1.\" 2.\" $FreeBSD$ 3.\" 4.Dd November 26, 2007 5.Dt IPFW 8 6.Os 7.Sh NAME 8.Nm ipfw 9.Nd IP firewall and traffic shaper control program 10.Sh SYNOPSIS 11.Nm 12.Op Fl cq 13.Cm add 14.Ar rule 15.Nm 16.Op Fl acdefnNStT 17.Op Cm set Ar N 18.Brq Cm list | show 19.Op Ar rule | first-last ... 20.Nm 21.Op Fl f | q 22.Op Cm set Ar N 23.Cm flush 24.Nm 25.Op Fl q 26.Op Cm set Ar N 27.Brq Cm delete | zero | resetlog 28.Op Ar number ... 29.Nm 30.Cm enable 31.Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive 32.Nm 33.Cm disable 34.Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive 35.Pp 36.Nm 37.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 38.Nm 39.Cm set move 40.Op Cm rule 41.Ar number Cm to Ar number 42.Nm 43.Cm set swap Ar number number 44.Nm 45.Cm set show 46.Pp 47.Nm 48.Cm table Ar number Cm add Ar addr Ns Oo / Ns Ar masklen Oc Op Ar value 49.Nm 50.Cm table Ar number Cm delete Ar addr Ns Op / Ns Ar masklen 51.Nm 52.Cm table Ar number Cm flush 53.Nm 54.Cm table Ar number Cm list 55.Pp 56.Nm 57.Brq Cm pipe | queue 58.Ar number 59.Cm config 60.Ar config-options 61.Nm 62.Op Fl s Op Ar field 63.Brq Cm pipe | queue 64.Brq Cm delete | list | show 65.Op Ar number ... 66.Pp 67.Nm 68.Cm nat 69.Ar number 70.Cm config 71.Ar config-options 72.Pp 73.Nm 74.Op Fl cfnNqS 75.Oo 76.Fl p Ar preproc 77.Oo 78.Ar preproc-flags 79.Oc 80.Oc 81.Ar pathname 82.Sh DESCRIPTION 83The 84.Nm 85utility is the user interface for controlling the 86.Xr ipfw 4 87firewall and the 88.Xr dummynet 4 89traffic shaper in 90.Fx . 91.Pp 92An 93.Nm 94configuration, or 95.Em ruleset , 96is made of a list of 97.Em rules 98numbered from 1 to 65535. 99Packets are passed to 100.Nm 101from a number of different places in the protocol stack 102(depending on the source and destination of the packet, 103it is possible that 104.Nm 105is invoked multiple times on the same packet). 106The packet passed to the firewall is compared 107against each of the rules in the firewall 108.Em ruleset . 109When a match is found, the action corresponding to the 110matching rule is performed. 111.Pp 112Depending on the action and certain system settings, packets 113can be reinjected into the firewall at some rule after the 114matching one for further processing. 115.Pp 116An 117.Nm 118ruleset always includes a 119.Em default 120rule (numbered 65535) which cannot be modified or deleted, 121and matches all packets. 122The action associated with the 123.Em default 124rule can be either 125.Cm deny 126or 127.Cm allow 128depending on how the kernel is configured. 129.Pp 130If the ruleset includes one or more rules with the 131.Cm keep-state 132or 133.Cm limit 134option, then 135.Nm 136assumes a 137.Em stateful 138behaviour, i.e., upon a match it will create dynamic rules matching 139the exact parameters (addresses and ports) of the matching packet. 140.Pp 141These dynamic rules, which have a limited lifetime, are checked 142at the first occurrence of a 143.Cm check-state , 144.Cm keep-state 145or 146.Cm limit 147rule, and are typically used to open the firewall on-demand to 148legitimate traffic only. 149See the 150.Sx STATEFUL FIREWALL 151and 152.Sx EXAMPLES 153Sections below for more information on the stateful behaviour of 154.Nm . 155.Pp 156All rules (including dynamic ones) have a few associated counters: 157a packet count, a byte count, a log count and a timestamp 158indicating the time of the last match. 159Counters can be displayed or reset with 160.Nm 161commands. 162.Pp 163Rules can be added with the 164.Cm add 165command; deleted individually or in groups with the 166.Cm delete 167command, and globally (except those in set 31) with the 168.Cm flush 169command; displayed, optionally with the content of the 170counters, using the 171.Cm show 172and 173.Cm list 174commands. 175Finally, counters can be reset with the 176.Cm zero 177and 178.Cm resetlog 179commands. 180.Pp 181Also, each rule belongs to one of 32 different 182.Em sets 183, and there are 184.Nm 185commands to atomically manipulate sets, such as enable, 186disable, swap sets, move all rules in a set to another 187one, delete all rules in a set. 188These can be useful to 189install temporary configurations, or to test them. 190See Section 191.Sx SETS OF RULES 192for more information on 193.Em sets . 194.Pp 195The following options are available: 196.Bl -tag -width indent 197.It Fl a 198While listing, show counter values. 199The 200.Cm show 201command just implies this option. 202.It Fl b 203Only show the action and the comment, not the body of a rule. 204Implies 205.Fl c . 206.It Fl c 207When entering or showing rules, print them in compact form, 208i.e., without the optional "ip from any to any" string 209when this does not carry any additional information. 210.It Fl d 211While listing, show dynamic rules in addition to static ones. 212.It Fl e 213While listing, if the 214.Fl d 215option was specified, also show expired dynamic rules. 216.It Fl f 217Do not ask for confirmation for commands that can cause problems 218if misused, 219.No i.e. Cm flush . 220If there is no tty associated with the process, this is implied. 221.It Fl i 222While listing a table (see the 223.Sx LOOKUP TABLES 224section below for more information on lookup tables), format values 225as IP addresses. By default, values are shown as integers. 226.It Fl n 227Only check syntax of the command strings, without actually passing 228them to the kernel. 229.It Fl N 230Try to resolve addresses and service names in output. 231.It Fl q 232While 233.Cm add Ns ing , 234.Cm zero Ns ing , 235.Cm resetlog Ns ging 236or 237.Cm flush Ns ing , 238be quiet about actions 239(implies 240.Fl f ) . 241This is useful for adjusting rules by executing multiple 242.Nm 243commands in a script 244(e.g., 245.Ql sh\ /etc/rc.firewall ) , 246or by processing a file of many 247.Nm 248rules across a remote login session. 249It also stops a table add or delete 250from failing if the entry already exists or is not present. 251If a 252.Cm flush 253is performed in normal (verbose) mode (with the default kernel 254configuration), it prints a message. 255Because all rules are flushed, the message might not be delivered 256to the login session, causing the remote login session to be closed 257and the remainder of the ruleset to not be processed. 258Access to the console would then be required to recover. 259.It Fl S 260While listing rules, show the 261.Em set 262each rule belongs to. 263If this flag is not specified, disabled rules will not be 264listed. 265.It Fl s Op Ar field 266While listing pipes, sort according to one of the four 267counters (total or current packets or bytes). 268.It Fl t 269While listing, show last match timestamp (converted with ctime()). 270.It Fl T 271While listing, show last match timestamp (as seconds from the epoch). 272This form can be more convenient for postprocessing by scripts. 273.El 274.Pp 275To ease configuration, rules can be put into a file which is 276processed using 277.Nm 278as shown in the last synopsis line. 279An absolute 280.Ar pathname 281must be used. 282The file will be read line by line and applied as arguments to the 283.Nm 284utility. 285.Pp 286Optionally, a preprocessor can be specified using 287.Fl p Ar preproc 288where 289.Ar pathname 290is to be piped through. 291Useful preprocessors include 292.Xr cpp 1 293and 294.Xr m4 1 . 295If 296.Ar preproc 297does not start with a slash 298.Pq Ql / 299as its first character, the usual 300.Ev PATH 301name search is performed. 302Care should be taken with this in environments where not all 303file systems are mounted (yet) by the time 304.Nm 305is being run (e.g.\& when they are mounted over NFS). 306Once 307.Fl p 308has been specified, any additional arguments as passed on to the preprocessor 309for interpretation. 310This allows for flexible configuration files (like conditionalizing 311them on the local hostname) and the use of macros to centralize 312frequently required arguments like IP addresses. 313.Pp 314The 315.Nm 316.Cm pipe 317and 318.Cm queue 319commands are used to configure the traffic shaper, as shown in the 320.Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 321Section below. 322.Pp 323If the world and the kernel get out of sync the 324.Nm 325ABI may break, preventing you from being able to add any rules. 326This can 327adversely effect the booting process. 328You can use 329.Nm 330.Cm disable 331.Cm firewall 332to temporarily disable the firewall to regain access to the network, 333allowing you to fix the problem. 334.Sh PACKET FLOW 335A packet is checked against the active ruleset in multiple places 336in the protocol stack, under control of several sysctl variables. 337These places and variables are shown below, and it is important to 338have this picture in mind in order to design a correct ruleset. 339.Bd -literal -offset indent 340 ^ to upper layers V 341 | | 342 +----------->-----------+ 343 ^ V 344 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1 345 | | 346 ^ V 347 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1 348 | | 349 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1 350 ^ V 351 | to devices | 352.Ed 353.Pp 354As can be noted from the above picture, the number of 355times the same packet goes through the firewall can 356vary between 0 and 4 depending on packet source and 357destination, and system configuration. 358.Pp 359Note that as packets flow through the stack, headers can be 360stripped or added to it, and so they may or may not be available 361for inspection. 362E.g., incoming packets will include the MAC header when 363.Nm 364is invoked from 365.Cm ether_demux() , 366but the same packets will have the MAC header stripped off when 367.Nm 368is invoked from 369.Cm ip_input() 370or 371.Cm ip6_input() . 372.Pp 373Also note that each packet is always checked against the complete ruleset, 374irrespective of the place where the check occurs, or the source of the packet. 375If a rule contains some match patterns or actions which are not valid 376for the place of invocation (e.g.\& trying to match a MAC header within 377.Cm ip_input 378or 379.Cm ip6_input ), 380the match pattern will not match, but a 381.Cm not 382operator in front of such patterns 383.Em will 384cause the pattern to 385.Em always 386match on those packets. 387It is thus the responsibility of 388the programmer, if necessary, to write a suitable ruleset to 389differentiate among the possible places. 390.Cm skipto 391rules can be useful here, as an example: 392.Bd -literal -offset indent 393# packets from ether_demux or bdg_forward 394ipfw add 10 skipto 1000 all from any to any layer2 in 395# packets from ip_input 396ipfw add 10 skipto 2000 all from any to any not layer2 in 397# packets from ip_output 398ipfw add 10 skipto 3000 all from any to any not layer2 out 399# packets from ether_output_frame 400ipfw add 10 skipto 4000 all from any to any layer2 out 401.Ed 402.Pp 403(yes, at the moment there is no way to differentiate between 404ether_demux and bdg_forward). 405.Sh SYNTAX 406In general, each keyword or argument must be provided as 407a separate command line argument, with no leading or trailing 408spaces. 409Keywords are case-sensitive, whereas arguments may 410or may not be case-sensitive depending on their nature 411(e.g.\& uid's are, hostnames are not). 412.Pp 413In 414.Nm ipfw2 415you can introduce spaces after commas ',' to make 416the line more readable. 417You can also put the entire 418command (including flags) into a single argument. 419E.g., the following forms are equivalent: 420.Bd -literal -offset indent 421ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8 422ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8 423ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8" 424.Ed 425.Sh RULE FORMAT 426The format of 427.Nm 428rules is the following: 429.Bd -ragged -offset indent 430.Bk -words 431.Op Ar rule_number 432.Op Cm set Ar set_number 433.Op Cm prob Ar match_probability 434.Ar action 435.Op Cm log Op Cm logamount Ar number 436.Op Cm altq Ar queue 437.Oo 438.Bro Cm tag | untag 439.Brc Ar number 440.Oc 441.Ar body 442.Ek 443.Ed 444.Pp 445where the body of the rule specifies which information is used 446for filtering packets, among the following: 447.Pp 448.Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact 449.It Layer-2 header fields 450When available 451.It IPv4 and IPv6 Protocol 452TCP, UDP, ICMP, etc. 453.It Source and dest. addresses and ports 454.It Direction 455See Section 456.Sx PACKET FLOW 457.It Transmit and receive interface 458By name or address 459.It Misc. IP header fields 460Version, type of service, datagram length, identification, 461fragment flag (non-zero IP offset), 462Time To Live 463.It IP options 464.It IPv6 Extension headers 465Fragmentation, Hop-by-Hop options, 466Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options. 467.It IPv6 Flow-ID 468.It Misc. TCP header fields 469TCP flags (SYN, FIN, ACK, RST, etc.), 470sequence number, acknowledgment number, 471window 472.It TCP options 473.It ICMP types 474for ICMP packets 475.It ICMP6 types 476for ICMP6 packets 477.It User/group ID 478When the packet can be associated with a local socket. 479.It Divert status 480Whether a packet came from a divert socket (e.g., 481.Xr natd 8 ) . 482.It Fib annotation state 483Whether a packet has been tagged for using a specific FIB (routing table) 484in future forwarding decisions. 485.El 486.Pp 487Note that some of the above information, e.g.\& source MAC or IP addresses and 488TCP/UDP ports, could easily be spoofed, so filtering on those fields 489alone might not guarantee the desired results. 490.Bl -tag -width indent 491.It Ar rule_number 492Each rule is associated with a 493.Ar rule_number 494in the range 1..65535, with the latter reserved for the 495.Em default 496rule. 497Rules are checked sequentially by rule number. 498Multiple rules can have the same number, in which case they are 499checked (and listed) according to the order in which they have 500been added. 501If a rule is entered without specifying a number, the kernel will 502assign one in such a way that the rule becomes the last one 503before the 504.Em default 505rule. 506Automatic rule numbers are assigned by incrementing the last 507non-default rule number by the value of the sysctl variable 508.Ar net.inet.ip.fw.autoinc_step 509which defaults to 100. 510If this is not possible (e.g.\& because we would go beyond the 511maximum allowed rule number), the number of the last 512non-default value is used instead. 513.It Cm set Ar set_number 514Each rule is associated with a 515.Ar set_number 516in the range 0..31. 517Sets can be individually disabled and enabled, so this parameter 518is of fundamental importance for atomic ruleset manipulation. 519It can be also used to simplify deletion of groups of rules. 520If a rule is entered without specifying a set number, 521set 0 will be used. 522.br 523Set 31 is special in that it cannot be disabled, 524and rules in set 31 are not deleted by the 525.Nm ipfw flush 526command (but you can delete them with the 527.Nm ipfw delete set 31 528command). 529Set 31 is also used for the 530.Em default 531rule. 532.It Cm prob Ar match_probability 533A match is only declared with the specified probability 534(floating point number between 0 and 1). 535This can be useful for a number of applications such as 536random packet drop or 537(in conjunction with 538.Nm dummynet ) 539to simulate the effect of multiple paths leading to out-of-order 540packet delivery. 541.Pp 542Note: this condition is checked before any other condition, including 543ones such as keep-state or check-state which might have side effects. 544.It Cm log Op Cm logamount Ar number 545When a packet matches a rule with the 546.Cm log 547keyword, a message will be 548logged to 549.Xr syslogd 8 550with a 551.Dv LOG_SECURITY 552facility. 553The logging only occurs if the sysctl variable 554.Va net.inet.ip.fw.verbose 555is set to 1 556(which is the default when the kernel is compiled with 557.Dv IPFIREWALL_VERBOSE ) 558and the number of packets logged so far for that 559particular rule does not exceed the 560.Cm logamount 561parameter. 562If no 563.Cm logamount 564is specified, the limit is taken from the sysctl variable 565.Va net.inet.ip.fw.verbose_limit . 566In both cases, a value of 0 removes the logging limit. 567.Pp 568Once the limit is reached, logging can be re-enabled by 569clearing the logging counter or the packet counter for that entry, see the 570.Cm resetlog 571command. 572.Pp 573Note: logging is done after all other packet matching conditions 574have been successfully verified, and before performing the final 575action (accept, deny, etc.) on the packet. 576.It Cm tag Ar number 577When a packet matches a rule with the 578.Cm tag 579keyword, the numeric tag for the given 580.Ar number 581in the range 1..65534 will be attached to the packet. 582The tag acts as an internal marker (it is not sent out over 583the wire) that can be used to identify these packets later on. 584This can be used, for example, to provide trust between interfaces 585and to start doing policy-based filtering. 586A packet can have mutiple tags at the same time. 587Tags are "sticky", meaning once a tag is applied to a packet by a 588matching rule it exists until explicit removal. 589Tags are kept with the packet everywhere within the kernel, but are 590lost when packet leaves the kernel, for example, on transmitting 591packet out to the network or sending packet to a 592.Xr divert 4 593socket. 594.Pp 595To check for previously applied tags, use the 596.Cm tagged 597rule option. 598To delete previously applied tag, use the 599.Cm untag 600keyword. 601.Pp 602Note: since tags are kept with the packet everywhere in kernelspace, 603they can be set and unset anywhere in kernel network subsystem 604(using 605.Xr mbuf_tags 9 606facility), not only by means of 607.Xr ipfw 4 608.Cm tag 609and 610.Cm untag 611keywords. 612For example, there can be a specialized 613.Xr netgraph 4 614node doing traffic analyzing and tagging for later inspecting 615in firewall. 616.It Cm untag Ar number 617When a packet matches a rule with the 618.Cm untag 619keyword, the tag with the number 620.Ar number 621is searched among the tags attached to this packet and, 622if found, removed from it. 623Other tags bound to packet, if present, are left untouched. 624.It Cm altq Ar queue 625When a packet matches a rule with the 626.Cm altq 627keyword, the ALTQ identifier for the given 628.Ar queue 629(see 630.Xr altq 4 ) 631will be attached. 632Note that this ALTQ tag is only meaningful for packets going "out" of IPFW, 633and not being rejected or going to divert sockets. 634Note that if there is insufficient memory at the time the packet is 635processed, it will not be tagged, so it is wise to make your ALTQ 636"default" queue policy account for this. 637If multiple 638.Cm altq 639rules match a single packet, only the first one adds the ALTQ classification 640tag. 641In doing so, traffic may be shaped by using 642.Cm count Cm altq Ar queue 643rules for classification early in the ruleset, then later applying 644the filtering decision. 645For example, 646.Cm check-state 647and 648.Cm keep-state 649rules may come later and provide the actual filtering decisions in 650addition to the fallback ALTQ tag. 651.Pp 652You must run 653.Xr pfctl 8 654to set up the queues before IPFW will be able to look them up by name, 655and if the ALTQ disciplines are rearranged, the rules in containing the 656queue identifiers in the kernel will likely have gone stale and need 657to be reloaded. 658Stale queue identifiers will probably result in misclassification. 659.Pp 660All system ALTQ processing can be turned on or off via 661.Nm 662.Cm enable Ar altq 663and 664.Nm 665.Cm disable Ar altq . 666The usage of 667.Va net.inet.ip.fw.one_pass 668is irrelevant to ALTQ traffic shaping, as the actual rule action is followed 669always after adding an ALTQ tag. 670.El 671.Ss RULE ACTIONS 672A rule can be associated with one of the following actions, which 673will be executed when the packet matches the body of the rule. 674.Bl -tag -width indent 675.It Cm allow | accept | pass | permit 676Allow packets that match rule. 677The search terminates. 678.It Cm check-state 679Checks the packet against the dynamic ruleset. 680If a match is found, execute the action associated with 681the rule which generated this dynamic rule, otherwise 682move to the next rule. 683.br 684.Cm Check-state 685rules do not have a body. 686If no 687.Cm check-state 688rule is found, the dynamic ruleset is checked at the first 689.Cm keep-state 690or 691.Cm limit 692rule. 693.It Cm count 694Update counters for all packets that match rule. 695The search continues with the next rule. 696.It Cm deny | drop 697Discard packets that match this rule. 698The search terminates. 699.It Cm divert Ar port 700Divert packets that match this rule to the 701.Xr divert 4 702socket bound to port 703.Ar port . 704The search terminates. 705.It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port 706Change the next-hop on matching packets to 707.Ar ipaddr , 708which can be an IP address or a host name. 709The next hop can also be supplied by the last table 710looked up for the packet by using the 711.Cm tablearg 712keyword instead of an explicit address. 713The search terminates if this rule matches. 714.Pp 715If 716.Ar ipaddr 717is a local address, then matching packets will be forwarded to 718.Ar port 719(or the port number in the packet if one is not specified in the rule) 720on the local machine. 721.br 722If 723.Ar ipaddr 724is not a local address, then the port number 725(if specified) is ignored, and the packet will be 726forwarded to the remote address, using the route as found in 727the local routing table for that IP. 728.br 729A 730.Ar fwd 731rule will not match layer-2 packets (those received 732on ether_input, ether_output, or bridged). 733.br 734The 735.Cm fwd 736action does not change the contents of the packet at all. 737In particular, the destination address remains unmodified, so 738packets forwarded to another system will usually be rejected by that system 739unless there is a matching rule on that system to capture them. 740For packets forwarded locally, 741the local address of the socket will be 742set to the original destination address of the packet. 743This makes the 744.Xr netstat 1 745entry look rather weird but is intended for 746use with transparent proxy servers. 747.Pp 748To enable 749.Cm fwd 750a custom kernel needs to be compiled with the option 751.Cd "options IPFIREWALL_FORWARD" . 752.It Cm nat Ar nat_nr 753Pass packet to a 754nat instance 755(for network address translation, address redirect, etc.): 756see the 757.Sx NETWORK ADDRESS TRANSLATION (NAT) 758Section for further information. 759.It Cm pipe Ar pipe_nr 760Pass packet to a 761.Nm dummynet 762.Dq pipe 763(for bandwidth limitation, delay, etc.). 764See the 765.Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 766Section for further information. 767The search terminates; however, on exit from the pipe and if 768the 769.Xr sysctl 8 770variable 771.Va net.inet.ip.fw.one_pass 772is not set, the packet is passed again to the firewall code 773starting from the next rule. 774.It Cm queue Ar queue_nr 775Pass packet to a 776.Nm dummynet 777.Dq queue 778(for bandwidth limitation using WF2Q+). 779.It Cm reject 780(Deprecated). 781Synonym for 782.Cm unreach host . 783.It Cm reset 784Discard packets that match this rule, and if the 785packet is a TCP packet, try to send a TCP reset (RST) notice. 786The search terminates. 787.It Cm reset6 788Discard packets that match this rule, and if the 789packet is a TCP packet, try to send a TCP reset (RST) notice. 790The search terminates. 791.It Cm skipto Ar number | tablearg 792Skip all subsequent rules numbered less than 793.Ar number . 794The search continues with the first rule numbered 795.Ar number 796or higher. 797It is possible to use the 798.Cm tablearg 799keyword with a skipto for a 800.Em computed 801skipto, but care should be used, as no destination caching 802is possible in this case so the rules are always walked to find it, 803starting from the 804.Cm skipto . 805.It Cm tee Ar port 806Send a copy of packets matching this rule to the 807.Xr divert 4 808socket bound to port 809.Ar port . 810The search continues with the next rule. 811.It Cm unreach Ar code 812Discard packets that match this rule, and try to send an ICMP 813unreachable notice with code 814.Ar code , 815where 816.Ar code 817is a number from 0 to 255, or one of these aliases: 818.Cm net , host , protocol , port , 819.Cm needfrag , srcfail , net-unknown , host-unknown , 820.Cm isolated , net-prohib , host-prohib , tosnet , 821.Cm toshost , filter-prohib , host-precedence 822or 823.Cm precedence-cutoff . 824The search terminates. 825.It Cm unreach6 Ar code 826Discard packets that match this rule, and try to send an ICMPv6 827unreachable notice with code 828.Ar code , 829where 830.Ar code 831is a number from 0, 1, 3 or 4, or one of these aliases: 832.Cm no-route, admin-prohib, address 833or 834.Cm port . 835The search terminates. 836.It Cm netgraph Ar cookie 837Divert packet into netgraph with given 838.Ar cookie . 839The search terminates. 840If packet is later returned from netgraph it is either 841accepted or continues with the next rule, depending on 842.Va net.inet.ip.fw.one_pass 843sysctl variable. 844.It Cm ngtee Ar cookie 845A copy of packet is diverted into netgraph, original 846packet is either accepted or continues with the next rule, depending on 847.Va net.inet.ip.fw.one_pass 848sysctl variable. 849See 850.Xr ng_ipfw 4 851for more information on 852.Cm netgraph 853and 854.Cm ngtee 855actions. 856.It Cm setfib Ar fibnum 857The packet is tagged so as to use the FIB (routing table) 858.Ar fibnum 859in any subsequent forwarding decisions. Initially this is 860limited to the values 0 through 15. See 861.Xr setfib 8 . 862Processing continues at the next rule. 863.El 864.Ss RULE BODY 865The body of a rule contains zero or more patterns (such as 866specific source and destination addresses or ports, 867protocol options, incoming or outgoing interfaces, etc.) 868that the packet must match in order to be recognised. 869In general, the patterns are connected by (implicit) 870.Cm and 871operators -- i.e., all must match in order for the 872rule to match. 873Individual patterns can be prefixed by the 874.Cm not 875operator to reverse the result of the match, as in 876.Pp 877.Dl "ipfw add 100 allow ip from not 1.2.3.4 to any" 878.Pp 879Additionally, sets of alternative match patterns 880.Pq Em or-blocks 881can be constructed by putting the patterns in 882lists enclosed between parentheses ( ) or braces { }, and 883using the 884.Cm or 885operator as follows: 886.Pp 887.Dl "ipfw add 100 allow ip from { x or not y or z } to any" 888.Pp 889Only one level of parentheses is allowed. 890Beware that most shells have special meanings for parentheses 891or braces, so it is advisable to put a backslash \\ in front of them 892to prevent such interpretations. 893.Pp 894The body of a rule must in general include a source and destination 895address specifier. 896The keyword 897.Ar any 898can be used in various places to specify that the content of 899a required field is irrelevant. 900.Pp 901The rule body has the following format: 902.Bd -ragged -offset indent 903.Op Ar proto Cm from Ar src Cm to Ar dst 904.Op Ar options 905.Ed 906.Pp 907The first part (proto from src to dst) is for backward 908compatibility with earlier versions of 909.Fx . 910In modern 911.Fx 912any match pattern (including MAC headers, IP protocols, 913addresses and ports) can be specified in the 914.Ar options 915section. 916.Pp 917Rule fields have the following meaning: 918.Bl -tag -width indent 919.It Ar proto : protocol | Cm { Ar protocol Cm or ... } 920.It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number 921An IP protocol specified by number or name 922(for a complete list see 923.Pa /etc/protocols ) , 924or one of the following keywords: 925.Bl -tag -width indent 926.It Cm ip4 | ipv4 927Matches IPv4 packets. 928.It Cm ip6 | ipv6 929Matches IPv6 packets. 930.It Cm ip | all 931Matches any packet. 932.El 933.Pp 934The 935.Cm ipv6 936in 937.Cm proto 938option will be treated as inner protocol. 939And, the 940.Cm ipv4 941is not available in 942.Cm proto 943option. 944.Pp 945The 946.Cm { Ar protocol Cm or ... } 947format (an 948.Em or-block ) 949is provided for convenience only but its use is deprecated. 950.It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports 951An address (or a list, see below) 952optionally followed by 953.Ar ports 954specifiers. 955.Pp 956The second format 957.Em ( or-block 958with multiple addresses) is provided for convenience only and 959its use is discouraged. 960.It Ar addr : Oo Cm not Oc Bro 961.Cm any | me | me6 | 962.Cm table Ns Pq Ar number Ns Op , Ns Ar value 963.Ar | addr-list | addr-set 964.Brc 965.It Cm any 966matches any IP address. 967.It Cm me 968matches any IP address configured on an interface in the system. 969.It Cm me6 970matches any IPv6 address configured on an interface in the system. 971The address list is evaluated at the time the packet is 972analysed. 973.It Cm table Ns Pq Ar number Ns Op , Ns Ar value 974Matches any IPv4 address for which an entry exists in the lookup table 975.Ar number . 976If an optional 32-bit unsigned 977.Ar value 978is also specified, an entry will match only if it has this value. 979See the 980.Sx LOOKUP TABLES 981section below for more information on lookup tables. 982.It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list 983.It Ar ip-addr : 984A host or subnet address specified in one of the following ways: 985.Bl -tag -width indent 986.It Ar numeric-ip | hostname 987Matches a single IPv4 address, specified as dotted-quad or a hostname. 988Hostnames are resolved at the time the rule is added to the firewall list. 989.It Ar addr Ns / Ns Ar masklen 990Matches all addresses with base 991.Ar addr 992(specified as an IP address, a network number, or a hostname) 993and mask width of 994.Cm masklen 995bits. 996As an example, 1.2.3.4/25 or 1.2.3.0/25 will match 997all IP numbers from 1.2.3.0 to 1.2.3.127 . 998.It Ar addr Ns : Ns Ar mask 999Matches all addresses with base 1000.Ar addr 1001(specified as an IP address, a network number, or a hostname) 1002and the mask of 1003.Ar mask , 1004specified as a dotted quad. 1005As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match 10061.*.3.*. 1007This form is advised only for non-contiguous 1008masks. 1009It is better to resort to the 1010.Ar addr Ns / Ns Ar masklen 1011format for contiguous masks, which is more compact and less 1012error-prone. 1013.El 1014.It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm } 1015.It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list 1016Matches all addresses with base address 1017.Ar addr 1018(specified as an IP address, a network number, or a hostname) 1019and whose last byte is in the list between braces { } . 1020Note that there must be no spaces between braces and 1021numbers (spaces after commas are allowed). 1022Elements of the list can be specified as single entries 1023or ranges. 1024The 1025.Ar masklen 1026field is used to limit the size of the set of addresses, 1027and can have any value between 24 and 32. 1028If not specified, 1029it will be assumed as 24. 1030.br 1031This format is particularly useful to handle sparse address sets 1032within a single rule. 1033Because the matching occurs using a 1034bitmask, it takes constant time and dramatically reduces 1035the complexity of rulesets. 1036.br 1037As an example, an address specified as 1.2.3.4/24{128,35-55,89} 1038or 1.2.3.0/24{128,35-55,89} 1039will match the following IP addresses: 1040.br 10411.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 . 1042.It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list 1043.It Ar ip6-addr : 1044A host or subnet specified one of the following ways: 1045.Pp 1046.Bl -tag -width indent 1047.It Ar numeric-ip | hostname 1048Matches a single IPv6 address as allowed by 1049.Xr inet_pton 3 1050or a hostname. 1051Hostnames are resolved at the time the rule is added to the firewall 1052list. 1053.It Ar addr Ns / Ns Ar masklen 1054Matches all IPv6 addresses with base 1055.Ar addr 1056(specified as allowed by 1057.Xr inet_pton 1058or a hostname) 1059and mask width of 1060.Cm masklen 1061bits. 1062.El 1063.Pp 1064No support for sets of IPv6 addresses is provided because IPv6 addresses 1065are typically random past the initial prefix. 1066.It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports 1067For protocols which support port numbers (such as TCP and UDP), optional 1068.Cm ports 1069may be specified as one or more ports or port ranges, separated 1070by commas but no spaces, and an optional 1071.Cm not 1072operator. 1073The 1074.Ql \&- 1075notation specifies a range of ports (including boundaries). 1076.Pp 1077Service names (from 1078.Pa /etc/services ) 1079may be used instead of numeric port values. 1080The length of the port list is limited to 30 ports or ranges, 1081though one can specify larger ranges by using an 1082.Em or-block 1083in the 1084.Cm options 1085section of the rule. 1086.Pp 1087A backslash 1088.Pq Ql \e 1089can be used to escape the dash 1090.Pq Ql - 1091character in a service name (from a shell, the backslash must be 1092typed twice to avoid the shell itself interpreting it as an escape 1093character). 1094.Pp 1095.Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any" 1096.Pp 1097Fragmented packets which have a non-zero offset (i.e., not the first 1098fragment) will never match a rule which has one or more port 1099specifications. 1100See the 1101.Cm frag 1102option for details on matching fragmented packets. 1103.El 1104.Ss RULE OPTIONS (MATCH PATTERNS) 1105Additional match patterns can be used within 1106rules. 1107Zero or more of these so-called 1108.Em options 1109can be present in a rule, optionally prefixed by the 1110.Cm not 1111operand, and possibly grouped into 1112.Em or-blocks . 1113.Pp 1114The following match patterns can be used (listed in alphabetical order): 1115.Bl -tag -width indent 1116.It Cm // this is a comment. 1117Inserts the specified text as a comment in the rule. 1118Everything following // is considered as a comment and stored in the rule. 1119You can have comment-only rules, which are listed as having a 1120.Cm count 1121action followed by the comment. 1122.It Cm bridged 1123Alias for 1124.Cm layer2 . 1125.It Cm diverted 1126Matches only packets generated by a divert socket. 1127.It Cm diverted-loopback 1128Matches only packets coming from a divert socket back into the IP stack 1129input for delivery. 1130.It Cm diverted-output 1131Matches only packets going from a divert socket back outward to the IP 1132stack output for delivery. 1133.It Cm dst-ip Ar ip-address 1134Matches IPv4 packets whose destination IP is one of the address(es) 1135specified as argument. 1136.It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address 1137Matches IPv6 packets whose destination IP is one of the address(es) 1138specified as argument. 1139.It Cm dst-port Ar ports 1140Matches IP packets whose destination port is one of the port(s) 1141specified as argument. 1142.It Cm established 1143Matches TCP packets that have the RST or ACK bits set. 1144.It Cm ext6hdr Ar header 1145Matches IPv6 packets containing the extended header given by 1146.Ar header . 1147Supported headers are: 1148.Pp 1149Fragment, 1150.Pq Cm frag , 1151Hop-to-hop options 1152.Pq Cm hopopt , 1153any type of Routing Header 1154.Pq Cm route , 1155Source routing Routing Header Type 0 1156.Pq Cm rthdr0 , 1157Mobile IPv6 Routing Header Type 2 1158.Pq Cm rthdr2 , 1159Destination options 1160.Pq Cm dstopt , 1161IPSec authentication headers 1162.Pq Cm ah , 1163and IPSec encapsulated security payload headers 1164.Pq Cm esp . 1165.It Cm fib Ar fibnum 1166Matches a packet that has been tagged to use 1167the given FIB (routing table) number. 1168.It Cm flow-id Ar labels 1169Matches IPv6 packets containing any of the flow labels given in 1170.Ar labels . 1171.Ar labels 1172is a comma seperate list of numeric flow labels. 1173.It Cm frag 1174Matches packets that are fragments and not the first 1175fragment of an IP datagram. 1176Note that these packets will not have 1177the next protocol header (e.g.\& TCP, UDP) so options that look into 1178these headers cannot match. 1179.It Cm gid Ar group 1180Matches all TCP or UDP packets sent by or received for a 1181.Ar group . 1182A 1183.Ar group 1184may be specified by name or number. 1185.It Cm jail Ar prisonID 1186Matches all TCP or UDP packets sent by or received for the 1187jail whos prison ID is 1188.Ar prisonID . 1189.It Cm icmptypes Ar types 1190Matches ICMP packets whose ICMP type is in the list 1191.Ar types . 1192The list may be specified as any combination of 1193individual types (numeric) separated by commas. 1194.Em Ranges are not allowed . 1195The supported ICMP types are: 1196.Pp 1197echo reply 1198.Pq Cm 0 , 1199destination unreachable 1200.Pq Cm 3 , 1201source quench 1202.Pq Cm 4 , 1203redirect 1204.Pq Cm 5 , 1205echo request 1206.Pq Cm 8 , 1207router advertisement 1208.Pq Cm 9 , 1209router solicitation 1210.Pq Cm 10 , 1211time-to-live exceeded 1212.Pq Cm 11 , 1213IP header bad 1214.Pq Cm 12 , 1215timestamp request 1216.Pq Cm 13 , 1217timestamp reply 1218.Pq Cm 14 , 1219information request 1220.Pq Cm 15 , 1221information reply 1222.Pq Cm 16 , 1223address mask request 1224.Pq Cm 17 1225and address mask reply 1226.Pq Cm 18 . 1227.It Cm icmp6types Ar types 1228Matches ICMP6 packets whose ICMP6 type is in the list of 1229.Ar types . 1230The list may be specified as any combination of 1231individual types (numeric) separated by commas. 1232.Em Ranges are not allowed . 1233.It Cm in | out 1234Matches incoming or outgoing packets, respectively. 1235.Cm in 1236and 1237.Cm out 1238are mutually exclusive (in fact, 1239.Cm out 1240is implemented as 1241.Cm not in Ns No ). 1242.It Cm ipid Ar id-list 1243Matches IPv4 packets whose 1244.Cm ip_id 1245field has value included in 1246.Ar id-list , 1247which is either a single value or a list of values or ranges 1248specified in the same way as 1249.Ar ports . 1250.It Cm iplen Ar len-list 1251Matches IP packets whose total length, including header and data, is 1252in the set 1253.Ar len-list , 1254which is either a single value or a list of values or ranges 1255specified in the same way as 1256.Ar ports . 1257.It Cm ipoptions Ar spec 1258Matches packets whose IPv4 header contains the comma separated list of 1259options specified in 1260.Ar spec . 1261The supported IP options are: 1262.Pp 1263.Cm ssrr 1264(strict source route), 1265.Cm lsrr 1266(loose source route), 1267.Cm rr 1268(record packet route) and 1269.Cm ts 1270(timestamp). 1271The absence of a particular option may be denoted 1272with a 1273.Ql \&! . 1274.It Cm ipprecedence Ar precedence 1275Matches IPv4 packets whose precedence field is equal to 1276.Ar precedence . 1277.It Cm ipsec 1278Matches packets that have IPSEC history associated with them 1279(i.e., the packet comes encapsulated in IPSEC, the kernel 1280has IPSEC support and IPSEC_FILTERTUNNEL option, and can correctly 1281decapsulate it). 1282.Pp 1283Note that specifying 1284.Cm ipsec 1285is different from specifying 1286.Cm proto Ar ipsec 1287as the latter will only look at the specific IP protocol field, 1288irrespective of IPSEC kernel support and the validity of the IPSEC data. 1289.Pp 1290Further note that this flag is silently ignored in kernels without 1291IPSEC support. 1292It does not affect rule processing when given and the 1293rules are handled as if with no 1294.Cm ipsec 1295flag. 1296.It Cm iptos Ar spec 1297Matches IPv4 packets whose 1298.Cm tos 1299field contains the comma separated list of 1300service types specified in 1301.Ar spec . 1302The supported IP types of service are: 1303.Pp 1304.Cm lowdelay 1305.Pq Dv IPTOS_LOWDELAY , 1306.Cm throughput 1307.Pq Dv IPTOS_THROUGHPUT , 1308.Cm reliability 1309.Pq Dv IPTOS_RELIABILITY , 1310.Cm mincost 1311.Pq Dv IPTOS_MINCOST , 1312.Cm congestion 1313.Pq Dv IPTOS_ECN_CE . 1314The absence of a particular type may be denoted 1315with a 1316.Ql \&! . 1317.It Cm ipttl Ar ttl-list 1318Matches IPv4 packets whose time to live is included in 1319.Ar ttl-list , 1320which is either a single value or a list of values or ranges 1321specified in the same way as 1322.Ar ports . 1323.It Cm ipversion Ar ver 1324Matches IP packets whose IP version field is 1325.Ar ver . 1326.It Cm keep-state 1327Upon a match, the firewall will create a dynamic rule, whose 1328default behaviour is to match bidirectional traffic between 1329source and destination IP/port using the same protocol. 1330The rule has a limited lifetime (controlled by a set of 1331.Xr sysctl 8 1332variables), and the lifetime is refreshed every time a matching 1333packet is found. 1334.It Cm layer2 1335Matches only layer2 packets, i.e., those passed to 1336.Nm 1337from ether_demux() and ether_output_frame(). 1338.It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N 1339The firewall will only allow 1340.Ar N 1341connections with the same 1342set of parameters as specified in the rule. 1343One or more 1344of source and destination addresses and ports can be 1345specified. 1346Currently, 1347only IPv4 flows are supported. 1348.It Cm { MAC | mac } Ar dst-mac src-mac 1349Match packets with a given 1350.Ar dst-mac 1351and 1352.Ar src-mac 1353addresses, specified as the 1354.Cm any 1355keyword (matching any MAC address), or six groups of hex digits 1356separated by colons, 1357and optionally followed by a mask indicating the significant bits. 1358The mask may be specified using either of the following methods: 1359.Bl -enum -width indent 1360.It 1361A slash 1362.Pq / 1363followed by the number of significant bits. 1364For example, an address with 33 significant bits could be specified as: 1365.Pp 1366.Dl "MAC 10:20:30:40:50:60/33 any" 1367.Pp 1368.It 1369An ampersand 1370.Pq & 1371followed by a bitmask specified as six groups of hex digits separated 1372by colons. 1373For example, an address in which the last 16 bits are significant could 1374be specified as: 1375.Pp 1376.Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any" 1377.Pp 1378Note that the ampersand character has a special meaning in many shells 1379and should generally be escaped. 1380.Pp 1381.El 1382Note that the order of MAC addresses (destination first, 1383source second) is 1384the same as on the wire, but the opposite of the one used for 1385IP addresses. 1386.It Cm mac-type Ar mac-type 1387Matches packets whose Ethernet Type field 1388corresponds to one of those specified as argument. 1389.Ar mac-type 1390is specified in the same way as 1391.Cm port numbers 1392(i.e., one or more comma-separated single values or ranges). 1393You can use symbolic names for known values such as 1394.Em vlan , ipv4, ipv6 . 1395Values can be entered as decimal or hexadecimal (if prefixed by 0x), 1396and they are always printed as hexadecimal (unless the 1397.Cm -N 1398option is used, in which case symbolic resolution will be attempted). 1399.It Cm proto Ar protocol 1400Matches packets with the corresponding IP protocol. 1401.It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar ipno | Ar any 1402Matches packets received, transmitted or going through, 1403respectively, the interface specified by exact name 1404.Ns No ( Ar ifX Ns No ), 1405by device name 1406.Ns No ( Ar if Ns Ar * Ns No ), 1407by IP address, or through some interface. 1408.Pp 1409The 1410.Cm via 1411keyword causes the interface to always be checked. 1412If 1413.Cm recv 1414or 1415.Cm xmit 1416is used instead of 1417.Cm via , 1418then only the receive or transmit interface (respectively) 1419is checked. 1420By specifying both, it is possible to match packets based on 1421both receive and transmit interface, e.g.: 1422.Pp 1423.Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1" 1424.Pp 1425The 1426.Cm recv 1427interface can be tested on either incoming or outgoing packets, 1428while the 1429.Cm xmit 1430interface can only be tested on outgoing packets. 1431So 1432.Cm out 1433is required (and 1434.Cm in 1435is invalid) whenever 1436.Cm xmit 1437is used. 1438.Pp 1439A packet may not have a receive or transmit interface: packets 1440originating from the local host have no receive interface, 1441while packets destined for the local host have no transmit 1442interface. 1443.It Cm setup 1444Matches TCP packets that have the SYN bit set but no ACK bit. 1445This is the short form of 1446.Dq Li tcpflags\ syn,!ack . 1447.It Cm src-ip Ar ip-address 1448Matches IPv4 packets whose source IP is one of the address(es) 1449specified as an argument. 1450.It Cm src-ip6 Ar ip6-address 1451Matches IPv6 packets whose source IP is one of the address(es) 1452specified as an argument. 1453.It Cm src-port Ar ports 1454Matches IP packets whose source port is one of the port(s) 1455specified as argument. 1456.It Cm tagged Ar tag-list 1457Matches packets whose tags are included in 1458.Ar tag-list , 1459which is either a single value or a list of values or ranges 1460specified in the same way as 1461.Ar ports . 1462Tags can be applied to the packet using 1463.Cm tag 1464rule action parameter (see it's description for details on tags). 1465.It Cm tcpack Ar ack 1466TCP packets only. 1467Match if the TCP header acknowledgment number field is set to 1468.Ar ack . 1469.It Cm tcpdatalen Ar tcpdatalen-list 1470Matches TCP packets whose length of TCP data is 1471.Ar tcpdatalen-list , 1472which is either a single value or a list of values or ranges 1473specified in the same way as 1474.Ar ports . 1475.It Cm tcpflags Ar spec 1476TCP packets only. 1477Match if the TCP header contains the comma separated list of 1478flags specified in 1479.Ar spec . 1480The supported TCP flags are: 1481.Pp 1482.Cm fin , 1483.Cm syn , 1484.Cm rst , 1485.Cm psh , 1486.Cm ack 1487and 1488.Cm urg . 1489The absence of a particular flag may be denoted 1490with a 1491.Ql \&! . 1492A rule which contains a 1493.Cm tcpflags 1494specification can never match a fragmented packet which has 1495a non-zero offset. 1496See the 1497.Cm frag 1498option for details on matching fragmented packets. 1499.It Cm tcpseq Ar seq 1500TCP packets only. 1501Match if the TCP header sequence number field is set to 1502.Ar seq . 1503.It Cm tcpwin Ar win 1504TCP packets only. 1505Match if the TCP header window field is set to 1506.Ar win . 1507.It Cm tcpoptions Ar spec 1508TCP packets only. 1509Match if the TCP header contains the comma separated list of 1510options specified in 1511.Ar spec . 1512The supported TCP options are: 1513.Pp 1514.Cm mss 1515(maximum segment size), 1516.Cm window 1517(tcp window advertisement), 1518.Cm sack 1519(selective ack), 1520.Cm ts 1521(rfc1323 timestamp) and 1522.Cm cc 1523(rfc1644 t/tcp connection count). 1524The absence of a particular option may be denoted 1525with a 1526.Ql \&! . 1527.It Cm uid Ar user 1528Match all TCP or UDP packets sent by or received for a 1529.Ar user . 1530A 1531.Ar user 1532may be matched by name or identification number. 1533.It Cm verrevpath 1534For incoming packets, 1535a routing table lookup is done on the packet's source address. 1536If the interface on which the packet entered the system matches the 1537outgoing interface for the route, 1538the packet matches. 1539If the interfaces do not match up, 1540the packet does not match. 1541All outgoing packets or packets with no incoming interface match. 1542.Pp 1543The name and functionality of the option is intentionally similar to 1544the Cisco IOS command: 1545.Pp 1546.Dl ip verify unicast reverse-path 1547.Pp 1548This option can be used to make anti-spoofing rules to reject all 1549packets with source addresses not from this interface. 1550See also the option 1551.Cm antispoof . 1552.It Cm versrcreach 1553For incoming packets, 1554a routing table lookup is done on the packet's source address. 1555If a route to the source address exists, but not the default route 1556or a blackhole/reject route, the packet matches. 1557Otherwise, the packet does not match. 1558All outgoing packets match. 1559.Pp 1560The name and functionality of the option is intentionally similar to 1561the Cisco IOS command: 1562.Pp 1563.Dl ip verify unicast source reachable-via any 1564.Pp 1565This option can be used to make anti-spoofing rules to reject all 1566packets whose source address is unreachable. 1567.It Cm antispoof 1568For incoming packets, the packet's source address is checked if it 1569belongs to a directly connected network. 1570If the network is directly connected, then the interface the packet 1571came on in is compared to the interface the network is connected to. 1572When incoming interface and directly connected interface are not the 1573same, the packet does not match. 1574Otherwise, the packet does match. 1575All outgoing packets match. 1576.Pp 1577This option can be used to make anti-spoofing rules to reject all 1578packets that pretend to be from a directly connected network but do 1579not come in through that interface. 1580This option is similar to but more restricted than 1581.Cm verrevpath 1582because it engages only on packets with source addresses of directly 1583connected networks instead of all source addresses. 1584.El 1585.Sh LOOKUP TABLES 1586Lookup tables are useful to handle large sparse address sets, 1587typically from a hundred to several thousands of entries. 1588There may be up to 128 different lookup tables, numbered 0 to 127. 1589.Pp 1590Each entry is represented by an 1591.Ar addr Ns Op / Ns Ar masklen 1592and will match all addresses with base 1593.Ar addr 1594(specified as an IP address or a hostname) 1595and mask width of 1596.Ar masklen 1597bits. 1598If 1599.Ar masklen 1600is not specified, it defaults to 32. 1601When looking up an IP address in a table, the most specific 1602entry will match. 1603Associated with each entry is a 32-bit unsigned 1604.Ar value , 1605which can optionally be checked by a rule matching code. 1606When adding an entry, if 1607.Ar value 1608is not specified, it defaults to 0. 1609.Pp 1610An entry can be added to a table 1611.Pq Cm add , 1612removed from a table 1613.Pq Cm delete , 1614a table can be examined 1615.Pq Cm list 1616or flushed 1617.Pq Cm flush . 1618.Pp 1619Internally, each table is stored in a Radix tree, the same way as 1620the routing table (see 1621.Xr route 4 ) . 1622.Pp 1623Lookup tables currently support IPv4 addresses only. 1624.Pp 1625The 1626.Cm tablearg 1627feature provides the ability to use a value, looked up in the table, as 1628the argument for a rule action, action parameter or rule option. 1629This can significantly reduce number of rules in some configurations. 1630If two tables are used in a rule, the result of the second (destination) 1631is used. 1632The 1633.Cm tablearg 1634argument can be used with the following actions: 1635.Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto 1636action parameters: 1637.Cm tag, untag, 1638rule options: 1639.Cm limit, tagged. 1640.Pp 1641When used with 1642.Cm fwd 1643it is possible to supply table entries with values 1644that are in the form of IP addresses or hostnames. 1645See the 1646.Sx EXAMPLES 1647Section for example usage of tables and the tablearg keyword. 1648.Pp 1649When used with the 1650.Cm skipto 1651action, the user should be aware that the code will walk the ruleset 1652up to a rule equal to, or past, the given number, and should therefore try keep the 1653ruleset compact between the skipto and the target rules. 1654.Sh SETS OF RULES 1655Each rule belongs to one of 32 different 1656.Em sets 1657, numbered 0 to 31. 1658Set 31 is reserved for the default rule. 1659.Pp 1660By default, rules are put in set 0, unless you use the 1661.Cm set N 1662attribute when entering a new rule. 1663Sets can be individually and atomically enabled or disabled, 1664so this mechanism permits an easy way to store multiple configurations 1665of the firewall and quickly (and atomically) switch between them. 1666The command to enable/disable sets is 1667.Bd -ragged -offset indent 1668.Nm 1669.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 1670.Ed 1671.Pp 1672where multiple 1673.Cm enable 1674or 1675.Cm disable 1676sections can be specified. 1677Command execution is atomic on all the sets specified in the command. 1678By default, all sets are enabled. 1679.Pp 1680When you disable a set, its rules behave as if they do not exist 1681in the firewall configuration, with only one exception: 1682.Bd -ragged -offset indent 1683dynamic rules created from a rule before it had been disabled 1684will still be active until they expire. 1685In order to delete 1686dynamic rules you have to explicitly delete the parent rule 1687which generated them. 1688.Ed 1689.Pp 1690The set number of rules can be changed with the command 1691.Bd -ragged -offset indent 1692.Nm 1693.Cm set move 1694.Brq Cm rule Ar rule-number | old-set 1695.Cm to Ar new-set 1696.Ed 1697.Pp 1698Also, you can atomically swap two rulesets with the command 1699.Bd -ragged -offset indent 1700.Nm 1701.Cm set swap Ar first-set second-set 1702.Ed 1703.Pp 1704See the 1705.Sx EXAMPLES 1706Section on some possible uses of sets of rules. 1707.Sh STATEFUL FIREWALL 1708Stateful operation is a way for the firewall to dynamically 1709create rules for specific flows when packets that 1710match a given pattern are detected. 1711Support for stateful 1712operation comes through the 1713.Cm check-state , keep-state 1714and 1715.Cm limit 1716options of 1717.Nm rules . 1718.Pp 1719Dynamic rules are created when a packet matches a 1720.Cm keep-state 1721or 1722.Cm limit 1723rule, causing the creation of a 1724.Em dynamic 1725rule which will match all and only packets with 1726a given 1727.Em protocol 1728between a 1729.Em src-ip/src-port dst-ip/dst-port 1730pair of addresses 1731.Em ( src 1732and 1733.Em dst 1734are used here only to denote the initial match addresses, but they 1735are completely equivalent afterwards). 1736Dynamic rules will be checked at the first 1737.Cm check-state, keep-state 1738or 1739.Cm limit 1740occurrence, and the action performed upon a match will be the same 1741as in the parent rule. 1742.Pp 1743Note that no additional attributes other than protocol and IP addresses 1744and ports are checked on dynamic rules. 1745.Pp 1746The typical use of dynamic rules is to keep a closed firewall configuration, 1747but let the first TCP SYN packet from the inside network install a 1748dynamic rule for the flow so that packets belonging to that session 1749will be allowed through the firewall: 1750.Pp 1751.Dl "ipfw add check-state" 1752.Dl "ipfw add allow tcp from my-subnet to any setup keep-state" 1753.Dl "ipfw add deny tcp from any to any" 1754.Pp 1755A similar approach can be used for UDP, where an UDP packet coming 1756from the inside will install a dynamic rule to let the response through 1757the firewall: 1758.Pp 1759.Dl "ipfw add check-state" 1760.Dl "ipfw add allow udp from my-subnet to any keep-state" 1761.Dl "ipfw add deny udp from any to any" 1762.Pp 1763Dynamic rules expire after some time, which depends on the status 1764of the flow and the setting of some 1765.Cm sysctl 1766variables. 1767See Section 1768.Sx SYSCTL VARIABLES 1769for more details. 1770For TCP sessions, dynamic rules can be instructed to periodically 1771send keepalive packets to refresh the state of the rule when it is 1772about to expire. 1773.Pp 1774See Section 1775.Sx EXAMPLES 1776for more examples on how to use dynamic rules. 1777.Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 1778.Nm 1779is also the user interface for the 1780.Nm dummynet 1781traffic shaper. 1782.Pp 1783.Nm dummynet 1784operates by first using the firewall to classify packets and divide them into 1785.Em flows , 1786using any match pattern that can be used in 1787.Nm 1788rules. 1789Depending on local policies, a flow can contain packets for a single 1790TCP connection, or from/to a given host, or entire subnet, or a 1791protocol type, etc. 1792.Pp 1793There are two modes of 1794.Nm dummynet 1795operation: 1796.Dq normal 1797and 1798.Dq fast . 1799The 1800.Dq normal 1801mode tries to emulate a real link: the 1802.Nm dummynet 1803scheduler ensures that the packet will not leave the pipe faster than it 1804would on the real link with a given bandwidth. 1805The 1806.Dq fast 1807mode allows certain packets to bypass the 1808.Nm dummynet 1809scheduler (if packet flow does not exceed pipe's bandwidth). 1810This is the reason why the 1811.Dq fast 1812mode requires less CPU cycles per packet (on average) and packet latency 1813can be significantly lower in comparison to a real link with the same 1814bandwidth. 1815The default mode is 1816.Dq normal . 1817The 1818.Dq fast 1819mode can be enabled by setting the 1820.Va net.inet.ip.dummynet.io_fast 1821.Xr sysctl 8 1822variable to a non-zero value. 1823.Pp 1824Packets belonging to the same flow are then passed to either of two 1825different objects, which implement the traffic regulation: 1826.Bl -hang -offset XXXX 1827.It Em pipe 1828A pipe emulates a link with given bandwidth, propagation delay, 1829queue size and packet loss rate. 1830Packets are queued in front of the pipe as they come out from the classifier, 1831and then transferred to the pipe according to the pipe's parameters. 1832.Pp 1833.It Em queue 1834A queue 1835is an abstraction used to implement the WF2Q+ 1836(Worst-case Fair Weighted Fair Queueing) policy, which is 1837an efficient variant of the WFQ policy. 1838.br 1839The queue associates a 1840.Em weight 1841and a reference pipe to each flow, and then all backlogged (i.e., 1842with packets queued) flows linked to the same pipe share the pipe's 1843bandwidth proportionally to their weights. 1844Note that weights are not priorities; a flow with a lower weight 1845is still guaranteed to get its fraction of the bandwidth even if a 1846flow with a higher weight is permanently backlogged. 1847.Pp 1848.El 1849In practice, 1850.Em pipes 1851can be used to set hard limits to the bandwidth that a flow can use, whereas 1852.Em queues 1853can be used to determine how different flow share the available bandwidth. 1854.Pp 1855The 1856.Em pipe 1857and 1858.Em queue 1859configuration commands are the following: 1860.Bd -ragged -offset indent 1861.Cm pipe Ar number Cm config Ar pipe-configuration 1862.Pp 1863.Cm queue Ar number Cm config Ar queue-configuration 1864.Ed 1865.Pp 1866The following parameters can be configured for a pipe: 1867.Pp 1868.Bl -tag -width indent -compact 1869.It Cm bw Ar bandwidth | device 1870Bandwidth, measured in 1871.Sm off 1872.Op Cm K | M 1873.Brq Cm bit/s | Byte/s . 1874.Sm on 1875.Pp 1876A value of 0 (default) means unlimited bandwidth. 1877The unit must immediately follow the number, as in 1878.Pp 1879.Dl "ipfw pipe 1 config bw 300Kbit/s" 1880.Pp 1881If a device name is specified instead of a numeric value, as in 1882.Pp 1883.Dl "ipfw pipe 1 config bw tun0" 1884.Pp 1885then the transmit clock is supplied by the specified device. 1886At the moment only the 1887.Xr tun 4 1888device supports this 1889functionality, for use in conjunction with 1890.Xr ppp 8 . 1891.Pp 1892.It Cm delay Ar ms-delay 1893Propagation delay, measured in milliseconds. 1894The value is rounded to the next multiple of the clock tick 1895(typically 10ms, but it is a good practice to run kernels 1896with 1897.Dq "options HZ=1000" 1898to reduce 1899the granularity to 1ms or less). 1900Default value is 0, meaning no delay. 1901.El 1902.Pp 1903The following parameters can be configured for a queue: 1904.Pp 1905.Bl -tag -width indent -compact 1906.It Cm pipe Ar pipe_nr 1907Connects a queue to the specified pipe. 1908Multiple queues (with the same or different weights) can be connected to 1909the same pipe, which specifies the aggregate rate for the set of queues. 1910.Pp 1911.It Cm weight Ar weight 1912Specifies the weight to be used for flows matching this queue. 1913The weight must be in the range 1..100, and defaults to 1. 1914.El 1915.Pp 1916Finally, the following parameters can be configured for both 1917pipes and queues: 1918.Pp 1919.Bl -tag -width XXXX -compact 1920.Pp 1921.It Cm buckets Ar hash-table-size 1922Specifies the size of the hash table used for storing the 1923various queues. 1924Default value is 64 controlled by the 1925.Xr sysctl 8 1926variable 1927.Va net.inet.ip.dummynet.hash_size , 1928allowed range is 16 to 65536. 1929.Pp 1930.It Cm mask Ar mask-specifier 1931Packets sent to a given pipe or queue by an 1932.Nm 1933rule can be further classified into multiple flows, each of which is then 1934sent to a different 1935.Em dynamic 1936pipe or queue. 1937A flow identifier is constructed by masking the IP addresses, 1938ports and protocol types as specified with the 1939.Cm mask 1940options in the configuration of the pipe or queue. 1941For each different flow identifier, a new pipe or queue is created 1942with the same parameters as the original object, and matching packets 1943are sent to it. 1944.Pp 1945Thus, when 1946.Em dynamic pipes 1947are used, each flow will get the same bandwidth as defined by the pipe, 1948whereas when 1949.Em dynamic queues 1950are used, each flow will share the parent's pipe bandwidth evenly 1951with other flows generated by the same queue (note that other queues 1952with different weights might be connected to the same pipe). 1953.br 1954Available mask specifiers are a combination of one or more of the following: 1955.Pp 1956.Cm dst-ip Ar mask , 1957.Cm dst-ip6 Ar mask , 1958.Cm src-ip Ar mask , 1959.Cm src-ip6 Ar mask , 1960.Cm dst-port Ar mask , 1961.Cm src-port Ar mask , 1962.Cm flow-id Ar mask , 1963.Cm proto Ar mask 1964or 1965.Cm all , 1966.Pp 1967where the latter means all bits in all fields are significant. 1968.Pp 1969.It Cm noerror 1970When a packet is dropped by a 1971.Nm dummynet 1972queue or pipe, the error 1973is normally reported to the caller routine in the kernel, in the 1974same way as it happens when a device queue fills up. 1975Setting this 1976option reports the packet as successfully delivered, which can be 1977needed for some experimental setups where you want to simulate 1978loss or congestion at a remote router. 1979.Pp 1980.It Cm plr Ar packet-loss-rate 1981Packet loss rate. 1982Argument 1983.Ar packet-loss-rate 1984is a floating-point number between 0 and 1, with 0 meaning no 1985loss, 1 meaning 100% loss. 1986The loss rate is internally represented on 31 bits. 1987.Pp 1988.It Cm queue Brq Ar slots | size Ns Cm Kbytes 1989Queue size, in 1990.Ar slots 1991or 1992.Cm KBytes . 1993Default value is 50 slots, which 1994is the typical queue size for Ethernet devices. 1995Note that for slow speed links you should keep the queue 1996size short or your traffic might be affected by a significant 1997queueing delay. 1998E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit 1999or 20s of queue on a 30Kbit/s pipe. 2000Even worse effects can result if you get packets from an 2001interface with a much larger MTU, e.g.\& the loopback interface 2002with its 16KB packets. 2003The 2004.Xr sysctl 8 2005variables 2006.Em net.inet.ip.dummynet.pipe_byte_limit 2007and 2008.Em net.inet.ip.dummynet.pipe_slot_limit 2009control the maximum lengths that can be specified. 2010.Pp 2011.It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p 2012Make use of the RED (Random Early Detection) queue management algorithm. 2013.Ar w_q 2014and 2015.Ar max_p 2016are floating 2017point numbers between 0 and 1 (0 not included), while 2018.Ar min_th 2019and 2020.Ar max_th 2021are integer numbers specifying thresholds for queue management 2022(thresholds are computed in bytes if the queue has been defined 2023in bytes, in slots otherwise). 2024The 2025.Nm dummynet 2026also supports the gentle RED variant (gred). 2027Three 2028.Xr sysctl 8 2029variables can be used to control the RED behaviour: 2030.Bl -tag -width indent 2031.It Va net.inet.ip.dummynet.red_lookup_depth 2032specifies the accuracy in computing the average queue 2033when the link is idle (defaults to 256, must be greater than zero) 2034.It Va net.inet.ip.dummynet.red_avg_pkt_size 2035specifies the expected average packet size (defaults to 512, must be 2036greater than zero) 2037.It Va net.inet.ip.dummynet.red_max_pkt_size 2038specifies the expected maximum packet size, only used when queue 2039thresholds are in bytes (defaults to 1500, must be greater than zero). 2040.El 2041.El 2042.Pp 2043When used with IPv6 data, 2044.Nm dummynet 2045currently has several limitations. 2046Information necessary to route link-local packets to an 2047interface is not available after processing by 2048.Nm dummynet 2049so those packets are dropped in the output path. 2050Care should be taken to insure that link-local packets are not passed to 2051.Nm dummynet . 2052.Sh CHECKLIST 2053Here are some important points to consider when designing your 2054rules: 2055.Bl -bullet 2056.It 2057Remember that you filter both packets going 2058.Cm in 2059and 2060.Cm out . 2061Most connections need packets going in both directions. 2062.It 2063Remember to test very carefully. 2064It is a good idea to be near the console when doing this. 2065If you cannot be near the console, 2066use an auto-recovery script such as the one in 2067.Pa /usr/share/examples/ipfw/change_rules.sh . 2068.It 2069Do not forget the loopback interface. 2070.El 2071.Sh FINE POINTS 2072.Bl -bullet 2073.It 2074There are circumstances where fragmented datagrams are unconditionally 2075dropped. 2076TCP packets are dropped if they do not contain at least 20 bytes of 2077TCP header, UDP packets are dropped if they do not contain a full 8 2078byte UDP header, and ICMP packets are dropped if they do not contain 20794 bytes of ICMP header, enough to specify the ICMP type, code, and 2080checksum. 2081These packets are simply logged as 2082.Dq pullup failed 2083since there may not be enough good data in the packet to produce a 2084meaningful log entry. 2085.It 2086Another type of packet is unconditionally dropped, a TCP packet with a 2087fragment offset of one. 2088This is a valid packet, but it only has one use, to try 2089to circumvent firewalls. 2090When logging is enabled, these packets are 2091reported as being dropped by rule -1. 2092.It 2093If you are logged in over a network, loading the 2094.Xr kld 4 2095version of 2096.Nm 2097is probably not as straightforward as you would think. 2098I recommend the following command line: 2099.Bd -literal -offset indent 2100kldload ipfw && \e 2101ipfw add 32000 allow ip from any to any 2102.Ed 2103.Pp 2104Along the same lines, doing an 2105.Bd -literal -offset indent 2106ipfw flush 2107.Ed 2108.Pp 2109in similar surroundings is also a bad idea. 2110.It 2111The 2112.Nm 2113filter list may not be modified if the system security level 2114is set to 3 or higher 2115(see 2116.Xr init 8 2117for information on system security levels). 2118.El 2119.Sh PACKET DIVERSION 2120A 2121.Xr divert 4 2122socket bound to the specified port will receive all packets 2123diverted to that port. 2124If no socket is bound to the destination port, or if the divert module is 2125not loaded, or if the kernel was not compiled with divert socket support, 2126the packets are dropped. 2127.Sh NETWORK ADDRESS TRANSLATION (NAT) 2128The nat configuration command is the following: 2129.Bd -ragged -offset indent 2130.Bk -words 2131.Cm nat 2132.Ar nat_number 2133.Cm config 2134.Ar nat-configuration 2135.Ek 2136.Ed 2137.Pp 2138. 2139The following parameters can be configured: 2140.Bl -tag -width indent 2141.It Cm ip Ar ip_address 2142Define an ip address to use for aliasing. 2143.It Cm if Ar nic 2144Use ip addres of NIC for aliasing, dynamically changing 2145it if NIC's ip address change. 2146.It Cm log 2147Enable logging on this nat instance. 2148.It Cm deny_in 2149Deny any incoming connection from outside world. 2150.It Cm same_ports 2151Try to leave the alias port numbers unchanged from 2152the actual local port numbers. 2153.It Cm unreg_only 2154Traffic on the local network not originating from an 2155unregistered address spaces will be ignored. 2156.It Cm reset 2157Reset table of the packet aliasing engine on address change. 2158.It Cm reverse 2159Reverse the way libalias handles aliasing. 2160.It Cm proxy_only 2161Obey transparent proxy rules only, packet aliasing is not performed. 2162.El 2163.Pp 2164To let the packet continue after being (de)aliased, set the sysctl variable 2165.Va net.inet.ip.fw.one_pass 2166to 0. 2167For more information about aliasing modes, refer to 2168.Xr libalias 3 2169. 2170See Section 2171.Sx EXAMPLES 2172for some examples about nat usage. 2173.Sh REDIRECT AND LSNAT SUPPORT IN IPFW 2174Redirect and LSNAT support follow closely the syntax used in 2175.Xr natd 8 2176. 2177See Section 2178.Sx EXAMPLES 2179for some examples on how to do redirect and lsnat. 2180.Sh SYSCTL VARIABLES 2181A set of 2182.Xr sysctl 8 2183variables controls the behaviour of the firewall and 2184associated modules 2185.Pq Nm dummynet , bridge . 2186These are shown below together with their default value 2187(but always check with the 2188.Xr sysctl 8 2189command what value is actually in use) and meaning: 2190.Bl -tag -width indent 2191.It Va net.inet.ip.dummynet.expire : No 1 2192Lazily delete dynamic pipes/queue once they have no pending traffic. 2193You can disable this by setting the variable to 0, in which case 2194the pipes/queues will only be deleted when the threshold is reached. 2195.It Va net.inet.ip.dummynet.hash_size : No 64 2196Default size of the hash table used for dynamic pipes/queues. 2197This value is used when no 2198.Cm buckets 2199option is specified when configuring a pipe/queue. 2200.It Va net.inet.ip.dummynet.io_fast : No 0 2201If set to a non-zero value, 2202the 2203.Dq fast 2204mode of 2205.Nm dummynet 2206operation (see above) is enabled. 2207.It Va net.inet.ip.dummynet.io_pkt 2208Number of packets passed to 2209.Nm dummynet . 2210.It Va net.inet.ip.dummynet.io_pkt_drop 2211Number of packets dropped by 2212.Nm dummynet . 2213.It Va net.inet.ip.dummynet.io_pkt_fast 2214Number of packets bypassed by the 2215.Nm dummynet 2216scheduler. 2217.It Va net.inet.ip.dummynet.max_chain_len : No 16 2218Target value for the maximum number of pipes/queues in a hash bucket. 2219The product 2220.Cm max_chain_len*hash_size 2221is used to determine the threshold over which empty pipes/queues 2222will be expired even when 2223.Cm net.inet.ip.dummynet.expire=0 . 2224.It Va net.inet.ip.dummynet.red_lookup_depth : No 256 2225.It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512 2226.It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500 2227Parameters used in the computations of the drop probability 2228for the RED algorithm. 2229.It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576 2230.It Va net.inet.ip.dummynet.pipe_slot_limit : No 100 2231The maximum queue size that can be specified in bytes or packets. 2232These limits prevent accidental exhaustion of resources such as mbufs. 2233If you raise these limits, 2234you should make sure the system is configured so that sufficient resources 2235are available. 2236.It Va net.inet.ip.fw.autoinc_step : No 100 2237Delta between rule numbers when auto-generating them. 2238The value must be in the range 1..1000. 2239.It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets 2240The current number of buckets in the hash table for dynamic rules 2241(readonly). 2242.It Va net.inet.ip.fw.debug : No 1 2243Controls debugging messages produced by 2244.Nm . 2245.It Va net.inet.ip.fw.dyn_buckets : No 256 2246The number of buckets in the hash table for dynamic rules. 2247Must be a power of 2, up to 65536. 2248It only takes effect when all dynamic rules have expired, so you 2249are advised to use a 2250.Cm flush 2251command to make sure that the hash table is resized. 2252.It Va net.inet.ip.fw.dyn_count : No 3 2253Current number of dynamic rules 2254(read-only). 2255.It Va net.inet.ip.fw.dyn_keepalive : No 1 2256Enables generation of keepalive packets for 2257.Cm keep-state 2258rules on TCP sessions. 2259A keepalive is generated to both 2260sides of the connection every 5 seconds for the last 20 2261seconds of the lifetime of the rule. 2262.It Va net.inet.ip.fw.dyn_max : No 8192 2263Maximum number of dynamic rules. 2264When you hit this limit, no more dynamic rules can be 2265installed until old ones expire. 2266.It Va net.inet.ip.fw.dyn_ack_lifetime : No 300 2267.It Va net.inet.ip.fw.dyn_syn_lifetime : No 20 2268.It Va net.inet.ip.fw.dyn_fin_lifetime : No 1 2269.It Va net.inet.ip.fw.dyn_rst_lifetime : No 1 2270.It Va net.inet.ip.fw.dyn_udp_lifetime : No 5 2271.It Va net.inet.ip.fw.dyn_short_lifetime : No 30 2272These variables control the lifetime, in seconds, of dynamic 2273rules. 2274Upon the initial SYN exchange the lifetime is kept short, 2275then increased after both SYN have been seen, then decreased 2276again during the final FIN exchange or when a RST is received. 2277Both 2278.Em dyn_fin_lifetime 2279and 2280.Em dyn_rst_lifetime 2281must be strictly lower than 5 seconds, the period of 2282repetition of keepalives. 2283The firewall enforces that. 2284.It Va net.inet.ip.fw.enable : No 1 2285Enables the firewall. 2286Setting this variable to 0 lets you run your machine without 2287firewall even if compiled in. 2288.It Va net.inet6.ip6.fw.enable : No 1 2289provides the same functionality as above for the IPv6 case. 2290.It Va net.inet.ip.fw.one_pass : No 1 2291When set, the packet exiting from the 2292.Nm dummynet 2293pipe or from 2294.Xr ng_ipfw 4 2295node is not passed though the firewall again. 2296Otherwise, after an action, the packet is 2297reinjected into the firewall at the next rule. 2298.It Va net.inet.ip.fw.verbose : No 1 2299Enables verbose messages. 2300.It Va net.inet.ip.fw.verbose_limit : No 0 2301Limits the number of messages produced by a verbose firewall. 2302.It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1 2303If enabled packets with unknown IPv6 Extension Headers will be denied. 2304.It Va net.link.ether.ipfw : No 0 2305Controls whether layer-2 packets are passed to 2306.Nm . 2307Default is no. 2308.It Va net.link.bridge.ipfw : No 0 2309Controls whether bridged packets are passed to 2310.Nm . 2311Default is no. 2312.El 2313.Pp 2314.Sh EXAMPLES 2315There are far too many possible uses of 2316.Nm 2317so this Section will only give a small set of examples. 2318.Pp 2319.Ss BASIC PACKET FILTERING 2320This command adds an entry which denies all tcp packets from 2321.Em cracker.evil.org 2322to the telnet port of 2323.Em wolf.tambov.su 2324from being forwarded by the host: 2325.Pp 2326.Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet" 2327.Pp 2328This one disallows any connection from the entire cracker's 2329network to my host: 2330.Pp 2331.Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org" 2332.Pp 2333A first and efficient way to limit access (not using dynamic rules) 2334is the use of the following rules: 2335.Pp 2336.Dl "ipfw add allow tcp from any to any established" 2337.Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup" 2338.Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup" 2339.Dl "..." 2340.Dl "ipfw add deny tcp from any to any" 2341.Pp 2342The first rule will be a quick match for normal TCP packets, 2343but it will not match the initial SYN packet, which will be 2344matched by the 2345.Cm setup 2346rules only for selected source/destination pairs. 2347All other SYN packets will be rejected by the final 2348.Cm deny 2349rule. 2350.Pp 2351If you administer one or more subnets, you can take advantage 2352of the address sets and or-blocks and write extremely 2353compact rulesets which selectively enable services to blocks 2354of clients, as below: 2355.Pp 2356.Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q" 2357.Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q" 2358.Dl "" 2359.Dl "ipfw add allow ip from ${goodguys} to any" 2360.Dl "ipfw add deny ip from ${badguys} to any" 2361.Dl "... normal policies ..." 2362.Pp 2363The 2364.Cm verrevpath 2365option could be used to do automated anti-spoofing by adding the 2366following to the top of a ruleset: 2367.Pp 2368.Dl "ipfw add deny ip from any to any not verrevpath in" 2369.Pp 2370This rule drops all incoming packets that appear to be coming to the 2371system on the wrong interface. 2372For example, a packet with a source 2373address belonging to a host on a protected internal network would be 2374dropped if it tried to enter the system from an external interface. 2375.Pp 2376The 2377.Cm antispoof 2378option could be used to do similar but more restricted anti-spoofing 2379by adding the following to the top of a ruleset: 2380.Pp 2381.Dl "ipfw add deny ip from any to any not antispoof in" 2382.Pp 2383This rule drops all incoming packets that appear to be coming from another 2384directly connected system but on the wrong interface. 2385For example, a packet with a source address of 2386.Li 192.168.0.0/24 2387, configured on 2388.Li fxp0 2389, but coming in on 2390.Li fxp1 2391would be dropped. 2392.Ss DYNAMIC RULES 2393In order to protect a site from flood attacks involving fake 2394TCP packets, it is safer to use dynamic rules: 2395.Pp 2396.Dl "ipfw add check-state" 2397.Dl "ipfw add deny tcp from any to any established" 2398.Dl "ipfw add allow tcp from my-net to any setup keep-state" 2399.Pp 2400This will let the firewall install dynamic rules only for 2401those connection which start with a regular SYN packet coming 2402from the inside of our network. 2403Dynamic rules are checked when encountering the first 2404.Cm check-state 2405or 2406.Cm keep-state 2407rule. 2408A 2409.Cm check-state 2410rule should usually be placed near the beginning of the 2411ruleset to minimize the amount of work scanning the ruleset. 2412Your mileage may vary. 2413.Pp 2414To limit the number of connections a user can open 2415you can use the following type of rules: 2416.Pp 2417.Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10" 2418.Dl "ipfw add allow tcp from any to me setup limit src-addr 4" 2419.Pp 2420The former (assuming it runs on a gateway) will allow each host 2421on a /24 network to open at most 10 TCP connections. 2422The latter can be placed on a server to make sure that a single 2423client does not use more than 4 simultaneous connections. 2424.Pp 2425.Em BEWARE : 2426stateful rules can be subject to denial-of-service attacks 2427by a SYN-flood which opens a huge number of dynamic rules. 2428The effects of such attacks can be partially limited by 2429acting on a set of 2430.Xr sysctl 8 2431variables which control the operation of the firewall. 2432.Pp 2433Here is a good usage of the 2434.Cm list 2435command to see accounting records and timestamp information: 2436.Pp 2437.Dl ipfw -at list 2438.Pp 2439or in short form without timestamps: 2440.Pp 2441.Dl ipfw -a list 2442.Pp 2443which is equivalent to: 2444.Pp 2445.Dl ipfw show 2446.Pp 2447Next rule diverts all incoming packets from 192.168.2.0/24 2448to divert port 5000: 2449.Pp 2450.Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in 2451.Pp 2452.Ss TRAFFIC SHAPING 2453The following rules show some of the applications of 2454.Nm 2455and 2456.Nm dummynet 2457for simulations and the like. 2458.Pp 2459This rule drops random incoming packets with a probability 2460of 5%: 2461.Pp 2462.Dl "ipfw add prob 0.05 deny ip from any to any in" 2463.Pp 2464A similar effect can be achieved making use of 2465.Nm dummynet 2466pipes: 2467.Pp 2468.Dl "ipfw add pipe 10 ip from any to any" 2469.Dl "ipfw pipe 10 config plr 0.05" 2470.Pp 2471We can use pipes to artificially limit bandwidth, e.g.\& on a 2472machine acting as a router, if we want to limit traffic from 2473local clients on 192.168.2.0/24 we do: 2474.Pp 2475.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 2476.Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes" 2477.Pp 2478note that we use the 2479.Cm out 2480modifier so that the rule is not used twice. 2481Remember in fact that 2482.Nm 2483rules are checked both on incoming and outgoing packets. 2484.Pp 2485Should we want to simulate a bidirectional link with bandwidth 2486limitations, the correct way is the following: 2487.Pp 2488.Dl "ipfw add pipe 1 ip from any to any out" 2489.Dl "ipfw add pipe 2 ip from any to any in" 2490.Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes" 2491.Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes" 2492.Pp 2493The above can be very useful, e.g.\& if you want to see how 2494your fancy Web page will look for a residential user who 2495is connected only through a slow link. 2496You should not use only one pipe for both directions, unless 2497you want to simulate a half-duplex medium (e.g.\& AppleTalk, 2498Ethernet, IRDA). 2499It is not necessary that both pipes have the same configuration, 2500so we can also simulate asymmetric links. 2501.Pp 2502Should we want to verify network performance with the RED queue 2503management algorithm: 2504.Pp 2505.Dl "ipfw add pipe 1 ip from any to any" 2506.Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1" 2507.Pp 2508Another typical application of the traffic shaper is to 2509introduce some delay in the communication. 2510This can significantly affect applications which do a lot of Remote 2511Procedure Calls, and where the round-trip-time of the 2512connection often becomes a limiting factor much more than 2513bandwidth: 2514.Pp 2515.Dl "ipfw add pipe 1 ip from any to any out" 2516.Dl "ipfw add pipe 2 ip from any to any in" 2517.Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s" 2518.Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s" 2519.Pp 2520Per-flow queueing can be useful for a variety of purposes. 2521A very simple one is counting traffic: 2522.Pp 2523.Dl "ipfw add pipe 1 tcp from any to any" 2524.Dl "ipfw add pipe 1 udp from any to any" 2525.Dl "ipfw add pipe 1 ip from any to any" 2526.Dl "ipfw pipe 1 config mask all" 2527.Pp 2528The above set of rules will create queues (and collect 2529statistics) for all traffic. 2530Because the pipes have no limitations, the only effect is 2531collecting statistics. 2532Note that we need 3 rules, not just the last one, because 2533when 2534.Nm 2535tries to match IP packets it will not consider ports, so we 2536would not see connections on separate ports as different 2537ones. 2538.Pp 2539A more sophisticated example is limiting the outbound traffic 2540on a net with per-host limits, rather than per-network limits: 2541.Pp 2542.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 2543.Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in" 2544.Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 2545.Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 2546.Ss LOOKUP TABLES 2547In the following example, we need to create several traffic bandwidth 2548classes and we need different hosts/networks to fall into different classes. 2549We create one pipe for each class and configure them accordingly. 2550Then we create a single table and fill it with IP subnets and addresses. 2551For each subnet/host we set the argument equal to the number of the pipe 2552that it should use. 2553Then we classify traffic using a single rule: 2554.Pp 2555.Dl "ipfw pipe 1 config bw 1000Kbyte/s" 2556.Dl "ipfw pipe 4 config bw 4000Kbyte/s" 2557.Dl "..." 2558.Dl "ipfw table 1 add 192.168.2.0/24 1" 2559.Dl "ipfw table 1 add 192.168.0.0/27 4" 2560.Dl "ipfw table 1 add 192.168.0.2 1" 2561.Dl "..." 2562.Dl "ipfw add pipe tablearg ip from table(1) to any" 2563.Pp 2564Using the 2565.Cm fwd 2566action, the table entries may include hostnames and IP addresses. 2567.Pp 2568.Dl "ipfw table 1 add 192.168.2.0/24 10.23.2.1" 2569.Dl "ipfw table 1 add 192.168.0.0/27 router1.dmz" 2570.Dl "..." 2571.Dl "ipfw add 100 fwd tablearg ip from any to table(1)" 2572.Ss SETS OF RULES 2573To add a set of rules atomically, e.g.\& set 18: 2574.Pp 2575.Dl "ipfw set disable 18" 2576.Dl "ipfw add NN set 18 ... # repeat as needed" 2577.Dl "ipfw set enable 18" 2578.Pp 2579To delete a set of rules atomically the command is simply: 2580.Pp 2581.Dl "ipfw delete set 18" 2582.Pp 2583To test a ruleset and disable it and regain control if something goes wrong: 2584.Pp 2585.Dl "ipfw set disable 18" 2586.Dl "ipfw add NN set 18 ... # repeat as needed" 2587.Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18" 2588.Pp 2589Here if everything goes well, you press control-C before the "sleep" 2590terminates, and your ruleset will be left active. 2591Otherwise, e.g.\& if 2592you cannot access your box, the ruleset will be disabled after 2593the sleep terminates thus restoring the previous situation. 2594.Pp 2595To show rules of the specific set: 2596.Pp 2597.Dl "ipfw set 18 show" 2598.Pp 2599To show rules of the disabled set: 2600.Pp 2601.Dl "ipfw -S set 18 show" 2602.Pp 2603To clear a specific rule counters of the specific set: 2604.Pp 2605.Dl "ipfw set 18 zero NN" 2606.Pp 2607To delete a specific rule of the specific set: 2608.Pp 2609.Dl "ipfw set 18 delete NN" 2610.Ss NAT, REDIRECT AND LSNAT 2611First redirect all the traffic to nat instance 123: 2612.Pp 2613.Dl "ipfw add nat 123 all from any to any" 2614.Pp 2615Then to configure nat instance 123 to alias all the outgoing traffic with ip 2616192.168.0.123, blocking all incoming connections, trying to keep 2617same ports on both sides, clearing aliasing table on address change 2618and keeping a log of traffic/link statistics: 2619.Pp 2620.Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports" 2621.Pp 2622Or to change address of instance 123, aliasing table will be cleared (see 2623reset option): 2624.Pp 2625.Dl "ipfw nat 123 config ip 10.0.0.1" 2626.Pp 2627To see configuration of nat instance 123: 2628.Pp 2629.Dl "ipfw nat 123 show config" 2630.Pp 2631To show logs of all the instances in range 111-999: 2632.Pp 2633.Dl "ipfw nat 111-999 show" 2634.Pp 2635To see configurations of all instances: 2636.Pp 2637.Dl "ipfw nat show config" 2638.Pp 2639Or a redirect rule with mixed modes could looks like: 2640.Pp 2641.Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66" 2642.Dl " redirect_port tcp 192.168.0.1:80 500" 2643.Dl " redirect_proto udp 192.168.1.43 192.168.1.1" 2644.Dl " redirect_addr 192.168.0.10,192.168.0.11" 2645.Dl " 10.0.0.100 # LSNAT" 2646.Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22" 2647.Dl " 500 # LSNAT" 2648.Pp 2649or it could be splitted in: 2650.Pp 2651.Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66" 2652.Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500" 2653.Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1" 2654.Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12" 2655.Dl " 10.0.0.100" 2656.Dl "ipfw nat 5 config redirect_port tcp" 2657.Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500" 2658.Pp 2659.Sh SEE ALSO 2660.Xr cpp 1 , 2661.Xr m4 1 , 2662.Xr altq 4 , 2663.Xr divert 4 , 2664.Xr dummynet 4 , 2665.Xr if_bridge 4 , 2666.Xr ip 4 , 2667.Xr ipfirewall 4 , 2668.Xr ng_ipfw 4 , 2669.Xr protocols 5 , 2670.Xr services 5 , 2671.Xr init 8 , 2672.Xr kldload 8 , 2673.Xr reboot 8 , 2674.Xr sysctl 8 , 2675.Xr syslogd 8 2676.Sh HISTORY 2677The 2678.Nm 2679utility first appeared in 2680.Fx 2.0 . 2681.Nm dummynet 2682was introduced in 2683.Fx 2.2.8 . 2684Stateful extensions were introduced in 2685.Fx 4.0 . 2686.Nm ipfw2 2687was introduced in Summer 2002. 2688.Sh AUTHORS 2689.An Ugen J. S. Antsilevich , 2690.An Poul-Henning Kamp , 2691.An Alex Nash , 2692.An Archie Cobbs , 2693.An Luigi Rizzo . 2694.Pp 2695.An -nosplit 2696API based upon code written by 2697.An Daniel Boulet 2698for BSDI. 2699.Pp 2700.An -nosplit 2701In-kernel NAT support written by 2702.An Paolo Pisati Aq piso@FreeBSD.org 2703as part of a Summer of Code 2005 project. 2704.Pp 2705Work on 2706.Nm dummynet 2707traffic shaper supported by Akamba Corp. 2708.Sh BUGS 2709The syntax has grown over the years and sometimes it might be confusing. 2710Unfortunately, backward compatibility prevents cleaning up mistakes 2711made in the definition of the syntax. 2712.Pp 2713.Em !!! WARNING !!! 2714.Pp 2715Misconfiguring the firewall can put your computer in an unusable state, 2716possibly shutting down network services and requiring console access to 2717regain control of it. 2718.Pp 2719Incoming packet fragments diverted by 2720.Cm divert 2721are reassembled before delivery to the socket. 2722The action used on those packet is the one from the 2723rule which matches the first fragment of the packet. 2724.Pp 2725Packets diverted to userland, and then reinserted by a userland process 2726may lose various packet attributes. 2727The packet source interface name 2728will be preserved if it is shorter than 8 bytes and the userland process 2729saves and reuses the sockaddr_in 2730(as does 2731.Xr natd 8 ) ; 2732otherwise, it may be lost. 2733If a packet is reinserted in this manner, later rules may be incorrectly 2734applied, making the order of 2735.Cm divert 2736rules in the rule sequence very important. 2737.Pp 2738Dummynet drops all packets with IPv6 link-local addresses. 2739.Pp 2740Rules using 2741.Cm uid 2742or 2743.Cm gid 2744may not behave as expected. 2745In particular, incoming SYN packets may 2746have no uid or gid associated with them since they do not yet belong 2747to a TCP connection, and the uid/gid associated with a packet may not 2748be as expected if the associated process calls 2749.Xr setuid 2 2750or similar system calls. 2751.Pp 2752Rule syntax is subject to the command line environment and some patterns 2753may need to be escaped with the backslash character 2754or quoted appropriately. 2755.Pp 2756Due to the architecture of 2757.Xr libalias 3 , 2758ipfw nat is not compatible with the tcp segmentation offloading 2759(TSO). Thus, to reliably nat your network traffic, please disable TSO 2760on your NICs using 2761.Xr ifconfig 8 . 2762.Pp 2763ICMP error messages are not implicitly matched by dynamic rules 2764for the respective conversations. 2765To avoid failures of network error detection and path MTU discovery, 2766ICMP error messages may need to be allowed explicitly through static 2767rules. 2768