#!/bin/bash
  
# ConfigurationDSL_STATS=/run/shm/dsl_info/dsl_info
 # Making sure DSL stats are available
[[ -f "$DSL_STATS" ]] && { 
        # Calculating upstream limit - 95% of the current bandwidth to cope with overhead        limit="$(awk '/Current upstream/ { split($0, data, "|"); upload = (data[2] / 8) * (95 / 100); print upload }' "$DSL_STATS")"
} 
# Making sure at least a conservative limit is set[[ -z $limit || $limit == "" ]] && limit=900
 # Giving ppp0 a proper queue length so prioritisation can actually happen, rather than dropping everything... is 3 by default!
ifconfig ppp0 txqueuelen 100 
# Add initial HTB qdisc on the roottc qdisc add dev ppp0 root handle 1: htb default 1
 # Actually add the HTB class that limits upload to 95% of sync rate (deals with overhead)
tc class add dev ppp0 parent 1:0 classid 1:1 htb rate "$limit"kibps ceil "$limit"kibps 
# Add a prio qdisc to this class to then use TOS to prioritise the packets into 3 bands, only dequeuing from higher ones when all the lower bands are emptiedtc qdisc add dev ppp0 parent 1:1 handle 100: prio

# TCP ACK packets with no or very little data payload (p2p traffic sets all packets to ACK packets otherwise, source of size: http://phix.me/dm/)
$IPTABLES -t mangle -A POSTROUTING -o ppp0 -p tcp --tcp-flags FIN,SYN,RST,ACK ACK -m length --length 40:89 -j TOS --set-tos Minimize-Delay