[Bridge] Re: tg3 bridge problems

Neil Horman nhorman at redhat.com
Mon Jan 10 11:41:34 PST 2005

Gergely Madarasz wrote:
> On Mon, Jan 10, 2005 at 12:40:57PM -0500, Neil Horman wrote:
>>Gergely Madarasz wrote:
>>>On Mon, Jan 10, 2005 at 11:04:55AM -0500, Neil Horman wrote:
>>>>Strange.  My concern was that the tg3 interface has its hardware reset 
>>>>whenever its set to be up, and part of that is a resetting of its 
>>>>receive mode.  If for some reason IFF_PROMISC was cleared after you set 
>>>>it using brctl, the interface might be taken out of promisc mode.  Do 
>>>>you have any iptables rules running that might drop bpdus?
>>>No iptables rules az all. Btw iptables wouldn't prevent tcpdump from
>>>seeing the packets, would it?
>>>Could it be that the driver perhaps has a problem setting promisc mode
>>>when resetting the hardware?
>>Not really sure about this.  One experiment is worth a thousand guesses 
>>I suppose.......  I'll try and let you know. :)
> I did some other checks, like adding an explicit ifconfig eth0 promisc,
> then looking at tcpdump output - I didn't see any stray packets like I
> usually do, just ethernet broadcasts and unicasts to my mac, this also
> points to a problem that the ethernet interface is actually not in
> promisc, while the driver thinks it is.
> And it is probably not a driver-only issue. I've got older machines with
> tg3 running fine with bridge (with an older tg3 driver), and eth1 on the
> same machine also runs fine. On another machine I tested today, an IBM
> x326, the same thing happens - eth0 broken, eth1 fine. Would access to one
> of these machines help? :)
> Greg
I've got a tg3 card here.  I'll try re-create it as soon as I have time. 
     Just out of curiosity, are you running tcpdump against the physical 
interface or the bridged interface?  I do recall some issues involving 
using PF_PACKET on virtual interfaces, that might cause you to not see 
some packets that the physical interface really does receive.


  *Neil Horman
  *Software Engineer
  *Red Hat, Inc.
  *nhorman at redhat.com
  *gpg keyid: 1024D / 0x92A74FA1

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