Updated: 2022/Sep/29

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NPFLOG(4)                    Device Drivers Manual                   NPFLOG(4)

NAME
     npflog - packet filter logging interface

SYNOPSIS
     pseudo-device npflog

DESCRIPTION
     The npflog interface is a pseudo-device which makes visible all packets
     logged by the npf(7) packet filter.  Logged packets can be monitored in
     real time by invoking tcpdump(8) on the npflog interface, or stored to
     disk using npfd(8).

     The npflog0 interface is created automatically at boot if npf(7) is
     enabled; further instances can be created using ifconfig(8).

     Each packet retrieved on this interface has a header associated that
     presently matches the format used by pf(4).  This header documents the
     address family, interface name, rule number, reason, action, and
     direction of the packet that was logged.  This structure looks like:

           struct npfloghdr {
                   uint8_t         length;
                   sa_family_t     af;
                   uint8_t         action;
                   uint8_t         reason;
                   char            ifname[IFNAMSIZ];
                   char            ruleset[NPFLOG_RULESET_NAME_SIZE];
                   uint32_t        rulenr;
                   uint32_t        subrulenr;
                   uint32_t        uid;
                   uint32_t        pid;
                   uint32_t        rule_uid;
                   uint32_t        rule_pid;
                   uint8_t         dir;
                   uint8_t         pad[3];
           };

EXAMPLES
     Monitor all packets logged on the default interface:

           # tcpdump -n -e -tttt -i npflog0

SEE ALSO
     inet(4), inet6(4), netintro(4), npf(7), ifconfig(8), npfd(8), tcpdump(8)

HISTORY
     The npflog device first appeared in NetBSD 6.0.

NetBSD 10.99                     June 29, 2023                    NetBSD 10.99