Technical data

B. Appendixes to optional packages

B.1. CHRONY - Inform other applications about timewarps

If chrony notes that the clock is signiﬁcantly away from the current time, it corrects the time

in one great step and starts scripts to inform other applications about this timewarp. For

example to inform imond about a timewarp, chrony does the following:

1. include scripts into the archive

Chrony includes two ﬁles to the archive:

start_imond yes etc/chrony.d/timewarp.sh mode=555 flags=sh

start_imond yes etc/chrony.d/timewarp100.imond mode=555 flags=sh

timewarp.sh starts all scripts in the same folder which names are timewarp 3

numbers . name .

2. provide script

chrony includes the following script into the archive:

# inform imond about time warp

imond-stat "adjust-time $timewarp 1"

Hence imond will be informed about the timewarp and is able to correct it’s internal

timebase.

B.2. DSL - PPPD and Active Filter

ﬂi4l uses the expression:

'outbound and not icmp[0] != 8 and not tcp[13] & 4 != 0'

and accomplishes that generally only packets sent from the local network to the internet keep

the connection open, with a few exceptions:

• TCP-RST: Answers to rejected connection from outside do not reset the timeout,

• ICMP: ICMP messages sent do not reset the timeout unless an echo request is sent.

This expression is converted by the PPPD into a packet-ﬁlter usable by the kernel. In this

example it looks like this:

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