Copyright (c) 2019 Mindaugas Rasiukevicius <rmind at netbsd org>
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.Dd May 31, 2020 .Dt NPF-PARAMS 7 .Os .Sh NAME .Nm npf-params .Nd tunable NPF parameters .Sh DESCRIPTION NPF supports a set of dynamically tunable parameters.
p
All parameter values are integers and should generally be between
zero and
.Dv 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").
.Sh PARAMETERS
l -tag -width "123456" ---
l -tag -width "123456" t Li bpf.jit BPF just-in-time compilation: enables or disables
.Xr bpfjit 4
support.
Some machine architectures are not presently supported by
.Xr 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.
.El
---
l -tag -width "123456" t Li ip4.reassembly Perform IPv4 reassembly before inspecting the packet.
Fragmentation is considered very harmful, so most networks are expected
to prevent it; reassembly is enabled by default.
However, while the packet should generally be reassembled at the receiver,
reassembly by the packet filter may be necessary in order to perform state
tracking.
Default: 1.
t Li ip6.reassembly Perform IPv6 reassembly before inspecting the packet.
Discouraged in general but not prohibited by RFC 8200.
Default: 0.
.El
---
l -tag -width "123456" t Li gc.step Number of connection state items to process in one garbage collection
(G/C) cycle.
Must be positive number.
Default: 256.
t Li gc.interval_min The lower bound for the sleep time of the G/C worker.
The worker is self-tuning and will wake up more frequently if there are
connections to expire; it will wake up less frequently, diverging towards
the upper bound, if it does not encounter expired connections.
Default: 50 (in milliseconds).
t Li gc.interval_max The upper bound for the sleep time of the G/C worker.
Default: 5000 (in milliseconds).
.El
---
t Li state.key The connection state is uniquely identified by an n-tuple.
The state behavior can be controlled by including (excluding)
some of the information in (from) the keys.
l -tag -width "123456" t Li interface Include interface identifier into the keys, making the connection
state strictly per-interface.
Default: 1.
t Li direction Include packet direction into the keys.
Default: 1.
.El
---
t Li state.generic Generic state tracking parameters for non-TCP flows.
All timeouts are in seconds and must be zero or positive.
l -tag -width "123456" t Li timeout.new Timeout for new ("unsynchronized") state.
Default: 30.
t Li timeout.established Timeout for established ("synchronized") state.
Default: 60.
t Li timeout.closed Timeout for closed state.
Default: 0.
.El
---
t Li state.tcp State tracking parameters for TCP connections.
All timeout values are in seconds.
l -tag -width "123456" t Li max_ack_win Maximum allowed ACK window.
Default: 66000.
t Li strict_order_rst Enforce strict order RST.
Default: 1.
-
t Li timeout.new Timeout for a new connection in "unsynchronized" state.
Default: 30.
t Li timeout.established Timeout for an established connection ("synchronized" state).
Default: 86400.
t Li timeout.half_close Timeout for the half-close TCP states.
Default: 3600.
t Li timeout.close Timeout for the full close TCP states.
Default: 10.
t Li timeout.time_wait Timeout for the TCP time-wait state.
Default: 240.
.El
---
t Li portmap.min_port Lower bound of the port range used when selecting the port
for dynamic NAT with port translation enabled.
Default: 1024 (inclusive; also the lowest allowed value).
t Li portmap.max_port Upper bound of the port range as described above.
Default: 49151 (inclusive; 65535 is the highest allowed value).
---
.El
-----
.Sh EXAMPLES
An example line in the
.Xr npf.conf 5
configuration file:
d -literal -offset indent 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
.Ed
-----
.Sh SEE ALSO
.Xr libnpf 3 ,
.Xr npfkern 3 ,
.Xr bpfjit 4 ,
.Xr npf.conf 5 ,
.Xr pcap-filter 7 ,
.Xr npfctl 8
-----
.Sh AUTHORS
NPF
was designed and implemented by
.An Mindaugas Rasiukevicius .
Indexes created Sun Sep 21 14:09:52 GMT 2025