2 .\" $FreeBSD: head/sbin/ipfw/ipfw.8 205372 2010-03-20 14:42:16Z gavin $
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 is either accepted or continues with the next rule, depending on
863 .Va net.inet.ip.fw.one_pass
867 for more information on
872 .It Cm setfib Ar fibnum
873 The packet is tagged so as to use the FIB (routing table)
875 in any subsequent forwarding decisions.
876 Initially this is limited to the values 0 through 15, see
878 Processing continues at the next rule.
880 Queue and reassemble ip fragments.
881 If the packet is not fragmented, counters are updated and processing continues with the next rule.
882 If the packet is the last logical fragment, the packet is reassembled and, if
883 .Va net.inet.ip.fw.one_pass
884 is set to 0, processing continues with the next rule, else packet is allowed to pass and search terminates.
885 If the packet is a fragment in the middle, it is consumed and processing stops immediately.
887 Fragments handling can be tuned via
888 .Va net.inet.ip.maxfragpackets
890 .Va net.inet.ip.maxfragsperpacket
891 which limit, respectively, the maximum number of processable fragments (default: 800) and
892 the maximum number of fragments per packet (default: 16).
894 NOTA BENE: since fragments do not contain port numbers, they should be avoided with the
897 Alternatively, direction-based (like
901 ) and source-based (like
903 ) match patterns can be used to select fragments.
905 Usually a simple rule like:
906 .Bd -literal -offset indent
907 # reassemble incoming fragments
908 ipfw add reass all from any to any in
911 is all you need at the beginning of your ruleset.
914 The body of a rule contains zero or more patterns (such as
915 specific source and destination addresses or ports,
916 protocol options, incoming or outgoing interfaces, etc.)
917 that the packet must match in order to be recognised.
918 In general, the patterns are connected by (implicit)
920 operators -- i.e., all must match in order for the
922 Individual patterns can be prefixed by the
924 operator to reverse the result of the match, as in
926 .Dl "ipfw add 100 allow ip from not 1.2.3.4 to any"
928 Additionally, sets of alternative match patterns
930 can be constructed by putting the patterns in
931 lists enclosed between parentheses ( ) or braces { }, and
936 .Dl "ipfw add 100 allow ip from { x or not y or z } to any"
938 Only one level of parentheses is allowed.
939 Beware that most shells have special meanings for parentheses
940 or braces, so it is advisable to put a backslash \\ in front of them
941 to prevent such interpretations.
943 The body of a rule must in general include a source and destination
947 can be used in various places to specify that the content of
948 a required field is irrelevant.
950 The rule body has the following format:
951 .Bd -ragged -offset indent
952 .Op Ar proto Cm from Ar src Cm to Ar dst
956 The first part (proto from src to dst) is for backward
957 compatibility with earlier versions of
961 any match pattern (including MAC headers, IP protocols,
962 addresses and ports) can be specified in the
966 Rule fields have the following meaning:
967 .Bl -tag -width indent
968 .It Ar proto : protocol | Cm { Ar protocol Cm or ... }
969 .It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number
970 An IP protocol specified by number or name
971 (for a complete list see
972 .Pa /etc/protocols ) ,
973 or one of the following keywords:
974 .Bl -tag -width indent
976 Matches IPv4 packets.
978 Matches IPv6 packets.
987 option will be treated as inner protocol.
995 .Cm { Ar protocol Cm or ... }
998 is provided for convenience only but its use is deprecated.
999 .It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports
1000 An address (or a list, see below)
1001 optionally followed by
1007 with multiple addresses) is provided for convenience only and
1008 its use is discouraged.
1009 .It Ar addr : Oo Cm not Oc Bro
1010 .Bl -tag -width indent
1011 .Cm any | me | me6 |
1012 .Cm table Ns Pq Ar number Ns Op , Ns Ar value
1013 .Ar | addr-list | addr-set
1016 matches any IP address.
1018 matches any IP address configured on an interface in the system.
1020 matches any IPv6 address configured on an interface in the system.
1021 The address list is evaluated at the time the packet is
1023 .It Cm table Ns Pq Ar number Ns Op , Ns Ar value
1024 Matches any IPv4 address for which an entry exists in the lookup table
1026 If an optional 32-bit unsigned
1028 is also specified, an entry will match only if it has this value.
1031 section below for more information on lookup tables.
1033 .It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list
1035 A host or subnet address specified in one of the following ways:
1036 .Bl -tag -width indent
1037 .It Ar numeric-ip | hostname
1038 Matches a single IPv4 address, specified as dotted-quad or a hostname.
1039 Hostnames are resolved at the time the rule is added to the firewall list.
1040 .It Ar addr Ns / Ns Ar masklen
1041 Matches all addresses with base
1043 (specified as an IP address, a network number, or a hostname)
1047 As an example, 1.2.3.4/25 or 1.2.3.0/25 will match
1048 all IP numbers from 1.2.3.0 to 1.2.3.127 .
1049 .It Ar addr Ns : Ns Ar mask
1050 Matches all addresses with base
1052 (specified as an IP address, a network number, or a hostname)
1055 specified as a dotted quad.
1056 As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match
1058 This form is advised only for non-contiguous
1060 It is better to resort to the
1061 .Ar addr Ns / Ns Ar masklen
1062 format for contiguous masks, which is more compact and less
1065 .It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm }
1066 .It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list
1067 Matches all addresses with base address
1069 (specified as an IP address, a network number, or a hostname)
1070 and whose last byte is in the list between braces { } .
1071 Note that there must be no spaces between braces and
1072 numbers (spaces after commas are allowed).
1073 Elements of the list can be specified as single entries
1077 field is used to limit the size of the set of addresses,
1078 and can have any value between 24 and 32.
1080 it will be assumed as 24.
1082 This format is particularly useful to handle sparse address sets
1083 within a single rule.
1084 Because the matching occurs using a
1085 bitmask, it takes constant time and dramatically reduces
1086 the complexity of rulesets.
1088 As an example, an address specified as 1.2.3.4/24{128,35-55,89}
1089 or 1.2.3.0/24{128,35-55,89}
1090 will match the following IP addresses:
1092 1.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 .
1093 .It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list
1095 A host or subnet specified one of the following ways:
1097 .Bl -tag -width indent
1098 .It Ar numeric-ip | hostname
1099 Matches a single IPv6 address as allowed by
1102 Hostnames are resolved at the time the rule is added to the firewall
1104 .It Ar addr Ns / Ns Ar masklen
1105 Matches all IPv6 addresses with base
1107 (specified as allowed by
1115 No support for sets of IPv6 addresses is provided because IPv6 addresses
1116 are typically random past the initial prefix.
1117 .It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports
1118 For protocols which support port numbers (such as TCP and UDP), optional
1120 may be specified as one or more ports or port ranges, separated
1121 by commas but no spaces, and an optional
1126 notation specifies a range of ports (including boundaries).
1130 may be used instead of numeric port values.
1131 The length of the port list is limited to 30 ports or ranges,
1132 though one can specify larger ranges by using an
1136 section of the rule.
1140 can be used to escape the dash
1142 character in a service name (from a shell, the backslash must be
1143 typed twice to avoid the shell itself interpreting it as an escape
1146 .Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any"
1148 Fragmented packets which have a non-zero offset (i.e., not the first
1149 fragment) will never match a rule which has one or more port
1153 option for details on matching fragmented packets.
1155 .Ss RULE OPTIONS (MATCH PATTERNS)
1156 Additional match patterns can be used within
1158 Zero or more of these so-called
1160 can be present in a rule, optionally prefixed by the
1162 operand, and possibly grouped into
1165 The following match patterns can be used (listed in alphabetical order):
1166 .Bl -tag -width indent
1167 .It Cm // this is a comment.
1168 Inserts the specified text as a comment in the rule.
1169 Everything following // is considered as a comment and stored in the rule.
1170 You can have comment-only rules, which are listed as having a
1172 action followed by the comment.
1177 Matches only packets generated by a divert socket.
1178 .It Cm diverted-loopback
1179 Matches only packets coming from a divert socket back into the IP stack
1181 .It Cm diverted-output
1182 Matches only packets going from a divert socket back outward to the IP
1183 stack output for delivery.
1184 .It Cm dst-ip Ar ip-address
1185 Matches IPv4 packets whose destination IP is one of the address(es)
1186 specified as argument.
1187 .It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address
1188 Matches IPv6 packets whose destination IP is one of the address(es)
1189 specified as argument.
1190 .It Cm dst-port Ar ports
1191 Matches IP packets whose destination port is one of the port(s)
1192 specified as argument.
1194 Matches TCP packets that have the RST or ACK bits set.
1195 .It Cm ext6hdr Ar header
1196 Matches IPv6 packets containing the extended header given by
1198 Supported headers are:
1204 any type of Routing Header
1206 Source routing Routing Header Type 0
1208 Mobile IPv6 Routing Header Type 2
1212 IPSec authentication headers
1214 and IPsec encapsulated security payload headers
1216 .It Cm fib Ar fibnum
1217 Matches a packet that has been tagged to use
1218 the given FIB (routing table) number.
1219 .It Cm flow-id Ar labels
1220 Matches IPv6 packets containing any of the flow labels given in
1223 is a comma separated list of numeric flow labels.
1225 Matches packets that are fragments and not the first
1226 fragment of an IP datagram.
1227 Note that these packets will not have
1228 the next protocol header (e.g.\& TCP, UDP) so options that look into
1229 these headers cannot match.
1231 Matches all TCP or UDP packets sent by or received for a
1235 may be specified by name or number.
1236 .It Cm jail Ar prisonID
1237 Matches all TCP or UDP packets sent by or received for the
1238 jail whos prison ID is
1240 .It Cm icmptypes Ar types
1241 Matches ICMP packets whose ICMP type is in the list
1243 The list may be specified as any combination of
1244 individual types (numeric) separated by commas.
1245 .Em Ranges are not allowed .
1246 The supported ICMP types are:
1250 destination unreachable
1258 router advertisement
1262 time-to-live exceeded
1274 address mask request
1276 and address mask reply
1278 .It Cm icmp6types Ar types
1279 Matches ICMP6 packets whose ICMP6 type is in the list of
1281 The list may be specified as any combination of
1282 individual types (numeric) separated by commas.
1283 .Em Ranges are not allowed .
1285 Matches incoming or outgoing packets, respectively.
1289 are mutually exclusive (in fact,
1293 .It Cm ipid Ar id-list
1294 Matches IPv4 packets whose
1296 field has value included in
1298 which is either a single value or a list of values or ranges
1299 specified in the same way as
1301 .It Cm iplen Ar len-list
1302 Matches IP packets whose total length, including header and data, is
1305 which is either a single value or a list of values or ranges
1306 specified in the same way as
1308 .It Cm ipoptions Ar spec
1309 Matches packets whose IPv4 header contains the comma separated list of
1310 options specified in
1312 The supported IP options are:
1315 (strict source route),
1317 (loose source route),
1319 (record packet route) and
1322 The absence of a particular option may be denoted
1325 .It Cm ipprecedence Ar precedence
1326 Matches IPv4 packets whose precedence field is equal to
1329 Matches packets that have IPSEC history associated with them
1330 (i.e., the packet comes encapsulated in IPSEC, the kernel
1331 has IPSEC support and IPSEC_FILTERTUNNEL option, and can correctly
1334 Note that specifying
1336 is different from specifying
1338 as the latter will only look at the specific IP protocol field,
1339 irrespective of IPSEC kernel support and the validity of the IPSEC data.
1341 Further note that this flag is silently ignored in kernels without
1343 It does not affect rule processing when given and the
1344 rules are handled as if with no
1347 .It Cm iptos Ar spec
1348 Matches IPv4 packets whose
1350 field contains the comma separated list of
1351 service types specified in
1353 The supported IP types of service are:
1356 .Pq Dv IPTOS_LOWDELAY ,
1358 .Pq Dv IPTOS_THROUGHPUT ,
1360 .Pq Dv IPTOS_RELIABILITY ,
1362 .Pq Dv IPTOS_MINCOST ,
1364 .Pq Dv IPTOS_ECN_CE .
1365 The absence of a particular type may be denoted
1368 .It Cm ipttl Ar ttl-list
1369 Matches IPv4 packets whose time to live is included in
1371 which is either a single value or a list of values or ranges
1372 specified in the same way as
1374 .It Cm ipversion Ar ver
1375 Matches IP packets whose IP version field is
1378 Upon a match, the firewall will create a dynamic rule, whose
1379 default behaviour is to match bidirectional traffic between
1380 source and destination IP/port using the same protocol.
1381 The rule has a limited lifetime (controlled by a set of
1383 variables), and the lifetime is refreshed every time a matching
1386 Matches only layer2 packets, i.e., those passed to
1388 from ether_demux() and ether_output_frame().
1389 .It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N
1390 The firewall will only allow
1392 connections with the same
1393 set of parameters as specified in the rule.
1395 of source and destination addresses and ports can be
1398 only IPv4 flows are supported.
1399 .It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar N
1400 Search an entry in lookup table
1402 that matches the field specified as argument.
1403 If not found, the match fails.
1404 Otherwise, the match succeeds and
1406 is set to the value extracted from the table.
1408 This option can be useful to quickly dispatch traffic based on
1409 certain packet fields.
1412 section below for more information on lookup tables.
1413 .It Cm { MAC | mac } Ar dst-mac src-mac
1414 Match packets with a given
1418 addresses, specified as the
1420 keyword (matching any MAC address), or six groups of hex digits
1421 separated by colons,
1422 and optionally followed by a mask indicating the significant bits.
1423 The mask may be specified using either of the following methods:
1424 .Bl -enum -width indent
1428 followed by the number of significant bits.
1429 For example, an address with 33 significant bits could be specified as:
1431 .Dl "MAC 10:20:30:40:50:60/33 any"
1436 followed by a bitmask specified as six groups of hex digits separated
1438 For example, an address in which the last 16 bits are significant could
1441 .Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any"
1443 Note that the ampersand character has a special meaning in many shells
1444 and should generally be escaped.
1447 Note that the order of MAC addresses (destination first,
1449 the same as on the wire, but the opposite of the one used for
1451 .It Cm mac-type Ar mac-type
1452 Matches packets whose Ethernet Type field
1453 corresponds to one of those specified as argument.
1455 is specified in the same way as
1457 (i.e., one or more comma-separated single values or ranges).
1458 You can use symbolic names for known values such as
1459 .Em vlan , ipv4, ipv6 .
1460 Values can be entered as decimal or hexadecimal (if prefixed by 0x),
1461 and they are always printed as hexadecimal (unless the
1463 option is used, in which case symbolic resolution will be attempted).
1464 .It Cm proto Ar protocol
1465 Matches packets with the corresponding IP protocol.
1466 .It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar ipno | Ar any
1467 Matches packets received, transmitted or going through,
1468 respectively, the interface specified by exact name
1469 .Ns No ( Ar ifX Ns No ),
1471 .Ns No ( Ar if Ns Ar * Ns No ),
1472 by IP address, or through some interface.
1476 keyword causes the interface to always be checked.
1483 then only the receive or transmit interface (respectively)
1485 By specifying both, it is possible to match packets based on
1486 both receive and transmit interface, e.g.:
1488 .Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1"
1492 interface can be tested on either incoming or outgoing packets,
1495 interface can only be tested on outgoing packets.
1500 is invalid) whenever
1504 A packet might not have a receive or transmit interface: packets
1505 originating from the local host have no receive interface,
1506 while packets destined for the local host have no transmit
1509 Matches TCP packets that have the SYN bit set but no ACK bit.
1510 This is the short form of
1511 .Dq Li tcpflags\ syn,!ack .
1512 .It Cm src-ip Ar ip-address
1513 Matches IPv4 packets whose source IP is one of the address(es)
1514 specified as an argument.
1515 .It Cm src-ip6 Ar ip6-address
1516 Matches IPv6 packets whose source IP is one of the address(es)
1517 specified as an argument.
1518 .It Cm src-port Ar ports
1519 Matches IP packets whose source port is one of the port(s)
1520 specified as argument.
1521 .It Cm tagged Ar tag-list
1522 Matches packets whose tags are included in
1524 which is either a single value or a list of values or ranges
1525 specified in the same way as
1527 Tags can be applied to the packet using
1529 rule action parameter (see it's description for details on tags).
1530 .It Cm tcpack Ar ack
1532 Match if the TCP header acknowledgment number field is set to
1534 .It Cm tcpdatalen Ar tcpdatalen-list
1535 Matches TCP packets whose length of TCP data is
1536 .Ar tcpdatalen-list ,
1537 which is either a single value or a list of values or ranges
1538 specified in the same way as
1540 .It Cm tcpflags Ar spec
1542 Match if the TCP header contains the comma separated list of
1545 The supported TCP flags are:
1554 The absence of a particular flag may be denoted
1557 A rule which contains a
1559 specification can never match a fragmented packet which has
1563 option for details on matching fragmented packets.
1564 .It Cm tcpseq Ar seq
1566 Match if the TCP header sequence number field is set to
1568 .It Cm tcpwin Ar win
1570 Match if the TCP header window field is set to
1572 .It Cm tcpoptions Ar spec
1574 Match if the TCP header contains the comma separated list of
1575 options specified in
1577 The supported TCP options are:
1580 (maximum segment size),
1582 (tcp window advertisement),
1586 (rfc1323 timestamp) and
1588 (rfc1644 t/tcp connection count).
1589 The absence of a particular option may be denoted
1593 Match all TCP or UDP packets sent by or received for a
1597 may be matched by name or identification number.
1599 For incoming packets,
1600 a routing table lookup is done on the packet's source address.
1601 If the interface on which the packet entered the system matches the
1602 outgoing interface for the route,
1604 If the interfaces do not match up,
1605 the packet does not match.
1606 All outgoing packets or packets with no incoming interface match.
1608 The name and functionality of the option is intentionally similar to
1609 the Cisco IOS command:
1611 .Dl ip verify unicast reverse-path
1613 This option can be used to make anti-spoofing rules to reject all
1614 packets with source addresses not from this interface.
1618 For incoming packets,
1619 a routing table lookup is done on the packet's source address.
1620 If a route to the source address exists, but not the default route
1621 or a blackhole/reject route, the packet matches.
1622 Otherwise, the packet does not match.
1623 All outgoing packets match.
1625 The name and functionality of the option is intentionally similar to
1626 the Cisco IOS command:
1628 .Dl ip verify unicast source reachable-via any
1630 This option can be used to make anti-spoofing rules to reject all
1631 packets whose source address is unreachable.
1633 For incoming packets, the packet's source address is checked if it
1634 belongs to a directly connected network.
1635 If the network is directly connected, then the interface the packet
1636 came on in is compared to the interface the network is connected to.
1637 When incoming interface and directly connected interface are not the
1638 same, the packet does not match.
1639 Otherwise, the packet does match.
1640 All outgoing packets match.
1642 This option can be used to make anti-spoofing rules to reject all
1643 packets that pretend to be from a directly connected network but do
1644 not come in through that interface.
1645 This option is similar to but more restricted than
1647 because it engages only on packets with source addresses of directly
1648 connected networks instead of all source addresses.
1651 Lookup tables are useful to handle large sparse sets of
1652 addresses or other search keys (e.g. ports, jail IDs).
1653 In the rest of this section we will use the term ``address''
1654 to mean any unsigned value of up to 32-bit.
1655 There may be up to 128 different lookup tables, numbered 0 to 127.
1657 Each entry is represented by an
1658 .Ar addr Ns Op / Ns Ar masklen
1659 and will match all addresses with base
1661 (specified as an IP address, a hostname or an unsigned integer)
1667 is not specified, it defaults to 32.
1668 When looking up an IP address in a table, the most specific
1670 Associated with each entry is a 32-bit unsigned
1672 which can optionally be checked by a rule matching code.
1673 When adding an entry, if
1675 is not specified, it defaults to 0.
1677 An entry can be added to a table
1679 or removed from a table
1681 A table can be examined
1686 Internally, each table is stored in a Radix tree, the same way as
1687 the routing table (see
1690 Lookup tables currently support only ports, jail IDs and IPv4 addresses.
1694 feature provides the ability to use a value, looked up in the table, as
1695 the argument for a rule action, action parameter or rule option.
1696 This can significantly reduce number of rules in some configurations.
1697 If two tables are used in a rule, the result of the second (destination)
1701 argument can be used with the following actions:
1702 .Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto
1710 it is possible to supply table entries with values
1711 that are in the form of IP addresses or hostnames.
1714 Section for example usage of tables and the tablearg keyword.
1718 action, the user should be aware that the code will walk the ruleset
1719 up to a rule equal to, or past, the given number, and should therefore try keep the
1720 ruleset compact between the skipto and the target rules.
1722 Each rule belongs to one of 32 different
1725 Set 31 is reserved for the default rule.
1727 By default, rules are put in set 0, unless you use the
1729 attribute when entering a new rule.
1730 Sets can be individually and atomically enabled or disabled,
1731 so this mechanism permits an easy way to store multiple configurations
1732 of the firewall and quickly (and atomically) switch between them.
1733 The command to enable/disable sets is
1734 .Bd -ragged -offset indent
1736 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
1743 sections can be specified.
1744 Command execution is atomic on all the sets specified in the command.
1745 By default, all sets are enabled.
1747 When you disable a set, its rules behave as if they do not exist
1748 in the firewall configuration, with only one exception:
1749 .Bd -ragged -offset indent
1750 dynamic rules created from a rule before it had been disabled
1751 will still be active until they expire.
1753 dynamic rules you have to explicitly delete the parent rule
1754 which generated them.
1757 The set number of rules can be changed with the command
1758 .Bd -ragged -offset indent
1761 .Brq Cm rule Ar rule-number | old-set
1765 Also, you can atomically swap two rulesets with the command
1766 .Bd -ragged -offset indent
1768 .Cm set swap Ar first-set second-set
1773 Section on some possible uses of sets of rules.
1774 .Sh STATEFUL FIREWALL
1775 Stateful operation is a way for the firewall to dynamically
1776 create rules for specific flows when packets that
1777 match a given pattern are detected.
1778 Support for stateful
1779 operation comes through the
1780 .Cm check-state , keep-state
1786 Dynamic rules are created when a packet matches a
1790 rule, causing the creation of a
1792 rule which will match all and only packets with
1796 .Em src-ip/src-port dst-ip/dst-port
1801 are used here only to denote the initial match addresses, but they
1802 are completely equivalent afterwards).
1803 Dynamic rules will be checked at the first
1804 .Cm check-state, keep-state
1807 occurrence, and the action performed upon a match will be the same
1808 as in the parent rule.
1810 Note that no additional attributes other than protocol and IP addresses
1811 and ports are checked on dynamic rules.
1813 The typical use of dynamic rules is to keep a closed firewall configuration,
1814 but let the first TCP SYN packet from the inside network install a
1815 dynamic rule for the flow so that packets belonging to that session
1816 will be allowed through the firewall:
1818 .Dl "ipfw add check-state"
1819 .Dl "ipfw add allow tcp from my-subnet to any setup keep-state"
1820 .Dl "ipfw add deny tcp from any to any"
1822 A similar approach can be used for UDP, where an UDP packet coming
1823 from the inside will install a dynamic rule to let the response through
1826 .Dl "ipfw add check-state"
1827 .Dl "ipfw add allow udp from my-subnet to any keep-state"
1828 .Dl "ipfw add deny udp from any to any"
1830 Dynamic rules expire after some time, which depends on the status
1831 of the flow and the setting of some
1835 .Sx SYSCTL VARIABLES
1837 For TCP sessions, dynamic rules can be instructed to periodically
1838 send keepalive packets to refresh the state of the rule when it is
1843 for more examples on how to use dynamic rules.
1844 .Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
1846 is also the user interface for the
1848 traffic shaper, packet scheduler and network emulator, a subsystem that
1849 can artificially queue, delay or drop packets
1850 emulating the behaviour of certain network links
1851 or queueing systems.
1854 operates by first using the firewall to select packets
1855 using any match pattern that can be used in
1858 Matching packets are then passed to either of two
1859 different objects, which implement the traffic regulation:
1860 .Bl -hang -offset XXXX
1866 with given bandwidth and propagation delay,
1867 driven by a FIFO scheduler and a single queue with programmable
1868 queue size and packet loss rate.
1869 Packets are appended to the queue as they come out from
1871 and then transferred in FIFO order to the link at the desired rate.
1875 is an abstraction used to implement packet scheduling
1876 using one of several packet scheduling algorithms.
1879 are first grouped into flows according to a mask on the 5-tuple.
1880 Flows are then passed to the scheduler associated to the
1882 and each flow uses scheduling parameters (weight and others)
1883 as configured in the
1886 A scheduler in turn is connected to an emulated link,
1887 and arbitrates the link's bandwidth among backlogged flows according to
1888 weights and to the features of the scheduling algorithm in use.
1893 can be used to set hard limits to the bandwidth that a flow can use, whereas
1895 can be used to determine how different flows share the available bandwidth.
1897 A graphical representation of the binding of queues,
1898 flows, schedulers and links is below.
1899 .Bd -literal -offset indent
1900 (flow_mask|sched_mask) sched_mask
1901 +---------+ weight Wx +-------------+
1902 | |->-[flow]-->--| |-+
1903 -->--| QUEUE x | ... | | |
1904 | |->-[flow]-->--| SCHEDuler N | |
1906 ... | +--[LINK N]-->--
1907 +---------+ weight Wy | | +--[LINK N]-->--
1908 | |->-[flow]-->--| | |
1909 -->--| QUEUE y | ... | | |
1910 | |->-[flow]-->--| | |
1911 +---------+ +-------------+ |
1914 It is important to understand the role of the SCHED_MASK
1915 and FLOW_MASK, which are configured through the commands
1916 .Dl "ipfw sched N config mask SCHED_MASK ..."
1918 .Dl "ipfw queue X config mask FLOW_MASK ..." .
1920 The SCHED_MASK is used to assign flows to one or more
1921 scheduler instances, one for each
1922 value of the packet's 5-fuple after applying SCHED_MASK.
1923 As an example, using ``src-ip 0xffffff00'' creates one instance
1924 for each /24 destination subnet.
1926 The FLOW_MASK, together with the SCHED_MASK, is used to split
1927 packets into flows. As an example, using
1928 ``src-ip 0x000000ff''
1929 together with the previous SCHED_MASK makes a flow for
1930 each individual source address. In turn, flows for each /24
1931 subnet will be sent to the same scheduler instance.
1933 The above diagram holds even for the
1935 case, with the only restriction that a
1937 only supports a SCHED_MASK, and forces the use of a FIFO
1938 scheduler (these are for backward compatibility reasons;
1939 in fact, internally, a
1941 pipe is implemented exactly as above).
1943 There are two modes of
1951 mode tries to emulate a real link: the
1953 scheduler ensures that the packet will not leave the pipe faster than it
1954 would on the real link with a given bandwidth.
1957 mode allows certain packets to bypass the
1959 scheduler (if packet flow does not exceed pipe's bandwidth).
1960 This is the reason why the
1962 mode requires less CPU cycles per packet (on average) and packet latency
1963 can be significantly lower in comparison to a real link with the same
1969 mode can be enabled by setting the
1970 .Va net.inet.ip.dummynet.io_fast
1972 variable to a non-zero value.
1974 .Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION
1980 configuration commands are the following:
1981 .Bd -ragged -offset indent
1982 .Cm pipe Ar number Cm config Ar pipe-configuration
1984 .Cm queue Ar number Cm config Ar queue-configuration
1986 .Cm sched Ar number Cm config Ar sched-configuration
1989 The following parameters can be configured for a pipe:
1991 .Bl -tag -width indent -compact
1992 .It Cm bw Ar bandwidth | device
1993 Bandwidth, measured in
1996 .Brq Cm bit/s | Byte/s .
1999 A value of 0 (default) means unlimited bandwidth.
2000 The unit must immediately follow the number, as in
2002 .Dl "ipfw pipe 1 config bw 300Kbit/s"
2004 If a device name is specified instead of a numeric value, as in
2006 .Dl "ipfw pipe 1 config bw tun0"
2008 then the transmit clock is supplied by the specified device.
2009 At the moment only the
2011 device supports this
2012 functionality, for use in conjunction with
2015 .It Cm delay Ar ms-delay
2016 Propagation delay, measured in milliseconds.
2017 The value is rounded to the next multiple of the clock tick
2018 (typically 10ms, but it is a good practice to run kernels
2020 .Dq "options HZ=1000"
2022 the granularity to 1ms or less).
2023 The default value is 0, meaning no delay.
2025 .It Cm burst Ar size
2026 If the data to be sent exceeds the pipe's bandwidth limit
2027 (and the pipe was previously idle), up to
2029 bytes of data are allowed to bypass the
2031 scheduler, and will be sent as fast as the physical link allows.
2032 Any additional data will be transmitted at the rate specified
2036 The burst size depends on how long the pipe has been idle;
2037 the effective burst size is calculated as follows:
2044 .It Cm profile Ar filename
2045 A file specifying the additional overhead incurred in the transmission
2046 of a packet on the link.
2048 Some link types introduce extra delays in the transmission
2049 of a packet, e.g. because of MAC level framing, contention on
2050 the use of the channel, MAC level retransmissions and so on.
2051 From our point of view, the channel is effectively unavailable
2052 for this extra time, which is constant or variable depending
2053 on the link type. Additionally, packets may be dropped after this
2054 time (e.g. on a wireless link after too many retransmissions).
2055 We can model the additional delay with an empirical curve
2056 that represents its distribution.
2057 .Bd -literal -offset indent
2058 cumulative probability
2068 +-------*------------------->
2071 The empirical curve may have both vertical and horizontal lines.
2072 Vertical lines represent constant delay for a range of
2074 Horizontal lines correspond to a discontinuity in the delay
2075 distribution: the pipe will use the largest delay for a
2078 The file format is the following, with whitespace acting as
2079 a separator and '#' indicating the beginning a comment:
2080 .Bl -tag -width indent
2081 .It Cm name Ar identifier
2082 optional name (listed by "ipfw pipe show")
2083 to identify the delay distribution;
2085 the bandwidth used for the pipe.
2086 If not specified here, it must be present
2087 explicitly as a configuration parameter for the pipe;
2088 .It Cm loss-level Ar L
2089 the probability above which packets are lost.
2090 (0.0 <= L <= 1.0, default 1.0 i.e. no loss);
2092 the number of samples used in the internal
2093 representation of the curve (2..1024; default 100);
2094 .It Cm "delay prob" | "prob delay"
2095 One of these two lines is mandatory and defines
2096 the format of the following lines with data points.
2098 2 or more lines representing points in the curve,
2099 with either delay or probability first, according
2100 to the chosen format.
2101 The unit for delay is milliseconds.
2102 Data points do not need to be sorted.
2103 Also, tne number of actual lines can be different
2104 from the value of the "samples" parameter:
2106 utility will sort and interpolate
2107 the curve as needed.
2110 Example of a profile file:
2111 .Bd -literal -offset indent
2116 0 200 # minimum overhead is 200ms
2122 #configuration file end
2126 The following parameters can be configured for a queue:
2128 .Bl -tag -width indent -compact
2129 .It Cm pipe Ar pipe_nr
2130 Connects a queue to the specified pipe.
2131 Multiple queues (with the same or different weights) can be connected to
2132 the same pipe, which specifies the aggregate rate for the set of queues.
2134 .It Cm weight Ar weight
2135 Specifies the weight to be used for flows matching this queue.
2136 The weight must be in the range 1..100, and defaults to 1.
2139 The following parameters can be configured for a scheduler:
2141 .Bl -tag -width indent -compact
2142 .It Cm type Ar {fifo | wf2qp | rr | qfq}
2143 specifies the scheduling algorithm to use.
2144 .Bl -tag -width indent -compact
2146 is just a FIFO scheduler (which means that all packets
2147 are stored in the same queue as they arrive to the scheduler).
2148 FIFO has O(1) per-packet time complexity, with very low
2149 constants (estimate 60-80ns on a 2Ghz desktop machine)
2150 but gives no service guarantees.
2152 implements the WF2Q+ algorithm, which is a Weighted Fair Queueing
2153 algorithm which permits flows to share bandwidth according to
2154 their weights. Note that weights are not priorities; even a flow
2155 with a minuscule weight will never starve.
2156 WF2Q+ has O(log N) per-packet processing cost, where N is the number
2157 of flows, and is the default algorithm used by previous versions
2160 implements the Deficit Round Robin algorithm, which has O(1) processing
2161 costs (roughly, 100-150ns per packet)
2162 and permits bandwidth allocation according to weights, but
2163 with poor service guarantees.
2165 implements the QFQ algorithm, which is a very fast variant of
2166 WF2Q+, with similar service guarantees and O(1) processing
2167 costs (roughly, 200-250ns per packet).
2171 In addition to the type, all parameters allowed for a pipe can also
2172 be specified for a scheduler.
2174 Finally, the following parameters can be configured for both
2177 .Bl -tag -width XXXX -compact
2179 .It Cm buckets Ar hash-table-size
2180 Specifies the size of the hash table used for storing the
2182 Default value is 64 controlled by the
2185 .Va net.inet.ip.dummynet.hash_size ,
2186 allowed range is 16 to 65536.
2188 .It Cm mask Ar mask-specifier
2189 Packets sent to a given pipe or queue by an
2191 rule can be further classified into multiple flows, each of which is then
2195 A flow identifier is constructed by masking the IP addresses,
2196 ports and protocol types as specified with the
2198 options in the configuration of the pipe or queue.
2199 For each different flow identifier, a new pipe or queue is created
2200 with the same parameters as the original object, and matching packets
2205 are used, each flow will get the same bandwidth as defined by the pipe,
2208 are used, each flow will share the parent's pipe bandwidth evenly
2209 with other flows generated by the same queue (note that other queues
2210 with different weights might be connected to the same pipe).
2212 Available mask specifiers are a combination of one or more of the following:
2214 .Cm dst-ip Ar mask ,
2215 .Cm dst-ip6 Ar mask ,
2216 .Cm src-ip Ar mask ,
2217 .Cm src-ip6 Ar mask ,
2218 .Cm dst-port Ar mask ,
2219 .Cm src-port Ar mask ,
2220 .Cm flow-id Ar mask ,
2225 where the latter means all bits in all fields are significant.
2228 When a packet is dropped by a
2230 queue or pipe, the error
2231 is normally reported to the caller routine in the kernel, in the
2232 same way as it happens when a device queue fills up.
2234 option reports the packet as successfully delivered, which can be
2235 needed for some experimental setups where you want to simulate
2236 loss or congestion at a remote router.
2238 .It Cm plr Ar packet-loss-rate
2241 .Ar packet-loss-rate
2242 is a floating-point number between 0 and 1, with 0 meaning no
2243 loss, 1 meaning 100% loss.
2244 The loss rate is internally represented on 31 bits.
2246 .It Cm queue Brq Ar slots | size Ns Cm Kbytes
2251 Default value is 50 slots, which
2252 is the typical queue size for Ethernet devices.
2253 Note that for slow speed links you should keep the queue
2254 size short or your traffic might be affected by a significant
2256 E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit
2257 or 20s of queue on a 30Kbit/s pipe.
2258 Even worse effects can result if you get packets from an
2259 interface with a much larger MTU, e.g.\& the loopback interface
2260 with its 16KB packets.
2264 .Em net.inet.ip.dummynet.pipe_byte_limit
2266 .Em net.inet.ip.dummynet.pipe_slot_limit
2267 control the maximum lengths that can be specified.
2269 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
2270 Make use of the RED (Random Early Detection) queue management algorithm.
2275 point numbers between 0 and 1 (0 not included), while
2279 are integer numbers specifying thresholds for queue management
2280 (thresholds are computed in bytes if the queue has been defined
2281 in bytes, in slots otherwise).
2284 also supports the gentle RED variant (gred).
2287 variables can be used to control the RED behaviour:
2288 .Bl -tag -width indent
2289 .It Va net.inet.ip.dummynet.red_lookup_depth
2290 specifies the accuracy in computing the average queue
2291 when the link is idle (defaults to 256, must be greater than zero)
2292 .It Va net.inet.ip.dummynet.red_avg_pkt_size
2293 specifies the expected average packet size (defaults to 512, must be
2295 .It Va net.inet.ip.dummynet.red_max_pkt_size
2296 specifies the expected maximum packet size, only used when queue
2297 thresholds are in bytes (defaults to 1500, must be greater than zero).
2301 When used with IPv6 data,
2303 currently has several limitations.
2304 Information necessary to route link-local packets to an
2305 interface is not available after processing by
2307 so those packets are dropped in the output path.
2308 Care should be taken to insure that link-local packets are not passed to
2311 Here are some important points to consider when designing your
2315 Remember that you filter both packets going
2319 Most connections need packets going in both directions.
2321 Remember to test very carefully.
2322 It is a good idea to be near the console when doing this.
2323 If you cannot be near the console,
2324 use an auto-recovery script such as the one in
2325 .Pa /usr/share/examples/ipfw/change_rules.sh .
2327 Do not forget the loopback interface.
2332 There are circumstances where fragmented datagrams are unconditionally
2334 TCP packets are dropped if they do not contain at least 20 bytes of
2335 TCP header, UDP packets are dropped if they do not contain a full 8
2336 byte UDP header, and ICMP packets are dropped if they do not contain
2337 4 bytes of ICMP header, enough to specify the ICMP type, code, and
2339 These packets are simply logged as
2341 since there may not be enough good data in the packet to produce a
2342 meaningful log entry.
2344 Another type of packet is unconditionally dropped, a TCP packet with a
2345 fragment offset of one.
2346 This is a valid packet, but it only has one use, to try
2347 to circumvent firewalls.
2348 When logging is enabled, these packets are
2349 reported as being dropped by rule -1.
2351 If you are logged in over a network, loading the
2355 is probably not as straightforward as you would think.
2356 The following command line is recommended:
2357 .Bd -literal -offset indent
2359 ipfw add 32000 allow ip from any to any
2362 Along the same lines, doing an
2363 .Bd -literal -offset indent
2367 in similar surroundings is also a bad idea.
2371 filter list may not be modified if the system security level
2372 is set to 3 or higher
2375 for information on system security levels).
2377 .Sh PACKET DIVERSION
2380 socket bound to the specified port will receive all packets
2381 diverted to that port.
2382 If no socket is bound to the destination port, or if the divert module is
2383 not loaded, or if the kernel was not compiled with divert socket support,
2384 the packets are dropped.
2385 .Sh NETWORK ADDRESS TRANSLATION (NAT)
2388 support in-kernel NAT using the kernel version of
2391 The nat configuration command is the following:
2392 .Bd -ragged -offset indent
2397 .Ar nat-configuration
2401 The following parameters can be configured:
2402 .Bl -tag -width indent
2403 .It Cm ip Ar ip_address
2404 Define an ip address to use for aliasing.
2406 Use ip address of NIC for aliasing, dynamically changing
2407 it if NIC's ip address changes.
2409 Enable logging on this nat instance.
2411 Deny any incoming connection from outside world.
2413 Try to leave the alias port numbers unchanged from
2414 the actual local port numbers.
2416 Traffic on the local network not originating from an
2417 unregistered address spaces will be ignored.
2419 Reset table of the packet aliasing engine on address change.
2421 Reverse the way libalias handles aliasing.
2423 Obey transparent proxy rules only, packet aliasing is not performed.
2426 To let the packet continue after being (de)aliased, set the sysctl variable
2427 .Va net.inet.ip.fw.one_pass
2429 For more information about aliasing modes, refer to
2433 for some examples about nat usage.
2434 .Ss REDIRECT AND LSNAT SUPPORT IN IPFW
2435 Redirect and LSNAT support follow closely the syntax used in
2439 for some examples on how to do redirect and lsnat.
2440 .Ss SCTP NAT SUPPORT
2441 SCTP nat can be configured in a similar manner to TCP through the
2444 The main difference is that
2446 does not do port translation.
2447 Since the local and global side ports will be the same,
2448 there is no need to specify both.
2449 Ports are redirected as follows:
2450 .Bd -ragged -offset indent
2456 .Cm redirect_port sctp
2457 .Ar ip_address [,addr_list] {[port | port-port] [,ports]}
2463 configuration can be done in real-time through the
2466 All may be changed dynamically, though the hash_table size will only
2471 .Sx SYSCTL VARIABLES
2473 .Sh SYSCTL VARIABLES
2476 variables controls the behaviour of the firewall and
2478 .Pq Nm dummynet , bridge , sctp nat .
2479 These are shown below together with their default value
2480 (but always check with the
2482 command what value is actually in use) and meaning:
2483 .Bl -tag -width indent
2484 .It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0
2487 responds to receipt of global OOTB ASCONF-AddIP:
2488 .Bl -tag -width indent
2490 No response (unless a partially matching association exists -
2491 ports and vtags match but global address does not)
2494 will accept and process all OOTB global AddIP messages.
2497 Option 1 should never be selected as this forms a security risk.
2499 establish multiple fake associations by sending AddIP messages.
2500 .It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5
2501 Defines the maximum number of chunks in an SCTP packet that will be parsed for a
2502 packet that matches an existing association.
2503 This value is enforced to be greater or equal than
2504 .Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit .
2506 a DoS risk yet setting too low a value may result in important control chunks in
2507 the packet not being located and parsed.
2508 .It Va net.inet.ip.alias.sctp.error_on_ootb: No 1
2511 responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets.
2512 An OOTB packet is a packet that arrives with no existing association
2515 and is not an INIT or ASCONF-AddIP packet:
2516 .Bl -tag -width indent
2518 ErrorM is never sent in response to OOTB packets.
2520 ErrorM is only sent to OOTB packets received on the local side.
2522 ErrorM is sent to the local side and on the global side ONLY if there is a
2523 partial match (ports and vtags match but the source global IP does not).
2524 This value is only useful if the
2526 is tracking global IP addresses.
2528 ErrorM is sent in response to all OOTB packets on both the local and global side
2532 At the moment the default is 0, since the ErrorM packet is not yet
2533 supported by most SCTP stacks.
2534 When it is supported, and if not tracking
2535 global addresses, we recommend setting this value to 1 to allow
2536 multi-homed local hosts to function with the
2538 To track global addresses, we recommend setting this value to 2 to
2539 allow global hosts to be informed when they need to (re)send an
2541 Value 3 should never be chosen (except for debugging) as the
2543 will respond to all OOTB global packets (a DoS risk).
2544 .It Va net.inet.ip.alias.sctp.hashtable_size: No 2003
2545 Size of hash tables used for
2547 lookups (100 < prime_number > 1000001).
2550 size for any future created
2552 instance and therefore must be set prior to creating a
2555 The table sizes may be changed to suit specific needs.
2556 If there will be few
2557 concurrent associations, and memory is scarce, you may make these smaller.
2558 If there will be many thousands (or millions) of concurrent associations, you
2559 should make these larger.
2560 A prime number is best for the table size.
2562 update function will adjust your input value to the next highest prime number.
2563 .It Va net.inet.ip.alias.sctp.holddown_time: No 0
2564 Hold association in table for this many seconds after receiving a
2566 This allows endpoints to correct shutdown gracefully if a
2567 shutdown_complete is lost and retransmissions are required.
2568 .It Va net.inet.ip.alias.sctp.init_timer: No 15
2569 Timeout value while waiting for (INIT-ACK|AddIP-ACK).
2570 This value cannot be 0.
2571 .It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2
2572 Defines the maximum number of chunks in an SCTP packet that will be parsed when
2573 no existing association exists that matches that packet.
2575 will only be an INIT or ASCONF-AddIP packet.
2576 A higher value may become a DoS
2577 risk as malformed packets can consume processing resources.
2578 .It Va net.inet.ip.alias.sctp.param_proc_limit: No 25
2579 Defines the maximum number of parameters within a chunk that will be parsed in a
2581 As for other similar sysctl variables, larger values pose a DoS risk.
2582 .It Va net.inet.ip.alias.sctp.log_level: No 0
2583 Level of detail in the system log messages (0 \- minimal, 1 \- event,
2584 2 \- info, 3 \- detail, 4 \- debug, 5 \- max debug). May be a good
2585 option in high loss environments.
2586 .It Va net.inet.ip.alias.sctp.shutdown_time: No 15
2587 Timeout value while waiting for SHUTDOWN-COMPLETE.
2588 This value cannot be 0.
2589 .It Va net.inet.ip.alias.sctp.track_global_addresses: No 0
2590 Enables/disables global IP address tracking within the
2593 upper limit on the number of addresses tracked for each association:
2594 .Bl -tag -width indent
2596 Global tracking is disabled
2598 Enables tracking, the maximum number of addresses tracked for each
2599 association is limited to this value
2602 This variable is fully dynamic, the new value will be adopted for all newly
2603 arriving associations, existing associations are treated as they were previously.
2604 Global tracking will decrease the number of collisions within the
2607 of increased processing load, memory usage, complexity, and possible
2610 problems in complex networks with multiple
2612 We recommend not tracking
2613 global IP addresses, this will still result in a fully functional
2615 .It Va net.inet.ip.alias.sctp.up_timer: No 300
2616 Timeout value to keep an association up with no traffic.
2617 This value cannot be 0.
2618 .It Va net.inet.ip.dummynet.expire : No 1
2619 Lazily delete dynamic pipes/queue once they have no pending traffic.
2620 You can disable this by setting the variable to 0, in which case
2621 the pipes/queues will only be deleted when the threshold is reached.
2622 .It Va net.inet.ip.dummynet.hash_size : No 64
2623 Default size of the hash table used for dynamic pipes/queues.
2624 This value is used when no
2626 option is specified when configuring a pipe/queue.
2627 .It Va net.inet.ip.dummynet.io_fast : No 0
2628 If set to a non-zero value,
2633 operation (see above) is enabled.
2634 .It Va net.inet.ip.dummynet.io_pkt
2635 Number of packets passed to
2637 .It Va net.inet.ip.dummynet.io_pkt_drop
2638 Number of packets dropped by
2640 .It Va net.inet.ip.dummynet.io_pkt_fast
2641 Number of packets bypassed by the
2644 .It Va net.inet.ip.dummynet.max_chain_len : No 16
2645 Target value for the maximum number of pipes/queues in a hash bucket.
2647 .Cm max_chain_len*hash_size
2648 is used to determine the threshold over which empty pipes/queues
2649 will be expired even when
2650 .Cm net.inet.ip.dummynet.expire=0 .
2651 .It Va net.inet.ip.dummynet.red_lookup_depth : No 256
2652 .It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512
2653 .It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500
2654 Parameters used in the computations of the drop probability
2655 for the RED algorithm.
2656 .It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576
2657 .It Va net.inet.ip.dummynet.pipe_slot_limit : No 100
2658 The maximum queue size that can be specified in bytes or packets.
2659 These limits prevent accidental exhaustion of resources such as mbufs.
2660 If you raise these limits,
2661 you should make sure the system is configured so that sufficient resources
2663 .It Va net.inet.ip.fw.autoinc_step : No 100
2664 Delta between rule numbers when auto-generating them.
2665 The value must be in the range 1..1000.
2666 .It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets
2667 The current number of buckets in the hash table for dynamic rules
2669 .It Va net.inet.ip.fw.debug : No 1
2670 Controls debugging messages produced by
2672 .It Va net.inet.ip.fw.default_rule : No 65535
2673 The default rule number (read-only).
2675 .Nm , the default rule is the last one, so its number
2676 can also serve as the highest number allowed for a rule.
2677 .It Va net.inet.ip.fw.dyn_buckets : No 256
2678 The number of buckets in the hash table for dynamic rules.
2679 Must be a power of 2, up to 65536.
2680 It only takes effect when all dynamic rules have expired, so you
2681 are advised to use a
2683 command to make sure that the hash table is resized.
2684 .It Va net.inet.ip.fw.dyn_count : No 3
2685 Current number of dynamic rules
2687 .It Va net.inet.ip.fw.dyn_keepalive : No 1
2688 Enables generation of keepalive packets for
2690 rules on TCP sessions.
2691 A keepalive is generated to both
2692 sides of the connection every 5 seconds for the last 20
2693 seconds of the lifetime of the rule.
2694 .It Va net.inet.ip.fw.dyn_max : No 8192
2695 Maximum number of dynamic rules.
2696 When you hit this limit, no more dynamic rules can be
2697 installed until old ones expire.
2698 .It Va net.inet.ip.fw.dyn_ack_lifetime : No 300
2699 .It Va net.inet.ip.fw.dyn_syn_lifetime : No 20
2700 .It Va net.inet.ip.fw.dyn_fin_lifetime : No 1
2701 .It Va net.inet.ip.fw.dyn_rst_lifetime : No 1
2702 .It Va net.inet.ip.fw.dyn_udp_lifetime : No 5
2703 .It Va net.inet.ip.fw.dyn_short_lifetime : No 30
2704 These variables control the lifetime, in seconds, of dynamic
2706 Upon the initial SYN exchange the lifetime is kept short,
2707 then increased after both SYN have been seen, then decreased
2708 again during the final FIN exchange or when a RST is received.
2710 .Em dyn_fin_lifetime
2712 .Em dyn_rst_lifetime
2713 must be strictly lower than 5 seconds, the period of
2714 repetition of keepalives.
2715 The firewall enforces that.
2716 .It Va net.inet.ip.fw.enable : No 1
2717 Enables the firewall.
2718 Setting this variable to 0 lets you run your machine without
2719 firewall even if compiled in.
2720 .It Va net.inet6.ip6.fw.enable : No 1
2721 provides the same functionality as above for the IPv6 case.
2722 .It Va net.inet.ip.fw.one_pass : No 1
2723 When set, the packet exiting from the
2727 node is not passed though the firewall again.
2728 Otherwise, after an action, the packet is
2729 reinjected into the firewall at the next rule.
2730 .It Va net.inet.ip.fw.tables_max : No 128
2731 Maximum number of tables (read-only).
2732 .It Va net.inet.ip.fw.verbose : No 1
2733 Enables verbose messages.
2734 .It Va net.inet.ip.fw.verbose_limit : No 0
2735 Limits the number of messages produced by a verbose firewall.
2736 .It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1
2737 If enabled packets with unknown IPv6 Extension Headers will be denied.
2738 .It Va net.link.ether.ipfw : No 0
2739 Controls whether layer-2 packets are passed to
2742 .It Va net.link.bridge.ipfw : No 0
2743 Controls whether bridged packets are passed to
2749 There are far too many possible uses of
2751 so this Section will only give a small set of examples.
2753 .Ss BASIC PACKET FILTERING
2754 This command adds an entry which denies all tcp packets from
2755 .Em cracker.evil.org
2756 to the telnet port of
2758 from being forwarded by the host:
2760 .Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet"
2762 This one disallows any connection from the entire cracker's
2765 .Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org"
2767 A first and efficient way to limit access (not using dynamic rules)
2768 is the use of the following rules:
2770 .Dl "ipfw add allow tcp from any to any established"
2771 .Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup"
2772 .Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup"
2774 .Dl "ipfw add deny tcp from any to any"
2776 The first rule will be a quick match for normal TCP packets,
2777 but it will not match the initial SYN packet, which will be
2780 rules only for selected source/destination pairs.
2781 All other SYN packets will be rejected by the final
2785 If you administer one or more subnets, you can take advantage
2786 of the address sets and or-blocks and write extremely
2787 compact rulesets which selectively enable services to blocks
2788 of clients, as below:
2790 .Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q"
2791 .Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q"
2793 .Dl "ipfw add allow ip from ${goodguys} to any"
2794 .Dl "ipfw add deny ip from ${badguys} to any"
2795 .Dl "... normal policies ..."
2799 option could be used to do automated anti-spoofing by adding the
2800 following to the top of a ruleset:
2802 .Dl "ipfw add deny ip from any to any not verrevpath in"
2804 This rule drops all incoming packets that appear to be coming to the
2805 system on the wrong interface.
2806 For example, a packet with a source
2807 address belonging to a host on a protected internal network would be
2808 dropped if it tried to enter the system from an external interface.
2812 option could be used to do similar but more restricted anti-spoofing
2813 by adding the following to the top of a ruleset:
2815 .Dl "ipfw add deny ip from any to any not antispoof in"
2817 This rule drops all incoming packets that appear to be coming from another
2818 directly connected system but on the wrong interface.
2819 For example, a packet with a source address of
2820 .Li 192.168.0.0/24 ,
2827 In order to protect a site from flood attacks involving fake
2828 TCP packets, it is safer to use dynamic rules:
2830 .Dl "ipfw add check-state"
2831 .Dl "ipfw add deny tcp from any to any established"
2832 .Dl "ipfw add allow tcp from my-net to any setup keep-state"
2834 This will let the firewall install dynamic rules only for
2835 those connection which start with a regular SYN packet coming
2836 from the inside of our network.
2837 Dynamic rules are checked when encountering the first
2844 rule should usually be placed near the beginning of the
2845 ruleset to minimize the amount of work scanning the ruleset.
2846 Your mileage may vary.
2848 To limit the number of connections a user can open
2849 you can use the following type of rules:
2851 .Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10"
2852 .Dl "ipfw add allow tcp from any to me setup limit src-addr 4"
2854 The former (assuming it runs on a gateway) will allow each host
2855 on a /24 network to open at most 10 TCP connections.
2856 The latter can be placed on a server to make sure that a single
2857 client does not use more than 4 simultaneous connections.
2860 stateful rules can be subject to denial-of-service attacks
2861 by a SYN-flood which opens a huge number of dynamic rules.
2862 The effects of such attacks can be partially limited by
2865 variables which control the operation of the firewall.
2867 Here is a good usage of the
2869 command to see accounting records and timestamp information:
2873 or in short form without timestamps:
2877 which is equivalent to:
2881 Next rule diverts all incoming packets from 192.168.2.0/24
2882 to divert port 5000:
2884 .Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in
2887 The following rules show some of the applications of
2891 for simulations and the like.
2893 This rule drops random incoming packets with a probability
2896 .Dl "ipfw add prob 0.05 deny ip from any to any in"
2898 A similar effect can be achieved making use of
2902 .Dl "ipfw add pipe 10 ip from any to any"
2903 .Dl "ipfw pipe 10 config plr 0.05"
2905 We can use pipes to artificially limit bandwidth, e.g.\& on a
2906 machine acting as a router, if we want to limit traffic from
2907 local clients on 192.168.2.0/24 we do:
2909 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
2910 .Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes"
2912 note that we use the
2914 modifier so that the rule is not used twice.
2915 Remember in fact that
2917 rules are checked both on incoming and outgoing packets.
2919 Should we want to simulate a bidirectional link with bandwidth
2920 limitations, the correct way is the following:
2922 .Dl "ipfw add pipe 1 ip from any to any out"
2923 .Dl "ipfw add pipe 2 ip from any to any in"
2924 .Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes"
2925 .Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes"
2927 The above can be very useful, e.g.\& if you want to see how
2928 your fancy Web page will look for a residential user who
2929 is connected only through a slow link.
2930 You should not use only one pipe for both directions, unless
2931 you want to simulate a half-duplex medium (e.g.\& AppleTalk,
2933 It is not necessary that both pipes have the same configuration,
2934 so we can also simulate asymmetric links.
2936 Should we want to verify network performance with the RED queue
2937 management algorithm:
2939 .Dl "ipfw add pipe 1 ip from any to any"
2940 .Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1"
2942 Another typical application of the traffic shaper is to
2943 introduce some delay in the communication.
2944 This can significantly affect applications which do a lot of Remote
2945 Procedure Calls, and where the round-trip-time of the
2946 connection often becomes a limiting factor much more than
2949 .Dl "ipfw add pipe 1 ip from any to any out"
2950 .Dl "ipfw add pipe 2 ip from any to any in"
2951 .Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s"
2952 .Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s"
2954 Per-flow queueing can be useful for a variety of purposes.
2955 A very simple one is counting traffic:
2957 .Dl "ipfw add pipe 1 tcp from any to any"
2958 .Dl "ipfw add pipe 1 udp from any to any"
2959 .Dl "ipfw add pipe 1 ip from any to any"
2960 .Dl "ipfw pipe 1 config mask all"
2962 The above set of rules will create queues (and collect
2963 statistics) for all traffic.
2964 Because the pipes have no limitations, the only effect is
2965 collecting statistics.
2966 Note that we need 3 rules, not just the last one, because
2969 tries to match IP packets it will not consider ports, so we
2970 would not see connections on separate ports as different
2973 A more sophisticated example is limiting the outbound traffic
2974 on a net with per-host limits, rather than per-network limits:
2976 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
2977 .Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in"
2978 .Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
2979 .Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
2981 In the following example, we need to create several traffic bandwidth
2982 classes and we need different hosts/networks to fall into different classes.
2983 We create one pipe for each class and configure them accordingly.
2984 Then we create a single table and fill it with IP subnets and addresses.
2985 For each subnet/host we set the argument equal to the number of the pipe
2987 Then we classify traffic using a single rule:
2989 .Dl "ipfw pipe 1 config bw 1000Kbyte/s"
2990 .Dl "ipfw pipe 4 config bw 4000Kbyte/s"
2992 .Dl "ipfw table 1 add 192.168.2.0/24 1"
2993 .Dl "ipfw table 1 add 192.168.0.0/27 4"
2994 .Dl "ipfw table 1 add 192.168.0.2 1"
2996 .Dl "ipfw add pipe tablearg ip from table(1) to any"
3000 action, the table entries may include hostnames and IP addresses.
3002 .Dl "ipfw table 1 add 192.168.2.0/24 10.23.2.1"
3003 .Dl "ipfw table 1 add 192.168.0.0/27 router1.dmz"
3005 .Dl "ipfw add 100 fwd tablearg ip from any to table(1)"
3007 To add a set of rules atomically, e.g.\& set 18:
3009 .Dl "ipfw set disable 18"
3010 .Dl "ipfw add NN set 18 ... # repeat as needed"
3011 .Dl "ipfw set enable 18"
3013 To delete a set of rules atomically the command is simply:
3015 .Dl "ipfw delete set 18"
3017 To test a ruleset and disable it and regain control if something goes wrong:
3019 .Dl "ipfw set disable 18"
3020 .Dl "ipfw add NN set 18 ... # repeat as needed"
3021 .Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18"
3023 Here if everything goes well, you press control-C before the "sleep"
3024 terminates, and your ruleset will be left active.
3025 Otherwise, e.g.\& if
3026 you cannot access your box, the ruleset will be disabled after
3027 the sleep terminates thus restoring the previous situation.
3029 To show rules of the specific set:
3031 .Dl "ipfw set 18 show"
3033 To show rules of the disabled set:
3035 .Dl "ipfw -S set 18 show"
3037 To clear a specific rule counters of the specific set:
3039 .Dl "ipfw set 18 zero NN"
3041 To delete a specific rule of the specific set:
3043 .Dl "ipfw set 18 delete NN"
3044 .Ss NAT, REDIRECT AND LSNAT
3045 First redirect all the traffic to nat instance 123:
3047 .Dl "ipfw add nat 123 all from any to any"
3049 Then to configure nat instance 123 to alias all the outgoing traffic with ip
3050 192.168.0.123, blocking all incoming connections, trying to keep
3051 same ports on both sides, clearing aliasing table on address change
3052 and keeping a log of traffic/link statistics:
3054 .Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports"
3056 Or to change address of instance 123, aliasing table will be cleared (see
3059 .Dl "ipfw nat 123 config ip 10.0.0.1"
3061 To see configuration of nat instance 123:
3063 .Dl "ipfw nat 123 show config"
3065 To show logs of all the instances in range 111-999:
3067 .Dl "ipfw nat 111-999 show"
3069 To see configurations of all instances:
3071 .Dl "ipfw nat show config"
3073 Or a redirect rule with mixed modes could looks like:
3075 .Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66"
3076 .Dl " redirect_port tcp 192.168.0.1:80 500"
3077 .Dl " redirect_proto udp 192.168.1.43 192.168.1.1"
3078 .Dl " redirect_addr 192.168.0.10,192.168.0.11"
3079 .Dl " 10.0.0.100 # LSNAT"
3080 .Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22"
3083 or it could be split in:
3085 .Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66"
3086 .Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500"
3087 .Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1"
3088 .Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12"
3090 .Dl "ipfw nat 5 config redirect_port tcp"
3091 .Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500"
3113 utility first appeared in
3118 Stateful extensions were introduced in
3121 was introduced in Summer 2002.
3123 .An Ugen J. S. Antsilevich ,
3124 .An Poul-Henning Kamp ,
3130 API based upon code written by
3134 Dummynet has been introduced by Luigi Rizzo in 1997-1998.
3136 Some early work (1999-2000) on the
3138 traffic shaper supported by Akamba Corp.
3140 The ipfw core (ipfw2) has been completely redesigned and
3141 reimplemented by Luigi Rizzo in summer 2002. Further
3143 options have been added by various developer over the years.
3146 In-kernel NAT support written by
3147 .An Paolo Pisati Aq piso@FreeBSD.org
3148 as part of a Summer of Code 2005 project.
3152 support has been developed by
3153 .An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au .
3154 The primary developers and maintainers are David Hayes and Jason But.
3155 For further information visit:
3156 .Aq http://www.caia.swin.edu.au/urp/SONATA
3158 Delay profiles have been developed by Alessandro Cerri and
3159 Luigi Rizzo, supported by the
3160 European Commission within Projects Onelab and Onelab2.
3162 The syntax has grown over the years and sometimes it might be confusing.
3163 Unfortunately, backward compatibility prevents cleaning up mistakes
3164 made in the definition of the syntax.
3168 Misconfiguring the firewall can put your computer in an unusable state,
3169 possibly shutting down network services and requiring console access to
3170 regain control of it.
3172 Incoming packet fragments diverted by
3174 are reassembled before delivery to the socket.
3175 The action used on those packet is the one from the
3176 rule which matches the first fragment of the packet.
3178 Packets diverted to userland, and then reinserted by a userland process
3179 may lose various packet attributes.
3180 The packet source interface name
3181 will be preserved if it is shorter than 8 bytes and the userland process
3182 saves and reuses the sockaddr_in
3185 otherwise, it may be lost.
3186 If a packet is reinserted in this manner, later rules may be incorrectly
3187 applied, making the order of
3189 rules in the rule sequence very important.
3191 Dummynet drops all packets with IPv6 link-local addresses.
3197 may not behave as expected.
3198 In particular, incoming SYN packets may
3199 have no uid or gid associated with them since they do not yet belong
3200 to a TCP connection, and the uid/gid associated with a packet may not
3201 be as expected if the associated process calls
3203 or similar system calls.
3205 Rule syntax is subject to the command line environment and some patterns
3206 may need to be escaped with the backslash character
3207 or quoted appropriately.
3209 Due to the architecture of
3211 ipfw nat is not compatible with the TCP segmentation offloading (TSO).
3212 Thus, to reliably nat your network traffic, please disable TSO
3216 ICMP error messages are not implicitly matched by dynamic rules
3217 for the respective conversations.
3218 To avoid failures of network error detection and path MTU discovery,
3219 ICMP error messages may need to be allowed explicitly through static
git://git.onelab.eu / ipfw.git / blob