mirror of
https://github.com/tonusoo/koduinternet-cpe
synced 2024-11-23 19:41:01 +02:00
75 lines
2.0 KiB
Plaintext
75 lines
2.0 KiB
Plaintext
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#!/usr/bin/env bash
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# Title : mac_to_ip6_ll_addr
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# Last modified date : 13.03.2023
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# Author : Martin Tonusoo
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# Description : Script finds the IPv6 link local address
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# from the MAC address.
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# Options : MAC address.
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# Notes : Script expects the MAC address as a
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# command line argument in the format
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# returned by "ip link" command, e.g
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# 52:54:00:db:99:99.
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mac_regex="^([0-9a-f]{2}:){5}([0-9a-f]{2})$"
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if [[ ! "$1" =~ $mac_regex ]]; then
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printf "%s\n%s\n" "Usage: ${0##*/} <MAC_addr>" \
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"Example: ${0##*/} 52:54:00:db:99:99" \
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>&2
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exit 1
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fi
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IFS=: read -r o1 o2 o3 o4 o5 o6 <<< "$1"
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# Convert the four least significant bits of
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# the first octet of the MAC address from hex
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# to decimal.
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o1_dec=$(( 16#"${o1:1:1}" ))
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# Loop through the four least significant bits of
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# the first octet of the MAC address by shifting
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# one bit to right and checking if the bit is set
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# or not on each cycle starting from the least
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# significant bit and moving towards the most
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# significant bit. This will convert the second
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# hex character of the MAC address reading from
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# left to binary.
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for (( n="$o1_dec"; n>0; n >>= 1 )); do
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o1_bits="$(( n & 1 ))$o1_bits"
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done
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# Prepend leading zeros if needed.
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o1_bits=$(printf "%04d" "$o1_bits")
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# Flip the second-least-significant bit of the
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# first octet of the MAC address and convert
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# four bits back to hex digit.
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flipped_bit=$(tr 01 10 <<< "${o1_bits:2:1}")
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o1_bits="${o1_bits:0:2}$flipped_bit${o1_bits:3:1}"
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o1_bits=$(printf "%x" $((2#"$o1_bits")))
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# Finally, rebuild the first octet of the MAC address.
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o1="${o1:0:1}$o1_bits"
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# Build the hextets for the IPv6 link local address.
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if [[ $o1 == 00 ]] && [[ $o2 == 00 ]]; then
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h5=""
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else
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# Strip possible leading zeros.
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h5="$(printf "%x:" "0x$o1$o2")"
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fi
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if [[ $o3 == 00 ]]; then
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h6="ff:"
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else
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h6="$(printf "%xff:" "0x$o3")"
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fi
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h7="fe$o4:"
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h8="$(printf "%x" "0x$o5$o6")"
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printf "fe80::%s%s%s%s\n" "$h5" "$h6" "$h7" "$h8"
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