I'm trying to configure a linux server that shapes both incoming and
outgoing traffic. The problem is that I get a kernel panic ("Unable to
handle kernel NULL pointer dereference at virtual address 0000003c...")
everytime I load the traffic shaping rules and then try to edit a file
with vim (!!??) via a remote connection using ssh.

I configured the server (RedHat 9) as follows:

1. Downloaded from www.kernel.org the 2.4.21 kernel sources and from
www.netfilter.org the iptables 1.2.8 sources

2. Patched both kernel and iptables sources with IMQ patches, build and
install both of them

3. Defined the following script:

#!/bin/sh
modprobe imq numdevs=1
tc qdisc add dev imq0 root handle 1: htb default 20 r2q 1
tc class add dev imq0 parent 1: classid 1:1 htb rate 256kbit ceil
256kbit
tc class add dev imq0 parent 1:1 classid 1:10 htb rate 25kbit ceil
256kbit
tc class add dev imq0 parent 1:1 classid 1:20 htb rate 231kbit ceil
256kbit
tc filter add dev imq0 protocol ip parent 1:0 prio 1 u32 match ip src
10.5.1.150 flowid 1:10
tc filter add dev imq0 protocol ip parent 1:0 prio 2 u32 match ip dst
10.5.1.150 flowid 1:10
iptables -t mangle -A POSTROUTING -o eth0 -j IMQ --todev 0
iptables -t mangle -A POSTROUTING -o eth1 -j IMQ --todev 0
iptables -t mangle -A PREROUTING -i eth0 -j IMQ --todev 0
ip link set imq0 up

4. The server's eth0 ip address is 10.5.220.220/16; I logon on to it
(using ssh) from 10.5.1.150, then I try to edit (using vim) the script
described in 3) and I get the kernel panic.

Anybody know what could be the cause of this strange behaviour? Are the
rules defined above wrong?
Any hint/suggestion/etc will be welcome :)

Best wishes,
Toshiro.




--
Toshiro Viera <tviera@arnaldocastro.com.uy>