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