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 792Skip all subsequent rules numbered less than 793.Ar number . 794The search continues with the first rule numbered 795.Ar number 796or higher. 797.It Cm tee Ar port 798Send a copy of packets matching this rule to the 799.Xr divert 4 800socket bound to port 801.Ar port . 802The search continues with the next rule. 803.It Cm unreach Ar code 804Discard packets that match this rule, and try to send an ICMP 805unreachable notice with code 806.Ar code , 807where 808.Ar code 809is a number from 0 to 255, or one of these aliases: 810.Cm net , host , protocol , port , 811.Cm needfrag , srcfail , net-unknown , host-unknown , 812.Cm isolated , net-prohib , host-prohib , tosnet , 813.Cm toshost , filter-prohib , host-precedence 814or 815.Cm precedence-cutoff . 816The search terminates. 817.It Cm unreach6 Ar code 818Discard packets that match this rule, and try to send an ICMPv6 819unreachable notice with code 820.Ar code , 821where 822.Ar code 823is a number from 0, 1, 3 or 4, or one of these aliases: 824.Cm no-route, admin-prohib, address 825or 826.Cm port . 827The search terminates. 828.It Cm netgraph Ar cookie 829Divert packet into netgraph with given 830.Ar cookie . 831The search terminates. 832If packet is later returned from netgraph it is either 833accepted or continues with the next rule, depending on 834.Va net.inet.ip.fw.one_pass 835sysctl variable. 836.It Cm ngtee Ar cookie 837A copy of packet is diverted into netgraph, original 838packet is either accepted or continues with the next rule, depending on 839.Va net.inet.ip.fw.one_pass 840sysctl variable. 841See 842.Xr ng_ipfw 4 843for more information on 844.Cm netgraph 845and 846.Cm ngtee 847actions. 848.It Cm setfib Ar fibnum 849The packet is tagged so as to use the FIB (routing table) 850.Ar fibnum 851in any subsequent forwarding decisions. Initially this is 852limited to the values 0 through 15. See 853.Xr setfib 8 854.El 855.Ss RULE BODY 856The body of a rule contains zero or more patterns (such as 857specific source and destination addresses or ports, 858protocol options, incoming or outgoing interfaces, etc.) 859that the packet must match in order to be recognised. 860In general, the patterns are connected by (implicit) 861.Cm and 862operators -- i.e., all must match in order for the 863rule to match. 864Individual patterns can be prefixed by the 865.Cm not 866operator to reverse the result of the match, as in 867.Pp 868.Dl "ipfw add 100 allow ip from not 1.2.3.4 to any" 869.Pp 870Additionally, sets of alternative match patterns 871.Pq Em or-blocks 872can be constructed by putting the patterns in 873lists enclosed between parentheses ( ) or braces { }, and 874using the 875.Cm or 876operator as follows: 877.Pp 878.Dl "ipfw add 100 allow ip from { x or not y or z } to any" 879.Pp 880Only one level of parentheses is allowed. 881Beware that most shells have special meanings for parentheses 882or braces, so it is advisable to put a backslash \\ in front of them 883to prevent such interpretations. 884.Pp 885The body of a rule must in general include a source and destination 886address specifier. 887The keyword 888.Ar any 889can be used in various places to specify that the content of 890a required field is irrelevant. 891.Pp 892The rule body has the following format: 893.Bd -ragged -offset indent 894.Op Ar proto Cm from Ar src Cm to Ar dst 895.Op Ar options 896.Ed 897.Pp 898The first part (proto from src to dst) is for backward 899compatibility with earlier versions of 900.Fx . 901In modern 902.Fx 903any match pattern (including MAC headers, IP protocols, 904addresses and ports) can be specified in the 905.Ar options 906section. 907.Pp 908Rule fields have the following meaning: 909.Bl -tag -width indent 910.It Ar proto : protocol | Cm { Ar protocol Cm or ... } 911.It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number 912An IP protocol specified by number or name 913(for a complete list see 914.Pa /etc/protocols ) , 915or one of the following keywords: 916.Bl -tag -width indent 917.It Cm ip4 | ipv4 918Matches IPv4 packets. 919.It Cm ip6 | ipv6 920Matches IPv6 packets. 921.It Cm ip | all 922Matches any packet. 923.El 924.Pp 925The 926.Cm ipv6 927in 928.Cm proto 929option will be treated as inner protocol. 930And, the 931.Cm ipv4 932is not available in 933.Cm proto 934option. 935.Pp 936The 937.Cm { Ar protocol Cm or ... } 938format (an 939.Em or-block ) 940is provided for convenience only but its use is deprecated. 941.It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports 942An address (or a list, see below) 943optionally followed by 944.Ar ports 945specifiers. 946.Pp 947The second format 948.Em ( or-block 949with multiple addresses) is provided for convenience only and 950its use is discouraged. 951.It Ar addr : Oo Cm not Oc Bro 952.Cm any | me | me6 | 953.Cm table Ns Pq Ar number Ns Op , Ns Ar value 954.Ar | addr-list | addr-set 955.Brc 956.It Cm any 957matches any IP address. 958.It Cm me 959matches any IP address configured on an interface in the system. 960.It Cm me6 961matches any IPv6 address configured on an interface in the system. 962The address list is evaluated at the time the packet is 963analysed. 964.It Cm table Ns Pq Ar number Ns Op , Ns Ar value 965Matches any IPv4 address for which an entry exists in the lookup table 966.Ar number . 967If an optional 32-bit unsigned 968.Ar value 969is also specified, an entry will match only if it has this value. 970See the 971.Sx LOOKUP TABLES 972section below for more information on lookup tables. 973.It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list 974.It Ar ip-addr : 975A host or subnet address specified in one of the following ways: 976.Bl -tag -width indent 977.It Ar numeric-ip | hostname 978Matches a single IPv4 address, specified as dotted-quad or a hostname. 979Hostnames are resolved at the time the rule is added to the firewall list. 980.It Ar addr Ns / Ns Ar masklen 981Matches all addresses with base 982.Ar addr 983(specified as an IP address, a network number, or a hostname) 984and mask width of 985.Cm masklen 986bits. 987As an example, 1.2.3.4/25 or 1.2.3.0/25 will match 988all IP numbers from 1.2.3.0 to 1.2.3.127 . 989.It Ar addr Ns : Ns Ar mask 990Matches all addresses with base 991.Ar addr 992(specified as an IP address, a network number, or a hostname) 993and the mask of 994.Ar mask , 995specified as a dotted quad. 996As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match 9971.*.3.*. 998This form is advised only for non-contiguous 999masks. 1000It is better to resort to the 1001.Ar addr Ns / Ns Ar masklen 1002format for contiguous masks, which is more compact and less 1003error-prone. 1004.El 1005.It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm } 1006.It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list 1007Matches all addresses with base address 1008.Ar addr 1009(specified as an IP address, a network number, or a hostname) 1010and whose last byte is in the list between braces { } . 1011Note that there must be no spaces between braces and 1012numbers (spaces after commas are allowed). 1013Elements of the list can be specified as single entries 1014or ranges. 1015The 1016.Ar masklen 1017field is used to limit the size of the set of addresses, 1018and can have any value between 24 and 32. 1019If not specified, 1020it will be assumed as 24. 1021.br 1022This format is particularly useful to handle sparse address sets 1023within a single rule. 1024Because the matching occurs using a 1025bitmask, it takes constant time and dramatically reduces 1026the complexity of rulesets. 1027.br 1028As an example, an address specified as 1.2.3.4/24{128,35-55,89} 1029or 1.2.3.0/24{128,35-55,89} 1030will match the following IP addresses: 1031.br 10321.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 . 1033.It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list 1034.It Ar ip6-addr : 1035A host or subnet specified one of the following ways: 1036.Pp 1037.Bl -tag -width indent 1038.It Ar numeric-ip | hostname 1039Matches a single IPv6 address as allowed by 1040.Xr inet_pton 3 1041or a hostname. 1042Hostnames are resolved at the time the rule is added to the firewall 1043list. 1044.It Ar addr Ns / Ns Ar masklen 1045Matches all IPv6 addresses with base 1046.Ar addr 1047(specified as allowed by 1048.Xr inet_pton 1049or a hostname) 1050and mask width of 1051.Cm masklen 1052bits. 1053.El 1054.Pp 1055No support for sets of IPv6 addresses is provided because IPv6 addresses 1056are typically random past the initial prefix. 1057.It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports 1058For protocols which support port numbers (such as TCP and UDP), optional 1059.Cm ports 1060may be specified as one or more ports or port ranges, separated 1061by commas but no spaces, and an optional 1062.Cm not 1063operator. 1064The 1065.Ql \&- 1066notation specifies a range of ports (including boundaries). 1067.Pp 1068Service names (from 1069.Pa /etc/services ) 1070may be used instead of numeric port values. 1071The length of the port list is limited to 30 ports or ranges, 1072though one can specify larger ranges by using an 1073.Em or-block 1074in the 1075.Cm options 1076section of the rule. 1077.Pp 1078A backslash 1079.Pq Ql \e 1080can be used to escape the dash 1081.Pq Ql - 1082character in a service name (from a shell, the backslash must be 1083typed twice to avoid the shell itself interpreting it as an escape 1084character). 1085.Pp 1086.Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any" 1087.Pp 1088Fragmented packets which have a non-zero offset (i.e., not the first 1089fragment) will never match a rule which has one or more port 1090specifications. 1091See the 1092.Cm frag 1093option for details on matching fragmented packets. 1094.El 1095.Ss RULE OPTIONS (MATCH PATTERNS) 1096Additional match patterns can be used within 1097rules. 1098Zero or more of these so-called 1099.Em options 1100can be present in a rule, optionally prefixed by the 1101.Cm not 1102operand, and possibly grouped into 1103.Em or-blocks . 1104.Pp 1105The following match patterns can be used (listed in alphabetical order): 1106.Bl -tag -width indent 1107.It Cm // this is a comment. 1108Inserts the specified text as a comment in the rule. 1109Everything following // is considered as a comment and stored in the rule. 1110You can have comment-only rules, which are listed as having a 1111.Cm count 1112action followed by the comment. 1113.It Cm bridged 1114Alias for 1115.Cm layer2 . 1116.It Cm diverted 1117Matches only packets generated by a divert socket. 1118.It Cm diverted-loopback 1119Matches only packets coming from a divert socket back into the IP stack 1120input for delivery. 1121.It Cm diverted-output 1122Matches only packets going from a divert socket back outward to the IP 1123stack output for delivery. 1124.It Cm dst-ip Ar ip-address 1125Matches IPv4 packets whose destination IP is one of the address(es) 1126specified as argument. 1127.It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address 1128Matches IPv6 packets whose destination IP is one of the address(es) 1129specified as argument. 1130.It Cm dst-port Ar ports 1131Matches IP packets whose destination port is one of the port(s) 1132specified as argument. 1133.It Cm established 1134Matches TCP packets that have the RST or ACK bits set. 1135.It Cm ext6hdr Ar header 1136Matches IPv6 packets containing the extended header given by 1137.Ar header . 1138Supported headers are: 1139.Pp 1140Fragment, 1141.Pq Cm frag , 1142Hop-to-hop options 1143.Pq Cm hopopt , 1144any type of Routing Header 1145.Pq Cm route , 1146Source routing Routing Header Type 0 1147.Pq Cm rthdr0 , 1148Mobile IPv6 Routing Header Type 2 1149.Pq Cm rthdr2 , 1150Destination options 1151.Pq Cm dstopt , 1152IPSec authentication headers 1153.Pq Cm ah , 1154and IPSec encapsulated security payload headers 1155.Pq Cm esp . 1156.It Cm fib Ar fibnum 1157Matches a packet that has been tagged to use 1158the given FIB (routing table) number. 1159.It Cm flow-id Ar labels 1160Matches IPv6 packets containing any of the flow labels given in 1161.Ar labels . 1162.Ar labels 1163is a comma seperate list of numeric flow labels. 1164.It Cm frag 1165Matches packets that are fragments and not the first 1166fragment of an IP datagram. 1167Note that these packets will not have 1168the next protocol header (e.g.\& TCP, UDP) so options that look into 1169these headers cannot match. 1170.It Cm gid Ar group 1171Matches all TCP or UDP packets sent by or received for a 1172.Ar group . 1173A 1174.Ar group 1175may be specified by name or number. 1176.It Cm jail Ar prisonID 1177Matches all TCP or UDP packets sent by or received for the 1178jail whos prison ID is 1179.Ar prisonID . 1180.It Cm icmptypes Ar types 1181Matches ICMP packets whose ICMP type is in the list 1182.Ar types . 1183The list may be specified as any combination of 1184individual types (numeric) separated by commas. 1185.Em Ranges are not allowed . 1186The supported ICMP types are: 1187.Pp 1188echo reply 1189.Pq Cm 0 , 1190destination unreachable 1191.Pq Cm 3 , 1192source quench 1193.Pq Cm 4 , 1194redirect 1195.Pq Cm 5 , 1196echo request 1197.Pq Cm 8 , 1198router advertisement 1199.Pq Cm 9 , 1200router solicitation 1201.Pq Cm 10 , 1202time-to-live exceeded 1203.Pq Cm 11 , 1204IP header bad 1205.Pq Cm 12 , 1206timestamp request 1207.Pq Cm 13 , 1208timestamp reply 1209.Pq Cm 14 , 1210information request 1211.Pq Cm 15 , 1212information reply 1213.Pq Cm 16 , 1214address mask request 1215.Pq Cm 17 1216and address mask reply 1217.Pq Cm 18 . 1218.It Cm icmp6types Ar types 1219Matches ICMP6 packets whose ICMP6 type is in the list of 1220.Ar types . 1221The list may be specified as any combination of 1222individual types (numeric) separated by commas. 1223.Em Ranges are not allowed . 1224.It Cm in | out 1225Matches incoming or outgoing packets, respectively. 1226.Cm in 1227and 1228.Cm out 1229are mutually exclusive (in fact, 1230.Cm out 1231is implemented as 1232.Cm not in Ns No ). 1233.It Cm ipid Ar id-list 1234Matches IPv4 packets whose 1235.Cm ip_id 1236field has value included in 1237.Ar id-list , 1238which is either a single value or a list of values or ranges 1239specified in the same way as 1240.Ar ports . 1241.It Cm iplen Ar len-list 1242Matches IP packets whose total length, including header and data, is 1243in the set 1244.Ar len-list , 1245which is either a single value or a list of values or ranges 1246specified in the same way as 1247.Ar ports . 1248.It Cm ipoptions Ar spec 1249Matches packets whose IPv4 header contains the comma separated list of 1250options specified in 1251.Ar spec . 1252The supported IP options are: 1253.Pp 1254.Cm ssrr 1255(strict source route), 1256.Cm lsrr 1257(loose source route), 1258.Cm rr 1259(record packet route) and 1260.Cm ts 1261(timestamp). 1262The absence of a particular option may be denoted 1263with a 1264.Ql \&! . 1265.It Cm ipprecedence Ar precedence 1266Matches IPv4 packets whose precedence field is equal to 1267.Ar precedence . 1268.It Cm ipsec 1269Matches packets that have IPSEC history associated with them 1270(i.e., the packet comes encapsulated in IPSEC, the kernel 1271has IPSEC support and IPSEC_FILTERTUNNEL option, and can correctly 1272decapsulate it). 1273.Pp 1274Note that specifying 1275.Cm ipsec 1276is different from specifying 1277.Cm proto Ar ipsec 1278as the latter will only look at the specific IP protocol field, 1279irrespective of IPSEC kernel support and the validity of the IPSEC data. 1280.Pp 1281Further note that this flag is silently ignored in kernels without 1282IPSEC support. 1283It does not affect rule processing when given and the 1284rules are handled as if with no 1285.Cm ipsec 1286flag. 1287.It Cm iptos Ar spec 1288Matches IPv4 packets whose 1289.Cm tos 1290field contains the comma separated list of 1291service types specified in 1292.Ar spec . 1293The supported IP types of service are: 1294.Pp 1295.Cm lowdelay 1296.Pq Dv IPTOS_LOWDELAY , 1297.Cm throughput 1298.Pq Dv IPTOS_THROUGHPUT , 1299.Cm reliability 1300.Pq Dv IPTOS_RELIABILITY , 1301.Cm mincost 1302.Pq Dv IPTOS_MINCOST , 1303.Cm congestion 1304.Pq Dv IPTOS_ECN_CE . 1305The absence of a particular type may be denoted 1306with a 1307.Ql \&! . 1308.It Cm ipttl Ar ttl-list 1309Matches IPv4 packets whose time to live is included in 1310.Ar ttl-list , 1311which is either a single value or a list of values or ranges 1312specified in the same way as 1313.Ar ports . 1314.It Cm ipversion Ar ver 1315Matches IP packets whose IP version field is 1316.Ar ver . 1317.It Cm keep-state 1318Upon a match, the firewall will create a dynamic rule, whose 1319default behaviour is to match bidirectional traffic between 1320source and destination IP/port using the same protocol. 1321The rule has a limited lifetime (controlled by a set of 1322.Xr sysctl 8 1323variables), and the lifetime is refreshed every time a matching 1324packet is found. 1325.It Cm layer2 1326Matches only layer2 packets, i.e., those passed to 1327.Nm 1328from ether_demux() and ether_output_frame(). 1329.It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N 1330The firewall will only allow 1331.Ar N 1332connections with the same 1333set of parameters as specified in the rule. 1334One or more 1335of source and destination addresses and ports can be 1336specified. 1337Currently, 1338only IPv4 flows are supported. 1339.It Cm { MAC | mac } Ar dst-mac src-mac 1340Match packets with a given 1341.Ar dst-mac 1342and 1343.Ar src-mac 1344addresses, specified as the 1345.Cm any 1346keyword (matching any MAC address), or six groups of hex digits 1347separated by colons, 1348and optionally followed by a mask indicating the significant bits. 1349The mask may be specified using either of the following methods: 1350.Bl -enum -width indent 1351.It 1352A slash 1353.Pq / 1354followed by the number of significant bits. 1355For example, an address with 33 significant bits could be specified as: 1356.Pp 1357.Dl "MAC 10:20:30:40:50:60/33 any" 1358.Pp 1359.It 1360An ampersand 1361.Pq & 1362followed by a bitmask specified as six groups of hex digits separated 1363by colons. 1364For example, an address in which the last 16 bits are significant could 1365be specified as: 1366.Pp 1367.Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any" 1368.Pp 1369Note that the ampersand character has a special meaning in many shells 1370and should generally be escaped. 1371.Pp 1372.El 1373Note that the order of MAC addresses (destination first, 1374source second) is 1375the same as on the wire, but the opposite of the one used for 1376IP addresses. 1377.It Cm mac-type Ar mac-type 1378Matches packets whose Ethernet Type field 1379corresponds to one of those specified as argument. 1380.Ar mac-type 1381is specified in the same way as 1382.Cm port numbers 1383(i.e., one or more comma-separated single values or ranges). 1384You can use symbolic names for known values such as 1385.Em vlan , ipv4, ipv6 . 1386Values can be entered as decimal or hexadecimal (if prefixed by 0x), 1387and they are always printed as hexadecimal (unless the 1388.Cm -N 1389option is used, in which case symbolic resolution will be attempted). 1390.It Cm proto Ar protocol 1391Matches packets with the corresponding IP protocol. 1392.It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar ipno | Ar any 1393Matches packets received, transmitted or going through, 1394respectively, the interface specified by exact name 1395.Ns No ( Ar ifX Ns No ), 1396by device name 1397.Ns No ( Ar if Ns Ar * Ns No ), 1398by IP address, or through some interface. 1399.Pp 1400The 1401.Cm via 1402keyword causes the interface to always be checked. 1403If 1404.Cm recv 1405or 1406.Cm xmit 1407is used instead of 1408.Cm via , 1409then only the receive or transmit interface (respectively) 1410is checked. 1411By specifying both, it is possible to match packets based on 1412both receive and transmit interface, e.g.: 1413.Pp 1414.Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1" 1415.Pp 1416The 1417.Cm recv 1418interface can be tested on either incoming or outgoing packets, 1419while the 1420.Cm xmit 1421interface can only be tested on outgoing packets. 1422So 1423.Cm out 1424is required (and 1425.Cm in 1426is invalid) whenever 1427.Cm xmit 1428is used. 1429.Pp 1430A packet may not have a receive or transmit interface: packets 1431originating from the local host have no receive interface, 1432while packets destined for the local host have no transmit 1433interface. 1434.It Cm setup 1435Matches TCP packets that have the SYN bit set but no ACK bit. 1436This is the short form of 1437.Dq Li tcpflags\ syn,!ack . 1438.It Cm src-ip Ar ip-address 1439Matches IPv4 packets whose source IP is one of the address(es) 1440specified as an argument. 1441.It Cm src-ip6 Ar ip6-address 1442Matches IPv6 packets whose source IP is one of the address(es) 1443specified as an argument. 1444.It Cm src-port Ar ports 1445Matches IP packets whose source port is one of the port(s) 1446specified as argument. 1447.It Cm tagged Ar tag-list 1448Matches packets whose tags are included in 1449.Ar tag-list , 1450which is either a single value or a list of values or ranges 1451specified in the same way as 1452.Ar ports . 1453Tags can be applied to the packet using 1454.Cm tag 1455rule action parameter (see it's description for details on tags). 1456.It Cm tcpack Ar ack 1457TCP packets only. 1458Match if the TCP header acknowledgment number field is set to 1459.Ar ack . 1460.It Cm tcpdatalen Ar tcpdatalen-list 1461Matches TCP packets whose length of TCP data is 1462.Ar tcpdatalen-list , 1463which is either a single value or a list of values or ranges 1464specified in the same way as 1465.Ar ports . 1466.It Cm tcpflags Ar spec 1467TCP packets only. 1468Match if the TCP header contains the comma separated list of 1469flags specified in 1470.Ar spec . 1471The supported TCP flags are: 1472.Pp 1473.Cm fin , 1474.Cm syn , 1475.Cm rst , 1476.Cm psh , 1477.Cm ack 1478and 1479.Cm urg . 1480The absence of a particular flag may be denoted 1481with a 1482.Ql \&! . 1483A rule which contains a 1484.Cm tcpflags 1485specification can never match a fragmented packet which has 1486a non-zero offset. 1487See the 1488.Cm frag 1489option for details on matching fragmented packets. 1490.It Cm tcpseq Ar seq 1491TCP packets only. 1492Match if the TCP header sequence number field is set to 1493.Ar seq . 1494.It Cm tcpwin Ar win 1495TCP packets only. 1496Match if the TCP header window field is set to 1497.Ar win . 1498.It Cm tcpoptions Ar spec 1499TCP packets only. 1500Match if the TCP header contains the comma separated list of 1501options specified in 1502.Ar spec . 1503The supported TCP options are: 1504.Pp 1505.Cm mss 1506(maximum segment size), 1507.Cm window 1508(tcp window advertisement), 1509.Cm sack 1510(selective ack), 1511.Cm ts 1512(rfc1323 timestamp) and 1513.Cm cc 1514(rfc1644 t/tcp connection count). 1515The absence of a particular option may be denoted 1516with a 1517.Ql \&! . 1518.It Cm uid Ar user 1519Match all TCP or UDP packets sent by or received for a 1520.Ar user . 1521A 1522.Ar user 1523may be matched by name or identification number. 1524.It Cm verrevpath 1525For incoming packets, 1526a routing table lookup is done on the packet's source address. 1527If the interface on which the packet entered the system matches the 1528outgoing interface for the route, 1529the packet matches. 1530If the interfaces do not match up, 1531the packet does not match. 1532All outgoing packets or packets with no incoming interface match. 1533.Pp 1534The name and functionality of the option is intentionally similar to 1535the Cisco IOS command: 1536.Pp 1537.Dl ip verify unicast reverse-path 1538.Pp 1539This option can be used to make anti-spoofing rules to reject all 1540packets with source addresses not from this interface. 1541See also the option 1542.Cm antispoof . 1543.It Cm versrcreach 1544For incoming packets, 1545a routing table lookup is done on the packet's source address. 1546If a route to the source address exists, but not the default route 1547or a blackhole/reject route, the packet matches. 1548Otherwise, the packet does not match. 1549All outgoing packets match. 1550.Pp 1551The name and functionality of the option is intentionally similar to 1552the Cisco IOS command: 1553.Pp 1554.Dl ip verify unicast source reachable-via any 1555.Pp 1556This option can be used to make anti-spoofing rules to reject all 1557packets whose source address is unreachable. 1558.It Cm antispoof 1559For incoming packets, the packet's source address is checked if it 1560belongs to a directly connected network. 1561If the network is directly connected, then the interface the packet 1562came on in is compared to the interface the network is connected to. 1563When incoming interface and directly connected interface are not the 1564same, the packet does not match. 1565Otherwise, the packet does match. 1566All outgoing packets match. 1567.Pp 1568This option can be used to make anti-spoofing rules to reject all 1569packets that pretend to be from a directly connected network but do 1570not come in through that interface. 1571This option is similar to but more restricted than 1572.Cm verrevpath 1573because it engages only on packets with source addresses of directly 1574connected networks instead of all source addresses. 1575.El 1576.Sh LOOKUP TABLES 1577Lookup tables are useful to handle large sparse address sets, 1578typically from a hundred to several thousands of entries. 1579There may be up to 128 different lookup tables, numbered 0 to 127. 1580.Pp 1581Each entry is represented by an 1582.Ar addr Ns Op / Ns Ar masklen 1583and will match all addresses with base 1584.Ar addr 1585(specified as an IP address or a hostname) 1586and mask width of 1587.Ar masklen 1588bits. 1589If 1590.Ar masklen 1591is not specified, it defaults to 32. 1592When looking up an IP address in a table, the most specific 1593entry will match. 1594Associated with each entry is a 32-bit unsigned 1595.Ar value , 1596which can optionally be checked by a rule matching code. 1597When adding an entry, if 1598.Ar value 1599is not specified, it defaults to 0. 1600.Pp 1601An entry can be added to a table 1602.Pq Cm add , 1603removed from a table 1604.Pq Cm delete , 1605a table can be examined 1606.Pq Cm list 1607or flushed 1608.Pq Cm flush . 1609.Pp 1610Internally, each table is stored in a Radix tree, the same way as 1611the routing table (see 1612.Xr route 4 ) . 1613.Pp 1614Lookup tables currently support IPv4 addresses only. 1615.Pp 1616The 1617.Cm tablearg 1618feature provides the ability to use a value, looked up in the table, as 1619the argument for a rule action, action parameter or rule option. 1620This can significantly reduce number of rules in some configurations. 1621The 1622.Cm tablearg 1623argument can be used with the following actions: 1624.Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd 1625action parameters: 1626.Cm tag, untag, 1627rule options: 1628.Cm limit, tagged. 1629.Pp 1630When used with 1631.Cm fwd 1632it is possible to supply table entries with values 1633that are in the form of IP addresses or hostnames. 1634See the 1635.Sx EXAMPLES 1636Section for example usage of tables and the tablearg keyword. 1637.Sh SETS OF RULES 1638Each rule belongs to one of 32 different 1639.Em sets 1640, numbered 0 to 31. 1641Set 31 is reserved for the default rule. 1642.Pp 1643By default, rules are put in set 0, unless you use the 1644.Cm set N 1645attribute when entering a new rule. 1646Sets can be individually and atomically enabled or disabled, 1647so this mechanism permits an easy way to store multiple configurations 1648of the firewall and quickly (and atomically) switch between them. 1649The command to enable/disable sets is 1650.Bd -ragged -offset indent 1651.Nm 1652.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 1653.Ed 1654.Pp 1655where multiple 1656.Cm enable 1657or 1658.Cm disable 1659sections can be specified. 1660Command execution is atomic on all the sets specified in the command. 1661By default, all sets are enabled. 1662.Pp 1663When you disable a set, its rules behave as if they do not exist 1664in the firewall configuration, with only one exception: 1665.Bd -ragged -offset indent 1666dynamic rules created from a rule before it had been disabled 1667will still be active until they expire. 1668In order to delete 1669dynamic rules you have to explicitly delete the parent rule 1670which generated them. 1671.Ed 1672.Pp 1673The set number of rules can be changed with the command 1674.Bd -ragged -offset indent 1675.Nm 1676.Cm set move 1677.Brq Cm rule Ar rule-number | old-set 1678.Cm to Ar new-set 1679.Ed 1680.Pp 1681Also, you can atomically swap two rulesets with the command 1682.Bd -ragged -offset indent 1683.Nm 1684.Cm set swap Ar first-set second-set 1685.Ed 1686.Pp 1687See the 1688.Sx EXAMPLES 1689Section on some possible uses of sets of rules. 1690.Sh STATEFUL FIREWALL 1691Stateful operation is a way for the firewall to dynamically 1692create rules for specific flows when packets that 1693match a given pattern are detected. 1694Support for stateful 1695operation comes through the 1696.Cm check-state , keep-state 1697and 1698.Cm limit 1699options of 1700.Nm rules . 1701.Pp 1702Dynamic rules are created when a packet matches a 1703.Cm keep-state 1704or 1705.Cm limit 1706rule, causing the creation of a 1707.Em dynamic 1708rule which will match all and only packets with 1709a given 1710.Em protocol 1711between a 1712.Em src-ip/src-port dst-ip/dst-port 1713pair of addresses 1714.Em ( src 1715and 1716.Em dst 1717are used here only to denote the initial match addresses, but they 1718are completely equivalent afterwards). 1719Dynamic rules will be checked at the first 1720.Cm check-state, keep-state 1721or 1722.Cm limit 1723occurrence, and the action performed upon a match will be the same 1724as in the parent rule. 1725.Pp 1726Note that no additional attributes other than protocol and IP addresses 1727and ports are checked on dynamic rules. 1728.Pp 1729The typical use of dynamic rules is to keep a closed firewall configuration, 1730but let the first TCP SYN packet from the inside network install a 1731dynamic rule for the flow so that packets belonging to that session 1732will be allowed through the firewall: 1733.Pp 1734.Dl "ipfw add check-state" 1735.Dl "ipfw add allow tcp from my-subnet to any setup keep-state" 1736.Dl "ipfw add deny tcp from any to any" 1737.Pp 1738A similar approach can be used for UDP, where an UDP packet coming 1739from the inside will install a dynamic rule to let the response through 1740the firewall: 1741.Pp 1742.Dl "ipfw add check-state" 1743.Dl "ipfw add allow udp from my-subnet to any keep-state" 1744.Dl "ipfw add deny udp from any to any" 1745.Pp 1746Dynamic rules expire after some time, which depends on the status 1747of the flow and the setting of some 1748.Cm sysctl 1749variables. 1750See Section 1751.Sx SYSCTL VARIABLES 1752for more details. 1753For TCP sessions, dynamic rules can be instructed to periodically 1754send keepalive packets to refresh the state of the rule when it is 1755about to expire. 1756.Pp 1757See Section 1758.Sx EXAMPLES 1759for more examples on how to use dynamic rules. 1760.Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 1761.Nm 1762is also the user interface for the 1763.Nm dummynet 1764traffic shaper. 1765.Pp 1766.Nm dummynet 1767operates by first using the firewall to classify packets and divide them into 1768.Em flows , 1769using any match pattern that can be used in 1770.Nm 1771rules. 1772Depending on local policies, a flow can contain packets for a single 1773TCP connection, or from/to a given host, or entire subnet, or a 1774protocol type, etc. 1775.Pp 1776There are two modes of 1777.Nm dummynet 1778operation: 1779.Dq normal 1780and 1781.Dq fast . 1782The 1783.Dq normal 1784mode tries to emulate a real link: the 1785.Nm dummynet 1786scheduler ensures that the packet will not leave the pipe faster than it 1787would on the real link with a given bandwidth. 1788The 1789.Dq fast 1790mode allows certain packets to bypass the 1791.Nm dummynet 1792scheduler (if packet flow does not exceed pipe's bandwidth). 1793This is the reason why the 1794.Dq fast 1795mode requires less CPU cycles per packet (on average) and packet latency 1796can be significantly lower in comparison to a real link with the same 1797bandwidth. 1798The default mode is 1799.Dq normal . 1800The 1801.Dq fast 1802mode can be enabled by setting the 1803.Va net.inet.ip.dummynet.io_fast 1804.Xr sysctl 8 1805variable to a non-zero value. 1806.Pp 1807Packets belonging to the same flow are then passed to either of two 1808different objects, which implement the traffic regulation: 1809.Bl -hang -offset XXXX 1810.It Em pipe 1811A pipe emulates a link with given bandwidth, propagation delay, 1812queue size and packet loss rate. 1813Packets are queued in front of the pipe as they come out from the classifier, 1814and then transferred to the pipe according to the pipe's parameters. 1815.Pp 1816.It Em queue 1817A queue 1818is an abstraction used to implement the WF2Q+ 1819(Worst-case Fair Weighted Fair Queueing) policy, which is 1820an efficient variant of the WFQ policy. 1821.br 1822The queue associates a 1823.Em weight 1824and a reference pipe to each flow, and then all backlogged (i.e., 1825with packets queued) flows linked to the same pipe share the pipe's 1826bandwidth proportionally to their weights. 1827Note that weights are not priorities; a flow with a lower weight 1828is still guaranteed to get its fraction of the bandwidth even if a 1829flow with a higher weight is permanently backlogged. 1830.Pp 1831.El 1832In practice, 1833.Em pipes 1834can be used to set hard limits to the bandwidth that a flow can use, whereas 1835.Em queues 1836can be used to determine how different flow share the available bandwidth. 1837.Pp 1838The 1839.Em pipe 1840and 1841.Em queue 1842configuration commands are the following: 1843.Bd -ragged -offset indent 1844.Cm pipe Ar number Cm config Ar pipe-configuration 1845.Pp 1846.Cm queue Ar number Cm config Ar queue-configuration 1847.Ed 1848.Pp 1849The following parameters can be configured for a pipe: 1850.Pp 1851.Bl -tag -width indent -compact 1852.It Cm bw Ar bandwidth | device 1853Bandwidth, measured in 1854.Sm off 1855.Op Cm K | M 1856.Brq Cm bit/s | Byte/s . 1857.Sm on 1858.Pp 1859A value of 0 (default) means unlimited bandwidth. 1860The unit must immediately follow the number, as in 1861.Pp 1862.Dl "ipfw pipe 1 config bw 300Kbit/s" 1863.Pp 1864If a device name is specified instead of a numeric value, as in 1865.Pp 1866.Dl "ipfw pipe 1 config bw tun0" 1867.Pp 1868then the transmit clock is supplied by the specified device. 1869At the moment only the 1870.Xr tun 4 1871device supports this 1872functionality, for use in conjunction with 1873.Xr ppp 8 . 1874.Pp 1875.It Cm delay Ar ms-delay 1876Propagation delay, measured in milliseconds. 1877The value is rounded to the next multiple of the clock tick 1878(typically 10ms, but it is a good practice to run kernels 1879with 1880.Dq "options HZ=1000" 1881to reduce 1882the granularity to 1ms or less). 1883Default value is 0, meaning no delay. 1884.El 1885.Pp 1886The following parameters can be configured for a queue: 1887.Pp 1888.Bl -tag -width indent -compact 1889.It Cm pipe Ar pipe_nr 1890Connects a queue to the specified pipe. 1891Multiple queues (with the same or different weights) can be connected to 1892the same pipe, which specifies the aggregate rate for the set of queues. 1893.Pp 1894.It Cm weight Ar weight 1895Specifies the weight to be used for flows matching this queue. 1896The weight must be in the range 1..100, and defaults to 1. 1897.El 1898.Pp 1899Finally, the following parameters can be configured for both 1900pipes and queues: 1901.Pp 1902.Bl -tag -width XXXX -compact 1903.Pp 1904.It Cm buckets Ar hash-table-size 1905Specifies the size of the hash table used for storing the 1906various queues. 1907Default value is 64 controlled by the 1908.Xr sysctl 8 1909variable 1910.Va net.inet.ip.dummynet.hash_size , 1911allowed range is 16 to 65536. 1912.Pp 1913.It Cm mask Ar mask-specifier 1914Packets sent to a given pipe or queue by an 1915.Nm 1916rule can be further classified into multiple flows, each of which is then 1917sent to a different 1918.Em dynamic 1919pipe or queue. 1920A flow identifier is constructed by masking the IP addresses, 1921ports and protocol types as specified with the 1922.Cm mask 1923options in the configuration of the pipe or queue. 1924For each different flow identifier, a new pipe or queue is created 1925with the same parameters as the original object, and matching packets 1926are sent to it. 1927.Pp 1928Thus, when 1929.Em dynamic pipes 1930are used, each flow will get the same bandwidth as defined by the pipe, 1931whereas when 1932.Em dynamic queues 1933are used, each flow will share the parent's pipe bandwidth evenly 1934with other flows generated by the same queue (note that other queues 1935with different weights might be connected to the same pipe). 1936.br 1937Available mask specifiers are a combination of one or more of the following: 1938.Pp 1939.Cm dst-ip Ar mask , 1940.Cm dst-ip6 Ar mask , 1941.Cm src-ip Ar mask , 1942.Cm src-ip6 Ar mask , 1943.Cm dst-port Ar mask , 1944.Cm src-port Ar mask , 1945.Cm flow-id Ar mask , 1946.Cm proto Ar mask 1947or 1948.Cm all , 1949.Pp 1950where the latter means all bits in all fields are significant. 1951.Pp 1952.It Cm noerror 1953When a packet is dropped by a 1954.Nm dummynet 1955queue or pipe, the error 1956is normally reported to the caller routine in the kernel, in the 1957same way as it happens when a device queue fills up. 1958Setting this 1959option reports the packet as successfully delivered, which can be 1960needed for some experimental setups where you want to simulate 1961loss or congestion at a remote router. 1962.Pp 1963.It Cm plr Ar packet-loss-rate 1964Packet loss rate. 1965Argument 1966.Ar packet-loss-rate 1967is a floating-point number between 0 and 1, with 0 meaning no 1968loss, 1 meaning 100% loss. 1969The loss rate is internally represented on 31 bits. 1970.Pp 1971.It Cm queue Brq Ar slots | size Ns Cm Kbytes 1972Queue size, in 1973.Ar slots 1974or 1975.Cm KBytes . 1976Default value is 50 slots, which 1977is the typical queue size for Ethernet devices. 1978Note that for slow speed links you should keep the queue 1979size short or your traffic might be affected by a significant 1980queueing delay. 1981E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit 1982or 20s of queue on a 30Kbit/s pipe. 1983Even worse effects can result if you get packets from an 1984interface with a much larger MTU, e.g.\& the loopback interface 1985with its 16KB packets. 1986The 1987.Xr sysctl 8 1988variables 1989.Em net.inet.ip.dummynet.pipe_byte_limit 1990and 1991.Em net.inet.ip.dummynet.pipe_slot_limit 1992control the maximum lengths that can be specified. 1993.Pp 1994.It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p 1995Make use of the RED (Random Early Detection) queue management algorithm. 1996.Ar w_q 1997and 1998.Ar max_p 1999are floating 2000point numbers between 0 and 1 (0 not included), while 2001.Ar min_th 2002and 2003.Ar max_th 2004are integer numbers specifying thresholds for queue management 2005(thresholds are computed in bytes if the queue has been defined 2006in bytes, in slots otherwise). 2007The 2008.Nm dummynet 2009also supports the gentle RED variant (gred). 2010Three 2011.Xr sysctl 8 2012variables can be used to control the RED behaviour: 2013.Bl -tag -width indent 2014.It Va net.inet.ip.dummynet.red_lookup_depth 2015specifies the accuracy in computing the average queue 2016when the link is idle (defaults to 256, must be greater than zero) 2017.It Va net.inet.ip.dummynet.red_avg_pkt_size 2018specifies the expected average packet size (defaults to 512, must be 2019greater than zero) 2020.It Va net.inet.ip.dummynet.red_max_pkt_size 2021specifies the expected maximum packet size, only used when queue 2022thresholds are in bytes (defaults to 1500, must be greater than zero). 2023.El 2024.El 2025.Pp 2026When used with IPv6 data, 2027.Nm dummynet 2028currently has several limitations. 2029Information necessary to route link-local packets to an 2030interface is not available after processing by 2031.Nm dummynet 2032so those packets are dropped in the output path. 2033Care should be taken to insure that link-local packets are not passed to 2034.Nm dummynet . 2035.Sh CHECKLIST 2036Here are some important points to consider when designing your 2037rules: 2038.Bl -bullet 2039.It 2040Remember that you filter both packets going 2041.Cm in 2042and 2043.Cm out . 2044Most connections need packets going in both directions. 2045.It 2046Remember to test very carefully. 2047It is a good idea to be near the console when doing this. 2048If you cannot be near the console, 2049use an auto-recovery script such as the one in 2050.Pa /usr/share/examples/ipfw/change_rules.sh . 2051.It 2052Do not forget the loopback interface. 2053.El 2054.Sh FINE POINTS 2055.Bl -bullet 2056.It 2057There are circumstances where fragmented datagrams are unconditionally 2058dropped. 2059TCP packets are dropped if they do not contain at least 20 bytes of 2060TCP header, UDP packets are dropped if they do not contain a full 8 2061byte UDP header, and ICMP packets are dropped if they do not contain 20624 bytes of ICMP header, enough to specify the ICMP type, code, and 2063checksum. 2064These packets are simply logged as 2065.Dq pullup failed 2066since there may not be enough good data in the packet to produce a 2067meaningful log entry. 2068.It 2069Another type of packet is unconditionally dropped, a TCP packet with a 2070fragment offset of one. 2071This is a valid packet, but it only has one use, to try 2072to circumvent firewalls. 2073When logging is enabled, these packets are 2074reported as being dropped by rule -1. 2075.It 2076If you are logged in over a network, loading the 2077.Xr kld 4 2078version of 2079.Nm 2080is probably not as straightforward as you would think. 2081I recommend the following command line: 2082.Bd -literal -offset indent 2083kldload ipfw && \e 2084ipfw add 32000 allow ip from any to any 2085.Ed 2086.Pp 2087Along the same lines, doing an 2088.Bd -literal -offset indent 2089ipfw flush 2090.Ed 2091.Pp 2092in similar surroundings is also a bad idea. 2093.It 2094The 2095.Nm 2096filter list may not be modified if the system security level 2097is set to 3 or higher 2098(see 2099.Xr init 8 2100for information on system security levels). 2101.El 2102.Sh PACKET DIVERSION 2103A 2104.Xr divert 4 2105socket bound to the specified port will receive all packets 2106diverted to that port. 2107If no socket is bound to the destination port, or if the divert module is 2108not loaded, or if the kernel was not compiled with divert socket support, 2109the packets are dropped. 2110.Sh NETWORK ADDRESS TRANSLATION (NAT) 2111The nat configuration command is the following: 2112.Bd -ragged -offset indent 2113.Bk -words 2114.Cm nat 2115.Ar nat_number 2116.Cm config 2117.Ar nat-configuration 2118.Ek 2119.Ed 2120.Pp 2121. 2122The following parameters can be configured: 2123.Bl -tag -width indent 2124.It Cm ip Ar ip_address 2125Define an ip address to use for aliasing. 2126.It Cm if Ar nic 2127Use ip addres of NIC for aliasing, dynamically changing 2128it if NIC's ip address change. 2129.It Cm log 2130Enable logging on this nat instance. 2131.It Cm deny_in 2132Deny any incoming connection from outside world. 2133.It Cm same_ports 2134Try to leave the alias port numbers unchanged from 2135the actual local port numbers. 2136.It Cm unreg_only 2137Traffic on the local network not originating from an 2138unregistered address spaces will be ignored. 2139.It Cm reset 2140Reset table of the packet aliasing engine on address change. 2141.It Cm reverse 2142Reverse the way libalias handles aliasing. 2143.It Cm proxy_only 2144Obey transparent proxy rules only, packet aliasing is not performed. 2145.El 2146.Pp 2147To let the packet continue after being (de)aliased, set the sysctl variable 2148.Va net.inet.ip.fw.one_pass 2149to 0. 2150For more information about aliasing modes, refer to 2151.Xr libalias 3 2152. 2153See Section 2154.Sx EXAMPLES 2155for some examples about nat usage. 2156.Sh REDIRECT AND LSNAT SUPPORT IN IPFW 2157Redirect and LSNAT support follow closely the syntax used in 2158.Xr natd 8 2159. 2160See Section 2161.Sx EXAMPLES 2162for some examples on how to do redirect and lsnat. 2163.Sh SYSCTL VARIABLES 2164A set of 2165.Xr sysctl 8 2166variables controls the behaviour of the firewall and 2167associated modules 2168.Pq Nm dummynet , bridge . 2169These are shown below together with their default value 2170(but always check with the 2171.Xr sysctl 8 2172command what value is actually in use) and meaning: 2173.Bl -tag -width indent 2174.It Va net.inet.ip.dummynet.expire : No 1 2175Lazily delete dynamic pipes/queue once they have no pending traffic. 2176You can disable this by setting the variable to 0, in which case 2177the pipes/queues will only be deleted when the threshold is reached. 2178.It Va net.inet.ip.dummynet.hash_size : No 64 2179Default size of the hash table used for dynamic pipes/queues. 2180This value is used when no 2181.Cm buckets 2182option is specified when configuring a pipe/queue. 2183.It Va net.inet.ip.dummynet.io_fast : No 0 2184If set to a non-zero value, 2185the 2186.Dq fast 2187mode of 2188.Nm dummynet 2189operation (see above) is enabled. 2190.It Va net.inet.ip.dummynet.io_pkt 2191Number of packets passed to 2192.Nm dummynet . 2193.It Va net.inet.ip.dummynet.io_pkt_drop 2194Number of packets dropped by 2195.Nm dummynet . 2196.It Va net.inet.ip.dummynet.io_pkt_fast 2197Number of packets bypassed by the 2198.Nm dummynet 2199scheduler. 2200.It Va net.inet.ip.dummynet.max_chain_len : No 16 2201Target value for the maximum number of pipes/queues in a hash bucket. 2202The product 2203.Cm max_chain_len*hash_size 2204is used to determine the threshold over which empty pipes/queues 2205will be expired even when 2206.Cm net.inet.ip.dummynet.expire=0 . 2207.It Va net.inet.ip.dummynet.red_lookup_depth : No 256 2208.It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512 2209.It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500 2210Parameters used in the computations of the drop probability 2211for the RED algorithm. 2212.It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576 2213.It Va net.inet.ip.dummynet.pipe_slot_limit : No 100 2214The maximum queue size that can be specified in bytes or packets. 2215These limits prevent accidental exhaustion of resources such as mbufs. 2216If you raise these limits, 2217you should make sure the system is configured so that sufficient resources 2218are available. 2219.It Va net.inet.ip.fw.autoinc_step : No 100 2220Delta between rule numbers when auto-generating them. 2221The value must be in the range 1..1000. 2222.It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets 2223The current number of buckets in the hash table for dynamic rules 2224(readonly). 2225.It Va net.inet.ip.fw.debug : No 1 2226Controls debugging messages produced by 2227.Nm . 2228.It Va net.inet.ip.fw.dyn_buckets : No 256 2229The number of buckets in the hash table for dynamic rules. 2230Must be a power of 2, up to 65536. 2231It only takes effect when all dynamic rules have expired, so you 2232are advised to use a 2233.Cm flush 2234command to make sure that the hash table is resized. 2235.It Va net.inet.ip.fw.dyn_count : No 3 2236Current number of dynamic rules 2237(read-only). 2238.It Va net.inet.ip.fw.dyn_keepalive : No 1 2239Enables generation of keepalive packets for 2240.Cm keep-state 2241rules on TCP sessions. 2242A keepalive is generated to both 2243sides of the connection every 5 seconds for the last 20 2244seconds of the lifetime of the rule. 2245.It Va net.inet.ip.fw.dyn_max : No 8192 2246Maximum number of dynamic rules. 2247When you hit this limit, no more dynamic rules can be 2248installed until old ones expire. 2249.It Va net.inet.ip.fw.dyn_ack_lifetime : No 300 2250.It Va net.inet.ip.fw.dyn_syn_lifetime : No 20 2251.It Va net.inet.ip.fw.dyn_fin_lifetime : No 1 2252.It Va net.inet.ip.fw.dyn_rst_lifetime : No 1 2253.It Va net.inet.ip.fw.dyn_udp_lifetime : No 5 2254.It Va net.inet.ip.fw.dyn_short_lifetime : No 30 2255These variables control the lifetime, in seconds, of dynamic 2256rules. 2257Upon the initial SYN exchange the lifetime is kept short, 2258then increased after both SYN have been seen, then decreased 2259again during the final FIN exchange or when a RST is received. 2260Both 2261.Em dyn_fin_lifetime 2262and 2263.Em dyn_rst_lifetime 2264must be strictly lower than 5 seconds, the period of 2265repetition of keepalives. 2266The firewall enforces that. 2267.It Va net.inet.ip.fw.enable : No 1 2268Enables the firewall. 2269Setting this variable to 0 lets you run your machine without 2270firewall even if compiled in. 2271.It Va net.inet6.ip6.fw.enable : No 1 2272provides the same functionality as above for the IPv6 case. 2273.It Va net.inet.ip.fw.one_pass : No 1 2274When set, the packet exiting from the 2275.Nm dummynet 2276pipe or from 2277.Xr ng_ipfw 4 2278node is not passed though the firewall again. 2279Otherwise, after an action, the packet is 2280reinjected into the firewall at the next rule. 2281.It Va net.inet.ip.fw.verbose : No 1 2282Enables verbose messages. 2283.It Va net.inet.ip.fw.verbose_limit : No 0 2284Limits the number of messages produced by a verbose firewall. 2285.It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1 2286If enabled packets with unknown IPv6 Extension Headers will be denied. 2287.It Va net.link.ether.ipfw : No 0 2288Controls whether layer-2 packets are passed to 2289.Nm . 2290Default is no. 2291.It Va net.link.bridge.ipfw : No 0 2292Controls whether bridged packets are passed to 2293.Nm . 2294Default is no. 2295.El 2296.Pp 2297.Sh EXAMPLES 2298There are far too many possible uses of 2299.Nm 2300so this Section will only give a small set of examples. 2301.Pp 2302.Ss BASIC PACKET FILTERING 2303This command adds an entry which denies all tcp packets from 2304.Em cracker.evil.org 2305to the telnet port of 2306.Em wolf.tambov.su 2307from being forwarded by the host: 2308.Pp 2309.Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet" 2310.Pp 2311This one disallows any connection from the entire cracker's 2312network to my host: 2313.Pp 2314.Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org" 2315.Pp 2316A first and efficient way to limit access (not using dynamic rules) 2317is the use of the following rules: 2318.Pp 2319.Dl "ipfw add allow tcp from any to any established" 2320.Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup" 2321.Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup" 2322.Dl "..." 2323.Dl "ipfw add deny tcp from any to any" 2324.Pp 2325The first rule will be a quick match for normal TCP packets, 2326but it will not match the initial SYN packet, which will be 2327matched by the 2328.Cm setup 2329rules only for selected source/destination pairs. 2330All other SYN packets will be rejected by the final 2331.Cm deny 2332rule. 2333.Pp 2334If you administer one or more subnets, you can take advantage 2335of the address sets and or-blocks and write extremely 2336compact rulesets which selectively enable services to blocks 2337of clients, as below: 2338.Pp 2339.Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q" 2340.Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q" 2341.Dl "" 2342.Dl "ipfw add allow ip from ${goodguys} to any" 2343.Dl "ipfw add deny ip from ${badguys} to any" 2344.Dl "... normal policies ..." 2345.Pp 2346The 2347.Cm verrevpath 2348option could be used to do automated anti-spoofing by adding the 2349following to the top of a ruleset: 2350.Pp 2351.Dl "ipfw add deny ip from any to any not verrevpath in" 2352.Pp 2353This rule drops all incoming packets that appear to be coming to the 2354system on the wrong interface. 2355For example, a packet with a source 2356address belonging to a host on a protected internal network would be 2357dropped if it tried to enter the system from an external interface. 2358.Pp 2359The 2360.Cm antispoof 2361option could be used to do similar but more restricted anti-spoofing 2362by adding the following to the top of a ruleset: 2363.Pp 2364.Dl "ipfw add deny ip from any to any not antispoof in" 2365.Pp 2366This rule drops all incoming packets that appear to be coming from another 2367directly connected system but on the wrong interface. 2368For example, a packet with a source address of 2369.Li 192.168.0.0/24 2370, configured on 2371.Li fxp0 2372, but coming in on 2373.Li fxp1 2374would be dropped. 2375.Ss DYNAMIC RULES 2376In order to protect a site from flood attacks involving fake 2377TCP packets, it is safer to use dynamic rules: 2378.Pp 2379.Dl "ipfw add check-state" 2380.Dl "ipfw add deny tcp from any to any established" 2381.Dl "ipfw add allow tcp from my-net to any setup keep-state" 2382.Pp 2383This will let the firewall install dynamic rules only for 2384those connection which start with a regular SYN packet coming 2385from the inside of our network. 2386Dynamic rules are checked when encountering the first 2387.Cm check-state 2388or 2389.Cm keep-state 2390rule. 2391A 2392.Cm check-state 2393rule should usually be placed near the beginning of the 2394ruleset to minimize the amount of work scanning the ruleset. 2395Your mileage may vary. 2396.Pp 2397To limit the number of connections a user can open 2398you can use the following type of rules: 2399.Pp 2400.Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10" 2401.Dl "ipfw add allow tcp from any to me setup limit src-addr 4" 2402.Pp 2403The former (assuming it runs on a gateway) will allow each host 2404on a /24 network to open at most 10 TCP connections. 2405The latter can be placed on a server to make sure that a single 2406client does not use more than 4 simultaneous connections. 2407.Pp 2408.Em BEWARE : 2409stateful rules can be subject to denial-of-service attacks 2410by a SYN-flood which opens a huge number of dynamic rules. 2411The effects of such attacks can be partially limited by 2412acting on a set of 2413.Xr sysctl 8 2414variables which control the operation of the firewall. 2415.Pp 2416Here is a good usage of the 2417.Cm list 2418command to see accounting records and timestamp information: 2419.Pp 2420.Dl ipfw -at list 2421.Pp 2422or in short form without timestamps: 2423.Pp 2424.Dl ipfw -a list 2425.Pp 2426which is equivalent to: 2427.Pp 2428.Dl ipfw show 2429.Pp 2430Next rule diverts all incoming packets from 192.168.2.0/24 2431to divert port 5000: 2432.Pp 2433.Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in 2434.Pp 2435.Ss TRAFFIC SHAPING 2436The following rules show some of the applications of 2437.Nm 2438and 2439.Nm dummynet 2440for simulations and the like. 2441.Pp 2442This rule drops random incoming packets with a probability 2443of 5%: 2444.Pp 2445.Dl "ipfw add prob 0.05 deny ip from any to any in" 2446.Pp 2447A similar effect can be achieved making use of 2448.Nm dummynet 2449pipes: 2450.Pp 2451.Dl "ipfw add pipe 10 ip from any to any" 2452.Dl "ipfw pipe 10 config plr 0.05" 2453.Pp 2454We can use pipes to artificially limit bandwidth, e.g.\& on a 2455machine acting as a router, if we want to limit traffic from 2456local clients on 192.168.2.0/24 we do: 2457.Pp 2458.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 2459.Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes" 2460.Pp 2461note that we use the 2462.Cm out 2463modifier so that the rule is not used twice. 2464Remember in fact that 2465.Nm 2466rules are checked both on incoming and outgoing packets. 2467.Pp 2468Should we want to simulate a bidirectional link with bandwidth 2469limitations, the correct way is the following: 2470.Pp 2471.Dl "ipfw add pipe 1 ip from any to any out" 2472.Dl "ipfw add pipe 2 ip from any to any in" 2473.Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes" 2474.Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes" 2475.Pp 2476The above can be very useful, e.g.\& if you want to see how 2477your fancy Web page will look for a residential user who 2478is connected only through a slow link. 2479You should not use only one pipe for both directions, unless 2480you want to simulate a half-duplex medium (e.g.\& AppleTalk, 2481Ethernet, IRDA). 2482It is not necessary that both pipes have the same configuration, 2483so we can also simulate asymmetric links. 2484.Pp 2485Should we want to verify network performance with the RED queue 2486management algorithm: 2487.Pp 2488.Dl "ipfw add pipe 1 ip from any to any" 2489.Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1" 2490.Pp 2491Another typical application of the traffic shaper is to 2492introduce some delay in the communication. 2493This can significantly affect applications which do a lot of Remote 2494Procedure Calls, and where the round-trip-time of the 2495connection often becomes a limiting factor much more than 2496bandwidth: 2497.Pp 2498.Dl "ipfw add pipe 1 ip from any to any out" 2499.Dl "ipfw add pipe 2 ip from any to any in" 2500.Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s" 2501.Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s" 2502.Pp 2503Per-flow queueing can be useful for a variety of purposes. 2504A very simple one is counting traffic: 2505.Pp 2506.Dl "ipfw add pipe 1 tcp from any to any" 2507.Dl "ipfw add pipe 1 udp from any to any" 2508.Dl "ipfw add pipe 1 ip from any to any" 2509.Dl "ipfw pipe 1 config mask all" 2510.Pp 2511The above set of rules will create queues (and collect 2512statistics) for all traffic. 2513Because the pipes have no limitations, the only effect is 2514collecting statistics. 2515Note that we need 3 rules, not just the last one, because 2516when 2517.Nm 2518tries to match IP packets it will not consider ports, so we 2519would not see connections on separate ports as different 2520ones. 2521.Pp 2522A more sophisticated example is limiting the outbound traffic 2523on a net with per-host limits, rather than per-network limits: 2524.Pp 2525.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 2526.Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in" 2527.Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 2528.Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 2529.Ss LOOKUP TABLES 2530In the following example, we need to create several traffic bandwidth 2531classes and we need different hosts/networks to fall into different classes. 2532We create one pipe for each class and configure them accordingly. 2533Then we create a single table and fill it with IP subnets and addresses. 2534For each subnet/host we set the argument equal to the number of the pipe 2535that it should use. 2536Then we classify traffic using a single rule: 2537.Pp 2538.Dl "ipfw pipe 1 config bw 1000Kbyte/s" 2539.Dl "ipfw pipe 4 config bw 4000Kbyte/s" 2540.Dl "..." 2541.Dl "ipfw table 1 add 192.168.2.0/24 1" 2542.Dl "ipfw table 1 add 192.168.0.0/27 4" 2543.Dl "ipfw table 1 add 192.168.0.2 1" 2544.Dl "..." 2545.Dl "ipfw add pipe tablearg ip from table(1) to any" 2546.Pp 2547Using the 2548.Cm fwd 2549action, the table entries may include hostnames and IP addresses. 2550.Pp 2551.Dl "ipfw table 1 add 192.168.2.0/24 10.23.2.1" 2552.Dl "ipfw table 1 add 192.168.0.0/27 router1.dmz" 2553.Dl "..." 2554.Dl "ipfw add 100 fwd tablearg ip from any to table(1)" 2555.Ss SETS OF RULES 2556To add a set of rules atomically, e.g.\& set 18: 2557.Pp 2558.Dl "ipfw set disable 18" 2559.Dl "ipfw add NN set 18 ... # repeat as needed" 2560.Dl "ipfw set enable 18" 2561.Pp 2562To delete a set of rules atomically the command is simply: 2563.Pp 2564.Dl "ipfw delete set 18" 2565.Pp 2566To test a ruleset and disable it and regain control if something goes wrong: 2567.Pp 2568.Dl "ipfw set disable 18" 2569.Dl "ipfw add NN set 18 ... # repeat as needed" 2570.Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18" 2571.Pp 2572Here if everything goes well, you press control-C before the "sleep" 2573terminates, and your ruleset will be left active. 2574Otherwise, e.g.\& if 2575you cannot access your box, the ruleset will be disabled after 2576the sleep terminates thus restoring the previous situation. 2577.Pp 2578To show rules of the specific set: 2579.Pp 2580.Dl "ipfw set 18 show" 2581.Pp 2582To show rules of the disabled set: 2583.Pp 2584.Dl "ipfw -S set 18 show" 2585.Pp 2586To clear a specific rule counters of the specific set: 2587.Pp 2588.Dl "ipfw set 18 zero NN" 2589.Pp 2590To delete a specific rule of the specific set: 2591.Pp 2592.Dl "ipfw set 18 delete NN" 2593.Ss NAT, REDIRECT AND LSNAT 2594First redirect all the traffic to nat instance 123: 2595.Pp 2596.Dl "ipfw add nat 123 all from any to any" 2597.Pp 2598Then to configure nat instance 123 to alias all the outgoing traffic with ip 2599192.168.0.123, blocking all incoming connections, trying to keep 2600same ports on both sides, clearing aliasing table on address change 2601and keeping a log of traffic/link statistics: 2602.Pp 2603.Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports" 2604.Pp 2605Or to change address of instance 123, aliasing table will be cleared (see 2606reset option): 2607.Pp 2608.Dl "ipfw nat 123 config ip 10.0.0.1" 2609.Pp 2610To see configuration of nat instance 123: 2611.Pp 2612.Dl "ipfw nat 123 show config" 2613.Pp 2614To show logs of all the instances in range 111-999: 2615.Pp 2616.Dl "ipfw nat 111-999 show" 2617.Pp 2618To see configurations of all instances: 2619.Pp 2620.Dl "ipfw nat show config" 2621.Pp 2622Or a redirect rule with mixed modes could looks like: 2623.Pp 2624.Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66" 2625.Dl " redirect_port tcp 192.168.0.1:80 500" 2626.Dl " redirect_proto udp 192.168.1.43 192.168.1.1" 2627.Dl " redirect_addr 192.168.0.10,192.168.0.11" 2628.Dl " 10.0.0.100 # LSNAT" 2629.Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22" 2630.Dl " 500 # LSNAT" 2631.Pp 2632or it could be splitted in: 2633.Pp 2634.Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66" 2635.Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500" 2636.Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1" 2637.Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12" 2638.Dl " 10.0.0.100" 2639.Dl "ipfw nat 5 config redirect_port tcp" 2640.Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500" 2641.Pp 2642.Sh SEE ALSO 2643.Xr cpp 1 , 2644.Xr m4 1 , 2645.Xr altq 4 , 2646.Xr divert 4 , 2647.Xr dummynet 4 , 2648.Xr if_bridge 4 , 2649.Xr ip 4 , 2650.Xr ipfirewall 4 , 2651.Xr ng_ipfw 4 , 2652.Xr protocols 5 , 2653.Xr services 5 , 2654.Xr init 8 , 2655.Xr kldload 8 , 2656.Xr reboot 8 , 2657.Xr sysctl 8 , 2658.Xr syslogd 8 2659.Sh HISTORY 2660The 2661.Nm 2662utility first appeared in 2663.Fx 2.0 . 2664.Nm dummynet 2665was introduced in 2666.Fx 2.2.8 . 2667Stateful extensions were introduced in 2668.Fx 4.0 . 2669.Nm ipfw2 2670was introduced in Summer 2002. 2671.Sh AUTHORS 2672.An Ugen J. S. Antsilevich , 2673.An Poul-Henning Kamp , 2674.An Alex Nash , 2675.An Archie Cobbs , 2676.An Luigi Rizzo . 2677.Pp 2678.An -nosplit 2679API based upon code written by 2680.An Daniel Boulet 2681for BSDI. 2682.Pp 2683.An -nosplit 2684In-kernel NAT support written by 2685.An Paolo Pisati Aq piso@FreeBSD.org 2686as part of a Summer of Code 2005 project. 2687.Pp 2688Work on 2689.Nm dummynet 2690traffic shaper supported by Akamba Corp. 2691.Sh BUGS 2692The syntax has grown over the years and sometimes it might be confusing. 2693Unfortunately, backward compatibility prevents cleaning up mistakes 2694made in the definition of the syntax. 2695.Pp 2696.Em !!! WARNING !!! 2697.Pp 2698Misconfiguring the firewall can put your computer in an unusable state, 2699possibly shutting down network services and requiring console access to 2700regain control of it. 2701.Pp 2702Incoming packet fragments diverted by 2703.Cm divert 2704are reassembled before delivery to the socket. 2705The action used on those packet is the one from the 2706rule which matches the first fragment of the packet. 2707.Pp 2708Packets diverted to userland, and then reinserted by a userland process 2709may lose various packet attributes. 2710The packet source interface name 2711will be preserved if it is shorter than 8 bytes and the userland process 2712saves and reuses the sockaddr_in 2713(as does 2714.Xr natd 8 ) ; 2715otherwise, it may be lost. 2716If a packet is reinserted in this manner, later rules may be incorrectly 2717applied, making the order of 2718.Cm divert 2719rules in the rule sequence very important. 2720.Pp 2721Dummynet drops all packets with IPv6 link-local addresses. 2722.Pp 2723Rules using 2724.Cm uid 2725or 2726.Cm gid 2727may not behave as expected. 2728In particular, incoming SYN packets may 2729have no uid or gid associated with them since they do not yet belong 2730to a TCP connection, and the uid/gid associated with a packet may not 2731be as expected if the associated process calls 2732.Xr setuid 2 2733or similar system calls. 2734.Pp 2735Rule syntax is subject to the command line environment and some patterns 2736may need to be escaped with the backslash character 2737or quoted appropriately. 2738.Pp 2739Due to the architecture of 2740.Xr libalias 3 , 2741ipfw nat is not compatible with the tcp segmentation offloading 2742(TSO). Thus, to reliably nat your network traffic, please disable TSO 2743on your NICs using 2744.Xr ifconfig 8 . 2745.Pp 2746ICMP error messages are not implicitly matched by dynamic rules 2747for the respective conversations. 2748To avoid failures of network error detection and path MTU discovery, 2749ICMP error messages may need to be allowed explicitly through static 2750rules. 2751