PXE Boot Timeout Issue...

PXE Boot Timeout Issue...

[Stuart Sheldon]

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Hi all,

Just upgraded to 12.3 user space tools from 11.0, and now when I attempt
to netboot a guest, it appears that the pxe rom is timing out on dhcp
before the bridge has enough time to come up.

Is there a command line switch to set the dhcp timeout, or a build
option that can be changed to set the timeout to a longer value, or
disable it entirely?

Thanks in advance...

Stu

- --
Spider Pig, Spider Pig, Does whatever a Spider Pig does.
Can he swing, from a web, no he can't, he's a pig.
Look Oouuuut! He is a Spider Pig....
		-- Matt Groening - "Spider Pig Lyrics"
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Re: PXE Boot Timeout Issue...

[Stefan Hajnoczi]

On Fri, Apr 23, 2010 at 1:45 AM, Stuart Sheldon <stu@actusa.net> wrote:
> Just upgraded to 12.3 user space tools from 11.0, and now when I attempt
> to netboot a guest, it appears that the pxe rom is timing out on dhcp
> before the bridge has enough time to come up.
>
> Is there a command line switch to set the dhcp timeout, or a build
> option that can be changed to set the timeout to a longer value, or
> disable it entirely?

The bridge shouldn't need significant amounts of time to come up.  Can
you describe the networking setup?  Are you using libvirt and with
what network config?

If you have a bridge configured, can you show the output of:

$ sudo brctl showstp $bridge_name

Stefan

Re: PXE Boot Timeout Issue...

[Stuart Sheldon]

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Stefan Hajnoczi wrote:
> On Fri, Apr 23, 2010 at 1:45 AM, Stuart Sheldon <stu@actusa.net> wrote:
>> Just upgraded to 12.3 user space tools from 11.0, and now when I attempt
>> to netboot a guest, it appears that the pxe rom is timing out on dhcp
>> before the bridge has enough time to come up.
>>
>> Is there a command line switch to set the dhcp timeout, or a build
>> option that can be changed to set the timeout to a longer value, or
>> disable it entirely?
> 
> The bridge shouldn't need significant amounts of time to come up.  Can
> you describe the networking setup?  Are you using libvirt and with
> what network config?
> 
> If you have a bridge configured, can you show the output of:
> 
> $ sudo brctl showstp $bridge_name

The network is fairly straight forward. PC with single NIC directly
attached to switch with a local DHCP server.

We do not use libvirt, we are using qemu with command switches.

Interestingly it appears that the -option-rom command switch doesn't do
anything any longer. It is using gPXE by default only.

Here is our current command line we are testing with:

export QEMU_AUDIO_DRV=alsa
qemu-system-x86_64 \
        -m 1024 \
        -soundhw es1370 \
        -name 'Net Boot Disk' \
        -net nic,macaddr=52:54:00:12:31:06,model=virtio \
        -net tap,ifname=tap6,script=/etc/kvm/kvm-ifup-br0 \
        -option-rom /usr/local/share/qemu/pxe-virtio.bin \
        -boot n \
        -daemonize


Here is the exact chain of events:

1) Start guest from command line
2) tap adapter is added to br0 and enters learning state on host while
gPXE starts DHCP request on guest.
3) after about 15 seconds, tap device enters promiscuous mode on host,
and at same time, gPXE reports "No bootable device." on guest
4) Drop to guest console and signal a system_reset, guest gets DHCP
address and netboots normally.

Here is the info you requested, both before and after guest startup.

Before guest startup:

linus:~# brctl show br0
bridge name	bridge id		STP enabled	interfaces
br0		8000.001cc092ba91	no		eth0

linus:~# brctl showstp br0
br0
 bridge id		8000.001cc092ba91
 designated root	8000.001cc092ba91
 root port		   0			path cost		   0
 max age		  20.00			bridge max age		  20.00
 hello time		   2.00			bridge hello time	   2.00
 forward delay		  15.00			bridge forward delay	  15.00
 ageing time		 300.00
 hello timer		   1.87			tcn timer		   0.00
 topology change timer	   0.00			gc timer		   8.87
 flags			


eth0 (1)
 port id		8001			state		     forwarding
 designated root	8000.001cc092ba91	path cost		  19
 designated bridge	8000.001cc092ba91	message age timer	   0.00
 designated port	8001			forward delay timer	   0.00
 designated cost	   0			hold timer		   0.87
 flags			

After guest startup:

linus:~# brctl show br0
bridge name	bridge id		STP enabled	interfaces
br0		8000.001cc092ba91	no		eth0
							tap6
linus:~# brctl showstp br0
br0
 bridge id		8000.001cc092ba91
 designated root	8000.001cc092ba91
 root port		   0			path cost		   0
 max age		  20.00			bridge max age		  20.00
 hello time		   2.00			bridge hello time	   2.00
 forward delay		  15.00			bridge forward delay	  15.00
 ageing time		 300.00
 hello timer		   1.00			tcn timer		   0.00
 topology change timer	   0.00			gc timer		   2.00
 flags			


eth0 (1)
 port id		8001			state		     forwarding
 designated root	8000.001cc092ba91	path cost		  19
 designated bridge	8000.001cc092ba91	message age timer	   0.00
 designated port	8001			forward delay timer	   0.00
 designated cost	   0			hold timer		   0.00
 flags			

tap6 (2)
 port id		8002			state		     forwarding
 designated root	8000.001cc092ba91	path cost		 100
 designated bridge	8000.001cc092ba91	message age timer	   0.00
 designated port	8002			forward delay timer	   0.00
 designated cost	   0			hold timer		   0.00
 flags			

Let me know if you need anything else...

Stu


- --
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The band is just fantastic, that is really what I think.
Oh by the way, which one's Pink?
               -- Pink Floyd - "Have a Cigar Lyrics"
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Re: PXE Boot Timeout Issue...

[Jim Paris]

Stuart Sheldon wrote:
> Stefan Hajnoczi wrote:
> > On Fri, Apr 23, 2010 at 1:45 AM, Stuart Sheldon <stu@actusa.net> wrote:
> >> Just upgraded to 12.3 user space tools from 11.0, and now when I attempt
> >> to netboot a guest, it appears that the pxe rom is timing out on dhcp
> >> before the bridge has enough time to come up.
....
> 3) after about 15 seconds, tap device enters promiscuous mode on host,
> and at same time, gPXE reports "No bootable device." on guest
...
>  forward delay		  15.00			bridge forward delay	  15.00

I've run into this issue as well and lowering the forwarding delay
with "brctl setfd br0 5" fixes it.

-jim

Re: PXE Boot Timeout Issue...

[Stuart Sheldon]

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Hash: SHA256

Jim Paris wrote:
> Stuart Sheldon wrote:
>> Stefan Hajnoczi wrote:
>>> On Fri, Apr 23, 2010 at 1:45 AM, Stuart Sheldon <stu@actusa.net> wrote:
>>>> Just upgraded to 12.3 user space tools from 11.0, and now when I attempt
>>>> to netboot a guest, it appears that the pxe rom is timing out on dhcp
>>>> before the bridge has enough time to come up.
> ....
>> 3) after about 15 seconds, tap device enters promiscuous mode on host,
>> and at same time, gPXE reports "No bootable device." on guest
> ...
>>  forward delay		  15.00			bridge forward delay	  15.00
> 
> I've run into this issue as well and lowering the forwarding delay
> with "brctl setfd br0 5" fixes it.
> 
> -jim
> 

Thanks Jim! I think that has it...

Stu


- --
Hey nineteen Thats retha franklin, She dont remember The queen of soul,
Its hard times befallen The sole survivors, She thinks Im crazy,
But Im just growing old
               -- Steely Dan - "Hey 19 - Lyrics"
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Re: PXE Boot Timeout Issue...

[Stefan Hajnoczi]

For reference, my libvirt managed virbr0 has forwarding delay 0.  This
is the default:

http://libvirt.org/formatnetwork.html#elementsConnect

I know that my VM is a leaf node (it only has one NIC and isn't going
to create a loop in the network) and therefore it makes sense to
eliminate the forwarding delay entirely.

You might be interested in this link about STP delay on physical networks:

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00800b1500.shtml

Stefan