path: root/sbin/pflogd/pflogd.8

.\"	$OpenBSD: pflogd.8,v 1.51 2019/08/30 17:51:47 jmc Exp $
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.Dd $Mdocdate: August 30 2019 $
.Dt PFLOGD 8
.Os
.Sh NAME
.Nm pflogd
.Nd packet filter logging daemon
.Sh SYNOPSIS
.Nm pflogd
.Bk -words
.Op Fl \&Dx
.Op Fl d Ar delay
.Op Fl f Ar filename
.Op Fl i Ar interface
.Op Fl s Ar snaplen
.Op Ar expression
.Ek
.Sh DESCRIPTION
.Nm
is a background daemon which reads packets logged by
.Xr pf 4
to a
.Xr pflog 4
interface, normally
.Pa pflog0 ,
and writes the packets to a logfile (normally
.Pa /var/log/pflog )
in
.Xr tcpdump 8
binary format.
These logs can be reviewed later using the
.Fl r
option of
.Xr tcpdump 8 ,
hopefully offline in case there are bugs in the packet parsing code of
.Xr tcpdump 8 .
.Pp
.Nm
closes and then re-opens the log file when it receives
.Dv SIGHUP ,
permitting
.Xr newsyslog 8
to rotate logfiles automatically.
.Dv SIGALRM
causes
.Nm
to flush the current logfile buffers to the disk, thus making the most
recent logs available.
The buffers are also flushed every
.Ar delay
seconds.
.Pp
If the log file contains data after a restart or a
.Dv SIGHUP ,
new logs are appended to the existing file.
If the existing log file was created with a different snaplen,
.Nm
temporarily uses the old snaplen to keep the log file consistent.
.Pp
.Nm
tries to preserve the integrity of the log file against I/O errors.
Furthermore, integrity of an existing log file is verified before
appending.
If there is an invalid log file or an I/O error, logging is suspended
until a
.Dv SIGHUP
or a
.Dv SIGALRM
is received.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl D
Debugging mode.
.Nm
does not disassociate from the controlling terminal.
.It Fl d Ar delay
Time in seconds to delay between automatic flushes of the file.
This may be specified with a value between 5 and 3600 seconds.
If not specified, the default is 60 seconds.
.It Fl f Ar filename
Log output filename.
Default is
.Pa /var/log/pflog .
.It Fl i Ar interface
Specifies the
.Xr pflog 4
interface to use.
By default,
.Nm
will use
.Pa pflog0 .
.It Fl s Ar snaplen
Analyze at most the first
.Ar snaplen
bytes of data from each packet rather than the default of 160.
The default of 160 is adequate for IP, ICMP, TCP, and UDP headers but may
truncate protocol information for other protocols.
Other file parsers may desire a higher snaplen.
.It Fl x
Check the integrity of an existing log file, and return.
.It Ar expression
Selects which packets will be dumped, using the regular language of
.Xr tcpdump 8 .
Tcpdump has been extended to be able to filter on the pfloghdr
structure defined in
.In net/if_pflog.h .
It can restrict the output
to packets logged on a specified interface, a rule number, a reason,
a direction, an IP family or an action.
.Pp
.Bl -tag -width "ruleset authpfXXX" -offset 3n -compact
.It ip
Address family equals IPv4.
.It ip6
Address family equals IPv6.
.It ifname kue0
Interface name equals "kue0".
.It on kue0
Interface name equals "kue0".
.It ruleset authpf
Ruleset name equals "authpf".
.It rulenum 10
Rule number equals 10.
.It reason match
Reason equals match.
Also accepts "bad-offset", "fragment", "short", "normalize",
"memory", "bad-timestamp", "congestion", "ip-option", "proto-cksum",
"state-mismatch", "state-insert", "state-limit", "src-limit",
and "synproxy".
.It action pass
Action equals pass.
Also accepts "block" and "match".
.It inbound
The direction was inbound.
.It outbound
The direction was outbound.
.El
.El
.Sh FILES
.Bl -tag -width /var/run/pflogd.pid -compact
.It Pa /var/log/pflog
Default log file.
.El
.Sh EXAMPLES
Log specific TCP packets to a different log file with a large snaplen
(useful with a
.Qq log all
rule to dump complete sessions):
.Bd -literal -offset indent
# pflogd -s 1600 -f suspicious.log port 80 and host evilhost
.Ed
.Pp
Log from another
.Xr pflog 4
interface, excluding specific packets:
.Bd -literal -offset indent
# pflogd -i pflog3 -f network3.log "not (tcp and port 23)"
.Ed
.Pp
Display binary logs:
.Bd -literal -offset indent
# tcpdump -n -e -ttt -r /var/log/pflog
.Ed
.Pp
Display the logs in real time (this does not interfere with the
operation of
.Nm ) :
.Bd -literal -offset indent
# tcpdump -n -e -ttt -i pflog0
.Ed
.Pp
Display the logs in real time of inbound packets that were blocked on
the wi0 interface:
.Bd -literal -offset indent
# tcpdump -n -e -ttt -i pflog0 inbound and action block and on wi0
.Ed
.Sh SEE ALSO
.Xr pcap_open_live 3 ,
.Xr pf 4 ,
.Xr pflog 4 ,
.Xr pf.conf 5 ,
.Xr newsyslog 8 ,
.Xr tcpdump 8
.Sh HISTORY
The
.Nm
command appeared in
.Ox 3.0 .
.Sh AUTHORS
.Nm
was written by
.An Can Erkin Acar Aq Mt canacar@openbsd.org .