man/ipmon.5

.TH IPMON 5
.SH NAME
ipmon, ipmon.conf \- ipmon configuration file format
.SH DESCRIPTION
The
.B ipmon.conf
file is optionally loaded by
.B ipmon
when it starts.  Its primary purpose is to direct
.B ipmon
to do extra actions when it sees a specific log entry from the kernel.
.PP
A line in the
.B ipmon.conf
file is either a comment or a
.B match
line.  Each line must have a matching segment and an action segment.
These are to the left and right of the word "do", respectively.
A comment line is any line that starts with a #.
.PP
.B NOTE:
This file differs from all other IPFilter configuration files because it
attempts to match every line with every log record received.  It does
.B not
stop at the
.B first
match or only use the
.B last
match.
.PP
For the action segment, a
.B match
line can delivery output to one of three destinations:
\fBfile\fR, \fBemail\fR or \fBcommand\fR.  For example:
.nf

match { type = ipf; } do { save("file:///var/log/ipf-log"); };
match { type = nat; } do { syslog; };
match { type = state; } do { execute("/bin/mail root"); };
.fi
.PP
and is roughly described like this:
.PP
match { \fImatch-it ,match-it, ...\fP } do { \fIaction, action, ...\fP};
.PP
where there can be a list of matching expressions and a list of actions
to perform if all of the matching expressions are matched up with by
the current log entry.
.PP
The lines above would save all ipf log entries to /var/log/ipf-log, send
all of the entries for NAT (ipnat related) to syslog and generate an email
to root for each log entry from the state tables.
.SH SYNTAX - MATCHING
.PP
In the above example, the matching segment was confined to matching on
the type of log entry generated.  The full list of fields that can be
used here is:
.TP
direction <in|out>
This option is used to match on log records generated for packets going
in or out.
.TP
dstip <address/mask>
This option is used to match against the destination address associated
with the packet being logged.  A "/mask" must be given and given in CIDR
notation (/0-/32) so to specify host 192.2.2.1, 192.2.2.1/32 must be given.
.TP
dstport <portnumber>
This option is used to match against the destination port in log entries.
A number must be given, symbolic names (such as those from /etc/services)
are not recognised by the parser.
.TP
every <second|# seconds|packet|# packets>
This option is used to regulate how often an \fBipmon.conf\fR entry is
actioned in response to an otherwise matching log record from the kernel.
.TP
group <name|number>
.TP
interface <interface-name>
This option is used to match against the network interface name associated
with the action causing the logging to happen.  In general this will be the
network interface where the packet is seen by IPFilter.
.TP
logtag <number>
This option is used to match against tags set by ipf rules in \fBipf.conf\fR.
These tags are set with "set-tag(log=100)" appended to filter rules.
.TP
nattag <string>
This option is used to match against tags set by NAT rules in \fBipnat.conf\fR.
.TP
protocol <name|number>
This option is used to match against the IP protocol field in the packet
being logged.
.TP
result <pass|block|nomatch|log>
This option is used to match against the result of packet matching in the
kernel.  If a packet is logged, using a \fBlog\fR rule in \fBipf.conf\fR
then it will match "log" here.  The "nomatch" option is for use with
matching log records generated for all packets as the default.
.TP
rule <number>
This option is used to match against the \fInumber\fR of the rule
causing the record to be generated.  The \fInumber\fR of a rule can be
observed using "ipfstat -ion".
.TP
srcip <address/mask>
This option is used to match against the source address associated
with the packet being logged.  A "/mask" must be given and given in CIDR
notation (/0-/32) so to specify host 192.2.2.1, 192.2.2.1/32 must be given.
.TP
srcport <portnumber>
This option is used to match against the source port in log entries.
A number must be given, symbolic names (such as those from /etc/services)
are not recognised by the parser.
.TP
type <ipf|nat|state>
The format for files accepted by ipmon is described by the following grammar:
.B NOTE:
At present, only IPv4 matching is available for source/destination address
matching.
.SH SYNTAX - ACTIONS
The list of actions supported is as follows:
.TP
save("file://<filename>")
save("raw://<filename>")
Write out the log record to the filename given.  This file will be closed
and reopened on receipt of a SIGHUP.  If the \fIraw\fP target is used,
binary log data, as read from the kernel, is written out rather than a
text log record. The filename should be an absolute target, including
the root directory. Thus, saving to /var/log/ipmon.log would be, as an
example, save("file:///var/log/ipmon.log").
.TP
syslog("<facility>.<priority>")
syslog("<facility>.")
syslog(".<priority>")
To log a text record via syslog, the \fBsyslog\fP action word is used.
The facility used by default is determined at first by the default
compiled into \fBipmon\fP (usually LOG_LOCAL0), which can be changed
via the command line (-L <facility>) or in an \fBipf.conf\fP rule
using the \fIlevel\fP option with logging.  If the facility is
specified here, it takes precedence over all other settings.
The same applies to the syslog priority. By default, ipmon will
determine a priority for the packet, depending on whether or not it
has been blocked, passed, etc. It is possible to force the complete
facility/priority value for each log entry or to choose to replace
only one of them.
.TP
execute("<command string>")
The
.B execute
action runs the specified command each time the log entry matches
and feeds the log entry, as text, to the command being executed.
The command string given is executed using /bin/sh.
.TP
nothing
Literally, do nothing.  Use this if you want to be verbose in your config
file about doing nothing for a particular log record.
.SH PLUGIN ACTIONS
It is possible to configure
.B ipmon
to use externally supplied modules to save log entries with.
These are added to
.B ipmon
using the
.I load_action
configuration line. The syntax of this line is:
.nf

load_action <name> <path>;
.fi
.TP
name
is a short name for the action. It does not need to correspond to the
name of the library file, but inside the library file, the functions
.B <name>destroy
,
.B <name>parse
and
.B <name>store
must be present.
.TP
path
specifies the path in the filesystem to the shared object
that contains the implementation of the new action. After the new
action has been declared using
.I load_action
it can then be used in any
.I do
statement.
.SH EXAMPLES
.PP
Some further examples are:
.nf

#
# log everything to syslog local4, regardless
#
match { ; } do { syslog("local4."); };
#
# keep a local copy of things packets to/from port 80
#
match { srcport = 80; } do { save("file:///var/log/web"); };
match { dstport = 80; } do { save("file:///var/log/web"); };
#
load_action local "/usr/lib/libmyaction.so";
match { dstip 127.0.0.1; } do { local("local options"); };
#
.fi
.SH MATCHING
.PP
All entries of the rules present in the file are
compared for matches - there is no first or last rule match.
.SH FILES
/dev/ipl
.br
/dev/ipf
.br
/dev/ipnat
.br
/dev/ipstate
.br
/etc/ipmon.conf
.SH SEE ALSO
ipmon(8), ipl(4)