21 lines
798 B
Plaintext
21 lines
798 B
Plaintext
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#!/bin/bash
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mask2cidr() {
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local mask=$1
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# In RFC 4632 netmasks there's no "255." after a non-255 byte in the mask
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local left_stripped_mask=${mask##*255.}
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local len_mask=${#mask}
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local len_left_stripped_mask=${#left_stripped_mask}
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local conversion_table=0^^^128^192^224^240^248^252^254^
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local number_of_bits_stripped=$(((len_mask - len_left_stripped_mask) * 2))
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local signifacant_octet=${left_stripped_mask%%.*}
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local right_stripped_conversion_table=${conversion_table%%$signifacant_octet*}
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local len_right_stripped_conversion_table=${#right_stripped_conversion_table}
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local number_of_bits_from_conversion_table=$((len_right_stripped_conversion_table / 4))
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echo $((number_of_bits_stripped + number_of_bits_from_conversion_table))
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}
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mask2cidr "$@"
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