Re: Trap 0x34 panic on 5.1 on Blade 100

On Tue, 17 May 2011 12:55:31 +0100
Julian Coleman <[email protected]> wrote:

> Hi,
> 
> > After further testing, it appears that I only get panics when using the
> > on-board gem interface with a 100Mb half-duplex connection.
> > Specifically, when connected to a 3Com SuperStack II Dual Speed Hub 500.
> 
> > I haven't configured any packet filters but I am using dhclient and
> > dhclient uses bpf. As a test, I disabled dhclient, set a static IP
> > address, and found that the panics stop. Instead I see network
> > errors like this:
> > 
> > gem0: discarding oversize frame (len=6330)
> > gem0: receive error: CRC error
> > gem0: discarding oversize frame (len=6330)
> > gem0: discarding oversize frame (len=6330)
> > gem0: receive error: CRC error
> > 
> > The oversize frame messages may be bogus, the hub has an RMON agent and
> > that reports collisions and fragments but no oversize packets.
> 
> I wonder what causes the gem interface to garble packets.  Does `ifconfig
> gem0` report full-duplex for the link?  A duplex mismatch could cause
> problems.  However, I'm still not sure what data causes the kernel to crash
> later.

The gem interface does appear to correctly detect half and full duplex,
when connected to my switch I see:

media: Ethernet autoselect (100baseTX full-duplex)

and when connected to the hub I see:

media: Ethernet autoselect (100baseTX)

However, the symptoms suggest that when operating in half-duplex mode
it may be passing collision fragments up to the higher layers as
garbled packets instead of dropping them.

George