openwrt/package/network/utils/iptables/files/l7/ntp.pat

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# (S)NTP - (Simple) Network Time Protocol - RFCs 1305 and 2030
# Pattern attributes: good fast fast overmatch
# Protocol groups: time_synchronization ietf_draft_standard
# Wiki: http://www.protocolinfo.org/wiki/NTP
# Copyright (C) 2008 Matthew Strait, Ethan Sommer; See ../LICENSE
#
# This pattern is tested and is believed to work.
# client|server
# Requires the server's timestamp to be in the present or future (of 2005).
# Tested with ntpdate on Linux.
# Assumes version 2, 3 or 4.
# Note that ntp packets are always 48 bytes, so you should match on that too.
ntp
^([\x13\x1b\x23\xd3\xdb\xe3]|[\x14\x1c$].......?.?.?.?.?.?.?.?.?[\xc6-\xff])