ipmon man page on FreeBSD

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ipmon(8)							      ipmon(8)

       ipmon - monitors /dev/ipl for logged packets

       ipmon [ -abBDFhnpstvxX ] [ -N <device> ] [ -L <facility> ] [ -o [NSI] ]
       [ -O [NSI] ] [ -P <pidfile> ] [ -S <device> ] [ -f <device> ] [	<file‐
       name> ]

       ipmon  opens  /dev/ipl for reading and awaits data to be saved from the
       packet filter.  The binary data read from the device  is	 reprinted  in
       human  readable	for,  however, IP#'s are not mapped back to hostnames,
       nor are ports mapped back to service names.  The output goes  to	 stan‐
       dard  output  by	 default  or a filename, if given on the command line.
       Should the -s option be used, output is	instead	 sent  to  syslogd(8).
       Messages	 sent via syslog have the day, month and year removed from the
       message, but the time (including microseconds), as recorded in the log,
       is still included.

       Messages	 generated  by	ipmon  consist of whitespace separated fields.
       Fields common to all messages are:

       1. The date of packet receipt. This is suppressed when the  message  is
       sent to syslog.

       2.  The	time  of  packet  receipt. This is in the form HH:MM:SS.F, for
       hours, minutes seconds, and fractions of a second (which can be several
       digits long).

       3. The name of the interface the packet was processed on, e.g., we1.

       4.  The	group  and  rule number of the rule, e.g., @0:17. These can be
       viewed with ipfstat -n.

       5. The action: p for passed, b for blocked,  for a short packet, n  did
       not match any rules or L for a log rule.

       6.  The	addresses.   This is actually three fields: the source address
       and port (separated by a comma), the ->	symbol,	 and  the  destination
       address and port. E.g.:,80 ->,1722.

       7. PR followed by the protocol name or number, e.g., PR tcp.

       8.  len	followed  by the header length and total length of the packet,
       e.g., len 20 40.

       If the packet is a TCP packet, there will be an additional field start‐
       ing  with  a hyphen followed by letters corresponding to any flags that
       were set.  See the ipf.conf manual page for a list of letters and their

       If  the	packet is an ICMP packet, there will be two fields at the end,
       the first always being `icmp', and the next being the ICMP message  and
       submessage  type,  separated  by	 a  slash,  e.g.,  icmp 3/3 for a port
       unreachable message.

       In order for ipmon to properly work,  the  kernel  option  IPFILTER_LOG
       must  be	 turned	 on  in	 your  kernel.	Please see options(4) for more

       ipmon reopens its log file(s) and rereads its configuration  file  when
       it receives a SIGHUP signal.

       -a     Open  all	 of  the device logfiles for reading log entries from.
	      All entries are displayed to the same output 'device' (stderr or

       -b     For  rules  which	 log the body of a packet, generate hex output
	      representing the packet contents after the headers.

       -B <binarylogfilename>
	      Enable logging of the raw, unformatted binary data to the speci‐
	      fied  <binarylogfilename>	 file.	This can be read, later, using
	      ipmon with the -f option.

       -D     Cause ipmon to turn itself into a daemon.	  Using	 subshells  or
	      backgrounding of ipmon is not required to turn it into an orphan
	      so it can run indefinitely.

       -f <device>
	      specify an alternative device/file from which to	read  the  log
	      information for normal IP Filter log records.

       -F     Flush  the  current  packet  log	buffer.	  The  number of bytes
	      flushed is displayed, even should the result be zero.

       -L <facility>
	      Using this option allows you to change the default syslog facil‐
	      ity that ipmon uses for syslog messages.	The default is local0.

       -n     IP  addresses  and  port numbers will be mapped, where possible,
	      back into hostnames and service names.

       -N <device>
	      Set the logfile to be opened for reading NAT log records from to

       -o     Specify  which  log  files  to actually read data from.  N - NAT
	      logfile, S - State logfile, I - normal IP Filter	logfile.   The
	      -a option is equivalent to using -o NSI.

       -O     Specify  which  log files you do not wish to read from.  This is
	      most sensibly used with the -a.  Letters available as parameters
	      to this are the same as for -o.

       -p     Cause  the port number in log messages to always be printed as a
	      number and never attempt to look it up  as  from	/etc/services,

       -P <pidfile>
	      Write  the  pid of the ipmon process to a file.  By default this
	      is //etc/opt/ipf/ipmon.pid (Solaris), /var/run/ipmon.pid	(44BSD
	      or later) or /etc/ipmon.pid for all others.

       -s     Packet  information  read in will be sent through syslogd rather
	      than saved to a file.  The default facility  when	 compiled  and
	      installed is security.  The following levels are used:

	      LOG_INFO	- packets logged using the "log" keyword as the action
	      rather than pass or block.

	      LOG_NOTICE - packets logged which are also passed

	      LOG_WARNING - packets logged which are also blocked

	      LOG_ERR - packets which have been logged and which can  be  con‐
	      sidered "short".

       -S <device>
	      Set  the logfile to be opened for reading state log records from
	      to <device>.

       -t     read the input file/device in a manner akin to tail(1).

       -v     show tcp window, ack and sequence fields.

       -x     show the packet data in hex.

       -X     show the log header record data in hex.

       ipmon expects data that it reads to be consistent with how it should be
       saved  and will abort if it fails an assertion which detects an anomaly
       in the recorded data.


       ipl(4), ipf(8), ipfstat(8), ipnat(8)

       If you find any, please send email to me at darrenr@pobox.com


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