Wednesday, December 14, 2005

ApacheCon US 2005

I got lucky and earned a scholarship from JCP to go to ApacheCon US 2005. The conference was really great and I can only encourage everybody who works in this field to attend it. The most impressive talks were for me (in order of appearnce not importnace):

Open Source for Business and Profit by Jim Driscoll
"If people never heard about your product you don’t have one" - the most important part of your Open Source Strategy is to get the word out, e.g. marketing. If your community only consists of yourself then you weren't successful.

Roller: An Open Source Blogging Platform by David Johnson
Roller is a great technology and you can find a PDF of the talk here.

Business Tips for the Open Source Consultant by Will Glass-Husain
Will talked about the importance to deliver high quality to have repeat business with the same customer and stressed the importance about keeping your sales funnel full. While working for one client you should have at least three new leads. He also emphasized the difference between consultant and contractor: The first one helps the business to make more revenue or save cost -- the later is managed b the first one to generate some code.

New (and old) Trends in Web Application Security Christian Wenz

Wenz showed a lot of (at least for me) surprising and unexpected exploits. If you ever find his prese be sure to have a good look at it. XPath injection was pretty new to me.

Java-XML Binding Approaches at Apache by Thomas Dudziak

The essemce of this talk was to use per default XML-Java mappers and Apache seems t have some...

Struts 2006: An Embarrassment of Riches by Don Brown, Ted Husted, Patrick Lightbody

As a Struts instructor for UCSD I was interested what they had to say. After the arrival of JSF I felt Struts was, well, somewhat dead. Anyway they now try to make two next generation Struts -- one based on Webworks which has all the features of "Ruby on Rails" and an another one based on JSF.

Shale: The Next Struts? by Craig McClanahan

For me Craig is the man -- I really believe in Shales and if I had the time I would really start rewriting all my old Struts applications. The most I like the Tapestry like marking of HTML designs, the full support of JSF, and some business logic (continuation, flow) -- a great concept.

HTTP Caching and Cache-busting for Content Publishers and Hacking Apache HTTP Server at Yahoo! by Michael Radwin

Both talks were fantastic. They showe what Yahoo! is doing to make their web page fast. Everine of his tips is probably worth trying. Bes sure to check out the presentation at

Keynote by Jaron Lanier
I am skipping here some talks though very good somehow redundant to the ones I mentioned so far and close with Jaron. Given that I will be teaching a multicore programming class in January I was really eager to learn what he had to say about that: Jaron is envisioning that real time computing will get more and more important. In order to achieve that computers and networks have to become faster. Though multicore processors are the wrong paradigm (nobody knows how to program them!) they might be ablt o help. In order to make them work he is proposing to add some virtualization to them so you can have one processor for each task, e.g. in a game one processor for the enemy, one for the ocean, etc. -- this will allow us programmers to focus on the stuff we know and not worry about the multicores too much. Neat idea and I will b e sujre to introduce that in my class.

Friday, December 09, 2005

VTK Nifi File Import Filter updated

I updated today the Nifti File import filter (see my original entry here).

Thursday, December 08, 2005

Xen 3.0, nx, and FC4

We recently upgraded our server to Fedora Core 4 (FC4) which neatly supports Xen. I think Xen is a much cleaner solution for our remote access service than jail -- furthermore I couldn't use the jail configuration I had for Redhat so I just embarked on the new Xen architecture.

The latest 3.0 rpms from Xen-Source worked right out of the box -- there are just two things you need to change:

The entry in /etc/grub.conf looks like:

title Xen (
root (hd0,0)
kernel /xen-3.gz com1=115200,8n1
module /vmlinuz- root=/dev/VolGroup00/LogVol00
ro maxcpus=1 console=tty1 console=ttyS0,115200n8
module /initrd-

Note the fc4 -- the documentation just forgets them and nothing works.

The second thing you need to do is replace the /etc/xen/scripts/network-bridge with the following:
#!/bin/sh -x
# Default Xen network start/stop script.
# Xend calls a network script when it starts.
# The script name to use is defined in /etc/xen/xend-config.sxp
# in the network-script field.
# This script creates a bridge (default xen-br0), adds a device
# (default eth0) to it, copies the IP addresses from the device
# to the bridge and adjusts the routes accordingly.
# If all goes well, this should ensure that networking stays up.
# However, some configurations are upset by this, especially
# NFS roots. If the bridged setup does not meet your needs,
# configure a different script, for example using routing instead.
# Usage:
# network (start|stop|status) {VAR=VAL}*
# Vars:
# bridge The bridge to use (default xen-br0).
# netdev The interface to add to the bridge (default eth0).
# antispoof Whether to use iptables to prevent spoofing (default yes).
# start:
# Creates the bridge and enslaves netdev to it.
# Copies the IP addresses from netdev to the bridge.
# Deletes the routes to netdev and adds them on bridge.
# stop:
# Removes netdev from the bridge.
# Deletes the routes to bridge and adds them to netdev.
# status:
# Print ifconfig for netdev and bridge.
# Print routes.

# Exit if anything goes wrong.
set -e

# First arg is the operation.

# Pull variables in args in to environment.
for arg ; do export "${arg}" ; done


echo "*network $OP bridge=$bridge netdev=$netdev antispoof=$antispoof" >&2

# Usage: transfer_addrs src dst
# Copy all IP addresses (including aliases) from device $src to device $dst.
transfer_addrs () {
local src=$1
local dst=$2
# Don't bother if $dst already has IP addresses.
if ip addr show dev ${dst} | egrep -q '^ *inet ' ; then
# Address lines start with 'inet' and have the device in them.
# Replace 'inet' with 'ip addr add' and change the device name $src
# to 'dev $src'.
ip addr show dev ${src} | egrep '^ *inet ' | sed -e "
s/inet/ip addr add/
s/${src}/dev ${dst}/
" | sh -e
# Remove automatic routes on destionation device
ip route list | sed -ne "
/dev ${dst}\( \|$\)/ {
s/^/ip route del /
}" | sh -e

# Usage: del_addrs src
del_addrs () {
local src=$1
ip addr show dev ${src} | egrep '^ *inet ' | sed -e "
s/inet/ip addr del/
s/${src}/dev ${src}/
" | sh -e

# Usage: transfer_routes src dst
# Get all IP routes to device $src, delete them, and
# add the same routes to device $dst.
# The original routes have to be deleted, otherwise adding them
# for $dst fails (duplicate routes).
transfer_routes () {
local src=$1
local dst=$2
# List all routes and grep the ones with $src in.
# Stick 'ip route del' on the front to delete.
# Change $src to $dst and use 'ip route add' to add.
ip route list | sed -ne "
/dev ${src}\( \|$\)/ {
s/^/ip route del /
s/^/ip route add /
}" | sh -e

# Usage: create_bridge bridge
create_bridge () {
local bridge=$1

# Don't create the bridge if it already exists.
if ! brctl show | grep -q ${bridge} ; then
brctl addbr ${bridge}
brctl stp ${bridge} off
brctl setfd ${bridge} 0
ifconfig ${bridge} up

# Usage: add_to_bridge bridge dev
add_to_bridge () {
local bridge=$1
local dev=$2
# Don't add $dev to $bridge if it's already on a bridge.
if ! brctl show | grep -q ${dev} ; then
brctl addif ${bridge} ${dev}

# Usage: antispoofing dev bridge
# Set the default forwarding policy for $dev to drop.
# Allow forwarding to the bridge.
antispoofing () {
local dev=$1
local bridge=$2

iptables -P FORWARD DROP
iptables -A FORWARD -m physdev --physdev-in ${dev} -j ACCEPT

# Usage: show_status dev bridge
# Print ifconfig and routes.
show_status () {
local dev=$1
local bridge=$2

echo '============================================================'
ifconfig ${dev}
ifconfig ${bridge}
echo ' '
ip route list
echo ' '
route -n
echo '============================================================'

op_start () {
if [ "${bridge}" == "null" ] ; then

create_bridge ${bridge}

if ifconfig 2>/dev/null | grep -q veth0 ; then

if ifconfig veth0 2>/dev/null | grep -q veth0 ; then
mac=`ifconfig ${netdev} | grep HWadd | sed -e 's/.*\(..:..:..:..:..:..\).*/\1/'`
if ! ifdown ${netdev} ; then
# if ifup didn't work, see if we have an ip= on cmd line
if egrep 'ip=[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+:' /proc/cmdline ;
kip=`sed -e 's!.*ip=\([0-9]\+\.[0-9]\+\.[0-9]\+\.[0-9]\+\):.*!\1!' /proc/cmdline`
kmask=`sed -e 's!.*ip=[^:]*:[^:]*:[^:]*:\([^:]*\):.*!\1!' /proc/cmdline`
kgate=`sed -e 's!.*ip=[^:]*:[^:]*:\([^:]*\):.*!\1!' /proc/cmdline`
ifconfig ${netdev} down
ip link set ${netdev} name p${netdev}
ip link set veth0 name ${netdev}
ifconfig p${netdev} -arp down
ifconfig p${netdev} hw ether fe:ff:ff:ff:ff:ff
ifconfig ${netdev} hw ether ${mac}
add_to_bridge ${bridge} vif0.0
add_to_bridge ${bridge} p${netdev}
ip link set ${bridge} up
ip link set vif0.0 up
ip link set p${netdev} up
if ! ifup ${netdev} ; then
if [ ${kip} ] ; then
# use the addresses we grocked from /proc/cmdline
ifconfig ${netdev} ${kip}
[ ${kmask} ] && ifconfig ${netdev} netmask ${kmask}
ifconfig ${netdev} up
[ ${kgate} ] && ip route add default via ${kgate}
# old style without veth0
transfer_addrs ${netdev} ${bridge}
transfer_routes ${netdev} ${bridge}

if [ ${antispoof} == 'yes' ] ; then
antispoofing ${netdev} ${bridge}

op_stop () {
if [ "${bridge}" == "null" ] ; then

brctl delif ${bridge} ${netdev}

if ifconfig veth0 2>/dev/null | grep -q veth0 ; then
brctl delif ${bridge} vif0.0
ifconfig vif0.0 down
mac=`ifconfig veth0 | grep HWadd | sed -e 's/.*\(..:..:..:..:..:..\).*/\1/'`
ifconfig ${netdev} down
ifconfig ${netdev} hw ether ${mac}
ifconfig ${netdev} arp up
transfer_addrs veth0 ${netdev}
transfer_routes veth0 ${netdev}
del_addrs veth0
ifconfig veth0 -arp down
ifconfig veth0 hw ether 00:00:00:00:00:00
transfer_routes ${bridge} ${netdev}

case ${OP} in


show_status ${netdev} ${bridge}

echo 'Unknown command: ' ${OP} >&2
echo 'Valid commands are: start, stop, status' >&2
exit 1

For some voodoo reason you have to execute /etc/ini.d/xend restart to get the network set up.

To configure a DomU follow the description on the Fedora Wiki -- be aware that you will need probably at least 3 or 4 GigaByte to do something useful. Once your DomU works (you will need another "public" IP-adress) you can add nx like already described in this blog.