9 .Nd User interface for firewall, traffic shaper, packet scheduler,
12 .Ss FIREWALL CONFIGURATION
21 .Op Ar rule | first-last ...
29 .Brq Cm delete | zero | resetlog
33 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
37 .Ar number Cm to Ar number
39 .Cm set swap Ar number number
45 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
48 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
51 .Oo Cm set Ar N Oc Cm table Ar name Cm create Ar create-options
53 .Oo Cm set Ar N Oc Cm table
57 .Oo Cm set Ar N Oc Cm table Ar name Cm modify Ar modify-options
59 .Oo Cm set Ar N Oc Cm table Ar name Cm swap Ar name
61 .Oo Cm set Ar N Oc Cm table Ar name Cm add Ar table-key Op Ar value
63 .Oo Cm set Ar N Oc Cm table Ar name Cm add Op Ar table-key Ar value ...
65 .Oo Cm set Ar N Oc Cm table Ar name Cm atomic add Op Ar table-key Ar value ...
67 .Oo Cm set Ar N Oc Cm table Ar name Cm delete Op Ar table-key ...
69 .Oo Cm set Ar N Oc Cm table Ar name Cm lookup Ar addr
71 .Oo Cm set Ar N Oc Cm table Ar name Cm lock
73 .Oo Cm set Ar N Oc Cm table Ar name Cm unlock
75 .Oo Cm set Ar N Oc Cm table
79 .Oo Cm set Ar N Oc Cm table
83 .Oo Cm set Ar N Oc Cm table
87 .Oo Cm set Ar N Oc Cm table
90 .Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER)
92 .Brq Cm pipe | queue | sched
98 .Brq Cm pipe | queue | sched
99 .Brq Cm delete | list | show
118 .Ss STATEFUL IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
120 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm create Ar create-options
122 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm config Ar config-options
124 .Oo Cm set Ar N Oc Cm nat64lsn
129 .Oo Cm set Ar N Oc Cm nat64lsn
133 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm stats Op Cm reset
134 .Ss STATELESS IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
136 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm create Ar create-options
138 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm config Ar config-options
140 .Oo Cm set Ar N Oc Cm nat64stl
144 .Oo Cm set Ar N Oc Cm nat64stl
148 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm stats Op Cm reset
149 .Ss IPv6-to-IPv6 NETWORK PREFIX TRANSLATION
151 .Oo Cm set Ar N Oc Cm nptv6 Ar name Cm create Ar create-options
153 .Oo Cm set Ar N Oc Cm nptv6
157 .Oo Cm set Ar N Oc Cm nptv6
161 .Oo Cm set Ar N Oc Cm nptv6 Ar name Cm stats Op Cm reset
162 .Ss INTERNAL DIAGNOSTICS
172 utility is the user interface for controlling the
176 traffic shaper/packet scheduler, and the
177 in-kernel NAT services.
179 A firewall configuration, or
183 numbered from 1 to 65535.
184 Packets are passed to the firewall
185 from a number of different places in the protocol stack
186 (depending on the source and destination of the packet,
187 it is possible for the firewall to be
188 invoked multiple times on the same packet).
189 The packet passed to the firewall is compared
190 against each of the rules in the
193 (multiple rules with the same number are permitted, in which case
194 they are processed in order of insertion).
195 When a match is found, the action corresponding to the
196 matching rule is performed.
198 Depending on the action and certain system settings, packets
199 can be reinjected into the firewall at some rule after the
200 matching one for further processing.
202 A ruleset always includes a
204 rule (numbered 65535) which cannot be modified or deleted,
205 and matches all packets.
206 The action associated with the
212 depending on how the kernel is configured.
214 If the ruleset includes one or more rules with the
221 the firewall will have a
223 behaviour, i.e., upon a match it will create
225 i.e., rules that match packets with the same 5-tuple
226 (protocol, source and destination addresses and ports)
227 as the packet which caused their creation.
228 Dynamic rules, which have a limited lifetime, are checked
229 at the first occurrence of a
234 rule, and are typically used to open the firewall on-demand to
235 legitimate traffic only.
242 for all packets (not only these matched by the rule) but
249 .Sx STATEFUL FIREWALL
252 Sections below for more information on the stateful behaviour of
255 All rules (including dynamic ones) have a few associated counters:
256 a packet count, a byte count, a log count and a timestamp
257 indicating the time of the last match.
258 Counters can be displayed or reset with
262 Each rule belongs to one of 32 different
266 commands to atomically manipulate sets, such as enable,
267 disable, swap sets, move all rules in a set to another
268 one, delete all rules in a set.
269 These can be useful to
270 install temporary configurations, or to test them.
273 for more information on
276 Rules can be added with the
278 command; deleted individually or in groups with the
280 command, and globally (except those in set 31) with the
282 command; displayed, optionally with the content of the
288 Finally, counters can be reset with the
295 The following general options are available when invoking
297 .Bl -tag -width indent
299 Show counter values when listing rules.
302 command implies this option.
304 Only show the action and the comment, not the body of a rule.
308 When entering or showing rules, print them in compact form,
309 i.e., omitting the "ip from any to any" string
310 when this does not carry any additional information.
312 When listing, show dynamic rules in addition to static ones.
316 is specified, also show expired dynamic rules.
318 Do not ask for confirmation for commands that can cause problems
321 If there is no tty associated with the process, this is implied.
323 When listing a table (see the
325 section below for more information on lookup tables), format values
327 By default, values are shown as integers.
329 Only check syntax of the command strings, without actually passing
332 Try to resolve addresses and service names in output.
334 Be quiet when executing the
344 This is useful when updating rulesets by executing multiple
348 .Ql sh\ /etc/rc.firewall ) ,
349 or by processing a file with many
351 rules across a remote login session.
352 It also stops a table add or delete
353 from failing if the entry already exists or is not present.
355 The reason why this option may be important is that
356 for some of these actions,
358 may print a message; if the action results in blocking the
359 traffic to the remote client,
360 the remote login session will be closed
361 and the rest of the ruleset will not be processed.
362 Access to the console would then be required to recover.
364 When listing rules, show the
366 each rule belongs to.
367 If this flag is not specified, disabled rules will not be
370 When listing pipes, sort according to one of the four
371 counters (total or current packets or bytes).
373 When listing, show last match timestamp converted with ctime().
375 When listing, show last match timestamp as seconds from the epoch.
376 This form can be more convenient for postprocessing by scripts.
378 .Ss LIST OF RULES AND PREPROCESSING
379 To ease configuration, rules can be put into a file which is
382 as shown in the last synopsis line.
386 The file will be read line by line and applied as arguments to the
390 Optionally, a preprocessor can be specified using
394 is to be piped through.
395 Useful preprocessors include
401 does not start with a slash
403 as its first character, the usual
405 name search is performed.
406 Care should be taken with this in environments where not all
407 file systems are mounted (yet) by the time
409 is being run (e.g.\& when they are mounted over NFS).
412 has been specified, any additional arguments are passed on to the preprocessor
414 This allows for flexible configuration files (like conditionalizing
415 them on the local hostname) and the use of macros to centralize
416 frequently required arguments like IP addresses.
417 .Ss TRAFFIC SHAPER CONFIGURATION
423 commands are used to configure the traffic shaper and packet scheduler.
425 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
426 Section below for details.
428 If the world and the kernel get out of sync the
430 ABI may break, preventing you from being able to add any rules.
431 This can adversely affect the booting process.
436 to temporarily disable the firewall to regain access to the network,
437 allowing you to fix the problem.
439 A packet is checked against the active ruleset in multiple places
440 in the protocol stack, under control of several sysctl variables.
441 These places and variables are shown below, and it is important to
442 have this picture in mind in order to design a correct ruleset.
443 .Bd -literal -offset indent
446 +----------->-----------+
448 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1
451 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1
453 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1
459 times the same packet goes through the firewall can
460 vary between 0 and 4 depending on packet source and
461 destination, and system configuration.
463 Note that as packets flow through the stack, headers can be
464 stripped or added to it, and so they may or may not be available
466 E.g., incoming packets will include the MAC header when
470 but the same packets will have the MAC header stripped off when
477 Also note that each packet is always checked against the complete ruleset,
478 irrespective of the place where the check occurs, or the source of the packet.
479 If a rule contains some match patterns or actions which are not valid
480 for the place of invocation (e.g.\& trying to match a MAC header within
484 the match pattern will not match, but a
486 operator in front of such patterns
490 match on those packets.
491 It is thus the responsibility of
492 the programmer, if necessary, to write a suitable ruleset to
493 differentiate among the possible places.
495 rules can be useful here, as an example:
496 .Bd -literal -offset indent
497 # packets from ether_demux or bdg_forward
498 ipfw add 10 skipto 1000 all from any to any layer2 in
499 # packets from ip_input
500 ipfw add 10 skipto 2000 all from any to any not layer2 in
501 # packets from ip_output
502 ipfw add 10 skipto 3000 all from any to any not layer2 out
503 # packets from ether_output_frame
504 ipfw add 10 skipto 4000 all from any to any layer2 out
507 (yes, at the moment there is no way to differentiate between
508 ether_demux and bdg_forward).
510 In general, each keyword or argument must be provided as
511 a separate command line argument, with no leading or trailing
513 Keywords are case-sensitive, whereas arguments may
514 or may not be case-sensitive depending on their nature
515 (e.g.\& uid's are, hostnames are not).
517 Some arguments (e.g., port or address lists) are comma-separated
519 In this case, spaces after commas ',' are allowed to make
520 the line more readable.
521 You can also put the entire
522 command (including flags) into a single argument.
523 E.g., the following forms are equivalent:
524 .Bd -literal -offset indent
525 ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8
526 ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8
527 ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8"
530 The format of firewall rules is the following:
531 .Bd -ragged -offset indent
534 .Op Cm set Ar set_number
535 .Op Cm prob Ar match_probability
537 .Op Cm log Op Cm logamount Ar number
547 where the body of the rule specifies which information is used
548 for filtering packets, among the following:
550 .Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact
551 .It Layer-2 header fields
553 .It IPv4 and IPv6 Protocol
554 SCTP, TCP, UDP, ICMP, etc.
555 .It Source and dest. addresses and ports
559 .It Transmit and receive interface
561 .It Misc. IP header fields
562 Version, type of service, datagram length, identification,
563 fragment flag (non-zero IP offset),
566 .It IPv6 Extension headers
567 Fragmentation, Hop-by-Hop options,
568 Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options.
570 .It Misc. TCP header fields
571 TCP flags (SYN, FIN, ACK, RST, etc.),
572 sequence number, acknowledgment number,
580 When the packet can be associated with a local socket.
582 Whether a packet came from a divert socket (e.g.,
584 .It Fib annotation state
585 Whether a packet has been tagged for using a specific FIB (routing table)
586 in future forwarding decisions.
589 Note that some of the above information, e.g.\& source MAC or IP addresses and
590 TCP/UDP ports, can be easily spoofed, so filtering on those fields
591 alone might not guarantee the desired results.
592 .Bl -tag -width indent
594 Each rule is associated with a
596 in the range 1..65535, with the latter reserved for the
599 Rules are checked sequentially by rule number.
600 Multiple rules can have the same number, in which case they are
601 checked (and listed) according to the order in which they have
603 If a rule is entered without specifying a number, the kernel will
604 assign one in such a way that the rule becomes the last one
608 Automatic rule numbers are assigned by incrementing the last
609 non-default rule number by the value of the sysctl variable
610 .Ar net.inet.ip.fw.autoinc_step
611 which defaults to 100.
612 If this is not possible (e.g.\& because we would go beyond the
613 maximum allowed rule number), the number of the last
614 non-default value is used instead.
615 .It Cm set Ar set_number
616 Each rule is associated with a
619 Sets can be individually disabled and enabled, so this parameter
620 is of fundamental importance for atomic ruleset manipulation.
621 It can be also used to simplify deletion of groups of rules.
622 If a rule is entered without specifying a set number,
625 Set 31 is special in that it cannot be disabled,
626 and rules in set 31 are not deleted by the
628 command (but you can delete them with the
629 .Nm ipfw delete set 31
631 Set 31 is also used for the
634 .It Cm prob Ar match_probability
635 A match is only declared with the specified probability
636 (floating point number between 0 and 1).
637 This can be useful for a number of applications such as
638 random packet drop or
641 to simulate the effect of multiple paths leading to out-of-order
644 Note: this condition is checked before any other condition, including
651 .It Cm log Op Cm logamount Ar number
652 Packets matching a rule with the
654 keyword will be made available for logging in two ways:
655 if the sysctl variable
656 .Va net.inet.ip.fw.verbose
657 is set to 0 (default), one can use
662 This pseudo interface can be created after a boot
663 manually by using the following command:
664 .Bd -literal -offset indent
665 # ifconfig ipfw0 create
668 Or, automatically at boot time by adding the following
672 .Bd -literal -offset indent
676 There is no overhead if no
678 is attached to the pseudo interface.
681 .Va net.inet.ip.fw.verbose
682 is set to 1, packets will be logged to
686 facility up to a maximum of
691 is specified, the limit is taken from the sysctl variable
692 .Va net.inet.ip.fw.verbose_limit .
693 In both cases, a value of 0 means unlimited logging.
695 Once the limit is reached, logging can be re-enabled by
696 clearing the logging counter or the packet counter for that entry, see the
700 Note: logging is done after all other packet matching conditions
701 have been successfully verified, and before performing the final
702 action (accept, deny, etc.) on the packet.
704 When a packet matches a rule with the
706 keyword, the numeric tag for the given
708 in the range 1..65534 will be attached to the packet.
709 The tag acts as an internal marker (it is not sent out over
710 the wire) that can be used to identify these packets later on.
711 This can be used, for example, to provide trust between interfaces
712 and to start doing policy-based filtering.
713 A packet can have multiple tags at the same time.
714 Tags are "sticky", meaning once a tag is applied to a packet by a
715 matching rule it exists until explicit removal.
716 Tags are kept with the packet everywhere within the kernel, but are
717 lost when packet leaves the kernel, for example, on transmitting
718 packet out to the network or sending packet to a
722 To check for previously applied tags, use the
725 To delete previously applied tag, use the
729 Note: since tags are kept with the packet everywhere in kernelspace,
730 they can be set and unset anywhere in the kernel network subsystem
733 facility), not only by means of the
739 For example, there can be a specialized
741 node doing traffic analyzing and tagging for later inspecting
743 .It Cm untag Ar number
744 When a packet matches a rule with the
746 keyword, the tag with the number
748 is searched among the tags attached to this packet and,
749 if found, removed from it.
750 Other tags bound to packet, if present, are left untouched.
752 When a packet matches a rule with the
754 keyword, the ALTQ identifier for the given
759 Note that this ALTQ tag is only meaningful for packets going "out" of IPFW,
760 and not being rejected or going to divert sockets.
761 Note that if there is insufficient memory at the time the packet is
762 processed, it will not be tagged, so it is wise to make your ALTQ
763 "default" queue policy account for this.
766 rules match a single packet, only the first one adds the ALTQ classification
768 In doing so, traffic may be shaped by using
769 .Cm count Cm altq Ar queue
770 rules for classification early in the ruleset, then later applying
771 the filtering decision.
776 rules may come later and provide the actual filtering decisions in
777 addition to the fallback ALTQ tag.
781 to set up the queues before IPFW will be able to look them up by name,
782 and if the ALTQ disciplines are rearranged, the rules in containing the
783 queue identifiers in the kernel will likely have gone stale and need
785 Stale queue identifiers will probably result in misclassification.
787 All system ALTQ processing can be turned on or off via
792 .Cm disable Ar altq .
794 .Va net.inet.ip.fw.one_pass
795 is irrelevant to ALTQ traffic shaping, as the actual rule action is followed
796 always after adding an ALTQ tag.
799 A rule can be associated with one of the following actions, which
800 will be executed when the packet matches the body of the rule.
801 .Bl -tag -width indent
802 .It Cm allow | accept | pass | permit
803 Allow packets that match rule.
804 The search terminates.
805 .It Cm check-state Op Ar :flowname | Cm :any
806 Checks the packet against the dynamic ruleset.
807 If a match is found, execute the action associated with
808 the rule which generated this dynamic rule, otherwise
809 move to the next rule.
812 rules do not have a body.
815 rule is found, the dynamic ruleset is checked at the first
822 is symbolic name assigned to dynamic rule by
827 can be used to ignore states flowname when matching.
830 keyword is special name used for compatibility with old rulesets.
832 Update counters for all packets that match rule.
833 The search continues with the next rule.
835 Discard packets that match this rule.
836 The search terminates.
837 .It Cm divert Ar port
838 Divert packets that match this rule to the
842 The search terminates.
843 .It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port
844 Change the next-hop on matching packets to
846 which can be an IP address or a host name.
847 The next hop can also be supplied by the last table
848 looked up for the packet by using the
850 keyword instead of an explicit address.
851 The search terminates if this rule matches.
855 is a local address, then matching packets will be forwarded to
857 (or the port number in the packet if one is not specified in the rule)
858 on the local machine.
862 is not a local address, then the port number
863 (if specified) is ignored, and the packet will be
864 forwarded to the remote address, using the route as found in
865 the local routing table for that IP.
869 rule will not match layer-2 packets (those received
870 on ether_input, ether_output, or bridged).
874 action does not change the contents of the packet at all.
875 In particular, the destination address remains unmodified, so
876 packets forwarded to another system will usually be rejected by that system
877 unless there is a matching rule on that system to capture them.
878 For packets forwarded locally,
879 the local address of the socket will be
880 set to the original destination address of the packet.
883 entry look rather weird but is intended for
884 use with transparent proxy servers.
885 .It Cm nat Ar nat_nr | tablearg
888 (for network address translation, address redirect, etc.):
890 .Sx NETWORK ADDRESS TRANSLATION (NAT)
891 Section for further information.
892 .It Cm nat64lsn Ar name
893 Pass packet to a stateful NAT64 instance (for IPv6/IPv4 network address and
894 protocol translation): see the
895 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
896 Section for further information.
897 .It Cm nat64stl Ar name
898 Pass packet to a stateless NAT64 instance (for IPv6/IPv4 network address and
899 protocol translation): see the
900 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
901 Section for further information.
903 Pass packet to a NPTv6 instance (for IPv6-to-IPv6 network prefix translation):
905 .Sx IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6)
906 Section for further information.
907 .It Cm pipe Ar pipe_nr
911 (for bandwidth limitation, delay, etc.).
913 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
914 Section for further information.
915 The search terminates; however, on exit from the pipe and if
919 .Va net.inet.ip.fw.one_pass
920 is not set, the packet is passed again to the firewall code
921 starting from the next rule.
922 .It Cm queue Ar queue_nr
926 (for bandwidth limitation using WF2Q+).
932 Discard packets that match this rule, and if the
933 packet is a TCP packet, try to send a TCP reset (RST) notice.
934 The search terminates.
936 Discard packets that match this rule, and if the
937 packet is a TCP packet, try to send a TCP reset (RST) notice.
938 The search terminates.
939 .It Cm skipto Ar number | tablearg
940 Skip all subsequent rules numbered less than
942 The search continues with the first rule numbered
945 It is possible to use the
947 keyword with a skipto for a
949 skipto. Skipto may work either in O(log(N)) or in O(1) depending
950 on amount of memory and/or sysctl variables.
953 section for more details.
954 .It Cm call Ar number | tablearg
955 The current rule number is saved in the internal stack and
956 ruleset processing continues with the first rule numbered
959 If later a rule with the
961 action is encountered, the processing returns to the first rule
964 rule plus one or higher
965 (the same behaviour as with packets returning from
970 This could be used to make somewhat like an assembly language
972 calls to rules with common checks for different interfaces, etc.
974 Rule with any number could be called, not just forward jumps as with
976 So, to prevent endless loops in case of mistakes, both
980 actions don't do any jumps and simply go to the next rule if memory
981 cannot be allocated or stack overflowed/underflowed.
983 Internally stack for rule numbers is implemented using
985 facility and currently has size of 16 entries.
986 As mbuf tags are lost when packet leaves the kernel,
988 should not be used in subroutines to avoid endless loops
989 and other undesired effects.
991 Takes rule number saved to internal stack by the last
993 action and returns ruleset processing to the first rule
994 with number greater than number of corresponding
997 See description of the
999 action for more details.
1005 and thus are unconditional, but
1007 command-line utility currently requires every action except
1010 While it is sometimes useful to return only on some packets,
1011 usually you want to print just
1014 A workaround for this is to use new syntax and
1017 .Bd -literal -offset indent
1018 # Add a rule without actual body
1019 ipfw add 2999 return via any
1021 # List rules without "from any to any" part
1025 This cosmetic annoyance may be fixed in future releases.
1027 Send a copy of packets matching this rule to the
1029 socket bound to port
1031 The search continues with the next rule.
1032 .It Cm unreach Ar code
1033 Discard packets that match this rule, and try to send an ICMP
1034 unreachable notice with code
1038 is a number from 0 to 255, or one of these aliases:
1039 .Cm net , host , protocol , port ,
1040 .Cm needfrag , srcfail , net-unknown , host-unknown ,
1041 .Cm isolated , net-prohib , host-prohib , tosnet ,
1042 .Cm toshost , filter-prohib , host-precedence
1044 .Cm precedence-cutoff .
1045 The search terminates.
1046 .It Cm unreach6 Ar code
1047 Discard packets that match this rule, and try to send an ICMPv6
1048 unreachable notice with code
1052 is a number from 0, 1, 3 or 4, or one of these aliases:
1053 .Cm no-route, admin-prohib, address
1056 The search terminates.
1057 .It Cm netgraph Ar cookie
1058 Divert packet into netgraph with given
1060 The search terminates.
1061 If packet is later returned from netgraph it is either
1062 accepted or continues with the next rule, depending on
1063 .Va net.inet.ip.fw.one_pass
1065 .It Cm ngtee Ar cookie
1066 A copy of packet is diverted into netgraph, original
1067 packet continues with the next rule.
1070 for more information on
1075 .It Cm setfib Ar fibnum | tablearg
1076 The packet is tagged so as to use the FIB (routing table)
1078 in any subsequent forwarding decisions.
1079 In the current implementation, this is limited to the values 0 through 15, see
1081 Processing continues at the next rule.
1082 It is possible to use the
1084 keyword with setfib.
1085 If the tablearg value is not within the compiled range of fibs,
1086 the packet's fib is set to 0.
1087 .It Cm setdscp Ar DSCP | number | tablearg
1088 Set specified DiffServ codepoint for an IPv4/IPv6 packet.
1089 Processing continues at the next rule.
1090 Supported values are:
1136 Additionally, DSCP value can be specified by number (0..64).
1137 It is also possible to use the
1139 keyword with setdscp.
1140 If the tablearg value is not within the 0..64 range, lower 6 bits of supplied
1142 .It Cm tcp-setmss Ar mss
1143 Set the Maximum Segment Size (MSS) in the TCP segment to value
1147 should be loaded or kernel should have
1148 .Cm options IPFIREWALL_PMOD
1149 to be able use this action.
1150 This command does not change a packet if original MSS value is lower than
1152 Both TCP over IPv4 and over IPv6 are supported.
1153 Regardless of matched a packet or not by the
1155 rule, the search continues with the next rule.
1157 Queue and reassemble IPv4 fragments.
1158 If the packet is not fragmented, counters are updated and
1159 processing continues with the next rule.
1160 If the packet is the last logical fragment, the packet is reassembled and, if
1161 .Va net.inet.ip.fw.one_pass
1162 is set to 0, processing continues with the next rule.
1163 Otherwise, the packet is allowed to pass and the search terminates.
1164 If the packet is a fragment in the middle of a logical group of fragments,
1166 processing stops immediately.
1168 Fragment handling can be tuned via
1169 .Va net.inet.ip.maxfragpackets
1171 .Va net.inet.ip.maxfragsperpacket
1172 which limit, respectively, the maximum number of processable
1173 fragments (default: 800) and
1174 the maximum number of fragments per packet (default: 16).
1176 NOTA BENE: since fragments do not contain port numbers,
1177 they should be avoided with the
1180 Alternatively, direction-based (like
1184 ) and source-based (like
1186 ) match patterns can be used to select fragments.
1188 Usually a simple rule like:
1189 .Bd -literal -offset indent
1190 # reassemble incoming fragments
1191 ipfw add reass all from any to any in
1194 is all you need at the beginning of your ruleset.
1196 Discard packets that match this rule, and if the packet is an SCTP packet,
1197 try to send an SCTP packet containing an ABORT chunk.
1198 The search terminates.
1200 Discard packets that match this rule, and if the packet is an SCTP packet,
1201 try to send an SCTP packet containing an ABORT chunk.
1202 The search terminates.
1205 The body of a rule contains zero or more patterns (such as
1206 specific source and destination addresses or ports,
1207 protocol options, incoming or outgoing interfaces, etc.)
1208 that the packet must match in order to be recognised.
1209 In general, the patterns are connected by (implicit)
1211 operators -- i.e., all must match in order for the
1213 Individual patterns can be prefixed by the
1215 operator to reverse the result of the match, as in
1217 .Dl "ipfw add 100 allow ip from not 1.2.3.4 to any"
1219 Additionally, sets of alternative match patterns
1221 can be constructed by putting the patterns in
1222 lists enclosed between parentheses ( ) or braces { }, and
1225 operator as follows:
1227 .Dl "ipfw add 100 allow ip from { x or not y or z } to any"
1229 Only one level of parentheses is allowed.
1230 Beware that most shells have special meanings for parentheses
1231 or braces, so it is advisable to put a backslash \\ in front of them
1232 to prevent such interpretations.
1234 The body of a rule must in general include a source and destination
1238 can be used in various places to specify that the content of
1239 a required field is irrelevant.
1241 The rule body has the following format:
1242 .Bd -ragged -offset indent
1243 .Op Ar proto Cm from Ar src Cm to Ar dst
1247 The first part (proto from src to dst) is for backward
1248 compatibility with earlier versions of
1252 any match pattern (including MAC headers, IP protocols,
1253 addresses and ports) can be specified in the
1257 Rule fields have the following meaning:
1258 .Bl -tag -width indent
1259 .It Ar proto : protocol | Cm { Ar protocol Cm or ... }
1260 .It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number
1261 An IP protocol specified by number or name
1262 (for a complete list see
1263 .Pa /etc/protocols ) ,
1264 or one of the following keywords:
1265 .Bl -tag -width indent
1267 Matches IPv4 packets.
1269 Matches IPv6 packets.
1278 option will be treated as inner protocol.
1286 .Cm { Ar protocol Cm or ... }
1289 is provided for convenience only but its use is deprecated.
1290 .It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports
1291 An address (or a list, see below)
1292 optionally followed by
1298 with multiple addresses) is provided for convenience only and
1299 its use is discouraged.
1300 .It Ar addr : Oo Cm not Oc Bro
1301 .Cm any | me | me6 |
1302 .Cm table Ns Pq Ar name Ns Op , Ns Ar value
1303 .Ar | addr-list | addr-set
1305 .Bl -tag -width indent
1307 matches any IP address.
1309 matches any IP address configured on an interface in the system.
1311 matches any IPv6 address configured on an interface in the system.
1312 The address list is evaluated at the time the packet is
1314 .It Cm table Ns Pq Ar name Ns Op , Ns Ar value
1315 Matches any IPv4 or IPv6 address for which an entry exists in the lookup table
1317 If an optional 32-bit unsigned
1319 is also specified, an entry will match only if it has this value.
1322 section below for more information on lookup tables.
1324 .It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list
1326 A host or subnet address specified in one of the following ways:
1327 .Bl -tag -width indent
1328 .It Ar numeric-ip | hostname
1329 Matches a single IPv4 address, specified as dotted-quad or a hostname.
1330 Hostnames are resolved at the time the rule is added to the firewall list.
1331 .It Ar addr Ns / Ns Ar masklen
1332 Matches all addresses with base
1334 (specified as an IP address, a network number, or a hostname)
1338 As an example, 1.2.3.4/25 or 1.2.3.0/25 will match
1339 all IP numbers from 1.2.3.0 to 1.2.3.127 .
1340 .It Ar addr Ns : Ns Ar mask
1341 Matches all addresses with base
1343 (specified as an IP address, a network number, or a hostname)
1346 specified as a dotted quad.
1347 As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match
1349 This form is advised only for non-contiguous
1351 It is better to resort to the
1352 .Ar addr Ns / Ns Ar masklen
1353 format for contiguous masks, which is more compact and less
1356 .It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm }
1357 .It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list
1358 Matches all addresses with base address
1360 (specified as an IP address, a network number, or a hostname)
1361 and whose last byte is in the list between braces { } .
1362 Note that there must be no spaces between braces and
1363 numbers (spaces after commas are allowed).
1364 Elements of the list can be specified as single entries
1368 field is used to limit the size of the set of addresses,
1369 and can have any value between 24 and 32.
1371 it will be assumed as 24.
1373 This format is particularly useful to handle sparse address sets
1374 within a single rule.
1375 Because the matching occurs using a
1376 bitmask, it takes constant time and dramatically reduces
1377 the complexity of rulesets.
1379 As an example, an address specified as 1.2.3.4/24{128,35-55,89}
1380 or 1.2.3.0/24{128,35-55,89}
1381 will match the following IP addresses:
1383 1.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 .
1384 .It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list
1386 A host or subnet specified one of the following ways:
1387 .Bl -tag -width indent
1388 .It Ar numeric-ip | hostname
1389 Matches a single IPv6 address as allowed by
1392 Hostnames are resolved at the time the rule is added to the firewall
1394 .It Ar addr Ns / Ns Ar masklen
1395 Matches all IPv6 addresses with base
1397 (specified as allowed by
1403 .It Ar addr Ns / Ns Ar mask
1404 Matches all IPv6 addresses with base
1406 (specified as allowed by
1411 specified as allowed by
1413 As an example, fe::640:0:0/ffff::ffff:ffff:0:0 will match
1415 This form is advised only for non-contiguous
1417 It is better to resort to the
1418 .Ar addr Ns / Ns Ar masklen
1419 format for contiguous masks, which is more compact and less
1423 No support for sets of IPv6 addresses is provided because IPv6 addresses
1424 are typically random past the initial prefix.
1425 .It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports
1426 For protocols which support port numbers (such as SCTP, TCP and UDP), optional
1428 may be specified as one or more ports or port ranges, separated
1429 by commas but no spaces, and an optional
1434 notation specifies a range of ports (including boundaries).
1438 may be used instead of numeric port values.
1439 The length of the port list is limited to 30 ports or ranges,
1440 though one can specify larger ranges by using an
1444 section of the rule.
1448 can be used to escape the dash
1450 character in a service name (from a shell, the backslash must be
1451 typed twice to avoid the shell itself interpreting it as an escape
1454 .Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any"
1456 Fragmented packets which have a non-zero offset (i.e., not the first
1457 fragment) will never match a rule which has one or more port
1461 option for details on matching fragmented packets.
1463 .Ss RULE OPTIONS (MATCH PATTERNS)
1464 Additional match patterns can be used within
1466 Zero or more of these so-called
1468 can be present in a rule, optionally prefixed by the
1470 operand, and possibly grouped into
1473 The following match patterns can be used (listed in alphabetical order):
1474 .Bl -tag -width indent
1475 .It Cm // this is a comment.
1476 Inserts the specified text as a comment in the rule.
1477 Everything following // is considered as a comment and stored in the rule.
1478 You can have comment-only rules, which are listed as having a
1480 action followed by the comment.
1484 .It Cm defer-immediate-action | defer-action
1485 A rule with this option will not perform normal action
1486 upon a match. This option is intended to be used with
1490 as the dynamic rule, created but ignored on match, will work
1495 .Cm defer-immediate-action
1496 create a dynamic rule and continue with the next rule without actually
1497 performing the action part of this rule. When the rule is later activated
1498 via the state table, the action is performed as usual.
1500 Matches only packets generated by a divert socket.
1501 .It Cm diverted-loopback
1502 Matches only packets coming from a divert socket back into the IP stack
1504 .It Cm diverted-output
1505 Matches only packets going from a divert socket back outward to the IP
1506 stack output for delivery.
1507 .It Cm dst-ip Ar ip-address
1508 Matches IPv4 packets whose destination IP is one of the address(es)
1509 specified as argument.
1510 .It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address
1511 Matches IPv6 packets whose destination IP is one of the address(es)
1512 specified as argument.
1513 .It Cm dst-port Ar ports
1514 Matches IP packets whose destination port is one of the port(s)
1515 specified as argument.
1517 Matches TCP packets that have the RST or ACK bits set.
1518 .It Cm ext6hdr Ar header
1519 Matches IPv6 packets containing the extended header given by
1521 Supported headers are:
1527 any type of Routing Header
1529 Source routing Routing Header Type 0
1531 Mobile IPv6 Routing Header Type 2
1535 IPSec authentication headers
1537 and IPsec encapsulated security payload headers
1539 .It Cm fib Ar fibnum
1540 Matches a packet that has been tagged to use
1541 the given FIB (routing table) number.
1542 .It Cm flow Ar table Ns Pq Ar name Ns Op , Ns Ar value
1543 Search for the flow entry in lookup table
1545 If not found, the match fails.
1546 Otherwise, the match succeeds and
1548 is set to the value extracted from the table.
1550 This option can be useful to quickly dispatch traffic based on
1551 certain packet fields.
1554 section below for more information on lookup tables.
1555 .It Cm flow-id Ar labels
1556 Matches IPv6 packets containing any of the flow labels given in
1559 is a comma separated list of numeric flow labels.
1561 Matches packets that are fragments and not the first
1562 fragment of an IP datagram.
1563 Note that these packets will not have
1564 the next protocol header (e.g.\& TCP, UDP) so options that look into
1565 these headers cannot match.
1567 Matches all TCP or UDP packets sent by or received for a
1571 may be specified by name or number.
1573 Matches all TCP or UDP packets sent by or received for the
1574 jail whose ID or name is
1576 .It Cm icmptypes Ar types
1577 Matches ICMP packets whose ICMP type is in the list
1579 The list may be specified as any combination of
1580 individual types (numeric) separated by commas.
1581 .Em Ranges are not allowed .
1582 The supported ICMP types are:
1586 destination unreachable
1594 router advertisement
1598 time-to-live exceeded
1610 address mask request
1612 and address mask reply
1614 .It Cm icmp6types Ar types
1615 Matches ICMP6 packets whose ICMP6 type is in the list of
1617 The list may be specified as any combination of
1618 individual types (numeric) separated by commas.
1619 .Em Ranges are not allowed .
1621 Matches incoming or outgoing packets, respectively.
1625 are mutually exclusive (in fact,
1629 .It Cm ipid Ar id-list
1630 Matches IPv4 packets whose
1632 field has value included in
1634 which is either a single value or a list of values or ranges
1635 specified in the same way as
1637 .It Cm iplen Ar len-list
1638 Matches IP packets whose total length, including header and data, is
1641 which is either a single value or a list of values or ranges
1642 specified in the same way as
1644 .It Cm ipoptions Ar spec
1645 Matches packets whose IPv4 header contains the comma separated list of
1646 options specified in
1648 The supported IP options are:
1651 (strict source route),
1653 (loose source route),
1655 (record packet route) and
1658 The absence of a particular option may be denoted
1661 .It Cm ipprecedence Ar precedence
1662 Matches IPv4 packets whose precedence field is equal to
1665 Matches packets that have IPSEC history associated with them
1666 (i.e., the packet comes encapsulated in IPSEC, the kernel
1667 has IPSEC support, and can correctly decapsulate it).
1669 Note that specifying
1671 is different from specifying
1673 as the latter will only look at the specific IP protocol field,
1674 irrespective of IPSEC kernel support and the validity of the IPSEC data.
1676 Further note that this flag is silently ignored in kernels without
1678 It does not affect rule processing when given and the
1679 rules are handled as if with no
1682 .It Cm iptos Ar spec
1683 Matches IPv4 packets whose
1685 field contains the comma separated list of
1686 service types specified in
1688 The supported IP types of service are:
1691 .Pq Dv IPTOS_LOWDELAY ,
1693 .Pq Dv IPTOS_THROUGHPUT ,
1695 .Pq Dv IPTOS_RELIABILITY ,
1697 .Pq Dv IPTOS_MINCOST ,
1699 .Pq Dv IPTOS_ECN_CE .
1700 The absence of a particular type may be denoted
1703 .It Cm dscp spec Ns Op , Ns Ar spec
1704 Matches IPv4/IPv6 packets whose
1706 field value is contained in
1709 Multiple values can be specified via
1710 the comma separated list.
1711 Value can be one of keywords used in
1713 action or exact number.
1714 .It Cm ipttl Ar ttl-list
1715 Matches IPv4 packets whose time to live is included in
1717 which is either a single value or a list of values or ranges
1718 specified in the same way as
1720 .It Cm ipversion Ar ver
1721 Matches IP packets whose IP version field is
1723 .It Cm keep-state Op Ar :flowname
1724 Upon a match, the firewall will create a dynamic rule, whose
1725 default behaviour is to match bidirectional traffic between
1726 source and destination IP/port using the same protocol.
1727 The rule has a limited lifetime (controlled by a set of
1729 variables), and the lifetime is refreshed every time a matching
1733 is used to assign additional to addresses, ports and protocol parameter
1734 to dynamic rule. It can be used for more accurate matching by
1739 keyword is special name used for compatibility with old rulesets.
1741 Matches only layer2 packets, i.e., those passed to
1743 from ether_demux() and ether_output_frame().
1744 .It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N Op Ar :flowname
1745 The firewall will only allow
1747 connections with the same
1748 set of parameters as specified in the rule.
1750 of source and destination addresses and ports can be
1752 .It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar name
1753 Search an entry in lookup table
1755 that matches the field specified as argument.
1756 If not found, the match fails.
1757 Otherwise, the match succeeds and
1759 is set to the value extracted from the table.
1761 This option can be useful to quickly dispatch traffic based on
1762 certain packet fields.
1765 section below for more information on lookup tables.
1766 .It Cm { MAC | mac } Ar dst-mac src-mac
1767 Match packets with a given
1771 addresses, specified as the
1773 keyword (matching any MAC address), or six groups of hex digits
1774 separated by colons,
1775 and optionally followed by a mask indicating the significant bits.
1776 The mask may be specified using either of the following methods:
1777 .Bl -enum -width indent
1781 followed by the number of significant bits.
1782 For example, an address with 33 significant bits could be specified as:
1784 .Dl "MAC 10:20:30:40:50:60/33 any"
1788 followed by a bitmask specified as six groups of hex digits separated
1790 For example, an address in which the last 16 bits are significant could
1793 .Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any"
1795 Note that the ampersand character has a special meaning in many shells
1796 and should generally be escaped.
1798 Note that the order of MAC addresses (destination first,
1800 the same as on the wire, but the opposite of the one used for
1802 .It Cm mac-type Ar mac-type
1803 Matches packets whose Ethernet Type field
1804 corresponds to one of those specified as argument.
1806 is specified in the same way as
1808 (i.e., one or more comma-separated single values or ranges).
1809 You can use symbolic names for known values such as
1810 .Em vlan , ipv4, ipv6 .
1811 Values can be entered as decimal or hexadecimal (if prefixed by 0x),
1812 and they are always printed as hexadecimal (unless the
1814 option is used, in which case symbolic resolution will be attempted).
1815 .It Cm proto Ar protocol
1816 Matches packets with the corresponding IP protocol.
1818 Upon a match, the firewall will create a dynamic rule as if
1821 However, this option doesn't imply an implicit
1825 .It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar table Ns Po Ar name Ns Oo , Ns Ar value Oc Pc | Ar ipno | Ar any
1826 Matches packets received, transmitted or going through,
1827 respectively, the interface specified by exact name
1831 by IP address, or through some interface.
1834 may be used to match interface by its kernel ifindex.
1837 section below for more information on lookup tables.
1841 keyword causes the interface to always be checked.
1848 then only the receive or transmit interface (respectively)
1850 By specifying both, it is possible to match packets based on
1851 both receive and transmit interface, e.g.:
1853 .Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1"
1857 interface can be tested on either incoming or outgoing packets,
1860 interface can only be tested on outgoing packets.
1865 is invalid) whenever
1869 A packet might not have a receive or transmit interface: packets
1870 originating from the local host have no receive interface,
1871 while packets destined for the local host have no transmit
1873 .It Cm set-limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N
1876 but does not have an implicit
1880 Matches TCP packets that have the SYN bit set but no ACK bit.
1881 This is the short form of
1882 .Dq Li tcpflags\ syn,!ack .
1884 Matches packets that are associated to a local socket and
1885 for which the SO_USER_COOKIE socket option has been set
1886 to a non-zero value.
1887 As a side effect, the value of the
1888 option is made available as
1890 value, which in turn can be used as
1895 .It Cm src-ip Ar ip-address
1896 Matches IPv4 packets whose source IP is one of the address(es)
1897 specified as an argument.
1898 .It Cm src-ip6 Ar ip6-address
1899 Matches IPv6 packets whose source IP is one of the address(es)
1900 specified as an argument.
1901 .It Cm src-port Ar ports
1902 Matches IP packets whose source port is one of the port(s)
1903 specified as argument.
1904 .It Cm tagged Ar tag-list
1905 Matches packets whose tags are included in
1907 which is either a single value or a list of values or ranges
1908 specified in the same way as
1910 Tags can be applied to the packet using
1912 rule action parameter (see it's description for details on tags).
1913 .It Cm tcpack Ar ack
1915 Match if the TCP header acknowledgment number field is set to
1917 .It Cm tcpdatalen Ar tcpdatalen-list
1918 Matches TCP packets whose length of TCP data is
1919 .Ar tcpdatalen-list ,
1920 which is either a single value or a list of values or ranges
1921 specified in the same way as
1923 .It Cm tcpflags Ar spec
1925 Match if the TCP header contains the comma separated list of
1928 The supported TCP flags are:
1937 The absence of a particular flag may be denoted
1940 A rule which contains a
1942 specification can never match a fragmented packet which has
1946 option for details on matching fragmented packets.
1947 .It Cm tcpseq Ar seq
1949 Match if the TCP header sequence number field is set to
1951 .It Cm tcpwin Ar tcpwin-list
1952 Matches TCP packets whose header window field is set to
1954 which is either a single value or a list of values or ranges
1955 specified in the same way as
1957 .It Cm tcpoptions Ar spec
1959 Match if the TCP header contains the comma separated list of
1960 options specified in
1962 The supported TCP options are:
1965 (maximum segment size),
1967 (tcp window advertisement),
1971 (rfc1323 timestamp) and
1973 (rfc1644 t/tcp connection count).
1974 The absence of a particular option may be denoted
1978 Match all TCP or UDP packets sent by or received for a
1982 may be matched by name or identification number.
1984 For incoming packets,
1985 a routing table lookup is done on the packet's source address.
1986 If the interface on which the packet entered the system matches the
1987 outgoing interface for the route,
1989 If the interfaces do not match up,
1990 the packet does not match.
1991 All outgoing packets or packets with no incoming interface match.
1993 The name and functionality of the option is intentionally similar to
1994 the Cisco IOS command:
1996 .Dl ip verify unicast reverse-path
1998 This option can be used to make anti-spoofing rules to reject all
1999 packets with source addresses not from this interface.
2003 For incoming packets,
2004 a routing table lookup is done on the packet's source address.
2005 If a route to the source address exists, but not the default route
2006 or a blackhole/reject route, the packet matches.
2007 Otherwise, the packet does not match.
2008 All outgoing packets match.
2010 The name and functionality of the option is intentionally similar to
2011 the Cisco IOS command:
2013 .Dl ip verify unicast source reachable-via any
2015 This option can be used to make anti-spoofing rules to reject all
2016 packets whose source address is unreachable.
2018 For incoming packets, the packet's source address is checked if it
2019 belongs to a directly connected network.
2020 If the network is directly connected, then the interface the packet
2021 came on in is compared to the interface the network is connected to.
2022 When incoming interface and directly connected interface are not the
2023 same, the packet does not match.
2024 Otherwise, the packet does match.
2025 All outgoing packets match.
2027 This option can be used to make anti-spoofing rules to reject all
2028 packets that pretend to be from a directly connected network but do
2029 not come in through that interface.
2030 This option is similar to but more restricted than
2032 because it engages only on packets with source addresses of directly
2033 connected networks instead of all source addresses.
2036 Lookup tables are useful to handle large sparse sets of
2037 addresses or other search keys (e.g., ports, jail IDs, interface names).
2038 In the rest of this section we will use the term ``key''.
2039 Table name needs to match the following spec:
2041 Tables with the same name can be created in different
2043 However, rule links to the tables in
2046 This behavior can be controlled by
2047 .Va net.inet.ip.fw.tables_sets
2051 section for more information.
2052 There may be up to 65535 different lookup tables.
2054 The following table types are supported:
2055 .Bl -tag -width indent
2056 .It Ar table-type : Ar addr | iface | number | flow
2057 .It Ar table-key : Ar addr Ns Oo / Ns Ar masklen Oc | iface-name | number | flow-spec
2058 .It Ar flow-spec : Ar flow-field Ns Op , Ns Ar flow-spec
2059 .It Ar flow-field : src-ip | proto | src-port | dst-ip | dst-port
2061 matches IPv4 or IPv6 address.
2062 Each entry is represented by an
2063 .Ar addr Ns Op / Ns Ar masklen
2064 and will match all addresses with base
2066 (specified as an IPv4/IPv6 address, or a hostname) and mask width of
2071 is not specified, it defaults to 32 for IPv4 and 128 for IPv6.
2072 When looking up an IP address in a table, the most specific
2075 matches interface names.
2076 Each entry is represented by string treated as interface name.
2077 Wildcards are not supported.
2079 maches protocol ports, uids/gids or jail IDs.
2080 Each entry is represented by 32-bit unsigned integer.
2081 Ranges are not supported.
2083 Matches packet fields specified by
2085 type suboptions with table entries.
2088 Tables require explicit creation via
2092 The following creation options are supported:
2093 .Bl -tag -width indent
2094 .It Ar create-options : Ar create-option | create-options
2095 .It Ar create-option : Cm type Ar table-type | Cm valtype Ar value-mask | Cm algo Ar algo-desc |
2096 .Cm limit Ar number | Cm locked
2102 Table algorithm to use (see below).
2104 Maximum number of items that may be inserted into table.
2106 Restrict any table modifications.
2109 Some of these options may be modified later via
2112 The following options can be changed:
2113 .Bl -tag -width indent
2114 .It Ar modify-options : Ar modify-option | modify-options
2115 .It Ar modify-option : Cm limit Ar number
2117 Alter maximum number of items that may be inserted into table.
2120 Additionally, table can be locked or unlocked using
2128 can be swapped with each other using
2131 Swap may fail if tables limits are set and data exchange
2132 would result in limits hit.
2133 Operation is performed atomically.
2135 One or more entries can be added to a table at once using
2138 Addition of all items are performed atomically.
2139 By default, error in addition of one entry does not influence
2140 addition of other entries. However, non-zero error code is returned
2144 keyword may be specified before
2146 to indicate all-or-none add request.
2148 One or more entries can be removed from a table at once using
2151 By default, error in removal of one entry does not influence
2152 removing of other entries. However, non-zero error code is returned
2155 It may be possible to check what entry will be found on particular
2161 This functionality is optional and may be unsupported in some algorithms.
2163 The following operations can be performed on
2168 .Bl -tag -width indent
2172 Removes all entries.
2174 Shows generic table information.
2176 Shows generic table information and algo-specific data.
2179 The following lookup algorithms are supported:
2180 .Bl -tag -width indent
2181 .It Ar algo-desc : algo-name | "algo-name algo-data"
2182 .It Ar algo-name: Ar addr:radix | addr:hash | iface:array | number:array | flow:hash
2184 Separate Radix trees for IPv4 and IPv6, the same way as the routing table (see
2190 Separate auto-growing hashes for IPv4 and IPv6.
2191 Accepts entries with the same mask length specified initially via
2192 .Cm "addr:hash masks=/v4,/v6"
2193 algorithm creation options.
2194 Assume /32 and /128 masks by default.
2195 Search removes host bits (according to mask) from supplied address and checks
2196 resulting key in appropriate hash.
2197 Mostly optimized for /64 and byte-ranged IPv6 masks.
2199 Array storing sorted indexes for entries which are presented in the system.
2200 Optimized for very fast lookup.
2202 Array storing sorted u32 numbers.
2204 Auto-growing hash storing flow entries.
2205 Search calculates hash on required packet fields and searches for matching
2206 entries in selected bucket.
2211 feature provides the ability to use a value, looked up in the table, as
2212 the argument for a rule action, action parameter or rule option.
2213 This can significantly reduce number of rules in some configurations.
2214 If two tables are used in a rule, the result of the second (destination)
2217 Each record may hold one or more values according to
2219 This mask is set on table creation via
2222 The following value types are supported:
2223 .Bl -tag -width indent
2224 .It Ar value-mask : Ar value-type Ns Op , Ns Ar value-mask
2225 .It Ar value-type : Ar skipto | pipe | fib | nat | dscp | tag | divert |
2226 .Ar netgraph | limit | ipv4
2228 rule number to jump to.
2232 fib number to match/set.
2234 nat number to jump to.
2236 dscp value to match/set.
2238 tag number to match/set.
2240 port number to divert traffic to.
2242 hook number to move packet to.
2244 maximum number of connections.
2246 IPv4 nexthop to fwd packets to.
2248 IPv6 nexthop to fwd packets to.
2253 argument can be used with the following actions:
2254 .Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto, setfib,
2262 action, the user should be aware that the code will walk the ruleset
2263 up to a rule equal to, or past, the given number.
2267 Section for example usage of tables and the tablearg keyword.
2269 Each rule or table belongs to one of 32 different
2272 Set 31 is reserved for the default rule.
2274 By default, rules or tables are put in set 0, unless you use the
2276 attribute when adding a new rule or table.
2277 Sets can be individually and atomically enabled or disabled,
2278 so this mechanism permits an easy way to store multiple configurations
2279 of the firewall and quickly (and atomically) switch between them.
2281 By default, tables from set 0 are referenced when adding rule with
2282 table opcodes regardless of rule set.
2283 This behavior can be changed by setting
2284 .Va net.inet.ip.fw.tables_sets
2286 Rule's set will then be used for table references.
2288 The command to enable/disable sets is
2289 .Bd -ragged -offset indent
2291 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
2298 sections can be specified.
2299 Command execution is atomic on all the sets specified in the command.
2300 By default, all sets are enabled.
2302 When you disable a set, its rules behave as if they do not exist
2303 in the firewall configuration, with only one exception:
2304 .Bd -ragged -offset indent
2305 dynamic rules created from a rule before it had been disabled
2306 will still be active until they expire.
2308 dynamic rules you have to explicitly delete the parent rule
2309 which generated them.
2312 The set number of rules can be changed with the command
2313 .Bd -ragged -offset indent
2316 .Brq Cm rule Ar rule-number | old-set
2320 Also, you can atomically swap two rulesets with the command
2321 .Bd -ragged -offset indent
2323 .Cm set swap Ar first-set second-set
2328 Section on some possible uses of sets of rules.
2329 .Sh STATEFUL FIREWALL
2330 Stateful operation is a way for the firewall to dynamically
2331 create rules for specific flows when packets that
2332 match a given pattern are detected.
2333 Support for stateful
2334 operation comes through the
2335 .Cm check-state , keep-state , record-state , limit
2341 Dynamic rules are created when a packet matches a
2347 rule, causing the creation of a
2349 rule which will match all and only packets with
2353 .Em src-ip/src-port dst-ip/dst-port
2358 are used here only to denote the initial match addresses, but they
2359 are completely equivalent afterwards).
2365 This name is used in matching together with addresses, ports and protocol.
2366 Dynamic rules will be checked at the first
2367 .Cm check-state, keep-state
2370 occurrence, and the action performed upon a match will be the same
2371 as in the parent rule.
2373 Note that no additional attributes other than protocol and IP addresses
2374 and ports and :flowname are checked on dynamic rules.
2376 The typical use of dynamic rules is to keep a closed firewall configuration,
2377 but let the first TCP SYN packet from the inside network install a
2378 dynamic rule for the flow so that packets belonging to that session
2379 will be allowed through the firewall:
2381 .Dl "ipfw add check-state :OUTBOUND"
2382 .Dl "ipfw add allow tcp from my-subnet to any setup keep-state :OUTBOUND"
2383 .Dl "ipfw add deny tcp from any to any"
2385 A similar approach can be used for UDP, where an UDP packet coming
2386 from the inside will install a dynamic rule to let the response through
2389 .Dl "ipfw add check-state :OUTBOUND"
2390 .Dl "ipfw add allow udp from my-subnet to any keep-state :OUTBOUND"
2391 .Dl "ipfw add deny udp from any to any"
2393 Dynamic rules expire after some time, which depends on the status
2394 of the flow and the setting of some
2398 .Sx SYSCTL VARIABLES
2400 For TCP sessions, dynamic rules can be instructed to periodically
2401 send keepalive packets to refresh the state of the rule when it is
2406 for more examples on how to use dynamic rules.
2407 .Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
2409 is also the user interface for the
2411 traffic shaper, packet scheduler and network emulator, a subsystem that
2412 can artificially queue, delay or drop packets
2413 emulating the behaviour of certain network links
2414 or queueing systems.
2417 operates by first using the firewall to select packets
2418 using any match pattern that can be used in
2421 Matching packets are then passed to either of two
2422 different objects, which implement the traffic regulation:
2423 .Bl -hang -offset XXXX
2429 with given bandwidth and propagation delay,
2430 driven by a FIFO scheduler and a single queue with programmable
2431 queue size and packet loss rate.
2432 Packets are appended to the queue as they come out from
2434 and then transferred in FIFO order to the link at the desired rate.
2438 is an abstraction used to implement packet scheduling
2439 using one of several packet scheduling algorithms.
2442 are first grouped into flows according to a mask on the 5-tuple.
2443 Flows are then passed to the scheduler associated to the
2445 and each flow uses scheduling parameters (weight and others)
2446 as configured in the
2449 A scheduler in turn is connected to an emulated link,
2450 and arbitrates the link's bandwidth among backlogged flows according to
2451 weights and to the features of the scheduling algorithm in use.
2456 can be used to set hard limits to the bandwidth that a flow can use, whereas
2458 can be used to determine how different flows share the available bandwidth.
2460 A graphical representation of the binding of queues,
2461 flows, schedulers and links is below.
2462 .Bd -literal -offset indent
2463 (flow_mask|sched_mask) sched_mask
2464 +---------+ weight Wx +-------------+
2465 | |->-[flow]-->--| |-+
2466 -->--| QUEUE x | ... | | |
2467 | |->-[flow]-->--| SCHEDuler N | |
2469 ... | +--[LINK N]-->--
2470 +---------+ weight Wy | | +--[LINK N]-->--
2471 | |->-[flow]-->--| | |
2472 -->--| QUEUE y | ... | | |
2473 | |->-[flow]-->--| | |
2474 +---------+ +-------------+ |
2477 It is important to understand the role of the SCHED_MASK
2478 and FLOW_MASK, which are configured through the commands
2479 .Dl "ipfw sched N config mask SCHED_MASK ..."
2481 .Dl "ipfw queue X config mask FLOW_MASK ..." .
2483 The SCHED_MASK is used to assign flows to one or more
2484 scheduler instances, one for each
2485 value of the packet's 5-tuple after applying SCHED_MASK.
2486 As an example, using ``src-ip 0xffffff00'' creates one instance
2487 for each /24 destination subnet.
2489 The FLOW_MASK, together with the SCHED_MASK, is used to split
2491 As an example, using
2492 ``src-ip 0x000000ff''
2493 together with the previous SCHED_MASK makes a flow for
2494 each individual source address.
2495 In turn, flows for each /24
2496 subnet will be sent to the same scheduler instance.
2498 The above diagram holds even for the
2500 case, with the only restriction that a
2502 only supports a SCHED_MASK, and forces the use of a FIFO
2503 scheduler (these are for backward compatibility reasons;
2504 in fact, internally, a
2506 pipe is implemented exactly as above).
2508 There are two modes of
2516 mode tries to emulate a real link: the
2518 scheduler ensures that the packet will not leave the pipe faster than it
2519 would on the real link with a given bandwidth.
2522 mode allows certain packets to bypass the
2524 scheduler (if packet flow does not exceed pipe's bandwidth).
2525 This is the reason why the
2527 mode requires less CPU cycles per packet (on average) and packet latency
2528 can be significantly lower in comparison to a real link with the same
2534 mode can be enabled by setting the
2535 .Va net.inet.ip.dummynet.io_fast
2537 variable to a non-zero value.
2539 .Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION
2545 configuration commands are the following:
2546 .Bd -ragged -offset indent
2547 .Cm pipe Ar number Cm config Ar pipe-configuration
2549 .Cm queue Ar number Cm config Ar queue-configuration
2551 .Cm sched Ar number Cm config Ar sched-configuration
2554 The following parameters can be configured for a pipe:
2556 .Bl -tag -width indent -compact
2557 .It Cm bw Ar bandwidth | device
2558 Bandwidth, measured in
2561 .Brq Cm bit/s | Byte/s .
2564 A value of 0 (default) means unlimited bandwidth.
2565 The unit must immediately follow the number, as in
2567 .Dl "ipfw pipe 1 config bw 300Kbit/s"
2569 If a device name is specified instead of a numeric value, as in
2571 .Dl "ipfw pipe 1 config bw tun0"
2573 then the transmit clock is supplied by the specified device.
2574 At the moment only the
2576 device supports this
2577 functionality, for use in conjunction with
2580 .It Cm delay Ar ms-delay
2581 Propagation delay, measured in milliseconds.
2582 The value is rounded to the next multiple of the clock tick
2583 (typically 10ms, but it is a good practice to run kernels
2585 .Dq "options HZ=1000"
2587 the granularity to 1ms or less).
2588 The default value is 0, meaning no delay.
2590 .It Cm burst Ar size
2591 If the data to be sent exceeds the pipe's bandwidth limit
2592 (and the pipe was previously idle), up to
2594 bytes of data are allowed to bypass the
2596 scheduler, and will be sent as fast as the physical link allows.
2597 Any additional data will be transmitted at the rate specified
2601 The burst size depends on how long the pipe has been idle;
2602 the effective burst size is calculated as follows:
2609 .It Cm profile Ar filename
2610 A file specifying the additional overhead incurred in the transmission
2611 of a packet on the link.
2613 Some link types introduce extra delays in the transmission
2614 of a packet, e.g., because of MAC level framing, contention on
2615 the use of the channel, MAC level retransmissions and so on.
2616 From our point of view, the channel is effectively unavailable
2617 for this extra time, which is constant or variable depending
2619 Additionally, packets may be dropped after this
2620 time (e.g., on a wireless link after too many retransmissions).
2621 We can model the additional delay with an empirical curve
2622 that represents its distribution.
2623 .Bd -literal -offset indent
2624 cumulative probability
2634 +-------*------------------->
2637 The empirical curve may have both vertical and horizontal lines.
2638 Vertical lines represent constant delay for a range of
2640 Horizontal lines correspond to a discontinuity in the delay
2641 distribution: the pipe will use the largest delay for a
2644 The file format is the following, with whitespace acting as
2645 a separator and '#' indicating the beginning a comment:
2646 .Bl -tag -width indent
2647 .It Cm name Ar identifier
2648 optional name (listed by "ipfw pipe show")
2649 to identify the delay distribution;
2651 the bandwidth used for the pipe.
2652 If not specified here, it must be present
2653 explicitly as a configuration parameter for the pipe;
2654 .It Cm loss-level Ar L
2655 the probability above which packets are lost.
2656 (0.0 <= L <= 1.0, default 1.0 i.e., no loss);
2658 the number of samples used in the internal
2659 representation of the curve (2..1024; default 100);
2660 .It Cm "delay prob" | "prob delay"
2661 One of these two lines is mandatory and defines
2662 the format of the following lines with data points.
2664 2 or more lines representing points in the curve,
2665 with either delay or probability first, according
2666 to the chosen format.
2667 The unit for delay is milliseconds.
2668 Data points do not need to be sorted.
2669 Also, the number of actual lines can be different
2670 from the value of the "samples" parameter:
2672 utility will sort and interpolate
2673 the curve as needed.
2676 Example of a profile file:
2677 .Bd -literal -offset indent
2682 0 200 # minimum overhead is 200ms
2688 #configuration file end
2692 The following parameters can be configured for a queue:
2694 .Bl -tag -width indent -compact
2695 .It Cm pipe Ar pipe_nr
2696 Connects a queue to the specified pipe.
2697 Multiple queues (with the same or different weights) can be connected to
2698 the same pipe, which specifies the aggregate rate for the set of queues.
2700 .It Cm weight Ar weight
2701 Specifies the weight to be used for flows matching this queue.
2702 The weight must be in the range 1..100, and defaults to 1.
2705 The following case-insensitive parameters can be configured for a
2708 .Bl -tag -width indent -compact
2709 .It Cm type Ar {fifo | wf2q+ | rr | qfq}
2710 specifies the scheduling algorithm to use.
2711 .Bl -tag -width indent -compact
2713 is just a FIFO scheduler (which means that all packets
2714 are stored in the same queue as they arrive to the scheduler).
2715 FIFO has O(1) per-packet time complexity, with very low
2716 constants (estimate 60-80ns on a 2GHz desktop machine)
2717 but gives no service guarantees.
2719 implements the WF2Q+ algorithm, which is a Weighted Fair Queueing
2720 algorithm which permits flows to share bandwidth according to
2722 Note that weights are not priorities; even a flow
2723 with a minuscule weight will never starve.
2724 WF2Q+ has O(log N) per-packet processing cost, where N is the number
2725 of flows, and is the default algorithm used by previous versions
2728 implements the Deficit Round Robin algorithm, which has O(1) processing
2729 costs (roughly, 100-150ns per packet)
2730 and permits bandwidth allocation according to weights, but
2731 with poor service guarantees.
2733 implements the QFQ algorithm, which is a very fast variant of
2734 WF2Q+, with similar service guarantees and O(1) processing
2735 costs (roughly, 200-250ns per packet).
2739 In addition to the type, all parameters allowed for a pipe can also
2740 be specified for a scheduler.
2742 Finally, the following parameters can be configured for both
2745 .Bl -tag -width XXXX -compact
2746 .It Cm buckets Ar hash-table-size
2747 Specifies the size of the hash table used for storing the
2749 Default value is 64 controlled by the
2752 .Va net.inet.ip.dummynet.hash_size ,
2753 allowed range is 16 to 65536.
2755 .It Cm mask Ar mask-specifier
2756 Packets sent to a given pipe or queue by an
2758 rule can be further classified into multiple flows, each of which is then
2762 A flow identifier is constructed by masking the IP addresses,
2763 ports and protocol types as specified with the
2765 options in the configuration of the pipe or queue.
2766 For each different flow identifier, a new pipe or queue is created
2767 with the same parameters as the original object, and matching packets
2772 are used, each flow will get the same bandwidth as defined by the pipe,
2775 are used, each flow will share the parent's pipe bandwidth evenly
2776 with other flows generated by the same queue (note that other queues
2777 with different weights might be connected to the same pipe).
2779 Available mask specifiers are a combination of one or more of the following:
2781 .Cm dst-ip Ar mask ,
2782 .Cm dst-ip6 Ar mask ,
2783 .Cm src-ip Ar mask ,
2784 .Cm src-ip6 Ar mask ,
2785 .Cm dst-port Ar mask ,
2786 .Cm src-port Ar mask ,
2787 .Cm flow-id Ar mask ,
2792 where the latter means all bits in all fields are significant.
2795 When a packet is dropped by a
2797 queue or pipe, the error
2798 is normally reported to the caller routine in the kernel, in the
2799 same way as it happens when a device queue fills up.
2801 option reports the packet as successfully delivered, which can be
2802 needed for some experimental setups where you want to simulate
2803 loss or congestion at a remote router.
2805 .It Cm plr Ar packet-loss-rate
2808 .Ar packet-loss-rate
2809 is a floating-point number between 0 and 1, with 0 meaning no
2810 loss, 1 meaning 100% loss.
2811 The loss rate is internally represented on 31 bits.
2813 .It Cm queue Brq Ar slots | size Ns Cm Kbytes
2818 Default value is 50 slots, which
2819 is the typical queue size for Ethernet devices.
2820 Note that for slow speed links you should keep the queue
2821 size short or your traffic might be affected by a significant
2823 E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit
2824 or 20s of queue on a 30Kbit/s pipe.
2825 Even worse effects can result if you get packets from an
2826 interface with a much larger MTU, e.g.\& the loopback interface
2827 with its 16KB packets.
2831 .Em net.inet.ip.dummynet.pipe_byte_limit
2833 .Em net.inet.ip.dummynet.pipe_slot_limit
2834 control the maximum lengths that can be specified.
2836 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
2838 Make use of the RED (Random Early Detection) queue management algorithm.
2843 point numbers between 0 and 1 (inclusive), while
2847 are integer numbers specifying thresholds for queue management
2848 (thresholds are computed in bytes if the queue has been defined
2849 in bytes, in slots otherwise).
2850 The two parameters can also be of the same value if needed. The
2852 also supports the gentle RED variant (gred) and ECN (Explicit Congestion
2853 Notification) as optional. Three
2855 variables can be used to control the RED behaviour:
2856 .Bl -tag -width indent
2857 .It Va net.inet.ip.dummynet.red_lookup_depth
2858 specifies the accuracy in computing the average queue
2859 when the link is idle (defaults to 256, must be greater than zero)
2860 .It Va net.inet.ip.dummynet.red_avg_pkt_size
2861 specifies the expected average packet size (defaults to 512, must be
2863 .It Va net.inet.ip.dummynet.red_max_pkt_size
2864 specifies the expected maximum packet size, only used when queue
2865 thresholds are in bytes (defaults to 1500, must be greater than zero).
2869 When used with IPv6 data,
2871 currently has several limitations.
2872 Information necessary to route link-local packets to an
2873 interface is not available after processing by
2875 so those packets are dropped in the output path.
2876 Care should be taken to ensure that link-local packets are not passed to
2879 Here are some important points to consider when designing your
2883 Remember that you filter both packets going
2887 Most connections need packets going in both directions.
2889 Remember to test very carefully.
2890 It is a good idea to be near the console when doing this.
2891 If you cannot be near the console,
2892 use an auto-recovery script such as the one in
2893 .Pa /usr/share/examples/ipfw/change_rules.sh .
2895 Do not forget the loopback interface.
2900 There are circumstances where fragmented datagrams are unconditionally
2902 TCP packets are dropped if they do not contain at least 20 bytes of
2903 TCP header, UDP packets are dropped if they do not contain a full 8
2904 byte UDP header, and ICMP packets are dropped if they do not contain
2905 4 bytes of ICMP header, enough to specify the ICMP type, code, and
2907 These packets are simply logged as
2909 since there may not be enough good data in the packet to produce a
2910 meaningful log entry.
2912 Another type of packet is unconditionally dropped, a TCP packet with a
2913 fragment offset of one.
2914 This is a valid packet, but it only has one use, to try
2915 to circumvent firewalls.
2916 When logging is enabled, these packets are
2917 reported as being dropped by rule -1.
2919 If you are logged in over a network, loading the
2923 is probably not as straightforward as you would think.
2924 The following command line is recommended:
2925 .Bd -literal -offset indent
2927 ipfw add 32000 allow ip from any to any
2930 Along the same lines, doing an
2931 .Bd -literal -offset indent
2935 in similar surroundings is also a bad idea.
2939 filter list may not be modified if the system security level
2940 is set to 3 or higher
2943 for information on system security levels).
2945 .Sh PACKET DIVERSION
2948 socket bound to the specified port will receive all packets
2949 diverted to that port.
2950 If no socket is bound to the destination port, or if the divert module is
2951 not loaded, or if the kernel was not compiled with divert socket support,
2952 the packets are dropped.
2953 .Sh NETWORK ADDRESS TRANSLATION (NAT)
2955 support in-kernel NAT using the kernel version of
2959 should be loaded or kernel should have
2960 .Cm options IPFIREWALL_NAT
2963 The nat configuration command is the following:
2964 .Bd -ragged -offset indent
2969 .Ar nat-configuration
2973 The following parameters can be configured:
2974 .Bl -tag -width indent
2975 .It Cm ip Ar ip_address
2976 Define an ip address to use for aliasing.
2978 Use ip address of NIC for aliasing, dynamically changing
2979 it if NIC's ip address changes.
2981 Enable logging on this nat instance.
2983 Deny any incoming connection from outside world.
2985 Try to leave the alias port numbers unchanged from
2986 the actual local port numbers.
2988 Traffic on the local network not originating from an
2989 unregistered address spaces will be ignored.
2991 Reset table of the packet aliasing engine on address change.
2993 Reverse the way libalias handles aliasing.
2995 Obey transparent proxy rules only, packet aliasing is not performed.
2997 Skip instance in case of global state lookup (see below).
3000 Some specials value can be supplied instead of
3002 .Bl -tag -width indent
3004 Looks up translation state in all configured nat instances.
3005 If an entry is found, packet is aliased according to that entry.
3006 If no entry was found in any of the instances, packet is passed unchanged,
3007 and no new entry will be created.
3009 .Sx MULTIPLE INSTANCES
3012 for more information.
3014 Uses argument supplied in lookup table.
3017 section below for more information on lookup tables.
3020 To let the packet continue after being (de)aliased, set the sysctl variable
3021 .Va net.inet.ip.fw.one_pass
3023 For more information about aliasing modes, refer to
3027 for some examples about nat usage.
3028 .Ss REDIRECT AND LSNAT SUPPORT IN IPFW
3029 Redirect and LSNAT support follow closely the syntax used in
3033 for some examples on how to do redirect and lsnat.
3034 .Ss SCTP NAT SUPPORT
3035 SCTP nat can be configured in a similar manner to TCP through the
3038 The main difference is that
3040 does not do port translation.
3041 Since the local and global side ports will be the same,
3042 there is no need to specify both.
3043 Ports are redirected as follows:
3044 .Bd -ragged -offset indent
3050 .Cm redirect_port sctp
3051 .Ar ip_address [,addr_list] {[port | port-port] [,ports]}
3057 configuration can be done in real-time through the
3060 All may be changed dynamically, though the hash_table size will only
3065 .Sx SYSCTL VARIABLES
3067 .Sh IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
3069 supports in-kernel IPv6/IPv4 network address and protocol translation.
3070 Stateful NAT64 translation allows IPv6-only clients to contact IPv4 servers
3071 using unicast TCP, UDP or ICMP protocols.
3072 One or more IPv4 addresses assigned to a stateful NAT64 translator are shared
3073 among several IPv6-only clients.
3074 When stateful NAT64 is used in conjunction with DNS64, no changes are usually
3075 required in the IPv6 client or the IPv4 server.
3078 should be loaded or kernel should have
3079 .Cm options IPFIREWALL_NAT64
3080 to be able use stateful NAT64 translator.
3082 Stateful NAT64 uses a bunch of memory for several types of objects.
3083 When IPv6 client initiates connection, NAT64 translator creates a host entry
3084 in the states table.
3085 Each host entry has a number of ports group entries allocated on demand.
3086 Ports group entries contains connection state entries.
3087 There are several options to control limits and lifetime for these objects.
3089 NAT64 translator follows RFC7915 when does ICMPv6/ICMP translation,
3090 unsupported message types will be silently dropped.
3091 IPv6 needs several ICMPv6 message types to be explicitly allowed for correct
3093 Make sure that ND6 neighbor solicitation (ICMPv6 type 135) and neighbor
3094 advertisement (ICMPv6 type 136) messages will not be handled by translation
3097 After translation NAT64 translator sends packets through corresponding netisr
3099 Thus translator host should be configured as IPv4 and IPv6 router.
3101 The stateful NAT64 configuration command is the following:
3102 .Bd -ragged -offset indent
3111 The following parameters can be configured:
3112 .Bl -tag -width indent
3113 .It Cm prefix4 Ar ipv4_prefix/plen
3114 The IPv4 prefix with mask defines the pool of IPv4 addresses used as
3115 source address after translation.
3116 Stateful NAT64 module translates IPv6 source address of client to one
3117 IPv4 address from this pool.
3118 Note that incoming IPv4 packets that don't have corresponding state entry
3119 in the states table will be dropped by translator.
3120 Make sure that translation rules handle packets, destined to configured prefix.
3121 .It Cm prefix6 Ar ipv6_prefix/length
3122 The IPv6 prefix defines IPv4-embedded IPv6 addresses used by translator
3123 to represent IPv4 addresses. This IPv6 prefix should be configured in DNS64.
3124 The translator implementation follows RFC6052, that restricts the length of
3125 prefixes to one of following: 32, 40, 48, 56, 64, or 96.
3126 The Well-Known IPv6 Prefix 64:ff9b:: must be 96 bits long.
3127 .It Cm max_ports Ar number
3128 Maximum number of ports reserved for upper level protocols to one IPv6 client.
3129 All reserved ports are divided into chunks between supported protocols.
3130 The number of connections from one IPv6 client is limited by this option.
3131 Note that closed TCP connections still remain in the list of connections until
3133 interval will not expire.
3136 .It Cm host_del_age Ar seconds
3137 The number of seconds until the host entry for a IPv6 client will be deleted
3138 and all its resources will be released due to inactivity.
3141 .It Cm pg_del_age Ar seconds
3142 The number of seconds until a ports group with unused state entries will
3146 .It Cm tcp_syn_age Ar seconds
3147 The number of seconds while a state entry for TCP connection with only SYN
3149 If TCP connection establishing will not be finished,
3150 state entry will be deleted.
3153 .It Cm tcp_est_age Ar seconds
3154 The number of seconds while a state entry for established TCP connection
3158 .It Cm tcp_close_age Ar seconds
3159 The number of seconds while a state entry for closed TCP connection
3161 Keeping state entries for closed connections is needed, because IPv4 servers
3162 typically keep closed connections in a TIME_WAIT state for a several minutes.
3163 Since translator's IPv4 addresses are shared among all IPv6 clients,
3164 new connections from the same addresses and ports may be rejected by server,
3165 because these connections are still in a TIME_WAIT state.
3166 Keeping them in translator's state table protects from such rejects.
3169 .It Cm udp_age Ar seconds
3170 The number of seconds while translator keeps state entry in a waiting for
3171 reply to the sent UDP datagram.
3174 .It Cm icmp_age Ar seconds
3175 The number of seconds while translator keeps state entry in a waiting for
3176 reply to the sent ICMP message.
3180 Turn on logging of all handled packets via BPF through
3184 is a pseudo interface and can be created after a boot manually with
3187 Note that it has different purpose than
3190 Translators sends to BPF an additional information with each packet.
3193 you are able to see each handled packet before and after translation.
3195 Turn off logging of all handled packets via BPF.
3198 To inspect a states table of stateful NAT64 the following command can be used:
3199 .Bd -ragged -offset indent
3208 Stateless NAT64 translator doesn't use a states table for translation
3209 and converts IPv4 addresses to IPv6 and vice versa solely based on the
3210 mappings taken from configured lookup tables.
3211 Since a states table doesn't used by stateless translator,
3212 it can be configured to pass IPv4 clients to IPv6-only servers.
3214 The stateless NAT64 configuration command is the following:
3215 .Bd -ragged -offset indent
3224 The following parameters can be configured:
3225 .Bl -tag -width indent
3226 .It Cm prefix6 Ar ipv6_prefix/length
3227 The IPv6 prefix defines IPv4-embedded IPv6 addresses used by translator
3228 to represent IPv4 addresses. This IPv6 prefix should be configured in DNS64.
3229 .It Cm table4 Ar table46
3232 contains mapping how IPv4 addresses should be translated to IPv6 addresses.
3233 .It Cm table6 Ar table64
3236 contains mapping how IPv6 addresses should be translated to IPv4 addresses.
3238 Turn on logging of all handled packets via BPF through
3242 Turn off logging of all handled packets via BPF.
3245 Note that the behavior of stateless translator with respect to not matched
3246 packets differs from stateful translator.
3247 If corresponding addresses was not found in the lookup tables, the packet
3248 will not be dropped and the search continues.
3249 .Sh IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6)
3251 supports in-kernel IPv6-to-IPv6 network prefix translation as described
3255 should be loaded or kernel should has
3256 .Cm options IPFIREWALL_NPTV6
3257 to be able use NPTv6 translator.
3259 The NPTv6 configuration command is the following:
3260 .Bd -ragged -offset indent
3269 The following parameters can be configured:
3270 .Bl -tag -width indent
3271 .It Cm int_prefix Ar ipv6_prefix
3272 IPv6 prefix used in internal network.
3273 NPTv6 module translates source address when it matches this prefix.
3274 .It Cm ext_prefix Ar ipv6_prefix
3275 IPv6 prefix used in external network.
3276 NPTv6 module translates destination address when it matches this prefix.
3277 .It Cm prefixlen Ar length
3278 The length of specified IPv6 prefixes. It must be in range from 8 to 64.
3281 Note that the prefix translation rules are silently ignored when IPv6 packet
3282 forwarding is disabled.
3283 To enable the packet forwarding, set the sysctl variable
3284 .Va net.inet6.ip6.forwarding
3287 To let the packet continue after being translated, set the sysctl variable
3288 .Va net.inet.ip.fw.one_pass
3291 Tunables can be set in
3297 before ipfw module gets loaded.
3298 .Bl -tag -width indent
3299 .It Va net.inet.ip.fw.default_to_accept: No 0
3300 Defines ipfw last rule behavior.
3301 This value overrides
3302 .Cd "options IPFW_DEFAULT_TO_(ACCEPT|DENY)"
3303 from kernel configuration file.
3304 .It Va net.inet.ip.fw.tables_max: No 128
3305 Defines number of tables available in ipfw.
3306 Number cannot exceed 65534.
3308 .Sh SYSCTL VARIABLES
3311 variables controls the behaviour of the firewall and
3313 .Pq Nm dummynet , bridge , sctp nat .
3314 These are shown below together with their default value
3315 (but always check with the
3317 command what value is actually in use) and meaning:
3318 .Bl -tag -width indent
3319 .It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0
3322 responds to receipt of global OOTB ASCONF-AddIP:
3323 .Bl -tag -width indent
3325 No response (unless a partially matching association exists -
3326 ports and vtags match but global address does not)
3329 will accept and process all OOTB global AddIP messages.
3332 Option 1 should never be selected as this forms a security risk.
3334 establish multiple fake associations by sending AddIP messages.
3335 .It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5
3336 Defines the maximum number of chunks in an SCTP packet that will be
3338 packet that matches an existing association.
3339 This value is enforced to be greater or equal than
3340 .Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit .
3342 a DoS risk yet setting too low a value may result in
3343 important control chunks in
3344 the packet not being located and parsed.
3345 .It Va net.inet.ip.alias.sctp.error_on_ootb: No 1
3348 responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets.
3349 An OOTB packet is a packet that arrives with no existing association
3352 and is not an INIT or ASCONF-AddIP packet:
3353 .Bl -tag -width indent
3355 ErrorM is never sent in response to OOTB packets.
3357 ErrorM is only sent to OOTB packets received on the local side.
3359 ErrorM is sent to the local side and on the global side ONLY if there is a
3360 partial match (ports and vtags match but the source global IP does not).
3361 This value is only useful if the
3363 is tracking global IP addresses.
3365 ErrorM is sent in response to all OOTB packets on both
3366 the local and global side
3370 At the moment the default is 0, since the ErrorM packet is not yet
3371 supported by most SCTP stacks.
3372 When it is supported, and if not tracking
3373 global addresses, we recommend setting this value to 1 to allow
3374 multi-homed local hosts to function with the
3376 To track global addresses, we recommend setting this value to 2 to
3377 allow global hosts to be informed when they need to (re)send an
3379 Value 3 should never be chosen (except for debugging) as the
3381 will respond to all OOTB global packets (a DoS risk).
3382 .It Va net.inet.ip.alias.sctp.hashtable_size: No 2003
3383 Size of hash tables used for
3385 lookups (100 < prime_number > 1000001).
3388 size for any future created
3390 instance and therefore must be set prior to creating a
3393 The table sizes may be changed to suit specific needs.
3394 If there will be few
3395 concurrent associations, and memory is scarce, you may make these smaller.
3396 If there will be many thousands (or millions) of concurrent associations, you
3397 should make these larger.
3398 A prime number is best for the table size.
3400 update function will adjust your input value to the next highest prime number.
3401 .It Va net.inet.ip.alias.sctp.holddown_time: No 0
3402 Hold association in table for this many seconds after receiving a
3404 This allows endpoints to correct shutdown gracefully if a
3405 shutdown_complete is lost and retransmissions are required.
3406 .It Va net.inet.ip.alias.sctp.init_timer: No 15
3407 Timeout value while waiting for (INIT-ACK|AddIP-ACK).
3408 This value cannot be 0.
3409 .It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2
3410 Defines the maximum number of chunks in an SCTP packet that will be parsed when
3411 no existing association exists that matches that packet.
3413 will only be an INIT or ASCONF-AddIP packet.
3414 A higher value may become a DoS
3415 risk as malformed packets can consume processing resources.
3416 .It Va net.inet.ip.alias.sctp.param_proc_limit: No 25
3417 Defines the maximum number of parameters within a chunk that will be
3420 As for other similar sysctl variables, larger values pose a DoS risk.
3421 .It Va net.inet.ip.alias.sctp.log_level: No 0
3422 Level of detail in the system log messages (0 \- minimal, 1 \- event,
3423 2 \- info, 3 \- detail, 4 \- debug, 5 \- max debug).
3425 option in high loss environments.
3426 .It Va net.inet.ip.alias.sctp.shutdown_time: No 15
3427 Timeout value while waiting for SHUTDOWN-COMPLETE.
3428 This value cannot be 0.
3429 .It Va net.inet.ip.alias.sctp.track_global_addresses: No 0
3430 Enables/disables global IP address tracking within the
3433 upper limit on the number of addresses tracked for each association:
3434 .Bl -tag -width indent
3436 Global tracking is disabled
3438 Enables tracking, the maximum number of addresses tracked for each
3439 association is limited to this value
3442 This variable is fully dynamic, the new value will be adopted for all newly
3443 arriving associations, existing associations are treated
3444 as they were previously.
3445 Global tracking will decrease the number of collisions within the
3448 of increased processing load, memory usage, complexity, and possible
3451 problems in complex networks with multiple
3453 We recommend not tracking
3454 global IP addresses, this will still result in a fully functional
3456 .It Va net.inet.ip.alias.sctp.up_timer: No 300
3457 Timeout value to keep an association up with no traffic.
3458 This value cannot be 0.
3459 .It Va net.inet.ip.dummynet.expire : No 1
3460 Lazily delete dynamic pipes/queue once they have no pending traffic.
3461 You can disable this by setting the variable to 0, in which case
3462 the pipes/queues will only be deleted when the threshold is reached.
3463 .It Va net.inet.ip.dummynet.hash_size : No 64
3464 Default size of the hash table used for dynamic pipes/queues.
3465 This value is used when no
3467 option is specified when configuring a pipe/queue.
3468 .It Va net.inet.ip.dummynet.io_fast : No 0
3469 If set to a non-zero value,
3474 operation (see above) is enabled.
3475 .It Va net.inet.ip.dummynet.io_pkt
3476 Number of packets passed to
3478 .It Va net.inet.ip.dummynet.io_pkt_drop
3479 Number of packets dropped by
3481 .It Va net.inet.ip.dummynet.io_pkt_fast
3482 Number of packets bypassed by the
3485 .It Va net.inet.ip.dummynet.max_chain_len : No 16
3486 Target value for the maximum number of pipes/queues in a hash bucket.
3488 .Cm max_chain_len*hash_size
3489 is used to determine the threshold over which empty pipes/queues
3490 will be expired even when
3491 .Cm net.inet.ip.dummynet.expire=0 .
3492 .It Va net.inet.ip.dummynet.red_lookup_depth : No 256
3493 .It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512
3494 .It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500
3495 Parameters used in the computations of the drop probability
3496 for the RED algorithm.
3497 .It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576
3498 .It Va net.inet.ip.dummynet.pipe_slot_limit : No 100
3499 The maximum queue size that can be specified in bytes or packets.
3500 These limits prevent accidental exhaustion of resources such as mbufs.
3501 If you raise these limits,
3502 you should make sure the system is configured so that sufficient resources
3504 .It Va net.inet.ip.fw.autoinc_step : No 100
3505 Delta between rule numbers when auto-generating them.
3506 The value must be in the range 1..1000.
3507 .It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets
3508 The current number of buckets in the hash table for dynamic rules
3510 .It Va net.inet.ip.fw.debug : No 1
3511 Controls debugging messages produced by
3513 .It Va net.inet.ip.fw.default_rule : No 65535
3514 The default rule number (read-only).
3516 .Nm , the default rule is the last one, so its number
3517 can also serve as the highest number allowed for a rule.
3518 .It Va net.inet.ip.fw.dyn_buckets : No 256
3519 The number of buckets in the hash table for dynamic rules.
3520 Must be a power of 2, up to 65536.
3521 It only takes effect when all dynamic rules have expired, so you
3522 are advised to use a
3524 command to make sure that the hash table is resized.
3525 .It Va net.inet.ip.fw.dyn_count : No 3
3526 Current number of dynamic rules
3528 .It Va net.inet.ip.fw.dyn_keepalive : No 1
3529 Enables generation of keepalive packets for
3531 rules on TCP sessions.
3532 A keepalive is generated to both
3533 sides of the connection every 5 seconds for the last 20
3534 seconds of the lifetime of the rule.
3535 .It Va net.inet.ip.fw.dyn_max : No 8192
3536 Maximum number of dynamic rules.
3537 When you hit this limit, no more dynamic rules can be
3538 installed until old ones expire.
3539 .It Va net.inet.ip.fw.dyn_ack_lifetime : No 300
3540 .It Va net.inet.ip.fw.dyn_syn_lifetime : No 20
3541 .It Va net.inet.ip.fw.dyn_fin_lifetime : No 1
3542 .It Va net.inet.ip.fw.dyn_rst_lifetime : No 1
3543 .It Va net.inet.ip.fw.dyn_udp_lifetime : No 5
3544 .It Va net.inet.ip.fw.dyn_short_lifetime : No 30
3545 These variables control the lifetime, in seconds, of dynamic
3547 Upon the initial SYN exchange the lifetime is kept short,
3548 then increased after both SYN have been seen, then decreased
3549 again during the final FIN exchange or when a RST is received.
3551 .Em dyn_fin_lifetime
3553 .Em dyn_rst_lifetime
3554 must be strictly lower than 5 seconds, the period of
3555 repetition of keepalives.
3556 The firewall enforces that.
3557 .It Va net.inet.ip.fw.dyn_keep_states: No 0
3558 Keep dynamic states on rule/set deletion.
3559 States are relinked to default rule (65535).
3560 This can be handly for ruleset reload.
3561 Turned off by default.
3562 .It Va net.inet.ip.fw.enable : No 1
3563 Enables the firewall.
3564 Setting this variable to 0 lets you run your machine without
3565 firewall even if compiled in.
3566 .It Va net.inet6.ip6.fw.enable : No 1
3567 provides the same functionality as above for the IPv6 case.
3568 .It Va net.inet.ip.fw.one_pass : No 1
3569 When set, the packet exiting from the
3573 node is not passed though the firewall again.
3574 Otherwise, after an action, the packet is
3575 reinjected into the firewall at the next rule.
3576 .It Va net.inet.ip.fw.tables_max : No 128
3577 Maximum number of tables.
3578 .It Va net.inet.ip.fw.verbose : No 1
3579 Enables verbose messages.
3580 .It Va net.inet.ip.fw.verbose_limit : No 0
3581 Limits the number of messages produced by a verbose firewall.
3582 .It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1
3583 If enabled packets with unknown IPv6 Extension Headers will be denied.
3584 .It Va net.link.ether.ipfw : No 0
3585 Controls whether layer-2 packets are passed to
3588 .It Va net.link.bridge.ipfw : No 0
3589 Controls whether bridged packets are passed to
3593 .Sh INTERNAL DIAGNOSTICS
3594 There are some commands that may be useful to understand current state
3595 of certain subsystems inside kernel module.
3596 These commands provide debugging output which may change without notice.
3598 Currently the following commands are available as
3601 .Bl -tag -width indent
3603 Lists all interface which are currently tracked by
3605 with their in-kernel status.
3607 List all table lookup algorithms currently available.
3610 There are far too many possible uses of
3612 so this Section will only give a small set of examples.
3614 .Ss BASIC PACKET FILTERING
3615 This command adds an entry which denies all tcp packets from
3616 .Em cracker.evil.org
3617 to the telnet port of
3619 from being forwarded by the host:
3621 .Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet"
3623 This one disallows any connection from the entire cracker's
3626 .Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org"
3628 A first and efficient way to limit access (not using dynamic rules)
3629 is the use of the following rules:
3631 .Dl "ipfw add allow tcp from any to any established"
3632 .Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup"
3633 .Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup"
3635 .Dl "ipfw add deny tcp from any to any"
3637 The first rule will be a quick match for normal TCP packets,
3638 but it will not match the initial SYN packet, which will be
3641 rules only for selected source/destination pairs.
3642 All other SYN packets will be rejected by the final
3646 If you administer one or more subnets, you can take advantage
3647 of the address sets and or-blocks and write extremely
3648 compact rulesets which selectively enable services to blocks
3649 of clients, as below:
3651 .Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q"
3652 .Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q"
3654 .Dl "ipfw add allow ip from ${goodguys} to any"
3655 .Dl "ipfw add deny ip from ${badguys} to any"
3656 .Dl "... normal policies ..."
3660 option could be used to do automated anti-spoofing by adding the
3661 following to the top of a ruleset:
3663 .Dl "ipfw add deny ip from any to any not verrevpath in"
3665 This rule drops all incoming packets that appear to be coming to the
3666 system on the wrong interface.
3667 For example, a packet with a source
3668 address belonging to a host on a protected internal network would be
3669 dropped if it tried to enter the system from an external interface.
3673 option could be used to do similar but more restricted anti-spoofing
3674 by adding the following to the top of a ruleset:
3676 .Dl "ipfw add deny ip from any to any not antispoof in"
3678 This rule drops all incoming packets that appear to be coming from another
3679 directly connected system but on the wrong interface.
3680 For example, a packet with a source address of
3681 .Li 192.168.0.0/24 ,
3690 option could be used to (re)mark user traffic,
3691 by adding the following to the appropriate place in ruleset:
3693 .Dl "ipfw add setdscp be ip from any to any dscp af11,af21"
3695 In order to protect a site from flood attacks involving fake
3696 TCP packets, it is safer to use dynamic rules:
3698 .Dl "ipfw add check-state"
3699 .Dl "ipfw add deny tcp from any to any established"
3700 .Dl "ipfw add allow tcp from my-net to any setup keep-state"
3702 This will let the firewall install dynamic rules only for
3703 those connection which start with a regular SYN packet coming
3704 from the inside of our network.
3705 Dynamic rules are checked when encountering the first
3714 rule should usually be placed near the beginning of the
3715 ruleset to minimize the amount of work scanning the ruleset.
3716 Your mileage may vary.
3718 For more complex scenarios with dynamic rules
3722 can be used to precisely control creation and checking of dynamic rules.
3723 Example of usage of these options are provided in
3724 .Sx NETWORK ADDRESS TRANSLATION (NAT)
3727 To limit the number of connections a user can open
3728 you can use the following type of rules:
3730 .Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10"
3731 .Dl "ipfw add allow tcp from any to me setup limit src-addr 4"
3733 The former (assuming it runs on a gateway) will allow each host
3734 on a /24 network to open at most 10 TCP connections.
3735 The latter can be placed on a server to make sure that a single
3736 client does not use more than 4 simultaneous connections.
3739 stateful rules can be subject to denial-of-service attacks
3740 by a SYN-flood which opens a huge number of dynamic rules.
3741 The effects of such attacks can be partially limited by
3744 variables which control the operation of the firewall.
3746 Here is a good usage of the
3748 command to see accounting records and timestamp information:
3752 or in short form without timestamps:
3756 which is equivalent to:
3760 Next rule diverts all incoming packets from 192.168.2.0/24
3761 to divert port 5000:
3763 .Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in
3765 The following rules show some of the applications of
3769 for simulations and the like.
3771 This rule drops random incoming packets with a probability
3774 .Dl "ipfw add prob 0.05 deny ip from any to any in"
3776 A similar effect can be achieved making use of
3780 .Dl "ipfw add pipe 10 ip from any to any"
3781 .Dl "ipfw pipe 10 config plr 0.05"
3783 We can use pipes to artificially limit bandwidth, e.g.\& on a
3784 machine acting as a router, if we want to limit traffic from
3785 local clients on 192.168.2.0/24 we do:
3787 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
3788 .Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes"
3790 note that we use the
3792 modifier so that the rule is not used twice.
3793 Remember in fact that
3795 rules are checked both on incoming and outgoing packets.
3797 Should we want to simulate a bidirectional link with bandwidth
3798 limitations, the correct way is the following:
3800 .Dl "ipfw add pipe 1 ip from any to any out"
3801 .Dl "ipfw add pipe 2 ip from any to any in"
3802 .Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes"
3803 .Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes"
3805 The above can be very useful, e.g.\& if you want to see how
3806 your fancy Web page will look for a residential user who
3807 is connected only through a slow link.
3808 You should not use only one pipe for both directions, unless
3809 you want to simulate a half-duplex medium (e.g.\& AppleTalk,
3811 It is not necessary that both pipes have the same configuration,
3812 so we can also simulate asymmetric links.
3814 Should we want to verify network performance with the RED queue
3815 management algorithm:
3817 .Dl "ipfw add pipe 1 ip from any to any"
3818 .Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1"
3820 Another typical application of the traffic shaper is to
3821 introduce some delay in the communication.
3822 This can significantly affect applications which do a lot of Remote
3823 Procedure Calls, and where the round-trip-time of the
3824 connection often becomes a limiting factor much more than
3827 .Dl "ipfw add pipe 1 ip from any to any out"
3828 .Dl "ipfw add pipe 2 ip from any to any in"
3829 .Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s"
3830 .Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s"
3832 Per-flow queueing can be useful for a variety of purposes.
3833 A very simple one is counting traffic:
3835 .Dl "ipfw add pipe 1 tcp from any to any"
3836 .Dl "ipfw add pipe 1 udp from any to any"
3837 .Dl "ipfw add pipe 1 ip from any to any"
3838 .Dl "ipfw pipe 1 config mask all"
3840 The above set of rules will create queues (and collect
3841 statistics) for all traffic.
3842 Because the pipes have no limitations, the only effect is
3843 collecting statistics.
3844 Note that we need 3 rules, not just the last one, because
3847 tries to match IP packets it will not consider ports, so we
3848 would not see connections on separate ports as different
3851 A more sophisticated example is limiting the outbound traffic
3852 on a net with per-host limits, rather than per-network limits:
3854 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
3855 .Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in"
3856 .Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
3857 .Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
3859 In the following example, we need to create several traffic bandwidth
3860 classes and we need different hosts/networks to fall into different classes.
3861 We create one pipe for each class and configure them accordingly.
3862 Then we create a single table and fill it with IP subnets and addresses.
3863 For each subnet/host we set the argument equal to the number of the pipe
3865 Then we classify traffic using a single rule:
3867 .Dl "ipfw pipe 1 config bw 1000Kbyte/s"
3868 .Dl "ipfw pipe 4 config bw 4000Kbyte/s"
3870 .Dl "ipfw table T1 create type addr"
3871 .Dl "ipfw table T1 add 192.168.2.0/24 1"
3872 .Dl "ipfw table T1 add 192.168.0.0/27 4"
3873 .Dl "ipfw table T1 add 192.168.0.2 1"
3875 .Dl "ipfw add pipe tablearg ip from 'table(T1)' to any"
3879 action, the table entries may include hostnames and IP addresses.
3881 .Dl "ipfw table T2 create type addr ftype ip"
3882 .Dl "ipfw table T2 add 192.168.2.0/24 10.23.2.1"
3883 .Dl "ipfw table T21 add 192.168.0.0/27 router1.dmz"
3885 .Dl "ipfw add 100 fwd tablearg ip from any to table(1)"
3887 In the following example per-interface firewall is created:
3889 .Dl "ipfw table IN create type iface valtype skipto,fib"
3890 .Dl "ipfw table IN add vlan20 12000,12"
3891 .Dl "ipfw table IN add vlan30 13000,13"
3892 .Dl "ipfw table OUT create type iface valtype skipto"
3893 .Dl "ipfw table OUT add vlan20 22000"
3894 .Dl "ipfw table OUT add vlan30 23000"
3896 .Dl "ipfw add 100 setfib tablearg ip from any to any recv 'table(IN)' in"
3897 .Dl "ipfw add 200 skipto tablearg ip from any to any recv 'table(IN)' in"
3898 .Dl "ipfw add 300 skipto tablearg ip from any to any xmit 'table(OUT)' out"
3900 The following example illustrate usage of flow tables:
3902 .Dl "ipfw table fl create type flow:flow:src-ip,proto,dst-ip,dst-port"
3903 .Dl "ipfw table fl add 2a02:6b8:77::88,tcp,2a02:6b8:77::99,80 11"
3904 .Dl "ipfw table fl add 10.0.0.1,udp,10.0.0.2,53 12"
3906 .Dl "ipfw add 100 allow ip from any to any flow 'table(fl,11)' recv ix0"
3908 To add a set of rules atomically, e.g.\& set 18:
3910 .Dl "ipfw set disable 18"
3911 .Dl "ipfw add NN set 18 ... # repeat as needed"
3912 .Dl "ipfw set enable 18"
3914 To delete a set of rules atomically the command is simply:
3916 .Dl "ipfw delete set 18"
3918 To test a ruleset and disable it and regain control if something goes wrong:
3920 .Dl "ipfw set disable 18"
3921 .Dl "ipfw add NN set 18 ... # repeat as needed"
3922 .Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18"
3924 Here if everything goes well, you press control-C before the "sleep"
3925 terminates, and your ruleset will be left active.
3926 Otherwise, e.g.\& if
3927 you cannot access your box, the ruleset will be disabled after
3928 the sleep terminates thus restoring the previous situation.
3930 To show rules of the specific set:
3932 .Dl "ipfw set 18 show"
3934 To show rules of the disabled set:
3936 .Dl "ipfw -S set 18 show"
3938 To clear a specific rule counters of the specific set:
3940 .Dl "ipfw set 18 zero NN"
3942 To delete a specific rule of the specific set:
3944 .Dl "ipfw set 18 delete NN"
3945 .Ss NAT, REDIRECT AND LSNAT
3946 First redirect all the traffic to nat instance 123:
3948 .Dl "ipfw add nat 123 all from any to any"
3950 Then to configure nat instance 123 to alias all the outgoing traffic with ip
3951 192.168.0.123, blocking all incoming connections, trying to keep
3952 same ports on both sides, clearing aliasing table on address change
3953 and keeping a log of traffic/link statistics:
3955 .Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports"
3957 Or to change address of instance 123, aliasing table will be cleared (see
3960 .Dl "ipfw nat 123 config ip 10.0.0.1"
3962 To see configuration of nat instance 123:
3964 .Dl "ipfw nat 123 show config"
3966 To show logs of all the instances in range 111-999:
3968 .Dl "ipfw nat 111-999 show"
3970 To see configurations of all instances:
3972 .Dl "ipfw nat show config"
3974 Or a redirect rule with mixed modes could looks like:
3976 .Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66"
3977 .Dl " redirect_port tcp 192.168.0.1:80 500"
3978 .Dl " redirect_proto udp 192.168.1.43 192.168.1.1"
3979 .Dl " redirect_addr 192.168.0.10,192.168.0.11"
3980 .Dl " 10.0.0.100 # LSNAT"
3981 .Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22"
3984 or it could be split in:
3986 .Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66"
3987 .Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500"
3988 .Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1"
3989 .Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12"
3991 .Dl "ipfw nat 5 config redirect_port tcp"
3992 .Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500"
3994 Sometimes you may want to mix NAT and dynamic rules. It could be achived with
3998 options. Problem is, you need to create dynamic rule before NAT and check it
3999 after NAT actions (or vice versa) to have consistent addresses and ports.
4002 option will trigger activation of existing dynamic state, and action of such
4003 rule will be performed as soon as rule is matched. In case of NAT and
4005 rule packet need to be passed to NAT, not allowed as soon is possible.
4007 There is example of set of rules to achive this. Bear in mind that this
4008 is exmaple only and it is not very usefult by itself.
4010 On way out, after all checks place this rules:
4012 .Dl "ipfw add allow record-state skip-action"
4013 .Dl "ipfw add nat 1"
4015 And on way in there should be something like this:
4017 .Dl "ipfw add nat 1"
4018 .Dl "ipfw add check-state"
4020 Please note, that first rule on way out doesn't allow packet and doesn't
4021 execute existing dynamic rules. All it does, create new dynamic rule with
4023 action, if it is not created yet. Later, this dynamic rule is used on way
4047 utility first appeared in
4052 Stateful extensions were introduced in
4055 was introduced in Summer 2002.
4057 .An Ugen J. S. Antsilevich ,
4058 .An Poul-Henning Kamp ,
4064 API based upon code written by
4068 Dummynet has been introduced by Luigi Rizzo in 1997-1998.
4070 Some early work (1999-2000) on the
4072 traffic shaper supported by Akamba Corp.
4074 The ipfw core (ipfw2) has been completely redesigned and
4075 reimplemented by Luigi Rizzo in summer 2002.
4078 options have been added by various developer over the years.
4081 In-kernel NAT support written by
4082 .An Paolo Pisati Aq Mt piso@FreeBSD.org
4083 as part of a Summer of Code 2005 project.
4087 support has been developed by
4088 .An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au .
4089 The primary developers and maintainers are David Hayes and Jason But.
4090 For further information visit:
4091 .Aq http://www.caia.swin.edu.au/urp/SONATA
4093 Delay profiles have been developed by Alessandro Cerri and
4094 Luigi Rizzo, supported by the
4095 European Commission within Projects Onelab and Onelab2.
4097 The syntax has grown over the years and sometimes it might be confusing.
4098 Unfortunately, backward compatibility prevents cleaning up mistakes
4099 made in the definition of the syntax.
4103 Misconfiguring the firewall can put your computer in an unusable state,
4104 possibly shutting down network services and requiring console access to
4105 regain control of it.
4107 Incoming packet fragments diverted by
4109 are reassembled before delivery to the socket.
4110 The action used on those packet is the one from the
4111 rule which matches the first fragment of the packet.
4113 Packets diverted to userland, and then reinserted by a userland process
4114 may lose various packet attributes.
4115 The packet source interface name
4116 will be preserved if it is shorter than 8 bytes and the userland process
4117 saves and reuses the sockaddr_in
4120 otherwise, it may be lost.
4121 If a packet is reinserted in this manner, later rules may be incorrectly
4122 applied, making the order of
4124 rules in the rule sequence very important.
4126 Dummynet drops all packets with IPv6 link-local addresses.
4132 may not behave as expected.
4133 In particular, incoming SYN packets may
4134 have no uid or gid associated with them since they do not yet belong
4135 to a TCP connection, and the uid/gid associated with a packet may not
4136 be as expected if the associated process calls
4138 or similar system calls.
4140 Rule syntax is subject to the command line environment and some patterns
4141 may need to be escaped with the backslash character
4142 or quoted appropriately.
4144 Due to the architecture of
4146 ipfw nat is not compatible with the TCP segmentation offloading (TSO).
4147 Thus, to reliably nat your network traffic, please disable TSO
4151 ICMP error messages are not implicitly matched by dynamic rules
4152 for the respective conversations.
4153 To avoid failures of network error detection and path MTU discovery,
4154 ICMP error messages may need to be allowed explicitly through static
4161 actions may lead to confusing behaviour if ruleset has mistakes,
4162 and/or interaction with other subsystems (netgraph, dummynet, etc.) is used.
4163 One possible case for this is packet leaving
4165 in subroutine on the input pass, while later on output encountering unpaired
4168 As the call stack is kept intact after input pass, packet will suddenly
4169 return to the rule number used on input pass, not on output one.
4170 Order of processing should be checked carefully to avoid such mistakes.
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