chrony/examples/chrony.nm-dispatcher.dhcp
Miroslav Lichvar fca8966ada examples: replace grep command in NM dispatcher script
Some grep implementations detect binary data and return success without
matching whole line. This might be an issue for the DHCPv6 NTP FQDN
check. The GNU grep in the C locale seems to check only for the NUL
character, which cannot be passed in an environment variable, but other
implementations might behave differently and there doesn't seem to be a
portable way to force matching the whole line.

Instead of the grep command, check for invalid characters by comparing
the length of the input passed through "tr -d -c".
2022-03-23 15:36:17 +01:00

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#!/bin/sh
# This is a NetworkManager dispatcher script for chronyd to update
# its NTP sources with servers from DHCP options passed by NetworkManager
# in the DHCP4_NTP_SERVERS and DHCP6_DHCP6_NTP_SERVERS environment variables.
export LC_ALL=C
interface=$1
action=$2
chronyc=/usr/bin/chronyc
server_options=iburst
server_dir=/var/run/chrony-dhcp
dhcp_server_file=$server_dir/$interface.sources
dhcp_ntp_servers="$DHCP4_NTP_SERVERS $DHCP6_DHCP6_NTP_SERVERS"
add_servers_from_dhcp() {
rm -f "$dhcp_server_file"
for server in $dhcp_ntp_servers; do
# Check for invalid characters (from the DHCPv6 NTP FQDN suboption)
len1=$(printf '%s' "$server" | wc -c)
len2=$(printf '%s' "$server" | tr -d -c 'A-Za-z0-9:.-' | wc -c)
if [ "$len1" -ne "$len2" ] || [ "$len2" -lt 1 ] || [ "$len2" -gt 255 ]; then
continue
fi
printf 'server %s %s\n' "$server" "$server_options" >> "$dhcp_server_file"
done
$chronyc reload sources > /dev/null 2>&1 || :
}
clear_servers_from_dhcp() {
if [ -f "$dhcp_server_file" ]; then
rm -f "$dhcp_server_file"
$chronyc reload sources > /dev/null 2>&1 || :
fi
}
mkdir -p $server_dir
case "$action" in
up|dhcp4-change|dhcp6-change)
add_servers_from_dhcp;;
down)
clear_servers_from_dhcp;;
esac
exit 0