Andrew Morton wrote:
Begin forwarded message:
Date: Thu, 21 Jul 2005 11:39:44 -0700
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Subject: [Bugme-new] [Bug 4922] New: Bug in netfilter.c when drivers do
hardware checksum generation.
http://bugzilla.kernel.org/show_bug.cgi?id=4922
Summary: Bug in netfilter.c when drivers do hardware checksum
generation.
Kernel Version: 2.6.12.2
Status: NEW
Severity: normal
Owner: [EMAIL PROTECTED]
Submitter: [EMAIL PROTECTED]
Distribution:
Has been reproduced in Fedora Core 2, Fedora Core 3, YDL 4.0.
with 2.6.8, 2.6.8.1 2.6.9, 2.6.10, 2.6.12.2
Hardware Environment:
x86 (tigon3 driver for BMC5705 tg3.c and ppc systems (mac mini) having ethernet
drivers that do hardware IP checksums.
Software Environment:
See kernel revs above.
Standard distributions.
Problem Description:
There is a bug in the Linux kernel from 2.6.7 through 2.6.12.2.
The problem occurs when packets are being diverted to user space through
ipq/netlink sockets on systems that have ethernet drivers with hardware IP
checksum capability. It has been reproduced when user code is mangling the
packet headers.
Where hardware has set ip_summed field in the skb and falsely indicates that the
checksum does not need to be re-generated after IP headers are mangled.
Please show how you use ip_queue (where are you calling -j QUEUE).
This bug was originally introduced with a change to net/core/netfilter.c in
the 2.6.8 distribution.
Steps to reproduce:
To reproduce the bug, divert packets through netlink ipq and change IP header
information.
The following patch fixes the problem on 2.6.12.2:
--- linux-2.6.12.2/net/core/netfilter.c.orig 2005-06-29 19:00:53.000000000
-0400
+++ linux-2.6.12.2/net/core/netfilter.c 2005-07-19 19:07:18.000000000 -0400
@@ -485,6 +485,14 @@
unsigned int verdict;
int ret = 0;
+ if ((*pskb)->ip_summed == CHECKSUM_HW) {
+ if (outdev == NULL) {
+ (*pskb)->ip_summed = CHECKSUM_NONE;
+ } else {
+ skb_checksum_help(*pskb, 0);
+ }
+ }
+
/* We may already have this, but read-locks nest anyway */
rcu_read_lock();
This code was never intended to fix up checksums of mangled queued
packets. It is the responsibility of the user to update the checksum
after mangling a packet.
Regards
Patrick
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