tc.sh

#!/bin/bash

# This script using tc (`man tc`) to shape egress traffic from a host to specific
# IP CIDR(s).

# RATES  Bandwidths  or  rates.  These parameters accept a floating point
# number, possibly followed by either a unit (both SI and IEC units supported),
# or a float followed by a '%' character to specify the rate as a percentage of
# the device's  speed  (e.g.  5%,  99.5%).  Warning:  specifying  the  rate as
# a percentage means a fraction of the current speed; if the speed changes, the
# value will not be recalculated.
#
#  default Bits per second
#
#  kbit    Kilobits per second
#
#  mbit    Megabits per second
#
#  gbit    Gigabits per second
#
#  tbit    Terabits per second
#
#  bps     Bytes per second
#
#  kbps    Kilobytes per second
#
#  mbps    Megabytes per second
#
#  gbps    Gigabytes per second
#
#  tbps    Terabytes per second
#

#
# Location of tc command
TC=/sbin/tc

# Network Interface (`ip a`) to shape.
IF=ens160

# Egress limit
UPLD=1mbit

# CIDR ranges
# There should be 1 per target edge network
EDGE_1=3.224.75.242/32    # Edge Site 1 Description
EDGE_2=3.224.75.242/32    # Edge Site 2 Description

# Filter options for limiting the intended interface.
U32="$TC filter add dev $IF protocol ip parent 1:0 prio 1 u32"

create () {
  echo "===> Setting up shaping"
  # Hierarchical Token Bucket (HTB) is used as it provides bandwidth-based shaping

  #   HTB    The Hierarchy Token Bucket implements a rich linksharing
  #   hierarchy of classes with an emphasis on conforming to existing
  #   practices. HTB facilitates guaranteeing bandwidth to classes, while
  #   also allowing specification of upper limits to inter-class sharing. It
  #   contains shaping elements, based on TBF and can prioritize classes.

  # root qdisc
  $TC qdisc add dev $IF root handle 1: htb default 30
  echo "===> Setup root qdisc on $IF"

  # child qdiscs
  # shapers of bandwidth
  # a child qdisc should exist for every edge network
  $TC class add dev $IF parent 1: classid 1:1 htb rate $UPLD
  $TC class add dev $IF parent 1: classid 1:2 htb rate $UPLD
  echo "===> Setup child qdisc(s) on $IF"

  # filters for child qdiscs
  # matches will go to the classid referenced after flowid
  # a filter should exist for every edge network
  $U32 match ip dst $EDGE_1 flowid 1:1
  $U32 match ip dst $EDGE_2 flowid 1:2
  echo "===> Setup filters"

  echo "===> Shaping configuration complete"
}

# clean removes *all* existing qdiscs from the target interface
clean () {
  echo "===> Deleting existing qdiscs on $IF"
  $TC qdisc del dev $IF root
  echo "===> Deleted existing qdiscs on $IF"
}

# run script; always clean then create
clean
create