[Bridge] received packet with own address as source address

[Bridge] received packet with own address as source address

[Matthew Kent]

Trying to determine if I have a misconfiguration, misunderstanding or
have stumbled on a bug.

Have a CentOS 5.2 server with 2 e1000e nics in a balance-xor bond, check
this out: 


Test 1 - arping the bond device @ 172.16.0.117 from a second machine
---
root@foo [/root]# arping -c 1 -b -I eth0 172.16.0.117
ARPING 172.16.0.117 from 172.16.0.116 eth0
Unicast reply from 172.16.0.117 [00:15:17:70:A3:88]  0.607ms
Unicast reply from 172.16.0.117 [00:15:17:70:A3:88]  0.648ms
Sent 1 probes (1 broadcast(s))
Received 2 response(s)

Nothing logged to the kernel ring buffer on the server. All looks good
and happy.


Test 2 - now add a bridge @ 172.16.0.117 with the bond as a port:
---
root@foo [/root]# arping -c 1 -b -I eth0 172.16.0.117
ARPING 172.16.0.117 from 172.16.0.116 eth0
Unicast reply from 172.16.0.117 [00:15:17:70:A3:88]  0.603ms
Unicast reply from 172.16.0.117 [00:15:17:70:A3:88]  0.642ms
Sent 1 probes (1 broadcast(s))
Received 2 response(s)

Looks good, traffic moves, etc but now the following gets logged on the
server for every broadcast packet:

[26489.040112] bond0: received packet with  own address as source
address


Capturing the traffic for both tests and comparing, they look identical,
but the bridge wants to throw the warning level message in
net/bridge/br_fdb.c br_fdb_update(). The printk warning, being rate
limited, seems to add a noticable lag. Disabling the warning with a
patch made things happy again.

Couple questions from this for the more knowledgeable folks:

1) Are the two arp replies from a balance-xor bond normal?

2) Should the bridge handle this or should I just not be tying an ip to
the bridge in balance-xor mode?

Thanks for your time!
-- 
Matthew Kent \ SA \ bravenet.com

Re: [Bridge] [Bonding-devel] received packet with own address as source address

[Jay Vosburgh]

Matthew Kent <matt@bravenet.com> wrote:

>Trying to determine if I have a misconfiguration, misunderstanding or
>have stumbled on a bug.
>
>Have a CentOS 5.2 server with 2 e1000e nics in a balance-xor bond, check
>this out: 

	I suspect your switch is misconfigured.
	
	The balance-xor mode is nominally "Etherchannel compatible" and
the switch ports connected to bonding balance-xor should be in
Etherchannel mode ("Trunking", etc, but not "LACP" or "802.3ad").

	If the switch doesn't know the ports are aggregated, it may very
well send broadcasts recieved on one port back out the other port, which
may be the cause of what you're seeing.  The switch might also whine
about flapping of the MAC address.

	If I set up bonding here with the switch unconfigured for
Etherchannel, I see the same behavior as this:

ARPING 172.16.0.117 from 172.16.0.116 eth0
Unicast reply from 172.16.0.117 [00:15:17:70:A3:88]  0.607ms
Unicast reply from 172.16.0.117 [00:15:17:70:A3:88]  0.648ms
Sent 1 probes (1 broadcast(s))
Received 2 response(s)

	Specifically the "Received 2 response(s)" part.  This happens
because the bond receives one copy of the packet on each port, and
responds to each.

	After I configure the switch ports correctly for Etherchannel,
there is only 1 response.  Without the switch configuration IPv6
addrconf also complains about duplicate address detected.

	-J

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com

Re: [Bridge] [Bonding-devel] received packet with own address as source address

[richardvoigt]

On Thu, Dec 4, 2008 at 12:46 AM, Jay Vosburgh <fubar@us.ibm.com> wrote:
> Matthew Kent <matt@bravenet.com> wrote:
>
>>Trying to determine if I have a misconfiguration, misunderstanding or
>>have stumbled on a bug.

I think there is a bug here although the description doesn't sound
like the buggy case.

Here is the specific configuration that produces the same message and
I think should not:

A bond in fail-over mode, either both or just one PHY connected.

VLANs configured on the bond device.

Two of the bond VLAN interfaces members of the same bridge, stp
enabled.  An external bridge device (actually a fancy transparent
traffic shaper with a history of occasional seizure) connecting the
same two VLANs.  A router on the higher-numbered (so less preferred by
STP) VLAN.  So the nominal case is for STP to block forwarding, but if
the traffic shaper fails then the bridge will start sending traffic
direct to the router.

Now when the traffic shaper is forwarding traffic, the BPDUs sent out
the preferred port come back on the non-preferred port and force it
into blocking mode as desired.  But the "received packet with own
address as source address" message is logged.

Re: [Bridge] [Bonding-devel] received packet with own address as source address

[Matthew Kent]

On Wed, 2008-12-03 at 16:46 -0800, Jay Vosburgh wrote:
> Matthew Kent <matt@bravenet.com> wrote:
> 
> >Trying to determine if I have a misconfiguration, misunderstanding or
> >have stumbled on a bug.
> >
> >Have a CentOS 5.2 server with 2 e1000e nics in a balance-xor bond, check
> >this out: 
> 
> 	I suspect your switch is misconfigured.
> 	
> 	The balance-xor mode is nominally "Etherchannel compatible" and
> the switch ports connected to bonding balance-xor should be in
> Etherchannel mode ("Trunking", etc, but not "LACP" or "802.3ad").
> 
> 	If the switch doesn't know the ports are aggregated, it may very
> well send broadcasts recieved on one port back out the other port, which
> may be the cause of what you're seeing.  The switch might also whine
> about flapping of the MAC address.
> 
> 	If I set up bonding here with the switch unconfigured for
> Etherchannel, I see the same behavior as this:
> 
> ARPING 172.16.0.117 from 172.16.0.116 eth0
> Unicast reply from 172.16.0.117 [00:15:17:70:A3:88]  0.607ms
> Unicast reply from 172.16.0.117 [00:15:17:70:A3:88]  0.648ms
> Sent 1 probes (1 broadcast(s))
> Received 2 response(s)
> 
> 	Specifically the "Received 2 response(s)" part.  This happens
> because the bond receives one copy of the packet on each port, and
> responds to each.
> 
> 	After I configure the switch ports correctly for Etherchannel,
> there is only 1 response.  Without the switch configuration IPv6
> addrconf also complains about duplicate address detected.
> 
> 	-J

Ah of course! :) Thanks for the helpful information. I should have read
the later section on balance-xor in bonding.txt more closely.
-- 
Matthew Kent \ SA \ bravenet.com