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59 lines
2.2 KiB
59 lines
2.2 KiB
#!/bin/sh
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#
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# script to determine and return SLAAC ipv6 address using prefix from a locally configured interface and the MAC address of the device
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# (c) 2018 Keve Mueller <keve at keve dot hu>
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#
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# activated inside /etc/config/ddns by setting
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#
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# option ip_source 'script'
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# option ip_script '/usr/lib/ddns/slaac_sample.sh br-lan AA:BB:CC:DD:EE:FF'
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#
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# the script is executed (not parsed) inside get_local_ip() function
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# of /usr/lib/ddns/dynamic_dns_functions.sh
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#
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# useful when this box is the only DDNS client in the network and other clients use SLAAC
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# so no need to install ddns client on every "internal" box
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#
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# NB: this will not catch the actual IPV6 used by the host when it is configured to use temporary addresses
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#NB: we need a valid MAC address that is fully expanded with leading zeroes on all positions
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format_eui_64() {
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local macaddr="$1"
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echo ${macaddr:0:1}$(echo ${macaddr:1:1}|tr 0123456789abcdefABCDEF 23016745ab89efcd89efcd)${macaddr:3:2}:${macaddr:6:2}ff:fe${macaddr:9:2}:${macaddr:12:2}${macaddr:15:2}
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}
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# expand :: in an ipv6 address specification to the appropriate series of 0:
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# result will have 8 ipv6 fragments separated by single colon
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# NB: input must be a valid IPv6 address, e.g. ::1
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# NB: numbers are not prepended with leading zeroes
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expand_ipv6_colons() {
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local ipv6=$1
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# we need :: to be in the middle, so prepend a 0 if the input starts with : and append 0 if it ends with it
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if [ "${ipv6:0:1}" = ":" ]; then ipv6=0${ipv6}; fi
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if [ "${ipv6: -1:1}" = ":" ]; then ipv6=${ipv6}0; fi
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# retain only the real colons
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local colons=${ipv6//::|[0123456789abcdefABCDEF]/}
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# count them
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local num_colons=${#colons}
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local filler=":0:0:0:0:0:0:"
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# replace the :: with the appropriate substring from filler
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local ipv6_x=${ipv6/::/${filler:0:(7-$num_colons)*2-1}}
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echo $ipv6_x
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}
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# obtain the first ipv6 address of the device passed in $1
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addr_net=$(ip -6 -o addr show dev $1 scope global up | cut -d" " -f 7 | head -1)
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#addr_net=$1
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addr=${addr_net%/*}
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# TODO: we assume /64 subnet
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# get the first 64 bits of the address
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prefix=$(expand_ipv6_colons $addr | cut -d: -f -4)
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# compute the SLAAC 64 bits from the MAC
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suffix=$(format_eui_64 "$2")
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echo -n $prefix:$suffix
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exit 0
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#echo "Should never come here" >&2
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#exit 2
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