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IP6FW(8)		  BSD System Manager's Manual		      IP6FW(8)

     ip6fw -- controlling utility for IPv6 firewall

     ip6fw [-nq] [-p preproc [-D macro[=value]]	[-U macro]] pathname
     ip6fw [-n]	[-f | -q] flush
     ip6fw [-nq] zero [number ...]
     ip6fw [-n]	delete number ...
     ip6fw [-aftN] list	[number	...]
     ip6fw [-ftN] show [number ...]
     ip6fw [-nq] add [number] action [log] proto from src to dst
	   [via	name | ipv6no] [options]

     To	ease configuration, rules can be put into a file which is processed
     using ip6fw as shown in the first synopsis	line.  An absolute pathname
     must be used.  The	file will be read line by line and applied as argu-
     ments to the ip6fw	utility.

     Optionally, a preprocessor	can be specified using -p preproc where
     pathname is to be piped through.  Useful preprocessors include cpp(1) and
     m4(1).  If	preproc	does not start with a slash (`/') as its first charac-
     ter, the usual PATH name search is	performed.  Care should	be taken with
     this in environments where	not all	file systems are mounted (yet) by the
     time ip6fw	is being run (e.g. when	they are mounted over NFS).  Once -p
     has been specified, optional -D and -U specifications can follow and will
     be	passed on to the preprocessor.	This allows for	flexible configuration
     files (like conditionalizing them on the local hostname) and the use of
     macros to centralize frequently required arguments	like IP	addresses.

     The ip6fw code works by going through the rule-list for each packet, un-
     til a match is found.  All	rules have two associated counters, a packet
     count and a byte count.  These counters are updated when a	packet matches
     the rule.

     The rules are ordered by a	"line-number" from 1 to	65534 that is used to
     order and delete rules.  Rules are	tried in increasing order, and the
     first rule	that matches a packet applies.	Multiple rules may share the
     same number and apply in the order	in which they were added.

     If	a rule is added	without	a number, it is	numbered 100 higher than the
     previous rule.  If	the highest defined rule number	is greater than	65434,
     new rules are appended to the last	rule.

     The delete	operation deletes the first rule with number number, if	any.

     The list command prints out the current rule set.

     The show command is equivalent to `ip6fw -a list'.

     The zero operation	zeroes the counters associated with rule number

     The flush operation removes all rules.

     Any command beginning with	a `#', or being	all blank, is ignored.

     One rule is always	present:

		       65535 deny all from any to any

     This rule is the default policy, i.e., do not allow anything at all.
     Your job in setting up rules is to	modify this policy to match your

     The following options are available:

     -a	   While listing, show counter values.	See also "show"	command.

     -f	   Do not ask for confirmation for commands that can cause problems if
	   misused (ie;	flush).	 Note, if there	is no tty associated with the
	   process, this is implied.

     -n	   Only	check syntax of	the command strings, without actually passing
	   them	into the kernel.

     -q	   While adding, zeroing or flushing, be quiet about actions (implies
	   '-f').  This	is useful for adjusting	rules by executing multiple
	   ip6fw commands in a script (e.g. sh /etc/rc.firewall), or by	pro-
	   cessing a file of many ip6fw	rules, across a	remote login session.
	   If a	flush is performed in normal (verbose) mode, it	prints a mes-
	   sage.  Because all rules are	flushed, the message cannot be deliv-
	   ered	to the login session, the login	session	is closed and the re-
	   mainder of the ruleset is not processed.  Access to the console is
	   required to recover.

     -t	   While listing, show last match timestamp.

     -N	   Try to resolve addresses and	service	names in output.


	 allow		   Allow packets that match rule.  The search termi-
			   nates.  Aliases are pass, permit, and accept.

	 deny		   Discard packets that	match this rule.  The search
			   terminates.	Drop is	an alias for deny.

	 reject		   (Deprecated.)  Discard packets that match this
			   rule, and try to send an ICMPv6 host	unreachable
			   notice.  The	search terminates.

	 unreach code	   Discard packets that	match this rule, and try to
			   send	an ICMPv6 unreachable notice with code code,
			   where code is a number from zero to 255, or one of
			   these aliases: noroute, admin, notneighbor, addr,
			   or noport, The search terminates.

	 reset		   TCP packets only.  Discard packets that match this
			   rule, and try to send a TCP reset (RST) notice.
			   The search terminates

	 count		   Update counters for all packets that	match rule.
			   The search continues	with the next rule.

	 skipto	number	   Skip	all subsequent rules numbered less than
			   number.  The	search continues with the first	rule
			   numbered number or higher.

     If	the kernel was compiled	with IPV6FIREWALL_VERBOSE, then	when a packet
     matches a rule with the "log" keyword or a	clear/resetlog is performed, a
     message will be logged to syslogd(8), or, if that fails, to the console.
     If	the kernel was compiled	with the IPV6FIREWALL_VERBOSE_LIMIT option,
     then logging will cease after the number of packets specified by the op-
     tion are received for that	particular chain entry.	 When this limit is
     reached, the limit	and rule number	will be	logged.	 Logging may then be
     re-enabled	by clearing the	packet counter for that	entry.

     The syslogd(8) logging and	the default log	limit are adjustable dynami-
     cally through the sysctl(8) interface.


	 ipv6		   All packets match.  The alias all has the same ef-

	 tcp		   Only	TCP packets match.

	 udp		   Only	UDP packets match.

	 ipv6-icmp	   Only	ICMPv6 packets match.

	 _number|name_	   Only	packets	for the	specified protocol matches
			   (see	/etc/protocols for a complete list).

     src and dst:

	 _address/prefixlen_ [ports]

     The _address/prefixlen_ may be specified as:

	 ipv6no		   An ipv6number of the	form fec0::1:2:3:4.

	 ipv6no/prefixlen  An ipv6number with a	prefix length of the form

     The sense of the match can	be inverted by preceding an address with the
     "not" modifier, causing all other addresses to be matched instead.	 This
     does not affect the selection of port numbers.

     With the TCP and UDP protocols, optional ports may	be specified as:


     Service names (from /etc/services)	may be used instead of numeric port
     values.  A	range may only be specified as the first value,	and the	length
     of	the port list is limited to IPV6_FW_MAX_PORTS (as defined in
     <netinet6/ip6_fw.h>) ports.

     Fragmented	packets	which have a non-zero offset (i.e., not	the first
     fragment) will never match	a rule which has one or	more port specifica-
     tions.  See the frag option for details on	matching fragmented packets.

     Rules can apply to	packets	when they are incoming,	or outgoing, or	both.
     The in keyword indicates the rule should only match incoming packets.
     The out keyword indicates the rule	should only match outgoing packets.

     To	match packets going through a certain interface, specify the interface
     using via:

	 via ifX	   Packet must be going	through	interface ifX.

	 via if*	   Packet must be going	through	interface ifX, where X
			   is any unit number.

	 via any	   Packet must be going	through	some interface.

	 via ipv6no	   Packet must be going	through	the interface having
			   IPv6	address	ipv6no.

     The via keyword causes the	interface to always be checked.	 If recv or
     xmit is used instead of via, then the only	receive	or transmit interface
     (respectively) is checked.	 By specifying both, it	is possible to match
     packets based on both receive and transmit	interface, e.g.:

	   ip6fw add 100 deny ip from any to any out recv ed0 xmit ed1

     The recv interface	can be tested on either	incoming or outgoing packets,
     while the xmit interface can only be tested on outgoing packets.  So out
     is	required (and in invalid) whenever xmit	is used.  Specifying via to-
     gether with xmit or recv is invalid.

     A packet may not have a receive or	transmit interface: packets originat-
     ing from the local	host have no receive interface,	while packets destined
     for the local host	have no	transmit interface.

     Additional	options:

	 frag		   Matches if the packet is a fragment and this	is not
			   the first fragment of the datagram.	frag may not
			   be used in conjunction with either tcpflags or
			   TCP/UDP port	specifications.

	 in		   Matches if this packet was on the way in.

	 out		   Matches if this packet was on the way out.

	 ipv6options spec  Matches if the IPv6 header contains the comma sepa-
			   rated list of options specified in spec.  The sup-
			   ported IPv6 options are: hopopt (hop-by-hop options
			   header), route (routing header), frag (fragment
			   header), esp	(encapsulating security	payload), ah
			   (authentication header), nonxt (no next header),
			   and opts (destination options header).  The absence
			   of a	particular option may be denoted with a	"!"
			   (not	working	yet).

	 established	   Matches packets that	have the RST or	ACK bits set.
			   TCP packets only.

	 setup		   Matches packets that	have the SYN bit set but no
			   ACK bit.  TCP packets only.

	 tcpflags spec	   Matches if the TCP header contains the comma	sepa-
			   rated list of flags specified in spec.  The sup-
			   ported TCP flags are: fin, syn, rst,	psh, ack, and
			   urg.	 The absence of	a particular flag may be de-
			   noted with a	"!".  A	rule which contains a tcpflags
			   specification can never match a fragmented packet
			   which has a non-zero	offset.	 See the frag option
			   for details on matching fragmented packets.

	 icmptypes types   Matches if the ICMPv6 type is in the	list types.
			   The list may	be specified as	any combination	of
			   ranges or individual	types separated	by commas.

     Here are some important points to consider	when designing your rules:

	 +o   Remember that you filter both packets going in and	out.  Most
	     connections need packets going in both directions.

	 +o   Remember to test very carefully.  It is a good idea to be near
	     the console when doing this.

	 +o   Do	not forget the loopback	interface.

     There is one kind of packet that the firewall will	always discard,	that
     is	an IPv6	fragment with a	fragment offset	of one.	 This is a valid
     packet, but it only has one use, to try to	circumvent firewalls.

     If	you are	logged in over a network, loading the KLD version of ip6fw is
     probably not as straightforward as	you would think	(not supported).  I
     recommend this command line:

		       kldload ip6fw &&	\
		       ip6fw add 32000 allow all from any to any

     Along the same lines, doing an

		       ip6fw flush

     in	similar	surroundings is	also a bad idea.

     not supported.

     This command adds an entry	which denies all tcp packets from to	the telnet port	of from being forwarded
     by	the host:

	   ip6fw add deny tcp from to 23

     This one disallows	any connection from the	entire hackers network to my

	   ip6fw add deny all from fec0::123:45:67:0/112 to

     Here is a good usage of the list command to see accounting	records	and
     timestamp information:

	   ip6fw -at l

     or	in short form without timestamps:

	   ip6fw -a l

     ip(4), ipfirewall(4), protocols(5), services(5), reboot(8), sysctl(8),

     A ip6fw utility first appeared in FreeBSD 4.0.

     Ugen J. S.	Antsilevich,
     Poul-Henning Kamp,
     Alex Nash,
     Archie Cobbs.

     API based upon code written by Daniel Boulet for BSDI.


     This program can put your computer	in rather unusable state.  When	using
     it	for the	first time, work on the	console	of the computer, and do	NOT do
     anything you do not understand.

     When manipulating/adding chain entries, service and protocol names	are
     not accepted.

BSD				March 13, 2000				   BSD


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