ip6fw man page on OpenDarwin

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

     ip6fw — controlling utility for IPv6 firewall

     ip6fw [-q] [-p preproc [-D macro[=value]] [-U macro]] pathname
     ip6fw [-f | -q] flush
     ip6fw [-q] zero [number ...]
     ip6fw delete number ...
     ip6fw [-aftN] list [number ...]
     ip6fw [-ftN] show [number ...]
     ip6fw [-q] 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 doesn't 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,
     until 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., don't allow anything at all.  Your
     job in setting up rules is to modify this policy to match your needs.

     The following options are available:

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

     -f	   Don't 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.

     -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
	   remainder 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 (not working yet).

	 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
     option 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

	 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
     /usr/src/sys/netinet6/ip6_fw.h) ports.

     Fragmented packets which have a non-zero offset (i.e. not the first frag‐
     ment) will never match a rule which has one or more port specifications.
     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
     together 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
			   denoted 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:

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

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

	 ·   Don't 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 /modules/ip6fw_mod.o && \
		       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
     hacker.evil.org to the telnet port of wolf.tambov.su from being forwarded
     by the host:

	   ip6fw add deny tcp from hacker.evil.org to wolf.tambov.su 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 my.host.org

     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),


     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 don't understand.

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

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

     API based upon code written by Daniel Boulet for BSDI.

     A ip6fw utility first appeared in FreeBSD 4.0.

BSD				March 13, 2000				   BSD

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