2 .\" $FreeBSD: head/sbin/ipfw/ipfw.8 211936 2010-08-28 16:32:01Z brucec $
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
46 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
49 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
53 .Cm table Ar number Cm add Ar addr Ns Oo / Ns Ar masklen Oc Op Ar value
55 .Cm table Ar number Cm delete Ar addr Ns Op / Ns Ar masklen
65 .Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER)
67 .Brq Cm pipe | queue | sched
73 .Brq Cm pipe | queue | sched
74 .Brq Cm delete | list | show
97 utility is the user interface for controlling the
101 traffic shaper/packet scheduler, and the
102 in-kernel NAT services.
104 A firewall configuration, or
108 numbered from 1 to 65535.
109 Packets are passed to the firewall
110 from a number of different places in the protocol stack
111 (depending on the source and destination of the packet,
112 it is possible for the firewall to be
113 invoked multiple times on the same packet).
114 The packet passed to the firewall is compared
115 against each of the rules in the
118 (multiple rules with the same number are permitted, in which case
119 they are processed in order of insertion).
120 When a match is found, the action corresponding to the
121 matching rule is performed.
123 Depending on the action and certain system settings, packets
124 can be reinjected into the firewall at some rule after the
125 matching one for further processing.
127 A ruleset always includes a
129 rule (numbered 65535) which cannot be modified or deleted,
130 and matches all packets.
131 The action associated with the
137 depending on how the kernel is configured.
139 If the ruleset includes one or more rules with the
144 the firewall will have a
146 behaviour, i.e., upon a match it will create
148 i.e. rules that match packets with the same 5-tuple
149 (protocol, source and destination addresses and ports)
150 as the packet which caused their creation.
151 Dynamic rules, which have a limited lifetime, are checked
152 at the first occurrence of a
157 rule, and are typically used to open the firewall on-demand to
158 legitimate traffic only.
160 .Sx STATEFUL FIREWALL
163 Sections below for more information on the stateful behaviour of
166 All rules (including dynamic ones) have a few associated counters:
167 a packet count, a byte count, a log count and a timestamp
168 indicating the time of the last match.
169 Counters can be displayed or reset with
173 Each rule belongs to one of 32 different
177 commands to atomically manipulate sets, such as enable,
178 disable, swap sets, move all rules in a set to another
179 one, delete all rules in a set.
180 These can be useful to
181 install temporary configurations, or to test them.
184 for more information on
188 Rules can be added with the
190 command; deleted individually or in groups with the
192 command, and globally (except those in set 31) with the
194 command; displayed, optionally with the content of the
200 Finally, counters can be reset with the
207 The following general options are available when invoking
209 .Bl -tag -width indent
211 Show counter values when listing rules.
214 command implies this option.
216 Only show the action and the comment, not the body of a rule.
220 When entering or showing rules, print them in compact form,
221 i.e., omitting the "ip from any to any" string
222 when this does not carry any additional information.
224 When listing, show dynamic rules in addition to static ones.
228 is specified, also show expired dynamic rules.
230 Do not ask for confirmation for commands that can cause problems
233 If there is no tty associated with the process, this is implied.
235 When listing a table (see the
237 section below for more information on lookup tables), format values
238 as IP addresses. By default, values are shown as integers.
240 Only check syntax of the command strings, without actually passing
243 Try to resolve addresses and service names in output.
245 Be quiet when executing the
255 This is useful when updating rulesets by executing multiple
259 .Ql sh\ /etc/rc.firewall ) ,
260 or by processing a file with many
262 rules across a remote login session.
263 It also stops a table add or delete
264 from failing if the entry already exists or is not present.
266 The reason why this option may be important is that
267 for some of these actions,
269 may print a message; if the action results in blocking the
270 traffic to the remote client,
271 the remote login session will be closed
272 and the rest of the ruleset will not be processed.
273 Access to the console would then be required to recover.
275 When listing rules, show the
277 each rule belongs to.
278 If this flag is not specified, disabled rules will not be
281 When listing pipes, sort according to one of the four
282 counters (total or current packets or bytes).
284 When listing, show last match timestamp converted with ctime().
286 When listing, show last match timestamp as seconds from the epoch.
287 This form can be more convenient for postprocessing by scripts.
290 .Ss LIST OF RULES AND PREPROCESSING
291 To ease configuration, rules can be put into a file which is
294 as shown in the last synopsis line.
298 The file will be read line by line and applied as arguments to the
302 Optionally, a preprocessor can be specified using
306 is to be piped through.
307 Useful preprocessors include
313 does not start with a slash
315 as its first character, the usual
317 name search is performed.
318 Care should be taken with this in environments where not all
319 file systems are mounted (yet) by the time
321 is being run (e.g.\& when they are mounted over NFS).
324 has been specified, any additional arguments are passed on to the preprocessor
326 This allows for flexible configuration files (like conditionalizing
327 them on the local hostname) and the use of macros to centralize
328 frequently required arguments like IP addresses.
330 .Ss TRAFFIC SHAPER CONFIGURATION
336 commands are used to configure the traffic shaper and packet scheduler.
338 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
339 Section below for details.
341 If the world and the kernel get out of sync the
343 ABI may break, preventing you from being able to add any rules.
345 adversely effect the booting process.
350 to temporarily disable the firewall to regain access to the network,
351 allowing you to fix the problem.
353 A packet is checked against the active ruleset in multiple places
354 in the protocol stack, under control of several sysctl variables.
355 These places and variables are shown below, and it is important to
356 have this picture in mind in order to design a correct ruleset.
357 .Bd -literal -offset indent
360 +----------->-----------+
362 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1
365 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1
367 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1
373 times the same packet goes through the firewall can
374 vary between 0 and 4 depending on packet source and
375 destination, and system configuration.
377 Note that as packets flow through the stack, headers can be
378 stripped or added to it, and so they may or may not be available
380 E.g., incoming packets will include the MAC header when
384 but the same packets will have the MAC header stripped off when
391 Also note that each packet is always checked against the complete ruleset,
392 irrespective of the place where the check occurs, or the source of the packet.
393 If a rule contains some match patterns or actions which are not valid
394 for the place of invocation (e.g.\& trying to match a MAC header within
398 the match pattern will not match, but a
400 operator in front of such patterns
404 match on those packets.
405 It is thus the responsibility of
406 the programmer, if necessary, to write a suitable ruleset to
407 differentiate among the possible places.
409 rules can be useful here, as an example:
410 .Bd -literal -offset indent
411 # packets from ether_demux or bdg_forward
412 ipfw add 10 skipto 1000 all from any to any layer2 in
413 # packets from ip_input
414 ipfw add 10 skipto 2000 all from any to any not layer2 in
415 # packets from ip_output
416 ipfw add 10 skipto 3000 all from any to any not layer2 out
417 # packets from ether_output_frame
418 ipfw add 10 skipto 4000 all from any to any layer2 out
421 (yes, at the moment there is no way to differentiate between
422 ether_demux and bdg_forward).
424 In general, each keyword or argument must be provided as
425 a separate command line argument, with no leading or trailing
427 Keywords are case-sensitive, whereas arguments may
428 or may not be case-sensitive depending on their nature
429 (e.g.\& uid's are, hostnames are not).
431 Some arguments (e.g. port or address lists) are comma-separated
433 In this case, spaces after commas ',' are allowed to make
434 the line more readable.
435 You can also put the entire
436 command (including flags) into a single argument.
437 E.g., the following forms are equivalent:
438 .Bd -literal -offset indent
439 ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8
440 ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8
441 ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8"
444 The format of firewall rules is the following:
445 .Bd -ragged -offset indent
448 .Op Cm set Ar set_number
449 .Op Cm prob Ar match_probability
451 .Op Cm log Op Cm logamount Ar number
461 where the body of the rule specifies which information is used
462 for filtering packets, among the following:
464 .Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact
465 .It Layer-2 header fields
467 .It IPv4 and IPv6 Protocol
469 .It Source and dest. addresses and ports
473 .It Transmit and receive interface
475 .It Misc. IP header fields
476 Version, type of service, datagram length, identification,
477 fragment flag (non-zero IP offset),
480 .It IPv6 Extension headers
481 Fragmentation, Hop-by-Hop options,
482 Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options.
484 .It Misc. TCP header fields
485 TCP flags (SYN, FIN, ACK, RST, etc.),
486 sequence number, acknowledgment number,
494 When the packet can be associated with a local socket.
496 Whether a packet came from a divert socket (e.g.,
498 .It Fib annotation state
499 Whether a packet has been tagged for using a specific FIB (routing table)
500 in future forwarding decisions.
503 Note that some of the above information, e.g.\& source MAC or IP addresses and
504 TCP/UDP ports, can be easily spoofed, so filtering on those fields
505 alone might not guarantee the desired results.
506 .Bl -tag -width indent
508 Each rule is associated with a
510 in the range 1..65535, with the latter reserved for the
513 Rules are checked sequentially by rule number.
514 Multiple rules can have the same number, in which case they are
515 checked (and listed) according to the order in which they have
517 If a rule is entered without specifying a number, the kernel will
518 assign one in such a way that the rule becomes the last one
522 Automatic rule numbers are assigned by incrementing the last
523 non-default rule number by the value of the sysctl variable
524 .Ar net.inet.ip.fw.autoinc_step
525 which defaults to 100.
526 If this is not possible (e.g.\& because we would go beyond the
527 maximum allowed rule number), the number of the last
528 non-default value is used instead.
529 .It Cm set Ar set_number
530 Each rule is associated with a
533 Sets can be individually disabled and enabled, so this parameter
534 is of fundamental importance for atomic ruleset manipulation.
535 It can be also used to simplify deletion of groups of rules.
536 If a rule is entered without specifying a set number,
539 Set 31 is special in that it cannot be disabled,
540 and rules in set 31 are not deleted by the
542 command (but you can delete them with the
543 .Nm ipfw delete set 31
545 Set 31 is also used for the
548 .It Cm prob Ar match_probability
549 A match is only declared with the specified probability
550 (floating point number between 0 and 1).
551 This can be useful for a number of applications such as
552 random packet drop or
555 to simulate the effect of multiple paths leading to out-of-order
558 Note: this condition is checked before any other condition, including
559 ones such as keep-state or check-state which might have side effects.
560 .It Cm log Op Cm logamount Ar number
561 When a packet matches a rule with the
563 keyword, a message will be
569 The logging only occurs if the sysctl variable
570 .Va net.inet.ip.fw.verbose
572 (which is the default when the kernel is compiled with
573 .Dv IPFIREWALL_VERBOSE )
574 and the number of packets logged so far for that
575 particular rule does not exceed the
580 is specified, the limit is taken from the sysctl variable
581 .Va net.inet.ip.fw.verbose_limit .
582 In both cases, a value of 0 removes the logging limit.
584 Once the limit is reached, logging can be re-enabled by
585 clearing the logging counter or the packet counter for that entry, see the
589 Note: logging is done after all other packet matching conditions
590 have been successfully verified, and before performing the final
591 action (accept, deny, etc.) on the packet.
593 When a packet matches a rule with the
595 keyword, the numeric tag for the given
597 in the range 1..65534 will be attached to the packet.
598 The tag acts as an internal marker (it is not sent out over
599 the wire) that can be used to identify these packets later on.
600 This can be used, for example, to provide trust between interfaces
601 and to start doing policy-based filtering.
602 A packet can have multiple tags at the same time.
603 Tags are "sticky", meaning once a tag is applied to a packet by a
604 matching rule it exists until explicit removal.
605 Tags are kept with the packet everywhere within the kernel, but are
606 lost when packet leaves the kernel, for example, on transmitting
607 packet out to the network or sending packet to a
611 To check for previously applied tags, use the
614 To delete previously applied tag, use the
618 Note: since tags are kept with the packet everywhere in kernelspace,
619 they can be set and unset anywhere in the kernel network subsystem
622 facility), not only by means of the
628 For example, there can be a specialized
630 node doing traffic analyzing and tagging for later inspecting
632 .It Cm untag Ar number
633 When a packet matches a rule with the
635 keyword, the tag with the number
637 is searched among the tags attached to this packet and,
638 if found, removed from it.
639 Other tags bound to packet, if present, are left untouched.
641 When a packet matches a rule with the
643 keyword, the ALTQ identifier for the given
648 Note that this ALTQ tag is only meaningful for packets going "out" of IPFW,
649 and not being rejected or going to divert sockets.
650 Note that if there is insufficient memory at the time the packet is
651 processed, it will not be tagged, so it is wise to make your ALTQ
652 "default" queue policy account for this.
655 rules match a single packet, only the first one adds the ALTQ classification
657 In doing so, traffic may be shaped by using
658 .Cm count Cm altq Ar queue
659 rules for classification early in the ruleset, then later applying
660 the filtering decision.
665 rules may come later and provide the actual filtering decisions in
666 addition to the fallback ALTQ tag.
670 to set up the queues before IPFW will be able to look them up by name,
671 and if the ALTQ disciplines are rearranged, the rules in containing the
672 queue identifiers in the kernel will likely have gone stale and need
674 Stale queue identifiers will probably result in misclassification.
676 All system ALTQ processing can be turned on or off via
681 .Cm disable Ar altq .
683 .Va net.inet.ip.fw.one_pass
684 is irrelevant to ALTQ traffic shaping, as the actual rule action is followed
685 always after adding an ALTQ tag.
688 A rule can be associated with one of the following actions, which
689 will be executed when the packet matches the body of the rule.
690 .Bl -tag -width indent
691 .It Cm allow | accept | pass | permit
692 Allow packets that match rule.
693 The search terminates.
695 Checks the packet against the dynamic ruleset.
696 If a match is found, execute the action associated with
697 the rule which generated this dynamic rule, otherwise
698 move to the next rule.
701 rules do not have a body.
704 rule is found, the dynamic ruleset is checked at the first
710 Update counters for all packets that match rule.
711 The search continues with the next rule.
713 Discard packets that match this rule.
714 The search terminates.
715 .It Cm divert Ar port
716 Divert packets that match this rule to the
720 The search terminates.
721 .It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port
722 Change the next-hop on matching packets to
724 which can be an IP address or a host name.
725 The next hop can also be supplied by the last table
726 looked up for the packet by using the
728 keyword instead of an explicit address.
729 The search terminates if this rule matches.
733 is a local address, then matching packets will be forwarded to
735 (or the port number in the packet if one is not specified in the rule)
736 on the local machine.
740 is not a local address, then the port number
741 (if specified) is ignored, and the packet will be
742 forwarded to the remote address, using the route as found in
743 the local routing table for that IP.
747 rule will not match layer-2 packets (those received
748 on ether_input, ether_output, or bridged).
752 action does not change the contents of the packet at all.
753 In particular, the destination address remains unmodified, so
754 packets forwarded to another system will usually be rejected by that system
755 unless there is a matching rule on that system to capture them.
756 For packets forwarded locally,
757 the local address of the socket will be
758 set to the original destination address of the packet.
761 entry look rather weird but is intended for
762 use with transparent proxy servers.
766 a custom kernel needs to be compiled with the option
767 .Cd "options IPFIREWALL_FORWARD" .
771 (for network address translation, address redirect, etc.):
773 .Sx NETWORK ADDRESS TRANSLATION (NAT)
774 Section for further information.
775 .It Cm pipe Ar pipe_nr
779 (for bandwidth limitation, delay, etc.).
781 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
782 Section for further information.
783 The search terminates; however, on exit from the pipe and if
787 .Va net.inet.ip.fw.one_pass
788 is not set, the packet is passed again to the firewall code
789 starting from the next rule.
790 .It Cm queue Ar queue_nr
794 (for bandwidth limitation using WF2Q+).
800 Discard packets that match this rule, and if the
801 packet is a TCP packet, try to send a TCP reset (RST) notice.
802 The search terminates.
804 Discard packets that match this rule, and if the
805 packet is a TCP packet, try to send a TCP reset (RST) notice.
806 The search terminates.
807 .It Cm skipto Ar number | tablearg
808 Skip all subsequent rules numbered less than
810 The search continues with the first rule numbered
813 It is possible to use the
815 keyword with a skipto for a
817 skipto, but care should be used, as no destination caching
818 is possible in this case so the rules are always walked to find it,
822 Send a copy of packets matching this rule to the
826 The search continues with the next rule.
827 .It Cm unreach Ar code
828 Discard packets that match this rule, and try to send an ICMP
829 unreachable notice with code
833 is a number from 0 to 255, or one of these aliases:
834 .Cm net , host , protocol , port ,
835 .Cm needfrag , srcfail , net-unknown , host-unknown ,
836 .Cm isolated , net-prohib , host-prohib , tosnet ,
837 .Cm toshost , filter-prohib , host-precedence
839 .Cm precedence-cutoff .
840 The search terminates.
841 .It Cm unreach6 Ar code
842 Discard packets that match this rule, and try to send an ICMPv6
843 unreachable notice with code
847 is a number from 0, 1, 3 or 4, or one of these aliases:
848 .Cm no-route, admin-prohib, address
851 The search terminates.
852 .It Cm netgraph Ar cookie
853 Divert packet into netgraph with given
855 The search terminates.
856 If packet is later returned from netgraph it is either
857 accepted or continues with the next rule, depending on
858 .Va net.inet.ip.fw.one_pass
860 .It Cm ngtee Ar cookie
861 A copy of packet is diverted into netgraph, original
862 packet continues with the next rule.
865 for more information on
870 .It Cm setfib Ar fibnum
871 The packet is tagged so as to use the FIB (routing table)
873 in any subsequent forwarding decisions.
874 Initially this is limited to the values 0 through 15, see
876 Processing continues at the next rule.
878 Queue and reassemble ip fragments.
879 If the packet is not fragmented, counters are updated and processing continues with the next rule.
880 If the packet is the last logical fragment, the packet is reassembled and, if
881 .Va net.inet.ip.fw.one_pass
882 is set to 0, processing continues with the next rule, else packet is allowed to pass and search terminates.
883 If the packet is a fragment in the middle, it is consumed and processing stops immediately.
885 Fragments handling can be tuned via
886 .Va net.inet.ip.maxfragpackets
888 .Va net.inet.ip.maxfragsperpacket
889 which limit, respectively, the maximum number of processable fragments (default: 800) and
890 the maximum number of fragments per packet (default: 16).
892 NOTA BENE: since fragments do not contain port numbers, they should be avoided with the
895 Alternatively, direction-based (like
899 ) and source-based (like
901 ) match patterns can be used to select fragments.
903 Usually a simple rule like:
904 .Bd -literal -offset indent
905 # reassemble incoming fragments
906 ipfw add reass all from any to any in
909 is all you need at the beginning of your ruleset.
912 The body of a rule contains zero or more patterns (such as
913 specific source and destination addresses or ports,
914 protocol options, incoming or outgoing interfaces, etc.)
915 that the packet must match in order to be recognised.
916 In general, the patterns are connected by (implicit)
918 operators -- i.e., all must match in order for the
920 Individual patterns can be prefixed by the
922 operator to reverse the result of the match, as in
924 .Dl "ipfw add 100 allow ip from not 1.2.3.4 to any"
926 Additionally, sets of alternative match patterns
928 can be constructed by putting the patterns in
929 lists enclosed between parentheses ( ) or braces { }, and
934 .Dl "ipfw add 100 allow ip from { x or not y or z } to any"
936 Only one level of parentheses is allowed.
937 Beware that most shells have special meanings for parentheses
938 or braces, so it is advisable to put a backslash \\ in front of them
939 to prevent such interpretations.
941 The body of a rule must in general include a source and destination
945 can be used in various places to specify that the content of
946 a required field is irrelevant.
948 The rule body has the following format:
949 .Bd -ragged -offset indent
950 .Op Ar proto Cm from Ar src Cm to Ar dst
954 The first part (proto from src to dst) is for backward
955 compatibility with earlier versions of
959 any match pattern (including MAC headers, IP protocols,
960 addresses and ports) can be specified in the
964 Rule fields have the following meaning:
965 .Bl -tag -width indent
966 .It Ar proto : protocol | Cm { Ar protocol Cm or ... }
967 .It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number
968 An IP protocol specified by number or name
969 (for a complete list see
970 .Pa /etc/protocols ) ,
971 or one of the following keywords:
972 .Bl -tag -width indent
974 Matches IPv4 packets.
976 Matches IPv6 packets.
985 option will be treated as inner protocol.
993 .Cm { Ar protocol Cm or ... }
996 is provided for convenience only but its use is deprecated.
997 .It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports
998 An address (or a list, see below)
999 optionally followed by
1005 with multiple addresses) is provided for convenience only and
1006 its use is discouraged.
1007 .It Ar addr : Oo Cm not Oc Bro
1008 .Bl -tag -width indent
1009 .Cm any | me | me6 |
1010 .Cm table Ns Pq Ar number Ns Op , Ns Ar value
1011 .Ar | addr-list | addr-set
1014 matches any IP address.
1016 matches any IP address configured on an interface in the system.
1018 matches any IPv6 address configured on an interface in the system.
1019 The address list is evaluated at the time the packet is
1021 .It Cm table Ns Pq Ar number Ns Op , Ns Ar value
1022 Matches any IPv4 address for which an entry exists in the lookup table
1024 If an optional 32-bit unsigned
1026 is also specified, an entry will match only if it has this value.
1029 section below for more information on lookup tables.
1031 .It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list
1033 A host or subnet address specified in one of the following ways:
1034 .Bl -tag -width indent
1035 .It Ar numeric-ip | hostname
1036 Matches a single IPv4 address, specified as dotted-quad or a hostname.
1037 Hostnames are resolved at the time the rule is added to the firewall list.
1038 .It Ar addr Ns / Ns Ar masklen
1039 Matches all addresses with base
1041 (specified as an IP address, a network number, or a hostname)
1045 As an example, 1.2.3.4/25 or 1.2.3.0/25 will match
1046 all IP numbers from 1.2.3.0 to 1.2.3.127 .
1047 .It Ar addr Ns : Ns Ar mask
1048 Matches all addresses with base
1050 (specified as an IP address, a network number, or a hostname)
1053 specified as a dotted quad.
1054 As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match
1056 This form is advised only for non-contiguous
1058 It is better to resort to the
1059 .Ar addr Ns / Ns Ar masklen
1060 format for contiguous masks, which is more compact and less
1063 .It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm }
1064 .It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list
1065 Matches all addresses with base address
1067 (specified as an IP address, a network number, or a hostname)
1068 and whose last byte is in the list between braces { } .
1069 Note that there must be no spaces between braces and
1070 numbers (spaces after commas are allowed).
1071 Elements of the list can be specified as single entries
1075 field is used to limit the size of the set of addresses,
1076 and can have any value between 24 and 32.
1078 it will be assumed as 24.
1080 This format is particularly useful to handle sparse address sets
1081 within a single rule.
1082 Because the matching occurs using a
1083 bitmask, it takes constant time and dramatically reduces
1084 the complexity of rulesets.
1086 As an example, an address specified as 1.2.3.4/24{128,35-55,89}
1087 or 1.2.3.0/24{128,35-55,89}
1088 will match the following IP addresses:
1090 1.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 .
1091 .It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list
1093 A host or subnet specified one of the following ways:
1095 .Bl -tag -width indent
1096 .It Ar numeric-ip | hostname
1097 Matches a single IPv6 address as allowed by
1100 Hostnames are resolved at the time the rule is added to the firewall
1102 .It Ar addr Ns / Ns Ar masklen
1103 Matches all IPv6 addresses with base
1105 (specified as allowed by
1113 No support for sets of IPv6 addresses is provided because IPv6 addresses
1114 are typically random past the initial prefix.
1115 .It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports
1116 For protocols which support port numbers (such as TCP and UDP), optional
1118 may be specified as one or more ports or port ranges, separated
1119 by commas but no spaces, and an optional
1124 notation specifies a range of ports (including boundaries).
1128 may be used instead of numeric port values.
1129 The length of the port list is limited to 30 ports or ranges,
1130 though one can specify larger ranges by using an
1134 section of the rule.
1138 can be used to escape the dash
1140 character in a service name (from a shell, the backslash must be
1141 typed twice to avoid the shell itself interpreting it as an escape
1144 .Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any"
1146 Fragmented packets which have a non-zero offset (i.e., not the first
1147 fragment) will never match a rule which has one or more port
1151 option for details on matching fragmented packets.
1153 .Ss RULE OPTIONS (MATCH PATTERNS)
1154 Additional match patterns can be used within
1156 Zero or more of these so-called
1158 can be present in a rule, optionally prefixed by the
1160 operand, and possibly grouped into
1163 The following match patterns can be used (listed in alphabetical order):
1164 .Bl -tag -width indent
1165 .It Cm // this is a comment.
1166 Inserts the specified text as a comment in the rule.
1167 Everything following // is considered as a comment and stored in the rule.
1168 You can have comment-only rules, which are listed as having a
1170 action followed by the comment.
1175 Matches only packets generated by a divert socket.
1176 .It Cm diverted-loopback
1177 Matches only packets coming from a divert socket back into the IP stack
1179 .It Cm diverted-output
1180 Matches only packets going from a divert socket back outward to the IP
1181 stack output for delivery.
1182 .It Cm dst-ip Ar ip-address
1183 Matches IPv4 packets whose destination IP is one of the address(es)
1184 specified as argument.
1185 .It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address
1186 Matches IPv6 packets whose destination IP is one of the address(es)
1187 specified as argument.
1188 .It Cm dst-port Ar ports
1189 Matches IP packets whose destination port is one of the port(s)
1190 specified as argument.
1192 Matches TCP packets that have the RST or ACK bits set.
1193 .It Cm ext6hdr Ar header
1194 Matches IPv6 packets containing the extended header given by
1196 Supported headers are:
1202 any type of Routing Header
1204 Source routing Routing Header Type 0
1206 Mobile IPv6 Routing Header Type 2
1210 IPSec authentication headers
1212 and IPsec encapsulated security payload headers
1214 .It Cm fib Ar fibnum
1215 Matches a packet that has been tagged to use
1216 the given FIB (routing table) number.
1217 .It Cm flow-id Ar labels
1218 Matches IPv6 packets containing any of the flow labels given in
1221 is a comma separated list of numeric flow labels.
1223 Matches packets that are fragments and not the first
1224 fragment of an IP datagram.
1225 Note that these packets will not have
1226 the next protocol header (e.g.\& TCP, UDP) so options that look into
1227 these headers cannot match.
1229 Matches all TCP or UDP packets sent by or received for a
1233 may be specified by name or number.
1234 .It Cm jail Ar prisonID
1235 Matches all TCP or UDP packets sent by or received for the
1236 jail whos prison ID is
1238 .It Cm icmptypes Ar types
1239 Matches ICMP packets whose ICMP type is in the list
1241 The list may be specified as any combination of
1242 individual types (numeric) separated by commas.
1243 .Em Ranges are not allowed .
1244 The supported ICMP types are:
1248 destination unreachable
1256 router advertisement
1260 time-to-live exceeded
1272 address mask request
1274 and address mask reply
1276 .It Cm icmp6types Ar types
1277 Matches ICMP6 packets whose ICMP6 type is in the list of
1279 The list may be specified as any combination of
1280 individual types (numeric) separated by commas.
1281 .Em Ranges are not allowed .
1283 Matches incoming or outgoing packets, respectively.
1287 are mutually exclusive (in fact,
1291 .It Cm ipid Ar id-list
1292 Matches IPv4 packets whose
1294 field has value included in
1296 which is either a single value or a list of values or ranges
1297 specified in the same way as
1299 .It Cm iplen Ar len-list
1300 Matches IP packets whose total length, including header and data, is
1303 which is either a single value or a list of values or ranges
1304 specified in the same way as
1306 .It Cm ipoptions Ar spec
1307 Matches packets whose IPv4 header contains the comma separated list of
1308 options specified in
1310 The supported IP options are:
1313 (strict source route),
1315 (loose source route),
1317 (record packet route) and
1320 The absence of a particular option may be denoted
1323 .It Cm ipprecedence Ar precedence
1324 Matches IPv4 packets whose precedence field is equal to
1327 Matches packets that have IPSEC history associated with them
1328 (i.e., the packet comes encapsulated in IPSEC, the kernel
1329 has IPSEC support and IPSEC_FILTERTUNNEL option, and can correctly
1332 Note that specifying
1334 is different from specifying
1336 as the latter will only look at the specific IP protocol field,
1337 irrespective of IPSEC kernel support and the validity of the IPSEC data.
1339 Further note that this flag is silently ignored in kernels without
1341 It does not affect rule processing when given and the
1342 rules are handled as if with no
1345 .It Cm iptos Ar spec
1346 Matches IPv4 packets whose
1348 field contains the comma separated list of
1349 service types specified in
1351 The supported IP types of service are:
1354 .Pq Dv IPTOS_LOWDELAY ,
1356 .Pq Dv IPTOS_THROUGHPUT ,
1358 .Pq Dv IPTOS_RELIABILITY ,
1360 .Pq Dv IPTOS_MINCOST ,
1362 .Pq Dv IPTOS_ECN_CE .
1363 The absence of a particular type may be denoted
1366 .It Cm ipttl Ar ttl-list
1367 Matches IPv4 packets whose time to live is included in
1369 which is either a single value or a list of values or ranges
1370 specified in the same way as
1372 .It Cm ipversion Ar ver
1373 Matches IP packets whose IP version field is
1376 Upon a match, the firewall will create a dynamic rule, whose
1377 default behaviour is to match bidirectional traffic between
1378 source and destination IP/port using the same protocol.
1379 The rule has a limited lifetime (controlled by a set of
1381 variables), and the lifetime is refreshed every time a matching
1384 Matches only layer2 packets, i.e., those passed to
1386 from ether_demux() and ether_output_frame().
1387 .It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N
1388 The firewall will only allow
1390 connections with the same
1391 set of parameters as specified in the rule.
1393 of source and destination addresses and ports can be
1396 only IPv4 flows are supported.
1397 .It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar N
1398 Search an entry in lookup table
1400 that matches the field specified as argument.
1401 If not found, the match fails.
1402 Otherwise, the match succeeds and
1404 is set to the value extracted from the table.
1406 This option can be useful to quickly dispatch traffic based on
1407 certain packet fields.
1410 section below for more information on lookup tables.
1411 .It Cm { MAC | mac } Ar dst-mac src-mac
1412 Match packets with a given
1416 addresses, specified as the
1418 keyword (matching any MAC address), or six groups of hex digits
1419 separated by colons,
1420 and optionally followed by a mask indicating the significant bits.
1421 The mask may be specified using either of the following methods:
1422 .Bl -enum -width indent
1426 followed by the number of significant bits.
1427 For example, an address with 33 significant bits could be specified as:
1429 .Dl "MAC 10:20:30:40:50:60/33 any"
1434 followed by a bitmask specified as six groups of hex digits separated
1436 For example, an address in which the last 16 bits are significant could
1439 .Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any"
1441 Note that the ampersand character has a special meaning in many shells
1442 and should generally be escaped.
1445 Note that the order of MAC addresses (destination first,
1447 the same as on the wire, but the opposite of the one used for
1449 .It Cm mac-type Ar mac-type
1450 Matches packets whose Ethernet Type field
1451 corresponds to one of those specified as argument.
1453 is specified in the same way as
1455 (i.e., one or more comma-separated single values or ranges).
1456 You can use symbolic names for known values such as
1457 .Em vlan , ipv4, ipv6 .
1458 Values can be entered as decimal or hexadecimal (if prefixed by 0x),
1459 and they are always printed as hexadecimal (unless the
1461 option is used, in which case symbolic resolution will be attempted).
1462 .It Cm proto Ar protocol
1463 Matches packets with the corresponding IP protocol.
1464 .It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar ipno | Ar any
1465 Matches packets received, transmitted or going through,
1466 respectively, the interface specified by exact name
1467 .Ns No ( Ar ifX Ns No ),
1469 .Ns No ( Ar if Ns Ar * Ns No ),
1470 by IP address, or through some interface.
1474 keyword causes the interface to always be checked.
1481 then only the receive or transmit interface (respectively)
1483 By specifying both, it is possible to match packets based on
1484 both receive and transmit interface, e.g.:
1486 .Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1"
1490 interface can be tested on either incoming or outgoing packets,
1493 interface can only be tested on outgoing packets.
1498 is invalid) whenever
1502 A packet might not have a receive or transmit interface: packets
1503 originating from the local host have no receive interface,
1504 while packets destined for the local host have no transmit
1507 Matches TCP packets that have the SYN bit set but no ACK bit.
1508 This is the short form of
1509 .Dq Li tcpflags\ syn,!ack .
1510 .It Cm src-ip Ar ip-address
1511 Matches IPv4 packets whose source IP is one of the address(es)
1512 specified as an argument.
1513 .It Cm src-ip6 Ar ip6-address
1514 Matches IPv6 packets whose source IP is one of the address(es)
1515 specified as an argument.
1516 .It Cm src-port Ar ports
1517 Matches IP packets whose source port is one of the port(s)
1518 specified as argument.
1519 .It Cm tagged Ar tag-list
1520 Matches packets whose tags are included in
1522 which is either a single value or a list of values or ranges
1523 specified in the same way as
1525 Tags can be applied to the packet using
1527 rule action parameter (see it's description for details on tags).
1528 .It Cm tcpack Ar ack
1530 Match if the TCP header acknowledgment number field is set to
1532 .It Cm tcpdatalen Ar tcpdatalen-list
1533 Matches TCP packets whose length of TCP data is
1534 .Ar tcpdatalen-list ,
1535 which is either a single value or a list of values or ranges
1536 specified in the same way as
1538 .It Cm tcpflags Ar spec
1540 Match if the TCP header contains the comma separated list of
1543 The supported TCP flags are:
1552 The absence of a particular flag may be denoted
1555 A rule which contains a
1557 specification can never match a fragmented packet which has
1561 option for details on matching fragmented packets.
1562 .It Cm tcpseq Ar seq
1564 Match if the TCP header sequence number field is set to
1566 .It Cm tcpwin Ar win
1568 Match if the TCP header window field is set to
1570 .It Cm tcpoptions Ar spec
1572 Match if the TCP header contains the comma separated list of
1573 options specified in
1575 The supported TCP options are:
1578 (maximum segment size),
1580 (tcp window advertisement),
1584 (rfc1323 timestamp) and
1586 (rfc1644 t/tcp connection count).
1587 The absence of a particular option may be denoted
1591 Match all TCP or UDP packets sent by or received for a
1595 may be matched by name or identification number.
1597 For incoming packets,
1598 a routing table lookup is done on the packet's source address.
1599 If the interface on which the packet entered the system matches the
1600 outgoing interface for the route,
1602 If the interfaces do not match up,
1603 the packet does not match.
1604 All outgoing packets or packets with no incoming interface match.
1606 The name and functionality of the option is intentionally similar to
1607 the Cisco IOS command:
1609 .Dl ip verify unicast reverse-path
1611 This option can be used to make anti-spoofing rules to reject all
1612 packets with source addresses not from this interface.
1616 For incoming packets,
1617 a routing table lookup is done on the packet's source address.
1618 If a route to the source address exists, but not the default route
1619 or a blackhole/reject route, the packet matches.
1620 Otherwise, the packet does not match.
1621 All outgoing packets match.
1623 The name and functionality of the option is intentionally similar to
1624 the Cisco IOS command:
1626 .Dl ip verify unicast source reachable-via any
1628 This option can be used to make anti-spoofing rules to reject all
1629 packets whose source address is unreachable.
1631 For incoming packets, the packet's source address is checked if it
1632 belongs to a directly connected network.
1633 If the network is directly connected, then the interface the packet
1634 came on in is compared to the interface the network is connected to.
1635 When incoming interface and directly connected interface are not the
1636 same, the packet does not match.
1637 Otherwise, the packet does match.
1638 All outgoing packets match.
1640 This option can be used to make anti-spoofing rules to reject all
1641 packets that pretend to be from a directly connected network but do
1642 not come in through that interface.
1643 This option is similar to but more restricted than
1645 because it engages only on packets with source addresses of directly
1646 connected networks instead of all source addresses.
1649 Lookup tables are useful to handle large sparse sets of
1650 addresses or other search keys (e.g. ports, jail IDs).
1651 In the rest of this section we will use the term ``address''
1652 to mean any unsigned value of up to 32-bit.
1653 There may be up to 128 different lookup tables, numbered 0 to 127.
1655 Each entry is represented by an
1656 .Ar addr Ns Op / Ns Ar masklen
1657 and will match all addresses with base
1659 (specified as an IP address, a hostname or an unsigned integer)
1665 is not specified, it defaults to 32.
1666 When looking up an IP address in a table, the most specific
1668 Associated with each entry is a 32-bit unsigned
1670 which can optionally be checked by a rule matching code.
1671 When adding an entry, if
1673 is not specified, it defaults to 0.
1675 An entry can be added to a table
1677 or removed from a table
1679 A table can be examined
1684 Internally, each table is stored in a Radix tree, the same way as
1685 the routing table (see
1688 Lookup tables currently support only ports, jail IDs and IPv4 addresses.
1692 feature provides the ability to use a value, looked up in the table, as
1693 the argument for a rule action, action parameter or rule option.
1694 This can significantly reduce number of rules in some configurations.
1695 If two tables are used in a rule, the result of the second (destination)
1699 argument can be used with the following actions:
1700 .Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto
1708 it is possible to supply table entries with values
1709 that are in the form of IP addresses or hostnames.
1712 Section for example usage of tables and the tablearg keyword.
1716 action, the user should be aware that the code will walk the ruleset
1717 up to a rule equal to, or past, the given number, and should therefore try keep the
1718 ruleset compact between the skipto and the target rules.
1720 Each rule belongs to one of 32 different
1723 Set 31 is reserved for the default rule.
1725 By default, rules are put in set 0, unless you use the
1727 attribute when entering a new rule.
1728 Sets can be individually and atomically enabled or disabled,
1729 so this mechanism permits an easy way to store multiple configurations
1730 of the firewall and quickly (and atomically) switch between them.
1731 The command to enable/disable sets is
1732 .Bd -ragged -offset indent
1734 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
1741 sections can be specified.
1742 Command execution is atomic on all the sets specified in the command.
1743 By default, all sets are enabled.
1745 When you disable a set, its rules behave as if they do not exist
1746 in the firewall configuration, with only one exception:
1747 .Bd -ragged -offset indent
1748 dynamic rules created from a rule before it had been disabled
1749 will still be active until they expire.
1751 dynamic rules you have to explicitly delete the parent rule
1752 which generated them.
1755 The set number of rules can be changed with the command
1756 .Bd -ragged -offset indent
1759 .Brq Cm rule Ar rule-number | old-set
1763 Also, you can atomically swap two rulesets with the command
1764 .Bd -ragged -offset indent
1766 .Cm set swap Ar first-set second-set
1771 Section on some possible uses of sets of rules.
1772 .Sh STATEFUL FIREWALL
1773 Stateful operation is a way for the firewall to dynamically
1774 create rules for specific flows when packets that
1775 match a given pattern are detected.
1776 Support for stateful
1777 operation comes through the
1778 .Cm check-state , keep-state
1784 Dynamic rules are created when a packet matches a
1788 rule, causing the creation of a
1790 rule which will match all and only packets with
1794 .Em src-ip/src-port dst-ip/dst-port
1799 are used here only to denote the initial match addresses, but they
1800 are completely equivalent afterwards).
1801 Dynamic rules will be checked at the first
1802 .Cm check-state, keep-state
1805 occurrence, and the action performed upon a match will be the same
1806 as in the parent rule.
1808 Note that no additional attributes other than protocol and IP addresses
1809 and ports are checked on dynamic rules.
1811 The typical use of dynamic rules is to keep a closed firewall configuration,
1812 but let the first TCP SYN packet from the inside network install a
1813 dynamic rule for the flow so that packets belonging to that session
1814 will be allowed through the firewall:
1816 .Dl "ipfw add check-state"
1817 .Dl "ipfw add allow tcp from my-subnet to any setup keep-state"
1818 .Dl "ipfw add deny tcp from any to any"
1820 A similar approach can be used for UDP, where an UDP packet coming
1821 from the inside will install a dynamic rule to let the response through
1824 .Dl "ipfw add check-state"
1825 .Dl "ipfw add allow udp from my-subnet to any keep-state"
1826 .Dl "ipfw add deny udp from any to any"
1828 Dynamic rules expire after some time, which depends on the status
1829 of the flow and the setting of some
1833 .Sx SYSCTL VARIABLES
1835 For TCP sessions, dynamic rules can be instructed to periodically
1836 send keepalive packets to refresh the state of the rule when it is
1841 for more examples on how to use dynamic rules.
1842 .Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
1844 is also the user interface for the
1846 traffic shaper, packet scheduler and network emulator, a subsystem that
1847 can artificially queue, delay or drop packets
1848 emulating the behaviour of certain network links
1849 or queueing systems.
1852 operates by first using the firewall to select packets
1853 using any match pattern that can be used in
1856 Matching packets are then passed to either of two
1857 different objects, which implement the traffic regulation:
1858 .Bl -hang -offset XXXX
1864 with given bandwidth and propagation delay,
1865 driven by a FIFO scheduler and a single queue with programmable
1866 queue size and packet loss rate.
1867 Packets are appended to the queue as they come out from
1869 and then transferred in FIFO order to the link at the desired rate.
1873 is an abstraction used to implement packet scheduling
1874 using one of several packet scheduling algorithms.
1877 are first grouped into flows according to a mask on the 5-tuple.
1878 Flows are then passed to the scheduler associated to the
1880 and each flow uses scheduling parameters (weight and others)
1881 as configured in the
1884 A scheduler in turn is connected to an emulated link,
1885 and arbitrates the link's bandwidth among backlogged flows according to
1886 weights and to the features of the scheduling algorithm in use.
1891 can be used to set hard limits to the bandwidth that a flow can use, whereas
1893 can be used to determine how different flows share the available bandwidth.
1895 A graphical representation of the binding of queues,
1896 flows, schedulers and links is below.
1897 .Bd -literal -offset indent
1898 (flow_mask|sched_mask) sched_mask
1899 +---------+ weight Wx +-------------+
1900 | |->-[flow]-->--| |-+
1901 -->--| QUEUE x | ... | | |
1902 | |->-[flow]-->--| SCHEDuler N | |
1904 ... | +--[LINK N]-->--
1905 +---------+ weight Wy | | +--[LINK N]-->--
1906 | |->-[flow]-->--| | |
1907 -->--| QUEUE y | ... | | |
1908 | |->-[flow]-->--| | |
1909 +---------+ +-------------+ |
1912 It is important to understand the role of the SCHED_MASK
1913 and FLOW_MASK, which are configured through the commands
1914 .Dl "ipfw sched N config mask SCHED_MASK ..."
1916 .Dl "ipfw queue X config mask FLOW_MASK ..." .
1918 The SCHED_MASK is used to assign flows to one or more
1919 scheduler instances, one for each
1920 value of the packet's 5-tuple after applying SCHED_MASK.
1921 As an example, using ``src-ip 0xffffff00'' creates one instance
1922 for each /24 destination subnet.
1924 The FLOW_MASK, together with the SCHED_MASK, is used to split
1925 packets into flows. As an example, using
1926 ``src-ip 0x000000ff''
1927 together with the previous SCHED_MASK makes a flow for
1928 each individual source address. In turn, flows for each /24
1929 subnet will be sent to the same scheduler instance.
1931 The above diagram holds even for the
1933 case, with the only restriction that a
1935 only supports a SCHED_MASK, and forces the use of a FIFO
1936 scheduler (these are for backward compatibility reasons;
1937 in fact, internally, a
1939 pipe is implemented exactly as above).
1941 There are two modes of
1949 mode tries to emulate a real link: the
1951 scheduler ensures that the packet will not leave the pipe faster than it
1952 would on the real link with a given bandwidth.
1955 mode allows certain packets to bypass the
1957 scheduler (if packet flow does not exceed pipe's bandwidth).
1958 This is the reason why the
1960 mode requires less CPU cycles per packet (on average) and packet latency
1961 can be significantly lower in comparison to a real link with the same
1967 mode can be enabled by setting the
1968 .Va net.inet.ip.dummynet.io_fast
1970 variable to a non-zero value.
1972 .Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION
1978 configuration commands are the following:
1979 .Bd -ragged -offset indent
1980 .Cm pipe Ar number Cm config Ar pipe-configuration
1982 .Cm queue Ar number Cm config Ar queue-configuration
1984 .Cm sched Ar number Cm config Ar sched-configuration
1987 The following parameters can be configured for a pipe:
1989 .Bl -tag -width indent -compact
1990 .It Cm bw Ar bandwidth | device
1991 Bandwidth, measured in
1994 .Brq Cm bit/s | Byte/s .
1997 A value of 0 (default) means unlimited bandwidth.
1998 The unit must immediately follow the number, as in
2000 .Dl "ipfw pipe 1 config bw 300Kbit/s"
2002 If a device name is specified instead of a numeric value, as in
2004 .Dl "ipfw pipe 1 config bw tun0"
2006 then the transmit clock is supplied by the specified device.
2007 At the moment only the
2009 device supports this
2010 functionality, for use in conjunction with
2013 .It Cm delay Ar ms-delay
2014 Propagation delay, measured in milliseconds.
2015 The value is rounded to the next multiple of the clock tick
2016 (typically 10ms, but it is a good practice to run kernels
2018 .Dq "options HZ=1000"
2020 the granularity to 1ms or less).
2021 The default value is 0, meaning no delay.
2023 .It Cm burst Ar size
2024 If the data to be sent exceeds the pipe's bandwidth limit
2025 (and the pipe was previously idle), up to
2027 bytes of data are allowed to bypass the
2029 scheduler, and will be sent as fast as the physical link allows.
2030 Any additional data will be transmitted at the rate specified
2034 The burst size depends on how long the pipe has been idle;
2035 the effective burst size is calculated as follows:
2042 .It Cm profile Ar filename
2043 A file specifying the additional overhead incurred in the transmission
2044 of a packet on the link.
2046 Some link types introduce extra delays in the transmission
2047 of a packet, e.g. because of MAC level framing, contention on
2048 the use of the channel, MAC level retransmissions and so on.
2049 From our point of view, the channel is effectively unavailable
2050 for this extra time, which is constant or variable depending
2051 on the link type. Additionally, packets may be dropped after this
2052 time (e.g. on a wireless link after too many retransmissions).
2053 We can model the additional delay with an empirical curve
2054 that represents its distribution.
2055 .Bd -literal -offset indent
2056 cumulative probability
2066 +-------*------------------->
2069 The empirical curve may have both vertical and horizontal lines.
2070 Vertical lines represent constant delay for a range of
2072 Horizontal lines correspond to a discontinuity in the delay
2073 distribution: the pipe will use the largest delay for a
2076 The file format is the following, with whitespace acting as
2077 a separator and '#' indicating the beginning a comment:
2078 .Bl -tag -width indent
2079 .It Cm name Ar identifier
2080 optional name (listed by "ipfw pipe show")
2081 to identify the delay distribution;
2083 the bandwidth used for the pipe.
2084 If not specified here, it must be present
2085 explicitly as a configuration parameter for the pipe;
2086 .It Cm loss-level Ar L
2087 the probability above which packets are lost.
2088 (0.0 <= L <= 1.0, default 1.0 i.e. no loss);
2090 the number of samples used in the internal
2091 representation of the curve (2..1024; default 100);
2092 .It Cm "delay prob" | "prob delay"
2093 One of these two lines is mandatory and defines
2094 the format of the following lines with data points.
2096 2 or more lines representing points in the curve,
2097 with either delay or probability first, according
2098 to the chosen format.
2099 The unit for delay is milliseconds.
2100 Data points do not need to be sorted.
2101 Also, the number of actual lines can be different
2102 from the value of the "samples" parameter:
2104 utility will sort and interpolate
2105 the curve as needed.
2108 Example of a profile file:
2109 .Bd -literal -offset indent
2114 0 200 # minimum overhead is 200ms
2120 #configuration file end
2124 The following parameters can be configured for a queue:
2126 .Bl -tag -width indent -compact
2127 .It Cm pipe Ar pipe_nr
2128 Connects a queue to the specified pipe.
2129 Multiple queues (with the same or different weights) can be connected to
2130 the same pipe, which specifies the aggregate rate for the set of queues.
2132 .It Cm weight Ar weight
2133 Specifies the weight to be used for flows matching this queue.
2134 The weight must be in the range 1..100, and defaults to 1.
2137 The following parameters can be configured for a scheduler:
2139 .Bl -tag -width indent -compact
2140 .It Cm type Ar {fifo | wf2qp | rr | qfq}
2141 specifies the scheduling algorithm to use.
2142 .Bl -tag -width indent -compact
2144 is just a FIFO scheduler (which means that all packets
2145 are stored in the same queue as they arrive to the scheduler).
2146 FIFO has O(1) per-packet time complexity, with very low
2147 constants (estimate 60-80ns on a 2Ghz desktop machine)
2148 but gives no service guarantees.
2150 implements the WF2Q+ algorithm, which is a Weighted Fair Queueing
2151 algorithm which permits flows to share bandwidth according to
2152 their weights. Note that weights are not priorities; even a flow
2153 with a minuscule weight will never starve.
2154 WF2Q+ has O(log N) per-packet processing cost, where N is the number
2155 of flows, and is the default algorithm used by previous versions
2158 implements the Deficit Round Robin algorithm, which has O(1) processing
2159 costs (roughly, 100-150ns per packet)
2160 and permits bandwidth allocation according to weights, but
2161 with poor service guarantees.
2163 implements the QFQ algorithm, which is a very fast variant of
2164 WF2Q+, with similar service guarantees and O(1) processing
2165 costs (roughly, 200-250ns per packet).
2169 In addition to the type, all parameters allowed for a pipe can also
2170 be specified for a scheduler.
2172 Finally, the following parameters can be configured for both
2175 .Bl -tag -width XXXX -compact
2177 .It Cm buckets Ar hash-table-size
2178 Specifies the size of the hash table used for storing the
2180 Default value is 64 controlled by the
2183 .Va net.inet.ip.dummynet.hash_size ,
2184 allowed range is 16 to 65536.
2186 .It Cm mask Ar mask-specifier
2187 Packets sent to a given pipe or queue by an
2189 rule can be further classified into multiple flows, each of which is then
2193 A flow identifier is constructed by masking the IP addresses,
2194 ports and protocol types as specified with the
2196 options in the configuration of the pipe or queue.
2197 For each different flow identifier, a new pipe or queue is created
2198 with the same parameters as the original object, and matching packets
2203 are used, each flow will get the same bandwidth as defined by the pipe,
2206 are used, each flow will share the parent's pipe bandwidth evenly
2207 with other flows generated by the same queue (note that other queues
2208 with different weights might be connected to the same pipe).
2210 Available mask specifiers are a combination of one or more of the following:
2212 .Cm dst-ip Ar mask ,
2213 .Cm dst-ip6 Ar mask ,
2214 .Cm src-ip Ar mask ,
2215 .Cm src-ip6 Ar mask ,
2216 .Cm dst-port Ar mask ,
2217 .Cm src-port Ar mask ,
2218 .Cm flow-id Ar mask ,
2223 where the latter means all bits in all fields are significant.
2226 When a packet is dropped by a
2228 queue or pipe, the error
2229 is normally reported to the caller routine in the kernel, in the
2230 same way as it happens when a device queue fills up.
2232 option reports the packet as successfully delivered, which can be
2233 needed for some experimental setups where you want to simulate
2234 loss or congestion at a remote router.
2236 .It Cm plr Ar packet-loss-rate
2239 .Ar packet-loss-rate
2240 is a floating-point number between 0 and 1, with 0 meaning no
2241 loss, 1 meaning 100% loss.
2242 The loss rate is internally represented on 31 bits.
2244 .It Cm queue Brq Ar slots | size Ns Cm Kbytes
2249 Default value is 50 slots, which
2250 is the typical queue size for Ethernet devices.
2251 Note that for slow speed links you should keep the queue
2252 size short or your traffic might be affected by a significant
2254 E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit
2255 or 20s of queue on a 30Kbit/s pipe.
2256 Even worse effects can result if you get packets from an
2257 interface with a much larger MTU, e.g.\& the loopback interface
2258 with its 16KB packets.
2262 .Em net.inet.ip.dummynet.pipe_byte_limit
2264 .Em net.inet.ip.dummynet.pipe_slot_limit
2265 control the maximum lengths that can be specified.
2267 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
2268 Make use of the RED (Random Early Detection) queue management algorithm.
2273 point numbers between 0 and 1 (0 not included), while
2277 are integer numbers specifying thresholds for queue management
2278 (thresholds are computed in bytes if the queue has been defined
2279 in bytes, in slots otherwise).
2282 also supports the gentle RED variant (gred).
2285 variables can be used to control the RED behaviour:
2286 .Bl -tag -width indent
2287 .It Va net.inet.ip.dummynet.red_lookup_depth
2288 specifies the accuracy in computing the average queue
2289 when the link is idle (defaults to 256, must be greater than zero)
2290 .It Va net.inet.ip.dummynet.red_avg_pkt_size
2291 specifies the expected average packet size (defaults to 512, must be
2293 .It Va net.inet.ip.dummynet.red_max_pkt_size
2294 specifies the expected maximum packet size, only used when queue
2295 thresholds are in bytes (defaults to 1500, must be greater than zero).
2299 When used with IPv6 data,
2301 currently has several limitations.
2302 Information necessary to route link-local packets to an
2303 interface is not available after processing by
2305 so those packets are dropped in the output path.
2306 Care should be taken to ensure that link-local packets are not passed to
2309 Here are some important points to consider when designing your
2313 Remember that you filter both packets going
2317 Most connections need packets going in both directions.
2319 Remember to test very carefully.
2320 It is a good idea to be near the console when doing this.
2321 If you cannot be near the console,
2322 use an auto-recovery script such as the one in
2323 .Pa /usr/share/examples/ipfw/change_rules.sh .
2325 Do not forget the loopback interface.
2330 There are circumstances where fragmented datagrams are unconditionally
2332 TCP packets are dropped if they do not contain at least 20 bytes of
2333 TCP header, UDP packets are dropped if they do not contain a full 8
2334 byte UDP header, and ICMP packets are dropped if they do not contain
2335 4 bytes of ICMP header, enough to specify the ICMP type, code, and
2337 These packets are simply logged as
2339 since there may not be enough good data in the packet to produce a
2340 meaningful log entry.
2342 Another type of packet is unconditionally dropped, a TCP packet with a
2343 fragment offset of one.
2344 This is a valid packet, but it only has one use, to try
2345 to circumvent firewalls.
2346 When logging is enabled, these packets are
2347 reported as being dropped by rule -1.
2349 If you are logged in over a network, loading the
2353 is probably not as straightforward as you would think.
2354 The following command line is recommended:
2355 .Bd -literal -offset indent
2357 ipfw add 32000 allow ip from any to any
2360 Along the same lines, doing an
2361 .Bd -literal -offset indent
2365 in similar surroundings is also a bad idea.
2369 filter list may not be modified if the system security level
2370 is set to 3 or higher
2373 for information on system security levels).
2375 .Sh PACKET DIVERSION
2378 socket bound to the specified port will receive all packets
2379 diverted to that port.
2380 If no socket is bound to the destination port, or if the divert module is
2381 not loaded, or if the kernel was not compiled with divert socket support,
2382 the packets are dropped.
2383 .Sh NETWORK ADDRESS TRANSLATION (NAT)
2386 support in-kernel NAT using the kernel version of
2389 The nat configuration command is the following:
2390 .Bd -ragged -offset indent
2395 .Ar nat-configuration
2399 The following parameters can be configured:
2400 .Bl -tag -width indent
2401 .It Cm ip Ar ip_address
2402 Define an ip address to use for aliasing.
2404 Use ip address of NIC for aliasing, dynamically changing
2405 it if NIC's ip address changes.
2407 Enable logging on this nat instance.
2409 Deny any incoming connection from outside world.
2411 Try to leave the alias port numbers unchanged from
2412 the actual local port numbers.
2414 Traffic on the local network not originating from an
2415 unregistered address spaces will be ignored.
2417 Reset table of the packet aliasing engine on address change.
2419 Reverse the way libalias handles aliasing.
2421 Obey transparent proxy rules only, packet aliasing is not performed.
2424 To let the packet continue after being (de)aliased, set the sysctl variable
2425 .Va net.inet.ip.fw.one_pass
2427 For more information about aliasing modes, refer to
2431 for some examples about nat usage.
2432 .Ss REDIRECT AND LSNAT SUPPORT IN IPFW
2433 Redirect and LSNAT support follow closely the syntax used in
2437 for some examples on how to do redirect and lsnat.
2438 .Ss SCTP NAT SUPPORT
2439 SCTP nat can be configured in a similar manner to TCP through the
2442 The main difference is that
2444 does not do port translation.
2445 Since the local and global side ports will be the same,
2446 there is no need to specify both.
2447 Ports are redirected as follows:
2448 .Bd -ragged -offset indent
2454 .Cm redirect_port sctp
2455 .Ar ip_address [,addr_list] {[port | port-port] [,ports]}
2461 configuration can be done in real-time through the
2464 All may be changed dynamically, though the hash_table size will only
2469 .Sx SYSCTL VARIABLES
2471 .Sh SYSCTL VARIABLES
2474 variables controls the behaviour of the firewall and
2476 .Pq Nm dummynet , bridge , sctp nat .
2477 These are shown below together with their default value
2478 (but always check with the
2480 command what value is actually in use) and meaning:
2481 .Bl -tag -width indent
2482 .It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0
2485 responds to receipt of global OOTB ASCONF-AddIP:
2486 .Bl -tag -width indent
2488 No response (unless a partially matching association exists -
2489 ports and vtags match but global address does not)
2492 will accept and process all OOTB global AddIP messages.
2495 Option 1 should never be selected as this forms a security risk.
2497 establish multiple fake associations by sending AddIP messages.
2498 .It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5
2499 Defines the maximum number of chunks in an SCTP packet that will be parsed for a
2500 packet that matches an existing association.
2501 This value is enforced to be greater or equal than
2502 .Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit .
2504 a DoS risk yet setting too low a value may result in important control chunks in
2505 the packet not being located and parsed.
2506 .It Va net.inet.ip.alias.sctp.error_on_ootb: No 1
2509 responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets.
2510 An OOTB packet is a packet that arrives with no existing association
2513 and is not an INIT or ASCONF-AddIP packet:
2514 .Bl -tag -width indent
2516 ErrorM is never sent in response to OOTB packets.
2518 ErrorM is only sent to OOTB packets received on the local side.
2520 ErrorM is sent to the local side and on the global side ONLY if there is a
2521 partial match (ports and vtags match but the source global IP does not).
2522 This value is only useful if the
2524 is tracking global IP addresses.
2526 ErrorM is sent in response to all OOTB packets on both the local and global side
2530 At the moment the default is 0, since the ErrorM packet is not yet
2531 supported by most SCTP stacks.
2532 When it is supported, and if not tracking
2533 global addresses, we recommend setting this value to 1 to allow
2534 multi-homed local hosts to function with the
2536 To track global addresses, we recommend setting this value to 2 to
2537 allow global hosts to be informed when they need to (re)send an
2539 Value 3 should never be chosen (except for debugging) as the
2541 will respond to all OOTB global packets (a DoS risk).
2542 .It Va net.inet.ip.alias.sctp.hashtable_size: No 2003
2543 Size of hash tables used for
2545 lookups (100 < prime_number > 1000001).
2548 size for any future created
2550 instance and therefore must be set prior to creating a
2553 The table sizes may be changed to suit specific needs.
2554 If there will be few
2555 concurrent associations, and memory is scarce, you may make these smaller.
2556 If there will be many thousands (or millions) of concurrent associations, you
2557 should make these larger.
2558 A prime number is best for the table size.
2560 update function will adjust your input value to the next highest prime number.
2561 .It Va net.inet.ip.alias.sctp.holddown_time: No 0
2562 Hold association in table for this many seconds after receiving a
2564 This allows endpoints to correct shutdown gracefully if a
2565 shutdown_complete is lost and retransmissions are required.
2566 .It Va net.inet.ip.alias.sctp.init_timer: No 15
2567 Timeout value while waiting for (INIT-ACK|AddIP-ACK).
2568 This value cannot be 0.
2569 .It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2
2570 Defines the maximum number of chunks in an SCTP packet that will be parsed when
2571 no existing association exists that matches that packet.
2573 will only be an INIT or ASCONF-AddIP packet.
2574 A higher value may become a DoS
2575 risk as malformed packets can consume processing resources.
2576 .It Va net.inet.ip.alias.sctp.param_proc_limit: No 25
2577 Defines the maximum number of parameters within a chunk that will be parsed in a
2579 As for other similar sysctl variables, larger values pose a DoS risk.
2580 .It Va net.inet.ip.alias.sctp.log_level: No 0
2581 Level of detail in the system log messages (0 \- minimal, 1 \- event,
2582 2 \- info, 3 \- detail, 4 \- debug, 5 \- max debug). May be a good
2583 option in high loss environments.
2584 .It Va net.inet.ip.alias.sctp.shutdown_time: No 15
2585 Timeout value while waiting for SHUTDOWN-COMPLETE.
2586 This value cannot be 0.
2587 .It Va net.inet.ip.alias.sctp.track_global_addresses: No 0
2588 Enables/disables global IP address tracking within the
2591 upper limit on the number of addresses tracked for each association:
2592 .Bl -tag -width indent
2594 Global tracking is disabled
2596 Enables tracking, the maximum number of addresses tracked for each
2597 association is limited to this value
2600 This variable is fully dynamic, the new value will be adopted for all newly
2601 arriving associations, existing associations are treated as they were previously.
2602 Global tracking will decrease the number of collisions within the
2605 of increased processing load, memory usage, complexity, and possible
2608 problems in complex networks with multiple
2610 We recommend not tracking
2611 global IP addresses, this will still result in a fully functional
2613 .It Va net.inet.ip.alias.sctp.up_timer: No 300
2614 Timeout value to keep an association up with no traffic.
2615 This value cannot be 0.
2616 .It Va net.inet.ip.dummynet.expire : No 1
2617 Lazily delete dynamic pipes/queue once they have no pending traffic.
2618 You can disable this by setting the variable to 0, in which case
2619 the pipes/queues will only be deleted when the threshold is reached.
2620 .It Va net.inet.ip.dummynet.hash_size : No 64
2621 Default size of the hash table used for dynamic pipes/queues.
2622 This value is used when no
2624 option is specified when configuring a pipe/queue.
2625 .It Va net.inet.ip.dummynet.io_fast : No 0
2626 If set to a non-zero value,
2631 operation (see above) is enabled.
2632 .It Va net.inet.ip.dummynet.io_pkt
2633 Number of packets passed to
2635 .It Va net.inet.ip.dummynet.io_pkt_drop
2636 Number of packets dropped by
2638 .It Va net.inet.ip.dummynet.io_pkt_fast
2639 Number of packets bypassed by the
2642 .It Va net.inet.ip.dummynet.max_chain_len : No 16
2643 Target value for the maximum number of pipes/queues in a hash bucket.
2645 .Cm max_chain_len*hash_size
2646 is used to determine the threshold over which empty pipes/queues
2647 will be expired even when
2648 .Cm net.inet.ip.dummynet.expire=0 .
2649 .It Va net.inet.ip.dummynet.red_lookup_depth : No 256
2650 .It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512
2651 .It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500
2652 Parameters used in the computations of the drop probability
2653 for the RED algorithm.
2654 .It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576
2655 .It Va net.inet.ip.dummynet.pipe_slot_limit : No 100
2656 The maximum queue size that can be specified in bytes or packets.
2657 These limits prevent accidental exhaustion of resources such as mbufs.
2658 If you raise these limits,
2659 you should make sure the system is configured so that sufficient resources
2661 .It Va net.inet.ip.fw.autoinc_step : No 100
2662 Delta between rule numbers when auto-generating them.
2663 The value must be in the range 1..1000.
2664 .It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets
2665 The current number of buckets in the hash table for dynamic rules
2667 .It Va net.inet.ip.fw.debug : No 1
2668 Controls debugging messages produced by
2670 .It Va net.inet.ip.fw.default_rule : No 65535
2671 The default rule number (read-only).
2673 .Nm , the default rule is the last one, so its number
2674 can also serve as the highest number allowed for a rule.
2675 .It Va net.inet.ip.fw.dyn_buckets : No 256
2676 The number of buckets in the hash table for dynamic rules.
2677 Must be a power of 2, up to 65536.
2678 It only takes effect when all dynamic rules have expired, so you
2679 are advised to use a
2681 command to make sure that the hash table is resized.
2682 .It Va net.inet.ip.fw.dyn_count : No 3
2683 Current number of dynamic rules
2685 .It Va net.inet.ip.fw.dyn_keepalive : No 1
2686 Enables generation of keepalive packets for
2688 rules on TCP sessions.
2689 A keepalive is generated to both
2690 sides of the connection every 5 seconds for the last 20
2691 seconds of the lifetime of the rule.
2692 .It Va net.inet.ip.fw.dyn_max : No 8192
2693 Maximum number of dynamic rules.
2694 When you hit this limit, no more dynamic rules can be
2695 installed until old ones expire.
2696 .It Va net.inet.ip.fw.dyn_ack_lifetime : No 300
2697 .It Va net.inet.ip.fw.dyn_syn_lifetime : No 20
2698 .It Va net.inet.ip.fw.dyn_fin_lifetime : No 1
2699 .It Va net.inet.ip.fw.dyn_rst_lifetime : No 1
2700 .It Va net.inet.ip.fw.dyn_udp_lifetime : No 5
2701 .It Va net.inet.ip.fw.dyn_short_lifetime : No 30
2702 These variables control the lifetime, in seconds, of dynamic
2704 Upon the initial SYN exchange the lifetime is kept short,
2705 then increased after both SYN have been seen, then decreased
2706 again during the final FIN exchange or when a RST is received.
2708 .Em dyn_fin_lifetime
2710 .Em dyn_rst_lifetime
2711 must be strictly lower than 5 seconds, the period of
2712 repetition of keepalives.
2713 The firewall enforces that.
2714 .It Va net.inet.ip.fw.enable : No 1
2715 Enables the firewall.
2716 Setting this variable to 0 lets you run your machine without
2717 firewall even if compiled in.
2718 .It Va net.inet6.ip6.fw.enable : No 1
2719 provides the same functionality as above for the IPv6 case.
2720 .It Va net.inet.ip.fw.one_pass : No 1
2721 When set, the packet exiting from the
2725 node is not passed though the firewall again.
2726 Otherwise, after an action, the packet is
2727 reinjected into the firewall at the next rule.
2728 .It Va net.inet.ip.fw.tables_max : No 128
2729 Maximum number of tables (read-only).
2730 .It Va net.inet.ip.fw.verbose : No 1
2731 Enables verbose messages.
2732 .It Va net.inet.ip.fw.verbose_limit : No 0
2733 Limits the number of messages produced by a verbose firewall.
2734 .It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1
2735 If enabled packets with unknown IPv6 Extension Headers will be denied.
2736 .It Va net.link.ether.ipfw : No 0
2737 Controls whether layer-2 packets are passed to
2740 .It Va net.link.bridge.ipfw : No 0
2741 Controls whether bridged packets are passed to
2747 There are far too many possible uses of
2749 so this Section will only give a small set of examples.
2751 .Ss BASIC PACKET FILTERING
2752 This command adds an entry which denies all tcp packets from
2753 .Em cracker.evil.org
2754 to the telnet port of
2756 from being forwarded by the host:
2758 .Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet"
2760 This one disallows any connection from the entire cracker's
2763 .Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org"
2765 A first and efficient way to limit access (not using dynamic rules)
2766 is the use of the following rules:
2768 .Dl "ipfw add allow tcp from any to any established"
2769 .Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup"
2770 .Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup"
2772 .Dl "ipfw add deny tcp from any to any"
2774 The first rule will be a quick match for normal TCP packets,
2775 but it will not match the initial SYN packet, which will be
2778 rules only for selected source/destination pairs.
2779 All other SYN packets will be rejected by the final
2783 If you administer one or more subnets, you can take advantage
2784 of the address sets and or-blocks and write extremely
2785 compact rulesets which selectively enable services to blocks
2786 of clients, as below:
2788 .Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q"
2789 .Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q"
2791 .Dl "ipfw add allow ip from ${goodguys} to any"
2792 .Dl "ipfw add deny ip from ${badguys} to any"
2793 .Dl "... normal policies ..."
2797 option could be used to do automated anti-spoofing by adding the
2798 following to the top of a ruleset:
2800 .Dl "ipfw add deny ip from any to any not verrevpath in"
2802 This rule drops all incoming packets that appear to be coming to the
2803 system on the wrong interface.
2804 For example, a packet with a source
2805 address belonging to a host on a protected internal network would be
2806 dropped if it tried to enter the system from an external interface.
2810 option could be used to do similar but more restricted anti-spoofing
2811 by adding the following to the top of a ruleset:
2813 .Dl "ipfw add deny ip from any to any not antispoof in"
2815 This rule drops all incoming packets that appear to be coming from another
2816 directly connected system but on the wrong interface.
2817 For example, a packet with a source address of
2818 .Li 192.168.0.0/24 ,
2825 In order to protect a site from flood attacks involving fake
2826 TCP packets, it is safer to use dynamic rules:
2828 .Dl "ipfw add check-state"
2829 .Dl "ipfw add deny tcp from any to any established"
2830 .Dl "ipfw add allow tcp from my-net to any setup keep-state"
2832 This will let the firewall install dynamic rules only for
2833 those connection which start with a regular SYN packet coming
2834 from the inside of our network.
2835 Dynamic rules are checked when encountering the first
2842 rule should usually be placed near the beginning of the
2843 ruleset to minimize the amount of work scanning the ruleset.
2844 Your mileage may vary.
2846 To limit the number of connections a user can open
2847 you can use the following type of rules:
2849 .Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10"
2850 .Dl "ipfw add allow tcp from any to me setup limit src-addr 4"
2852 The former (assuming it runs on a gateway) will allow each host
2853 on a /24 network to open at most 10 TCP connections.
2854 The latter can be placed on a server to make sure that a single
2855 client does not use more than 4 simultaneous connections.
2858 stateful rules can be subject to denial-of-service attacks
2859 by a SYN-flood which opens a huge number of dynamic rules.
2860 The effects of such attacks can be partially limited by
2863 variables which control the operation of the firewall.
2865 Here is a good usage of the
2867 command to see accounting records and timestamp information:
2871 or in short form without timestamps:
2875 which is equivalent to:
2879 Next rule diverts all incoming packets from 192.168.2.0/24
2880 to divert port 5000:
2882 .Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in
2885 The following rules show some of the applications of
2889 for simulations and the like.
2891 This rule drops random incoming packets with a probability
2894 .Dl "ipfw add prob 0.05 deny ip from any to any in"
2896 A similar effect can be achieved making use of
2900 .Dl "ipfw add pipe 10 ip from any to any"
2901 .Dl "ipfw pipe 10 config plr 0.05"
2903 We can use pipes to artificially limit bandwidth, e.g.\& on a
2904 machine acting as a router, if we want to limit traffic from
2905 local clients on 192.168.2.0/24 we do:
2907 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
2908 .Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes"
2910 note that we use the
2912 modifier so that the rule is not used twice.
2913 Remember in fact that
2915 rules are checked both on incoming and outgoing packets.
2917 Should we want to simulate a bidirectional link with bandwidth
2918 limitations, the correct way is the following:
2920 .Dl "ipfw add pipe 1 ip from any to any out"
2921 .Dl "ipfw add pipe 2 ip from any to any in"
2922 .Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes"
2923 .Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes"
2925 The above can be very useful, e.g.\& if you want to see how
2926 your fancy Web page will look for a residential user who
2927 is connected only through a slow link.
2928 You should not use only one pipe for both directions, unless
2929 you want to simulate a half-duplex medium (e.g.\& AppleTalk,
2931 It is not necessary that both pipes have the same configuration,
2932 so we can also simulate asymmetric links.
2934 Should we want to verify network performance with the RED queue
2935 management algorithm:
2937 .Dl "ipfw add pipe 1 ip from any to any"
2938 .Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1"
2940 Another typical application of the traffic shaper is to
2941 introduce some delay in the communication.
2942 This can significantly affect applications which do a lot of Remote
2943 Procedure Calls, and where the round-trip-time of the
2944 connection often becomes a limiting factor much more than
2947 .Dl "ipfw add pipe 1 ip from any to any out"
2948 .Dl "ipfw add pipe 2 ip from any to any in"
2949 .Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s"
2950 .Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s"
2952 Per-flow queueing can be useful for a variety of purposes.
2953 A very simple one is counting traffic:
2955 .Dl "ipfw add pipe 1 tcp from any to any"
2956 .Dl "ipfw add pipe 1 udp from any to any"
2957 .Dl "ipfw add pipe 1 ip from any to any"
2958 .Dl "ipfw pipe 1 config mask all"
2960 The above set of rules will create queues (and collect
2961 statistics) for all traffic.
2962 Because the pipes have no limitations, the only effect is
2963 collecting statistics.
2964 Note that we need 3 rules, not just the last one, because
2967 tries to match IP packets it will not consider ports, so we
2968 would not see connections on separate ports as different
2971 A more sophisticated example is limiting the outbound traffic
2972 on a net with per-host limits, rather than per-network limits:
2974 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
2975 .Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in"
2976 .Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
2977 .Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
2979 In the following example, we need to create several traffic bandwidth
2980 classes and we need different hosts/networks to fall into different classes.
2981 We create one pipe for each class and configure them accordingly.
2982 Then we create a single table and fill it with IP subnets and addresses.
2983 For each subnet/host we set the argument equal to the number of the pipe
2985 Then we classify traffic using a single rule:
2987 .Dl "ipfw pipe 1 config bw 1000Kbyte/s"
2988 .Dl "ipfw pipe 4 config bw 4000Kbyte/s"
2990 .Dl "ipfw table 1 add 192.168.2.0/24 1"
2991 .Dl "ipfw table 1 add 192.168.0.0/27 4"
2992 .Dl "ipfw table 1 add 192.168.0.2 1"
2994 .Dl "ipfw add pipe tablearg ip from table(1) to any"
2998 action, the table entries may include hostnames and IP addresses.
3000 .Dl "ipfw table 1 add 192.168.2.0/24 10.23.2.1"
3001 .Dl "ipfw table 1 add 192.168.0.0/27 router1.dmz"
3003 .Dl "ipfw add 100 fwd tablearg ip from any to table(1)"
3005 To add a set of rules atomically, e.g.\& set 18:
3007 .Dl "ipfw set disable 18"
3008 .Dl "ipfw add NN set 18 ... # repeat as needed"
3009 .Dl "ipfw set enable 18"
3011 To delete a set of rules atomically the command is simply:
3013 .Dl "ipfw delete set 18"
3015 To test a ruleset and disable it and regain control if something goes wrong:
3017 .Dl "ipfw set disable 18"
3018 .Dl "ipfw add NN set 18 ... # repeat as needed"
3019 .Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18"
3021 Here if everything goes well, you press control-C before the "sleep"
3022 terminates, and your ruleset will be left active.
3023 Otherwise, e.g.\& if
3024 you cannot access your box, the ruleset will be disabled after
3025 the sleep terminates thus restoring the previous situation.
3027 To show rules of the specific set:
3029 .Dl "ipfw set 18 show"
3031 To show rules of the disabled set:
3033 .Dl "ipfw -S set 18 show"
3035 To clear a specific rule counters of the specific set:
3037 .Dl "ipfw set 18 zero NN"
3039 To delete a specific rule of the specific set:
3041 .Dl "ipfw set 18 delete NN"
3042 .Ss NAT, REDIRECT AND LSNAT
3043 First redirect all the traffic to nat instance 123:
3045 .Dl "ipfw add nat 123 all from any to any"
3047 Then to configure nat instance 123 to alias all the outgoing traffic with ip
3048 192.168.0.123, blocking all incoming connections, trying to keep
3049 same ports on both sides, clearing aliasing table on address change
3050 and keeping a log of traffic/link statistics:
3052 .Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports"
3054 Or to change address of instance 123, aliasing table will be cleared (see
3057 .Dl "ipfw nat 123 config ip 10.0.0.1"
3059 To see configuration of nat instance 123:
3061 .Dl "ipfw nat 123 show config"
3063 To show logs of all the instances in range 111-999:
3065 .Dl "ipfw nat 111-999 show"
3067 To see configurations of all instances:
3069 .Dl "ipfw nat show config"
3071 Or a redirect rule with mixed modes could looks like:
3073 .Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66"
3074 .Dl " redirect_port tcp 192.168.0.1:80 500"
3075 .Dl " redirect_proto udp 192.168.1.43 192.168.1.1"
3076 .Dl " redirect_addr 192.168.0.10,192.168.0.11"
3077 .Dl " 10.0.0.100 # LSNAT"
3078 .Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22"
3081 or it could be split in:
3083 .Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66"
3084 .Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500"
3085 .Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1"
3086 .Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12"
3088 .Dl "ipfw nat 5 config redirect_port tcp"
3089 .Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500"
3111 utility first appeared in
3116 Stateful extensions were introduced in
3119 was introduced in Summer 2002.
3121 .An Ugen J. S. Antsilevich ,
3122 .An Poul-Henning Kamp ,
3128 API based upon code written by
3132 Dummynet has been introduced by Luigi Rizzo in 1997-1998.
3134 Some early work (1999-2000) on the
3136 traffic shaper supported by Akamba Corp.
3138 The ipfw core (ipfw2) has been completely redesigned and
3139 reimplemented by Luigi Rizzo in summer 2002. Further
3141 options have been added by various developer over the years.
3144 In-kernel NAT support written by
3145 .An Paolo Pisati Aq piso@FreeBSD.org
3146 as part of a Summer of Code 2005 project.
3150 support has been developed by
3151 .An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au .
3152 The primary developers and maintainers are David Hayes and Jason But.
3153 For further information visit:
3154 .Aq http://www.caia.swin.edu.au/urp/SONATA
3156 Delay profiles have been developed by Alessandro Cerri and
3157 Luigi Rizzo, supported by the
3158 European Commission within Projects Onelab and Onelab2.
3160 The syntax has grown over the years and sometimes it might be confusing.
3161 Unfortunately, backward compatibility prevents cleaning up mistakes
3162 made in the definition of the syntax.
3166 Misconfiguring the firewall can put your computer in an unusable state,
3167 possibly shutting down network services and requiring console access to
3168 regain control of it.
3170 Incoming packet fragments diverted by
3172 are reassembled before delivery to the socket.
3173 The action used on those packet is the one from the
3174 rule which matches the first fragment of the packet.
3176 Packets diverted to userland, and then reinserted by a userland process
3177 may lose various packet attributes.
3178 The packet source interface name
3179 will be preserved if it is shorter than 8 bytes and the userland process
3180 saves and reuses the sockaddr_in
3183 otherwise, it may be lost.
3184 If a packet is reinserted in this manner, later rules may be incorrectly
3185 applied, making the order of
3187 rules in the rule sequence very important.
3189 Dummynet drops all packets with IPv6 link-local addresses.
3195 may not behave as expected.
3196 In particular, incoming SYN packets may
3197 have no uid or gid associated with them since they do not yet belong
3198 to a TCP connection, and the uid/gid associated with a packet may not
3199 be as expected if the associated process calls
3201 or similar system calls.
3203 Rule syntax is subject to the command line environment and some patterns
3204 may need to be escaped with the backslash character
3205 or quoted appropriately.
3207 Due to the architecture of
3209 ipfw nat is not compatible with the TCP segmentation offloading (TSO).
3210 Thus, to reliably nat your network traffic, please disable TSO
3214 ICMP error messages are not implicitly matched by dynamic rules
3215 for the respective conversations.
3216 To avoid failures of network error detection and path MTU discovery,
3217 ICMP error messages may need to be allowed explicitly through static
git://git.onelab.eu / ipfw.git / blob