PFLOGD(8) FreeBSD System Manager's Manual PFLOGD(8)
NAME
pflogd - packet filter logging daemon
SYNOPSIS
pflogd [-Dx] [-d delay] [-f filename] [-i interface] [-s snaplen]
[expression]
DESCRIPTION
pflogd is a background daemon which reads packets logged by pf(4) to a
pflog(4) interface, normally pflog0, and writes the packets to a logfile
(normally /var/log/pflog) in tcpdump(8) binary format. These logs can be
reviewed later using the -r option of tcpdump(8), hopefully offline in
case there are bugs in the packet parsing code of tcpdump(8).
pflogd closes and then re-opens the log file when it receives 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
controlling 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.
-i interface
Specifies the pflog(4) interface to use. By default, pflogd will
use pflog0.
-s snaplen
Analyze at most the first 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.
-x Check the integrity of an existing log file, and return.
expression
Selects which packets will be dumped, using the regular language
of tcpdump(8). Tcpdump has been extended to be able to filter on
the pfloghdr structure defined 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.
ip Address family equals IPv4.
ip6 Address family equals IPv6.
ifname kue0 Interface name equals "kue0".
on kue0 Interface name equals "kue0".
ruleset authpf Ruleset name equals "authpf".
rulenum 10 Rule number equals 10.
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".
action pass Action equals pass. Also accepts "block"
and "match".
inbound The direction was inbound.
outbound The direction was outbound.
FILES
/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
Log from another pflog(4) interface, excluding specific packets:
# pflogd -i pflog3 -f network3.log "not (tcp and port 23)"
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
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
pcap_open_live(3), pf(4), pflog(4), pf.conf(5), newsyslog(8), tcpdump(8)
HISTORY
The pflogd command appeared in OpenBSD 3.0.
AUTHORS
pflogd was written by Can Erkin Acar <
[email protected]>.
FreeBSD 14.1-RELEASE-p8 August 30, 2019 FreeBSD 14.1-RELEASE-p8