origin_asn_analyzer.bash

#!/usr/bin/env bash

# Find IPv4 prefixes which have non-unique origin AS number, i.e. the rightmost AS number.

get_origin_asn() {

    last_asn_elem="${1##* }"
    case "$last_asn_elem" in
        "{"*"}")
            # It's an AS-set.
            last_asn_elem="${last_asn_elem#\{}"
            last_asn_elem="${last_asn_elem%\}}"
            last_asn_elem="${last_asn_elem//,/ }"
        ;;
    esac

    echo "$last_asn_elem"
}


while IFS='|' read -r _ _ _ _ prefix as_path _; do

    if [[ -z "$last_prefix" ]] || [[ "$prefix" == "$last_prefix" ]]; then

        # Double quotes around the command substitution are missing in order to
        # add possibly multiple AS-set members as separate array elements.
        origin_asns+=( $(get_origin_asn "$as_path") )

    else

        mapfile -t unique_origin_asns < <(printf "%s\n" "${origin_asns[@]}" | sort -un)

        (( ${#unique_origin_asns[@]} > 1 )) && echo "$last_prefix:" "${unique_origin_asns[@]}"

        origin_asns=()
        origin_asns+=( $(get_origin_asn "$as_path") )

    fi

    last_prefix="$prefix"

done < <(bgpkit-parser --ipv4-only latest-bview.gz)

mapfile -t unique_origin_asns < <(printf "%s\n" "${origin_asns[@]}" | sort -un)
(( ${#unique_origin_asns[@]} > 1 )) && echo "$last_prefix:" "${unique_origin_asns[@]}"