Problem with bridged tap interface

Problem with bridged tap interface

[andreas.ames]

Hi all,

sorry for the previous partial e-mail, I hit the send button accidentally 
;-).

I have a setup with a kvm-based virtual machine running a stock RedHat 6.1 
(yes, that old) on a rather current debian host.

1. uname in host: 2.6.26-2-amd64 #1 SMP Wed May 12 18:03:14 UTC 2010 
x86_64 GNU/Linux

2. uname in guest: 2.2.12-20 #1 Mon Sep 27 10:40:35 EDT 1999 i686 unknown

eth0 of the guest is connected via tap0 to a kernel bridge, that is in 
turn connected via the host's eth1 to a Gigabit link.  On the kvm 
command-line I configure the guest-nic as "model=ne2k_pci".

The problem is, that I frequently loose network access from/to the guest.

I can see following diagnostics:

1. on the host:

ifconfig output:

brvm0     Link encap:Ethernet  Hardware Adresse 00:24:81:f9:9c:ee
          inet Adresse:10.0.2.11  Bcast:10.0.2.255  Maske:255.255.255.0
          inet6-Adresse: fe80::224:81ff:fef9:9cee/64 
Gültigkeitsbereich:Verbindung
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metrik:1
          RX packets:1120958 errors:0 dropped:0 overruns:0 frame:0
          TX packets:373699 errors:0 dropped:0 overruns:0 carrier:0
          Kollisionen:0 Sendewarteschlangenlänge:0
          RX bytes:138554311 (132.1 MiB)  TX bytes:32663228 (31.1 MiB)

eth0      ...

eth1      Link encap:Ethernet  Hardware Adresse 00:24:81:f9:9c:ee
          inet6-Adresse: fe80::224:81ff:fef9:9cee/64 
Gültigkeitsbereich:Verbindung
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metrik:1
          RX packets:3563790 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2393282 errors:0 dropped:0 overruns:0 carrier:0
          Kollisionen:0 Sendewarteschlangenlänge:1000
          RX bytes:4059696847 (3.7 GiB)  TX bytes:185671712 (177.0 MiB)
          Interrupt:19 Speicher:fa000000-fa012100

lo        ...

tap0      Link encap:Ethernet  Hardware Adresse 00:ff:19:c8:e6:04
          inet6-Adresse: fe80::2ff:19ff:fec8:e604/64 
Gültigkeitsbereich:Verbindung
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metrik:1
          RX packets:3244437 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5080877 errors:0 dropped:96605 overruns:0 carrier:0
          Kollisionen:0 Sendewarteschlangenlänge:500
          RX bytes:286049649 (272.7 MiB)  TX bytes:4114169266 (3.8 GiB)


netstat -i looks similar:

Iface   MTU Met   RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR 
Flg
brvm0      1500 0   1121135      0      0 0        373788      0      0  0 
BMRU
eth0       ...
eth1       1500 0   3563962      0      0 0       2393370      0      0  0 
BMRU
lo         ...
tap0       1500 0   3244471      0      0 0       5081115      0  96605  0 
BMRU

I see a lot of dropped frames on tap0/TX.


2. In the guest:

eth0      Link encap:Ethernet  HWaddr 02:11:BD:12:01:00
          inet addr:10.0.2.12  Bcast:10.0.2.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3517949 errors:459 dropped:0 overruns:0 frame:6
          TX packets:2439841 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          Interrupt:11 Base address:0xc100

lo        ...


netstat -i:

Iface   MTU Met    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP 
TX-OVR Flg
eth0   1500   0  3518044    459      0      0  2439871      0      0 0 BRU
lo     ...

There is lost data on eth0/RX.

Also there are related messages from dmesg in the guest:

eth0: bogus packet size: 22597, status=0x16 nxpg=0xb3.
eth0: next frame inconsistency, 0xb3
eth0: bogus packet size: 64780, status=0xf3 nxpg=0x38.
eth0: bogus packet size: 60666, status=0xc5 nxpg=0x28.
eth0: bogus packet size: 40656, status=0x7f nxpg=0xfd.
eth0: next frame inconsistency, 0xfd
eth0: bogus packet size: 56339, status=0xc nxpg=0x27.
eth0: bogus packet size: 18323, status=0x4b nxpg=0xc4.
eth0: next frame inconsistency, 0xc4

Can someone please tell me, what might be the problem? Or point me to the 
right direction, if this is OT here.


TIA,

aa

-- 
  
Please consider the environment before you print / Merci de penser à 
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(Vorsitzender/Chairman), Luc Charlemagne, Stefan Schönholz, Gregorius 
Peters 
Sitz der Gesellschaft / Principal Office: Berlin 
Registergericht / Registration Court: Amtsgericht Charlottenburg, HRB 
64838 



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Re: Problem with bridged tap interface

[Daniel P. Berrange]

On Wed, Feb 23, 2011 at 12:34:45PM +0100, andreas.ames@de.transport.bombardier.com wrote:
> Hi all,
> 
> sorry for the previous partial e-mail, I hit the send button accidentally 
> ;-).
> 
> I have a setup with a kvm-based virtual machine running a stock RedHat 6.1 
> (yes, that old) on a rather current debian host.
> 
> 1. uname in host: 2.6.26-2-amd64 #1 SMP Wed May 12 18:03:14 UTC 2010 
> x86_64 GNU/Linux
> 
> 2. uname in guest: 2.2.12-20 #1 Mon Sep 27 10:40:35 EDT 1999 i686 unknown
> 
> eth0 of the guest is connected via tap0 to a kernel bridge, that is in 
> turn connected via the host's eth1 to a Gigabit link.  On the kvm 
> command-line I configure the guest-nic as "model=ne2k_pci".
> 
> The problem is, that I frequently loose network access from/to the guest.

There have been QEMU NIC model implementation bugs that exhibit
that characteristic. If you have the drivers available in the
guest, then I'd recommend trying out different NIC models than
ne2k, since that's probably the least actively maintained NIC
model. At least try rtl8139, but ideally the e1000 too.

Regards,
Daniel
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Re: Problem with bridged tap interface

[andreas.ames]

Hi Daniel, all,

"Daniel P. Berrange" <berrange@redhat.com> schrieb am 23.02.2011 14:37:16:

> There have been QEMU NIC model implementation bugs that exhibit
> that characteristic. If you have the drivers available in the
> guest, then I'd recommend trying out different NIC models than
> ne2k, since that's probably the least actively maintained NIC
> model. At least try rtl8139, but ideally the e1000 too.

thanks a lot for the information.  If I remember correctly, I switched 
from the default rtl8139 to ne2k exactly beccause I had similar issues 
with the former model, but that was quite some time ago with a previous 
version of kvm/qemu.  e1000 is unfortunately not supported by the stock 
RedHat kernel my guest uses, if rtl8139 doesn't work flawlessly, I will 
try to compile an e1000 driver.

What I'm still concerned about is my general setup esp. the mix between a 
real Gigabit link on the host and a simulated 10MBit or FastEthernet 'NIC' 
in the guest connected via a kernel bridge in the host.  Are there any 
configuration parameters that I could try to use influencing flow control 
or something in the bridge; I guess something like auto-negotiation 
doesn't work for a simulated NIC and a kernel bridge.  But maybe this 
configuration is not a problem at all in a simulated environment, I don't 
know enough about the inner workings.  Maybe someone more knowledgable 
than me can help me out with more information? (Obviously grading down my 
Gigabit link to FastEthernet would only be a last resort.)


TIA,

aa

-- 
  
Please consider the environment before you print / Merci de penser à 
l'environnement avant d'imprimer / Bitte denken Sie an die Umwelt bevor 
Sie drucken 

Bombardier Transportation GmbH 
Vorsitzender des Aufsichtsrats / Chairman of Supervisory Board: Prof. Dr. 
Wilhelm Bender 
Geschäftsführung / Executive Board: Dr. Klaus Baur 
(Vorsitzender/Chairman), Luc Charlemagne, Stefan Schönholz, Gregorius 
Peters 
Sitz der Gesellschaft / Principal Office: Berlin 
Registergericht / Registration Court: Amtsgericht Charlottenburg, HRB 
64838 


_______________________________________________________________________________________________________________ 

This e-mail communication (and any attachment/s) may contain confidential 
or privileged information and is intended only for the individual(s) or 
entity named above and to others who have been specifically authorized to 
receive it. If you are not the intended recipient, please do not read, 
copy, use or disclose the contents of this communication to others. Please 
notify the sender that you have received this e-mail in error by reply 
e-mail, and delete the e-mail subsequently. Please note that in order to 
protect the security of our information systems an AntiSPAM solution is in 
use and will browse through incoming emails. 
Thank you. 
_________________________________________________________________________________________________________________ 


Ce message (ainsi que le(s) fichier(s)), transmis par courriel, peut 
contenir des renseignements confidentiels ou protégés et est destiné à 
l?usage exclusif du destinataire ci-dessus. Toute autre personne est, par 
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entrants.
Merci. 
_________________________________________________________________________________________________________________