Re: peth1: received packet with own address as source address

[Nivedita Singhvi <niv@us.ibm.com>]

Andrew Theurer wrote:
> Arnd Schmitter wrote:
> 
>> David F Barrera wrote:
>>
>>> On Mon, 2005-10-17 at 20:50 +0200, Arnd Schmitter wrote:
>>>  
>>>
>>>> David F Barrera wrote:
>>>>   
>>>>
>>>>> peth1: received packet with  own address as source address
>>>>>
>>>>> Is this something that I should care about? I don't see an obvious
>>>>> impact to the machine.          
>>>>
>>>>
>>>> This means normaly two things: Packets you send out are returning or 
>>>> there is another PC with the same address.
>>>> The Linuxkernel drops this packets as he think its a knd of address 
>>>> spoofing.
>>>> If all networking is working fine you will only have a minimal 
>>>> impact on performance. But it could indicate that something with 
>>>> your network configuration is wrong
>>>>     
>>>
>>>
>>> Arnd, thanks for your response. My network configuration appears to be
>>> OK; it is simple, one NIC and its IP address, and everything seems to be
>>> working well. Also, there are no two machines with the same address. So,
>>> I am wondering if this is a problem with Xen. I have opened up a
>>> bugzilla report, as I would like to have a definitive answer as to
>>> whether this is a bug or a network configuration issue.
>>>
>>> http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=339
>>>   
>>
>>
>>
>> Only one NIC and peth1 ??
>>
>> Take a look at your ifconfig output. Maybe there are two 
>> Virtual-Interfaces witch the same MAC.
> 
> 
> Unless the network-bridge script has changed the generated mac for eth0 
> (which gets renamed to peth0), all systems probably have the same mac 
> for peth0 & xen-br0: fe:ff:ff:ff:ff:ff.  I have tried using unique macs 
> (for just peth0, vif0.0, and xen-br0, other vifs still have fe:ff...), 
> and these messages disappear.  So, why would the mac for a veth0 or 
> xen-br0 get sent to another system?  Not sure, since they should not 
> have an ip address, and should not respond to an arp request.  I do 
> notice that peth0 has 'noarp' but xen-br0 does not.  Perhaps adding 
> noarp to xen-br0 will fix this.

This is what I thought it was, until Anthony said he was seeing
it even without guest domains, and without xend starting.  I'd
thought the network rename was in vif-bridge, but misremembered,
it's in network-bridge, so it really doesn't need xend to run to
run into the problem.

The MAC address is expected to be unique in a network, so it is
a problem if it's not.

The non-public MAC should not be going out, and if someone could just
say which the "same MAC address" reported in the message is, that
would confirm it. But xen-br0 shouldn't need a noarp(?) (checking...)


thanks,
Nivedita