Limit macOS Network Speed

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Again, starting writing something … Let’s begin with some easy stuff.

Days ago, I would like to limit my macOS network speed. In Linux, we can use tc command to do that, but in macOS we will use dnctl+pfctl. For tc usage, checkout with this post

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#!/bin/bash

# Reset dummynet to default config
dnctl -f flush

# Compose an addendum to the default config: creates a new anchor
(cat /etc/pf.conf &&
echo 'dummynet-anchor "my_anchor"' &&
echo 'anchor "my_anchor"') | pfctl -q -f -

# Configure the new anchor
cat <<EOF | pfctl -q -a my_anchor -f -
no dummynet quick on lo0 all
dummynet out proto tcp from any to any pipe 1
EOF

# Create the dummynet queue, we can tune this number, say, make as 409600000 ~ 400MB
# which could means, unlimited for network speed
dnctl pipe 1 config bw 4096byte/s

# Activate PF
pfctl -E

# to check that dnctl is properly configured: 
sudo dnctl list

Also remeber to reset this network speed control:

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sudo dnctl -f flush
sudo pfctl -f /etc/pf.conf
sudo dnctl list

Here is a full list of function to be invoked in .bashrc / .bash_profile / .zshrc:

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speed_limit() {
  local direction=${1-"up"}
  # clear
  sudo dnctl -f flush
  sudo pfctl -f /etc/pf.conf
  sudo pfctl -E

  (cat /etc/pf.conf &&
  echo 'dummynet-anchor "my_anchor"' &&
  echo 'anchor "my_anchor"') | sudo pfctl -q -f -

  cat <<EOF | sudo pfctl -q -a my_anchor -f -
no dummynet quick on lo0 all
dummynet out proto tcp from any to any pipe 1
EOF
  
  if [[ "$direction" == "up" ]]; then
    sudo dnctl -f flush
    sudo pfctl -f /etc/pf.conf
    sudo pfctl -E
    sudo dnctl list
  else
    sudo dnctl pipe 1 config bw 4096byte/s
    sudo pfctl -E
    sudo dnctl list
  fi
}

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