NPF-PARAMS(7)

NAME
npf-params - tunable NPF parameters

DESCRIPTION
NPF supports a set of dynamically tunable parameters.

All parameter values are integers and should generally be between zero 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").

PARAMETERS

bpf.jit
    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.

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.

ip6.reassembly
    Perform IPv6 reassembly before inspecting the packet. Discouraged in general but not prohibited by RFC 8200. Default: 0.

gc.step
    Number of connection state items to process in one garbage collection (G/C) cycle. Must be positive number. Default: 256.

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).

gc.interval_max
    The upper bound for the sleep time of the G/C worker. Default: 5000 (in milliseconds).

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.

    interface
        Include interface identifier into the keys, making the connection state strictly per-interface. Default: 1.

    direction
        Include packet direction into the keys. Default: 1.

state.generic
    Generic state tracking parameters for non-TCP flows. All timeouts are in seconds and must be zero or positive.

    timeout.new
        Timeout for new ("unsynchronized") state. Default: 30.

    timeout.established
        Timeout for established ("synchronized") state. Default: 60.

    timeout.closed
        Timeout for closed state. Default: 0.

state.tcp
    State tracking parameters for TCP connections. All timeout values are in seconds.

    max_ack_win
        Maximum allowed ACK window. Default: 66000.

    strict_order_rst
        Enforce strict order RST. Default: 1.

    timeout.new
        Timeout for a new connection in "unsynchronized" state. Default: 30.

    timeout.established
        Timeout for an established connection ("synchronized" state). Default: 86400.

    timeout.half_close
        Timeout for the half-close TCP states. Default: 3600.

    timeout.close
        Timeout for the full close TCP states. Default: 10.

    timeout.time_wait
        Timeout for the TCP time-wait state. Default: 240.

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).

portmap.max_port
    Upper bound of the port range as described above. Default: 49151 (inclusive; 65535 is the highest allowed value).

EXAMPLES
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

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

AUTHORS
NPF was designed and implemented by Mindaugas Rasiukevicius.