pflogd(8)

NAME

pflogd - packet filter logging daemon

SYNOPSIS

pflogd  [-Dx]  [-d  delay]  [-f   filename]   [-s   snaplen]
[expression]

DESCRIPTION

pflogd is a background daemon which reads packets logged by
pf(4) to the
packet logging interface pflog0 and writes the packets to a
logfile (normally /var/log/pflog) in tcpdump(1) binary format. These
logs can be
reviewed later using the -r option of tcpdump(1), hopefully
offline in
case there are bugs in the packet parsing code of tcp
dump(1).
pflogd closes and then re-opens the log file when it re
ceives SIGHUP,
permitting newsyslog(8) to rotate logfiles automatically.
SIGALRM causes
pflogd to flush the current logfile buffers to the disk,
thus making the
most recent logs available. The buffers are also flushed
every delay
seconds.
If the log file contains data after a restart or a SIGHUP,
new logs are
appended to the existing file. If the existing log file was
created with
a different snaplen, pflogd temporarily uses the old snaplen
to keep the
log file consistent.
pflogd 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 SIGHUP or a SIGALRM is received.
The options are as follows:
-D Debugging mode. pflogd does not disassociate from
the control
ling terminal.
-d 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.
-f filename
Log output filename. Default is /var/log/pflog.
-s snaplen
Analyze at most the first snaplen bytes of data from
each packet
rather than the default of 96. The default of 96 is
adequate for
IP, ICMP, TCP, and UDP headers but may truncate pro
tocol information for other protocols. Other file parsers may
desire a higher
snaplen.
-x Check the integrity of an existing log file, and re
turn.
expression
Selects which packets will be dumped, using the reg
ular language
of tcpdump(1).

FILES

/var/run/pflogd.pid Process ID of the currently running
pflogd.
/var/log/pflog Default log file.

EXAMPLES

Log specific tcp packets to a different log file with a
large snaplen
(useful with a log-all rule to dump complete sessions):

# pflogd -s 1600 -f suspicious.log port 80 and host
evilhost
Display binary logs:

# tcpdump -n -e -ttt -r /var/log/pflog
Display the logs in real time (this does not interfere with
the operation
of pflogd):

# tcpdump -n -e -ttt -i pflog0
Tcpdump has been extended to be able to filter on the
pfloghdr structure
defined in <net/if_pflog.h>. Tcpdump can restrict the out
put to packets
logged on a specified interface, a rule number, a reason, a
direction, an
IP family or an action.
ip Address family equals IPv4.
ip6 Address family equals IPv6.
ifname kue0 Interface name equals "kue0".
on kue0 Interface name equals "kue0".
rulenum 10 Rule number equals 10.
reason match Reason equals match. Also accepts "bad-off
set", "frag
ment", "bad-timestamp", "short", "normalize"
and "memory".
action pass Action equals pass. Also accepts "block".
inbound The direction was inbound.
outbound The direction was outbound.
Display the logs in real time of inbound packets that were
blocked on the
wi0 interface:

# tcpdump -n -e -ttt -i pflog0 inbound and action
block and on wi0

SEE ALSO

tcpdump(1), pcap(3), pf(4), pflog(4), pf.conf(5), newsys
log(8)

HISTORY

The pflogd command appeared in OpenBSD 3.0.

AUTHORS

Can Erkin Acar
BSD July 9, 2001
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