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.\" $OpenBSD: pflog.4,v 1.10 2007/05/31 19:19:51 jmc Exp $
.\"
.\" Copyright (c) 2001 Tobias Weingartner
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.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.
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