This patch makes struct pfsync_state contents configurable by sending out new versions of the structure in separate subheader actions. Both old and new version of struct pfsync_state can be understood, so replication of states from a system running an older kernel is possible. The version being sent out is configured using ifconfig pfsync0 … version XXXX. The version is an user-friendly string - 1301 stands for FreeBSD 13.1 (I have checked synchronization against a host running 13.1), 1400 stands for 14.0. A host running an older kernel will just ignore the messages and count them as "packets discarded for bad action".
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