[Bridge] Re: tg3 bridge problems

Gergely Madarasz gorgo at broadband.hu
Mon Jan 10 11:49:14 PST 2005

On Mon, Jan 10, 2005 at 02:41:34PM -0500, Neil Horman wrote:
> 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. 

Sounds great, but I expect it will not occur with a random tg3 card,
explained above... 

>     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.

The physical interface of course. I wouldn't have a chance seeing the
bpdu's on the bridge interface because they're handled by the bridge
driver and not passed on :)


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