got it working under Sun JDS/3 (Suse 9.1)
after adding the bridge-util's rpm.

After some experimentation, I found that once I setup
the bridge on my primary interface, (eth0) and I used
the qemu-ifup script, the tunnels would automatcially
attach to the bridge, and when qemu shuts down, they
automatically go away.

primary-ifup
Code:

#!/bin/sh
/sbin/brctl addbr br0
/sbin/ifconfig eth0 0.0.0.0 promisc up
/sbin/ifconfig eth0 192.168.1.2 netmask 255.255.255.0 broadcast 192.168.1.255 up
/sbin/brctl stp br0 off
/sbin/brctl setfd br0 1
/sbin/brctl sethello br0 1
/sbin/brctl addif br0 eth0
/sbin/route add default gw 192.168.1.1

Then I ran qemu with a "-n ./qemu-ifup" (not the default /etc/qemu-ifup script) and the Damn Small Linux connected to the tun0 interface and got a DHCP address from the LAN's dhcp server.  This was pretty exciting, given that I asked
a bunch of non-qemu networking questions trying to 
understand the tunnels and bridges.

qemu-ifup

#!/bin/sh
/sbin/ifconfig $1 0.0.0.0 promisc up
/sbin/brctl addif br0 $1 

Thanks to pbrook and nox- for helping my find this
gem. Now if I could only get bridging to work on
Solaris like this. 

Re: [Qemu-devel] Dynamic bridging

[Paul Brook]

On Wednesday 18 May 2005 01:52, Ben Taylor wrote:
> I was trying to get the bridging working (with the help
> of pbrook and nox- on the irc #qemu channel) and
> eventually got it working under Sun JDS/3 (Suse 9.1)
> after adding the bridge-util's rpm.
>
> After some experimentation, I found that once I setup
> the bridge on my primary interface, (eth0) and I used
> the qemu-ifup script, the tunnels would automatcially
> attach to the bridge, and when qemu shuts down, they
> automatically go away.
>
> primary-ifup
> Code:
>
> #!/bin/sh
> /sbin/brctl addbr br0
> /sbin/ifconfig eth0 0.0.0.0 promisc up
> /sbin/ifconfig eth0 192.168.1.2 netmask 255.255.255.0 broadcast \
>   192.168.1.255 up

This line should be changes to ifconfig br0 ...., and moved to the end of the 
script. 

You shouldn't give the component devices an IP address, just the br interface. 
Using the component interfaces directly is liable to lead to weird problems 
on the host.

Also, if youdon't want to use a static IP, you can just run dhclient
(or equivalent) on the br0 interface as normal.

My setup looks someting like:

/sbin/brctl addbr br0
/sbin/ifconfig eth0 0.0.0.0 up
/sbin/brctl addif br0 eth0
dhclient br0

Paul