Re: [Xen-devel] Re: Linux Stubdom Problem

[Jiageng Yu <yujiageng734@xxxxxxxxx>]

2011/11/10 Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>
> On Wed, 9 Nov 2011, Jiageng Yu wrote:
> > The keyboard driver is OK now. I am working on network device. In
> > linux stubdom, I have udev, ifconfig and brctl tools. After udevd
> > started, stubdom executes "ifconfig eth0 IPadderss netmask netgate up"
> > to setup the network. When qemu in stubdom creates a tapxx interface
> > for hvm guest, Âthe script should be executed to build a net bridge.
> >
> > Â Â Â /sbin/brctl addbr eth0
> > Â Â Â /sbin/brctl addif eth0 tapXX
> >
> > Therefore, the hvm guest has the network device. Is this plan
> > reasonable? Or have better one?
>
> The bridge should be called xenbr0, the stubdom's network interface
> (that should probably called eth0) should be added to the bridge at boot
> time.
>
> Like you said, when qemu starts is going to create a tap interface, on
> Linux usually we rely on a udev script to add the tap interface to the
> bridge. The script is tools/hotplug/Linux/vif-setup, that calls
> tools/hotplug/Linux/vif-bridge.
>
> So at the end you have:
>
> xenbr0 (bridge)
> ||
> |+-------------------------------+
> | Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â|
> eth0 Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
> (stubdom network interface) Â Â ÂtapXX
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â (qemu's tap interface)


Hi Stefano,

 ÂÂI have a prototype of network of linux based stubdom, as shown in
attached figure. I list my designÂpoints, please comment on them.

    1. Qemu-ifup script in Linux stubdom.

     Qemu in stubdom invokes qemu-ifup script to setup the
bridge(net/tap.c). Because the linux stubdom only has nash and can not
execute the qemu-ifup script, I implement a c version of qemu-ifup
script. Using the following way, the qemu will invoke qemu-ifup
program in stubdom.

diff -r 0f36c2eec2e1 tools/libxl/libxl_dm.c
--- a/tools/libxl/libxl_dm.c    Thu Jul 28 15:40:54 2011 +0100
+++ b/tools/libxl/libxl_dm.c    Thu Nov 17 22:41:29 2011 +0000
@@ -29,9 +29,12 @@
 #include "libxl.h"
 #include "flexarray.h"

-static const char *libxl_tapif_script(libxl__gc *gc)
+static const char *libxl_tapif_script(libxl__gc *gc,
+                                      libxl_device_model_info *info)
 {
 #ifdef __linux__
+    if(info->device_model_linux_stubdomain)
+        return libxl__sprintf(gc, "/bin/qemu-ifup");
     return libxl__strdup(gc, "no");
 #else
     return libxl__sprintf(gc, "%s/qemu-ifup", libxl_xen_script_dir_path());

     I do not use libxl_xen_script_dir_path() to determine the path of
qemu-ifup, because we don't want include xen-unstable.hg/Config.mk in
linux stubdom. Therefore, I hardcoded this path.

    2. Network tools.

    Our linux based stubdom do not have the real shell and IP stack,
so we must custom the network tools. I notice the bridge-utils-1.5
version creates AF_LOCAL socket, so brctl can be used without
modification. But ifconfig would not be so luck. I need to rewrite
ifconfig and make it only support bring up the interfaces.

    3. The mac address.

    If we declare the mac address in stubdom-cfg file, the eth0 in
stubdom and eth0 in hvm guest will be set to the same mac address.

   do_domain_create (or libxl__create_stubdom)
         -->libxl_device_nic_add

   As a temporary solution, I hardcoded a static mac address for linux
stdubom in libxl__create_stubdom().


  Thanks.


Jiageng Yu.

Attachment: Screenshot-QEMU (fedora14-dm)-1.png
Description: PNG image

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