.\"	$OpenBSD: pflog.4,v 1.10 2007/05/31 19:19:51 jmc Exp $
.\"
.\" Copyright (c) 2001 Tobias Weingartner
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.Dd October 29, 2021
.Dt PFLOG 4
.Os
.Sh NAME
.Nm pflog
.Nd packet filter logging interface
.Sh SYNOPSIS
.Cd "device pflog"
.Sh DESCRIPTION
The
.Nm pflog
interface is a device which makes visible all packets logged by
the packet filter,
.Xr pf 4 .
Logged packets can easily be monitored in real
time by invoking
.Xr tcpdump 1
on the
.Nm
interface, or stored to disk using
.Xr pflogd 8 .
.Pp
The pflog0 interface is created when the
.Nm
module is loaded;
further instances can be created using
.Xr ifconfig 8 .
The
.Nm
module is loaded automatically if both
.Xr pf 4
and
.Xr pflogd 8
are enabled.
.Pp
Each packet retrieved on this interface has a header associated
with it of length
.Dv PFLOG_HDRLEN .
This header documents the address family, interface name, rule
number, reason, action, and direction of the packet that was logged.
This structure, defined in
.Aq Pa net/if_pflog.h
looks like
.Bd -literal -offset indent
struct pfloghdr {
	u_int8_t	length;
	sa_family_t	af;
	u_int8_t	action;
	u_int8_t	reason;
	char		ifname[IFNAMSIZ];
	char		ruleset[PF_RULESET_NAME_SIZE];
	u_int32_t	rulenr;
	u_int32_t	subrulenr;
	uid_t		uid;
	pid_t		pid;
	uid_t		rule_uid;
	pid_t		rule_pid;
	u_int8_t	dir;
	u_int8_t	pad[3];
	u_int32_t	ridentifier;
};
.Ed
.Sh EXAMPLES
Create a
.Nm
interface
and monitor all packets logged on it:
.Bd -literal -offset indent
# ifconfig pflog create
pflog1
# ifconfig pflog1 up
# tcpdump -n -e -ttt -i pflog1
.Ed
.Sh SEE ALSO
.Xr tcpdump 1 ,
.Xr inet 4 ,
.Xr inet6 4 ,
.Xr netintro 4 ,
.Xr pf 4 ,
.Xr ifconfig 8 ,
.Xr pflogd 8
.Sh HISTORY
The
.Nm
device first appeared in
.Ox 3.0 .
.Sh BUGS
FreeBSD does not set a process id in the
.Fa pid
field in pfloghdr.