twam.info @ iPad

During the last weeks I tried several themes and designs for a twam.info layout. Finally I decided to adapt a theme called Cool Blue by themelab. I changed a lot in the header and in footer of the theme to get a nice compressed layout.

My webpage user statictics say, that less than 7 percent of my visitors are using a display with a display width of less than 1280 pixels. As some of them are mobile devices like smartphones or tablets there is only a very small percentage of users who would not be able to display a theme with a fixed width of 1280 pixels without scrolling. So I decided to use a template width of 1151 pixels. The main advantage of increasing the template width was that the content column has now a width of 670 pixels allowing the display of 640 pixel width content without resizing. This is very nice to display videos, screenshots or full-size webcam images.

twam.info @ iPhone 4

Another goal of the new template was to work nice on mobile devices like iPhone or iPad. I changed the layout to fit exactly to the screen width of iPhone and iPad without showing any empty columns on the left or right side of the layout. This is done very easily by setting the CSS max-width property of the most outer div block to the exact width of the design.

Furthermore I started to integrate social pages like Facebook and twitter and the social micro-payment system flattr. So if you like my posts, feel free to flattr them.

Last, but not least, the website was moved to a new server providing much more resources. So pages should be delivered my faster and there is plenty of space for a whole bunch of new panoramas. The new server also supports native IPv6.

Today I got an request by email to include support for integer conversion from YUV422 to RGB as descriped by Wikipedia. So I included it and did some style adjustments, too.

You can download it here: v4l2grab Version 0.2

To use integer conversion you have to compile with an additional

-DNTSC

for NTSC like conversion or

-DITU_R_INT

for ITU-R integer conversion. Both standars are explained in the referenced wikipedia article. The use of

-DITU_R_FLOAT

uses the previous floating point version of ITU-R which is default if no compiling options are specified. More information about compilation can be found on the original post.

The current version of V4L2grab can be found on github.

Here comes bonding (sometimes called (port) trunking or link aggregation) to play. It connects two ore more ethernet ports to one virtual port with only one MAC and so mostly one IP address. Wheres earlier only two hosts (with the same OS running) or two switches (from the same vendor) could be connected, nowadays there’s a standard protocol which makes it easy: LACP which is part of IEEE 802.3ad. Linux supports difference bonding mechanisms including 802.3ad. To enable bonding at all there are some kernel settings needed:

Device Drivers  --->
[*] Network device support  --->
<*>   Bonding driver support

After compiling and rebooting, we need a userspace tool for configuring the virtual interface. It’s called ifenslave and provided with the Linux kernel. You can either compile it by hand

/usr/src/linux/Documentation/networking
gcc -Wall -O -I/usr/src/linux/include ifenslave.c -o ifenslave
cp ifenslave /sbin/ifenslave

or install it by emerge if you run Gentoo Linux:

emerge -va ifenslave

Now we can configure the bonding device, called bond0. Firstofall we need to set the 802.3ad mode and the MII link monitoring frequency by

echo "802.3ad" > /sys/class/net/bond0/bonding/mode
echo 100 >/sys/class/net/bond0/bonding/miimon

Now we can up the device and add some ethernet ports:

ifconfig bond0 up
ifenslave bond0 eth0
ifenslave bond0 eth1

Now bond0 is ready to be used. Run a dhcp client or set an IP by

ifconfig bond0 192.168.1.2 netmask 255.255.255.0

These steps are needed on each reboot. If you’re running gentoo, you can use baselayout for this. Add

config_eth0=( "none" )
config_eth1=( "none" )
preup() {
	# Adjusting the bonding mode / MII monitor
	# Possible modes are : 0, 1, 2, 3, 4, 5, 6,
	#     OR
	#   balance-rr, active-backup, balance-xor, broadcast,
	#   802.3ad, balance-tlb, balance-alb
	# MII monitor time interval typically: 100 milliseconds
	if [[ ${IFACE} == "bond0" ]] ; then
		BOND_MODE="802.3ad"
		BOND_MIIMON="100"
		echo ${BOND_MODE} >/sys/class/net/bond0/bonding/mode
		echo ${BOND_MIIMON}  >/sys/class/net/bond0/bonding/miimon
		einfo "Bonding mode is set to ${BOND_MODE} on ${IFACE}"
		einfo "MII monitor interval is set to ${BOND_MIIMON} ms on ${IFACE}"
	else
		einfo "Doing nothing on ${IFACE}"
	fi
	return 0
}
slaves_bond0="eth0 eth1"
config_bond0=( "dhcp" )

to your /etc/conf.d/net. I found this nice preup part in the Gentoo Wiki Archive.

Now you have to configure the other side of the link. You can either use a Linux box and configure it the same way or a 802.3ad-capable switch. I used an HP Procurve 1800-24G switch. You have to enable LACP on the ports you’re connected:

HP Procurve 1800-24G LACP Configuration

Now everything should work and you can enjoy a 2 GBits (or more) link. Further details can be found in the kernel documentation.

In earlier times I used a commented bash script to setup the rules after booting, but using Gentoo nowadays there is a nice init script saving and restoring my tables. Using this I stopped commenting the firewall rules, but yesterday I found a very nice solution for this problem.

Iptables has a special “match” for comments. You have to enable it in your kernel config like

  [*] Networking support  --->
     Networking options
        [*] Network packet filtering framework (Netfilter)  --->
           Core Netfilter Configuration  --->
              -*- Netfilter Xtables support (required for ip_tables)
              <*>   "comment" match support

or as a module.

Then you’re able to add rules like

iptables -A INPUT -m state --state RELATED,ESTABLISHED \
  -m comment --comment "allow all established connections" -j ACCEPT

And if you list your rules you get something like

Chain INPUT (policy DROP)
target  prot opt source     destination
ACCEPT  all  --  anywhere   anywhere   state RELATED,ESTABLISHED
                                       /* allow all established connections */

It’s a pity that I never saw this in any iptables tutorials.

But wget prefers IPv4 over IPv6, meaning if your download mirror supports IPv6, wget doesn’t use it by default. You can change this behavior by setting

prefer-family = IPv6

either in /etc/wgetrc for everybody or in $HOME/.wgetrc for a user only.

So enable it and tell portage to use an IPv6 enabled mirror, by setting GENTOO_MIRROR in /etc/make.conf. You’ll find a list of IPv6 capable mirrors on gentoo.org (look for mirrors marked with *).

server ~ # dig AAAA twam.info
; <<>> DiG 9.6.0-P1 <<>> AAAA twam.info
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58653
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;twam.info.                     IN      AAAA

;; ANSWER SECTION:
twam.info.              600     IN      AAAA    2a01:198:200:436::2

Ich bin gespannt, wieviele der Verbindungen jetzt über IPv6 kommen.

… wie wir es kennen naht. Das die IPv4-Adresse knapp sind ist unter Computer-Experten weitläufig bekannt.

Heute habe ich ein nettes Skript entdeckt, welches das Datum berechnet, an dem alle IPv4 Adressen belegt sind. Das will ich natürlich nicht vorenthalten

Das die IANA wie im Februar letztes Jahres wieder alte unbenutzte Netze findet und frei gibt ist unwahrscheinlich. Also wird es wirklich dringend Zeit auf IPv6 zu migrieren.

Außer der reinen Darstellung der Information kann das Addon auch auf bestimmte Dinge reagieren. So kann es z.B. warnen falls der Browser nicht aktuell ist oder noch IPv4 verwendet wird. Bei was gewarnt werden soll und was überhaupt angezeigt werden soll, kann einfach im Administrationsbereich eingestellt werden.

Zur Bestimmung des Browser habe ich dazu Browscap verwendet. Die Bestimmung des Ortes aus der IP-Adresse übernimmt GeoIP.

Das Plugin läßt sich rechts oben in Aktion sehen. Es warnt im Moment bei alten Browsern. Die IPv4 Warnung ist im Moment noch deaktiviert, solange die IPv6 Anbindung des Servers noch nicht vollständig ausgetestet ist.

Im Rahmen des Google over IPv6 Programms bietet Google aber größeren IPv6-Providern die Möglichkeit ihren DNS als “trusted tester” zu registrieren und dann für alle Google Services AAAA Records bereit zustellen.

SiXXs bietet nun seit gestern die Möglichkeit, dies über ihre DNS Server zu nutzen, wenn man sie aus einem SiXXs-Subnet anfragt. Das musste natürlich sofort getestet werden und siehe da:

server ~ # dig AAAA www.google.de
; <<>> DiG 9.6.0-P1 <<>> AAAA www.google.de
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32996
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 13, ADDITIONAL: 12

;; QUESTION SECTION:
;www.google.de.                 IN      AAAA

;; ANSWER SECTION:
www.google.de.          303016  IN      CNAME   www.google.com.
www.google.com.         391617  IN      CNAME   www.l.google.com.
www.l.google.com.       284     IN      AAAA    2001:4860:a005::68

Ich bin gespannt, wann andere große Websiten nachziehen.

Das Programm AICCU initialisiert die Tunnel und benötigt als Konfiguration lediglich SiXXs-Benutzername und Passwort sowie eine Tunnel Nummer. Das Programm gibt es als net-misc/aiccu als Ebuild für Gentoo.

Ist der Tunnel erfolgreich eingerichtet kann auch ein IPv6 Subnet beantragt werden und weitere PCs im Heimnetz ans IPv6 Netz zu bekommen. Der Gentoo-IPv6-Router-Guide erklärt wie man radvd und dhcpv6 konfiguriert.

Seit heute gibt es twam.info in neuem Look und in Blog-Form. Die meisten alten Einträge habe ich konvertiert.

Viel Spaß damit!