ipmon

Monitor /dev/ipl for logged packets

Syntax:

ipmon  [-abDFhnpstvxX] [-N device] [-o [NSI]] [-O [NSI]] 
[-P pidfile] [-S device] [-f device] [filename]

Options:

-a

Open all device logfiles for reading log entries. All entries are displayed to the same output "device" (stderr or syslog).

-b

Generate hex output representing the packet contents after the headers.

-D

Turn ipmon into a daemon, so it can run indefinitely.

-f device

Specify an alternative device or file from which to read the log information for normal IP filter log records.

-F

Flush the current packet log buffer, in bytes -- even if the result is zero.

-n

Map IP addresses and port numbers, where possible, into hostnames and service names.

-N device

Open the logfile to read NAT log records from device.

-o

Specify 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 log files you don't wish to read from. This is most sensibly used with the -a option. Letters available as parameters to this are the same as for -o.

-p

Print the port number (in log messages) as a number and never attempt to look it up from /etc/services.

-p pidfile

Write the pid of the ipmon process to a file. By default, we use /var/run/ipmon.pid.

-s

Send packet information read through syslogd instead of saving to a file. The default facility when compiled and installed is local0. The following levels are used:

LOG_INFO

Logged packets use the "log" keyword as the action rather than passed or blocked.

LOG_NOTICE

Logged packets logged that are also passed.

LOG_WARNING

Logged packets that are also blocked.

LOG_ERR

Logged packets that are considered "short".

-S device

Open the log file reading state log records from device.

-t

Read the input device or file similar to tail.

-v

Show TCP window, acknowledge and sequence fields.

-x

Show the packet data in hex.

-X

Show the log header record data in hex.

Description:

The ipmon utility opens /dev/ipl for reading and saving data from the packet filter. The binary data read from the device is reprinted in human readable form. The IP numbers, however, are not mapped back to hostnames, nor are ports mapped back to service names. The output goes to standard output by default or to a filename, if given on the command line. For -s, output is sent to syslogd. Messages sent via syslog include time (in microseconds) but don't have the day, month, and year.

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 number of the rule, e.g. @0:17 that is viewed with ipfstat -n.
5. The action: p for passed, b for blocked, S for a short packet, n did not match any rules, L for a log rule. The order of precedence in showing flags is: S, p, b, n, L. When P or B is used, it implies that the packet has been logged due to a global logging setting, not a particular 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.: 209.53.17.22,80 -> 198.73.220.17,1722 .
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 starting with a hyphen followed by letters corresponding to any flags that were set. See the ipf.conf page for a list of letters and their flags.

If the packet is an ICMP packet, there will be two fields at the end:

• "icmp"
• ICMP message and the submessage type, seperated by a slash.

Example is 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 the options for more details.

Files

/dev/ipl 
/dev/ipnat 
/dev/ipstate 
/etc/services

Diagonistics

The ipmon utility expects data to be consistent with how it is saved and will abort if it fails an assertion detecting an anomaly in the recorded data.

See also:

ipf, ipfs, ipfstat, ipnat, lsm-ipfilter.so