Saturday, 15. August 2015 Week 33
Wednesday, 12. August 2015 Week 33

Downgrade Quagga on Debian 8

The Quagga version in Debian 8 (v0.99.23.1) suffers from a bug in ospf6d, which causes that no IPv6 routes are exchanged via point-to-point interfaces.

In order to workaround this problem (and re-establish IPv6 connectivity), a downgrade of the quagga package can be done.
For this we add the 'oldstable' entry to sources.list and pin the quagga package to the old version.

Entry to add to /etc/apt/sources.list:

deb http://mirror.switch.ch/ftp/mirror/debian/ oldstable main

Entry to add to /etc/apt/preferences:

Package: quagga
Pin: version 0.99.22.*
Pin-Priority: 1001

After the entries have been added, run apt-get update followed by apt-get install quagga to downgrade to the old quagga package.

Sunday, 19. July 2015 Week 29
Sunday, 12. July 2015 Week 28

Scapy and IP Options

Create packets with custom IPv4 IP Option fields using Scapy:

>>> packet=IP(src="203.0.113.1",dst="203.0.113.2",options=[IPOption('%s%s'%('\x86\x28','a'*38))])
>>> ls(packet)
version    : BitField             = 4               (4)
ihl        : BitField             = None            (None)
tos        : XByteField           = 0               (0)
len        : ShortField           = None            (None)
id         : ShortField           = 1               (1)
flags      : FlagsField           = 0               (0)
frag       : BitField             = 0               (0)
ttl        : ByteField            = 64              (64)
proto      : ByteEnumField        = 0               (0)
chksum     : XShortField          = None            (None)
src        : Emph                 = '203.0.113.1'   (None)
dst        : Emph                 = '203.0.113.2'   ('127.0.0.1')
options    : PacketListField      = [<IPOption  copy_flag=1L optclass=control option=commercial_security length=40 value='aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' |>] ([])
>>> sr1(packet)

The above code results in the following packet (as seen by Wireshark):

Wireshark showing the packet with the custom IP Option

Saturday, 11. July 2015 Week 28

Upgrade to Debian 8 without systemd

To avoid the automatic installation/switch to systemd during the upgrade to Debian 8, it is enough to prevent the installation of the systemd-sysv package.

This can be done by creating a file /etc/apt/preferences.d/no-systemd-sysv with the following content:

Package: systemd-sysv
Pin: release o=Debian
Pin-Priority: -1

(via)

Sunday, 5. July 2015 Week 27
Tuesday, 24. February 2015 Week 9
Sunday, 11. January 2015 Week 2
Thursday, 25. December 2014 Week 52
Monday, 22. December 2014 Week 52