bandwidth-limit

#!/bin/bash

# Script to dynamically restrict the bandwidth of an ethernet host when
# sharing the wifi internet connection.
# See: http://markmaunder.com/2011/01/26/how-to-reliably-limit-the-amount-of-bandwidth-your-room-mate-or-bad-office-colleague-uses/

if [ "$UID" != "0" ]
then
 CMD=`which $0`
 sudo "$CMD"
 exit $?
fi

# Device we want to restrict
BOX_IP=10.43.0.180

HIGH_BW=2Gbit
LOW_BW=500Kbit
BANDWIDTH=${HIGH_BW}

# Old systems use eth0/wlan0. Modern systems use those unpredictable enp0s31f6 and wlp0s20f3 names.
ETH0=$(/sbin/ifconfig -a | grep '^enp' | sed 's/[: ].*$//' | head -n 1)
ETH1=$(/sbin/ifconfig -a | grep '^enx' | sed 's/[: ].*$//' | head -n 1)
WLAN0=$(/sbin/ifconfig -a | grep '^w' | sed 's/[: ].*$//' | head -n 1)

# sh function to be used with trap
ctrl_c() {
 # Delete old rules
 tc filter delete dev ${ETH1}
 exit 0
}

function manual() {
 read -e -p "Enter limit bandwidth in kbps (empty to exit): " -i "${BANDWIDTH}" BANDWIDTH

 if [ -z "${BANDWIDTH}" ]
 then
  tc qdisc del dev ${ETH1} root handle 1: cbq avpkt 1000 bandwidth 100mbit
  break
 fi

 if [[ "${BANDWIDTH}" =~ ^[0-9]*$ ]]
 then
  BANDWIDTH="${BANDWIDTH}kbit"
 fi
}

function auto() {
 if [ "${BANDWIDTH}" == "${HIGH_BW}" ]
 then
  BANDWIDTH="${LOW_BW}"
 else
  BANDWIDTH="${HIGH_BW}"
 fi

 read -e -p "Enter to change to ${BANDWIDTH}"
}

if [ "$(cat /proc/sys/net/ipv4/ip_forward)" != "1" ]
then
 echo "Enable wifi -> ethernet Internet connection sharing before applying bandwidth limits"
fi

# Prepare for ^C
trap ctrl_c INT

# Delete old rules
tc filter delete dev ${ETH1}

tc qdisc add dev ${ETH1} root handle 1: cbq \
 avpkt 1000 bandwidth ${BANDWIDTH}

tc class add dev ${ETH1} parent 1: classid 1:1 cbq \
 rate ${BANDWIDTH} allot 1500 prio 5 bounded isolated

while true
do
 BANDWIDTH="$(tc class list dev ${ETH1} parent 1: classid 1:1 | { read _ _ _ _ _ _ X _; echo $X; })"
 IP="$(tc -p filter list dev ${ETH1} parent 1: | grep src | { read _ _ _ X; echo $X; } | sed 's#/.*$##')"

 if [ -z "${IP}" ]
 then
  IP=${BOX_IP}

  tc filter add dev ${ETH1} parent 1: protocol ip \
   prio 16 u32 match ip dst ${IP} flowid 1:1

  tc filter add dev ${ETH1} parent 1: protocol ip \
   prio 16 u32 match ip src ${IP} flowid 1:1

  IP="$(tc -p filter list dev ${ETH1} parent 1: | grep src | { read _ _ _ X; echo $X; } | sed 's#/.*$##')"
 fi

 echo "Bandwidth: ${BANDWIDTH}"
 echo "Filtered IP: ${IP}"
 echo

 #manual
 auto

 tc class change dev ${ETH1} parent 1: classid 1:1 cbq \
  rate "${BANDWIDTH}" allot 1500 prio 5 bounded isolated
done

# Delete old rules
tc filter delete dev ${ETH1}

exit 0