John’s Tidbits

Moo - Development, Trouble-shooting and Random thoughts…

Firefox 3 and howtoforge.com

Published March 19th, 2008 in Hacks | 1 Comment »

There is currently a bug in firefox 3 which causes it to crash with an XError BadAloc when you go to any page hosted on howtoforge.

This seems to be related to the image at http://howtoforge.com/themes/htf_glass/images/bg_header_bottom_left15.png. I suggest you don’t click on that link :)

Apparently this image is 10,000 pixels wide. It looks like this is probably a GTK issue since the same problem happended when I opened the image with evince!

I tried writing a greasemonkey script to get around this problem but it loads too late to avert the crash. So iptables to the rescue.

iptables -I OUTPUT -d howtoforge.com -m string –algo bm –to 70 –string “GET /themes/htf_glass/images/bg_header_bottom_left15.png” -j DROP

iptables  
    -I OUTPUT \ # Match packets levaing my laptop
    -d howtoforge.com  \ # Only packets going to howtoforge
    -m string \ # Invoke the string matcher
    --algo bm \ # Pick a matching algorithm
    --to 70 \ # Only check the first 70 bytes of each packet
    --string "GET /themes/htf_glass/images/bg_header_bottom_left15.png" \
    -j DROP # Drop the sucker

Ubuntu, VLANs and Bridges

Published April 30th, 2007 in Sysadmin | No Comments »

Bridge and VLAN support has improved dramatically under Ubuntu and probably Debian as well since I last looked into it. once upon a time to create a bridge linked to a VLAN interface you would have to do horrible things like.

auto eth0
ifconfig eth0 inet manual
    pre-up /sbin/vconfig set_name_type VLAN_PLUS_VID_NO_PAD || true

auto vlan7
iface vlan7 inet manual
    pre-up /sbin/vconfig add eth0 7 || true
    post-down /sbin/vconfig rem vlan7 || true

auto br0
    pre-up brctl addbr br0
    pre-up brctl addif br0 vlan7
    post-down brctl delbr br0
    address 10.38.38.1
    netmask 255.255.255.0
    network 10.38.38.0
    broadcast 10.38.38.255

Now the bridge-utils and vlan packages provide hooks into the ifup and ifdown commands so you can simply do

auto br-vlan4
iface br-vlan4 inet static
    address 10.38.38.1
    netmask 255.255.255.0
    network 10.38.38.0
    broadcast 10.38.38.255
    vlan-raw-device eth1
    bridge_ports vlan4
    bridge_maxwait 0
    bridge_fd 0
    bridge_stp off

Which will automagically

  • Bring up eth1
  • Create vlan4 bound to the eth1 interface
  • Bring up vlan4
  • Create the br0 with vlan4 attached
  • Give eth1 the same HW address as br0
  • Bring up br0 with the IP address

Nifty!