/etc/dhcp/dhclient-exit-hooks.d/rfc3442-classless-routes is in isc-dhcp-client 4.3.5-3ubuntu7.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 | # set classless routes based on the format specified in RFC3442
# e.g.:
# new_rfc3442_classless_static_routes='24 192 168 10 192 168 1 1 8 10 10 17 66 41'
# specifies the routes:
# 192.168.10.0/24 via 192.168.1.1
# 10.0.0.0/8 via 10.10.17.66.41
RUN="yes"
if [ "$RUN" = "yes" ]; then
if [ -n "$new_rfc3442_classless_static_routes" ]; then
if [ "$reason" = "BOUND" ] || [ "$reason" = "REBOOT" ]; then
set -- $new_rfc3442_classless_static_routes
while [ $# -gt 0 ]; do
net_length=$1
via_arg=''
case $net_length in
32|31|30|29|28|27|26|25)
if [ $# -lt 9 ]; then
return 1
fi
net_address="${2}.${3}.${4}.${5}"
gateway="${6}.${7}.${8}.${9}"
shift 9
;;
24|23|22|21|20|19|18|17)
if [ $# -lt 8 ]; then
return 1
fi
net_address="${2}.${3}.${4}.0"
gateway="${5}.${6}.${7}.${8}"
shift 8
;;
16|15|14|13|12|11|10|9)
if [ $# -lt 7 ]; then
return 1
fi
net_address="${2}.${3}.0.0"
gateway="${4}.${5}.${6}.${7}"
shift 7
;;
8|7|6|5|4|3|2|1)
if [ $# -lt 6 ]; then
return 1
fi
net_address="${2}.0.0.0"
gateway="${3}.${4}.${5}.${6}"
shift 6
;;
0) # default route
if [ $# -lt 5 ]; then
return 1
fi
net_address="0.0.0.0"
gateway="${2}.${3}.${4}.${5}"
shift 5
;;
*) # error
return 1
;;
esac
# take care of link-local routes
if [ "${gateway}" != '0.0.0.0' ]; then
via_arg="via ${gateway}"
fi
# set route (ip detects host routes automatically)
ip -4 route add "${net_address}/${net_length}" \
${via_arg} dev "${interface}" >/dev/null 2>&1
done
fi
fi
fi
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