Disable MDNS in Chrome via Chrome policies on the commandline

disable-mdns-chrome.sh

#!/bin/bash
#
# This assumes you are using "Chrome" from the official Google site via the .deb or .rpm
# This may or may not work with your distributions "Chromium" or "Chrome" package!
# 
# Run this script then restart Chrome, you will see it is no longer bound to UDP:5353
#
mkdir -p /etc/opt/chrome/policies/{managed,recommended} || echo FAIL, ARE YOU ROOT
chmod go-w /etc/opt/chrome/policies/managed || echo FAIL, ARE YOU ROOT
cat > /etc/opt/chrome/policies/managed/managed_policy.json << 'EOF'
{ "EnableMediaRouter": false }
EOF

#
# UPDATE: Unfortunately, there is another option that must be set as of latest versions of Chrome
# stable. It can not be set in the policy file but must be set manually in chrome://flags. Without
# this additional change, Chrome will still spam IGMP group requests on all interfaces at boot-time
#
# The flag is: #enable-webrtc-hide-local-ips-with-mdns
# It must be set to 'Disabled'
#

actually, now I'm seeing the same thing @davehayes is. Eventually Chrome goes back to mDNS listening and resolving every ._googcast._tcp.local. service every time one is announced... If you have a lot of Chromecasts and GHome on your network then that means your Chrome will be constantly busy. (GDevices are spammy and their mDNS broadcast traffic rates grows O(n^2) where n is the number of GDevices)

The #enable-webrtc-hide-local-ips-with-mdns flag no longer showed up for me on chrome 87.0.4280.88. Enabling the flag #temporary-unexpire-flags-m85 showed this flag again but after finally setting #enable-webrtc-hide-local-ips-with-mdns to Disabled, the mDNS entries reappeared again after a while as others mentioned.

You can try setting the immutable flag on the configuration file after you modify it. You’ll need elevated privileges to do so, though

The simplest way to do a basic test would be to shut down all chrome instances, make the change, then sudo chattr +i . Until you chattr -i the file, it won’t be mutable by any users (not even root)

The file has to be on an ext-based file system because it uses the extfs extended attributes

You could also try just chowning it to root, but it’s possible it could be deleted and recreated as a normal user since the directory will be owned by a normal user

good luck, let me know if you figure anything out. I stopped using Chrome entirely a while ago so haven’t looked at it all on probably over a year

BTW- there are probably extensions that can disable the mDNS- but a pure configuration change is so much better than adding more code to your system- even if it is (mostly) sandboxed