on_verify_babel

#!/bin/bash
# https://forum.freifunk.net/t/bessere-verteilung-von-knoten-clients-auf-sn-unter-fastd/12445

# peer limit may be used as a failsafe and not be changed.
# use this script as fastd on_verify to roughly balance peers. 
# If you feel that management should be even stricter and cause 
# fastd-peers to re-connect to other gateways, then also use the 
# cron-script that is adjusting the peer limit. This may be useful after 
# an outage.
#
# Managing client count per gateway would be a lot nicer, but the
# client count for the whole network can only be obtained by querying 
# other infrastructure (map/api). While there is a way to determine client
# count in babel networks today, with future optimizations of l3roamd this
# feature may be dropped (by communicating only routes that are actually
# needed instead of everything).
set -ix
# things to adjust to your server
MINPEERS=50
BUFFERPERCENTAGE=10
NODENETPREFIX="2a06:8187:fbab:1:"
NODENETINTERFACE="(mesh-vpn-1312|mesh-vpn-1492) "
GWINTERFACE="(mesh-vpn) "
GWPREFIX="2a06:8187:fbab:3:"

gwamount=$(ip -6 r s t 0|grep $GWPREFIX|grep -E "dev $NODENETINTERFACE"|cut -d" " -f3|sort -u|wc -l)

## dirty count fastdconnections, 
connected_peer_amount=$(ip -6 r s t 0|grep $NODENETPREFIX|grep -E "dev $NODENETINTERFACE"|cut -d" " -f3|sort -u|wc -l)

# estimate network size and amount of gateways
net_peer_amount=$(( $(ip -6 r s t 0|grep $NODENETPREFIX|grep -E "dev $GWINTERFACE"|cut -d" " -f3|sort -u|wc -l) + connected_peer_amount))


# set connection limit and doing so, consider a buffersize
connection_average_estimate=$(( net_peer_amount / gwamount )) 
connection_limit_estimate=$((connection_average_estimate + (connection_limit_estimate * BUFFERPERCENTAGE)/100))

[[ $connection_limit_estimate -lt $MINPEERS ]] && connection_limit_estimate=$MINPEERS

# get actual peer limit
peerlimit=$(grep -oP '(?<=^peer\slimit\s)[0-9]+(?=\s*;$)' $fastdconf)

[[ $peerlimit -gt $connection_limit_estimate ]] &&
[[ $connection_limit_estimate -gt $connected_peer_amount ]] && exit 0

exit 1