Subject: Re: PCI network driver -- receive pkts with 0xDEADBEEF
To: Michael Richardson <>
From: Shashi Rao <>
List: tech-net
Date: 02/07/2001 11:51:44
Le Wed, Feb 07, 2001 at 01:43:37PM -0500, Michael Richardson <> a ecrit:
:   Is the packet otherwise intact? I.e. is 0xDEADBEEF prepended?

nope. it is all garbage (sometimes causing my input path to generate
page faults), and with the aid of the kernel debugger, and
breakpoints on the transmit path, i've determined that i dont
consciously ever "add" this packet to the transmit queue or write a
descriptor with bogus data. i'm suspecting some sort of race
condition in either the network card or the driver itself which
causes the transmit logic to pick a descriptor which i didnt plan on
using (something that might be stale from prior use and had its mbuf
freed, maybe)...

also, using a pci bus analyzer shows that the device actually goes
out and fetches (what seems like) a legitimate transmit descriptor
except that this descriptor seems to be pointing to an mbuf that
contains garbage (which i never put in there)

i mailed to this list in the hope that i would be pointed at "ah,
that you're getting 0xdeadbeef's in your bogus packets implies that
you're using freed pages/clusters/whatever and the kernel diagnostic
code writes the first four bytes on released structures just so you
can easily track it down", etc...

Shashi Rao