RE: how to setup user mode network backend and test it?

[ckim]

Hi, Peter Maydell,

With 
-netdev user,id=n1 -device e1000,netdev=n1
And adding this two lines in the init script
Ifconfig eth0 10.0.2.15 netmask 255.255.255.0 up
Route add default gw 10.0.2.2
Made pin to 10.0.2.2 work! (I think I wrongly tried 10.0.2.1 as the router 
before)
And also tftp worked with this command.
Tftp -g -r hello 129.254.132.47

/ # tftp -g -r hello 129.254.132.47
[   12.331087] random: fast init done
hello                 88% |****************************    | 3082k  0:00:00 
ETA[   16.403920] random: crng init done
hello                100% |********************************| 3494k  0:00:00 ETA

thanks!
Chan Kim

> -----Original Message-----
> From: ckim@etri.re.kr <ckim@etri.re.kr>
> Sent: Friday, April 16, 2021 7:35 AM
> To: 'Peter Maydell' <peter.maydell@linaro.org>
> Cc: 'qemu-discuss' <qemu-discuss@nongnu.org>
> Subject: RE: how to setup user mode network backend and test it?
> 
> Hello Peter Maydell,
> 
> I thought I can set real IP address to the VM(I know with tap networking
> it's possible). 129.254.254.x is the address used in our department.
> OK, I'll understand that, with just "-netdev user,id=n1 -device
> e1000,netdev=n1" option, there are DHP server, DNS server and SMB server
> at 10.0.2.x as shown in the document provided to me. The document says
> "You can use a DHCP client to automatically configure the network in the
> QEMU VM. The DHCP server assigns addresses to the hosts starting from
> 10.0.2.15." Then, do I get 10.0.2.15 automatically? After linux boots, I
> don't see that address assigned to eth0. My initial eth0 state is like
> this (no IP address)
> 
> 2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop qlen 1000
>     link/ether 52:54:00:12:34:56 brd ff:ff:ff:ff:ff:ff
> 
> How should I 'run dhcp client'? (maybe I don't know how I can set linux
> Image to use DHCP for network setting, I tried ip=dhcp in kernel command
> line to no avail.)
> 
> Also, in the document it says : "you can download the linux-test-
> xxx.tar.gz archive and copy the script qemu-ifup in /etc", but where can I
> get this linux-test-xxx.tar.gz file? (I have used tap networking for qemu
> and rtems in the past and have those scripts on another machine, but I'm
> not sure they are correct/optimal, there are several variants/blocked
> commands I tried).
> 
> Thank you!
> Chan Kim
> 
> > -----Original Message-----
> > From: Peter Maydell <peter.maydell@linaro.org>
> > Sent: Thursday, April 15, 2021 10:41 PM
> > To: Chan Kim <ckim@etri.re.kr>
> > Cc: qemu-discuss <qemu-discuss@nongnu.org>
> > Subject: Re: how to setup user mode network backend and test it?
> >
> > On Thu, 15 Apr 2021 at 14:22, <ckim@etri.re.kr> wrote:
> > > I tried qemu networking but it doesn’t work and I can’t figure out
> > > what
> > is wrong.
> > >
> > > I first tried “-netdev user,id=n1 -device e1000,netdev=n1” as
> > > network
> > option,(I added e1000 driver in the linux kernel build too.).
> > >
> > > By `ip link show` I can see there is the ‘eth0’ interface. So I gave
> > > commands below
> > >
> > >
> > >
> > > ifconfig eth0 129.254.32.55 netmask 255.255.255.0 up
> > >
> > > route add default gw 129.254.32.1
> >
> > Where are you getting these IP addresses from ?
> >
> > The usual thing with user mode networking is to run a dhcp client
> > inside the guest and let that deal with it (there is a fake DHCP
> > server provided by QEMU that the guest will see on the usermode
> > network). You should get an address in the 10.0.2.x range.
> >
> > https://qemu-project.gitlab.io/qemu/system/net.html#using-the-user-mod
> > e-
> > network-stack
> >
> > thanks
> > -- PMM