apologies for the drawing got messed up:
(UDP Server daemon)
|
|
socket
|
|
[my_bridge 172.16.0.2]----tap1---VM2
|
|
tap0
|
virtual machine1
172.16.0.3
-thanks
On Sat, Jul 18, 2009 at 1:51 PM, Deepjyoti Kakati<dkakati73@xxxxxxxxx> wrote:
> I am facing a issue with bridge that apparently stops fwding and
> hoping someone can point out what
> is going wrong or give some clues.
>
> am using linux 2.6.27 and corresponding bridgeutils pkg.
>
> my topology inside the machine is like this
>
> 172.16.0.3
> 172.16.0.2
> (Server_daemon)....udp socket......[ my_bridge
> ].............tap0......[Virtual machine1]
> atop kernel ! !
> ! !
> tap1
> tap2........[virtual machine3]
> !
> [virtual machine2]
>
>
> I create a few virtual machines using qemu and have their tap
> interfaces hook into
> the bridge.
>
> virtual machine1 internally assigns 172.16.0.2 to its virtual nic
>
> the bridge itself has address 172.16.0.3
>
> my server binds a UDP socket to a {fixed port, 172.16.0.3} and takes
> heartbeats and messages
> from virtual machine1 who is UDP client and binds to 172.16.0.2
>
> things work fine and packets flow both ways
>
> STP is turned off by default as per "brctl show"
>
> trouble starts when I shut down virtual machine2 or 3 and detach the
> tap1 or tap2 from
> the bridge. the detach sequence I used is:
>
> ifconfig tap1 down
> brctl delif br_internal tap1
> ifconfig tap1 up
>
> I would expect the bridge to keep on forwarding pkts to and from tap0
> port which is
> still attached, however i see sometimes the bridge receives frames from tap0
> (heartbeats from virtual machine1) but my socket never gets it and is
> blocked in recvfrom()
>
> this condition lasts from 10-40 seconds before things get back to normal.
>
> I think my socket is ok because I sent a message to it from another
> thread while this
> condition was happening and this dummy message instantly came to recvfrom().
>
> tried turning on STP and setting fwd delay of 0 to no avail. also
> tried explicitly setting the
> promiscuous flag with ifconfig.
>
> /var/log/messages does not show tap0 going out of forwarding state. it
> appears normal.
> the port thats detached goes into disabled state which is expected.
>
> if there is anything wrong with my approach or there is some known
> issue with bridge
> forwarding during topology change, kindly let me know.
>
> I need to be able to attach and detach taps dynamically without
> affecting traffic on
> other ports as the VLANs used by the virtual machines can be changed on the fly.
> multiple virtual machine tap's could be hooked onto the same bridge
> (vlan) hence the
> issue.
>
> thanks
> Deepjyoti Kakati
>
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