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Re: [Xen-devel] peth1: received packet with own address as source addres

To: Andrew Theurer <habanero@xxxxxxxxxx>
Subject: Re: [Xen-devel] peth1: received packet with own address as source address
From: Nivedita Singhvi <niv@xxxxxxxxxx>
Date: Mon, 17 Oct 2005 14:32:01 -0700
Cc: David F Barrera <dfbp@xxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Arnd Schmitter <arnd_xen@xxxxxxxx>
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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




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