Kernel configuration file GENERIC contains:

    #pseudo-device  ipfilter                # IP filter, NAT
    #pseudo-device  pf                      # PF packet filter
    #pseudo-device  pflog                   # PF log if

I tried to compile kernel with pf pseudo-device and found that it
needs PFILL_HOOKS. I think there should be also such line in GENERIC
to make life easier:

    #options         PFIL_HOOKS      # pfil(9) packet filter hooks


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