prom_bird_metadata.sh

#!/bin/sh

prefix=
preamble_printed=

PREAMBLE() {
[ "$preamble_printed" != 1 ] || return 0
cat << EOF
# HELP bird_route_metadata
# TYPE bird_route_metadata gauge

# HELP bird_route_bgp_metadata
# TYPE bird_route_bgp_metadata gauge

# HELP bird_route_bgp_metadata_as_pathlen
# TYPE bird_route_bgp_metadata_as_pathlen gauge
EOF
preamble_printed=1
}

birdc_dump_routes() {
  # dump routes for
  # V4
  for cmd in birdc birdc4; do
    "$cmd" < /dev/null > /dev/null 2> /dev/null || continue
    "$cmd" sh route all
    continue
  done
  # V6
  for cmd in birdc6; do
    "$cmd" < /dev/null > /dev/null 2> /dev/null || continue
    "$cmd" sh route all
    continue
  done
}

generate_metrics() {
  while read line; do
    case "$line" in
      [0-9a-f:.]*[]/[1-9]* )

        prefix="${line%% *}"
        # trim leading and trailing white spaces, and double spaces
        # execve is more expensive on embedded systems
        # this forks, forks are cheap, IFS is cool
        line="$( echo "${line#$prefix}" | ( read line; echo "$line" ) )"

        protocol=
        nexthopinfo=
        as_path=
        as_pathlen=
        as_origin=
        as_peer=
        device=
        nexthop=
        proto=
        ;;
    esac

    [ -n "$prefix" ] || \
      continue

    case "$line" in
      "dev "* | "via "* )
        parse_nexthop_info "$line"
        ;;
      "Type: "* )
        # same prefix, new route via another protocol
        # dump current values
        if [ -n "$protocol" ]; then
          PREAMBLE
          assemble_metric bird_route_metadata 1 prefix device nexthop
          if [ "$protocol" = BGP ]; then
            assemble_metric bird_route_bgp_metadata_as_pathlen $as_pathlen prefix as_peer as_path
            assemble_metric bird_route_bgp_metadata 1 prefix as_peer as_origin
          fi
        fi

        protocol="${line#Type: }"
        protocol="${protocol%% *}"
        ;;
      "BGP.as_path: "* )
        as_path="${line#BGP.as_path: }"
        as_pathlen="$(echo "$as_path" | wc -w)"
        as_origin="${as_path##* }"
        as_peer="${as_path%% *}"
        ;;
    esac
  done
}

shiftv() {
  local _shiftv_new_ _shiftv_prev_
  eval "_shiftv_prev_=\"\${$1}\""
  eval "_shiftv_new_=\"\${$1#* }\""
  if [ "$_shiftv_prev_" = "$_shiftv_new_" ]; then
    eval "$1=''"
  else
    eval "$1='$_shiftv_new_'"
  fi
}

parse_nexthop_info() {
  local line="$line"

  while [ -n "$line" ]; do
    case "$line" in
      "dev "* | "on "* )
        shiftv line
        device="${line%% *}"
        ;;
      "via "* | "on "* )
        shiftv line
        nexthop="${line%% *}"
        ;;
    esac
    shiftv line
  done
}

assemble_metric() {
  local _metric_="$1"
  shift
  local _value_="$1"
  shift

  local _a_ _v_ _attributes_=
  for _a_; do
    eval "_v_=\"\${$_a_}\""
    [ -n "$_v_" ] || \
      continue

    [ -z "$_attributes_" ] || \
      _attributes_="${_attributes_},"

    _attributes_="${_attributes_}${_a_}=\"${_v_}\""
  done

  echo "$_metric_{$_attributes_} $_value_"
}

birdc_dump_routes | generate_metrics