.\" $NetBSD: npflog.4,v 1.2 2023/06/29 23:20:02 gutteridge Exp $
.\" $OpenBSD: pflog.4,v 1.10 2007/05/31 19:19:51 jmc Exp $
.\"
.\" Copyright (c) 2001 Tobias Weingartner
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.\" Copyright (c) 2023 The NetBSD Foundation, Inc.
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.\" Portions of this documentation are derived from text contributed by
.\" David H. Gutteridge.
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.Dd June 29, 2023
.Dt NPFLOG 4
.Os
.Sh NAME
.Nm npflog
.Nd packet filter logging interface
.Sh SYNOPSIS
.Cd "pseudo-device npflog"
.Sh DESCRIPTION
The
.Nm 
interface is a pseudo-device which makes visible all packets logged by
the
.Xr npf 7
packet filter.
Logged packets can be monitored in real time by invoking
.Xr tcpdump 8
on the
.Nm
interface, or stored to disk using
.Xr npfd 8 .
.Pp
The npflog0 interface is created automatically at boot if
.Xr npf 7
is enabled;
further instances can be created using
.Xr ifconfig 8 .
.Pp
Each packet retrieved on this interface has a header associated
that presently matches the format used by
.Xr 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:
.Bd -literal -offset indent
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];
};
.Ed
.Sh EXAMPLES
Monitor all packets logged on the default interface:
.Bd -literal -offset indent
# tcpdump -n -e -tttt -i npflog0
.Ed
.Sh SEE ALSO
.Xr inet 4 ,
.Xr inet6 4 ,
.Xr netintro 4 ,
.Xr npf 7 ,
.Xr ifconfig 8 ,
.Xr npfd 8 ,
.Xr tcpdump 8
.Sh HISTORY
The
.Nm
device first appeared in
.Nx 6.0 .