NPF-PARAMS(7) Miscellaneous Information Manual NPF-PARAMS(7)

npf-params
tunable NPF parameters

NPF supports a set of dynamically tunable parameters.

All parameter values are integers and should generally be between and INT_MAX, unless specified otherwise. Some parameters values can be negative; such values would typically have a special meaning. Enable/disable switches should be represented as boolean values 0 ("off") or 1 ("on").

BPF just-in-time compilation: enables or disables bpfjit(4) support. Some machine architectures are not presently supported by bpfjit(4). Setting this parameter to off stops NPF from trying to enable this functionality, and generating a warning if it is unable to do so. Default: 1.
Number of connection state items to process in one garbage collection (G/C) cycle. Must be positive number. Default: 256.
Generic state tracking parameters for non-TCP flows. All timeouts are in seconds and must be zero or positive.
Timeout for new ("unsynchronized") state. Default: 30.
Timeout for established ("synchronized") state. Default: 60.
Timeout for closed state. Default: 0.
State tracking parameters for TCP connections. All timeout values are in seconds.
Maximum allowed ACK window. Default: 66000.
Enforce strict order RST. Default: 1.
Timeout for a new connection in "unsynchronized" state. Default: 30.
Timeout for an established connection ("synchronized" state). Default: 86400.
Timeout for the half-close TCP states. Default: 3600.
Timeout for the full close TCP states. Default: 10.
Timeout for the TCP time-wait state. Default: 240.
Lower bound of the port range used when selecting the port for dynamic NAT with port translation enabled. Default: 1024 (also the lowest allowed value).
Upper bound of the port range as described above. Default: 65535 (also the highest allowed value).

An example line in the npf.conf(5) configuration file:
set state.tcp.strict_order_rst on       # "on" can be used instead of 1
set state.tcp.timeout.time_wait 0       # destroy the state immediately

libnpf(3), npfkern(3), bpfjit(4), npf.conf(5), pcap-filter(7), npfctl(8)

NPF was designed and implemented by Mindaugas Rasiukevicius.
August 3, 2019 NetBSD 9.0