Updated: 2022/Sep/29

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IPF(8)                      System Manager's Manual                     IPF(8)

       ipf - alters packet filtering lists for IP packet input and output

       ipf [ -6AcdDEInoPrsvVyzZ ] [ -l <block|pass|nomatch> ] [ -T
       <optionlist> ] [ -F <i|o|a|s|S> ] -f <filename> [ -f <filename> [...]]

       ipf opens the filenames listed (treating "-" as stdin) and parses the
       file for a set of rules which are to be added or removed from the
       packet filter rule set.

       Each rule processed by ipf is added to the kernel's internal lists if
       there are no parsing problems.  Rules are added to the end of the
       internal lists, matching the order in which they appear when given to

       -6     This option is required to parse IPv6 rules and to have them

       -A     Set the list to make changes to the active list (default).

       -c <language>
              This option causes ipf to generate output files for a compiler
              that supports language.  At present, the only target language
              supported is C (-cc) for which two files - ip_rules.c and
              ip_rules.h are generated in the CURRENT DIRECTORY when ipf is
              being run.  These files can be used with the IPFILTER_COMPILED
              kernel option to build filter rules staticly into the kernel.

       -d     Turn debug mode on.  Causes a hexdump of filter rules to be
              generated as it processes each one.

       -D     Disable the filter (if enabled).  Not effective for loadable
              kernel versions.

       -E     Enable the filter (if disabled).  Not effective for loadable
              kernel versions.

       -F <i|o|a>
              This option specifies which filter list to flush.  The parameter
              should either be "i" (input), "o" (output) or "a" (remove all
              filter rules).  Either a single letter or an entire word
              starting with the appropriate letter maybe used.  This option
              maybe before, or after, any other with the order on the command
              line being that used to execute options.

       -F <s|S>
              To flush entries from the state table, the -F option is used in
              conjunction with either "s" (removes state information about any
              non-fully established connections) or "S" (deletes the entire
              state table).  Only one of the two options may be given.  A
              fully established connection will show up in ipfstat -s output
              as 5/5, with deviations either way indicating it is not fully
              established any more.

              For the TCP states that represent the closing of a connection
              has begun, be it only one side or the complete connection, it is
              possible to flush those states directly using the number
              corresponding to that state.  The numbers relate to the states
              as follows: 5 = close-wait, 6 = fin-wait-1, 7 = closing, 8 =
              last-ack, 9 = fin-wait-2, 10 = time-wait, 11 = closed.

              If the argument supplied to -F is greater than 30, then state
              table entries that have been idle for more than this many
              seconds will be flushed.

       -f <filename>
              This option specifies which files ipf should use to get input
              from for modifying the packet filter rule lists.

       -I     Set the list to make changes to the inactive list.

       -l  <block|pass|nomatch|none|state|nat>
              Use of the -l flag toggles default logging of packets.  Valid
              arguments to this option are pass, block, nomatch, none, state,
              and nat.  When an option is set, any packet which exits
              filtering and matches the set category is logged.  This is most
              useful for causing all packets which don't match any of the
              loaded rules to be logged.

       -n     This flag (no-change) prevents ipf from actually making any
              ioctl calls or doing anything which would alter the currently
              running kernel.

       -o     Force rules by default to be added/deleted to/from the output
              list, rather than the (default) input list.

       -P     Add rules as temporary entries in the authentication rule table.

       -r     Remove matching filter rules rather than add them to the
              internal lists

       -s     Swap the active filter list in use to be the "other" one.

       -T <optionlist>
              This option allows run-time changing of IPFilter kernel
              variables.  Some variables require IPFilter to be in a disabled
              state (-D) for changing, others do not.  The optionlist
              parameter is a comma separated list of tuning commands.  A
              tuning command is either "list" (retrieve a list of all
              variables in the kernel, their maximum, minimum and current
              value), a single variable name (retrieve its current value) and
              a variable name with a following assignment to set a new value.
              Some examples follow.
              # Print out all IPFilter kernel tunable parameters
              ipf -T list
              # Display the current TCP idle timeout and then set it to 3600
              ipf -D -T fr_tcpidletimeout,fr_tcpidletimeout=3600 -E
              # Display current values for fr_pass and fr_chksrc, then set fr_chksrc to 1.
              ipf -T fr_pass,fr_chksrc,fr_chksrc=1

       -v     Turn verbose mode on.  Displays information relating to rule

       -V     Show version information.  This will display the version
              information compiled into the ipf binary and retrieve it from
              the kernel code (if running/present).  If it is present in the
              kernel, information about its current state will be displayed
              (whether logging is active, default filtering, etc).

       -y     Manually resync the in-kernel interface list maintained by IP
              Filter with the current interface status list.

       -z     For each rule in the input file, reset the statistics for it to
              zero and display the statistics prior to them being zeroed.

       -Z     Zero global statistics held in the kernel for filtering only
              (this doesn't affect fragment or state statistics).


       ipftest(1), mkfilters(1), ipf(4), ipl(4), ipf(5), ipfstat(8), ipmon(8),

       Needs to be run as root for the packet filtering lists to actually be
       affected inside the kernel.

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