How to filter packets based on source port without using direct rules

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 8
  • firewalld firewall

Issue

  • Is there an option to filter packets via firewalld based on source port without having to use direct rules?

Resolution

The firewalld rich language can be used to allow source ports into a zone, eg:

firewall-cmd --add-rich-rule='rule source-port port="9001" protocol="udp" accept'
firewall-cmd --runtime-to-permanent

Root Cause

Rich rules are explained in detail on the manual at: man firewalld.richlanguage

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