1.\" 2.\" $FreeBSD$ 3.\" 4.Dd October 2, 2017 5.Dt IPFW 8 6.Os 7.Sh NAME 8.Nm ipfw 9.Nd User interface for firewall, traffic shaper, packet scheduler, 10in-kernel NAT. 11.Sh SYNOPSIS 12.Ss FIREWALL CONFIGURATION 13.Nm 14.Op Fl cq 15.Cm add 16.Ar rule 17.Nm 18.Op Fl acdefnNStT 19.Op Cm set Ar N 20.Brq Cm list | show 21.Op Ar rule | first-last ... 22.Nm 23.Op Fl f | q 24.Op Cm set Ar N 25.Cm flush 26.Nm 27.Op Fl q 28.Op Cm set Ar N 29.Brq Cm delete | zero | resetlog 30.Op Ar number ... 31.Pp 32.Nm 33.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 34.Nm 35.Cm set move 36.Op Cm rule 37.Ar number Cm to Ar number 38.Nm 39.Cm set swap Ar number number 40.Nm 41.Cm set show 42.Ss SYSCTL SHORTCUTS 43.Nm 44.Cm enable 45.Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive 46.Nm 47.Cm disable 48.Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive 49.Ss LOOKUP TABLES 50.Nm 51.Oo Cm set Ar N Oc Cm table Ar name Cm create Ar create-options 52.Nm 53.Oo Cm set Ar N Oc Cm table 54.Brq Ar name | all 55.Cm destroy 56.Nm 57.Oo Cm set Ar N Oc Cm table Ar name Cm modify Ar modify-options 58.Nm 59.Oo Cm set Ar N Oc Cm table Ar name Cm swap Ar name 60.Nm 61.Oo Cm set Ar N Oc Cm table Ar name Cm add Ar table-key Op Ar value 62.Nm 63.Oo Cm set Ar N Oc Cm table Ar name Cm add Op Ar table-key Ar value ... 64.Nm 65.Oo Cm set Ar N Oc Cm table Ar name Cm atomic add Op Ar table-key Ar value ... 66.Nm 67.Oo Cm set Ar N Oc Cm table Ar name Cm delete Op Ar table-key ... 68.Nm 69.Oo Cm set Ar N Oc Cm table Ar name Cm lookup Ar addr 70.Nm 71.Oo Cm set Ar N Oc Cm table Ar name Cm lock 72.Nm 73.Oo Cm set Ar N Oc Cm table Ar name Cm unlock 74.Nm 75.Oo Cm set Ar N Oc Cm table 76.Brq Ar name | all 77.Cm list 78.Nm 79.Oo Cm set Ar N Oc Cm table 80.Brq Ar name | all 81.Cm info 82.Nm 83.Oo Cm set Ar N Oc Cm table 84.Brq Ar name | all 85.Cm detail 86.Nm 87.Oo Cm set Ar N Oc Cm table 88.Brq Ar name | all 89.Cm flush 90.Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER) 91.Nm 92.Brq Cm pipe | queue | sched 93.Ar number 94.Cm config 95.Ar config-options 96.Nm 97.Op Fl s Op Ar field 98.Brq Cm pipe | queue | sched 99.Brq Cm delete | list | show 100.Op Ar number ... 101.Ss IN-KERNEL NAT 102.Nm 103.Op Fl q 104.Cm nat 105.Ar number 106.Cm config 107.Ar config-options 108.Pp 109.Nm 110.Op Fl cfnNqS 111.Oo 112.Fl p Ar preproc 113.Oo 114.Ar preproc-flags 115.Oc 116.Oc 117.Ar pathname 118.Ss STATEFUL IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 119.Nm 120.Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm create Ar create-options 121.Nm 122.Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm config Ar config-options 123.Nm 124.Oo Cm set Ar N Oc Cm nat64lsn 125.Brq Ar name | all 126.Brq Cm list | show 127.Op Cm states 128.Nm 129.Oo Cm set Ar N Oc Cm nat64lsn 130.Brq Ar name | all 131.Cm destroy 132.Nm 133.Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm stats Op Cm reset 134.Ss STATELESS IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 135.Nm 136.Oo Cm set Ar N Oc Cm nat64stl Ar name Cm create Ar create-options 137.Nm 138.Oo Cm set Ar N Oc Cm nat64stl Ar name Cm config Ar config-options 139.Nm 140.Oo Cm set Ar N Oc Cm nat64stl 141.Brq Ar name | all 142.Brq Cm list | show 143.Nm 144.Oo Cm set Ar N Oc Cm nat64stl 145.Brq Ar name | all 146.Cm destroy 147.Nm 148.Oo Cm set Ar N Oc Cm nat64stl Ar name Cm stats Op Cm reset 149.Ss IPv6-to-IPv6 NETWORK PREFIX TRANSLATION 150.Nm 151.Oo Cm set Ar N Oc Cm nptv6 Ar name Cm create Ar create-options 152.Nm 153.Oo Cm set Ar N Oc Cm nptv6 154.Brq Ar name | all 155.Brq Cm list | show 156.Nm 157.Oo Cm set Ar N Oc Cm nptv6 158.Brq Ar name | all 159.Cm destroy 160.Nm 161.Oo Cm set Ar N Oc Cm nptv6 Ar name Cm stats Op Cm reset 162.Ss INTERNAL DIAGNOSTICS 163.Nm 164.Cm internal iflist 165.Nm 166.Cm internal talist 167.Nm 168.Cm internal vlist 169.Sh DESCRIPTION 170The 171.Nm 172utility is the user interface for controlling the 173.Xr ipfw 4 174firewall, the 175.Xr dummynet 4 176traffic shaper/packet scheduler, and the 177in-kernel NAT services. 178.Pp 179A firewall configuration, or 180.Em ruleset , 181is made of a list of 182.Em rules 183numbered from 1 to 65535. 184Packets are passed to the firewall 185from a number of different places in the protocol stack 186(depending on the source and destination of the packet, 187it is possible for the firewall to be 188invoked multiple times on the same packet). 189The packet passed to the firewall is compared 190against each of the rules in the 191.Em ruleset , 192in rule-number order 193(multiple rules with the same number are permitted, in which case 194they are processed in order of insertion). 195When a match is found, the action corresponding to the 196matching rule is performed. 197.Pp 198Depending on the action and certain system settings, packets 199can be reinjected into the firewall at some rule after the 200matching one for further processing. 201.Pp 202A ruleset always includes a 203.Em default 204rule (numbered 65535) which cannot be modified or deleted, 205and matches all packets. 206The action associated with the 207.Em default 208rule can be either 209.Cm deny 210or 211.Cm allow 212depending on how the kernel is configured. 213.Pp 214If the ruleset includes one or more rules with the 215.Cm keep-state 216or 217.Cm limit 218option, 219the firewall will have a 220.Em stateful 221behaviour, i.e., upon a match it will create 222.Em dynamic rules , 223i.e., rules that match packets with the same 5-tuple 224(protocol, source and destination addresses and ports) 225as the packet which caused their creation. 226Dynamic rules, which have a limited lifetime, are checked 227at the first occurrence of a 228.Cm check-state , 229.Cm keep-state 230or 231.Cm limit 232rule, and are typically used to open the firewall on-demand to 233legitimate traffic only. 234See the 235.Sx STATEFUL FIREWALL 236and 237.Sx EXAMPLES 238Sections below for more information on the stateful behaviour of 239.Nm . 240.Pp 241All rules (including dynamic ones) have a few associated counters: 242a packet count, a byte count, a log count and a timestamp 243indicating the time of the last match. 244Counters can be displayed or reset with 245.Nm 246commands. 247.Pp 248Each rule belongs to one of 32 different 249.Em sets 250, and there are 251.Nm 252commands to atomically manipulate sets, such as enable, 253disable, swap sets, move all rules in a set to another 254one, delete all rules in a set. 255These can be useful to 256install temporary configurations, or to test them. 257See Section 258.Sx SETS OF RULES 259for more information on 260.Em sets . 261.Pp 262Rules can be added with the 263.Cm add 264command; deleted individually or in groups with the 265.Cm delete 266command, and globally (except those in set 31) with the 267.Cm flush 268command; displayed, optionally with the content of the 269counters, using the 270.Cm show 271and 272.Cm list 273commands. 274Finally, counters can be reset with the 275.Cm zero 276and 277.Cm resetlog 278commands. 279.Pp 280.Ss COMMAND OPTIONS 281The following general options are available when invoking 282.Nm : 283.Bl -tag -width indent 284.It Fl a 285Show counter values when listing rules. 286The 287.Cm show 288command implies this option. 289.It Fl b 290Only show the action and the comment, not the body of a rule. 291Implies 292.Fl c . 293.It Fl c 294When entering or showing rules, print them in compact form, 295i.e., omitting the "ip from any to any" string 296when this does not carry any additional information. 297.It Fl d 298When listing, show dynamic rules in addition to static ones. 299.It Fl e 300When listing and 301.Fl d 302is specified, also show expired dynamic rules. 303.It Fl f 304Do not ask for confirmation for commands that can cause problems 305if misused, i.e., 306.Cm flush . 307If there is no tty associated with the process, this is implied. 308.It Fl i 309When listing a table (see the 310.Sx LOOKUP TABLES 311section below for more information on lookup tables), format values 312as IP addresses. 313By default, values are shown as integers. 314.It Fl n 315Only check syntax of the command strings, without actually passing 316them to the kernel. 317.It Fl N 318Try to resolve addresses and service names in output. 319.It Fl q 320Be quiet when executing the 321.Cm add , 322.Cm nat , 323.Cm zero , 324.Cm resetlog 325or 326.Cm flush 327commands; 328(implies 329.Fl f ) . 330This is useful when updating rulesets by executing multiple 331.Nm 332commands in a script 333(e.g., 334.Ql sh\ /etc/rc.firewall ) , 335or by processing a file with many 336.Nm 337rules across a remote login session. 338It also stops a table add or delete 339from failing if the entry already exists or is not present. 340.Pp 341The reason why this option may be important is that 342for some of these actions, 343.Nm 344may print a message; if the action results in blocking the 345traffic to the remote client, 346the remote login session will be closed 347and the rest of the ruleset will not be processed. 348Access to the console would then be required to recover. 349.It Fl S 350When listing rules, show the 351.Em set 352each rule belongs to. 353If this flag is not specified, disabled rules will not be 354listed. 355.It Fl s Op Ar field 356When listing pipes, sort according to one of the four 357counters (total or current packets or bytes). 358.It Fl t 359When listing, show last match timestamp converted with ctime(). 360.It Fl T 361When listing, show last match timestamp as seconds from the epoch. 362This form can be more convenient for postprocessing by scripts. 363.El 364.Ss LIST OF RULES AND PREPROCESSING 365To ease configuration, rules can be put into a file which is 366processed using 367.Nm 368as shown in the last synopsis line. 369An absolute 370.Ar pathname 371must be used. 372The file will be read line by line and applied as arguments to the 373.Nm 374utility. 375.Pp 376Optionally, a preprocessor can be specified using 377.Fl p Ar preproc 378where 379.Ar pathname 380is to be piped through. 381Useful preprocessors include 382.Xr cpp 1 383and 384.Xr m4 1 . 385If 386.Ar preproc 387does not start with a slash 388.Pq Ql / 389as its first character, the usual 390.Ev PATH 391name search is performed. 392Care should be taken with this in environments where not all 393file systems are mounted (yet) by the time 394.Nm 395is being run (e.g.\& when they are mounted over NFS). 396Once 397.Fl p 398has been specified, any additional arguments are passed on to the preprocessor 399for interpretation. 400This allows for flexible configuration files (like conditionalizing 401them on the local hostname) and the use of macros to centralize 402frequently required arguments like IP addresses. 403.Ss TRAFFIC SHAPER CONFIGURATION 404The 405.Nm 406.Cm pipe , queue 407and 408.Cm sched 409commands are used to configure the traffic shaper and packet scheduler. 410See the 411.Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 412Section below for details. 413.Pp 414If the world and the kernel get out of sync the 415.Nm 416ABI may break, preventing you from being able to add any rules. 417This can adversely affect the booting process. 418You can use 419.Nm 420.Cm disable 421.Cm firewall 422to temporarily disable the firewall to regain access to the network, 423allowing you to fix the problem. 424.Sh PACKET FLOW 425A packet is checked against the active ruleset in multiple places 426in the protocol stack, under control of several sysctl variables. 427These places and variables are shown below, and it is important to 428have this picture in mind in order to design a correct ruleset. 429.Bd -literal -offset indent 430 ^ to upper layers V 431 | | 432 +----------->-----------+ 433 ^ V 434 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1 435 | | 436 ^ V 437 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1 438 | | 439 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1 440 ^ V 441 | to devices | 442.Ed 443.Pp 444The number of 445times the same packet goes through the firewall can 446vary between 0 and 4 depending on packet source and 447destination, and system configuration. 448.Pp 449Note that as packets flow through the stack, headers can be 450stripped or added to it, and so they may or may not be available 451for inspection. 452E.g., incoming packets will include the MAC header when 453.Nm 454is invoked from 455.Cm ether_demux() , 456but the same packets will have the MAC header stripped off when 457.Nm 458is invoked from 459.Cm ip_input() 460or 461.Cm ip6_input() . 462.Pp 463Also note that each packet is always checked against the complete ruleset, 464irrespective of the place where the check occurs, or the source of the packet. 465If a rule contains some match patterns or actions which are not valid 466for the place of invocation (e.g.\& trying to match a MAC header within 467.Cm ip_input 468or 469.Cm ip6_input ), 470the match pattern will not match, but a 471.Cm not 472operator in front of such patterns 473.Em will 474cause the pattern to 475.Em always 476match on those packets. 477It is thus the responsibility of 478the programmer, if necessary, to write a suitable ruleset to 479differentiate among the possible places. 480.Cm skipto 481rules can be useful here, as an example: 482.Bd -literal -offset indent 483# packets from ether_demux or bdg_forward 484ipfw add 10 skipto 1000 all from any to any layer2 in 485# packets from ip_input 486ipfw add 10 skipto 2000 all from any to any not layer2 in 487# packets from ip_output 488ipfw add 10 skipto 3000 all from any to any not layer2 out 489# packets from ether_output_frame 490ipfw add 10 skipto 4000 all from any to any layer2 out 491.Ed 492.Pp 493(yes, at the moment there is no way to differentiate between 494ether_demux and bdg_forward). 495.Sh SYNTAX 496In general, each keyword or argument must be provided as 497a separate command line argument, with no leading or trailing 498spaces. 499Keywords are case-sensitive, whereas arguments may 500or may not be case-sensitive depending on their nature 501(e.g.\& uid's are, hostnames are not). 502.Pp 503Some arguments (e.g., port or address lists) are comma-separated 504lists of values. 505In this case, spaces after commas ',' are allowed to make 506the line more readable. 507You can also put the entire 508command (including flags) into a single argument. 509E.g., the following forms are equivalent: 510.Bd -literal -offset indent 511ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8 512ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8 513ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8" 514.Ed 515.Sh RULE FORMAT 516The format of firewall rules is the following: 517.Bd -ragged -offset indent 518.Bk -words 519.Op Ar rule_number 520.Op Cm set Ar set_number 521.Op Cm prob Ar match_probability 522.Ar action 523.Op Cm log Op Cm logamount Ar number 524.Op Cm altq Ar queue 525.Oo 526.Bro Cm tag | untag 527.Brc Ar number 528.Oc 529.Ar body 530.Ek 531.Ed 532.Pp 533where the body of the rule specifies which information is used 534for filtering packets, among the following: 535.Pp 536.Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact 537.It Layer-2 header fields 538When available 539.It IPv4 and IPv6 Protocol 540SCTP, TCP, UDP, ICMP, etc. 541.It Source and dest. addresses and ports 542.It Direction 543See Section 544.Sx PACKET FLOW 545.It Transmit and receive interface 546By name or address 547.It Misc. IP header fields 548Version, type of service, datagram length, identification, 549fragment flag (non-zero IP offset), 550Time To Live 551.It IP options 552.It IPv6 Extension headers 553Fragmentation, Hop-by-Hop options, 554Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options. 555.It IPv6 Flow-ID 556.It Misc. TCP header fields 557TCP flags (SYN, FIN, ACK, RST, etc.), 558sequence number, acknowledgment number, 559window 560.It TCP options 561.It ICMP types 562for ICMP packets 563.It ICMP6 types 564for ICMP6 packets 565.It User/group ID 566When the packet can be associated with a local socket. 567.It Divert status 568Whether a packet came from a divert socket (e.g., 569.Xr natd 8 ) . 570.It Fib annotation state 571Whether a packet has been tagged for using a specific FIB (routing table) 572in future forwarding decisions. 573.El 574.Pp 575Note that some of the above information, e.g.\& source MAC or IP addresses and 576TCP/UDP ports, can be easily spoofed, so filtering on those fields 577alone might not guarantee the desired results. 578.Bl -tag -width indent 579.It Ar rule_number 580Each rule is associated with a 581.Ar rule_number 582in the range 1..65535, with the latter reserved for the 583.Em default 584rule. 585Rules are checked sequentially by rule number. 586Multiple rules can have the same number, in which case they are 587checked (and listed) according to the order in which they have 588been added. 589If a rule is entered without specifying a number, the kernel will 590assign one in such a way that the rule becomes the last one 591before the 592.Em default 593rule. 594Automatic rule numbers are assigned by incrementing the last 595non-default rule number by the value of the sysctl variable 596.Ar net.inet.ip.fw.autoinc_step 597which defaults to 100. 598If this is not possible (e.g.\& because we would go beyond the 599maximum allowed rule number), the number of the last 600non-default value is used instead. 601.It Cm set Ar set_number 602Each rule is associated with a 603.Ar set_number 604in the range 0..31. 605Sets can be individually disabled and enabled, so this parameter 606is of fundamental importance for atomic ruleset manipulation. 607It can be also used to simplify deletion of groups of rules. 608If a rule is entered without specifying a set number, 609set 0 will be used. 610.br 611Set 31 is special in that it cannot be disabled, 612and rules in set 31 are not deleted by the 613.Nm ipfw flush 614command (but you can delete them with the 615.Nm ipfw delete set 31 616command). 617Set 31 is also used for the 618.Em default 619rule. 620.It Cm prob Ar match_probability 621A match is only declared with the specified probability 622(floating point number between 0 and 1). 623This can be useful for a number of applications such as 624random packet drop or 625(in conjunction with 626.Nm dummynet ) 627to simulate the effect of multiple paths leading to out-of-order 628packet delivery. 629.Pp 630Note: this condition is checked before any other condition, including 631ones such as keep-state or check-state which might have side effects. 632.It Cm log Op Cm logamount Ar number 633Packets matching a rule with the 634.Cm log 635keyword will be made available for logging in two ways: 636if the sysctl variable 637.Va net.inet.ip.fw.verbose 638is set to 0 (default), one can use 639.Xr bpf 4 640attached to the 641.Li ipfw0 642pseudo interface. 643This pseudo interface can be created after a boot 644manually by using the following command: 645.Bd -literal -offset indent 646# ifconfig ipfw0 create 647.Ed 648.Pp 649Or, automatically at boot time by adding the following 650line to the 651.Xr rc.conf 5 652file: 653.Bd -literal -offset indent 654firewall_logif="YES" 655.Ed 656.Pp 657There is no overhead if no 658.Xr bpf 4 659is attached to the pseudo interface. 660.Pp 661If 662.Va net.inet.ip.fw.verbose 663is set to 1, packets will be logged to 664.Xr syslogd 8 665with a 666.Dv LOG_SECURITY 667facility up to a maximum of 668.Cm logamount 669packets. 670If no 671.Cm logamount 672is specified, the limit is taken from the sysctl variable 673.Va net.inet.ip.fw.verbose_limit . 674In both cases, a value of 0 means unlimited logging. 675.Pp 676Once the limit is reached, logging can be re-enabled by 677clearing the logging counter or the packet counter for that entry, see the 678.Cm resetlog 679command. 680.Pp 681Note: logging is done after all other packet matching conditions 682have been successfully verified, and before performing the final 683action (accept, deny, etc.) on the packet. 684.It Cm tag Ar number 685When a packet matches a rule with the 686.Cm tag 687keyword, the numeric tag for the given 688.Ar number 689in the range 1..65534 will be attached to the packet. 690The tag acts as an internal marker (it is not sent out over 691the wire) that can be used to identify these packets later on. 692This can be used, for example, to provide trust between interfaces 693and to start doing policy-based filtering. 694A packet can have multiple tags at the same time. 695Tags are "sticky", meaning once a tag is applied to a packet by a 696matching rule it exists until explicit removal. 697Tags are kept with the packet everywhere within the kernel, but are 698lost when packet leaves the kernel, for example, on transmitting 699packet out to the network or sending packet to a 700.Xr divert 4 701socket. 702.Pp 703To check for previously applied tags, use the 704.Cm tagged 705rule option. 706To delete previously applied tag, use the 707.Cm untag 708keyword. 709.Pp 710Note: since tags are kept with the packet everywhere in kernelspace, 711they can be set and unset anywhere in the kernel network subsystem 712(using the 713.Xr mbuf_tags 9 714facility), not only by means of the 715.Xr ipfw 4 716.Cm tag 717and 718.Cm untag 719keywords. 720For example, there can be a specialized 721.Xr netgraph 4 722node doing traffic analyzing and tagging for later inspecting 723in firewall. 724.It Cm untag Ar number 725When a packet matches a rule with the 726.Cm untag 727keyword, the tag with the number 728.Ar number 729is searched among the tags attached to this packet and, 730if found, removed from it. 731Other tags bound to packet, if present, are left untouched. 732.It Cm altq Ar queue 733When a packet matches a rule with the 734.Cm altq 735keyword, the ALTQ identifier for the given 736.Ar queue 737(see 738.Xr altq 4 ) 739will be attached. 740Note that this ALTQ tag is only meaningful for packets going "out" of IPFW, 741and not being rejected or going to divert sockets. 742Note that if there is insufficient memory at the time the packet is 743processed, it will not be tagged, so it is wise to make your ALTQ 744"default" queue policy account for this. 745If multiple 746.Cm altq 747rules match a single packet, only the first one adds the ALTQ classification 748tag. 749In doing so, traffic may be shaped by using 750.Cm count Cm altq Ar queue 751rules for classification early in the ruleset, then later applying 752the filtering decision. 753For example, 754.Cm check-state 755and 756.Cm keep-state 757rules may come later and provide the actual filtering decisions in 758addition to the fallback ALTQ tag. 759.Pp 760You must run 761.Xr pfctl 8 762to set up the queues before IPFW will be able to look them up by name, 763and if the ALTQ disciplines are rearranged, the rules in containing the 764queue identifiers in the kernel will likely have gone stale and need 765to be reloaded. 766Stale queue identifiers will probably result in misclassification. 767.Pp 768All system ALTQ processing can be turned on or off via 769.Nm 770.Cm enable Ar altq 771and 772.Nm 773.Cm disable Ar altq . 774The usage of 775.Va net.inet.ip.fw.one_pass 776is irrelevant to ALTQ traffic shaping, as the actual rule action is followed 777always after adding an ALTQ tag. 778.El 779.Ss RULE ACTIONS 780A rule can be associated with one of the following actions, which 781will be executed when the packet matches the body of the rule. 782.Bl -tag -width indent 783.It Cm allow | accept | pass | permit 784Allow packets that match rule. 785The search terminates. 786.It Cm check-state Op Ar :flowname | Cm :any 787Checks the packet against the dynamic ruleset. 788If a match is found, execute the action associated with 789the rule which generated this dynamic rule, otherwise 790move to the next rule. 791.br 792.Cm Check-state 793rules do not have a body. 794If no 795.Cm check-state 796rule is found, the dynamic ruleset is checked at the first 797.Cm keep-state 798or 799.Cm limit 800rule. 801The 802.Ar :flowname 803is symbolic name assigned to dynamic rule by 804.Cm keep-state 805opcode. 806The special flowname 807.Cm :any 808can be used to ignore states flowname when matching. 809The 810.Cm :default 811keyword is special name used for compatibility with old rulesets. 812.It Cm count 813Update counters for all packets that match rule. 814The search continues with the next rule. 815.It Cm deny | drop 816Discard packets that match this rule. 817The search terminates. 818.It Cm divert Ar port 819Divert packets that match this rule to the 820.Xr divert 4 821socket bound to port 822.Ar port . 823The search terminates. 824.It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port 825Change the next-hop on matching packets to 826.Ar ipaddr , 827which can be an IP address or a host name. 828For IPv4, the next hop can also be supplied by the last table 829looked up for the packet by using the 830.Cm tablearg 831keyword instead of an explicit address. 832The search terminates if this rule matches. 833.Pp 834If 835.Ar ipaddr 836is a local address, then matching packets will be forwarded to 837.Ar port 838(or the port number in the packet if one is not specified in the rule) 839on the local machine. 840.br 841If 842.Ar ipaddr 843is not a local address, then the port number 844(if specified) is ignored, and the packet will be 845forwarded to the remote address, using the route as found in 846the local routing table for that IP. 847.br 848A 849.Ar fwd 850rule will not match layer-2 packets (those received 851on ether_input, ether_output, or bridged). 852.br 853The 854.Cm fwd 855action does not change the contents of the packet at all. 856In particular, the destination address remains unmodified, so 857packets forwarded to another system will usually be rejected by that system 858unless there is a matching rule on that system to capture them. 859For packets forwarded locally, 860the local address of the socket will be 861set to the original destination address of the packet. 862This makes the 863.Xr netstat 1 864entry look rather weird but is intended for 865use with transparent proxy servers. 866.It Cm nat Ar nat_nr | tablearg 867Pass packet to a 868nat instance 869(for network address translation, address redirect, etc.): 870see the 871.Sx NETWORK ADDRESS TRANSLATION (NAT) 872Section for further information. 873.It Cm nat64lsn Ar name 874Pass packet to a stateful NAT64 instance (for IPv6/IPv4 network address and 875protocol translation): see the 876.Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 877Section for further information. 878.It Cm nat64stl Ar name 879Pass packet to a stateless NAT64 instance (for IPv6/IPv4 network address and 880protocol translation): see the 881.Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 882Section for further information. 883.It Cm nptv6 Ar name 884Pass packet to a NPTv6 instance (for IPv6-to-IPv6 network prefix translation): 885see the 886.Sx IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6) 887Section for further information. 888.It Cm pipe Ar pipe_nr 889Pass packet to a 890.Nm dummynet 891.Dq pipe 892(for bandwidth limitation, delay, etc.). 893See the 894.Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 895Section for further information. 896The search terminates; however, on exit from the pipe and if 897the 898.Xr sysctl 8 899variable 900.Va net.inet.ip.fw.one_pass 901is not set, the packet is passed again to the firewall code 902starting from the next rule. 903.It Cm queue Ar queue_nr 904Pass packet to a 905.Nm dummynet 906.Dq queue 907(for bandwidth limitation using WF2Q+). 908.It Cm reject 909(Deprecated). 910Synonym for 911.Cm unreach host . 912.It Cm reset 913Discard packets that match this rule, and if the 914packet is a TCP packet, try to send a TCP reset (RST) notice. 915The search terminates. 916.It Cm reset6 917Discard packets that match this rule, and if the 918packet is a TCP packet, try to send a TCP reset (RST) notice. 919The search terminates. 920.It Cm skipto Ar number | tablearg 921Skip all subsequent rules numbered less than 922.Ar number . 923The search continues with the first rule numbered 924.Ar number 925or higher. 926It is possible to use the 927.Cm tablearg 928keyword with a skipto for a 929.Em computed 930skipto. Skipto may work either in O(log(N)) or in O(1) depending 931on amount of memory and/or sysctl variables. 932See the 933.Sx SYSCTL VARIABLES 934section for more details. 935.It Cm call Ar number | tablearg 936The current rule number is saved in the internal stack and 937ruleset processing continues with the first rule numbered 938.Ar number 939or higher. 940If later a rule with the 941.Cm return 942action is encountered, the processing returns to the first rule 943with number of this 944.Cm call 945rule plus one or higher 946(the same behaviour as with packets returning from 947.Xr divert 4 948socket after a 949.Cm divert 950action). 951This could be used to make somewhat like an assembly language 952.Dq subroutine 953calls to rules with common checks for different interfaces, etc. 954.Pp 955Rule with any number could be called, not just forward jumps as with 956.Cm skipto . 957So, to prevent endless loops in case of mistakes, both 958.Cm call 959and 960.Cm return 961actions don't do any jumps and simply go to the next rule if memory 962cannot be allocated or stack overflowed/underflowed. 963.Pp 964Internally stack for rule numbers is implemented using 965.Xr mbuf_tags 9 966facility and currently has size of 16 entries. 967As mbuf tags are lost when packet leaves the kernel, 968.Cm divert 969should not be used in subroutines to avoid endless loops 970and other undesired effects. 971.It Cm return 972Takes rule number saved to internal stack by the last 973.Cm call 974action and returns ruleset processing to the first rule 975with number greater than number of corresponding 976.Cm call 977rule. 978See description of the 979.Cm call 980action for more details. 981.Pp 982Note that 983.Cm return 984rules usually end a 985.Dq subroutine 986and thus are unconditional, but 987.Nm 988command-line utility currently requires every action except 989.Cm check-state 990to have body. 991While it is sometimes useful to return only on some packets, 992usually you want to print just 993.Dq return 994for readability. 995A workaround for this is to use new syntax and 996.Fl c 997switch: 998.Bd -literal -offset indent 999# Add a rule without actual body 1000ipfw add 2999 return via any 1001 1002# List rules without "from any to any" part 1003ipfw -c list 1004.Ed 1005.Pp 1006This cosmetic annoyance may be fixed in future releases. 1007.It Cm tee Ar port 1008Send a copy of packets matching this rule to the 1009.Xr divert 4 1010socket bound to port 1011.Ar port . 1012The search continues with the next rule. 1013.It Cm unreach Ar code 1014Discard packets that match this rule, and try to send an ICMP 1015unreachable notice with code 1016.Ar code , 1017where 1018.Ar code 1019is a number from 0 to 255, or one of these aliases: 1020.Cm net , host , protocol , port , 1021.Cm needfrag , srcfail , net-unknown , host-unknown , 1022.Cm isolated , net-prohib , host-prohib , tosnet , 1023.Cm toshost , filter-prohib , host-precedence 1024or 1025.Cm precedence-cutoff . 1026The search terminates. 1027.It Cm unreach6 Ar code 1028Discard packets that match this rule, and try to send an ICMPv6 1029unreachable notice with code 1030.Ar code , 1031where 1032.Ar code 1033is a number from 0, 1, 3 or 4, or one of these aliases: 1034.Cm no-route, admin-prohib, address 1035or 1036.Cm port . 1037The search terminates. 1038.It Cm netgraph Ar cookie 1039Divert packet into netgraph with given 1040.Ar cookie . 1041The search terminates. 1042If packet is later returned from netgraph it is either 1043accepted or continues with the next rule, depending on 1044.Va net.inet.ip.fw.one_pass 1045sysctl variable. 1046.It Cm ngtee Ar cookie 1047A copy of packet is diverted into netgraph, original 1048packet continues with the next rule. 1049See 1050.Xr ng_ipfw 4 1051for more information on 1052.Cm netgraph 1053and 1054.Cm ngtee 1055actions. 1056.It Cm setfib Ar fibnum | tablearg 1057The packet is tagged so as to use the FIB (routing table) 1058.Ar fibnum 1059in any subsequent forwarding decisions. 1060In the current implementation, this is limited to the values 0 through 15, see 1061.Xr setfib 2 . 1062Processing continues at the next rule. 1063It is possible to use the 1064.Cm tablearg 1065keyword with setfib. 1066If the tablearg value is not within the compiled range of fibs, 1067the packet's fib is set to 0. 1068.It Cm setdscp Ar DSCP | number | tablearg 1069Set specified DiffServ codepoint for an IPv4/IPv6 packet. 1070Processing continues at the next rule. 1071Supported values are: 1072.Pp 1073.Cm CS0 1074.Pq Dv 000000 , 1075.Cm CS1 1076.Pq Dv 001000 , 1077.Cm CS2 1078.Pq Dv 010000 , 1079.Cm CS3 1080.Pq Dv 011000 , 1081.Cm CS4 1082.Pq Dv 100000 , 1083.Cm CS5 1084.Pq Dv 101000 , 1085.Cm CS6 1086.Pq Dv 110000 , 1087.Cm CS7 1088.Pq Dv 111000 , 1089.Cm AF11 1090.Pq Dv 001010 , 1091.Cm AF12 1092.Pq Dv 001100 , 1093.Cm AF13 1094.Pq Dv 001110 , 1095.Cm AF21 1096.Pq Dv 010010 , 1097.Cm AF22 1098.Pq Dv 010100 , 1099.Cm AF23 1100.Pq Dv 010110 , 1101.Cm AF31 1102.Pq Dv 011010 , 1103.Cm AF32 1104.Pq Dv 011100 , 1105.Cm AF33 1106.Pq Dv 011110 , 1107.Cm AF41 1108.Pq Dv 100010 , 1109.Cm AF42 1110.Pq Dv 100100 , 1111.Cm AF43 1112.Pq Dv 100110 , 1113.Cm EF 1114.Pq Dv 101110 , 1115.Cm BE 1116.Pq Dv 000000 . 1117Additionally, DSCP value can be specified by number (0..64). 1118It is also possible to use the 1119.Cm tablearg 1120keyword with setdscp. 1121If the tablearg value is not within the 0..64 range, lower 6 bits of supplied 1122value are used. 1123.It Cm tcp-setmss Ar mss 1124Set the Maximum Segment Size (MSS) in the TCP segment to value 1125.Ar mss . 1126The kernel module 1127.Cm ipfw_pmod 1128should be loaded or kernel should have 1129.Cm options IPFIREWALL_PMOD 1130to be able use this action. 1131This command does not change a packet if original MSS value is lower than 1132specified value. 1133Both TCP over IPv4 and over IPv6 are supported. 1134Regardless of matched a packet or not by the 1135.Cm tcp-setmss 1136rule, the search continues with the next rule. 1137.It Cm reass 1138Queue and reassemble IP fragments. 1139If the packet is not fragmented, counters are updated and 1140processing continues with the next rule. 1141If the packet is the last logical fragment, the packet is reassembled and, if 1142.Va net.inet.ip.fw.one_pass 1143is set to 0, processing continues with the next rule. 1144Otherwise, the packet is allowed to pass and the search terminates. 1145If the packet is a fragment in the middle of a logical group of fragments, 1146it is consumed and 1147processing stops immediately. 1148.Pp 1149Fragment handling can be tuned via 1150.Va net.inet.ip.maxfragpackets 1151and 1152.Va net.inet.ip.maxfragsperpacket 1153which limit, respectively, the maximum number of processable 1154fragments (default: 800) and 1155the maximum number of fragments per packet (default: 16). 1156.Pp 1157NOTA BENE: since fragments do not contain port numbers, 1158they should be avoided with the 1159.Nm reass 1160rule. 1161Alternatively, direction-based (like 1162.Nm in 1163/ 1164.Nm out 1165) and source-based (like 1166.Nm via 1167) match patterns can be used to select fragments. 1168.Pp 1169Usually a simple rule like: 1170.Bd -literal -offset indent 1171# reassemble incoming fragments 1172ipfw add reass all from any to any in 1173.Ed 1174.Pp 1175is all you need at the beginning of your ruleset. 1176.El 1177.Ss RULE BODY 1178The body of a rule contains zero or more patterns (such as 1179specific source and destination addresses or ports, 1180protocol options, incoming or outgoing interfaces, etc.) 1181that the packet must match in order to be recognised. 1182In general, the patterns are connected by (implicit) 1183.Cm and 1184operators -- i.e., all must match in order for the 1185rule to match. 1186Individual patterns can be prefixed by the 1187.Cm not 1188operator to reverse the result of the match, as in 1189.Pp 1190.Dl "ipfw add 100 allow ip from not 1.2.3.4 to any" 1191.Pp 1192Additionally, sets of alternative match patterns 1193.Pq Em or-blocks 1194can be constructed by putting the patterns in 1195lists enclosed between parentheses ( ) or braces { }, and 1196using the 1197.Cm or 1198operator as follows: 1199.Pp 1200.Dl "ipfw add 100 allow ip from { x or not y or z } to any" 1201.Pp 1202Only one level of parentheses is allowed. 1203Beware that most shells have special meanings for parentheses 1204or braces, so it is advisable to put a backslash \\ in front of them 1205to prevent such interpretations. 1206.Pp 1207The body of a rule must in general include a source and destination 1208address specifier. 1209The keyword 1210.Ar any 1211can be used in various places to specify that the content of 1212a required field is irrelevant. 1213.Pp 1214The rule body has the following format: 1215.Bd -ragged -offset indent 1216.Op Ar proto Cm from Ar src Cm to Ar dst 1217.Op Ar options 1218.Ed 1219.Pp 1220The first part (proto from src to dst) is for backward 1221compatibility with earlier versions of 1222.Fx . 1223In modern 1224.Fx 1225any match pattern (including MAC headers, IP protocols, 1226addresses and ports) can be specified in the 1227.Ar options 1228section. 1229.Pp 1230Rule fields have the following meaning: 1231.Bl -tag -width indent 1232.It Ar proto : protocol | Cm { Ar protocol Cm or ... } 1233.It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number 1234An IP protocol specified by number or name 1235(for a complete list see 1236.Pa /etc/protocols ) , 1237or one of the following keywords: 1238.Bl -tag -width indent 1239.It Cm ip4 | ipv4 1240Matches IPv4 packets. 1241.It Cm ip6 | ipv6 1242Matches IPv6 packets. 1243.It Cm ip | all 1244Matches any packet. 1245.El 1246.Pp 1247The 1248.Cm ipv6 1249in 1250.Cm proto 1251option will be treated as inner protocol. 1252And, the 1253.Cm ipv4 1254is not available in 1255.Cm proto 1256option. 1257.Pp 1258The 1259.Cm { Ar protocol Cm or ... } 1260format (an 1261.Em or-block ) 1262is provided for convenience only but its use is deprecated. 1263.It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports 1264An address (or a list, see below) 1265optionally followed by 1266.Ar ports 1267specifiers. 1268.Pp 1269The second format 1270.Em ( or-block 1271with multiple addresses) is provided for convenience only and 1272its use is discouraged. 1273.It Ar addr : Oo Cm not Oc Bro 1274.Cm any | me | me6 | 1275.Cm table Ns Pq Ar name Ns Op , Ns Ar value 1276.Ar | addr-list | addr-set 1277.Brc 1278.Bl -tag -width indent 1279.It Cm any 1280matches any IP address. 1281.It Cm me 1282matches any IP address configured on an interface in the system. 1283.It Cm me6 1284matches any IPv6 address configured on an interface in the system. 1285The address list is evaluated at the time the packet is 1286analysed. 1287.It Cm table Ns Pq Ar name Ns Op , Ns Ar value 1288Matches any IPv4 or IPv6 address for which an entry exists in the lookup table 1289.Ar number . 1290If an optional 32-bit unsigned 1291.Ar value 1292is also specified, an entry will match only if it has this value. 1293See the 1294.Sx LOOKUP TABLES 1295section below for more information on lookup tables. 1296.El 1297.It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list 1298.It Ar ip-addr : 1299A host or subnet address specified in one of the following ways: 1300.Bl -tag -width indent 1301.It Ar numeric-ip | hostname 1302Matches a single IPv4 address, specified as dotted-quad or a hostname. 1303Hostnames are resolved at the time the rule is added to the firewall list. 1304.It Ar addr Ns / Ns Ar masklen 1305Matches all addresses with base 1306.Ar addr 1307(specified as an IP address, a network number, or a hostname) 1308and mask width of 1309.Cm masklen 1310bits. 1311As an example, 1.2.3.4/25 or 1.2.3.0/25 will match 1312all IP numbers from 1.2.3.0 to 1.2.3.127 . 1313.It Ar addr Ns : Ns Ar mask 1314Matches all addresses with base 1315.Ar addr 1316(specified as an IP address, a network number, or a hostname) 1317and the mask of 1318.Ar mask , 1319specified as a dotted quad. 1320As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match 13211.*.3.*. 1322This form is advised only for non-contiguous 1323masks. 1324It is better to resort to the 1325.Ar addr Ns / Ns Ar masklen 1326format for contiguous masks, which is more compact and less 1327error-prone. 1328.El 1329.It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm } 1330.It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list 1331Matches all addresses with base address 1332.Ar addr 1333(specified as an IP address, a network number, or a hostname) 1334and whose last byte is in the list between braces { } . 1335Note that there must be no spaces between braces and 1336numbers (spaces after commas are allowed). 1337Elements of the list can be specified as single entries 1338or ranges. 1339The 1340.Ar masklen 1341field is used to limit the size of the set of addresses, 1342and can have any value between 24 and 32. 1343If not specified, 1344it will be assumed as 24. 1345.br 1346This format is particularly useful to handle sparse address sets 1347within a single rule. 1348Because the matching occurs using a 1349bitmask, it takes constant time and dramatically reduces 1350the complexity of rulesets. 1351.br 1352As an example, an address specified as 1.2.3.4/24{128,35-55,89} 1353or 1.2.3.0/24{128,35-55,89} 1354will match the following IP addresses: 1355.br 13561.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 . 1357.It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list 1358.It Ar ip6-addr : 1359A host or subnet specified one of the following ways: 1360.Bl -tag -width indent 1361.It Ar numeric-ip | hostname 1362Matches a single IPv6 address as allowed by 1363.Xr inet_pton 3 1364or a hostname. 1365Hostnames are resolved at the time the rule is added to the firewall 1366list. 1367.It Ar addr Ns / Ns Ar masklen 1368Matches all IPv6 addresses with base 1369.Ar addr 1370(specified as allowed by 1371.Xr inet_pton 1372or a hostname) 1373and mask width of 1374.Cm masklen 1375bits. 1376.It Ar addr Ns / Ns Ar mask 1377Matches all IPv6 addresses with base 1378.Ar addr 1379(specified as allowed by 1380.Xr inet_pton 1381or a hostname) 1382and the mask of 1383.Ar mask , 1384specified as allowed by 1385.Xr inet_pton. 1386As an example, fe::640:0:0/ffff::ffff:ffff:0:0 will match 1387fe:*:*:*:0:640:*:*. 1388This form is advised only for non-contiguous 1389masks. 1390It is better to resort to the 1391.Ar addr Ns / Ns Ar masklen 1392format for contiguous masks, which is more compact and less 1393error-prone. 1394.El 1395.Pp 1396No support for sets of IPv6 addresses is provided because IPv6 addresses 1397are typically random past the initial prefix. 1398.It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports 1399For protocols which support port numbers (such as SCTP, TCP and UDP), optional 1400.Cm ports 1401may be specified as one or more ports or port ranges, separated 1402by commas but no spaces, and an optional 1403.Cm not 1404operator. 1405The 1406.Ql \&- 1407notation specifies a range of ports (including boundaries). 1408.Pp 1409Service names (from 1410.Pa /etc/services ) 1411may be used instead of numeric port values. 1412The length of the port list is limited to 30 ports or ranges, 1413though one can specify larger ranges by using an 1414.Em or-block 1415in the 1416.Cm options 1417section of the rule. 1418.Pp 1419A backslash 1420.Pq Ql \e 1421can be used to escape the dash 1422.Pq Ql - 1423character in a service name (from a shell, the backslash must be 1424typed twice to avoid the shell itself interpreting it as an escape 1425character). 1426.Pp 1427.Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any" 1428.Pp 1429Fragmented packets which have a non-zero offset (i.e., not the first 1430fragment) will never match a rule which has one or more port 1431specifications. 1432See the 1433.Cm frag 1434option for details on matching fragmented packets. 1435.El 1436.Ss RULE OPTIONS (MATCH PATTERNS) 1437Additional match patterns can be used within 1438rules. 1439Zero or more of these so-called 1440.Em options 1441can be present in a rule, optionally prefixed by the 1442.Cm not 1443operand, and possibly grouped into 1444.Em or-blocks . 1445.Pp 1446The following match patterns can be used (listed in alphabetical order): 1447.Bl -tag -width indent 1448.It Cm // this is a comment. 1449Inserts the specified text as a comment in the rule. 1450Everything following // is considered as a comment and stored in the rule. 1451You can have comment-only rules, which are listed as having a 1452.Cm count 1453action followed by the comment. 1454.It Cm bridged 1455Alias for 1456.Cm layer2 . 1457.It Cm diverted 1458Matches only packets generated by a divert socket. 1459.It Cm diverted-loopback 1460Matches only packets coming from a divert socket back into the IP stack 1461input for delivery. 1462.It Cm diverted-output 1463Matches only packets going from a divert socket back outward to the IP 1464stack output for delivery. 1465.It Cm dst-ip Ar ip-address 1466Matches IPv4 packets whose destination IP is one of the address(es) 1467specified as argument. 1468.It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address 1469Matches IPv6 packets whose destination IP is one of the address(es) 1470specified as argument. 1471.It Cm dst-port Ar ports 1472Matches IP packets whose destination port is one of the port(s) 1473specified as argument. 1474.It Cm established 1475Matches TCP packets that have the RST or ACK bits set. 1476.It Cm ext6hdr Ar header 1477Matches IPv6 packets containing the extended header given by 1478.Ar header . 1479Supported headers are: 1480.Pp 1481Fragment, 1482.Pq Cm frag , 1483Hop-to-hop options 1484.Pq Cm hopopt , 1485any type of Routing Header 1486.Pq Cm route , 1487Source routing Routing Header Type 0 1488.Pq Cm rthdr0 , 1489Mobile IPv6 Routing Header Type 2 1490.Pq Cm rthdr2 , 1491Destination options 1492.Pq Cm dstopt , 1493IPSec authentication headers 1494.Pq Cm ah , 1495and IPsec encapsulated security payload headers 1496.Pq Cm esp . 1497.It Cm fib Ar fibnum 1498Matches a packet that has been tagged to use 1499the given FIB (routing table) number. 1500.It Cm flow Ar table Ns Pq Ar name Ns Op , Ns Ar value 1501Search for the flow entry in lookup table 1502.Ar name . 1503If not found, the match fails. 1504Otherwise, the match succeeds and 1505.Cm tablearg 1506is set to the value extracted from the table. 1507.Pp 1508This option can be useful to quickly dispatch traffic based on 1509certain packet fields. 1510See the 1511.Sx LOOKUP TABLES 1512section below for more information on lookup tables. 1513.It Cm flow-id Ar labels 1514Matches IPv6 packets containing any of the flow labels given in 1515.Ar labels . 1516.Ar labels 1517is a comma separated list of numeric flow labels. 1518.It Cm frag 1519Matches packets that are fragments and not the first 1520fragment of an IP datagram. 1521Note that these packets will not have 1522the next protocol header (e.g.\& TCP, UDP) so options that look into 1523these headers cannot match. 1524.It Cm gid Ar group 1525Matches all TCP or UDP packets sent by or received for a 1526.Ar group . 1527A 1528.Ar group 1529may be specified by name or number. 1530.It Cm jail Ar prisonID 1531Matches all TCP or UDP packets sent by or received for the 1532jail whos prison ID is 1533.Ar prisonID . 1534.It Cm icmptypes Ar types 1535Matches ICMP packets whose ICMP type is in the list 1536.Ar types . 1537The list may be specified as any combination of 1538individual types (numeric) separated by commas. 1539.Em Ranges are not allowed . 1540The supported ICMP types are: 1541.Pp 1542echo reply 1543.Pq Cm 0 , 1544destination unreachable 1545.Pq Cm 3 , 1546source quench 1547.Pq Cm 4 , 1548redirect 1549.Pq Cm 5 , 1550echo request 1551.Pq Cm 8 , 1552router advertisement 1553.Pq Cm 9 , 1554router solicitation 1555.Pq Cm 10 , 1556time-to-live exceeded 1557.Pq Cm 11 , 1558IP header bad 1559.Pq Cm 12 , 1560timestamp request 1561.Pq Cm 13 , 1562timestamp reply 1563.Pq Cm 14 , 1564information request 1565.Pq Cm 15 , 1566information reply 1567.Pq Cm 16 , 1568address mask request 1569.Pq Cm 17 1570and address mask reply 1571.Pq Cm 18 . 1572.It Cm icmp6types Ar types 1573Matches ICMP6 packets whose ICMP6 type is in the list of 1574.Ar types . 1575The list may be specified as any combination of 1576individual types (numeric) separated by commas. 1577.Em Ranges are not allowed . 1578.It Cm in | out 1579Matches incoming or outgoing packets, respectively. 1580.Cm in 1581and 1582.Cm out 1583are mutually exclusive (in fact, 1584.Cm out 1585is implemented as 1586.Cm not in Ns No ). 1587.It Cm ipid Ar id-list 1588Matches IPv4 packets whose 1589.Cm ip_id 1590field has value included in 1591.Ar id-list , 1592which is either a single value or a list of values or ranges 1593specified in the same way as 1594.Ar ports . 1595.It Cm iplen Ar len-list 1596Matches IP packets whose total length, including header and data, is 1597in the set 1598.Ar len-list , 1599which is either a single value or a list of values or ranges 1600specified in the same way as 1601.Ar ports . 1602.It Cm ipoptions Ar spec 1603Matches packets whose IPv4 header contains the comma separated list of 1604options specified in 1605.Ar spec . 1606The supported IP options are: 1607.Pp 1608.Cm ssrr 1609(strict source route), 1610.Cm lsrr 1611(loose source route), 1612.Cm rr 1613(record packet route) and 1614.Cm ts 1615(timestamp). 1616The absence of a particular option may be denoted 1617with a 1618.Ql \&! . 1619.It Cm ipprecedence Ar precedence 1620Matches IPv4 packets whose precedence field is equal to 1621.Ar precedence . 1622.It Cm ipsec 1623Matches packets that have IPSEC history associated with them 1624(i.e., the packet comes encapsulated in IPSEC, the kernel 1625has IPSEC support, and can correctly decapsulate it). 1626.Pp 1627Note that specifying 1628.Cm ipsec 1629is different from specifying 1630.Cm proto Ar ipsec 1631as the latter will only look at the specific IP protocol field, 1632irrespective of IPSEC kernel support and the validity of the IPSEC data. 1633.Pp 1634Further note that this flag is silently ignored in kernels without 1635IPSEC support. 1636It does not affect rule processing when given and the 1637rules are handled as if with no 1638.Cm ipsec 1639flag. 1640.It Cm iptos Ar spec 1641Matches IPv4 packets whose 1642.Cm tos 1643field contains the comma separated list of 1644service types specified in 1645.Ar spec . 1646The supported IP types of service are: 1647.Pp 1648.Cm lowdelay 1649.Pq Dv IPTOS_LOWDELAY , 1650.Cm throughput 1651.Pq Dv IPTOS_THROUGHPUT , 1652.Cm reliability 1653.Pq Dv IPTOS_RELIABILITY , 1654.Cm mincost 1655.Pq Dv IPTOS_MINCOST , 1656.Cm congestion 1657.Pq Dv IPTOS_ECN_CE . 1658The absence of a particular type may be denoted 1659with a 1660.Ql \&! . 1661.It Cm dscp spec Ns Op , Ns Ar spec 1662Matches IPv4/IPv6 packets whose 1663.Cm DS 1664field value is contained in 1665.Ar spec 1666mask. 1667Multiple values can be specified via 1668the comma separated list. 1669Value can be one of keywords used in 1670.Cm setdscp 1671action or exact number. 1672.It Cm ipttl Ar ttl-list 1673Matches IPv4 packets whose time to live is included in 1674.Ar ttl-list , 1675which is either a single value or a list of values or ranges 1676specified in the same way as 1677.Ar ports . 1678.It Cm ipversion Ar ver 1679Matches IP packets whose IP version field is 1680.Ar ver . 1681.It Cm keep-state Op Ar :flowname 1682Upon a match, the firewall will create a dynamic rule, whose 1683default behaviour is to match bidirectional traffic between 1684source and destination IP/port using the same protocol. 1685The rule has a limited lifetime (controlled by a set of 1686.Xr sysctl 8 1687variables), and the lifetime is refreshed every time a matching 1688packet is found. 1689The 1690.Ar :flowname 1691is used to assign additional to addresses, ports and protocol parameter 1692to dynamic rule. It can be used for more accurate matching by 1693.Cm check-state 1694rule. 1695The 1696.Cm :default 1697keyword is special name used for compatibility with old rulesets. 1698.It Cm layer2 1699Matches only layer2 packets, i.e., those passed to 1700.Nm 1701from ether_demux() and ether_output_frame(). 1702.It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N Op Ar :flowname 1703The firewall will only allow 1704.Ar N 1705connections with the same 1706set of parameters as specified in the rule. 1707One or more 1708of source and destination addresses and ports can be 1709specified. 1710.It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar name 1711Search an entry in lookup table 1712.Ar name 1713that matches the field specified as argument. 1714If not found, the match fails. 1715Otherwise, the match succeeds and 1716.Cm tablearg 1717is set to the value extracted from the table. 1718.Pp 1719This option can be useful to quickly dispatch traffic based on 1720certain packet fields. 1721See the 1722.Sx LOOKUP TABLES 1723section below for more information on lookup tables. 1724.It Cm { MAC | mac } Ar dst-mac src-mac 1725Match packets with a given 1726.Ar dst-mac 1727and 1728.Ar src-mac 1729addresses, specified as the 1730.Cm any 1731keyword (matching any MAC address), or six groups of hex digits 1732separated by colons, 1733and optionally followed by a mask indicating the significant bits. 1734The mask may be specified using either of the following methods: 1735.Bl -enum -width indent 1736.It 1737A slash 1738.Pq / 1739followed by the number of significant bits. 1740For example, an address with 33 significant bits could be specified as: 1741.Pp 1742.Dl "MAC 10:20:30:40:50:60/33 any" 1743.It 1744An ampersand 1745.Pq & 1746followed by a bitmask specified as six groups of hex digits separated 1747by colons. 1748For example, an address in which the last 16 bits are significant could 1749be specified as: 1750.Pp 1751.Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any" 1752.Pp 1753Note that the ampersand character has a special meaning in many shells 1754and should generally be escaped. 1755.El 1756Note that the order of MAC addresses (destination first, 1757source second) is 1758the same as on the wire, but the opposite of the one used for 1759IP addresses. 1760.It Cm mac-type Ar mac-type 1761Matches packets whose Ethernet Type field 1762corresponds to one of those specified as argument. 1763.Ar mac-type 1764is specified in the same way as 1765.Cm port numbers 1766(i.e., one or more comma-separated single values or ranges). 1767You can use symbolic names for known values such as 1768.Em vlan , ipv4, ipv6 . 1769Values can be entered as decimal or hexadecimal (if prefixed by 0x), 1770and they are always printed as hexadecimal (unless the 1771.Cm -N 1772option is used, in which case symbolic resolution will be attempted). 1773.It Cm proto Ar protocol 1774Matches packets with the corresponding IP protocol. 1775.It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar table Ns Po Ar name Ns Oo , Ns Ar value Oc Pc | Ar ipno | Ar any 1776Matches packets received, transmitted or going through, 1777respectively, the interface specified by exact name 1778.Po Ar ifX Pc , 1779by device name 1780.Po Ar if* Pc , 1781by IP address, or through some interface. 1782Table 1783.Ar name 1784may be used to match interface by its kernel ifindex. 1785See the 1786.Sx LOOKUP TABLES 1787section below for more information on lookup tables. 1788.Pp 1789The 1790.Cm via 1791keyword causes the interface to always be checked. 1792If 1793.Cm recv 1794or 1795.Cm xmit 1796is used instead of 1797.Cm via , 1798then only the receive or transmit interface (respectively) 1799is checked. 1800By specifying both, it is possible to match packets based on 1801both receive and transmit interface, e.g.: 1802.Pp 1803.Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1" 1804.Pp 1805The 1806.Cm recv 1807interface can be tested on either incoming or outgoing packets, 1808while the 1809.Cm xmit 1810interface can only be tested on outgoing packets. 1811So 1812.Cm out 1813is required (and 1814.Cm in 1815is invalid) whenever 1816.Cm xmit 1817is used. 1818.Pp 1819A packet might not have a receive or transmit interface: packets 1820originating from the local host have no receive interface, 1821while packets destined for the local host have no transmit 1822interface. 1823.It Cm setup 1824Matches TCP packets that have the SYN bit set but no ACK bit. 1825This is the short form of 1826.Dq Li tcpflags\ syn,!ack . 1827.It Cm sockarg 1828Matches packets that are associated to a local socket and 1829for which the SO_USER_COOKIE socket option has been set 1830to a non-zero value. 1831As a side effect, the value of the 1832option is made available as 1833.Cm tablearg 1834value, which in turn can be used as 1835.Cm skipto 1836or 1837.Cm pipe 1838number. 1839.It Cm src-ip Ar ip-address 1840Matches IPv4 packets whose source IP is one of the address(es) 1841specified as an argument. 1842.It Cm src-ip6 Ar ip6-address 1843Matches IPv6 packets whose source IP is one of the address(es) 1844specified as an argument. 1845.It Cm src-port Ar ports 1846Matches IP packets whose source port is one of the port(s) 1847specified as argument. 1848.It Cm tagged Ar tag-list 1849Matches packets whose tags are included in 1850.Ar tag-list , 1851which is either a single value or a list of values or ranges 1852specified in the same way as 1853.Ar ports . 1854Tags can be applied to the packet using 1855.Cm tag 1856rule action parameter (see it's description for details on tags). 1857.It Cm tcpack Ar ack 1858TCP packets only. 1859Match if the TCP header acknowledgment number field is set to 1860.Ar ack . 1861.It Cm tcpdatalen Ar tcpdatalen-list 1862Matches TCP packets whose length of TCP data is 1863.Ar tcpdatalen-list , 1864which is either a single value or a list of values or ranges 1865specified in the same way as 1866.Ar ports . 1867.It Cm tcpflags Ar spec 1868TCP packets only. 1869Match if the TCP header contains the comma separated list of 1870flags specified in 1871.Ar spec . 1872The supported TCP flags are: 1873.Pp 1874.Cm fin , 1875.Cm syn , 1876.Cm rst , 1877.Cm psh , 1878.Cm ack 1879and 1880.Cm urg . 1881The absence of a particular flag may be denoted 1882with a 1883.Ql \&! . 1884A rule which contains a 1885.Cm tcpflags 1886specification can never match a fragmented packet which has 1887a non-zero offset. 1888See the 1889.Cm frag 1890option for details on matching fragmented packets. 1891.It Cm tcpseq Ar seq 1892TCP packets only. 1893Match if the TCP header sequence number field is set to 1894.Ar seq . 1895.It Cm tcpwin Ar tcpwin-list 1896Matches TCP packets whose header window field is set to 1897.Ar tcpwin-list , 1898which is either a single value or a list of values or ranges 1899specified in the same way as 1900.Ar ports . 1901.It Cm tcpoptions Ar spec 1902TCP packets only. 1903Match if the TCP header contains the comma separated list of 1904options specified in 1905.Ar spec . 1906The supported TCP options are: 1907.Pp 1908.Cm mss 1909(maximum segment size), 1910.Cm window 1911(tcp window advertisement), 1912.Cm sack 1913(selective ack), 1914.Cm ts 1915(rfc1323 timestamp) and 1916.Cm cc 1917(rfc1644 t/tcp connection count). 1918The absence of a particular option may be denoted 1919with a 1920.Ql \&! . 1921.It Cm uid Ar user 1922Match all TCP or UDP packets sent by or received for a 1923.Ar user . 1924A 1925.Ar user 1926may be matched by name or identification number. 1927.It Cm verrevpath 1928For incoming packets, 1929a routing table lookup is done on the packet's source address. 1930If the interface on which the packet entered the system matches the 1931outgoing interface for the route, 1932the packet matches. 1933If the interfaces do not match up, 1934the packet does not match. 1935All outgoing packets or packets with no incoming interface match. 1936.Pp 1937The name and functionality of the option is intentionally similar to 1938the Cisco IOS command: 1939.Pp 1940.Dl ip verify unicast reverse-path 1941.Pp 1942This option can be used to make anti-spoofing rules to reject all 1943packets with source addresses not from this interface. 1944See also the option 1945.Cm antispoof . 1946.It Cm versrcreach 1947For incoming packets, 1948a routing table lookup is done on the packet's source address. 1949If a route to the source address exists, but not the default route 1950or a blackhole/reject route, the packet matches. 1951Otherwise, the packet does not match. 1952All outgoing packets match. 1953.Pp 1954The name and functionality of the option is intentionally similar to 1955the Cisco IOS command: 1956.Pp 1957.Dl ip verify unicast source reachable-via any 1958.Pp 1959This option can be used to make anti-spoofing rules to reject all 1960packets whose source address is unreachable. 1961.It Cm antispoof 1962For incoming packets, the packet's source address is checked if it 1963belongs to a directly connected network. 1964If the network is directly connected, then the interface the packet 1965came on in is compared to the interface the network is connected to. 1966When incoming interface and directly connected interface are not the 1967same, the packet does not match. 1968Otherwise, the packet does match. 1969All outgoing packets match. 1970.Pp 1971This option can be used to make anti-spoofing rules to reject all 1972packets that pretend to be from a directly connected network but do 1973not come in through that interface. 1974This option is similar to but more restricted than 1975.Cm verrevpath 1976because it engages only on packets with source addresses of directly 1977connected networks instead of all source addresses. 1978.El 1979.Sh LOOKUP TABLES 1980Lookup tables are useful to handle large sparse sets of 1981addresses or other search keys (e.g., ports, jail IDs, interface names). 1982In the rest of this section we will use the term ``key''. 1983Table name needs to match the following spec: 1984.Ar table-name . 1985Tables with the same name can be created in different 1986.Ar sets . 1987However, rule links to the tables in 1988.Ar set 0 1989by default. 1990This behavior can be controlled by 1991.Va net.inet.ip.fw.tables_sets 1992variable. 1993See the 1994.Sx SETS OF RULES 1995section for more information. 1996There may be up to 65535 different lookup tables. 1997.Pp 1998The following table types are supported: 1999.Bl -tag -width indent 2000.It Ar table-type : Ar addr | iface | number | flow 2001.It Ar table-key : Ar addr Ns Oo / Ns Ar masklen Oc | iface-name | number | flow-spec 2002.It Ar flow-spec : Ar flow-field Ns Op , Ns Ar flow-spec 2003.It Ar flow-field : src-ip | proto | src-port | dst-ip | dst-port 2004.It Cm addr 2005matches IPv4 or IPv6 address. 2006Each entry is represented by an 2007.Ar addr Ns Op / Ns Ar masklen 2008and will match all addresses with base 2009.Ar addr 2010(specified as an IPv4/IPv6 address, or a hostname) and mask width of 2011.Ar masklen 2012bits. 2013If 2014.Ar masklen 2015is not specified, it defaults to 32 for IPv4 and 128 for IPv6. 2016When looking up an IP address in a table, the most specific 2017entry will match. 2018.It Cm iface 2019matches interface names. 2020Each entry is represented by string treated as interface name. 2021Wildcards are not supported. 2022.It Cm number 2023maches protocol ports, uids/gids or jail IDs. 2024Each entry is represented by 32-bit unsigned integer. 2025Ranges are not supported. 2026.It Cm flow 2027Matches packet fields specified by 2028.Ar flow 2029type suboptions with table entries. 2030.El 2031.Pp 2032Tables require explicit creation via 2033.Cm create 2034before use. 2035.Pp 2036The following creation options are supported: 2037.Bl -tag -width indent 2038.It Ar create-options : Ar create-option | create-options 2039.It Ar create-option : Cm type Ar table-type | Cm valtype Ar value-mask | Cm algo Ar algo-desc | 2040.Cm limit Ar number | Cm locked 2041.It Cm type 2042Table key type. 2043.It Cm valtype 2044Table value mask. 2045.It Cm algo 2046Table algorithm to use (see below). 2047.It Cm limit 2048Maximum number of items that may be inserted into table. 2049.It Cm locked 2050Restrict any table modifications. 2051.El 2052.Pp 2053Some of these options may be modified later via 2054.Cm modify 2055keyword. 2056The following options can be changed: 2057.Bl -tag -width indent 2058.It Ar modify-options : Ar modify-option | modify-options 2059.It Ar modify-option : Cm limit Ar number 2060.It Cm limit 2061Alter maximum number of items that may be inserted into table. 2062.El 2063.Pp 2064Additionally, table can be locked or unlocked using 2065.Cm lock 2066or 2067.Cm unlock 2068commands. 2069.Pp 2070Tables of the same 2071.Ar type 2072can be swapped with each other using 2073.Cm swap Ar name 2074command. 2075Swap may fail if tables limits are set and data exchange 2076would result in limits hit. 2077Operation is performed atomically. 2078.Pp 2079One or more entries can be added to a table at once using 2080.Cm add 2081command. 2082Addition of all items are performed atomically. 2083By default, error in addition of one entry does not influence 2084addition of other entries. However, non-zero error code is returned 2085in that case. 2086Special 2087.Cm atomic 2088keyword may be specified before 2089.Cm add 2090to indicate all-or-none add request. 2091.Pp 2092One or more entries can be removed from a table at once using 2093.Cm delete 2094command. 2095By default, error in removal of one entry does not influence 2096removing of other entries. However, non-zero error code is returned 2097in that case. 2098.Pp 2099It may be possible to check what entry will be found on particular 2100.Ar table-key 2101using 2102.Cm lookup 2103.Ar table-key 2104command. 2105This functionality is optional and may be unsupported in some algorithms. 2106.Pp 2107The following operations can be performed on 2108.Ar one 2109or 2110.Cm all 2111tables: 2112.Bl -tag -width indent 2113.It Cm list 2114List all entries. 2115.It Cm flush 2116Removes all entries. 2117.It Cm info 2118Shows generic table information. 2119.It Cm detail 2120Shows generic table information and algo-specific data. 2121.El 2122.Pp 2123The following lookup algorithms are supported: 2124.Bl -tag -width indent 2125.It Ar algo-desc : algo-name | "algo-name algo-data" 2126.It Ar algo-name: Ar addr:radix | addr:hash | iface:array | number:array | flow:hash 2127.It Cm addr:radix 2128Separate Radix trees for IPv4 and IPv6, the same way as the routing table (see 2129.Xr route 4 ) . 2130Default choice for 2131.Ar addr 2132type. 2133.It Cm addr:hash 2134Separate auto-growing hashes for IPv4 and IPv6. 2135Accepts entries with the same mask length specified initially via 2136.Cm "addr:hash masks=/v4,/v6" 2137algorithm creation options. 2138Assume /32 and /128 masks by default. 2139Search removes host bits (according to mask) from supplied address and checks 2140resulting key in appropriate hash. 2141Mostly optimized for /64 and byte-ranged IPv6 masks. 2142.It Cm iface:array 2143Array storing sorted indexes for entries which are presented in the system. 2144Optimized for very fast lookup. 2145.It Cm number:array 2146Array storing sorted u32 numbers. 2147.It Cm flow:hash 2148Auto-growing hash storing flow entries. 2149Search calculates hash on required packet fields and searches for matching 2150entries in selected bucket. 2151.El 2152.Pp 2153The 2154.Cm tablearg 2155feature provides the ability to use a value, looked up in the table, as 2156the argument for a rule action, action parameter or rule option. 2157This can significantly reduce number of rules in some configurations. 2158If two tables are used in a rule, the result of the second (destination) 2159is used. 2160.Pp 2161Each record may hold one or more values according to 2162.Ar value-mask . 2163This mask is set on table creation via 2164.Cm valtype 2165option. 2166The following value types are supported: 2167.Bl -tag -width indent 2168.It Ar value-mask : Ar value-type Ns Op , Ns Ar value-mask 2169.It Ar value-type : Ar skipto | pipe | fib | nat | dscp | tag | divert | 2170.Ar netgraph | limit | ipv4 2171.It Cm skipto 2172rule number to jump to. 2173.It Cm pipe 2174Pipe number to use. 2175.It Cm fib 2176fib number to match/set. 2177.It Cm nat 2178nat number to jump to. 2179.It Cm dscp 2180dscp value to match/set. 2181.It Cm tag 2182tag number to match/set. 2183.It Cm divert 2184port number to divert traffic to. 2185.It Cm netgraph 2186hook number to move packet to. 2187.It Cm limit 2188maximum number of connections. 2189.It Cm ipv4 2190IPv4 nexthop to fwd packets to. 2191.It Cm ipv6 2192IPv6 nexthop to fwd packets to. 2193.El 2194.Pp 2195The 2196.Cm tablearg 2197argument can be used with the following actions: 2198.Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto, setfib, 2199action parameters: 2200.Cm tag, untag, 2201rule options: 2202.Cm limit, tagged. 2203.Pp 2204When used with the 2205.Cm skipto 2206action, the user should be aware that the code will walk the ruleset 2207up to a rule equal to, or past, the given number. 2208.Pp 2209See the 2210.Sx EXAMPLES 2211Section for example usage of tables and the tablearg keyword. 2212.Sh SETS OF RULES 2213Each rule or table belongs to one of 32 different 2214.Em sets 2215, numbered 0 to 31. 2216Set 31 is reserved for the default rule. 2217.Pp 2218By default, rules or tables are put in set 0, unless you use the 2219.Cm set N 2220attribute when adding a new rule or table. 2221Sets can be individually and atomically enabled or disabled, 2222so this mechanism permits an easy way to store multiple configurations 2223of the firewall and quickly (and atomically) switch between them. 2224.Pp 2225By default, tables from set 0 are referenced when adding rule with 2226table opcodes regardless of rule set. 2227This behavior can be changed by setting 2228.Va net.inet.ip.fw.tables_set 2229variable to 1. 2230Rule's set will then be used for table references. 2231.Pp 2232The command to enable/disable sets is 2233.Bd -ragged -offset indent 2234.Nm 2235.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 2236.Ed 2237.Pp 2238where multiple 2239.Cm enable 2240or 2241.Cm disable 2242sections can be specified. 2243Command execution is atomic on all the sets specified in the command. 2244By default, all sets are enabled. 2245.Pp 2246When you disable a set, its rules behave as if they do not exist 2247in the firewall configuration, with only one exception: 2248.Bd -ragged -offset indent 2249dynamic rules created from a rule before it had been disabled 2250will still be active until they expire. 2251In order to delete 2252dynamic rules you have to explicitly delete the parent rule 2253which generated them. 2254.Ed 2255.Pp 2256The set number of rules can be changed with the command 2257.Bd -ragged -offset indent 2258.Nm 2259.Cm set move 2260.Brq Cm rule Ar rule-number | old-set 2261.Cm to Ar new-set 2262.Ed 2263.Pp 2264Also, you can atomically swap two rulesets with the command 2265.Bd -ragged -offset indent 2266.Nm 2267.Cm set swap Ar first-set second-set 2268.Ed 2269.Pp 2270See the 2271.Sx EXAMPLES 2272Section on some possible uses of sets of rules. 2273.Sh STATEFUL FIREWALL 2274Stateful operation is a way for the firewall to dynamically 2275create rules for specific flows when packets that 2276match a given pattern are detected. 2277Support for stateful 2278operation comes through the 2279.Cm check-state , keep-state 2280and 2281.Cm limit 2282options of 2283.Nm rules . 2284.Pp 2285Dynamic rules are created when a packet matches a 2286.Cm keep-state 2287or 2288.Cm limit 2289rule, causing the creation of a 2290.Em dynamic 2291rule which will match all and only packets with 2292a given 2293.Em protocol 2294between a 2295.Em src-ip/src-port dst-ip/dst-port 2296pair of addresses 2297.Em ( src 2298and 2299.Em dst 2300are used here only to denote the initial match addresses, but they 2301are completely equivalent afterwards). 2302Rules created by 2303.Cm keep-state 2304option also have a 2305.Ar :flowname 2306taken from it. 2307This name is used in matching together with addresses, ports and protocol. 2308Dynamic rules will be checked at the first 2309.Cm check-state, keep-state 2310or 2311.Cm limit 2312occurrence, and the action performed upon a match will be the same 2313as in the parent rule. 2314.Pp 2315Note that no additional attributes other than protocol and IP addresses 2316and ports and :flowname are checked on dynamic rules. 2317.Pp 2318The typical use of dynamic rules is to keep a closed firewall configuration, 2319but let the first TCP SYN packet from the inside network install a 2320dynamic rule for the flow so that packets belonging to that session 2321will be allowed through the firewall: 2322.Pp 2323.Dl "ipfw add check-state :OUTBOUND" 2324.Dl "ipfw add allow tcp from my-subnet to any setup keep-state :OUTBOUND" 2325.Dl "ipfw add deny tcp from any to any" 2326.Pp 2327A similar approach can be used for UDP, where an UDP packet coming 2328from the inside will install a dynamic rule to let the response through 2329the firewall: 2330.Pp 2331.Dl "ipfw add check-state :OUTBOUND" 2332.Dl "ipfw add allow udp from my-subnet to any keep-state :OUTBOUND" 2333.Dl "ipfw add deny udp from any to any" 2334.Pp 2335Dynamic rules expire after some time, which depends on the status 2336of the flow and the setting of some 2337.Cm sysctl 2338variables. 2339See Section 2340.Sx SYSCTL VARIABLES 2341for more details. 2342For TCP sessions, dynamic rules can be instructed to periodically 2343send keepalive packets to refresh the state of the rule when it is 2344about to expire. 2345.Pp 2346See Section 2347.Sx EXAMPLES 2348for more examples on how to use dynamic rules. 2349.Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 2350.Nm 2351is also the user interface for the 2352.Nm dummynet 2353traffic shaper, packet scheduler and network emulator, a subsystem that 2354can artificially queue, delay or drop packets 2355emulating the behaviour of certain network links 2356or queueing systems. 2357.Pp 2358.Nm dummynet 2359operates by first using the firewall to select packets 2360using any match pattern that can be used in 2361.Nm 2362rules. 2363Matching packets are then passed to either of two 2364different objects, which implement the traffic regulation: 2365.Bl -hang -offset XXXX 2366.It Em pipe 2367A 2368.Em pipe 2369emulates a 2370.Em link 2371with given bandwidth and propagation delay, 2372driven by a FIFO scheduler and a single queue with programmable 2373queue size and packet loss rate. 2374Packets are appended to the queue as they come out from 2375.Nm ipfw , 2376and then transferred in FIFO order to the link at the desired rate. 2377.It Em queue 2378A 2379.Em queue 2380is an abstraction used to implement packet scheduling 2381using one of several packet scheduling algorithms. 2382Packets sent to a 2383.Em queue 2384are first grouped into flows according to a mask on the 5-tuple. 2385Flows are then passed to the scheduler associated to the 2386.Em queue , 2387and each flow uses scheduling parameters (weight and others) 2388as configured in the 2389.Em queue 2390itself. 2391A scheduler in turn is connected to an emulated link, 2392and arbitrates the link's bandwidth among backlogged flows according to 2393weights and to the features of the scheduling algorithm in use. 2394.El 2395.Pp 2396In practice, 2397.Em pipes 2398can be used to set hard limits to the bandwidth that a flow can use, whereas 2399.Em queues 2400can be used to determine how different flows share the available bandwidth. 2401.Pp 2402A graphical representation of the binding of queues, 2403flows, schedulers and links is below. 2404.Bd -literal -offset indent 2405 (flow_mask|sched_mask) sched_mask 2406 +---------+ weight Wx +-------------+ 2407 | |->-[flow]-->--| |-+ 2408 -->--| QUEUE x | ... | | | 2409 | |->-[flow]-->--| SCHEDuler N | | 2410 +---------+ | | | 2411 ... | +--[LINK N]-->-- 2412 +---------+ weight Wy | | +--[LINK N]-->-- 2413 | |->-[flow]-->--| | | 2414 -->--| QUEUE y | ... | | | 2415 | |->-[flow]-->--| | | 2416 +---------+ +-------------+ | 2417 +-------------+ 2418.Ed 2419It is important to understand the role of the SCHED_MASK 2420and FLOW_MASK, which are configured through the commands 2421.Dl "ipfw sched N config mask SCHED_MASK ..." 2422and 2423.Dl "ipfw queue X config mask FLOW_MASK ..." . 2424.Pp 2425The SCHED_MASK is used to assign flows to one or more 2426scheduler instances, one for each 2427value of the packet's 5-tuple after applying SCHED_MASK. 2428As an example, using ``src-ip 0xffffff00'' creates one instance 2429for each /24 destination subnet. 2430.Pp 2431The FLOW_MASK, together with the SCHED_MASK, is used to split 2432packets into flows. 2433As an example, using 2434``src-ip 0x000000ff'' 2435together with the previous SCHED_MASK makes a flow for 2436each individual source address. 2437In turn, flows for each /24 2438subnet will be sent to the same scheduler instance. 2439.Pp 2440The above diagram holds even for the 2441.Em pipe 2442case, with the only restriction that a 2443.Em pipe 2444only supports a SCHED_MASK, and forces the use of a FIFO 2445scheduler (these are for backward compatibility reasons; 2446in fact, internally, a 2447.Nm dummynet's 2448pipe is implemented exactly as above). 2449.Pp 2450There are two modes of 2451.Nm dummynet 2452operation: 2453.Dq normal 2454and 2455.Dq fast . 2456The 2457.Dq normal 2458mode tries to emulate a real link: the 2459.Nm dummynet 2460scheduler ensures that the packet will not leave the pipe faster than it 2461would on the real link with a given bandwidth. 2462The 2463.Dq fast 2464mode allows certain packets to bypass the 2465.Nm dummynet 2466scheduler (if packet flow does not exceed pipe's bandwidth). 2467This is the reason why the 2468.Dq fast 2469mode requires less CPU cycles per packet (on average) and packet latency 2470can be significantly lower in comparison to a real link with the same 2471bandwidth. 2472The default mode is 2473.Dq normal . 2474The 2475.Dq fast 2476mode can be enabled by setting the 2477.Va net.inet.ip.dummynet.io_fast 2478.Xr sysctl 8 2479variable to a non-zero value. 2480.Pp 2481.Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION 2482The 2483.Em pipe , 2484.Em queue 2485and 2486.Em scheduler 2487configuration commands are the following: 2488.Bd -ragged -offset indent 2489.Cm pipe Ar number Cm config Ar pipe-configuration 2490.Pp 2491.Cm queue Ar number Cm config Ar queue-configuration 2492.Pp 2493.Cm sched Ar number Cm config Ar sched-configuration 2494.Ed 2495.Pp 2496The following parameters can be configured for a pipe: 2497.Pp 2498.Bl -tag -width indent -compact 2499.It Cm bw Ar bandwidth | device 2500Bandwidth, measured in 2501.Sm off 2502.Op Cm K | M | G 2503.Brq Cm bit/s | Byte/s . 2504.Sm on 2505.Pp 2506A value of 0 (default) means unlimited bandwidth. 2507The unit must immediately follow the number, as in 2508.Pp 2509.Dl "ipfw pipe 1 config bw 300Kbit/s" 2510.Pp 2511If a device name is specified instead of a numeric value, as in 2512.Pp 2513.Dl "ipfw pipe 1 config bw tun0" 2514.Pp 2515then the transmit clock is supplied by the specified device. 2516At the moment only the 2517.Xr tun 4 2518device supports this 2519functionality, for use in conjunction with 2520.Xr ppp 8 . 2521.Pp 2522.It Cm delay Ar ms-delay 2523Propagation delay, measured in milliseconds. 2524The value is rounded to the next multiple of the clock tick 2525(typically 10ms, but it is a good practice to run kernels 2526with 2527.Dq "options HZ=1000" 2528to reduce 2529the granularity to 1ms or less). 2530The default value is 0, meaning no delay. 2531.Pp 2532.It Cm burst Ar size 2533If the data to be sent exceeds the pipe's bandwidth limit 2534(and the pipe was previously idle), up to 2535.Ar size 2536bytes of data are allowed to bypass the 2537.Nm dummynet 2538scheduler, and will be sent as fast as the physical link allows. 2539Any additional data will be transmitted at the rate specified 2540by the 2541.Nm pipe 2542bandwidth. 2543The burst size depends on how long the pipe has been idle; 2544the effective burst size is calculated as follows: 2545MAX( 2546.Ar size 2547, 2548.Nm bw 2549* pipe_idle_time). 2550.Pp 2551.It Cm profile Ar filename 2552A file specifying the additional overhead incurred in the transmission 2553of a packet on the link. 2554.Pp 2555Some link types introduce extra delays in the transmission 2556of a packet, e.g., because of MAC level framing, contention on 2557the use of the channel, MAC level retransmissions and so on. 2558From our point of view, the channel is effectively unavailable 2559for this extra time, which is constant or variable depending 2560on the link type. 2561Additionally, packets may be dropped after this 2562time (e.g., on a wireless link after too many retransmissions). 2563We can model the additional delay with an empirical curve 2564that represents its distribution. 2565.Bd -literal -offset indent 2566 cumulative probability 2567 1.0 ^ 2568 | 2569 L +-- loss-level x 2570 | ****** 2571 | * 2572 | ***** 2573 | * 2574 | ** 2575 | * 2576 +-------*-------------------> 2577 delay 2578.Ed 2579The empirical curve may have both vertical and horizontal lines. 2580Vertical lines represent constant delay for a range of 2581probabilities. 2582Horizontal lines correspond to a discontinuity in the delay 2583distribution: the pipe will use the largest delay for a 2584given probability. 2585.Pp 2586The file format is the following, with whitespace acting as 2587a separator and '#' indicating the beginning a comment: 2588.Bl -tag -width indent 2589.It Cm name Ar identifier 2590optional name (listed by "ipfw pipe show") 2591to identify the delay distribution; 2592.It Cm bw Ar value 2593the bandwidth used for the pipe. 2594If not specified here, it must be present 2595explicitly as a configuration parameter for the pipe; 2596.It Cm loss-level Ar L 2597the probability above which packets are lost. 2598(0.0 <= L <= 1.0, default 1.0 i.e., no loss); 2599.It Cm samples Ar N 2600the number of samples used in the internal 2601representation of the curve (2..1024; default 100); 2602.It Cm "delay prob" | "prob delay" 2603One of these two lines is mandatory and defines 2604the format of the following lines with data points. 2605.It Ar XXX Ar YYY 26062 or more lines representing points in the curve, 2607with either delay or probability first, according 2608to the chosen format. 2609The unit for delay is milliseconds. 2610Data points do not need to be sorted. 2611Also, the number of actual lines can be different 2612from the value of the "samples" parameter: 2613.Nm 2614utility will sort and interpolate 2615the curve as needed. 2616.El 2617.Pp 2618Example of a profile file: 2619.Bd -literal -offset indent 2620name bla_bla_bla 2621samples 100 2622loss-level 0.86 2623prob delay 26240 200 # minimum overhead is 200ms 26250.5 200 26260.5 300 26270.8 1000 26280.9 1300 26291 1300 2630#configuration file end 2631.Ed 2632.El 2633.Pp 2634The following parameters can be configured for a queue: 2635.Pp 2636.Bl -tag -width indent -compact 2637.It Cm pipe Ar pipe_nr 2638Connects a queue to the specified pipe. 2639Multiple queues (with the same or different weights) can be connected to 2640the same pipe, which specifies the aggregate rate for the set of queues. 2641.Pp 2642.It Cm weight Ar weight 2643Specifies the weight to be used for flows matching this queue. 2644The weight must be in the range 1..100, and defaults to 1. 2645.El 2646.Pp 2647The following case-insensitive parameters can be configured for a 2648scheduler: 2649.Pp 2650.Bl -tag -width indent -compact 2651.It Cm type Ar {fifo | wf2q+ | rr | qfq} 2652specifies the scheduling algorithm to use. 2653.Bl -tag -width indent -compact 2654.It Cm fifo 2655is just a FIFO scheduler (which means that all packets 2656are stored in the same queue as they arrive to the scheduler). 2657FIFO has O(1) per-packet time complexity, with very low 2658constants (estimate 60-80ns on a 2GHz desktop machine) 2659but gives no service guarantees. 2660.It Cm wf2q+ 2661implements the WF2Q+ algorithm, which is a Weighted Fair Queueing 2662algorithm which permits flows to share bandwidth according to 2663their weights. 2664Note that weights are not priorities; even a flow 2665with a minuscule weight will never starve. 2666WF2Q+ has O(log N) per-packet processing cost, where N is the number 2667of flows, and is the default algorithm used by previous versions 2668dummynet's queues. 2669.It Cm rr 2670implements the Deficit Round Robin algorithm, which has O(1) processing 2671costs (roughly, 100-150ns per packet) 2672and permits bandwidth allocation according to weights, but 2673with poor service guarantees. 2674.It Cm qfq 2675implements the QFQ algorithm, which is a very fast variant of 2676WF2Q+, with similar service guarantees and O(1) processing 2677costs (roughly, 200-250ns per packet). 2678.El 2679.El 2680.Pp 2681In addition to the type, all parameters allowed for a pipe can also 2682be specified for a scheduler. 2683.Pp 2684Finally, the following parameters can be configured for both 2685pipes and queues: 2686.Pp 2687.Bl -tag -width XXXX -compact 2688.It Cm buckets Ar hash-table-size 2689Specifies the size of the hash table used for storing the 2690various queues. 2691Default value is 64 controlled by the 2692.Xr sysctl 8 2693variable 2694.Va net.inet.ip.dummynet.hash_size , 2695allowed range is 16 to 65536. 2696.Pp 2697.It Cm mask Ar mask-specifier 2698Packets sent to a given pipe or queue by an 2699.Nm 2700rule can be further classified into multiple flows, each of which is then 2701sent to a different 2702.Em dynamic 2703pipe or queue. 2704A flow identifier is constructed by masking the IP addresses, 2705ports and protocol types as specified with the 2706.Cm mask 2707options in the configuration of the pipe or queue. 2708For each different flow identifier, a new pipe or queue is created 2709with the same parameters as the original object, and matching packets 2710are sent to it. 2711.Pp 2712Thus, when 2713.Em dynamic pipes 2714are used, each flow will get the same bandwidth as defined by the pipe, 2715whereas when 2716.Em dynamic queues 2717are used, each flow will share the parent's pipe bandwidth evenly 2718with other flows generated by the same queue (note that other queues 2719with different weights might be connected to the same pipe). 2720.br 2721Available mask specifiers are a combination of one or more of the following: 2722.Pp 2723.Cm dst-ip Ar mask , 2724.Cm dst-ip6 Ar mask , 2725.Cm src-ip Ar mask , 2726.Cm src-ip6 Ar mask , 2727.Cm dst-port Ar mask , 2728.Cm src-port Ar mask , 2729.Cm flow-id Ar mask , 2730.Cm proto Ar mask 2731or 2732.Cm all , 2733.Pp 2734where the latter means all bits in all fields are significant. 2735.Pp 2736.It Cm noerror 2737When a packet is dropped by a 2738.Nm dummynet 2739queue or pipe, the error 2740is normally reported to the caller routine in the kernel, in the 2741same way as it happens when a device queue fills up. 2742Setting this 2743option reports the packet as successfully delivered, which can be 2744needed for some experimental setups where you want to simulate 2745loss or congestion at a remote router. 2746.Pp 2747.It Cm plr Ar packet-loss-rate 2748Packet loss rate. 2749Argument 2750.Ar packet-loss-rate 2751is a floating-point number between 0 and 1, with 0 meaning no 2752loss, 1 meaning 100% loss. 2753The loss rate is internally represented on 31 bits. 2754.Pp 2755.It Cm queue Brq Ar slots | size Ns Cm Kbytes 2756Queue size, in 2757.Ar slots 2758or 2759.Cm KBytes . 2760Default value is 50 slots, which 2761is the typical queue size for Ethernet devices. 2762Note that for slow speed links you should keep the queue 2763size short or your traffic might be affected by a significant 2764queueing delay. 2765E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit 2766or 20s of queue on a 30Kbit/s pipe. 2767Even worse effects can result if you get packets from an 2768interface with a much larger MTU, e.g.\& the loopback interface 2769with its 16KB packets. 2770The 2771.Xr sysctl 8 2772variables 2773.Em net.inet.ip.dummynet.pipe_byte_limit 2774and 2775.Em net.inet.ip.dummynet.pipe_slot_limit 2776control the maximum lengths that can be specified. 2777.Pp 2778.It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p 2779[ecn] 2780Make use of the RED (Random Early Detection) queue management algorithm. 2781.Ar w_q 2782and 2783.Ar max_p 2784are floating 2785point numbers between 0 and 1 (inclusive), while 2786.Ar min_th 2787and 2788.Ar max_th 2789are integer numbers specifying thresholds for queue management 2790(thresholds are computed in bytes if the queue has been defined 2791in bytes, in slots otherwise). 2792The two parameters can also be of the same value if needed. The 2793.Nm dummynet 2794also supports the gentle RED variant (gred) and ECN (Explicit Congestion 2795Notification) as optional. Three 2796.Xr sysctl 8 2797variables can be used to control the RED behaviour: 2798.Bl -tag -width indent 2799.It Va net.inet.ip.dummynet.red_lookup_depth 2800specifies the accuracy in computing the average queue 2801when the link is idle (defaults to 256, must be greater than zero) 2802.It Va net.inet.ip.dummynet.red_avg_pkt_size 2803specifies the expected average packet size (defaults to 512, must be 2804greater than zero) 2805.It Va net.inet.ip.dummynet.red_max_pkt_size 2806specifies the expected maximum packet size, only used when queue 2807thresholds are in bytes (defaults to 1500, must be greater than zero). 2808.El 2809.El 2810.Pp 2811When used with IPv6 data, 2812.Nm dummynet 2813currently has several limitations. 2814Information necessary to route link-local packets to an 2815interface is not available after processing by 2816.Nm dummynet 2817so those packets are dropped in the output path. 2818Care should be taken to ensure that link-local packets are not passed to 2819.Nm dummynet . 2820.Sh CHECKLIST 2821Here are some important points to consider when designing your 2822rules: 2823.Bl -bullet 2824.It 2825Remember that you filter both packets going 2826.Cm in 2827and 2828.Cm out . 2829Most connections need packets going in both directions. 2830.It 2831Remember to test very carefully. 2832It is a good idea to be near the console when doing this. 2833If you cannot be near the console, 2834use an auto-recovery script such as the one in 2835.Pa /usr/share/examples/ipfw/change_rules.sh . 2836.It 2837Do not forget the loopback interface. 2838.El 2839.Sh FINE POINTS 2840.Bl -bullet 2841.It 2842There are circumstances where fragmented datagrams are unconditionally 2843dropped. 2844TCP packets are dropped if they do not contain at least 20 bytes of 2845TCP header, UDP packets are dropped if they do not contain a full 8 2846byte UDP header, and ICMP packets are dropped if they do not contain 28474 bytes of ICMP header, enough to specify the ICMP type, code, and 2848checksum. 2849These packets are simply logged as 2850.Dq pullup failed 2851since there may not be enough good data in the packet to produce a 2852meaningful log entry. 2853.It 2854Another type of packet is unconditionally dropped, a TCP packet with a 2855fragment offset of one. 2856This is a valid packet, but it only has one use, to try 2857to circumvent firewalls. 2858When logging is enabled, these packets are 2859reported as being dropped by rule -1. 2860.It 2861If you are logged in over a network, loading the 2862.Xr kld 4 2863version of 2864.Nm 2865is probably not as straightforward as you would think. 2866The following command line is recommended: 2867.Bd -literal -offset indent 2868kldload ipfw && \e 2869ipfw add 32000 allow ip from any to any 2870.Ed 2871.Pp 2872Along the same lines, doing an 2873.Bd -literal -offset indent 2874ipfw flush 2875.Ed 2876.Pp 2877in similar surroundings is also a bad idea. 2878.It 2879The 2880.Nm 2881filter list may not be modified if the system security level 2882is set to 3 or higher 2883(see 2884.Xr init 8 2885for information on system security levels). 2886.El 2887.Sh PACKET DIVERSION 2888A 2889.Xr divert 4 2890socket bound to the specified port will receive all packets 2891diverted to that port. 2892If no socket is bound to the destination port, or if the divert module is 2893not loaded, or if the kernel was not compiled with divert socket support, 2894the packets are dropped. 2895.Sh NETWORK ADDRESS TRANSLATION (NAT) 2896.Nm 2897support in-kernel NAT using the kernel version of 2898.Xr libalias 3 . 2899The kernel module 2900.Cm ipfw_nat 2901should be loaded or kernel should have 2902.Cm options IPFIREWALL_NAT 2903to be able use NAT. 2904.Pp 2905The nat configuration command is the following: 2906.Bd -ragged -offset indent 2907.Bk -words 2908.Cm nat 2909.Ar nat_number 2910.Cm config 2911.Ar nat-configuration 2912.Ek 2913.Ed 2914.Pp 2915The following parameters can be configured: 2916.Bl -tag -width indent 2917.It Cm ip Ar ip_address 2918Define an ip address to use for aliasing. 2919.It Cm if Ar nic 2920Use ip address of NIC for aliasing, dynamically changing 2921it if NIC's ip address changes. 2922.It Cm log 2923Enable logging on this nat instance. 2924.It Cm deny_in 2925Deny any incoming connection from outside world. 2926.It Cm same_ports 2927Try to leave the alias port numbers unchanged from 2928the actual local port numbers. 2929.It Cm unreg_only 2930Traffic on the local network not originating from an 2931unregistered address spaces will be ignored. 2932.It Cm reset 2933Reset table of the packet aliasing engine on address change. 2934.It Cm reverse 2935Reverse the way libalias handles aliasing. 2936.It Cm proxy_only 2937Obey transparent proxy rules only, packet aliasing is not performed. 2938.It Cm skip_global 2939Skip instance in case of global state lookup (see below). 2940.El 2941.Pp 2942Some specials value can be supplied instead of 2943.Va nat_number: 2944.Bl -tag -width indent 2945.It Cm global 2946Looks up translation state in all configured nat instances. 2947If an entry is found, packet is aliased according to that entry. 2948If no entry was found in any of the instances, packet is passed unchanged, 2949and no new entry will be created. 2950See section 2951.Sx MULTIPLE INSTANCES 2952in 2953.Xr natd 8 2954for more information. 2955.It Cm tablearg 2956Uses argument supplied in lookup table. 2957See 2958.Sx LOOKUP TABLES 2959section below for more information on lookup tables. 2960.El 2961.Pp 2962To let the packet continue after being (de)aliased, set the sysctl variable 2963.Va net.inet.ip.fw.one_pass 2964to 0. 2965For more information about aliasing modes, refer to 2966.Xr libalias 3 . 2967See Section 2968.Sx EXAMPLES 2969for some examples about nat usage. 2970.Ss REDIRECT AND LSNAT SUPPORT IN IPFW 2971Redirect and LSNAT support follow closely the syntax used in 2972.Xr natd 8 . 2973See Section 2974.Sx EXAMPLES 2975for some examples on how to do redirect and lsnat. 2976.Ss SCTP NAT SUPPORT 2977SCTP nat can be configured in a similar manner to TCP through the 2978.Nm 2979command line tool. 2980The main difference is that 2981.Nm sctp nat 2982does not do port translation. 2983Since the local and global side ports will be the same, 2984there is no need to specify both. 2985Ports are redirected as follows: 2986.Bd -ragged -offset indent 2987.Bk -words 2988.Cm nat 2989.Ar nat_number 2990.Cm config if 2991.Ar nic 2992.Cm redirect_port sctp 2993.Ar ip_address [,addr_list] {[port | port-port] [,ports]} 2994.Ek 2995.Ed 2996.Pp 2997Most 2998.Nm sctp nat 2999configuration can be done in real-time through the 3000.Xr sysctl 8 3001interface. 3002All may be changed dynamically, though the hash_table size will only 3003change for new 3004.Nm nat 3005instances. 3006See 3007.Sx SYSCTL VARIABLES 3008for more info. 3009.Sh IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 3010.Nm 3011supports in-kernel IPv6/IPv4 network address and protocol translation. 3012Stateful NAT64 translation allows IPv6-only clients to contact IPv4 servers 3013using unicast TCP, UDP or ICMP protocols. 3014One or more IPv4 addresses assigned to a stateful NAT64 translator are shared 3015among serveral IPv6-only clients. 3016When stateful NAT64 is used in conjunction with DNS64, no changes are usually 3017required in the IPv6 client or the IPv4 server. 3018The kernel module 3019.Cm ipfw_nat64 3020should be loaded or kernel should have 3021.Cm options IPFIREWALL_NAT64 3022to be able use stateful NAT64 translator. 3023.Pp 3024Stateful NAT64 uses a bunch of memory for several types of objects. 3025When IPv6 client initiates connection, NAT64 translator creates a host entry 3026in the states table. 3027Each host entry has a number of ports group entries allocated on demand. 3028Ports group entries contains connection state entries. 3029There are several options to control limits and lifetime for these objects. 3030.Pp 3031NAT64 translator follows RFC7915 when does ICMPv6/ICMP translation, 3032unsupported message types will be silently dropped. 3033IPv6 needs several ICMPv6 message types to be explicitly allowed for correct 3034operation. 3035Make sure that ND6 neighbor solicitation (ICMPv6 type 135) and neighbor 3036advertisement (ICMPv6 type 136) messages will not be handled by translation 3037rules. 3038.Pp 3039After translation NAT64 translator sends packets through corresponding netisr 3040queue. 3041Thus translator host should be configured as IPv4 and IPv6 router. 3042.Pp 3043Currently both stateful and stateless NAT64 translators use Well-Known IPv6 3044Prefix 3045.Ar 64:ff9b::/96 3046to represent IPv4 addresses in the IPv6 address. 3047Thus DNS64 service and routing should be configured to use Well-Known IPv6 3048Prefix. 3049.Pp 3050The stateful NAT64 configuration command is the following: 3051.Bd -ragged -offset indent 3052.Bk -words 3053.Cm nat64lsn 3054.Ar name 3055.Cm create 3056.Ar create-options 3057.Ek 3058.Ed 3059.Pp 3060The following parameters can be configured: 3061.Bl -tag -width indent 3062.It Cm prefix4 Ar ipv4_prefix/mask 3063The IPv4 prefix with mask defines the pool of IPv4 addresses used as 3064source address after translation. 3065Stateful NAT64 module translates IPv6 source address of client to one 3066IPv4 address from this pool. 3067Note that incoming IPv4 packets that don't have corresponding state entry 3068in the states table will be dropped by translator. 3069Make sure that translation rules handle packets, destined to configured prefix. 3070.It Cm max_ports Ar number 3071Maximum number of ports reserved for upper level protocols to one IPv6 client. 3072All reserved ports are divided into chunks between supported protocols. 3073The number of connections from one IPv6 client is limited by this option. 3074Note that closed TCP connections still remain in the list of connections until 3075.Cm tcp_close_age 3076interval will not expire. 3077Default value is 3078.Ar 2048 . 3079.It Cm host_del_age Ar seconds 3080The number of seconds until the host entry for a IPv6 client will be deleted 3081and all its resources will be released due to inactivity. 3082Default value is 3083.Ar 3600 . 3084.It Cm pg_del_age Ar seconds 3085The number of seconds until a ports group with unused state entries will 3086be released. 3087Default value is 3088.Ar 900 . 3089.It Cm tcp_syn_age Ar seconds 3090The number of seconds while a state entry for TCP connection with only SYN 3091sent will be kept. 3092If TCP connection establishing will not be finished, 3093state entry will be deleted. 3094Default value is 3095.Ar 10 . 3096.It Cm tcp_est_age Ar seconds 3097The number of seconds while a state entry for established TCP connection 3098will be kept. 3099Default value is 3100.Ar 7200 . 3101.It Cm tcp_close_age Ar seconds 3102The number of seconds while a state entry for closed TCP connection 3103will be kept. 3104Keeping state entries for closed connections is needed, because IPv4 servers 3105typically keep closed connections in a TIME_WAIT state for a several minutes. 3106Since translator's IPv4 addresses are shared among all IPv6 clients, 3107new connections from the same addresses and ports may be rejected by server, 3108because these connections are still in a TIME_WAIT state. 3109Keeping them in translator's state table protects from such rejects. 3110Default value is 3111.Ar 180 . 3112.It Cm udp_age Ar seconds 3113The number of seconds while translator keeps state entry in a waiting for 3114reply to the sent UDP datagram. 3115Default value is 3116.Ar 120 . 3117.It Cm icmp_age Ar seconds 3118The number of seconds while translator keeps state entry in a waiting for 3119reply to the sent ICMP message. 3120Default value is 3121.Ar 60 . 3122.It Cm log 3123Turn on logging of all handled packets via BPF through 3124.Ar ipfwlog0 3125interface. 3126.Ar ipfwlog0 3127is a pseudo interface and can be created after a boot manually with 3128.Cm ifconfig 3129command. 3130Note that it has different purpose than 3131.Ar ipfw0 3132interface. 3133Translators sends to BPF an additional information with each packet. 3134With 3135.Cm tcpdump 3136you are able to see each handled packet before and after translation. 3137.It Cm -log 3138Turn off logging of all handled packets via BPF. 3139.El 3140.Pp 3141To inspect a states table of stateful NAT64 the following command can be used: 3142.Bd -ragged -offset indent 3143.Bk -words 3144.Cm nat64lsn 3145.Ar name 3146.Cm show Cm states 3147.Ek 3148.Ed 3149.Pp 3150.Pp 3151Stateless NAT64 translator doesn't use a states table for translation 3152and converts IPv4 addresses to IPv6 and vice versa solely based on the 3153mappings taken from configured lookup tables. 3154Since a states table doesn't used by stateless translator, 3155it can be configured to pass IPv4 clients to IPv6-only servers. 3156.Pp 3157The stateless NAT64 configuration command is the following: 3158.Bd -ragged -offset indent 3159.Bk -words 3160.Cm nat64stl 3161.Ar name 3162.Cm create 3163.Ar create-options 3164.Ek 3165.Ed 3166.Pp 3167The following parameters can be configured: 3168.Bl -tag -width indent 3169.It Cm table4 Ar table46 3170The lookup table 3171.Ar table46 3172contains mapping how IPv4 addresses should be translated to IPv6 addresses. 3173.It Cm table6 Ar table64 3174The lookup table 3175.Ar table64 3176contains mapping how IPv6 addresses should be translated to IPv4 addresses. 3177.It Cm log 3178Turn on logging of all handled packets via BPF through 3179.Ar ipfwlog0 3180interface. 3181.It Cm -log 3182Turn off logging of all handled packets via BPF. 3183.El 3184.Pp 3185Note that the behavior of stateless translator with respect to not matched 3186packets differs from stateful translator. 3187If corresponding addresses was not found in the lookup tables, the packet 3188will not be dropped and the search continues. 3189.Sh IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6) 3190.Nm 3191supports in-kernel IPv6-to-IPv6 network prefix translation as described 3192in RFC6296. 3193The kernel module 3194.Cm ipfw_nptv6 3195should be loaded or kernel should has 3196.Cm options IPFIREWALL_NPTV6 3197to be able use NPTv6 translator. 3198.Pp 3199The NPTv6 configuration command is the following: 3200.Bd -ragged -offset indent 3201.Bk -words 3202.Cm nptv6 3203.Ar name 3204.Cm create 3205.Ar create-options 3206.Ek 3207.Ed 3208.Pp 3209The following parameters can be configured: 3210.Bl -tag -width indent 3211.It Cm int_prefix Ar ipv6_prefix 3212IPv6 prefix used in internal network. 3213NPTv6 module translates source address when it matches this prefix. 3214.It Cm ext_prefix Ar ipv6_prefix 3215IPv6 prefix used in external network. 3216NPTv6 module translates destination address when it matches this prefix. 3217.It Cm prefixlen Ar length 3218The length of specified IPv6 prefixes. It must be in range from 8 to 64. 3219.El 3220.Pp 3221Note that the prefix translation rules are silently ignored when IPv6 packet 3222forwarding is disabled. 3223To enable the packet forwarding, set the sysctl variable 3224.Va net.inet6.ip6.forwarding 3225to 1. 3226.Pp 3227To let the packet continue after being translated, set the sysctl variable 3228.Va net.inet.ip.fw.one_pass 3229to 0. 3230.Sh LOADER TUNABLES 3231Tunables can be set in 3232.Xr loader 8 3233prompt, 3234.Xr loader.conf 5 3235or 3236.Xr kenv 1 3237before ipfw module gets loaded. 3238.Bl -tag -width indent 3239.It Va net.inet.ip.fw.default_to_accept: No 0 3240Defines ipfw last rule behavior. 3241This value overrides 3242.Cd "options IPFW_DEFAULT_TO_(ACCEPT|DENY)" 3243from kernel configuration file. 3244.It Va net.inet.ip.fw.tables_max: No 128 3245Defines number of tables available in ipfw. 3246Number cannot exceed 65534. 3247.El 3248.Sh SYSCTL VARIABLES 3249A set of 3250.Xr sysctl 8 3251variables controls the behaviour of the firewall and 3252associated modules 3253.Pq Nm dummynet , bridge , sctp nat . 3254These are shown below together with their default value 3255(but always check with the 3256.Xr sysctl 8 3257command what value is actually in use) and meaning: 3258.Bl -tag -width indent 3259.It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0 3260Defines how the 3261.Nm nat 3262responds to receipt of global OOTB ASCONF-AddIP: 3263.Bl -tag -width indent 3264.It Cm 0 3265No response (unless a partially matching association exists - 3266ports and vtags match but global address does not) 3267.It Cm 1 3268.Nm nat 3269will accept and process all OOTB global AddIP messages. 3270.El 3271.Pp 3272Option 1 should never be selected as this forms a security risk. 3273An attacker can 3274establish multiple fake associations by sending AddIP messages. 3275.It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5 3276Defines the maximum number of chunks in an SCTP packet that will be 3277parsed for a 3278packet that matches an existing association. 3279This value is enforced to be greater or equal than 3280.Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit . 3281A high value is 3282a DoS risk yet setting too low a value may result in 3283important control chunks in 3284the packet not being located and parsed. 3285.It Va net.inet.ip.alias.sctp.error_on_ootb: No 1 3286Defines when the 3287.Nm nat 3288responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets. 3289An OOTB packet is a packet that arrives with no existing association 3290registered in the 3291.Nm nat 3292and is not an INIT or ASCONF-AddIP packet: 3293.Bl -tag -width indent 3294.It Cm 0 3295ErrorM is never sent in response to OOTB packets. 3296.It Cm 1 3297ErrorM is only sent to OOTB packets received on the local side. 3298.It Cm 2 3299ErrorM is sent to the local side and on the global side ONLY if there is a 3300partial match (ports and vtags match but the source global IP does not). 3301This value is only useful if the 3302.Nm nat 3303is tracking global IP addresses. 3304.It Cm 3 3305ErrorM is sent in response to all OOTB packets on both 3306the local and global side 3307(DoS risk). 3308.El 3309.Pp 3310At the moment the default is 0, since the ErrorM packet is not yet 3311supported by most SCTP stacks. 3312When it is supported, and if not tracking 3313global addresses, we recommend setting this value to 1 to allow 3314multi-homed local hosts to function with the 3315.Nm nat . 3316To track global addresses, we recommend setting this value to 2 to 3317allow global hosts to be informed when they need to (re)send an 3318ASCONF-AddIP. 3319Value 3 should never be chosen (except for debugging) as the 3320.Nm nat 3321will respond to all OOTB global packets (a DoS risk). 3322.It Va net.inet.ip.alias.sctp.hashtable_size: No 2003 3323Size of hash tables used for 3324.Nm nat 3325lookups (100 < prime_number > 1000001). 3326This value sets the 3327.Nm hash table 3328size for any future created 3329.Nm nat 3330instance and therefore must be set prior to creating a 3331.Nm nat 3332instance. 3333The table sizes may be changed to suit specific needs. 3334If there will be few 3335concurrent associations, and memory is scarce, you may make these smaller. 3336If there will be many thousands (or millions) of concurrent associations, you 3337should make these larger. 3338A prime number is best for the table size. 3339The sysctl 3340update function will adjust your input value to the next highest prime number. 3341.It Va net.inet.ip.alias.sctp.holddown_time: No 0 3342Hold association in table for this many seconds after receiving a 3343SHUTDOWN-COMPLETE. 3344This allows endpoints to correct shutdown gracefully if a 3345shutdown_complete is lost and retransmissions are required. 3346.It Va net.inet.ip.alias.sctp.init_timer: No 15 3347Timeout value while waiting for (INIT-ACK|AddIP-ACK). 3348This value cannot be 0. 3349.It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2 3350Defines the maximum number of chunks in an SCTP packet that will be parsed when 3351no existing association exists that matches that packet. 3352Ideally this packet 3353will only be an INIT or ASCONF-AddIP packet. 3354A higher value may become a DoS 3355risk as malformed packets can consume processing resources. 3356.It Va net.inet.ip.alias.sctp.param_proc_limit: No 25 3357Defines the maximum number of parameters within a chunk that will be 3358parsed in a 3359packet. 3360As for other similar sysctl variables, larger values pose a DoS risk. 3361.It Va net.inet.ip.alias.sctp.log_level: No 0 3362Level of detail in the system log messages (0 \- minimal, 1 \- event, 33632 \- info, 3 \- detail, 4 \- debug, 5 \- max debug). 3364May be a good 3365option in high loss environments. 3366.It Va net.inet.ip.alias.sctp.shutdown_time: No 15 3367Timeout value while waiting for SHUTDOWN-COMPLETE. 3368This value cannot be 0. 3369.It Va net.inet.ip.alias.sctp.track_global_addresses: No 0 3370Enables/disables global IP address tracking within the 3371.Nm nat 3372and places an 3373upper limit on the number of addresses tracked for each association: 3374.Bl -tag -width indent 3375.It Cm 0 3376Global tracking is disabled 3377.It Cm >1 3378Enables tracking, the maximum number of addresses tracked for each 3379association is limited to this value 3380.El 3381.Pp 3382This variable is fully dynamic, the new value will be adopted for all newly 3383arriving associations, existing associations are treated 3384as they were previously. 3385Global tracking will decrease the number of collisions within the 3386.Nm nat 3387at a cost 3388of increased processing load, memory usage, complexity, and possible 3389.Nm nat 3390state 3391problems in complex networks with multiple 3392.Nm nats . 3393We recommend not tracking 3394global IP addresses, this will still result in a fully functional 3395.Nm nat . 3396.It Va net.inet.ip.alias.sctp.up_timer: No 300 3397Timeout value to keep an association up with no traffic. 3398This value cannot be 0. 3399.It Va net.inet.ip.dummynet.expire : No 1 3400Lazily delete dynamic pipes/queue once they have no pending traffic. 3401You can disable this by setting the variable to 0, in which case 3402the pipes/queues will only be deleted when the threshold is reached. 3403.It Va net.inet.ip.dummynet.hash_size : No 64 3404Default size of the hash table used for dynamic pipes/queues. 3405This value is used when no 3406.Cm buckets 3407option is specified when configuring a pipe/queue. 3408.It Va net.inet.ip.dummynet.io_fast : No 0 3409If set to a non-zero value, 3410the 3411.Dq fast 3412mode of 3413.Nm dummynet 3414operation (see above) is enabled. 3415.It Va net.inet.ip.dummynet.io_pkt 3416Number of packets passed to 3417.Nm dummynet . 3418.It Va net.inet.ip.dummynet.io_pkt_drop 3419Number of packets dropped by 3420.Nm dummynet . 3421.It Va net.inet.ip.dummynet.io_pkt_fast 3422Number of packets bypassed by the 3423.Nm dummynet 3424scheduler. 3425.It Va net.inet.ip.dummynet.max_chain_len : No 16 3426Target value for the maximum number of pipes/queues in a hash bucket. 3427The product 3428.Cm max_chain_len*hash_size 3429is used to determine the threshold over which empty pipes/queues 3430will be expired even when 3431.Cm net.inet.ip.dummynet.expire=0 . 3432.It Va net.inet.ip.dummynet.red_lookup_depth : No 256 3433.It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512 3434.It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500 3435Parameters used in the computations of the drop probability 3436for the RED algorithm. 3437.It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576 3438.It Va net.inet.ip.dummynet.pipe_slot_limit : No 100 3439The maximum queue size that can be specified in bytes or packets. 3440These limits prevent accidental exhaustion of resources such as mbufs. 3441If you raise these limits, 3442you should make sure the system is configured so that sufficient resources 3443are available. 3444.It Va net.inet.ip.fw.autoinc_step : No 100 3445Delta between rule numbers when auto-generating them. 3446The value must be in the range 1..1000. 3447.It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets 3448The current number of buckets in the hash table for dynamic rules 3449(readonly). 3450.It Va net.inet.ip.fw.debug : No 1 3451Controls debugging messages produced by 3452.Nm . 3453.It Va net.inet.ip.fw.default_rule : No 65535 3454The default rule number (read-only). 3455By the design of 3456.Nm , the default rule is the last one, so its number 3457can also serve as the highest number allowed for a rule. 3458.It Va net.inet.ip.fw.dyn_buckets : No 256 3459The number of buckets in the hash table for dynamic rules. 3460Must be a power of 2, up to 65536. 3461It only takes effect when all dynamic rules have expired, so you 3462are advised to use a 3463.Cm flush 3464command to make sure that the hash table is resized. 3465.It Va net.inet.ip.fw.dyn_count : No 3 3466Current number of dynamic rules 3467(read-only). 3468.It Va net.inet.ip.fw.dyn_keepalive : No 1 3469Enables generation of keepalive packets for 3470.Cm keep-state 3471rules on TCP sessions. 3472A keepalive is generated to both 3473sides of the connection every 5 seconds for the last 20 3474seconds of the lifetime of the rule. 3475.It Va net.inet.ip.fw.dyn_max : No 8192 3476Maximum number of dynamic rules. 3477When you hit this limit, no more dynamic rules can be 3478installed until old ones expire. 3479.It Va net.inet.ip.fw.dyn_ack_lifetime : No 300 3480.It Va net.inet.ip.fw.dyn_syn_lifetime : No 20 3481.It Va net.inet.ip.fw.dyn_fin_lifetime : No 1 3482.It Va net.inet.ip.fw.dyn_rst_lifetime : No 1 3483.It Va net.inet.ip.fw.dyn_udp_lifetime : No 5 3484.It Va net.inet.ip.fw.dyn_short_lifetime : No 30 3485These variables control the lifetime, in seconds, of dynamic 3486rules. 3487Upon the initial SYN exchange the lifetime is kept short, 3488then increased after both SYN have been seen, then decreased 3489again during the final FIN exchange or when a RST is received. 3490Both 3491.Em dyn_fin_lifetime 3492and 3493.Em dyn_rst_lifetime 3494must be strictly lower than 5 seconds, the period of 3495repetition of keepalives. 3496The firewall enforces that. 3497.It Va net.inet.ip.fw.dyn_keep_states: No 0 3498Keep dynamic states on rule/set deletion. 3499States are relinked to default rule (65535). 3500This can be handly for ruleset reload. 3501Turned off by default. 3502.It Va net.inet.ip.fw.enable : No 1 3503Enables the firewall. 3504Setting this variable to 0 lets you run your machine without 3505firewall even if compiled in. 3506.It Va net.inet6.ip6.fw.enable : No 1 3507provides the same functionality as above for the IPv6 case. 3508.It Va net.inet.ip.fw.one_pass : No 1 3509When set, the packet exiting from the 3510.Nm dummynet 3511pipe or from 3512.Xr ng_ipfw 4 3513node is not passed though the firewall again. 3514Otherwise, after an action, the packet is 3515reinjected into the firewall at the next rule. 3516.It Va net.inet.ip.fw.tables_max : No 128 3517Maximum number of tables. 3518.It Va net.inet.ip.fw.verbose : No 1 3519Enables verbose messages. 3520.It Va net.inet.ip.fw.verbose_limit : No 0 3521Limits the number of messages produced by a verbose firewall. 3522.It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1 3523If enabled packets with unknown IPv6 Extension Headers will be denied. 3524.It Va net.link.ether.ipfw : No 0 3525Controls whether layer-2 packets are passed to 3526.Nm . 3527Default is no. 3528.It Va net.link.bridge.ipfw : No 0 3529Controls whether bridged packets are passed to 3530.Nm . 3531Default is no. 3532.El 3533.Sh INTERNAL DIAGNOSTICS 3534There are some commands that may be useful to understand current state 3535of certain subsystems inside kernel module. 3536These commands provide debugging output which may change without notice. 3537.Pp 3538Currently the following commands are available as 3539.Cm internal 3540sub-options: 3541.Bl -tag -width indent 3542.It Cm iflist 3543Lists all interface which are currently tracked by 3544.Nm 3545with their in-kernel status. 3546.It Cm talist 3547List all table lookup algorithms currently available. 3548.El 3549.Sh EXAMPLES 3550There are far too many possible uses of 3551.Nm 3552so this Section will only give a small set of examples. 3553.Pp 3554.Ss BASIC PACKET FILTERING 3555This command adds an entry which denies all tcp packets from 3556.Em cracker.evil.org 3557to the telnet port of 3558.Em wolf.tambov.su 3559from being forwarded by the host: 3560.Pp 3561.Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet" 3562.Pp 3563This one disallows any connection from the entire cracker's 3564network to my host: 3565.Pp 3566.Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org" 3567.Pp 3568A first and efficient way to limit access (not using dynamic rules) 3569is the use of the following rules: 3570.Pp 3571.Dl "ipfw add allow tcp from any to any established" 3572.Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup" 3573.Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup" 3574.Dl "..." 3575.Dl "ipfw add deny tcp from any to any" 3576.Pp 3577The first rule will be a quick match for normal TCP packets, 3578but it will not match the initial SYN packet, which will be 3579matched by the 3580.Cm setup 3581rules only for selected source/destination pairs. 3582All other SYN packets will be rejected by the final 3583.Cm deny 3584rule. 3585.Pp 3586If you administer one or more subnets, you can take advantage 3587of the address sets and or-blocks and write extremely 3588compact rulesets which selectively enable services to blocks 3589of clients, as below: 3590.Pp 3591.Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q" 3592.Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q" 3593.Dl "" 3594.Dl "ipfw add allow ip from ${goodguys} to any" 3595.Dl "ipfw add deny ip from ${badguys} to any" 3596.Dl "... normal policies ..." 3597.Pp 3598The 3599.Cm verrevpath 3600option could be used to do automated anti-spoofing by adding the 3601following to the top of a ruleset: 3602.Pp 3603.Dl "ipfw add deny ip from any to any not verrevpath in" 3604.Pp 3605This rule drops all incoming packets that appear to be coming to the 3606system on the wrong interface. 3607For example, a packet with a source 3608address belonging to a host on a protected internal network would be 3609dropped if it tried to enter the system from an external interface. 3610.Pp 3611The 3612.Cm antispoof 3613option could be used to do similar but more restricted anti-spoofing 3614by adding the following to the top of a ruleset: 3615.Pp 3616.Dl "ipfw add deny ip from any to any not antispoof in" 3617.Pp 3618This rule drops all incoming packets that appear to be coming from another 3619directly connected system but on the wrong interface. 3620For example, a packet with a source address of 3621.Li 192.168.0.0/24 , 3622configured on 3623.Li fxp0 , 3624but coming in on 3625.Li fxp1 3626would be dropped. 3627.Pp 3628The 3629.Cm setdscp 3630option could be used to (re)mark user traffic, 3631by adding the following to the appropriate place in ruleset: 3632.Pp 3633.Dl "ipfw add setdscp be ip from any to any dscp af11,af21" 3634.Ss DYNAMIC RULES 3635In order to protect a site from flood attacks involving fake 3636TCP packets, it is safer to use dynamic rules: 3637.Pp 3638.Dl "ipfw add check-state" 3639.Dl "ipfw add deny tcp from any to any established" 3640.Dl "ipfw add allow tcp from my-net to any setup keep-state" 3641.Pp 3642This will let the firewall install dynamic rules only for 3643those connection which start with a regular SYN packet coming 3644from the inside of our network. 3645Dynamic rules are checked when encountering the first 3646occurrence of a 3647.Cm check-state , 3648.Cm keep-state 3649or 3650.Cm limit 3651rule. 3652A 3653.Cm check-state 3654rule should usually be placed near the beginning of the 3655ruleset to minimize the amount of work scanning the ruleset. 3656Your mileage may vary. 3657.Pp 3658To limit the number of connections a user can open 3659you can use the following type of rules: 3660.Pp 3661.Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10" 3662.Dl "ipfw add allow tcp from any to me setup limit src-addr 4" 3663.Pp 3664The former (assuming it runs on a gateway) will allow each host 3665on a /24 network to open at most 10 TCP connections. 3666The latter can be placed on a server to make sure that a single 3667client does not use more than 4 simultaneous connections. 3668.Pp 3669.Em BEWARE : 3670stateful rules can be subject to denial-of-service attacks 3671by a SYN-flood which opens a huge number of dynamic rules. 3672The effects of such attacks can be partially limited by 3673acting on a set of 3674.Xr sysctl 8 3675variables which control the operation of the firewall. 3676.Pp 3677Here is a good usage of the 3678.Cm list 3679command to see accounting records and timestamp information: 3680.Pp 3681.Dl ipfw -at list 3682.Pp 3683or in short form without timestamps: 3684.Pp 3685.Dl ipfw -a list 3686.Pp 3687which is equivalent to: 3688.Pp 3689.Dl ipfw show 3690.Pp 3691Next rule diverts all incoming packets from 192.168.2.0/24 3692to divert port 5000: 3693.Pp 3694.Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in 3695.Ss TRAFFIC SHAPING 3696The following rules show some of the applications of 3697.Nm 3698and 3699.Nm dummynet 3700for simulations and the like. 3701.Pp 3702This rule drops random incoming packets with a probability 3703of 5%: 3704.Pp 3705.Dl "ipfw add prob 0.05 deny ip from any to any in" 3706.Pp 3707A similar effect can be achieved making use of 3708.Nm dummynet 3709pipes: 3710.Pp 3711.Dl "ipfw add pipe 10 ip from any to any" 3712.Dl "ipfw pipe 10 config plr 0.05" 3713.Pp 3714We can use pipes to artificially limit bandwidth, e.g.\& on a 3715machine acting as a router, if we want to limit traffic from 3716local clients on 192.168.2.0/24 we do: 3717.Pp 3718.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 3719.Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes" 3720.Pp 3721note that we use the 3722.Cm out 3723modifier so that the rule is not used twice. 3724Remember in fact that 3725.Nm 3726rules are checked both on incoming and outgoing packets. 3727.Pp 3728Should we want to simulate a bidirectional link with bandwidth 3729limitations, the correct way is the following: 3730.Pp 3731.Dl "ipfw add pipe 1 ip from any to any out" 3732.Dl "ipfw add pipe 2 ip from any to any in" 3733.Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes" 3734.Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes" 3735.Pp 3736The above can be very useful, e.g.\& if you want to see how 3737your fancy Web page will look for a residential user who 3738is connected only through a slow link. 3739You should not use only one pipe for both directions, unless 3740you want to simulate a half-duplex medium (e.g.\& AppleTalk, 3741Ethernet, IRDA). 3742It is not necessary that both pipes have the same configuration, 3743so we can also simulate asymmetric links. 3744.Pp 3745Should we want to verify network performance with the RED queue 3746management algorithm: 3747.Pp 3748.Dl "ipfw add pipe 1 ip from any to any" 3749.Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1" 3750.Pp 3751Another typical application of the traffic shaper is to 3752introduce some delay in the communication. 3753This can significantly affect applications which do a lot of Remote 3754Procedure Calls, and where the round-trip-time of the 3755connection often becomes a limiting factor much more than 3756bandwidth: 3757.Pp 3758.Dl "ipfw add pipe 1 ip from any to any out" 3759.Dl "ipfw add pipe 2 ip from any to any in" 3760.Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s" 3761.Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s" 3762.Pp 3763Per-flow queueing can be useful for a variety of purposes. 3764A very simple one is counting traffic: 3765.Pp 3766.Dl "ipfw add pipe 1 tcp from any to any" 3767.Dl "ipfw add pipe 1 udp from any to any" 3768.Dl "ipfw add pipe 1 ip from any to any" 3769.Dl "ipfw pipe 1 config mask all" 3770.Pp 3771The above set of rules will create queues (and collect 3772statistics) for all traffic. 3773Because the pipes have no limitations, the only effect is 3774collecting statistics. 3775Note that we need 3 rules, not just the last one, because 3776when 3777.Nm 3778tries to match IP packets it will not consider ports, so we 3779would not see connections on separate ports as different 3780ones. 3781.Pp 3782A more sophisticated example is limiting the outbound traffic 3783on a net with per-host limits, rather than per-network limits: 3784.Pp 3785.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 3786.Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in" 3787.Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 3788.Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 3789.Ss LOOKUP TABLES 3790In the following example, we need to create several traffic bandwidth 3791classes and we need different hosts/networks to fall into different classes. 3792We create one pipe for each class and configure them accordingly. 3793Then we create a single table and fill it with IP subnets and addresses. 3794For each subnet/host we set the argument equal to the number of the pipe 3795that it should use. 3796Then we classify traffic using a single rule: 3797.Pp 3798.Dl "ipfw pipe 1 config bw 1000Kbyte/s" 3799.Dl "ipfw pipe 4 config bw 4000Kbyte/s" 3800.Dl "..." 3801.Dl "ipfw table T1 create type addr" 3802.Dl "ipfw table T1 add 192.168.2.0/24 1" 3803.Dl "ipfw table T1 add 192.168.0.0/27 4" 3804.Dl "ipfw table T1 add 192.168.0.2 1" 3805.Dl "..." 3806.Dl "ipfw add pipe tablearg ip from 'table(T1)' to any" 3807.Pp 3808Using the 3809.Cm fwd 3810action, the table entries may include hostnames and IP addresses. 3811.Pp 3812.Dl "ipfw table T2 create type addr ftype ip" 3813.Dl "ipfw table T2 add 192.168.2.0/24 10.23.2.1" 3814.Dl "ipfw table T21 add 192.168.0.0/27 router1.dmz" 3815.Dl "..." 3816.Dl "ipfw add 100 fwd tablearg ip from any to table(1)" 3817.Pp 3818In the following example per-interface firewall is created: 3819.Pp 3820.Dl "ipfw table IN create type iface valtype skipto,fib" 3821.Dl "ipfw table IN add vlan20 12000,12" 3822.Dl "ipfw table IN add vlan30 13000,13" 3823.Dl "ipfw table OUT create type iface valtype skipto" 3824.Dl "ipfw table OUT add vlan20 22000" 3825.Dl "ipfw table OUT add vlan30 23000" 3826.Dl ".." 3827.Dl "ipfw add 100 ipfw setfib tablearg ip from any to any recv 'table(IN)' in" 3828.Dl "ipfw add 200 ipfw skipto tablearg ip from any to any recv 'table(IN)' in" 3829.Dl "ipfw add 300 ipfw skipto tablearg ip from any to any xmit 'table(OUT)' out" 3830.Pp 3831The following example illustrate usage of flow tables: 3832.Pp 3833.Dl "ipfw table fl create type flow:flow:src-ip,proto,dst-ip,dst-port" 3834.Dl "ipfw table fl add 2a02:6b8:77::88,tcp,2a02:6b8:77::99,80 11" 3835.Dl "ipfw table fl add 10.0.0.1,udp,10.0.0.2,53 12" 3836.Dl ".." 3837.Dl "ipfw add 100 allow ip from any to any flow 'table(fl,11)' recv ix0" 3838.Ss SETS OF RULES 3839To add a set of rules atomically, e.g.\& set 18: 3840.Pp 3841.Dl "ipfw set disable 18" 3842.Dl "ipfw add NN set 18 ... # repeat as needed" 3843.Dl "ipfw set enable 18" 3844.Pp 3845To delete a set of rules atomically the command is simply: 3846.Pp 3847.Dl "ipfw delete set 18" 3848.Pp 3849To test a ruleset and disable it and regain control if something goes wrong: 3850.Pp 3851.Dl "ipfw set disable 18" 3852.Dl "ipfw add NN set 18 ... # repeat as needed" 3853.Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18" 3854.Pp 3855Here if everything goes well, you press control-C before the "sleep" 3856terminates, and your ruleset will be left active. 3857Otherwise, e.g.\& if 3858you cannot access your box, the ruleset will be disabled after 3859the sleep terminates thus restoring the previous situation. 3860.Pp 3861To show rules of the specific set: 3862.Pp 3863.Dl "ipfw set 18 show" 3864.Pp 3865To show rules of the disabled set: 3866.Pp 3867.Dl "ipfw -S set 18 show" 3868.Pp 3869To clear a specific rule counters of the specific set: 3870.Pp 3871.Dl "ipfw set 18 zero NN" 3872.Pp 3873To delete a specific rule of the specific set: 3874.Pp 3875.Dl "ipfw set 18 delete NN" 3876.Ss NAT, REDIRECT AND LSNAT 3877First redirect all the traffic to nat instance 123: 3878.Pp 3879.Dl "ipfw add nat 123 all from any to any" 3880.Pp 3881Then to configure nat instance 123 to alias all the outgoing traffic with ip 3882192.168.0.123, blocking all incoming connections, trying to keep 3883same ports on both sides, clearing aliasing table on address change 3884and keeping a log of traffic/link statistics: 3885.Pp 3886.Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports" 3887.Pp 3888Or to change address of instance 123, aliasing table will be cleared (see 3889reset option): 3890.Pp 3891.Dl "ipfw nat 123 config ip 10.0.0.1" 3892.Pp 3893To see configuration of nat instance 123: 3894.Pp 3895.Dl "ipfw nat 123 show config" 3896.Pp 3897To show logs of all the instances in range 111-999: 3898.Pp 3899.Dl "ipfw nat 111-999 show" 3900.Pp 3901To see configurations of all instances: 3902.Pp 3903.Dl "ipfw nat show config" 3904.Pp 3905Or a redirect rule with mixed modes could looks like: 3906.Pp 3907.Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66" 3908.Dl " redirect_port tcp 192.168.0.1:80 500" 3909.Dl " redirect_proto udp 192.168.1.43 192.168.1.1" 3910.Dl " redirect_addr 192.168.0.10,192.168.0.11" 3911.Dl " 10.0.0.100 # LSNAT" 3912.Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22" 3913.Dl " 500 # LSNAT" 3914.Pp 3915or it could be split in: 3916.Pp 3917.Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66" 3918.Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500" 3919.Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1" 3920.Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12" 3921.Dl " 10.0.0.100" 3922.Dl "ipfw nat 5 config redirect_port tcp" 3923.Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500" 3924.Sh SEE ALSO 3925.Xr cpp 1 , 3926.Xr m4 1 , 3927.Xr altq 4 , 3928.Xr divert 4 , 3929.Xr dummynet 4 , 3930.Xr if_bridge 4 , 3931.Xr ip 4 , 3932.Xr ipfirewall 4 , 3933.Xr ng_ipfw 4 , 3934.Xr protocols 5 , 3935.Xr services 5 , 3936.Xr init 8 , 3937.Xr kldload 8 , 3938.Xr reboot 8 , 3939.Xr sysctl 8 , 3940.Xr syslogd 8 3941.Sh HISTORY 3942The 3943.Nm 3944utility first appeared in 3945.Fx 2.0 . 3946.Nm dummynet 3947was introduced in 3948.Fx 2.2.8 . 3949Stateful extensions were introduced in 3950.Fx 4.0 . 3951.Nm ipfw2 3952was introduced in Summer 2002. 3953.Sh AUTHORS 3954.An Ugen J. S. Antsilevich , 3955.An Poul-Henning Kamp , 3956.An Alex Nash , 3957.An Archie Cobbs , 3958.An Luigi Rizzo . 3959.Pp 3960.An -nosplit 3961API based upon code written by 3962.An Daniel Boulet 3963for BSDI. 3964.Pp 3965Dummynet has been introduced by Luigi Rizzo in 1997-1998. 3966.Pp 3967Some early work (1999-2000) on the 3968.Nm dummynet 3969traffic shaper supported by Akamba Corp. 3970.Pp 3971The ipfw core (ipfw2) has been completely redesigned and 3972reimplemented by Luigi Rizzo in summer 2002. 3973Further 3974actions and 3975options have been added by various developer over the years. 3976.Pp 3977.An -nosplit 3978In-kernel NAT support written by 3979.An Paolo Pisati Aq Mt piso@FreeBSD.org 3980as part of a Summer of Code 2005 project. 3981.Pp 3982SCTP 3983.Nm nat 3984support has been developed by 3985.An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au . 3986The primary developers and maintainers are David Hayes and Jason But. 3987For further information visit: 3988.Aq http://www.caia.swin.edu.au/urp/SONATA 3989.Pp 3990Delay profiles have been developed by Alessandro Cerri and 3991Luigi Rizzo, supported by the 3992European Commission within Projects Onelab and Onelab2. 3993.Sh BUGS 3994The syntax has grown over the years and sometimes it might be confusing. 3995Unfortunately, backward compatibility prevents cleaning up mistakes 3996made in the definition of the syntax. 3997.Pp 3998.Em !!! WARNING !!! 3999.Pp 4000Misconfiguring the firewall can put your computer in an unusable state, 4001possibly shutting down network services and requiring console access to 4002regain control of it. 4003.Pp 4004Incoming packet fragments diverted by 4005.Cm divert 4006are reassembled before delivery to the socket. 4007The action used on those packet is the one from the 4008rule which matches the first fragment of the packet. 4009.Pp 4010Packets diverted to userland, and then reinserted by a userland process 4011may lose various packet attributes. 4012The packet source interface name 4013will be preserved if it is shorter than 8 bytes and the userland process 4014saves and reuses the sockaddr_in 4015(as does 4016.Xr natd 8 ) ; 4017otherwise, it may be lost. 4018If a packet is reinserted in this manner, later rules may be incorrectly 4019applied, making the order of 4020.Cm divert 4021rules in the rule sequence very important. 4022.Pp 4023Dummynet drops all packets with IPv6 link-local addresses. 4024.Pp 4025Rules using 4026.Cm uid 4027or 4028.Cm gid 4029may not behave as expected. 4030In particular, incoming SYN packets may 4031have no uid or gid associated with them since they do not yet belong 4032to a TCP connection, and the uid/gid associated with a packet may not 4033be as expected if the associated process calls 4034.Xr setuid 2 4035or similar system calls. 4036.Pp 4037Rule syntax is subject to the command line environment and some patterns 4038may need to be escaped with the backslash character 4039or quoted appropriately. 4040.Pp 4041Due to the architecture of 4042.Xr libalias 3 , 4043ipfw nat is not compatible with the TCP segmentation offloading (TSO). 4044Thus, to reliably nat your network traffic, please disable TSO 4045on your NICs using 4046.Xr ifconfig 8 . 4047.Pp 4048ICMP error messages are not implicitly matched by dynamic rules 4049for the respective conversations. 4050To avoid failures of network error detection and path MTU discovery, 4051ICMP error messages may need to be allowed explicitly through static 4052rules. 4053.Pp 4054Rules using 4055.Cm call 4056and 4057.Cm return 4058actions may lead to confusing behaviour if ruleset has mistakes, 4059and/or interaction with other subsystems (netgraph, dummynet, etc.) is used. 4060One possible case for this is packet leaving 4061.Nm 4062in subroutine on the input pass, while later on output encountering unpaired 4063.Cm return 4064first. 4065As the call stack is kept intact after input pass, packet will suddenly 4066return to the rule number used on input pass, not on output one. 4067Order of processing should be checked carefully to avoid such mistakes. 4068