PFLOGD(8)               OpenBSD 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 er-
     rors.  Furthermore, integrity of an existing log file is verified before
     appending.  If there is an invalid log file or an I/O error, the log file
     is moved out of the way and a new one is created.  If a new file cannot
     be created, logging is suspended until a SIGHUP or a SIGALRM is received.

     pflogd will also log the pcap statistics for the pflog(4) interface to
     syslog when a SIGUSR1 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.

     -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 116.  The default of 116 is adequate
             for IP, ICMP, TCP, and UDP headers but may truncate protocol in-
             formation 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).

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

     Tcpdump has been extended to be able to filter on the pfloghdr structure
     defined in <net/if_pflog.h>.  Tcpdump 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", "frag-
                      ment", "short", "normalize", "memory", "bad-timestamp",
                      "congestion", "ip-option", "proto-cksum", "state-mis-
                      match", "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.

     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(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 <canacar@openbsd.org>.

OpenBSD 4.7                    December 3, 2009                              2
