Pf Configuration Incompatible With Pf Program Version Instant

The error "pf configuration incompatible with pf program version" typically occurs when using Packet Filter (pf) on BSD systems (FreeBSD, OpenBSD, macOS) or in environments running PF-based firewalls (e.g., some Linux distributions with PF from ports). It means the binary pfctl (or the kernel PF module) expects a different syntax or rule format than the one used in your config file — often due to version mismatches between userland tools and the kernel.

Goals

• Detect version-incompatibility between a pf.conf and running pf binary before/when loading.
• Provide precise, user-friendly messages explaining which constructs or keywords are unsupported.
• Offer automated remediation suggestions (convert, disable, or pin versions).
• Integrate with tools that manage pf (rc scripts, systemctl, firewall UIs, pkg managers).
• Maintain minimal runtime overhead and privacy-safe logging.

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1. Understanding the Two Core Components

To grasp the error, you must understand two separate but interrelated parts of the PF system:

• The Userland Tool (pfctl): This is the binary located at /sbin/pfctl or /usr/sbin/pfctl. When you run pfctl -f /etc/pf.conf, the userland program parses the configuration file, validates syntax, and translates rules into a binary structure. It then sends that binary data to the kernel via a system call (ioctl).

• The Kernel Module (pf.ko on FreeBSD, built into the kernel on OpenBSD/macOS): This is the code running inside the operating system kernel that actually inspects packets, tracks state, and enforces the rules. It has its own internal data structures and API version.

The error “configuration incompatible with program version” means the binary structure generated by your pfctl does not match what the kernel module expects. The kernel is effectively saying: “I don’t understand the format of the rules you just sent me.”

Tier 5: For Custom Kernels – Rebuild pf Module

If you compile a custom kernel and exclude device pf, but later load the module, the pre-built pf.ko might be incompatible. Rebuild only the module: pf configuration incompatible with pf program version

cd /usr/src/sys/modules/pf
make clean
make
make install
kldunload pf
kldload pf

Step 1 – Identify the pfctl Version

Run:

pfctl -V

or

pfctl -v 2>&1 | grep version

Output example:

pfctl version: FreeBSD 14.0-RELEASE-p4

3) Safe diagnostic commands

Run these (as root) and record output for troubleshooting:

• Show pf version and status:

  • pfctl -v
  • pfctl -s info

• Check active rules and anchors:

  • pfctl -sr
  • pfctl -sa

• Validate config syntax (no load):

  • pfctl -nf /etc/pf.conf

• Check kernel and userland package versions:

  • uname -a
  • pkg info | grep pf (FreeBSD/OpenBSD package commands vary)

• Show loaded pf kernel module (BSDs):

  • kldstat | grep pf

On macOS:

• sysctl net.pf (or pfctl -v; macOS pf version info is limited)

Step 1: Check Your OS Version and Patch Level

Run the following command:

freebsd-version -kru | uniq

Or for OpenBSD:

sysctl kern.version

You are looking for discrepancies between the -k (kernel) and -u (userland). If they differ, you have found the culprit.

Option A: Upgrade your config to the target version

Obtain the correct syntax reference:

man -s 5 pf.conf   # on the target system

Common fixes for specific errors:

• "scrub" is invalid → replace scrub in all with match in all scrub (no-df)
• "set limit states" error → rename to set limit state
• "max-mss" unknown → use set mss inside match